Upload
carlos-humberto-velez-useche
View
242
Download
0
Embed Size (px)
Citation preview
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 1/12
BULK SOLIDS H NDLING
n I ntroduction to the Practice and
echnology
C R
WOODCOCK, DipTech, MSc, PhD, CEng, MIMechE
Formerly Chief Executive
o
Centre or Industrial Bulk Solids Handling,
Glasgow Caledonian University
and
J
S MASON, BSc, PhD, CEng, FIMechE, FIMarE, MIMinE
Principal and Vice-Chancellor. Glasaow Caledonian Universitv
t1l
BL CKIE C DEMIC
c t
PROFESSION L
An
Imprint
o
Chapman Hall
London· Glasgow· Weinheim . New York· Tokyo· Melbourne· Madras
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 2/12
Published by
Blackie Academic Professional, an
imprint
of Chapman Hall,
Wester Cleddens Road, Bishopbriggs, Glasgow G64 2NZ
Chapman HalI,
2 6
Boundary Row, London SEI 8HN,
UK
B ackie Academic Professional, Wester Cleddens Road, Bishopbriggs,
Glasgow G64
2NZ
UK
Chapman HaII GmbH, Pappelallee 3 69469 Weinheim, Germany
Chapman HaII USA,
liS
Fifth Avenue, Fourth Floor, New York,
NY 10003, USA
Chapman HaII Japan, ITP-Japan, Kyowa Building, 3F, 2-2-1 Hirakawacho,
Chiyoda-ku, Tokyo 102, Japan
DA Book Aust.) Pty Ltd, 648 Whitehorse Road, Mitcham 3132, Victoria,
Australia
Chapman Hall India, R. Seshadri, 32 Second Main Road, CIT East,
Madras 600 035, India
First edition 1987
Reprinted 1993, 1995
© 1987 Chapman Hall
Softcover reprint
of
the hardcover 1st edition 1987
Typeset in 101l2pt Times by Thomson Press India) Ltd., New Delhi
ISBN-13: 978-94-010-7689-0
DOl: 10.1007/978-94-009-2635-6
e-ISBN-13: 978-94-009-2635-6
Apart from any fair dealing for the purposes of research or private study, or
criticism or review as permitted under the UK Copyright Designs and Patents
Act, 1988, this publication may not be reproduced, stored, or transmitted, in
any form
or
by any means, without the prior permission in writing
of
the
publishers, or in the case of reprographic reproduction only in accordance with
the terms of the licences issued by the Copyright Licensing Agency in the UK,
or in accordance with the tenns of licences issued by the appropriate
Reproduction Rights Organization outside the UK. Enquiries concerning
reproduction outside the terms stated here should be sent to the publishers at the
Glasgow address printed on this page.
The publisher makes no representation, express or implied, with regard to the
accuracy of the information contained in this book and cannot accept any legal
responsibility or liability for any errors or omissions that may be made.
A catalogue record for this book
is
available from the British Library
Library of Congress Catalog Card Number: 85-29147
00
Printed
on
acid-free text paper, manufactured in accordance with
ANSIINISO Z39.48-1992 permanence of Paper)
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 3/12
reface
An understanding ofthe properties and the handling characteristics of liquids
and gases has long been regarded as an essential requirement for most
practising engineers. It
is therefore
not
surprising that over the years there has
been a regular appearance of books dealing with the fundamentals of fluid
mechanics fluid flow
hydraulics and related topics. What is surprising is that
there has been no parallel development of the related discipline of Bulk Solids
Handling despite its increasing importance in modern industry across the
world. t is only very recently that a structured approach to the teaching and
learning of the subject has begun to evolve.
A reason for the slow emergence of Bulk Solids Handling as an accepted
topic of study in academic courses on mechanical agricultural chemical
mining and civil engineering is perhaps that the practice
is
so often taken for
granted. Certainly the variety of materials being handled in bulk is almost
endless ranging in size from fine dust to rocks in value from refuse to gold and
in temperature from deep-frozen peas to near-molten metal. Almost everyone
has seen a belt conveyor in operation perhaps carrying grain on the local
farm or stone and rock from a nearby
quarry but
how many would know
that belt conveyors are now being developed to transport bulk solids at rates
in excess of 30 000 tonnes per hour? The domestic vacuum cleaner is a familiar
machine in which dust particles are conveyed through a pipe in a stream of air
but few people would appreciate that large lumps of coal and rock and even
fish can be transported in a similar way. Examples of bulk solids handling can
be found in almost every kind of industry and the problems associated with the
design installation and operation of plant for the storage and transport of
materials in bulk are many and varied.
