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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.

Coal is a potential source of valuable elements such as rare earth elements and yttrium (REY). In this work, REY concentrations in U.S. domestic coals were evaluated using data from the USGS COALQUAL Database Version 3.0. The database contains a total of 7657 non-weathered, full-bed coal samples. The number of samples containing REY data points varies among elements. Assessment of data quality indicates that some of the REY data are semi-quantitative and should be used with caution. Different analytical instruments and methods with varying accuracies and precisions are thought to be the main sources of errors. Inclusion of qualified data also accounts for the sawtooth pattern of the UCC-normalized REY distribution. A new set of Q factor values was thus proposed to adjust qualified data. Consequently, mean concentrations of REY in U.S. coals were obtained with a total REY concentration of 65.5 ppm on a moisture-free whole coal basis. Further evaluation of REY in 5378 selected coal samples indicates that about 9–13% of the samples fall into the combined category of promising and highly promising coals for REY, according to the classification of Dai et al. (2017). Taking sampling bias into consideration, we further found that bituminous coal, particularly from the central Appalachian region, has the highest probability of being a source for beneficial recovery of REY. More specifically, bituminous coal from eastern Kentucky is likely to be the best option. Finally, we conclude that U.S. domestic coal is a promising, alternative source for beneficial recovery of REY to meet the U.S. REY demand for economic growth.

Exposure to 7 MPa of helium at room temperature alters the texture of Upper Freeport coal in a lump form. The differences in texture and porosity between coal powder and lumps may affect the transport and interaction of fluids and coal. In this work, the information about the coal texture and micro- and meso-porosity was obtained via the BET, BJH, and Dubinin–Astakhov analyses. We further investigated the free-fluid-phase volume (free-volume) effects due to helium interaction with the powder and the lumps. During the manometric experiment, helium penetration into the dry coal matrix resulted in slow relaxation of pressure. After exposure of coal to helium, there have been no significant changes of the macroscopic dimensions observed and the relaxation process can be attributed to microscopic ‘free-volume’ effects. Evolution of the sorption–desorption rates indicates that exposure to helium may change the texture and apparent (helium) density of dry coal.

The permeability of coal samples from Pittsburgh Seam was determined using carbon dioxide as the flowing fluid. The confining pressure was varied to cover a wide range of depths. The permeability was determined as a function of exposure time of carbon dioxide while the confining stress was kept constant. The porosities of the coal samples were found to be very low and most of the samples had porosities less than 1%. The permeability of these coal samples was very low—less than 1 μD. Since the objective of this study was to investigate the influence of CO2 exposure on coal permeability, it was necessary to increase the initial permeability of the coal samples by introducing a fracture. A longitudinal fracture was induced mechanically, and CT scans were taken to ensure that the fracture was present throughout the sample and that the sample was not damaged otherwise during the process. In this study, the permeability of coal was determined by using pressure transient methods. Two types of pressure pulses were used: A-spike and Sine-6 pressure transients. It was first established that the permeability of fractured coal samples did not change with exposure time when an inert gas (Argon) was used as the fluid medium in the experiments. However, the permeability of coal samples decreased significantly when carbon dioxide was used as the fluid medium. This reduction can be attributed to the coal swelling phenomenon. The results show that the permeability reduction in fractured coal samples can be over 90% of the original value, and the exposure time for such reductions can range from 1.5 days up to a week, typically about 2 days under laboratory conditions. The permeability decreased significantly with the increase in confining pressure. The higher confining pressure appears to close internal fractures causing a reduction in permeability.

Aqueous zinc oxide (ZnO) suspensions were prepared using a two-step preparation method in which an aggregated nanocrystalline ZnO powder was dispersed in water using a polyelectrolyte. The fluid showed anomalously high thermal conductivity when compared with the Maxwell and Hamilton-Crosser predictions. However, analysis of the particle size distribution showed that the fluid contained aggregated 20 nm crystallites of ZnO with a high volume fraction of particles larger than 100 nm. Sedimentation experiments revealed that particles settled out of the stationary fluid over times ranging from 0.1 hours to well over 10,000 hours. The size of the particles remaining in suspension agreed well with predictions made using Stoke's law, suggesting flocculation was not occurring in the fluids. Finally, a new concept of nanofluid stability is introduced based on the height of the fluid, sedimentation, Brownian motion and the kinetic energy of the particles.

Laser ablation of magnesium in deionized water (DW), solutions of DW and sodium dodecyl sulfate (SDS) with different concentrations, acetone and 2-propanol has been conducted. The results showed that ablation in acetone and 2-propanol yielded MgO and Mg nanocrystallites as isolated particles and agglomerated chains probably intermixed with organic residues resulting from the alteration/decomposition of the solvents under the high-energy conditions. Brucite-like Mg(OH)2 particles were mainly produced by laser ablation of Mg in either DW or DW-SDS solutions. Ablation in DW yielded particles of fiber-like shapes having a diameter of about 5-10nm and length-as long as 150 nm. Materials produced in DW-SDS solutions were composed of various size and shape particles. Some had rough surfaces with irregular shapes. Small particles were about 20-30 nm and larger particles were about 120 nm. Particles with rodlike, triangular, and plate-like shapes were also observed.

