High Oxygen Concentrations Research Articles

(Keynote) Experimental Insights for Extra-Terrestrial Application of Molten Oxide Electrolysis

Molten oxide electrolysis (MOE) has been considered for several decades for oxygen generation from extra-terrestrial oxides. It consists in the electrolytic decomposition of the rocks or soils, which are mixture of the common earth oxides (silica, iron oxide(s), alumina, magnesia...). Therein the oxides mixture is acting as the electrolyte, in the molten state. The target anodic product is oxygen gas, and the cathodic product is a metal. In one version of MOE, the temperature is high enough to sustain the production of a liquid metal, offering the opportunity to conceive a fully continuous process thanks to periodic tapping of the cathodic product. A key attribute of such approach is the high current density (productivity) that can be anticipated thanks to the high concentration of oxygen and metal present in the electrolyte. This leads to electrochemical engineering questions that are not commonly discussed in other electrolysis methods. This presentation offers to review some of the prior findings related to the underlying thermodynamic of the process, as well as the oxygen evolution and transport phenomena that support the development of MOE. Recent findings combining a container-less method and advanced electrochemical techniques will be presented.

Rationalizing the impact of oxygen vacancy on polysulfide conversion kinetics for highly efficient lithium-sulfur batteries

The “shuttle effect” of lithium polysulfides (LiPSs) is a huge challenge for practical use of high-energy-density lithium-sulfur (Li-S) batteries, and one of the main reasons is the sluggish kinetics of sulfur conversion. Metal oxides are able to expedite the sulfur electrochemistry, and the structural defects enhance the adsorption-conversion ability of metal oxides for polysulfides. However, a significant research gap still remains regarding the relationship between the oxygen vacancy concentration and the adsorptive-catalytic performance of metal oxides. Herein, we establish a correlation between oxygen vacancy concentration and adsorptive-catalytic properties by using tungsten oxide (WOx) as model catalysts. It is revealed that high-concentration oxygen vacancy is beneficial for enhancing the binding between tungsten oxide and LiPSs, reducing the energy barrier of Li2S decomposition, and promoting polysulfide conversion kinetics. Consequently, the Li-S batteries using the tungsten oxide with high-concentration oxygen vacancies deliver high initial discharge capacity of 1169 mA h g−1 at 0.2 C and 865 mA h g−1 at 2 C, low attenuation rate of 0.064% per cycle over 1100 cycles at 2 C. With a high sulfur area loading of 5.34 mg cm−2, the Li-S batteries still exhibit high initial gravimetric capacity of 982 mA h g−1 at 0.1 C and areal capacity of 5.92 mA h cm−2. This work promotes the feasibility of defect engineering on metal oxides as an effective mean to enhance the practicality of Li-S batteries.

Hyperbaric Oxygen Therapy: An Emerging Therapy for Post–COVID-19 Condition

What Is the Issue?
 
 Post–COVID-19 condition presents an important challenge to health care decision-makers in Canada and across the world due to the high volume of potential patients, diverse presentations of symptoms, few clinical guidelines and treatments, and unknown pathophysiology.
 
 What Is the Technology?
 
 Hyperbaric oxygen therapy (HBOT) is an established treatment for certain wound injuries, vascular conditions, and in specific medical emergencies. It is now being tested for post–COVID-19 condition, also known as long COVID. The therapy delivers a high concentration of oxygen inside specialized pressure chambers. HBOT has been proposed as a treatment to help resolve prominent symptoms of post–COVID-19 condition, such as fatigue and brain fog. The therapy may induce physiological changes that aid in recovering from the long-term effects and tissue damage due to severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) infection.
 
 What Is the Potential Impact?
 
 Results from early studies indicate that HBOT could improve a range of post–COVID-19 symptoms and its use is generally safe with few adverse effects. These results are based on 2 randomized control trials and small nonrandomized studies and case reports. However, published results have been based on studies with limited sample sizes and limited long-term follow-up.
 HBOT could offer a therapy option that could support millions of people around the world with post–COVID-19 condition if the ongoing and subsequent studies show efficacy.
 
