液化天然气(LNG)联合循环电站热力学分析

Thermodynamic analysis for LNG combined cycle power plants

基于系统部件的质量、能量和平衡,对以液化天然气(LNG)为燃料的联合循环电站,建立其计算模型,进行能量分析和分析,确定各个过程因热量、质量、功的传递以及不可逆损失导致的变化。结果表明,燃烧室和燃气透平的损失最大,占总损失的75%;燃料供应系统用海水为热源气化LNG,此过程因为输送海水要消耗大量的泵功,且浪费了LNG中蕴藏的大量高品位冷能,相对损失达2.21%。根据热力学分析结果,提出了进一步提高LNG联合循环电站效率的建议。

A computational model for a liquefied natural gas （LNG） fuelled combined cycle power plant was developed, considering mass, energy and exergy balances for every component. In addition, both energy and exergy analyses were conducted to determine the exergy changes caused by heat, mass or work transfer irrevesibilities of each process. The results show that the great exergy loss takes place at the combustion chamber and gas turbine, which is about 75% of the overall exergy losses. The fuel supply system uses sea water as the heat source to vaporize LNG, and this process consumes 0.1 MW of electric power for operating the sea water pump and wastes plenty of physical cold energy, in which relative irreversibility is about 2.21%. Some constructive suggestions are proposed to improve the efficiency of the system based on results of the thermodynamic analysis.