DOCSLIB.ORG

Designing and Process Simulation of a Single Column Crude Distillation Unit for Refineries

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Designing and Process Simulation of a Single Column Crude Distillation Unit for Refineries Imperial Journal of Interdisciplinary Research (IJIR) Vol-2, Issue-9, 2016 ISSN: 2454-1362, http://www.onlinejournal.in Designing and Process Simulation of A Single Column Crude Distillation Unit for Refineries Shalabh Sharma1 & Raman Ghosh2 1&2Department of Chemistry, ITM University Gwalior-474 001, Madhya Pradesh, India. Abstract: There is quick development in the Subsequently, refining is the starting stage in utilization and interest of unrefined petroleum in refining foul petroleum. The fractionation is done different modern fields. Thus, the cost of the petrol in a vast tower that is worked at atmospheric is ascending because of the stronger-than- pressure. The tower contains various plates where anticipated interest for petroleum items. With the hydrocarbon gasses and fluids cooperate. The accessible information, most of the distillation liquids flow down the tower and the gases up. The models used today is only steady state models. This parts that ascent most elevated in the segment work aimed at a newly designed single column before gathering are called light portions, and those distillation unit which works on both atmospheric that consolidate on the least plate are called heavy and vacuum condition. The procedure for this work portion. The extremely lightest division is refinery was firstly forming a McCabe graph for the gas, which is utilized as a fuel as a part of the theoretical stage of the column. Then based on the refinery heaters. Next in place of instability come partial Douglas equation, the relationship between fuel (utilized for making petrol), kerosene, and data variable and yield variable was contemplated. light and overwhelming gas oils lastly long After that, physical and geometrical dimensions of deposit[2]. A simulation test system for refining is CDU were calculated by Douglas 1988 method and done by Chemsep Software [3]. It consolidates the finally a design of a single column was made. Next, excellent harmony stage section model with non- a dynamic simulation of CDU in Chemsep software equilibrium column shows in one simple and was run and the element conduct of CDU model instinctive interface. They can be connected in the was mulled over taking into account the outcomes configuration of unrefined petroleum refining acquired. From the theoretical calculations, it was segment in view of the data got from a working proven that the single distillation chamber works unrefined petroleum refining section of a refinery. on both atmospheric and vacuum pressure conditions. As the conclusion says, the dynamic The crude separation process involves numerous simulation results describe the whole CDU working complex phenomena which must be controlled in and a good control strategy. Thus, this work was its best position. The input variables of rough extremely useful in comprehension dynamic refining section are typically vitality supply inputs, conduct of CDU and used to expand the product flow rates and reflux ratio, while the yield variables are the oil thing qualities, system working productivity of refining methodology which [4] additionally builds the yield of the item and execution or the plant advantage .If specifications decreases the plant setup support cost. of oil products cannot be reached, the oil supply can bring about a few issues in plant KEYWORDS: single column distillation; Douglas administration. Controlling refining section begins method; McCabe; simulation; Distillation by recognizing controlled, load variables and designing. manipulation. Controlled variables are those variables that must be kept up at a definite quality 1. Introduction to satisfy section destinations. These variables for unrefined petroleum fractionators ordinarily Crude oil distillation is the separation of the incorporate composition of product, column hydrocarbons in unrefined petroleum into parts in temperatures, column pressure and accumulator view of their boiling points. It is changed over to levels. The objective of this study is to design and petrol, diesel, kerosene, aviation turbine fuel, simulate single column distillation unit that will bitumen, refinery gas and sulphur[1]. These portions works for the distillation of crude at both are mixtures containing hydrocarbon compounds atmospheric and vacuum pressure to obtain the whose boiling points exist in a predefined extent. petroleum product shown in figure 1[5]. Imperial Journal of Interdisciplinary Research (IJIR) Page 985 Imperial Journal of Interdisciplinary Research (IJIR) Vol-2, Issue-9, 2016 ISSN: 2454-1362, http://www.onlinejournal.in Figure 1. Schematic Diagram of Crude Distillation Unit. perspective of bits of learning got from crush In recent years, the exploration of rough refining examination. Another methodology for advancing procedure was centred around the subject of existing refinery refining sectionson pinch analysis methodology control and optimization on principles based and thorough model based proposing adjustments to the refining section and [12] simulation was given by Bagajewicz .An the heat exchanger system with a specific end goal integrated approach regarding designing of the to lessen the consumption of energy. [6] crude oil distillation system was developed Sittig recommended that with a specific end goal [13] Suphanit . In this study, the shortcut distillation to enhance the proficiency of the refining model was used based on pinch analysis and a framework, new internals with higher efficiency streamlining system, to create vitality productive should be installed and recommended the use of grassroots section plan. During the past two intermediate reboilers. Bannon and Marple[7] decades, there has been a growing awareness proposed other column modifications, such as the among the educated community and mechanical installation of pump-arounds. Adding pre-flash specialists with respect to the control of unrefined drums and pre-fractionator column can save energy petroleum refining segment. After thorough Harbert[8] as can adding pump-arounds and investigation of above researchers, it could be reducing operating pressure Fraser and drawn that various approaches used by various sloley[9].Pinch analysis principles guided many scientist were not considering the existing researchers Linnloff, et al, Dhole and Buckingham distillation column with details with its huge plant [10] to identify modifications to distillation columns size which must use a capital investment without for reducing energy consumption and improving efficient material use. the performance of the system. Liebmann[11] proposed a two-step approach for improving the The extent of this study is to enhance the expense execution of refinery refining segments, in adequacy and to rearrange the refining procedure Imperial Journal of Interdisciplinary Research (IJIR) Page 986 Imperial Journal of Interdisciplinary Research (IJIR) Vol-2, Issue-9, 2016 ISSN: 2454-1362, http://www.onlinejournal.in with new CDU. A new design of CDU implies the (ii) Heat effects are negligible, and (iii) For every new process of producing various petroleum mole of vapour condensed, another mole of liquid products at reduced production cost. A part from is vaporized. The liquid and vapour leaving the tray that, the scope of this proposed study also include is in equilibrium with the vapour and liquid the study on the process and descriptions with this entering the tray. If an equilibrium curve[16] is not new CDU design which contains a single column given, draw a Y-X diagram (Y representing the that works for both atmospheric and vacuum vapour phase and X the liquid). The equilibrium distillation. Thus, another conservative model of curve can be obtained by relating the relative CDU will be produced taking into account the volatility to the composition of the liquid: consistent states CDU model. This newly designed Y = A*X/ (1+X (A-1)) model of CDU may reduce the plant size, and though reduces maintenance cost, and which saves This shows the bubble-point and dew point of a time and money on production. binary mixture at constant pressure. An equilibrium line describes the compositions of the liquid and 2. Methodology vapour in equilibrium at a fixed pressure (Figure 2). Actually this design includes a compact model of distillation unit, which contains both atmospheric and vacuum distillation process in a single column. So we need a newly designed distillation column which works for both alternatively. And though, to design a column following parameters we need to calculate: (i) The composition of distillates and feed rate; (ii) The Reflux ratio; (iii) Number of Trays; (iv) Column Height and Diameter. Determining these according to Douglas method, the column height needs the actual number of trays and which is determined through the McCabe graph by known reflux ratio and the feed rate are summarized below. 2.1. Determination of the Composition of Distillates by Assuming Feed Rate Figure 2. McCabe Equilibrium Curve Let us assume the feed rate with known The description of the figure 2 is as follows: composition, purity of distillate and bottoms, and The equilibrium line crossing the forty-five degree the quality of the feed. Performing overall material line is an indication of an azeotropic mixture. and component balances to determine the compositions of the distillate and bottoms.[14] Forty Five Degree Line: Drawing the diagonal line connecting the points (0.0,0.0) to (1.0,1.0). This is your forty-five degree line. F*ZF=XD*D+XB*B Feed Line (q-Line): The feed line can be F=D+B constructed by locating the point on the forty- five degree line that corresponds to the feed Where, F = Feed rate of input stream; ZF = composition. This point can be extended with a Composition of light component in feed; XD slope of q/(q-1) where q is the feed quality. The =Mole Fraction of light in distillate; XB =Mole feed line can be directly plotted through the Fraction of light in Bottom; D =Total distillate following equation: amount; B =Total bottom amount. This number of composition signifies the number of light and Y = q/ (q-1)X - ZF/(q-1) heavy distillates to be obtained from the feed, and Upper Operating Line: Draw the operating line for as when the composition is known, and then the the enriching section.
