Supercritical extraction of coal is removal of a select fraction of the coal by a solvent which is slightly above its critical temperature and above its critical pressure. The objective of this dissertation was to understand the mechanism of supercritical extraction, to test some promising solvents, and to explore the design implications of the findings. Supercritical extraction of Wyodak coal was studied by passing various solvents upwards through a 15-gram sample of 12-20 mesh coal. For the high temperature experiments, the coal was heated to 375°C and 425°C in a hot fluidized sand bath. The main solvent used was toluene, while extractions with n-pentane, xylene, methanol, and water were also done. The extract was fractionated into oils, asphaltenes, and asphaltols. Supercritical extraction of coal near pyrolysis temperatures affords an opportunity to remove unstable decomposition products from the reaction environment to avoid repolymerization and pore blinding. Stronger aromatic solvents removed the decomposition products as they were formed. However, product degradation even with the strongest solvents was inevitable during the initial few minutes. For the low temperature experiments (below 95°C), the solvent was carbon dioxide. Effects of liquid entrainers (pre-mixed with the coal), and heat-pretreatment of the coal (at 400°C for 1 hour) were also studied. The major difference between the high and low temperature extractions was that coal reactions occurred at high temperatures simultaneously with solubilization. Extraction of raw coal and heat-pretreated coals with carbon dioxide was negligible. However, extractions as high as 12% were possible when small amounts of liquid entrainers such as pyridine, toluene, and tetralin were pre-mixed with the coal. The entrainers were almost completely recovered with the extract. The process design implications of the supercritical extractions of coal were studied using the method developed by ESCOE (Engineering Societies Commision On Energy Inc.). Preliminary design estimates showed that the following supercritical extraction processes were possible alternatives to present commercialization efforts and deserve further attention: 1. Gasification of the extraction residua; 2. Satellite plants operating in parallel with coal-burning utilities; 3. Entrainer-aided extraction. / Ph. D.

A formulation was developed for the rheological characterization of highly concentrated suspensions, accounting for the physical effects of particle size distribution. A number of dimensionless parameters were developed signifying the physical characteristics of the solids and the vehicle fluid, and functionally related to the yield-stress and a flow parameter. Each of these expressions of the formulation contains an empirical dimensionless coefficient accounting for the interparticle and fluid/solid interactions that are not explained by the physical parameters involved. A formulation and a methodology were also developed for predicting the shear viscosity behavior of highly concentrated suspensions at low and high shear-rates through the use of three parameters signifying effects of particle size distribution. A number of applications were made using various non-coal and limited coal-liquid mixture data reported in the literature to demonstrate the general validity of the formulations. A methodology was proposed for the analysis of the particle size distribution effects on the overall optimum energy efficiency during hydraulic transportation and particle size reduction. The computer model developed for this purpose was employed to evaluate the transportation energy consumption and the energy consumed in the grinding process to prepare the slurry, in pipes of various sizes and lengths for a coal slurry of various specified particle size distributions and concentrations. Correlations obtained indicated the sensitivity of transportation energy efficiency to various parameters including the maximum packing concentration, relative concentration, specific surface area of particles, surface area mean size, pipe size and length, and annual mixture throughput. The results of combined energy calculations have shown that the particle size distribution and related physical parameters can significantly affect the energy efficiency due to both grinding and transportation, and the delivered cost of slurry fuels. / Ph. D.

