利用液化天然气冷能的冷热电联供系统热力分析与优化

Thermal analysis and optimization of combined cooling,heating and power system using LNG cold energy

为解决以甲烷作为燃料的固体氧化物电池余热利用、碳捕集以及液化天然气冷能利用问题,建立了一种新型的冷热电联供系统。该系统包括改进再压缩超临界混合工质布雷顿循环、跨临界CO_(2)回热朗肯循环和二级混合工质有机朗肯循环,对循环系统进行热力学分析、设备[火用]分析、经济成本分析,并利用遗传算法对系统参数进行多目标优化。仿真分析结果表明:提升改进再压缩超临界混合工质布雷顿循环的膨胀机入口压力、跨临界CO_(2)回热朗肯循环的膨胀机入口温度与二级朗肯循环中R14的质量分数可提升系统循环净功、热效率、[火用]效率并降低平均单位成本;在最优工况条件下,系统热效率、[火用]效率、平均单位成本分别为64.70%、47.85%、24.20美元/GJ。

In order to solve the problems of waste heat utilization,carbon capture and LNG cold energy utilization of solid oxide batteries fueled by methane,a new type of combined cooling,heating and power system was established.The system includes the improved recompression supercritical mixed working fluid Brayton cycle,the transcritical CO_(2) heat recovery Rankine cycle and the secondary mixed working fluid organic Rankine cycle,and the thermodynamic analysis,equipment analysis,economic cost analysis of the circulation system,and the multi-objective optimization of the system by using the genetic algorithm in MATLAB.The results show that increasing P1,T16 and the mass fraction of R14 in the second-stage Rankine cycle can improve the network,thermal efficiency,and exergy efficiency of the system,and reduce the average unit cost.Under the optimal working conditions,the thermal efficiency,the exergy efficiency and the average unit cost of the system were 64.7%,47.85%and 24.2$/GJ.The research results can efficiently recover heat and cold energy for power generation,which is conducive to saving resources.