scholarly journals Oxidation and Characterization of Low-Concentration Gas in a High-Temperature Reactor

Processes ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 481
Author(s):  
Jinhua Chen ◽  
Guangcai Wen ◽  
Song Yan ◽  
Xiangyun Lan ◽  
Lu Xiao
Keyword(s):  
High Temperature ◽  
Pressure Difference ◽  
High Temperature Oxidation ◽  
Air Pressure ◽  
Oxidation Products ◽  
Temperature Oxidation ◽  
Low Concentration ◽  
Temperature Environment ◽  
Explosion Limit ◽  
High Temperature Environment

To achieve the efficient utilization of low-concentration mine gas, reduce resource waste and alleviate environmental pollution, the high-temperature oxidation of low-concentration gas at a concentration range of 1.00% to 1.50%, which is directly discharged into the atmosphere during coal mine production, was carried out to recover heat for reuse. The gas oxidation equipment was improved for the heating process and the safety of low-concentration gas oxidation under a high-temperature environment was evaluated. The experimental results showed that the reactor could provide a 1000 °C high-temperature oxidation environment for gas oxidation after installing high-temperature resistant ceramics. The pressure variation curves of the reactor with air and different concentrations of gas were similar. Due to the thermal expansion, the air pressure slightly increased and then returned to normal pressure. In contrast, the low-concentration gas exhibited a stable pressure response in the high-temperature environment of 1000 °C. The outlet pressure was significantly greater than the inlet pressure, and the pressure difference between the inlet and outlet exhibited a trend to increase with the gas concentration. The minimum pressure difference was 4 kPa (air) and the maximum was 11 kPa (1.50% gas). The explosion limit varied with the temperature and the blend of oxidation products. The ratio of measured gas pressure to air pressure after oxidation was below the explosion criterion, indicating that the measured concentration of gas is still safe after the shift of the explosion limit, which provides a safe concentration range for the efficient use of low-concentration gas in the future.

scholarly journals Oxidation and Characterization of Low Concentration Gas in High-Temperature Reactor

2020 ◽  
Author(s):  
Jinhua Chen ◽  
Guangcai Wen ◽  
Song Yan ◽  
Xiangyun Lan ◽  
Lu Xiao
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Air Pressure ◽  
Oxidation Products ◽  
Heating Process ◽  
Temperature Oxidation ◽  
Low Concentration ◽  
Temperature Environment ◽  
Explosion Limit ◽  
High Temperature Environment

To achieve efficient utilization of low-concentration mine gas, reduce resource waste, and alleviate environmental pollution, high-temperature oxidation of low-concentration gas at a concentration range of 1.00% to 1.50% that is directly discharged into the atmosphere during coal mine production was oxidized to recover heat for reuse. The gas oxidation equipment was improved for the heating process, and the safety of low-concentration gas oxidation under high-temperature environment was evaluated. Experimental results showed that the reactor could provide a 1000 ℃ high-temperature oxidation environment for gas oxidation after installing high-temperature resistant ceramics. The pressure variation curves of the reactor with air and different concentrations of gas were similar. Due to the thermal expansion, the air pressure slightly increased and then returned to normal pressure. In contrast, the low-concentration gas exhibited a stable pressure response in the high-temperature environment of 1000 ℃. The outlet pressure was significantly greater than the inlet pressure, and the pressure difference between the inlet and outlet exhibited a trend to increase with the gas concentration. The explosion limit varied with the temperature and the blend with oxidation products. The ratio of measured gas pressure to air pressure after oxidation was below the explosion criterion, indicating that the measured concentration gas is still safe after the shift of explosion limit, which provides a safe concentration range for efficient use of low-concentration gas in the future.