No
book can be a substitute for the
technical skill acquired through long experience in the industry. Nevertheless
we have attempted to present here a foundation of knowledge generally with a
practical rather than an academic emphasis upon which expertise in various
specialized aspects of bulk solids handling can be developed subsequently.
Governments of many nations are now recognizing that the education and
training of engineers in many fields should include some study of the
technology of bulk solids covering the properties storage flow and transport
of a wide range of materials in particulate or granular form. n the United
Kingdom for example recent initiatives emanating from the Department of
Industry have led to conferences courses and various publications aimed at
promoting a greater awareness of the unique features of bulk solids. The
School of Engineering at Thames Polytechnic and in particular the staff of its
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 4/12
IV
PREF CE
Bulk Solids Handling Unit, have been deeply involved in these initiatives from
the outset and this book
is
the result of a clearly perceived need for an
introduction to the subject that would identify and set out a structure for the
area of study that
is
becoming known by the convenient, if not entirely
accurate, title Bulk Solids Handling . Many specialist treatments are already
available: works
on
particle technology, hopper design, fluidization, dust
control, pneumatic conveying, and others, can be found on library shelves and
in most cases these are excellent and valuable works of reference for the
experienced engineer. However, for the student and for the engineer who
requires an overview of the emerging discipline of bulk solids handling,
supported by an adequate coverage of fundamentals, this book should
provide essential reading.
n
common with most books of similar size and scope, this one should really
be regarded as the product of a team effort. We as authors and editors, would
unhesitatingly acknowledge the contributions, both direct and indirect, of our
colleagues in the Bulk Solids Handling Unit at Thames Polytechnic, notably
r David Mills and r Alan Reed. n their various ways the academic and
technician staff of the School of Engineering, together with many of our
postgraduate and undergraduate students, have played some part in the
events leading up to the conception, preparation and, ultimately, the
production of this book. Although it
is
perhaps a little unfair to mention
individuals by name,
we
do gratefully acknowledge the patient and tolerant
efforts of Mrs Pam Colley in undertaking the massive task of typing the
manuscript. Finally, our sincere thanks and appreciation goes to our
respective families, especially to our wives Angela and Fran, for the patience,
understanding and considerable fortitude that they have shown during the
months that this book has been in preparation, and indeed during the many
years that we have both been so deeply involved in the multitude of activities
arising out of our interest in the fascinating subject of Bulk Solids Handling.
CRW
JSM
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 5/12
ontents
PART 1 CHARACTERIZATION, FLOW AND STORAGE
1
The nature o bulk solids
1
1 1 Introduction
1
1 2
Sampling
3
1 2 1 Obtaining a gross sample
3
1 2 2
Preparing laboratory and test samples
4
1 3
Voidage and bulk density
7
1 4 Particle density
9
1 5 Particle size
10
1 5 1 Definition of size and size distribution
10
1 5 2 Measurement of particle size
15
1 6
Particle shape
25
1 7
Surface area
26
1 8
Particle hardness
28
1 9 Cohesion and adhesion
29
1 9 1
Angle of repose
31
1 9 2 Shear strength
33
1 9 3
The shear cell as a means of determining shear strength
35
1 9 4
Wall friction 39
1 9 5 Measurement of wall friction
40
1 9 6
Arching phenomena
41
1 10 Moisture content
43
1 11 Explosiveness
44
1 12 Notation
45
