Investigation Of Flow Characteristics Of A Fluidized Bed By Pressure And Process Tomography Measurement

Fluidized beds have been widely used in industry for powder drying、 granulation and coating. It is difficult to measure the details information based on single-point measurement, i.e. pressure and temperature probes, due to the complex gas-solid two-phase flows characteristics. In this research, electrical capacitance tomography (ECT) combined pressure sensor was used to investigate the two-phase flow behavior inside the fluidized bed with and without Wurster tube. This new combined method has the advantages that they can provide both local and cross-sectional area information. Based on the proposed measurement strategy, the hydrodynamics of different structure of fluidized bed and top-spraying process have been investigated. Electrical capacitance tomography (ECT) and microwave tomography (MWT) was used in static experiments to investigate the influence of water content on different tomography method.In the top-spraying process, the minimum fluidization velocity of particles with different size and water content were investigated by pressure drop analysis. Different fluidization conditions were investigated by ECT and pressure method. The results indicate that there is a larger value of the minimum fluidization velocity for the bed material with large particle size and high water content. The results also indicate that the water content has strong effect on the bubble size and the bubble size varies in a wide range when the water content of particle changes from high to low value. In the top-spraying process, discrete wavelet transforms (DWT) analysis indicates that the ECT signal is more sensitive than pressure to the water content.Li the static measurement by ECT and MWT, the result illustrates that there is an obvious influence of water content of particle on ECT, especially when the high water content particle is taken as high reference. However, MWT is slightly affected by particle water content, which means MWT could be used with high water contents materials. The preliminary results indicate that there is a complementary space for ECT and MWT with different water content conditions.