Hydrogen capture in low pressure industrial processes using metal hydrides

MILIDONI M.; BORZONE E. M.; BARUJ A.; BLANCO M. V.; MEYER G. O.

Florianópolis

Congreso; XI Congresso SBPMat; 2012

SBPMAT - Sociedade Brasileira de Pesquisa em Materiais

Hydride forming materials are mainly studied for hydrogen storage and batteries applications, but their affinity with hydrogen suggest they could be used for hydrogen purification, capture or separation from mixed gaseous sources. In particular, AB5 alloys are  good candidates for this purpose, as they show fast reaction kinetics with hydrogen and can be tailored to react with hydrogen at a given pressure and temperature. A case of particular interest arises when contaminants are inert gases, for most standard separation processes, based on adsorption of the impurities, are not suitable.In this work we present different schemas using metal hydrides to capture and separate  hydrogen from a hydrogen/inert gas mixture. Simulations are performed considering the use of LaNi5-xSnx alloys. The case study consists of a 96:4 mixture stored in a 500 liters tank at an initial pressure of 0.95 bar. This situation corresponds to a real industrial problem observed in the final stage of a radioisotope production plant.Different scenarios are considered based on measured properties of the alloys:- Hydrogen capture process with the vessel containing the hydride is directly connected to the tank- The use of a mechanical compression stage (diaphragm compressor/pump) between the tank and the vessel containing the hydride.- Variations in the composition of the alloy LaNi5-xSnx (0 ≤ x ≤ 0.5).- Effect of the volume of the different parts of the system if a compressor is used.Minimum attainable tank pressure and elapsed time to reach a given final tank pressure are the selected parameters used to compare the results.