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TitleHandbook of Powder Science and Technology
File Size30.6 MB
Total Pages914
Table of Contents
1 Particle Size Characterization
2 Particle Shape Characterization
3 Structural Properties of Packings of Particles
4 Fundamental and Rheological Properties of Powders
5 Vibration of Fine Powders and Its Application
6 Size Enlargement by Agglomeration
7 Pneumatic Conveying
8 Storage and Flow of Paniculate Solids
9 Fluidization Phenomena and Fluidized Bed Technology
10 Spouting of Particulate Solids
11 Mixing of Powders
12 Size Reduction of Solids Crushing and Grinding Equipment
13 Sedimentation
14 Filtration of Solids from Liquid Streams
15 Cyclones
16 The Electrostatic Precipitator: Application and Concepts
17 Granular Bed Filters
18 Wet Scrubber Particulate Collection
19 Fire and Explosion Hazards in Powder Handling and Processing
20 Respirable Dust Hazards
Document Text Contents
Page 1






edited by

Muhammad E. Fayed
Lambert Otten


International Thomson Publishing

New York • Albany • Bonn • Boston • Cincinnati • Detroit • London • Madrid • Melbourne
Mexico City • Pacific Grove • Paris • San Francisco • Singapore • Tokyo • Toronto • Washington


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Copyright © 1997 by Chapman & Hall, New York, NY

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Handbook ot powder science & technology / edited by M E Fayed, L Otten — 2nd ed
p cm

Rev ed ol Handbook oi powder science and technoilogy cl984
Includes bibliographical references and index
ISBN 0-412-99621-9 (alk paper)
1 Particles 2 Powders I Fayed, M E (Muhammad E ) II Otten, L (Lambert)
III Title Handbook ot powder science and technology IV Handbook ot powder
science and technology
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Page 457

STORAGE OF PARTICULATE SOLIDS 443 Jen ike & Johanson Quality
Control Tester

This device is intended for routine measure-
ments of the relative flowability of a bulk
solids, mainly for quality control applications,
where rapid off-line measurements can pro-
vide guidance in recognizing and diagnosing
problems in solids processing control.

A solids sample is placed in a sample con-
tainer configured with a cylindrical section

above a converging hoppers section, as shown
schematically in Figure 8.72. A perforated slide
gate covers the hopper opening when the solids
sample is gently filled into the container. After
loading, the container top is sealed, and the
container pressurized to a predetermined
pressure for about 30 s to consolidate the
sample as air permeates out through the screen
opening at the bottom of the cone. After 30 s,
the pressure is reduced to zero, the screen

Air supply fitting

Air pressure gage

Plan View

Covertrover -j

1 /

1 I
\ I



slide gate


Front Elevation

Figure 8.72. Jenike & Johanson Inc. Quality Control Tester.170

Page 458


slide gate is removed, and the pressure reap-
plied until the arch at the outlet breaks and
solids flow from the container. The peak pres-
sure is recorded by a digital pressure indicator.

The consolidating and failure procedures
are repeated several times and an average
peak pressure value is calculated. This peak
pressure value, corresponding to the
"strength" of the material, can be compared
to a reference value to establish relative
flowability of the sample170. Three different
size containers are available with the tester, to
accommodate a range of particle sizes. POSTEC-Research Uniaxial Tester

Scientific testers like biaxial or modified triax-
ial testers are indirect shear testers where the
shear zone is independent of the design of
apparatus. The data from these testers can
define the stress-strain relationships and flow
functions directly but are too complex for rou-
tine industrial use.

POSTEC-Research [171] has developed an
interesting Uniaxial Tester that shows a po-
tential for a rapid and direct method of mea-
suring the unconfined yield strength (fc) of a

powder. In theory, the unconfined yield stress
of a powder can be determined by consolidat-
ing a supported column of powder under a
stress crv then removing the support and ap-
plying a vertical stress on the unsupported
column until it fails (at / c ) . The obvious prob-
lem with this test is how to maintain an unsup-
ported powder column. This is handled in the
Postec device as shown in Fig. 8.73.

