ECT Studies of Gas−Solid Fluidized Beds of Different Diameters

Abstract

The bed dynamic behavior in three gas−solid fluidized beds, 0.05, 0.1, and 0.3 m in diameters, is studied using the electrical capacitance tomography (ECT). The ECT employs the neural network multicriteria optimization image reconstruction technique. The time-averaged solids concentrations obtained by the ECT are generally in good agreement with those obtained by the optical fiber probe. The 0.1 m ID fluidized bed exhibits the spiral motion of rising bubbles in the bubbling regime. However, for the 0.3 m ID fluidized bed, more than one spiral motion of bubble swarms is observed in the bubbling regime. The small fluidized bed exhibits the round-nosed slug motion. The ECT studies reveal a radial symmetry of the time-averaged solids concentration distribution for the turbulent regime. Furthermore, the ECT provides the time-averaged and transient properties of the bubble/void phase and the emulsion phase. For a large fluidized bed, the standard deviations of the fluctuations of the cross-sectional averaged so...