Determination of Vanadium Solubility in the Al₂O₃-CaO(30 Mass Pct)-SiO₂ and Al₂O₃-CaO(35 Mass Pct)-SiO₂ System

The solubility of vanadium oxide in the Al₂O₃-CaO(30 mass pct)-SiO₂ system and Al₂O₃-CaO(35 mass pct)-SiO₂ system was determined experimentally at 1873 K (1600 °C) and at a fixed oxygen potential of 9.37 × 10⁻¹¹ bar. EPMA microanalyses were employed to identify the phases and their compositions in the quenched samples. The solubility of vanadium oxide in the liquid phase was found to decrease with increasing CaO content in the liquid. The vanadium oxide solubility was especially low when both CaO and Al₂O₃ contents were high in the liquid phase. The maximum solubility of vanadium oxide was up to 7 mass pct (as V). Two solid phases were found, a solid solution of Al₂O₃ and vanadium oxide and an Al₂O₃-rich solid phase with 16.7 mass pct V₂O₃. The Al₂O₃ solubility in the solid solution was found to increase with increasing Al₂O₃ content in the liquid, the impact of the CaO content in the liquid on the solubility of Al₂O₃ in V₂O₃ was found to be small. The Al₂O₃-rich solid phase was identified as the mineral hibonite with fractionation of V into the crystal structure.