The U.S. Department of Energy (DOE), through the Federal Energy Technology Center (FETC), manages the largest funded program in the country for developing (1) an understanding of mercury emissions, (2) measurement of these emissions, and (3) control technology (-ies) for these emissions for the U.S. coal-fired electric generating industry. DOE has initiated, or has collaborated with other government and industrial organizations in, these and other efforts relating to mercury and other hazardous air pollutants (HAPs), also known as air toxics. One of DOE's first reports on trace elements in coal was conducted from 1976 through 1978 by researchers at DOE's Pittsburgh Energy Technology Center (PETC, now FETC) and the Pittsburgh Mining Operations of the Department of the Interior's Bureau of Mines. The report was completed less than two years after DOE was formed, and 13 years before Title III of the 1990 Clean Air Act Amendments was enacted (Cavallaro et al., March 1978).This work was conducted at PETC facilities years before the terms "hazardous air pollutants" and "air toxics" came into vogue. The work indicated, from 10 different coal beds, that most of the trace elements of interest are concentrated in the heavier specific gravity fractions of the coal, and, therefore, are associated with the mineral matter. It was speculated that the removal of the mineral matter should result in significant trace element reductions ranging up to 88%. (Cavallaro et al., March 1978) Since that time, many collaborative efforts on trace element research (focused on mercury) have been realized between DOE/FETC and EPA, the U.S. Geological Survey (USGS), the Electric Power Research Institute (EPRI), the utility industry, other government agencies at both the federal and state levels, and other U.S. and foreign research organizations. Most efforts in trace element research have been conducted in this decade, and many of the most important efforts in the understanding of mercury have been conducted during the last six years.EPRI and DOE/FETC collaborated on the sampling and analyses of a possible 189 listed HAPs resulting from coal combustion and indicated by EPA as potentially impacting our ecosystems and human health. The combined EPRI and DOE/FETC efforts provided comprehensive HAPs assessments from over 30 different coal-fired power plants in the United States to the EPA for both of their congressionally mandated reports: the Mercury Study Report and the Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units-Final Report to Congress (EPRI, 1994; U.S DOE, 1996).Through an interagency government review process, DOE/FETC and DOE's Policy Office were also involved with some of the results of the data and conclusions contained in these two reports. With FETC managing the largest mercury control program, the Mercury Study Report stressed during the review period that for the promising technologies, "Given the relative low maturity level of these technologies, commercial deployment is still at le...

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Based on the available evidence of health effects, the U.S. Environmental Protection Agency (EPA) has been evaluating the need to regulate mercury releases to the environment. In response to the congressional mandates in The 1990 Clean Air Act Amendments (CAAA), the EPA has issued the Mercury Study Report and the Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units Report. In spite of the enormous effort represented by these reports, as well as the efforts of both the U.S. Department of Energy (DOE) and the Electric Power Research Institute (EPRI), in conducting the field measurement programs that form the basis for these reports, a definitive answer on the need for mercury regulation has not been found. However, the EPA, as well as other regulatory agencies and health researchers, have suggested a "plausible link" between anthropogenic sources emitting mercury and the methylation, bioaccumulation in the food chain, and adverse health effects in humans and wildlife. Policy-makers have recognized that regulations must be based on good science and that a number of issues still remain. These issues can generally be grouped into four main categories: emissions inventory, control technology, fate of releases, and health effects. This paper will discuss recent, ongoing, and planned studies to address the remaining issues regarding the presence of mercury in the environment, with an emphasis on those studies that are directly related to the DOE/Federal Energy Technology Center's (FETC) programmatic effort.

New data and analyses are presented for describing gas and solids behavior in a slurry bubble column. Axial solids concentration and bubble size distributions were measured in a 0.108 m ID slurry bubble column apparatus operated at steady state conditions. The column was operated with and without internal baffles. The slurry and gas superficial velocities ranged from 0.0077 to 0.009 m / s and from 0.031 to 0.24 m/s, respectively. The solid phase consisted of glass spheres in a narrow size range with a mean diameter of 96.5 pm; the liquid phase consisted of tap water.With a one-dimensional sedimentation-dispersion model, the data have been used to predict average solids loadings and axial distributions of the solids for specified operating conditions. Local bubble size and concentration measurements indicate that the slurry bubble column was operated in the churn-turbulent flow regime throughout the entire range of operating conditions used in this study. The impact of internal baffles and solids concentration on the gas and solids behavior is discussed.