二次再热机组锅炉烟气余热利用方案研究

Study on Waste Heat Utilization Scheme of Boiler Flue Gas of Secondary Reheat Unit

以某典型超超临界二次再热机组为例,利用EBSILON软件,建立锅炉汽机一体化余热回收利用静态仿真模型,对4种余热回收方案(排挤一次再热前抽汽、排挤二次再热前抽汽、排挤全部高压加热器抽汽和排挤高压加热器-低压加热器抽汽)进行仿真计算,确定机组的热经济性。结果表明:排挤一次再热前抽汽的方案符合能量梯级利用和提高回热再热循环效率原则,节能效果最好,设计工况下发电标准煤耗率减少了7.24 g/(kW·h);变工况时不仅煤耗率相对减少率最大,而且变化幅度较为平缓,节能效果也最好。

In this paper,with a typical ultra-supercritical secondary reheat unit as an example,a static simulation model for the integrated waste heat recovery and utilization of boiler-steam turbine was established with the software of EBSILON.Four waste heat recovery schemes were simulated(squeezing out steam before reheating,squeezing out steam before secondary reheating,squeezing all high pumping steam and squeezing high-low pumping steam),and the corresponding thermal economy of the unit was determined.The results showed that the scheme 1 of pumping steam before primary reheating confirms to the principle of energy cascade utilization and improvement of reheating and heat recycling efficiency,resulting in the best energy saving effect under the design condition,and 7.24 g/(kW·h)reduction in the standard coal consumption rate of power generation.Under the varying operating conditions,scheme 1 has not only the largest relative reduction rate of coal consumption,but also a relatively smooth change range.