• 대한기계학회논문집B
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• 제40권11호
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• pp.745-753
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• 2016

초소형 연료전지용 메탄올-수증기 개질기의 경우 저온상태($250^{\circ}C$ 이하)에서 수증기와 반응하여 개질반응이 일어나기 때문에 수소를 효율적으로 생산할 수 있다. 본 연구는 이러한 개질기에 대하여 수치해석적 연구를 수행하였다. 먼저, 개질기 벽면 온도를 100, 140, 180, $220^{\circ}C$로 설정하였고 메탄올 전환율은 각 0, 0.072, 3.83, 46.51%로 나타났다. 다음으로 촉매의 공극률을 0.1, 0.35, 0.6, 0.85로 설정하였고, 메탄올 전환율에는 큰 차이가 없었으나 압력강하 값이 각 4645.97, 59.50, 5.12, 0.45 kPa로 나타났다. 메탄올-수증기 개질기는 $180^{\circ}C$ 이하의 온도에서는 거의 반응하지 않으며 공극률은 개질기를 흐르는 유체가 개질기와 충분히 접촉하여 활성화 에너지를 낮추어 준다면 메탄올 전환율에 크게 영향을 미치지 않는다는 것을 확인하였다.

• 설비공학논문집
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• 제26권6호
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• pp.269-274
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• 2014

The experimental performance evaluation of a cylindrical steam reformer with various thermal conditions has been conducted. The bottom space of the cylindrical reactor was packed with Ruthenium (Ru) catalyst. A three-segment furnace was installed to create the axially variable boundary temperature distribution. Six K-type thermocouples were inserted into the catalyst layer, and three exhaust ports were fabricated on the side wall along the flow direction. The exhausted gases at each port were analyzed by using gas chromatograph (GC) system. The experimental results showed that the reforming reaction occurs intensively in the upstream region and more hydrogen is obtained when the intake gas is sufficiently heated up through the enhanced steam reforming (SR) reaction. The axially increasing boundary temperature setup provided the maximally accumulated reforming efficiency of 74.8%, when the reactor was placed at the 3rd section of the furnace.

• 한국수소및신에너지학회논문집
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• 제17권4호
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• pp.403-408
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• 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.

• 한국수소및신에너지학회논문집
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• 제21권4호
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• pp.286-294
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• 2010

According to the propagation of fuel cell system, the importance of that system efficiency is being magnified. Thus, the efficiency improvement of reformer which is the important part of fuel cell system will be required. In structural aspect, the reformer is classified into cylindrical and plate type. Plate type reformer features better maintenance and space efficiency compared with cylindrical type. In this study, we changed the shape of combustion chamber to improve the reforming efficiency. And then we performed the CFD simulation to predict the spacial distribution of temperature. Analysis cased contains with baffles, fins, baffles and fins, and without those. In case of only with-baffle, temperature distributions were uneven because the high temperature stream was concentrated near the baffle end. In case of with-fin, the temperature distributions were relatively even than other cases.

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

• 한국수소및신에너지학회논문집
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• 제13권4호
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• pp.304-312
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• 2002

In this study, the performance of the $5Nm^3/hr$ compact type steam reformer which was developed for application of fuel cell or hydrogen station was evaluated in terms of gas process efficiency. For these purposes, reforming efficiency and total efficiency with system load change were analyzed. The reforming efficiency was calculated from the total molar flow of hydrogen output over total fuel flow input to the reformer and the burner on the higher heating value(HHV). In the case of the total efficiency, recovered heat at the heat recovery exchanger was considered. From the results, it was known that system performance was stable, because methane conversion showed the a slight decline which is about 2% though increasing system load to full. Reforming efficiency was increased from 20% to 58%, respectively as increasing system load from 10% to 90%. It was found that total efficiency was higher then reforming efficiency because of terms of heat recovered. As a results, it was known that total efficiency was increased form 75% to 83% at the 10% and 90% system load, respectively. From these results, it is concluded that compact steam reformer which is composed of stacking plate-type reactors is suitable to on-site hydrogen generator or to fuel cell application because of quick start within 1 hr and good performance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2015-2020
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• 2007

Diesel is an excellent candidate fuel for fuel cell applications due to its high hydrogen density and well-established infrastructure. But, it is hard to guarantee desirable performance of diesel reformer because diesel reforming has several problems such as sulfur poisoning of catalyst and carbon deposition. We have been focusing on diesel autothermal reforming(ATR) for substantial period. It is reported that ATR of diesel has several technical advantages such as relatively high efficiency and fuel conversion compared to steam reforming(SR) and partial oxidation(POX). In this paper, we investigate characteristics of diesel reforming under various ratios of reactants(oxygen to carbon ratio, steam to carbon ratio) for improvement of reforming performances(high reforming efficiency, high fuel conversion, low carbon deposition). We also exhibit calculated heat balance of autothermal reformer at each condition to help thermal management of SOFC system.

• 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.

• Environmental Engineering Research
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• 제10권3호
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• pp.122-130
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• 2005

Gasification of carbonaceous wastes such as shredded tire, waste lubricating oil, plastics, and powdered coal initiates a single-stage reforming reactor(reformer) Without catalyst and a syngas burner. Syngas is combusted with $O_2$ gas in the syngas burner to produce $H_2O\;{and}\;CO_2$ gas with exothermic heat. Reaction products are introduced into the reforming reactor, reaction heat from syngas burner elevates the temperature of reactor above $1,200^{\circ}C$, and hydrogen gas fraction reaches 65% of the product gas output. Reactants and heat necessary for the reaction are provided through the syngas burner only. Neither $O_2$ gas nor steam is injected into the reforming reactor. Multiple syngas burners may be connected to the reforming reactor in order to increase the syngas output, and the product syngas is recycled into syngas burner.

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