References and bibliography
46
2 ravity flow o
bulk
solids
7
2 1
Introduction 47
2 2 Pressure distribution in a bulk solid
49
2 2 1 Bulk solid
at
rest 49
2 2 2
The effect of flow on the pressure distribution
52
2 3 Flow of bulk solids from hoppers
54
2 3 1
Introduction
54
2 3 2
Core flow
54
2 3 3
Mass flow
55
2 3 4 Obstructions to gravity flow
55
2 3 5 Predicting the solids discharge rate
56
2 4 Flow of bulk solids in chutes
64
2 4 1 Introduction
64
2 4 2
Flow patterns in straight inclined chutes
65
2 4 3 Flow patterns in curved chutes
68
2 4 4 Chute design
69
2 5 Flow of bulk solids in vertical pipes
74
2 5 1 Introduction 74
2 5 2
Mode of flow 76
2 5 3
Flow control J valves and L-valves
79
2 6
Notation
81
References and bibliography
82
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 6/12
vi
CONTENTS
3 Dynamics
o
fluid solids systems 84
3 1
Introduction 84
3 2
Flow through beds of fixed particles 84
3 2 1 Characteristics of
flow in
porous media 84
3.2.2 The prediction of pressure-drop across a fixed particula te bed
85
3 3 Settling behaviour of particles 91
3 3 1 Motion of a spherical particle settling in a stationary fluid 91
3.3.2 The settling of non-spherical particles
95
3 3 3 The settling of concentrations of particles (hindered settling) 98
3.3.4 Classification and sorting of particles
98
3 4 Fluidization 99
3 4 1
The fluidization process 99
3.4.2 The prediction of minimum fluidizing velocity
104
3 4 3 Entrainment of particles from a fluidized bed 109
3.4.4 The porous membrane, or distributor 109
3 4 5 The influence of particle size and density
110
3 5
Spouted bed behaviour
113
3 6 Gas/solids
flow in
pipes 116
3 6 1 Introduction
116
3.6.2 The
flow
of gas/solids suspensions in horizontal pipes 117
3 6 3 The flow of gas/solids suspensions in vertical pipes 122
3.6.4 Flow around 90° bends 124
3 6 5 The prediction o pressure-drop in flowing gas/solids suspensions 125
3 7 Liquid/solids flow in pipes 138
3 7 1 Flow characteristics of liquid/solids mixtures (slurries) 138
3.7.2 Non-Newtonian
flow
models for homogeneous suspension 139
3 7 3 The modelling of heterogeneous suspensions
148
3 8 Notation
150
References and bibliography 152
4 he design of storage
bins
and hoppers 154
4 1 Introduction 154
4 2 Hopper geometry 156
4 2 1 Shape 156
4.2.2 Overall dimensions 159
4 3 Outlet size and cone angle 162
4 3 1
Jenike s flow-no flow criterion
162
4.3.2 Flow Functions and
flow
factors 165
4.3.3 Outlet dimension and cone angle 166
4.4 Period of storage and time consolidation effects 168
4 4 1
Caking
169
4.4.2 Testing for time consolidation 170
4 4 3
Practical ways of minimizing time consolidation 171
4 5 The effect of moisture 171
4.6 Overcoming space limitations 172
4 6 1 The use of low-friction linings 173
4.6.2 Changing hopper shape
175
4.7 Structural design 176
4 8 Control and measurement o discharge rate 178
4 9 Feeders 180
4 9 1
Introduction
180
4.9.2 Belt feeders 181
4 9 3
Apron feeders and rotary feeders
183
4.9.4 Rotary table feeders
184
4 9 5 Screw feeders 185
4.9.6 Vibratory feeders 187
4 1
0 Discharge aids 187
4 1 0 1
Introduction 187
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 7/12
4.10.2 Pneumatic methods
4 10 3 Vibrational methods
4.10.4 Mechanical methods
4 11
Notation
References and bibliography
5 Dust control
5 1 Introduction
5 2 Dust as a hazard to health
5 2 1 Dust particle size
CONTENTS
5 2 2 Dust concentration limits
5 3 Dust suppression
5 3 1
Elimination of dust
5 3 2 Control of dust dispersion
5 4 Gravity and inertial separators
5 5 Air cleaners cyclones
5 5 1
Principle of operation
5 5 2 Prediction of collecting efficiency
5 5 3 Prediction of pressure drop
5 5 4 Cyclone selection
5 6 Air
cleaners wet
washers or scrubbers
5 6 1 Principle of operation
5 6 2 Low pressure drop wet washers
5 6 3 High pressure drop wet washers
5 7 Air
cleaners filters
5 7 1 Mechanism of filtration
5 7 2 Filter media
