Search Results (413)

Combustion of aviation jet fuel emits a complex mixture of pollutants linked to adverse health outcomes among airport personnel and nearby communities. While epidemiological studies showed the detrimental effects of aviation-derived air pollutants on human health, the molecular mechanisms of the interactions of these pollutants with cellular biomolecules like proteins that drive the adverse health effects remain poorly understood. In this study, we performed molecular docking simulations of 272 pollutant–protein complexes using AutoDock Vina 1.2.7 to characterize the binding strength of the pollutants with the selected proteins. We selected 34 aviation-derived pollutants that constitute three chemical categories of pollutants: volatile organic compounds (VOCs), polyaromatic hydrocarbons (PAHs), and organophosphate esters (OPEs). Each pollutant was docked to eight proteins that play critical roles in endocrine, metabolic, transport, and neurophysiological functions, where functional disruption is implicated in disease. The effect of binding of multiple pollutants was analyzed. Our results indicate that aliphatic and monoaromatic VOCs display low (<6 kcal/mol) binding affinities while PAHs and organophosphate esters exhibit strong (>7 kcal/mol) binding affinities. Furthermore, the binding strength of PAHs exhibits a positive correlation with the increasing number of aromatic rings in the pollutants, ranging from nearly 7 kcal/mol for two aromatic rings to more than 15 kcal/mol for five aromatic rings. Analysis of intermolecular interactions showed that these interactions are predominantly stabilized by hydrophobic, pi-stacking, and hydrogen bonding interactions. Simultaneous docking of multiple pollutants revealed the increased binding strength of the resulting complexes, highlighting the detrimental effect of exposure to pollutant mixtures found in ambient air near airports. We provide a priority list of pollutants that regulatory authorities can use to further develop targeted mitigation strategies to protect the vulnerable personnel and communities near airports. Full article

Canola oil (rapeseed oil, RO), despite being a potential source of biofuel, needs some modifications of its properties to be effectively used as a fuel. The reason RO needs to be altered lies above all in its viscosity, fatty acid composition, and other chemical properties, which affect its efficiency as a fuel. These properties of RO can be changed by mixing it with various bioadditives, among other methods. For this reason, studies of the physicochemical properties of mixtures including RO, n-hexane (Hex), and ethyl oleate (EO) were carried out. These mixtures were prepared at a constant EO concentration and a ratio of n-hexane in the mixture with RO in the range from 0 to 1. For these mixtures, the surface tension, density and viscosity were measured. The obtained results were considered to determine the chemical properties of particular components of the mixtures. From these considerations, it results that based on the properties of these components, the surface tension and density of the studied mixtures can be described, and their viscosity can be predicted. These facts and results of the measurements suggest that based on the properties of the mixture components, we can determine the composition of a mixture whose surface tension, density, and viscosity are close to those of diesel fuel. The results obtained from the measurements also suggest that the addition of 10% n-hexane to RO causes a considerable reduction in the surface tension, viscosity, and density of RO. The addition of 10% of EO to this mixture results in a further reduction in RO + Hex viscosity and increases its density and surface tension slightly. As such, a mixture of RO with Hex and EO may be appropriate as a biofuel. Full article

Municipal solid waste (MSW) and refuse-derived fuel (RDF) incineration generate over 20 million tons of residues annually in the EU. These include bottom ash (IBA), fly ash (FA), and air pollution control residues (APCr), which pose significant environmental challenges due to their leaching potential and hazardous properties. While these residues contain valuable metals and reactive mineral phases suitable for carbonation or alkaline activation, chemical, techno-economic, and policy barriers have hindered the implementation of sustainable, full-scale management solutions. Accelerated carbonation technology (ACT) offers a promising approach to simultaneously sequester CO₂ and enhance residue stability. This review provides a comprehensive assessment of waste incineration residue carbonation, covering 227 documents ranging from laboratory studies to field applications. The analysis examines reactor designs and process layouts, with a detailed classification based on material characteristics, operating conditions, investigated parameters, and the resulting pollutant stabilization, CO₂ uptake, or product performance. In conclusion, carbonation-based approaches must be seamlessly integrated into broader waste management strategies, including metal recovery and material repurposing. Carbonation should be recognized not only as a CO₂ sequestration process, but also as a binding and stabilization strategy. The most critical barrier remains chemical: the persistent leaching of sulfates, chromium(VI), and antimony(V). We highlight what we refer to as the antimony problem, as this element can become mobilized by up to three orders of magnitude in leachate concentrations. The most pressing research gap hindering industrial deployment is the need to design stabilization approaches specifically tailored to critical anionic species, particularly Sb(V), Cr(VI), and SO₄²⁻. Full article

