Addition of pebbles to a ball-mill to improve grinding efficiency

The theory of pebble wear was developed during this investigation, for application to batch grinding tests. The size distribution of the pebbles was measured after each test and the theory was used to calculate the pebble wear rate (mm h−1) and the specific wear rate (kg h−1 kg−1) for all screen fractions. The wear rate of pebbles in the presence of balls was higher than that for pebbles alone. When the proportion of pebbles in the mill charge was low (up to 30%), the larger pebbles wore away significantly faster than expected, based on a constant surface wear rate. This could be due to size segregation in the mill.