Distributed optical fiber sensors for thermal reaction and fouling monitoring in a continuous tubular emulsion polymerization reactor

Abstract

Distributed Optical Fiber Sensors (DOFS) are currently not part of the traditional chemical engineering toolkit. Rayleigh Optical Frequency Domain Reflectometry (OFDR) DOFS allow spatially resolved temperature measurement on a sub-centimeter scale and are therefore particularly interesting for applications during which hot- or cold spots and thermal gradients need to be considered. The implementation of DOFS in a laboratory-scale continuous tubular reactor setup (3 m length, 6 mm inner reactor diameter) is shown in the present text and hotspot monitoring is used for mathematical modelling of fouling deposition in the reactor during reaction. Calorimetric data of an exothermal reaction is calculated from DOFS data via heat flow measurement based on the placement of DOFS at different distances to the inner reactor space. The heat loss through the reactor wall can be calculated in this manner.

The reaction engineering problem that was chosen to be elucidated with DOFS technology was the emulsion copolymerization of vinyl acetate and vinyl neodecanoate. The reaction was carried out at a 24 w% monomer content using a redox initiator system consisting of tert-butyl hydroperoxide, ascorbic acid and ammonium iron(III) sulfate. As emulsifier and stabilizer polyvinyl alcohol was used (Mowiol 4-88®). This reaction has been studied by the research group of Dr. Pauer and the University of Hamburg, the group of Dr. Ing. W. Augustin at the Technical University of Braunschweig and by the group surrounding Prof. Dr. Asua from the Polymat in Basque country. It has been used as a model reaction for a fouling-heavy emulsion polymerization reaction and as a challenging choice for process intensification by synthesis in a continuous manner. Therefore, fouling information about this reaction is known and has been used as reference points for the findings based on the DOFS data.

The three publications created for the presented cumulative disstertation are the following: 1. M. Klippert, W. Pauer, Distributed optical fiber sensors for real-time tracking of fouling buildup for tubular continuous polymerization reactors, Chemical Engineering Research and Design 211, p. 168–178 (2024). doi: https://doi.org/10.1016/j.cherd.2024.10.007. Impact Factor (IF) at time of publication: 3.95. 2. M. Klippert, W. Pauer, Determination of the clogging time for continuous emulsion copolymerization in a tubular reactor using distributed optical fiber sensors, Chemical Engineering Research and Design 215, p. 465–475 (2024). doi: https://doi.org/10.1016/j.cherd.2025.02.012. IF at time of publication: 4.34. 3. M. Klippert, W. Pauer, Spatially resolved reaction calorimetry and fouling monitoring in a continuous tubular emulsion polymerization reactor, Industrial & Engineering Chemistry Research: Special Issue “Celebrating the legacy of Prof. José M. Asua: Emulsion Polymerization and Polymer Reaction Engineering”, 64 (41), p. 19817-19830 (2025). doi: https://doi.org/10.1021/acs.iecr.5c02548. IF at time of publication: 4.01.