Fuels, Volume 6, Issue 4 (December 2025) – 7 articles

Coal mining has entered the stage of deep mining, and the prevention and control of gas disasters are facing significant challenges. Coal seam water injection, as an effective means of preventing and controlling gas disasters, has dual effects of pressure relief, permeability enhancement, and displacement sodium dodecyl benzene sulfonate (SDBS), as an anionic surfactant, can reduce surface tension to a certain extent in its aqueous solution and is therefore commonly used in coal seam water injection technology. In order to clarify the effect of SDBS on the water absorption capacity of coal and whether it will affect the gas adsorption capacity of coal, imbibition tests were conducted on dried coal samples in different concentrations of SDBS solutions, as well as gas adsorption tests on dried coal samples after imbibition was completed. Research shows that the key concentration range of SDBS for practical application is 0.050–0.075 wt%. When the concentration of SDBS solution is lower than 0.050 wt%, as the concentration of SDBS solution increases, the spontaneous imbibition capacity of coal increases significantly, and the adsorption capacity of coal to gas decreases significantly. When the concentration of SDBS solution is higher than 0.075 wt%, the spontaneous imbibition water capacity and gas adsorption capacity of coal hardly change significantly with the increase in solution concentration. Considering the effects of SDBS on coal water absorption and gas adsorption capacity, as well as environmental protection factors, it is recommended to use SDBS as a surfactant with a solution concentration of 0.050 wt%. Full article

A multiscale 3D CFD model of CO₂ methanation over Ni/Al₂O₃ was developed in COMSOL Multiphysics 6.3 for a lab-scale isothermal fixed-bed Sabatier reactor and validated against published data. The multiscale approach integrated bulk convection–diffusion, fluid flow, and pressure distribution with intraparticle diffusion–reaction phenomena coupled with Langmuir–Hinshelwood–Hougen–Watson-based kinetics, thus solving mass-transfer limitations without empirical effectiveness factors. Model validation was carried out by (i) kinetics, (ii) reactor performance, and (iii) hydrodynamics. Simulation results showed strong diffusion-dominated species transport at the bed entrance that lessened downstream as partial pressures decreased and products accumulated, resulting in a diffusion-relieved regime near the outlet. Sensitivity studies identified 320–350 °C and up to 10 bar as favorable conditions for high CH₄ yield. Additionally, slightly H₂-rich feed accelerated approach to equilibrium, while lower flow rates achieved near-complete conversion within the first half of the reactor bed. Simulations were carried out in COMSOL Multiphysics 6.3 on a dual Intel Xeon Platinum 8168 (48 cores at 2.7 GHz) workstation with 512 GB RAM to solve a 12-million-element mesh. The developed framework identifies a practical operating window and quantifies the conversion–throughput trade-off with flow rate, guiding operating condition selection and providing a basis for process intensification and lab-to-pilot scale-up of CO₂ methanation. Full article

In this study, the impact of the electric motor size and the hybridization ratio of a Fuel Cell Electric Bus on its vehicle performance (i.e., gradeability and acceleration) and fuel consumption was investigated using the ADVISOR software. The investigation first involved a parametric analysis with different electric motor and fuel cell sizes for the dynamic performance metrics, specifically the 0–60 km/h vehicle acceleration and the maximum gradeability (%) at a constant speed of 20 km/h. The results revealed that the acceleration is most sensitive to fuel cell power. Regarding gradeability, a more complex relationship was observed: when the electric motor power was below 215 kW, gradeability remained consistently low regardless of the fuel cell size. However, for motors exceeding 215 kW, fuel cell power then became a significant influencing factor on the vehicle’s climbing capability. Subsequently, the analysis focused on the effect of the hybridization ratio, which represents the power balance between the fuel cell and the energy storage system, varied between 0 and 0.8. Results showed that increasing the hybridization ratio decreases gradeability and acceleration performance and increases total energy consumption. This trade-off is quantitatively illustrated by the results over the Central Business District (CBD) driving cycle. For instance, the pure battery-electric configuration (a hybridization ratio of 0), featuring a 296 kW battery system, recorded a gradeability of 12.4% and an acceleration time of 16.3 s, while consuming 28,916 kJ. At an intermediate hybridization ratio of 0.4 (composed of a 118.4 kW fuel cell and a 177.6 kW battery), performance remained high with a gradeability of 12.2% and an acceleration of 17.3 s, but the energy consumption increased to 43,128 kJ. Finally, in the fuel-cell-dominant configuration with a hybridization ratio of approximately 0.8 (a 236.8 kW fuel cell and a 59.2 kW battery), gradeability dropped to 8.4%, acceleration time deteriorated to 38.9 s, and total energy consumption increased further to 52,678 kJ over the CBD driving cycle. Full article

