Oxygen-enriched Air Research Articles

Exergy analysis of municipal solid waste incineration processes: The use of O2-enriched air and the oxy-combustion process

This work provides a complete exergy analysis of municipal solid waste incineration process. The work was based on a previous study, and was enriched considering the possibility to increase the O2 %mol in the combustion air, up to oxy-combustion conditions. Two configurations have been considered, with and without flue gas recirculation, and the environmental aspects of oxy-combustion were taken into account, as well as its exergetic cost. The flue gas was used in a boiler for high pressure steam production, expanded in three turbines for power generation. The exergy analysis allowed to identify the process units characterized by major irreversibility and exergy loss as waste. The results showed that the flue gas recirculation led to an exergy efficiency increase of the whole process of about 3% (from 31.1% up to 34% at adiabatic flame temperature equal to 1200 °C). The O2 %mol increase in the combustion air allowed to reduce the flue gas flowrate, leading to environmental benefits. Oxygen-enriched air adoption led to limited exergetic improvements, due to the exergy cost of the air separation unit. The specific energy generation of the plant increased at fixed combustion chamber temperature adopting flue gas recirculation.

Oxygen enrichment of air: Performance guidelines for membranes based on techno-economic assessment

The use of oxygen-enriched air (OEA) is an important strategy for reducing process cost and CO2 emissions in several industrial processes. Membrane-based processes, attributing to their high energy efficiency, are promising alternatives to cryogenic distillation and pressure-swing adsorption (PSA) at small to medium scales. However, so far, the techno-economic assessment of membrane processes has been focused on the production of low-purity O2. This study assesses O2 enrichment by membrane-based processes in a large purity range (30–95%), and reports significant energy and cost savings when high-performance membranes, marked by O2 permeance of 500–1000 GPU and O2/N2 selectivity in the range of 2–20, are developed. The analysis identifies that O2/N2 selectivities of 2–4, 6–15, and 20 are optimal for target purity of 30–40%, 50–65%, and >70%, respectively, leading to specific costs in the range of 20–50 $/tonEPO2 when blending with air is not considered. Purity target below 75% can be achieved by the single-stage process while double-stage processes are needed for higher purity targets. If highly-selective membranes are available, the cost of lower purity OEA can be further reduced by blending higher purity OEA with air.We demonstrate the benefits of the membrane process for four important applications. For natural gas combustion, optimal energy and cost savings of 41% and 22%, respectively, are predicted using membranes with selectivity of 4. An optimized hybrid system combining membrane enricher and post-combustion capture reduces energy consumption (22%) and cost (6%) with respect to the standalone capture. The production of medical-grade oxygen (90% purity) from membranes is economical (0.4 $/kL) compared to that from PSA (0.6–0.8 $/kL). Finally, 95% O2 can also be produced for oxycombustion with a specific cost of 32 $/tonEPO2.

An Experimental Investigation of In Situ Combustion in High Permeability Contrast Systems

Abstract A significant portion of world oil reserves reside in naturally fractured reservoirs and a considerable amount of these resources includes heavy oil and bitumen. Thermal enhanced oil recovery methods (EOR) are mostly applied in heavy oil reservoirs to improve oil recovery. In situ combustion (ISC) is one of the thermal EOR methods that could be applicable in a variety of reservoirs. Unlike steam, heat is generated in situ due to the injection of air or oxygen enriched air into a reservoir. Energy is provided by multi-step reactions between oxygen and the fuel at particular temperatures underground. This method upgrades the oil in situ while the heaviest fraction of the oil is burned during the process. The application of ISC in fractured reservoirs is challenging since the injected air would flow through the fracture and a small portion of oil in the/near fracture would react with the injected air. Only a few researchers have studied ISC in fractured or high permeability contrast systems experimentally. For in situ combustion to be applied in fractured systems in an efficient way, the underlying mechanism needs to be understood. In this study, the major focus is permeability variation that is the most prominent feature of fractured systems. The effect of orientation and width of the region with higher permeability on the sustainability of front propagation are studied. The contrast in permeability was experimentally simulated with sand of different particle size. These higher permeability regions are analogous to fractures within a naturally fractured rock. Several ISC tests with sand-pack were carried out to obtain a better understanding of the effect of horizontal, vertical, and combined (both vertical and horizontal) orientation of the high permeability region with respect to air flow to investigate the conditions that are required for a self-sustained front propagation and to understand the fundamental behavior. Within the experimental conditions of the study, the test results showed that combustion front propagated faster in the higher permeability region. In addition, horizontal orientation almost had no effect on the sustainability of the front; however, it affected oxygen consumption, temperature, and velocity of the front. On the contrary, the vertical orientation of the higher permeability region had a profound effect on the sustainability of the combustion front. The combustion behavior was poorer for the tests with vertical orientation, yet the produced oil API gravity was higher. Based on the experimental results, a mechanism has been proposed to explain the behavior of combustion front in systems with high permeability contrast.

