촉매 연소를 열원으로 한 수증기-메탄개질반응 전산유체해석

이정섭,이강훈,유상석,안국영,강상규 한국수소및신에너지학회 2013 한국수소 및 신에너지학회논문집 Vol.24 No.2

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.

Steam reforming of monohydric alcohols and polyalcohols: Influence of single or multiple hydroxyl group(s) on nature of the coke

Yiran Wang,Chao Li,Shu Zhang,Leilei Xu,Xun Hu 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.110 No.-

Alcohols like ethanol and glycerol have been extensively investigated as potential feedstock for on-sitehydrogen production by steam reforming. The varied number of hydroxyl group in the alcohols inevitablyaffects the reaction intermediates generated and eventually properties of coke formed. In this study, fouralcohols (ethanol, ethylene glycol, 1-propanol and glycerol) with the single or multiple hydroxyl groupswere steam reformed, focusing on the influence of the hydroxyl group on the properties of the coke. Theresearch results showed that steam reforming of ethanol and glycerol produced more coke than that insteam reforming of 1-propanol or ethylene glycol, while the Ni/SBA-15 catalyst deactivated to a higherextent in steam reforming of ethylene glycol or glycerol with multiple hydroxyl group, due to the cokeof varied properties. The coke produced by steam reforming of ethanol and 1-propanol contained moredefective structures but more aromatic. However, the generated coke from the steam reforming of ethyleneglycol and glycerol had more aliphatic structures, especially in that from ethylene glycol. On theother hand, the carbon nanotubes formed by the steam reforming of ethanol or 1-propanol had thin wallthickness and smooth surface, while that in steam reforming of ethylene glycol and glycerol had thickwall and very rough surface, resulting from the distinct reaction intermediates formed.

Rapid evaluation of coke resistance in catalysts for methane reforming using low steam-to-carbon ratio

Jeon, Jiyoon,Nam, Seongju,Ko, Chang Hyun Elsevier 2018 CATALYSIS TODAY - Vol.309 No.-

<P><B>Abstract</B></P> <P>The formation and subsequent accumulation of coke is one of the major reasons for the catalyst deactivation in methane reforming reaction. Although the investigation of coke-resistant catalysts is closely related to their long-term stability of given catalysts, it takes a long time to quantitatively measure the amount of carbon deposition on catalysts under normal reaction operational conditions. To overcome this problem, we used the steam deficient reaction condition, i.e. a low steam-to-carbon ratio (S/C) of 0.5 to accelerate the carbon deposition on catalysts. In this condition, the base catalyst of 10wt.% Ni/alumina rapidly lost its catalytic activity, indicating fast coke deposition. However, adding proper additives, such as Ru among various precious metals (Ru, Rh, Pt, and Pd) and alkaline earth metals (Mg, Ca, Sr, and Ba) with the appropriate loading (5wt.%) effectively suppressed coke formation. The optimized catalyst composition is 0.5wt.% Ru/5wt.% Mg/10wt.% Ni/alumina, which displayed coke resistance in the long-term stability test of steam methane reforming and 40h test of dry reforming of methane. These experimental results indicate that the method developed in this study is useful for the rapid evaluation of given catalysts for their coke resistance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effect of steam-to-carbon ratio on coke formation during methane reforming studied. </LI> <LI> Coke formation measured within 5h using low steam-to-carbon ratio and high WHSV. </LI> <LI> Quick development of Ru-Mg catalysts with high coke resistance. </LI> <LI> Long-term stability for both steam and dry methane reforming demonstrated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Low Temperature Methane Steam Reforming for Hydrogen Production for Fuel Cells

Hyun-Seog Roh,전기원 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.1

Low temperature methane steam reforming to produce H2 for fuel cells has been calculated thermodynamically considering both heat loss of the reformer and unreacted H2 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 H2 for fuel cells by burning both unconverted CH4 and H2 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 H2 and heat loss of the reformer. If unreacted H2 increases, less methane is required because unreacted H2 can be burned to supply the heat. As a consequence, it is suitable to increase the reaction temperature for getting higher CH4 conversion and more H2 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 CH4, resulting in decreasing the reforming temperature. Experimentally, it has been confirmed that low temperature methane steam reforming is possible with stable activity.

Low Temperature Methane Steam Reforming for Hydrogen Production for Fuel Cells

Roh, Hyun-Seog,Jun, Ki-Won Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.1

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.

Heat flux analysis of a cylindrical steam reformer by a modified Nusselt number

Park, J.,Lee, S.,Lim, S.,Bae, J. Pergamon Press ; Elsevier Science Ltd 2009 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.34 No.4

A numerical method is used to investigate a steam reformer. The reactor is assumed as a porous medium, because it is filled with catalysts of a packed-bed type, and a pseudo-homogeneous model is incorporated for a chemical reaction model. The steam reforming (SR) reaction, water-gas shift (WGS) reaction, and direct steam reforming (DSR) reaction are assumed to be dominant reactions in the steam reformer. The difference in temperature between the inside and outside of the reactor is a driving force in heat transfer, and is affected by the amount of heat adsorption by an endothermic reaction. A modified Nusselt number (Nu<SUB>M</SUB>) can represent the heat transfer rate of the endothermic reactor, and thus Nu<SUB>M</SUB> can be used to describe the performance of the steam reformer. The SR reaction rate is sufficiently activated when Nu<SUB>M</SUB> around the inlet region is greater than 10, and fuel conversion exceeds 0.9 when the difference in Nu<SUB>M</SUB> value between the inlet area and outlet area is greater than 5. The correlation between fuel conversion and operating conditions has also been studied by using Nu<SUB>M</SUB>.

