COMPARISON OF ENERGY-CONSUMPTION IN THE BREAKAGE OF SINGLE PARTICLES IN A RIGIDLY MOUNTED ROLL MILL WITH BALL MILL GRINDING

More than sixty size distributions resulting from the breakage of single particles of four minerals in rigidly mounted rolls with different combinations of feed size and roll gap have been analyzed in great detail as to their shape, structure and the effect of energy consumption. A number of interesting and useful "regularities" have been observed. The most important ones are that the size distributions are self-similar in a dimensionless size which has been rescaled by the median size. The inverse of the median size in turn varies linearly with grinding energy. The grinding energy is determined in the first instance by the material, feed size and roll gap. Comparison based on equal energy input shows that single particle crushing is invariably significantly more efficient than ball milling. The rate of increase in the reduction ratio - an index of the size reduction achieved - per unit of energy input is 3 to 5 times more in single-particle comminution in the initial stages of grinding and subsequently up to 2 times more when the size spectra have become self-preserving. © 1990.