• 한국환경보건학회지
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• 제25권3호
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• pp.29-35
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• 1999

Quantity and composition of biogas from semi-continuous anaerobic digestion of straw were obtained experimentally in laboratory scale digesters fed with 1 liter of 5% straw-water mixture and maintained at 35$^{\circ}C$. Experiments were carried out for hydraulic retention time(HRT) of 8, 10 and 15days, respectively. The amount and composition of biogas produced were measured until steady-state was achieved for each run. The amount of biogas and methane percent go through a maximum and decrease continuously towards the steady-state after three times operation of hydraulic retention time(HRT). Methane gas production rates at steady-state increase with the increasing of HRT. Biogas production of 0.45 liter/day with 25% methane, 0.42 liter/day with 33.7% methane and 0.492 liter/day with 31.7% methane were obtained for 8, 10 and 15days of HRT, respectively. The high proportion of soluble carbohydrates present in straw makes the volatile fatty acids to build up within the digester causing a drop in pH that inhibits digestion. Regular control of pH is therefore necessary by adding alkalinity. Reductions in COD increase with increase in HRT. The stratification of plant material within the digester is different from that of manure, and modifications in design and operation of digesters may be necessary if they are fed with plant matter.

• 한국수소및신에너지학회논문집
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• 제18권2호
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• pp.132-139
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• 2007

Popular techniques for producing synthesis gas by converting methane include steam reforming and catalyst reforming. However, these are high temperature and high pressure processes limited by equipment, cost and difficulty of operation. Low temperature plasma is projected to be a technique that can be used to produce high concentration hydrogen from methane. It is suitable for miniaturization and for application in other technologies. In this research, the effect of changing each of the following variables was studied using an AC Glidarc system that was conceived by the research team: the gas components ratio, the gas flow rate, the catalyst reactor temperature and voltage. Glidarc plasma reformer was consisted of 3 electrodes and an AC power source. And air was added for the partial oxidation reaction of methane. The result showed that as the gas flow rate, the catalyst reactor temperature and the electric power increased, the methane conversion rate and the hydrogen concentration also increased. With $O_2/C$ ratio of 0.45, input flow rate of 4.9 l/min and power supply of 1 kW as the reference condition, the methane conversion rate, the high hydrogen selectivity and the reformer energy density were 69.2%, 36.2% and 35.2% respectively.

• 한국지반환경공학회 논문집
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• 제12권5호
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• pp.37-42
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• 2011

본 연구는 부산항만 내에 퇴적된 퇴적물에 대한 현재의 성분 및 혐기성 상태에서의 잠재메탄발생량을 평가하기 위해 수행되었다. 부산항만 내 10곳의 지점을 선정하여 퇴적물을 채취하였고, 퇴적물 특성을 파악하기 위해 특성을 강열감량, 원소분석, XRD, XRF 분석을 실시하였다. 모든 특성을 구성성분은 균일하였으며, 강열감량 경우 8~10% 높은 값을 보였다. 총 5개의 시료에 대한 BMP 실험 경우 최대메탄발생량은 11.9~15.5mL methane/g VS로 시료간에 편차가 존재하였다. 기존 연구와 비교 시 음식물과 종이류에 비해 발생되는 메탄양은 작으나 발생속도는 5배에서 20배가량 큰 값을 보여주었다.

• 한국초지조사료학회지
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• 제36권2호
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• pp.104-108
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• 2016

본 실험은 동일 사료원료 조건에서 농후사료와 조사료를 혼합 급여하는 섬유질배합사료(TMR)와 분리급여 방식이 메탄발생량에 미치는 효과를 조사하기 위하여 홀스타인 거세 숫소 6두(평균체중 $203{\pm}24.8kg$)를 공시하여 changeover design으로 실험을 수행하였다. TMR구는 육성기용 배합사료, 티모시 건초 그리고 비지를 생중량 기준 각각 40, 48, 12% 비율로 매일 혼합 급여하였고, 분리급여구는 배합사료와 비지만을 급여 전 혼합하여 대사틀에 설치된 사료통에 먼저 넣고 그 위에 티모시를 올려주었다. 사료급여량은 공시축이 전량 섭취할 수 있도록 약 0.2 kg의 일당증체 수준으로 제한 급여하였기 때문에 처리구간 차이가 없었고, 메탄발생량(g/d)에서도 유의적인 차이가 없었다(P>0.1). 그러나 메탄 전변율(Ym, 메탄 에너지/GE intake)은 TMR구가 분리급여구 보다 유의적으로 높았다(p=0.05). 두 처리 평균 메탄 배출계수(kg $CH_4$/head/year)는 21.4였고, 평균 메탄 전변율은 0.05이었으며, 공시축의 대사체중(metabolic BW, $kg^{0.75}$)과 메탄발생량(g/d)과는 높은 상관관계($R^2=0.8057$, p<0.001)를 보였다. 반추가축의 대표적인 사료급여방식 차이가 메탄발생량에 미치는 효과에 대한 결론을 얻기 위해서는 보다 많은 연구가 필요할 것으로 사료된다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.761-764
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• 2009

The thermocatalytic decomposition of methane is an environmentally attractive approach to $CO_2$-free production of hydrogen. The fluidized bed was proposed for the continuous withdraw of product carbon from the reactor. The usage of carbon black was reported as stable catalyst for decomposition of methane. Therfore, carbon black (DCC-N330) is used as catalyst. A fluidized bed reactor made of quartz with 0.055 m I.D. and 1.0 m in height was selected for the thermo-catalytic decomposition. The porpane-containg methnae decomposition reaction was operated at the temperature range of 850-900 $^{\circ}C$ methane gas velocity of 1.0 $U_{mf}$ and the operating pressure of 1.0 atm. In this work, propane was added as reactant to make methane conversion higher. Therefore we compared with methane conversion and pre-experiment methane conversion that using only methane as reactant. The carbon black, after experiment, was measured in particle size and surface area and analyzed surface of the carbon black by TEM.