The die and piston are aligned and fixed in
position. A flexible rubber membrane is fitted
to the edge of the piston and the lower end of
the die. The membrane is stretched, so that it
will contract as the piston moves downward,
and, with lubricant between membrane and
die, sliding and wall friction will be reduced to
a minimum. The die is filled upside down, with
the bottom plate removed. The assembly is
then mounted upright, and the sample consoli-
dated by moving the piston slowly downward
until a predetermined stress crl has been
reached. After a period of time for stabiliza-
tion, the compaction stress cr1 is reduced to a
minimum value and the die is pulled up allow-
ing the sample to stand by itself. The piston
then moves slowly downward until the value of

(a) Consolidation (b) Compressive Failure

Figure 8.73. POSTEC-Research Uniaxial Shear Tester.171

Page 913


Stress, 587-588
concentration, 591-594
maximal tensile, 207
rupture stress, 213
theories, 411-413

calculations, 413-416
transmitting substance, 207
waves, 194-196

Strip thickness, 352
Structure parameters, 54-61 {see also packing struc-

Carman-Kozeny equations, 56-58
mean voidage, 54
permeability and inertia parameters, 55-56 J

reduced breahthrough capillary pressure, 59-61
resistivity factor, 61
specific surface, 54

Structured mixtures, 568
Stokes diameter, 2, 12, 20
Structured walk, 44 {see also fractal dimension)
Superficial fluid velocity, 116, 536, 537
Superficial gas velocity, 382
Surface-active substance, 231
Surface area, in agglomeration, 229
Surface equivalent diameter, 208, 227
Surface factor {see Hausner shape indices)
Surface filtration, 685-686
Surface finish, 432-433 {see also hopper)
Surface instability waves, 536
Surface nodes, 77
Surface roughness, 219, 224
Surface tension, 208
Surging, 262 {see also balling drum circuits)
Suspended particles, 254
Suspended solids agglomeration, 254
Suspension flow, 379
Suspensions, aggregated, 648-653
Switch pressures, 407
Switch stress, 412
System pressure drop, 383 {see also pneumatic convey-

Szego mill, 626-628

bulk density, 335
durability, 335-336
failure, 322
formulations, 332-336
machines, 314, 328-332
thickness, 335

Tableting, 327-336
feeds, 270

Talmage-Firch method, 662 {see also thickening)
Tamping, 331 {see also tabletting)
Tangetial gas velocity, 731-733
Tap-density, 351
Tapping, 113-114 {see also powder compaction)

Temperature, 426 {see also storage)
control in fluidization, 502-512
drying in agglomeration, 215

Tensil strength, 123-133
in agglomeration, 207
ultimate tensile strength, 127-132

TEOM, 874-876 {see also respirable dust hazards)
Terminal velocity, 515-516
Termination mechanisms, 536 {see also maximum

spoutable bed depth)
Terzaghi's equation, 112 {see also compaction pressure)
Textural fractal dimension, 47
Theory of densification, 348
Theory of rolling, 349
Thickening, 638, 657-666

design procedures, 658-663
Thixotropic behavior, 312 {see also spheronizing)
Three-phase spouting, 558
Threshold pressue, 304 {see also pelleting machines)
Throughput, 350-351 {see also roller presses)
Time of flight instruments, 18-20
Time yield locus, 419-420
Tooling, 313 {see also withdrawal processes)
Tooling design, 322-327
Top-sealed vessel, 555
Topology, 44 {see also fractal geometry)
Toroidal rings (see pendular rings)
Tortuosity, 57, 97
Total bed efficiency, 772-773
Tramp material, 341
Transfer number matrix, 606
Transient fluidized bed, 576
Transport disengaging height, 516
Trajectory of falling particles, 450 {see also particle

