源自燃烧的汞排放是一个全球性问题,其中几乎一半左右的汞排放到达了北极圈.燃煤烟气中的汞以最基本的三种形式存在:元素汞(Hg0),氧化态汞(Hg2+)和颗粒态汞(HgP).本文选用一台美国现役燃煤电厂锅炉(250MW),在其空气预热器入口和静电除尘器出口烟气中的汞浓度进行了监测.烟气中的汞浓度同时使用安大略湿法(OHM或OH方法)和半连续排放监控系统(SCEM)两种检测方法进行监测,并对测试结果进行了分析比较.结果显示OHM和SCEM方法测得的总汞(零价汞与二价汞之和)浓度十分吻合,而零价汞或二价汞浓度存在较大差异.最后分析了两种测量方法测量结果差异产生的原因并建议对SCEM的现场采样方法应做进一步的研究.
Mercury (Hg) from combustion of fossil fuels and waste is the dominant source of anthropogenic Hg emissions with increasing environmental impacts. Nearly half of the Hg emissions reaches the Arctic. Coal-fired utility boilers are currently the largest known source of mercury emissions in the world. Mercury in coal-flue gas survives in three species, i. e. , elemental, oxidized and particulate. Mercury emission tests were done at the air preheater (APH) inlet and the electrostatic precipitator (ESP) outlet for a tangentially fired furnace with capacity of 250MW in Massachusetts, USA. The comparisons were presented for the mercury emission measurements among the Ontario Hydro Method (OHM) and Semi-Continuous Emission Monitors (SCEM). The results indicate the good agreements between the OHM and SCEM measurements on the total mercury species. Some SCEM results were not well consisted, especially the elemental species, with the OHM data due to the different port-installation of probes even through at the same sampling locations and they were more strongly influenced by the uneven distribution of mercury concentration in the turbulent flue gas across the flue duct section. The reasons were putatively addressed for the data deviations between the two methods and the more investigations should be done for the in situ samplings of SCEM for the more accurate species measurements.