Axial heat conduction and heat supply effects on methanol-steam reforming performance in micro-scale reformers

摘要

The methanol-steam reforming (MSR) performance in micro-scale tubular reformers made by various materials is numerically studied. The physical domain considered includes an inlet section for methanol-steam mixture supply, a reformer section packed with CuO/ZnO/Al_2O_3 catalyst particles and an outlet section for reformed gas collection. The heat transfer effect with three different heat supply mechanisms on the MSR performance is addressed. For heat supplies from the applied heat fluxes at the reformer outer wall surface and from internal heat generation in the reformer wall, it is found that the axial conduction plays an important role in both heat transfer characteristics and MSR performance. It is suggested that the reformer have a small axial conduction parameter for high MSR performance which can be achieved by designing the reformer with low wall thermal conductivity, thin wall thickness and a small reactants feed rate. It is also found that an excess heat supply can be obtained when the axial conduction parameter is small. This excess heat supply enhances the MSR performance compared with the infinitely-thin walled reformer. For the reformer with a constant wall outer surface temperature, the wall material effect on the MSR performance is insignificant due to uniformly distributed reformer wall temperature.