Chemical and Biomolecular Engineering, Department of


Date of this Version


Document Type



Patent Number: 4,492,637


Appl. No.: 554,947


To reduce the amount of high quality energy utilized in removing water from a dilute ethanol solution, a two-stage process is used. The first stage removes eighty-five percent of the water using a low temperature apparatus and process and the remainder of the energy is removed by any of the other conventional processes. In the first stage, anhydrous sodium sulfate is dissolved in a dilute aqueous solution of 10 weight percent alcohol at approximately thirty degrees centrigrade. The solution is cooled to approximately twenty degrees centrigrade, at which temperature decahydrate crystals of sodium sulfate precipitate from the solution are removed. The solution is increased to a value in excess of 45% of alcohol which requires removal of approximately 82 percent of the water in the form of crystals. The crystals are dried to the anhydrous state at substantially room temperature and reused.