Study On The Kinetics Of Phosphorus Gasification In Pre-reduction Sintering Process Of Bayan Obo Iron Concentrate

In recent years,China’s stable and rapid economic development has led to the recovery of China’s iron and steel enterprises.At the same time,the consumption of iron ore is also increasing.However,China’s high-quality iron ore resources are less,so that it is highly dependent on foreign iron ore imports.In order to make a better comprehensive use of China’s rich medium and high phosphorus iron ore resources,this paper studies the gasification and removal of phosphorus in the pre reduction sintering process of Bayan Obo iron concentrate.The purpose is to accelerate the reaction rate of pre reduction sintering gasification dephosphorization,reduce the residence time of the reduced phosphorus gas in the pre reduction sintering process,prevent the phosphorus gas from entering the metal iron phase again,and remove more phosphorus elements from the Bayan Obo iron concentrate.In this experiment,TG-DSC curve was obtained,activation energy of gasification dephosphorization reaction was calculated,reaction mechanism function was determined,and mechanism of gasification dephosphorization was revealed.The pre reduction sintering process is operated by negative pressure（0.9atm）,not under1atm（standard state）,so the dephosphorization reaction under standard and non-standard state is calculated and analyzed by factsage thermodynamics software.The results show that the addition of Na₂CO₃ pure reagent,change of alkalinity and negative pressure operation can improve the gasification dephosphorization in the pre reduction sintering process,and the theoretical calculation results are as follows The results showed that the carbothermal reduction temperature of apatite decreased from 1750K to 1054K.In order to find out the kinetic mechanism of the dephosphorization reaction,TG and DSC data were obtained through experiments.The dephosphorization rate of iron concentrate is 5℃/min,10℃/min,15℃/min and 20℃/min.The average activation energy of the reaction is 418.89kJ/mol,the pre exponential factor lnA(s^-1)=36.13,the reaction mechanism function is:g（α）=1-（1-α）^1/2,the limiting link is the two-dimensional cylinder boundary reaction;2 The temperature rising rate of dephosphorization reaction of calcium acid reagent is 5℃/min,7.5℃/min,10℃/min,12.5℃/min and 15℃/min.The average activation energy of reaction is 167.58kJ/mol,lnA(s^-1)=10.23,the reaction mechanism function is:g（α）=1-（1-α）^1/3,the limiting link is three-dimensional shrinkage Sphere boundary reaction.The kinetic model of gasification and dephosphorization in pre reduction sintering was established.The model considered that the gasification and dephosphorization was a gas-solid reaction.According to the established model,the reaction mechanism function is calculated and fitted,which conforms to the phase boundary equation,and the boundary phase reaction is the limiting link.During the preparation of prereduced sinter,the kinetic conditions of gasification dephosphorization reaction can be improved by the following operations:（1）pre reduction sintering process with high carbon content of about 20%,can increase the reducibility of sinter and make more phosphorus minerals be reduced;（2）adding appropriate amount of SiO₂ and Na₂CO₃ dephosphorization agent can reduce the initial reduction temperature of apatite and make dephosphorization reaction easier to occur;（3）improving sintering The permeability of the coalescence layer（increase the porosity of the layer,control the width of the combustion zone,etc.）can accelerate the adsorption and desorption accompanied by the chemical reaction at the interface,which is conducive to the rapid removal of phosphorus gas and prevent it from entering the reduced metal iron phase again.