Effect of Na₂O and B₂O₃ on the Distribution of P₂O₅ between Solid Solution and Liquid Phases Slag

Abstract

With the development of multiphase slag system for hot-metal treatment to achieve better dephosphorization efficiency, it is very important to improve the distribution ratio of P₂O₅ between the solid solution (2CaO·SiO₂–3CaO·P₂O₅) and liquid phase slag. This study was carried out to investigate the effects of Na₂O and B₂O₃ on P₂O₅ distribution ratio and morphologies of corresponding solid solutions in CaO–SiO₂–Fe₂O₃–P₂O₅ slag system. The results indicated that the distribution ratio of P₂O₅ would be improved with the increase of Na₂O content due to the formation of (2CaO·SiO₂–Na₂O·2CaO·P₂O₅) solid solution with a similar morphology as that of reference solid solution (2CaO·SiO₂–3CaO·P₂O₅) in the reference slag. While B₂O₃ plays an opposite role, it would not only reduce the phosphorus distribution ratio, but also change the morphology of its corresponding solid solution due to the formation of complex solid solution (2CaO·SiO₂–Ca_9.93(P_5.84B_0.16O₂₄) (B_0.67O_1.79)). Besides, the effect of cooling rate on the size of the solid solution was also studied. It would provide an instructive way for the design of multiphase slag for hot metal treatment.