Production of hydrogen-rich syngas from methane reforming by steam microwave plasma

최대현,천세민,마숙활,홍용철 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.34 No.-

Steam-methane reforming (SMR) is most commonly carried out in a catalytic reactor at temperaturesfrom 700 to 1000 8C. During the reforming reaction, the catalyst agglomerates under the hightemperatures, showing degradation of catalytic performance with carbon deposition on the catalystsurface. Here, we report methane reforming in a steam plasma generated by microwaves at atmosphericpressure without the use of catalysts. The plasma reforming system is mainly composed of a 2.45 GHzmicrowave plasma torch and a plasma nozzle. Methane gas is introduced into the steam microwaveplasma, which is stabilized by a swirl flow. The steam microwave plasma provides highly active speciesand a high-temperature plasma flame, enhancing the chemical reaction rate and eliminating the need forcatalysts. We investigated the dependence of the hydrogen concentration on the steam to carbon ratio ata given plasma power. Using a specially designed plasma nozzle, we achieved high hydrogenconcentrations (>70 vol.%) in the effluent streams.

메탄올 증기개질을 위한 Cu/γ-alumina 기반 촉매의 촉진제 사용에 따른 특성 연구

김기범,홍성철,이병인,장성호,서정민,시바쿠마르,박제성,정은상 한국도시환경학회 2021 한국도시환경학회지 Vol.21 No.4

To prevent global warming due to the use of fossil fuels, many studies have been conducted on hydrogen production through methanol steam reforming. nevertheless, the effect of steam reforming by the promoters of the catalyst prepared by the use of the support and the impregnation method requires further study. therefore, through this study, basic physical properties such as catalyst surface properties and crystal state were observed according to the impregnation ratio of the promoters based on the Cu/γ-alumina support. in addition, by implementing methanol steam reforming, the effect of the composition of Zn and Zr used as promoters on the composition of steam reforming products was investigated. the basic physical properties of the catalyst could be observed through SEM-EDS, TPR, XRD. The hydrogen composition effect by zinc, which was expected to increase the hydrogen composition, was not clearly shown. however the effect on the carbon dioxide selectivity was well shown for both zirconium and zinc, and the Cu/Zn ratio of 1 showed better carbon dioxide selectivity by zirconium than the case of 2.5. 화석연료 사용으로 인한 지구온난화 방지를 위해 메탄올 증기개질을 통한 수소 생산 연구가 많이 진행되었으나, 지지체 사용 및 함침법으로 제조된 촉매에서의 촉진제에 의한 증기개질 영향은 더 많은 연구가 필요하다. 따라서 본 연구를통해 Cu/γ-alumina 지지체를 기반으로 촉진제 함침 비율에 따른 촉매 표면특성과 결정상태 등의 기초적인 물성을 확인하고 메탄올 증기개질을 시행함으로서 촉진제로 사용된 Zn, Zr의 조성에 따른 증기개질 생성물 조성에 미치는 영향을 파악하고자 하였다. 촉매의 기초 물성은 SEM-EDS, TPR, XRD를 통해 확인할 수 있었다. 수소 조성을 증가시킬 것으로 예상되었던 Z n에 의한 수소 조성 영향은 본 실험에서 명확하게 나타나지 않았으나 이산화탄소 선택도에 대한 영향은 Z r과Zn 모두 그 특성이 잘 나타났으며, Cu/Zn 비율이 1인 경우가 2.5인 경우에 비해 Zr에 의한 이산화탄소 선택도 면에서 더좋게 나타났다.

Autothermal reforming over a Pt/Gd-doped ceria catalyst: Heat and mass transport limitations in the steam reforming section

Lim, Sungkwang,Bae, Joongmyeon Elsevier 2010 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.35 No.13

<P><B>Abstract</B></P><P>Autothermal reforming (ATR) has several advantages for fuel cell applications, such as a compact reactor structure and fast response. Using oxidation reactions inside the reactor, ATR does not have the external heat transfer limitations associated with steam reforming. However, mass and heat transfer limitations inside and outside the catalyst particles are still anticipated. In this study, transport limitations in the steam reforming section of ATR over a Pt/Gd-doped ceria catalyst are analyzed by numerical simulations based on a reaction rate equation in which parameters are adjusted to measured kinetic data. The simulation results show that significant transport limitations characterize the steam reforming section of packed-bed ATR reactors. The activity per catalyst bed volume is highly dependent on the particle size, and only the thin exterior layer of the particles is involved in catalyzing the reactions. Based on the results, it is shown that an eggshell type catalyst particle could reduce catalyst material significantly without a considerable decline in the activity per catalyst bed volume.</P>

Methane Reforming Reactions over Stable Ni/ θ -Al₂O₃ Catalysts

Hyun-Seog Roh,전기원,Wen-Sheng Dong,Seung-Chan Baek,Sang-Eon Park 한국공업화학회 2002 Journal of Industrial and Engineering Chemistry Vol.8 No.5

NiO/θ-Al2O3 catalysts were prepared and investigated after reduction treatment in the methane conversion reactions, such as oxy-reforming, steam reforming and oxy-steam reforming. Among the catalysts with various Ni loading, 12% Ni loading exhibits not only the highest catalytic activity and selectivity but also remarkable stability. The TPR results reveal that strong interaction between Ni and support results in forming stable NiOx species. Reducibility of NiO and the population of NiOx compared with NiO and/or NiAl2O4 play very important roles in the catalytic activity and stability of Ni/θ-Al2O3. Metallic Ni sites formed from the reduction of both NiO weakly interacting with the support and NiOx strongly interacting with the support are active sites for methane reforming reactions. Even though free NiO sites are prerequisite for high activity, the increase of NiO population in high Ni loading favorably promotes Ni sintering resulting in undesirable catalytic properties.