• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.8
• /
• pp.839-845
• /
• 2011

We performed numerical simulations of freely propagating premixed flames at atmospheric pressure to investigate the influence of trifluoromethane on $CH_4/O_2/N_2$ flames under oxygen enrichment. Trifluoromethane significantly contributed toward a reduction in flame speed, the magnitude of which was larger in terms of the physical effect than the chemical effect. More trifluoromethane could be added and consumed on oxygen-enriched $CH_4/O_2/N_2$ flames. $CHF_3$ was decomposed primarily via $CF_3{\rightarrow}CF_2{\rightarrow}CF{\rightarrow}CF:O{\rightarrow}CO$ and $CHF_3+M{\rightarrow}CF_2+HF+M$ played an important role in oxygen-enhanced flames. When an inhibitor was added to oxygen-enriched flames, the position of the maximum concentration of active radicals was shifted to a relatively low temperature range, and the net rate of OH became higher than that of H.

• Journal of Life Science
• /
• v.17 no.6 s.86
• /
• pp.791-797
• /
• 2007

We studied the inhibitory effect of solvent fractions from doenjang on mutagenicity using Salmonella typhimurium TA100 in Ames test. We also investigated the effect of solvent fractions from doenjang on the growth of tumor cells and the production of interleukin-2 (IL-2). The treatment of dichlorormethane and ethylacetate fractions (2.5 mg/assay) from doenjang to Ames test system inhibited aflatoxin B$_1$ (AFB$_1$) induced mutagenicity by 96% and 97%, respectively, and showed a higher antimutagenic effect than other solvent fractions. In case of N-methyl-N'-nitro-N-nitrosoguamidine (MNNG) induced mutagenicity, the ethylacetate fraction showed the highest inhibitory effect (by 75%) among the other sol-vent fractions, although the inhibitory effect was not stronger compared to AFB$_1$ induced mutagenicity. The treatment of dichloromethane and ethylacetate fractions markedly inhibited the growth of Yac-1 (by 80% and 94%, respectively) and sacroma-180 cancer cells (by 60% and 96%, respectively) after 4 days of incubation at 37${\circ}$C. To elucidate the immunological mechanism of antitumor activity of doenjang, spleen cells of Balb/c mouse were exposed to the dichloromethane and ethyl-acetate fractions for 24 hours at 37${\circ}$C . The culture supernatants following the treatment of djchloromethane and ethylacetate factions to spleen cells increased the production of IL-2. These results indicated that the anticarcinogenic effect of doenjang was mediated by the production of IL-2.

• Journal of the Korean Institute of Gas
• /
• v.5 no.3 s.15
• /
• pp.55-62
• /
• 2001

This paper describes about the formation of methane hydrate that is artificially made in jacket-type stirred reactor and is observed the change of hydrate shape during the course of reaction. The combustion of manufactured methane hydrate is showed the probability of a storage and transport of gas. And the influence of various experimental conditions of temperature, pressure and stirring rate on the manufacture of methane hydrate is measured. The growth rate and the induction time of methane hydrate is observed according to the conditions. Especially it is important to investigate the effect of temperature and pressure on the growth of hydrate such as the nuclear creation and the structure formation of hydrate in order to study the storage and transport of gas.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.5
• /
• pp.849-859
• /
• 2000

This study was conducted to identify the characteristics of methane fermentation and lysis effects of pre-treated microalgae. Chemical compositions of microalgae showed that the VS(volatile solid) was 86.1% of TS(total solid), and the protein was 63.5% of VS. These values were higher than those of activated sludge. The cell lysis test of raw microalgae biomass was conducted by many physicochemical methods. presenting that the degree of cell lysis was affected by following order: ultrasonic(100min.), alkali(pH 13), ultrasonic(10min), thermal($120^{\circ}C$), thermal($50^{\circ}C$), and acidic(pH 3) treatment. Methane fermentation with many pre-treated samples was performed, showing that the concentration of acetic acid was the highest. followed by propionic acid, butylic acid and valerie acid among all VFA(volatile fattic acid). In methane production. ultrasonic samples were only more effective than untreated one in total gas and methane productivity. but other samples were less effective. Especially. the alkalic sample had an inhibitation effect on methanogens.

• Journal of Energy Engineering
• /
• v.15 no.1 s.45
• /
• pp.52-59
• /
• 2006

This paper examined the conversion of methane to hydrogen and other higher hydrocarbons using dielectric barrier discharge with AC pulse power. Two metal electrodes of a coaxial-type plasma reactor were separated by gas gap and an alumina tube. The inner electrode was located inside the alumina tube. The alumina tube was located inside the stainless steel tube, which was used as the outer electrode. Effect of feed gas composition (methane, oxygen, argon, water and helium), flow rate, applied frequency, input volt-age on methane conversion and product distribution were studied. The major products of plasma chemical reactions were ethylene, ethane, propane, buthane, hydrogen, carbon monoxide and carbon dioxide. The increment of applied voltage and the usage of inert gas as the background (helium and argon) enhanced the selectivity of hydrocarbons and methane conversion. The addition of water in the feed stream enhanced the conversion of methane and yield of hydrogen. Higher voltage leads to higher yield of $C_2H_6,\;C_3H_8,\;C_4H_{10}$ and yield or $C_2H_2\;and\;C_2H_4$ appeared highly in lower voltage.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.6B
• /
• pp.683-687
• /
• 2006

