ISBN 9783843918336

978-3-8439-1833-6, Reihe Verfahrenstechnik

Inga Bürger
Investigation of a New Reactor Concept for Hydrogen Storage in Complex Hydrides

157 Seiten, Dissertation Universität Stuttgart (2014), Softcover, A5

Zusammenfassung / Abstract

In the present thesis, a new reactor concept for hydrogen storage in solid-state hydride materials is investigated for automotive applications. The new concept focuses on the applicability of complex hydride materials (CxH). These materials show very high potential H2 storage capacities. However, their reaction rates are very low at automotive absorption and desorption conditions. In the presented concept, this limitation is overcome by the addition of a conventional metal hydride material (MeH) to a separate compartment of the CxH storage reactor. This innovative combination reactor can store high amounts of hydrogen due to the CxH material, but still shows a satisfying dynamic performance at automotive absorption (fuelling) and desorption (driving) conditions.

As a reference CxH material, 2LiNH2 1.1MgH2 0.1LiBH4 3wt.%ZrCoH2 (Li-Mg-N-H) is selected and the relevant physical properties are determined. Then, model equations for the reaction rate are presented for the first time. For the metal hydride material, LaNi4.3Al0.4Mn0.3 is chosen due to thermodynamic reasons. Using the newly determined parameters, a 2D model for reactor design simulations is developed. Furthermore, several absorption experiments are performed in lab-scale using the pure Li-Mg-N-H reactor and the combination reactor concept. With these experiments, the developed 2D model is validated and this tool can be used for future reactor design simulations. Finally, desorption experiments are performed in lab-scale and complemented by simulations that show the desorption interaction of the two materials.

The experiments and simulations performed in this thesis show that for absorption the fuelling time in an automotive application can be reduced from 10 minutes for the pure Li-Mg-N-H system to 2 - 3 minutes in the combination reactor. Furthermore, during the desorption process, the reactor dynamics can be improved, and the desorption efficiency of the Li-Mg-N-H material is increased. Concerning the storage density, for the present reference system the value decreases from 3.2 wt.%, for the pure Li-Mg-N-H material, to 2 wt.% for the combination reactor. However, it has to be emphasized that only the combination reactor is able to absorb and desorb at automotive conditions. Thus, this concept significantly reduces the kinetic requirements for newly developed complex hydride materials offering high hydrogen storage capacities.