Search Results (289)

This study aims to quantify total VOC emissions and evaluate how torrefaction alters the heat of combustion of three agricultural residues. The work examines the amount of VOC emissions during the torrefaction process at various temperatures and investigates the changes in the heat of combustion of agri-biomass resulting from the torrefaction process. The process was carried out at the following temperatures: 225, 250, 275, and 300 °C. Total VOC emission factors were determined. The reaction kinetics analysis revealed that meadow hay exhibited the most stable thermal behavior with the lowest activation energy. At the same time, rye straw demonstrated higher thermal resistance and complex multi-step degradation characteristics. The authors analyze three types of agricultural biomass: meadow hay, rye straw, and oat straw. The research was divided into five stages: determination of moisture content in the sample, determination of ash content, thermogravimetric analysis, measurement of total VOC emissions from the biomass torrefaction process, and determination of the heat of combustion of the obtained torrefied biomass. Based on the research, it was found that torrefaction of biomass causes the emission of torgas containing VOC in the amount of 2–10 mg/g of torrefied biomass, which can be used energetically, e.g., to support the torrefaction process, and the torrefied biomass shows a higher value of the heat of combustion. Unlike prior studies focused on single feedstocks or limited temperature ranges, this work systematically compares three major crop residues across four torrefaction temperatures and directly couples VOC quantifications. Full article

Carbon monoxide (CO) is a major toxic gas emitted from vehicle exhaust, industrial processes, and incomplete fuel combustion, posing serious environmental and health risks. Catalytic oxidation of CO into less harmful CO₂ is an effective strategy to reduce these emissions. In this study, we investigated the catalytic performance of platinum (Pt) single atoms doped on C₃N monolayers with various vacancy defects, including single carbon (C_V) and nitrogen (N_V) vacancies, using density functional theory (DFT) calculations. Our results demonstrate that Pt@N_V-C₃N exhibited the most favorable catalytic properties, with the highest O₂ adsorption energy (−3.07 eV). This performance significantly outperforms Pt atoms doped at other vacancies. It can be attributed to the strong binding between Pt and nitrogen vacancies, which contributes to its excellent resistance to Pt aggregation. CO oxidation on Pt@N_V-C₃N proceeds via the Eley–Rideal (ER2) mechanism with a low activation barrier of 0.41 eV for the rate-determining step, indicating high catalytic efficiency at low temperatures. These findings suggest that Pt@N_V-C₃N is a promising candidate for CO oxidation, contributing to developing cost-effective and environmentally sustainable catalysts. The strong binding of Pt atoms to the nitrogen vacancies prevents aggregation, ensuring the stability and durability of the catalyst. The kinetic modeling further revealed that the ER2 mechanism offers the highest reaction rate constants over a wide temperature range (273–700 K). The low activation energy barrier also facilitates CO oxidation at lower temperatures, addressing critical challenges in automotive and industrial pollution control. This study provides valuable theoretical insights for designing advanced single-atom catalysts for environmental remediation applications. Full article

Petroleum oily sludge (OLS), a hazardous by-product of the petroleum industry, and high-alkali lignite (HAL), an underutilized low-rank coal, pose significant challenges to sustainable waste management and resource efficiency. This study systematically investigated the combustion behavior, reaction pathways, and gaseous-pollutant-release mechanisms across varying blend ratios, utilizing integrated thermogravimetric-mass spectrometry analysis (TG-MS), interaction analysis, and kinetic modeling. The key findings reveal that co-combustion significantly enhances the combustion performance compared to individual fuels. This is evidenced by reduced ignition and burnout temperatures, as well as an improved comprehensive combustion index. Notably, an interaction analysis revealed coexisting synergistic and antagonistic effects, with the synergistic effect peaking at a blending ratio of 50% OLS due to the complementary properties of the fuels. The activation energy was found to be at its minimum value of 32.5 kJ/mol at this ratio, indicating lower reaction barriers. Regarding gas emissions, co-combustion at a 50% OLS blending ratio reduces incomplete combustion products while increasing CO₂, indicating a more complete reaction. Crucially, sulfur-containing pollutants (SO₂, H₂S) are suppressed, whereas nitrogen-containing emissions (NH₃, NO₂) increase but remain controllable. This study provides novel insights into the synergistic mechanisms between OLS and HAL during co-combustion, offering foundational insights for the optimization of OLS-HAL combustion systems toward efficient energy recovery and sustainable industrial waste management. Full article

