FINITE-ELEMENT MODEL FOR A CATALYTIC MONOLITH REACTOR

The development of a comprehensive 2-D finite-element model for a single channel of a honeycomb type monolith catalytic reactor is described. This includes a description of the weak variational form of the heat and mole balance equations derived using the Galerkin method. A description of the complex nonlinear boundary conditions is given and various schemes are compared for dealing with the convection term, including the method of characteristics, the standard Galerkin method and the Petrov-Galerkin method. The best results were obtained using a standard quadratic discretization for both temperature and concentration. For the transient case, several time discretization schemes were tested. including implicit Gear and Euler methods, the Crank-Nicholson method, as well as a fourth-order Runga Kutta scheme. The Runga Kutta scheme gave the most stable solution. The effects of radiation, homogeneous reaction, heterogeneous reaction and solid-phase conduction are addressed. Radiation and conduction were found to affect the outlet temperature, with axial conduction being more significant.