Mechanism of Directional Reduction Strengthening of Nickel Laterite Ore Under Fluidization Condition

The nickel laterite ore-fluidized reduction roasting technology is a clean and efficient metallurgical. To achieve the nickel enrichment effect, accomplish the controlled reduction of nickel and iron, and reduce nickel to the metallic state while controlling the metallization rate of iron, it is necessary to carry out experimental studies on the directional selective reduction of it. This study investigated the effects of temperature, additive amount, and reductant type on the selective reduction effect of nickel-iron oxides in nickel laterite ore with an iron grade of 24.30 pct and nickel grade of 1.45 pct. The physical phase, micro-morphology, and valence changes of nickel–iron elements of the reduced samples were also analyzed in depth by combining XRD, SEM-EDS, XPS, et al. The results showed that the best reduction effect of H₂ was achieved at the reduction temperature of 800 °C and the reduction time of 60 minutes, and the metallization rates of nickel and iron were 95.96 and 14.85 pct, respectively, under this condition. The selective reduction of nickel laterite by Na₂SO₄ was apparent. The appropriate amount of Na₂SO₄ has a more significant increase in the metallization rate of nickel in the mixed gas atmosphere, roasting at 800 °C for 60 minutes. When the addition of Na₂SO₄ is 6 pct, the metallization rate of nickel reaches a maximum of 92.05 pct; when the Na₂SO₄ increases from 0 to 8 pct, the nickel grade reaches a maximum of 3.65 pct, and the recovery of nickel reaches a maximum of 87.78 pct. The XRD results show that the addition of Na₂SO₄ destroys the olivine phase in nickel laterite ore, which allows the nickel stored therein to be released to participate in the reaction, thus increasing the rate of nickel metallization. This study provides theoretical support for the further application of fluidized roasting technology on nickel laterite ore smelting.