In circulating fluidized bed (CFB) boilers, the flue gas recirculation (FGR) is an important technical means to promote de-NO_x combustion. However, the conventional injection position of recycled gas seriously hinders the combustion efficiency and the flexibility of load regulation. To solve this, thermal-state experiments are conducted on a lab-scale CFB combustor to explore the feasibility of adopting novel FGR and air staging technology to achieve low NO_x emission and sufficient combustion efficiency. The effects of FGR/supplementary burnout air (SBA) injection positions and operating parameters on temperature profile, combustion efficiency and original NO_x emission in the furnace are discussed in detail. The synergistic effect of FGR and SBA on combustion characteristics and NO_x reduction is also analyzed. Eventually, a systematic approach to enhance NO_x control and combustion efficiency in fluidized bed is proposed. The key results indicate that the NO_x reduction rate reaches 46.15% by adopting middle FGR and top SBA, which exceeds the reduction performance of utility boilers with conventional FGR. Also, the furnace outlet temperature and combustion efficiency can be ensured to be over 860 °C and 98.4% respectively, thus to provide new technical basis for enhancing de-NO_x combustion in CFB boiler at low load, as well as the prospective guidance for FGR retrofitting of various fluidized bed combustors.

在循环流化床（CFB）锅炉，烟道气再循环（FGR）是一种重要的技术手段，以促进脱NO _X燃烧。然而，常规的再循环气体注入位置严重地阻碍了燃烧效率和负荷调节的灵活性。为了解决这个问题，热态实验在实验室规模的燃烧器CFB进行探索采用新颖FGR和空气分级技术来实现低NO的可行性_X排放和足够的燃烧效率。FGR的/补充倦怠空气（SBA）注射位置和上温度分布，燃烧效率和原始NO操作参数的影响_X详细讨论了炉内的排放。FGR和SBA对燃烧特性和NO的协同效应_X还原进行了分析。最终，以增强NO系统化的方法_X控制和流化床燃烧效率提出。关键结果表明，采用中等FGR和顶部SBA工艺可使NO _x的还原率达到46.15％，超过了常规FGR的电站锅炉的还原性能。另外，炉出口温度和燃烧效率可确保分别将超过860℃和98.4％，因此，以用于增强提供新技术依据DE-NO _X CFB锅炉在低负荷下的燃烧，以及各种流化床燃烧器的FGR改造的前瞻性指导。