Solar extraction of copper: on application of concentrated sunlight in extractive metallurgy

Abstract

The direct decomposition of copper sulphides under an oxygen free atmosphere in a solar furnace is an intriguing approach for producing copper. The use of concentrated sunlight to affect the decomposition reaction consequently avoids the generation of both toxic sulphur dioxide and carbon dioxide in the extraction process. Analysis of insolation maps shows that many important copper mining districts, e.g. in Chile or Southern Africa, as well as other places close to the growing Asian market, receive sufficient sunlight that recommends its use on an industrial scale. Decomposition experiments on synthetic copper sulphides in an imaging furnace confirmed formation of metallic copper at temperatures between 2000 and 2200 K and provided the parameters for preliminary calculations of the energy demand. They indicate that at suitable places 200 t of copper can be produced per day with a thermal input onto the heliostat field between 40 and 165 MW. Such plant sizes are at the lower limit compared with solar power plants dedicated to the production of solar electricity or of solar fuels. The reduced cost analysis further revealed that the expected production costs for solar copper are up to 30% lower but always comparable with those for conventional production because there is a need neither for SO2 processing nor for an oxygen plant. The concept of a solar driven extraction can also be applied to other base metal concentrates with similar benefits.