集成SCO_2动力循环的燃煤电站余热回收系统研究

Study on Heat Recovery System of Coal-Fired Power Plant Integrated With SCO_2 Power Cycle

低温烟气热能的高效梯级利用是火电厂节能减排的重要方向之一。本文结合某1000 MW超临界机组,对常规低温省煤器烟气余热利用系统进行了热力学分析,发现该系统可使系统发电标准煤耗率降低2.50 g·(kW·h)^(-1),但分析发现,空气预热器耗散占输入媚的22.03%,多于锅炉排烟所携带的。为此,本文提出了集成SCO_2动力循环的火电厂低温烟气热能利用系统,旨在减少空气预热器中的耗散。对SCO_2动力循环参数进行了优化,在优化参数下该系统可以使发电标准煤耗率降低3.62 g.(kW·h)^(-1),进一步集成低温省煤器可使发电标准煤耗率降低达5.58 g·(.kW·h)^(-1),最后采用分析结果解释了系统节能的本质原因。

The efficient use of energy carried by low temperature flue-gas is a hot topic of energy saving in thermal power plant. The thermodynamic analyses on conventional low temperature economizer with a reference case of 1000 MW supercritical power plant were carried out. Results show that the standard coal consumption rate for power generation could be decreased by 2.50 g.（kW.h）^-1. However a big portion of exergy was destructed in air pre-heater, about 22.03% to the total exergy put into the air pre-heater, which is bigger than the exergy carried by the boiler exhaust. Therefore, a waste heat utilization system integrated with SCO2 power cycle was proposed in this paper, which is designed to decrease the exergy destruction in air pre-heater. Then parameters of SCO2 power cycle were optimized. The standard coal consumption rate for power generation could be decreased by 3.62 g-（kW-h）^-1 with optimal parameters. The standard coal consumption rate for power generation could be further decreased by 5.58 g.（kW.h）^-1 when low temperature economizer were also integrated. Finally the essential reason for the energy saving were revealed by exergy analysis.