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Keywords = atmospheric flow and dispersion

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16 pages, 26026 KiB  
Article
Computational Fluid Dynamics-Based Modeling of Methane Flows Around Oil and Gas Equipment
by Abhinav Anand, Stuart Riddick, Kira B. Shonkwiler, Aashish Upreti, Michael Moy, Elijah Kiplimo, Mercy Mbua and Daniel J. Zimmerle
Atmosphere 2025, 16(7), 811; https://doi.org/10.3390/atmos16070811 - 2 Jul 2025
Viewed by 343
Abstract
Recent studies estimate that emissions from oil and gas production facilities contribute between 20 and 50% of the total methane (CH4) emitted in the US; therefore, quantifying and reducing these emissions are crucial for achieving climate goals. Methane quantification [...] Read more.
Recent studies estimate that emissions from oil and gas production facilities contribute between 20 and 50% of the total methane (CH4) emitted in the US; therefore, quantifying and reducing these emissions are crucial for achieving climate goals. Methane quantification depends on both measuring methane concentrations and converting them to emissions through a modeling framework. Currently, simple atmospheric dispersion models are primarily used to quantify emissions and concentrations, but these estimates are highly uncertain when quantifying emissions from complex aerodynamic sources, such as oil and gas facilities. This investigation used a CFD modeling approach, which can account for aerodynamic complexity but has hitherto not been used to model methane concentrations downwind of a methane release of a known rate, and compared it against in situ measurements. High-time-resolution (1 Hz) methane concentration and meteorological data were measured during experiments conducted at the METEC on 21 March and 11 July 2024. The METEC site configuration, measured wind data, and controlled emission rates were used as input for the CONVERGE CFD model to model downwind CH4 concentration. The modeling was carried out between 20 and 70 m, from two different points of release in two separate controlled-release experiments, one from a separator and another from a wellhead. In these experiments, we found that the CFD model could predict the CH4 concentrations downwind of the release to a good degree. The model was evaluated on multiple metrics to assess its performance in estimating methane concentrations at typical fence line distances (∼30 m). These results help us to understand external flows and the ability of CFD models to predict downwind concentrations in aerodynamically complex environments. Full article
(This article belongs to the Section Atmospheric Techniques, Instruments, and Modeling)
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22 pages, 3948 KiB  
Article
Self-Standing Carbon Fiber Electrodes Doped with Pd Nanoparticles as Electrocatalysts in Zinc–Air Batteries
by Cristian Daniel Jaimes-Paez, Miguel García-Rollán, Francisco José García-Mateos, Ramiro Ruiz-Rosas, Juana M. Rosas, José Rodríguez-Mirasol, Tomás Cordero, Emilia Morallón and Diego Cazorla-Amorós
Molecules 2025, 30(12), 2487; https://doi.org/10.3390/molecules30122487 - 6 Jun 2025
Viewed by 592
Abstract
In this work, the effect of the palladium precursor on the Oxygen Reduction Reaction (ORR) performance of lignin-based electrospun carbon fibers was studied. The fibers were spun from a lignin-ethanol solution free of any binder, where different Pd salts were added at two [...] Read more.
