Measurement-based Optimization of a Polymerization Process


Emulsion polymerization is one of the most subtle of all polymerization processes. Despite its relative complexity, batch emulsion polymerization is the method of choice whenever specifications on conversion, particle size or molecular weight distribution are stringent.
A typical dynamic optimization problem for batch polymerizations reactions is to minimize batch time with respect to path and terminal constraints. Path constraints are typically bounds on temperature or heat generation and terminal constraints involve both quality and quantity specifications, i.e. conversion and average molecular weight have to be higher than a specified value at final time. To minimize the batch time while not violating the constraints, reactor temperature is the most approriate manipulated variable as it strongly influences the molecular weight distribution, conversion and rate of reaction. Moreover, initiator concentration can be used as an extra manipulated variable, especially towards the end of the reaction if the constraint on the conversion is stringent.
The optimal temperature profile consists of initially being at the maximum temperature and then coming down to a value that exhibits a compromise between molecular weight and conversion. So, the temperature profile can be parameterized using two parameters, the switching time and the compromise temperature value. Using measurements on the final conversion and molecular weight, these two input parameters are iteratively adapted towards optimality.
The above mentioned methodology is studied with several emulsion polymerization reactions, that include copolymerization of styrene/alpha-methylstyrene and the copolymerization of acrylamide with quaternary ammonium cationic monomers. The optimization considers the presence of constraints, of uncertainty regarding the kinetic parameters and of noisy meaurements.
This project is carried out in collaboration with Aqua+Tech.

Welz C., G. Francois , B. Srinivasan , D. Bonvin and D. Hunkeler. Trajectory Following for the Optimization of a Batch Polymerization Reactor. BatchPro Symposium Preprints, Poros, Greece, June 6-9, 153-159

Francois G., B. Srinivasan , D. Bonvin and D. Hunkeler. Optimisation basée sur les mesures d’un réacteur industriel de copolymérisation. 6ème Ecole de Printemps Francophone de Casablanca – Contrôle et Procédés de Polymérisation et de Cristallisation, Casablanca, Maroc, 17-19 Mai 2004

Francois G., B. Srinivasan , D. Bonvin and D. Hunkeler. Measurement-Based Optimization of an Emulsion Polymerization Process. Polymer Reaction Engineering: Modelling, Optimization and Control, Lyon, France (December 2003), 16-19

Francois G., B. Srinivasan and D. Bonvin. Run-to-run Optimization of Batch Emulsion Polymerization. IFAC World Congress 2002, Barcelona, Spain (July 2002), 1258-1263