Activities of FeO in CaO-Al2O3-SiO2-FeO and CaO-Al2O3-CaF2-FeO slags

Abstract

Activity coefficients of FeO in molten CaO-Al2O3-SiO2-FeO (<5%) slags were determined at 1 673 and 1 873 K by equilibrating the slags with copper-iron alloys in a controlled oxygen partial pressure (Po2 = 5.71 × 10-12 atm at 1 673 K, 1.90×10-10 atm at 1873K). Activity coefficients of iron in copper-iron (<4%) alloys at 1 673 K were preliminarily determined by controlling the activity of iron using FeO· Cr2O3 saturated with Cr2O3 in a various oxygen partial pressures (Po2 = 3.66×10-12-9.14×10-11 atm). It was found that the activity coefficients of FeO obey Henry's law, and have the maximum value when the ratio of NCaO/NSiO2 is about 2 at a constant Al2O3 content. The activity coefficients of iron in copper-iron alloy referred to pure liquid were determined as In γFe=2.76-11.3NFe. The effect of a CaF2 addition to the CaO-Al2O3-FeO system on the activity coefficient of FeO was also investigated at 1 723 K.