Chemical Engineering August 2012 - 52

Minimum fluidization velocity (per
Wen and Yu) = 0.0262 m/s
Complete fluidization velocity.
Complete fluidization velocity is calculated
by substituting dsvm (or Sauter
mean diameter) by d95 in the correlation
for minimum fluidization.
This velocity is often used to define
the operating point of fluidized bed
processes.
Comment on distributor design.
To achieve uniform distribution of
gas in a fluidized bed, it is recommended
that the pressure drop across
the distributor be at least 30% of the
bed pressure drop, or at least 10 in.
H2O column (2,500 Pa) on an absolute
basis. More in-depth discussion
on distributor design can be found in
Yang [12].
Summary
Despite eight decades of research and
development of powerful computer
tools, the core of fluidization technology
remains largely empirical. Scaleup
and design of large-scale processes
based on small-scale cold flow data
still remains a challenging problem.
In this article, we have touched upon
key concepts of fluidization technology
and summarized key equations for
particle characterization, particle and
bed hydrodynamics. For in-depth understanding
of the subject, the books
by Geldart [3], Kunni-Levenspiel [7],
Yang [11, 12] and Zenz-Othmer [14]
are excellent resources.
■
Edited by Suzanne Shelley
Acknowledgement
We appreciate the valuable comments
and suggestions offered by Ray Cocco,
president and CEO of Particulate
Solid Research Inc. (Chicago, Ill.).
References
1. Brown, G.G. and others, " Unit Operations, "
Wiley, New York, 1950, pp. 210-216.
2. Geldart, D., Powder Technology, Vol. 7, 1973,
pp. 285-292.
3. Geldart, D. (ed.), " Gas Fluidization Technology, "
John Wiley & Sons, 1986.
4. Gibilaro L.G. and others, Chem. Eng. Sci.,
Vol. 40, 1985, pp.1817-1823.
5. Grace, J., The Canadian Journal of Chem.
Eng., Vol. 64, June 1986, pp. 353-363.
6. Haider, A. and Levenspiel, O., Powder Technology,
Vol. 58, 1989, pp. 63-70.
7. Kunni, D. and Levenspiel, O., " Fluidization
Engineering " (2nd Ed.), Butterworth-Heinemann
Series in Chemical Engineering, 1991.
8. Pell, M., " Gas Fluidization, " Elsevier, 1990.
9. Richardson, J.F. and Zaki, W.N., Trans. Instn.
Chem. Engrs., Vol. 32, 1954, pp. 35-53.
10. Turton, R. and Levenspiel, O., Powder Technology,
Vol. 47, 1986, p. 83.
11. Wen, C.Y. and Yu, Y.H., AIChE Journal, May
1966, pp. 610-612.
12. Yang, W.C. (Ed.), " Fluidization, Solids Handling
and Processing, " Noyes Publication,
1999.
13. Yang, W.-C. (Ed.), " Handbook of Fluidization
and Fluid Particle Systems, " Marcel-Dekker
Inc., 2003.
14. Zenz, F.A. and Othmer, D.F, " Fluidization and
Fluid-Particle Systems, " Reinhold Chemical
Engineering Series, 1960.
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