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Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

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]

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]

This paper presents a series of surface experiments simulating underground coal gasification (UCG). The main goal of the experiments was to investigate the influence of the gasification medium and the coal rank on the gasification process. Four multi-day trials were carried out using a laboratory gasification facility designed for the large-scale experimental simulations of UCG and located in the Experimental Mine "Barbara", located at Mikołów, Poland. Two Polish bituminous coals were investigated: coal sourced from "Piast-Ziemowit" mine and coal sourced from "Wesoła" mine. Each of the two coals was gasified in two separate experiments using oxygen-enriched air (OEA) and pure oxygen as the respective gasifying agents. Gasification with oxygen resulted in significantly higher gas quality and higher process efficiency than gasification with OEA. Higher concentrations of hydrogen (23.2% and 25.5%) and carbon monoxide (31.8% and 33.4%) were obtained when oxygen was used as a gasifying reagent, while lower concentrations were obtained in the case of gasification with OEA (7.1% and 9.5% of hydrogen; 6.4% and 19.7% of carbon monoxide). Average gas calorific values were 7.96 MJ/Nm3 and 9.14 MJ/Nm3 for the oxygen experiments, compared to 2.25 MJ/Nm3 and 3.44 MJ/Nm3 for the OEA experiments ("Piast-Ziemowit" coal and "Wesoła" coal, respectively). The higher coalification degree of "Wesoła" coal (82.01% of carbon) compared to the "Piast-Ziemowit" coal (68.62% of carbon) definitely improves the gas quality and energy efficiency of the process. The rate of water condensate production was higher for the oxygen gasification process (5.01 kg/h and 3.63 kg/h) compared to the OEA gasification process (4.18 kg/h and 2.63 kg/h, respectively), regardless of the type of gasified coal. Additionally, the textural characteristics (porosity development) of the chars remaining after coal gasification experiments were analyzed. A noticeable development of pores larger than 0.7 nm was only observed for the less coalified "Piast-Ziemowit" coal when analyzed under the more reactive atmosphere of oxygen. [ABSTRACT FROM AUTHOR]

Composite fuel is a promising energy source that allows for solving the problems of waste disposal with energy generation. Such fuel is the most accessible fuel and is cheap in comparison with fossil fuels widely used in industrial thermal power engineering. This paper presents the results of experimental studies on the effect of the initial temperature and the addition of combustible liquids and solid components on the ignition characteristics of composite fuel single droplets. Composite liquid fuels were prepared using the main components: bituminous coal, coal processing waste (filter cake), rapeseed oil, turbine oil, and water. The research was carried out for fuel droplets with an initial temperature from −60 to +60 and an ambient temperature from 700 to 1000 °C. The differences in the ignition delay times at conditions close to the limiting ones were 2–3.5 times. A promising direction for intensifying the processes of the ignition and combustion of composite liquid fuels under relatively intense heating is self-grinding into a large number of small fragments up to complete disintegration due to the dispersion effect. It has been experimentally found that the addition of highly flammable liquids (gasoline, kerosene, diesel fuel, formic acid) to the fuel composition in an amount of 5% is characterized by an intensification of ignition and burnout of droplets by about two times. The ignition delay time is reduced by 20–40%, while the size of the dispersion area is increased by 20–70%. The addition of formic acid to the composite fuel has a positive effect on the main ignition characteristics from 5 to 50%, and the addition of a similar amount of diesel fuel by 20–64%. [ABSTRACT FROM AUTHOR]

Coal is a carrier of carbon enrichment, so it has the potential for the preparation of coal-based carbon materials. In this paper, LT anthracite and TSG bituminous coal were selected, and the corresponding graphitized samples were prepared from high-temperature treatment. The effects of silicon-containing minerals on coal evolution during the high-temperature pre-graphitization stage were investigated by XRD, Raman spectroscopy, and SEM. The results showed that with increasing temperature, the silicon-containing samples showed smaller d002 and ID1/IG, and higher Lc, while La presented a slight increase. It was found by SEM that the micromorphology of all samples was mainly massive structures. Meanwhile, irregular polyhedral structures also were observed in silicon-containing samples at 1300 °C, which were related to the formation and deposition of SiC. The carbothermal reactions of silicon-containing minerals continued to generate SiC and precipitate with increasing temperature, resulting in the gradual transformation of the needle-like structures into polyhedral structures. However, SiC was completely decomposed at 2800 °C. These changes indicated that during the pre-graphitization stage, silicon-containing minerals form SiC to advance the reduction of the interlayer spacing and the increase of longitudinal layer stacking height, thereby enhancing structural ordering and graphitization degree, while it had less effect on the lateral size. This will help to further understand the role of silicon-containing minerals in the coal pre-graphitization stage and also provide useful information about synthetic coal-based graphite. [ABSTRACT FROM AUTHOR]

