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.
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.
Nitrogen-containing volatile organic compounds (N-VOCs) and nitrogen oxides (NOx) are critical pollutants in chemical industries, yet their co-treatment remains challenging due to limited integrated technologies. Here, we developed a coupling catalytic system using Ag-based catalysts for simultaneous removal of N-VOCs and NOx via the NH3 generation process. Three Ag-based catalysts were evaluated, with Ag/TiO2 exhibiting superior performance: complete degradation of model N-VOCs Monoethanolamine (MEA) at 290 degrees C with 100% NH3 yield. When coupled in series with a commercial V2O5/WO3-TiO2 (VW/Ti) SCR catalyst in a single reactor, the system achieved 100% NO conversion at 290 degrees C without detectable byproducts. Mechanistic insights from DFT calculations and characterization (MEA-TPD, XPS et al.) revealed that the optimized Ag0-Ag + redox sites on Ag/Ti enhanced NH3 selectivity. However, the coupled system showed strong sensitivity to H2O, mainly due to suppression of NH3 generation over the upstream Ag/Ti catalyst, which limits the practical applicability of the current system under humid flue-gas conditions. The coupling catalytic approach leverages spatially separated reactions, N-VOCs -> NH3 conversion (Ag/Ti) followed by NH3-SCR (VW/Ti), to overcome traditional limitations in multi-pollutant control. The strategy shows the objective of "waste control by waste" by using the N element from N-VOCs, which is meaningful to the development of recycling industry.
The combustion behavior of fuel droplets plays a crucial role in controlling emissions and combustion efficiency in internal combustion engines. Droplet heating, evaporation, and burning characteristics strongly influence ignition delay, combustion duration, and soot formation. Oxymethylene ethers (OMEs), particularly oxymethylene ether-3 (OME3), have attracted interest as drop-in diesel alternatives due to their high oxygen content and clean combustion potential. This study experimentally investigates the combustion of a single fuel droplet suspended on a thermocouple and exposed to a controlled environment at 500 degrees C and atmospheric pressure. Four fuels were examined: neat diesel and diesel blends containing 20, 40, and 60 vol% OME3. High-speed imaging was used to analyze ignition delay, combustion duration, and flame luminosity, complemented by scanning electron microscopy (SEM) of collected particulates. Increasing OME3 content significantly reduced ignition delay (by similar to 65-70% for D40-O60) while increasing combustion duration by similar to 25-30%. Flame luminosity decreased markedly, indicating suppression of macroscopic soot. This behavior is primarily attributed to the high oxygen content of OME3, which promotes oxidation pathways that limit soot precursors formation. SEM analysis revealed a shift toward finer particles, with sub-micrometer particle counts increasing from similar to 120 mm(-2) to similar to 340 mm(-2). These results demonstrate that reduced flame luminosity does not necessarily correspond to lower particulate emissions but instead reflects a shift toward ultrafine particle formation. Overall, OME3 modifies combustion behavior by reducing visible soot while increasing ultrafine particle number density, highlighting a critical trade-off in oxygenated fuel performance.
Following a hierarchical strategy for chemical kinetic model development, the CH4/NOx system represents an important foundation for understanding the complex interactions between higher hydrocarbons and nitrogen oxides. In this work, a comprehensive kinetic model, XJTUC1NO-2025, was developed by integrating a reevaluated CH4-NOx sub-mechanism with our previously established H2/CO/NOx core mechanism (XJTUNO-2021). The model specifically incorporates refined pathways for NOx-sensitized CH4 oxidation, reburning De-NOx, and prompt NO formation, with key rate parameters selected and updated based on systematic kinetic evaluation. The model was extensively validated against 391 experimental datasets, spanning shock tubes, rapid compression machines, jet-stirred reactors, flow reactors, laminar flame speeds, and burner-stabilized flames. XJTUC1NO-2025 shows improved overall performance compared with four representative existing models. The mechanism effectively characterizes the non-linear coupling between C1 intermediates and nitrogen species, clarifying key NOx evolution pathways under diverse thermochemical conditions. This work provides a consistently validated kinetic framework and useful kinetic insights for developing cleaner, low-NOx combustion simulations and strategies.
