循环流化床锅炉炉内颗粒分布平衡模型

PARTICLE POPULATION MODEL FOR CIRCULATING FLUIDIZED BED BOILER FURNACE

在对循环流化床锅炉炉内颗粒特性分析的基础上 ,提出同时以粒径和密度两参数来描述炉内颗粒特性。结合循环流化床锅炉特殊的炉内流体动力特性 ,建立了包括炉膛密相区和稀相区在内的循环流化床锅炉炉内宽筛分的颗粒分布模型 ,其中密相区假设为浓度分布均匀的湍流床 ,而稀相区则为核心 边壁区的流动结构。模型同时耦合炉内颗粒所经历的爆裂、燃烧、磨损及气固分离等物理和化学过程。应用以所建的颗粒分布平衡模型为子模型的循环流化床锅炉总体数学模型模拟了一台 12MW循环流化床锅炉燃用烟煤时满负荷运行的工况。计算时把炉内颗粒分为 70档 ,其中颗粒粒径在 0～ 8mm之间分为 10档 ,密度在 110 0～ 2 40 0kg/m3 之间分为 7档。模拟计算所得的炉内颗粒分布合理正确 ,与试验研究结果吻合良好 ,表明所建立的颗粒分布模型可以用来描述循环流化床锅炉炉内颗粒分布特性。

According to the analysis for the particle properties in circulating fluidized bed (CFB) furnace, the particles may be described by particle size and/or density. In combination with the special hydrodynamic in the furnace, the particle population model for the CFB boiler furnace has been developed. The hydrodynamic in a CFB boiler furnace is characterized by two flow regimes: a dense bed at bottom and a dilute region in the upper section of the furnace. It is assumed that the dense bed operates in turbulent fluidization regime with uniform solid concentration while there exists a core annulus flow structure in the upper dilute region. Accordingly, the particle population models for the dense bed and the dilute region are developed separately. Meanwhile, the developed model couples the related physical and chemical processes including coal fragmentation, char combustion, attrition of particles and gas solid separation. To validate the developed particle population model, it is integrated into the overall model of CFB boiler developed earlier by the authors to simulate the operation of a 12 MW CFB boiler fired bituminous coal. The particles in the furnace are divided into 70 different classes, i.e., 10 size classes from 0 to 8mm and 7 density classes from 1100?kg/m 3 to 2400?kg/m 3. The main simulation results for the particle population in the dense bed or the dilute region of the furnace were reasonable and agreed well with the measurements. It indicates that the developed model may be used to describe the particle population in a CFB boiler.