Simulation Of Hydrodynamic Performance Of φ38Standard Pulsed Sieve-Plate Extraction Column Using A Population Balance Model

Liquid-liquid extraction processes are widely used in chemical industry. In spent fuelreprocessing, pulsed sieve-plate extraction columns is the key extraction equipment. The masstransfer efficiency of an extraction column depends heavily on hydrodynamic performance ofthe dispersed phase, especially hold-up and the mean diameter.The Population balance model (PBM) was adopted to describe the complexhydrodynamic behavior of countercurrent liquid-liquid extraction columns, in which thedispersed phase was treated as separated droplets with certain size distribution and theinfluence of drop breakage and coalescence was taken into account. The Population balanceequations (PBE) takes drop volume as internal coordinate, time as external coordinate. Assource terms in PBE involve single or multiple integrals, the resulting PBE are integro-partialdifferential equations (IPDE) that rarely have an analytical solution, therefore numericalcalculation is employed in general. Quadrature method of moments is used to solve PBE, inwhich the drop size distribution is not tracked directly, but through its moments integratedover the internal coordinate. The Gaussian integral assumption is introduced to solve theclosure problem of moment equation.Dispersed phase holdup and mean diameter under certain operating conditions have beenmeasured in a38mm diameter standard pulsed sieve-plate extraction column for the systemof30%tributyl phosphate (TBP) in kerosene-nitric acid-deionized water, and was simulatedthough numerical calculation of PBE by Quadrature method of moments. The influences ofthe residence time, breakage parameters, coalescence parameters were studied. In quadraturemethod of moments10characteristic volumes was determined from Vandermonde matrix torepresent drop size distribution. The values of breakage and aggregation coefficiences inpublished fitting correlations were used, and dynamic curves of the dispersed phase holdupand mean diameter based on the PBM was obtained. The results show that the models andmethods adopted could predict the behavior of the dispersed phase drop well. As the pulsationintensity increases, the residence time of the drop in the column gets longer, the hold up ofdispersed phase increases when the two phase flow in the column reaches steady state. Thedynamic simulation of the dispersed phase hold-up and the mean diameter have been found to be in agreement with experimental data and some published theoretical results. Thus, themodel can be reliably applied to study the extraction process and predict the38mm diameterstandard pulsed sieve-plate column hydrodynamic performance.