Modeling of the lithium hydride hydrolysis under low relative humidity. (17th August 2017)

• Record Type: Journal Article
• Authors: Oury, Alexandre; Namy, Patrick; Bellat, Jean-Pierre; Sciora, Elisabeth; Besnard, Rémy
• Is Part Of: International journal of hydrogen energy. Volume 42:Number 33(2017)
• Page Start: 21105
• Page End: 21113
• Publication Date: 2017-08-17
• Subjects: Lithium hydride -- Hydrolysis -- Modeling -- Moist atmosphere; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2017.06.182
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: A reactional mechanism describing the hydrolysis of lithium hydride (LiH) under moist atmosphere is proposed and modeled. It involves the formation of lithium oxide (Li2 O) at low vapor pressure and both lithium oxide and lithium hydroxide (LiOH) at higher vapor pressures, with diffusion of water in these layers. A numerical model based on this mechanism is implemented with COMSOL Multiphysics to simulate the hydrolysis of LiH particles in open system (constant water vapor pressure). Kinetic parameters such as rate constant of reactions and diffusion coefficient of water in Li2 O and LiOH are first fitted against experimental data. The best agreements are obtained when the diffusion coefficient of water is 10 times higher in LiOH than in Li2 O. The resulting model accurately predicts the hydrolysis rates experimentally measured for a wide range of water vapor pressures (0.3–17 Pa). The hydrolysis mechanisms are compatible with a Li2 O production limited by water diffusion and a LiOH production governed by the kinetics. Finally, simulation suggest that the thickness of the Li2 O layer does not depends much on the water vapor pressure whereas that of LiOH increases drastically at high water vapor pressures. Highlights: A chemical mechanism for the hydrolysis of lithium hydride is proposed. Li2 O is formed at low vapor pressures and Li2 O + LiOH at higher pressures. A numerical model is implemented to simulate the hydrolysis of LiH. Reaction rate constants and water diffusivity in the formed layers are fitted. Computed extent of reaction is compared to experimental data with good agreement.