The settling of fine cohesive powders

Abstract

We investigate the settling of an initially fluidized bed of a fine cohesive powder. Experimental results on the sedimentation rate cannot be fitted by theoretical and empirical equations existing in the literature and derived for non-cohesive spheres. We extend these equations to account for the adhesion-induced aggregation of fine particles. The number of particles per aggregate N and the ratio of aggregate radius R to particle radius, a, have been chosen as fitting parameters. Results from two independent approaches are in very good agreement with the experimental data for approximately the same values of N and R. Pictures taken from the fluidized bed show that the average aggregate radius matches the predicted one.