The probability of particle capture by an isolated bubble rising through a suspension of particles has been determined using fundamental principles of fluid mechanics. This analysis has allowed the rate constant for flotation to be evaluated as functions of bubble sine, particle size, flotation column diameter, air flow rate and critical film rupture thickness. The last parameter is a measure of the hydrophobicity of the particles to be floated. Using the theoretically determined rate constant, a population balance model has been developed for the flotation of fine coal in a column. The model is capable of predicting the dynamic response of the flotation column to changes in a wide range of operational conditions. Model simulations have been found to be in reasonable agreement with experiments conducted using a bench-scale column. / Ph. D. / incomplete_metadata

The direct current plasma is an excitation cell that should be well suited to rapid analysis of coal slurries by virtue of its tolerance for various sample matrices. Problems which are encountered in coal analysis by emission spectrometry include incomplete atomization of analyte by formation of metal oxides, lack of adequate methodology for sulfur analysis, and ineffective sample transport for coarse coal slurries. Atomization of metal oxides can be improved by addition of small amounts of propane (Ca 45 mL/min) to the nebulizing argon of the direct current plasma. However, the improved atomization is manifested above the normal viewing zone, and the enhancement effect of propane on analytical signals is offset by severe depression of emission signals caused by temperature reduction in the lower regions of the plasma. Sulfur in coal can be determined by direct current plasma emission spectrometry. Emission lines accessible to the echelle grating of the DCP are not suitable for such analysis, so that the deep-UV lines from 180-183 nm must be utilized for such work. A relatively simple purge system with low argon consumption (5 L/min) is adequate for sulfur analysis, and the beforementioned analytical lines provide detection limits that are adequate for sulfur determination in 1% slurries of coal. However, transport of the coal sample to the plasma is incomplete when compared to that of aqueous solutions, precluding the use of such solutions as calibration standards. Transport of the coal can be improved by increasing the viscosity of sample and standards, which increases the droplet size from the nebulizer and hence the particle size transportable• The increased droplet size causes a decrease in sensitivity due to reduced desolvation/vaporization, but does permit the use of aqueous solutions and as calibration standards for determination of sulfur, iron, aluminum, silicon in coal. / Ph. D.

Coal strip mining leaves widespread degraded soil throughout the southeastern US. These soils tend to have low pH, high bulk density, impacted hydrologic processes, and an accumulation of heavy metals that limit revegetation and reforestation efforts. Shortleaf pine (Pinus echinata) can tolerate these poor conditions on post-mined sites and has the largest native pine range in the southeastern US, making it an ideal species for restoration efforts. Additionally, the use of soil amendments to improve soil physical and chemical parameters is expected to lead to improved plant establishment and growth. To address the challenges associated with degraded post-mined landscapes, two studies were conducted using a biochar (BC) and microbial amendment (MA). Few empirical studies have been conducted on the success of soil amendments for soil physical properties, chemical properties, and tree growth. To fill this knowledge gap, a three year field trial was established on a reclaimed mining site in Alabama. Shortleaf pine seedlings were planted in a complete randomized block design with two soil amendment treatments: BC and MA. The second study then evaluated how climate change impacts restoration efforts. Specifically, this study observed how precipitation uncertainty affects the effectiveness of existing restoration techniques. This comprehensive 6-month greenhouse experiment in Mississippi examined shortleaf pine restoration under dry and wet moisture regimes. Soil amendments were applied to one year old seedlings replicated across moisture treatments including the same mixtures of amendments as the field experiment in addition to a no tree treatment, a pot with only post-mined soil. Findings from both studies indicate that BC did not improve measured soil properties or tree growth as expected, while the MA induced short-term impacts on soil physical and chemical properties that impacted tree growth. The greenhouse results also indicated that changes in precipitation do not impact the effects of any soil amendment. Additionally, MA may have the potential to change the allocation of biomass for shortleaf pine, which has implications for survival and restoration. In the short-term, the application of commercially recommended levels of treatments were ineffective at supporting tree growth through improvements to measured soil characteristics.

