Thermal decomposition mechanism and kinetics of bastnaesite in suspension roasting process:A comparative study in N_(2) and air atmospheres  

作　　者：Wenbo Li Jijia Chen Shaokai Cheng Junyan Sun Xiaolong Zhang 

机构地区：[1]School of Resources and Civil Engineering,Northeastern University,Shenyang,110819,China [2]National-Local Joint Engineering Research Center of High-Efficient Exploitation Technology for Refractory Iron Ore Resources,Shenyang,110819,China

出　　处：《Journal of Rare Earths》2024年第9期1809-1816,I0006,共9页稀土学报（英文版）

基　　金：Project supported by the National Key R&D Program of China (2022YFC2905800);National Natural Science Foundation of China(52174242)。

摘　　要：To investigate the thermal decomposition behavior and reaction kinetics of bastnaesite in suspension roasting,the gas and solid products of bastnaesite roasted in N2 and air atmospheres were examined using a gas analyzer,X-ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive spectrometry(EDS).Subsequently,the kinetic parameters of bastnaesite in the suspension roasting process were derived and calculated using the isothermal method.The results show that the decomposition product of bastnaesite in N_(2) is CeOF.However,once the roasting temperature exceeds 600℃,CO is generated in addition to CO_(2),and all the XRD diffraction peaks of CeOF are shifted to the right,indicating that CO_(2) can oxidize CeOF and lead to the transformation of Ce(Ⅲ) into Ce(Ⅳ).When roasted in air,the decomposition product CeOF can be completely converted to CeF3 and Ce_(7)O_(12) as it easily oxidizes.Additionally,the reaction rate of bastnaesite in air is higher than that of N_(2),and the starting reaction temperature is lower than that of N_(2).A large number of irregular cracks and holes appear on the surface of solid-phase products following suspension roasting,which are due to the thermal decomposition of bastnaesite that produces CO_(2) as well as the reconstruction of the lattice of the solid-phase products.The reaction kinetic model of bastnaesite roasted in N_(2)(temperature range 600-750℃) and air(temperatu re range 500-575℃) confo rms to the A_(3/2) model with the mechanism function G(α)=-ln(1-α)^(2/3),and the reaction activation energy is 59.78 kj/mol and lnA is 1.65 s^(-1) in N_(2) atmosphere.In air,the reaction activation energy is 100.30 kj/mol and lnA is 9.63 s^(-1).

关 键 词：Rare earths BASTNAESITE Suspension roasting Thermal decomposition mechanism Reaction kinetics 

分 类 号：TF046.2[冶金工程—冶金物理化学]