Abstract This paper proposed a cryogenic power generation system composed of Rankine cycles and direct expansion cycle, aiming at the efficient utilization of flue gas waste heat and liquefied natural gas (LNG) cold energy. Both the sensible heat and latent heat of the humid flue gas are recovered to meet the heat demand of a typical LNG terminal. Performance analysis was conducted to reveal the potential improvement direction and determine the key parameters. Then, parametric study was carried out to evaluate the effects of key design parameters on system performance. Four combinations of working fluids were compared, and the system performance was analyzed at different flow rates of natural gas. Results indicate that the net power output decreases as the condensing temperature of the bottoming Rankine cycle increases, and there exists a volcano-type relationship between the net power output and natural gas expansion pressure. R290/R1150 is the preferred combination of working fluids under the design conditions, and the maximum thermal efficiency, exergy efficiency, and specific power can reach 27.07%, 48.42%, and 74.15 kWh/ton-LNG, respectively. Moreover, the specific power decreases with the increase of LNG flow rate. R1270/R1150 becomes the best combination of working fluids, when the LNG flow rate exceeds 120.28 kg/s.

中文翻译：

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一种回收烟气显热和潜热的低温发电系统的热力学分析

摘要 针对烟气余热和液化天然气(LNG)冷能的高效利用，提出了一种由朗肯循环和直接膨胀循环组成的低温发电系统。湿烟气的显热和潜热都被回收，以满足典型 LNG 接收站的热量需求。进行性能分析以揭示潜在的改进方向并确定关键参数。然后，进行参数研究以评估关键设计参数对系统性能的影响。比较了四种工质组合，分析了不同天然气流量下的系统性能。结果表明，随着底部兰金循环冷凝温度的升高，净功率输出降低，净发电量与天然气膨胀压力之间存在火山型关系。R290/R1150是设计工况下优选的工质组合，最大热效率、火用效率和比功率分别达到27.07%、48.42%和74.15 kWh/ton-LNG。而且，比功率随着LNG流量的增加而降低。当LNG流速超过120.28 kg/s时，R1270/R1150成为工质的最佳组合。比功率随着LNG流量的增加而降低。当LNG流速超过120.28 kg/s时，R1270/R1150成为工质的最佳组合。比功率随着LNG流量的增加而降低。当LNG流速超过120.28 kg/s时，R1270/R1150成为工质的最佳组合。