Coating and Stacking
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.
The support rock is closely sized, typically to -15
+5mm. Concentrate slurry is pumped from an agitated
stock tank to the head of the stacking conveyor.
The coating is applied to the support by contacting
the thickened concentrate slurry with the support
rock by spraying or by mixing in a
coating box.
The heap is loaded and reclaimed using the "moving slot" method. When a panel has been stacked, it is placed under irrigation and stacking continues on the adjacent panel. At the same time, material is reclaimed from the "oldest" panel of the heap, where biooxidation is complete. Between the panel being stacked and the panel being reclaimed, the working slot panel surface is prepared by recovering compacted areas and spreading the barren support band.
This results in the formation of a thin (less than one millimeter thick), relatively uniform coating on the support rock surface. The concentrate coating is quite stable and will not wash off the rock except for the first several layers of rock exposed to direct irrigation. The concentrate will not wash out of the heap, even in periods of heavy or prolonged rainfall.