Rate of Dephosphorization of Liquid Iron by Solid Lime

Abstract

Dephosphorization of liquid iron by solid lime was studied by melting metals containing phosphorus in lime crucibles under gas flows of H₂O-H₂-Ar, H₂O-Ar and O₂-Ar. The rate of reaction was determined by the chemical analysis of samples taken from the bath at appropriate intervals. The results obtained were as follows:
i) Dephosphorization reaction proceeded at nearly constant rate.
ii) The rate of dephosphorization increased with increase of the oxygen potential of gases. Effect of the temperature on the reaction rate was weak.
iii) At low PH₂o/PH₂ ratio of gas mixtures phosphorus and oxygen contents changed during a run along the equilibrium with solid tetracalciumphosphate and calcium oxide, but at higher ratio those were higher than equilibrium values.
iv) Under present experimental condition, the rate of dephosphorization was determined by the rate of oxygen supply from gas to the liquid iron.
v) In the case of metals containing carbon, decarburization preferentially occurred prior to dephosphorization due to the differeaces of the reaction surface and of the affinity to oxygen.