A Packed Column Extractor consists of a vertical cylindrical vessel fitted with packing. The packings used in column extractor are similar to the ones used in distillation.
It is important that the packing be wetted preferentially by the continuous phase, thus ensuring that the drops of dispersed phase will not be severely coalesced within the packed volume.
Packed Column Extractors have better efficiency because of improved contacting and reduced backmixing. Light and heavy liquids, either one of which is dispersed in the form of droplets, pass counter-currently through the column.
At the top or bottom of the column, the dispersed phase coalesces at an interface layer.
Because the packing elements reduce the cross-sectional area for flow and decrease the velocity of the dispersed phase, the column diameter for a given rate will always be greater than for a spray column because the reduced flow capacity is less important than the improved mass transfer.