Search

The principle of the conventional ultrasound test states that the detectable voids cannot be smaller than the acoustic wavelength. However, by using effective medium approximation, the fraction of small voids can be estimated by the variation of the effective density. In this study, a non-contacting ultrasound-based porosity fraction mapping methodology is developed for estimated small voids in coal with long operating wavelength in air. This novel ultrasonic technique based on the mechanical properties of coal offers a rapid scan of the effective density mapping and distribution of void fraction over a large sample area, which overcame the limitation of small voids detection in the conventional ultrasound testing. [ABSTRACT FROM AUTHOR]

To investigate the oxygen adsorption characteristics of coal with different moisture contents, a molecular model of bituminous coal from Datong coalfield was constructed based on 13C-NMR and XPS analysis, combined with molecular mechanics (MM) and molecular dynamics (MD) methods. The oxygen adsorption characteristics of coal were studied using the Grand canonical Monte Carlo (GCMC) method at a temperature of 293.15 K, with a pressure range of 0–10 MPa, and moisture contents of 3.27%, 5.13%, 6.92%, and 8.65%, respectively. The results show that the molecular formula of the Datong bituminous coal structure model is C159H134O35N2S, with a density of 1.35 g/cm3. High moisture content coal has a lower molecular surface area and porosity, and oxygen adsorption on coal molecules follows type I isotherms. The amount of physical oxygen adsorption decreases with increasing moisture content. The heat of physical adsorption is negatively correlated with pressure, and high moisture content accelerates the decrease in heat of physical adsorption caused by increased pressure. [ABSTRACT FROM AUTHOR]

Coal is a crucial energy source globally, but it poses environmental challenges due to high temperatures and harmful missions during combustion. This study investigates bituminous coal's oxidation combustion in low-oxygen environments using thermogravimetry and differential thermogravimetry tests. We explore the thermal behavior and kinetic properties of three coal samples during combustion. Our findings reveal that, as oxygen concentration decreases, the combined combustion index of the coal samples also decreases during the oxygen-absorption stage. Additionally, the apparent activation energy of coal increases with its conversion rate (temperature). We observe a shift in the reaction mechanism from three-dimensional dissipation mode to two-dimensional as the oxygen concentration decreases. Notably, the activation energy initially rises and then decreases with increasing conversion (temperature) during the pyrolysis combustion stage, with a shortened phase of increased activation energy at lower oxygen concentrations. Furthermore, the kinetic mechanism transitions from stochastic nucleation and growth to one-dimensional phase-boundary mode with decreasing oxygen concentration. These insights enhance our understanding of coal oxidation combustion in low-oxygen environments, contributing to strategies for mitigating coal spontaneous combustion. [ABSTRACT FROM AUTHOR]

To improve the efficiency of coalbed methane and recoverability of reservoirs, enhanced fracturing technology is usually required to improve the low porosity and permeability status of coal reservoirs. As a feasible method for strengthening permeability, microwave–LN2 freeze–thaw (MLFT) cycles modify the microscopic pore structure of coal through the coupled effect of temperature stress changes, phase change expansion, and fatigue damage. 1H nuclear magnetic resonance combined with fractal dimension theory was used to characterize quantitatively the pore system and geometric features of coal. The geometric fractal model constructed using the T2 spectrum indicates that the fractal dimensions Dp and De have high fitting accuracy, demonstrating that percolation and effective pores exhibit good fractal characteristics. Dp and De are correlated negatively and positively, respectively, with the cyclic parameters. The relevance analysis shows that the NMR fractal method can reflect the pore–fracture heterogeneity of coal, which has a significant effect on the percentage of fluid migration space. This study reveals that MLFT cycles have significant enhancement effects on promoting the extension of multi-type pores structures within the coal matrix, as well as the connectivity and permeability of cracks. [ABSTRACT FROM AUTHOR]

Facilitating the transition and new application of fossil energy sources are crucial to attaining carbon neutrality. Conversion of coals into graphitic carbons represents an effective route to achieve their high‐value utilization, while this process always involves corrosive/toxic chemical reagents and time‐intensive heating treatment. Here, this work reports a green, rapid, and efficient flash Joule heating (FJH) technique to produce high‐quality carbons from diverse coals within 1 s. The surface groups, defects, and graphitization degree of the resultant carbon materials are controlled during the instantaneous thermal shock process, and the relationships between the coal structures and the product properties are established. The results suggest that the anthracite with high coalification degree tends to form highly graphitic carbons at a peak temperature of ≈3300 K, presenting higher rate capability (79.1% capacity retention at 30 A g–1) and low relaxation time constant (τ0 = 0.27 s) toward capacitive energy storage. Besides, the flash carbon materials derived from lignite and bituminous coal with low coal rank show better capacitive performance with capacity above 80 F g–1 at 1 A g–1. This study evidences that the FJH technology holds great potential to steer coals into valuable carbon materials. [ABSTRACT FROM AUTHOR]

The effect of different oxygen concentration conditions on the heat release behaviour of bituminous coal during spontaneous combustion was investigated. Thermal analysis experiments were conducted using differential scanning calorimetry (DSC) and laws governing feature peak changes. Heat flow curves were utilised to identify thermal reaction stages, and the impact of oxygen concentration on heat flows during spontaneous coal combustion (SCC) was assessed. The determinants of heat release rates according to temperature and different oxygen concentration conditions were shown. The heat release process exhibited varying heat proportions at distinct stages. Using the feature point analysis method, the DSC curves could be used to show the apparent activation energy of the total SCC process for different oxygen concentrations. Findings showed a noteworthy influence of oxygen concentration on the overall SCC process. As oxygen concentration increased, the characteristic peak of the heat flow curve appeared earlier, the range of heat release and its heat release temperature rose, and the apparent activation energy also increased. A critical oxygen concentration range, between 7 and 12%, was identified, causing fluctuations in the development process of SCC. This article provided a theoretical basis for further investigation into the SCC process and mechanisms. [ABSTRACT FROM AUTHOR]

The extraction of coal from open-pit mines significantly contributes to environmental degradation, posing grave risks to human health and the operational stability of machinery. In this milieu, microbial dust suppressants leveraging microbially induced carbonate precipitation (MICP) demonstrate substantial potential for application. This manuscript undertakes an exploration of the dust mitigation efficiency, consolidation attributes, and the fundamental mechanisms of microbial dust suppressants across coal dust samples with varying metamorphic gradations. Empirical observations indicate that, in resistance tests against wind and rain, lignite coal underwent mass losses of 7.43 g·m−2·min−1 and 98.62 g·m−2·min−1, respectively. The production of consolidating agents within the lignite dust, attributable to the microbial suppressants, was measured at 0.15 g per unit mass, a value of 1.25 and 1.07 times greater than that observed in bituminous coal and anthracite, respectively. Scanning electron microscopy coupled with X-ray energy-dispersive spectroscopy (SEM–EDS) and X-ray diffraction (XRD) analyses illuminated that the consolidating products within the coal dust predominantly constituted calcite and vaterite forms of calcium carbonate. The consolidation mechanism of coal dust via microbial suppressants is articulated as follows: Subsequent to the application on coal dust, the suppressants induce the formation of carbonate precipitates with inherent adhesive properties. These carbonates affix to the surfaces of coal dust particles, progressively encapsulating them. Furthermore, they play a pivotal role in bridging and filling the interstices between adjacent dust particles, thereby culminating in the genesis of a dense, cohesive mass capable of withstanding erosive forces. [ABSTRACT FROM AUTHOR]

