Internal reforming

AbstractIn addition to its high conversion efficiency, the solid oxide fuel cell (SOFC) is very attractive from the fuel flexibility point of view. Natural gas has been regarded as the most suitable fuel for the SOFC. Methane, natural gas and hydrocarbons can be readily converted upon direct introduction by a reforming reaction on the Ni/yttria‐stabilized zirconia fuel electrode in the direct internal reforming operation. Internal reforming is attractive not only from the point of view of the simple system, but also the high efficiency due to combined generation with the endothermic reforming reaction. Carbon deposition is one of the damaging factors for the cell for direct internal reforming. The carbon deposition region is determined from thermodynamic equilibrium. Even in the calculated carbon free region, deposition was sometimes observed due to decomposition of hydrocarbon and rapid growth on the Ni catalyst. The selection of the oxide component as well as a metallic component in the cermet should be effective in achieving high performance in the electrode reaction and in avoiding carbon deposition. Stress analysis has been carried out for the internal reforming operation of planar cells. Internal reforming has been successfully carried out in 1 kW planar, several tens of kilowatt scale MOLB type and 10 kW tubular type modules.