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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]

The frequency conversion ventilation has achieved good results in the practical application of preventing the gas concentration of the coal mining face exceeding the limit. However, its impact on the spontaneous combustion of coal in the goaf is uncertain. Therefore, this paper studies the spontaneous combustion of three types of coal samples at different ventilation rates under frequency conversion ventilation. The results show that frequency conversion ventilation can reduce the average CO concentration compared with constant ventilation, and the inhibiting effect will weaken with the average ventilation rate increased. In three variable frequency ventilation rates, the rate of 10-30-50cm3/min has the best inhibiting effect. At this condition, the inhibiting effect is related to the type of coal, the inhibition rate on anthracite and lignite is proportional to the temperature, while the inhibition rate on bituminous coal is inversely proportional to the temperature. During one cycle around 120°C, the heat released by the oxidation reaction of bituminous coal, lignite, and anthracite decreased by 0.030 J/g, 0.144 J/g, and 0.034 J/g, respectively. Thus, the frequency conversion ventilation can affect the elementary reaction of coal, resulting in a reduction in the heat release from the coal oxidation reaction. [ABSTRACT FROM AUTHOR]

Coal spontaneous combustion (CSC) has been endangering the safety of the coal industry. Spontaneous combustion of coal may lead to coal seam combustion and gas explosions in coal mines, causing a lot of damage. At the same time, CSC will produce a large amount of carbon dioxide, which seriously endangers the ecological environment. Therefore, what reduces the spontaneous combustion of coal is necessary. Ionic liquid (IL) is a new kind of green organic solvent. It has the characteristics of good stability and can be used as a flame retardant for CSC. In this study, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (Bmim[Ntf2]) was selected as the flame retardant of bituminous coal spontaneous combustion, where thermal stability of bituminous coal treated by Bmim[Ntf2] and raw bituminous coal was studied by the simultaneous thermogravimetric analyzer. The apparent activation energy was calculated by the FWO method. The decomposition gas products of bituminous coal and bituminous coal treated with Bmim[Ntf2] were analyzed by Fourier-transformed infrared spectrometer to investigate the effect of intramolecular hydrogen bond on bituminous coal spontaneous combustion. The results show that Bmim[Ntf2] inhibits the spontaneous combustion of bituminous coal. The addition of Bmim[Ntf2] increases the decomposition temperature of bituminous coal, where the apparent activation energy is increased. The results of Fourier-transformed infrared spectrometry show that the reduction in hydrogen bonds reduces the risk of spontaneous combustion of bituminous coal. [ABSTRACT FROM AUTHOR]

With the increasing complication of production and geology conditions, and the increase of mining intensity and depth in coal mine, the coal structure presents varying degrees of deformation. In order to study the influence of uniaxial tension–compression effect on mechanical properties of coal matrix and CH4/CO2 adsorption characteristics, a macromolecular model reflecting the realistic bituminous coal structure was established. Results demonstrate that the influence of tension strain on the microporous structural parameters is greater than that of compression strain, and the tension strain weakens the mechanical properties but enhances the adsorbates adsorption amount. For the pure gases adsorption, there is a negative linear correlation between the total energy and adsorption amount. Additionally, the strain ranging from −0.20 to 0.20, the distribution of punctated adsorbates density develops to that of banded adsorbates density, and the mean adsorption density and saturated adsorption amount increase linearly. For the binary components adsorption (1:1), the CH4 adsorption strength increases while the CO2 adsorption strength slightly decreases. The minimum of total energy decreases in a quadratic polynomial relationship with the strain, and the proportion of van der Waals energy is 75.8–85.5%. Nevertheless, the competitive adsorption and strain have little effect on the potential energy range of the adsorbates. Furthermore, the diffusibility of CO2 molecular layers is relatively good, and the strain enhances the stability of CH4 molecular layers for the saturated binary adsorption. The findings provide essential guidance for the improvement of carbon capture and storage and CO2-enhanced coalbed methane technologies in the deformation area of coal seam. [ABSTRACT FROM AUTHOR]