Jean-Léon Houzelot

Mass transfer in annular cylindrical reactors in laminar flow

Abstract Radial diffusional mass transfer is studied in a fluid flowing in fully developed laminar flow in an annular cylindrical reactor in which a first order heterogeneous reaction is taking place at the wall. The asymptotic behaviour of the concentration decrease far from the reactor inlet is especially investigated. Limiting values of Sherwood numbers are numerically determined and represented by semi-empirical expressions. Additivity relationships between homogeneous and heterogeneous contributions are established. Theoretical results are found in excellent agreement with those yielded by a new experimental method based on heterogeneous decomposition of ozone. Annular reactors exhibit a mass transfer efficiency which is noticeably higher than that of empty tubes. This efficiency may be characterized by three criteria related to inner space utilization, catalytic surface utilization and/or mechanical energy degradation.

Optimal operation of a semi-batch reactor by self-adaptive models for temperature and feed-rate profiles

A heuristic method was developed, which is both fast and efficient to identify stoichiometric and kinetic tendency models for reaction taking place in batch or semi-batch reactors. A general control strategy for simultaneous optimization of temperature and feed rate profiles together with usual control parameters was also developed. The method is fairly robust with respect to analytical inaccuracies as only convergence to optimal conditions is looked at. The method relying on both algorithms was found very performing by several validations issued from real life industrial problems. On these occasions the fast determination of the optimal operating conditions was especially appreciated

Sequential method for the determination of operating conditions for optimizing end-use properties of a terpolymer

An efficient method based on tendency modelling is presented to design operating conditions aiming at optimization of end-use properties of a terpolymer used as a viscosity index improver. In order to implement this strategy, a copolymerization model and relationships between the terpolymer structure and the properties are set up according to a sequential procedure. Six preliminary runs were required to start the process. Further runs were performed according to the predictions of an adaptive tendency model in order to minimize a performance index related to reaction time and end-use properties of the terpolymer. It was found that quasi-optimal conditions were reached after only four runs calculated according to this method.