A combination of mechanical sieving and triboelectrostatic separation were used to separate fly ash. The results indicate that a simple separation of unburned carbon from fly ash is achievable at particle sizes of 74 and 44 microns. Subsequently, triboelectrostatic separations were conducted via a louvered plate separator. The results show that the final carbon content in the products, which can be as low as 1.5 % or as high as 60 % with different mineral components, can be further adjusted with the combination of sieving, louvered plate separator with a tribocharger made of different materials (copper and Teflon), and the location on the louvered plate where the fly ash particles were collected.

Many types of materials e.g., rubber, polymer, coal, change their volume and structure after absorption of gaseous and liquid substances. Various kinds of volume changes affect the accuracy of absorption measurements by gravimetric and manometric methods, the two major techniques currently employed. The errors associated with the volumetric effects, specifically, the case of carbon dioxide sorption on coal, were investigated. It was demonstrated that the resulting error in the buoyancy correction in the gravimetric method is equivalent to the corresponding error in the assumed void volume in the manometric method. It is suggested that the integration of the two methods, combined with the binary gas mixture technique of in-situ volume measurement, will contribute to dramatically improve the accuracy of absorption measurements for plastic materials.

The capture of CO2 from gas streams has been achieved by the utilization of amine-enriched fly ash carbon sorbent system. The initial fly ash carbon sorbents were generated by the chemical treatment of carbon-enriched fly ash concentrates with a 3-chloropropylamine-hydrochloride (CPAHCL) solution at 25 ◦ C. It was determined that these amine-enriched fly ash carbon sorbents performed at a 9% CO2 capture capacity based on commercially available sorbents. The chemical sorption performance of these amine-enriched fly ash carbon sorbents will be described within this paper. © 2003 Elsevier B.V. All rights reserved.

An industrial fly ash sample was cleaned by three different processes, which were triboelectrostatic separation, ultrasonic column agglomeration, and column flotation. The unburned carbon concentrates were collected at purities ranging up to 62% at recoveries of 62%. In addition, optical microscopy studies were conducted on the final carbon concentrates to determine the carbon forms (inertinite, isotropic coke and anisotropic coke) collected from these various physical-cleaning processes. The effects of the various cleaning processes on the production of different carbon forms from high carbon fly ashes will be discussed.

Triboelectrostatic separation has been investigated as a method for separating unburned carbon from coal combustion fly ash. It was found that when a fly ash is exposed to moisture before it undergoes separation, the charging properties of the components of the fly ash change significantly. The mineral and carbon components of the fly ash appear to charge oppositely to how they were charged before exposure to moisture. A correlation was found between the degree of charge reversal and the relative amounts of leachable ions, especially calcium and sodium ions, present on the surface of the ash.

Dry beneficiation of three high loss-on-ignition (LOI) fly ashes were conducted. The combination of two different types of dry separation techniques—ultrasonic sieving and triboelectrostatic separation—were used for this study. The results indicate that a simple separation of unburned carbon from fly ash is achievable at particle sizes of 149, 74 and 44 μm, and screening could be utilized as the rough separation mechanism for fly ash. Subsequently, triboelectrostatic separations were conducted on these different particle size fractions of the fly ash and indicated that the final carbon content in the products, as low as 2.5% or as high as 60%, can be further adjusted with the combination of dry sieving and triboelectrostatic separation.

A promising oil agglomeration process has been developed for the beneficiation of fly ash using a six-ft agglomeration column. Carbon concentrates have been isolated in recoveries greater than 60% and purities of 55–70%. The parameters studied include agitation speeds, airflow rates, slurry feed rates, solvent/ash ratios, and the use of various solvents as agglomerating agents. The effects of these variables on the quality of separation are discussed.

An ultrasonic technique was developed to measure the slurry concentration in an autoclave reactor. Preliminary measurements were conducted on slurries consisting of molten FT-200 wax, glass beads, and nitrogen bubbles at a typical Fischer–Tropsch (FT) synthesis temperature of 265 °C. The data show that the velocity and attenuation of the sound are well-defined functions of the solid and gas concentrations in the molten FT-200 wax. The results suggest possibilities for directly measuring solids concentration during operation of a three-phase slurry reactor under the reaction temperature and with molten FT-200 wax.

