1 0 w0 Chemical Reaction 6.f 2 2 0 3- Engineering—Plenary Lectures 8 9 1 k- b 1/ 2 0 1 0. 1 oi: d 3 | 8 9 1 8, 2 y ul J e: at D n o ati c bli u P 1 0 0 w 6.f 2 2 0 3- 8 9 1 k- b 1/ 2 0 1 0. 1 oi: d 3 | 8 9 1 8, 2 y ul J e: at D n o ati c bli u P Chemical Reaction Engineering—Plenary Lectures James Wei, EDITOR Massachusetts Institute of Technology Christos Georgakis, EDITOR 1 0 0 w Massachusetts Institute of Technology 6.f 2 2 0 3- 8 9 1 k- b 1/ 2 0 1 Based on the 7th 0. 1 oi: 3 | d International Symposium 8 9 1 8, on Chemical Reaction Engineering 2 y ul J e: in Boston, Massachusetts, at D n atio October 4-6, 1982 c bli u P 226 ACS SYMPOSIUM SERIES AMERICAN CHEMICAL SOCIETY WASHINGTON, D.C. 1983 Library of Congress Cataloging in Publication Data International Symposium on Chemical Reaction Engineering (7th: 1982: Boston, Mass.) Chemical reaction engineering—plenary lectures. 1 0 (ACS symposium series, ISSN 0097-6156; 226) 0 w 6.f Includes bibliographies and index. 22 1. Chemical engineering—Congresses. 2. Chemical 3-0 reactions—Congresses. I. Wei, James, 1930- 8 II. Georgakis, Christos, 1947- . III. Series. 9 1 k- TP5.I67 1982a 660.2'99 83-11876 1/b ISBN 0-8412-0793-3 2 0 1 0. 1 oi: d 3 | 8 9 1 8, 2 y ul J e: at D n o cati Copyright © 1983 bli u American Chemical Society P All Rights Reserved. The appearance of the code at the bottom of the first page of each article in this volume indicates the copyright owner's consent that reprographic copies of the article may be made for personal or internal use or for the personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay the stated per copy fee through the Copyright Clearance Center, Inc. for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. 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PRINTED IN THE UNITED STATES OF AMERICA ACS Symposium Series 1 0 0 w 6.f M. Joan Comstock, Series Editor 2 2 0 3- 8 9 1 k- b 1/ 2 0 Advisory Board 1 0. 1 oi: David L. Allara Robert Ory d 3 | 98 Robert Baker Geoffrey D. Parfitt 1 8, 2 y Donald D. Dollberg Theodore Provder ul J ate: Brian M. Harney Charles N. Satterfield D n atio W. Jeffrey Howe Dennis Schuetzle c bli Pu Herbert D. Kaesz Davis L. Temple, Jr. Marvin Margoshes Charles S. Tuesday Donald E. Moreland C. Grant Willson 1 0 0 w 6.f FOREWORD 2 2 0 3- 8 9 The ACS SYMPOSIUM SERIES was founded in 1974 to provide 1 k- a medium for publishing symposia quickly in book form. The b 21/ format of the Series parallels that of the continuing ADVANCES 0 0.1 IN CHEMISTRY SERIES except that in order to save time the 1 oi: papers are not typeset but are reproduced as they are sub 3 | d mitted by the authors in camera-ready form. Papers are re 8 viewed under the supervision of the Editors with the assistance 9 1 8, of the Series Advisory Board and are selected to maintain the 2 y integrity of the symposia; however, verbatim reproductions of ul e: J previously published papers are not accepted. Both reviews at and reports of research are acceptable since symposia may D n embrace both types of presentation. o ati c bli u P PREFACE 01 IN THE NARROW SENSE, CHEMICAL REACTION ENGINEERING (CRE) is 0 pr concerned with the design, operation, optimization, and control of process 6. 2 ing equipment called chemical reactors. CRE is the counterpart to unit 2 0 3- operations (UO), which is concerned with processing equipment in which 8 19 no chemical reactions take place. Both chemical reaction engineering and k- b unit operations integrate many disciplines to attain practical engineering 1/ 02 goals. They differ from the engineering science subjects of kinetics, thermo 1 0. dynamics, fluid mechanics, and transport phenomena that seek to isolate 1 oi: and analyze an individual aspect of a complex piece of machinery or to d 3 | understand and describe quantitatively the material behavior at micro 8 9 scopic or molecular scales. 1 28, The main difference between chemical reaction engineering and unit y ul operations lies in the presence or absence of chemical reactions. Except J e: for purely separational processes, such as the production of oxygen from at D air, the heart of any chemical process is one or more chemical reactions n atio that transform less valuable feed material to more valuable products. In blic the case of combustion, the main products are heat and energy rather than Pu material products. In the case of pollution control equipment, the conver sion of a harmful feed to harmless products is the main objective. Chemical reactors lie in the heart of any chemical plant, and the unit operations equipment serves the needs or compensates for the inadequacies of the chemical reactors. The design of a chemical plant must start with the chemical reactors, which usually run 10-20% of the total plant cost. When you look over the flowchart of a process, you will find the chemical reactor as a small unit in a very large network; yet, the design of all other equip ment revolves around the chemical reactors. The optimum design of a chemical reactor does not necessarily lead to the optimum design of a chemical plant. The peripheral equipment of unit operations (the tail) usually wags the chemical reactors (the dog). A good design engineer chooses the dog that has the smallest tail. ix In a comparison of the salient features, the following may be noted: Chemical Reactors Unit Operations Function Chemical reactions Physical operations needed to service the reactors Design Individually tailored Modular; often can be for each reaction ordered from catalogs Cost 10-20% of total plant 80-90% of total plant Performance Highly nonlinear due to Nearly linear kinetic dependence on 1 0 0 temperature and concen­ pr 6. trations 2 2 0 3- Intellectual Chemists and chemical Mechanical engineers 8 9 1 Collaborators engineers k- b 1/ 2 0 1 0. 