5 7 3 Bag filters design and selection
5 7 4 Filter cleaning
5 8
Air cleaners electrostatic precipitators
5 9
Notation
References and bibliography
6 Explosion hazards
6 1
Introduction
6 2 Characteristics of dust explosions
6 2 1 Ignition
6 2 2 Explosibility limits
6 2 3
Expansion effects and explosion pressures
6 3 Measurement of explosion parameters
6 4
Explosion risks and system design
6 4 1 Minimizing sources of ignition and prevention of ignition
6 4 2 Containment
6 4 3 Explosion relief venting
6.4.4 Detection and suppression
6 5 Static electricity
6 6 Conclusion
References and bibliography
PART MECHANICAL H NDLING
7 Belt conveyors
7 1 Introduction
7 2 Features of belt conveyors
7 2 1 Belt construction
7.2.2 Idlers
7 2 3
Drive arrangements
V
188
192
198
200
201
2 3
203
204
204
208
208
208
209
211
213
213
215
218
218
218
218
220
222
224
224
226
227
230
232
233
233
235
235
238
238
239
240
241
246
248
249
250
253
256
258
258
26
260
261
261
265
268
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 8/12
viii
CONTENTS
7 2 4
The power unit
7 2 5 Loading and discharge arrangements
7 2 6
Belt cleaners
7 3
Belt conveyor design
7 3 1 The bulk solid to
be
transported
7 3 2 Belt speed
7 3 3 Belt width
7 3 4
Belt tension
7 3 5
Idler spacing
7 3 6 Power requirements
7 4 Belt conveyor variants
7 4 1
The cable belt conveyor
7 4 2
Belt conveyors without idlers
7 4 3 Closed-belt or pipe conveyors
7 4 4 Sand wich belts
7.5. Notation
References and bibliography
8 Bucket elevators
8 1 Introduction
8 2
Principal types of bucket elevator
8 2 1 Centrifugal discharge elevators
8 2 2
Continuous bucket elevators
8 2 3
Pivoted buckets
8.2.4 Profiled-belt elevators
8 3
Design and selection of bucket elevators
8 3 1 Design features
8 3 2
Loading
8 3 3
Discharge
8.3.4 Capacity
8 3 5
Driving power
8 4 Notation
References and bibliography
9 Chain and flight conveyors
9 1
Introduction
9 2 rag conveyors
9 3 En-masse conveyors
9 3 1
Design features
9.3.2 Performance calculations
9 3 3
Applications of en-masse conveying
9.4 Tubular drag conveyors
9 5
Apron conveyors
9 6 Aerial ropeways
9 7 Notation
References and bibliography
1 Screw conveying
10 1
Introduction
10 2 Principle of operation of screw conveyors
10 3 The enclosed screw or auger conveyor
10 3 1
Constructional features
10 3 2
Prediction of the performance of an auger conveyor
10 4 The industrial screw conveyor or V-trough conveyor
10 4 1 Constructional features
10 4 2 The conveyed product
271
7
273
274
274
275
277
281
284
284
289
289
290
291
293
295
296
98
298
300
300
301
303
304
305
305
308
309
312
315
316
317
3 8
318
318
321
321
323
325
327
328
331
333
334
335
335
337
338
338
340
342
342
344
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 9/12
10.4.3 Conveyor selection
10.4.4 Conveyor power
CONTENTS
10.4.5 Inclined screw conveyors
10.5
Vertical screw conveyors
10.6 Conclusion
10.7
Notation
References and bibliography
11 Vibratory conveyors
11.1 Introduction
11.2 Movement of a bulk solid in a vibrating trough
11 .2.1
The motion of the trough
11.2.2 The motion of bulk material in the trough
11.2.3 Average conveying velocity
11.2.4 The influence of the design parameters
11.2.5
Two-phase trough motion
11.3
Design features
11.3.1 Drive mechanism
11.3.2 Mounting systems
11.4 Applications of vibratory conveying
11.5 Spiral elevators
11.6 Notation
References and bibliography
P RT
3 PNEUM TIC ND
HYDR ULIC
TR NSPORT
2 Basic pneumatic conveying systems
12.1 Introduction
12.2 Modes of conveying-dilute-phase and dense-phase
12.3 Low-pressure pneumatic conveying systems
12.3.1 Positive-pressure systems
12.3.2
Negative-pressure vacuum) systems
12.3.3
Combined negative/positive pressure systems
12.4 High-pressure systems
12.4.1 General features
12.4.2 Single blow tank systems
12.4.3
Twin blow tanks and continuously operating systems
12.4.4 Long-distance conveying
12.5
Low-velocity conveying and the use of supplementary air
feeds
