Study of the Foaming Behaviour of a Bubble Column

The effect of different alcohols on gas hold-up and bubble size in a semi-batch bub-ble column has been investigated. Even little amounts of alcohols added to the liquid preserve the homogeneous bubble flow up to higher gas velocities and gas hold-ups (up to 50 %). For a detailed description it is necessary to divide the flow into two flow regimes - bubble flow and foam. This work presents results from comparative meas-urements with three different methods: needle probes, gamma-densitometry and high speed video observation. The obtained information was used to check the qual-ity of existing foam models. It was found that the vertical gas hold-up profiles in wet unstable alcoholic foams deviate from the theoretical predictions closely above the bubble flow region and again at the top of the foam layer. The first is caused by the effect of inertia hindering the drainage additionally to the viscosity effects, the sec-ond is a consequence of the progressing coalescence. There is a need to improve the existing models for the application in wet unstable foams.