Co-electrolysis of steam and carbon dioxide using a high temperature electrolysis process can provide carbon monoxide and hydrogen, or syngas, that may be used as a feed stream to a Fischer Tropsch process to generate synthetic fuels. In order to evaluate the potential syngas-production performance of large-scale high-temperature co-electrolysis (HCE) operations, we have developed an engineering process model at INL using the commercial system-analysis code HYSYS. Using this code, several detailed process flow sheets have been defined that include all of the components that would be present in an actual HCE plant such as pumps, compressors, heat exchangers, turbines, and the electrolyzer. However, since the actual electrolyzer is not a standard HYSYS component, a custom one-dimensional co-electrolysis model was developed for incorporation into the overall process flow sheet. The one-dimensional model accounts for the chemical equilibrium of the components via the shift reaction and the electrolytic reduction of the system. The electrolyzer model also allows for the determination of the average Nernst potential, cell operating voltage, gas outlet temperatures, and electrolyzer efficiency for any specified inlet steam, hydrogen, carbon dioxide, and sweep-gas flow rates, current density, cell active area, and external heat loss or gain. A parametric study has been performed using the engineering process model to study the effects of various system configurations and operating conditions on the overall system performance for the production of syngas. This paper presents the results of this study.

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