Anthracite Samples Research Articles

Ignition of anthracite microparticles by continuous laser radiation with wavelengths of 450 and 808 nm

The energy and spectral-kinetic characteristics of ignition of anthracite microparticle powders with a bulk density of 0.5 g/cm3 were measured when exposed to continuous laser radiation at wavelengths λ = 450 and 808 nm with an exposure time of 1 second. Ignition delay times were measured depending on the radiation power density and critical values of the ignition energy density of anthracite samples were determined. The energy cost of igniting anthracite for radiation with λ = 450 nm is less than for radiation with λ = 808 nm. In the emission spectra of anthracite resulting from the absorption of laser radiation, there is a glow associated with the release and ignition of volatile substances (flame CO, glow of excited molecules CO, C2 and H2O) and thermal glow associated mainly with the heated surface of the samples, as well as the flight of incandescent carbon particles.

Heat transfer deformation test and model of coal during LN2 cyclic freezing and thawing process

Exploring the temperature response and deformation characteristics of coal during the freeze–thaw process is crucial for maintaining coal seam stability under liquid nitrogen (LN2) treatment and enhancing gas extraction efficiency. This study investigates the temperature diffusion and deformation characteristics of coal during LN2 cyclic freeze–thaw processes, using saturated and dry anthracite samples. Real-time monitoring of the freeze–thaw characteristics of the anthracite samples was conducted using temperature and strain detectors to quantitatively analyze the evolution of coal temperature and strain. Additionally, a nuclear magnetic resonance (NMR) testing system was used to monitor the pore evolution characteristics of the coal before and after LN2 treatment. The results indicate: After LN2 cyclic freeze–thaw, the internal pores of the saturated samples were highly developed, and fracture connectivity was enhanced, whereas the pores in the dry samples significantly decreased, leading to a sharp reduction in overall connectivity. The cooling and heating rates of the saturated samples were higher than those of the dry samples, both exhibiting exponential trends. This variation is primarily due to the phase change of pore water and the formation and expansion of the internal fracture network within the coal. The deformation magnitude of both sample types showed an overall exponential decline, with the saturated samples exhibiting higher deformation magnitudes than the dry samples. The presence of fracture water not only accelerates coal deterioration during the freeze–thaw process but also enhances coal cementation, maintaining deformation stability. Furthermore, this paper derives a temperature-strain coupling model for coal subjected to LN2 F-T cycles, aiming to provide a reference for understanding the freeze–thaw damage mechanism of coal and the practical application of LN2 fracturing.

Reformation of coal reservoirs by microorganisms and its significance in CBM exploitation

The study investigates the variations in surface morphology and micro-nano-scale pore structure of coal matrix during the process of biodegradation. Comprehensive reservoir characterization techniques, including field emission scanning electron microscope, mercury intrusion porosimetry, and low-temperature N2 adsorption, are employed on four anthracite samples. The significance of the relationship between coal reservoir bio-reformation and coalbed methane (CBM) exploitation is proposed. The main findings indicate that organic matter on the surface of the coal matrix can undergo biodegradation, resulting in the generation of new pores. Microbial metabolism does not alter pore type but only modifies pore size and volume of coal. After microbial degradation, there is an increase in average pore width, while both Brunauer-Emmett-Teller specific surface area and Barrett-Joyner-Halenda pore volume decrease. Furthermore, bioconversion leads to a reduction in both surface and volume dimensions of coal, resulting in a smoother coal matrix surface and simplified complexity of its pore structure. This benefits desorption, migration, and exploitation of CBM. These findings further reinforce the pivotal role of microbial-enhanced coalbed methane production technology in improving CBM production and promoting the clean utilization of coal resources.

