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It is essential to measure and monitor the particle flow characteristics in a Wurster fluidized bed to understand and optimize the coating processes. In this article, two electrical capacitance tomography (ECT) sensors are used to measure the particle concentration in different regions in a Wurster fluidized bed for the “cold” particle flows. One ECT sensor has a 12-4 internal-external electrodes and another has eight electrodes. The 12-4-electrode ECT sensor is used to measure the particle concentration in the annular fluidization region (outside of the Wurster tube) and the eight-electrode ECT sensor is used to measure the particle flow in the central region (inside the Wurster tube). The effect of particle type, particle moisture, fluidization velocity, and geometrical parameters on the Wurster fluidization process is studied based on the two ECT measurements. The radial particle concentration profiles in the annular fluidization and central flow regions with different operation parameters are given. Fast Fourier Transform analysis of the particle concentration in the Wurster tube is performed with different superficial air velocities. The optimum operating ranges of the Wurster fluidization process for different particles are given. In the end of the article, computational fluids dynamics simulation results are given and used to compare with the measurement results by ECT for a typical Wurster fluidized bed. © 2014 American Institute of Chemical Engineers AIChE J 60: 4051–4064, 2014

Fluidization conditions in a circulating-fluidized bed (CFB) can vary dramatically, from bubbling to circulating regimes. The granular Eurlerian models have been used to simulate the bubbling and slugging behavior of gas and solids in CFB. Considering the dielectric properties and rapid movement of solids in CFB, electrical capacitance tomography (ECT) is particularly suitable for measuring the concentration and distribution of solids in CFB to verify the simulation results. The simulation results by computational fluid dynamics (CFD) analysis and experimental results obtained by ECT are reported, and compares the simulation and experimental results first time, including the solids concentration profile, temporal variation of average-solids concentration, autocorrelation coefficient and frequency spectrum. © 2006 American Institute of Chemical Engineers AIChE J, 2006

It is important to investigate the behavior of circulating fluidized beds (CFB) for efficient coal combustion. Electrical capacitance tomography (ECT) was applied to the measurement of gas/solids distribution in square CFBs. An iterative method was used to achieve improved image reconstruction over the commonly used linear back-projection algorithm. The solids concentration profile, temporal variation of average solids concentration, and frequency spectra, which were obtained from the ECT data, are presented.

Mathematical modeling, computational fluid dynamics (CFD) analysis and electrical capacitance tomography (ECT) is used to develop an understanding of batch fluidized-bed drying, which is a complex air-solids, multiphase process. The mathematical model is based on a three-phase theory that describes the mass-and heat-transfer between the air and solids phases. The CFD model is based on a two-fluid model (TFM) approach, in which both phases are considered to be continuous and fully interpenetrating. The hydrodynamic parameters used to model the heat-and mass-transfer between the two phases are determined by a correlation approach, and the estimated parameters are incorporated into a user defined function (UDF) in FLUENT. The moisture diffusion in the air and solids phases is simulated using the user defined scalar (UDS) transport equation in the software package. ECT is used for the online solids concentration and moisture measurement, based on dynamic calibration. Comprehensive comparisons between results from mathematical modeling, CFD simulation and ECT measurement are presented, and are validated using experiment results. Online measurement of moisture content is compared with a static calibration. The mathematical model, CFD and ECT presented are being integrated into an online process control system for a batch fluidized-bed drying application in the pharmaceutical industry. © 2007 American Institute of Chemical Engineers AIChE J, 2008