• Journal of Korean Society of Environmental Engineers
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• v.34 no.12
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• pp.840-846
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• 2012

Global climate changes caused by $CO_2$ emissions are currently debated around the world; green sources of energy are being sought as alternatives to replace fossil fuels. The sustainable use of biogas for energy production does not contribute to $CO_2$ emission and has therefore a high potential to reduce them. Catalytic steam reforming of a model biogas ($CH_4:CO_2$ = 60%:40%) is investigated to produce $H_2$-rich synthesis gas. The biogas utilized 3D-IR matrix burner in which the surface combustion is applied. The ruthenium catalyst was used inside a reformer. Parametric screening studies were achieved as Steam/Carbon ratio, biogas component ratio, Space velocity and Reformer temperature. When the condition of Steam/Carbon ratio, $CH_4/CO_2$ ratio, Space velocity and Refomer temperature were 3.25, 60% : 40%, $14.7L/g{\cdot}hr$ and $550^{\circ}C$ respectively, the hydrogen concentration and methane conversion rate were showed maximum values. Under the condition mentioned above, $H_2$ yield, $H_2$/CO ratio, CO selectivity and energy efficiency were 0.65, 2.14, 0.59, 51.29%.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.4
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• pp.277-285
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• 2014

The usage of efficient microorganism (EM) is increasing in concern for server purposes including odor removal during carcasses degradation. In this study, we have studied the type of soil and its effect on efficient microorganisms for the removal of odorous gases during buried carcasses degradation in lab-scale reactor. The carcasses are buried in the reactor with various soil types such as normal soil, 20% sandy and 20% clay soil with the efficient microorganism KEM. The efficient microorganisms KEM have the ability to stabilize the degradation of carcasses of the burial site. We have focused on the analysis of odorous gases such tri-methylamine (TMA), hydrogen sulfide ($H_2S$), methyl mercaptan (MM), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), carbon dioxide ($CO_2$), and methane ($CH_4$) along with the changes of microbial community changed during complete degradation of buried carcasses for a year. The results suggested that the 20% sandy soil contain lesser level of $H_2S$ and MM (0.09 and 0.35 mg) but 20% clay has higher nitrogen compound removing effect and leave only less amount of ammonia and TMA (0.31 and 2.06 mg). The 20% sandy soil also has the ability to breakdown the carcasses more quality compared with other types of soil. Based on the data obtained in this study suggesting that, the use of 20% sandy soil can effectively control sulfur compounds whereas 20% clay soil controls nitrogen compounds in the buried soil. Depending on the type of the soil, the dominant of microbial communities and the distribution was change.

• Elastomers and Composites
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• v.46 no.4
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• pp.343-351
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• 2011

We prepared polyurethane foam/cloisite30B/phosphates composites and characterized their rise time, density, cell morphology, and thermal properties. The composites were synthesized with polyadipatediol-cloisite30B composite (f=2.0), polyether-polyol (f=4.6), polymeric 4,4-diphenyl methane diisocyanate (f=2.5), and D-580 (phenyl polyoxyalkenyl phosphate). As a blowing agent, cyclopentane and distilled water were used at various concentrations of D-580 from 0 to 2.81 wt%. The rise times of PUF/Closite30B/Phosphate composites blown with distilled water were faster than those blown with cyclopentane by 30%. The composites blown with cyclopentane had spherical-shape cells and the cell diameter was decreased with increasing D-580 wt%. While $T_g$ of the composites blown with cyclopentane linearly decreased with increasing the D-580 content, the $T_g$ of the composites blown with distilled water increased with the D-580 content. All PUF/Closite30B/Phosphate composites began to decompose from $250^{\circ}C$. The composites blown with cyclopentane showed the second thermal decomposition at temperatures higher than $500^{\circ}C$. The thermal stability of all composites increased with the D-580 content. The effect of D-580 on the thermal stability of the composites was measured higher at the composites blown with distilled water.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.1
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• pp.104-111
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• 2011

