Design and Dynamic Evaluation of Next-Generation LNG Boil-Off Gas Re-Liquefaction Systems Using Hybrid Cryogenics

Abstract

Abstract The increasing complexity of global Liquefied Natural Gas (LNG) supply chains had intensified the need for high-efficiency, low-emission boil-off gas (BOG) re-liquefaction systems, yet existing technologies, despite advances in compression-free cold-energy cycles, cryogenic CO2 capture hybrids, and liquid-air refrigeration, had continued to exhibit limitations in dynamic performance, large-scale integration, and experimental validation. In response, the study aimed to develop a unified and experimentally validated BOG re-liquefaction framework capable of enhancing efficiency, reliability, and adaptability under realistic operating conditions. The methodology involved analyzing the dynamic and control behavior of compression-free and hybrid cycles under fluctuating BOG loads, evaluating pinch-point constraints, scalability, and integration feasibility at terminal scale, and conducting experimental assessments to validate heat-exchange behavior, stability, and safety during off-design operation. The results showed that the integrated framework improved thermodynamic efficiency, reduced operational instability under variable loads, and demonstrated feasible coupling of LNG cold energy, liquid-air systems, and cryogenic CO2 capture. Analysis further revealed that hybridization strategies strengthened energy recovery while lowering emissions and minimizing equipment oversizing. Overall, the study concluded that the unified framework offered a practical, flexible, and energy-optimized approach to BOG management, providing a foundation for next-generation re-liquefaction technologies suitable for both terminal and marine environments.