Design for a Medium to Small-Scale Hydrogen Liquefaction Plant

Hydrogen is currently drawing attention as a clean fuel producing less carbon dioxide. The transport and storage, however, require more energy and rather complex infrastructure than fossil fuels. Hydrogen may be stored as liquid, compressed gas, or hydrides.

Liquid hydrogen has relatively small density of 50~70 kg/m3, i.e., the volume of hydrogen shrinks less than other gas when it is transformed to a liquid. Moreover, it has low boiling point, and its spin conversion during liquefaction consumes a significant amount of energy. 20~30% of its energy content is required for transport and storage of hydrogen in the liquid state, while compression of hydrogen gas requires 15%. Although such features of hydrogen makes it more complicated to be liquefied, compression of hydrogen gas to 350~700 bar also has technological barriers to be realized. Compression and high pressure storage require larger facilities and heavier storage vessels. It also involves safety concerns, and the compression technology has not yet been matured enough. In this regard, the most economic state of hydrogen for transport and storage is likely to be liquid although the decision may vary according to technological developments.

A precooled Claude cycle and a He refrigerated cycle are investigated to develop a pilot scale hydrogen liquefaction system. The simulation results provide the specifications for component development, as well as the advantages of each type of liquefaction cycles.