Abstract: The pulsed extraction columns with discs and doughnuts play a critical role in the field of spent fuel reprocessing. The countercurrent contact between liquid-liquid two-phase fluids in the column is facilitated through periodic pulses, which significantly influences the separation and purification processes of chemical elements. Although a considerable amount of research on pulse extraction columns with discs and doughnuts has been conducted through simulation, few studies have utilized the actual industrial structure of these columns as examples. A gas-liquid-liquid three-phase flow model coupled with PBM (Polulation Balance Model) to evaluate discrete phase droplet diameter distribution, reflecting the actual structure of pulsed extraction column with discs and doughnuts, was established using CFD (Computational Fluid Dynamics) simulation technology. And it verified the accuracy of the modeling through multiple calculation cases, aiming to investigate the influence of pulse amplitude on the evolution of flow field inside a pulsed extraction column. The model's accuracy was demonstrated through comparison with public literature, and the impact of pulse amplitude on the micro-flow behavior inside the pulsed extraction column was calculated, analyzed and verified. Under the working condition with a pulse amplitude of 1.2 cm, the amplitude had a relatively small impact on the motion of water and oil phases, and the water phase accumulated on the baffle. Under the working conditions of pulse amplitudes of 7.2 and 14.4 cm, the amplitude had a significant impact on the direction and velocity of the water and oil phases, with the water phase separating from the baffle and dispersing into smaller droplets. Furthermore, it was found that as the pulse amplitude increased, both the turbulence kinetic energy and turbulence energy dissipation rate also increased, reaching a maximum value in the region where the fluid impacted the solid wall. Finally, from the distribution of droplet diameter fraction, it was evident that as the pulse amplitude increased, the proportion of small diameter aqueous droplets was higher, which enhanced the extraction. This study used the Euler-Euler two-phase flow model coupled with the PBM to accurately simulate the gas-liquid-liquid three-phase evolution phenomenon in pulse extraction columns, providing a reference for the design and process optimization of subsequent pulsed baffle extraction columns, which laid the foundation for introducing the mass transfer model and heat transfer model through CFD method to analyze the chemical process inside the column in further study.

Key words: pulsed extraction column with discs and doughnuts, gas-liquid-liquid three-phase flow, Euler-Euler model, population balance model, pulse amplitude

摘要： 基于CFD模拟技术建立了脉冲折流板萃取柱的气-液-液三相流模型，探究了脉冲振幅对折流板萃取柱内宏观流场演化的影响规律。结果表明，脉冲振幅为1.2 cm的工况下，振幅对水相、有机相两相的运动影响较小，水相在挡板上积聚，脉冲振幅为7.2和14.4 cm的工况下，振幅对水相、有机相两相的运动方向和速度大小均有显著影响，水相脱离挡板分散成更小的液滴；随脉冲振幅增大，湍动能与湍动能耗散率随之增大，在流体冲击固体壁面的区域出现最大值，随脉冲振幅增大，小直径的水相液滴占比更高，强化了萃取过程。本研究使用Euler-Euler两相流模型耦合群体平衡模型模拟脉冲折流板萃取柱内的气-液-液三相演化现象，可为后续脉冲折流板萃取柱的设计及工艺优化提供参考。

关键词: 脉冲折流板萃取柱, 气-液-液三相流, Euler-Euler模型, 群体平衡模型, 脉冲振幅