利用LNG冷能液化二氧化碳的动力循环技术分析

Analysis of the Power Cycle Technologies for CO_2 Liquefaction with LNG Coldness Energy

对以LNG冷能液化CO2的朗肯循环式和耦合循环式技术方案进行了综述和分析。提出了改进的朗肯循环式技术方案并作了深入探讨,新方案采用CO2作为工质,利用LNG作为低温冷源和燃气轮机的排放废气作为高温热源来实现CO2的跨临界朗肯循环。而从燃气轮机排放的CO2废气在朗肯循环中放出热量后经压缩再和工质CO2一起与LNG换热进一步冷却成液态产品。利用Hysis软件优化计算,结果显示该工艺的比功为304.1 kJ/kg LNG,CO2液化率为0.5385 kg/kg LNG,有效能效率为43.70%。与现有技术方案相比,本技术方案的比功和有效能效率适中,CO2液化率最高。

The two methods,i. e. Rankine cycle and coupled cycle,for CO2 liquefaction with LNG coldness energy were summarized and analyzed. An improved Rankine cycle method was proposed and discussed in detail. In the newly developed method,the Rankine cycle of transcritical CO2 ,the working medium,was achieved with LNG as the cold sink and with the exhaust gas for combustion gas turbine as hot sink. CO2 containing exhaust gas,will release heat in Rankine cycle,be compressed,and then be liquefied by LNG together with the working medium. The optimization result from Hysis software shows that the specific work is 304. 1 kJ/ kg LNG,the ratio of CO2 liquefaction is 0. 5385 kg/ kg LNG and the exergy efficiency is 43. 70% for the new method. Compared with the existing methods,the new method is moderate of specific work and the exergy efficiency,meanwhile with the maximum ratio CO2 liquefaction.