Direct methane solid oxide fuel cell working by gradual internal steam reforming: Analysis of operation

Klein, Jean-Marie; Hénault, Marc; Roux, Claude; Bultel, Yann; Georges, Samuel

doi:10.1016/j.jpowsour.2008.11.122

Cited by 68 publications

(82 citation statements)

References 15 publications

(27 reference statements)

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“…Below 1/3, the system will not release enough steam to ensure itself complete conversion, and methane will diffuse into the cermet yielding fast coking. More details concerning this concept will be found in our previous work (7)(8)(9)(10)(11)(12). This simplified principle mechanism was applied here study and the faradaïc efficiency was first optimized in H 2 above 1/3 by adjusting the experimental parameters (fuel concentration and flow rates).…”

Section: Resultsmentioning

confidence: 99%

SOFC Long Term Operation in Pure Methane by Gradual Internal Reforming

et al. 2013

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A solid oxide fuel cell was designed to be operated in pure methane, without reforming or carrier gas. The fuel cell was built up from conventional NiO-YSZ anode supported cell with a specific Pt screen-printed anodic collecting system and a Ir-CGO catalytic layer. The operation principle is based on Gradual Internal Reforming. After an initiation in H 2 for 30 minutes, the cell was operated for almost 2000 hours in pure and dry CH 4 with a fuel utilization rate of 30 %. Intrinsic gradual degradation of 15 %/1000 h was observed, but no coking occurred at the anodic side.

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Section: Resultsmentioning

confidence: 99%

SOFC Long Term Operation in Pure Methane by Gradual Internal Reforming

et al. 2013

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“…This carbon deposit on the anode surface can obviously block the fuel supply and the transfer of the oxide ions, leading to a decrease in the power efficiency of the cell. Previous published studies highlighted that a Table 3 Kinetic parameters and equilibrium constants [7,[12][13][14]17] catalyst layer thickness equal to 1 mm seems reasonable to avoid carbon deposition into the cermet anode [5,8].…”

Section: Resultsmentioning

confidence: 99%

“…Figure 1 presents the principle of GIR coupled with electro-catalytic dissociation [8]. To avoid cracking by contact with methane, anodic current collection cannot be made with conventional grids pressed onto the anode because of the addition of the catalyst layer.…”

Section: Anodementioning

confidence: 99%

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SOFC fuelled by methane without coking: optimization of electrochemical performance

2010

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In recent years, fuel cell technology has attracted considerable attention from several fields of scientific research as fuel cells produce electric energy with high efficiency, emit little noise, and are non-polluting. Solid oxide fuel cells (SOFCs) are particularly important for stationary applications due to their high operating temperature (1,073-1,273 K). Methane appears to be a fuel of great interest for SOFC systems because it can be directly converted into hydrogen by direct internal reforming (DIR) within the SOFC anode. Unfortunately, internal steam reforming in SOFC leads to inhomogeneous temperature distributions which can result in mechanical failure of the cermet anode. Moreover this concept requires a large amount of steam in the fed gas. To avoid these problems, gradual internal reforming (GIR) can be used. GIR is based on local coupling between steam reforming and hydrogen oxidation. The steam required for the reforming reaction is obtained by the hydrogen oxidation. However, with GIR, Boudouard and cracking reactions can involve a risk of carbon formation. To cope with carbon formation a new cell configuration of SOFC electrolyte support was studied. This configuration combined a catalyst layer (0.1%Ir-CeO 2 ) with a classical anode, allowing GIR without coking. In order to optimise the process a SOFC model has been developed, using the CFD-Ace? software package, and including a thin electrolyte. The impact of a thin electrolyte on previous conclusions has been assessed. As predicted, electrochemical performances are higher and carbon formation is always avoided.However a sharp decrease in the electrochemical performances appears at high current densities due to steam clogging.Keywords SOFC Á Gradual internal reforming Á Simulation Á CFD-Ace? List of symbols D iDiffusion coefficient of the i-th species (m 2 s -1 ) D i,eff Effective diffusion coefficient of the i-th species (m 2 s -1 ) E 0 Voltage between the electrolyte and the nickel at equilibrium (V) F Faraday constant (96500) (C mol -1 ) J i Diffusion flux of the i-th species (mol m -2 s -1 ) K E1 Equilibrium constant of steam methane reforming reaction (Pa 2 ) K E2 Equilibrium constant of water gas shift reaction (-) K B Equilibrium constant of Boudouard reaction (Pa -1 ) K C Equilibrium constant of Cracking reaction (Pa) M Molecular weight of the mixture of gases (kg kmol -1 ) P i Partial pressure of the i-th species (Pa) R Universal gas constant (8.314) (J mol -1 K -1 ) (S/V) eff Effective surface-to-volume ratio (m 2 m -3 ) T Temperature (K) a c Carbon activity (-) d pore Pore diameter (M) H Gas mixture enthalpy (J kg -1 ) h B Solid-phase enthalpy (J kg -1 ) iCurrent density (A m -2 ) [i] Molar concentration of the i-th species (kmol m -3 )

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“…External reforming requires additional fuel processing units for methane steam reforming and water gas shift (WGS) reactions, thus increasing the system's overall cost and complexity [29][30][31][32][33][34][35]. For comparison, direct internal reforming (DIR) eliminates the need of an external reformer as the high working temperature enables DIR reaction as well as WGS reaction for H 2 production [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52]. Thus the SOFC system can be simpler and compact.…”

Section: Introductionmentioning

confidence: 99%

Electrolytic effect in solid oxide fuel cells running on steam/methane mixture

2011

Journal of Power Sources

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a b s t r a c tA two-dimensional model is developed to study the performance of a planar solid oxide fuel cell (SOFC) running on steam/methane mixture. The model considers the heat/mass transfer, electrochemical reactions, direct internal reforming of methane (CH 4 ), and water gas shift reaction in an SOFC. It is found that at an operating potential of 0.8 V, the upstream and downstream of SOFC work in electrolysis and fuel cell modes, respectively. At the open-circuit voltage, the electricity generated by the downstream part of SOFC is completely consumed by the upstream through electrolysis, which is contrary to our common understanding that electrochemical reactions cease under the open-circuit conditions. In order to inhibit the electrolytic effect, the SOFC can be operated at a lower potential or use partially pre-reformed CH 4 as the fuel. Increasing the inlet gas velocity from 0.5 m s −1 to 5.0 m s −1 does not reduce the electrolytic effect but decreases the SOFC performance.

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Direct methane solid oxide fuel cell working by gradual internal steam reforming: Analysis of operation

Cited by 68 publications

References 15 publications

SOFC Long Term Operation in Pure Methane by Gradual Internal Reforming

SOFC Long Term Operation in Pure Methane by Gradual Internal Reforming

SOFC fuelled by methane without coking: optimization of electrochemical performance

Electrolytic effect in solid oxide fuel cells running on steam/methane mixture

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