• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.153-156
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• 2009

Low temperature methane steam reforming to produce $H_2$ for fuel cells has been calculated thermodynamically considering both heat loss of the reformer and unreacted $H_2$ in fuel cell stack. According to the thermodynamic equilibrium analysis, it is possible to operate methane steam reforming at low temperatures. A scheme for the low temperature methane steam reforming to produce $H_2$ for fuel cells by burning both unconverted $CH_4$ and $H_2$ to supply the heat for steam methane reforming has been proposed. The calculated value of the heat balance temperature is strongly dependent upon the amount of unreacted $H_2$ and heat loss of the reformer. If unreacted $H_2$ increases, less methane is required because unreacted $H_2$ can be burned to supply the heat. As a consequence, it is suitable to increase the reaction temperature for getting higher $CH_4$ conversion and more $H_2$ for fuel cell stack. If heat loss increases from the reformer, it is necessary to supply more heat for the endothermic methane steam reforming reaction from burning unconverted $CH_4$, resulting in decreasing the reforming temperature. Experimentally, it has been confirmed that low temperature methane steam reforming is possible with stable activity.

• 한국연소학회:학술대회논문집
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• 2005.10a
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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.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.2
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• pp.113-120
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• 2013

A steam reformer is a chemical reactor to produce high purity hydrogen from fossil fuel. In the steam reformer, since endothermic steam reforming is heated by exothermic combustion of fossil fuel, the heat transfer between two reaction zones dominates conversion of fossil fuel to hydrogen. Steam Reforming is complex chemical reaction, mass and heat transfer due to the exothermic methane/air combustion reaction and the endothermic steam reforming reaction. Typically, a steam reformer employs burner to supply appropriate heat for endothermic steam reforming reaction which reduces system efficiency. In this study, the heat of steam reforming reaction is provided by anode-off gas combustion of stationary fuel cell. This paper presents a optimization of heat transfer effect and average temperature of cross-section using two-dimensional models of a coaxial cylindrical reactor, and analysis three-dimensional models of a coaxial cylindrical steam reformer with chemical reaction. Numerical analysis needs to dominant chemical reaction that are assumed as a Steam Reforming (SR) reaction, a Water-Gas Shift (WGS) reaction, and a Direct Steam Reforming(DSR) reaction. The major parameters of analysis are temperature, fuel conversion and heat flux in the coaxial reactor.

• Journal of the Korean Society of Combustion
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• v.16 no.1
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• pp.36-45
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• 2011

The heat-flow characteristics and reforming efficiency of steam reformer with combustor are numerically investigated at various operating conditions. SCR(Steam to Carbon Ratio) and GHSV(Gas Hourly Space Velocity) are adopted as important operating conditions. User-Defined-Function(UDF) was used to simultaneously calculate reforming and combustion reaction. Numerical results show that hot burned gas rise by a buoyant force and heat exchange between reforming reactors and cocurrent flow occurs in the combustion region. The results also indicate that an increase of SCR leads to decrease the mole fraction of hydrogen at the reactor outlet. As GHSV increases, conversion rate decreases.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.3
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• pp.236-242
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• 2012

This study has been carried out the experiment for the possibility of biogas reforming using waste heat. The source of this waste heat is the exhaust gas from a small-sized gas engine generator. For recovering the waste heat, Two-stage heat exchanger is manufactured. The two-stage heat exchanger is composed of a heat exchanger for the exhaust gas and a heat exchanger for the water. This two-stage heat exchanger is used for reforming the biogas by means of on-site hydrogen production at the small-sized gas engine generator. The two-stage heat exchanger is coupled with the biogas reformer which is a kind of catalytic reformer. To confirm a heat recovery efficiency of the two-stage heat exchanger, temperature differences of inlet and outlet locations are measured. Also, the variations of syngas concentrations with various biogas flow rates are investigated. As a result using manufactured two-stage heat exchanger, the biogas can be reformed from waste heat recovery. This experiment suggests that the exhaust gas heat exchanger is available for reforming the biogas.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.112-116
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• 2011

In this paper, a preconverter of MCFC for an emergence electric power supplier is numerically simulated to increase the hydrogen production from natural gas (methane). 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). To get 10% fuel conversion rate in preconverter. the required external heat flux is supplied from outer wall of preconverter. The calculated results show that very nonuniform temperature distribution and chemical reaction happen near the wall of preconverter. These phenomena can be explained by the low heat conductivity of porous catalyst and the endothermic reforming reaction.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.172-175
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• 2006

Steam reforming of methane using Xe-arc solar simulator was studied for converting solar radiation into energy foam that one can readily utilize. The Xe-arc lamp produce a spectrum similar to that of the sun. SiC ceramic foam, resist high temp.$(>900^{\circ}C)$, is used to catalytically active foam absorber, and to support of reforming catalyst. The catalyst on the surface of foam were directly irradiated with solar simulated xe-light in order to carry out the steam reforming of methane. The reactor was made of stainless steel and quartz window was located on a place of the xe-light irradiation and temperature was controlled using K-type thermocouple in contact with catalyst located inside the reactor. The result show that a possibility of solar reforming using catalytically active foam absorber is exist.

• Journal of the Korean Institute of Gas
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• v.17 no.2
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• pp.78-84
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• 2013

A numerical study on the heat and fluid flow has carried out for the design of the steam reforming reactor which consists of six reforming tubes and one burner. Reforming reaction calculation is coupled with the heat and fluid flow one. The burner type in the reforming reactor is chosen through the fluid flow calculation according to different type of burner structure. It is shown that the significant temperature gradient exists in the reforming reactor, affecting the component variation along the length of reforming tube. The component ratio of reforming gas is changed by the variation of SCR and GHSV.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.158.2-158.2
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• 2011

DME is acronym of dimethyl ether, which is spotlighted as an ideal fuel to produce hydrogen due to its high hydrogen/carbon ratio, high energy density and easiness to carry. In this research, we calculated thermodynamic hydrogen (or syngas) yield from DME autothermal reforming and compared to other fuels. The reforming efficiency was about 80% above $700^{\circ}C$. Lower OCR has higher reforming efficiency but, it requires additional heat supply since the reactions are endothermic. SCR has no significant effect on the reforming efficiency. The optimized condition is $700^{\circ}C$, SCR 1.5, OCR 0.45 without additional heat supply. Comparing to other commercial gaseous fuels (methane and propane), DME has higher selectivity of $H_2O$ and $CO_2$ than the others due to the oxygen atom in the molecule. To apply DME autothermal reforming to real system, a proper catalyst is required. Therefore, it is performed the experiment comparing various novel metal catalysts based on CGO. Experiments were performed at calculated condition. The composition of product was measured and reforming efficiency was calculated. The catalysts have similar efficiency at high temperature(${\sim}800^{\circ}C$) but, CGO-Ru has the highest efficiency at low temperature ($600^{\circ}C$).

• New & Renewable Energy
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• v.2 no.4 s.8
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• pp.56-63
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• 2006

In this paper, heat and mass transfer characteristics through experimental and numerical study are extensively investigated in steam reforming reactor under given operating conditions. In order to get simulated data at outlet of the reformer, heterogeneous reactor model is incorporated. As the reaction also takes place in porous media, two medium approach is used to take into account thermally non-equilibrium phenomena between catalyst and bulk gas. From various parametric studies, significance of heat transfer is emphasized in steam reforming reaction.