(554f) Gas Holdup in Bubble Columns with and without Vibrating Internals

Bubble columns are extensively used in a wide variety of chemical, petrochemical and bio-chemical processes. In many applications, it is necessary to provide internals, such as heating/cooling tubes, partitions or particles in packed bed form for catalytic/non-catalytic reactions. Introduction of such obstacles in bubble column adds to the complexity of the hydrodynamic phenomena. Internals can be characterized by their volume fraction and surface area of contact with the fluid around. For a given volume fraction, surface area increases with decrease in diameter or thickness of the internals. There is a limit on thickness/diameter at which mechanical strength of the internal declines to such an extent it cannot hold itself. Further decrease can make the internal collapse unless supported otherwise. Such internals can vibrate and may offer advantages hitherto unforeseen.

Experimental observations on the effect of vibrating internals and non-vibrating internals on gas holdup in bubble columns are presented. Increase in volume fraction of internals increases the gas holdup, as compared to bubble column without internals. For a given volume fraction of the internals, gas holdup with vibrating internals is higher than that of non-vibrating internals. A simple conceptual model for gas holdup in bubble columns with and wihtout vibrating internals is developed. The model predicts the gas holdup with satisfactory accuracy for a wide range of experimental conditions. Model predictions are compared with the existing correlations and a good agreement is found.