Continuous separator column - for mixed materials of different melting points

One end of the column is encased in a heating jacket and the other end in a cooling jacket. The higher m.pt. material being extracted from the hot end and the lower m.pt. material esp. crystalline from the cool end, the mixture inlet being intermediate. A pair of equal dia., pitch, thread depth and angular velocity counter rotating worms, with the same direction of lay, are closely fitted to the walls of the inner column and their threads overlap in plan view.