Central Appalachian Coal Research Articles

Prevalence of nano-sized coal mine dust in North and Central Appalachian coal mines – Insights from SEM-EDS imaging

The increasing prevalence of coal mine dust-related lung diseases in coal miners calls for urgent and meticulous scrutiny of airborne respirable coal mine dust (RCMD), specifically focusing on particles at the nano-level. This necessity is driven by expanding research, including the insights revealed in this paper, that establish the presence and significantly increased toxicity of nano-sized coal dust particles in contrast to their larger counterparts. This study presents an incontrovertible visual proof of these tiny particulates in samples collected from underground mines, utilizing advanced techniques such as scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The intricate elemental composition of nano-sized coal dust identified through EDS analysis reveals the presence of elements such as silica and iron, which are known to contribute to lung pathologies when inhaled over prolonged periods. The outcomes of the statistical analyses reveal significant relationships between particle size and elemental composition, highlighting that smaller particles tend to have higher carbon content, while larger particles exhibit increased concentrations of elements like silica and aluminum. These analyses underscore the complex interactions within nano-sized coal dust, providing critical insights into their behavior, transport, and health impacts. The nano-sized coal dust could invade the alveoli, carrying these toxic elements from where they are impossible to exhale. The revelation of nano-sized coal dust's existence and the associated health hazards necessitate their incorporation into the regulatory framework governing the coal mining industry. This study lays the groundwork for heightened protective measures for miners, urging the invention of state-of-the-art sampling instruments, comprehensive physicochemical profiling of RCMD nanoparticles, and the pursuit of groundbreaking remedies to neutralize their toxic impact. These findings advocate for a paradigm shift in how the coal mining industry views and handles particulate matter, proposing a re-evaluation of occupational health standards and a call to action for protecting coal miners worldwide.

Petrology and geochemistry of the Fire Clay coalbed, Martin County, Inez 7 ½′ quadrangle, Kentucky, USA

The Middle Pennsylvanian Duckmantian-age Fire Clay coal in the vicinity of Inez, Martin County, Kentucky, USA, is about 80-km northeast of the intensely studied Fire Clay coal in central eastern Kentucky. The moderate-ash, high-S, high volatile B bituminous Martin County Fire Clay coal does not have an obvious volcanic ash parting, one of the major contributors to the rare earth element (REE)-rich central eastern Kentucky Fire Clay coal, and is further from the Pine Mountain thrust fault, the primary driver of hydrothermal metamorphism in the region. Terrigenous input and infiltrational mode of REE emplacement and redistribution were likely factors in the development of the REE chemistry of the Martin County coals, but, without the tuffaceous and strong hydrothermal influences, the overall level of the REE concentration is generally below the levels seen in many other central Appalachian coals.

Corporate Violence in the Central Appalachian Coal Industry: From Roots to Repercussions

Corporate Violence in the Central Appalachian Coal Industry: From Roots to Repercussions

Leaching of lanthanide and yttrium from a Central Appalachian coal and the ashes obtained at 550–950 °C

In this work, we investigated leaching of lanthanide and yttrium (REY) from a Central Appalachian coal and its ashes obtained at 550–950 °C with the main purpose of understanding the impact of ashing temperature on REY leachability in water, ammonium sulfate, and hydrochloric acid. It is found that the coal contains a negligible amount of water-soluble REY, less than 1% ion-exchangeable REY, and about 28% of HCl-soluble REY. Ashing leads to dramatic changes in REY leachability in both ammonium sulfate and hydrochloric acid solutions, which is believed to be related to transformation and redistribution of organically-associated REY in coal during the ashing process. Ashing temperature significantly affects REY leaching from coal ashes; higher ashing temperature results in lower REY leachability in both solutions. Clay minerals may play a significant role in changing the leachability of REY after ashing. In addition, the results also suggest that the organic matter in the coal is relatively enriched in heavy REY.

Distribution of rare earth elements in fly ash derived from the combustion of Illinois Basin coals

