chemica process design and integration

Chemical Process Design and Integration
Robin Smith
Centre for Process Integration,
School of Chemical Engineering and Analytical Science,
University of Manchester.

Chemical Process Design and Integration

Chemical Process Design and Integration
Robin Smith
Centre for Process Integration,
School of Chemical Engineering and Analytical Science,
University of Manchester.
Previous edition published by McGraw Hill
Copyright
 2005 John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester,
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Library of Congress Cataloging-in-Publication Data
Smith, R. (Robin)
Chemical process design and integration / Robin Smith.
p. cm.
Includes bibliographical references and index.
ISBN 0-471-48680-9 (HB) (acid-free paper) – ISBN 0-471-48681-7 (PB) (pbk. :
acid-free paper)
1. Chemic al processes. I. Title.
TP155.7.S573 2005
660

.2812 – dc22
2004014695
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
ISBN 0-471-48680-9 (cloth)
0-471-48681-7 (paper)
Typeset in 10/12pt Times by Laserwords Private Limited, Chennai, India
Printed and bound in Spain by Grafos, Barcelona
This book is printed on acid-free paper responsibly manufactured from sustainable forestry

in which at least two trees are planted for each one used for paper production.
To my family

Contents
Preface xiii
Acknowledgements xv
Nomenclature xvii
Chapter1 TheNatureofChemicalProcess
Design and Integration 1
1.1 Chemical Products 1
1.2 Formulation of the Design Problem 3
1.3 Chemical Process Design and
Integration 4
1.4 The Hierarchy of Chemical Process
Design and Integration 5
1.5 Continuous and Batch Processes 9
1.6 New Design and Retrofit 10
1.7 Approaches to Chemical Process
Design and Integration 11
1.8 Process Control 13
1.9 The Nature of Chemical Process
Design and Integration – Summary 14
References 14
Chapter 2 Process Economics 17
2.1 The Role of Process Economics 17
2.2 Capital Cost for New Design 17
2.3 Capital Cost for Retrofit 23
2.4 Annualized Capital Cost 24
2.5 Operating Cost 25
2.6 Simple Economic Criteria 28

2.7 Project Cash Flow and Economic
Evaluation 29
2.8 Investment Criteria 30
2.9 Process Economics – Summary 31
2.10 Exercises 32
References 33
Chapter 3 Optimization 35
3.1 Objective Functions 35
3.2 Single-variable Optimization 37
3.3 Multivariable Optimization 38
3.4 Constrained Optimization 42
3.5 Linear Programming 43
3.6 Nonlinear Programming 45
3.7 Profile Optimization 46
3.8 Structural Optimization 48
3.9 Solution of Equations
using Optimization 52
3.10 The Search for Global
Optimality 53
3.11 Summary – Optimization 54
3.12 Exercises 54
References 56
Chapter 4 Thermodynamic Properties and
Phase Equilibrium 57
4.1 Equations of State 57
4.2 Phase Equilibrium for Single
Components 59
4.3 Fugacity and Phase Equilibrium 60
4.4 Vapor–Liquid Equilibrium 60
4.5 Vapor–Liquid Equilibrium Based on

Activity Coefficient Models 62
4.6 Vapor–Liquid Equilibrium Based on
Equations of State 64
4.7 Calculation of Vapor–Liquid
Equilibrium 64
4.8 Liquid–Liquid Equilibrium 70
4.9 Liquid–Liquid Equilibrium Activity
Coefficient Models 71
4.10 Calculation of Liquid–Liquid
Equilibrium 71
4.11 Calculation of Enthalpy 72
4.12 Calculation of Entropy 74
4.13 Phase Equilibrium and Thermodynamic
Properties – Summary 74
4.14 Exercises 74
References 76
Chapter 5 Choice of Reactor I – Reactor
Performance 77
5.1 Reaction Path 77
5.2 Types of Reaction Systems 78
5.3 Reactor Performance 81
5.4 Rate of Reaction 82
5.5 Idealized Reactor Models 83
5.6 Choice of Idealized Reactor Model 90
5.7 Choice of Reactor Performance 94
viii Contents
5.8 Choice of Reactor
Performance – Summary 94
5.9 Exercises 95
References 96

Chapter 6 Choice of Reactor II - Reactor
Conditions 97
6.1 Reaction Equilibrium 97
6.2 Reactor Temperature 100
6.3 Reactor Pressure 107
6.4 Reactor Phase 108
6.5 Reactor Concentration 109
6.6 Biochemical Reactions 114
6.7 Catalysts 114
6.8 Choice of Reactor
Conditions – Summary 117
6.9 Exercises 118
References 120
Chapter 7 Choice of Reactor III – Reactor
Configuration 121
7.1 Temperature Control 121
7.2 Catalyst Degradation 123
7.3 Gas–Liquid and Liquid–Liquid
Reactors 124
7.4 Reactor Configuration 127
7.5 Reactor Configuration for
Heterogeneous Solid-Catalyzed
Reactions 133
7.6 Reactor Configuration from
Optimization of a Superstructure 133
7.7 Choice of Reactor
Configuration – Summary 139
7.8 Exercises 139
References 140
Chapter 8 Choice of Separator for

