Ronald H. Affolter

The US Geological Survey's national coal resource assessment: The results

Abstract The US Geological Survey and the State geological surveys of many coal-bearing States recently completed a new assessment of the top producing coal beds and coal zones in five major producing coal regions—the Appalachian Basin, Gulf Coast, Illinois Basin, Colorado Plateau, and Northern Rocky Mountains and Great Plains. The assessments, which focused on both coal quality and quantity, utilized geographic information system technology and large databases. Over 1,600,000 million short tons of coal remain in over 60 coal beds and coal zones that were assessed. Given current economic, environmental, and technological restrictions, the majority of US coal production will occur in that portion of the assessed coal resource that is lowest in sulfur content. These resources are concentrated in parts of the central Appalachian Basin, Colorado Plateau, and the Northern Rocky Mountains.

High chromium contents in Tertiary coal deposits of northwestern Washington — A key to their depositional history

Abstract Chromium contents obtained from 20 coal and 5 associated rock samples collected from the basal part of the Eocene Chuckanut Formation, in Skagit and Whatcom counties, northwest Washington, range between 30 and 300 ppm (mean 120 ppm whole-coal basis). The lenticular coals, ranging in rank from subbituminous to anthracite, and with an ash content of 12–46%, crop out along the western flank of the Cascade Range. Results of X-ray diffraction analysis of low-temperature ash show that the mineral matter in the coal samples consists predominantly of quartz and clay (kaolinite, illite and chlorite group). However, accessory minerals, isolated from the coal samples and analyzed by X-ray diffraction, scanning electron microscope and optical methods, contain angular fragments and euhedral crystals of the spinel group (chromite, magnetite and trevorite ), kaolinite-serpentine group (antigorite and chrysotile), chlorite group, amphibole group and pyroxene group minerals (augite, diopside and enstatite), all of which are commonly enriched in chromium. Although associated primarily with the inorganic fraction of the coal, concentrations of chromium in the samples show no statistically significant correlation with ash content. Localized concentrations of chromium in the coal are the result of natural contamination from the alteration of detrital chromium-bearing mineral grains introduced into the peat-forming mires from nearby Jurassic ophiolite bodies. The coals formed in the early Eocene, in rapidly subsiding small basins that developed during the uplift and erosion of the pre-Tertiary ophiolite terrain. Scattered bodies of source rock, random distribution of chromium-bearing minerals within the coal and sample heterogeneity account for the variation in Cr contents of the samples.

Geochemistry of Coal from Cretaceous Corwin and Chandler Formations, National Petroleum Reserve in Alaska (NPRA): ABSTRACT

The Cretaceous, coal-bearing Corwin and Chandler Formations accumulated in two river-dominated deltas on the North Slope. The larger Corwin delta (Corwin Formation), in the western portion of NPRA, prograded northeastward and eastward, and the smaller Umiat delta (Chandler Formation), in the southeastern part of NPRA, prograded northward. Ninety coal samples from these formations within NPRA were collected and analyzed in order to evaluate coal quality and elemental distribution. Their apparent rank ranges from lignite A in the northern part of NPRA to high-volatile A bituminous coal in the southern part. Mean vitrinite reflectance values range from 0.65 to 0.74%. Some Corwin Formation coal samples west of NPRA have coking potential with free-swelling indexes between 3.0 and 5.0. Compared to other western United States Cretaceous coal, NPRA coal is significantly lower in ash, volatile matter, 0, Si, Al, Ca, Fe, Ti, Cu, F, Li, Mn, Mo, Pb, Sb, Se, Th, and Zn. Statistical comparisons of element concentrations indicate that the mean content of Si, Al, K, Li, Sc, Y, and Yb increases as the mean ash content increases (correl tion coefficient at least 0.7). Sulfur values are extremely low (0.1%), and elements that normally show positive correlation with sulfur, such as Fe, As, Cd, Co, Cu, Mo, Pb, and Zn, are also low. Therefore, coal from NPRA can be characterized by low ash and sulfur contents and low contents of elements of environmental concern, such as As, Be, Hg, Mo, Sb, and Se. The elements found to have positive correlations with ash content are probably present as aluminosilicate or stable oxide minerals. Variations in element content and quality of NPRA coal were probably influenced by the geochemical conditions that existed in the Corwin and Umiat delta systems. End_of_Article - Last_Page 655------------

Geochemical database of feed coal and coal combustion products (CCPs) from five power plants in the United States

The principal mission of the U.S. Geological Survey (USGS) Energy Resources Program (ERP) is to (1) understand the processes critical to the formation, accumulation, occurrence, and alteration of geologically based energy resources; (2) conduct scientifically robust assessments of those resources; and (3) study the impacts of energy resource occurrence and (or) their production and use on both the environment and human health. The ERP promotes and supports research resulting in original, geology-based, non-biased energy information products for policy and decision makers, land and resource managers, other Federal and State agencies, the domestic energy industry, foreign governments, non-governmental groups, and academia. Investigations include research on the geology of oil, gas, and coal, and the impacts associated with energy resource occurrence, production, quality, and utilization. The ERP’s focus on coal is to support investigations into current issues pertaining to coal production, beneficiation and (or) conversion, and the environmental impact of the coal combustion process and coal combustion products (CCPs). To accomplish these studies, the USGS combines its activities with other organizations to address domestic and international issues that relate to the development and use of energy resources.

