Liquefied natural gas (LNG) technology, particularly the propane precooled mixed refrigerant (C3MR) process, has demonstrated efficiency and emerged as a distinctive dual-refrigerant technology widely used in LNG production. However, the liquefaction process is the highest energy-intensive stage within its supply chain as it consumes about 8 % of the LNG energy content. Thus, for the first time, this study proposes systematic knowledge-based and constrained Bayesian optimization approaches to identify the optimal operation of the C3MR process. These approaches optimize both the operational parameters (pressures and flow rates) and the composition of the mixed refrigerant with practical equipment specifications and rigorous constraints. The results show that the specific energy consumption (SEC) is reduced to 0.264 kWh/kg, which is 14.6 %, and 26 % lower than the basic C3MR process (unoptimized case) and typical industrial C3MR processes, respectively. In addition, the optimized SEC in this study is 14.5 % to 38.6 % lower than those reported in the literature. At large-scale LNG production (10,000 tons per day), the reduction in the SEC is translated into an 18 MW decrease in compression power, saving approximately 4.7 million $ per year for each C3MR train. Moreover, the coefficient of performance (COP) of the C3MR process was improved by about 15 %, and the CO emissions were reduced by 17 % (7 tons per year) compared to the basic C3MR process, indicating potential advancements in large-scale LNG liquefaction processes.

中文翻译：

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丙烷预冷混合制冷剂液化天然气工艺的运行优化：基于知识和约束贝叶斯优化方法的新颖集成


液化天然气（LNG）技术，特别是丙烷预冷混合制冷剂（C3MR）工艺，已经证明了效率，并成为广泛应用于液化天然气生产的独特双制冷剂技术。然而，液化过程是其供应链中能源密集度最高的阶段，因为它消耗了约 8% 的液化天然气能源。因此，本研究首次提出了基于知识的系统约束贝叶斯优化方法来确定 C3MR 过程的最佳操作。这些方法通过实用的设备规格和严格的约束来优化操作参数（压力和流量）和混合制冷剂的成分。结果表明，单位能耗（SEC）降低至0.264 kWh/kg，分别比基本C3MR工艺（未优化情况）和典型工业C3MR工艺低14.6%和26%。此外，本研究中优化后的 SEC 比文献报道的低 14.5% 至 38.6%。在大规模液化天然气生产（每天 10,000 吨）中，SEC 的减少意味着压缩功率减少 18 MW，每辆 C3MR 列车每年节省约 470 万美元。此外，与基本C3MR工艺相比，C3MR工艺的性能系数（COP）提高了约15%，二氧化碳排放量减少了17%（每年7吨），表明在大规模液化天然气方面具有潜在的进步液化过程。