基于多孔介质模型的大型循环流化床锅炉流化特性的数值模拟

Numerical Simulation on Fluidization Characteristics of Large-scale CFB Using Porous Model

对于480 t/h以上的大型循环流化床锅炉,实际运行时,由于床层流化不均,风室内会出现不同程度的漏煤现象。为了改善床料的流化质量,文中采用多孔介质模型对布风板的结构进行了简化,模拟时采用三维双欧拉多相流模型,并结合颗粒动力学理论使方程封闭,研究了480 t/h循环流化床在不同布风板阻力下的流化特性,模拟结果表明,增大布风板阻力能有效改善煤层流化均匀性,减少风室漏煤。因此,大型循环流化床锅炉设计时,需要对布风板结构、开孔尺寸精心设计,合理增加布风板阻力。

Due to the maldistribution of coal fluidization,coal leakage may occur inside wind-box during operation of large-scale 480t/h CFB or more.In order to improve the fluidization quality of bed materials,the porous model and 3D Eulerian-Eulerian multiphase model with closure law according to the kinetic theory of granular flow were applied to simplify the wind distributor and to simulate the fluidization characteristics with different pressure losses of wind distributor.The results show that,under the condition of increasing pressure loss of wind distributor,the uniformity of coal fluidization can be improved with the low leakage of coal in windbox.Therefore,during the design of the large-scale CFB,the structure of wind-box and size of orifice have to be designed carefully with the increasing of the wind distributor pressure losses properly.