Thermodynamic analysis of a dual reverse Brayton cycle (dual-RBC) hydrogen liquefaction process precooled by mixed-refrigerant

Abstract

In order to reduce hydrogen liquefaction power consumption, a dual reverse Brayton cycle (dual-RBC) process is proposed and analyzed in this paper, which consists of a mixed-refrigerant J-T cycle for precooling, a hydrogen RBC for hydrogen liquefaction, and a helium RBC for liquid hydrogen subcooling. Compared with typical dual-Claude processes, the two-phase low-pressure cycling hydrogen for liquid hydrogen product subcooling is replaced by an independent helium RBC, reducing the temperature difference and exergy loss in subcooling heat exchangers. Consequently, the specific power consumption (SPC) of dual-RBC process is 4.16% lower than dual-Claude process under the same conditions. The mixed-refrigerant J-T cycle (driven by single-stage oil-lubricated compressor, no liquid/two-phase expanders) could reduce precooling power consumption by >45% comparing with liquid nitrogen. The dual-RBC process could reach a SPC of 7.08 kWh kg−1 under typical conditions. While it is more realizable with mature technologies than novel processes.