Mount Isa Mines turns a waste stream into a value-adding product

The Mount Isa Mines (MIM) Copper Concentrator Metallurgy team has designed an innovative process for recovering silica from its own ore sources from Black Rock Cave, to supply the site with a low-cost flux material to be used in the copper smelter.

The innovative process converts a previous waste stream to a value-adding product, making MIM a more sustainable operation and reducing the final tailings footprint.

The silica-rich stream is being recovered from tailings, by pumping the tailing to cyclones, to separate the fines from the course material, which is used for flux in the copper smelter. The tailings would otherwise be sent to the tailings storage facility.

Silica is important in the smelting process to create the fayalite slag which removes iron and other elements from the concentrates. Silica flux lowers the melting point and density of the slag.

Historically, MIM bought its silica and milled it in the concentrator which was a cost-intensive exercise given Mount Isa’s remote location.

However, consistently low flux quality drove the search for a new source of silica, and tailings from the Black Rock Cave ore held a suitable amount of silica for recovery.

Modifications to the silica circuit were made to utilise this stream. The silica circuit upgrade has resulted in the concentrator producing a high-quality product from what was previously a waste stream.

The MIM silica circuit is a synergistic approach to the production of a value adding stream from tailings.

Lucian Cloete, Superintendent – Metallurgy Copper Concentrator says the project’s successes include increased copper recovery, saving on equipment maintenance and consumables, and delivering a low-cost flux material.

“We’ve benefited from a 2% to 3% gain in metal recovery, while reducing the cost of reagents and power,” says Lucian.

“Another benefit is repurposing the flotation bank used for the silica, which is now used for additional pre-float capacity for MICO ore.”