脱硫废水液滴与飞灰颗粒碰撞特性数值研究

Numerical Simulation of Collision Characteristics Between Desulfurization Wastewater Droplets and Fly Ash Particles

在利用烟道余热喷雾蒸发脱硫废水时,烟道中的飞灰会与喷雾液滴发生碰撞,进而影响废水处理效率.本文利用大涡模拟(LES)和离散相模型(DPM),模拟脱硫废水喷入烟道的雾化过程及粒径分布,重点考察了烟道飞灰与喷雾液滴碰撞时烟道流场分布及液滴空间分布,分析了Stokes数和喷雾角对流场和空间分布的影响规律.研究结果表明,采用空气雾化喷嘴雾化333.33 L·h^(-1)的脱硫废水,喷雾液滴的粒径分布为20～250μm;无飞灰进入烟道时,Stokes小于1时喷雾液滴速度衰减极快,Stokes大于1时喷雾液滴速度衰减最慢,且喷雾角较大时衰减更快;含飞灰进入烟道时,由于动量交换,喷雾液滴速度衰减更快,且碰撞主要发生于速度衰减到35 m·s^(-1)后的位置.

Using the flue gas waste heat to spray evaporation is an efficient and economical way to evaporate the desulphurization wastewater.However,the wastewater treatment efficiency will be affected due to the phenomenon that fly ash will collide with the droplets.In this paper,the atomization process and particle size distribution of desulfurization wastewater were simulated by using large-eddy simulation (LES)and discrete phase model (DPM).Importantly,the flue flow field distribution and the droplet spatial distribution were simulated in the process of collision.Moreover, the influence of the Stokes number and the spray angle on the flow field and the spatial distribution was analyzed in detail.In the case of flue gas flow rate of 333.33L·h^-1 and the spray droplets particle size distribution between 20μm to 250μm,the results show that the attenuation rate of spray droplet velocity is fast when the Stokes number is less than 1 and faster when the spray angle is larger with no fly ash.Contrarily,the attenuation rate of spray droplet velocity is slowest when the Stokes number is bigger than 1.When there is fly ash in the flue,the attenuation rate of spray droplet velocity is faster and the collision occurred mainly at the droplet velocity less than 35m·s^-1 due to the momentum exchange.