In this work, the effect of the palladium precursor on the Oxygen Reduction Reaction (ORR) performance of lignin-based electrospun carbon fibers was studied. The fibers were spun from a lignin-ethanol solution free of any binder, where different Pd salts were added at two concentration levels. The system implemented to perform the spinning was a coaxial setup in which the internal flow contains the precursor dispersion with the metallic precursor, and ethanol was used as external flow to help fiber formation and prevent drying before generating the Taylor cone. The obtained cloths were thermostabilized in air at 200 °C and carbonized in nitrogen at 900 °C. The resulting carbon fibers were characterized by physicochemical and electrochemical techniques. The palladium precursor significantly affects nanoparticle distribution and size, fiber diameter, pore distribution, surface area and electrochemical behavior. The fibers prepared with palladium acetylacetonate at high Pd loading and carbonized at 900 °C under a CO2 atmosphere showed high mechanical stability and the best ORR activity, showing near total selectivity towards the 4-electron path. These features are comparable to those of the commercial Pt/C catalyst but much lower metal loading (10.6 wt.% vs. 20 wt.%). The most promising fibers have been evaluated as cathodes in a zinc–air battery, delivering astonishing stability results that surpassed the performance of commercial Pt/C materials in both charging and discharging processes. Full article
(This article belongs to the Special Issue Materials for Emerging Electrochemical Devices—2nd Edition)
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19 pages, 9007 KiB  
Article
Impact of Atmospheric Stability on Urban Bioaerosol Dispersion and Infection Risk: Insights from Coupled WRF–CFD Modeling
by Zhijian Liu, Chenglin Ye, Chenxing Hu, Zhijian Dong, Yuchen He, Li Chen, Zhixing Wang and Rui Rong
Sustainability 2025, 17(6), 2540; https://doi.org/10.3390/su17062540 - 13 Mar 2025
Viewed by 706
Abstract
The rapid pace of global urbanization has exacerbated the urban wind-heat environment, posing a severe threat to public health and sustainable urban development. This study explores the aerodynamic transport characteristics of bioaerosols in a local urban area of Beijing following an accidental bioaerosol [...] Read more.
The rapid pace of global urbanization has exacerbated the urban wind-heat environment, posing a severe threat to public health and sustainable urban development. This study explores the aerodynamic transport characteristics of bioaerosols in a local urban area of Beijing following an accidental bioaerosol release. By coupling the Weather Research and Forecasting (WRF) model with a Computational Fluid Dynamics (CFD) model, the research accounts for the temporality of urban airflow and atmospheric stability. A dose–response model was employed to assess the exposure risks to Beijing Institute of Technology personnel. The findings reveal substantial differences in flow fields and bioaerosol dispersion under varying atmospheric stability: the infection area ratio was 42.19% under unstable conditions and 37.5% under stable conditions. Infection risk was highest near the release source, decreasing with distance. Under the three stability conditions, the probability of infection is highest near the release source and decreases with increasing distance. Contaminants propagate more rapidly under unstable conditions, while stable conditions have a higher concentration of high-risk areas. Gender-based analysis indicated a higher infection probability for males due to elevated inhalation rates. This study elucidates the critical role of atmospheric stability in bioaerosol dispersion and provides a robust scientific foundation for biosafety planning, including early warning, mitigation, and emergency evacuation strategies. Full article
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17 pages, 13526 KiB  
Article
Thermal Barrier Coating on Diamond Particles for the SPS Sintering of the Diamond–ZrO2 Composite
by Lucyna Jaworska, Michał Stępień, Małgorzata Witkowska, Tomasz Skrzekut, Piotr Noga, Marcin Podsiadło, Dorota Tyrała, Janusz Konstanty and Karolina Kapica
Materials 2025, 18(4), 869; https://doi.org/10.3390/ma18040869 - 17 Feb 2025
Cited by 1 | Viewed by 723
Abstract
The aim of this work was to obtain a protective ZrO2 coating on diamond particles, which was to protect diamond from oxidation and graphitization, enabling sintering of diamond at higher temperatures and lower pressures than its thermodynamic stability in atmospheric conditions. The [...] Read more.
