Calculation of Two-Stage Metal Hydride Hydrogen Compressors Using a Model of Intermetallic Compound–Hydrogen Phase Equilibria

— The operation of a two-stage metal hydride thermal sorption hydrogen compressor based on LaNi 5 or LaNi 4.9 Sn 0.1 (first stage) and La 0.5 Ce 0.5 Ni 5 (second stage) has been modeled using a semiempirical model of phase equilibria ( PCT diagrams) in systems of hydrogen gas and metals or alloys, which ensures realistic extrapolation to beyond experimentally accessible temperature and hydrogen pressure ranges. The results demonstrate that, all other factors being the same, replacing LaNi 5 by LaNi 4.9 Sn 0.1 as the hydride-forming material in the first compressor stage ensures a 10% increase in compressor productivity, with a 17% increase in heat consumption. In addition, this change substantially improves compressor operation stability to changes in suction pressure and cooling temperature. The observed effects are attributable to the better stability of the intermetallic hydride, the decrease in the energy loss due to hysteresis, and the increase in the slope of the plateau at low degrees of tin substitution for nickel in LaNi 5 .