Simulation Of Hydrodynamic Behavior Of Pulsed Sieve-Plate Extraction Column Based On Population Balance Model

Liquid-liquid extraction is an important separation process encountered in numerous chemical process industries. In column extractors offering high throughputs,this technology is often applied. In the field of nuclear fuel recycle and reprocessing,the Pulsed Sieve Extraction (PSE) column is often used. In this work, on the concept of population balance, simulation of PSE is preformed which considers the droplets hydrodynamic behavior of breakup and aggregation. Three numerical methods for continuous Population Balance Equations (PBE) are discussed and the hydrodynamic behavior under steady state is simulated with the stage-wise model.The three numerical methods for solving PBEs introduced here are: Fixed Pivot Technique (FPT), Method Developed by Attarakih (MDA) and Cell Averaged Technique (CAT). Differences and accuracies are also discussed. In the part of solving the breakage equations, in order to eliminate the significant deviation of number density in the left boundary of FPT, a slight modification is recommended, and the numerical results show good agreement with that from the other two algorithms. In the argument of aggregation problem, only FPT and CAT are chosen, and source of"over-prediction" in FPT is analyzed in detail. All of the three numerical solutions for differential equations set are approached by fourth-order Runge-Kutta method, and the algorithms are programmed by C programming language. The numerical results show that the FPT and MDA have the same accuracy under identical conditions, while the CAT is of better accuracy and efficiency, which show a prosperous future in solving the simultaneous breakage and aggregation equations.In order to dimension the extraction column, a stage-wise hydrodynamic model has been presented on the basis of Drop Population Balance (DPB), which take into account the drops breakage and coalescence in each stage. A software named Pulsed Sieve Extraction Module has been developed, which could give the terminal velocity,holdup, Sauter mean diameter and volumetric distribution for each individual droplet diameter along the column height.Through simulating extraction column with diameter of 80mm and 4mm hole diameter, choosing systems of butylacetate-water under steady-sate, no mass transfer, the volumetric distributions show Gauss-distribution. The terminal velocity after correction show good agreement with the experimental data. The deviation between hold-ups calculated and measured is about 10%, and Sauter mean diameter 5%.