James C. Hower

Lanthanide, yttrium, and zirconium anomalies in the Fire Clay coal bed, Eastern Kentucky

Abstract The Fire Clay coal bed in the Central Appalachian basin region contains a laterally-persistent tonstein that is found in the coal throughout most of its areal extent. The tonstein contains an array of minerals, including sanidine, β-quartz, anatase and euhedral zircon, that constitutes strong evidence for a volcanic origin of the parting. For this study, five samples of the tonstein and four sets of coal samples underlying the tonstein were collected from five sites in eastern Kentucky. Inductively coupled plasma-mass spectroscopy (ICP-MS) analysis of the tonstein and underlying coal collected from four sites in eastern Kentucky show that although Zr concentrations are high in the tonstein (570–1820 ppm on a coal-ash basis (cab)), they are highest in the coal directly underlying the tonstein (2870–4540 ppm (cab)). A similar enrichment pattern is observed in the concentration of Y plus the sum of the rare earth elements (Y+∑REE): total Y+∑REE concentrations in the five tonstein samples range from 511 to 565 ppm (cab). However, Y+∑REE contents are highest in the coals directly underlying the tonsteins: values range from 1965 to 4198 ppm (cab). Scanning electron microscopy of samples from coal which directly underlies two of the tonstein samples show that REE-rich phosphate, tentatively identified as monazite, commonly infills cracks in clays and cells in clarain and vitrain. Zircon is rare and commonly subhedral. On the basis of coal chemistry and grain morphology, we suggest that volcanic components in the tonstein were leached by ground water. The leachate, rich in Y and REE precipitated as authigenic mineral phases in the underlying coal.

Mercury capture by native fly ash carbons in coal-fired power plants.

The control of mercury in the air emissions from coal-fired power plants is an on-going challenge. The native unburned carbons in fly ash can capture varying amounts of Hg depending upon the temperature and composition of the flue gas at the air pollution control device, with Hg capture increasing with a decrease in temperature; the amount of carbon in the fly ash, with Hg capture increasing with an increase in carbon; and the form of the carbon and the consequent surface area of the carbon, with Hg capture increasing with an increase in surface area. The latter is influenced by the rank of the feed coal, with carbons derived from the combustion of low-rank coals having a greater surface area than carbons from bituminous- and anthracite-rank coals. The chemistry of the feed coal and the resulting composition of the flue gas enhances Hg capture by fly ash carbons. This is particularly evident in the correlation of feed coal Cl content to Hg oxidation to HgCl2, enhancing Hg capture. Acid gases, including HCl and H2SO4 and the combination of HCl and NO2, in the flue gas can enhance the oxidation of Hg. In this presentation, we discuss the transport of Hg through the boiler and pollution control systems, the mechanisms of Hg oxidation, and the parameters controlling Hg capture by coal-derived fly ash carbons.

An examination of fly ash carbon and its interactions with air entraining agent

Four fly ash samples, which had previously been found to effect concrete air entrainment in a manner inconsistent with their respective loss on ignition, were investigated using several physico-chemical techniques. This study focused on characterization of the high-carbon fraction of each fly ash, obtained by a triboelectric separation process. While the four samples displayed varying reactivities toward AEA adsorption, the BET specific surface area of all four samples was determined to be essentially the same. Thermal analysis and petrographic examination revealed that the higher demand for air entraining agents exhibited by two of the samples could be directly related to the presence of a higher proportion of optically isotropic, amorphous carbon. Liquid and vapor phase adsorption analysis suggested that the surface chemistry characteristics of the isotropic carbon resulted in a higher adsorption capacity for polar compounds such as air entraining surfactants.

