侧流电除尘增效机理与检验
Collection enhancement mechanism and test of side flow electrostatic precipitation
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摘要: 针对现有许多电除尘器难以满足日益严苛的颗粒物排放要求而面临提效改造的现状，根据经典电除尘理论，降低电场风速是电除尘器提效的一个有效途径，进而提出一种通过改变烟气流向成倍降低电场风速的侧流电除尘器。首先，为阐明侧流电除尘器的增效机理，基于已有的关于紊流情况下流速对颗粒悬浮作用的研究结果，通过受力分析给出了在有悬浮升力影响下带电颗粒的电除尘效率理论表达式，证明了降低电场风速的增效作用比增加电场长度更有效。然后，在极配结构和处理流量相同、平均入口含尘浓度约1 400 mg·m-3和场强在2.5~4.5 kV·cm-1的情况下，采用中位径为3.5 μm的硅微粉进行了侧流电除尘器和常规电除尘器的减排效果对比实验研究。结果表明，侧流电除尘器的平均排放浓度比常规电除尘器降低45％，减排作用突出。Abstract: Nearly all electrostatic precipitators (ESPs) have to be reformed to improve the collection performance nowadays since the particulate emission standard is becoming more and more rigorous. According to the classical collection theory, it is noticed obviously that to reduce the gas velocity in the electric field is one of the most effective ways of the collection efficiency enhancement. Thus, a side flow ESP is proposed. The gas velocity in the electric field of this ESP can be greatly reduced while the gas flow rate keeps no change. Firstly, based on the results of other researchers about the relation of the lift force and gas velocity in turbulent flow, a theoretical expression of the collection efficiency is derived from the balance equation of the lift force and the electric force acting upon the charged particles. It is proved that the efficiency enhancement effect of decreasing the gas velocity in the electric field is more effective than that of increasing the field length. And then, the comparison experiment of the collection efficiency is carried out. The silica powder with 3.5 μm medium diameter is used in the experiment. The average inlet dust concentration is about 1 400 mg·m-3. The electric field strength is in the range from 2.5 to 4.5 kV·cm-1. The experimental results have shown that the emission concentration of side flow ESP is 45% lower than that of the conventional ESP under the same electrode configuration and gas flow rate.
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