Mercury Emissions Control
In anticipation of the 1990 CAAAs, specifically the draft Title III regarding the characterization of potential HAPs from electric steam generating units, DOE initiated a new Air Toxics Program in 1989. The DOE Mercury Measurement and Control Program evolved as a result of the findings from the comprehensive assessment of hazardous air pollutants studies conducted by DOE from 1990 through 1997. DOE, in collaboration with EPRI, performed stack tests at a number of coal-fired power plants (identified on map below) to accurately determine the emission rates of a series of potentially toxic chemicals. These tests had not been conducted previously because of their cost, about $1 million per test, so conventional wisdom on emissions was based on emission factors derived from analyses of coal. In general, actual emissions were found to be about one-tenth previous estimates, due to a high fraction of the pollutants being captured by existing particulate control systems. These data resulted in a decision by EPA that most of these pollutants were not a threat to the environment, and needed no further regulation at power plants. This shielded the coal-fired power industry from major (tens of millions) costs that would have resulted from further controlling these emissions. However, another finding of these studies was that mercury was not effectively controlled in coal-fired utility boiler systems. Moreover, EPA concluded that a plausible link exists between these emissions and adverse health effects. Ineffective control of mercury by existing control technologies resulted from a number of factors, including variation in coal composition and variability in the form of the mercury in flue gases. The volatility of mercury was the main contributor for less removal, as compared to the less volatile trace elements/metals which were being removed at efficiencies over 99% with the fly ash. In addition, it was determined that there was no reliable mercury speciation method to accurately distinguish between the elemental and oxidized forms of mercury in the flue gas. These two forms of mercury respond differently to removal techniques in existing air pollution control devices utilized by the coal-fired utility industry.
Projects shown on the map were part of a comprehensive assessment of hazardous air pollutants study conducted by DOE from 1990 through 1997. Results of the study can be referenced in the following publications.
A Comprehensive Assessment of Toxic Emissions From Power Plants: Phase I Results
From The USDOE Study; Prepared by EERC, September 1996. [PDF-3.72MB]
Summary of Air Toxics Emissions Testing at Sixteen Utility Power Plants;
Prepared by Burns and Roe, July 1996. [PDF-7.15MB]
A Study of Toxic Emissions from a Coal-fired Gasification Plant;
Final Report, December 1995. [PDF-28.1MB]
Because mercury was found to be emitted in both particulate and gaseous forms, with the gaseous forms predominantly escaping currently installed technologies, DOE's R&D program focused on understanding mercury transformation in combustion and developing cheaper and more effective control technologies. Cost of control was substantially reduced by this research.
NETL collaborated with EPRI, EPA , CONSOL Inc., and The University of North Dakota and Environmental Research Center (UNDEERC) by providing technical information on the sampling of coal for determining mercury concentrations, and the flue gas mercury speciation method selection for 1999/2000 EPA's Information Collection Request (ICR). DOE provided reports on its mercury sampling efforts (including speciated mercury), which included plans for other sites to be tested with DOE funding during the ICR request period. DOE collaborated with EPRI to conduct and subsequently analyze the sampling efforts for mercury speciation measurements of the approximately seventy utility boiler systems selected by EPA. DOE further contributed funding for the quality assurance and quality control auditing of some of the sampling contractors who performed mercury speciation measurements under the ICR.