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构建LNG低温朗肯循环发电系统是冷能利用的主要方式之一。为了提高LNG冷能回收效率,根据LNG气化特性,笔者提出了冷能的分段利用模型,并采用分析的方法对低温朗肯循环各环节的火用损失进行了分析,得出如下结论:①LNG气化曲线存在较为明显的分段规律,为建立高效的冷能发电循环提供了基础;②LNG低温朗肯循环发电系统的损失主要集中在换热设备当中,因而系统的优化重点应放在对于换热设备尤其是冷凝器的优化上,减少平均换热温差能有效降低换热器的传热不可逆损失;③对LNG按不同温度段进行回收利用,构建梯级循环发电系统,能有效减小循环冷损失,提高LNG冷能回收效率。根据LNG气化特性构建的梯级循环流程较单极循环流程而言,总的冷损失显著减少,冷火用利用效率提高了16.2%。
Building LNG Low Rankine cycle power generation system is one of the main ways to utilize cold energy. In order to improve the efficiency of cold energy recovery of LNG, according to the characteristics of LNG gasification, the author proposed a sub-utilization model of cold energy and analyzed the exergy loss of every link of Low Rankine cycle using analysis method, and concluded as follows : ①LGG gasification curve has obvious subdivision rules, which provide the foundation for the establishment of efficient cold power generation cycle; ②LNG low temperature Rankine cycle power generation system, the loss is mainly concentrated in the heat exchanger equipment, so the system optimization should focus on In the optimization of the heat exchange equipment, especially the condenser, reducing the average heat transfer temperature difference can effectively reduce the irreversible loss of the heat transfer of the heat exchanger; (3) Recycling LNG at different temperature ranges to construct a cascade cycle power generation system, which can effectively reduce Small cycle cold loss, improve LNG cold energy recovery efficiency. The cascade circulation process based on the gasification characteristics of LNG shows a significant reduction in total cold loss and a 16.2% improvement in utilization efficiency of cold fire compared with the unipolar circulation process.