The commercial development of the H 2YCELL — A rare earth metal hydride storage device

Abstract

A new storage source for ultrapure hydrogen that is compact, portable and convenient has been developed by Laboratory Data Control (LDC). The device, named H 2YCELL®, employs encapsulated LaNi 5 housed in a rugged canister. Up to 8 ft 3 (2261) of hydrogen can be stored in the production version. Safe usage by inexperienced laboratory technicians has been a major design consideration. Storage at densities greater than that of liquid hydrogen are achieved but at room temperature and low pressure (about 25 lbf in −2, absolute, at 75 °F). About 1 l of gaseous hydrogen is present at any one time in the H 2-YCELL. An internal heater permits the pressure and the hydrogen output flow rate to be increased. For example, at 200 lbf in −2 a flow rate of up to 170 l h −1 is obtained. The H 2YCELL has a unique advantage over hydrogen cylinders and Fe-Ti storage devices: the rare earth metal hydride releases the hydrogen at a nearly constant pressure over the range from about 2% to 98% of the total capacity. Thus for many applications a regulator valve is unnecessary. Since the metal hydride is specific in the absorption of only hydrogen, the hydrogen supplied by the H 2YCELL is ultrapure. If an impure hydrogen source, e.g. a cylinder, is used to “recharge” the H 2YCELL, only the hydrogen is retained and all other gases can be bled off. Thus the H 2YCELL also functions as a purifier. Atomic absorption data reveal impurity concentrations of less than 50 ppb in the H 2YCELL output. A companion unit, the LDC ELHYGEN electrolytic hydrogen generator, can be used to recharge the H 2YCELL “overnight” since low pressures (60 lbf in −2, gauge) and low flow rates (18 l h −1) are involved.