scholarly journals Oxygen-enriched combustion mechanism of lignite

2020 ◽  
Vol 24 (4) ◽  
pp. 2411-2418
Author(s):  
Xiangyun Chen ◽  
Yongfeng Zhang ◽  
Yinmin Zhang
Keyword(s):  
Oxygen Concentration ◽  
Combustion Mechanism ◽  
Isothermal Method ◽  
N2 Atmosphere ◽  
Málek Method ◽  
Oxygen Conditions ◽  
Burning Model ◽  
Dynamical Function ◽  
D Model ◽  
Oxygen Concentrations

In this work, thermogravimetric experiments were carried out in a thermogravi-metric analyzer under O2/N2 atmosphere with an oxygen content ranging from 21 vol.% to 70 vol.%. Malek method combined with iso-conversional method and non-isothermal method was employed to determine the burning dynamical function of lignite in high temperature burning region with different oxygen concentrations. The results indicated that the lignite has different burning dynamical function in different oxygen conditions. The combustion mechanism function of lignite belonged to 3-D model when the oxygen concentration is below 30%. The combustion mechanism of lignite belongs to a random successive nucleation growth model when the oxygen concentration is between 40% and 50%. Kinetic burning model of lignite in high burning temperature region with different oxygen concentrations was established. The kinetic parameters were obtained from the kinetic burning model of lignite using Kissinger-Akah-Sunose method.

scholarly journals The spatial variation of oxygen condition in carp pond located in nature reserve „Stawy Milickie” / Przestrzenne zróżnicowanie warunków tlenowych w stawie karpiowym położonym w rezerwacie przyrody „Stawy Milickie”

2013 ◽  
Vol 19 (1) ◽  
pp. 47-52 ◽  
Author(s):  
Bartosz Jawecki ◽  
Tomasz Jaroszewicz-Smyk ◽  
Andrzej Drabiński
Keyword(s):  
Dissolved Oxygen ◽  
Spatial Variation ◽  
Oxygen Concentration ◽  
Water Concentration ◽  
Open Water ◽  
Average Concentration ◽  
Optimum Level ◽  
Emergent Plants ◽  
Oxygen Conditions ◽  
Oxygen Condition

Abstract The paper presents the results of research on the spatial variation of oxygen condition in a carp pond. The analysis of dissolved oxygen was carried out in the summer in 29 measuring points. In the analysed months the differences were determined between dissolved oxygen concentration in the strip of rushes and the part of the pond free from macrophytes. In the strip of rushes, the average concentration of dissolved oxygen was between 4.69-6.49 mg O2·dm-3. In the part of pond located near the strip of rushes the oxygen concentration was between 6.23-7.91 mg O2·dm-3 and in open water concentration of dissolved oxygen was in range 7.60-9.09 mg O2·dm-3. It was found that the biggest differences in oxygen concentration occur between the strip of rushes and the open water column: 40% in June, 26% in July, 28% in August, 38% in September, respectively. In the south-western part of the pond, covered with macrophytes and shaded by trees, the worst oxygen conditions were observed - below the optimum level for carps, sometimes reaching lethal values. The best oxygen conditions, noted in July and August, were in the central and northern part of the pond including the fishery and feeding point. In order to improve the oxygen conditions in macrophytes zone it is recommended to remove the rushes periodically and to remember to leave the part of emergent plants that are necessary for breeding and living avifauna. The scope and timing of the removal of plants has to be consulted and co-ordinated with the Regional Conservator of Nature.

Large Eddy Simulation of Multiple-Stage Ignition Process of n-Heptane Spray Flame

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Wanhui Zhao ◽  
Lei Zhou ◽  
Wenjin Qin ◽  
Haiqiao Wei
Keyword(s):  
Oxygen Concentration ◽  
Mixture Fraction ◽  
Ignition Process ◽  
Low Oxygen ◽  
Nonpremixed Combustion ◽  
Eddy Simulation ◽  
Spray Flames ◽  
Large Eddy ◽  
Initial Oxygen ◽  
Oxygen Concentrations

