Minor-element behavior and iron partition during the cleaning of copper converter slag under reducing conditions

A mathematical model has been developed to describe the reduction process and the minor-element behavior during the cleaning of copper converter slag under equilibrium conditions. The results of simulation show that large fractions of Pb, Bi, Sb and As, but little of Zn, are absorbed into the recovered copper phase. Generally, the distribution behavior of minor elements is affected by temperature and CO partial pressure, but not by the initial amounts of these elements in the slag or by the activity of FeO. There is a limit to the recovery of copper by reducing Cu2O from the slag because iron oxides are also reduced at low oxygen potentials to form a solid copper-iron alloy which is impossible to separate from the slag. The limit was 90% recovery of copper (0.3% Cu in slag) at 1250°C for the converter slag of typical composition used in this study. The predicted results were compared with the actual observed data from pilot plant operation in which pulverized coal was used as a reductant. Consistent trends between the two cases were obtained.