基于正交设计的旋流管式除雾器性能的数值分析

Numerical Analysis of Performance of Cyclone-Tube Demister Based on Orthogonal Design

随着国家工业烟气排放要求日益严格,针对折流板除雾器对粒径小于20μm的微细雾滴去除效率低的问题,设计了一种新型旋流管式除雾器。采用欧拉-拉格朗日的方法,对旋流管式除雾器内烟气的流动进行数值模拟,使用刚性球形水滴代替雾滴,采用RNG k-ε模型和离散相模型(DPM)模型进行连续相和离散相的交替耦合计算;研究了不同流速下旋流管式除雾器性能的变化;并在基于正交设计的模拟实验下研究旋流管式除雾器结构参数对除雾性能的影响。对基础结构旋流管式除雾器的模拟结果表明:在3~7 m/s的流速下对直径大于20μm的雾滴去除效率在99%以上;对直径在10~20μm的雾滴去除效率在86.5%以上;对直径在2~10μm的雾滴去除效率在51.3%以上;压降61.4~321.3 Pa,对微细雾滴的去除效率有显著提升。通过分析正交模拟试验结果,得到扭转角度(a)的增大和单管直径(d)的减小有利于提高雾滴的去除效率;随着a的增大、d的增大、H的减小会加大烟气流过除雾器的压降;得出了参数范围内以2~10μm除雾效率为指标的最佳结构d=100 mm,H=2000 mm,a=900°;以10~20μm除雾效率为指标的最佳结构d=100 mm,H=1600 mm,a=900°;以除雾器进出口压降为指标的最佳结构d=100 mm,H=2400 mm,a=540°。本研究所提出的旋流管式除雾器能够显著提升微细雾滴的去除效率,对工业烟气的超洁净排放有着重要意义。

Facing the increasingly strict requirements of industrial flue gas emission in China,this paper designed a new type of cyclone-tube demister to overcome the low removal efficiency of fine droplets that particle size less than 20μm by wave-plate demister.The flow of flue gas in the cyclone tube demister was numerically simulated by using Euler-Lagrangian method,using rigid spherical water drops instead of fog drops.And the RNG k-εmodel and DPM model were used for the alternating coupling calculation of continuous phase and discrete phase.The performance changes of the cyclone-tube demister under different flow velocities were studied.Based on the simulation experiment of orthogonal design,the influence of the structural parameters of the cyclone-tube demister on the demisting perfor⁃mance was studied.The simulation results of basic structure cyclone-tube demister show that,under the flow rate of 3~7 m/s,the removal efficiency of droplets with diameter greater than 20μm is more than 99%;the removal efficiency of droplets with a diameter of 10~20μm is above 86.5%;the removal efficiency of droplets with a diameter of 2~10μm is above 51.3%;when the pressure drop is 61.4~321.3 Pa,it can significantly improve the removal efficiency of fine droplets.By analyzing the results of orthogonal simulation test,it is found that the increase of a and the decrease of d are beneficial to improve the removal efficiency of droplets.With the increase of a,d and H,the pressure drop of flue gas flowing through the demister will be increased.The optimum structure with demister efficiency of 2~10μm as index is d=100 mm,H=2000 mm,a=900°,the optimum structure with demister efficiency of 10~20μm as index is d=100 mm,H=1600 mm,a=900°,the optimum structure with the pressure drop as index d=100 mm,H=2400 mm,a=540°are obtained.The cyclone-tube demister proposed in this study can significantly improve the removal efficiency of fine droplets,which is of great significance to the ultra clean emissions of coal-fired power plants.