Unit operations of chemical engineering

UNIT OPERATIONS
OF CHEMICAL ENGINEERING


McGraw-Hill Chemical Engineering Series
Editorial Advisory Board
James J. Carberry, Professor of Chemical Engineering, University of Notre Dame
James R. Fair, Professor of Chemical Engineering, University of Texas, Austin
William P. Schowalter, Dean, School of Engineering, University of Illinois
Matthew Tirrell, Professor of Chemical Engineering, University of Minnesota
James Wei, Dean, School of Engineering, Princeton University
Max S. Peters, Emeritus, Professor of Chemical Engineering, University of Colorado

Building the Literature of a Profession
Fifteen prominent chemical engineers first met in New York more than 60 years
ago to plan a continuing literature for their rapidly growing profession. From
Industry came such pioneer practitioners as Leo H. Baekeland, Arthur D. Little,
Charles L. Reese, John V. N. Dorr, M. C. Whitaker, and R. S. McBride. From
the universities came such eminent educators as William H. Walker, Alfred H.
White, D. D. Jackson, J. H. James, Warren K. Lewis, and Harry A. Curtis. H. C.
Parmelee, then editor of Chemical and Metallurgical Engineering, served as
chairman and was joined subsequently by S. D. Kirkpatrick as consulting editor.
After several meetings, this committee submitted its report to the McGrawHill Book Company in September 1925. In the report were detailed specifications
for a correlated series of more than a dozen texts and reference books which have
since become the McGraw-Hill Series in Chemical Engineering and which became
the cornerstone of the chemical engineering curriculum.
From this beginning there has evolved a series of texts surpassing by far the
scope and longevity envisioned by the founding Editorial Board. The McGrawHill Series in Chemical Engineering stands as a unique historical record of the
development of chemical engineering education and practice. In the series one finds
the milestones of the subject's evolution: industrial chemistry, stoichiometry, unit

operations and processes, thermodynamics, kinetics, and transfer operations.
Chemical engineering is a dynamic profession, and its literature continues
to evolve. McGraw-Hill, with its editor, B. J. Clark and its consulting editors,
remains committed to a publishing policy that will serve, and indeed lead, the
needs of the chemical engineering profession during the years to come.


The Series
Bailey and Ollis: Biochemical Engineering Fundamentals
Bennett and Myers: Momentum, Heat, and Mass Transfer
Brodkey and Hershey: Transport Phenomena: A Unified Approach
Carberry: Chemical and Catalytic Reaction Engineering
Constantinides: Applied Numerical Methods with Personal Computers
Coughanowr: Process Systems Analysis and Control
de Nevers: Fluid Mechanics for Chemical Engineers
Douglas: Conceptual Design of Chemical Processes
Edgar and Himmelblau: Optimization of Chemical Processes
Gates, Katzer, and Schuit: Chemistry of Catalytic Processes
Holland: Fundamentals of Multicomponent Distillation
Holland and Liapis: Computer Methods for Solving Dynamic Separation Problems
Katz and Lee: Natural Gas Engineering: Production and Storage
King: Separation Processes
Lee: Fundamentals of Microelectronics Processing
Luyben: Process Modeling, Simulation, and Control for Chemical Engineers
McCabe, Smith, and Harriott: Unit Operations of Chemical Engineering
Mickley, Sherwood, and Reed: Applied Mathematics in Chemical Engineering
Middleman and Hochberg: Process Engineering Analysis in Semiconductor Device
Fabrication
Nelson: Petroleum Refinery Engineering
Perry and Chilton (Editors): Perry -s Chemical Engineers' Handbook

Peters: Elementary Chemical Engineering
Peters and Timmerhaus: Plant Design and Economics for Chemical Engineers
Reid, Prausnitz, and Rolling: Properties of Gases and Liquids
Smith: Chemical Engineering Kinetics
Smith and Van Ness: Introduction to Chemical Engineering Thermodynamics
Treybal: Mass Transfer Operations
Valle-Riestra: Project Evaluation in the Chemical Process Industries
Wei, Russell, and Swartzlander: The Structure of the Chemical Processing Industries
Wentz: Hazardous Waste Management