 What Else Do We Need to Know?
 
 As of now, there are uncertainties about how to effectively deliver and dose the therapy and the potential safety implications for people with post–COVID-19 condition. Implementation considerations, such as the number and location of hyperbaric oxygen chambers, will be important if HBOT is appropriate for a large number of people. As the evidence base develops, the potential role of HBOT in therapy for people with post–COVID-19 condition will become clearer and will provide an indication of what kind of health system planning may be needed to provide HBOT for those who can benefit.

Enhanced mechanical performance of duplex stainless steels via dense core-shell nano-inclusions in-situ formed upon selective laser melting

In this study, with aid of selective laser melting (SLM) and minor Ti addition, we obtain a high density of core-shell structured nano-inclusions with an oxide core and a TiN shell in an S2205 DSS, where the high oxygen concentration originates from the severe oxygen contamination during the making of feedstock powders. These nano-inclusions can not only refine the microstructure by inhibiting the motion of austenite/ferrite interfaces upon the post-SLM annealing, but also contribute to a notable precipitation strengthening increment up to ∼230MPa. The current nano-inclusions strengthened DSS exhibits an attractive mechanical performance with a tensile strength of ∼910MPa and a total elongation of ∼52% yet non-deteriorative corrosion resistance, which has surpassed most of the reported 2205 DSSs. Our results provide a novel route for developing a wide range of nano-architectured SLM alloys with drastically enhanced properties.

Study on Nitrogen Injection Fire Prevention and Extinguishing Technology in Spontaneous Combustion Gob Based on Gob-Side Entry Retaining.

Under the gob-side entry retaining mining mode with roof cutting and pressure relief (GERRC), the gob and retained roadway section are interconnected to create an open area. Owing to the increased airflow, the coal remnants in the gob are more prone to spontaneous combustion. This study aimed to investigate the distribution of oxygen concentration within a gob and identify optimal parameters for nitrogen injection. The engineering context was the "110 method" introduced in the 1201 working face of the South Five mining area at Daxing. Computational fluid dynamics simulation software was used to analyze the effects of various nitrogen injection treatment parameters on the overall performance of the gob, including their impact on oxygen distribution. The simulation results showed that air leakage within the gob primarily originates from the working face adjacent to the intake roadway, as well as gaps within the retained roadway. The increased air leakage causes the high O2 concentration range in the gob to expand, and the retained roadway section is connected to an area with a high concentration of oxygen near the working face, which increases the risk of residual coal spontaneous combustion. The results show that the optimal nitrogen injection conditions for inerting and reducing the risk of spontaneous combustion within the gob require an injection quantity of 500 m3/h, with the injection point located at a depth of 60 m. With these parameters, the range of the oxidation zone was significantly reduced. To monitor the O2 concentration and temperature change curves in the gob during the project implementation, a bundle tube monitoring system was used, considering the actual mining situation. By varying the nitrogen injection spacing and quantity, we found that injecting nitrogen at a spacing of 30 m and at a quantity of 500 m3/h effectively placed most areas of the gob in the suffocation zone, reducing the risk of spontaneous combustion of residual coal. The accuracy of the simulation was verified. The study offers valuable insights into improving safety in coal mines and reducing spontaneous combustion incidents, providing important reference significance for fire prevention and control.

KLa based scale-up cultivation of the extremophilic archaeon Sulfolobus acidocaldarius: from benchtop to pilot scale.

The two major scale-up criteria in continuously stirred bioreactors are 1) constant aerated power input per volume (Pg/Vl), and 2) the volumetric O2 mass transfer coefficient (kla). However, Pg/Vl is only influenced by the stirrer geometry, stirrer speed, aeration and working volume, while the kla is additionally affected by physiochemical properties of the medium (temperature, pH, salt content, etc.), sparging of gas and also by the bioreactor design. The extremophilic archaeon Sulfolobus acidocaldarius, thriving at 75°C and pH 3.0, has the potential for many biotechnological applications. However, previous studies imply that the family Sulfolobaceae might be affected by higher oxygen concentration in the headspace (>26%). Hence, adequate oxygen supply without being toxic has to be ensured throughout the different scales. In this study, the scale-up criteria Pg/Vl and kla were analyzed and compared in a 2L chemostat cultivation of S. acidocaldarius on a defined growth medium at 75°C and a pH value of 3.0, using two different types of spargers at the same aerated power input. The scale-up criterion kLa, ensuring a high specific growth rate as well as viability, was then used for scaleup to 20L and 200L. By maintaining a constant kla comparable dry cell weight, specific growth rate, specific substrate uptake rates and viability were observed between all investigated scales. This procedure harbors the potential for further scale-up to industrial size bioreactors.

