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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]

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]

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]

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]

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]

Combustion of bituminous coal and pinus sawdust blends was investigated experimentally within a drop tube furnace (DTF) with the aim of determining particle residence times and temperatures during the process. Evaluation of these parameters gives useful information to engineers who want to optimise the co-combustion process of coal and biomass blends. The DTF experimental approach was used to investigate fuel blends with a pinus sawdust mass substitution of 0, 10, 20, and 30% at different furnace temperatures of 1273, 1473 and 1673 K. Results showed that during stage 1 of the experimental setup which mimics devolatilisation, particle residence time at a distance of 520 mm from the injection point decreased from 0.8 to 0.7 s as blending by pinus sawdust increased from 0 to 30 %. During stage 2 of the experimental setup which mimics char combustion, particle residence time at a distance of 1320 mm from the injection point decreased from 3.9 to 2.0 s as blending by pinus sawdust increased from 0 to 30 %. The blending ratios under investigation demonstrated similar profiles of particle temperature at different furnace positions though further analysis showed that the highly blended samples required less time to attain high temperatures. By extension, since fuel blends with higher percentages of pinus sawdust were able to attain higher temperatures at shorter residence time, combustion intensity was deduced to increase with the blending ratio whilst stability decreased. As such, caution should be taken with materials used for furnace and burner design as high-temperature zones move backwards towards the injection point as blending increases.

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]

The energy demand increased dramatically owing to the evolution of industrial and domestic requirements and the associated decrease in oil and gas resources. This study aims to evaluate El-Maghara coal (with about 52 MT reserve) as a potential hydrocarbon source. The collect samples were subjected to petrographic, chemical analyses and Rock–Eval pyrolysis to investigate the detailed characteristics of this coal. Chemically, this coal is high volatile bituminous coal with high H and S content. The high H/C ratio indicates the high extraction yield of coal. The main maceral group in the studied samples is vitrinite (62.8%) followed by liptinite (31.3%) and inertinite (5.8%). The content of liptinite indicates the capability of this coal for petroleum production. Based on Rock–Eval Pyrolysis results and TOC content, the coal has excellent petroleum potential. The hydrogen index (HI) and H/C atomic ratio indicate the II kerogen type (oil prone) of this coal. This coal has Tmax and vitrinite reflectance values around 415.8 °C and 0.37%, respectively, indicating the immature stage of kerogen. The high reactive maceral content (94.2%), oil-yield (65.5%) and conversion from coal to oil (95.4%), indicated that this coal has a hydrocarbon generation potential for oil. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3)-coal co-firing is a promising technology to reduce CO 2 emission. The strong interaction between ammonia and coal during the co-pyrolysis has a considerable impact on nitrogen migration and transformation and will further affect the NO x formation. In this paper, to investigate the effect of the volatile fraction on the migration of N, Shenhua (SH) and Wanxiang (WX) bituminous coals were devolatilized to different levels in the first pyrolysis step and were then co-pyrolyzed with NH 3 in the second pyrolysis step. It is found that the migration of N from the gas to solid is more significant than the release of N with the volatile, especially when the temperature in the first pyrolysis step is low. Given the same pyrolysis condition, WX coal/char has more oxygen-containing functional groups than SH, thus the increase of N content during the NH 3 /coal co-pyrolysis is more significant for WX. The absolute contents of pyridinic N (N-6), pyrrolic N (N-5), and protonated pyridinic N or quaternary N (N-Q) are calculated before and after the co-pyrolysis step according to the results of elemental analysis and X-ray photoelectron spectroscopy. An obvious increase of N-6 is observed in chars with lower degree of devolatilization for both coals. A transformation of N-5 to other types of N is observed for SH coal/char. In contrast, the transformation of N-5 is less obvious for WX, which is due to the presence of alkali metal chlorides in WX. Moreover, WX coal/char has less aromatic structure and more aliphatic groups, which promotes the transformation of N from NH 3 to N-5. Based on these results, possible reaction pathways of N migration and transformation during NH 3 /coal co-pyrolysis are proposed. • Migration of N during ammonia-coal co-pyrolysis are investigated. • Migration of N onto char is more significant than release of N from char. • N that migrates from NH3 to char mainly exists as pyridinic N and pyrrolic N. • Possible reaction pathways of N migration are proposed. [ABSTRACT FROM AUTHOR]

Utilizing oil palm trunk (OPT) residue as a co-fuel in coal-fired plants offers an environmentally favorable solution to agricultural waste disposal and fossil fuel combustion impacts. This study investigates the potential of hydrochar from OPT (HTC-OPT) as a coal-like solid fuel for co-combustion. The combustion characteristics of coal, HTC-OPT, and their blends (10–50% HTC-OPT) were analyzed via thermogravimetric analysis with heating rates ranging from 10 to 30°C/min. The Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) models were employed to explore co-combustion interactions and kinetic parameters. Results reveal enhanced combustion efficiency with HTC-OPT addition to coal. Higher HTC-OPT ratios correlate with increased maximum combustion rates, ignition and comprehensive combustibility indices, and decreased ignition and burnout temperatures. Additionally, blended fuels exhibit a proportionally synergistic co-combustion interaction. Both KAS and FWO models indicate similar trends in activation energies, with the lowest values (49.94 kJ/mol for KAS and 60.90 kJ/mol for FWO) at a 10% HTC-OPT ratio. [ABSTRACT FROM AUTHOR]

