QUALITY CHARACTERISTICS OF TERTIARY LIGNITE SAMPLES FROM WESTERN KENTUCKY AND TENNESSEE

As a part of the U.S. Geological Survey’s (USGS) coal resource assessment of the Gulf Coastal Plain region, ten Tertiary lignite samples from the Mississippi Embayment of western Kentucky and Tennessee were collected from fresh exposures in three clay-mining pits developed in the Eocene Claiborne Group (Tennessee) and Jackson Formation (Kentucky). Proximate and ultimate analyses were performed on all ten lignite samples, and seven samples were analyzed for major and trace element concentrations by inductively coupled plasma emission spectrometry and inductively coupled plasma mass spectrometry. Results indicate that the lignite samples have a gross calorific value ranging from 5,400 to 6,280 British thermal units per pound (Btu/lb) on a moist, mineral-matter-free (m,mmf) basis and are classified as Lignite B following the American Society of Testing and Materials D388 classification. When compared to analyses of all Gulf Coast lignite samples in the USGS’s coal quality database (COALQUAL), the samples on the average are lower in rank than other Gulf Coast lignite (average 7,500 Btu/lb, m,mmf basis). On a dry basis, average sulfur content of the samples is 1.1 percent, which is below the average of Gulf Coast lignite (1.7 percent), and average ash yield is 24 percent, which is higher than the Gulf Coast average (19.8 percent). Of the twelve environmentally sensitive trace elements that have been identified as possible hazardous air pollutants in the United States Clean Air Act Amendments of 1990, average concentrations of As, Be, Cd, Cr, Co, Hg, Ni, Pb, Sb, and U exceed the average of Gulf Coast lignite samples in COALQUAL (whole-coal, remnant moisture basis). Concentrations of Pb and Sb in one sample exceed the maximum published values for Gulf Coast lignite samples by 15 and 0.1 parts per million, respectively. The average concentration of Cr in the samples is two times the average concentration of this element for all U.S. coal and the average concentration of Hg is three times the average concentration for all U.S. coal.