Online characterization of operational parameters in an SOFC system with anode‐exhaust gas recirculation by oxygen sensors

Abstract

In solid oxide fuel cell (SOFC) system with anode-exhaust gas recirculation (AEGR), a part of the depleted anode-exhaust gas is recirculated and mixed with fresh natural gas prior to entering the reformer, resulting in a high potential of direct current-efficiencies of up to 65%. However, for SOFC systems, it is of crucial importance to monitor relevant characteristic parameters and keep them within safe and durable operating limits. Such characteristic parameters are oxygen-tocarbon-ratio and fuel utilization, which must not exceed system-specific thresholds. Monitoring and control of these characteristic parameters is not trivial and a challenging task due to the enhanced system complexity. The authors present an approach and studies for determination and controlling characteristic parameters in an SOFC system with AEGR based on oxygen sensors. Therefore, the oxygen sensors, being a mature and easily available technology, are aimed to be in the fuel gas path at anode inlet and outlet of an SOFC-stack. Analytical correlations of the output value of oxygen sensors to characteristic parameters and simulative studies on the basis of a reference natural gas composition are shown.Additionally, first results of experimental studies of oxygen sensors in representative gas compositions for the anode inlet and outlet of an SOFC system with AEGR are presented.

Overview of the use of oxygen sensors in automotive applications

“…As a solution, the industry adopted TiO2-based sensors, which function more properly due to the fact that this sensor does not need a reference gas. The small dimension, low production cost, better durability, and high operation temperature [4,5].…”