Influence of Al2O3 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.