Oxygen-enriched Air Decreases Ventilation during High-intensity Fin-swimming Underwater.

Oxygen-enriched air is commonly used in the sport of SCUBA-diving and might affect ventilation and heart rate, but little work exists for applied diving settings. We hypothesized that ventilation is decreased especially during strenuous underwater fin-swimming when using oxygen-enriched air as breathing gas. Ten physically-fit divers (age: 25±4; 5 females; 67±113 open-water dives) performed incremental underwater fin-swimming until exhaustion at 4 m water depth with either normal air or oxygen-enriched air (40% O 2 ) in a double-blind, randomized within-subject design. Heart rate and ventilation were measured throughout the dive and maximum whole blood lactate samples were determined post-exercise. ANOVAs showed a significant effect for the factor breathing gas (F(1, 9)=7.52; P=0.023; η 2 p =0.455), with a lower ventilation for oxygen-enriched air during fin-swimming velocities of 0.6 m·s −1 (P=0.032) and 0.8 m·s −1 (P=0.037). Heart rate, lactate, and time to exhaustion showed no significant differences. These findings indicate decreased ventilation by an elevated oxygen fraction in the breathing gas when fin-swimming in shallow-water submersion with high velocity (>0.5 m·s −1 ). Applications are within involuntary underwater exercise or rescue scenarios for all dives with limited gas supply.

Experimental study on evaluation of underground coal gasification with a horizontal hole using two different coals

Underground coal gasification (UCG) is a technique to extract coal energy with heat energy and combustible gases through chemical reactions in the underground gasifier. In this study, an application of a coaxial UCG system with a horizontal hole is discussed by means of the model UCG experiments with a large-scale simulated coal seam having dimensions of 550 × 600 × 2740 mm. The two types of coal having 30.18 MJ/kg of calorific value with 7.9% of ash (type 1) and 22.66 MJ/kg of calorific value with 28.3% of ash (type 2) were used for the experiments to evaluate the effect of coal quality on temperature distribution of the gasification area and product gas quality. The oxygen-enriched air was used. The injection rate of the gasification agents was elevated during the experiments to analyze the effect on the product gas. The results show that the gasification area is expanded along the wall of a coaxial hole, not upwards for the type 2 coal with high ash content. The average calorific value of product gas for types 1 and 2 is 8.05 MJ/m3 and 6.91 MJ/m3 respectively, while an increase of injection flow rate produces an improvement of the calorific value for both types of coal. Additionally, it is suggested that the reacted carbon and the product gas volume can be estimated with the volume of oxygen injected regardless of the coal quality if the gasification efficiency and the reaction temperature are similar. These results help to estimate several important parameters, e.g. reacted coal amount, recovered gas volume, and recovered energy from the coal when the actual field implementation is designed.

Oxygen Enrichment Mitigates High-Altitude Hypoxia-Induced Hippocampal Neurodegeneration and Memory Dysfunction Associated with Attenuated Tau Phosphorylation.