The use of CH₄ as an energy source is increasing every day. To increase the efficiency of CH₄ combustion and ensure that the equipment meets ecological requirements, it is necessary to measure the CH₄ concentration in the exhaust gases of combustion systems. To this end, sensors are required that can withstand extreme operating conditions, including temperatures of at least 600 °C, as well as high pressure and gas flow rate. ZnGa₂O₄, being an ultra-wide bandgap semiconductor with high chemical and thermal stability, is a promising material for such sensors. The synthesis and investigation of the structural and CH₄ sensing properties of ceramic pellets made from pure and Er-doped ZnGa₂O₄ were conducted. Doping with Er leads to the formation of a secondary Er₃Ga₅O₁₂ phase and an increase in the active surface area. This structural change significantly enhanced the CH₄ response, demonstrating an 11.1-fold improvement at a concentration of 10⁴ ppm. At the optimal response temperature of 650 °C, the Er-doped ZnGa₂O₄ exhibited responses of 2.91 a.u. and 20.74 a.u. to 100 ppm and 10⁴ ppm of CH₄, respectively. The Er-doped material is notable for its broad dynamic range for CH₄ concentrations (from 100 to 20,000 ppm), low sensitivity to humidity variations within the 30–70% relative humidity range, and robust stability under cyclic gas exposure. In addition to CH₄, the sensitivity of Er-doped ZnGa₂O₄ to other gases at a temperature of 650 °C was investigated. The samples showed strong responses to C₂H₄, C₃H₈, C₄H₁₀, NO_2, and H₂, which, at gas concentrations of 100 ppm, were higher than the response to CH₄ by a factor of 2.41, 2.75, 3.09, 1.16, and 1.64, respectively. The study proposes a plausible mechanism explaining the sensing effect of Er-doped ZnGa₂O₄ and discusses its potential for developing high-temperature CH₄ sensors for applications such as combustion monitoring systems and determining the ideal fuel/air mixture. Full article

Nickel’s durability and catalytic properties make it essential in the aerospace, automotive, electronics, and fuel cell technology industries. Wastewater analysis typically relies on sensitive but costly techniques such as ICP-MS, AAS, and ICP-AES, which require complex equipment and are unsuitable for on-site testing. This study introduces a novel screen-printed electrode array with 16 chemically and, optionally, electrochemically coated Au electrodes. Its electrochemical response to Ni²⁺ was tested using Na₂SO₃ and ChCl-EG deep eutectic solvents as electrolytes. Ni²⁺ solutions were prepared from NiCl₂·6H₂O, NiSO₄·6H₂O, and dry NiCl₂. In Na₂SO₃, the linear detection ranges were 20–196 mM for NiCl₂·6H₂O and 89–329 mM for NiSO₄·6H₂O. High Ni²⁺ concentrations (10–500 mM) were used to simulate industrial conditions. Two linear ranges were observed, likely due to differences in electrochemical behaviour between NiCl₂·6H₂O and NiSO₄·6H₂O, despite the identical Na₂SO₃ electrolyte. Anion effects (Cl⁻ vs. SO₄²⁻) may influence response via complexation or ion pairing. In ChCl-EG, a linear range of 0.5–10 mM (R² = 0.9995) and a detection limit of 1.6 µM were achieved. With a small electrolyte volume (100–200 µL), nickel detection in the nanomole range is possible. A key advantage is the array’s ability to analyze multiple analytes simultaneously via customizable electrode configurations. Future research will focus on nickel detection in industrial wastewater and its potential in the multiplexed analysis of toxic metals. The array also holds promise for medical diagnostics and food safety applications using thiol/Au-based capture molecules. Full article

