PROCESS CONTROL
DESIGNING PROCESSES AND CONTROL
SYSTEMS FOR DYNAMIC PERFORMANCE
McGraw-Hill Chemical Engineering Series
Editorial Advisory Board
Eduardo D. Glandt, Professor of ChemicalEngineering, University
ofPennsylvania
Michael T. Klein, Professor of Chemical Engineering, Rutgers University
Thomas F. Edgar,Professor of Chemical Engineering, University of Texas
at Austin
Bailey and Ollis: Biochemical Engineering Fundamentals
Bennett and Myers: Momentum, Heat andMass Transfer
Carberry: Chemical and Catalytic Reaction Engineering
Coughanown Process Systems Analysis andControl
de Nevers: Air Pollution Control Engineering
de Nevers: Fluid Mechanicsfor ChemicalEngineers
Douglas: Conceptual Design of Chemical Processes
Edgar andHimmelblau: Optimization of Chemical Process
Gates, Katzer, and Schuit: Chemistry ofCatalytic Processes
Gupta and Kumar: Fundamentals of Polymers
King: Separation Processes
Luyben: Essentials of Process Control
Luyben: Process Modeling, Simulation, and Controlfor Chemical Engineers
Marlin: Process Control: Designing Processes and Control Systemsfor
DynamicPerformance
Middleman and Hochberg: Process Engineering Analysis inSemiconductor
Device Fabrication
Perry andGreen: Perry's Chemical Engineers'Handbook
Peters and Tlmmerhaus: PlantDesign andEconomicsfor Chemical Engineers
Reid, Prausnitz, and Poling: Properties ofGasses andLiquids
Smith,Van Ness, and Abbott: Introduction to Chemical Engineering
Thermodynamics
Treybal: Mass Transfer Operations
Wentz: Hazardous Waste Management
PROCESS CONTROL
DESIGNING PROCESSES AND CONTROL
SYSTEMS FOR DYNAMIC PERFORMANCE
2nd Edition
Thomas E. Marlin
McMaster University
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PROCESS CONTROL
DESIGNING PROCESSES ANDCONTROL SYSTEMS FORDYNAMIC PERFORMANCE
International Editions 2000
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ISBN 0-07-039362-1
Library of CongressCataloging-in-Publication Data
Marlin, Thomas E.
Process control: designing processes and control systems fordynamic performance /
Thomas E. Marlin. -2nd ed.
p.
cm.
Includes index.
ISBN 0-07-039362-1
1. Chemical process control.
TP155.75.M365
I. Title.
2000
660\2815-dc21
When ordering this title, use ISBN 0-07-116357-3
Printed in Singapore
99-026739
About the
Author
Thomas E. Marlin is a professor of Chemical Engineering at McMasterUniversity
in Hamilton, Ontario, Canada, where he held the NSERC Industrial Research Chair
in Process Control. He received his Ph.D.. from the University of Massachusetts
in 1972. Then, he worked in industry for 15 years where he applied simulation
and control to a wide range of continuous process in the chemical and petroleum
industries. In 1987, he served as the Visiting Fellow in Sydney, Australia, for the
Warren Centre Study on benefits from process control. A team of 40 engineers
investigated 7 case studies while refining methods for quantifying benefits from
automation. Dr. Marlin is currently Director of the McMaster Advanced Control
Consortium, which is a collaboration between university researchers and numer
ous companies, resulting in leading research that is focused on challenges of great
relevanceto industrial practitioners. He teaches university courses in process con
trol,process analysis, problemsolving, and processdesign. Inaddition, he presents
industrial short courses on process control, benefitsestimation, and optimization.
Dr. Marlin's research interests include real-time optimization and processcontrol
design.
Preface
Automation via feedback is not new. Early application of automatic control prin
ciples appeared in antiquity, and widespread use of automation began in the nine
teenth century when machinery was becoming the dominant method for manu
facturing goods. Great advances have been made in theory and practice so that
automation is now used in systems as commonplaceas room heatingand as excit
ing as the navigation of interplanetary exploration and telecommunications. The
great change over the recent years is the integral—at times essential—role of au
tomation in our daily lives and industrial systems.
Process control is a sub-discipline of automatic control that involves tailoring
methods for the efficient operation of chemical processes. Proper application of
process control can improve the safety and profitability of a process, while main
taining consistently high product quality. The automation of selected functions
has relieved plant personal of tedious, routine tasks, providing them withtime and
data to monitor andsupervise operations. Essentially every chemical engineer de
signing or operating plants is involved with and requires a background in process
control. This book provides an introduction to process control with emphasis on
topics that are of useto the general chemical engineer as well as the specialist.
GOALS OF THE BOOK
The intent of this book is to present fundamental principles with clear ties to
applications and with guidelines on their reduction to practice. The presentation
is based on four basic tenets.
vn
viii
Preface
Fundamentals
First,engineers should master control technology fundamentals, since there is no
set of heuristics or guidelines that can serve them through their careers. Since
these fundamentals must be presented with rigor, needed mathematical tools are
presentedto assistthe student. It maybe worthrecallingthat these principles were
selected because they provide the simplest approaches for solving meaningful
problems.
Practice
Second, we are not efficient if we "start from scratch" every time we encounter
a problem; similar situationscan be analyzed to develop guidelines for a defined
set of applications. Also, the fundamental concepts can be best reinforced and
enriched through the presentation of good engineering practice. With this per
spective, important design guidelines and enhancements are presented as logical
conclusions and extensions to the basic principles. Coverage of implementation
issuesincludes pitfalls with thestraightforward "textbook" approaches alongwith
modifications for practical application.
Complexity
Third, the presentation in this book follows the guideline"Everythingshould be
made as simple as possible, and no simpler." Naturally, many issues are easily
resolved using straightforward analysismethods. However, the engineer must un
derstand the complexity of automating a system, even when a closed-form solution
does not exist at the present time.
Design
Fourth, designis a capstone topic thatenables engineers to specify, buildandoper
ate equipment that satisfiespredeterminedgoals. Currently, closed-form solutions
do not exist for this activity; thus, a comprehensive design method for managing
the numerous interlocking designtasks is presented along with a step-by-step ap
proach to guide the engineer through problem definition, preliminary analysis of
degreesof freedomandcontrollability, andselectingprocessand control structures.
Many guidelines,checklists,and examplesaid the student in making well-directed
initial decisions and refining themthrough iterations to achievethe design goals.
THE READERS
Hopefully, readers with different backgrounds will find value in this treatment of
process control. A few comments are now addressed to the three categories of
likely readers of this book: university students, instructors, and practitioners.
Students
Many students find process control to be one of the most interesting and enjoyable
courses in the curriculum, because they apply the skills built in fluid mechanics,
heat transfer, thermodynamics, masstransfer, andreactordesign.This presentation