From the study of the dephosphorization of liquid iron by the Na
2O-SiO
2-Fe
2O
3 fluxes containing CaO, MnO
2, or Al
2O
3 at 1600°C, the contributions of CaO, MnO, and Al
2O
3 on the phosphorus distribution between liquid iron and Na
2O-MgO-Fe
tO-SiO
2 slaps were derived.
The phosphorus distribution ratio and the equilibrium quotient were expressed by the following equations including the terms of (%CaO), (%MnO), and (%Al
2O
3). (i) log {(%P)/[%P]}=0.092{(%Na
2O)+0.8(%CaO) +0.6(%MnO)-0.9(%Al
2O
3)}+2.5log(%T.Fe) -3.54 (1600°C) (ii) log[(%P
2O
5)/{[%P]
2•(%Fe
tO)
5}]=8.87log{(%Na
2O) +0.1(%MgO)+0.7(%CaO)+0.6(%MnO) -0.9(%Al
2O
3)}-14.94 (1600°C)
The activity coefficients of P
2O
5 and Fe
tO were expressed in terms of the mole fraction of the slag components, and the effects of CaO, MnO, and Al
2O
3 on these activity coefficients were investigated.
The relationship between phosphate capacity and theoretical optical basicity for the Na
2O-based slags containing CaO, MnO, or Al
2O
3 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.
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