Geochemistry of the Pond Creek coal bed, Eastern Kentucky coalfield

The Pond Creek coal bed (Middle Pennsylvanian Breathitt Formation) is an important low-sulfur resource in Pike and Martin countries in the Eastern Kentucky coalfield. The mined area is crossed by the N20°E-trending Belfry anticline. The Pond Creek coal bed has a higher sulfur content on the west side of the anticline. The vertical trends in the ash geochemistry also vary across the anticline. The sites to the east of the anticline represent deposition of peat through periods of relative stability with slow deposition (bright lithotypes) interspersed with periods of relatively rapid clastic deposition (dull lithotypes), both generally removed from marine influence. Comparison of elemental trends between the lowest bright lithotype and the second bright lithotype suggest that the swamp became less acidic with time. An upward decrease in minor-element concentration may be related to the influx of clays and other silicates present in the bone lithotype. This bone may have acted as a relatively low-nutrient soil for the growth of the plants which contributed to the overlying bright lithotype. The sites to the west of the anticline were subjected to a greater marine influence than the eastern sites. High K2O/Al2O3 ratios at the bottom and top of the coal bed and a high TiO2Zr dull clarain near the bottom of the coal point to clastic influences on the geochemistry. The relatively high CaO percentages in the middle third of the coal bed suggest deposition at near-neutral pH. The upper third of the coal bed was dominated by syngenetic and epigenetic pyrite emplacement.

Clausthalite in coal

A lead selenide mineral, tentatively identified as clausthalite (PbSe) based on optical microscopy, scanning electron microscopy with energy-dispersive X-ray (EDAX), electron microprobe, and scanning proton microprobe (SPM), has been described in a number of coals. While clausthalite has been mentioned as a possible source of Se in coal, it is present in such small quantities and sizes, that the mineral identification has not been absolutely confirmed. The mineral specimens examined in this study would contribute, not only to the Pb and Se concentrations in the coal, but also, in at least one case, to Hg concentrations.

Mechanisms of coal metamorphism: case studies from Paleozoic coalfields

Controls on coal metamorphism can be complex. In this paper, we examine four Paleozoic coalfields: the western Kentucky portion of the Illinois Basin, the Pennsylvania anthracite fields, the South Wales Coalfield, and the Bowen Basin. An increase in temperature with depth of burial is certainly a factor in coal metamorphism. In many coalfields, however, including the coalfields reviewed here, it has become apparent that such a simple mechanism does not explain the coal rank patterns observed. The flow of hydrothermal fluids through the coals has been proposed as a cause of coal metamorphism. Evidence includes inverted rank gradients, elevated CFL as an indicator of brine fluids, isotopic evidence for hydrothermal fluids, and vein and cleat mineral assemblages. In any case, multiple hypotheses must often be evaluated in the examination of any coalfield since the simple paradigm of coal rank increases with a simple increase in temperature with increasing depth does not fit the evidence observed in many cases.

Characterization of fly ash from Kentucky power plants

Abstract Fly ashes from 21 Kentucky power plants were grouped according to the sulfur content of the feed coal. The highest-carbon fly ashes tended to be from the lowest-sulfur feed coals, partly because many of those plants were smaller and older than the higher-sulfur units. Iron oxide content increased at the expense of aluminium and silicon oxides in the higher-sulfur feed ashes. An increase in calcium and magnesium oxides towards the higher-sulfur feed ashes was due to the greater abundance of carbonate minerals in the higher-sulfur Illinois Basin coals. The highest arsenic values were among electrostatic precipitator ashes from medium-sulfur sources. The arsenic and lead contents of low- and medium-sulfur central Appalachian coals could be higher than those of high-sulfur Illinois Basin coals. Where direct comparison of fly ash and bottom ash was possible, the bottom ash was enriched in Fe 2 O 3 relative to the fly ash and most minor elements were depleted in the bottom ash relative to the fly ash. TCLP testing of selected fly ashes indicated that all of the leachates would pass the established RCRA limits. Some of the higher As and Cr levels were from fly ashes in the highest-sulfur category. For As, though, there is no significant correlation between fly ash As and leachate As.

Petrology, mineralogy, and chemistry of magnetically-separated sized fly ash

A class F fly ash from a high-sulfur coal source was wet-sieved at 100, 200, 325, and 500 mesh and each of the five size fractions was then magnetically separated. Each fraction was examined for petrography by optical microscopy, mineralogy by X-ray diffraction, and major and minor element chemistry by proton-induced X-ray emission (PIXE). Spinel (magnetite) is the major magnetic mineral, with hematite being another major iron oxide phase. As expected, the magnetite is most abundant in the magnetic fractions, but, due to mixed-phase fly ash particles, is not the only component in the magnetic fractions nor is it totally excluded from the non-magnetic fractions. Other mineral phases include quartz, mullite, and calcite, the latter being a secondary phase produced in the wet-sieving procedure from lime in the original fly ash. Chromium, likely associated with the spinels, is one minor element which is significantly higher in the magnetic versus non-magnetic fractions.

