造粒塔粉尘洗涤过程中流体力学特性与除尘效率研究

Hydrodynamic Characteristics and Particle Removal Efficiency Off-gas from Urea Prilling Tower in Spraying Scrubber

针对造粒塔粉尘易溶于水的特性,利用喷淋洗涤的方式脱除更加方便高效。研究基于液滴捕集粉尘的理论,实现了喷淋除尘过程的模拟。采用数值模拟与实验相结合的方法,研究了洗涤塔内气液固三相的流动特性,分析了空塔气速、喷淋密度及粉尘粒径对除尘效率的影响。研究结果表明:壁面附近空气速度出现峰值,存在壁流现象,从而引起粉尘逃逸;喷淋密度增大,除尘效率单调递增,但增长速率有所减缓;空塔气速增大,除尘效率并不仅仅是单调递减变化,喷淋密度为2 m?h^(-1),空塔气速增大到2.5 m?s^(-1)时,除尘效率反而有所提高。粒径大于10μm的粉尘,除尘效率能达到95%以上,而10μm以下的粉尘由于运动随机性强,难以脱除。在计算工况内,改变气速对粉尘的脱除效果并不明显,增大喷淋密度更为有效。

Spray scrubbing is effective to remove hydrophilic particles from Urea Prilling Tower. Simulation of dust removal based on particle capture mechanism was investigated for spray scrubbing process. Numerical simulation and experiments were conducted to study flow characteristics and key factors such as gas velocity, spraying density and particle size were analyzed. The results show that： 1） air flow near wall has maximum velocity with wall flow, which leads to dust escape. 2） particle removal efficiency increases with the increase of spraying density, but the increase rate gradually decreases. Dust removal efficiency does not always decrease with the increase of gas velocity. For example, when spraying density is 2 m×h^（-1） and gas velocity is 2.5 m×s^（-1）, removal efficiency increases. 3） Removal efficiency of particles 10μm can reach 95%. However, the removal of particles 10 μm is difficult due to the random movement of fine particles. 4） gas velocity has few effects on particle removal efficiency. Therefore, it is more effective to improve particle removal efficiency by increasing spraying density.