Cai, Jing, Junyong Ruan, Xi Shao, Yuanjun Ding, Kangning Xie, Chi Tang, Zedong Yan, Erping Luo, and Da Jing. Oxygen enrichment mitigates high-altitude hypoxia-induced hippocampal neurodegeneration and memory dysfunction associated with attenuated tau phosphorylation. High Alt Med Biol. 22:274-284, 2021. Background: Brain is predominantly vulnerable to high-altitude hypoxia (HAH), resulting in neurodegeneration and cognitive impairment. The technology of oxygen enrichment has proven effective to decrease the heart rate and improve the arterial oxygen saturation by reducing the equivalent altitude. However, the efficacy of oxygen enrichment on HAH-induced cognitive impairments remains controversial based on the results of neuropsychological tests, and its role in HAH-induced hippocampal morphological and molecular changes remains unknown. Therefore, this study aims to systematically investigate the effects of oxygen enrichment on the memory dysfunction and hippocampal neurodegeneration caused by HAH. Materials and Methods: Fifty-one male Sprague-Dawley rats were equally assigned to three groups: normal control, HAH, and HAH with oxygen enrichment (HAHO). Rats in the HAH and HAHO groups were exposed to hypoxia for 3 days in a hypobaric hypoxia chamber at a simulated altitude of 6,000 m. Rats in the HAHO group were supplemented with oxygen-enriched air, with 12 hours/day in the hypobaric hypoxia chamber. Results: Our results showed that oxygen enrichment improved the locomotor activity of HAH-exposed rats. The Morris water maze test revealed that oxygen enrichment significantly ameliorated HAH-induced spatial memory deficits. Oxygen enrichment also improved morphological alterations of pyramidal cells and the ultrastructure of neurons in the hippocampal CA1 region in rats exposed to acute HAH. Tau hyperphosphorylation at Ser396, Ser262, Thr231, and Thr181 was also significantly attenuated by oxygen enrichment in HAH-exposed rats. Conclusions: Together, our study reveals that oxygen enrichment can ameliorate HAH-induced cognitive impairments associated with improved hippocampal morphology and molecular expression, and highlights that oxygen enrichment may become a promising alternative treatment against neurodegeneration for humans ascending to the plateau.

Effect of Breathing Oxygen-Enriched Air on Exercise Performance in Patients With Pulmonary Hypertension Due to Heart Failure With Preserved Ejection Fraction: A Randomized, Placebo-Controlled, Crossover Trial.

Objective: To evaluate the effects of breathing oxygen-enriched air (oxygen) on exercise performance in patients with pulmonary hypertension due to heart failure with preserved ejection fraction (PH-HFpEF).Methods: Ten patients with PH-HFpEF (five women, age 60 ± 9 y, mPAP 37 ± 14 mmHg, PAWP 18 ± 2 mmHg, PVR 3 ± 3 WU, resting SpO2 98 ± 2%) performed two-cycle incremental exercise tests (IET) and two constant-work-rate exercise test (CWRET) at 75% maximal work-rate (Wmax), each with ambient air (FiO2 0.21) and oxygen (FiO2 0.5) in a randomized, single-blinded, cross-over design. The main outcomes were the change in Wmax (IET) and cycling time (CWRET) with oxygen vs. air. Blood gases at rest and end-exercise, dyspnea by Borg CR10 score at end-exercise; continuous SpO2, minute ventilation (V'E), carbon dioxide output (V'CO2), and cerebral and quadricep muscle tissue oxygenation (CTO and QMTO) were measured.Results: With oxygen vs. air, Wmax (IET) increased from 94 ± 36 to 99 ± 36 W, mean difference (95% CI) 5.4 (0.9–9.8) W, p = 0.025, and cycling time (CWRET) from 532 ± 203 to 680 ± 76 s, +148 (31.8–264) s, p = 0.018. At end-exercise with oxygen, Borg dyspnea score and V'E/V'CO2 were lower, whereas PaO2 and end-tidal PaCO2 were higher. Other parameters were unchanged.Conclusion: Patients with PH-HFpEF not revealing resting hypoxemia significantly improved their exercise performance while breathing oxygen-enriched air along with less subjective dyspnea sensation, a better blood oxygenation, and an enhanced ventilatory efficiency. Future studies should investigate whether prolonged training with supplemental oxygen would increase the training effect and, potentially, daily activity for PH-HFpEF patients.Clinical Trial Registration: [clinicaltrials.gov], identifier [NCT04157660].

