From the study of the dephosphorization of liquid iron by the Na₂O-SiO₂-Fe₂O₃ fluxes containing CaO, MnO₂, or Al₂O₃ at 1600°C, the contributions of CaO, MnO, and Al₂O₃ on the phosphorus distribution between liquid iron and Na₂O-MgO-Fe_tO-SiO₂ slaps were derived.
The phosphorus distribution ratio and the equilibrium quotient were expressed by the following equations including the terms of (%CaO), (%MnO), and (%Al₂O₃). (i) log {(%P)/[%P]}=0.092{(%Na₂O)+0.8(%CaO) +0.6(%MnO)-0.9(%Al₂O₃)}+2.5log(%T.Fe) -3.54 (1600°C) (ii) log[(%P₂O₅)/{[%P]²•(%Fe_tO)⁵}]=8.87log{(%Na₂O) +0.1(%MgO)+0.7(%CaO)+0.6(%MnO) -0.9(%Al₂O₃)}-14.94 (1600°C)
The activity coefficients of P₂O₅ and Fe_tO were expressed in terms of the mole fraction of the slag components, and the effects of CaO, MnO, and Al₂O₃ on these activity coefficients were investigated.
The relationship between phosphate capacity and theoretical optical basicity for the Na₂O-based slags containing CaO, MnO, or Al₂O₃ was examined and compared with that for the CaO-based slag. The phosphate capacities of these slags could not be represented uniquely by the theoretical optical basicity. Furthermore, the manganese distribution observed in this experiment was analyzed and compared with that reported for the CaO-based slag.