低氮改造对四角切圆锅炉NO_x生成特性的影响

Effects of Low-NO_x Retrofit on NOx Formation in a Tangentially-fired Boiler

对某300 MW四角切圆锅炉低氮改造前后NOx的生成特性进行了数值计算,分析了低氮改造对NOx生成特性的影响.结果表明:原有双通道自稳燃型燃烧器稳燃腔的设计明显加速了热力型NOx的生成;新型水平浓淡燃烧器浓侧和淡侧煤粉均处于偏离化学当量比条件下燃烧,喷口附近火焰温度明显降低,有利于控制热力型NOx的生成,缺氧燃烧降低了煤粉的燃烧效率,冷灰斗区域及三次风以上区域燃料型NOx的生成速率有所增大.

Numerical simulation was conducted to NOx formation characteristics in a 300 MW tangentially- fired boiler before and after low-NOx retrofit, so as to analyze the effects of low-NOx retrofit on the NOx formation characteristics. Results show that the design of stabilized combustion cavity in the original dual- channel self-stabling burner obviously increases its thermal NOx emission. The combustion of both dense and dilute pulverized coal-air mixture flow in the new horizontal bias burner is under the condition devia- ting from the chemical equivalent ratio, which lowers the flue gas temperature around burners and com- presses the emission of thermal NOx. Rare oxygen combustion also reduces the combustion efficiency, and increases the production of fuel NOx in cold ash hopper and in upper furnace area above tertiarv air flow