Hassan Aghdasinia

Natural gas (NG) is increasingly vital as a cleaner energy source due to its lower carbon emissions compared to other fossil fuels. Liquefaction facilitates efficient long-distance transportation. While numerous studies address NG liquefaction's technical aspects, holistic research remains limited. This study presents a comprehensive 4E (energy, exergy, exergoeconomic, and exergoenvironmental) analysis of five conventional NG liquefaction processes (including SMR-Linde, SMR-APCI, C3MR-Linde, DMR-APCI, and MFC-Linde), employing production volume-independent parameters for comparison. Simulations show that  the MFC-Linde cycle as the most efficient regarding specific energy consumption (0.2563  ), coefficient of performance (3.184), and exergy efficiency (52.32%). It also demonstrates the lowest unit exergy cost ( ) and environmental impact ( ). Multi-objective optimization, considering both exergetic-economic and exergetic-environmental criteria, using neural networks and genetic algorithms in MATLAB identifies Pareto-optimal conditions for all processes. For the MFC-Linde, as the most efficient process, optimal operating conditions in the exergetic-economic trade off scenario are:   and   ; at  ,  , and  . Finally, a feasibility study for large-scale LNG production in Iran shows promising results, with a return on investment of 32.24   and a payback period of 2.34 years, indicating the project's potential success in regions with abundant NG reserves.