Pressure leaching of nickel-copper leach residue.

The leach residue at Bindura contains about 12% of the nickel, 65% of the copper and all the sulphur, as well as significant values of platinum group metals. An evaluation of several treatment options led to selection of a process based on a Sherritt non-oxidising pressure leach of the residue in sulphuric acid solution. This produces a copper sulphide concentrate with 70% Cu, 20% S, less than 1% Ni and 0.5% As, which is suitable for smelting and fire refining to anode copper. High-grade cathode copper will be produced by electrorefining and the precious metals will be recovered from the anode slimes. The flowsheet developed after development testwork includes dissolution of copper in an agitated tank, pressure leaching to remove Ni, As and Fe from the dissolution residue while maximising the Cu and S content of the product solids, and precipitation of Fe and As from the pressure-leach discharge solution.
The leach residue at Bindura contains about 12% of the nickel, 65% of the copper and all the sulphur, as well as significant values of platinum group metals. An evaluation of several treatment options led to selection of a process based on a Sherritt non-oxidising pressure leach of the residue in sulphuric acid solution. This produces a copper sulphide concentrate with 70% Cu, 20% S, less than 1% Ni and 0.5% As, which is suitable for smelting and fire refining to anode copper. High-grade cathode copper will be produced by electrorefining and the precious metals will be recovered from the anode slimes. The flowsheet developed after development testwork includes dissolution of copper in an agitated tank, pressure leaching to remove Ni, As and Fe from the dissolution residue while maximising the Cu and S content of the product solids, and precipitation of Fe and As from the pressure-leach discharge solution.