Numerical Modeling of Single-Chamber SOFCs with Hydrocarbon Fuels

Abstract

A two-dimensional numerical model of a single-chamber solid oxide fuel cell (SCFC) operating on hydrocarbon fuels is developed. The SCFC concept is a simplification of a conventional solid oxide fuel cell in which the anode and cathode are both exposed to the same premixed fuel-air mixture, and selective catalysts promote electrochemical oxidation of the fuel at the anode and simultaneous electrochemical oxygen reduction at the cathode. Optimization of SCFC stacks requires considering complex, coupled chemical and transport processes. The model accounts for the coupled effects of gas channel fluid flow, heat transfer, porous media transport, catalytic reforming-shifting chemistry, electrochemistry, and mixed ionic-electronic conductivity. It solves for the velocity, temperature, and species distributions in the gas, profiles of gaseous species and coverages of surface species within the porous electrodes, and the current density profile in an SCFC stack for a specified electrical bias. The model is general, and can be used to simulate any electrode processes for which kinetics are known or may be estimated. A detailed elementary mechanism is used to describe the reactions over the anode catalyst surface. Different design alternatives including yttria-stabilized zirconia vs Ce0.8Sm0.2O1.9 electrolytes, the effects of mixed conductivity, and the optimal fuel-to-air ratio are explored.

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