FINE GRINDING AND THE PRODUCTION OF COARSE PARTICULATES

Is is shown that fine, dry grinding consists of two phases. The first is Rittinger's phase where specific surface increases directly with energy input. The second phase is one of aggregation of ground particles, which results in a grinding equilibrium. As a consequence of the oversupply of energy in this latter phase, irreversible agglomeration occurs leading to the production of coarse particulates. The effect of grinding aids is to reduce surface energy thereby delaying, but not preventing, the onset of agglomeration. Mechanical activation is a common occurrence in fine dry grinding and results in numerous chemical and physical changes, including agglomeration, which has potential utilization as a granulation operation.