燃煤电厂可吸入颗粒物中痕量元素的排放规律研究

Study on emission characteristics of trace elements in PM_(10) from coal-fired power plant

在2个燃煤电厂除尘器入口和出口处利用荷电低压捕集器（ELPI）和稀释采样系统,对烟气中的可吸入颗粒物（PM10）进行现场采样,对其中的痕量元素的粒径分布、富集机理和排放因子进行了研究。电厂除尘器前后PM10中痕量元素的质量粒径分布,与PM10质量浓度粒径分布相似,大多呈现双模态。初步推测所测痕量元素在亚微米颗粒上的富集过程由异相化学反应控制,而在粗颗粒上的富集则可能由异相凝结或化学反应两种机制控制。相对富集因子的计算结果显示,除了Mn在PM10中呈亏损趋势外,其他元素在亚微米颗粒物中均有富集趋势。由于电除尘器对0.1~1μm粒径范围内的颗粒物去除效率较低,其对PM1、PM2.5和PM10中多数元素的去除效率均低于相应的除尘效率。除尘器后PM10中各元素的排放因子差别较大,其排放总量及导致的环境效应值得关注。

Through ELPI （Electrical Low-Pressure Impactor） and dilution sampling system, the mass size distribution, enrichment mechanism, and emission factor of trace elements in PM10 was studied experimentally at the inlet and outlet of electrostatic precipitator （ESP） at two pulverized coal-fired boilers. Results showed that a bimodal mass size distribution of trace elements occurred, similar as that of PM10. It was presumed that the enrichment of trace elements in submicron mode should be controlled by heterogeneous chemical reaction, while the enrichment in supermicron mode by either chemical reaction or heterogeneous coagulation. According to the relative enrichment factors calculated, all studied elements showed enrichment trend in submicron mode except that Mn showed exhaustion trend in PM10. Since the removal efficiency of ESP is low in the particulate size range of0.1-1 μm, the removal efficiency of most trace elements is lower than that of particulate in PM1, PM2.5, and PM10. Although the emission factors of trace elements varied much after ESP, the total emission of trace elements may be large and the environmental impacts should be much concerned.