Co-feeding strategy alleviates hypoxic stress in large-scale bioreactor for optimal production of secretory recombinant proteins in Pichia pastoris.

The loss of mixing efficiency inherent to bioreactor process operated at large-scale yields to the formation of concentration gradient and thus to heterogeneous culture conditions. For processes operated with methanol feeding, P. pastoris faces oscillatory culture conditions that significantly affect the cell ability to produce secretory recombinant proteins at high yield. Extended cell residence time in microenvironments of high methanol concentration and low oxygen availability that are typically found in the upper part of the bioreactor near the feeding point, triggers the unfolded protein response (UPR) and thus impairs proper protein secretion. Methanol co-feeding with sorbitol was shown herein to reduce the UPR response and to restore productivity of secreted protein.

Remediation and mitigation measures to counteract orchard soil degradation by treated wastewater irrigation

Recent studies have shown that long-term irrigation with treated wastewater (TWW11Treated wastewater irrigation (TWW): Freshwater (FW): Blended TWW:FW in a 1:1 ratio (MIX): Low-frequency TWW-irrigation (LFI): TWW irrigated tuff trenches (TUF)) can lead to land degradation and reduction of crop performance in clayey soils due to additions of salts and organic compounds. This study investigated the effects of two remediation and two mitigation methods intended to alleviate the damage to soil properties following long-term irrigation with TWW. The experiment was conducted in a ‘Hass’ avocado orchard (Persea americana Mill.) grown on a clayey soil irrigated with TWW since 2009. The treatments implemented in 2016 included: TWW (control), freshwater (FW), blended TWW:FW in a 1:1 ratio (MIX), low-frequency TWW-irrigation (LFI), and TWW irrigated tuff trenches (TUF). The results showed that FW and MIX significantly reduced total salinity, salinity-related ions (Na and Cl), and sodium adsorption ratio (SAR) to (i) depths of 90 cm and 30 cm under drippers, respectively, and (ii) depths of 60 cm (except for chloride) and 30 cm between drippers, respectively, compared with TWW. TUF and LFI reduced soil salinity and sodicity under drippers but not between drippers compared with TWW. Moreover, FW significantly increased aggregate stability to a depth of 30 cm. TUF had the highest oxygen concentration in the root zone (35 cm depth), followed by FW. Considering the scarcity of freshwater, MIX and TUF are suggested as possible measures for reducing soil salinity and sodicity, and increasing aeration of clayey soils under long-term irrigation with TWW, respectively. Our findings contribute valuable insights into strategies for remediating and mitigating the detrimental effects of TWW irrigation on soil, thus promoting sustainable agriculture in regions facing water scarcity.

Comparison of the Effectiveness of Nasal Cannula Versus Face Mask With Reservoir Bag in Postoperative Patients Undergoing General Anesthesia: A Prospective Randomized Controlled Trial.

