Carbothermic reduction of chalcopyrite in the presence of a desulfurizer in a plasma medium

An alternative route to the current sulfide smelting technology where control of sulfur dioxide is a major problem is direct reduction of sulfide concentrates in the presence of a desulfurizer. Some laboratory investigations of the reduction of chalcopyrite in the presence of a desulfurizer conducted under conventional thermal conditions have been reported,^1-4but so far there is no reported work on chalcopyrite reduction with a desulfurizer in a plasma environment. This paper discusses the results of the initial experiments carried out on the reduction of a fine particulate mixture of chalcopyrite, lime, and carbon in a plasma medium. The reduction was carried out in-flight within a plasma cone and the products were rapidly quenched in a free-fall chamber and analyzed using optical microscopy, scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), and electron probe microanalysis (EPMA) together with wet chemical analysis techniques. The effect of process parameters such as particle size, feed rate, and oxygen injection on copper metallization are discussed. A description of the plasma reactor is given and the in-flight mineral particle-plasma interactions are discussed with respect to process control, reduction mechanism(s), and degree of metallization achieved.