A novel method for CO2 injection direct smelting vanadium steel: Dephosphorization and vanadium retention

Abstract A novel method for CO2 injection direct smelting vanadium steel (CIDSVS) is proposed. Achieving selective oxidation of phosphorus is essential for the applicability of the suggested process. Under the guidance of thermodynamics, the mechanisms of CO2 injection dephosphorization and vanadium retention were investigated with CO2 flow rate and dephosphorization slag composition as experimental variables. The results indicate that CO2 as an oxygen source can remove 73.8% of phosphorus, while the oxidation rate of vanadium is 17.5%. The dephosphorization process can be divided into two stages: FeO- and CO2-dominated experimental processes. In the initial stage of slag feeding, [V] and [P] undergo fast oxidation, and the oxidation amount is positively correlated with the initial FeO content. The high basicity (CaO/SiO2 ratio) reduces the activity of V2O3 in the slag and promotes the oxidation of [V]. Under the experimental conditions of 1,400°C, the optimal conditions were determined to be a CO2 flow rate of 1.5 mL·g−1·min−1, a FeO content of 40%, and a basicity B of 2.5. Following the CIDSVS steelmaking operation, 80% of the vanadium is retained, and the impurity elements fulfill the specifications for steel. This method enhances vanadium utilization and is environmentally friendly.