Effect of modified basicity in selective reduction process of limonitic nickel ore

Basicity is an important parameter in the smelting of nickel laterite to obtain low-temperature melting point and low-liquidus slag viscosity, resulting in less energy consumption and a more effective smelting process ferronickel production. Nevertheless, it is still less studied in selective reduction of nickel laterite. In this work, the effect of binary, ternary, and quaternary basicity limonitic nickel ore had been investigated clearly to reveal the appropriate basicity in the selective reduction process. The basicity was modified with the addition of CaO, MgO, SiO₂, and Al₂O₃ in nickel laterite. The reduction process was conducted in a muffle furnace at 1150 °C for 60 min. It was continued with the magnetic separation process to separate concentrate and tailing. The appropriate basicity type in selective reduction of limonitic ore was 0.3 of ternary basicity (B_T1) and 0.2 of quaternary basicity (B_Q1), which had a similar nickel grade and recovery, i.e., 6.08% and 88.33%, respectively. At low basicity, the addition of CaO and SiO₂ could suppress the metallization of iron through troilite and fayalite formation, respectively. Nevertheless, more CaO addition at high basicity could inhibit the ferronickel agglomeration due to the formation of high melting point structures, i.e., melilite. Modifying basicity with the addition of MgO and Al₂O₃ resulted in a negative effect in selective reduction due to the formation of a complex structure of forsterite and magnesioferrite (with an aluminum substitute), which was more difficult to reduce than magnetite.