The elutriation of fine powders (group C or group A powders in Geldart’s classification) from a fluidized bed of fine-coarse particle mixtures in a steady state is investigated. FCC and alumina particles of 12 μm to 91 μm in diameter (group C and group A powders) were used as fines. Alumina particles of 69 μm to 650 μm in diameter (group A and group B particles) were used as coarse particles. The effects of the weight fraction of powder in the bed, superficial gas velocity, size of fine powder, size of coarse particle, and mean diameter of bed particles on the elutriation rate constant were investigated.
The following results are obtained. The elutriation rate constant of group A particles is affected by the properties of the elutriated particles and gas and by operating conditions such as gas velocity. However, the elutriation rate constant of group C powders is not only affected by the above conditions, but also by the weight fraction of the elutriated powder in the bed and sizes of both coarse particles and elutriated powder in the bed, that is, the mean diameter of the bed particles. The elutriation rate constant of group C powders decreases with increases in the mean diameter of bed particles and with decreases in the size of group C powders under the condition of a constant superficial gas velocity. This finding is quite different from that of elutriation of group A or group B particles.
2000 The Society of Chemical Engineers, Japan