Modeling of a SOFC Fueled by Methane:Anode Barrier to Allow Gradual Internal Reforming Without Coking

Abstract

International audienceNatural gas appears to be a highly attractive fuel for solid oxide fuel cell systems. To avoid the cooling effect occurring in direct internal reforming, 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 from hydrogen oxidation on the anode side. Previous studies have demonstrated that the cooling effect has disappeared. However, with GIR, the risk of carbon formation is greater. To deal with this issue, a different cell configuration was studied. This configuration combines a catalyst layer with a cermet anode, allowing GIR without coking. The study comprised simulations, using the CFD Research Corporation software package, of the behavior of a tubular solid oxide fuel cell when using GIR. A thermodynamic study based on the partial pressure distributions within the cell was also carried out to investigate the occurrence of carbon formation. A parametric analysis of the reforming rate and the thickness of the layer were then performed. The simulations indicate that the risk of carbon deposition is strongly reduced if the configuration is used for a catalyst layer of 900 µm and at a reforming rate in the catalyst only ten times higher than the reforming rate in nickel

SOFC Long Term Operation in Pure Methane by Gradual Internal Reforming

“…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).…”

“…This optimal thickness was evaluated from simulation studies (8)(9). The cell, 19 mm in diameter with an electrochemically active surface given by the cathode surface of 0.79 cm 2 , was inserted in a 3 atmospheres setup using an alumina ring.…”

Effect of Ethane and Propane in Simulated Natural Gas on the Operation of Ni–YSZ Anode Supported Solid Oxide Fuel Cells

“…On the other hand, there have been a number of cases where stable, coke-free operation has been reported for Ni-cermet anodes with novel microstructures [12][13][14]. One strategy that has been successfully employed to prevent coking with Ni-cermet anodes involves utilising an anode diffusion barrier, a porous layer of a non-coking material placed between the anode and fuel flow channel [15][16][17][18]. The barrier layer slows the entry of methane into the anode and impedes the exit of reaction products (H 2 O and CO 2 ) such that, above a critical current density, a non-coking gas composition is maintained in the anode [5,6,15,19].…”

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

“…Such a configuration can be used in the case of a low electrical conductivity of the catalyst: as an example, the controlled partial oxidation of hydrocarbons has been recently modeled (Figure 12.10c) [59]. Another example concerns the decomposition of the global reaction in two independent steps: such an electrode design was developed for the partial oxidation of isooctane [60], or for the internal reforming of methane in SOFCs without water vapor excess [61,62] (Figure 12.10d). The methane is reformed on the porous catalyst, which is insensitive for methane cracking; the hydrogen produced diffuses through the catalyst layer and is oxidized on the Ni-YSZ anode, which also serves as the current collector.…”