Pilot-scale plant study on non-molten metalized reduction–magnetic separation for magnesium-rich nickel oxide ores to produce ferronickel concentrate

In this study, semi-pilot and pilot scale tests were carried out to treat magnesium-rich low-nickel oxide ore, based on experimental results of non-molten state metalized reduction of nickel oxide ores followed by magnetic separation to produce ferronickel concentrate, which was developed by our research team in the previous study. The semi-pilot tests were conducted in a rotary kiln of 0.45 m inner diameter and 7.5 m length, and the pilot ones were conducted in another rotary kiln of 3.2 m inner diameter and 72 m length. The process mainly consists of four steps: feed preparation, solid-state metalized reduction, quenching and ball milling, and magnetic separation. During 50 days of continuous semi-pilot tests, approximate 20 tons nickel oxide ores were consumed. the overall recoveries of nickel and iron reached 91.3% and 73.8%, while the nickel and iron grades of the ferronickel concentrate were 7.4% and 69.6%. And meanwhile, the nickel loss to residue was only 0.16%. In the 15 days of continuous pilot tests, approximate 8000 tons ores were consumed, whose results were similar to those of the above semi-pilot tests. The results further verified the stability and feasibility of industrial application. Preliminary calculation suggested that the electricity consumption was only approximate 300 kW·h when one ton ferronickel concentrate was produced, i.e. 52.5 kW·h/t-ore. In all, magnesium-rich nickel oxide ore can be fully metalized reduced at a non-molten temperature using the proposed technology in order to beneficiate nickel and iron.