Flame Coal Research Articles

Impact of atomizer design on slurry fuel atomization behavior

The paper presents experimental findings on the atomization characteristics of coal–water slurries with and without petrochemicals. The fuels were based on flame coal filter cake (slime), which is a typical coal processing waste, flame coal of different particle sizes, wood biomass (sawdust), used transformer oil, and water. The atomized flow characteristics—droplet size and velocity as well as jet angle—were found to depend on the atomizer dimensions and slurry rheology. The experimental data were used to calculate the slurry atomization efficiency factor. The findings were generalized to provide a mathematical description of how the slurry composition and atomizer geometry affect the slurry atomization behavior. Approximations were obtained for atomization characteristics that can be used to predict the jet angle as well as droplet radii and velocities. The developed mathematical tool can be employed to calculate the spraying characteristics when using devices like external-mix twin-fluid atomizers. The approach proposed for data generalization can be applied to adapt the set of approximation equations to other types of nozzles.

Experimental and molecular dynamics study on the influence of surfactants on the wettability of different rank coal

This study sought to enhance the wettability of coal surfaces to minimize coal mine dust generation and improve underground working conditions. To this end, we evaluated the effect of different surfactants on different coal ranks. Through molecular dynamics simulations, we constructed different coal-surfactant-water molecular systems and elucidated the microscopic migration pattern of water molecules on coal surfaces. Our findings thus provided insights into the wetting mechanisms of coal of varying ranks from multiple perspectives. Our findings indicated that the wettability of coal decreases with higher coal metamorphism. However, adding surfactants to water significantly improves the wetting effect of liquids on coal. Notably, a 1.0 wt% sodium dodecyl sulfate (SDS) solution exhibited the smallest indirect contact angles with long flame coal and gas coal samples, measuring 25.1° and 25.8°, respectively. Conversely, a coconut diethanolamide (CDEA) solution at a 1.0 wt% concentration demonstrated superior wetting effects on anthracite coal samples, with a contact angle of 25.7°. Upon surfactant addition, the diffusion coefficient of water molecules notably increased, with maximum values reaching 2.32Å2/ps, 2.56Å2/ps, and 2.15Å2/ps, respectively. Moreover, both the total potential energy of the coal molecular layer and the surface electrostatic potential exhibited an increasing trend. This enhancement strengthens the adsorption capacity of coal molecular surfaces for water molecules, thereby promoting coal wettability. Collectively, our findings provide new insights for optimizing surfactant use and efficiently mitigating dust in coal mines.

Selective hydroconversion of ethanolyzed soluble portion from the ethanolysis of Hanglaiwan long flame coal extraction residue over highly active Ni/SAPO-34 catalyst

The ethanolyzed soluble portion (SPE) prepared from the ethanolysis of Hanglaiwan long flame coal (HLFC) extraction residue was converted to catalytically hydroconverted SPE (CHSPE) by the catalytic hydroconversion (CHC) over Ni10 %/SAPO-34 at 200 °C under an initial hydrogen pressure of 5 MPa for 24 h. The possible mechanisms for the origin and synergic effect of active hydrogen had been speculated according to the reactions of HLFC-related model compounds. H2 can be activated by Ni10 %/SAPO-34 to produce H···H, H+, and H-, the synergic effect of which leads to cleaving >C-O- bonds. After the CHC, arenes and heteroatom-containing aromatic compounds in SPE are converted to cyclanes, indicating that aromatic ring hydrogenation and heteroatom removal occur simultaneously during the CHC of SPE. The relative abundance (RA) of CH-containing species in CHSPE is larger than that in SPE, while the RAs of oxygen- and nitrogen-containing species in CHSPE are smaller than those in SPE. In addition, Ni10 %/SAPO-34 has excellent cyclability for the CHC of SPE, and the relative content of cyclanes decreases only by 17.4 % after five recycles. Undoubtedly, this investigation provides an effective strategy for directional upgrading of derived soluble portion from low metamorphic coals.