Heterogeneous Mixtures 143
8.1 Homogeneous and Heterogeneous
Separation 143
8.2 Settling and Sedimentation 143
8.3 Inertial and Centrifugal Separation 147
8.4 Electrostatic Precipitation 149
8.5 Filtration 150
8.6 Scrubbing 151
8.7 Flotation 152
8.8 Drying 153
8.9 Separation of Heterogeneous
Mixtures – Summary 154
8.10 Exercises 154
References 155
Chapter 9 Choice of Separator for
Homogeneous Fluid Mixtures
I – Distillation 157
9.1 Single-Stage Separation 157
9.2 Distillation 157
9.3 Binary Distillation 160
9.4 Total and Minimum Reflux
Conditions for Multicomponent
Mixtures 163
9.5 Finite Reflux Conditions for
Multicomponent Mixtures 170
9.6 Choice of Operating Conditions 175
9.7 Limitations of Distillation 176
9.8 Separation of Homogeneous Fluid
Mixtures by Distillation – Summary 177
9.9 Exercises 178

References 179
Chapter 10 Choice of Separator for
Homogeneous Fluid Mixtures
II – Other Methods 181
10.1 Absorption and Stripping 181
10.2 Liquid–Liquid Extraction 184
10.3 Adsorption 189
10.4 Membranes 193
10.5 Crystallization 203
10.6 Evaporation 206
10.7 Separation of Homogeneous Fluid
Mixtures by Other
Methods – Summary 208
10.8 Exercises 209
References 209
Chapter 11 Distillation Sequencing 211
11.1 Distillation Sequencing Using
Simple Columns 211
11.2 Practical Constraints Restricting
Options 211
11.3 Choice of Sequence for Simple
Nonintegrated Distillation Columns 212
11.4 Distillation Sequencing Using
Columns With More Than Two
Products 217
11.5 Distillation Sequencing Using
Thermal Coupling 220
11.6 Retrofit of Distillation Sequences 224
11.7 Crude Oil Distillation 225
11.8 Distillation Sequencing Using

Optimization of a Superstructure 228
11.9 Distillation Sequencing – Summary 230
11.10 Exercises 231
References 232
Contents ix
Chapter 12 Distillation Sequencing for
Azeotropic Distillation 235
12.1 Azeotropic Systems 235
12.2 Change in Pressure 235
12.3 Representation of Azeotropic
Distillation 236
12.4 Distillation at Total Reflux
Conditions 238
12.5 Distillation at Minimum Reflux
Conditions 242
12.6 Distillation at Finite Reflux
Conditions 243
12.7 Distillation Sequencing Using an
Entrainer 246
12.8 Heterogeneous Azeotropic
Distillation 251
12.9 Entrainer Selection 253
12.10 Trade-offs in Azeotropic Distillation 255
12.11 Multicomponent Systems 255
12.12 Membrane Separation 255
12.13 Distillation Sequencing for
Azeotropic Distillation – Summary 256
12.14 Exercises 257
References 258
Chapter 13 Reaction, Separation and Recycle

Systems for Continuous Processes 259
13.1 The Function of Process Recycles 259
13.2 Recycles with Purges 264
13.3 Pumping and Compression 267
13.4 Simulation of Recycles 276
13.5 The Process Yield 280
13.6 Optimization of Reactor Conversion 281
13.7 Optimization of Processes Involving
a Purge 283
13.8 Hybrid Reaction and Separation 284
13.9 Feed, Product and Intermediate
Storage 286
13.10 Reaction, Separation and Recycle
Systems for Continuous
Processes – Summary 288
13.11 Exercises 289
References 290
Chapter 14 Reaction, Separation and Recycle
Systems for Batch Processes 291
14.1 Batch Processes 291
14.2 Batch Reactors 291
14.3 Batch Separation Processes 297
14.4 Gantt Charts 303
14.5 Production Schedules for Single
Products 304
14.6 Production Schedules for Multiple
Products 305
14.7 Equipment Cleaning and Material
Transfer 306
14.8 Synthesis of Reaction and

Separation Systems for Batch
Processes 307
14.9 Optimization of Batch Processes 311
14.10 Storage in Batch Processes 312
14.11 Reaction and Separation Systems for
Batch Processes – Summary 313
14.12 Exercises 313
References 315
Chapter 15 Heat Exchanger Networks
I – Heat Transfer Equipment 317
15.1 Overall Heat Transfer Coefficients 317
15.2 Heat Tr ansfer Coefficients and
Pressure Drops for Shell-and-Tube
Heat Exchangers 319
15.3 Temperature Differences in
Shell-and-Tube Heat Exchangers 324
15.4 Allocation of Fluids in
Shell-and-Tube Heat Exchangers 329
15.5 Extended Surface Tubes 332
15.6 Retrofit of Heat Exchangers 333
15.7 Condensers 337
15.8 Reboilers and Vaporizers 342
15.9 Other Types of Heat Exchange
Equipment 346
15.10 Fired Heaters 348
15.11 Heat Tr ansfer
Equipment – Summary 354
15.12 Exercises 354
References 356
Chapter 16 Heat Exchanger Networks

II – Energy Targets 357
16.1 Composite Curves 357
16.2 The Heat Recovery Pinch 361
16.3 Threshold Problems 364
16.4 The Problem Table Algorithm 365
16.5 Nonglobal Minimum Temperature
Differences 370
16.6 Process Constraints 370
16.7 Utility Selection 372
16.8 Furnaces 374
16.9 Cogeneration (Combined Heat and
Power Generation) 376
16.10 Integration Of Heat Pumps 381
16.11 Heat Exchanger Network Energy
Targets – Summary 383
x Contents
16.12 Exercises 383
References 385
Chapter 17 Heat Exchanger Networks
III – Capital and Total Cost
Targets 387
17.1 Number of Heat Exchange Units 387
17.2 Heat Exchange Area Targets 388
17.3 Number-of-shells Target 392
17.4 Capital Cost Targets 393
17.5 Total Cost Targets 395
17.6 Heat Exchanger Network and
Utilities Capital and Total
Costs – Summary 395
17.7 Exercises 396

