Viscosity and structure evolution of molten vanadium slag during carbothermic reduction process

Abstract

In this study, the viscosity and structure evolution of molten vanadium slag at different stages during carbothermic reduction process were investigated through employing the rotating cylinder technique, Fourier transformation infrared (FTIR) and Raman spectroscopy. The results showed that both the viscosity and apparent activation energy of the slag continuously increased with the decrease of FeO and MnO contents, while decreased with the decrement of Cr2O3 and V2O3 contents. The mole fractions of Q2 and Q3 units in the silicate melt increased significantly due to the decrease in the concentration of free oxygen with the reduction of FeO and MnO, and the structural units transformed from prevalent Q0 and Q1 to Q2 and Q3 dominant, resulting in the fact that the trough depth of the [SiO4]-tetrahedral band was obviously enhanced and its center shifted to a higher wavenumber region in the FTIR spectroscopy. On the contrary, the reduction of Cr2O3 and V2O3 brought a gradual increasing Q0 and Q1 concentration and lower polymerization degree of molten slag, while the trough depth of the [SiO4]-tetrahedral band was weakened and its center shifted to a lower wavenumber region, which responded well to the viscosity variation of the slag.