To the problem of forming the equation system for pressure swing adsorption mathematical model

Abstract The complexity of the pressure swing adsorption (PSA) mathematical model, the need for its multiple calculations to reach the cyclic steady state and a large number of functional dependencies lead to unstable numerical circuits, physically unrealistic oscillations in adsorption profiles, an increase in the calculation time, and the failure of the solver. The paper proposes an approach to optimizing the calculation process, which consists in finding a reasonable balance between the completeness of the PSA mathematical model and the accuracy of the results obtained. The effectiveness of the approach is demonstrated on the example of air oxygen enrichment and hydrogen recovery from synthesis gas. The gas separation processes were simulated for the two-adsorber PSA unit with a granulated 13X adsorbent. The effect of the changes in the model coefficients on its accuracy in the operating range of input variables is investigated. A distinctive feature of this study is the recommendations for choosing a set of the model equations to calculate the PSA processes which are particularly relevant when solving optimization problems with uncertainty. The productivity, cycle duration, the diameter of the adsorbent particles and the flow rate, at which it is advisable to use the isothermal and external diffusion reduced PSA model in the calculations, are established, which will save at least 24.3 and 47.1% of the CPU time with a small loss in accuracy. The proposed approach can be used to form a set of equations for the PSA, rPSA, ultra rPSA, VSA, VPSA models, separation of various gas mixtures on various adsorbents.

Determination of the effects of oxygen-enriched air with the help of zeolites on the exhaust emission and performance of a diesel engine

The aim of the present experimental study is to reduce exhaust emissions and improve performance by feeding a diesel engine with oxygen enriched air by the help of natural and synthetic zeolites. Oxygen enrichment process is carried out by a zeolite filter (ZF) system that operates by the pressure swing adsorption (PSA) method. In the experiments, clinoptilolite-type natural zeolite (NZ) in 1.3–3 mm fractions and 0.4–0.8 mm 13X HP type synthetic zeolite (SZ) were used. Scanning electron microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) were used to observe the surface and particle structures of NZ and SZ and to perform the elemental analysis. According to the data obtained from the ZF system, NZ and SZ provided oxygen increases of 18.57% and 41.91%, respectively, when compared to the rate of oxygen in the air of the test environment. As a result of feeding the intake line of the engine with oxygen enriched air by using NZ and SZ, decreases in the carbon monoxide (CO), hydrocarbon (HC), smoke density, and brake specific fuel consumption (BSFC) values and increases in the nitrogen oxide (NOX), vibration, noise, exhaust gas temperature (EGT), and brake thermal efficiency (BTE) values were observed.

Experimental evaluation of thermal radiation and soot concentration rates for syngas flames in lean condition and oxygen enhanced combustion

The combustion process is a major source of energy for future decades. However, this process negatively impacts the environment with the emission of particulate matter into the atmosphere, known as soot. Therefore, it is desirable that more sustainable and efficient combustion processes are researched. For this reason, the use of biomass gasification has been studied, resulting in a fuel known as syngas, largely composed of hydrogen and carbon monoxide. This gas can reduce emissions as it is derived from biomass. Another way to reduce emissions is using syngas in lean conditions. In this context, the present work aims to present the experimental study of the correlation of a synthetic syngas as fuel produced with a hydrogen and carbon monoxide mixture, and the technique of enriching the air with oxygen in lean conditions using a diffuse flame. A test bench was developed to evaluate the presence of soot and the emission of thermal radiation in the flame, with oxygen-enriched air and equivalence ratios in lean conditions. It was noted that the use of oxygen-enhanced combustion increases the formation of soot and thermal radiation. The highest concentration of soot occurs in an equivalence ratio of 1, for a mixture with 41% hydrogen and 23% oxygen. It reaches more than 3.5 parts per million of soot, more than double the amount of soot when compared with 21% of oxygen in the same conditions. The best results for the mean radiation of the flame occur in the equivalence ratio of 0.9, where values higher than 120 kW/m2 are achieved with 21.7% of oxygen and 33.7% of hydrogen. In addition, the fuel with a higher percentage of CO induces less soot formation and lower emissions of thermal radiation at the beginning of the flame.

Effect of fill flow rate on flame acceleration in a detonation channel

In a pulse detonation engine, filling fresh reactive mixtures into the detonation chamber is an indispensable process. The fill flow rate would significantly influence the subsequent flame acceleration and detonation initiation processes. Nevertheless, the existing works regarding the flame acceleration and detonation initiation are mostly performed on the quiescent mixtures. This work, therefore, investigates the effect of fill flow rate on the flame acceleration process in a square cross-section, obstructed detonation channel. Ethylene was utilized as the fuel, and oxygen-enriched air with an oxygen volume fraction of 40% as the oxidizer. The flame acceleration processes of quiescent and moving mixtures were observed by high-speed Schlieren and chemiluminescence techniques. It was found in this work that the fill flow rate dominates the flame propagation in the early stage of the flame acceleration (i.e., to the sound velocity of reactants). The initial flame structures vary from smooth (quiescent) to wrinkled (50 g/min) and cellular (100 g/min and 150 g/min), and to turbulent (200 g/min) with the increase of the fill flow rate. The Schlieren measurements of the filling processes show that the flow instabilities and the shear layer shedding from the obstacle surfaces into the mainstream are responsible for the promoted flame acceleration in high fill flow rate cases.