Local gas holdup, bubble diameter and bubble rise velocity in the nitrogen/Drakeol-10 oil system were measured at both laboratory (ambient temperature and pressure) and industrially relevant (high temperature and pressure) conditions using a dual conductivity probe in a slurry-bubble-column reactor. It was found that a constant superficial velocity, the Sauter mean bubble diameter decreases with increasing pressure and temperature. The bubble rise velocity significantly decreases as the pressure increases. Large bubbles rise faster than smaller bubbles. Akita and Yoshida's correlation [1] was utilized to compute the bubble size. Predicted values agree with the experimental data at high temperature.

Deactivation of Raney nickel is studied using the methanation rate data in a plug-flow reactor. It is shown that a model consisting of a constant and a monoexponential term describes the deactivation rate data very well suggesting that the catalytic activity of nickel is controlled by two components. One component seems to show a steady catalytic activity where the activity of the other component appears to decline exponentially. Transient tracing of the methanation on Raney nickel using 13 CO indicates that these correspond to two forms of intermediates adsorbed on two distinct catalyst sites. These findings are supported by rigorous statistical analyses of the correlation between model parameters and the goodness of the fit of data to the model.

An ultrasonic technique was developed to measure the concentration of solids in a three-phase slurry reactor. Preliminary measurements were taken on slurries consisting of water, glass beads, and nitrogen bubbles. The data show that the speed and attenuation of the sound are well defined functions of the solid and gas concentrations in the slurries. A simple model is proposed to correlate the concentration of solids with the measured characteristics of the ultrasonic signals.

The presence of Cu on Rh/SiO2 inhibited H2 chemisorption at 303 K and suppressed CO hydrogenation. TPD study shows that chemisorption of H2 on Cu−Rh/SiO2 is an activated process at 303 K.

A systematic temperature-programmed desorption (TPD) study of Mn-Fe catalysts was conducted. Hydrogen chemisorption on Mn-Fe catalysts is a highly activated process. Fe, MnO and MnFe 2 O 4 related desorption spectra have been assigned. Hydrogen does adsorb on the spinel phase (MnFe 2 O 4 ) in the form of activated adsorption. Carbon monoxide does not adsorb on the spinel phase. The results suggest that the spinel phase alone may not be an active phase for syngas conversion.

Multi-beam laser ablation in liquid was used to synthesize nanofluids of silver, Zinc, and aluminum in liquids. In our experiments, two single-mode, Q-switched Nd-Yag lasers operating at 1064 nm, pulse duration of 5.5 ns and 10 Hz rep rate were used. Our results have shown that both laser intensities and multi-beam ablation can increase the ablation rate and promote reduction of the particle sizes and particle size distribution. For silver, we have generated various samples of nanofluids with particles of sizes mainly in the range of 20 to 30 nm. These samples were stable for several months without the need of using dispersants or surfactants. However, for aluminum, the generated fluids were not stable and significant amount of solid precipitates were observed in the stock solutions. The size distribution was from about 5 nm to 300 nm indicating that the particle agglomerated and large distribution in sizes. Typical results from TEM analysis indicated that, for silver-water nanofluids, Ag nanoparticles were fcc single crystals. For aluminum, the particles had different shapes and sizes. These shapes were triangular, rectangular, and fibrous.

An industrial fly ash sample was cleaned by three different processes, which were triboelectrostatic separation, ultrasonic column agglomeration, and column flotation, cleaned an industrial fly ash sample. The unburned carbon concentrates were collected at purities ranging up to 62% at recoveries of 62%. In addition, optical microscopy studies were conducted on the final carbon concentrates to determine the types of carbon (inertinite, isotropic coke and anisotropic coke) collected from these various cleaning processes. The effects of the various cleaning processes on the production of different carbon types from fly ash will be discussed.

The U.S. Department of Energy has identified mineral sequestration as a promising CO2 sequestration technology option, converting anthropogenic CO2 and magnesium silicates into permanent carbonate minerals. Advantages of a mineral CO2 mitigation scheme include (1) enormous deposits of ultramafic rock such as serpentine [Mg3Si2O5(OH)4] and olivine [(Mg,Fe)2SiO4], exist in nature, providing a large potential capacity for CO2 sequestration, (2) resulting magnesite (MgCO3) product is thermodynamically stable and environmentally benign, and (3) overall process is exothermic with potential to be implemented with acceptable economics. High carbonation efficiencies were attained at elevated temperatures and supercritical CO2 pressures employing magnesium silicate ores. However, unlike olivine, serpentine required an additional high temperature pre-treatment step to drive off hydroxyl groups prior to carbonation. X-ray diffraction analysis (XRD) identified magnesite as the primary reaction product. Mechanistic aspects of mineral dissolution/magnesium carbonate precipitation were investigated with the aid of scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) of polished cross sections of solid process grains. Alterations to both thermally pre-treated serpentine and natural olivine grains revealed outer surfaces to be noticeably depleted in magnesium in comparison to its inner core. Formation of silica rims on the reaction surfaces may slow further dissolution of magnesium from silicate grains