In separating azeotropic mixtures, normal ditillation has separation limits. Conventional processes for separating such azeotropic mixture are two-pressure rectification and azeotropic distillation and extractive distillation.
Azeotropic mixtures are separated by a new separation process so called diffusion distillation. The use of an inert gas filter represents an alternative to the conventional methods of separating azeotropic mixture. An inert gas can be used to separate azeotropes by taking advantage of differences in relative rate of diffusion. Separation effect is not only based on relative volatility of components concerned but also on their diffusivity in the inert gas. Large molecule diffuses more slowly for large molecule has frequent collision with inert gas molecules. If ethanol-water mixture with azeotropic composition is evaporated, the water passes preferentially because of ethanol molecule larger than water molecule. In wetted-wall column consisting of two concentric tubes, separation effect was achieved. The advantages of diffusion distillation process are evident; No auxiliaries are necessary and there is no change of pressure in the system. Heat sensitive product can be distilled under mild conditions at low temperature.
Several experiments were carried out with a binary ethanol-water mixture, at several evaporation side temperatures, with different inert gas and annular width in the wetted-wall column.
