Coal Miners Research Articles

Partitioning Behavior of Lithium and Rare Earth Elements During Coal Preparation and Their Differences in Mode of Occurrence

ABSTRACT Coal preparation technology is an important and widely useful way to achieve clean utilization of coal. Furthermore, it has a huge effect on the recovery of critical elements in coal, including lithium (Li) and rare earth elements (lanthanides and yttrium, REY). In this study, the migration of Li and REY during coal preparation was investigated from industrial practice and laboratory. After industrial separation, Li is significantly enriched in the coal gangue with high ash content, while REY mainly migrates to fine coal, clean coal, and coal slime. Results of screening and float-and-sink from the laboratory show that Li is enriched in the +3 mm particle size fraction and the +2.0 g/cm3 density fraction, while REY is greatly enriched in the −0.5 mm particle size fractions and the −1.8 g/cm3 density fractions. Modes of occurrence of Li and REY greatly affect their migration routes during separation. Results of sequential chemical extraction and oxidation decomposition reveal that more REY occurs in organic matter-bound form compared to Li. REY-bearing minerals (monazite and bastnaesite) in feed coal were found by SEM-EDS, but they are embedded in organic matter. In addition, oxidation decomposition experiments confirmed that REY can directly bind to organic matter in coal, especially heavy REY. These findings demonstrate that REY is closely associated with the organic fractions, while the majority of Li occurs in inorganic minerals for these coals. This research could give support to clarify the Li and REY migration during coal preparation and their extraction in the future.

Trace Element Geochemistry and Stable Isotopic (δ13C and δ15N) Characterisation of Nevşehir Coals, Türkiye

The Nevşehir coals are located in the Central Anatolian Crystalline Complex (CACC), Türkiye, and no reports exist on trace element, nitrogen, and carbon isotope composition data of the Nevşehir coals. The present study aims to geochemically characterise the Nevşehir coals to determine their trace elemental enrichment patterns and possible sources. Nevşehir coals are found within Late Miocene Kızılöz Formation (Arafa Member) rocks. These coals are part of the huminite maceral group; the dominant maceral group is ulminites. The minerals in coals are inorganic, such as oxidised framboidal pyrite, iron oxide minerals, quartz, clay, and carbonate minerals. Coals have great potential regarding trace elements. Benefits might arise from mining and using some of the critical elements derived from coal. Compared with the world coal average, the coal samples in this study are enriched in As (149.25 μg/g), V (245 μg/g), Cr (159 μg/g), Ga (18 μg/g), Ni (216 μg/g), Th (17 μg/g), Zn (143 μg/g), and U (54 μg/g). The arsenic content in this study is associated with inorganic components such as oxidised framboidal pyrite. Vanadium in coal is mainly associated with aluminosilicates and organic matter. Chromium originates from the clay minerals within coals. Uranium in coal is mainly associated with organic matter. Nickel and zinc in coal are predominantly associated with sulphides. The δ15N contents of the samples are comparable to those of several references, including plants, terrestrial creatures, and organic nitrogen. The δ13C–δ15N isotopic range and average values for four coal samples ranged from −25.66‰ to −25.91‰ (−25.80‰) and 3.6‰ to 4.3‰ (3.9‰), respectively, demonstrating that C3 type modern terrestrial vegetation was common in the palaeomires of the studied coal seams.

Clean Carbon Steelmaking: Evaluating the Replacement of Mineral Coal with Malt Biochar in Iron Ore Pelletization

Clean Carbon Steelmaking: Evaluating the Replacement of Mineral Coal with Malt Biochar in Iron Ore Pelletization

Ecological and health risk assessments of heavy metal contamination in soils surrounding a coal power plant

