Conceptual design of a high efficiency large capacity hydrogen liquefier

The aim of this paper is to propose a hydrogen liquefier with very high efficiency. One important theoretical tool is the exergy analysis of the single process step as well as the overall cycle. This will be needed for the choice of the optimum hydrogen feed pressure as well as for the handling of the ortho-para conversion. Modern helium refrigerators are being built with up to 10 expansion turbines placed strategically in the cycle to obtain overall optimum efficiency. We are proposing to do the same for the hydrogen liquefier and to choose a helium-neon mixture as refrigerant, which allows the use the best available compression system. The preliminary design of the plant shows that a thermodynamic efficiency of the total plant in the order of 60% is feasible. This results in an overall power requirement of 5 to 7 kW-h per kg of liquid hydrogen, depending on the pressure of the feed and the temperature of the product. These values for the power consumption are recommended as bench marks for future studie...