Search Results (134)

In the mining process of shallow-buried and close-distance coal seam groups in western China, the interconnected collapse fractures between the overlying goaf and the surface form large-area composite goafs, which aggravate surface air leakage and elevate oxygen levels within the goaf. This, in turn, leads to hazardous conditions such as CO over-limits and O₂ deficiency at the working face’s return air corner, which seriously threatens the respiratory health of underground operators and the safe production of mines. Taking the 104 working face of a coal mine in Shenfu-Dongsheng Mining Area as the engineering background, this paper comprehensively adopts SF₆ tracer gas test, fuzzy cluster analysis, and CFD numerical simulation methods to systematically study the distribution characteristics of three-dimensional air leakage channels in composite goafs and their influence mechanism on gas migration in goafs, and proposes a dynamic pressure equalization ventilation (PEV) regulation technology system. The research results show that a multi-dimensional three-dimensional air leakage channel of “surface-interlayer-own layer-roadway” exists in the research area, in which the surface fracture air leakage velocity is about 0.068 m/s, and the interlayer and internal goaf air leakage velocity is about 0.384 m/s. The atmospheric pressure difference between the working face and the surface is the main controlling factor inducing the O₂ deficiency disaster of the working face. Every 100 Pa change in atmospheric pressure difference causes an O₂ concentration fluctuation of about 0.30% at the return air corner, and the critical pressure difference for activating PEV is determined to be 300 Pa. Setting the PEV regulation point at the return air outlet of the working face and adopting the combined dynamic regulation system of fans and air windows can realize accurate pressure balance between the working face and the overlying composite goaf. Full article

To elucidate the structural evolution of fracture networks around gas drainage boreholes and their controlling mechanisms on grouting sealing performance, a coal seam in the Zhongmacun Mine (No. 2-1 coal seam) was selected as the engineering background. An integrated approach combining borehole camera observation, gray-level co-occurrence matrix (GLCM) texture analysis, and fractal theory was adopted to systematically characterize the development behavior, spatial heterogeneity, and fractal evolution of fracture networks under different stress zones surrounding the borehole. Furthermore, the quantitative relationship between fracture structure characteristics and grouting parameters was explored. Results indicate that three axial stress-related zones are formed, including a stress-relief zone (0–4 m), a post-peak stress concentration zone (4–20 m), and a pre-peak stress concentration zone (>20 m), with fracture development strongly dependent on stress state. Quantitative analysis based on GLCM parameters and their coefficients of variation reveals a progressive transition from highly complex and strongly heterogeneous fracture structures in the stress-relief zone to simpler and weakly heterogeneous characteristics in the pre-peak stress concentration zone. The fractal dimension (D) decreases from 1.847–1.907 to 1.676–1.713 across these zones, consistent with the evolution trends of GLCM metrics. Based on the relationship between fractal dimension and fracture connectivity, a prediction model for the equivalent permeability of fracture networks based on fractal dimension was established, and the quantitative relationship between grouting pressure and fractal dimension, slurry viscosity, and diffusion radius was derived, providing a theoretical method for analyzing the correlation between fracture structure characteristics and grouting parameters. On this basis, a zonal differentiated grouting sealing optimization scheme was proposed, and a theoretical calculation method for grouting pressure and sealing section length based on fractal parameters was established, providing theoretical references and technical support for precise sealing of gas drainage boreholes. Full article

