(511b) Probabilistic Model for Correcting Directional Sensitivity of Optical Measurements

This work reports findings on the probabilistic model for correcting directional sensitivity of the optical probe technique commonly used in gas-liquid multiphase reactors. Optical signals are collected from the tapered end optical probe¹ in a lab scale gas-liquid stirred tank reactor at various directions under wide range of operating conditions. Based on the fact that the optical probe measurements are reliable when the bubble impaction angles are within 180 degrees,² contributions to the overall gas phase dispersions (holdups) from the bubbles traveling at two opposite directions, i.e., from left to right and right to left, are quantified. It is found that significant underestimations of gas holdup can be detected when the probe is not oriented properly. These results demonstrate optical probe technique’s ability to accurately measure true gas holdup in regions where the direction of major bubble movement has not been previously determined.

1. Xue J. Bubble Velocity, Size and Interfacial Area Measurements in Bubble Columns. Saint Louis: Department of Chemical Engineering, Washington University; 2004.

2. Bombač A, ?un I, Filipič B, ?umer M. Gas-filled cavity structures and local void fraction distribution in aerated stirred vessel. AIChE Journal. 1997;43(11):2921-2931.