Coal combustion at power plants is a significant source of environmental pollution, with the deposition of heavy metals in soils leading to extensive ecosystem contamination and exacerbating the harmful impacts of human activities. This study presents a field investigation of heavy metal concentrations in soils around a coal-fired power plant, with monitoring sites located 1.7 to 15.2km from the plant. Data collection occurred in 2015, 2020, and 2024 across 11 monitoring sites. X-ray fluorescence analysis was used to assess heavy metal concentrations in soil. A life cycle assessment (LCA) with ReCiPe method was conducted to evaluate the impacts on both ecological and human health. The results revealed that the concentrations of Pb, Zn, Cu, Ni, Mn, Cd, and Cr exceeded threshold levels set by both the World Soil Average and the Regional Geochemical Background. The correlation analysis shows that organic matter and clay content play vital roles in reducing the mobility of heavy metals in soil through adsorption. Notably, strong correlations between Pb and Cd suggest a common origin from coal seam minerals. The LCA shows that freshwater ecotoxicity, marine ecotoxicity, terrestrial ecotoxicity, and human toxicity increased by over 30% compared to the World Soil Average pollutant levels. Nickel was identified as the primary contributor to marine and freshwater ecotoxicity, while manganese had the most significant impact on human toxicity. This study provides a better understanding of the long-term consequences of heavy metal accumulation in soils near coal-fired power plant. The data on anthropogenic impacts are crucial for developing effective strategies to mitigate environmental risks associated with pollution.

Transforming sludge into energy: impact of blend percentage on energy recovery potential and environmental benefits of co-combustion of wastewater sludge and coal in Brazil.

Proper waste management and sustainable energy production are crucial for human development. For this purpose, this study evaluates the impact of blending percentage on energy recovery potential and environmental benefits of co-combustion of wastewater sludge and Brazilian low-rank coal. The sludge and coal were characterised in terms of their potential as fuel and co-combustion tests were carried out in a pilot-scale bubbling fluidised bed focused on the influence of the percentage of sludge mixture on the behaviour of co-combustion with coal in terms of flue gas composition and fluidised bed temperature stability. Sludge has a higher heating value (16.276MJ/kg) than coal (15.486MJ/kg) and a higher fuel ratio (8.48 vs. 0.21). The O2 and CO2 levels found in the co-combustion tests, together with a very low CO concentration, indicate good combustion. However, the NOx emission was considerable, varying from 825.2±94.5 to 1,320.5±33.8mg/m3 (O2ref=7%), pointing to the need for actions to reduce atmospheric pollution. Coal had higher ash content (52.64% vs. 25.00% d.b.). The temperatures in the bed region and in the combustion region showed similar behaviour for all the fuels. The addition of sewage sludge to mineral coal reduced the ash content without increasing the ash fusibility risk in the combustion temperature range evaluated. These findings suggest that sludge addition in co-combustion with coal offers promising results for both energy production and environmental sustainability.

Contribution of the Geodiversity knowledge to social, economic, and environmental health development

With the support of this study, based on published information, this article highlights that Geosciences enable the research of methods and perspectives aimed at optimizing the management of natural resource use, aligning them with ecological limitations and incorporating environmental and social variables into the territorial planning process. Geoscientific information, knowledge, and learning establish a foundation for the supply of essential resources and provide technical and scientific support across various sectors and topics of societal interest. These include mining, where knowledge and proper utilization of essential mineral resources are crucial for human survival and quality of life; energy, which relies on petroleum, gas, coal, peat, and other minerals for nuclear energy generation, as well as for renewable energy sources like wind and solar power. Agriculture, which depends on fertilizers, soil remineralizers, conditioners, and a reliable water supply. In the field of public health, geoscientific knowledge helps ensure the quality of water, soil, and air. In urban planning, it guides land-use restrictions or expansion. In housing, the availability of construction materials is essential. In civil defense, geoscientific insights are crucial for managing landslides, floods, earthquakes, subsidence, and erosion. Regarding infrastructure, geosciences support both social (housing, sanitation, education, healthcare) and economic (energy, transportation, communications) developments. Tourism benefits from geoparks and scenic areas, while environmental studies focus on impact assessments, disaster prevention, and the rehabilitation of degraded areas. Moreover, geoscientific knowledge is indispensable for planning across various sectors of the economy, regions, and societal issues. This applies to public institutions, civil society organizations, private companies, and watershed committees, aiding in the formulation of Regional Development Plans, Ecological-Economic Zoning, Territorial Planning, and strategies for the utilization of continental shelves, coastal environments, and accident prevention. We are entirely dependent on the geological characteristics of natural environments, as they provide the raw materials—such as minerals, water, and food—necessary for our survival and socio-economic development. As geoscientific knowledge and understanding of land and environmental suitability and limitations increase, Geodiversity can play a more significant role in shaping public policies related to urban and rural land use, infrastructure, and the sustainable economic exploitation of mineral and water resources, aligning with Municipal Master Plans, State Development Plans, and the National Territorial Planning Strategy.

