Exploring ball size distribution in coal grinding mills - ResearchGateDec 19, 2017 . Tube mills use steel balls as grinding media. Due to wear in the abrasive environment it is necessary to charge new balls periodically to maintain a steady balanced ball charge in the mill. The amount and ball size distribution in this charge, as well as the frequency with which new balls are added to the mill,.ball charge for coal slurry ball mill,ball charge for coal slurry ball mill,Effect of Milling Environment on the Breakage Rates in Dry and Wet .In general, wet ball milling gives higher mill capacities than dry grinding, providing the slurry density is not so high that the mill charge becomes highly viscous. It is well-known that wet-batch milling exhibits time-dependent breakage rates. In the least, differential settling of particles in the slurry causes preferential breakage.