Effects of minerals in ferric bauxite on sodium carbonate decomposition and volatilization

HU Wen-tao(胡文韬)¹, WANG Hua-jun(王化军)¹, LIU Xin-wei(刘欣伟)¹, SUN Chuan-yao(孙传尧)^{1, 2}

(1. Key Laboratory of High-Efficient Mining and Safety of Metal Mines (USTB) of Ministry of Education
(University of Science and Technology Beijing), Beijing 100083, China;
2. State Key Laboratory of Mineral Processing Science and Technology
(Beijing General Research Institute of Mining and Metallurgy), Beijing 100070, China;)

Abstract:Direct reduction is an emerging technology for ferric bauxite utilization. However, because of sodium volatilization, its sodium carbonate consumption is considerably higher than that in ordinary bauxite processing technology. TG-DSC and XRD were applied to detecting phase transformation and mass loss in direct reduction to reveal the mechanism on sodium volatilization. The results show that the most significant influence factor of ferric bauxite on sodium volatilization in direct reduction system is its iron content. Sodium volatilization is probably ascribed to the instability of amorphous substances structure. Amorphous substances are the intermediate-products of the reaction, and the volatilization rate of sodium increases with its generating rate. These amorphous substances are volatile, thus, more sodium is volatilized with its generation. A small amount of amorphous substances are generated in the reaction between Na₂CO₃ and Al₂O₃; thus, only 3.15% of sodium is volatilized. Similarly, the volatilization rate is 1.87% in the reaction between Na₂CO₃ and SiO₂. However, the volatilization rate reaches 7.64% in the reaction between Na₂CO₃ and Fe₂O₃ because of the generation of a large amount of amorphous substances.

Key words:Na₂CO₃ decomposition; Na₂CO₃ volatilization; ferric bauxite; direct reduction