High-concentration oxygen delivery via a face mask (FM) with a reservoir bag is a common practice to prevent postoperative hypoxemia; however, it may also lead to atelectasis and other respiratory complications. Lower concentrations delivered via nasal cannula (NC) may be equally effective in preventing postoperative hypoxemia. The present study aimed to compare peripheral oxygen saturation (SpO_2) delivered via NC versus FM with a reservoir bag in patients who have undergone general anesthesia (GA). Eighty-four patients scheduled for GA were randomized to receive either oxygen via NC (NC group, n = 42) or FM with a reservoir bag (FM group, n = 42) for 30 minutes after GA at a postanesthesia care unit (PACU). All patients were assessed based on SpO_2 value, adverse events, and patient satisfaction (measured using a 100-mm visual analog scale). The overall difference between groups in the change of SpO_2 over 30 minutes at the PACU was -0.004 (95% confidence interval, -0.015 to 0.008; P = 0.527). SpO_2 during the first five minutes was lower in NC group, but the difference was not statistically significant. No desaturation occurred in either group, and there was no observed difference between groups in terms of adverse events. Patient satisfaction scores were also similar (P = 0.612). Oxygen supplementation via NC and via FM with a reservoir bag were equally effective in preventing postoperative hypoxemia after GA.

Enhanced transmittance of Y2O3 transparent ceramics from near-UV to near-infrared through reduced atmosphere annealing

Y2O3 transparent ceramics were annealed under different atmospheric conditions. The samples annealed in H2 containing atmosphere were colorless and had high in-line transmittances from the near-UV to the mid-infrared wavelength range. This is due to the elimination of carbon contamination and preventing the formation of high concentration oxygen interstitial defects in the sintered samples. Annealing in oxygen containing atmosphere resulted in stronger optical absorption in the visible wavelength region. High temperature annealing in O2 or hot isostatic pressing under high partial pressure of O2 (O2 HIP) led to obviously declining of transparency in a broader wavelength range of 230–800 nm. The Er:Y2O3 ceramics annealed in H2 containing atmosphere had high in-line transmittance of about 80% at 400 nm as well. Room temperature laser oscillation at 2.7 µm was also obtained on the 5%H2/95%Ar atmosphere annealed Er:Y2O3 ceramics.

Combustion and Emission of Castor Biofuel Blends in a Single-Cylinder Diesel Engine

Fossil fuels confront the problem of strategic resource depletion since they have been continuously utilized for more than 200 years and cause serious damages to the ecological environment of the planet. In this work, the transesterification of castor plant oil was utilized to make biodiesel, and castor biodiesel’s physicochemical qualities were assessed. On a single-cylinder, four-stroke, water-cooled agricultural diesel engine, an experimental study was conducted to compare and analyze the engine performance and emission characteristics of diesel and biodiesel blends in various amounts. The B20, B40, B60, and B80 biodiesel blends were evaluated at different engine speeds (1200, 1400, 1600, and 1800 rpm) with a constant engine load (50%). According to the experimental findings, the brake thermal efficiency (BTE) declines as the engine speed rises, and the biodiesel fuel blend has a lower brake thermal efficiency (BTE) than diesel fuel because of its higher density and viscosity and lower calorific value. The amount of gasoline required to create power increases as the speed does, and the brake-specific fuel consumption (BSFC) trend is upward. Due to their low calorific value and high viscosity properties, biodiesel blends have a greater brake-specific fuel consumption (BSFC) than diesel. The fuel’s exhaust gas temperature (EGT) has an upward trend with an increased rotational speed. The biodiesel blend’s high cetane number shortens the ignition delay and lowers the exhaust gas temperature (EGT) compared to diesel. A fuel with oxygen added, biodiesel enhances combustion, increases the combustion temperature, speeds up the oxidation process, and lowers carbon monoxide (CO) and hydrocarbon emissions. B80 produces the lowest carbon monoxide and hydrocarbon emissions at 1800 rpm, at 0.33%, and 30 ppm, respectively. On the other hand, increased carbon dioxide (CO2) emissions result from a high oxygen concentration. In addition, compared to diesel fuel, biodiesel’s greater combustion temperature causes the creation of increased nitrogen oxide (NOx) emissions. According to the research findings, a castor biodiesel fuel blend is an excellent alternative fuel for engines since it can be utilized directly without modifying the current engine construction and has good engine and exhaust emission performance.

