双极荷电细颗粒物加速诱导凝并的机理研究

Along with our country's fast urbanization and industrialized process, PM2.5 pollution has became a prominent environmental problem, which aroused the attention of the government. Conventional dust collecting equipments, such as electrostatic precipitator, bag filter, etc., can't effectively capture the particles which size is less than 2.5μm. To increase the collection efficiency of aerosol particles and prevent air pollution, one possible solution is to shift the aerosol particles to larger particles in the gas flow by bipolar charged agglomeration. Taking the bipolar charged aerosol agglomeration in electrostatic precipitator as the research object, this project intends to use internal components and alternating electric field to accelerate the bipolar charged aerosol agglomeration. Through the building of computational fluid model which contains particles coulomb interaction and charged particle coagulation, the space distribution, the motion state and agglomeration velocity of charged particles will be analyzed. Combining with the experimental measurement results, the effect of the turbulence flow field and alternating electric field to bipolar charged aerosol agglomeration will be illustrated; the mechanism of the acceleration of bipolar charged aerosol agglomeration will be concluded. The prediction model, including corona charger, agglomerator and electrostatic precipitator, will be established, which will provide theoretical guidance and experimental basis to the optimization design of bipolar charged agglomeration electrostatic precipitator.

随着我国城市化和工业化进程日益加快，PM2.5污染已成为突出的环境问题，已引起国家的高度重视。常规除尘设备如静电除尘器、布袋除尘器等，对于粒径小于2.5μm的颗粒不能有效捕集，采用双极荷电凝并技术使小颗粒凝并为大颗粒成为提高除尘效率、降低PM2.5排放的主要途径。本项目拟以电除尘器中双极荷电细颗粒物的凝并为研究对象，以增加内构件及交变电场作为加速颗粒凝并的技术手段，通过构建包含颗粒间库仑相互作用、荷电颗粒凝并的流体力学模型，对诱导凝并区内荷电颗粒的空间分布、运动状态及凝并情况进行模拟分析，结合实验测量结果，阐释湍流流场及交变电场对双极荷电颗粒凝并的影响规律，归纳分析双极荷电颗粒加速诱导凝并机理，建立综合一次积尘与荷电区、诱导凝并区及二次积尘区的预测模型，为双极荷电凝并电除尘器的优化设计提供理论指导和实验依据。

PM2.5污染已成为突出的环境问题，常规除尘设备如静电除尘器、布袋除尘器等，对于粒径小于2.5μm的颗粒不能有效捕集，采用双极荷电凝并技术使小颗粒凝并为大颗粒成为提高除尘效率、降低PM2.5排放的主要途径。本项目以电除尘器中双极荷电超细颗粒物为研究对象，分析了诱导凝并区内荷电颗粒的空间分布、运动状态及凝并情况，并研究了餐厨油烟、VOCs等PM2.5污染源的排放控制技术，具体如下：(1) 基于CFD模拟技术研究了颗粒表面结构、流场、相含率、粒径分布、外加电场等因素对颗粒运动及凝并的影响，归纳关键控制因素，设计了双极荷电-直流电场强化颗粒聚集-交变电场强化颗粒碰撞频率组合强化细颗粒物凝并的方法；(2)设计了油烟首先通过惯性分离的方法捕获大的油滴，剩余的VOCs及细粒子经催化氧化生成对环境无害的CO2和水的油烟净化流程，基于双流体模型开发了折板式及六棱柱式两种油滴净化设备，均可以以较小的压损获得90%以上的净化效率；(3) 针对VOCs催化氧化用Pt/SiO2催化剂的制备过程，建立了描述Pt团簇在SiO2中扩散、凝并的群平衡模型，通过催化剂表面活性面积与催化剂性能进行关联，获得了催化剂制备过程中加热温度/加热时间共同作用下催化剂性能的调控机制，为催化剂的大规模制备时的能量优化提供了数据基础。研究成果作为成套技术的一部分已应用于工业空气净化装置。