LNG冷能用于CO_2跨临界朗肯循环和CO_2液化回收

LNG cold energy utilized in a transcritical CO_2 Rankine cycle and CO_2 recovery by liquefaction

提出了一种利用LNG冷能的新方案。一方面,采用CO2作为工质,利用燃气轮机的排放废气作为高温热源和LNG作为低温冷源来实现CO2的跨临界朗肯循环。由于高低温热源温差较大,循环能够顺利进行;另一方面,从燃气轮机排放的CO2废气在朗肯循环中放出热量后经LNG进一步冷却成液态产品。这样,不但利用了LNG冷能,而且天然气燃烧生成的大部分CO2也得以回收。计算分析了相关参数对跨临界循环特性的影响,包括循环最高温度和压力对系统的比功和火用效率的影响,并分析了回收的液态CO2的质量流量的变化情况。结果表明,这种新的LNG冷能利用方案是一种环境友好的高效方案。

A new scheme of utilizing LNG cold energy was presented in this paper. A CO2 transcfitical Rankine cycle was suggested, with emission from a gas turbine as its heat source and LNG as its cold sink. With CO2 working transcritically, large temperature difference for the Rankine cycle was realized. Moreover, the CO2 in the gas turbine emission was further cooled and liquefied by LNG after transferring heat to the Rankine cycle. In this way, the cold energy is not only utilized, but also a large part of the CO2 from burning of the vaporized LNG was recovered. In this paper, the system performance of this transcritical cycle was calculated. The influences of the highest cycle temperature and pressure to system specific work, exergy efficiency and liquefied CO2 mass flow rate were analyzed. The exergy loss in each of the heat exchangers was also discussed. It turns out that this novel cycle is energy- efficient and environment -friendly.