• 상하수도학회지
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• 제22권3호
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• pp.299-306
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• 2008

This study has been conducted to derive the bio-energy, hydrogen and methane production, from mixture of food wastewater and swine wastewater, the high strength organic wastewater and to increase effluent quality. To overcome this limitation in one-phase anaerobic process, two-phase anaerobic process combining hydrogen fermenter and methane fermenter was applied. In this system $2,323ml\;H_2/L$ was produced daily from Run II where 500 ml of heattreated sludge in methane fermenter was injected, and methane produced from methane fermenter did not show big difference regardless of the amount of returning sludge at each Run. It was concluded that the two-phase anaerobic process was the appropriat process to produce hydrogen and methane simultaneously and stably. Influent $TCOD_{Cr}$ to two-phase anaerobic process showed the range of 132~145 g/L(average 140 g/L), and effluent $TCOD_{Cr}$ range was 25~40 g/L(average 32 g/L), and organic removal efficiency showed 71~82%(average 76.3%).

• Environmental Engineering Research
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• 제21권1호
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• pp.69-73
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• 2016

Generation of food waste is a serious issue that needs to be addressed worldwide. Developing suitable treatment methods while generating energy (methane) is a common practice for sustainable treatment of waste. In this study, methane generation by food waste was investigated in mesophilic and thermophilic regimes at various hydraulic retention times (HRTs) and organic loading rates (OLR). In temperature regimes, influent concentrations and HRTs ranged from 30 to 110 g COD/L and 18 to 30 days, respectively, which corresponding to an OLR of 1.0 to $6.1kg\;COD/m^3-d$. Better methane production and organic removal was observed under thermophilic conditions because of the enhanced hydrolysis of complex polymers and microbial activity at higher temperature. The peak methane productivities attained in thermophilic and mesophilic regimes were 1.30 and $0.99m^3/m^3-d$, respectively. The maximum methane yields were achieved at 50 g COD/L and HRT of 24 d in both cases, and the values were 264 and $221m^3/ton$ COD, respectively. The results of this study will facilitate the development of sustainable methane production technologies using food waste as a feedstock.

• 한국수소및신에너지학회논문집
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• 제22권5호
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• pp.649-655
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• 2011

Methane direct cracking can be utilized to produce $CO_x$ and $NO_x$-free hydrogen for PEM fuel cells, oil refineries, ammonia and methanol production. We present the results of a systematic study of methane direct cracking using a mixed conducting oxide, Y-doped $BaZrO_3$ ($BaZr_{0.85}Y_{0.15}O_3$), membrane. In this paper, dense $BaZr_{0.85}Y_{0.15}O_3$ membrane with disk shape was successfully sintered at $1400^{\circ}C$ with a relative density of more 93% via addition of 1 wt% ZnO. The ($BaZr_{0.85}Y_{0.15}O_3$) membrane is covered with Pd as catalyst for methane decomposition with an DC magnetron sputtering method. Reaction temperature was $800^{\circ}C$ and high purity methane as reactant was employed to membrane side with 1.5 bar pressure. The $H_2$ produced by the reaction was transported through mixed conducting oxide membrane to the outer side. In addition, it was observed that the carbon, by-product, after methane direct cracking was deposited on the Pd/ZnO-$BaZr_{0.85}Y_{0.15}O_3$ membrane. The produced carbon has a shape of sphere and nanosheet, and a particle size of 80 to 100 nm.

• 청정기술
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• 제29권1호
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• pp.53-58
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• 2023

This study shows the summary of the economic performance of excess electricity conversion to hydrogen as well as methane and returned conversion to electricity using a fuel cell. The methane production process has been examined in a previous study. Here, this study focuses on the conversion of methane to electricity. As a part of this study, capital expenditure (CAPEX) is estimated under various sized plants (0.3, 3, 9, and 30 MW). The study shows a method for economic optimization of electricity generation using a fuel cell. The CAPEX and operating expenditure (OPEX) as well as the feed cost are used to calculate the discounted cash flow. Then the levelized cost of returned electricity (LCORE) is estimated from the discounted cash flow. This study found the LCORE value was ¢10.2/kWh electricity when a 9 MW electricity generating fuel cell was used. A methane production plant size of 1,500 Nm³/hr, a methane production cost of $11.47/mcf, a storage cost of $1/mcf, and a fuel cell efficiency of 54% were used as a baseline. A sensitivity analysis was performed by varying the storage cost, fuel cell efficiency, and excess electricity cost by ±20%, and fuel cell efficiency was found as the most dominating parameter in terms of the LCORE sensitivity. Therefore, for the best cost-performance, fuel cell manufacturing and efficiency need to be carefully evaluated. This study provides a general guideline for cost performance comparison with LCORE.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XIII)
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• pp.129-134
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• 2003

Anaerobic hydrogen production was executed using mixed anaerobic sludge. pH control (pH $5.5^{\sim}6.2)$ and heat treatment of anaerobic sluge at $92^{\circ}C$ was not effective for repressing the methane formation. The addition of $nitrate(500^{\sim}2,000\;mg/L\;KNO_3)$ made it possible to repress the methane formation, which resulted in the improvement of hydrogen production. By using SEM(Scanning Electron Microscope), less methane forming microbial with spagetti shape was observed when nitrate was supplied to anaerobic reactor.