CFD在电除尘器超低排放设计中的应用

On the practical application of CFD to the design of ESP for ultra-low pollutants emission

由于我国环保排放要求的日益严格,电除尘器超低排放成为最受关注的问题之一。流场作为影响电除尘器超低排放性能的重要因素,具有重要的工程意义。基于CFD（计算流体力学）模拟方法,并结合工程实际应用,从流量分配、本体气流分布设计、本体阻力、电场极配型式、绝缘系统热风吹扫设计等方面对电除尘器流场设计进行阐述和对比分析。结果表明：电除尘器流场优化既要考虑流量分配均匀,又要考虑粉尘量分配均匀,电除尘器入口烟道导流板的合理设计不但可以解决流量分配平衡问题,也可以使粉尘量的偏差得到大幅度改善;进出口喇叭角度不但对本体流场均匀性有影响,对除尘器本体阻力也有较大影响,进口喇叭扩张角、出口喇叭收缩角越大,本体速度分布均匀性越差,本体阻力也越大;灰斗阻流板的合理设计有助于减轻收尘区下沿高速区与灰斗的强回流现象;在不同极配型式中,针刺线平行于极板比针刺线垂直于极板的击穿电压更高,电流密度更均匀,更有利于粉尘收集;改进绝缘系统热风吹扫的方式有助于解决绝缘系统短路现象。

This paper intends to provide a reasonable layout of the flow optimization of the ESP（electrostatic precipitators） based on the CFD（Computational Fluid Dynamics） simulation method and its corresponding practical engineering application of the ESP.As is known,the said ESP method can not only help to balance the emission flow distribution,but can greatly improve the deviation of the dust amount,too.The simulation method we have developed has just started from the more and more strict demands for the environmental protection and research progress in this way.As one of the key factors influencing the efficiency of ESP,the goal for heightening the said efficiency may include the following aspects：the branch flow deviation;the chamber flow distribution;the flow resistance;the selection of the electrode configuration,and the hot air circulation system for the insulator chamber,etc.which are of great significance to the environment,particularly from the point of view of the conic angles of the inlet and outlet.The simulation results we have done show that it is of great significance to take into account the flow distribution and the dust amount deviation.With the increase of the expanding conic angle of the inlet and the shrinking conic angle of the outlet,it is prone to spoil the uniformity distribution of ESP body velocity and lead to the enlargement of its resistance.Therefore,reasonable design of the hopper baffle will be of great help to alleviate the high speed area at the bottom of the chambers and reduce the strong backward flow produced in the hoppers.What is more,for the electrode configuration types,since the type-needle parallel line to the plate is superior to the perpendicular one in considering the higher breakdown voltage,more uniform current density will be more favorable for the dust collection.At the same time,the improved hot air blowing system can also help to solve the short circuit of the insulation system.Therefore,the optimization of the flow field through the CFD improvement can be expected to provide a highly valuable reference for EPS design,operation and diagnosis analysis.