1 oi: In the broader sense, chemical reaction engineering is also concerned 3 | d with the components needed for the synthesis of chemical reactors, such as 8 kinetics, catalysis, catalyst design, mixing, multiphase systems, fluid me­ 9 1 8, chanics and transport in fixed and fluidized beds, and solid movement 2 y mechanics in moving and fluidized beds. Study of the maldistribution of gas ul e: J and liquid flow in trickle beds can be considered as a branch of fluid at mechanics, but this subject is very seldom studied by the major researchers D n in fluid mechanics. However, it is a subject that is studied by major re­ o ati searchers in reaction engineering. On the other hand, paper-making c bli machines would seem to be very suitable subjects for reaction engineers, u P but are hardly ever studied. Polymerization reactors are enormously impor­ tant in the chemical industries and are beginning to attract serious re­ searchers with backgrounds in reaction engineering. Reaction engineers form a living and changing tribe that keeps in touch through professional meetings and journals. They share a common set of textbooks and tools, the same vocabulary and analytical scheme to analyze problems, and the same set of triumphant classic achievements in the past. They agree on what are proper problems to be tackled and what are proper standards for admissible reports and papers. In short, they form a paradigm of their own. New people are constantly recruited by this tribe through the process of apprenticeship and junior partnership, or by adoption into this tribe of brilliant outsiders with brand new ideas. Whatever is accomplished by a member of this tribe will be shared with the rest of the members and is by definition chemical reaction engineering. χ In this volume, we print the six plenary speeches given at the 7th Inter national Symposium on Chemical Reaction Engineering at Boston. First, the intellectual foundation of chemical reaction engineering is described by Aris, and second, the study of alternative reactors for the methanol-to- gasoline process is described by Penick. These two chapters form a powerful contrast between the academic intellectual approach and the industrial pragmatic approach. Fluidized beds are reviewed by Rowe, and fluidized- bed combustors are reviewed by Sarofim. These two chapters are concerned with one of the most powerful reactors, in which scale up by design engi neers is still done with great trepidation, and one of its most important future applications. If fluidized-bed combustors for coal are well engi neered, there will be little demand for clean synthetic fuels, except for liquid fuels for transportation. Combustion should have been one of the 1 0 0 most central problems in reaction engineering. Only historical events decree pr 6. that it should be a meeting ground of chemical engineers, mechanical engi 2 2 0 neers, and chemists with their own Combustion Institute and highly suc 3- 98 cessful International Symposium series. It is overdue for us to build bridges 1 k- to these outstanding people. Micromixing is reviewed by Villermaux, and b 1/ polymerization reactors are reviewed by Ray. These two chapters are con 2 0 1 cerned with homogeneous phase and nearly homogeneous phase reactors 0. oi: 1 that are of growing importance. Most textbooks of reaction engineering have d rather short sections on polymerization, a subject found more often in 83 | polymer textbooks. These reviews will go a long way toward remedying 9 1 8, this defect. 2 y The plenaries serve as a powerful centralizing force among reaction ul e: J engineers, who are always in danger of moving off in their own individual Dat rivulets and drying out. These plenaries should be read by all students of on chemical reaction engineering, whatever their subspecialty. They augment cati the basic textbooks as part of "what every educated reaction engineer ubli should know." P JAMES WEI Massachusetts Institute of Technology Cambridge, MA October 22, 1982 xi 1 Chemical Reaction Engineering as an Intellectual Discipline R. ARIS University of Minnesota, Department of Chemical Engineering and Materials Science, Minneapolis, MN 55455 1 0 What, you are entitled to ask, do you mean by an intellectual 0 ch discipline? Before attempting any formal answer, let me turn to 26. two of the traditional disciplines and try to sketch some of the 2 3-0 characteristics that they may have or induce in their adepts. 8 I take my text from the advice given to President Gilman, the 9 1 k- first of the Johns Hopkins University, to start with the best 1/b classical scholar and the best mathematician that he could find. 02 The latter was none other than the great James Joseph Sylvester, 1 0. retired from Woolwich since 1870 and spending his time in the 1 oi: enjoyment of the classics, playing chess and versification on the d principles of his "Laws of Verse"—a pamphlet by which he set great 83 | store. With his appointment to Hopkins at the age of 62 there came 9 1 the second flowering of his genius and with it his exploration of 28, the fundamental system of invariants and the syzygies of algebraic uly forms. J e: Sylvester's career had not been an easy one ÇL) . After his at studies at Cambridge had been interrupted by illness he took his D n degree in 1837 as Second Wrangler in the same class as George o ati Green. To say that he took his degree is not quite accurate, for c bli Sylvester, who says of himself that he was one of the first Pu holding "the faith in which the founder of Christianity was educated" to compete for the mathematical tripos, could not com plete his degree without subscribing to the 39 Articles of the Church of England—a subscription he was unwilling to make. He therefore went to Trinity College, Dublin from which he received his degrees in 1841. His Cambridge degree he did not receive until 1872, when the religious barriers had at length been removed. In 1890 he was given an honorary Sc.D. at the same time as Benjamin Jowett, Henry Perry Liddon and other notables. The Public Orator could, by then, bracket him with Newton as "Sylvester noster" in the accolade: "Nonnulla quae Newtonus noster, quae Fresnelius, Iacobius, Sturmius, alii, imperfecta reliquerunt, Sylvester noster, aut elegantius explicavit aut argumentis veris comprobavit." After two years at University College, he crossed the Atlantic to the University of Virginia but 0097-6156/83/0226-0001$06.00/0 © 1983 American Chemical Society