Influence of Al 2 O 3 modification on phosphorus enrichment in high phosphorus slag

Abstract

The phosphorus enrichment in solid phases during solidification of converter slag was studied by the modification with Al₂O₃. The mineral phase of the original and modified high phosphorus slags were analysed by SEM + EDS and XRD. The mechanism of Al₂O₃ modification was discussed based on thermodynamic modelling using the FactSage package. The results show that Ca₃(PO₄)₂ and Ca₂SiO₄ precipitated first and formed the n2CaO·SiO₂–3CaO·P₂O₅ (nC₂S–C₃P) solid solution. The content of Al₂O₃ has no significant impact on the initial precipitation amount of nC₂S–C₃P solid solution. High phosphorus solid solution (n′C₂S–C₃P) was generated by the constant reaction between nC₂S–C₃P (n′<n) solid solution and Al₂O₃. The concentration of phosphoric pentoxide in phosphorus-rich phase increased to 19.0%, 20.7% and 35.5% with the addition of 5.0%, 8.0% and 11.0% Al₂O₃, respectively. The initially precipitated solid solution nC₂S–C₃P reduced and even disappeared with the increase of the Al₂O₃ content. The results demonstrated that the addition of Al₂O₃ has a positive influence on the phosphorus enrichment.