Alexandre C. Dimian and
Costin Sorin Bildea
Chemical Process Design
S. Engell (Ed.)
Logistic Optimization of Chemical Production
Processes
2008
ISBN 978-3-527-30830-9
L. Puigjaner, G. Heyen (Eds.)
Computer Aided Process and Product Engineering
2006
ISBN 978-3-527-30804-0
K. Sundmacher, A. Kienle, A. Seidel-Morgenstern (Eds.)
Integrated Chemical Processes
Synthesis, Operation, Analysis, and Control
2005
ISBN 978-3-527-30831-6
Related Titles
Chemical Process Design
Computer-Aided Case Studies
Alexandre C. Dimian and Costin Sorin Bildea
The Authors
Prof. Alexandre C. Dimian
University of Amsterdam
FNWI/HIMS
Nieuwe Achtergracht 166
1018 WW Amsterdam
The Netherlands
Prof. Costin Sorin Bildea
University “Politehnica” Bucharest

Registered names, trademarks, etc. used in this
book, even when not specifi cally marked as such,
are not to be considered unprotected by law.
Printed in the Federal Republic of Germany
Printed on acid-free paper
Cover design wmx design, Heidelberg
Typesetting SNP Best-set Typesetter Ltd.,
Hong Kong
Printing Strauss GmbH, Mörlenbach
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Heppenheim
ISBN: 978-3-527-31403-4
Preface XV
1 Integrated Process Design 1
1.1 Motivation and Objectives 1
1.1.1 Innovation Through a Systematic Approach 1
1.1.2 Learning by Case Studies 2
1.1.3 Design Project 3
1.2 Sustainable Process Design 5
1.2.1 Sustainable Development 5
1.2.2 Concepts of Environmental Protection 5
1.2.2.1 Production-Integrated Environmental Protection 6
1.2.2.2 End-of-pipe Antipollution Measures 7
1.2.3 Effi ciency of Raw Materials 7
1.2.4 Metrics for Sustainability 9
1.3 Integrated Process Design 13
1.3.1 Economic Incentives 13
1.3.2 Process Synthesis and Process Integration 14
1.3.3 Systematic Methods 15
1.3.3.1 Hierarchical Approach 16

2.4.3 Economic Potential 36
2.5 Reactor/Separation/Recycle Structure 41
2.5.1 Material-Balance Envelope 41
2.5.1.1 Excess of Reactant 43
2.5.2 Nonlinear Behavior of Recycle Systems 43
2.5.2.1 Inventory of Reactants and Make-up Strategies 43
2.5.2.2 Snowball Effects 44
2.5.2.3 Multiple Steady States 45
2.5.2.4 Minimum Reactor Volume 45
2.5.2.5 Control of Selectivity 45
2.5.3 Reactor Selection 45
2.5.3.1 Reactors for Homogeneous Systems 46
2.5.3.2 Reactors for Heterogeneous Systems 46
2.5.4 Reactor-Design Issues 47
2.5.4.1 Heat Effects 47
2.5.4.2 Equilibrium Limitations 48
2.5.4.3 Heat-Integrated Reactors 48
2.5.4.4 Economic Aspects 49
2.6 Separation System Design 49
2.6.1 First Separation Step 50
2.6.1.1 Gas/Liquid Systems 50
2.6.1.2 Gas/Liquid/Solid Systems 51
2.6.2 Superstructure of the Separation System 51
2.7 Optimization of Material Balance 54
2.8 Process Integration 55
2.8.1 Pinch-Point Analysis 55
2.8.1.1 The Overall Approach 56
2.8.2 Optimal Use of Resources 58
2.9 Integration of Design and Control 58
2.10 Summary 58

