Further validation of DEM modeling of milling: effects of liner profile and mill speed

Grinding mills are usually lined with lifters to improve their efficiency. During the course of operation, the lifters are worn away. This will affect the energy efficiency and capacity of mills and the behavior of the load in the mill and finally leads to a relining to replace the worn lifters. However, the effects of the profiles of lifters are not taken into account in all the previous power models for rotary mills. Discrete element method (DEM) is capable of demonstrating the effects of lifter profiles on mill power and load behavior. In this paper, two types of lifter profiles, square and trapezoidal, are investigated in terms of mill power and load behavior with a 2D mill and a DEM simulator, Millsoft, over a wide range of rotational speed. DEM satisfactorily predicted the load behavior and power draw for different lifter profiles at sub-critical speeds comparing with the experimental results. It is found that the trapezoidal lifters draw more power than the square lifters. An attempt has been made to explain the difference between measured and simulated power using photographs of experimental load behavior.