The growing use of local coal in Ethiopia has created challenges for cement factories due to inconsistencies in grade and quality. This paper presents the main areas rich in coal resource and potential sites for their development. Field studies have been conducted extensively in some areas to explore coal and analyze its compostion for potential use as major energy source in addressing the high energy demands for cement production across the country. Ethiopian coal beds vary in thickness from a few centimeters to 6 m and encompass a range of ranks from lignite to bituminous coal. Quality also varies widely, with ash content being a significant parameter of concern, as some studies indicate elevated levels. However, because of insufficient data, it is challenging to generalize other quality parameters accurately. Ethiopia's coal exploration dates back to the 1940s, with rough estimated deposits totaling 600 million tons nationwide. Currently, small‐scale producers satisfy 66% of the cement industries coal demand, which is the major consumers. Efficient coal mining enables the country to substitute significant amounts of imported coal, reducing large expenditures in foreign currency. Local coal production offers cost savings, job creation, streamlined transport, and reduced import reliance, thereby preserving hard‐earned foreign currency and granting the country a competitive edge. [ABSTRACT FROM AUTHOR]

The cause of Paget's disease of bone (PDB) is unknown. It emerged as a distinct entity in Britain in the late nineteenth century when it was prevalent, and florid presentation not uncommon. Epidemiological surveys in the 1970s showed that Britain had a substantially higher prevalence of PDB than any other country. Studies in the late twentieth and early twenty-first centuries have documented an unexplained change in presentation, with a greatly reduced prevalence and less severe disease than formerly. The emergence of PDB in Britain coincided with rapid industrialization which, in turn, was driven by the use of coal for energy. In the home, bituminous coal was customarily burnt on an open hearth for heating. Using data on coal production, population size, and estimates of domestic use, the estimated exposure to domestic coal burning rose threefold in Britain during the nineteenth century and began to fall after 1900. This pattern fits well with the decline in PDB documented from death certification and prevalence surveys. Colonists moving from Britain to North America, Australia and New Zealand established coal mines and also used coal for domestic heating. PDB was found in these settler populations, but was largely absent from people indigenous to these lands. In all parts of the world PDB prevalence has fallen as the burning of coal in open hearths for domestic heating has reduced. The nature of the putative factor in coal that could initiate PDB is unknown, but possible candidates include both organic and inorganic constituents of bituminous coal. [ABSTRACT FROM AUTHOR]

Acid baking treatment is widely used to extract rare earth elements (REEs) from refractory rare earth bearing minerals such as monazite and xenotime. Since these REE minerals have been identified in coal-based sources, a parametric study was conducted to evaluate the impact and optimize the parametric values associated with the acid-baking process when treating a bituminous coal source. The parameters studied using a three-level statistical experimental program were acid baking time, acid solution concentration, baking temperature, and acid solution-to-solids ratio and each were found to significantly impact REE and contaminant element recovery. An increase in baking temperature up to around 250°C improved the light and heavy REE recovery values by more than 50 absolute percentage points relative to performances achieved when direct leaching. Acid baking was needed to dehydroxylate the clays and liberate the REE minerals, which allowed access for the acid to solubilize the REEs. Acid concentration of the solution used for acid baking was studied as a means of minimizing the amount of acid needed to achieve a target REE recovery. However, thermo-gravimetric and differential scanning calorimetry analysis (TGA-DSC) of sulfuric acid under oxidizing atmosphere revealed that the addition of water decreased the evaporation temperature, which explains the lower REE recovery values obtained when using lower acid concentrations. Using pure sulfuric acid at an acid-to-solid ratio of 0.8:1 resulted in recovery values of around 70% for both LREEs and HREEs. The decomposition reaction time was relatively quick with 65% of the TREEs recovered within the first 10 minutes. Water leaching experiments performed on the acid-baked products under a temperature of 25°C instead of 75°C revealed an increase in REE recovery by 10 absolute percentage points, which was likely due to the high solubility of REE-sulfates at room temperatures. [ABSTRACT FROM AUTHOR]

This investigation assessed the influence of a cationized pyrolysis oil (PO) produced by the pyrolysis of used car tires on coal flotation using an extended Historical Data (HD) design. The effect of operating factors, including pulp solid content, diesel oil, pine oil, and pyrolysis oil dosages, was examined using experimental and statistical analyses. Fourier Transform Infrared Spectroscopy (FTIR) measurement showed that PO contains hydrocarbons and their oxides (alkane, ester, or carboxylic acid). Statistical analysis using analysis of variance (ANOVA) revealed that concentrate ash content is influenced by solid content and pyrolysis oil concentration through a non-linear trend such that maximum ash removal may be obtained at the middle level of solid content and in the absence of PO. The solid content and diesel oil had a significant impact on process yield. Maximum yield was achieved at the low and middle levels of solid content and collector dosage, respectively. A comparison of individual and interaction effects of significant operating variables showed their complicated effects on process responses. Overall, the PO affected the coal flotation efficiency adversely, which can be due to the interaction between hydrophilic groups in the PO structure and the oxide nature of non-combustible materials in coal particles. [ABSTRACT FROM AUTHOR]

Autoignition and smoldering of coal dust have gained great safety concern in both industry and mining due to their high susceptibility to heating. To better understand their controlling mechanism, autoignition and smoldering of bituminous coal particles (1-mm diameter) and coal powders (0.1-mm diameter) in the form of bulk layer heated by 4–45 kW m−2 thermal radiation levels were systematically studied. The results showed that the critical heat flux was between 4 and 5 kW m−2 for both samples. Under 5 kW m−2, no morphology change was detected on surface, but internal ignition and smoldering occurred. Partial oxidation and intense glowing ignition were observed under heat fluxes of 10 and 15–45 kW m−2, respectively. The average glowing temperature was 782.4 ± 19.6 K, while the maximum temperature during smoldering changed in 976–1206 K. Smoldering spread rate of powder sample was larger than that of particle sample due to emerged cracks during heating and larger specific surface area, and both spread rates linearly depended on heat flux. The linear dependency of ignition time to the power of − 0.5 on heat flux in classical ignition theory was found still valid for glowing ignition of both samples, and apparent thermal inertia and critical heat fluxes were quantitatively estimated. In all smoldering tests, mass loss rates exhibited a bimodal feature, with first peak charactering moisture evaporation, while the second peak indicating coal-oxygen reaction. Under 35 and 45 kW m−2 heat fluxes, a unique faint blue flame appeared which depended more on surface temperature than on mass flux of pyrolyzates. This contribution may deliver useful reference for evaluation of coal fire risk and help mitigate hazard of smoldering in practical applications. [ABSTRACT FROM AUTHOR]

It is paramount that solutions to questions of energy security for a developing nation be addressed through its internal resources. India, endowed with 23.8 billion tons of deep un-minable lignite, faces the challenge of economically sustainable extraction. This study presents a comprehensive assessment of lignite's suitability for underground coal gasification (UCG) compared to bituminous coal. Employing a multi-dimensional approach, combining single-step and distributed activation energy model of pyrolysis kinetic modeling with extensive physicochemical analysis (proximate and ultimate analyses, FTIR, SEM–EDX, XRD), revealed that lignite has a lower activation energy making it suitable for UCG. This finding, highlighted by kinetic modeling, is substantiated by the lignite's structural properties as identified in physicochemical analysis. This study leverages machine learning for higher heating value prediction, finding long short-term memory as the most effective model compared to five other models based on the R2 score and error values. Additionally, an XGBoost algorithm-based model predicts syngas heating value and yield while showcasing the application of machine learning in enhancing energy prediction accuracy. The economic analysis, applied for a 50 MW power plant framework, determines the unit costs for syngas and electricity production to be 7.49 and 6.71 $/GJ and 53.68 and 59.93 $/MWh for the samples of lignite and bituminous coal, respectively. The sensitivity analysis revealed that the energy content in syngas is the most significant parameter. These comprehensive findings validate lignite's potential for energy production in India, offering insights for similar resource optimization in other developing countries. [ABSTRACT FROM AUTHOR]

