The Desulfurization and Digestion Property of High-Sulfur Bauxite with Coarse-Grained Particles by Roasting: Desulfurization Ratio and Digestion Kinetics

A three-stage method (grinding, roasting and digestion) was adopted to study the effect of particle size on the desulfurization rate and digestion performance of high-sulfur bauxite in the process of producing alumina. The results demonstrated that the desulfurization efficiency of coarse-grained bauxite was significant by roasting, the sulfur content of raw ores with 380 μm size reduced to 0.42% from 1.5%. The results of the SEM and a laser particle size analyzer indicated that a number of cracks, pores and layered structures were found on surface of coarse-grained bauxite and the particle size obviously reduced. The digestion experiment showed that the Al2O3 digestion ratio of coarse-grained roasted ores (> 250 μm) was higher than fine-grained ones, the optimal digestion ratio of roasted ore was at 380 μm of 84.1% under the conditions (t = 75 min, T = 270 °C, W(CaO) = 8% and Nk = 255 g L−1), The digestion process of coarse-grained roasted ores was controlled by chemical reaction and its apparent activation energy of 840, 380 and 250 μm particle size roasted ore were 60.63 kJ mol−1, 89.1 kJ mol−1and 53.03 kJ mol−1, respectively.