This study examined rare earth element (REE) trends for Illinois Basin coal-sourced fly ashes, with the goal of understanding the elemental composition and resource potential for various fly ash fractions. Illinois Basin coals have a high volatile C through A bituminous rank with a moderate ash content (slightly>12% ash (dry basis)), about 3% sulfur, and, in general, lower concentrations of hazardous and other trace elements than many Central Appalachian coals. Fly ash from the combustion of Illinois Basin coals tends to have a high Fe2O3 content owing to the amount of pyrite in the feed coals. The rare earth element (REE) concentrations in Illinois Basin coal-sourced fly ashes are less than that for fly ashes from the combustion of Central Appalachian coals. The Upper continental crust-corrected fly ashes show an H-type enrichment, a positive EuN/EuN*, and, in some cases, a sharp Gd peak. For comparison, a suite of fly ashes from the combustion of a blend of eastern Kentucky coals had an H-type enrichment, a positive EuN/EuN*, but only a minimal Gd peak. In contrast, fly ash from the combustion of the Fire Clay coal, a REE-rich coal, had a negative EuN/EuN* and a sharp Gd peak. These results highlight the importance of feed coal composition on trace element contents of respective combustion fly ash fractions and also the unique REE enrichment patterns of the Illinois Basin fly ashes relative to the better studied fly ashes of eastern Kentucky and Central Appalachia.

Application of the coal mine floor rating (CMFR) to assess the floor stability in a Central Appalachian Coal Mine

Estimating the overall floor stability in a coal mine using deterministic methods which require complex engineering properties of floor strata is desirable, but generally it is impractical due to the difficulty of gathering essential input data. However, applying a quantitative methodology to describe floor quality with a single number provides a practical estimate for preliminary assessment of floor stability. The coal mine floor rating (CMFR) system, developed by the University of New South Wales (UNSW), is a rock- mass classification system that provides an indicator for the competence of floor strata. The most significant components of the CMFR are uniaxial compressive strength and discontinuity intensity of floor strata. In addition to the competence of the floor, depth of cover and stress notch angle are input parameters used to assess the preliminary floor stability. In this study, CMFR methodology was applied to a Central Appalachian Coal Mine that intermittently experienced floor heave. Exploratory drill core data, overburden maps, and mine plans were utilized for the study. Additionally, qualitative data (failure/non-failure) on floor conditions of the mine entries near the core holes was collected and analyzed so that the floor quality and its relation to entry stability could be estimated by statistical methods. It was found that the current CMFR classification system is not directly applicable in assessing the floor stability of the Central Appalachian Coal Mine. In order to extend the applicability of the CMFR classification system, the methodology was modified. A calculation procedure of one of the CMFR classification system’s components, the horizontal stress rating (HSR), was changed and new parameters were added to the HSR.

Aspects of rare earth element enrichment in Central Appalachian coals

The concentration of lanthanides, Y, and Sc, collectively rare earth elements (REE), and their modes of emplacement in Appalachian coals, with emphasis on Manchester and Fire Clay coals in eastern Kentucky are the focus of this investigation. Those coals have distinct REE concentrations and relationships related to the position of the lithotype within the coal seam, such as the ratio of light to heavy lanthanides (LREE/HREE). In the Manchester coal, the high-S upper lithotypes have lower REE concentrations and different LREE/HREE than the low-S lithotypes. In the Fire Clay coal, the position of the lithotype relative to the REE-enriched tonstein is important, with the coal immediately below the tonstein having significantly higher REE than other lithotypes. Lithotypes in the middle of the coal bench above the tonstein have high LREE/HREE, possibly indicating a hydrothermal influence on the REE emplacement.

Leaching of Rare Earth Elements from Central Appalachian Coal Seam Underclays

Rare earth elements (REE) are necessary for advanced technological and energy applications. To support the emerging need, it is necessary to identify new domestic sources of REE and technologies to separate and recover saleable REE product in a safe and economical manner. Underclay rock associated with Central Appalachian coal seams and prevalent in coal utilization waste products is an alternative source of REE to hard rock ores that are mainly composed of highly refractory REE-bearing minerals. This study utilizes a suite of analytical techniques and benchtop leaching tests to characterize the properties and leachability of the coal seam underclays sampled. Laboratory bench-top and flow-through reactor leaching experiments were conducted on underclay rock powders to produce a pregnant leach solution (PLS) that has relatively low concentrations of gangue elements Al, Si, Fe, and Th and is amenable to further processing steps to recover and produce purified REE product. The leaching method described here uses a chelating agent, the citrate anion, to solubilize elements that are adsorbed, or weakly bonded to the surface of clay minerals or other mineral solid phases in the rock. The citrate PLS produced from leaching specific underclay powders contains relatively higher concentrations of REE and lower concentrations of gangue elements compared to PLS produced from sequential digestion using ammonium sulfate and mineral acids. Citrate solution leaching of underclay produces a PLS with lower concentrations of gangue elements and higher concentrations of REE than achieved with hydrochloric acid or sulfuric acid. The results provide a preliminary assessment of the types of REE-bearing minerals and potential leachability of coal seam underclays from the Central Appalachian basin.

