On the Track to Understanding Three Phases in One Tower

Packed towers are widely used for distillation processes due to their higher separation efficiency and capacity in comparison to tray towers. The separation performance of the tower depends strongly on the liquid flow behaviour inside the packing, which becomes more complex with the appearance of a second liquid phase. This type of flow behaviour can be observed in the three-phase distillation process in packed and tray towers, whereas in packed towers two immiscible liquid phases flow down the packing co-currently and vapour phase flows in counter-current flow. For a better understanding of this process it is necessary to investigate the three-phase flow behaviour inside packed towers in detail. Therefore, a simplified setup of two immiscible liquids running down an inclined steel plate is applied for the first studies. Numerical investigations are carried out with CFD and are validated with own flow measurements of the liquid spreading, surface velocity and fluid thickness on the inclined plate. Additionally, the application of the validated CFD model to the more complex geometry of a packing segment is shown in this contribution.