Phase Equilibrium studies in the system “FeO”–SiO2–Al2O3–CaO–MgO at 1200 °C and Po2 10-8atm

Iron oxides and silica are the major components of copper smelting slag. The oxides of aluminum, calcium and magnesium are also present in the slag that is introduced through copper concentrate, flux and refractories. Liquidus temperatures of the copper smelting slags are usually controlled by Fe/SiO2. The concentrations of Al2O3, CaO and MgO, and FeO/Fe2O3 in the slag can also affect the liquidus temperatures where FeO/Fe2O3 is a function of oxygen partial pressure. High temperature equilibration under controlled oxygen partial pressure followed by quenching and electron probe microanalysis were used to determine the compositions of the liquid and solid phases at 1200 °C and Po2 10-8 atm. The experimental results are presented in the forms of pseudo-ternary sections “FeO”-CaO-SiO2 at fixed 2, 4 and 6 wt pct MgO, and 2 + 2, 4 + 4 and 6 + 6 wt pct MgO + Al2O3. Spinel and tridymite are the major primary phases in the composition range investigated. In addition, CaSiO3, pyroxene, olivine, and melilite are also present. The isotherms in the spinel and tridymite primary phase fields move towards higher SiO2 concentration directions with increasing CaO, Al2O3, and MgO concentrations. The experimentally determined results are compared with the FactSage calculations.