Recent studies funded by the US Department of energy have shown that coal and coal byproducts contain elevated contents of Rare Earth Elements (REEs), making them a potential resource for these critical materials. The approach employed in this research focused on the concentration and extraction of REEs from fine coal refuse derived from various preparation plants in the Appalachian coal basin of the United States. Initial efforts in this research focused on the identification and characterization of REEs in various fine coal refuse streams from nine distinct industrial preparation plants in Appalachia. The average REE content in these materials was determined to be approximately 200 ppm, but the REE content showed a strong correlation to the aluminum content, suggesting that the REEs are closely associated with the clay minerals present in the refuse. Given the relatively low REE concentrations, initial efforts sought to concentrate the REEs through decarbonization and dispersive liberation steps. In these tests, high-shear agitation in the presence of a polyelectrolyte, followed by sedimentation was able to isolate the REE-enriched fine clay particles from siliceous gangue minerals. Following the dispersive liberation step, all samples were found to have an REE content greater than 300 ppm, a benchmark used for many initial exploratory studies. In one case, the REE content was increased by more than 125%. Subsequent extraction tests initially utilized a direct ion-exchange leaching approach with ammonium sulfate as lixiviant. In all cases, the simple ion-exchange leaching process failed to recover significant quantities of rare earth elements, ultimately suggesting that the REEs in fine coal waste may be passivated or bound in a colloidal phase. To access this colloidal phase, several alternative approaches were evaluated, including leaching with alternative ion-exchange lixiviants, reductive leaching, gas-purged leaching, and others. The approach that showed the most promise was strong alkaline pretreatment, followed by ion-exchange leaching with ammonium sulfate at pH 4. A combination of strong alkali and high-temperatures treatment successfully liberated the REEs, converting them to a form amenable to ion-exchange leaching. The highest REE recovery achieved with this method was determined to be 39%. Lastly, bench-scale solvent extraction tests were used to further concentrate REEs in the leach solution and demonstrate that mixed rare earth concentrates can be successfully produced from fine coal refuse. / Master of Science / Since the introduction of personal electronics, rare earth elements (REEs) have become essential raw materials for modern life. They are used in many common household goods such as cell phones, computers, and flat screen TVs. They are also vital components in various industrial, medical, and military applications. Currently, the majority of the world's supply is obtained from China, which has raised concerns on the vulnerability of the supply chain and the potential impacts of supply disruption on clean energy technologies. In light of this risk, the US Department of Energy has classified a number of REEs as critical elements and has subsequently funded research to investigate ways to diversify the supply chain through alternative resources. The approach employed in this research seeks to extract and recover REEs from fine coal refuse. This industrial waste is a byproduct of the coal mining and beneficiation processes. Given the long legacy of coal mining in the Appalachian region, hundreds of millions of tons of fine waste are currently being stored in surface impoundments, and millions of tons of additional fine coal waste is being produced each year from active mining and beneficiation operations. By valorizing this waste material through REE recovery, mining companies will be incentivized to reprocess existing impoundments, ultimately promoting superior economic and environmental outcomes. Despite their name, rare earths are not "rare" from the standpoint of raw abundance; however, their scarcity is derived from the complexity of the extraction and separation processes. In China, the majority of the heavy rare earth elements are produced from ion-exchangeable clays. These clays have REEs weakly attached to the surface, so that they can be readily recovered by washing them with a salt solution that remove the positively charged rare earth ions from surface. The technical approach employed in this project sought to replicate this process for the clay materials found in fine coal refuse. Additional steps were needed to properly concentrate, activate, and extract the REEs; however, the end-to-end processing tests confirmed that mixed rare earth concentrates can be produced from fine coal wastes consisting primarily clay minerals.

M.S.

