• Membrane Journal
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• v.23 no.5
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• pp.367-374
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• 2013

In the present study, Pebax-2533 plate membranes were prepared by drying precursor solutions which were obtained by dissolving Pebax-2533 polymer in 1-Propanol/n-Butanol mixed solvents. And then the $CO_2$ and $N_2$ permeation behaviors were tested by using a time-lag system. The prepared Pebax-2533 plate membranes showed a considerable $CO_2/N_2$ separation performance : the $CO_2$ permeability was 130 to 288 barr, and the $CO_2/N_2$ permselectivity was 5-8. The $CO_2$ permeation data obtained by varying feed pressure, permeation temperature, and solvent composition announced that not only the $CO_2$ sorption but also the $CO_2$ diffusion is equally important in the overall $CO_2$ permeation.

• Journal of Environmental Science International
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• v.12 no.8
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• pp.853-860
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• 2003

Plants sequester atmospheric CO$_2$, a major agent of climate change, during the growing periods and mitigate its rising accumulation in the atmosphere. Pinus densiflora and Quercus mongolica are the native tree species dominant in the temperate forests of Korea. This study quantified the annual CO$_2$ uptake by the two species at forest sites in Chuncheon in the middle of the country. The quantification was based on seasonal measurements of CO$_2$ exchange rates under natural conditions by an infrared gas analyzer over the growing season (1999). The monthly CO$_2$ uptake per unit leaf area ranged from 1.6-6.7 mg/d㎡/h for P. densiflora and from 3.7-8.9 mg/d㎡/h for Q. mongolica, with a maximum in mid-summer. An equation for each species was generated to estimate easily the annual CO$_2$ uptake by total leaf area per tree, which subtracted the CO$_2$ release (i.e. respiration) by leaves and woody organs from the gross CO$_2$ uptake (diurnal uptake and release by leaves). Annual CO$_2$ release by leaves and woody organs accounted for 58-73％ of the gross CO$_2$ uptake across tree specimens. Annual CO$_2$ uptake per tree increased with increasing dbh (stem diameter at breast height) for the study diameter range, and was greater for Q. mongolica than for P. densiflora in the same dbh sizes. This was mainly associated with a greater total leaf area in the former. For example, the annual CO$_2$ uptake by one tree with dbh of 25 cm was 35.6 kg/yr for P. densiflora and 47.9 kg/yr for Q. mongolica. The results from this study can be applied to evaluate an atmospheric CO$_2$ reduction of woody plants by forest type and age class.

• Journal of Environmental Science International
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• v.28 no.6
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• pp.553-559
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• 2019

In this study, zeolitic materials at $Na_2CO_3/CFA$ ratio of 0.6 - 1.8 were synthesized from coal fly ash from a thermal power plant using a fusion/hydrothermal method. The zeolitic materials were found to have cubic crystals structure and X-ray diffraction (XRD) peaks of Na-A zeolite by XRD and SEM analysis. When the zeolitic materials were synthesized from the coal fly ash, the XRD peaks of the zeolitic materials at $Na_2CO_3/CFA$ ratios of 0.9-1.8 had the same location as the XRD peaks of commercial Na-A zeolite. The XRD peaks of the Na-A zeolite ($Na_{12}Al_{12}Si_{12}O_{48}27.4H_2O$) were confirmed in the $2{\theta}$ in the range of 7.18-34.18. However, it was also confirmed that peaks of $CaCO_3$, an impurity inhibiting synthesis of Na-A zeolite from CaO and $Na_2CO_3$ in the coal fly ash, occurred in the XRD peaks of the zeolitic materials at $Na_2CO_3/CFA$ ratio of 1.5-1.8. The crystallinities of the zeolitic materials tended to increase gradually within the $Na_2CO_3/CFA$ ratio range of 0.6-1.8.