Load more

Recommended publications
  • Distillation 6
    CHAPTER Energy Considerations in Distillation 6 Megan Jobson School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, UK CHAPTER OUTLINE 6.1 Introduction to energy efficiency ....................................................................... 226 6.1.1 Energy efficiency: technical issues................................................... 227 6.1.1.1 Heating.................................................................................... 227 6.1.1.2 Coolingdabove ambient temperatures...................................... 229 6.1.1.3 Coolingdbelow ambient temperatures ...................................... 230 6.1.1.4 Mechanical or electrical power.................................................. 232 6.1.1.5 Summarydtechnical aspects of energy efficiency ..................... 233 6.1.2 Energy efficiency: process economics............................................... 233 6.1.2.1 Heating.................................................................................... 233 6.1.2.2 Cooling..................................................................................... 235 6.1.2.3 Summarydprocess economics and energy efficiency ............... 237 6.1.3 Energy efficiency: sustainable industrial development........................ 237 6.2 Energy-efficient distillation ............................................................................... 237 6.2.1 Energy-efficient distillation: conceptual design of simple columns...... 238 6.2.1.1 Degrees of freedom in design ..................................................
    [Show full text]
  • Review of Extractive Distillation. Process Design, Operation
    Review of Extractive Distillation. Process design, operation optimization and control Vincent Gerbaud, Ivonne Rodríguez-Donis, Laszlo Hegely, Péter Láng, Ferenc Dénes, Xinqiang You To cite this version: Vincent Gerbaud, Ivonne Rodríguez-Donis, Laszlo Hegely, Péter Láng, Ferenc Dénes, et al.. Review of Extractive Distillation. Process design, operation optimization and control. Chemical Engineering Research and Design, Elsevier, 2019, 141, pp.229-271. 10.1016/j.cherd.2018.09.020. hal-02161920 HAL Id: hal-02161920 https://hal.archives-ouvertes.fr/hal-02161920 Submitted on 21 Jun 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Open Archive Toulouse Archive Ouverte OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible This is an author’s version published in: http://oatao.univ-toulouse.fr/239894 Official URL: https://doi.org/10.1016/j.cherd.2018.09.020 To cite this version: Gerbaud, Vincent and Rodríguez-Donis, Ivonne and Hegely, Laszlo and Láng, Péter and Dénes, Ferenc and You, Xinqiang Review of Extractive Distillation. Process design, operation optimization and control. (2018) Chemical Engineering Research and Design, 141.
    [Show full text]
  • Distillation Theory
    Chapter 2 Distillation Theory by Ivar J. Halvorsen and Sigurd Skogestad Norwegian University of Science and Technology Department of Chemical Engineering 7491 Trondheim, Norway This is a revised version of an article published in the Encyclopedia of Separation Science by Aca- demic Press Ltd. (2000). The article gives some of the basics of distillation theory and its purpose is to provide basic understanding and some tools for simple hand calculations of distillation col- umns. The methods presented here can be used to obtain simple estimates and to check more rigorous computations. NTNU Dr. ing. Thesis 2001:43 Ivar J. Halvorsen 28 2.1 Introduction Distillation is a very old separation technology for separating liquid mixtures that can be traced back to the chemists in Alexandria in the first century A.D. Today distillation is the most important industrial separation technology. It is particu- larly well suited for high purity separations since any degree of separation can be obtained with a fixed energy consumption by increasing the number of equilib- rium stages. To describe the degree of separation between two components in a column or in a column section, we introduce the separation factor: ()⁄ xL xH S = ------------------------T (2.1) ()x ⁄ x L H B where x denotes mole fraction of a component, subscript L denotes light compo- nent, H heavy component, T denotes the top of the section, and B the bottom. It is relatively straightforward to derive models of distillation columns based on almost any degree of detail, and also to use such models to simulate the behaviour on a computer.