References 397
Chapter 18 Heat Exchanger Networks
IV – Network Design 399
18.1 The Pinch Design Method 399
18.2 Design for Threshold Problems 404
18.3 Stream Splitting 405
18.4 Design for Multiple Pinches 408
18.5 Remaining Problem Analysis 411
18.6 Network Optimization 413
18.7 The Superstructure Approach to
Heat Exchanger Network Design 416
18.8 Retrofit of Heat Exchanger
Networks 419
18.9 Addition of New Heat Transfer Area
in Retrofit 424
18.10 Heat Exchanger Network
Design – Summary 425
18.11 Exercises 425
References 428
Chapter 19 Heat Exchanger Networks
V – Stream Data 429
19.1 Process Changes for Heat
Integration 429
19.2 The Trade-Offs Between Process
Changes, Utility Selection, Energy
Cost and Capital Cost 429
19.3 Data Extraction 430
19.4 Heat Exchanger Network Stream
Data – Summary 437
19.5 Exercises 437

References 438
Chapter 20 Heat Integration of Reactors 439
20.1 The Heat Integration Characteristics
of Reactors 439
20.2 Appropriate Placement of Reactors 441
20.3 Use of the Grand Composite Curve
for Heat Integration of Reactors 442
20.4 Evolving Reactor Design to Improve
Heat Integration 443
20.5 Heat Integration of
Reactors – Summary 444
Reference 444
Chapter 21 Heat Integration of Distillation
Columns 445
21.1 The Heat Integration Characteristics
of Distillation 445
21.2 The Appropriate Placement of
Distillation 445
21.3 Use of the Grand Composite Curve
for Heat Integration of Distillation 446
21.4 Evolving the Design of Simple
Distillation Columns to Improve
Heat Integration 447
21.5 Heat Pumping in Distillation 449
21.6 Capital Cost Considerations 449
21.7 Heat Integration Characteristics of
Distillation Sequences 450
21.8 Heat-integrated Distillation
Sequences Based on the
Optimization of a Superstructure 454

21.9 Heat Integration of Distillation
Columns – Summary 455
21.10 Exercises 456
References 457
Chapter 22 Heat Integration of Evaporators
and Dryers 459
22.1 The Heat Integration Characteristics
of Evaporators 459
22.2 Appropriate Placement of
Evaporators 459
22.3 Evolving Evaporator Design to
Improve Heat Integration 459
22.4 The Heat Integration Characteristics
of Dryers 459
22.5 Evolving Dryer Design to Improve
Heat Integration 460
22.6 Heat Integration of Evaporators and
Dryers – Summary 461
Contents xi
22.7 Exercises 462
References 463
Chapter 23 Steam Systems and Cogeneration 465
23.1 Boiler Feedwater Treatment 466
23.2 Steam Boilers 468
23.3 Steam Turbines 471
23.4 Gas Turbines 477
23.5 Steam System Configuration 482
23.6 Steam and Power Balances 484
23.7 Site Composite Curves 487
23.8 Cogeneration Targets 490

23.9 Optimization of Steam Levels 493
23.10 Site Power-to-heat Ratio 496
23.11 Optimizing Steam Systems 498
23.12 Steam Costs 502
23.13 Choice of Driver 506
23.14 Steam Systems and
Cogeneration – Summary 507
23.15 Exercises 508
References 510
Chapter 24 Cooling and Refrigeration Systems 513
24.1 Cooling Systems 513
24.2 Recirculating Cooling Water
Systems 513
24.3 Targeting Minimum Cooling Water
Flowrate 516
24.4 Design of Cooling Water Networks 518
24.5 Retrofit of Cooling Water Systems 524
24.6 Refrigeration Cycles 526
24.7 Process Expanders 530
24.8 Choice of Refrigerant for
Compression Refrigeration 532
24.9 Targeting Refrigeration Power for
Compression Refrigeration 535
24.10 Heat Integration of Compression
Refrigeration Processes 539
24.11 Mixed Refrigerants for Compression
Refrigeration 542
24.12 Absorption Refrigeration 544
24.13 Indirect Refrigeration 546
24.14 Cooling Water and Refrigeration

Systems – Summary 546
24.15 Exercises 547
References 549
Chapter 25 Environmental Design for
Atmospheric Emissions 551
25.1 Atmospheric Pollution 551
25.2 Sources of Atmospheric Pollution 552
25.3 Control of Solid Particulate
Emissions to Atmosphere 553
25.4 Control of VOC Emissions to
Atmosphere 554
25.5 Control of Sulfur Emissions 565
25.6 Control of Oxides of Nitrogen
Emissions 569
25.7 Control of Combustion Emissions 573
25.8 Atmospheric Dispersion 574
25.9 Environmental Design for
Atmospheric Emissions – Summary 575
25.10 Exercises 576
References 579
Chapter 26 Water System Design 581
26.1 Aqueous Contamination 583
26.2 Primary Treatment Processes 585
26.3 Biological Treatment Processes 588
26.4 Tertiary Treatment Processes 591
26.5 Water Use 593
26.6 Targeting Maximum Water Reuse
for Single Contaminants 594
26.7 Design for Maximum Water Reuse
for Single Contaminants 596

