Effect of the friction coefficient in the discrete element method simulation on media motion in a wet bead mill

In order to provide information on different sample materials to be ground by a bead mill under wet conditions, we have investigated the effect of the friction coefficient in the discrete element method (DEM) simulation on bead motion in the mill. This is also a joint attempt of simulation and experimental works - the former employs the DEM to simulate the bead motion in the mill and the latter is based on the observation of the bead motion in the same mill by a video recorder. Two kinds of sample, gibbsite and limestone, were used for the milling and they were suspended in water at solid concentrations from 2.5 to 10.0 wt%. The bead velocity simulated at different friction coefficients in the DEM was compared with the experimental data and the coefficient classified into two: one is the coefficient between bead and bead, mu(i), and the other between bead and wall, mu(w). The proper mu(i) and mu(w) are 0.2 and 0.25 for gibbsite and 0.2 and 0.3 for limestone according to the joint work, irrespective of milling conditions.