Inco roast-reduction smelting of nickel concentrate

Roast-reduction smelting (RRS) of nickel concentrate, in conjunction with flash smelting of copper concentrate, was evaluated by Inco as a strategy to achieve its sulphur dioxide abatement goals at the Copper Cliff operations in 1994. The RRS process entails deep roasting of nickel concentrate within fluid bed roasters. Subsequent to roasting, the off-gas is processed in a sulphuric acid plant, while the low-sulphur calcine undergoes reduction smelting utilizing coke in an electric furnace, yielding a sulphur-deficient matte. This matte is further processed into Bessemer matte via Peirce-Smith converters, minimizing sulphur dioxide emissions, with the converter slag redirected to the electric furnace. The results indicated excellent recoveries of nickel and cobalt, showcasing the effectiveness of the RRS technique. This paper elucidates the development trajectory of the RRS process, incorporating findings from extensive commercial scale tests conducted at Inco's Thompson Smelter and detailing the pivotal operating parameters that influence the process.