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Investigation of non-equilibrium crystallization of mixed gas clathrates hydrates : an experimental study compared to thermodynamic modeling with and without flash calculations

Abstract : The scientific goal of this thesis is based on the acquisition of experimental data and the modeling of the composition of clathrates gas hydrate. The domains of application concern the gas separation and storage, water purification, and energy storage using change phase materials (PCMs).Our research team has recently demonstrated that the composition of gas hydrates was sensitive to the crystallization conditions, and that the phenomenon of formation was out of thermodynamic equilibrium. During this thesis, we have investigated several types of crystallization, which are based on the same initial states. The goal is to point out the differences between the initial solution composition and the final solution composition, and to establish a link between the final state and the crystallization rate.Depending on the rate of crystallization (slow or fast), the acquisition time of experimental data lasted from a few days to several weeks. The experimental tests were performed inside a stirred batch reactor (autoclave, 2.44 or 2.36 L) cooled with a double jacket. Real-time measurements of the composition of the gas and the liquid phases have been performed, in order to calculate the composition of the hydrate phase using mass balance calculations. Depending on the crystallization mode, we have identified several variations of the composition of the hydrate phase and final hydrate volume.We have established a successful thermodynamic model, which indicates the composition of the hydrate phase and hydrate volume in thermodynamic equilibrium state using a gas mixture which had never been used before in the literature. So this thermodynamic model has required an extremely slow experimental test. These tests were also long in order to be sure of the thermodynamic equilibrium state.We are currently establishing a kinetics model in order to model the deviations from the reference point of equilibrium of our experimental tests which were carried out at a high crystallization rate.
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https://tel.archives-ouvertes.fr/tel-01665152
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Submitted on : Friday, December 15, 2017 - 3:39:56 PM
Last modification on : Wednesday, June 24, 2020 - 4:19:11 PM

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Quang-Du Le. Investigation of non-equilibrium crystallization of mixed gas clathrates hydrates : an experimental study compared to thermodynamic modeling with and without flash calculations. Other. Université de Lyon, 2016. English. ⟨NNT : 2016LYSEM002⟩. ⟨tel-01665152⟩

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