Optimization of Inorganic Refrigerants in Cascade LNG Liquefaction Systems: A Response Surface Methodology Approach for Enhanced Energy Efficiency and Sustainability
Author(s):
Chukwuka D Offodum1*, Akuma Oji1
and Ifeanyichukwu U Onyenanu2
The global energy transition has intensified the demand for sustainable liquefied natural gas (LNG) production, necessitating advanced refrigeration systems with minimal environmental impact. This study presents a comprehensive thermodynamic optimization of inorganic refrigerants (xenon, argon, krypton, nitrogen) in cascade LNG liquefaction cycles using response surface methodology (RSM). Through Aspen HYSYS modeling and I-optimal design experiments, key performance metrics—coefficient of performance (COP), cooling capacity, specific work, exergetic efficiency, and overall thermal efficiency—were evaluated across varying evaporating temperatures (−50°C to −30°C) and pressure regimes (10–30 bar). Results demonstrate that xenon achieves superior performance, with a COP of 3.6 and exergetic efficiency of 89% at optimal conditions (−44.5°C, 10.78 bar), outperforming conventional mixed refrigerants (C3MR) by 16.6% in specific energy consumption. Exergy analysis reveals that xenon minimizes irreversibility in compression and heat exchange stages, reducing exergy destruction by 21% compared to nitrogen. However, economic constraints due to xenon’s high cost highlight the trade-offs between efficiency and scalability. This work advances sustainable LNG production by identifying energy-efficient refrigerant alternatives while providing a robust RSM framework for industrial process optimization.