Pyrolysis of oil palm biomass residue can convert the rich organic matter in biomass into sustainable green energy, thereby addressing the challenge of surplus oil palm biomass residue generated during cultivation. Nonetheless, the pyrolysis of oil palm leaves (OPLs) has received limited attention. In this study, design of experiment‐response surface methodology (DoE‐RSM) was employed to identify the optimal combination of reaction temperature, residence duration, and nitrogen (N₂) flow rate for maximum biochar yield. The elemental analysis, high heating value (HHV), functional group, morphology, pore structure, and thermal behavior were assessed. By varying the operational parameters using response surface methodology, the biochar yield increased by 32.6–85.3%. The DoE‐RSM predicted a theoretical yield of 52.1% at 344 °C, 146 min, and 3.2 scfh N₂ flow rate. The experiment confirmed a comparable yield of 53.7% at the stated parameters. The HHV of 24.14 MJ kg−1 was recorded under optimal conditions, and was comparable to sub‐bituminous and bituminous coal. Fourier transform infrared analysis validated the OPL biochar by weakening O‐H, C=O, C‐OH, and C‐H peaks. Scanning electron microscopy images revealed enlarged pores and altered morphology in the OPL biochar. X‐ray diffraction showed lower crystallinity of the OPL biochar than the feedstock. Raman spectroscopy showed higher ID/IG, indicating a more disordered carbon structure in the OPL biochar. Thermogravimetric analysis confirmed higher temperature for main devolatilization of OPL biochar, and the differential thermogravimetric analysis curve pattern resembled that of Mukah Balingan coal. The findings are helpful for an initiative to convert a large amount of leftover OPLs produced during cultivation and to turn them into high value‐added material for a sustainable contribution to a circular carbon economy. [ABSTRACT FROM AUTHOR]

Coalbed methane (CBM) reservoirs' permeability is the result of dynamic variations influenced by tectonics, hydrology and the CBM production process. Taking samples from the southeastern Ordos Basin, China, the permeability evolution of bituminous coal and its control were analyzed in three steps: (1) the coal fracture permeability evolution was acquired via X-ray CT scanning and permeability evolution experiments; (2) the permeability variation was determined while considering the coupling characteristics effective stress, gas slippage, and matrix shrinkage effect and its influencing factors; and (3) a dynamic permeability model was built while considering those effects. For samples in which neither fractures nor bedding developed, the permeability decreased first and then increased as the gas pressure increased. For samples with fractures that developed parallel to the axial direction, with a gradual increase in gas pressure, the permeability also increased. As the gas pressure decreased, the matrix shrinkage effect became positive, resulting in a permeability increase. The gas slippage effect was positive in the low-pressure stage, which also resulted in a permeability increase. [ABSTRACT FROM AUTHOR]

The existing research on CH4 displacement by N2 mainly focuses on the gas injection displacement mechanism and the factors affecting displacement efficiency. And most of them are theoretical analyses at the model level or multifactor analyses at the simulation test level, while there are few targeted physical simulation tests and quantitative analyses. Given the above problems, the experiment system was used to study the gas migration evolution law and time-varying characteristics of CH4 displacement by N2 in coal under different injection pressures. The experimental results show that the whole process of CH4 displacement by N2 can be divided into three stages: stage I (original equilibrium stage); stage II (dynamic balance stage); stage III (new equilibrium stage). The concentration of CH4 and N2 presents an opposite variation trend, and the variation rate of CH4 and N2 increased first and then decreased. The breakthrough time was 50 minutes, 45 minutes, 35 minutes, 25 minutes, and 20 minutes, respectively, under different injection pressures. The displacement efficiency increased with the injection pressures, while the replacement ratio decreased with the injection pressures. The maximum flow rate of CH4 was 0.085 mL/min, 0.110 mL/min, 0.130 mL/min, 0.222 mL/min, and 0.273 mL/min, respectively, under different injection pressures. The accumulated production of CH4 was 3.59 mL, 3.91 mL, 4.39 mL, 5.58 mL, and 5.94 mL, respectively, under different injection pressures. The effective injection pressure range was 1.6~2 MPa. This research can provide a reference for the theoretical research of N2-ECBM-related technology in low permeability reservoirs and the selection of injection pressure in the field technology implementation. [ABSTRACT FROM AUTHOR]

Microalgae have been recognized as promising competitors for bioenergy production, because of their high lipid content and quick biomass development. In this work, freshwater microalgae Scenedesmus dimorphus was cultivated in a synthetic wastewater media with the object of investigating the bioenergy potential by physicochemical characterization. Batch experiments were performed photoautotrophically for biomass generation supplemented with different levels of CO2 concentration. Maximum biomass production was in the limit of 373 mg/L to 587 mg/L under different CO2 feed concentrations. Cultivation of microalgae along with CO2 supplementation found a substantial impact on buildup of lipid in microalgae biomass. Maximum 29% and 32% lipid content were achieved for 2% and 6% CO2 enrichment respectively, under nitrogen-depleted conditions. Fourier transform infrared spectroscopy, thermogravimetric analysis, and carbon, hydrogen, nitrogen, sulfur elemental analyzer instrumental tools were used to perform physicochemical characterization on biomass in order to determine its proximate analysis, ultimate analysis, higher heating value (HHV), and macromolecular composition, The higher heating value (HHV) of Scenedesmus dimorphus biomass achieved 33.26 MJ/kg with almost zero sulfur content. This HHV value is significantly higher than that of other microalgae sp. Moreover, this HHV value is also even higher than that of bituminous coal (24.3 MJ/kg) and other types of lignocellulosic biomass. Scenedesmus dimorphus biomass indicates that it can be a potential fuel feedstock for environmentally friendly bioenergy production. [ABSTRACT FROM AUTHOR]

For the first time, bituminous-based mesoporous carbon/zinc oxide (BMC/ZnO) nanocomposite was synthesized and its hydrogen storage capacity was investigated. At first, ZnO nanoparticles were prepared via the homogeneous precipitation technique using green tea extract as a participant agent. In the second step, mesoporous carbon was made from bituminous coal; then, BMC/ZnO nanocomposite was prepared with a facile technique. Detailed investigation of structural and physical properties of the prepared BMC/ZnO nanocomposite was conducted using X-ray diffractometer (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), and Fourier transform infrared spectrometer (FTIR). Hydrogen storage capacity of produced nanocomposite was inspected using the chronopotentiometry technique. As a result, BMC/ZnO nanocomposite as storage material shows a high electrochemical hydrogen storage equal to 4648 mAh/g. The well-structured, easily prepared and high hydrogen storage performance BMC/ZnO nanocomposite offers hopeful potential to support progressive systems of hydrogen storage. [ABSTRACT FROM AUTHOR]

