Industrial Investigation of Milling and Leaching Process: An Attainable Region Approach

• Size reduction is an integral and expensive part of almost all mining processes especially for the downstream leaching process. Therefore, significant energy and cost savings exist even with slightest increase in milling efficiency to a certain degree of liberation. In this work, the attainable region (AR) is used to explore the effect of grinding media fill level, grinding media size and grinding time on the resulting size distribution. The resulting particle sizes are then leached to determine the optimal size for maximum gold recovery as a function of operation time (grinding and leaching), energy consumption and other operational variables. Preliminary leaching results show that the majority of gold is found in the smaller size classes (-150 microns) and the difference in grade between -150+75microns and -75+25microns is small, suggesting that a size of -150 microns is an adequate cut-off for milling, rather than the -75microns currently employed. Therefore an integrated grinding and milling process is investigated.