Development of a tower mill model using hardgrove mill tests

The gravity-induced low speed stirred milling technology, commonly referred to as tower mills, are widely used for fine grinding due to their high energy efficiency compared to conventional tumbling mills. Moreover, the lower operating cost, shorter installation period and simpler operating strategy make it attractive for many mines. Researchers have attempted to develop an ore characterization method and mathematical models for tower mills. However, there is no well-established universal fine material characterization method for both the grindability assessment and modeling of tower mills. In this study, a modified Hardgrove mill fine material characterization method was developed for the tower mill grindability assessment. The test result was integrated into the fmat breakage model, which incorporates both the effect of specific energy and particle size. Several industrial tower mill grinding circuit surveys were conducted to provide the information regarding the operating conditions and grinding product size distribution. The ore breakage model, the size specific energy level model, internal classification model and tower mill power models were integrated into a mass-size balance model to simulate the tower mill performance. A sensitivity analysis was conducted to simulate the tower mill performance under varied stirrer speed and media charge. Results obtained from the model and simulation work show that the developed model is capable of predicting the tower mill grinding product size distribution with adequate accuracy. The sensitivity analysis indicated a new opportunity to control the tower mill performance by adjusting the stirrer speed rather than by the conventional media addition strategy.Applied Science, Faculty ofMining Engineering, Keevil Institute ofGraduat