High Oxygen Concentrations Research Articles

Aerobic denitrification as an N2O source from microbial communities.

Nitrous oxide (N2O) is a potent greenhouse gas of primarily microbial origin. Oxic and anoxic emissions are commonly ascribed to autotrophic nitrification and heterotrophic denitrification, respectively. Beyond this established dichotomy, we quantitatively show that heterotrophic denitrification can significantly contribute to aerobic nitrogen turnover and N2O emissions in complex microbiomes exposed to frequent oxic/anoxic transitions. Two planktonic, nitrification-inhibited enrichment cultures were established under continuous organic carbon and nitrate feeding, and cyclic oxygen availability. Over a third of the influent organic substrate was respired with nitrate as electron acceptor at high oxygen concentrations (>6.5mg/L). N2O accounted for up to one-quarter of the nitrate reduced under oxic conditions. The enriched microorganisms maintained a constitutive abundance of denitrifying enzymes due to the oxic/anoxic frequencies exceeding their protein turnover-a common scenario in natural and engineered ecosystems. The aerobic denitrification rates are ascribed primarily to the residual activity of anaerobically synthesised enzymes. From an ecological perspective, the selection of organisms capable of sustaining significant denitrifying activity during aeration shows their competitive advantage over other heterotrophs under varying oxygen availabilities. Ultimately, we propose that the contribution of heterotrophic denitrification to aerobic nitrogen turnover and N2O emissions is currently underestimated in dynamic environments.

Study on the Effect of High-Concentration Oxygen Enrichment on Engine Performance and Exhaust Emissions Using Diesel Fuel and Palm Biodiesel Substitute Fuel

Air pollution remains a big issue in many countries. One form of air pollution comes from the use of fossil fuels as the primary fuel in the power generating and transportation sectors. Diesel engines are employed in a variety of industries due to their dependability, durability, and efficiency. Enhancing the availability of oxygen within the combustion chamber is one technique for reducing exhaust gas emissions and optimizing diesel engine combustion. The aim of this study is to investigate how oxygen enrichment in diesel engines with diesel fuel and biodiesel affects their performance and emissions. The modeling in this research was carried out using AVL BOOST version 2011 software based on experimental results of the YANMAR TF 155 R-DI diesel engine at 1200 rpm with and without oxygen enrichment. Modeling was performed based on the baseline parameter of a diesel engine with gradual loads at 50%, 75%, and 100%. The oxygen concentration was increased to 30.6%, 37.8%, 45%, and 54% by mass. The results show an increase in the maximum heat release rate (HRR) and the mass fraction burned (MFB) up to 90% for both fuels. The peak heat release rate of biodiesel shifts around 6 J/degree and the brake-specific fuel consumption (BSFC) is up to 0.0035 kg/kWh higher than that of diesel fuel. When compared to diesel fuel, the thermal efficiency and BSFC of biodiesel usage are around 0.3% and 0.028 kg/kWh, respectively. NOx emissions increase due to higher combustion temperatures and more oxygen availability. Biodiesel emits 50% less NOx than diesel fuel, presumably due to a lower combustion temperature. As a result, while high-concentration oxygen enrichment improves combustion and lowers soot emissions, it raises NOx emissions. Soot emissions were reduced as a result of the enhanced combustion process, while NOx emissions rose due to higher combustion temperatures and increased oxygen availability.

Aryl hydrocarbon receptor (AhR) is regulated by hyperoxia in premature infants

Objective To investigate whether aryl hydrocarbon receptor (AhR) is involved in hyperoxia-mediated oxidative stress by observing the relationship between AhR and reactive oxygen species (ROS) in peripheral blood mononuclear cells (PBMCs) after oxygen exposure in premature infants. Methods After 48 h of oxygen inhalation at different concentrations, discarded peripheral blood was collected to separate PBMCs and plasma. ROS were labeled with MitoSOXTM Red and detected by fluorescence microscopy in PBMCs. The level of MDA in plasma was detected by thiobarbituric acid colorimetry, the level of MCP-1 in plasma was detected by enzyme-linked immunosorbent assay (ELISA), the localization of AhR was detected by immunofluorescence, and the level of AhR expression in PBMCs was detected by Western blotting. Results As the volume fraction of inspired oxygen increased, compared with those in the air control group, the levels of ROS, MDA in plasma, and MCP-1 in plasma increased gradually in the low concentration oxygen group, medium concentration oxygen group and high concentration oxygen group. The cytoplasm-nuclear translocation rate of AhR gradually increased, and the expression level of AhR gradually decreased. The levels of ROS in PBMCs, MDA in the plasma and MCP-1 in the plasma of premature infants were positively correlated with the cytoplasm-nuclear translocation rate of AhR but negatively correlated with the level of AhR expression. Conclusion Aryl hydrocarbon receptor (AhR) is regulated by hyperoxia in premature infants.