The aim of this work was to obtain a protective ZrO2 coating on diamond particles, which was to protect diamond from oxidation and graphitization, enabling sintering of diamond at higher temperatures and lower pressures than its thermodynamic stability in atmospheric conditions. The coatings were obtained by mixing diamond with zirconium and oxidizing in air or oxygen. Mixtures of diamond and 80 wt% zirconium were sintered by SPS method at temperatures of 1250 °C and 1450 °C. To stabilize the tetragonal structure of ZrO2, 3 mol% Y2O3 was added to zirconium before the milling process. The composition of powder phases, morphology, and microstructures of sintered materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). Diffraction studies show the presence of zirconium monoclinic and tetragonal oxides in coatings, after oxidation in air, and in oxygen. Oxidation in oxygen flow is possible for lower temperatures (75 °C), which results in the presence of unreacted zirconium. In ZrO2 doped with yttria after the oxidation process in oxygen, there is no monoclinic ZrO2. It is possible to sinter the ZrO2–diamond composite at 1250 °C using the spark plasma sintering method without graphitization of the diamond. The sintered material consists of monoclinic and tetragonal ZrO2 structures. Full article
(This article belongs to the Special Issue Surface Engineering in Materials (2nd Edition))
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21 pages, 4929 KiB  
Article
Climatic Background and Prediction of Boreal Winter PM2.5 Concentrations in Hubei Province, China
by Yuanyue Huang, Zijun Tang, Zhengxuan Yuan and Qianqian Zhang
Atmosphere 2025, 16(1), 52; https://doi.org/10.3390/atmos16010052 - 7 Jan 2025
Viewed by 751
Abstract
This study investigates the climatic background of winter PM2.5 (particulate matter with a diameter of 2.5 micrometers or smaller) concentrations in Hubei Province (DJF-HBPMC) and evaluates its predictability. The key findings are as follows: (1) Elevated DJF-HBPMC levels are associated with an upper-tropospheric [...] Read more.
This study investigates the climatic background of winter PM2.5 (particulate matter with a diameter of 2.5 micrometers or smaller) concentrations in Hubei Province (DJF-HBPMC) and evaluates its predictability. The key findings are as follows: (1) Elevated DJF-HBPMC levels are associated with an upper-tropospheric northerly anomaly, a deepened southern branch trough (SBT) that facilitates southwesterly flow into central and eastern China, and a weakened East Asian winter monsoon (EAWM), which reduces the frequency and intensity of cold air intrusions. Near-surface easterlies and an anomalous anticyclonic circulation over Hubei contribute to reduced precipitation, thereby decreasing the dispersion of pollutants and leading to higher PM2.5 concentrations. (2) Significant correlations are observed between DJF-HBPMC and sea surface temperature (SST) anomalies in specific oceanic regions, as well as sea-ice concentration (SIC) anomalies near the Antarctic. For the atmospheric pattern anomalies over Hubei Province, the North Atlantic SST mode (NA) promotes the southward intrusion of northerlies, while the Northwest Pacific (NWP) and South Pacific (SPC) SST modes enhance wet deposition through increased precipitation, showing a negative correlation with DJF-HBPMC. Conversely, the South Atlantic–Southwest Indian Ocean SST mode (SAIO) and the Ross Sea sea-ice mode (ROSIC) contribute to more stable local atmospheric conditions, which reduce pollutant dispersion and increase PM2.5 accumulation, thus exhibiting a positive correlation with DJF-HBPMC. (3) A multiple linear regression (MLR) model, using selected seasonal SST and SIC indices, effectively predicts DJF-HBPMC, showing high correlation coefficients (CORR) and anomaly sign consistency rates (AS) compared to real-time values. (4) In daily HBPMC forecasting, both the Reversed Unrestricted Mixed-Frequency Data Sampling (RU-MIDAS) and Reversed Restricted-MIDAS (RR-MIDAS) models exhibit superior skill using only monthly precipitation, and the RR-MIDAS offers the best balance in prediction accuracy and trend consistency when incorporating monthly precipitation along with monthly SST and SIC indices. Full article
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20 pages, 20078 KiB  
Article
Pollutant Dispersion Dynamics Under Horizontal Wind Shear Conditions: Insights from Bidimensional Traffic Flow Models
by Anis Chaari, Waleed Mouhali, Nacer Sellila, Mohammed Louaked and Houari Mechkour
Fluids 2024, 9(11), 265; https://doi.org/10.3390/fluids9110265 - 14 Nov 2024
Viewed by 1272
Abstract
Meteorological factors, specifically wind direction and magnitude, influence the dispersion of atmospheric pollutants due to road traffic by affecting their spatial and temporal distribution. In this study, we are interested in the effect of the evolution of horizontal wind components, i.e., in the [...] Read more.