Travelling grate, 258
Tray towers, 827-828
Trommel screen, 262
Tubular filter, 707, 711, 712
Tumble agglomeration, 246, 252-293

definitions, 253
mechanisms of, 254

Tumbler centrifuge, 722-723

behavior, 4
ball mills, 600-601

analysis of, 616-619
mixer, 572

transient; fluidized bed, 572
in dust explosion, 853

Turbulent agitation, 502 {see also fluidization)
Turbulent flow (in sedimentation), 641
Turbulent mixture, 577
Turbulizers, 257
Turner structures, 68 {see also dead end pores)

Page 914


Ultimate mixture, 577
Ultimate tensile strength, 127-132 {see also tensile

Ultrasonic screening, 235
Ultrafiltration, 690
Unconfined yield strength, 422
Underflow concentration, 663
Undesired agglomeration, 229
Unit cell, 62
Unit operations, 202 {see also mechanical process tech-

size reduction, 586

Unwanted agglomeration, 231
Upflow solids contact, 674-675

Vacuum filters, 710-715
Van der Waals force, 119, 210 {see also cohesive forces)
Van der Waals lines, 215

conveying, 239
incipient fluidization, 515
interstitial, 57
minimum conveying, 378, 382
minimum spouting, 534
sliding, 171-172
seepage, 57
superficial, 116, 117, 382

aggregated suspensions, 652
nonspherical particle, 642
of a sphere, 639

solids, 382
wave, 149

propagation, 193
Venturi scrubber, 817-822
Vertical compressive deformation, 183-184
Vertical gas velocity, 733
Vertical tensile test, 123 {see also tensile strength)
Very loose random packing, 66
Vibrated shear strength, 174-175
Vibrating ball mills, 601-602
Vibrating feeders, 461-463
Vibrating insert, 188-190
Vibration, 113-114, 146-198 {see also powder com-

boundary shear, 175-178
compaction, 181-185
failure criterion, 171-175
flow promotion, 185-190
fluidized beds, 150
inertia model, 161-171
in particle segregation, 450
in storage, 427
measurement of dynamic shear, 152-155
powder mechanics, 150
random vibration exitation, 178-180
stress waves, 194-196

transmission through bulk mass, 190-194
wall friction, 175-178

Vibration energy transfer, 190-194
Vibratory devices, 464-468 {see also flow promotion)
Viscous bonding media, 206
Viscous damping, 167, 170
V-mixer, 578

critical, 150
fraction, 54, 97, 140
ratio, 97

Voidage, 54 {see also porosity)
Voidage distribution, 542
Voids, 56-57 {see also Carman-Kozeny equation)
Volume, specific, 97
Voxel, 84

Wall clamping method, 124-125 {see also specimen

Wall effect, 66-67, 657
Wall friction, 175-178

method, 212 {see also crushing strength)
Wall yield locus, 423-424
Wave propagation, 193-194

acoustic, 23
forms, 39
and damping, 193
Rayleigh, 195

Weepage flow, 518
Wen-Yu approximation, 535
Wet agglomerate, 257
Wet bag pressing, 337 {see also isostatic pressing)
Wet classifiers, 205
Wet grinding, 234
Wetted packed beds, 825-827
Wet pastes, 308 {see also pelleting machines)
Wet scrubbers, 803-840

collection efficiency, 811-814
costs, 837-840
design considerations, 836-837
power consumption, 810-811

Wet scrubbing, 216
Wettability, 87-88
Wetted perimeter, 57
Wetting angle, 208
Wetting fluid, 59
Withdrawal presses, 313-314
Windows, 57 {see also Carman-Kozeny equation)

Yardstick measure, 44 {see also fractal dimension)
Yield loci, 160-161 {see also dynamic shear)

determination of, 419-421
solids characteristics, 421-423

Y-mixer, 578
Yoshioka method, 661-662 {see also thickening)
Young's modulus, 587

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