Enhancements and optimization of LNG cold energy recovery via advanced binary working fluid power cycle systems

This study investigated the optimization of power generation systems for liquefied natural gas (LNG) cold energy recovery through systematic evaluations of working fluid selections and cycle configurations. Two-stage power cycles operating between LNG regasification temperatures and ambient conditions were optimized using genetic algorithms across 30 single fluids and 49 binary mixtures, and four advanced cycle configurations. The designs were evaluated for an LNG regasification terminal with 216 t·h−1 receiving capacity. Screening of single fluids identified R116 and R170 as the optimal working fluids, achieving 7.5 MW net power and 24.1% thermal efficiency. R116 demonstrated consistent superiority in upper cycle applications due to its non-isothermal heat rejection characteristics and high evaporation temperature. Mixed working fluids offered comparable performance and enhanced consistency, showing less than 5% variation among all R116-based combinations. The analysis of advanced configurations revealed substantial performance differences among enhancement strategies. The Rankine cycle with reheating achieved a net power output of 9.2 MW using the R1150–R170 mixture, representing 22% and 19% improvements over the optimal single and mixed-fluid scenarios. Conversely, Kalina integration and regeneration modifications provided negligible benefits, with optimal configurations achieving marginally comparable performance to the baseline Rankine cycles. The results demonstrate that two-stage Rankine cycles with reheating represent the most effective configuration for LNG cold energy recovery applications.