In order to assess the performance of co-digester using pig slurry and food waste at the farm scale biogas production facility, the anaerobic facility that adopts the one-stage CSTR of 5 $m^3\;day^{-1}$ input scale was designed and installed under the conditions of the OLR of 2.33 kg $m^3\;day^{-1}$ and HRT of 30 days in an pig farmhouse. Several operation parameters were monitored for assessment of the process performance. The anaerobic facility was operated in three stages to compare the performance of the anaerobic co-digester. In the Stage I, that was fed with a mix of pig slurry to food waste ratio of 7:3 in the input volume, where input TS content was 4.7 (${\pm}0.8$) %, and OLR was 0.837-1.668 kg-VS $m^3\;day^{-1}$. An average biogas yield observed was 252 $Nm^3\;day^{-1}$ with methane content 67.9%. This facility was capable of producing an electricity of 626 kWh $day^{-1}$ and a heat recovery of 689 Mcal day-1. In Stage II, that was fed with a mixture of pig slurry and food waste at the ratio of 6:4 in the input volume, where input TS content was 6.9 (${\pm}1.9$) %, and OLR was 1.220-3.524 kg-VS $m^3\;day^{-1}$. The TS content of digestate was increased to 3.0 (${\pm}0.3$) %. In Stage III, that was fed with only pig slurry, input TS content was 3.6 (${\pm}2.0$) %, and OLR was 0.182-2.187 kg-VS $m^3\;day^{-1}$. In stage III, TS and volatile solid contents in the input pig slurry were highly variable, and input VFAs and alkalinity values that affect the performance of anaerobic digester were also more variable and sensitive to the variation of input organic loading during the digester operation. The biogas produced in the stage III, ranged from 11.3 to 170.0 $m^3\;day^{-1}$, which was lower than 222.5-330.2 $m^3\;day^{-1}$ produced in the stage II.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.3
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• pp.214-221
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• 2009

Denitrification efficiency associated with incorporation of the diffrent carbon substrates with the anaerobic sludge was investigated. For this each kinetic constant such as methane reaction and specific denitrification rate (SDNR) were determined in each treated sludge. In the pure methanogenesis, the specific methanogenesis activity (SMA) value was the highest at $0.76COD/g\;VSS{\cdot}day$ when the acetate was incorporated with the anaerobic sludge which has already been adapted at consistent C/N ratio 5 for reatively higher denitrifier population. The anaerobic dinitrificaition and methanogenesis reaction were dependent on both the types of carbon substrate and sludge showing the higher denitrificaition reaction constant at $1.96hr^{-1}$ with incorporation of acetate with the anaerobic sludge at C/N ratio 5 than any other carbon sources examined. When the glucose was introduced as electron donor for the anaerobic sludge adapted with different carbon substrates the SDNR showed the highest value with the sludge adapted to glucose followed by the sludge adapted to piggery sludge and acetate.

• Clean Technology
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• v.26 no.1
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• pp.55-64
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• 2020

According to the Korean Renewable Energy 3020 Implementation Plan, the installation capacity of renewable energy is expected to increase whereas technology for storing excess electricity and stabilizing the power supply of renewable energy sources is extremely required. Power-to-Gas is one of energy storage technologies where electricity is converted into gas fuel such as hydrogen and methane. Basically, Power-to-Gas system could be effectively utilized to store excess electricity generated by an imbalance between supply and demand. In this study, the economic feasibility analysis of Power-to-Gas reflecting the domestic situation was carried out. Total revenue requirement method was utilized to estimate the levelized cost of hydrogen. Validation on the economic analysis method in this study was conducted by comparison of the result, which is published by the International Energy Agency. The levelized cost of hydrogen of a 100-MW Power-to-Gas system reflecting the current economic status in Korea is 8,344 won kg^-1. The sensitivity analysis was carried out, applying the main analysis economic factors such as electricity cost, electrolyser cost, and operating year. Based on the sensitivity analysis, the conditions for economic feasibility were suggested by comparing the cost of producing hydrogen using renewable energy with the cost of producing natural gas reformed hydrogen with carbon capture and storage.

• Journal of Ecology and Environment
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• v.29 no.3
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• pp.305-321
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• 2006

Atmospheric Acid Deposition: Nitrogen Saturation of Forests: Volume weighted annual average wet deposition of nitroge at 33 sites in Korea during 1999-2004 ranged 7.28 to $21.05kgN{\cdot}ha^{-1}{\cdot}yr^{-1}$ with average $12.78kgN{\cdot}ha^{-1}{\cdot}yr^{-1}$, which values are similar level with nitrogen deposition of Europe and North America. The temperate forests that suffered long-term high atmospheric nitrogen deposition are gradually saturated with nitrogen. Such nitrogen saturated forest watersheds usually leach nitrate ion ($NO_3^-$) in stream water and soil solution. It may be likely that Korean forest ecosystems are saturated by much nitrogen deposition. In leaves with nitrogen saturation ratios of N/P, N/K and N/Mg are so enhanced that mineral nutrient system is disturbed, suffered easily frost damage and blight disease, reduced fine-root vitality and mycorrhizal activity. Consequently nitrogen saturated forests decrease primary productivity and finally become forest decline. Futhermore understory species are replaced the nitrophobous species by the nitrophilous one. In soil with nitrogen saturation uptake of methane ($CH_4$) is reduced and emission of nitrogen monoxide (NO) and nitrous oxide ($N_{2}O$) are increased, which gases are greenhouse gas accelerating global warming.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.250-255
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• 2011

