To investigate the impact of multiple combustible gases produced by long-flame coal spontaneous combustion on the gas explosion limit and to guide the reoperation of the coal mine goaf and fire area, the influence of gas generated by coal spontaneous combustion on gas explosion limit is investigated in this paper using a temperature-programmed device and a 20L spherical explosion device. The results show that the volume fraction of CO produced during the spontaneous combustion of coal samples is 0.47, followed by CH₄ and C₂H₆, and C₂H₄ has the lowest content. Simultaneously, the coal spontaneous combustion is divided by 30°C, 80°C, and 170°C as the threshold, depending on the different gas characteristics. Organic C₂H₄ and C₂H₆ produced by coal spontaneous combustion have a greater impact on the CH₄ explosion limit than inorganic CO. The lower and upper limits of CH₄ explosion were reduced to 2.98 and 12.2, respectively, by 0.8 C₂H₆. C₂H₄ and C₂H₆ explosion limits change dramatically when mixed with CH₄. The CO and CH₄ mixture explosion limit decreases first and then increases. C₂H₄ and C₂H₆ have a significant impact on the explosion pressure of mixed gas and the lower explosion limit of gas. The lower explosion limit falls from 5.1 to 4.3 as the explosion pressure rises from 0.25MPa to 0.29MPa.

The goal of this study was to investigate coal quality features and their relationship to coal spontaneous combustion characteristics in multi-seam coal mines to better predict when coal spontaneous combustion is likely to occur. To that end, coal samples of various particle sizes were obtained from five coal seams (Nos. 6, 8, 9, 12 and 20) in the Shuangyashan City Xin’an Coal Mine. The samples were then respectively heated using a temperature programming system to observe and compare similarities and differences in the spontaneous combustion process of different particle sizes in response to rising temperature. The experimental results show, that in all five coal seams, the concentration of CO, C2H4, and C2H6 increased with a certain degree of regularity as a function of rising temperature. However, of these three gasses, only CO and C2H4 can be used as indicators to predict coal mine spontaneous combustion. The critical temperature for samples from all five coal seams ranged from 50–85°C, while the dry cracking temperature of coal seams 8 and 12 (80–100°C) were lower than those of 6, 9, and 20 (100–120°C). Furthermore, the production rate of CO, C2H4, and C2H6 is related to both coal particle size and temperature. The smaller the particle size, the faster the production rate; and the higher the temperature, the more gas that gets produced. All five coal seems are mainly composed of long flame coal. However, they differ in that the No. 12 coal seam contains weak cohesive coal; the No. 8 coal seam contains lean and gas coal; and the Nos. 6, 9, and 20 coal seams contain a certain amount of anthracite. During the programmed coal heating, the CO, C2H4, and C2H6 release trend for the coal seams was No. 12 > No. 8 > Nos. 6, 9, and 20. These results demonstrate that the presence of weak cohesive coal and anthracite highly influence the concentration of CO, C2H4, and C2H6 released during coal spontaneous combustion.

To maintain the stability of soft rock tunnels, the research team proposed a support scheme involving “floor grouting + floor anchors + sealing material”. This scheme incorporates a new sealing material with excellent mechanical properties, airtightness, and cost-effectiveness. To develop the sealing material, a series of proportioning tests and optimization designs were conducted to investigate how various experimental factors influence material performance. Based on these experiments, a regression prediction model was established to reveal the characteristics of factor interactions and determine the optimal mix ratio. Practical engineering validation confirmed that this support scheme effectively controls floor heave in soft rock tunnels.

To address the issue of rockburst in deep return airways caused by thick, hard sandstone roofs in the Hulusu Coal Mine, this study proposes a deep borehole pressure relief technique based on hydraulic fracturing. The goal is to proactively weaken the hard roof structure and effectively mitigate rockburst hazards. The research integrates numerical modeling, theoretical analytics, and field application to systematically delve into the unstable mechanism of deep hard rock and determine the crack propagation patterns and optimal borehole parameters. Engineering validation was carried out at the 21,103 mining face. Results indicate that when the borehole inclination is 45°, the spacing is 15 m, the diameter is 65 mm, the borehole depth is 24 m over the coal pillar (CP) and 30 m on the operating face, the pressure relief effect is optimal. This configuration effectively forms a pressure relief zone in the roof, significantly reduces surrounding rock stress concentration, and enhances structural stability. Field monitoring shows that the roof energy is released stably through crack propagation, effectively reducing the risk of rockburst. The proposed technique provides theoretical and engineering support for rockburst prevention in deep hard rock mining conditions.

Coal mine methane (CMM) separation faces significant challenges due to high humidity and multicomponent conditions, under which the selective adsorption performance of CH₄ is substantially degraded compared with idealized laboratory scenarios. This review systematically analyzes the fundamental causes of this discrepancy by integrating water vapor occupation, competitive adsorption, and structural constraints into a unified framework. Water molecules preferentially occupy high-energy adsorption sites and reconstruct the interfacial energy landscape, while strongly adsorbing components such as CO₂ further suppress CH₄ uptake through competitive displacement. These coupled effects lead to a pronounced deviation between theoretical adsorption capacity and actual separation performance. To address this issue, this work proposes an evaluation paradigm centered on effective working capacity, which reflects the practically recoverable CH₄ under cyclic operation rather than equilibrium limits. The applicability of this framework is demonstrated through comparative analysis across different adsorbent systems, highlighting the critical roles of moisture resistance, structural stability, and competitive resilience. Finally, key material design strategies and process-level optimization approaches are discussed to enhance sustainable CH₄ separation under realistic conditions. This review provides a process-oriented perspective for bridging the gap between material performance and engineering application in CMM utilization.

To investigate the structural characteristics of Ir_n clusters (n = 9–30) and their interaction with NH₃, the CALYPSO structure-prediction method was employed to identify the lowest-energy configurations. The Lennard–Jones potential was then used to compute the binding energy and average binding energy, thereby evaluating size-dependent stability. The results show that Ir_n clusters evolve from relatively open motifs to compact three-dimensional frameworks as n increases. Meanwhile, the average binding energy increases overall and exhibits several locally stable size regions, indicating a pronounced size effect. Based on slab and cluster models, NH₃ adsorption was further examined on the Ir₁₃ cluster as a representative system due to its high structural stability as a “magic-number” cluster. The calculated adsorption energies demonstrate that the Ir₁₃ cluster exhibits substantially stronger adsorption than the bulk Ir surface, with low-coordinated Ir atoms playing a key role in strengthening the interaction and enhancing adsorption activity. Adsorption-configuration analysis indicates that NH₃ preferentially binds to active surface sites via the N lone pair. These findings clarify the relationship between structural stability and adsorption performance of Ir clusters and provide theoretical support for Ir-based materials in NH₃ catalytic conversion and high-sensitivity gas detection, and offer insights relevant to improving NH₃ monitoring in underground coal mine environments.