(691a) Direct Measurement of Mercury in Simulated Coal Combustion Flue Gas

Coal-fired power plants are the greatest anthropogenic source of mercury emissions in the United States. Mercury exists in coal combustion flue gas in a variety of forms depending on the coal type and combustion conditions, i.e., elemental, oxidized, and particulate. Understanding mercury speciation during combustion and how the transformations occur between different forms of mercury is essential to develop an effective control mechanism for removing mercury from flue gas. Homogeneous oxidation of mercury in the flue gas of coal combustion utility boilers has been studied for many years to understand the speciation of mercury. In spite of a vast amount of experimental studies, supported by modeling efforts, there are still many questions to be answered and the speciation of mercury is not fully understood yet. One needs to be able to make precise mercury measurements to understand the mercury speciation and accurately predict the extents of mercury oxidation. Traditionally ?difference? techniques are used which involves the direct measurement of elemental mercury. These techniques do not allow for distinguishing between the two different oxidized forms, Hg+ and Hg+2 which makes it difficult to understand mercury speciation. It has recently been shown that mercury measurements performed with wet chemical conditioning systems are biased, resulting in inaccurate partitioning between oxidized and elemental mercury species. Given the shortcomings of the difference techniques, it is essential to measure oxidized and elemental mercury directly and hence separately to have a complete understanding of mercury speciation. In this study an electron ionization quadrupole mass spectrometer will be used to directly measure mercury species in combustion flue gas. A benefit of employing a mass spectrometer is, unlike traditional impinger methods, the oxidized forms can be isolated and individually identified because it separates the products based on their mass to charge ratio. By directly measuring mercury species accurately, one can determine the actual extent of mercury oxidation in the flue gas, which will aid developing effective mercury control technologies.