Direct Alloying of Molten Steel with Vanadium Slag: Self-reduction of Vanadium Slag Briquette with Graphite Powder and Hybrid Reductant of Graphite Powder-Aluminum Dross

In this work, a direct alloying technology of molten steel by the self-reduction briquette composed of vanadium slag and graphite powder was proposed. The reduction behavior of vanadium slag briquette was thermodynamically and experimentally investigated, and relevant reaction mechanisms were discussed. The results show that the increases in C/O molar ratio and reduction temperature would promote the further reduction of vanadium slag. The reduction degrees of FeO, Cr 2 O 3 , MnO, and V 2 O 5 increased from 85.24, 47.98, 9.05, and 75.70 pct to 92.10, 64.53, 42.52, and 79.62 pct, respectively, with increasing temperature from 1500 °C to 1600 °C. As the C/O molar ratio increased from 0.8 to 1.2, the reduction degrees of FeO, Cr 2 O 3 , MnO, and V 2 O 5 sharply increased from 86.56, 18.38, 43.38, and 50.91 pct to 92.10, 64.53, 50.02, and 79.62 pct, respectively, and then slowly increased or nearly remained constant. The briquette basicity exhibits an obvious positive influence on the reduction of vanadium slag to a certain extent, and the reduction degrees of FeO, Cr 2 O 3 , MnO, and V 2 O 5 increase from 92.10, 64.53, 42.50, and 76.14 pct to 97.21, 81.04, 75.64, and 88.50 pct with increasing the basicity from 0 to 0.5, leading to a significant decrease in the reduction degree of vanadium slag when the basicity increased from 0.5 to 1.5. For the hybrid reductant of aluminum dross and graphite powder, when the proportion of aluminum dross exceeds 52 pct, a considerable amount of solid compound (magnesia-alumina spinel) would be precipitated from liquid slag, which strongly affects the thermophysical properties of molten slag. Under the optimal conditions, C/O molar ratio of 1.2, reduction temperature of 1600 °C, and briquette basicity of 0.5, the reduction degrees of FeO, Cr 2 O 3 , V 2 O 5 , and MnO could reach the maximum of 97.21, 81.04, 88.50, and 75.64 pct, respectively, and a crude Fe–V alloy mixture containing 23.40 pct V could be obtained.