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

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