The discrete element method for the simulation of ball mills

The discrete element method (DEM) is a proven numerical technique for modelling the multibody collision behavior of particulate systems. This method is used here to study the motion of ball charge in tumbling mills. To get meaningful results, it is essential that the parameters involved in the model be carefully determined. These parameters embody essentially the material properties of the system: stiffness, damping, and friction. In this study, all the parameters are carefully determined experimentally for different operating mill conditions. A computer code based on DEM has been developed to model the motion of the balls in tumbling mills. The code incorporates a scheme to calculate the applied torque, and hence power input to the mill. A 55-cm ball mill is simulated for two different liner cross-sections— rectangular and triangular. Results of the simulations pertaining to applied torque are compared with the experiments. It is found that, with a particular model for the coefficient of friction, the predicted torque agrees well with the experiments.