Light Gas Research Articles

Desulfurization of light and heavy gas oil from crudes of Kurdistan region-Iraq by oxidation and solvent extraction

This study analyzes four distinct crude oil varieties from the Kurdistan Region-Iraq: Taq-Taq (TQ), Sarqala (SA), Khurmala (Kh), and Tawke (TA). Fractionation produced five categories: naphtha, kerosene, light gas oil (LGO), heavy gas oil (HGO), and fuel oil. The research focused on distillation cuts of LGO (241–300°C) and HGO (301–360°C), which contained organic sulfur compounds, contributing to environmental pollution and health hazards during combustion. Oxidative desulfurization (ODS) using hydrogen peroxide and acetic acid at 75°C for 12 hours significantly reduced sulfur content. LGO sulfur content decreased from 0.72% to 0.11% wt in SA and from 2.02% to 0.50% wt in TA, achieving desulfurization efficiencies of 84.72% and 74.25%, respectively. In HGO, sulfur content dropped from 3.67% to 1.78% wt in Kh, with 51.49% efficiency. Gas oil recovery after oxidation ranged from 92.71% to 96.28%. Solvent extraction with acetonitrile, methanol, and acetic acid further enhanced desulfurization, with pre-oxidation extraction achieving 19.42% efficiency in LGO, increasing to 86% post-oxidation. Gas chromatography with a flame photometric detector (PFPD) assessed sulfur removal, highlighting the combined effects of oxidation and extraction on sulfur compound reduction. This approach demonstrated the efficiency of ODS in mitigating sulfur-related impacts.

Dual-stream gas targets for a point source of vacuum and extreme ultraviolet radiation supported by focused electromagnetic radiation

The article presents the results of visualization of two-stream gas targets for a point source of vacuum ultraviolet and extreme ultraviolet radiation. Measurements of the gas concentration spatial distribution were carried out using a Michelson interferometer. It is shown that adding a light gas to the peripheral channel significantly moves the region of breakdown concentration of injected gas through the central channel away from the nozzle, while maintaining the overall gas flow and background pressure.

A Chemically Robust Microporous Zn-MOF for C2H2 Separation from CO2 and Industrially Relevant Four Component Gas Mixtures.

The separation and purification of acetylene from the light hydrocarbon gas mixtures is considered as one of the most industrially challenging task for the production of fine chemicals. Though metal-organic frameworks (MOFs) are promising candidates for such separation and offer a cost and energy-efficient pathway, achieving the trade-off between sorption capacity and separation selectivity along with framework robustness is a daunting task and demands effective design. Herein, a new 3D chemically stable MOF, IITKGP-24 (stable over a wide range of aqueous pH solution, pH = 2-12) is developed, displaying excellent separation selectivity of 13.9 for C2H2/CO2 (50:50) even at ambient conditions and maintained a trade-off between sorption capacity and separation selectivity. Most importantly, the breakthrough performance analysis under the industrially relevant gas mixture composition revealed that the developed framework possesses excellent separation of acetylene from not only C2H2/CO2 (50:50) gas mixtures but also from the quaternary C2H2/C2H4/C2H6/CO2 (25:25:25:25) feed gas streams. Separation of C2H2 from such a four component gas mixture by MOFs is unexplored. The exceptional framework robustness, high C2H2/CO2 uptake ratio, low heat of adsorption, and excellent recyclability with easy regenerability made the developed framework promising candidate toward this challenging separation.

Reading Dye-Based Colorimetric Inks: Achieving Color Consistency Using Color QR Codes