References 101
4 Reactor/Separation/Recycle Systems 103
4.1 Introduction 103
4.2 Plantwide Control Structures 106
4.3 Processes Involving One Reactant 108
4.3.1 Conventional Control Structure 108
4.3.2 Feasibility Condition for the Conventional Control Structure 111
4.3.3 Control Structures Fixing Reactor-Inlet Stream 112
4.3.4 Plug-Flow Reactor 114
4.4 Processes Involving Two Reactants 115
4.4.1 Two Recycles 115
4.4.2 One Recycle 117
4.5 The Effect of the Heat of Reaction 118
4.5.1 One-Reactant, First-Order Reaction in PFR/Separation/Recycle
Systems 118
VIII Contents
4.6 Example – Toluene Hydrodealkylation Process 122
4.7 Conclusions 126
References 127
5 Phenol Hydrogenation to Cyclohexanone 129
5.1 Basis of Design 129
5.1.1 Project Defi nition 129
5.1.2 Chemical Routes 130
5.1.3 Physical Properties 131
5.2 Chemical Reaction Analysis 132
5.2.1 Chemical Reaction Network 132
5.2.2 Chemical Equilibrium 133
5.2.2.1 Hydrogenation of Phenol 133
5.2.2.2 Dehydrogenation of Cyclohexanol 135
5.2.3 Kinetics 137

6.2.3 Thermal Effects 180
6.2.4 Chemical Equilibrium 181
6.2.5 Kinetics 181
6.3 Reactor/Separator/Recycle Structure 183
6.4 Mass Balance and Simulation 185
6.5 Energy Integration 187
6.6 Complete Process Flowsheet 192
6.7 Reactive Distillation Process 195
6.8 Conclusions 199
References 200
7 Vinyl Chloride Monomer Process 201
7.1 Basis of Design 201
7.1.1 Problem Statement 201
7.1.2 Health and Safety 202
7.1.3 Economic Indices 202
7.2 Reactions and Thermodynamics 202
7.2.1 Process Steps 202
7.2.2 Physical Properties 205
7.3 Chemical-Reaction Analysis 205
7.3.1 Direct Chlorination 206
7.3.2 Oxychlorination 208
7.3.3 Thermal Cracking 210
7.4 Reactor Simulation 212
7.4.1 Ethylene Chlorination 212
7.4.2 Pyrolysis of EDC 212
7.5 Separation System 213
7.5.1 First Separation Step 213
7.5.2 Liquid-Separation System 215
7.6 Material-Balance Simulation 216
7.7 Energy Integration 219

9 Isobutane Alkylation 261
9.1 Introduction 261
9.2 Basis of Design 263
9.2.1 Industrial Processes for Isobutane Alkylation 263
9.2.2 Specifi cations and Safety 263
9.2.3 Chemistry 264
9.2.4 Physical Properties 265
9.2.5 Reaction Kinetics 265
9.3 Input–Output Structure 267
9.4 Reactor/Separation/Recycle 268
9.4.1 Mass-Balance Equations 268
9.4.2 Selection of a Robust Operating Point 272
9.4.3 Normal-Space Approach 274
9.4.3.1 Critical Manifolds 274
9.4.3.2 Distance to the Critical Manifold 275
9.4.3.3 Optimization 277
9.4.4 Thermal Design of the Chemical Reactor 278
9.5 Separation Section 280
9.6 Plantwide Control and Dynamic Simulation 281
9.7 Discussion 284
9.8 Conclusions 285
References 285
10 Vinyl Acetate Monomer Process 287
10.1 Basis of Design 287
10.1.1 Manufacturing Routes 287
10.1.2 Problem Statement 288
10.1.3 Health and Safety 289
Contents XI
10.2 Reactions and Thermodynamics 289
10.2.1 Reaction Kinetics 289

11.8.3 Catalyst Waste 335
11.9 Final Flowsheet 335
11.10 Further Developments 337
11.11 Conclusions 337
References 338
12 Biochemcial Process for NO
x
Removal 339
12.1 Introduction 339
12.2 Basis of Design 341
12.3 Process Selection 341
12.4 The Mathematical Model 343
12.4.1 Diffusion-Reaction in the Film Region 343
XII Contents
12.4.1.1 Model Parameters 346
12.4.2 Simplifi ed Film Model 348
12.4.3 Convection-Mass-Transfer Reaction in the Bulk 351
12.4.3.1 Bulk Gas 351
12.4.3.2 Bulk Liquid 352
12.4.4 The Bioreactor 354
12.5 Sizing of the Absorber and Bioreactor 355
12.6 Flowsheet and Process Control 357
12.7 Conclusions 358
References 360
13 PVC Manufacturing by Suspension Polymerization 363
13.1 Introduction 363
13.1.1 Scope 363
13.1.2 Economic Issues 363
13.1.3 Technology 365
13.2 Large-Scale Reactor Technology 365

