STUDY ON BALL MILL GRINDING OF A CASSITERITEPOLYMETALLIC SULFIDE ORE

摘要

To solve the problem frequently involved in grinding of cassiterite-polymetallic sulfide ores in Guangxi of China that either fine grinding causes cassiterite overground, or coarse grinding leads to not enough liberation of sulfide minerals, this article investigated the influences of ball grinding medium on the grinding product size distribution using a laboratory-scale mill. Two types of ball filling patterns, ie single-sized and multi-sized ball medium grinding, were adopted in the wet batch grinding tests. The grinding results on the effect of grinding time shows that increase in grinding time results in a rapid increase of minus 0.038 mm particles and a slight increase of the Sn grade in this fine size fraction due to the brittleness of cassiterrite mineral particles. The results of the single-sized medium grinding tests indicate that the effect of ball size on the grinding product size distribution is greatly dependent on the ball charge filling fraction of the mill volume. The smaller the ball filling fraction, the more obviously the ball size affects the grinding product size distribution. The variation of the grinding product size distribution with the ball size becomes complicated with the increase of the ball filling fraction. Moreover, larger ball filling fractions result in coarser grinding products. The obvious fluctuation phenomena in the plotting of the percentages of the discussed size fractions against the ball size are observed when the balling filling fraction is larger than 30 per cent. The results of the multi-sized medium grinding tests show that the grinding product size distribution is closely related to the mixed ball sizes and their composition percentages. In most cases, the increase of the smaller size ball in the mixture of two sizes balls causes the decrease of plus 0.154 mm coarse particles and -0.154+0.038 mm qualified size fraction, and the increase of minus 0.038 mm fine particles.