Kinetics of Hydrogen Reduction of Chalcopyrite Concentrate
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E majority of copper ores currently available around the world are in the form of sulfides, especially chalcopyrite (CuFeS2) and to a lesser extent chalcocite (Cu2S).[1] The conventional pyrometallurgical method of copper extraction from these ores has several steps: roasting, smelting, converting, fire refining, and electrorefining. The steps involve the oxidation of sulfides which results in the generation of polluting sulfur dioxide gas. An alternative to this environment-unfriendly, lengthy process may be the reduction of sulfides by hydrogen or other reducing agents. Although this alternative seems to be attractive for its simplicity, its major problem is its unfavorable thermodynamics with a small equilibrium constant. To overcome this barrier, lime, which is a suitable material to fix the produced hydrogen sulfide gas in the form of solid calcium sulfide, has been successfully used by many researchers.[2–6] RITAYAN CHATTERJEE, formerly Graduate Student with the Department of Metallurgical and Materials Engineering, Jadavpur University, Kolkata 700032, India, is now Assistant Professor with the Department of Applied Sciences, Haldia Institute of Technology, Haldia 721657, West Bengal, India. DINABANDHU GHOSH, Professor, Department of Metallurgical and Materials Engineering, Jadavpur University. Contact e-mail: [email protected] Manuscript submitted February 27, 2015 METALLURGICAL AND MATERIALS TRANSACTIONS B
However, the addition of lime, which is a strongly hygroscopic material, introduces handling problem and imposes an additional task of separating the solid waste of calcium sulfide from the produced metal. Still another simple method to overcome the thermodynamic barrier is to accept the poor utilization of the reducing gas and use sufficiently large quantity of it.[7,8] The excess cost thus involved may be considerably offset by the saving caused by doing away with the lime; in addition, the copper produced will be much cleaner. Notably, in the previous studies of sulfide reduction, pure, synthetic materials were used and the possible role of gangue minerals was not considered. The reduction of sulfide ores or concentrates could be a more challenging and industrially important study. Accordingly, the main objective of the current work was to study the kinetics of hydrogen reduction of chalcopyrite concentrate, without adding lime to the system. In addition, it was intended to synthesize copper-silica composite, a valuable commercial product, by acid leaching of the reduction product, followed by sintering. Further separation of copper from silica, which would complete the making of copper from chalcopyrite concentrate, could not, however, be taken up in the current study. Different methods of synthesis of Cu-SiO2 composite, as have been reported in the literature, include gammaray irradiation,[9] electrodeposition,[10] microemulsion processing,[11] ambient drying,[12,13] and doping of Cu in
fused SiO2.[14] Compared to these, the method used in the current work is much simpler and more cost effective. Regarding its im
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