CaO–SiO₂–Fe₂O₃系スラグにおけるP₂O₅のダイカルシウムシリケートと液相スラグ間の固液分配

抄録

In most cases, the slag used in hot metal dephosphorization exists in a solid–liquid coexisting state, containing dicalcium silicate as the solid phase. It is known that dicalcium silicate (C₂S) and tricalcium phosphate (C₃P) form a solid solution with a wide range of composition. A large distribution ratio of P₂O₅ between a solid solution and liquid slag phases has also been reported. To clarify the maximum concentration of P₂O₅ in this solid solution phase, the measurement of the distribution ratio of P₂O₅ in slag containing a high concentration of P₂O₅ is performed in this research, and the influence of MgO and MnO on the distribution ratio is investigated. CaO–SiO₂–Fe₂O₃ slag containing a maximum of 18% P₂O₅ is melted at 1873K and cooled to 1673K at a cooling rate of 10K/min. During cooling, the solid solution of dicalcium silicate and tricalcium phosphate precipitates from the liquid slag. A good relation is found between the distribution ratio of P₂O₅ and (T.Fe); this relation is independent of slag composition and P₂O₅ content. The concentration of P₂O₅ in the solid solution is strongly influenced by the mixing ratio of P₂O₅ and the slag composition. It is clarified that if the slag composition is controlled adequately, the concentration of P₂O₅ in the C₂S–C₃P solid solution can be increased up to 100% of C₃P. The change in the distribution ratio with the addition of MgO and MnO is not large.