High Temperature Oxidation Behaviour of Detonation-Gun-Sprayed Cr3C2-NiCr-CeO2 Coatings on Inconel-718 at 900°C

2014 ◽  
Author(s):  
Sekar Saladi ◽  
Jyoti V. Menghani ◽  
Satya Prakash
Keyword(s):  
High Temperature ◽  
Inconel 718 ◽  
High Temperature Oxidation ◽  
Parabolic Rate Constant ◽  
Coated Specimen ◽  
Oxidation Products ◽  
Temperature Oxidation ◽  
X Ray ◽  
Heating And Cooling ◽  
Detonation Gun

The high temperature oxidation behavior of detonation-gun sprayed Cr3C2-NiCr coatings with and without 0.4 wt. % CeO2 additive on Ni-based superalloy inconel-718 is comparatively discussed in the present study. Oxidation studies were carried out at 900°C for 100 cycles in air under cyclic heating and cooling conditions on bare and coated superalloys. The thermo-gravimetric technique was used to establish kinetics of oxidation. X-ray diffraction, SEM/EDAX and X-ray mapping techniques were used to analyze the oxidation products of bare and coated samples. The results indicate that Cr3C2-NiCr-CeO2 coated specimen showed better oxidation resistance. The overall weight gain and parabolic rate constant of Cr3C2-NiCr-CeO2 coated specimen was found to be lowest in the present study signifying that the addition of CeO2 in Cr3C2-NiCr powder has contributed to the development of adherent and dense oxide scale on the coating at elevated temperature.

Effects of temperature and Ti addition on high-temperature oxidation behaviors of Co-Al-W based superalloys

2020 ◽  
Vol 67 (5) ◽  
pp. 445-451
Author(s):  
Chunmei Ma ◽  
Songting Yang ◽  
Yuheng Zhang ◽  
Kaikun Wang ◽  
Huadong Fu
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Oxidation Products ◽  
Temperature Oxidation ◽  
Content Type ◽  
Oxidation Rates ◽  
Oxidation Stage ◽  
Effects Of Temperature ◽  
Ti Addition

Purpose Due to the special service environment of superalloys, this paper aims to obtain effects of temperature and Ti addition on high temperature oxidation behavior of Co-Al-W-B alloys. Design/methodology/approach Isothermal oxidation experiment of Co-Al-W-based alloys were carried out at 800°C, 900°C and 1000°C for different times (3, 5, 10, 20, 50 and 100 h) referring to the method of HB5258-2000. Oxidation weight gain curves and oxidation products were detected. Findings The results showed that the average oxidation rates of Co-Al-W-B alloy at 800 °C and 900 °C were 0.489 g·m−2·h−1 and 0.888 g·m−2·h−1, respectively, which belonged to an antioxidant grade. However, the average oxidation rate at 1000 °C was 2.068 g m−2·h−1, belonging to the secondary oxidation resistance class. In the alloy with Ti addition, dense Ti oxides film were formed at the early oxidation stage and then gradually diffused later, which can increase the oxidation resistance of the alloys to some extent. By analyzing the oxidation products of Co-Al-W-B alloy, it was found that a dense Al2O3 layer could be formed when the alloy was oxidized at 800°C. The continuous Al2O3 layer would prevent the oxygen from further spreading and make the alloy into the stable oxidation stage. However, only a non-dense Al2O3 layer were observed with 900°C oxidation. Originality/value It can provide references for the composition design, preparation process optimization and protective coating selection of the γ′ phase strengthened cobalt-base superalloys.

Effect of heating temperature on oxidation behavior of low density steels with medium manganese content

2020 ◽  
Vol 117 (6) ◽  
pp. 623
Author(s):  
Li Shujia ◽  
Lyu Naibing ◽  
Deng Suhuai ◽  
Luo Zhijun ◽  
Xu Shixin
Keyword(s):  
Weight Gain ◽  
High Temperature ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Heating Temperature ◽  
Manganese Content ◽  
Energy Dispersive Spectrometer ◽  
Oxidation Products ◽  
Low Density ◽  
Temperature Oxidation