The development of combustion experiments in a controlled environment is essential for comparing different fuels and quantifying the influence of different key parameters. It is fundamental to understand the transport phenomena at the particle level to obtain reliable results and information for further proper biomass combustion modeling of large-scale equipment. Hence, this paper presents a comprehensive analysis of the thermal decomposition and kinetic of eight samples of forest biomass fuels in terms of combustion behavior by using the thermogravimetric analysis (TGA) technique. The tests were carried out in an oxidizing atmosphere at a heating rate between 5 and 100 °C/min up to 900 °C. It was observed that, for all samples, fuel conversion follows a sequence of drying, devolatilization, and char combustion. Furthermore, differences in chemical and physical composition, as well as in structures and their thermal stability, justify the differences observed between the mass-loss curves of the different fuels. For this, the complexity of kinetic study is addressed in this paper by using different approaches: isoconversional and model-fitting methods. However, the use of isoconversional methods proved ineffective for determining reliable kinetic parameters, due to their sensitivity to particle conversion. A significant variation in activation energy was observed during the devolatilization stage, ranging from 47.92 to 101.30 kJ/mol. For the char oxidation stage, it ranged from 14.97 to 35.48 kJ/mol. These results highlight Eucalyptus as the most reactive species among those studied. Full article

This study provides a comprehensive thermochemical characterization of common nut residues—almonds, walnuts, hazelnuts, peanuts, and pistachios shells—as potential biomass fuels, examining their chemical composition, calorific values, and emissions profiles. Their suitability as renewable energy sources was systematically assessed by verifying compliance with ISO 17225-2 standards for pellet production. The nut residues demonstrated promising energy characteristics, with higher heating values ranging from 17.75 to 19.12 MJ/kg and most samples fulfilling ISO 17225-2 classifications A1 or A2. Specifically, the walnut residues met the highest quality classification (A1), whereas the almond, hazelnut, and pistachio residues met the A2 classification, and the peanut residues were classified as B due to higher nitrogen content. A Life Cycle Assessment (LCA) was also performed to quantify the environmental impacts, focusing on CO₂ emissions from energy recovery and transportation. The results showed significantly lower CO₂ emissions from all the nut residues compared to fossil fuels such as coal, natural gas, fuel oil (HFO), and LPG. The almond residues exhibited the lowest total CO₂ emissions at 1669.27 kg CO₂ per ton, while the peanuts had the highest at 1945.93 kg CO₂ per ton. Even the highest-emitting nut residues produced substantially lower emissions compared to coal, which emitted approximately 4581.12 kg CO₂ per ton. These findings highlight the potential of nut residues as low-carbon, renewable energy sources, providing both environmental advantages and opportunities to support local agricultural economies. 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

As the attention to using hydrogen as a potential energy storage medium for power generation and mobility increases, hydrogen production, storage, and transportation safety should be considered. For instance, hydrogen’s extreme physical and chemical properties and the wide range of flammable concentrations raise many concerns about the current safety measures in processing other flammable gases. Hydrogen cloud accumulation in the case of leakage in confined spaces can lead to reaching the hydrogen lower flammability limit (LFL) within seconds if the hydrogen is not properly evacuated from the space. At Jülich Research Centre, hydrogen mixed with natural gas is foreseen to be used as a fuel for the central heating system of the campus. In this work, the release, dispersion, formation, and spread of the hydrogen cloud in the case of hydrogen leakage inside the central utility building of the campus are numerically simulated using the OpenFOAM-based containmentFOAM CFD codes. Additionally, different ventilation scenarios are simulated to investigate the behavior of the hydrogen cloud. The results show that locating exhaust openings close to the ceiling and the potential leakage source can be the most effective way to safely evacuate hydrogen from the building. Additionally, locating the exhaust outlets near the ceiling can decrease the combustible cloud volume by more than 25% compared to side openings far below the ceiling. Also, hydrogen concentrations can reach the LFL in case of improper forced ventilation after only 8 s, while it does not exceed 0.15% in the case of natural ventilation under certain conditions. The results of this work show the significant effect of locating exhaust outlets near the ceiling and the importance of natural ventilation to mitigate the effects of hydrogen leakage. The approach illustrated in this study can be used to study hydrogen dispersion in closed buildings in case of leakage and the proper design of the ventilation outlets for closed spaces with hydrogen systems. Full article