Large eddy simulation of n-heptane spray flames is conducted to investigate the multiple-stage ignition process under extreme (low-temperature, low oxygen, and high-temperature, high-density) conditions. At low oxygen concentrations, the first-stage ignition initiates in the fuel-rich region and then moves to stoichiometric equivalence ratio regions by decreasing the initial temperature. It is also clear that at high temperatures, high oxygen concentrations, or high densities, the reactivity of the mixture is enhanced, where high values of progress variable are observed. Analysis of key intermediate species, including acetylene (C2H2), formaldehyde (CH2O), and hydroxyl (OH) in the mixture fraction and temperature space provides valuable insights into the complex combustion process of the n-heptane spray flames under different initial conditions. The results also suggest that C2H2 appears over a wider range in the mixture fraction space at higher temperature or oxygen concentration condition, implying that it mainly forms at the fuel-rich regions. The initial oxygen concentration of the ambient gas has great influence on the formation and oxidization of C2H2, and the maximum temperature depends on the initial oxygen concentration. OH is mainly formed at the stoichiometric equivalence ratio region, which moves to high-temperature regions very quickly especially at higher oxygen concentrations. Finally, analysis of the premixed and nonpremixed combustion regimes in n-heptane spray flames is also conducted, and both premixed and nonpremixed combustion coexist in spray flames.

scholarly journals The FLASH effect depends on oxygen concentration

2020 ◽  
Vol 93 (1106) ◽  
pp. 20190702 ◽  
Author(s):  
Gabriel Adrian ◽  
Elise Konradsson ◽  
Michael Lempart ◽  
Sven Bäck ◽  
Crister Ceberg ◽  
...  
Keyword(s):  
Oxygen Concentration ◽  
Underlying Mechanism ◽  
Oxygen Depletion ◽  
Therapeutic Window ◽  
High Dose ◽  
Dose Rates ◽  
Conventional Dose ◽  
Oxygen Concentrations

Objective: Recent in vivo results have shown prominent tissue sparing effect of radiotherapy with ultra-high dose rates (FLASH) compared to conventional dose rates (CONV). Oxygen depletion has been proposed as the underlying mechanism, but in vitro data to support this have been lacking. The aim of the current study was to compare FLASH to CONV irradiation under different oxygen concentrations in vitro. Methods: Prostate cancer cells were irradiated at different oxygen concentrations (relative partial pressure ranging between 1.6 and 20%) with a 10 MeV electron beam at a dose rate of either 600 Gy/s (FLASH) or 14 Gy/min (CONV), using a modified clinical linear accelerator. We evaluated the surviving fraction of cells using clonogenic assays after irradiation with doses ranging from 0 to 25 Gy. Results: Under normoxic conditions, no differences between FLASH and CONV irradiation were found. For hypoxic cells (1.6%), the radiation response was similar up to a dose of about 5–10 Gy, above which increased survival was shown for FLASH compared to CONV irradiation. The increased survival was shown to be significant at 18 Gy, and the effect was shown to depend on oxygen concentration. Conclusion: The in vitro FLASH effect depends on oxygen concentration. Further studies to characterize and optimize the use of FLASH in order to widen the therapeutic window are indicated. Advances in knowledge: This paper shows in vitro evidence for the role of oxygen concentration underlying the difference between FLASH and CONV irradiation.

Monitoring of Fish Tank Oxygen Concentration Using a Digital Recorder

1971 ◽  
Vol 28 (8) ◽  
pp. 1196-1197 ◽  
Author(s):  
K. R. Scott
Keyword(s):  
Computer Program ◽  
Oxygen Concentration ◽  
Paper Tape ◽  
Operating Conditions ◽  
Digital Recorder ◽  
Fish Tank ◽  
Oxygen Concentrations

A method for monitoring fish tank oxygen concentrations at 10-min intervals is described. The millivolt output from a temperature-compensated oxygen meter is connected to a clocked digital datalogger system having a perforated paper tape output. Results from two widely different sets of operating conditions are analysed and automatically plotted using a prewritten computer program.

Influence of some factors on oxygen uptake of canine cardiac Purkinje fibers

1963 ◽  
Vol 204 (1) ◽  
pp. 5-8 ◽  
Author(s):  
Kalman Greenspan ◽  
Paul F. Cranefield
Keyword(s):  
Oxygen Uptake ◽  
Oxygen Concentration ◽  
Diffusion Limitation ◽  
Purkinje Fibers ◽  
Ambient Oxygen ◽  
Cardiac Purkinje Fibers ◽  
Lower Oxygen ◽  
Wet Weight ◽  
Oxygen Tensions ◽  
Oxygen Concentrations

The rate of oxygen uptake of quiescent Purkinje fibers of the dog's heart was determined using a flow respirometer and oxygen polarography. At ambient oxygen concentrations of 60% or higher the rate of uptake was 0.739 mm3/mg wet weight per hr at 35 C. The temperature coefficient over the range 25–35° was 2.3. The uptake was independent of the ambient oxygen concentration at oxygen concentrations equal to or greater than 60% of an atmosphere. In lower oxygen concentrations the rate of uptake was found to be depressed. The depression of uptake in the lower oxygen tensions is probably the result of diffusion limitation; it may, however, reflect dependence of resting uptake on oxygen concentration.

