Gamma ray tomography—An experimental analysis of fractional gas hold-up in bubble columns

Gas hold-up is one of the most important hydrodynamic parameters involved in the design, development, scale-up and troubleshooting of multiphase systems. Gamma ray tomography (GRT) is an extensively used non-destructive and non-invasive technique for the measurement of the gas hold-up profiles in multiphase system such as bubble columns and stirred vessels. The tomographic measurements can be subsequently used for the qualitative as well as quantitative estimation of the performance of multiphase system under given set of operating conditions. The non-destructive technique of grid scanning which forms the basis of GRT was used to analyze the performance of the laboratory scale bubble column as well as industrial scale sectionalized bubble column. The later had a total height of 8.5 m divided into 10 equal sections. The hydrodynamic performance obtained in the form of chordal gas hold-up was shown to be highly influenced as a result of the sparger design altercations. The non-performance of spargers due to the hole blockage was studied in a bubble column of 0.2 m diameter by analyzing the reconstructed gas hold-up profile at two different axial locations. An industrial sectionalized bubble column was also studied to obtain the desired information on the change in gas hold-up in the axial direction as a result of increased ε¯G due to intrinsic reaction kinetics giving rise to the formation of additional gas at every stage.