The phosphorus distribution ratios between CaO-MgO_sat.-Fe_tO-SiO₂-P₂O₅(≤3wt%)-MnO(2-5wt%) or CaO-MgO_sat.-Fe_tO-SiO₂-P₂O₅(4-5wt%) Slags and liquid iron have been obtained in the temperature range from 1550 to 1650°C. The dephosphorization quotients can be expressed by the following three different equations.
(i) log (P₂O₅)/([P]²(Fe_tO)⁵)=0.145[(%CaO)+0.3(%MgO) -0.5(%P₂O₅)+0.6(%MnO)]+22810/T-20.506
(ii) log (P₂O₅)/([P]²(Fe_tO)⁵)=7.87 log[(%CaO) +0.3(%MgO)-0.05(%Fe_tO)-0.5(%P₂O₅) +0.6(%MnO)]+22240/T-27.124
(iii) log (P)/([P](T.Fe)^5/2)=0.0720[(%CaO)+0.3(%MgO) +0.6(%P₂O₅)+0.6(%MnO)]+11570/T-10.520
The activity coefficient of P₂O₅ by Turkdogan and Pearson's treatment can be expressed as follows: log γP₂O₅=-1.02(23N_CaO+17N_MgO+8N_FetO -26N_P2O5+13N_MnO)-22990/T+9.490
In the plot of logarithms of activity coefficient of Fe_tO against mole fraction of SiO₂, the values for log γFe_tO tend to increase with increase of the P₂O₅ content and with the addition of MnO in the range of N_SiO2<0.1.