Meteorological factors, specifically wind direction and magnitude, influence the dispersion of atmospheric pollutants due to road traffic by affecting their spatial and temporal distribution. In this study, we are interested in the effect of the evolution of horizontal wind components, i.e., in the plane perpendicular to the altitude axis. A two-dimensional numerical model for solving the coupled traffic flow/pollution problem, whose pollutants are generated by vehicles, is developed. The numerical solution of this model is computed via an algorithm combining the characteristics method for temporal discretization with the finite-element method for spatial discretization. The numerical model is validated through a sensitivity study on the diffusion coefficient of road traffic and its impact on traffic density. The distribution of pollutant concentration, computed based on a source generated by traffic density, is presented for a single direction and different magnitudes of the wind velocity (stationary, Gaussian, linearly increasing and decreasing, sudden change over time), taking into account the stretching and tilting of plumes and patterns. The temporal evolution of pollutant concentration at various relevant locations in the domain is studied for two wind velocities (stationary and sudden change). Three regimes were observed for transport pollution depending on time and velocity: nonlinear growth, saturation, and decrease. Full article
(This article belongs to the Section Mathematical and Computational Fluid Mechanics)
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34 pages, 41034 KiB  
Article
The Dynamics of Air Pollution in the Southwestern Part of the Caspian Sea Basin (Based on the Analysis of Sentinel-5 Satellite Data Utilizing the Google Earth Engine Cloud-Computing Platform)
by Vladimir Tabunshchik, Aleksandra Nikiforova, Nastasia Lineva, Polina Drygval, Roman Gorbunov, Tatiana Gorbunova, Ibragim Kerimov, Cam Nhung Pham, Nikolai Bratanov and Mariia Kiseleva
Atmosphere 2024, 15(11), 1371; https://doi.org/10.3390/atmos15111371 - 14 Nov 2024
Cited by 2 | Viewed by 1593
Abstract
The Caspian region represents a complex and unique system of terrestrial, coastal, and aquatic environments, marked by an exceptional landscape and biological diversity. This diversity, however, is increasingly threatened by substantial anthropogenic pressures. One notable impact of this human influence is the rising [...] Read more.
The Caspian region represents a complex and unique system of terrestrial, coastal, and aquatic environments, marked by an exceptional landscape and biological diversity. This diversity, however, is increasingly threatened by substantial anthropogenic pressures. One notable impact of this human influence is the rising concentration of pollutants atypical for the atmosphere. Advances in science and technology now make it possible to detect certain atmospheric pollutants using remote Earth observation techniques, specifically through data from the Sentinel-5 satellite, which provides continuous insights into atmospheric contamination. This article investigates the dynamics of atmospheric pollution in the southwestern part of the Caspian Sea basin using Sentinel-5P satellite data and the cloud-computing capabilities of the Google Earth Engine (GEE) platform. The study encompasses an analysis of concentrations of seven key pollutants: nitrogen dioxide (NO2), formaldehyde (HCHO), carbon monoxide (CO), ozone (O3), sulfur dioxide (SO2), methane (CH4), and the Aerosol Index (AI). Spatial and temporal variations in pollution fields were examined for the Caspian region and the basins of the seven rivers (key areas) flowing into the Caspian Sea: Sunzha, Sulak, Ulluchay, Karachay, Atachay, Haraz, and Gorgan. The research methodology is based on the use of data from the Sentinel-5 satellite, SRTM DEM data on absolute elevations, surface temperature data, and population density data. Data processing is performed using the Google Earth Engine cloud-computing platform and the ArcGIS software suite. The main aim of this study is to evaluate the spatiotemporal variability of pollutant concentration fields in these regions from 2018 to 2023 and to identify the primary factors influencing pollution distribution. The study’s findings reveal that the Heraz and Gorgan River basins have the highest concentrations of nitrogen dioxide and Aerosol Index levels, marking these basins as the most vulnerable to atmospheric pollution among those assessed. Additionally, the Gorgan basin exhibited elevated carbon monoxide levels, while the highest ozone concentrations were detected in the Sunzha basin. Our temporal analysis demonstrated a substantial influence of the COVID-19 pandemic on pollutant dispersion patterns. Our correlation analysis identified absolute elevation as a key factor affecting pollutant distribution, particularly for carbon monoxide, ozone, and aerosol indices. Population density showed the strongest correlation with nitrogen dioxide distribution. Other pollutants exhibited more complex distribution patterns, influenced by diverse mechanisms associated with local emission sources and atmospheric dynamics. Full article
(This article belongs to the Special Issue Study of Air Pollution Based on Remote Sensing (2nd Edition))
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16 pages, 11277 KiB  
Article
Microstructural and Oxidation Effects of Nb Additions to U3Si2
by Geronimo Robles, Joshua T. White, Scarlett Widgeon Paisner and Elizabeth S. Sooby
Metals 2024, 14(11), 1239; https://doi.org/10.3390/met14111239 - 30 Oct 2024
Cited by 1 | Viewed by 895
Abstract
U3Si2 is a long term, accident-tolerant nuclear fuel candidate for light-water reactors because of its superior thermal conductivity and increased uranium density when compared to traditional uranium dioxide (UO2). While reducing internal thermal stresses and increasing efficiency, U [...] Read more.
