Patent ID: 8129573

Claim:
A method for purifying an aqueous solution of fermentation alcohol to give anhydrous alcohol, comprising: (step 1) feeding an aqueous solution of fermentation alcohol to a mash column, distilling a distillate containing an alcohol/water mixed vapor by heating an aqueous solution of fermentation alcohol in the mash column, and feeding the distillate or a first condensate obtained by condensing the distillate into a distillation column; (step 2) distilling an alcohol/water mixed vapor from the distillation column by heating the distillate or the first condensate, refluxing a part of a second condensate obtained by condensing the mixed vapor to the distillation column, and feeding the remaining part of the second condensate to an evaporator; and then, (step 3) generating an alcohol/water mixed vapor by heating the second condensate in the evaporator, feeding the alcohol/water mixed vapor to a membrane separator, and selectively removing the water vapor from the alcohol/water mixed vapor, wherein the mash column is controlled in such a manner that an alcohol concentration of the alcohol/water mixed vapor distilled from the mash column in step 1 is less than 50% by weight, and a reflux amount of the condensate to the distillation column is controlled in such a manner that an alcohol concentration of the alcohol/water mixed vapor distilled from the distillation column in step 2 is 65 to 85% by weight.