Experimental study of charge dynamics in a laboratory-scale ball mill

Abstract

To understand and describe the behavior of charge dynamics in mills, a series of dry and wet grinding tests were performed on a laboratory-scale ball mill. The comparisons between experimental results and grinding media trajectory simulations were addressed. Results show that the grinding media trajectory simulations exhibit a good agreement with the experimental results. The shoulder angle was proportional to mill speed and ball filling. The toe angle was inversely proportional to ball filling, but the impact point angle was appeared to invariant to ball filling and inversely proportional to mill speed. By means of motion analysis of the charge, a good grinding efficiency can be obtained when the ball filling ranging from 20% to 40% and the mill speed ranging from 70% to 80%. For dry tests, the orthogonal analysis indicates that the influence order of four factors on power-mass ratio is ball filling, mill speed, powder-grinding media ratio and lifter profile and the influence order of four factors on −0.074 mm yield is mill speed, ball filling, powder-grinding media ratio and lifter profile. The best dry tests are a combination of 70% of critical speed, 20% of ball filling, 0.8 of powder-grinding media ratio and waveform lifter. Correspondingly, the power-mass ratio can increase by 28.27% and the production of −0.074 mm can increase by 50.38%. For wet tests, the variations of −0.074 mm yield on mill speed and moisture content increase up to a maximum and then decrease rapidly. The −0.074 mm yield can reach a maximum at the 80% of mill speed and 50% of moisture content.