U3Si2 is a long term, accident-tolerant nuclear fuel candidate for light-water reactors because of its superior thermal conductivity and increased uranium density when compared to traditional uranium dioxide (UO2). While reducing internal thermal stresses and increasing efficiency, U3Si2 exhibits energetic oxidation during certain off-normal and accident scenarios, which include coolant or steam exposure. To mitigate this, Nb is investigated as an alloy constituent to enhance corrosion resistance and increase mechanical strength. The work presented investigates the response of Nb-alloyed U3Si2 to steam atmospheres. A thermogravimetric analysis is conducted in flowing steam to T > 1000 °C to assess oxidation resistance. The phase characterization of as-melted, thermally annealed and post-oxidation compositions with up to 12 vol% Nb by powder X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy is reported. Full article
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23 pages, 19515 KiB  
Article
Analysis of Wind Power Fluctuation in Wind Turbine Wakes Using Scale-Adaptive Large Eddy Simulation
by Jagdeep Singh and Jahrul M Alam
Wind 2024, 4(4), 288-310; https://doi.org/10.3390/wind4040015 - 18 Oct 2024
Cited by 1 | Viewed by 2036
Abstract
In large wind farms, the interaction of atmospheric turbulence and wind turbine wakes leads to complex vortex dynamics and energy dissipation, resulting in reduced wind velocity and subsequent loss of wind power. This study investigates the influence of vortex stretching on wind power [...] Read more.
In large wind farms, the interaction of atmospheric turbulence and wind turbine wakes leads to complex vortex dynamics and energy dissipation, resulting in reduced wind velocity and subsequent loss of wind power. This study investigates the influence of vortex stretching on wind power fluctuations within wind turbine wakes using scale-adaptive large eddy simulation. The proper orthogonal decomposition method was employed to extract the most energetic contributions to the wind power spectra. Vertical profiles of mean wind speed, Reynolds stresses, and dispersive stresses were analyzed to assess energy dissipation rates. Our simulation results showed excellent agreement when compared with wind tunnel data and more advanced numerical models, such as the actuator line model and the actuator line model with hub and tower effects. This highlights the important role of coherent and energetic flow components in the spectral behavior of wind farms. The findings indicate a persistent energy cascading length scale in the wake of wind turbines, emphasizing the vertical transport of energy to turbine blades. These results complement existing literature and provide new insights into the dynamics of wind turbine wakes and their impact on wind farm performance. Full article
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17 pages, 3242 KiB  
Article
Risks and Safety of CO2 Pipeline Transport: A Case Study of the Analysis and Modeling of the Risk of Accidental Release of CO2 into the Atmosphere
by Paweł Bielka, Szymon Kuczyński, Tomasz Włodek and Stanisław Nagy
Energies 2024, 17(16), 3943; https://doi.org/10.3390/en17163943 - 9 Aug 2024
Cited by 3 | Viewed by 2796
Abstract
In the field of CO2 capture and sequestration, ensuring the safety of pipeline infrastructure is paramount to successful climate change mitigation efforts. This study investigates the dynamics of CO2 dispersion from pipeline systems, assessing not only the transport process but also [...] Read more.
