Fluidized Bed Selective Oxidation-Sulfation Roasting of Nickel Sulfide Concentrate: Part II. Sulfation Roasting

The fluidized bed sulfation roasting process followed by water leaching was investigated as an alternative process to treat nickel sulfide concentrate for nickel production. The effects of several roasting parameters, such as the sulfation gas flow rate, roasting temperature, the addition of Na₂SO₄, and the roasting time, were studied. 79 pct Ni, 91 pct Cu, and 95 pct Co could be recovered with minimal dissolution of Fe of 4 pct by water leaching after two-stage oxidation-sulfation roasting under optimized conditions. The sulfation roasting mechanism was investigated, showing that the outermost layer of sulfate melt and the porous iron oxide layer create a favorable sulfation environment with high partial pressure of SO₃. Sulfation of the sulfide core was accompanied by the conversion of the sulfide from Ni_1?x S to Ni₇S₆ as well as inward diffusion of the sulfation gas.