X-ray computed tomography (XCT) study of jetting in a fluidized bed: Measurement method development and single component fluidization

Abstract

Air injected into a fluidized bed through a perforated plate distributor may form individual jets above the distributor plate, which can have a significant impact on the gas–solid flow and heat/mass transfer in the dense phase region. Therefore, it is important to study the jetting characteristics in a fluidized bed, but the measurement of such jets is extremely challenging because of the opaque dense phase region. In this paper, an X-ray computed tomography (XCT) measurement system was constructed, and three-dimensional reconstruction software based on the cone beam filtered back projection algorithm (FDK) was implemented. A jet recognition and quantification algorithm was also developed and tested. Based on these methods, the influence of the jet velocity (U_j) and bed material size (d_p) on the structure and shape of the jets was studied. The results show that when the jet velocity increases, the average jet length (L), jet maximum diameter (D), and jet volume (V) increase, while the average jet half angle (θ) fluctuates around a constant value. Under the same jet velocity (U_j), the average jet length (L), jet maximum diameter (D), and jet volume (V) are inversely proportional to the bed material size (d_p), while the average jet half angle (θ) is directly proportional to the bed material size (d_p). Finally, a correlation for jet length (L) in a fluidized bed is proposed. This study provides a new characterization method for jetting in a fluidized bed, and offers unique experimental data for CFD model validation in fluidized bed simulations.