In this study, by using the polymeric membrane separation process, the $CO_{2}/CH_{4}$ separation and $H_{2}S$ removal from biogas were performed in order to $CH_{4}$ purification and enrichment for the fuel cell energy source application. Fibers were spun by dry/wet phase inversion method. The module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy(SEM) studies showed that the produced fibers typically had an asymmetric structure; a dense top layer supported by a porous, sponge substructure. The permeance of $CO_{2}$ and $CO_{2}/CH_{4}$ selectivity increased with pressure and temperature. Mixture gas with increasing pressure and temperature, removal efficiency of the $CO_{2}$ and $H_{2}S$ were decreased while concentration of $CH_{4}$ was increased up to 100%. When retentate flow rate was increased with the decreasing of pressure and temperature the $CH_{4}$ recovery ratio in retentate side was increased while the $CH_{4}$ purity in retentate side was decreased.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.6
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• pp.30-37
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• 1989

The PIN type a-SiC:H/a-Si:H heterojunction solar cells were fabricated by using the rf glow discharge decomposition of $SiH_4$ mixed with $CH_4,B_2,H_6\;and\;PH_3.$ The efficiency of the solar cell of the $SnO_2/ITO$ was higher than that of ITO transparent oxide layer by 1.5%. The P layer was prepared with the thickness of $100{\AA}$ and $CH_4/SiH_4$ ration of 5. The I layer has been deposited on the P layer and it is not pure intrinsic but near N type. So $SiH_4$ mixed with $B_2H_6$ of 0.3ppm was used to change this N type nature to intrinsic having the thickness of 5000${\AA}$. And consecutively, the N layer was deposited with t ethickness of $400{\AA}$ using $SiH_4/PH_3$ mixtures. The solar cell demonstrated 0.94V of $V_{oc'}$ 14.6mA/cm of $J_{sc}$ and 58.2% of FF, resulting the efficiency of 8.0%. To minimize loss by the reflection of light, $MgF_2$ layer was coated on the lgass and the efficiency was improved by 0.5%. Therefore, the solar cell indicated overall efficiency of 8.5%.

• Journal of Environmental Health Sciences
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• v.13 no.1
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• pp.17-33
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• 1987

As a result of technical advances and industrialization, the characteristics of domestic and industrial wastes are becoming more complex. Accordingly, improved treatment and disposal systems are being continuously sought to take account of complex characteristics and to comply with economic restrictions. In this study, an application of pyrolysis to the treatment of industrial wastes, including waste scrap rubber, waste raw material used in making the slipper bottom and waste PVC pipe, and the effectiveness of pyrolysis in resource recovery from these wastes were investigated. Batches of wastes were pyrolysed by external heating to a temperature of 400-800$\circ$C in a 32 mm diameter x 0.9 m long silica tube to produce combustible gases, oils and chars. Before the start of pyrolysis runs, the entire system was purged with nitrogen gas to exclude the air. The temperature inside the retort was controlled by the thermocouple in the gas stream, and referred to as the pyrolysis temperature. Under these conditions three products were separately collected and further analyzed. The results were summarized as follows. 1. More gases and less chars were produced with higher pyrolyzing temperature and with higher rates of heating, but the yields of oils tended downwards at temperatures above 700$\circ$C. Accordingly, operating conditions of pyrolysis should be varied with desired material. 2. Calorific values and sulfur contents of produced oils were sufficient and suitable for fuel use. Chars from waste rubber had high heating values with low sulfur contents, but calorific values of chars from waste PVC and waste slipper were as low as 3, 065-4, 273 kcal/kg and 942-2, 545 kcal/kg, respectively. Therefore, char from these wastes are inappropriate for fuel. 3. Soluble contents of Pb, Cd, Cu and Zn in chars from waste rubber and waste slipper were below the Specific Hazardous Waste Treatment Standards. However soluble contents of Pb and Cd in chars from waste PVC were one or two times and five or seven times exceedingly the Specific Hazardous Waste Treatment Standards, respectively. 4. Post high heating is desirable for treatment method of waste PVC which generates toxic hydrogen chloride. 5. The proportions of hydrogen, methane and ethane in produced gases were in the range of 3.99-35.61% V/V, 18.22-32.50% V/V and 5.17-5.87% V/V, respectively. 6. Pyrolysis is a useful disposal method in case of waste slipper, which was hardly combustible, and thus investigations of this kind of materials are required for effective management of industrial waste. 7. Based upon the possible market development for products, overall pyroly economics to take account of treatment values of noncombustible or hazardous materials should be evaluated.