Dephosphorization of Hot Metal Containing High Phosphorus Using F-free CaO–SiO2–Al2O3–Fe2O3 Slag

With the extensive usage of domestic low-grade iron ore with high phosphorus, abundant high (> 0.35%) phosphorus hot metal generates in China. To solve the dephosphorization issue of high-P hot metal under the premise of avoiding the environmental problem caused by CaF 2 flux agent, a type of F-free CaO–SiO 2 –Al 2 O 3 –Fe 2 O 3 slag was designed for the dephosphorization of high-P hot metal and systematically tested and analyzed combined with FactSage software under 1400 °C in this paper. The results show that it is an effective approach to remove phosphorus from hot metal-containing high phosphorus using F-free CaO–SiO 2 –Al 2 O 3 –Fe 2 O 3 slag. The major driving force for this dephosphorization comes from the precipitation of Ca 2 SiO 4 · n Ca 3 (PO 4 ) 2 (C2S-C3P) phase which lowers the activity of phosphorus in liquid slag by providing a site to stabilize phosphorus in slag. The increase of basicity enhances the dephosphorization process by promoting the precipitation of the P-rich C2S-C3P phase. The Fe 2 O 3 in slag favors the removal of phosphorus from hot metal-containing high phosphorus using CaO–SiO 2 –Al 2 O 3 –Fe 2 O 3 slag by improving the oxidability of slag. The Al 2 O 3 in slag will compete with P 2 O 5 to combine with CaO and SiO 2 , which inhibits the formation of C2S-C3P and thus weakens the dephosphorization ability of slag.