Process System Innovation by Design
Towards a Sustainable Petrochemical Industry
Process System Innovation by Design
Towards a Sustainable Petrochemical Industry
Proefschrift
ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof. dr .ir. J.T. Fokkema, voorzitter van het College voor Promoties, in het openbaar te verdedigen op maandag 13 september 2004 om 13:00 uur
door
Gerhard Pieter Jan DIJKEMA
ingenieur in de chemische technologie geboren te Norg
Dit proefschrift is goedgekeurd door de promotoren: Prof. dr. ir. M.P.C. Weijnen Prof. ir. J. Grievink
Samenstelling promotiecommissie:
Rector Magnificus, voorzitter Prof. ir. J. Grievink, Technische Universiteit Delft, promotor Prof. dr. ir. M.P.C. Weijnen, Technische Universiteit Delft, promotor Prof. dr. M.A. Reuter, Technische Universiteit Delft, Universiteit Stellenbosch, SA Prof. dr. ir. A.A.H. Drinkenburg, Technische Universiteit Eindhoven Prof. A.W. Westerberg PhD, Carnegie-Mellon University, US Prof. D. Bogle PhD, University College, London, UK dr. ir. S.A. Lemkowitz, Technische Universiteit Delft
Published and distributed by:
G.P.J. Dijkema p/a Delft University of Technology P.O. Box 5015 2601 GA Delft The Netherlands e-mail: [email protected]
Library of Congress Catalogue Data: ISBN 90-5638-127-X
Keywords: fuel cells, functional modelling, innovation, olefins, petrochemical industry, process systems engineering, sustainable development
Cover design: M. Mallee/P. Rüpp, www.kunstopmaat.info.
Copyright © 2004 G.P.J. Dijkema, Voorburg.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission in writing of the proprietor.
Printed in the Netherlands
Preface
This dissertation is a synthesis of research that was completed in the better part of a decade. The origins of some of the concepts and case studies date back to my stay with Interduct. Most of the research presented was conducted in the multidisciplinary, system-oriented academic environment of the faculty of Technology, Policy and Management. I would like to thank Margot Weijnen for offering me the opportunity to change career-path, for her patience in awaiting the forthcoming of this thesis and for the stimulating discussions and suggestions that set the stage for this work. I am most grateful to Johan Grievink for his encouraging in-depth reviews and his suggestions on formalisation of the work and its embedding in process systems engineering. To me, a brew of green tea will for always be associated with a discussion in Johan's office. I would like to thank all my committee members for their positive feedback and constructive criticisms. I owe special thanks to Art Westerberg for his painstaking review of the content, my English and punctuation. Markus Reuter I thank for many intriguing discussions and for his moral support. Many people have helped me to shape and sharpen the concepts presented. This thesis is a tribute to Han Jonk of SIPM, Odd Asbjørnsen of NTNU, Aad Montfoort of TU Delft and Pieter-Jan Jongman of the Port of Rotterdam. My colleagues at Interduct, the E&I section and the faculty I thank for creating a stimulating, pleasant and supportive working environment. Rob Stikkelman involved me in the project on fuel cell vehicles and in many creative sessions. Kas Hemmes I thank for sharing his knowledge on fuel cells and his encouragement to complete this work. In the office we shared, Paulien Herder put up with me and my sometimes messy filing. I appreciated the in-depth discussions on life, research and education with Zofia Verwater-Lukszo. I would like to hear Petra Heijnen sing more often and to learn more Indian wisdom from Harish Goel. I expect to have more discussions on electricity with Laurens de Vries. I am grateful for the swift help of Ivo and Mirjam Bouwmans with the wording and translation of my propositions. I acknowledge the indispensable support of Connie van Dop, Angelique Nauta and Rachel Kievits of our secretariat. My parents I thank for their love and for creating the conditions for my personal development. Finally, I treasure Elly's support and Roeland and Jenske's appreciation.
Gerard Dijkema Voorburg, July 2004
Contents
PREFACE...... V
CONTENTS ...... VII
1 INTRODUCTION...... 1 1.1 OVERVIEW: WHAT, WHY AND HOW?...... 1 1.2 READER'S GUIDE ...... 1 1.3 A SYSTEM IMAGE OF THE PETROCHEMICAL INDUSTRY...... 2 1.4 INDUSTRY DEVELOPMENT, INNOVATION AND SUSTAINABILITY...... 17 1.5 A NEED FOR PROCESS SYSTEM INNOVATION? ...... 29 1.6 RESEARCH APPROACH AND STRUCTURE OF THESIS ...... 34
2 PROCESS SYSTEM INNOVATION SOURCES...... 37 2.1 INTRODUCTION...... 37 2.2 SOURCES OF INNOVATIONS ...... 37 2.3 SYSTEM THINKING FOUNDATIONS ...... 46 2.4 PROCESS SYSTEM ENGINEERING ...... 51 2.5 SYSTEM DECOMPOSITION ...... 59 2.6 CONCLUSIONS...... 63
3 PROCESS SYSTEM INNOVATION BY DESIGN ...... 65 3.1 INTRODUCTION...... 65 3.2 SYSTEMATICALLY TOWARDS INNOVATION CONTENT? ...... 66 3.3 FUNCTIONAL MODELLING FOR PROCESS SYSTEM INNOVATION ...... 93 3.4 CONCLUSIONS...... 112
4 INNOVATION AROUND OLEFINS ...... 115 4.1 INTRODUCTION...... 115 4.2 THE INDUSTRIAL OLEFINS SYSTEM ...... 117 4.3 SYSTEMATICALLY TOWARDS INNOVATIONS?...... 123 4.4 FUNCTIONAL MODELLING OF THE OLEFINS SYSTEM ...... 137 4.5 DISCUSSION AND CONCLUSIONS ...... 151
5 FUEL CELLS AND TRIGENERATION ...... 153 5.1 INTRODUCTION...... 153 5.2 FUEL CELLS IN THE CHEMICAL INDUSTRY...... 154 5.3 THE DEVELOPMENT OF TRIGENERATION SYSTEM CONCEPTS ...... 175 5.4 DISCUSSION AND CONCLUSION ...... 187
viii Process System Innovation by Design
6 FUEL CELL VEHICLES AND INDUSTRY DEVELOPMENT ...... 188 6.1 ABSTRACT ...... 188 6.2 INTRODUCTION ...... 189 6.3 FUNCTIONAL MODELLING...... 190 6.4 SCENARIO DEVELOPMENT AND MODELLING...... 197 6.5 THE 'SUPERIOR PEMFC VEHICLES' SCENARIO...... 203 6.6 PROCESS SYSTEM INNOVATIONS FOR INDUSTRY DEVELOPMENT...... 211 6.7 DISCUSSION AND CONCLUSION...... 218
7 CONCLUSIONS AND RECOMMENDATIONS ...... 223 7.1 INTRODUCTION...... 223 7.2 PROCESS SYSTEM INNOVATIONS FOR SUSTAINABILITY...... 223 7.3 (ENGINEERING) SCIENCE CONTRIBUTIONS ...... 224 7.4 RESEARCH APPROACH...... 225 7.5 RECOMMENDATIONS...... 226
REFERENCES ...... 227
SYMBOLS ...... 241
ABBREVIATIONS ...... 245
APPENDICES...... 249
SUMMARY...... 279
SAMENVATTING...... 283
CURRICULUM VITAE...... 289
1 Introduction
1.1 Overview: what, why and how? What is this petrochemical industry that is the subject of this thesis? What are its economic and ecological characteristics? To elucidate these questions, this introductory chapter gives an overview of the petrochemical industry by presenting it as a system in its surroundings. It is a layered networked system embedded in and linked to the global material cycles. The system image is presented by addressing system definition, boundary selection, system content and surroundings (§1.3). Why do the historic development of the petrochemical industry, its current status and resource horizon merit a reconsideration of its technologies, process systems and petrochemical networks for sustainability? Why must we contemplate 'process system innovations', which “… are defined as changes in the system structure or system design of the petrochemical industry, its industrial complexes, or individual plants (…) enabled by technological inventions or vice versa” (Dijkema et al. 2003)? To address these questions, the meaning and implication of sustainability for industry is discussed. The development of the chemical industry is analysed with respect to drivers of and barriers to change, the process of change, R&D and the scope for innovation (§1.4). How can innovation for sustainability be fostered in the largely mature petrochemical industry that consists of technologically advanced systems? The dilemma of lack of economic incentive for much needed innovation for sustainability has given cause to our central research theme - how to specify process system innovation1 content for a sustainable petrochemical industry (§1.5). The meta-model of the research (§1.6) summarizes how the above questions have been addressed and converted into the present thesis.
1.2 Reader's guide The system image of the petrochemical industry (§1.3) is included to introduce the object of the research and to serve as basis for those unfamiliar with this important sector of the industrial economy. Readers with a chemistry or chemical engineering background may find the system representation to be a useful refresher. In 'industry development, innovation processes and sustainability' (§1.4) insights from technology management, innovation theory and economics are combined and linked to the petrochemical industry system image and scientific and chemical engineering development. 'The need for process system innovation' (§1.5) is the core section of this chapter. The dilemma's and problems associated with change and innovation for sustainability are identified, which leads to the research theme, research questions and hypothesis.
1 Where in process system engineering (PSE) the focus is on single plant process systems, the definition of 'Process system innovation' is based on the notion of layered networked process systems, which structure and content can be modified at each level.
2 Process System Innovation by Design
1.3 A system image of the petrochemical industry
1.3.1 SYSTEM CONTENT, INTERFACES AND SURROUNDINGS Since the beginning of the 20th century, petrochemical facilities have been continuously improved and major breakthroughs have been realized by the invention and application of novel catalysts, reactor concepts, separation technology and process system concepts. In many cases, the interplay of technological development, economies-of-scale and market-growth made older, smaller and less efficient plants obsolete. In many locations petrochemical complexes have developed consisting of multiple interconnected and interdependent plants. Today, petrochemicals are produced in bulk quantities in large-scale out-door facilities that have become the blueprint image of the chemical industry in the industrialised countries. Whilst these are complex installations in appearance, they can all be represented as a system wherein a number of physical inputs is transformed into a number of outputs, e.g. a steam cracker transforms naphtha to olefins and aromatics (e.g. Rudd et al. 1973; Smith 1995).
Reserves and Renewables? Earth Timely and economic exploration? Carrying Capacity?
New Resources Resource Improved Extraction Novel Deposits
Technology Timely process innovation? Systems More use of proven technology?
Products Product New or improved Services
Captive or end-user market? Market Market growth or decline Sustainability awareness?
RPMT- Combination
Figure 1-1: The Pmt-R concept. Any such system is part of a Product-Market-Technology combination (Pmt) (Dijkema and Stikkelman 1999). The existence of any Pmt, however, depends on the availability of resources (Figure 1-1). The steam cracker, for example, requires the
Introduction 3
availability of crude oil for the production of naphtha. Since system structure and technology may change because of changing market demand and because of changing resource availability, we prefer the label Pmt-R to emphasize the relationship between product markets, technology and resource use for the system. In the petrochemical industry, many Pmt-R's are linked, as it is a complex system of interconnected processes and process routes. The entire petrochemical industry, however, can be modelled as a black box that is part of and contributes to our industrial society via the inputs it requires and the outputs it generates (Figure 1-2). Inputs are required for day-to-day system operation, for the erection of new facilities and for rejuvenation or end-of-life system abatement (Grievink 1994). Physical inputs comprise feedstock and utilities, construction material and equipment. Other inputs are market information, skilled labour, technological know-how, system design, project organisation and management skills, investments and working capital. Physical outputs include products, by-products, waste and emissions as well as industrial plants and complexes. Other outputs are know-how and services rendered, salaries, fees, taxes and dividends paid.
Non-Physical Surroundings Know-how Investment Regulations Skilled Labour Operating Cost Operating
Emissions Feedstock
Products
Utilities Waste System: The Petrochemical Industry
Interface Salaries Revenue Experience
(Dis)comfort Surroundings
Non-Physical Surroundings
Figure 1-2: System image of the petrochemical industry. Together, inputs and outputs represent the interface between the petrochemical industry and its surroundings over the system boundary. Development of system content is driven by market demand, feedstock availability, production cost, and legislation. These are the non-physical -economic, societal, managerial, scientific, regulatory- system 'surroundings' (e.g. Stobaugh 1988; Kuipers 1999; Dijkema and Kuipers 2001). Feedstock cost, product revenue, capital flow, direct labour and
4 Process System Innovation by Design
services affect system economics (e.g. Peters and Timmerhaus 1991). Inputs from and outputs to the physical surroundings result in adverse ecological effects, such as resource depletion, toxic waste and harmful emissions. These have resulted in societal concern, economic effects, environmental regulation, scientific interest, technology development and shifting design criteria and changing design space (e.g. Carson and Darling 1962; World Commission on Economic Development 1987; Smith 1995; van Breda and Dijkema 1998; Wood 2001). The industry's present ecologic impact is largely determined by its system content and characteristics, which results from past decisions on product and technology development, process system design, management, economics and regulation. In competitive markets, the economic health of individual companies depends on information and knowledge on how and when to properly bring novel products and innovative production systems into being (e.g. Wei et al. 1979; Pisano 1997; Linse 2002; van Klaveren 2003). Company prosperity requires effective use of current assets -technology, systems, skills and organisation- and strategic capabilities to anticipate market dynamics, shifting societal concerns and changing regulation to ensure sustainability. The system image of the petrochemical industry therefore includes a summary of present developments in its surroundings.
1.3.2 A DEFINITION OF 'PETROCHEMICAL INDUSTRY' AND 'PETROCHEMICAL' Obviously, the petrochemical industry is part of the chemical industry. The prefix 'petro' serves to further limit the system to those establishments that use petroleum- derived feedstock. Typically, the petrochemical industry employs large-scale, continuous process plants. Relatively small facilities that produce dyes, resins, insecticides or pharmaceuticals from petroleum-derived feedstock are ‘chemical industry’ but not petrochemical industry because of their limited scale of operation. The large-scale manufacture of fertilizer and detergents respectively are chemical industry because these industries predominantly use non-petroleum-derived feedstock. A common characteristic of ‘the (petro)chemical industry’ is that chemical reactions are effectuated in a commercial fashion in specifically designed chemical reactors that are the heart of any chemical process plant (see Figure 1-4, p.13). Using this description, however, many industrial operations would be classified as ‘petrochemical industry’ that generally are not perceived as such. One can think of, for example, steel mills and aluminium smelters that use petroleum coke. The Standard Industrial Classification (SIC) by the US bureau of the Budget circumvents this problem by defining SIC 28 as “the major group that includes establishments producing basic chemicals, and establishments manufacturing products by predominantly chemical processes (Wei et al. 1979: 25).” Thus, one has developed a classification code that is both product-oriented and process-oriented. In the professional community, the petrochemical industry is synonym for the large-scale chemical industry that uses petroleum products as feedstock or materials that are primarily obtained from petroleum products, e.g. olefins and aromatics from the steam cracker and refinery operations. Using the systems view presented in Figure 1-2, and using the above definitions we define the petrochemical industry as 'the subsystem of industry where large-scale
Introduction 5
chemical processes are employed to convert petroleum-derived feedstock into base chemicals'. A petrochemical then is a base chemical that is predominantly produced by the petrochemical industry.
1.3.3 MARKETS AND SOCIETY The outputs of the petrochemical industry are used in important industrial sectors such as agriculture, building and construction, electric power, automobiles and fuels, electronics, food and health care, textiles, consumer durables and packaging. (Wei et al. 1979; Weissermel and Arpe 1994; Mol 1995). Thus, this industry plays an essential part in the fulfilment of all categories of human needs in the hierarchy of Maslow: food, clothing, shelter, transport, entertainment and the need for self-expression (Maslow 1954)2. Consumers purchase a myriad of industrial products and services from a variety of industrial sectors to fulfil their needs (Figure 1-3). Hardly any consumer knowingly buys petrochemicals, however, and to the general public this industry is mainly known because of its perceived safety hazards, toxic waste and harmful emissions. Its role as a major enabler and contributor to our current standard-of-living remains largely unknown and unappreciated. Many of its products do reach consumers, however, via various industries that incorporate synthetic polymers in their products (Figure 1-3). Generally known as plastics, these materials and their building blocks have enabled successful introduction of a myriad of innovative products. Presently, polymerisation is used to produce thermoplastics, thermoset resins, resins and coatings, rubbers, foams and industrial fibres. All these polymer categories comprise chemically stable products. With the exception of some special resins for adhesive and coatings applications, the products sold are characterised by non-existent or very low chemical reactivity. Since the World War II the demand for synthetic polymeric materials has grown dramatically. As a consequence, today the majority of products of the petrochemical industry are polymer building blocks. Ethylene and propylene, for example, are used to manufacture polyethylene and polypropylene for a variety of packaging applications, toys, synthetic carpets, cutlery and automobile parts. Copolymers of styrene, acrylonitrile and butadiene are produced in high-grade semi-bulk for the electronics and automobile industry. These industries also use a myriad of specialty polymers or engineering plastics that are produced in small volumes, for example for mobile phone exteriors, switchboards and car parts. Apart from polymers, petrochemicals are used as precursors for fine chemicals and pharmaceuticals, electronics, fertilizer as well as automotive fuels and de-icers. Thus, the petrochemical industry has become an essential supplier of our modern industrial society. It can be labelled the industry’s industry (Brennan 1998).
1.3.4 PRODUCTS The chemical industry produces intermediates that are used in many industrial sectors to cater for consumer demand (Figure 1-3). Most chemical products are not sold to consumers, however, and the product spectrum of the industry remains relatively unknown to the general public.
2 Cited in (van der Graaf 1980)
6 Process System Innovation by Design
The products of the chemical industry can be categorised as undifferentiated vs. differentiated (Wei et al. 1979; Stobaugh 1988; Brennan 1998:14-16) and as large,- volume versus small and very small volumes produced (Table 1.1). Differentiated products are also known as performance products. These possess at least one unique characteristic. The large-volume segment mainly consists of bulk - polymers (e.g. PE, PP, PS, PVC). These pseudo-commodity plastics are produced in many different grades for specific applications. The small-volume segment by definition includes thousands of specialty chemical products, resins and specialty plastics and active ingredients of crop protection chemicals, veterinary medicines and pharmaceuticals.
Table 1.1: Classification of petrochemical industry products (after Brennan 1998) Product classification Production volume Undifferentiated Differentiated Large Commodity Pseudo-Commodity Small Fine Chemical Specialty Chemical Very Small Pharmaceutical
An undifferentiated product has a specific chemical formula, and a standard particular specification, regardless of its producer. The commodities category includes products that are traded internationally under stringent AA-quality specifications such as ammonia, sulphuric acid, ethylene, styrene and standard grade plastics such as HDPE, LLDPE and PP. 'Fine chemicals' includes agrochemicals, food additives and 'commoditized' medicines such as aspirin. Most petrochemicals are undifferentiated commodity products. Worldwide, annual production capacity for some 60-100 petrochemicals exceeds a million metric tons each (Appendix A. 1).
1.3.5 FEEDSTOCK AND ENERGY USE The carbon-hydrogen skeleton of petrochemicals originates from crude oil. Oxygen from the air is incorporated in petrochemicals via partial oxidation. The chlorine in PVC is produced electrochemically from common rock salt (NaCl). Once, coal used to be the chemical industry's most important feedstock. Presently, however, coal use is largely restricted to electric power generation and coke production for steel works. In coke ovens limited quantities of aromatics are produced from the coal tar by-product (Franck and Stadelhofer 1988). The exception is Sasol in South Africa, where it is still economic to convert coal to logistic fuels (gasoline, diesel, fuel oil) via partial oxidation to syngas and subsequent Fischer-Tropsch synthesis. The primary carbon and hydrogen sources for the petrochemical industry today comprise oil products, natural gas liquids and natural gas. Since crude oil cannot be converted directly into petrochemicals economically, the industry's feedstock is obtained primarily from oil refineries. These separate crude oil into a range of so- called petroleum ‘cuts’, of which naphtha and gas oil are suitable and economic feedstock for steam crackers that produce ethylene and propylene, other olefins and aromatics (Figure 1-3 and Ch. 4).
Introduction 7 Households Consumers / Food Other Paper Textile Energy Pharma Building Farming Materials Sectors Industry Machinery Packaging Electronics Transport / Automobiles Agriculture Process Process Shaping Moulding Polym. Polym. Polym. Polym. Polymer Industry Polymer Network Production Monomers Fine Chemicals Fine Fuels Bitumen Lubricants network Production Chemical Industry Olefins Aromatics Production network Production network Fertiliser Industry Fertiliser s Methanol & Derivatives & Methanol Petrochemical industry Petrochemical Steam- Cracker Complexe Gasoil Naphtha Oil Refineries Industry Refining Gas Natural Winning Winning
Figure 1-3: 'Chemical industry', 'petrochemical industry', 'polymer Industry' and society.
8 Process System Innovation by Design
Many oil fields co-produce associated gas or 'condensate' -ethane, propane and butanes-. Natural gas wells often co-produce natural gas liquids (NGL) -butanes to heptanes-. Both condensate and NGL are premium feedstock for steam crackers. The butanes are the preferred feedstock for MTBE. Natural gas3 is important as a carbon and hydrogen source for industry, as it is the dominant feedstock for methanol via the production of synthesis gas (Figure 1-3). In the Netherlands the large-scale process industry - petroleum refining, petrochemical industry, polymer industry, fertilizer production and base metal production - together account for over 30% of the end-use of fossil energy resources (Dijkema et al. 1995). Combined, these sectors represent no less than 67% of annual Dutch industrial energy end-use, which includes feedstock use and net energy use for production. Worldwide some 10-15% of annual fossil resource use is consumed by these industries. These data indicate that the Dutch economy is characterised by a relatively large process industry sector, which accounts for some 1020 PJ4 end-use on a total Dutch energy account of some 2700 PJ in 1990 (3100 PJ in 2001) (CBS 1992; 2002)56. With the exception of natural gas, some offshore oil production and a limited share of renewables, the Netherlands is completely dependent on imported crude oil and coal for its internal energy use and the associated industrial production.
1.3.6 UNWANTED BY-PRODUCTS: WASTE AND EMISSIONS Apart from desirable outputs, petrochemical operations also result in by-products, emissions and waste that can be detrimental to our environment. Smokestacks of industrial (boiler) furnaces have been the trademark of industry since the early days of the industrial revolution. It was after World War II, however, that smokestacks taller than 100 metres where erected to combat local pollution. In the 1960-70's, a period of rapid economic growth, the petrochemical industry obtained the label ‘Dirty, Damaging, and Dangerous’. This was largely due to the rapid expansion of petrochemical production, associated increasing waste volumes and Rachel Carson's 'wake-up call' that even very small quantities of chemicals can have a devastating effect on the environment (Carson and Darling 1962).
3 Hydrogen and nitrogen are converted to ammonia (NH3) in the Haber-Bosch process (Anonymous 1991; Jennings 1991). This is the industrial route for nitrogen fixation from air, and the basis of the world nitrogen fertiliser industry. The primary source for hydrogen is natural gas (CH4). 4 Pèta Joule = 1015 Joule; One PJ is the energy content of 24 Thousand Tons Oil Equivalent (TOE). Thus the net end-use of fossil resources in the Dutch process industry equates to some 24 Million TOE; Total Dutch fossil resource use equates to some 74 Million TOE. 5 Since for many products of the process industry, fewer than three companies operate facilities in the Netherlands, the Dutch Statistics Office CBS cannot disclose a detailed break-down between feedstock, energy-use and production. The industry associations (VNCI, FediChem, FOI) do report total sector energy use, but these figures exclude feedstock consumption. Based on the case studies done in 'de grondstoffenstudie' (Dijkema et al. 1994a; 1995) we estimate the total amount of fossil resources that does not end up in petrochemical products in the Dutch petrochemical industry at 350-400PJ. 6 Other use of fossil fuels in the Netherlands concerns energy conversion for electric power generation (some 480-500PJ for 300-320 PJe), mobility (380-400PJ), space-heating (400-420PJ) and miscellaneous industry and services (600 PJ).
Introduction 9
The environmental catastrophes thus exposed and a number of serious incidents in the 1970's gave cause to general public concern on safety, health and environmental risks of chemicals and the chemical industry. At the time, for example, untreated effluents polluted watersheds and toxic waste was dumped in uncontrolled, unprotected landfills. Without change, the industry was at peril of loosing its 'license- to-operate' in the 1970-1980's. The pre-1960 environmental ‘disasters’ exposed the chemical industry. Not only did these result in growing public concern during the 60's, 70's and 80's, also governments responded by environmental policy development that led to extensive and more stringent regulation on environmental pollution (e.g. VROM 1972). The chemical industry focused on improving its environmental performance with respect to harmful emissions to air, water and soil. Initially, this focus on environmental pollution caused by the industries’ inadvertent outputs led to better operating procedures and so-called end-of-pipe solutions such as flue-gas cleaning and chemical waste incineration. Later improved designs for novel and existing plants emerged that include process-integrated solutions for emission-control and waste- abatement. In addition, a framework for environmental management was developed and adopted. With respect to environmental management the chemical industry appears to positively distinguish itself from a number of other sectors. In a recent survey the European Environmental Agency concluded that the status of our environment is not improving anymore. Amongst others, the agency attributes this to the many sectors of the European Economy that to date have only implemented end-of-pipe solutions (Anonymous 2003b). In the chemical industry, nowadays environmental management is usually amongst the responsibility of senior management (Mol 1995), and for many a company in the petrochemical industry “the environment” has become a strategic issue. Major refining and chemical corporations have included Responsible Care for the environment in their mission statement. As a result, the chemical industry has ensured its continued license-to-operate (Mayer and Dijkema 1999). In the petrochemical industry waste quantities per unit product are generally low, as any significant amount of hydrocarbons can be (re)utilised as feedstock or converted into power or heat. Weber (1909) distinguished between “Verlustrohstoffe” and “Reinrohstoffe” (Weber 1909). The former type of resource carries a high amount of useless material. Upon processing, inevitably a significant amount of waste material must be discarded. By contrast, a Reinrohstoff constitutes primarily usable components. Crude oil changed from a Verlustrohstoff to a Reinrohstoff as a consequence of the late 19th century developments in crude oil refining, transportation and the chemical industry. In accordance with Weberian location theory, this not only affected the location pattern of refineries worldwide, but also implied that the absolute amount of waste generated in the refining and petrochemical industry is limited. In many industrial regions where petrochemical industries are concentrated, these have jointly realised facilities for final treatment of hazardous waste, for example AVR in Rotterdam, Indaver in Antwerp. In the refining industry, however, waste potentially may become a problem when heavy residues and asphalt cannot be fully
10 Process System Innovation by Design
marketed anymore for heavy transportation fuel (ships) or road construction. In the future, it can be expected that additional conversion technology is required to further upgrade these streams, and capture sulphur, heavy metals, and ashes in an environmentally acceptable way. In other large-scale processes, notably base metal, low-value or waste by-product generation remains the rule, as well as in coal processing. Today, in response to global treaties some classes of harmful products, such as chlorinated hydrocarbons and CFC's, have largely been phased out. Inadvertent emission losses of volatile organics (VOC) have been reduced. Design and performance of fired-equipment has been improved to reduce VOC, NOx, CO and soot emissions. Thus, in the petrochemical industry, the environmental “sanitation” of the production systems is considered to be on track, and harmful emissions are continuously monitored, whilst process performance is continuously improved. As in waste management, three decades of development and corporate experience with environmental management systems should enable the industry to respond appropriately to whatever environmental demand or regulation on harmful emissions. The reduction of global human CO2 emissions, however, presents a relatively new and formidable challenge. Production and combustion of oil products, natural gas, petrochemicals or polymers inevitably yields CO2. Thus its formation is linked to the industry's feedstock and energy supply and to the use and final degradation of its products. Hence, allowed CO2 emission can become an active constraint, and CO2 emission control a key to the industry's license to grow.
1.3.7 ECONOMICS The traditional and major chemical economies are the US, the EU and Japan. In general, OECD countries “have rather similar chemical industries with only minor variations between these industrialized nations” (Mol 1995: 127). Today, growth regions are the Middle East, South-East Asia and to a lesser extent Eastern Europe. Around the globe, the petrochemical industry is characterised by - the use of large-scale to very large-scale continuously operated facilities - large sunk costs - a huge amount of capital invested - links with both cyclical and largely non-cyclical markets - oligopolistic market structure - a high level of internalisation, both in trade and production sites. - a dependence on abundant, low-priced resources - being capital intensive, labour extensive and knowledge intensive - a relatively low return on investment (ROI) or return on asset capital employed (ROACE) (Linse 2002) (e.g. Wei et al. 1979; Stobaugh 1988; Brennan 1998; Whitehead 2000). The volumes of many undifferentiated commodities merit continuously operated facilities over batch wise operation because of achievable process efficiencies, asset utilisation and investment per unit product. Investment for new continuous chemical p plants generally is given by I = I0 * (C/C0) , where I is total plant Investment, C is plant capacity, and suffix 0 denotes some known investment I0 at a known capacity
Introduction 11
C0. Since p has a value of around 0.6, a chemical plant of twice a nominal capacity will cost only 50% more (Chauvel 1981). Generally it will require the same number of operating personnel, and have similar overhead costs. Whilst in (pseudo)-commodities, investments are huge (100-1500 million US$ per facility), the profit margin or value added per unit product over feedstock cost is relatively low (e.g. Wei et al. 1979). This margin, however, must be sufficient to allow recovery of all operating costs and the investment-related costs, i.e. average costs. Since petrochemical plants often exhibit a long technical lifespan -30-50 years- would-be competitors in an established petrochemical market do face ‘marginal competition’. Established manufacturers ('incumbents') compete on the basis of the marginal cost of their facilities only because the original investment is a 'sunk cost' that either has been recovered or written off in previous operating years. Investments in new facilities, however, are justified only when sufficient return over total cost can be realised. As a consequence, incumbents may operate economically at efficiencies considerably below state-of-the-art. The gap between marginal revenue and average revenue often can only be closed by combining innovative process technology and economies-of-scale. Existing facilities are expanded and modernized or phased out; in newly built plants state-of-the-art technology is used and capacity is at the technically feasible design limit. Thus, knowledge intensity, scale-of-operation and investments continuously increase to bring down cost per kilogram of product. The typically low margins of petrochemical operations must be sufficient to realise return-on-investment targets. These target levels are relatively low in the petrochemical industry - around 10% -. The financial risk, however, is substantial due to the cyclical nature of markets, the risk of overcapacity and the technically and economically limited flexibility of petrochemical plants in capacity-utilisation (Kuipers 1999). A typical petrochemical plant has a physical turndown ratio of some 50%, whilst the average economic turndown ratio of a new plant may be as small as only 10%. Thus, usually utilisation-factors at or below 80% indicate that the owner is not recovering average cost. In the early 1990's, for example, many companies invested in plants for PET - the plastic used for sodas sport drinks bottles, 'single service disposable containers' - and its precursor, purified terephtalic acid because of expected high market-growth. A few years later, however, the resulting capacity build-up grossly exceeded real market growth. As a consequence, PET/TPA producers suffered from low capacity utilisation and depressed market prices around the turn of the century. The PET/TPA market is an example of cyclicality, where the supply-demand balance can only be restored by continued market growth or by phase-out of existing capacity. At times of limited market growth -or decline- closure of facilities may only be expected when their marginal cost cannot be recovered anymore and revamping cannot be justified. Since capacity build-up was realised in a few years, most capacity is in modern plants with similar performance. The inevitable result is price erosion from which all players suffer. In order to reduce risk, over time many major petrochemical companies have stated they prefer to be number one or two in their respective markets or else exit.
12 Process System Innovation by Design
Thereby, these companies apparently prefer to be active in oligopolistic markets - markets with only a few major players. It is well known that in such markets individual companies possess market power and have flexibility to set prices to recover cost and realise target ROI or ROACE (Lipsey and Steiner 1991). The oligopolistic market structure and the characteristics of petrochemical production represent formidable ‘entry-barriers’ for new players. These must have sufficient capital, access to resources and markets or create their own outlets. A competitive edge must be established with respect to established producers (Wei et al. 1979), which implies a company must have the technical and organisational skills to build, finance and operate modern large-scale facilities and to market and sell its products. Vertical integration is another strategy to achieve economy-of-scale and create entry barriers. Vertically integrated companies control significant parts of supply chains or production networks wherein many petrochemical plants produce for captive use. At the company boundaries, feedstock supply, utilities and product sales generally are arranged under long-term contracts with reliable local suppliers, which results in only small volumes to be obtained via global sourcing or to be sold on the free-market respectively. Whilst the petrochemical industry is a truly global business with exchange of technology and operating practices through multinational corporations, the actual volume of petrochemicals traded between the geographic regions mentioned above remains relatively small compared to internal trade (e.g. Anonymous 2001b)). Apart from vertical integration, apparently the global exchange of market information and adaptation of prices leads to a situation where transport at volumes at or above the level of a single plant of typical world-scale is not competitive. Thus, a sufficient local market for low-priced commodity chemicals is important and has led to the formation of huge petrochemical complexes in for example Antwerp, Singapore, Houston and Rotterdam. These enable operating companies to reduce transport costs and risks. The Rotterdam Chemical Cluster, for example represents a vested investment of some 10 billion euros, only 13.000 direct jobs and some 60.000 indirect jobs, and is largely based on low-priced international oil-supply (Kuipers 1999). Once established, these agglomerations represent huge advantages because of the very availability of product outlet and feedstock, hard- and soft infrastructure - pipelines and utilities; knowledge and service providers and professional authorities. As a consequence, the establishment of new “grass-root” complexes in the developed countries is hardly to be expected because of the economic cluster advantages rather than because of the fear of “NIMBY” sentiments. The very existence of petrochemical complexes contributes to the industry's inflexibility, which is caused by sunk cost, capital intensity, ROI/ROACE targets, technical lifespan of facilities and their interdependence if not vertical integration.
1.3.8 TECHNOLOGY AND PROCESS SYSTEMS Specialty chemicals often are produced in batch-wise multi-purpose production facilities. As these are often located within a building, they are generally unnoticed, except for odorous smells or cases of pollution. Commodities and pseudo- commodities, however, are produced in bulk quantities in large-scale out-door
Introduction 13
continuous operations that have become the blueprint image of the petrochemical industry in the industrialised countries. Such large-scale continuous plants are complex installations in appearance. Indeed at a detailed technical level, they consist of a variety of interconnected apparatus, instruments, pipes, and construction. As stated, however, any petrochemical plant can be represented as a system where a number of physical inputs are transformed into a number of outputs. As far as the representation of system content or design is concerned, each petrochemical plant can be completely characterised by a single configuration of a limited number of process sections or functional units, such as feed-preparation, reaction, separation, final product purification, process flows, process recycle flows and utilities (Montfoort et al. 1989; Dijkema et al. 1998). In Figure 1-4 this is illustrated by a simple general implementation of a chemical process. The core of the process is some reaction subsystem, which often consists of multiple reactors. Since most chemical reactions do not give 100% yield of the desired product only, a separation subsystem is required to achieve product specification. As a matter of course, intermediate separation in multi-reactor systems is a possibility. A particular characteristic of continuous processing is the recycle structure, which in its simplest form is the recycling of unconverted feedstock back to the reactor. In multi-reactor / multi- separation systems, the recycle structure is an important degree-of-freedom in system design.
Feed T Product
Fuel Feed Puri- preparation Reaction Separation fication Purge
Recycle Flow
Figure 1-4: General representation of a petrochemical process system.
Since in refining and the petrochemical industry distillation is the dominant choice for product separation, the image of this industry is formed by the well-known arrays of distillation towers. Especially at night petrochemical plants offer a spectacular sight when the pipes, distillation tower, reactors, vessels and a whole range of other equipment are illuminated. Second in dimension to the distillation towers are the huge cracking reactors in the refining industry, the largest being the Exxon Flexicoker and Shell Hycon reaction systems, followed by continuous cat crackers
14 Process System Innovation by Design
and hydro crackers. In the petrochemical industry, industrial furnaces together with their chimneys have developed into installations of enormous physical dimensions. These also are the prime exception to the relatively small physical size of reactors in the petrochemical industry: steam cracker furnaces and reformer furnaces are fired reactors for the production of crude ethylene and synthesis gas respectively. In contrast, a plant for the production of styrene, the reactor only is of limited size.
Chemical plant
Inputs Chemical plant Chemical plant Outputs
Outputs >> Inputs Exchange
Chemical plant Flow Chemical plant Info
Category
System Chemical plant Chemical plant Element
System Surroundings The Petrochemical Industry Boundary
Figure 1-5: System model of the petrochemical industry. Modern continuous chemical plant designs often exhibit complex structures to optimise the internal process structure for plant performance. Multiple reaction and separation subsystems may be present, as well as multiple recycles. Feed preparation and product polishing may be integrated with reaction and separation, respectively. In advanced designs, reaction and separation may be integrated. Since operating conditions can be selected to meet a range of objectives, the design of any commercial petrochemical plant is only one out of a large set of feasible configurations (Montfoort 1992). A number of alternative process systems for the production of, for example, propylene oxide and methanol therefore are currently in use. Over time, in the industry many petrochemical processes have been developed to upgrade novel feedstock, waste and by-products. The result is a petrochemical network that is characterised by interconnectivity and interdependence.
Introduction 15
Cadre 1-1: System analysis and Input /Output modelling
Both in thermodynamic analysis and in system analysis, any process may be divided into the system and the surroundings by drawing a hypothetical envelope or system boundary around the operating units or system elements studied. The surroundings are everything that is not in the system (Seader 1982), i.e. the complement set to the system set. Inputs and outputs may cross the system boundary. A trivial system model of the petrochemical industry, for example, consists of individual chemical plants that exchange intermediate products (Figure 1-5, Table 1.2). A net amount of feedstock and utilities cross the system boundary, as well as a net amount of industry products and waste material. Irrespective of what happens inside a system's boundary, a production system's performance can be characterised completely by its inputs and outputs. An analysis based on this notion is commonly labelled a 'black-box' approach (e.g. Blair and Whitston 1971). In economics, this has become known as input-output analysis, or I/O analysis, and the associated type of modelling is Input-Output modelling. Upon opening the box, any system consist of a structured collection of system elements or sub-systems, which itself forms a new black-box or system (Asbjørnsen 1992). Not only the system can be fully described by its inputs and outputs, the same holds true for a system element or network node, in our case an individual chemical plant. When the system boundary is expanded, a hierarchy of systems appears, where at each level a system may become an element of a higher- level system. The 'Surroundings' and 'System Elements' labels then change from 'Petrochemical Industry' and 'Chemical Plant' respectively (see Figure 1-5). Each system aggregation level thus has its unique labels, as given in Table 1.2. Only a limited number of labels are required for all aggregate system levels to describe inputs and outputs, interconnecting flows and the exchange with the system' surroundings The entire petrochemical industry, any of its petrochemical complexes or any of its individual process plants or parts thereof can be characterised by their ingoing and outgoing streams only. It may thus be seen that I/O modelling provides a sound basis to provide a quantitative image of the petrochemical industry and to assess the performance of its constituting elements to the level of detail required. Does resource utilisation improvement in propylene oxide production, for example, require a focus on improvement of existing industrial technologies, a focus on the development of alternative production routes, on the expansion of the existing networked systems with additional conversion steps or maybe a focus on the development of alternative polyurethane precursors? I/O modelling allows one both to select a suitable aggregate level and to change level to help evaluating resource utilisation from a variety of perspectives.
16 Process System Innovation by Design
A petrochemical plant, complex and the entire industry can be represented as a structured configuration of individual system elements that are connected by some kind of flow (Figure 1-5, Table 1.2, p. 16). These convert oil products, other fossil resources and intermediates to suitable feedstock for the polymer industry and other sectors (Figure 1-3).
Table 1.2: Overview of aggregation levels in and around the petrochemical industry7 System Chemical Plant Petrochemical (Inter)National Boundary Industry Industry Surroundings Petrochemical National Industry World Material (dominant) Industry Cycles System element Unit Operation Chemical Plant Industry Sectors Flows: Materials, Energy, (Exergy) Inputs, Outputs: Resources, Products, Waste, Emissions Exchange Flows: Intermediate Products, By-Products, Energy Intensive properties of Flows: Composition, Pressure, Temperature
As with the designs employed for methanol or propylene oxide production, the present configuration is only one instance of a very large set of possible system structures (Table 1.3). Where single plants are characterised by a combination of 'once through' interconnectivity and intra-connectivity via recycling between reaction and separation, the petrochemical complexes and the industry predominantly exhibit 'once-through' intra-connectivity from feedstock to product. The majority of chains originate from the steam cracker and re-unite somewhere in the polymer industry, e.g. where polyurethanes are produced and moulded into car seat-cushions (Ch.4). In the petrochemical industry, the major chemical activities are the chemical rearrangement and partial oxidation of hydrocarbons. Thus it has become an extremely fast element of the world's fast carbon cycle8 that is driven primarily by life-on-earth. Biomass grows and decays, which maintains a balance of carbon as
CO2 in the atmosphere. A limited amount of biomass is temporarily extracted from the cycle by fossilisation. Fossil resource extraction for use in power generation, industry, transportation and households has resulted in a rapid reintroduction of carbon fossilized over millions of years and which has induced a steep increase in atmospheric CO2 content (IPCC 2001).
7 Currently, a great many (petro-)chemical plants are part of an industrial cluster. Thus, the petrochemical industry' system element may also be defined as a petrochemical complex, with the possibility in some cases the element or 'complex' only comprises of a single petrochemical plant. 8 The slow carbon cycle concerns geochemical processes where over millions of years erosion releases carbon. In this slow cycle invertebrae sequester carbon by the formation of shells composed of lime (CaCO3). The calcination of lime for cement production thus has become part of this slow carbon- cycle.
Introduction 17
Table 1.3: System levels in the petrochemical industry System System Intra -Connectivity Degree-of-freedom elements Petrochemical Complexes / Mass flow, Selection & configuration of elements; Industry Plants infrastructures Feedstock/product state and composition Complex Chemical Mass & energy Selection & configuration of elements; Plants flows; utility Feedstock/product state and composition infrastructure Chemical Unit Mass & energy Selection & configuration of elements; Plant Operations flows; utility Conditions & flow composition network Unit Apparatus Direct transfer of Selection & configuration of elements; Operation mass, heat, power, Principle & design impulse; Apparatus “Internals“ Mechanical, Selection & configuration of elements; Electrical, Chemical Operating conditions
Industrial development has created novel interconnectivity between material cycles. The fast carbon cycle is linked with other material cycles via fertiliser production and through the contaminants present in coal and crude oil that range from heavy metals to sulphur, phosphorus and nitrogen. The production of iron, for example, requires carbon, aluminium and zinc plants use carbon electrodes, and many non- hydrocarbon components are added to commercial plastics (TiO2, ZnO, Chlorine),. Since the majority of fossil fuels are burnt, and only a fraction of the plastics produced is subject to back-to-feedstock recycling, the majority of fossilized carbon is dissipated into the atmosphere as CO2.
1.4 Industry development, innovation and sustainability
1.4.1 DEVELOPMENT OF THE CHEMICAL INDUSTRY The Dutch petrochemical industry has developed to its present state over some 350 years. In his overview Mol (1995) distinguishes four periods of development in the chemical industry. In the subsequent overview a subdivision of the period after World War II results in five characteristic periods of development. The 17th and 18th century. In the 17th century the Netherlands held a prominent position in the international chemical and metallurgical industry of the time; activities included the production of mercury compounds, madder dyes, such as lead white, blue, soap work, litmus and volatile oils. During the 18th century the industry's importance decreased, with the exception of madder dyes, the candle industry, lead- white and soap. The 19th century until World War I. In the 19th century, major developments in inorganic chemistry took place, e.g. development of alkali, sulphuric and phosphate processes. Large breakthroughs were realized internationally through the work of renowned chemists. The industry prospered and grew, albeit not in the Netherlands, which Mol largely attributes to the role of universities, where teaching in chemistry was largely absent. Notably, in other historical studies, the importance of scientific research and education is also labelled as an important factor (Homburg et al. 1998).
18 Process System Innovation by Design
Processes Sinks
Natural Physical, Chemical, BiologicalGeochemical and
Wasted' Outputs Sinks 'Emitted or 'Emitted
Interconnected Material Cycles Material Sources System Boundary System World >> Economic System Plants >> Process Units Nations >> Industrial Complexes Industrial >> Nations Complexes >> Plants >> Complexes Europe National >> Economies System Levels Inputs Processes
'Extracted' Sources Space Occupied Natural Physical, Chemical, Biological and GeochemicalBiological and Solar Radiation
Figure 1-6: Worldwide Interconnected material cycles.
Introduction 19
In addition, economic growth stagnated, and Dutch industry was still focused on the maritime industry and trade. By some it was considered ‘backward’ in comparison with the rest of Europe, notably Germany, France and Great Britain. Gas production from coal, and the work-up of the coal-tar by-products were important activities, with around 180 factories in operation around 1900. The products, coal tars and its aromatic distillates, were largely exported because vested interests of natural dye producers prevented the set up of a Dutch synthetics dye industry. The only surviving coal-tar refinery today, Cindu in Uithoorn was established in 1922. The 20th century - interbellum. The development towards the petrochemical industry known today started after World War I, when a transformation from agriculture- based products to ‘chemical-based products’ started. In the Netherlands chemical operations of well-known companies such as DSM, Akzo, and Shell Chemicals were started. Before World War II, the Netherlands remained a net importer of chemical intermediates. World War II - second oil crisis. After the war, industry successfully developed because of the Marshall plan, the national industrial policy adopted to rebuild the Netherlands and the forced reduction of competing German coal tar refineries. In order to understand the present structure of what is known today as the petrochemical industry, the post World War II period is most important. The war initiated a large number of product innovations demanded by the military. As a consequence, both production facilities and new products became available for the civil sector. A second major development was the rapid-transformation from coal-based to crude-oil based operations. According to Chauvel and Lefebvre, the transition from coal to crude oil was mainly initiated by the continuously growing demand for ethylene, the precursor of three important plastics, viz. polyethylene, polyvinyl chloride and polystyrene (cf. Ch. 4). Initially, ethylene was produced from coal, mainly via the processing of coke-oven gas, a by-product of large-scale steel production (Chauvel and Lefebvre 1989a). Although the pyrolysis of light petroleum fractions9 was developed in the U.S. for the production of ethylene as early as 1920, coal-based supply for ethylene and other chemical products became rapidly insufficient after the World War II. In addition, economics were favourable at the time and large newly discovered oil reserves led to an abundant supply of cheap raw material. Industrial plants could be realised at lower investment costs for the installations whilst delivering better quality products. At the time, chemical science and engineering rapidly developed and provided novel chemical synthesis routes enabled by new or improved catalysts. Industrial process plant development benefited from advances in process technology that range from reactor technology to separation and rotating equipment. As a consequence, for most petrochemical products, by the end of the sixties this transition was complete. Since the Netherlands did not have a large coal-based chemical industry, the growing demand for petrochemical products opened an opportunity for competition with the German industry, which historically was largely based on coal, and continued to be based on coal-derived aromatic products for a long time (Molle and Wever 1984). In the sixties and early seventies, double-digit growth continued in the chemical
9 This technique is nowadays is generally known as 'steam cracking'
20 Process System Innovation by Design
industry, largely as a result of worldwide economic growth. The availability of fossil resources, both for feedstock and energy supply, despite yearly consumption continued to increase due to new discoveries. During the sixties, an important stimulus for the Dutch industry was the discovery of large resources of natural gas, notably the Slochteren field. A number of industrial projects were launched to further the industrialisation of the Netherlands. In Delfzijl, for example the methanol-plant started operation in 1973, and the Aluminium-smelter of Aldel was built - later acquired by Hoogovens, and presently part of Corus. In Geleen and Sluiskil, large fertiliser complexes were constructed that used natural gas for the production of ammonia. The purpose of these investments was both to quickly reap the benefits of the natural gas and to create local jobs. The introduction and market growth of new products increased demand for fuels and chemicals, where sometimes a large amount of low-value by-products were generated. In the entire petrochemical industry the availability of such previously low-valued by-products provided an incentive to develop products and processes that allowed upgrading of these by-products. The existence of previously unexploited economies-of-scale, combined with a relatively low-cost of transportation for most chemicals led to the formation of petrochemical complexes and a continuous increase in plant capacities, a development that continues today. After the second oil crisis. The second oil crisis of 1979 severely impacted the world economy and is seen to be the prelude to the worldwide economic recession in the '80s (Woltjer 2002). In 1979, concerted OPEC actions resulted in a tripling of oil prices. Meanwhile, due to the monetary policy of the Reagan administration real interest rates steeply increased worldwide. This exposed the weak financial and competitive position of companies and countries. After three decades of continuous high growth, most petrochemical markets decelerated, and overcapacity in the early 80’s resulted from new plants coming on-stream for non-existent market demand. In the last two decades of the century, the industry went through a number of 'boom and bust' cycles: it had become a 'cyclical industry'. In times of saturated markets the risk of constructing overcapacity is very real. Thus, the establishment of a new facility in an existing product market is difficult to justify. Moreover, it is uncertain whether the cost of process innovations can be recovered (after Stobaugh 1988). The response of a number of large firms in the petrochemical industry has been to reassess their core competences and core business (Hamel and Pralahad 1994). Some have decided to move out of the (semi)-commodities market and to move increasingly into specialties, fine chemicals and the highly specialized production of pharmaceuticals that are perceived as attractive because of their high profit-margins (viz. Asselbergs 1998). These companies leave value-extraction from existing facilities thus to the new owners and management, who more often than not aspire for economy-of-scale through mergers and acquisitions (Dijkema 2000). The result is an oligopolistic structure of many chemical markets, i.e. markets dominated by only a few firms (Wei et al. 1979: 251). In the nineties, the companies in the petrochemicals business have restructured their organisations, often at the expense of corporate functions, administrative overhead, internal services and support, and R&D and engineering departments. These have been labelled 'cost-cutters (Whitehead 2000). In construction or expansion projects,
Introduction 21
there has been a strong focus on minimising investment and initial time-to-market, in order to obtain revenues as quickly as possible. Thus there has been a strong emphasis on efficient organisation of the project execution from conceptual design to start-up. Concepts used include, amongst others, 'concurrent engineering' to shorten project execution elapsed time, 'front-end-loading, which is a strategy to amass all crucial information and elucidate white-spots as early as possible and not to allow any changes after an early date in the project and 'value engineering', where project items are scrutinised for value-creation potential versus cost (Herder 1999).
1.4.2 THE PROCESS OF CHANGE Between periods of dramatic change and 'outbursts' of innovation The mechanism of continuous change operates via the complex interplay of markets and competition, policy and regulation, strategic management, technology and system development, public image and scientific development at large (e.g. Twiss 1992). This complex interplay often is reduced to technology-push versus market-pull (e.g. Grunert et al. 1997), which reflects two diametrically opposed views on the origin of innovations. In developing an analysis framework, Grunert et al. combined technology-change fuelled by R&D and market orientation respectively (Figure 1-7).
R& D
Invention
Feedback Feedforward
Innovation Market Public
Diffusion
Feedback Feedback Performance
Figure 1-7: Framework for the innovation process in the petrochemical industry; adapted from (Grunert et al. 1997: 3).
Market orientation is a proactive attitude towards the detection of novel, as yet unfulfilled customer needs that can lead to successful innovations. The petrochemical industry, however, is a provider of intermediates to a myriad of industrial customers, i.e. it largely operates in a business-to-business market where innovation through market orientation gets the form of co-makership and co-
22 Process System Innovation by Design
development. Its products remain largely invisible and unknown to the general public. Where consumers thus interact only indirectly with the industry, a variety of other stakeholders directly influence its change and innovation. Apart from shareholders, competitors and would-be competitors include the public at large, governments, non-governmental organisations, pressure groups and universities. Necessitating a 'Public orientation' (Figure 1-7), petrochemical companies have realised they must ensure their license-to-operate and respond to environmental, safety and sustainability concerns. Together with sustained value creation, these factors determine long-term competitiveness and continuity and thereby have become drivers for innovation by the industry and its knowledge and service-providers such as universities, technology licensors and engineering contractors. The changes or innovations in the industry vary in level of detail, scope and time- scale. Production volume change, for example involves day-to-day utilisation adjustment, small plant changes, incremental capacity increase by revamping, and closure or erection of facilities, while for many products the market stimulates sustained capacity increases. Short-term competition drives day-to-day operation and organisation; long-term competition involves process innovation, which leads to phase-out of currently employed facilities. Increasing public awareness of impact of suspect chemicals combined with cumulating scientific knowledge and evidence may call for the phase-out of particular products, production processes or production routes. In other cases, product innovation leads to successful substitute competitive products, and total phase-out of current facilities.
1.4.3 INNOVATION AND THE PETROCHEMICAL INDUSTRY “An innovation refers to any good, service, or idea that is perceived by someone as new. The idea may have long history, but it is an innovation to the person who sees it as new” (Kotler 1991)10, or in more general terms, the audience or the stakeholder who perceives it as new. This implies, for example, that past process innovations by some chemical company that become publicised must be perceived as an innovation by for example public policy makers or competitors! The process of change was emphasized and decomposed by Schumpeter into invention, innovation and diffusion (Schumpeter 1942; cited in Ferguson and Ferguson 1988). Invention, the generation of any new idea, must be followed by innovation, where amongst others technological development, manufacturing organisation and scale-up enable commercialisation to bring the invention to the market. The final stage is diffusion, acceptance by consumers (products) or employment by producers (processes). Considerable time may lapse between these phases. Inventors may protect their ideas from competitors, to prevent them from subsequent innovation and commercialisation. The scientific and patent literature may serve as a database of ideas awaiting innovation. Notably, Schumpeter argued that invention is not limited to developments that require scientific advance, i.e. inventions may originate from new ideas that combine existing technologies in new process system designs (Schumpeter 1942; cited in Ferguson and Ferguson 1988).
10 cited in [Grunert, 1997 #67
Introduction 23
Products (including services), production systems, and organisations can be innovated, and are typically referred to as product innovation, process innovation, organisation (private sector) and institutional (public domain) innovation , respectively. In addition, Schumpeter identified the development of new markets and sources of supply (feedstock!) as distinct categories of innovation. Product innovation, process innovation and organisational innovation are closely related. A new product or service often depends on an innovative production process or organisation, respectively. Many innovative services such as 'Air-Miles' have only emerged through ICT-enabled organisation; many new material products can only be produced because of new production processes. The primary objective of a process innovation is to further manufacturing in a particular sector, whilst a new product can affect a multitude of sectors. Taking this perspective on 'type of use' to the extreme, an innovation that is used outside its sector of invention must be labelled a product innovation; only if it is used within a sector itself it is labelled a process innovation (Pavitt 1984). In the engineering sciences, however, a common understanding of a process innovation is 'any improvement of the process of production or the production system through the development or application of new technology.' For example mechanical engineers consider the application of gas turbines in electric power generation from 1963 and later a process innovation, whilst according to Pavitt’s definition it is a product innovation because the gas turbine is used outside the turbine machinery industry. For the purpose of this introduction we focus on process innovations, which we define as ‘any improvement of a manufacturing system, be it a sector, industrial complex, individual plant or unit operation'.
Cadre 1-2: Petrochemicals - a mature industry
Since the early nineties, the petrochemical industry's development is characterised by limited growth rates and maturation (see § 1.4.1 below). At a time of limited or non-existent market-growth, a new facility that comes on stream results in overcapacity. As a consequence, the market price for its products can be expected to deteriorate for all producers, who also will suffer from a decrease in average plant utilisation. Meanwhile, each individual plant has its own break-even utilisation, which is a function of historic investment, current margin between product and feedstock, energy-efficiency as a function of plant capacity, flexibility and fixed operating cost (operating personnel, insurance, maintenance, overhead). Only when there is no technically feasible utilisation where a net marginal profit results, an existing facility will be shut down completely. In all other cases, ownership of existing facility can be transferred to optimise return on asset capital employed by each individual company. A mature industry is now characterised by the fact that possible innovations do not provide sufficient edge to make existing installations economically obsolete.
24 Process System Innovation by Design
1.4.4 INNOVATION AND CHANGE In a time frame of 50 years the petrochemical industry has gone through a typical S- shaped growth curve. Around World-War II, product innovations initiated its development. Rapid market growth led to the invention of a myriad of new products and to a continuous demand for new and more effective processes. Subsequently, during two or three decades, it dramatically improved its performance by process innovations that allowed, amongst others, the exploitation of economies-of-scale. Since the beginning of the nineties, the industry's development is characterised by limited growth rates and maturation. Thus it exhibited the general pattern where process innovation follows product innovations (Abernathy and Utterback 1978). The petrochemical industry has been classified a science-based industry (Pavitt 1984) and has an impressive record of process innovation at or below the level of single plants, where fundamental and applied research have fuelled continuous improvement of e.g. catalysts, reactors, separation technology and scale-up of operations (e.g. Weijnen and Drinkenburg 1993). Science-based’ industry's “main sources of technology are the R&D activities of firms in the sectors, based on the rapid development of the underlying sciences in the universities and elsewhere.” Pavitt argues, however, that for “large-scale producers, particular inventions are not in general of great significance, (…). Technological leads are reflected in the capacity to design, build and operate large-scale continuous processes … Technological leads are maintained through know-how and secrecy around process innovations, and through inevitable lags in technical imitation, as well as through patent protection” (Pavitt 1984: 359). Based on elaborate studies into US petrochemical companies, Stobaugh observed that successful companies use process innovation through scientific advancements to maintain their competitiveness in predominantly oligopolistic markets (Stobaugh 1988). He demonstrated that innovation must be part of overall company strategy to protect market-share by effectively discouraging potential competitors from market- entry. Others have shown that firms in the petrochemical industry produced a relatively high proportion of their own process technology and product technology (Pavitt 1984: 362; Hutcheson et al. 1995). Schumpeter's observation that science often is not a necessary requirement for innovation and Pavitt and Hutcheson's findings explain why petrochemical companies tend to be very secretive, e.g. about their operating practices and project execution tactics: know-how and know-to together bring a competitive edge in design, construction, financing and operating chemical plants. Indeed, secrecy has a long tradition in this industry where companies compete by the performance of their process technology (van Breda and Dijkema 1998). In the 90's, 3rd generation R&D management was adopted to match existing portfolios to present and future business (Roussel et al. 1991). The adopted strategies differ somewhat among companies, the effect being the same: major reorganisation and budget-cuts, stripping and even closure of R&D facilities. As an exception to the rule, a company like Air Products continues to recognize one of its strengths being its proprietary technological know-how in large-scale air separation (Govaerts 1999). The general trend, however, has been to cut in-house R&D
Introduction 25
directed at large-scale processing. As a result, rarely do real breakthrough process innovations make it to the market place. Meanwhile, there appears to be a strong drive on 'reinventing' organisations. If product and process innovation do not offer sufficient scope for improvement, what else is there to face competition than to cut cost by streamlining organisation? Thus petrochemical corporations went from vertically integrated corporations to 'loose' conglomerates of strategic business units focused on oligopolistic product markets. As of the last decade of the 20th century, they are in the process of organising their way of doing business around the previously unexploited benefits of ICT-enabled organisation (Dijkema 2001a).
1.4.5 SUSTAINABILITY With the 1989 publication of ‘Our common future’, the worries about the status of our planet and worldwide society were coined by the caption of a need for ‘sustainable development’, which in Brundtlandt’s definition is (economic) development and consumption that does not hamper the needs of future generations (World Commission on Economic Development 1987). Welford argues that ever since There exists a strange and fruitless search for a single definition of sustainable development amongst people who do not fully understand that we are really talking here of a process rather than a tangible outcome. This search is most apparent amongst positivist researchers who grope for a hard core of definitions and data that they can manipulate to produce simple solutions and singular answers to very complex concepts. Such simplifications cannot exist in the post modern world and they simply hide a scientific research bias, which is not appropriate to a highly political issue such as sustainable development (Welford 1997). Although the above is valid for the economy at large, we do believe that for the petrochemical industry some criteria can be formulated. As we have argued, today harmful emissions and the wastes produced by the petrochemical industry have become 'managed problems', with the exception maybe of SO2 and NOx emissions associated with burning fuel oil and natural gas. It is the large quantities of fossil resources processed that will become the future problem of the industry. At the output side, large quantities of CO2 are emitted to atmosphere. At the input side the industry depends on crude oil and natural gas. In the near term future, we expect society to require continued availability of petrochemical products and derivatives. It may not before long, however, before these will have to be produced from much more expensive fossil resources, under more stringent arrangements with respect to the fate of CO2 generated, or from alternative feedstock altogether. But how has the petrochemical industry responded to the demand for sustainability? In retrospect, the petrochemical industry has done a good job in improving its day- to-day operations as well as technology and systems portfolio. The benefits from increased resource utilisation provided sufficient incentive for R&D efforts, which indeed have led to a substantial reduction in the consumption of fossil resources per unit of product. Meanwhile, however, the industry has demonstrated almost
26 Process System Innovation by Design
continuous growth since 1950, and as a consequence net fossil resource use increased dramatically. Although we labelled the petrochemical industry as being furthest in embarking on strategies for sustainable development(Mayer and Dijkema 1999), there is no evidence that suggests that these strategies involve drastic process innovation. On the contrary, whilst from 1989 onwards there has been a renewed growth in the world-wide petrochemical industry and its consumption of fossil resources, the number of successful petrochemical process innovations expressed as novel industrial processes that were commercialised has declined for three decades (Satterfield 1991). Despite the continued interest in the use of biomass and coal, the increased demand for the building-blocks of commodity-plastics has largely been met by the construction of an increasing number of steam crackers that use naphtha or gas oil for feedstock. Exceptions are the first methanol-to-olefins cracker project (Dijkema and Kuipers 2001) and Fischer-Tropsch synthesis that uses coal- or natural gas-derived synthesis gas. Since their economic life-time is long, the fossil resource demand and the products that result from these installations will dominate the industry for decades. Despite process and product improvements, e.g. by the use of new catalysts or separation technology, the net industries' share of fossil resource consumption will remain at a high level. Presently, in the commodity markets of the petrochemical industry, it is hard to foresee that innovative products will be developed short-term that will completely replace current products. Quite the contrary, many long-established products still demonstrate considerable growth rates. As a consequence, improvement of the sector largely has to be fuelled by process innovation. But according to Abernathy and Utterback, the rate of such innovations eventually will fall off as prospective incomes fall (Abernathy and Utterback 1978). Indeed, in the last decade the sector appears to increasingly emphasize organisational and even inter-organisational innovation. Product-chain management and sustainability are elements of the Responsible Care (RC) programme, a strategic communication programme that first has been developed by the petrochemical industry of Canada. The concept of RC expresses the notion that a chemical company is part of its environment. Consequently it must act responsibly and precautionary towards the environment and society. The RC-programme encompasses the aspects of health, safety, environment, welfare and responsible entrepeneuring. As stated, however, Responsible Care is primarily a strategy for adequate communication with all the stakeholders of a chemical company, in society, politics, and business. It also helps, however, to provide arguments such as that “we have done enough, others outside our company must now take action first“, or as one respondent remarked, a mechanism to buy time, so that investments required for environmental improvement can be matched with the right time for business (Mayer and Dijkema 1999). Thus, Responsible Care and similar programmes can create both incentives and disincentive for the much needed process innovations. In the Netherlands, the petrochemical industry has negotiated voluntary agreements on energy-efficiency improvement, and it appears that the petrochemical industry is on-target with respect to the objective of 20% energy reduction (VNCI 1998). These agreements largely focus on the net ‘utility’ energy efficiency. As stated, however, in
Introduction 27
contrast to the other manufacturing industries, in the petrochemical industry fossil resources are both feedstock and 'utility' energy supplier. Feedstock efficiency, however, appears largely to be left outside the agreements and the industry structure remains unchallenged. Sustainability, however, cannot be achieved by optimisation of utility energy use alone.
1.4.6 RESOURCE OUTLOOK While fuels of fossil origin are used for energy supply throughout our industrial society, the use of these carbonaceous materials as feedstock is largely limited to oil refineries, electric power plants, coke-ovens and the petrochemical industry and related chemical industry (Figure 1-3). In base metal production, for example, carbon-based products are of primary importance to enable the production of iron, zinc and aluminium. Blast-ovens for steel manufacture consume coke for energy supply and the reduction of iron ore. Aluminium smelters, zinc plants etc. use carbon electrodes. In these cases, however, no significant amount of carbon ends up in the product; the feedstock of these industries is metal ore. Coke and carbon electrodes are required utilities to enable production. The energy need of refineries and petrochemical plants generally is covered by combustion of product waste, fossil fuels and electricity. Thus, oil refining and the petrochemical industry share a unique characteristic: the use of fossil fuels for both energy-supply and feedstock purposes. Since oil and gas power the world, the resource situation of these industries is intrinsically linked with global energy supply and demand and the amount of 'proven reserves'. Presently, world proven crude-oil reserves are estimated to suffice for some 45 years of current total global consumption. The ratio of resource to yearly production (and consumption), the R/P ratio, is 65 and 250 years for natural gas and coal, respectively (Anonymous 2004). Net annual consumption, however, is expected to grow significantly as the result of population growth, increased standards of living and economic growth. Especially a large impact of developments in South-East Asia is expected. As a consequence, the real horizons may turnout to be much shorter than predicted on the basis of the R/P ratios calculated using simple data. Indeed, as early as in 1972 the Club of Rome first warned for the rapid worldwide depletion of resources based on a system dynamics model that predicted patterns of resource availability, human lifespan and welfare based on the interrelated dynamics of population, standard-of-living, healthcare, resource consumption, economics of resource exploration, technological advancement, land-use and environmental stress (Meadows et al. 1972). Although events have not yet taken the dramatic turn ('system collapse') as predicted by this model in a number of scenario runs, it is obvious that total fossil resources of the system Earth are being depleted continuously. Reassuringly, since the discovery of crude oil in the United States, its R/P ratio grew almost continuously as a result of new discoveries, market changes and technological development. Since the mid-90's, however, combined developments only have compensated for current use, despite the recent discoveries of previously unknown large reserves of oil and natural gas. With global energy-demand expected to grow
28 Process System Innovation by Design
significantly, the OECD predicts that around 2015-2020 the time horizons for availability of oil and gas resources will start to shrink (OECD 1999). After the Gulf War (1991), abundant oil-supply by eager producing countries combined with free market conditions drove down oil prices to historically low levels. This development appears to support Grubbard's scenario where oil-price remains relatively low, until the moment where the time-horizon of perceived shortage becomes comprehensible (Grubbard 1992). Then oil-prices rise to levels never seen before, largely because the perceived abundance of oil not only results in low energy prices and limited exploration and development of oil fields, but also to a lack of economic incentive for R&D and innovation to reduce and change our energy use. Indeed, currently OPEC and other producing countries control their oil production to manage the supply-demand balance to maintain oil-prices and optimise revenues. Other scenarios have been developed, however, wherein such managed oil prices rise slowly but steadily in response to awareness of a definite dwindling of known economic oil reserves. These scenarios recognise that price increases create additional incentive for exploration and for the development of previously uneconomic resources. Managed crude oil availability and managed price- levels, however, still adversely affect investments in and R&D into improved energy resource utilisation and alternative energy sources. Long-term, however, it is certain we will run out of relatively cheap oil and gas and that alternative energy sources must be developed. As a matter of fact, crude oil already is being replaced by natural gas as the world's most important energy source. Researchers of IIASA11 investigated and modelled the evolution of the use of energy carriers by humankind. They modelled the use of a particular energy carrier by it's share f as a function of time on a logarithmic scale, where (f/(1-f)) exhibits linear growth for a number of decades, peaks, and subsequently declines linearly (Marchetti and Nakicenovic 1979; cited in Spiro and Stigliani 1996: 54). Historic data for the market share of wood, coal, crude oil and natural gas were found to be in fair accordance with this model. During the industrial revolution coal replaced wood as major energy carrier. In the 20th century oil replaced coal. Currently, the share of natural gas is growing to replace crude oil as the major energy carrier. History indicates that energy carriers start being replaced when the most economic sources have been depleted. Thus, due to the availability of fossil resources and ongoing biomass depletion, the share of biomass in worldwide energy supply has dwindled. Initially, during the industrial revolution it was replaced by coal. Since World-war II, the use of biomass and coal declined due to substitution by oil products and natural gas. Nuclear fission for electric power generation started to develop in the sixties and seventies, and at the time nuclear fission and fusion were expected to become the next major energy source for humankind. The inevitable changes in fossil resource availability and price represent major incentives for innovation in the petrochemical industry. To ensure its continuity as the industry's infrastructure, current feedstock must be used even more efficiently;
11 The International Institute for Applied Systems Analysis, Laxenburg, Austria
Introduction 29
novel process systems must be developed to utilise alternative feedstock. Changes in product demand and product slate must be anticipated and catered for. At a worldwide share of 8-12 %, the petrochemical industry is only a modest consumer of crude oil, the major share of oil products being used in automotive transport and household fuel. The industry presently can only react to crude oil price fluctuations. Its activities have limited to no influence on long-term feedstock exploration (e.g. Stobaugh 1988; Fahy 1990). Ironically, however, it is only in the petrochemical industry that some advantage is taken from complex molecular structure of the chemical substances in crude oil and oil products. In retrospect, a relatively young petrochemical industry could grow rapidly in a period that lasted roughly from 1960 to 1980 on the basis of uninhibited depletion of scarce resource. In the 21st century, however, the petrochemical industry may have to face accelerated depletion of its current resource base and economic conditions unfavourable for its innovation. This is a situation unanticipated at the time of its initial development and in the period of massive growth of the industry, when basically a 'once-through processing' structure was adopted throughout the industry. Combined with the long- lead times of the development of new technology or new processes in the petrochemical industry, this justifies the economic significance of timely efforts to improve technology! In addition, strategies must be developed to avoid entrenchment in technology and systems that are characterised by insufficient resource efficiency.
1.5 A need for process system innovation?
1.5.1 TOWARDS A SUSTAINABLE PETROCHEMICAL INDUSTRY? The global industrial economy has been dependent on a glut of oil, gas and coal for more than a century. The present use of fossil resources by far exceeds the use of renewable energy sources. As a consequence, oil and natural gas are expected to become scarce resources in maybe as early as 2020 (OECD 1999). The CO2 liberated in fossil fuel conversion for the greater part has accumulated in our atmosphere and oceans. It has caused a steep increase in atmospheric CO2 concentration never seen before in the Earth's geological history. Evidence gathered in a variety of scientific studies has led the UN Intergovernmental Panel on Climate Change to acknowledge that emissions of human industrial society cause an enhanced greenhouse effect that drives global climate change (IPCC 2001). Today the developed countries depend on and benefit most from the use of the world's fossil energy resources. The OECD countries have consumed the major share of oil and natural gas resources. While the economic development of China and India will foster continued growth in world energy-use, world consumption patterns will remain far from equitable. These ecological and societal concerns have been coined in the early definition of sustainable development “Development that meets the needs of the present without compromising the ability of future generations to fulfil their own needs” (World Commission on Economic Development 1987), which also implies suitable economic development that stipulates equity throughout the globe.
30 Process System Innovation by Design
Whilst the depletion of fossil resources and the threat of global-warming have led the public, governments and NGOs to believe that dramatic change is required in industry to achieve sustainability, only few companies have acknowledged that sustainability is crucial for their long-term prosperity (Dijkema and Mayer 2001a).
