Influence of slag composition and oxygen potential on thermodynamic behavior of vanadium in FeO-TiO2-MgO-SiO2-Al2O3 smelting slag and molten iron

Abstract

The influence of slag composition of FeO/TiO2 (=F/T) ratio, Al2O3/(SiO2 +Al2O3) (=A/(S+A)) ratio and oxygen partial pressure (po(2) = 10(-10) to 10(-9) atm) on the thermodynamic behavior of vanadium oxide in molten ilmenite smelting slag, i.e., FetO-TiO2-MgO-Al2O3 -SiO2 system, was investigated at 1550 degrees C. The distribution ratio of vanadium (=L-v) between molten iron and FetO-TiO2-MgO-Al2O3-SiO2 slag increases with increasing F/T ratio, while it decreases with increasing A/(S+A) ratio. In addition, logL(v) generally increases with increasing theoretical optical basicity of the slag (=Lambda(slag)). Vanadium oxide (VOx) is expected to behave as an acidic component in the present system. Vanadium in ilmenite smelting slags primarily consist of V3+, V4+, and V5+ ions, as determined by Gaussian deconvolution of X-ray photoelectron spectra. A linear relationship between log (wt%V4+/wt%V3+) and logpo(2) is confirmed. Both (wt% V-3(-)) and (wt% V5+) ions increase with increasing F/T ratio, whereas (wt% V4+) ions show the opposite behavior with increasing F/T ratio, irrespective of A/(S+A) ratio. Meanwhile, (wt% V3+) increase while (wt% V4+) and (wt% V5+) decrease with increasing A/(S+A) ratio. The linear relationship between log (wt%V3+/wt%V5+) and log (wt% V4+) has a slope of 1.8, which is good agreement with the theoretical slope of 2.0, which indicates that multi-valent vanadium ion species, i.e., V3+, V4+, and V5+, are thermodynamically balanced based on redox equilibria. (C) 2021 The Author(s). Published by Elsevier B.V.