Evolution of Viscosity and Structure Property during Aluminothermic Reduction of Vanadium-Enriched Slag

Aluminum dross is a promising reductant for extracting vanadium to enable the direct production of ferrovanadium alloy in pre-reduced vanadium-rich slag (PVS). The evolution of the viscosity of PVS is measured with various A/M ratios (w(Al2O3)/w(FeO + Cr2O3 + MnO + V2O3 + Al2O3)), representing different reduction stages. The compositions and structural properties of the melts are analyzed using X-ray powder diffraction, scanning electron microscopy, and Raman spectroscopy. The results show that with an increase in the mass ratio of Al2O3 to (FeO+Cr2O3+MnO+V2O3+Al2O3) in the slag transformed from a solid-liquid mixture to a single liquid phase at 1873 K. When A/M increases from 0.29 to 0.53, Q(0) and Q(1) polymerize into Q(2), resulting in a slow increase in viscosity from 0.091 to 0.158 Pa s. As A/M further increased to 1.00, Q(0) disappeared, Q(3) appeared, and the fraction of Al-O-Si increased to 37.7%, indicating that the simple aluminosilicate structural units are polymerized into complex structural units. Meanwhile, the viscosity increases to 0.338 Pa s. Al2O3 acts as a network former and strengthens the degree of polymerization of the melt. The variation ranges of the apparent activation energy, structural complexity, and the average number of non-bridging oxygen are 139.23-215.12 kJ mol(-1), 0.57-2.97, and 2.16-1.05, respectively.