The Dutch Scientific Council for Government Policy recently has categorized CO2 emission, climate change, biodiversity and the continuously growing energy-use as wicked problems (Wetenschappelijke Raad voor het Regeringsbeleid 2003). These are labelled wicked because to date these have largely escaped (inter)national policy and regulation. Upon a series of wake-up calls on environmental pollution (Carson and Darling 1962), in the past 30 years many tough environmental problems have been turned into manageable problems. The interplay of end-of-pipe measures, technology development, process improvements, investments, environmental legislation and covenants has fuelled a continuous process of improvement. Wicked problems also must be addressed effectively to enable sustainable development. Effective communication on wicked problems is difficult, however because there is no direct exposure to the associated adverse effects that develop gradually over decades in a global context. Moreover, vested interests are huge, access to cheap energy being pivotal to the prosperity of many an economy or private company.
Drastic reduction of resource consumption and CO2 emission is a wicked problem for the petrochemical industry because the core business of the industry is the conversion of petroleum products, its CO2 production is linked to its present use of these fossil feedstock, and most companies compete in global markets where opinions on CO2 and global-warming vary. Thus, despite efficiency gains, the industry's CO2 emission has remained high largely because of the continuous growth of production volume, which is illustrated by the doubling of ethylene production in the past 25 years (see Ch. 4). A sustainable petrochemical industry is characterised by appropriate resource selection, effective resource utilisation, the avoidance of waste and emissions and a product slate that fosters a sustainable society. While “innovative design and clever process modifications are essential to the economic health of the producer of commodity chemicals” (Wei et al. 1979: 255), companies or sectors differ in their degree and development with regard to innovation strategies for sustainability. Amongst others via environmental management and technological development the petrochemical industry has reduced its harmful emissions. In addition, the industry has realised that it must continuously renew its license-to-operate obtained from local communities and other stakeholders. Through the Responsible Care programme, therefore, the industry has been developing its communication and image with local communities and the general public (VNCI 1998). There are a few 'early adopters' or trendsetters that have realised and acknowledged that sustainability is crucial for their long-term continuation. Some companies have formulated a sustainability strategy in interaction with external stakeholders, others perceive sustainability as a continuous development process, in which the specific goals repeatedly need redefinition and reformulation (Mayer and
Dijkema 1999). In the petrochemical industry, notably substantial CO2 emission reduction, however, cannot be realised by environmental management only. Good-
Introduction 31
housekeeping or end-of-pipe measures do not suffice because its CO2 production is linked to its present use of fossil feedstock and its maximum efficiency of operations achievable. Therefore, changes in feedstock, process systems, process routes and products are required. In addition, it has been argued that these changes must, somehow, be enabled by technological development, if not technological breakthroughs. The need for sustainable development provides a major incentive to elucidate the question of process system innovation in the petrochemical industry. Can changes in system structure or system design of the industry, its industrial complexes, or individual plants that are enabled by technological inventions or vice versa foster bringing into being a sustainable petrochemical industry?
1.5.2 CENTRAL RESEARCH THEME AND RESEARCH QUESTION The emergent need for sustainability at a time where the economics of process innovation are unfavourable poses a dilemma. There is a need for a resurrection of process innovation to anticipate changes in resource availability and to deal with wicked environmental problems such as global climate change. Grossmann and Westerberg suggested to broaden the scope of process system engineering to span a chemical supply chain -from mastering the molecules to chemical enterprises- (Grossmann and Westerberg 2000: 1700). We conjectured that in order to contribute to sustainable development, industrial complexes, industrial sectors need to be modelled, or possibly worldwide economies and material cycles (Dijkema and Reuter 1999). Any new approach to innovation in the petrochemical industry however, must have sound technological and system content in order to have a chance to achieve some impact in industry. The questions arise therefore as to what innovations are required to meet the challenge of a sustainable petrochemical industry and from where can the innovations required for the petrochemical industry originate. The third and main question addressed in this thesis is
how can technological or systemic content of innovation required for sustainability be specified?
We argued that while end-user markets are catered for by newly innovated products, the products of the petrochemical industry are probably here to stay for a prolonged period. To meet sustainability demands, therefore, and to produce alternative products, innovation of the 'T', the process systems, is required. Presently, however, economically, the industry is in a mature phase. In a response to perceived shareholder pressure, shareholder-driven CEOs lead the industry on an ever- accelerating pace of mergers and acquisitions to capture the benefits of economy-of- scale. At the same time R&D budgets are being cut or activities in (pseudo)commodity markets are divested. An image of current business climate emerges that is unfavourable for process innovation initiated from within the industry. This dichotomy between industry
32 Process System Innovation by Design
climate and need for global sustainability demonstrates the relevance of our central research theme: The systemic, top-down specification of the desired technological content for innovation in the petrochemical industry in relation with business and societal needs.
The central research question addressed is Is it possible and worthwhile to devise some procedure to structure the search of the process system innovation space and to foster the specification of innovation content?
Our research objective was The development of a systemic approach to specify the desired content of process system innovations. “These are defined as changes in the system structure or system design of the petrochemical industry, its industrial complexes, or individual plants. These can be enabled by technological inventions or vice versa” (Dijkema et al. 2003).
Preferably, an approach results that includes and links system analysis and subsequent synthesis and conceptual specification of options for R&D: process system innovation by design.
1.5.3 CONJECTURE AND HYPOTHESIS In this thesis the focus is on the technology and the structure of the industrial systems in the petrochemical industry. How to achieve sustainability is an open problem that cannot be solved by planning and optimisation of system structure or traditional R&D and technology development alone. In the majority of the scientific community the system design of the industry has been considered fixed and the effect of most research and development (R&D) on industry structure is not planned. Over time petrochemical clusters have developed that are characterised by interconnectivity, interdependence and inflexibility12 (Kuipers 1999). With the maturation of the industry (see Cadre 1-2), changes or extensions of the industry's structure have become incidental consequences of successful fundamental R&D. Thus it may be seen that one cannot be sure that the largely ‘bottom-up’ approach employed in the scientific community will provide sufficient and timely solutions to support sustainability of the petrochemical industry.
12 Each chemical plant in a particular cluster may be seen as the result of an individual company's strategy. Each company innovates its slate of technologies employed and its organisation for efficient realisation of large-scale facilities. Once completed, these represent huge sunk-costs, have very long technical lifespan, and require large number of highly trained and skilled personnel. The facilities are 'sticky', and while expansions or additions to the cluster may cease sometime, existing facilities remain in operation ofter for decades before closure. Thus, the dynamics-of-change for the cluster are slow.
Introduction 33
We conjecture that in order to prepare for the future of the petrochemical industry, integrated innovation at all system levels (Table 1.3) is required, from material to apparatus to plant to petrochemical complex and industry configuration. Furthermore, the industry system structure must be considered a degree-of-freedom in the search and specification of yet unknown technological developments, as well as in the adoption of extra-sector innovations. Our hypothesis is that there exists scope for improvement of the petrochemical industry by process innovation, not withstanding the dramatic improvement of the chemical industry’s performance with respect to economic and ecological efficiency. Secondly, our proposition is that this scope for improvement cannot be reaped by progress in the existing disciplines of chemistry, physics and engineering alone, but rather that a large source of innovation remains unexplored: process system innovations.
1.5.4 RESEARCH QUESTIONS It is the general belief of many an environmentalist and policy-maker that the scope for improvement within the petrochemical industry is substantial. Meanwhile, the chemical industry appears to be entrenched in accepted, accredited methods of production that are advocated and supported by its management. The problem, thus is twofold: how to assess the scope, and subsequently, how to arrive at a specification or identification of options for process innovation that go beyond the normal trajectories of innovation in the petrochemical industry and that merits the allocation of substantial R&D capacity. This leads to three research questions: (1) is it possible to develop methods for the assessment of the resource utilisation and the scope for improvement of the production systems of the petrochemical industry that are objective, systemic, effective, versatile and data-proof? (2) can the search of the innovation space be structured to foster the specification of process system innovation content - is process system innovation by design feasible?
The research by Pavitt (1984) demonstrated that traditionally innovation has come from within the sector, whilst presently the capacity for R&D within the sector is reduced. This dilemma of stimulation of process innovation in a mature industry has been explored from a technological perspective. This has been addressed under the third research question: (3) what is the usefulness and scope of application of the methods developed? Do the methods result in innovative concepts at industry, complex or plant level? Is the application of outside sector innovations supported or facilitated?
1.5.5 RELEVANCE In the past, systems in the industry , such as entire chemical plants or steam cracker complexes (see Table 1.3, p.17), were dramatically improved. Presently, however, the
34 Process System Innovation by Design
scope for improvement within the system boundary of many petrochemical processes appears to be limited by the absence of major breakthroughs. With the maturation of the industry, the added value and the adoption of process innovations depend more and more on the industry system structure. However, there is not a single stakeholder that decides on innovation or evolution of the industry system structure. Moreover, at the level of the industry opportunities for system improvement are hard to elucidate because of its structural and technological complexity. Thus, the invention or specification of process system innovations is not straightforward. This thesis is an attempt to address this problem, with the intent to help all stakeholders involved to bring-into-being yet unknown process system innovations!
1.6 Research approach and structure of thesis
1.6.1 META-MODEL OF RESEARCH ACTIVITIES The methodology for 'process system innovation by design' (Ch.3) has been based on the body-of-knowledge of system theory, thermodynamics, process system engineering and computer systems modelling, respectively. An overview of the body-of-knowledge of system theory can be obtained from (e.g. Boulding 1956; Truxal 1972; Asbjørnsen 1992; Blanchard and Fabrycky 1998). On computer systems modelling notably (Baylin, 1990) has been used. A useful introduction to applied thermodynamics comprises (e.g. Denbigh 1956; Seader 1982; Kotas 1985; Smith et al. 2001). An overview of relevant process system engineering knowledge is offered by (e.g. Rudd and Watson 1968; Douglas 1988; Siirola 1996; Seider et al. 1999; Grossmann and Westerberg 2000). The methodology has been specified and refined via case studies (Ch. 4, 5 and 6) that cover a range of system aggregation levels. Whilst its actual development required many iterations and adjustments, often along erratic trajectories, the activities involved and results reported can be represented in a meta-model (Figure 1-8) that matches the classic framework for conducting scientific research. Thus, further to the research theme and questions formulated, the 'meta' question addressed is whether it is possible and worthwhile to develop, underpin, test and validate some systemic innovation procedure that enables 'top-down' process system innovation by design. In the meta-model, a modelling strategy is required to allow proper set up of assessment criteria and a reproducible assessment procedure of the industry or parts thereof. Its completion must lead to increased understanding of system design and operation and thereby provide starting points for the innovation procedure. Finally, the approach can be subject to validation:: does the entire approach provide useful results and is its scope sufficient? As indicated, the outcome of the validation may be fed back to the various activities in the meta-model.
Introduction 35
5.2
1.1 Straightforward Model 1.2 Modeling & 5.1 Decomposition Strategy
1. Select / Develop
Model 4.1 1.2
5. Validation 4.5 4. Develop 2. Select / Define
Process System Innovation Assessment Feedback Innovation for procedure Criteria Sustainability?
5.4
3.4 2.3 4.1. Systematic Search R&D options 3. Design / Compile 4.2. Specification 2.1 Losses, of Innovation Efficiency Assessment Content Procedure
3.1 Priority list 5.3 Weak Elements
x.y Legenda: Activity Objective Result Info-label Information from x to y
Figure 1-8: Meta-model of activities.
1.6.2 STRUCTURE OF THESIS The work reported in this thesis is the result of two completions of the circle of activities in the meta-model. In chapter 2, an overview of innovation sources for the petrochemical industry is given, and review of relevant process system engineering literature is presented. Combined with other sources, this serves as basis for the method developed for the specification of process system innovation content in the petrochemical industry. In chapter 3 the methods developed for petrochemical complex assessment and the specification of process system innovation content are presented and illustrated by the case of industrial aromatics production and consumption. The first part of the chapter represents the first completion of the meta-model activities, the second part together with chapters 4, 5, and 6 represent the second completion with an emphasis on illustration and validation.
36 Process System Innovation by Design
Chapter 4 is a case study into the worldwide system around olefins, where ethylene ranks first, with global production capacity exceeding 100 Million Tons per annum. Use of the methods developed enables the specification of process system innovations. Chapter 5 demonstrates the use of the method in investigating innovative use of fuel cells in the chemical industry. Notably, the early evaluation of system concepts developed is addressed. This is expanded into a treatise on the design of trigeneration systems. Chapter 6 is a case study into the development of an industrial cluster beyond the traditional petrochemical industry. The advent of novel technology, again fuel cells, is used to assess the impact on petrochemicals and the global platinum material cycle. A number of process system innovations are specified. Chapter 7 contains final conclusions and recommendations.
2 Process System Innovation Sources
2.1 Introduction The objective of our research was the development of a systemic approach to specify the desired content of process system innovations, which “… are defined as changes in the system structure or system design of the petrochemical industry, its industrial complexes, or individual plants. These can be enabled by technological inventions or vice versa” (Dijkema et al. 2003). In this chapter, the scope and foundations are explored of such 'process system innovation by design'. First the past and present sources for inventions relevant for the chemical industry are reviewed. These range from basic science, chemistry and chemical engineering to top-down system and policy studies. Since it is impossible to review this massive literature base, an eclectic overview is presented. Thus, the usefulness and potential is analysed of relevant knowledge domains. Subsequently because process system engineering was identified as a source of building blocks for said systemic approach, the vast body-of-knowledge of system theory and process system engineering is explored to underpin and define the concepts of 'system', system elements, system analysis and system design. Third, results from a literature search are reported to unearth concepts and methods useful for process system innovation by design. Specific attention is given to system decomposition and to process synthesis.
2.2 Sources of innovations
2.2.1 OVERVIEW Past innovations in the chemical industry may appear to be the result of a chaotic process. In reality, the process of change and innovation is driven by public R&D policy and funding, corporate R&D programmes to ensure continuity by sustained competitiveness and by individual scientist's curiosity and preferences. Scientific literature often only reveals the results of research programmes, projects and initiatives. In addition, corporate R&D strategies and goals generally remain beyond scrutiny, although some results do land in the literature or patents. What follows, therefore is a structured overview of 'innovation sources' classified in categories relevant for process system innovation in the petrochemical industry. Apart from serendipity, innovations relevant for the petrochemical industry may be seen to originate or emerge from 1. basic scientific developments Virtually all disciplines of the natural sciences and the engineering sciences may yield inventions that allow conceptualisation of new unit operations, improvement of existing technologies and realisation of novel reactions towards new or existing products. Within specific scientific or application domains, exploratory research attempts to go beyond what is already known.
38 Process System Innovation by Design
2. R&D in chemistry, chemical engineering and related disciplines In general, more focused R&D provides a path towards utilisation of scientific knowledge. Common denominators are the focus on development and realisation of new technology, the creation of novel realisations of unit operations and new products. Much R&D is directed to improve known technology or products. As a matter of course, all sub disciplines of chemical engineering and related engineering disciplines play an important role. Process system engineering (PSE) is a body-of-knowledge to bring industrial process plants into being, which requires a system focus to integrate information and knowledge from a variety of engineering (sub) disciplines. In a Schumpeterian view on innovation, each combination or plant design is an invention, and when built, an innovation.
3. System, policy or management studies The (petro) chemical industry contributes significantly to GNP in many countries. It also has a history of serious environmental impact and is characterised by oligopoly. To no surprise, therefore it has been the subject of many a policy and management study. In addition to elucidating incentives and barriers for innovation, these may represent valuable sources of systemic innovations for the sector.
2.2.2 BOTTOM-UP: CHEMISTRY AND CHEMICAL ENGINEERING The petrochemical industry is a ‘science-based’ industry (Pavitt 1984). Historically, R&D expenses accrue to 3 to 4 percent of sales, and a large number of patents administrated are claimed by the chemical industry. As stated, traditionally much R&D is focused on process technology, and a small improvement can have a marked effect on processing cost (Wei et al. 1979; Brennan 1998). The first companies that were involved in chemical operations in the 17th century, however, were small, and did not exploit scientific knowledge. The modern profession of the chemist developed around 1840. A major process innovation, however, had then already been developed: the Leblanc process for the production of alkali, which replaced the traditional potash process that used timber. Subsequently, the Solvay process succeeded the Leblanc process. The first synthetic dye was developed in 1856 (Freshwater 1997), which led to the foundation of the Badische Anilin und Soda Fabrik, or BASF. Today, chemistry, amongst other scientific disciplines such as physics and biology, allows us to understand how both the living and non-living world functions at a fundamental (sub-microscopic) level. Chemistry is focused on the micro-scale of molecular structures and change involving chemical reactions, for example the development of synthesis paths, catalysts, membranes for separation etc. Notably the co-evolution of chemical engineering together with chemistry has proven to be an enormous source of innovation. Technical chemistry provides the toolkit for the development of new (chemical) products, the elucidation of reaction mechanisms on a sub-microscopic scale, and the basic phenomena for separation equipment. Also in the petrochemical industry
Process System Innovation Sources 39
chemistry plays a pivotal role, but it is chemical engineering science that has shaped the industry through the development of catalyst systems, chemical reactors, separation equipment, and integrated continuous process designs. Innovation of chemical factories at first proceeded at a slow pace. The products developed by 17-19th century chemists were directly put to work in simple chemical factories. From 1880 onwards the development of chemical processes and plants rapidly evolved ‘from art to science’. In Europe and the US chemical engineering programs were started, and in 1923 chemical engineering was firmly established by the publication of the “classic text ‘Principles of Chemical Engineering’ (Walker and Lewis, 1923)” (cited in Freshwater 1997). Academic chemical (process) engineering science was rapidly recognized as essential to carry out chemical processes safely and competitively. Its application for the transformation of laboratory-scale synthesis routes to industrial scale facilities became common practice. Today, the Institution of Chemical Engineers defines chemical engineering as 'the design, development and management of a wide and varied spectrum of industrial processes' (IChemE 2003). In chemical engineering, methods and tools have been developed for scientific underpinning of the understanding, analysis and design of chemical operations at industrial scale. Continuously operated systems were developed, initially in crude oil refining, ammonia production, sulphuric acid and other processes. Today, chemical engineering has developed into a myriad of sub disciplines which range from the microscopic level of underlying transport phenomena in reactors, to the macroscopic level of equipment and plant specification. The Ullmann encyclopaedia of chemical technology (Anonymous 1995b) now comprises 26 volumes, and hundreds of journals have been established on every sub discipline of chemical engineering. One fundamental concept of chemical engineering is that any process plant is considered a structured collection of unit operations, the first paradigm for the discipline (NRC 1988). Sub disciplines of chemical engineering focus on single classes, or even subclasses, of unit operations, such as reactors or separation systems, which have specific links with their underlying basic sciences. Examination of unit operations from a more fundamental point of view became a second paradigm for the discipline. In addition, some unit operations remain largely the realm of mechanical engineers, e.g. 'rotating equipment' such as compressors and pumps, whilst other such as industrial furnace and heat-exchanger design require specialization and are increasingly supported by Computational Fluid Dynamics models. In the NRC report one distinguished between the microscale, mesoscale and macroscale. At the microscale, among other molecular reactions and heat and mass transfer phenomena are studied. At the mesoscale, the selection of a particular set of unit operations, the specification of each unit operation and the design of the structure between the unit operations is the realm of process design. Conceptual process system design involves the analysis and anticipation of process plant performance, as well as process synthesis to meet plant design objectives in a sound and safe combination of unit operations. At the macroscale, entire plants must be developed that satisfy the needs and requirements of a complex environment that may require integration of multiple plants and synthesis of supply-
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chains, enterprise modelling and life-cycle models (NRC 1988; Li and Kraslawski 2004). Notably the conceptual design of chemical plants was established as a topical sub discipline after the seminal publication by Douglas, who put forward a structured method to arrive at a design of a chemical plant (Douglas 1988) based on and bundling the experience of generations of process design engineers. Today conceptual process design is part of the body-of-knowledge of process system engineering, which is elaborated in section 2.4.
2.2.3 TOP-DOWN: SYSTEM AND POLICY STUDIES Studies relating to the entire petrochemical industry fall into the following categories:
1. Studies on the development of the industry Academic research with relevance for the entire petrochemical industry includes studies by industrial historians, regional economists or economic geographers on location, regional, national and sometimes continental or global development of the chemical industry, its establishment and business. Important contributions to the theory on location development for the petrochemical industry are (Weber 1909; Molle and Wever 1984; Witlox 1998; and Kuipers 1999). These studies largely address the economic and ecologic drivers in the “surroundings” of the petrochemical industry or parts thereof. The technology and system structure are merely seen as enablers to achieve economic or ecologic objectives; the global or local 'organisation' or structure of the industry changes over time, however, as a result of the implemented strategies. Weber postulated that processing of Verlustrohstoffe is most economic at or close to the resource deposit, whilst Reinrohstoffe best be processed near the end-user markets. Thus, the early location pattern of refineries and petrochemical industry could be explained. Molle and Wever (1984) took a descriptive approach “to picture the patterns of growth and stagnation of one of Europe’s major industries“, viz. oil refining and petrochemicals production, with a major emphasis on location adaptation of the industry. Of particular relevance is their verification of the extent of complex formation in the petrochemical industry, which confirms regional development theory and location theory that industries linked in a product chain tend to locate in one another’s vicinity to save on transport costs. A complex is then a joint location of linked industries that exchange feedstock and products. In their chapter heading, this concept is labelled functional linkage, which is defined as 'connection of production units by feedstock and product streams'. Interesting enough, they found that ‘vicinity linkage’ often is preferred over ‘concern linkage’. A range of specialised consultants also monitors the development of sectors or sub sectors of the chemical industry, its establishment and business. More often than not, however, their focus is on providing reliable data, while the breadth and depth of their analysis is often limited (e.g. Anonymous 1995a).
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2. Studies that use economic Input/Output analysis According to (Wei, 1979) the “very powerful bookkeeping technique of input- output analysis“, hereafter I/O analysis, was developed by Leontieff in the 1930s to account for inter-industry interaction, and to allow segregation of the value- added contribution to GNP by industry sectors. I/O analysis provides a mechanism to determine the specific contribution to, for example, GNP, resource use and emissions of the various sub sectors of an economy. Thus, inter-industry studies “are useful for both structural analysis and policy guidance ” (Chenery and Clark 1959: 7). The technique may also be used to assess the performance of the industry or parts thereof by valuation of the I/O analysis results. A specific example for the US chemical industry is reported by Thompson (Thompson et al. 1978). In 1993, a Dutch Research consortium13 compiled input-output tables of the Dutch economy for the purpose of monitoring material flows at a meso-level (Konijn 1994; Smits and Dijkema 1994). The results of these studies repeatedly emphasize the importance of the chemical industry as a supplier to agriculture. The results appear to be useful to set priorities for industry, environmental and innovation policy.
3. Studies that employ mathematical optimisation techniques As early as 1951, Linear Programming (LP)14 was developed and used for activity analysis in single plants, firms and in inter-industry economics (Chenery and Clark 1959). The planning and optimisation of refinery- and petrochemical complexes, however, has been largely the domain of Operations Research. LP- models by process system engineers are usually limited to a single level of aggregation, and limited to the modelling of some existing process network for optimisation. Stadtherr and co-workers were the first to report the use of LP to investigate the performance of the US chemical industry. (Stadtherr and Rudd 1976; 1978). The results of the studies initiated as early as 1972 were also published in a book (Rudd et al. 1981). The objective of their work was Defining the inherent technical structure within which the world-wide petrochemical industry must function. The structure is formed by the large but limited number of chemical syntheses that are available on the commercial scale and by the rigid feedstock, by-product, and energy requirements of these chemical syntheses. The products of one segment of the industry becomes the feedstock for other segments of the industry, thereby defining a network of material and energy flows that constrains business activities. Their assessment focused on giving insight into the questions “what are the ultimate performance characteristics of the industry, in terms of feedstock, energy, and investment capital use, (…) is it possible to anticipate the effects on the industry of changing product lines and raw material resources” and “what are
13 The Dutch Office of Statistics, the CBS executed this study that was commissioned by the Ministry of Vrom and RIVM. The study was completed with the help of DHV, TNO and Interduct, the Delft University Clean Technology Institute. 14 The use of LP and related techniques in conceptual process system design is addressed in Ch. 5.
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the characteristics of new processes and products that lead to their eventual adoption in the economy.” In order to answer these questions, they developed and employed a linear, economic input/output model that was used to establish the optimal structure of the petrochemical industry with respect to production costs. Out of an extensive data catalogue on industrially applied processes, the 1977 (and 1940, 1950, 1960, 1970) structure of the industry could be reconstructed. By changing the available technology catalogue, the impact of novel processes becoming available was assessed. In all cases, the existing industry proved to be a barrier to selection of novel processes, which was modelled by applying capacity constraints to the model selections. We adapted their model to investigate the use of novel technologies in existing
process networks (Dijkema et al. 1997). Optimisation of C4 networks in retrospect confirmed maturity of this part of the industry. We concluded that the existing industrial process network has a large flexibility towards feedstock economics, which implies that new processes must offer significant advantage to overcome this barrier to implementation. These kind of studies appeared particularly useful to establish the scope for innovation and for some prioritisation of R&D efforts. 4. Scenario studies to elucidate the need for resource and energy conservation. The work reported by the ‘Club of Rome’ (1972) was the first to address the resource situation of our global industrial society using the system dynamics modelling approach. The energy sector, base metals, and the petrochemical industry were explicitly recognized and modelled as an important sector (Meadows et al. 1972). The Club of Rome warned for major resources becoming unavailable for society in the foreseeable future. In contrast with common belief, however, the report did not state a definite horizon but merely pointed out that the modelling exercises gave similar scenario patterns over a very wide range of parameter for birth rates, economic-growth, welfare etc. The authors conclude that a drastic change in lifestyle would be needed for sustainability. Partly responding to criticism on the original model, the authors published the results of an improved global model in 1992 (Meadows et al. 1992), where they argued that the model supported that a status of sustainability at the time was still achievable, however that the 'escape'-window had become much smaller, which implied more drastic adaptations to our global society were needed. Governments and major oil companies have developed their own scenarios for world energy developments to help developing business strategies. In the Netherlands, the energy research centre ECN has developed various scenario models, the most well-known “Nederland in Drievoud” (Gielen 1999). 5. Sector-wide studies to find general means of improvement of resource and energy efficiency In the Netherlands, around the time of the Club of Rome report, a first Cabinet letter on the environment was issued (VROM 1972). Not much later results of sector wide policy studies on efficiency improvement were published. Examples of studies that addressed energy improvement potential are (Boot and van Wees 1982; Melman et al. 1991; Worrell 1994). In all of these studies feedstock supply and sector structure are taken for granted, and the possibilities of improvements
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are addressed largely at a technological level. An exception is the report issued by Quakernaat et al., who proposed a dramatic strategy: to initiate a complete transition of the energy sector to use hydrogen derived from coal. This would open the way towards development and use of solar hydrogen plants. It was suggested to locate these e.g. in the Sahara desert and connect Western Europe by pipeline (Quakernaat 1981). Boot and van Wees (1982) were the first in the Netherlands to investigate the utilisation of fuel in the Dutch industry. From the database on industrial emissions they computed an estimation of the net use of heat at various temperature levels in the industry. Their basic intent was to investigate the possibilities for cogeneration capacity expansion. Others have reported attempts to identify so-called 'cross-cutting' technologies, that would be applicable in many sectors of industry to achieve resource and energy conservation (e.g. Melman et al. 1991; Worrell 1994). 6. Studies with an emphasis on environmental impact Notably Life-Cycle-Analyses fall into this category. Early LCA- studies were primarily product oriented and not so much process oriented. An exception is the work done by CE and others on the evaluation of processing routes for mixed plastic waste. (Dijkema and Stougie 1994; Sas et al. 1994a). In order to elucidate the effects of a particular product, often large parts of the industries involved have to be accounted for. Through journal and Setac publications LCA has evolved into Lifecycle Inventory (LCI) followed by Life Cycle Assessment, LCA. Not only emissions and waste discarded into the environment are accounted, but also the net withdrawal of resources. The valuation of these inputs and outputs, however, remains a controversial issue. Objective allocation of emissions and withdrawals in networked production systems is difficult. In case LCAs are conducted as part of the formulation or evaluation of public policy and regulation, valuation and allocation often are the result of negotiation between stakeholders involved (Dijkema and Stougie 1994; Sas et al. 1994a; Bretz and Fankhauser 1997; Bras- Klapwijk 2001). In addition, on the basis of interviews in eight industry sectors, we concluded that only few LCAs are completed, primarily because the benefits of the exercise do not justify the cost (Dijkema and Mayer 2001b). Product LCAs, however, can yield insights into which products to innovate or where production systems must be improved. Too often, however, the interconnection between systems, mutually dependent performance, and technological content and constraints are neglected in formulating solutions (Reuter and Dijkema 2003). 7. Studies with a policy or management focus. Stobaugh investigated and analysed the mechanisms of the development of global petrochemical business largely for an industry perspective: how-to ensure continued success in this business (Stobaugh 1988). One element, for example, is vertical integration, which was taken one step further in the concept of Integrated-substance-chain management (VNCI 1989). The latter developed from the notion that all outputs from an industrial system must originate from some input. It may be seen as an early attempt to develop some system perspective that combines system surroundings (economy, ecology), structure
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(substance-chain) and organisation and management. Based on results of a number of consultant studies into the performance of chemical companies Whitehead argues that it is not portfolio restructuring through (de) mergers and acquisition, nor cost cutting and reorganisation, but value creation that should be the objective of any company's strategy. Innovation and innovativeness are the most important ingredients (Whitehead 2000). 8. Studies with a holistic character Recently, the concepts of Industrial Ecology (Graedel and Allenby 1995; Ayres and Ayres 1996) and Industrial Ecosystems (Allenby and Richards 1994) have been developed to contribute to sustainable development by mimicking the functioning of nature’s ecosystems in industrial operations. Addressing the aggregation levels beyond a single plant and cross-sectoral exchange, Industrial Ecologists develop a body-of-knowledge on how to use analogies and examples from natural ecosystems for the analysis and conceptual design of industrial networks and industrial society at large. An early example addressed by the industrial ecologists was the investigation of inter-company networks (Frosch and Gallopoulos 1989). A much cited example is the Kalundborg industrial estate in Denmark (Verhoef et al. 2004b). As has been the experience of a great many (petro)chemical companies indeed the nearby location of similar industrial operations can offer synergies by exchange of mass and energy flows, utilities and other site services and infrastructure. This has been used to explain the large degree of clustering and the very emergence of petrochemical complexes (e.g. Molle and Wever 1984). Today, the availability of such amenities is a conditio-sine-qua-non for many a petrochemical company when confronted with the task of site-selection for new process plants (Dijkema and Kuipers 2001). Whilst existing clusters continue to evolve, to bring-into- being new clusters is tedious, amongst others because the demonstration and allocation of the benefits of industrial cluster concepts is not trivial. . We developed a decision support system based on I/O techniques to assess industrial park performance (Dijkema and Stikkelman 1999). To support the Regional Development agency, van Zanten constructed an I/O model of part of the Rotterdam Chemical Cluster and applied Linear Programming to identify potential candidates for improvement of the cluster (van Zanten and Dijkema 2002). Quantitative I/O analysis and Linear Programming to assess the optimality of an industrial network from a variety of perspectives, however, appears to be largely lacking in Industrial Ecology. The need for closure of material cycles is another example that has been advocated in the industrial ecology community (e.g. Ayres and Ayres 1996). Modelling of heavy metals in Zn, Cu, Al, Si, Mn, and Mg production and their interconnected material cycles appears natural as, except for nuclear reactions and space travel, the chemical elements never vanish from the earth (Reuter 1998). Indeed, many scholars have addressed these metal cycles, and a large inventory of Cu and Zn flows around the world has recently been completed (Graedel 2003). Metal production, however, is not only characterised by interconnectivity, but also by interdependence, and for many metals no primary production exists, only co-production (Verhoef et al. 2004a). Presently, largely
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dissipative once-through supply-chains cater for consumer demand for short- lived products and packaging. These span the metal industries, crude oil refining, the petrochemical industry and polymer production (Figure 1-3). A recent survey of the European Environmental Agency, for example, revealed that per capita waste production in the European Union is 415 kg/yr and continues to rise (Anonymous 2003b). Meanwhile, society has developed and depends on end-of- pipe waste management infrastructure, land-filling and incineration (Dijkema et al. 2000). The result is loss of material and loss of quality material. In the nineties, sustainability has also been address from the perspective “how much do we need to improve societies effectiveness in using resources, the environment and use of natural ecosystems.” Factor-10 or Factor-20 have been coined. The Factor 4 approach (von Weiszacker 1996) starts at the needs-side, which leads to an orientation to product development: what concepts are required in the future to satisfy human needs with a limited input of resources? Therein it is implicitly assumed that change of the production systems will follow because of the interest and commitment of parties involved. In the Netherlands, a sustainable technology program ('DTO') was launched and executed. In the program scenario methodology and back casting were combined to develop both images of a sustainable future and a roadmap or multi-stakeholder process to get there (Mulderink et al. 1997). Both in Industrial Ecology and in holistic sustainability studies, such as (Mulderink et al. 1997), the entrenchment caused by the presence of existing production systems appears to be largely neglected (Verhoef et al. 2004a). In addition, both approaches appear to suffer from lack-of-content (Boulding 1956). The analogies from ecology and the scenario/back casting approach, however, do offer significant potential to develop useful concepts for innovation towards sustainability, such as using the integration of recycling and production systems in closed material cycles (Verhoef et al. 2004a).
2.2.4 ANALYSIS AND OBSERVATIONS Generally speaking, holistic and system, policy and management approaches suffer from lack-of-content (Boulding 1956). A few exceptions noted, in most cases a largely descriptive approach is used to capture features of the industry, the petrochemical industry or industrial complexes. A number of models have a macro- economic orientation and use I/O analysis to predict performance of industry and technology used. These subsequently provide a basis of descriptions of what a - more- sustainable future should look like and what should be done to get there. Only in a limited number of cases, however, ingredients with (technological) substance or analysis of existing production systems are linked with the images created. The analysis results do not relate to single plants or particular technology because they do not include aspects that are required for meaningful assessment of technology such as, for example, a sound thermodynamic basis. As a consequence, the usability to formulate R&D strategies appears to be limited as there is no coupling with ‘technological reality’. On the other end of the spectrum, “Traditionally, chemical engineers have been rather more micro-oriented in their engineering approach to the process industries,
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typically working in a plant or focused business area as a technical or technological specialist” (Brennan 1998: 255). This even appears to be largely the case in process system engineering, where many congress and journal papers appear that focus on mathematically sophisticated solutions to problems of limited scope. Thus, our literature survey indicates there is a gap between system and policy studies centred around industrial sectors or beyond, and the work done in chemistry and chemical engineering on products and industrial processes. In publicly funded chemistry, chemical engineering and related disciplines the selection of R&D focus is largely left to accredited specialists from academia who focus funding on fundamentals at micro- and molecular scale. Adequate R&D portfolio management across the various scales - from molecule to process to industrial network to industry - to foster sustainable development appears to be lacking. Industrial R&D addresses relevant product sectors and all relevant scale of process engineering. No methodology or recipe for the effectuation of sustainability in the large-scale process industry presently exists. In the scientific community at large the system design of the industry has been considered fixed. With the maturation of the industry (Ch. 1), changes or extensions of the industry's structure have become incidental consequences of successful fundamental R&D. Systemic innovations, however, do require a long-time period for development and implementation irrespective of the mechanism by which they have been identified. Thus it may be seen that one cannot be sure that the largely ‘bottom-up’ approach employed in the scientific community will provide sufficient and timely solutions to support a transition to a sustainable petrochemical industry. The gap identified represents a niche for 'systems thinking', notably process system engineering to effectuate and combine industrial ecology concepts and policy analysis and management theories.
2.3 System thinking foundations
2.3.1 OVERVIEW This section firstly introduces (general) system theory and system engineering. Subsequently we address and define 'system', 'system elements', system assessment, design and analysis.
2.3.2 SYSTEM THEORY AND SYSTEM ENGINEERING In many industrial sectors scientific, knowledge and advancement is turned into an advantage through subsequent applied R&D and system engineering. Based upon this recognition, general system theory was coined (Boulding 1956), and general system engineering principles were developed that augment detailed subject knowledge by offering methodologies to bring complex systems into being (Asbjørnsen 1992). Contributions originate from aerospace and defence industries (e.g. Corrigan and Kaufman 1965), the automobile industry, electronics industry, computer systems, information, communication and telecom infrastructure (e.g. Blanchard and Fabrycky 1998; Arnbak and Weber 1999).
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The chemical engineering community has been very successful in adopting system concepts (Villermaux 1996). Process system engineering has emerged as a sub discipline where methods for optimal design of chemical plants have been developed, both with respect to the selection of technology content and of system structure. According to Prof. Villermaux, it is the mere training of chemical engineering students in systems thinking that allows them to be productive in so many sectors of science, engineering and business (Villermaux 1996). After the original publications of (Boulding 1956) and (von Bertalanffy 1951), system theory has grown into a vast area with sub disciplines that address hard- vs. soft systems; static and dynamic systems, system analysis and system design. (Corrigan and Kaufman 1965: 29) describe the activities of system engineering as “a progressive definition and integration of functions and design decisions at every level of system complexity.” Nelson addresses system engineering in terms of functional activities performed “in the conduct of a system definition/design (Nelson 1972 216: vi). INCOSE has defined system engineering as “an engineering discipline whose responsibility is creating and executing an interdisciplinary process to ensure that the customer's and the stakeholder's needs are satisfied in a high quality, trustworthy, cost efficient and schedule compliant manner throughout a system's entire life cycle” (Incose 2004). According to Asbjørnsen, “systems engineering and systems thinking are formalized common sense”(Asbjørnsen 1995). Blanchard & Fabrycky coined the phrase “bringing systems into being” as the emphasis in the overall activity of systems engineering (Blanchard and Fabrycky 1998: xiii). System engineering thus includes the definition of needs, requirements analysis, functional analysis, design synthesis and finally system evaluation. The latter is the objective of systems analysis, which prime domain of use is the improvement of systems that are already in existence. (Hartmann and Kaplick 1990) also distinguish between system analysis and system synthesis steps. According to Sargent, David Rippin would have described the objective of the systems engineering approach “as the provision of a systematic framework for tackling the solution of complex problems” (Sargent 1998). “Process synthesis is the invention of conceptual chemical process designs” (Siirola 1996: 10), and the question whether “the invention of chemical process designs can be organised, systematised, or even automated” is at the focus of process synthesis research. (Siirola 1996: 3). From these definitions , we conjectured that system theory, and more specifically (process) systems engineering would provide useful insight and procedures to address complex industrial systems. In our case, the system constitutes the whole petrochemical industry. Its present structure is the result of a long process that by some has been labelled chaotic. In addition, the utilisation phase of commercial chemical plants often is very long, “much longer than the life of artefacts15 and artefact-making machinery” (Siirola
15 An 'artifact' is “… an ornament, tool, or other object that is made by a human being …” [Sinclair, 1995 #59 :82]. By using this term, Siirola (1996) succinctly captures the differences and analogy between the production of consumer goods (including intermediates) and capital goods. The output
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1996: 2). Indeed, the economic lifespan of many a chemical facility is extended over and over again by multiple rejuvenation phases (Grievink 1994). It is to be expected, therefore, that elements of the present petrochemical industry will be in existence for a long time to come. Referring to industrial practice, Siirola hints at the relatively scarcely addressed problem of having to generate flow sheets from scratch, as often flow sheets from previously realised plants are available (Siirola 1996: 13). Genuinely novel process system concepts, such as distributed chemical manufacturing (Rowe et al. 1997) are scarcely reported. It may thus be seen that system engineering per se is out of the question because it is focused on the technology acquisition phase (Blanchard and Fabrycky 1998:13). A more realistic objective appears to be to provide a contribution to system re-engineering or a re-direction of the system’s general direction of development or transition towards sustainability. The initial activity then comprises a thorough analysis and assessment of the present system such as presented in chapter 3, to be followed by a creative but possibly systematised phase during which novel, innovative system concepts are specified.
2.3.3 DEFINITION OF 'SYSTEM' We have freely used the concept of ‘system’, which to some is natural, or even trivial. Dictionary descriptions vary from “a system is a way of working, organizing, or doing something which follows a fixed plan or set of rules (..) the English legal system“, “a device or set of devices powered by electricity (…) a computer system“, or “your system is your body’s organs and other parts that together perform particular functions” (Sinclair 1995). Thus, the interpretation and use of the term system exhibits many variations. How then to define ‘system’ unambiguously for the purpose of devising a suitable modelling strategy for the petrochemical industry? Nelson defines a system as “a combination of elements that work together to perform a preconceived mission” (Nelson 1972). Blair and Whitston define a system as “a set of objects, ideas, activities, or a combination thereof with a unifying organization, and distinguish between ‘real-world’ systems (objects) and conceptual systems (ideas). They mention the hierarchical nature of systems. In addition, they state (Blair and Whitston 1971: 66) that a system can be “analytically described in terms of (1) the attributes and functions of its individual unit parts and (2) various relationships of these components with each other. The function or functions of the overall system are the resultant of the component interactions.” After quoting a dictionary definition “A system is an assemblage or combination of elements or parts forming a complex or unitary whole,” Blanchard and Fabrycky (1998) do not coin a definition of ‘system’, but. merely restrict themselves to a list of features that distinguishes a system from a random set of objects: systems are composed of components, attributes, and relationships, that together work toward a common objective or purpose. “A common system function is that of altering material, energy, or information” (Blanchard and Fabrycky 1998). In addition, the hierarchical nature of systems is emphasized: every component or subsystem can be broken down into smaller components, subsystems or system elements.
of continuous chemical process plants, mass production or the assembly facilities for consumer products are artefacts, so are the production facilities.
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Using the foundations laid out by these and other authors, Asbjørnsen (1992) coined a definition of system that appears to avoid ambiguity and to be suitable for the purpose of devising a modelling strategy for the petrochemical industry. Thus, a system is defined as “a structured assemblage of elements and subsystems, which interact through interfaces. The interaction occurs between system elements and between the system and its environment. The elements and their interactions constitute a total system, which satisfies functional, operational, and physical characteristics, as defined by the user and customer needs and requirements, over a defined total system life cycle of the system existence, including the life cycle of bringing the system into being” (Asbjørnsen 1992).
2.3.4 SYSTEM ELEMENTS The lowest level of detail of a system structure consists of the system elements, which Nelson defines as “fundamental building blocks that comprise a system” (Nelson 1972). He indicated both hardware (equipments, facilities) as well as software (skilled personnel, procedural data) as possible system elements. According to Asbjørnsen (1992), the functional characteristics of a system element are technology- free. The element is fully described by its inputs and outputs, irrespective of how the relationship between inputs and outputs has come about, notably irrespective of what technology (hardware) and procedures (software) bring about the transformation between inputs and outputs. This relates to the common ‘black-box’ approach in engineering, where the treatment is concerned with what goes into the unit, what comes out of it, and what happens to anything while inside, without being concerned with the details of how it happens (Blair and Whitston 1971: 67). This very principle allows the engineer to design, construct and control complex systems, as for example in plant design not every detail of the operation of a pump needs to be known. In addition, gaps-in- knowledge can be filled by establishing empirical correlations, proper assumptions, and observing system behaviour. Not only a system element or network node can be fully described by it’s inputs and outputs, the same is true for the system. Thus it may be seen that input-output characterisation can be performed at any aggregate system level. In the petrochemical industry, for example, the levels suggested in (Table 1.2, p.16). It must be noted that at each level the analysis can be performed irrespective of the further decomposition selected of the system under analysis. As a corollary, whenever a system is modelled as structured collection of system elements, the modelling result is dependent on the decomposition selected! In process system flow sheet simulation, for example, a process system is considered a structured collection of unit operations, which are technology-free representations of the process system' elements. Process flow sheet simulators are commonly constructed around these unit operations. The user must define the inputs and required output of the system, and the connection structure between unit operations. The simulator then provides unit operation models and thermodynamic property estimators to proceed from the input of a single unit operation to the outputs. Finally, a solver routine ensures that all internal flows in the system will match.
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Another example is the successful use of the ‘black-box’ approach found in control system design (e.g. Aström and Wittenmark 1984)), where only the black-box’ response to input changes and/or measured disturbances need to be known over the range of operating conditions for most common types of controllers. Nothing of the physical realisation of the black-box needs to be known, its contents are incognito. The system can equally comprise an area inhabited by rabbits and foxes, a stirred- tank, or a ship. The dynamic response patterns can be established by observation, analysis or experiments. In a ‘grey-box’ approach, knowledge about the contents of the box is used to conjecture an expected dynamic transfer function, which is validated and calibrated by experiments. In a ‘white-box’ approach, finally, a model is constructed from first principles and the available knowledge on the box’s technological contents. It follows that process flow sheet simulators follow a white-box approach at the level of unit operations, as the input-outputs relations obey the thermodynamic models thought applicable. The actual apparatus that would constitute the unit operation, however, is still considered a black box. The definition of system elements by Asbjørnsen provides a means to identify analogies, and explains the impact of information systems engineering on the development of general systems engineering theory. “Like materials and energy, information is acquired, transmitted, stored, retrieved, and processed (...) Like materials, information is processed by separating, combining or otherwise transforming its parts. (...). Information flow and processing constitute, along with flow and processing of materials and energy, fundamental aspects of systems operation” (Blair and Whitston 1971: 28-33). In our modelling strategy, therefore we have adopted the system concept as phrased by Asbjørnsen, with the specific notion that the system’s lowest level is an element that is only defined by its functional characteristics. This then opens the way to develop new technological concepts to bring about the transformation between inputs and outputs.
2.3.5 SYSTEM ASSESSMENT, SYSTEM ANALYSIS AND SYSTEM DESIGN (Corrigan and Kaufman 1965 :19) define the process of 'system analysis' as “the process of reducing or breaking down a whole [system] into an organization of parts while relating the parts to each other and to the whole.” This definition relates to the above definition of 'system'. Others, (e.g. Nauman 1988), perceive system analysis to be a specific domain of applied mathematics. To avoid this ambiguity, we prefer the term system assessment, which we define as a combination of quantitative analysis to assess performance and qualitative analysis, which includes both (sub)system boundary selection and system decomposition, to understand structure and assignment of sub functions to understand the system's purpose. A number of authors quote the iterative nature of system engineering activity, where system analysis precedes and follows upon system design (Corrigan and Kaufman 1965; Blair and Whitston 1971; Blanchard and Fabrycky 1998). This is best illustrated in the General Design Paradigm that was first postulated by French in
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1971 (French 1999). An extended graphical version of this Paradigm is given in Figure 2-1 (p. 55). According to Asbjørnsen, in system engineering theory a technology-free specified system element is the building block in system design. The functionality of each block and the connection structure between blocks together yield the complete system (Asbjørnsen 1992). As a corollary, in systems analysis it is the smallest item of which the performance is assessed. In process system engineering, 'process system design' generally is decomposed into systems analysis and system synthesis (e.g. Douglas 1988; Hartmann and Kaplick 1990; Biegler et al. 1997). “System analysis is the formal decomposition of a process into its constituents and their investigation with respect to the different hierarchic levels. A term which actually means the same thing is process analysis, which is understood as the scientific, technical and economic investigation of a chemical process system. The purpose of such studies consists in finding bottlenecks, showing possible improvements and extensions and finding measures for their implementation” (Hartmann and Kaplick 1990: 17). In process synthesis, the objective is to generate the optimal system design out of a given set of available and tuneable building blocks. The synthesis thus involves assembling alternative process configurations and final selection. As of late, process synthesis techniques have been used for the development of new chemicals (e.g. Marcoulaki and Kokossis 2000) and the importance of the relation between product and process research has been emphasised (Charpentier 2002).
2.4 Process system engineering
2.4.1 OVERVIEW Inventions may originate from basic science or R&D in chemistry, chemical engineering and related disciplines and from studies with a system, policy or management focus. The latter necessarily employ a meso- or macro-perspective opposed to the micro-oriented approach in science and engineering. Any invention becomes an innovation only when realized in an industrial plant or product. Therefore, process system engineering is crucial for innovation in the petrochemical industry. Indeed, reflecting on and summarising the advancements of thirty years of process synthesis efforts in PSE, Siirola “describes a framework for the industrial chemical plant innovation process, showing how process synthesis fits into that structure and how that framework has in turn influenced the development of systematic process synthesis methods” (Siirola 1996: 2). As a result of the work of and interaction among academia, the chemical and related process industry and its knowledge providers, PSE has evolved as a sub discipline of chemical engineering. Its focus is bringing into being chemical plants that exhibit excellent operation characteristics and performance with respect to economy, ecology and safety. The quality of a design, however, is not uniquely quantifiable. There exists not “the quality“, but many quality factors, some of which can be exactly quantified, while others lack quantitative precision. The result is a “fingerprint” of quality factors of a design (Herder 1999).
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Over time, elaborate knowledge of chemistry, thermodynamics and technology has been incorporated into a range of unit operation models. Sophisticated numerical solver routines enable computations around complex systems that may incorporate multiple recycles whilst respecting a variety of constraints. Thus, today PSE allows ex-ante evaluation, synthesis and simulation of innovative plant designs. It's body-of- knowledge enables us to establish the feasibility of new plant designs as well as the potential of novel, presently technically or economically infeasible technology or unit operations (e.g. Dijkema 1998). Traditionally PSE is limited to analysis, synthesis and design of individual chemical plants, which may involve selection and structures of unit operations (e.g. Smith 1995). According to Grossmann and Westerberg, however, “PSE is concerned with the understanding and development of systematic procedures for the design and operation of chemical process systems, ranging from microsystems to industrial- scale, continuous and batch processes ” (Grossmann and Westerberg 2000: 1700).
Cadre 2-1: The CAPE community In Europe, research groups on chemical process system design collaborate in the Working Party on Computer Aided Process Engineering (CAPE) of the European Federation of Chemical Engineering EFChE. For a number of years, this Working Party has organised a symposium series, known as Escape as of 1992 (Grievink and Schijndel 2002). Its equivalent in the United States is the Annual AIChE symposium series. In the US every five years an Engineering Foundation Symposium is organised respectively for process design (FOCAPD), process control (CPC) and process operations (FOCAPO). Every three years a world-wide symposium is organised - PSE-, which circulates over three continents -America, Europe and Asia When landed in Europe, PSE is combined with the Escape symposium. Refereed contributions to these conferences have appeared in Computers and Chemical Engineering, an Elsevier Science publication. In addition, from these research communities a number of books have emerged, notably (Douglas 1988; Hartmann and Kaplick 1990; Smith 1995, Anderson, 1996; Biegler et al. 1997; and Seider et al. 1999), which were preceded by the founding work of Rudd and Watson (Rudd and Watson 1968). The most relevant themes addressed in the Escape-12 symposium were Integrated Product and Process Design, Process Synthesis and Plant Design and Sustainable CAPE education and careers for chemical engineers (Grievink and Schijndel 2002).
The body-of-knowledge of PSE has been developed over some thirty-five years (Edgar et al. 1999). Today it includes (1) process systems analysis through mass and energy balancing, second-law analysis and flow sheeting (Denbigh 1956; Rudd et al. 1973; Kotas 1985; Seider et al. 1999 respectively) (2) process system design supported by elaborate design knowledge formalised in heuristics for conceptual design (Sherwood 1963; Rudd and Watson 1968; Douglas 1988; Siirola 1996) and by algorithms for process synthesis that have been developed for specific sub domains
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of chemical process system design such as heat exchanger networks, separation networks and reactor networks (Floudas 1995; Westerberg and Wahnschafft 1996; Grossmann et al. 2000) (3) Methods and algorithms for control, optimisation and scheduling to enable and support the operation (Stephanopoulos 1984; Biegler et al. 1997; Edgar et al. 2001; Heijnen and Verwater-Lukszo 2003). The emphasis of PSE efforts in R&D, however, is the support of design of chemical plants using known (process) technology. Where Rudd and Watson advocate to start from a primitive problem - 'an ill-defined statement of a need' (Rudd and Watson 1968: 4) -, at present often a known basic system design is used. Referring to industrial practice, Siirola hints at the relatively scarcely addressed problem of having to generate flow sheets from scratch, as often flow sheets from previously realised plants are available (Siirola 1996). Genuinely novel process system concepts, such as distributed chemical manufacturing (Rowe et al. 1997) are scarcely reported. This matches the conservatism in the chemical industry, which can be explained by its high-capital intensity and the associated risk. Common tactics are to use proven concepts for novel chemical plants, to change these in small steps in conceptual design, and to adopt a minimum-change standard in detailed design, no- change during construction. Despite the suggestions by Grossmann and Westerberg (Grossmann and Westerberg 2000), in process system engineering work concerning process systems that consist of multiple plants have been largely limited to optimisation, notably (MINLP) approaches to the optimisation of refinery operation planning, and investment selection, the work of Stadtherr and Rudd being one of the exceptions (see section 2.2.3). Another subject area where considerable work has been reported is the work on the synthesis of reactor and reactor/separation networks (e.g. Papalexandri and Pistikopoulos 1996; Glasser and Hildebrandt 1997; Sargent 1998). Ismail et al. reported some work on exploring some solution-space beyond existing system concepts where process alternatives have not been pre-postulated (Ismail et al. 2001). Literature reports on the conceptual design of petrochemical complexes comprising multiple plants are lacking, let-alone true multiscale approaches that link the industrial complex, single plant and the unit operation level. With respect to what can be known about corporate R&D, it appears that for a long time true process system innovations were hardly known or recognized and have not been capitalised upon in corporate R&D, which suspicion is confirmed by findings of a study into DuPont's R&D (Hounshell and Smith 1989). Some successful 'dual-scale' process system innovations are known, such as the optimisation of the Refinery-Steam Cracker interface and the development of integrated unit operations for reactive- distillation. Generally speaking, however, the potential of networked process system innovations is a largely unexplored 'white spot' in PSE. In the past decade, the inclusion of environmental impact minimisation into process synthesis was addressed (Buxton et al. 1997; Yang and Shi 2000). The inclusion of environmental criteria into the design process was elucidated (Herder 1999; Sharratt 1999). The inherent multicriteria design problem of pollution prevention and waste management was addressed (Steffens et al. 1999; Mellor et al. 2002; Linke and Kokossis 2004) as well as the incorporation of Life-Cycle Assessment into optimal
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chemical process system design (Azapagic 1999; Burgess and Brennan 2001; Khan et al. 2001). Others incorporated engineering thermodynamics into process design and optimisation and suggested thorough consideration of the available energy resources and their conversion to useful work (Kalitventzeff et al. 2001; Bakshi 2002). While the PSE community has realised that “The process industries are facing a range of growing commercial pressures and challenges” (Bogle and Perris 1999), PSE research contributions that address sustainability are relatively few in number.
2.4.2 PROCESS SYNTHESIS “Process synthesis is the invention of conceptual chemical process designs” (Siirola 1996) and the selection of the better ones based on incomplete information (Westerberg 1989). The question whether “the invention of chemical process designs can be organised, systematised, or even automated” is at the focus of process synthesis research. (Siirola 1996: 10, 3). Daichendt and Grossmann, however, equate process synthesis to conceptual process design (!) and describe it as being “concerned with the identification of the best flow sheet structure (process system) to perform a given task (Daichendt and Grossmann 1997). They distinguish two major approaches to address the process synthesis problem: hierarchical decomposition developed by Douglas and mathematical programming using Mixed Integer Non Linear Programming (MINLP). In the former approach one appears to focus on conceptual design whilst in the latter approach the value of rigorous simulation is emphasized. Kaibel and Schoenmakers distinguish between the heuristic approach and the superstructure/thermodynamic principles approach (Kaibel and Schoenmakers 2002). According to Daichendt and Grossmann, Fonyo and Mizsey (1990) were among the first to attempt and combine the two approaches, hierarchical decomposition and mathematical programming, in a procedure starting with (1) hierarchical decomposition, followed by (2) user-driven synthesis techniques to reduce the design space and finally (3) rigorous profit calculations based on flow sheet simulations (Fonyo and Mizsey 1990)16. Daichendt and Grossmann present an attempt to combine the two via the construction of a high-level process system superstructure, but restricted to a process system that has been (pre)decomposed hierarchically into the subsystems reaction, separation and heat integration. They present a computational procedure that includes a multi-level tree-search and algorithm for selecting optimal process system options at the conceptual design stage, i.e. to support step (1), hierarchical decomposition of the design problem into successive levels of system detailing and system design solution. In such approaches, however, the possible outcome is limited by the system boundary selected, by the type of system element available for selection and modification, and by the original set of alternative elements included. In addition, the solution selected may represent a compromise to deal with multiple objectives. Given the huge number of scientific papers on development and case studies using methods of either category, both are well established in the CAPE17 community.
16 (cited in Daichendt and Grossmann 1997) 17 Computer Aided Process Engineering- see Cadre 2-1, p. 52.
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Need
Define Primitive Problem Analysis of Problem Gather Cognate Facts
Statement Systematic Create Specific of Problem Generation Problems of superstructure
Screen Specific Evolutionary Problems Conceptual Design Modification of superstructure
Optimisation Selected Structure and Design
Feedback Schemes Critique / Evaluate of Alternatives Embodiment of Schemes
Detailing
Working Drawings etc.
Rudd & Watson French Siirola (1968) (1971) (1996)
Figure 2-1: Expansion of the General Design Paradigm for process synthesis (after Rudd and Watson 1968; Siirola 1996; Herder 1999).
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(Kaibel and Schoenmakers 2002: 11) of BASF, however, comment that above restrictions are disadvantages of both approaches. They recommend that “the inclusion of a process in the company's process chain and the site conditions must be specified. Finally, they state that “both methods are used in industry (…), however, that neither of these methods is used regularly.” Indeed, Sargent reiterates Rippin's concern “Will computer-aided synthesis of complete plants be used by industry in due time (…) Are the methods too simple to cope with real industry problems-or too complex for everyday use by industry engineers?” (Sargent 1998). Notably Pistikopoulos et al. have addressed chemical process design, integrating four domains of interests, viz. (a) the process system (b) the control (c) the operations - static and dynamic optimisation thereof - (d) the production planning and scheduling in a supply-chain (Bansal et al. 2000; Bansal et al. 2002; Ryu et al. 2004). For any pair of domains {a,b}, {b,c}, {c,d} and {a,c} convincing studies have been published concerning the feasibility of such approaches for realistic sections of a process plant. Dealing with any of these domain-pairs for a full scale plant appears to be beyond current computational capability. Similarly, whilst the concept is there, actually dealing with all four domains for a realistic plant section is computationally too demanding at present. Kussi et al. of Bayer formulate a work-flow procedure for the effective use of computer tools in the optimisation of existing chemical plants. They stipulate that the interlinkage between the different types of modelling approaches and their tools is a major obstacle to the effective use in industry of computer-aided process design and optimisation. Whilst the vision has been coined to integrate simulation, design, control and optimisation capabilities into a single model to support chemical operations over a plant's life-cycle, they observe that rigorous modelling, black box modelling and hybrid modelling are still 'living apart together' (Kussi et al. 2002). Sherwood defined 'engineering design' as “the process of applying the various techniques and scientific principles for the purpose of defining a device, a process, or a system in sufficient detail to permit its physical realization” (Sherwood 1963). In teaching design his approach was to continually remove biases suggested by the terms used to get students to think outside the box (Westerberg 2004). “A complete process design includes a critical review of the idea that there should be any process, the invention or selection of an appropriate process (…).” (Sherwood 1963). Rudd and Watson also emphasize the synthesis of plausible alternatives and elaborate on generating ideas prior to engineering solutions. From an ill-defined, primitive problem they suggest to arrive at a limited set of specific problems that can be subject to engineering solutions (Rudd and Watson 1968). No use of mathematical models is made in this phase; only relevant knowledge, information and data is extracted from those concerned, experts and scientific information. This approach fits with the General Design Paradigm (French 1999), which was expanded by Siirola for the conceptual design or synthesis of chemical processes. The relations are depicted in Figure 2-1. Siirola distinguishes four fundamental phases in a process synthesis strategy, viz. (1) systematic generation, (2) evolutionary modification 3) optimisation of structure and design parameters and (4) evaluation of best alternatives with respect to criteria not in the optimisation problem (Siirola 1996). In
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this strategy, the first two phases have found both heuristic and algorithmic implementations, the third is the natural domain of mathematical programming, notably MINLP-techniques and the fourth stipulates to evaluate the mathematical programming results in a wider context. Indeed, through the execution of every design process, not only the particular design at hand may be improved, but also the methods employed in each phase. Difficulties, however, arise when one seeks to assess the quality of a particular design (Herder and Weijnen 1999). Chemical processes can be modelled as objects that transform materials from an initial state to a goal state. Usually, property differences are observed between raw materials, products and intermediates. According to Siirola, the purpose of “an industrial chemical process is to apply technologies in such sequence that these property differences are systematically eliminated and the raw materials thereby become transformed to the desired product” (Siirola 1996). With regard to process synthesis steps, Seider et al. appear to define the main objective in chemical process design as to arrive at elimination of property differences (between input, intermediate and output materials in the process). The correction of such difference can be seen to be effected by operators, the essence of means-ends analysis (Simon 1969). According to Seider, such formal, logic based strategies for process synthesis, means-end analysed have only been developed for simple processes (Seider et al. 1999: 44). Meanwhile, the informal or heuristic approach initially introduced by Rudd has been applied widely (Rudd et al. 1973). It involves the rules for structuring process plant operations as indicated in Table 2.1.
Table 2.1: Process synthesis procedure (adapted from Seider et al. 1999: 44); underlining added; original italics Synthesis Step Process Operations 1 eliminate difference in molecular types Chemical Reactions 2 distribute the chemicals by matching sources and Mixing sinks 3 eliminate differences in composition Separation 4 eliminate differences in temperature, pressure and T, P, phase change phase 5 integrate tasks, i.e. combine operations into unit processes These steps appear in recommended order of execution (ibid: 112).
Elaborating upon means-ends analysis, Siirola distinguishes between synthetic, forward and opportunistic directed operators used in engineering, in contrast with the retro synthetic or backward oriented operators (from desired products) used by research chemists. He points out that problems emerge when property-changing operators can only be applied within a pre-specified range for other properties, which creates sub problems, and which explains the natural hierarchy found in successful design. Means-ends analysis, however, is recursive but not iterative, which creates problems with process recycles for mass and energy as commonly exploited in chemical process plants.
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Case-based reasoning (CBR) is an algorithmic technique to capture past experience and appears to augment heuristics by reusing past solutions to new problems, albeit in a limited problem and solution space (Avramenko et al. 2002). According to Avramenko et al., establishment of similarity is a main problem. In their case-based reasoning for decision support of the heuristic approach to conceptual design of a reactive distillation unit they use symbolic data divided into subclasses simple, structuring and classifying. Their representation of the CBR process can be expanded to represent the functional modelling process for expansion of the solution space. In his functional approach to process synthesis, after (Kondili et al. 1993) Sargent suggests to represent a “process” as a “state-task-network,” and to equate each unit operation to a task or device “for transforming material from one state to another” (Sargent 1998). Conceptual process design to effect a required transformation then implies making choices from a finite and known collection of chemical reactions and technology that can be interlinked in only a finite number of ways: a closed combinatorial problem of considerable dimension. He subsequently points out that in this solution space many combinations must be excluded because there is strong linkage of decisions and because of the hierarchical nature of design decisions (after Douglas 1988), with “broad choices at one level devolving into subsidiary choices at lower levels.” Sargent strongly advocates to make the choices in whatever design approach explicit, and suggests the use of two type of models. Performance models define the relationship between inputs and outputs for the task's range of feasible operation, and thus must inform the designer whether a process or task is fit-for-purpose, feasible and meets additionally the requirements. Value models assign a net “value” (Sargent's quotations marks) to the execution of each task. It allows to choose between alternative tasks that perform the same function. Both types of models can be very simple in early phases of design, or extensive for use in rigorous simulation during detailed design, but Sargent points out that to allow their use in subsequent design phases, the confidence regions of more refined models should be fully contained in those of simpler models, an objective which is hard to realise in practice (Sargent 1998). In a state-task network there must be a connected path from each feedstock to some product and vice-versa, and each intermediate state must be on one such path. Using these rules and models, for any given problem all possible state-task-network realisations can be enumerated, evaluated and possibly subjected to more refined analysis. Based on a case study of distillation network synthesis, Sargent concludes that Douglas' hierarchical approach can be embedded in a rigorous enumeration procedure, which provides the option to select refinement and accuracy of the models used as required, and that feasible networks can be generated by defining a set of elementary tasks and assigning a purpose or function to each of these. The more tasks that are available for use, the greater the variety of flow sheets generated! Seider et al. discern among process invention, algorithmic process synthesis and detailed design including design optimisation (Seider et al. 1999: v). They note that design problems are open-ended and that “design is the most creative of engineering activities, with many opportunities to invent imaginative new processes. It is also the essence of engineering, differentiating an engineer from a scientist” (Seider et al.
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1999: 6). In process invention, the focus is on process creation, i.e. the formulation and preliminary analysis of a promising base case design. The importance of simulation tools and heuristics in process analysis and synthesis respectively is emphasized. Whilst process invention is not defined, the goal of the procedures outlined appears to be to create an attractive, economically feasible, environmentally sound and safe process design package. This is in accordance with the Schumpeterian definition of innovation (Ch. 1). In this view process synthesis activities lead to innovation when the object of the synthesis activities, the process plant, is realised. Process synthesis itself, however, is also the subject of innovation: each novel method of conceptual process creation, if adopted in the community, represents an innovation. Beyond single plants, a vast body of process synthesis research concerns the design and optimisation of energy-exchange or utility networks. The pinch analysis ideas were pioneered by Hohmann and rediscovered by Linnhoff in 1978, who subsequently pursued its adoption by industry (Hohmann 1971; Linnhoff 1993). A massive body-of-knowledge has been developed on the optimum exchange of heat - using temperature level and pinch based decision methods - and later the exchange of water, hydrogen and solvents - using purity level and pinch. On an alternate, applied thermodynamics and optimisation track, exergy analysis and exergy-based optimisation of energy systems were developed (e.g. Kotas 1985; Yee and Grossmann 1990; Yee et al. 1990; Cornelissen 1997). In a recent review paper, however, Li and Kraslawski conclude that the picture of conceptual process synthesis given in (NRC 1988) is still current (Li and Kraslawski 2004). They argue that process synthesis “at the meso-scale has attained a high degree of scientific maturation” and that “a strong demand for new, innovative products and processes has attracted a lot of attention to the phenomena at the microscopic level”. Despite the suggestions by Grossmann and Westerberg (Grossmann and Westerberg 2000), however, process synthesis research at the macro-scale and conscious analysis or re-design of the industry system structure beyond single plants has only attracted limited attention.
2.5 System decomposition
2.5.1 OVERVIEW In the overview of system engineering and PSE (section 2.1) definitions have been given of 'system', 'system element', 'system engineering', and 'system assessment', 'system analysis' and 'system design'. These appear to be sufficient for a modelling strategy that supports process system innovation of the petrochemical industry. What is missing, however, is a conscious decision process on selection of the system boundaries, formulation of the boundary conditions for inputs and outputs, and system decomposition. Since the global petrochemical industry has never been designed as a single system, difficulties can be expected in decomposition. What is a suitable system boundary and aggregation level for the elements of the system studied? How to break down
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the petrochemical industry system into progressively smaller units, so that the model meets the objectives stated? Difficulties in devising a conceptual classification scheme or typology of systems are encountered in many sciences. In summing up the problems encountered when addressing world agriculture, for example, Grigg mentions that criteria for assignment to a certain class must both be developed and tested (Grigg 1974). Reviewing the system engineering literature and the process system engineering literature, we have searched for elements and theories that would help develop a solution for this problem. Texts on system engineering address the topic of system boundary selection and system decomposition in general terms only, reiterating that in system design it is not only useful to discern between systems and system elements, but also to group system elements into subsystems that together constitute the total system (e.g. Blair and Whitston 1971; Blanchard and Fabrycky 1998). Where (Corrigan and Kaufman 1965) use the analogy of the magnification setting of a microscope as a means to increase the level of detail of analysis, Asbjørnsen quotes the familiar top-down decomposition in trees, which says that each system can be decomposed into ever smaller level of detail (Asbjørnsen 1992). No indication is given, however, on how to achieve an optimum magnification-setting, when to abstained from opening increasingly smaller boxes or when the system content has become known in sufficient detail. In other words, no stop-criterion is given for the decomposition-depth.
2.5.2 PROCESS SYSTEM ENGINEERING In the process systems engineering literature, decomposition more often than not is addressed in general terms only. Hartmann and Kaplick for example, state that “The decomposition and aggregation (…) are decisive in the methodical consideration of the objects under study” but hardly address decomposition strategies of existing systems” (Hartmann and Kaplick 1990: 14). The exception, of course is hierarchical decomposition by Douglas (1988), which is an established approach to break down the conceptual process design and conceptual design procedure. In general, however, it appears that “pragmatism prevails over principle” (Grigg 1974). In flow sheet simulation for process design, the unit operation concept has been adopted (Ch. 1). In a well-known cost-estimation method for novel plants a process system is decomposed in functional units (Zevnik and Buchanan 1963). Where Hartmann and Kaplick introduce the process stage, Douglas uses the concept of a process unit (Douglas 1988; Hartmann and Kaplick 1990). In order to get an up-to- date impression of the work done in the CAPE community (Ch. 1, Cadre 1-2), we have searched the Escape symposium series (Pierucci 2000; Grievink and Schijndel 2002), as well as the Web-of-Science with respect to literature on decomposition methods. In line with earlier observations, (Dijkema and Reuter 1999), it appeared that system decomposition is only addressed sparsely, superficially or implicitly in the symposium proceedings and other publications. No clear-cut guidelines are given when to label a set of apparatus as a single piece of equipment, a unit operation, a process stage or a process unit and subdivision of processes or grouping of subsystems by use of these concepts appears to be largely anecdotic. Douglas, however, prescribes a procedure for the decomposition of existing chemical processes with the objective to modify the subsystems, without limiting the solution
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space of the decomposition to arrangements of unit operations (Douglas 1988: 17). Biegler et al. address the decomposition of decisions for process design, with the objective to limit the solution space for the process synthesis problem (Biegler et al. 1997). This is the commonality of all literature cited: the system modelling strategy is developed for a relatively clearly defined domain of application, and solutions are found in a fairly delineated space. Siirola appears to be among the few exceptions, when addressing systematic generation of process system alternatives through means-ends analysis (Siirola 1996: 13-15). In developing a computer implementation of means-end analysis, a set of useful rules are presented which resemble some form of decomposition: 1. keep task identification distinct from task integration and equipment design. “Form follows function.” 2. do not adhere inflexibly (to the property hierarchy) 3. be wary of convenience These three rules developed by Siirola for conceptual process design are useful to understand and guide the development of methods for specification of system innovations because they (1) relate to the concept of 'technology-free' system characterisation and specification, (2) prompt consideration of inflexibilities or lock- in caused by current industrial practice and (3) stipulated to be wary of risk avoidance, for example when accepting only minor deviations from proven technology or concepts. Siirola's work is reassuring, as he gives an example of a real process system innovation attributed to employing this methodology: a novel process system concept for methyl acetate production. “It is not clear how such a design might have been conceived without the explicit separation of task identification, task integration and equipment design” (Siirola 1996: 28). Finally, Siirola envisages a process synthesis paradigm of the future where existing approaches -systematic generation of alternatives, evolutionary modification of existing designs and structural optimisation- are combined whilst exploiting all available methods (algorithmic, heuristic, mathematical programming), labelling it “generate-evolve-optimise-critique.”