In order to exploit unconventional gas and estimate carbon dioxide storage potential in shale formations and coal seams, two key questions need to be initially answered: 1) What is the total gas-in-place (GIP) in the subsurface reservoirs? 2) What is the exact ratio between bulk gas content and adsorbed gas content? Both questions require precise estimation of adsorbed phase capacity of gases (methane and carbon dioxide) and their adsorption behavior in shale and coal. This dissertation therefore analyzes adsorption isotherms, thermodynamics, and kinetics properties of methane and carbon dioxide in shale and coal based on experimental results to provide preliminary answers to both questions. It was found that the dual-site Langmuir model can describe both methane and carbon dioxide adsorption isotherms in shale and coal under high pressure and high temperature conditions (up to 27 MPa and 355.15K). This allows for accurate estimation of the true methane and carbon dioxide GIP content and the relative quantity of adsorbed phases of gases at in situ temperatures and pressures representative of deep shale formations and coal seams. The concept of a deep shale gas reservoir is then proposed to optimize shale gas development methodology based on the successful application of the model for methane adsorption in shale. Based on the dual-site Langmuir model, the isosteric heat of adsorption is calculated analytically by considering both the real gas behavior and the adsorbed phase under high pressure, both of which are ignored in the classic Clausius–Clapeyron approximation. It was also found that the isosteric heat of adsorption in Henry's pressure region is independent of temperature and can serve as a quantified index to evaluate the methane adsorption affinity on coal. In order to understand the dynamic response of gas adsorption in coal for carbon sequestration, both gas adsorption kinetics and pore structure of coal are investigated. The pseudo-second order model is applied to simulate the adsorption kinetics of carbon dioxide in coals under different pressures. Coal particle size effects on pore characterization of coal and carbon dioxide and nitrogen ad/desorption behavior in coal was also investigated. / Ph. D. / Shale gas is natural gas that is found trapped within subsurface shale formations, and the in-situ pressure and temperature of shale formations can go up to 27MPa and 86℃. Shale gas, the main component of which is methane, mainly consists of adsorbed phase and free compressed gas in shale formations. The adsorbed phase accounts for 20-85% of the total gas-in-place resource. Thus, the estimation of amount of methane adsorbed in shale under in-situ conditions are extremely important for determining the total gas-in-place quantity and the working life of a shale gas production well and its economic viability. This work provides a method for accurate estimation of the shale gas-in-place resource under in-situ shale formation conditions. The method is based on laboratory methane adsorption test data in shale at high pressure (up to 27MPa) and high temperature (up to 82℃) conditions. According to this method, it was found that for depths greater than 1000 m (> 15 MPa) in the subsurface, the shale gas resources have historically been significantly overestimated. For Longmaxi shale (2500 – 3000 m in depth), classical approaches overestimate the GIP by up to 35%. The ratio of the adsorbed phase compared to the free gas has been significantly underestimated. Shale gas production follows pressure depletion of shale formations. The pressure depletion process allows methane in the adsorbed phase to become free gas, which is known as the physical desorption process. Desorption is an endothermic process while adsorption is an exothermic process, both of them are reversible. Thus, the heat transfer process during shale gas production requires a thermodynamic analysis of methane adsorption in shale. This work investigates the isosteric heat of adsorption for methane in shale by considering both the real gas behavior and the volume effect of the adsorbed phase, not previously considered for methane in shale. The temperature dependence as well as the uptake dependence of the isosteric heat can be readily investigated by the applied method. This study lays the foundation for future investigations of the thermodynamics and heat transfer characteristics of the interaction between high pressure methane and shale. This work also investigates gas adsorption kinetics properties in coal and the particle size effect on pore characterization of coal using the gas adsorption approach. Results show that particle size of coal samples can significantly influence the sorption behavior of gas in coal, which finally affects pore characterization of coal. It is difficult to characterize the pore structure of coal using only one coal particle size. Carbon dioxide adsorption kinetics in coal, which can be modelled by the pseudo-second order model, is a combination of both bulk diffusion-controlled and surface interaction-controlled processes; the former dominates the initial stage while the latter controls the majority of the overall process.

