2017 Volume 57 Issue 12 Pages 2131-2140
A process of H2 reduction followed by the slag/metal separation for the utilization of high-phosphorus oolitic hematite has been proposed. The H2 reduction was conducted at 1073 K in a horizontal rotary electric resistance furnace, which significantly promotes the metallization ratio of reduced ore fines. Thermodynamic calculation of H2 reduction for apatite and XRD analysis of ore samples before and after H2 reduction confirmed that gangue minerals containing P, Al and Si in oolitic hematite hardly be reduced. The slag/metal separation was carried out in an induction furnace at 1873 K. After separation, metal block and slag were obtained, and most of gangue minerals combined with lime and calcium fluoride formed the slag, but some impurities remained in the form of slag inclusions in the metal. Based on the SEM-EDS examination of P-containing slag inclusions and ternary phase diagram of Fe–P–O system computed by FactSageTM 6.4 at 1873 K, phosphorus in the metal product can be precipitated as iron phosphate or iron phosphide, and the evolution of P-containing slag inclusions is Fe2P(l) + Fe3(PO4)2(l)→Fe3(PO4)2(l)→FeO(l) along with the increase of slag basicity, melt separation time and additive CaF2. A satisfactory metal product with 99.80 wt% T. Fe, 0.027 wt% P, 0.0013 wt% Si, 0.004 wt% Al and 0.05 wt% O was achieved by the slag/metal separation under the optimum conditions: slag basicity of 2, melt separation time of 10 min, CaF2 mixing ratio of 4 wt% and metallization ratio of reduced fines of 85.9%.