Study of direct alloying of steels by carbon reduction of Cr2O3 under vacuum

Currently, steel is mainly alloyed by adding ferrochrome alloys in the production of chromium-containing steels. However, the production of ferrochrome consumes a lot of electricity and produces a large number of additional products that are extremely harmful to the environment. For the consideration of the above problems, the experiment studied the reduction behavior of Cr2O3 using carbon powder as the reductant under different ambient pressures, different reductant dosages, and different initial oxygen contents in the molten steel. The results show that CO bubbles can be formed by decreasing the air pressure and increasing the amount of reductant, thus the reduction rate and reduction efficiency of Cr2O3 can be increased. It was found that the ambient air pressure mainly affected the reduction rate of Cr2O3, and the fastest reduction rate of Cr2O3 was found in vacuum environment. The reductant dosage has great influence on the reduction rate, reduction efficiency, density and size of inclusions of Cr2O3. Addition of carbon powder with a carbon-to-oxygen molar ratio of 2 will significantly improve the reduction rate of Cr2O3. The yield of [Cr] in steel can reach more than 95 %. In addition, the density of inclusions in steel is stabilized below 0.2/mm−2. The addition of carbon powder with nc:no ≤ 1.0 significantly reduces the reduction rate of Cr2O3 due to the decrease of carbon concentration in the steel. The density of inclusions in steel also increased significantly up to 210.4/mm−2. The initial oxygen content in the molten steel had little effect on the reduction of Cr2O3. However, the reduction rate of Cr2O3 is lower in steel with high oxygen concentration than in steel with low oxygen concentration. Under the optimum reduction conditions-nc:no = 2.0, initial oxygen content of 3 × 10−4, and ambient air pressure of 50 Pa. The yield of [Cr] in steel can reach 96.85 %, the total oxygen content can be reduced to 1.6 × 10−5, the density of inclusions is 0.04/mm−2, and the size of inclusions is below 1.8 μm.

A Comparative Analysis of HBOT and L-HBOT: An Innovative Possibility to Enhance HBOT?

Oxygen is a vital component of wound healing. When trauma occurs, causing a wound, it is difficult to get oxygen to the wound site because of the damage that is present. Hyperbaric oxygen chamber therapy (HBOT) is employed to combat hypoxia in wounds by having the patient inhale high concentrations of oxygen at elevated atmospheric pressures, accelerating the rate at which oxygen dissolves into the bloodstream at a faster rate. HBOT has been used to treat a variety of conditions like diabetic foot ulcers, Crohn’s disease, and chronic wounds. Yet, the limited body of literature and the risk of complications have limited the application of HBOT. Medical professionals have proven the significance of oxygen on wound healing from stimulating most of the vital functions to initiating the production of certain genes, oxygen is the keystone for successful complete wound healing. On the other hand, the risk of oxygen toxicity is one of the main contraindications of HBOT. Contrary to common knowledge, recent studies have shown that HBOT administered at a lower atmospheric pressure with a lower oxygen concentration can decrease this risk significantly. Low-pressure hyperbaric oxygen therapy (L-HBOT) may still be as effective as traditional high-pressure hyperbaric oxygen therapy (H-HBOT) without the unpredictable complications that medical professionals are unsure of. In all, this review aims to analyze recent studies to provide a clear comparison between these two variations of HBOT.

The effect of hyperbaric oxygen therapy on psychological state and wound healing: a case report.

