中小燃煤锅炉PM2.5排放特征实测研究

中小燃煤锅炉是我国工业和民用部门最主要的供热方式,掌握其一次颗粒物的排放特征对于研究大气PM2.5的来源和控制途径具有重要意义.本研究通过实测中小燃煤锅炉烟气,获得了中小燃煤锅炉PM2.5及以下粒径段的排放因子和分布,并分析了各粒径段的颗粒密度及除尘装置的去除效率.研究发现,PM2.5质量排放因子平均为(0.123±0.061)kg·t-1,PM2.5粒子数的排放因子平均为(3.17±1.65)×105t-1,烟气中70~120 nm粒径段的积聚模态颗粒在质量和数量上都高于其他粒径段.锅炉燃烧负荷是影响锅炉PM2.5排放的重要因素,锅炉的燃烧负荷越低,PM2.5排放将随之降低.实测锅炉的PM2.5排放因子显著低于物料衡算结果,说明采用物料衡算方法可能极大地高估了现有排放清单中工业燃煤锅炉的一次PM2.5排放量.

Emission characteristics of PM2.5 from medium and small capacity coal-fired boilers in service

Medium and small boiler is a main type of industrial and civil heat supply in China. Understanding the primary emission characteristics from coal-fired medium and small boilers is therefore important to investigate PM_2.5 sources and control measures. In this work the PM_2.5 emission factor and its size distribution from medium and small boiler was determined by direct measurements of the flue gases. Particle density of different size ranges and the removal efficiency of the dust collection unit were explored. Averaged PM_2.5 mass emission factor was (0.123±0.061) kg · t^-1 while the averaged number emission factor was (3.17±1.65)×10⁵ · t^-1. Particles in the size range of 70~120 nm were the largest in terms of both mass and number of particles. The load of boiler is the key factor of the PM_2.5 emission from boiler. A lower load of boiler can reduce the emission of PM_2.5. The PM_2.5 emission factor from direct measurement was significantly lower than that from mass balance calculation, indicating that the mass balance method may over-estimate the primary PM_2.5 emission from industrial boilers in current emission inventories.