Propagation mode analysis of rotating detonation waves fueled by liquid kerosene

The propagation modes of rotating detonation waves supplied with liquid kerosene and oxygen-enriched air were experimentally investigated. Experiments were conducted while maintaining the equivalence ratio at approximately 0.7 and varying the mass flow rate of the oxidizer from 585.3 to 1493.8 g/s. Three propagation modes were obtained, and the propagation characteristics of rotating detonation waves in each mode were extensively analyzed. The results reveal that for the test model with an equivalence ratio of 0.7, the rotating detonation waves exhibit three types of modes in sequence as the mass flow rate of the oxidizer increases, namely, single-wave mode, single/dual-wave hybrid mode, and dual-wave mode. The propagation modes of rotating detonation waves vary randomly in the single/dual-wave hybrid mode, and the mode transition processes are more likely to be accompanied by transient detonation wave extinction due to the lower activity of liquid kerosene. For the single/dual-wave hybrid mode, the pressure feedback of rotating detonation waves to oxidizer plenum in the single-wave mode is greater than that in the dual-wave mode, which is related to the higher pressure peaks of rotating detonation waves in the single-wave mode. Moreover, the relative standard deviation of the propagation frequency is calculated to evaluate the propagation stability of the rotating detonation wave. It was found that the rotating detonation waves possess higher propagation stability in the dual-wave mode than in the single-wave mode.

Investigating the effects of oxygen enrichment with modified zeolites on the performance and emissions of a diesel engine through experimental and ANN approach

Oxygen enrichment of intake air in internal combustion engines (ICE) is one of the effective methods used to reduce exhaust emissions and increase performance. In this study, oxygen enrichment process was performed with pressure swing adsorption (PSA) method using two zeolite types including acid-modified zeolite (AMZ) and base-modified zeolite (BMZ). In the experiments, clinoptilolite-type natural zeolite in 1.6–3 mm fractions was used. HCI, NH4NO3 and NaOH solutions were used to obtain AMZ and BMZ. Engine experiments were carried out using a four-stroke, single cylinder, direct injection, air-cooled diesel engine. In addition, by designing an artificial neural network (ANN) model with the capability to estimate the experimental results, its performance was tested. When the oxygen rate (21%) in the medium air, where the experiments were carried out, was compared with the oxygen rates in the air obtained with the use of AMZ and BMZ in zeolite filter (ZF) system, an increase of 17.14% and 21.90% was observed, respectively. As a result of the addition of oxygen-enriched air to the fresh air drawn into the combustion chamber in the ZF system, the carbon monoxide (CO), hydrocarbon (HC), smoke density and brake specific fuel consumption (BSFC) values decreased and the nitrogen oxide (NOX), vibration, noise, exhaust gas temperature (EGT) and brake thermal efficiency (BTE) values increased when compared to standard diesel engine (SDE). According to the obtained results, ANN estimated the exhaust emission and performance parameters with the regression values (R) of 0.99423–0.99990 and low error rates in the range of 0.002–6.93%.

Hyperoxia in Depression

Several studies of normobaric hyperoxia in some neurological conditions have demonstrated clinical benefits. Oxygen enriched air may increase oxygen pressure in brain tissue and have biochemical effects such as on brain erythropoietin gene expression, even in patients without lung disease.