Cryogenic compressed hydrogen (CcH2) technology achieved a storage density close to hydrogen liquefaction while consuming only 60% of the energy required for densification. It has shown great potential in hydrogen storage and transportation. However, safety issues associated with cryogenic hydrogen must be fully addressed before practical application. This study investigated the flame and induced thermal plume behavior at initial temperatures (80-300 K) and pressures (2-10 MPa) through field experiments. The Background Oriented Schlieren (BOS) technique facilitated the visualization of flow field structures generated by horizontal jet flame induced thermal plume. The results demonstrate that the lift-off length of the flame increases with initial pressure but decreases with initial temperature. A dimensionless correlation between the lift-off length and the jet velocity has been established by incorporating a temperature correction factor for data normalization. A good agreement was achieved between the measurements and the empirical correlation proposed by Bradley. Furthermore, a centerline trajectory prediction model was developed by dividing the flow field into momentumdominated and buoyancy-dominated areas. The model prediction agrees well with the BOS images in the momentum-dominated region and the initial part of the buoyancy-dominated region, but due to the natural wind disturbances, the deviations appear in the downstream. This model is mainly applicable to high-velocity momentum-dominated jet flames.
The presence of shale pore water significantly affects the occurrence and flowability of shale oil, thereby impacting oil recovery. Current experiments encounter obstacles, including the disruptions of the oil occurrence state during drilling, exposing and core sampling, and the inadequacies of current microscopic techniques in precisely characterizing the occurrence and flow properties of shale oil in nanopores. In this study, the occurrence and flow characteristics of shale oil in both kerogen and illite nanopores are investigated using Molecular Dynamics simulations, and the impact of water content was considered. Due to multicomponent competitive adsorption, different components in shale oil exhibit varying flowability. When the pressure gradient increases from 5 MPa center dot nm-1 to 10 MPa center dot nm-1, the flow velocity of light hydrocarbons in kerogen pores rises by 192.8%, while heavy hydrocarbons increase by 168.7%. However, resins and asphaltenes adsorb up to 100% in pores, confining them to the adsorption layer and significantly limit mobility. Due to wettability differences, water forms clusters in kerogen pores, which impedes the flow of heavy hydrocarbons, ultimately leading to a reduction in the total mobility of the shale oil. Water forms films in the illite pores, when water content exceeds 20%, water in the illite exists as water bridges, which impede shale oil flow by occupying pore volume. This work is expected to establish a theoretical foundation for evaluating the sweet spots in water-bearing shale considering both the mobility and producibility of shale oil, and provide valuable insights for the development of flow models in nanoscale porous media in shale.
Closed-loop chemical recycling of poly(methyl methacrylate) (PMMA) via pyrolysis to recover the high-value methyl methacrylate (MMA) monomer is critical for a circular economy. The overall conversion process is highly sensitive to the complex interplay of transport processes, intrinsic pyrolysis reaction kinetics, and secondary gas-phase decomposition. This study investigates PMMA pyrolysis in a small-scale fluidized bed reactor under flash conditions, utilizing detailed ex-situ Fourier-transform infrared (FTIR) gas analysis to achieve robust mass balance closure. Apart from the MMA monomer, its fragments (especially CO, CO2, CH4, and C3H6) are present in the product spectrum. Regarding the reaction rate, two distinct regimes are identified: At temperatures below 698 K, the reaction is primarily controlled by intrinsic reaction kinetics, accurately modeled by a single first-order reaction (SFOR) with pre-exponential factor A = 1.85 & sdot;109 s-1 and an activation energy Ea = 144 kJ mol-1. For higher temperatures, the apparent reaction rate is significantly reduced. A one-dimensional shell model is used to correlate the reduction with a limitation due to insufficient heat transport in relation to the highly endothermic pyrolysis reaction. However, the experimental results show an even lower apparent reaction rate than the model prediction, suggesting that reduced intra-particle thermal conductivity-likely caused by monomer vapor bubble formation-and the mass transport resistance play a significant role under the flash pyrolysis conditions.