Demand for a cleaner source of energy is increasing in India. In the search for alternate energy sources, coal bed methane gas receives considerable attention for its potential as a good energy source. During the coalification process, methane gas is captured in the coal seams and later released during coal mining operations. Coal bed methane separation is crucial for both economic benefit and methane emission reduction. The methane production from seams is an efficient way to reduce greenhouse emissions and provide a safe mining operation environment. In India, the production of coal bed methane on a commercial scale has been recently observed. In the present paper, an attempt is made to understand and establish a 3-D excavation of coal bed methane from reservoir simulation (COMET3) for Gondwana coal seams in the Sitarampur block of the Raniganj coalfield in India. The simulation study was carried out for a period of 25 years for the recovery of methane from the reservoir. It is observed from the simulation study that 372 million cubic meters CO2 equivalent greenhouse gas emissions can be prevented by the extraction of methane with space and time. The fracture gas concentration increases with time, and it is observed that fractures are fully saturated with gas in 3000 days. [ABSTRACT FROM AUTHOR]

Humanity is a fossil-fueled civilization with a large influence on the environment. The World Health Organization (WHO) has pointed out that air pollution is now the single biggest environmental threat to human health. The air quality in Petroșani, a traditional mining region from the Jiu Valley bituminous coal basin, Romania, is rarely debated; however, it is not often investigated. In this paper, the main air pollution sources of Petroșani are identified and the performed measurements emphasize the air quality in the area of its transit road. The monitoring program set out the objectives, parameters, and points of the monitoring system, as well as the frequency and duration of the program and other monitoring parameters. The equipment used was provided by the National Institute for Research and Development in Mine Safety and Protection to Explosion from Petroșani, within an institutional partnership with the University of Petroșani. The monitoring of the air quality parameters was conducted from March to July 2020, at six points located on the road that crosses the city. It was thus possible to capture a variety of concentrations of the monitored parameters in different weather conditions to determine the air quality in this area. Based on the variation of the measured values in one of the most important historical Romanian bituminous coal mining basins, the preliminary results suggest a worsening of local air quality parameters in relation to the decarbonization process. [ABSTRACT FROM AUTHOR]

The paper presents the results of a comparative investigation into the kinetic and energy characteristics of the ignition of microparticles of low-metamorphized coal ranks (lignite coal and high volatile C bituminous coal) under the impact of laser radiation at the wavelengths λ = 450 nm and λ = 808 nm with an exposure time of 1 sec. Coal ignition is carried out only during irradiation. There is no transition to stationary combustion. The ignition delay time decreases monotonically with increasing radiation power density. It is established that the energy costs of ignition of the studied coal ranks may be made more economical by using laser radiation with a wavelength of λ = 450 nm. It is concluded from the results of measuring the energy characteristics of coal ignition that the absorption of radiation has a quantum nature. Two components contribute to the coal particles emission spectra measured at the initial stage of ignition: CO (CO2*) flame and thermal glow associated with emitted carbon particles heated to T>2000 K for both coal ranks. At subsequent stages, only the glow of heated carbon particles with the thermal spectrum at T~2000 K is observed in the spectra. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the evolution of the chemical structure of coal char during pyrolysis. Two bituminous coals (coals A and B) and one lignite (coal C) were pyrolyzed in a fixed bed in N2 from 600 °C to 1100 °C. The chemical structure of coal char was characterized by Raman spectroscopy and X-ray diffraction (XRD). The carbon and oxygen functionalities of coal char were analyzed by X-ray photoelectron spectroscopy (XPS). The Raman spectroscopic parameters AD/AG (AD1/AG, AD2/AG, and AD3/AG) increased from 600 °C to 900 °C and then decreased after 900 °C, indicating that the degree of order of coal char first decreased and then increased with increasing pyrolysis temperatures (600–1100 °C). The content of graphite-like microcrystalline carbon decreased and then increased with an increase in temperature. Prominent diffraction peaks of microcrystalline carbon for coal chars A and B were observed, but only minerals were shown in diffraction patterns of coal char C since the ash content of coal chars A and B is much lower that that of coal char C. The lateral size of the crystallite plane (La) generally increased between 600 °C and 1100 °C. The relative content of C=O and COOH in coal chars A and B generally decreased as the temperature increased, suggesting an increase in the degree of order at higher temperatures. The oxygen functionalities of coal char were composed of organic oxygen and oxygen-containing bonds of minerals. [ABSTRACT FROM AUTHOR]

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • The large pore volume of coal increased after treatment with [C 12 mim][Cl]-NaCl composite solution. • The Pearson correlation coefficient is utilized for detecting the correlation properties of the wetting parameters. • The macroporous volume of bituminous coal is negatively correlated with the contact angle. • 0.6 mol/L NaCl + 10 mmol/L [C 12 mim][Cl] is the optimal ratio of compound solution. Water injection technology is a compelling technical measure to improve the water content of coal seams and reduce dust generation during mining. At present, the methods to enhance the wetting effect in the research progress are limited to increasing the dosage of a single wetting agent and using a variety of anionic and cationic wetting agents in large doses. More research is needed on the synergistic enhancement of the wetting effect by inorganic salts and ionic liquids. Aiming at this problem, this paper studies the influence of the combination of NaCl and surface active ionic liquid [C 12 mim][Cl] on the wetting effect and pore structure of bituminous coal. The influence of composite solution and ratio change on coal pore structure and wetting characteristics is studied based on Pearson correlation coefficient, combined with the experimental results of nitrogen adsorption at low temperature, scanning electron microscope and wetting characterization. The results show that bituminous coal exhibits different sizes of hysteresis rings after [C 12 mim][Cl] and NaCl treatments. With the change in composite ratio, the pore connectivity of coal samples is improved, and the surface roughness of modified bituminous coal is affected by the shift in composite ratio. With the enhancement of the wetting effect, the pore depth increases. On the other hand, adding 0.6 mol/L NaCl makes the composite solution reach a critical micelle concentration, which could synergistically enhance the surface activity and wetting effect of [C 12 mim][Cl] solution. There is a negative correlation between the volume of bituminous coal macropores and the contact angle, which indicates that the optimal solution ratio can be determined by analyzing the bituminous coal macropore volume change. [ABSTRACT FROM AUTHOR]

