Roasting Pre-Treatment of High-Sulfur Bauxite for Sulfide Removal and Digestion Performance of Roasted Ore

Abstract

Alumina refineries in China continue to face challenges in achieving clean and efficient utilization of high-sulfur bauxite. Disulfide ions, \({\text{S}}_{2}^{{2 - }},\) in FeS₂ can be considered as active components in the Bayer process for alumina production, but they lead to corrosion of the equipment used in the processing of bauxite. Our research investigates the transformation rules of \({\text{S}}_{2}^{{2 - }}\) in bauxite during roasting, and the impact of digestion conditions on the digestion efficiency of the roasted ore and \({\text{S}}_{2}^{{2 - }}\) distribution. The results revealed that the onset temperature of kaolinite dehydration was approximately 700°C. The standard Gibbs free energy of all other reactions, including pyrite oxidation at 500–750°C, was negative. Dehydration began at 433.0°C, attained its maximum rate at 508.5°C, and ended at 593.0°C. Roasting pre-treatment removed approximately 95% of the sulfide, promoted digestion of alumina in bauxite, and reduced the active sulfur content by ~27%.