Appalachian surface coal mining operations fracture rocks (termed mine spoils), resulting in the weathering of minerals and release of water-soluble ions to streams. Collectively, the concentration of water-soluble ions in streams is called total dissolved solids (TDS) and streams with elevated TDS often have altered biota. The surficial, subsurface, and discharge properties of mine spoils influence TDS discharge concentrations. This study aimed to improve understanding of how hydrologic and hydrochemical processes occur and function in coal mining areas. These processes were characterized by infiltration and dye staining tests, mine spoil leaching experiments and modeling, and mining-influenced stream discharge monitoring. Results indicate that many factors influence hydrologic and hydrochemical processes in Appalachian coal mining areas, but these processes evolve over time as subsurface flow paths develop, mine rocks weather, and TDS is released from mine spoils. Fourteen years after placement, mean infiltration rates of mine soils reclaimed with trees were statistically greater than areas reclaimed with grasses, and different subsurface flow types were evident, indicating vegetation type influenced hydrologic processes. Specific conductance (SC) leaching patterns from mine spoils conformed to an exponential decay and linear segmented regression model. Maximum SC values (1108 ± 161 µS cm⁻¹) occurred initially during leaching, exponentially decayed, then exhibited linear SC releases (276 ± 25 µS cm⁻¹) that were elevated relative to natural background levels at the end of leaching. Major element (S, Ca, Mg, K, Na) leaching patterns resembled those of SC, whereas trace elements (As, Cd, Cu, Ni, Pb, Se) transitioned to linear release earlier in the leaching period. Mining-influenced stream SC discharge patterns varied by season and by precipitation amounts during storm events. Storm responses were characterized by either infiltration-excess overland flow or delayed SC releases due to internal flow through the VF. Given these results, mining companies wishing to control TDS discharges may be selective and pre-test mine spoils for total S and paste SC to determine TDS-generation potential. Isolation of spoils with high-TDS release potentials (i.e. unweathered sandstones and mudstones) from water-rock contact may help improve TDS discharges. / Ph. D. / The Appalachian surface coal mining process removes rock from above a coal seam by fracturing it with explosives. The fractured rock is then used to reconstruct the original shape of the mountain, and any rock left over after that reconstruction is often placed adjacent to the mining area in landforms constructed to direct water from the mine site to a natural stream. During the mining process, the minerals in the rocks rapidly break down, and when rainwater causes the weathering products (e.g. elements such as calcium, magnesium, sulfur, selenium, and arsenic) to discharge to a stream, the aquatic ecosystem of that stream is usually affected. The objective of this study was to characterize the processes occurring in coal mining areas that ultimately influence the water quality discharged by the mine. Results indicate that many factors influence how rainwater travels through coal mining rocks and the eventual quality of waters discharged from mine rocks, and that these factors evolve over time. A study of 14-year-old mine soils indicated that the type of vegetation (i.e. trees vs. grass) planted after mining influences how water infiltrates into soils and the pathways water travels through once infiltrated. Laboratory studies of mine rocks found that many of those rocks conformed to a single mathematical model that described their elemental release patterns. The model indicated that the quality of waters discharged from mining areas is elevated above natural conditions in the initial phase after mining. Those levels appear to decline over time, but may still have long-term effects on aquatic ecosystems. Field studies of five mining-influenced streams also found that the water quality in those streams was above levels which are detrimental to aquatic ecosystems at all flow levels. It may be helpful to mining companies to test mine rocks prior to mining to determine the best location to place the rocks after mining for mitigation of water quality issues. Isolating mine rocks with the highest potentials to impact water quality may improve post-mining water quality effects.