Shale oil is one of the most important oil resources in the United States, yet recovery remains challenging due to its extremely low permeability. Horizontal drilling and multi-stage hydraulic fracturing improve productivity, but depressurization recovery remains below 10% of OOIP, leaving substantial oil unrecovered and many horizontal wells on the verge of abandonment. This study systematically evaluates and compares the effectiveness of water-based chemical EOR agents-including surfactants, nanoparticles, and ketones-for enhancing shale oil recovery under reservoir conditions. A comprehensive experimental workflow was implemented, in which chemical candidates were first screened for aqueous stability and compatibility under high-temperature, highsalinity (HTHS) conditions, followed by evaluation of oil/water interfacial tension reduction and wettability alteration. Static spontaneous imbibition and dynamic Huff-n-Puff experiments were performed using Mancos shale outcrops (5% porosity, 100-200 nD permeability), supported by nuclear magnetic resonance (NMR) analysis employed to support pore-scale interpretation of recovery mechanisms. Four surfactants and two nanoparticles were selected based on aqueous stability and compatibility; one anionic and one zwitterionic surfactant were selected due to their wettability alteration capabilities. The spontaneous imbibition experiments demonstrated that the anionic surfactant achieved higher oil recovery than the zwitterionic one, while the surfactant/nanoparticle blend and the ketone exhibited slightly superior performance. Consistent recovery trends were observed during the Huff-n-Puff experiments, indicating similar chemical effectiveness under dynamic conditions. This work advances understanding of chemical EOR in shale reservoirs by providing a unified evaluation of surfactants, nanoparticles, and ketones under identical shale-relevant thermobaric conditions. The results highlight key differences in recovery behavior among these chemical agents and clarify their relative effectiveness in enhancing shale oil recovery. While laboratory-scale improvements were observed, further investigation is recommended to assess scalability and performance under field conditions.
This experimental study focuses on the changes to the component composition of rapeseed oil, distilled tall oil, and tall oil fatty acids biodiesel during storage. These changes define the density, dynamic viscosity, ignition, combustion, and anthropogenic emissions of microemulsion fuels prepared with biodiesel as an additive. Density of fresh FAME samples ranged from 880 to 935 kg/m3 at 25 degrees C, with noticeable decrease after storage for RO and DTO samples. Dynamic viscosity of rapeseed FAME was closest to diesel fuel, while DTO and FATO FAME viscosities were approximately twice as high. After storage, significant changes were observed: 13% increase in saturated fatty acid methyl esters in rapeseed FAME; 11-17% change in fatty acid concentrations across all samples; 37% variation in oxygen-containing hydrocarbons in rapeseed FAME. Biodiesel is produced by transesterification using methanol and an alkaline catalyst. Microemulsion blends stabilized with a 9:1 mixture of non-ionic surfactants (Neonol AF 9-6 and isoamyl alcohol) are based on diesel fuel, an 8 wt% bio-additive, and 3.5 wt% distilled water. The findings demonstrate the significant effect of biodiesel microemulsification on fuel ignition and combustion under temperature conditions comparable to those in real power plants. Furthermore, microemulsification reduces harmful emissions by 40-70%, depending on the type of biodiesel used. 10-16% decrease in ignition delay at temperatures above 800 degrees C. These results demonstrate the feasibility of using microemulsion fuel containing biodiesel additives in existing power plants.
Accurate characterization of nanoscale pore geometry and pore size distributions (PSDs) in hydrocarbon-bearing unconventional reservoirs (e.g., shale) is crucial for evaluating hydrocarbon storage and fluid mobility. However, a reliable inversion of PSDs from small-angle scattering (SAS) analyses of such dense porous geomaterials remains challenging. We extend empirical-Bayes/Maximum Entropy (MaxEnt) inversion in two directions: joint nonparametric PSD-S(q; theta) inference, and a Poisson-consistent hierarchical inference strategy with profiled regularization. Specifically, structure-factor parameters, which characterize effective inter-pore spatial correlations in dense geological media, are estimated in the outer layer by Laplace-profile evidence, while PSDs are reconstructed in positivity-preserving log space in the inner layer through a Poisson-MaxEnt maximum a posteriori solve. This Poisson formulation models count statistics directly through a Poisson likelihood rather than a Gaussian approximation. Across synthetic tests and shale samples with small-and very-small-angle neutron scattering (SANS/VSANS) applications, the joint treatment reduces correlation-induced false large-size PSD features relative to the baseline of a unity structure-factor and yields more stable PSD derivation. The framework supports more reliable nanoscale pore-structure characterization for unconventional reservoir evaluation, hydrocarbon storage and mobility assessment, and subsurface energy-storage applications.