A Novel Microbial Compound Inhibitor and Its Efficacy in Preventing and Controlling Mine Fire Risks: A Case Study on Low-Rank Coal Spontaneous Combustion.

To guarantee the safety and sustainability of coal mining by effectively mitigating the substantial risk associated with coal spontaneous combustion, this study proposes a multifaceted prevention strategy aligned with green environmental principles. A compound flame retardant with a physicochemical control mechanism was prepared using indigenous microorganisms to mineralize residual coal after mining, utilizing Bacillus pasteurelli as a substitute material for inorganic salts. Under laboratory conditions simulating coal self-combustion, biobased flame retardants were employed to investigate the physical and chemical transformations of heat and mass evolution from ambient temperature to combustion in two representative low-rank coals. By quantitatively comparing alterations in microbiome-based groups among raw lignite, bioretarded lignite, and two control samples, the inhibitory mechanism of biobased materials on the oxygen reaction pathway was elucidated. The findings substantiated that biobased modification can consolidate the methyl and methylene groups present in aliphatic hydrocarbon side chains, which are prone to instigating low-temperature oxidation reactions. Additionally, the preventive performance of biobased flame retardants was assessed through temperature-programmed experiments, which involved estimating the critical self-heating temperature, oxygen consumption, and gas production rates of compared coal samples. The results demonstrated significant enhancements in the resistance to spontaneous combustion following bioretarded modification. Notably, the identification grade of long flame coal shifted from easy to moderate susceptibility to spontaneous combustion. Furthermore, biobased flame retardants exhibited remarkable flame retardancy rates of approximately 80% for lignite, thereby validating their efficacy as more environmentally friendly and technologically advanced substitute materials for inhibiting spontaneous combustion in low-rank coals.

Preparation of Bio-Based microemulsion collector and its flotation performance for coal slime

Cardanol polyoxyethylene ether (CPE) is a green bio-degradable surfactant. Herein, we used CPE as an emulsifier to prepare a new environmentally friendly and high-efficiency bio-based microemulsion collector (HE-BMC) for coal slime flotation. The phase behavior studies showed that the single-phase microemulsion (SPM) area proportion was the largest at the mass ratio of CPE-12 to n-pentanol of 1.2. The dilution integrity study results demonstrated that the microemulsion collector average particle size was stabilized at nearly 30 nm when the mass ratio of SACS to n-dodecane was greater than 6: 4, with water content higher than 20 %. Based on the above research, the relationship model between the microemulsion collector size and the component contents was constructed using the mixture design method. Consequently, the optimal formulation for HE-BMC was obtained and consisted of 24.75 % CPE-12, 20.62 % n-pentanol, 27.69 % n-dodecane, and 26.94 % water, with an average size of 25.83 nm. The physical properties study results elucidated that HE-BMC has good daily storage and transportation as well as better dispersibility in water. The particle size in water was 2.28 μm when the cumulative particle size distribution reached 90 %. The flotation test results revealed that the HE-BMC yielded 3.91 % more clean coal than n-dodecane while maintaining a similar clean coal ash content. However, the dosage of HE-BMC was only 41.67 % of that required for n-dodecane. Furthermore, long flame coal slime flotation utilizing HE-BMC could be achieved without the need for adding frother.

Erratum to: Insight into Upgrading Caking Property of Shenmu Long Flame Coal Using Low-temperature Slow Pyrolysis Treatment

Erratum to: Insight into Upgrading Caking Property of Shenmu Long Flame Coal Using Low-temperature Slow Pyrolysis Treatment

Qualitative analysis of hydrophilic headgroup water molecular space dependence and wetting effects of solution systems on polluting coal dust

