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- Title
循环流化床二次风射流及床料粒径对流化特性的影响.
- Authors
张 曜; 林 晨; 于 娟; 冯 帆; 张忠孝
- Abstract
The formation control of NOxis related to fluidized bed fluidization characteristics and gas-solid flow, and the cold state test can more directly reflect the gas-solid flow state and fluidization effect, so the results of the cold state test can provide reference for the parameter selection of the reaction thermal experiment of fluidized bed denitration. Previous researches mostly used narrow screening bed material particles, and mostly focused on the traditional wall type secondary air arrangement. Few scholars comprehensively studied the penetration performance of secondary air arrangement in the center and its influence on the fluidization characteristics of the furnace.Therefore, the influence of central secondary air distribution and bed material with wide and narrow screening on fluidization characteristics was studied on the cold experimental bench of circulating fluidized bed. The dimensionless residual temperature, material circulation rate and apparent particle volume fraction were used to quantitatively describe the secondary air penetration, material circulation efficiency and particle concentration distribution. The experimental results show that the particle concentration near the jet height increases with the increase of the secondary air jet. When the secondary air injection height is 15 cm, in the dense phase area below 35 cm, the larger the proportion of secondary air is, the more obvious the increase of particle concentration is. The penetration performance of the secondary air jet can be effectively improved by increasing the proportion of secondary air jet, increasing the velocity of the secondary air jet and improving the jet position of the secondary air jet. When the injection height of secondary air is 5 cm from the bottom of the furnace, the jet penetration rate is 0.4; When the injection height is 15 cm, the jet penetration rate is 0. 84. When the injection height continues to rise by10 cm, the jet penetration rate reaches 1.0. The reason for this phenomenon is that the closer to the bottom of the furnace is, the greater the concentration of the bed material particles is, and the secondary wind resistance increases sharply. With the decrease of the average particle size of the narrow screening bed material, the overall pressure drop in the furnace increases, and the pressure drop tends to be stable at a higher position in the furnace, and the circulation flow rate of the material also increases. This indicates that more particles can be carried out of the furnace along with the uplift of fluidized wind and enter the separator to participate in the circulation outside the furnace. Different from the narrow sieve bed material, the proportion of fine particles in the bed material determines the furnace pressure drop, particle concentration distribution and material circulation rate of the wide sieve bed material. The higher the proportion of fine particles is, the greater the pressure drop in furnace and the circulating flow rate of materials are. In wide screening, the particle concentration distribution and material circulating flow rate of bed materials with large average particle size are not necessarily small, because under the experimental wind speed, particles with particle size less than 300 μm are more likely to be carried to the furnace outlet along with the elutriation action of fluidized wind. The higher the proportion of these fine particles is, the greater the particle concentration distribution and the material circulation rateare. Coarse particles tend to concentrate at the bottom of the furnace.
- Subjects
AIR jets; PARTICULATE matter; AIR mattresses; FURNACES; WIND speed; COLD gases; PRESSURE drop (Fluid dynamics)
- Publication
Clean Coal Technology, 2020, Vol 26, Issue 3, p68
- ISSN
1006-6772
- Publication type
Article
- DOI
10.13226/j.issn.1006-6772.CFB20040401