Myringosclerosis Caused by Increased Oxygen Concentration in Traumatized Tympanic Membranes Experimental Study

1995 ◽  
Vol 104 (8) ◽  
pp. 625-632 ◽  
Author(s):  
Cecilia Mattsson ◽  
Karin Magnuson ◽  
Sten Hellström
Keyword(s):  
Experimental Study ◽  
Oxygen Concentration ◽  
Middle Ear ◽  
Oxygen Radicals ◽  
Ambient Air ◽  
Fourth Group ◽  
Oxygen Concentrations ◽  
Tympanic Membranes

The purpose of this study was to elucidate possible relationships between the oxygen concentration of the middle ear cavity and the development of myringosclerosis. Three groups of rats with myringotomized tympanic membranes were exposed to different oxygen concentrations of 10%, 15%, and 40%, respectively, for 1 week. A fourth group was kept in ambient air. Two other groups of rats with myringotomized and intubated tympanic membranes were exposed to oxygen concentrations of 10% and 40%, respectively, for the same period of time. Otomicroscopically, all hyperoxic animals had more numerous myringosclerotic lesions compared with the ambient air group, and also displayed a pronounced hyperplasia of the keratinizing epithelium around the perforation border. By contrast, the hypoxic animals showed less pronounced myringosclerotic lesions or even completely lacked them. It is inferred that an increased oxygen concentration in the middle ear cavity will increase the likelihood of myringosclerotic deposits. The mechanism involved could be related to the formation of oxygen radicals.

Effect of Oxygen Concentration on Aging of Rubber Vulcanizates. II. Effect of Partial Pressure of Oxygen on Changes in Physical Properties Accompanying Oxidation

1953 ◽  
Vol 26 (3) ◽  
pp. 643-654 ◽  
Author(s):  
J. Reid Shelton ◽  
William L. Cox
Keyword(s):  
Physical Properties ◽  
Partial Pressure ◽  
Oxygen Concentration ◽  
Chain Scission ◽  
Cross Linking ◽  
Partial Pressure Of Oxygen ◽  
Aging Behavior ◽  
Storage Temperatures ◽  
Normal Storage ◽  
Oxygen Concentrations

Abstract The over-all rate of deterioration of physical properties increases with the oxygen concentration, as would be expected from the increased rate of oxygen absorption: The nature of the deterioration resulting from a given amount of oxygen absorbed is influenced also by changes in the partial pressure of oxygen in the aging atmosphere. It appears that chain scission is favored at higher oxygen concentrations, while cross-linking becomes of greater relative importance at lower oxygen concentrations. These data suggest that R⋅ radicals are more effective than RO2⋅ radicals in reacting with double bonds to form crosslinks. Heat aging in the absence of oxygen, as observed by heating a vulcanizate in lamp-grade nitrogen, results in considerable stiffening, particularly in the case of a GR-S black stock. This effect is observed primarily in the first few hours of heating, and may account for some of the erratic behavior observed in the early stages of aging when changes in physical properties are compared on the basis of amount of oxygen absorbed. Higher oxygen concentration brings about a more rapid oxidation, and also results in a higher proportion of chain scission compared to cross-linking for a given amount of oxygen absorbed. As tensile decay is the most evident sign of deterioration of Hevea stocks, it follows that the aging behavior of natural rubber in air at normal storage temperatures will be better than that predicted by high temperature testing in oxygen. In the case of GR-S stocks, on the other hand, oxidative hardening is the most serious result of aging, and consequently, the aging behavior of GR-S stocks in air at normal storage temperatures is poorer than would be expected on the basis of comparative tests in oxygen at higher temperatures.

