Study On Oxygen-enriched Volatile Bath Smelting Of Stibnite Concentrate And Slag-type

In conventional pyrometallurgical process of antimony smelting, the generally exist problems such as high energy consumption, high cost anddifficulty of acid production with low concentrations SO2. In contrast, oxygen-enriched bath smelting demonstrates merits including high melting efficiency, low energy consumption, wide adaptability of raw materials, easy production of SO2gas with higher concentrations and so on. Therefore, metallurgists applied the oxygen-enriched bath smelting to the antimony metallurgy, and proved its feasibility. However, the problems of high antimony content in slag and poor stability remain unsolved. In this paper, aiming at the existing problems in the volatile oxygen-enriched bath smelting of stibnite, combined smelting process system with reasonable slag-type research to explore effective ways to reduce antimony content in slag.The project was supported by the HuNan Nonferrous Metals Fund.In this paper, effective method to reduce slag-containing antimony was explored based on the thermodynamics analysis combined with smelting process principles and slag process mineralogy and reasonable slag-type study, and achieved following results:According to the main reactions in the oxygen-enriched volatile bath smelting system of stibnite, its thermodynamic calculations were obtained, and thermodynamic predominance balance diagrams of Sb-S-O system was drawn with thermodynamic calculation software Fcatsage6.2. The results showed that in the temperature range of1000～1350℃, Gibbs free energy for the volatile oxidation reaction of Sb2S3was negative, and could progress spontaneously; experimental temperature must be greater than1133℃to avoid thermal generation of Sb2O4and Sb2O5; predominance diagrams of Sb-S-O system showed little effect of temperature on the regional strengths of Sb2O3, Sb2S3predominance region decreased rapidly with increasing temperature, and Sb stable region increased with increasing temperature.The preliminary calculation for the viscosity of FeO-CaO-SiO2slag was conducted using software FactSage6.2. The results showed that the slag used in this research was with high viscosity, and its viscosity reduced slightly as the temperature increased in the range of11501350℃. At1200℃, the viscosity of the slag increaseed with increasing SiO2content, and in general reduced with increasing FeO content.The effects of reaction temperature, oxygen concentration, reaction time, gas pressure etc. on the slag-containing antimony in the oxygen-enriched volatilebath smelting system of stibnite were studied, and optimum conditions were determined as follows:reaction temperature is1200℃, reaction time is60min, the concentration of enriched oxygen is80%, and the gas pressure is0.18MPa. In the verification test carried out under optimum conditions, slag-containing antimony was as low as0.33%, crude antimony rate was6.8%, and crude antimony grade was up to94.79%.Based on the technology research for volatile oxygen-enriched bath smelting of stibnite, further investigation of effects of Fe/SiO2, CaO/SiO2on the slag-containing antimony was studied and reasonable slag-type ratio was determined as follows:Fe/SiO20.7, CaO/SiO20.5. The verification test carried out under this ratio showed that, slag-containing antimony was as low as0.37%, and rate of crude antimony was2.2%.