    [Show full text]
  • Distillation ­ Accessscience from Mcgraw­Hill Education
    6/19/2017 Distillation ­ AccessScience from McGraw­Hill Education (http://www.accessscience.com/) Distillation Article by: King, C. Judson University of California, Berkeley, California. Last updated: 2014 DOI: https://doi.org/10.1036/1097­8542.201100 (https://doi.org/10.1036/1097­8542.201100) Content Hide Simple distillations Fractional distillation Vapor­liquid equilibria Distillation pressure Molecular distillation Extractive and azeotropic distillation Enhancing energy efficiency Computational methods Stage efficiency Links to Primary Literature Additional Readings A method for separating homogeneous mixtures based upon equilibration of liquid and vapor phases. Substances that differ in volatility appear in different proportions in vapor and liquid phases at equilibrium with one another. Thus, vaporizing part of a volatile liquid produces vapor and liquid products that differ in composition. This outcome constitutes a separation among the components in the original liquid. Through appropriate configurations of repeated vapor­liquid contactings, the degree of separation among components differing in volatility can be increased manyfold. See also: Phase equilibrium (/content/phase­equilibrium/505500) Distillation is by far the most common method of separation in the petroleum, natural gas, and petrochemical industries. Its many applications in other industries include air fractionation, solvent recovery and recycling, separation of light isotopes such as hydrogen and deuterium, and production of alcoholic beverages, flavors, fatty acids, and food oils. Simple distillations The two most elementary forms of distillation are a continuous equilibrium distillation and a simple batch distillation (Fig. 1). http://www.accessscience.com/content/distillation/201100 1/10 6/19/2017 Distillation ­ AccessScience from McGraw­Hill Education Fig. 1 Simple distillations. (a) Continuous equilibrium distillation.
    [Show full text]
  • Computer Simulation Applied to Studying Continuous Spirit Distillation and Product Quality Control
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Food Control 22 (2011) 1592e1603 Contents lists available at ScienceDirect Food Control journal homepage: www.elsevier.com/locate/foodcont Computer simulation applied to studying continuous spirit distillation and product quality control Fabio R.M. Batista, Antonio J.A. Meirelles* Laboratory EXTRAE, Department of Food Engineering, Faculty of Food Engineering, University of Campinas e UNICAMP, Campinas, Brazil article info abstract Article history: This work aims to study continuous spirit distillation by computational simulation, presenting some Received 7 June 2010 strategies of process control to regulate the volatile content. The commercial simulator Aspen (Plus and Received in revised form dynamics) was selected. A standard solution containing ethanol, water and 10 minor components rep- 2 March 2011 resented the wine to be distilled. A careful investigation of the vaporeliquid equilibrium was performed Accepted 8 March 2011 for the simulation of two different industrial plants. The simulation procedure was validated against experimental results collected from an industrial plant for bioethanol distillation. The simulations were Keywords: conducted with and without the presence of a degassing system, in order to evaluate the efficiency of Spirits fi Distillation this system in the control of the volatile content. To improve the ef ciency of the degassing system, fl Simulation a control loop based on a feedback controller was developed. The results showed that re ux ratio and Aspen Plus product flow rate have an important influence on the spirit composition. High reflux ratios and spirit Degassing flow rates allow for better control of spirit contamination.
    [Show full text]
  • Distillation Technology and Modelling Techniques
    ● DISTILLATION Distillation Technology and Modelling Techniques Commercial distillations Part 1: Concepts in Distillation Instead of the single-stage batch pot still described above, commercial In this review of distillation technology and modelling distillations are typically performed in a continuous manner, with multiple techniques, Konrad Miller and Katherine Shing offer a pot still equivalents (or ‘stages’) used broad survey of the science of distillation, including a to increase separation power. Consider conceptual framework of distillation; distillation column the set-up in Figure 1. Three pot stills are connected in a series of stages; components and, in part two, shortcut distillation design where the vapour from one stage rises methods such as the McCabe Thiele method and the and intermingles with the liquid in the stage above it, and liquid from a stage Fenske Underwood Gilliland algorithm. In part three, drains down to intermingle with the Konrad Miller will apply these principles to the production vapour in the stage below it. Since a series of connected pot processes of a modern brandy distillery. stills is an ineffi cient and needlessly complex design, distillation columns hat is distillation? Think back to water, so imagine your parents were are used industrially to achieve the Wyour childhood, when you fi rst boiling wine for a sauce. Water boils at same results. The internals of a distil- observed a pan of boiling water: you 100°C, but ethyl alcohol (the alcohol in lation column are comprised of a se- watched water vapour rise from the the wine) boils at 78.4°C. The liquid no ries of ‘plates’ or ‘trays’, each of which liquid surface at a temperature of ap- longer boiled at 100°C, but now some- allows for the thorough mixing of proximately 100°C (212°F).