Characterization of the pore structure in Chinese anthracite coal using FIB-SEM tomography and deep learning-based segmentation

Coalbed methane (CBM) is an unconventional natural gas that possesses significant impacts on energy supply, mining safety, and environmental conservation. CBM is primarily stored within the pores of coal, highlighting the significance of pore structures for both methane storage and migration. However, comprehensively understanding the intricate pore structures in coal pose challenges. This study employed focused ion beam-scanning electron microscopy (FIB-SEM) tomography and deep learning-based segmentation to characterize the pore structures within a Chinese anthracite sample. The obtained pore structures exhibited a considerable degree of disconnection, comprising numerous separate pore components. Isolated pores prevailed in number, while connected pores dominated in surface area and pore volume. Mesopores (100–1000 nm) contributed the most to pore number, surface area, and pore volume. Pore size distribution analysis revealed distinct patterns among different pore structure properties, with pore number exhibiting an intensive distribution while surface area and pore volume displaying dispersed distributions. Pore structure connectivities exhibited a hierarchical nature and held distinct meanings at the levels of pore, pore component, and pore network. The pore structure characteristics observed in this study have implications for primary CBM recovery, emphasizing the necessity to improve connectivity between pore components and fractures to enhance production rates and recoverability.

Response of anthracite microcrystalline structure due to multi-phase CO2 injection

CO2 injection in coal causes permeability reduction, but also affects the microcrystalline structure. To quantify the different response of microcrystalline structure of anthracite after multi-phase CO2 injection, anthracite samples from the Qinshui basin, the samples were demineralized by HF-HCl before CO2 injection, then subjected dry, demineralized samples to CO2 injection experiments at 4 MPa (gaseous), 6 MPa (subcritical) and 8 MPa (supercritical) pressure, the microcrystalline quantification was obtained using X-ray diffraction and image analysis of HRTEM micrographs, the morphological characteristics of ultramicropore were quantitatively characterized by HRTEM image analysis. With increasing injection pressure, the interplanar spacing (d002) and aromaticity (fa) of the coal gradually increased, while the average number of aromatic layers (Nc) and unit stacking height (Lc) gradually decreased; the variation in the unit lateral size (La) also became more complex. Thus, the coal crystal structure was altered after CO2 treatment and the degree of damage increased with pressure. Further, the average length of coal lattice fringes becomes shorter with the increase of pressure, while the length, width and area of ultra-micropores in subcritical and supercritical SH and ZZ coal increase. In addition, the average curvature of the lattice fringes became larger, and the directional ordering decreased after CO2 intrusion. Thus, CO2 injection led to the transformations of crystal structure, generating intermolecular structural defects, and a reduction in order in the striation direction. This study presents the microcrystalline structure and ultra-micropore response of anthracite due to CO2 injection, which also helps with in-depth understanding of the impact of CO2-ECBM.

Improving the slurryability of high ash coal by blending anthracite of different particle size range

ABSTRACT Hydraulic transportation of lignite and high ash coal (HAC) is economically unviable due to their poor slurryability and stability. The study suggests and shows how the proper selection of appropriate size range and proportion of anthracite for blending can aid in the economical preparation of highly concentrated HAC slurry. Fine (+0–53 µm), coarse (+53–106 µm), and coarser (+106–150 µm) anthracite particles were added to the HAC sample. The proportion of anthracite particles was varied in the range of 10–40% (by weight), to obtain 12 blended tetra-modal samples. To determine the optimum size range and proportion of anthracite, the stability and rheological characteristics of both tri-modal HAC and blended tetra-modal coal samples were assessed. The addition of a fine anthracite sample (+0–53 µm) has an adverse impact on the rheological characteristics. The optimum size range and proportion of anthracite particles for enhanced slurryability and low apparent viscosity are found to be +106–150 µm and 30%, respectively. Optimal blending yields a 68% maximum solid concentration slurry. By taking advantage of both the tetra-modal particle size distribution and anthracite’s high slurryability characteristics, the maximum achievable solid concentration of HAC slurry increases by 17%.

