HOLD-UP OF FINE PARTICLES IN A POWDER-PARTICLE SPOUTED BED

Hold-up of cohesive fine particles in a powder-particle spouted bed un der continuous fines feeding was investigated. Nine powders, aluminium hydroxide and aluminium oxide materials, ranging in particle size fro m 0.51 mu m to 3.5 mu m (Group C powders in Geldart's classification) were used. Silica sand particles of 920 mu m in average diameter (Grou p D powders in Geldart's classification) were used as coarse particles . Cohesive force of the fines was determined by the tensile strength m ethod. The effects of superficial gas velocity, the feed rate of fines , the size of fines and cohesive force among fines on the hold-up of f ines in the bed at a steady state were examined experimentally. It is found that fines hold-up is dominated by cohesive force and the effect of operating conditions upon the fines hold-up could be explained fro m the view point of the cohesive force.