Hyperbaric oxygen therapy (HBOT), in which patients receive high concentrations of oxygen in a pressurized chamber, has been used in clinical practice to improve wound healing. More recent applications of HBOT have resulted in successful management of a wide range of conditions; however, the psychosomatic factors associated with these conditions remain understudied and require clarification. To investigate the effects of HBOT in a female patient without diabetes who presented with an atypical wound of 9 years' duration with no sign of healing as well as with psychosomatic factors. The patient underwent 20 once-daily sessions of HBOT for 120 minutes per session every Monday through Friday for 4 weeks at 2.4 ATA (atmosphere absolute pressure) and received daily dressing changes with a nonadherent dressing containing silver, alginate, and carboxymethylcellulose. The 36-Item Short Form Health Survey and the Hospital Anxiety and Depression Scale quality-of-life questionnaires were administered before treatment and after 1 year of treatment. HBOT resulted in complete lasting wound remission as well as subjective improvement in quality of life and in levels of anxiety and depression. HBOT has known therapeutic effects on wound healing, and it may also have a substantial effect on psychosomatic mechanisms.

MINIMUM EXPLOSIBLE CONCENTRATION MEASUREMENTS OF HYBRID ROCKET SOLID FUEL DUST

Hybrid rockets are considered safe because there is no affinity between the fuel and oxidizer. However, if the solid fuel turns to dust, the dust might cause rapid combustion. Therefore, the dustification of fuel has been evaluated using crushing tests. In an earlier study by the authors, wax was used as a specimen. It was crushed by explosives in a balloon filled with air and oxygen. Then pressure waves near the balloon were measured. Results show that the pressure fluctuation in the oxygen-filled case was greater than that in the air-filled case, but it could not be ascertained whether this result was attributable to the combustion of the wax that had become dust or to the combustion of the wax surface which the explosive contacted. Therefore, the authors measured the lower explosion limit concentration of wax dust under atmospheric conditions and in an atmosphere with a high oxygen concentration to obtain knowledge related to the wax dust mixture flammability. A blow-up type dust explosion test apparatus was used to measure the lower explosion limit. The specimens were produced by grinding and sieving the wax pellets. Powders of four types were produced: 850 μm, 500 μm, 212 μm, and 53 μm. The dust concentration was calculated by dividing the sample mass by the volume of the explosion cylinder. Based on the test results, the lower explosion limits were identified for 212 μm and 53 μm, but not for 850 μm and 500 μm.

Exclusive generation of a superoxide radical by a porous aromatic framework for fast photocatalytic decontamination of mustard gas simulant in room air.

Mustard gas and other chemical warfare agents (CWAs) are a global threat to public security, arising from unpredictable emergencies and chemical spill accidents. So far, photocatalysts such as metal clusters, polyoxometalates and porous solids have been exploited for oxidative degradation of mustard gas, commonly with 1O2 as reactive species. However, the production of 1O2 is oxygen-dependent and requires a high oxygen concentration to sustain the detoxication process. For safety and operation process considerations, it is always preferable to rapidly detoxify dangerous chemicals in the atmosphere of room air. In this work, a porous aromatic framework, PAF-68, was synthesized as a metal-free photocatalyst. In the presence of PAF-68, fast detoxication occurred in typical room air atmosphere. The half-life (t 1/2) for the complete conversion of mustard gas simulant to nontoxic product in room air was only 1.7 min, which is comparable to the performance in pure oxygen, surpassing that of any other porous photocatalysts. It was found that ˙O2 - rather than 1O2 is the predominant reactive species initiated by PAF-68 for mustard gas detoxication. Unlike the formation of 1O2 which prefers the environment of pure oxygen, generation of the ˙O2 - is an oxygen-independent process. It is suggested that amorphous PAFs possess low exciton binding energy and long decay lifetime, which facilitate the generation of ˙O2 -, and this offers a general design strategy to detoxifying chemical warfare agents under real-world conditions.

Research progress on high-concentration oxygen therapy after cerebral hemorrhage.