Groundnut shells (GNS) are renewable and sustainable sources that can reinforce polypropylene for composites intended for interior building and other applications. However, the hydrophilicity, low thermal and noise insulation of GNS reinforced polypropylene (PP) necessitate the use of additives to improve properties. In this work, non-coking bituminous coal was used as an additive to improve the properties of GNS-PP composites. Up to 30% of coal particles were included and the changes in tensile, flexural properties and noise and thermal insulation were studied. Morphological analysis showed limited interaction of coal with GNS or PP and consequently, there was only marginal improvement in the mechanical properties. However, moisture sorption of the composites decreased by 25% and the limited oxygen index increased to 27 from 24 without any coal. The presence of coal increases sound absorption and the noise absorption coefficient showed high absorption at specific frequencies. Coal is an abundantly available natural material which is suitable to improve the performance of composites. Graphical Abstract [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]

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]

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]

Underground in-situ pyrolysis of coal is a new trend in the utilization of coal resources in the future. It is especially critical to investigate the coal pore-fissure structure, its spatial distribution and connectivity under different pyrolysis methods, and the existing studies on the pore-fissure structure parameters of coal after pyrolysis are in non-stress condition and lack of the comparison of pore-fissure structure parameters under different pyrolysis methods. Based on the above deficiencies, using the self-made triaxial testing machine of thermo-fluid-mechanical-chemical coupling at high temperature and pressure, combined with the micro-CT technology, the fissure structure differences of bituminous coal under the conditions of natural and steam in-situ pyrolysis (600 ℃) were investigated, and then the mechanism of the differences was explored. The results show that ① After the natural and steam in-situ pyrolysis at 600 °C, the fissure forms generated inside the coal sample are mainly slender cracks and holes, and the fissure scale is further improved after steam pyrolysis. The fissure network is more abundant and complex. ② Under the stress condition of 5 MPa axial pressure and 3 MPa confining pressure, after natural pyrolysis, the fissure rate is 2.68 times of the original fissure rate. However, after steam pyrolysis, the fissure rate is 3.65 times of the original fissure rate, and the fissure rate of each layer is more uniform. ③ Steam pyrolysis makes the bituminous coal heated evenly, with large heat exchange area and more adequate pyrolysis of organic matter. The displacement effect ensures the continuous production of pyrolysis products. The local stress effect of pore pressure not only expands the original pore-fissure volume, but also destroys the weak surface of pore wall, which greatly increases the pore connectivity. The steam denudation effect will “scour and transport” the tar with high viscosity attached to the blind fissures out of the coal body. Hydrogen-rich environment promotes the cracking of heavy tar and enhances the fluidity of oil. ④ There are large differences in the fissure rate and fissure morphology between in-situ and non-stress of coal pyrolysis. Steam pyrolysis is the optimal heating method for the engineering practice of in-situ thermal injection coal mining.

With industrial development and innovation, the demand for key metal minerals dominated by rare earth elements is increasing day by day. More experts believe that coal measures mineral resources have the potential to obtain key metal minerals, and such resources have therefore received high attention at home and abroad. Huaibei coalfield in China is rich in coal resources. In order to study the geochemical characteristics of trace elements in its coal and judge the industrial potential of rare metals, No. 5 coal, No. 8 coal and No. 10 coal in Zhuzhuang Coal Mine were selected as the research objects. The samples were analyzed by means of industrial analysis, XRF and ICP-MS. The results show that compared with the world coal, most trace elements in Zhuzhuang Coal Mine are highly enriched, such as Li, Cr, Co, etc. Compared with 5 coal and 8 coal, the concentration of trace elements in 10 coal is low, and the contents of V, Mn, Rb and Cs belong to the normal range. Through the analysis of w (Al2O3)/ w (TiO2) ratio and element geochemical characteristics, it is concluded that the sedimentary source area of the study area is felsic source rock, the paleosalinity from Shanxi formation to Lower Shihezi Formation changes from marine facies to saline water facies, and the paleoclimate is a warm and humid reduction environment. In addition, rare earth elements are enriched in light and medium rare earth elements, and Eu, Y positive anomalies and Ce negative anomalies all show that the sedimentary environment of Zhuzhuang mine is affected by seawater and magmatic hydrothermal solution. Therefore, the abnormal enrichment of trace elements in Zhuzhuang Coal Mine may be affected by the sedimentary environment, seawater and hydrothermal solution. In addition, the study area is relatively rich in rare earth elements, and its total content is close to or even higher than the industrial grade. Through the comparison of REY prospect coefficient (Coutl) and a variety of sediment minerals, it is considered that the rare earth elements of coal 5 and coal 8 in the sample of the study area are promising as REY raw materials, while the effect of coal 10 is poor.

