Effect of CaCl2 Addition on Phosphorus Distribution in CaO-SiO2-FeOx-P2O5 Converter Slags

Laboratory experiments are carried out to investigate the effect of CaCl2 addition on the phosphorus distribution in CaO-SiO2-FeOx-P2O5 converter slags. Some slags with different slag basicity [R = w(CaO)/w(SiO2)] and P2O5 contents are melted at steelmaking temperature and further analyzed by scanning electron microscope (SEM). It is found that the nature of liquid is generally seen in the slags with low basicity (R = 1.0). With the increase in slag basicity and CaCl2 content, the proportion of 2CaO center dot SiO2-3CaO center dot P2O5 (C2S-C3P) solid solution in the slags climbs in general, but the P content in C2S-C3P is degraded. A new P-rich phase Ca5Cl(PO4)(3) (C5P3Cl) with a fixed P content can be observed in the high-basicity slags (R >= 1.5), when the contents of CaCl2 and P2O5 are sufficiently high. Higher contents of both CaCl2 and P2O5 can further promote the proportion of C5P3Cl. The addition of CaCl2 is unfavorable for the recycling of P from CaCl2-added slags, but its effect is still limited in case of a small amount.

Automated summary

The addition of CaCl2 and increasing slag basicity can enhance the proportion of C2S-C3P solid solution in the slag, but decrease the phosphorus content in C2S-C3P. A new P-rich phase Ca5Cl(PO4)3 (C5P3Cl) can be observed in high-basicity slags, while higher contents of CaCl2 and P2O5 further promote the proportion of C5P3Cl.