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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]

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]

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]

Coal spontaneous combustion often occurs in coal seam mining, which may lead to mine fires and other disasters. It is essential to investigate the detailed differences in combustion processes, characteristic temperatures, characteristic parameters of mass loss, combustion characteristic indices, and reaction kinetic characteristics of coal with different metamorphic degrees. Therefore, long-flame coal, non-caking coal, gas coal, and anthracite were selected as experimental samples. The microphysical properties of coal were studied by the proximate and ultimate analyzer, and scanning electron microscope, then the coal combustion characteristics were compared by simultaneous thermal analyzer. The results clearly indicated that the heating rate was positively correlated with the five characteristic temperatures, two mass loss rates, and two combustion characteristic indices of coal. Moreover, with the increase of metamorphic degree, the porosity of the coal surface structure decreased, the corresponding five characteristic temperatures increased, and the two combustion characteristic indices decreased. Significantly, the burnout temperature was mainly affected by the heating rate, and the maximum exothermic peak temperature was affected by the metamorphic degree. The combustion of the four kinds of coal as the first-order chemical reaction, the apparent activation energy of long-flame coal was the lowest, the easiest to burn, and the risk of spontaneous combustion was the greatest. These results revealed the thermodynamic characteristics of coal spontaneous combustion in specific mines from a microscopic viewpoint and provided basic data for the prevention of mine fires. [ABSTRACT FROM AUTHOR]