In order to clarify the adsorption pattern between coal and CO, CO2 and O2, the competition between CO and CO2 and O2 in coal is studied. Qianjiaying bituminous coal is used as the research object, and the molecular unit parameters are calculated by quantitative analysis method based on the experimental results of Fourier transform infrared spectroscopy (FTIR). The molecular cell structure of Qianjiaying bituminous coal is constructed (C1160H860O80N20). To verify the accuracy of the model, the infrared spectrum of molecules is simulated by quantum chemical calculation, and the calculated results are basically consistent with the experimental results. On this basis, the effects of pressure(0−16 MPa) and temperature(20−60 ℃) on the adsorption of CO, CO2 and O2 by coal are investigated by using the Grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) methods. From the experimental results, it can be concluded that the fitted isothermal adsorption curves conformed to the Langmuir equation. Under the same pressure, the adsorption capacity of CO, CO2 and O2 is weaker as the temperature increases. At the same temperature, there is a positive correlation trend between the burial pressure of coal seam and the adsorption amount. The magnitude of adsorption of single gases CO, CO2 and O2 is CO2 > O2 > CO, and CO2 can reach saturation adsorption state in the first. The competitive adsorption results of binary gases show that the adsorption selectivity of CO2/CO has obvious advantages in low-pressure or shallow buried coal seams. However, the adsorption selectivity of O2/CO did not change significantly with the change of pressure. The competitive adsorption capacity of CO2 is greater than that of CO, and the adsorption capacity of CO2 decreases with the increase of CO concentration; The competitive adsorption of O2 is greater than CO when the ratio of CO to O2 molar concentration is ≤ 1, but the adsorption of CO is greater than O2 when the molar concentration of CO is much greater than O2. Therefore, the molar concentration of CO is high, which inhibits the adsorption capacity of CO2 and O2. In other words, in bituminous coal seams with high abnormal CO concentration, the effect of using CO2 injection to control fire extinguishing is not significant, so the amount of air leakage from the working face should also be controlled to prevent CO from desorption to the coal body and to ensure that the CO concentration in the well is within the permissible range.

Understanding the molecular structure characteristics of coal at the molecular level is of great significance to realize the rational utilization and efficient conversion of coal. This paper gives insights into the acquisition of characterization parameters of coal molecular microstructure by testing and analyzing the long flame coal from Qinggangping (QGP) Coal Mine through proximate analysis, ultimate analysis, vitrinite reflectance determination, fourier transform infrared Spectroscopy test (FTIR), X-ray photoelectron epectroscopy test (XPS), carbon nuclear magnetic resonance (13C-NMR) and X-ray diffraction (XRD). The results show that benzene rings in the QGP coal are mainly connected in a disubstituted way, accounting for 36.48%. Oxygen atoms mainly exist in the oxygen-containing functional groups such as the ether C–O, C=O and –COO. Aliphatic hydrocarbons in the aliphatic group are mainly of symmetrical -CHx stretching vibration. Hydroxyl groups are mainly composed of OH–OH and OH–O hydrogen bonds, accounting for 29.21% and 21.53%, respectively. Nitrogen atoms exist in the form of C4H5N. The coal molecular is mainly of aromatic carbon structure, where the ratio of bridge aromatic carbon to peripheral carbon is 0.198. There are benzene, naphthalene and anthracene in the coal molecular structure, and the former two chemicals play a dominating role. According to the analysis results, the molecular formula of the QGP coal is finally determined as C205H181O29N3S. On this basis, the two-dimensional and three-dimensional macromolecular models are constructed with the assistance of simulation software. In addition, the 13C-NMR spectra and densities of the constructed molecular models are calculated, which verifies the rationality of the models. The macromolecular structure model of bituminous coal constructed in this study provides a theoretical model basis for the optimal surfactant. [ABSTRACT FROM AUTHOR]

Barkinite is termed as a maceral in the Chinese bituminous coal, but it has not been recognized by International Committee for Coal and Organic Petrology, which is related to the unclear chemical structure of barkinite. The abnormal thermal behaviors of barkinite/bark coal were reported in our previous works, but the reason is not fully understood. For discussing these issues, the chemical structural model of barkinite with a molecular formula of C128H166N2O11 was constructed by elemental analysis, 13C nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. Besides, a heat up simulation of barkinite model was also performed by ReaxFF. The results showed that the chemical structural model of barkinite has long aliphatic chains and many hydroxyl and ether functional groups, which act as side chains and bridges. Naphthalene is main aromatic unit. When barkinite model system was heated from 300 to 2850 K, the change trends of pyrolysis products were described from four pyrolysis stages. The most noticeable changes of tar yields occurred in the simulated temperature range of 2100–2600 K, which caused the abnormal thermal behaviors of barkinite. According to the reaction pathways, the formation of tar products is related to the cleavage of aliphatic chains and the recombination of small molecular free radicals. [ABSTRACT FROM AUTHOR]

Copyrolysis, being an active area of research due to its synergistic impact in utilizing diverse fuel resources, including waste materials, like, peach stone (PS), has been the focal point for this study. PS, produced in vast quantities annually and typically intended for landscaping or insulation purposes, is being studied in combination with low‐grade bituminous coal for energy utilization focusing on thermokinetics and synergistic aspects. Coal‐peach stone (C‐PS) blends were formulated at different ratios and subjected to comprehensive characterization techniques, including ultimate analysis (CHN‐S), gross calorific value (GCV), Fourier transform infrared spectroscopy, and thermogravimetric analyzer (TGA). The ultimate analysis revealed an enhancement in carbon and hydrogen content from 45.38% to 68.08% and from 3.89% to 6.96%, respectively. Additionally, a reduction in sulfur and nitrogen content from 0.54% to 0.11% and from 1.16% to 0.42%, respectively, was observed with an increase in the ratio of PS in the C‐PS blends. The GCV of C‐PS blends ranged from 20.75 to 26.01 MJ kg−1. The pyrolysis conditions simulated in TGA are pivotal for evaluating thermokinetics and synergistic effects. The 60C:40PS blend shows a positive synergy index (SI) value of 0.0203% concerning total mass loss (MLT) indicating a favorable condition for bio‐oil generation. Coats–Redfern model‐fitting method reveals that the activation energy (Ea) of C‐PS blends increases in Section II with the addition of PS, and conversely, it decreases in Section III. The Ea for 100PS and 100C was 106.76 and 45.85 kJ mol−1 through (D3) and (F1), respectively, which was improved through the optimal blend 60C:40PS with an Ea of 94.56 and 27.58 kJ mol−1 through (D3) and (F2), respectively. The values obtained from linear regression prove that the kinetic models are effective while the thermodynamic analysis indicates that the pyrolytic behavior of C‐PS blends is characterized as endothermic, nonspontaneous, and capable of achieving thermodynamic equilibrium more rapidly. [ABSTRACT FROM AUTHOR]

