• 한국수소및신에너지학회논문집
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• 제17권4호
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• pp.362-370
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• 2006

The purpose of this paper was to investigate the reforming characteristics and optimum operating condition of the plasmatron assisted $CH_4$ reforming reaction for the hydrogen-rich gas production. Also, in order to increase the hydrogen production and the methane conversion rate, parametric screening studies were conducted, in which there were the variations of the $CH_4$ flow ratio, $CO_2$ flow ratio, vapor flow ratio, mixing flow ratio and catalyst addition in reactor. High temperature plasma flame was generated by air and arc discharge. The air flow rate and input electric power were fixed 5.1 l/min and 6.4 kW, respectively. When the $CH_4$ flow ratio was 38.5%, the production of hydrogen was maximized and optimal methane conversion rate was 99.2%. Under these optimal conditions, the following synthesis gas concentrations were determined: $H_2$, 45.4%; CO, 6.9%; $CO_2$, 1.5%; and $C_2H_2$, 1.1%. The $H_2/CO$ ratio was 6.6, hydrogen yield was 78.8% and energy conversion rate was 63.6%.

• Journal of Biosystems Engineering
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• 제43권2호
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• pp.110-118
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• 2018

Purpose: In this study, the potential for biogas production, degradation rates, and lag-phase of diauxic growth of carbohydrate-based material, which is one of the proximate compositions, were investigated. Methods: This study was conducted using starch as a carbohydrate-based material. In experimental condition 1, the biogas potential of carbohydrate-based material was measured. In experimental condition 2, the effect of feed to microorganism ratio (F/M ratio) on lag-phase of diauxic growth from carbohydrate-based material was tested. Biochemical methane potential tests were performed at five different feed to microorganism ratios (0.2, 0.4, 0.6, 0.8, and 1.0) under mesophilic conditions. The biogas production patterns, lag-phase, total volatile fatty acids to total alkalinity ratio (TVFA/TA ratio), and time required for 90 percent biogas production were used to evaluate biogas production based on the biochemical methane potential tests. Results: In experimental condition 1, unlike previous studies, biogas was produced in the TVFA/TA ratio ranging from 1.131 to 2.029 (approximately 13-19 days). The methane content in the biogas produced from the digesters was 7% on day 9 and increased rapidly until approximately day 27 (approximately 72%). In experimental condition 2, biogas yield was improved when the feed to microorganism ratio exceeded 0.6, with an initial lag-phase. Conclusions: Even if the TVFA/TA ratio was greater than 1.0, the biogas production was processed continuously, and the $CO_2$ content of the biogas production was as high as 60%. The biogas yield was improved when the F/M ratio was increased more than 0.6, but the lag-phase of carbohydrate-based material digestion became longer starting with high organic loading rate. To clarify the problem of the initial lag-phase, our future study will examine the microbial mechanisms during anaerobic digestion.

• 상하수도학회지
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• 제10권2호
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• pp.47-54
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• 1996

UASB reactor was operated for treating wastewater containing high sulfate to assess their performance, competition between sulfate-reducing bacteria(SRB) and methane-producing bacteria(MPB), and the change in the characteristics of microbial granules according to change of hydraulic retention time(HRT) in the reactor. The reactor was fed with a synthetic moderate strength wastes(glucose, 2000 mgCOD/l) containing high sulfate($2400mgSO_4{^{2-}}/l$). The organic loading rate(OLR) ranged from 1.5 to 3.0 gCOD/l.d as HRT maintained 15 to 30 hrs in the stage I. The COD removal efficiency was between 80 to 92%. During this period, methane yield rapidly decreased from 0.3 to 0.1 1 $CH_4$/gCODremoved. While sulfide concentration in the effluent increased from 80 to 200 mgS/l. This indicates that SRB becomes dominant over MPB at a relatively long HRT in the excess sulfate. When OLR of reactor maintained from 5 to 8 gCOD/l.d in the stage II, methane yield increased from 0.1 to 0.17 1 $CH_4$/gCODremoved regardless of decrease of COD removal efficiency. This indicates that SRB is more sensitive to the change of a short HRT than MPB. In the competition between SRB and MPB, about 30% of the removed COD was utilized by SRB at HRT of 30 hrs during the start-up period, while about 73% was used by SRB at HRT of 15hrs at the final step of second experimental stage. Whereas after shock exposure of OLR about 62% was utilized by SRB at HRT of 5hrs. It indicates that SRB is strongly suppressed by the wash-out of significant dispersed SRB since a large electron flow is distributed to the MPB. In addition, the granulation in the presence of high sulfate is unfavoured at a long HRT because of substrate transport limitations into MPB like Methanothrix spp. which is an important factor in the composition of the granules. Accordingly, granule sizes in the UASB reactor decreased with time due to weak network frame of granules by the decreased activity of MPB.