The effects of water soaking on the microstructure and spontaneous combustion characteristics of coal samples were investigated by scanning electronic microscopy (SEM), Fourier transform infrared (FTIR) spectrometer, and temperature programmed testing system (TPTS). The SEM results showed that the pore structures on the surface of water−soaked coal were more developed than raw coal, the pores increased and enlarged, and the phenomenon of water absorption swelling occurred. At the same time, water soaking had a certain influence on the functional groups in coal. The results of FTIR clearly illustrated that the surface functional groups of water−soaked coal were more active, and the contents of functional groups such as hydroxyl, methylene, aliphatic ether and aromatic ether all increased to varying degrees. During the low−temperature oxidation process, the analysis results of TPTS indicated that the oxygen consumption rate and the production of CO, C2H4, and other gases of water−soaked coal were higher. Based on the analysis method of CO, CO/CO2 and C2H4 gas growth rate, the three peaks of the curve obtained correspond to the characteristic temperatures of each oxidation stage of the coal samples. The critical temperature, dry cracking temperature and fission temperature of water−soaked coal were 60 ± 10 ℃, 90 ± 10 ℃ and 120 ± 10 ℃, respectively, which was 10 ℃ lower than raw coal. The apparent activation energy (Ea) of coal was calculated by the CO model and fitted in sections. It can be seen that the Ea of water−soaked coal at different stages of low−temperature oxidation was lower, and the maximum difference was 2.1 kJ/mol. Therefore, from the above results, it inferred that the activity of bituminous coal became stronger after soaking in water, which may be due to the effect of soaking on the surface structure and active groups of coal, thus showing a higher risk of spontaneous combustion. [ABSTRACT FROM AUTHOR]

Implementing a co-combustion technology in coal-fired plants using biomass waste is a promising option to alleviate environmental pollution, reduce fuel costs, and minimize waste. The considerable potential of palm oil waste is believed to be able to substitute coal as a raw material in a coal-fired power plant. However, since each coal has different compositions and biomass generally has a high alkali content, the propensity of slagging and fouling during co-combustion needs to be clarified. This research evaluates the co-combustion ash characteristics of different types of coal, which is co-combusted with 25% palm oil biomass waste. The combustion test employs a drop tube furnace, where the produced ash composition and its morphology are investigated using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction. The results show that the ash melting temperature of the three types of coal mixed with biomass is reduced, although insignificant. Bituminous coal has a low potential for slagging and fouling since SiO2 and Al2O3 dominate the coal ash composition. In addition, lignite coal has low SiO2 and Al2O3 contents but high alkali contents (K and Na). As confirmed by SEM-EDS analysis, probe observations also show that lignite coal co-combustion with empty fruit bunch and frond waste has higher slagging and fouling risks. [ABSTRACT FROM AUTHOR]

Currently spray dust reduction is one of the most widely used dust removal methods in coal mines. The wetting performance of water on coal has a direct impact on spray dust reduction, therefore, adding wetting agents such as surfactants in water can improve the wetting performance of water on coal. In order to investigate the effect of various surfactants on the wettability of bituminous coal dust, four types of surfactants, namely, Rapid Penetrant T, 1227, BS-12 and APG, were used to investigate the wettability of bituminous coal by combining molecular simulation techniques and laboratory experiments. On the one hand, the interfacial system of surfactant aqueous solution was constructed by means of molecular simulation, the hydrophilicity of surfactant itself was analyzed based on the theory of the number of hydrogen bond formation and the radial distribution function, and the surface tension experiments of 4 reagents were carried out, and it was found that the Rapid Penetrant T reagent forms the most number of hydrogen bonds being 398, and the radial distribution function curve peaks at 1.99 ×10−10 m at the earliest time, which is the easiest to be adsorbed with H2O molecules, and the experimental results also showed that the Rapid Penetrant T reagent has the strongest weakening of the surface tension of the water, i.e., the smallest surface tension, which is 24.4 mN/m. On the other hand, through the electrostatic potential calculation, combined with the constructed surfactant/water/bituminous coal ternary adsorption system interaction energy analysis, the effect of four surfactants on the wettability of bituminous coal was investigated, and the experiments on the settlement and contact angle of bituminous coal in 4 reagents were carried out respectively. The results showed that the potential difference between the site and the water molecules after the Rapid Penetrant T molecules combined with the bituminous coal molecules is the largest, being 6.8535 eV, and the interaction energy between it and the bituminous coal is also the largest, being −2705.12 kJ/mol, and the experimental results also showed that the two kinds of bituminous coal have the smallest settling time in the Rapid Penetrant T reagent being 26.3 and 10.22 s respectively, and the smallest contact angle are 25.8° and 21.7° respectively. Thus, the study shown that the molecular simulation results are in agreement with the experimental results, and all of them validate that the anionic surfactant Rapid Penetrant T has the best wettability performance on bituminous coal.

The vitrinite-rich concentrates were extracted respectively from the Datong bituminous coal and the Xinjiang bituminous coal by the density gradient centrifugation method. The activated carbons were prepared by physical activation with carbon dioxide using the above raw coals and vitrinite. The structural properties of vitrinite and the corresponding raw coals were compared, and the characteristics of crystallite and pore structure were analyzed after the carbonization and CO2 activation process. The differences of aromatic and aliphatic hydrocarbon structures of coal and its vitrinite samples were analyzed by Fourier transform infrared spectroscopy. Microcrystalline structure parameters and aromaticity index of coals, chars and activated carbons were analyzed by X-ray diffractometer. The pore structure parameters of chars and activated carbons were studied by the low-temperature nitrogen adsorption method. Compared with raw coals, the crystallite unit sizes of vitrinite were smaller, the length of aliphatic hydrocarbon chain was shorter, and the number of branch chains was larger than those of the corresponding coals, which was beneficial to enhance the fluidity in the carbonization process. Moreover, the weight loss rates of vitrinite were higher, and the weight loss peaks were wider than that of the coals during the carbonization process by thermogravimetric analyzer. The above differences of structural properties and carbonization reactivity of coal and its vitrinite samples could affect the structure characteristics of chars. The results showed that the crystallite lamella size and stacking thickness of vitrinite chars were both increased after carbonization at 850 ℃, while the stacking thickness of crystallite in coal chars was decreased, which indicated that the differences of maceral mainly affected the vertical stacking of crystallite lamella during carbonization. Meanwhile, it led to higher aromaticity and larger BET specific surface area of both vitrinite chars. After the CO2 activation process, the stacking thickness and lamella size of crystallite in activated carbons were lower than that of the corresponding chars, indicating that the crystallite unit got burnt by CO2 activation. The dominant micropore structures were obtained after activation process. The BET specific surface areas of activated carbons from vitrinite reached 744.1 and 797.4 m2/g, respectively, which were significantly higher than that of activated carbons from coals. The micropore and mesopore volumes of vitrinite-based activated carbons were both higher than that of coal-based activated carbons, and the micropore volumes were 1.7−2.2 times more than that of coal-based activated carbons. The above results indicated that the chars with higher aromaticity and more porosity were beneficial to generate micropore structure during activation process.

Purpose. Definition of correlation between residual gas content in coal stored in closed temporary storages and coal’s natural gas content, which depends on the weather, train’s transportation time and the amount of air ventilating closed storage needed to maintain methane concentration below threshold limit value. Methods. Analysis of the transportation process from excavation site to the temporary storages, which takes into account transportation duration, carriages type and atmospheric temperature; experimental determination of effective diffusion coefficient for methane in coal fragments; theoretical research of thermal pattern dynamic for coal mass in train carriages; computational analysis of coal’s gas content dynamic during transportation and correlation between residual coal’s gas content and required airflow rate for temporary storage ventilation. Findings. This paper represents the results of research of change of coal’s gas content during excavation, transportation to the surface and further transportation to temporary storages by train by evaluating influence of physical and chemical properties of coal, effective diffusion coefficient in particular, and mean atmospheric temperature. According to procured data, value of effective diffusion coefficient, which depends on coal transportation time and its mean particle diameter, increases with the rise of mean coal mass temperature. Calculation of mean coal mass temperature per unit of volume during transportation is based on approximate method of Bubnov – Galerkin. Residual coal’s gas content after transportation is calculated as difference between value of coal’s gas content after loading into carriages and coal’s gas content after delivery to temporary storages. Correlation between residual coal’s gas content and required airflow rate for temporary storage ventilation has been established. Application field of research. The results of the study can be used to ensure methane safety during temporary storage of coal raw materials in closed warehouses.