14.1.1 Types of Alternative Fuels 399
14.1.2 Economic Aspects 401
14.2 Fundamentals of Biodiesel Manufacturing 402
14.2.1 Chemistry 402
14.2.2 Raw Materials 404
14.2.3 Biodiesel Specifi cations 405
14.2.4 Physical Properties 406
14.3 Manufacturing Processes 409
14.3.1 Batch Processes 409
14.3.2 Catalytic Continuous Processes 411
14.3.3 Supercritical Processes 413
14.3.4 Hydrolysis and Esterifi cation 414
14.3.5 Enzymatic Processes 415
14.3.6 Hydropyrolysis of Triglycerides 415
14.3.7 Valorization of Glycerol 416
14.4 Kinetics and Catalysis 416
14.4.1 Homogeneous Catalysis 416
14.4.2 Heterogeneous Catalysis 419
14.5 Reaction-Engineering Issues 420
14.6 Phase-Separation Issues 422
14.7 Application 423
14.8 Conclusions 426
References 427
15 Bioethanol Manufacturing 429
15.1 Introduction 429
15.2 Bioethanol as Fuel 429
15.3 Economic Aspects 431
15.4 Ecological Aspects 433
15.5 Raw Materials 435
15.6 Biorefi nery Concept 437

XV
Chemical Process Design: Computer-Aided Case Studies. Alexandre C. Dimian and Costin Sorin Bildea
Copyright © 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 978-3-527-31403-4
“ I hear and I forget. I see and I remember. I do and I understand. ”
Confucius
Chemical process design today faces the challenge of sustainable technologies for
manufacturing fuels, chemicals and various products by extended use of renew-
able raw materials. This implies a profound change in the education of designers
in the sense that their creativity can be boosted by adopting a systems approach
supported by powerful systematic methods and computer simulation tools. Instead
of developing a single presumably good fl owsheet, modern process design gener-
ates and evaluates several alternatives corresponding to various design decisions
and constraints. Then, the most suitable alternative is refi ned and optimized with
respect to high effi ciency of materials and energy, ecologic performance and
operability.
This book deals with the conceptual design of chemical processes illustrated by
case studies worked out by computer simulation. Typically, more than 80% of the
total investment costs of chemical plants are determined at the conceptual design
stage, although this activity involves only 2 – 3% of the engineering costs and a
reduced number of engineers. In addition, a preliminary design allows critical
aspects in research and development and/or in searching subcontractors to be
highlighted, well ahead of starting the actual plant design project.
The book is aimed at a wide audience interested in the design of innovative
chemical processes, especially chemical engineering undergraduate students com-
pleting a process and/or plant design project. Postgraduate and PhD students will
fi nd advanced and thought - provoking process - design methods. The information
presented in the book is also useful for the continuous education of professional
designers and R & D engineers.
This book uses ample case studies to teach a generic design methodology and