This research investigated the effect of aeration pretreatment for anaerobic seed sludge on hydrogen production. Aeration time for anaerobic sludge was maintained at 0, 1, 3, 6, 12, and 24 hours in batch tests. Two continuous anaerobic reactors (aerated and non-aerated) were also operated. All experiments were conducted at $35^{\circ}C$ using mineral salts-glucose (20 g/l) medium. Methane production decreased with the increase in aeration time. Aeration for 6 hours was determined as an optimum from the amount of hydrogen produced. Hydrogen was steadily produced in the continuous reactor seeded with aerated sludge while no methane production was observed. However, small amount of hydrogen was produced in the non-aerated reactor for short period of time from the start even though short HRT (2 days) and low pH (5.5) were maintained.

• Korean Journal of Soil Science and Fertilizer
• /
• v.43 no.2
• /
• pp.242-251
• /
• 2010

In comparison with other terrestrial ecosystems, rice paddies are unique because they provide the primary food source for over 50% of the world's population, and act as major sources of global methane. The present paper summerizes a long-term field study that combine carbon isotopes, and canopy-scale flux measurements in an irrigated rice paddy, in conjugation with continuous monitoring of environmental, and vegetational factors. Both $CO_2$, and methane fluxes were largely influenced by soil temperature, and moisture conditions, especially across drainage events. Soil-entrapped $CO_2$, and methane showed a gradually increasing trend throughout growing season, but rapidly decreased upon flood water drainage. These variations in flux were well correlated with changes in concentration, and isotope ratio of soil $CO_2$, and methane, and of atmospheric $CO_2$, and methane within, and above the canopy. The isotopic signature of the gas exchange process varied markedly in response to change in contribution of soil respiration, belowground storage, fraction of $CO_2$ recycled, magnitude, and direction of $CO_2$ exchange, transport mechanism, and fraction of methane oxidized. Our results clearly demonstrate that stable isotope analysis can be a useful tool to study underlying mechanisms of gas exchange processes under natural conditions.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.7
• /
• pp.739-745
• /
• 2005

Simultaneous denitrification and methanogenesis at various influent COD/Nitrate-N(below C/N) ratio was investigated with two different anaerobic sludges of which one was inoculated with glucose only and the other was inoculated with glucose and nitrate. Three different C/N ratios of 30, 20, and 10 were applied with each anaerobic sludge in serum bottles agitated in a rotary shaker to monitor the time related changes of amount of gas production and gas composition. Glucose was used as a single carbon source, which was adjusted to 1,000 mg/L as COD and potassium nitrate was used as a nitrogen source to adjust the each C/N ratio. COD removal by methanogenesis was dominant at higher C/N ratios, while COD removal by denitrification was dominant at lower C/N ratios. With the sludges cultured at C/N ratios below 10, SMA and SDNR rising different carbon substrates were investigated. The most efficient carbon substrate was acetate and the highest SMA and SDNR were 0.76 g COD/g VSS day with pure anaerobic sludge and 1.38 g ${NO_3}^--N/g$ VSS day with sludge cultured at C/N ratio of 5, respectively.

• Applied Chemistry for Engineering
• /
• v.10 no.2
• /
• pp.242-246
• /
• 1999

For the fluorination of $CF_2Cl_2$, the yield of $CF_4$ was found to be increased with the contact time and the reaction temperature. When the mole ratio of HF/$CF_2Cl_2$ is 3 or above, the yield of $CF_4$ was attained to 100% at $370^{\circ}C$ and contact time of 3 seconds. In the case of the fluorination of $CCl_4$ with HF, the yield of $CF_4$ was obtained above 90% at the reaction temperature of $500^{\circ}C$, the contact time of 3 seconds, and the mole ratio of HF/$CCl_4$ of 5.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.24 no.1
• /
• pp.21-29
• /
• 2016

We mix food waste leachate and sewage sludge by the proportion of 1:9, 3:7 and 5:5. It turns out that they produced 233, 298 and 344 $CH_4{\cdot}mL/g{\cdot}VS$ of methane gas. The result suggests that as the mixing rate of food waste leachate rises, the methane gas productions increases as well. And more methane gas is made when co-digesting sewage sludge and food waste leachate based on the mixing ratio, rather than digesting only sewage sludge alone. Modified Gompertz and Exponential Model describe the BMP test results that show how methane gas are produced from organic waste. According to the test, higher the mixing rate of food waste leachate is, higher the methane gas productions is. The mixing ratio of food waste leachate that produces the largest volume of methane gas is 3:7. Modified Gompertz model and Exponential model describe the test results very well. The correlation values($R^2$) that show how the results of model prediction and experiment are close is 0.92 to 0.98.