The prevention of coal mine fires and the sequestration of CO₂ represent two grand challenges that have traditionally been addressed separately. Here we report a CO₂-modified bentonite-based sealing material that concurrently achieves fire resistance, gas sealing and mineral-carbonation CO₂ uptake through rational materials engineering. In this work, “carbon-negative” is used as a comparative property: the material’s cradle-to-gate embodied emissions combined with its measured 28-day mineral uptake are lower than the cradle-to-gate footprint of a conventional cement-based benchmark under the stated system boundary. High-pressure CO₂ intercalation expanded the montmorillonite d-spacing from 12.48 to 14.79 Å and introduced carbonate functional groups (1435 cm⁻¹), as confirmed by FTIR and XRD. Systematic optimization of a bicomponent formulation incorporating municipal solid waste incineration slag and CO₂-saturated zeolite yielded a material with 28-day compressive strength of 37.9 MPa, a fire resistance limit of 186 s and O₂ reduction from 13.7% to 4.9%. Notably, carbon sequestration reached 24–40 kg CO₂ per ton through mineral carbonation, validated by carbonate peaks in FTIR and calcite detection in XRD. Carbon accounting based on a cradle-to-gate inventory (342–408 kg CO₂-eq/t) combined with the measured 28-day mineral uptake (24–40 kg CO₂/t) yields a comparative net balance of −46 to −188 kg CO₂-eq/t relative to a conventional cement-based benchmark under the stated system boundary. The synergistic mechanism involves CO₂-modified bentonite-regulating layer spacing, alkali-activated slag releasing Ca²⁺/Mg²⁺ for carbonate precipitation, and zeolite providing endogenous carbon slow-release. This work establishes a materials-chemistry paradigm for transforming industrial waste streams into functional carbon sinks while addressing critical mining safety needs. Full article

To address the major safety hazard that heat released from mining polyurethane (PU) reinforcement materials may induce spontaneous combustion of residual coal in goaf, this study selected No. 3 coal from Wangzhuang Coal Mine, Shanxi Lu’an, as the research object. A self-developed large-capacity, large-scale experimental system was used to conduct programmed heating experiments on 2.0 kg multi-particle-size coal-PU mixed samples. The effects of PU content on characteristic gas release, crossing point temperature (CPT), residue morphology, and TGA-DSC characteristic temperatures were systematically investigated, and the reaction-kinetic evolution was further analyzed using the distributed activation energy model (DAEM). The results show that coal and PU exhibit a significant synergistic enhancement effect during co-heating. As the PU content increased, the release concentrations of CO, C₂H₄, and C₂H₆ increased markedly, and their initial release temperatures decreased, whereas CH₄ generation was inhibited by hydrogen-radical competition; no C₂H₂ was produced below 400 °C. The CPT decreased linearly with an increasing PU content, with an average decrease of approximately 8.5 °C for every 10% increase in PU content. Residue morphology showed clear critical features: glassy agglomerates appeared when the PU content exceeded 16.67%, and dense bulk coking occurred when the PU/coal mass ratio was greater than 1:10. TGA-DSC analysis showed that when the PU/coal ratio was lower than 1:10, the ignition temperature of the mixed sample was higher than that of pure coal, indicating an inhibitory synergistic effect. When the ratio exceeded 1:10, the ignition temperature decreased significantly, and the synergy shifted to promotion; increasing the heating rate shifted the characteristic temperatures to higher values and increased the reaction intensity. DAEM analysis further confirmed that when the PU ratio exceeded 1:10, the apparent activation energy of the mixed samples was lower than that of pure coal. Coal powder also acted as a physical skeleton that effectively dispersed molten PU, eliminated the activation-energy peaks of pure PU in the conversion ranges of 30–50% and 70–90%, and substantially improved combustion stability. Mechanistically, low-temperature PU melting and coating optimized heat and mass transfer, medium-temperature pyrolysis released active radicals and combustible gases that altered coal pyrolysis pathways and the radical reaction environment, and high-temperature hydrogen-radical competition reshaped the gas-product distribution. Together, these processes form a complete chain of synergistic spontaneous combustion. This study identifies key safety threshold parameters for PU reinforcement materials, recommends a PU content of ≤9.10%, and identifies CO and C₂H₄ as priority early-warning gases, providing direct experimental evidence for characteristic-gas-based early warning and mine fire prevention. Full article

