燃煤电厂电除尘PM10和PM2.5的排放控制IV:采用二维PIV 除尘

 利用粒子成像测速法(PIV)和电子低压冲击仪(ELPI),研究实验室规模的电除尘器(ESP)内电场强度、电晕放电功率和气流场等因素对PM₁₀(粒径小于10 μm 的颗粒物)分级收尘效率.电除尘器为线-板式电极结构,其中板-板间距为200 mm,高电压电极为单根或双根.实验颗粒物采用艾灸烟作为示踪粒子,气体流量85 m³/h,颗粒物初始质量浓度33 mg/m³左右.实验结果表明,随着电场强度或电晕放电功率的增加,在高压电晕极线周围气流场从有规律的单个涡旋发展为相互作用的多个涡旋,优化电晕放电离子风分布是提高PM₁₀收集效率和降低电耗的关键.从颗粒物个数浓度、外加电场或电晕放电功率看,可将电除尘器性能以电场强度为3 kV/cm 为界分为2 个区域.当电场强度低于3 kV/cm 时,分级除尘效率随着电场强度或电除尘指数的增加而增加.然而,当电场强度远大于3 kV/cm 时,收尘效率基本不变或降低.

PM10 and PM2.5 Emission Control by Electrostatic Precipitator (ESP) for Coal-fired Power Plants IV: Investigations on Electrostatic Precipitation by Means of 2D PIV Technique

This paper discusses PM₁₀ (particle matter with a diameter less than 10 μm) grade collection efficiencies of a laboratory electrostatic precipitator (ESP) in terms of the electric field, corona discharge power, and gas flow patterns by means of the particle image velocimetry(PIV)and the electrical low pressure impactor (ELPI) technique. The wire-plate ESP has a plate-plate distance of 200 mm, together with a single or two high-voltage electrodes. Moxa-moxibustion smoke is used as the tracer for evaluation of the gas flow and particle grade collection efficiency. Experiments, performed in air with a total gas flow rate of 85 m³/h and initial particle mass concentration of around 33 mg/m³, show that with increasing the field strength or corona discharge power, the flow changes from regular vortexes around the corona wire to multi-vortexes inter-reacting each other. As a result, optimizing the distribution of corona discharge ion wind is the key to increase PM₁₀ collection efficiencies and reduce the power consumption. In terms of the particle number concentration and the applied electric field or corona discharge power, two ESP performance regions can be distinguished: Below 3 kV/cm, the grade collection efficiency increases with the rise of field strength or ESP index; it tends to saturate or drop when the field becomes higher than 3 kV/cm.