Thermodynamic study of direct reduction of high-chromium vanadium–titanium magnetite (HCVTM) based on phase equilibrium calculation model

Abstract

High-chromium vanadium–titanium magnetite (HCVTM) is a good valuable resource with high iron content in the form of complex iron ore which contains various valuable metal elements such as iron, vanadium, titanium, chromium. Direct reduction of HCVTM is studied based on thermodynamic analysis. Combined TG experimental verification and equilibrium calculation model was used to analyze the reaction sequence and equilibrium amount in this paper. The contents in HCVTM reduction system are simplified as 18 kinds of chemical compositions. Reductions of Fe3O4 and FeO·TiO2 are the main reduction reactions and are mainly reduced by C. The reduction reaction sequence of FeO·TiO2 is FeO·TiO2, TiO2, TiC, and Ti; the reduction reaction sequence of Fe3O4 is Fe3O4, FeO, and Fe. The minimum reduction temperature of HCVTM is 860 °C. The reduction of Cr is difficult to implement, and the minimum reduction temperature of V is above 700 °C. The gas phase in this system is mainly CO when the temperature is above 1000 °C. CO partial pressure curve of gasification reaction is in the shape of ‘S’ with increase of temperature. When the temperature is 1350 °C, C/O is 1.0 and reduction time is 30 min, HCVTM can be reduced thoroughly and the reduction degree can reach to 0.98. When C/O is lower than 1.0, FeTi2O5 is the reduction intermediate products from FeO·TiO2. When C/O is 1.0, diffraction peaks of Fe3O4 and FeO·TiO2 disappear, and they are reduced to Fe and TiO2.