Co-thermal chemical conversion of coal and biomass is one of the important ways to realize efficient and clean utilization of coal. In this study, a typical Ningdong coal-Yangchangwan bituminous coal and cow manure were used to study the synergistic effect of intrinsic alkali, alkaline earth metals (AAEM) and organic matter on the co-gasification of coal and biomass by thermogravimetry analyzer (TG). The results showed that AAEM had obvious synergistic promotion effect on the gasification of a bituminous coal-cow manure mixture in the isothermal gasification (1000 ℃), whereas the organic matter will show the opposite effect on the process. To further investigate the effect of organic matter on the gasification process, the influence of organic matter on non-isothermal (25-1000 ℃) gasification reaction was investigated with heating rate of 10 ℃ /min, the kinetic parameters of the gasification reaction were obtained by Coats-Redfern method. The increase of biomass mass fraction in the sample facilitates the migration of alkali metals from the material to the solid phase. The possible mechanism of the synergistic effect of intrinsic AAEM/organic matter on the co-gasification process was proposed. [ABSTRACT FROM AUTHOR]

Co-combustion of coal and biomass can reduce carbon emissions from fossil fuel use and enable cleaner energy use. The combustion process of bituminous coal (BC) with three typical biomasses: agricultural waste (Wheat Straw, WS), forest waste (Pine, P), and marine biomass waste (Enteromorpha, EN) was investigated using the TGA and the controlled diffusion mechanism model. When the combustion thermodynamic behavior of the blends was analyzed, it was found that when the proportion of biomass blending increases, the ignition point temperature of its blend with coal decreases and improves the combustion performance of the fuel. WS and P promote combustion of BC/WS and BC/P blends, respectively. EN incorporation gives BC/EN blend a slagging tendency and reduces the burnout of the blend. The kinetic parameters of the three fuel blends were calculated using Coats–Redfern method. The kinetic mechanism analysis shows that the combustion mechanisms of the three biomass-coal blends are in accordance with the diffusion mechanism model, and the activation energy of the blends decreases with the increase in the biomass blending ratio after the temperature increases to 350 °C. After adding biomass its co-combustion with coal has obvious synergistic interactions, in which coal and enteromorpha synergistic effect is the best. The change of activation energy of mixed combustion of coal and biomass is affected by the content of volatiles in biomass. Coal-biomass mixtures can improve bituminous coal combustion. Alkali metals in biomass have an inhibitory effect on co-combustion of the coal-biomass mixture. [ABSTRACT FROM AUTHOR]

This essay provides a revised history of the James River Canal, the first navigational canal with locks in the United States. It corrects previous assumptions about the location of the canal and emphasizes the importance of preserving the canal-related archaeological sites and structures. The construction of the canal involved the work of John Ballendine and his son Thomas, as well as the James River Company. The canal played a significant role in transportation and trade in colonial America, particularly in the Richmond area. Although it was eventually overshadowed by railroads, the remains of the canal can still be seen today in the James River Park system. [Extracted from the article]

Purpose: In coal mining regions, soil organic carbon content is elevated by the deposition of coal dust through natural settling and transportation. However, the contribution of organic carbon content from coal dust of varying coalification degrees is inconsistent. Its active involvement in soil carbon transformation processes and its influence on soil bacterial communities remain to be elucidated. Methods: This study conducted a 120-day indoor constant-temperature soil incubation experiment, with sampling carried out at 5, 15, 30, 50, 80, and 120 days of incubation. The research aimed to investigate the impact mechanisms of three coalification degrees of coal dust, lignite, bituminous coal, and anthracite, along with a corresponding control group, on soil carbon dioxide (CO2-C) accumulation mineralization, soil active organic carbon, and soil bacterial community structure. Results: Lignite exhibited the highest promotion of soil CO2-C mineralization, showing a 9.74% increase compared to the control (CK). The impact of the three types of coal dust on soil readily oxidizable organic carbon (ROC) and microbial biomass carbon (MBC) content decreased to varying degrees with increasing incubation time. Furthermore, coal dust was found to enhance the prevalence of dominant bacterial taxa in the soil, with an increase in groups such as Proteobacteria, Actinobacteria, and Acidobacteria, and the extent of the increase was correlated with the coalification degree. Conclusion: Coal dust with lower coalification degrees has a stronger impact on the soil compared to higher coalification degrees, and these effects tend to manifest in the short term. Therefore, further exploration of this aspect should focus on long-term effects. [ABSTRACT FROM AUTHOR]

Coal based thermal power plants contribute about ~ 72% of the power generation in India. Indian coal is of bituminous type, having a high ash content with 55–60% ash. Due to considerable environmental importance the collected fly ash has become a subject of worldwide interest in recent years. In the present study radon exhalation rate and the activity concentration of 226Ra, 232Th and 40K radionuclides in fly ash samples from Kasimpur Thermal Power Plant, Aligarh, Uttar Pradesh, India have been measured by 'Sealed Can technique' using LR-115 type II detectors and a low-level NaI (Tl)- based gamma-ray spectrometer, respectively. Radon exhalation rate has been found to vary from 57.1 ± 5.3 to 119.4 ± 7.7 mBq m−2 h−1 with an average value of 87.3 ± 5.8 mBq m−2 h−1. Activity concentration of 226Ra ranged from 20.0 ± 8.5 to 30.0 ± 9.7 Bq kg−1 with an average value 23.4 ± 9.0 Bq kg−1, 232Th ranged from 17.0 ± 9.9 to 69.0 ± 13.8 Bq kg−1 with an average value of 46.5 ± 12.1 Bq kg−1 and 40K ranged from 130.0 ± 7.2 to 332.0 ± 11.1 Bq kg−1 with an average value of 177.0 ± 8.1 Bq kg−1. [ABSTRACT FROM AUTHOR]

Investigating surfactant effects on the floatability of Wiser bituminous coal holds significant importance in improving coal cleanliness and utilization value. Using density functional theory and molecular dynamics simulation methods, this study constructed models of Wiser bituminous coal and examined the impact of different surfactants, including the anionic surfactant sodium dodecyl benzene sulfonate, the cationic surfactant hexadecyl trimethyl ammonium bromide (CTAB), and the non-ionic surfactant fatty alcohol ethoxylated ether. The focus was on investigating the charge distribution characteristics of these molecules and the modifying effect of binary surfactants on the hydrophobicity of bituminous coal. Results revealed that the maximum electrostatic potential was concentrated near oxygen/nitrogen/sulfur-containing functional groups like sulfonic acid groups, quaternary ammonium cations, ethylene oxide, hydroxyl groups, carboxyl groups, and sulfur bonds. These functional groups exhibited a propensity for accepting/delivering electrons to form hydrogen bonds. Among the surfactants tested, CTAB revealed the slightest difference in frontier orbital energy, measuring 3.187 eV, thereby demonstrating a superior trapping ability compared with the other two surfactants. Adsorption reactions within the system were determined to be spontaneous, with over 60% of the interaction force attributed to electrostatic forces. Moreover, the repulsive force magnitude with water molecules followed the trend: sulfonate group (2.20 Å) < ethylene oxide (2.43 Å) < quaternary ammonium cation (2.57 Å), indicating more excellent water repellency of CTAB. Findings showed that CTAE binary surfactants proved most effective in modifying the hydrophobicity of bituminous coal. This study offers valuable insights into reducing waste, pollution, and resource wastage. [ABSTRACT FROM AUTHOR]

Coalbed methane (CBM) is the only unconventional gas in Poland with estimated recoverable resources. The prospects for developing deep CBM have been explored in recent years by drilling deep exploration wells within the depocenter of the Upper Silesian Coal Basin. The purpose of this study is to analyze the occurrence and potential for CBM extraction in this area of the basin, which can be considered prospective due to the confirmed presence of significant amounts of gas and thick coal seams at depths > 1500 m. The study examined the vertical and horizontal variability of the gas content in the studied area, the coal rank in the seams, thermal conditions, and coal reservoir parameters. The gas content in the seams, reaching more than 18 m3/t coaldaf at a depth of 2840 m, and indicative estimated gas resources of 9 billion m3 were found. The high gas content is accompanied by positive thermal and coal rank anomalies. The permeability and methane saturation of the coal seams are low, and therefore, potential methane production may prove problematic. However, the development of CBM extraction technologies involving directional drilling with artificial fracturing may encourage gas production testing in the study area. [ABSTRACT FROM AUTHOR]

