• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
• /
• pp.156.1-156.1
• /
• 2011

It is of great importance to predict operating parameter characteristics of an integrated fuel processor by the increased life-time and system performance. In this study, computational analysis is performed to gain fundamental insights on transport phenomena and chemical reactions in reformer which consists of preheating, steam reforming, and water gas shift reaction beds. Also, a top-fired burner locates inside of the reforming system. The combustor is providing thermal energy necessary for the steam reforming bed which is a endothermic catalytic reactor. Two-dimensional numerical model of the integrated fuel processing system is introduced for the analysis of heat and mass transport phenomena as well as surface kinetics and catalytic process. A kinetic model was developed and then computational results were compared with the experimental data available in the literature. Subsequently, parameter study using the validated steam methane reforming model was conducted by considering operating parameters, i.e. steam to carbon ratio and temperature.

• 한국가스학회지
• /
• 제20권5호
• /
• pp.27-33
• /
• 2016

본 연구의 목적은 실제 산업현장에서 사용되는 수소 개질로 내 개질가스의 수증기-메탄 혼합비에 따른 튜브 내 온도 및 화학반응 특성을 수치 해석하는 것이다. 탄화수소의 수증기 개질반응은 800 K - 1000 K 이상의 고온에서 발생하기 때문에 대류, 전도 및 복사 열전달을 고려한 복합 열전달을 고려해야 한다. 수치해석은 상용 전산유체역학(CFD) 코드(ANSYS Fluent V.13.0)를 사용하였다. 본 연구에서 해석을 위해 Reynolds-Averaged Navier-Stokes, 운동량 및 에너지 방정식을 사용하고, 화학반응이 발생하는 튜브 내부는 니크롬 재질의 다공성 영역으로 가정하였다. 개질 튜브 내 온도 및 화학반응 특성을 비교하기 위해 메탄과 수증기의 혼합비를 1-6으로 증가시켜 비교 분석하였다. 수치해석 결과, 메탄에 대한 수증기 비율이 높을수록 튜브 내부의 온도가 증가하고, 메탄의 전화율이 증가한다. 그러나 수소 개질량은 수증기와 메탄의 비율이 5일 때 가장 많은 것을 알 수 있다.

• 한국수소및신에너지학회논문집
• /
• 제22권1호
• /
• pp.100-108
• /
• 2011

The use of biogas as an energy source reduces the chance of possible emission of two greenhouse gases, $CH_4$ and $CO_2$, into the atmosphere at the same time. Its nature of being a reproducible energy source makes its use even more attractive. This research if for the hydrogen production through the steam reforming of the biogas. The biogas utilized 3D-IR matrix burner in which the surface combustion is applied. The nickel catalyst was used inside a reformer. Parametric screening studies were achieved as Steam/Carbon ratio, biogas component ratio, Space velocity and Reformer temperature. When the condition of Steam/Carbon ratio, $CH_4/CO_2$ ratio, Space velocity and Refomer temperature were 3.25, 60%:40%, 19.32L/$g{\cdot}hr$ and $700^{\circ}C$ respectively, the hydrogen concentration and methane conversion rate were showed maximum values. Under the condition mentioned above, $H_2$ concentration was 73.9% and methane conversion rate was 98.9%.

• 한국수소및신에너지학회논문집
• /
• 제33권6호
• /
• pp.749-760
• /
• 2022

An efficient computational fluid dynamics model was proposed for simulating microchannel-type steam/methane reformers with thin washcoat catalyst layers. In this model, by using the effectiveness factor correlations, the overall reaction rate that occurs in the washcoat catalyst layer could be accurately estimated without performing the detailed calculation of heat transfer, mass transfer, and reforming reactions therein. The accuracy of the proposed model was validated by solving a microchannel-type reformer, once by fully considering the complex steam/methane reforming (SMR) process inside the washcoat layer and again by simplifying the SMR calculation using the effectiveness factor correlations. Finally, parametric studies were conducted to investigate the effects of operating conditions on the SMR performance.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
• /
• pp.50-57
• /
• 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
• /
• 제17권4호
• /
• pp.403-408
• /
• 2006

The plate reformer consisting of combustion chamber and reforming chamber for 25 kW MCFC stack has been operated and computational fluid dynamics was applied to estimate reactions and thermal fluid behavior in the reformer. The methane air 2-stage reaction was assumed in the combustion chamber, and three step steam reforming reactions were included in the calculation. Flow uniformity, reaction rate and species distribution, and temperature distribution were analyzed. In particular, temperature distribution was compared with the measurements to show good agreement in the combustion chamber, however, inappropriate agreement in the reformer chamber.