Color consistency when reading colorimetric sensors is a key factor for this technology. Here, we demonstrate how the usage of machine-readable patterns, like QR codes, can be used to solve the problem. We present our approach of using back-compatible color QR codes as colorimetric sensors, which are common QR codes that also embed a set of hundreds of color references as well as colorimetric indicators. The method allows locating the colorimetric sensor within the captured scene and to perform automated color correction to ensure color consistency regardless of the hardware used. To demonstrate it, a CO2-sensitive colorimetric indicator was printed on top of a paper-based substrate using screen printing. This indicator was formulated for Modified Atmosphere Packaging (MAP) applications. To verify the method, the sensors were exposed to several environmental conditions (both in gas composition and light conditions). And, images were captured with an 8M pixel digital camera sensor, similar to those used in smartphones. Our results show that the sensors have a relative error of 9% when exposed with a CO2 concentration of 20%. This is a good result for low-cost disposable sensors that are not intended for permanent use. However, as soon as light conditions change (2500–6500 K), this error increases up to ϵ20 = 440% (rel. error at 20% CO2 concentration) rendering the sensors unusable. Within this work, we demonstrate that our color QR codes can reduce the relative error to ϵ20 = 14%. Furthermore, we show that the most common color correction, white balance, is not sufficient to address the color consistency issue, resulting in a relative error of ϵ20 = 90%.

Study on the Explosion Mechanism of Low-Concentration Gas and Coal Dust

In coal mines, the mixture of coal dust and gas is more ignitable than gas alone, posing a high explosion risk to workers. Using the explosion tube, this study examines the explosion propagation characteristics and flame temperature of low-concentration gas and coal dust mixtures with various particle sizes. The CPD model and Chemkin-Pro 19.2 simulate the reaction kinetics of these explosions. Findings show that when the gas concentration is below its explosive limit, coal dust addition lowers the gas’s explosive threshold, potentially causing an explosion. Coal particle size significantly affects explosion propagation dynamics, with smaller particles producing faster flame velocities and higher temperatures. Due to their larger surface area, smaller particles absorb heat faster and undergo thermal decomposition, releasing combustible gases that intensify the explosion flame. The predicted yield of light gases from both coal types exceeds 40 wt% daf, raising combustible gas concentrations in the system. When accumulated reaction heat elevates the gas concentration to its explosive limit, an explosion occurs. These results are crucial for preventing gas and coal dust explosion accidents in coal mines.

Thermal performance evaluation of a novel solar-driven pyrolysis reactor

Utilizing concentrated radiation from the sun to drive solid waste pyrolysis can address the carbon-emission issue during the heating process. This study proposed a novel directly irradiated solar-driven pyrolysis reactor with a simplified structure, consisting of alumina insulation, quartz glass tubes, and porous ceramics. The reactor's numerical model, considering the radiative heat transfer at short-wavelength radiation and long-wavelength infrared radiation, was developed for its thermal performance evaluation. The effects of operating conditions (gas inlet velocity and lamp power) and porous media structural parameters (pore size and porosity) on the reactor's thermal performance were investigated to guide the practical application of the solar-driven pyrolysis reactor. The present study also found that using SiC as a porous skeleton increased the energy absorption of porous media from 17.8 % to 30.0 % due to the higher absorptivity of SiC compared to Al2O3 for solar radiation. The findings revealed the superior thermal performance of the novel reactor structure proposed in the present study, given that the energy absorbed by the porous media was three times that of the directly irradiated reactor with a conventional structure using SiC porous ceramics. This study might broaden the solar thermal utilization pathway and offer the possibility of commercializing solar-driven pyrolysis.

Effects of Culture Systems and Nutrients on the Growth and Toxin Production of Karenia selliformis.

Harmful algal blooms (HABs) formed by toxic microalgae have seriously threatened marine ecosystems and food safety and security in recent years. Among them, Karenia selliformis has attracted the attention of scientists and society due to its acute and rapid neurotoxicity in mice. Herein, the growth and gymnodimine A (GYM-A) production of K. selliformis were investigated in diverse culture systems with different surface-to-volume (S/V) ratios and nitrogen/phosphorus concentrations. The results showed that the specific growth rates (μ), maximal cell yields, and GYM-A production levels of K. selliformis increased with higher S/V, but no significant differences were observed under different culture volumes with the same S/V, which indicated that light penetration and gas exchange in the seawater culture systems actually influenced the growth and GYM-A production of K. selliformis. The maximum cell density and photosynthetic efficiency of K. selliformis decreased under nitrogen (N) and phosphorus (P) deficiency, suggesting that the growth of K. selliformis was significantly inhibited by the deficiency in N or P. Both N and P limitation conditions, especially P deficiency, promoted the cellular GYM-A quotas of K. selliformis. In this study, a scientific basis is provided for understanding the effects of culture systems and nutrient concentrations on the growth and toxin production of K. selliformis.

