Evaluation of Mercury Speciation at Power Plants Using Scr and Sncr Nox Control Technologies
نویسندگان
چکیده
Since the U.S. Environmental Protection Agency (EPA) regulatory determination in 2000 that it intended to regulate emissions from coalfired power plants, many utilities have stepped up proactive steps to investigate methods to control and reduce emissions. However, a lack of sound data still exists which documents the effect of selective catalytic reduction (SCR), selective noncatalytic reduction (SNCR), and ammonia (NH3) on the speciation and removal of mercury at power plants. Although both SCR and SNCR systems are effective at nitrogen oxide reduction, each system may impact mercury speciation differently. In addit ion, some utilities have utilized NH3 and/or sulfur trioxide (SO3) to improve electrostatic precipitator performance by changing the resistivity characteristics of the ash. This project investigates the impact that SCR, SNCR, and flue gas-conditioning systems have on total mercury emissions and on the speciation of mercury. If SCR and/or SNCR systems enhance mercury conversion/capture, then they could be thought of as multipollutant technologies. Data from this project can be used for environmental planning purposes as well as to assist in regulatory decisions. Previous Energy & Environmental Research Center pilotscale tests investigated the role that coal type plays in mercury speciation with the addition of NH3 and the use of SCR. The results indicated that SCR and NH3 may enhance mercury capture, although it appeared that the impact was highly coal-specific. However, there were significant concerns as to the applicability of the pilot-scale results to full-scale power plants. To validate pilot-scale results, sampling must be conducted at the full scale.
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