Further studies of the kinetics of spherical agglomeration in a stirred vessel

Abstract

The agglomeration behaviour of silica sand, glass and calcium carbonate powders (average diam. 4 – 76 μm) in stirred suspensions was investigated. The powders were dispersed as 0.1 – 4 vol.% suspensions in carbon tetrachloride and agglomerated with aqueous calcium chloride solution as model systems. The work extends a previous investigation [3] to lower suspension concentrations and much finer particle sizes. In all the experiments the agglomeration kinetics could be represented as a first-order process, indicating a high degree of particle interaction and control of the proess by the level of systematic agitation. Differences in behaviour were observed between the finer and coarser particles. The finer particles were found to require much less bridging liquid (referred to the porosity of the dry packed state) for satisfactory agglomeration and to exhibit an induction period of slow growth followed by rapid, heteogeneous coalescence. The spread of agglomerate sizes increased with decreasing particle size. These differences were explained in terms of the greater surface/volume ratio of the fines and the relatively greater surface forces which exist between them.