Mechanism of carbothermic reduction of a sulfur-containing nickeliferous limonitic laterite ore

Abstract

An increasing amount of nickel is currently being extracted from the nickeliferous laterite ores, rather than from the sulfide deposits. Consequently, new processes are being developed to extract the nickel from these ores and selective reduction is one possibility. In these processes, it has been shown that the addition of sulfur can improve the grade and/or the recovery. In the current work, the mechanism of the carbothermic reduction of a sulfur-containing nickeliferous limonitic laterite ore was investigated by utilising TGA/DTA and both thermodynamic and kinetic analyses. It was found that, in addition to dehydroxylation and reduction, the reaction sequence also consisted of the following major stages: (1) conversion of pyrite to pyrrohtite and (2) subsequent desulfurisation. Analyses of the reacted samples showed that both the particle size and the amount of ferronickel increased with both particle growth temperature and retention time at temperature. The thermodynamic predictions were in general agreement with the experimental findings and were consistent with the postulated formation of an iron-sulfur-oxygen solution.