煤/生物质混烧灰的电场内颗粒行为与捕集机制研究

Both in the perspectives of energy use and environmental protection, power generation by coal/biomass co-firing are very favorable, but there still exists the pollution emissions of particulate matter during coal/biomass co-firing. Currently, it is rarely reported on the physical properties of ash from co-firing and its effect on the electric field characteristics of electrostatic precipitator (ESP), interaction between mixed ash particles, driving behavior and capturing mechanism according to its properties change. Based on the original research of mine, the project will intend to study the issue via experimental research and theoretical models, ash physical properties such as true density, wettability, viscosity, specific resistance, etc. will be studied using a combination of four kinds of biomass and bituminous coal, anthracite coal co-firing at different blending rate, thereby the degree and mechanism of influence on the charge properties of particles, electric field characteristics of ESP, the current density distribution characteristics on anode plate. Another, the particle interaction between coal ash and biomass ash, the driving behavior of particles will be studied, and described by establishing the mathematical model, to ascertain the capturing mechanism of co-firing ash. Besides, the classification capturing efficiency and capturing process of biomass ash and coal ash by each electric field of ESP will be clarified. Based on this study, the scheme of high removal efficiency for dust from coal/biomass co-firing will be put forward, which provides a theoretical basis and feasible method for dust emission control in the co-firing power plants.

煤/生物质混烧发电从能源利用与环境保护的双重角度来看都是非常有利的,但煤与生物质的混烧仍然存在颗粒物的污染排放问题。而目前就混烧后灰的物性特征及其变化对电除尘器电场特性、混合灰颗粒间的相互作用、电场内颗粒的驱进行为与捕集机制等方面影响的研究却鲜有报道。本项目拟在原有研究基础之上，采用实验研究与理论模型相结合的方法，将常用的4种生物质分别与烟煤、无烟煤按不同掺混率混烧，研究混烧灰的真密度、浸润性、粘性、比电阻等物性特征及变化规律，以及由此引起的对颗粒荷电性能、电除尘器伏安特性、阳极板电流密度分布特性等的影响程度及机理；研究并描述电除尘器内相互混合的煤灰与生物质灰颗粒之间的相互作用和颗粒驱进行为，建立相应的数学模型，探究混烧灰的捕集机制；探明电除尘器各电场分别对混烧灰中煤灰与生物质灰的分级捕集能力与捕集过程。基于此研究，提出煤/生物质混烧灰高效脱除的方案，为混烧锅炉的烟尘排放控制提供理论依据。

化石燃料的过量使用，使得能源短缺与环境污染问题日益凸显。煤与生物质混烧已经成为一种发展趋势，而煤与生物质混烧在火力发电厂的应用也是形势所趋。生物质通过混烧改变了燃烧特性，也必将使混烧灰在电除尘器中的荷电、电场特性、电场内颗粒间的相互作用及颗粒驱进行为、捕集机制等方面与煤粉的不同。.对荷电特性与电场特性研究采用常见的生物质燃料玉米秸、花生壳、木头屑。对于电场内颗粒间的相互作用及颗粒驱进行为、捕集机制的研究均选取的燃料分别为常见的生物质燃料玉米秸秆与无烟煤。以上研究均按照总热量0、5%、10%、15%、20%、100%的比例分别与无烟煤和烟煤混燃，制成一系列混燃灰。荷电特性通过采用法拉第荷电量检测系统和静电低压撞击器（ELPI）测量混燃灰的总体、分级荷质比，结果发现:随着生物质的加入，混烧灰成分发生变化，使得介电常数变大，比电阻增大，从而使得总体荷质比有上升趋势，若排除粒径影响，分级荷电能力得以增强，但影响较小。同时生物质种类、被掺煤种均有影响。电场伏安特性测定采用自行设计装置和网格型微元电流信号法，研究混烧灰物性特征对其的影响因素。，结果发现：不同种类、不同比例生物质混燃灰对电流密度大小产生影响，对其电流密度分布均匀性没有影响。另外电晕线型是影响混燃灰板电流密度分布特性的重要因素。颗粒间相互作用及驱进行为的模拟研究表明：电除尘器颗粒团聚主要以电团聚为主。三者共同为微米级颗粒的团聚起到十分重要的促进作用。对捕集效率的研究采用实验室自制静电捕集系统测定灰样的分级捕集效率。选取具有代表性的一组捕集后的灰样采用加速器质谱仪法测定其14C值，通过14C技术精准的核算相同和不同电场的捕集效率。结果发现：微观形貌、成分分析、比电阻、密度以及粒径分布均对不同电场中的煤灰和生物质灰的捕集效率有影响。