A MATHEMATICAL MODEL FOR INTERNAL REFORMING AT COMPOSITE ANODES FOR SOLID OXIDE FUEL CELLS

摘要

The rate of methane reforming on Ni-YSZ cermet anodes under current load is calculated from a one-dimensional model, including non-linear kinetics, gas-phase diffusion and effects of particle connectivity. The overall rate of the reforming reaction is strongly dependent on anode thickness. However, the current-collector potential at a given current is approximately independent of thickness for thicknesses larger than 10 μm. The ratio between the rates of the reforming and the electrochemical reactions can therefore be controlled within certain limits by optimizing thickness, without significant loss in cell power. Cermet porosity, volume fraction of Ni and Ni-particle size were varied within the constraints set by the requirement of percolation in the gas-phase and the Ni- and YSZ-networks. These parameters appear to have a moderate effect in controlling the rate balance.