Heap Reclaim and Concentrate Separation

Rinsing the biooxidized heap with fresh water is an integral part of the GEOCOAT^® process. In the treatment of refractory gold sulfide concentrates, rinsing reduces downstream cyanide consumption by removing soluble species from the oxidized concentrate before it is separated from the support rock.

When a heap section has been biooxidized to the target level, solution application is stopped and the panel is allowed to drain. The panel is then rinsed with fresh water.

A front-end loader or hydraulic shovel transfers the oxidized material from the heap to the feed hopper of a grasshopper conveyor, which feeds a horizontal conveyor running alongside the pad. The loader operates on the drainage layer, which protects the liner and solution collection and air distribution piping from damage. The conveyor delivers the material to the feed hopper of the washing screen or trommel. Large operations may justify the use of bucket wheel reclaimers and mobile conveyors.

Oxidized concentrate is separated from the support rock on a horizontal vibrating screen or in a trommel. The tumbling action of the screen or trommel loosens the oxidized coating for removal from the support rock by water sprays. The washed support rock is conveyed to the stockpile and from there it is recoated with fresh concentrate and restacked.

The underflow from the trommel or screen is pumped to the oxidized concentrate thickener. Thickener underflow is sent for processing in a precious metals recovery circuit (e.g., CIL) after pH adjustment, or in the case of base metal biooxidation without significant precious metal content, to a tailings impoundment.

The thickener overflow contains high concentrations of adapted bacteria and is recycled to the on-solution pond for reapplication to the heap.