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Controlling Power Plant Emissions: Control Technology
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Controlling Power Plant Emissions
There are a number of currently available control technologies that coal-fired power plants can use to reduce their emissions of mercury to the atmosphere. For example, controls for sulfur dioxide, oxides of nitrogen and small particles that have already been installed remove some of the mercury before it is released from the stack. The effectiveness of these technologies for mercury removal varies, depending on characteristics of the coal and the configuration of the power plant. In some cases a plant might consider changing the type of coal that it burns in order to get better mercury control from its existing control devices.
Control technologies used to reduce mercury emissions on many facilities that burn municipal solid waste can also be adapted for use on coal-fired power plants. One such technology injects carbon particles into the exit gas flow, downstream of the boiler. The mercury attaches to the carbon particles and is removed in a traditional particle control device. Although no power plants are currently using this technology (except for testing), it has been demonstrated to be somewhat effective on several U.S. coal-fired power plants. For some types of coal, another option is to treat the coal to remove some of themercury from the coal before it is burned in the boiler. This technique works best with coals that have a high moisture content, usually found in the western US. A facility is currently under construction to treat coal in this way. Other technologies to reduce mercury emissions from coal-fired power plants are being developed and tested but have not yet been deployed at the commercial scale.
The fifth "Mega" Symposium on air pollutant controls for power plants was co-sponsored in August 2004 by the U.S. Environmental Protection Agency (EPA), the Electric Power Research Institute (EPRI), the U.S. Department of Energy (DOE), and the Air & Waste Management Association (A&WMA). This multi-pollutant conference showcased the latest developments and operational experience with state-of-the-art methods for reducing air emissions from fossil-fueled boilers. Three papers were presented by EPA at the conference.
Potential Mercury Control Technologies
1. Controlling Mercury with Existing Controls
Data from EPA's Mercury Information Collection Request
(ICR) and other research revealed that many power
plants have existing mercury reduction as a co-benefit of air pollution
control technologies
for NOx, SO2, and particulate
matter (PM). These existing controls offer a significant
opportunity for mercury capture. More
information about existing controls
2. Mercury-specific controls
Mercury-specific controls, most notably activated
carbon injection (ACI), are used on municipal waste
combustor (MWC) and medical waste incinerator (MWI)
facilities in the U.S. and Europe. At present, ACI
is the most widely studied of the mercury-specific
control technologies for coal-fired power plants and
shows the potential to achieve moderate-to-high levels
of mercury control. However, the experience with ACI
applications on MWC and MWI facilities is not directly
transferable to applications on coal-fired boilers
for several reasons. More
information about mercury-specific controls
Additional Information
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Papers presented at the August 2004 "Mega" Symposium
- Preliminary
Estimates of Performance and Cost of Mercury Emission
Control Technology Applications on Electric Utility
Boilers: an Update (PDF) (34 pp, 189 K)
URL: epa.gov/mercury/control_emissions/preliminary_estimates.pdf - Practical
Applications from Observations of Mercury
Oxidation and Binding Mechanisms (PDF) (14 pp, 197 K)
URL: epa.gov/mercury/control_emissions/practical_applications.pdf - Effect of SCR Catalyst
on Mercury Speciation (PDF) (17 pp, 196 K)
URL: epa.gov/mercury/control_emissions/scr_catalyst.pdf
Control
of Mercury Emissions from Coal Fired Electric Utility Boilers: An Update (PDF) (59pp, 856K)
An update to the January 2004 paper, released March
15th.
URL: epa.gov/ttn/atw/utility/ord_whtpaper_hgcontroltech_oar-2002-0056-6141.pdf
Control
of Mercury Emissions from Coal-Fired Electric Utility
Boilers (PDF) (15 pp, 279K)
This paper presents the results of an assessment by
EPA's Office of Research and Development of the state
of mercury control technology as of January 1, 2004.
URL: epa.gov/ttn/atw/utility/hgwhitepaperfinal.pdf
Mercury Control
Technology (PDF) (7 pp, 73KB)
This memo presents DOE’s views regarding the
status of technologies for control of mercury emissions
from coal-fired power plants as of January 8, 2004.
URL: epa.gov/mercury/control_emissions/mercurytechnologiesjan04.pdf
Environmental
Technology Verification Program
Information about mercury continuous emission monitors
(CEMs).
URL: epa.gov/etv/verifications/vcenter1-11.html
National
Energy Technology Laboratory: Mercury Emissions
(NETL)
NETL currently manages the largest funded research
program in the country for developing an understanding
of fossil combustion-based mercury emissions, including
their measurement, characterization, and the development
of cost-effective control technologies for the U.S.
coal-fired electric generating industry.
URL: www.netl.doe.gov/technologies/coalpower/ewr/mercury/index.html