Hierarchical Approach . An effi cient methodology is proposed aiming to minimize
the interactions between the synthesis and integration steps. The core activity
concentrates on the reactor/separation/recycle structure as defi ning the process
architecture, by which the reactor design and the structure of separations
are examined simultaneously by considering the effect of recycles on fl exibility
and stability. By placing the reactor in the core of the process, the separators
receive clearly defi ned tasks of plantwide perspective, which should be
fulfi lled later by the design of the respective subsystems. The heat and material
balances built upon this structure supply the key elements for sizing the units
and assessing capital and operation costs, and on this basis establish the process
profi tability.
Chapter 3 deals with the Synthesis of the Separation System . A task - oriented
approach is proposed for generating close - to - optimum separation sequences for
which both feasibility and performance of splits are guaranteed. Emphasis is
placed on the synthesis of distillation systems by residue curve map methods.
Chapter 4 deals in more detail with the analysis of the Reactor/Separation/Recycle
Systems . Undesired nonlinear phenomena can be detected at early conceptual
stages through steady - state sensitivity and dynamic stability analysis. This
approach, developed by the authors, allows better integration between process
design and plantwide control. Two different approaches to plantwide control are
discussed, namely controlling the material balance of the plant by using the self -
regulation property or by applying feedback control.
Preface XVII
The fi rst case study of Chapter 5 Cyclohexanone by Phenol Hydrogenation devel-
oped in a tutorial manner, allows the reader to navigate through the key steps of
the methodology, from thermodynamic analysis to reactor design, fl owsheet syn-
thesis and simulation. The key issue is designing a plant that complies with fl exi-
bility and selectivity targets. The initial design of the plant contains two reaction
sections, but selective catalyst and adequate recycle policy allow an effi cient and
versatile single reactor process to be developed. In addition, the case study deals

possibility of designing a multiproduct reactive distillation column by slightly
adjusting the operation conditions. The residue curve map analysis brings useful
insights. The esterifi cation with propanols raises the problem of breaking the
alcohol/water azeotrope . The solution passes by the use of an entrainer. The equip-
ment is simple and effi cient. The availability of an active and selective catalyst
remains the key element in technology.
Chapter 9 Isobutane/Butene Alkylation illustrates in detail the integration of
design and plantwide control. Special attention is paid to the reaction/separation/
XVIII Preface
recycle structure, showing how plantwide control considerations are introduced
during the early stages of conceptual design. Thus, a simplifi ed plant mass balance
based on a kinetic model for the reactor and black - box separation models is used
to generate plantwide control alternatives. Nonlinear analysis reveals unfavourable
steady state behavior, such as high sensitivity and state multiplicity. An important
part is devoted to robustness study in order to ensure feasible operation when
operation variables change or the design parameters are uncertain.
The case study on Vinyl Acetate Process , developed in Chapter 10 , demonstrates
the benefi t of solving a process design and plantwide control problem based on
the analysis of the reactor/separation/recycles structure. In particular, it is dem-
onstrated that the dynamic behavior of the chemical reactor and the recycle policy
depend on the mechanism of the catalytic process, as well as on the safety con-
straints. Because low per pass conversion of both ethylene and acetic acid is
needed, the temperature profi le in the chemical reactor becomes the most impor-
tant means for manipulating the reaction rate and hence ensuring the plant fl exi-
bility. The inventory of reactants is adapted accordingly by fresh reactant make - up
directly in recycles.
Chapter 11 Acrylonitrile by Ammoxidation of Propene illustrates the synthesis of
a fl owsheet in which a diffi cult separation problem dominates. In addition, large
energy consumption of both low - and high - temperature utilities is required.
Various separation methods are involved from simple fl ash and gas absorption to

biodiesel process based on homogeneous catalysis is performed. The study dem-
onstrates that employing heterogeneous catalysis can lead to a much simpler and
more effi cient design. The availability of superactive and robust catalysts is still an
open problem.
Bioethanol Manufacturing is handled in Chapter 15 . The case study examines
different aspects of today ’ s technologies, such as raw materials basis, fermentation
processes and bioreactors. The application deals with the design of a bioethanol
plant of the second generation based on lignocellulosic biomass. Emphasis is
placed on getting realistic and consistent material and energy balances over the
whole plant by means of computer simulation in order to point out the impact
of the key technical elements on the investment and operation costs. To achieve
this goal the complicated biochemistry is expressed in term of stoichiometric reac-
tions and user - defi ned components. The systemic analysis emphasizes the key role
of the biomass conversion stage based on simultaneous saccharifi cation and
fermentation.
The book is completed with Annexes on the analysis of reactive mixtures by
residue curve maps, design of heat exchangers, selection of construction materials,
steam tables, vapor pressure of typical chemical components and conversion table
for the common physical units.
The authors acknowledge the contribution to this book of many colleagues and
students from the University of Amsterdam and Delft University of Technology,
The Netherlands. Special thanks go to the Dutch Postgraduate School for Process
Technology (OSPT) for supporting our postgraduate course in Advanced Process
Integration and Plantwide Control, where the integration of design and control is
the main feature. The authors express their appreciation to the software companies
AspenTech and MathWorks for making available for education purposes an out-
standing simulation technology.
And last but not the least we express our gratitude and love to our families, for
continuous support and understanding.
January 2008 Alexandre C. Dimian

