Conceptual design of chemical process (1988)

CONCEPTUAL DESIGN OF CHEMICAL PROCESSES • James M Douglas U"hJImed In II data base or retrieval system, without the prior written permission of the publisher This book was sel in Times Roman The editors were B.J Oat1l: and James W.Bradtey The production supervisors were Diane Renda and LDuise Karam Ubrary of Congress Cataloging-in-Publieation Dala Douglas,James M.(James Merrill) CoooeptuaJ design 01 chemical processes (McGraw-Hili chemical engineering series) Bibliography:p Includes index O"Iemical prooesse5 I Tille II Series TPI55.7.D67 1988 ISBN 0-07.{}ln62·7 660.2'81 87·21359 When ordering this title use ISBN O-07· 100195 S Printed In Singapore James M Douglas Ph.D is currently a professor of chemical engineering at the University of Massachusetts Previously he taught at the University of Rochester and al the University of [klaware Before entering leaching he spen t five years at ARea, working on reactor design and control problems l-Ie has published extensively in areas of reacting engineering, process control (including two books) and conceptual process design He won the Post-Doctoral FellowshIp Award al AReO, the Faculty Fellowship Award at the University of MassachusellS, and the Computing and ChemIcal Engmeering Award of A1ChE DEDI CATED TO: The loves of my life, M y lovely wife Mary E (Betsy) Douglas M y mo ther, Ca rolyn K • and the memory of my father Merrill H Douglas, My two wonderful kids, Lynn and Bob, and to my colleagues, wbo bave taugbt me so much about design and trol, Mike Doherty, Mike Malone, Ka Ng and Erik Ydstie, and to my st udents who have suffered so much CONTENTS Preface Part ) " A Strategy for Process Synthesis and Analysis The Nature of Process Synthesis and Analysis I-I 1-' 1-' 2-1 '-2 ,-, '-4 2-' ,- '-7 3-1 3-' Creall\c A5pc!;IS of I'roces~ Design A Ihcrarchl!;al Approach to Com::c:plual Design Summary, Eac:rc~, lind Nomenclature Engineering Economics CoSI Information Requned Estimating Capital and Opcrallog Costs TOlal Capilal Investment and TOlal Produce Costs Time Value of M onty Measures of Process Profitability SlmphfYlng the EconomIC AnalysIs for Conceptual Designs Summary, E.trcises and Nomenclature • I' " 2J 32 37 ." Economic Decision Making : Design of a Solvent Recovery System 72 Problem Definition and General Considerations 72 Design or II Gas Absorber Flnwshccl, Malena1 and Energy Balances, and Stream 3-3 3-4 3-' , COSIS equipment Design Considerat ions Rules o f Thumb Summary, ExercISeS, and Nomenclatllre "" " 90 x; xii 00"""" ~, Part II 4-1 4-2 4-3 '-I '-2 '-3 ,-4 6-1 6-2 6-3 6-4 6-' 6-6 6-7 6- 7-1 7-2 7-J 7A 7-' 7-6 '-1 '-2 '-J ,-4 -, '-6 '_7 - -, 8-10 -11 Developing a Conceptual Design and Finding the Best Flowsheet Input Infonnation and Batch versus Continuous Input InConnation level-I Decision - Balch venus Continuous Summary, ElerC1scs, and Nomenclature Cost Diagrams and the Quick Screening of Process Alternatives Cost Diagrams Cost Diagrams for Complex Processes QUICk Screening of Process Ahemati,-es HDA Process Summary, Exerclsc, and Nomenclature 289 289 297 303 30S 31' Part III Other Design Tools and Applications 117 97 " " 107 III Inpul·Qutput Structure of the Flowsheet 11 Decisions for the Input-Output Structure Design Variable!, ~ral1 Material Balances and Stream CoslS Pl"ocess Altematives SUmmal'}', Elerciscs, and Nomenclature 116 l2l 132 132 Recycle Structure of the Flowsheet Oec1Slons thaI Determine the Recycle Slructure Recycle Material Balances Rea ctor Heal Errects Equilibnum Limitations Compressor DesIgn and Cmu Reactor DesIgn Recycle EconomIC EvaluatIOn Summary Elelc1SCS, and Nomenclatule 117 137 142 146 149 III 136 138 1>9 Separation System 163 General Structure of the Separallon System Vapor Reoovery System Uquid Separation System AzcotroptC Sy5lems Rtgorous Material Balances Summary, Elerciscs, and Nomenclature 163 168 172 189 "" Heat·Exchanger Networks 216 Minimum Heating and Cooling Requin:ments Mmimum Number of ElchangeD Area Esumates Design of Minimum-Energy tleat-ElChaDger Networks Loops and Paths Reducing the Number of Elchan~n A More Complete Design Algorithm Stream Splitting Heat and Power Integration Il eal and DISlillalion HOA Process Summary, E.ercises, and Nomenclatule 216 230 2JJ 236 '-I '-2 '-3 ,A ,-, 10 10-1 10-2 10-3 10-4 10-' 11 11 · 11 -2 11 -3 12 12·' 12-2 12·) 12A 13 211 24' 251 '" 261 264 21J 284 xiii 13-1 13-2 13·) Preliminary Process