Particle-fluid systems

F. A. Zenz and D. F. Othmer, Eluidi tion and Fluid Particle Systems Reinhold Publishing Corp., New York, 1960. 

FIG. 17-2 Schematic phase diagram in the region of upward gas flow. W = mass flow solids, lh/(h fr) E = fraction voids Pp = particle density, Ih/ft Py= fluid density, Ih/ft Cd = drag coefficient Re = modified Reynolds uum-her. (Zenz and Othmei Fluidization and Fluid Particle Systems, Reinhold, New York, 1960. )... 

ZBN7. F. A, and OTHMER, D. H Fluidization and Fluid-Particle Systems (Reinhold, New York. I960). 

Noymer, P. D., Hyre, M. R., and Glicksman, L. R., The Influence of Bed Diameter on Hydrodynamics and Heat Transfer in Circulating Fluidized Beds, Fluidization and Fluid-Particle Systems, AIChE, pp. 86-90 (1995)... 

Pressure and Temperature Effects in Fluid-Particle Systems... 

As a result, most of the information on how temperature and pressure affect fluidized beds has been obtained during the last twenty-five years. Much of this research has been conducted in a piecemeal fashion by several researchers. However, enough information is available to allow the construction of an overall picture of how these two parameters affect fluidized beds, and fluid-particle systems in general. 

Temperature and pressure affect the operation of fluid-particle systems because they affect gas density and gas viscosity. It is the variation in these two parameters that determine the effects of temperature and pressure on fluid-particle systems. Increasing system temperature causes gas density to decrease and gas viscosity to increase. Therefore, it is not possible to determine only the effect of gas viscosity on a system by changing system temperature because gas density is also changed and the resulting information is confused. Very few research facilities have the capability to change system pressure to maintain gas density constant while the temperature is being changed to vary gas viscosity. 

Zenz, F. A., and Kelleher, E. G., Studies of Attrition Rates in Fluid-Particle Systems via Free Fall, Grid Jets, and Cyclone Impact, J. of Powder Bulk Technol., 4 13 (1980)... 

Geldart, D., and Abrahamsen, A. R., ( Fluidization of Fine Porous Powders, Recent Advances in Fluidization and Fluid-Particle Systems, AIChE Symp. Series, AIChE, 77(205) 160-165, New York (1981)... 

Thus, in summary, the two necessary conditions for correspondence between the notional-particle system and the fluid-particle system in constant-density flows are... 

Phase Diagram (Zenz and Othmer) As shown in Fig. 17-2, Zenz and Othmer, (Fluidization and Fluid Particle Systems, Reinhold, New York, 1960) developed a gas-solid phase diagram for systems in which gas flows upward, as a function of pressure drop per unit length versus gas velocity with solids mass flux as a parameter. Line OAB in Fig. 17-2 is the pressure drop versus gas velocity curve for a packed bed, and line BD is the curve for a fluidized bed with no net solids flow through it. Zenz indicated that there was an instability between points D and H because with no solids flow, all the particles will be... 

Zenz, F. A. and Othmer, D. F. Fluidization and Fluid-particle Systems (Reinhold, 1960). 

KEAIRNS, D. L. (ed.) Fluidization and Fluid-Particle Systems. A.I.Ch.E. Symposium Series 70 No 141 (1974). KEAIRNS, D. L. (ed.) Fluidization Technology. Proc. Int. Fluidisation Conf., Pacific Grove, California, 1975. KUNII, D. and Levenspiel, O. Fluidization Engineering, 2nd edn. (Butterworth-Heinemann, 1991). 

Zandi, I. (ed.) Advances in Solid-Liquid Flow in Pipes and its Application (Pergamon Press, Oxford, 1971). Zenz, F. A. and OTHMER, D. F. Fluidization and Fluid-Particle Systems (Reinhold, 1960). 

In multiphase flow equipment, the size distribution of drops and bubbles is commonly determined by the dynamics of break up and coalescence. Coalescence involves multiple fluid-particle systems and hence is beyond the scope of this book. A number of processes may cause breakup and these are discussed here. 

Chen, J.C Fluidization ami Fluid Particle Systems Recent Reseaioh and Deselop-niciu. American Institute of Chemical Engineers, New York, NY, 1998,... 

King, D, Adwares in Fluidization nod fluid Particle Systems. American Institute of Chemical F.ngtncers. New York, NY, 1997 Ferry, R.W.. D.W1. Green Perry s Chemical Engineers Handbook. 7th Edition. The McGraw-Hill Companies. Inc, New York. NY. 1997. 

Fluidization and Fluid-Particle Systems Figure 2. Coal particle residence time vs. particle size. Hb at 1500 psi + 700°C. 

Further discussion on scaling relationships for various fluid-particle systems is given in Glicksman et al. (1994). 

Knowlton, T. M. (1992). Pressure and Temperature Effects in Fluid-Particle System. In Fluidization VII. Ed. Potter and Nicklin. New York Engineering Foundation. 

The two-phase theory of fluidization has been extensively used to describe fluidization (e.g., see Kunii and Levenspiel, Fluidization Engineering, 2d ed., Wiley, 1990). The fluidized bed is assumed to contain a bubble and an emulsion phase. The bubble phase may be modeled by a plug flow (or dispersion) model, and the emulsion phase is assumed to be well mixed and may be modeled as a CSTR. Correlations for the size of the bubbles and the heat and mass transport from the bubbles to the emulsion phase are available in Sec. 17 of this Handbook and in textbooks on the subject. Davidson and Harrison (Fluidization, 2d ed., Academic Press, 1985), Geldart (Gas Fluidization Technology, Wiley, 1986), Kunii and Levenspiel (Fluidization Engineering, Wiley, 1969), and Zenz (Fluidization and Fluid-Particle Systems, Pemm-Corp Publications, 1989) are good reference books. 

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