Alkaline earth elements have emerged as crucial electronic modifiers for regulating active sites in catalytic systems, yet the influence of metal–support interactions (MSIs) between alkaline earth compounds and active metals remains insufficiently understood. This study systematically investigated Pt nanoparticles supported on alkaline earth carbonates (Pt/MCO₃, M = Mg, Ca, Ba) for low-temperature propylene combustion. The Pt/BaCO₃ catalyst exhibited outstanding performance, achieving complete propylene conversion at 192 °C, significantly lower than Pt/MgCO₃ (247 °C) and Pt/CaCO₃ (282 °C). The enhanced activity stemmed from distinct MSI effects among the supports, with Pt/BaCO₃ showing the poorest electron enrichment and lowest propylene adsorption energy. Through kinetic analyses, ¹⁸O₂ isotope labeling, and comprehensive characterization, the reaction was confirmed to follow the Mars–van Krevelen (MvK) mechanism. Pt/BaCO₃ achieves an optimal balance between propylene and oxygen adsorption, a critical factor underlying its superior activity. Full article

Combustion processes in compression ignition engines lead to the inevitable generation of nitrogen oxides, which cannot be limited to the currently desired levels just by optimising the in-cylinder processes. Therefore, simulation-based engine development needs to include all engine-related aspects which contribute to tailpipe emissions. Among them, the SCR (selective catalytic reduction) aftertreatment-related processes, such as urea–water solution injection, urea decomposition, mixing, NOx catalytic reduction, and deposits’ formation, are the most challenging, and require as much attention as the processes taking place inside the cylinder. Over the last decade, the urea-SCR aftertreatment systems have evolved from underfloor designs to close-coupled (to the engine) architecture, characterised by the short mixing length. Therefore, they need to be tailor-made for each application. This study presents the CFD-based development of a multi-platform SCR system with a short mixing length for mobile non-road applications, compliant with Stage V NRE-v/c-5 emission standard. It combines multiphase dispersed flow, including wall wetting and urea decomposition kinetic reaction modelling to account for the critical aspects of the SCR system operation. The baseline system’s design was characterised by the severe deposit formation near the mixer’s outlet, which was attributed to the intensive cooling in the mounting area. Moreover, as the simulations suggested, the spray was not appropriately mixed with the surrounding gas in its primary zone. The proposed measures to reduce the wall film formation needed to account for the multi-platform application (ranging from 56 to 130 kW) and large-scale production capability. The performed simulations led to the system design, providing excellent UWS–exhaust gas mixing without a solid deposit formation. The developed system was designed to be manufactured and implemented in large-scale series production. Full article

Combustion modeling using computational fluid dynamics (CFD) offers detailed insights into the flame structure and thermo-chemical processes. Furthermore, it has been extensively used in the past to optimize industrial furnaces. Despite the increasing computational power, the prediction of the reaction kinetics in flames is still related to high calculation times, which is a major drawback for large-scale combustion systems. To speed-up the simulation, artificial neural networks (ANNs) were applied in this study to calculate the chemical source terms in the flame instead of using a chemistry solver. Since one ANN may lack accuracy for the entire input feature space (temperature, species concentrations), the space is sub-divided into four regions/ANNs. The ANNs were tested for different fuel mixtures, degrees of turbulence, and air-fuel/oxy-fuel combustion. It was found that the shape of the flame and its position were well predicted in all cases with regard to the temperature and CO. However, at low temperature levels (<800 K), in some cases, the ANNs under-predicted the source terms. Additionally, in oxy-fuel combustion, the temperature was too high. Nevertheless, an overall high accuracy and a speed-up factor for all simulations of 12 was observed, which makes the approach suitable for large-scale furnaces. Full article

