Optimization and analysis of a hydrogen liquefaction process: Energy, exergy, economic, and uncertainty quantification analysis

To reduce the specific energy consumption (SEC) of the hydrogen liquefaction process, a conceptual design of a hydrogen liquefaction process that integrates a modified natural gas single mixed refrigerant process and a hydrogen expansion cycle. The energy efficiency of the process is improved by operating each refrigeration cycle at different pressures. The process is optimized using a particle swarm optimization algorithm. Furthermore, the uncertainty levels of the SEC and the minimum internal temperature approach of the heat exchanger with varying parameters are investigated by applying uncertainty quantification (UQ). The results indicate SEC is 5.963 kWh/kg with 52.61% exergy efficiency. The thermodynamic evaluation shows that the coefficient of performance and figure of merit are 0.2218 and 0.526. The UQ analysis reveals that the SEC is strongly influenced by changing the flow rate and pressure of the sub-cooling refrigerant, with a distribution of SEC between 5.479 and 6.451 kWh/kg. Finally, the economic evaluation yields a total annualized cost of $25.42 million/y. This study is expected to provide an insight into designing an energy-efficient hydrogen liquefaction process by introducing a natural gas mixed refrigerant process.