26.8 Targeting and Design for Maximum
Water Reuse Based on Optimization
of a Superstructure 604
26.9 Process Changes for Reduced Water
Consumption 606
26.10 Targeting Minimum Wastewater
Treatment Flowrate for Single
Contaminants 607
26.11 Design for Minimum Wastewater
Treatment Flowrate for Single
Contaminants 610
26.12 Regeneration of Wastewater 613
26.13 Targeting and Design for Effluent
Treatment and Regeneration Based
on Optimization of a Superstructure 616
26.14 Data Extraction 617
26.15 Water System Design – Summary 620
26.16 Exercises 620
References 623
Chapter 27 Inherent Safety 625
27.1 Fire 625
27.2 Explosion 626
27.3 Toxic Release 627
27.4 Intensification of Hazardous
Materials 628
xii Contents
27.5 Attenuation of Hazardous Materials 630
27.6 Quantitative Measures of Inherent
Safety 631
27.7 Inherent Safety – Summary 632

27.8 Exercises 632
References 633
Chapter 28 Clean Process Technology 635
28.1 Sources of Waste from Chemical
Production 635
28.2 Clean Process Technology for
Chemical Reactors 636
28.3 Clean Process Technology for
Separation and Recycle Systems 637
28.4 Clean Process Technology for
Process Operations 642
28.5 Clean Process Technology for
Utility Systems 643
28.6 Trading off C lean Process
Technology Options 644
28.7 Life Cycle Analysis 645
28.8 Clean Process Technology –
Summary 646
28.9 Exercises 646
References 647
Chapter 29 Overall Strategy for Chemical
Process Design and Integration 649
29.1 Objectives 649
29.2 The Hierarchy 649
29.3 The Final Design 651
Appendix A Annualization of Capital Cost 653
Appendix B Gas Compression 655
B.1 Reciprocating Compressors 655
B.2 Centrifugal Compressors 658
B.3 Staged Compression 659

Appendix C Heat Transfer Coefficients and
Pressure Drop in Shell-and-tube
Heat Exchangers 661
C.1 Pressure Drop and Heat Transfer
Correlations for the Tube-Side 661
C.2 Pressure Drop and Heat Transfer
Correlations for the Shell-Side 662
References 666
Appendix D The Maximum Thermal
Effectiveness for 1–2
Shell-and-tube Heat Exchangers 667
Appendix E Expression for the Minimum
Number of 1–2 Shell-and-tube
Heat Exchangers for a Given Unit 669
Appendix F Algorithm for the Heat Exchanger
Network Area Target 671
Appendix G Algorithm for the Heat Exchanger
Network Number of Shells Target 673
G.1 Minimum Area Target for Networks
of 1–2 Shells 674
References 677
Appendix H Algorithm for Heat Exchanger
Network Capital Cost Targets 677
Index 679
Preface
This book deals with the design and integration of chemical
processes, emphasizing the conceptual issues that are
fundamental to the creation of the process. Chemical
process design requires the selection of a series of
processing steps and their integration to form a complete

manufacturing system. The text emphasizes both the design
and selection of the steps as individual operations and their
integration to form an efficient process. Also, the process
will normally operate as part of an integrated manufacturing
site consisting of a number of processes serviced by a
common utility system. The design of utility systems has
been dealt with so that the interactions between processes
and the utility system and the interactions between different
processes through the utility system can be exploited to
maximize the performance of the site as a whole. Thus,
the text integrates equipment, process and utility system
design.
Chemical processing should form part of a sustainable
industrial activity. For chemical processing, this means
that processes should use raw materials as efficiently as is
economic and practicable, both to prevent the production
of waste that can be environmentally harmful and to
preserve the reserves of raw materials as much as possible.
Processes should use as little energy as is economic and
practicable, both to prevent the buildup of carbon dioxide
in the atmosphere from burning fossil fuels and to preserve
reserves of fossil fuels. Water must also be consumed in
sustainable quantities that do not cause deterioration in the
quality of the water source and the long-term quantity of the
reserves. Aqueous and atmospheric emissions must not be
environmentally harmful, and solid waste to landfill must
be avoided. Finally, all aspects of chemical processing must
feature good health and safety practice.
It is important for the designer to understand the
limitations of the methods used in chemical process design.

The best way to understand the limitations is to understand
the derivations of the equations used and the assumptions
on which the equations are based. Where practical, the
derivation of the design equations has been included in
the text.
The book is intended to provide a practical guide to
chemical process design and integration for undergraduate
and postgraduate students of chemical engineering, practic-
ing process designers and chemical engineers and applied
chemists working in process development. For undergrad-
uate studies, the text assumes basic knowledge of mate-
rial and energy balances, fluid mechanics, heat and mass
transfer phenomena and thermodynamics, together with
basic spreadsheeting skills. Examples have been included
throughout the text. Most of these examples do not require
specialist software and can be solved using spreadsheet soft-
ware. Finally, a number of exercises have been added at
the end of each chapter to allow the reader to practice the
calculation procedures.
Robin Smith

Acknowledgements
The author would like to express gratitude to a number
of people who have helped in the preparation and have
reviewed parts of the text.
From The University of Manchester: Prof Peter Heggs,
Prof Ferda Mavituna, Megan Jobson, Nan Zhang, Constanti-
nos Theodoropoulos, Jin-Kuk Kim, Kah Loong Choong,
Dhaval Dave,Frank DelNogal, Ramona Dragomir, Sungwon
Hwang, Santosh Jain, Boondarik Leewongtanawit, Guil-

ian Liu, Vikas Rastogi, Clemente Rodriguez, Ramagopal
Uppaluri, Priti Vanage, Pertar Verbanov, Jiaona Wang, Wen-
ling Zhang.
From Alias, UK: David Lott.
From AspenTech: Ian Moore, Eric Petela, Ian Sinclair,
Oliver Wahnschafft.
From CANMET, Canada: Alberto Alva-Argaez, Abde-
laziz Hammache, Luciana Savulescu, Mikhail Sorin.
From DuPont Taiwan: Janice Kuo.
From Monash University, Australia: David Brennan,
Andrew Hoadley.
From UOP, Des Plaines, USA: David Hamm, Greg
Maher.
Gratitude is also expressed to Simon Perry, Gareth
Maguire, Victoria Woods and Mathew Smith for help in
the preparation of the figures.
Finally, gratitude is expressed to all of the member
companies of the Process Integration Research Consortium,
both past and present. Their support has made a considerable
contribution to research in the area, and hence to this text.

