Computational thermodynamic modelling of direct to blister copper smelting

Abstract

All sulphide copper concentrates can be smelted directly to blister copper in a flash furnace, but whether or not this is economically viable depends on the iron content of the concentrates. In this work, a computational thermodynamic model of direct to blister copper smelting is described and then used to examine the differences between the smelting of a high iron chalcopyrite concentrate and a low iron bornite concentrate. The rapid decrease in copper recovery as the iron content of the concentrates increases is clearly seen. In practice, the slag has a higher copper content than expected from equilibrium considerations, and this is due to the entrainment of copper bearing material. It is shown that this entrainment can be satisfactorily accommodated in a thermodynamic model so that its impact on copper recovery can be appreciated. Finally, the effect of changing the fluxing regime on copper recovery is examined, and it is seen that adding some lime to the slag increases copper recovery. Whether or not this lime flux addition is economically justified is discussed. It is concluded that computational thermodynamic modelling is a convenient tool for developing a deeper understanding of the effect of process variables on direct to blister copper smelting.