Thesis - Oztek_Muzaffer_T_200508_MA

4. CONCLUSIONS
This study has been a contribution to the unexplored field of separation of
hydrogen and helium mixtures. The study has concentrated on LaNi 5 as the separating
agent. In the small scale DSC, it exhibited fast kinetics with H 2 at ambient temperatures
and at about 5 atm of pressure. The presence of He negatively influenced these
parameters in the small scale. The effect was reduced to a large extent by applying a thin
platinum coating on LaNi 5 ; however, this approach would be costly due to the use of Pt
in the large scale.
The scaled up analyses of LaNi 5 and its derivatives were done with batch and
continuous systems. The LaNi 5 in the batch system reacted rapidly with H 2 even in the
presence of He, provided that the partial pressure of H 2 was high enough.
The continuous U-tube reactor system was successful in producing pure He.
However the full capacity of the LaNi 5 was not achieved therefore the efficiency was
low. The low capacity was due to short residence time of the gaseous reactant in the
reactor, with the used equipment. With the addition of flow control equipment, the
residence time in the reactor can be increased and the continuous system can be a
stronger candidate to be used at the Kennedy Space Center for the recovery of hydrogen
and helium.
The XRD analysis of LaNi 5 and LaNi 5 Al x suggested that, by ball milling, LaNi 4 Al
could be produced. However, the extent of conversion was not quantified in this thesis.
LaNi 4 Al, if it had formed, was shown by DSC analysis that, absorbed less H 2 than LaNi 5 .
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