Paleoecology of the Fire Clay coal bed in a portion of the Eastern Kentucky Coal Field

Vertically continuous increment samples of the Fire Clay coal bed (mid-Middle Pennsylvanian, late Westphalian B), collected from a portion of the Central Appalachian Basin, were studied palynologically, petrographically and geochemically in order to partially reconstruct the paleoecology and processes associated with peat formation in the ancient Fire Clay paleomire. Results indicate that four compositional groups can be identified. They are: (1) a Lycospora—vitrinite dominant group, characterized by high percentages of Lycospora and vitrinite macerals and generally low, but variable ash yields and sulfur contents; (2) a mixed palynoflora-high vitrinite group that petrographically is similar to group 1 except that it contains a more diverse palynoflora; (3) a mixed palynoflora-moderate/low vitrinite group characterized by various admixtures of lycopsid, fern and calamite miospores, increased percentages of liptinite and inertinite macerals, and low ash yields and sulfur contents; and (4) a mixed palynoflora-high ash yield group characterized by high percentages of small lycopsid, fern, and occasionally calamite and cordaite miospores, high liptinite and inertinite contents, high ash yields, and moderate to high sulfur contents. The Fire Clay coal bed contains a distinctive flint clay parting of probable volcanic origin that naturally divides the bed into two benches. These two benches, (upper and lower), are highly disparte in occurrence, appearance and composition. In the study area the lower bench generally is thin (< 0.5 m), laterally discontinuous and mainly composed of dull (mainly durain) coal lithotypes. Ash yields typically are high; sulfur contents generally are moderate to high. Compositional group 4, the mixed palynoflora—high ash yield group defines all of the increments examined from the lower bench. In contrast, the upper bench is thick (> 0.75 m), laterally continous and mainly comprised of bright (mainly clarain) coal lithotypes. Overall ash yields and sulfur contents for this bench are generally low, although vertical variation is apparent. All of the compositional groups occur in the upper bench; in some columns, notably those that are thick and uninterrupted by clastic partings, groups 1 and 4 often occupy basal coal layers and groups 2 and 3 occur in higher layers. Other columns, especially those taken in areas of thin (< 0.5 m) Fire Clay coal, are dominated by groups 1 and 4.

Evidence for a diachronous Late Permian marine crisis from the Canadian Arctic region

A high-resolution chemostratigraphic study of a 24-m-thick section at West Blind Fiord on Ellesmere Island (Canadian Arctic) documents stepwise environmental deterioration in the marine Sverdrup Basin during the late Changhsingian (late Late Permian) as a result of volcanic disturbances to surrounding landmasses. A horizon within the upper Lindstrom Formation (datum A) is characterized by increased Fe-oxyhydroxide fl uxes and weathering intensity as well as modest shifts toward more reducing watermass conditions and higher marine productivity, recording an initial disturbance that washed soils into the marine environment. The contact between chert of the Lindstrom Formation and silty shale of the overlying Blind Fiord Formation, which is 1.6 m higher and ~50 k.y. younger than datum A, records a large increase in detrital sediment fl ux, more strongly enhanced marine productivity, and a regional extinction of siliceous sponges, herein termed the “Arctic extinction event.” The horizon equivalent to the latest Permian mass extinction of Tethyan shallow-marine sections is 5.6 m higher and ~100 k.y. younger than the Arctic extinction event, demonstrating the diachronous nature of the marine biotic and environmental crisis at a global scale; it is associated with intensifi ed anoxia and possible changes in phytoplankton community composition in the study section. Marine environmental deterioration in the Sverdrup Basin, probably triggered by terrestrial ecosystem deterioration and elevated detrital sediment fl uxes, was under way by the early part of the late Changhsingian, well before the onset of main-stage Siberian Traps fl ood basalt volcanism. The event sequence at West Blind Fiord may record the deleterious effects of early-stage explosive silicic eruptions that affected the Boreal region, possibly through deposition of toxic gas and ash within a restricted latitudinal band, while having little impact on marine ecosystems in the peri-equatorial Tethyan region.