Biogenic or microbial methane (CH₄) emissions, believed to be the main driver of the recent surge in global atmospheric CH₄ emissions, have altered monitoring, measurement, and mitigation of fossil-fuel emissions. As of 1981, over 20% of the world’s natural gas reserves were biogenic in origin. Additional biogenic CH₄ reserves from coal have been discovered since 1981 mixed (40–80%) with thermogenic CH₄. Biogenic CH₄ accumulates up to 100% in coal reservoirs in the Powder River Basin (PRB), USA. Biogenic CH₄ is generated by microbial breakdown of fossil organic matter as an early-stage (primary) type during burial over geologic time and is rarely preserved. Also, biogenic CH₄ is generated as a late-stage (secondary) type from recent geologic to present times and is commonly preserved. Late-stage biogenic CH₄ is sustained by nutrients and microbes in meteoric/surface waters discharged into coal aquifers. Groundwater is pumped from wells in coal aquifers to desorb and produce CH₄ and dewater coal mines. The co-produced water with dissolved CH₄ is discharged into diverse surface aquatic systems. The emission factors (EFs) of co-produced water are 2.0522 × 10⁻⁹ Gg CH₄/gal of water in the PRB and 2.0694 × 10⁻³ Gg CH₄/well in the Black Warrior Basin, U.S. Accurate data on biogenic CH₄ emissions from coal sources is a major gap in the accounting of current global groundwater-driven CH₄ whose average flux is estimated to be 3.9 ± 6.2 mmol/m²/day or accounting for up to 70% of CH₄ emissions from surface aquatic systems. Biogenic CH₄ emissions from coal mining and coalbed gas extractions and related infrastructures are overlooked because the focus has been on coalmine methane (CMM) emissions. CMM data from ground-based measurements is highly variable and used by the Intergovernmental Panel on Climate Change three-tier system to estimate EFs for national inventories. However, 90% of CMM emissions are attributable to a small group of the most coal-consuming-and-producing countries but fails to capture other coal sources worldwide. This created gaps and “blind spots” in “unstructured” low-concentration, diffused biogenic CH₄ emission data. These key “blind spots” include sources from flooded, abandoned coal mines; coalbed methane (CBM) co-produced water with dissolved CH₄ and infrastructures/facilities; and groundwater drawdown from water withdrawals during coal mining and CBM extraction. Also, a critical “blind spot” is the mixing of biogenic CH₄ emissions from subsurface coals with biogenic CH₄ generated at the surface from wetlands, agriculture, and landfills/wastes, which grew 85% from 2008 to 2020. Limited understanding of the mixing of biogenic CH₄ from diverse sources and their contributions to global methane requires accurate attribution of overlapping isotopic signatures (δ¹³C_CH4 and δD). This paper addresses knowledge gaps in coalbed biogenic CH₄ emissions by a systematic review of the literature and specific study cases, which provided insights on key “blind spots” in their mitigation. Full article

CO₂-enhanced coalbed methane recovery and storage (CO₂-ECBM) is a promising approach for improving methane recovery and increasing CO₂ storage in low-permeability coal seams. However, limited injectivity and insufficient criteria for injection parameter optimization remain major constraints. Taking the No. 11-2 coal seam of the Zhangji Coal Mine in the Huainan mining area as the study object, this study established a thermo–hydro–mechanical coupled model that considers CO₂/CH₄ competitive adsorption, matrix diffusion, fracture seepage, gas–water two-phase flow, coal deformation, and porosity–permeability evolution. A 10-year numerical simulation was conducted to evaluate the effects of initial porosity, initial permeability, elastic modulus, CO₂ injection pressure, and injection scheme on CO₂-ECBM performance. The comprehensive sensitivity results show that initial porosity, CO₂ injection pressure, and initial permeability are the dominant controlling factors, whereas elastic modulus has a relatively weak influence. Initial porosity mainly determines reservoir storage space and CO₂ sequestration potential; permeability controls pressure propagation and gas migration; and injection pressure directly affects CH₄ displacement intensity, CO₂ storage capacity, and reservoir safety margin. Multi-objective evaluation indicates that the injection pressure should be controlled within 8.0–9.0 MPa, with 8.0–8.5 MPa recommended for long-term stable operation. When the engineering objective prioritizes CO₂ storage or CH₄ recovery and sufficient safety margin is confirmed, the injection pressure may be increased to approximately 9.0 MPa. Continuous constant-pressure injection favors cumulative CH₄ production and CO₂ storage, whereas stepwise pressurization reduces early pressure disturbance and improves later-stage injectivity. Therefore, an injection strategy combining early-stage stepwise pressurization with middle- and late-stage constant-pressure injection is recommended. These results provide a reference for injection parameter optimization in similar low-permeability coal reservoirs. Full article