Polyethersulfone (PES) membranes are essential in separation processes; however, their inherent hydrophobicity can limit their effectiveness in water-intensive applications. This study aims to enhance PES membranes by modifying them with a NiFe₂O₄–nanoclay composite nanoparticle to improve both their hydrophilicity and photocatalytic potential as a photocatalytic membrane. The nanoparticles were synthesized using the sol–gel auto-combustion method and incorporated into PES membranes through mixed-matrix embedding (1 wt% and 3 wt%) and surface coating. X-ray diffraction confirmed the cubic spinel structure of the composite nanoparticles, which followed the second order kinetic reaction during the photodegradation–adsorption of crystal violet. The mixed-matrix membranes displayed a remarkable 170% increase in water flux and a 25% improvement in mechanical strength, accompanied by a slight decrease in contact angle at 1 wt% of nanoparticle loading. In contrast, the surface-coated membranes demonstrated a significant reduction in contact angle to 18°, indicating a highly hydrophilic surface and increased roughness. All membranes achieved high dye removal rates of 98–99%, but only the coated membrane system exhibited approximately 50% photocatalytic degradation, following mixed kinetics. These results highlight the critical importance of surface modification in advancing PES membranes, as it significantly reduces fouling and enhances water–material interaction qualities essential for future filtration and photocatalytic applications. Exploring hybrid strategies that combine both embedding and coating approaches may yield even greater synergies in membrane functionality. Full article

This study investigated the combustion performance of pig manure, straw, and coal at various blending ratios using thermogravimetric analysis. The synergistic effect of coal and pig manure at various ratios was analyzed, and kinetic analysis was performed using the Coats–Redfern method. The results showed that the overall combustion performance and stability of the blended fuel improved as the blending ratio of pig manure and straw increased. Increasing the ratio of pig manure reduced the ignition temperature of blended fuel from 696 K to 675 K. Additionally, the combustion of pig manure and coal exhibited a significant synergistic effect, strongest at a 5% blending ratio. For combustion reactions with conversion rates between 0.2 and 0.8, the activation energy required was 75.82 kJ mol⁻¹ for a 10% pig manure blending ratio and 44.33 kJ mol⁻¹ for a 30% blending ratio. These results demonstrate that lower activation energies suggest that the combustion reaction is more likely to proceed. The activation energy of straw was higher than that of pig manure at all blending ratios. These findings suggest that pig manure burns more easily when blended with coal than straw. Full article

Hydroperoxyalkylperoxy radicals (•OOQOOH) are important intermediates in the low-temperature oxidation chemistry of conventional fuels. In these species, a hydrogen atom may migrate from a non-adjacent carbon to the peroxy group, forming a dihydroperoxyalkyl radical (•P(OOH)₂). This research delves into the theoretical kinetics of a set of 110 H-migration reactions in normal-alkyl cyclohexanes, calculating high-pressure limit rate constants for these reactions. The reactions are further classified into 15 subclasses based on distinctions in the reaction center and its environment, with rate rules derived by averaging the rate constants within each subclass. A comparison of our calculated rate constants for specific H-migration reactions of •OOQOOH with existing mechanisms and similar reactions in non-cyclic alkanes reveals significant disparities, emphasizing the necessity for precise rate constants tailored to normal-alkyl cyclohexanes. Ethyl cyclohexane mechanisms and n-propyl cyclohexane mechanisms sourced from studies have been improved with high-pressure limit rate constants from this study. Simulations of the low-temperature combustion of ethyl cyclohexane and n-propyl cyclohexane show that the predictions from the updated mechanisms align more closely with the experimental data under specific conditions compared to the original mechanism. Full article

