MODELLING AND IDENTIFICATION OF A CATALYTIC PACKED BED REACTOR

This report describes an experimental investigation of the steady state and dynamic behavior of a wall-cooled catalytic packed bed tubular reactor. The reaction is the oxidation of methanol to formaldehyde over an industrial iron oxide - molybdenum oxide catalyst. The reactor is interfaced with a PDP-11/55 minicomputer for data acquisition and control. Experiments were performed over a range of feed and coolant temperatures of 220 - 260 C and over a range of methanol feed mole fraction of 0 - 0.05. Axial and radial temperature profiles were obtained from steady state and dynamic experiments and axial concentration profiles were obtained from steady state experiments.;A heterogeneous model and a pseudohomogeneous model are used to predict reactor performance both with and without reaction. The models are discretized into a set of ordinary differential equations by the method of othogonal collocation. Heat transfer parameters which were successful in matching data from experiments without reaction were not successful in matching temperature data from experiments with reaction. This made it necessary to decrease the fluid radial Peclet number to obtain good fit. Good fit was obtained for steady state composition profiles by optimizing selected frequency factors and the activation energy for methanol. A redox rate expression for the oxidation of formaldehyde to carbon monoxide was proposed since a simple first-order rate expression published in the literature did not fit the data. The pseudohomogeneous model gave results similar to the heterogeneous model for both steady state and dynamic experiments and has been recommended for future experimental state estimation and control studies.