Backfilling the industrial solid waste coal gangue into deep coal mine goafs for CO₂ geological sequestration is a crucial pathway to achieve the synergistic effect of pollution reduction and carbon mitigation. However, in complex deep geological environments, the chemical evolution of multiple mineral phases of coal gangue under gas–water–rock coupling effects and the carbon-controlling mechanism of residual total organic carbon (TOC) remain unclear. In this study, coal gangue from the goaf of the Xiaobaodang Coal Mine was used as the research object. Relying on a customized high-temperature and high-pressure reaction system to simulate the deep in situ environment (45 °C, 10 MPa), and combined with X-ray diffraction (XRD), total organic carbon determination, and isothermal CO₂ adsorption experiments, the geochemical mechanism by which inorganic minerals and organic residual carbon synergistically control the ultimate CO₂ adsorption potential was systematically revealed. The results show that the modification of the CO₂ adsorption potential of coal gangue by gas–water–rock reactions exhibits strong mineral phase differentiation. Systems rich in active silicates generate a large amount of secondary clay minerals through intense carbonation alteration, achieving a significant increase in micro–nano pores and absolute adsorption capacity. Systems rich in carbonates steadily release deep primary adsorption potential by widening mass transfer channels through mineral dissolution. In contrast, systems rich in primary clay minerals face an irreversible attenuation of adsorption space due to physical clogging of pore throats caused by fluid migration. Furthermore, the initial organic carbon content exerts a significant non-linear regulatory effect on the development of the micropore network. The physical adsorption sites provided by the high relative content of layered clay minerals (>41%), coupled with the interfacial enhancement effect exerted by a moderate organic carbon content (0.12~0.16%), constitute an optimal physicochemical synergistic enhancement network, which is the core geological reason for stimulating the ultimate carbon sequestration capacity of coal gangue. The results of this study not only enrich the multiphase interfacial thermodynamic theory of complex heterogeneous geological bodies but also provide solid theoretical support for the precise optimization of target areas and the long-term evaluation of carbon sinks in goaf CO₂ sequestration engineering. Full article

Fractured coal in the residual-strength stage is a primary medium for gas migration and drainage in deep mining areas. To investigate the hydro–mechanical seepage response of post-peak fractured coal under constant-pressure-difference conditions, triaxial CO₂ seepage tests were conducted on coal specimens collected from the Xinyuan Coal Mine. A Weibull-based damage constitutive model was established to characterize the confining-pressure-induced hysteresis in the damage-evolution path. The flow-rate evolution and Reynolds number analysis indicated that gas flow remained within the linear Darcy regime. A controlled-variable analysis was used to examine the competing effects governing permeability evolution. Mechanical compaction induced an exponential decrease in permeability, whereas the decrease in permeability with increasing pore pressure was interpreted, within the proposed model framework, as the combined effect of possible adsorption-induced matrix swelling and weakened gas slippage. To address the limitations of conventional constant-slip-factor models, a pressure-dependent slip modulation coefficient was introduced into a composite permeability equation incorporating effective stress, adsorption-related deformation, and dynamic gas slippage. Global nonlinear fitting yielded R² = 0.97 and an RMSE of 0.1909, with the residuals generally distributed around zero, supporting the fitting reliability of the model within the investigated stress–pressure range. Response-surface analysis identified mechanical compaction as the dominant controlling mechanism, while adsorption-related deformation and gas slippage acted as secondary correction mechanisms. The proposed framework provides a quantitative basis for distinguishing the mechanical and fluid-related effects governing permeability evolution in post-peak fractured coal. Full article