Recently, the role of high-concentration oxygen therapy in cerebral hemorrhage has been extensively discussed. This review describes the research progress in high-concentration oxygen therapy after cerebral hemorrhage. High-concentration oxygen therapy can be classified into two treatment methods: hyperbaric and normobaric high-concentration oxygen therapy. Several studies have reported that high-concentration oxygen therapy uses the pathological mechanisms of secondary ischemia and hypoxia after cerebral hemorrhage as an entry point to improve cerebral oxygenation, metabolic rate, cerebral edema, intracranial pressure, and oxidative stress. We also elucidate the mechanisms by which molecules such as Hypoxia-inducible factor 1-alpha (HIF-1α), vascular endothelial growth factor, and erythropoietin (EPO) may play a role in oxygen therapy. Although people are concerned about the toxicity of hyperoxia, combined with relevant literature, the evidence discussed in this article suggests that as long as the duration, concentration, pressure, and treatment interval of patients with cerebral hemorrhage are properly understood and oxygen is administered within the treatment window, it can be effective to avoid hyperoxic oxygen toxicity. Combined with the latest research, we believe that high-concentration oxygen therapy plays an important positive role in injuries and outcomes after cerebral hemorrhage, and we recommend expanding the use of normal-pressure high-concentration oxygen therapy for cerebral hemorrhage.

Oxidation behavior and kinetics of shale oil under different oxygen concentrations

The oxidation behavior and kinetics of crude oil within tight shale differ from those of traditional light and heavy oils. In this study, the static oxidation tests on tight shale samples were conducted under different oxygen concentrations (11%, 16%, 21%, and 26%), followed by analysis of effluent gas and oxidized oil. Specifically, the compositional changes in shale oil at the molecular level were studied. Additionally, the self-ignition potential of shale oil under different oxygen concentrations was evaluated using accelerating rate calorimetry, and the corresponding kinetic parameters were determined. The results indicated that as the oxygen concentration increased from 16% to 26%, the relative abundance of O1 species decreased from 10.96% to 8.66%, whereas that of O3 species increased from 6.16% to 8.46%. Also, the relative abundance of chain saturated aliphatic acids and tricyclic naphthenic acids was observed to decrease and increase, respectively, in the shale oil oxidized at 26% oxygen concentration compared to the other shale oils oxidized at oxygen concentration lower than 26%. The shale oil displayed significant oxidation activity under different oxygen concentrations (16%, 21%, and 26%), and an increased oxygen partial pressure resulted in a shorter induction period of oxidation and higher combustion intensity. The kinetics results showed that the combustion activity of coke was enhanced while increasing oxygen concentration from 16% to 26%. The shale oil encountered fewer concentration-dependent oxidation reactions under higher oxygen concentration. Overall, this study provides valuable insights into the oxidation behavior of crude oil within tight shale.

The use of small emitter flow rate in drip irrigation favored methane uptake in arid potato fields

Drip irrigation has been widely used in agriculture, while the mechanism underlying the effect of drip irrigation system design and management on soil methane (CH4) uptake have not been fully studied. A two-year experiment was conducted to explore the effects of different emitter flow rates of drip irrigation (1.3, 2.0, and 3.0 L/h) on CH4 uptake in potato fields in an arid region of Northwest China. Results showed that compared to emitter flow rates of 2.0 and 3.0 L/h, the 1.3 L/h flow rate significantly increased the cumulative CH4 uptake by 6.3–16.2%, mainly due to the increase in the abundance of the pmoA gene by 15.2–49.5%, and by the decrease of water-filled pore space (WFPS), increasing the effective CH4 diffusion coefficient (Dp) and soil oxygen concentration in the topsoil. A hump-shaped relationship was found between WFPS and CH4 uptake flux, and the optimum WFPS for CH4 uptake was about 44.8%. The treatment with an emitter flow rate of 1.3 L/h exhibited the highest frequency (28.6%) of favorable WFPS for CH4 uptake, compared to the 2.0 and 3.0 L/h treatments. In addition, significant negative quadratic relationships were observed between both Dp and soil oxygen with CH4 uptake, and optimal values were 0.02 cm2 s−1 and 18.7%, respectively. There was no significant difference in CH4 uptake between 2.0 and 3.0 L/h treatments in 2021 and 2022, due to high WFPS and low oxygen concentrations in both treatments. Multiple linear regressions indicated that soil oxygen concentration became a major limiting factor under emitter flow rates of 2.0 and 3.0 L/h. This study provides insights into mechanisms of soil CH4 uptake in drip-irrigated farmland, which gives guidance on developing irrigation strategies for sustainable production and CH4 mitigation in irrigated arid land.

