Chemical Engineering November 2014 - 64

Solids Processing
changer will vary with location.
An analytical solution exists [5]
for the system of equations that can
be used to calculate the temperature
profile of the solids leaving the
cooler, as shown in Equation (7):
Ts
Tgin
Tsin
Tsin
= 1 exp
j
j=0
Axxha
GCpg
j!
k=0
j
Az
Hha
SCpg
k
AzHha
SCps
k!
(7)
Equations (6) and (7) are valid
provided that heat losses to the surroundings
and radiation heat transfer
can be neglected and heat transfer
by convection dominates.
[
m˙ f pickup
]
Closing thoughts
Hoppers, bins and silos that are
used to handle bulk solids can also
be used as heat exchangers that
heat or cool the materials. The
moving-bed processor must allow
[
m˙ f feeder leakage
]
Fw d × ×3π ηg Vrad
= p
×
[
m˙ f pickup
]
m
s
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m
s
Circle 22 on p. 180 or go to adlinks.che.com/50982-22
64 ChemiCal engineering www.Chemengonline.Com noVemBer 2014
m
s
TM
Oils and Greases, as well as a family of PTFE Release
 Custom Catalyst
 Milling / Grinding
 Calcining / Drying
 Solids or Liquid
 Mixing/Blending/
Packaging
Color Logo
YS Inc.
4531 County Road 458
Collinsville, AL 35961
888-356-3343
m
s
support@miller-stephenson.com
miller-stephenson.com
www.ys-inc.com
ysinc@ys-inc.com
Circle 37 on p. 180 or go to adlinks.che.com/50982-37
m
s
 ISO 9001:2008
 Screening
 Vacuum Impregnating
 Metal Reclaim
 Pelletizing
= m˙ f blowerinlet
[
R e l e a s e A g e n t
]
S y n t h e t i c L u b r i c a n t
K r y t o x ®
F l o r i n a t e d
m
s
m
s
[
= m˙ f blower inlet
[
]
[
m˙ f bleed
]
Axxha
GCpg
uniform flow of solids and gas, and
the dimensions of the vessel must
ensure that instabilities do not result
from high gas velocities. The
gas must be injected at a rate high
enough to ensure a temperature difference
between the solids and gas
phases throughout the column and
the volume must be great enough to
provide the required residence time.
Obtaining fundamental, bulk-solid
flow properties, including cohesive
strength, wall friction, compressibility
and permeability, along with
thermal properties and heat-transfer
rate information, is necessary
to ensure that the moving-bed heat
exchanger will operate as desired. n
Edited by Suzanne Shelley
References
1. ASTM D-6128, Standard Test Method for
Shear Testing of Bulk Solids Using the Jenike
Shear Cell, ASTM International, 2006.
2. Jenike, A.W., Storage and Flow of Solids, Bulletin
123, University of Utah Engineering
Station, 1964, Revised 1976.
3. ASTM D-6773, Standard Shear Test Method
for Bulk Solids Using the Schulze Ring Shear
Tester, ASTM International, 2008.
4. Royal, T.A. and Carson, J.W., Fine Powder
Flow Phenomena in Bins, Hoppers, and
Processing Vessels, presented at Bulk 2000:
Bulk Material Handling Toward the Year
2000, London, 1991.
5. Almendros-Ibáñez, Soria-Verdugo, A., RuizRivas,
U., and Santana, D., Solid conduction
effects and design criteria in moving
bed heat exchangers, App. Therm. Engr., 31,
1200, 2011.
Author
Greg Mehos is a senior project
engineer with Jenike &
Johanson, Inc. (400 Business
Park Dr., Tyngsboro, Mass.;
Phone: 978-649-3300; Email:
gmehos@jenike.com), and an
adjunct professor at the University
of Rhode Island.
Mehos has been involved in a
wide range of bulk solids handling
projects, including designs
of hoppers, dryers, gasifiers
and moving-bed reactors, as well as
analyses of purge and conditioning columns. He
received his B.S. and Ph.D. in chemical engineering
from the University of Colorado and an
M.S.Ch.E. from the University of Delaware. He
is a registered Professional Engineer in Colorado
and Massachusetts and a member of AIChE. He
served on the executive board of AIChE's Particle
Technology Forum and is a past chair of the
Boston AIChE section.
m˙ f bleed
]
R e l e a s e A g e n t
D r y L u b r i c a n t
R e l e a s e A g e n t
m
s
TOLL MANUFACTURE
SINCE 1982
[
m˙ f feederleakage
]
Y S
INC.
http://www.ys-inc.com http://www.miller-stephenson.com http://adlinks.che.com/50982-22 http://adlinks.che.com/50982-37 http://www.Chemengonline.Com
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