NUMERICAL SIMULATION OF CATALYTIC PACKED BED REACTORS

Abstract

For the simulation of a packed bed catalytic reactor, it is necessary to establish the model that best represents the reactor behavior . In most cases, mathematical models that accurately describe industrial reactors cannot be solved analytically. Gas phase oxidation catalytic reactors with strong heat effects are no exception. For most gas phase oxidation reactors, the model's result is a set of nonlinear ordinary or partial differential equations. With the aid of a computer, a variety of numerical methods can be used to solve the model. In the present study two gas phase oxidation reactors are studied ; the reaction of sulphur dioxide to sulphur trioxide and o-xylene to phthalic anhydride. Mathematical models that describe various transport phenomena in a packed bed reactor were solved using a suitable numerical technique . Phenomena studied included heterogeneous effects, radial dispersion and axial dispersion. Criteria were taken from literature to estimate the importance of these phenomena a: priori. These criteria were compared with the results of the computer simulations. In most cases, the criteria accurately predict which phenomena are important to a particular reactor simulation. When the estimate from the criterion is borderline, computer simulations can be used to investigate the phenomenon's significance. Based on the comparative study of the criteria's predictions and the results of computer simulations a model sufficient to predict the conversion and hot spot temperature in the reactor, without incorporating undue complexities , been obtained for each reactor. Finally all the models have been combined and a simulation package developed which calculates the temperature and conversion profiles for the reactor and the model of the reactor chosen by the user.