Nomenclature
a Activity (–), or
constant in cubic equation of state
(N·m
4
·kmol
−2
),or
correlating coefficient (units depend on

application), or
cost law coefficient ($), or
order of reaction (–)
A Absorption factor in absorption (–), or
annual cash flow ($), or
constant in vapor pressure correlation
(N·m
−2
, bar), or
heat exchanger area (m
2
)
A
CF
Annual cash flow ($·y
−1
)
A
DCF
Annual discounted cash flow ($·y
−1
)
A
I
Heat transfer area on the inside of tubes
(m
2
), or
interfacial area (m
2

,m
2
·m
−3
)
A
M
Membrane area (m
2
)
A
NETWORK
Heat exchanger network area (m
2
)
A
O
Heat transfer area on the outside of
tubes (m
2
)
A
SHELL
Heat exchanger area for an individual
shell (m
2
)
AF Annualization factor for capital cost (–)
b Capital cost law coefficient (units
depend on cost law), or

constant in cubic equation of state
(m
3
·kmol
−1
),or
correlating coefficient (units depend on
application), or
order of reaction (–)
b
i
Bottoms flowrate of Component i
(kmol·s
−1
,kmol·h
−1
)
B Bottoms flowrate in distillation
(kmol·s
−1
,kmol·h
−1
),or
breadth of device (m), or
constant in vapor pressure correlation
(N·K·m
−2
,bar·K), or
total moles in batch distillation (kmol)
B

C
Baffle cut for shell-and-tube heat
exchangers (–)
BOD Biological oxygen demand (kg·m
−3
,
mg·l
−1
)
c Capital cost law coefficient (–), or
order of reaction (–)
c
D
Drag coefficient (–)
c
F
Fanning friction factor (–)
c
L
Loss coefficient for pipe or pipe fitting
(–)
C Concentration (kg·m
−3
,kmol·m
−3
,
ppm), or
constant in vapor pressure correlation
(K), or
number of components (separate

systems) in network design (–)
C
B
Base capital cost of equipment ($)
Ce Environmental discharge concentration
(ppm)
C
E
Equipment capital cost ($), or
unit cost of energy ($·kW
−1
,$·MW
−1
)
C
F
Fixed capital cost of complete
installation ($)
C
P
Specific heat capacity at constant
pressure (kJ·kg
−1
·K
−1
,
kJ·kmol
−1
·K
−1

)
C
P
Mean heat capacity at constant pressure
(kJ·kg
−1
·K
−1
,kJ·kmol
−1
·K
−1
)
C
V
Specific heat capacity at constant
volume (kJ·kg
−1
·K
−1
,
kJ·kmol
−1
·K
−1
)
C
∗
Solubility of solute in solvent (kg·kg
solvent

−1
)
CC Cycles of concentration for a cooling
tower (–)
COD Chemical oxygen demand (kg·m
−3
,
mg·l
−1
)
COP
HP
Coefficient of performance of a heat
pump (–)
COP
REF
Coefficient of performance of a
refrigeration system (–)
xviii Nomenclature
CP Capacity parameter in distillation
(m·s
−1
)or
heat capacity flowrate (kW·K
−1
,
MW·K
−1
)
CP

EX
Heat capacity flowrate of heat engine
exhaust (kW·K
−1
,MW·K
−1
)
CW Cooling water
d Diameter (µm, m)
d
i
Distillate flowrate of Component i
(kmol·s
−1
,kmol·h
−1
)
d
I
Inside diameter of pipe or tube (m)
D Distillate flowrate (kmol·s
−1
,kmol·h
−1
)
D
B
Tube bundle diameter for shell-and-tube
heat exchangers (m)
D

S
Shell diameter for shell-and-tube heat
exchangers (m)
DCFRR Discounted cash flowrate of return (%)
E Activation energy of reaction
(kJ·kmol
−1
), or
entrainer flowrate in azeotropic and
extractive distillation (kg·s
−1
,
kmol·s
−1
), or
extract flowrate in liquid–liquid
extraction (kg·s
−1
,kmol·s
−1
), or
stage efficiency in separation (–)
E
O
Overall stage efficiency in distillation
and absorption (–)
EP Economic potential ($·y
−1
)
f Fuel-to-air ratio for gas turbine (–)

f
i
Capital cost installation factor for
Equipment i (–), or
feed flowrate of Component i
(kmol·s
−1
,kmol·h
−1
), or
fugacity of Component i (N·m
−2
,bar)
f
M
Capital cost factor to allow for material
of construction (–)
f
P
Capital cost factor to allow for design
pressure (–)
f
T
Capital cost factor to allow for design
temperature (–)
F Feed flowrate (kg·s
−1
,kg·h
−1
,

kmol·s
−1
,kmol·h
−1
), or
future worth a sum of money allowing
for interest rates ($), or
volumetric flowrate (m
3
·s
−1
,m
3
·h
−1
)
F
LV
Liquid–vapor flow parameter in
distillation (–)
F
T
Correction factor for noncountercurrent
flow in shell-and-tube heat
exchangers (–)
F
Tmin
Minimum acceptable F
T
for

noncountercurrent heat exchangers
(–)
g Acceleration due to gravity (9.81
m·s
−2
)
g
ij
Energy of interaction between
Molecules i and j in the NRTL
equation (kJ·kmol
−1
)
G Free energy (kJ), or
gas flowrate (kg·s
−1
,kmol·s
−1
)
G
i
Partial molar free energy of Component
i (kJ·kmol
−1
)
G
O
i
Standard partial molar free energy of
Component i (kJ·kmol

