Numerical modeling of methane combustion on palladium catalyst for gas turbine applications

The development of lean-premixed catalytic reactors for ultra-low emission combustors in gas turbines has raised many design challenges and operability issues which can not be well addressed with convectional catalytic reactor models that rely on steady-state formulations with one-step chemistry mechanisms. These challenges and issues largely involve transient phenomena, which include light-off from low-temperatures, deactivation during intermediate temperature operation, and hysteresis in catalytic activity. To address these issues, both transient quasi-one- and two-dimensional catalytic channel reactor models and a multi-step surface chemistry mechanism of methane on supported palladium-based catalysts have been developed to explore such behaviors in catalytic combustors.; The surface chemistry submodel developed in this study has been partially validated through light-off experimental data. This surface chemistry mechanisms can capture the catalyst deactivation by water, and predict hysteresis loop of Pd ↔ PdO transformation and catalytic activity variation in methane oxidation upon heating and cooling.; The surface chemistry submodel has been incorporated for investigating lean catalytic combustion of methane on supported palladium-based catalysts. The current study has investigated the effects of combustor operating conditions, such as pressure, inlet temperature, and velocity and equivalence ratio on catalytic reactor ignition and intermediate temperature deactivation. The transient modeling reveals conditions wherein Pd-catalyst undergoes deactivation at intermediate temperature and further provides curves for catalyst ignition as a function of pressure and velocity and equivalence ratio. The model results are compared with some transient experimental measurements, and some implications for catalytic combustor design and operation in gas turbine applications are discussed.