Converting municipal solid waste (MSW) into valuable feedstocks, such as refuse-derived fuel (RDF), is a sustainable method according to the concept of waste management hierarchy. A heterogeneous composition with a good calorific value and lower emissions allows RDF to be used for energy recovery purposes. We have earlier analyzed the generation and thermochemical characteristics of the MSW produced in Kazakhstan. This work aims to study the combustion characteristics in terms of emissions and ash composition to evaluate the possibility of RDF co-firing with Ekibastuz coal. In particular, RDF is blended with high ash bituminous coal (Ekibastuz coal) and co-fired in the laboratory scale bubbling fluidized bed reactor (BFB) at a bed temperature of 850 °C. The co-firing tests of RDF to coal samples were conducted under various proportions to analyze flue gas compositions. Experiments were carried in the presence of bed material (sand), and the fuel particles were fed in batch mode into the hot riser. The BFB reactor had a height of 760 mm and internal diameter of 48 mm. The gaseous products in the flue gas were analyzed by FTIR spectrometry (Gasmet Dx4000). Ash composition was examined by XRD, XRF, SEM, and PSD. The results showed that a high RDF content decreased SO2 emissions to 28 ppm, while it negatively affected NOx release to 1400 ppm, owing to excess air. The emissions of gases from different blended samples and mineral transformations were investigated and discussed in this study. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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

• FS-50 is more effective in suppressing bituminous coal dust than FS-3100. • FS-50 achieves more efficient wettability and agglomeration than FS-3100. • FS-3100 achieved higher diffusion coefficient and lesser absolute wetting area. • The electrostatic potential energy and hydrogen bonds are key influencing factors. • The higher LUMO value and band gap energy deteriorates the performance of FS-3100. This paper carried out a multi-scale investigation on the wetting and agglomerating mechanism of short-chain fluorocarbon surfactant suppressing coal dust. As investigated, FS-50 achieves higher dedusting rate and shorter suppression time than FS-3100, which is attributed to its better wettability and more sufficient agglomeration on coal particles. Simulation indicates that FS-3100 with longer chain length is easier to generate chemical bond rotation, which results in a distorted spatial structure, higher steric hindrance, and poorer ability of FS-3100 in retaining H 2 O molecules and adsorbing surround the coal particles. The hydrophilic group of FS-50 is dominated by the induced effect and presenting larger charge density and electron-absorbing nature. Higher electrostatic potential difference with coal molecules, more hydrogen bonds, shorter bond length and larger bond angle are key factors to endorse FS-50 a better wetting and agglomerating performance. The C atom connected with the fluorocarbon tail chain of FS-3100 is linked to a carboxyl group with lone pair electrons. This carboxyl group enlarges the LUMO value of FS-3100 and weaken its ability to attract the electrons of coal particles. On the contrary, the lower LUMO value, lower band gap energy, and smoother spatial configuration jointly bring FS-50 better wetting and agglomerating ability. [ABSTRACT FROM AUTHOR]

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

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

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

In this paper, lignite, bituminous coal, anthracite, and biomass were used as reducing agents for carbon thermal reduction of vanadium-extracted waste slag. The energy consumption analysis and environmental impact assessment were carried out on the vanadium-extracted waste slag by reducing with different reducing agents via thermodynamic analysis, providing a reference for energy saving and emission reduction work. [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]

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]

This paper presents a metamaterial sensor using a double slit complementary square ring resonator (DS-CSRR) that has been utilized for the measurement of dielectric materials, especially coal powder. The design is optimized for best performance of deep notch depth in transmission coefficient (Magnitude of S 21 ). Sensitivity analysis of transmission coefficient with respect to structure dimensions has been carried out. Metamaterial properties of double negative permitivity and permeability were extracted from the S–parameters of this sensor. The optimized structure is fabricated using low cost FR-4 PCB board. Measured result shows resonance frequency of 4.75 GHz with a deep notch up to −41 dB. Simulated and measured results show good agreement in desired frequency band. For material characterization, first, two known materials are characterized using this metamaterial sensor. Their respective resonances and dielectric constants are known, so the transcendental equation of the sensor is formulated. Afterwards, the proposed sensor is used for dielectric measurement of two types of coal powder, i.e., Anthracite and Bituminous. The measured value of dielectric constant of Anthracite coal is 3.5 and of Bituminous coal is 2.52. This is a simple and effective nondestructive measurement technique for material testing applications. [ABSTRACT FROM AUTHOR]

