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

Abstract

Natural 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 and at a reforming rate in the catalyst only ten times higher than the reforming rate in nickel.