Comparative Thermodynamic Analysis of Inorganic Refrigerants in Cascade LNG Liquefaction Systems: A Performance Metrics

Abstract

The increasing demand for energy-efficient and environmentally friendly liquefied natural gas (LNG) production has led to the exploration of alternative refrigerants in cascade liquefaction systems. This study presents a comparative thermodynamic analysis of inorganic refrigerants in cascade liquefied natural gas (LNG) liquefaction systems, focusing on performance metrics. The research aims to evaluate the exergy losses, coefficient of performance (COP), energy requirements, and overall thermodynamic efficiency of various refrigerants, including Argon, Krypton, Xenon, Nitrogen, and the conventional C3MR (Propane Mixed Refrigerant). Results reveal significant variations in refrigerant performance. C3MR demonstrates the highest COP (4.25) but exhibits moderate exergy efficiency (63%) and high energy losses in compressors. Noble gases show contrasting trends: argon achieves exceptional exergy efficiency (83%) but poor COP (1.38), while xenon has low exergy efficiency (36%) but a competitive COP (2.99). Nitrogen incurs catastrophic exergy losses during depressurization (345,439 kJ/hr), highlighting operational challenges. The study underscores the need for component-specific refrigerant optimization and suggests hybrid systems combining C3MR’s heat transfer advantages with argon’s exergy efficiency. These findings advance LNG liquefaction technology by providing a nuanced framework for balancing thermodynamic performance, environmental impact, and operational feasibility