Mechanism of heel build-up on adsorbents through oxygen induced reactions

Oxygen induced reactions during the desorption of volatile organic compounds (VOCs) from adsorbents (such as activated carbon) promote heel buildup and reduce the adsorbent’s lifetime. This study aims to improve the understanding of heel build-up mechanisms in the presence of oxygen in the desorption purge gas. Three activated carbons (ACs) and one zeolite adsorbent were exposed to an extreme condition of 1,2,4-trimethylbenzene (TMB) and high oxygen concentration at three temperatures (150, 200, and 250 °C). Thermogravimetric analysis and gas chromatography-mass spectrometry (GC–MS) were used to assess the thermal stability and chemical structure of the formed heel, respectively. Additionally, nitrogen adsorption was performed to evaluate the effect of heel formation on the adsorbent’s pore properties. Increasing the desorption temperature in the presence of oxygen was found to reduce the BET surface area and increase the oxygen-induced reactions on the adsorbents. Among the three tested temperatures, minimum heel formation was obtained at the intermediate temperature, 200 °C. Compared to zeolite, ACs were more susceptible to oxygen induced reactions at elevated temperatures due to their wide pore size distribution. Further analysis using GC–MS revealed that oxygen presence during the desorption process can form a broad range of organic species in terms of molecular weight, chemical structure, and functional group.

Effect of Oxygen Concentration on the Growth and Cathodoluminescence Properties of MgO Nanowires

MgO nanowires were grown by a thermal evaporation method at different N2/O2 gas ratios in order to investigate the effect of oxygen concentration on the growth and luminescence properties of the MgO nanowires. A thermal evaporation process was conducted at 1000oC and under a pressure of 500Torr. No nanowires were grown in a pure N2 gas atmosphere. Nanowires were formed at oxygen concentrations above 25% in a mixture of N2 and O2 gases. X-ray diffraction analysis showed that the MgO nanowires had a cubic crystal structure. Compared to the nanowires formed at high oxygen concentration, the nanowires grown at low oxygen concentration had larger diameters and rougher side surfaces. Nanowires with very smooth side surfaces were formed at high oxygen concentrations. The difference in surface roughness was supposed to be due to the change in the growth habit of nuclei. Two visible emissions were observed in the cathodoluminescence spectra of the MgO nanowires. One was an emission peak centered near 400 nm and the other was an emission peak with a central wavelength of 500 nm. As the oxygen concentration increased, the emission intensity of the 400 nm band decreased and the emission intensity of the 500 nm band increased. The maximum emission at 500 nm was observed from the nanowires formed in a pure O2 atmosphere. The full width at half maximum of the emission peak at 500 nm was narrower than that of the emission peak at 400 nm.

Diluted oxygen realizes high productivity of 2,5-Furandicarboxylic acid under ambient temperature

The oxidation of biomass-derived 5-hydroxymethyl furfural (HMF) into 2,5-Furandicarboxylic acid (FDCA) is a favorable reaction since FDCA is an ideal alternative to petroleum-based monomer terephthalic acid in bio-based polyester industry. However, producing FDCA with high yield under mild conditions is still challenging, especially at energy-saving near-ambient temperatures. Here, we present a Pd nanoparticles catalyst supported on Vulcan XC-72 carbon (Pd/VC) that can completely convert HMF and achieve an encouraging FDCA yield (92.4%) at 30 ℃. The most important observations include yield declines at pure oxygen bubbling, and the transformation of intermediates becomes stagnant; instead, switching to the diluted oxygen is effectively driving the tandem oxidation as the over-oxidation, and thus, rapid deactivation of the Pd surface could be alleviated. The negative effect of high oxygen concentration also occurs in the dehydrogenation and oxygenation of an extended substrate. Since the decisive influence of oxygen content has often been neglected in past investigations of oxidative transformation over Pd-based catalysts, the current study may offer a critical reminder for other liquid-phase oxidation reactions.

Arterial partial pressure of oxygen as a marker of airway closure does not correlate with the efficacy of pre-oxygenation: A prospective cohort study.

