The investigation of the kinetics of breakage as a first step towards the assessment of the economics of ultra-fine grinding of a British low-rank coal

Abstract

The characteristics of breakage of a low-rank, semi-bituminous British coal were investigated from batch grinding tests in a laboratory ball mill. For short periods of grinding, first-order breakage occurred, but as fine material built up in the mill, a slowing down of the rates of breakage was observed. The specific rate of breakage of particles smaller than 1400 μm was found to be a simple power function of size. The breakage distribution parameters were found to be a normalised function of size. The reduction in the rates of breakage was correlated in terms of the size distribution of particles in the mill with reasonable accuracy. Finally the removal of fine particles at regular intervals during the grinding restored the first-order kinetics.