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Rôle des diagnostics optiques en temps réel dans le contrôle d'une colonne d'extraction liquide-liquide type pulsée - comparaison expérience / modèle

Ousmane Syll 
Abstract : The design of a liquid-liquid extraction column is based on energy transfer phenomenon leading to a fragmentation of the light phase in droplets allowing the mass transfer with the heavy phase. However, this mechanism suggests a recurring coalescence of the drops followed by a fragmentation to each plate. The process studied in this Thesis is based on the use of a pulsated column attached by optical techniques (analyzes images and Anemometry Doppler Laser) in order to investigate the processes of transfer and the hydrodynamic of the column. The selected experimental model consists of the study of the mass transfer from the dispersed phase (ethyl acetate) to the continuous phase (water) under the standard conditions. A better understanding of pulsed liquid-liquid extraction columns was obtained by using an online digital image analysis system to characterize emulsion drop. The system enabled drop size distribution (DSD) in the emulsion to be qualified with physical (flow rate, stirring pulse) and thermodynamic (surface tension) parameters. The surface tension was investigated by static contact angle measurement as a function of the mixture composition. Mass transfer and energy transfer, characterized by the surface/volume ratio of the droplets were compared with the working parameters such as surface tension of the liquid in order to interpret restrictive phenomena such as hold up, flooding; transfer mass velocity and column efficiency. However, the adhesion work between liquid and plate surface determined by contact angle measurements indicates that interface property variations, as a function of solute concentration, must be taken into account in the theoretical correlations. A simulation code was used in order to estimate each plate's efficiency and to determine the limit of the energy transfer which is responsible for the flooding phenomena. The droplet rates and their residence time between each plate were estimated by ADL measurements and we simulate under Comsol 3.4 current lines and the phenomena turbulence for a pulsed system.
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Submitted on : Thursday, April 2, 2009 - 8:00:00 AM
Last modification on : Thursday, April 2, 2009 - 8:00:00 AM
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  • HAL Id : pastel-00004981, version 1



Ousmane Syll. Rôle des diagnostics optiques en temps réel dans le contrôle d'une colonne d'extraction liquide-liquide type pulsée - comparaison expérience / modèle. Chemical Sciences. Chimie ParisTech, 2008. English. ⟨pastel-00004981⟩



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