2015 Volume 55 Issue 1 Pages 200-206
A novel de-Phosphorisation & V-extraction process (de-P & V-extraction) is proposed in which lime is added during the production of vanadium slag. This is expected to promote both phosphorus removal and environment-friendly vanadium extraction from the vanadium-containing hot metal simultaneously. The influence of CaO addition on the chemical components and mineralogical morphology of vanadium-containing phase in vanadium slags has been investigated by XRD and SEM/EDS. Results show that the increase in CaO contents changes both species of vanadium-containing phase and the morphologies of vanadium-containing spinels in vanadium slags. Vanadium concentrates as (Mn,Fe,Mg)V2O4 in the spinel phase in vanadium slag with CaO content less than 10 mass%. When CaO content is higher than 12.89 mass%, vanadium exists both as (Mn,Fe,Mg)V2O4 in dendritic-like spinel and as Ca3V2(SiO4)3 in goldmanite in the matrix. Precipitation of perovskite results in the dendritic-like shape of spinels while V3+ diffusing away from spinel lattice leads to the formation of goldmanite Ca3V2(SiO4)3. Thermodynamic calculation of phase equilibrium has been conducted to understand the phase evolution. This work demonstrates the influence of CaO addition on the existence form of vanadium-containing phase in vanadium slag and thus provides the theoretical foundation for the proposed novel de-P & V-extraction process.