Stress intensity in stirred media mills and its effect on specific energy requirement

Abstract

The comminution of limestone and fused corundum in stirred media mills has been investigated regarding specific energy requirement. The experimental results show that the tip speed of stirrer discs as well as the density and the size of grinding media affect the specific energy required to achieve a certain product fineness. Moreover, for comminution of fused corundum, the Young's modulus of grinding media and of product particles influences the specific energy requirement. The kinetic energy of grinding media is transferred from the grinding media to the product particles during each stress event. For product materials with a high Young's modulus (e.g., fused corundum), the transferred energy strongly depends on the Young's modulus of grinding media, whereas the transferred energy is nearly independent of the Young's modulus of grinding media for weak product materials. The effect of the operating parameters tip speed of stirrer, grinding media size, grinding media density and Young's modulus of grinding media on the comminution result can be described by the stress intensity. The stress intensity is proportional to the energy, which is transferred from the grinding media to the product particles during a stress event. For each stress intensity, a certain relation between product fineness and specific energy exists. Therefore, the comprehensive influencing parameters on comminution of limestone and fused corundum in stirred media mills are the stress intensity and the specific energy.