Research on cavity evolution and motion characteristics of supercavitating projectiles during asynchronous parallel water entry

Abstract To study the performance of supercavitating projectiles in asynchronous parallel entry into water, this paper establishes a numerical simulation method for supercavitating projectiles in asynchronous parallel water entry based on finite volume method, VOF multi phase flow model, and overlapping grid technology. At the same time, high-speed cameras and light gas guns were used to conduct high-speed water entry experiments on a single projectile, and the reliability of the numerical method was verified by comparing simulation results with experimental results. Subsequently, numerical simulations and analyses were conducted on the cavity evolution and motion characteristics of the front and rear projectiles under different initial spacing and different water entry sequences. The research results indicate that when the initial distance between the front and rear projectiles is 0.5 times the length of the projectile, the front projectile is unable to generate complete cavities to wrap the projectile body due to severe compression from the rear projectile, which seriously affects its movement and ultimately leads to instability. As the initial spacing increases, the influence of the rear projectile on the surrounding cavities of the front projectile weakens. Whether the upper projectile enters the water first or the lower projectile enters the water first, both move smoothly. For the rear projectile, due to the continuous effect of the front projectile cavity, its cavity is always asymmetric, and its motion stability is affected. When the spacing is 0.5 times the length of the projectile, the rear launched projectile deflects inward and becomes unstable. When the spacing is 1 time the length of the projectile, it moves steadily. When the spacing is 2 and 3 times the length of the projectile, it deflects outward and becomes unstable. Regardless of which projectile enters the water first, this motion pattern is basically consistent.

Thermal Conversion of Coal Bottom Ash and Its Recovery Potential for High-Value Products Generation: Kinetic and Thermodynamic Analysis with Adiabatic TD24 Predictions.

Thermal decomposition (pyrolysis) of coal bottom ash (collected after lignite combustion in coal-fired power plant TEKO-B, Republic of Serbia) was investigated, using the simultaneous TG-DTG techniques in an inert atmosphere, at various heating rates. By using the XRD technique, it was found that the sample (CBA-TB) contains a large amount of anorthite, muscovite, and silica, as well as periclase and hematite, but in a smaller amount. Using a model-free kinetic approach, the complex nature of the process was successfully resolved. Thermodynamic analysis showed that the sample is characterized by dissociation reactions, which are endothermic with positive activation entropy changes, where spontaneity is achieved at high reaction temperatures. The model-based method showed the existence of a complex reaction scheme that includes two consecutive reaction steps and one single-step reaction, described by a variety of reaction models as nucleation/growth phase boundary-controlled, the second/n-th order chemical, and autocatalytic mechanisms. It was established that an anorthite I1 phase breakdown reaction into the incongruent melting product (CaO·Al2O3·2SiO2) represents the rate-controlling step. Autocatalytic behavior is reflected through chromium-incorporated SiO2 catalyst reaction, which leads to the formation of chromium(II) oxo-species. These catalytic centers are important in ethylene polymerization for converting light olefin gases into hydrocarbons. Adiabatic TD24 prediction simulations of the process were also carried out. Based on safety analysis through validated kinetic parameters, it was concluded that the tested sample exhibits high thermal stability. Applied thermal treatment was successful in promoting positive changes in the physicochemical characteristics of starting material, enabling beneficial end-use of final products and reduction of potential environmental risks.

Long-Tune Natural Logarithmic Wavelength Modulation Spectroscopy for Gas Sensing.