optimization design methods aided by powerful computer - simulation tools.
Creativity is a major issue in process design. This is not a matter only of engi-
neering experience, but above all of adopting the approach of process systems. This
consists of a systemic viewpoint in problem analysis supported by systematic
methods in process design.
A systematic and systems approach has at least two merits:
1. Provides guidance in assessing fi rstly the feasibility of the process design as a
whole, as well as its fl exibility in operation, before more detailed design of
components.
2 1 Integrated Process Design
2. Generates not only one supposed optimal solution, but several good alternatives
corresponding to different design decisions . A remarkable feature of the systemic
design is that quasioptimal targets may be set well ahead detailed sizing of
equipment. In this way, the effi ciency of the whole engineering work may improve
dramatically by avoiding costly structural modifi cations in later stages.
The motivation of this book consists of using a wide range of case studies to teach
generic creative issues, but incorporated in the framework of a technology of
industrial signifi cance. Computer simulation is used intensively to investigate the
feasibility and support design decisions, as well as for sizing and optimization.
Particular emphasis is placed on thermodynamic modeling as a fundamental tool
for analysis of reactions and separations. Most of the case studies make use of
chemical reactor design by kinetic modeling.
A distinctive feature of this book is the integration of design and control as the
current challenge in process design. This is required by higher fl exibility and
responsiveness of large - scale continuous processes, as well as by the optimal
operation of batchwise and cyclic processes for high - value products.
The case studies cover key applications in chemical process industries, from
petrochemistry to polymers and biofuels. The selection of processes was con-
fronted with the problem of availability of suffi cient design and technology data.
The development of the fl owsheet and its integration is based on employing a

3. complications in the case of failure of project management or leadership,
4. possibility of unfair evaluation.
The above drawbacks, merely questions of project organization, can be reduced to
a minimum by taking into account the following measures:
1. provide clear defi nition of content, deliverables, scheduling and evaluation,
2. provide adequate support, regular evaluation of the team and of each member.
If possible, separate support end evaluation, as customer/contractor relation,
3. evaluate the project by public presentation, but with individual marks,
4. propose challenging subjects issued from industry or from own research,
5. attract specialists from industry for support and evaluation.
1.1.3
Design Project
Teaching modern chemical process design can be organized at two levels:
• Teach a systems approach and systematic methods in the framework of a process
design and integration introductory course. A period of 4 – 6 weeks fulltime (160 to
240 h) should be suffi cient. Here, a fi rst process - integration project is proposed,
which can be performed individually or in small groups.
• Consolidate the engineering skills in the framework of a larger plant design
project . A typical duration is 10 – 12 weeks full time with groups of 3 – 5 students.
Although dissimilar in extension and purpose, these projects largely share the
content, as illustrated by Fig. 1.1 . The main points of the approach are as follows:
1. Provide clear defi nition of the design problem. Collect suffi cient engineering
data. Get a comprehensive picture of chemistry and reaction conditions, thermal
effects and chemical equilibrium, as well as about safety, toxicity and environ-
mental problems. Examine the availability of physical properties for compo-
nents and mixtures of signifi cance. Identify azeotropes and key binaries. Defi ne
the key constraints.
2. The basic fl owsheet structure is given by the reactor and separation systems.
Alternatives can be developed by applying process - synthesis meth ods. Use com-
puter simulation to get physical insights into different conceptual issues and