• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.170-177
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• 2006

Hydrogen can extend the lean misfire limit to a large extent when it is mixed with conventional fuels for a spark ignition engine. In this study, hydrogen-enriched gaseous fuels by reforming process were simulated according to their proportions of $H_2$, CO, $CO_2$ and $N_2$ gases. Pure hydrogen and two different hydrogen-enriched gaseous mixtures(A-, B-composition) were tested for their basic effects on the engine performances and emissions in a single cylinder research engine. A- and B-composition showed different results from 100% $H_2$ addition because air/fuel mixtures were more diluted by their additions. Even though the energy fraction of reformed gases was increased, combustion stabilities and lean misfire limits were not sensitively improved. It means that combustion augmentation by $H_2$ addition was offset by the charge dilution of $N_2$ and $CO_2$. In addition, the low flammability of CO gas deteriorated thermal efficiencies. CO emission was drastically increased with B-composition which included higher CO component. However, $NO_x$ was reduced as energy fraction($X_e$) rised except for the case of 100% $H_2$ addition at $\lambda=1.2$ and was, for A-composition, lowered to a factor of ten when compared with that of $H_2$ addition. HC emissions were largely influenced by $COV_{imep}$ due to misfire and partial burns.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.77-83
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• 2023

Energy consumption is increased by rapid industrialization. As a result, climate change is accelerating due to the increase in CO₂ concentration in the atmosphere. Therefore, a shift in the energy paradigm is required. Hydrogen is in the spotlight as a part of that. Currently 95% of hydrogen is fossil fuel-based reforming hydrogen which is accompanied by CO₂ emissions. This is called gray hydrogen, if the CO₂ is captured and emission of CO₂ is reduced, it can be converted into blue hydrogen. There are 3 technologies to capture CO₂: absorption, adsorption and membrane technology. In order to select CO₂ capture technology, the analysis of the exhaust gas should be carried out. The concentration of CO₂ in the flue gas from the hydrogen production process is higher than 20%if water is removed as well as the emission scale is classified as small and medium. So, the application of the membrane technology is more advantageous than the absorption. In addition, if LNG cold energy can be used for low temperature CO₂ capture system, the CO₂/N₂ selectivity of the membrane is higher than room temperature CO₂ capture and enabling an efficient CO₂ capture process. In this study, we will analyze the flue gas from hydrogen production process and discuss suitable CO₂ capture technology for it.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.3
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• pp.213-218
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• 2012

Steam reforming of methane (SRM) is the primary method to produce hydrogen. Commercial Ni-based catalysts have been optimized for SRM with excess steam ($H_2O/CH_4$ > 2.5) at high temperatures (> $700^{\circ}C$). However, commercial catalysts are not suitable under severe conditions such as stoichiometric steam over methane ratio ($H_2O/CH_4$ = 1.0) and low temperature ($600^{\circ}C$). In this study, 15wt.% Ni catalysts supported on $Ce_{0.8}Zr_{0.2}O_2$ were prepared at various calcination temperatures for SRM at a very high gas hourly space velocity (GHSV) of $621,704h^{-1}$. The calcination temperature was systematically varied to optimize 15wt.% $Ni-Ce_{0.8}Zr_{0.2}O_2$ catalyst at a $H_2O/CH_4$ ratio of 1.0 and at $600^{\circ}C$. 15wt.% $Ni-Ce_{0.8}Zr_{0.2}O_2$ catalyst calcined at $500^{\circ}C$ exhibited the highest $CH_4$ conversion as well as stability with time on stream. Also, 15wt.% $Ni-Ce_{0.8}Zr_{0.2}O_2$ catalyst calcined at $500^{\circ}C$ showed the highest $H_2$ yield (58%) and CO yield (21%) among the catalysts. This is due to complex NiO species, which have relatively strong metal to support interaction (SMSI).

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.53-56
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• 2007

