Milling circuit optimization study for Kroondal no. 1 platinum concentrator

Abstract

Multotec was engaged by MINOPEX to provide support aimed at improving the performance of the milling circuit at Kroondal no. 1 concentrator. A sampling campaign was carried out around the circuit with the objectives of minimizing scats generation, increasing product fineness to meet the envisaged grinds, and investigating the possibility of increasing throughput. The scope of work included determining the optimum lifter profile that would provide the necessary mode of breakage, the optimum top ball size required to break the top feed size, as well as the energy required to achieve the target grind for the current F80. The lifters installed and operating conditions were analysed to determine the impacts they might have on the performance of the mill. This led to optimization of the liner design to effect the improvements. Changes to the lifter profile aimed at achieving the required charge behaviour without adversely affecting liner life were recommended for the primary and secondary mills. No changes were recommended regarding the top ball sizes. There were limitations to what the primary mill could achieve because of the available mill power and operating conditions. The secondary mill was observed to draw more power than was necessary. This power was being lost without achieving the required milling. Recommendation was made to reduce power input for the secondary mill from 4410 kW to 3630 kW. This would not have an adverse effect on the grind. Other options to improve the grind included consideration of mill filling and percentage solids. These required further grinding laboratory tests for verification. The impact of the recommended changes is being evaluated and consultation is ongoing.