• 대한기계학회논문집B
• /
• 제32권8호
• /
• pp.636-644
• /
• 2008

The objective of this paper is to investigate characteristics of an autothermal reformer at various operating conditions. Numerical method has been used, and simulation model has been developed for the analysis. Pseudo-homogeneous model is incorporated because the reactor is filled with catalysts of a packed-bed type. Dominant chemical reactions are Full Combustion reaction, Steam Reforming(SR) reaction, Water-Gas Shift(WGS) reaction, and Direct Steam Reforming(DSR) reaction. Simulation results are compared with experimental results for code validation. Operating parameters of the autothermal reformer are inlet temperature, Oxygen to Carbon Ratio(OCR), Steam to Carbon Ratio(SCR), and Gas Hourly Space Velocity(GHSV). Temperature at the reactor center, fuel conversion, species at the reformer outlet, and reforming efficiency are shown as simulation results. SR reaction rate is improved by increased inlet temperature. Reforming efficiency and fuel conversion reached the maximum at 0.7 of OCR. SR reaction and WGS reaction are activated as SCR increases. When GHSV is increased, reforming efficiency increases but pressure drop from the increased GHSV may decrease the system efficiency.

• 대한기계학회논문집B
• /
• 제40권12호
• /
• pp.793-799
• /
• 2016

폐열을 열원으로 사용하는 저온형 개질기는 하이브리드 연료전지 시스템의 효율향상을 위해 사용되고 있다. 저온형 개질기의 경우 저온의 열적상태에서 높은 열전달 효율을 내는 것이 중요하며, 이를 위한 형상 최적화의 과정이 필요하다. 본 연구에서는 제한된 열공급 상황에서 개질기의 형상인자 변화에 따른 온도 및 반응특성을 전산해석을 통하여 알아보고자 하였다. 해석결과 저온형 개질기의 반응이 활발히 일어나는 영역은 온도가 높은 후단에 제한되는 현상을 보여 고온형 개질기와의 차이를 나타내었다. 또한 개질기의 기체공간속도(Gas hourly space velocity, GHSV)를 감소시키거나 열전달 면적을 증대시킴으로써 효율을 향상 시킬 수 있음을 확인하였고 종횡비에 따른 해석을 실시한 결과 저온형 개질기의 경우 길이방향보다는 반경방향의 열전달을 증대시키는 방법이 효과적임을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2008년도 추계학술대회 논문집
• /
• pp.25-28
• /
• 2008

Steam reforming reaction is a matured technology to get hydrogen from hydrocarbon fuels compared with other reforming reactions such as partial oxidation(POX), autothermal reforming(ATR). It is so endothermic that it needs heat source to activate the reaction. Due to the reaction characteristics, heat transfer limitation phenomena generally occur in the steam reformer. As one of new ideas, the effect of discontinuous gas feeding is investigated based on heat transfer characteristics. The new operating method is usually favorable at high GHSV region(i.e. over $10,000h^{-1}$). In order to numerically simulate the physical issues, numerical approach is adopted based on heterogeneous reaction model, two-equation model in energy equation, and other constitutive models in porous media.

• 대한기계학회논문집B
• /
• 제32권7호
• /
• pp.497-503
• /
• 2008

Hydrogen is considered as a fuel of the future for its renewability and environmental compatibility. The reforming of hydrocarbon fuels is currently the most important source of hydrogen, which is expected to continue for next several decades. In this study, extensive CFD simulations on the steam-methane reforming process were conducted to study the performance of four reaction models, i.e. three Arrhenius-type models and a user-defined function (UDF) model. The accuracies of different reaction models for various operating temperatures and steam carbon ratios (SCRs) were evaluated by comparing their CFD results with zero-dimensional intrinsic model of Xu and Froment. It was found that the UDF model generally produced more accurate results than Arrhenius-type models. However, it was also shown that Arrhenius-type models could be made sufficiently accurate by choosing appropriate reaction coefficients, and thus could also be useful for the simulation of the steam-methane reforming process.