Abstract: The experiment was conducted in a 220 MW cogeneration boiler in Beijing. The Dekati Gravimetric Impacter system was used to sample particulate matter (PM) at the inlets of selective catalytic reduction (SCR), electrostatic precipitation (ESP) and flue gas desulfurization (FGD) in this boiler, to investigate the migration characteristics of trace elements in the flue gas tunnel. In addition, distribution of trace elements in solid combustion residues was also studied. The concentrations of As, Cd, Cr and Pb in PM at the inlet of ESP were obviously higher than those at the inlet of SCR. The masses of gaseous As, Cd, Cr and Pb converted to solid in the process of flue gas flow from SCR to ESP accounted for 26%, 16%, 12%, 11% of the total masses in coal respectively. In the process of flue gas flow from ESP to FGD, the concentrations of As and Cd in PM slightly increased, while those of Cr and Pb were almost constant. The concentrations of Mn at the three sampling sites were almost the same. Most trace elements remained in the fly ash collected by ESP, and at the outlet of ESP, the masses of As, Cd, Cr and Pb in the four size segments with size <10 μm increased with decreasing particle size, however, mass distribution of Mn was similar with that of PM.

Key words: coal combustion, cogeneration boiler, trace element, particulate matter, migration, distribution, pollution

摘要： 本实验在北京某220 MW热电联产锅炉上进行。采用承重撞击器系统对该锅炉选择性催化还原（SCR）前、电子除尘（ESP）前以及烟气脱硫（FGD）前的颗粒物进行采集，研究了痕量元素在烟道沿程上的迁移特性，另外，还给出了痕量元素在各固体燃烧产物中的分布。结果表明：ESP前的颗粒物上As、Cd、Cr和Pb的浓度明显高于SCR前的浓度；在从SCR到ESP的过程中，As、Cd、Cr、Pb从气态迁移到固态的质量分别占到了原煤中总质量的26%、16%、12%和11%；从ESP到FGD的过程中，颗粒物上As与Cd的浓度有略微增加，而Cr和Pb的浓度几乎不变；Mn在3个采样点的浓度几乎一致；大部分痕量元素存在于ESP捕获的飞灰中，在ESP出口处，As、Cd、Cr、Pb在<10 μm的4个粒径段上的质量随着粒径的减小而增大，而Mn的质量分布与颗粒物质量分布类似。

关键词: 煤燃烧, 热电联产锅炉, 痕量元素, 颗粒物, 迁移, 分布, 污染