Pneumatic transport of solids in a riser has a unique nonuniform flow structure, characterized by the core solids acceleration and the wall solids deceleration along the riser, which causes the down-flow of solids and hence back mixing. To predict this nonuniform flow structure, this paper presents a mechanistic model that includes two controlling mechanisms: the interparticle collision damping for axial transport of solids and the effects of collision-induced diffusion and turbulent convection for radial transport of solids. The model predictions are partially validated against available measurements, such as axial and radial distributions of concentration and velocity of solids.

References

References
1.
Li
,
Y.
, and
Kwauk
,
M.
,
1980
, “
The Dynamics of Fast Fluidization
,”
Fluidization
,
Springer
,
New York
, pp.
537
544
.
2.
Issangya
,
A. S.
,
Grace
,
J. R.
,
Bai
,
D.
, and
Zhu
,
J.
,
2000
, “
Further Measurements of Flow Dynamics in a High-Density Circulating Fluidized Bed Riser
,”
Powder Technol.
,
111
(
1
), pp.
104
113
.
3.
Pärssinen
,
J. H.
, and
Zhu
,
J.-X.
,
2001
, “
Particle Velocity and Flow Development in a Long and High-Flux Circulating Fluidized Bed Riser
,”
Chem. Eng. Sci.
,
56
(
18
), pp.
5295
5303
.
4.
Herb
,
B.
,
Dou
,
S.
,
Tuzla
,
K.
, and
Chen
,
J. C.
,
1992
, “
Solid Mass Fluxes in Circulating Fluidized Beds
,”
Powder Technol.
,
70
(
3
), pp.
197
205
.
5.
Du
,
B.
,
Warsito
,
W.
, and
Fan
,
L.
,
2004
, “
ECT Studies of the Choking Phenomenon in a Gas–Solid Circulating Fluidized Bed
,”
AIChE J.
,
50
(
7
), pp.
1386
1406
.
6.
Harris
,
B. J.
, and
Davidson
,
J. F.
,
1994
, “
Modeling Options for Circulating Fluidized Beds: A Core/Annulus Deposition Model for Circulating Fluidized Beds
,”
Circulating Fluidized Bed Technology IV
,
AIChE
,
New York
, pp.
32
39
.
7.
Louge
,
M.
, and
Chang
,
H.
,
1990
, “
Pressure and Voidage Gradients in Vertical Gas-Solid Risers
,”
Powder Technol.
,
60
(
2
), pp.
197
201
.
8.
Louge
,
M. Y.
,
Mastorakos
,
E.
, and
Jenkins
,
J. T.
,
1991
, “
The Role of Particle Collisions in Pneumatic Transport
,”
J. Fluid Mech.
,
231
(
1
), pp.
345
359
.
9.
Büssing
,
W.
, and
Reh
,
L.
,
2001
, “
On Viscous Momentum Transfer by Solids in Gas–Solids Flow Through Risers
,”
Chem. Eng. Sci.
,
56
(
12
), pp.
3803
3813
.
10.
Zhu
,
C.
, and
You
,
J.
,
2007
, “
An Energy-Based Model of Gas–Solid Transport in a Riser
,”
Powder Technol.
,
175
(
1
), pp.
33
42
.
11.
Bolton
,
L. W.
, and
Davidson
,
J. F.
,
1988
, “
Recirculation of Particles in Fast Fluidized Risers
,”
Circulating Fluidized Bed Technology II
,
Pergamon Press
,
Oxford, UK
, pp.
139
146
.
12.
Senior
,
R. C.
, and
Brereton
,
C.
,
1992
, “
Modeling of Circulating Fluidised-Bed Solids Flow and Distribution
,”
Chem. Eng. Sci.
,
47
(
2
), pp.
281
296
.
13.
Richardson
,
J. F.
, and
Zaki
,
W. N.
,
1954
, “
Sedimentation and Fluidisation: Part I
,”
Trans. Inst. Chem. Eng.
,
32
, pp.
35
53
.
14.
You
,
J.
,
Patel
,
R.
,
Wang
,
D.
, and
Zhu
,
C.
,
2010
, “
Role of Inter-Particle Collision on Solids Acceleration in Riser
,”
Particuology
,
8
(
1
), pp.
13
18
.
15.
Zhu
,
C.
,
Liang
,
S. C.
, and
Fan
,
L. S.
,
1994
, “
Particle Wake Effects on the Drag Force of an Interactive Particle
,”
Int. J. Multiphase Flow
,
20
(
1
), pp.
117
129
.
16.
Wang
,
D.
,
You
,
J.
, and
Zhu
,
C.
,
2010
, “
Modeling of Core Flow in a Gas–Solids Riser
,”
Powder Technol.
,
199
(
1
), pp.
13
22
.
17.
Zhu
,
C.
,
Jun
,
Y.
,
Patel
,
R.
, and
Wang
,
D.
,
2011
, “
Interactions of Flow and Reaction in Fluid Catalytic Cracking Risers
,”
AIChE J.
,
57
(
11
), pp.
3122
3131
.
18.
He
,
P.
,
Zhu
,
C.
, and
Ho
,
T. C.
,
2015
, “
A Two-Zone Model for Fluid Catalytic Cracking Riser With Multiple Feed Injectors
,”
AIChE J.
,
61
(
2
), pp.
610
619
.
19.
Nieuwland
,
J. J.
,
Meijer
,
R.
,
Kuipers
,
J. A. M.
, and
Van Swaaij
,
W. P. M.
,
1996
, “
Measurements of Solids Concentration and Axial Solids Velocity in Gas-Solid Two-Phase Flows
,”
Powder Technol.
,
87
(
2
), pp.
127
139
.
20.
Wei
,
F.
,
Lin
,
H.
,
Cheng
,
Y.
,
Wang
,
Z.
, and
Jin
,
Y.
,
1998
, “
Profiles of Particle Velocity and Solids Fraction in a High-Density Riser
,”
Powder Technol.
,
100
(
2
), pp.
183
189
.
21.
Qi
,
X.
,
Huang
,
W.
, and
Zhu
,
J.
,
2008
, “
Comparative Study of Flow Structure in Circulating Fluidized Bed Risers With FCC and Sand Particles
,”
Chem. Eng. Technol.
,
31
(
4
), pp.
542
553
.
22.
Patel
,
R.
,
He
,
P.
,
Zhang
,
B.
, and
Zhu
,
C.
,
2013
, “
Transport of Interacting and Evaporating Liquid Sprays in a Gas–Solid Riser Reactor
,”
Chem. Eng. Sci.
,
100
, pp.
433
444
.
You do not currently have access to this content.