Underground coal gasification (UCG) is a promising technology due to its potential for reducing CO2 and mitigating ecological impacts. However, the autothermal nature of oxygen injection and the associated inefficient reaction characteristics still result in substantial CO2 emissions during conversion. This study proposes a method for converting in situ coal seams to H2 via thermal plasma to simultaneously provide heat and highly reactive gasifiers. By eliminating oxygen injection, the process drives direct carbon reduction reactions, thereby preventing CO2 emissions from carbon combustion. Continuous plasma-driven underground coal gasification (PUCG) experiments were conducted for 420 min using sub-bituminous coal and anthracite. Results show that the ultrahigh-temperature, high-velocity plasma jet rapidly heats the coal seam above 1000 degrees C within 10 min. The plasma continuously supplies highly reactive species such as OH, O, and H, overcoming the low reactivity of high-rank coals and enabling sustained production of high-quality, low-carbon syngas. The average effective gas content from PUCG approaches 89%, with H2 reaching approximately 50%. The process yields up to 1609 Nm3 of H2, 2544 Nm3 of syngas, and 32.69 GJ of energy per ton of coal. CO2 emissions are as low as 0.12 Nm3 per Nm3 of syngas produced. Compared to conventional UCG, PUCG increases H2 yield by 1.9-26.7 times, boosts syngas output by 3.9-39.4 times, and can reduce CO2 emissions by up to 99% during conversion. This strategy enables efficient, low-carbon syngas production directly within coal seams, holding considerable potential to transform coal-based energy systems and advance the transition to a low-carbon future.
Coking wastewater represents a major challenge for industrial wastewater management due to the abundance of emulsified oils, phenolic compounds, and nitrogen-containing heterocycles that strongly inhibit biological degradation. Herein, a high-performance hierarchical carbon/zeolite composite (C/PZ) was synthesized from coal gasification slag (CGS) via a coupled acid-leaching/alkali-hydrothermal strategy, offering an integrated approach for solid-waste valorization and advanced wastewater pretreatment. Optimization of synthesis conditions identified 3 M HCl leaching followed by hydrothermal crystallization in 2 M NaOH at 95 degrees C for 10 h as the optimal route, producing PZ2-95-10, with well-developed Na-P1 zeolite crystals dispersed in a porous carbon skeleton. The obtained composite possessed a specific surface area of 278 m2/g and a hierarchical micro-mesoporous network conducive to rapid molecular diffusion and efficient adsorption. When applied to real coking residual ammonia water, PZ2-95-10 delivered COD and oil removal efficiencies of 52.29% and 98.86%, respectively, under optimal conditions of an adsorbent dosage of 40 g/L, a contact time of 60 min, and a temperature of 80 degrees C. GC-MS results confirmed the substantial elimination of refractory pollutants, notably phenols, pyridine, indole, and isoquinoline. Adsorption data were best described by the Freundlich isotherm and pseudosecond-order kinetic model, indicating heterogeneous multilayer adsorption with chemisorption as the dominant mechanism. Mechanistically, the superior performance arises from the cooperative action of hydrophobic adsorption and pore-filling in the carbon phase, together with hydrogen-bonding and ion-exchange interactions on zeolitic sites. This work establishes a practical "waste-derived material for waste remediation" paradigm and highlights the strong potential of CGS-derived composites for the pretreatment of highly contaminated coking wastewater.