2.5.3 OTHER KNOWLEDGE DOMAINS The literature reviewed for innovation sources (§2.2) was readdressed for system decomposition methodology and theory. In economic input/output analysis, as employed by economic statisticians, the system element has been selected on the basis of the availability of data, and a logical classification of coherent economic activities (CBS 1992). Thus, the I/O analysis yields a suitable picture of the economic activities in a country. The economic statistics may also underpin environmental policy making, e.g. by calculation of the cumulative consumption and emissions for single types of products. To allow reliable use of the statistics, however, implies a retrofit of the models and system decomposition. Konijn, for example, used 'economic activity' - a subset of the industrial activities in a single SBI- code - to disaggregate economic sectors and to correctly relate economic data and physical reality (Konijn 1994). In the retrofit process it was revealed that parts of coherent 'economic activities' had been included in the statistics of a variety of
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economic sectors. No specific treatise, however, was found on the problems of decomposition and (re-use) of input/output analysis results. In system thinking, the function of an apparatus, plant, or product is the prime concern. In Life-Cycle-Assessment (LCA) this has been formalised in the requirement for a clear definition of the functional unit to which the net resource input and waste and emission generated in a production-consumption chain are to be related. In such a way, the net balance of the alternative packaging of for example a litre of milk can be compared for the cases of using a recycled glass bottle and a carton respectively. The case for LCA is argued as that it should open the way for (both product and process) innovation. The system elements in many an LCA study, however, have been selected for the purpose of analysis of emissions to the environment, and the net withdrawals (resource use) from that same environment, in order to relate everything to a single functional unit, e.g. packaging. The formal decomposition of products or systems subject to LCA appears not to have been addressed. The solution space following an LCA is limited to either product substitution, which implies replacement of the related production system, or improvement of elements of said production system. It remains questionable, however, whether the method offers useful information for process technology innovation because LCA takes the system structure for granted at any level of aggregation18. In computer science, system decomposition is addressed under the heading of “cohesion methods”, which according to Baylin is a well-known subject in computer system design and programming literature (Baylin 1990: 349). The subject relates primarily to how to arrive at a sophisticated and useful breakdown of (computer) programs or information system. Cohesion thus assumes the system decomposition is executed with the objective to arrive at a set of highly cohesive, loosely coupled set of modules. A number of cohesion principles or types can be distinguished, however. When cohesion is coincidental the system elements have no function, data or procedure in common, i.e. the decomposition does not serve a prior purpose. When a system decomposition exhibits logical cohesion, the elements perform certain logical classes of functions or procedures. In a temporal cohesive decomposition the modules or elements are related logically and by time of execution, but they do not necessarily share a common procedure. A decomposition exhibits sequential cohesion when no other relation exists than that output of one element provides input to the next. Procedural cohesion is achieved when all system elements share a similar procedural context, in other words when all elements exhibit similarity in how activities are performed. In a communicational cohesive system the elements all operate on the same set of data (object-orientation). Details and examples on these cohesion methods are given in Appendix A. 3. Finally, a decomposition of a system's functions exhibits functional cohesion when it suits to keep together related elements, keeps apart unrelated elements while at the same time avoiding duplication
18 The improvement of ‘the refining of crude oil’, for example, requires improved and new system elements and networked process system design. Its optimisation, modification or substitution for its performance in a single product-chain will have an effect on all other product-chains that depend on this operation.
Process System Innovation Sources 63
and conflict. Thus functional cohesion underpins an abstract, iterative method for the conceptualisation of a system's functional structure19.
2.6 Conclusions In academia presently a gap exists between studies on industrial sectors or economies, and chemical R&D and engineering on products and industrial processes. Integrated conceptual design of the petrochemical industry's systems above the level of single plants is a largely unexplored 'white spot'. Conscious attempts at structured or planned innovation for sustainability at and beyond the level of single plants appear to be largely absent. Process system engineering was identified as a resourceful body-of-knowledge to bridge this gap and address the research question elaborated in this thesis: how can technological or systemic innovation content be specified that enables a transition towards a sustainable petrochemical industry? PSE, however, focuses on the invention and realisation of single plants, and the central question addressed in process synthesis research is whether “the invention of chemical process designs can be organised, systematised, or even automated” (Siirola 1996: 3). In process synthesis research indeed methods are being developed to automate some parts of process invention. To date, however, the PSE-body-of-knowledge does not offer a procedure to specify process system innovation content20. Despite the suggestions by Grossmann and Westerberg (Grossmann and Westerberg 2000), conscious analysis or re-design of the industry system structure beyond single plants has hardly attracted attention. A literature review confirmed that the conceptual design of petrochemical complexes comprising multiple plants is a largely unexplored 'white spot' in process synthesis R&D. Thus, it is no surprise that true multi-scale process synthesis approaches that link the complex, single plant, unit operation and molecular level appear only to have been suggested (Charpentier 2002). In process synthesis the computer-based automation of the generation of and selection among design alternatives receives much attention. It is the work on conscious articulation of primitive problems into specific design problems (Rudd and Watson 1968; Douglas 1988) (Siirola 1996), however, that offer some building blocks for a methodology to explore process system innovation. From a limited literature-search focused on development of system simulation models and tools for process system design and synthesis, we have only found superficial coverage of the problem of devising suitable system decompositions. In none of the literature sources is a stop-criterion given for the opening of the box, i.e. the decomposition and the 'depth' of the model. Careful consideration of system decomposition, however, is of utmost importance to avoid unwanted ‘lock-in’ situations that limit the applicability of the model (such as in an economic I/O analysis and LCA). In PSE, the system decomposition of the industry adopted
19 Functional cohesion is one of the foundations of the method reported in §3.3 Functional modelling for process system innovation. 20 These observations are largely based on the literature reviewed to unearth previous work on methodologies useful for the specification of process system innovation content. This work is presented in detail in Chapter 3, this thesis and has been published in part as (Dijkema et al. 2003).
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appears to be considered trivial and the aggregate level of single process plants taken for granted. Cohesion methods, a topic in computer science, appear useful for system decomposition and modelling. In academic R&D the industry system structure is considered rather fixed and has remained largely unchallenged, except for the notion that the tasks represented in this structure may be integrated (Douglas 1988; Siirola 1996). As a consequence, the search for improvements implicitly is confined to the system boundary of the battery limits of individual plants, and the potential of networked process system innovations has remained largely unexplored.
3 Process System Innovation by Design
Somewhere, (…) between the specific that has no meaning and the general that has no content there must be, for each purpose and at each level of abstraction, an optimum degree of generality (Boulding 1956: 302).
For the sanity of the engineer and his chances of success in design, we would prefer the simplest possible mathematical model (Truxal 1972).
3.1 Introduction While 'sustainability' has been adopted as a strategic principle for business, it has been difficult to translate this notion into guidelines or recipes for technology and business development (e.g. Scholes 1999; Dijkema and Mayer 2001b). We conjectured that a transition towards a sustainable petrochemical industry21 requires innovation at all system levels, from reaction path to process system, from chemical plant to petrochemical complex or industry (Ch. 1). Such process system innovation reaches beyond traditional R&D and beyond the optimisation of proven technology, proven system concepts and established process networks. The overview of innovation sources (Ch. 2) revealed that there presently exists a 'gap' between the aggregation level of the economy or its sectors, and the topics addressed in chemistry, chemical engineering and process system engineering. According to Brennan “The chemical engineering profession has thus far been slow to develop a techno-economic taxonomy or classifications system, useful for understanding the structure and performance of the process industry sectors” (Brennan 1998: 255). We conjectured that innovation opportunities must exist that have never been explored systematically - process system innovations where explicitly the network structure is considered a degree-of-freedom. In this chapter, methods are presented to explore this 'innovation-space'. Thus, the second part of this thesis' central research question is addressed: how can technological or systemic innovation content be specified that enables a transition towards a sustainable petrochemical industry? The methods presented are based on system representation and characterisation using the input-output paradigm (Appendix A. 4). It is assumed that the function of a system, (Σ), is to generate a behaviour B to transform a set of inputs (Su) into a set of outputs (Sy), which relate the system to its surroundings (the external world). The performance (Ω) of a system is assessed by means of criteria or value functions (P).
21 A sustainable petrochemical industry is characterised by appropriate resource selection, effective resource utilisation, the avoidance of waste and emissions and a product slate that fosters a sustainable society (Dijkema et al. 2003).
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In section 3.2 the focus is on system modelling and characterisation for assessment of resource utilisation, the main indicator for sustainability (see Cadre 3-3: Effective resource utilisation). Input/output modelling, engineering thermodynamics and the stream-valuation concept allow formulation of value functions used in a performance assessment procedure. A priority list of weak performing elements provides a starting point for the search and specification of promising R&D themes. Subsequently, in section 3.3, a new method for the specification of innovation content is reported based on the concepts of functional modelling (Baylin 1990). Re- addressing system modelling and system decomposition (meta-model, Ch.1, p. 35) has led to a new modelling-decomposition-synthesis strategy, which serves as a basis for a procedure for the specification of process system innovation content. Throughout the chapter the industrial systems around aromatics (benzene, toluene and xylenes) are used to illustrate and test the methods.
3.2 Systematically towards innovation content?
3.2.1 MODELLING AND STREAM VALUATION When the Earth, its interconnected material cycles, and parts thereof are modelled as a system (see Cadre 1-1), in a single analysis the depletion of resources may be assessed as well as the fate of toxic materials such as heavy metals and harmful organic components. Using systems representation and characterisation based on the input-output paradigm (Appendix A. 4), its performance may be assessed with respect to resource utilisation and, preferably, world sustainability (Cadre 3-3 and Figure 1-6) (after Dijkema and Reuter 1999). The Club of Rome attempted such a modelling exercise using a systems dynamics approach (Meadows et al. 1972). A characteristic of the system dynamics approach, however, is that only aggregate (dynamic) relations are established for the underlying performance of technology. The structure and content of interconnected industrial systems is lacking. In refining, petrochemicals and metals, however, systems have evolved to a varying state of interconnectivity (e.g. Weissermel and Arpe 1994; Reuter 1998). Their content, structure, performance and utilisation are influenced by (1) present economics and know-how - the markets of feedstock, products, capital, labour, technology and knowledge (2) continuous change - induced by economic prospects, changing demands, emerging environmental problems, shifting regulation, strategies for sustainability, product innovation and the emergence of feasible novel technology and plant designs through process innovation. Technology required to realise conversions for the closure of material cycles, however, may not be feasible or available, which for example is the case for mixed plastic waste and for various grades of zinc- containing residues (Sas et al. 1994b; Südholter et al. 1996). The scope for change and the speed of adaptation are constrained by industry structure, company strategies including innovation, and the technology, economics and ecology of existing facilities, notably the scale-of-operations. The very existence of integrated petrochemical complexes implies interdependence or even entrapment. As a consequence, exceptions noted, trajectories for change of the petrochemical industry span decades. It is characterised by relatively slow dynamics of change. In the assessment, therefore, steady state can be assumed.
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System Decomposition Together, the process plants and complexes in the petrochemical industry are a single system (see Ch. 1, Figure 1-5). This can be modelled as a collection of system elements between which material and energy (exergy) are exchanged. Within each element a set of inputs (Su) is manipulated and converted to a set of outputs (Sy). In studies of the petrochemical industry, a single commercial plant within battery limits appears (see Cadre 3.1) to be the implicit system element of choice (cf. Dijkema and Reuter 1999). The system image of the petrochemical industry thus comprises a networked system that is decomposed into nodes and arcs. Single plants are the transformation nodes and the material flows are the connecting arcs. This is the model that has been adopted implicitly in chemical engineering and in most of the work in process system engineering.
Cadre 3-1: Individual (petro) chemical plants
In a logical decomposition of the petrochemical industry, the individual chemical plant appears to be a suitable system element candidate. In industrial practice the ‘battery limits’ represent a clear distinction between individual plants or processes and their surroundings. The ‘inside battery limits’ of a safe, environmentally sound, and economic industrial plant consists of many system elements. In chemical engineering these have been logically grouped in classes of unit operations, which include operations such as reaction, mixing, pumping, heating, cooling, distillation, extraction, flashing, compression, expansion etc. The classification is based on the recognition that one can model any industrial plant by a combination of unit operations. Their selection and physical implementation is a function of the transformation or Pmt-R required (Ch.1, Figure 1-1). A particular selection constitutes the physical embedding of any particular plant. Many industrial plants produce substances that are generally perceived chemical products, without the application of any chemical process. A traditional hydro skimming oil-refinery, for example, is not a chemical plant because it involves physical operations only, notably distillation. A chemical plant or process thus is characterized by the presence of at least one reactor. Its unique characteristic appears to be ‘transformation by chemical reaction of substances A, B, C etc. into products, substances D, E, F etc.’ Many types of industrial plants, however, employ chemical processes. Examples include power plants, waste incineration facilities, flue gas cleaning installations and some types of waste-water treatment. Some do include chemical reactors, such as margarine-hardening by hydrogenation in the food industry. In energy conversion, fuel cell systems include an electrochemical reactor while in cogeneration facilities the gas turbine combustion chamber is yet another type of chemical reactor. Traditionally, however, these systems are not labelled chemical plants because their purpose is not the generation of a chemical product. A precise definition therefore is: 'a chemical plant is a facility for the production of a chemical and includes at least one chemical reactor'. A petrochemical plant is a special class of chemical plant that uses petroleum-derived feedstock.
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Many chemical plants are part of industrial complexes, which together with 'stand- alone' individual plants make up the petrochemical industry. The existence of integrated petrochemical sites may both enhance and hamper the assessment of the petrochemical industry with respect to resource utilisation. The aggregate data available on complex performance provides a means to check the data of individual plants for consistency. As a result of integration the performance of petrochemical complexes is expected to be better than the simple sum of the individual plants. The results of assessments based on literature data of individual plants therefore can be biased. On the other hand, options for performance improvement can be masked by the very existence of petrochemical complexes, the structure of which might change considerably in case novel technology for existing plants is offered. The site-wide integration of technologies, however, in many cases is not so much governed by the scope of technology, but more by the type organisation, the quality of management, and by the prevailing economic incentives. Thus one may argue that rather than assessing the industry as an assemblage of individual plants, the industry assessment must also address petrochemical complexes, which can be decomposed into a set of interconnected plants. Thus, a more-or-less intuitive, or logical decomposition of the petrochemical industry has been formulated as a set of individual petrochemical plants, some of which are more closely linked by their location in a petrochemical complex.
Cadre 3-2: Petrochemical complexes
A petrochemical process site or petrochemical complex is a system element or system aggregate level that seems to neatly fit into to the hierarchy of system aggregation levels (Ch. 1, Table 1.2, p.16). The grouping of various chemical plants in a petrochemical complex offers significant economic and organisational advantages. Investment and operating costs may be reduced by shared utility systems (power, heat, cooling water, industrial gases) shared maintenance services, administrative and technological support, transfer of feedstock and products and reuse of waste via direct process linkages, site energy optimisation, e.g. by pinch analysis and site emission and waste management. As a consequence, in the petrochemical industry plants are hardly ever built as so-called stand-alone units because more margin can be generated within a petrochemical complex. Since the facilities investment represent considerable 'sunk cost', the increased earning power per facility may be at the expense of long-term flexibility caused by the introduced interdependencies, however. In regional development theory and location theory a complex is defined as a joint location of industries linked in a product chain. A petrochemical complex can then be defined as 'a number of petrochemical plants that are located in one another’s vicinity', where ‘vicinity’ is determined by practice, e.g. the existing pipeline infrastructure (Molle and Wever 1984: 98-99). Further to vicinity linkages, company linkages provide incentive for the formation of complexes and may justify a considerable geographical distance between production facilities.
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I/O modelling, mass and energy balancing Any system can be viewed as a network of system elements connected internally by relations or flows and connected to the external world via its set of inputs and outputs (Su, Sy). A stream of material can be characterised by its mass flow, its composition, energy flow or exergy flow. Since energy and exergy are thermodynamic state properties of a material, their value depends only on present conditions, notably material composition, pressure and temperature (see Appendix A. 2). A material flow's energy content and other properties such as carbon-content cannot be calculated, therefore, if mass flow and composition are unknown. In a node of the system or system element both mass and energy are conserved. The Law of Conservation of matter states that in the absence of nuclear reactions the mass of a closed system is constant. It applies to complex materials and individual chemical element (Carbon, Oxygen, Nitrogen etc.) alike. The First Law of Thermodynamics states that the energy of the Universe remains constant. Thus, the total mass and energy of an open system and its surroundings are constant. In other words, neither mass nor energy can be lost or generated, and for an open system such as a continuous chemical process, which is in steady state, the sum of the inputs equals the sum of the outputs22. Thus around each system several balances can be set up and completed for mass per chemical element, total mass and energy respectively. Variations in accumulation in the system over time can be included in each balance, so that finally the formula results:
• t1 T T κ = ∫to {u(t) •κu (t) - y(t) •κy (t)} dt (Eq. 3.1) Where u(t) = vector of input flows [flow unit/time] y(t) = vector of output flows [flow unit/time] t = time [time unit]
κu,y(t) = vectors of flow conversion factors to chemical element, mass, or energy [unit/flow unit ] κ• = net accumulation of chemical element, mass or energy [unit] In steady state, κ• = 0. The completion of an energy balance for a system or system element requires mass and composition of all inputs and outputs. A proper mass balance therefore is key to all other computations for system characterisation.
Stream valuation by labelling An experienced process engineer can quickly get an impression of a plant's performance using information from a mass and energy balance. Molle (1984) used mass balances to explain the location of refineries and petrochemical complexes effectively (Molle and Wever 1984). SRI (1989) published an overview of mass balances of industrial processes, which quickly gives an impression on the selectivity of the industrial chemistry involved (SRI 1989). Sheldon (1993) interpreted mass
22 In case the system is not in steady state, the effects of temporary accumulation or depletion of mass or energy stored in the system must be taken into account.
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balances to assess the real function of fine chemical plants (Sheldon 1993). In all these cases, however, implicitly some stream valuation is used. Generally, two perspectives are used to assess the performance of a particular production system or part thereof: economy and ecology. In the Brundtlandt definition of Sustainability, economy, ecology and society are related (World Commission on Economic Development 1987). In a much used conception of sustainability, 'People, Planet, Profit', these three dimensions return. We have left out the societal dimension explicitly in the assessment of production system performance because it would require a thorough analysis of system surroundings, economic structure, market dynamics, division-of-wealth (equity) and ecological impact. The economy and ecology do impact peoples lives, however - if economics are favourable, production systems will be realised and continue operations, jobs will be created and consumer needs will be fulfilled. If ecological characteristics are unfavourable, people will react either because their health or environment is at risk and demand change. The set of stream labels presented in Figure 3-1 is an attempt to combine the valuation of economic and ecological impacts. To allow operation of the system material and/or energy resources are extracted from natural cycles to provide feedstock and utilities. Their cost depends on availability or scarcity, market demand, taxes levied and regulation. The associated ecological impact depends on the origin, extent and characteristic of such extraction. Ubiquities such as seawater or air are neither scarce nor does their extraction pose a significant ecological impact. A long- term risk is involved, however because these may become subject to taxation. The processing of waste has a positive ecological impact and results in a fee. Using an economic perspective, in case a market demand exists, inputs are obtained at a cost, ubiquities are for free, and waste processing brings a fee. At the output side, main products and co-products are sold at revenue, which must lead to gross profits, i.e. revenue exceeds average total cost. 'Wanted' by-products yield at least marginal profits, i.e. revenue exceeds feedstock and operating cost. 'Unwanted' by-products include those sold at revenue less than marginal cost and those that must be disposed off at a cost. Main products that are in demand bring such revenue that a profit results under appropriate market conditions. Wanted by- products add to the margin realised by operating the system. Unwanted but accepted by-products remain in the cycle but do not add any margin for the operator of the system. Emissions in many cases cannot be avoided. In case regulatory restrictions apply, disposal requires treatment at a cost. The ecological impact of the output categories depends on their use and end-of-life characteristics. Unaccepted, unwanted by-products represent a loss from the system, will leave the industrial material cycle, and thus will directly impact the environment. Finally, emissions can be labelled constrained to limit their adverse ecological impact at a cost, and unlimited because of their perceived lack-of-impact, which represents a risk. The scheme illustrates that between inputs and outputs the economic and ecological perspectives often do not align: in the manufacture of many products, some adverse emissions or waste to the environment are accepted.
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impact impact impact (u, ch,eol) (u, ch,eol) (u, ch,eol) (u, ch,eol) (u, f f f f Risk Cost Cost Profit Profit Margin Margin - + Wasted Accepted Wanted Not Desired Allowed Limited ByProducts Emissions Reference Co-Products Main Products Main Output Labels Output System Industrial ife) l f- o nd- e Waste aracteristics, Primary Scarce Co-feeds Ubiquties Incidental Resources ch Feedstocks Input Labels se, or u Cost Risk Cost Cost Fee rigin, rigin, unction of o Environmental Impact f Economic Impact Stream Label (o,ch) (o,ch) (o,ch) (o,ch) none f f f f Legenda
Figure 3-1: Labels for streams around an industrial system.
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In electric power production, for example scarce resources are used to generate a wanted product, electricity, at the expense of unwanted thermal waste - cooling water effluent-, CO2 emission and solid waste - flue gas dust and slags-. Slags of coal-fired power plants are applied as road foundation material, however. Thus these have been 'upgraded' to a status somewhere in between unwanted waste and wanted by-product, as there is no revenue or net disposal cost. The classification in Table 3.1 has been based on the notion that any industrial process has at least one main product, the reference product. To enable reproducible calculations all process data are expressed as ratios: the quantity required for the production of 1 kg reference product. Usually, with the reference product a primary feed is associated which delivers the bulk of the product. Often, a process has been specifically designed for co-products and by-products result for which the system has not been intentionally designed. These may be chemicals that are produced in small quantities, and that can be sold at a net profit margin, such as for example the C4 stream in a steam cracker. Over time, stream labels around a process system may change. By-products, for example, may become key to process economics and thus be labelled co-products.
Table 3.1: Overview of stream labels around a system or system element Stream Label Symbol Suffixe │ Symbol Suffixe Inputs I Outputs O Scarce resources S Main Product M Primary f Reference r Co-feed c Co-product c Incidental i By Product B UbiquiTies T Wanted/Desired d Waste W Not desired Accepted n Wasted w Emission E Limited l Allowed a Grey-box approach -see text Process-related p Process-related p Utility-related u Utility-related u
Note: The set of Inputs I, for example has subset Scarce resources S, Ubiquities T and Waste W. Adopting a grey-box model( Figure 3-2, p.74), these may be process related or utility related.
Illustration: Aromatics production in a steam cracker complex The classification summarized in Table 3.1 can be applied to a typical aromatics plant that processes pyrolysis gasoline or C5+ -gasoline. Pyrolysis gasoline is a by-
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product of steam cracking (see Chapter 4) and consists of simple aromatics, non- + + aromatics, olefins (C5 ) and complex aromatics (C9 ). The non-aromatics, olefins and diolefins present are recovered and recycled to the steam cracker. To that end, - olefins/diolefins are selectively reacted with hydrogen and recovered as a C5 cut by- + product. A mixture of simple aromatics is isolated and a C9 fraction is recovered as by-product that has fuel value. Often, aromatics plants are designed for the production of Benzene and para-Xylene only. Sometimes, styrene recovery is feasible. This is due to lack-of-demand for the other aromatics present in pyrolysis gasoline, viz. toluene, m-xylene and o-xylene. Therefore, after separation of benzene and p-xylene, these simple aromatics are converted to benzene and p-xylene. To operate, the aromatics plant requires fuel, steam, electricity and cooling agent (Chauvel and Lefebvre 1989a). In the past decade, in some aromatics facilities recovery units for styrene have been implemented. From this description, the labels given in Table 3.2 seem appropriate.
Table 3.2: Stream labels for an industrial aromatics complex Inputs I Outputs O Pyrolysis Gasoline S f p Benzene M r p Hydrogen S c p p-Xylene M c p Fuel S c u Styrene B d p
Electricity S cu C5-C8-non-aromatics B d p + Cooling agent T c u C9 B n p Steam S c u Condens Water B n u Catalysts S i p Spent Catalyst B w p
In every system, some energy conversion takes place to complete the system's operation in a finite time-span. In a chemical plant, the chemical transformation of feedstock to desired chemical product also involves an energy conversion. The Second Law of Thermodynamics dictates that part of the Gibb's free energy ∆G is converted to waste-heat. When the conversion of feedstock turns some chemical energy ∆G into power and heat and the generated amounts exceed the plant's internal demand it becomes a net exporter of heat or power. An industrial ammonia plant, for example, has been labelled a power plant with ammonia as a lucky by- product (Montfoort 1993). A distinction between 'process' and 'utility' related streams therefore appears useful, where utility includes non-energy related streams such as lubrication, inert gas, process water and organic solvents. Thereby a system is decomposed into a process subsystem and utility subsystem or subsystems. At the process-side streams are subject to some chemical reaction or some physical operation. A significant part of the input ends up in the output. Utility streams enter and leave the process system to supply or withdraw energy from the system or to provide other utility functions, e.g. to facilitate separation or product purification via solvent extraction. They are not chemically converted with the process streams. The utility category consists of streams that enter and leave the process-side unchanged except for their energy and related physical state (P, T, composition,
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phase, momentum). An example is steam that is used in a great many industrial reactors as a diluent and energy supplier. This classification is a 'grey-box' approach (Figure 3-2) because it requires limited knowledge of the inner workings of the system. The additional classification comprises two mutually exclusive stream categories as included in Table 3.1. Since the other labels remain valid, this sub classification applies to both the generators of industrial products and of the generators of utilities!
Process Process input 1...m 1...n Process Outputs Side
Energy transfer
Utilities Utilities input 1...p Side 1...q Utilities output
Mass Circulation
Figure 3-2: A process system represented as a 'grey-box.' In a number of industrial operations the distinction between process and utility is ambiguous. In cement kilns, for example, co-fed organic or polymer waste reduces and replaces fuel input (utility) and feedstock (process). The kiln utilizes the polymer waste energy and minerals content simultaneously (e.g. Vanderborght and Dijkema 1996; Delissen 1997; Verhoef et al. 2002a). In the grey-box approach the waste co- feed to a cement kiln would be labelled a process-stream: in the petrochemical industry and in other process industry energy supply through exothermic reaction of part of the feedstock is common practice. The grey-box approach allows an additional check on the systems energy balance and allows one to distinguish between two categories of process system improvements. These are (1) improvements that do not directly affect the process, such as end-of-pipe and utility system improvements; Examples are optimal heat- exchanger networks and the closure of industrial water-cycles and (2) improvements that do affect the process, such as changes in feedstock quality or composition, catalysts system, process technology employed, process system design including recycle structure as a function of feedstock and product labelling.
3.2.2 ASSESSMENT CRITERIA: LOSSES AND EFFICIENCIES In this section the quantitative criteria are formulated that can be used in the assessment procedure using input/output modelling and stream labelling. Preferably, these criteria can be applied to each type of system element, ranging from unit operation to national economy (Table 1.2).
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Effective resource utilisation expresses the notion that depletable resources that have been extracted from the earth or from its ecosystems in order to satisfy human need must be utilised to their full potential, both with respect to quantity and quality (see Cadre 3-3). The development or selection of criteria suitable for an assessment of resource utilisation is not trivial. In many (petro-) chemical operations hydrocarbon material of fossil origin is both feedstock and energy supplier. Resources and material flows exhibit properties that are conserved in the Universe or part thereof, such as mass and energy. Entropy, which relates to quality, however, is a non- conserved property. Thus, while mass and energy cannot be lost in the Universe, it is implicit that something is 'lost' by ineffective resource utilisation: loss of quality and loss from the system to the surroundings.
Operation performance criteria or a life-cycle approach? Life-cycle costing and environmentally oriented life-cycle analysis are so-called cradle-to-grave analysis where it is conjectured that for proper analysis and comparison of systems and their alternatives one should take into account bringing- into-being the system studied, expected life-span of operation and its end-of-life. Boustead (1979) has coined the terms primary, secondary, tertiary and quaternary resource/energy use. Primary resource/energy use is directly related to production - to create the product and to sustain system operation. Secondary denotes the resource/energy use for creation of the system's inputs. Tertiary and quaternary denote resource/energy use to bring the system into being and producing the construction materials respectively. (Boustead and Hancock 1979). A petrochemical plant consists of thousands of tons of concrete, steel and other material from energy/resource intensive production. In petrochemical operation, at typical annual throughputs of hundreds of thousand tons over a lifespan that typically exceeds 20 years, millions of tons of materials are converted in these facilities. Thus, in cradle-to-grave analysis, total energy/resource use of a petrochemical production facility is dominated by its primary material/energy use. Efficiency improvement at the expense of increased tertiary and quaternary energy/resource is favourable except for extreme cases because at end-of-life, concrete, steel and aluminium can be recycled using the available industrial infrastructure for primary production obtaining recycled material at a fraction of the primary resource and energy use for virgin material (Verhoef et al. 2001). Secondary resource/energy use is significant for many petrochemical plants. The evaluation must focus on primary resource/energy use, however because the assessment objective is to identify and prioritise system elements with respect to non-renewable fossil resource utilisation.
Physical or economic assessment criteria? Since we are after the specification of innovation content for improved sustainability, both ecology and economy appear to be required in some assessment. Economic criteria, however, appear unsuitable for quantitative assessment due to: 1) Unavailability of data. Petrochemical plants produce undifferentiated commodity products. Thus, one competes by cost of goods sold. Cost leadership can be established through economy-of-scale, which amongst others can be achieved by
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Cadre 3-3: Effective resource utilisation
The future of the petrochemical industry depends on the continued availability of and access to suitable resources. In our present industrial economy, however, for the greater part non-renewables are used. High quality fossil resources represent a state of low entropy. When used in petroleum refineries and the petrochemical
industry these are degraded eventually to CO2, water, and heat. This 'downhill' conversion process implies a loss of well defined and highly ordered structures of the components present in fossil feedstock. The reverse operation, the 'uphill'
conversion of CO2 and water to suitable structured petrochemical feedstock or energy resource, requires that part of the energy restored in the components formed is (shaft) Work done on the “uphill” conversion system. According to the Second Law of Thermodynamics, in every energy conversion that takes place in a closed system in interaction with it's surrounding, inevitably some quality of energy is lost, i.e. exergy, the potential to do Work. According to Georgescu-Roegen (1991) there is a true misunderstanding about “the entropy of matter. In mechanical engineering, for example, one studies the engines or apparatus for energy conversion to minimise quality loss or the degradation of energy resources. There is a tendency, however, to study energy conversion in isolation from the chemical conversions involved. For the greater part, however, energy supply for heat engines is by the combustion of fossil fuels, a chemical process. In the combustion of fuels derived from crude oil complex organic compounds
are destroyed and forever reduced to CO2 and H2O, which is an extreme example of degradation of material resources. The combustion process itself and the
associated emissions into the environment of CO2, SO2 etc. are an example of dissipation of matter, a term first introduced by Planck (1897). In the combustion of natural gas, a fuel that may consist of pure methane, for example, the gas is
mixed with air and converted to a mixture of nitrogen, oxygen, CO2, H2O and a host of other products of (incomplete) combustion and compounds present in the air used. Another example is the metals extracted from natural ores. These will also become completely dissipated in the environment eventually. A rather extreme example is dispersion of lead by the use of ethyl-lead compounds in motor-gasoline, a practice that has presently been phased out in large parts of the world. Both the dissipation of energy and of matter are forms of degradation, or entropy generation. As the entropy increases, the quality of energy or matter is reduced. A consequence of, for example, the mixing of essentially pure components, a not uncommon operation in the petrochemical industry, is an increase of entropy or degradation. Effective use of resources thus implies that one strives for minimal dissipation of matter (Planck, 1897) (cited in Planck 1926; Georgescu-Roegen 1991). Effective resource utilisation therefore is defined as the prevention and postponement of all forms of degradation of resources to the maximum extent.
Process System Innovation by Design 77
continued process innovation, by efficient organisation and by a sound investment strategy. Confidentiality of the underlying economic data is the norm, and it may be expected that improving process economics has been a main incentive to unearth process innovations throughout the industry. 2) Market dynamics. The flexibility of petrochemical clusters to meet market fluctuations is very limited (Kuipers 1999). Petrochemical economics dictate plant utilisation of 75% or higher to create a net return on asset capital employed. Individual plants, however, will only be phased out in case they are worn-out or do not create sufficient marginal revenue (Ch.1). Petrochemical markets exhibit cyclicality in capacity and supply-demand balance. The cost of capital equipment, labour and the value of products are influenced by internal market structure and dynamics. The price of its dominant feedstock, crude oil, is severely affected by the OPEC, which attempts to maintain a favourable world supply-demand balance. Thus, market prices are no suitable indicator of the prospect of future resource scarcity, environmental impact or sustainability. 3) Mismatch of economic incentives and conditions for innovation. In the life cycle of a petrochemical plant bringing-into-being the facility is an important phase. The initial capital-invested must be recovered through the operational margin throughout the plant's life span. In a mature market, however, realisation of a new facility is only advantageous when the total cost of production in the new plant is less than the marginal operating cost in existing plants (Ch.1). Older possibly less efficient plants are only phased out gradually, which is confirmed by a recent overview of worldwide polypropylene production (Linse 2002). Thus, considerable time may pass before one may reap the benefits of increased economy-of-scale and efficiency realised through innovation. In addition, to reduce risk and time-to-plant completion, a rule-of-thumb in many an investment project is to stick to 'proven technology', i.e. technology that has been proven to function reliably in at least one other industrial application of similar scale. Innovation activity - as measured by number of patents filed - is high throughout the chemical industry compared to other sectors (Stobaugh 1988). The number of fundamentally new processes introduced to the market, however, is limited, some processes having been around since the beginning of the past century (e.g. Jennings 1991; Satterfield 1991). This may be due to market dynamics and economic incentives addressed. A large time-to-market characterises fundamental innovations, such as a new synthesis route, and slow diffusion to the market of major process innovations, such as entire new plant concepts. Shareholders, however, increasingly demand short-term profit increases. As a consequence, many companies have opted to move away from exploratory R&D on petrochemical production systems. As a corollary, the analysis of current economic conditions hints at the existence of an untapped reservoir of major process system innovations!
A Second-Law based criterion? Any system, including chemical process systems or reaction systems, can be considered a black-box where the transformation effected involves a change in
78 Process System Innovation by Design
Internal energy, ∆U23, between input and output materials and some exchange of Work w and Heat q with the system's surroundings (Figure 3-3). Internal energy is a state property (Appendix A. 2). According to the first law of Thermodynamics,
∆U = q + w (Eq. 3.2) Enthalpy is a state property defined as
∆H = ∆U + ∆(PV). (Eq. 3.3) It follows from eq. 3.1 and 3.2 that in case only PV work is allowed on a system (i.e. no shaft Work, w=0) that ∆H = qp. According to the Second Law of Thermodynamics the sum of the entropy changes in the system and its surroundings can only be positive or zero. Entropy, or disorder, is defined as
∆S = q / T. (Eq. 3.4) Whenever a transformation process proceeds, changes occur both in the entropy of the materials involved and the entropy of the system surroundings. According to the Second Law, the created entropy σ is given by
σ = ∆Siirr., created = ∆Ssystem + ∆Ssurrounding >= 0 (Eq. 3.5) The Gibb's free energy of a system is defined as:
∆G = ∆H - T∆S (Eq. 3.6) It has been shown that the total Work requirement of a process is given by Eq. 3.7 (after Denbigh 1956):
wt = T0 •σ + ∆G0 (Eq. 3.7)
Thus, for a process where materials enter and leave at standard conditions (Po,To) the total Work requirement equals the change in Gibb's free energy plus the lost work due to irreversibilities. This is illustrated in Figure 3-3.
The formal definition of Exergy or Availability A resembles that of G24:
Ex = A = (H-Ho) – To (S-So) (Eq. 3.8) B is a state property that can be computed for any stream. According to Eq. 3.7, B equals zero for heat qP exchanged at the reference temperature T0 (H=Ho; S=So). The exergy of a heat reservoir or flow is given by the familiar Carnot factor:
Ex = A = q (1 – To/T) (Eq. 3.9) Due to unavoidable irreversibilities, the exergy balance around any real process system cannot be completed. A proper exergy balance of the petrochemical industry
23 In eqn. 3.1 - 3.10, the change in property X (X = Ex, G, H, S or U) between input and outputs is denoted as ∆X = Xout - Xin 24 Gibb's free energy is a state variable that combines enthalpy and entropy change, accounting for any change in conditions (P,T,x) associated with the transition; exergy or availability denotes the work available or required when transforming from the present state to standard conditions.
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or parts thereof can be set up, however, to calculate exergy loss, ∆Exloss. The exergy loss that is irrevocably related to the system's implementation and operation is calculated from the exergy change represented by the material transformation, combined with and the net other exergy inputs or outputs of the system. The exergy of materials relates to the Gibb’s free energy at standard conditions (Po,To). Since G is a state property (see Appendix A. 2), whether a chemical conversion takes place in the system or whatever its exact route is irrelevant for the analysis25.
Process System Inputs Outputs G
To Sirr. Heat (q)
Work G>0 G<0 Work
Figure 3-3: Work and a process system. In case ∆G > 0, Work needs to be delivered to the process; in case ∆G < 0 the process can deliver Work.
Results from inventorying feedstock, products and utilities for mass and energy balancing can be used to calculate the exergy value of all streams around a process. Exergy loss is obtained as
∆Exloss = ΣExin - ΣExout (Eq. 3.10)
∆Exloss = Σ(φm •∆G0) in - Σ (φm •∆G0 )out
+ (Σwin - Σwout )
+ (Σ qin (1 – To/Tin) - Σ qout (1 – To/Tout) (Eq. 3.11)
where φm indicates the material streams.
According to Eq. 3.7, the theoretical amount of Work associated with a chemical transformation can be determined from a Gibb's free energy input/output balance of feedstock and products by assuming 100 % reversible conversion. The delivered actual amount of work, wact , will be less due to the process implementation selected
25 It is safe to assume for most industrial processes the final state of both inputs and outputs of a process system are standard conditions P0 and T0 Notable exceptions of course are steam, cogeneration and heating systems
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and irreversibilities. The minimum amount of work required for an endothermic process equals ∆G0, the actual amount wact supplied to the process must be larger:
wact = ∆(Σ (φm •∆G0)) + ∆Exloss ; ∆Exloss >0 (Eq. 3.12) Thus it appears exergy loss is a basis for a suitable criterion for the assessment of resource utilisation. In the assessment of individual plants or system elements a more pronounced 'landscape' impression of the petrochemical industry is obtained when the indicator is normalised by division with the minimum achievable change in exergy
θ =∆Exloss / ∆(Σ (φm •∆G0)) (Eq. 3.13) θ could be labelled a 'Thermodynamic distance to target'. An appropriate thermodynamic efficiency for a process is
η = ∆(Σ (φm •∆G0))/ wact (Eq. 3.14) Substituting Eq. 3.12
η = ∆(Σ (φm •∆G0))/ (∆(Σ (φm •∆G0)) + ∆Exloss ) (Eq. 3.15) In industrial practice this thermodynamic efficiency may be down to only a few percent due to irreversibilities. In exothermic processes, θ can assume a negative value. In such a case, a transformation that theoretically could supply work has been implemented such that a net input of work is required for the operation to complete!
Assessment criteria: losses and efficiencies In the previous section we have identified exergy as an indicator energy quality. Due to the internal irreversible operation of a system there is always some internal exergy loss associated with the working of any system The First Law of Thermodynamics implies that there cannot be an internal energy loss, The Law of Conservation of matter implies there cannot exist an internal mass loss in a process system. Using stream valuation, however, external losses can be defined as mass, energy or exergy transferred to the system surroundings that cannot be utilised in the system or in its surroundings without further processing. Using the set of stream labels summarized in Table 3.1 (p. 72), industrial systems can be identified where mass loss from the system occurs, for example in the form of waste material or CO2. Similarly, energy can be 'lost' or wasted in the form of heat that is rejected to the environment, which is a common approach in large-scale electric power generation. External mass loss and external energy loss can be calculated. An overview is given in Table 3.3. Examples of external mass loss are the flue gas from a process furnace, light-gases that are being flared, waste, spills, and fugitive emissions. Associated with these streams is an external energy loss. Other external energy losses from closed systems are radiation losses, and notably heat removed from the system by cooling water or in cooling towers. The set can be used in the petrochemical industry and beyond at any aggregate system level (Table 1.2, p.16); its application is not limited to this industry. It helps to understand the (mis)use of the term 'energy consumption' such energy either ends up in the product or goes unnoticed as external system loss.
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Table 3.3: Formulation of a sound criterion is possible yes / no Type of Loss Criterion Internal External Mass No Yes Energy No Yes Exergy Yes Yes
For streams around a process system or part thereof (Figure 3-1, p.71) all (sub)sets of streams as indicated in Table 3.1 (p.72) can be completed by assigning valuation labels to all streams around a system. External losses per unit main product and system efficiencies can be defined for any conserved property. Thereby, a set of performance indicators is defined whereby an impression or “fingerprint” is obtained of system performance in relation to its surroundings. Each performance indicator has a unique value function: Reference Loss - any scarce resource that does not end up in main product:
La = ((Σ I(S) - Σ O(M)) / Mr) (Eq. 3.16) Product Loss - any scarce resource that does not end up in 'desired' products:
Lb = (Σ I(S) - Σ O(M, Bd ) / Mr) (Eq. 3.17) Emission Loss: any scarce resource that does not end up in products
Lc ((Σ I(S) - Σ O(M, B) / Mr) (Eq. 3.18) Total Emission Loss: any input that does not end up in product or product utilities
Ld = ((Σ I - Σ O (M, B)) / Mr (Eq. 3.19) Balance Loss:
Le = (Σ I - Σ O)/ Mr (Eq. 3.20)
It follows from the system balance equation that for mass and energy Le = 0, whilst for exergy Le> 0
By selecting Scarce Resources S as a basis for calculation La, Lb and Lc, a net negative loss may result for systems that upgrade Ubiquities such as air or Waste material by incorporating part of this material in some of their products. In some systems, this of course is a basis for their economic feasibility ('make money out of thin air'), but it also offers a means to identify the dependence of systems on the free use of ubiquities and their vulnerability with respect to changes in the applicable regime. In addition, it provides a quantitative affirmation of the reuse of waste material, which may also become scarce resource for other production processes . To obtain values for Losses that relate to Scarce Resources only, the incorporation of Ubiquities and Waste Material in Products must be corrected for. This requires a further opening of the black box and additional assumptions because this
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information often can only be estimated from a system mass and energy balance and the applicable overall stoechiometric chemical reaction26.
The indicators La…Ld can be calculated for the entire system or for the process or utility-side respectively. Notably comparison of La…d and La…d, p will yield information on the amount of utilities required to operate a particular process system, and where the utility material or energy supplied does end up. As a matter of course, the stream sets can also be used to define system efficiencies for materials and energy use, such as: - the reference efficiency:
ηa = Σ O(Mr) /Σ I(S) (Eq. 3.21) - the product efficiency:
ηb = Σ O(M, Ba) /Σ I(S) (Eq. 3.22) - The emission efficiency:
ηc = Σ O(M, B) /Σ I(S) (Eq. 3.23) - The total emission efficiency:
ηd = Σ O (M, B) /Σ I (Eq. 3.24)
La and ηa directly relate to the primary objective of the system analysed: most continuous chemical plants are designed for the production of a single chemical product, a plant with a number of co-products being the exception. When these indicators are low, a substantial loss from the system occurs.
Lb and ηb relate to economic objective of a system, i.e. a process may be designed for a main product and a range of valuable by-products to realise sufficient margin. Loss b is the amount of feedstock material or energy that is either lost to unwanted products that must be sold at a negative margin or as outputs classified as emissions.
Lc and ηc are indicators of the total flow of material or energy required to effect the transformation in the system assessed. The material efficiency ηc must be close to or equal 1, and Emission loss Lc must be close to or equal zero, except for cases where there are large process-related emissions or downgrading of by-products to utility material.
Ld and ηd are meaningful to single out system elements (chemical plants, chemical complexes) that require a large flow of utilities to sustain their operation. This utility use can be a cause of a low energetic efficiency of these process systems because all these utilities need to be flow around the system and recovery is required of spent utilities. Similar to loss Lc, Total emission loss Ld must be close or equal to zero. A significant value of Total Emission Loss d implies that there are large process-
26 In the petrochemical industry, oxygen from air for (partial) oxidation processes is the most commonly used Ubiquity. Waste materials are hardly used. In the assessment of the current system, therefore, to obtain corrected values for L can be based on an element balance for oxygen. Assuming that any organic feedstock not accounted for in O is converted to Emission of CO2 and H2O allows to complete the material balance for each system.
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related, utility-related emissions or that for example unwanted organic products are downgraded to utilities, where they are eventually converted to CO2 and H2O.
Together, ηa…d and La….d provide a “fingerprint” of the system element with respect to resource utilisation. For any higher system level (complex, industry), combined with capacities installed the La….d provides an impression of relative importance of system element losses.
3.2.3 ASSESSMENT PROCEDURE The modelling and the assessment criteria have been integrated in a logical procedure for assessment of the petrochemical industry: 1) Inventory and define the system assessed a. System: select system boundary and identify the petrochemical plants within the boundary and estimate the nameplate capacities installed. b. System elements: assemble the information required per petrochemical plant as for a 'typical' plant, viz. (1) Process description (2) Set of input / output (3) Capacity range commercially applied;. c. Inputs and outputs: Except for heat and electricity these are substance flows. A set of input/output data set that represents a typical plant must be assembled, validated and completed. Underlying information must be assembled that is required for the determination of mass, energy and exergy properties of inputs and outputs. 2) Obtain quantitative system image for system evaluation: d. System performance: After assignment of stream labels, system losses and system performance indicators can be calculated. Using installed capacities, an indication of Losses can be calculated. The procedure can be applied to a petrochemical plant, a subsystem thereof, or a sector of the industry or the total system. e. Networked industrial systems: A total material and energy balance of interconnected petrochemical systems can be computed from the capacities installed and the input/output characteristics of typical plants. 3) System evaluation and analysis interpretation f. 'Fingerprint': a comparison between the four efficiencies will provide a first insight in the effectiveness and selectivity of the process system and system elements assessed. g. Prioritisation of the elements of each system analysed. This can be done with respect to various indicators.
Upon completion of this procedure a snapshot of industry structure, content and performance may be obtained, as well as a priority-list of weak system elements and indication of root causes.
Ad 1) Inventory and define the system assessed In this procedure a logical static system model of the petrochemical industry is adopted. The industry is viewed as a structured collection of networked chemical
84 Process System Innovation by Design
plants. At both these aggregate levels the Laws of Conservation of Matter and Energy apply. The system boundary must be selected to include large-scale petrochemical plants for undifferentiated, commodity products. Since the focus is on improvement of current systems and technologies, the product range is fixed. Some of these products, however, are directly extracted from intermediate oil refinery products. Therefore, system boundary and feedstock restrictions must accommodate inclusion of, for example, refinery production of aromatics from reformed naphtha and propylene from cat-cracked gases. Often in system assessments, only information is available from open literature. Such data sets often consist of vendor-supplied data or aggregated input/output data for a 'typical' plant. The limitation to open literature sources is hard to overcome, as current performance data on existing petrochemical plants is considered strategic information, because it is process innovation by which the mature petrochemical industry competes (Ch.1). This kind of information is assembled, aggregated, made anonymous and exchanged via consultants for benchmarking purposes and the industry is extremely cautious to expand the exchange of quantitative information (Dijkema and Mayer 2001a). Using open source data a somewhat dated image of the industry's plants performance is obtained, certainly not an image of current 'Dutch industry', nor the performance of an individual company. Open source data on petrochemical complexes, the industry and parts thereof is even more scarce. Construction from individual plant data is possible, however, assuming that synergies achieved in industrial chemical complexes are exploited and reflected in the labelling of streams adopted (§ 3.2.1, p.66). A fairly extensive publication of 1990 name-plate27 capacities is available (Anonymous 1990), which can be augmented with material from various other sources. Thus, soundness, speed and simplicity can be matched to the magnitude of the system addressed, time and data available. Using the data available, a sufficient 'proxy' to industry performance is obtained for first prioritisation between system elements (see § 4.3.2, p.123 for an example). To validate the results, the data used can be compared with company or consultant data and industrial complex or national economy aggregate data. Complete data sets on industrial plants are extremely hard to find and there is no clear standard of representation of performance data. Thus, Input-Output analysis combined with the valuation of streams as introduced in this chapter is to be adopted as a standard of representation. Data sets from the literature must be converted prior to their use in the assessment. Data reconciliation involves a check for data-consistency and completeness per data set on an individual plant (an example is given in Appendix A. 6). To construct a complete the process for useful and sufficiently reliable results the following may serve as a guideline:
27 The so-called name-plate capacity is the production capacity for which a chemical plant originally is constructed. Over the years, so-called 'capacity-creep' occurs for a great many plants through operating experience, plant changes, debottlenecking and/or revamping. Such progress often remains the proprietary knowledge of plant owners.
Process System Innovation by Design 85
- with respect to corrections, assumptions must be underpinned on a case-by case basis by intricate process knowledge. - with respect to additions for completion of a petrochemical plant's mass balances, assume that a deficiency (i.e. more mass going into the process than
going out) is caused by the generation of light gases that are emitted as CO2 and H2O. This assumption can be considered valid, since most petrochemical process schemes include an off-gas treatment section that remains otherwise unspecified, whilst 'hydrocarbons' can always be utilised as fuel after proper
treatment. The carbon and hydrogen thus lost will eventually end up as CO2 and H2O. - the specific energy content of streams not reported in a particular data set can be estimated. However, since often nothing is known about the energy content or the application of these streams, for the analysis assume that these are zero. Mass and energy balancing can be used to check the validity of data obtained; with a few assumptions the mass and energy balances can be completed. However, mass loss La, Lb and mass efficiency ηa, ηb do not require complete datasets, they immediately give an impression of the performance of the process. Calculation of these indicators does not require an assumption with respect to the fate of the external mass loss!
Ad 2) Obtain quantitative system image for system evaluation Simple criteria are to be preferred in the assessment because the system analysed is extensive, its dynamics are relatively slow and data availability is limited. The modelling approach developed allows the use of conserved properties (mass and energy) and for one to derive the related indicators La…e and ηa..d. Combined these provide a fingerprint of system performance. The calculations can be based on input/output data, a few assumptions to satisfy mass balances and system capacities installed28. In addition, losses of type a,b, c and d for energy expressed as Lower Heating Value were calculated. These calculations require the combination of material flow and composition data with conserved properties (mass, energy). Under the assumption that most products and resources are at standard conditions, information from thermodynamic property tables suffices29 (Stull et al. 1969).
Should exergy be used as a criterion in the procedure? With proper precautions, exergy, a non-conserved property, can be used to assess system resource utilisation (Table 3.3, p.81). Exergy loss or efficiency appear to be perfect indicators for one to obtain a quantitative system image because exergy- based indicators express the system's internal and external utilisation of thermodynamic potential. In a number of early case studies on styrene and natural gas derivatives, however, it was found that the use of exergy-based indicators in the
28 Since it was neither the objective nor possible to judge the actual situation in individual production locations, the data used relate to the situation in or before 1990 are considered to be suitable. 29 Of course, many processes and product flows in the petrochemical industry are at elevated pressure. The energy-change with respect to the reference state is small, however, even for significant pressure increase. Care has been taken to use data of the appropriate phase (gas, liquid, solid).
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assessment of networked process systems is difficult and data-intensive and yields subjective results. It appeared to be impossible to establish accurate exergy values of non-pure substances such as oil products. These are composed of many chemical components and the precise composition simply is not available. Thus the exergy of a steam cracker feed such as naphtha must be estimated. Typical mass and energy values (as LHV), however, almost always are available. At the level of 'a network of petrochemical plants' the results of the case studies were similar when using either (labels + energy)-based or exergy-based indicators. Inspection of these results revealed that many petrochemical processes exhibit similar exergy and energy losses. These processes involve the rearrangement only of hydrocarbons, which results in a significant enthalpy-change but a low entropy creation. When prioritising the element's performance of the system analysed (step 3), the use of exergy indicators only results in a different priority-list when the enthalpy change and the entropy effect of a reaction are comparable. Notably partial oxidation processes do possess this characteristic. Finally, whilst exergy appears to be an objective criterion based on the Second Law of Thermodynamics, in a system's context it is not. “But what has made the problem of entropy truly exasperating has been the general fashion to extend the denotation of that term to problems other than the transformation of energy” (Georgescu- Roegen 1991). Exergy values shaft-Work above all other manifestations of energy, for example complex organic chemical compounds. The heat liberated due to oxidation cannot be converted entirely to Work but is still exported from the system as a valuable by-product (cf. Denbigh 1956). While exergy is an objective measure of the potential of a substance or substance flow to do Work, our industrial society requires and utilises a significant amount of substances and energy carriers that represent a low potential to do Work. Labelling streams thus appears to be more suitable to reflect current status of our industrial societal needs than the 'single but thermodynamically sound' property exergy. In the subsequent search for improvements qualitative exergy analysis can help unearth the root cause of low resource utilisation and help specify novel system concepts. On the basis of early case study results, we concluded that in the assessment of networked system resource utilisation, a proxy of exergy is to be preferred that can be reliably and reproducibly computed and that the indicators La…e and ηa..d. are such proxies of exergy. These indicators are based on mass and energy balancing and stream labelling. Together, they provide a fingerprint of system and system element performance with respect to resource utilisation.
Ad 3) System evaluation and analysis interpretation The objective of the analysis is to develop a quantitative image of the production system and its parts. A common objective of industrial process systems analysis is to establish the process’ bottlenecks that limit plant capacity or plant performance. Once established, these provide starting points for plant changes, revamp studies and R&D. By analogy, at the aggregate level of networked industrial systems also bottlenecks or weak elements may be present where resource utilisation is less effective than in some or all other elements of the system. The assessment objective
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thus is to determine the position of processes relative to each other, in order to obtain a global priority of weak elements as starting points for the search for improvements for improved resource utilisation.
Illustration: Assessment of the Dutch Aromatics System Assessment of the Dutch industrial aromatics system in 1990, using name-plate capacities reported in (Anonymous 1990) and process information available in literature data (Chauvel and Lefebvre 1989a) serves to illustrate the approach. At the time, the Dutch industrial aromatics system consisted of some 40 petrochemical plants. An aggregate overview of the system is given in Figure 3-4. In the BTXProc subsystem, Benzene (B), Toluene (T) and Xylenes (ortho-Xylene, oX and para- Xylene, pX) are produced from pyrolysis gasoline and reformed naphtha. These intermediate are co-products of steam cracking of naphtha and crude oil refining respectively. The purified individual aromatics serve as intermediates for a number of petrochemical production chains that lead to, amongst others, polystyrene, styrene copolymers such as ABS, nylon and polyethyleneterephtalate (PET).
B Crude oil Refinery BTX plant T
St. Cracker
Cokes Coke oven oX pX BTXProd
B Process Process Polymerisation
PS T ABS Nylon etc.
oX Process Process Polymerisation pX BTXCon
Figure 3-4: Overview of the Dutch industrial aromatics system.
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Analysis of the industrial aromatics system
The overall mass efficiency ηb of the Dutch aromatics system is some 89%, and annually some total 1.3 Mton of material is ‘lost’ by degradation to inferior, unwanted by-products and emissions - mainly as CO2 and water -. The overall energy efficiency ηb is some 77%, annually some total 110 PJ is ‘lost’. The associated energy is removed from the system as waste-heat by cooling, via flue gases or in the form of unwanted by-product flows. The results for the aromatics system are presented in Table 3.4: Results for the aromatics system.
Table 3.4: Results for the aromatics system
Process ηb,mass Lb,mass ηb,energy Lb,energy [%] [MTA] [%] [PJ/yr] BTX-Prod 93 0.65 86 53 BTX-Con 86 0.69 68 63 BTX-Tot 89 1.34 77 116
100 Potential 40 External % Energy Loss PJ/yr 80 30 BTXCon
60 BTXProd 20
40
10 20
0 0 PyGsl BTXExtr. RefGsl CaproLtm Phenol1 PhtcAnh HDA oXylSep BTXSep Stryren1 Styren2 Phenol2 Cumene
Scope for improvement (100-ηb) % External energy loss per process
Figure 3-5: Results of energy analysis of the Dutch aromatics system; processes ranked according to scope for improvement (100-ηb). The total losses of the analysed aromatics system BTX-Tot are evenly spread over the two parts. As part of the assessment procedure, however, also the performance and loss of individual petrochemical plants is determined. Ranking based on the results yields a number of relatively weak performing chemical processes, notably Caprolactam, Phenol and Phtalic Anhydride production, as illustrated in the bar
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graph in Figure 3-5. This illustrates that over 90% of the energy loss reported for the aromatics system can be attributed to the 13 processes in the bar graph. Of these 13, only 8 exhibit significant scope for improvement. Thus, albeit the Dutch aromatics system includes some 40 process-plants installed, all else being equal, in order to improve resource utilisation as a start we only need to examine 20% of these processes.
Small Scope [%] 0 BTXSep BTXExtr. oXylSep RefGsl Effective 10 Effective but high Loss Cumene
20 40 PyGsl 30 20 10 0 High Styren1 Small Loss Loss [PJ/Yr] 30 Styren2 [PJ/Yr] Phenol2
Ineffective HDA 40 Ineffective but small Loss PhtcAnh 50 CaproLtm Phenol1 Large Scope [%]
Figure 3-6: Aromatics case study - assessment of processes in the system. An alternative representation of the results is given in Figure 3-6. In this drawing, the axes have been chosen to let effective elements of the system assessed end up in the upper right quadrant. These elements (industrial plants) are relatively efficient and do generate a moderate external loss. This kind of drawing helps to identify weak elements and may help to visualize two strategies for improvement: to move from the lower-left quadrant upwards via efficiency improvement, and to the right by reducing the volumes processed. As a matter of course the classification shown depends on ranges of both axes, and only serves to provide a first indication where to look for improvements or possible innovations. The preliminary conclusion for the aromatics case is that large-scale processes (exceptions noted) appear to have reached a high degree of effectiveness over time. A number of plants that are operated on a small-scale provide scope for improvement, albeit a limited absolute effect). In the 'BTXProd' subsystem analysis it was impossible for mixed substances such as naphtha or pyrolysis gasoline to obtain an exergy-value consistent with the ∆G based exergy for pure substances. As a consequence, a thermodynamically sound and
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reproducible assessment of this system cannot be completed without sophisticated methods to estimate the thermodynamic properties of the mixtures involved. The criteria based on stream labelling and energy balancing represent a proxy to exergy, by which the analysis of the entire system and its subsystems could be completed.
3.2.4 SEARCH FOR R&D OPPORTUNITIES
Starting points for the search Assume that (1) there will be a continued demand for the product spectrum of the petrochemical industry and that (2) the availability of fossil resources is ensured in the mid- to long-term. The major question then appears to be “What technological opportunities exist to produce the current set of products of the petrochemical industry by using less energy and fewer fossil resources.” Under the two assumptions given above, the functions of the petrochemical industry remain unquestioned and the results expected from some assessment of resource utilisation provide starting points for the exploration of R&D opportunities within the existing system boundary. The ranking of relatively poor performing petrochemical processes is the starting- point for the procedure to specify directions for R&D and possible innovation content.
Analysing weak elements Establishment of the causes for the losses calculated is half the solution. Inspection of the “fingerprint” of the losses and efficiencies from the assessment gives a first clue in what form mass or energy is lost from the system. Detailed process analysis, design studies and expert knowledge can help to elucidate the causes of internal exergy loss and external material, energy and exergy loss from the system. In the industrial aromatics system for example, the caprolactam process produces a large amount of ammonium sulphate. On the basis of literature (e.g. Chauvel and Lefebvre 1989a) this was labelled an unwanted by-product. Hydrodealkylation is implemented largely as a thermal process. As a consequence, its selectivity is relatively poor and unwanted by-products result. Thermodynamic inefficiencies are caused not only by the use of non-ideal conversion routes, but also by system designs that result in operation at much lower efficiencies than theoretically achievable. Phenol production, for example, involves partial oxidation where chemical energy is largely converted to low-quality heat. The large number of steps in the complicated caprolactam process leads to a substantial internal exergy loss. In other processes, available catalysts and reaction conditions favour only limited conversion per reactor pass. The associated separation and recycle result in losses and inefficiencies, in particular when these require significant volumes of gas to be recompressed.
Systematic search Three main classes of improvement options exist for a petrochemical process that has been labelled a weak system element:
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1. modification of system content In any process system, the selection and arrangement of system elements as well as their principle, design and operating conditions may be altered. This can affect system performance by quantitative improvement (yield, selectivity) or by an upgrade of output quality to match with product material specifications that enable a stream valuation change. 2. a shift in the classification of streams around a particular process Albeit determined by economy and ecological considerations, and sometimes formalised by Law or regulations, the classification adopted of both inputs and outputs is subjective. Such a change in stream valuation can be effected by development and adoption of alternative material applications in the enveloping system. As a consequence, while the system internals remain
unchanged, its performance indicators do change ( except Le and ηe). 3. Modification of system content of the petrochemical industry Technology development for the reduction of the margin between ideal reversibility and irreversible practice must include alternative process routes. Opportunities that involve system change outside the chemical plant system boundary must be explored with the explicit condition that technology and structure of subsystems within each chemical plant are a degree-of-freedom. 4. Generalisation of options identified The specific weak elements identified allow identification of specific innovation content for a single plant. The opportunities thus identified may have wider applicability, possibly to all weak elements of the petrochemical industry identified. Combined, these may be of sufficient ‘global’ character to allow the formulation of more widely applicable concepts and directions for R&D.
In the mature petrochemical industry, process innovation is a much-applied element of competitive strategies. Process innovation predominantly focuses on everything within the system boundary of an existing plant or plant conceptual design. Indeed, open literature gives proof that improvement opportunities for almost every commercially applied chemical processes are being investigated. Process innovation can be realised by a combination of expert knowledge, literature search, process simulation and laboratory work. Options considered can involve changes in process system design, the set of unit operations applied, change in operating conditions, the selection of the technology for a particular unit operation, and last but not least the catalyst system employed. However, the thermodynamic efficiency limit of industrial processes is constrained not only by the technology selected and catalyst available, but also by the particular chemical reaction completed. Indeed, after (Denbigh 1956), it is the responsibility of the process engineer to make “a suitable choice of the path between the given initial and final states, i.e. the choice of the details of operation.” The 'grey-box' approach (§3.2.1), for example, is widespread and entrenched in chemical engineering. In the analysis of the petrochemical industry it gives useful clues of what is going wrong. In the search for innovations, however, it must be realised always that the distinction between process and utility is an artificial one, one
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determined by technological skill and accepted or best technological practice at the time of construction of some facility. Relatively straightforward opportunities can be identified by looking beyond the system boundary of the particular process studied and considering options for change of the stream labels around individual petrochemical plants, for example to reconsider the fate of unwanted by-products. In many plants their utilisation is within the plant system-boundary by recovering the fuel-value only. To upgrade their utilisation requires fuel replacement and identification of some destination of the by-products. Nevertheless, to upgrade by-products and to reap the associated benefits is a longstanding tradition in the petrochemical industry, which in many cases has led to new business development. In modern styrene units, for example, the hydrogen present in recycle off-gas is captured for pure hydrogen production. In caprolactam, the large exergy loss and ammonium sulphate production were an incentive for the development of a new generation of caprolactam processes. In catalyst research traditionally, much research and development is devoted to finding the ultimate catalyst that combines high selectivity and conversion. Looking beyond the boundary of a single plant, however, suggest the development of effective catalysts for “high conversion” that are not necessarily selective to a single product. These catalysts must be employed in intensive process systems where the combination of unselective reaction and product separation can be effectuated at the expense of limited exergy loss. Concurrently, the utilisation of all products and the associated business must be developed to ensure their being labelled co-products or wanted by-products. In the petrochemical industry structure and content changes when new types of plants are included or existing ones are phased out or changed. Therefore, technology development for the reduction of the margin between ideal reversibility and irreversible practice must include modification or replacement of process routes. Thereby, an under performing process can be phased out. In the production chain for PET, for example, developing a one-step process from ortho-Xylene to polymer- grade terephthalic acid that avoids the production of intermediate DMT has reduced energy-loss. A multiplier-effect may be achieved when general but sufficiently specific R&D themes can be formulated. This was the central conjecture of 'de grondstoffenstudie' (Weijnen 1991). The development of trigeneration systems (Ch. 6, Dijkema 2001b) is such a theme that is a generalisation of the integration of energy conversion technology in chemical plant design. Trigeneration implies a change of the structure and content of the petrochemical industry. In trigeneration designs utility outputs no longer are considered 'unwanted but accepted' by-products, but 'wanted' co-products. As the industry had been assessed and explored, upon completion of the methods presented in § 3.2, however, only a limited number of promising R&D directions emerged (Dijkema et al. 1995), possibly because of the long process of development, evolution and maturation that led to a petrochemical industry characterised by strong procedural cohesion. Whilst in the analysis, the adherence to procedural cohesion could only be determined after examination of sufficient systems, the search results indicate that for the petrochemical industry the supposed multiplier effect of procedural cohesion is limited. In retrospect, this may be explained by the
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industry's evolution. While the scientific knowledge of chemistry, chemical engineering and related disciplines expanded continuously, process economics and innovation strategies contributed to the emergence of 'best-practices'. In response to some company's (procedural) process innovation, the other players in the industry will adopt and apply these to their advantage and competitive. Meanwhile, regulations, environmental and quality increasingly have been translated into procedural standards. Similar developments have shaped many ‘engineering disciplines or sub disciplines’, which exhibit some procedural cohesion that allows their use in various domains of application. Anyone trained in chemical engineering, for example, can apply his/her knowledge not only in the chemical industry but, amongst others, also in power systems, oil refining and pulp and paper where the concept of unit operation has proven to be very useful. In the base metal industry, a similar transition is being effected making use of the unit operation concept, progress, however is tedious because of the complexity of the physical and chemical processes in many metallurgical plants (Reuter 1998).
3.3 Functional modelling for process system innovation
3.3.1 INTRODUCTION In every design of a novel industrial plant for the production of commodities, e.g. ethyl benzene, the particular selection of unit operations, their implementation and interconnections are degrees-of-freedom. In actual practice, however, a ‘best’ or common design appears to have been developed for a great many plants. The design-space is limited and process flow sheets are hardly ever produced from scratch (Siirola 1996). Designs of industrial chemical plants thus show considerable procedural cohesion. As a consequence, by outsiders the development of the petrochemical industry is perceived to have entered ‘the end-of-the S-curve’, where there is only scope for 'incremental' improvements when adhering to existing plant structures. Meanwhile, process engineers are hardly ever confronted with 'ill-defined statements of a need', primitive problems (Rudd and Watson 1968). Despite the research agenda's suggested (Ch.2), the focus of process system engineering still is individual chemical plants. To ‘get out of’ this lock-in and foster process system innovation, functional modelling is introduced, and related to 'technology-free' systems representation (section 2.3.3) using the input-output paradigm. Functional cohesion is used as a basis for system decomposition because modelling using logical decomposition (§3.2) suffers from difficulties in system boundary selection and lacks a stop-criterion for decomposition-depth.
3.3.2 FUNCTION AND MODELLING The description of function in a contemporary English Dictionary is “The function of something or someone is the useful thing that they do or are intended to do” (Sinclair 1995). This captures two aspects of ‘function’, viz. the organisational notion of function, for example ‘the R&D function“, and the objective of some entity or artefact that combines behaviour and performance valuation, for example, ‘the
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function of R&D is timely development of new products’, or ‘the function of a clock is to show the right time’. In technical objects, a function is synonymous with ‘a black-box filled with operations leading to the fulfilment of an objective’. Hence, a system with function X may serve to achieve objective Y. The function is generally concerned with what should be achieved, not how, and thus opens the way to various means of action. This relates to the definition by Asbjørnsen, who essentially argued that the specification of a system element should be technology-free (see §2.5) (Asbjørnsen 1992). In a system representation and characterisation using the input-output paradigm, we assume that the function Φ of a system (Σ) is to generate a behaviour (B) to transform a set of inputs (Su) into a set of outputs (Sy), which relate the system to the external world. The performance of the system (Ω) is assessed by means of value functions (P) (see Appendix A. 4). The completion of this transformation at suitable performance then is the system's objective. This representation is a ‘technology-free’ specification of a system or system element. Let's define the system functions and technology30. A system (Σ) is characterised by:
B: SU => SY (Eq. 3.25)
P: SU * SY => Ω (Eq. 3.26)
Σ = { SU , SY , Ω, B, P }. (Eq. 3.27)
The function of the system (Φ) is defined by the selection of { SU , SY , Ω }. The system boundary (Λ) is defined by the selection of { SU , SY }.
Φ = { SU , SY , Ω }. (Eq. 3.28)
Λ = { SU , SY }. (Eq. 3.29)
Functional decomposition is based on the ability to decompose the system with function Φ into sub-systems with sub-functions {Φk}, where k counts the sub- systems. This representation captures the objective-defined functions introduced by Baylin as a basis for decomposition. “The mission (...) of each system is accomplished by achieving a number of intermediate objectives, up to and including fulfilment of the final system objective(s) An objective defined function is “a sub-set of the operations of a system, consisting of only those operations directly necessary to the achievement of the same specific objective (…)” (Baylin, 1990: 92). A physical system thus is completely specified by its objective-defined functions Φ. Since neither the
30 This section is largely based on personal communications (Grievink 1998) and internal research notes (Grievink 2003) that elaborate on (Dijkema et al. 2003).
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technological means nor implementation for achieving behaviour B have been specified, the description is technology-free. It may be seen that the technology issue is very much related to the characterisation of the system behaviour and its realisation. The system behaviour is the effect of transformations induced by technological actions that obey the Laws of conservation of mass, energy, momentum and electrical charge. These technological actions always involve the transformations of physical and information variables. A technological action can be characterised by the sources and the sinks of the transformation and the associated rates of change. In the petrochemical industry and chemical engineering practice the obvious transformations encountered are the conversion of chemical species, which are characterised by stoichiometry and rate of the reactions. In addition and often simultaneously, transformation of energy occurs (chemical -> thermal; chemical -> electrical; thermal -> mechanical, …). Other transformations, for example, are physical quantity into an information signal (measurements) and the transformation of an information signal into mechanical action (e.g. change of valve position). Given these considerations, it may be seen that the behaviour (B) can be defined as the joint result of conservation laws of nature (N) and the transformations (Ψ) within the system boundary (Λ), induced by application of technologies (T) and the state of the stream(s) σ, on which T are acting:
B = [ N | ΨΛ(T, σ) ] (Eq. 3.30)
A technology T, is defined as a mapping from an initial set of stream states, σ, in a domain DT , to target stream states, ϕ ∈ DT (in the same domain):
T: DT => DT (Eq. 3.31) Algebraically:
ϕ = T (σ) (Eq. 3.32) The transformation can be expressed as:
Ψ Λ (T, σ) = ϕ - σ (Eq. 3.33)
The above description is analysis driven. Given σ and T one can determine Ψ, and hence B. In a synthesis situation one has to deal with the inverse case. No unique inverse relationship, however, exists to map from a specified transformation (Ψ’Λ) onto a particular technology T’:
’ ’ {Ψ Λ, σ} ≠ T (Eq. 3.34) This implies there exists a design or innovation space that can be explored.
