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

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