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 Abstract

 
Characterization of Mercury-Enriched Coal Combustion Residues from Electric Utilities Using Enhanced Sorbents for Mercury Control (222 pp, 3.8 MB) February 2006

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This report evaluates changes that may occur to coal-fired power plant air pollution control residues from the use of activated carbon and other enhanced sorbents for reducing air emissions of mercury and evaluates the potential for captured pollutants leaching during the disposal or use of these residues. Leaching of mercury, arsenic, and selenium during land disposal or beneficial use of coal combustion residues (CCRs) is the environmental impact pathway evaluated in this report. Coal combustion residues refer collectively to fly ash and other air pollution control solid residues generated during the combustion of coal collected through the associated air pollution control system. This research is part of an on-going effort by U.S. Environmental Protection Agency (EPA) to use a holistic approach to account for the fate of mercury and other metals in coal throughout the life-cycle stages of CCR management.

The specific objectives of the research reported here are to:

  1. Evaluate the potential for leaching to groundwater of mercury, arsenic, and selenium removed from coal-fired power plant air emissions by air pollution control technology and, as a result, are contained in CCRs;
  2. Provide the foundation for assessing the impact of enhanced mercury and multi-pollutant control technology on leaching of mercury and other constituents of potential concern from CCRs during the lifecycle of CCR management, including storage, beneficial use, and disposal; and
  3. Perform these assessments using the most appropriate evaluation methods currently available.

Air pollution control residues were obtained from coal combustion electric utility facilities with a representative range of facility configurations (including air pollution controls) and coal types combusted. Each of the residues sampled has been analyzed for selected physical properties, and for total content and leaching characteristics. Results of laboratory leaching tests were used to develop estimates of constituent release under field management scenarios. Laboratory leaching test results also were compared to field observations of leaching.

This report focuses on facilities that use injected sorbents for mercury control. It includes four facilities with activated carbon injection (ACI) and two facilities using brominated ACI. Fly ash has been obtained from each facility with and without operation of the sorbent injection technology for mercury control. Each fly ash sampled was evaluated in the laboratory for leaching as a function of pH and liquid-to-solid ratio. Mercury, arsenic and selenium were the primary constituents of interest; results for these elements are presented here.

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Susan Thorneloe


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