燃煤源微细颗粒物的生成机理及排放因子研究

Fine particle from coal combustion is a major source of atmospheric particulate pollution. Concerning the pulverized coal furnace, circulating fluidized bed furnace, grate furnace and household coal-furnace in northern China, the formation mechanism and emission factors of fine particles in coal combustion are investigated from the combustion science perspective considering the factors of coal type, combustion temperature, air distribution et al. The particle size distribution and emission characteristics of fine particles at boiler outlet will be quantitatively determined and calculated that come from the vaporization of volatile inorganic salts, non-volatile components and trace elements. The experimental research will be carried out in a small-scale pilot furnace for the verification of the simulation and calculation results. The data from the field measurements will be used to check that from the theoretical analysis and experimental results. Based on the accurate knowledge of the fine particles formation mechanism of coal-fired furnace, finally, the calculation model of particulate emission will be obtained as the function of coal type, combustion modes, combustion conditions, dust removal, desulfurization and denitration methods, fully considering the impact of ammonium bisulfate aerosols from the flue gas denitrification process and the effect for emission factors from calcium sulfate aerosols generated by the desulfurization process.

燃煤排放的微细颗粒物是大气颗粒物污染的主要来源之一。本项目针对华北地区煤粉炉、循环流化床锅炉、层燃炉和民用燃煤炉四种炉型，从煤种、燃烧温度、配风等燃烧科学的角度出发，重点研究各炉型中微细颗粒物的形成机理和排放特性，定量计算通过易挥发性无机盐的气化、难挥发组分的还原气化以及痕量元素的气化产生的微细颗粒物的粒径分布和炉膛出口排放量，搭建相应小型实验台进行验证，并结合大量的现场测量对理论分析和实验室结果进行校核。在准确掌握燃煤锅炉微细颗粒物生成特性的基础上，充分考虑烟气脱硝过程中硫酸氢氨气溶胶及脱硫过程中硫酸钙气溶胶的生成对排放因子的影响，最终得到以煤种、燃烧方式、燃烧条件、除尘方式、脱硫和脱硝方式等为输入条件的燃煤源微细颗粒物排放因子计算模型。

燃煤源微细颗粒物是大气污染物的重要来源之一，随着燃烧技术与污染物脱除技术的进步，燃煤源颗粒物的产排特性需深入研究，颗粒物排放因子数据库有待更新。本项目针对燃煤源微细颗粒物，重点研究了：民用燃料的颗粒物生成特性；工业锅炉、电站锅炉、水泥炉窑的颗粒物产排特性和超低排放技术路线下烟气处理系统对颗粒物的脱除特性；煤粉和生物质燃烧过程中微细颗粒物的生成特性；研发了一种基于相变凝聚技术的湿式相变凝聚器，对细颗粒物、硫酸盐、重金属、水蒸气有良好的协同脱除效果，成功应用于某660 MW燃煤电厂。主要成果如下：.1.烟煤排放的PM主要为不完全燃烧产生的有机物质，洁净型煤和兰炭排放的PM主要为易挥发无机盐气化凝结形成的无机颗粒。Na+、Cl-、SO42-是 PM2.5中含量最高的水溶离子。.2.超低排放技术路线下，循环流化床锅炉布袋除尘器对PM10、PM2.5的脱除效率为98.12%~99.56%；链条炉布袋除尘器对PM10、PM2.5的脱除效率为90.0%~93.6%。湿法脱硫和湿式静电除尘器对PM2.5的联合脱除效率为50%~60%。.3.超低排放燃煤电厂SCR使PM1增加35%；静电除尘器对PM1，PM2.5，PM10的脱除效率均大于98%；湿法脱硫使PM1质量增加59%；湿式静电除尘器对PM1，PM2.5，PM10的脱除效率均大于45%。.4.超低排放水泥炉窑最终排放的PM10，PM2.5为14.4~16.1 mg/Nm3，6.1~8.5 mg/Nm3；窑头、窑尾袋除尘对PM1，PM2.5，PM10脱除效率分别为95.3%~96.1%，99.7%~99.9%。.5.煤粉、生物质燃烧过程中易挥发无机元素和难熔矿物质的气化还原主导了亚微米颗粒物的形成，碱金属、碱土金属的硫酸盐对微细颗粒物贡献巨大。.6.燃煤电厂废气中SO2、NO2、NH3及水蒸气四元反应体系有快速显著的成核能力，NO2对气溶胶生成影响最大，其次是SO2，NH3。.7.研发的湿式相变凝聚器可实现：颗粒物超低排放5mg/Nm3，联合脱除颗粒物、重金属；脱除可溶性硫酸盐；回收烟气含水与汽化潜热。.以上研究结果揭示了燃煤源微细颗粒物产排特性，丰富了排放因子数据库，研发的湿式相变凝聚器能够实现多污染物协同脱除并实现工业示范。