Modeling of catalytic plate reactors for fuel processor seystems

Abstract

The mathematical model of a catalytic plate reactor (CPR) in which hydrogen is produced by two different reaction pairs, namely, exothermic methane total oxidation coupled with either ethanol steam reforming or ethane dehydrogenation (both of which are endothermic) is constructed and the steady state and dynamic behaviors are investigated. A two-dimensional heterogeneous model including conservation of momentum, mass and energy is used to describe reactor performance in steady-state operation as a function of various operational and dimensional parameters such as feed composition on different sides of the plate including water/hydrocarbon and oxygen/hydrocarbon ratios, plate material and wall thickness. Simulations using stoichiometric ratios of reactants and standard materials of construction result in small transverse and axial temperature gradients and realistic reactor performance in terms of reactant conversions for both reaction pairs. Parametric investigations conducted by variation of plate material and wall thickness lead to minor changes only in thermal patterns and indicate no significant effects on reactor performance. On the other hand, variations in operational parameters such as the water/hydrocarbon and oxygen/hydrocarbon ratios result in notable changes in the reactor output. In ethanol steam reforming, water-deficient feed in the reforming channel reduces ethanol conversion and hydrogen production dramatically. In both ethanol reforming and ethane dehydrogenation cases, reduction in the oxygen content of the oxidation channel causes the methane conversion values to be significantly lower, leading to lower heat production/consumption rates. The start-up behavior of the reactor is also analyzed via dynamic simulations, which show that in both reaction pairs, the temporal and spatial evolutions of transients converge to the steady state solution..