IHOSR/extractive distillation for ethanol separation. [Distillation with intermediate heat pumps and sidestream return]

Journal Article · Thu Nov 01 04:00:00 EST 1984 · Chem. Eng. Prog.; (United States)

OSTI ID:5629565

Lynd, L R; Grethlein, H E

Separation of ethanol-water mixtures is difficult because: 1) fermentation-derived feeds are dilute (less than 10wt.% ethanol); 2) ethanol and water form a low-boiling azeotrope at approximately 95 wt.% ethanol; and 3) the internal reflux ratio is limited to relatively high values (approximately 0.86) by the tangential pinch at high ethanol concentrations. Work reviewed by Furter and Cook demonstrate that the vapor-liquid equilibrium (VLE) relationship can be altered by adding a variety of salts to eliminate both the azeotrope and the tangential pinch. However, extractive distillation with salt addition is not widely used for separating ethanol-water mixtures at present, partly because other methods can break the azeotrope. In addition elimination of the constraint of the internal reflux ratio by the tangential pinch offers little advantage when the ratio is constrained by the dilute character of the feed. This article discusses the technique which combines extractive distillation with an innovative approach to using heat pumps in distillation ''distillation with intermediate heat pumps and optimal sidestream return'' (IHOSR distillation). A particular embodiment of the IHOSR concept, described here, is useful for separating dilute feeds such as ethanol water mixtures. The combination of IHOSR distillation with extractive distillation appears to make it possible to take advantage of the relaxation of the tangential pinch accompanying salt addition while producing anhydrous ethanol. A system composed of a column with an IHOSR heat pump, an extractive distillation column, an evaporator, and a spray drier is proposed which includes extensive heat integration. Potential advantages of this system include the capability to produce anhydrous ethanol, and columns with fewer stages and smaller diameters than conventional systems for separating ethanol and water.

• Research Organization: Dartmouth College, Hanover, NH
• OSTI ID: 5629565
• Journal Information: Chem. Eng. Prog.; (United States), Journal Name: Chem. Eng. Prog.; (United States) Vol. 80:11; ISSN CEPRA
• Country of Publication: United States
• Language: English

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ALCOHOLS
AZEOTROPE
DISTILLATION
DISTILLATION EQUIPMENT
EQUIPMENT
ETHANOL
EVAPORATION
EXTRACTION
HEAT PUMPS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SEPARATION PROCESSES
TECHNOLOGY ASSESSMENT
WATER