Geochemical Characterization of Rocky Mountain, Northern Great Plains, and Interior Province Coals: ABSTRACT

Statistical summaries of proximate and ultimate analyses, heat of combustion, and content of 36 major, minor, and trace elements were calculated for 37 Eocene, 470 Paleocene, and 419 Cretaceous coal samples from 31 coal fields or areas in the Rocky Mountain and Northern Great Plains coal provinces and for 503 Pennsylvanian coal samples from 14 areas in the Interior coal province. These analyses show that coals within an age group have similar ranges in composition, and that each group has its own distinctive compositional characteristics. Most variability in element content can be related to changes in rank and differences in ash and total sulfur contents. Mean contents of Ca, Mg, Na, Ba, and Sr are related to rank and decrease as apparent coal rank increases from lignite A to high-volatile B bituminous coal. Mean contents of Si, Al, K, Ti, Ga, Li, Sc, Th, V, Y, and Yb increase as the mean ash content increases (correlation coefficients 0.6), suggesting that these elements are present as aluminosilicates, stable oxides, or phosphate mineral phases. Mean contents of Fe, As, Cd, Co, Cu, Mo, Ni, Pb, Sb, and Zn show high correlation with total sulfur. Contents of these elements are low in Paleocene (0.6% sulfur) and Cretaceous (0.7% sulfur) coals, higher in Eocene (1.8% sulfur) coals, and generally highest in Pennsylvanian (3.9% sulfur) coals. The mean contents of B, Be, Cr, F, Hg, Mn, Nb, Se, U and Zr show no direct relationships to changes in rank or ash and total sulfur contents. Decrease in element content with increased rank probably is related to loss o functional groups that act as cation-exchange sites on organic matter. Ash and sulfur contents are dependent on pH-controlled levels of bacterial activity in ancestral peat swamps. End_of_Article - Last_Page 447------------

Weathering-Induced Chemical Changes in Surface Coals from Paleocene Fort Union Formation, Red Rim Area, Sweetwater and Carbon Counties, Wyoming: ABSTRACT

Statistically significant differences in chemical composition between 20 outcrop and 22 stratigraphically equivalent core coal samples were demonstrated by proximate and ultimate analyses, heat-of-combustion and forms-of-sulfur determinations, and chemical analyses for 37 elements. The outcrop samples were collected from depths of 30 to 72 in. (75 to 180 cm) on very steep (> 45°) slopes. Core samples were from depths of 31 to 190 ft (9 to 58 m) at distances between 300 and 1,500 ft (91 and 457 m) from the outcrop. Mean annual precipitation in the Red Rim area is ~ 11 in. (28 cm); mean monthly temperatures range from 22°F (-5.5°C) in January to 68°F (20°C) in July. Apparent rank of unweathered coal is subbituminous C coal. Compared with the core samples (moisture and Btu/lb, as-received basis, all others moisture-free basis) the outcrop samples have significantly higher mean moisture (37.4 vs 23.8%), volatile matter (43.8 vs 35.1%), oxygen (24.9 vs 15.6%), and nitrogen (1.0 vs 0.8%); lower ash (13.3 vs 18.2%), hydrogen (3.0 vs 4.7%), sulfur (0.6 vs 1.1%) and heat of combustion (5,330 vs 7,690 Btu/lb); similar fixed carbon (42.5 vs 46.6%) and carbon contents (56.7 vs 60.3%). The sulfate part of the total sulfur increased from 5% in core to 18% in outcrop samples; pyritic sulfur decreased from 14 to 10%, and organic sulfur decreased from 84 to 71%. As indicated by differences in element/Al ratios between core and outcrop samples, the relative rates of removal of Si, K, B, Cr, Ga, La, Li, and V from coal during weathering are signi icantly greater than Al; Cd, Co, F, Ni, Se, and Zn are significantly greater than Al; Cd, Co, F, Ni, Se, and Zn are significantly less than Al; and Ca, Mg, Na, Fe, Ti, As, Ba, Be, Cu, Mg, Mn, Mo, Nb, Pb, Sb, Se, Sr, Th, U, Y, Yb, and Zr are similar to Al. Additional significant chemical changes in outcrop samples should be expected in areas of warmer, more humid climates, where coal is of lower rank, or in samples collected on less-steep slopes or at shallower depths. End_of_Article - Last_Page 936------------