磁场环境下静电除尘器中PM2.5捕集的多场耦合机理与PIV实验研究

The existing electrostatic precipitator (ESP) in thermal power plant has the deficiencies of high power consumption, expensive maintenance fee and low collection efficiency of PM2.5. In this project, the action mechanism investigation on the intercoupling between the gas flow field, the particle dynamic field and the electromagnetic field in the process of trapping PM2.5 under the environment of magnetic field will be carried out by introducing magnetic field into ESP while considering the effects of electric charging, diffusion charging and ion wind. The theoretic and numerical models under multi-field coupling will also be established to simulate the trapping process of PM2.5, which is much closer to the actual working condition. The experiments including flow field Measurement by particle image velocimetry (PIV) and corona characteristics test are going to be conducted, and data of flow field information, electric field characteristics and dust concentration will be obtained to verify and optimize mathematic model and methods and computational program. The escaping status and the collection efficiency of PM2.5 will be employed to measure the removal performance to reveal the influences of magnetic field, diffusion charging and ion wind on collection efficiency. Furthermore, in order to greatly decrease the ESP power consumption and reduce the PM2.5 emission, the parameters’ range of magnetic induction density, applied potential and inlet gas velocity is calculated and searched when the collection efficiency of ESP is optimal. All the work to be done will provide the analysis approach and frame for macroscopic theoretic research on electrostatic dust removal technology under the environment of magnetic field, and offer the technical reference and the theoretic basis for the novel ESP design in aspects of economy and efficiency.

现有火力发电厂的静电除尘器存在功耗大、运行维护费用高、对PM2.5捕集效率低的问题。本项目拟将磁场引入静电除尘器中，在考虑电场荷电、扩散荷电及离子风的情形下，研究磁场环境下PM2.5捕集的气体流场、颗粒动力场与电磁场相互耦合的作用机理，建立多场耦合作用下的理论和数值模型，模拟贴近实际工况中PM2.5的捕集过程。开展粒子图像测速仪（PIV）的流场测试和电晕特性实验，测量流场信息、电场特性及粉尘浓度等数据，验证和优化上述数学模型和方法及计算程序。拟采用PM2.5逃逸状况和除尘效率来衡量除尘效果，揭示磁场、扩散荷电、离子风对捕集效率的影响规律，计算搜索PM2.5捕集效果最优时磁感应强度、工作电压、入口烟气速度等参数范围，以此大幅度地降低静电除尘器功耗和减少PM2.5的排放。结果可为磁场环境下静电除尘技术的宏观理论研究提供分析途径与框架，并为新型静电除尘器的经济高效性设计提供技术参考和理论依据。

雾霾目前已成为全球各国重点关注的对象，其主要成分是PM2.5。火力发电厂是大气中PM2.5的重要排放源之一，静电除尘器（ESP）作为燃煤电厂最常用的除尘设备，如何提高ESP对细微颗粒物的有效控制成为当前亟待解决的重要课题。.项目针对火力发电厂静电除尘器捕集细微颗粒物效率低的问题开展了磁场环境下PM2.5脱除的多场耦合机理与PIV实验研究，揭示了磁场、扩散荷电、离子风作用下的颗粒物除尘机理，建立了磁场环境下多场耦合理论和数值模型，利用粒子图像测速技术（PIV）探究了磁场环境下ESP中的流场分布和颗粒运动轨迹，实现了多场耦合模型的求解，得到了研究磁场、扩散荷电、离子风对除尘性能的影响规律。.研究结果表明：1）磁场的引入延长了PM2.5粉尘颗粒在静电除尘器中的停留时间，使其更容易被收尘板所吸附，有效提升了除尘效果；2）PIV实验证实了磁约束作用使ESP中颗粒作更为复杂的螺旋运动，直观地显示了颗粒偏向收尘板的幅度有明显提高；3）扩散荷电效应对PM2.5捕集的影响比外加磁场作用更为显著，扩散荷电与外加磁场联合作用下的PM2.5捕集效果要好于单独考虑任何一种作用下的情形；4）离子风作用下的PM2.5除尘效率高于不考虑离子风下的情形，并随磁感应强度的增大而增大；5）工作电压、烟气流速和粒径分布参数均对ESP捕集性能产生影响，随着工作电压和R-R分布中位粒径的增大以及烟气流速的减小，PM2.5综合除尘效率均呈增大的趋势，粒径分布指数对除尘效率的影响规律因静电除尘器种类不同而不同。.研究结果不仅丰富了除尘技术的相关理论，奠定了静电除尘器科学应用的技术价值，而且为降低火电厂PM2.5排放和电压功耗提供思路和方法，并为设计经济高效的新型静电除尘器提供技术参数和理论指导。