Bubble size distributions with a shadowgraphic optical probe

The in-line image analysis of local bubble size distributions (BSD) in a bubble column with a diameter of 0.1 m and superficial gas velocities up to 2.1 cm/s is presented. The BSD is acquired via a telecentric shadowgraphic image analysis using a modified Optical Multimode Online Probe (OMOP). The column is operated in batch mode by using different alcohol/water mixtures aerated with compressed air, purged through a sintered glass plate (dp= 100-160 µm). At a total holdup up to 35%, the specific surface area is calculated out of the BSD by the optical method and compared to an empirical correlation.