Utilization of limonitic nickel laterite to produce ferronickel concentrate by the selective reduction-magnetic separation process

Abstract

Attempts to economically upgrade low nickel content laterite ore face a number of challenges, including limited ability to beneficiate the ore prior to processing due to its complex association and dissemination structure. Limonitic nickel laterite, characterized by its relatively high iron grade and low nickel content, is very difficult to upgrade. The current work explores improving the beneficiation of nickel from limonitic laterite ore through interaction of silica and calcium sulfate in a selective reduction-wet magnetic separation process. The results show that the ferronickel concentrate assaying 5.0% Ni can be obtained at a nickel recovery of 95.9%, when limonitic laterite ore is reduced at 1250 °C for 60 min with the addition of 3 wt% CaSO4, 8 wt% silica and 3 wt% graphite. The mechanism of additives in promoting the selective reduction of nickel laterite ore was also investigated by XRD, VSM, SEM-EDS and EPMA. The silicate reacted with iron oxide to form the liquid, which decreased the iron metallization ratio. S2 from the thermal decomposition of CaSO4 in a strong reducing atmosphere significantly promoted γ Fe–Ni particle growth by formation of an Fe-FeS eutectic with a low melting point.