Hydrogen storage systems based on metal hydrides require appropriate quantitative kinetic description for simulations and designs, in particular for the crucial absorption process. This investigation proposes an empirical kinetic model for the hydrogen absorption of sodium alanate material doped with aluminium-reduced TiCl 4 , produced in kg-scale. The model is based on kinetic data obtained by volumetric titration measurements performed on each of the two absorption steps of sodium alanate, within a range of experimental conditions varying from 10 bar to 110 bar and from 100 °C to 180 °C. It is shown that each step is best described by the JMA model with n = 1.33. The kinetic equations are implemented in a mass balance and used to predict the reaction rate of the two steps of hydrogen absorption. Even when they proceed simultaneously, the predictions agree well with experimental results. The second paper of this investigation presents the results for the kinetic model of the corresponding hydrogen desorption.
Thermodynamic and heat transfer properties of the 2LiBH 4-MgH 2 composite (Li-RHC) system are experimentally determined and studied as a basis for the design and development of hydrogen storage tanks. Besides the determination and discussion of the properties, different measurement methods are applied and compared to each other. Regarding thermodynamics, reaction enthalpy and entropy are determined by pressure-concentration-isotherms and coupled manometric-calorimetric measurements. For thermal diffusivity calculation, the specific heat capacity is measured by high-pressure differential scanning calorimetry and the effective thermal conductivity is determined by the transient plane source technique and in situ thermocell. Based on the results obtained from the thermodynamics and the assessment of the heat transfer properties, the reaction mechanism of the Li-RHC and the issues related to the scale-up for larger hydrogen storage systems are discussed in detail.
Among different Reactive Hydride Composites (RHCs), the combination of LiBH 4 and MgH 2 is a promising one for hydrogen storage, providing a high reversible storage capacity. During desorption of both LiBH 4 and MgH 2 , the formation of MgB 2 lowers the overall reaction enthalpy. In this work, the material has been compacted to pellets for further improvement of the volumetric hydrogen capacity. The influence of compaction pressure on the apparent density, thermal conductivity and sorption behaviour for the Li-based RHC during cycling has been investigated for the first time. Although LiBH 4 melts during cycling, decrepitation or disaggregation of the pellets is not observed for any of the investigated compaction pressures. However, a strong influence of the compaction pressure on the apparent hydrogen storage capacity is detected. The influence on the reaction kinetics is rather low. To provide explanations for the observed correlations, SEM analysis before and after each sorption step was performed for different compaction pressures. Thus, the low hydrogen sorption in the first cycles and the continuously improving sorption for low pressure compacted pellets with cycling may be explained by some surface observations, along with the form stability of the pellets.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.