Embryonic disc development and subsequent viability of cattle embryos following culture in two media under two oxygen concentrations

2004 ◽  
Vol 16 (8) ◽  
pp. 787 ◽  
Author(s):  
A. E. Fischer-Brown ◽  
B. R. Lindsey ◽  
F. A. Ireland ◽  
D. L. Northey ◽  
R. L. Monson ◽  
...  
Keyword(s):  
Oxygen Concentration ◽  
Latin Square ◽  
Bovine Embryos ◽  
Morphological Evaluation ◽  
Embryonic Disc ◽  
Developmental Capacity ◽  
Series Of Experiments ◽  
Oxygen Concentrations

Bovine embryos were produced in vitro using a 2 × 2 design of modified medium (KSOM or SOF) and oxygen concentration (5% or 20%). Day 7 blastocysts were transferred in bulk (n = 11, on average) to recipient heifers and recovered non-surgically at Day 14. In two replications of a Latin square, eight heifers received embryos from each combination of factors. Recovered embryos were evaluated for trophoblast length and width, as well as the presence and diameter of an embryonic disc (ED). An ED was detected in a higher percentage of embryos that had been cultured in KSOM than SOF (72% v. 46%, respectively; P < 0.05). The aim of a second series of experiments was to associate Day 14 morphology with subsequent developmental capacity. In vitro-produced blastocysts were transferred (n = 17–20) on Day 7 to each of eight heifers and recovered at Day 14. Thirty-eight blastocysts were retransferred to heifers following morphological evaluation. Embryos in which an ED with no signs of degeneration had been detected maintained more pregnancies than other embryos in which an ED had either shown signs of degeneration or had not been detected (5/8 v. 2/30, respectively; P < 0.01). Further investigation into ED integrity at the elongating stage may contribute to our understanding of pregnancy establishment and maintenance.

Mass Spectrometric Detection of Ionic and Neutral Species During Highly Preheated Air Combustion by Alkali Element Ion Attachment

2002 ◽  
Vol 124 (4) ◽  
pp. 749-756 ◽  
Author(s):  
T. Ishiguro ◽  
A. Matsunami ◽  
K. Matsumoto ◽  
K. Kitagawa ◽  
N. Arai ◽  
...  
Keyword(s):  
Oxygen Concentration ◽  
Chemical Species ◽  
Ionic Species ◽  
Combustion Mechanism ◽  
Low Oxygen ◽  
Neutral Species ◽  
Alkali Element ◽  
Compact Size ◽  
Ion Attachment ◽  
Low Oxygen Concentration

The use of high temperature and low oxygen concentration air as the oxidizer for regenerative combustion has become of increasing interest because this technology results in higher thermal efficiency, low energy consumption, and reduced emission of pollutants, such as NOx and CO2, and compact size of the equipment. In this study information is provided on the effect of preheating the low oxygen concentration air on the formation and detection of chemical ions and neutral species formed in flames. These ions and species were detected directly using mass spectrometry. Such information also assists in determining the combustion mechanism. The intact ionic species have been detected only at downstream position of the flames. By applying an alkali element Li+ ion attachment technique, neutral species, such as Li+-attached ions have been also detected successfully. Three specific flame cases have been examined. They include using normal air (flame I), preheated air (flame II), and preheated air with low (diluted) oxygen concentration in air (flame III). The results show significant change in the spectra of the intact ionic species and the Li+-adduct neutral species amongst the three flames. The results also show that preheating the combustion air increases the number of chemical species formed in the flames. However, these chemical species decrease with low oxygen concentration (diluted) combustion air.

Oxygen–fauna relationships in the pitcher plant Sarracenia purpurea L. with reference to the chironomid Metriocnemus knabi Coq.

1977 ◽  
Vol 55 (12) ◽  
pp. 2018-2023 ◽  
Author(s):  
C. J. Cameron ◽  
G. L. Donald ◽  
C. G. Paterson
Keyword(s):  
Oxygen Concentration ◽  
High Oxygen ◽  
Community Respiration ◽  
Sarracenia Purpurea ◽  
Dissolved Oxygen Concentration ◽  
High Oxygen Concentration ◽  
Pitcher Plant ◽  
Metriocnemus Knabi ◽  
Plant Photosynthesis ◽  
Oxygen Concentrations

The aquatic habitat contained within the leaf of the pitcher plant Sarracenia purpurea has a dissolved oxygen concentration consistently in excess of 77% saturation in spite of a high community respiration rate. The oxygen concentration is maintained primarily by diffusion through the wall of the sarcophagus and is not affected by plant photosynthesis. Because of the consistently high oxygen concentrations, the inquiline Metriocnemus knabi is not tolerant of lowered oxygen concentrations as it is adapted to a habitat with a consistently high oxygen concentration.

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