Abstract: Severe environmental protection policies have put forward higher requirements for coal combustion power generation. As a mature clean coal power generation technology, the circulating fluidized bed (CFB) boiler has broad research prospects. CFB post-combustion technology is a new type of fluidized bed out-of-stock technology that has been applied to 75 t/h CFB coal slime boilers and achieved ultra-low NOx emissions. Exploring the feasibility and effectiveness of post-combustion technology in larger-scale CFB boilers has become the focus of future research. In this study, a numerical model of the flow and combustion of a 150 t/h CFB boiler in full-loop was established using the method of computational particle fluid dynamics (CPFD). The availability of the model was verified by comparing it with industrial data. The effects of excess air ratio in CFB, primary air ratio, and ratio of upper and lower secondary air on furnace combustion and NOx emissions were studied after the addition of post-combustion technology. The results showed that there was a typical core-circulation structure in the furnace. On the one hand, oxygen-poor combustion inhibited NOx generation, and on the other hand, the high CO concentration zone caused by combustion was also conducive to NOx reduction. After the use of post-combustion technology, the reduction atmosphere of the furnace increased, and the NOx emission reduced from 174.6 mg/m3 to 114.2 mg/m3. Combined with the air stage, optimizing the primary air ratio and the ratio of upper and lower secondary air, CO emission increased from 3.4×10-5 in the basic working condition to 7.1×10-5, the combustion efficiency was slightly reduced, and NOx emission was further reduced. Under optimal working conditions, NOx emission decreased from 174.6 mg/m3 to 76.3 mg/m3, NOx emission decreased by 56.3%, and the furnace temperature distribution was uniform. The research results can provide valuable theoretical insights for the application of post-combustion technology in CFB boilers and provide support for its practical application.

Key words: circulating fluidized bed, post-combustion, computational particle fluid dynamics, air staged, low nitrogen combustion

摘要： 为促进循环流化床(Circulating Fluidized Bed, CFB)锅炉氮氧化物(NOx)深度抑制，采用计算颗粒流体动力学(Computational Particle Fluid Dynamics, CPFD)方法建立了CFB锅炉全回路流动及燃烧数值模型，通过与锅炉运行数据的对比验证了模型的可靠性。耦合后燃烧技术后，分别研究循环流化床中过量空气比、一次风率和上下二次风比对炉膛燃烧和NOx排放的影响。结果表明，贫氧燃烧造成的高CO摩尔分数区有利于NOx还原。使用后燃烧技术后，炉膛还原氛围增强，NOx排放由174.6 mg/m3降至114.2 mg/m3。结合空气分级，优化一次风率及上下二次风比例后，CO排放由基础工况的3.4×10-5增至7.1×10-5，燃烧效率略微降低，NOx排放进一步减少。较优工况下，NOx排放由174.6 mg/m3降至76.3 mg/m3，NOx排放减少了56.3%，炉膛温度分布均匀。研究结果可为后燃烧技术应用于CFB锅炉提供理论支持。

关键词: 循环流化床, 后燃烧, 计算颗粒流体动力学, 空气分级, 低氮燃烧