    [Show full text]
  • Design of Batch Distillation Columns Using Short-Cut Method at Constant Reflux
    Hindawi Publishing Corporation Journal of Engineering Volume 2013, Article ID 685969, 14 pages http://dx.doi.org/10.1155/2013/685969 Research Article Design of Batch Distillation Columns Using Short-Cut Method at Constant Reflux Asteria Narvaez-Garcia,1 Jose del Carmen Zavala-Loria,2 Luis Enrique Vilchis-Bravo,1 and Jose Antonio Rocha-Uribe1 1 Universidad Autonoma de Yucatan, (UADY), Periferico Norte km 33.5, 97203 Merida, YUC, Mexico 2 Universidad Autonoma del Carmen, (UNACAR), Calle 56 No. 4, Colonia Benito Juarez, 24180 Ciudad del Carmen, CAM, Mexico Correspondence should be addressed to Jose Antonio Rocha-Uribe; [email protected] Received 17 December 2012; Revised 12 March 2013; Accepted 20 March 2013 Academic Editor: M. Angela Meireles Copyright © 2013 Asteria Narvaez-Garcia et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A short-cut method for batch distillation columns working at constant reflux was applied to solve a problem of four components that needed to be separated and purified to a mole fraction of 0.97 or better. Distillation columns with 10, 20, 30, 40, and 50 theoretical stages were used; reflux ratio was varied between 2 and 20. Three quality indexes were used and compared: Luyben’s capacity factor, total annual cost, and annual profit. The best combinations of theoretical stages and reflux ratio were obtained for each method. It was found that the best combinations always required reflux ratios close to the minimum.
    [Show full text]
  • Optimization and Dynamics of Distillation Column Using Aspen Plus®
    Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 148 ( 2016 ) 978 – 984 4th International Conference on Process Engineering and Advanced Materials Optimization and Dynamics of Distillation Column using Aspen Plus® Syed A. Taqvia , Lemma Dendena Tufaa,*, Shuhaimi Muhadizira aChemical Engineering Department, Universiti Teknologi Petronas, 32610 Bandar Seri Iskandar, Perak Darul Ridzuan, Malaysia Abstract Ever increasing global energy demand necessitates the need to enhance energy generation and efficient utilization. As energy prices continue to rise, energy conservation is the prime concern for every industry. Distillation is probably the most studied unit operation in terms of optimization and control. Since distillation columns are major energy-intensive units in chemical plants and given the recent increase in fuel cost, the plant engineers are obliged to find better operating strategies and control systems. One of the significant sections that can be worked upon is finding the optimum feed tray locations of distillation columns. The energy consumptions during distillation can have a strong impact on overall profitability. Hence, the optimization of a column is aimed towards greater production and an increase in quality. Since a column is multivariable system, disturbance in any parameter can affect the overall performance as well as production loss. This paper shows how an acetone manufacturing process can be conveniently simulated first to get temperature, pressure and composition profile followed by application of optimization techniques to enhance performance. It was performed by the means of using a simulator Aspen Plus®. Rebolier heat duty (MW) and minimum reflux ratio were successfully optimized by manipulating feed stage location and number of stages respectively.
    [Show full text]
  • Workshop 12: Instruction Sequence
    Materials for Participants – Module Instruction Sequence and Problem Statements by Core Course Workshop 12 “Simulators for Design Across the Curriculum” ASEE Summer School, Colorado, August 2002 Workshop Leaders: Daniel R. Lewin (DRL), Dept. of Chemical Engineering, Technion. Warren D. Seider (WDS), Dept. of Chemical Engineering, Penn. Workshop Objective: During the senior year design project, teams of students carry out an integrated process design, determining its technical, environmental, safety, and economic feasibility. Due to the problem scale, this inevitably involves the use of a process simulator to formulate and solve the material and energy balances, with phase and chemical equilibria and chemical kinetics, for cost estimation and economic evaluation. The availability of a reliable process model allows the design team to assess rapidly the economic potential for alternative designs, as well as to derive operating conditions using optimization methods that incorporate economics. To ensure that students are prepared to meet the challenges of the design project, they should be prepared for the competent and critical use of the process simulators. This is best achieved by a gradual exposure to aspects of their use through various exercises in the core courses. This workshop, which is intended for chemical engineering faculty, shows one way to achieve this objective. Contents: This document is an assembly of: (1) suggested instruction sequences, using the multimedia CD-ROM (Using Process Simulators in Chemical Engineering: A Multimedia Guide for the Core Curriculum), henceforth referred to as the multimedia, and (2) problem statements and solutions for class exercises and projects using process simulators to support many of the chemical engineering core courses.
