SIMULATION OF CHARGE MOTION IN BALL MILLS .2. NUMERICAL SIMULATIONS

The formulation and verification of the discrete element model for the ball charge motion in a ball mill are described in Part I. Here, the model is used to simulate the charge motion in an industrial size mill . Many unobservable facts about charge motion are revealed by this sim ulation approach: It is shown that larger balls segregate to the cente r at high speeds and to the shell at lower speeds. The frequency of co llisions in a 4.75 m diameter mill mostly lie within one joule. The fr iction between the ball charge and the mill shell can increase the pow er draft. The center of the ball mass shifts in distance as much as 4% of the mill diameter during a complete rotation. Finally, the distrib ution of collision energy and the spatial locations of high- and low-e nergy collisions are shown. While many of the simulated results may ne ver be verified experimentally, these results are closer to actual val ues since the simulation is based on sound principles of physics. Abov e all, the simulation provides collision frequency information which i s the key to mill design and optimization.