UNIT
OPERATIONS
OF CHEMICAL
ENGINEERING
Fifth Edition

Warren L. McCabe
Late R J. Reynolds Professor in Chemical Engineering
North Carolina State University

Julian C. Smith
Emeritus Professor of Chemical Engineering
Cornell University

Peter Harriott
Fred H. Rhodes Professor of Chemical Engineering
Cornell University

McGraw-Hill, Inc.
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UNIT OPERATIONS OF CHEMICAL ENGINEERING
International Editions 1993
Exclusive rights by McGraw-Hill Book Co. - Singapore for manufacture and export. Tllis
book cannot be re-exported from the cowttry to which it is consigned by McGraw-Hill.
Copyright © 1993, 1985, 1976, 1967, 1956 by McGraw-Hill, Inc. All rights reserved.
Except as pernlitted under the United States Copyright Act of 1976, no part of this
publication may be reproduced or distributed in any fonn or by any means, or stored in a data
base or retrieval system, without the prior written permission of the publisher.
I 2 3 4 5 6 7 8 9 0 CWP PMP 9 8 7 6 5 4 3

This book was set in Times Roman.
The editors were B.J. Clark and Eleanor Castellano;
the production supervisor was Louise Karam.
The cover was designed by Joseph Gi!lians.
Library of Congress Cataloging-in-Publication Data

McCabe, Warren L. (Warren Lee), (date).
Unit operations of chemical engineering I Warren L. McCabe, Julian C. Smitl1,
Peter Harriott. -5th ed.
p. em. - (McGraw-Hill chemical engineering series)
Includes index.
ISBN 0-07-044844-2
I. Chenlical processes.
I. Snlith, Julian C. (Julian Cleveland), (date).

II. Harriott, Peter.
III. Title.
IV. Series.
1P155. 7. M393
1993
660'. 2842-dc20
92-36218
When ordering this title, use ISBN 0-07-112738-0

Printed in Singapore


ABOUT THE AUTHORS

Julian C. Smith (B.Chem., Chem.E., Cornell University) is Professor Emeritus
of Chemical Engineering at Cornell University, where he joined the faculty in 1946.
He was Director of Continuing Engineering Education at Cornell from 1965 to
1971, and Director of the School of Chemical Engineering from 1975 to 1983. He
retired from active teaching in 1986. Before joining the faculty at Cornel~ he was
employed as a chemical engineer by E.I. duPont de Nemours and Co. He has
served as a consultant on process development to Du Pont, American Cyanamid,
and many other companies, as well as government agencies. He is a member of
the American Chemical Society and a Fellow of the American Institute of Chemical
Engineers.
Peter Harriott (B. Chem.E., Cornell University, SeD., Massachusetts Institute of
Technology) is the Fred H. Rhodes Professor of Chemical Engineering at Cornell
University. Before joining the Cornell faculty in 1953, he worked as a chemical
engineer for the E.L duPont de Nemours and Co. and the General Electric Co.
In 1966 he was awarded an NSF Senior Postdoctoral Fellowship for study at the
Institute for Catalysis in Lyon, France, and in 1988 he received a DOE fellowship

for work at the Pittsburgh Energy Technology Center. Professor Harriott is the
author of Process Control and a member of the American Chemical Society and
the American Institute of Chemical Engineers. He has been a consultant to the
U.S. Department of Energy and several industrial firms on problems of mass
transfer, reactor design, and air pollution control.