The microwave-assisted hydrogen peroxide-citric acid desulfurization of coal was optimized by response surface methodology, and the samples were characterized before and after desulfurization by proximate analysis, ultimate analysis, sulfur forms determination, X-ray diffraction (×RD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (×PS), and scanning electron microscopy (SEM) and so on. The quantum chemical calculations were selected to investigate desulfurization mechanism of microwave-assisted hydrogen peroxide-citric acid, and data analysis shows that the citric acid dose is the main factor affecting the desulfurization rate. Under optimized conditions, the actual desulfurization rate can reach 72.23%, the sulfur removal rate of pyrite up to 92.19%. The mineral content of the coal sample was significantly reduced. The oxygen-containing functional groups in the coal sample increased, and more inorganic sulfur and sulfoxide in the low valence state were oxidized to sulfone and sulfate in the high valence state. The microwave effect of pyrite will react with hydrogen ions to produce Fe2+, Fe2+ and citric acid reaction to form a complex. Quantum chemical calculations prove that the addition of an applied electric field can reduce the energy required for the coordination reaction and facilitate the reaction. [ABSTRACT FROM AUTHOR]

Wide-angle X-ray scattering (WAXS) based upon synchrotron radiation is ideal for the in situ study of crystal structural changes during heating at high temperatures. This contribution describes a small furnace for in situ WAXS. The furnace has a wide coverage of scattered/diffracted angle from 0 to 135°, heats samples from room temperature to 1000 °C at 20 °C/min, and is suitable for in situ WAXS and radial distribution function of materials. Temperature calibration and safety verification are provided. The use of the furnace is demonstrated by in situ WAXS for the carbonization of bituminous coal. [ABSTRACT FROM AUTHOR]

High sulfur anthracite has high research value and application prospects in the preparation of carbon adsorbent due to its excellent coal quality conditions, but the pore structure changes and sulfur migration dynamics in the preparation process are not clear. In this paper, using SEM, pore structure analysis, Raman, FTIR and XPS, the feasibility of preparing carbon adsorbent from high-sulfur coal blending was analyzed from the perspective of apparent morphology, pore structure parameters, graphite crystal structure, and functional groups and content, while the occurrence form of sulfur in carbon adsorbent was explored. The results showed that the carbon adsorbent prepared from high-sulfur anthracite was mainly microporous, and the specific surface area was up to 1103.23 m2/g, which was the highest among the known high-sulfur coal materials. The degree of disorder of raw coal and the size of graphite crystal particles synergistically formed a rich pore structure. Sulfur in coal mainly exists in the form of thiophene and sulfide. An increase in the bituminous coal proportion promotes the transformation of carbon adsorbent to an alkaline environment. Thiophene sulfur is removed at 900°C, and sulfide is transformed into sulfoxide and sulfone under steam oxidation and Fe catalysis. [ABSTRACT FROM AUTHOR]

Efficient utilization of natural resources and possible valorization of solid waste materials such as sewage sludge into secondary materials via thermal conversion and simultaneously recovering energy is vital for sustainable development. The continuous increase in metropolises leads to an enormous production of wet sewage sludge, which creates major environmental and technical issues. In this paper, the samples of sewage sludge from Astana's waste water treatment plant are analyzed for their thermochemical properties, followed by thermogravimetric and kinetic analysis using the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods. Overall, the calorific value of sewage sludge sample was 18.87 MJ/kg and was comparable to that of the bituminous coal samples. The activation energy varied from 140 to 410 kJ/mol with changing conversion from 0.1 to 0.7. Further, mono-combustion and co-combustion experiments of the sewage sludge with high ash bituminous coal were conducted using the laboratory scale bubbling fluidized bed rig, respectively. The difference in NOx emissions between mono-combustion of sewage sludge and co-combustion with coal were at around 150 ppm, while this value for SO2 was similar in average, but fluctuates between 150 and 350 ppm. Overall, the findings of this study will be useful in developing a co-combustion technology for a sustainable disposal of municipal sewage sludge. [ABSTRACT FROM AUTHOR]

The awareness of environmental pollution has been continuously growing in recent decades and is currently reaching its maximum. Europe and most developed countries are determined to ensure safe breathing air for their citizens, and the measures to do so are stricter than ever before. Combustion procedures remain the primary means of producing energy and warmth in Poland. Among the notable constituents of flue gases produced as a result of fuel combustion, solid particles (or particulate matter) hold significant prominence. The paper presents the chemical characterisation of particulate matter emitted from stationary and automotive emission sources. Stationary emission sources included the combustion process of fossil fuels (soft wood, bituminous coal, ecopea coal, culm) in domestic heating units and the process of combustion of bituminous coal in a power plant. Automotive emission sources included light duty and medium duty vehicles fuelled by diesel. Exhaust toxicity tests were carried out maintaining the real conditions of PM emission. In all field measurements particulate matter was gravimetrically measured and collected on quartz or glass fibre filters. Subsequently, the content of carbonaceous fraction, inorganic ions, and metals and metalloids was analyzed using different analytical techniques. The chemical composition of the particulate matter differed depending on the emission source. With respect to stationary combustion sources, the main factors determining solid particle emission are related primarily to the fuel quality. The duty of vehicles was also a factor that influenced the chemical characterisation of the particulate matter emitted from the engines. [ABSTRACT FROM AUTHOR]

The coal dust explosion tests have been conducted using an explosion chamber 20-L with coal dust sizes of 53–44 µm (average particle size is 48.5 µm) for subbituminous coal from Indonesia. The coal dust explosion has been tested with various energies of the ignitor, i.e., 4.2 kJ, 6.3 kJ, and 8.4 kJ, to obtain the effect of ignitor energy on the coal dust's Minimum Explosion Concentration (MEC). The results show that the MEC for the 4.2 kJ, 6.3 kJ, and 8.4 kJ ignitor energy are 120 g/m3, 100 g/m3, and 70 g/m3, respectively. The present study in subbituminous coal resulted in a relatively higher MEC compared to previous studies conducted in bituminous coal. [ABSTRACT FROM AUTHOR]

