Coal Materials Research Articles

Regulating Closed Pore Structure of Coal-Based Hard Carbon Anode by Preoxidation for High-Rate Performance Sodium-Ion Batteries.

Coal-derived hard carbons (CHCs) have considerable potential as sodium storage materials because of their abundant resources and structural diversity. Nevertheless, the smaller layer spacing and ordered carbon microstructure of CHCs bring about low charge/discharge rates and poor cycle life of sodium-ion batteries (SIBs), rendering it challenging to support large-scale energy storage applications. Herein, the preoxidation strategy is employed to achieve multiscale structure optimization of CHCs and improve its sodium storage capacity. The oxygen content in preoxidized coal reached 15.2%, contributing to increasing the cross-linked structure of the coal materials. Particularly, insertion of Na+ is facilitated by large layer spacing of 0.394 nm, as well as the closed pores (0.162 cm3 g-1) improving the diffusion of Na+. Consequently, the rate performance of the as-optimized anode (OCHC3) is superior to that of directly carbonized. Specifically, OCHC3 exhibits a commendable rate performance (201 mAh g-1) and achieves outstanding cycling stability (96.2%) over 500 cycles. Furthermore, galvanostatic intermittent titration reveals the "adsorption-insertion-filling" of OCHC3. This study enlightens the rational design of high-performance HC anodes for SIBs and beyond.

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.

Deamination mechanism of modified magnesium slag using wet aging and its performance evolution as backfill material.

The purpose of this study is to solve the problem of ammonia (NH3) release when modified magnesium slag (MMS) is used as coal mine backfill cementitious material, and to explore its chemical mechanism and put forward effective solutions. Uniaxial compressive strengths (UCS) hydration kinetics, scanning electron microscope (SEM), and thermogravimetric analysis-derivative thermogravimetry (TG-DTG), X-ray diffractometer (XRD) and other testing methods were used to study the evolution of the properties of MMS-based backfill material, which provided a scientific basis for the safe utilization of MMS. First, the chemical mechanism underlying the release of NH3 from MMS was identified, and it was confirmed that Mg3N2 and Li3N are the main nitrogen sources. This conclusion is based on thermochemical theory and the Pidgeon method. Secondly, the wet aging method was proposed to reduce the NH3 release from MMS-based backfill material. In addition, a continuous on-line gas detection system was used to determine the NH3 release pattern of MMS-based cementitious material under various aging water contents. The experiment showed a significant reduction in NH3 release with a lower aging water content of 3% and a reduction ratio as high as 81.55%. As the aging water content increased, the 28-day UCS gradually decreased. However, compared to the dry aging group, it remained above 3MPa when the aging water content was below 6%. The wet aging method can significantly shorten the pre-induction, induction, and acceleration periods of MMS-based cementitious material. The microstructure of the wet aging group exhibited fewer needle-like and rod-like ettringite (AFt) crystals as well as less flocculent hydrated calcium silicate (C-S-H) gel, whereas the unhydrated group had more fly ash (FA) and pores. Considering the UCS and NH3 release performance of MMS-based cementitious material, it is recommended to adopt a 3% aging water content and control the aging period to 7 days to effectively reduce NH3 release while ensuring the material's strength, thereby meeting the application requirements for coal mine backfill cementitious material.

Durability and microscopic mechanisms of coal gangue-calcium carbide residue geopolymer binder material

To evaluate the durability of coal gangue (CG)–calcium carbide residue (CCR) geopolymer in aggressive environments, full immersion tests were performed in H2SO4, Na2SO4, and MgSO4 solutions. Changes in compressive strength, mass loss, and performance degradation were examined. Degradation mechanisms were studied using XRD, FTIR, TGA, MIP, and SEM to analyze erosion products, microstructure, and pore evolution. An optimal liquid-to-solid ratio of 0.45 was identified for CG–CCR geopolymers. The material exhibited excellent resistance to Na2SO4 due to ettringite and C-A-S-H gel formation, enhancing pore structure and bonding strength. However, resistance to H2SO4 and MgSO4 was poor, driven by aluminum and calcium leaching and C-A-S-H transformation into non-cementitious M-A-S-H gels. A dense protective layer and corrosion-resistant C-A-S-H gel provided superior durability compared to OPC, with CCR addition further improving structural integrity and C-A-S-H gel generation. These findings highlight the potential of industrial waste-based geopolymers for durable, sustainable construction.