There has been little research on volatile releasing characteristics of pulverized coals under moderate or intense low-oxygen dilution (MILD) oxy-combustion (MO) conditions. For the first time, volatile releasing characteristics of bituminous coal and semi-anthracite under both MILD air-combustion (MA) and MO conditions were investigated using a flat-flame assisted entrained flow reactor. Both heating rate (~105 K/s) and residence time (65 ms) were carefully selected to mimic the conditions in typical industrial boilers. The combustion processes and properties of the volatiles were characterized through direct observation and char analysis. The results showed that the lower diffusion rate of the volatile in CO2 resulted in the decreasing of the volatile envelope flame size and a longer volatile burnout time (more than 20%). For bituminous coal (volatile content of 25%), the lower amount of apparent volatile yield under MO conditions reduced the heating value of the volatile. For semi-anthracite coal (volatile content of 7%), the short devolatilization time led to char-CO2 gasification reaction, which increased the apparent volatile yield and the heating value of the volatile by 47% and the volatile-N by 19%. This paper indeed provided new insight into the MILD oxy-combustion of solid fuels. [ABSTRACT FROM AUTHOR]

The coupled combustion of biomass and organic solid wastes including oil sludge has attracted much attention. Although the optimal mixing ratio of different coal types and biomass has been extensively studied, little attention has been paid to oil sludge that has undergone co-combustion. In this study, the combustion characteristics of blended fuel for coal, biomass and oil sludge under different mixing ratios are studied via a thermogravimetric test and differential thermal analysis. Kinetic analysis of tri-fuel is performed using the Flynn–Wall–Ozawa (FWO) and Dolye methods. The results show that the bituminous coal combustion process mainly involves the combustion of fixed carbon (236.0–382.0 °C). Wood pellet combustion (383.0–610.0 °C) has two processes involving the combustion of compound carbon and fixed carbon. Blending wood pellets effectively enhances combustion efficiency. Wood pellets from Korla (KOL) have the most obvious effect on reducing the ignition temperature. The blending combustion of bituminous coal (SC), wood pellets from Hutubi (HTB) and oil sludge (OS) have significant synergistic effects. As the OS mixing ratio increases from 10% to 20% with 45% HTB, Ti and Th decrease from 354.9 and 514.3 °C to 269.8 and 452.7 °C, respectively. In addition, f(α) is [−ln(1 − α)]2 for tri-fuel in most mixing ratios when α < 0.5, while f(α) becomes [−ln(1 − α)]3 at α > 0.5. At a high-HTB-level mixing ratio, increasing the OS content causes a decrease in activation energy to 35.87 kJ mol−1. The moderate blending of oil sludge improves the pre-finger factor and the combustion performance. [ABSTRACT FROM AUTHOR]

The present study aims to investigate the physico-chemical structural evolution characteristics of char structure of CO2 atmosphere torrefaction pretreated sludge with Yangchangwan bituminous coal (YC) during co-gasification. The co-gasification reactivity of torrefied sludge and YC was measured using a thermogravimetric analyzer. The co-gasification reactivity of torrefied sludge with YC was thoroughly explored in depth by in situ heating stage microscope coupled with traditional characterization means of char sample (Scanning electron microscope, nitrogen adsorption analyzer, laser Raman spectroscopy). The results show that the gasification reaction rate of sludge treated under CO2 atmosphere and coal blended char was better than other char samples at 1100–1200 °C. The torrefied sludge under CO2 atmosphere promoted its thermal decomposition to the maximum extent, so that it eventually was transformed into a large number of small broken particles. The specific surface area and ID1/IG ratio of blended char of torrefied sludge under CO2 atmosphere and YC were 1.70 and 1.07 times higher than that of YC, respectively. The in situ technique revealed that YC char with the addition of torrefied sludge undergo gasification by shrinking core modes and the presence of obvious ash melting flow phenomenon. It was more obvious than that of YC. [ABSTRACT FROM AUTHOR]

As a kind of solid waste from coal chemical production, the disposal of coal gasification fine slag poses a certain threat to the environment and the human body. It is essential for gasification slag (GS) to realize rational utilization. GS contains fewer combustible materials, and the high heating value is only 9.31 MJ/Kg, which is difficult to burn in combustion devices solely. The co-combustion behavior of the tri-fuel blends, including bituminous coal (BC), gasification slag (GS), and bamboo residue (BR), was observed by a thermogravimetric analyzer. The TGA results showed that the combustibility increased owing to the addition of BC and BR, and the ignition and burnout temperatures were lower than those of GS alone. The combustion characteristics of the blended samples became worse with the increase in the proportion of GS. The co-combustion process was divided into two main steps with obvious interactions (synergistic and antagonistic). The synergistic effect was mainly attributed to the catalysis of the ash-forming metals reserved with the three raw fuels and the diffusion of oxygen in the rich pore channels of GS. The combustion reaction of blending samples was dominated by O1 and D3 models. The activation energy of the blending combustion decreased compared to the individual combustion of GS. The analysis of the results in this paper can provide some theoretical guidance for the resource utilization of fine slag. [ABSTRACT FROM AUTHOR]

