Evaluation of Mercury Emissions from Coal-Fired Facilities with SCR and FGD Systems
CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) and the Electric Power Research Institute (EPRI), is evaluating the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP)--wet flue gas desulfurization (FGD) combination or a spray dyer absorber--fabric filter (SDA-FF) combination. In this program CONSOL is determining mercury speciation and removal at 10 coal-fired facilities. The principal purpose of this work is to develop a better understanding of the potential mercury removal ''co-benefits'' achieved by NO{sub x}, and SO{sub 2} control technologies. It is expected that these data will provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. Ultimately, this insight could help to design and operate SCR and FGD systems to maximize mercury removal. The objectives are (1) to evaluate the effect of SCR on mercury capture in the ESP-FGD and SDA-FF combinations at coal-fired power plants, (2) evaluate the effect of SCR catalyst degradation on mercury capture; (3) evaluate the effect of low load operation on mercury capture in an SCR-FGD system, and (4) collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. This document, the ninth in a series of topical reports, describes the results and analysis of mercury sampling performed on Unit 1 at Plant 7, a 566 MW unit burning a bituminous coal containing 3.6% sulfur. The unit is equipped with a SCR, ESP, and wet FGD to control NO{sub x}, particulate, and SO{sub 2} emissions, respectively. Four sampling tests were performed in August 2004 during ozone season with the SCR operating; flue gas mercury speciation and concentrations were determined at the SCR inlet, SCR outlet, air heater outlet (ESP inlet), ESP outlet (FGD inlet), and at the stack (FGD outlet) using the Ontario Hydro method. Three sampling tests were also performed in November 2004 during non-ozone season with the SCR bypassed; flue gas mercury speciation and concentrations were determined at the ESP outlet (FGD inlet), and at the stack (FGD outlet). Process samples for material balances were collected during the flue gas measurements. The results show that, at the point where the flue gas enters the FGD, a greater percentage of the mercury was in the oxidized form when the SCR was operating compared to when the SCR was bypassed (97% vs 91%). This higher level of oxidation resulted in higher mercury removals in the FGD because the FGD removed 90-94% of the oxidized mercury in both cases. Total coal-to-stack mercury removal was 86% with the SCR operating, and 73% with the SCR bypassed. The average mercury mass balance closure was 81% during the ozone season tests and 87% during the non-ozone season tests.
- Research Organization:
- Consol Energy Inc
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FC26-02NT41589
- OSTI ID:
- 903183
- Country of Publication:
- United States
- Language:
- English
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EVALUATION OF MERCURY EMISSIONS FROM COAL-FIRED FACILITIES WITH SCR AND FGD SYSTEMS
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