미량의 Ru을 증진제로 첨가하여 니켈 촉매의 반응 활성을 증진시킴으로써, 저온 환원성과 장시간 반응에 대한 안정성을 확보하고자 하였다. Ni의 담지량은 12 wt%로 고정하였으며 이에 Ru을 각각 0.1, 0.3, 0.5 wt%로 변화시켜 2차 담지하였다. 메탄의 수증기/이산화탄소 복합 개질 반응에 있어 니켈 촉매에 Ru을 2차 담지 한 촉매는 800 $^{\circ}C$, GHSV(gas hourly space velocity) 265,000 $h^{-1}$ 하에서 100 %에 가까운 $CH_{4}$ 전환율을 보였으며, GHSV 1,060,000 $h^{-1}$ 일 때에도 10시간 동안 90 %의 $CH_{4}$ 전환율을 기록하였다. 또한 이 중 0.3 wt%의 Ru를 담지한 경우가 1,060,000 $h^{-1}$의 조건하에서도 95 %이상으로 가장 높은 $CH_{4}$ 전환율로 유지되었다. $H_{2}-TPR$ 분석 결과, Ni(12)/$MgAl_{2}O_{4}$ 와 비교해 볼 때 Ru(0.5)/Ni(12)/$MgAl_{2}O_{4}$와 Ru(0.3)/Ni(12)/$MgAl_{2}O_{4}$ 촉매의 경우 150 $^{\circ}C$에서 저온 환원이 가능한 $RuO_{2}$의 존재를 확인할 수 있었다.

• Journal of the Korean Applied Science and Technology
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• v.24 no.4
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• pp.427-435
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• 2007

에너지원으로서 수소를 생산하기 위하여 하니컴 구조를 갖는 모노리스에 10 wt% $Ni/CeO_2-ZrO_2$ 촉매를 담지한 후 메탄의 수증기 개질 실험을 수행하였다. 다른 $CeO_2/ZrO_2$ 몰비를 갖는 촉매들 중에서, $Ni/CeO_2-ZrO_2(CeO_2/ZrO_2=4/1)$촉매가 $700-800^{\circ}C$에서 높은 메탄의 전환율을 보여 주었다. 10wt% $Ni/CeO_2-ZrO_2$ 촉매가 담지된 금속 모노리스 촉매체는 높은 열전도도와 비표면적들로 인하여 좋은 촉매 특성을 보여줌을 확인할 수 있었다. 또한, 금속모노리스 촉매체는 반응물에서 과다의 수증기에 의한 수소 수율에서 크게 영향을 받지 않음을 알 수 있었다. $GHSV=30,000h^{-1}$, 반응물 비$(H_2O/CH_4=3.0)$ 반응온도 $800^{\circ}C$에서 금속모노리스 촉매체는 98%이상의 메탄의 전환율을 보여주었다. 생성물 가스에서 $CO_2/CO$의 비는 수증기/메탄의 반응물비가 증가할수록 수성가스화 반응에 의하여 증가됨을 알 수 있었다.

• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.336-345
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• 2020

Nickel-doped lanthanum cobalt oxide (LaCo_1-xNi_xO_3-δ, LCN) was investigated as an alternative anode material for solid oxide fuel cells. To improve its catalytic activity for steam methane reforming (SMR) reaction, Ni²⁺ was substituted into Co³⁺ lattice in LaCoO₃. LCN anode, synthesized using the Pechini method, reacts with yttria-stabilized zirconia (YSZ) electrolyte at high temperatures to form an electrochemically inactive phase such as La₂Zr₂O₇. To minimize the interlayer by-products, the LCN was coated via a double-tape casting method on the Ni/YSZ anode as a catalytic functional layer. By increasing the Ni doping amount, oxygen vacancies in the LCN increased and the cell performance improved. CH₄ fuel decomposed to H₂ and CO via SMR reaction in the LCN functional layer. Hence, the LCN-coated Ni/YSZ anode exhibited better cell performance than the Ni/YSZ anode under H₂ and CH₄ fuels. LCN with 12 mol% of Ni (LCN12)-modified Ni/YSZ anode showed excellent long-term stability under H₂ and CH₄ conditions.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.813-818
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• 2008

Various additives were added in small amounts on Ni/YSZ anode of SOFC (solid oxide fuel cell) in order to improve reactivity and to inhibit deactivation due to coke deposition during methane reforming using a low mole ratio steam ($H_2O/CH_4=1.5$) at $800^{\circ}C$. Ni/YSZ catalysts added with various perovskites did not show any improvement but exhibited a gradual decrease in the methane conversion. K-doped Ni/YSZ showed a steady increase and maintenance of the conversion up to 42 hours, after which there was an abrupt deactivation of catalyst owing to potassium loss by volatilization. Addition of 5% of $K_2Ti_2O_5$ on Ni/YSZ showed a stable maintenance of the conversion without K loss, and was able to prevent coke formation during a long time operation. Deactivation of catalyst during the reaction was mainly caused by the accumulation of graphidic carbon on the catalyst surface.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.656-662
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• 2007