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Usually, one will set targets for the transformation from system inputs to outputs; then, it will be possible to set targets for the required behaviour (Btarget ) and the associated transformations: Ψ Λ , target .
Btarget = [ N | Ψ Λ , target ] (Eq. 3.35) There can be multiple technologies {T} and stream states {σ} whereby the target transformation Ψ Λ ,target can be achieved within the system boundary Λ selected. In process synthesis it is recognized that often the candidate technologies {T’} will belong to some superset of technologies capable of acting on certain type domains of stream vectors. Whilst the synthesis problem then can have multiple feasible solutions, the multi-objective optimisation of system performance can provide a unique mapping or a non-unique mapping of a Pareto set of solutions. Process synthesis can be represented as smart search strategy over the available technologies to minimise the distance between the achievable transformations ’ Ψ(T Λ, σ) and the targets Ψ Λ ,target :
’ Minimise || Ψ Λ (T , σ) - Ψ Λ ,target || (Eq. 3.36) {T’, σ}
The above equation expresses that known transformations in the petrochemical industry are optimised in a design space that is limited by available or known technologies T. Indeed, our literature review indicated that the PSE community largely focuses on the development of “new flow sheets for existing problems” (Ch.2, §2.4). In exploring possible innovations, however, one must avoid being limited, or entrenched in the current way things are being done, i.e. avoid 'lock-in' in a 'closed' problem formulation for optimisation only. The functional approach may focus, foster and enrich the discussion to address the question of 'what innovative concepts', not 'how to improve realisation of known concepts'. By specifying functions Φ it gives decision-makers with a non-technical expertise a chance to participate and to specify new system options by (re) defining system functions or expansion of the system boundary. Subsequently, identification and specification of the corresponding transformations Ψ must include expansion of the set of technologies and streams {T’, σ} in concert with the system boundary Λ selected.
In summary, for process system innovation a system Σtarget is defined by selection of its system boundary and specification of the:
function Φ = { SU , SY , Ω } system boundary Λ = { SU , SY} targets for behaviour: Btarget targets for performance: Ptarget
Hence: Σtarget = {Φ, Btarget, Ptarget, Λ }.
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The above treatise is focused on a formal representation of a system with a potential realisation of its functions by means of transformation technologies T. In the subsequent section, the focus shifts towards the constituting parts of a system, the system elements, which are specifications of technologies T.
3.3.3 FUNCTIONAL COHESION “Cohesion methods” is a well-known subject in computer system design and programming literature (Baylin 1990: 349). The subject relates primarily to how to arrive at a sophisticated and useful breakdown of (computer) programs or information system. A number of cohesion principles31 or types exist, which we assumed can also be applied to chemical process systems modelling. Traditional or logical cohesion covers the signalled trivial but logical breakdown of the petrochemical industry into in complexes and single plants. In the design of a chemical plant, sequential cohesion must be achieved between its unit operations. At the aggregate level of the industry, however, the decomposition is not obvious: where does crude oil refining end, where does the petrochemical industries’ operations start. How must an ‘aromatics’ refinery be classified. In petrochemical complexes the exact subsystem boundaries are not always clear. Within the boundary of a single petrochemical plant it is often difficult to exactly identify or decompose the unit operations. The stop criterion for the decomposition appears to be based on pragmatism - down at the level of unit operations the number of alternatives explodes- rather than having been embedded in some theoretical basis. We found little treatise of 'decomposition' in the literature reviewed (§2.5 System decomposition, p.59). Baylin indicated that ‘existing texts give a merely superficial coverage of how to conceptualise a system’s functional (operational) structure” (Baylin 1990: xi)(italics added). In functional modelling a system is broken down in such a way that each subsystem corresponds to the sub-set of system operations that achieve one of the intermediate or the final (system) objective-defined functions. This involves system abstraction and decomposition in a trial and error procedure - but when is an adequately structured model built and a suitable decomposition achieved? The functional cohesion principle, as developed for (information) system decomposition, involves “…keeping together related system elements, and keeping apart unrelated system elements while at the same time avoiding both duplication and conflict” (Baylin 1990: 57). This definition indicates that decomposition is in part subjective. Recognizing that a single system may have multiple functionality and may serve multiple objectives, Baylin extended his definition of an objective-defined function to “a sub-set of the operations of a system, consisting of only those operations directly necessary to the achievement of the same specific objective, or the same ‘mutually contingent’ [see §3.3.3] specific set of objectives” (Baylin, 1990: 92).
31 See §2.5.3p.61 and Appendix A. 3, Overview of cohesion types for definitions and details on logical, procedural and other types of cohesion.
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This concept of mutual contingency thus offers a more objective criterion for adherence to the functional cohesion principle. The selection of objective-defined functions, however, remains subject to interpretation. When in functional modelling the condition of mutual contingency is met the decomposition adopted is functionally cohesive. Functional modelling of the system is successfully completed when functional cohesion has been achieved at each (sub) system level. If not, the model and the decomposition must be modified. Thus, mutual contingency provides both the foundation for a definition of functional cohesion and a stop-criterion for the functional decomposition procedure.
A set S of functional objectives Φ is said to be mutually contingent in case
∇ (ΦX, ΦY) ∈ S (for all possible pairs of objectives)
ΦXY = (ΦX AND ΦY ); (both achieved in parallel) OR
ΦXY = ( (ΦX OR ΦY) AND NOT (ΦX AND ΦY ) ); (mutual exclusion, either one achieved, but not both.) OR
ΦXY = (ΦX →ΦY) (achievement of ΦX leads to achievement of ΦY).
In Figure 3-7 this is illustrated: if the complete set of objectives S is decomposed into subsets S1 and S2, mutual contingency is achieved; the decomposition result (subset S1 and S3), however, is not mutually contingent. Consider for example a system Σ that is characterised by three objective-defined functions, ΦX, ΦY and ΦZ. Each ΦX..Z can be realised (True) or not (False). The system Σ then has a limited set of system states as listed in Table 3.5 that is not mutually contingent because instances 1 and 3: {1 (ΦX AND ΦY), 3 (ΦY)} do not comply with the condition for mutual exclusiveness. The subset (ΦY, ΦZ), however, does meet the criterion of mutually contingency.
Table 3.5: Instances of example system characterised by three objective-defined functions X, Y and Z Objective ΦX ΦY ΦZ Instance 1 True True Instance 2 True Instance 3 True
A (pseudo) algorithm has been written for the test for the criterion for mutual contingency in functional system decomposition (Appendix A. 5).
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Objective-Defined Functions
{S1} Specific Specific Objective Objective A B
Specific Objective
C Objective-Defined Functions {SFunctions
Objective-Defined Functions
{S2} 3
Specific } Objective Specific D Objective E
Figure 3-7: Mutual contingency of sets of objective-defined functions ΦA….E. The above definition opens the way to a decomposition method for the breakdown of systems by selecting appropriate objective-defined functions. Each objective- defined function must relate to “a sub-set of the operations of a system”, i.e. a subsystem, which objectives serve to fulfil the general objective or mission of the system in accordance with the system definition of Blair quoted above (Blair and Whitston 1971). A hierarchy of functions appears, where objective-defined functions are composed of a number of functional items, which can be either intermediate functions, or functional elements (Figure 3-8). Intermediate functions are conceptual components of an objective-defined function. At least one intermediate objective equates to the system objective. These decomposition principles, including adherence to functional cohesion, must be applicable to all three selection features of a system's function Φ, which has been defined as { SU , SY , Ω } (Eq. 3.28) , i.e. the set of inputs, outputs and performance. This is not much of an issue in selection of inputs and outputs, as long as: a) The input and output streams are consistently characterised by the same attributes (“stream vector“). b) The merging and splitting of streams (arcs) is only done in “nodes“, which qualify to be part of a (sub-) system.
Illustration: Styrene production Let us consider a petrochemical complex where important precursors for plastics are manufactured, viz. styrene and propylene oxide starting from naphtha as a feedstock. In addition, TBA is produced, a gasoline additive (Figure 3-9). The owner of the complex has some flexibility in catering for the markets of these three products. Is a
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logical decomposition of a production site by the processes shown also a mutual contingent one?
Objective Defined Function
Intermediate functional item
Functional Functional Element Element
Intermediate functional item
Functional Functional Element Element
Figure 3-8: A hierarchy of objective-defined functions. The overview of the system (Figure 3-9) is only a summary that lists objective outputs only. To check the decomposition shown for mutual contingency, the possible states or instances of the system are related to the production of a single molecule of the objective output or outputs. Thus, in the test a molecule of propylene produced can only be used for a single objective. To circumvent the problem of defining the composition of petroleum cuts and the variety in product spectrum, in this example it is assumed that out of ‘1 pseudo molecule’ of naphtha, simultaneously 1 molecule of ethylene, propylene, isobutane and benzene are produced. The system thus is defined by its objective-defined functions: produce PO, styrene, and TBA. The subsystems are defined by the intermediate objective outputs: produce ethyl benzene, or petrochemical ethylene, propylene, benzene or isobutane. The instances that will realise each pair of objectives are listed in Table 3.6. Each instance is a set of processes by which a single molecule of naphtha can be transformed. The objectives to produce a single molecule of ethyl benzene and PO, for example, are achieved in parallel, when EB and PO-TBA are operated, or sequential, when EB produced is used in the PO-Styrene process. The decomposition of the system for the production of propylene-oxide, styrene and TBA presented is a mutual contingent set of objectives (Table 3.6). Especially the objectives to produce styrene and TBA are mutually exclusive because out of a single molecule of naphtha a single molecule of propylene results, which must be sent to either the PO-TBA process, or to the PO-SM process. From the scheme a ‘mutual contingent’ option for process integration is obvious, i.e. the production of EB as an integrated part in the PO-SM process. Let us now consider an industrial complex where additional commercially available technology for the production of these chemicals is to be incorporated. This leads to a system where novel technology has been added for the production of PO and
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styrene respectively (Figure 3-10). In a model of the complex, these technologies can be grouped to yield a subsystem that is similar to the PO-Styrene plant, a logical approach for the comparison of system alternatives. The decomposition of the complete industrial complex by these subsystems, however, does not meet the criterion of mutual contingency! In the new subsystem, the objectives of ‘produce PO, ‘produce styrene’ are not mutually contingent: when the subsystem is part of the larger system, depending on the route of both PO and EB, either one can be achieved, or both! The possible instances for the processing of a single molecule of naphtha are listed in Table 3.7. The solution, of course, is to modify the decomposition, and to separate the PO and Styrene-process again. This decomposition is mutually contingent.
From these examples we see that: • Production systems can be objective-defined by their products • A logical decomposition based on similar activities may not always result in a mutually-contingent set of objectives • Domain-specific knowledge is required to arrive at such decomposition. • A mutually contingent set of objectives is arrived by iteration: a first attempt at decomposition is checked for mutual-contingency. Based on the results, the decomposition is either accepted or improved. • Some subsystems generate ‘non-objective’ outputs.
Cohesion in process system design Baylin states that the functional cohesion method can be applied to any kind of business. We conjectured that -with modification and extension- the method of functional decomposition increases our understanding of large-scale manufacturing systems as found in the petrochemical industry. The characteristics that determine the dynamics and the scope for change differ considerably between physical production systems and information system. These, however, are outside the scope of this thesis. Relevant differences are found in the coupling between system elements and the integration of functions respectively. Cohesion methods and system decomposition methods aspire to arrive at an adequate degree of ‘loose-coupling’ between subsystems, or system elements. Types of coupling are no coupling, pooled or indirect coupling, sequential coupling and reciprocal coupling. Keeping unrelated things apart then mainly is concerned with the activity to study coupling, and eliminating the undesirable ones (Baylin 1990: 35). In business information systems, these concern couplings between data, and procedures that act on data. In physical production systems, couplings have a physical implementation: some intermediate storage facility and transportation by road, rail, water or air, or, in the continuous process industry, direct coupling via pipelines. In production systems, however, at any one time, there will be found ‘reciprocal couplings’ in the form of recycle streams, that involve a number of subsystems or system elements identified.
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TBA Oxide Oxide Styrene Propylene Propylene PO-TBA process epoxidation dehydration epoxidation per-oxidation per-oxidation PO-Styrene process PO-Styrene Oxygen Oxygen Propylene Propylene Isobutane Ethylbenzene output Objective- Benzene Steam Cracker Steam alkylation separation Ethylbenzene process Ethylbenzene Output steam cracking steam Objective- Intermediate Ethylene Input Naphtha
Legenda Figure 3-9: Overview of the production system for styrene and propylene oxide.
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Table 3.6: Instances of the styrene /propylene oxide production system Objective output Petro- Ethyl Propylene- Styrene chemicals benzene oxide ΦX / ΦY Petrochemicals - Ethyl benzene A1 (NAF,EB) - Propylene-oxide A1 (NAF, Pl ((EB, PO- - EB, PO-SM) TBA) or A1 or (NAF,PO- (EB, PO- TBA) SM)) Styrene A1 (NAF, A1 (EB,PO- Pl (PO-SM) - EB, PO-SM) SM) or Mx (PO- TBA) TBA A1 Pl (EB, PO- Pl (PO-TBA) M (PO-SM, (NAF,PO- TBA) or Mx (PO- PO-TBA) TBA) SM)
Notation used in Table 3.6 and Table 3.7 (p.105)
Petrochemicals = (ethylene, propylene, butylenes, benzene)
Labels of instances:
Pl = (ΦX AND ΦY) (parallel)
M = (ΦX XOR ΦY) (mutual exclusive OR);
Mx = only ΦX can be achieved; both (ΦX AND ΦY) and (only ΦY) are not
possible (singularly exclusive towards ΦX - condition M is not met, only condition Mx is met).
Ax = ΦX implies ΦY (achievement of ΦY through ΦX)
Ay = ΦY implies ΦX (achievement of ΦX through ΦY)
O = ΦX OR ΦY (inclusive OR: ΦX, ΦY or ΦX AND ΦY)
Parameter values for X and Y: When X or Y indicate operate process … naphtha cracker' = NAF ethyl benzene = EB PO-Styrene = PO-SM PO-TBA = PO-TBA
104 Process System Innovation by Design HCl NaCl TBA Oxide Oxide Oxide Styrene Styrene Hydrogen Propylene Propylene Propylene PO-TBA process PO-TBA PO-Styrene process PO-Styrene epoxidation epoxidation dehydration hydrochlorination per-oxidation per-oxidation de-hydrogenation dehydrochlorination PO / Styrene processes / Styrene PO Water NaOH Oxygen Oxygen Chlorine Ethylbenzene Ethylbenzene Isobutane Propylene Propylene Propylene output Objective- Benzene Steam Cracker Steam alkylation separation Ethylbenzene process Ethylbenzene steam cracking Output Objective- Intermediate Ethylene Input Naphtha Legenda
Figure 3-10: Instances of the extended SM/PO system.
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Table 3.7: Overview of instances in the extended Styrene /PO production system Objective output Petro- Ethyl Propylene- Styrene chemicals benzene oxide ΦX / ΦY Petrochemicals - Ethyl benzene A1 (NAF, - EB) Propylene-oxide A1 ((NAF, Pl (EB, PO- - PO-SM) or TBA) or (NAF,PO- A1((EB, PO- TBA) or PO- SM2) ((EB, SM2) PO-SM), Styrene A1 (NAF, A1(EB, PO- Pl ((PO-SM) - PO-SM) or SM) or (EB, or (PO-SM2) (NAF, PO- PO-SM2) or (PO-SM2, SM2) PO-TBA) TBA A1 Mx(EB, PO- Pl (PO-TBA) M (PO-SM, (NAF,PO- TBA, PO- PO-TBA) TBA) SM2)
Note: for explanation of table and symbols, see notes below Table 3.6, p.103
These result in a reversal of activity flow and introduce feedback loops, which may introduce complex dynamics that affect system performance. An equivalent reversal of information flow appears to be largely avoided in business information systems. Information and control systems do create direct couplings in physical production and couplings between production control systems, scheduling and management information systems. At the bottom level control system feedback loops represent reciprocal couplings that may span multiple unit operations or plant sections. The feedback from management information systems, scheduling and optimisation also may introduce reciprocal coupling. The ‘process recycle’ must be considered an important part of a great many (petro) chemical plants. Its functions often are multiple: -reprocess unconverted material; provide initiator/seed for reaction; circulate catalyst; allow safe process conditions; intensify the use of reactors etc. Indeed, an important step in conceptual design is the definition of the recycle structure (Douglas 1988). At the level of industrial clusters, industrial networks, or industrial infrastructure notably materials are recycled through a series of networked plants, the major problem in the metals industry being how to keep metals within the cycle, maintain their quality and availability (Verhoef et al. 2004a). The recycles create interdependency between the system elements. Using functional decomposition of process systems, it may be seen that a process recycle that results in a reciprocal coupling is only a technological implementation of some function in the black-box of a chemical plant that purposely must convert substances A and B to product C. In Chapter 5, Fuel cells and Trigeneration, it is demonstrated that
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considering the recycle as a crucial functional system element leads to dramatic improvements in system design. At the level of industrial networks, it is a long- standing tradition in the petrochemical industry to not only upgrade by-products as much as possible, but also to allow 'reciprocal couplings' over a multitude of plants. One well-known example is the treatment of aromatic mixtures in an aromatics complex to Benzene, Toluene and Xylene, which is implemented as a series of plants that includes a number of intra-process recycles (Chauvel and Lefebvre 1989a). In industrial ecology, these concepts have been labelled 'interconnecting and cascading' material and energy flows; however, this emerging inter-discipline does not offer a unified approach to recycles in interconnected systems (Graedel and Allenby 1995; Ayres and Ayres 1996; 2002). As we have shown, the use of objective-defined functions is in accordance with the above definition quoted from (Asbjørnsen 1992), where a system element specification is technology-free. What is imminent from the case in Ch. 5 is that in a great many production systems, at various levels, there is an increasing level of integration of system functions, i.e. in the technological specification of systems, single items achieve seemingly inseparable multiple functions. Reactive distillation, for example, offers an example where chemical reaction and subsequent separation/purification are combined in a single apparatus. At first glance, in information systems there does not appear to be the equivalent of incorporating multiple functionalities by combining functions in a single item. Of course, ‘system integration’ is a well-known aspect of both hard- and software but this largely is concerned with gluing system elements together to a properly function system. Thus is this a unique characteristic of manufacturing systems in the process industry? Is it only in appearance that computer systems combine functions in single items, while apart from parallel supercomputer, transputers and neural networks most microprocessors only allow sequential execution of system functions? Without answering these questions, the cases presented in this thesis support that functional modelling is a very effective means to identify, illustrate and manipulate multiple functionality of technological systems or parts thereof.
3.3.4 DECOMPOSITION PROCEDURE In the preceding sections the functional cohesion concept has been introduced, formalised and illustrated. The analogy and difference between physical systems and information systems were discussed. In this section, first a procedure is presented to arrive at a functionally cohesive decomposition using the mutual contingency criterion. The initial functional modelling strategy subsequently is improved by analysing model decompositions employed for the petrochemical industry or parts thereof. To that end, the literature discussed (chapter 2) was readdressed with the question 'has functional cohesion been achieved in the models of the chemical industry or have other types of cohesion been achieved'. Finally, the functional decomposition procedure is embedded in a framework of cohesion methods.
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Functional decomposition procedure To achieve functional cohesion in system decomposition, all system elements that are closely related, either directly or indirectly, to the same intermediate or final mutually contingent set of objectives must be clustered together within the same subsystem. This can be tested for. At the system level, there are also some exceptions: 1. Some subsystems may not be adequately coupled 2. Subsystem selection would result in duplication of system elements 3. The selection would result in subsystem conflict Duplication or subsystem conflict can result when some system elements are closely related to more than one intermediate or final set of system objectives. To avoid duplication, the elements must not be placed in more than one subsystem. In order to avoid subsystem conflict the elements involved must not be placed in anyone of the subsystems that correspond to the common objective, but, rather, into a separate, distinct subsystem of their own. By obeying these principles, functional cohesion attempts to achieve optimal independence of different subsystems. Using these concepts, a list of approximate steps to follow in actual practice can be given, as illustrated by Figure 3-11: #1 “Identify intermediate objectives of the parent system, and then group all (cluster) together all the system elements closely related to each intermediate objective, or to the final objective“ #2 “eliminate from each group (identified in #1) those elements not closely related to the objective(s) of the group (cluster).” #3 separate sub-groups of system elements into distinct subsystems of their own which are: • Insufficiently coupled within the group • Common to a number of different groups already identified • Tightly coupled to a number of different groups already identified #4 Check for functional cohesion at system, subsystem(s) and system element levels. #Repeat steps #1-3 depending on the outcome of step #4. An initial step is required where the functional objective of the parent system is identified. As indicated, an iterative procedure results. Describing the functions of systems, subsystems and system elements requires domain specific knowledge and multidisciplinary input. The procedure implies some ‘trial-and-error’ because execution of step 1 already assumes some consideration of the systems objectives and possible formulation of system intermediate objectives. To start the iteration, it is suggested to use an initial guess that can be based on present knowledge of the decomposition of a particular system. Depending on the result of #2-#4 the decomposition must be modified, i.e. begin at step 1. In this way, a complete procedure for the functional decomposition of systems has been defined.
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Decomposition in Industry Studies and Design In this section, decompositions of industry or parts thereof as applied in studies reported in the literature are analysed with respect to functional cohesion. The examples align with the presentation of studies of relevance to 'petrochemical industry' adopted in Chapter 2, Process System Innovation Sources, i.e. from 'top- down' to process design of chemical plants.
Identify 1 Intermediate Objectives
Eliminate 2 Unrelated Elements
Separate 3 Modify / Adjust Sub-groups
Check for 4 Functional Cohesion
Complete
Figure 3-11: The functional decomposition procedure.
In 1909, Weber published his theory on the location of industrial operations (Weber 1909). He decomposed the processing industry into two subsystems, viz. one where “Reinrohstoffe” are being processed and another where “Verlustrohstoffe” are being processed. The petrochemical industry falls completely into the first category, since crude oil and natural gas must be considered a Weberian Reinrohstoff, i.e. a resource that can almost completely be converted into useful products at the expense of only limited generation of solid-waste. On the contrary, most ores are Weberian Verlustrohstoffe, since for the greater part they consist of rock that is considered ballast. Weber's decomposition is still useful for the explanation of the general location pattern of process’ industry facilities. In retrospect we conjecture that it is a functionally cohesive decomposition: the process industries’ activities were decomposed in a subsystem where activities are grouped together that completely
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process feedstock to saleable products, and a subsystem where the operations generate a large ‘non-objective’ output. In explaining the location patterns of oil refineries and the petrochemical industry in Europe, (Molle and Wever 1984) distinguished 4 categories of complexes. Coastal complexes are located in seaport regions, which offer tremendous advantage for the shipping of bulk feedstock and product. Today, their nucleus more often than not is an oil refinery that provides feedstock for petrochemical plants, although some argue that at least a naphtha cracker is required for long-term complex viability (Dijkema and Kuipers 2001). Older established inland complexes are found in the regions where the chemical industry historically developed based on traditional feedstock, coal or river access. Over time, the facilities on these sites gradually were adapted or replaced by new plants that use oil products as feedstock. Hybrid complexes developed inland around newly established oil-refineries as a response to local market development. Subsequently, these could also meet feedstock demand of new petrochemical plants. Growth-pole complexes developed where public authorities stimulated joint construction of both oil refineries and the petrochemical industry largely by support beyond the provision of 'public infrastructure'. Molle and Wever’s is a logical classification that is of value to understand current location patterns. It is not a functionally cohesive decomposition, but largely a description of the result of a chaotic decision process under changing market conditions, availability of transport modalities, and the role of public authorities. The result of these evolutions exhibit largely ‘coincidental’ cohesion only. Their study supports the impact of entrenchment in the petrochemical industry: new facilities preferentially are constructed at or in the vicinity of existing petrochemical sites. Thus, all petrochemical complexes exhibit 'relational cohesion', as all industrial operations relate to the object-class ‘manufacture of chemicals’ The objective-defined functions we can extract from Molle and Wever's classification are (#1-Produce oil products; #2-Produce petrochemical feedstock; #3-Produce (petro) chemicals for local markets; #4-Provide jobs to stimulate local job market). In order to provide economic feasibility, relations with the system environment must include (#5-Access to large-scale transport facilities or cheap connection to global resource market; #6-Closeness to local market or optimal position with respect to regional markets and transportation costs and #7-access to service industry). In conceptual process system design the system element is the unit operation. The composition of an appropriate set of unit operations is the basis of current conceptual process design (Douglas 1988; Biegler et al. 1997). The unit operation classification is procedural cohesive. Unit operation specification is not completely technology-free, as by the mere training of chemical (process) engineers, each unit operation has become associated with a series of methods of realisation. In addition, when realising process functions the number of alternative combinations of unit operations is virtually unlimited. The simple function ‘move a substance from reactor A to B’ for example can be performed for a liquid by the single unit operation ‘pumping’. Generally, requirement and realisation of the unit operation ‘pipeline’ conveniently is taken for granted. An alternative realisation of moving a liquid from A to B would be the series of unit operations ‘evaporate’, ‘compress’,
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‘pipeline’, ‘condense’. In this case, or in the case of moving vapour, the unit operation 'compress' is considered early on in the design process because of the substantial cost of compressors. In conceptual plant design, pipelines are not normally considered a unit operation. 'To move substances from A to B', however, is an important functional element in industrial process plants. This function can be implemented using current state-of- the art technology and system or by realisation of the concept of a pipeless plant (Drinkenburg 1999). Douglas emphasized that in conceptual design not only the selection, conditions and arrangement of unit operations are important, but also the recycle structure (Douglas 1988; Biegler et al. 1997). We suggested considering 'recycle' in a chemical plant to be a unit operation (Ch. 5). In the (strategic) planning process for the erection of new chemical plants early estimation of investment costs is of imminent importance. Due to the large-scale of operations, it is well known that the actual investment will dominate the net earning power of the project for a long time. Over time, various methods for the generation of investment cost estimates have been developed (Chauvel 1981; Peters and Timmerhaus 1991). In estimating the costs for a new plant, the design of plant must be broken down into individual units. In their founding article on their method for the estimation of the investment costs for a chemical plant, Zevnik and Buchanan actually defined the system element of a chemical process system to be a functional unit and labelled their method functional unit method (FUM) (Zevnik and Buchanan 1963). At DSM, this cost estimation method has been expanded upon the recognition that required functions in a process plant can be identified. Each function can be given an estimated cost prior to knowing or specifying its technological content. (Drinkenburg 1994; van Geem 1994). Thus, even in the very early phase of R&D, if some new technology appears to be useful to create a new production process, a cost estimate can be generated. A drawback of the method is that in process system design, it is often difficult to clearly define a functional unit, which very often turns out to consist of more than one unit operation. Possibly, the procedure outlined in Figure 3-11 offers a workable recipe for the functional unit method for cost engineering, especially when a basic, expandable set of functional units that is applicable to all chemical plants can be identified. When this is the case, a (historic) database of possibly a context dependent cost factor for each functional unit can be derived. In simple product assessment, the performance or fit-for-purpose of two alternatives are compared. In energy analysis, primary, secondary, tertiary and quaternary resource/energy use may be accounted for (Boustead and Hancock 1979) (§3.2.2) In Life Cycle Analysis (LCA), such analysis is extended to the complete production system that is required to bring a particular product into being. Modern LCA or cradle-to-grave analysis attempts to determine and allocate to a single product or 'functional unit' the effect of mining, operations, production, consumption and waste processing, recycling and disposal (Setac 1994). Whilst this decomposition commonly adopted in LCA analysis probably is functionally cohesive at the level of production systems, the entire approach of many an LCA-study is not. LCAs are often executed to obtain a fingerprint of a particular product and its related production chain or network. The result is claimed to offer a
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starting point for improvement by selecting other products or production processes . Where in LCA analysis, assessment of production systems and products, however, are tightly coupled, in searching for solutions they should be considered loosely connected. The process network that currently creates a particular product's LCA fingerprint is only one out of many possible system realisations. In addition, in many an LCA study it is neglected that production systems for a variety of products are not only linked but also interdependent (Verhoef et al. 2002b). This interdependence does cause problems when allocation of environmental effects for product assessment is required, and introduces complexity when developing solutions. Thus, often process system innovations are either excluded from the solution space or modifications are proposed that do not take into account the interdependencies in the process network. LCA thus suffers from over specification of the production systems analysed. The studies evaluated indicate that the decomposition is largely implicitly adopted. As a consequence, most underlying classifications are useful only for the specific study. Relational cohesion has explanatory power for the location of industrial operations, and visualise the importance of the relations with the systems environment. Procedural cohesion in retrospect explains a large part of the current status in chemical process systems engineering, where the unit operation concept is widely used and allows the breakdown of process systems in elements, thereby creating the opportunity to rearrange the process system configuration and reselect the technology implemented. Its procedurally cohesive character, however, also presents a barrier to process system innovation because it is difficult to step away from 'best practice' both in process system design and unit operation implementation. Functional cohesion explains the success some companies have had with extended versions of the functional unit methodology in cost estimation for novel chemical plants.
A recipe for Innovation and sustainability? By specifying systems, subsystems and system elements by objective-defined functions one opens the way to a technology-free system description. The other cohesion methods, except relational cohesion, all require some classification or typology of technology, and inadvertently will bring in the limitations associated with those technologies, and the classification scheme. Often, logical classification schemes are also functionally cohesive. They, however, do not open the way to innovative concepts, as equipment always must be classified within an existing category. The introduction of a new category often is a lengthy process and there is always technology that does not fit in any category. Another drawback of logical and procedural classification schemes is that when these cohesion methods are applied in high-level system decomposition, subsystem duplication or conflict may result. This may lead to endless reconsideration, reordering and restructuring of classification schemes. In the process the focus on and scope for improvement is lost. The use of logical classification at a lower subsystem level, e.g. in equipment engineering, appears natural to engineers. It seems logical, for example, to distinguish between pumps and heat exchangers. Procedural cohesion can be useful
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in developing new equipment by examining similarity. In mechanical engineering, for example, ‘rotating equipment’ can be considered a procedural category that includes well-known equipment, such as compressors, turbines and pumps. A hypothesis of a major study into more effective resource utilisation (Weijnen 1991) was that industrial operations in process industries, oil refining, base metals and chemicals, exhibit procedural cohesion. The objective of the study was to elucidate the 'bottlenecks' and derive innovative solutions that because of procedural cohesion could be transferred to other operations in the industry. While logical and procedural cohesion help in the initial stages of both modelling and assessment, upon re-evaluation of the results (Dijkema et al. 1995) we conclude that functional cohesion is to be preferred for the search and specification of process system innovation content. Subsequently, procedural cohesion can play a role in the transposition of solutions found in one sector to solutions in the other sector. A complete recipe to improve the ‘sustainability’ of a sector by assessing what the activities within the sector are thus can be formulated as: • Qualitatively investigate a suitable ‘top-level’, preferably by functional analysis, and determine the appropriate system level. • Look for possible procedural or logical decompositions, and search the literature along the lines of these decomposition schemes • Use the information thus gathered to develop a functionally cohesive scheme for decomposition of the system under study. Define the lowest (sub) system level, the system element, down to which functional cohesion has to be met. • Identify subsystems where in current practice strong procedural cohesion is manifest. When these subsystem coincides with subsystems with a relatively low performance, the functional decomposition can be used as a stepping-stone towards novel procedural = technology implementations to meet the objectives identified.
3.4 Conclusions In this chapter, the second part of this thesis' central research question was elaborated: how can technological or systemic innovation content be specified that enables a transition towards a sustainable petrochemical industry? Firstly, a method has been developed for system modelling and characterisation for assessment of resource utilisation, the main indicator for sustainability. Its foundations are system representation using the input/output paradigm and straightforward system decomposition where the petrochemical industry is considered a structured collection of single chemical plants. Mass and energy balancing, thermodynamics and system engineering were combined in a suitable, reliable and versatile assessment procedure, which provides a quantitative image of the petrochemical industry or parts thereof from information that is available in open literature. The criteria or indicators calculated in the procedure could be developed employing subjective but robust valuation by labelling system input/output flows. These labels combine economic and ecological considerations.
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Together with energy values, these provide a sufficient 'proxy' for exergy. In addition, the stream labelling approach presented provides an interface between all stakeholders involved. The assessment results can be condensed into an overview of 'scope for improvement' versus 'current loss generated'. Obviously, petrochemical plants or complexes that exhibit a large scope for improvement and a high current loss must be high on the innovation priority list. Starting from such a priority list, a systematic search for innovations must include identification of causes within the 'weak element' combined with inspection of its system surroundings. Since inefficiencies and losses are manifested as material or energy streams with inferior quality labels; these labels may be changed to reduce the perceived loss and efficiency of process systems or petrochemical complex involved. Thus a technology-oriented procedure has been developed to systematically explore the 'innovation-space' for the petrochemical industry. This includes the network structure, which is explicitly considered a degree-of-freedom. We suspected that such a procedure would be most effective to foster the science- and technology-fuelled innovation process (Figure 1-7), as well as help to balance short-term consumer needs, mid-term business objectives and long-term sustainability of our industrial society at large. The illustrations for the industrial aromatics system are no proof, but do demonstrate the usefulness of the method compiled. Application of the procedure does yield options for improvement viz. conceptual specification of innovation content. Elsewhere, more extensive results have been reported that cover the entire petrochemical industry (Dijkema et al. 1995). Overall, as stated, both the specific results per process or complex, and more generic results, however, were meagre. This may be due to very character of the petrochemical industry, a science-based industry with an impressive track record of technological innovation driven by economic and environmental incentives. Alternatively, the results can be viewed as confirmation that reduction of resource consumption and CO2 emission indeed is a wicked problem for the petrochemical industry (Ch. 1). Section 3.2 represents the first completion of the circle of the meta-model of activities (Figure 1-8) where the subsystem decomposition and boundary selection remained unexplored. In short, a relatively straightforward systemic approach was compiled for the structured identification of innovation opportunities in the petrochemical industry, notably R&D options for improved resource utilisation. In section 3.3, the modelling strategy itself was considered a degree-of-freedom, notably system characterisation and system decomposition. Functional modelling (Baylin 1990) was linked and formally embedded into the system representation using the input/output paradigm. Functional cohesion was adopted as the principle for decomposition and modelling strategy. A decomposition procedure was developed using mutual contingency as a stop-criterion. Our review of process system engineering literature (Ch.2) indicated that until 2002 the process system engineering community has been largely focused on the development of “new flow sheets for existing problems,” thereby optimising known transformations in the petrochemical industry while operating in a limited design and solution space. Functional modelling, however, provides a mechanism for abstraction that is expected to open the way to redefine functions of the existing
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industry and its production systems, explore novel means of achieving said functions through system rearrangement and/or novel technology, and finally to explore creative applications of available technology. In providing a means to decouple from current practice it resembles and relates to state-task representation: functional modelling allows the proper formulation of objective-defined functions of existing operations based on past design. Hidden or new, emergent objective-defined functions required for sustainable process systems may be identified. Thus, the functional modelling strategy presented may become an activity that precedes process synthesis, which mainly assists in primitive problem formulation and specification of the design-space to be explored in process synthesis. To use the approach requires a thorough consideration of the functional objectives of the (production) system studied, and in essence will yield a subjective decomposition and model. The general system representation explains the limits of process synthesis for process system innovation. System boundary selection and functional modelling are a means to identify and specify novel or alternative system functions and include or specify novel technology in the innovation space. Thus, re-addressing system modelling and system decomposition (meta-model, Ch.1) has led to a new modelling-decomposition-synthesis strategy or a procedure for the specification process system innovation content.
4 Innovation around Olefins
4.1 Introduction In this chapter, the focus is on innovation for improved resource utilisation in the industrial system for the manufacture of olefins32 and their derivatives. The system around olefins was selected because ethylene and propylene are the key products of the petrochemical industry because olefins represent the major non-fuel application of crude oil products and because the mature 'olefins' industry represents a 'perfect' case to elucidate the specification and the potential of process system innovations. Olefins are key products of the petrochemical industry. Since these are the building block of many plastics33 they are of major importance to our industrial economy. Today polymers34 are used in over 20,000 grades in a myriad of applications, which include packaging almost everything, synthetic clothing and carpets, toys and consumer electronics, construction materials and automobile parts. The availability of olefins is essential for the manufacture of many of these polymers. They are the single building block in polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC), while polystyrene (PS) is produced from ethylene and benzene. In addition, olefins are essential components for the manufacture of specialty polymers such as polyesters (e.g. PET-bottles), polyurethanes (insulation foam, cushions), polyacetates (paints), polyacrylamides (clothing) and a vast range of intermediate chemical products. Some 70-80% of world ethylene and propylene production is used for polymer production (Stanley 2001). The total 79 Million Ton per Year (MTA) world polyolefin35 production represents approximately 63% of the global plastics business (CMAI 2001b). The group of olefin chemicals thus includes the most important building blocks manufactured in the petrochemical industry, viz. ethylene and propylene. In fact, only sulphuric acid and ammonia are produced in quantities that exceed ethylene production (Brennan 1998). Olefins represent the major non-fuel application of crude oil products. Current nameplate capacity for ethylene is estimated at some 100 MTA worldwide, with current capacity utilisation around 90% at prices that fluctuate between US$380 and $550 per ton in the last decade (CMAI 2000a). These units have a capacity for co- producing some 40 MTA of propylene. Since production quantities are large, the associated use of feedstock and fossil energy sources is high, roughly 200 MTA.
32 'Olefins' is the common trivial name for the group of mono-unsaturated hydrocarbons with a carbon skeleton that consist of 2 atoms (ethylene) to 5 (isoprene) or even 8 atoms (1-octene). The presence of a double C=C bond in these molecules causes them to exhibit significant reactivity, which makes them a suitable feedstock for a host of chemical processes. The double carbon-carbon bond is labelled 'unsaturated' as it can be saturated by reaction with a single molecule of hydrogen. 33 'Plastic' is a trivial name for polymers that originates from the label 'thermoplastic resins', polymers such as polyethylene that slowly weaken and melt at elevated temperature. Thermoset resins do not exhibit this behaviour. Today, main categories of polymer use are plastics (PE, PP, PS, SAN), resins (paints, epoxy resins), foam (PS, PUR), rubber (EPDM, SBR) and fibers (Nylon, Kevlar). 34 Polymers is the common name of molecules that are formed from many small monomer molecules. 35 Polyolefins is the commercial group label for polymers derived from olefins, viz. polyethylenes (LDPE, LLDPE, HDPE), polypropylenes and polybutylenes.
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Today, these solely comprise non-renewables, notably oil products and natural gas liquids (NGL). These are estimated to account for some 5-8% of global oil equivalent consumption (Anonymous 2001a). Thus, only small improvements of the global system around olefins (production, consumption, end-use) could result in avoidance of considerable CO2 emissions from this system, which are roughly estimated to total some 500 MTA36. Since steam crackers for ethylene and propylene production exhibit an average net energy efficiency of some 70% there appears to be scope for improvement with respect to resource utilisation. Olefins represent a 'perfect' case to demonstrate the specification of process system innovation content because not only is the industry's state-of-the-art rooted in a large body-of-knowledge that was developed over a number of decades, it is also largely a mature industry where the steam crackers built or revamped today are built for decades of operation (Zeppenfeld and Walzl 2001). Over time the industry has become linked and integrated at both the supply-side and product side. Polyethylene and propylene plants do appear to be primarily located in the vicinity of steam crackers, or ethylene / propylene pipelines. Styrene plants are located near producers of ethylene and benzene, the exceptions obtaining their benzene from other locations of the same company. The same holds for cumene production plants. Vinyl chloride presents an interesting case, as both ethylene and chlorine are costly to transport. Most sites, however, were also found to be located near ethylene producers. The exceptions were plants that had switched from acetylene based production, and hooked on an ethylene pipeline. These observations led Molle and Wever to conclude that “there appears to be a very strong spatial linkage among functionally related chemical activities” (Molle and Wever 1984). Determining factors for the location of olefins facilities are the difficult transport of olefins, the vertical integration in the petrochemical industry, and the pull that an existing complex exerts on new settlers because of the agglomeration economy, the availability of existing infrastructure, services etc. The present structure of the industry and the technology applied are a result of a process that was driven by economic motives, technological innovation and regulation (Dijkema and Kuipers 2001). Olefins production by steam cracking is considered “a fairly mature technology” (Stanley 2001). A characteristic of this maturity is that the potential impact and associated earning power of R&D expenditure is perceived to be low compared to other industry sectors. It is well known that such a situation is detrimental for the rate of process innovation and that gradually the “quest for profitability improvements” focuses on organisational restructuring to reduce cost (Hutcheson et al. 1995). Although the industry around olefins has a history of continuous process technology improvement, real process system innovations have been largely lacking. This is illustrated by the structure of the industry that is dominated by steam crackers and where novel processes adopted in commercial practice have been few. In ethylene production, for example, production capacity has double from 50 MTA in 1984 to 100 MTA in 2001 (Chauvel and Lefebvre 1989a; CMAI 2000a). Despite
36 Assume (1) that each ton of ethylene represents a total use of two tons of hydrocarbon as feedstock and utility source for all steam cracker products (2) that, eventually, all hydrocarbon / polymer derivatives degrade to CO2. Then per ton of hydrocarbon feedstock 2.5 tons of CO2 result.
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this dramatic expansion, “the process chemistry and fundamental flow sheet configuration {of the steam cracker} have remained relatively unchanged” during the past 25 years (Stanley 2001). The historic average growth-rate of some 4% per year of ethylene production capacity is a trend that is expected to continue up to 2004, when world capacity is expected to increase by 20 MTA to a total of 120 MTA ethylene installed (CMAI
2000a), and total system-related CO2 emission increases by 100 MTA to 600 MTA. As we have argued elsewhere, however, the petrochemical industry must respond to the call for reduction of greenhouse gas emissions, and timely anticipate the depletion of fossil resources (Dijkema et al. 2001). Therefore, the procedures developed to identify weak system elements and to specify process system innovation were applied to the industrial system for olefins and their derivatives, notably ethylene and propylene. The olefins system in the Netherlands was used to develop the case study where it was assumed initially that the product spectrum of the petrochemical industry remains relatively unchanged. First, the entire system was assessed for weak elements with respect to resource utilisation. The results provide the starting point for a structured search for possible innovations in the olefins system: options addressed within the boundary of single plants and changes that imply a change in network structure or feedstock. The structured search for innovation options for the steam cracker is reported to illustrate the scope and limitations of the methods reported in chapter 3. Secondly, a functional model was constructed on the basis of all information gathered in the assessment, structured search and literature review. This model was used to categorise the innovations reported in the literature reviewed and to explore additional process system innovation options to cater for the set of functions of the olefins system. Thereby, changes within or beyond the boundary of single plants are considered that rely on a change in network structure or feedstock. Finally, economic and ecological aspects in evaluating the innovations reported in the literature and proposed in this study are discussed and conclusions drawn.
4.2 The industrial olefins system
4.2.1 OVERVIEW OF THE PRODUCTION OF OLEFINS Olefins today are produced primarily by steam cracking of preferably aliphatic hydrocarbons37. This operation yields a product-mix of light olefins, with an average ethylene to propylene ratio of 10:4, and a small share of butylenes (C4) and C5 - olefins. In Figure 4-1 an overview is presented of the olefins production system. About 70% of propylene is a co-product of ethylene manufacture by steam crackers, 28% is recovered as a by-product of refinery catalytic cracking operations (CMAI 2001a). Refineries located in Rotterdam, for example, have erected facilities to increase their propylene recovery from cracking operations. As indicated, the remaining 2% of propylene is produced by catalytic dehydrogenation of propane,
37 Aliphatic or saturated hydrocarbons are linear or branched hydrocarbons such as methane, ethane, propane, octane, iso-octane etc. of the general formula CnH2n+2. These do not contain double or triple bonds, nor special reactive side-groups attached to the carbon skeleton. The larger the molecule, the more susceptible it is to cleavage and abstraction of hydrogen (dehydrogenation).
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which may originate from natural gas winning and production or from crude oil refining.
Figure 4-1: The present olefins production system. When light olefins are considered the major product of steam cracking, its major by- product is pyrolysis gasoline. This co-product has a boiling-range similar to naphtha, the main constituent of motor gasoline. Pyrolysis gasoline is rich in aromatics38. Many steam cracker complexes therefore include an aromatics extraction facility to co-produce pure aromatics from pyrolysis gasoline. In a refinery, reforming of
38 Aromatics are hydrocarbons that contain at least one triple-unsaturated C6 ring (C6H6-n)R1..n. In the simplest aromatic, benzene, the C6H6-skeleton, is both heavily unsaturated and more stable than the corresponding aliphatic hexane, C6H12. Aromatics in steam cracker feedstock largely yield undesired unwanted products because of the relative stability and unfavourable C/H ratio of the aromatic structures.
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straight-run naphtha is used to increase the aromatics content by the abstraction of hydrogen, and catalytic cracking is an operation where the aromatics content of the product streams (cat cracked-naphtha, -gas oil, - kerosene) is much higher than that of their 'straight-run' equivalents as obtained from the crude-distiller. Thus, also in a refinery, aromatics-rich streams are sourced for on-site co-production of pure aromatics.
4.2.2 FEEDSTOCK & RESOURCES The present system for olefins production, and consequently olefins consumption including polymer production, depends on the availability of fossil resources (Figure 4-1). Straight-run naphtha and gas oil from crude-distillation in refineries are the dominant steam cracker feedstock because of their low aromatics content. Another attractive feedstock is the Natural Gas Liquids (NGLs) that largely consist of the preferred lower aliphatic hydrocarbons. Examples are ethane/propane mixtures, gas condensate that contain ethane, propane up to hexanes and Liquefied Petroleum Gas (LPG) fractions that largely consist of propane and butanes. Other sources (not shown in Figure 4-1) are synthetic crude-oil fractions from Fischer-Tropsch synthesis plants that use synthesis gas that may originate from Coal (Sasol), natural gas (SMDS by Shell) or Mixed Plastic Waste processing (Veba Oel) (Dijkema and Stougie 1994). According to CMAI (CMAI 2000b), “By 2002, (…) naphtha/gas-oil based capacity will make-up 57 % of global ethylene capacity.” Large regional differences do exist, however. The available data confirms that where European capacity is largely naphtha-based, in the US ethane and LPG have remained the preferred feedstock over the years (Table 4.1). The one significant change over the years being a preference for naphtha over gas oil cracking.
Table 4.1: Steam cracker feedstock use. Data sources: 2000 (Chauvel and Lefebvre 1989a; Kvisle et al. 2001). 2000 1986 Feedstock Europe US World Europe US World [%] [%] [$] [%] [%] [%] Ethane 5 55 29 8.0 57.5 30.5 LPG 10 17 11 11.0 19.0 11.0 Naphtha 75 23 54 69.0 9.5 49.0 Gas oil 9 4 6 12.0 14.0 8.5 Others 1 1 1 - - 1.0
4.2.3 ETHYLENE AND DERIVATIVES Ethylene is the most important building block in the petrochemical industry. Many chemical products are derived from ethylene (overview: Figure 4-2) (based on information from Kniel et al. 1980; Chauvel and Lefebvre 1989a; Anonymous 1990; 2000). The reactivity of the double bond in ethylene is used in polymerisation, in halogenations that lead to a vast range of chlorinated products, in hydratations to produce industrial alcohols, and in oxidation routes to produce ethylene oxide and
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acetaldehyde. In these products ethylene becomes the major constituent. In alkylation processes, ethylene is a functional (chemical) additive to, for example, aromatics. As is illustrated by this drawing, the route towards a finished product can be rather short (polyolefins), or long (coatings ingredients). The data in Table 4.2 gives an impression of the percentage ethylene production used for important applications. Since the early 80s, notably the production of linear low-density polyethylene, LLDPE has grown significantly.
Table 4.2: Worldwide ethylene application (after Chauvel and Lefebvre 1989a) Production of USA, 1983 Europe, 1983 Japan, 1983 [MTA] [MTA] [MTA] Ethylene 13.0 9.5 3.7 [%] [%] [%] LLDPE-LDPE 28.5 35.5 29.8 Ethylene oxide 17.0 12.0 11.2 HDPE 20.4 15.2 19.8 Ethylene dichloride 13.9 18.8 18.2 Ethyl benzene 6.9 8.2 9.1 Ethanol/Acetaldehyde 3.6 5.6 4.7 Vinyl acetate 2.5 * 3.1 Other 7.2 4.7 4.1
4.2.4 PROPYLENE AND DERIVATIVES Similarly to ethylene, the amount of products derived from propylene is huge (Figure 4-3). Superficially, the only chemical difference between ethylene and propylene is the methyl group (-CH3) present in propylene. The different size and structure of the propylene molecule, however, results in distinctly different chemical reactivity characteristics. In polymerisation, four different organic groups are attached to the central propylene monomer's carbon-atom. This implies that so-called stereo isomers are found in the polymer product. Whilst ethylene is polymerised to a suitable product at high pressure (HDPE-process) since 1938, the industrial production of isotactic polypropylene (the favoured stereo-isomer of PP) only took off 20 years later after the catalyst development by Ziegler and Natta for stereo- specific polymerisation and the subsequent development of a commercial process by Stauffer Chem. Co. (Piduhn 1999). While propylene finds similar application in polymerisation and partial oxidation, there are also striking differences in their respective patterns of application. In alkylation its most important application is the production of cumene, which is the most important precursor of phenol. Chlorination of propylene is relatively unimportant. In addition to propylene glycol a range of commercially important products are derived from propylene oxide (PO). Since a direct oxidation process for PO has not been successfully commercialised
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yet39, hydrohalogenation (with HCl) of propylene is still a relatively important route to PO compared to the indirect oxidation routes towards styrene/PO and tert-butyl- alcohol (TBA) and PO. Propylene production capacities are intrinsically linked to ethylene production capacity. The exception is refinery propylene production (see Figure 4-1). Propylene consumption, however, grows at a higher rate than consumption of ethylene (CMAI 2001a). Notably polypropylene demand is growing faster than any other polyolefin. The result is a gradual shift in the demand ratio between ethylene and propylene.
Table 4.3: Worldwide propylene use (after Chauvel and Lefebvre 1989a; Anonymous 1995b) 1990 1980 Production of [MTA] [MTA] Propylene 30.320 18.600 % % Polypropylene 44 30 Acrylonitrile 14 19 Oxo-alcohols 15 19 Propylene oxide 9 9 Cumene 8 10 Oligomers 4 8 Other 6 5
4.2.5 C4'S AND C5'S Over the years, steam cracker installations have been extended with facilities to extract and upgrade C4 and C5 olefins, notably butadiene, 1-butylene, 2-butylene, 1- pentylene and isoprene. Quantities available from the steam cracker are dependent on steam cracker feedstock selection and operation conditions. For some of these products, specific markets grew rapidly, however: 1-butylene is sought after, as a grafting monomer in LLDPE productions, 2-butylene is a precursor of MTBE, a gasoline additive40. Therefore, alternative feedstock is exploited, notably natural gas liquids (NGLs). A summary overview of the system has been published elsewhere (Dijkema et al. 1997).
39 Lyondell recently announced construction of pilot facilities, however, to test said direct conversion of propylene to propylene oxide (www.lyondell.com/news/09.10.02). 40 MTBE, methyl-tert-butyl-ether, has succeeded tetra-ethyl-Lead (TeL) in gasoline as an additive for the improvement of gasoline quality - notably research octane number, which indicates the gasolines anti-knock characteristics. TeL has been phased out because of health and environmental risks associated with distributed Lead emissions from vehicles. In the US, MTBE has become the subject of a controversy because of leakage from storage tanks and MTBE ending up in groundwater. These spills, however, appear to have little to do with the actual use of MTBE in gasoline.
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4.2.6 OUTLOOK Today, the production of olefins, notably ethylene, is considered a mature market that however exhibits moderate growth rates of some 4 to 5% per year for ethylene and propylene (CMAI 2001a; Stanley 2001). The sector is in its 'systemic phase' of innovation (Hutcheson et al. 1995) where the focus is on cost reduction by reorganisation of the business. Presently, this is manifested in the trend towards global-sized sites (Dijkema and Kuipers 2001), where larger individual plants for production and consumption of olefins are combined at lower cost per ton of product. A second trend is the shift of the ownership of petrochemicals operations to refiners41. The development of competing products for the market niches of ethylene-derived products (e.g. propylene!) has not yet resulted in a decline in demand for ethylene. On the contrary, with the growth-rates anticipated, by 2018 ethylene production capacity will have doubled to 200 MTA! Thus ethylene remains a keystone to the petrochemical industry while at the same time the importance of propylene continues to increase. Today, a single type of commercial process dominates ethylene production, the steam cracker, which also produces the majority of propylene. Their continued operation worldwide depends on the availability of crude-oil and NGLs. A major share of propylene is being produced in refineries. The increased world gas reserves and the launch of Lurgi's MegaMethanol technology has initiated renewed interest in methanol based routes to olefins, which have lead to successful operation of a demonstration facility and plans for the erection of at least one commercial plant in the coming 5 years (Bekkum 2001).
4.2.7 CONCLUSION On the basis of the olefins system overview and assessment, we conclude that long- term 'sustainability' is not yet the major concern in this industry today. Where health, safety and environment issues are high on the industry's agenda to ensure continuation of its license-to-operate, the still limited efficiency of its major process, steam cracking, appears to be largely accepted. Its consequence, a significant contribution to CO2 emission worldwide , is hardly penalized. Major petrochemical corporations, however, have recognized that CO2 regulation at some point in the future will be put into effect. Therefore, they experiment with emission trading and other clean development mechanisms. More important, however, ethylene producers appear to be trapped in the systemic phase of innovation, where competition requires continuous cost reduction, which are realised amongst others by increasing the scale-of-operations. This reduces the industry's flexibility with respect to developments in feedstock availability, market demand and alternative technology development. To sustain current and future olefin production levels at some point in time alternative feedstock must be sourced and the associated processes must be developed and employed. Most imminent at the demand side is the changing ratio
41 This is illustrated by the recent takeover of DSM Petrochemicals by Sabic and the refocusing of Shell Chemicals on olefins ethylene and propylene.
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between propylene and ethylene demand, which cannot be met by exploiting additional NGLs because these simply are not available. It appears that mid-term, more refinery feedstock will be employed and possibly natural gas via the methanol- to-olefins route. Long-term the industry must anticipate and adapt its systems for resource scarcity and a ban on CO2 emission. In the next section, we will demonstrate that ample options do exist for this industry to contribute to sustainability by increasing its resource utilisation and avoiding CO2 emissions.
4.3 Systematically towards innovations?
4.3.1 INTRODUCTION The 1990 Olefins system in the Netherlands has been assessed using the method described in chapter 3. In this analysis, the steam cracker has been identified as the major weak system element with respect to resource utilisation. Therefore, after an overview of the olefins system analysis is given, the focus is on innovations in or around the steam cracker. The steam cracker is described by a summary status of the technology and technology development. A systematic search for innovation/improvement options is completed for the steam cracker as per the approach presented in chapter 3.
4.3.2 ASSESSMENT
The case: olefins in the Netherlands In the past century, in the Netherlands three companies developed and operated Olefins complexes, viz. Dow Chemical, DSM42 and Shell Chemicals. Over time, these have been connected by ethylene pipelines and propylene pipelines (partly). Both Dow and DSM operated two distinct cracker complexes, while Shell operates a single complex. In 1990 the joint production Dutch capacity amounted to some 2.55 MTA ethylene and (Anonymous 1990) and some 1.0 MTA propylene. This situation has changed dramatically over the past years, as both Dow and Shell Chemicals have completed large revamp and expansion projects on their steam cracker sites. Notably Dow has expanded its existing facilities in Terneuzen, and effectively operates three cracker complexes with a combined capacity of 1.7 MTA ethylene (0.9 MTA name- plate capacity in 1990). Its feedstock includes NGLs apart from naphtha. At the Shell Moerdijk's 1973 cracker complex also a major revamp and debottlenecking project has recently been completed. It is scheduled for another 25 years of operation at a capacity of 0.9 MTA ethylene with feedstock flexibility towards naphtha and gas oil. The DSM crackers have been overhauled and expanded in the mid-90's, where also some new functionality has been added. Combined, these projects have increased total Dutch ethylene capacity to some 3.8 MTA ethylene and 1.5 MTA propylene. The basic outline of these complexes, however, has not changed.
42 The DSM steam cracker installations in Geleen were sold to Saudi Aramco Basic Industries (Sabic) as part of DSM's spin-off of its petrochemicals activities in 2002.
124 Process System Innovation by Design Insulation Packaging, Toys Packaging, Coatings, Resins Boat Hulls, Clothing PET-Bottles, Fleece Food-packaging Films Food-packaging Disposables, Packaging, Furniture, Toys Packaging, Furniture, Toys Pipes, Film, Wire Insulation Film, Pipes, SmoothMedical & Products PS PET PVC PTFE LDPE PdVC HDPE LLDPE PE/VAc Polyesters copolymer Ethylene PET VCM Chloride Ethylene Ethylene Diamines Vinylidene Tetrafluoro Glycol Ethylene form EDC Chloro- subsystem 3 Styrene to C to 2 From C Acid Glycol Styrene Ethylene Terephtalic Ethyl- Benzene Vinyl Ethyl- Oxide Acetate Ethylene Benzene Acid Acetic Organic Chlorine Ethylene p-Xylene 1-octene Benzene (Di-)Acids 1-butylene;
Figure 4-2: Industrial production of ethylene derivatives and example applications.
Innovation around Olefins 125 Plexiglas Fiber clothing Artificial windows - Foams; Car cushions Car Foams; Car parts; Electronics Transparent Car parts Electronics; Adhesives CD's; Artificial windows Car &door windowseals Packaging; Furniture; Toys PP ABS Poly SAN Poly- Poly- EPDM PMMA Epoxyr Resins Rubber Additive Gasolline Urethanes Carbonates Acrylamides Ethylene ethers MTBE Glycidyl Glycol Ethylene A MMA Glycol MIBK (BDO) Polyols PG Ether Polyether Propylene Butanediol Bisphenol subsystem 3 Styrene to C to 2 TBA From C Oxide Hydrin Phenol Styrene Acetone Propylene Epichloro- Ethyl- Benzene Allyl- Alcohol Chloride Cumene Isopropyl Acrylonitril Iso- Benzene cyanates Isobutane Propylene
Figure 4-3: Industrial production of propylene derivatives and example applications.
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System (boundary) selection Combined, Figure 4-2 and Figure 4-3 represent the 1990 Olefins system in the Netherlands. They provide an overview of the industrially employed conversions of ethylene, propylene and their derivatives respectively. The system boundary selection for an olefins system is not trivial. Propylene oxide is produced in combination with either styrene or tert-butyl-alcohol (TBA). Other products manufactured from olefins lead to end products that only include a small portion of material of olefin origin (such as styrene that is used for the (co-) polymers PS; ABS, SAN). Therefore, a selection was based on predominance of material content of olefin origin. In Figure 4-2 and Figure 4-3, industrial processes included in the olefins system are indicated by a grey-fill.
Method applied, information sources, data input and manipulation The assessment has been developed to arrive at a satisfactory starting point for the search for innovations in this complex industry. A priority weak element analysis has been completed for the 1990 Olefins system in the Netherlands according to the method described in chapter 3. An overview of the industrial plants in operation in 1990 is given in Appendix A. 6 and summarized in Figure 4-2 and Figure 4-3. In order to enable the assessment, data from various sources had to be gathered, checked and properly combined. To establish the input/output characteristic of industrial petrochemical plants use has been made of performance data of 'typical plants' available in the open literature (e.g. Chauvel and Lefebvre 1989a). For a limited number of plants in operation a data set was compiled by using confidential sources. The sets of stream data on industrial plants had to be reconciled without exception. In order to arrive at closed mass balances, corrections were made based on component balances and sound engineering judgement. Additional assumptions were made with respect to unreported energy losses from the systems assessed. The corrected plant input/output data were combined with thermodynamic data on the substances involved to allow the calculation of process system energy balances.
This included adoption of the reference state 'standard conditions', i.e. P0 = 1 Bar, T0 = 298 K. Thus, per plant, efficiencies and losses could be calculated according to the equations given in chapter 3. System losses were obtained by proper combination with plant capacity data as reported in reputable sources: (Anonymous 1990), open literature, permit requests, commercial bulletins. Input/output data of the production and consumption subsystem and the total olefins system were obtained by linear addition of individual plant data, under the assumption of maximum internal exchange and the absence of synergistic effects on plant performance.
Interpretation of results The result of the assessment is not a performance assessment of the Dutch olefins industry as it existed in 1990 or yesterday, let alone an assessment of a single
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company or facility43. Although an attempt was made to compile reliable datasets that represent the industrial state-of-affairs, the assessment results presented must be interpreted with care. Information on industrial plant performance available often lacks a time-stamp and may be out-of-date. As a matter of course, actual plant design and operation can differ from 'typical installations'. The results obtained, however, are of sufficient quality beyond an 'order-of- magnitude' to merit an initial ranking of weak elements and a guestimate scope for improvement. The information incorporated in this data set thus primarily serves the objective of this study: the development and underpinning of some systematic approach to process system innovation for the benefit of a complex olefins industry that is largely mature. Even with the limitations of the raw data available, the conclusions based on the case study results are believed to be valid. Consequently, the results are of significance to the further development of the olefins industry, both with respect to the weak elements identified and the innovation options discussed.
Assessment results The system analysed is decomposed in olefins production and olefins consumption. Production is the subsystem illustrated in Figure 4-1; consumption predominantly comprises conversion into polymers, often via a production chain of chemical derivatives (Figure 4-2 and Figure 4-3), where strictly speaking polymer production is outside the system boundary of the petrochemical industry. A complete overview of the system analysed and results is given in Appendix A. 6.
Table 4.4: Key results of the olefin system analysis (1990 data) Capacity Mass Loss Energy Loss
Lb Le Lb Le [MTA] [MTA] [MTA] [PJ/Yr] [PJ/Yr] Production Olefins 3.57 0.70 1.21 47.5 47.5 Consumption Ethylene 2.28 0.44 3.01 16.7 17.0 Propylene 1.67 0.42 4.74 32.8 32.9 Total 3.95 0.86 7.74 49.6 49.9 Polymerisation Ethylene 1.57 0.04 1.71 11.3 12.0 Propylene 0.54 0.04 0.35 4.8 4.8 Total 2.11 0.08 2.06 16.1 16.9 Olefins Total 8.61 1.29 11.01 89.4 90.5 Notes to Table 4.4: 1. Olefins production capacity is only ethylene and propylene; efficiencies and losses are listed for a steam cracker that co-produces C4/C5 and aromatics. 2. The capacity of the olefins consumption subsystem exceeds that of ethylene and propylene production because some derivatives produced include oxygen and chlorine. 3. The relatively small capacity of polymerisation indicates other use and export of monomers from the Netherlands.
43 In case one is particularly interested in such assessment, it is suggested to contact one of the many consultancy firms that specialise in tracking the global (petro)chemical industry's development and performance.
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The key results of the analysis are summarised in Table 4.4 for process net mass and energy losses b (material/energy supplied that ends up elsewhere than wanted main or by-products) and total mass and energy loss e (process energy/material + utilities supplied that does not end up in products/by-products). Losses b and e have been calculated as defined in chapter 3 (Eq. 3.21-3.24). The entire system around olefins requires a total feedstock and energy input that is equivalent to some 6 [MTA] naphtha, or some 250 PJ/Yr. Its chemical and polymer represent some 135 PJ/Yr, and some 115 PJ is lost from the system annually. It follows that the gross energy efficiency (on the basis of LHV) of the system around Olefins is some 54%. Thus, the energy efficiency of this complex chemical production system exceeds the efficiency of Dutch electricity generation (which currently is some 45%).
Weak elements? The results of the system analysis as presented in Table 4.4 can be interpreted in various ways. Olefins production and consumption for conversion into petrochemicals require attention when the results are analysed using the aggregate system level perspective where the system around olefins is thought to be decomposed into a subsystem for olefins production, conversion into petrochemicals and final consumption for polymer production. The results of the analysis show that both mass and energy loss Lb of olefins consumption for conversion just exceeds the losses associated with of olefins production. The losses associated with polymerisation are the smallest. These results should be interpreted with care, however, as the results on polymer production do not include the losses associated with PS and other polymers that include material with an olefin origin. In addition, the Dutch capacity installed for polymer production does not match the quantity of monomers produced. A considerable amount of petrochemicals is exported. In case the exported monomers would have been converted in the Netherlands, the associated losses would total some two-thirds of the losses in olefins production and associated conversion respectively. The energy incorporated into the olefins by steam cracking is largely retained when olefins are converted to more complex monomers, as the energy-rich double bond remains unchanged in the conversion or is converted into an epoxy structure. Eventually, however, the greater part of the monomer's increased energy level is used to effect polymerisation, which results in energy loss from the system as waste-heat. Inspection of Figure 4-2 and Figure 4-3 reveals that while olefins production (Figure 4-1) only involves the steam cracker and propylene from catalytic cracking, olefin conversion involves some 20 distinct industrial conversion processes and some 10 polymerisation processes that each contribute to their respective subsystem losses. Therefore, a proper conclusion is to take special notice of the large loss of the steam cracker, and to inspect the results for olefin conversion in more detail. Indeed, when the analysis results are inspected at the aggregate level of individual plants and when all processes in the olefins systems are ranked, the steam cracker
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ranks first with respect to net energy loss and mass loss . In 1990, steam cracker plants only had an overall energy efficiency of some 65%44. The results can also be interpreted using an ethylene and propylene subsystem division. In the subsystem around ethylene the total energy loss, the loss allocated to steam cracker ethylene production, equals the combined losses associated with EDC/VCM, ethylene oxide and ethylene glycol. In the propylene consumption subsystem, especially propylene oxide production is the exception because its net loss exceeds the loss allocated to steam cracker propylene production. The energy efficiencies vary from a 39% low (ethylene diamine) to a 93% high (PE/Vac copolymerisation). Especially endothermic processes (steam cracker), partial oxidation (ethylene oxide, propylene oxide) and other exothermic processes (ethylene glycol) have a relatively high scope for improvement index. In all these processes there is a relatively large energy transformation between heat and chemical energy where the Second Law of Thermodynamics dictates that retention of energy quality is impossible and maximum retention of quantity is economically infeasible.
4.3.3 IN-DEPTH ANALYSIS OF INDUSTRIAL STEAM CRACKING In the assessment of the industrial olefins system, the steam cracker has been identified as a major weak system element because of its net mass and energy loss. The indices calculated (Appendix A. 6) merit a thorough investigation of some 6 weak elements identified. Since our purpose is to test the possibilities and limitations of the methods proposed in Ch. 3, we have opted to focus on the analysis of industrial olefins production by steam cracking in this chapter. In the method described in Ch. 3 one must use weak elements identified as a starting point for the search for improvements. This search, however, must be preceded by a thorough analysis of the causes for the losses calculated. Therefore in this section an introductory overview of steam cracking essentials and development is given. In the process, the 'black-box' of steam cracking is opened, and the subsections of this industrial system, its unit operations and internal interconnectivity are analysed (see Ch. 3, Table 3.1). Using the knowledge thus assembled, intra process causes are identified and options for improvement postulated. These are limited to intra- process; potential modifications involving re-labelling of process outputs and the petrochemical system around the cracker will be addressed in the subsequent section using functional modelling. Since the steam cracker is the feedstock generator for the petrochemical industry, the body-of-knowledge and the available literature on this process is immense. Extensive introduction and background information can be found (e.g. Kniel et al. 1980; Chauvel and Lefebvre 1989a; Anonymous 2000; and Stanley 2001).
44 It is not the objective of this analysis to assess technology improvement, i.e. the effect of process innovation during the past decade. Benchmarking has revealed, however, that the Dutch steam crackers rank amongst the top-10% of steam cracker installations worldwide. Because of the confidentiality of performance data on individual installed plants, however, it is not possible to verify and compare current performance data. Suffice to say that if, through process innovation, performance has indeed risen to some 70-75%, this is a tremendous achievement and proof of the technological capabilities of the industry and its technology suppliers.
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Steam cracking is pivotal to the petrochemical industry because it serves to create reactive chemical components from relatively unreactive hydrocarbons present in fossil feedstock. Thus it allows the utilisation of fossil resources for the production of durable and consumer goods. Steam cracking exhibits a variety of characteristics that are typical of the processing industry: a large-scale of operations (current single- train capacities up to one MTA ethylene per year), integrated production complexes where a variety of products and co-products are further processed or recycled to maximise the net revenue of the steam cracker site, high capital requirements, high knowledge intensity, relatively low labour-intensity. We have argued that each chemical process can be described as a system that comprises feedstock preparation, reaction, separation, a process recycle, and final product purification (Dijkema et al. 1998). In addition, we argued that the key function of the process recycle is often misunderstood. The steam cracker also fits into this general model, however, with an important deviation that the process recycle is sent to a special reactor for recycle processing. This is a system design option that also has been developed and applied elsewhere, for example in cumene production (Dow Chemical Benelux 1994). In the literature a steam cracker is usually described as comprising two or sometimes three major system elements, viz. a hot reactor section, a compression section, and a cold separation section. The latter two are often combined and labelled the separation section, while quenching and stabilising are seen as part of the front-end or hot reaction section (Figure 4-4). Another important system element is the recycle of ethane and propane, which consists of unconverted feedstock or co-product formed in the hot section. Today these are usually recycled to a dedicated reaction furnace. When the recovery of co- produced pure aromatics is included, the so-called raffinate from aromatics extraction is an additional feedstock recycle to the cracker. The hot reaction section consists of a series of furnaces where the feedstock is diluted with steam and heated to some 800 to 900 oC to effect the cracking reactions. Immediately after the cracking furnaces, the reaction mixture is cooled rapidly ('quenched'). Water and heavy components ('tar, pyrolysis gasoline') are removed in a stabiliser. In the separation section, the lighter products (up to C6) are compressed and sent to the cold separation section that yields the individual light olefins as essentially pure products.
Hot section: the cracking furnace Apart from paraffins and iso-paraffins, the feedstock of a steam cracker can contain significant amounts of aromatics and naphtenes (polycyclic aromatics. In the process, these are broken-down and rearranged via a large array of chemical reactions. The worlds most used kinetic model of a steam cracker, SpyroTM includes over 2000 chemical reaction steps (Overwater 2001). These reactions can be divided in primary and secondary reactions.
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Figure 4-4: Steam cracker overview.
132 Process System Innovation by Design
Major primary reactions in the steam cracker are: • Dehydrogenation, An organic molecule loses two hydrogen atoms, e.g. from ethane to ethylene:
H3C-CH3 Æ H2C=CH2 + H2 • Cracking An organic molecule is cleaved, e.g. hexane yields propane and propylene: C-C-C-C-C-C Æ C-C-C + C-C=C.
