Tenth International Mining Geology Conference 2017

Event: Tenth International Mining Geology Conference 2017

Date: 20-22 September 2017

Location: Hobart, Australia

Paper: Driving Productivity by Increasing Feed Quality as Well as Quantity through Application of Innovative Grade Engineering® Technologies



Driving Productivity by Increasing Feed Quality as Well as Quantity through Application of Innovative Grade Engineering® Technologies


Grade Engineering




Dr Stephen Walters







Abstract text:

The minerals industry is facing a productivity and investment crisis. The ‘Millennium Super Cycle’ from 2003-11 was an unprecedented period of growth and investment resulting in increased throughput and development of lower grade resources to meet demand. During the boom quantity became more important than quality with throughput the key metric. This was accompanied by a general trend of decreasing feed grades across all commodities which was offset with higher production volumes.

Current industry perception is that feed grade depletion is an unavoidable consequence of ore deposit geology and mass mining technologies for increasingly mature mining operations. In typical crush-grind-float operations, value recovery only takes place ~100 micron particle size at 3-4 orders of magnitude size reduction compared to primary feed. For increasingly low grade deposits the cost of energy and capital intensity required to process and reject worthless material at micron scale drives poor productivity. An alternative is to deploy a range of coarse rejection technologies. Grade Engineering® is an integrated approach to coarse rejection that matches a suite of separation technologies to ore specific characteristics and compares the net value of rejecting low value components in current feed streams to existing mine plans.

Coarse rejection can be used on size distributions ranging from ROM to SAG discharge. Grade Engineering® is based on five rock based ‘levers’ linked to combinations of screening, sensor-based sorting and heavy media separation. These involve exploitation of preferential grade deportment to specific size fractions during breakage: differential blasting to condition grade by size at bench scale; sensor based sorting at truck and conveyor scale; and differential particle density.

Grade Engineering is being developed and implemented by a consortium of over 30 mining companies, equipment suppliers and research organisations. Emerging results from collaborative site activities demonstrate potential for generating significant value which can reverse the trend of declining productivity due to feed grade depletion.




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