CFD Simulation of a Hydrogen-Permeable Membrane Reactor for CO_2 Reforming of CH_4: The Interplay of the Reaction and Hydrogen Permeation

摘要

A symmetric two-dimensional computational fluid dynamic model of a catalytic membrane reactor for dry reforming of methane is built up. A nondimensionalization method is employed and the governing equations are simplified. Crucial factors including the DamkOhler number (Da), the Peclet number (Pe), and the relative permeability number (Pm) are obtained. The reaction and hydrogen permeation phenomena in the membrane reactor are visualized and analyzed to reveal the interplay between them. Variation of Da and Pm shows that high hydrogen permeability combined with a moderate catalysis rate is beneficial to obtain a high methane conversion at the retentate side and a large hydrogen amount at the permeate side. The effect of the reverse water-gas shift reaction (RWGS) is also examined, and it turns out that the membrane with high hydrogen permeance could inhibit RWGS, thus declining the steam concentration at the outlet nearly by half (from similar to 0.6 to similar to 0.3 mol m(-3)). Besides, the effect of counter-current sweep gas and the inflow rate of reactants are investigated and it indicates that counter-current sweep gas configuration is more efficient, especially in the high inflow rate condition. This work also shows that the hydrogen permeation flux profile could be a crucial indicator for membrane reactor design.