Monitoring a lab-scale wurster type fluidized bed process by electrical capacitance tomography

In this research, two types of electrical capacitance tomography (ECT) sensors, i.e. 12-4-8 combined electrodes and 8-8 dual planes sensors, were designed and used to monitor the gas-solids flow inside a Wurster type fluidized bed. For the 12-4-8 combined electrodes sensor, the measurement was conducted synchronously both inside and outside of the tube, i.e. coating zone and annulus zone, to achieve a fully understand the gas-solids flow characteristics in the bed. For the dual planes ECT sensor, the flow through the two cross-section areas inside the Wurster tube was measured and solids velocity was calculated based on cross-correlation method. A series of test were carried out by varying the operational parameters including the gap between the Wurster tube and air distributor, fluidization air velocity and materials loading. Different flow regimes as well as the flow stability were evaluated based on the ECT measurement results. To evaluate the flow characteristics inside the bed, power spectra density (PSD) and standard deviation (SD) were applied to investigate the fluctuation characteristics in the coating and annulus zones. Experiment results indicate that ECT technology is a powerful tool to monitor the Wurster type fluidized bed process and analysis the gas-solids flow characteristics inside the bed.