Thermodynamic optimization of the Al2O3–FeO–Fe2O3–SiO2 oxide system

Abstract

A complete literature review, critical assessment, and thermodynamic modeling of the phase diagrams and thermodynamic properties of oxide phases in the Al2O3–FeO–Fe2O3–SiO2 system at a total pressure of 1 atm are presented. A set of optimized model parameters for all phases was obtained to reproduce all previously published thermodynamic and phase equilibrium data. Some discrepancies in the literature data were identified, particularly for liquidus measurements and the Fe3+/(Fe2+ + Fe3+) ratio in the slag phase (liquid oxide phase) at high temperatures. Analysis of internal consistency with the Al2O3–FeO–Fe2O3, FeO–Fe2O3–SiO2 and Al2O3–SiO2 sub-systems allowed to resolve the discrepancies. Previously published model parameters for the slag phase in the Al2O3–FeO–Fe2O3 system were slightly modified to achieve better overall agreement. The final set of model parameters for oxide phases reproduces all available data within experimental error limits. The Modified Quasichemical Model was used for modeling of the slag phase. The models based on the Compound Energy Formalism were applied for spinel and mullite solid oxide solutions. The database of model parameters optimized in the present study can be used along with software for Gibbs energy minimization to describe thermodynamic equilibria at all compositions and oxygen partial pressures, from the lowest corresponding to equilibrium with metal up to the highest P(O2) of 1 atm. The database was incorporated into the larger database for the multi-component Al–Ca–Cu–Fe–Mg–Pb–Zn–O–S–Si–(As, Sb, Bi, Sn, Ag, Au, Ni) chemical system and successfully used for calculations of equilibria relevant to copper, lead, zinc smelting and recycling.