Experimental and theoretical study of the effect of particle size on the forward propagation of smoldering coal

Effect of 915‐MHz low‐temperature microwave irradiation on the molecular structure of coking coal

“…20 Under low-temperature irradiation conditions, microwave energy can change the molecular-space configuration of the thiophene structure in coal, which facilitates the removal of thiophene sulfur 21 ; 42.87% of benzothiophene from the loaded coal could be removed under 915-MHz microwaveassisted citric acid treated at 90 C. 22 The construction of coal molecular structure model has always been the core of coal scientific research. 23,24 The results show that the coal molecular structure model can be constructed by carbon-13 nuclear magnetic resonance ( 13 C-NMR), high resolution transmission electron microscope (HRTEM), Fourier transform infrared spectrometer (FTIR), and X-ray photoelectron spectroscopy (XPS) combined with the characteristic distribution of the coal structure. 25 13 C-NMR, XPS, Raman, and FTIR can determine the structural parameters and functional group information of coal, analyze the microstructure of coal, obtain structural parameters of coal, and combine computer-aided simulation to construct and optimize the molecular structure model of coal by combining density functional and molecular dynamics.…”

Laboratorial Investigation of Coal Fire Extinguishing and Re-burning Risk in Underground Coal Mines

“… 5 − 8 Generally, for underground mines with complex conditions and restricted fire-extinguishing approaches, the method of closure of the fire area is often used to control spontaneous fire hazards. 9 − 12 However, when re-opening the fire area to normalize coal recovery, re-burning accidents emerge as required, resulting in further casualties and property losses. 13 − 15 Therefore, research on re-burning of fire areas has become a major issue to be addressed.…”

“…As a significant source of fossil fuel energy, the production of coal is often accompanied by frequent spontaneous fires, which poses a great threat to the safety of underground miners. − Although the existing fire prevention and treatment techniques are multifarious, the control of underground coal fire remains extraordinarily challenging. − Generally, for underground mines with complex conditions and restricted fire-extinguishing approaches, the method of closure of the fire area is often used to control spontaneous fire hazards. − However, when re-opening the fire area to normalize coal recovery, re-burning accidents emerge as required, resulting in further casualties and property losses. − Therefore, research on re-burning of fire areas has become a major issue to be addressed. After the fire area is closed progressively, the coal within is gradually extinguished due to insufficient O 2 supply, but the heat hardly dissipates and further accumulates, resulting in the long-term maintenance of a high-temperature regime. − During the enclosed period of the fire area in an underground coal mine, it is impossible to see the development of the fire, but it is necessary to investigate the state of the combustion in the fire area. − At present, as the common practice to understand indirectly the fire condition, we rely on gas indicators, as shown in Table .…”