In the field of CO2 capture and sequestration, ensuring the safety of pipeline infrastructure is paramount to successful climate change mitigation efforts. This study investigates the dynamics of CO2 dispersion from pipeline systems, assessing not only the transport process but also the physical properties and associated hazards. Advanced simulation techniques are used to model how different states of CO2 (gas, liquid, and supercritical) and varying pipeline characteristics—such as perforation sizes, flow rates, and orientations—affect the dispersion patterns in the event of a leak. Simulations cover a range of atmospheric conditions, emphasizing the role of atmospheric stability and wind speed in shaping dispersion and defining potential impact zones. An analysis of historical pipeline accidents is included to inform risk management strategies. The results show that the orientation of the pipeline has a significant effect on dispersion, with downward leaks causing the largest impact zones, particularly under supercritical conditions. The results highlight the need for adaptive safety strategies that take into account real-time CO2 transport conditions and localized environmental data. By integrating these factors, the study recommends refining safety protocols and emergency response strategies to improve pipeline resilience and public safety against potential leaks. Key findings include the quantification of the relationship between leak parameters and dispersion areas, providing a valuable framework for future safety improvements. Full article
(This article belongs to the Section B: Energy and Environment)
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45 pages, 14884 KiB  
Article
The Consistency of Subjective and Objective Factors Influencing Walking Path Choice around Rail Transit Stations
by Qiwei Chen, Yuchen Qin, Minfeng Yao, Yikang Zhang and Zhijunjie Zhai
Buildings 2024, 14(7), 2225; https://doi.org/10.3390/buildings14072225 - 19 Jul 2024
Cited by 1 | Viewed by 1784
Abstract
The station–city integration development strategy, guided by the Transit-Oriented Development (TOD) model, has enhanced the coupling relationship between rail transit stations and urban areas. Walking, as a core mode of low-carbon urban transport, plays a significant role in the connectivity between stations and [...] Read more.
The station–city integration development strategy, guided by the Transit-Oriented Development (TOD) model, has enhanced the coupling relationship between rail transit stations and urban areas. Walking, as a core mode of low-carbon urban transport, plays a significant role in the connectivity between stations and urban areas and in the rate of passenger flow dispersal. During peak periods, large volumes of passengers flood the streets, forming complex and diverse walking paths that penetrate urban neighborhoods. Route choice is a complex decision-making process influenced by both subjective and objective factors. Previous studies on pathfinding activities have often focused on either subjective or objective factors in isolation, with limited research on their interaction. This paper establishes a comparative analysis framework based on the translation of subjective and objective information and behavioral feedback mechanisms. Using Lvcuo Station, a transit station on Xiamen’s Metro Line 1 in Fujian Province, China, as a case study, we collected walking data from 410 passengers through field surveys. We used the Kappa consistency coefficient test method to analyze the performance of the interaction between the objective environment and subjective environmental cognitive factors when pedestrians exit the rail transit station and walk to their destinations. We also used multinomial logistic regression (MLR) to analyze the correlation between subjective perception variables and objective built environment variables and to consider the influence of individual pedestrian characteristics and attributes on path selection. The results revealed the following: (1) Overall, there is a significant deviation effect of subjective and objective factors on passengers’ pathfinding behavior, with some spatial correlation with the built environment of the streets. (2) The consistency of influences on walking activities varies significantly across different travel periods, distances, and purposes. (3) Visual elements, urban life with a bustling atmosphere, street permeability, and route connectivity positively correlate with subjective perception while “supporting walking facilities” and “meeting consumption needs along the way” negatively correlate with subjective perception. These findings underscore the need to enhance the understanding of the built environment in the street spaces within rail transit station areas from the perspectives of pedestrians to improve the walkability of these streets. Full article
(This article belongs to the Section Architectural Design, Urban Science, and Real Estate)
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18 pages, 5980 KiB  
Article
Investigation of Partial Oxidation of Methane at Different Reaction Parameters by Adding Ni to CeO2 and ZrO2 Supported Cordierite Monolith Catalyst
by Ilke Ilicak Bayraktar and Halit Eren Figen
Processes 2024, 12(7), 1463; https://doi.org/10.3390/pr12071463 - 12 Jul 2024
Cited by 1 | Viewed by 1780
Abstract
The climate crisis, driven by increasing CO2 levels in the atmosphere, has heightened the need for new, environmentally friendly energy sources. Hydrogen gas, which can meet our energy needs, has become a particularly intriguing topic. This study investigated the partial oxidation reaction [...] Read more.
