冷凝除雾器分级除尘效率影响因素模拟研究

Numerical Simulation Study on the Influence Factors of Graded Dust Collection Efficiency of Condensed Mist Eliminator

冷凝式除雾器协同除尘作用可进一步降低燃煤烟尘排放浓度。该文建立描述冷凝除雾器内三相运动的数学模型和计算方法,对除雾器协同除尘过程进行数值模拟,分析吸收塔入口烟气速度、相对温差、相对湿度及除雾器的换热面积影响对颗粒粒径增长和脱除的影响规律。结果表明:初始粒径小于2.05μm的颗粒以热泳捕集为主;初始粒径小于1.03μm的颗粒捕集效率受烟气湿度影响明显;初始粒径大于2.05μm的颗粒以惯性捕集为主;除雾器换热面积越大,颗粒的捕集效率越高。可知,在入口处烟气温度保持在50℃以上,烟气相对湿度在95%以上,除雾器壁面温度在25℃以下,烟气流速大于3.14m/s,除雾器通道间隙保持在20mm以内,通道长度在350mm以上,峰的数量大于或等于2时,有利于提升冷凝除雾器协同除尘性能。研究结果可为冷凝式除雾器装置结构优化和工程应用提供理论指导。

The synergetic effect of condensed mist eliminator can further reduce the emission of particulate matter from the coal-fired plants. The mathematical model and numerical method were established to describe the three-phase movement in the condensing mist eliminator, and the process of the influence of graded dust collection efficiency of condensed mist eliminator was simulated. Furthermore, the influence of flue gas velocity, relative temperature difference, relative humidity and heat exchange area of demister on particle size growth and removal were analyzed. The results showed that the major mechanism for capturing particles(≤2.05μm) was thermo phoresis;the capture efficiency of particles(≤1.03μm) was obviously affected by the humidity of flue gas;particles(≥2.05μm) were captured mainly by inertial capture mechanism;the collection efficiency of particles increased with the increase of the heat exchange area of the demister. It can be seen that when the inlet flue gas temperature was kept above 50℃, the relative humidity of flue gas is above 95%, the wall temperature of the demister is below 25 ℃, the flue gas flow rate was greater than 3.14 m/s, the channel gap of the demister was kept within 20 mm, the length of the channel was more than 350 mm, and the number of peaks was greater than or equal to 2, which was conducive to improve the collaborative dust removal performance of the condensing mist eliminator. The research results can provide theoretical guidance for structure optimization and engineering application of condensing mist eliminator.