(Invited) the Removal of Bisphenols from Wastewaters with Atmospheric Pressure Plasma

Bisphenols represent one of the most recognised harmful contaminants found in environment as a result of their extensive use for the industrial production of polycarbonate, epoxy resins, and thermal paper. They are known for their ability to act as endocrine disruptors, as well as for their potential to cause genotoxicity and cytotoxicity. 1. Although the awareness of their toxicity is high and the use of some of their representatives already limited or restricted in EU 2, they still represent a potential threat for public health. Due to their insufficient elimination with standard water treatment methods, the effluent from the wastewater treatment plants continues to be the major source of bisphenol environmental contamination. Thus, it is necessary to develop a new more efficient method.Cold atmospheric pressure plasma (CAP) is a promising technology with tremendous potential in removal of various hazardous contaminants from wastewater 3. Essentially, plasma is the fourth state of matter, created by introducing gas into a strong electrical field resulting in ionisation, dissociation, and excitation of gaseous molecules. CAP, which is produced by using air and electricity, is a source of high concentration of reactive oxygen and nitrogen species (RONS). This property makes it a highly promising, cost-effective, and environmentally-friendly method for decontamination 4.To demonstrate its potential, we investigated the application of air CAP for the removal of bisphenol A (BPA) and bisphenol S (BPS) from aqueous systems. Plasma was generated with surface barrier discharge systems, using different exposure times and discharge operating powers, which led to the formation of different plasma chemistries. Additionally, radical scavenger methanol was used to simulate environmental conditions. The highest degradation efficacies were observed at longest exposure time (480 s) and at high discharge power and was significantly affected by the presence of methanol. Moreover, radical scavenger influenced the formation of CAP generated RONS in liquid as well, resulting in lower concentrations of ˙OH, H2O2, and NO2 -. With non-target approach, we were able to identify 11 BPA and 5 BPS transformation products (TPs) and propose transformation pathways of both compounds. The toxicological examination performed with in vitro HepG2 cell model demonstrated that the mixture of transformation products formed during CAP treatment is less toxic than BPA and BPS. According to these results it was suggested that CAP is an effective and safe method for degradation of bisphenols. The European Parliament and the Council. Regulation (EU) 2020. Official Journal of the European Union.2018/840/EC. Commission Implementing Decision (EU) 2018/840 of 5 June 2018 Establishing a Watch List of Substances for Union-Wide Monitoring in the Field of Water Policy. J. Eur. Union 2018, L 141 (March 2015), 9–12.Sanito, R. C.; You, S. J.; Wang, Y. F. Degradation of Contaminants in Plasma Technology: An Overview. Hazard. Mater. 2022, 424 (PA), 127390.Dickenson A.; Morabit Y.; Hasan M. I.; Walsh J. L. Directional mass transport in an atmospheric pressure surface barrier discharge. Scientific Reports 2017, 7, 14003.

Temporal evolution and mechanism of secondary streamers in N2/O2 mixtures at atmospheric pressure under DC voltage

In this work, the temporal evolution of secondary streamers in N2/O2 mixtures at atmospheric pressure under DC voltage were investigated using a two-dimensional axisymmetric fluid model. The effects of voltage amplitude, polarity and oxygen concentration were analyzed. The propagation of secondary streamers is divided into two stages: fast propagation followed by slow propagation. The interior of secondary streamers is filled with positive space charges, while the exterior contains negative space charges. The reduced electric field in the secondary streamer is initially linearly proportional to the applied voltage and decreases linearly with the length of secondary streamers. The length of secondary streamers is primarily determined by the applied voltage, regardless of the oxygen concentration. A reversed propagation direction is simulated under negative applied voltage. We propose a different mechanism for secondary streamers. The high-density positive charge layer near the electrode initiates the propagation of secondary streamers, and the extension of positive charge region dominates the propagation. The distribution of electric field along the channel is mainly determined by the distribution of net space charge. The propagation direction is opposite to the direction of electron drift. The secondary streamer eventually stagnates due to the decrease in electron density in high oxygen concentration, while it is caused by the uniform current density at the front of the secondary streamer in low oxygen concentration.

