Analysis of a novel hydrogen liquefaction process based on a mixed refrigerant Brayton cryogenic cycle utilizing LNG cooling: energy, exergy, economy and environment

The hydrogen liquefaction process (HLP) is crucial for promoting the development of hydrogen, yet it is currently constrained by high energy consumption and low efficiency. This research introduces an innovative conceptual HLP based on a mixed refrigerant (MR) Brayton refrigeration cycle utilizing liquefied natural gas (LNG) cold energy for precooling. The cold energy released during LNG gasification is not only used for hydrogen precooling and coupled with a binary organic Rankine cycle (ORC) for power generation but also employed to balance the self-precooling heat load of the cryogenic refrigerant. The unique thermodynamic properties of hydrogen are fully considered in the simulation. Targeted analyses encompassing energy, exergy, economic, and environmental aspects are performed on the HLP. The results indicate that the new HLP exhibits high energy efficiency, with a specific energy consumption (SEC) of 4.150 kWh/kgLH2, an exergy efficiency (EXE) of 47.82 %, and a coefficient of performance (COP) of 0.2859. In addition, the carbon dioxide (CO2) emissions are reduced by 37.03 % compared with those of the base reference process. This study achieves resource coupling utilization and energy conservation while reducing emissions, contributing to the improvement and optimization of practical engineering projects.