Divided Solids Transport

186 Pages·2016·4.157 MB·English

by  Jean-Paul Duroudier

Divided Solids Transport
There are no such things as applied sciences,
only applications of science.
Louis Pasteur (11 September 1871)

Dedicated to my wife, Anne, without whose unwavering support, none of this
would have been possible.
Inndustrial EEquipmentt for Chemmical Engineering SSet
cooordinated by
Jean-Paul Durooudier

Divvidedd Solidds Trranspport

Jeaan-Pauul Durouudier
First published 2016 in Great Britain and the United States by ISTE Press Ltd and Elsevier Ltd
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Notices
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broaden our understanding, changes in research methods, professional practices, or medical treatment
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ISBN 978-1-78548-183-3

Printed and bound in the UK and US
Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
Chapter 1. Re-entrainment of Solid
Particle Beds Swept by a Fluid Current . . . . . . . . . . . . . . . . . . . . 1
1.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1. Significance of the problem . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.2. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2. Shear velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1. Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.2. Flat plate (edge perpendicular to fluid flow) . . . . . . . . . . . . . . 4
1.3. Strength and lift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.1. Hypotheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.2. Mean thrust velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.3. Drag force and lift force . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4. Entrainment criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4.1. Attachment forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.5. Quantity entrained . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.5.1. Probability and frequency . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.5.2. Results of Wu et al. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.6. Entrainment limit velocity (simplified method) . . . . . . . . . . . . . . 11
1.6.1. Mean geometry of spherical particles
on the surface of the bed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.6.2. Velocity of sweeping for entrainment . . . . . . . . . . . . . . . . . . 12
1.6.3. Angular particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.6.4. Cleaning speed and non-entrainment velocity . . . . . . . . . . . . . 17
1.7. Entrained flowrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.7.1. Probability of entrainment and entrained flow . . . . . . . . . . . . . 18
vi Divided Solids Transport
Chapter 2. Mechanical Conveying
of Divided Solids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.1. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.1.1. Separation due to fall and
pouring: dust formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.1.2. Flowrate and storage capacity
combinations (notions) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.1.3. Organization of divided solid circulation . . . . . . . . . . . . . . . . 23
2.1.4. Extractors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2. Chutes and airslides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.2.1. Chutes inclined horizontally . . . . . . . . . . . . . . . . . . . . . . . 26
2.2.2. Vertical chute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.2.3. Interruption or modulation of chute flow . . . . . . . . . . . . . . . . 29
2.2.4. Airslides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.3. Conveyor belts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.3.1. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.3.2. Use criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.3.3. Flow regulation by belt scale . . . . . . . . . . . . . . . . . . . . . . . 33
2.3.4. Safeguards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.3.5. Choice of belt width . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.3.6. Flowrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.3.7. Power consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.3.8. Effort incurred by the belt . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.3.9. Loading systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.3.10. Discharge systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.3.11. Metal conveyor belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.4. Chain conveyor(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.4.1. Crossbar conveyor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.4.2. Scraper conveyors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
2.4.3. Metal pallet conveyors . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
2.5. Vibrating conveyor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
2.5.1. Operational principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
2.5.2. Types of conveyors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
2.5.3. Progression rate of the product
in the trough . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
2.5.4. Flowrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
2.5.5. Power consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
2.5.6. Advantages and drawbacks
of vibrating conveyors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Contents vii
2.6. Elevators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
2.6.1. Bucket elevator principle . . . . . . . . . . . . . . . . . . . . . . . . . 59
2.6.2. Types of elevators and discharge . . . . . . . . . . . . . . . . . . . . . 59
2.6.3. Methods of filling buckets . . . . . . . . . . . . . . . . . . . . . . . . . 61
2.6.4. Should a belt or chain be used? . . . . . . . . . . . . . . . . . . . . . . 61
2.6.5. Flowrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
2.6.6. Power consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
2.6.7. Vibrating elevator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
2.6.8. Screw lifts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
2.7. Screw conveyor for divided solids . . . . . . . . . . . . . . . . . . . . . . 64
2.7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
2.7.2. Choice of screw characteristics . . . . . . . . . . . . . . . . . . . . . . 65
