, Volume 15, Issue 1, pp 127-133

Oxidation of nickel sulfide

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The oxidation of nickel sulfide whose atomic fraction of sulfur,x s, is 0.40 to 0.44 was studied in a mixed O2-N2 gas stream at 923, 973, and 1023 K. The oxygen partial pressure was maintained at 2.0 x 104 Pa. In the oxidation of nickel sulfide ofx s = 0.40 and 0.41, a dense NiO layer was formed on the sulfide surface without the evolution of SO2 gas, because of the low sulfur activity. Diffusion of nickel within the inner sulfide core toward the surface controlled the oxidation rate during the first one minute of oxidation. Subsequently, the oxidation rate was controlled by the diffusion of nickel through the formed NiO layer. In the oxidation of nickel sulfide ofx s = 0.44 at 973 and 1023 K, the reaction proceeded irregularly to the interior of the sulfide core with the evolution of SO2 gas, and a porous oxide layer was formed, due to the high sulfur activity of nickel sulfide. For the same reason, this oxidation was also accompanied by the dissociation of nickel sulfide. Under the experimental conditions ofx s = 0.42, 1023 K and xs = 0.44,923 K, the oxidation started with weight increase and without the evolution of SO2 gas, and in the subsequent stage the weight decreased and SO2 gas was evolved.