The effects of lifter configurations and mill speeds on the mill power draw and performance

Abstract

Grinding mills used in the mining industries are the most energy-intensive operation and require a large number of wear resistant materials as well. The 1-m mill was used to investigate the effects of three lifter configurations, namely Hi (High), Rail and Hi-Lo (High-Low), and mill speeds on the mill performance. The MillTraj software was also utilized to simulate the outermost charge trajectories of the mill. At the given operating conditions, the power draw of Hi lifter was slightly lower than that of the Rail and the Hi-Lo and thus, the Hi lifter showed improvement in the mill efficiency. The product size distributions of the different lifters are very close and the size distribution of Hi-Lo lifter is slightly finer than those of the other lifters. At 74% critical speed, the size distributions of the Rail and Hi-Lo lifters were finer than at 70% critical speed, while that of Hi lifter otherwise occurs. At 80% critical speed, the size distributions of the lifters were coarser than at 74% critical speed. In this case, the outer charge trajectories of each lifter could go down on the mill shell rather than on the toe of the mill charge, resulting in ineffective grinding. Increasing face angles and/or mill charge would allow the mill to be operated at higher speeds.