Compartmental Modeling of a Structured Heat Exchanger Reactor: Conversion and Temperature Profiles Predictions

Abstract

Since the last ten years numerous studies have been carried out to develop micro-reactors or micro-structured reactors in order to improve scale of production, economics, safety and environmental impact of chemical production. Consequently Alfa Laval Vicarb has developed a new structured heat exchanger reactor. The design of the reactor is based on high performances heat plate exchanger in which small inserts allow a good mixing of the reactants and to improve the heat transfer phenomena or to increase the heat transfer coefficient. This new technology of heat plate exchange reactors has a modular structure where the exchange zones have two possible configurations: co- and counter counter-current. The structure of the reactor is also flexible, that makes possible to have multiple reactants injections and different local temperature control points. In order to have a rapid prediction of conversion and temperature profiles, a mathematical model conserving the same notion of the structure of the reactor has been developed. This mathematical model is a simple compartmental model which presents advantages in terms of flexibility, possible online simulations and rapid prediction simulations. The structure of the model has been determined with the help of tracer experiment and computational fluid dynamics simulations. Heat and mass transfer equations are written considering each cell and using experimental heat transfer data then chemical kinetics from literature are introduced to the model. A sub-compartmental model has been developed in order to predict the micro-mixing phenomena. Four reactions for which the kinetic laws of reactions are well known have been selected to test the model: alkaline hydrolysis of ethyl acetate, alkaline hydrolysis of ethylene glycol diacetate, oxidation of sodium thiosulphate by hydrogen peroxide and Bourne reactions. The results of comparison between simulations and experimental data in terms of yield, selectivity, temperature profiles and micro-mixing characteristics are in reasonable agreement.