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Détermination d'un critère prédisant l'efficacité du procédé d'électrocoalescance sur la destabilisation d'émulsions eau-pétrole brut

Abstract : The present thesis deals with the electrostatically assisted removal of water coproduced with crude oil in the form of stable emulsions during recovery and desalting operations. This process, referred to as electrocoalescence, exploits the ability of electric forces to promote attraction and merging of adjacent water droplets to increase their size and related natural rate of sedimentation under gravity. Still, even one century after the first experimental observations, a lot of gray areas remain, particularly on the optimization of efficiency in state-of-the-art separators. To address this question, an approach combining multi-physics simulation and experiments has been used to investigate the phenomena of motion, deformation and instability of electrically influenced water-oil (droplets) interfaces. The main contribution concerns the modeling and analysis of the mechanism of oil film thinning between droplets approaching under the effect of electrostatic forces. Results from simulations highlight the strong singularity of the present problem and the inadequacy of existing theoretical lubrication models usually employed to represent coalescence events in two phase flows. For the small emulsified droplets, a new asymptotic expression for the drainage time is obtained and allows to deduce a criterion predicting the probability of electrocoalescence resulting from a shear flow induced collision. In parallel, a sophisticated setup, enabling to experimentally investigate the phenomenon and to improve the criterion relevance with regards to the actual processing conditions, has been assembled. At last and as an answer to an otherwise unfulfilled requirement defined in the design of the latter, an innovative actuation technique for the synchronous on-demand injection of two charge free conductive droplets in an insulating viscous liquid, relying on the application of a high electric field pulse, has been implemented.
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https://tel.archives-ouvertes.fr/tel-00684414
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Submitted on : Monday, April 2, 2012 - 9:35:36 AM
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Jonathan Raisin. Détermination d'un critère prédisant l'efficacité du procédé d'électrocoalescance sur la destabilisation d'émulsions eau-pétrole brut. Autre. Université de Grenoble, 2011. Français. ⟨NNT : 2011GRENI016⟩. ⟨tel-00684414⟩

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