Effects of Reducing Parameters on the Size of Ferronickel Particles in the Reduced Laterite Nickel Ores

Crude ferronickel alloy can be produced by the carbothermal reduction of laterite ore-coal composite. The size of ferronickel particles in semi-molten state is crucial for the subsequent magnetic separation between the ferronickel and slag. Aimed to better understand the effects of reducing parameters on the size of ferronickel particles in the reduced laterite nickel ores, a series of carbothermal reduction experiments of laterite ore-coal composite in tall pellets bed was carried out. The experimental results indicated that, higher reducing temperature, longer reducing time and more CaO additive were beneficial for the aggregation and growth of ferronickel particles. Temperature (1400 °C) is the most important parameter. Less CaO additive needs longer reducing time, more CaO additive needs shorter reducing time. Excessive CaO amount (CaO = 10 pct) may prevent ferronickel particles from aggregation and growth due to its rapid melting. The importance ranking of these parameters should be temperature > time > CaO additive. The optimum reduction parameters were “1400 °C, 45 minutes, CaO = 0 pct” and “1400 °C, 30 minutes, CaO = 5 pct”. Under these conditions, all the ferronickel particles in 4 layers were clear and bigger. The percentages of + 50 μm of particles were about 65 and 59 pct respectively, and the recovery rates of Ni were about 88 and 85 pct. The findings from this work may provide guidelines for the improvement of ferronickel alloy production by laterite nickel ores.