A study shows producers a possible pathway to sizable energy-use reduction by employing high pressure grinding roll (HPGR) technology — in combination with other commonly available equipment — to replace conventional wet ball-mill circuits.

Corem, a Canadian non-profit that offers mining corporations a range of specialized research services that help them develop and optimize key mineral processing technologies, recently announced it has found a way to replace wet ball milling circuits with other proven, available equipment that can reduce energy consumption by more than half. The Québec-based company, supported by a Natural Resources Canada investment, said it partnered with the University of British Columbia, two mining companies, six equipment manufacturers and numerous grinding experts to develop and demonstrate a method for replacement of wet ball milling with high-pressure grinding rolls ahead of mineral separation. 

Data and samples needed for pilot plant testing were collected from two milling operations: a small gold operation and a large-tonnage copper producer. Pilot circuits using high-pressure grinding rolls, in closed circuit with sizing screens, were run in batch-locked cycle mode to steady-state conditions. Moisture content to the grinding rolls was controlled to a level achievable with high-capacity filtering by solids and water blending. 

Some of the major findings from the study:

• HPGR energy consumption (kWh/t) was 38% compared with that of the ball mills or 62% lower.

• HPGR total circuit energy usage was still less than 50% of the ball mill circuits even with different auxiliary equipment.

• Fines removal from HPGR feed increased grinding efficiency in the compression zone by 25%-30%.

• There was no excessive fines production with HPGR. Micro-cracking was greater, and downstream processing was similar or better.

With the higher cost of the HPGR circuit equipment, preliminary economics were shown to be most favorable where energy costs are highest. Corem said this study, however, demonstrated the technical feasibility of the novel flow sheet to simply replace an existing circuit.