COATING AND STACKING

The sized support rock is coated with flotation or gravity concentrate by contacting a thickened slurry with the stream of support rock as it discharges from the head of the stacking conveyor onto the pad. This approach obviates the need to convey support rock already coated with concentrate, simplifying operation and maintenance of the conveyors and stacker.

Support rock is withdrawn from a stockpile by a front-end loader or by vibrating feeders, and fed to the hopper of the first of a series of conveyors which feed the stacker. For a small heap, several grasshopper conveyors will suffice. A larger heap will require a fixed horizontal conveyor running parallel to the long dimension of the heap, with a tripper to feed one or more grasshoppers and the stacker. Concentrate slurry is pumped from an agitated stock tank to the head of the stacking conveyor, where it is contacted with the falling support rock.

The coating ratio (mass ratio of concentrate to support rock) is typically in the range of 1:5 to 1:10. Testwork is required to determine the optimum coating ratio. In a full-scale operation the coating ratio is maintained at the desired value by controlling the relative flow rates of the support rock and the concentrate slurry. A weightometer on the conveyor system measures the mass flow rate of support rock. A density gauge and flow meter are installed in the slurry delivery line, allowing the mass flow of concentrate solids to be measured. Simple ratio control allows the coating ratio to be maintained at the selected set-point.

GEOCOAT® heaps are typically stacked to a height of 6m. However, heat balance considerations, particularly in extreme climates, may dictate higher or lower heaps.

GeoBiotics, LLC has developed an innovative, proprietary biooxidation technology, GEOCOAT®, for the recovery of gold from refractory gold ores and concentrates, and base metals from sulfide ores and concentrates. The GEOCOAT® technology offers significant economic benefits compared to other processes for oxidizing sulfide ores and concentrates.

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