This article presents a gas sensing method based on long-tune natural logarithmic wavelength modulation spectroscopy (long-tune ln-WMS) and explores means to improve its accuracy. The long-tune spectrum can detect multiple gases with high precision. In ln-WMS, due to the natural logarithm algorithm, the harmonic magnitude which is related to gas concentration would not be affected by the light intensity fluctuations. However, the background signal of the harmonic will become strong and nonlinear in the long-tune spectrum. Three CO2 absorption lines and one H2O line near 2004 nm are applied to verify the proposed theory. The effects of light intensity, modulation depth, gas concentration, and phase shift on the harmonics are tested separately through both simulations and experiments. The results reveal that our proposed method can always keep the harmonics at their maximum which ensures high measurement precision. Moreover, the background signal only varies with the modulation depth, not the concentration and light intensity. Even the mechanical vibrations cannot disturb the harmonics, which enables the proposed method to be suitable for gas detection in harsh environments, especially for heavy dust and severe mechanical vibrations. The CO2 concentration detection results indicate that when the background is eliminated, the accuracy can be achieved with a relative error of below 0.5%, while the error would be greater than 5% with background presence. The proposed long-tune ln-WMS method is effective for trace gas detection (weak absorption) or over-modulation conditions and has potential applications in field inspection.

The influence of the shock-to-reshock time on the Richtmyer–Meshkov instability in reshock

Experiments on the Richtmyer–Meshkov instability (RMI) in a dual driver vertical shock tube (DDVST) are described. An initially planar, stably stratified membraneless interface is formed by flowing air from above and sulfur hexafluoride from below the interface location using the method of Jones & Jacobs (Phys. Fluids, vol. 9, issue 1997, 1997, pp. 3078–3085). A random three-dimensional, multi-modal initial perturbation is imposed by vertically oscillating the gas column to produce Faraday waves. The DDVST design generates two shock waves, one originating above and one below the interface, with these shocks having independently controllable strengths and interface arrival times. The shock waves have nominal strengths of $M_L=1.17$ and $M_H=1.18$ for the shock wave originating in the light and heavy gas, respectively, with these strengths chosen to result in arrested bulk interface motion following reshock. The influence of the length of the shock-to-reshock time, as well as the order of shock arrival, on the post-reshock RMI is examined. The mixing layer width grows according to $h\propto t^\theta$ , where $\theta _H=0.36\pm 0.018$ (95 %) and $\theta _L=0.38\pm 0.02$ (95 %) for heavy and light shock first experiments, respectively, indicating no strong dependence on the order of shock wave arrival. Volume integrated specific turbulent kinetic energy (TKE) in the mixing layer versus time is found to decay according to $E_{tot}/\bar {\rho }\propto t^p$ with $p_H=-0.823\pm 0.06$ (95 %) and $p_L=-1.061\pm 0.032$ (95 %) for heavy and light shock first experiments, respectively. Notably, the 95 % confidence intervals do not overlap. Analysis on the influence of the shock-to-reshock time on turbulent length scales, transition criteria, spectra and mixing layer anisotropy are also presented.

Advances in Membranes from Microporous Materials for Hydrogen Separation from Light Gases

With the pressing concern of the climate change, hydrogen will undoubtedly play an essential role in the future to accelerate the way out from fossil fuel‐based economy. In this case, the role of membrane‐based separation cannot be neglected since, compared with other conventional process, membrane‐based process is more effective and consumes less energy. Regarding this, metal‐based membranes, particularly palladium, are usually employed for hydrogen separation because of its high selectivity. However, with the advancement of various microporous materials, the status quo of the metal‐based membranes could be challenged since, compared with the metal‐based membranes, they could offer better hydrogen separation performance and could also be cheaper to be produced. In this article, the advancement of membranes fabricated from five main microporous materials, namely silica‐based membranes, zeolite membranes, carbon‐based membranes, metal organic frameworks/covalent organic frameworks (MOF/COF) membranes and microporous polymeric membranes, for hydrogen separation from light gases are extensively discussed. Their performances are then summarized to give further insights regarding the pathway that should be taken to direct the research direction in the future.

Effects of CO2 Aeration and Light Supply on the Growth and Lipid Production of a Locally Isolated Microalga, Chlorella variabilis RSM09