Influences of the Introduced O-Containing Functional Groups on the Gaseous Pyrolysis Product of Superfine Pulverized Coal

An O-containing structure in coal can affect the pyrolysis process; however, the influence of the introduced O-containing functional groups has rarely been investigated. To study this issue, two kinds of representative coal were selected for superfine pulverization and chemical oxidation. The 13C-NMR and FTIR experiments demonstrated that O-containing functional groups, such as carboxyl, could be added into the carbon skeleton after 5 wt% peracetic acid modification. It was found that 1 wt% and 5 wt% hydrogen peroxide solutions had no such ability, but the 1 wt% solution could expand the pore structure and increase the specific surface area. Thermogravimetric experiments in the air showed that peracetic acid oxidation could increase the weight loss rate below 400 °C and reduce ignition temperatures. Pyrolysis experiments in the tube furnace proved that the amount of CO released increased and the commencing temperature decreased by 50 °C after the modification of peracetic acid. The generation paths of C2H4 and C6H6 changed; new generation peaks appeared near 200 °C. It has been strongly confirmed that superfine pulverization and chemical oxidation modification has obvious synergistic effects on the introduction of O-containing functional groups, especially for anthracite samples.

The effect of petrographically determined parameters on reductant reactivity in the production of high-carbon ferromanganese

In pyrometallurgical processes, metal oxides are reduced from molten slag through carbothermic reduction. It is of interest to evaluate the reactivity of the carbonaceous materials towards substances such as slag. Characterization techniques such as coal petrography can provide insight into the influence of feed coal properties and how they potentially dictate reductant performance. This study aimed to compare the petrographically determined organic composition of coal to reductant reactivity. Two South African medium-rank C bituminous coals and one anthracite sample were investigated together with high-carbon ferromanganese industrial slag. The reductant reactivity tests were conducted at 1500°C in a muffle furnace to assess the potential of carbonaceous reductant in reacting with the main slag components. SEM-EDS was applied to understand the extent of MnO (and to a lesser extent, SiO2) reduction from the slag. Coal 2, consisting of a greater proportion of vitrinite (59.5 vol% on a mineral matter-free basis and 54.7 vol% including mineral matter) was the most reactive reductant. The anthracite sample, with the highest inert maceral proportions (71.8 vol% including mineral matter and 76.8 vol% on a mineral matter-free basis), was the least reactive reductant.

Activation of anthracite combustion by copper acetate: mechanism, effect of particle size and introduction method

This paper addressed the effect of copper acetate on the combustion characteristics of anthracite depending on the fractional composition of fuel and additive introduction method. Anthracite was impregnated with 5 wt% of Cu(CH3COO)2 by mechanical mixing and incipient wetness impregnation. Four anthracite samples of different fraction with d < 0.1 mm, d = 0.1–0.5 mm, d = 0.5–1.0 mm, and d = 1.0–2.0 mm were compared. According to EDX mapping, incipient wetness impregnation provides a higher dispersion of the additive and its uniform distribution in the sample. The ignition and combustion characteristics of the modified anthracite samples were studied by thermal analysis and high-speed video recording of the processes in a combustion chamber (at heating medium temperature of 800 °C). It was found that copper acetate increases anthracite reactivity, which was evidenced by decreased onset temperature of combustion (ΔTi) by 35–190 °C and reduced ignition delay time (Δτi) by 2.1–5.4 s. Copper acetate reduces fuel underburning (on average by 70%) in the ash residue of anthracite and decreases the amount of CO and NOx in gas-phase products (on average by 18.5% and 20.8%, respectively). The mechanism for activation of anthracite combustion by copper acetate is proposed.

Study on the Occurrence Difference of Functional Groups in Coals with Different Metamorphic Degrees.

