Characteristics and Mechanism of Reduction and Smelting-separation Process of Copper Slag

The characteristics and mechanism of the reduction and smelting-separation process of the copper slag were studied by investigating the variation rule of metallization ratio, yield as well as carbon content of iron nuggets. The formation of molten slag is necessary for slag-iron separation, and iron is in half-molten state during smelting-separation process, the carbon content of which is about 1.25%. Carburization occurs through direct contact between carbon and iron in essence, no matter in solid or molten state. The carburization rate is slow below 1200 °C, which is inhibited by the existence of slag. Residual FeO in molten slag tends to form fayalite with SiO2 in the copper slag, which is the root cause for the low melting temperature of copper slag. The addition of CaO improves the reducibility of the copper slag, but Al2O3 addition has no obvious effect. The melting temperature of slag affects the carburization extent in solid state, while the content of FeO in molten slag affects that in molten state, both of which co-determine the carbon content in iron nuggets.