Production of anydrous alcohol

Abstract

Substantially anhydrous (absolute) ethanol is economically distilled at high thermal efficiency from any dilute feedstock such as, for example, a fermentate ('beer') or the ethanol obtained from the hydration of ethylene in apparatus including a rectifying column for concentrating the ethanol, an anhydrous column for azeotropically distilling the ethanol and a decanter for separating the azeotrope-forming agent from the aqueous ethanol. Thermal values which would otherwise be lost in overhead vapors and/or stillage effluent are utilized for preheating the ethanol feed thereby leading to a significant improvement in overall thermal efficiency. Low boiling impurities, e.g., ethyl acetate, which may be present in the feed and which could interfere with proper operation of the decanter are removed from the feed to the extent necessary in a heads stripping column operated with heat supplied from the rectifying column. During the concentration procedure, the higher boiling impurities which may be present in the feed, e.g., fusel oil, are removed from the rectifying column as a liquid sidestream. Additional features providing still greater process efficiency include the operation of the anhydrous column under elevated pressure to permit the recovery of heat for running the rectifying column and the use of cyclohexane as the azeotrope-forming agent.