The high temperature oxidation behavior of Fe–C (0.22%)–Mn (5.3%)–Al (2.5–3.2%)–Si (2.2%) low density steel was studied in the atmosphere of (2%O2 + Ar) by high temperature oxidation simulation tests. The samples were kept at 900 °C–1300 °C for 30 minutes and the morphology and the content distribution of oxide layer in the scale were characterized by scanning electron microscope combined with energy dispersive spectrometer. The results show that: when the holding temperature is below 1150 °C, the oxidized weight gain increases parabolically with time; when the temperature is maintained above 1200 °C, the oxidized weight gain increases linearly. Oxidation activation energy decreases with experimental temperature from 225.31 to 43.4 kJ/mol and due to formation of liquid oxidation products the value of Ea decreases sharply from 1100 °C.For all range of temperature the outer layer of the scale is FeOn–MnO oxide while the scale is mainly SiO2–Al2O3–FeOn–MnO near the matrix. Few variations could be observed for the morphology of scales when the heating temperature ranged from 900 °C to 1100 °C. When the heating temperature is over 1150 °C the liquid Fe2SiO4 and FeO–SiO2–MnO phases in the scale were newly formed, leading to the penetration of liquid oxide scale into the steel, which makes descaling difficult. Therefore, to facilitate the descaling operation before hot rolling, temperature should be controlled below 1150 °C in the reheating furnace.

scholarly journals HIGH TEMPERATURE AND ELECTROCHEMICAL CORROSION OF Zn0.5Al ALLOY DOPED WITH CALCIUM IN VARIOUS MEDIA

2020 ◽  
Vol 63 (11) ◽  
pp. 21-26
Author(s):  
Ziyodullo R. Obidov ◽  
Jamshed Kh. Dzhailoev ◽  
Izatullo N. Ganiev ◽  
Odiljon N. Nazarov ◽  
Rakhmatjon Usmanov ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
High Temperature ◽  
Oxidation Rate ◽  
High Temperature Oxidation ◽  
Atmospheric Oxygen ◽  
Electrochemical Corrosion ◽  
Oxidation Products ◽  
Alkaline Media ◽  
Potential Sweep ◽  
Temperature Oxidation

The article presents the results of a study of high-temperature and electrochemical corrosion of Zn0.5Al alloy doped with calcium in the various media. The thermogravimetric method was used to study the interaction of the Zn0.5Al alloy doped with calcium with atmospheric oxygen in the temperature range 523–623 K in the solid state. The kinetic and energy parameters of the process of high-temperature oxidation of alloys are determined. The process of high-temperature oxidation of Zn-Al-Ca alloys system is characterized by a monotonic decrease in the true oxidation rate and an increase in the effective activation energy when the alloying component in the initial Zn0.5Al alloy is up to 1.0 wt% doping with zinc-aluminum alloy 0.5 and 1.0 wt%. Calcium shows a slight increase in the oxidation rate of alloys. It was revealed that the oxidation process of the studied alloys with oxygen of the gas phase obeys the hyperbolic law. It was found that calcium supplements in the range of 0.01 - 0.1 wt%. The oxidizability of the initial Zn0.5Al alloy is reduced significantly, and the oxidation products of the alloys were ZnO, Al2O3, Al2O3 ∙ ZnO, CaO, Al2O3 ∙ CaO. By potentiostatic methods in the potentiodynamic mode with a potential sweep speed of 2 mV/s, it has been shown that for all samples of the Zn0.5Al-Ca alloys system in the acidic, neutral, and alkaline media, electrochemical potentials of corrosion, pitting formation, and repassivation are shifted to the region of negative values. It was revealed that zinc-aluminum alloys doped with calcium are most resistant to pitting corrosion in all studied media, respectively, in acidic (0.01n.), neutral (0.03-, 0.3-, 3.0 wt%) and alkaline (0.01n.) electrolytes of HCl, NaCl and NaOH. It has been established that calcium additions in the range of 0.01 - 0.1 wt.% reduce the corrosion rate of zinc-aluminum alloy Zn0.5Al by a factor of 2–3. Calcium alloys are recommended as anodic coatings and protectors for corrosion protection of steel products and structures operating at high temperatures.

scholarly journals High Temperature Oxidation and Thermal Shock Properties of La2Zr2O7 Thermal Barrier Coatings Deposited on Nickel-Based Superalloy by Laser-Cladding

Coatings ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 370 ◽  
Author(s):  
Kaijin Huang ◽  
Wei Li ◽  
Kai Pan ◽  
Xin Lin ◽  
Aihua Wang
Keyword(s):  
High Temperature ◽  
Thermal Shock ◽  
Laser Cladding ◽  
High Temperature Oxidation ◽  
Isothermal Oxidation ◽  
Oxidation Products ◽  
Thermal Barrier ◽  
Temperature Oxidation ◽  
Nickel Based Superalloy ◽  
Barrier Coating