The Occurrence and Concentration of Rare Earth Elements in Acid Mine Drainage and Treatment Byproducts. Part 2: Regional Survey of Northern and Central Appalachian Coal Basins

Many modern industries rely on rare earth elements (REEs) to produce products that are essential to both civil and defense applications. In a prior study (Vass et al., 2019), the authors showed that REE grades in acid mine drainage (AMD) and associated byproduct precipitates from AMD treatment (AMDp) warrant evaluation as a feedstock for REE production. The current work extends that effort through a broad survey of 141 AMD treatment sites in Northern and Central Appalachia. In this study, 185 raw AMD and 623 AMDp field samples were obtained and analyzed to assess the REE and major metal concentrations. Results show that an average of 282 μg/L and 724 g/tonne of REEs occur in AMD and AMDp respectively. Additionally, both basins contained similar distributions of REEs, and these distributions tended to favor heavy and critical REEs when compared with traditional REE ore deposits. Geospatial analysis identified a total resource of 340 tonnes stored at the 141 sites sampled in this study. While this analysis did not quantify the basin-wide REE inventory, it does indicate the impact that processing cut-off grades will have on the overall AMDp resource base.

Organic and inorganic associations of rare earth elements in central Appalachian coal

Coal contains trace amounts of rare earth elements (REE). They are either in the form of discrete minerals or chemically bound to organic matter. Methods of distinguishing the organic and inorganic associations of REE in coal have been mostly based on the correlations between the REE concentrations and the ash yields. Quantitative characterization of organically associated REE is still very challenging. In this work, we confirm the existence of organically-associated REE in coal and present an approach to quantifying its mass fraction. The coal sample used in this study was a cleaned low-ash coal collected from a coal preparation plant in Kentucky, USA and originally from the central Appalachian basin coal region. The results from particle size and density separations of the coal suggested that the REE are associated with both organic and inorganic matters. It was found that as the ash yield increases, both the total REE concentration on the whole coal basis and the LREE/HREE ratio increase, while the total REE concentration on the ash basis reduces dramatically. The results also suggested that the organic matter is relatively enriched in HREE. Based on these observation and findings, a method was developed to quantitatively determine the distribution of REE in the organic and inorganic phases of the coal. It was found that the total REE concentrations in the organic and inorganic phases are 31ppm and 1141ppm, respectively. The results also showed that in the low-ash Appalachian coal sample used in this work, 25% of the REE is associated with the organic matter. The method developed in this work for quantitative evaluation of the organic/inorganic mode of occurrence may be applied to other coal samples and for many other trace elements in coals.

Selecting and implementing a fuel blend for scrubbed units at a pulverized coal power plant

The DTE Power Plant includes four boilers, each generating up to 5.7millionlbs/h of supercritical steam, and each supporting the generation of up to 800MWe (net) of electricity. At the time of the testing two units were equipped with both scrubber and selective catalytic reduction systems in addition to electrostatic precipitators. Over a two year period, the Plant modeled and tested a wide variety of fuels and fuel combinations with a base fuel of Wyoming Powder River Basin (PRB) subbituminous coal and Central Appalachian bituminous coal. Fuels incorporated into the blend included petroleum coke, northern PRB subbituminous coal, and northern Appalachian bituminous coal. Various blend combinations were considered and/or tested. Operation with 100% PRB was also tested. The objective was to optimize the fuel blend from both technical and economic perspectives. The blend proven to be optimal from both technical and economic perspectives included 10% petroleum coke with PRB coal and, as necessary, Central Appalachian coal. This blend was implemented.

Development of ecosystem structure and function on reforested surface-mined lands in the Central Appalachian Coal Basin of the United States

