Dephosphorization behavior of reduced iron and the properties of high-P-containing slag

Reduced iron (1.74% P) is produced from oolitic hematite ore by coal-based reduction and magnetic separation. To realize the comprehensive utilization of Fe and P, the dephosphorization behavior of the reduced iron is investigated in the presence of CaO–SiO2–FeO–Al2O3 slag. The P content of the final iron and the P2O5 content of the high-P-containing slag are determined, and the phase composition and P2O5 solubility of the slag are analyzed. The P content can be decreased to 0.2% when the initial slag has a basicity of 3.5 and contains 55% FeO and 6% Al2O3. The phases of the high-P-containing slag are mainly Ca2Al2SiO7, Ca2SiO4, Ca5(PO4)2SiO4, and FeO, and P exists in the form of Ca5(PO4)2SiO4. Excessively high basicity or low content of FeO and Al2O3 results in free CaO, which affects the dephosphorization results. The change rule of the intensity of the Ca5(PO4)2SiO4 diffraction peak agrees well with the dephosphorization indexes, which further verify the accuracy of the dephosphorization experiments. Moreover, the P2O5 content and P2O5 solubility of the high-P-containing slag reached as high as 14.41 and 94.54%, respectively, indicating that it can be used as a phosphate fertilizer.