In order to quantitatively study the difference in occurrence content of functional groups in coals with different metamorphic degrees, the samples of long flame coal, coking coal, and anthracite of three different coal ranks were characterized by FTIR and the relative content of various functional groups in different coal ranks was obtained. The semi-quantitative structural parameters were calculated, and the evolution law of the chemical structure of the coal body was given. The results show that with the increase in the metamorphic degree, the substitution degree of hydrogen atoms on the benzene ring in the aromatic group increases with the increase in the vitrinite reflectance. With the increase in coal rank, the content of phenolic hydroxyl, carboxyl, carbonyl, and other active oxygen-containing groups gradually decreased, and the content of ether bonds gradually increased. Methyl content increased rapidly first and then increased slowly, methylene content increased slowly first and then decreased rapidly, and methylene content decreased first and then increased. With the increase in vitrinite reflectance, the OH-π hydrogen bond gradually increases, the content of hydroxyl self-association hydrogen bond first increases and then decreases, the oxygen-hydrogen bond of hydroxyl ether gradually increases, and the ring hydrogen bond first significantly decreases and then slowly increases. The content of the OH-N hydrogen bond is in direct proportion to the content of nitrogen in coal molecules. It can be seen from the semi-quantitative structural parameters that with the increase in coal rank, the aromatic carbon ratio fa, aromatic degree AR and condensation degree DOC increase gradually. With the increase in coal rank, A(CH2)/A(CH3) first decreases and then increases, hydrocarbon generation potential 'A' first increases and then decreases, maturity 'C' first decreases rapidly and then decreases slowly, and factor D gradually decreases. This paper is valuable for analyzing the occurrence form of functional groups in different coal ranks and clarifying the evolution process of structure in China.

Effect of pressure on the evolution of vitrinite graphitized mesophases: An experimental study on anthracite under high temperature and pressure

In this study, the influence of pressure on the evolution of the intermediate phase of graphitization of vitrinite was determined. Using samples of Taixi anthracite from the Rujigo Coal Mine (Ordos Basin, China), experiments were conducted in a piston cylinder press at a constant temperature of 1073 K and pressures from 500 MPa to 1 GPa. Raman spectroscopy, high-resolution transmission electron microscopy, selective electron diffraction, and electron loss energy spectra were used to characterise the microcrystalline morphology, structural order, and atomic valence states of the samples. Under confined conditions, pressure significantly promoted the graphitization process; however, the effect of different pressures on such process in vitrinite varied. Low pressure (<700 MPa) promoted an ordered growth of aromatic rings; meanwhile, a medium pressure (700–800 MPa) destroyed the microporous structure of vitrinite, leading to a less-ordered carbon layer and a sp3 metastable carbon structure resembling nano-diamond. Notably, high pressure (>900 MPa) promoted the condensation and directionalisation of the carbon layer of the vitrinite by destroying the microporous structure, resulting in a rapid growth of microcrystalline graphite. This suggests a transition to the key stage of anthracite graphitization, which may be an important feature in the formation of intermediate phases. In fact, pressure has been shown to exert an important role in the rupture of microporous structures in vitrinite, whose mechanism may be related to the sp3 metastable carbon formed between the basic structural units in different high-pressure environments. These findings provide insight into the formation mechanism of coal graphite, bringing new understanding of the transition from multi-faceted nanocrystals to graphitization in an orogenic metamorphic zone (e.g., in high-pressure schist and hornblende).

Quantitative characterization of the pore volume fractal dimensions for three kinds of liquid nitrogen frozen coal and its enlightenment to coalbed methane exploitation

Liquid nitrogen fracturing technology is an important means to improve the permeability of coal seams and realize unconventional natural gas extraction. In order to study the fractal characteristics of pore structure of coal frozen by liquid nitrogen, the pores of both nonfrozen and frozen samples of lignite, bituminous coal, and anthracite were measured with a high-pressure adsorption meter, a mercury porosimeter, and a low-field nuclear magnetic resonance (NMR). The test results showed that after freezing in liquid nitrogen, the pores of coal were effectively expanded. Among them, Nitrogen adsorption of lignite, bituminous coal and anthracite increased by 20.82%, 6.54% and 20.39%. The conversion rates from adsorption pore to seepage pore were 2.16%, 0.78% and 3.57%. The research results of pore fractal dimension showed that the multifractal characteristics of macropores were higher than that of mesopores and micropores. After liquid nitrogen freezing, the pore fractal dimension of lignite, bituminous coal and anthracite decreased by 0.031, 0.009 and 0.003, and the pore structure tends to be smooth. It showed the liquid nitrogen freezing coal enhances the migration and drainage of coalbed methane, which has reference significance for the further research of liquid nitrogen fracturing technology.

