Applied Separations constructs unique counter-current extraction columns that use supercritical carbon dioxide to fractionate components contained in a liquid feed. Counter-current extraction using supercritical carbon dioxide is an alternative to conventional distillation and solvent extraction for purification of components of low volatility. This process offers the use of a “green solvent” with enhanced selectivity and mild operating conditions.

Counter-current separation achieves a multistage separation. This scheme reduces the amount of CO₂ consumed, increases product concentration and is operated continuously. Various components in the feed distribute between the CO₂ solvent (extract phase) and the liquid (raffinate phase) which counter currently flow through the separation column. This type of multistage separation is absolutely necessary for achieving a reasonable separation between two substances with a relatively low separation factor.