To enhance the combustion efficiency and reduce NOx emissions in large-scale semicoke and bituminous coal blends, an extensive numerical study was conducted. The focus of this study was to optimize the quaternary air vane angle (αv) through detailed analysis of the temperature and flow fields, turbulence–chemistry interactions, char burnout, and NOx formation in a carefully scaled 1:5 dual-swirl burner. The results showed that with increasing αv, the high-temperature flame region was narrowed and the peak temperature was reduced along with the broadened inner recirculation zone and the shrunken external recirculation zone due to better pulverized fuel-oxidant blending and reinforced convective heat transfer. The peak turbulent Damköhler number Dat evidently increased from 197.5 to 496 with increasing αv, which implied a strengthened homogeneous combustion. Additionally, the corresponding mixing time scales increased while the chemical kinetics time scales decreased, which denoted that an intense diffusing flame was generated with a strong turbulent intensity. The peak heterogeneous Damköhler number Das-O2 showed a reduction from 2.54 to 2.27, while the peak values of Das-CO2 and Das-H2O decreased from 0.1 to 0.077 and from 0.02 to 0.015, respectively. The char–O2 reaction was controlled by diffusion/kinetics; both char–CO2 and char–H2O reactions were determined by kinetics, and all gas‒solid reactions showed a kinetically controlled regime. With increasing αv, the enlarged inner recirculation region increased the residence time, and a higher dilution level lessened the peak temperature, which led to reductions in fuel-NOx and the thermal-NOx. The αv range of 30–45° (or swirl number Sn = 0.55–0.95) was suggested by taking the high burnout and low-NOx formation into account. [ABSTRACT FROM AUTHOR]

At the Gowanus Canal Superfund site in Brooklyn, New York, layers comprising different granular activated carbon (GAC)/sand blends are being placed as part of a multilayer reactive capping system required for the approved remedy. Depending on the capping zone, the targeted GAC contents can vary from 6% to 60% by dry weight (%). The construction quality assurance (CQA) method for verifying the GAC content of each GAC/sand stockpile consists of loss on ignition (LOI) testing performed at an offsite laboratory with a turnaround time of 3 days. To mitigate construction delays and site congestion at the upland blending site, rapid field (onsite) testing methods to verify the GAC content of the GAC/sand blends were sought. Portable X-ray fluorescence (pXRF) was successfully used on oven dried and crushed GAC/sand materials to develop three linear elemental [calcium (Ca), silicon (Si), and sulfur (S)] correlations with goodness of fit (R2) values greater than 0.95 for Ca and S. Sulfur was not detected in the sand and appeared linked to the bituminous coal source materials for manufacturing the GAC and thus became the primary element to track the GAC content. The measured GAC contents of the CQA samples by pXRF were within 2 to 3 percentage points of the values determined by LOI testing and were obtained onsite within hours. In addition, the pXRF measurements more closely matched the initially batched materials on site that were intentionally overdosed by up to 25% of the GAC blending target to avoid failure. The preliminary correlation presented here provides strong promise for the use of pXRF as the CQA method to furnish accurate GAC content results for the GAC/sand blends onsite within hours (not days) during the implementation of the Gowanus Canal capping remedy. [ABSTRACT FROM AUTHOR]

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The objective of the present research is to use the standard turbulent kinetic energy and turbulent dissipation (k-e) model to do a numerical modelling and simulation of the gasification chamber or reactor which was used to gasifier Lafia-Obi bituminous coal. The numerical modelling and simulation were implemented with the aid of AutoCAD and Ansys softwares. The gasifier/reactor geometry was modelled using AutoCAD and then imported to Ansys workbench for simulation. Results show the modelled reactor geometry comprising a height of 0.9m, diameter of 0.5m and volume of 0.177m3. Simulation results show mass fraction of producer gas components comprising of 16% carbon monoxide, 14% hydrogen, 2.7% methane and 18% carbon dioxide. The producer gas yield is in conformity with standard producer gas yield. Temperature profile around the modelled gasifier/reactor was displayed with a maximum of 960K. [ABSTRACT FROM AUTHOR]

Botswana coal found within the Karoo Basin has received little attention primarily due to limited data on its properties. Several previous researches have been conducted using data for South African coal. However, coal is a heterogeneous material with properties varying not only across different geographic sites but also in iso-seams. Thus, it is important to conduct a study on Botswana coal to determine its combustion characteristics and reactivity. Thermogravimetric analysis was used to study thermal decomposition and determine coal kinetic parameters of coals from the Morupule, Mmamabula and Mabesekwa coalfields. Coal samples were subjected to non-isothermal heating at a heating rate of 25 °C/min in an oxygen atmosphere until a maximum temperature of 1000 °C was reached. Different combustion parameters such as combustion temperatures, and maximum combustion rate were determined from thermogravimetric analysis/derivative thermogravimetric curves. Also determined were the five comprehensive combustion indices for further appreciation of the samples' combustion traits. Furthermore, the samples were classified based on the chemical composition of the ash. Combustion temperatures were found to be 512.93 ± 3.53 °C to 532.571.36 ± °C ignition temperature, 524.431.17 ± °C to 689.40.56 ± °C peak maximum temperature and 662.771.42 ± °C to 749.73 ± 0.86 °C burnout temperature. Basic oxides in ash could be used to establish the similarities between the coal ash samples via principal component analysis. Proximate-ultimate properties were used to characterize the coal samples into high volatile bituminous and lignite coal. Coal kinetics calculated using pseudo-first-order Arrhenius method yielded activation energies between 42.31 and 60.11 kJ mol−1. [ABSTRACT FROM AUTHOR]

Thermogravimetric-differential thermal analysis (TG-DSC) has been used to obtain information on combustion characteristics of bituminous coal and anthracite incorporating Cu(NO3)2, KNO3, ZnO and MnO2, and the apparent kinetic parameters were determined by the first-order Coats & Redfern method based on the TG-DSC results. Experiments were conducted from the 303 K–1172 K at heating rate of 10 K min−1. The ignition index, burning intensity, burnout index and activation energy were used as evaluation indexes. The weight of evaluation indexes was given by relative comparison method, The catalyst activity was evaluated by linear weighted synthesis method. It was indicated that those of bituminous coal and anthracite, the relative active sequence of catalysts to the comprehensive combustion performance of bituminous coal could be described as follows: Cu(NO3)2>KNO3>ZnO > MnO2. The relative active sequence of catalysts to the comprehensive combustion performance of anthracite could be described as follows: Cu(NO3)2>ZnO > MnO2>KNO3.