Surface mining in the Appalachian Coal Basin drastically disturbs the landscape. Post-mining reforestation efforts have reached reliable tree survivability and growth; however, it is unclear whether these reforestation efforts also restore the ecological functions associated with the native forest ecosystem. The objectives of this study were to quantify the rate at which certain key ecosystem functions return to the landscape, and to relate the development of those functions to structural attributes of the ecosystem. A chronosequence of four reclaimed and reforested stands (ages 5, 11, 21 and 30 years) and unmined reference stands representing pre-mining conditions, were identified on the Appalachian Plateau in southwestern Virginia. Total soil nitrogen (N) and component (mineral soil, forest floor, root, and aboveground biomass) ecosystem carbon (C) pools were quantified. Throughout the growing season, monthly samples for soil gas fluxes [i.e., carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4)], available inorganic-N [nitrate (NO3 −) and ammonium (NH4 +)], and total and active microbial biomass were measured. As expected, soil organic C (SOC) and total ecosystem C returned to the mined landscape, although at levels still less than half of the unmined reference after 30 years. Ecosystem C accumulation was significantly correlated with soil N (r = 0.80; p = 0.0003) as well as total and active microbial biomass (r = 0.92; p = <0.0001 and r = 0.86; p = <0.0001, respectively). Surprisingly, available inorganic-N and gas fluxes of CO2 and N2O showed no significant differences among any of the mined and unmined stands; however, the reforested mined soils showed a significantly diminished capacity for CH4 uptake, where upland soils typically represent the largest global biogenic sink of atmospheric CH4. Thus, although many ecosystem components (e.g., forest and microbial biomass) and functions (e.g., N cycling), rapidly returned to the reclaimed landscape, some critical ecosystem functions (e.g., methanotrophy) exhibited a fundamentally different rate of return, if present at all. Our results indicate that reforestation of native hardwoods on reclaimed surface mined lands is largely successful at restoring many ecosystem functions, but that certain functional attributes are decoupled from the observed redevelopment of ecosystem structure. Thus, reforestation and forest ecosystem restoration are not necessarily the same thing, and a better understanding of potential disconnects between the two concepts can be critical in guiding both the science and the practice into the future.

Notes on the Potential for the Concentration of Rare Earth Elements and Yttrium in Coal Combustion Fly Ash

Certain Central Appalachian coals, most notably the Fire Clay coal with a REY-enriched volcanic ash fall tonstein, are known to be enriched in rare earth elements. The Fire Clay tonstein has a greater contribution to the total coal + parting REY than would be inferred from its thickness, accounting for about 20%–35% of the REY in the coal + parting sequence. Underground mining, in particular, might include roof and floor rock and the within-seam partings in the mined product. Beneficiation, necessary to meet utility specifications, will remove some of the REY from the delivered product. In at least one previously published example, even though the tonstein was not present in the Fire Clay coal, the coal was enriched in REY. In this case, as well as mines that ship run-of-mine products to the utility, the shipped REY content should be virtually the same as for the mined coal. At the power plant, however, the delivered coal will be pulverized, generally accompanied by the elimination of some of the harder rock, before it is fired into the boiler. Overall, there are a wide range of variables between the geologic sample at the mine and the power plant, any or all of which could impact the concentration of REY or other critical materials in the coal combustion products.

Comparison of Mortality Disparities in Central Appalachian Coal- and Non-Coal-Mining Counties.

Determine whether select cause of death mortality disparities in four Appalachian regions is associated with coal mining or other factors. We calculated direct age-adjusted mortality rates and associated 95% confidence intervals by sex and study group for each cause of death over 5-year time periods from 1960 to 2009 and compared mean demographic and socioeconomic values between study groups via two-sample t tests. Compared with non-coal-mining areas, we found higher rates of poverty in West Virginia and Virginia (VA) coal counties. All-cause mortality rates for males and females were higher in coal counties across all time periods. Virginia coal counties had statistically significant excesses for many causes of death. We found elevated mortality and poverty rates in coal-mining compared with non-coal-mining areas of West Virginia and VA. Future research should examine these findings in more detail at the individual level.

Intermodal Network Model of Coal Distribution in the United States

This paper describes an intermodal network model based on the geographic information system for the shipment of coal in the United States. The research contributes to a better understanding of a portion of the energy transportation system and how rail, water, and highway are integrated to deliver energy goods. Coal movements were modeled across the network with the Energy Information Administration's 2010 data, providing detailed origin, destination, primary mode, and volume information for coal movements in the United States. The model identifies the optimum routes for coal shipments on the basis of a rate structure that accounts for the relative costs of shipping by each of the modes. The model results reveal the wide distribution of Powder River Basin coal, with a market area that reaches across the West and the Midwest. Both Texas and Illinois, the two largest coal consumers by state, derive virtually all their coal from the West or from within state. Appalachian Basin coal serves domestic and export markets primarily in the east and southeastern United States. Only the Ohio River provides significant movement of Central Appalachian Basin coal to the West and the South. The presented research demonstrates the potential for integrated models to accommodate energy-related or similar data. The model is a tool freight planners can use to identify energy transportation corridors of significance. Results from this model can inform efforts related to the Moving Ahead for Progress in the 21st Century Act for developing a national freight network and a national freight strategic plan.

