CIRCULATORY FLOW AND MIXING OF THE CONTIN UOUS-PHASE IN BUBBLE-COLUMNS

Bubbles columns are widely used as reactors and mass transfer equipmen t between gas and liquid or solid phases in many areas of the material s-transforming industry. The results known from theoretical and experi mental research on flow and mixing of the continuous liquid phase and the relative gas content in bubble columns having diameters up to 0.30 m are presented. Evidence is presented for stable circulatory flow. T he field of flow of the two phases is then described with the aid of m ass and momentum balance equations. These are solved simultaneously by an analytical and a numerical procedure. Non-linear flow instabilitie s in the form of several circulation cells are demonstrated as a resul t of the calculation. In the field of flow of circulation cells the lo cal gas content increases towards the centre of the cell. This is a se cond-order fluid-dynamic effect which has so far eluded description in two-phase flow using the numerical calculation techniques applied hit herto. The results provide the first possibility of calculating severa l circulation cells.Theoretical prediction of mixing the continuous ph ase and the transition from the homogeneous to the heterogeneous flow state in a semi-industrial scale bubble column has thus become possibl e.