Solute-solute interactions in dilute Nb-X-O alloys from first principles

Recent efforts to develop Refractory Multi-Principal Element Alloys (RMPEAs) for high temperature applications have led to a renewed interest in elucidating fundamental properties of refractory metals. These metals can dissolve high concentrations of interstitial oxygen to the detriment of their mechanical properties and oxidation resistance. Strategies are therefore sought to control the oxygen solubility of refractory alloys. Even in simple dilute refractory alloys, the underlying mechanisms driving binding energies between substitutional solutes and oxygen is not fully understood. We have used first principles calculations of Nb-X-O alloys to examine the interactions between interstitial oxygen and dilute substitutional solutes X = Al, Si, Sc, Ti, V, Cr, Y, Zr, Mo, Ru, Hf, Ta, W, and Re in BCC Nb. Electronegativity differences drive charge transfer between the Nb matrix and both the substitutional and interstitial solutes. This transfer of charge results in strong electrostatic interactions at short distances that play a key role in determining X-O binding energies. The solute misfit volume, which leads to local straining of the surrounding BCC Nb lattice, is also found to have a strong effect on the X-O binding energies. Finally, we identify a repulsive interaction, of significance for a subset of X-O pairs, that arises from a closed-shell hybridization between localized orbitals on solutes.

Superior corrosion resistance of a slurry FeAl coating on 316LN stainless steel in 550 ℃ liquid lead-bismuth eutectic

An intermetallic Fe-Al coating was successfully produced on 316LN austenite stainless steel by slurry Aluminizing. The coating greatly enhanced the corrosion resistance of substrate in LBE (lead-bismuth eutectic) containing low (10−7 wt%) and high (1.8 ×10−3 wt%) oxygen concentrations at 550 ℃ and the coating was mostly intact after 1500 h exposure test. The high corrosion resistance results from the formation of a uniform layer of alumina oxide on the coating which can be achieved when the dissolved oxygen is above 10−18 wt%. This FeAl coating maybe a promising option for protecting structure material in the fourth LBE-cooled fast reactor.

Low abundance and high patchiness of decapod fauna sampled with van Veen grab on the West African continental margin (Gulf of Guinea, Ghana)

Sixty morphospecies of Decapoda (Malacostraca: Crustacea) representing 34 families were recorded in the material collected in 2012 from 265 van Veen grab (0.1 m2) samples, from the nine transects distributed along the coast of Ghana in the 25–1000 m depth range. The examined material was dominated by the Diogenidae, Panopeidae, Leucosiidae, Pilumnidae and Xanthidae families. Species accumulation curves showed undersampling of the studied area and a large number of the morphospecies comprised singletons and doubletons. Panopeus africanus was the most frequent morphospecies in the analysed material (9.1% of all samples). We observed a substantial decrease of diversity (Shannon Index) and abundance along a depth gradient. Species richness also decreased with depth, starting from the highest number of morphospecies ‒ 38 at 25 m depth, then 33 at 50 m, 17 at 100 m, 11 at 250 m, 8 at 500 m and ending with 1 morphospecies at 1000 m bottom depth. Higher diversity was observed on the continental shelf (25–250 m – 57 morphospecies), while on the slope (500–1000 m) only eight morphospecies were recorded. Numerous factors of natural and anthropogenic origin may affect decapod communities on the coast of Ghana. Since our material was collected using a sampler collecting material at a very small scale, the observed patterns might be affected by the sampling method.

Reverse combustion propagation in an oxygen-limited and -enriched N2/O2 flow for a bed packed with rice husk

Propagation characteristics of reverse combustion significantly impact the conversion of solid fuels in packed beds, especially under variable reaction atmosphere conditions. In this study, the propagation of reverse combustion was experimentally studied in an oxygen-limited and -enriched O2/N2 flow with an oxygen concentration range of 21–100 % for a bed packed with rice husk. The temperature profile measured by thermocouples along the bed height was processed to appreciate the driving mechanism of combustion front, as well as the reaction structure inside the bed. Besides, the contribution of volatiles gas-phase oxidation and char surface oxidation to reverse combustion was also evaluated. Results show that compared to the air case, an oxygen-enriched condition broadens the operating range of oxygen flow rate for the oxygen-limited reverse combustion. Under high oxygen concentration conditions, the low-temperature oxidation of rice husk inside the reaction front becomes enhanced. Such chemical reaction effect widens the whole reaction front thickness and thereby reduces the oxidation intensity in local regions, resulting in a faster ignition rate and a lower temperature for combustion front. It is found that this process is dominated by the gas-phase oxidation of volatiles, of which oxygen consumed is above 60 % of the supplied. As oxygen concentration increases, the gas-phase oxidation of volatiles becomes further enhanced. Correspondingly, the oxidation ratio of char is gradually approaching a limit, about 12 %, especially at the oxygen concentration above 50 %. These findings will facilitate a better fundamental understanding of driving mechanism of this special combustion process and thereby provide an important theoretical basis for efficient thermal conversion of solid fuels.

