燃煤细颗粒物化学团聚促进机制的研究

China is one of serious coal flue gas pollution country, and the emission of PM 2.5 from coal-fired power plant has caused seriously environmental problem. The proposal project is focus on fine particles in coal-fired flue gas, the multidisciplinary theory of combustion, interfacial chemistry, flocculation theory, and spray drying is combined to reveal the mechanism of chemical agglomeration of fine particles. The quantitative relationship between heavy metal enrichment in the fine particles will be analyzed, the agglomeration promote mechanisms of fine particles at the low temperature zone before the electrostatic precipitator will be investigated, systematic agglomeration experiments will be conducted to improve the agglomeration process of fine particles. The fly ash resistivity will be adjusted to enhance its wettability. The liquid bridge force and transformed solid bridge force between the particles will be quantitative described. The flocculation theory will be used to simulate and analyze the influence of agglomeration agent on the agglomeration of fine particles. The agglomeration process dynamic will be simulated using spray drying theory, the flow process simulation of fine particles movement and collision will be analyzed using fluid dynamics theory. Finally, a novel quantitative description method of fine particles chemical agglomeration will be developed by the combination of experimental and simulation results. Which will provide a theoretical basis and technical support for the removal efficiency of the electrostatic precipitator, and the effective control of the coal-fired fine particle emissions.

我国属于重度煤烟型污染的国家，燃煤PM2.5的排放已对大气环境造成了严重危害。以燃煤烟气中细颗粒物为研究出发点，结合燃烧学、界面化学、絮凝理论以及喷雾干燥理论等多学科理论，揭示化学团聚作用机制。系统分析重金属在细颗粒物上富集的定量关系；建立团聚实验系统，研究静电除尘器前低温区团聚剂对细颗粒物团聚的促进机制；进行多工况燃煤烟气颗粒物团聚实验，完善细颗粒物团聚工艺。调节飞灰比电阻，增强飞灰润湿性，定量描述促进剂在颗粒之间产生的液桥力以及转化为的固桥力。利用絮凝理论模拟团聚剂对细颗粒的团聚过程，探讨对细颗粒物团聚的促进作用；利用喷雾干燥理论进行细颗粒促聚和共聚动力学模拟；利用流体动力学理论进行细颗粒运动、碰撞和流动过程模拟。综合多种实验和模拟计算结果，建立细颗粒物化学团聚定量描述方法。提高静电除尘器对细颗粒物的脱除效率，为有效控制燃煤细颗粒物排放提供理论基础和技术支撑。

本项目针对燃煤电厂细颗粒物脱除效率较低的问题，提出一种化学团聚强化除尘新方法。在除尘器前将细颗粒物通过化学团聚形成大颗粒团，强化除尘器对细颗粒物的捕捉，提高除尘效率。利用X射线荧光探针、X射线衍射仪、电感耦合等离子质谱分析仪、场发射扫描电镜+能谱分析、zeta电位分析仪、比电阻测试仪等先进分析测试，揭示了飞灰比电阻与元素含量的定量关系，飞灰悬浮液zeta电位与元素含量的定量关系，飞灰中重金属元素富集规律。系统分析了不同电厂燃煤飞灰颗粒物的物理化学特性，进行了化学团聚强化细颗粒物排放控制的理论与实验研究。考察了化学团聚剂组成、浓度、溶液pH值、K+离子浓度以及表面活性剂、烟气温度等因素对细颗粒物团聚效率的影响，并探究了化学团聚剂溶液间的协同作用。研究了不同因素对飞灰细颗粒物悬浮液zeta电位的影响，探究了溶液zeta电位与细颗粒物脱除效率之间的关系。建立了颗粒物化学团聚模型，模拟了液滴的密度、粘度、流量及粒径等因素对团聚的影响，研究了温度对液滴与颗粒间团聚效果的影响。进行了细颗粒物化学团聚工业应用工程示范，化学团聚方法提高静电除尘器效率30%以上，强化除尘效果明显。化学团聚对电厂运行参数，包括SO2、NOx、O2浓度、烟气温度、烟气湿度等的影响在可接受范围，具有经济、灵活的特点，为大规模工业应用奠定了基础。项目共发表论文37篇，其中SCI收录论文20篇，EI收录论文9篇，授权专利2项，参加国际会议13人次，国内学术会议18人次，培养研究生5名。