Oxy-fuel combustion in internal combustion engines (OFC-ICE) is emerging as a potential technology for carbon capture and practically zero-NOx emissions in the context of the global warming issue. This innovative combus tion concept involves fuel oxidation in an atmosphere composed of molecular oxygen diluted with exhaust gas. In recent years, experimental and simulation studies have been conducted to assess this unconventional combustion mode in ICEs under different dilution strategies. In this framework, the quasi-steady sub-models available today are not well suited to operate in a highly enriched O2 atmosphere. Thus, the objective of this study is to com mission two different turbulence and combustion models and assess their capabilities to reproduce the behavior of a single-cylinder research engine operating under premixed OFC conditions in a 0D-1D simulation tool. The considered sub-models are the fractal combustion and the eddy burn-up models. The study is grounded in an experimental campaign where the engine is tested at medium load levels (8-10 bar IMEP) and rotational speed (3000 rpm), under different oxygen/fuel proportions (lambda=1-1.2), EGR ratios (66-75%) and intake temperatures (70-80 degrees C). As a preliminary step, a novel laminar flame speed correlation for OFC is developed, which is es sential to enable the predictive capability of the combustion models. This is obtained on the basis of the results of 1D Thermo-Chemical simulations in a freely propagated flame tube under different oxygen content, residual gas proportions, pressure and temperature levels. Once the accuracy of the 1D engine model in terms of cycle-averaged performances (lambda, IMEP, etc.) is verified, the two combustion models are compared. These are tuned, adopting a unique set of tuning constants for all investigated operating conditions. The simulations demonstrate that both models can predict in-cylinder pressures and burn rates with satisfactory accuracy. The fractal approach performs globally better than the eddy burn-up model, leading to average errors of 2.0 CAD and 3.5 CAD on the combustion phasing (CA50), and average errors of 3.3 CAD and 5.1 CAD on the combustion duration (CA90-10), respectively.
To enhance the reactivity and cyclic stability of red mud-based oxygen carriers in biomass chemical looping gasification (BCLG), carbide slag was introduced to construct a Ca-Fe synergistically modified oxygen carrier, and its reaction behavior was systematically assessed. The results show that, compared with the pristine red mud (RM), the modified sample (R5C5) significantly improves the yield of hydrogen-rich syngas, achieving a maximum syngas yield of 543 mL mL/gbio and a 42.4% increase in H2 yield. During ten consecutive gasification cycles, R5C5 maintained a high average total gas yield of 815.4 mL/gbio and an average syngas yield of 493.4 mL/gbio, indicating superior cyclic stability. The Ca-based sorption phase promotes the water-gas shift reaction by lowering the CO2 partial pressure through in-situ CO2 capture. Meanwhile, the introduced basic sites adsorb and activate tar molecules, facilitating their further cracking into light gaseous products. The Ca-Fe synergistic effect not only enhances lattice oxygen mobility and oxygen transfer capacity but also suppresses the agglomeration of active phases through a physically cooperative interaction. This segregated Ca-Fe synergistic structure avoids the formation of chemically locked calcium ferrite phases that would otherwise hinder oxygen redox kinetics. Overall, this work advances the development of sorption-enhanced chemical looping gasification (SE-CLG) and provides a feasible strategy for the valorization of industrial solid waste in designing dual functional oxygen carriers.
