Optimization and advanced exergy assessment of a propane-free dual mixed-refrigerant LNG liquefaction process

Liquefied natural gas (LNG) production is an energy-intensive process, and mixed-refrigerant cycles dominate industrial applications. This study proposes and optimises a novel propane-free dual mixed refrigerant (DMR) configuration for LNG liquefaction using Aspen HYSYS v14 with the Peng-Robinson EOS. The system eliminates propane to enhance operational safety while maintaining high thermodynamic efficiency. Energy, exergy, and advanced exergy analyses reveal a specific energy consumption (SEC) of 0.29 kW/kg LNG and an exergy efficiency of 67.27 %. The advanced exergy assessment identifies that 68.40 % of total exergy destruction is avoidable, indicating significant potential for further efficiency gains. Comparative benchmarking confirms that the proposed configuration achieves one of the lowest reported SEC values among both propane-based and propane-free DMR cycles. This research provides a technically validated and safer pathway towards sustainable LNG production.