Continuous grinding in a small wet ball mill. Part III. A study of distribution of residence time

Abstract

The effect of changes in several grinding variables on the flow characteristics of liquid and solids through a small continuous wet ball mill has been studied. The distribution of residence time has been determined as a function of feed rate for both liquid and solids, and as a function of initial size, ball diameter, hold-up weight, mill length, feed pulp density, ball load, and mill r.p.m. for quartz tracers. The flow characteristics of unbreakable particles and of a range of different minerals have also been determined. The results show that the general form of the distribution of residence time function was not significantly altered by changes in the grinding variables studied but that large changes in the mean residence time could occur due to induced changes in hold-up weight. Simulation studies of the consequences of incorrect representation of the flow characteristics in mathematical models of continuous grinding have shown that predicted product size distributions may be in error, particularly for large changes in feed rate.