CONTENTS

Preface

xix

Section 1 Introduction
1 Definitions and Principles

3

Unit Operations
Unit Systems
Physical Quantities
SI Units
Cgs Units
Gas Constant
Fps Engineering Units
Conversion of Units
Units and Equations
Dimensional Analysis
Basic Concepts

Equations of State of Gases
Symbols
Problems
References

4
5
5
5
9

10
II

12
14
16
18
18
20
22
23

Section 2 Fluid Mechanics

25

2 Fluid Statics and Its Applications

27

39

Symbols
Problems
References

40
41
ix


X

CONTENTS

3 Fluid-Flow Phenomena
Turbulence
Symbols
Problems
References

4

Basic Equations of Fluid Flow
Symbols
Problems

References

42

48
61
62
62
64
81
82
82

5 Flow of Incompressible Fluids in Conduits and Thin Layers 83
Flow of Incompressible Fluids in Pipes
Laminar Flow in Pipes
Turbulent Flow in Pipes and Closed Channels
Flow of Liquids in Thin Layers
Symbols
Problems
References

6

Flow of Compressible Fluids
Processes of Compressible Flow
How through Variable-Area Conduits
Adiabatic Frictional Flow
Isothermal Frictional Flow
Symbols
Problems

References

7 Flow Past Immersed Bodies
Friction in Flow through Beds of Solids
Motion of Particles through Fluids
Fluidization
Symbols
Problems

References

8 Transportation and Metering of Fluids
Pipe, Fittings, and Valves
Fluid-moving Machinery
Pumps
Positive-Displacement Pumps
Centrifugal Pumps
Fans, Blowers, and Compressors
Measurement of Flowing Fluids
Full-Bore Meters
Insertion Meters

83
86
92

112
115
117
119
120
125

126
133
137
139
141
142
143
151
155
165
177
178
180
181
181
188
189
193
195
204
214
215
229


Symbols
Problems
References

9 Agitation and Mixing of Liquids

Agitation of Liquids
Circulation, Velocities, and Power Consumption in Agitated Vessels
Blending and Mixing
Suspension of Solid Particles

Dispersion Operations
Symbols
Problems
References

Section 3 Heat Transfer and Its Applications

231
233
234
235
236
243
257
264
269
279
281
282

285

Heat Transfer by Conduction

289

Steady-State Conduction
Unsteady-State Conduction
Symbols
Problems
References

292

299
306
307
308

Principles of Heat Flow in Fluids

309

Energy Balances
Rate of Heat Transfer
Overall Heat-Transfer Coefficient
Individual Heat-Transfer Coefficients
Effective Coefficients for Unsteady-State Heat Transfer
Symbols
Problems
References

313

12 Heat Transfer to Fluids without Phase Change

330

10

11

315
315
319
327
328
329
329

Heat Transfer by Forced Convection in Laminar Flow

333

Heat Transfer by Forced Convection in Turbulent Flow
Transfer by Turbulent Eddies and Analogy between Transfer
of Momentum and Heat
Heat Transfer in Transition Region between Laminar and Turbulent Flow
Transfer to Liquid Metals
Heating and Cooling of Fluids in Forced Convection outside Tubes
Natural Convection
Symbols
Problems
References

340
348
353
355
359
362
369
371
373


XII

CONTENTS

13 Heat Transfer to Fluids with Phase Change
Heat Transfer from Condensing Vapors
Heat Transfer to Boiling Liquids
Symbols
Problems
References

14

Radiation Heat Transfer
Emission of Radiation
Absorption of Radiation by Opaque Solids
Radiation between Surfaces
Radiation to Semitransparent Materials
Combined Heat Transfer by Conduction-Convection and Radiation

Symbols
Problems
References

15 Heat-Exchange Equipment
Heat Exchangers
Condensers
Boilers and Calandrias
Ext•nded Surface Equipment
Heat Transfer in Agitated Vessels
Scraped-Surface Exchangers
Heat Transfer in Packed Beds
Symbols
Problems
References

16 Evaporation
Types of Evaporators
Performance of Tubular Evaporators
Evaporator Capacity
Evaporator Economy
Vapor Recompression
Symbols
Problems
References

374
374
385
394

395
396
397
398
402
405
416
422
423
425
426
427
428
439
442
445
451
453
455
457
459
461
463
465
470
470
476
490
492
492

494

Section 4 Mass Transfer and Its Applications
17 Equilibrium-Stage Operations
Principles of Stage Processes
Equilibrium-Stage Calculations for Multicomponent Systems