The hydrophilic head groups of the surfactants affect the interfacial tension of surfactant solutions and the internal micelle structure of the bulk surfactants. Because of this, investigating the effect of the hydrophilic head groups on the adsorption performance of surfactants is helpful in terms of revealing the wetting mechanism of surfactants on coal at the molecular level. In this work we combine molecular dynamics simulations and quantum chemistry calculations with a collection of experiments to analyze the interaction patterns between sodium dodecyl sulfonate (SDSO), sodium dodecyl sulfate (SDS), sodium fatty alcohol polyoxyethylene ether carboxylate (SSN), and sodium lauryl phosphate (LSN) with coal. The radial distribution results show that SDSO formed the closest first peak of the hydrated layer at 1.31 Å, with a probability peak of 3.92, which exhibited strong hydrogen bonding interactions that are consistent with the relative concentration and average azimuthal shift trends obtained from molecular trajectory simulations. The priority interaction types between four surfactants and water molecules were determined using the energy difference of molecular orbitals in quantum mechanics. The weak interaction between hydrophilic head groups and water molecules was qualitatively and quantitatively analyzed using the Independent Gradient Model (IGMH), and the fundamental reasons affecting the wetting of long flame coal were obtained.

Static-dynamic wetting characteristics and microscopic synergistic mechanism of compound surfactant on coal dust with different metamorphic degrees

The compound surfactant has a synergistic effect on the wetting ability of coal dust. In the study, the wettability of compound surfactant on coal dust with different metamorphic degrees was studied from static wetting experiment, dynamic wetting experiment, and micro molecular simulation. The results showed that the contact angle of the anionic-nonionic compound surfactant solution on any coal sheet was significantly smaller than that of the single component, which was 14.04%～63.31% lower than that of the single component. The contact angle of the anionic-anionic compound surfactant on the six kinds of coal dust test pieces was not smaller than the contact angle of each single component, only a compromise of contact angle of single component. The dust suppression efficiency of the gas coal in 0.025 wt% fatty acid methyl esters ethoxylate sulfonate (FMES) and 0.025 wt% coconutt diethanolamide (CDEA) compound solution was the highest, which was 78.4%. Lignite coal, long flame coal, non-caking coal, coking coal, and anthracite all have the highest dust suppression efficiency when sprayed with 0.025 wt% sodium alcohol ether sulphate (AES) and 0.025 wt% CDEA, which were 91.53%, 88.24%, 85.7%, 73.25%, and 80.57%, respectively. For any metamorphic degree of coal sample dust, the anionic-nonionic compound surfactant shows obvious synergistic effect on improving the wettability of coal dust. Furthermore, when the surfactant is adsorbed on the surface of coal molecules, the concentration of water molecules on the surface of coal molecules is increased, the hydrophilicity of the solid–liquid interface is improved, and the water molecules are more intensely diffused on the surface of coal dust. And the absolute value of the adsorption energy of the surfactant on the surface of the coal dust is higher, and the more hydrogen bonds formed by the hydrophilic groups, the better the wettability of the coal dust surface.

Investigation on the preparation of coal slime flotation microemulsion collector: A combination of experimental and simulation method

Microemulsion collector is a new type of highly efficient collector for coal slime flotation, but the research on their formulation is complexity and time-consuming, which restricts the development and application of the collector. In this work, an efficient method was designed for preparing microemulsion collectors through combined experiments and simulation. The dissipative particle dynamics simulation studies showed that CPE-12 was the surfactant for the preparation of microemulsion collector, and n-pentanol was the cosurfactant. And the Km value range was between 1.0 and 1.5. The experimental studies based on simulation showed that the Km value was 1.2 and the content of water was greater than 20%. The composition of the microemulsion collector was 22.91% CPE-12, 19.09% n-pentanol, 28.00% n-dodecane, and 30.00% water. The centrifugation and short-term storage experiments showed HB-MC has good stability for daily storage and transportation. The flotation test studies showed that, under the condition of similar ash content of clean coal, the yield of clean coal floated by the HB-MC was 1.42% higher than that of n-dodecane, and its dosage was 18.18% of that of n-dodecane. Moreover, the flotation of long flame coal slime using HB-MC without adding frother.

