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High-temperature coal oxidation generates a substantial amount of CO and CO2, especially CO, rapidly, which is a primary factor leading to casualties. The oxygen concentration is the predominant factor affecting the high-temperature oxidation of coal, particularly in the generation of CO and CO2. Understanding the generation patterns and relationship characteristics of CO and CO2 under various oxygen concentrations is important for predicting high-temperature coal oxidation and ensuring personnel safety. The paper used TG–MS and FTIR to study the formation characteristics of isothermal oxidation of CO and CO2 in long-flame coal under different oxygen concentrations. The results indicate that there exists an optimal threshold for CO production when the oxygen concentration is about 9% during the isothermal temperature oxidation process at 200.00–350.00 °C. When the oxygen concentration is less than 13%, the influence of oxygen on CO2 production is weakened. As the temperature increases, the pattern of CO + CO2 production and CO/CO2 is reversed, with CO + CO2 increasing and CO/CO2 decreasing. The relationship between the total production of CO and CO2 and the loss of coal mass follows the function y = a + bx at the isothermal temperatures of 300.00 °C and 350.00 °C. An increase in oxygen concentration does not alter the linear relationship. In the isothermal oxidation process of coal, carbonyl and carboxyl groups are the key groups for CO and CO2 production. At 200.00 °C and 250.00 °C, carbonyl and carboxyl groups increase, and other groups are being converted to carbonyl and carboxyl groups while decomposing into CO and CO2. At 300.00 °C and 350.00 °C, the relative content of carboxyl groups decreases. The research findings play a fundamental role in coal mine disaster prevention and control. [ABSTRACT FROM AUTHOR]

To accomplish various and efficient inhibitions of coal spontaneous combustion (CSC) and solve the safety hazards of CSC encountered in the production and operation of coal mining enterprises, inhibitors play an important role in the prevention and management of CSC. Herein, we report quercetin, which is selection as an antioxidant to prepare a composite solid lipid inhibitor. The concentration of the composite solid lipid inhibitor with the best inhibition effect on the active groups is selected by Fourier pressure infrared experiments, the change pattern of gas content and characteristic temperature released from coal samples during an oxidation process warming process was tested by using a programmed warming test system and simultaneous thermal analysis experiments, and finally, the inhibitory rate and combustion characteristic index were calculated. The results of the research showed that 10 mass% of quercetin had the most impact on the various groups, the highest inhibitor rate of the composite solid lipid inhibitor is 80.67% in the coal low-temperature oxidation process, compared to the raw coal, the heat release of coal treated with the composite solid lipid inhibitor was decreased by 507.65 J g−1, the maximum amount of heat emitted was lowered by 60%, and the flammability index was reduced by 56.4. A composite solid lipid inhibitor containing quercetin developed in this paper indicated high effectiveness in inhibiting CSC, which is vital for coping with the safety management of coal mine production. [ABSTRACT FROM AUTHOR]

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]

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]

Spontaneous combustion of oxidized coal was one of the serious hazards during coal mining and utilization. However, spontaneous combustibility of oxidized coal affected by the first oxidation of coal was still unclear. In this paper, the influence of pre-heating with different oxygen concentrations on coal secondary spontaneous combustion behaviors was studied. Temperature-programmed heating experiments were carried out to prepare pre-heated coal samples by heating at the preset temperature of 80 °C in mixture atmosphere of N2 and O2 with different oxygen proportions of 0%, 5%, 10%, 15%, 20%. Pre-heated and raw coals were heated programmatically in an air atmosphere of 120 mL min−1 with a heating rate of 0.33 °C min−1. The gaseous compounds of O2, CO and CO2 were analyzed to identify spontaneous combustion behaviors of pre-heated and raw coals. The results showed that pre-heating at 80 °C promoted oxygen physisorption at low temperatures and lowered oxidability at high temperatures in the coal secondary oxidation process. Pre-heating at 80 °C with higher oxygen content reduced oxidability and exothermicity of coal secondary spontaneous combustion, but had no obvious effect on oxygen physisorption of coal low-temperature oxidation. [ABSTRACT FROM AUTHOR]

