Investigation of wetting and drying process in a gas-solid fluidized bed by electrical capacitance tomography and pressure measurement

J. L. Zhang, M. X. Mao, J. M. Ye, H. G. Wang, Wuqiang Yang

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Top-spray configurations are widely used in pharmaceutical fluidized beds for particle coating and granulation. The process is complex due to the change of particle moisture as well as particle density. It is important to investigate the flow hydrodynamics in the process. In this paper, electrical capacitance tomography (ECT) combined with pressure transducers are used to investigate the flow hydrodynamics of gas-solids flow in a top-spray fluidized bed for wetting and drying. The flow characteristics investigated include bubble size, dominant frequency and standard deviation. Discrete wavelet transforms (DWT) and Fast Fourier Transform (FFT) are used to analyze the capacitance and pressure signals. The effects of key process parameters, including superficial velocity, particle size and spraying conduction on the flow hydrodynamics, are analyzed. The result indicates that both the material moisture and particle size influence the minimum fluidized velocity and bubble characteristics during the wetting and drying process. The result also indicates that the moisture content of particles and superficial fluidization velocity are two main factors, which determine the bubble characteristics in the top-spray process. The bubble size presents a complex trend, which is influenced by the spray pressure. The fluctuation frequency of bubbles presents a different trend in the wetting and drying stage.

    Original languageEnglish
    Pages (from-to)1148-1158
    Number of pages11
    JournalPowder Technology
    Volume301
    Early online date30 Jul 2016
    DOIs
    Publication statusPublished - 1 Nov 2016

    Keywords

    • Electrical capacitance tomography
    • Fluidized bed
    • Gas-solid flow
    • Top spraying

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