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 simulation approach: It is shown that larger balls segregate to the center at high speeds and to the shell at lower speeds. The frequency of collisions in a 4.75 m diameter mill mostly lie within one joule. The friction between the ball charge and the mill shell can increase the power draft. The center of the ball mass shifts in distance as much as 4% of the mill diameter during a complete rotation. Finally, the distribution of collision energy and the spatial locations of high- and low-energy collisions are shown. While many of the simulated results may never be verified experimentally, these results are closer to actual values since the simulation is based on sound principles of physics. Above all, the simulation provides collision frequency information which is the key to mill design and optimization.