Review Article: Interlocked Block Added With Mineral Coal Burning Waste For Rural Road Paving

Objective: The objective of this study is to present a scientific bibliographic review article on the use of light ash on interlocked concrete floors and identify possible scientific gaps related to the reuse of light ash, which is a by-product from thermoelectric plants, in terms of technical feasibility for the production of the material and in the exploitation of the sustainable potential for reuse. Theoretical reference: It is based on concepts of environmental sustainability, reuse of industrial waste, and improvements in concrete properties through the addition of fly ash, a byproduct of the burning of coal in thermoelectric plants. It uses authors and studies that address the reduction of environmental impacts in civil construction and the technical feasibility of sustainable materials for paving. Method: Searches were carried out on scientific databases, using the advanced search mechanism of the ScienceDirect platform, published by Elsevier (www.sciencedirect.com). The keywords used for the research in the first filter were "fly ash" and "paver block", and the summary of articles and keywords were analyzed, the selected articles prioritized publications of the last five years (2019-2024), in order to include recent advances and technological developments. In a second filter, a new review of the articles already collected was carried out, in the software management of bibliographic reviews and citations Zotero (https://www.zotero.org/), through keyword search and search in the full text of the articles. Results and Discussion: The results and discussions of the article address the properties and impacts of the incorporation of light ash into concrete, highlighting technical, environmental and economic aspects. Main points covered, Properties of light ash and resulting concrete, environmental impacts, practical applications and challenges and limitations. Research Implications: The practical and theoretical implications of this research are discussed, providing insights into how the results can be applied or influence practices in the field of environmental impacts and CO2 emissions, as well as economic and social implications. These implications may include an alignment with sustainable policies and sustainable waste management. Originality/Value: This study contributes to the literature by the innovative and specific theme, with a combination of infrastructure and sustainability. The relevance and value of this research is evidenced by its contribution to environmental sustainability and strategic relevance.

Control technology of roadway floor heave based on a new grouting material

Abstract In the mining process of the working face, mining activities will inevitably damage the surrounding rock of the roadway near the working face and pose a threat to the safety of coal miners. The stability of the roadway is of great significance for the safe production of coal mines. In this paper, a new type of grouting material is used to treat the failure characteristics of the roadway with rock bolts and bottom plate unloading grooves, and the deformation of the roadway after treatment is monitored. The results show that stress concentration occurs after the mining of the working face, with a large influence range and broken surrounding rock. The new grouting material has a wide setting time range, which can meet the grouting needs of different broken surrounding rocks. The dry shrinkage and bleeding rate of the stone-forming body are small, and the slurry has good stability. The strength of consolidated coal after 8 hours can reach 13.1 MPa. After roadway treatment, the displacements of the roadway are 59 mm and 46 mm respectively. The deformation of the roadway is effectively controlled.

