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Reduction of Nickel and Iron from Low-Grade Nickel Laterite Ore via a Solid-State Deoxidization Method Using Methane

This work focuses on the solid-state deoxidization of low-grade nickel laterite ore under various conditions using methane. The effects of the reduction temperature, reduction time, and methane concentration on the metallization rates of nickel and iron were investigated. The nickel metallization rate increased as the temperature increased to 600°C; it then decreased as the temperature was further increased. The iron metallization rate increased gradually as the temperature increased. The nickel metallization rate sharply increased to over 90% when the CH4 concentration was increased to 20 vol%. The reduction time, which ranged from 30­90min, had a negligible effect on the reduction of nickel and iron. In the case of the reduced product, the nickel and iron metallization rates were 91.17% and 23.67%, respectively. The optimal conditions were determined to be a reduction temperature of 700°C, a reaction time of 60min, and a CH4 concentration of 20 vol%. The nickel oxide was almost completely reduced to metallic nickel, and the majority of the iron was reduced to low-valence iron oxide. During the reduction process, a magnesium olivine phase (Mg2SiO4) was produced by the recrystallization of amorphous silicate in the reduction process, and hindered the reduction of nickel and iron. [doi:10.2320/matertrans.M2017351]