In order to reduce the difficulty and cost of manufacturing and improve the high temperature oxidation and thermal shock properties of nickel-based superalloy, a thin La2Zr2O7 thermal barrier coating without bond coat was successfully prepared by laser-cladding using La2Zr2O7 powders on a nickel-based superalloy substrate. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods were used to characterize the microstructure of the coating. The high temperature oxidation and thermal shock properties of the coating were evaluated by the air isothermal oxidation method at 1100 °C for 110 h and thermal cycling method at 25~1100 °C, respectively. The results show that the coating is mainly composed of La2Zr2O7 phase. The oxidation weight gain rate of the coating is about two-thirds of that of the substrate, and the first crack thermal shock lifetime of the coating is about 1.67 times of that of the substrate. The oxidation products of the coating are mainly Fe2O3, Cr2O3, NiCr2O4, Nb2O5 and La2Zr2O7. The existence of La2Zr2O7 phase in the coating is the main reason for the improvement of its oxidation resistance at 1100 °C and its thermal shock resistance at 25~1100 °C.

Effects of Cr and Al on High Temperature Oxidation Resistance of Nb-Si System Intermetallics

2007 ◽  
Vol 546-549 ◽  
pp. 1485-1488 ◽  
Author(s):  
Shi Yu Qu ◽  
Ya Fang Han ◽  
Jin Xia Song ◽  
Yong Wang Kang
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Oxidation Products ◽  
X Ray Diffraction ◽  
Temperature Oxidation ◽  
X Ray ◽  
Scanning Electron

The effects of Cr and Al on high temperature oxidation resistance of Nb-Si system intermetallics have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and weight gain method. The results showed that the high temperature oxidation resistance can be substantially improved by proper Cr or Al addition. The further analysis revealed that Cr promotes the formation of CrNbO4 in scale and improve the adherence between the oxide scale and the substrate. It also found that Al improves the surface morphology of oxide scale and changes oxidation products by promoting the AlNbO4 formation.

High-temperature oxidation of Moss—Mo3Si alloys doped with Sc or Y in air and in a steam-air mixture

2021 ◽  
pp. 12-22
Author(s):  
L.Yu. Udoeva ◽  
◽  
A.V. Larionov ◽  
K.V. Pikulin ◽  
S.N. Agafonov ◽  
...  
Keyword(s):  
Rare Earth ◽  
Phase Composition ◽  
High Temperature ◽  
Rare Earth Elements ◽  
High Temperature Oxidation ◽  
Oxidation Products ◽  
Metal Silicide ◽  
Temperature Oxidation ◽  
Molybdenum Alloys ◽  
Isothermal Mode

For continuation of investigations aimed at studying the effect of rare earth elements (RRE) on the behavior of metal-silicide molybdenum alloys in oxidizing environments, the results of experimental modeling of high-temperature oxidation of alloys based on Mo—15 (at.%) Si and doped with Sc or Y in the isothermal mode in the air and in a steam-air environment are presented. New data on the effect of REE on oxidation resistance of alloys of the Mo—Si system of hypoeutectic composition, the formation of scale on their surface, the phase composition and the structure of oxidation products was obtained.

Electron petrography of high-temperature oxidation in olivine from the Rhum Layered Intrusion

1979 ◽  
Vol 43 (326) ◽  
pp. 293-296 ◽  
Author(s):  
A. Putnis
Keyword(s):  
Electron Microscope ◽  
High Temperature ◽  
High Temperature Oxidation ◽  
Intermediate Phase ◽  
Layered Intrusion ◽  
Decomposition Process ◽  
Oxidation Products ◽  
Temperature Oxidation ◽  
Cellular Decomposition ◽  
Olivine Structure

SummaryElectron-microscope observations of the oxidation products of olivine suggest that oxidation results in the formation ofplatelets of an ‘oxidized olivine’ phase, which has a superstructure of the olivine structure. Subsequently this intermediate phase breaks down by a cellular decomposition process to a eutectoidal intergrowth of magnetite and pyroxene. This intergrowth is responsible for the dendritic magnetite inclusions commonly observed in some olivines from Rhum.

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