• 한국환경과학회지
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• 제31권2호
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• pp.141-148
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• 2022

In this study, the inhibition of ammonia on anaerobic digestion of butyric acid was evaluated and the potential alleviating effects of such ammonia inhibition by the addition of magnetite particles were investigated. Independent anaerobic batch tests fed with butyric acid as a sole organic source were conducted in twenty 60-mL glass bottles with 10 different treatment conditions, comprising ammonia: 0.5, 2.0, 4.0, 6.0, and 7.0 g total ammonia nitrogen (TAN)/L and magnetite particles: 0 mM and 20 mM. The increase in ammonia concentration did not cause significant inhibition on methane yield; however, a significant inhibition on lag time and specific methane production rate was observed. The IC₅₀ in the control treatments (without magnetite addition) was estimated as 6.2654 g TAN/L. A similar inhibition trend was observed in magnetite-added treatments; however, the inhibition effect by ammonia was significantly alleviated in lag time and specific methane production rate when compared to those in the control treatments. The lag time was shortened by 1.6-46.3%, specific methane production rate was improved by 6.0-69.0%. In the magnetite-added treatments, IC₅₀ was estimated as 8.5361 g TAN/L. This study successfully demonstrated the potential of magnetite particles as an enhancer in anaerobic digestion of butyric acid under conditions of ammonia stress.

• Animal Bioscience
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• 제34권8호
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• pp.1415-1424
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• 2021

Objective: Portable laser methane detectors (LMDs) may be an economical means of estimating CH₄ emissions from ruminants. We validated an LMD-based approach and then used that approach to evaluate CH₄ emissions from indigenous dairy cows in a dryland area of Ethiopia. Methods: First, we validated our LMD-based approach in Simmental crossbred beef cattle (n = 2) housed in respiration chambers and fed either a high- or low-concentrate diet. From the results of the validation, we constructed an estimation equation to determine CH₄ emissions from LMD CH₄ concentrations. Next, we used our validated LMD approach to examine CH₄ emissions in Fogera dairy cows grazed for 8 h/d (GG, n = 4), fed indoors on natural-grassland hay (CG1, n = 4), or fed indoors on Napier-grass (Pennisetum purpureum) hay (CG2, n = 4). All the cows were supplemented with concentrate feed. Results: The exhaled CH₄ concentrations measured by LMD were linearly correlated with the CH₄ emissions determined by infrared-absorption-based gas analyzer (r² = 0.55). The estimation equation used to determine CH₄ emissions (y, mg/min) from LMD CH₄ concentrations (x, ppm m) was y = 0.4259x+38.61. Daily CH₄ emissions of Fogera cows estimated by using the equation did not differ among the three groups; however, a numerically greater milk yield was obtained from the CG2 cows than from the GG cows, suggesting that Napier-grass hay might be better than natural-grassland hay for indoor feeding. The CG1 cows had higher CH₄ emissions per feed intake than the other groups, without significant increases in milk yield and body-weight gain, suggesting that natural-grassland hay cannot be recommended for indoor-fed cows. Conclusion: These findings demonstrate the potential of using LMDs to valuate feeding regimens rapidly and economically for dairy cows in areas under financial constraint, while taking CH₄ emissions into consideration.

• Journal of Biosystems Engineering
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• 제37권1호
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• pp.58-64
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• 2012

Purpose: The objective of this study was to investigate the feasibility of anaerobic digestion of Chinese cabbage waste juice (CCWJ) and swine manure(SM). Methods: The anaerobic digestion test was conducted under batch and continuous conditions at mesophilic temperature ($36-38^{\circ}C$). The batch test was divided into Experiment I and II. In the Experiment I, biogas potential and production rate of CCWJ was evaluated. In Experiment II the effect of F/M ratio (2.0, 3.2, 4.9) at mixture ratio of 25:75(CCWJ: SM, % vol. basis) on biogas yield was studied. Results: CCWJ produced biogas and methane yield of 929 and 700 mL/g VS added respectively. The biogas yield from the mixture of CCWJ and SM was almost same at F/M ratio of 2.0 and 3.2 but dropped by 14% when F/M ratio increased from 3.2 to 4.9. In continuous test the mixture of CCWJ and SM (25:75, % vol. basis) produced biogas yield of 352 mL/g VS added which is around 11% higher compared to biogas yield from SM alone. Addition to biogas yield digester performance was also improved with co-digestion of CCWJ with SM. Conclusions: The results showed that the anaerobic digestion of CCWJ with SM could be promising for improving both the biogas yield and digester performance at mesophilic temperature.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2232-2237
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• 2007