The synergistic utilization of post-mining spaces and geothermal energy through underground seasonal thermal energy storage (USTES) provides a promising pathway for sustainable heating and the low-carbon redevelopment of mining regions. To advance the thermal management and reveal the thermo-hydraulic evolution patterns within these repurposed environments, this study proposes an integrated approach that utilizes post-mining roadways as heat storage reservoirs, within the scope of a single idealized case study. A comprehensive USTES heating system model was established to systematically evaluate operational characteristics and environmental impacts under diverse conditions assuming homogeneous rock properties and idealized thermal boundaries. Results demonstrate that the surrounding ground temperature and the low thermal conductivity of the rock mass contribute to limiting heat dissipation and maintaining stable seasonal storage performance. For a roadway with a 20,000 m³ water storage capacity and an optimal 3900 m² solar collector area, the system successfully satisfies the thermal demand of 30,000 m² of building area. The configuration achieves 1239 MWh of cumulative heat storage over a 245-day cycle, maintaining a direct heating-to-heat-pump-upgraded heating ratio of 1.02. Furthermore, the implementation of variable-frequency thermal management strategies demonstrates remarkable economic and environmental superiority, yielding a 35.8% cost reduction compared to coal-fired heating, an overall energy saving rate of 77.5% relative to electric heating systems and a 13.5% decrease in CO₂ emissions relative to gas-fired systems. This research provides fundamental design parameters for the synergistic exploitation of mineral and geothermal resources, advancing the development of green heating and the sustainable utilization of post-mining spaces. Full article

Accurate measurement of coal seam gas content forms the core foundation for coal mine disaster prevention and coalbed methane resource development. However, as coal mining in China extends into deeper strata, multi-component gases (CH₄, CO₂, N₂, etc.) exhibit competitive adsorption effects and dynamic differentiation characteristics. These behaviors pose significant challenges to traditional measurement standards based on the “single methane-dominated system” assumption. This study systematically analyzes the competitive adsorption mechanisms of multi-component gases. By integrating gas data from major coal-producing provinces in China (such as Guizhou, Anhui, and Xinjiang), we reveal the heterogeneous distribution characteristics of gas components and their controlling factors, including coalification degree, burial depth, and maceral components. Case studies from Henan and Shanxi provinces demonstrate that neglecting the strong adsorption hysteresis of CO₂ and the rapid desorption characteristics of N₂ induces a systematic error exceeding 25% in total gas content measurements within areas high in non-methane components. To address these issues, we propose a “hierarchical measurement and real-time correction” framework for multi-component gas content. This framework categorizes gas measurement into four levels—ranging from single-component to all components—based on the complexity of geological conditions. It combines differentiated measurement with dynamic correction to improve the accuracy of gas content evaluation under complex geological conditions. This research provides a more reliable theoretical basis for gas pressure prediction and mine gas grade identification, offering substantial theoretical significance and engineering value for enhancing safety guarantees in deep coal mining. Full article

