Regasification of LNG for combustion in power plants typically employ seawater as a heat carrier in Open-Rack Vaporizers (ORV), causing much of the cold energy to be lost to the ambient. A comprehensive literature review shows that, thus far, no studies have been conducted to simultaneously consider the impacts of the exergy, economy and environment in the optimal design of a hybrid LNG recovery system. This paper aims to address this knowledge gap by establishing a multi-objective optimization model for a novel cascading quad-generation cold energy LNG recovery system. Single- and multi-objective optimizations based on Fuzzy method and Pareto optimal method are carried out on the proposed system to obtain the optimal operating parameters and component sizing, as well as the corresponding performances for each condition. The optimal sizing for each stage is computed for the maximizing of exergy efficiency and CO₂ savings rate, and the minimizing of capital cost. The exergy efficiency obtained from the triple-objective optimization yields 12.3% improvement compared to the best result from the single-objective optimization with a 5 kg/s LNG mass flow rate. In addition, when the LNG mass flow is larger than 1 kg/s, the maximized exergy efficiency remains constant (around 0.13) with increasing LNG mass flow rate while the maximized CO₂ emission reduction rate and minimized total cost per year increase linearly with the LNG mass flow rate. It has been demonstrated in this work that the system is able to maintain consistency in performance for the optimal design conditions over a wide range of LNG demands and hence good scalability for possible industrial and commercial settings.

用于发电厂燃烧的 LNG 再气化通常使用海水作为开架式汽化器 (ORV) 中的热载体，导致大部分冷能流失到环境中。综合文献综述表明，迄今为止，还没有研究在混合 LNG 回收系统的优化设计中同时考虑火用、经济和环境的影响。本文旨在通过为新型级联四代冷能 LNG 回收系统建立多目标优化模型来解决这一知识差距。对所提出的系统进行基于模糊方法和帕累托优化方法的单目标和多目标优化，以获得最佳运行参数和组件尺寸，以及每种条件下的相应性能。₂储蓄率，以及资金成本的最小化。与 5 kg/s LNG 质量流量的单目标优化的最佳结果相比，从三目标优化获得的火用效率提高了 12.3%。此外，当 LNG 质量流量大于 1 kg/s 时，随着 LNG 质量流量的增加，最大火用效率保持恒定（约 0.13），而最大 CO ₂减排率和最小每年总成本随着LNG 质量流量。在这项工作中已经证明，该系统能够在各种 LNG 需求的最佳设计条件下保持性能的一致性，因此对于可能的工业和商业环境具有良好的可扩展性。