The board of directors of Australian nickel producer Western Areas Ltd. has approved an A$22 million mill recovery enhancement project for its Forrestania operations in southwest Western Australia. Completion of the project will increase nickel recoveries in the mill by 3% to 5% over the life of the mine and add 1,200 mt/y of nickel in concentrate to its production. Unit cash operating cost is estimated at A$2.42/lb of nickel in concentrate.
The mill enhancement project will employ Western Areas’ patented BioLeach technology. GR Engineering Services has been awarded the EPC contract. Western Areas has committed to purchase the long lead items and complete detailed engineering by year-end 2015. Given a short estimated construction time of six months, the company believed the project could begin commissioning and ramp-up as early as July 1.
The mill enhancement process was developed in-house by Western Areas for the specific purpose of treating Forrestania ore. It will process a tailings stream from one of the flotation plants that contains nickel that cannot be recovered into concentrate by traditional flotation methods. This stream will be leached at atmospheric pressure in fiberglass-reinforced PVC tanks to recover the additional contained nickel.
The BioLeach process has been developed to operate at a pH of 3-3.5, which enables the removal of iron and other gangue elements during the leaching stage to form stable compounds for safe disposal in the existing tailings storage facility.
A conventional thickener and filter are used for dewatering of the leach circuit. The solids are discarded to tailings, and the filtrate is passed to a sulphide-precipitation circuit. Sodium sulphide is used to recover the nickel from the solution, producing a nickel in concentrate product grading 50% to 60% nickel.
This high-grade concentrate is then combined with the processing plant’s normal nickel concentrate (14% to 14.5% nickel) to produce an overall slightly higher grade nickel concentrate. The time period to produce a nickel concentrate for blending into existing material is seven days.