Basic Research On Heterogeneous Dephosphorization Of Converter Slag

In order to improve the dephosphorization ability of converter slag and reduce the discharge of waste slag,a new heterogeneous dephosphorization technology based on the coexistence of solid-liquid phase has been proposed by metallurgical scholars in recent years.This technology is mainly to enrich phosphorus in liquid slag in solid phase to form 2CaO·SiO₂-3CaO·P₂O₅ solid solution,so as to maintain high dephosphorization capacity of liquid slag and reduce lime consumption and steel slag emission.It has been regarded as one of the important means to realize less slag smelting in converter in the future.However,the basic researches on heterogeneous slag are mostly focused on CaO-SiO₂-FeO_x-P₂O₅ slag system,but the actual converter slag also contains 10%～15%MgO,MnO and other compounds.The mechanism of these compounds in the formation process of 2CaO·SiO₂-3CaO·P₂O₅ solid solution is not clear,which leads to the imperfect theory of heterogeneous slag dephosphorization technology.Therefore,in this paper,the phase equilibrium of CaO-SiO₂-P₂O₅-FeO-MgO（MnO）slag system was studied by using the thermodynamic software Factage7.2,and the effects of four factors,such as MgO content,temperature,oxygen partial pressure and P₂O₅ content,on the primary crystal region and liquid region of phosphorus containing solid solution were analyzed,The composition points near the liquidus of CaO-SiO₂-P₂O₅（5mass%）-FeO-MgO（4mass%）system at 1773 K were verified by high temperature equilibrium experiment,and the experimental results were consistent with the thermodynamic software simulation results;After that,the effect of MgO and MnO addition on the formation of phosphorus containing solid solution in CaO-SiO₂-P₂O₅-FeO-MgO（MnO）slag system was studied by high temperature experiment,and the slag activity model of CaO-SiO₂-P₂O₅-FeO-MgO（MnO）slag system was established based on the theory of ion molecule coexistence,According to the calculation results,the curve of the activity of main products with the content of magnesium oxide（manganese oxide）was drawn;Finally,the kinetics of the formation process of CaO-SiO₂-P₂O₅-FeO-MgO（4mass%）phosphorous solid solution at 1400℃was studied.Firstly,the restrictive links of the formation of 2CaO·SiO₂-3CaO·P₂O₅solid solution in CaO-SiO₂-P₂O₅-FeO-MgO（MnO）slag system were analyzed,and the diffusion and mass transfer coefficients of phosphorus were obtained.Finally,the kinetic equation of the formation of phosphorus containing solid solution in CaO-SiO₂-P₂O₅-FeO-MgO（MnO）slag system was derived and solved.The formation of phosphorus containing solid solution in CaO-SiO₂-P₂O₅-FeO-MgO（MnO）slag system was studied by experiments and software simulation in this paper.On the one hand,it can provide a reference for the improvement and development of heterogeneous slag dephosphorization theory.The relevant models and theoretical knowledge obtained from thermodynamics and kinetics can be used as the basic research of heterogeneous slag dephosphorization.On the other hand,the experimental results obtained from the research can provide reference for relevant enterprises to control the amount of CaO used in the dephosphorization process of converter,reduce the production cost and improve the dephosphorization efficiency.At the same time,it can greatly reduce the generation and accumulation of steel slag,which not only meets the needs of modern metallurgical process with less slag smelting,but also has a positive significance for environmental protection...