CFD Simulation of Two-Phase Flow in a Hybrid Pulsed Sieve-Plate Solvent Extraction Column: Prediction of Holdup and Axial-dispersion Coefficients

Abstract

Two-phase computational fluid dynamics (CFD) models for a hybrid pulsed sieve plate solvent extraction column as well as a standard pulsed sieve plate column have been developed with commercial software ANSYS FLUENT. Hydrodynamic performance including two-phase distribution and velocity fields are generated with the models and comparisons are made between two columns. Important parameters including holdup and axial dispersion coefficients are studied systematically, and CFD successfully predicts the higher holdup and lower axial dispersion coefficients for the hybrid pulsed sieve plate column as measured in the experiments.CFD also gives reasonable predictions for the effect of pulsation intensity, dispersed phase velocity and continuous phase velocity on holdup, except for the effect of pulsation intensity in low pulsation region, and the cause has been discussed from the perspective of droplet breakage and coalescence. Comparison with literature data shows that CFD underestimates the holdup of 3 hybrid pulsed sieve plate column and standard pulsed sieve plate column by 23.3% and 31.4% respectively, and the cause has been discussed from the perspective of drag law. CFD gives good prediction of axial dispersion coefficients for the hybrid pulsed sieve plate column and the standard pulsed sieve plate column with ARD of 12.0% and 14.3% respectively. This study shows CFD to be a useful tool to predict performance for the novel hybrid pulsed sieve plate column as well as the standard pulsed sieve plate column.

A new method to quantify droplet size distribution based on Monte Carlo simulation in liquid–liquid solvent extraction

“…However, several studies have shown that the use of PBM cannot provide a correct prediction of the holdup under high pulsation intensities. 17,18 This implies that d 32 introduces uncertainties and causes significant errors at high pulsation. The basic cause is the d* does not meet the requirement of d 32 .…”

“…It determines the number densities of different droplet sizes and provides d 32 as the interface area for the CFD solver. However, several studies have shown that the use of PBM cannot provide a correct prediction of the holdup under high pulsation intensities 17,18 . This implies that d 32 introduces uncertainties and causes significant errors at high pulsation.…”

Investigation of Velocity Field Inside a Single-Phase Pulsed Sieve Plate Column Using Radioactive Particle Tracking

“…Sen et al 27 reported a CFD-PB model that can be used to numerically estimate the continuous phase axial dispersion coefficient in two-phase flow. Yi et al 28 reported a two-phase CFD model to predict the drop size and axial dispersion coefficient in hybrid pulsed sieve plate columns. However, in all of these attempts, validation of CFD models is carried out by comparing predicted macroscopic variables like holdup or droplet diameter against experimentally measured values.…”

Interfacial relaxation of droplets caused by mass transfer in a pulsed column

“…[15][16][17] Pulsed extraction columns have been widely used because of their many advantages, such as a small footprint, large processing flux, no rotating internal parts, and the ability to handle materials containing solid particles. 18 Because the interfacial tension is a key physical property in multiphase flow, 19 it is important for predicting hydraulic properties, such as the Sauter mean diameter (SMD) of liquid droplets, 20 flooding characteristics, 21 and dispersed phase holdup 22 in pulsed extraction columns. Studies have shown that under masstransfer conditions, dynamic changes in the interfacial tension occur, resulting in changes in the hydraulic behavior of the extraction devices.…”