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Grinding Circuit Improvements at Edna May

Adrian Dance
Wednesday, October 15, 2014
First presented: 
October 15, 2014

Resurrected from its former life at the Big Bell operation, the grinding circuit at Evolution Mining's Edna May operation in Western Australia has many a story to tell. The task of optimising a plant designed for another orebody provides as many challenges as opportunities. Initially faced with a blend of primary and oxide ore, the circuit achieved in excess of 320 t/h until the oxide was depleted, leaving only the much harder primary feed.

The 2.0 MW semi-autogenous grinding (SAG) mill and 3.7 MW ball mill were assisted by a 150 kW pebble crusher, but the power limitation of the SAG mill resulted in a drop in throughput. Edna May personnel have been involved in a number of progressive improvements to restore the design capacity of the concentrator and work towards 3 Mt/a or even higher ahead of the gravity and leach recovery circuits.

These improvements include:

• a crush forward configuration of the SAG mill scats

• partial to full secondary crushing

• variable speed drive upgrade of the SAG mill

• lifter and grate design changes

• ball mill circuit grinding efficiency.

This paper summarises the chronology of events that has resulted in significant improvements in throughput by conventional (and in some cases, novel) methods of reconfiguring the existing grinding mills. Lessons learned and hindsight perspectives will be summarised, sharing this educational experience with other operations in a similar situation.

Feature Author

Adrian Dance
With over 25 years in his field, Adrian has both industrial and consulting experience, working at operations in Australia, Canada and Peru. Recently, Adrian has established himself as an authority in comminution circuit operation and practices a proven methodology in gaining improvements from “Mine-to-Mill” optimisation projects. Adrian has spent most of his career working with existing operations to gain added efficiency. With SRK, he is now providing similar expertise to green or brownfield sites to get similar benefits very early in the mine life, in particular, the development of mill forecasting models embedded in the resource/geological block model, or geometallurgical modelling.
Plant Optimization Specialist
PhD in Mineral Processing
SRK Vancouver
SRK Africa