Development of a new approach for the kinetic modeling of the lithium reactive hydride composite (Li-RHC) for hydrogen storage under desorption conditions
Publication date
2023-03-06
Document type
Forschungsartikel
Author
Organisational unit
Publisher
Elsevier
Series or journal
Chemical Engineering Journal
ISSN
Periodical volume
464
Article ID
142274
Part of the university bibliography
✅
Language
English
Keyword
Hydrogen storage
Kinetic Modeling
Borohydrides
Reactive hydride composite
Metal hydride
Finite Element Simulations
Abstract
Among some promising candidates for high-capacity energy and hydrogen storage is the Lithium-Boron Reactive Hydride Composite System (Li-RHC: 2 LiH + MgB₂/2 LiBH₄ + MgH₂). This system desorbs hydrogen only at relatively high temperatures and presents a two-step series of reactions occurring in different time scales: first, MgH₂ desorbs, followed by LiBH₄. Hitherto, the dehydrogenation kinetic behavior of such a system has been described for different temperatures at specific values of operative pressure. However, a comprehensive model representing its dehydrogenation kinetic behavior under different operative conditions has not yet been developed. Herein, the separable variable method is applied to develop a comprehensive kinetic model, including the two-step dehydrogenation series reaction. The MgH₂ decomposition is described with the one-dimensional interface-controlled reaction rate Johnson-Mehl-Avrami-Erofeyev-Kholmogorov (JMAEK) with a (Pequilibrium/Poperative) pressure functionality and an Arrhenius temperature dependence activation energy of 63 ± 3 kJ/mol H₂. The LiBH₄ decomposition is modeled applying the autocatalytic Prout-Tompkins model. A novel approach to describe the
Prout-Tompkins t₀ parameter as a function of the operative temperature and pressure model is proposed. This second reaction step presented a (Pequilibrium – Poperative/Pequilibrium)² pressure dependence and an Arrhenius temperature dependence with activation energy 94 ± 13 kJ/mol H₂. The proposed approach is experimentally and computationally validated, successfully describing the decomposition kinetic behavior of MgH₂ and LiBH₄ under three-phase gas, liquid and solid environment and shows good agreement between experimental and modeled curves.
Prout-Tompkins t₀ parameter as a function of the operative temperature and pressure model is proposed. This second reaction step presented a (Pequilibrium – Poperative/Pequilibrium)² pressure dependence and an Arrhenius temperature dependence with activation energy 94 ± 13 kJ/mol H₂. The proposed approach is experimentally and computationally validated, successfully describing the decomposition kinetic behavior of MgH₂ and LiBH₄ under three-phase gas, liquid and solid environment and shows good agreement between experimental and modeled curves.
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