Supercritical combustion is a promising technique for improving the efficiency and reducing the emissions of next-generation gas turbines. However, accurately modeling combustion under these conditions remains a challenge, particularly due to the complexity of chemical kinetics. This study aims to evaluate the applicability of a reduced global reaction mechanism compared to the detailed Foundational Fuel Chemistry Model 1.0 (FFCM-1) when performing hydrogen combustion with supercritical carbon dioxide and argon as diluents. Computational fluid dynamics simulations were conducted in two geometries: a simplified tube for isolating chemical effects and a combustor with cooling channels for practical evaluation. The analysis focuses on the evaluation of velocity, temperature, and the water vapor mass fraction distributions inside the combustion chamber. The results indicate good agreement between the global and detailed mechanisms, with average relative errors below 2% for supercritical argon and 4% for supercritical carbon dioxide. Both models captured key combustion behaviors, including buoyancy-driven flame asymmetry caused by the high density of supercritical fluids. The findings suggest that global chemistry models can serve as efficient tools for simulating supercritical combustion processes, making them valuable for the design and optimization of future supercritical gas turbine systems. Full article

Antioxidant gel foams are promising materials for coal mine fire prevention due to their unique physicochemical properties. To address the limitations of conventional suppression methods under high-temperature conditions, this study investigates a newly developed antioxidant gel foam and its mechanism in inhibiting coal spontaneous combustion. A novel antioxidant gel foam was formulated by incorporating TBHQ and modified montmorillonite into a sodium alginate-based gel system. This formulation enhances the thermal stability, water retention, and free radical scavenging capacity of the gel. This study uniquely combines multi-scale experimental methods to evaluate the performance of this material in coal fire suppression. Multi-scale experiments, including FTIR, leakage air testing, programmed temperature rise, and small-scale fire extinction, were conducted to evaluate its performance. Experimental results indicate that the antioxidant gel foam exhibits excellent thermal stability in the temperature range of 200–500 °C. Its relatively high decomposition temperature enables it to effectively resist structural damage in high-temperature environments. During thermal decomposition, the gel releases only a small amount of gas, while maintaining the integrity of its internal micro-porous structure. This characteristic significantly delays the kinetics of coal oxidation reactions. Further research revealed that the spontaneous combustion ignition temperature of coal samples treated with the gel was significantly higher, and the oxygen consumption rate during spontaneous combustion was significantly reduced, indicating that the gel not only effectively suppressed the acceleration of the combustion reaction but also significantly reduced the release of harmful gases such as HCl. Scanning electron microscope analysis confirmed that the gel maintained a good physical structure under high temperatures, forming an effective oxygen barrier, which further enhanced the suppression of coal spontaneous combustion. These findings provide important theoretical and practical guidance for the application of antioxidant gel foams in coal mine fire prevention and control, confirming that this material has great potential in coal mine fire safety, offering a new technological approach to improve coal mine safety. Full article

To investigate the combustion characteristics of moxa under a nitrogen atmosphere, this study employed an integrated approach combining experimental and theoretical analysis. Twelve moxa floss samples with different leaf-to-floss ratios, geographical origins, and storage durations were selected for thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) of their carbonized products in nitrogen environment. Through TG-DTG analysis, the thermal degradation patterns of the twelve moxa floss samples under nitrogen atmosphere were systematically examined to elucidate their pyrolysis behaviors, with particular emphasis on the influence of pyrolysis temperature and leaf-to-floss ratio on combustion characteristics. The pyrolysis process occurred in three distinct stages, with the most significant mass loss (120–430 °C) observed in the second stage. Higher leaf–fiber ratios and longer storage years were found to promote more complete pyrolysis. Kinetic analysis was performed to fit thermogravimetric data, establishing a reaction kinetic model for moxa pyrolysis. Results indicated that samples with higher leaf–fiber ratios required greater activation energy, while storage duration showed negligible impact. Notably, Nanyang moxa demanded higher pyrolysis energy than Qichun moxa. FTIR analysis identified the primary components of carbonized products as water, ester compounds, flavonoids, and cellulose. These findings suggest that moxa carbonization products retain chemical reactivity, demonstrating potential applications in adsorption and catalysis processes. Full article

