The fluidised bed process (drying, granulation and coating) is an important procedure in pharmaceutical industry and the end point of product quality is strongly depended on the properly setting of operation parameters. However, due to the complex gas-solid two phases flow behavior in these processes and fast flow velocity, it is difficult to monitor and measure the process characteristics using conventional tools, such as pressure and optical fiber sensors. For a multi-phase flow process, a non-intrusive imaging methodology provides a useful tool for process monitoring and fault diagnosis. Compared with other process tomography techniques and considering non-conductive material in the pharmaceutical industry, ECT is the most suitable imaging technique for measuring fluidised bed multi-processes because it is fast (>100 frames per second) and can reconstruct a permittivity distribution as well as solid moisture content. The aim of this research is to investigate the behaviour of drying and granulation process in a fluidised bed by ECT with and without wurster tube, which can provide online monitoring and fault diagnosis and possibly provide a new approach to process control. To achieve such objective, an ECT sensor with 8 electrodes was used to monitor the fluidised bed process with different operation parameters. Key process parameters including cross-sectional area solid concentration, time averaged process raw capacitance signals, averaged solids concentration in the chamber, the effect of wurster tube on hydrodynamic behavior and the domain frequency spectrum distribution in the chamber were analyzed. Experiment results indicate that process moisture change can be addressed from the raw capacitance of adjacent electrode pair combined with calibration model. The results show that ECT technology can be used in pharmaceutical fluidised bed process and future work is given in the end of this paper.
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