Molten carbonate fuel cell performance model update

A new porous electrode model, termed the heterogeneous film model, which is intended to be a reasonable depiction of ERC's ceramic coated Ni anodes and to serve as a first approximation to GE's and ANL's Ni/Cr anodes is described. In the model the electrode is pictured as a highly crosslinked three dimensional network of Ni or Ni/Cr filaments. The Ni or Ni/Cr is coated by a porous layer of ceramic or chromite. Most of the fine scale porosity of the electrode is found in the layer and most of the electrolyte resides in this layer which then forms a heterogeneous film on the Ni or Ni/Cr surface. The film coated Ni or Ni/Cr network is idealized as a random packing of short cylinders. The theoretical development of the model includes mathematical descriptions of ionic conduction, liquid phase diffusion through the heterogeneous film, and electrode kinetics on the Ni or Ni/Cr surface. The geometric parameters of the model are expressed in observable properties of the electrode. A mathematical analysis of the development of vertical concentration gradients in the gas flow channels is described. A general solution is presented and applied to the cathode and anode flow channels. Application to the anode requires modifications which is due to the occurrence of the water gas shift reaction on the channel hardware surfaces.