Mass transfer analysis of microchannel steam reforming reactors with different segmented catalyst layer thicknesses

The dimensionless Sherwood number data are presented for illustrating the effect of segmented catalyst layer thickness on the mass transfer operation of microchannel steam reforming reactors. The microchannel reactor is configured for simultaneous oxidation and steam reformation of methanol. In each endothermic steam reforming channel, the catalyst layer is reduced by half in amount. The catalyst segments are uniformly positioned relative to each other. More specifically, the catalyst segments have a uniform distribution of length, and the spacing between catalyst segments is equal to their length. Accordingly, the catalyst segments are spaced apart from each other with a distance of one millimeter, and the catalyst segments are one millimeter in length. The extent of catalyst segmentation is balanced so as to reduce the likelihood of mechanical failure. Consequently, catalyst segmentation does not have a significant impact on the mechanical integrity. The dimensionless Sherwood number represents the ratio of the convective mass transfer to the rate of diffusive mass transport. Using dimensional analysis, the dimensionless Sherwood number can also be further defined as a function of the Reynolds and Schmidt numbers. Since Reynolds number and Schmidt number are both dimensionless numbers, the Sherwood number is also dimensionless. The channels are 0.7 millimeters in height and in width and 30.0 millimeters in length. The oxidation catalyst consists essentially of oxides of copper, zinc and aluminum. The reforming catalyst consists essentially of copper and oxides of zinc and aluminum. The exothermic and endothermic processes are conducted at a pressure of 0.8 megapascals, with a methanol-air equivalence ratio of 0.8 and a steam-to-methanol molar ratio of 1.17. The inlet temperature of the mixtures is 373 degrees Kelvin. The temperature of the reactor can be regulated by the balance of the flow rates so that the catalyst is not overheated by the exothermic process and thus damaged. The gas velocity is 2.0 meters per second at the reforming channel inlets and 0.6 meters per second at the oxidation channel inlets, thereby assuring sufficient heat in the reactor to carry out endothermic reforming of methanol. Heterogeneous reactions at a catalytically active surface affect the heat and mass balance at the surface. In addition, surface reactions create sources and sinks of chemical species on the surface and in the gas phase. The mass fluxes of gas-phase species at the phase boundaries are balanced by the production rates of gas-phase species by surface reactions. Contributor: Junjie Chen, E-mail address: [e-mail], ORCID: 0000-0002-5022-6863, Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China