Research of microstructure and permeability evolution of coal following LN2 treatment elucidate the process of cryogenic fracturing due to environmentally friendly behavior in comparison with conventional hydraulic fracturing. The evolution of the 2D microstructure of bituminous coal before and after LN2 treatment was examined using a high-resolution camera. The image processing was implemented using functions from the OpenCV Python library that are sequentially applied to digital images of original coal samples. The images were converted into binary pixel matrices to identify cracks and to evaluate the number of cracks, crack density, total crack area, and average crack length. Results were visualized using Seaborn and Matplotlib Python libraries. There were calculations of total crack area (TCA), total number of cracks (TNC), crack density (CD), the average length of cracks (Q2), first (Q1) and third (Q3) quartiles in fracture length statistics. Our findings demonstrate a progressive increase in the Total Crack Area (δTCA) with longer freezing times and an increased number of freezing–thawing cycles. In contrast, the change in crack density (δCD) was generally unaffected by freezing time alone but exhibited a significant increase after several freezing–thawing cycles. Among the freezing times investigated, the highest crack density (CD) value of 300 m−1 was achieved in FT60, while the lowest CD value of 31.25 m−1 was observed in FT90 after liquid nitrogen (LN2) treatment. Additionally, the FTC4 process resulted in a 50% augmentation in the number of cracks, whereas the FTC5 process tripled the number of small cracks. [ABSTRACT FROM AUTHOR]

According to the characteristics of "Three Soft" outburst coal seams in the Henan area with large gas content, poor air permeability, and extremely difficult extraction, the hydraulic fracturing and punching technology of soft coal with packer tool string sealing method was studied. Xinzheng Coal Electric Power Company is a coal and gas outburst mine, and the second coal seam is a typical soft outburst coal seam. In 14201, upper bottom drainage roadway, which has a broken top plate, a test of penetration hydraulic pressure thrust-enhanced permeability technology based on packer sealing mode was carried out. The average concentration in the press-punching area was 4.8 times that in the non-press-punching area (to be tested), and the average pure volume of 100 holes in the test area was 42 times that in the untested area. During hydraulic pressure punching in the test area, affected by fracturing disturbance, the concentration and purity of the test area and the adjacent test area significantly increased. The test verifies that the large range of fracturing communication cracks at the same time through the interception hole punching plays a synergic permeability and pressure relief effect, providing a new idea and technical support for the hydraulic permeability increase technology in this area. [ABSTRACT FROM AUTHOR]

Oxy–fuel (O2/CO2) combustion technology shows great potential for carbon reduction. However, difference in the combustion atmosphere would affect coal combustion characteristics and pollutant emissions. In order to explore oxy–fuel combustion characteristics, two typical Chinese coals, sub–bituminous and lean coal, were utilized. Based on thermogravimetry and pilot–scale test, the ignition and burnout characteristics under oxy–fuel and air combustion atmosphere were investigated. Besides, the NOx emission characteristics were also investigated on the pilot–scale test. Through experimental results, these two kinds of coal showed different combustion characteristics, mainly due to differences in coal quality. Compared with air combustion, oxy–fuel combustion affected the coal combustion process. Firstly, the ignition temperature of sub–bituminous and lean coal decreased from 418 and 477 °C to 405 and 415 °C, respectively; the burnout temperature also decreased from 855 and 985 °C to 808 and 838 °C, respectively. Then, coal combustion performance was evaluated by comprehensive combustion characteristics (S); with an increase in S from, respectively, 3.659 and 2.013 to 4.826 and 3.545 × 10−8(min−2 × K−3), the combustion performance significantly improved. Then, the char burnout time was advanced for 1~3 min. Similar results were obtained on the pilot–scale test. The ignition temperatures decreased from 505 and 552 to 490 and 512 °C, respectively. Moreover, the char burnout rate increased by 0.5~5% and 2~11%, respectively. Lastly, the NOx concentration in flue gas was 2.2~2.6 and 2.0~2.3 times higher for the two kinds of coal under oxy–fuel combustion. [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]

CO2 adsorption is one of the promising CCS technologies, and activated coke is a solid adsorbent with excellent adsorption properties. In this study, activated coke was prepared by using bituminous coal and coconut shells activated with KOH or CaCl2 in a physically activated atmosphere and modified with ammonia. The effect of the active agent impregnation ratio on the physicochemical properties of activated coke was investigated by N2 adsorption isotherms, scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). The CO2 adsorption performance of activated coke was tested, and the effect of nitrogen-containing functional groups on CO2 adsorption was investigated by experiments and simulations. The results showed that the specific surface area of activated coke reached 629.81 m2/g at a KOH impregnation ratio of 0.5 and 610.66 m2/g at a CaCl2 impregnation ratio of 1. The maximum CO2 adsorption capacity of activated coke reached 71.70 mg/g and 90.99 mg/g for conventional power plant flue gas and oxy–fuel combustion flue gas, respectively. After ammonia modification, the CO2 adsorption capacity of activated coke was further increased. Simulations showed that pyrrole and pyrrole functional groups changed the polarity of graphene and established weak interactions with CO2. [ABSTRACT FROM AUTHOR]

