宽粒径分布流化床的微观尺度模拟与分析

Micro-scale Simulation and Analysis of Gas-solid Fluidized Bed With Wide Size Distribution of Particles

采用计算流体力学–离散单元(CFD-DEM)耦合方法对三维宽粒径分布流化床进行数值模拟研究,对比了两种不同表观气速下流化床内颗粒的分离和混合情况,并对计算结果进行了详细分析。在宽粒径分布流化床内,存在不同程度的颗粒分层现象。当表观气速较低,处于最小颗粒的最小流化速度与最大颗粒的最小流化速度之间时,会出现明显的分层,整体上为大颗粒在下、小颗粒在上的分层结构,而当表观气速较高,大于最大颗粒的最小流化速度时,床内不再出现明显的分层现象。最后对两种不同表观气速下床内颗粒的分层和混合的详细运动行为进行了分析和讨论。

A three-dimensional gas-solid fluidized bed in which particles have wide size distribution was simulated by using computational fluid dynamics-discrete element method （CFD-DEM） coupling method. By comparing the mixing and segregation behavior of particles at two different superficial gas velocities in the simulation results, it was found that the segregation phenomenon always exist in the fluidized bed. When the superficial gas velocity is lower, in the range of the minimum fluidization velocity of the smallest particles to the minimum fluidization velocity of the biggest particles, the obviously segregation that big particles move down and small particles move up will occurs. When the superficial gas velocity is higher than the minimum fluidization velocity of the biggest particles, the clear segregation will not occur. The detail mixing and segegation behavior of particles at two different superficial gas velocities were analyzed and discussed.