摘要
介绍了在炉膛中央设置水平布置杆式二次风和竖直布置柱式二次风两种结构。在冷态循环流化床上,研究了中心二次风的布置形式和布置高度,以及二次风率对床内沿高度方向的颗粒浓度分布的影响,并与同样高度的常规壁面二次风进行了对比。实验发现,空气分级后二次风下方的颗粒浓度随二次风率的提高而增大。二次风高度的增加伴随着底部密相区向上延伸。几种二次风布置形式中,水平杆式二次风结构布置时底部浓度最大。通过对射流的示踪发现,在高二次风速时中心二次风扩散到壁面区域,而在中心区域则缺少二次风气体,这不利于对中心区域的氧气补充。而水平杆式中心二次风射流在横向动量的作用下,射流进入床内时发生偏转,能够在床内形成较大的扩散面。另外,还讨论了中心二次风进一步在实际循环流化床锅炉中的应用所需要注意和解决的问题。
Described were two types of secondary air structure,i.e. horizontally arranged rod type and vertically arranged pillar type,both of which are located in the center of a furnace. On a cold-state circulating fluidized bed (CFB),the influence of the arrangement pattern,height and secondary air flow rate of the centered secondary air on the particle concentration distribution along the height direction inside the bed was studied and compared with that of the conventional wall-surface secondary air at the same height. It has been found that after the division of air into stages,the particle concentration below the staged secondary air increases with an increase of the secondary air flow rate. An increase in the secondary air height will be accompanied by the dense-phase zone at the bottom extending upwards. Among the secondary air arrangement patterns,the horizontal rod type secondary air arrangement pattern can make the concentration at the bottom attain a maximal value. A trajectory tracking of the jet flow shows that when the secondary air speed is high,the centrally located secondary air can be diffused to the wall-surface zones,but in the central area there is a lack of secondary air. This is unfavorable for the oxygen replenishment to the central area. The horizontal rod type centered secondary air jet flow,however,will swerve and deflect under the action of a lateral momentum when it enters into the bed and can form a relatively large diffusion area. The authors have also mentioned the problems meriting attention and requiring solutions when the centered secondary air is further applied in practical CFB boilers.
出处
《热能动力工程》
CAS
CSCD
北大核心
2010年第1期51-56,共6页
Journal of Engineering for Thermal Energy and Power
基金
国家科技支撑计划子课题基金资助项目(2006BAA03B01-07)
关键词
循环流化床
中心二次风
轴向颗粒浓度分布
二次风的扩散
circulating fluidized bed (CFB),centrally located secondary air,axial particle concentration distribution,diffusion of secondary air
