In this study,the Bayan Obo rare earth concentrates mixed with Na2CO3 were used for roasting research.The phase change process of each firing stage was analyzed.The kinetic mechanism model of the continuous heating process was calculated.This study aims to recover valuable elements and optimize the production process to provide a certain theoretical basis.Using X-ray diffraction(XRD),Fourier infrared spectroscopy,scanning electron microscopy with energy dispersive spectrometry,the reaction process and the existence of mineral phases were analyzed.The variable temperature XRD and ther-mogravimetric method were used to calculate the roasting kinetics.The phase transition results show that carbonate-like substances first decompose into fine mineral particles,and CaO,MgO,and SiO2 react to form silicates,causing hardening.Further,REPO4 and NaF can directly generate CeF3 and CeF4 at high temperatures,and a part of CeF4 and NaF forms a solid solution substance Na3CeF7.Rare earth oxides calcined at a high temperature of 750℃were separated to produce Ce0.6Nd0.4O1.8,Ce4O7,and LaPrO3+x.Then,BaSO4,Na2CO3,and Fe2O3 react to form barium ferrite BaFe12O19;the kinetic calculation results show that during the continuous heating process,the apparent activation energy E reaches the minimum in the entire reaction stage in the temperature range of 440-524℃,and the reaction order n reaches the maximum,which indicates that the decomposition product REFO significantly impacts the reaction system and reduces the activation energy.The mechanism function is F(α)=[-ln(1-α)]13.The reaction order n reaches the minimum in the temperature range of 680-757℃,and the apparent activation energy E is large.The difficulty of the reaction increases during the final stage.The reaction mechanism function isF(α)=[1-(1-α)1/3]2.Observing the entire reaction stage,the step of controlling the reaction rate changes from random nucleation to three-dimensional diffusion(spherical symmetry).

Peng Zu;Jie Li;Jingxuan Wu;Wenhao Zhang;Jiawei Lin;Shiwen Yi;Wenrou Su

Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resource,School of Materials and Metallurgy,Inner Mongolia University of Science and Technology,Baotou 014010,China;Key Laboratory of New Metal Materials of Inner Mongolia Autonomous Region,Inner Mongolia University of Science and Technology,Baotou 014010,China

稀土学报（英文版）

[1]Peng Zu;Jie Li;Jingxuan Wu;Wenhao Zhang;Jiawei Lin;Shiwen Yi;Wenrou Su-.In-situ measurement of mineral phase transition and kinetics in roasting process of Bayan Obo mixed rare earth concentrate by sodium carbonate)[J].稀土学报（英文版）,2022(07):1134-1147

mogravimetric,CeF4,Na3CeF7,6Nd0,4O1,Ce4O7,LaPrO3+x,REFO,isF

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