An energy-saving hydrogen liquefaction process with efficient utilization of liquefied natural gas cold energy

Abstract

Storage and transportation of hydrogen in liquid form offers considerable advantages, but the high energy consumption of hydrogen liquefaction processes needs to be addressed. In this study, a novel hydrogen liquefaction process integrated with a dual-pressure organic Rankine cycle (DORC) is proposed. It offers significant energy-saving by efficiently utilizing the cold energy of liquefied natural gas (LNG). The key parameters in the proposed process are investigated, and the results are combined with an improved genetic algorithm for efficient optimization of the process. The optimal exergy efficiency of the proposed process is 48.7%, and the minimal energy consumption is 6.29 kWh/kgLH2. Thanks to the power output (381.3 kW) of the DORC and the energy saved by the cryogenic compression of nitrogen (586.6 kW), energy consumption of the proposed process is reduced by approximately 3.1% compared to that of the process without a DORC. Moreover, an improved helium Brayton refrigeration cycle for hydrogen cryo-cooling is simpler, but less the refrigerant usage and energy consumption compared to the previously proposed cycles. The proposed process demonstrates excellent performance in terms of energy saving and efficiency improvement, providing a low-cost scheme to produce liquid hydrogen.