循环流化床电站排放烟尘特性及痕量重金属分析

Studies on the characteristics of aerosol and trace metals emitted from a CFB coal-fired power plant

对35t h循环流化床电厂电除尘器入口和出口的烟气气溶胶进行分级取样,得到飞灰浓度和粒度分布以及电除尘器的分级脱除效率.电除尘器对PM10、PM2 5的脱除效率分别为94 34%和91 38%,使部分可吸入烟尘颗粒穿透除尘设备而直接排放到大气环境中.同时对不同粒度飞灰中重金属含量进行了测试,得到痕量元素浓度从高到低依次为Ni,Cr,Cu,Cd,Pb,Hg.痕量重金属含量与飞灰粒径有一定依附关系,其分布规律与煤成分、锅炉燃烧方式和痕量元素自身的挥发特性等因素有关.

The emission of primary particulates and trace toxic metals from coal-fired power plants is an important environmental issue. Experiments were performed in a 35?t/h circulating fluidized boiler (CFB) power plant, where particulate samples in flue gas were retained at the inlet and outlet of the ESP and segregated in a cascade impactor. Size-dependent capture efficiencies of the ESP to flue gas particulates were calculated, with an average of 94.3% for PM_(10) and 91.4% for PM_(2.5) respectively. Some fine particles were emitted to the atmosphere directly and formed primary inhalable particles. Concentrations of several trace metals were analyzed with furnace atomic absorption spectrometer (FAAS) after acid digestion. Size-dependent concentration distribution of flue gas particles and trace toxic metals were obtained at the inlet of ESP in a decreasing order of Ni,Cr,Cu,Cd,Pb,Hg. Trace heavy metals concentrations in flue gas particles were dependent both on particle size and specific element. Such characteristics were likely ascribed to the coal composition, combustion condition, element volatility during combustion.