Reduction Mechanism of P2O5 in Steel Slag

The high P content in steel slag limits its use in the next heats of steelmaking. Therefore, in this experiment, P2O5-containing slag was reduced by carbon at high temperatures in the flowing N2 and P-containing substances in the off-gas were water-cooled and collected. Both XRD analysis and thermodynamic calculations indicate that the reduction products are mainly composed of P2. The analysis with scanning electron microscope shows that the plate-like 2CaO·SiO2 and 3CaO·SiO2 phases in the steel slag were smashed into granular shape by the gas (P2 and CO) generated during the reduction. The reduction of P2O5 in the P-rich 2CaO·SiO2 and 3CaO·SiO2 phases in the steel slag is insufficient, while that in P-lean RO phase is complete. The single-factor experiments proves that the phosphorus vaporization rate increases with the moderate increase in temperature, FeO content and N2 flow rate, but decreases with the increase in of basicity.