Optimization and Practice of a High-Strength Acoustic Wave Indirect Penetration Enhancement Scheme for the Drilling of Structural Coal Seams

The structural coal seam drilling process often faces challenges such as shallow drilling depth, low hole formation rate, and the presence of blind areas in gas control. To address these issues, this study proposes a novel high-strength acoustic penetration approach and optimization design method under in situ conditions. Field tests were conducted at the Yunnan Bailongshan Coal Mine and Huainan Xieqiao Coal Mine to evaluate the effectiveness of this technique. The results demonstrate that the coal seam or its roof can act as an acoustic energy converter to generate high-intensity acoustic waves that penetrate the coal seam, and the field test results confirm the efficacy of this method in increasing gas extraction. This study proposes a novel ‘hole replaces seam’ technique, optimizing the extraction process and reducing the risk of explosions and providing a more efficient and safer method for gas control in structural coal seams. Accordingly, a new technical method for replacing the bottom (top) extraction lane is proposed.

Experimental Investigation of the Effect of Microstructure on Coalbed Methane Adsorption Characteristics Affected by Chemical Solvents.

Coalbed methane (CBM) reservoir modification based on chemical solvent treatment could change the coal microstructure, which further affects the adsorption capacity and flow characteristics of this clean energy. Coal samples were extracted by tetrahydrofuran (THF), carbon disulfide (CS2), and hydrochloric acid (HCl). Low-pressure nitrogen adsorption, carbon dioxide adsorption, Fourier transform infrared spectroscopy, and methane isothermal adsorption test were adopted. The variations of pore structure and chemical composition in coal were evaluated by density functional theory, Barrett-Joyner-Halenda model, and peak fitting method, and their impacts on methane adsorption characteristics were studied. Results show that (1) the micropores less than 2 nm show a bimodal distribution. After acidification, micropore specific surface areas of coal samples I and II increase by 16.79% and 11.72%, respectively, while that of coal sample III-HCl decreases by 4.29% closely related to carbonate and silicate minerals in coal. Microporous specific surface areas of sample II-CS2 and III-CS2 affected by solvent rise by 4.28% and 4.17%, respectively. (2) Among the three original coal samples, the highest level of OH-OH hydrogen bonds content is observed. Solvents have a tendency to interact with -CH2 groups, which shorten the length of fat chains and increase the number of branched chains. THF tends to dissolve C-O-C groups and carbonyl C═O groups. Following CS2 treatment, samples II and III show 38.42% and 47.76% decrease in aromatic C═C area, respectively. (3) The methane adsorption capability in three coal samples is I > III > II. Except for sample I-HCl and sample III-THF, other coal samples have a lower methane adsorption capability than raw coal. Methane adsorption is reduced not just by a decrease in the number of micropores but also by aliphatic groups, aromatic structures, and oxygen-containing structures. Relevant results could deliver guiding significance for understanding methane adsorption and flow characteristics in coal after chemical solvent modification.

EEG-Based Measurement for Detecting Distraction in Coal Mine Workers

In the high-attention-demanding environment of underground coal mines, distraction is a major cause of unsafe behavior and decreased safety performance. Research on the cognitive neural mechanisms and monitoring of distraction in miners is limited. This study used an electroencephalogram (EEG) to examine the correlation between distraction and brain activity in coal miners, aiming to provide an objective method for monitoring distraction in coal miners. Thirty participants completed a simulated hazard recognition task, using the Sustained Attention to Response Task (SART) and noise to induce distraction. Brain activity was recorded and labeled as focused or distracted based on the correctness of the hazard recognition task. EEG features were extracted and selected, and a Random Forest model for distraction identification was constructed based on the selected features. In the focused state, delta power in the temporal region and theta power in the frontal region increased significantly. In the distracted state, alpha power in the temporal and occipital regions and beta power in the occipital and parietal regions increased. The selected EEG features could be used to identify distraction with 84% accuracy. This method can objectively identify distraction in coal miners, highlighting the potential of using EEG for real-time distraction monitoring.

