六旋风分离器循环流化床内气固流动特性数值模拟

Numerical Simulation of Gas-Solid Flow Characteristics in Circulating Fluidized Bed with Six Cyclone Separators

以六旋风分离器循环流化床为研究对象,基于计算颗粒流体力学方法,建立全循环数值模型;在通过模拟与实验对比确定最优曳力模型的基础上,探究物料量、入口气速对炉膛内气固流动特性及出口物料分配均匀性的影响,得到不同物料量、入口气速时炉膛颗粒速度、体积分数、质量流率与循环流率分布。结果表明:当炉膛内物料稳定运行时,颗粒体积分数沿轴向呈下大上小的S型分布,沿径向呈中间小两边壁面处大的U型分布;炉膛6个出口存在明显气固流动不均匀现象,炉膛左、右两侧对应出口截面颗粒水平速度、体积分数及旋风分离器入口段颗粒水平质量流率、循环流率相差不大,呈现对称分布,在同侧3个回路间呈现中间回路的小两角回路的大的分布规律,并且中间回路出口的明显小于两角回路出口的,气固流动不均匀性主要发生在同侧3个回路出口端。

Taking a circulating fluidized bed with six cyclone separators as a research object,a full cycle numerical model was established on the basis of computational particle fluid dynamics method.Based on the optimal drag model determined by using simulation and experimental comparison,the effect of material quality and inlet gas velocity on gas-solid flow characteristics in furnace and homogeneity of material distribution at outlet was researched.The distributions of particle velocity,volume fraction,mass flow rate,and circulation flow rate in the furnace with different material quality and inlet gas velocity were obtained.The results show that when the materials in the furnace operate stably,the volume fraction of particles presents an S-shaped distribution large at the bottom and small at the top along axial direction,and a U-shaped distribution small in the middle and large on both sides along radial direction.Obvious flow non-uniformity exists at the six outlets.The horizontal velocity and volume fraction of particles in the corresponding outlet cross section on the left and right sides of the furnace,as well as the horizontal mass flow rate and circulating flow rate of particles in the inlet section of the cyclone separator are not much different,showing a symmetrically distributed.The distribution law between the three circuits on the same side is small in the middle and large in the two corners,and the distribution of the middle outlet is significantly smaller than that of the two corners.The gas-solid flow inhomogeneity mainly occurs across the three outlet ends on the same side.