Proposal of an innovative, high-efficiency, large-scale hydrogen liquefier

An innovative, efficient and large hydrogen liquefier is described. Innovations lie in the fact that (i) the feed, 10 kg s−1, is refrigerated in heat exchangers catalytically promoting the ortho–para conversion (ii) down to the low temperature of 20.5 K and at the high pressure of 60 bar at which it is available and (iii) lastly expanded to the storage conditions of 1.5 bar and 20 K through a liquid-phase turbomachine; (iv) refrigeration is via four helium recuperative Joule–Brayton cycles arranged so that the refrigerant follows the cooling curve of hydrogen and the volume flow rates in compression and expansion processes are typical of axial-flow high-efficiency turbomachines; (v) compression is accomplished in 15 intercooled 8-stage devices derived from gas turbine technology. Heat exchangers require specific surfaces comparable to current state-of-the-art liquefiers. Nevertheless, the predicted work of approximately 18 MJ kg−1 is half as much as the requirement of those liquefiers and corresponds to a second-law efficiency of almost 48%.