−1
)
h Settling distance of particles (m)
h
C
Condensing film heat transfer
coefficient (W·m
−2
·K
−1
,
kW·m
−2
·K
−1
)
h
I
Film heat transfer coefficient for the
inside (W·m
−2
·K
−1
,kW·m
−2
·K
−1
)
h
IF

Fouling heat transfer coefficient for the
inside (W·m
−2
·K
−1
,kW·m
−2
·K
−1
)
h
L
Head loss in a pipe or pipe fitting (m)
h
NB
Nucleate boiling heat transfer
coefficient (W·m
−2
·K
−1
,
kW·m
−2
·K
−1
)
h
O
Film heat transfer coefficient for the
outside (W·m

−2
·K
−1
,kW·m
−2
·K
−1
)
h
OF
Fouling heat transfer coefficient for the
outside (W·m
−2
·K
−1
,kW·m
−2
·K
−1
)
h
W
Heat transfer coefficient for the tube
wall (W·m
−2
·K
−1
,kW·m
−2
·K

−1
)
H Enthalpy (kJ, kJ·kg
−1
,kJ·kmol
−1
),or
height (m), or
Henry’s Law Constant (N·m
−2
,bar,
atm), or
stream enthalpy (kJ·s
−1
,MJ·s
−1
)
H
T
Tray spacing (m)
Nomenclature xix
H
O
i
Standard heat of formation of
Component i (kJ·kmol
−1
)
H
O

Standard heat of reaction (J, kJ)
H
COMB
Heat of combustion (J·kmol
−1
,
kJ·kmol
−1
)
H
O
COMB
Standard heat of combustion at 298 K
(J·kmol
−1
,kJ·kmol
−1
)
H
P
Heat to bring products from standard
temperature to the final temperature
(J·kmol
−1
,kJ·kg
−1
)
H
R
Heat to bring reactants from their initial

temperature to standard temperature
(J·kmol
−1
,kJ·kmol
−1
)
H
STEAM
Enthalpy difference between generated
steam and boiler feedwater (kW,
MW)
H
VAP
Latent heat of vaporization (kJ·kg
−1
,
kJ·kmol
−1
)
HETP Height equivalent of a theoretical plate
(m)
HP High pressure
HR Heat rate for gas turbine (kJ·kWh
−1
)
i Fractional rate of interest on money
(–), or
number of ions (–)
I Total number of hot streams (–)
J Total number of cold streams (–)

k Reaction rate constant (units depend on
order of reaction), or
thermal conductivity (W·m
−1
·K
−1
,
kW·m
−1
·K
−1
)
k
G,i
Mass transfer coefficient in the gas
phase (kmol·m
−2
·Pa
−1
·s
−1
)
k
ij
Interaction parameter between
Components i and j in an equation
of state (–)
k
L,i
Mass transfer coefficient in the liquid

phase (m·s
−1
)
k
0
Frequency factor for heat of reaction
(units depend on order of
reaction)
K Overall mass transfer coefficient
(kmol·Pa
−1
·m
−2
·s
−1
) or
total number of enthalpy intervals in
heat exchanger networks (–)
K
a
Equilibrium constant of reaction based
on activity (–)
K
i
Ratio of vapor to liquid composition at
equilibrium for Component i (–)
K
M,i
Equilibrium partition coefficient of
membrane for Component i (–)

K
p
Equilibrium constant of reaction based
on partial pressure in the vapor phase
(–)
K
T
Parameter for terminal settling velocity
(m·s
−1
)
K
x
Equilibrium constant of reaction based
on mole fraction in the liquid phase
(–)
K
y
Equilibrium constant of reaction based
on mole fraction in vapor phase (–)
L Intercept ratio for turbines (–), or
length (m), or
liquid flowrate (kg·s
−1
,kmol·s
−1
),or
number of independent loops in a
network (–)
L

B
Distance between baffles in
shell-and-tube heat exchangers (m)
LP Low pressure
m Mass flowrate (kg·s
−1
),or
molar flowrate (kmol·s
−1
),or
number of items (–)
M Constant in capital cost correlations
(–), or
molar mass (kg·kmol
−1
)
MP Medium pressure
MC
STEAM
Marginal cost of steam ($·t
−1
)
n Number of items (–), or
number of years (–), or
polytropic coefficient (–), or
slope of Willans’ Line (kJ·kg
−1
,
MJ·kg
−1

)
N Number of compression stages (–), or
number of moles (kmol), or
number of theoretical stages (–), or
rate of transfer of a component
(kmol·s
−1
·m
−3
)
N
i
Number of moles of Component i
(kmol)
N
i0
Initial number of moles of Component
i (kmol)
N
PT
Number of tube passes (–)
N
R
Number of tube rows (–)
xx Nomenclature
N
SHELLS
Number of number of 1–2 shells in
shell-and-tube heat exchangers (–)
N

T
Number of tubes (–)
N
UNITS
Number of units in a heat exchanger
network (–)
NC Number of components in a
multicomponent mixture (–)
NPV Net present value ($)
p Partial pressure (N·m
−2
,bar)
p
C
Pitch configuration factor for tube
layout (–)
p
T
Tube pitch (m)
P Present worth of a future sum of money
($), or
pressure (N·m
−2
, bar), or
probability (–), or
thermal effectiveness of 1–2
shell-and-tube heat exchanger (–)
P
C
Critical pressure (N·m

