JIANG Lin¹，ZHANG Tongwang²，LIU Rongzheng¹，SHAO Youlin¹，LIU Bing¹，LIU Malin¹

1.Institute of Nuclear and New Energy Technology，Tsinghua University，Beijing 100084，China；2.Research Institute of Petroleum Processing Co.，Ltd.，SINOPEC，Beijing 100083，China

Abstract

Objective　Tristructural-isotropic（TRISO）nuclear fuel particles serve as the primary barrier to ensure the inherent safety of high- temperature gas-cooled reactors（HTGRs）.These particles are coated with four layers using the fluidized bed-chemical vapor deposition（FB-CVD）technique.The fluidizing medium contains high-density uranium dioxide particles，reaching up to 10.8 g/cm³，and the par-ticle motion directly affects the coating quality.Therefore，it is necessary to measure the motion characteristics of high-density par-ticles in a shallow spouted bed and analyze the mathematical relationship between fluidization states and operating parameters.

Methods　Initially，bed pressure drop curves and minimum spouting velocities were obtained for particle systems with different loadings,and the fluidization behavior of high-density particles was explored.Then，magnetic particle tracking（MPT）and computational fluid dynamics-discrete element method（CFD-DEM）were employed.The local residence time of particles in the annular region was measured expe-rimentally under different particle loadings（N=500，1 000，2 000）and gas inlet velocities，and the results were compared with simu-lation results. Finally，fast Fourier transform（FFT）analysis was applied to the signal curves of magnetic field strength，enabling rapid determination of particle flow patterns under certain loadings and gas velocities.

Results and Discussion　The results showed that in high-density particle systems，the bed pressure drop increased continuously with increasing inlet gas velocity，and the flow pattern transitioned from a fixed state to a spouted bed state，without a distinct pressure drop or a plateau phase.The turning point on the fluidization curve，corresponding to the transition in flow pattern，determined the minimum spouting velocity and was influenced by particle density，loading，and gas inlet diameter. MPT measurements showed that the local residence time of individual particles in the three-dimensional space tracked by two detectors varied randomly.Increased loading stabilized fluidization and facilitated particle circulation in a "spouting-fountain-annular region" pattern. Simulation results showed that at a particle loading of 2 000（N=2 000），as the inlet gas velocity increased from 45 m/s to 55 m/s，the local residence time（TL）fluctuated randomly within a certain value range，with the average time decreasing from 0.032 s to 0.028 s.The experimental results were highly consistent with the simulation results.FFT analysis of detector-1's signal curves showed a dominant frequency and regular spouting pattern at a moderate gas velocity（e.g.,U_g =55.26 m/s）.

Conclusion　The distinctive fluidization characteristics for high-density particles，including bed pressure drop behavior and minimum spouting gas velocity，are revealed.A novel method for tracking the motion of individual particles in three-dimensional space is estab-lished.The MPT method can effectively measure the TL of high-density particles in a shallow spouted bed under different operating con-ditions and quickly identify flow patterns and fluidization states.The method can support the process optimization and scale-up design for coating applications.

Keywords： high-density particles；spouted bed；residence time；magnetic tracking；discrete element method；numerical simulation

Get Citation:JIANG Lin，ZHANG Tongwang，LIU Rongzheng，et al.Experimental and simulation study on fluidization behavior of high-density particles in a shallow spouted bed［J］.China Powder Science and Technology，2025，31（2）：1−14.

Received: 2024-09-14，Revised:2024-10-28，Online:2024-12-31. 

Funding Project:国家科技重大专项项目，编号：ZX06901；国家万人计划青年拔尖人才项目，编号：20224723061；国家自然科学基金项目，编号：22478220。

First Author:蒋琳（1998—），女，博士生，研究方向为多相流 CFD-DEM 模拟、流态化行为测量。E-mail：jiang-l20@mails.tsinghua.edu.cn。

Corresponding Author:刘马林（1983—），男，副教授，博士，博士生导师，研究方向为核燃料制备。E-mail：liumalin@tsinghua. edu. cn。

DOI：10.13732/j.issn.1008-5548.2025.02.001

CLC No:TB021.1；TB4         Type Code:A

Serial No:1008-5548（2025）02-0001-14