Carbon Thermal Reduction of Nickel Laterite Leaching Slag for Efficient Enrichment and Retrieval Efficiency of Iron

As a representative solid waste in the domain of the nickel laterite ore industry, the resource utilization of nickel laterite leaching slag is always a difficult problem for the metallurgical industry. In this paper, the method of non-molten roasting reduction magnetic separation with anthracite as the reducing agent was investigated to enrich and recover iron from nickel laterite ore leaching slag. The reduction mechanism of the process was analyzed by thermodynamic calculations and equilibrium simulations of the physical phase. The effects of roasting temperature, holding time, and anthracite dosage on the conversion rate of iron-bearing minerals were studied. The response surface has been used to analyze the interaction of influencing factors. The optimum reduction conditions were: roasting temperature of 1320 °C, duration of 60 min, and reductant dosage of 25 wt.%. The iron purity and retrieval efficiency in the concentrate were 76.08% and 95.19%, respectively. The physical phase composition, microstructure, and magnetization intensity of the reduction products were studied by XRD, SEM-EDS, and VSM. The reduction mechanism of reactants and the aggregation process of products were studied.