3D CFD model of high temperature H2O/CO2 CO-electrolysis

A three-dimensional computational fluid dynamics (CFD) model has been created to model high-temperature coelectrolysis of steam and carbon dioxide in a planar solid oxide electrolyzer (SOE) using solid oxide fuel cell technology. A research program is under way at the Idaho National Laboratory (INL) to simultaneously address the research and scale-up issues associated with the implementation of planar solid-oxide electrolysis cell technology for syngas production from CO ₂ and steam. The CFD model represents a single cell as it would exist in an electrolysis stack. Details of the model geometry are specific to a stack that was fabricated by Ceramatec, Inc. and tested at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, anodeside gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean CFD model results are shown to compare favorably with results obtained from a one-dimensional co-electrolysis model and with experimental results obtained from an actual ten-cell stack tested at INL over a range of operating conditions.