This study proposes a sorption-enhanced biorefinery concept for decentralised methanol production from raw bio gas, integrating Sorption-Enhanced Steam Reforming (SESR) and Sorption-Enhanced Methanol Synthesis (SEMS) within a unified thermodynamic framework. The process combines in situ CO2 capture during reforming with water removal during synthesis, both mediated by a circulating CaO loop, in order to reduce biogas upgrading requirements and enhance carbon utilisation under idealised equilibrium conditions. Thermodynamically con sistent equilibrium models were implemented to compare three process configurations under identical boundary conditions: fully integrated SESR-SEMS (Case Study 1), SESR coupled to conventional methanol synthesis (Case Study 2), and a green-H2+CO2 hydrogenation route (Case Study 3). For a representative 1000 Nm3h-1 raw biogas feed, the equilibrium-based SESR-SEMS configuration predicts a crude methanol yield of 34.13 kmolh-1 (0.927 kg m-3), an overall carbon conversion efficiency to methanol of 51.8%, and a carbon capture efficiency of 90.4%. The corresponding specific energy demand is 2.42 kWh m-3, higher than that of SESR coupled with conventional synthesis (1.52 kWh m-3) owing to the additional regeneration duty associated with the sorbent loop. Secondary equilibrium indicators suggest high theoretical hydrogen purities and strong thermo dynamic driving forces for CO2 conversion and H2O removal within the SEMS reactor. Sensitivity analyses on gas hourly space velocity, steam-to-carbon ratio, and synthesis pressure identify thermodynamic operating re gions in which SEMS suppresses reverse water-gas shift and favours increased single-pass methanol productivity. The model is intentionally equilibrium-based and does not account for reaction kinetics, catalyst deactivation, transport limitations, or transient reactor behaviour. Accordingly, the reported performance metrics should
This work demonstrates the electrochemical valorization of a real wine-industry biomass waste (currently lacking industrial use) using a metal-free Vulcan XC-72R anode, enabling cathodic hydrogen evolution at low cell potentials. As a preliminary approach, the feedstock was characterized by thermogravimetric analysis as containing approximate to 10 wt% water, 18 wt% hemicellulose, 36 wt% cellulose, 30 wt% lignin, and 6 wt% ash. It becomes largely soluble in alkaline media, with the important exception of cellulose, which likely remains undissolved. Electrochemical measurements reveal that Vulcan XC-72R exhibits remarkable anodic activity toward the oxidation of lignin- and hemicellulose-derived functional groups, likely mediated by oxygenated surface species formed under anodic polarization, as supported by previous in-situ spectroscopic studies on related systems (lignin electrooxidation). As a result, the higher anodic currents observed at 1.1-1.6 V (vs RHE) suggest enhanced cathodic hydrogen evolution compared with conventional water electrolysis in 1 M NaOH, with onset voltages below the OER threshold. These findings establish metal-free carbon materials as efficient, low-cost, and scalable anodic electrocatalysts able of simultaneously valorizing an otherwise unused biomass waste and improving the energy efficiency of alkaline H2 generation.
Direct coal liquefaction (DCL) relies on the dynamic transformation of catalyst active phases, yet the transformation pathway of Fe-based catalysts and their regulation of products distribution remain insufficiently understood. In this work, alpha-Fe2O3 precursor was employed to decouple catalyst phase transformation via quenching at different temperatures and their catalysis characteristics during liquefaction process, and Density Functional Theory (DFT) calculations were integrated to explicitly resolve the correlation between sulfidation mechanisms and liquefaction properties. Experimental results reveal that the transformation pathway for active phase during heating (150-450 degrees C) followed Fe2O3-* Fe3O4-* high S/Fe sulfides (FeS2/Fe3S4)-* pyrrhotite (FeS/Fe1-xS), along with a progressively decreasing S/Fe ratio and different liquefaction performances at corresponding quenched temperature. At low temperature, the removal of surface lattice oxygen from Fe2O3 generates oxygen vacancies that promote surface-dominated sulfidation under high hydrogen pressure, whereas increasing temperature favors sulfur redistribution and bulk phase evolution in catalyst. Nevertheless, these intermediates will form final active phase Fe1-xS at liquefaction temperature of 450 degrees C. When the quenched intermediates were used as the precursor, the pre-formed pyrrhotite as dominant active phase significantly enhanced liquefaction behaviors, resulting in coal conversion increase from 76.42 wt% to 80.10 wt% and the maximum oil yield of 54.44 wt%. DFT calculations reveal that catalyst sulfurization favors the pathway involving H2-induced deoxygenation and vacancy-mediated sulfur incorporation, whereas the reductive deoxygenation path via H2S needs high energy barrier (2.419 eV). Lower sulfurized catalysts preferentially adsorb H2S to promote gaseous hydrogen supply. The fully sulfurized catalysts more effectively utilize the gaseous hydrogen. The transformation from Fe2O3 to iron sulfides drives coal conversion into heavy intermediates through solvent hydrogen and gas hydrogen from catalytic decomposition of H2S, while the subsequent evolution into pyrrhotite enables deep hydrocracking and improves hydrogen utilization. This study provides mechanistic understanding of the surface-dominated sulfidation, hydrogen activation and phase-dependent hydrogen utilization during DCL.