501
505.
519


Symbols
Problems
References

18 Distillation
Flash Distillation
Continuous Distillation with Reflux (Rectification)
Material Balances in Plate Columns
Number of Ideal Plates; McCabe-Thiele Method
Enthalpy Balances for Fractionating Columns
Design of Sieve-Plate Columns
Plate Efficiency
Rectification in Packed Towers
Batch Distillation
Symbols
Problems
References

19 Introduction to Multicornponent Distillation
Flash Distillation of Multicomponent Mixtures
Fractionation of Multicomponent Mixtures
Azeotropic and Extractive Distillation
Symbols
Problems
References

20 Leaching and Extraction
Leaching
Leaching Equipment
Principles of Continuous Countercurrent Leaching
Liquid Extraction
Extraction Equipment
Principles of Extraction
Supercritical Fluid Extraction
Symbols
Problems
References

21 Principles of Diffusion and Mass Transfer between Phases
Theory of Diffusion
Mass-Transfer Coefficients and Film Theory
Penetration Theory of Mass Transfer
Experimental Measurement of Mass-Transfer Coefficients
Coefficients for Mass Transfer through Known Areas
Mass Transfer to Pipes and Cylinders
Mass Transfer to Particles
Two-Film Theory
Stage Efficiencies

519
519
520
521
521
525
529
531
553
560
568
576
576
580
582
587
588
592
593
609
610
611
613
614
614
615
617
623
624

632
641
643
644

646
647
648
658
662
663
665
666
670
674
676


XIV

CONTENTS

Symbols
Problems
References

22 Gas Absorption
Design of Packed Towers
Principles of Absorption
Rate of Absorption

Mass-Transfer Correlations
Absorption in Plate Columns
Absorption from Rich Gases
Absorption with Chemical Reaction
Other Separations in Packed Columns
Symbols
Problems

References

23 Humidification Operations
Wet-Bulb Temperature and Measurement of Humidity
Equipment for Humidification Operations
Theory and Calculation of Humidification Processes
Symbols
Problems

References

24 Drying of Solids
Principles of Drying
Phase Equilibria
Cross-Circulation Drying
Through-Circulation Drying
Drying of Suspended Particles
Drying Equipment
Dryers for Solids and Pastes
Dryers for Solutions and Slurries
Selection of Drying Equipment
Symbols

Problems
References

25 Adsorption
Adsorption Equipment
Equilibria; Adsorption Isotherms
Principles of Adsorption
Basic Equations for Adsorption
Solutions to Mass-Transfer Equations
Adsorber Design
Symbols
Problems
References

681
683
685
686
686
697
701
713
721
722
728
730
732
734
736
738

747
751
753
763
764
766
767
769
774
776
788
791
791
791
801
805
806
808
809
810
811
814
818
825
826
832
834
835
837

26 Membrane Separation Processes
Separation of Gases
Separation of Liquids
Dialysis

Membranes for Liquid-Liquid Extraction
Pervaporation
Reverse Osmosis

Symbols
Problems
References

27 Crystallization
Crystal Geometry
Principles of Crystallization

Equilibria and Yields
Nucleation

Crystal Growth
Crystallization Equipment
Applications of Principles to Design

MSMPR Crystallizer
Crysta11ization from Melts
Symbols
Problems

References

838
838
859
860
862
864
871
878
879
881
882
883
884
884

892
899
902
909
909
918
920
921
923

Section 5 Operations Involving Particulate Solids

925

28 Properties, Handling, and Mixing of Particulate Solids

927

Characterization of Solid Particles

927

Properties of Particulate Masses
Storage of Solids
Mixing of Solids
Types of Mixers
Mixers for Cohesive Solids
Mixers for Free-Flowing Solids
Symbols
Problems
References

936
939
941
942
943
952
957
958
959

29 Size Reduction

Principles of Comminution
~ ·. Computer Simulation of Milling Operations
Size-Reduction Equipment

