Phosphorus Gasification during the Carbothermic Reduction of Medium Phosphorus Magnetite Ore by Adding Na₂CO₃

抄録

For medium phosphorus magnetite ore, effects of carbon mixing ratio, reduction temperature and basicity on phosphorous gasification and iron metallization during carbothermic reduction were investigated using XRD, SEM-EDS and FactSage software, as well as the existing status of Fe and P in the Bayan Obo raw ore and the appropriate addition of Na₂CO₃. The obtained results show that magnetite grains and phosphorous containing minerals (apatite and monazite) are finely disseminated and closely associated with gangue minerals of carbonate, silicate and aluminosilicate. Moreover, adding 5 mass% Na₂CO₃ is capable of breaking the abovementioned gangue mineral weaved structure and promoting the reduction of phosphorous ores. Furthermore, the optimum condition for phosphorus gasification is carried out at reduction temperature of 1050°C, with the carbon mixing ratio and basicity of 15 mass% and 0.5, respectively. The corresponding dephosphorization and iron metallization are 31.61% and 96.35%, respectively. Both of the increased carbon mixing ratio and reduction temperature lead that the reduced phosphorous gas tends to migrate in the metallic iron phase. Besides, thermodynamic analysis demonstrates that the presence of SiO₂ not only promotes the dephosphorization but reacts with FeO resulting in the formation of fayalite, which prevents FeO from deeper reduction to metallic iron. Meanwhile, the combination of CaO, CaF₂ and SiO₂ produces cuspidine and decreases the quantity of liquid phase, consequently increasing the dephosphorization more or less.