Thermodynamic re-optimisation of the CaO-FeO-Fe2O3 2 O 3 system integrated with experimental phase equilibria studies (Part I)

New experimental measurements of phase equilibria in the CaO-FeO-Fe2O3 2 O 3 system at 1120-1740 degrees C over a wide range of oxygen partial pressures (pO2 2 = 1, 10-- 0.68, , 10- 2 , 10- 6 , 10- 8 , 10- 10 atm) and in equilibrium with metallic Fe has been obtained. The study was undertaken using equilibration/quenching and electron probe Xray microanalysis (EPMA) technique enabling the compositions of the liquid and solid phases in equilibrium at temperature to be accurately measured. The data have been used to define the liquidus of hematite (Fe2O3), 2 O 3 ), spinel (Fe,Ca)3O4+x, 3 O 4+x , lime (Ca,Fe)O, wustite (Fe,Ca)O1+x, 1+x , 2CaO center dot Fe2O3 2 O 3 (C2F), 2 F), CaO center dot Fe2O3 2 O 3 (CF), CaO center dot 2Fe2O3 2 O 3 (CF2), 2 ), and a solid phase with composition close to (CaO)15(FeO)8(FeO1.5)77, 15 (FeO) 8 (FeO 1.5 ) 77 , which is believed to belong to the Silico-Ferrite of Calcium and Aluminium (SFCA-I) ) solid solution. Direct oxygen concentration measurements in the liquid and solid phases using EPMA were also undertaken in the present study to determine the Fe2+/Fe3+ 2+ /Fe 3+ ratio in these phases. The experimental data obtained in the present study will be used for thermodynamic re-optimisation of the CaO-FeO-Fe2O3 2 O 3 system, undertaken as part of the study of the 20-component Pb-Zn-Cu-Fe-Si-Ca-O-S-Al-Mg-Cr-Na-As-Sn-Sb-Bi-Ag-Au-NiCo system directly relevant to the applications in the ferrous and non-ferrous metallurgical industries.