Optimization and Analysis of integrated hydrogen production and liquefaction system combining LNG and CO2 Regeneration Rankine Cycle

Improving the efficiency of hydrogen (H2) liquefaction systems, reducing carbon dioxide (CO2) emissions and recovering waste heat have become critical research topics nowadays. An integrated hydrogen production and liquefaction system was developed with CO2 regeneration Rankine cycle combining liquefied natural gas (LNG) and mixed refrigerant (MR). Thermodynamic analysis, exergy analysis and economic analysis of the system were conducted and compared with other cases. In addition, original optimization model was used for multi-objective optimization. The optimization results show that: Original is superior for the optimization of this system compared to genetic algorithm (GA), the values of specific energy consumption (SEC),coefficient of performance (COP), figure of merit (FOM) and exergy efficiency (ηex) are 5.51 kWh/kgLH2, 0.24, 0.76 and 65.81 %, respectively. The primary exergy losses occur in the heat exchangers and turbines. The proposed system exhibits superior economic performance by the 10th year of operation. Compared to pre-cooling with LNG or MR alone, the combined pre-cooling of LNG and MR reduces SEC by 14.9 % and 10.45 %, and increases ηex by 5.60 % and 10.34 %, respectively. These findings contribute to energy conservation and environmental protection.