A novel expansion configuration for a hydrogen liquefaction plant

Abstract

This study proposes a pathway to improve the efficiency of the hydrogen liquefaction process by including single-phase turboexpanders in the final hydrogen expansion. A sensitivity study compares three configurations. All three expansions have the same inlet and outlet pressures, while the inlet temperature is the same for Cases A and C but not for Case B. Case A is a standard isenthalpic expansion using a Joule-Thomson valve. Case B uses a fully wet turboexpander which expands on the liquid side of the two-phase curve and hence requires more cooling prior to the expansion. Case C is a compromise where the single-phase expansion is done by a turboexpander and the two-phase expansion by a Joule-Thomson valve. For the WE-NET configuration analysed (and a 50-bar top pressure), Case C has an increase in yield of 13.3% points and in exergetic efficiency of 4.6% points, compared to the baseline (Case A).