Chemical Reactor Design - Harriot (2003).pdf

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CHEMICAL
REACTOR
DESIGN
Peter Harriott
Cornell University
Ithaca, New York, U.S.A
Marcel Dekker, Inc.
Copyright © 2003 by Taylor & Francis Group LLC
New York
•
Basel
Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.
Library of Congress Cataloging-in-Publication Data
A catalog record for this book is available from the Library of Congress.
ISBN: 0-8247-0881-4
This book is printed on acid-free paper.
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Copyright
#
2003 by Marcel Dekker, Inc. All Rights Reserved.
Neither this book nor any part may be reproduced or transmitted in any form or by
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Copyright © 2003 by Taylor & Francis Group LLC
Preface
This book deals with the design and scaleup of reactors that are used for the
production of industrial chemicals or fuels or for the removal of pollutants
from process streams. Readers are assumed to have some knowledge of
kinetics from courses in physical chemistry or chemical engineering and to
be familiar with fundamental concepts of heat transfer, fluid flow, and mass
transfer. The first chapter reviews the definitions of reaction rate, reaction
order, and activation energy and shows how these kinetic parameters can be
obtained from laboratory studies. Data for elementary and complex homo-
geneous reactions are used as examples. Chapter 2 reviews some of the
simple models for heterogeneous reactions, and the analysis is extended to
complex systems in which the catalyst structure changes or in which none of
the several steps in the process is rate controlling.
Chapter 3 presents design equations for ideal reactors —
ideal
mean-
ing that the effects of heat transfer, mass transfer, and partial mixing can
be neglected. Ideal reactors are either perfectly mixed tanks or packed bed
and pipeline reactors with no mixing. The changes in conversion with
reaction time or reactor length are described and the advantages and
problems of batch, semibatch, and continuous operation are discussed.
Examples and problems are given that deal with the optimal feed ratio,
the optimal temperature, and the effect of reactor design on selectivity.
The design of adiabatic reactors for reversible reactions presents many
Copyright © 2003 by Taylor & Francis Group LLC
optimization problems, that are illustrated using temperature-conversion
diagrams.
The major part of the book deals with nonideal reactors. Chapter 4 on
pore diffusion plus reaction includes a new method for analyzing laboratory
data and has a more complete treatment of the effects of complex kinetics,
particle shape, and pore structure than most other texts. Catalyst design to
minimize pore diffusion effects is emphasized. In Chapter 5 heat transfer
correlations for tanks, particles, and packed beds, are reviewed, and the
conditions required for reactor stability are discussed. Examples of unstable
systems are included. The effects of imperfect mixing in stirred tanks and
partial mixing in pipeline reactors are discussed in Chapter 6 with examples
from the literature. Recommendations for scaleup or scaledown are pre-
sented.
Chapters 7 and 8 present models and data for mass transfer and
reaction in gas–liquid and gas–liquid–solid systems. Many diagrams are
used to illustrate the concentration profiles for gas absorption plus reaction
and to explain the controlling steps for different cases. Published correla-
tions for mass transfer in bubble columns and stirred tanks are reviewed,
with recommendations for design or interpretation of laboratory results.
The data for slurry reactors and trickle-bed reactors are also reviewed and
shown to fit relatively simple models. However, scaleup can be a problem
because of changes in gas velocity and uncertainty in the mass transfer
coefficients. The advantages of a scaledown approach are discussed.
Chapter 9 covers the treatment of fluidized-bed reactors, based on
two-phase models and new empirical correlations for the gas interchange
parameter and axial diffusivity. These models are more useful at conditions
typical of industrial practice than models based on theories for single bub-
bles. The last chapter describes some novel types of reactors including riser
reactors, catalyst monoliths, wire screen reactors, and reactive distillation
systems. Examples feature the use of mass and heat transfer correlations to
help predict reactor performance.
I am greatly indebted to Robert Kline, who volunteered to type the
manuscript and gave many helpful suggestions. Thanks are also extended to
A. M. Center, W. B. Earl, and I. A. Pla, who reviewed sections of the
manuscript, and to D. M. Hackworth and J. S. Jorgensen for skilled profes-
sional services. Dr. Peter Klugherz deserves special credit for giving detailed
comments on every chapter.
Peter Harriott
Copyright © 2003 by Taylor & Francis Group LLC
Contents
Preface
Appendix
Diffusion Coefficients for Binary Gas Mixtures
1. Homogeneous Kinetics
Definitions and Review of Kinetics for Homogeneous Reactions
Scaleup and Design Procedures
Interpretation of Kinetic Data
Complex Kinetics
Nomenclature
Problems
References
2. Kinetic Models for Heterogeneous Reactions
Basic Steps for Solid-Catalyzed Reactions
External Mass Transfer Control
Models for Surface Reaction
Rate of Adsorption Controlling
Allowing for Two Slow Steps
Desorption Control
Changes in Catalyst Structure
Copyright © 2003 by Taylor & Francis Group LLC

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