Particle mixing in rotating fluidized beds: Inferences about the fluidizedstate

Particle motion in a rotating fluidized bed was studied by observing the mi xing of two layers of particles of different colors. The particles in the t wo layers were either nearly identical, except for their color or were of d ifferent density and size distribution. All of the particles were in the Ge ldart-A classification for conventional fluidized beds. After fluidization, but before mixing, the bed exhibited some fluid-like behavior that is, the inner surface became radially uniform. For particle layers of the same mat erial, mixing occurred after U-mfc was reached, with bubbles observed at th e mixing velocity No experimental difference between U-mb and U-mfc could b e discerned; they either coincided or were nearly equal. Bubbles appeared t o be responsible for particle motion and mixing. When the denser particles are placed on the distributor, the mixing behavior was similar to that obse rved for layers of the same material However, when the less dense particles ave placed on the distributor mixing is dominated by differences in densit y and occurs before bubbles are visible.