• 한국응용과학기술학회지
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• 제24권3호
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• pp.272-277
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• 2007

Catalytic activity changes of perovskite catalysts were examined with their A-site substitution. For the preparation of catalysts, Mn was used for B-site component and La, Ce, Sr, Ba, Ca, Ag were used for A-site component of the perovskite $catalysts(ABO_3)$ The effect of calcination temperature on methane combustion and perovskite structure was also investigated. The surface area and adsorbed oxygen species were tested with BET apparatus and $O_2-TPD$, respectively. Perovskite catalysts whose A-site was partially substituted needed higher calcination temperature than un-substituted one to form the perovskite structure. From $O_2-TPD$ experiment, it was found that methane combustion activity was directly related to the oxygen desorbing ability of the catalysts. The prepared catalyst(LM-7) was stable at $600^{\circ}C$ for 72 hours of reaction.

• 한국연소학회지
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• 제22권1호
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• pp.8-13
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• 2017

Ignition delay time of methane/oxygen mixture is measured experimentally with the shock tube in order to obtain the data for high pressure conditions where gas turbines and internal combustion engines are operating. The shock tube experiment is validated first over the temperature range of 1400-2000 K at 10 bar and with the various equivalence ratios of 0.5, 1 and 2. The measured ignition delays are compared with the data from the literatures. And then, experiments are conducted for non-explored conditions, i.e., at 40 bar and with the equivalence ratio of 1.5. The present experimental data show a good agreement with the available ones from the literatures and reasonable dependence on pressure and equivalence ratio. In addition, the effects of the temperature and equivalence ratio on ignition delay time are analyzed.

• Bulletin of the Korean Chemical Society
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• 제22권12호
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• pp.1323-1327
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• 2001

The catalyst Ni/MgO (Ni : 15 wt%) has been applied to methane reforming reactions, such as steam reforming of methane (SRM), partial oxidation of methane (POM), and oxy-steam reforming of methane (OSRM). It showed high activity and good stability in all the reforming reactions. Especially, it exhibited stable catalytic performance even in stoichiometric SRM (H2O/CH4 = 1). From TPR and H2 pulse chemisorption results, a strong interaction between NiO and MgO results in a high dispersion of Ni crystallite. Pulse reaction results revealed that both CH4 and O2 are activated on the surface of metallic Ni over the catalyst, and then surface carbon species react with adsorbed oxygen to produce CO.

• 대한기계학회논문집B
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• 제33권5호
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• pp.343-348
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• 2009

The present study has experimentally investigated the effects of $CO_2$ diluted oxygen on the structure of swirl-stabilized flame in a lab-scale combustor. The methane fuel and oxidant mixture gas ($CO_2$ and $O_2$) were mixed in a pre-mixer and introduced to the combustor through different degrees of swirl vanes. The flame characteristics were examined for various amount of carbon dioxide addition to the methane fuel and various swirl strengths. The effects of carbon dioxide addition and swirl intensity on the combustion characteristics of pre-mixed methane flames were examined using chemiluminescence techniques to provide information about flow field. The results show that the hot combustion zone increases at the upstream reaction zone because of an increase in the recirculation flow for an increase in swirl intensity. The hot combustion zone is also increased at the downstream zone by recirculation flow because of an increase in swirl intensity which results in higher centrifugal force. The OH and CH radical intensities of reaction zone decrease with carbon dioxide addition because the carbon dioxide plays a role of diluted gas in the reaction zone.

• 한국대기환경학회지
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• 제23권5호
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• pp.557-562
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• 2007

The purpose of this paper is to investigate the reforming characteristics and maximum operating condition for the hydrogen production by methane reforming using the compression ignition engine induced partial oxidation. An dedicated compression engine used for methane reforming was decided operating range. The partial oxidation reforming was investigated with oxygen enrichment which can improve hydrogen production, compared to general reforming. Parametric screening studies were achieved as $O_2/CH_4$ ratio, total flow rate, and intake temperature. When the variations of $O_2/CH_4$ ratio, total flow rate, and intake temperature were 1.24, 208.4 L/min, and $400^{\circ}C$, respectively, the maximum operating conditions were produced hydrogen and carbon monoxide. Under the condition mentioned above, synthetic gas were $H_2\;22.77{\sim}29.22%,\;CO\;21.11{\sim}23.59%$.

• Animal Bioscience
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• 제36권5호
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• pp.818-828
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• 2023

Objective: The purpose of this study was to analyze the effect of the hydrothermal pretreatment of anaerobic digestion sludge cake (ADSC) of cattle manure on the solubilization of organic matter and the methane yield to improve the anaerobic digestion efficiency of cattle manure collected from the sawdust pens of cattle. Methods: Anaerobic digestion sludge cake of cattle manure was thermally pretreated at 160℃, 180℃, 200℃, and 220℃ by a hydrothermal pressure reactor, and the biochemical methane potential of ADSC hydrolysate was analyzed. Methane yield recovered by the hydrothermal pretreatment of ADCS was estimated based on mass balance. Results: The chemical oxygen demand solubilization degree (COD_s) of the hydrothermal hydrolysate increased to 63.56%, 67.13%, 70.07%, and 66.14% at the hydrothermal reaction temperatures of 160℃, 180℃, 200℃, and 220℃, respectively. Considering the volatile solids content obtained after the hydrothermal pretreatment, the methane of 10.2 Nm³/ton-ADSC was recovered from ADSC of 1.0 ton, and methane yields of ADSC hydrolysate increased to 15.6, 18.0, 17.4, and 17.2 Nm³/ton-ADSC. Conclusion: Therefore, the optimal hydrothermal reaction temperature that yielded the maximum methane yield was 180℃ based on mass balance, and the methane yield from cattle manure containing sawdust was improved by the hydrothermal pretreatment of ADSC.

