5 • • CH CH+ H + + 26 24 2 26 3 2 4 C H CH C H CH Next Generation Steam Cracking Reactor Concept Marco van Goethem Next Generation Steam Cracking Reactor Concept Next Generation Steam Cracking Reactor Concept PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof. ir. K.C.A.M. Luyben, voorzitter van het College voor Promoties, in het openbaar te verdedigen op dinsdag 23 november 2010 om 15:00 uur door Marco Willie Marie VAN GOETHEM chemisch ingenieur geboren te Terneuzen. Dit proefschrift is goedgekeurd door de promotoren: Prof. ir. J. Grievink Prof. dr. J.A. Moulijn Copromotor: Dr. ir. P.J.T. Verheijen Samenstelling promotiecommissie: RectorMagnificus voorzitter Prof. ir. J. Grievink Technische Universiteit Delft, promotor Prof. dr. J.A. Moulijn Technische Universiteit Delft, promotor Dr. ir. P.J.T. Verheijen Technische Universiteit Delft, copromotor Prof.dr.G.B.Marin UniversiteitGent Prof. dr. ir. A.I. Stankiewicz Technische Universiteit Delft Prof.dr.E.Ranzi PolitecnicodiMilano Ir.S.Barendregt Technip,adviseur Prof. dr. M.T. Kreutzer Technische Universiteit Delft, reservelid Copyright c 2010 by M.W.M. van Goethem All rights reserved. No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without the prior permission of the author. isbn 978-90-8570-695-3 Author email: [email protected] He has made everything beautiful in its time. He has also set eternity in the hearts of men; yet they cannot fathom what God has done from beginning to end. (Ecc. 3:11) God heeft alles wat er is de goede plaats in de tijd gegeven, en ook heeft hij de mens inzicht in de tijd gegeven. Toch kan de mens het werk van God niet van begin tot eind door- gronden. (Pred. 3:11) Be warned, my son, of anything in addition to them. Of making many books there is no end, and much study wearies the body. Now all has been heard; here is the conclu- sion of the matter: Fear God and keep his commandments, for this is the whole duty of man. (Ecc. 12:12-13a) En tot slot, mijn zoon, nog deze waarschu- wing: er komt geen einde aan het aantal boe- ken dat geschreven wordt, en veel lezen mat het lichaam af. Alles wat je hebt gehoord komt hierop neer: heb ontzag voor God en leef zijn geboden na. (Pred. 12:12-13a) Preface The work in front of you was initiated in the year 1998. In this year I received my Master of Science degree, which is the most logical moment to start with a PhD position. I already received a job offer from Technip Benelux B.V. (at that time KTI). In that same year my wife and I would get married and she would start her study at the college university in Rotterdam. The decision to take the job offer was clearly a reflected of my wish to start a family. My job at Technip was a continuation of my master’s project, to develop an equation-based version of the SPYRO R program, which I claimed to be feasible. Together with several colleagues, under the guidance of Dr. Cor van Leeuwen (past away in 1999) the first version of this new program was created. During the annual performance evaluation I always mentioned my desire to do a PhD. Technip Benelux B.V. has an innovative working environment and exploratory research opportunities come along from time to time. This resulted mid 2001 in an invitation from my manager Simon Barendregt to write a research proposal for a PhD project. In July 2003 I started my research to the “next generation steam cracking process” in the Process System Engineering group at Technical University of Delft under the supervision of Johan Grievink, Peter Verheijen and Jacob Moulijn. The research project had to be combined with my regular work at Technip, for four years I could spend two days per week on my PhD work. The challenge for my supervisors was to get me out of the engineering mindset and push me into the scientific mindset. This scientific working environment was a necessary prerequisite to obtain a deep understanding in the fundamentals of the steam cracking reactor. The partitioning of work was in the first couple of years not an issue but as my carrier progressed I had to execute higher priority project at Technip. This resulted in a delay of one and a half year. At the end of 2008 I had completed all my scientific work, which is described in four articles. After playing around with the phenomena patients I got the approval for the defence of my PhD thesis, early 2010. Now my work is completed, I can state that the final i ii PREFACE outcome of my research project fills me with pride. At this point in time, I wish to express my gratitude to all the people who have contributed to this thesis. Firstly, I would like to thank Simon Barendregt for making this research project possible and his support during all these years. Secondly, I