基于LNG冷能利用的多联产系统模拟与性能优化

Simulation and performance optimization of a poly-generation system based on LNG cold energy utilization

为解决发电系统中有机工质在中高温下易热分解的问题,根据“温度对口,梯级利用”原则,将超临界CO_(2)与跨临界CO_(2)结合用于回收余热,构建了一种基于LNG冷能利用的多联产系统。利用Aspen HYSYS软件对系统工艺流程进行模拟,从热力性能与经济角度对系统进行评估,分析主要参数对系统性能的影响,进而利用Matlab软件进行系统性能多目标优化。结果表明:超临界CO_(2)再压缩布雷顿循环分流比与制冷循环压比的降低不仅可以提高系统效率,还可以降低系统平均单位成本;优化后联合系统发电效率、效率、平均单位成本分别为55.83%、52.23%、16.57美元/GJ,发电效率较集成单一超临界CO_(2)再压缩布雷顿循环的系统提高了14.05%。研究成果为LNG冷能利用及余热回收在发电系统中的应用提供了新的技术思路。(图9,表4,参26)

In order to solve the problem that the organic working medium of a power generation system is easy to thermal decomposition at medium and high temperature,the waste heat was recovered with the supercritical and transcritical CO_(2) used in combination on the principle of“appropriate temperature and cascade utilization”,and a poly-generation system based on LNG cold energy utilization was established.Herein,the system was simulated by Aspen HYSYS in terms of the process flow and evaluated from the prospective of thermal performance and exergoeconomy.Besides,the effect of main parameters on system performance was analyzed,and on this basis,the multi-objective optimization of system performance was carried out using Matlab.The results show that the reduction of split ratio in supercritical CO_(2) recompression Brayton cycle and compression ratio in refrigeration cycle can not only improve the system efficiency,but also reduce the average unit cost.In addition,the power generation efficiency,exergy efficiency and average unit cost of the optimized poly-generation system are 55.83%,52.23% and 16.57$/GJ,respectively,and the power generation efficiency has been enhanced by 14.05% in comparison to the system integrated with the single supercritical CO_(2) recompression Brayton cycle.Generally,the research results could provide an application idea for the utilization of LNG cold energy and the recovery of waste heat.(9 Figures,4 Tables,26 References)