利用LNG冷火用的CO_2Rankine循环方案探析

CYCLE THERMODYNAMIC RESEARCH ON A CLOSED CO_2 RANKINE USING LNG CRYOGENIC EXERGY

我国已经决定引进液化天然气(LNG)。由于其储存温度和供气温度之间存在约为160℃的温差,应该充分利用其冷火用出功以提高能源利用水平。为此,该文建议了一种以CO2作为工作介质的闭式超临界Rankine循环,以亚临界的LNG作为冷源,燃气轮机余热作为热源。通过热力学参数分析,结果表明该循环在自变量的选取、流程的优化、循环特性等方面都不同于常规的Rankine循环。最后文中还给出了在这种循环中,燃气轮机排气流量、汽化的LNG流量和循环工质流量三者之间的定量耦合关系。

China has decided to import Liguified Natural Gas (LNG). Due to a large difference in temperature (about 160℃) between deposit condition and supply conditions, it is better to convert its cryogenic exergy into power to improve the energy utilization. For this purpose, we proposed a possible closed CO2 Rankine cycle with subcritical LNG as cold sink and gas turbine exhaust as heat source. Through thermodynamic analysis of parameters, the results show that the selection of chief independent parameters, optimization of flow processes and cycle characteristics are different from an ordinary Rankine cycle. At the same time, the quantitative relation, in the proposed cycle, among the gas turbine exhaust flow, the vaporized LNG flow and the CO2 working medium flow, is shown in this paper.