In the context of the implementation or tightening of mercury emission limits on a national (German) and European level the question may be raised how mercury emissions can be measured reliably at very low concentrations. Furthermore, especially upstream of a wet scrubber for flue gas desulphurization, the oxidation stage of the mercury in the flue gas is of specific importance to achieve further reduction of mercury emissions. The European standard reference method for determination of total mercury in flue gases EN 13211 is not adequate to control emission limits in the range of 1 - 3 μg/m~3, as already proposed and partly agreed for single new build projects of power plants in Europe. In addition, the standard reference method delivers only numbers for total mercury but does not allow differentiation between elemental (metallic) mercury and oxidized mercury which can be removed in a wet scrubber much more easily. In this project, which has been funded by VGB, alternative manual and automatic measuring methods following the adsorption principle, as well as alternative continuous measuring methods have been compared with each other and with the standard reference method. In the scope of two measuring campaigns, performance data regarding the equivalency of alternative methods and standard reference method and the uncertainty of measurement have been determined. Conventional and newly developed continuous monitoring systems have been included in the comparison. During this work the so-called Dowex/Charcoal method for differentiation of oxidized and elemental mercury in flue gases has been validated in terms of total mercury determination. This allows a significant simplification of flue gas measurements in the future which focus on further optimization of mercury oxidation and removal from the flue gas.
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