Liquid CO2 is a non-polar fluid, and the injection of CO2 fluid into a coal seam causes a strong water–rock interaction between the inorganic minerals and organic matter in the coal and acidic fluid. The minerals in the coal are thereby corroded and precipitated to different degrees, and the organic matter is dissolved and extracted, which further changes the physical and chemical properties of the coal and rock. Three kinds of coal samples with different metamorphic degrees were selected as the research objects, and the research methods of theoretical analysis and experimental testing were used to carry out the related research on the modification of coal by liquid CO2 extraction and dissolution. After the three kinds of coal samples were extracted by liquid CO2, the pore specific surface area decreased and the CO2 adsorption decreased with the increase in extraction pressure. The reduction in anthracite adsorption was greater than that of bituminous coal and lignite; after being corroded by different CO2 pressures, the adsorption capacity of bituminous coal gradually increased with the increase in corrosion pressure, and the increase in adsorption capacity of bituminous coal was larger than that of anthracite and lignite. After corrosion, bituminous coal was suitable for CO2 geological storage. [ABSTRACT FROM AUTHOR]

Low-temperature plasma (LTP) oxidation has been widely used to study the mineralogy of the mineral matter existing in coal sources. The current study investigated the potential of LTP oxidation as a pre-treatment method to improve rare earth element (REE) leachability from coal and its by-products. Representative density-fractionated samples of Baker and Fire Clay coarse refuse seam materials were ground to a top size of 180 µm and subjected to low-temperature plasma oxidation. Subsequently, the treated samples were leached at 1% w/v solids concentration and 75 °C for 5 h using (i) de-ionized (DI) water, (ii) 0.1 mol/L of ammonium sulfate, and (iii) 1.2 mol/L of sulfuric acid. It was determined that LTP treatment improved REE leaching characteristics, especially the leaching of heavy REEs (HREE), existing in the lighter density fractions of the Baker seam coarse refuse material. For instance, the HREE recovery for the 1.6 specific gravity (SG) float fraction increased from 8% to 33% using 0.1 mol/L of ammonium sulfate solution after 32 h of LTP treatment. This finding indicated that HREEs associated with the organic matter were released by the LTP treatment and adsorbed onto the surfaces of highly negative charged mineral matter and was exchanged with ammonium to allow their recovery. Similarly, when using 1.2 mol/L of sulfuric acid, the HREE recovery increased from 23% to 53% for the 1.6 SG float fraction. Interestingly, LTP oxidation did not provide significant improvement in REE recovery from the 2.2 sink density fractions, which was likely due to its lower organic content. No significant benefits were observed when treating the Fire Clay coarse refuse material, which was likely due to the lack of organic affinity and the difficult-to-leach REE minerals associated with the coal source such as monazite, xenotime, and zircon. Conversely, high-temperature oxidation within a temperature range of 600–750 °C significantly improved REE leaching characteristics for both coal sources. Improvement in REE recovery was due to decarbonization of the material, clay dehydroxylation and subsequent conversion of liberated REE-bearing minerals into a more leachable form. However, increasing the temperature above 800 °C decreased REE recovery due to the conversion of meta-kaolinite into mullite, which is chemically stable. [ABSTRACT FROM AUTHOR]

Demand for a cleaner source of energy is increasing in India. In the search for alternate energy sources, coal bed methane gas receives considerable attention for its potential as a good energy source. During the coalification process, methane gas is captured in the coal seams and later released during coal mining operations. Coal bed methane separation is crucial for both economic benefit and methane emission reduction. The methane production from seams is an efficient way to reduce greenhouse emissions and provide a safe mining operation environment. In India, the production of coal bed methane on a commercial scale has been recently observed. In the present paper, an attempt is made to understand and establish a 3-D excavation of coal bed methane from reservoir simulation (COMET3) for Gondwana coal seams in the Sitarampur block of the Raniganj coalfield in India. The simulation study was carried out for a period of 25 years for the recovery of methane from the reservoir. It is observed from the simulation study that 372 million cubic meters CO2 equivalent greenhouse gas emissions can be prevented by the extraction of methane with space and time. The fracture gas concentration increases with time, and it is observed that fractures are fully saturated with gas in 3000 days.

Polyvinyl chloride (PVC) plastic wastes can bring a series of problems during pyrolysis or incineration such as the emission of dioxins, corrosion, slagging in the reactors, etc. Hydrothermal treatment of PVC plastics has been intensively studied as it can efficiently remove chlorine from PVC plastics under relatively mild reaction conditions (220–300 °C) to provide value-added products. Meanwhile, the research progress, knowledge gaps, and challenges in this field have not been well addressed yet. This paper gives a comprehensive review of hydrothermal dechlorination of PVC plastics regarding reactors, process variables and fundamentals, possible applications, and challenges. The main pathways of hydrothermal dechlorination of PVC plastics are elimination and –OH nucleophilic substitution. Catalytic hydrothermal and co-hydrothermal optimize the chemical reactions and transportation, boosting the dechlorination of PVC plastics. Hydrochar derived from PVC plastics, on the one hand, is coalified close to sub-bituminous and bituminous coal and can be used as low-chlorine solid fuel. On the other hand, it is also a porous material with aromatic structure and oxygen-containing functional groups, with good potential as adsorbent or energy storage materials. Further studies are expected to focus on waste liquid treatment, revealing the energy and economic balance, reducing the dechlorination temperature and pressure, expanding the application of products, etc. for promoting the implementation of the hydrothermal treatment of PVC plastic wastes. [Display omitted] • Lab-scale and pilot-scale reactors for PVC waste hydrothermal dechlorination is compared. • The dechlorination chemistry of PVC by hydrothermal treatment and the knowledge gaps are discussed. • The possible applications of PVC waste hydrothermal treatment are enumerated. • Challenges and the perspective study orientation about PVC waste hydrothermal treatment are proposed. [ABSTRACT FROM AUTHOR]

