The Effect of Na2O and K2O on the Partition Ratio of Phosphorus between CaO-SiO2-FetO-P2O5 Slag and Carbon-Saturated Iron

In the present study, the experiments for the phosphorus equilibrium partition between CaO-SiO2-FetO-P2O5 slags with Na2O or K2O addition and solid pure iron foil were performed at 1573, 1623, and 1673K, respectively. The experimental results showed that both Na2O and K2O addition can enhance the dephosphorization ability of CaO-SiO2-FetO-P2O5 based slags and they have similar dephosphorization ability under the same temperature and main slag composition. The phosphorous partition ratio between slag and carbon-saturated hot metal increased with the increase of basicity with a peak value in the range of R around 1.3-1.5. The phosphorous partition ratio decreased with the increasing of (w(CaO)+w(Na2O))/w(FetO) value in slags. The dephosphorization ability of CaO-SiO2-FetO-P2O5 based slags was relatively higher when the (w(CaO)+w(Na2O))/w(FetO) values fell in the range of 0.5-0.8. The phosphorous partition ratio decreased with the temperature increase. The linear relationships between the logarithm phosphorous partition ratio and the reciprocal of temperature were obtained for CaO-SiO2-FetO-P2O5 based slags with Na2O. The information provides by present study would be useful for optimization of dephosphorization in hot metal pretreatment.