• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.223.2-223.2
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• 2010

용융탄산염 연료전지(MCFC)는 $650^{\circ}C$에서 작동하는 고온형 연료전지 시스템이다. 이 시스템은 천연가스 등을 개질하여 생산된 수소를 바로 전기로 생산할 수 있는 시스템으로 열효율이 높으며, 현재 대체 발전시스템으로 각광을 받고 있다. MCFC는 개질방식에 따라 내부개질 방식과 외부개질 방식이 있다. 내부개질 방식은 수소를 생산하는 개질기가 스택내부에 장착된 형식으로 천연가스를 스택내부에서 개질하여 바로 전기를 생산하는 방식이다. 이 내부개질반응에 사용되는 촉매로는 알루미나에 담지된 니켈(Ni) 계열촉매이 주로 쓰이고 있다. 또한 내부개질촉매의 형태는 작은 원주형의 촉매형태로 성형되어 사용된다. 이 성형된 촉매의 크기가 바로 내부개질 스택의 크기를 결정하는 중요한 요소이다. 그래서 촉매의 크기는 되도록이면 작게 성형하는 것이 중요하다. 그러나 촉매의 크기가 너무 작으면 촉매를 성형하는데 큰 어려움이 생기게 된다. 본 연구에서는 니켈 촉매를 공침법이 아닌 균일용액침전법을 이용하여 제조하였으며, 이 촉매를 이용하여 지름이 약 2 mm 이하로 촉매를 압출성형하는 방법을 연구하였다. 먼저 요소(urea)를 이용한 균일용액침전법으로 촉매를 제조하였다. 최적의 촉매 합성조건을 살펴보기 위해서, 반응 온도를 80, 85, 90, 95, $100^{\circ}C$로 변화 시키면서 제조된 촉매의 특성을 살펴보았다. 그리고 촉매의 적절한 니켈 양을 알아보기 위해서 니켈의 양을 30, 40, 50, 60, 70 wt%로 변화 시켰으며, 조촉매로 사용되는 MgO 양을 5, 10, 15, 20 wt%로 변화 시켜서 제조된 촉매의 특성을 살펴보았다. 물성을 비교하기 위해서, X-선 회절분석(XRD) 및 TPR, 물리화학흡착을 하였다. 그 결과 침전반응온도가 $80^{\circ}C$에서 촉매가 가장 좋은 물성을 보였으며, 우수한 개질성능을 보였다. 그리고 촉매 활성물질인 니켈의 함량은 50 wt% 정도가 가장 적절한 함량이었으며, MgO의 함량이 15 wt%일 때 가장 우수한 물성과 개질 성능을 보여주었다. 이 촉매들은 공침법으로 제조된 상용촉매와 비교하였을 때, 보다 우수한 물성과 개질성능 보였다. 그래서 이 촉매를 균일침전법을 이용하여 대량으로 제조한 다음 압출성형 방법을 이용하여 촉매를 원주형으로 제조하였다. 먼저 제조된 촉매는 별도의 분쇄작업(볼밀 혹은 제트밀)을 거치지 않아도 입자사이즈가 약 $4{\mu}m$ 수준이 나오도록 촉매 제조조건을 조절 하였다. 그리고 소량의 Methyl cellulose(MC) 바이더와 물만 사용하여 촉매를 혼합한 다음 스크류 압출기를 이용하여 촉매를 성형하였다. 이 촉매는 지름이 약 2 mm 이하로 제조할 수 있었으며, 기계적 강도는 타정기로 성형한 상용촉매보다 우수하였다. 그리고 촉매 성능 또한 상용촉매와 비교하였을 때, 우수한 성능 보였다. MCFC용 내부개질 촉매로 균일용액침전법을 사용한 촉매가 적합하다고 판단되며, 압출성형에도 적합하다고 판단되었다.

• 한국태양에너지학회 논문집
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• 제21권3호
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• pp.1-8
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• 2001

고온의 태양열을 저장하기 위한 한 방편으로 화학반응을 이용한 태양에너지의 화학에너지로의 변환공정을 고려하였다. 태양에너지의 저장은 메탄의 수증기 개질반응으로 선정하였으며, 이 흡열반응에서 메탄의 전화율 특성을 살펴보았다. 반응기는 직경, 6.25 mm, 그리고 길이 30 cm 인 stainless steel을 코일형태로 제작하였다. 반응온도 범위내에서 메탄의 전화율은 반응온도에 따라서 선형적으로 증가하였으며 반응온도 $500^{\circ}C{\sim}900^{\circ}C$ 범위에서 메탄의 전화율은 약 $60%{\sim}90%$ 로 측정되었다. 이 실험을 통하여 태양열 저장을 위한 메탄의 수증기 개질반응의 타당성을 확인하였다.

• 한국정밀공학회지
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• 제28권1호
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• pp.108-114
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• 2011

Steam reformer was organized with steam reforming process and CO removing process. The steam reforming process needed high temperature, 600~900 $^{\circ}C$, for catalytic-reaction which was extract of hydrogen from steam and hydrocarbon. The effects of the evaporator configuration on its heat transfer characteristics were investigated both experimentally and numerically to pursue the miniaturization. In this study, three configurations were considered where the different structures were tested; empty, embossing and mesh filled. For the comparison of heat transfer performance of shape evaporator disk, numerical analysis using SC-Tetra code and experiment were carried out. In case of reformer system design, it should be considered heat transfer rate, differential pressure and fluid flow direction.

