• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.42-46
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• 2008

Even though fuel cell have high efficiency when pure hydrogen from gas tank is used as a fuel source, it is more beneficial to generate hydrogen from city gas (mainly methane) in residential application such as domestic or office environments. Thus hydrogen is generated by reforming process using hydrocarbon. Unfortunately, the reforming process for hydrogen production is accompanied with unavoidable impurities. Impurities such as CO, $CO_2$, $H_2S$, $NH_3$, $CH_4$, and $CH_4$ in hydrogen could cause negative effects on fuel cell performance. Those effects are kinetic losses due to poisoning of the electrode catalysts, ohmic losses due to proton conductivity reduction including membrane and catalyst ionomer layers, and mass transport losses due to degrading catalyst layer structure and hydrophobic property. Hydrogen produced from reformer eventually contains around 73% of $H_2$, 20% or less of $CO_2$, 5.8% of less of $N_2$, or 2% less of $CH_4$, and 10ppm or less of CO. This study is aimed at investigating the effect of carbon dioxide on fuel cell performance. The performance of PEM fuel cell was investigated using current vs. potential experiment, long run(10 hr) test, and electrochemical impedance measurement when the concentrations of carbon dioxide were 10%, 20% and 30%. Also, the concentration of impurity supplied to the fuel cell was verified by gas chromatography(GC).

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.2
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• pp.220-229
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• 2016

A numerical study on lifted flame structure in impinging jet geometry with syngas composition ratio was investigated. The numerical calculations including chemical kinetic analysis were conducted using SPIN application of the CHEMKIN Package with Davis-Mechanism. The flame temperature and velocity profiles were calculated at the steady state for one-dimensional stagnation flow geometry. Syngas mixture compositions were adjusted such as $H_2:CO=10:90(10P)$, 20 : 80 (20P), 30 : 70 (30P), 40 : 60 (40P), 50 : 50 (50P). As composition ratios are changed from 10P to 50P, the axial velocity and flame temperature increase because the contents of hydrogen that have faster burning velocity increase. This phenomenon is due to increase in good reactive radicals such as H, OH radical. As a result of active reactivity, the burning velocity is more faster and this is confirmed by numerical methods. Consequently, combustion reaction zone was moved to burner nozzle.

• Korean Journal of Food Science and Technology
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• v.18 no.1
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• pp.71-76
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• 1986

Changes in pH, titratable acidity, some organic acids and brix of the strawberry stored at the different levels of $CO_2$, in air were measured. The changing trends in pH and the acidity of the strawberries were not clear among the storage treatments, and pH of the strawberries in all the treatments was increased(r=0.9615) by contrast to decrease in the acidity(r=-0.8483). Ascorbic acid content of the strawberries at control lot was higher than the contents of the CA stored for the initial 2 weeks after storage. This trend was reversed after that period and the strawberries in air with 30% $CO_2$, showed the highest retention rate, 28% of the initial content after 5 weeks. Among the analyzed organic acids, malic acid was gradually decreased in all the treatments during storage and the decreasing rates of the strawberries in air with 30% $CO_2$, was somewhat stupider than those in the others. Pyruvic acid was reduced in the control lot during storage but drastically increased in the strawberries stored at the CA storage conditions between the 2nd and the 3rd week after storage, and then it was decreased.

• Journal of Energy Engineering
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• v.8 no.1
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• pp.23-33
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• 1999

용융탄산염 연료전지의 대형화에 관한 기본 기술을 확립하기 위하여 전극의 유효면적이 625 $\textrm{cm}^2$인 단위전지를 20단 적층한 내부 분배형 용융탄산염 연료전지 스택을 제작하고 그 성능을 살펴보았다. 연료로 72% H2/18% CO2/10% H2O를 , 산화제로는 70% air/30% CO2의 혼합 기체를 사용하여 운전한 결과 전류밀도가 150 mA/$\textrm{cm}^2$이고 연료 및 산화제의 이용율이 0.4일 때, 스택 전압이 16.62 V로 1.56 kW의 높은 초기출력을 나타내었다. 스택 내 분리판에서의 온도 분포는 가스 흐름 방향으로 온도가 증가하였으며 스택출력이 높아질수록 가스 배출 부분의 온도가 상승하였다. 스택 내 각 단위전지간의 성능 분포는 균일하지 않았으며, 가스이용율에 따라 그 편차가 증가하였다. 연속 운전 300시간 후부터 스택의 성능이 감소하였으며, 그 원인을 분석한 겨로가 탄소 석출과 부식 생성물에 의한 전기 단락 때문으로 밝혀졌다. 본 연구를 통하여 anode 출구에서의 가스 조성을 분석함으로써 전기 단락에 의한 전압 손실량을 계산하는 기법을 확립하였다. 또한 본 연구에서 얻은 결과를 통하여 향후 스택의 대형화와 장수명화에 대한 대책을 제시하였다.

