燃煤锅炉SCR脱硝系统及其流场优化研究

Research on SCR Denitrification System and Its Flow Field Optimization for Coal-Fired Boilers

为解决燃煤机组瞬态过程中选择性催化还原技术(Selective Catalytic Reduction,SCR)系统精准喷氨困难的问题,基于数值计算结果对燃煤锅炉的省煤器出口烟道导板和SCR顶部导流板进行优化,建立被控系统和动态响应模型,利用人工智能算法在线完善模型,以实现精准喷氨。改造后,SCR入口烟道A、B侧烟气流速分别为9.0 m/s和9.2 m/s,相对标准偏差CV值为11.4%和10.7%。SCR入口烟道A、B侧NOx平均质量浓度为250.7 mg/m3和260.5 mg/m3,相对标准偏差CV值分别为4.8%和5.0%。SCR出口烟道A、B侧NOx平均放质量浓度为47.1 mg/m3和51.6 mg/m3,相对标准偏差CV值分别为12.3%和12.5%,基本实现了超低排放的要求。液氨单耗从改造前0.2783 kg/MWh下降到0.2152 kg/MWh,下降了27.8%。

In order to address the difficulty of precise ammonia injection in the Selective Catalytic Reduction(SCR)system during the transient process of coal-fired power units,the author optimizes the outlet flue guide plate and SCR top guide plate of the economizer of a coal-fired boiler based on numerical calculation results,establishes a controlled system and dynamic response model,and improves the model online using artificial intelligence algorithms to achieve precise ammonia injection.After the renovation,the flue gas flow rates on the A and B sides of the SCR inlet flue are 9.0 m/s and 9.2 m/s respectively,with relative standard deviation(CV)values of 11.4% and 10.7%.The average concentrations of NO_(x) on the A and B sides of the SCR inlet flue are 250.7 mg/m^(3) and 260.5 mg/m^(3) respectively,with CV values of 4.8% and 5.0%.The average NO_(x) on the A and B sides of the SCR outlet flue are 47.1 mg/m^(3) and 51.6 mg/m^(3) respectively,with CV values of 12.3% and 12.5%.These values meet the requirements of ultra-low emissions.The unit consumption of liquid ammonia decreases from 0.2783 kg per MWh before the renovation to 0.2152 kg per MWh,with a decrease of 27.8%.