燃尽风喷口位置对NOx排放的影响

针对一台采用旋流式燃烧器的煤粉炉NOx排放质量浓度较高的问题，采用空气分级燃烧方式以降低NOx排放量，基于CFD软件平台，在额定负荷下，分别对3种不同燃尽风喷口位置的改造方案进行了炉内燃烧及污染物生成的数值模拟，并通过综合比较炉内各参数的变化确定了最佳燃尽风喷口位置．结果表明：燃尽风喷口位置的上移降低了主燃区氧气的体积分数，同时使炉膛内的最高温度降低了23～29K．燃尽风喷口位置对NO，的还原效果、出口烟气温度以及煤粉焦炭转化率的影响较大．当燃尽风喷口位置升高时，NOx质量浓度降低，炉膛出口烟气温度升高，煤粉焦炭转化率下降．经综合比较炉膛出口烟气温度、NOx质量浓度以及煤粉焦炭转化率得出，距最上层燃烧器7．7m处为最佳燃尽风喷口位置．

Influence of OFA Nozzle Position on NOx Emission

To reduce the NOx emission of a coal-fired boiler with swirl burners, a retrofit scheme was pro posed by adopting the air-staged combustion mode, based on which a numerical simulation was carried out on the in-furnace combustion and pollutant formation respectively at 3 positions of OFA nozzle using CFD software platform at rated load, so as to determine the optimum position of OFA nozzle. Results show that the uplifting of OFA nozzle will reduce the O2 volumetric fraction in the main combustion zone and there- fore reduce the highest temperature in the furnace by 23-29 K; the position of OFA nozzle plays a role in influencing the NOx reduction, outlet gas temperature and coal/coke conversion rate; with the lifting of OFA nozzle position, the NO, mass concentration reduces, the outlet gas temperture rises and the coal/ coke conversion rate drops. Considering above effects comprehensively, the optimal position of OFA nozzle is finally determined as 7.7 m away from the burner of upper layer.