Pitch-derived Multifunctional Carbon and Bimetallic Sulfide Composite Electrodes for Aqueous Energy Storage

Pitch-derived Multifunctional Carbon and Bimetallic Sulfide Composite Electrodes for Aqueous Energy Storage

Oil discovery, energy transition, and the decline in wholesale prices during the Great Depression

AbstractStatistical tests are used to examine the role of prices for petroleum, coal, and farm products in the Great Depression. A new empirical mapping of relationships between monthly energy and farm product prices and key macroeconomic variables shows how biophysical factors intersected with the price system in the 1930s US economy. Deflation was a critical feature of the Depression, with the US aggregate wholesale price index falling by 37 percentage points between October 1929 and February 1933. Petroleum product prices and farm product prices can explain 89% of changes to the aggregate wholesale price index over the 1930s. Granger causality tests show that petroleum product prices led changes to money supply in the 1930s, by 8 months, while farm product and all‐commodities prices Granger caused changes to industrial production. Changes in prices from October 1929 to February 1933 varied substantially between commodities, with prices of coal, metals, and building materials—the essential ingredients for capital formation—all increasing in real terms. Real bituminous coal prices are found to Granger cause changes to money supply, personal income, and industrial production over the 1930s. Overall, the results add further support to the hypothesis that the Great Depression was caused by an energy transition, following discovery of large quantities of petroleum in the US Southwest.

Review on Gallium in Coal and Coal Waste Materials: Exploring Strategies for Hydrometallurgical Metal Recovery.

Gallium, a critical and strategic material for advanced technologies, is anomalously enriched in certain coal deposits and coal by-products. Recovering gallium from solid residues generated during coal production and utilization can yield economic benefits and positive environmental gains through more efficient waste processing. This systematic literature review focuses on gallium concentrations in coal and its combustion or gasification by-products, modes of occurrence, gallium-hosting phases, and hydrometallurgical recovery methods, including pretreatment procedures that facilitate metal release from inert aluminosilicate minerals. Coal gangue, and especially fly ashes from coal combustion and gasification, are particularly promising due to their higher gallium content and recovery rates, which can exceed 90% under optimal conditions. However, the low concentrations of gallium and the high levels of impurities in the leachates require innovative and selective separation techniques, primarily involving ion exchange and adsorption. The scientific literature review revealed that coal, bottom ash, and coarse slag have not yet been evaluated for gallium recovery, even though the wastes can contain higher gallium levels than the original material.

Микроэлементный состав золошлаковых отходов Забайкальского края

Fossil coal consists of organic and inorganic parts. The inorganic part is in the form of minerals. In the composition of inorganic matter, two chemical groups of elements are distinguished: ash-forming or main, constituting about 99 % of all inorganic matter; impurity or minor elements (about 1 % of the total inorganic matter). Among the impurity elements there may be rare valuable metals such as Ge, Ga, U, etc. Sometimes, the cost of rare metals in coal may exceed the cost of the coal itself, and then these coals are considered as low-balance mineral raw materials, and their organic matter found in their composition as a by-product. The article provides overview information on the results of studies already conducted and currently ongoing on the issue of the safe inclusion of ash and slag waste, which occupies vast areas near coal-fired power plants, into industrial circulation through their integrated use. The object of the research is coal combustion waste. The subject of the study is ash and slag waste from Transbaikal coal power plants. The purpose of the work is to assess the mineral composition of ash and slag waste in the Transbaikal Territory. The objective of the research is to obtain reliable information about the content and distribution of chemical elements in the inorganic matter of Transbaikal coals, which turn into ash and slag waste after combustion. The research methods are as follows: analytical research and processing of archival materials from previously carried out work; field testing of ash and sludge waste using modern instruments; processing of laboratory samples using modern laboratory equipment. The result of the research will be: assessment of the elemental composition of inorganic matter in coals based on the analysis of ash and slag waste and their potential impact on the ecological state of adjacent areas during combustion; typification of chemical elements of inorganic matter in Transbaikal coals: valuable components, potentially valuable, toxic, potentially toxic, technologically harmful and technologically useful.