The Chlorophyceae algae, specifically Chlorella spp., have been extensively researched for biodiesel production. This study focused on the alga Chlorella variabilis RSM09, which was isolated from a brackish-water environment at Raksamae Bridge in Klaeng District, Rayong Province, Thailand. The effects of the carbon dioxide gas (CO2) concentration (0.03%, 10%, 20%, 30%, 40%, and 50% v/v), light intensity (3000, 5000, and 7000 Lux), and photoperiod (12:12, 18:6, and 24:0 h L/D) on algal growth and lipid production were investigated. The results indicated that C. variabilis RSM09 achieved optimal growth under 20% v/v CO2 aeration, with an optical density of approximately 2.91 ± 0.27, a biomass concentration of 1.32 ± 0.14 g/L, and a lipid content of 21.96 ± 0.29% (wt.). Among the three different light intensities, higher optical density (4.20 ± 0.14), biomass (1.79 ± 0.25 g/L), and lipid content (20.75 ± 2.0% wt.) were at the 5000 Lux of light intensity. Additionally, the photoperiod of 24:0 h (L/D) produced the highest biomass at 1.86 ± 0.21 g/L, followed by the 18:6 h light/dark photoperiod with a biomass of 1.65 ± 0.17 g/L, and the 12:12 h light/dark photoperiod with 1.35 ± 0.43 g/L. In contrast, the 18:6 h L/D photoperiod yielded a higher lipid concentration of 25.22 ± 2.06% (wt.) compared to the others. All cultured microalgae showed significant effects on fatty acid composition. Palmitic (16:0), linoleic (C18:2), and linolenic (C18:3) acids were predominant in C. variabilis RSM09 under all photoperiods. This study exhibited that the microalga C. variabilis RSM09 has great potential as a feedstock for biodiesel production.

Biofilm Inhibition Activity of Fennel Honey, Fennel Essential Oil and Their Combination.

The eradication of bacterial biofilms remains a persistent challenge in medicine, particularly because an increasing number of biofilms exhibit resistance to conventional antibiotics. This underscores the importance of searching for novel compounds that present antibacterial and biofilm inhibition activity. Various types of honey and essential oil were proven to be effective against a number of biofilm-forming bacterial strains. The current study demonstrated the effectiveness of the relatively unexplored fennel honey (FH), fennel essential oil (FEO), and their combination against biofilm-forming bacterial strains Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and Escherichia coli, with a series of in vitro experiments. The authenticity of FH and FEO was checked with light microscopy and gas chromatography-mass spectrometry, respectively. Minimum inhibitory concentrations were determined using the microdilution method, and antibiofilm activity was assessed with crystal violet assay. Structural changes in bacterial cells and biofilms, induced by the treatments, were monitored with scanning electron microscopy. FEO and FH inhibited the biofilm formation of each bacterial strain, with FEO being more effective compared to FH. Their combination was the most effective, with inhibitory rates ranging between 87 and 92%, depending on the bacterial strain. The most sensitive bacterium was E. coli, while P. aeruginosa was the most resistant. These results provide justification for the combined use of honey and essential oil to suppress bacterial biofilms and can serve as a starting point to develop an effective surface disinfectant with natural ingredients.

Quasi-1D numerical analysis and Bayesian optimization of two-stage light gas gun operational parameters

Quasi-1D numerical analysis and Bayesian optimization of two-stage light gas gun operational parameters

FINEX PCI fuel diversification for techno-economical operations: Impact of high-volatile coal agglomeration on combustion

Large-scale (volume > 2000 m3) blast furnaces (BFs) requiring expensive, high-grade coal are currently used in the iron and steel industry. High-volatile coal (HVC) must provide a substitute for high-grade coal to facilitate economical operations. This study determines the applicability of HVC and thermal coal within the fine particle extraction (FINEX) and conventional BF steelmaking processes using a drop-tube furnace. Furthermore, the characteristics of single- and blending-coal-carbon conversions are analyzed using unburned carbon (UBC). In the BF, an increase in agglomeration leads to an increase in UBC, where approximately 20 % agglomeration can be achieved. However, under FINEX conditions, due to the high oxygen concentration approximately 50 % agglomeration can be achieved. To determine the principle of the agglomeration phenomenon, a chemical-percolation-devolatilization model is used to analyze the amount of tar, light gas, and char generated during the devolatilization process. Using HVC achieves 89.7 % agglomeration which generates a 30 % tar volume during devolatilization. Tar has a significant effect on agglomeration and facilitates bridging, causing agglomeration into a large particle as identified from the structural agglomeration of a scanning electron microscopy image. This phenomenon affects raceway formation and the combustion stability of pulverized coal injections.