Spontaneous coal combustion is a serious hazard that affects mining safety. Since the coal seams are thin and their resistivity dramatically changes during spontaneous combustion, locating the burned cavities or caving zones using electromagnetic (EM) methods is challenging. The conventional transient electromagnetic (TEM) method with a loop transmitter is ineffective, as the main targets are mostly horizontal and resistive. We propose in this paper to apply TEM with an electrical source to detect the resistive targets of spontaneous coal combustion. Considering that its areas generally have very complex geometry, we adopt the unstructured finite-element method for accurate EM forward modeling. For the time discretization, we choose the unconditionally stable backward Euler scheme. Numerical experiments for typical spontaneous combustion models show the high sensitivity of TEM for an electrical source to the burned cavities, and based on this we further use the limited-memory BFGS method to do 3D inversions. To obtain high-resolution imaging results, we bound the resistivity based on the measurements to the coal mine. The inversion results show that the 3D TEM inversions can effectively recover the locations and resistivities of the burned cavities, implying TEM is a valid tool for detecting spontaneous coal combustion. [ABSTRACT FROM AUTHOR]

For further understanding the coal spontaneous combustion in goaf, the dynamic evolution of the oxygen concentration field influenced by the condition of negative pressure of cross-cut were analyzed. Based on the on-site testing results, the range of the oxidation zone on the headentry and tailentry side is determined as 30 ~ 75 m and 15 ~ 65 m respectively. This paper adopts a new method called "fixed grid, dynamic attribute" to dynamically describe the spatial change of goaf caused by working face advancing. The validated model which developed by field measured data is used to study the dynamic evolution of negative pressure impact of cross-cut on oxygen concentration field in goaf. The results demonstrate that when the cross-cut is located at different positions of three zones of coal spontaneous combustion, the negative pressure of the cross-cut has different impact rules on the distribution of oxygen concentration field. The results are hopeful for providing effective guidance for coal mine fire prevention in goaf. [ABSTRACT FROM AUTHOR]

Mine fire is a major problem for the Indian coal mining industry and exists since beginning of the mining. A huge amount of the prime coking coal reserves of different coalfields are blocked due to existence of fire and thus cannot be extracted without extinguishing it. Many approaches have been attempted in this direction to minimize this socio-technological problem. Use of chemical retardants to inhibit smouldering combustion phenomenon is an important method, which can be adopted to prevent or delay its occurrences. In this situation, it may sometimes be necessary to use fire retardants for reducing the intensity of fire so that the coal production will not be hampered. This paper presents the impact of chemical additives on coal oxidation process, studied from the mechanistic perspective aiming to search effective retardant materials to prevent and control coal self-heating phenomenon. A numbers of chemicals and combinations along with coal, which are moderately prone to smouldering combustion, were studied to determine its efficacy to prevent and combat it. In the process CPT, IPT and DSC study of coal samples and chemicals were observed. Based on the results, suitable retardants were selected and mixed with coal samples. The mixtures were further analysed for above properties. Finally, the best suitable combination of inhibitors were determined and applied in the field, which gave desired results. [ABSTRACT FROM AUTHOR]

The paper presents laboratory and in situ research data on interaction of geomechanical and physicochemical processes in Kuzbass coal of various ranks, considering temperature effect. Under analysis is the relation of stress-strain state, temperature and infrared radiation of coal. The authors study the role of temperature and microstructure of coal in energy and mass exchange processes (variation of mass, volatile yield, specific surface, internal energy of methane adsorption capacity decrease and moisture content). Interrelation of outburst hazard and fire hazard in coal is discussed from the viewpoint of uniform stagewise thermomechanics and thermochemistry of coal behavior in the course of coal formation and extraction. The article introduces a generalized factor for quantitative description of petrographic properties of coal. Using this factor, the authors classify and describe petrographic groups of Kuzbass coal. [ABSTRACT FROM AUTHOR]