Abstract:

The erosion of dust collection electrode and distribution of water film are the main factors affecting stability and reliability in successive operation of wet electrostatic precipitators (WESP). To address these problems, modification of carbon steel made by cold rolling was made to provide corrosion protective coating and additional water affinity. The surface wetting characteristics of various modified anode plates were investigated under single strand feed water condition. The influence of Reynolds number on surface wetting characteristics of optimum modified plate was studied, aiming at providing theoretical foundation of rinse water distribution of WESP. Corrosion protective coating had negative impact on the surface wetting characteristics of substrate. With similar surface wetting characteristics, epoxy resin and glass fiber cloth Ⅰ had no effect on hydrophilic modification. The surface wetting characteristics of epoxy resin modified by sand, glass beads and glass fiber filament were similar and had little effect on hydrophilic modification. TL carbon fiber cloth had the largest liquid holdup of 0.0028—0.0054 g·cm^-2, increased by 1.0—2.2 times compared with carbon steel sheet (CSS). Sand needed the least surface flow rate to wet the whole test sample, which was decreased by 36% compared with CSS; while sand had the largest film rate, increased by 50%—60% compared with CSS. The average thickness of water film was about 0.3—0.7 mm, and TL carbon fiber cloth could reach 1.4 mm. The degree of tightness of glass fiber cloth attached on the surface of epoxy resin depended on adhesion technology, which had direct effect on surface wetting characteristics. GFC series modification methods (GFCⅡ, GFCⅢ, GFCⅣ) had favorable effect on hydrophilic modification, and average thickness of water film was less than 0.35 mm. GFCⅢ, GFCⅣ surface could get wetted quickly, and critical time was shorter than 3 min. Surface flow rate of GFCⅡ, GFCⅢ, GFCⅣ could decrease by 94%—97% compared with CSS to wet the same size surface. Among them, adhesion technology Ⅲ had the best performance. The pitch of blowhole could be set as 10 cm or wider. Effective washing could be obtained, when the waves on the liquid film were fluctuating laminar at Reynolds number about 2000.

Key words: wet electrostatic precipitator, corrosion, water film, wetting characteristic, rinse water distribution

摘要：

湿式静电除尘技术收尘极表面的易腐蚀和水膜均布问题是影响该技术连续可靠运行的重要因素。针对这两个问题,对碳素钢冷轧成型板进行了抗腐蚀保护层和在保护层基础上黏附不同附加亲水层的改性。使用称重法和平面成像法进行了单股流布水不同Reynolds数下不同改性表面持液量、表面流量、成膜率、水膜平均厚度等润湿特性的研究。结果表明:抗腐蚀保护层降低基材的润湿特性,附加亲水层中台丽碳纤维布的持液量较基材碳钢表面增加1.0～2.2倍,细沙粒成膜率比基材碳钢增加50%～60%,水膜厚度均在0.3～0.7 mm之间(最大达1.4 mm);玻璃纤维布黏附在环氧树脂表面的疏松程度直接影响表面的润湿特性,涂刷第3层环氧树脂后自然晾晒12 h,120℃加热1 h后敷设玻纤布,自然冷却至固化得到的表面润湿特性最佳,其持液量可达0.014～0.021 g·cm^-2,临界饱和时间 < 3 min,实现完全润湿,成膜率较基材增加34～40倍;改性材料表面布水参数:喷水孔间距≥10 cm、Reynolds数超过2000,此时表面液膜为波动层流,可获得理想冲刷效果。

关键词: 湿式静电除尘, 腐蚀, 水膜, 润湿特性, 布水