Investigations of high-speed projectile impact on symmetric sandwich structures containing solid propellant with core perforations

The response of solid rocket motors (SRMs) to high-speed fragment impacts is crucial for their safety design and operational use in scenarios such as rocket launches and space applications. The visualized Burn to Violent Reaction (BVR) test is used to observe intense reactions induced by high-speed projectile impacts. Employing a two-stage light gas gun and optical diagnostic techniques including high-speed schlieren imaging and direct photography, the impact-induced deflagration/explosion behavior, and reaction growth behavior were investigated. The damage mechanisms of the casing and propellant samples were assessed, and the reaction growth and afterburn effects of the impact-induced fragment cloud were quantitatively analyzed. The results indicate that the ignition delay time is inversely correlated with the impact velocity, decreasing from ms to μs scale. Across a wide range of velocities (1050–2058 m/s), higher projectile velocities induce more sustained and vigorous combustion reactions within the propellant. Furthermore, increasing the propellant air gap to 7.8 cm does not trigger further reactions under the studied configurations. The reaction mechanisms are closely linked to the characteristics of the fragment cloud induced by the impact. The developed Smoothed Particle Hydrodynamics (SPH) method, incorporating material constitutive models, ignition criteria, and reaction growth models, was used to study the influence of projectile velocity on the reaction mechanisms. The simulation results were compared with experimental data, demonstrating satisfactory accuracy.

Empirical Models for Predicting Two-Stage Light Gas Gun Muzzle Velocity

Empirical Models for Predicting Two-Stage Light Gas Gun Muzzle Velocity

Dynamic Constitutive Model of Tungsten‐Whisker‐Reinforced Aluminum/Polytetrafluoroethylene Composite Material and Quantitative Determination of Impact Reaction Release Energy in Vacuum Environment

To meet the strength requirements of aluminum/polytetrafluoroethylene (Al/PTFE) in practical applications, tungsten (W) whisker is added into the traditional formula Al/PTFE (26.5%/73.5%) to improve the dynamic compressive strength of the reactive material. Mechanical properties of reactive material specimens prepared by sintering are tested. In the results, it is shown that the dynamic compressive strength of Al/PTFE‐reactive material reinforced by tungsten whisker with volume fraction of 13.1% can reach 141 MPa at strain rate of 1800 s−1. The constitutive model of dynamic compression for tungsten‐whisker‐enhanced Al/PTFE‐reactive material is constructed, and the results are basically consistent with the experimental results. The quantitative impact energy release of reactive material specimens under vacuum environment are performed by using the two‐stage light gas gun loading system, and the quantitative impact release energies of Al/PTFE‐reactive material reinforced by tungsten whisker under different whisker percentage content and diameter are obtained.

Two-Stage Global Biomass Pyrolysis Model for Combustion Applications: Predicting Product Composition with a Focus on Kinetics, Energy, and Mass Balances Consistency

This work presents a comprehensive model for lignocellulosic biomass pyrolysis, addressing kinetics, energy balances, and gas product composition with the aim of its application in wood combustion. The model consists of a two-stage global mechanism in which biomass initially reacts into tar, char, and light gases (non-condensable gases), which is followed by tar reacting into light gases and char. Experimental data from the literature are employed for determining Arrhenius kinetic parameters and key energy parameters, like tar and char heating values and the specific enthalpy of primary and secondary reactions. A methodology is introduced to derive correlations, allowing the model’s application to diverse biomass types. This work introduces several novel approaches. Firstly, a pyrolysis model that determines the composition of light gases by solving mass, species, and energy balances is developed, limiting the use of correlations from the literature only for tar and char elemental composition. The mass rate of light gases, tar, and char being produced is also determined. Secondly, kinetic parameters for primary and secondary reactions are determined following a Shafizadeh and Chin scheme but with a modified Arrhenius form dependent on Tn, significantly enhancing the accuracy of product composition prediction. Additionally, correlations for the enthalpies of reactions, both primary and secondary, are determined as a function of pyrolysis temperature. Primary reactions exhibit an overall endothermic behavior, while secondary reactions exhibit an overall exothermic behavior. Finally, the model is validated using cases reported in the literature, and results for light gases composition are presented.