Important secondary reactions in the steam cracker are: • Dehydrocyclisation In this case, a ring is formed from one or more olefins, after which hydrogen is lost to yield an aromatic ring
C=C-C=C + C=C Æ C6H10 Æ C6H6 + 2H2 • Dealkylation This is a reaction where aliphatic side-chains of aromatic rings are removed. The end product is benzene or naphthalene (double ring)
C6H5-C2H5 Æ C6H6 + C=C
The most important desired reactions are the primary reactions, where light olefins are formed. The secondary reactions largely occur following the primary reactions. They are responsible for the heavier components in the cracked-gas such as benzene and butadiene. Tertiary reactions include the formation of coke on the furnace pipe surface. Coke formation occurs via a variety of reactions, by which large carbon networks are formed. These reactions are favoured by high-pressure. In order to suppress coke formation, in the steam cracking process the feedstock is diluted with steam to lower the reactants partial pressure. The steam cracking reactions occur largely in the gas phase. The reaction mechanism is via free organic radicals (Chauvel and Lefebvre 1989a). The reactions are initiated by bond-cleavage that yields two organic free radicals. In propagation, these radicals can react with the other components to yield desired products + additional free radicals. Finally, in a gas mixture where the radical concentration increases, recombination of radicals terminates the chain of steam cracking reactions. An inevitable consequence of this mechanism is the formation of a substantial amount of hydrogen and methane in the product mix. All of the individual reaction steps involved have different thermodynamic and kinetic characteristics, which are a function of Pressure, Temperature and chemical composition. The product mix of a steam cracker furnace thus is a function of feedstock composition, furnace radial tube temperature distribution and longitudinal profile and the residence time. In SpyroTM all these effects are accounted for to achieve an optimal design. The steam cracking furnaces today largely have been designed as and operate as single-pass reactors because the substantial energy requirements to operate the cold separation dictate that a limited share of recycles must be sent through the process.
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To achieve favourable process economics, therefore thermodynamic equilibrium conditions achieved must be such that product yield is 50-60% or higher per furnace pass. Thermodynamics determines the equilibrium reaction mixture composition per chemical reaction. Its kinetics determines the speed by which this equilibrium is approached. The equilibrium of cracking reactions is favourable from 300 oC and beyond, while the equilibrium for dehydrogenation is favourable from 700oC onwards. The rate of these reactions becomes significant above 700o (cracking) and 800o C (dehydrogenation). These characteristics have large consequences for the 'facility' of cracking of a particular feedstock. For example, ethane or propane cracking requires a high temperature (850 oC because substantial dehydrogenation must occur. In gas oil cracking, however, cracking reactions dominate, and a lower temperature (750 oC) can be selected in furnace operation. A catalyst can suppress or accelerate the speed of a particular reaction. A consequence of the thermodynamics, however, is that the use of a catalyst appears to be relatively useless to improve the process. Economics and the thermodynamics dictate high operating temperatures, where the required reactions occur at high speed spontaneously. The use of catalyst, such as in catalytic cracking in a crude-oil refinery, would then require both an expensive catalyst and an expensive reactor / regenerator system to burn-off coke deposits. To match the thermodynamics of the steam cracker reactions, the reaction furnaces are laid out such that an optimal temperature profile in the furnace tubes is achieved. In the entry-zone the temperature is some 400 oC, while the highest temperatures are reached at the exit. Thus, cracking can occur first, followed by dehydrogenation. Most primary and secondary reactions that yield olefins are strongly endothermic. Thus, a large supply of energy to the feedstock / reaction mixture is required . The energy is supplied in cracking furnaces where the heat liberated by burning natural gas, liquid fuels and co-products of the cracking process is transferred to the reaction mixture in the furnace pipes. The furnace and furnace-tubes have such a layout that the specific heat-transfer requirements for the cracking and dehydrogenation reactions are matched: feedstock entry in the convection zone, final exit after passing the hot radiant zone. To freeze the reaction mixture, it is rapidly cooled in a quench system, which is a combination of in-line heat exchangers that generate high-pressure steam, and in-line quenching for direct heat-transfer to a quench-oil. In each of these operations a significant part of the potential to do Work, exergy, is lost. In transferring energy to the reaction mixture the chemically stored exergy in the fuel is transformed to heat. According to the Second-Law, the heat then can only be partly converted back into chemical exergy, the remainder is lost as waste heat. Subsequently, the high-temperature reaction mixture is rapidly cooled down, where the energy is recovered only as heat, and again potential to do Work is lost. In short, the process employs crude, large-driving forces, which thermodynamically inevitably lead to irreversible losses of exergy. Since the exergy required presently is supplied by burning fossil fuels, there is a direct link with the process' CO2 emission.
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separation. First, the cracked-gas is compressed to some 35 bar to allow cryogenic separation at acceptable temperature levels. Given the capacity, gas composition and pressure difference, the cracked-gas compressor rank amongst the most advanced centrifugal compressors in the world. It consists of four to five stages with gas- intercooling to prevent oligomerisation, and is usually driven by steam turbines. At each interstage, liquids are collected. Sulphur compounds in the cracked gas originate from the feed and from trace sulphur components added to the steam cracker feed to avoid furnace-tube deterioration. Therefore, just before the final compression stage, the gas is desulphurised and CO2 removed by an absorption process (employing caustic soda or ethanol amines). Finally, the cracked gas is dried over molecular sieves to very low moisture content in order to avoid the formation of ice. In the cold separation section, essentially the following operations must be completed: - Removal of non-condensable gases These include hydrogen and methane. In a traditional cracker design, this is done in the first column, the demethaniser, where the lowest temperature is achieved (-100oC) - Removal of acetylenic compounds. These compounds are removed by selective dehydrogenation from the ethylene produced, and sometimes also from propylene. - Production of essentially pure ethylene
This involves separating the C2's (ethane/ethylene), followed by ethane/ethylene separation - Production of essentially pure propylene
This involves separating the C3's (propane/propylene) followed by propane/propylene separation. + The C4 fraction may be subject to C4/C5 splitting and butylenes, butadiene and C5 + olefins recovery. The remainder C5 gasoline is rich in aromatics, especially benzene, and thus may be sent to an aromatics plant. Depending on the composition of the cracked-gas and local economics, a variety of process schemes may be considered. Optimisation of the separation section configuration has led to considerable energy saving over the years. Similar to supplying heat, cold represents a deviation from the reference state. A driving force is required to create it. In effect, the cycles used to supply cold have a thermodynamic upper limit to their efficiency. Work must be supplied to pump heat from a lower temperature to a higher temperature, part of which is lost as waste heat. Subsequently, the cold streams created provide the proper conditions and part of the driving force to the separation process. A large part of the exergy supplied via the cold streams is lost, however.
Intra process causes The steam cracker is a weak element in the olefin-system because of its large energy 'loss' to the environment. In addition, it is characterised by a considerable mass loss:
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part of the feedstock is eventually used as fuel and converted to CO2 and water instead of desired products. This is caused by a variety of process characteristics: (1) the reactions towards olefins are strongly endothermic, and are effected at elevated temperatures in milliseconds. As a consequence, the energy efficiency of the furnaces is limited to some 85-90% today. In addition, the net transfer of heat liberated from fuel combustion to the reactor mix is limited, the remainder can only be recovered as heat. (2) Thermal cracking leads to a mixture of products that inevitably require separation. In this particular case, some of the products (hydrogen, methane, ethylene) are separated in commercial installations at high pressure and very low temperature, in large cryogenic distillation columns. Both the thermodynamic efficiency of such columns is limited, as well as the efficiency of the cryogenic operations. Finally, the maximum thermodynamic efficiency achievable in gas compression is only some 35%. (3) The product spectrum of the cracking section is such that a relatively large part of the product mix must be transported through a large part of the separation system, which increases the section's energy-use.
Intra process solutions Over the past 40 years, steam-cracking technology has development into an advanced but mature technology (Stanley 2001). Within the constraints set by thermodynamics, reaction kinetics, feedstock availability and process economics, a host of innovations has been developed and implemented in new or existing cracker installations. Hutcheson et al. (1995) give an overview of some 50 cracker innovations which all can be characterised as intra-process (Hutcheson et al. 1995). The fundamental problems or limits described above, however, are still valid today. A non-exhaustive overview is presented below. The crux of steam cracking is to rapidly achieve and freeze a favourable reaction mix. The progression of undesired reactions to their thermodynamic equilibrium must be prevented. Thus, where 'quenching' enabled the first successful steam cracking operations, the development of the Milliseconds Technology represents a major process innovation. Short residence times in the Milliseconds furnace result in higher selectivity towards ethylene, but require a higher furnace temperature. Other developments, such as in burner and tube design as well as furnace layout contribute to continued improvement of thermal cracking selectivity. Steam cracker furnace technology therefore is an extremely important area of research. Its scope, however, is largely within the boundaries and limits of the technological concept of steam cracking. When one is confronted with a thermal and therefore by definition unselective process, the very first option to be considered is the development of some catalyst that offers selectivity at acceptable yield. It is well known that cracking reactions can be accelerated by the use of catalysts. At high operating temperatures, excessive coke-formation presents a problem. In catalytic cracking in refining, this problem has been addressed by applying a reactor-regenerator system, where the deactivated catalyst is reactivated in the regenerator by burning of the coke. Analogous catalyst / reactor / regenerator combinations for steam cracking, however, are not in commercial use. This may be because dehydrogenation is one crucial and final reaction step in the production of ethylene from heavy organics. The
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thermodynamics of this reaction step prohibits the use of a catalyst for dehydrogenation at low temperature for the conversion of ethane to ethylene. Alternative reaction paths to avoid said thermodynamic limitation of ethane dehydrogenation have been extensively investigated. Oxidative dehydrogenation is one possibility, but any catalyst must prevent the oxidation from running to completion. Eastman et al. (1990) summarize the developments and conclude, however, that this route was not commercially viable because at the time no suitable catalyst had been found (Eastman et al. 1990).
Energy use Thermodynamically, the 'process path' in a steam cracker deviates considerably from the optimum, reversible path. One major indication for this is the extreme differences between the temperature levels of operation. A second indication is the requirement of rapid heating, followed by rapid cooling. Thermodynamically this equates to the use of large driving forces, which imply large losses (Prigogine and Stengers 1984). Apparently, economic trade-offs drives one into this particular direction. The consequence of this is that a large amount of Work, or exergy, is used in the hot reaction section, the compressor and the cold separation section respectively. This is observable in the difference between feedstock and product exergy. The difference is liberated as heat, only part of which can be utilised. Improvement, i.e. reduction of the net energy supplied to a steam cracker of existing design, can be achieved via three major routes: 1. Optimal matching of heat demand and heat generated as a consequence of the process paths selected. This is the objective in the use of Pinch technology, to achieve the thermodynamic optimum in heat integration. 2. Modification of the temperature levels by adding equipment in various heat streams that convert part of those streams into work: process & energy integration. One option is the use of a gas turbine that provides part of the heat of reaction to the furnaces, whilst producing shaft-work (Dijkema et al. 1998). 3. Modifications in the process system design, e.g. in the cold separation section or recycle structure. These modifications can be enabled by the advent of new technology, e.g. in cold separation technology. Their adoption by industry is subject to the total expected lifecycle cost trade-off between energy-saved and additional investment. Examples are adsorption-cooling and open cooling systems that use product streams with direct contact. Modifications to the system design also can comprise a combination of 'utility optimisation' and feedstock/product utilisation. For example, styrene in the aromatics fraction can be hydrogenated and extracted as ethyl benzene, but it can also be separated as a by-product. In the latter case, further processing steps from ethyl benzene are avoided, and utility hydrogen otherwise required can be saved for other applications.
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4.3.4 CONCLUSION The use of the systematic assessment procedure and systematic search for options for improvement (Ch. 3) has been illustrated for the case of steam cracker technology. Since the scope of the analysis and search for improvement was limited within the steam cracker system boundary, only intra-process improvements were suggested. It is well known, however, that the upgrading of waste products to by product (C4/C5 olefins, aromatics) and eventually co product (propylene) has been a successful strategy of stream cracker operators. The concept, however, can still be useful today with respect to ethyl benzene and styrene isolation, and the recovery of methyl acetylenics instead of their saturation. Some of the options thus identified will require a market to develop and further changes in the petrochemical industry to materialise.
4.4 Functional modelling of the olefins system
4.4.1 FUNCTIONAL MODELLING The previous section illustrates that an in-depth review of intra process causes initially leads to improvement options within the scope of the existing process concept. As a matter of course a brainstorming session could be organised to try and arrive at novel alternative concepts of the steam cracker or parts thereof. Our present objective, however, is to demonstrate that functional modelling (Ch. 4) provides a method to structure 'rethinking and reinventing' systems while linking various system aggregate levels. Functional modelling can be employed to specify the content of process system innovations of the technological part of systems, in this case the steam cracker process for the production of olefins. Thus, although it may be argued that one of the objective-defined functions (ODF) of every privately owned technological system is to generate cash flow, profit, or a return on investment, this is not the only starting point to look for innovations. As a matter of fact, in a mature industry like that of olefins production, cost probably has been used a million times as a starting point for innovations. Therefore one can better use the (strategic) perspective of the 'end-user' of the system's function involved, which can then be easily expanded to include societal goals such as sustainability. The procedure presented in chapter 4 around functional modelling consists of (1) Generalise at some top system level (…) (2) Visualise the link of this subsystem of our industrial economy to other industrial sectors or parts thereof, thereby eventually allowing some linkage with needs of society catered for by ‘industry’ (…) (3) Arrive at a suitable functional decomposition of the petrochemical industry that finally allows the specification of technological or system content of innovations. (…) (4) Question and adapt system boundaries. Because functional decomposition is based on system and subsystem boundary selection it opens the way for consideration of alternative systems by expanding the set of functions in the model at a particular system level, or to view the system as a part of a larger system” (Dijkema et al. 2001).
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The Polymer Industry
Function Function 1 S
M o s n n o fi m le e O r The Petrochemical Industry s
Olefins BTX Production Consumption Function Functio Function Function M P 1 n 1
P G y B r , a o o ly T s X o s , , li m is n p e X BTX X Production , a h l i G t h P O p Function L s Function a a 1 N N G
ed rm a o th ef h R ap Refining N
Function Function 1 R
Figure 4-5: Decomposition around the olefins system (reprinted from Dijkema et al. 2003). Since the concept of functions allows technology-free specification of systems, in the process alternative methods of fulfilment - innovations - can be explored. Thus for example at the level of 'packaging' being the major driver of olefins production and consumption, one may consider devoting some attention at the 'reinvention' of packaging and the associated systems to fulfil our (basic) human needs.
4.4.2 GENERALISATION AND VISUALISATION The olefins system is part of the petrochemical industry, which primary ODF may be described as “to produce suitable feedstock for polymer production” (Figure 4-5). The generalisation achieved by the model presented in Figure 4-5, however, does not offer clues for specification of innovation. Thus the functional decomposition and system boundary were questioned. As a result of inspection and interpretation of
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Figure 4-2 and Figure 4-3, a slightly different decomposition and boundary selection was adopted to include the system level beyond the petrochemical industry. Thereby it may be seen that the 'olefins' or 'polyolefins system' is part of an industrial infrastructure, which major ODF is to provide packaging material, construction material and raw material for more durable consumer goods (Figure 4-6). With this model we can consider the whole chain from crude oil or gas to fulfilling the function of 'packaging' by a polyolefin. In this system the net energy consumption is very high. All the energy put into incorporating reactivity into the olefin is lost again in polymerisation. Subsequently, after end-use, most polymer material is either land filled or incinerated in the waste management infrastructure. The net result is that exergy; the potential to do work is lost. The functional model of our present system given in Figure 4-6 also indicates that recycling to each other element may be realised possibly via some recycling industry. Exceptions noted, however, present implementations of this functional element 'recycling' are relatively scarce. The conversion of plastic waste to feedstock, for example, to date has not been commercially exploited on a large-scale for the petrochemical industry nor the polymer industry. A continuous process of scientific and technological development has enabled the production of thinner and thinner packaging material, thereby consuming fewer kilograms of polymer per packaging application45. For several decades, however, packaging and consumer product supply chains have co-evolved, which for example led to the supermarket of today that sells pre-packed fresh pizza's in competition with pizza-restaurants. Such development illustrates that the improvements in material have lead to an increase in the application spectrum. The net result is a growth in the end-use of plastic, which trickles through to, amongst others, the production capacity employed of ethylene and propylene: the doubling of ethylene capacity in the past 16 years cannot be attributed to the population increase and welfare increase in emerging economies alone. This growth is accompanied by growth of two 'non-objective outputs' (Ch 4): resource depletion and CO2 emission (Figure 4-6). This illustrates that sustainability of the petrochemical industry requires innovation at higher system levels. In natural ecosystems, the 'decomposers' sustain complex ecosystems such as rainforests by enabling the high rate of nutrient cycling at a relatively constant (solar) energy input. Long-term innovation of the petrochemical industry should enable realisation of a similar industrial society, where essential materials are retained and recycled at constant net energy input and acceptable CO2 emission.
4.4.3 FUNCTIONAL REPRESENTATION OF THE OLEFINS SYSTEM Similarly to the case of aromatics (Dijkema et al. 2001), and as a matter of fact to any chemical that is not produced for end-use by consumers, we can decompose the industrial olefins system into a production system and a consumption system. The main ODF of the Olefins production system today is to cater for the demand for ethylene, propylene and butylenes. An additional function is the provision of aromatics.
45 This is an example of progressisve 'dematerialization' - to fulfil functions with less or no material.
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The ODF of the olefins consumption system is NOT olefins consumption, but this is a consequence of fulfilling its ODFs.
Satisfaction /
CO2-emission End Use Fulfilment (non-ODF) FE 1 FE N FE 2
Manufacturing Industry
FE 1 FE N FE 2
s .. r d r. e o o o f g m ts G ls in u c Waste a g s u le ri a n d b k o o a te c C r r a a P u M P D
Polymer production Recycling FE N FE 1 Industry FE 2 rs e m o n FE 1 o M
Petrochemical Industry FE 2 Fuels for... FE 1 FE N FE 2
p h o e Fe w a t e i FE N er n d F tr G g s a t u e o n e s n c p l o k rt Energy Industry Waste (Non-ODF) FE 1 FE N Depletion of Resources FE 2 (non_ODF)
Figure 4-6: Functional decomposition of industrial society around the petrochemical industry.
Olefins production system The main functions of the Olefins production system today are to cater for the demand for ethylene, propylene and butylenes. An additional function is the provision of aromatics. These functions presently are performed by its major system element, the steam cracker. A significant part of the provision of propylene as well as that of aromatics is by refineries through their cat cracking operations. At this system level, the functional difference between steam cracking and cat cracking is that the primary ODF is 'produce olefins' and 'produce a high-value naphtha cut for use in the gasoline-pool' respectively. An additional difference is that the steam cracking operation is limited to feedstock up to gas oil, whilst cat cracking uses heavy-gas oil, vacuum gas oil or light residue. The realisation of the ODF ' produce olefins' thus appears to be a combination of feedstock and technology,
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which is a common characteristic of production processes in the petrochemical industry. The actual selection of the preferred (feedstock, technology) combination to execute these ODFs depends on a host of factors, including system investment cost, time-to- investment, match of the product spectrum to the relative demand for ethylene to propylene to butylenes, feedstock availability, operating cost, availability of proven technology and last-but-not least, regulation. The petrochemical industry is characterised as a 'regulatory-driven industry' (Stobaugh 1988), which means that its present state is optimised with respect to prevailing regulation. A change therein can severely impact process economics. Changes may directly impact the economy of new and existing installations, e.g. when emission limits are reduced or a CO2 tax is levied. More often, regulation indirectly impacts part of the industry. For example the EU Auto Oil regulation on the aromatics content in gasoline, for example, has a significant impact on pre-Auto Oil steam cracker economics because a reduction in gasoline-allowed aromatics content will lead to a surplus of aromatics and lower their value. This requires changes in steam cracker operation or technology to maintain the process' profitability. We will address these issues again when discussing evaluation of improvement options identified. In the remainder of this section, we will develop and use functional modelling to specify possible content of process system innovation. The functional model of olefins production is summarised in Figure 4-7. The main operation of steam cracking and cat cracking is to breakdown large molecules into (preferably unique) smaller ones. The precise set of ODFs is largely dependent on the particular feedstock available and the system context. An overview is presented in Table 4.5.
Table 4.5: Functional characteristics of olefins production Feedstock Product ODF (s) Context 1 Ethane Ethylene, Convert light, aliphatic propylene feedstock to Ethylene, Propylene
2 Ethane/Propane Idem Idem Petro- 3 LPG or butanes + Butylenes Idem, and butylenes Chemical 4 Naphtha + Aromatics Convert heavier, Complex predominantly aliphatic feedstock to Olefins and aromatics 5 Gas oil Idem Idem 6 Vacuum Gas oil CC-Naphtha + Convert heavy feedstock propylene into high-value gasoline blending component & Refinery propylene 7 Residue CC-Naphtha + Idem propylene
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The major by-product of steam cracking is an aromatics-rich stream. In the drawing it is indicated that these are also produced from refineries and as a by-product from coke-oven production. In Figure 4-7these main functions have been visualised. In addition to the primary functions of a refinery, fuels production, and a steam cracker complex, olefins production, a novel function has been introduced over time, which is generalised as co-product recovery. With the development of cat crackers with increased propylene production, the cat cracking may become more a part of olefins production than refining (Figure 4-7). This drawing also explains the present move of refiners and petrochemicals producers to integrate their business or function(s).
CO2-emission (non-ODO)
Olefins Production System
,X B,T e len Recover thy Nat Convert E . Gas Light- Aromatic Liquids Aliphatic Byproducts e opylen Hydro- Pr carbons to Olefins G) 1-But (LP ylene ane But e / pan Pro Convert Naphtha Heavier Convert Hydro-carbons Heavy Oil to Olefins Fractions to Gasoline l soi blending Ga component; Recover Propylene l oi as e G u y id v s ea e H R c. a V
Figure 4-7: Functional model of olefins production.
At this functional level, thus it is obvious that not only refinery fractions are eligible feedstock, but also other sources shown, such as synthetic crude-oil fractions from Fischer-Tropsch synthesis plants that use synthesis gas that either originates from
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Coal (Sasol) or natural gas (SMDS). The processing of (mixed) polymer waste in for example the Veba process would also provide a suitable feedstock because its main product is a synthetic crude that contains large and aliphatic naphtha and gas oil fractions (Dijkema and Stougie 1994). Thus, the present fulfilment of packaging visualised in Figure 4-6 indeed can be realised in a material cycle. As stated above, the steam cracker can be decomposed into two system elements, viz. a hot section and a cold separation/purification section. If we inspect the steam cracker system diagram in Figure 4-4 a bit more closely, however, we see that a cracker complex consists of a number of distinct functional elements, viz. 1. Feed selection and feed preparation 2. Fuel selection, preparation and application 3. Various types of cracking furnaces (optimised for various feedstock) 4. A quench operation to provide rapid-cooling of the reaction mixture 5. A stabiliser to separate gases (olefins + saturated hydrocarbons + light gases) and liquids (aromatics, non-aromatics) 6. A compression section to bring the gases up to suitable pressure for subsequent cold separation 7. A cold separation section that produces individual olefins and a number of by- products 8. By product recycle(s), respectively to cracker feedstock and energy supply 9. A separation section that produces individual aromatics and a number of by- products
Function 1 and 2 are a consequence of the operation and feedstock selected in the cracking furnaces, while 5 and 6 are a requirement for 7 and result in 8 and 9. (Figure 4-8). A logical, high-level decomposition therefore would be one where this system has four main functional elements, viz. a reactor, separation section, recycle and product purification . Thus, we are back at the 'standard' model of any chemical plant (Dijkema et al. 1998) . In order to enable more specific starting points for system innovation, at the next level of detail, these three functional system elements can be further decomposed. From the descriptions above it may be seen that in the reactor section the range of functions is performed consecutively and/or simultaneously as listed in Table 4.6. Following the flow of the feedstock / reactants through the installation, functions 1 to 3 take place largely consecutively. On the level of the chemical reactions taking place in the tubes, both decoking and coking takes place continuously, but as coking outweighs decoking, a special furnace operation mode of decoking is required. Obviously, functions (1,4), (2,5) and (3,6) are paired.
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CO2-emission (non-ODF)
Aromatics ,X Recovery ,T Heavies Conversion B (non-ODF) FE 1 FE 1
FE N Product FE 2 Purification ne yle Eth Recycle FE 1 e Propylen FE N Feed FE 2 N Selection & at. Product 1 Gas Preparation -Butylene Liq Separation uids FE 1 FE N Prop FE 1 ane / B utane (LPG) FE 2 Fuel ha Napht Selection & FE N Preparation oil FE N Gas FE 1
FE 2 soil Ga Light gases avy He Nat (non-ODF) ural FE N Gas
Figure 4-8: Functional model of the steam cracker.
Table 4.6: Objective-defined functions in the reactor section Operation ODF 1 Heat-up Create favourable conditions 2 Chemical reaction Generate desired products 3 Cool-down Prevent product degeneration 4 Supply Energy for Heating Transfer energy to reaction mixture 5 Supply Energy for Cracking Idem 6 Withdraw Energy for Cooling Transfer energy from reaction mixture 7 Supply energy for Flow Transfer energy to reaction mixture 8 Decoke (Remove coke deposit) Ensure continued correct operation
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In the general model of a chemical process, separation is a consequence of the imperfection of the reactions carried out. In the steam cracker, this is profoundly the case because a complex mix of products is obtained from the cracking furnaces that require a substantial range of operations to achieve the final ODF of the installation, the production of essentially pure olefins. The sections' major ODFs have been summarised in Table 4.7.
Table 4.7: Functional elements of the Purification / Separation section Operation ODF 1a Split light-gases / liquids 1b Compress the light-gas Create favourable conditions for cryogenic separation 1c Cool the light gas 2 Olefins purification Remove unconverted feedstock, undesired
co-products (acetylenics, CH4, H2) 3 Ethylene isolation Produce pure ethylene 4 Propylene isolation Produce pure propylene
5 C4 isolation Produce C4 mixture 6 Withdraw Energy by Cooling Transfer energy from gas/liquid flow 7 Supply Energy for Heating Transfer energy to liquid/gas flow 8 Supply energy for Flow Transfer energy to gas or liquids
This is largely a mutually contingent set of ODFs in the case of steam cracker cold separation, possibly with the exception of ODFs (1b,8) because gas-compression serves both to increase gas pressure, and to let the gas flow through the installation. From the table it is clear that the operation selected for olefins isolation, cryogenic separation requires a host of supporting functional elements.
Olefins consumption system The function of the Olefins consumption system in the petrochemical industry is to provide monomer material that can be used by the polymer industry. In addition, it supplies some solvents and disposables (notably anti-freeze and cleaning agents). Over time, the realisation of conversion of olefins to alternate monomers has developed into the industrial network depicted in Figure 4-2 and Figure 4-3. The existence of this network and its ODFs are intrinsically related to the ODFs to be met by polymeric materials such as polyurethanes. Since the special performance characteristics of polyurethanes are much appreciated, their production volume growth has created considerable demand for propylene oxide, the precursor of propylene glycol and propylene glycol ethers that are essential polyurethane ingredients. The petrochemical industry, notably Daicel, Oxirane (later Arco, now Lyondell) and Shell Chemicals has responded to this growth in demand and environmental concerns on the chlorohydrin route by developing alternate realisations of PO production. Of the many possible realisations (hydrogen peroxide route, organic peroxide routes, organic peroxy acid routes), only the
146 Process System Innovation by Design
TBA/PO and Styrene/PO routes appeared to both chemically and industrially feasible. Despite process improvements, the original chlorohydrin route (Dow Chemical) became environmentally suspect. Direct oxidation still has not been successfully realised. In case alternative fulfilment of the ODFs of polyurethanes would be developed, however, over time the entire ODF to meet polyurethane monomer material demand would disappear. Thus, the ODFs of olefins consumption are 'meet the demand of a set of monomer materials'.
4.4.4 TOWARDS PROCESS SYSTEM INNOVATIONS Now that we have formulated a functional model, we can (1) categorize innovations reported/found in the literature and validate the model by identifying matching conventional and new ODFs and (2) try and prove our methodology by the specification of original innovations. The functional model is a technology-free specification of systems around olefins, and “because the decomposition is based on system and subsystem boundary selection it opens the way for consideration of alternative systems by expanding the set of functions in the model at a particular system level, or to view the system as a part of a larger system” (Dijkema et al. 2001). As the objective of this case study is to demonstrate the usefulness of functional modelling and to 'prove' the methodology for process system innovation by design, rather than to provide an exhaustive review and outlook for olefins production overview, only a limited number literature resources have been used to categorise some of the 'present state-of-the- art'. Notably the proceedings of the DGMK- tagung 2001 (Emig et al. 2001) and Albright (Albright et al. 1992) provide a good overview of the state-of-affairs and the change therein that is suitable for our purposes. At the system level beyond the steam cracker, also some of our work on waste management and industrial ecology has been incorporated. In the methodology innovations comprise the specification of novel realisations of existing ODFs or the identification of novel ODFs and their possible realisations. Both types of innovations have been categorized and specified for the system within the boundaries of the steam cracker model as well as for a larger system, e.g. when the system boundary is expanded to span olefins production or the entire olefins system. In this section firstly innovations are categorised and specified to fulfil the ODFs within the system boundary of the steam cracker. Subsequently, the system boundary is expanded to olefins production and finally to span the entire system around olefins.
Innovations within the steam cracker process system Functional model. Over the years, the set of ODFs of steam cracking complexes has expanded. Initially, ethane/propane crackers were built for ethylene and propylene production, and were seen as a good opportunity to upgrade these co-products from 'wet-gas' production. The main ODF for these plants thus was to' upgrade wet-gas co-products'. With the growth of the ethylene and propylene markets, notably in Europe, crackers operating on naphtha feedstock were built to cater for this demand. The main ODF for these plants thus was (and is) to 'produce sufficient
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ethylene and propylene'. One of the co-products of these plants, aromatic pyrolysis- gasoline was soon recognized as providing a source for functions, the production of essentially pure B, T and X. Another function introduced was the isolation of pure
C4-olefins. Lately, C5-olefin isolation and hydrogen recovery have been introduced, and processes for the isolation of ethyl benzene and styrene have been developed. Today, the major ODF of steam crackers appears to be 'produce an economic mix of ethylene and propylene'. (1) Categorize/validate. Within the steam cracker flow sheet, major innovations have been developed and implemented over the years (Hutcheson et al. 1995). In the hot section, amongst others, these include: • Improved furnace-tube materials and design, which led to higher olefin selectivity, yield and reduced coking (fulfilment of functions 1&2) • Improved furnace design for greater capacity (process intensification) and greater furnace efficiency • Milliseconds technology for improved selectivity and yield
In the separation section these include: • Improved compressor design allowing greater cracked-gas compressor single- train capacity at improved efficiency • Improved distillation tower design, allowing greater capacity and separation efficiency • New 'cold-box' technology that leads to significant reduction in power consumption for cooling
All these changes and improvements fall under the umbrella of the functional model of the cracker and its elements presented, as they deal with improved 'fulfilment' of said functions. As stated above, these have increased the efficiency of operations considerably, with the possible exception of the milliseconds technology. It is easily calculated, however, that today's efficiency of a steam cracker is still only some 65- 75% (based on LHV of feedstock and (co-) products. Process system innovations have been developed that must be categorised as 'novel ODFs/functional elements. At the level of the flow sheet, these include the concept of 'side-cracking' furnaces for dedicated ethane/propane recycle, the isolation of individual butylenes and the inclusion of metathesis to shift the relative yield of olefins (Stanley 2001)). (2) 'Proof' of the methodology. The core of this thesis is a methodology to arrive at specification of the content of innovations in complex systems. Using functional modelling and decomposition the ODFs of the steam cracker have been established. Subsequently, the expert knowledge and results combined in (Dijkema et al. 1995) and literature cited was combined. The functional model was used to identify alternative ODFs for the system and to identify alternatives for fulfilment of the ODFs in the steam cracker model. Together, these have led to the following suggestion for innovations within the system boundary of the steam cracker complex:
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1. The transformation of a steam cracker to a trigeneration concept (Dijkema 2001b). We have argued that chemical reactors that operate/require energy supply at a high-temperature offer a large possible heat sink for energy conversion devices for the production of electric power. Similarly to the implementation of cogeneration, a cracker-furnace could thus be equipped with gas turbine(s) where heat is supply to the cracking furnace from the GT-'s exhaust (Loffel and Schulz 1984). Although this option has been implemented in a few cracker units worldwide, it has not been part of the recent cracker revamps. The concept
should be re-evaluated in the present liberalised electricity market and CO2 emission-trading schemes whilst taking into account the present state of furnace technology. 2. Introduction or enhancement of steam cracker feed preparation (of naphtha and gas oil) to eliminate (TX-) aromatics being sent to the cracker furnaces. This would reduce the amount of methane due to dealkylation in the cracked gas, and would allow direct utilisation of these aromatics. To absorb and effectively utilise the 'glut' of aromatics that results after Auto Oil I and II, similar to an ethane/propane side cracker, an aromatics side cracker or aromatics extraction + conversion (hydrogenation) could be developed. Alternatively, in- situ selective aromatics hydrogenation may be an attractive option despite the requirement for hydrogen. 3. Steam cracker process system for flexible operation The main ODF of any steam cracker is “to produce an economic mix of ethylene and propylene”. This implies that operation flexibility with respect to feedstock diet and product spectrum must be catered for. Apart from increased furnace operational flexibility, the inclusion or addition of novel functional elements can help achieve this. Examples are 'Side-cracking' furnaces for ethane/propane, 'metathesis' reactors and aromatics converters (see below). 4. The exploration of reactor concepts where (the functions of) dehydrogenation and cracking regimes are implemented largely separately. By physically separating dehydrogenation and cracking, the former and possibly the latter then may be conducted catalytically at greater yield and selectivity. 5. Enhanced-recovery of steam cracking co-products The steam cracking operation produces a variety of chemicals in the cracked-gas that presently are labelled 'impurities' or as invaluable. Both the resource utilisation and economics of steam crackers could improve if one would consider • Co-production of various-grades of hydrogen / methane mixture • Co-production of styrene by isolation of styrene • Co-production of di-olefins, acetylene and acetylenics for use in specialty chemicals production
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6. Extraction of olefins, use of aliphatic hydrocarbons produced for syngas generation.
It is well known that syngas (CO/H2-mixtures) are can be produced from higher aliphatic hydrocarbons under relatively mild conditions. Thus, instead of using
the higher aliphatic hydrocarbons (C5-C8) that are present in straight-run naphtha as steam cracker feed, these may be selectively converted to syngas and C3-C4. Such an option, however, also requires effective separation of C3/C4 from the syngas mixtures produced. In other words a number of process innovations are required to bring said process system innovation into being.
Innovations beyond the steam cracker system Functional model. In the currently available systems for olefins production, notably the yield of ethylene and propylene does not match the demand of these products. Propylene demand is growing much faster than ethylene demand; even to an extent refinery propylene is not expected to be able to match these demands. Thus, the past ten years (Stanley 2001), companies worldwide have been active in developing new ways to manufacture propylene. These options represent novel functional elements in the olefins production system model. (1) Categorize/validate. An important category is the processes that exploit methanol as a feedstock: • Methanol-To-Olefins (MTO) A process to convert methanol to largely ethylene and propylene. After initial development in the eighties (van Geem 1994), currently a scheme via the intermediate production of dimethyl ether (DME) is favoured. This process is nearly commercialised, with the first plant being constructed. Functional element ODF: convert MeOH to ethylene and propylene Important additional Function: produce water! Actually, from some 1.7 MTA MeOH, the plant will produce 0.9 MTA water, and 0.59 MTA propylene • Methanol-To-Propylene (MTP) A process that is developed by Lurgi that is in its demonstration phase. Important additional Function: produce (process) water. Actually, from some 1.7 MTA MeOH, the plant will produce 0.9 MTA water, and 0.59 MTA propylene. Where Lurgi (Rothaemel and Holtmann 2001) argues the process water can be made suitable for agricultural purposes, we would suggest that both an MTO or an MTP plant could play an important role in the water (cycle) management of an industrial site. In both cases trace chemical species in the water must be taken care of. Another option is a function-shift of cat cracking, such as developed by UOP (Greer et al. 2001). Where the latter is probably limited by the amount of aromatics by product, the routes via methanol have largely been developed on the incentive of 'monetizing' remote natural gas-fields that otherwise must be considered stranded. Combined with the launch of the MegaMethanol
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technology by Lurgi, a route that is competitive with oil-based olefins appears to be in reach. Metathesis of olefins is a function that is best described as 'conversion of a particular olefin into a spectrum of other olefins'. Thus, metathesis has been developed for a variety of feedstock, notably butylenes and higher for the production of additional ethylene and propylene. Presently, the function is advocated for inclusion in the steam cracker flow sheet because of the need of subsequent separation of the olefins produced. It is expected, however, that such flow sheets exhibit a lower resource utilisation than present ones. This is because realisation of this function requires additional operations with inevitable losses due to irreversibilities. Another chemical conversion of use in the olefins systems comprise 'Deep-FCC' for propylene production: refinery cat crackers can be equipped with modified catalysts and be operated at conditions optimised for propylene yield. Aromatics may be subject to hydrogenation followed by ring opening and use as steam cracker feedstock. This requires the availability of hydrogen, however. Oxidative coupling is a 'holy-grail' in industrial organic chemistry: combine two molecules of methane and a single molecule of oxygen to yield ethylene and water. Unfortunately, to favourably execute this reaction has been impossible for the past three decades. Oxidative dehydrogenation of ethane is another candidate to realise ethylene production. (2) 'Proof' of methodology. The inclusion of novel functions in a system preferably should help exclude those functions within the system that can only be implemented at relatively low resource utilisation. Such functions can be entire processes (functions) in a network or parts thereof such as the steam cracker separation section. Upon first inspection the options given above do not meet this criterion. In the olefins system, however, the development of suitable polymers and polymerisation of ethylene/propylene mixtures would greatly simplify the cracker separation section and contribute to system flexibility. Options that span multiple systems could also result in the avoidance of costly separation, e.g. cannot an ethylene / ethane mixture be used for polymerisation, where eventually ethane is recycled back to a steam cracker? At the feedstock end, mild cracking could be introduced as an additional feed preparation to off-load (inefficient) cracking furnaces. When waste-heat in such installations would be used, this present a case where efficiency is increased by splitting an existing function into two complementary functions.
Innovations beyond the petrochemical industry Functional model. Moving beyond olefins production and consumption, it may be seen that these functional elements are part of a longer chain, the fast carbon material cycle (Ch.1). To date the route back from consumer goods to polymer feedstock appears to be via CO2 emissions to the atmosphere. Obviously, for polymers direct mechanical recycling is to be preferred because this does not involve chemical conversion - cracking or depolymerisation, purification and repolymerisation. In many cases such direct recycling cannot be realized, however, because no suitable technology exists, e.g. to recycle polymers in non-ferro automobile shredder waste. In other cases, the recovery chain is economically
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infeasible. As a consequence, the implementations of recycling routes that include industrial chemical processing are largely lacking, with the exception of large-scale incineration. (1) Categorize/validate. The R&D effort on the recycling of plastics involving some industrial processing has been immense. As indicated in Figure 4-6, either an existing facility for the production of olefins can use polymers, or it may convert polymer waste-derived feedstock. In both cases, a more efficient exploitation of the industrial part of our global carbon cycle would result. A number of ODFs can be distinguished: 'enable recycling of polymeric material' ('back-to-polymer'), 'convert waste polymer to useful monomer materials' ('back-to-monomer') and 'convert waste polymer to suitable hydrocarbon mixtures' ('back-to-feedstock'). A few commercial plants are in operation that employ depolymerisation and back-to- feedstock processing. Around packaging, one option that was heavily debated in the Netherlands after implementation of the 'Duales System Deutschland' in Germany was the recycling of mixed plastic waste. In a system study on the Veba-Oel route for the processing of Mixed Plastic Waste (MPW), a back-to-feedstock route, the system's ecology appeared to be favourable but the economics were not. In addition, the organisational aspects and public acceptance of MPW collection were considered questionable. At the time, however, olefin and polyolefin manufacturers feared that successful recycling would be detrimental to the economy of their operations, as they anticipated a loss of market share for the production of virgin material (Dijkema and Stougie 1994; Sas et al. 1994a). In the study cited, only one option to fulfil the ODF 'convert MPW' back-to-feedstock has been evaluated. In the near future, however, olefin and polyolefin manufacturers may be threatened by a competing system for provision of the ODF 'packaging' that is based on biopolymers, especially when these can be produced with a CO2 neutral - label. On a different track, in the present system for the ODF 'packaging' a lot progress has been made to 'dematerialise packaging' by reducing thickness of the polymer sheet used. (2) 'Proof' of methodology. Functional modelling indicates a system solution is required where needs are fulfilled instead of materials being supplied. Since a finite amount of materials always will be used, recycling technology is required. A novel functional element in the material cycle around olefins and polymers would be 'back- to-infrastructure'. Rather than using recycling technology on location for a specific product, the end-of-life conversion of polymers can be connected to electricity, natural gas, synthesis gas or hydrogen infrastructure to realise effective conversion, recycling and distribution of the recycle products. Specific realisations will comprise of integrated system designs that can make use of depolymerisation, pyrolysis, gasification, product purification and incineration with energy-recovery.
4.5 Discussion and Conclusions In addressing possible innovation around olefins, the value of a structured approach has been illustrated. Assessment based on a 'trivial' decomposition of the industry provides a starting point for a systematic analysis and search for options for R&D. The results, however, are largely confined to the initial process concept. Functional modelling provides a structured method of abstraction of the current method of
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'fulfilment' of the present ODFs of the industry. In addition, it allows an integration between system levels and innovation thereof. In the case of the steam cracker, it has been demonstrated that categorisation of innovations reported in the literature using the functional model developed provides a validation of methodology. The novel functions and novel methods of realisation of the functions categorized or specified are 'proof' of the methodology for process system innovation by design. Thus, functional modelling does indeed provide a route to specify the content of process system innovations in the industrial systems around olefins.
5 Fuel cells and Trigeneration
5.1 Introduction This thesis includes three chapters on application of the methodology for 'process system innovation by design' as developed and presented in Ch. 3. In the previous chapter, a case study on an important sector of the petrochemical industry, olefins, has been reported (Ch.4). Process system innovation content was specified assuming a largely unchanged system external world. In Ch. 6 the impact and opportunities are addressed that are related to a dramatic change in the external world of the petrochemical industry, the emergence of PEM fuel cell vehicles in automotive transport. This chapter focuses on using the methodology to explore and specify innovations for chemical process systems that make intelligent use of an extra-sector innovation, fuel cells. These are a novel class of electrochemical energy-conversion technologies, which are being developed for the energy sector and automotive transport (see also Ch. 6). The crux of this chapter is the recognition that it is the combination of fuel cell functions that must be exploited in process system innovations. The first part of this chapter consists of an in-depth analysis of the use of fuel cells in the petrochemical industry at three system aggregate levels - unit operation/reactor, process system and industrial complex. This work has been presented at the 1999 Joint International Meeting of the Electrochemical Society46. In the second part of this chapter, the concept of trigeneration is explored. Trigeneration is the combined production of chemicals, electric power and heat. Functional modelling is used to develop innovative system concepts to realise trigeneration. A paper on this work has been presented at the 6th World Congress on Chemical Engineering, 200147.
46 Dijkema, G.P.J. (1999a,b), Fuel Cells in the Chemical Industry, Proc. Electrochem. Soc., 196, 1013 (Abstract); Carbonate Fuel Cell Technology V, 306-321 (Paper); Hawaii, The Electrochemical Society, Inc. 47 Dijkema, G.P.J. (2001) The Development of Trigeneration System Concepts, Proc. 6th World Congress on Chemical Engineering, Melbourne, Australia.
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5.2 Fuel Cells in the Chemical industry
5.2.1 ABSTRACT The use of fuel cells in the chemical industry leads to trigeneration systems that produce useful chemical products, electricity, and heat simultaneously. Firstly, stand-alone fuel cell cogeneration systems can be used to upgrade a chemical plant’s by-product hydrogen or CO (Figure 5-1). Secondly, fuel cell stacks can be employed as a multifunctional unit operation in chemical process system design, which results in process-integrated applications (Figure 5-2). Finally, fuel cell reactors combine the production of chemicals, electric power and heat in a single electrochemical apparatus (Figure 5-3). In retrospect, the use of fuel cell technology can thus be reviewed and categorised. In the chemical industry, however, the interest in fuel cell application appears to be limited to date. In the paper therefore the focus is on early identification, adequate representation, and early economic evaluation of the possible applications of fuel cell technology in the chemical industry. A systematic approach for the identification of fuel cell applications in the chemical industry comprises three steps: (i) identify all functions of a fuel cell device; (ii) identify all functions required of auxiliary system equipment; (iii) select suitable chemical processes that can offer some of the auxiliaries’ functionality (Dijkema et al. 1998). A novel schematising technique is introduced that supports this method by adequately representing the fuel cell system and the functions of its elements. The method can be combined with elementary mass-balancing and thermodynamic calculations.
A trigeneration system was developed for a new MCFC with separate CO2 supply (Hemmes and Dijkema 1998). The result demonstrates that the approach developed is a powerful tool to screen the potential of a technical innovation. The early assessment of the scope for fuel cell application in the chemical industry is completed by the development of an early economic evaluation method. The additional profits from trigeneration largely determine the allowable investment for the fuel cell (Vayenas et al. 1991b). In addition, the leverage effect on chemical plant cost must be accounted for. The results revealed that the economics of fuel cell use in the chemical industry are favourable compared to stand-alone fuel cell systems for electric power generation. In the upgrading of hydrogen by-product the fuel cell only offers a competitive advantage when the electric power revenue exceeds the value-added of the recovery and the subsequent conversion of the hydrogen to chemical products. The use of process-integrated fuel cell modules is attractive because no alternative technology exists that offers similar functionality. In addition, employing fuel cells this way improves the performance of the chemical plant, which can provide leverage to a fuel cell project. Since fuel cells lack economy-of-scale, it was expected that fuel cell reactors could be competitive only in suitable small-scale applications. Based on calculations on potential electric power generation from a number of industrially important
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reactions, however, it was concluded that only relatively small-scale fuel cell units (6- 40MWe) are required for common large chemical plants. In addition, fuel cell reactors appear economically competitive for most partial oxidation reactions. Notably the partial oxidation of toluene to phenol stands out as a prime candidate for further exploratory research.
Chemical plant
Feed Reactor Separator Product
Byproduct H2 / CO
Fuel cell Electricity system
Heat
Figure 5-1: Trigeneration through by-product utilisation with a cogeneration fuel cell system.
Chemical plant Feed Reactor Separator Product
Fuel cell Electricity stack
Heat
Figure 5-2: Trigeneration through process-integrated use of a fuel cell stack.
Chemical plant
Fuel cell Separator Product Feed reactor Electricity
Heat
Figure 5-3: Trigeneration by implementation of a fuel cell reactor.
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5.2.2 INTRODUCTION Traditionally, fuel cells have been promoted because of their high thermodynamic efficiency for the generation of electric power. Their second advantage proclaimed is their cleanliness (Hirschofer et al. 1994). As of late, it has been realised, however, that the best fuel cell system not necessarily is the thermodynamically most efficient system. Rather fuel cell systems must uniquely meet customer demands at acceptable cost. In the chemical industry ample opportunities exist for such fuel cell applications. Not only because equipment can be shared, but also because the fuel cell application can have an effect on the performance of the entire plant and thereby provides economic leverage to a fuel cell project (Dijkema et al. 1994a; Schinkel et al. 1994). The overall impression of the literature on fuel cell application in the chemical industry is one of incidental, fragmented publishing of possible uses. The trigeneration system concept therefore is used in this chapter to present all prospective fuel cell applications in the chemical industry under a single systematic framework. Firstly fuel cell system design is addressed and the “functional scheme technique” is presented. Subsequently, an overview of the literature is given per category of prospective fuel cell use in the chemical industry (see Figure 5-1, Figure 5-2and Figure 5-3). Thirdly, the functional scheme technique is used to augment the identification of fuel cell applications (Dijkema et al. 1998). The merits of the combination are illustrated by the development of a trigeneration system for a the newly invented improved MCFC with separated CO2 supply (Dijkema 1998; Hemmes et al. 1998). Finally, a method for early economic evaluation of fuel cell applications in the chemical industry is presented and results are reported.
5.2.3 FUEL CELL SYSTEM DESIGN (Kordesch and Simader 1996) give an extensive overview of fuel cell development for stand-alone power generation with a high thermodynamic efficiency. In the preface of their book, they state that the prime development goal for fuel cell technology is ‘dispersed, efficient power production’ and ‘... that a long life is needed for power plants ...’. As a revelation, the authors quote that the real bottleneck in fuel cell technology is the fuel to be used, i.e. that hydrogen is far too costly. This kind of conclusion is typical for the outcome of system design studies, as they must provide guidance for R&D. In many publications fuel cell systems are presented as process flow schemes, with a varying amount of detail. Usually, however, important individual equipment items are shown to the level of individual apparatus such as heat exchangers, pumps, compressors, burners etc. The account, however, of the actual design process unfortunately is often limited. More often than not, the focus is on system simulation and design calculations to evaluate the system’s performance, rather than on the arguments for the decisions reached on the basis of design. In addressing fuel cell system design for the guidance of R&D, we can draw from the literature on system engineering, which has been defined as “a progressive definition and integration of functions and design decisions at every level of system complexity”
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(Corrigan and Kaufman 1965). Systems can be decomposed into progressively smaller subsystems, where system elements are the lowest level of detail of a system structure. System complexity can be dealt with appropriately in design, when the focus is on system functions because the functional characteristics of a system element are technology-free (Asbjørnsen 1992; Dijkema and Reuter 1999). This means that when a system element is described by it’s inputs and outputs, and labelled by one or more functions it performs, the description is complete and independent from the actual technical realisation of the element (Figure 5-4). The technical content of the element only determines how the relationship between inputs and outputs has come about. Thus it may be seen that such a technology-free description opens the way to search for alternative technologies in system design. Consider, for example a system that must use natural gas for the generation of electric power. When we consider a conventional large-scale power plant, we see that the system’s inputs are natural gas and oxygen, its outputs electric power, flue gas, and a waste stream. If we leave out the technical details, we see that the system representation has become technology free. The next step is to consider other options to bring about the required function, power generation from natural gas. In Figure 5-4 two alternative options are shown, the use of a gas turbine and a fuel cell respectively, where in both systems it appears that we require fewer apparatus.
Air supply Exhaust Air Energy Air Energy transformation Exhaust supply transformation Step IIa Air E E Power Fuel T Power Abstraction Fuel
Ste p II Alternative Realisation I Step I b
Air Energy transformation supply Exhaust Air Energy supply transformation Air Fuel Anode Exhaust Cathode
E Power T Power Air Fuel Current Realisation Alternative Realisation II
Figure 5-4: System development – fuel to electric power (redrawn). By focusing on the functional description, however, in this case we have applied rather sloppy descriptions for the inputs and outputs. In the case of the GT, we still produce flue gas, but it also contains waste heat around some 450-500 oC. In the
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case of the fuel cell, the flue gas will contain unconverted feedstock. In all cases we have assumed the feed is at the right condition (P, T). We suggest, therefore, that at each level of system complexity, the following procedure can be applied: 1. Review an existing (similar) system design and identify the crucial system functions; 2. Draw a functional scheme 3. Briefly describe each system element 4. Explore alternative technical realization options per system elements 5. Explore possible combinations of functions in a single apparatus 6. Consider alternative recycle schemes to achieve 5&6; the flow sheet recycle structure needs careful attention (Douglas 1988).
In Figure 5-5 an early fuel cell system design is represented that operates on natural gas. In this drawing, the system decomposition has been visualised. The system elements have been enclosed by grey boxes. Each box’ title represents an element’s function. The representation essentially is technology-free: the drawing is still valid when the detail in the boxes is left out. The content depicted represent only one of the possible technical realisations of the system elements. The particular arrangement of system elements also represents a single possibility to ‘materialize’ the fuel cell system. Indeed, the second important feature of the drawing is the system boundary combined with its title, which is a system element at one aggregation level up. Note that all feed and product streams have been labelled outside the system boundary.
Feed Exhaust Off-gas saturation Fuel cell module processor
reformer Water Anode Power burner Cathode Fuel Fuel processor
Compression Air Cathode cooling
Cold Hot medium medium
Figure 5-5: Example: functional scheme for a stand-alone fuel cell system. A third important feature of this drawing technique is that system elements where multiple, physically unseparated functions are performed have been enclosed by an equal number of system element boundaries (effectuation of step 6). In this way
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alternative arrangements for the design of the system offered by the integration of functions are visualised. Besides the fuel cell module, the stand-alone system includes 4 other elements, steam supply, fuel processor, oxidant supply, cell cathode cooling, and off-gas processor. Steam supply is a function implied by the particular selection of fuel processing in this system, steam-reforming. Prior to reforming, methane needs to be mixed with steam. The option shown is to integrate the steam supply in the fuel processor by installing a feed-saturator that employs waste-heat. Fuel processing consists of hydrogen generation and fuel purification. Since no natural resources of hydrogen are known, it must be generated from hydrogen- containing species.
Visualization of system improvements An advanced fuel cell system is the Smarter system (Fellows et al. 1998). In this system concept, gas-gas heat exchangers have been totally eliminated (Figure 5-6). The main feature of the Smarter system is the use of a hot-recycle blower, which allows the arrangement of a smart recycle scheme that replaces a number of system elements by the integration of system functions.
Fuel cell module
Fuel Anode Cathode Hot exhaust Feed preheat Feed compression Fuel processor
burner Power Air
Off-gas processor
Air supply O2 supply
CO2 supply Cathode preheat
Figure 5-6: Functional scheme of the Smarter system. Recycling part of the anode off gas back to the inlet of an internal reforming fuel cell eliminates the feed saturation system, since the off-gas will contain the water
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required for the steam-reforming reaction. In an external reforming fuel cell system the off gas can be recycled to the reformer inlet. The other essential feature of the Smarter system concept is the integration of the off-gas processor and cathode oxidant and CO2 supply. The outlet of the off-gas processor, a catalytic burner, is sent to the cathode of the direct internal reforming MCFC together with excess air for quenching. In retrospect, the system design procedure developed clearly illustrates the advantages of the Smarter System compared to a common stand-alone fuel cell system. The integration of multiple functions in a single apparatus and the usefulness of recycles are apparent. The Smarter system is a dramatic breakthrough in system simplification, and is a case in point for the use of the system design approach presented.
5.2.4 FUEL CELLS IN THE CHEMICAL INDUSTRY
The use of fuel cells to upgrade by-product hydrogen The possibility of utilising low-BTU off-gases in the process industry by implementing fuel cells on-site has been identified as a possible high added-value application in the fuel cell research and development community (Hirschofer et al. 1994). Hydrogen-containing by-product streams are produced in a large number of plants in the process industry indeed. Examples include oil refineries, steel blast furnaces, and chemical plants that produce methanol, ammonia, ethylene, or aromatics. The conversion of by-product hydrogen or carbon monoxide into electric power by fuel cell systems that were developed for stand-alone power generation can be effected as an add-on to existing chemical plants, and effectively is an end-of-pipe solution. A patent was issued to Haldor Topsøe on the use of ammonia-synthesis off-gas as a fuel for an MCFC (Frydenlund 1993). ICI received a patent on the similar use of methanol synthesis off-gas for the utilisation of industrial by product hydrogen-rich gas (Pinto 1977). The utilisation of hydrogen by-product in the manufacture of chlorine has been studied also (Lance 1984). Recently, Ansaldo-ClC reported the design of hydrogen-based PAFC unit, specifically intended for the upgrading of hydrogen by-product (Caserza et al. 1996). The concept of by-product utilisation, however, appears not to have been commercially applied. This may be due to the limited availability of commercial fuel cell stacks and the limited track record of fuel cells in industrial service, which together impede acceptance by the chemical industry as ‘proven technology’. In addition, the development track selected by the fuel cell companies has been focused on packaged systems for stand-alone power generation. More important, however, is the fact that the economics of upgrading by-product hydrogen through the use of fuel cells is apparently not good enough, which is illustrated by results reported on the use of hydrogen by-product in chlorine electrolysis (Lance 1984), and on the use of phosphorus-oven off-gas in an MCFC (Goossens 1995).
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On the basis of a preliminary investigation of the use of fuel cells in conventional ammonia production, we found that using fuel cell stacks to utilise off-gas only is attractive when a considerable electricity revenue is obtained, and when the cost of the fuel cell equipment is relatively low (Dijkema et al. 1996). Pressure-swing- adsorption technology (PSA) provides an economic solution for removal of the greater part of the hydrogen from the synthesis-loop off-gases, allowing the hydrogen to be recycled to the ammonia process. As a consequence, the incentive to develop fuel cell applications is limited.
Process-integrated application of fuel cells At the process system level, any chemical plant is designed as an interconnected set of unit operations, i.e., reactors, separators, compressors, pumps etc. A stand-alone fuel cell system design consists of a fuel cell stack and the so-called ‘balance-of- plant’, which can also be viewed as an interconnected set of unit operations. A fuel cell stack not only converts hydrogen into water by electrochemical reaction with oxygen, which produces DC-power, but also acts as an active device for hydrogen removal, oxygen depletion of air, etc. (Schinkel et al. 1994; Dijkema 1996). Thus a fuel cell stack can be viewed as a multi-functional unit operation that can be a part of any chemical plant, in the same as any other unit operation, such as a pump, compressor, etc. Since this use of fuel cells involves the complete integration of a fuel cell stack in a chemical plant, it is called a process-integrated application. The aforementioned use of an MCFC in a conventional ammonia plant (Frydenlund 1993) is to be considered such a process-integrated application. Hydrogen-rich ammonia synthesis loop off-gas is fed to an MCFC-anode. The pure CO2 produced in the ammonia plant is mixed with air and sent to the MCFC-cathode. Anode and cathode off-gases are sent to the reformer furnace. The amount of auxiliary equipment used thus remains limited. Synthesis gas, the common label for process gases that consist of a mixture of hydrogen and CO, is an important intermediate in the chemical industry, e.g. for the production of methanol and higher alcohols, and the production of ammonia. Synthesis gas production is also the first step in most hydrogen plants. The production of synthesis gas for fuel cells in a “fuel processor” is analogous to these systems, except for the scale-of-operation, and to some extent the desired syngas composition. The combination of these two therefore appears to be a natural one. A patent was issued to CF Braun & Co on the integration of a fuel cell in an ammonia plant based on the Braun Purifier concept (Jungerhans 1984). The patented process system includes ammonia make-gas production by reforming, HT-
CO-shift, and purification of the syngas by PSA for the removal of CO2, residual methane and water. The fuel cell is fed by part of the syngas produced. The anode and cathode-gases are subsequently combined in a deoxygenating unit to produce an oxygen-free nitrogen-rich, inert stream that is used for purging the PSA unit, thereby producing waste-fuel. (Sederquist et al. 1993) claim a fuel cell arrangement for the production of such pure nitrogen-gas, whereby the fuel cell operating mode is optimised for the maximum consumption of oxygen. (Drenckhahn et al. 1995) reported on the prospects for the use of the PAFC in the chemical industry, in particular those chemical complexes that include the large-scale
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generation of synthesis gas by reforming. Their objective was to investigate whether the PAFC could play a role in consuming the intermediate product hydrogen gas from the reforming section, when the demand for the end plants suffers a reduction which forces a reduction of operating capacity. From the paper we deduce that they investigated PAFC use in an ammonia plant, which includes a liquid nitrogen-wash for the removal of residual methane, which is the underlying principle of the Braun- Purifier process for ammonia. They conclude that the most promising take-off point for PAFC feed is where the synthesis gas has been fully treated to ammonia make- gas. We investigated the design of an ammonia-MCFC-based trigeneration system, where a single syngas production facility is used to feed both an ammonia synthesis loop and an arrangement of fuel cell stacks (Dijkema et al. 1996). The fuel cell off-gases are sent to the primary reformer furnace as fuel and high temperature oxidant. The economics of this system are comparable with the economics of the use of the hydrogen-rich purge stream. The results indicate, however, that the production of ammonia alone is more profitable than trigeneration, as electricity revenue is low. Another illustration is the use of a molten carbonate fuel cell stack in the much- applied ICI low-pressure methanol process. In this process, the reformer produces synthesis gas that contains too much hydrogen for the methanol synthesis. Normally, this excess hydrogen is purged from the methanol reactor loop. By the integration of a MCFC-stack located directly after the primary reformer the syngas composition can be corrected before it enters the reactor loop, prior to syngas make-up compression (Farooque 1988). It was demonstrated that another option, viz. to direct only part of the hydrogen to the fuel cell and to reroute the CO2-rich anode off-gas to the process, provides sufficient leverage to plant performance to make this application economically attractive (Dijkema et al. 1994b).
Fuel cell reactors It is a well-known theorem in thermodynamics that, for a reaction that releases chemical energy, the theoretical maximum of available chemical energy would be converted to useful work in the case where the reaction is performed in a reversible manner in a fuel cell device. Though a fuel cell can never operate completely reversibly in practice, the essence of employing a fuel cell would be that in the fuel cell the energy conversion to useful work is not limited by the well-known Carnot limitation of a heat engine. Ketelaar investigated the potential of combining the generation of electric power and useful chemical products. In principle, any chemical reaction that runs spontaneously, i.e. ∆Gr < 0, can be used for the generation of electric power (Ketelaar 1968). He distinguished between electrochemical reactors, where the chemical produced is the main product, and fuel cells, which main product is electric power. In essence, he concludes that only industrial partial oxidation reactions are candidates for electrochemical reactors. Electrochemical reactors have long been applied on an industrial scale, notably for the production of aluminium, zinc, steel, chlorine and adipic acid. Vayenas and co- workers labelled this use of fuel cells “chemical cogeneration” (Vayenas 1988). We prefer the term fuel cell reactors, to avoid confusion with the term “cogeneration”.
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Electrochemical reactors have long been applied on an industrial scale, notably for the production of aluminium, zinc, steel, chlorine and adipic acid. According to Yentekakis et al., however, the feasibility of electrochemical fuel cell reactors was demonstrated for the first time in 1980, notably for the conversion of ammonia into nitric oxide, one of the prime steps of nitric acid in fertiliser production, in a SOFC (Vayenas et al. 1992). Other industrially important reactions include the oxidative dehydrogenation of ethyl benzene to styrene, and of 1-butene to butadiene respectively, the ammoxidation of methane to hydro cyanic acid, the partial oxidation of methanol to formaldehyde, and the oxidation of H2S to SO2(Yentekakis and Vayenas 1989). (Malhotra and Dattra 1996) mention tentative development of a novel fuel cell for the trigeneration of electricity and acetaldehyde from ethanol. The applications of the electrochemical reactors described above comprise trigeneration of electricity and a useful chemical by controlled partial oxidation. Synthesis gas-proper is another candidate product that can be produced by partial oxidation. (Alqahtany et al. 1993) investigated the production of synthesis gas in a solid electrolyte cell that incorporates electrochemical oxygen pumping (EOP). They conclude that EOP allows control of CO-formation. Since H2 formation remains largely unaffected, the H2 /CO ratio can be controlled by EOP. Finally, they suggest to use their results for the development of an in-situ methane reforming SOFC, which the authors claim to perform equally or better than existing industrial methods under the co-production of electrical power. Mazanec et al. were issued a patent on the use of certain materials in membrane reactor or fuel cell arrangements for oxidation reactors. They list examples of methane to synthesis gas or unsaturated compounds, the partial oxidation of ethane, substitution of aromatic compounds, and, notably the extraction of oxygen from oxygen-containing gases which they deem useful for exhaust gas cleanup (Mazanec 1993).
Conclusions from the literature review Various examples of by-product hydrogen use in fuel cell systems have been reported (see §0, p.160). In all of these cases, the valorisation of by-product hydrogen in fuel cells competes with the simple use of hydrogen as co-fuel in process furnaces or nearby power plants. In other cases the purification of the hydrogen may be feasible. The recovered hydrogen then can be recycled to the plant or be sold via pipeline or bottling station. Process system concepts that integrate fuel cell modules in the chemical plant design have been suggested for ammonia, methanol and pure nitrogen production (§0, p.161). Generally speaking, fuel cell modules may be integrated in chemical plants that include the generation of synthesis gas, pure hydrogen or pure CO streams. as Since the economics favour chemicals production over electricity generation, system energy efficiency improvement must compensate the production amount shifted from chemical to electricity. Many “proof-of-principle” of fuel cell reactors have been reported (see §Fuel cell reactors, p.162. To date, however, no commercial application of fuel cell reactors is known.
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5.2.5 IDENTIFICATION OF FUEL CELL APPLICATIONS IN THE CHEMICAL INDUSTRY: THE IMCFC As fuel cells and other energy conversion devices are expected to contribute to an improvement in resource utilisation in the chemical industry, we developed a systematic method to identify promising trigeneration options for fuel cells and gas turbines (Dijkema et al. 1998). The essence of the method is that the arrangement of fuel cell modules is considered a multifunctional unit operation that can be used in any process system design. In addition, it is considered which fuel cell system functions can be performed by the process plant, which results in equipment sharing between the production process or processes and the fuel cell system. The method will be illustrated by the design of a trigeneration system for the iMCFC (Hemmes et al. 1998).
The iMCFC During the initial testing of the iMCFC concept, the question emerged “Do market- niches exist where only the iMCFC would fit, and what is the scope of the iMCFC with respect to system improvement.”
recycle
CO / H2 Anode CO / H O / inert Matrix 2 2
N / O 2 2 N2 / O2
recycle
Figure 5-7: iMCFC-module, 2 inputs - 2 outputs. A trigeneration system was specifically designed to exploit the unique features of the iMCFC, and to co produce electric power and synthesis gas. Other system designs for the iMCFC are reported elsewhere (Dijkema 1998). The main characteristic that distinguishes the iMCFC from a conventional MCFC is the CO2 supply to the fuel cell matrix (Figure 5-7). No CO2 needs to be present in the cathode feed. Hence the CO2 and oxygen supply to the fuel cell have been decoupled, which offers an additional degree-of-freedom in system design: both the
CO2-supply and the oxygen supply can be designed for optimal cell performance and cell cooling.
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Not only the cell’s performance improves, however, but also a 3 input - 3 output fuel cell results. These unique features must be exploited in the design of a system to fill some market-niche unique to the iMCFC. To be competitive, any system design for the iMCFC must consist of a minimum amount of equipment, notably gas-gas heat exchangers. iMCFC sandwich system design To introduce the iMCFC and to illustrate these concepts, considered the system design in Figure 5-7. A recycle of anode off-gas to both anode inlet and matrix inlet is used, whereby the number of both inputs and outputs is reduced to two again (Figure 5-7). The required amount of additional equipment is limited. Such a module can effectively be used in a stand-alone fuel cells system design replacing a conventional MCFC stack, or in process-integrated applications. In the system design that we have labelled the ‘sandwich system’, an iMCFC is located between a reformer and partial oxidation (Figure 5-8). The core of the Sandwich System comprises a gas heated reformer (GHR) with a product gas outlet temperature that matches the MCFC inlet temperature, viz. 600-700 °C, the iMCFC, and a partial oxidation reactor (POX) that converts anode and cathode off-gases of the MCFC. The hot POX product gas provides the heat required to operate the GHR. Both the iMCFC anode- and cathode off-gas are sent to the POX directly. A system study has shown that the sandwich system is thermodynamically feasible (Dijkema 1998). As indicated by the functional scheme technique, a number of functions around the iMCFC have been integrated into a single apparatus, viz. off gas processing and syngas manufacture. The iMCFC, however, also requires additional system functions, such as the supply of CO2 to the matrix (not shown in Figure 5-8). This can be realised by a separate gas-loop, or by a bleed-stream from the anode off-gas (Figure 5-7).
Off-gas cooling Feed preparation Syngas production Fuel Cell Module Syngas production Feed Fuel Anode saturation Gas-heated reformer Matrix POX Water Cathode
Oxydant preparation
Air Oxygen plant Syngas
Figure 5-8: The iMCFC sandwich system. The particular combination of functions was derived from knowledge of the thermodynamic equilibria in the reformer, that dictate that methane conversion is
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favoured by low operating pressure and high operating temperatures. Increasing the pressure from 1 to 10 bar dramatically reduces the conversion of methane at otherwise equal conditions. At 10 bar and iMCFC inlet temperature of 650 °C and a Steam-to-carbon (SC) ratio of 2 the methane conversion is as low as 35%. As a consequence, however, the heat load of the GHR is also reduced! The remainder of the methane is converted in the partial oxidation reactor (POX), or autothermal secondary reformer: oxidation of part of the gas drives the reforming of the methane present. Thus, by sandwiching the iMCFC between GHR and POX heat- load is shifted away from the GHR. Because the GHR involves physical heat- transfer, and the POX ‘chemical’ energy transfer, this shift increases system efficiency. The net result is that with the same amount of feedstock, synthesis gas can be made and electricity produced. The iMCFC operation at an elevated pressure is advantageous for the sandwich system design. An elevated pressure previously was limited by cathode dissolution, but is no issue in the iMCFC because of the decoupling of CO2 and oxygen supply to the cell. pCO2 can be kept at a very low value (10-3 atm.) to reduce NiO dissolution.
Conclusion The early identification method combined with the functional scheme technique has proven to be useful to exploit fuel cell innovations by the early development of a trigeneration system concept.
5.2.6 EARLY ECONOMIC EVALUATION OF FUEL CELL APPLICATIONS IN THE CHEMICAL INDUSTRY Technology selection for new power systems is done in the early phases of a project on the basis of investment cost and margin expected. The prospects for the use of stand-alone fuel cell systems therefore are not good because to date investment costs for stand-alone fuel cell systems and gas turbine differ by an order of magnitude (1996: ONSI-PAFC $6000/kW, GT cogeneration system $800/kW). Lately, therefore, in the fuel cell community it has been realised that probably only in niche markets where the unique features of fuel cells are exploited the costs associated can be justified. Generally the cost-structure of a project is broken down into capital related cost (capex), and operation-related cost (opex). The revenues from the operation of the facility must compensate for both capex and opex. In power generation projects the initial investment - cost per kW installed- largely determines project profitability because it represents a large fixed annual cost throughout the expected lifetime of the project. The electricity revenue must exceed the total of the fixed annual investment cost, fuel cost and other operating cost in order to realise some return-on-investment. In capital-intensive industries such as the chemical industry and the power industry, also a large part of the capex is the investment cost for the new facility. The exact quantity of these costs, however, is hard to estimate. At the initial (screening) phases of a project it is therefore accepted that the estimate still has wide margins. In the chemical industry at the basis of design phase a +/- 40% margin in the investment estimate is generally accepted (Chauvel 1981).
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Finally, it may be seen that in all the economic methods for early project evaluation the problem is reduced to a closed problem by sufficiently defining the system. In the early economic evaluation of fuel cell applications in the chemical industry in general we are after some general insights into the attractiveness of fuel cell technology in the chemical industry, an open problem where we attempt to explore an endless solution-space to help define promising directions for R&D!
