To address the challenges of unclear coal dust migration laws and ineffective pollution control in fully mechanized caving mining of thick coal seams in gas mines, a typical high air volume fully mechanized top-coal caving (FMTC) face in a gas mine in Shanxi, China, was selected as the research object. Based on field measurements of wind speed and dust characteristics and laboratory analysis data, a precise dust release method based on a source-specific parameter matrix and particle size-mass conversion was proposed.The airflow field of the working face was calculated using finite element discretization combined with the Euler-Lagrange gas-solid two-phase flow method, and the migration trajectories of coal dust and spray droplets were simulated. The airflow distribution characteristics, combined pollution laws of multi-source coal dust, and source-specific contribution mechanisms of the FMTC face under downwind and upwind cutting conditions were revealed. A comprehensive wet dust suppression system was arranged according to the spray wind resistance test results, and its dust reduction effect was verified with the dust suppression mechanism elucidated.The results demonstrate that dust generated by shearer cutting forms a high-concentration dust pollution zone within 100 m between the downwind supports and the coal wall, with a maximum total dust concentration of 925.37 mg/m(3), which is the main dust source on the downwind side of the working face. The pollution severity of drum cutting dust to the pedestrian walkway area follows the order: upwind drum > downwind drum during downwind cutting, and the opposite during upwind cutting. The process of hydraulic support advancing and face guard retracting causes a large amount of coal to collapse, forming an extensively polluted "coal flow waterfall" between supports. Dust generated from this operation is characterized by high concentration, high wind speed, and high respirable dust proportion, making it the main source of respirable dust in the downwind pedestrian walkway. The pollution degree of support advancing dust to the pedestrian walkway is higher during upwind cutting than during downwind cutting. During top coal caving, dust leakage occurs through the gaps between supports due to top coal collapse, with respirable dust accounting for up to 63.8 % of the total dust. The pollution degree of top coal caving dust to the pedestrian walkway is higher during downwind cutting than during upwind cutting.The deflection degree of spray morphology is positively correlated with airflow velocity. High-pressure nozzles exhibit better wind resistance performance than pneumatic nozzles, with the high-pressure flat-head conical nozzle showing the optimal wind resistance. By arranging the dust suppression system targeting the core principles of "tracking and covering main dust sources with wind-resistant sprays, cutting off the core channels of dust diffusion, and adapting to source-specific contributions under multiple working conditions", precise prevention and control of dust pollution in the working face was achieved. The maximum total dust reduction efficiency in key dust pollution areas reached 91.29 %, and the maximum respirable dust reduction efficiency for all particle sizes reached 98.44 %. The research results can provide a theoretical basis and technical support for the precise prevention and control of multi-source dust pollution in FMTC faces of gas mines, and are of great significance for ensuring the safe and efficient mining of gas coal mines.
Hybrid Multigeneration energy systems can play a key role in supporting sustainable development in densely populated and resource-constrained regions such as the Gaza Strip (GS). This study proposes an integrated wind-hydrogen-desalination system comprising a 1000 MW wind farm, 750 MW electrolyzer, 338 MW fuel cell, 5,617 m(3) hydrogen storage tank, 17.78 MW compressor (7.8 t H-2/h at 100 MPa), and 235 kW reverse osmosis desalination unit (84 t/h). The system is capable of covering an annual electricity deficit of 241,852 MWh while producing hydrogen equivalent to 2,222,747 MWh for transport applications. Economic analysis shows total capital investment is $3.345 billion, a positive net Present Value (NPV) of $152.27 million, and payback time money (PBTM) of 9.07 years. The levelized Cost of Energy (LCOE) and Levelized Cost of Hydrogen (LCOH) were estimated at $0.124/kWh and $3.726/kg, respectively, rising to $0.146/kWh and $4.872/kg when social and environmental externalities are included. Environmentally, the system could reduce similar to 777,732 tons of CO2 emission annually, generating an estimated environmental benefit of $54.44 million/year. The findings demonstrate that integrated renewable energy and hydrogen systems can provide a technically feasible and environmentally sustainable solution for energy, fuel, and water security in Gaza and similar regions.
