Motion and stress intensity of grinding beads in a stirred media mill. Part 2: Stress intensity and its effect on comminution

Abstract

Experimental investigations concerning the comminution of limestone in a stirred media mill have been carried out. The results show that the circumferential velocity of the stirrer discs as well as the density and the size of the grinding beads affect the specific energy consumption necessary to achieve the required product fineness. The influence of these three operating parameters on the comminution result can be fully described by the stress intensity of the grinding beads. Therefore, specific energy consumption and stress intensity of the grinding beads are the comprehensive influencing variables on the comminution of limestone in stirred media mills. It is expected that this relationship is also valid for the comminution of other materials in stirred media mills. For a fixed specific energy input, an optimum stress intensity exists, for which the finest product is achieved. With increasing specific energy input, and therefore increasing product fineness, the optimum stress intensity decreases. Since the specific energy is proportional to the product of stress intensity and stress frequency, the comminution result can also be correlated to the stress frequency and the stress intensity. With increasing stress intensity, the stress frequency required for a certain product fineness decreases.