民用煤燃烧排放PM_(2.5)的微观形貌和化学组分

Microscopy Morphology and Chemical Composition of PM_(2.5) From Household Coal Combustion

设计和搭建室内煤燃烧–稀释系统,分别燃烧烟煤和无烟煤,获取不同煤种燃烧排放PM_(2.5)样品,使用带能谱的透射电镜观察单颗粒的物理化学特征。根据颗粒的微观形貌、化学组分及电子束作用下的稳定性,将颗粒分成7种类型:富Si、富Ca、富S、富K、有机、碳烟和金属颗粒。燃煤排放的碳烟多聚集在一起,呈链状;有机颗粒多呈球形或近似球形;富Si和金属颗粒多呈不规则形状,球形颗粒数量相对较少,原因是民用煤的燃烧温度相对较低,不能使煤中大部分矿物质呈熔融状态。烟煤燃烧排放碳烟的相对数量百分比高于无烟煤,是由于烟煤的挥发分高于无烟煤。燃煤排放富S颗粒的相对数量百分比随煤中含S量增加而升高。

A combustion-dilution system of coal was designed and set up. PM_（2.5） samples from bituminous and anthracitic coal combustion were collected. Physicochemical characteristics of individual particle were determined by a transmission electron microscope equipped with an energy dispersive X-ray spectrometer（TEM-EDX）. Based on the chemical composition, morphology and stability under electron beam, the particles were classified into the following seven types： Si-rich, Ca-rich, S-rich, organic, soot and metal particles. Soot from coal combustion tend to agglomerate and is chain-like. Morphologies of most organic particles are spherical or approximately spherical. Most Si-rich and metal particles are irregular shape. Several Si-rich and metal particles are spherical because most minerals in coal are not molten state in the relatively low temperature process of household coal combustion. Relative number percentage of soot particles from bituminous coal combustion is higher than it from anthracitic coal combustion because volatile components of bituminous coal are higher than volatile components of anthracitic coal. Relative number percentage of S-rich particles emitted from coal combustion increase with the increase of sulfur content.