A precise model for predicting liquid-liquid extraction column efficiency based upon assumed hydrodynamic, axial mixing and mass transfer behaviour has been formulated and solved numerically.
The complex nature of the dispersed phase can be better described by drop-size-dependent residence time distribution (RTD). Both the variation of axial velocities due to drops of different sizes, i.e. forward mixing, and the axial dispersion for the drops of the same size have been considered in this model.
The computed results reveal that the effects of both varying velocities and dispersion of drops on extraction efficiency are appreciable and cannot be neglected, and the efficiency may be overestimated if only a forward mixing model is adopted. The comparison of the experimental values of NODP with those predicted shows that the mass transfer data obtained in RDC agree well with the values predicted by the present model for the case of solute transfer in cd direction, and are slightly higher than the predicted ones for the transfer in dc direction.
On a formule et resolu numeriquement un modele precis pour prevoir l'efficacite d'une colonne d'extraction liquide-liquide base sur un comportement hydrodynamique hypothetique, le melange axial et le transfert de masse ayant ete formules et resolus numeriquement.
On peut mieux decrire la nature complexe de la phase dispersee par une distribution de temps de sejour qui depend de la dimension des gouttes. On a considere, dans ce modele, a la fois la variation des vitesses axiales avec la dimension des gouttes (melange devance) et la dispersion axiale pour les gouttes de memes dimensions.
Les resultats calcules revelent que l'effet de la variation des vitesses et celui de la dispersion des gouttes sur l'efficacite d'extraction sont appreciables et ne peuvent etre negliges; l'efficacite peut etre surestimee si seul un modele de melange devance est adopte. La comparaison des valeurs experimentales de Nodp avec les valeurs predites indique que les donnees de transfert de matiere obtenues dans RDC concordent bien avec les valeurs prevues par ce modele dans le cas du transfert du solute dans la direction c d; les valeurs experimentales sont legerement plus elevees que les valeurs prevues dans le cas du transfert dans la direction d c.
[1]
J.J.C. Cruz-Pinto,et al.
Experimental confirmation of the influence of drop size distribution on liquid—liquid extraction column performance
,
1980
.
[2]
J. Hinze.
Fundamentals of the hydrodynamic mechanism of splitting in dispersion processes
,
1955
.
[3]
R. B. Olney,et al.
Droplet characteristics in a countercurrent contactor
,
1964
.
[4]
G. V. Jeffreys,et al.
Drop-Size Distribution and Dispersed Phase Hold-up in a Large Rotating Disc Contactor
,
1981
.
[5]
T. Miyauchi,et al.
Longitudinal dispersion in rotating impeller types of contactors
,
1966
.
[6]
A. Hamielec,et al.
Mass transfer inside drops
,
1960
.
[7]
G. Ackerman,et al.
Fundamental aspects of rotating disk contactor performance
,
1962
.
[8]
M. Moo-young,et al.
The continuous phase heat and mass transfer properties of dispersions
,
1961
.
[9]
Thomas Baron,et al.
Mass and heat transfer from drops in liquid‐liquid extraction
,
1957
.
[10]
W. J. Korchinsky,et al.
Drop breakage in counter current flow liquid-liquid extraction columns
,
1981
.
[11]
S. H. Zhang,et al.
Hydrodynamicst axial mixing and mass transfer in rotating disk contactors
,
1981
.