Kitchen waste (KW) has high water content and organic matter, which has great potential for energy application, but how to treat it effectively has always been a difficult problem. In this study, the feasibility of transforming kitchen waste into hydrochar as a solid fuel to replace the primary energy by hydrothermal carbonization (HTC) is put forward. An experimental study of proportioned KW under HTC conditions (reaction temperature, residence time, liquid–solid ratio) is carried out by elemental analysis, industrial analysis, energy density calculation, and calorific value measurement. The results show that a proper extension of the residence time to 3.5 h at a liquid–solid ratio of 10 and a reaction temperature of 265 °C for the kitchen waste after HTC would result in a maximum calorific value of 30.933 MJ/Kg for the prepared hydrochar. The maximum ash content of hydrochar at a 265 °C reaction temperature is 3.94% < 10%, which is much lower than the standard of extra-low-ash coal, and the study shows that the hydrochar prepared from kitchen waste by HTC for combustion will greatly improve the combustion efficiency. The three types of kitchen waste under HTC conditions are compared with the three typical types of coal in China by the van Krevelen diagram. The results show that the combustion properties of hydrochar from kitchen waste prepared by the HTC method are better than those of lignite close to bituminous coal and can provide a theoretical basis for replacing primary energy in the future. Finally, by combining thermogravimetric analysis with mathematical modeling, it is calculated that the hydrochar of kitchen waste has a lower activation energy than those of other biomass, which can better facilitate the reaction. The experimental results further determine the feasibility of hydrochar as an alternative primary energy source and provide a theoretical basis for the future conversion of kitchen waste into hydrochar as a solid fuel through HTC. [ABSTRACT FROM AUTHOR]

The chemical composition, structural and plastometric properties of different-ranked coals from Mongolia deposits were studied. The non-isothermal iso-conversion Ozawa–Flynn–Wall and Friedman model-free methods were used to assess kinetic parameters and to differentiate decomposition steps. Key peculiarities of the pyrolysis kinetics of brown and bituminous coals were revealed and discussed in terms of the composition and plastometric properties. Brown coal was shown to undergo three decomposition steps with ever increasing activation energy as temperature increased because of the decomposition of thermally more and more stable molecular fragments. The pyrolysis of bituminous coals occurred in four steps, the activation energy having extreme mode of temperature dependence. An important new finding was that the temperature range of the second, major pyrolysis step well corresponded to that between the softening and re-solidification temperatures according to Gieseler plastometry. The yield and composition of the pyrolysis products obtained under isothermal conditions were also characterized depending on coal rank and temperature, and the ways for qualified utilizations were offered. [ABSTRACT FROM AUTHOR]

To effectively improve the dust reduction rate of fine dust and prevent the occurrence of secondary dust, surfactant-charged water mist dust reduction technology is proposed. First, the water mist induction-charged atomization mechanism was perfected by an induction-charged spray experiment and the optimal atomization-charged voltage was determined to be 10 kV. Second, by surface tension and spray experiments on AEO-9-charged solutions, the lower the surface tension and viscosity of the solution, the better the atomization effect; the best atomization solution was 10 kV and 0.02% AEO-9. Finally, according to an electrostatic adsorption experiment, it was identified that there was an electrostatic interaction between coal dust and charged droplets. The contact angle experiment showed that the contact angle of the AEO-9 droplets decreased by 68.44% compared with water after 3 s of contact with coal dust. The wetting effect of bituminous coal was significantly improved by adding AEO-9 to water. A molecular simulation was used to study the molecular interaction mechanism among the H2O, AEO-9, and bituminous coal molecules. The simulation results showed that AEO-9 was more active than water, it easily interacted with bituminous coal, and the hydrophilic group covered the surface of the bituminous coal molecules, which increased the electrostatic interaction between the water molecules and bituminous coal surface molecules. After adding AEO-9 to H2O, the intermolecular interaction energy of the H2O/AEO-9/bituminous coal system was enhanced more than that of the H2O/bituminous coal system. This study provides the basis for the application of surfactant-charged water mist dust reduction technology. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization is a thermal technique that offers numerous environmental benefits, particularly in managing solid waste streams by decomposing the raw materials of solid wastes and converting them into the renewable source of energy known as hydro-char. This study evaluates the heating value of hydro-char produced through the hydrothermal carbonization of cigarette butts, taking into account influential factors such as time, temperature, and pressure, as well as its benefits and economic implications, using a novel approach involving simulations aimed at reducing the number of required tests, saving time, and cutting costs. The range of 150 to 350 ℃ for temperature and 30 to 240 minutes for reaction time were considered and resulted in a thermal value range of 15.94 to 23.12 MJ/Kg for hydro-char, which makes its heat value greater than lignite coal and within the range of bituminous coal. The findings also indicated that temperature and time have a direct impact on the heat value, with time being the more influential factor, although high temperatures can expedite the reaction rate and should not be disregarded. Finally, the economic analysis of the project was conducted using the NPV method, which demonstrated that the viability of this method depends on the cost of coal, making it a promising alternative for accessing new and cost-effective fuel resources while considering environmental benefits. Besides, this study highlights the potential of hydrothermal carbonization as a viable and advantageous method for producing fuel resources from biomass and organic waste, and provides quantitative and comparable evidence of the applicability and benefits of the proposed hydrothermal carbonization methodology in comparison to conventional methods. [ABSTRACT FROM AUTHOR]