The effect of the density difference between supercritical CO2 and supercritical CH4 on their adsorption capacities: An experimental study on anthracite in the Qinshui Basin

Deep unmineable coals are considered as economic and effective geological media for CO2 storage and CO2 enhanced coalbed methane (CO2-ECBM) recovery is the key technology to realize CO2 geological sequestration in coals. Anthracite samples were collected from the Qinshui Basin and subjected to mercury intrusion porosimetry, low-pressure CO2 adsorption, and high-pressure CH4/CO2 isothermal adsorption experiments. The average number of layers of adsorbed molecules (ANLAM) and the CH4/CO2 absolute adsorption amounts and their ratio at experimental temperatures and pressures were calculated. Based on a comparison of the density of supercritical CO2 and supercritical CH4, it is proposed that the higher adsorption capacity of supercritical CO2 over supercritical CH4 is the result of their density differences at the same temperature. Lastly, the optimal depth for CO2-ECBM in the Qinshui Basin is recommended. The results show that: (1) the adsorption capacity and the ANLAM of CO2 are about twice that of CH4 on SH-3 anthracite. The effect of pressure on the CO2/CH4 absolute adsorption ratio decreases with the increase of pressure and tends to be consistent. (2) A parameter (the density ratio between gas free and adsorbed phase (DRFA)) is proposed to assess the absolute adsorption amount according to the supercritical CO2/CH4 attributes. The DRFA of CO2 and CH4 both show a highly positive correlation with their absolute adsorption amounts, and therefore, the higher DRFA of CO2 is the significant cause of its higher adsorption capacity over CH4 under the same temperature and pressure. (3) CO2 adsorption on coal shows micropore filling with multilayer adsorption in the macro-mesopore, while methane exhibits monolayer surface coverage. (4) Based on the ideal CO2/CH4 competitive adsorption ratio, CO2 storage capacity, and permeability variation with depth, it is recommended that the optimal depth for CO2-ECBM in the Qinshui Basin ranges from 1000 m to 1500 m.

Geochemical signatures of potassium metasomatism in anthracite from the Himalayan fold-thrust belts of Sikkim, India

The present study focuses on the inorganic geochemical features of the bituminous coal samples from the Raniganj and the Jharia Basins, as well as the anthracite samples from the Himalayan fold-thrust belts of Sikkim, India. The SiO2 content (48.05 wt% to 65.09 wt% and 35.92 wt% to 50.11 wt% in the bituminous and anthracite samples, respectively) and the ratio of Al2O3/TiO2 (6.97 to 17.03 in the bituminous coal samples and 10.34 to 20.07 in the anthracite samples) reveal the intermediate igneous source rock composition of the minerals. The ratio of the K2O/Al2O3 in the ash yield of the bituminous coal samples (0.03 to 0.09) may suggest the presence of kaolinite mixed with montmorillonite, while its range in the ash yield of the anthracite samples (0.16 to 0.27) may imply the presence of illite mixed with kaolinite. The chemical index of alteration values may suggest the moderate to strong chemical weathering of the source rock under sub-humid to humid climatic conditions. The plot of the bituminous coal samples in the A–CN–K diagram depicts the traditional weathering trend of parent rocks, but the anthracite samples plot near the illite field and are a bit offset from the weathering trend. This may imply the plausible influences of the potassium-metasomatism at post coalification stages, which is further supported by high K2O/Na2O ratio (29.88–80.13). The Fourier transform infrared spectra further reveal the hydroxyl stretching intensity of illite in the anthracite samples substantiating the effect of the epigenetic potassium-metasomatism. The decrease in total kaolinite intensity/compound intensity of quartz and feldspar may provide additional evidence towards this epigenetic event.