−2
,bar)
P
max
Maximum thermal effectiveness of 1–2
shell-and-tube heat exchangers (–)
P
M,i
Permeability of Component i for a
membrane (kmol·m·s
−1
·m
−2
·bar
−1
,
kg solvent ·m
−1
·s
−1
·bar
−1
)
P
M,i
Permeance of Component i for a
membrane (m
3
·m
−2

·s
−1
·bar
−1
)
P
N−2N
Thermal effectiveness over N
SHELLS
number of 1–2 shell-and-tube heat
exchangers in series (–)
P
1−2
Thermal effectiveness over each 1–2
shell-and-tube heat exchanger in
series (–)
P
SAT
Saturated liquid–vapor pressure
(N·m
−2
,bar)
Pr Prandtl number (–)
q Heat flux (W·m
−2
,kW·m
−2
), or
thermal condition of the feed in
distillation (–), or

Wegstein acceleration parameter for the
convergence of recycle calculations
(–)
q
C
Critical heat flux (W·m
−2
,kW·m
−2
)
q
C1
Critical heat flux for a single tube
(W·m
−2
,kW·m
−2
)
q
i
Individual stream heat duty for Stream
i (kJ·s
−1
),or
pure component property measuring the
molecular van der Waals surface area
for Molecule i in the UNIQUAC
Equation (–)
Q Heat duty (kW, MW)
Qc Cooling duty (kW, MW)

Qc
min
Target for cold utility (kW, MW)
Q
COND
Condenser heat duty (kW, MW)
Q
EVAP
Evaporator heat duty (kW, MW)
Q
EX
Heat duty for heat engine exhaust (kW,
MW)
Q
FEED
Heat duty to the feed (kW, MW)
Q
FUEL
Heat from fuel in a furnace, boiler, or
gas turbine (kW, MW)
Q
H
Heating duty (kW, MW)
Q
Hmin
Target for hot utility (kW, MW)
Q
HE
Heat engine heat duty (kW, MW)
Q

HEN
Heat exchanger network heat duty (kW,
MW)
Q
HP
Heat pump heat duty (kW, MW)
Q
LOSS
Stack loss from furnace, boiler, or gas
turbine (kW, MW)
Q
REACT
Reactor heating or cooling duty (kW,
MW)
Q
REB
Reboiler heat duty (kW, MW)
Q
REC
Heat recovery (kW, MW)
Q
SITE
Site heating demand (kW, MW)
Q
STEAM
Heat input for steam generation (kW,
MW)
r Molar ratio (–), or
pressure ratio (–), or
radius (m)

r
i
Pure component property measuring the
molecular van der Waals volume for
Molecule i in the UNIQUAC
Equation (–), or
rate of reaction of Component i
(kmol
−1
·s
−1
),or
recovery of Component i in separation
(–)
R Fractional recovery of a component in
separation (–), or
Nomenclature xxi
heat capacity ratio of 1–2
shell-and-tube heat exchanger (–), or
raffinate flowrate in liquid–liquid
extraction (kg·s
−1
,kmol·s
−1
),or
ratio of heat capacity flowrates (–), or
reflux ratio for distillation (–), or
removal ratio in effluent treatment (–),
or
residual error (units depend on

application), or
universal gas constant
(8314.5 N·m·kmol
−1
K
−1
=
J·kmol
−1
K
−1
,
8.3145 kJ·kmol
−1
·K
−1
)
R
min
Minimum reflux ratio (–)
R
F
Ratio of actual to minimum reflux ratio
(–)
R
SITE
Site power-to-heat ratio (–)
ROI Return on investment (%)
Re Reynolds number (–)
s Reactor space velocity (s

−1
,min
−1
,
h
−1
),or
steam-to-air ratio for gas turbine (–)
S Entropy (kJ·K
−1
,kJ·kg
−1
·K
−1
,
kJ·kmol
−1
·K
−1
),or
number of streams in a heat exchanger
network (–), or
reactor selectivity (–), or
reboil ratio for distillation (–), or
selectivity of a reaction (–), or
slack variable in optimization (units
depend on application), or
solvent flowrate (kg ·s
−1
,kmol·s

−1
),or
stripping factor in absorption (–)
S
C
Number of cold streams (–)
S
H
Number of hot streams (–)
t Time (s, h)
T Temperature (
◦
C, K)
T
BPT
Normal boiling point (
◦
C, K)
T
C
Critical temperature (K), or
temperature of heat sink (
◦
C, K)
T
COND
Condenser temperature (
◦
C, K)
T

E
Equilibrium temperature (
◦
C, K)
T
EVAP
Evaporation temperature (
◦
C, K)
T
FEED
Feed temperature (
◦
C, K)
T
H
Temperature of heat source (
◦
C, K)
T
R
Reduced temperature T/T
C
(–)
T
REB
Reboiler temperature (
◦
C, K)
T

S
Stream supply temperature (
◦
C)
T
SAT
Saturation temperature of boiling liquid
(
◦
C, K)
T
T
Stream target temperature (
◦
C)
T
TFT
Theoretical flame temperature (
◦
C, K)
T
W
Wall temperature (
◦
C)
T
WBT
Wet bulb temperature (
◦
C)

T
∗
Interval temperature (
◦
C)
T
LM
Logarithmic mean temperature
difference (
◦
C, K)
T
min
Minimum temperature difference
(
◦
C, K)
T
SAT
Difference in saturation temperature
(
◦
C, K)
T
THRESHOLD
Threshold temperature difference (
◦
C,
K)
TAC Total annual cost ($·y