Treatment of a fine soil of high plasticity with mineral coal bottom ash activated with cement, for use as a road subgrade

The current trend in soil stabilization involves the application of sustainable alternatives utilizing local materials. This study proposes the treatment of high plasticity fine soil sourced from Cajamarca, Perú, using mineral coal bottom ash (BA) and cement. The soil was classified as A-7-5 (27) of the AASHTO system, has low-quality as a subgrade, with a CBR 2.0% that does not meet resistance specifications. With the addition of BA, an improvement in the geotechnical properties was evidenced by a reduction in plasticity and fines content, however, the CBR only increased from 2.0% to 2.4% with 30% BA content. To enhance the effectiveness of BA, Type I Portland cement was incorporated at dosages of 1.0%, 1.5%, 2%, and 4.0%, the results were satisfactory, CBR values exceeded the required minimum. In a soil sample with 1% cement and 30% BA, CBR 14.1% was obtained. With 1.5% cement and BA between 10% and 30% the CBR increased ranging 13.7% to 72% respectively. This study concludes that the addition of a small quantity of cement significantly impacts the pozzolanic reaction, and the CBR increases according to the BA content.

LORAWAN BASED COALMINERS RESCUE AND HEALTH MONITORING SYSTEM USING IOT

The coal mining industry is one of the industries that possess inherent risks since workers are faced with a range of risks that include health risks, the extreme environment, and geology. To address these daunting tasks, we propose the deployment of an Integrated Safety and Monitoring System (ISMS) enhanced with LoRaWAN and IoT gadgets. A wide range of detectors, such as thermal sensors, gaseous detectors, oxygen and cardiac monitors, and state-of-the-art minerals analysis technologies, are integrated into our comprehensive ISMS design. Together, these detectors keep surveillance of the health of colliers along with their surroundings. The primary feature of ISMS is the continuous data transmit capability of the LoRaWAN invention, which permits the error-free transfer of critical sensor facts to a storage system that is remotely placed. This is acting as a kind of control station, giving officials data they can use to tackle safety problems and make things less dangerous quickly. Another special provision that ISMS offers is a series of coloured indicators representing severity levels. The device also saves the lives of coal miners in critical situations as it improves response time for search and rescue operations. Such powerful safety precautions during coal mining operations in this case can be considered as a huge advancement with the integration of smart appliances and LoRaWAN technology into ISMS. This improves operational efficiency as well, incites smart choices, and makes more powerful already existing security mechanisms. The proposed system, ISMS, is innovative and progressive, leading to the development of new safety layers in the high-risk arena of mining.

Drillers and bulldozer operators have experienced exceptionally high exposures to respirable crystalline silica in US surface coal mines

IntroductionPrevious studies suggest respirable crystalline silica (RCS) is an important driver of resurgent pneumoconiosis among US coal miners. Although greater attention has been focused on dust exposures in underground coal...

Robust Miner Detection in Challenging Underground Environments: An Improved YOLOv11 Approach

To address the issue of low detection accuracy caused by low illumination and occlusion in underground coal mines, this study proposes an innovative miner detection method. A large dataset encompassing complex environments, such as low-light conditions, partial strong light interference, and occlusion, was constructed. The Efficient Channel Attention (ECA) mechanism was integrated into the YOLOv11 model to enhance the model’s ability to focus on key features, thereby significantly improving detection accuracy. Additionally, a new weighted Complete Intersection over Union (CIoU) and adaptive confidence loss function were proposed to enhance the model’s robustness in low-light and occlusion scenarios. Experimental results demonstrate that the proposed method outperforms various improved algorithms and state-of-the-art detection models in both detection performance and robustness, providing important technical support and reference for coal miner safety assurance and intelligent mine management.

The effect of workplace environment on coal miners' gut microbiota in a mouse model.