The prerequisites for the early formation of anaesthesia-related atelectasis are pre-oxygenation with its resulting high alveolar oxygen content, and airway closure. Airway closure increases with age, so it seems counterintuitive that atelectasis formation during anaesthesia does not. One proposed explanation is that pre-oxygenation is impaired in the elderly by airway closure present in the waking state. The extent of airway closure cannot be assessed at the bedside, but arterial partial pressure of oxygen (PaO2) as a surrogate variable of the resulting ventilation to perfusion mismatch can. The primary aim was to test the hypothesis that a decreased efficacy of pre-oxygenation, measured as the fraction of end-tidal oxygen (FE'O2) after 3 min of pre-oxygenation, correlates with decreased PaO2 on room air. We also re-investigated the influence on FE'O2 by age. Prospective observational study. Two regional hospitals, Västerås and Köping County Hospitals, Västmanland, Sweden, between 30 October 2018 and 17 September 2021. We included 120 adults aged 40 to 79 years presenting for elective noncardiac surgery. An arterial blood gas was sampled before commencing pre-oxygenation. No linear correlation was found between FE'O2 at 3 min and PaO2 or age (Pearson's r = -0.038, P = 0.684; and Pearson's r = -0.113, P = 0.223, respectively). The mean ± SD FE'O2 at 3 min for the population studied was 0.87 ± 0.05. The lack of correlation between FE'O2 at 3 min and PaO2 or age during pre-oxygenation has implications for further studies concerning the interaction between airway closure and atelectasis. After 3 min of pre-oxygenation, FE'O2, even in the elderly, indicated a high enough alveolar oxygen concentration to promote atelectasis after induction, therefore, it is still unclear why atelectasis formation diminishes after middle age. ClinicalTrials.gov, identifier: NCT03395782.

Formulation, optimization, and sensitivity of NitrOMZv1.0, a biogeochemical model of the nitrogen cycle in oceanic oxygen minimum zones

Abstract. Nitrogen (N) plays a central role in marine biogeochemistry by limiting biological productivity in the surface ocean; influencing the cycles of other nutrients, carbon, and oxygen; and controlling oceanic emissions of nitrous oxide (N2O) to the atmosphere. Multiple chemical forms of N are linked together in a dynamic N cycle that is especially active in oxygen minimum zones (OMZs), where high organic matter remineralization and low oxygen concentrations fuel aerobic and anaerobic N transformations. Biogeochemical models used to understand the oceanic N cycle and project its change often employ simple parameterizations of the network of N transformations and omit key intermediary tracers such as nitrite (NO2-) and N2O. Here we present a new model of the oceanic N cycle (Nitrogen cycling in Oxygen Minimum Zones, or NitrOMZ) that resolves N transformation occurring within OMZs and their sensitivity to environmental drivers. The model is designed to be easily coupled to current ocean biogeochemical models by representing the major forms of N as prognostic tracers and parameterizing their transformations as a function of seawater chemistry and organic matter remineralization, with minimal interference in other elemental cycles. We describe the model rationale, formulation, and numerical implementation in a one-dimensional representation of the water column that reproduces typical OMZ conditions. We further detail the optimization of uncertain model parameters against observations from the eastern tropical South Pacific OMZ and evaluate the model's ability to reproduce observed profiles of N tracers and transformation rates in this region. We conclude by describing the model's sensitivity to parameter choices and environmental factors and discussing the model's suitability for ocean biogeochemical studies.

High Oxygen Shocking Reduces Postharvest Disease and Maintains Satisfying Quality in Fresh Goji Berries during Cold Storage by Affecting Fungi Community Composition

Fresh goji (Lycium barbarum L.) berries were treated with high-concentration (50% and 90%) oxygen shocking for 30 min and then stored at 0 ± 0.5 °C for 30 d. Decay, aerobic plate count, firmness, weight loss, total soluble solid (TSS), and titratable acidity (TA) were evaluated during storage. A total of 90% O2 shocking more effectively reduced decay and maintained the weight loss and firmness of goji berries. Subsequently, changes in fungi communities were analyzed using high-throughput sequencing (HTS) in the 90% O2-shocking and control groups. The results showed that 90% O2 shocking retained the richness and diversity of fungi communities and the microbiome was related to the quality properties of the fruit. Thus, we inferred that high oxygen shocking inhibited the development of natural decay and maintained the satisfying quality of goji berries by affecting the fungi community composition, which reduced the growth of pathogenic fungi and harmful saprotrophic fungi in the genera, such as Filobasidium sp., Alternaria sp., and Cladosporium sp. We provide a new insight into the disease development and quality changes during the storage of postharvest goji berries.

