Hydrodynamic characteristics of bubbles in bubbling fluidized bed with internals

Abstract

The hydrodynamic characteristics of bubbles in bubbling fluidized beds with internals were investigated. The signal range of the optical fiber probe was calibrated from 0.5 V (the bubble phase) to 4.5 V (the emulsion phase). Data sampling involved an optical probe at a rate of 903 Hz for 725 s. To obtain improved bubble data, the data were analyzed by three processes: threshold determination, bubble analysis, and erroneous bubble elimination. The data on the bubble rise velocity and bubble frequency were measured and compared to the bed height (0.2-0.7 m), superficial gas velocity (4-7 U mf ), radial position r/R (0.22-0.95), number of distributor nozzles (2, 3, and 7), and the use of the internals with different hydraulic diameters of 0.19, 0.17, and 0.15 m. The experimental data were compared with several reported empirical correlations. Both the bubble rise velocity and bubble frequency increased with decreasing number of distributor nozzles. Furthermore, in the presence of internals, the bubble rise velocity decreased, whereas the bubble frequency increased with decreasing hydraulic diameter of the cross-sectional area divided by internals. Moreover, bubble breaking occurred at a specific position of r/R=0.7, not at the edge of the internals.