CHARACTERIZATION OF COAL COMBUSTION PRODUCTS FROM POWER PLANTS UTILIZING CENTRAL APPALACHIAN BASIN AND COLORADO PLATEAU COALS

The U.S. Geological Survey (USGS) worked cooperatively with coal-fired power plants in the Central Appalachian basin and Colorado Plateau to determine the distribution of major, minor, and trace elements in feed coals and coal combustion products (CCPs). The Central Appalachian basin plant utilized a high-sulfur (average of 3.8 weight percent) Pittsburgh coal and operated with electrostatic precipitator and flue gas desulfurization (FGD) systems. The Colorado Plateau plant utilized a low-sulfur (average of 0.73 weight percent) blend of three coals, and operated with several bag houses (fabric filters), a processing facility for fly ash (cyclone separation process), and an inhibited oxidizing scrubber for flue gas. Samples from the Appalachian basin plant, collected twice weekly over an 8-week period in 2006, included as-received coal, feed coal, pulverized coal, pyrite rejects, bottom ash, economizer fly ash, fly ash, and FGD sludge. Samples from the Colorado Plateau plant, collected daily over an 18-day period in 2007, included pulverized feed coal, bottom ash, a mixture of fly ash and economizer fly ash, fly ash, and cyclone-separated coarse and fine fractions of fly ash (fine fractions sold as product). All samples were analyzed by USGS laboratories for major, minor, and trace elements. The following preliminary results are based on comparisons of the means of selected trace elements between CCP sample types (not including pyrite rejects) within each power plant. For the Appalachian basin plant, the highest concentrations of mercury occur in fly ash and FGD sludge. At the Colorado Plateau plant, the highest concentrations of mercury are found in fly ash and fly ash product. These results may be related to fly ash particle size, the carbon content of fly ash, and temperatures at sample collection points. The highest concentrations of arsenic at the Appalachian basin plant are found in economizer fly ash, in contrast to the Colorado Plateau plant, where the highest levels of arsenic are found in fly ash and fly ash product. Further work is being conducted to statistically evaluate the distribution of environmentally sensitive trace elements in CCPs from each power plant.