Development of a simple equation for fuel cell evaluation Spillmann and co-workers developed an economic evaluation methodology that they labelled differential economic analysis (Spillman et al. 1984) and applied it to fuel cell reactors. In the differential analysis of chemical production, the reaction is considered to be a source for additional revenue by the direct cogeneration of electricity. The economic evaluation only involves the cost difference between (chemical transformation + electricity generation) and chemical transformation alone. The time-value of money is not taken into account. Based on the basic notion of thermodynamics that the maximum amount of useful work or electric power that can be extracted from a chemical reaction is equal to the change in Gibb’s free energy ∆G, an indicator λth of fuel cell reactor attractiveness was derived by Spillmann (1981).
0 λth = ε • ((-∆G )/M ) • (re / (rp - rf)) (Eq. 5.1)
The equation for λth is an expression for the electricity revenue from the chemical reaction divided by the value added of the chemical operation per se. Trigeneration becomes more attractive in case λth increases relative to chemical transformation alone. The indicator particularly quantifies the leverage of trigeneration; it does not, however, yield a direct clue on the investment allowed for the changeover from conventional chemical reaction to trigeneration. Spillmann concluded that trigeneration in a fuel cell reactor would be attractive for reactions that are carried out in industry on a bulk-scale, where the margin per unit product is small. He argued that, in such cases, the additional generation of electricity could have a large effect on the net operational margin. Notably Vayenas et al. used and extended this method for the comparison of the economics of a fuel cell reactor and the use of a conventional reactor. A simple equation is derived that gives a first impression of the attractiveness of a fuel cell reactors (Vayenas et al. 1991b; 1991a). This is summarised and expanded below. According to Vayenas, the early economic analysis need only focus on the alternate energy conversion because the chemical output of the two types of reactors is the same. In the early economic analysis of a fuel cell reactor two systems are compared, a convential reactor and the fuel cell reactor. These process the same feedstock to the same product slate. In case the reaction is exothermic, in the conventional reactor only heat is produced from the chemical reaction, while in an electrochemical reactor both electric power and heat are produced. A fuel cell reactor is then more profitable in case the following relationship is satisfied,
(Rf, e+ Rf,h) •θf - Rc,h•θc > If - Ic (Eq. 5.2)
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In words: the total additional revenue from trigeneration throughout the technical lifespan of the fuel cell must exceed the difference in initial investment.
Evaluation of using by-product hydrogen When we use the ‘fuel cell’ perspective, the use of by-product hydrogen eliminates the need for a fuel processor, which may represent some 20-30% of system cost which is the common argument to promote such an application. Differential economic analysis helps to understand by-product hydrogen utilisation in the chemical industry. It appears, however, that no equivalent single equation for by- product use can be derived because there is more than one alternative to be taken into account, for example 1. By-product hydrogen to-flare 2. Simple firing in furnace (heat value = lowest) 3. Utilise in gas turbine-based cogeneration system 4. Upgrade to electric power and heat in fuel cell 5. Recover and reprocess in plant 6. Recover and sell as product We can safely assume, however, there is an economic incentive for the conversion of hydrogen into electric power or heat rather than to waste it to a flare (option 1). In addition, the use in a GT-based system is limited, as a GT can only accommodate fuel gas with limited hydrogen content. Recovery and reprocess in the plant apparently offers no economic incentive. Finally, option six probably in most cases requires substantial investments and organisation to realise either delivery of pure hydrogen to a pipeline grid, or delivery of bottled hydrogen. A proper first indication of the merits of upgrading by-product hydrogen in a fuel cell system therefore can be obtained by comparison of the options: recovery of the hydrogen heat value in some furnace, and recovery of electric power and heat in a fuel cell system. The modified relationship (5.2) holds:
(Rf, e + Rf,h) •θf - Rc,h, (H2)•θc > (1-γ)•If - Ic (Eq. 5.3)
θc and Ic represent the lifespan and investment of furnace modifications for hydrogen firing. Coefficient γ allows one to apply a correction for the investment in the fuel cell system, e.g. to account for special provisions required to use by-product hydrogen. The actual incentive for the use of a fuel cell system to upgrade by-product hydrogen in cases where all other options except simple firing are exhausted depends on the magnitude of the investments avoided in furnace equipment, net fuel cell investment, and the margin between electricity revenue and fuel value. The equation shows that a trigeneration system may offer an advantage both because of savings in plant investment and savings in fuel cell system investment.
Evaluation of process-integrated fuel cells Process-integrated applications of fuel cells are expected to require only a fraction of the cost of a stand-alone fuel cell system per kWh because fewer auxiliaries are
Fuel Cells and Trigeneration 169
required, in some cases not even a reformer. This type of fuel cell application can provide an additional competitive edge over stand-alone fuel cell systems by improving chemical plant efficiency and/or increasing plant capacity. In other words, the fuel cell module incorporation results in a leverage effect on plant performance. In the methanol plant, for example, the energy consumption of the syngas compressors is significantly reduced, and plant capacity is increased by some 8%. As we have shown in earlier work (Dijkema et al. 1994b; Dijkema et al. 1998), the main advantage of a process-integrated fuel cell originates from the leverage effect on chemical plant performance. When we consider the function of hydrogen in chemical plants there are four possibilities: A) Hydrogen is a feedstock B) Hydrogen is part of an (intermediate) feedstock in the plant, for example in ammonia or methanol production via synthesis gas. C) Hydrogen is a by-product of the chemical reactions only, for example in dehydrogenation processes or dealkylation of toluene to benzene. D) Hydrogen is a process agent (catalyst, diluent, promotor, reductor etc.)
But do all these options require their own modified equation (6.2)? In case A and D it may be argued that there is no case for trigeneration using process-integrated fuel cells: hydrogen is required for the chemical reactions themselves, any consumption by the fuel cell would only add to the consumption of the plant. Note that in case D usually some waste-hydrogen stream results, which then can be used in a fuel cell system as has been analysed in the previous section. The same applies to case C. In case B, however, an important incentive for trigeneration is the sharing of facilities, which can offer advantages of economy-of-scale. In commercial plants, however, hydrogen-production facilities often already are scaled to the maximum technically feasible size. Only if there is a mismatch between maximum-size of hydrogen generation and hydrogen consumption part of a chemical plant is there scope for trigeneration, e.g. in ammonia production (Dijkema et al. 1996). What remains is the incentive created by a leverage effect on plant performance, as illustrated by the integration of a fuel cell stack in a methanol plant. In this case, (Eq.
5.2) can be extended with a term that quantifies this incentive, Rchem, trigen – Rchem, plant The use of fuel cells to boost the performance of the plant at present appear the most attractive market niche for fuel cells in the chemical industry. The exact incentive, however, can only be estimated when performance data are available from a preliminary process system design.
Evaluation of fuel cell reactors
As stated, the thermodynamically most attractive route for reactions where ∆Gr < 0 is a reversible fuel cell reactor. This implies, however, at a technical level a specific (catalytic) fuel cell must replace each conventional reactor. But which reactions are economically the most favourable?
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Because the investment cost normally quoted for fuel cells is in [$/kW], whilst that for chemical reactors is quoted in [$/(ton/day)], we introduce α to relate the two:
α = ε • (∆Gr) • 4.1828 [kcal/mol] • [J/Cal] (Eq. 5.4)
-6 / (M•10 • 3600 • 24 [g/mol] • [ton/g] • [s/day]
α = 48.4 ε • (∆Gr) / M [kW/(ton/day)] (Eq. 5.5) α is an expression for the electric power produced per ton capacity of a chemical [kW/(ton/day)] as a function of fuel cell reactor electrical efficiency ε.
Ic = αIe,f (Eq. 5.6) Equation (5.2) then becomes
(Rf, e + Rf,h) • θf - Rc,h • θc > α • Ie,f - Ic (Eq. 5.7) For an initial estimate, the revenues can be calculated from the enthalpy and free energy change of reaction at standard conditions:
0 Rc,h = β • rh • (-∆H )/M (Eq. 5.8)
0 Rf, e = β • re • ε • (-∆G )/M (Eq. 5.9)
0 0 Rf,h = β • rh • ((-∆H )/M) - ε • ((-∆G )/M)) (Eq. 5.10) β is a unit conversion factor. Under the (optimistic) assumption that the lifetime of a cogenerative fuel cell equals that of a conventional reactor, θf = θc, the total profit difference V between the investment in the fuel cell or conventional reactor can be calculated as
V = 24 α • (re – rh) • θf / (α • Ie,f - Ic) > 1 (Eq. 5.11)
Assuming a worst case, Ir = 0, i.e. there is no investment required for a conventional reactor, this reduces to
V = 24 (re – rh) • θf / Ie,f > 1 (Eq. 5.12)
or Ie,f < 24 (re – rh) • θf (Eq. 5.13) If, in addition to Vayenas, we assume that the revenue for heat equals its fuel equivalent, whilst electricity represents double that value (as a worst case) the inequality reduces to
Ie,f < 12 re • θf (Eq. 5.14) Thus a simple equation has been derived to estimate the allowable additional investment for fuel cell reactor. This implies, for example that at a technical lifespan of 5 years, for example, and an electricity revenue of 5 ¢/kWh, the investment in the fuel cell is allowed to be 1095 $/kW!
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Application to fuel cells in the chemical industry A first selection of industrial reactions that appeared promising for trigeneration in a fuel cell reactor was obtained by Ketelaar, who calculated its maximum electric output at standard conditions, assuming a maximum thermodynamic efficiency of such an electrochemical reactor of 70% (Ketelaar 1968). In essence, he concluded that only industrial partial oxidation reactions display both a high open-cell voltage and a significant electric power output per unit product. In addition, he expected high investment costs for such reactors. In the development of equation (5.14) the perspective of a fuel cell developer has been used, and the result has been expressed in a [$/kW] figure. In order to compare the fuel cell reactor with a conventional reactor, the above formulas must be transformed into an expression in chemical product capacity. This is straightforward using α.
If = α • Ie,f< 12 re • θf • α (Eq. 5.15) The allowable investment in a fuel cell reactor is a linear function of electricity revenue, fuel cell lifespan, and α. The equation represents a worst case because the investment of a conventional reactor is assumed to be zero, and the electrical efficiency only 50%. In Table 1, heading Fuel Cell Reactor, both the input data for equation (5.14) are listed, and the results, notably the calculated maximum allowable investment for the fuel cell reactor, expressed as 1000$ per [ton/day] capacity. The results apply to a fuel cell reactor with a minimum technical lifespan of 5 years, and an electricity revenue 5 ¢/kWh. Under the heading ‘Trigeneration system data’ these results have been related to data that apply for chemical plants of typical commercial production capacity. Per chemical reaction, the maximum allowable investment in fuel cell reactors has been calculated by multiplication of Ic and C. In addition, the power rating P has been calculated by multiplication of α and C. Finally, the maximum allowable investment for a fuel cell reactor has been expressed as a percentage of typical plant investment.
Example evaluation Consider, for example, the direct electrochemical partial oxidation of propylene to propylene oxide, PO (Table 5.1, reaction 12). From the thermodynamic data in (Stull et al. 1969), the Gibb’s free energy change of the reaction at standard conditions can be calculated, -21.2 kCal/mole. Using equation (5.5) results in α = 8.8 kW/(ton/day). The allowable investment at a technical lifespan of 5 years (5*365 days) and at an electricity revenue of 5 ¢/kWh follows from equation (5.14). The allowable investment is 10 k$ per (ton/day) of propylene oxide production capacity. By division with α, we obtain the familiar result of 1095 [$/kW] allowed investment for the fuel cell reactor.
Table 5.1: Fuel cell reactor evaluation for the chemical industry Chemical Operation Fuel Cell Reactor Trigeneration system data Max. Typical Fuel Cell Fuel Cell/ Typical ∆I as % of Allowed plant Power Conventional Plant Inv. Plant Inv. I Reactor Max ∆I ∆Gr M α If Co Rating Reaction Kcal g/mole k$/ ton/day MW Million $ Million $ % /mole (ton/day)
1 Hydrogen oxidation H2 ½ O2 → H2O -54.6 18 73.4 80 n.a. n.a. 0.0 0 0
2 Carbon partial oxidation C + ½ O2 → CO -32.8 28 28.3 31 n.a. n.a. 0.0 0 0
3 Carbon oxidation C + O2 → CO2 -94.3 44 51.8 57 n.a. n.a. 0.0 0 0
4 Syngas by partial oxidation CH4 + ½ O2 →CO + 2 H2 -20.7 30 16.7 18 2000 33.3 36.5 80 46
5 Syngas by reforming CH4 + H2O → CO + 3 H2 34.0 70 -11.7 -13 2000 -23.5 -25.7 0 0
6 Methanol by direct partial CH4 + ½ O2 → CH3OH -26.7 32 20.2 22 1800 36.3 39.7 130 31 oxidation
7 Formaldehyde CH4 + O2 → CH2O + H2O -14.1 30 11.4 12 285 3.2 3.6 6 59
8 Acetaldehyde C2H5OH + O2 → C2H4O H2O -46.3 44 25.4 28 285 7.2 7.9 19 42
9 Acetic acid via CH3OH + CO → CH3COOH -18.4 44 10.1 11 230 2.3 2.5 28 9 carbonylation
10 Ethyleneoxide C2H4 + ½ O2 → C2H4O -19.4 44 10.7 12 400 4.3 4.7 58 8
11 Ethyleneglycol C2H4O + H2O → C2H5(OH)2 -34.4 62 13.4 15 285 3.8 4.2 12 35
12 Propyleneoxide C3H6 + ½ O2 → C3H6O -21.2 58 8.8 10 285 2.5 2.8 102 3
13 Butadiene C4H8 + ½ O2 → C4H6 + H2O -34.4 54 15.4 17 140 2.2 2.4 26 9
14 Phenol by toluene C6H5(CH3) + 2O2 → C6H5OH + CO2 + -131.3 78 40.7 45 140 5.7 6.2 39 16 oxidation H2O
15 Styrene by C6H5(C2H5) + ½O2 → C6H5(C2H3) + -34.8 104 8.1 9 1000 8.1 8.8 52 17 oxydehydrogenation H2O
16 TPA C6H4(CH3)2 + 3O2 → C6H4(COOH)2 + -279.6 166 40.7 45 285 11.6 12.7 85 15 2H2O
17 Nitrous oxide NH3 + 1 ¼ O2 → NO + 1½ H2O 20.7 30 0.0 0 0 0.0 0.0 0 0
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A common capacity for a commercial industrial facility is some 285 ton per day PO, or 100.000 ton per annum (Chauvel and Lefebvre 1989b), which implies that the total allowable investment for the fuel cell reactor amounts to 2.85 Million dollars (assumptions: investment conventional PO reactor zero; electricity revenue 5 ¢/kWh, minimum lifespan fuel cell 5 years). Any company involved in PO-production can easily insert the correct figures for refinement of the result, for example: ◊ Actual feasible single train conventional reactor capacity must be used ◊ A portion of conventional reactor investment can be added ◊ Fuel cell lifespan can be corrected to compare with conventional catalyst replacement cost and frequency
Evaluation of results The calculation was completed for a number of important partial oxidation reactions as they are carried out in the petrochemical industry today (Chauvel and Lefebvre 1989b). In addition, results are listed for candidate reactions to replace presently employed reactions, for example methanol by direct partial oxidation. A high value of α indicates that along with chemical production a high amount of electric power can be potentially extracted. The combination with economic figures allows additional assessment of the fuel cell reactor’s attractiveness: the higher the maximum allowable investment, the higher the possible benefits. In the table, not only reactions are included that result in some useful product, but also the conventional fuel cell reaction, the oxidation of hydrogen appear favourable, as shown by their high values of α. The following observations can be made by inspection of these results: 1. The conversion of light molecules leads to high values of α.
2. CO2 formation in partial oxidation yields high α’s 3. The power rating of a trigeneration fuel cell reactor calculated, 6-40MW is reasonable for world scale, chemical plants. In addition, the allowable investment calculated for the fuel cell reactors offers substantial scope for development of the technique for a number of reactions, notably the partial oxidation of toluene to phenol. The electrochemical trigeneration of formaldehyde by partial oxidation of methane appears attractive because of the allowable investment represents a high portion of the plant’s total investment. Since partial oxidation reactions involve the use of oxygen, the production of pure oxygen is avoided in the case of employing a fuel cell reactor that uses air. This must be taken into account, e.g. by adding an additional term in equation 5.2, (Rc,O2 – Rr,O2), where R is negative, i.e. a cost. The results also support the current focus on cogeneration fuel cell reactors, as the figures for hydrogen and CO oxidation are most favourable. These are precisely the overall reactions carried out in currently developed fuel cells. One could think of selling pure water or CO2 as a trigeneration product of the fuel cell reactor. Note
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that the equation developed remains valid because of the assumed zero-cost of the chemical reactor. Please note that in the calculation of all these results, it was assumed that the cost of a conventional reactor equals zero, i.e. economy-of-scale does not play a role!
5.2.7 CONCLUSIONS The trigeneration concept is a suitable basis for a systematic framework to evaluate fuel cell application in the chemical industry. The development of a trigeneration system for a novel fuel cell type, the iMCFC has demonstrated the value of system design in the earliest phase of R&D. The functional scheme technique developed has proven to be valuable in the identification and development of novel fuel cell systems. It is expected that it will also be useful in the development of process systems, and that it may serve as a communication framework for system development and system integration. We expected that only qualitative early economic assessment of fuel cell use in the chemical industry would be possible, and that the analysis would confirm the meagre prospects of fuel cell use in the chemical industry. On the contrary, however, a simple criterion could be derived for the evaluation of fuel cell reactors as the heart of a chemical plant. The results show that the prospects for fuel cell reactors as the heart of trigeneration systems are worthwhile exploring. Trigeneration yields additional profits even when substantial investment is required, the allowable investment in fuel cell reactors calculated is in the range of 15-60% of total plant investment. The use of by-product hydrogen has been shown to be only a last resort, when all other options are exhausted. Finally, process-integrated use of fuel cells appears to be most attractive when some leverage effect on plant performance or cost can be realized.
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5.3 The Development of Trigeneration System Concepts 48
5.3.1 ABSTRACT Trigeneration is the simultaneous production of chemicals, heat, and power. A procedure is presented and illustrated for the development of trigeneration system concepts from the industry level down to the level of individual plants and parts thereof. It is shown for trigenerate petrochemical complexes that the selection of system elements for minimal fuel consumption depends on the amount of trigenerate electric power that can be exported. The avoidance of some 190 kg CO2 per MWh can be achieved for a typical complex. This net reduction in the total CO2 emission related to chemicals, heat and power production can be achieved because the chemical industry acts as a heat sink. Finally, the realisation of trigeneration in the chemical industry involves a shift in perception of the industry: rather than considering it a threat because of pollution, safety and health risks, it must be considered an enabler of a reduction of total human CO2 emission.
5.3.2 INTRODUCTION Trigeneration systems are facilities for the simultaneous production of useful (chemical) products, electricity, and heat. One may argue that today such facilities do not exist, but actually, they do! Today, for example, national economies or even the EU are systems where a net amount of chemicals, electricity and heat are produced. At numerous petrochemical sites the initial application of cogeneration systems has led to the development of the on-site utility island concept. Current petrochemical systems, however, have not been 'designed' for trigeneration. In addition, these systems do not operate somewhere close to the maximum thermodynamic efficiency achievable. In accordance with the Second Law of Thermodynamics, in each process the total entropy of a system and its environment increases -some minimum amount of Exergy is lost- and a net amount of feedstock, fuel or heat is expended to provide a process' driving-force. Since the economic operation of a great many petrochemical processes requires operation at elevated temperature and pressure, the total exergy loss increases. Thus, whilst a large part of the chemical reactions completed in industry is exothermic and the net change in free energy could allow production of Work, a net input of heat and Work is required. Trigeneration offers a means to minimise the combined inputs for electricity, chemicals and heat production, albeit at the expense of additional investment. Today, the threat of global warming has led many people to believe that some reduction of human CO2 emissions into the global atmosphere is urgently required. Therefore we explored whether the adoption of trigeneration in the petrochemical industry can help reduce total human CO2 emissions by improving total fossil resource utilisation.
48 The contents of this section have been published as (Dijkema 2001b).
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Outline of section In the past edition of the World congress, we presented a paper on the integration of energy-conversion devices in chemical plants (Dijkema 1996). This was largely 'technology-oriented' and focused on single chemical plants. Since then we have been elaborating the concept of 'trigeneration' and developed functional modelling (Dijkema and Reuter 1999; Dijkema and Grievink 2000) to help identify system innovation options. This method was successfully applied to develop and evaluate trigeneration system concepts for a range of chemical processes and a number of energy technologies, notably fuel cells (Hemmes and Dijkema 1998; Dijkema 1999), gas turbines and cogeneration systems. In this chapter, we will address the development of trigeneration system concepts for the level of industrial complex to individual plant level. Firstly, some background, the problem addressed and the definition of trigeneration will be elaborated, and the research approach summarised. Subsequently, functional modelling will be introduced to help understand and develop trigeneration concepts. Third, trigeneration as 'leitmotiv' for an industrial complex or area is investigated from an ecological and economic perspective, and the potential of CO2 emission reduction will be analysed. The prospects of trigeneration in the European Electricity markets are briefly discussed. Finally, some conclusions are presented.
5.3.3 TOWARDS TRIGENERATION CONCEPTS?
Background & context of the work Elsewhere we have reported some of our work on the development of methods to support the conceptual development of process system innovations (Dijkema et al. 2001). These are defined as technological innovations that enable or rely upon changes in the system structure or design of the petrochemical industry, its industrial complexes, or individual plants. It may be seen that trigeneration represents a class of such process system innovations. According to Wei, “(… ) innovative design and clever process modifications are essential to the economic health of the producer of commodity chemicals” (Wei et al. 1979). Indeed, the petrochemical industry has an impressive record of technological innovation within single plants. However, in contrast with science- based innovation within chemical plants, the concept of trigeneration suggests innovation beyond the boundary of individual plants, complexes or even the industry. Thus trigeneration is a concept to consider while exploring integrated conceptual design of the petrochemical industry's systems, which to date represents a largely unexplored 'white spot' in R&D (Dijkema et al. 2001).
Definition We have defined trigeneration systems as facilities for the simultaneous production of useful (chemical) products, electricity and heat (Dijkema 1996). Notably in utility engineering, sometimes the term trigeneration is used for the simultaneous generation of electric power, heat and cold. In chemical engineering and R&D, the term chemical cogeneration has been used to describe systems that produce electric power and chemical products, notably fuel cell reactors (Vayenas 1988).
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In our view, however, trigeneration best coins the view of any production plant as a possible supplier of not only products, but also energy products viz. electric power and heat.
Research approach We conjectured that the development of trigeneration may contribute to achieve sustainability, notably by avoidance of CO2 emissions and by increasing total resource utilisation. Our first objective was to apply the systemic approach developed (Dijkema 1996) for identification of trigeneration options and the specification of desired system content. Our second objective was to demonstrate that options for system improvement in the petrochemical industry exist beyond the straightforward application of cogeneration. Thus the research questions addressed are (1) whether this method is applicable and (2) whether trigeneration is worthwhile with respect to sustainability not only ecologically but also economically. We used functional modelling to develop trigeneration concepts. A straightforward LP-model was constructed to demonstrate the effect of trigeneration on the selection of energy conversion facilities. The model was also used to assess the extent of CO2 reduction when effecting trigeneration in an industrial complex. Early economic evaluation was used to obtain a first impression of the economics involved.
5.3.4 TRIGENERATION SYSTEMS AND THE CHEMICAL INDUSTRY
Classes of trigeneration systems The combination of chemical reaction and energy conversion is fundamental to chemical engineering and crucial to achieving proper plant design. Surprisingly, however, trigeneration is not, and only has emerged recently under the label of 'multifunctional reactors'. Notably at the level of unit operations fuel cell reactors include some ceramic or polymeric membrane to effect a chemical reaction and separation simultaneously. Trigeneration, however, can also be effected by combining systems beyond this level. This is illustrated by presenting some classes of trigeneration systems in the petrochemical industry below. 1. The Petrochemical industry At this level, the industry can be considered a trigeneration system for the production of base-chemicals, base-load electric power, and heat at various temperature levels. All other options mentioned in this list are in fact technology/system specifications that 'bring-into-being' a trigenerate petrochemical industry! 2. Petrochemical cluster At the level of a geographically clustered number of petrochemical complexes or plant, cogeneration facilities can be employed to supply power and heat both to industry and society, employing the industry as a sink for high-level heat (power production), and a source for low-level heat. In the Rotterdam Cluster, for example, a number of joint Cogeneration facilities have been or are under
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construction that supply electric power and steam to a number of customers in the cluster, whilst exporting electric power to the grid. 3. Petrochemical complexes For many petrochemical complexes -single site or part thereof-, the combination of the so-called utility-islands and petrochemical plants can be considered trigeneration systems in cases where they are net exporters of electric power and heat. 4. Petrochemical plants At this level, a number of options exist. Firstly, cogeneration systems can be used to upgrade a chemical plant’s off-gases; the system is extended and/or the system boundary shifted. Secondly, within the existing system boundary of a petrochemical plant, energy conversion technologies can be employed as unit operations in chemical process system design. Thirdly, chemical reactors can be designed for optimal product-to-heat ratios for inclusion in traditional power cycles: the heat of reaction drives some cycle for heat-to-power conversion. 5. Functional elements New functional elements for use in chemical plant design are crucial for achieving optimal material and energy balances in trigeneration. At this level, some options must be developed to (a) employ the petrochemical industry as a heat-sink for power generation, (b) create leverage by creating novel functional units to enable trigeneration and improve plant performance simultaneously, (c) allow a shift in the balance between power and chemical production costs and revenues and (d) directly convert feedstock to chemical products whilst capturing part of the free energy change of reaction as electric power, thereby approaching the thermodynamic optimum.
5.3.5 DEVELOPMENT OF TRIGENERATION CONCEPTS
Functional modelling Applied thermodynamics teaches us that trigenerate conversions must be direct, in order to obtain the highest efficiency, and traditionally an ideal fuel cell reactor is assumed to prove the case (e.g. Denbigh 1956)). At the other end of the spectrum is isolated or stand-alone conversion of fossil feedstock into chemicals, electric power or heat respectively. Present petrochemical systems are somewhere in-between, largely through the longstanding tradition of process- and energy-integration, while the introduction and spread of the use of cogeneration also has improved its fuel utilisation. This use of cogeneration can be considered a form of trigeneration. In addressing the analysis and formulation of trigeneration system concepts we have used functional modelling. The central idea of functional modelling is to enable 'opening-up' established or proven systems or technology concepts. System engineering has been defined as “a progressive definition and integration of functions and design decisions at every level of system complexity” (Corrigan and Kaufman 1965). Systems can be decomposed into progressively smaller subsystems, where system elements are the lowest level of detail of a system structure. System complexity can now be dealt with effectively when the focus is on system functions rather than system content because the functional characteristics of a system element are
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technology-free (Asbjørnsen 1992; Dijkema and Reuter 1999). In other words, a system or system element can be described completely by its inputs and outputs and the functions it performs. Specification of its technological content is not required; rather the functional description is complete and independent from the actual technical realisation of the element. For complex systems, functional modelling offers a means to arrive at some functional decomposition (Dijkema and Grievink 2000). It may be seen that a technology-free description enabled by functional modelling opens the way to search for alternatives in trigeneration system design.
Functional scheme technique A power system's functional decomposition has been visualised in the top left diagram in Figure 5-4: System development – fuel to electric power (redrawn), page 157, where the functional system elements have been enclosed by grey boxes. Each box title represents an element’s function. The representation essentially is technology-free when the system has been properly decomposed: note that the drawing is still valid when no technological details are included in the boxes. At the level of single elements, the content depicted represents only one possibility that 'realises' the system elements. At the system level, the particular selection and arrangement of system elements also represents a single possibility to ‘realise’, for example, a fuel cell system. At this level, the system inputs and outputs, its boundary and its title describe it as a system element at the aggregation level of 'complexes' or clusters. Note that all feed and product streams have been labelled outside the system boundary. A third important feature of this drawing technique is that system elements, where multiple, physically unseparated functions are performed, must be enclosed by an equal number of system element-boundaries. Thus alternative arrangements for the design of the system offered by the integration of functions are visualised.
Formulation of system concepts Let us assume that we must develop a system concept for the use of natural gas for the generation of electric power (Figure 5-4). When we consider a conventional large-scale power plant, we see that the system’s inputs are natural gas and oxygen (in air); its outputs are electric power, flue gas exhaust, and a waste-heat stream (from 'cold' to 'hot'). As stated, the central idea of functional modelling is to enable 'opening-up' established or proven systems or technology concepts. When we leave out the technical details of the system, as indicated by arrow I, it may be seen that the system representation has become technology free. The next step in system design is to consider other options to bring about the required functions, in this case power generation from natural gas. The technology- free system representation opens the way to alternative realisations depicted by arrow IIa and IIb in Figure 5-4, the use of a gas turbine and a fuel cell respectively. When focusing on the functional description, rather general descriptions for the inputs and outputs suffice initially. More detail can be added once a system concept has been established.
180 Process System Innovation by Design
In the case of the gas turbine, for example, flue gas is produced that contains a significant amount of waste heat at a temperature of some 450-500 oC, instead of transferring heat to some cold stream - e.g. cooling water. In the case of the fuel cell, apart from energy the flue gas will contain unconverted feedstock and some cell cooling may be required. For the sake of simplicity, in all cases we have assumed that the feed is at the right conditions (Pressure, Temperature, composition). We suggested that in process system design at each level of system complexity, the same procedure can be applied: (Dijkema 1999). Trigeneration system development, however, implies that there must be an initial focus on what possible alternative realisations of a particular system (step 4 and 5 in the procedure given below) may exist involving trigenerate functions. Thus, such a procedure must be extended with (1) determination of the aggregate system level used to start the analysis, (2) assessment of the (possible) system environment and (3) selection of the most appropriate system boundary and system products. In marketing studies, the latter is certainly done for a plant's main product, however, a mechanism for identifying and evaluating other possible products should be included. In trigeneration in the petrochemical industry, for example, CO2-credits may be obtained that can be marketed under an Emission-trading system. A procedure for trigeneration system development thus may look something like: I. Review an existing system design by functional modelling: 1. Determine the aggregate system level 2. Identify the crucial system functions 3. Draw a functional scheme 4. Briefly describe each system element II. Explore the options for trigeneration by 5. Assessment of the (possible) system environment 6. Addition of system outputs 7. Modifying the system boundary 8. Addition of system elements 9. Alternative realisations per system element or combination thereof III. Specify and select system concept(s) for early evaluation
5.3.6 ILLUSTRATION: TRIGENERATE PETROCHEMICAL COMPLEXES From the above classification it may be seen that in the chemical industry ample opportunities exist for trigeneration. Elsewhere we have used the trigeneration system concept to present prospective fuel cell applications in the chemical industry under a single systematic framework @(Dijkema 1999) and the previous section of this thesis. In petrochemical plants, heat is traditionally supplied in industrial furnaces and reaction furnaces such as the naphtha-cracker- and the ethylene dichloride (EDC) cracking furnaces. A study of the heat demand of the Dutch industry (Boot and van Wees 1982) concluded that the chemical industry largely requires heat at a temperature level between 300 and 800 oC at a total fossil fuel consumption of 164 PJ for energy supply (excluding naphtha cracking). These results led them to the remark that ample opportunity existed for cogeneration in this industry. Indeed most
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petrochemical sites in the Netherlands either already included cogeneration at the time or such facilities have been erected since. Often, however, due to lack of a heat- demand from residential areas these appear to have been designed on the basis of industrial - process - heat demand with the surplus power being transported to the grid. With the liberalisation of the European power markets, however, the dynamics of this market has increased, and, for any new cogeneration project in the Dutch petrochemical industry, the long-term marketability of yet more base-load must be thoroughly assessed. Our objective, however, is to support identification of system innovations. Therefore, in this section, as an example, the procedure outlined above will be used.
Use of the procedure for development of trigeneration system I. Review an existing system design by functional modelling: This part of the procedure for trigeneration system development comprises three steps, viz. (1) Determine the aggregate system level, (2) Identify the crucial system functions, (3) Draw a functional scheme and (4) Briefly describe each system element Step 1: The aggregate level is that of individual plants, or plant sections. Step 2: The crucial system functions are the production of various chemicals, electric power, and heat at various temperature levels. The power has 'base- load' characteristics, and has limited technical and economic scope for 'turn-down' Step 3: The scheme is similar to the ones given in Figure 5-4 Step 4: At this aggregate level, system elements are chemical plants (inside battery- limits), power plants and heat conversion plants. The latter energy conversions can be integrated sections of a single power plant, energy complex or petrochemical complex.
II. Explore the options for trigeneration The following steps must be completed to ensure some systematic exploration of possible options: 1. Assessment of the (possible) system environment 2. Addition of system outputs 3. Modification of the system boundary 4. Addition of system elements 5. Alternative realisations per system element or combination thereof
In addition to the global chemical and polymer industry that largely represent the markets for petrochemicals, the system environment assessed for the case of trigeneration must include the electric power consumers or traders, and possible consumers of heat. Apart from surplus electric power and heat, system outputs to be considered are tradable CO2 emission rights. The system boundary of the petrochemical complex changes because facilities for the generation of power and heat are included. These include stand-alone power and heat generation respectively, cogeneration options and others. At the single plant level, subsystem boundaries
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may shift, e.g. because of the integration of gas turbines in furnace design for optimal preheat and power generation. Finally, gas turbines, steam turbines, fuel cells etc. represent possible added system elements and these may offer new options for realisation or combination of system elements.
III. Selection of system concept for early evaluation In this particular case, our objective was to evaluate the impact of converting a petrochemical complex to a trigenerate petrochemical complex. Thus we compared two situations: (1) a petrochemical complex which power and heat demand are met internally, whilst external power demand is catered for by stand-alone generation and (2) a trigenerate complex which must cater for both internal and external power demand. To allow for this comparison, in the elementary evaluation presented we have added to a hypothetical petrochemical complex the possibility of inclusion of - stand-alone power generation (Power plant) - cogeneration type 3, heat-to-power ratio 3:1 (Cogen-3) - cogeneration type 4, heat-to-power ratio 4:1 (Cogen-4) - steam turbine operating between 600 oC and 200 oC (StmTurbine) - steam generator, 600 oC (StmGen-1) - steam generator, 200 oC (StmGen-2) These are common options available to meet the utility demand of any industrial complex. The particular selection is not exhaustive, but provides a minimum set of typical alternatives that are currently employed throughout the chemical industry. Any set of options can be selected to meet the particular heat and power demand of an industrial complex. Thereby a first impression of the possible selection of system elements for a trigenerate industrial complex is obtained. It may be seen that this list can be expanded for a more detailed analysis (e.g. more temperature levels) as the need arises. Notably the 600 oC level produced by cogen-3 or cogen-4 can also be perceived as the temperature level of the heat sink presented by industrial furnaces or industrial reaction furnaces. Thus, the analysis also leads to insights about the merits of trigenerate petrochemical plants, by coupling of gas turbines to industrial furnaces.
LP-modelling for system element selection A Linear Programming or LP-model was constructed to select the optimal combination of system elements for heat and power generation. This was implemented in Microsoft Excel. The optimal solutions were calculated using the Excel Solver functionality. The model (after Stadtherr and Rudd 1976; 1978)
Acc + r - p = 0 Eq. 5.16
The elements of matrix Ac are the coefficients that define each input-output relation per system element. c is the vector of capacities; c ≥ 0;
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r is the vector of feedstocks; r ≤ s(upply); p is the vector of products; p ≥ d(emand); An LP-model in standard form (Ax = 0) is obtained by using
A = [Ac I - I] Eq. 5.17
x = [c r p ]T Eq. 5.18
The optimal network design variables x0 are found by optimisation. T minx f x subject to Ax = 0 Eq. 5.19 f is a vector of some objective function’s coefficients
The coefficients of the A-matrix listed in Table 5.2 reflect the performance or efficiency of 'state-of-the-art' technology. These have been expressed in megawatts (MW). A negative sign indicates an input, a positive sign an output. To avoid to optimistic results with respect to trigeneration, the efficiency of stand-alone power generation has been set at 50%. In this case, f is set such that r, which represents total fuel input, is minimised. Thus, under the assumption that only fossil fuel combustion drives these energy conversions in the installations listed, the net CO2 emission will also be minimised in this optimisation. Obviously, the actual CO2 emission depends on the fuel-mix employed. A first indication is obtained in all cases by considering natural gas (CH4) as the fuel of choice. Table 5.2: Coefficients used in the A-matrix. Includes net loss per element (MW) System elements Energy carriers Cogen-3 Cogen-4 Power StmGen-1 StmGen-2 Stmtrbine Fuel -1 -1-1 -1 -1 0 Electricity 0.24 0.19 0.5 -0.02 -0.02 0.14 Heat - 600 oC 0.71 0.76 0 0.85 0 -1 Heat - 200oC 0 0 0 0 0.85 0.76
Loss 0.05 0.050.5 0.17 0.17 0.1
LP model Results In Figure 5-9 the results of the optimisation are given for the case where there is a net demand in the Petrochemical complex of heat at 600 oC and 200 oC respectively in a fixed ratio of 4:8:E (E=electric power) [MW]. From these figures it may be seen that: - when export of electricity is not allowed, Cogen-4 caters for internal electricity demand (0.5 MW), and there is stand-alone generation of 600 oC (HT) and 200 oC (LT) steam - when electricity export is allowed but limited, first Cogen-4 capacity is expanded, subsequently Steam Turbine capacity is added - allowing more electricity export brings Cogen-3 into being, thereby providing the optimal match between electric power and heat required
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Above an export demand of 6 MW (per 12 MW of heat HT:LT = 4:8), only Cogen- 3, a steam turbine and Stand-alone Power Plant capacity are selected for optimal trigeneration. In other words, anywhere in the region of 0 to 6 MW of electricity export, trigeneration is preferred over stand-alone power generation. The analysis clearly shows that the optimal selection of system elements picked for minimum fuel consumption varies with the amount of electric power exported from an industrial complex while satisfying its internal heat demand. The minimum fuel consumption calculated for trigeneration demonstrates the possibility of using an industrial complex as a heat sink for electric power production.
Total Power Generation [MW] 12
10
8 StmTurbine 6 Power Plant 4 Cogen-4 Cogen-3 2
0 0123456789101112 -2 Total Electric Power Export Allowed [MW]
Fuel Consumption [MW] 35 30
25 StmGen2 20 StmGen1 15 Power Plant Cogen-4 10 Cogen-3 5 0 -5 0123456789101112 Total Electric Power Export Allowed (MW)
Figure 5-9: System element selection for minimal fuel consumption.
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5.3.7 EARLY ECONOMIC EVALUATION OF TRIGENERATION SYSTEMS Generally the cost-structure of a project is broken down into capital related cost or capital expenditure, and operation-related cost. Throughout the life cycle of the project, the revenues obtained from the operation of the facility must compensate for both types of expenditure. In addition, many companies require a minimum return-on-investment or maximum payback period for an investment to be accepted. In power generation projects the initial investment - cost per kW installed- largely determines project profitability because it represents a large fixed annual cost throughout the expected lifetime of the project. The electricity revenue must exceed the total of the fixed annual investment cost, fuel cost and other operating cost in order to realise some return-on-investment. Technology selection for new power systems is done in the early phases of a project on the basis of investment cost and margin expected. Also in capital-intensive industries such as the chemical industry and the power industry, a large part of the capital expenditure is the investment costs for the new facility. The exact quantity of these costs, however, is hard to estimate. At the initial (screening) phases of a project it is therefore accepted that the estimate still has wide margins. In the chemical industry, a +/- 40% margin in the investment estimate is generally accepted as the basis for the design phase (Chauvel 1981). By analogy with (Vayenas et al. 1991b), our early economic analysis only focuses on the alternate energy conversion because the chemical output of the systems is the same i.e. the trigenerate petrochemical complex must process the same feedstock to the same petrochemical product state. The trigenerate system is then more profitable when the following relationship is satisfied:
(Rt, e+ Rt,h) • θt - Rs,e • θe > It - Is Eq. 5.20
In words: the total (discounted) additional revenue flux R from the trigenerate petrochemical complex throughout its technical lifespan θ must exceed the difference in initial investment I for trigeneration and stand-alone power generation. The initial investment for the trigenerate petrochemical complex may include both energy-conversion equipment and cost of adaptation of petrochemical installations.
Minimisation of CO2 emission The analysis results demonstrate that in trigeneration more efficient energy conversion can be selected to meet total power and heat demand. As a consequence, transformation to a trigenerate petrochemical complex leads to avoidance of CO2 emission. This may become an additional source of income under some scheme for emission trading. In table 2 the amount of CO2 avoided is listed per extra megawatt (MW) of trigenerate electricity exported on top of internally produced 8:4 LT:HT heat when optimal selection of system elements for trigeneration was allowed (Figure 5-9). The exact figures are valid assuming all fuel is natural gas (methane) with a LHV of 50 [MJ/kg], which represents a 'worst case' with respect to the fossil fuel mix because CO2 emissions of oil product or coal exceed those of natural gas. These figures confirm that whenever a combination of power and heat production is
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feasible, total CO2 emissions are reduced, which provides a clear incentive to convert chemical complexes to trigenerate chemical complexes.
Transition of electricity markets In trigeneration system development, one is faced with uncertainties with respect to initial capital expenditure, whilst the margins to be expected depend on both electricity, heat and chemicals revenue. It must be considered, however, that trigeneration is largely an option for long-term 'base-load' because the utilisation level of facilities must usually be above 85% in the petrochemical industry to ensure some positive margin. Until recently, in Europe electricity production companies were state-owned and total capacity was centrally planned per country. In the Netherlands, for example, the parent company of all production companies, SEP was obliged to issue electricity plans on a regular basis. Currently, however, the sector is in transition to allow 'more market' by privatising, liberalising and re-regulating the sector or parts thereof. Trigeneration then represents only one of the innovation options for the new electricity companies. In the market, a price will be set for the 'base-load' electric power from the trigenerate petrochemical industry. This price may increase when trigenerate electricity is labelled 'green electricity', a product that presently is in short supply in the Netherlands, whereas of July 1st 2001 every consumer is free to select its green electricity supplier. Finally, the net amount of CO2 emission avoided by adoption of trigeneration represents an economic output when a system of tradable
CO2 emission rights is established.
Table 5.3: Avoided amount of CO2 [kg/MWh] per interval of extra trigenerated electricity exported [MW]
Trigenerate Export CO2 Avoided [MW] [kg/MWh] 1st 276 2nd 191 3rd 191 4th 191 5th 191 6th 190 7th 73 8th - 12th 0
5.3.8 CONCLUSIONS By introducing functional modelling, the options for the simultaneous production of chemicals, power and heat can be explored at each aggregate level by translating existing system concepts to a technology-free specification. Thereby, an opening is created towards development of innovative concepts. A procedure to systematically complete this task was formulated and illustrated for the case of trigenerate petrochemical complexes.
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By employing a straightforward LP-model, we demonstrated that the selection of trigeneration system elements for minimal fuel consumption depends on the ratio between the heat sink available and the amount of power that can be exported from the system. For an industrial complex with a typical heat ratio for low level to high- level heat of 4:8, the first 6 MW electricity exported per 12MW heat (LT+HT) results in avoidance of some 190 kg CO2/MWh. Thus, parts of the large-scale petrochemical industry can act as a large heat sink enabling a net global CO2 emission reduction by trigeneration. These results support the proposed paradigm-shift in the perception of the petrochemical industry. Rather than considering the industry a possible and threatening source of pollution, safety and health risks, it can be an enabler for reduction in global CO2 emission by increased fossil resource utilisation. This can help to effect a change in perception of (petro)chemical plants and/or complexes by all its stakeholders in society, and may help to ensure the industry's license-to- operate.
5.4 Discussion and conclusion As stated in the introduction, the crux of this chapter is the recognition that it is the combination of fuel cell functions that must be exploited in developing process system innovations. In addition, the system boundaries can be suggested but altered to see the effect. As a matter of course, both the choice of functions to describe a system and the selection of the system boundary rely on the experience of the engineer or a development team. Functional modelling, however, provides a codification of that very experience and a route towards a first 'primitive' specification of a process system innovation such as trigeneration. The subsequent early economic analysis of fuel cell reactors and the effects of trigeneration gives rise to consequent innovations once the initial proposal has been formulated. In conclusion, innovative use of fuel cells in the chemical industry were categorised and used to develop functional modelling. Subsequently, 'proof' of the methodology of process system innovation is given by the development of innovative system concepts to realise trigeneration.
6 Fuel Cell Vehicles and Industry Development
6.1 Abstract Functional modelling has been applied to develop innovative system concepts for the chemical industry to anticipate and exploit changes in logistic fuel demand related to the market penetration of fuel cell vehicles. Within a decade polymer electrolyte membrane (PEM) fuel cell vehicles may enable a true transition in 'automotive transport'. We conjectured that part of these will be methanol-fuelled. Scenarios were constructed for automotive PEM fuel cell market developments, technological progress and fuel diet. Simulations up to the year 2030 visualise the dynamics and scope relevant for the chemical industry. In the conservative 'Superior PEM vehicles' scenario, 10% of the annual sales of passenger vehicles and heavy- duty vehicles are fuel cell powered by 2020. In addition, all combustion engine passenger vehicles sold have a 42V PEM fuel cell auxiliary system on board. The share of methanol in the fuel diet is expected to drop from an initial 100% to only 50% in all these markets. Technology advancement yields a 70% reduction in PEM platinum-loading and an extension the economic lifespan of fuel cell stacks to 5 years. Technology to recycle fuel cells and recover platinum is developed. In this scenario the production of the PEM fuel cell systems causes a peak in gross annual platinum (Pt) demand of some 105 tons/year. Since fuel cell stacks are being recycled, net demand for virgin Pt peaks at 95 tons per year around 2018, after which it drops to a negligible level. Sustainable Pt use requires that a stack/Pt recycling industry is developed in time. The main business opportunities lie in the development of a stack platinum recycling industry and the associated transport infrastructure because the long term dynamics of Pt-recycling appear much more favourable than the dynamics of virgin Pt production. In the chemical industry the main opportunity is the supply of methanol. The scenario results in an annual demand of 70 MTA methanol after a period of high demand growth. Using the methodology for process system innovation by design, new objective-defined functions of the petrochemical industry and possible system concepts for implementation in the Rotterdam industrial cluster were explored. One option is the realisation of a unique integrated industrial complex around the flexible manufacture and use of synthesis gas. The initial feedstock can be natural gas, but oil residue, coal, biomass and biomass waste can also be converted to synthesis gas. Methanol can consume a major share of the synthesis gas, but hydrogen manufacture, metals processing, olefins and other chemical processes also benefit from the variety of syngas qualities available in such a 'green' complex. The only real barrier to these developments is the advancement of PEM fuel cell technology and its final breakthrough to the marketplace. The networked process system innovations presented illustrate the use of functional modelling. Combined with scenario-building and dynamic modelling, a powerful set of methods results to anticipate and respond to changes in the world outside the industry. Thus, it enables the chemical industry to reap-the-benefits of a transition in automotive transport.
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6.2 Introduction The automotive transport sector worldwide today includes automobiles in all their varieties, low- and heavy-duty trucks, buses, vans, and utility vehicles. Transport accounts for roughly one-third of world energy resource use (WRI 2003). Worldwide 20 million passenger vehicles and 600,000 heavy-duty vehicles (trucks, buses) are sold each year (Anonymous 2003a; van den Hoed 2004). The automotive sector represents a major market to the chemical industry. Today, synthetic materials such as polymers, fibres and ceramics increasingly replace steel bodywork and engine parts. Automotive fuel additives such as oxygenates are produced in bulk quantities to augment gasoline quality. Its development continues to create incentives for innovation and growth of the (petro)chemical industry. Apart from the continuous stream of largely 'incremental' innovations, a transition of 'automotive transport' initiated by the availability and breakthrough of polymer electrolyte membrane fuel cell (PEMFC) technology could be realised in the near future. Such transition will have major consequences for the petrochemical and related industry. By first inspection of the requirements of PEM fuel cell vehicles and the associated industrial activities, we conjectured that development of PEMFC powered transport markets will open novel opportunities for networked process 49 system innovations around methanol , hydrogen and carbon dioxide (CO2) production. Available technologies may become part of an integrated system that caters for transport, electricity, and product needs. These products are manufactured via the generation of synthesis gas, which provides a generic link to a range of conventional and novel feedstock, such as natural gas, coal, crude oil and biomass.
The use of biomass and CO2 sequestration contributes to sustainability. Thus, a route towards a greener chemical industry can be opened. Within a decade polymer electrolyte membrane (PEM) fuel cell vehicles may enable a true transition in automotive transport, which is one of the most important outlets of the chemical industry. We conjectured that alternative fulfilment of the objective- defined function 'automotive transport' may be (in part) by methanol-fuelled PEM fuel cell vehicles. In this chapter, we report the use of functional modelling (Ch. 3) to explore the possibilities, implications and opportunities related to the transition. This represents a test case for the functional modelling approach and procedures developed: Does functional modelling provide an adequate means for abstraction from currently employed system concepts and do the procedures enable or facilitate the specification of innovative system content? The qualitative analysis is augmented with a quantitative assessment based on system dynamics modelling and scenario analysis, in order to obtain a first impression of the impact and constraints in potential transition scenarios.
49 Methanol can be used in combustion engines but has never penetrated the logistic fuel markets on a significant scale. Amongst others the Association of Methanol Producers for many years has advocated the use of methanol as a suitable fuel for passenger vehicles. Such use of methanol represents a major opportunity for those involved in the methanol supply-chain - natural gas producers, methanol companies and suppliers of technology and equipment - to grow their business.
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Firstly, a functional model is developed that captures the possible outcome of industry and automotive developments (§ 6.3). To this end, developments in automotive transport around PEM fuel cell innovation are summarised. The options for PEM fuel cell use in 'automotive transport' are identified, described and categorised. Secondly, scenarios for 'automotive transport' realisation by methanol- fuelled PEM fuel cell technology are constructed (§ 6.4). A dynamic model is presented that allows visualisation and forecasting of the effects of PEM fuel cell developments. Thirdly, scenario results are presented, their impact on the world methanol industry and the global platinum material cycle analysed and PEMFC related opportunities discussed (§ 6.5). Fourth, realisations of the functional image thus created are conceptualised through integrated network system design based on functional modelling and scenario analysis (§ 6.6). Elements for a transition strategy for part of the petrochemical industry are combined in networked process system innovations, notably the system concept for an integrated 'green' industrial complex that could be located in the Port or Rotterdam. Finally, the results are briefly discussed and conclusions drawn with respect to functional modelling (§ 6.7).
6.3 Functional modelling
6.3.1 'AUTOMOTIVE TRANSPORT' SYSTEMS The objective-defined function of all transport systems used by mankind is the realisation of 'automotive transport'. In the Twentieth century, the possibility to realise affordable 'automotive transport' amongst others has led to the creation of an immense industrial infrastructure to cater for automobile manufacture and automotive fuel supply respectively (Figure 6-1).
Figure 6-1: The present industrial infrastructure for 'automotive transport'.
'Automotive transport' today comprises 'individual' vehicles that are able to move as stand-alone items and 'system-linked' vehicles that are always attached to some infrastructure. Existing and future realisations of individual vehicles (aircraft, marine vessels) can be categorised around (1) the conventional combustion engines, (2) electrochemical fuel cells, (3) batteries, (4) pneumatic systems and (5) solar or wind- powered systems. System-linked vehicles comprise (6) combustion engine powered and (7) electrically powered. The system-link may be rail tracks (diesel trains), electricity supply from the grid (trolley-buses), or both (electric trains, metro systems, city trams). Special system-links are sky trains and automatically guided vehicle systems (AGVs). As a matter of course, (1) represents current realisation of ' individual vehicles' such as automobiles, trucks and auto buses. Presently, gasoline, diesel and LPG are employed worldwide as fuel, while ethanol, bio-diesel and natural gas are employed in various regions at a limited-scale only. The use of methanol, diesel/methanol
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mixtures and dimethylether (DME) have been demonstrated. Only recently, BMW has developed a prototype of their 730 model that operates through internal combustion of pure hydrogen. Options (3) and (4) appear to be developments for transport with limited range. Vehicles for city transport have been developed and tested that use compressed air to provide shaft power. The use of battery-powered vehicles is largely limited to utility vehicles. The weight to energy-storage ratio is less favourable for long-range transport using the current and emerging generation of batteries. Advanced battery subsystems are being incorporated in PEM fuel cell systems to cater for peak- and start-up power. Options (6) and (7) are the well-known realisations of public transport. Compared to transport based on (1) combustion engines, options (2) around electrochemical fuel cells are expected to achieve much higher 'well-to-wheel' efficiencies whilst largely avoiding harmful emissions (Geissler et al. 2001). Initial developments on alkaline fuel cells and phosphoric acid fuel cells were not successful. Today, polymeric electrolyte membrane, PEM, appears to be the fuel cell technology most suited for automotive application. Various demonstrations have been launched, which all featured conventional vehicles propelled by PEM fuel cell systems instead of combustion engines. Since PEM fuel cells electrochemically convert hydrogen, on-board storage of hydrogen and an infrastructure for hydrogen distribution is required. Many studies and efforts of governments, fuel cell technology developers and automobile companies focus on on-board storage of hydrogen and the associated infrastructure for hydrogen supply. In the refining and petrochemical industry, however, it is well known that hydrogen is expensive to manufacture, to handle and to transport. In contrast, the use of logistic fuels for fuel cell vehicles that incorporate on-board conversion to hydrogen would require only limited adaptation of the present industrial infrastructure (refining, gasoline stations etc.). Therefore, developments are under way to demonstrate that on-board fuel conversion to hydrogen is technically and commercially feasible. Fuel candidates are (clean) gasoline, diesel, LPG, ethanol, methanol, and DME. The best result would be the realisation of so- called Flexible Fuel Reformer (FFR) technology, because this would open the way to economy-of-scale in the mass production of only a single type of reformer for various fuels50.
6.3.2 A FUNCTIONAL MODEL FOR 'AUTOMOTIVE TRANSPORT' The abstraction 'from well-to-wheel' appears to be a functional model of the industrial infrastructure and automobile industry that together allow us to realise 'automotive transport' through individual vehicles. However, it does not indicate that intermediate functional elements are required in between a 'well' and the final realisation of transport via 'wheels'. More importantly, it is not a technology-free specification, as it hints at the use of an (oil or gas) well and at a transport concept that employs wheels. Thus, the concept is not suited to open the way to think of historic or innovative transport concepts that do not use (oil and gas) wells, wheels
50 R&D is being conducted into the realisation of systems where methanol may be used without prior conversion to hydrogen (and CO2) in a 'direct methanol PEM fuel cell'.
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or both. One may think of, for example, bicycles, solar powered vehicles, aircraft, marine vessels, sailing ships, magnetic trains, hot-air balloons, rockets, zeppelins, snow gliders and sky trains. Therefore, we prefer the concept of 'automotive transport'. Its functional model essentially consists of the functional elements (1) 'realising availability': some (energy) resource is made available to be used for automotive transport and (2) 'realise automotive transport': employ or convert the energy resource to (shaft) power that drives a suitable vehicle. Thus, the functional model for automotive transport is similarly decomposed as the model for petrochemical systems around aromatics (Ch. 3) and Olefins (Ch. 4), where 'production and consumption' systems were discerned.
Emissions(non-ODF)
FE 1 FE 2 Provide suitable port Provide Trans Fossil energy source resources automotive of goods transport Renewable FE 1 Energy Transp resources FE 1 ort Source of people FE 2 es FE 2 sourc Flow Tr ansport FE N of live FE N stock
Figure 6-2: Functional model around 'automotive transport.' On a sailing ship or a solar power driven vehicle, these two functional elements suffice to realise automotive transport, whenever there is a sufficient breeze or sunlight respectively. In all other cases, functional element (1) will include substantial infrastructure to distribute the energy source to be used. Thus, functional element (1) may be further decomposed into (1.1) initial extraction -by depletion of a reservoir or by adequately tapping a flow source (such as hydropower, solar power) - , (1.2) resource processing (such as oil processing in a refinery, or the conversion of biomass to ethanol) and (1.3) supply/distribution (through some wholesale/retail infrastructure). Functional element 2 is the “front-end” or market end of the total industrial infrastructure that offers the possibility to realise (individual) automotive transport. It may be further decomposed into all functional sub elements that together constitute a vehicle (of various type and utilisation), and also includes the entire industrial infrastructure to bring said vehicles into being. (Figure 6-2).
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The above model and decomposition match the current implementation of 'automotive transport'. A top-level decomposition between (1) 'make 'automotive power' available', (2) 'distribute 'automotive power' to users' and (3) 'provide transport' represents an improved abstraction. These functional elements may overlap. Thus, an improved model is obtained that emphasizes that on the one hand an industrial infrastructure must exist to create availability of motive power, on the other hand some 'hardware' to realise transport itself, whilst in between somehow motive power must be made available through distribution (Figure 6-3).
Emissions(non-ODF)
FE 1 FE 2 FE 3 Fo Convert to port ssil Distribute Provide Trans res suitable power ource power source automotive of goods s source transport FE 1 FE 1 FE 1 Transport Energy Source of people e abl new FE 2 FE 2 FE 2 Re ces Tran our sport res of li vestoc FE N FE N FE N k
w s lo e F rc u o s
Figure 6-3: Improved functional model of 'automotive transport.' Currently, two rather extreme type of realisations of 'automotive transport' exist that are captured by this model: (1) railroad- or other system-bound transport (trams, metro, sky trains), which combines a fixed track with an infrastructure for motive power supply and (2) road-based vehicles that depend on a system of motive power supply from crude oil refining and distributed through a network of stations. Trolley buses are somewhat of an exception, as they do employ a fixed infrastructure for power supply. The model also captures novel concepts, such as magnetic trains.
6.3.3 AUTOMOTIVE TRANSPORT AND INNOVATION The drive to capture and keep a share of the huge market of road vehicles has supported a continuous innovative development of the automobile industry and its suppliers. The demand for acceptable cost had to be met whilst realising enhanced vehicle safety and comfort, whilst reducing the environmental impact of 'automotive transport' that is subject to increasingly stringent regulation. From a functional systems perspective, however, the systems in the automobile industry, its co-makers and suppliers are largely characterised by maturity. Although new market niches continue to be found, notably in the automobile sector, and products and technology applied continue to be improved and optimised, the essentials of 'automotive transport' have not changed for a century, i.e. since the
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introduction of the Model T Ford. At a (networked) systems level, innovations in fuel supply and car manufacture are largely incremental in character. Combined, these have led to automobiles that make optimal use of the system concept around combustion engine technology. The maximum achievable well-to-wheel efficiency, however, is low when using combustion technology. The hydrocarbon fuels used result in continued emission of CO2, even from so-called ultra-low or zero-emission vehicles. Thus there are many similarities between the development and status of the automobile sector and one of its suppliers, the petrochemical industry (Ch. 1). In the global quest for sustainability and in response to climate change concerns, many advocate a transition towards a hydrogen economy. In the automobile sector, this transition is to be enabled by fuel cell technology. 'Automotive transport' appears to be one of the promising applications for fuel cells because of the limited efficiency of currently employed gasoline and diesel engines, the potential size of the market and the potential ecological advantages. Since both diesel and gasoline combustion engines convert fuel to heat and heat to shaft-power, their performance is limited by the maximum achievable Carnot-efficiency. Current engine efficiency is some 15-25%. In theory, the achievable efficiency of direct electrochemical conversion of chemical fuel energy to shaft-Work is about twice as large, some 40-50%. Capturing a share of the market of vehicles produced would allow realisation of mass production of fuel cell units, which would greatly reduce cost per kW power unit. Apart from protecting vested interests in the current automotive fuel infrastructure, these are the main incentives that have led to a number of global alliances between oil companies, fuel cell developers and automobile manufacturers such as Shell- Ballard-Siemens-Daimler-Chrysler and ExxonMobil-Ballard-General Motors (e.g. van den Hoed 2004). The ecological advantages of fuel cell powered vehicles are a third incentive for fuel cell application in 'automotive transport'. A system solution around PEMFC vehicles prevents diffusive emissions. Conventional engines suffer from a host of emissions that are detrimental to local and regional air quality. These comprise soot, aerosol particles, NOx, SO2 and volatile organics (Spiro and Stigliani 1996). Although innovative engine technology and exhaust catalysts have successfully reduced many of these emissions, a significant level of emission remains. Where combustion engines can be equipped with exhaust catalysts, a classic example of an 'end-of-pipe' solution, one cannot avoid diffusive CO2 emission without a change of fuel. Hydrogen powered vehicles that use combustion engines would emit water and some NOx. Vehicles that employ hydrogen and fuel cell technology would emit water only. Presently hydrogen is produced from fossil fuels. When using fuel cell technology, however, the total CO2 emission of 'automotive transport' decreases because of the improved 'well-to-wheel' efficiency that reduces net system fossil fuel input (Geissler et al. 2001). In addition, hydrogen can be generated in central production facilities that use fossil resources and sequester the CO2 by-product.
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Reduction of fossil fuel use and CO2 emission of 'automotive transport' requires a transition in vehicle technology (FE 3) and an alternative realization of resource conversion and distribution (FE 1 and 2; see Figure 6-3).
Cadre 6-1: From Well-to-wheel with methanol and PEM fuel cells
To realise a 'sustainable', notably clean, quiet and cost-effective system for automotive transport, an alternative system may be implemented, where polymeric electrolyte (PEM) fuel cells systems are used to propel vehicles and where methanol is used as a logistic fuel. Methanol is already available from the petrochemical industry, where it is produced in bulk quantities from natural gas. Since it is a liquid, small-scale distribution costs are relatively low. Methanol is a safe and sound source of hydrogen via relatively mild on-board fuel reforming. An infrastructure around Methanol-fuelled PEMFC propelled vehicles represents a realisation of the functional model described (Figure 6-3). Functional element FE 1 is realised through the winning of natural gas and conversion to methanol, possibly combined with the use of biomass. FE 2 is the supply/distribution of methanol to customers through some wholesale/retail infrastructure. As winning and conversion in FE 1 may not be at the same location, nor conversion at the location of entry of FE 2, intermediate transport functions are required, such as pipeline infrastructure for natural gas, liquefaction facilities and shipping of LNG and shipping and storage of methanol. An overview of the system from 'well-to- wheel' is given in (Figure 6-4).
One option is the fulfilment of the ODF 'automotive transport' by PEM fuel cell vehicles. Since on-board conversion of methanol to hydrogen is technically and commercially feasible, PEMFC vehicles may be built with on-board storage of hydrogen or methanol. In both cases, the associated fuel supply and distribution infrastructure must be developed. In contrast, the use of logistic fuels - (clean) gasoline, diesel, LPG - would require only minimum changes in supply and distribution.
Figure 6-4: 'Automotive transport' realisation by PEM fuel cells and methanol.
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As a matter of course, the use of methanol and logistic fuels will result in production- related CO2 emission and diffusive emission from the vehicles. The use of methanol is expected to yield the smallest amount of total emission. In addition, where presently almost all methanol is produced from natural gas, an efficient system would result when combining the production of methanol from natural gas and biomass (Stikkelman 2001).
6.3.4 NETWORKED PROCESS SYSTEM INNOVATIONS The existing realisations of automotive transport serve to illustrate that system content and system input can be varied to yield similar output to meet the same objective-defined function, 'automotive transport'. The alternatives may involve the entire system or they may be limited to the 'front-end' functional element FE 3 (vehicle) or 'back-end' functional elements FE 2 and 3 (vehicle and distribution system), respectively (Figure 6-3). The realisation of 'automotive transport' through PEM fuel cell technology (FE 3, Figure 6-3 and Figure 6-4) in combination with the use of existing logistic fuels (gasoline, diesel, LPG) appears to be completely within the currently employed system concept, with innovation remaining largely limited to the engine concept used beneath the hood. Indeed, the industry has demonstrated that (prototype) fuel cell cars do not have to look any different from their conventional counterparts. Thus, fuel cell driven cars would be introduced as a new fuel channel and technology beneath the hood, however with no consequences to car exterior, nor to its objective function, the provision of automotive transport. Whenever this concept for PEM fuel cell vehicles becomes reality, however, the product spectrum of refineries must change, depending on the characteristic of FFR technology. It is, for example, well known that reforming of aromatics is difficult. Thus, FFR introduction may require that the composition of gasoline and diesel be modified. In case this is to be done for substantial volumes, process system innovation of refineries may well be required. In case hydrogen or methanol would become the preferred fuel for distribution to PEM vehicles, an alternative realisation of FE 2 is added to the current situation, i.e. hydrogen and methanol become a logistic fuel. Upon first inspection, the extent of networked process system innovation appears to be limited. The adoption of methanol, however, does imply the use of natural gas instead of crude oil. Initiation and subsequent growth of a methanol-fuelled fleet of PEM fuel cell vehicles will require substantial growth of industrial methanol capacity. This may finally imply a change in characterization of methanol from chemical to fuel (Fahy 1990). This opens the way to innovative networked process systems (see § 6.6). Advocates of a transition to a 'hydrogen economy' envisage production and distribution of hydrogen on a large-scale. Various options for system realisation have been proposed and are being tested, such as centralized hydrogen production and compression, trucking the hydrogen to distribution stations and retail (BMW demonstration, Germany). At the other end of the spectrum is decentralised electrolysis of water and compression of the hydrogen using electric power from the grid. Alternatively, an integrated industrial infrastructure for the supply of hydrogen
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can be envisaged, where hydrogen is distributed via some pipeline infrastructure, which may or may not be integrated with the natural gas distribution grid (Weijnen 1999). A system for distributed generation of hydrogen via from some logistic fuel or methanol also appears to be feasible, in which case one may opt for hydrogen production/compression at retail stations or for on-board hydrogen generation via methanol reforming, as demonstrated by the Daimler/BASF NeCar 5. A transition towards PEM fuel cell propelled 'automotive transport' thus requires fuel cell technology and may require networked process system innovations to realise feasible alternative fuel infrastructure and associated industry.
6.4 Scenario development and modelling Within a decade polymer electrolyte membrane fuel cell vehicles may enable a true transition in automotive transport, which is one of the most important outlets of the chemical industry. We conjectured that alternative fulfilment of the objective- defined function 'automotive transport' may be (in part) by methanol-fuelled PEM fuel cell vehicles. In order to help industry to anticipate and shape this transition in 'automotive transport', quantitative scenarios were constructed that combine automotive PEM fuel cell market developments, technological progress and fuel diet evolution. Simulations up to the year 2030 visualise the dynamics and scope relevant for the chemical industry.
6.4.1 TECHNOLOGICAL PROGRESS On the basis of an authorative review (Arthur D. Little 2000a) - summarized in Appendix A. 7, four key aspects were identified that must be incorporated in the model used to calculate the scenario results: 1. Dominant system characteristics. The net PEMFC system efficiency determines the yearly fuel requirement for a typical vehicle and its gross power rating. 2. Status and outlook of PEM technology development. The required PEM platinum-loading per kW stack output and the gross power rating determine the net amount of platinum required for the production of a new system. 3. PEMFC system lifespan and recycling. The system operating lifespan and the development of stack recycling for at least precious metals (platinum, ruthenium) recovery will determine the development of net Pt demand for the PEMFC automotive markets. 4. Fuel selection In PEMFCs hydrogen is converted electrochemically with oxygen to water. Thus, on-board hydrogen storage or on-board hydrogen production is required, for example from LPG or methanol.
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6.4.2 DETERMINANTS OF MARKET SCENARIOS Our objective of sketching possible futures for PEMFC vehicles, scenarios, was to visualise their consequences to the external world. With suitable scenarios and modelling a projection can be made of the scope and development of methanol demand, platinum demand and the impact on total transport related CO2 emission. We have opted to use the development of PEMFC economics and PEMFC competitiveness as the main determinants of market scenarios. This leads to the four scenarios that have been summarised in Figure 6-5. The economics of PEMFC vehicle use and production are related. The total cost of ownership and use, TCOU, of a vehicle is determined by the required investment - the annualised cost of acquiring the vehicle - and by the subsequent operational costs: fuel, maintenance, repair, spare parts and taxes levied on car ownership and fuel. The cost to manufacture a PEMFC vehicle depends on production volume and technology status. Higher production volumes result in lower development and assembly cost per vehicle. Meanwhile, automobile development and mass production facilities require massive investments, which can only be recovered at sufficient output levels. The status of PEMFC technology influences TCOU via the impact on cost per vehicle. At present, major cost items are materials needed to manufacture PEMFC systems (platinum) and the combined cost of many system components and system complexity. Thus, at $1000/kW, the of a 30 kW PEMFC engine is 20 times that of a conventional 30kW gasoline or diesel engine purchased at some $1500/engine. Similarly important, however, technology status determines cost of operation of the vehicle. Targets and status with respect to technology development have been summarised in Appendix A. 9, based on (Arthur D. Little 2000a). Major items are the limited PEM fuel cell stack lifetime, which requires costly replacement after 4-5 years of operation. PEMFC competitiveness, its cost and benefits compared to other types of vehicles, determine its adoption in the market place. Apart from social and psychologically determined preferences, which are important in automobile sales, it is safe to assume that PEMFC automobiles and trucks will offer competitive performance characteristics. Then market development will depend primarily on PEMFC sustained competitiveness over the full life cycle of car ownership and usage, i.e. TCOU. Governments may influence the TCOU by tax differentiation between car type and fuel - logistic fuel, natural gas, biogas, hydrogen or methanol. In addition, PEMFC competitiveness may be improved by the creation of a level-playing-field with respect to emission levels in vehicle exhausts (CO, NOx, SO2, soot, hydrocarbons, lead, metals) and the total well-to-wheel CO2-emission. Finally, tax incentives may be created to favour investment in new vehicle production facilities. Finally, an important parameter is well-to-wheel efficiency and net amount of energy resources used for automotive transport. In combination with fuel characteristics of logistic fuels replaced by natural gas via methanol, this gives an impression of the total amount of CO2 avoided. Vogel (2001) has calculated that for methanol - PEMFC this efficiency is moderately higher than the well-to-wheel efficiency of gasoline /diesel operated automotive transport @(Vogel 2001). In case other
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sources of methanol, e.g. biomass, are employed a significant improvement may be expected (Stikkelman 2001).
6.4.3 MARKET SCENARIOS In Figure 6-5, four possible scenarios have been depicted for different combinations of development of PEMFC economics and PEMFC competitiveness respectively.
High Competitiveness
'Superior PEMFC 'PEMFC Vehicles' breakthrough' become available Rapid fleet for a limited market replacement by share PEMFC technology'
Unimproved Improved Economics Economics
'PEMFC, 'PEMFC the eternal promise' Outcompeted' Science & technology Market power of cannot deliver feasible vested players solutions remains unchallenged
Low Competitiveness
Figure 6-5: Scenarios for PEM in automotive transport.
In 'PEMFC, the eternal promise', effectively no introduction of PEMFC vehicles of any kind occurs, as both economics and competitiveness remain as is. This scenario has been reality for the last decade, where science and technology breakthroughs, though anticipated, have not materialised into an affordable automobile; a number of demonstrations (cars, automobiles, van) have been launched though. 'PEMFC outcompeted' is a scenario where PEMFC does not make it successfully to the market despite technological advancement and improved economics. This is largely the scenario exhibited by steady-state fuel cell applications. These systems have been dramatically improved. Meanwhile, however, cogeneration technology also has been improved. Both in stationary power generation and in automotive transport, vested interests and past investments are immense. Therefore, vested players are reluctant to favour a level playing field or to allow temporary incentives for PEMFC systems.
