Study On Dephosphorization Process Of High Phosphorus Iron

With the booming development of metallurgical and materials industry, the requirements for the performance of the iron and steel materials are more and more strict, and needing a lower phosphorus content in steel as a result of the influence of phosphorus on it further. The higher dependence on foreign iron ore resource makes the cost very high, because of the higher price and the great demands. Due to the long-term development and utilization of the low-phosphorous iron ore, its reserves declined sharply. On the other hand, a large number of high-phosphorous iron ore are7450million tons, and about14.68%of the total iron ore reserves couldn’t be used economically, especially a plentiful of vanadium-titanium magnetite ore and other high phosphorus iron ore in the southwest of china. The fundamental cause of this phenomenon is the lack of Dephosphorization technology for high-phosphorus molten iron, so it is important, also urgent to investigate this technology.This experiment using Semi-steel of containing3.0wt pct P and3.9wt pct C, and these chemically pure substances including SiO2, CaO, Fe2O3, Na2CO3, CaF2and Al2O3, are the raw materials in this study. The views covered in the present research mainly includes:the effect of different flux in oxidizing Dephosphorization slag on phosphorus partition ratio; the effect of times for feeding slag on phosphorus partition ratio; the kinetics of Dephosphorization for molten iron.Thermodynamic study on Dephosphorization shows that the high alkalinity, strong oxidizing and low temperature are good for deep degree of Dephosphorization for molten iron. CaO is regarded as the most appropriate basic oxide isWhen the flux is CaF2, The optimum process parameters for Dephosphorization has been identified to be the basicity of4, CaF2of6%, Fe2O3of60%, slag and iron ratio of20%, process temperature of1350℃and twice-joining slag. The optimum conditions resulted in a molten iron with a Dephosphorization ratio of92%, phosphorus content of0.024%.When the flux is Al2O3, The optimum process parameters for Dephosphorization has been identified to be the basicity of4, Al2O3of6%, Fe2O3of60%, slag and iron ratio of20%, process temperature of1350℃and twice-joining slag. The optimum conditions resulted in a molten iron with a Dephosphorization ratio of94%, phosphorus content of0.018%. When the flux is Na2O, the results are similar to Al2O3: Dephosphorization ratio of93.66%and phosphorus content of0.019%.When the flux is a mixture of Al2O3and Na2O, The optimum process parameters for Dephosphorization has been identified to be the basicity of4, Al2O3of4%, Na2O of2%, Fe2O3of60%, slag and iron ratio of20%, process temperature of1350℃and twice-joining slag. The optimum conditions resulted in a molten iron with a Dephosphorization ratio of95.66%, phosphorus content of0.013%.The effects of Dephosphorization with twice-joining slag are better than the effects of once-joining.The kinetics of Dephosphorization based on the two-film theory showed that: the relationship between the end phosphorus content and the time some related kinetic parameters (kp=1.69×10-3-2.87x10-3cm2.s, k0=10.0142-0.0202cm·s-1), when the flux iron ratio is0.2, the slag basicity is4,the reaction temperature is1350℃, joining the slag agent of Al2O、Na2O or Al2O3+Na2O twice times. We can get the influence of Dephosphorization reaction rate is mixing transfer of phosphorus between slag and iron, but the mainly diffusion transfer is the diffusion transfer of phosphorus in the molten iron.In the end, choosing the mixture slag of4%Al2O3and2%Na2O in the ternary slag series CaO—FeO—SiO2, and twice-joining slag, it can make the phosphorus content lower than0.018%in the end.