Effects of Fe/SiO2 Ratio and MgO Content on the Viscous Behaviors of the SiO2–FeO–MgO–12 Wt Pct Fe2O3–8 Wt Pct CaO–3 Wt Pct Al2O3 Slag System

The present study investigated the effects of Fe/SiO2 and MgO content on the viscous behaviors of the slag formed by the charging of secondary resources into the copper-smelting furnace. It is determined that the increase of Fe/SiO2 (0.8–1.2) and the addition of MgO (1–7 wt pct) both reduce the slag viscosity. The addition of MgO accelerates the transition of breaking temperature of slags to higher temperatures, while the effect of Fe/SiO2 on that is relatively complicated. Fourier transform infrared spectroscopy (FTIR) and Raman spectra indicate that increases in either Fe/SiO2 or MgO content contribute to depolymerization of silicate network structures in high-temperature melts. The [AlO6]9− octahedra in the melt tended to increase with increasing Fe/SiO2 and MgO content, while the opposite change is observed for [FeO4]5− tetrahedra. Moreover, an increase in Fe/SiO2 or MgO content also leads to a gradual decrease in the activation energy of slag viscous flow, except in the case of Fe/SiO2 of 1.2 and MgO content of 7 wt pct. This unexpected discrepancy can be accounted for different types of flow units that arise in the slag at high temperatures.