On-site catalytic wastewater remediation by sustainably produced H2O2 via scalable single-atomic Fe-incorporated Janus membrane

Electrosynthesis of hydrogen peroxide (H2O2) from oxygen is a green and sustainable route toward on-site wastewater treatment. Nevertheless, the performance mismatch of the catalyst species and gas-diffusion components gives rise to low O2 utilization efficiency and limited H2O2 production rate in a practical cell. Herein, we propose a flexible and scalable Janus electrode comprising hydrophilic single-atomic Fe-incorporated catalytic layer and hydrophobic gas-attraction layer. The hydrophobic layer enables efficient oxygen diffusion, and the hollow-structured catalysts allow oxygen gas trapping with a high local oxygen concentration, resulting in a high Faradaic efficiency and fast H2O2 production rate. Accordingly, an 80 h electrocatalytic H2O2 synthesis could be gained at 80 mA cm−2. The Janus electrode delivers a H2O2 selectivity of 92% and a yield of 592 mmol g−1 h−1 in a flow cell. The thus-produced H2O2 allows for an in situ antibiotic removal, with the potential for on-site eco-restoration.

A Computational Fluid Dynamics Analysis of Hydrogen Leakage and Nitrogen Purging of a Solid Oxide Fuel Cell Stack

A computational study of the nitrogen purging of a solid oxide fuel cell stack enclosed in a hot box is presented. The stack operates on ammonia as a fuel, and in the case of a hydrogen leakage, the entire compartment is immediately purged with nitrogen to ensure that there are no regions with high oxygen concentrations. In addition to this, the speed at which a hydrogen leak can be detected is determined. The results are then compared to a case with a relocated nitrogen inlet. A computational fluid dynamics (CFD) model is developed using the Reynolds-averaged Navier–Stokes equations for compressible flow in combination with conservation of energy and species equations in OpenFOAM. The results suggest that for the maximum concentration of oxygen to be below 5%, the hot box should be purged for 35 s, corresponding to 1.1 kg of nitrogen, if the hot box was already heated. If the hot box was at T = 300 K, it should be purged for 95 s, corresponding to 3.0 kg of nitrogen. The purge of the heated hot box results in a heat loss of 18 kW on average. A leak could be detected in 3.2 s during open circuit voltage tests. Changing the location of the outlet does not affect the cold purge, but results in a minimum purge period of 48 s during the hot purge, and the leak could be detected in 2 s. This paper demonstrates how CFD methods can be employed in order to address questions related to hydrogen safety.

Influence of PODE1 additive into ethanol-gasoline blends (E10) on fuel properties and phase stability

Polyoxymethylene dimethyl ethers (PODEn, n = 1–8) as an oxygenated fuel are a promising alternative fuel with a high oxygen concentration, a low C:H ratio, and no C–C bonds in their chemical structure. This could lead to smoke-free combustion. In this study, we chose to focus on PODE1 because of its lower cetane number, which makes it more suitable for use in spark ignition (SI) engines. However, its lower boiling point and octane number remain challenges. A low boiling point may lead to high vapour pressure and require storage and handling comparable to gaseous fuels. We investigated the effect of adding PODE1 to gasoline-ethanol blends (E10) on fuel properties, including distillation curve, octane number, phase stability, C/O/H ratio, heat of combustion, kinematic viscosity, and density. Our results showed that the blended fuels of E10 and PODE1 are stable up to 10 % PODE1, and there was no phase separation. Additionally, up to 10 % PODE1 additive had no significant side effect on the fuel properties of E10, particularly boiling point and octane number. Thus, work offers creative points by proposing a new candidate for additive fuel to gasoline-ethanol blends, which contributes to reducing the soot emission of GDI engines.