Coal is one of the world's largest remaining mineral resources. The supply of this rich source of fuel and chemicals is sufficient to serve the world for several thousand years. Coal is used directly and is also heat treated at high and low temperatures to produce fuel and by-products. Of the several methods of treatment that can be used, low-temperature carbonization is one of the most promising. Nearly all of the coke and coal chemicals produced today come from the production of high temperature coke. However, there are many lower rank coals not suited for metallurgical purposes that will produce an excellent char and high yields of by-products. One of the disadvantages of many lower rank coals is their tendency to swell and become plastic when heated to carbonization temperatures, and this property has to a great extent made the operation of the retorts difficult. In an effort to reduce or circumvent this undesirable property, several methods of pretreating the raw coal have been tried including preoxidation, dilution with non-coking coal, preheating, and weathering. The type and severity of the pretreatments vary in their effects on the coking properties of different coals. The purpose of this investigation was to study the effect of preoxidation on the coking properties and the quantities and composition of the byproducts and char obtained from the low-temperature carbonization of Penn-Lee coal. / Master of Science

The usage of the coal is very extensive. For each particular process, there is always a better method to burn some kinds of coals than the others. Each application of the combustion of coal is an individual problem. This problem involves not only the single factor of burning of coal but also the factors of the economy, materials, and manufacture. An efficient burning process is not always the suitable one to be used. On some practical field of coal combustion the testing, or trial method serves very satisfactorily for finding the best firing method. The boiler and furnace testing method applied in the steam power plant is an excellent example. However, there is an important thing in common in all the coal firing processes which is the burning of coal. An understanding of the fundamental characteristics of the coal burning is obviously very helpful to the practical usages, especially to the design of a new process. / Master of Science

During the past decade, carbon capture, utilization, and storage (CCUS) has gained considerable recognition as a viable option to mitigate carbon dioxide (CO2) emissions. This process involves capturing CO2 at emission sources such as power plants, refineries, and processing plants, and safely and permanently storing it in underground geologic formations. Many CO2 injection tests have been successfully conducted to assess the storage potential of CO2 in saline formations, oil and natural gas reservoirs, organic-rich shales, and unmineable coal reservoirs. Coal seams are an attractive reservoir for CO2 storage due to coal's large capacity to store gas within its microporous structure, as well as its ability to preferentially adsorb CO2 over naturally occurring methane resulting in enhanced coalbed methane (ECBM) recovery. A small-scale CO2 injection test was conducted in Southwest Virginia to assess the storage and ECBM recovery potential of CO2 in a coalbed methane reservoir. The goal of this test was to inject up to 20,000 tons of CO2 into a stacked coal reservoir of approximately 15-20 coal seams. Phase I of the injection test was conducted from July 2, 2015 to April 15, 2016 when a total of 10,601 tons of CO2 were injected. Phase II of the injection was conducted from December 14, 2016 to January 30, 2017 when an additional 2,662 tons of CO2 were injected, for a total of 13,263 total tons of CO2 injected. A customized monitoring, verification, and accounting (MVA) plan was created to monitor CO2 injection activities, including surface, near-surface, and subsurface technologies. As part of this MVA plan, chemical tracers were used as a tool to help track CO2 plume migration within the reservoir and determine interwell connectivity. The work presented in this dissertation will discuss the development and implementation of chemical tracers as a monitoring tool, detail wellbore-scale tests performed to characterize CO2 breakthrough and interwell connectivity, and present results from both phases of the CO2 injection test. / PHD / During the past decade, carbon capture, utilization, and storage (CCUS) has gained considerable recognition as a viable option to mitigate carbon dioxide (CO2) emissions. This process involves capturing CO2 at emission sources such as power plants, refineries, and processing plants, and safely and permanently storing it in underground geologic formations. Many CO2 injection tests have been successfully conducted to assess the storage potential of CO2 in saline formations, oil and natural gas reservoirs, organic-rich shales, and unmineable coal reservoirs. Coal seams are an attractive reservoir for CO2 storage due to coal’s large capacity to store gas within its microporous structure, as well as its ability to preferentially adsorb CO2 over naturally occurring methane resulting in enhanced coalbed methane (ECBM) recovery. A small-scale CO2 injection test was conducted in Southwest Virginia to assess the storage and ECBM recovery potential of CO2 in a coalbed methane reservoir. The goal of this test was to inject up to 20,000 tons of CO2 into a stacked coal reservoir of approximately 15-20 coal seams. Phase I of the injection test was conducted from July 2, 2015 to April 15, 2016 when a total of 10,601 tons of CO2 were injected. Phase II of the injection was conducted from December 14, 2016 to January 30, 2017 when an additional 2,662 tons of CO2 were injected, for a total of 13,263 total tons of CO2 injected. A customized monitoring, verification, and accounting (MVA) plan was created to monitor CO2 injection activities, including surface, near-surface, and subsurface technologies. As part of this MVA plan, chemical tracers were used as a tool to help track CO2 plume migration within the reservoir and determine interwell connectivity. The work presented in this dissertation will discuss the development and implementation of chemical tracers as a monitoring tool, detail wellbore-scale tests performed to characterize CO2 breakthrough and interwell connectivity, and present results from both phases of the CO2 injection test.