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In 'Superior PEM vehicles' the economics are sufficiently improved and incentives have been created so that PEMFC vehicles are considered superior goods. Thus, they will obtain a share of the market that depends on economic prosperity. Conventional gasoline and diesel vehicles continue to dominate the world's vehicle fleets. Many automobile companies do introduce novel models with PEM fuel cells to deliver auxiliary power. 'PEM Breakthrough' materializes when general awareness of the threat of Global Warming, technological progress, venture capital investment and clever marketing result in a sweeping introduction and acceptance of PEMFC vehicles worldwide. Subsequently, in OECD economies, in a short period of time legislation is passed and enforced to phase out gasoline and diesel operated vehicles. The time of abundant, inefficient use of oil products in transport ends relatively abruptly. A massive restructuring of the refining industry worldwide follows to supply logistic fuels suitable for use in PEMFC vehicles. This includes natural gas and crude oil conversion into methanol and hydrogen combined with carbon fixation or CO2 sequestration. At present, it may be seen that PEMFC vehicle development resides in the lower- left quadrant. Indeed, many are of the opinion that fuel cell technology will remain an eternal promise. Recently, however, considerable investments in R&D programmes, demonstration and commercialisation have been launched to move the technology to the upper-left quadrant. Whether the 'Superior PEMFC vehicles' is the most plausible scenario remains unknown. There is, however, considerable risk that said programmes are not sufficient, which would imply that 'PEMFC outcompeted' is the near future where 'PEMFC-the eternal promise' remains the perception of many believers. A dramatic success of R&D would open the way to realise the ultimate scenario, 'PEMFC breakthrough', which is also the most dramatic of possible futures.
6.4.4 FUEL DIET AND VEHICLE INTRODUCTION PEMFCs and other types of fuel cells eventually convert hydrogen electrochemically with oxygen to water. PEMFC vehicles may be equipped with on-board storage of hydrogen or with a fuel processor. In the former case, the associated hydrogen supply and distribution infrastructure must be developed. In a variety of (PEM) fuel cell markets, indeed hydrogen is expected to be one of the fuels of choice. Air/hydrogen mixtures, however, are highly explosive when an ignition-source is available. Although worldwide the chemical industry has a good track record in dealing with hydrogen, people are naturally concerned about the risks of hydrogen. The cost of pipeline transport of hydrogen is high. Therefore, it may be attractive to develop on-site generation of hydrogen, which is possible via dissociation of methanol at low-temperatures or the reforming of logistic fuels. Incorporation of any of these conversion processes in the vehicles themselves requires miniaturisation and economic down-scaling. At fuel stations, however, the conversion process can be erected as a medium-scale stand-alone stationary facility. Thus, a fuel service station that wants to sell hydrogen in the future may opt for either methanol dissociation, FFR of logistic fuels or the electrolysis of water. Similarly, on a local scale a neighbourhood that wants to produce PEMFC power can be supplied with
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hydrogen via a shared methanol reformer (Arthur D. Little 2000b). In a liberalised fuel market methanol may thus provide a route towards distribution of hydrogen. Bringing-into-being 'automotive transport by methanol', as illustrated in Figure 6-4, p. 195, is subject to competition from the vested players in the logistics fuel infrastructure markets. In addition, entrenchment caused by currently preferred automobile characteristics may slow down alternative fuel market penetration. Therefore, a 'thinkable' test case for methanol PEM fuel cell vehicle demonstration was conceptualised and modelled, automatically-guided vehicles (AGVs). In consultation with some parties in and around the Port of Rotterdam, the case of internal transport on container terminals was selected. Around the world, two major types of container terminals are in operation, viz. terminals where containers are lifted and transported by movable cranes, and terminals where lifting is by fixed cranes. In the latter case internal transport is by 'container trains' pulled by (automatically-guided) tractor vehicles. These AGVs, which are also used at airports, are high-power diesel engine driven. Related emissions and noise present a problem. The extent of applicable vehicle legislation is limited, however, because the AGVs are used on private property only. Therefore, real tests may be conducted in an early phase of development.
6.4.5 A DYNAMIC MODEL FOR SCENARIO SIMULATION PEM fuel cell technology is being developed for both stationary power generation and for automotive applications (see Appendix A. 7). The model includes the 5 market segments for PEM fuel cell technology as identified in the literature (e.g. Arthur D. Little 2000a). Per market segment, the model is set up to characterise and visualise the dynamics of a fleet of systems (see Appendix A. 8). In the model the platinum required for new systems, the methanol used as fuel and the platinum recovered from recycled systems are calculated as a function of technological progress, pattern of use and market development51. Each year the composition of the running fleet is calculated as a function of the number of systems that have been built in all previous years and the phase-out pattern of systems of a particular production-year. At the input side, the development of the fleet is driven by the market demand foreseen in a particular scenario, which is nothing more than the number of new systems produced per year to cater for expected demand. Market scenarios are defined by two parameters: the total demand per year, and the fraction of systems that are methanol fuelled. The output or removal of systems from the running fleet is determined by the phase-out pattern, which is a function of the technical lifespan, the economic lifespan and the operational use. The characteristic distribution of end-of-life vehicles recently has been determined (van Schaik and Reuter 2004). In our scenario model these parameters change each production year due to technological progress. An approximation of the phase-out pattern is included in the model as a normal distribution around average technical lifespan.
51 The model equations for each market segment are the same; only the model parameters differ between the market segments. The model is given in Appendix A. 8.
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The balance of inputs and outputs is used to calculate the 'presence' of systems produced in each previous year. In the 'Superior PEMFC vehicles' scenario (see below), for example, in 2003 the first 10 light-duty passenger vehicle 30 kW systems are introduced. These have an expected technical lifespan of 1000hrs of operation. They are used 200 hrs per year to drive some 16,000 kilometres. Thus their average technical lifespan is five years. One of the systems, however, breaks down to a status beyond repair in 2003, the others are in operation successfully until 2007 (1), 2008 (2), 2009(4) and 2010 (2). Thus the actual operational lifespan shows some variation around the 1000hrs design value, which reflects the effects of variations in style of use. The phase-out or 'end-of-life' scenario and the technology status at time of production determine the net volume of platinum to be recycled. In the model, therefore, the variation by which systems break-down can be specified. Also the fraction can be specified of systems that are removed from the world-wide fleet in operation due to other reasons than PEM fuel cell breakdown (accidents, fire, change of lifestyle, misuse etc.). The combination of scenarios for market demand (input), system use and end-of-life (output) provides a projection of the running fleet. From this dynamic forecast of the size of the running fleet, its characteristics and use, the implications for methanol and platinum demand can be computed. In addition, the net amount of
CO2 and other emissions can be calculated. In order to get a realistic impression of the dynamics and scope for platinum and methanol, the key parameters that are affected by technological progress have been incorporated in the model. These are the total Pt-loading required (expressed as g Pt per net kW system output), the system expected operational-economic lifespan (< 5% power degradation), and the overall system efficiency of methanol-to-mileage. From the typical system power-rating and use pattern the net demand for methanol is calculated. The total methanol demand is determined by the sales volume. In the model, the fraction of methanol-fuelled PEMFC can be varied. The typical power-rating and technology status with respect to required Pt-loading determine the net Pt-demand for a system produced in a particular year. Once produced, the net amount of Pt remains unchanged until the system ceases operation and thus becomes available for recycling. In the calculations, a 100% platinum recovery from these systems has been assumed. In summary, the dynamics of future PEMFC-related methanol demand, the net 'virgin' platinum demand, the demand for Pt-recycling and the net amount of Pt- stored in the PEMFC fleet are calculated. The model can be extended to visualise future (avoided) CO2 and other emissions, the net content of Pt (g/kg) in systems recycled (requires forecast of development of PEMFC specific weight development), and the amount of hydrogen required for the hydrogen-fuelled fraction of the PEMFC fleet.
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6.5 The 'Superior PEMFC vehicles' scenario We have opted to visualise the consequences for platinum and methanol if the 'Superior PEM vehicles' scenario would become reality. An overview of this scenario is given in Cadre 6-2.
6.5.1 DESCRIPTION OF THE SCENARIO Technological development in this scenario affects PEM platinum loading and stack lifespan (Figure 6-6). The dependency of the PEM fuel cell operation on platinum- coated membranes, both anode and cathode side, is seen as a serious constraint for market introduction. In a recent cost estimation study for PEM fuel cell systems, Arthur D. Little (2000a) concluded that at 2000 technology status, the fuel processor and tail gas burner together require 30 g of Pt as catalyst ingredient. At a 50-kW net output, a PEM fuel cell system requires some 180 g of platinum loading for the fuel cell stack alone (Arthur D. Little 2000a). Massive R&D efforts have led to this current status in Pt-loading of the membrane electrode assembly (MEA). Hampden- Smith claims to have developed a MEA with only a third of the Pt-Loading quoted by Arthur D. Little (Hampden-Smith 2000). No proof, however, has been found that this technology is used in commercial fuel cells. A typical heavy-duty truck using PEM technology available today in a 300kW system would include a total of 1.2 kg of Pt at current cost of $18.00052. This cost could drop to some $7000/system if Pt- loading reduction for MEA becomes a reality.
Cadre 6-2: Superior PEM vehicles scenario summary Market development for Automotive only: • Total number of cars sold worldwide = 20 Million[systems/yr]. (2003-2030) 1. total penetration of fuel cell auxiliary power: 20 Million [systems/year] 2. PEM fuel cell powered vehicles: up to 2 Million [systems/year] 3. Heavy duty PEMFC vehicles (trucks, buses): 60,000 [systems/Year] 4. PEM fuel cell AGV's: 2000 [systems/Year] • In each category, initial market share of methanol is 100%; mature market share is 50% • Technology development: 1. Pt-loading: present PEMFC technology status = 3.8 [g of Pt/kW] 2. Pt-loading improves to only 0.8 [g of Pt/kW] (2020-2030). 3. Stack lifespan increases from 1 000 to 40 000 [hrs/system]. 4. System efficiency is constant at some 40% LHV • Material cycle development 5. Spent PEM's are processed to completely recover platinum
52 At a typical Pt price of some $15/g. Current prices can be found e.g. at www.kitco.com.
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In the scenario a number of breakthroughs that result in stepwise decremented PEM platinum loading. Continuous improvement gradually reduces required Pt- loading. Similarly, an increase in system economic lifespan is modelled as a number of steps in combination with incremental improvement. In the scenario, technological progress yields a 70% reduction in PEM platinum-loading and an extension the economic lifespan of fuel cell stacks to five years. Since PEMFC vehicles will incorporate battery systems, regenerative breaking and advanced transmission, the rated fuel cell power output is 30 kW for passenger vehicles. Heavy duty PEMFC vehicles average 160 kW of system power output, which together with peak battery power yields a performance characteristics similar to conventional diesel engine powered vehicles.
Stack development
6
5 Tech. Lifetime Oper. 4 [Years]
3
Platinum
[g/kW], [Years] [g/kW], 2 Loading [g/kW] 1
0 2005 2010 2015 2020 2025 2030 Year
Figure 6-6: Stack development scenario: Platinum loading and technical lifespan for automotive PEMFC systems. Market development expressed as the number of systems sold determines the order-of- magnitude of the platinum and methanol demand, respectively. Today, worldwide 20 million passenger vehicles and 600,000 heavy-duty vehicles (trucks, buses) are sold each year (Anonymous 2003a; van den Hoed 2004). In the conservative 'Superior PEM vehicles' scenario, 10% of these annual sales are fuel cell powered by 2020.
New systems per year Running fleet (No. of systems in operation) 25 300 Total 250 20
200 Auxiliary 15
150
Million 10 Million Heavy- 100 Duty*100
5 50 Light-Duty
0 0 2005 2010 2015 2020 2025 2030 2005 2010 2015 2020 2025 2030 Year Year
Figure 6-7: Market development scenario for automotive PEMFC systems.
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Auxiliary power systems. Developments are underway to change the voltage of passenger vehicles on-board electric DC-power. In cars the electric power consumption of auxiliary systems continues to increase. Amongst others, fuel cells are expected to be integrated into automobile electric systems. In the scenario, all combustion engine passenger vehicles sold are expected to have a 42V PEM fuel cell auxiliary system on board. Fuel diet. The share of methanol in the fuel diet is expected to drop from an initial 100% to only 50% in all these markets. We expect that methanol will be the only fuel used initially because we believe methanol will be more readily accepted, and on-board methanol storage and reforming using engine waste-heat does not present serious problems. We do expect that hydrogen technology picks up after a few years for auxiliary systems. This gradual change is incorporated in the scenario. In PEM fuel cell equipped cars, we do expect competition between methanol fuelled and flexible fuel reformer (FFR) equipped cars that may use LPG, gasoline or diesel. In the scenario, we have assumed that the introduction of these FFR-PEM systems will limit the final methanol share of the fuel cell car market to 50%. In heavy-duty applications we expect a similar situation to develop. Notably, the calculated methanol estimates do not include the possible development of on-site manufacture of hydrogen from methanol in the fuel distribution infrastructure. Mass production development has been modelled to reflect realism and above given market penetration. All three vehicle markets' forecasts are characterised by a very low volume up till 2005, followed by rapid growth characterised by two steps in feasible levels of mass production per facility: tens of thousands of systems per facility from 2005-2010; hundreds of thousands of systems from 2010 to 2015, and sufficient growth to justify mass production plants for 500,000 systems each. Demand stabilises after 2019 to obtain some idea of the 'steady-state' of the scenario.
6.5.2 IMPACTS ON PLATINUM In Figure 6-8, the relation between the world's platinum market, the methanol market and the various PEMFC markets is visualised: the four major markets for PEMFC clearly will represent magnificent drivers for both methanol and the platinum related industry. Mass production of PEM fuel cells for passenger vehicles appears to have the potential to dramatically impact the world platinum market because it can introduce a substantial imbalance in worldwide supply and demand. Using the above characteristics, Arthur D. Little calculated that an annual production of 500,000 cars requires 52 metric tons of Pt at the current level of technology. This represents some 30% of current worldwide production capacity from mining operations, which amounts to some 160 metric tons (Johnson Matthey, Platinum Today). Platinum requirements for PEM automotive fuel cell systems represent a completely new type of demand, which comes on top of demand for other platinum applications (Figure 6-8, page 206). Successful introduction of PEM technology may therefore lead to platinum scarcity and soaring prices. When one considers the above estimates for PEM-related platinum demand, one may conclude only a small percentage the worlds 200-300 Million vehicles can be replaced by PEMFC vehicles.
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This would imply that some or all of these markets may never blossom. In other words, the limited size of the world platinum market appears to be a serious constraint for PEMFC vehicle market development.
Stationary - Small (1-5kW) PEM FC Production Passenger Vehicles (30 kW) Trucks, Buses (300 kW) Vehicles Auxiliary (0.2 kW) Natural Supply MeOH Distribution Winning Gas Infrastructure production Infra
MTBE>Gasoline additive Platinum Pt- Platinum MMA>PMMA windows Mining Markets / Catalysts for oil refining Ore Extraction Distribution Catalyst for chemical plants Other: (plastic) materials Computer harddisks
Jewellery LCD manufacture Gasoline: Pt-Loadign Down Exhaust catalysts Diesel: Pt-Loading Investors Industrial Up
Figure 6-8: Overview of related platinum, methanol and PEM fuel cell markets. Therefore, we calculated a forecast for a period of 30 years. The results are visualised in Figure 6-9. The combined developments - the number of systems sold increases while the amount of platinum per system decreases - result in a peak of total Pt-demand of 160 tons per annum. Due to the lifespan of PEMFC power systems, Pt-supply from PEM Pt-recovery operations trails behind some 5 to 7 years. In the scenario, however, the Pt recycled from one early vehicle can be used in multiple new vehicles that use more advanced technology. As a consequence, in the scenario virgin-Pt demand peaks at some 100 ton per annum in 2012 and decreases rapidly to extinction around 2020 when markets and technology have matured. Finally, the amount of platinum from recycling will match or exceed net Pt demand for new systems, in this scenario after some 30 years. Thus, a net inflow of Pt from the PEMFC fleet changes to a net outflow of Pt from the PEMFC fleet. This implies that Pt-production capacity must be carefully planned and that capacity required for Pt recycling is fairly predictable and reaches some steady-state level. Obviously total PEM related platinum demand and virgin demand levels will go down if technology advancement with respect to Pt-loading is more successful. The shape of the curve, however, remains the same: total Pt-demand will rise until PEMFC markets have matured (in our scenario: around 2022, i.e. in 20 years time), and then drop to a quasi steady-state level that is a function of technology status. In Figure 6-9 the total amount is plotted of Pt stored in the PEMFC automotive fleet as well: the first 20 years, it grows dramatically, then levels off to a steady-state of some 800 tons (!). Thus, the long-term dynamics of the worldwide Pt material cycle have been elucidated. An important question is: can the systems in the worldwide platinum material cycle respond adequately to the dramatic dynamics resulting from only moderately
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successful PEM technology introduction? Can production capacity of virgin Pt and the availability of Pt from spent PEM fuel cell recycling be adequately managed? The model predicts a net increased demand for an already scarce and precious material. Indeed, according to Johnson Matthey (2000) the steep increase of Pt- prices in early 2000 was due to the announcement of a number of consortia between Ballard Power Systems, the leading fuel cell manufacturer, automobile companies and oil companies. Johnson Matthey analysts, however, attribute the same price effects to the erratic issue of Pt export quota's by Russia's prime minister Putin! By mid-2001 supply-demand balance had largely been restored, and prices have dropped to 'normal' levels again of some $450/troy oz.
125
100 Pt - demand
75
50 Pt - recovered [Ton/Year] 25
0 Pt - virgin 2005 2010 2015 2020 2025 2030 -25 Year
Figure 6-9: Model forecast for world Pt-demand, 'Superior PEM vehicles' scenario. From statistics compiled by Johnson & Matthey (www.johnsonmatthey.com), it can easily be seen that Pt supply has doubled since 1975, from a net supply of 81 ton/year to the current level of 174 ton/year. This development has occurred largely in response to continuously increasing demand. In their most recent yearly outlook (2001) Johnson Matthey quote that for example South Africa have huge yet undeveloped Pt resources, and that both prospecting activity worldwide has increased as well as expansion of mining and refining planned. In addition, where (e.g. Hampden-Smith 2000) states that Pt markets are extremely volatile and its price unpredictable, Johnson Matthey indicates that the relatively large jewellery market share effectively results in a price-cap at some $650/troy oz. where jewellery consumers will simply stop buying the material, which would allow a shift from e.g. jewellery to fuel cell manufacture by Pt. For example, in case jewellery consumption would go back to 1991 levels, some 44 tons of Pt would become available on the market. Supply and demand data also show that with the introduction of auto- exhaust catalysts and the development of a new market outlet for Pt, a few years later also Pt becomes available from recycling of said catalysts for, amongst others, the recovery of Pt. The historic data suggest that a net decline in Pt-demand for automobile exhaust catalyst is foreseeable. Together with the continuous growth in supply, there is thus no reason to believe that Pt availability is a constraint for the development of a fuel cell vehicle fleet!
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6.5.3 METHANOL FORECASTS Where platinum is required to manufacture the required hardware, methanol is one of the possible fuels for PEMFC powered transport. Using the model, a forecast has been calculated of the methanol capacity required in the Superior PEM vehicles scenario (Cadre 6-2, p.203). In Figure 6-10, the total forecast for PEM fuel cell related methanol demand is given, as the total supply required, and the change of supply per year. By inspection of these graphs it becomes clear that total methanol- demand increases continuously to a level of at some 70 MTA. The required methanol capacity addition is 0.5 MTA/year in 2008, grows to some 1.5 MTA/year in the from 2009 to 2013 to explode to some 5 MTA/year from 2014-2018. In this conservative scenario, methanol demand growth would require a single MegaMethanol53 plant to be built every two years initially. Subsequently, a single MegaMethanol plant is required. At peak growth, three of four such plants must be built in a single year! In the scenario, after 2018 demand growth slows down because of technological progress and changing fuel diet.
80
60 MeOH demand 0
40
20
MeOH new [MTA], [MTA/Yr]*1 [MTA], 0 capacity*10 2005 2010 2015 2020 2025 2030 -20 Year
Figure 6-10: Total automotive methanol demand and yearly capacity growth.
An increase in PEM fuel cell system efficiency will only imply a somewhat slower growth in methanol demand after 2010, when the more efficient systems are put on the road. The effects are minimal in relation to the uncertainties in market development and mileage covered per vehicle. The shape of the curves remains the same: methanol -demand will rise until PEM fuel cell markets have matured (in our scenario: around 2022, i.e. in 20 years time), and then level or drop slightly to a quasi steady-state level that is a function of technology status and fuel diet.
53 MegaMethanolTM is the tradename of the state-of-the-art methanol plant design developed by Lurgi. The development of this process system concept represented a step-change in feasible single- train methanol capacity. The resulting economy-of-scale has dramatically driven down methanol production cost.
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There are three underlying questions to ask whether such development of methanol demand represents a constraint to PEMFC vehicles market development: 1. What are the long term dynamics of the worldwide methanol market? Can this system adequately respond to the forecast - temporary - dramatic growth in methanol demand for PEM fuel cell related use? 2. Does automotive transport through PEM offer a “sure” future methanol outlet? Although investments in PEM fuel cell research and development have been large and an increasing number of companies are entering the PEM fuel cell community, the current status of the technology is still not good enough to make large-scale introduction a commercial success (see Appendix A. 9). This would imply that the 'PEM outcompeted' scenario or 'PEM - the eternal promise' become reality Figure 6-5, p. 204). 3. What are the costs and risks of a methanol distribution infrastructure? Can a feasible strategy be developed to bring-into-being a methanol distribution infrastructure that supports the operation of a PEMFC vehicle fleet? (1) Long term dynamics. In the Superior PEM vehicles scenario, the methanol required for PEM automotive fuel cell systems (Figure 6-10, p. 208) represents a completely new type of demand. Ultimately a demand of 180 MTA methanol is created, which is about 5 times the current methanol output levels and between 2015-2030 100 new world scale plants would have to be realised. The effects on world oxygenate production for the gasoline is considered to be minimal. The present worldwide nameplate capacity for methanol is some 35 MTA, and present level of the demand54 is some 30 MTA (Tazelaar 2001). This is a normal balance between capacity and demand at an utilisation of some 85%. Supply and demand data also show that with the introduction of oxygenates-enriched fuel, methanol demand in existing fuel has steeply increased in the past two decades. In the period 1994-2000 for example worldwide capacity increased from 26 MTA to 35 MTA, or some 1.5 MTA per year. (2) Uncertainties At present, some older methanol capacity is being phased out, whilst a few new large scale plants are under construction and various studies for “Megascale” methanol have been initiated (Tazelaar 2001). There is a concern, however, that a possible ban on MTBE in the US will lead to a situation of serious oversupply. As a consequence, world methanol prices may become depressed just at a time when demand from PEM fuel cell cars may be growing. Today, a new methanol plant can be erected and operational in some 3-4 years time. The question really is: can new capacity added match the demand growth-rate .
54 At present, methanol is used in a variety of chemical and fuel applications. In Western Europe, only the volumes used for formaldehyde manufacture exceed those for gasoline additive production. MTBE is the most important oxygenate that replaces lead-additives in gasoline to ensure proper combustion (anti-knock) of the fuel. Other important -chemical- applications include the production of acetic acid and methyl methacrylate. The chemical markets can be considered mature. The MTBE market faces some uncertainty because of possibly forthcoming legislation banning its use in gasoline in the U.S. Substitute oxygenates are being introduced, but some of these also require methanol.
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The forecast calculated for automotive methanol demand alone implies a definite change of the character of methanol from chemical to fuel. PEMFC methanol demand may have dramatic impact on the structure of the worldwide industry. The trend towards megascale methanol plants will be accelerated and older plants that have operating capacities well below the megascale plants may be phased out. As in platinum, the evolution of worldwide methanol production capacity must be carefully considered before adding new methanol capacity. Contrary to Pt, in such an analysis, the effects of existing methanol plants being outcompeted and subsequently being phased out must be taken into account, as well as the possible ban on MTBE, the world's largest current methanol outlet. (3) Distribution infrastructure. The development of methanol distribution to fuel service stations for the consumer market has the characteristics of a catch-22; because the number of methanol-fuelled cars is limited, it is not attractive to invest in distribution infrastructure; because of lacking distribution infrastructure, consumers do not invest in methanol-fuelled cars. In recent years by introducing Shell PuraTM this company has shown that in a relatively short time period an additional fuel outlet can created. The World Methanol Institute (1999) has calculated the installation costs for methanol outlet per station to some 80,000 euro55 (Stikkelman 2001). In the Netherlands the track record of change of fuel stations is very good. Companies, for example, have invested significantly in environmental precautions induced by legislation. The government funded part of the changeover costs. There is no reason why a similar scheme could not be developed for the expansion of fuel stations to include methanol outlets. The Netherlands is home to a total of 2600 fuel service stations (CBS). The total cost of a maximum fine-grid of methanol distribution in the Netherlands therefore would amount to 2,600 * 100,000 = 260 Million Euro, which is about half the investment for a single world scale methanol plant. Together with the present growth in natural gas supply, there is thus reason to believe that 1. The development of a methanol distribution system is no less feasible than the development of any other fuel distribution system, and thus with careful business development is not expected to present a problem. 2. Ample methanol supply capacity can be developed in time, and thus methanol shortage or high prices do not by themselves constrain the development of a fuel cell vehicle fleet. 3. The status of the technology and the pace of technological progress largely cause uncertainty with respect to the development of methanol PEM fuel cell markets. PEMFC vehicle development may result in methanol becoming a new 'logistic fuel', which opens the way for dramatic investment in methanol production capacity and distribution facilities.
55 This quote includes all the necessary work and hardware per station. As a matter of course, other costs will be incurred to create a methanol-to-consumer distribution system, e.g. for the set up or adaptation of administrative and other information systems.
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6.6 Process system innovations for industry development In the previous sections we have presented a functional model of 'automotive transport' and categorized innovations that may enable its transition. The superior PEMFC vehicles scenario considerably impacts the worldwide platinum material cycle and the production and distribution of methanol. The dynamics involved not only have to be catered for, however, they present tremendous opportunities for networked process system innovations. When the industry developments lands in a region such as the Port of Rotterdam (PoR), innovative chemical complexes may be created. As 'proof' of the methodology for process system innovation by design, in this section innovations are specified for industry, which thereby may benefit from and shape the transition to 'automotive transport' by PEM fuel cell vehicles. The results have been obtained by combining the functional model developed (§ 6.3), the scenario background (§ 6.4), the model results (§ 6.5) and our knowledge on metal cycles (Verhoef et al. 2004a) and the petrochemical industry and chemical process systems (this thesis and references cited). Finally, the process of bringing into being specific process system innovations is discussed.
6.6.1 PLATINUM-RELATED OPPORTUNITIES When the functional element 'Provide Automotive Transport' (Figure 6-3, p. 193) is realized by PEMFC vehicles, platinum is a key resource and fuel cell stacks need to be produced, replaced and recycled. These activities are part of a global platinum material cycle management. Amongst others the PoR appears to be a suitable location for platinum trading, material handling and logistics, fuel cell assembly, fuel cell recycling and (precious) metal recovery. While the supply of virgin-Pt is largely a concern for the countries where Pt-ore is found, mined and processed, there is no reason whatsoever why a large-scale production facility for PEM fuel cells or parts-thereof cannot be located in the PoR. On the contrary, the PoR has all the logistics facilities to bring in the variety of materials needed and the skill-level in the Netherlands is high. The PoR management could approach the industry association FME in this respect to enquire after developments in the metals and electronics sector. With the successful development of Autorecycling Nederland as an example, the presence of the London Metal Exchange in Rotterdam, and the recent developments in metal recycling activity, the development of superior PEM vehicles is an interesting option for Rotterdam to become a centre for platinum material cycle management. When in Europe 500,000 PEMFC vehicles are sold, initially at the midlife of these cars their fuel cell stacks need to be replaced and recycled. Total vehicle recycling is at the end-of life is mandatory (10-15 years). This represents a huge potential volume of stack recycling and metal recovery operations. Via low- urgency shipping scrapped FC stacks and/or systems can be shipped to Rotterdam from around the world for processing. Thus, superior PEMFC vehicles could superbly position the PoR for a major role in the recycling of all platinum and other metals contained in industrial and consumer goods. The associated activities
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includes collection, disassembly, transportation and storage of systems, components and/or materials, and finally extraction to obtain the Pt and other valuable metals. Such a role in material cycle management and the associated spectrum of activities would largely contribute to sustainable metal use. Careful planning and management is required, however, to effectively deal with market developments. A focus on recycling activities, however, appears to bear limited risk. The supply forecast for virgin Pt is that additional capacity is only required for a decade or so. This implies all else remaining equal that plants will become obsolete. In stack recycling and metal recovery, however, capacity must be built and is there to stay: the platinum and metals cycle through the system at limited or no consumption of virgin material. In addition, the capacity for Pt recovery and recycling can be realised gradually as the market expands. It may be expected, though, that at the time when net demand for virgin Pt collapses, the prices for Pt from recovery operations will also collapse because it is a single market. A certificate system could prevent some of this, labelling the Pt from virgin and recovery, e.g. to distinguish between adverse environmental effects. In Figure 6-11, p. 213, an overview is given of innovations in the worldwide platinum material cycle and of associated opportunities for the Port of Rotterdam
6.6.2 METHANOL-RELATED INNOVATIONS In the superior PEMFC vehicles scenario it is assumed that FE 1 'Convert to suitable power source' is realized initially as methanol production. The projected market development would imply a dramatic growth in global methanol capacity. In addition, a distribution infrastructure (FE 2) must be realized. In the Netherlands, a single methanol plant in Delfzijl has been in operation since 1973. The Port of Rotterdam, however, is the methanol seaport with the largest volume of methanol landed in Western Europe and the associated jetty, storage and facilities for distribution inland by ship, rail and road. Since the PoR offers off- loading and storage for large ocean-going vessels, it has benefited from the shift of worldwide methanol production towards remote locations where isolated natural gas field are exploited successfully. Rotterdam-Rijnmond, however, also appears to be a perfect location for a large-scale methanol production facility. Such a plant would match the existing (petro) chemical cluster; all kinds of utility and logistics facilities are available, which include liquid-bulk storage and a connection to the Hi-Cal natural gas grid. Personnel of appropriate skill-level are available from the greater Rotterdam region. Notably, natural gas pipeline capacity is expected to be available for a world scale methanol plant because a large ammonia plant recently has been shutdown. The only reason why a methanol plant would not be erected in Rotterdam is the competition from low-cost methanol manufactured in remote locations. With demand growing, due to fuel cell developments, however, capacity in Rotterdam may become required in the not too distant future.
6.6.3 HYDROGEN INFRASTRUCTURE OPTIONS In the superior PEMFC vehicles scenario it is assumed that FE 1 'Convert to suitable power source' is realized ultimately in part by hydrogen or on-board conversion of logistic fuels.
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Figure 6-11: The opportunities for the PoR in the world platinum material cycle.
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Today, the industrial markets for hydrogen represent a large-volume market56, where regional, national and international pipeline grids for hydrogen transport have been established. In the PoR area, for example, Air Products exploits a regional hydrogen infrastructure, and Air Liquide exploits a 'basin' hydrogen infrastructure that spans Rotterdam, Antwerp up to Lille in France. The network, however, largely has the function of a backup facility for local hydrogen production facilities, which indicates that hydrogen transport over large distances by pipeline is still uneconomic. Worldwide pure hydrogen is produced predominantly by steam reforming of natural gas, which has favourable economics compared to the use of other fossil resources. The syngas produced is subject to a number of CO-shift and purification processes. In crude oil refineries hydrogen make-up (95% hydrogen) is presently also produced via residue gasification followed by treatment of the product gas. Due to the nature of refinery processes, a significant level of (CO) content is allowed, which makes this route economic. Depending on the CO-tolerance of PEMFCs, both hydrogen production from natural gas or oil products may become economic in the future. Alternative sources of (relatively pure) hydrogen are a number of petrochemical processes that include dehydrogenation, notably styrene. The existence of hydrogen pipeline infrastructure in the PoR offers the possibility to tie in both 'virgin' and 'waste' hydrogen production, as has been done with the Air Liquide network, which takes in purified waste hydrogen from the Dow Terneuzen styrene plants and the General Electric chlorine plants in Bergen op Zoom. The possibilities with respect to hydrogen in relation to fuel cells have been indicated in Figure 6-11 and Figure 6-12. Hydrogen is part of the precursor of methanol, synthesis gas that is a mixture of CO, CO2 and H2. As the demand for hydrogen increases, possible synergies may emerge in the production of synthesis gas for methanol and hydrogen production respectively. In both cases, synthesis gas can be produced out of a variety of resources, the synergy being that for each mix of resources available an optimal mix of syngas qualities can be produced: for hydrogen production the syngas H2 :CO ratio needs to be as high as possible, whilst methanol synthesis requires an optimal ratio of 2:1, and allows the presence of some CO2. Thus, natural gas and biomass can be combined to yield an optimal syngas composition. In the PoR and in the region the hydrogen can be distributed via pipeline or bottles. A facility for small containers can readily be added to the existing facilities. In other studies, the use of hydrogen as an additive to the Dutch natural gas grid for households has been advocated. Hydrogen capacity thus can be built to first cater for this market, and later to cater (partly) for the fuel cell market, thus providing a smooth growth and/or transition. The combination of a hydrogen pipeline infrastructure and a growing market for hydrogen may provide synergy to other industries that generate hydrogen as a co-product that in other locations must be used for (furnace)-fuel only.
56 The small-volume market of hydrogen is mainly catered for by bottled hydrogen in industrial cylinders. These are transported by road-cargo. An intermediate-volume market also exists, where hydrogen is generated at a customer-site.
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6.6.4 A 'GREEN' INDUSTRIAL COMPLEX Using the building blocks discussed in the previous sections, a transition can be realized towards a green methanol production, distribution and supply system. In the green complex design (Figure 6-12, p.217) a number of 'supply-chains' is integrated in an innovative single networked process system or green complex, which consists of (1) natural gas to methanol, (2) natural gas to hydrogen, (3) crude oil to oil products and (4) biomass to agro- and food products. The activities in the 'left' part of these supply-chains often are based in 'remote' locations, which range from 'just outside the PoR' area, to 'the other end of the world'. The major opportunity for the PoR is the provision and integration of syngas production as a system link between resources from remote locations, the industry already located in the Rotterdam port area and the distribution of automotive fuels and other products to consumers.57. The elements located in Rotterdam that are relatively unaffected by the green complex are drawn as plain boxes in Figure 6-12. An example is the agro-and food industry. Elements that do exist today, but which can be expanded considerably in the development of a green complex, are indicated by a grey-fill of half the shape. An example is the conventional production of hydrogen. Finally, elements of the green complex that are not present in the PoR today, such as a methanol plant, have been given a complete fill. The production of methanol, hydrogen and oil products can be located on many sites around the world. In practice, however, sites are selected on the basis of the economics expected. The complex configuration presented in Figure 6-12 offers a lot of synergies, which translate into favourable economics and ecology. At the input-side, in Rotterdam a connection with the Dutch Hi-Cal high-pressure natural gas grid is available. This allows the supply of Dutch, Norwegian and even Russian gas. Other remote locations may be connected via LNG-facilities, for which a terminal is available in the PoR. Both for hydrogen gas and liquid methanol transfer facilities are available, as well as a distribution infrastructure and storage. This implies that for hydrogen and methanol plants, the outside battery limit investments can be reduced. Kuipers argued that the industrial cluster in the PoR is characterised by limited flexibility (Kuipers 1999). The creation of a synthesis gas complex, however, opens the way to a more flexible cluster.
Syngas is a mixture of CO, hydrogen and CO2. It is in intermediate product, of which each application requires a particular composition. At the production side, each combination of feedstock (residue, natural gas, coal, biomass, waste) and technology (reforming, partial oxidation, pyrolysis) yields a particular syngas composition, and a varying quantity and spectrum of impurities. Thus, whenever a range of feedstock and technologies is available at a single location, as well as a spectrum of syngas
57 At the beginning of the twentieth century a similar opportunity in Rotterdam was seized by the Bataafsche Petroleum Maatschappij. The construction of its refinery in Pernis initiated the development of the Port of Rotterdam into one of the world's major transport hubs and conversion centres for crude-oil and oil products. Shell Refining Company still operates what today is one of the four worldscale oil refineries located in the Port of Rotterdam area.
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consumers, optimum flexibility can be achieved, albeit at the possibility of under utilisation of some production units. When purification is added to the system, the syngas product quality increases (no or few impurities, CO2 can be removed), which results in yet more flexibility of the system. Adding purification units would allow the production of 'clean' synthesis gas from a variety of sources. The pure hydrogen manufactured would be suitable for chemical processes that require clean synthesis gas or hydrogen. The syngas purification could include the removal of CO2 to achieve the correct composition for methanol synthesis or any other required
CO/H2 ratio suitable for other chemical processes. The syngas produced could be used to match synthesis gas produced from natural gas and for the co-production of pure CO2. In the PoR refineries, large-scale gasification of heavy residue from refinery operations is already practiced. The hydrogen produced is largely used within these refineries to 'whiten-the-barrel' and to remove the sulphur present in crude oil and its straight-run products. These fractions from crude distilling are subjected to a series of conversion and upgrading operations to obtain a maximum of 'white products', viz. gasoline, kerosene and diesel out of each barrel of oil processed. Chemically bound sulphur is converted to hydrogen sulphide in the process. In the various refinery processes various qualities of hydrogen can be used, which can open the way for hydrogen obtained from other sources at acceptable cost. Combining residue gasification, which is basically a waste conversion process, with the gasification of other hydrocarbon-containing waste streams58 could provide some additional economy-of-scale. These networked process system innovations would result in more optimal realisations of fossil resource use. Eventually, however, a true sustainable industry and energy supply must be based on renewable energy sources (solar, wind, tidal, water, biomass) and renewable or recyclable materials (biomass, metals). Biomass, however, today is primarily cultivated for our world food-supply, a host of agro- industrial crops, timber and wood-supply to the pulp and paper industry. The use of biomass for heating and electricity supply often is from natural biomass stock (forests), and cannot be considered sustainable. Biomass-to-energy presents little added value when the final products are heat (space-heating) and electric power. The conversion of biomass-to-fuel, notably methanol, however, may be economically and ecologically attractive (Stikkelman 2001). The integration of biomass conversion and hydrocarbon processing an optimal utilisation of resources can be achieved. In a green complex, valuable organic components may be extracted prior to the bulk conversion of biomass to liquid fuel. Both the extraction and conversion can be by chemical process technology or via bioprocessing. Location of a large-scale facility in PoR would have the major advantage that shipping of biomass waste from all-around the world can moderate regional seasonal variations. The associated CO2 -credits (if any!) would have to split somehow between the supplying country and the Netherlands.
58 Mixed plastic waste, paper, wood, tyres, textiles etc.
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Figure 6-12: Opportunities in the industrial infrastructure around syngas.
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Notably biomass waste presents an attractive source for final conversion to synthesis gas because it is considered waste, and generally cannot be used for food or other purposes anymore; it originates from the large agro-industry and can be considered at least CO2 neutral. At the product end the realisation of large-scale hydrogen production from methanol is an alternative that allows the use of methanol as a long-distance hydrogen-carrier. Location in the PoR is attractive because industrial waste-heat can be used to run such an installation. The co-produced pure CO2 could be fed to a local pipeline infrastructure and used for supercritical extraction, welding, urea manufacture or to promote plant growth in nearby greenhouses. In (Dijkema and Kuipers 2001) it was advised to the port authority to concentrate and coordinate efforts to realise an olefins production facility, notably a naphtha cracker in the region. The ethylene, propylene and butylenes from such a facility would greatly enhance the strength of the existing chemical cluster, and ensure adequate supply of these key chemicals in the region. Methanol developments to cater for Superior PEM vehicles related demand may very well be combined with methanol development to provide feedstock for a methanol-to-olefins (MTO) facility in PoR (Kvisle et al. 2001). Such a plant produces largely ethylene and propylene by pyrolysis of methanol. Only low quantities of aromatics are produced, which is an advantage because of the glut of aromatics that have to be taken out of the gasoline-pool. The size of the methanol market forecasted would allow the development of a global-sized site for methanol and olefins that would cater competitively for both methanol fuel and feedstock requirements of the region as well as the demand for olefins. Thus, either harbour facilities, storage and other logistics facilities may be erected in Rotterdam initially to cater for such a plant. A local methanol plant, however, would provide a perfect physical and economic backup or balancing facility. In the design of such a facility, there must be additional synergies that can be exploited, e.g. the reuse and recycle of hydrogen and/or methane produced in the MTO plant. Thus, a number of degrees-of-freedom are introduced. These allow selection of system element configuration and capacity that is optimal with respect to product flexibility, economy and ecology.
6.7 Discussion and Conclusion In this chapter we have illustrated the use of functional modelling for analysis and innovation of sectors in relationship with their environment. Fuel cell development for automotive transport was analyzed in a system context; functional models, scenarios and a dynamic model were presented. We have shown that market development, technology breakthrough, economy and ecology may not only dramatically impact part of the petrochemical industry, they also may present tremendous opportunities for networked process system innovation. In the previous section, a number of such innovations have been synthesized. What are the odds that these are actually brought into being?
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Setting the stage for MeOH-to-consumer distribution The situation described with respect to the distribution infrastructure for methanol is a typical catch-22 that must be breached to support the market development of PEMFC powered vehicles. What is the current and future role of oil companies in this? Large oil companies typically are vertically integrated to control the entire value-chain from well to wheel. All logistic fuels (LPG, gasoline, diesel) originate from crude oil and major oil companies have large stakes in exploration, winning and production, refining, wholesale and retail. This vertical integration together with the oligopolistic character of oil production, refining and distribution presents a formidable barrier to market entry. Exceptions noted, in many countries the majors have dominated the logistic fuel markets for many years. Thus, introduction of an entirely new logistic fuel, which is not derived from crude oil, appears to be difficult and risky because it requires the realisation of an entire new production and value-chain under fierce competition from vested players with considerable market power. Indeed, competition between alternative fuel infrastructures is virtually non-existent. Major oil companies, however, increasingly have become energy companies that also have a large stake in the worldwide natural gas business, and companies like Statoil have built their own methanol facilities, albeit primarily for captive-use of the methanol produced in oxygenates. One may argue, however, that new style oil companies in the near future may want to extract additional value themselves out of the gas-to-consumer supply-chain. The supply of methanol as a logistic fuel thus can well become part of their strategy. Other options to bring methanol to the consumer that may be considered are forced 'market defragmentation' through legislative and regulatory reform. Some Third- Party-Access regime to fuel service stations may provide a key element to develop methanol distribution. Under such a regime, vested fuel service station owners or franchisers would be obliged to allow a Third Party access to their site to sell a different fuel than LPG, gasoline or diesel. Such a regime-change could be arranged during or in the aftermath of auctioning concessions to exploit A-locations along the highways etc. Thus, a possible market niche and viable entry-point is created for all players in the natural gas, hydrogen and methanol market.
Methanol and platinum - opportunities or constraint? We have argued that 'automotive transport' realised through methanol and PEM fuel cell technology would not only open up a complete new 'fuel channel', but may also enable a true transition of 'automotive transport' towards the use of non-oil derived fuels. In addition, if successful it will have a dramatic impact on the world methanol industry through the sheer volume of methanol required to fuel an expanding fleet of methanol PEM vehicles. Simply put, if the technology and infrastructure materialises and a substantial number of methanol-fuelled mileage is realised, the associated methanol demand cannot be met by existing production capacity. New plants will thus be built. Investors will employ the most competitive technology available (e.g. Lurgi MegaMethanolTM), which may give the prospective owners of these plants possibly some leverage to out compete vested methanol producers in the petrochemical industry. In refining, depending on the fuel-of-choice for PEM
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vehicles, the fuel mix to be produced will change. Possibly, aromatics will be phased out in logistic fuels for PEM altogether, as these require more sophisticated on- board reforming, if at all feasible. Similarly, MTBE, which is required for anti-knock properties (RON), may not be required anymore as a gasoline constituent. A second important sector that will be affected is the world's platinum material cycle (and Ruthenium) because PEM fuel cells do contain significant amounts of these precious metals. The key parameter is the total amount of Pt per fuel cell system. Today, the major uncertainty is the speed of technology advancement required to bring down this amount. Backed by a scenario study, we conclude, however, that stack lifetime and stack Pt-content do not pose a serious problem with respect to bringing-into-being a worldwide PEM fuel cell system. We conclude that the only real barrier to all these developments is the technological advancement of PEM fuel cell technology and consequently the final breakthrough of the technology to the marketplace. Not the platinum content, not the fuel consumption, nor the emissions, but simply the total anticipated lifecycle cost to a PEM vehicle owner is crucial to final demand for these systems. The present barrier may very well be overcome by the already initiated introduction of small-scale systems for vehicle auxiliary power generation. PoR must then be prepared to facilitate the launch of the development of said synthesis gas cluster and further develop its position in the world's platinum markets by developing the PEM Pt- recycling infrastructure. The only reason technology advancement is mandatory is to bring down system cost significantly, and improve user characteristics. In our analysis, we have concluded that, with adequate planning and management of the world's platinum material cycle, availability and these precious metals need not be a problem.
Networked process system innovations The main business opportunity for the chemical industry is the supply of methanol. The scenario results in a final annual demand of 70 MTA methanol phenomenal demand growth, with a true explosion of required added methanol capacity between 2015 and 2020. Anticipating that some of the required methanol capacity could be realised in PoR, new objective-defined functions of the petrochemical industry and possible system concepts for implementation in the Rotterdam industrial cluster were explored. The existing industrial cluster and harbour facilities would allow the realisation of unique integrated industrial complexes around the flexible manufacture and use of synthesis gas. At the feedstock side, a connection with the European natural gas network already exists, but oil residue, coal, biomass and biomass waste can also be upgraded/converted to synthesis gas. Although methanol would consume the major share of the synthesis gas, hydrogen manufacture, metals processing, olefins and other chemical processes could be part of the such complexes. Synergy is achieved because all feedstock mentioned yield different qualities of synthesis gas, and a spectrum of applications would allow a perfect match. In case of methanol, transport, distribution and storage facilities already exist. The presence of the agro- food industry in PoR combined with a syngas cluster could make PoR the port in the Western hemisphere for the processing and upgrading of biomass and agro-food
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waste. The possible 'course-of-events' sketched illustrates that this could very well provide a route towards real greening of the Port's chemical industry.
Realising networked process system innovations in Rotterdam The development of PEM fuel cell market for a long time hinged on lack-of-funding and lack-of-involvement of vested industry. With the forging of joint ventures between notably Ballard Power systems, automobile manufacturers, oil companies and other technology suppliers, the latter barrier has been removed. With these joint ventures, also industry funding of PEM fuel cell development has increased dramatically the past 5 years. The scenario's results indicate that ample opportunities exist in development of the platinum material cycles, both with respect to platinum winning and primary production, as well as platinum recovery and recycling. In the previous section, we have outlined a number of networked process system innovations that appear attractive for Port of Rotterdam in view of the conclusions of a recent study for PoR (Dijkema and Kuipers 2001), were we among others concluded that - whilst the effects of technological developments in the petrochemical industry in general span decades, two major developments appear to have taken-off and impact the industry in Rotterdam at large: (1) biotechnology and (2) the conversion of methanol to olefins. - With respect to business developments, although there is significant capacity- build-up in the regions that have large reserves of oil and natural gas, the refining and petrochemical industry is to stay in Western-Europe for a period measuring decades. - With respect to policy developments, the environmental pressure on vested industries from external stakeholders is a fact and it will increase. Companies are responding adequately by increasingly effective communication with their stakeholders. - Regulations with respect to construction and environmental permits are considered to be clear, stringent but just. The associated procedures can be executed swiftly in cooperation with the authorities when regulations are met, and thus the meeting of milestones may be anticipated in project planning.
Interpreting these developments in combination with the existing Port facilities and Industrial Cluster in the PoR area, the timely launch of a PEMFC-AGV project can provide a nucleus and a driver for a methanol or synthesis gas based industrial infrastructure or complex in the Port of Rotterdam.
Functional modelling, scenario-building and dynamic modelling In this chapter, we have used functional modelling to explore and analyse possible alternative realisations of automotive transport. The qualitative analysis was augmented with a quantitative assessment based on system dynamics modelling and scenario analysis. Thus, the impact and constraints in potential transition scenarios could be analysed and system concepts for the transition were formulated.
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Through abstraction from currently employed system concepts, we were able to specify novel system content. Opportunities and barriers for realisation of said options have been discussed. Thus, we have combined novel and proven technology or system concepts in networked system designs to yield industrial complexes of optimal structure with respect to economic and ecological performance. The networked system innovations developed are 'proof' of the methodology for process system innovation by design. Combined with scenario-building and dynamic modelling, a powerful set of methods results to anticipate and respond to changes in the world outside the industry. By realisation of the innovations developed the chemical industry may reap the benefits of a transition in automotive transport.
7 Conclusions and Recommendations
7.1 Introduction Process system innovations are defined as changes in the system structure or system design of an industry, its industrial complexes, or individual plants that can be enabled by technological inventions or vice versa. The central theme of this thesis is the specification of process system innovation content for a sustainable petrochemical industry. The main result is a methodology for said specification that is based on system representation using the input-output paradigm and functional modelling. In the subsequent sections, the innovations specified are reviewed. The contributions to (engineering) science are discussed and the overall research approach is reflected upon. Finally, recommendations are given.
7.2 Process system innovations for sustainability A number of innovation options have been specified for olefins production. In the steam cracker, separate dehydrogenation and cracking may increase olefin yield. Aromatics extraction from the cracker feed could reduce methane by-product, increase efficiency and allow direct aromatics use. Together with an aromatics converter, the aromatics banned from logistic fuels could be effectively utilised. The integration of olefins and syngas production from aliphatic hydrocarbons would represent a true process system innovation, which exploits the conditions favourable for syngas production from C5-C8 and steam cracking of the C2-C3-C4 co-products. Trigeneration systems for the production of chemicals, electricity and heat represent a class of process system innovations for improved resource utilisation. A trigeneration system was developed and patented for a new type of fuel cell. Promising candidates for trigenerate fuel cell reactors were explored using early economic evaluation. Process-integrated applications of fuel cells in chemical plants are feasible when creating a leverage effect on chemical plant capacity and performance. Trigenerate petrochemical complexes significantly reduce total CO2 emissions. The methanol capacity required for fuel cell vehicles would provide a favourable climate for process system innovation and transition of existing petrochemical clusters. The associated platinum use requires adequate material cycle management for continued platinum availability. In two or three decades, clusters around methanol and platinum may emerge that serve as the industry's infrastructure for sustainable transport and sustainable packaging. Together, the case study results illustrate that the methodology developed fosters 'out-of-the-box' thinking for the use of unit operations, single plants, industrial sectors and complexes alike. It allows process system innovation content categorisation and specification. Thus, it may help to develop a roadmap for transition towards a sustainable petrochemical industry.
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7.3 (Engineering) Science contributions We conjectured the process system engineering community has been largely focused on the development of “new flow sheets for existing problems.” Sustainable development, however, requires innovation at all system levels, from reaction path to process system, from chemical plant to petrochemical complex or industry. In short, sustainability requires a systems approach that addresses multiple system aggregate levels in concert. This is the ambition of the emerging discipline of industrial ecology, which to date, however, suffers from 'lack-of-content'. The petrochemical industry is a mature industry where the erection of any new processing plant represents a huge capital project that requires adequate risk management. The industry is conservative in the adoption of novel technology or systems and often prefers 'proven designs'. To be accepted, any innovation suggested must have sound technological and system content. We believe that the methodology presented in this thesis helps to meet this criterion because it is firmly embedded in chemical process system engineering. As such, it is a system engineering foundation for industrial ecology. A method has been developed to translate the need for sustainable networked industrial systems into primitive problem formulations suitable for exploration and detailing under the General Design Paradigm. Starting from mathematical system theory using the input-output paradigm, a coherent system representation was formulated that links system function, behaviour and transformation to system performance characterisation and valuation. This representation is the foundation of a practical approach for system assessment by the combination of stream-valuation and material/energy balancing. The combination provides a proxy to the more complicated approach of Second Law based analysis or exergy analysis. While system modelling and decomposition is not a trivial task, the decomposition strategy is hardly addressed explicitly, not in studies reported in the literature and not in textbooks. Functional modelling is a means to arrive at a coherent system decomposition using mutual contingency as a stop-criterion when formulating appropriate objective-defined functions of existing systems. Identification of hidden or new, emergent objective-defined functions required for sustainable process systems involves abstraction of the current method of 'fulfilment' or realisation of the functions of industry or parts thereof. Innovations reported in the literature can easily be categorised and related. The case study on olefins illustrates that when using said abstractions an innovation space that spans multiple system levels can be explored for novel functions and alternative ways of function 'fulfilments'. In the specification of trigeneration systems, chemical engineering, power system engineering and cost engineering are combined. The availability of fuel cell technology, an innovative energy transformation, was translated into coherent innovations involving the transport sector, petrochemicals, hydrogen and metals production. We developed a modelling-decomposition-synthesis strategy for primitive problem formulation, specification and exploration of the design-space available to solve wicked environmental problems by synthesis of sustainable systems.
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7.4 Research approach We conjectured that a transition towards sustainability not only requires adequately engineered decision processes59, but also specification of process system innovation content. Since it appeared there is a 'white-spot' in R&D with respect to this type of innovations, our central research question was 'is it possible and worthwhile to devise some procedure to structure the search of the process system innovation space and to foster the specification of innovation content'. The methods and procedure developed have been specified and refined in the course of a number of case studies that cover a range of system aggregate levels. At the level of single petrochemical plants, exploratory system research into the potential use of fuel cells in the chemical industry has led to a number of patents. This work also led to the conceptualisation of trigeneration options and a framework for trigeneration analysis. Application of the methodology to olefins provided a concise system description, a convenient classification of published inventions and R&D and a number process system innovation concepts. Methanol-fuelled fuel cell vehicles and the associated infrastructure represent a radical system innovation initiated outside the petrochemical industry. By using the specification procedure, it was demonstrated that these developments present a tremendous window of innovation opportunities for the creation of a sustainable industry. The methods and procedures developed can be labelled successful if their use results in many innovations that foster sustainability. The case study results serve as an illustration of the usefulness albeit not a formal proof or validation of the methods. This is a common problem in system-oriented studies, which it shares with, for example, macro-economics where measures are proposed to shape the economy at large. In contrast with the natural sciences, it is not possible to conduct experiments in an environment where all but the parameters of interest are varied. These considerations have been coined in a meta-model of the research, which in retrospect is a roadmap to arrive at the innovation procedure developed. Another question is whether the innovation concepts specified could not have been developed otherwise. The answer to this question is: yes, but the extensive literature research conducted and reported did not reveal similar structured methods that link creative thinking with assessment of performance, structure and technology of existing complex systems. Functional modelling provides a structured method for abstraction that allows one to freely consider novel realisations of existing functions of the chemical industry at every system level of interest. It allows one to 'unfreeze' from the 'common, established, proven, accepted' ways 'things are done'. In combination with prioritisation of weak elements, it represents one method out of many to address the open problem of process system innovation. Only after new concepts have been developed, the hard work can begin to achieve their realisation and adoption through R&D and assessment of their economic and ecological performance.
59 A premises of the M.Sc. in Systems Engineering, Policy Analysis and Management curriculum of TU Delft is that multi-stakeholder decision processes can be engineered to address effectively a variety if problems and opportunities that for example exhibit a varyiety of scale, complexity and impact over a number of timescales,
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7.5 Recommendations Focus on sustainable “supply chain level” or “networked industrial systems.” Sustainability cannot be achieved in petrochemical plants or by promising technologies alone. These must leverage system sustainability of supply chains or networked industrial systems that adequately link with multiple interconnected material cycles. Integrate or relate process system engineering and industrial ecology. The methodology developed and the theoretical formulation provide a bridge between industrial ecology concepts and the body-of-knowledge of process system engineering. Only one example is the conceptual specification of a coal-based industrial complex for base metal, hydrogen and synthesis gas production that is currently contemplated by Port of Rotterdam and the industrial stakeholders. Explore the implications of biotechnology for the petrochemical industry. In the long run, fossil resources must be replaced by renewable bio-resources. If the slate of high-volume petrochemicals remains and define the sector, the nature of the conversion technologies must change from a chemical conversion paradigm to a biological paradigm. Or some hybrid conversion paradigm may be adopted. The related innovation space around biotechnology must be explored. Efficient fossil resource use by trigeneration. Trigeneration would contribute significantly to
CO2 reduction. The steam cracker is one of many candidate processes. The feasibility of trigeneration in liberalised and re-regulated energy markets must be evaluated, the incentives of CO2 emission-trading elucidated whilst taking into account the possibilities of modern furnace technology and design. Build a coherent set of models and tools for innovation. Qualitative tests involving experts should be developed to further underpin the approach. Quantitative evaluation should be extended and incorporate dynamics and economics of system innovation concepts. Thus, a portfolio of generic tools to foster innovation would result. Transfer and use of research results in industry and society at large The methods can be used to address 'wicked' environmental problems of industrial sectors and society at large. They will foster the specification of innovation content and will particularly be transferable to the sectors characterised procedurally cohesive as the 'process industry': refining, base metal, pulp and paper, agro- and food industry. Their use need not be limited to these sectors or sustainability! Link to policy analysis and strategy Functional modelling must be linked to (inter)national public policy development and regulation and corporate strategy development. While the conceptual process system innovations require further detailing, we trust the examples presented stimulate you as a stakeholder in any process industry characterised by maturation to help reinvent your industry. Incorporate the methods in transition management As one of 'the industries of industry', a petrochemical industry is essential to achieve sustainability. Its relation with the public at large is indirect and characterised by lack-of-interest, discomfort and lack-of-acceptance. Use of the methods, however, is expected to forge a link between societal needs, business strategy and process system innovation as these can facilitate interaction in process development teams and between stakeholders involved in a transition towards a sustainable society.
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Symbols
Chapter 1 I total plant Investment C plant capacity p parameter
Suffix denotes: 0 standard or reference condition
Chapter 3 A Availability [ J ] B By-product output ( Stream label ) B behaviour of a system D Domain ∆ Difference or change (∆G, ∆H, ∆U, ∆S) E Emission output ( Stream label ) Ex Exergy [ J ] ηa Reference efficiency ηb Product efficiency ηc Emission efficiency ηd Total emission efficiency H Enthalpy [ J/mole ] I Inputs ( Stream label ) Λ system boundary Σ sum Σ system σ set of streams σ Entropy created [ J/K ] S Scarce resources input ( Stream label ) S Entropy [ J/K ] Su set of inputs Sy set of outputs S1 set of objective-defined functions S2 set of objective-defined functions T Technology T Ubiquities input ( Stream label ) T Temperature [ K ] t time [ time unit ] κu,y(t) vectors of conversion factors [ unit/flow unit ] κ• net accumulation of chemical element, mass or energy [ unit ] La Reference Loss [ unit ] Lb Product Loss [ unit ] Lc Emission Loss [ unit ] Ld Total Emission Loss [ unit ] Le Balance Loss [ unit ] M Main Product output ( Stream label )
242 Process System Innovation by Design
O Outputs ( Stream label ) Ω performance of a system P value function P Pressure [ N/m2 ] Φ function of a system φ flow [ unit / time ] Ψ transformations within a system q heat [ J ] U Internal Energy [J] u(t) vector of input flows [ flow unit/time ] V Volume [m3] W Waste inputs ( Stream label ) w Work [J] X general variable Y general variable y(t) vector of output flows [ flow unit/time ] Z general variable
Suffix denotes: 0 ‘at standard conditions’ a allowed ( Stream label ) c co- (feed or product) ( Stream label ) d desired ( Stream label ) f primary ( Stream label ) i incidental ( Stream label ) irr. irreversible l limited ( Stream label ) m material n accepted ( Stream label ) p process-related ( Stream label ) r reference ( Stream label ) r reaction u utility-related ( Stream label ) w wasted ( Stream label )
Chapter 5
Ac matrix of input-output coefficients α electric power per ton unit capacity [ kW/(ton/day) ] 3 β conversion factor 1,16 *10 [ J/Cal]•[g/ton]•[kJ/kWh ] c vector of capacities d vector of demands f vector of some objective function’s coefficients ∆G0 Gibb’s free energy change at standard conditions [ kCal/mole ]
∆Gr Gibb’s free energy change of reaction [ kcal/mol ] ε electrical efficiency [ 0..1 ] γ fraction of fuel cell system investment [ γ ≤ 1 ] I Unity matrix I Investment, expressed as dollars per unit capacity [ $/(ton/day) ] Ie Investment, expressed as dollars per unit power generated [ $/kW ] λth ratio of the electricity revenue and value added of the chemical
Symbols 243
M molecular weight of product [ kg/kmole ] p vector of products Rh revenue flux for heat produced [ $/day ] Re revenue flux electricity [ $/day ] Rr,h,(H2) flux of substitute fuel value of hydrogen [ $/day ] r vector of feedstocks re revenue for electricity [ $/kWh ] rf revenue for feedstock [ $/ton ] rh revenue per unit heat [ $/kWh ] rp revenue for product [ $/ton ] s vector of supply θ the technical lifespan of a facility [ days ] x0 vector of design variables V profit difference between fuel cell or conventional reactor [ $ ]
Suffix denotes: c ‘conventional reactor’ or ‘conventional plant’ e ‘expression in electric dimensions’ (e.g. Ie) f ‘fuel cell reactor’ or ‘fuel cell use in plant’ s ‘stand-alone power generation’ t ‘trigeneration’:
Abbreviations
ABS Acrylonitrile Butadiene Styrene copolymer AC Alternating Current AIChE American Institute of Chemical Engineers Akzo Akzo Nobel (company, NL) Al Aluminium AVR Afvalverwerking Rijnmond (company, NL) B Benzene BASF Badische Anilin und Soda Fabrik (company, Germany) BDO Butanediol BMW Bayerische Motorwerke AG (company, Germany) BTU British Thermal Unit BTX Benzene, Toluene and Xylenes BTXCon Consumption system BTX BTXExtr. BTX Extraction process BTXProd Production system BTX BTXSep BTX separation BTXTot Total system BTX C Carbon C1 Hydrocarbons with only one C-atom C2 Hydrocarbons with two C-atoms (e.g. ethane, ethylene) C3 Hydrocarbons with three C-atoms (e.g. propane, propylene) + C4 Hydrocarbons with four or more C-atoms + C5 Hydrocarbons with five or more C-atoms CaCO3 Lime or Calcium Carbonate CAPE Computer Aided Process Engineering CBR Case-Based Reasoning CBS Centraal Bureau voor de Statistiek (organisation, NL) CE Centrum voor Energiebesparing (company, NL) CEO Chief Executive Officer CFC Chlorinated Fluoro Carbons CH4 Methane (natural gas) Cl2 Chlorine CMAI Chemical Marketing Associates Inc. (company, US) CO Carbon monoxide CO2 Carbon dioxide CPC Computer and Process Control Cu Copper DC Direct Current DHV The Dutch company DHV DME Dimethylether DMT Dimethyl Terephtalate DSM The Dutch company DSM DTO Duurzame Technologie Ontwikkeling EB Ethylbenzene ECN Energie Centrum Nederland (research centre, NL) EDC Ethylene Dichloride EOP Electrochemical Oxygen Pumping EPDM Ethylene Propylene Dimonomer
246 Process System Innovation by Design
Escape European Symposium on Computer Aided Process Engineering EU European Union FCC Fluid Catalytic Cracking FE Functional Element FFR Flexible Fuel Reformer FME Federatie Metaal Elektro (association, NL) FOCAPD Foundations of Computer Aided Design FOCAPO Foundations of Computer Aided Operations FOI Faciliterende Organisatie Industrie (organisation, NL) FUM Functional Unit Method g gramme GHR Gas Heated Reformer GNP Gross National Product GT Gas turbine H2 Hydrogen H2O Water H2S Hydrogen disulfide HDA Hydro Dealkylation process HDPE High Density Polyethylene Hi-Cal High Calorific HT High Temperature HTU Hydrothermal Upgrading I/O Input/Output IChemE The Institution of Chemical Engineers (association, UK) ICI Imperial Chemical Industries (company, UK) ICT Information, Communication and Telecom IIASA International Institute for Applied Systems Analysis (research centre) iMCFC Improved Molten Carbonate Fuel Cell INCOSE International Council on Systems Engineering (organisation) IPCC Intergovernmental Panel on Climate Change (organisation, UN) kg kilogramme kW kilowatt kWe kilowatt electric kWh kilowatt-hour LCA Life Cycle Analysis LCI Life Cycle Inventory LDPE Low Density Polyethylene LHV Lower Heating Value LLDPE Linear Low Density Polyethylene LNG Liquefied Natural Gas LP Linear Programming LPG Liquefied Petroleum Gas LT Low Temperature MCFC Molten Carbonate Fuel Cell MEA Membrane electrode assembly MeOH Methanol Mg Magnesium MIBK Methyl isobutyl ketone MINLP Mixed Integer Non-Linear Programming MMA Methylmethacrylate Mn Mangan MTA Million Ton per Annum
Abbreviations 247
MTBE Methyl-tert-butyl-ether MW Megawatt MWh Megawatt hour mX meta-Xylene NaCl Sodium Chloride (rock salt) NGL Natural Gas Liquids NGO Non Governmental Organisation NH3 Ammonia NIMBY Not In My Backyard NL The Netherlands NOx Nitrogen oxides NRC National Research Council (organisation, US) ODF Objective-defined Function OECD Organisation for Economic Co-operation and Development OPEC Organisation of the Oil Exporting Countries oX ortho-Xylene oXylSep ortho-Xylene separation PAFC Phosphoric Acid Fuel Cell pc Personal Communication pCO2 Partial CO2 pressure PdVC Polydivinylchloride PE Polyethylene PEM Polymer Electrolyte Membrane PEMFC Polymer Electrolyte Membrane fuel cell PET Poly Ethylene Terephtalate PG Propylene Glycol Phenol1 Phenol process 1 Phenol2 Phenol process 2 PJ Pèta Joule (1015 Joule) PMMA Polymethylmethacrylate Pmt Product-market-technology combination Pmt-R Product-market-technology-Resource combination PO Propylene Oxide PoR Port of Rotterdam POX Partial Oxidation PP Polypropylene PS Polystyrene PSA Pressure Swing Adsorption PSE Process System Engineering Pt Platinum PtcAnh Phtalic Anhydride PTFE Poly tetra fluoro ethylene PUR Polyurethane resin PVC Poly vinylchloride pX para-Xylene PyGsl Pyrolysis Gasoline production R&D Research and Development R/P Resource to Production ratio RC Responsible CareTM RefGsl Refinery Gasoline production RIVM Rijksinstituut voor Volksgezondheid en Milieu (research centre, NL) ROACE Return on Asset Capital Employed
248 Process System Innovation by Design
ROI Return on Investment RON Research Octane Number Sabic Saudi Aramco Basic Industries (company, Saudi Arabia) SAN Styrene Acrylonitrile copolymer Sasol Sasol (company, South Africa ) SBR Styrene Butadiene Rubber SEP Samenwerkende Elektriciteits Producenten (association, NL) SETAC Society of Environmental Toxicology and Chemistry Si Silicium SIC Standard Industrial Classification SM Styrene monomer SMDS Shell Middle Distillates Synthesis SO2 Sulphur dioxide SOFC Solid Oxide Fuel Cell SRI Stanford Research Institute (company, US) Styren1 Styrene process 1 Styren2 Styrene process 2 T Toluene TBA Tert-butyl-alcohol TCOU Total Cost of Ownership and Use TiO2 Titanium dioxide TNO Toegepast-Natuurwetenschappelijk Onderzoek (research centre, NL) TOE Ton Oil Equivalent TPA Terephtalic Acid UK United Kingdom UN United Nations US United States of America VCM Vinylchloride Monomer VNCI Vereniging Nederlandse Chemische Industrie (association, NL) VROM Volksgezondheid, Ruimtelijke Ordening en Milieu (Ministerie) VOC Volatile Organic Compounds WRI World Resource Institute (organisation) X Xylene Zn Zinc ZnO Zinc Oxide
Appendices
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Appendices 251
A. 1 Overview of petrochemical products, Pmt-Rs and supply chains. Basic inorganic chemicals such as sulphuric acid, ammonia, phosphoric acid, sodium hydroxide, chlorine and nitrogen fertilizers have long dominated listings of chemicals’ production volumes. This reflects the importance of the high-volume industry of fertilizer production that supported the massive increase in agricultural productivity world-wide. Ethylene, the major organic base chemical has moved up these ranks, however, at least in the US (Brennan 1998), which reflects the dramatic growth of the petrochemical industry in the ‘60-‘70s driven by increasing demand and production of polymers such as polyethylene, polyvinyl chloride (PVC) and polystyrene.
The top-30 chemicals production listing, USA, 1996. Chemical USA Annual Chemical USA Annual prod. cap. Growth prod. cap. Growth ‘85-’95’ ‘85-’95’ (MTA) (%) (MTA) (%) 1 Sulphuric Acid 43.3 0 16 Vinyl 6.8 5 Chloride 2 Ethylene 21.3 6 17 PVC+copol. 5.6 6 3 Ammonia 16.2 0 18 Styrene 5.2 4 4 Diammonium 14.3 4 19 Methanol 5.1 8 phosphate 5 Phosphoric 11.9 2 20 Polypropylene 4.9 Acid 6 Sodium 11.9 2 21 Formaldehyde 3.7 4 hydroxide 7 Propylene 11.7 6 22 DMT 3.6 2 8 Polyethylene 11.7 5 23 Ethylene 3.5 3 (LD+HD) oxide 9 Chlorine 11.4 2 24 Hydrochloric 3.3. 3 acid 10 Nitric acid 7.8 1 25 Cumene 2.6 5 11 MTBE 8.0 25 26 Polystyrene + 2.6 3 copolymers 12 Ethylene 7.8 4 27 Ethylene 2.4 2 Dichloride glycol 13 Ammonium 7.3 2 28 Ammonium 2.4 2 Nitrate sulphate 14 Urea 7.1 2 29 Mono- 2.4 5 Ammonium Phosphate 15 Ethylbenzene 6.2 6 30 Acetic Acid 2.1 5 Note 1: Data taken from (Brennan 1998: 22) (based on Chem. Eng. News, 24.06.’96). Note 2: Font used indicates product class: Petrochemicals, petroleum-derived end- products, chemicals from natural gas. Inorganics
252 Process System Innovation by Design
A. 2 Applied thermodynamics State properties In thermodynamics, the concept of state properties has proven to be very useful. A state property of a particular substance, mixture or stream only depends on the particular state (pressure, temperature, composition), and not on how that state has been realised. The value of a state property is always quoted relative to some reference state60. Important state properties are internal energy U, enthalpy H, free energy G (all [J/mol] and entropy S [J/mol/K]. These have been defined in chapter 3:
∆U = q + w (Eq. 3.2) The internal energy of a system changes in case heat q or work w flow in or out of the system. Properties correctly derived from combinations of state properties also are state properties. Enthalpy is a state property defined as
∆H = ∆U + ∆(PV). (Eq. 3.3.) It follows from eqn. 3.2 and 3.3 that in case only PV work is allowed on a system
(i.e. no shaft Work, w=0) that ∆H = qp.