12.5.1 General features
12.5.2 Plug-forming systems
12.5.3
Plug-limiting systems
12.5.4 Air-injection and booster systems
References and bibliography
3 Components
o
pneumatic conveying systems
13.1 Introduction
13.2 The air supply
13.2.1 General requirements
13.2.2 Fans and turbo-blowers
13.2.3 Roots-type blowers
13.2.4 Sliding-vane rotary compressors
13.2.5 Screw compressors
13.2.6 Reciprocating compressors
13.2.7 Vacuum pumps
IX
345
349
351
354
356
356
357
358
358
361
361
365
367
369
370
370
370
374
375
376
378
379
38
380
386
386
386
390
392
392
392
393
396
398
399
399
401
403
405
407
4 8
408
408
408
409
411
411
412
414
416
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 10/12
x
13 3 Feeding devices
13 3 1
Rotary valves
13 3 2 Screw feeders
13 3 3 Venturi feeders
13 3 4 Gate lock valves
13 3 5 Blow tanks
CONTENTS
13 3 6 Entrainment devices for vacuum systems
13 4 The pipeline
13 5 Disengaging and collecting devices
13 6 Notation
References and bibliography
4 Pneumatic conveyor design
14 1 Introduction
14 2 General design procedure
14 2 1 Conveying velocity and volumetric air flow rate
14 2 2 Solids mass flowrate and solids loading ratio
14 2 3
Pipeline diameter
14.2.4 Pressure drop
14 2 5 Stepped pipelines
14 2 6 Selection of the air mover
14 3 Summary of preliminary design procedure for dilute phase systems
14 4
Designing from available test data
14 4 1 Conveying characteristics
14 4 2 Scaling for pipe size and conveying distance
14 5
Notation
References and bibliography
5
Air assisted
gravity
conveying
15 1 Introduction
15 2 The flow of fluidised solids
15 3 Practical air assisted gravity conveying
15 4 Design parameters for air gravity conveyors
15 4 1 Slope of channel
15 4 2
Conveying distance
15 4 3
Width of conveying channel
15 4 4 Air requirement
15 5 Properties of bulk solids for air gravity conveying
15 6
Air float conveyors for horizontal and upward transport
15 7 Energy consumption of air gravity conveyors
15 8 Notation
References and bibliography
6 Hydraulic
conveying
16 1 Introduction
16 2 Components of a hydraulic conveying system
16 2 1 Pumps
16 2 2 Slurry preparation plant
16 2 3 The pipeline
16 2 4 De watering equipment
16 3 System design
16 3 1 General design approach
16 3 2 Flow characreristics and pressure drop
16 4
Recent development
References and bibliography
7 Capsule transport
17 1
Introduction
417
417
425
426
427
428
431
433
436
436
436
438
438
439
439
441
442
443
446
446
447
448
448
449
454
454
456
456
458
461
465
465
466
466
468
470
47
475
476
476
478
478
481
481
485
486
487
489
489
490
491
492
494
494
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 11/12
CONTENTS
17 2
Capsule transport in a pneumatic pipeline
17 2 1 General features of a pneumo capsule system
17 2 2
The capsules
17 2 3
The pipeline
17.2.4 The air supply
17 2 5 Loading nd unloading stations
17 3
Capsule transport in a hydraulic pipeline
17 3 1 General features of a hydro capsule system
17 3 2
The capsules
17 3 3 The pipeline
17 3 4
The water supply and pump system
17 3 5 Injection nd ejection of capsules
17 4
Size of capsule fleet
17 5
Notation
References
ndex
xi
498
498
499
501
502
503
504
504
504
505
505
508
508
510
510
5 3
7/25/2019 Bulk Solids Handling.pdf
http://slidepdf.com/reader/full/bulk-solids-handlingpdf 12/12
when you ca meaS\lfe what you are speaking about, and express it in numbers, you know
something
about
it;
but
when you cannot measure it, when you cannot express it in numbers, your
knowledge
is of
a meagre
and
unsatisfactory kind: it may be the beginning
of
knowledge,
but
you
have scarcely, in your thoughts, advanced to the state o SCIENCE, whatever the matte r may be.
(Lord Kelvin, as Sir William Thomson, speaking on Electrical Units
of
Measurement
at
the
Institution
of
Civil Engineers, London, 3 May 1883.)
(Arab proverb, freely translated as Experience without learning
is
better than learning without
experience .)