Study On Thermal Decomposition And Sulfide Volatilization Of Brittle Sulfur Lead Bismuth Ore

Jamesonite (Pb₄FeSb₆S₁₄) is a kind of complex antimony sulfate minerals which accounts for 30?40% of the total antimony resources in our country. The effective separation of lead and antimony is the key problem to use this resource, on the one hand the main reason is the complex composition and structure of jamesonite, in which nested lead and antimony are in the natural sulfide minerals sosoloid; on the other hand is the similar physical and chemical properties between lead and antimony, which leads to the similar behavior in metallurgical process. According to the unique molecular structure of Jamesonite and the characteristics of vacuum metallurgy, this paper puts forward a new method of dealing with Jamesonite by vacuum metallurgy processing. PbS, Sb₂S₃, FeS and, PbS were obtained after the decomposition, volatilization and condensation of Pb₄FeSb₆S₁₄, respectively. Lead and antimony in jamesonite were separated by the forms of PbS and Sb₂S₃. According to above ideas, the following work has been carried out:?1? The mineral structure of the Jamesonite concentrate was investigated. The phase transformation of jamesonite during thermal decomposition was studied by TG/DSC and XRD methods. With increasing temperature, Pb₄FeSb₆S₁₄ was decomposed into Pb2Sb2S5, Pb4Sb4S13, Pb5Sb4S11 and other complex lead antimony sulfide gradually, and the final products were PbS, Sb₂S₃ and FeS. The decomposition temperature of Pb₄FeSb₆S₁₄ was reduced in vacuum condition, while Pb₄FeSb₆S₁₄ was decomposed at 573 K under the pressure of 10-20 Pa.?2? The thermal stabilities of PbS, Sb₂S₃ and FeS were analyzed by thermodynamics, such as decomposition temperature, reaction temperature, and thermodynamic equilibrium constants. The results showed that under 50-300 Pa, when the temperature was lower than 1362 K, PbS did not decompose. When the temperature was lower than 1097 K, Sb₂S₃ did not decompose. When the temperature was lower than 1573 K, FeS existed stably. The process and volatile forms of material volatilization, and molecular motion characteristics under the condition of vacuum were theoretically analyzed. The kinetics of material volatilization was studied under the vacuum atmosphere. The rate-determining steps for pure substance in the vacuum were the melt surface volatilization and gas phase diffusion. The corresponding calculation formula for the mass transfer rate was deduced.Based on this result, the thermogravimetric method was selected for investigating the evaporation of PbS, Sb₂S₃ and FeS in vacuum. The results showed that the vacuum evaporation rate is Sb₂S₃>PbS> FeS. Under the condition of 50-300 Pa and 823?1123 K, the gas phase diffusion was the rate-determine step for Sb₂S₃. The volatilization rate was related to the temperature and pressure, which was similar to the metal that the logarithm of volatilization rate yielded a line with the reciprocal of temperature and pressure. Its volatilization rate was between 0?0.023 g·cm^-2·s. The apparent activation energy was between 65.834?60.608 kJ/mol. In the temperature range of 923?1123 K, PbS sublimated and the gas phase diffusion was the rate-determining step. The volatilization quantity was between 0.001?0.05g/s. The apparent activation energy was 131.539?112.064 kJ/mol. In the temperature range of 923?1123 K, PbS sublimates and the gas phase diffusion was the rate-determine step. The volatilization quantity was between 0.001?0.05g/s. In the temperature range of 1073?1323K, FeS did not evaporate. In addition, the volatilization rate of Sb₂S₃ and diffusion in the gas phase were greater than PbS. The variation of pressure and temperature affected the volatilization of Sb₂S₃ and PbS significantly, respectively.?3? At first, the saturation vapor pressures of ZnS, Cu₂S, CaO, SiO₂, PbS, Sb₂S₃, and FeS were compared. The result showed that, under 50?100 Pa and 1473?1573 K, gas phase mainly existed as PbS and Sb₂S₃ in jamesonite vacuum decomposition and volatilization. Then the thermodynamics of PbS and Sb₂S₃ in vapor condensation were also analyzed. Condensation reaction theory, reaction temperature, dew point temperature, and the corresponding pressure control system of PbS and Sb₂S₃ showed that the condensing temperature can separate PbS and Sb₂S₃ mixture vapor. Under 50?100 Pa,823?1173 K, PbS vapor condensation was solid, Sb₂S₃ vapor condensed into a fluid, while the temperature of PbS and Sb₂S₃ condensation at the same pressure under the condition was close to 100 K.Jamesonite concentrate as raw material and home-made equipment was used to carry out the PbS and Sb₂S₃ mixed vapor condensation separation experiments, the results showed that the condensates of PbS, Sb₂S₃ and residues, which mainly was FeS, it could be obtained both by vacuum decomposition and fractional condensation. Under pressure of 50?100 Pa, the optimum process conditions were:heating temperature of 1473?1573 K, heat-retaining time of 30?60 min, condensing temperature of 998?1048 K. The optimum process conditions of different components of jamesonite concentrate showed that the yield and mass percentage of the residues of FeS and the condensates of PbS and Sb₂S₃ were all more than 90%, lead and antimony separation was also effective.Jamesonite is an important nonferrous metal resource in China, whose reserves are more than a single antimony sulfide ore. In this thesis, the new idea of vacuum metallurgy in lead and antimony separation was put forward to realize the separation of lead and antimony mineral source in environmental friendly and facile process. It also solved the technical problems of crude separation of lead antimony alloy, which laid a solid foundation in theory and practical usage. Vacuum metallurgy has a great status in the development of efficient and green lead antimony metallurgy.