Influence of aggregate stemming in blasting on the SAG mill performance

The practice of using aggregate stemming in production blasting has typically been justified in terms of the improvements in fines generation, consistent with the benefits of confining more explosive energy in the rock during blasting. However, at the Red Dog mine in Alaska, ongoing Mine-to-Mill efforts have identified a further benefit from stemming that had previously not been quantified, specifically the marked reduction in SAG feed size and throughput variability. These reductions represent a substantial benefit in terms of flotation circuit stability, which have allowed the Mill Operations to better optimize the grade and recovery. A secondary but important benefit to come out of the change in stemming practice has been the reduced wear in the gyratory crusher, resulting in a significantly longer period between relines. This paper compares the key mill performance indicators when the mine moved from drill cuttings to aggregate as stemming in the blast holes.