The coal mine workplace environment is a significant factor in inducing occupational health issues, such as intestinal dysfunction in coal miners. However, the mechanism by which the coal mine workplace environment induces intestinal dysfunction is still unclear. Therefore, we applied the Coal Mine Workplace Environment Biological Simulation (CEBS) model which was previously constructed to detect the intestinal pathological manifestations and changes in the gut microbiota of mice from the perspectives of intestinal function, tissue morphology, and cell molecules. CEBS mice showed increased fecal water content, shortened colon length, significant activation of MPO+ and CD11b+ numbers, and significant changes in IL-1b, IL-6, and IL-12 expression levels. In addition, we also found an imbalance in the proportions of Firmicutes, Bacteroidetes, Lactobacillus, and Parabacteroides in CEBS mice, resulting in significant changes in gut microbial diversity. After intervention with compound probiotics, the intestinal function of CEBS + Mix mice was improved and inflammation levels were reduced. Results indicated that stress in the coal mine workplace environment can lead to intestinal dysfunction and inflammatory damage of the colon and use of compound probiotics can improve intestinal dysfunction in CBES mice. In our study, we revealed that there is a correlation between coal mine workplace environment and diversity disorders of gut microbiota. This discovery has enhanced the relevant theories on the causes of intestinal dysfunction in coal miners and has suggested a new approach to intervention.

Inorganic Geochemistry of Coal from Patappa Village, Bone District, and Masenrengpulu Village, Barru District, South Sulawesi Province Using XRF Method

The chemical composition of coal is almost the same as that of plant tissue, containing the main elements of elements C, H, O, N, S, and P. An in-depth study of coal inorganic compounds is needed because coal inorganic compounds are the primary variable in ash formation during coal combustion. This study uses the X-ray fluorescence method to reveal the differences and similarities in inorganic chemical composition contained in coal in Bone Regency and Barru Regency. Coal in Masenrengpulu Village has the Al2O3 compound as the most dominant compound, while coal in Patappa Village has the SiO2 compound as the most prevalent compound. The concentration of inorganic sulfide minerals in the village of Masenrengpulu was influenced by igneous rock intrusion and deposition processes. In contrast, the deposition process only affected the inorganic sulfide minerals of coal in Patappa village. The significant elements found in coal in the Masenrengpulu and Patappa Villages are Si, Al, Fe, S, Ca, K, and Ti. Coal inorganic sulfide minerals in Masenrengpulu Village with Patappa Village have high concentrations in the bottom channel of the coal seam and a low concentration in the middle channel and top of the seam. Coal inorganic sulfide minerals in Masenrengpulu Village and Patappa Village have high concentrations in the coal seam's lower channel and low concentrations in the middle and upper channels. Keywords: Coal Comparison, Mallawa Formation, XRF, Inorganic Geochemistry.

Damage Mechanism of Deep Coalbed Methane Reservoir and Novel Anti-Waterblocking Protection Technology

Coalbed Methane (CBM) accounts for about 5% of China’s domestic gas supply, which has been regarded as one of the most promising energies for alleviating the energy supply–demand imbalance. Deep CBM reservoirs have the characteristics of low permeability, low porosity, and low water saturation, which easily experience reservoir damage during the drilling process, further affecting the gas productivity. Based on the analysis of coal mineral composition, pore structure distribution, and the surface micromorphology change in coal surface before and after hydration, a possible mechanism for CBM formation damage was revealed. It was found that the damage caused by drilling fluid intrusion can be divided into three stages: stripping, migration, and plugging. Based on the water-sensitive, acid-sensitive, and stress-sensitive evaluation tests, a novel anti-waterblocking agent with both wettability alteration and surface tension reduction was developed; then a reservoir protection drilling fluid for deep coal formation in Daning-Jixian block was constructed; then the reservoir protection performance of drilling fluid was evaluated. The results show that as the concentration of the anti-waterblocking agent FSS increases from 0% to 1%, the surface tension of the water phase is significantly reduced from 72.15 mN/m to 26.58 mN/m, while the maximum contact angle of water on the surface reaches 117°. This enhancement in wettability leads to an improvement in the permeability recovery rate from 56.6% to 80.0%, indicating a substantial reduction in waterblocking effects and better fluid mobility within the reservoir. These findings highlight the efficacy of FSS in mitigating formation damage and optimizing gas production in coalbed methane reservoirs. The drilling fluid has good wettability alteration, inhibition, and sealing performance, which is of great significance for protecting gas well productivity.