Catalytic ethanolysis of Hanglaiwan long flame coal to organic small-molecular compounds under mild conditions over SAPO-34-supported nickel nanoparticle catalyst

SAPO-34-supported nickel nanoparticle catalyst Ni/SAPO-34 was prepared by a modified deposition-precipitation method and nickel nanoparticles were uniformly dispersed onto the SAPO-34 crystal surface. Hanglaiwan long flame coal (HLFC) was subjected to the catalytic ethanolysis (CE) over Ni10%/SAPO-34 at 300 °C under 1 MPa of initial nitrogen pressure for 4 h to obtain more soluble organic small-molecule compounds (SOSMCs). Ni10%/SAPO-34 can effectively activate ethanol to release H+, +CH2CH3, and H-, and then precisely cleave >CH-O- and >Car-O- bridged bonds in HLFC. As a result, the total yield of soluble portion (SP) increases from 43.2 to 60.5 wt%. Arenes and oxygen-containing organic compounds are the main SOSMCs detected in SPCE from the CE and SPNCE from the ethanolysis, and the yields of arenes, hydroarenes, and phenols in SPCE are higher than those in SPNCE. In addition, compared to SPNCE, the condensation degree of aromatic rings in SPCE is higher. This investigation provides a promising alternative to the clean and value-added utilization of low-rank coals.

Effect of Solvent Treatment on the Composition and Structure of Santanghu Long Flame Coal and Its Rapid Pyrolysis Products.

Easily soluble organic components in Santanghu long flame coal (SLFC) from Hami (Xinjiang, China) were separated by CS2 and acetone mixed solvent (v/v = 1:1) under ultrasonic condition, and the extract residue was stratified by carbon tetrachloride to obtain the light raffinate component (SLFC-L). The effect of solvent treatment on the composition and structure of the coal and its rapid pyrolysis products was analyzed. Solvent treatment can reduce the moisture content in coal from 9.48% to 6.45% and increase the volatile matter from 26.59% to 28.78%, while the macromolecular structure of the coal changed slightly, demonstrating the stability of coal's complex organic structure. Compared with raw coal, the relative contents of oxygen-containing functional groups and aromatic groups in SLFC-L are higher, and the weight loss rates of both SLFC and SLFC-L reached the maximum at about 450 °C. In contrast, the loss rate of SLFC-L is more obvious, being 33.62% higher than that of SLFC. Pyrolysis products from SLFC at 450 °C by Py-GC/MS are mainly aliphatic hydrocarbons and oxygenated compounds, and the relative contents of aliphatic hydrocarbons decreased from 48.48% to 36.13%, while the contents of oxygenates increased from 39.07% to 44.95%. Overall, the composition and functional group in the coal sample were changed after solvent treatment, resulting in a difference in the composition and distribution of its pyrolysis products.

Research on Explosion Pressure Characteristics of Long Flame Coal Dust and the Inhibition Effect of Different Explosion Suppressants.

To discuss the inhibition of long flame coal dust explosion pressure, NaHCO3, KHCO3, and NH4H2PO4 are selected as explosion suppression dust for explosion pressure tests under different conditions. The results show that when 25-38 and 38-45 μm coal dust are mixed in 1:1 ratio, the maximum explosion pressure is the largest, the maximum pressure is 0.79 MPa, and the maximum pressure rise rate is 74.89 MPa·s-1. The suppression dusts have good inhibition effect on explosion, the order of inhibition is NaHCO3, KHCO3, and NH4H2PO4 from the smallest to the largest. With the reduction of particle size of NH4H2PO4, its inhibition effect on explosion pressure is increasing, because more NH4H2PO4 particles move around coal dust particles, blocking the heat transfer and kinetic energy exchange. The above three suppression dust and their suppression methods can provide important data for dust prevention and control and have certain reference significance for carrying out explosion suppression work.

