Experimental study the impact forces of tumbling mills

Abstract

Impact forces are one of the mechanisms for grinding in mill. This takes place when the particles elevated by the lifters get into cascade motion and their fall on the load causes the breakage of other particles. The present paper aimed to study the impact forces in terms of variables like: mill speed, solid charge filling (ball filling), slurry concentration, and slurry filling. In this work, the influence of these operating parameters was investigated using a pilot mill. To this end, a copper ore was used to prepare slurry at different solid concentration. The tests covered a range of slurry filling from 0 to 2 with five different balls filling between 12% and 36% of mill volume and six different speeds between 60% and 85% of critical speed. The results delineate that the increase in the mill speed leads to a remarkable increase in the amount and frequency of the impact forces. Increasing the charge volume leads to decrease the maximum impact forces. The results show that with the increase in slurry filling and the resulting formation of a pool, the impact forces will decrease. Moreover, it is found that with the increase in slurry concentration, the slurry will act as a damper decreasing the impact forces.