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POWER PLANT EVALUATION OF THE EFFECT OF SCR TECHNOLOGY ON MERCURY
Citation:
Chu, P., D. L. Laudal, L. A. Brickett, AND C W. Lee*. POWER PLANT EVALUATION OF THE EFFECT OF SCR TECHNOLOGY ON MERCURY. Presented at DOE/EPRI/EPA/A&WMA Power Plant "Mega" Symposium, Washington, DC, 19-22 May 2003.
Description:
The paper presents results of research on the impact that selective catalytic reduction (SCR) systems have on speciation and total emissions of mercury. Although SCR systems are designed to reduce nitrogen oxides (NOx), they may oxidize elemental mercury (Hg0) to Hg2+, which is more easily captured by a wet flue gas desulfurization (FGD) system. If SCR systems enhance mercury conversion/capture, then they could be thought of as multipollutant technologies. Six power plants were chosen for full-scale sampling to investigate the impact of SCR [as well as ammonia (NH3) injection] on mercury speciation. Sampling was conducted both prior to and after the SCR unit and/or NH3 injection using the wet-chemistry Ontario Hydro (OH) method. Mercury measurements at the particulate and sulfur dioxide (SO2) control inlets and outlets were conducted using both the OH method as well as continuous mercury monitors. Mercury concentration, speciation, and variability were evaluated. Additional sampling involved the use of EPA Method 26A to test for chlorides, a selective condensation method to measure sulfur trioxide (SO3), and EPA Method 27 for NH3 slip. Fly ash and coal samples were also collected to obtain the mercury balance across the control devices. The results obtained thus far indicate that SCRs can assist in converting Hg0 to Hg2+. However, the effect appears to be coal-specific and, possibly, catalyst-specific.