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Courtesy of Hamid Arastoopour, Dept. of Chemical and Environmental
Engineering, Illinois Institute of Technology
For 25 years, Hamid Arastoopour, Max McGraw Professor of Energy/Environment/
Economics at the Department of Chemical and Environmental Engineering
at Illinois Institute of Technology (IIT) and his research group have
made numerous contributions to fields involving the combined flow of
fluid and particles. His work has been both experimental and theoretical
in nature, and the applications have ranged from fluidized beds to the
pulverization and agglomeration of particles. As an invited speaker at
the 2001 US UGM, Prof. Arastoopour described several areas of his work,
two of which are summarized below.
- Fluid/Particle Flow Systems
& Fluidization
- Pulverization
Fluid/Particle Flow Systems & Fluidization
Over the years, Prof. Arastoopour’s group has performed experimental
measurements of fluid/particle flow systems using Laser Doppler Anemometry
(LDA), resulting in detailed in-situ data on particle size, velocity concentration,
and fluctuating velocity components in dilute gas/solid, liquid/solid,
and liquid/solid/bubble flow systems 1,2. In particular, these
measurements have shown that in the riser section of a circulating fluidized
bed (CFB), larger particles have a tendency to move toward the wall of
the riser. Similar measurements have been carried out on liquid/solid
systems and three-phase systems with a very high solid concentration 1.
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Prof. Arastoopour and his research team were among the first to initiate
the development of CFD models and computer codes for gas/particle flow
systems. During the late 1970s and early 1980s, they compared different
models for describing the flow in the riser section of a CFB using the
concept of particle cluster. They incorporated particle size distribution
and particle collisions for the first time in gas/solid flow models 3,4.
Their contribution to the kinetic theory approach has been an extension
of this theory to include cohesive particles, and recently, an extension
to describe a mixture of multi-sized particles. Figure 1 shows an example
of a gas/solid flow simulation using the kinetic theory approach in FLUENT.
In this example, the flow of gas and solids in two inlet configurations
to a riser are compared. For the horizontal inlet channel, solids accumulate
at the bottom of the channel prior to entry into the riser (top left and
center). When the inlet is aerated with a gas flow (top right) the solids
no longer accumulate and a more uniform mixture is delivered to the riser.
Inclining the inlet at a 45° angle (bottom) has a similar effect,
in that a more uniform mixture is obtained prior to entering the riser.
Aerated inlet
Figure 1. Transient solids volume fraction and velocity
profiles in a horizontal solids inlet (top) and a 45° inclined solids
inlet (bottom)
Pulverization
During the past decade, Prof. Arastoopour and his colleagues received
five patents on their novel Solid State Shear Extrusion (SSSE) pulverization
technique for producing powders from a broad range of polymers and rubbers,
without using cryogenic fluid. Figure 2 shows the schematic diagram of
the SSSE process. As can be seen, this process consists of three zones:
Zone 1, for processing and conveying, Zone 2, for heating and compression,
and Zone 3, for cooling and pulverization. This process is based on the
large compressive shear deformation of granulates, and in turn, storage
of a large amount of strain energy in Zone 3. When the stored energy reaches
a critical level, the material cannot sustain itself. As a result, the
stored energy is converted into surface energy through the formation of
new surfaces, and pulverization occurs 5,6. Analysis of the
produced particles has revealed the capability of this technology to produce
a desired particle size with a high surface area and breakage of the cross-linked
chemical bonds. One targeted application is the partial devulcanization
of rubber during pulverization, which carries with it the potential to
revolutionize rubber recycling.
Figure 2. Schematic diagram of the single screw Solid
State Shear Extrusion pulverization process
References
- Arastoopour, H. and S. Shao, in Non-Invasive Monitoring of Multiphase
Flows, Edited by J. Chaouki, F. Larachi, and M. P. Dudukovic (1997).
- Mathiesen, V., T. Solberg, H. Arastoopour, and B. H. Hjertager, AIChE
Journal, Vol. 45, No. 12, 2503-2518 (1999).
- 3 Arastoopour, H., S. C. Lin, and S. A. Weil, AIChE Journal, Vol.
28, No. 3, pp. 467-473 (1982).
- Arastoopour, H. and D. Gidaspow, Ind. Eng. Chem. Fundam., Vol. 18,
No. 2, pp. 123-130 (1979).
- Bilgili, E., H. Arastoopour, and B. Bernstein, Powder Technology Journal,
Vol. 115, pp. 265-276 (2001).
- Bilgili, E., H. Arastoopour, and B. Bernstein, Powder Technology Journal,
Vol. 115, pp. 277-289 (2001).
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