Heavy metal contamination in wastewater has been an issue for the environment and human health nowadays. If these wastewaters are exposed directly to the environment, it will be hazardous for the environment and personal health. So, it is very necessary to treat these ground and surface wastewater before exposing into environment. For this, an effective technique were developed which removed heavy metals from wastewater easily, economically and effectively. The cellulose nano-crystals (CNC) were isolated from banana rachis fibres by a series of chemical treatments as well as 50% H2SO4 hydrolysis successively. On the other hand, raw Indonesian type's bituminous coal was collected from Noapara industrial area, Jashore, Khulna and was pyrolysed at 700°C, activated by 2M HCl at 700°C and also carbonised at 500°C followed by activation with 30% H3PO4 acid. In this process, adsorbent of modified charcoal-CNC composites was used for the removal of methyl orange dye and five heavy metals, such as Ni(II), Pb(II), Cr(III), Cd(II) and Co(II)), from wastewater and the uptake capacity, selectivity and removal efficiency were also discussed. The filtering efficiency of wastewater purifications were characterised by FTIR, X-RD, TGA, SEM analysis. Finally, wastewater solution and the filtrates solutions were characterised by UV-Vis, and AAS techniques. [ABSTRACT FROM AUTHOR]

To effectively utilize ventilation air methane (VAM), it is proposed to pass it into the boiler of the coal‐fired power plant for mixed combustion. However, the different types of thermal coal utilized present distinct characteristics when mixed with VAM. In this paper, lignite, bituminous coal, and anthracite are selected to study the CH4 conversion rate, system ignition temperature, and NO emission characteristics of the VAM‐pulverized coal coupled system on a fluidized bed experimental platform. The experimental results show that the ignition temperatures of VAM are 748, 736, and 732 °C when the CH4 concentration is 0.25, 0.5, and 0.75%. After the addition of thermal coal, the ignition temperature decreased significantly. When the CH4 concentration is 0.25%, the ignition temperature of the lignite‐VAM system is the lowest, which is 450 °C. Anthracite has the strongest catalytic effect on CH4 combustion. When the heating rate is 5 °C /min, the reaction rate of CH4 is the fastest in the anthracite‐VAM coupled system. Under laboratory conditions, the peak NO concentration in the coal‐VAM coupled system was lignite > bituminous coal > anthracite at different CH4 concentrations, and the CH4 in VAM had a reducing action on the NO generated during mixed combustion, with a stronger reducing effect observed as the CH4 concentration increased. The results of this study can lay the foundation for the industrial application of the mixed combustion of VAM and thermal coal, and be of great significance for solving the practical problems caused by the change of boiler coal types. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Understanding the macro-kinetics of coal–oxygen reactions is the theoretical foundation for combating coal spontaneous combustion, with focus on obtaining kinetic parameters. There are still open questions, including which thermal analysis kinetics processing methods (TAKPMs) output more confident kinetic parameters, and how these TAKPMs respond in terms of computational accuracy when experimental conditions change. This study evaluated these questions quantitatively, and yielded the following noteworthy findings. (1) Integral processing-based multi-scan methods were more data-friendly than differentials, which produced over 40% error due to thermal noise. (2) Combined 29 widely used most probable reaction mechanism functions (MPRMFs), like Jander, Ginstling–Brounshtein, and Zhuralev–Lesokin–Tempelman, with five popular single-scan methods, and ran 870+ calculations under six experimental conditions. Using traditional model fitting to identify MPRMFs can introduce errors of 4.08–275.49% (median 121.99%). (3) Applied spectroscopy–Málek–Popescu coupling for high-confidence MPRMFs. Its integration into single-scan methods improved computational accuracy, reducing error to the range of 1.84–76.20%. However, a median of 37.76% error indicates that some single-scan methods still failed to yield satisfactory results. (4) Notably, the accuracy of single-scan methods correlated significantly with heating rate, with various methods showing positive or negative correlations. From 5 to 15 K/min, the increase/decrease in accuracy ranged 10.63–244.25% (with median of 51.40%). These findings underline the need for a case-by-case selection of TAKPMs based on experimental conditions, ensuring more confident kinetic parameters. This study introduced a workflow, exemplified with bituminous coal, to assist researchers in selecting the optimal TAKPMs for diverse experimental scenarios. [ABSTRACT FROM AUTHOR]

This study investigates the paleodepositional conditions of the No. 6 Seam of the Madzaringwe Formation in Makhado and Voorburg south area of the Soutpansberg Coalfield (Limpopo Province, South Africa) utilizing organic petrography and inorganic geochemical proxies. The coals are predominantly high-volatile bituminous B-A rank with high ash yields (avg. 36.1 wt%), characterized by high-vitrinite (~ 41.5 vol%), moderate-to-high inertinite (9.8 vol%–33.7 vol%) and low liptinite (~ 2.3 vol%). The distribution of inertinite varies among different coal horizons (from bottom-lower to middle-upper), suggesting differential oxidation conditions and/or paleofire occurrence. Vitrinite-to-inertinite (V/I) ratio, tissue preservation–gelification index (TPI–GI), and groundwater–vegetation index (GWI–VI) plots, indicate that the peat-forming forest-swamp vegetation accumulated under mesotrophic-to-rheotrophic hydrological conditions. The presence of structured macerals (i.e., telinite, collotelinite, fusinite, and semifusinite) suggests well-preserved plant tissues, whereas framboidal pyrite and sulphur content (0.24 wt%–2.16 wt%) point to brackish-water influence at the peat stage. The coals contain quartz, kaolinite, siderite, muscovite, dolomite, calcite, and pyrite minerals, most of which were likely sourced from felsic igneous rocks. The Al/(Al+Fe+Mn) and (Fe+Mn)/Ti ratios for the studied samples range between 0.24–0.97 and 0.57–70.10, respectively. The ratios, Al–Fe–Mn plot, and presence of massive botryoidal-type pyrite imply some influence of meteoric waters or fluids from hydrothermal activity post-deposition. Moreover, the chemical index of alteration (CIA: 98.25–99.67), chemical index of weathering (CIW: 92.04–97.66), and A–CN–K ternary diagram suggest inorganic matter suffered strong chemical weathering, indicating warm paleoclimatic conditions during the coal formation. [ABSTRACT FROM AUTHOR]

During chemical looping combustion (CLC) and chemical looping gasification (CLG) of coal, the release, migration, and speciation of mercury in coal are significantly influenced by oxygen-carrier materials; however, the underlying mechanism remains inadequately addressed. In this work, the effect of a typical iron-based oxygen carrier on the release behavior of mercury from a bituminous coal and a lignite was investigated based on the Ontario-Hydro method. It is found that the effect of the iron-based oxygen carrier is attributed to three aspects: the enhanced release rate of mercury from coal, the adsorption of the released mercury, and the oxidization of gaseous Hg0 into Hg2+. With the increasing temperature, the adsorbance of mercury by the iron-based oxygen carrier decreases, while the oxidation of mercury enhances. Even at 900 °C, the adsorbance of mercury by the oxygen carrier remained at 0.1687 g/g, with a relative content of Hg2+ at 22.55%. Additionally, it was observed that iron-based oxygen carriers can physically absorb both Hg0 and Hg2+, while chemisorption refers to complex-compound formation between the iron-based oxygen carrier and mercury. [ABSTRACT FROM AUTHOR]