Organic modes of occurrence and evolution mechanism of germanium and lithium in coal: Insights from density functional theory

Critical elements in coal, such as Ge and Li, recently have attracted attention due to their economic significance. Modes of occurrence of these critical elements are academically and practically important, because they can not only provide evidence for sources of elements and minerals in coal and regional geological background information, but also help with design of recovery methods. However, conventional analytical methods are unable to observe precisely the organic binding sites of Ge and Li in coal, and this limits the understanding of their enrichment mechanism and the improvements for recovery techniques. In this study, organic modes of occurrence and evolution mechanism of Ge4+ and Li+ were investigated at the atom level by constructing molecular models of Ge- and Li-rich coals combined with density functional theory (DFT) methods. The solid-state 13C nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and helium pycnometry analyses indicate that the molecular formulas of Ge- and Li-rich coals are C166H162N2O32 and C153H174N2O24S, respectively. The DFT analysis reveals that the binding sites for Ge4+ in Ge-rich coal are located near the carboxyl group (-COOH) and the pyrrole ring, while those for Li+ in Li-rich coal are near the carbonyl group (-C=O) and the pyrrole ring. The Ge4+ is immobilized in the Ge-rich coal molecular model through coordination bonds with the O atom in the -COOH and the C atom in the pyrrole ring, while being away from the N atom in the pyrrole ring. Li+ forms a coordination bond with the O atom in the -C=O and additional coordination bond with the nearby hydroxyl group during binding to the pyrrole ring. The impact of coal rank on the organic modes of occurrence of Ge4+ and Li+ was investigated using Wender coals of different ranks, which were one of the earliest proposed coal models. At the lignite stage, oxygen-containing functional groups and aromatic rings show a strong binding ability to Ge4+ and Li+, facilitating their enrichment in coals. Along with coal rank advance to bituminous coal, the reduction of oxygen-containing functional groups (e.g., -COOH and -C=O) and the relatively low condensation of aromatic rings decrease binding sites for Ge4+ and Li+, and the binding ability also decline, resulting in a decrease in their concentration. In anthracite stage, highly condensed aromatic rings provide binding sites for Ge4+ and Li+. The strong binding ability of aromatic rings to Ge4+ indicates that it is probably enriched in anthracite, whereas Li+ is difficult to enrich owing to its relatively weak binding ability to aromatic rings. The low content of oxygen-containing functional groups in anthracite reduces their effect on the organic modes of occurrence of Ge4+ and Li+. This study elucidates the organic modes of occurrence and evolution mechanism of Ge4+ and Li+ from the perspective of coal structure, providing fundamental insights for future research on the interaction between organic and inorganic matter within coal.

Study on physical and chemical structure modification law and mechanism of coal based on organic acidification

Deep coal seams in China have the characteristics of low permeability, low porosity, and poor gas permeability, which makes the extraction of coalbed methane very difficult. To study the modification effect of acidic solutions on coal pore structure and mineral components, this study used three different concentrations (5%, 10%, and 15%) of organic acids (HCOOH and CH3COOH) to treat coal. Through industrial/elemental analysis, low-temperature nitrogen adsorption experiments, and x-ray fluorescence spectroscopy detection experiments, the pore size distribution, mineral elements, and oxides of the acidified coal were analyzed. The strength of the acid solution's modification effect on coal was analyzed, as well as the relationship between different mineral elements and changes in pore structure. The results show that the two acids have a pore expanding effect on coal, with an increase in average pore size; the pore size distribution is between 2 and 50 nm, belonging to mesopores; acetic acid has a stronger overall dissolution efficiency on inorganic minerals, while formic acid has a better effect on the removal of Ca and P elements, but none of them can effectively remove silicoaluminates; the content of Ca element in coal is positively correlated with the specific surface area provided by mesopores; and iron dolomite is not sensitive to the reaction with acetic acid, resulting in an opposite trend in Fe content and mesoporous specific surface area. Organic acid solution changes the pore and fracture distribution structure of coal through chemical dissolution by dissolving the mineral components inside the coal, thereby affecting its internal structural characteristics.