• Ocean and Polar Research
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• 제44권1호
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• pp.1-11
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• 2022

Hypoxia can affect water-atmosphere methane flux by controlling the production and consumption processes of methane in coastal areas. Seasonal methane concentration and fluxes were quantified to evaluate the effects of seasonal hypoxia in Dangdong Bay (Gyeongsangnamdo, Jinhae Bay, South Korea). Sediment-water methane flux increased more than 300 times during hypoxia (normoxia and hypoxia each 6, 1900 µmol m^-2 d^-1), and water-atmospheric methane flux and bottom methane concentration increased about 2, 10 times (normoxia and hypoxia each 190, 420 µmol m^-2 d^-1; normoxia and hypoxia each 22, 230 nM). Shoaling of anaerobic decomposition of organic matter in the sediments during the hypoxia (August) was confirmed by the change of the depth at which the maximum hydrogen sulfide concentration was detected. Shoaling shortens the distance between the water column and methanogenesis section to facilitate the inflow of organic matter, which can lead to an increase in methane production. In addition, since the transport distance of the generated methane to the water column is shortened, consumption of methane will be reduced. The combination of increased production and reduced consumption could increase sediment-aqueous methane flux and dissolved methane, which is thought to result in an increase in water-atmospheric methane flux. We could not observe the emission of methane accumulated during the hypoxia due to stratification, so it is possible that the estimated methane flux to the atmosphere was underestimated. In this study, the increase in methane flux in the coastal area due to hypoxia was confirmed, and the necessity of future methane production studies according to oxygen conditions in various coastal areas was demonstratedshown in the future.

• 한국세라믹학회지
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• 제27권4호
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• pp.513-520
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• 1990

Diamond film was deposited on Si wafer substrate from a gas mixture of methane, hydrogen and oxygen by microwave plasma-assisted chemical vapor deposition. The effects of the pre-treatments of the substrate and of the oxygen addition on the diamond film synthesis are described. In order to obtain diamond film, the substrate was pre-treated with 3 kinds of methods. When the substrate was ultrasonically vibrated within the ethyl alcohol dispersed with 25${\mu}{\textrm}{m}$ diamond powder, the denset diamond film was deposited. Addition of oxygen in the gas mixture of methane and hydrogen improved the crystallinity of the deposited diamond film and also increased the deposition rate of the diamond film more than two times.

• Environmental Engineering Research
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• 제19권1호
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• pp.75-81
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• 2014

Methanotrophic denitrification under a non-aerated condition (without external supply of oxygen or air) was investigated in a bioreactor coupled with a membrane diffuser. Batch experiment demonstrated that both methane consumption and nitrogen production rates were not high in the absence of oxygen, but most of the nitrate was reduced into $N_2$ with 88% recovery efficiency. The methane utilized for nitrate reduction was determined at 1.63 mmol $CH_4$/mmol $NO_3{^-}$-N, which was 2.6 times higher than the theoretical value. In spite of no oxygen supply, methanotrophic denitrification was well performed in the bioreactor, due to enhanced mass transfer of the methane by the membrane diffuser and utilization of oxygen remaining in the influent. The denitrification efficiency and specific denitrification rate were 47% and 1.69 mg $NO_3{^-}-N/g\;VSS{\cdot}hr$, respectively, which were slightly lower than for methanotrophic denitrification under an aerobic condition. The average concentration of total organic carbon in the effluent was as low as 2.45 mg/L, which indicates that it can be applicable as a post-denitrification method for the reclamation of secondary wastewater effluent. The dominant fatty acid methyl ester of mixed culture in the bioreactor was $C_{16:1{\omega}7c}$ and $C_{18:1{\omega}7c}$, which was predominantly found in type I and II methanotrophs, respectively. This study presents the potential of methanotrophic denitrification without externally excess oxygen supply as a post-denitrification option for various water treatment or reclamation.

• 한국수소및신에너지학회논문집
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• 제25권6호
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• pp.570-576
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• 2014

LFG (Land-Fill Gas) includes components of $CH_4$, $CO_2$, $O_2$, $N_2$, and water. The preparation of synthesis gas from LFG as a DME (Dimethyl Ether) feedstock was studied by methane reforming of $CO_2$, $O_2$ and steam over NiO-MgO-$CeO_2$/$Al_2O_3$ catalyst. Our experiments were performed to investigate the effects of methane conversion and syngas ratio on the amount of LFG components over NiO-MgO-$CeO_2$/$Al_2O_3$ catalyst. Results were obtained through the activity reaction experiments at the temperature of $900^{\circ}C$ and GHSV of 4,000. The results were as following; it has generally shown that methane conversion rate increased with the increase of oxygen and carbon dioxide amounts. Highly methane conversion of 92~93% and syngas ratio of approximately 1.0 were obtained in the feed of gas composition flow-rate of 243ml/min of $CH_4$, 241ml/min of $CO_2$, 195ml/min of $O_2$, 48ml/min of $N_2$, and 360ml/min of water, respectively, under reactor pressure of 15 bar for 50 hrs of reaction time. Also, it was shown that catalyst deactivation by coke formation was reduced by excessively adding oxygen and steam as an oxidizer of the methane reforming.