Structure and combustion characteristics of semi-cokes from a pilot-scale entrained flow gasifier using oxygen-enriched air

To explore the structural characteristics and further utilize the semi-cokes obtained from a self-designed pilot-scale entrained flow gasifier at the temperatures of 800–1200 °C with oxygen-enriched air as gasifying agents (21, 50, and 100% O2 in N2), the gasified semi-cokes were characterized by N2 adsorption, scanning electron microscopy (SEM), and X-ray diffraction (XRD) methods, and their combustion performances and kinetic analysis were explored using a thermogravimetric analyzer. Results indicated that the volatile release was significantly enhanced with rising gasification temperature, which would contribute to the rapid development of pore structure in semi-cokes. The increasing oxygen concentration mainly worked on promoting both the volatile release and the carbon conversion through enhancing the oxidation reactions with carbon matrix, which would result in the dramatic decrease of both surface area and micropore volume. Thermal analysis showed that the ignition and comprehensive combustion performances of semi-cokes got worse as the gasification temperature and oxygen concentration increased, indicating that the volatile matter is vitally important to promote the ignition as well as maintain the combustion stability. While their combustion intensity and burnout index were more dependent on the pore structure. The activation energy of semi-cokes calculated by both FWO and KAS methods increased with the temperature and oxygen concentration, and different order reaction models (ranged from 0.8 to 2.1) were responsible for the combustion of semi-cokes. It is notable that the volatile content and pore structure are the key factors affecting the variation of activation energy with conversion degree and the magnitude of the reaction kinetic model.

Combustion of waste gas in a low-swirl burner under syngas and oxygen enrichment

A biomethane production from biogas could result in an emission of waste gas to the atmosphere. As these gases consist of methane up to 15 vol%, they should be utilized onsite to reduce the impact of climate change. However, due to low calorific value, the combustion process of these gases could be complicated or even impossible inconvenient gas burners. For this reason, this work focuses on an investigation to clarify a complex of measures affecting the flammability limits and effectiveness of burning waste gas in a designed low swirl burner with different swirlers. The swirlers were made with vanes angles of 37°, 45°, and 53°. Critical regions of the flame structure were experimentally examined by means of chemiluminescence to determine the intensity of OH* emissions under syngas and oxygen enrichment. It revealed that the most appropriate combustion conditions taking into account the stable flame and lowest CO emissions were achieved using the swirler with a vanes angle of 45°. Moreover, under the syngas enrichment (by the addition from 0 to 25 vol% of syngas), it is possible to achieve more stable combustion conditions, taking into account the low CO and NOx emissions, when oxygen-enriched air is additionally supplied. However, the oxygen enrichment levels must be selected according to the lift-off height threshold to avoid flashbacks due to the declining trend in the velocity of the flow.

Hyperoxia in depression

IntroductionSeveral studies of normobaric hyperoxia in some neurological conditions have demonstrated clinical benefits. Oxygen enriched air may increase oxygen pressure in brain tissue and have biochemical effects such as on brain erythropoietin gene expression, even in patients without lung disease.ObjectivesThis pilot, randomized, double-blind study examined the efficacy of normobaric hyperoxia as a treatment for depression.MethodsFifty-five consenting patients aged 18-65 years with mild to moderate depression were included in the study. Participants underwent a psychiatric inclusion assessment and a clinical evaluation by a psychiatric nurse at baseline, 2 and 4 weeks after commencement of study intervention. Participants were randomly assigned to normobaric hyperoxia of 35% fraction of inspired oxygen or 21% fraction of inspired oxygen (room air), through a nasal tube, for 4 weeks, during the night. Patients were rated blindly using the Hamilton Rating Scale for Depression (HRSD); Clinical Global Impression (CGI) questionnaire; Sheehan Disability Scale (SDS).Results The present study showed a significant improvement in HRSD (p<0.0001), CGI (p<0.01) and in SDS (p<0.05) among patients with depression who were treated with oxygen-enriched air, as compared to patients who were treated with room air. In CGI, 69% of the patients who were treated with oxygen-enriched air improved compared to 23% patients who were treated with room air.ConclusionsThis small pilot study showed a beneficial effect of normobaric hyperoxia on some symptoms of depression.DisclosureNo significant relationships.

