Experimental Investigation Of Pharmaceutical Fluidized Bed Processes By Electrical Capacitance Tomography

The pharmaceutical fluidized bed is a complex gas-solids two-phase flows system. The process efficiency and end-point product quality is strongly depended on several key particle parameters, i.e. particle moisture, particle concentration and particle velocity. It is important to provide and develop an online monitor tool to diagnose the above key parameters. Due to no-invasive and no-intrusive nature, electrical capacitance tomography (ECT) is applied to investigate the pharmaceutical fluidized bed process. In this paper, a pharmaceutical fluidized bed with laboratory scale was designed and ECT sensor was constructed in the fluidized bed to investigate the gas-particle flow characteristics.To address the particle moisture effect on the ECT measurement, firstly, dynamic calibrations were done in a fluidized bed drying process.24capacitance readings for certain electrode pairs were used for the particle moisture measurement. Virtual3D ECT images combined with power spectrum analysis were used to reveal the complicated particle flow behaviors in the drying process. Different inlet temperature and air velocities were implied to investigate the bubble characteristics including bubble coalescence in the conical chamber.For a Wurster fluidized bed process, a hybrid ECT sensor, i.e. internal-external electrodes ECT (IEE) sensors with/without internal screen were designed and compared using Ansoft-Maxwell(?) and MatLab(?). The IEE sensor with internal screen was chosen to measure the particle concentration in the annular region, an8electrodes ECT sensor was used to measure the particle behaviors in the coating region. Several processes with different operation parameters were monitored by the combined ECT sensors and key process parameters were recorded and analyzed. The radial particle concentration profiles in the annular and coating region with different operation parameters are given. The operating ranges of the Wurster fluidized bed process for different particles are given based on power spectrum analysis.The experimental results demonstrate that ECT sensors can be used to measure particle moisture and concentration successfully in a lab-scale pharmaceutical fluidized bed.