The climate crisis, driven by increasing CO2 levels in the atmosphere, has heightened the need for new, environmentally friendly energy sources. Hydrogen gas, which can meet our energy needs, has become a particularly intriguing topic. This study investigated the partial oxidation reaction of methane with cordierite monolith catalysts. The Ni-coated catalysts were supported with γ-Al2O3, CeO2, ZrO2, and CeO2-ZrO2. The catalysts were tested at temperatures of 750, 800, and 850 °C with different flow rates and methane feed concentrations (2%, 5%, and 10%). It was demonstrated that catalyst activity varies depending on these parameters. It has been found that high gas hourly space velocity (GHSV) and CH4 feed rates decrease catalyst activity. The obtained reaction results indicated that the optimal reaction parameters were 800 °C, a GHSV of 1 × 104 h−1, and a CH4 feed concentration of 2%. By optimizing these parameters, catalysts with high CH4 conversion and selectivity for H2 and CO were achieved. The prepared catalysts were characterized using scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and temperature-programmed reduction (TPR). Full article
(This article belongs to the Section Catalysis Enhanced Processes)
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27 pages, 2091 KiB  
Article
Zonons Are Solitons Produced by Rossby Wave Ringing
by Nimrod Cohen, Boris Galperin and Semion Sukoriansky
Atmosphere 2024, 15(6), 711; https://doi.org/10.3390/atmos15060711 - 14 Jun 2024
Cited by 1 | Viewed by 1062
Abstract
Along with the familiar Rossby–Haurwitz waves, two-dimensional flows on the surface of a rotating sphere in the regime of zonostrophic turbulence harbor another class of waves known as zonons. Zonons are wave packets produced by energetic large-scale Rossby–Haurwitz wave modes ‘enslaving’ other wave [...] Read more.
Along with the familiar Rossby–Haurwitz waves, two-dimensional flows on the surface of a rotating sphere in the regime of zonostrophic turbulence harbor another class of waves known as zonons. Zonons are wave packets produced by energetic large-scale Rossby–Haurwitz wave modes ‘enslaving’ other wave modes. They propagate westward with the phase speed of the enslaving modes. Zonons can be visualized as enslaving modes’ ‘ringing’ in the enslaved ones with the frequencies of the former, the property that renders zonons non-dispersive. Zonons reside in high-shear regions confined between the opposing zonal jets yet they are mainly attached to westward jets and sustained by the ensuing barotropic instability. They exchange energy with the mean flow while preserving their identity in a fully turbulent environment, a feature characteristic of solitary waves. The goal of this study is to deepen our understanding of zonons’ physics using direct numerical simulations, a weakly non-linear theory, and asymptotic analysis, and ascertain that zonons are indeed isomorphic to solitary waves in the Korteweg–de Vries framework. Having this isomorphism established, the analysis is extended to eddies detected in the atmospheres of Jupiter and Saturn based upon the observed mean zonal velocity profiles and earlier findings that circulations on both planets obey the regime of zonostrophic macroturbulence. Not only the analysis confirms that many eddies and eddy trains on both giant planets indeed possess properties of zonons, but the theory also correctly predicts latitudinal bands that confine zonal trajectories of the eddies. Full article
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23 pages, 15648 KiB  
Article
Sensitivity Analysis of Modelled Air Pollutant Distribution around Buildings under Different Meteorological Conditions
by Anton Petrov, Emilia Georgieva and Elena Hristova
Atmosphere 2024, 15(6), 638; https://doi.org/10.3390/atmos15060638 - 25 May 2024
Cited by 2 | Viewed by 1350
Abstract
The distribution of air pollutants in urban areas is significantly influenced by the presence of various geometric structures, including buildings, bridges, and tunnels. In built-up environments, meteorological conditions may influence the accumulation or dispersion of air pollutants in specific zones. This study examines [...] Read more.
