Caractérisation et modélisation du comportement des alliages TiFe dédiés au stockage solide d'hydrogène. : Application à l'amélioration des performances d'un réservoir à hydrures métalliques

Abstract : He environmental and economic problems caused by the use of petroleum products and the scarcity of these fossil fuels have led to the search for alternative sources of energy, which are renewable and respectful of the environment. Many of these sources are intermittent and require storage solutions. Hydrogen gas appears as a good candidate for this function. The hydrogen element, abundant in nature, has in its gaseous form a calorific value of 140 MJ / kg, i.e. 2.5 times that of gasoline. The 'hydrogen' sector is based on 3 pillars: production, storage, distribution and use. The storage of hydrogen is traditionally carried out by compression, under pressures ranging from a few bars to several hundreds, and by liquefaction at 20 K. The low density of these two types of storage (42 and 70 kgH2 / m3) associated with serious problems of safety and mechanical design, make solid storage in metal alloys particularly relevant for some applications. This solution favors the development of safe, compact design tanks with a high density of 120 kgH2/m3for TiFe alloys, for example. This type of hydride has been retained in this work because it has operating conditions of temperatures and pressures that are relatively close to ambient conditions, and also because it does not contain rare earth elements. The aim of this study is to characterize and model the hydriding/dehydriding behavior of the TiFe0.9Mn0.1 alloy, in order to improve its performance when it is integrated into a storage system. We first tried to characterize the alloy TiFe0.9Mn0.1 in powder form by describing it morphologically, chemically and thermodynamically. Then, two strategies of improvement were tested, the first one based on a mechanical treatment by planetary ball milling, the second considers a thermochemical treatment at given temperature and duration. Both strategies accelerated the process of powder activation, but the planetary ball milling significantly impaired the apparent desorption kinetics. The thermo-chemical treatment did not degrade the equilibrium domains and thus did not have an adverse effect on the reaction kinetics. The two most important parameters of this treatment, temperature and holding time, have been optimized. Other parameters remain to be refined.In addition to this experimental characterization, we have undertaken to describe the hydriding / dehydriding reaction macroscopically. The model allows to account for the thermodynamic response of the hydride within a reservoir. This work presents the results obtained on a tank containing 4 kg of TiFe0.9Mn0.1 powder when different hydrogen loading / unloading scenarios are considered: (i) loading / unloading under constant pressure, (ii) loading / unloading under an initial dose ( Method of Sievert), iii) loading / unloading under inlet or outlet flux of hydrogen. For each scenario, the effect of the coupling with a heat exchange system on the filling / emptying times is analyzed and optimal operating conditions are proposed. Finally, a sensitivity study using the Morris method is presented, and the most influential parameters of the model on the reaction rates are identified. The design of a solid hydrogen storage system requires a good understanding of the macroscopic as well as the microscopic aspects of the hydriding reaction and therefore requires further research to find new directions for improving its performance.
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Ali Zeaiter. Caractérisation et modélisation du comportement des alliages TiFe dédiés au stockage solide d'hydrogène. : Application à l'amélioration des performances d'un réservoir à hydrures métalliques. Mécanique [physics.med-ph]. Université Bourgogne Franche-Comté, 2017. Français. ⟨NNT : 2017UBFCD007⟩. ⟨tel-01810345⟩

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