Radon exhalation characteristics after pyrolysis of long flame coal

Coal pyrolysis is a important method for classifying and utilizing coal resources and contributes to enhanced comprehensive resource utilization. However, In high-temperature areas such as coal pyrolysis, there is an abnormal phenomenon release of radioactive gas radon, understanding the relationship between temperature and radon exhalation characteristics, as well as the underlying mechanisms, holds great importance for assessing radon pollution in mining areas. After coal undergoes pyrolysis under high temperature conditions, its material composition, pore structure, water content, and other properties have changed. The pyrolysis products in different atmosphere environments have differences, and the characteristics of radon emission are also different. To address this, the present study conducted coal pyrolysis experiments in both aerobic and anaerobic environments, using long flame coal sourced from Yulin, China. The radon release concentration of the pyrolysis products was measured. The research findings indicate that during pyrolysis at elevated temperatures, the ratio of coal mass loss is constantly increasing. High temperatures promote the development of pores and fissures, and significant changes in coal properties at temperature thresholds (300 °C and 500 °C). The specific surface area, pore volume, and fracture ratio all display substantial increases, and the amplitude of change is greater under aerobic conditions. The fractal dimension of total pores and macropores shows continuous growth, while the specific surface area, pore volume, and fracture ratio exhibit a strong negative correlation with the radon emission rate of pyrolysis products. The expansion and penetration of pores and cracks, along with the release of a substantial amount of pyrolysis gas, accelerate the transformation, migration, and exhalation of radon, resulting in a negative correlation between the heat treatment temperature and the radon release rate of pyrolysis products. Under aerobic conditions, the radon release rate of pyrolysis products decreases more significantly.

Structural characterization analysis and macromolecular model construction of coal from Qinggangping coal mine

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.

A detailed magnetic characterization of combustion products from various metamorphic grade coals

The magnetic properties of combustion products from various metamorphic grade coals including lignite, flame coal, gas coal, fat coal, baking coal and lean coal and anthracite coal, were analyzed. This study was carried out by means of basic magnetic parameters, thermomagnetic and hysteresis measurements. The mass magnetic susceptibility (χ) values ranged from 327 × 10−8 m3/kg to 1722 × 10−8 m3/kg, with an average value of 892 × 10−8 m3/kg, demonstrating a considerable amount of ferrimagnetic minerals in these burned coal samples. The lower χ and SIRM values for the burned lignite were probably due to the lower content of magnetite. A characteristic feature of combustion products was their high values of frequency dependent susceptibility (χfd%), indicating the presence of a large amount of superparamagnetic grains of ferrimagnetic minerals within the combustion products. Thermomagnetic analyses of various combustion products showed the dominant role of magnetite-like phase. Moreover, a significant amount of hematite was also only identified in the combustion product from Flame coal. While the combustion products from Flame coal and Fat coal were characterized by a relatively narrow loop, characteristic of magnetically soft ferrimagnetic minerals, other combustion products including lignite, gas coal, baking coal, lean coal and anthracite coal displayed wasp-waisted loops, indicating the presence of two or more coercivity fractions.

Preparation of flotation refined carbon from gasification slag

Highly efficient and environmentally friendly utilization of coal gasification slag is a hot research subject in the coal chemical industry at present. The preparation of activated carbon with a flotation refined carbon from gasification slag, a long flame coal, a high temperature coal tar containing 70% asphalt and an active agent in proper proportion was carried out. The influence of activation temperature and time on the surface properties and compressive strength of the produced activated carbon was investigated in a tube furnace. The oxygen functional group, pore structure and absorption performance of the produced activated carbon were characterized by FT-IR, N2 adsorption-desorption, SEM and iodine adsorption. The COD removal from biochemical waste water by the produced activated carbon was verified. The results show that the key factors for the effective formation and expansion of pore are the suitable activation temperature and time for the floatation refined carbon from gasification slag as the feedstock. The activated carbon prepared by carbonization at 550 °C for 30 min and steam activation at 950 °C for 2 h exhibits a crisscross morphology of organic carbon components and minerals. The surface area, pore capacity and average pore diameter are 566 m2/g, 0.5611 mL/g and 5.1 nm, respectively, with the characteristics of a concentrated pore distribution and a certain quantity of mesopore. Both iodine value (650 mg/g) and methylene blue value (128 mg/g) meet the requirements of the Chinese standard “Technical Specifications and Test Methods of Activated Carbon for Purification of Industrial Wastewater”. The COD in biochemical waste water treated by the activated carbon for 60 min with a solid-to-liquid ratio of 0.6 g/L can be reduced to lower than 30 mg/L, meeting the B class water quality of the Chinese standard “Integrated Discharge Standard of Water Pollutants” (DB11/307—2013).

