Spreadsheet-based modeling of liner wear impact on charge motion in tumbling mills

Abstract

Grinding remains the major constituent of the total cost of processing minerals in most applications. Charge motion is one of the key parameters affecting grinding efficiency and mill power draw. Although there have been numerous investigations on the effect of liner design on charge motion, the effect of charge profile due to liner wear during mill operation along the mill length has not received much attention. In this research, Powell’s analytical approach to calculate the charge trajectory with respect to the liner profile was used to develop a software based on Microsoft Excel© . As a case study, the liner wear profile of the Sarcheshmeh copper complex SAG mill was used to model the liner wear rate and calculate the changes of lifter face angle and lifter height during mill operation. Results were then used to determine charge motion in the SAG mill at any given operation time. The results indicated that after 4000 h of operation the lifters face angle increased from 14° to 47.1° and the height of lifters decreased from 15.2 to 5.8 cm. Modeling charge motion in the mill after 3000 h of operation showed 34° difference between the maximum and minimum of angles of impact along the mill length due to the nonuniform wear profile. It was also found that the variation in the pattern of the charge motion depends on the mill working hours and the distance of the desired point from the feed end. It was determined that the ratio of spacing to the height of lifters (S/H) plays an important role in the grinding efficiency and throughput. After 4000 h of operation, S/H ratio of the Sarcheshmeh SAG mill increased from 1.7 to 4.6.