Reaction Behaviors of Associated Minerals in Molten Salt Smelting of Stibnite and Kilogram-Class Trials

• Main Authors: Zhen Ouyang, Longgang Ye, Chaobo Tang, Yuntao Xin
• Format: Article
• Language: English
• Published: MDPI AG 2019-12-01
• Series: Metals
• Subjects: molten salt; antimony metallurgy; thermodynamic; tg-dta; stibnite
• Online Access: https://www.mdpi.com/2075-4701/10/1/43

The molten salt metallurgy of Sb, which involves the smelting of stibnite in a binary NaCl-Na₂CO₃ salt with sulfur-fixing and the addition of a reductant, has been proposed as a clean method for Sb extraction. However, the reacting behaviors of the minerals associated with stibnite (Sb₂S₃) during the smelting are still unclear, and industrial tests have not been conducted. This study investigated the behaviors of PbS, FeS₂, SiO₂, and CaCO₃, which are the main minerals associated with stibnite, during reducing smelting by using the NaCl-Na₂CO₃ molten salt. The results showed that PbS could react with Na₂CO₃ to generate metallic Pb at 950 °C. FeS₂ and SiO₂ formed stable NaFeS₂ and Na₂SiO₃ with the molten salt at a high temperature, respectively. CaCO₃ formed an unstable intermediate product of Na₂Ca(CO₃)₂ at 675 °C and decomposed with increasing temperature. Kilogram-class trials were also performed using 50 kg of concentrate and more than 300 kg of mixture material, and the results showed that the direct recovery rate of Sb and Au reached maximum values of 93.22% and 92.06% at temperature 920 °C in eutectic Na₂CO₃-NaCl molten salt, respectively, while the total sulfur-fixing ratio reached 99.49%. Thus, the associated minerals consumed the molten salt, and the feasibility of molten salt smelting was verified by this kilogram-class pilot experiment.