Kinetics Of Gasification And Dephosphorization Of Apatite Reduced By SiC

Exploitation and utilization of domestic medium and high phosphorus iron ore is an effective measure to reduce iron ore import and production cost.The entry of medium and high phosphorus molten iron into the converter will not only increase the burden of dephosphorization of steelmaking,but also cause a vicious cycle of phosphorus in the whole steel manufacturing process.It is of great significance to reduce the harm of phosphorus in the whole process of iron and steel manufacturing if dephosphorization agent can be added in the sintering process to transform phosphorus into phosphorus containing gas and remove it by gasification.In this thesis,SiC was used as reducing agent to study the effect of auxiliary dephosphorization agent and reduction temperature on the kinetics of apatite gasification and dephosphorization,and the activation energy,reaction mechanism function and limiting link of apatite gasification and dephosphorization reaction were determined.The results provided a theoretical basis for the realization of gasification and dephosphorization in sintering process.In this thesis,the thermodynamic conditions of SiC apatite reduction with and without auxiliary dephosphorization agents were explored by the method of Fact Sage thermodynamic simulation and experimental study.The results show that when the roasting temperature is 1300℃and no auxiliary dephosphorization agent is added,the gasification dephosphorization rate is only 17.8%.Na₂CO₃,Si O₂ and Al₂O₃ were selected as auxiliary dephosphorization agents,and the kinetic conditions of the dephosphorization reaction were improved by generating Nephelite Na Al Si O₄ and opening gangue to generate liquid phase.The highest dephosphorization rate of 86.5%could be obtained for the system with Na₂CO₃content of 8wt%.In order to explore the kinetic mechanism of SiC reduction of apatite,on the basis of thermodynamic study,SiC,Ca₃（PO₄）₂,Na₂CO₃,Si O₂,Al₂O₃ pure chemical reagents were used to prepare sample 1#,and the reaction data were obtained through TG-DSC experiment for kinetic analysis.As the weight loss of sample 1#includes the volatilization of CO₂ and phosphate-containing gases,which will affect the accuracy of kinetic analysis of gasification and dephosphorization.In this thesis,Na₂CO₃,Al₂O₃ and Si O₂ reagents are proported,mixed and pressed according to stoichiometric relationship to prepare Na Al Si O₄ sample.Then,SiC,Ca₃（PO₄）₂ and Na Al Si O₄ were used to prepare sample 2,and TG-DSC kinetic experiment was conducted.The heating rates were controlled at 5℃/min,7.5℃/min,10℃/min,12.5℃/min and 15℃/min,respectively.The activation energy of dephosphorization reaction E_a=392.84k J/mol,ln A(s^-1)=35.98,the mechanism function of the reaction is g（α）=（1-α）^-1-1,and the limiting link is the interfacial chemical reaction.