Exertional Desaturation in Idiopathic Pulmonary Fibrosis: The Role of Oxygen Supplementation in Modifying Cerebral-Skeletal Muscle Oxygenation and Systemic Hemodynamics

Background: In patients with idiopathic pulmonary fibrosis (IPF) with isolated exertional desaturation, there are limited data regarding the effectiveness of oxygen supplementation during exercise training; the underlying mechanisms that contribute to these responses are unknown. Objectives: To examine in these IPF patients the effects of oxygen supplementation during submaximal exercise (vs. medical air) on cerebral/skeletal muscle oxygenation and systemic hemodynamics. Methods: In this randomized, cross-over, placebo-controlled trial, IPF patients (n = 13; 63.4 ± 9.6 years) without resting hypoxemia but a significant desaturation during maximal cardiopulmonary exercise testing underwent 2 steady-state exercise trials (65% peak-work-load), breathing either oxygen-enriched or medical air. Cerebral/skeletal muscle oxygenation (near-infrared spectroscopy) and beat-by-beat hemodynamics (photoplethysmography) were monitored. Results: In the air protocol, from the initial minutes of submaximal exercise, patients exhibited a marked decline in cerebral oxygenated hemoglobin (O2Hb) and an abrupt rise in deoxygenated hemoglobin (HHb). Oxygen supplementation alleviated desaturation, lessened dyspnea, and prolonged exercise duration (p < 0.01). Oxygen supplementation during exercise (i) attenuated cerebral deoxygenation (cerebral-HHb: 0.7 ± 1.9 vs. 2.5 ± 1.5 μmol/L, O2 and air protocol; p = 0.009) and prevented cerebral-Hbdifference decline (2.1 ± 2.7 vs. −1.7 ± 2.0 μmol/L; p = 0.001), (ii) lessened the decline in muscle O2-saturation index, and (iii) at isotime exercise, it resulted in lower muscle-HHb (p = 0.05) and less leg fatigue (p < 0.05). No differences between protocols were observed in exercise cardiac output and vascular resistance. Conclusions: IPF patients with isolated exertional hypoxemia exhibit an inability to increase/maintain cerebral oxygenation during submaximal exercise. Correcting desaturation with O2 supplementation prevented the decline in brain oxygenation, improved muscle oxygenation, and lessened dyspnea, suggesting an efficacy of acute oxygen supplementation during exercise training in protecting brain hypoxia in these IPF patients.

Hydrogen-rich syngas produced from co-gasification of municipal solid waste and wheat straw in an oxygen-enriched air fluidized bed

The gasification characteristics of solid waste and wheat straw were investigated in an oxygen-rich atmosphere by using a laboratory-scale continuous fluidized bed reactor in the range of oxidation equivalent (ER) of 0.2~0.5 and reaction temperature of 600 °C~900 °C. Gasification of biomass and waste is an economical method for hydrogen production. When air is used as a carrier gas to gasify municipal solid waste, increasing the oxygen concentration can effectively increase the hydrogen concentration of the syngas. The product distribution of gasification reaction under different mixing ratios and reaction parameters was obtained. As is shown in the results, first, when the ER is between 0.2 and 0.5, if ER decreases by 0.1, the hydrogen concentration of gas production will increase by about 30%; second, if the oxygen concentration increases by 5%, the hydrogen concentration of gas production will increase by about 14%, and the calorific value of gas production will increase by about 14–18%; third, after adding wheat straw in a ratio of 1:1, due to the reduction of plastics, the overall yield of syngas decreased, but the yield of hydrogen increased, and the concentration of hydrogen in syngas increased by 6.4%.

Numerical investigation on distribution characteristics of oxidation air in a lime slurry desulfurization system with rotary jet agitators

Rotary jet agitator is an effective device for mixing, dispersing, dissolving, and suspending dispersed phases in liquid, and is particularly advantageous to the homogenization of oxygen-enriched air within the lime slurry desulfurization system. The distribution of oxygen-enriched air in agitators is vital for the process of gypsum crystallization and the homogeneous and sufficient oxygen-enriched air can promote the formation of an economically useful by-product. The present study investigated the diffusion performance of oxygen-enriched air in a rotary jet agitator during the wet flue gas desulfurization process by utilizing computational fluid dynamics. The consistency of numerical and experimental results is validated under identical conditions. Investigation results show that the rotation velocities and the inlet velocities of rotary jet machines significantly affect the distribution and homogeneity of the oxygen-enriched air distribution. However, these effects deteriorate with increasing rotation angular and jet outlet velocities. Under the optimal condition, the oxygen-enriched air concentration, within the cross-sections, fluctuates by approximately 20%. The Rotary jet agitator appears to be a remarkable method for the homogenization of oxygen-enriched air in the lime slurry tank, and in other gas-liquid stirring tanks, due to its high efficacy and good stirring effect.