The hydrodynamic behavior of a pulsed disc and doughnut column has been investigated using three different systems in the absence of mass transfer. Sauter-mean drop diameter (d32), flooding velocity and holdup at flooding have been measured at different operating conditions. The following operating variables have been studied: pulsation intensity and flow rate of both liquid phases. As expected, smaller mean drop sizes are obtained with the increase of pulsation intensity. The results also show no significant effect of continuous phase flow rate on mean drop size, which increases with increase of dispersed phase flow rate for the operating conditions investigated. A single correlation for the prediction of d32 in the mixer-settler, transition and emulsion regimes of operation is proposed with a mean deviation of 7.32%. The maximum throughput is influenced mainly by pulsation intensity and interfacial tension. Two precise correlations are proposed for predicting flooding velocities in this column. The first is based on operating variables, column geometry, and system physical properties. The second one considers the same variables, except column geometry. Good agreement between prediction and experiments is found for all operating conditions investigated.

Flooding and drop size in a pulsed disc and doughnut extraction column

Modeling of a two-phase countercurrent pulsed sieve plate extraction column—A hybrid CFD and radiotracer RTD analysis approach

Fluid dynamics of the single-phase and two-phase flow in a segment of a rotating disc contactor (RDC) liquid–liquid extraction column with 450 mm inner diameter were studied by performing computational fluid dynamics (CFD) simulations and particle image velocimetry (PIV) measurements. The fluid dynamics were investigated to test the predictivity of CFD at industrial scale. Different turbulence models in conjunction with the Eulerian approach were applied in the single-phase and two-phase simulations. The turbulent flow characteristics were analyzed by PIV measurements to validate the CFD simulations. An iso-optical system composed of CaCl2/water–butylacetate allows for the two-phase PIV measurements. Local turbulent energy dissipation was derived from velocity gradients in PIV data. In this connection, the influence of the PIV spatial resolution on the measured energy dissipation was also analyzed, and different fit functions were tested to scale the measured energy dissipation. Simulated velocity fields as well as the energy dissipation were compared with the experimental PIV data. The results from the simulations and experiments are in good agreement. The work shows that CFD can predict hydrodynamic characteristics even at bigger scales but is still subject to some minor restrictions. © 2010 American Institute of Chemical Engineers AIChE J, 2011

CFD simulations and particle image velocimetry measurements in an industrial scale rotating disc contactor

Computational Fluid Dynamics (CFD) simulations of two-phase flow to predict dispersed phase hold up in a pulsed sieve-plate column have been performed and validated with reported experimental data. Suitability of different drag models for predicting dispersed phase hold up has been evaluated. Drag models applicable for concentrated dispersions are found to be better than the drag models applicable for lean dispersions. Kumar–Hartland drag model is found to be the best among the reported drag models with average error between predicted and experimental hold up being about 15%. Parameters of the Kumar–Hartland drag model are modified to further reduce the error to about 10%.

CFD simulation of two-phase flow in pulsed sieve-plate column – Identification of a suitable drag model to predict dispersed phase hold up

Dispersed phase hold-up and flooding behavior were investigated in a pilot plant scale perforated rotating disc contactor (PRDC) using three different liquid–liquid systems. The influence of various operational parameters including rotor speed, continuous and dispersed phases flow rates on flooding velocities and hold-up have been studied. Changes in the continuous phase velocity has a minor effect on dispersed phase hold-up while increasing dispersed phase flow rate and rotor speed results in an increase in dispersed phase hold-up. Moreover, based on physical properties of liquid systems and operating conditions two empirical correlations were derived for the flooding point and dispersed phase hold-up. The proposed empirical correlations are then validated through comparing with experimental data. Therefore, due to a lack of experimental data on this type of column, these predictive empirical correlations can be used for accurate design of perforated rotating disc contactor.

S. Retieb

Papers

Hold-up within two-phase countercurrent pulsed columns via Eulerian simulations

Numerical determination of dispersed-phase hold-up in pulsed extraction columns