Ammonia combustion has garnered increasing attention due to its potential as a carbon-free fuel. Globally swirling flow in a rectangular furnace generates flameless conditions by high flue gas recirculation. The reverse air injection (RAI) technique enabled stable swirling flameless combustion of pure ammonia without auxiliary methods. Experiments with pure ammonia combustion in a swirling flameless furnace demonstrated an operable equivalence ratio (ER) range of 0.3–1.05, extending conventional flammability limits of pure ammonia as a fuel. NO emissions were reduced by 40% compared to conventional combustion, with peak concentrations of 1245 ppm at ER = 0.71 and near-zero emissions at ER = 1.05. Notably, flameless combustion exhibited lower temperature sensitivity in NO formation; however, the ER has a serious effect. Developing a simplified reaction model for ammonia combustion is crucial for computational fluid dynamics (CFD) research. A reduced kinetic mechanism comprising 36 reactions and 16 chemical species was introduced, specifically designed for efficient and precise modeling of pure ammonia flameless combustion. Combustion simulation using the eddy dissipation concept (EDC) approach confirmed the mechanism’s predictive capability, maintaining acceptable accuracy across the operating conditions. Full article

Under China’s “dual carbon” goals (carbon peaking and carbon neutrality), the utilization of high-chlorine coal faces significant challenges due to its abundant reserves in regions such as Xinjiang and its notable environmental impacts. This study systematically investigates the combustion characteristics, environmental risks, and control strategies for high-chlorine coal. Key findings reveal that chlorine release occurs in three distinct stages, namely low-temperature desorption, medium-temperature organic bond cleavage, and high-temperature inorganic decomposition, with release kinetics governed by coal metamorphism and the reaction atmosphere. Chlorine synergistically enhances mercury oxidation through low-activation-energy pathways but exacerbates boiler corrosion via chloride–sulfate interactions. Advanced control technologies—such as water washing, calcium-based sorbents, and integrated pyrolysis–gasification systems—demonstrate substantial emission reductions. However, challenges remain in addressing high-temperature corrosion and optimizing multi-pollutant synergistic control. This study provides critical insights into the clean utilization of high-chlorine coal, supporting sustainable energy transitions. Full article

Jet fuel from direct coal liquefaction (DCL) is an important alternative kerosene and represents a high-performance fuel for specific applications in civil applications. The study on its chemical positions and combustion properties is critical for the development of surrogate models and related combustion reaction mechanisms, which is valuable for promoting its usage in aeroengines. However, research on DCL-derived jet fuel is rather scarce. Herein, this work reports a systematic study on a DCL-derived jet fuel and its blends with traditional RP-3 jet fuel in two different ratios. Specifically, major physicochemical properties related to the aviation fuel airworthiness certification process are measured. Advanced two-dimensional gas chromatography (GC × GC) analysis is used to analyze the detailed chemical compositions on the DCL derived jet fuel and its blend with RP-3, which is then employed for surrogate model development. Moreover, ignition delay times (IDTs) are measured by using a heated shock-tube (ST) facility for the blended fuels over a wide range of conditions. Combustion reaction mechanisms based on the surrogate models are developed to predict the experimental measured IDTs. Finally, sensitivity analysis and rate-of-production analysis are carried out to identify the key chemical kinetics controlling the ignition characteristics. This work extends the understanding of the physicochemical properties and ignition characteristics of alternative jet fuels and should be valuable for the practical usage of DCL derived jet fuels. Full article