The understanding of liquefaction behaviors, related to a coal's properties and a recycle solvent's composition, is essential for the development of an efficient direct liquefaction process. In this dissertation, a study of the liquefaction behaviors of an Eastern us bituminous and four Western US subbituminous coals is presented. The experimental approach has been to examine their behaviors under various reaction conditions with in-house microautoclave reactor and Kerr McGee pilot plant liquefaction runs. In-house runs involved surveys of coal types and process solvent compositions with variations in reaction times, temperatures and atmospheres. Runs performed at Kerr McGee examined the use of tetrahydroquinoline (TBQ) as a process solvent with a Wyoming coal. Liquefaction activities were assessed through determinations of coal conversion to both solvent-soluble products and distillate yields. Per the in-house liquefaction studies, a novel microautoclave reactor design and product recovery methods were developed, evaluated and employed. The reaction chemistries of !n !!S!! metal species and basic nitrogen heterocycles were investigated specifically. Changes in trace element concentrations were ascertained by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) and Size Exclusion Chromatography/ICP-AES (SEC/ICP-AES). Pates of basic nitrogen components in distillate and solvent-soluble residuum products were examined by nitrogen mass balance determinations, Gas Chromatography/Pourier Transform Infrared Spectrometry (GC/PTIR) and Gas Chromatography/Mass Spectrometry (GC/MS). Conversions to soluble products demonstrated the expected dependencies of liquefaction on coal rank, elemental composition and petrography. The western subbituminous coals showed extreme sensitivity to drying and solvent-soaking pretreatments. Metal content analyses revealed that metals exist as complexed species in the liquefaction process. Higher conversions to toluene-soluble materials were obtained with THQ in contrast to other H-donor solvents. Adduction of THQ was significant in the non-distillate product stream, however. The direct coupling of Reversed Phase HPLC separations with PTIR (RP-HPLC/PTIR) detection through on-line, post-column extraction was developed. Though intended for application to coal-liquefied product (CLP) analysis, this system was evaluated rigorously for both chromatographic and spectral performance. Throughout this investigation, the overall utility of these hyphenated methods for CLP analysis was explored. These methods demonstrated exceptional performance in providing a wealth of qualitative and quantitative information in a rapid manner. / Ph. D. / incomplete_metadata

The precombustion desulfurization of coal was investigated by photochemical methods and by the application of a novel pyrite depressant in froth flotation. Semiconductor photoelectrochemical catalysis was extensively examined. As much as 41% of the organic sulfur was removed and 72% overall desulfurization of micronized Illinois No. 2 coal was obtained. Zinc oxide, in colloidal suspension, produced a small increase in the overall desulfurization at longer reaction times when compared to direct photolysis. The major limiting factor in organic sulfur removal from coal appears to be accessibility rather than reactivity. Kinetic experiments conducted with the model organosulfur compound, dibenzothiophene, showed high photochemical reactivity with nearly complete conversion occurring in 5 minutes in a saturated solution at 25°C. Scanning electron microscopic examination of product coals showed empty casts in places once occupied by iron pyrite. Additionally, a novel process was developed for separating clean coal from metal sulfide minerals such as pyrite and marcasite. The process comprises depressing the metal sulfide minerals with a reagent resulting from the alkaline oxidation and polymerization of a polyphenol or a quinone, and selectively floating clean coal from the depressed metal sulfide minerals. The process was investigated using microflotation, conventional Denver cell flotation, and microbubble column flotation. Up to 90% pyritic sulfur rejection was achieved from a coal and coal pyrite synthetic mixture. The process efficiency is a function of pH with greater improvements generally occurring at acidic pH when compared with the results obtained in the absence of the quinonoid reagent. However, in the case of microbubble column flotation with micronized coals, the largest overall pyritic sulfur and ash rejection occurred under alkaline conditions. Data from x-ray photoelectron spectroscopy and calorimetry indicate the quinonoid reagent modified the surface properties of minerals by reversible adsorption. / Ph. D.

