Redox Equilibria in Al₂O₃-CaO-FeO_x-SiO₂ and Al₂O₃-CaO-FeO_x-MgO-SiO₂ Slags

Abstract

Measurements of the Fe³⁺/Fe²⁺ ratio in Al₂O₃-CaO-FeO_x-SiO₂ and Al₂O₃-CaO-FeO_x-MgO-SiO₂ slags in equilibrium with Ar-CO-CO₂ gas mixtures have been made in the temperature range of 1400 to 1500°C and oxygen potentials between 3×10^-9 and 10^-5 atm. The results from these experiments indicate that in Al₂O₃-CaO-FeO_x-SiO₂ slags with 0-10 wt% MgO, the ratio of activity coefficients of ferrous oxide to that of ferric oxide decreases sharply as the total iron oxide content increases from about 0.8 to 3 wt%. However, at total iron contents of greater than 6 wt% the ratio of the activity coefficients of iron oxides becomes virtually independent of the iron content of the slag.