Online monitoring of semi-continuous emulsion copolymerization: Comparing constrained extended Kalman filtering to feed-forward calorimetry

Abstract

Semi-continuous emulsion copolymerization (SCEP) is one of the major processes for the production of polymer latexes. For tailor-made copolymers, SCEP is employed because better control of polymer quality is possible compared to batch operation. To efficiently produce high quality polymers, recipe optimization and good feedback process control is required. For optimization or control purposes it is necessary to measure important product qualities such as the composition of the copolymer or the average chain length of the macromolecules. Measurements of these properties for this multi-phase process are expensive and usually not available online. State estimation and reaction calorimetry are possibilities to overcome this problem. Starting from a complex model for the considered process we develop a simplified model which enables us to estimate the concentrations of the monomers in the particle phase and thus the composition of the copolymer using a Constrained Extended Kalman Filter (CEKF). We compare this to earlier approaches based on simple feed-forward calorimetry and show that it is more robust to modelling errors and to the choice of initial value.