Crushers
Grinders
Ultrafine Grinders
Cutting Machines

960
961
965
970
971
975
982
986


Xl'l

CONTENTS

Equipment Operation

Symbols
Problems
References

30 MechaniCal Separations

Screening
Screening Equipment
Filtration

Cake Filters
Centrifugal Filters
Principles of Cake Filtration
Clarifying Filters

Liquid Clarification
Gas Cleaning
Principles of Clarification
Crossftow Filtration
Types of Membranes
Permeate Flux for Ultrafiltration
Concentration Polarization
Partial Rejection of Solutes
Microfiltration
Separation Based on the Motion of Particles through Fluids
Gravity Settling Processes
Centrifugal Settling Processes

Symbols
Problems
References

Appendixes
Appendix I Cgs and SI Prefixes for Multiples and Submultiples
Appendix 2 Values of Gas Constant

987
990
992
992
994
994
995
1002
1003
1011
1016
1030
1030
1031
1032
1033
1034
1036
1037
1043
1046
1047
1048
1060
1072
1074
1076
1079
1079
1080

Appendix 3

Conversion Factors and Constants of Nature

1081

Appendix
Appendix
Appendix
Appendix
Appendix
Appendix
Appendix

Dimensionless Groups
Dimensions, Capacities, and Weights of Standard Steel Pipe
Condenser and Heat-Exchanger Tube Data
Properties of Saturated Steam and Water
Viscosities of Gases
Viscosities of Liquids
Thermal Conductivities of Metals

1084
1086
1088
1090
1092
1094
1097

4
5
6
7
8
9
10

Appendix 11 Thermal Conductivities of Various Solids and Insulating

Appendix 12
Appendix 13
Appendix 14
Appendix,15
Appendix 16
Appendix 17

Materials
Thermal Conductivities of Gases and Vapors
Thermal Conductivities of Liquids Other Than Water
Properties of Liquid Water
Specific Heats of Gases
Specific Heats of Liquids
Prandtl Numbers for Gases at I atm and I00°C

1098
1100
1101
1102

1103
1104
1105


Appendix 18 Prandtl Numbers for Liquids

1106

Appendix 19 Diffusivities and Schmidt Numbers for Gases in Air at 0°C

and I atm
Appendix 20 Tyler Standard Screen Scale
Appendix 21 K Values for Light Hydrocarbons (Low Temperatures)
Appendix 22 K Values for Light Hydrocarbons (High Temperatures)

1107
1108
1110
1111

Index

1113



PREFACE

This revised edition of the text on the unit operations of chemical engineering

contains much updated and new material, reflecting, in part, the broadening of
the chemical engineering profession into new areas such as food processing,
electronics, and biochemical applications. Its basic structure and general level of
treatment, however, remain unchanged from previous editions. It is a beginning
text, written for undergraduate students in the junior or senior years who have
completed the usual courses in mathematics, physics, chemistry, and an introduction to chemical engineering. An elementary knowledge of material and energy
balances and of thermodynamic principles is assumed.
Separate chapters are devoted to each of the principal operations, which are
grouped in four main sections: fluid mechanics, heat transfer, equilibrium stages
and mass transfer, and operations involving particulate solids. One-semester or
one-quarter courses may be based on any of these sections or combinations of
them.
In this edition SI units are emphasized much more than in previous editions,
but the older cgs and fps systems have not been completely eliminated. Chemical
engineers must still be able to use all three systems of units. The great majority
of the equations and correlations, it should be noted, are dimensionless and may
be used with any set of consistent units.
A new chapter on membrane separations has been added, and the order of
the chapters on multi component distillation, extraction, drying, and crystallization
has been made more logical. The discussion of particulate solids has been
shortened and two former chapters on properties and handling of solids and of
solids mixing have been combined into one. New material has been added on flow
measurement, dispersion operations, supercritical extraction, pressure-swing adsorption, crystallization techniques, crossflow filtration, sedimentation, and many
other topics. The treatment of dimensional analysis has been condensed and moved
from the appendixes to Chapter 1.

xix


A.A.