Introduction: Humic substances (HS) are increasingly being applied as crop plant biostimulants because they have been shown to increase plant productivity, especially under environmentally stressful conditions. There has been intense interest in elucidating the HS molecular structures responsible for eliciting the plant biostimulant response (PBR). The polar and weakly acidic carboxylic (COOH) and phenolic hydroxyl (ArOH) functional groups play major roles in the acid nature, pH dependent solubilities, conformation, and metal- and saltbinding capabilities of HS. Reports on the role played by these groups in the PBR of HS found growth parameters being both positively and negatively correlated with COOH and ArOH functionalities. Materials and methods: To investigate the role of COOH and ArOH in HS biostimulant activity we used a humic acid (HA), purified from an oxidized sub bituminous coal to prepare HAs with COOH groups methylated (AHA), ArOH groups acetylated (OHA), and with both COOH and ArOH groups methylated (FHA). The original HA was designated (NHA). The four HAs were subjected to elemental, 13C-NMR, FTIR, and EPR analyses and their antioxidant properties were assessed using the trolox equivalents antioxidant capacity assay (TEAC). 13C-NMR and FTIR analysis revealed significant alkylation/acetylation. To determine the effects of alkylating/acetylating these functional groups on the HA elicited PBR, the HAs were evaluated in a plant bioassay on corn (Zea mays L.) seedling under nutrient and non-nutrient stressed conditions. Treatments consisted of the four HAs applied to the soil surface at a concentration of 80 mg C L-1, in 50 ml DI H2O with the control plants receiving 50ml DI H2O. Results: The HA-treated plants, at both fertilization rates, were almost always significantly larger than their respective control plants. However, the differences produced under nutrient stress were always much greater than those produced under nutrient sufficiency, supporting previous reports that HA can reduce the effects of stress on plant growth. In addition, for the most part, the HAs with the alkylated/acetylated groups produced plants equal to or larger than plants treated with NHA. Conclusion: These results suggests that COOH and ArOH groups play a limited or no role in the HA elicited PBR. Alternatively, the HA pro-oxidant to antioxidant ratio may play a role in the magnitude of the biostimulant response. [ABSTRACT FROM AUTHOR]

Dr. Arthur Harold Victor Smith, a highly respected palynologist, passed away in January 2023 at the age of 99. He dedicated his career to studying pollen and spores, particularly in relation to coal resources in Britain. Dr. Smith's research focused on Carboniferous palynology, coal petrology, coal provenance, and thermal maturation. His most notable achievement was the publication of "Smith and Butterworth," a comprehensive account of Late Carboniferous pollen and spores. Dr. Smith's work made him one of the most influential palynologists of his time. In addition to his contributions to the field of palynology, he was also involved in bird monitoring and conservation efforts in South Yorkshire. [Extracted from the article]

Due to the semi-enclosed space of underground coal seams and the implementation of nitrogen injection measures, most coalfield fires occur in multi-atmosphere environments. At present, there is little research on the combustion situations and kinetics of coal under multi-atmosphere conditions. In this paper, simultaneous thermal analysis experiments were conducted to investigate the combustion behaviors of bituminous coal and anthracite in O2-CO2-N2 atmospheres with different volume fractions. A new index for quantitative characterization of coal combustion situation in multi-gas mixing atmospheres was proposed based on the combustion situation intensity index and heat release rate. Furthermore, a method to predict the coal combustion situation using artificial neural network (ANN) was proposed. The results showed that the combustion rate decreased with the increase in CO2 volume fraction and the decrease of N2 volume fraction under multi-gas mixing atmospheres. The volume fraction changes in inert gases had little effect on the ignition temperature or burnout temperature and had a greater effect on the combustion reactivity of bituminous coal. In a 15% O2-5% CO2-80% N2 atmosphere, the combustion could be inhibited for bituminous coal, while being promoted by anthracite. The combustion situation of bituminous coal in a 15% O2-25% CO2-60% N2 atmosphere was greater than that in air. Based on the proposed coal combustion situation index and the selected optimal ANN model, the coal combustion situation in O2-CO2-N2 atmospheres could be well predicted. This paper provides a reliable theoretical basis for judging the coal combustion spread in the coalfield fire area. [ABSTRACT FROM AUTHOR]

This study systematically investigates the impact of pre-stretching amount (PSA) on the acceleration, motion status, and screening efficiency of the Flip-flow screen plate (FFSP). Initially, a nonlinear spring-multi-body model of the FFSP is established. Subsequently, the acceleration signals at the midpoint of the FFSP under various PSAs are measured and analyzed. The nonlinear stiffness coefficient of FFSP along the vertical direction is then determined and it is found that simplifying the nonlinear spring-multi-body system to a nonlinear spring-tri-body system under the experimental conditions can maintain the calculation error of FFSP's acceleration within 30%. Phase and Poincaré mapping diagrams of the FFSP under different PSAs are subsequently created to illustrate the impact of PSA on the motion status of the FFSP. Finally, screening experiments are performed to study the optimal PSA for a kind of bituminous coal from Shanxi province. [ABSTRACT FROM AUTHOR]

Fly ash is currently a problem in different companies, mainly in thermoelectric plants, which must follow a production and consumption model that involves reusing, renewing, and recycling, thus contributing to the circular economy. This work aims to evaluate the reactivity and compressive strength of different types of ashes in concrete monoliths. For this purpose, sugarcane bagasse (SCBA), bituminous coal (BC), and untreated hazardous waste (RUD) were evaluated as replacements for cement. Monoliths and mortars have been manufactured in different mixtures, taken to a curing room, and their compressive strength and reactivity have been determined at different times (up to 28 days for the monoliths and up to 90 for the mortars), mainly in order to check the formation of calcium silicate hydrate (CSH) gels. In the monolith tests, the best performances have been with SCBA and BC, which have been used for the manufacture of the mortars. On day 56, the behavior of the replacement of 30% fly ash (15% BC:15% SCBA) presents a type H mortar behavior, with better results than the control. By day 90, all replacements had the same resistance as M mortars and even higher resistances than the control. This demonstrates the feasibility of its use in the production of Portland cement for the manufacture of low‐performance inputs. This implies the possible reduction of impacts, both in waste disposal sites and in emissions caused by the construction industry, thus contributing to the circular economy. [ABSTRACT FROM AUTHOR]

Coal, extensively used in many countries across various industries, particularly as a fuel in the energy sector, poses significant environmental challenges due to process-related implications and their complex characteristics. A notable obstacle arises from its heterogeneous and complex submicron–nano-molecular structure, often leading to operational issues that are challenging to predict. This research aims to comprehensively assess the environmental impact of bituminous coal sourced from the Barapukuria Coal Mine (NW Bangladesh). This study focuses on elucidating the intrinsic properties of coal, with specific attention to its thermal behavior, structural composition, and surface morphology, aiming to understand the implications for energy production. Advanced techniques, such as TGA/DTG, CHNS-O, XRD, FTIR, XRF, ICP-OES, XPS, SEM with EDX, and TEM, were employed. Rigorous experimentation and analysis provided valuable insights into combustion and pyrolysis processes, illuminating the release of environmentally hazardous pollutants and their negative consequences associated with the utilization of Barapukuria coal for energy generation. Thermogravimetric analysis indicates coal bond breakdown at 573–933 K, releasing gases and liquids during the breakdown stage, resulting in mass loss from moisture evaporation, protogenic gas release, and volatile matter loss. Despite being of the bituminous type, the coal exhibits a mean carbon concentration of 78.24% and a low sulfur content of 0.42%, signifying relative environmental friendliness compared to high-sulfur coals, which is crucial for preventing acid rain. The average higher heating value (31.04 ± 0.74 MJ kg−1) and calorific value (30.20 ± 0.95 MJ kg−1) indicate that the studied coals have high energy potential. This study also suggests that optimizing thermochemical conversion for power generation may enhance energy efficiency and mitigate potential environmental impacts. The research findings contribute to the scientific understanding of coal thermal properties, serving as a foundation for informed decision-making in energy production strategies that prioritize both efficiency and environmental sustainability. [ABSTRACT FROM AUTHOR]

