Effect of outer secondary-air vane angle on the flow and combustion characteristics and NOx formation of the swirl burner in a 300-MW low-volatile coal-fired boiler with deep air staging
Effect of outer secondary-air vane angle on the flow and combustion characteristics and NOx formation of the swirl burner in a 300-MW low-volatile coal-fired boiler with deep air staging
复制标题
外二次风导叶角度对300MW深度空气分级低挥发分燃煤锅炉旋流燃烧器流动、燃烧特性及NOx生成的影响
DOI：
10.1016/j.joei.2016.01.005
复制
发表时间：
2017-04-01
影响因子：
5.7
通讯作者：
Zhang, Xiqian
中科院分区：
文献类型：
--
作者：
Li, Song;Chen, Zhichao;Zhang, Xiqian
在一台300 MW的燃用低挥发分煤的亚临界锅炉上，进行了单燃烧器模型气流的小型实验室试验和集中式富油低NOx旋流燃烧器在深度空气分级条件下的工业试验。对不同叶片角的燃烧器喷口区域外二次风的空气动力特性、烟气温度和烟气浓度进行了测量。结果表明，在深度空气分级条件下，燃烧器喷口区域出口附近形成了一个稳定、对称的中心回流区。随着叶片角度的减小，i）气流的最大轴向、径向和切向速度以及旋流强度增加; ii）在X/D = 0和X/D = 0.8之间，速度衰减率增加; iii）中心回流区的最大直径、长度和射流发散角增加;以及iv）相对回流率增加。当一次风浓度略有降低时，最大一次风浓度随叶片角度的减小而迅速降低。相反，最大轴向相对混合率在初始阶段沿着气流方向增加。叶片角度的减小使烟气温度增加，增加的速率指示无烟煤和贫煤的点火位置沿燃烧器的气流方向沿着更近。燃烧初期O-2消耗率和NOx生成率增加，燃烧后期CO浓度显著增加，O-2浓度基本保持在1%以下。CO浓度可以超过20，000 ppm，这抑制了NOx的形成并显著降低了NOx浓度，但超过X' = 0.8m，NOx浓度几乎保持恒定。对于侧壁区域中不同的叶片角度，烟气温度略有变化。在水冷壁附近，O-2浓度超过4%。沿径向1.8375 m，O-2浓度低于2%，CO浓度沿着在5000 ppm以上
Small-scale laboratory experiments of airflow through a single burner model and industrial-scale experiments on the centrally fuel-rich, low NOx swirl burner on a 300-MW wall-fired subcritical boiler burning low-volatile coal under deep air staging were performed. The aerodynamic characteristics, flue gas temperature, and gas concentrations were measured for various vane angles of outer secondary air in the burner nozzle region. The results show that a stable, symmetric central reverse-flow zone forms close to the exit of the burner nozzle region under deep air staging. With decreasing vane angle, i) the maximum axial, radial, and tangential velocities and swirl intensity of the airstream increase; ii) the decaying rate of velocity increases between X/D = 0 and X/D = 0.8; iii) the maximum diameter, length, and the jet divergence angle of the central reverse-flow zone increase; and iv) the relative reverse-flow rate increases. While the primary air concentration decreases slightly, the maximum primary air concentration decreases rapidly with decreasing vane angle. In contrast, the maximum axial relative mixing rate increases in the initial stage along the airstream direction. A decrease in vane angle increases the flue gas temperature, the rate of increase indicating a closer ignition position of the anthracite and lean coal along the airstream direction of the burner. The O-2 consumption rate and NOx formation rate increase in the initial stage of combustion, whereas in the later stage the CO concentration increases notably and the O-2 concentration remains almost constant below 1%. The CO concentration can exceed 20,000 ppm, which restrains the NOx formation and reduces the NOx concentration notably, but beyond X' = 0.8 m, the NOx concentration remains almost constant. The flue gas temperature varies slightly for different vane angles in the side-wall region. The O-2 concentration exceeds 4% near the location of the water-cooled wall. The O-2 concentrations are below 2% and the CO concentrations are above 5000 ppm along the radial direction 1.8375 m