Experimental investigation of mechanical characteristics of coal samples at different drying temperatures

The drying and mechanical properties of long flame coal and anthracite after exposure to various drying temperatures were investigated in this study. Coal samples were processed and screened, treated with a nondestructive water immersion device, and dried separately at different temperatures. Uniaxial compression experiment, acoustic emission tests, and fractal dimension calculation were then conducted. Experimental results show that the degree of drying of coal samples rose as the drying temperature increased. Peak stress and elastic modulus decreased while the damage variables and brittleness rose in dried anthracite samples with increasing drying temperature. The Acoustic emission characteristics were consistent with the mechanical characteristics. The stress-strain curves changed from stepped type to perpendicular type in the post-peak stage. This was accompanied by intense damage of the coal samples and increases in the fractal dimension of the broken blocks. Our findings shed light on how coal samples dry and provide recommendations for enhancing drying methods in laboratory mechanics tests.

Characterization of Pore Structures with Mercury Intrusion Porosimetry after Electrochemical Modification: A Case Study of Jincheng Anthracite.

Quantitative characterization of the change in the cleat and pore structures and fractal dimensions in anthracite after electrochemical modification is crucial for better understanding of the modification effect. Thus, lump anthracite samples were electrochemically modified in our manufactured device with 0, 0.5, 1, and 2 V/cm potential gradients. The changes in heterogeneity and porosity after modification were tested and analyzed by mercury intrusion porosimetry (MIP) and fractal theory. The results indicated that the total volume of the pores increased after electrochemical treatment and continuously increased with increasing potential gradient during the treatment process. After modification, the number of pores or fractures with a pore size between 6 and 20 μm in coal after modification increases significantly. According to the intrusion pressure, three stages were defined as lower (PM < 0.1 MPa), intermediate (0.1 ≤ PM < 10 MPa), and higher regions (PM ≥ 10 MPa), which are characterized by fractal dimensions D1, D2, and compression stages, respectively. After modification, the fractal dimension D1 showed an increasing trend, while the fractal dimension D2 showed a decreasing trend, indicating that the fracture system became more complicated and that the pore system became more regular after electrochemical treatment. The evolution mechanism of heterogeneity and porosity and their fractal dimensions were explained by the dissolution of minerals, change in pH values, and dynamics of temperatures during the process of modification. The results obtained in this work are of important guiding significance for coalbed methane (CBM) extraction via in situ modification by electrochemical treatment.

Experimental investigation of spontaneous combustion of anthracite controlled by the chemical deposition of two-phase (hydroxide and CO2) aerosols

To explore an efficient and sustainable approach to prevent coal spontaneous combustion in underground goaf, chemical deposits produced by a reaction of two-phase aerosols (CO2 and hydroxide) were utilized to prevent the spontaneous combustion of anthracite. A Henan anthracite sample (0.18 mm-0.25 mm) was treated with aerosols continuously. Ba(OH)2-CO2, Ca(OH)2-CO2, Na2SiO3-CO2 and NaAlO2-CO2 aerosols flowed through the surface of the coal sample simultaneously. After 50–55 s, in addition to Ca(OH)2-CO2, white deposits or transparent colloidal deposits appeared and accumulated gradually. After 20 mins, the weight of the produced deposits (dry mass) reached 0.95%-5.10% of the original weight of the samples. According to the results of scanning electron microscope, X-ray diffraction, thermogravimetry and differential scanning calorimetry, physical experiments and quantum chemistry simulations, we inferred that the two-phase aerosols formed dense ultrafine columnar or flocculent coatings on the coal surface. The main components of the deposits were BaCO3, CaCO3, H2SiO3, Al(OH)3, hydrates, etc. The number of residues after the combustion of the coal samples increased by 6.57%-16.12%, and the maximum exothermic peak decreased to 69.0%-86.2% of the raw coal. Ba2+ in the aerosol formed two-ligand, three-ligand and four-ligand complexes with the characteristic structure containing S in the coal samples. It can be concluded that the two-phase aerosols exhibit excellent barrier-crossing ability and a higher inhibitory effect on re-ignition for extinguishing fires.

