Analysis of power draw in ball mills by the discrete element method

Ball mills, like other comminution devices, consume large amounts of energy . Mill operators often have to assess the power draft of mills for an entir ely different set of operating conditions or for a reconfigured circuit. It is shown that the power draft can be accurately predicted from analysis of the motion of the charge. The motion of the charge is rigorously simulated with a numerical technique known as Discrete Element Method (DEM). In this technique, the coordinates and velocities of each individual ball are comp uted From a knowledge of forces arising when balls collide with each other and with mill shell and lifter walls. First, simulation results on a wide r ange of ball mills are compared with available experimental data. Then the power draft predictions as a function of a few operating variables are show n. The unique feature of this method is that the mill power can be predicte d for a mixture of ball sizes, different lifter geometry and lifter spacing , which is absent in other methods proposed in the literature. (C) 1999 Can adian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd . All rights reserved.