(395f) CFD Studies of Shaped Steam Reforming Catalyst Particles
AIChE Annual Meeting
2010
2010 Annual Meeting
Catalysis and Reaction Engineering Division
Computational Fluid Dynamics in Chemical Reaction Engineering
Wednesday, November 10, 2010 - 10:15am to 10:36am
Interactions between reaction rates, conduction and diffusion inside catalyst particles can be complex, especially when influenced by non-uniform surface conditions produced by the flow field external to the particle, or by the highly-directional temperature field near a heated tube wall. These non-uniform fields can produce strongly locally-varying rates of reaction, heat transfer and carbon deposition, resulting in local deactivation of the catalyst, over-heating and tube failure. In this work a three-dimensional, realistic flow field is coupled to species and energy simulations in catalyst particles for the highly endothermic methane steam reforming reaction. The simulation domain was a 120-degree segment of a packed tube of tube-to-particle diameter ratio (N) = 4, packed with cylinders. The simulations employed computational fluid dynamics (CFD) and user-defined-codes, to examine packings of shaped particles, including multi-holed cylinders and cylinders with external features. The catalyst geometries modeled were full cylinder, 1-hole, 3-hole, 4-hole, 4-hole with vertical grooves, and 6-hole cylinders. The simulations were carried out under industrial conditions typical of reactor tube inlet and also of mid-reactor tube, at constant pressure drop for each case. The detailed pellet surface and intra-particle temperature, species and reaction rate distributions were obtained for the near-wall particle, along the particle radius and axis. It was concluded that the 4-hole with grooves and 6-hole catalyst particles offered the best temperature distribution and reaction rate. However, the 4-hole with grooves had a significantly larger void fraction, allowing a higher mass flow rate for a set pressure drop.