Abstract: In order to improve demisting efficiency of baffle demisters for different droplets and reduce droplet entrainment in the wet flue gas desulfurization (WFGD) system, the computational fluid dynamics (CFD) method was used to simulate numerically the two phase flow of gas and liquid in baffle demister in the WFGD system. By changing the structural parameters and operating parameters of the baffle demister, such as plate spacing, blade-shape and gas-velocity, demisting efficiency and droplets' separation efficiency of different sizes were investigated. The movement behavior and deposition of droplets with different sizes were obtained. The removal efficiency of droplets less than 10 μm would show irregular fluctuations if flow rate was increasing, but almost remained unchanged with increasing plate spacing. In that case removal efficiency was not affected by blade shape. The removal efficiency of droplets over 16.3 μm would increase with increasing flow rate, and decreased significantly with increasing plate spacing. The demisting efficiency of trapezoidal plates was greater than that of triangle plates with plate spacing of 38 mm, and the difference in demisting performance for these two plates was not significant in smaller plate spacing. Removal of the droplets less than 20 μm required higher airflow uniformity at lower gas flow rate. Increased airflow disturbance was in favor of small droplets' collision-coalescence when gas flow rate was less than 3 m·s^-1, and increased airflow disturbance was not conducive to small droplets' collision-coalescence when gas flow rate was over 3 m·s^-1.

Key words: CFD, numerical simulation, gas-liquid flow, demister efficiency, droplet motion, deposition

摘要： 利用流体动力学计算方法对湿法脱硫折流板除雾器内气液两相流动进行数值模拟.分析了除雾器叶片间距、板型及流速对不同粒径雾滴的分级除雾效率和总除雾效率的影响,获得了不同粒径雾滴的运动和捕集规律.研究结果表明,粒径小于10 μm的雾滴去除效率随流速增加呈现不规律的波动,随板间距增加而下降的趋势不明显,不受叶片形状变化影响;粒径大于16.3 μm的雾滴去除效率随流速增加而增大,随板间距增加而显著下降;在板间距为38 mm时,梯形板除雾效率大于三角形板,在板间距较小的情况下两种板型的性能相差不大;流速小于3 m·s^-1时,粒径小于20 μm的雾滴的去除对气流均匀性要求较高,气流扰动增加利于小雾滴的碰撞聚并;流速高于3 m·s^-1时,气流扰动增强增加了小雾滴运动的随机性,不利于小雾滴的碰撞聚并.

关键词: 计算流体力学, 数值模拟, 气液两相流, 除雾效率, 雾滴运动, 雾滴捕集特性