Using wavelet analysis to characterize the transition from bubbling to turbulent fluidization

Turbulent fluidized bed (TFB) regime has demonstrated many advantages such as a combination of enhanced gas-solids contact and increased gas throughput, making it an optimal reactor in many industrial chemical and metallurgical processes. While the transition from bubbling to turbulent bed has been extensively investigated, some details still remain unclear such as the local transition velocity and the corresponding flow characteristics during the transition process. In this work, experiments were conducted in a conventional fluidized column with 0.267 m in diameter and 2.46 m in height and solids holdup was measured using an optical fiber probe in a superficial velocity range of 0.1–1.0 m/s. A discrete wavelet analysis method was proposed to extract quantitative information of bubbles/voids including the count and the lasting time. The local transition details and the onset velocity to the TFB regime in the fluidized bed were more clearly identified based on the extracted bubble/void information.