Investigation on the catalytic performance of magnetic copper ferrite nanoparticles in the catalytic hydroconversion of Hanglaiwan long flame coal

Magnetic copper ferrite (CuFe2O4) was prepared by hydrothermal synthesis method and used for the catalytic hydroconversion (CHC) of Hanglaiwan long flame coal (HLFC) in cyclohexane under 1 MPa of initial hydrogen pressure (IHP) at 300 °C for 4 h. The total yield of soluble portion (SP) from the CHC is 33.7 wt%, significantly being higher than that (10.5 wt%) from the non-CHC (NCHC) under the same conditions. The main compounds detected in SPCHC (for CHC) are arenes and oxygen-containing organic compounds (OCOCs). Benzyloxybenzene (BOB), 2-(benzyloxy)naphthalene (BON), oxybis(methylene)dibenzene (OBMDB), oxydibenzene (ODB), and 2,2′-oxydinaphthalene (ODN) were used as HLFC-related model compounds to investigate the catalytic activity of CuFe2O4 and understand the CHC mechanism of HLFC. According to the model reactions, CuFe2O4 activates H2 to biatomic active hydrogen (H…H) and splits H…H to mobile H+ and immobile H-. H+ addition to oxygen atoms (OAs) in >C-O- bridged bonds (BBs) cleaves the BBs and releases SP during the CHC of HLFC.

Mechanism of slime coating on coal surface with different metamorphic degrees

Slime coating is an important phenomenon that deteriorates the recovery and quality of clean coal in fine coal flotation process. The quantitative determination and underlying mechanism of slime coating on coal surface with different metamorphic degrees that has discrepancy in both chemical composition and physical structure remains undiscovered. In order to explore the differences of slime coating on the surface of coal with different metamorphic degrees, the degree of slime coating was observed using an in-situ particle vision and measurement (PVM) probe and quantified by image processing. The chemical and physical properties of coal were analyzed using Fourier Transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Low-Field Nuclear Magnetic Resonance (LF NMR) to underly its mechanism. It was found that slime coating on anthracite was the severest, followed by long flame coal and coking coal. The FTIR and XPS measurements indicated that the chemical composition was contradictory with the slime coating results. The results of SEM and LF NMR showed that there were more cracks and large-scale pores on anthracite compared to long flame coal and coking coal. Therefore, there were more covering sites on anthracite that were favorable for slime coating. The difference in physical property is the controlling factor for the difference of slime coating on coal surface with different metamorphic degrees.

Oxidation and exothermic properties of long flame coal spontaneous combustion under solid-liquid-gas coexistence and its microscopic mechanism analysis

Coal spontaneous combustion (CSC) wastes valuable resources and does great damage to the environment. To study the oxidation and exothermic properties of CSC under solid-liquid-gas coexistence conditions, a C600 microcalorimeter was used to analyze the heat released by the oxidation of raw coal (RC) and water immersion coal (WIC) under different air leakage (AL) conditions. The experimental results showed that the AL was negatively correlated with the heat release intensity (HRI) in the initial stages of coal oxidation, but as the oxidation proceeded, the AL and the HRI gradually showed positive correlations. The HRI of the WIC was lower than that of the RC under the same AL conditions. However, since water participated in the generation and transfer of free radicals in the coal oxidation reaction and promoted the development of coal pores, the HRI growth rate of the WIC was higher than that of the RC during the rapid oxidation period, and the self-heating risk was higher. The heat flow curves for the RC and WIC in the rapid oxidation exothermic stage could be fitted with quadratic functions. The experimental results provide an important theoretical basis for the prevention of CSC.

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.