Characterization and control of autothermal reformer for SOFC applications

Autothermal reforming (ATR) is a common technique for processing of hydrocarbon fuels in SOFC applications. Pre-reforming in SOFC applications is necessary in order to remove the hydrocarbons higher than methane, which may coke the SOFC anode. Another important aspect of the pre-reforming is to control the methane content in the reformate fuel feed. As the steam reforming reaction is endothermic, the temperature profile of the SOFC can be controlled with the methane content [2]. An effective control of the methane content reduces also the need of excess air at the cathode otherwise necessary for stack cooling. Other important control requirements in the operation of ATR include the steam-to-methane ratio, which has to be high enough in order to prevent coking of the anode, and the faradic equivalent current of the reformate fuel feed, which is needed to maintain the fuel utilization of the SOFC at a desired level. In this study, a natural gas fuelled ATR unit designed for a 5 kWe SOFC demonstration system is characterized and a method based on equilibrium calculations to estimate and control the faradic equivalent current, methane content and steam-to-methane ratio in the reformate gas is presented.