基于CFD的液固分选流化床数值模拟

利用RNG k-ε湍流模型、VOF(Volume of Faction)多相流模型模拟了液固分选流化床(LSFBS)内外气液两相流场。待气液两相流场稳定后,耦合离散相模型(DPM)模拟了粗煤泥颗粒在LSFBS内部的分选过程。模拟结果能很好地吻合实验结果,其中与试验结果相比所有密度级在重产物中分配率的均方根误差为2.47,预测精煤产率相对误差为2.38%。在此基础上,分析了LSFBS速度场的分布特点;研究了上升水流速度和不同脉动周期、脉动波形的上升水流对分选效果的影响;得到了分选密度和可能偏差与上升水流速度间的函数关系;发现脉动水流分选精度低于均匀上升水流,对于脉动上升水流,最佳脉动周期为1.25 s,最佳波形为矩形。

Numerical studies of liquid-solid fluidized bed separator using CFD

The gas-liquid flow fields of Liquid Solid Fluidized Bed Separator (LSFBS) were simulated using VOF (Volume of Faction) multiphase model with the RNG k-ε Model as a turbulence closure model.After the relatively stable two-phase flow fields were reached，the separation processes in the LSFBS of multi-solid particles with different sizes and densities were simulated using the Lagrangian Discrete Phase Model (DPM).The simulation results match well with the experimental results.The root-mean-square error (RMSE) between the predicted separation results and the experimental values is 2.47 while the relative error of predicted clean coal yield is 2.38%.The distribution of LSFBS’s velocity fields was discussed.The impacts on the separation performance of the upward currents’flow rate as well as the pulsating upward currents’ cycles and waveforms were explored.The mathematical relationships between separation density and upward current rate，Ep value and upward current rate were set up.According to the simulation results，the separation performances of steady upward currents are better than those of pulsating upward currents.For pulsating upward currents，the optimal cycle is 1.25 s while the best waveform is rectangular.