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Alternatives for processing metal sulfides without SOX emissions

Abstract : One of the major sources of the SOX emissions is the metallurgical processing of metal sulfides of Cu, Ni, Pb, Zn, etc. Although new technologies for metal sulfide smelting decrease these emissions, the generated quantity of sulfur oxides is considered as a serious threat to environment. Moreover, these emissions may be considered as an economic loss of the marketable sulfur. On the other hand, conversion of sulfur oxides to H2SO4 requires its consumption on the production sites as the cost of its transportation and stocking are important. Besides, the current state of the sulfuric acid market and the new regulations make the conversion of SOX to sulfuric acid less attractive. This paper deals with the low temperature treatment of complex sulfide ores 'CSO' or concentrates 'CSC' under neutral, reducing and chlorinating atmospheres or their combination. Treatment of CSC with nitrogen, at temperatures lower than 1000°C, allows the decomposition of the pyritic matrix to pyrrhotite and the volatilization of sulfur and As, Cd, Bi, Hg, Ge, Pb, etc., compounds. Using the same reactor, a reducing atmosphere will lead to the reduction of sphalerite to zinc and to a solid containing Cu°, Fe° and silicoaluminates. Selective dissolution of copper may be done by a hydrometallurgical process. Generated hydrogen sulfide could react with pyrrhotite to form pyrite and hydrogen. A flow - sheet of the suggested process is proposed. Complete chlorination of chalcopyrite concentrate was possible above 300°C. Iron and sulfur chlorides were fully volatilized and recovered by selective successive cooling of the gas phase. The chlorination residue is composed of valuable metals' chlorides. However, such process generates hazardous sulfur chlorides 'SXCly'. A part of sulfur chlorides such as SCl2 can be recycled as a chlorinating agent of metal sulfides. On the other hand, SXCly was either hydrolyzed, leading to the recovery of more than 90 pct of elemental sulfur or reduced by hydrogen, at temperatures lower than 600°C allowing the recovery of up to 90 pct of elemental sulfur. A flow sheet for the chlorination of metal sulfides and the treatment of sulfur chlorides is suggested.
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Eric Allain, I. Gaballah, Ndue Kanari, K. Malau, J.C. Mugica, et al.. Alternatives for processing metal sulfides without SOX emissions. TMS Fall Extraction and Processing Conference, 1999, San Sebastian, Spain. pp. 1855-1864. ⟨hal-01509737⟩



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