Upgrading low nickel content laterite ores using selective reduction followed by magnetic separation

The processing of nickel laterite ore to produce ferronickel is energy intensive, especially when low nickel content ores are processed. The selective reduction–beneficiation of laterite ore to produce high nickel content nickeliferous concentrate and abandon gangue minerals before smelting potentially offers an effective pre-treatment to this process. In this work, the authors conducted selective reduction of nickel laterite ores at 1100 °C for 60 min with addition of 6% calcium sulfate and 5% reductant coal. The reduced ore was then wet magnetic separated. The experiments show that high nickel content nickeliferous concentrate containing 6.0% Ni with nickel recovery of 92.1% could be produced with over 75% of the reduced ore, containing low nickel concentration, rejected. The tests indicated that the selectivity of reduction depends mainly on reduction atmosphere and silica level. According to the microscopic study, nickel oxide had been reduced and nickel was mainly enriched into a γ Fe–Ni phase. The presence of sulfur significantly promoted γ Fe–Ni particle growth, from 5.8 μm to 16.1 μm, and improved the Ni enrichment in metallic phases.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Selective reduction and magnetic separation was conducted on low grade nickel laterite ore. ► High grade nickeliferous concentrate could be produced from these laterite ores. ► The addition of calcium sulphate promoted nickel concentration. ► Nickel was mainly concentrated into a γ Fe–Ni phase in the reduced ore. ► Calcium sulphate improved the growth of γ Fe–Ni phase.