火电机组烟水复合回热系统节能解析

Energy-saving Analysis of the Flue Gas-water Compound Regenerative System in a Thermal Power Unit

针对采用新型烟气余热深度利用技术的烟水复合回热系统，以600MW超临界汽轮机组为例，运用热量平衡、火用平衡两种手段进行了节能分析。优化系统设置了空预器烟气旁路，布置高、低压换热器加热给水,设置回收低品位余热的前置空预器。通过定功率全系统热力计算表明，优化系统深度利用锅炉排烟余热，主蒸汽流量减少，供电标准煤耗率减小5．13g／（kW·h）。优化系统锅炉传热炯损失、回热加热器炯损失减少。机组总火用损失减少．效率提高。工程应用表明，改造后机组实际供电标准煤耗降低了6．78g／（kW·h）。

For a flue gas compound regenerative system adopting a novel flue gas waste heat in-depth utilization technology, with a 600 MW supercritical steam turbine unit serving as an example, the two methods such as the heat quantity balance and exergy one were employed to conduct an energy-saving analysis. The optimized system was installed with a flue gas bypass pipeline to the air preheater and a high and low pressure heat exchanger were equipped and arranged to heat the feedwater. In addition, a front-located air preheater was also provided to recover the low grade waste heat. The thermal calculation results of the whole system at a constant power output indicate that the optimized system can in-depth utilize the waste heat from the flue gases outgoing from the boiler, thus lowering the main steam flow rate and reducing the standard power supply coal consumption rate by 5.13 g/（kW · h）. As a result, the heat transfer exergy loss of the optimized system will decrease together with that of the regenerative heater. Subsequently, the total exergy loss of the steam turbine unit will go down and the efficiency up. The results of applications in practical engineering projects show that the practical standard power supply coal consumption rate decrease by 6.78 g/（kW · h） after the reconstruction.