Thermochemical Study on High Temperature Process of Zinc Production without Exhaustion of Carbon Dioxide

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Aiming at development of a new pyrometallurgical zinc production process, in which molten copper is used as a reactant to reduce zinc sulfide in the concentrate and which makes metallic zinc without exhaustion of carbon dioxide gas, the new process was thermodynamically and thermochemically evaluated in the present study.Firstly, the solubilities of ZnS and PbS in the ternary CuィイD22ィエD2S-ZnS-FeS and CuィイD22ィエD2S-ZnS-PbS mattes at 1473 and 1523 K were experimentally determined and it was clarified that the solubility of ZnS in the liquid matte was considerably small at less than 6 wt%. This result indicates that a part of ZnS in the concentrate charge in the smelting stage is not dissolved in the matte phase in the case that the amount of the circulated CuィイD22ィエD2S is comparably small. The Raoultian activity coefficients of ZnS and PbS in the matte were found to be 9.8 and 1.3, respectively.Secondly, based on the thermochemical and thermodynamic data obtained in the present study, the … More material and heat balances were evaluated for the new process and the following results were obtained. A huge amount of liquid CuィイD22ィエD2S with 100 - 160 ton per one ton of recovered metallic zinc must be circulated to avoid the over-heating of the reaction furnaces. Hence, the development of a technology to smoothly circulate the CuィイD22ィエD2S medium will be a key to the new process. The heat of oxidation f the sulfides in the concentrates is only one credit in the heat balance in the process, and the combustion of coal or coke will be needed in the oxidation stage to compensate the lacking heat. A use of the oxygen-enriched air for the combustion will be effective to remarkably decrease the amount of the carbonaceous materials to be used. The sensible heats of the produced slag and the exhaust gas were evaluated to be enormous, and their recovery and utilization are significantly important. The gas discharged from the volatilization stage is fundamentally free from COィイD22ィエD2 and SOィイD22ィエD2 and the reoxidation of zinc vapor by these gases will be avoidable. This gives a possibility to refine zinc directly from the discharged gas by means of selective condensation. The use of liquid copper and high grade matte as smelting media was considered to be profitable for recovering the precious metals but to be inadvantageous for eliminating the detrimental elements of arsenic and antimony. Less