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Approche expérimentale d’écoulement gaz/liquide en milieu poreux modèle : application aux lits fixes pour la catalyse hétérogène

Abstract : Heterogeneously catalyzed reactions involving a gas and a liquid phase are frequently achieved in fixed bed reactors. These reactors can be described as a porous medium. The complex nature of this medium makes the understanding of the interplay between phases difficult, and requires a thorough study at the global andlocal scale to identify the key parameters of hydrodynamics, mass and heat transfers. Therefore, we have developed a miniaturized two-dimensional system that is transparent to allow the direct observation of the flow with very high spatial and temporal resolution. While varying the total flow rate and the gas/liquid flow rate ratio, we observe the appearance of the trickle and the pulse flow regime, which can be observed in threedimensional beds. Thanks to some image analysis techniques, we are able to quantify and to map the local apparent liquid saturation and the morphology of the phases. Variances analysis allowed the study of the transition for different liquid properties. This approach allowed the comparison with the existing state of art, but also the study of the onset and propagation mechanisms of the instabilities during the transition. We report that the onset of instabilities responsible for the destabilization of the trickle flow regime occurs at a fixed Weber number. This indicates that the pulsed regime is due to the destabilization of the gas/liquid interface by inertial forces. Finally, a preliminary study of thermal transfers in the device was realized. The device was used to perform the exothermic hydrogenation of alpha-methylstyrene. A simple model is used to characterize the temperature increase in the device. Although this approach does not allow quantitative measurements, it opens up the perspective of monitoring thermal transfers with an infra-red camera.
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https://tel.archives-ouvertes.fr/tel-01661605
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Submitted on : Tuesday, December 12, 2017 - 2:17:06 AM
Last modification on : Friday, October 23, 2020 - 11:55:25 AM

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Marie François. Approche expérimentale d’écoulement gaz/liquide en milieu poreux modèle : application aux lits fixes pour la catalyse hétérogène. Génie chimique. Université de Bordeaux, 2016. Français. ⟨NNT : 2016BORD0216⟩. ⟨tel-01661605⟩

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