Ignition delay time (IDT) is a critical parameter for evaluating the autoignition characteristics of aviation fuels. However, its accurate prediction remains challenging due to the complex coupling of temperature, pressure, and compositional factors, resulting in a high-dimensional and nonlinear problem. To address this challenge for the complex aviation kerosene RP-3, this study proposes a multi-stage hybrid optimization framework based on a five-input, one-output BP neural network. The framework—referred to as CGD-ABC-BP—integrates randomized initialization, conjugate gradient descent (CGD), the artificial bee colony (ABC) algorithm, and L2 regularization to enhance convergence stability and model robustness. The dataset includes 700 experimental and simulated samples, covering a wide range of thermodynamic conditions: 624–1700 K, 0.5–20 bar, and equivalence ratios φ = 0.5 − 2.0. To improve training efficiency, the temperature feature was linearized using a 1000/T transformation. Based on 30 independent resampling trials, the CGD-ABC-BP model with a three-hidden-layer structure of [21 17 19] achieved strong performance on internal test data: R² = 0.994 ± 0.001, MAE = 0.04 ± 0.015, MAPE = 1.4 ± 0.05%, and RMSE = 0.07 ± 0.01. These results consistently outperformed the baseline model that lacked ABC optimization. On an entirely independent external test set comprising 70 low-pressure shock tube samples, the model still exhibited strong generalization capability, achieving R² = 0.976 and MAPE = 2.18%, thereby confirming its robustness across datasets with different sources. Furthermore, permutation importance and local gradient sensitivity analysis reveal that the model can reliably identify and rank key controlling factors—such as temperature, diluent fraction, and oxidizer mole fraction—across low-temperature, NTC, and high-temperature regimes. The observed trends align well with established findings in the chemical kinetics literature. In conclusion, the proposed CGD-ABC-BP framework offers a highly accurate and interpretable data-driven approach for modeling IDT in complex aviation fuels, and it shows promising potential for practical engineering deployment. 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

Hydrogen possesses distinctive characteristics that position it as a potential energy carrier to substitute fossil fuels. Nonetheless, there is still an essential need to create secure and effective storage solutions prior to its broad application. The use of hydride-forming metals (HFMs) for hydrogen storage is a method that has been researched thoroughly over the past several decades. This study investigates the structural and chemical modifications in titanium (Ti) and zirconium (Zr) thin coatings over aluminum hydroxide (AlO₃) granules before and after hydrogenation. The materials were subjected to hydrogenation at 400 °C and 5 atm of hydrogen pressure for 2 h, with a hydrogen flow rate of 0.8 L/min. The SEM analysis revealed significant morphological changes, including surface roughening, a grain boundary separation, and microcrack formations, indicating the formation of metal hydrides. The EDS analysis showed a reduction in Ti and Zr contents post-hydrogenation, likely due to the formation of hydrides. The presence of hydride phases, with shifts in diffraction peaks indicating structural modifications due to hydrogen absorption, is confirmed by the XRD analysis. The FTIR analysis revealed dihydroxylation, with the removal of surface hydroxyl groups and the formation of new metal–hydride bonds, further corroborating the structural changes. The formation of metal hydrides was confirmed by the emergence of new peaks within the 1100–1200 cm⁻¹ range, suggesting the incorporation of hydrogen. Mathematical modeling based on the experimental parameters was conducted to assess the hydride formation and the rate of hydrogen penetration. The hydride conversion rate for Ti- and Zr-coated AlO₃ granules was determined to be 3.5% and 1.6%, respectively. While, the hydrogen penetration depth for Ti- and Zr-coated AlO₃ granules over a time of 2 h was found to be 1200 nm and 850 nm approximately. The findings had a good agreement with the experimental results. These results highlight the impact of hydrogenation on the microstructure and chemical composition of Ti- and Zr-coated AlO₃, shedding light on potential applications in hydrogen storage and related fields. Full article

