Porous medium burners are characterized by high efficiency and good stability. In this study, a new burner was proposed based on the combustion mechanism of the methane-air mixture in the porous medium and the preheating effect. The new burner is a two-section and double-deck porous medium with gas inlets at both ends. A mathematical model for the gas mixture combustion in the porous medium was established. The combustion performance of the burner was simulated under different equivalence ratios and inlet velocities of premixed gas. The methane combustion degree, as well as the temperature and pressure distribution, was estimated. In addition, the concentrations of emissions of NO_x for different equivalence ratios were investigated. The results show that the new burner can not only realize sufficient combustion but also save energy. Furthermore, the emission concentration of NO_x is very low. This study provides new insights into the industrial development and application of porous medium combustion devices.

Low-temperature oxidation leads to the accumulation of heat in coal, and it is an important trigger for coal spontaneous combustion (CSC). The oxidation effects induce irreversible damage in the pore and fracture structures of coal, which provide a way for the infiltration of oxygen. In this work, the evolution of pores and cracks of coal in the progress of low-temperature oxidation is researched based on nitrogen adsorption, scanning electron microscopy (SEM), and ultrasonic testing. The results show that the oxidation effect increases microporous structures and promotes the development of mesopores and macropores in coal. Besides, as the temperature increases, the oxidation effect becomes more significant, while the pore morphology has not changed significantly yet. Meanwhile, the oxidation effect causes coal particles to block or collapse in the macropores, and the plugging degree increases with increasing temperature.

Gas extraction is most commonly used to control gas disasters in coal mines. The distribution of the plastic zone around a borehole and the sealing quality are key factors affecting gas extraction. In this paper, the plastic zone was simulated by COMSOL, and a theoretical equation of the plastic zone radius was derived. In addition, an antispray hole equipment and the “two plugging and one injection” sealing technology were proposed. The results show that a larger borehole pore size corresponds to a larger plastic zone and larger range of pressure relief of the borehole. The error between the calculated and simulated plastic zone radii is within 1%, and the modified equation is applicable to Puxi mine. The loss and harm caused by borehole spraying are reduced by applying antispray hole equipment. By applying the “two plugging and one injection” sealing technology and phosphogypsum-based self-produced gas expansion paste material to block the borehole, the sealing quality is improved and an accurate gas mixing flow, pure flow, and concentration were obtained. As the plastic zone enlarges, the gas extraction flow gradually increases with, but the relative variation of flow first increases and subsequently decreases. Considering the safety and economy of construction, the optimal radius of the plastic zone is 64.9 mm.

The production practices in Shendong mining area show that the CO concentration at the return air corner of shallow coal seams often exceeds the limit, but the temperature of the residual coal in the goaf has not significantly increased, and no other indicative gas of spontaneous combustion in coal seams has been detected. In order to provide scientific basis for CO management at the return air corner of the fully mechanized mining face in Shendong mining area and the prevention and control of coal seam spontaneous combustion fires, based on the “three zones” distribution parameters of spontaneous combustion of coal in goaf and the characteristic parameters of spontaneous combustion of coal, and based on the mechanism of CO production in shallow buried mining area, the source and influencing factors of CO in working face were analyzed, and the calculation model of CO concentration at the return air corner in working face was established. The concentrations of CO at the return air corner in different working faces in Shendong mining areas were calculated by using the model. The results showed that the relative error between the observed and measured values remained between 0.32% and 6.92%. The quantitative analysis of the proportion of CO production from each source to the total production of CO in the return air corner is of great significance to the effective control of CO concentration in the air return corner of the working face.