Fuel reformer using plasma and shift reactor for CO oxidation were designed and manufactured as $H_2$ supply device to operate a polymer electrolyte membrane fuel cell (PEMFC). $H_2$ selectivity was increased by non-thermal plasma reformer using GlidArc discharge with Ni catalyst simultaneously. Shift reactor was consisted of steam generator, low temperature shifter, high temperature shifter and preferential oxidation reactor. Parametric screening studies of fuel reformer were conducted, in which there were the variations of the catalyst temperature, gas component ratio, total gas ratio and input power. and parametric screening studies of shift reactor were conducted, in which there were the variations of the air flow rate, stema flow rate and temperature. When the $O_2/C$ ratio was 0.64, total gas flow rate was 14.2 l/min, catalytic reactor temperature was $672^{\circ}C$ and input power 1.1 kJ/L, the production of $H_2$ was maximized 41.1%. And $CH_4$ conversion rate, $H_2$ yield and reformer energy density were 88.7%, 54% and 35.2% respectively. When the $O_2/C$ ratio was 0.3 in the PrOx reactor, steam flow ratio was 2.8 in the HTS, and temperature were 475, 314, 260, $235^{\circ}C$ in the HTS, LTS, PrOx, the conversion of CO was optimized conditions of shift reactor using simulated reformate gas. Preheat time of the reactor using plasma was 30 min, component of reformed gas from shift reactor were $H_2$ 38%, CO<10 ppm, $N_2$ 36%, $CO_2$ 21% and $CH_4$ 4%.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.6
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• pp.534-541
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• 2021

In this study, a novel microwave-matrix reformer was proposed to convert CH₄, which is a major component, to a high quality hydrogen energy. And to identify this performance, it was investigated for O₂/C ratio, steam feed amount and reformed gas recirculation which are affected for methane conversion and product gas yield. Through the parametric screening studies, optimal operating conditions were that O₂/C ratio, steam feed amount and recirculation rate were 1.1, 10 mL/min and 30 L/min. In this conditions, CH₄ conversion was 68.1%, H₂ selectivity 77.2 and H₂/CO ratio 2.62 which are possible applying SOFC stack for RPG (residential power generator).

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.231-234
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• 2005

수소 기반의 에너지 사회는 중소규모 분산 발전과 연료 전지 자동차에서 시작될 거라는 예측이 지배적이다. 가정용 고분자 연료전지 시스템은 상업화에 가장 가까운 소규모 분산 발전 시스템중의 하나이며, 에너지기술연구위원에서는 가정용 고분자 연료전지에 수소를 공급하기 위한 천연가스 수증기 개질시스템의 개발을 진행해 왔다. 효율 향상과 제작의 용이성, 그리고 소형화에 초점을 맞추어 개발된 prototype-I은 $2.0Nm^3/hr$의 순수 수소 생산 용량을 가지고 있으며, 수증기 개질기와 수성가스 전이 반응기 수중기 생성 장치, 그리고 반응열 공급에 필요한 버너 등을 이중 동심원관에 통합한 형태이다. 수중기 개질과 수성가스 전이 반응을 거쳐 나오는 개질 가스의 조성은 $72.3\%\;H_2,\;4.8\%\;CH_4,\;0.7\%\;CO,\;22.2\%\;CO_2$이며, 이때 S/C 비율은 2.5였다. 고분자 연료 전지 공급 시 요구되는 CO 농도가 10ppm 이하이기 때문에, 본 시스템에는 선택적 산화 반응기를 2단으로 설치하여 CO. 농도를 10ppm 이하로 낮추어주었다. 전체 시스템의 열효율은 LHV 기준으로 $68\%$. Prototype-I의 운전을 통해 설계 개선안을 도출하였으며, 이를 적용해 제작한 prototype-II가 시험 운전 중이다,. 통합된 개질 시스템에서는 각 단위 반응기사이의 열교환을 최적화하여 단위 반응들이 적정 온도 범위에서 일어나도록 유도하는 것이 중요하다. Prototype-II는 수증기 개질 반응기와 WGS 반응기, 수증기 생성 장치 사이의 열교환율을 향상시켜 농도를 $2.5\%$로 감소시키면서 CO의 농도는 $1\%$이하로 유지하였다. 이 결과를 바탕으로 얻어진 메탄 전환율은 $87\%$이고, 열효율은 LHV 기준으로 $75\%$이다. 아울러 개선점을 적용한 선택적 산화 반응기를 제작하였다. 개질 가스와 산소의 혼합을 유도하고, 반응기 온도의 제어를 통해 선택적 산화 반응의 속도와 선택성을 향상시키고자 한다. 시스템의 운전을 통해 메탄 전환율과 열효율의 개선을 진행할 예정이다.