Surface coal-mining is a source of selenium (Se) contamination in streams of the Appalachian coalfields. Selenium dynamics in aquatic systems are complex and largely controlled by site-specific factors, but have been understudied in Appalachian headwater streams. In this study, we evaluated the degree and dynamics of Se enrichment and bioaccumulation in headwater streams influenced by coal-mining. Based on Se concentrations in macroinvertebrates collected from 23 headwater streams, nine sites were selected for further study: three reference streams with no history of coal-mining, and six streams influenced by coal mining. Mining-influenced streams were further separated into high-Se and low-Sestreams based on macroinvertebrate tissue Se concentrations. Water-column, sediment, biofilm, leaf detritus, and prey and predator macroinvertebrates were collected and analyzed for Se concentration during two sample periods, Sept. - Oct. 2015 and Feb.-March 2016. Selenium concentrations in all media were found to be elevated in mining-influenced over reference streams and in high-Se over low-Se streams. Selenium dynamics, enrichment in particulate media (sediment, biofilm and leaf detritus) and trophic transfer of Se to prey from particulate media and to predators from prey, did not exhibit major differences among streams of differing Se levels. Water column Se concentrations were predicative of Se concentrations in macroinvertebrate tissues. Findings from this study indicate headwater streams influenced by coal-mining are capable of a high degree of Se bioaccumulation in macroinvertebrate populations. / Master of Science / Surface coal-mining is a source of selenium (Se) contamination in streams of the Appalachian coalfields. Selenium dynamics in aquatic systems are complex and largely controlled by sitespecific factors, but have been understudied in Appalachian headwater streams. In this study, we evaluated the degree and dynamics of Se enrichment and bioaccumulation in headwater streams influenced by coal-mining. Based on Se concentrations in macroinvertebrates collected from 23 headwater streams, nine sites were selected for further study: three reference streams with no history of coal-mining, and six streams influenced by coal mining. Mining-influenced streams were further separated into “high-Se” and “low-Se” streams based on macroinvertebrate tissue Se concentrations. Water-column, sediment, biofilm, leaf detritus, and prey and predator macroinvertebrates were collected and analyzed for Se concentration during two sample periods, Sept. - Oct. 2015 and Feb.- March 2016. Selenium concentrations in all media were found to be elevated in mining-influenced over reference streams and in high-Se over low-Se streams. Selenium dynamics, enrichment in particulate media (sediment, biofilm and leaf detritus) and trophic transfer of Se to prey from particulate media and to predators from prey, did not exhibit major differences among streams of differing Se levels. Water column Se concentrations were predicative of Se concentrations in macroinvertebrate tissues. Findings from this study indicate headwater streams influenced by coal-mining are capable of a high degree of Se bioaccumulation in macroinvertebrate populations.

The occurrence of multiple fatality events in the U.S. underground coal mining industry, such as the Upper Big Branch mine explosion, illustrates the need for improved methods of major safety hazard identification and control. While many solutions to reducing the risk of mine disasters have been proposed, including stricter regulation and improved technology, a comprehensive risk management approach has yet to be fully integrated in the U.S. mining industry. Comprehensive risk management systems have been developed and implemented across a multitude of heavy industries, most notably the Australian minerals industry. This research examines the successful application of risk management in these industries, along with barriers towards U.S. implementation of risk management, which include the existence of competing safety models (e.g. behavior-based safety) and compliance regulation which consumes company resources, and limits incentive for beyond compliance safety measures. Steps towards the risk-based approach, including increased regulatory pressure and proactive initiation by high-ranking industry individuals, begin with the development of risk-based knowledge within the U.S. mining community. This research reviews the development of mine safety regulation in the U.S., and identifies regulatory constraints which have affected the diffusion of risk management. The development of a risk-based online platform which could complement the existing safety systems of U.S. underground coal operations, based on the Australian RISKGATE tool, is the central work of this research. This online platform has been developed by the research participants and industry professionals whose total underground coal mining experience exceeds 1,290 years. This joint effort has yielded a body-of-knowledge which may be used as a complementary safety control reference for U.S. mine operators who wish to employ risk management policies and practices at their own operations, or identify gaps within their own safety control systems. / Master of Science / Over the last century, the safety record of the U.S. coal mining industry has steadily improved, with annual fatal incidents reaching historically low values over the last decade. Advancements in mine safety are largely attributed to increased regulatory and enforcement efforts and the enhancement of mining technology. While fatal incidents have become more intermittent, the U.S. underground coal mining industry has yet to reach its zero harm goals through current industry standards and mining practices. Risk management, the systematic mitigation of risk through proper identification, assessment, and control, has been successfully utilized by various heavy industries (chemical, aviation, military, nuclear energy, etc.) to improve worker health and safety outcomes. However, risk management has yet to be comprehensively adopted by and applied to the U.S. coal mining industry. This research examines the potential application of risk management in U.S. underground coal mining, and describes the development of a U.S.-based risk management body-of-knowledge, RISKGATE-US COAL, designed to assist U.S. coal mining operators (e.g. frontline workers, engineers, mine managers) in the identification and mitigation of the unique hazards encountered in the underground coal mine environment. RISKGATE-US COAL is contained within an online platform (alpha.riskgate.org) devised as a reference tool for U.S. underground coal mining practitioners to identify gaps within their own safety control systems.

