Table Of ContentGAS FLUIDIZATION
HANDBOOK OF POWDER
TECHNOLOGY
Edited by J.C. WILLIAMS
School of Powder Technology, University of Bradford, Bradford, West Yorkshire,
England
and T. ALLEN
Senior Consultant Engineer, E.I. DuPont de Nemours & Co., Inc., Wilmington,
Delaware, U.S.A.
The Handbook presents, in convenient form, existing knowledge in all specialized areas
of Powder Technology.
Information that can be used for the design of industrial processes involving the pro
duction, handling and processing of particulate materials so far did not exist in a form in
which it is readily accessible to design engineers. Scientists responsible for character
izing particulate materials, specifying the requirements of industrial processes, operat
ing plants, or setting up quality-control tests all have similar problems in their fact-finding
missions through the scattered and scanty literature. The aim of this handbook is to
remedy this deficiency by providing a series of thematic volumes on various aspects of
powder technology. Each volume is written as a monograph and can be used indepen
dently of other volumes.
Emphasis is placed on setting out the basic concepts of the subject and discussing
their applications to the design, selection and operation of equipment of an industrial
scale. To ensure timely publication, each volume will be published as soon as the mate
rial has been delivered by the authors.
Vol. 1. Particle Size Enlargement (C.E. Capes)
Vol. 2. Fundamentals of Gas-Particle Flow (G. Rudinger)
Vol. 3. Solid-Gas Separation (L. Svarovsky)
Vol. 4. Dust Explosions (P. Field)
Vol. 5. Solid-Liquid Separation Processes and Technology (L. Svarovsky)
Vol. 6. The Packing of Particles (D.J. Cumberland and R.J. Crawford)
Vol. 7. Dispersing Powders in Liquids (R.D. Nelson)
Vol. 8. Gas Fluidization (M. Pell)
Further volumes are in preparation.
(For further information on Volumes 1 -7, see p. 123 of this volume.)
GAS
FLUIDIZATION
MEL PELL
Consultant Engineering Services Division,
E.I. du Font de Nemours & Co., Inc., Newark, Delaware, U.S.A.
ELSEVIER
Amsterdam — Oxford — New York — Tokyo 1990
ELSEVIER SCIENCE PUBLISHERS B.V.
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Distributors for the United States and Canada:
ELSEVIER SCIENCE PUBLISHING COMPANY INC.
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New York, NY 10010, U.S.A.
Camera-ready copy prepared by the author
using Micro-TEX® and Almost Modern Roman typeface.
Library of Congress Cataloging-in-Publication Data
Pe11, Me 1vyn.
Gas fluidization / Mel Pe11.
p. cm. — (Handbook of powder technology ; v. 8)
Includes bibliographical references.
ISBN 0-444-88335-5 (U.S.)
1. Fluidization. I. Title. II. Series.
TP156.F65P45 1990
660 ' . 284292—dc20 89-23487
CIP
ISBN 0-444-88335-5 (Vol. 8)
ISBN 0-444-41843-1 (Series)
© Elsevier Science Publishers B.V., 1990
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or
transmitted in any form or by any means, electronic, mechanical, photocopying, recording or
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Special regulations for readers in the USA - This publication has been registered with the Copyright
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Printed in The Netherlands
v
Dedication
TO THE GIANTS WHO TAUGHT ME WELL
Arthur Squires
George Curran
Fred Zenz
VI
Acknowledgements
To make this work possible required the assistance of many peo
ple.
My wife Ellen who waited patiently as I spent endless hours
toiling at the computer.
DuPont management who encouraged me to proceed with this
step in my personal development.
Ralph Nelson for numerous instances of assistance as I learned
to use the MicroT^X program to prepare camera-ready copy.
Leslie Apple and Meinrad Leckie of the DuPont Art Group for
so much of the graphics.
vii
Preface
This is intended to serve as a handbook for the practitioner of
fluidization on an industrial scale. There are few plants that
do not have a fluid bed process operating somewhere on the
site. Yet most engineers have never been formally trained in the
subject. College courses often emphasize academic issues rather
than industrial needs and if one tries to study the literature, there
is an overwelming abundance of correlations and experimental
data. Unhappily, too much work is done on small scale equipment
under ambient conditions. This leads to good small scale science
but not to design procedures that apply to industrial systems.
I have minimized theoretical development of fundamental equa
tions in favor of giving correlations that have been developed for
large scale equipment. In some cases, where several correlations
might apply, I have chosen one or two that work best based upon
my own experience.
The book gives design procedures that should assist the designer
and the operator of fluid beds to improve his process and to avoid
some of the pitfalls that have befallen others in the early days of
fluidization science.
This material serves well as a secondary text to a course on
fluidization. After the student is out in the field, reference to
its contents will be easy and straightforward. The emphasis on
commercial design is a stimulating counterpoint to a strongly
academic viewpoint.
Wilmington DE Mel Pell
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ix
TABLE OF CONTENTS
Dedication v
Acknowledgements vi
Preface vii
1. INTRODUCTION TO GAS FLUIDIZATION
1.1 Introduction 1
1.2 Regimes of Fluidization 2
1.3 Effects of Particle Size and Density 3
1.4 Effects of Gas Density and Viscosity 5
1.5 References 6
2. FIRST CALCULATIONS
2.1 Average Particle Size 9
2.2 Experimental Evaluation vs. Calculation 10
2.3 Minimum Fluidization Velocity 11
2.4 Minimum Bubbling Velocity 14
2.5 Terminal Velocity 15
2.6 Bed Expansion 15
2.7 A Second Look at the Minimum Bubbling Condition .. .17
2.8 Bed Pressure Drop 18
2.9 References 18
3. GAS DISTRIBUTOR DESIGN
3.1 Functions of the Grid 21
3.2 Grid Pressure Drop 21
3.3 Hole Size and Number 23
3.4 Jet Length 24
3.5 Particle Attrition 26
3.6 Grid Variations 28
3.7 Grid Seals 28
3.8 Plenum Design 29
3.9 References 29
4. BUBBLE GROWTH AND STABILITY
4.1 Overview 31
4.2 Bubble Growth 32
4.3 Slugging 32
4.4 Maximum Stable Bubble Size 33
4.5 Effect of Bubble Size on Bed Expansion 35
4.6 References 36
