循环工质对LNG冷能发电系统性能的影响  

Effect of circulating working fluids on performance of LNG cold energy power generation systems

作　　者：王荧光 蔡东旭 梁勇 张帅 冷绪林 陈伟 龚文政 胡大鹏[2] WANG Yingguang;CAI Dongxu;LIANG Yong;ZHANG Shuai;LENG Xulin;CHEN Wei;GONG Wenzheng;HU Dapeng(PipeChina Engineering Technology Innovation Co.,Ltd.,Tianjin 300450,China;Department of Chemical Machinery and Safety,School of Chemical Engineering,Dalian University of Technology,Dalian 116012,Liaoning,China)

机构地区：[1]国家管网集团工程技术创新有限公司,天津300450 [2]大连理工大学化工学院化工机械与安全系,辽宁大连116012

出　　处：《低碳化学与化工》2024年第10期119-128,135,共11页Low-Carbon Chemistry and Chemical Engineering

基　　金：国家重点研发计划(2018YFA0704602);国家石油天然气管网集团有限公司科研项目(DTXNY202202);中央高校基本科研业务费(DUT22LAB604)。

摘　　要：朗肯循环可将液化天然气(LNG)冷量[火用]转化为电能,是一种有效的冷能回收利用技术。结合工程实际,将LNG冷能发电系统内最低压力设置为高于常压,探究了循环工质对系统性能的影响。将7种常用工质作为备选,以系统净输出功最大为目标函数,在相同工况下对单级联合循环(CC)、串联联合循环(CCC)和并联联合循环(PCC)3种常见的LNG冷能发电系统进行了优化。分析了选择不同工质时系统性能的差异及其原因,探究了有无直接膨胀过程对工质选择的影响。结果表明,CC、CCC和PCC系统的最优工质分别为CH_(2)F_(2)、C_(2)H_(6)+C_(3)H_(8)和C_(2)H_(4)+C_(3)H_(8)。选择最优工质情况下,CCC系统通过对LNG冷能的有效分段利用,减少了系统内的不可逆[火用]损失,所以性能相对最优,其热效率相比CC和PCC系统分别提升了54.8%和35.4%,且所需换热面积并未显著增加。有无直接膨胀不影响系统内工质选择,但无直接膨胀会导致最大系统净输出功略有降低。The Rankine cycle can convert liquefied natural gas(LNG)cold energy into electrical energy,which is an effective cold energy recovery and utilization technology.Based on engineering practice,the lowest pressure in the LNG cold energy power generation system was set to be higher than normal pressure,and the effect of circulating working fluids on system performance was explored.Seven commonly used working fluids were selected as candidates,with the objective function of maximizing the net output power of the system.Under the same operating conditions,three common cold energy power generation systems,namely single-stage combined cycle(CC),cascade combined cycle(CCC)and parallel combined cycle(PCC),were optimized.The differences in system performance and their reasons when selecting different working fluids were analyzed,and the effect of direct expansion process on working fluid selection was explored.The results show that the optimal working fluids for CC,CCC and PCC systems are CH_(2)F_(2),C_(2)H_(6)+C_(3)H_(8) and C_(2)H_(4)+C_(3)H_(8),respectively.When selecting the optimal working fluid,the CCC system reduces irreversible energy loss within the system by effectively segmenting the utilization of LNG cold energy,resulting in relatively optimal performance.Compared with CC and PCC systems,the thermal efficiency of CCC system increases by 54.8%and 35.4%,and the required heat exchange area does not significantly increase.The presence or absence of direct expansion does not affect the selection of working fluids within the system,while the absence of direct expansion can lead to a slight decrease in the maximum net output power of the system.

关 键 词：LNG冷能发电 遗传算法优化 朗肯循环 工质选择 系统性能对比 直接膨胀 

分 类 号：TE09[石油与天然气工程] TM619[电气工程—电力系统及自动化]