Respirable coal mine dust (RCMD) continues to pose serious health hazards to workers. Over the past few decades, new regulations, monitoring technologies, and improved dust controls have emerged, and all are based on the presumption that limiting RCMD on the basis of mass will effectively mitigate the exposure hazards. Given the latency of exposure outcomes, it will be some time before the full impact of these strategies can be evaluated. In the meantime, there is increasing awareness that RCMD particle characteristics, in addition to mass, might be important. This dissertation comprises four separate studies which explore the effects of primary RCMD sources and/or engineering controls on particle size and constituents. To enable a direct comparison of dust generation from primary dust sources, a field study was conducted to investigate the dust generation and particle characteristics between coal and the rock strata. Results indicated that finer and more dust was generated when mining predominantly into the rock strata versus the coal strata, while the operation of a flooded bed scrubber and an increase in water sprays pressure and volume generally suppressed dust. Prior government research, conducted within the Mining Research Division of the National Institute of Occupational Safety and Health (NIOSH) evaluated the dust mass concentrations removal efficiency of different dust controls (i.e., a dry and wet scrubber, canopy air curtain, and a wet versus dry dust collection boxes). In the second and third studies, preserved samples from these prior NIOSH dust control studies were re-analyzed and evaluated to understand their effects on dust characteristics. Results indicated that the efficiency of dust controls was particle size dependent, as these controls mostly showed no appreciable effects on dust constituents. Generally, the cleaning of dust from a novel wet dust collection box versus a traditional dry dust box led to a reduction in operator exposure to hazardous dust. In the final study, a laboratory prototype flooded bed scrubber was evaluated to understand its efficiency on dust between different particle size bins (i.e., by particle count) ranging from 0.3-10 µm. From the results, removal efficiencies were generally low – and sometimes negative, for dust particles mostly in each of the size bins less than 2 µm. The results presented here highlight the need to holistically evaluate dust controls to understand their efficiency on dust of different particle sizes and constituents, so that informed decisions can be made on the best controls to adopt in mine operations. / Doctor of Philosophy / Coal production contributes significantly to steel making and electricity generation in the US. During the mining process, very fine dust is generated—called "respirable" dust— which represents a significant health hazard to workers. Indeed, many cases of occupational lung diseases linked to respirable dust have been reported over the past few decades, and disease rates remain high. Dust monitoring and control efforts are largely based on limiting the total mass of respirable dust. However, there is growing evidence that specific types of dust present disproportionate hazards—including the smallest particles, which do not contribute much to total mass, and mineral particles such as silica. The research in this dissertation explores the effects of primary dust sources and controls on respirable dust size and constituents. The major findings are as follows: when using typical equipment, mining into the rock strata that surrounds the target coal seam can generate much more dust than mining the coal itself. This dust generated can be finer and contain more mineral dust like silica and silicates. Furthermore, most dust controls used to suppress dust do not appear to be selective with respect to particle type but are generally less efficient for removing finer particles. This implies that, while dust mass removal efficiency may be high, controls might still be needed where very fine dust particles pose substantial hazards. Additionally, mine operations could develop monitoring techniques and re-orient their dust controls to target and better mitigate the most hazardous primary sources of dust such as dust from the rock strata.