Bituminous coal reservoirs exhibit pronounced heterogeneity, which significantly impedes the production capacity of coalbed methane. Therefore, obtaining a thorough comprehension of the pore characteristics of bituminous coal reservoirs is essential for understanding the dynamic interaction between gas and coal, as well as ensuring the safety and efficiency of coal mine production. In this study, we conducted a comprehensive analysis of the pore structure and surface roughness of six bituminous coal samples (1.19% < Ro,max < 2.55%) using various atomic force microscopy (AFM) techniques. Firstly, we compared the microscopic morphology obtained through low-pressure nitrogen gas adsorption (LP-N2-GA) and AFM. It was observed that LP-N2-GA provides a comprehensive depiction of various pore structures, whereas AFM only allows the observation of V-shaped and wedge-shaped pores. Subsequently, the pore structure analysis of the coal samples was performed using Threshold and Chen's algorithms at ×200 and ×4000 magnifications. Our findings indicate that Chen's algorithm enables the observation of a greater number of pores compared to the Threshold algorithm. Moreover, the porosity obtained through the 3D algorithm is more accurate and closely aligns with the results from LP-N2-GA analysis. Regarding the effect of magnification, it was found that ×4000 magnification yielded a higher number of pores compared to ×200 magnification. The roughness values (Rq and Ra) obtained at ×200 magnification were 5–14 times greater than those at ×4000 magnification. Interestingly, despite the differences in magnification, the difference in porosity between ×200 and ×4000 was not significant. Furthermore, when comparing the results with the HP-CH4-GA experiment, it was observed that an increase in Ra and Rq values positively influenced gas adsorption, while an increase in Rsk and Rku values had an unfavorable effect on gas adsorption. This suggests that surface roughness plays a crucial role in gas adsorption behavior. Overall, the findings highlight the significant influence of different methods on the evaluation of pore structure. The 3D algorithm and ×4000 magnification provide a more accurate description of the pore structure. Additionally, the variation in 3D surface roughness was found to be related to coal rank and had a notable effect on gas adsorption. [ABSTRACT FROM AUTHOR]

Accurately predicting fuel blends' lower heating values (LHV) is crucial for optimizing a power plant. In this paper, we employ multiple artificial intelligence (AI) and machine learning‐based models for predicting the LHV of various fuel blends. Coal of two different ranks and two types of biomass is used in this study. One was the South African imported bituminous coal, and the other was lignite thar coal extracted from the Thar Coal Block‐2 mine by Sind Engro Coal Mining Company, Pakistan. Two types of biomass, that is, sugarcane bagasse and rice husk, were obtained locally from a sugar mill and rice mill located in the vicinity of Sahiwal, Punjab. Bituminous coal mixture with other coal types and both types of biomass are used with 10%, 20%, 30%, 40%, and 50% weight fractions, respectively. The calculation and model development procedure resulted in 91 different AI‐based models. The best is the Ridge Regressor, a high‐level end‐to‐end approach for fitting the model. The model can predict the LHV of the bituminous coal with lignite and biomass under a vast share of fuel blends. [ABSTRACT FROM AUTHOR]

Sorting coal and gangue is important in raw coal production; accurately identifying coal and gangue is a prerequisite for effectively separating coal and gangue. The method of extracting coal and gangue using image grayscale information can effectively identify coal and gangue, but the recognition rate of the sorting process based on image grayscale information needs to substantially higher than that which is needed to meet production requirements. A sorting method of coal and gangue using object surface grayscale-gloss characteristics is proposed to improve the recognition rate of coal and gangue. Using different comparative experiments, bituminous coal from the Huainan area was used as the experimental object. It was found that the number of pixel points corresponding to the highest level grey value of the grayscale moment and illumination component of the coal and gangue images were combined into a total discriminant value and used as input for the best classification of coal and gangue using the GWO-SVM classification model. The recognition rate could reach up to 98.14%. This method sorts coal and gangue by combining surface greyness and glossiness features, optimizes the traditional greyness-based recognition method, improves the recognition rate, makes the model generalizable, enriches the research on coal and gangue recognition, and has theoretical and practical significance in enterprise production operations. [ABSTRACT FROM AUTHOR]

Blending bituminous coal (BC) in semi‐coke (SC) is a promising approach to improve the combustion behaviors of SC, while the nitrogen conversion characteristics during the co‐combustion are still unclear. This paper deals with the oxidation characteristics of volatile‐N and char‐N and their contributions to total NO during the co‐combustion of SC and BC using a volatile–char separated combustion system. By comparing the volatile–char separated combustion with the entrained flow combustion, the interaction between volatile‐N and char‐N has also been elucidated. Results indicated volatile‐N was the main contribution to total NO formation for both SC and BC at temperatures above 1000°C. The volatile‐NO and char‐NO conversion ratios presented distinct variations along with the temperature, and the temperature had different impact on the two combustion modes. The char‐NO was more sensitive to the variation of oxygen concentration, and the nitrogen conversion of SC was more susceptible to oxygen compared with that of BC. The blending of BC inhibited the volatile‐NO and char‐NO formation of SC, and the inhibition effect enhanced in pace with the blending ratio of BC. The influence of volatile–char interaction on nitrogen conversion was temperature‐dependent and fuel‐varying: for SC, it was more significant in pyrolysis stage in the temperature range of 900°C to 1400°C, and sufficient pyrolysis measures can effectively reduce the NO formation; however, the identical result occurred when the temperature exceeded 1100°C for the blend. [ABSTRACT FROM AUTHOR]