Entropy, or disorder, is defined as
∆S = q / T. (Eq. 3.4) According to the Second Law of Thermodynamics the sum of the entropy changes in the system and its surroundings can only be positive or zero. In chemical engineering thermodynamics Gibb's free energy is used. The Gibb's free energy of a system is defined as:
∆G = ∆H - T∆S (Eq. 3.6) In a chemical reaction, thus the change of Gibb's free energy thus is a function of the enthalpy of reaction, the temperature, and the change in entropy between the final and entry states. Since G is a state property, ∆G is independent of the course of the transformation process in the system It can be shown that the maximum amount of Work that can be extracted from a chemical reaction equals the ∆G of that reaction. Alternatively, for a reaction to occur, the minimum amount of Work to be supplied also equals ∆G of that reaction. A reaction where ∆G is sufficiently negative will complete spontaneously once initiated. An example are combustion and explosion reactions, where both ∆H is
60 For thermodynamic properties such as enthalpy, this is the state of the elements and standard conditions (P=1 atm, T=298 K). For industrial properties such as the Lower Heating Value and exergy, one prefers to use the lowest energy state found on Earth (i.e. CO2 + water). The definition of a reference state for other elements is somewhat arbitrary, as their natural appearance may vary. As a consequence, discussions have been ongoing in the scientific community to arrive at a consensus that can be used for consistent energy and exergy efficiency calaculations (e.g. Kotas 1985).
Appendices 253
negative, and ∆S is positive (entropy creation), which results in a strongly negative ∆G. (Stull et al. 1969). A chemical reaction where the number of reactants is the same as the number of products, which occurs at infinitesimal slow speed, and which is considered an isolated system, represents a reversible system where dS = 0. As a consequence, ∆G = ∆H. To enable calculations around energy transformations that involve chemical o reactions, the state property Enthalpy of formation, Hf [kJ/mol] is used: in case the Enthalpy of formation of products and reactants is known, the enthalpy change between products and reactants equals the enthalpy of reaction ∆Hr. In energy statistics, the Lower Heating Value or LHV [MJ/kg], is a common measure of energy content of fuels. It is a measure of the amount of heat q released when the fuel is combusted. The LHV is an expression of the amount of chemical energy stored in a material; the LHV is equal to the reaction enthalpy of combustion of the fuel with oxygen under standard conditions to gaseous products. Thus, this excludes the amount of energy that is released when part of these products, the water vapour, is condensed to liquid at standard conditions . In the Higher Heating Value (HHV) of a material this amount of energy is included. Since internal energy, enthalpy, LHV and HHV are a thermodynamic properties of state, in the calculation of system energy balances the energy content of streams can be expressed as ∆H0, LHV or HHV or any other energy measure, but the same expression must be used for all streams in the final calculation.
Open, closed and isolated systems In thermodynamics, a distinction is made between isolated, closed, and open systems. A totally isolated system can neither exchange matter nor energy with its surroundings. A thermally isolated system can only exchange Work with its environment. A closed system can only exchange energy with its surroundings. Finally, an open system can exchange both matter and energy with its environment (Seader 1982; Georgescu-Roegen 1991). A chemical reactor that operates perfectly adiabatically is a thermally isolated system. A heat-engine based on the famous Carnot-cycle is a closed system, as the specific system requirement is that the 'working medium' is brought back to its original state in the process of converting heat to work. The Earth can be considered a closed system, for all practical purposes, in case the input of meteorites and the slow loss of Helium to the Universe are neglected. A chemical plant and the petrochemical industry are open systems because these exchange at least feedstock and product streams with their surroundings.
Manifestations of energy Energy has many forms or manifestations. The best known manifestation of energy is heat, in the form of radiation, convection, or direct heat transfer. Other energy forms are movement (kinetic energy), gravitational potential energy, and of course electrical potential energy.
254 Process System Innovation by Design
Energy can be stored in materials as chemical energy or chemical potential. Some of these materials are our commonly used fuels Energy can be converted from one form into another. An overview is presented in Figure A.2-1.
Oil Heat Mechanical Crude Oil Electricity Propulsion Products Thigh Energy 1 2 5 6
Powering Coal Equipment
Natural Gas Lighting
Powering Equipment 7
Propulsion 8
Heat Industrial
Tmedium Processing 3 9
Heat Space-
Tlow heating 4 10 Energy sources or stocks Forms of energy or energy-carriers Energy use
Figure A.2-1: Energy conversions in the utilisation of fossil fuels. Legenda for number labels Figure A.2-1 No. Conversion Conversion 1 Conversion / separation (refinery) 6 Shaft power-to-electricity (generator) 2 Combustion (power plants) 7 Shaft-power to equipment (machinery, electronics) 3 Combustion (industrial furnace) 8 Shaft-power to propulsion (transport) 4 Combustion (Central Heating) 9 Heat transfer (industrial heat-exchangers) 5 Heat-to-Power (e.g. turbomachinery) 10 Heat transfer (radiators Central Heating)
The First Law of Thermodynamics According to the First Law of Thermodynamics, energy cannot be lost not created. This implies that the energy of the Universe is constant. Thus, the internal energy of a system can only increase when simultaneously the energy of the system surroundings decreases. In energy analysis confusion results when the First Law of thermodynamics is not properly understood by engineers, scientists, or policy- makers and consultants who have had only limited or no formal training in thermodynamics. Particularly the use of the misnomen 'energy consumption' is widespread. Instead of 'energy consumption', however, we rather speak of energy use. Energy is often reported as Lower Heating Value. This LHV requires consistent calculation, as its value depends on the reference state selected. In the promotion material for boilers
Appendices 255
to be used in central heating systems, for example, misuse of LHV leads to common 'deceit'. Boiler efficiencies greater than 100% are proclaimed for systems that utilise the energy released during condensing the water vapour present in the flue gas. The energy content of the natural gas consumed is listed as the Lower Heating Value, a measure which assumes that water vapour is not condensed. Thus, both exergy and LHV are thermodynamically sound properties once the 'dead' reference state has been defined, which must include the phase state of the components included.
The Second-Law of Thermodynamics Where the First Law states that energy cannot be lost nor created, the Second Law implies that the total energy quality of the Universe must deteriorate whenever any real process completes. The Second Law of thermodynamics states that the result of any process that completes in a finite time-span is that the total entropy S of the Universe increases . It implies that in a closed system heat cannot be converted completely into Work: there will always be some heat that is rejected to the environment. The maximum conversion of heat-to-Work is obtained in a Carnot- cycle (Carnot 1824; cited in Kondepudi and Prigogine 1998: 69). The associated Carnot-efficiency depends only on the temperature of the heat reservoir and the temperature of the heat sink between which part of the heat is converted into Work. The potential to perform useful Work can be determined for any form of energy. It is a measure of the quality of energy and has been coined exergy (e.g. Kotas 1985). In case we select a reference temperature To for the heat sink in the Carnot-cycle, the exergy of a heat reservoir or stream q at temperature T is given by the familiar Carnot factor:
Ex = A = q (1 – To/T) (Eq. 3.9) This equation coins the familiar result that when the temperature T of a heat • reservoir q or heat flow q approaches T0 its Exergy decreases to zero.
In case the transformation of (chemical) material occurs at T0,
∆Ex = ∆H - To∆S = ∆G0
The work of Denbigh (1956) provides a link between energy systems and chemical reaction systems as he derived the equation wt = To σ + ∆A
This equation states that the total Work wt required to let a process progress at a finite speed equals the wasted work To σ or irreversible entropy production plus the change in of availability the process materials ∆B. In case the transformation occurs and T0, this equals ∆G0
256 Process System Innovation by Design
A. 3 Overview of cohesion types In this appendix, an overview of cohesion types is given. Each is illustrated by an explanatory example. Subsequently, the applicability of various cohesion types in the petrochemical industry is briefly addressed. • coincidental: ‘no common function, data, procedure’, i.e. not serving some purpose It may be seen that coincidental cohesion in systems decomposition and modelling is to be avoided. A decomposition of a nations industry by companies, for example, may result in 'coincidental cohesion' unsuitable for any modelling or analysis. The very establishment of the fact that the only cohesion in a business organisation is perceived as coincidental may explain a lot of business reorganisations, as the very conclusion is this case unavoidably is that the organisation does not serve a purpose or mission. • logical: the elements ‘perform certain logical classes of functions’ Logical cohesion involves identification of subsystems by grouping them according to some conceptual classification scheme. In a logical system decomposition the elements ‘perform certain logical classes of functions’. The best example in the industrial economy is the SBI-code used in economic statistics (CBS 1992). • temporal: modules are related logically and by time of execution, but not necessary by procedure Temporal cohesion is important in the daily operation of systems, when sound timing of activities must be achieved, and in weekly or yearly planning of systems. • sequential: no other relation than that output of one element provides input to the next Other than in temporal cohesion, in this case there is either a physical or information link between system elements. It relates, for example, to the traditional method of project execution in the chemical industry. The subsequent project phases (e.g. 'Strategic idea', 'Conceptual Design', 'Basic Design', 'Detailed Design', 'Plant Construction' (van Breda and Dijkema 1998) are executed sequentially based on the information packages generated in the previous phase. It may be seen that in actual practice, when further decomposition of system elements is required, procedural cohesion can be applied, or temporal cohesion when timing is important. • procedural: elements are all part of a procedure Procedural cohesion can be achieved when grouping of subsystem is done according to a common procedural context, based on similarity on how specific activities are performed. A procedural decomposition of the chemical industry, for example, is the distinction between continuous processing, and batch processing. This is widely used in chemical engineering literature, and even in the formulation of research programmes and proposals. Procedural cohesion is useful to understand existing production systems: realising production objective-functions must be done in an economic context. At any given time because of the set of available technology, (market) regulations (arrangement),
61 Only if the initial and final (P,T) of the materials processed is the same, and equals (P,T) of the medium at which the process exchanges heat with the environment.
Appendices 257
control mechanisms, notably information technology, often a particular type of procedure for operation is economically the most advantageous. This largely explains the procedural cohesion in the chemical industry, where on the one hand large-scale operations prevail for high-volume products, on the other hand batch-wise operations for small-scale, flexible production for fine-chemicals and pharmaceuticals. Exceptions often can be explained by lack-of-suitable technology (e.g. batch wise polymerisation for PVC, a product produced in bulk-quantities). As the systems environment changes, the procedural cohesion may no longer be valid and can disappear, which e.g. is occurring in the power industry which is ‘in transition’ through the dramatic changes in regulation and to promote economic restructuring. • communicational: the elements all operate on the same set of data (object- orientation) Communicational cohesion, for example, relates to emerging concept of concurrent engineering, where the prime cohesion in activity is indeed that they relate to the same object (a chemical plant) that must be designed, engineered, and built. Communicational cohesion can also be labelled relational cohesion. It is then provides a means for cohesive modelling of a system’s environment, and it may provide a powerful means to explain the impact of such concepts as ‘substance- chain management’, Product Stewardship, supply-chain management etc., which relate a chain of operation to a common object or substance. Another area of relevance is that of infrastructures. In an increasing number of infrastructure sectors new roles are defined, e.g. for network and market regulation. The actors involved all act on and relate to one infrastructure. • functional cohesion (see Chapter 3, §3.3 p. 93
Cohesion types and the petrochemical industry When attempting to achieve procedural cohesion the focus is on the types of activity of a particular industry, sector or plant. Fossil resources are being used or converted for the greater part in power generation and the process industry. The latter term is a collocation of those industries that employ large-scale continuously operated processes (see Figure A.3.1). In a largely a logical classification one may distinguish 'winning and treatment of mineral ores', 'crude-oil refining', 'petrochemical industry', 'chemical industry', 'base metals industry', 'fertilizer industry', 'food industry' and 'polymer industry'. The use of large-scale continuous processes is the common procedural denominator of the activities in these sectors.
258 Process System Innovation by Design
Base Metal
Coke Food Inorganic Chemicals factories industry
Fertilizers Large-scale process industry Other Organic Chemicals
Power Plants
Polymers
Petroleum Refineries Petrochemicals
Figure A.3.1: Industry sectors that employ large-scale, continuous processing. A further suitable procedural decomposition of continuous large-scale plants in all the industries mentioned is not trivial. In the petrochemical industry, each chemical plant constitutes a specific network of unit operations. In the design of a chemical plant, sequential cohesion between its unit operations must be achieved. In chemical engineering, the classes of unit operations, reactors, pumps, compressors, separators etc. represent a procedural decomposition at this aggregate level. The equivalent of these operations again are found in most of the process industry sectors illustrated (Figure A.3.1). A further procedural decomposition in, for example, reactor engineering is the distinction between gas, liquid, solids, homogeneous, heterogeneous, gas/liquid, gas/solid etc. Another decomposition of the chemical industry can be completed by considering the procedural denominators in parts of the production chains or process routes. At the beginning of the production chains, a common denominator is that multi- purpose or mixed feedstock is converted to pure, single- or limited-purpose feedstock for individual chemical plants. The primary example in the petrochemical industry is the naphtha cracker, gasification to synthesis gas and the MTO-process62. Further down chemical production chains consist of chemical plants that can only convert a limited span of feedstock to a limited number of products. Finally, at the end of many production chains products are made in very small quantities in plants that are truly ‘multi-purpose’: they can process a variety of feedstock into a variety of final products.
62 Methanol To Olefins 63 Shell Middle Distillate Synthesis
Appendices 259
A. 4 Systems representation with the input-output paradigm64 Characterisation of dynamics systems according to the lines of thought in mathematical systems theory (MST), using the input-output paradigm. We abstain from the more general concept of a dynamic system in which the distinction between inputs and outputs is dropped and the interaction between system and environment is represented by interaction variables, which can act both in an input and an output fashion, changing over in time. We develop the input-output description using the state-space concept initially. Using this concept with the associated time evolution of the states presumes knowledge about the internal workings of the system. Then we relax on this knowledge of internal workings and drop the state concept, taking the system to be of the black-box Input-Output type with time evolution. Finally, the time evolution is discarded. It is assumed that the function of the system, Σ, is to generate a behaviour B to transform a set of inputs (Su) into a set of outputs (Sy), which relate the system to the external world. The performance of the system (Ω) is assessed by means of value functions (P). The specification of the system , Σ, is built up in two steps, viz. (1) defining the behaviour (2) defining the performance. Starting with (1) the behaviour, B , first three different spaces are defined for the inputs u ∈SU, the outputs y ∈ SY and the internal states x ∈ SX. To account for the evolution of the system in time, the scalar time variable t is introduced in space T. Each space is given a properties, like a metric in order to be able to define size of an element and distance between objects in the space. Next, one defines the mappings: * from input space to state space,
G: SU => SX , * the evolution from state space and time to state space and time,
F: SX * T => SX * T, * and from state space to output space,
H: SX => SY . The mappings satisfy certain general smoothness properties. For mapping F special conditions apply, relating to the transitivity aspects of time operations:
F(x0, t0 => x2, t2 ) = F(x0, t0 => x1, t1 ) * F(x1, t1 => x2, t2 ) The precise nature of the mappings and the specific properties define the specific behaviour B of the system Σ:
Bstate={G o F o H}. Note that the causality of the system is rooted in the specification of the flow of information from inputs to states to outputs in combination with the transitivity property of F.
64 This appendix is largely based on internal discussions and research note (Grievink 2003).
260 Process System Innovation by Design
Now that the behaviour of the system has been defined, the next item is the measures for the performance of the system. The performance will be measured by so-called values ω ∈ Ω. These values are elements of the performance space Ω. Again this space is given an internal structure to make sure that the elements have a size and that a distance measure is in place. The performance values are obtained from a performance functions (P) , which is a mapping from the inputs, outputs and, possibly, the states over a certain time interval of evolution to the performance measures:
Pstate: SU * SX * SY * T => Ω The mapping P to the performance space is called the value map.
The values can be written as a functional over time interval [t0,t1]: t1 ω = P(∫t0 p(u(t),y(t),x(t),t) dt Some examples of performance values are: controllability, controllability and economic profit, technological indicators, like exergy losses. Hence, the system Σstate, is now fully characterised by:
Σstate = { SU , SX , SY , T, Ω, Bstate, Pstate }
An example of such a system description will now specified for linear dynamic systems.
The behaviour, Blin, can be characterised by a triplet of matrices:
Blin = {B, A, C}. The corresponding behaviour is given by: d x(t) /dt = A.x(t) + B.u(t) and y(t) = C. x(t) The performance of such linear systems is often specified in a quadratic fashion: T T ω(t1 ,t0 ) = x(t0) .W0.x(t0) + x(t1) .W1.x(t1)
+ ∫tot1[u(t)T.Wu.u(t) + y(t)T.Wy.y(t)] dt
Hence, the performance functional can now be characterised by the matrix quartet:
Pquadratic = {W0, W1, Wu, Wy }
For a black-box type of input – output description, where the internal state is not considered, the behavioural description will reduce to:
BI-O: SU * T => SY * T
The performance model reduces to:
PI-O: SU * SY * T => Ω
Hence, the system ΣI-O, is now fully characterised by:
ΣI-O = { SU , SY , T, Ω, BI-O, PI-O }
Appendices 261
When evolution in time is not considered (e.g. representing the steady state of a system) the description further simplifies to:
BI-O,ss: SU => SY ,
PI-O,ss: SU * SY => Ω
ΣI-O, ss = { SU , SY , Ω, BI-O,ss, PI-O,ss }.
In conclusions, any system is characterised by the specification of its: o Input space (SU) o Output space (SY) o Performance space(Ω) o Behaviour map (B) o Value map (P)
262 Process System Innovation by Design
A. 5 Algorithm to check for mutual contingency The criterion for mutual contingency of a set objective-defined functions { Ф } (Ch. 3, §3.3.3 p. 97) can be written as a (pseudo) algorithm, which returns the Boolean S where S: { Ф }= Mutual Contingent Set.
{the system has m possible instances, and n objectives Ф 1…n}
{an instance equates to a possible system state expressed as a 'value' of Ф 1…n } {Start - init} S=TRUE {Loop over all objectives Ф (1…n)} FOR i=1…n FOR j=1…n {per pair of objectives Loop over all instances of the system (1..m)} {init} k = 0 P = FALSE M = FALSE A = FALSE While k < m k = k+1 {parallel?} Pk = (Фi,k AND Фj,k) {mutually exclusive?} Mk = ((Фi,k OR Фj,k) AND NOT (Фi,k AND Фj,k)) {achievement?} Ak = OR (Фi,k AND Фj,k+1) {Thus it is implicitly determined when there is no relation between Фi and Фj in any of the instances because Mk contains Фi or Фj, never both {add result of this instance to result for pair i,j} {latch P when parallel achievement in some instance of the system} P= P OR Pk {latch M} M= M OR Mk {latch A} A = A OR Ak END {while} {test whether in the set pairs of instances exist that are both parallel and mutually exclusive; if this is the case, then mutual contingency has not been achieved} Si,j = (P OR M OR A) AND (NOT (P AND M)) S = S AND Sij END {FOR j} END {FOR i}
Appendices 263
A. 6 Assessment of the Dutch industrial olefins system
Production facilities (1990) included in the assessment In the tables below, an overview is given of the Dutch production facilities that together formed the industrial olefins systems in the Netherlands as of 1990. To date, both Shell and Dow have completed major rejuvenation/revamp/expansion projects on their steam cracker complexes. DSM has spun off its petrochemicals, PE an PP activities to Sabic Petrochemicals.
Table A.6.1: Production capacities for ethylene and propylene Process company Capacity [ ton/year] Remarks Steam cracker (LPG, Dow Benelux ethylene: 1.000.000 expansion: naphtha, gas oil) propylene: 400.000 ethylene: 100.000 Steam cracker DSM ethylene: 925.000 expansion: (naphtha, gas oil) propylene: 470.000 ethylene: 100.000 Steam cracker (LPG, Shell Moerdijk ethylene: 625.000 naphtha, gas oil) propylene: 350.000
As indicated in Figure 4-2: Industrial production of ethylene derivatives and example applications and in Figure 4-3: Industrial production of propylene derivatives and example applications (p. 124-125) are relatively 'loosely' connected, while they share a common source, the steam cracker. Therefore, production capacities of ethylene and propylene derivatives are listed separately below (Tables A.6.2 and A.6.3)
Table A.6.2: Capacities of ethylene derivatives in the Dutch industrial olefins system From / to ... Capacity Company Remarks [ton/year] Ethylene 2.550.000 Dow, DSM, Shell expansion: 200.000 Polyethylene LDPE 580.000 Dow, DSM LLDPE <380.000 Dow, DSM DSM: one plant for both HDPE <110.000 DSM LLDPE and HDPE UHMWPE 5.000 DSM “Dyneema” fibre EPDM rubber 65.000 DSM expansion: 10.000 PE/VAc copolymer 20.000 Vinamul expansion: 24.000 Vinylchloride and derivatives Ethylene dichloride 600.000 Rovin Vinyl chloride 480.000 Rovin Ethylene diamine 49.000 Dow, Delamine estimate Polyvinylchloride 410.000 Rovin, Limburgse expansion: 80.000 Vinyl Unie Glycols Ethylene oxide 285.000 Dow, Shell Ethyleneglycol 345.000 Dow, Shell Glycol ethers 74.000 Dow, Shell Various Vinylacetaat 60.000 diversen estimate
264 Process System Innovation by Design
Table A.6.3: Capacities of propylene derivatives in the Dutch industrial olefins system Product Capacity [ton/year] Company Remarks Propylene 1.220.000 Dow, DSM, Shell Polypropylene 480.000 DSM, Basf, Shell Expansion: 190.000 Propylene oxide 370.000 Shell, Arco Propylene glycol 60.000 Arco Propylene glycol ether 100.000 Arco Polyols 180.000 Dow, Du Pont, Estimate ICI, Shell Acrylonitrile 175.000 DSM acrylamide 15.000 Cytec Estimate polyacrylamide 15.000 Cytec Estimate isopropylalcohol 290.000 Shell diisopropylether ? Shell Acetone 150.000 Shell PMMA 9.500 ICI Methylisobutyl ketone 60.000 Shell Estimate Methylisobutyl carbinol Allylchloride 80.000 Shell Epichloro hydrin 80.000 Shell Bisphenol A 90.000 Shell Epoxy resins 55.000 Shell
Modelling and assessment The assessment has been executed using the methods described in chapter 3. These were implemented in a database system and a spreadsheet programme. The olefins system was modelled as a single industrial complex. The set of system elements consists of the industrial processes in commercial use. The subsystems 'olefins production' and 'olefins consumption' were included by appropriate selection of system elements. Subsystems and system elements are connected by internal flows, the inputs and outputs of single process plants (as depicted in Figure 3.2). The net inputs and outputs of the subsystems and the entire complex were calculated in a linear model on the basis of actual capacity-installed (100% utilisation), maximum internal deliveries, and the input/output characteristic of each individual plant viz. subsystem. Input-output data on individual plants used was largely taken from open-literature data on 'typical plants', such as published in (Chauvel and Lefebvre 1989a). These were augmented and corrected by using information and data supplied by various companies65. Although some datasets used may have been outdated or incomplete, these were thought to suffice to for the objective of the analysis, which was to illustrate the possibilities of networked petrochemical system assessment to obtain entry-points to look for improvements, and not the assessment of individual plants.
65 Data and information were supplied with the understanding that these would be treated as confidential.. Therefore, analysis results are only presented in aggregate form. Details on the data set used and the reconciliation process applied are available from the author.
Appendices 265
The data sets obtained were converted prior to their use in the assessment. The data reconciliation involved a check for data-consistency and completeness per data set on an individual plant. Intricate process knowledge and mass and energy balancing were used to correct or complete data sets. To be able to complete the process the following assumptions had to be made: - with respect to additions for completion of plant's mass balances, is was assumed that a deficiency (i.e. more mass going into the process than going out)
is caused by the generation of light gases that are emitted as CO2 and H2O. This assumption can be considered valid, since most process schemes include an off- gas treatment section that remains otherwise unspecified, whilst 'hydrocarbons' can always be utilised as fuel after proper treatment. The carbon and hydrogen
thus lost will eventually end up as CO2 and H2O. - the specific energy content of streams not reported in a particular data set can be estimated. However, since often nothing is known about the energy content or the application of these streams, these are assumed to be zero in the analysis.
Mass loss La, Lb and mass efficiency ηa, ηb do not require complete datasets, they immediately give an impression of the performance of the process. Calculation of these indicators does not require an assumption with respect to the fate of the external mass loss! Computation of Industrial System Performance indicators The energy content and exergy content of the input and output streams can conveniently be estimated from thermodynamic data reported in the literature (Stull et al. 1969). The computation of Lower Heating Value and exergy require adherence to a suitable thermodynamic reference state (P0, T0, standard composition of the environment). This is acceptable for the analysis performed, which is intended to obtain an overall picture in a reasonable amount of time, which is reasonably accurate and which can serve to make a first selection of starting points for an assessment of the (technological) potential for improvement. Because most production plants take-in feedstock at ambient temperature. In specific cases, however, the actual losses may differ substantially from the ones calculated in the analysis. As with mass balances, however, hardly ever the data reported on industrial processes result in a closed energy balance because streams are missing. Energy leaving an industrial process, for example, as flue gas, cooling water, or condensate are hardly ever listed. In addition, some losses occur by radiation. Properly defined, energy is a thermodynamic property of state. Energy content, however, also represents a valuation of streams. In chapter 3, it was argued it is a prime candidate for use in process system assessment for sustainability.
266 Process System Innovation by Design
Table A.6.4: Assessment result olefins system, Mass Indicators
Mass Efficiency Loss 0…100% [kton/year] ab e a b e System Subsystem Process name Capacity Production Ethylene Steam cracker 73 73 44 2550 350 350 1211 Production Propylene Steam cracker 73 73 44 1220 350 350 1211 Production C4/C5/PyGsl/Steam cracker 0 0 0 1043.1 0 0 0 Consumption Ethylene EDC+VCM 85 85 47 480 88 88 549 Consumption Ethylene Ethylene diamine 40 40 23 49 74 74 164 Consumption Ethylene Ethylene oxide 54 54 11 285 242 242 2255 Consumption Ethylene Ethylene glycol 81 92 92 345 79 32 32 Consumption Ethylene Glycol ethers 81 81 94 74 17 5 5 Consumption Propylene Propylene oxide 91 94 90 370 151 93 166 Consumption Propylene Propylene glycol 81 90 90 60 14 7 7 Consumption Propylene Propylene glycolether 81 90 90 60 24 13 13 Consumption Propylene Polyols 96 97 88 180 8 6 25 Consumption Propylene Acrylonitril 64 72 20 175 97 77 760 Consumption Propylene Acrylamide 75 75 39 15 5 5 23 Consumption Propylene Isopropylalcohol 89 89 57 290 37 37 216 Consumption Propylene DIPA 000 0 0 0 0 Consumption Propylene Acetone 90 90 64 150 16 16 85 Consumption Propylene MEK 75 75 75 60 10 10 10 Consumption Propylene Allylchloride 49 93 93 80 84 12 12 Consumption Propylene Epichloro hydrin 38 38 2 80 131 131 3400 Consumption Propylene Bisphenol A 86 86 83 90 15 15 18 Consumption Propylene VinylAcetate 000 600 0 0 Polymerisation Ethylene LDPE 97 97 52 580 18 18 536 Polymerisation Ethylene LLDPE 98 98 90 380 9 9 35 Polymerisation Ethylene HDPE 97 97 91 110 3 3 11 Polymerisation Ethylene UHMWPE 97 97 64 5 0 0 3 Polymerisation Ethylene EPDM Rubber 98 98 90 65 1 1 7 Polymerisation Ethylene PE/Vac Copol 98 98 56 20 1 1 19 Polymerisation Ethylene PVC 99 99 27 410 4 4 1099 Polymerisation Propylene Polypropene 96 97 86 480 21 16 77 Polymerisation Propylene PMMA 100 100 8 9.5 0 0 116 Polymerisation Propylene Epoxy resins 68 68 26 55 26 26 159
Appendices 267
TableA.6.5: Assessment results, olefins system, Energy Indicators
Energy Efficiency Loss 0…100% [PJ/Yr] ab e a b e System Subsystem Process name Capacity Production Ethylene Steam cracker 65 65 65 2550 23.7 23.7 23.7 Production Propylene Steam cracker 65 65 65 1220 23.7 23.7 23.7 Production C4/C5/PyGsl/Steam cracker 0 0 0 0 0.0 0.0 0.0 Consumption Ethylene EDC+VCM 64 64 64 480 5.2 5.2 5.2 Consumption Ethylene Ethylene diamine 39 39 39 49 2.3 2.3 2.3 Consumption Ethylene Ethylene oxide 65 65 64 285 4.2 4.2 4.4 Consumption Ethylene Ethylene glycol 52 61 61 345 5.4 4.4 4.4 Consumption Ethylene Glycol ethers 65 75 75 74 1.0 0.7 0.7 Consumption Propylene Propylene oxide 76 80 80 370 15.5 13.1 13.1 Consumption Propylene Propylene glycol 61 70 70 60 0.8 0.6 0.6 Consumption Propylene Propylene glycolether 69 78 78 60 1.2 0.9 0.9 Consumption Propylene Polyols 78 79 79 180 1.3 1.2 1.2 Consumption Propylene Acrylonitril 51 56 56 175 5.3 4.9 4.8 Consumption Propylene Acrylamide 71 71 68 15 0.1 0.1 0.2 Consumption Propylene Isopropylalcohol 63 63 63 290 5.3 5.3 5.3 Consumption Propylene DIPA 0 0 0 0 0.0 0.0 0.0 Consumption Propylene Acetone 50 50 50 150 3.3 3.3 3.3 Consumption Propylene MEK 97 97 97 60 0.0 0.0 0.0 Consumption Propylene Allylchloride 58 68 68 80 1.4 1.0 1.0 Consumption Propylene Epichloro hydrin 54 54 54 80 1.2 1.2 1.2 Consumption Propylene Bisphenol A 73 73 71 90 1.1 1.1 1.2 Consumption Propylene VinylAcetate 0 0 0 60 0.0 0.0 0.0 Polymerisation Ethylene LDPE 83 83 83 580 5.1 5.1 5.1 Polymerisation Ethylene LLDPE 86 86 84 380 2.3 2.3 2.7 Polymerisation Ethylene HDPE 86 86 84 110 0.8 0.8 0.9 Polymerisation Ethylene UHMWPE 83 83 83 5 0.0 0.0 0.0 Polymerisation Ethylene EPDM Rubber 78 78 78 65 0.8 0.8 0.8 Polymerisation Ethylene PE/Vac Copol 93 93 88 20 0.0 0.0 0.1 Polymerisation Ethylene PVC 76 76 75 410 2.3 2.3 2.4 Polymerisation Propylene Polypropene 82 83 83 480 4.7 4.5 4.5 Polymerisation Propylene PMMA 87 87 86 9.5 0.0 0.0 0.0 Polymerisation Propylene Epoxy resins 88 82 81 55 0.3 0.3 0.3
268 Process System Innovation by Design
Once the composition of a stream is known, the LHV and the exergy value can easily be computed from thermodynamic basic data and the reference state. In oil and petrochemicals, however, often only an approximate composition is known and thermodynamic basic data may be lacking or inaccessible. Therefore a pragmatic approach has been used: for hydrocarbon mixtures such as 'naphtha', exergy has been equated to LHV reported in reputable sources66. In the computation of Industrial System Performance indicators as suggested in Chapter 3, energy is calculated as Lower Heating Value (LHV) with respect to a standard reference environment, the so-called dead state (see e.g. Kotas 1985)). The LHV and exergy of the dead state are zero, i.e. energy is at a minimum, and entropy is at a maximum. As a result, LHV and exergy of most hydrocarbons greater than zero, which allows us to define exergetic efficiencies.
The assessment results are given in Tables A.6.4 and A.6.5on the previous pages.
Calculation example: The Showa-Denko process for epichloro hydrin The definitions and the use of these indicators are illustrated below for the production of epichloro hydrin (ECH). As per the method developed in Chapter 3, the ECH process is considered as a black box characterised by its inputs and outputs of feedstock, (spent) utilities, (spent) processing agents, products, by-products and wastes. The process data used in this example were taken from the preliminary process design by three chemical engineering students of Delft. Their design was based on the Showa-Denko process for the production of epichloro hydrin, ECH, which is one of the constituents of epoxy resins. The main steps in this process are 1 allyl acetate production from propylene, acetic acid and oxygen 2 conversion of allyl acetate with water to allyl alcohol, whereby acetic acid is recovered 3 reaction of allyl alcohol and chlorine to dichloro hydrin, where HCl is a catalyst 4 conversion of dichlorohydrin with calcium hydroxide to ECH and calcium chloride The overall mass balance calculated in a student process design (Bouma et al., 1996) is listed in Table A.6.6. These data suffice to get a first impression of the eco- efficiency of the process design. The first step is to label the process input streams as either feedstock, processing agents, or utilities. Processing agents, such as solvents and catalysts, typically are not consumed, but can be used over and over again in a continuous production process. Energy utilities, such as electricity, and steam typically do not end up in the process’ product, but only supply the energy required to operate the process. At the output side, we must distinguish between wanted
66 Reconciliation was done per individual plant. Details of thermodynamic calculations can be obtained from the author.
Appendices 269
products, i.e. the main product and some valuable by-products, and the unwanted products, such as low-quality by-products, emissions, and wastes. From the summary of main process steps of the Showa-Denko process, we conclude that propylene, oxygen, chlorine, and calcium hydroxide are feedstock, whereas water, steam, hydrochloric acid, and acetic acid are processing agents. Water also is a reactant of the first process step, but the overall process reaction does not include water. propylene + ½ oxygen + chlorine + ½ calcium hydroxide --> ECH + ½ calcium chloride The main product is ECH, there are no wanted by-products. Propane, waste gas, waste water, and organic chlorines are all labelled as unwanted by-products.
Table A.6.6: Overall mass balance for a Showa-Denko preliminary process design (from Bouma et al., 1996) In [kg/s] Out [kg/s] Oxygen 1,06 ECH 3,44 Propylene 2,18 Propane 0,69 Water 1,06 Waste gas 1,15 Acetic acid 0,004 Waste water 38,16 (CaCl2) (2,2) Hydrochloric 0,13 Organic 0,39 acid chlorines Chlorine 2,91 Aqueous lime 32,1
(Ca(OH)2 (1,6) Steam 4,37 Total 43,83 Total 43,83
The direct efficiency expresses how fit for purpose the process evaluated is. The
Showa-Denko process design has an ηa of only 0,44. The product efficiency of the process ηb is equal to ηa, as there are no wanted by-products. Both indicators ηa and
ηb can also be expressed as the quotient of products and all inputs, i.e. feedstock, and processing agents combined. Only ηc provides additional information, however. In case of the Showa-Denko process design the total efficiency is only 0,078, which indicates that the process uses a lot of additional resources that are degraded to waste. Most of these unwanted by-products can be recovered, however, at the expense of additional process equipment and energy input.
270 Process System Innovation by Design
A. 7 PEMFC - the important markets projected beyond 2005 The focus of the fuel cell community has long been the development of PEMFC systems suitable for the passenger-vehicle market, for buses and for heavy-duty vehicles. Automobile companies have joined forces and invested in these fuel cell companies to integrate PEMFC systems in to existing and novel car concepts. Oil companies have largely focused on the possibilities of on-board conversion of 'logistic fuels', a label for the commonly distributed motor fuels, gasoline, diesel and to a lesser extent LPG. A survey of internet resources of reputable character reveals that at present PEM fuel cells and PEMFC systems are being developed for 6 classes of applications: I. Stationary applications: 1. small-scale (1-5 kWe) for household micro-cogeneration systems 2. medium scale (500 kW - 2 MWe) for utility building applications II. Automotive applications 3. light duty vehicles (50 kWe): passenger vehicles 4. heavy duty vehicles (205 kWe): trucks and buses 5. heavy duty vehicles (300 kWe): AGVs 6. auxiliary power (1 kW): 42 V on board - next generation passenger vehicles III. Portable applications 7. a variety of (+/- 200 We) 'large battery' applications IV.Other applications 8. motive power for ships and submarines (0.5 - 100 MW) 9. motive power for (cargo) trains (0.5 - 100 MW) Various companies have been producing stacks viz. systems and have demonstrated working systems for category I - III. Above application represent an equal number of markets for fuel cell use. At present, it appears that a number of the PEM fuel cell markets that are currently targeted may become -at least partly- methanol-powered fuel cell markets. Automotive applications today appear to be the most likely candidates for methanol FC development. In all classes mentioned under category II, currently methanol PEMFC systems are in an advanced state of development. In these markets there will be competition from Flexible Fuel Reformer (FFR) based systems that tie in to the existing infrastructures for logistics fuels. A major disadvantage of these systems, however, is their high operating temperature (900-1100 oC) of the flexible fuel processor that would be able to convert LPG, gasoline, diesel and methanol. In addition, FFRs are more complex, less efficient, and more costly than methanol reformers, and their current track record appears to be less advanced than that of MeOH-based systems(ADL, 2000a). According to Vogel (2001) the 'well-to-wheel' efficiency of FFR on logistic fuels and methanol systems are similar. Additional competition must be expected from hydrogen powered light-duty vehicles, which according to ADL (2000a) represent the fastest route to the market today, with projected on-board 300 bar hydrogen storage, or the use of certain metal
Appendices 271
hydrides. Notably BMW appears to be investing heavily in this system concept. Health and safety issues around hydrogen and their perception, however, are expected to remain a risk to general public acceptance. Auxiliary power systems face competition from hydrogen based systems: as the fuel requirement of these systems is limited, probably cost effective and safe hydrogen storage can be incorporated in a next generation conventional cars. Methanol powered auxiliary PEMFC systems, however, would allow the use of engine waste- heat for methanol reforming, thereby increasing the overall 'well-to-wheel' efficiency. Ballard Power (2001) have recently launched their NexaTM system concept. In Stationary Power application we foresee some use of methanol based systems in small-scale applications: those households that do not have a connection to a natural gas grid. As in automotive, in that case the 'well-to-kW' efficiency and cost of a methanol based fuel cell system can be expected to be the same or better than that of a logistics fuel FFR based system. In medium-scale applications, especially those employed in Uninterrupted Power Supply service (UPS), there may also be a substantial share of methanol, the alternative again being logistics fuel (UPS) or natural gas (other). The fuel of choice for Portable applications is bottled hydrogen: only a fuel cell stack is needed for power generation. With respect to the other applications mentioned: it may well be the case that other types of fuel cells will be employed in these applications, notably Solid Oxide Fuel Cells. Finally, in case the Direct Methanol Fuel Cell development is successful, reformer based FC systems are expected to be phased out entirely in automotive and stationary, non-natural gas grid connected micro-cogeneration. The required breakthroughs in technology, however, are dramatic. Realistically, commercial systems cannot be expected the coming 10-15 years.
272 Process System Innovation by Design
A. 8 Fuel cell, Pt and MeOH scenario model equations To analyse the possible effects of PEMFC fuel cell developments on platinum and methanol markets, a scenario model has been developed. A scenario for systems that incorporate fuel cell technology is translated into total associated platinum and methanol demand.
Let i = 1….n denote scenario year 1…n Let j = 1….n denote year of system production 1…n Let k = 1….m denote market segment 1…m Let p = 1…q denote parameter 1..q
Let Π be a two-dimensional matrix π[p,k]of parameters for typical 'market' systems characteristics. Π(1,k) is economic lifespan [year], π(2,k) is rated system output [kW], π(3,k) is typical system fuel input [ton/kW]. Let D be a two-dimensional matrix of elements d(i, k) denoting market demand per market segment [no. of systems/year]. Let Τ denote a matrix of scenario parameters, T(j, k) denoting average Technical Lifespan [year] per year cohort. Let θ denote a matrix of scenario parameters θ(p,k) determining system phase-out characteristics per market segment [fraction]. Let R denote a matrix of fractions r(i,j,k) of systems phased out per market segment [fraction/year]
R = f(T, θ, Π). (Eq. A.8.1)
Let s = (j-i)/ min (π[1,k], T(j,k)) (Eq. A.8.2)
Then the modelling of R as a function T and θ is such that
- ∇ k | ∇ i ≤ j | r(i, j, k) = 0 (Eq. A.8.3)
- ∇ k | i = j | r(i, j, k) = θ(1, k) (Eq. A.8.4)
- ∇ k | i > j | r(i, j, k) = θ(2, k) (Eq. A.8.5)
- ∇ k | 0.6 Thereby a proxy normal distribution of cohort phase out is modelled around the average lifespan, which standard deviation increases with average lifespan. Appendices 273 Let A denote a three-dimensional matrix of elements a(i, j, k) denoting number of systems in the running fleet [no. of systems]. ∇ k | i ≤ j a(i, j, k) = 0 ; (Eq. A.8.7) ∇ k | i > j a(i, j, k) = a(i-1, j-1, k)*(1-r(i-1, j-1, k)) + d(i-1, k) (Eq. A.8.8) Let PL be a matrix of scenario parameters, PL(i, k) denoting platinum loading of systems produced [g/kW]. Let Pt be a matrix of elements Pt (p, i, k) indicating platinum total demand Pt (1, i, k) , recycling demand/supply Pt (2, i, k) and net platinum virgin demand Pt(3, i, k), all in [g/year] Pt (1,i,k) = d(i,k)* π(2,k)*PL(i,k) (Eq. A.8.9) Pt (2,i,k) = ∑j=1,i {a(i-1, j-1, k)*r(i-1, j-1, k))*π(2,k)*PL(i-1,k)} (Eq.A.8.10) Pt (3,i,k) = Pt (1, i, k) - Pt(3, i, k) (Eq.A.8.11) Pt_stored = ∑i ∑k Pt (3,i,k) (Eq.A.8.12) Let MF be a matrix of scenario parameters, MF(i, k) denoting fraction of systems fuelled by methanol[fraction]. Let MeOH be a matrix of elements MeOH(i, k) indicating methanol fuel demand [ton/year] MeOH (i) = ∑k ∑j=1,i {a(i, j, k))*π(3,k) (Eq.A.8.13) 274 Process System Innovation by Design A. 9 Key issues with respect to PEMFC success The success or breakthrough of PEMFC is driven viz. depends on the economy, ecology and technology of PEMFC systems for the realisation of 'automotive transport'. Ecology leads to an ever increasing 'sense-of-urgency' with respect to the necessity of fuel cell technology to become successful for the benefit of mankind. On a global scale, there is the threat of global warming by human CO2 and other hydrocarbon emissions, as well as the concern for depletion of fossil resources. On a macro-scale, notably in the US there is a growing concern of the country's dependence of (foreign) oil. On a meso- or micro-scale there is the issue of air quality, that is seriously affected by soot-emissions (diesel engines) and CO and unconverted hydrocarbons (gasoline) that result in heavy, toxic smog in cities such as Athens, Mexico City and Greater Los Angeles. Smog-related problems have been the driving factor behind the series of Policy and Legislative packages issued by the State of California over the last 20 years. On a meso- and micro-scale, noise pollution is an issue that increasingly puts a constraint on expansion of transport-related activities. Economy of fuel cell systems appears to become less and less a critical issue, as more and more niche markets are developed, mass production is foreseen to begin in 2005, and regulatory constraints on the automotive and logistics fuel systems become increasingly tighter. Technology development today, however, is still largely focused on (Chalk, 2000) (1) bringing down 'System and Component' costs The fuel cell requires 60% of current system costs calculated at $300/kW for a 50 kW system (ADL, 2000a), the fuel processor some 20%, system assembly and 'Balance-of-Plant' accounting for the remainder 10%. Notably, the cost of the so-called Membrane Electrode Assembly (MEA) must go down. According to ADL, the cost of the stack in today's 50kW systems still accounts for almost 50% of system cost (76% of fuel cell cost). At least 30% of FC system cost are material related, and platinum alone accounts for 20- 25% of system cost, or some $60/kW! (2) increasing durability to extend the operating lifespan of key components Throughout the life of a fuel cell, its performance (% fuel converted to usable power) decays slowly. Today, some 40,000 hrs of continued feasible PEMFC operation is possible (ADL, 2000a). Especially for stationary systems, this figure (5 yrs of continued service) is still to low. In automotive systems, due to the nature of drive-cycles to be expected, stack life is expected to be much less. Indeed, according to Chalk, durability of MEAs and fuel processor catalysts up to 5,000 hrs. has not been demonstrated yet, and according to ADL, system's durability beyond 2000 hrs of service with power degradation (< 5%) must still be demonstrated. Appendices 275 (3) improving the dynamic performance and reliability of fuel processors The CO content of hydrogen-rich gas sent to the FC stack presently must be lower than 100 ppm in order not to poison the catalytic MEA and thereby avoid drastic reduction of its lifespan. Catalyst development and MEA development is under way for higher 'CO-tolerance'. Meanwhile, system start-up times of 20-30 seconds must be realised, compared to the current 6 to 20 minutes. (4) Improvement of air management Both air delivery (sub-component: air compression) and utilisation (sub- component: the fuel cell) must be improved to improve overall system efficiency, volume and weight. (5) health and safety Health and safety issues must be addressed. Specifically, the high operating temperature of gasoline-based systems is seen as problematic (ADL 2000a). The perceived risks of hydrogen are high, whilst in actual practice huge hydrogen distribution networks have operated without problems for decades. The current 'distance-to-target is summarized for a number of critical performance characteristics for Passenger Vehicles operating on Gasoline is indicated in Figure A.9.1. This serves to illustrate why MeOH-fuelled PEMFC powered AGVs present such an interesting option: • Specific Power, Power Density and Start-up to Full Power are non-critical issues for AGVs. A large weight is an advantage. • Transient response is less of an issue, as driving cycles for AGVs are considered less demanding than for passenger vehicles • In relation to noise and other emissions, cost is not so much of an issue. Energy efficiency must move from 34 to some 50% of system efficiency to achieve acceptable 'well-to-wheel' efficiency • System durability is for methanol powered vehicles is probably a much less problematic issue than in gasoline powered FC-cars. Extensive tests are underway with hydrogen and methanol fuelled cars and buses to prove durability. Apparently, there is still a durability issue in gasoline reformer catalysts that must operate around 900-1100 oC. In methanol reforming, a different catalyst can be used, and operation is around 350 oC. 276 Process System Innovation by Design Figure A.9.1: Status of 50 kW gasoline operated PEMFC development (from ADL, 2000a:3). Finally, with respect to health and safety methanol does not have the disadvantage of high-temperatures and it avoids storage of hydrogen. Compared to gasoline, health issues appear to be rather similar (Stikkelman, 2001). Summary In the petrochemical industry large-scale chemical processes are employed to convert petroleum-derived feedstock into base chemicals. Huge industrial complexes of many interconnected processes are the blue-print image of this industry, which is linked to virtually all important economic sectors such as agriculture, automobiles, construction, electronics, housing, pharma, textiles, consumer durables and packaging. The core business of this industry of industries is to transform finite resources of fossil origin into building blocks of polymers - plastics, resins, fibres. Petrochemical operations also generate by-products that can be detrimental to our health, safety and environment if emitted or wasted. In the 1960-70's, the state-of- the-art industrial practice led to the persistent label ‘Dirty, Damaging, and Dangerous’ of 'chemical industry'. Over time, however, the control and prevention of harmful emission and waste management have improved dramatically. Carbon dioxide, however, continues to be emitted because CO2 formation is linked with petrochemical process energy supply, feedstock, product and polymer degradation. To accommodate stable or modest growth in petrochemicals demand, the industry must timely respond to the prospects of fossil resource depletion and a cap on CO2 emission induced by global-warming concerns. A petrochemical industry is required that is characterised by appropriate resource selection, effective resource utilisation, the avoidance of waste and emissions and a product slate that fosters a sustainable society. How can these objectives be met? In addressing this question, one must realize that the petrochemical industry has the structure of an interconnected network. The nodes represent the processing plants, the vertices are the exchange flows of intermediate products and energy. The networked petrochemical industry has an impressive record of innovation of its industrial plants by invention and improvement of system components - e.g. catalysts, reactors, separation technology- and products enabled by fundamental and applied science. Industry maturation, however, has reduced the scope for process innovation by “inventing new flow sheets for existing problems.” Changes of its structure caused by R&D breakthroughs or by the use of extra-sector innovations have become incidental. The system structure of the industry generally has been considered fixed and the effect of most R&D on industry network structure is not planned. A literature review revealed that conceptual design of the industry structure and the specification of R&D themes for multiscale systemic industry change is a 'white spot' on the science and engineering map. The discipline of engineering science that comes closest to dealing with these issues is process system engineering. PSE has evolved as a sub discipline of chemical engineering that “is concerned with the understanding and development of systematic procedures for the design and operation of chemical process systems, ranging from microsystems to industrial scale, continuous and batch processes.” In PSE multiscale process synthesis approaches that “span a chemical supply chain -from mastering the molecules to chemical enterprises-” only have been suggested, however. 280 Process System Innovation by Design Starting from a higher level of aggregation , economy and policy studies could offer options, but these suffer from technological lack-of-content. We conjectured therefore a sustainable petrochemical industry requires process system innovation, which is defined as “change in the system structure or system design of the petrochemical industry, its industrial complexes, or individual plants. These can be enabled by technological inventions or vice versa.” In technology and systems development and in the adoption of extra-sector innovations the industry structure explicitly must be considered a degree-of-freedom. Therefore, the central theme of this thesis is the specification of system innovation content for a sustainable petrochemical industry. Systemic innovations do require a long time for development and implementation. Early identification of promising concepts thus is preferred to facilitate sustainable development at affordable and acceptable costs and to maximise the effect of R&D. Therefore, the research questions addressed in this dissertation were (1) what is a suitable method to assess the resource utilisation and the scope for improvement of the production systems in the petrochemical industry, (2) can the search of the innovation space be structured to foster the specification of process system innovation content and (3) what is the usefulness and the scope of application of the methods thus developed? These research questions have been addressed using system theory, thermodynamics, PSE and computer systems modelling. The concept of and the methodology for 'process system innovation by design' was developed, validated and tested in case studies that each span multiple system aggregate levels. In a technology-free systems representation using the input/output paradigm, any system is considered a ‘black-box’, which upon opening may consist of a structured collection of system elements or sub-systems. At each system aggregate level it is assumed that the function of a system is to generate a behaviour to transform a set of inputs into a set of outputs in order to satisfy an objective. Together, these relate the system to its external world. Its performance is assessed by means of criteria or value functions. The petrochemical industry is a system embedded and linked to the global material cycles. In a layered networked system view, its system elements are petrochemical complexes and individual plants. In chemical engineering, these plants are modelled as structured collections of unit operations connected by flows. To define indicators for sustainability, mass and energy balancing and stream valuation on the basis of input scarcity, output fate, economy and ecology were combined in criteria for system resource utilisation. In quantitative analysis these indicators yield an image of performance. Together with known plant capacities, such quantitative system assessment results in a ranking of petrochemical plants with respect to performance and scope for improvement. This ranking is a starting point for systematic search for R&D options and themes. An early revelation of our research was that inclusion of fuel cells in chemical plants would have a dramatic effect on plant performance by exploiting hitherto unrecognised fuel cell functionality, which allows efficient interconversion of chemical, electric and thermal energy. The functional description of the fuel cell as a unit operation and the subsequent recognition petrochemical plants throughout the Summary 281 industry as candidates for fuel cell integration, however, requires some suitable method for system decomposition. Functional modelling for computer system design, was related to and adapted for the technology-free petrochemical system representation using the input-output paradigm. It enables cohesive system decomposition using 'mutual contingency' as a stop-criterion, which indicates the system decomposition exhibits loose coupling and sufficient relation between the system elements. The criterion is formalised in a logical algorithm. In the multiscale modelling exercise subjective functions describe the system and parts thereof. Upon completion of a mutual contingent decomposition the functional model is built. The modelling of system functions rather than system technology provides a mechanism for abstraction from current design and physical realisation of industrial systems. Stream valuation and functional modelling were the missing links between resource utilisation assessment and the systemic exploration of the multiscale innovation space for chemical conversion and energy interconversion. In system synthesis, these links enable the specification of process system innovation content - or the formulation of primitive problems under the General Design Paradigm. The main result is a methodology for said specification that is based on system representation using the input-output paradigm and functional modelling. The use of fuel cells in the petrochemical industry leads to trigeneration systems that produce useful chemical products, electricity, and heat. Functional modelling helps to specify new trigenerate system concepts at the aggregate level of reactors, petrochemical plants and complexes, one of which was patented. Addressing innovation for the industrial olefins system showed that ongoing R&D and innovations reported can be categorised and augmented. Quantitative assessment using stream valuation allows one to focus on 'the weakest link'. Functional modelling enabled specification of a true process system innovation, the integration of olefins and syngas production from aliphatic hydrocarbons. To exploit a radical extra-sector innovation, the advent of methanol-fuelled fuel cell vehicles, process system innovations were specified around the Rotterdam petrochemical cluster, whereby the Rotterdam process industry becomes a key industrial infrastructure in methanol, olefins and platinum. The results of these case studies illustrate that the methodology fosters 'out-of-the- box' thinking at the aggregate level of unit operations, single plants, industrial complexes and clusters alike. Since quantitative evaluation of each innovation specified requires extensive work, some proxy methods for evaluation have been adopted, such as economic assessment of fuel cell reactor concepts and dynamic simulation of fuel cell vehicle adoption and its consequences for methanol and platinum. The innovation results and proxy evaluations do not constitute formal proof or validation of the methodology. It remains possible that the concepts specified could have been developed otherwise. Extensive literature research, however, did not reveal similar structured methods that link creative thinking with assessment of performance, structure and technology of existing complex systems. The methodology and concepts presented in this dissertation can be improved and extended. Qualitative tests that involve experts can be developed to further underpin the innovations specified. Thereby process system innovation can be linked to 282 Process System Innovation by Design (inter)national public policy development, regulation and corporate strategy. In the design process and PSE the relation between innovation, systems analysis, synthesis and conceptual design can be elaborated. The quantitative assessment should be extended dynamic modelling of global material cycles. A transition from chemical conversion to bio-chemical conversion would enable a global carbon-cycle that includes fossil resources, renewable bio-resources, petrochemicals, polymer waste and control of global atmospheric CO2. Thereby a bridge between industrial ecology concepts and the body-of-knowledge of process system engineering would be forged. Thus the methodology can be expanded to a portfolio of methods, procedures and tools, which allows dealing with 'wicked' environmental problems by fostering innovation for sustainability in many industries - refining, base metal, pulp and paper, agro- and food industry. The role of the petrochemical industry as 'an industry of industries' is critical to achieve sustainability. The methodology described in this dissertation can help this industry, its technology suppliers, engineering service providers and academia to specify process system innovations. In addition, the methodology can facilitate interaction between all stakeholders involved in a transition towards a sustainable society by forging a link between societal needs, business strategy and process system innovation. Samenvatting In de petrochemische industrie worden grootschalige chemische processen gebruikt voor de omzetting van aardoliegrondstoffen in basischemicaliën. Grote industriële complexen die bestaan uit veel onderling verbonden processen bepalen het beeld van deze industrie. De petrochemie heeft een relatie met bijna alle economisch belangrijke sectoren, te weten de landbouw, de automobiel industrie, de weg- en waterbouw, elektronica, woning- en utiliteitsbouw, de farmaceutische industrie, de textielindustrie, duurzame consumptiegoederen en verpakkingen. De kernactiviteit van deze industrie van industrieën is de omzetting van eindige grondstoffen van fossiele oorsprong in bouwstenen van polymeren - plastics, harsen en vezels. Petrochemische fabrieken genereren ook bijproducten die schadelijk kunnen zijn voor onze gezondheid en veiligheid en het leefmilieu wanneer ze worden uitgestoten of gestort als afval. Door de toenmalige stand der techniek en industriële praktijk verkreeg de chemische industrie in de jaren '60 en '70 het etiket 'Vies, Schadelijk en Gevaarlijk'. Dit etiket is erg hardnekkig gebleken, ondanks het sterk terugdringen van schadelijke emissies en het ontstaan van gevaarlijk afval. Echter, de emissie van koolstofdioxide, CO2, gaat onverminderd door omdat de vorming van CO2 direct gekoppeld is aan het grondstofgebruik en de energievoorziening van petrochemische installaties en een onvermijdelijk gevolg is van de uiteindelijke afbraak van organische verbindingen zoals basischemicaliën en polymeren. Om tegemoet te kunnen blijven komen aan de naar verwachting blijvende en stijgende vraag naar petrochemische producten moet de industrie tijdig maatregelen nemen. Ze zal adequaat moeten anticiperen op de uitputting van fossiele grondstoffen én op de instelling van een plafond aan de toegestane CO2 uitstoot in verband met wereldwijde zorg om klimaatverandering. Er is kortom een petrochemische industrie nodig die wordt gekenmerkt door de keuze van geschikte grondstoffen, door effectief gebruik van deze grondstoffen, door het vermijden van afval en emissies, en door een productspectrum dat helpt een duurzame samenleving te realiseren. Hoe zijn deze doelen te realiseren? Bij de beantwoording van deze vraag is het goed ons te realiseren dat de petrochemische industrie een netwerkstructuur heeft. De knopen in het netwerk zijn de petrochemische fabrieken, langs de lijnen worden tussenproducten en energie uitgewisseld. Deze genetwerkte petrochemische industrie heeft een indrukwekkende staat van dienst wat betreft procesinnovatie en productontwikkeling ondersteund door fundamenteel- en toegepast- wetenschappelijke kennis. Voor haar fabrieken worden voortdurend systeemcomponenten verbeterd en nieuwe componenten ontwikkeld zoals katalysatoren, reactoren en scheidingstechnologieën. Omdat de volwassen chemische industrie nog slechts matig groeit zijn er slechts beperkte financiële prikkels voor procesinnovatie - het vinden van nieuwe processchema's voor bestaande problemen. Fundamentele wijzigingen van haar structuur onder invloed van wetenschappelijk doorbraken of door de toepassing van innovaties van buiten de sector zijn incidenteel. De structuur van de industrie ligt in hoofdzaak vast en effecten van R&D op deze netwerkstructuur zijn meestal niet gepland. 284 Process System Innovation by Design Een literatuurstudie heeft laten zien dat conceptueel ontwerp van de industriestructuur en de specificatie van R&D die een verandering van de industrie op meerder schaalniveaus bewerkstelligt een witte vlek is op de onderzoekskaart. De technische discipline die in aanzet dit probleem aanpakt is chemisch fabrieksontwerp of 'process systems engineering' (PSE). Dit vakgebied heeft zich ontwikkeld als een subdiscipline van de scheikundige technologie en is gericht op 'het begrijpen van en de ontwikkeling van systematische procedures voor het ontwerp en de operatie van chemische voortbrengingsprocessen, van het microschaalniveau van moleculen tot de microschaal van de industrie, van continue en van ladingsgewijs bedreven processen". In PSE zijn echter tot dusver ontwerpmethoden die "een gehele chemische voortbrengingsketen omspannen - van het beheersen van moleculen tot meerdere chemiebedrijven" slechts gesuggereerd. Economisch of beleidsmatig georiënteerde studies zouden geschikte aanknopingspunten kunnen bieden omdat ze juist van dit hogere macroschaalniveau uitgaan, maar dit type studies lijdt over het algemeen aan een gebrek aan technologische inhoud. Wij postuleerden daarom dat voor een duurzame petrochemische industrie proces systeeminnovatie nodig is. Dit is gedefinieerd als "veranderingen in de systeemstructuur of het systeemontwerp van de petrochemische industrie, haar industriële complexen, of individuele fabrieken. Deze worden mogelijk gemaakt door technologische inventies en omgekeerd". In de ontwikkeling van technologie en systemen en bij het gebruik van innovaties van buiten de sector moet de industriestructuur expliciet beschouwd worden als een vrijheidsgraad. Daarom is het centrale thema van dit proefschrift de specificatie van de inhoud van systeeminnovatie voor een duurzame petrochemische industrie. Systeeminnovaties vergen een lange periode voor ontwikkeling en implementatie. Vroege identificatie heeft daarom de voorkeur om duurzame ontwikkeling mogelijk te maken tegen betaalbare en acceptabele kosten. Doel is het te verwachten effect van R&D inspanningen te maximaliseren. Daarom zijn in dit proefschrift de volgende onderzoeksvragen uitgewerkt: (1) wat is een geschikte methode om de benutting van grondstoffen en energiedragers te beoordelen en het verbeteringspotentieel vast te stellen? (2) Kan het verkennen van de innovatieruimte worden gestructureerd ter bevordering van de specificatie van systeeminnovaties? (3) wat is de gebruikswaarde en de reikwijdte van de aldus ontwikkelde methodes? Deze onderzoeksvragen zijn uitgewerkt onder gebruikmaking van systeemtheorie, thermodynamica, PSE en modellering van computer- en informatiesystemen. Het concept en de methode voor 'systeeminnovatie op recept' is ontwikkeld, gevalideerd en bewezen in een drietal case studies die elk meerdere schaalniveaus bestrijken. In een technologievrije representatie van een systeem gebruikmakend van het input/output paradigma kan elk systeem beschouwd worden als een zwarte doos, die als ze geopend wordt bestaat uit een gestructureerde verzameling systeemelementen of subsystemen. Op elk aggregatieniveau wordt aangenomen dat de systeemfunctie is 'het genereren van gedrag om een set inputs te transformeren in een set outputs en daarmee een doelstelling te bewerkstelligen'. Gezamenlijk relateren deze het systeem aan de wereld buiten het systeem. De systeemprestatie wordt beoordeeld met behulp van criteria of waardefuncties. De petrochemische industrie is een systeem dat onlosmakelijk verbonden is met wereldwijde materiaalcycli. In een gelaagde en genetwerkte systeemvisie zijn haar Samenvatting 285 systeemelementen industriecomplexen of chemische fabrieken. In de scheikundige technologie worden deze gemodelleerd als gestructureerde verzamelingen van eenheidsbewerkingen (zgn. 'unit operations') die met elkaar zijn verbonden door massa- en energiestromen. In dit proefschrift zijn indicatoren voor duurzaamheid van systemen geformuleerd door het opstellen van massa- en energiebalansen te combineren met de waardering van stromen op basis van de schaarste van grondstoffen en energiedragers, de bestemming van producten en economische en ecologische aspecten. Deze combinatie levert criteria voor grondstofbenutting van systemen waarmee in een kwantitatieve analyse de prestatie van individuele fabrieken kan worden beoordeeld. Door de resultaten te combineren met de capaciteit van fabrieken kan een rangorde naar prestatie of verbeteringspotentieel worden verkregen van alle petrochemische installaties in de industrie. De zwakste schakels vormen een startpunt voor het gestructureerd zoeken naar R&D onderwerpen en thema's. Een vroege constatering op basis van ons onderzoek was dat de integratie van brandstofcellen in chemische fabrieken een dramatische verbetering van de prestatie van de laatste kan bewerkstelligen. Dat komt omdat voorheen niet onderkende functionaliteit van de brandstofcel in een chemische fabriek kan worden benut om meer efficiënte omzetting van chemische, elektrische en thermische energie te realiseren. De functionele beschrijving van de brandstofcel als een 'unit operation' die onderdeel kan uitmaken van een chemisch procesontwerp, de integratie van de brandstofcel in het procesontwerp en de zoektocht naar kandidaat-industriële processen vroeg echter om een goede methode voor het onderverdelen van systemen in subsystemen en systeemelementen - systeemdecompositie. Het modelleren met behulp van objecten en functies - hierna functioneel modelleren - zoals ontwikkeld voor het ontwerpen van computer- en informatiesystemen is gemodificeerd en gerelateerd aan de technologievrije representatie van chemische processen onder gebruikmaking van het input-output paradigma. De zo ontwikkelde methode maakt functioneel coherente systeemdecompositie mogelijk. Daarbij wordt als stopcriterium het bereiken van 'mutual contingency' gehanteerd. Dit betekent zoveel als 'een verdeling die wordt gekarakteriseerd door een balans tussen wederkerige afhankelijkheid en voldoend onderscheidende ontkoppeling'. Dit criterium is geformaliseerd in een logisch algoritme. Tijdens het functioneel modelleren worden - subjectief - op meerder systeemniveaus functies geformuleerd die betrekking hebben op het systeem of delen daarvan. Als aan het criterium wordt voldaan, is de decompositie functioneel coherent en het model voltooid. Het modelleren van functies in plaats van de technologie van systemen biedt een mechanisme voor abstractie van bekende ontwerpen en bestaande fysieke realisatie van industriële systemen. Het waarderen van stromen en functioneel modelleren vormen de ontbrekende schakels tussen het beoordelen van grondstofbenutting/energiegebruik en de het op meerdere schaalniveaus tegelijk verkennen van de innovatieruimte voor chemische conversie en energieomzetting. In de synthese van systemen zijn het deze schakels die specificatie van de inhoud nodig voor 'systeeminnovatie op recept' mogelijk maken. Met andere woorden, de formulering van primitieve problemen in het Algemeen Ontwerp Paradigma wordt hiermee gefaciliteerd. 286 Process System Innovation by Design Het hoofdresultaat beschreven in dit proefschrift is een methodologie voor 'systeeminnovatie op recept' gebaseerd op de representatie van systemen onder het input/output paradigma en gebruik makend van functioneel modelleren. Het gebruik van brandstofcellen in de petrochemische industrie leidt tot trigeneratiesystemen die tegelijkertijd bruikbare chemische producten, elektriciteit en warmte produceren. Functioneel modelleren maakt het mogelijk om nieuwe systeemconcepten voor trigeneratie te specificeren op het systeemniveau van reactoren, fabrieken en industriecomplexen. Op een dergelijk concept is octrooi verleend. De case studie naar innovatie rond olefines heeft laten zien dat functioneel modelleren te gebruiken is voor het ordenen van lopend onderzoek en in de literatuur gerapporteerde innovaties. De kwantitatieve analyse leidde inderdaad tot de zwakste schakels in het systeem. Een echte systeeminnovatie is op recept ontwikkeld, namelijk de combinatie van synthese gas- en olefine-productie uit lineaire koolwaterstoffen. Om de chemie een radicale innovatie van buiten de sector te laten benutten - de komst van brandstofcelauto's op methanol- zijn genetwerkte systeeminnovaties ontwikkeld voor het Rotterdams petrochemisch cluster. Indien deze systeeminnovaties werkelijk worden gerealiseerd, dan wordt de Rotterdamse procesindustrie een belangrijke schakel in de industriële infrastructuur voor methanol, olefines en platina. De resulaten van de case studies laten zien dat methodologie voor 'systeeminnovatie op recept' het denken buiten bestaande kaders stimuleert cq. faciliteert, of het nu het schaal niveau van unit operations, fabrieken, industriecomplexen of industriesectoren betreft. Omdat verdere uitwerking en kwantitatieve analyse van elke innovatie op recept zeer veel werk met zich mee zou brengen, zijn een aantal methoden ontwikkeld voor evaluatie op hoofdlijnen, te weten economische analyse van brandstofcelreactoren en een dynamisch model dat markt- en technologiescenario's voor brandstofcelvoertuigen simuleert. Daarmee kunnen in een vroeg stadium de consequenties voor methanol en platina worden geïllustreerd. De gespecificeerde systeeminnovaties en de evaluaties vormen geen formeel bewijs of sluitende validatie voor de ontwikkelde methodologie. Immers, de gespecificeerde concepten zouden ook op een andere wijze kunnen worden ontwikkeld. Uitgebreide literatuurstudie heeft echter geen vergelijkbare gestructureerde methoden opgeleverd die creativiteit verbinden met prestatieanalyse en de structuur en technologie van bestaande complexe systemen. De methodologie en de concepten gepresenteerd in dit proefschrift kunnen op een aantal punten worden uitgewerkt. Kwalitatieve testprocedures dienen te worden ontwikkeld waarin experts worden geraadpleegd. Daarmee kunnen de gespecificeerde concepten verder worden onderbouwd en uitgewerkt. Ook kan zo 'systeeminnovatie op recept' gerelateerd worden aan (inter)nationale beleidsontwikkeling, regulering en de strategie van bedrijven. De relatie tussen innovatie, systeemanalyse en -ontwerp voor duurzaamheid kan verder worden uitgewerkt door de kwantitatieve analyse uit te breiden naar de wereldwijde materiaalcycli en de analyse van dynamische systemen. In het ontwerpproces en in PSE dient de relatie tussen de probleemformulering, systeemanalyse, synthese van het primitief ontwerpen en het conceptueel systeemontwerp verder uitgewerkt te worden. Een transitie van chemische conversie naar biochemische conversie zou een Samenvatting 287 wereldwijde koolstofcyclus mogelijk maken waarin optimaal gebruik wordt gemaakt van fossiele bronnen, hernieuwbare biogrondstoffen, petrochemische producten, plastic afval terwijl tegelijkertijd het atmosferisch CO2-gehalte wordt beheerst. Daardoor wordt een brug geslagen worden tussen de concepten zoals geformuleerd in industriële ecologie en de opgebouwde kennis in 'process systems engineering'. De methodologie voor 'systeeminnovatie op recept' kan zo worden uitgebouwd tot een palet van methodes, procedures en hulpmiddelen waarmee een oplossing voor de 'taaie' milieuproblemen van deze tijd dichterbij komt. Gebruik van dit palet zal helpen innovatie voor duurzaamheid tot stand te brengen in vele sectoren van de economie - olieraffinage, basismetaal, de pulp- en papierindustrie en de agro- en voedings- en genotmiddelenindustrie. De rol van de petrochemische industrie als een industrie van industrieën is cruciaal voor de verduurzaming van onze samenleving. De methodologie beschreven in dit proefschrift kan de spelers in deze industrie, haar technologie- en diensten leveranciers en universitaire onderzoekers helpen om systeeminnovaties te specificeren. Door het tot stand brengen van interactie tussen alle spelers in de kenniseconomie en door afstemming van systeeminnovaties op de strategie van bedrijven en de behoeften van de samenleving, tenslotte, zal het gebruik van de methodologie de transitie naar een meer duurzame samenleving bevorderen. Curriculum Vitae Gerhard Pieter Jan Dijkema was born in Veenhuizen, municipality Norg. He completed the Gymnasium-β in Assen at the “Dr. Nassau College” (1980) and graduated as a chemical engineer (hons.) from Twente University of Technology (1986). After his graduation he joined Shell International in the Hague. Among others, he spent 2 years on the start-up team of the NAM sour-gas-desulphurisation plant in Emmen. In 1990 he married Elly van der Gugten. Together they have two children, Jenske (1990) and Roeland (1992). In 1991 he joined Interduct, the Delft University Clean Technology Institute, where his research focused on the large-scale process industry and infrastructures for power generation and waste management. Since mid-1996 he is affiliated with the faculty of Technology, Policy and Management, section Energy and Industry. The theme of most of his education and research is the interaction between industry, government and management, with an emphasis on innovation for improved sustainability through system thinking and sound technology. A second focus is decision support for the development and transition of large-scale systems that span industry and infrastructure sectors. Since 1999 he is Academia Liaison for the local section of the American Institute of Chemical Engineers.