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

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 flowrate, roasting temperature, the addition of Na2SO4, and the roasting time, were studied. 79% Ni, 91% Cu and 95% Co could be recovered with minimal dissolution of Fe of 4% by water leaching after two-stage oxidation-sulfation roasting under optimized conditions. The sulfation roasting mechanism was investigated, showing that the outermost layer of sulfates 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 Ni1-xS to Ni7S6 as well as inward diffusion of the sulfation gas.The authors wish to thank Xstrata Process Support (Sudbury, Ontario, Canada) for providing the concentrate and both Xstrata and Vale for sponsoring the project. We acknowledge the constructive comments received from Dr. Gus Van Weert of the ORETOME Ltd. The funding for this research was provided by the Natural Sciences and Engineering Research Council (NSERC) of Canada