Specific conductivity (SC) and total dissolved solids (TDS) are increasingly being used as a parameter used to judge the aquatic health of streams that are impacted by coal mining operations in the Appalachian region of the United States. Due to this, government environmental regulatory bodies have been considering issuing a regulation on SC for all mining operation outfalls. Sulfate typically has the greatest dissolved ion presence in coal mine waters. In literature examining the treatment of mine waters, SC and TDS analysis is typically not reported. The technologies examined in this study were nanofiltration membrane technology and biological sulfate reducing bioreactors. In the nanofiltration study, three different nanofiltration membranes were evaluated for SC reduction: NF270, DK, and NFX. The DK and NFX nanofilters were able to reduce SC levels by an average of 84 percent for both mine waters tested and were able to reach SC levels below the proposed limit of 500 S/cm. The SC levels achieved by the NF270 nanofilters were observed to have much higher variability. The inclusion of microfiltration and simulated-sand filtration were also introduced as a pre-treatment stage in order to determine whether or not nanofiltration performance would improve in terms of SC reduction. In the biological sulfate reducing bioreactor study, multiple bioreactors were established to identify the optimal organic mixture to foster both SC and sulfate reduction. Sulfate reduction began to occur approximately 20 days after the establishment of each bioreactor. SC levels were greater than 13,000 S/cm in each of the bioreactors sampled by the fortieth day of sampling. The probable cause of the increase SC was identified to be the manure/compost used in the study. Future testing should incorporate more sampling in the early phases of experimentation in order to ensure the ability to monitor changes in water quality. / MS / Treatment technologies used to treat coal mine waters have traditionally focused on mitigating pH, dissolved oxygen, ferric iron, and aluminum levels. Specific conductivity (SC) and total dissolved solids (TDS) have been identified in recent years to be deterrents of aquatic health in coal mine waters. Sulfate in particular has been found to be a contributor of SC and TDS that can cause a deterioration in aquatic health. There is an apparent gap of knowledge as it pertains to the reporting of the reduction of SC and TDS in coal mine waters. The objective of this study was to evaluate the utilization of nanofiltration membrane technology and biological sulfate reduction as methods for reducing SC and TDS in coal mine waters of southwestern Virginia. Three nanofiltration membranes with various characteristics were tested in order to determine whether they could meet literature recommended SC levels. Microfiltration and simulated sand filtration were incorporated as pretreatment steps in order to determine if these could stimulate further SC reduction. Major water quality characteristics were monitored after nanofiltration as well. Multiple biological sulfate reduction reactors were designed in the second part of the study and allowed to treat coal mine waters for a 40-day period. Each reactor tested used varying mixtures in order to determine the optimal mixture for both sulfate and SC reduction. Reactors were sampled periodically for the monitoring of major water quality parameters.

This thesis has four main objectives which are as follows 1. To make a detailed study of the environment of a selected low-income group of families on a comparative basis with low-income families of similar characteristics. 2. To relate the knowledge acquired from this study to the analysis and planning of a housing project. 3. To design dwellings for this project with a maximum of livability, structural soundness, pleasing aesthetic quality, and economy. 4. To investigate the financing of this housing project with several types of ownership in order to ascertain their feasibility, and to determine which offers the greater advantage to the group, to be housed. / M.S.

