超低排放机组湿式电除尘器颗粒物脱除特性分析

Analysis of Particle Removal Characteristics on Wet Electrostatic Precipitator for Ultra-low Emission Coal-fired Power Unit

对26台超低排放机组湿式电除尘器(wetelectrostatic precipitator,WESP)进出口颗粒物排放情况进行测试,分析湿式电除尘器工艺对PM和PM2.5脱除效果,从而得到入口颗粒物浓度、烟气流速、停留时间及雾滴脱除效果对湿式电除尘器颗粒物脱除效果、排放因子和脱除能耗的影响。结果表明,经过湿式电除尘器的除尘作用,烟气中PM和PM2.5的浓度可分别控制在10mg/m^3和3mg/m^3以内,可实现烟尘超低排放的要求;同时PM和PM2.5的排放因子分别在10~20g/(MW·h)和5~10g/(MW·h),较超低排放改造前有大幅度的降低;且随着雾滴脱除效率的增加,湿式电除尘器颗粒物的脱除效果也相应增加,但颗粒物脱除效率要大于雾滴脱除效率,且湿式电除尘器出口PM2.5占总尘的比重较入口平均增加了13.76%,出口主要为粒径小于2.5μm的颗粒物;另外在烟气流速为2.0m/s且极板电流密度为0.4m A/m^2时,湿式电除尘器具有较高的PM2.5脱除效率;在烟气停留时间在2.9s左右时,颗粒物的脱除能耗较低,且随着颗粒物粒径的减小,其脱除能耗会急剧增加。因此湿式电除尘器可以通过控制烟气流速和极板电流密度、增大集尘面积和延长烟气停留时间来提高颗粒物的脱除效果。

Tested the particulate matter emissions at the inlet and outlet of WESP in 26 ultra-low emission units, and analyzed the effect of WESP on the removal of PM and PM2.5. The effects of inlet PM concentration, flue gas flow rate, residence time, and droplet removal effect for the PM removal, emission factors and energy consumption of WESP were obtained. The measurement results indicate that WESP has an outstanding PM removal efficiency. The outlet concentration of PM and PM2.5 in the flue gas can be controlled at 10 mg/m^3 and 3 mg/m^3 respectively, and can achieve the requirements of ultra-low emission. The emission factors of PM and PM2.5 are 10~20 g/(MW·h) and 5~10 g/(MW·h), which are greatly reduced compared with those before ultra-low emission transformation. With the increase of the removal efficiency of the droplets, the removal effect of the PM increases correspondingly, but the removal efficiency of the PM is greater than the removal efficiency of the droplets. The outlet PM2.5 ratio of PM increase by 13.76% compare to inlet of WESP, that leads to the particle diameter of PM at the outlet is mainly below 2.5μm. When the flue gas flow rate is 2.0 m/s and the current density of the electrode plate is 0.4 m A/m^2, the WESP has a high fine PM2.5 removal efficiency. And when the residence time of the flue gas is about 2.9 s, the energy consumption of the PM is low, and with the decrease of particle diameter, the energy consumption of the PM will increase sharply. Therefore, the WESP can improve the removal effect of PM by controlling the flue gas flow rate and the current density of electrode plate, and increasing the dust collection area and extending the residence time of flue gas.