The distribution of air pollutants in urban areas is significantly influenced by the presence of various geometric structures, including buildings, bridges, and tunnels. In built-up environments, meteorological conditions may influence the accumulation or dispersion of air pollutants in specific zones. This study examines the impact of wind and atmospheric stability on the dispersion of air pollutants around an apartment building situated in close proximity to a busy boulevard in a residential district of Sofia, Bulgaria. A series of dispersion simulations were conducted using the Graz Lagrangian Model (GRAL v.22.09) for a range of meteorological conditions, defined as combinations of the direction and velocity of the approaching flow, and of stability conditions within the study area of 1 × 1 km, with a horizontal resolution of 2 m. The resulting spatial distribution revealed the presence of hotspots and strong gradients in the concentration field. A simulation with meteorological data was also conducted, which was aligned with a campaign to monitor vehicular traffic. The sensitivity tests indicate that GRAL is capable of reproducing high-resolution pollutant fields, accounting for building effects at relatively low computational costs. This makes the model potentially attractive for city-wide simulations as well as for air pollution exposure estimation. Full article
(This article belongs to the Special Issue Urban Air Pollution, Meteorological Conditions and Human Health)
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20 pages, 8018 KiB  
Article
Highly Efficient PtSn/Al2O3 and PtSnZnCa/Al2O3 Catalysts for Ethane Dehydrogenation: Influence of Catalyst Pretreatment Atmosphere
by Seetharamulu Podila, Abdulrahim A. Al-Zahrani, Muhammad A. Daous and Hesham Alhumade
Catalysts 2024, 14(5), 312; https://doi.org/10.3390/catal14050312 - 9 May 2024
Viewed by 1670
Abstract
Increased demand for ethylene has motivated direct ethane dehydrogenation over Pt-based catalysts. PtSn/γ-Al2O3 and PtSnZnCa/γ-Al2O3 catalysts were investigated with the aim of understanding the effect of the pretreatment environment on the state of dispersed Pt for ethane [...] Read more.
Increased demand for ethylene has motivated direct ethane dehydrogenation over Pt-based catalysts. PtSn/γ-Al2O3 and PtSnZnCa/γ-Al2O3 catalysts were investigated with the aim of understanding the effect of the pretreatment environment on the state of dispersed Pt for ethane dehydrogenation. The catalysts were prepared by the impregnation method and pretreated in different environments like static air (SA), flowing air (FA), and nitrogen (N2) atmospheres. A comprehensive characterization of the catalysts was performed using Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), Temperature-Programmed Reduction (TPR), NH3 Temperature-Programmed Desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM) techniques. The results reveal that the PtSn on Al2O3 catalyst pretreated in the static air environment (PtSn-SA) exhibits 21% ethylene yield with 95% selectivity at 625 °C. XPS analysis found more platinum and tin on the catalyst surface after static air treatment. The overall acidity of the catalysts decreased after thermal treatment in static air. Elemental mapping demonstrated that Pt agglomeration was pronounced in catalysts calcined under flowing air and nitrogen. These factors are responsible for the enhanced activity of the PtSn-SA catalyst compared to the other catalysts. The addition of Zn and Ca to the PtSn catalysts increases the yield of the catalyst calcined in static air (PtSnZnCa-SA). The PtSnZnCa-SA catalyst showed the highest ethylene yield of 27% with 99% selectivity and highly stable activity at 625 °C for 10 h. Full article
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