Residential coal combustion is a major source of air pollution in developing countries, including China. Indeed, precisely measuring the real-time emission of major air pollutants is often challenging and can hardly be repeated at a lab-scale. In this study, for the first time, two clean coals initiated from raw bituminous coal were burned for real-time estimation of air pollution characteristics and their thermal efficiencies in different stoves. Moreover, thermodynamic equilibrium simulations were investigated for slagging parameters using Factsage 7.1 at reaction temperature 800~1600 °C. Results revealed that the firepower of clean coals (Briquetted coal and Semi-coke) was much higher (2.2 kW and 2.1 kW) than raw coal (1.8 kW) in a traditional stove. However, the thermal efficiencies were remarkably increased (13.3% and 13.5%) in an improved stove for briquetted coal and semi-coke, respectively. The emission of major air pollutants including carbon monoxide (CO), sulfur dioxide (SO2), particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), non-methane hydrocarbons (NMHCs) from both coal and semi-coke was significantly reduced. Thermodynamic equilibrium calculations indicate that briquetted coal is not susceptible to slagging under the reaction conditions in the household stove. The current study provides guidance for the selection of alternative and efficient clean coal fuels in rural areas for household purposes coupled with public health and safety. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) technology was used to carbonize and improve biomass raw material to obtain hydrochar. The effects of HTC temperature and holding time on the yield, composition, structure, combustion behavior, and safety of hydrochar were studied systematically. In addition, the results show that with the increase in HTC temperature and the prolongation of holding time, the yield of hydrochar gradually reduces, the fixed carbon content of hydrochar increases, the volatile content decreases, and a large number of ash and alkali metals enter the liquid phase and are removed. Further, the analysis of the combustion properties and the structure of hydrochar can be observed in that, as the HTC process promotes the occurrence of polymerization reactions, the specific surface area gradually reduces, the degree of carbon ordering increases, and the combustion curve moves toward the high-temperature zone and gradually approaches bituminous coal. Since biomass hydrochar has the characteristic of being carbon neutral, blast furnace injection hydrochar can reduce CO2 emissions, and every 1 kg/tHM of biomass hydrochar can reduce CO2 emissions by 1.95 kg/tHM. [ABSTRACT FROM AUTHOR]

Water distribution can affect the storage and transport of methane in coal. There are many reports involving the distribution of water and methane in coal, but the microscopic mechanism of water-methane interaction is still unclear. In this study, realistic molecular structure models of bituminous and anthracite coals were constructed based on the chemical structures of two coal samples. And the chemical structures were analyzed by solid-state nuclear magnetic resonance, Fourier-transform infrared, and X-photoelectron spectroscopy. Then slit-pore models with different pore sizes were constructed based on the molecular structures to simulate the methanewater interaction in bituminous and anthracite coals. Results show that water molecules tend to form water bridges and water films in the pores of bituminous and anthracite coals, respectively. The significant displacement of pre-adsorbed water by methane was observed through simulation. It is found that the water molecules on the pore surface and the interfaces of small-size water bridges are more easily displaced by methane. In the larger pores, methane molecules mainly drive water molecules to agglomerate larger water bridges in bituminous coal. While methane molecules mainly drive water molecules to cover the pore surface and form a thicker water film in anthracite coal. This study provides new insights into the microscopic distribution and interaction mechanism of fluids in coal. [ABSTRACT FROM AUTHOR]

For enhancing the effect of gas extraction, applying Wuyang Coal Mine in China as the engineering background, the technology of hydraulic cavitation at the top and bottom of soft coal (HCTBSC) with low permeability was put forward. FLAC3D was utilized to build the calculation model, and Tecplot was employed to process data of the results, revealing the characteristics of stress variation in coal seam for different cavitation radius and different distribution forms of cavitation. The field test scheme of HCTBSC was determined to verify the simulation results. Results show that the effectiveness of stress relief (ESR) is controlled by the cavitation radius and cavitation distribution forms. The dimension of pressure relief emanates via the cavitation elongating outward with the cavitation radius, and the stress changes in the coal are different due to different cavitation distribution forms. The field test proves that the technology of HCTBSC is more effective in relieving pressure, increasing the productiveness of gas extraction, and decreasing the scourge of coal and gas protrusion. The obtained conclusions in this study provide guidance for the hydraulic cavitation application in soft coal. [ABSTRACT FROM AUTHOR]