Effects of gas properties on the behavior of fluidized beds of small particles.

The quality of fluidization of FCC particles (dp = 60μm) was studied by using six kinds of fluidizing gases in a 0.081 m diameter column. As several investigators have described, minimum fluidization velocity was inversely proportional to gas viscosity and was almost independent of gas density. The expansion ratio of the emulsion phase was, however, dependent on gas density and increased with viscosity and density. Both measured bubble frequency and deviation of pressure fluctuations were also influenced considerably by the gas properties. The voidage of the emulsion phase was considered to be dominated by the properties of the gas flowing through the emulsion phase. Thus the apparent viscosity of the emulsion, i.e. the quality of fluidization, is influenced by those properties of gases.