Influence Mechanism of Ce₂O₃ on Dephosphorization Process using CaO–Al₂O₃–SiO₂–MnO Based Slag

Abstract

To improve the dephosphorization capacity of CaO–Al₂O₃–SiO₂–MnO based ferromanganese slag, this work attempts to introduce Ce₂O₃ as a strong phosphorus fixative into the slag, and the influence mechanism of Ce₂O₃ on the dephosphorization process is investigated by thermodynamic analysis, structural analysis, melting temperature, and viscosity tests. The results show that after adding 20 mass% Ce₂O₃ into the slag, Ce₂O₃ can release the O²⁻ and promote the P-O⁰ bond to P-O⁻ bond transformation, thus improving the phosphorus fixation capacity of melted slag. Also, the phosphorus enrichment phases are nCa₂SiO₃–Ca₃P₂O₈ solid solution and CePO₄ phase in Ce₂O₃-containing slow cooling slag. Furthermore, the melting temperature of slag with 0–20 mass% Ce₂O₃ addition is always about 1623 K, but increases obviously when the addition of Ce₂O₃ exceeds 20 mass%. Also, adding appropriate Ce₂O₃ content into the CaO–Al₂O₃–SiO₂–MnO based slag can decrease the viscosity of slag, and the viscosity can remain relatively low with adding 15 mass%–25 mass% Ce₂O₃. In conclusion, adding appropriate Ce₂O₃ content into the CaO–Al₂O₃–SiO₂–MnO based slag can improve the phosphorus fixation capacity of slag and ameliorate the fluidity of slag, and consequently, it is conducive to remove phosphorus from ferromanganese. Finally, the high-temperature ferromanganese dephosphorization experiments were carried out, and the results show that after adding 20 mass% Ce₂O₃ into the slag, the lowest [P] content decreases from 0.31% to 0.25%, and the dephosphorization rate increases from 31.1% to 45.6%. The above results not only verify that the feasibility of Ce₂O₃ as a strong phosphorus fixative used in the ferromanganese dephosphorization slag, but also provide the theoretical guidance for optimizing the composition of Ce₂O₃-containing dephosphorization slag.