The role of oxygen tension in cell fate and regenerative medicine: implications of hypoxia/hyperoxia and free radicals.

Oxygen pressure plays an integral role in regulating various aspects of cellular biology. Cell metabolism, proliferation, morphology, senescence, metastasis, and angiogenesis are some instances that are affected by different tensions of oxygen. Hyperoxia or high oxygen concentration, enforces the production of reactive oxygen species (ROS) that disturbs physiological homeostasis, and consequently, in the absence of antioxidants, cells and tissues are directed to an undesired fate. On the other side, hypoxia or low oxygen concentration, impacts cell metabolism and fate strongly through inducing changes in the expression level of specific genes. Thus, understanding the precise mechanism and the extent of the implication of oxygen tension and ROS in biological events is crucial to maintaining the desired cell and tissue function for application in regenerative medicine strategies. Herein, a comprehensive literature review has been performed to find out the impacts of oxygen tensions on the various behaviors of cells or tissues.

Preparation of low-oxygen titanium powder by magnesiothermic reduction of TiO2 in KCl–MgCl2–YCl3 molten salt

The Kroll process is currently the only effective method in industry to produce sponge titanium with a low-oxygen concentration (500 ppm). However, it has several limitations, such as a long processing time, low efficiency, and high energy consumption, resulting in the high production cost of titanium. To reduce the production cost, a method to prepare low-oxygen titanium powder by magnesiothermic reduction of TiO2 in KCl–MgCl2–YCl3 molten salt was designed. The thermodynamic calculation results showed that it was feasible to prepare titanium powder by the magnesiothermic reduction of TiO2 at 1073, 1173, and 1273 K. In addition, the deoxidation limits of Mg under Mg/MgCl2/YCl3/YOCl equilibrium were 3, 12, and 38 ppm at 1073, 1173, and 1273 K, respectively. The experimental results showed that titanium powder with a high oxygen concentration of approximately 10,000 ppm was obtained when the reduction was conducted in KCl–MgCl2 molten salt (i.e., the activity of YCl3 (aYCl3) was 0). Low-oxygen titanium powder was prepared with the addition of YCl3 in the molten salt and formed yttrium oxychloride (YOCl) (TiO2 (s) + 2Mg (l) + 2YCl3 (l) = Ti (s) + 2MgCl2 (l) + 2YOCl (s)). Moreover, at 1173 K, when the activity of YCl3 (aYCl3) was 1, titanium powder with an oxygen concentration as low as 150 ppm was obtained. Based on these results, a novel process for preparing low-oxygen titanium powder was designed. The proposed process is fast and highly efficient, and its future application in industry is anticipated.

Experimental study on the fire behavior of the corrugated cartons under low-pressure environment with oxygen-enriched

Oxygen-enriched indoor in the high plateau can validly address the plateau reaction, but increases the probability of fire and the hazards after it occurs. The intention of this article was to estimate the influence of oxygen enrichment in low-pressure environment on the combustion behavior of characteristic combustibles based on indoor corrugated cartons, which is believed to be profitable for high plateau indoor fire safety. The ignition time, mass loss, flue gas properties, heat flux and axial temperature were investigated in comparative trials performed in a hypobaric chamber to emulation the particular environment. A new correlations to predict the burning rate of solid materials under varying pressures and oxygen concentrations was proposed and fitted by experimental data showing a good agreement. The results show that inhibition of solid combustion by low pressure can be significantly weaken by oxygen enrichment. As oxygen concentration increases, flame shape had a thin high type into a wide low type, the color had a blue-yellow gradually turned into a bright color. Moreover, at high oxygen concentration, pressure is weakly correlated with ignition time, mass loss and heat production. The fire performance index and thermal release index indicators show a significant raise in fire hazard of oxygen-enriched atmosphere.