Effect of FeO and Al2O3 on the MgO Solubility in CaO–SiO2–FeO–Al2O3–MgO Slag System at 1823 K

Abstract

AbstractThe MgO solubility in CaO–SiO2–FeO–Al2O3–MgO quinary slag system at 1823 K was measured to evaluate the effect of FeO and Al2O3 on the MgO solubility. It was found that the MgO solubility was decreased with higher optical basicity, FeO concentration, and increased with higher Al2O3 concentration. The MgO solubility was affected by activity coefficient of Mg2+ ($\gamma _{{\rm Mg}_{{\rm 2 + }} } $). Increase of the activity coefficient of Mg2+ ($\gamma _{{\rm Mg}_{{\rm 2 + }} } $) with higher FeO or lower Al2O3 decreased the MgO solubility. The increment in MgO solubility is remarkably reduced beyond a critical $X_{{\rm Al}_{2} {\rm O}_{{\rm 3}} } /(X_{{\rm Al}_{2} {\rm O}_{{\rm 3}} } + X_{{\rm FeO}} )$ ratio. The significant decrease of the increment of MgO solubility is caused by the change of the molten slag structure. The excess stability function of Al2O3 and the Fourier transform infrared (FT‐IR) analysis were applied to indirectly verify the existence of the spinel structure in the CaO–SiO2–FeO–Al2O3–MgO slag system.