Use of electron microscopy to determine presence of coal dust in a neighborhood bordering an open-air coal terminal in Curtis Bay, Baltimore, Maryland, USA

Despite decreasing US consumption, over 90 million metric tons of coal were exported by the US in 2023, requiring significant infrastructure for transport, handling, and storage of coal at export terminals. Residents in Curtis Bay, Baltimore, Maryland, USA live at the fenceline of an open-air coal terminal and have, for decades, reported rapid accumulation of black dust at their homes. Community-level exposure to coal dust originating from coal handling and storage terminals has remained largely unexplored. To investigate community-identified concerns and use a community-driven approach to determine the presence/absence of coal dust on Curtis Bay surfaces. Passive settled dust samples were collected from two residential areas, 345m and 1235m from the coal terminal, using conductive carbon tape. Scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX) of standard reference coal material and positive control material from the coal terminal in Curtis Bay were used to optimize the morphological and elemental classification criteria for coal dust. A manual SEM-EDX protocol was developed to identify coal particles in settled dust collected on conductive carbon tape in community settings. SEM-EDX analysis confirmed presence of coal dust sampled at both residential locations. Estimated coal dust particle loading at the proximal and distal site were 13.2 and 3.4 coal particles/mm2, respectively. The coal dust particles identified met specific criteria, including size (>5μm), morphology, and elemental composition (≥75% carbon, ≤20% oxygen). These findings are consistent with longstanding community concerns and lived experiences regarding the presence of coal dust in Curtis Bay, which neighbors a major open-air coal terminal. This approach has potential for other communities neighboring coal terminals to assess similar concerns with residential coal dust exposure.

Chemical and mineral composition of altered volcanic ash in coals of the Kharanorskoe Deposit, Eastern Siberia

Relevance. The necessity to assess the role of altered volcanic ash on the formation of mineral and geochemical characteristics of coal-bearing deposits. Traces of volcanic material in coals are diagnosed mainly in the form of clay horizons – tonsteins. The study of the chemical and mineral composition of clay tuffaceous horizons and the host coals allows us to answer a number of questions concerning volcanic material impact on coal accumulation. Tonsteins are known in Paleozoic, Mesozoic and Cenozoic coal-bearing deposits. Finds of Mesozoic tonsteins are relatively rare. In this regard, the Kharanorskoe brown coal deposit is a unique object for the study of altered layers of volcanic ash in Cretaceous coal-bearing deposits. Aim. Comprehensive study of altered volcanic ash in Cretaceous coals of the Zabaikalsky Krai. Methods. Field studies; the mineral composition was studied by optical microscopy, scanning electron microscopy, X-ray diffractometry; chemical composition was determined by inductively coupled plasma mass spectrometry, inductively coupled plasma atomic emission spectrometry, and instrumental neutron activation analysis. Results and conclusions. The paper presents data on the mineral and chemical composition of tonstein in the Early Cretaceous Novy-1a coal seam of the Kharanorskoe deposit located in the southeast of the Eastern Siberia (Russia). The mineral composition of the tonstein is represented by kaolinite, quartz, and feldspar. Accessory minerals are zircon, ilmenite, monazite-(Ce), and xenotime-(Y). The tonstein is characterized by high concentrations of Ga, Nb, Hf, Ta, Hg, Th and U. The highest concentrations of rare trace elements in the coal, and especially in the coal ash of the Novy-1a seam, are localized in the areas of contact between the tonstein and the coal. The enrichment with REE, Zr, Nb, Y, Ta, Hf, Th and U is the most significant. Mineralogical and geochemical characteristics of the studied tonstein indicate its formation from volcanic ash of alkaline composition.

