New paths for a SO2-free copper production

Sulfur dioxide (SO2) generation is an inherent disadvantage of conventional copper extraction from sulfides. Here, three different approaches for a SO2-free copper production are evaluated: the conversion of copper–iron sulfides to oxides with oxygen and steam, with steam alone, and directly into copper and iron sulfide. Chemical equilibrium calculations show that the proposed reaction scheme with oxygen and steam is limited to reactors with plug flow behaviour and hence, not generally applicable. Similar calculations show that the reaction of chalcopyrite with steam can theoretically fulfill the requirement for a SO2-free process. However, a large excess of steam is required and chalcopyrite (CuFeS2) conversion with steam becomes very energy-intensive. Finally, a more rigorous approach, namely the direct decomposition of sulfides into copper, iron sulfide and elementary sulfur is proposed. This final approach demonstrates a promising path to effect a direct conversion by the use of concentrated solar radiation.