A One-Dimensional Equivalent Model to Evaluate Overall Reaction Rates in Catalytic Pellets

NÉSTOR JAVIER MARIANI; SERGIO DARÍO KEEGAN; OSVALDO MIGUEL MARTÍNEZ; GUILLERMO FERNANDO BARRETO

Chemical Engineering Research and Design

The Institution of Chemical Engineers

Lugar: Rugby, Inglaterra.; Año: 2003 vol. 81 p. 1033 - 1042

0263-8762

The problem of finding a one-dimensional (1D) model to approximate the behaviour of actual three dimensional (3D) catalyst pellets is undertaken. It is shown that the 1D model proposed by Burghardt and Kubaczka (1996), called here Generalized Cylinder (GC) model, is most suitable for this purpose, provided that its main parameter (the shape power s) is fitted to the behaviour of the actual pellet at low reaction rates. Calculations from the GC model are expected to be precise at 1% for most geometrical cases of practical interest. The evaluation of s for a given pellet geometry involves the solution of a Poisson equation. An approximate method that greatly simplifies this task for finite cylinders of any cross-section shape is developed. The procedure assumes the knowledge of s just for the cross-section (at most, a 2D problem). This is readily available for some practical cases, but if not, a suitable numerical procedure based on the Boundary Element Method (BEM) is proposed. BEM is also suitable for the general 3D case.