To explore the application prospects of higher-molecular-weight gases (HMWGs) in forecasting coal spontaneous combustion (CSC), the emission characteristics of HMWGs during the oxidation of seven bituminous coals with different degrees of metamorphism were studied using gas chromatography. By analyzing the gas samples released from the oxidation of experimental samples, a total of 20 HMWGs with hydrocarbons as the main component was detected. The concentration of HMWGs changed regularly during the oxidation of experimental samples. The concentrations of most representative hydrocarbon gases increased significantly with increasing temperature but plateaued or even decreased when the temperature exceeded about 210°C. The relationship between HMWG production and the metamorphic degree indicators was nonlinear. The volatile matter content and vitrinite reflectance of coal cannot be used directly to evaluate HMWG production. The initial appearance temperatures of HMWGs during the oxidation of different coal samples also varied. The accuracy of CSC forecasting technology can be significantly improved if HMWGs are used as complementary index gases to forecast the different development stages of bituminous CSC. [ABSTRACT FROM AUTHOR]

Excessive fluoride emissions threaten ecological stability and human health. Previous studies have noted that industrial sources could be significant. However, quantifying industrial fluoride emissions has not been yet reported. In this study, both bottom-up and top-down approaches were used to estimate the fluoride emissions in the Nansi Lake Basin. Global and local spatial autocorrelation were adopted to reveal the spatial agglomeration effects. The fluoride emissions calculated by the bottom-up approach were larger than those calculated by the top-down method. The highest fluoride input mainly occurred in Zoucheng and Mudan. The highest fluoride emissions mainly occurred in Zoucheng and Rencheng using the bottom-up approach. The highest fluoride emissions mainly occurred in Zoucheng and Yanzhou using the top-down approach. Mining and washing of bituminous coal and anthracite (BAW) was the most significant source of fluoride input and emissions. A significant spatial agglomeration effect of fluoride emissions was found. These findings could provide a method for accurate industrial fluoride emission estimation, complement the critical data on the fluoride emissions of main industrial sectors, and provide a scientific basis for tracing fluoride sources. [ABSTRACT FROM AUTHOR]

Introduction: The study employed novel non-destructive testing techniques for coal sample such as resonant column testing, cyclic torsional technique, and ultra-sonic pulse velocity analysis. Methodology: The study confirms the coal in the present study as bituminous coal by analyzing the microstructure and composition of coal using scanning electron microscope and energy-dispersive X-ray spectroscopy method. Objective: The damping characteristics (resonant frequency, damping ratio) and dynamic shear modulus of the coal are determined using the resonant column test and the ultrasonic pulse velocity test. Further, numerical simulations using the finite-element method (FEM) in ABAQUS software are performed to obtain resonant frequencies for intact coal samples under torsional and flexural vibrations, and the results of the experimental and numerical studies are found to be in good agreement. Conclusion: The study has established a critical damping factor range based on the input frequency that can help ensure sustainable design of underground and surface mines. [ABSTRACT FROM AUTHOR]

With the aim of determining the damage characteristics and a reasonable positional arrangement of the surrounding rock in a bottom-pumping roadway influenced by mining in a high-gas mine, the boundary equation for the plastic zone of the surrounding rock in a circular roadway under an unequal compressive stress field was adopted to analyze the relationship between the distribution characteristics of the plastic zone of the bottom-pumping roadway and the stability of the rock surrounding the bottom-pumping roadway under different bidirectional stress ratios. This was carried out in the bottom-pumping roadway of the working face of Licun coal mine 3301 as the engineering background, where the nature of the coal seams mined is bituminous coal, and the absolute gas outflow is 0.5 m3/min−1. A numerical simulation was used to analyze the distribution characteristics of the surrounding rock stress and the bidirectional stress ratio, as well as the deformation and damage characteristics of the surrounding rock at different positions in the bottom-pumping roadway. A numerical simulation was applied to analyze the distribution characteristics of the surrounding rock stress and the two-way stress ratio, as well as the deformation and damage characteristics of the rock surrounding the bottom-pumping roadway when the bottom-pumping roadway was arranged in different locations. The results show that, with an increase in the bidirectional stress ratio, the plastic zone of the perimeter rock in the bottom-pumping roadway shows nonuniform "butterfly" distribution characteristics, which seriously affects the stability of the rock on the perimeter of the roadway; the stress on the bottom plate of the working face after excavation can be divided into four areas according to the size of the bidirectional stress ratio and the stress loading and unloading states. In addition, the size of the perimeter rock deformation can be sorted into four areas according to the damage range of the perimeter of the rock plastic zone in the bottom-pumping roadway. The size of the deformation in the surrounding rock can be sorted as follows: unpressurized high-stress ratio > unpressurized stress ratio stable area > pressurized low-stress ratio area > original rock stress ratio area. Accordingly, we found that the reasonable location of the bottom-pumping roadway is arranged at the 15 m position outside the hollow area below the coal pillar, along the limestone upper medium-grained sandstone layer along the bottom. The study's results were applied to the field. The industrial experiments on the site show that the deformation of the surrounding rock is reasonable when the bottom-pumping roadway is dug along the limestone roof and arranged 15 m outside the fault of the mining hollow area below the coal pillar. [ABSTRACT FROM AUTHOR]

Geoscientists now identify coal layers using conventional well logs. Coal layer identification is the main technical difficulty in coalbed methane exploration and development. This research uses advanced quantile–quantile plot, self-organizing maps (SOM), k-means clustering, t-distributed stochastic neighbor embedding (t-SNE) and qualitative log curve assessment through three wells (X4, X5, X6) in complex geological formation to distinguish coal from tight sand and shale. Also, we identify the reservoir rock typing (RRT), gas-bearing and non-gas bearing potential zones. Results showed gamma-ray and resistivity logs are not reliable tools for coal identification. Further, coal layers highlighted high acoustic (AC) and neutron porosity (CNL), low density (DEN), low photoelectric, and low porosity values as compared to tight sand and shale. While, tight sand highlighted 5–10% porosity values. The SOM and clustering assessment provided the evidence of good-quality RRT for tight sand facies, whereas other clusters related to shale and coal showed poor-quality RRT. A t-SNE algorithm accurately distinguished coal and was used to make CNL and DEN plot that showed the presence of low-rank bituminous coal rank in study area. The presented strategy through conventional logs shall provide help to comprehend coal-tight sand lithofacies units for future mining. [ABSTRACT FROM AUTHOR]

The paper discusses specifics of the process of carbothermic reduction of metallurgical silicon in ore-smelting furnaces. The reaction zone represents a heating area for the charge materials, formed around the electrodes in all electric furnaces, and facilitates the release of thermal energy by passing electric current through a resistance and/or by creating an electric arc, change in the aggregate state of the loaded materials (e.g., quartzite, bituminous coal, needle coke), and a complex of chemical reactions that occur within such materials. When properly controlled, the operating conditions of the ore-smelting furnace provide optimal specific performance relative to specific power consumption. However, in case of deviations, such as high or low placement of the electrodes, excess or lack of reducing agent in the charge material, furnace throat level being too high or too low relative to technical guidelines, electrode voltage imbalance, etc., the furnace performance can be significantly reduced due to a non-conformant granulometric composition. If the furnace is operated with such deviations for extended periods of time, an emergency shutdown may occur. If the power generated at the electrode is insufficient, the reaction zone becomes significantly narrower, this leads to a change in the rate of chemical reactions. The excessive power levels, on the other hand, may cause intensive entrainment of microsilica along with the formation of blowholes capable of disabling water-cooled panels or shutting down the furnace transformer due to an overload. The location of the reaction zone in the furnace space plays a key role in ensuring effective operation of the ore-smelting furnace. Shifting of the reaction zone upward or downward may result in the grade drop of metallurgical silicon and reduced performance of the furnace, which will subsequently increase the product cost. [ABSTRACT FROM AUTHOR]