Fuels obtained from woody forest resources such as oaks have been traditionally used in various regions due to their availability and energy properties. In the search for sustainable bioenergy sources and the transition towards cleaner alternatives, biomass-derived fuels, such as charcoal and pellets, represent a relevant option for rural and urban communities. This study determines the chemical composition, physical and mechanical properties, and energy quality of pellets from two oak species (Quercus laurina and Q. rugosa) in San Sebastián Coatlán, Miahuatlán, Oaxaca. The chemical composition was determined in an Ankom fiber analyzer; the energetic, physical, and mechanical analysis was carried out with UNE-EN ISO and ASTM standards. On average, 56.18% and 54.63% cellulose, 17.81% and 17.87% lignin, and 13.96% and 13.78% hemicelluloses were obtained for Quercus laurina and Q. rugosa, respectively. Mechanical durability ranged from 87% to 95% for Q. laurina stump and Q. rugosa stem, respectively; for calorific value, values from 19.79 MJ Kg⁻¹ to 20.31 MJ Kg⁻¹ were recorded for Q. laurina stem and Q. rugosa stump, respectively. The forest biomass of both oak species is viable for pellet production. Full article

Hydrogen fuel cell vehicles are one of the most promising alternatives to achieve transport decarbonization targets, thanks to their moderately high efficiency and low refueling time, combined with their zero-exhaust-emission operation. In order to reach reasonable power density figures, fuel cell systems are generally supercharged by radial compressors, which can encounter significant limitations associated with surge and choke operation, especially at high altitudes. Alternatively, the current paper explores the altitude operation of a fuel cell system combined with a Roots compressor. First, the balance of the plant model is built in the Simscape platform, combining a physical and chemical 1D fuel cell model for the stack, calibrated against literature data at different pressure and temperature values, as well as the characteristic maps of the Roots compressor. Then, the model is used to explore the balance-of-plant operation in a working range between 10 and 200 kW and an altitude range between sea level and 5 km. The results show that the compressor is capable of operating around the highest efficiency area (between 60 and 70%) for a wide range of altitude and power conditions, limiting the negative impact of the altitude on the system efficiency to up to 3%. However, once the compressor efficiency falls below 60%, the balance-of-plant performance rapidly drops, overcoming the benefits of the working pressure on the fuel cell stack operation and limiting the peak net power produced. Full article

Given the high proportion of global fossil energy consumption, the Ordovician karst water in the North China-type coalfield, as a green energy source that harnesses both water and heat, holds significant potential for mitigating environmental issues associated with fossil fuels. In this work, we collected geothermal water samples and conducted borehole temperature measurements at the Xinhu Coal Mine in the Huaibei Coalfield, analyzed the chemical composition of regional geothermal water, elucidated the characteristics of thermal storage, and explored the influence of regional structure on the karst geothermal system in the northern region. The results indicate that the geothermal water chemistry at the Xinhu Coal Mine is of the Na-K-Cl-SO₄ type, with its chemical composition primarily controlled by evaporation and concentration processes. The average temperature of the Ordovician limestone thermal reservoir is 48.2 °C, and the average water circulation depth is 1153 m, suggesting karst geothermal water undergoing deep circulation. The geothermal gradient at the Xinhu Coal Mine ranges from 22 to 33 °C/km, which falls within the normal range for ground-temperature gradients. A notable jump in the geothermal gradient at well G1 suggests a strong hydraulic connection between deep strata within the mine. The heat-accumulation model of the hydrothermal mine geothermal system is influenced by strata, lithology, and fault structures. The distribution of high ground-temperature gradients in the northern region is a result of the combined effects of heat conduction from deep strata and convection of geothermal water. The Ordovician limestone and extensional faults provide a geological foundation for the abundant water and efficient heat conduction of the thermal reservoirs. Full article