Optimizing calcination temperature to improve the compressive strength of coal gasification slag-based alkali-activated materials by reducing carbon content and adjusting polymerization degree

Optimizing calcination temperature to improve the compressive strength of coal gasification slag-based alkali-activated materials by reducing carbon content and adjusting polymerization degree

Experimental study on creep characteristics of cemented coal gangue backfill under uniaxial compression

ABSTRACT The uniaxial compression creep test is used to study the cemented coal gangue backfill body specimens with different cement-sand ratios (1:4,1:6,1:8, respectively). Through the processing and analysis of the creep curve, we discussed the influence of different cement-sand ratios, stress load and loading time on the strain, creep rate and long-term strength of the backfill body. These studies have revealed the creep law of the backfill body and obtained accurate conclusions. The results show that: (1) Different proportions of cemented coal gangue backfill body under the action of the set step by step axial loading stress, the strain is positively correlated with the change of loading stress. (2) With the increase of axial stress, the instantaneous deformation of cemented coal gangue backfill with three kinds of cement–sand ratio increases with the decrease of cement–sand ratio under the same axial stress. (3) With the increase of the axial stress of the three kinds of cement–sand ratio cemented coal gangue backfill body, the strain rate of the deceleration creep speed and the constant creep stage increases, and the duration of the deceleration creep stage increases. The average creep strain rate of the three kinds of cement–sand ratio cemented coal gangue backfill materials before entering the accelerated creep stage is determined. (4) Using an improved steady-state creep rate inflection point method, the long-term strength of three kinds of cement–sand ratio of cemented coal gangue backfill is determined, and it is concluded that the long-term strength decreases with the decrease of cement–sand ratio, which is positively correlated.

Study on preparation and influencing factors of coal gangue fill slurry material

Study on preparation and influencing factors of coal gangue fill slurry material

Investigation of the interference between organic and mineral matter in coal and carbonaceous shale using FTIR spectroscopy

ABSTRACT Thirty-two coal (lignite-bituminous in rank) and carbonaceous shale samples, ranging from immature to overmature, were collected from the various coal-bearing basins (Saurashtra Basin, Bikaner Nagaur Basin, Damodar Basin, Mahanadi Basin, and Foreland Basin) in India and characterized petrographically (vitrinite reflectance and maceral composition), geochemically (total organic carbon and total sulfur) and chemically (Fourier Transform Infrared spectroscopy, FTIR). This paper explores utilization of FTIR study on bulk non-demineralized carbonaceous shale and coal to examine the interference between mineral and organic matter visible on FTIR spectra and application of such techniques to assess organic matter chemistry based on FTIR signal. Mineral matter is considerably affecting the organic matter FTIR signal in the region between 1700–1350 and 900–700 cm−1, while the 3100–2800 cm−1 region is unaffected. The general trends of organic matter evolution with thermal maturity, i.e. a decrease of aliphatic and oxygen-bearing groups and increase in aromatic signal, are visible in bulk non-demineralized samples; however, the interpretation of the signal is problematic due to the dilution-related signal weakening and region-specific overlapping. The quality of the FTIR signal is lower than the signal from demineralized kerogens or targeted specific maceral grains via combination of FTIR with microscopy. The spectra can still be useful for more qualitative aspects of FTIR, like assessment of organic functional groups, study of coal impurities, or as a complementary method in conjunction with other analytical techniques such as X-ray for mineral matter characterization.