Flip-flow vibrating screens (FFVSs) effectively tackle the challenges posed by the dry deep-screening of wet, fine, low-grade bituminous coal, thereby facilitating advancements in the thermal coal preparation process. The tensile lengths of the screen panels not only influence the service lives of the screen panels but also play a pivotal role in determining the screening performance of the FFVSs. To investigate the effect of the screen-panel tensile length on the screening performance of an FFVS, this study constructs a dual-mass flip-flow screening test rig. The experimental results reveal that when the fine-particle content and the external water content in the feed of low-grade bituminous coal are 55% and 16%, respectively, the most favorable tensile length of the screen panels is 2 mm. With a fine-particle content of 55% in the feed of low-grade bituminous coal and an increase in the external water content from 4% to 20%, the screening efficiency of the FFVS initially decreases and then increases. Notably, low-grade bituminous coal with 16% external water content poses the most challenging screening conditions. Furthermore, when the external water content of the low-grade bituminous coal is 16% and the fine-particle content in the feed increases from 25% to 55%, the screening efficiency of the FFVS gradually improves. [ABSTRACT FROM AUTHOR]

Gas adsorption–migration in coal is of crucial importance for coalbed methane (CBM) recovery; however, the effect of coal deformation on it is not yet very clear, especially at the molecular level. In this study, the effects of uniaxial tension–compression strains on the CH4/CO2/N2 adsorption–migration characteristics in bituminous coal matrix were investigated by integrating the grand canonical Monte Carlo and molecular dynamics methods. The results show that the dual-mode equation fits the isothermal adsorption results, and the adsorption concentration and Langmuir volume are positively correlated with strain. Tension strain has a small effect on a thermodynamic factor but a large effect on Henry constant. In addition, the swelling resistance of coal matrix is positively correlated with tension strain which has a greater impact on the shear resistance of coal matrix containing CO2. The average mass density of the gas is linearly positively correlated with strain that has a large impact on N2 stability. More significantly, the self-diffusion coefficient (Ds) of CH4 is larger than that of CO2/N2, and the relationship between Fick diffusion coefficient and strain is roughly similar to that between Ds and strain. Also, the mass transfer of CO2 permeation is more significant compared to N2, especially for tension strain. These research results provide a basis for the optimization design of CBM recovery in deformed coal reservoirs. [ABSTRACT FROM AUTHOR]

Microorganisms can affect coal biodegradation by driving elemental biogeochemical cycling. A detailed description of the sulfur conversion process led by indigenous bacteria during coal degradation is important. This study obtained sulfur-containing compounds conversion bacteria through indoor enrichment and conducted anaerobic culture experiments using coal supplemented with enriched bacteria. The study showed that the addition of enriched bacteria changed the microbial composition, particularly the microbial groups within Pseudomonadota and Bacillota. In addition, the sulfur-containing compounds conversion bacteria increased the pore volume and specific surface area of micropores (<10 nm) and transition pores (10–100 nm), as well changed the content of sulfur-containing organic components including polypeptides, aromatic compounds, alkyl compounds, and thiazoles. The genera related to inorganic sulfur conversion were mainly belonging to Bacillota and Actinomycetota. Additionally, functional genera that can degrade sulfur-containing organic compounds of dibenzothiophenes through the ring-opening of benzene rings were found within Pseudomonadota, Bacillota and Actinomycetota. In summary, organic sulfur-related Pseudomonadota, Bacillota and Actinomycetota and inorganic sulfur-related Bacillota and Actinomycetota detected in this study could accelerate the sulfur-containing compounds conversion and ultimately increase micropores in coal, and this holds great significance for understanding the biogeochemical cycling process of coal. [ABSTRACT FROM AUTHOR]

Semi-coke is the coproduct of low-rank coal in the preparation of oil and gas, but the current utilization rate of fine-powder semi-coke is low, which limits the development of the low-rank coal pyrolysis industry. This paper uses the numerical simulation method to study the co-combustion characteristics of a large proportion of bituminous coal mixed with semi-coke in a swirl burner. The results show that, in the primary combustion region, with the increase of the blend ratio of semi-coke, the flue gas temperature and NO concentration are lower, and the O2 concentration increase is higher. In the over-fired air (OFA) nozzle area, with the increase of the blend ratio of semi-coke, the flue gas temperature and NO concentration are higher, and O2 concentration is lower. In addition, with the increase of the blend ratio of semi-coke, the main combustion position of the fuel is transferred to the vicinity of the OFA nozzle area, which weakens the degree of air-staging combustion of the furnace. The synergistic effect of co-combustion of semi-coke and bituminous coal helps to reduce the NO concentration at the furnace outlet and improve the combustion efficiency. By comprehensive considering the stable operation of the boiler, burnout rate, and NO emission concentration, the recommended blend ratio of semi-coke should not exceed 60%. [ABSTRACT FROM AUTHOR]

A key factor restricting the application of biochar in the steel industry is its high-quality upgrading. This paper evaluated the characteristics of hydrochar produced by HTC (hydrothermal carbonization) process of corncob to be used as a solid fuel. HTC temperatures (240–300 °C) and HTC water-reused times (1–3 times) were examined for their effects on hydrochar yield, physicochemical characteristics, and combustion properties. The results showed hydrochar yields, O/C, and H/C parameters decreased as HTC temperature and water-reused times increased, while its high heating value increased. Due to dehydration and decarboxylation, hydrochar showed similar characteristics to those in bituminous coal. The removal efficiency of alkali metal K reached 99% after HTC treatment. Carbonaceous hydrochar had become more compact, orderly, and stable with increasing amounts of aromatic functional groups, C = C, and C = O. Hydrochar, as a biofuel, has higher ignition energy and is more stable than corncob due to its high carbonaceous order degree. To calculate combustion kinetic parameters, the Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) methods were applied. The results revealed that Eα (average activation energy) was quite similar between the two models. HC-300 had an Eα of 262 kJ/mol. HTC could be an efficient way to reutilize corncob biomass into clean biofuels with high calorific value. [ABSTRACT FROM AUTHOR]

In this study, we compare the effect of various precursor‐based graphene oxide (GO) nanofillers on enhancing the mechanical performance of E‐glass fiber‐reinforced epoxy resin composites (EGFPs). GO derived from bituminous coal (BC‐GO) and graphite (Gr‐GO) were dispersed into an epoxy resin matrix. The resulting mixture was combined with E‐glass fiber mats using vacuum‐assisted resin infusion molding. Notable improvements (38.9% in flexural strength, 22.9% in tensile strength, and 21.6% in impact strength) were observed in BC‐GO‐reinforced EGFPs at 0.25 phr loading of BC‐GO. The improvements for Gr‐GO‐reinforced EGFPs were 28%, 9.3%, and 6.8%, respectively. XRD analysis of BC‐GO showed a diffraction peak at 2θ = 20.9°. Except for this peak, no other crystalline peaks were observed when BC‐GO was incorporated into EGFPs. FTIR spectra of both composite samples, with or without the nanofiller, were similar due to the spectral peaks overlap. TEM demonstrated the exfoliated morphology of BC‐GO in EGFPs. These findings underscore the potential of BC‐GO as a cost‐effective reinforcement for polymer nanocomposites across various industrial applications, including the development of lightweight and strong materials for aerospace and automotive industries, protective coatings, petroleum, and aerospace production systems. Highlights: BC‐GO demonstrates superior mechanical performance compared to Gr‐GO in EGFPs.0.25 phr BC‐GO improves 38.9% flexural, 22.9% tensile, and 21.6% impact strengths.Beyond 0.25 phr, BC‐GO and Gr‐GO showed a decline in mechanical enhancement.Role of particle size, loading & adhesion to matrix analyzed using XRD, FTIR, and DLS.Coal‐GO is an attractive alternative nanofiller for EGFPs. [ABSTRACT FROM AUTHOR]

At the turn of the twentieth century, advocates for shorter working hours often claimed that workers were so fatigued by the end of the workday, that shortening daily hours from ten to eight would have little effect on output. This study examines the record for U.S. coal mining, analyzing both state-level and mine-level panel data during the transition to the eight-hour day. The hypothesis of zero effect is easily rejected. Instead, output declined almost proportionately with hours, but advancing technology made up for the lost output fairly quickly. There is some evidence that employment increased when the eight-hour day was adopted, as unionists hoped, but the effect is not precisely measured. [ABSTRACT FROM AUTHOR]