Increasing the efficiency of grinding operation through liner design change by discrete element method (DEM) - Case sudies: Gol-E-Gohar iron ore and Sarcheshmeh copper complex SAG mills

At the Gol-E-Gohar iron ore concentration plant and the Sarcheshmeh copper complex SAG mills with the diameter of 9 and 10 m and length of 2 and 4.9 m, respectively, are used to reduce the size of the ore. Monitoring of the operation in these two plants indicated that the tonnage of the Gol-E-Gohar mill was lower than the nominal value with large variations and the Sarcheshmeh mill experienced liner breakages which in turn increased the non-scheduled shutdowns. To simulate the charge trajectory KMPCDEM software which has been developed based on discrete element method (DEM) was used. The results of simulations using two different liner designs were verified with a 1-m diameter and 22-cm length model mill. The comparison indicated that at the worst case the difference between the shoulder and toe positions of the simulated and measured charges was found to be less than 4 degrees which was not significant. The simulations showed that cataracting particles do not impact toe rather they hit shell liners. In order to solve this problem, various liner designs at the plant operating conditions were simulated with the objective of reaching a state where the falling charge impact the toe region. To arrive at such a condition, for the Gol-E-Gohar SAG mill the release angle was increased from 7 to 30 degrees and for the Sarcheshmeh case the number of lifters was decreased from 60 to 40 and the release angle increased from 15 to 30 degrees. The proposed liner designs were constructed and installed in the industrial SAG mills. At Gole-E-Gohar, the feed rate increased by 17% and its variation reduced by 31% which indicated more stable operation. At Sarcheshmeh, on average the number of broken liners decreased from 4.2 to 1 and the variation of feed rate decreased by 30%.