−1
)
TOD Total oxygen demand (kg·m
−3
,mg·l
−1
)
u
ij
Interaction parameter between Molecule
i and Molecule j in the UNIQUAC
Equation (kJ·kmol
−1
)
U Overall heat transfer coefficient
(W·m
−2
·K
−1
,kW·m
−2
·K
−1
)
v Velocity (m·s
−1
)
v
T
Terminal settling velocity (m·s

−1
)
v
V
Superficial vapor velocity in empty
column (m·s
−1
)
V Molar volume (m
3
·kmol
−1
),or
vapor flowrate (kg·s
−1
,kmol·s
−1
),or
volume (m
3
),or
volume of gas or vapor adsorbed
(m
3
·kg
−1
)
V
min
Minimum vapor flow (kg·s

−1
,
kmol·s
−1
)
VF Vapor fraction (–)
w Mass of adsorbate per mass of
adsorbent (–)
W Shaft power (kW, MW), or
shaft work (kJ, MJ)
W
GEN
Power generated (kW, MW)
W
INT
Intercept of Willans’ Line (kW, MW)
xxii Nomenclature
W
SITE
Site power demand (kW, MW)
x Liquid-phase mole fraction (–) or
variable in optimization problem (–)
x
F
Mole fraction in the feed (–)
x
D
Mole fraction in the distillate (–)
X Reactor conversion (–) or
wetness fraction of steam (–)

X
E
Equilibrium reactor conversion (–)
X
OPT
Optimal reactor conversion (–)
X
P
Fraction of maximum thermal
effectiveness P
max
allowed in a 1–2
shell-and-tube heat exchanger (–)
XP Cross-pinch heat transfer in heat
exchanger network (kW, MW)
y Integer variable in optimization (–), or
vapor-phase mole fraction (–)
z Elevation (m), or
feed mole fraction (–)
Z Compressibility of a fluid (–)
GREEK LETTERS
α Constant in cubic equation of state (–),
or
constants in vapor pressure correlation
(units depend on which constant), or
fraction open of a valve (–)
α
ij
Ideal separation factor or selectivity of
membrane between Components i

and j (–), or
parameter characterizing the tendency
of Molecule i and Molecule j to be
distributed in a random fashion in the
NRTL equation (–), or
relative volatility between Components
i and j (–)
α
LH
Relative volatility between light and
heavy key components (–)
β
ij
Separation factor between Components
i and j (–)
γ Ratio of heat capacities for gases and
vapors (–)
γ
i
Activity coefficient for Component i
(–)
δ
M
Membrane thickness (m)
ε Extraction factor in liquid–liquid
extraction (–), or
pipe roughness (mm)
η Carnot factor (–), or
efficiency (–)
η

BOILER
Boiler efficiency (–)
η
COGEN
Cogeneration efficiency (–)
η
GT
Efficiency of gas turbine (–)
η
IS
Isentropic efficiency of compression or
expansion (–)
η
MECH
Mechanical efficiency of steam turbine
(–)
η
P
Polytropic efficiency of compression or
expansion (–)
η
POWER
Power generation efficiency (–)
η
ST
Efficiency of steam turbine (–)
θ Fraction of feed permeated through
membrane (–), or
root of the Underwood Equation (–)
λ Ratio of latent heats of vaporization (–)

λ
ij
Energy parameter characterizing the
interaction of Molecule i with
Molecule j (kJ·kmol
−1
)
µ Fluid viscosity (kg·m
−1
·s
−1
,
mN·s·m
−2
= cP)
π Osmotic pressure (N·m
−2
,bar)
ρ Density (kg·m
−3
,kmol·m
−3
)
σ Surface tension
(mN·m
−1
= mJ·m
−2
= dyne·cm
−1

)
τ Reactor space time (s, min, h) or
residence time (s, min, h)
φ Cost-weighing factor applied to film
heat transfer coefficients to allow for
mixed materials of construction,
pressure rating, and equipment types
in heat exchanger networks (–), or
fugacity coefficient (–)
ω Acentric factor (–)
SUBSCRIPTS
B Blowdown, or
bottoms in distillation
BFW Boiler feedwater
Nomenclature xxiii
cont Contribution
C Cold stream, or
contaminant
CN Condensing
COND Condensing conditions
CP Continuous phase
CW Cooling water
D Distillate in distillation
DS De-superheating
e Enhanced, or
end zone on the shell-side of a heat
exchanger, or
environment
E Extract in liquid–liquid extraction
EVAP Evaporator conditions

EX Exhaust
final Final conditions in a batch
F Feed, or
fluid
G Gas phase
H Hot stream
HP Heat pump, or
high pressure
i Component number, or
stream number
I Inside
IS Isentropic
in Inlet
j Component number, or
stream number
k Enthalpy interval number in heat
exchanger networks
L Liquid phase
LP Low pressure
m Stage number in distillation and
absorption
max Maximum
min Minimum
M Makeup
MIX Mixture
n Stage number in distillation and
absorption
out Outlet
O Outside, or
standard conditions

p Stage number in distillation and
absorption
prod Products of reaction
P Particle, or
permeate
react Reactants
R Raffinate in liquid–liquid extraction
REACT Reaction
S Solvent in liquid–liquid extraction
SAT Saturated conditions
SF Supplementary firing
SUP Superheated conditions
T Treatment
TW Treated water
V Vapor
w Window section on the shell-side of a
heat exchanger
W Conditions at the tube wall, or
water
∞ Conditions at distillate pinch point
SUPERSCRIPTS
I Phase I
II Phase II
III Phase III
L Liquid
O Standard conditions
V Vapor
* Adjusted parameter