PKI::t'ACE

About two-thirds of the problems at the ends of the chapters are new or
revised, with a large majority of them expressed in SI units. Nearly all the problems
can be solved with the aid of a pocket calculator, although a computer solution
may be preferred in some cases.
McGraw-Hill and the authors would like to thank Edward Cussler, University of Minnesota, and Robert Kabel, Pennsylvania State University, for their
helpful reviews of the manuscript.
The senior author, Dr. Warren L. McCabe, died in August 1982. This book
is dedicated to his memory.
Julian C. Smith
Peter Harriott


SECTION

I
INTRODUCTION



CHAPTER

1
DEFINITIONS
AND
PRINCIPLES

Chemical engineering has to do with industrial processes in which raw materials

are changed or separated into useful products. The chemical engineer must
develop, design, and engineer both the complete process and the equipment used;
choose the proper raw materials; operate the plants efficiently, safely, and economically; and see to it that products meet the requirements set by the customers.
Chemical engineering is both an art and a science. Whenever science helps the
engineer to solve a problem, science should be used. When, as is usually the case,
science does not give a complete answer, it is necessary to use experience and
judgment. The professional stature of an engineer depends on skill in utilizing all
sources of information to reach practical solutions to processing problems.
The variety of processes and industries that call for the services of chemical
engineers is enormous. Products of concern to chemical engineers range from
commodity chemicals like sulfuric acid and chlorine to high-technology items like
polymeric lithographic supports for the electronics industry, high-strength composite materials, and genetically modified biochemical agents. The processes described in standard treatises on chemical technology and the process industries
give a good idea of the field of chemical engineering, as does the 1988 report on
the profession by the National Research Counci!.'·'t

t Superior numerals in

the text correspond to the numbered references at the end of each chapter.

3


't

INTRODUCTION

Because of the variety and complexity of modern processes, it is not
practicable to cover the entire subject matter of chemical engineering under a
single head. The field is divided into convenient, but arbitrary, sectors. This text
covers that portion of chemical engineering known as the unit operations.

UNIT OPERATIONS
An economical method of organizing much of the subject matter of chemical
engineering is based on two facts: (1) although the number of individual processes
is great, each one can be broken down into a series of steps, called operations,
each of which in turn appears in process after process; (2) the individual operations
have common techniques and are based on the same scientific principles. For
example, in most processes solids and fluids must be moved; heat or other forms
of energy must be transferred from one substance to another; and tasks like drying,
size reduction, distillation, and evaporation must be performed. The unit-operation
concept is this: by studying systematically these operations themselves-operations that clearly cross industry and process lines-the treatment of all processes
is unified and simplified.
The strictly chemical aspects of processing are studied in a companion area
of chemical engineering called reaction kinetics. The unit operations are largely
used to conduct the primarily physical steps of preparing the reactants, separating
and purifying the products, recycling unconverted reactants, and controlling the
energy transfer into or out of the chemical reactor.
The unit operations are as applicable to many physical processes as to
chemical ones. For example, the process used to manufacture common salt consists
of the following sequence of the unit operations: transportation of solids and
liquids, transfer of heat, evaporation, crystallization, drying, and screening. No
chemical reaction appears in these steps. On the other hand, the cracking of
petroleum, with or without the aid of a catalyst, is a typical chemical reaction
conducted on an enormous scale. Here the unit operations-transportation of
fluids and solids, distillation, and various mechanical separations-are vital, and
the cracking reaction could not be utilized without them. The chemical steps
themselves are conducted by controlling the flow of material and energy to and
from the reaction zone.
Because the unit operations are a branch of engineering, they are based on
both science and experience. Theory and practice must combine to yield designs

for equipment that can be fabricated, assembled, operated, and maintained. A
balanced discussion of each operation requires that theory and equipment be
considered together. An objective of this book is to present such a balanced
treatment.
SCIENTIFIC FOUNDATIONS OF UNIT OPERATIONS. A number of scientific
principles and techniques are basic to the treatment of the unit operations. Some
are elementary physical and chemical laws such as the conservation of mass and