Investigation of the Thermodynamic Properties of Vanadium Oxides in the CaO–VOx–Al2O3–SiO2 Slag at 1873 K
摘要
In order to minimize the vanadium oxide concentration in slag during the basic oxygen furnace process, the mixed-valence states and activity coefficients of vanadium oxides in the CaO–VOx–Al2O3–SiO2 slag were investigated at 1873 K in the present study. At the oxygen partial pressures of 1.94 × 10−11 and 1.90 × 10−7 atm, the mixed-valence states of VO, VO1.5, VO2, and VO2.5 in the slag were measured by using XPS analysis. V2+/V3+ and V3+/V4+ were the major redox pairs at 1.94 × 10−11 atm, and the V3+/V4+ redox pair was major at 1.90 × 10−7 atm. With respect to the increase of slag basicity and oxygen partial pressure, vanadium oxides in the slag showed oxidizing tendency. Simultaneously, the activity coefficients of VO, VO1.5, and VO2 in the slag were measured at the oxygen partial pressure of 7.91 × 10−11 atm. When the slag basicity increased, the activity coefficients of VO and VO1.5 increased, while those of VO2 decreased. With increasing alumina concentration, the activity coefficients of VO and VO1.5 decreased, and those of VO2 increased. Then, the activity coefficients of VOx in the slag were integrated. With respect to the increase of slag basicity, the integrated activity coefficients of VOx in the slag increased in the low slag basicity region. They decreased in the high slag basicity region, showing a downward concave trend. When the alumina concentration increased, the integrated activity coefficients decreased. To minimize the vanadium oxide concentration during the BOF process, it is preferable to maintain the slag basicity near 1 and to decrease the alumina concentration in the slag.