Clean and SO 2 -Free Method for Bismuth Extraction from Bismuthinite by Multiphase Roasting: Thermodynamic Equilibria an
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https://doi.org/10.1007/s11837-020-04250-0 Ó 2020 The Minerals, Metals & Materials Society
INTERFACIAL STABILITY IN MULTI-COMPONENT SYSTEMS
Clean and SO2-Free Method for Bismuth Extraction from Bismuthinite by Multiphase Roasting: Thermodynamic Equilibria and Reaction Mechanisms LONGGANG YE,1,3 PING WEN,1 ZHEN OUYANG,1 YUJIE HU,1 CHAOBO TANG,2 and ZHIMEI XIA1 1.—College of Metallurgy and Material Engineering, Hunan University of Technology, Zhuzhou 412007, China. 2.—School of Metallurgy and Environment, Central South University, Changsha 410083, China. 3.—e-mail: [email protected]
A clean method for bismuth extraction was investigated by multiphase roasting and beneficiation. Iron oxide and carbon, used as the sulfur-fixing agent and reductant, were roasted with Bi2S3, yielding Bi metal and iron sulfide. The products were separated by gravity separation. The predominance-area diagrams of Bi-Fe-S-O indicated that the stable zone of Bi + FeS increases with increasing temperature. The reaction equilibrium simulations among Bi2S3, Fe2O3, and C verified that Bi and FeS were the final products at > 400°C and without SO2 generation when the reductant was sufficient. Reaction process investigations of the Bi2S3-Fe2O3-C multiphase system indicated that the Bi generation rate and sulfur-fixing rate reached 94.17% and 96.79% at 800°C. In the kilogram confirmation test of the entire process, the recovery rate of metallic Bi and the sulfur-fixing rate reached 92.28% and 95.17%. The new process reduces the smelting temperature and improves SO2 emissions.
INTRODUCTION Bismuth is widely used in the production of alloy casting, medicine, electronic devices, flame-resistant materials, semiconductors, and other chemical materials.1–3 In 2018, bismuth consumption in the world was reported to be 15,500 tons. It is economical to extract Bi from bismuthinite, bismite, and secondary sources yielded from nonferrous smelters, such as anode slime, bismuth slags, and copper converter dusts.4–6 Current Bi extraction includes pyrometallurgical and hydrometallurgical processes, with the former being the main industrial process. Pyrometallurgical methods, including reduction smelting, replacement smelting, mixed smelting, and oxygen-enriched smelting, are the primary means to extract bismuth. Reduction smelting mainly produces bismuth and other oxide materials,7 with the smelting conducted at 1150–1250°C with a large reductant and flux addition. Because bismuth oxide concentrate yields less, this method is mainly used to treat bismuth oxide slag generated
in lead and tin smelters and copper converter dusts.8 Replacement smelting employs scrap iron to replace bismuth in Bi2S3 and produces FeS, thus eliminating sulfur dioxide emission.9 Though the process is a simple operation with a short flow, it requires an excess of scrap iron and soda, resulting in a large matte output. Mixed smelting, used for smelting of mixed sulfide and oxide ores,10 utilizes the following main reactions: Bi2 S3 þ Bi2 O3 þ 3C þ 3Fe ! 4Bi þ 3COðgÞ þ 3FeS ð1Þ and Bi2 S
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