Detailed Numerical Modeling of a Microchannel Reactor for Methane-Steam Reforming

Numerical modeling of methane-steam reforming is performed in a microchannel with heat input through Palladium-deposited channel walls corresponding to the experimental setup of Eilers [1]. The low-Mach number, variable density Navier-Stokes equations together with multicomponent reactions are solved using a parallel numerical framework. Methane-steam reforming is modeled by three reduced-order reactions occurring on the reactor walls. The surface reactions in the presence of Palladium catalyst are modeled as Neumann boundary conditions to the governing equations. Use of microchannels with deposited layer of Palladium catalyst gives rise to a non-uniform distribution of active reaction sites. The surface reaction rates, based on Arrhenius type model and obtained from literature on packed-bed reactors, are modified by a correction factor to account for these effects. The reaction-rate correction factor is obtained by making use of the experimental data for specific flow conditions. The modified reaction rates are then used to predict hydrogen production in a microchannel configuration at different flow rates and results are validated to show good agreement. It is found that the endothermic reactions occurring on the catalyst surface dominate the exothermic water-gas-shift reaction. It is also observed that the methane-to-steam conversion occurs rapidly in the first half of the mircochannel. A simple one-dimensional model solving steady state species mass fraction, energy, and overall conservation of mass equations is developed and verified against the full DNS study to show good agreement.