A model for predicting the relationship between maximum voidage in homogeneous fluidization and emulsion phase voidage in bubbling fluidization.

Abstract

A model was proposed to describe the expansion behavior of a gas fluidized bed of fine particles by using the elastic wave velocity. The difference between the maximum bed voidage in homogeneous fluidized beds, εmb, and the emulsion-phase voidage in bubbling beds, εe could be explained by the proposed model. These voidages were calculated by comparing the voidage propagation velocity with the elestic wave velocity, the latter being represented as a function of the volume elasticity and the rigidity for uniformly expanded beds. In the emulsion phase of bubbling fluidized beds, however, the rigidity was neglected. This difference reflected the fact that εmb was larger than εe in any gas–solid system of fine particles. Since it was difficult to formulate quantitatively the value of the elastic wave velocity based on the theoretical approach, it was modified by experimental data in the literature.