Year: 2012
Type: dissertation
Abstract: This thesis, conducted in cooperation with AstraZeneca, presents a novel microwavebased measurement technique for 3D monitoring of fluidised bed processes in pharmaceutical industry.Fluidised beds can be used for spray-coating of particles, which is an important step in the manufacturing process for certain tablets.The process to be monitored is hosted by a closed metallic vessel, which is treated as a microwave cavity resonator.The resonance frequencies of this cavity are utilized to reconstruct the permittivity distribution inside it.The permittivity can, in a post-processing step, be related to other quantities of interest for process control, such as the density of particles and their moisture content.By using the electric and magnetic field solutions for the lowest eigenmodes, a set of parameters in a low-order description of the effective permittivity are determined from the measured resonance frequencies using a perturbation approach.A simplified experiment used to validate the basic principle of the measurement system is built and tested with promising results.Moreover, a real fluidised bed process equipped with microwave sensors is used to evaluate the performance of the measurement system under realistic process conditions.The presence of particles in the fountain region of the vessel is shown to be clearly detecteable, although more sophisticated measurements are required to be able to accurately determine the particle density and moisture content in the fountain.Temperature variations are shown to have significant impact on the measurements in the current experimental setup, but there are several ways to mitigate disturbances caused by varying temperatures in a refined version of the experiment.
Author: Johan Nohlert
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
Funders: AstraZeneca, Chalmers Tekniska Högskola
OpenAlex ID: W14185098