Optimization DesIgn Variables and Economic Trade-offs COSt Models for Process Units A Cmt Model for a Simple Process Approlimate Optlmiution Analysis Summar), Elercisc5 and NomencialUre A- I A-2 A-J AA '" Process Retrofit s ll3 A Syslematic Procedure for Process Fetrofits HDA Process Summary and ElerClSCS 354 338 368 Computer· Aided Design Programs (FLOWTRAN) J69 General Structure of Computer-Aided Design Programs Malenal Balance Calculallons Com plete Plant Simulation Summary and E.erciscs 370 Summary or the Conceptual Des ign Procedure and Extensions of the Method A Revie · of the Hierarchical Decision Procedure ror Petrochemical Processes Deugn of Sohds Processes and Batch Processes Other Significant Aspects of the Design Problem Part IV Appendixes A 31' 320 321 lJ2 340 Shortcut Procedures for Equipment Design Number o(Trays fOI Gas Absorber Distillation Columns : Number of Trays Design o f Gas Absorbers and Distillation Columns Distillation Column 5cquencing J7l J97 4" 40' 406 40' 41 423 '" '" 436 '" 461 xit' CONTEP'lT$ A·' H A·7 A·' A·lO A-II Complex Distillation Columns Energy Integralion of Distillation Columns Heal_Exchan ger Design Gas Compressors Design of Refrigeration SyStems Reactors Summary of Shortcut Equipment Design GUidelines and Nomenclature for Appendix A 466 18 86 90 90 S07 S07 B HDA Case Study '" C Design Data 543 Hydrocarbon Vapor-Liquid Equilibria Temperature Ranges for some Materials 543 547 FLOWTRAN Input forms , C·I C·, D D·I D·' D·3 D4 D·' D·6 D·7 D·8 D·' D -IO D-ll E E·I E·' F Component List IFLSH A.FLSH SEPR ADD SPLIT PUMP GCOMP SCVW DSTWU REACT Cost Data PREFACE 548 "" '" '" '56 '" '" "" SSl '54 '6' S68 Operating Costs Summary of Cost CorrelaUons '" 56' Conversion Factors S78 Indexes Author Index Subject Index "I ,,3 '" llLis book describes a systematic procedure for the conceptual design of a limited class of chemical processes The goal of a conceptual design is 10 find the best process fiowsheet (i.e., to select the process units and the interconnections among Ihese: unils) and estimate the optimum design conditions The problem is difficult because very many process alternatives could be considered In additIOn, experience indicates that less than I % of ideas for new designs ever become commercialized Thus, there are many possibilities 10 consider with only a small chance of sUCGCss In man} cases the processing costs associated with the various process alternatives differ by an order of magnitude or more, so that we can use shoncut calculations to screen the alternatives However, we must be certain that we are in the neighborhood ortne o ptimum design conditions for each alternative, to prevent discarding ao alternative because of a poor choice of design variables Hence, we use cost studies as an initial screening to eliminate ideas for designs that are unprofitable If a process appears to be profitable, then we must consider other factors, including safety environmental constraints, controllability, etc We approach tne synthesis and analysis problem by cstablishjng a hierarchy of design decisions With this approach, we decompose: a very large and complex problem into a number of smaller problems that are much simpler to handle By focusing on the decisions that must be made at each level in the hierarchy (e.g., Do we want to add a solvent recovery system?), we can identify the existing technologies that could be used to solve the problem (e.g., absorption, adsorption condensation) without precluding the possibility that some new teth nology (e.g., a membrane process) might provide a better solution Moreover, by 'listing the alternative solutions we can propose: for each decision, we can systematically generate a list of process alternatives In some cases it is possible to use: design guidelines (rules of thumb or heuristics) to make some deciSIOns about the structu re of the flowshect and/or to set the values of some of the design variables We usc order-of-magnitude " arguments to denve many of these heuristics, and .e use a simple analysis of this type to identify the III111ta1l0ns of the heunstics Tn many cases, no heuristics are available, and therefore we de\elop shortcut design methods that can be uscd as a basis for makmg decisions By followmg this hierarchical decision procedure a beginning designer can substItute the evaluation of a number of extra calculations for experience during the devdopmenl of a conceptual desIgn Since