A World-Ecological Perspective on Socio-Ecological Transformation in the Appalachian Coal Industry

This article discusses the exhaustion of socio-ecological relations in the coalfields of West Virginia. We use the term socio-ecological to signify "the interwoven character and the indispensable unity of social and natural life" (Araghi 2009: 115). In particular we use classic literatures on labor history in the coalfields of central Appalachia and contemporary studies of mountaintop removal to think about phases of socio-ecological relations of the coal industry. We argue for the interrelationality of the social and the ecological in place of conventional eco-M arxist approaches which treat these as relatively independent units. This enables us to situate nature as an active component of capitalist developmental processes. We argue that the exhaustion of socio-ecological relations in the coalfields of West Virginia is an outcome of material practices within the phase of extraction using mountaintop removal, historical changes in the conditions of production in the coalfields, and of new forms of competition from other regions and energy sources. We find that the relative exhaustion of central Appalachian coal is tempered by favorable international markets and a specialization in metallurgical coal.

The Suspicious, Untrusting Hillbilly in Political-Economic Contexts: Stereotypes and Social Trust in the Appalachian Coalfields

Over the past fourteen years, the authors of this article have collaborated on two community-based participatory action research projects in Appalachian Kentucky. One focused on assessing the social impacts of a major environmental disaster (2000-2014) and the other involves partnering with a small community seeking to transition a struggling, coal-driven economy to a more diverse and sustainable one (2013-present). In what follows, we discuss our experiences working with these Appalachian coalfield communities, which are characterized by low levels of social trust, a situation complicated by negative stereotypes and confused thinking by non-residents about Appalachian coalfield culture. First, we discuss stereotypes of Appalachian culture, among them suspicion and hostility toward "outsiders" and native tendencies toward violence. After debunking the myth that Appalachian culture creates distrust of outsiders, we identify the political economic structures, which have eroded trust in the Central Appalachian coal communities, with particular attention to institutional, structural, and intraregional variation in social trust. Finally, we identify strategies to engage effectively in communities characterized by low levels of trust in government, corporations, and neighbors.

Specific conductivity sensor performance: I. Laboratory evaluation

The focus on specific conductivity in the Central Appalachian Coal Fields of the USA has highlighted the need to obtain accurate specific conductivity measurements, particularly in light of the US Environmental Protection Agency (USEPA) guidance that water discharged from mine sites in this region should have specific conductance levels less than 300–500 μS cm−1. Being able to accurately determine the specific conductance levels of mine discharged waters has significant implications for the USEPA as well as mine operators particularly when specific conductance levels approach this designated threshold. Presently, a number of sensors are available on the market for recording specific conductance measurements; however, a detailed study comparing sensor performance under controlled conditions (e.g. temperature and specific conductance levels) has not been performed. This paper compares the performance of four commonly used sensors YSI 6600 V2-4 data sonde, HOBO U-24-001, Solinst Model 3001 LTC Levelogger Junior, and In-situ Aqua TROLL 100. Results of this laboratory study indicated that for conditions more frequently encountered in Kentucky streams, the HOBO and Solinst sensors were most accurate.

Illite crystallinity and coal metamorphism for selected central Appalachian coals and shales

Abstract Three Central Appalachian boreholes, each representing a distinct coal rank range (high volatile A bituminous, medium through low volatile bituminous, and semianthracite), were analyzed for vitrinite maximum reflectance and illite crystallinity for the coals and shales, respectively. The results reflect differential perfection of illite along its 001 crystallographic axis and its internal elemental arrangement, resulting from variations in ionic composition and strength of interstitial fluids and/or the type and composition of the dominant illite precursors. Despite the differences in the rate of metamorphic reaction in illite and vitrinite, generally, among the Weaver, Flehmig, and Kubler illite crystallinity indices, the Kubler index shows the best correlation with vitrinite maximum reflectance.

Managing slagging at Monroe Power Plant using on-line coal analysis and fuel blending

Monroe Power Plant of DTE Energy is a 3100 MW (net) station in southeastern Michigan. This station consists of four Babcock & Wilcox wall-fired boilers firing blends of southern Powder River Basin (PRB) subbituminous coal along with Central Appalachian bituminous coals. The station manages the coal properties in the various fuel blends using an on-line analyzer. This analyzer measures the complete proximate analysis, the heating value, and the ash chemistry of the coal being loaded into the silos. The on-line analyzer program has been used to control the slagging properties of the coal being burned, with the result being a dramatic reduction in costly slagging incidents at the plant. The on-line analyzer is used to guide modifications to the blend; it is also used to provide guidance to operators concerning the fuel being fed to pulverizers and burners. This paper describes this effort in the context of an overall combustion program and it details the results of that program.