A novel integrated hydrogen and natural gas liquefaction process utilizing a modified double mixed refrigerant process pre-cooling system

The hydrogen liquefaction process is energy-intensive due to the lower liquefaction temperature. To improve the energy efficiency of the hydrogen liquefaction process, a novel integrated liquefaction process employing a modified double mixed refrigerant process pre-cooling is proposed and analyzed. The three-stage adiabatic ortho–para hydrogen conversion makes the process compact. Furthermore, the particle swarm optimization algorithm is utilized to find the optimal decision variables. The result reveals that the total specific energy consumption (SEC) of the process is 6.5921 kWh/kgLH2-LNG, which is 15.83% lower than the base case. The SECs for the production of LNG and LH2 are 0.2445 kWh/kgLNG and 6.3476 kWh/kgLH2. Moreover, the exergy analysis and thermodynamic evaluation reveal that the exergy efficiency, coefficient of performance, and figure of merit of the process are 49.26%, 0.2306, and 0.49, exhibiting high thermodynamic performance. Finally, the sensitivity analysis indicates that the evaporation pressure of the sub-cooling refrigerant has the greatest impact on the performance of the process. The proposed process has an important reference value in the design of the combined production of LH2 and LNG from industrial by-products and the H2 liquefaction process.