Numerical Simulation Of Pulsed Sieve-Plate Extraction Column Based On The Euler-Lagrange Model

Pulsed sieve plate extraction column is commonly used as a spent fuel reprocessing equipment in the nuclear industry. Its production capacity and the extraction efficiency are always influenced by two-phase flow characteristics, and the micro motion behavior of dispersed droplets is one of key factors. This paper is to simulate the variation tendency of droplet diameter distribution in a standard sieve plate extraction column of38mm inner diameter, by the computational fluid dynamics software, Fluent14. The research provides new useful information for the future modeling and enlargement.The two-phase flow equations by the Euler-Lagrange method are established, taking no account of the droplet poly crushing behavior but the droplet movement drag force, buoyancy, saffman lift and pressure gradient suffered in the process. Spherical drag model (Schiller and Nauman’s and Newton’s model) is selected as the drag model. With choosing pressure-velocity coupling solver and discrete algorithm SIMPLE to solve equation group, the speed distribution of the two-phase flow is calculated finally. After that, the common points and differences about the dispersed phase state between a relatively uniform diameter and R-R (Rosin-Rammler) diameter distribution are analyzed. Finally, it is necessary to discuss the droplet diameter distribution in the different operating conditions.The two-phase turbulence equations under the unification droplet diameter of2mm are solved. The simulation results show that the velocity distribution of continuous phase is susceptible to be affected by the dispersed phase droplets, especially near the center of impact is more significant. The velocity distribution of droplets at the different moments is similar and no apparent periodic variation. The length of the residence time is substantially opposite to the size of the droplet velocity. The turbulence control equation of continuous phase is calculated using the standard k-ε turbulence model. The radial velocity distribution of continuous phase has little difference affected by the injected droplets of R-R diameter distribution, and the residence time distribution is discussed, the center of the plane of incidence of different droplet movement speed injection to produce the effect of radial diffusion, the smaller the size of the droplets the more prone to radial diffusion, droplet velocity contours show large droplets is easy to run into the wall and wall absorption. Close to the wall surface at the points (-0.05,-0.03) m, residence time distribution of the different droplets show that the residence time of the large-diameter droplets has shorter residence time than the small-diameter droplets. However, the residence time of2mm diameter is consistent with the maximum residence time of the droplets in unification2mm diameter. The variation tendency of droplet diameter distribution is simulated and analyzed under different operating conditions. The analysis results show that the proportion of the number of large diameter droplets continuously reduces as the continuous phase velocity increases constantly, and continuously decreases with the dispersed phase velocity increasing; continues to decrease as the pulse speed increases. The relation curve of R-R distribution function and droplet sizes under different conditions by Linear Regression is fitted. Results show that, the square of correlation coefficient greater than0.95on the particle size of dispersed phase agrees well with the R-R distribution function. The simulation results of the Sauter mean diameter are in a good accordance with those of experiment values.