鼓泡流化床排渣流动的模拟与实验研究

基于计算颗粒流体力学(CPFD)方法,研究了鼓泡流化床的排渣流动特点,获得了不同管径的排渣管对流化床排渣流率的影响,并对排渣流动的流场进行了详细分析。模拟结果表明,布风板上开孔排渣会影响床内的正常流态化,随排渣管径的增大所影响的区域也会逐渐增大;排渣流率与流化风速、床层压降和管径的平方呈现出正相关性。根据流体力学拟流体理论所建立的公式能较好地预测排渣流率的变化趋势,从排渣流动过程中颗粒体积分数的梯度分布可知,布风板上排渣口的上方存在一个拱形临界面,此临界面是排渣过程中颗粒流动形态发生转变的分界面。

Numerical simulation and experimental study on bottom ash discharge of bubbling fluidized bed

The flow behavior of bottom discharge was studied in a fluidized bed using the computational particle fluid dynamic (CPFD) numerical method.The effect of discharging pipe diameters in a fluidized bed was obtained,and the detailed flow features were investigated.The calculation results showed that the fluidization behavior was influenced by discharging pipe,and the increasing pipe diameter would enlarged the affected area in fluidized bed.The solid flow rate increased with bed height,gas velocity and the square of pipe diameter.A correlation was derived based on the hydrodynamics of pseudo fluid,which could predict the variation tendency of bottom ash discharge.According to the distribution of the gradient of particle volume fraction in fluidized bed,there existed a vaulted critical plane above the openings of the air distributor,which divided the flow region into two parts with different flow behaviors of bottom ash discharge.