The process

A five-stage process takes place at FWGR to reclaim, retreat and deposit tailings.

TAILINGS RECLAMATION

Process water is pressurised through a four-stage pumping system and pumped through a 450mm diameter pipeline to monitoring guns at the Driefontein 5 reclamation site to form slurry. Repulped slurry then flows across a scalping screen into a sump where three slurry pumps pump the tailings into reception tanks at DP2.

SLURRY CLASSIFICATION

Classification of the slurry to determine whether it goes to the mills or the thickeners takes place through a three-stage cyclone system. The slurry reception tanks’ contents are firstly pumped into two cyclones and underflow from these flows to a secondary sump and the overflow transfers to a tertiary sump.

CYCLONE PROCESSING

The slurry in the tertiary sump is then pumped to two tertiary cyclones and additional underflow is transferred to the secondary sump. Slurry in the secondary sump is pumped to a secondary cyclone, and the underflow from the secondary cyclones reports to the mill. After milling, the slurry is pumped to the carbon in leach (CIL) circuit.

CIL CIRCUIT PROCESSING

The CIL circuit consists of seven leach tanks each with a capacity of 1 600m3. Cyanide is added in either the first or second tank and oxygen is injected into the first four tanks. During this process, gold metal is absorbed on to activated carbon. The gold-loaded carbon is removed at a rate of 9t per day and bagged. The bags are then transported to Sibanye-Stillwater’s Driefontein 1 plant for elution, electrowinning and smelting.

TAILINGS DEPOSITION

Tailings from the CIL circuit are pumped to a residue tank and then to the Driefontein 4 TSF. Driefontein 4 TSF has been converted to a cyclone dam consisting of six banks with 140 by 250mm cyclones. Water is drawn off the dam through a newly installed floating penstock and is then reused for reclamation activities.