Bubble characterization in a fluidized bed by means of optical probes

The objective of this paper is to show and discuss the applicability of optical probes to measure the bubble size and bubble rise velocity in fluidized beds. Therefore, a bubble linking algorithm based on regression techniques is proposed. The algorithm is demonstrated using optical probe signals measured in a lab-scale fluidized bed with Geldart A/B particles, at two probe heights and for four gas velocities. In a sensitivity study, it is shown that results from optical probe measurements are always dependent on the choice of an appropriate set of parameters and constraints in the bubble linking algorithm. Both an increased gas velocity and an elevated probe height lead to larger bubbles and a modified bubble size distribution. Due to slugging and wall effects, the bubble rise velocity does not show a clear trend.