Accurate characterization of coal pore and fissure structure based on CT 3D reconstruction and NMR

In order to accurately achieve the full-scale characterization of coal pore and fissure structure, a comprehensive characterization method based on Computed Tomography (CT) 3D reconstruction, Nuclear Magnetic Resonance (NMR) T2 spectrum and Nuclear Magnetic Imaging (NMI) are proposed. CT scanning and NMR experiments are carried out on the samples of gas coal and anthracite to verify this method. And the characteristics of pore size distribution (PSD), porosity and permeability are studied. It is found that the main seepage channels can be obtained by CT 3D reconstruction, and that the observation defect of CT scanning can be compensated by NMI because micro seepage pores and adsorption pores can be visualized. Furthermore, CT 3D reconstruction results indicate that the larger the pore size, the smaller the number of pores, and the larger the porosity component while the NMR T2 spectrum of pore size distribution show that the porosity component of micro adsorption pores is largest. With the advantage of CT macro-scale observation and NMR micro-scale observation combined, porosities are calculated accurately. Besides, seepage characteristics observed in the NMR experiments under different water injection pressures are analyzed, and the results are consistent with the analysis results of the CT 3D reconstruction of coal connectivity.

Electrochemical Modification on CH4 and H2O Wettability of Qinshui Anthracite Coal: A Combined Experimental and Molecular Dynamics Simulation Study

The wettability of gas and liquid on the coal surface is one of the fundamental factors that affect the depressurization process during the coalbed methane (CBM) extraction. The wettability of coal surface changed after electrochemical modification, leading to the change in methane adsorption/desorption and water movement in coal reservoirs. Thus, the CH4 adsorption amount, desorption ratio, and coal–water contact angle of raw and modified anthracite samples were measured and simulated. The mechanism of electrochemical modification was analyzed by functional groups, surface free energy, pore characteristics, interaction energies, and coal swelling. The experimental results showed that the saturated adsorption amount of methane decreased from 41.49 to 34.72 mL/g, and the simulation results showed that the saturated adsorption amount of methane decreased from 2.01 to 1.83 mmol/g. The coal–water contact angle also decreased from 81.9 to 68.6°. Electrochemical modification mainly affects the wettability of CH4 and H2O by changing the functional groups and pore structures of anthracite, and the influence on functional groups of coal surface is greater. This work provided a basis for enhancing CBM extraction by electrochemical modification.

Activation of Anthracite Combustion Using Pyrolysis Oil from Thermal Conversion of Waste Car Tires.

The ignition and combustion of anthracite modified by the addition of pyrolysis oil obtained during thermal processing of waste car tires (WCTs) had been studied. The mass fraction of WCT pyrolysis oil was varied in the range from 5 to 30 wt %. The additive was applied by the drop impregnation method. Ignition and combustion of obtained samples were carried out in a combustion chamber at temperatures of the heating medium Tg = 600–800 °C. The gas-phase combustion products were analyzed using an in-line gas analyzer. The application of WCT pyrolysis oil as a combustion modifier contributed to an increase in the reactivity of anthracite, which was expressed in a decrease in the minimum ignition temperature (by 23–104 °C) and a reduction in the ignition delay time. The high-speed video recording indicated that the combustion of both initial and modified with 5 wt % pyrolysis oil anthracite samples was realized in oxidation mode. For samples with more than 10 wt % pyrolysis oil additive, the formation of a visible flame was observed near the sample surface. With an increase in the mass fraction of the additive, the rate of combustion front propagation was increased. The application of WCT pyrolysis oil as a combustion modifier also contributed to the reduction or even the almost complete elimination of unburnt carbon content in the ash residue formed after anthracite combustion.