Traditional coal mining methods have led to prominent issues of coal resource waste and large-scale solid waste emissions. The integrated “excavation–backfilling–retention” mining technology for inter-section coal pillars and gate roads is one of the key technologies to solve these problems. However, the excavation and mining process associated with this technology imposes higher requirements on the ventilation system. Aiming at addressing the ventilation challenges existing during the implementation of the “excavation–backfilling–retention” method, research on ventilation safety assurance technology for inter-section coal pillars was carried out. Using COMSOL5.5 software, a full-stage ventilation system design model was constructed, adopting a ventilation mode that combines full-air-pressure ventilation with auxiliary local ventilation. The dynamic variation characteristics of the ventilation system under the “excavation–backfilling–retention” method and its capability to prevent and control the risks of O₂ and CO gas accumulation and coal spontaneous combustion were studied. The results show that during the bypass excavation period, the air supply from the auxiliary fan is sufficient, and during the excavation period for the two gate roads, due to the increased ventilation distance, insufficient airflow occurs near the heading face, accompanied by temperature rise, O₂ concentration decrease, and local CO accumulation, posing risks of coal spontaneous combustion and toxic gas accumulation. During the inter-section coal pillar excavation period and the cyclic operation period, after the full-air-pressure ventilation system is established, the airflow becomes stable, ventilation resistance decreases, and both temperature and gas concentrations are controlled within safe limits. However, in the corner areas, auxiliary local ventilation measures are still required due to insufficient O₂ and CO accumulation. The study verifies the feasibility and safety of the integrated “excavation–backfilling–retention” ventilation system, providing a safe ventilation approach for the integrated mining method and supporting the green mining of coal mines and the synergistic development of coal-based solid waste resource utilization. Full article

Coal spontaneous combustion in gob areas is a major disaster endangering safe production in underground coal mines, and accurate prediction of carbon monoxide (CO), the core signature gas of coal oxidation, is critical for early warning and targeted prevention of mine fire disasters. However, CO concentration in gob areas is governed by complex gas–solid thermal–chemical multi-field coupling, presenting strong nonlinear characteristics. Traditional numerical methods suffer from prohibitive computational cost, purely data-driven models have inherent black-box defects, and conventional Physics-Informed Neural Networks (PINNs) require explicit full governing equations, which are hard to establish for such complex systems. This paper first proposes a Physics-Informed Modified Kolmogorov–Arnold Network (PIM-KAN), which deeply integrates domain physical knowledge with KAN architecture via a physics encoding layer, a residual-modified KAN layer, a multi-physics attention mechanism, and a multi-term physical consistency constraint framework. Experiments on 3125 real coal mine field samples show that the PIM-KAN achieves R² = 0.9965 and RMSE = 0.9290 ppm, reducing RMSE by 19.5% compared with MLP, and outperforming all baseline models. Ablation studies confirm the significant contribution of each innovation module, and attention weight analysis is highly consistent with Arrhenius reaction kinetics, verifying its superior prediction accuracy, physical consistency and intrinsic interpretability. Full article

This study estimates China’s methane (CH₄) emissions from 43 specific emission sources in 2020 and projects future trends through 2050 under two scenarios: Current Legislation (CLE) and Maximum Technically Feasible Reduction (MFR). The analysis utilises the Greenhouse gas and Air pollution Interactions and Synergies (GAINS) model methane framework, incorporating updated province-level activity data to capture the pronounced regional heterogeneity inherent in emission profiles and mitigation capacities. The results reveal a national CH₄ budget of 1114 MtCO₂e in 2020, with the energy sector (59%) and agriculture (28%) emerging as the primary contributors. A substantial technical mitigation potential is identified; by 2050, emissions could be curtailed by up to 48% relative to the CLE scenario, representing a 46% reduction from 2020 levels. The energy and waste sectors emerge as the primary contributors to this potential. Specifically, coal mining CH₄ abatement constitutes 58% of the energy sector’s total reduction potential, while enhanced solid waste management accounts for 97% of the mitigation within the waste sector. Key measures include ventilation air methane (VAM) oxidation and pre-mining degasification, as well as anaerobic digestion and recovery and utilization for energy use. Owing to regional disparities in hydrothermal conditions (representing the combined influence of temperature and moisture), demographic status, economic development, the most effective mitigation strategies vary across provinces. For example, pre-mining degasification and VAM oxidation are most impactful in major coal-producing regions such as Shanxi, Inner Mongolia, and Shaanxi. In contrast, anaerobic digestion, recovery and utilization, and waste incineration play a dominant role in more economically developed and densely populated provinces such as Jiangsu, Shandong and Zhejiang. By delineating region-specific technological priorities, this study quantifies the maximum technical mitigation potential for China and offers guidance for other nations facing similar mitigation challenges. Full article

