Effects of Na₂SO₄ on iron and nickel reduction in a high-iron and low-nickel laterite ore

This study investigates the reactions of Na₂SO₄ and its effects on iron and nickel reduction in the roasting of a high-iron and low-nickel laterite ore through gas composition, X-ray diffraction, and scanning electron microscope analyses. Results showed that a reduction reaction of Na₂SO₄ to SO₂ was performed with roasting up to 600℃. However, no clear influence on iron and nickel reductions appeared, because only a small amount of Na₂SO₄ reacted to produce SO₂. Na₂SO₄ reacted completely at 1000℃, mainly producing troilite and nepheline, which remarkably improves selective reduction of nickel. Furthermore, the production of low-melting-point minerals, including troilite and nepheline, accelerated nickel reduction and delayed iron reduction, which is attributed to the concurrent production of magnesium magnetite, whose structure is more stable than the structure of magnetite. Reduction reactions of Na₂SO₄ resulted in weakening of the reduction atmosphere, and the main product of Na₂SO₄ changed and delayed the reduction of iron. Eventually, iron metallization was effectively controlled during laterite ore reduction roasting, leading to iron mainly being found in wustite and high iron-containing olivine.