Steam reforming and catalytic reforming of $CH_4$ conversion to produce synthesis gas require both high temperatures and high pressure. Non-thermal plasma is considered to be a promising technology for the hydrogen rich gas production from methane. In this study, three phase AC GlidArc plasma system was employed to investigate the effects of gas composition, gas flow rate, catalyst reactor temperature and applied electric power on the $CH_4$ and $H_2$ yield and the product distribution. The studied system consisted of three electrode and it connected AC generate power system different voltages. In this study, air was used for the partial oxidation of methane. The results showed that increasing gas flow rate, catalyst reactor temperature, or electric power enhanced $CH_4$ conversion and $H_2$ concentration. The reference conditions were found at a $O_2$/C molar ratio of 0.45, a feed flow rate of 4.9 ${\ell}$/min, and input power of 1kW for the maximum conversions of $CH_4$ with a high selectivity of $H_2$ and a low reactor energy density.

• 한국수소및신에너지학회논문집
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• 제14권2호
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• pp.105-113
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• 2003

The pyrolysis for production of hydrogen and high quality carbon black from natural gas were studied. The reactivities in tubular reactor and FVR(free volume reactor) for the methane pyrolysis were compared, in order to prevent the formation of undesirable carbon product such as pyrocarbon, the FVR was designed. The hydrogen yield and the formation of carbon black from methane pyrolysis in this reactor were investigated at temperature range between 1443 and 1576K. From the result of TEM (transmission electron microscopy) analysis, it was confirmed that the CFC(catalytic filamentous carbon) was formed without pyrocarbon.

• 한국토양비료학회지
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• 제44권6호
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• pp.1245-1251
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• 2011

본 연구는 축산부문에서 주요한 가축종인 돼지의 사육과 정과 도축 가공과정에서 발생하는 양돈 바이오매스의 발생특성을 조사 분석하고, 전과정 평가 기법을 활용하여 물질(퇴 액비) 및 에너지 (바이오가스) 자원화 잠재량을 평가함으로써 지역단위 바이오매스 순환단지 조성을 위한 기초자료를 확립하고자 하였으며, 이를 위해 양돈 바이오매스의 발생 단계를 사양단계와 도축 가공단계로 구분하여 각각의 단계에서 발생하는 양돈바이오매스의 물질 및 에너지 자원화 잠재량을 평가하였다. 사양단계는 성장단계(사육기간, 평균체중)에 따라 자돈 (1~9주, 23.4 kg), 육성돈 1기 (10~15주, 50 kg), 육성돈 2기 (16~21주, 80 kg), 비육돈 (22~26주, 110 kg)의 단계로 분류하고 도축 가공단계에서 발생하는 혈액과 폐내장류, 장내 잔재물로 구분하여 생산량을 산정하여 양돈 바이오매스의 물질 및 에너지 자원 잠재량을 평가한 결과 돼지 1두에서 발생하는 바이오매스의 총량은 542.02 kg로 나타났다. 양돈 바이오매스는 분 $210.68kg\;head^{-1}$, 뇨 $315.78kg\;head^{-1}$가 발생하는 것으로 평가되었으며, 분뇨 발생량은 성장단계별로 자돈 14.2%, 육성돈 1기 19.6%, 육성돈 2기 30.9%, 비육돈 35.2%를 차지하는 것으로 나타났다. 양돈 바이오매스에서 기인하는 매탄 생산 잠재량은 $24.56Nm^3\;head^{-1}$이였으며, 사양 단계에서 기인하는 메탄 생산 잠재량이 92.9%를 차지하는 것으로 나타났다. BMP 시험에 의한 최대 메탄생산량은 $16.58Nm^3\;head^{-1}$로 나타나 매탄 생산 잠재량의 67.5%가 에너지로 전환 가능하였으며, 94.4%가 사양 단계에서 기인하는 것으로 나타났다.

• 한국작물학회지
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• 제61권4호
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• pp.251-256
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• 2016

벼 재배시 경운과 재배방법 따른 메탄 발생량 및 토양탄소함량변화를 구명하기위해 경운-이앙, 경운-무논점파, 최소경운-건답직파 및 무경운-건답직파를 비교하는 시험을 수행한 결과 다음과 같다. 1. 메탄 발생량은 경운-이앙 처리구에서 가장 많았으며 경운-무논점파>최소경운-건답직파=무경운 건답직파 순으로 적었다. 2. 메탄의 발생량과 벼 생육과의 관계를 보면 생육초기 작물의 생체량이 많아질수록 메탄 발생량이 증가는 경향을 보였다. 3. 토양 탄소함량은 시험전과 비교하여 경운-이앙 처리구에서 가장 낮은 값을 나타내었고, 최소경운-건답직파와 무경운 처리구에서 높은 값을 나타내었다. 4. 최소경운-건답직파 및 무경운 처리구의 쌀수량이 경운-이앙 처리구에 비해 다소 적었으나 통계적으로 유의한 차이는 없었다.