Study On Carbothermal Reduction Of FeNb₂O₆ In Microwave Field

In recent years,China has developed many sets of smelting processes for producing ferroniobium from the niobium resources in Bayan Obo ore,but there are many problems such as high energy consumption,high cost and environmental pollution,which lead to the insufficient utilization of niobium resources.Niobium resources in Bayan Obo ore mainly occur in the form of niobite,and the main component of niobite is FeNb₂O₆.Therefore,the study of the reduction characteristics of FeNb₂O₆is of great significance for the efficient utilization of niobium resources in Bayan Obo ore.In this paper,microwave heating is combined with the reduction characteristics of FeNb₂O₆ in niobite,which provides a theoretical basis for microwave carbothermal reduction of niobium concentrate in Bayan Obo ore,In order to explore the feasibility of microwave carbothermal reduction of niobite,the synthesis of FeNb₂O₆ by pure reagents Fe powder,Nb₂O₅ and Fe₂O₃in microwave field was studied in this paper,and the characteristics of FeNb₂O₆ temperature rise curve in microwave field were investigated.The results show that FeNb₂O₆ can be prepared by mixing Nb₂O_5,Fe₂O₃ and Fe in the molar ratio of 3?1?1,heating up to 1050?,holding for 6h,and injecting argon as a protective gas throughout the process.This method can produce FeNb₂O₆ which meets the experimental requirements.In the case of microwave heating,FeNb₂O₆ has a good heating curve and heating characteristics in the microwave field.Under the condition that the mass of FeNb₂O₆ remains the same,the heating rate of FeNb₂O₆ can be improved by increasing the power appropriately.The effects of temperature,particle size,carbon content and power on the reduction reaction were investigated.XRD,SEM-EDS and other analytical methods were used to characterize the process of microwave carbothermal reduction of FeNb₂O₆.The results show that the weight loss rate of the reduction reaction can be significantly improved by increasing the temperature,particle size,carbon content and power.Under the same holding time and temperature,the reduction effect of FeNb₂O₆ in microwave field is better than that of conventional heating;Thermodynamic reduction steps of FeNb₂O₆ under microwave heating are divided into two stages.In the first stage,when the temperature is raised to 1100?,FeNb₂O₆ reacts with graphite powder to produce Nb O₂ Nb C and Fe elemental reduction products at the same time.As the temperature rises,it enters the second stage,in which Nb O₂ gradually transforms into Nb C.When the temperature is raised to 1300?,the main reduction products are Nb C and Fe,and the microstructure of the reduction products Nb C and Nb O₂ is bright white block shape and dark gray oval shape.In this paper,the kinetics of microwave heating carbothermal reduction of FeNb₂O₆was studied.The influence factors of microwave carbothermal reduction reaction rate were explored and the macroscopic kinetics equation was established.The results show that the kinetic reaction model of FeNb₂O₆ carbothermal reduction in microwave field is consistent with the shrinkage sphere model:G(A)=3[1-(1-?)^(1/3)]=kt.The Arrhenius relation is lnk=10.55-19773.7/T,and the apparent activation energy is 164.4k J/mol.