超临界二氧化碳增压流化床燃煤发电系统方案及特性研究

Study on Characteristics of Supercritical Carbon Dioxide Pressurized Fluidized Bed Coal fired Power Generation System

增压流化床炉(pressurized fluidized bed combustion boiler,PFBCB)超临界二氧化碳(supercritical carbon dioxide,S-CO_(2))循环燃煤发电系统具备实现发电系统整体小型化与提高发电效率的潜力。围绕S-CO_(2)循环应用于燃煤发电领域面临的烟气热能全温区吸收这一共性问题,该文基于再热再压缩循环(Recompression cycle with reheating,RC+RH)提出两类耦合增压流化床炉的S-CO_(2)燃煤发电系统,可分别称为PFBCB-(RC+RH+RC)和PFBCB-(RC+RH),同时提出应用空气压缩机燃气轮机(air compressor-gas turbine,AC-GT)系统替代常压锅炉空气预热器系统的方案。根据计算可知,方案PFBCB-(RC+RH+RC)的效率低于PFBCB-(RC+RH),因为后者取消了RC底循环,因此系统布置更为简单,效率更高。但方案PFBCB-(RC+RH+RC)的炉内压力可维持在1~2MPa,而方案PFBCB-(RC+RH)炉内压力可达2.8~4.5MPa,故从锅炉侧看,前者更容易实施。此外,PFBCB-(RC+RH)系统可通过高压运行AC-GT,实现热能的回收,可有效解决余热问题。当主气温度处于620℃/30MPa时,该系统的发电效率为47.97%,当主气温度处于700℃/35MPa时,系统的发电效率为51.15%,体现出明显的效率优势。

It is potential for the S-CO_(2) coal-fired power system with a pressurized fluidized bed combustion boiler(PFBCB)to reduce the overall system volume and improve electrical efficiency.The supercritical carbon dioxide Brayton cycle(S-CO 2)is difficult to absorb flue gas heat in a whole temperature range.Focusing on this problem,this paper originally proposes two S-CO_(2) coal-fired power systems based on PFBCB,named as PFBCB-(RC+RH+RC)and PFBCB-(RC+RH),respectively.Meanwhile,the scheme of the AC-GT system is proposed to substitute that of the traditional air preheater.It is found that the efficiency of PFBCB-(RC+RH)is higher than that of PFBCB-(RC+RH+RC)and the system arrangement of the former is simpler than the latter,as the latter eliminates the bottom cycle.However,the furnace pressure of PFBCB-(RC+RH+RC)remains 1~2MPa,while the furnace pressure of PFBCB-(RC+RH)can reach as high as 2.8~4.5MPa.Therefore,from the view of a boiler,PFBCB-(RC+RH+RC)is easier for construction.From another point of view,the PFBCB-(RC+RH)system coupled with AC-GT can recover flue gas waste heat.At the main vapor temperature of 620℃/30MPa,the electrical efficiency of the system reaches 47.97%;and at the main vapor temperature of 700℃/35MPa,the efficiency can reach as high as 51.15%,which shows obvious efficiency advantage over the traditional coal-fired power plant.