AN INVESTIGATION OF THE KINETICS OF GRANULATION USING A HIGH-SHEAR MIXER

A study is reported of the kinetics of granulation of a fine powder with a low viscosity binder in a mixer fitted with both impeller and chopper blades. The impeller torque was used to monitor the binder distribution, nucleation, compaction and coalescence phases of granulation and to detect the establishment of steady state conditions in which coalescence was the dominant process. Measurements are reported of the effects of varying processing conditions on granule growth and size distribution. Data were interpreted using theories for growth by the coalescence mechanism. It was that, for the particular system studied, coalescence only occurred when the granules were saturated, or near saturated, with liquid binder. Within experimental errors, mean granule size was found to increase linearly with time. The interpretation of this result is discussed and shown to be evidence for the probability of coalescence being size dependent. The changes in the size distribution with time are also discussed in terms of kinetic theory and the effect of chopper rotation on size distribution is established.