LAUSR

The phosphorus content in hot metal will increase in future, because iron ores are steadily deteriorating in quality. Na2O addition to slag is considered an effective method for increasing the efficiency of dephosphorization. In addition, Na2O modification also facilitates phosphorus recovery from dephosphorization slag with high P2O5 content by selective leaching. Therefore, it is necessary to investigate the distribution ratios of P2O5 and Na2O between solid solution and liquid phase in the CaO-SiO2-Fe2O3-P2O5-Na2O slag system. A linear relationship was found between the distribution ratio of P2O5 and the Na2O content in slag, and was independent of P2O5 content. When the Na2O content was high, the Na2O content in the solid solution approached saturation and a new 2CaO·SiO2-2CaO·Na2O·P2O5 solid solution formed. The addition of Na2O decreased the P2O5 content in solid solution, while it increased the mass fraction of solid solution in slag. The distribution ratio of P2O5 increased with increase in the Fe2O3 content and basicity of slag. An increase in P2O5 content in slag results in an increase in the activity coefficient of P2O5 both in the liquid phase and in the solid solution.