Investigation into Oxygen-Enriched Bottom-Blown Stibnite and Direct Reduction
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RODUCTION
ANTIMONY is a silvery and brittle metal with poor electrical and heat conductivity,[1] and it is mainly used as an alloying element to enhance the mechanical strength of other metals (e.g., lead in wet-cell batteries).[2–5] Antimony is seldom found as a natural metal because of its strong affinity to sulfur and other metals such as copper, lead, silver, and gold.[6] More than 100 minerals of antimony have been found in nature, and the most important and abundant one is stibnite, an antimony sulfide (Sb2S3), exploited for the recovery of antimony and precious metals (e.g., gold and silver). The world’s largest natural resource of antimony is in China, and it primarily contains stibnite (Sb2S3) associated with pyrite, arsenopyrite, jamesonite, and various oxides if the deposits are oxidized.[1,6] The major methods for extractive metallurgy of antimony from stibnite are pyrometallurgical processes.[1,7–9] Traditionally, the commercial route involves roasting of concentrate, volatilization of antimony trioxide in a blast furnace, and carbon-based reduction of the trioxide to metallic antimony in a reverberatory furnace. In these processes, however, antimony smelting at a high temperature will cause (1) serious environmental pollution during roasting and smelting because abundant antimony sulfide and some relevant volatile WEI LIU, YONGXING ZHENG, and KANG YANG, Doctors, and HONGLIN LUO and JUNWEI HAN, Masters, WENQING QING, Professor, are with the School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, P.R. China. Contact e-mail: [email protected] Manuscript submitted January 6, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
metals (e.g., lead, arsenic and cadmium), together with a certain amount of SO2, are emitted through volatilization, and (2) large energy consumption, so a lot of high-quality coal is consumed to sustain the required temperature [1373 K to 1673 K (1100 °C to 1500 °C)]. Currently, more than three tons of high-quality coal is required to produce one ton of antimony in China. Hydrometallurgical methods can also be employed for processing simple antimony materials or complex ones containing several metals.[1–4,10–12] Normal hydrometallurgical practices call for two steps: leaching and electrodeposition. In reality, two solvent systems are used in antimony hydrometallurgy: an alkaline sulfide system (dominant) and an acidic chloride system. The alkaline sulfide system has been employed industrially in the former Soviet Union, China, Australia, and the United States, but both scientific research and industrial practice show the limitations in processing high-grade stibnite using this method. Furthermore, when the ores contain precious metals and copper, the hydrometallurgical methods fail to achieve satisfactory recoveries of these metals.[5,10,13,14] There are some improved methods, such as direct reducing-matte smelting of stibnite concentrate in pyrometallurgy, and electrowinning of antimony in hydrometallurgy.[7,9,11,14–17] However, no method for recovery of a
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