Research on effects of rotating speed on grinding efficiency of ESKOM tumbling mill with consideration of lifter wear using DEM simulation

Abstract

Grinding efficiency of particles inside tumbling mill is determined by rotating speed of mill and affected by lifter wear. In this study, a verified DEM-based model with predictable function in lifter wear is introduced to simulate charge motion in an ESKOM tumbling mill of ϕ4267 mm with 60 curved lifters under different rotating speeds from 50% to 150% critical mill speed. Average collision energies among particles in charge motion of mill at filling rate of 24.2% are compared under different rotating speeds and different lifters’ life spans for finding out the best mill speed that achieves higher grinding efficiency. During each DEM simulation of charge motion, boundary geometries of mill lifters evolve with their wear caused by particle impacts. The results showed that ESKOM mill is most productive at mill speed of about 110% critical mill speed, and lifters wear is conducive to improving grinding efficiency as rotating speed is closing to 110% critical mill speed. Moreover, when mill speed is smaller than 110% critical mill speed, lifter wear reduces grinding efficiency of mill; while grinding efficiency increases with increasing wear of lifters, as mill speed exceeds 110% critical mill speed.