am indebted to Johan Grievink for improving my abstract thinking and his effort to complete this thesis. I am grateful to Jacob Moulijn for showing the importance of the broad outlines. Special thanks for Peter Verheijen who encouraged me to seek my boundaries and beyond. Also his critical remarks and scientific awareness are very much appreciated. Thirdly, I would like to thank all my colleagues at Technip Benelux B.V. and students at the Delft University of Technology, all of whom supported me during my research period. Special thanks to all my family and friends for their interest in my research work. Finally, I thank my lovely wife Karin for her love, support and above all her patients to endure my long times behind my laptop. Also my children, Lo¨ıs, Jonas and Levi, I want to thank them for their sympathy when I was working instead of playing, irrespective of their understanding of my activities. Delft, Marco van Goethem August 2010 Summary Next generation steam cracking reactor concept The steam cracking process is an important asset in the hydrocarbon processing industry. The main products are lower olefins (ethylene, propylene, butylenes) and hydrogen, with ethylene being the world’s largest volume organic chemical at a worldwide capacity of ≈120 million tonnes per year. Feed stocks are hydrocarbons (C2+) such as: ethane, LPG, naphtha’s, gas condensates and gas oil. The olefin yield is predominantly determined by the steam cracking furnaces. These are retrofits of common heating furnaces made capable of adding a large energy flux at high temperature levels to drive endothermal cracking reactions. Evolutionary design has led to the current state-of-the-art cracking furnaces. The steam cracking technology has developed from an empirical approach to de- sign and operations to a deep, model-based understanding. Models can predict what is happening in the cracking coils and the resulting olefin yields, given the feed conditions, the coil configuration and incoming heat fluxes. Due to extensive optimisation of design and operation, current steam cracking has become “ma- ture”. Yet, a clear insight is lacking how far current olefin yields are removed from the theoretical maximum according to fundamental mechanisms. Finding a significant potential for yield improvement would justify a step-out in cracking reactor technology. Identifying such a potential is the main driver for this thesis research. The approach taken is to explore and exploit the fundamental opportu- nities the chemistry “offers” instead of taking the more restrictive view of what the current equipment is “capable of” or “limiting to”. The research goal is to search for the intrinsic optimal steam cracking reac- tion conditions, pushing the olefin yields to the maximum that the fundamental reaction kinetic models allow for. Such optimal conditions can serve as targets for developing a next generation steam cracking reactor. This search is based on iii iv SUMMARY mathematical modelling and optimisation, needed prior to any expensive experi- mental validation. To get to that goal we have: First Identified alternative process concepts published in the literature and as- sessed against a set of ideal performance requirements; Second Developed the concepts and software for an equation based modelling tool suitable for optimisation of large scale reaction kinetic models; Third Developed a modelling strategy for olefins yield optimisation capable of embedding fundamental kinetic models into a model of a new reactor con- cept for homogeneous reactions with distributed feed allocation and macro- mixing; Fourth Applied the optimisation tool to the reactor concept model and an ad- vanced reaction kinetic model for steam cracking, SPYRO R , for a model- based synthesis of optimal reaction conditions for maximum olefin yields, covering a wider range of operating conditions than currently feasible. First we have reviewed alternative process concepts from literature for the production of ethylene on industrial scale. These alternative process concepts are assessed on their compliance with a new set of ideal (performance) requirements. The features of an ideal process involve a maximum olefin yield, no remains of energy carriers or auxiliary chemicals in the product, minimal ecological impact, minimum energy input per unit product, high availability, and a low degree of complexity of the reaction section. It appears that specific energy requirements of the processes are poorly reported in the available literature. Therefore, these requirements are systematically determined from simulations with Aspen Plus software and the aid of SPYRO R for an ethylene plant with a fixed ethane feed.