不同烟气再循环方案对1000 MW超超临界二次再热锅炉的影响

Influence of Different Flue Gas Recirculation Schemes on 1 000 MW Ultra-supercritical Double Reheat Boiler

为了分析不同再循环烟气抽取点和引入点对某1 000 MW超超临界二次再热锅炉运行参数的影响,提出分别从省煤器和引风机后抽取烟气,并引入到炉膛底部和上部共4种烟气再循环方案。进行热力计算,分析不同负荷、不同再循环率下各方案对锅炉参数的影响。结果表明:烟气再循环会降低炉膛出口烟温和升高排烟温度,抽取点为引风机后,排烟温度升高幅度较大,引入点为炉膛上部时,炉膛出口烟温下降幅度较大;再循环烟气引入炉膛底部可以提高再热蒸汽温度和主蒸汽温度,引入点为炉膛上部不能明显提高再热蒸汽温度且会降低主蒸汽温度;随着再循环率的增加以及负荷降低,烟气再循环对蒸汽温度的影响程度增加;从省煤器后抽取烟气的方案对锅炉热效率的影响较小,但再循环风机磨损较严重,从引风机后抽取烟气对锅炉热效率影响较大。

In order to analyze the influence of different recycle gas extraction points and introduction points on the operation parameters of a 1 000 MW ultra-supercritical double reheat boiler,four kinds of flue gas recirculation schemes are proposed;including extracting it from the economizer and induced draft fan,and introducing it into the bottom or upper part of the furnace.The influence of different schemes on boiler under different loads and different recycle rates is calculated and analyzed by the thermodynamic calculation.The results show that the flue gas recirculation will reduce the flue gas temperature at the outlet of the furnace and raise the exhaust gas temperature.With the extraction point located at the induced draft fan,the exhaust gas temperature increases greatly.With the introduction point located at the upper part of the furnace,the furnace outlet flue gas temperature decreases greatly.The introduction of recirculating flue gas into the bottom of the furnace can increase the temperature of the reheat steam and the main steam.The introduction form the furnace upper part cannot evidently improve the reheat steam temperature and will reduce the main steam temperature.With the increase of recycle rate and the decrease of the load,the influence of flue gas recirculation on steam temperature increases.The scheme of extracting flue gas from economizer has little effect on boiler efficiency,but the wear of the recirculating fan is serious,and the scheme of extracting gas from the induced draft fan has a clear influence on boiler efficiency.