A Study on the Copper Recovery from the Slag of the Outokumpu Direct-to-Copper Process

The work was aimed at the investigation of the influence of the carbon reducer’s surface on the rate of copper removal from the slag obtained from the flash direct-to-blister process at the G?ogów smelter in Poland. It was found that, under our experimental conditions, the copper recovery from the slag slightly increases as the slag/carbon interface increases. It is very likely that the results depend on the geometry of the investigated system as well as the slag foaming phenomenon. The increase of the slag/carbon interface does not noticeably change the final copper content in the slag. The obtained results do not follow any of the reaction rate equations. Therefore, it can be suggested that the slag foaming plays the key role in the experiments by increasing the reduction surface. In addition, the investigated slag has a high viscosity, which hampers the mass transfer in this slag. This hypothesis is supported by the fact that the slag layer situated below the graphite penetrator was found to be of a different color than the slag in the vicinity of that penetrator, where it was agitated by the CO and CO₂ gases generated by the reactions of the slag reduction. Also, the slag in the layer under the penetrator contained more copper than the slag above this layer.