Modeling and application of stirred mill for the coarse grinding of PGE bearing chromite ore

Platinum group of elements (PGE) mineral is a valuable resource for platinum and other elements. Grinding experiments were conducted in a laboratory-scale stirred mill on a low-grade PGE bearing chromite ore. High-Pressure Grinding Rolls (HPGR) product of -1 mm was used as feed material to the stirred mill experiments. A four-factor (stirrer speed, grinding time, pulp density, and media filling) and a five-level Central Composite Design matrix (CCD) was applied to investigate the stirred mill performance in coarse grinding. The stirred mill grinding efficiency was evaluated based on the particle size distribution and energy consumption. The experimental results showed that the stirrer speed, grinding time, and media filling significantly affect the product size and energy consumption. Pulp density had little influence on the process responses. 3D response surface plots were also discussed in detail to better understand the process variables. A finer size product of 274.7 mu m (reduction ratio of 2.63) was achieved at optimal conditions of the stirred mill with an expense of 26.01 kWh/t energy. The results stated that good performance was obtained with the coarser feed size in the stirred mill.