贵阳市小型燃煤锅炉烟气中汞的形态及释放

Mercury Speciation and Emissions in the Flue Gas of a Small-Scale Coal-Fired Boiler in Guiyang

选择贵阳市某厂的1台安装有湿法脱硫除尘的燃煤锅炉,研究湿法脱硫除尘前后燃煤烟气中颗粒态汞(Hgp)、氧化态汞(Hg2+)、原子态汞(Hg0)以及总汞(Hgt)的含量和形态分布。结果显示,湿法脱硫除尘后的颗粒态汞、氧化态汞、原子态汞分别约占总汞的10 4%,6 0%,83 6%。湿法脱硫除尘器对氧化态汞与颗粒态汞有很好的去除效率(分别为87 9%,76 1%),而对原子态汞的去除效率较差(为30 4%)。由于对该锅炉的年燃煤量统计有一定的误差以及烟气采样分析方法本身存在的误差,该锅炉输出的总汞略大于输入的总汞,质量平衡结果为:输出输入=103 6%～107 4%。煤经过燃烧后,总汞的释放因子为:41 7%残留在底灰中,65 7%进入烟气中,其中经过湿法脱硫除尘器的净化,26 7%的汞随除尘废水排放到水环境中,7 8%存在于经过除尘后的渣中,25 05%随清洁烟气释放到大气中。

Chemical speciation and distribution of mercury in the flue gas were studied in a small-scale coal-fired boiler with wet flue gas precipitator and desulfurization(WFGPD) system of Guiyang.In the flue gas cleaned by the WFGPD system,the percentage of Hg^p,Hg^(2+) and Hg^0 with regard to Hg^t were 10.4%,6.0%,83.6%,respectively.The removal efficiency of Hg^(2+) (87.9%) and Hg^p (76.1%)by the WFGPD system were higher than that of Hg^0(30.4%).The total output mercury of this boiler is a little higher than the total input mercury of the boiler because of statistical error of the fired coal per year and the Ontario Hydro sampling-analytical error of mercury in flue gas.The ratio of output Hg^t to input Hg^t is 103.6%～107.4%.The mercury emission factors were that:41.7% of Hg^t was found in clinkers and 65.7% of Hg^t entered into flue gas before the WFGDP system.When the flue gas was cleaned by the WFGDP system,only 25.05% Hg^t was emitted to the atmosphere, 26.7% Hg^t discharged into the water and 7.8% Hg^t into the cinder.