• Journal of Environmental Science International
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• v.20 no.2
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• pp.251-260
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• 2011

$TiO_2$- and $SiO_2$-supported $Co_3O_4$, Pt and $Co_3O_4$-Pt catalysts have been studied for CO and $C_3H_8$ oxidations at temperatures less than $250^{\circ}C$ which is a lower limit of light-off temperatures to oxidize them during emission test cycles of gasoline-fueled automotives with TWCs (three-way catalytic converters) consisting mainly of Pt, Pd and Rh. All the catalysts after appropriate activation such as calcination at $350^{\circ}C$ and reduction at $400^{\circ}C$ exhibited significant dependence on both their preparation techniques and supports upon CO oxidation at chosen temperatures. A Pt/$TiO_2$ catalyst prepared by using an ion-exchange method (IE) has much better activity for such CO oxidation because of smaller Pt nanoparticles, compared to a supported Pt obtained via an incipient wetness (IW). Supported $Co_3O_4$-only catalysts are very active for CO oxidation even at $100^{\circ}C$, but the use of $TiO_2$ as a support and the IW technique give the best performances. These effects on supports and preparation methods were indicated for $Co_3O_4$-Pt catalysts. Based on activity profiles of CO oxidation at $100^{\circ}C$ over a physical mixture of supported Pt and $Co_3O_4$ after activation under different conditions, and typical light-off temperatures of CO and unburned hydrocarbons in common TWCs as tested for $C_3H_8$ oxidation at $250^{\circ}C$ with a Pt-exchanged $SiO_2$ catalyst, this study may offer an useful approach to substitute $Co_3O_4$ for a part of platinum group metals, particularly Pt, thereby lowering the usage of the precious metals.

• Bulletin of the Korean Chemical Society
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• v.25 no.8
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• pp.1253-1256
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• 2004

• Journal of the Korean Magnetics Society
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• v.18 no.5
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• pp.185-189
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• 2008

We observe the change of coercivity and exchange bias, depending on inserting material and thickness in a [Pd(0.6 nm)/$Co(0.2)]_5$/ FeMn(10) multilayer structure with perpendicular anisotropy. When 0.78 and 1.28 nm thick NiFe substitutes for Co in a $[Pd(0.6 nm)Co(0.2)]_4$/Pd(0.6)/NiFe(t)/FeMn(10) structure, we obtain the exchange bias of 360 Oe. In addition, when $Co_8Fe_2$ and $Co_9Fe_1$ are inserted for Co/FeMn interface, we obtain the exchange bias of 380 nm for a 0.68 nm thick $Co_8Fe_2$ and 580 Oe for a 0.52 nm thick $Co_9Fe_1$.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.1002-1007
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• 2008

The purpose of this paper studied the optimal hydrogen production condition of plasma reforming system to operate the PEMFC. Plasma reforming reactor used with Ni catalyst reactor at the same time, So $H_2$ concentration increased. Also the WGS and PrOx reactor were designed to remove CO concentration under 10 ppm, because CO has effect on catalyst poisoning of PEMFC. The maximum $H_2$ production condition in plasma reforming system was S/C ratio 3.2, $CH_4$ flow rate 2.0 L/min, catalytic reactor temperature $700{\pm}5^{\circ}C$ and input power 900 W. At this time, the concentration of produced syngas was $H_2$ 70.2%, CO 7.5%, $CO_2$ 16.2%,$CH_4$ 1.8%. The hydrogen yield, hydrogen selectivity and $CH_4$ conversion rate were 56.8%, 38.1% and 92.2% respectively. The energy efficiency and specific energy requirement were 37.0%, 183.6 kJ/mol. In additional, The experiment of $CO_2/CH_4$ ratio proceeded. Also WGS reactor experiment was proceeding on optimum condition of plasma reactor and the exit concentration were $H_2$ 68%, CO 337 ppm, $CO_2$ 24.0%, $CH_4$ 2.2%, $C_2H_4$ 0.4%, $C_2H_6$ 4.1%. At this time, experiment result of PrOx reactor were $H_2$ 51.9%, CO 0%, $CO_2$ 17.3%.

