Three-phase Distillation in Packed Columns: Guidelines for Development, Design and Scale-up

INTRODUCTION Multi stage distillation processes are normally operated in columns, equipped with trays or packing to obtain counter current flow of vapour and liquid. In tray columns the liquid is moving from the inlet over the active area to the exit downcomer. The necessary mass transfer area between the phases is achieved by intense mixing of vapour and liquid on the bubbling area. In packed columns the flow of both phases is directed by the packing itself. Liquid is wetting the packing surface and flowing downwards counter currently to the ascending vapour. The necessary mass transfer area is provided by high packing surface area. In either case the substantial hydraulic characteristic of the different constructions is that the counter current flow of vapour and liquid is directed through the column internals. Internals such as dual flow commonly show instabilities in operation due to insufficient direction of the phases, especially when they are operated beyond the designed load point.