Gradual internal reforming of methane: A demonstration

Georges, Samuel; Parrour, Gaëlle; Hénault, Marc; Fouletier, J.

doi:10.1016/j.ssi.2006.01.033

Cited by 34 publications

(19 citation statements)

References 4 publications

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“…Vernoux et al [14,15] have proposed a new concept -gradual internal reformingwhich is based on a local coupling of the steam reforming on the catalyst dispersed on the anode material and the electrochemical oxidation of the in situ-produced hydrogen (see Figure 12.7). This concept has been demonstrated both experimentally [16] and, more recently, in model form [17].…”

Section: Fuel Cell Modementioning

confidence: 92%

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High‐Temperature Applications of Solid Electrolytes: Fuel Cells, Pumping, and Conversion

Fouletier

Ghetta

2009

Solid State Electrochemistry I

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High-temperature, solid-state electrochemical reactors have numerous current and potential applications. In this chapter, we briefly review the various modes of operation of cells involving a solid electrolyte conducting by oxide ions or protons, either for energy generation or fine chemicals production. The specific requirements of the materials constituting the cell core are outlined, after which examples of current applications are briefly described. These include oxygen and hydrogen pumping, atmosphere control, intermediate-and high-temperature solid oxide fuel cells, and catalytic membrane reactors. IntroductionCeramic electrochemical reactors are currently undergoing intense investigation, the aim being not only to generate electricity but also to produce chemicals. Typically, ceramic dense membranes are either pure ionic (solid electrolyte; SE) conductors or mixed ionic-electronic conductors (MIECs). In this chapter we review the developments of cells that involve a dense solid electrolyte (oxide-ion or proton conductor), where the electrical transfer of matter requires an external circuitry. When a dense ceramic membrane exhibits a mixed ionic-electronic conduction, the driving force for mass transport is a differential partial pressure applied across the membrane (this point is not considered in this chapter, although relevant information is available in specific reviews).Solid-state electrochemical cells based on pure ionic conductors -which often are referred to as solid-electrolyte membrane reactors (SEMRs) -have numerous current or potential applications, including the production of high-purity oxygen by separating nitrogen and oxygen from the air; the control of oxygen in a gas or in a molten metal (oxygen pump or an oxygen getter, a form of oxygen-trapping device);

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Section: Fuel Cell Modementioning

confidence: 92%

“…16 Oxygen variation in the lead bath as a function of the quantity of electricity Q passing through the pump at 527 C.…”

mentioning

confidence: 99%

High‐Temperature Applications of Solid Electrolytes: Fuel Cells, Pumping, and Conversion

Fouletier

Ghetta

2009

Solid State Electrochemistry I

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“…In this method, the mole fraction of steam supplied to methane input to reformer is not sufficient to accelerate the steam reforming reaction. Therefore, the steam and heat provided from electrochemical reaction increase the electrochemical reaction rate gradually [13,14].…”

Section: Introductionmentioning

confidence: 99%

“…So, steam concentration is a predominant parameter in the reaction kinetics. Modeling of an electrolyte-supported tubular SOFC fueled by methane with DIR and GIR operations and using finite volume method was studied by Klein et al [18] to account the experimental results presented by Georges et al [14].…”

Section: Introductionmentioning

confidence: 99%

Study of thermal effects on the performance of micro-tubular solid-oxide fuel cells

Mirahmadi

Valefi

2011

Ionics

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Mathematical modeling of methane-fed anodesupported micro-tubular solid-oxide fuel cell (MT-SOFC) is developed. Steam reforming of methane is considered in two cases of: direct internal reforming (DIR) and gradual internal reforming (GIR). The polarization curves and temperature distribution of a cell fed with three variations of fueling (i.e., DIR and GIR of methane and pure hydrogen) are compared with each other. The simulation results are verified through temperature and performance measurements of a MT-SOFC sample operating on above three variations of fueling. In DIR operating condition, a drop in the anode gas temperature at a short distance after entering the cell takes place which results in high temperature gradient. In GIR operating condition, the temperature distribution in axial direction is steadier. The ohmic loss is lower in the case of pure hydrogen fuel than internal reforming of methane, but the concentration loss is lower in methane-fed operating conditions. Nomenclature A E v Reactive surface area per unit volume of electrode (m 2 m −3 ) c i Concentration of species: i (mol m −3 ) c O 2 Oxygen concentration (mol m −3 ) c H 2 Hydrogen concentration (mol m −3 ) c O 2 ;ref Oxygen reference concentration (mol m −3 ) c H 2 ;ref Hydrogen reference concentration (mol m −3 ) c p Total heat capacity (J kg −1 K −1 ) D eff Effective diffusion coefficient (m 2 s −1 ) E E Apparent activation energy for the electrode reaction (J mol −1 ) F Faraday's constant (96,487 Cmol −1 ) F amb Ambient view factor in radiative heat transfer G m Mutual irradiation arriving from other surfaces in the modeled geometry (W m −2 ) h i Enthalpy of species: i (J mol −1 ) I Cell average current density (A) I Unit 3×3 matrix J E i Electrode normal ionic current flow (A m −2 ) J E e Electrode normal electronic current flow (A m −2 ) J E 0 Electrode reference exchange current density (A m −2 ) J E 0;ref Reference temperature current density (A m −2 ) N D i Species diffusion vector (mol m −2 s −1 ) n CH 4 Molar flow rate of the input fuel (mol s −1 ) n air Molar flow rate of the input air (mol s −1 ) n species Normal flux of species (mol m −2 s −1 ) P Pressure (Pa) P species Partial pressure of species (Pa) Q Volumetric heat generation rate (J m −3 ) q Surface heat transfer (J m −3 ) R Universal gas constant (8.3143 Jmol −1 K −1 ) t E rl

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“…Indeed the steam used by the reforming reaction is produced by the electrochemical reaction all along the cell. This approach is based on the works of Vernoux et al [2], Georges et al [3] and Klein et al [4] who have studied the feasibility of GIR in SOFCs.…”

Section: Introductionmentioning

confidence: 99%

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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Gradual internal reforming of methane: A demonstration

Cited by 34 publications

References 4 publications

High‐Temperature Applications of Solid Electrolytes: Fuel Cells, Pumping, and Conversion

High‐Temperature Applications of Solid Electrolytes: Fuel Cells, Pumping, and Conversion

Study of thermal effects on the performance of micro-tubular solid-oxide fuel cells

SOFC fuelled by methane without coking: optimization of electrochemical performance

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