Studies on coal permeability at high temperatures (> 300 ℃) under the thermo–hydro–mechanical–chemical (THMC) coupling effect are few and their conclusions are divergent. Herein, the influence of different volumetric stresses (12, 24, and 36 MPa) on bituminous coal permeability is discussed. Moreover, the permeability evolution law of bituminous coal under different pore pressures (0.2–0.8 MPa) and temperatures (300 ℃–600 ℃) are studied using a self-made triaxial test machine with the THMC coupling effect. The experimental findings and micro-computed tomography (micro-CT) test results of coal samples under different temperatures in situ are reported. The obtained results show that (1) bituminous coal permeability underwent a negative logarithmic change with pore pressure (0.2–0.8 MPa) at different temperatures because of gas adsorption–expansion, gas slippage, and shear deformation. (2) Bituminous coal permeability varied with temperature in stages; this result differs from traditional research results. At 300 ℃–450 ℃, the permeability continuously decreased and slightly increased at 450 ℃–600 ℃; however, it was still lower than that at 300 ℃. The micro-CT results show consistent porosity evolution with permeability. (3) At 300 ℃–450 ℃, the permeability attenuation of bituminous coal mainly resulted from coal softening deformation. The continuous increase in the coefficient of linear thermal expansion increased the permeability decay rate. With the increasing temperature from 450 ℃ to 600 ℃, the accelerated pyrolysis of the coal sample enhanced the permeability, the coefficient of linear thermal expansion exhibited a negative correlation with temperature, and the inhibition effect of coal compression on permeability was weakened, slightly increasing the permeability at this stage. However, the continuous compression accumulation effect of stress still played a principal role, inducing low permeability. (4) Under the same temperature and pore pressure, the correlation between the permeability and volumetric stress of the coal samples decreased exponentially. Highlights: The permeability evolution of bituminous coal under high temperature and triaxial pressure was studied Bituminous coal permeability decreases with temperature at 300 ℃–450 ℃, and increases with temperature at 450 ℃–600 ℃ The microstructure evolution of bituminous coal under in situ high temperature condition was studied by in situ micro-CT scanning technology The weakening mechanism of bituminous coal under high temperature was clarified The differences with previous research results were discussed and explained [ABSTRACT FROM AUTHOR]

To further explore the mechanism of coal spontaneous combustion and better grasp the laws of spontaneous combustion, this article studied the adsorption behavior of O2 in coal. Materials studio software was applied to study the adsorption of oxygen under different water content, different pore sizes, and different oxygen-containing functional groups by means of grand canonical Monte Carlo and molecular dynamics simulation methods. The results show that the adsorption capacity of O2 decreases with the increase in water content. With the increase of molecular pore size of coal, the adsorption capacity of O2 increases, and the tight adsorption amounts decrease. The equivalent adsorption heat is less than 42 kJ/mol, indicating that the adsorption of O2 in coal pores is physical adsorption. The smaller the physical adsorption energy and charge transfer value of the hydroxyl group for O2, it indicates that the hydroxyl group is the active group for the physical adsorption of O2. [ABSTRACT FROM AUTHOR]

Wood biomass is an alternative to fossil fuels. However, biomass use has several limitations. Torrefaction, in which reduction conditions prevail to overcome these limitations, has been suggested. Here, torrefaction using different wood chips (Liriodendron tulipifera, Populus canadensis, Pinus rigida, and Pinus koraiensis) was conducted under oxygen-rich and oxygen-lean conditions to determine the effects of oxygen. Torrefaction was conducted at 230–310 °C for 1 h. A mass yield difference of 3.53–20.02% p (percentage point) was observed between oxygen-lean and oxygen-rich conditions. The calorific value increased by a maximum of 50.95% and 48.48% under oxygen-rich and oxygen-lean conditions, respectively. Decarbonization (DC), dehydrogenation (DH), and deoxygenation (DO) occurred in the following order because of dehydration and devolatilization during biomass torrefaction: DO > DH > DC. The calorific value of the torrefied biomass increased linearly with the extent of all three processes. The combustibility index and volatile ignitability were calculated based on proximate composition to suggest the optimal conditions for replacing anthracite and bituminous coal. This study provides suggestions for stable operation in a standard boiler design. [ABSTRACT FROM AUTHOR]

Dust control has always been a difficult problem in the process of safe mining. Using composite surfactants becomes a simple and effective dust suppression method. However, the micro mechanism of the effect of composite ratio on coal wettability was still unclear. In this study, the experimental combined with molecular dynamics (MD) simulations were used to research the effect of different composite ratios of SDS (Sodium dodecyl sulfate)/JFC (Fatty alcohol polyoxyethylene ether) surfactant on bituminous coal wettability. The experiment results showed that the mixed JFC and SDS solution had good wettability on bituminous coal. The contact angle and surface tension decreased as the proportion of JFC increased in the compound solution. Zeta potential experiment results indicated that adding JFC improved the aggregation ability between coal dust and promoted the settlement of coal dust in the mixed surfactant. The best synergistic wetting effect was achieved at a molar ratio of 1:3 (SDS/JFC). The simulation results showed that the thickest coal/water adsorption layer was formed at a 1:3 (SDS/JFC) mixing ratio. At this ratio, the diffusion coefficients of water molecules increased significantly, which promote the probability of coal collision with water molecules. Finally, the mechanism of the optimal synergistic ratio promoting coal wetting was explained by analyzing the distribution configuration of surfactant molecules. The whole work is of great significance to coal dust prevention and provides a new idea for exploring the synergistic composite ratio of wetting agents. [Display omitted] [ABSTRACT FROM AUTHOR]