Abstract
To improve the recovery of copper, the viscosity of copper molten slag is decreased by the reduction of magnetic iron, which, in turn, accelerates the settling and separation of copper droplets from the slag. A new technology is proposed in which waste cooking oil is used as a reductant to reduce magnetic iron in the copper smelting slag and consequently reduce carbon emissions in the copper smelting process. A kinetic model of the reduction of magnetic iron in copper slag by waste cooking oil was built using experimental data, and the accuracy of the model was verified. The results indicated that the magnetic iron content in the copper slag decreased with increasing reduction time and an increase in temperature more efficiently reduced magnetic iron in the copper slag. The magnetic iron in the copper slag gradually transformed to fayalite, and the viscosity of the copper molten slag decreased as the magnetic iron content decreased during the reduction process. The reduction of magnetic iron in the copper molten slag using waste cooking oil was a first-order reaction, and the rate-limiting step was the mass transfer of Fe3O4 through the liquid boundary layer.
Highlights
Energy is indispensable to human beings, and the development of human society is closely related to the development and utilization of energy
It is highly significant that waste cooking oil is used in a copper slag depletion process to achieve waste resource utilization and reduce carbon emissions
Electric furnace copper slag was found to be composed of magnetic iron (Fe3O4), fayalite (Fe2SiO4), calcium magnesium oxide, and a silicate solid solution
Summary
Change in the magnetic iron content in the copper slag during the reduction process. Figure 2 and Fig. 3 show the changes in the content and reduction rate of magnetic iron with respect to the reduction reaction time at different temperatures. The waste cooking oil decreased the slag viscosity by reducing the magnetic iron content in the copper slag. The reduction of magnetic iron in the copper slag by waste cooking oil is controlled by liquid phase mass transfer[15, 16]. The pyrolysis of waste cooking oil rapidly forms small gaseous molecules and coke at high temperature; the reduction of magnetic iron in copper slag is a gas-liquid-solid phase reaction. The results show that the experimental data are consistent with the calculated results
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