• 한국전산유체공학회지
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• 제16권1호
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• pp.42-47
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• 2011

In this paper, various operating parameters of stream reforming process from methane in stream reformer and preconverter for MCFC is studied by numerical method. Commercial code is used to simulated the porous catalyst with user subroutine to model three dominant chemical reactions which are Stream Reforming(SR), Water-Gas Shift(WGS), and Direct Stram Reforming(DSR). The hydrogen production is tested with different wall temperature and different reactor shapes. The calculated results of the concentration of hydrogen in stream reformer are very well consistent with experimental results. This numerical study gives the design reactor wall temperature condition and size of reactor to satisfy the required fuel conversion.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.477-480
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• 2006

In this study, we investigated operating characteristics of the LNG burner for steam methane reforming. The developed LNG burner and catalytic reactor to supply an efficient heat transfer between the combustion gas and catalyst got a good response of various operating load within 5-7 minute and high efficiency for steam methane reforming as a conversion of methane over 90%. We calculated the volume of catalyst for $1Nm^3/hr$ steam LNG reforming as $211cc/(Nm^3/hr\;H_2)$ and got the operating condition and design data of the burner and steam reforming for LNG.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.50-57
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• 2005

The aim of this study is to numerically investigate a compact reformer system currently under development and to design a better reforming system with more efficient heat transfer and reforming reactions. Numerical models were established separately for both the combustion part and the reforming reaction part. A comparison between the calculation results and experimental data showed that the concentration of the reformate at the exit of the reforming system was in good agreement with the measured data, but for the temperature at the exit little difference between them was found. After checking the validity of the numerical models, the heat transfer between the combustion gas and reforming catalysts was estimated and the behavior of the catalyst bed was investigated as a function of the operation parameters.

• 한국수소및신에너지학회논문집
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• 제30권5호
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• pp.411-417
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• 2019

An adsorption chiller is connected to the fuel processing/fuel cell system to increase the energy efficiency of the system. Since, the minimum temperature of $70^{\circ}C$ is needed to operate the adsorption chiller, HT-PEMFC is used as a heating source and $80^{\circ}C$ hot water in the water tank at the system is supplied to the chiller. Experimentally measured COP of the adsorption chiller was between 0.4-0.5 and the total calcuated efficiency of the connected system was between 60% and 70% comparing to 47% without adsorption chilling system.

• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.445-452
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• 2015

A tubular packed bed reactor for the steam-$CO_2$ combined reforming of natural gas to produce the synthesis gas of a target $H_2/CO$ ratio 2.0 was simulated. The effects of the reactor dimension, the feed gas composition, and the gas feeding temperature upon the possibility of coke formation across the catalyst bed were investigated. For this purpose, 2-dimensional heterogeneous reactor model was used to determine the local gas concentrations and temperatures over the catalyst bed. The thermodynamic potential distribution of coke formation was determined by comparing the extent of reaction with the equilibrium constant given by the reaction, $CH_4+2CO{\Leftrightarrow}3C+2H_2O$. The simulation showed that catalysts packed in the central region nearer the entrance of the reactor were more prone to coking because of the regional characteristics of lower temperature, lower concentration of $H_2O$, and higher concentration of CO. With the higher feeding temperature, the feed gas composition of the increased $H_2O$ and correspondingly decreased $CO_2$, or the decrease in the reactor diameter, the volume fraction of the catalyst bed subsequent to coking could be diminished. Throughout the simulation, reactor dimension and reaction condition for coking-free operation were suggested.

• 한국수소및신에너지학회논문집
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• 제27권5호
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• pp.494-502
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• 2016

A 1-dimensional heterogeneous reactor model with the gas-solid interfacial phase gradients was developed for the simulation of the packed bed reactor where the exothermic reversible water gas shift reaction for the natural gas steam reformed gas was proceeding in adiabatic mode. Experimental results obtained over the WGS catalyst, C18-HA, were best simulated when the frequency factor of the reaction rate constant was adjusted to a half the value reported over another WGS catalyst, EX-2248, having the same kinds of active components as the C18-HA. For the reactor of the inside diameter 158.4 mm and the bed length 650 mm, the optimum feeding temperature of the reformed gas was simulated to be $194^{\circ}C$, giving the lowest CO content in the product gas by 1.68 mol% on the basis of dried gas. For reactors more extended in the bed length, the possible lowest CO content in the product gas with the optimum feeding temperature of the reformed gas were suggested.

• 한국수소및신에너지학회논문집
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• 제27권5호
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• pp.571-580
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• 2016

In this paper, performance of the gas turbine combined cycle(GTCC) using pre-combustion carbon capture technology was comparatively analysed. Steam reforming and autothermal reforming were used. In the latter, two different methods were adopted to supply oxygen for the reforming process. One is to extract air form gas turbine compressor (air blowing) and the other is to supply oxygen directly from air separation unit ($O_2$ blowing). To separate $CO_2$ from the reformed gas, the chemical absorption system using MEA solution was used. The net cycle efficiency of the system adopting $O_2$ blown autothermal reforming was higher than the other two systems. The system using air blown autothermal reforming exhibited the largest net cycle power output. In addition to the performance analysis, the influence of fuel reforming and carbon capture on the operating condition of the gas turbine and the necessity of turbine re-design were investigated.