Hydrogen storage alloys for high-pressure suprapure hydrogen compressor

In this work, AB5 type rare earth-based and AB2 type TiCr2-based hydrogen storage alloys were studied for the purpose of high-pressure hydrogen compression. A pair of hydrogen storage alloys, Ml0.55Mm0.2Ca0.25Ni5 (Ml: La-rich mischmetal; Mm: Ce-rich mischmetal) and (Ti0.97Zr0.03)1.1Cr1.6Mn0.4, with favorable hydrogen storage properties was developed as the alloys for a double-stage high-pressure metal hydride hydrogen compressor (MHHC). With the developed alloy pair, we designed and built a MHHC prototype with hydrogen capacity of 100 L, which could produce high-pressure ultrapure hydrogen with pressure of 45 MPa and purity of 99.9999% from industrial grade hydrogen (98% purity) at pressure of around 2 MPa. During the compression procedure, only hot water is used as the heating source. The compression characteristics were studied and the thermal efficiency was calculated.