Value addition of copper sulphide from nickel refining: Process modelling and simulation

The aim of the study was to develop a process option for the value addition of a leach residue from hydrometallurgical nickel refining. The residue in question is copper-rich (58 %) with sulphur (23 %), nickel (3 %) and iron (2 %) as the other main constituents. The prevailing phases are covellite and antlerite and the residue is already a marketable product as such. The current study suggests a flow sheet with moderate temperature autogenous pressure leach, selenium removal and copper electrowinning. Precious and platinum group metals will enrich the solid phase. Further solution purification is to be considered if London Metal Exchange grade copper is desired. The process was modelled in a steady-state and a proposal was made for integration into nickel refining. The bleed requirement from the developed copper circuit was 51 % of the spent electrolyte, which may be treated and utilised in the preceding nickel refining. In addition, sensitivity analysis was conducted to obtain data for adapting the copper circuit to suit nickel refining and navigate the way forward in the development project. The process simulation showed that the copper circuit, in the case of pressure leaching, would produce more than 300 kg of acid per tonne of feed, which would need to be bled out.