Dephosphorization of Liquid Iron by the Slag of Na₂O-SiO₂ System

Abstract

As one of fundamental research on the refining of molten iron by sodium carbonate, the experiments were made of the dephosphorization of liquid iron by the flux added Fe₂O₃ or sodium carbonate (Na₂CO₃) to sodium silicate having various ratio of Na₂O and SiO₂ at temperature of 1 550, 1 600, and 1 650°C.
The results of these experiments indicated clearly the effects of addition of Fe₂O₃, slag basicity, temperature, and initial phosphorus content in liquid iron on the dephosphorization by the slag of Na₂O-SiO₂ system, and investigation also showed the refining actions of Na₂CO₃ in the slag.
Furthermore, a discussion was made on the equilibrium relationship of dephosphorization reaction by the slag of Na₂O-SiO₂ system, and a following expression was obtained;
2P + 5(FeO) = (P₂O₅) + 5Fe log k_p = log (%P₂O₅)/[%P]²(%T.FeO)⁵=8.67 log(%Na₂O)-14.55(1 600°C)
From the comparison of this expression with that of the slag of CaO system reported previously, it became clear that the dephosphorization by the slag of Na₂O system is more effective than by that of CaO system.