Three dimensional modeling of autothermal reforming of methane in a Pt-Ni washcoated micro-channel reactor

Abstract

Steady state behavior of hydrogen production from oxidative steam reforming of methane in a Pt-Ni bimetallic washcoated Al2O3 microchannel reactor was modeled and simulated three dimensionally by using CFD program. Internal channels of Al2O3 monolith reactor are covered with Pt and Ni in given metal loadings; in the simulations Pt and Ni clusters are considered randomly distributed according to ratio of 1/20 and 1/30. It is assumed that on Pt covered areas total oxidation of methane and on Ni covered areas steam reforming and water-gas shift reactions occur. Simulations are performed for cases with different steam to carbon and carbon to oxygen feeding ratios for 723-1023 K inlet temperature range by using FLUENT™. The system performance is evaluated on the basis of the obtained methane conversion, hydrogen yield and hydrogen to carbon monoxide selectivity ratio at the exit. An inlet temperature of 723 K was proven to be too low for efficient system performance. The results of the simulations reveal that methane conversion and hydrogen yield increases but H2/CO selectivity ratio decreases with the increase in inlet temperature, for all feed compositions. Thus, an optimum "feed composition-inlettemperature- catalyst composition" combination should be selected according to required hydrogen yield and H2/CO selectivity at the exit of the OSR system. Sizing of microchannel reactor has been done to provide hydrogen for 5 kWe PEM fuel cell for each case.