Coal structure evaluation and morphological properties that affect the coal usage in industries

The contemporary research article is central to understanding coal structure evaluation and the morphological development impacting its utilization in different applications. Through Mineral Liberation Analysis (MLA) designs high content phyllosilicates minerals and swelling clay minerals were rationalized to provides a novel insight into enhanced coal beneficiation and the benefits of coal by-product re-utilization progressions that encourage safer environments and economic sustainability. This work commences with collection of five (5) different coal samples from the central district region in Botswana, sample characterization deploying Thermogravimetric coal analysis (TGA), x-ray fluorescence spectroscopy (XRF), x-ray diffraction (XRD), scanning electron microscopy (SEM) and the Hardgrove Grindability Index (HGI) test that was directed to quantification of the coal hardness and fracture toughness during milling. The cumulative objective was to understand the correlation that exists between the natural composition of the coal sample and their adaptation and application in various carbonaceous products. A solid connection was thus identified in the sulfur and phosphorus weight percentage inclusions in all the coal materials hence higher significance in sphalerite mineral phases (Zn, Fe) S critically increased the fracture toughness and hardness properties. Moreover, mineral amalgams intrinsic to the coal maceral such as aluminum oxides (Al2O3), silicate (SiO2), calcites (CaO), Iron oxide (Fe2O3), potassium feldspars (K − AlSi3O8), albite (Na − AlSi3O8), and anorthite (Ca − Al2Si2O8) compounds in alkali feldspars were detected in larger quantities. The coal industry has attracted much industrial attention to manufacturing foundations producing cement, ceramic tiles, paving bricks, and material synthesis and will continue to supply other economic sectors in the conceivable future.Graphical

Preparation and properties of phosphogypsum-based calcined coal gangue composite cementitious materials

Preparation and properties of phosphogypsum-based calcined coal gangue composite cementitious materials

Enhancing carbonation resistance of low-activity coal gangue-based LC3 cementitious materials with Ca(OH)₂ and gypsum additives

Enhancing carbonation resistance of low-activity coal gangue-based LC3 cementitious materials with Ca(OH)₂ and gypsum additives

Relationship between the molecular structure of soluble organic matter in a subbituminous coal and the electrochemical properties of prepared supercapacitor

Relationship between the molecular structure of soluble organic matter in a subbituminous coal and the electrochemical properties of prepared supercapacitor

Accident Prevention of BOXN Wagon Train

The safety and efficiency of railway freight transportation are critical to the functioning of many national economies, and India is no exception. BOXN wagons, widely used in the Indian railway system for transporting heavy goods such as coal, minerals, and other bulk materials, are essential for supporting industries across the country. However, due to their size, weight, and the volume of cargo they carry, these wagons are prone to accidents if not properly managed. Accidents involving BOXN trains can result in severe consequences, including loss of life, damage to property, and environmental degradation. One of the biggest and most significant industries in the world is the Indian goods railway sector. It is essential for the transportation of materials and goods across the nation. Indian Railways seeks to shorten commute times by boosting the average freight train speed efficiently from 22 mph to 50 mph. The adoption of new technologies is anticipated to have positive effects on the Indian goods railway sector as well. Smart Innovations, for instance, smart goods cars and digital signaling can contribute to reducing train accidents and help to increase railroad productivity using smart mobility.

Geochemical features of coals of the Mezhegey deposit

An analysis of the correlations between the ash content of coal (Adср) and the content of ash-forming elements was carried out. Significant positive pairwise correlations were revealed in the accumulations of SiO2, Al2O3, TiO2 and each of them with ash content Adср (rcr0.05=0.23). In the group Fe2O3, MgO, CaO, a significant positive correlation is observed between the accumulations of only Fe2O3 and MgO, but each of them correlates negatively with Adср. A qualitative analysis of the distributions of petrochemical modules (GM, AM, ZhM, TM) of coal ash from the 2.2-Ulug seam of the Mezhegey deposit was carried out. Hydrolyzate destruction of the mineral matter of coal in 94% of the studied sample (n = 70) is represented by superhydrolysates (GMmin 2.07, GMmax 7.45), normohydrolysates (GMmin 0.86, GMmax 1.95), hypohydrolysates (GMmin 0.56, GMmax 0.84). A combined analysis of correlations between the ash content of coal (Adср) and the contents of ash-forming elements and petrochemical modules of ash made it possible to establish the origin of ash-forming elements - ash-carrier Fe is aquagenic, ash-carriers Al, Ti are allotigenic.