• Advances in Energy Research
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• v.8 no.4
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• pp.265-273
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• 2022

In this study, a product gas yield and carbon conversion were measured during the coal pyrolysis. The pyrolysis process occurred under two different atmospheres such as subcritical (45 bar, 10℃) and supercritical CO₂ condition (80 bar, 35℃). Under the same pressure (80 bar), the atmosphere temperature increased from 35℃ to 45℃ to further examine temperature effect on the pyrolysis at supercritical CO₂ condition. For all three cases, a power input supplied to heating wire placed below coal bed was controlled to make coal bed temperature constant. The phase change of CO₂ atmosphere and subsequent pyrolysis behaviors of coal bed were observed using high-resolution camcorder. The pressure and temperature in the reactor were controlled by a CO₂ pump and heater. Then, the coal bed was heated by wire heater to proceed the pyrolysis under supercritical CO₂ condition.

• Journal of Bio-Environment Control
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• v.32 no.4
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• pp.416-422
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• 2023

This study was aimed to determine the changes in CO₂ concentration according to the temperatures of daytime and nighttime in the CO₂ supplemental greenhouse, and to compare calculated supplementary CO₂ concentration during winter and spring cultivation seasons. CO₂ concentrations in experimental greenhouses were analyzed by selecting representative days with different average temperatures due to differences in integrated solar radiation at the growth stage of leaf area index (LAI) 2.0 during the winter season of 2022 and 2023 years. The CO₂ concentration was 459, 299, 275, and 239 µmol·mol^-1, respectively at 1, 2, 3, and 4 p.m. after the CO₂ supplementary time (10:00-13:00) under the higher temperature (HT, > 18℃ daytime temp. avg. 31.7, 26.8, 23.8, and 22.4℃, respectively), while it was 500, 368, 366, 364 µmol·mol^-1, respectively under the lower temperature (LT, < 18℃ daytime temp. avg. 22.0, 18.9, 15.0, and 13.7℃, respectively), indicating the CO₂ reduction was significantly higher in the HT than that of LT. During the nighttime, the concentration of CO₂ gradually increased from 6 p.m. (346 µmol·mol^-1) to 3 a.m. (454 µmol·mol^-1) in the HT with a rate of 11 µmol·mol^-1 per hour (240 tomatoes, leaf area 330m²), while the increase was very lesser under the LT. During the spring season, the CO₂ concentration measured just before the start of CO₂ fertilization (7:30 a.m.) in the CO₂ enrichment greenhouse was 3-4 times higher in the HT (>15℃ nighttime temperature avg.) than that of LT (< 15℃ nighttime temperature avg.), and the calculated amount of CO₂ fertilization on the day was also lower in HT. All the integrated results indicate that CO₂ concentrations during the nighttime varies depending on the temperature, and the increased CO₂ is a major source of CO₂ for photosynthesis after sunrise, and it is necessary to develop a model formula for CO₂ supplement considering the nighttime CO₂ concentration.

• Journal of Climate Change Research
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• v.8 no.4
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• pp.357-367
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• 2017

Electricity generation in Korea mainly depends on thermal power and nuclear power. Especially the coal power has led to the increase in $CO_2$ emissions. This paper intends to analyze the current status of $CO_2$ emissions from electricity generation in Korea during the period 1990~2016, and apply the logarithmic mean Divisia index (LMDI) technique to find the nature of the factors influencing the changes in $CO_2$ emissions. The main results as follows: first, $CO_2$ emission from electricity generation has increased by $165.9MtCO_2$ during the period of analysis. Coal products is the main fuel type for thermal power generation, which accounts about 73% $CO_2$ emissions from electricity generation. Secondly, the increase of real GDP is the most important contributor to increase $CO_2$ emissions from electricity generation. The carbon intensity and the electricity intensity also affected the increase in $CO_2$ emission, but the energy intensity effect and the dependency of thermal power effect play the dominant role in decreasing $CO_2$ emissions.