Quantitative evaluation of pore-scale oil-water spatial distribution is pivotal for understanding fluid mobility and enhancing recovery in shale reservoirs. However, existing methodologies, such as Chart, Centrifugal, and Heating methods, primarily quantify total free/adsorbed fluid contents but fail to quantify the spatial distribution differences of oil-water in the pores between samples. To bridge this gap, we propose a novel mathematical model that quantitatively resolves the pore volumes occupied by four distinct spatial distribution patterns: "full of oil", "water-wrapped oil", "oil-wrapped water", and "full of water". This model is established based on centrifugal experiments and 2D nuclear magnetic resonance (NMR) data from 23 sealed shale cores from the Paleogene Shahejie Formation, Bohai Bay Basin. Our results reveal that "full of water" pores dominate (avg. 43.99 %), followed by "full of oil" pores (avg. 32.29 %) and "water-wrapped oil" pores are minimally developed with only 4.42 %. Fluid spatial distribution patterns are governed by pore wettability and pore-scale capillary dynamics during the hydrocarbon generation and micro-migration. The model also introduces a wettability assessment based on wetted pore surface area (PSA), showing strong correlation with traditional pore volume (PV) methods, and successfully quantifies adsorbed oil/water film thicknesses (0.50-4.63 nm and 0.61-2.33 nm, respectively). The model-derived oil-film thickness aligns remarkably with independent low temperature N2 adsorption (LTNA) measurements, providing robust validation. This study significantly enhances the mechanistic understanding of shale oil occurrence and provides quantitative insights critical for optimizing hydraulic fracturing design and EOR strategies in shale reservoirs.
Currently, studies on hydrogen-blended methane explosions and their suppression mechanisms under lowpressure conditions remain insufficient. To systematically investigate the suppression effect of CO2 on the explosion of hydrogen-blended natural gas under low-pressure conditions, the deflagration behavior of the mixture gas under the initial pressure of 60-100 kPa was investigated by using a 7-m-long duct. The deflagration characteristics data, such as pressure peak, flame schlieren image, and critical explosion suppression concentration, were obtained. In addition, adiabatic flame temperature, temperature sensitivity, laminar burning flame velocity, and the physical-chemical dual effects were analyzed through chemical kinetics calculations. The results showed that as the initial pressure decreases, the CO2 suppression effect on the mixture increases (60-100 kPa). With 50 % hydrogen blending, adding the same amount of CO2 resulted in an average decrease of 72.48 % in peak explosion pressure throughout the duct, from 70 kPa to 100 kPa. At an initial pressure of 60 kPa, the critical explosion suppression concentration of CO2 is 3.5 %, which has excellent explosion suppression properties. Kinetic analysis showed that lower initial pressure results in lower adiabatic flame temperature and laminar burning flame velocity, leading to a decrease in reaction rate. Namely, adding the same amount of CO2 will result in more significant heat loss. Macroscopically, this means that the lower the initial pressure, the more obvious the pressure drop effect of CO2. Under low-pressure conditions, the physical inhibition of CO2 plays a dominant role. Specifically, at 60 kPa, adding 3 % CO2 can achieve a physical contribution rate of 83.2 %.
Profile control in heterogeneous reservoirs is often hindered by poor injectivity and non-selective plugging, particularly at elevated temperature and salinity. Here, a CO2-regulated organic acid salt system based on the reversible conversion between water-soluble choline 4-(n-propyl) benzoate (4PAS) and water-insoluble 4-propylbenzoic acid (4PA) was developed. The 4PAS solutions exhibit low viscosities (<10 mPa & centerdot;s), which is favorable for injectivity. Upon CO2 injection, the decrease in pH triggers liquid to solid transition via the in-situ precipitation of 4PA when the pH below 7. The precipitation efficiency increases significantly at lower pH, indicating the potential for nearly complete conversion under high-pressure CO2-acidified conditions. The system remains transparent and maintains stable viscosity in brines up to 200,000 ppm NaCl. Displacement experiment shows a negligible pressure rise during 4PAS injection, followed by pronounced permeability reduction after CO2 activation, achieving a plugging efficiency of 95.3% and an incremental oil recovery of 13.6%. Furthermore, the temperature-dependent solubility of 4PA in oil enables selective water control and facilitates 4PA recovery (up to 98.65%) via a two-step pH adjustment. These results indicate that the CO2-regulated 4PAS-4PA system represents a promising approach for profile control in heterogeneous reservoirs under harsh conditions.
