PM2.5 collection using surface-modified hydrophilic carbon steel collector

doi:10.11949/j.issn.0438-1157.20160150

Abstract

Abstract:

Fine particles with aerodynamic diameters of <2.5 μm (PM_2.5) are significant pollution sources. Dust emission is restricted to less than 10 mg·m^-3 under 6% oxygen in eastern China and wet electrostatic precipitators (ESPs) are encouraged for efficient removal of various fine particles in aerosol, especially in coal-fired power plant where strict air pollutant emission standards drive wide use of wet ESP as terminal control equipment. Previous studies showed wetting properties of a hydrophilically modified rigid collector and this study focused on fine particle collection performance of the modified collector at pilot scale. The characteristics of PM_2.5 collection, mechanism of uniform water film and effect of main operation parameters on enhancement of particle collection efficiency were investigated. The results showed that the surface fiber layer of the modified rigid collectors reduced flue gas recoiling and particle electro-transportation resistance. A uniform and stable water film was maintained on surfaces of the modified rigid collectors at low washing water flowrate, which inhibited back corona occurrence and a secondary entrainment of dust as well as increased discharge current and flue gas humidity by evaporation of water film. The increase of particle charge number and electro-transportation speed enhanced the particle collection efficiency. With the increase of flue gas temperature, both discharge current and thermophoresis force gradually increased which could improve the particle collection efficiency. However, the increase of gas viscosity reduced the particles collection efficiency. The extension of residence time and the increase of applied voltage improved particle collection, whereas the inlet concentration of particles and the flushing water flowrate had little influence on particle collection. The wet ESPs of modified rigid collectors exhibited reduction of circulating water consumption per square meter by 86 percent and significant increase of particle collection efficiency for ultrafine particles with size of 0.04-0.48 μm as well as overall collection efficiency of all particles at low electric voltage. Hence, the modified rigid collectors had good potentials for application.

Key words: wet ESPs, modified rigid collector, PM_2.5, particle collection efficiency, water film

摘要：

火电厂大气污染物排放标准日趋严格，湿式静电除尘器作为终端治理设备逐渐得到广泛应用。以亲水改性刚性极板为研究对象，建立了卧式湿式静电除尘器中试实验台，开展了PM_2.5脱除特性的实验研究，研究了改性极板表面水膜增强颗粒物脱除效率的机制，考察了气体温度、停留时间、工作电压、初始浓度、冲洗水流量等主要运行参数对颗粒物脱除效率的影响规律。结果表明：改性刚性极板表面的纤维层可以减少反冲气流，减少颗粒的电迁移阻力；表面在小水量情况下亦可维持均匀稳定的水膜，水膜的存在抑制了反电晕和二次扬尘的发生，使得电晕电流高且水膜蒸发使烟气湿度提高，颗粒荷电量和电迁移速度提高，这两方面均提高了颗粒脱除效率。停留时间延长、工作电压提高均会引起颗粒脱除效率的增加，但颗粒物入口浓度、冲洗水流量对颗粒脱除效率影响不大。使用改性刚性极板的湿式静电除尘器可减少阳极冲洗水量，对粒径0.04～0.48 μm的颗粒有较高脱除效率，可在低电压下达到较高的颗粒物总脱除效率，具有较好的应用前景。

关键词: 湿式静电除尘, 改性刚性极板, PM_2.5, 脱除效率, 水膜

CLC Number:

XU Chunyan, CHANG Jingcai, WANG Xiang, ZHANG Jing, CUI Lin, ZHANG Bo, MA Chunyuan. PM_2.5 collection using surface-modified hydrophilic carbon steel collector[J]. CIESC Journal, 2016, 67(10): 4446-4454.

徐纯燕, 常景彩, 王翔, 张静, 崔琳, 张波, 马春元. 亲水改性碳钢极板用于PM_2.5脱除[J]. 化工学报, 2016, 67(10): 4446-4454.

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