Pilot-scale plant study on solid-state metalized reduction-magnetic separation for magnesium-rich nickel oxide ores

An innovative technology named solid-state metalized reduction-magnetic separation (SSMRMS) was developed to produce ferronickel concentrates from magnesium-rich nickel oxide ores. A pilot-scale plant with a daily processing capacity of 500 kg of dry ores was assembled and tested. SSMRMS involves four steps: feed preparation, solid-state metalized reduction, quenching and ball milling, and magnetic separation. After 40 days of continuous tests, the operational stability of the proposed technology was good, and accretion did not form in a rotary kiln. Results revealed that (i) an appropriate positive pressure in the kiln terminal was beneficial to metallization; (ii) the overall recoveries of nickel and iron could reach 91.3% and 73.8%, respectively, whereas the nickel and iron grades of the produced ferronickel concentrate could be 7.4% and 69.6%, respectively; (iii) residual nickel to tailings was 0.16%; and (iv) the return ratio of dusts was approximately 8%. Notably, nickel could be released and sufficiently metalized at an appropriate temperature once the structures of the Ni-bearing silicates were destroyed in the presence of fluorite. The metalized nickel aggregated with the metalized iron surrounding the margins of the minerals. Therefore, fluorite could promote the generation and growth of ferronickel alloy particles, thereby increasing the recoveries of nickel and iron. Preliminary calculation showed that the electricity consumption of the solid-state metalized process was 52.5 kWh/t-ore. Hence, SSMRMS is a competitive strategy for the processing of magnesium-rich nickel oxide ores.