Mechanism of sodium sulfate in promoting selective reduction of nickel laterite ore during reduction roasting process

A high nickel grade ferronickel was produced from laterite ore using the selective reduction-wet magnetic separation process, with the addition of sodium sulfate (Na2SO4). The ferronickel concentrate assaying 9.87% Ni, with a nickel recovery of 90.90% can be obtained, when laterite ore was reduced at 1200 °C for 50 min with the addition of 10 wt.% Na2SO4 and 2 wt.% coal. Based on the results of the X-ray Diffraction, Scanning Electron Microscopy, and Energy Dispersive X-ray Spectroscopy analyses, the thermal decomposition and reduction reaction of Na2SO4 were carried out. Sodium oxide from the thermal decomposition of Na2SO4 reacted with silicate minerals to form nepheline. The formation of the molten phase accelerated the migration rate of the metallic particles and suppressed the reduction of the ferrous minerals in the weak reduction atmosphere. Sulfur reacted with metallic iron to form troilite, thereby facilitating the aggregation of ferronickel particles to form bigger particles.