Influence of desulfurization slag containing oxides of vanadium and titanium on semi-steel pre-desulfurization

The desulfurization and resulfurization of slag containing oxides of vanadium and titanium (CaO–SiO₂–MgO–Al₂O₃–V₂O₃–TiO₂–FeO) in the pretreatment of semi-steel desulfurization at 1623 K were investigated. Based on the ionic structure theory of slag, it could be concluded that V₂O₃ and TiO₂ combined with (O^2–) to form complex anions including \({\mathrm{VO}}_{3}^{3-}\), \({\text{Ti}}{\text{O}}_{4}^{{4}-},\) etc., which reduced the activity of (O^2–) and decreased the sulfur partition ratio (L_S). And FeO enhanced the activity of [O] at the slag–metal interface, which decreased the desulfurization capacity of the slag. Compared to the binary basicity, the presented basicity expression containing V₂O₃ and TiO₂ described the relationship between L_S and basicity more accurately. Considering the problems of dilute slag, a large amount of residual slag and much resulfurization in the slagging-off process after pretreatment, the effect of CaO + C-based slag modifier on the resulfurization, melting point and viscosity of the desulfurization slag was investigated. It was proposed that adding 5%–10% of the slag modifier to the desulfurization slag after desulfurization decreased the resulfurization effectively. And the added modifier adjusted the slag viscosity well, which helped to reduce iron loss and residual slag.