2.7.3. Darnell and Mol’s theoretical
calculations for screw flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
2.7.4. Screw power consumption . . . . . . . . . . . . . . . . . . . . . . . . 69
2.8. Transport by loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
2.8.1. Containers and skips . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
2.8.2. Roller conveyor for boxes . . . . . . . . . . . . . . . . . . . . . . . . . 72
2.8.3. Material lifters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2.9. Several properties of divided solids . . . . . . . . . . . . . . . . . . . . . 73
2.9.1. Abrasiveness – classes of abrasiveness . . . . . . . . . . . . . . . . . 73
2.9.2. Apparent density – friction with wall . . . . . . . . . . . . . . . . . . 74
2.9.3. Relationship between equipment and
product flowability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
2.9.4. Release of dust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
2.10. Storage and transport logistics . . . . . . . . . . . . . . . . . . . . . . . . 75
Chapter 3. Pneumatic Conveying of
Divided Solids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.1. Pneumatic conveying: introduction . . . . . . . . . . . . . . . . . . . . . . 77
3.1.1. Description of flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.1.2. Compacting of a sediment
(or de-aeration of a fluidized bed) . . . . . . . . . . . . . . . . . . . . . . . . 78
3.1.3. Measurement of stiffness, k . . . . . . . . . . . . . . . . . . . . . . . . 81
3.1.4. Various regimes of horizontal
pneumatic conveying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
3.2. Properties of divided solids . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3.2.1. Density and porosity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3.2.2. Geldart classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
3.2.3. Precautions and choice
according to products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
viii Divided Solids Transport
3.3. Operational curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
3.3.1. Types of operational curves . . . . . . . . . . . . . . . . . . . . . . . . 90
3.3.2. Power expression according
to Hilgraf in dense state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
3.4. Velocity and pressure drops . . . . . . . . . . . . . . . . . . . . . . . . . . 96
3.4.1. Conveying velocity and loading
rate – dense and diluted phases . . . . . . . . . . . . . . . . . . . . . . . . . . 96
3.4.2. Velocity of air for diluted state . . . . . . . . . . . . . . . . . . . . . . 98
3.4.3. Velocity for horizontal conveyance
in dense phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
3.4.4. Yang blockage criteria for a vertical
tube in dense phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
3.4.5. Power consumption in a tube . . . . . . . . . . . . . . . . . . . . . . . 103
3.5. Special study of vertical tubes . . . . . . . . . . . . . . . . . . . . . . . . . 110
3.5.1. Preliminary study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
3.5.2. Numerical simulation of Desgupta et al. . . . . . . . . . . . . . . . . 110
3.5.3. Minimal length of solid
plugs (simplified estimate) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
3.5.4. Crossing solid plugs with gas . . . . . . . . . . . . . . . . . . . . . . . 113
3.5.5. Friction of solid plugs on a pipe . . . . . . . . . . . . . . . . . . . . . 113
3.5.6. Practical proceedings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
3.6. Ancillary equipment for pneumatic conveying . . . . . . . . . . . . . . . 120
3.6.1. Feeding systems for continuous installations . . . . . . . . . . . . . . 120
3.6.2. Expedition by discontinuous
loads (dense phase) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
3.6.3. Criteria for the correct design
of load conveying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
3.6.4. Separation of the product and carrier gas . . . . . . . . . . . . . . . . 126
3.6.5. Conclusion for these systems . . . . . . . . . . . . . . . . . . . . . . . 127
3.6.6. Block valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
3.6.7. Tubes for pneumatic conveyance . . . . . . . . . . . . . . . . . . . . 128
3.6.8. Receptors (gas–solid receptors) . . . . . . . . . . . . . . . . . . . . . 129
3.6.9. Control of solid flow: starting and stopping . . . . . . . . . . . . . . 129
3.6.10. Choice of driving machine for the gas . . . . . . . . . . . . . . . . . 130
Chapter 4. Hydraulic Conveying of
Divided Solids: Standpipe and L-valve . . . . . . . . . . . . . . . . . . . . 133
4.1. Power dissipated in slurry . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
4.1.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
4.1.2. Agitation of slurry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
4.1.3. Pumping power of slurry . . . . . . . . . . . . . . . . . . . . . . . . . 135
4.1.4. Pressure drop in conveying slurry . . . . . . . . . . . . . . . . . . . . 137
Contents ix
4.2. Descent tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
4.2.1. Standpipe characteristics: use . . . . . . . . . . . . . . . . . . . . . . . 137
4.2.2. Description of the divided solid
in the tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
4.2.3. Operative mechanism of descenders . . . . . . . . . . . . . . . . . . . 139
4.2.4. Slip velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
4.2.5. Flow-pressure cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
4.2.6. Principle of performance curve calculation . . . . . . . . . . . . . . . 144
4.2.7. Standpipe simulation by calculation . . . . . . . . . . . . . . . . . . . 146
4.2.8. Aeration studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
4.2.9. Placing gas injection at the top of the tube . . . . . . . . . . . . . . . 147
4.2.10. Injection study: theory and experience . . . . . . . . . . . . . . . . 148
4.2.11. Conclusion: standpipes in industrial
processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
4.3. L-valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
4.3.1. Description and operation . . . . . . . . . . . . . . . . . . . . . . . . . 150
4.3.2. Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
Appendix 1. Mohs Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Appendix 2. Apparent Density of
Loose Divided Solids (kg.m−3) . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169