Design and analysis of an efficient hydrogen liquefaction process based on helium reverse Brayton cycle integrating with steam methane reforming and liquefied natural gas cold energy utilization

Abstract

In order to solve the high energy consumption of the hydrogen liquefaction process, the conceptual design of an integrated hydrogen liquefaction system is proposed and performed by integrating the steam methane reforming (SMR) process and the utilization of liquefied natural gas (LNG) cold energy. Before LNG enters the SMR process, its cooling energy is utilized in the pre-cooling section, which can reduce the use of liquid nitrogen (LN2) and improve performance. The inert gas helium is relatively safe as a refrigerant in the cooling and cryogenic section and performs well in small and medium-sized hydrogen liquefaction systems. The proposed design which produces 5 t/d of liquid hydrogen (LH2) is compared to a based case only using LN2 for pre-cooling to verify its effectiveness and feasibility. Comprehensive comparative analysis reveals that the specific energy consumption (SEC) of the proposed process is reduced from 10.78 kWh/kg LH2 to 7.948 kWh/kg LH2, and the COP is improved from 0.1205 to 0.1634. The use of LNG cold energy makes the fuel cost of the proposed system only account for 73.7% of the base case, which makes it perform better in terms of recurring investment. In conclusion, the present method and results can provide a reference for the design of integrated hydrogen production and liquefaction system by reducing energy consumption, taking into account the recovery of the cold energy of LNG.