This study presents an integrated petrophysical workflow for the comprehensive characterization of the Upper Dalan and Kangan carbonate gas reservoirs in the Shanul Field, southwest Iran. By combining advanced cross-plot techniques (including M-N, MID, and RHOma-Uma plots) with probabilistic porosity modeling calibrated to core data, this work achieves a higher-resolution discrimination of lithology and more robust estimation of fluid properties compared to conventional single-log approaches. The results reveal significant heterogeneity within both formations but demonstrate the superior reservoir quality of the Upper Dalan, particularly within the UD2 subzone, and in the Ka-2a subzone of the Kangan. The improved workflow enables more accurate zonation and identification of high-quality, productive intervals, supporting optimized field development strategies. These findings provide methodological advances for challenging and heterogeneous carbonate systems, offering a reference framework for similar reservoirs in the Zagros Basin and beyond. Full article

The chemical looping steam reforming of methane (CLSR) employing Fe-containing oxygen carriers can produce syngas and hydrogen simultaneously. However, Fe-based oxygen carriers exhibit low CH₄ activation ability and cyclic stability. In this work, oxygen carriers with fixed Fe content and different Fe/Ni ratios were synthesized by the sol–gel method to investigate the effects of Ni-Fe-Al interactions on CLSR performance. Ni-Fe-Al interactions promote the growth of the spinel structure and regulate both the catalytic sites and the available lattice oxygen, resulting in the CH₄ conversion and CO selectivity being maintained at 96–98% and above 98% for the most promising oxygen carrier, with an Fe₂O₃ content of 20 wt% and Fe/Ni molar ratio of 10. The surface, phase, and particle size were kept the same over 90 cycles, leading to high stability. During the CLSR cycles, conversion from Fe³⁺ to Fe²⁺/Fe⁰ occurs, along with transformation between Ni²⁺ in NiAl₂O₄ and Ni⁰. Overall, the results demonstrate the feasibility of using spinel containing earth-abundant elements in CLSR and the importance of cooperation between oxygen release and CH₄ activation. Full article

Emissions of carbon dioxide (CO₂) resulting from steam-driven enhanced oil recovery (EOR) operations present an environmental challenge as well as an opportunity to further enhance oil recovery. Using numerical simulations with realistic input data from field and laboratory measurements, we demonstrate a prudent approach to reduce CO₂ emissions by capturing CO₂ from steam generators of a steam-driven enhanced oil recovery (EOR) project and injecting it in a nearby oil field to improve oil recovery in this neighboring field. The proposed use of CO₂ as a water-alternating-CO₂ (WAG-CO₂) EOR project in a small, 144-acre, sector of a target limestone reservoir would yield 42% incremental EOR oil while sequestering CO₂ with a net utilization ratio (NUR) of 3100 standard cubic feet CO₂ per stock tank barrel (SCF/STB) of EOR oil in a single five-spot pattern consisting of a central producer and four surrounding injectors. This EOR application sequesters 135,000, 165,000, and 213,000 metric tons of CO₂ in five, ten, and twenty years in the single five spot pattern (i.e., our sector target), respectively. As a related matter, the CO₂ emissions from nearby steam oil recovery project consisting of ten 58-ton steam/hr boilers amounts to 119,000 metric tons of CO₂ per year with an estimated social cost of USD 440 million over 20 years. Upscaling the results from the single five-spot pattern to a four-pattern field scale increases the sequestered amount of CO₂ by a factor of 4 without recycling and to 11 with recycling produced CO₂ from the EOR project. Furthermore, the numerical model indicates that initiating CO₂ injection earlier at higher residual oil saturations improves EOR efficiency while somewhat decreases sequestration per incremental EOR barrel. The most significant conclusion is that the proposed venture is an economically viable EOR idea in addition to being an effective sequestration project. Other sources of CO₂ emissions in oil fields and nearby refineries or power generators may also be considered for similar projects. Full article

Pelletizing enhances competitiveness of lignocellulosic biomass (LCB) as a fuel by increasing its bulk and energy density. However, LCB pellets are prone to degradation from moisture, have high ash, and pose safety risks due to carbon monoxide (CO) emissions during storage. Hot water extraction (HWE), a mild hydrothermal treatment particularly effective for angiosperms, removes most hemicelluloses (xylans), reduces ash, and increases lignin content in remaining HWE-LCB. Based on the current understanding of CO formation, these changes suggested that HWE could reduce CO emissions. In this study, we evaluated the effects of HWE on pellets made from shrub willow, miscanthus, and wheat straw. A statistical analysis was conducted on ash, energy content, bulk density, durability, pellet length and density, moisture absorption, and CO emissions. All HWE-LCB pellets demonstrated significant increases in energy content (up to 3.54%) and reductions in moisture absorption (up to 23.84%). Although not all effects reached statistical significance, HWE generally had positive effects on ash content, bulk density, durability, and average pellet length and density. Contrary to expectations, HWE-LCB pellets emitted significantly more CO under both ambient and isothermal temperature conditions (up to 4.25 times overall increase), although still less than commercial hardwood/softwood blend pellets (<200 ppm in HWE-LCB vs. >300 ppm). Full article