Study of Binary, Ternary, and Quaternary Basicity in Reduction of Saprolitic Nickel Ore

In the selective reduction process of lateritic nickel ore, the formation of the liquidus phase could be obtained by increasing the temperature and additive, resulting in an uneconomic process. Nevertheless, it could also be obtained by modifying the ore basicity by adding low-cost fluxes, such as CaO, SiO₂, MgO, and Al₂O₃. In this work, the effect of three types of basicity (binary, ternary, and quaternary) in selective reduction of saprolitic nickel ore on metallic grade and recovery, phase transformation, and microstructure of ferronickel was investigated clearly. The nickel ore, sodium sulfate, coal, and flux mixture was reduced to 1150 °C for 60 min. Then, the wet magnetic separation process was continued to separate ferronickel from impurities. The result showed that the optimum basicity for the selective reduction of saprolitic nickel ore was 0.6 of ternary basicity (CaO + MgO/SiO₂), modified by CaO addition. It produced 16.11% and 50.57% for nickel grade and recovery in concentrate, respectively. Modified basicity with CaO addition is more effective than MgO, Al₂O₃, and SiO₂ addition due to its ability to break the forsterite structure and release iron and nickel. It also could be reacted with magnesium silicate structure to form calcium–magnesium silicate structure such as melilite and monticellite.