The impact of silica to a SiO2–MgO–FeOx slag

The sensitivity of silica concentration from 20 to 50 wt% in SiO2–MgO–FeOx nickel smelting slags is studied at three Fe(tot)/MgO ratios of 4, 5 and 6 using calculated phase equilibria in slag‐cleaning conditions in an electric furnace. This study uses the thermodynamic software package MTDATA and the slag database of MIRO MTOX for covering the melting equilibria of the oxide system of Fe–O–MgO–SiO2 with limited modifying additions of CaO and Al2O3. According to the constructed phase diagrams, when the silica concentration exceeds 40 wt% SiO2 the liquidus temperature increases rapidly. The results also show that the addition of CaO decreases the liquidus temperature more than the addition of Al2O3 except for the area just in front of the steep liquidus temperature increase at SiO2 concentrations over 40 wt%. The primary precipitating phases are olivine at SiO2 concentrations less than 40 wt% and for concentrations over tridymite and cristobalite.