The swelling and caking propensity of coals may cause operational problems such as channelling and excessive pressure build-up in combustion, gasification and specifically in fluidised-bed and fixed-bed operations. As a result, the swelling and caking characteristics of certain coals make them less suitable for use as feedstock in applications where swelling and/or caking is undesired. Therefore, various studies have focused on the manipulation of the swelling and/or caking propensity of coals, and have proven the viability of using additives to reduce the swelling and caking of powdered coal (<500 μm). However, there is still a lack of research specifically focused on large coal particle devolatilisation behaviour, particularly swelling and caking, and the reduction thereof using additives. A comprehensive study was therefore proposed to investigate the swelling and caking behaviour of large coal particles (5, 10, and 20 mm) of typical South African coals, and the influence of the selected additive (potassium carbonate) thereon. Three different South African coals were selected based on their Free Swelling Index (FSI): coal TSH is a high swelling coal (FSI 9) from the Limpopo province, GG is a medium swelling coal (FSI 5.5-6.5) from the Waterberg region, and TWD is a non-swelling coal (FSI 0) from the Highveld region. Image analysis was used to semi-quantitatively describe the transient swelling and shrinkage behaviour of large coal particles (-20+16 mm) during lowtemperature devolatilisation (700 °C, N2 atmosphere, 7 K/min). X-ray computed tomography and mercury submersion were used to quantify the degree of swelling of large particles, and were compared to conventional swelling characteristics of powdered coals. The average swelling ratios obtained for TWD, GG, and TSH were respectively 1.9, 2.1 and 2.5 from image analysis and 1.8, 2.2 and 2.5 from mercury submersion. The results showed that coal swelling measurements such as FSI, and other conventional techniques used to describe the plastic behaviour of powdered coal, can in general not be used for the prediction of large coal particle swelling. The large coal particles were impregnated for 24 hours, using an excess 5.0 M K2CO3 impregnation solution. The influence of K2CO3-addition on the swelling behaviour of different coal particle sizes was compared, and results showed that the addition of K2CO3 resulted in a reduction in swelling for powdered coal (-212 μm), as well as large coal particles (5, 10, and 20 mm). For powdered coal, the addition of 10 wt.% K2CO3 decreased the free swelling index of GG and TSH coals from 6.5 to 0 and from 9.0 to 4.5, respectively. The volumetric swelling ratios (SRV) of the 20 mm particles were reduced from 3.0 to 1.8 for the GG coal, and from 5.7 to 1.4 for TSH. In contrast to the non-swelling (FSI 0) behaviour of the TWD powders, the large particles exhibited average SRV values of 1.7, and was found not be influenced by K2CO3-impregnation. It was found that the maximum swelling coefficient, kA, was reduced from 0.025 to 0.015 oC-1 for GG, and from 0.045 to 0.027 oC-1 for TSH, as a results of impregnation. From the results it was concluded that K2CO3-impregnation reduces the extent of swelling of coals such as GG (medium-swelling) and TSH (high-swelling), which exhibit significant plastic deformation. Results obtained from the caking experiments indicated that K2CO3-impregnation influenced the physical behaviour of the GG coal particles (5, 10, and 20 mm) the most. The extent of caking of GG was largely reduced due to impregnation, while the wall thickness and porosity also decreased. The coke from the impregnated GG samples had a less fluid-like appearance compared to coke from the raw coal. Bridging neck size measurements were performed, which quantitatively showed a 25-50% decrease in the caking propensity of GG particles. Coal TWD did not exhibit any caking behaviour. The K2CO3-impregnation did not influence the surface texture or porosity of the TWD char, but increased the overall brittleness of the devolatilised samples. Both the extent of caking and porosity of TSH coke were not influenced by impregnation. However, impregnation resulted in significantly less and smaller opened pores on the surface of the devolatilised samples, and also reduced the average wall thickness of the TSH coke. The overall conclusion made from this investigation is that K2CO3 (using solution impregnation) can be used to significantly reduce the caking and swelling tendency of large coal particles which exhibits a moderate degree of fluidity, such as GG (Waterberg region). The results obtained during this investigation show the viability of using additive addition to reduce the caking and swelling tendency of large coal particles. Together with further development, this may be a suitable method for modifying the swelling and caking behaviour of specific coals for use in fixed-bed and fluidised-bed gasification operations. / PhD (Chemical Engineering), North-West University, Potchefstroom Campus, 2015