• Journal of the Korean Society of Combustion
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• v.20 no.3
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• pp.8-12
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• 2015

The CO reduction characteristics of hot air stream diluted with exhaust gas in a perfectly stirred reactor (PSR) were investigated numerically. The dilution ratio ($\Omega$), inlet temperature ($T_{in}$), and residence time ($\tau$) were considered as parameters to investigate the effects of those on the emission indices for CO and $CO_2$ (EICO and $EICO_2$). The roles of dominant reactions and the production rates of major species were analyzed. It was found from the EICO trend that the supplied CO in the air stream was consumed. The EICO increased negatively with $T_{in}$ at fixed $\tau$ regardless of $\Omega$. However, the magnitude of EICO and minimum inlet temperature for CO reduction showed complicated trend according to the variation of $\tau$. It was identified that the OH radical, generated from the reactions, $O_2+H{\leftrightarrow}O+OH$ and $2OH{\leftrightarrow}H+H_2O$, affected the CO reduction by the reaction, $CO+OH{\leftrightarrow}H+CO_2$. However, the CO emission ratio increased at sufficiently high inlet temperature range due to the thermal dissociation of $CO_2$.

• Journal of the Korean Society of Combustion
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• v.10 no.3
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• pp.10-16
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• 2005

Detailed flame structures of the counterflow flames of $CH_4/Air$ formed with $CO_2$ and $H_2O$ addition are studied numerically. The detailed chemical reactions are modeled by using the OPPDIF and CHEMKIN-II code. Only the $CO_2$ and $H_2O$ are assumed to participate in radiative heat transfer while all other gases are assumed to be transparent. The discrete ordinates method(DOM) and the narrow band based WSGGM with a gray gas regrouping technique(WSGGM-RG) are applied for modeling the radiative transfer through non-homogeneous and non-isothermal combustion gas mixtures generated by the counter flow flames. The results compared with the SNB model show that the WSGGM-RG is successful in modeling the counterflow flames with non-gray gas mixture. The numerical results show that the addition of $CO_2$ and $H_2O$ to the oxidant nozzle lowers the peak temperature and the NO concentration in flame.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.653-657
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• 2011

Conversion characteristics of $CH_4$ and $CO_2$ was studied using an atmospheric pressure plasma for the preparation of synthesis gas composed of $H_2$ and CO. The effects of delivered power, total gas flow rate, and gas residence time in the reactor on the conversion of $CH_4$ and $CO_2$ were evaluated in a plasma reactor with the type of dielectric barrier discharge. The increase of reactor temperature did not affect on the increase of conversion if the temperature does not reach to the appropriate level. The conversion of $CH_4$ and $CO_2$ largely increased with increasing the delivered power. As the $CH_4/CO_2$ ratio increased, the $CH_4$ conversion decreased, whereas the $CO_2$ conversion increased. Generally, the $CH_4$ convesion was higher than the $CO_2$ conversion through the variation of the process parameters.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.618-624
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• 2007

thermochemical methane reforming consisting of two steps on Cu/Fe/Zr mixed oxide media was carried out using a fixed bed infrared reactor. In the first step, the metal oxide was reduced with methane to produce CO, $H_2$ and the reduced metal oxide in the temperature of 1173 K. In the second step, the reduced metal oxide was re-oxidized with steam to produce $H_2$ and the metal oxide in the temperature of 973 K. The reaction characteristics on the added amounts of Cu in Cu/Fe/Zr mixed oxide media and the cyclic tests were evaluated. With the increase of the added amount of Cu in Cu/Fe/Zr mixed oxide media, the conversion of $CH_4$, the selectivity of $CO_2$ and the $H_2/CO$ molar ratio were increased, while the selectivity of CO was decreased in the first step. On the other hand, the evolved amount of $H_2$ was decreased with increasing the added amount of Cu in the second step. The $Cu_xFe_{3-x}O_4/ZrO_2$ medium added with Cu of x = 0.7 showed good regeneration properties in the 10th cyclic tests indicating that the medium had high durability. In addition, the gasification of the deposited carbon in the water splitting step was promoted with the addition of Cu in the media.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.2
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• pp.133-140
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• 2008

A reduced chemical kinetic mechanism is developed in order to predict the flame phenomena in premixed $CO/H_2/Air$ flames at atmospheric pressure, aimed at studying the coal gas combustion for the IGCC applications. The reduced mechanism is systematically derived from a full chemical kinetic mechanism involving 11 reacting species and 66 elementary reactions. This mechanism consists of four global steps, and is capable of explicitly calculating the concentration of 7 non-steady species and implicitly predicting the concentration of 3 steady state species. The fuel blend contains two fuels with distinct thermochemical properties, whose contribution to the radical pool in the flame is different. The flame speeds predicted by the reduced mechanism are in good agreement with those by the full mechanism and experimental results. In addition, the concentration profiles of species and temperature are also in good agreement with those by the full mechanism.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.300-303
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• 1991

Sulphur-hexafluoride has extensively been used as an insulating gas of electric power equipment in substation for its high dielectric strength, non-toixity and non-flammable properties. But it is very expensive and is liquidizable under the condition of low temperature and high pressure. And it is very sensible to the locally high electric field strength. To resolve these problems, we studied 50% FOV and V-t characteristics of $SF_6-N_2$ mixtures under positive and negative lightning impulses using a 25mm rod-plane gap. 50% FOV of $SF_6-N_2$ 50% mixture was about 85% of pure $SF_6$ and it was known that $SF_6-N_2$ mixtures can be used as an economic substitution insulating gas for $SF_6$.