Against the backdrop of the global pursuit of carbon neutrality, research on coal pore structure has shifted from a single focus on coal mine safety to a dual orientation of hazard prevention and carbon sequestration, forming two distinct research directions worldwide. To clarify the evolutionary trajectory, research heterogeneity and integration paths of this field, this study systematically analyzes 722 core publications on coal pore structure from the CNKI and Web of Science core databases during 2015–2025, combining knowledge visualization analysis and systematic literature sorting (using CiteSpace as an auxiliary analysis tool). The results show that global research on coal pore structure has experienced three developmental stages (embryonic, developmental, and explosive growth) and entered an exponential growth phase after 2020, driven by the dual carbon goals. A clear research divergence has formed between regional engineering practices and international theoretical models: Chinese research is highly oriented to on-site coal mine engineering needs, focusing on the characterization of coal pore structure and its engineering application in gas extraction and outburst prevention of structural coal; international research prioritizes the theoretical exploration of carbon sequestration and CO₂-ECBM, with core research on gas adsorption kinetics, multiphysics coupling mechanisms of coal pore structure, and numerical simulation of reservoir modification. This research disconnect between engineering practice and theoretical modeling has become a key bottleneck restricting the safe application of coal pore structure theory in carbon capture, utilization, and storage (CCUS) projects. To address this issue, a Safety–Sustainability Nexus framework is proposed, which integrates field-based mine safety protocols with theoretical carbon storage models, and realizes cross-scale validation from micro-scale pore characterization to field-scale engineering application. Further, this study points out that the cross-scale data fusion of artificial intelligence and machine learning is the core direction to bridge the gap between engineering practice and theoretical models. In future CO₂-ECBM pilot projects, traditional gas outburst prevention indicators must be taken as mandatory safety thresholds to realize the dynamic matching of carbon injection parameters and coal reservoir stress sensitivity. This study sorts out the global research context and hotspots of coal pore structure, and provides a theoretical and practical reference for the synergy and integration of coal mine gas control engineering and carbon sequestration theoretical research under the dual carbon goals. CBM, coalbed methane; CNKI, China National Knowledge Infrastructure; WOS, Web of Science; CCUS, carbon capture, utilization, and storage; ECBM, Enhanced Coalbed Methane; CO₂-ECBM, CO₂-Enhanced Coalbed Methane. Full article

This paper investigates the combustion dynamics of interacting lazy multi-component gas plumes (i.e., buoyancy-dominated gas releases with a low initial momentum flux), a configuration relevant to coal mining waste emissions. By coupling a three-dimensional large eddy simulation (mesh size of 10⁻² m; paralleling with 2048 processors) with detailed chemical kinetics (GRI-Mech 3.0), we analyzed the sensitivity of the flow structure and plume stabilization to the vent spacing of twin hydrogen-rich multi-component gas plumes (H₂-CO-CH₄-air). The results identified a distinct topological transition. While gas plumes from vents spaced at $\delta /D=5$ ($\delta$ and D are the spacing and width of gas vents, respectively) evolve independently, those at closely spaced sources ($\delta /D=5/4$) exhibit rapid coalescence driven by hydrodynamic shielding. This hydrodynamic merging results in a unified column with an effective hydraulic diameter of $D_{eff}\approx \sqrt{2}D$. This leads to a significant reduction in the surface-to-volume ratio available for ambient air entrainment, maintaining a coherent combustible-rich core to higher altitudes than isolated-source correlations would predict. However, despite this mass retention, the rapid vertical acceleration of buoyancy-dominated flows induces high strain rates, significantly disrupting the reaction zone structure. These findings establish that, for clustered emission sources, the dispersion hazard is governed by a coupling between hydrodynamic coalescence, which maintains reactant concentration, and finite-rate chemistry, restricting oxidation efficiency. This paper provides critical insights for designing gas capture infrastructure and assessing flammability limits in multi-vent systems. Full article