    [Show full text]
  • Batch Processing
    4 Batch Distillation CONTENTS 4.1 Early Theoretical Analysis ........................................... 43 4.1.1 Simple Distillation ............................................. 45 4.1.2Copyrighted Operating Modes ............................................... 46 4.2 Hierarchy of Models .................................................. 53 4.2.1 Rigorous Model ................................................ 53 4.2.2 Low Holdup Semirigorous Model .............................. 53 4.3 Shortcut Model ........................................................ 55 4.4 Optimization and Optimal Control ................................... 58 4.5 Complex Systems ...................................................... 59 4.5.1 Azeotropic Distillation ......................................... 60 4.5.2 Reactive DistillationMaterial........................................... 61 4.6 Computer Aided Design Software ..................................... 62 4.7 Summary .............................................................. 63 Notations .............................................................. 63 - Batch distillation1 is the oldest separation processTaylor and the most widely used unit operation in pharmaceutical and specialty chemical industries. The most outstanding feature of batch distillation is its flexibility. This flexibility allows one to deal with uncertainties in feed stock or product specification. In the distillation process, it is assumed that the vapor& formed within a short pe- riod is in thermodynamic equilibrium with the liquid.
    [Show full text]
  • Batch Distillation Ki-Joo Kim Postdoctoral Researcher, Systems Analysis Branch, U.S
    DK3017_C005.fm Page 107 Wednesday, April 27, 2005 9:24 AM 5 Batch Distillation Ki-Joo Kim Postdoctoral Researcher, Systems Analysis Branch, U.S. Environmental Protection Agency, Cincinnati, OH ([email protected]) Urmila Diwekar Professor, BioEngineering, Chemical, and Industrial Engineering, University of Illinois, Chicago ([email protected]) CONTENTS 5.1 Introduction..............................................................................................108 5.2 Early Theoretical Analysis ......................................................................112 5.2.1 Simple Distillation.......................................................................112 5.2.2 Operating Modes .........................................................................114 5.2.2.1 McCabe–Thiele Graphical Method .............................114 5.2.2.2 Constant Reflux Mode .................................................115 5.2.2.3 Variable Reflux Mode..................................................117 5.2.2.4 Optimal Reflux Mode ..................................................118 5.3 Hierarchy of Models................................................................................120 5.3.1 Rigorous Model...........................................................................121 5.3.2 Low Holdup Semirigorous Model ..............................................124 5.3.3 Shortcut Model and Feasibility Considerations..........................125 5.3.4 Collocation-Based Models ..........................................................127 5.3.5 Model
    [Show full text]
  • Design Concept of Crude Oil Distillation Column Design
    2/16/2015 NPTEL :: Chemical Engineering ­ Petroleum Refinery Engineering Design concept of crude oil distillation column design. Distillation Column Design The design of a distillation can be divided in the following steps. Specify the degree of separation:­ Set product specification. Select the operating conditions:­ Operating pressure. Determine the stage and reflux requirement:­ The number of equilibrium stages. Select type of contacting device:­ Plates or packing. Size the column:­ Diameter, number of real stages. Design the column internals:­ Plates,Distributors,Packing Supports etc. Mechanical design:­ Vessel and Internal fittings. Arrangement of Towers Three types of arrangements ( How heat is removed) 1. Top Tray Reflux : Reflux is only at top tray only Reflux is cooled and sent into the Tower. Heat input: Through Tower bottom. Removal: at the top. Thus requires large tower diameter. Improper reflux and poor quality of fraction. Economic utilization of heat is not possible. 2. Pump back reflux. 3. Pump around Reflux. data:text/html;charset=utf­8,%3Ctable%20width%3D%2280%25%22%20border%3D%220%22%20align%3D%22center%22%20cellpadding%3D%220%22%… 1/24 2/16/2015 NPTEL :: Chemical Engineering ­ Petroleum Refinery Engineering Fig:2.25 Vacuum Distillation Unit Overview [7] Pump back Reflux: Reflux is provided at regular intervals. This helps every plate to act as a true fractionator.( because there is always good amount of liquid). Tower is uniformly loaded, hence uniform and lesser diameter tower will do. Heat from external refluc can be utilised as it is at progressively higher temperatures. However design of such tower is costly, but provides excellet service.
    [Show full text]