Distillation process for the production of dehydrated ethanol

A distillation process for the production of dehydrated ethanol from a dilute aqueous solution of ethanol comprising:

• (a) providing a distillation system having a rectification column and a dehydration column;
• (b) feeding an impure dilute aqueous solution of ethanol to the rectification column, said dilute aqueous solution having been preheated by indirect heat exchange with the sump product withdrawn from said rectification column;
• (c) operating said rectification column at a sump pressure of 2-8 bars and producing an overhead vapor containing 75-95% by wt. of ethanol;
• (d) withdrawing from the rectification column a liquid stream enriched in impurities having a higher boiling point than ethanol from a point above the feed point of the dilute aqueous solution to the column;
• (e) subjecting said liquid stream enriched in impurities having a higher boiling point than ethanol to a phase seperation wherein a lower aqueous phase is returned to the rectification column at a point below the withdrawal point for the liquid stream enriched in impurities having a higher boiling point than ethanol and an upper organic phase is discarded, thereby removing the impurities boiling higher than ethanol introduced in said dilute aqueous solution of ethanol and accumulating in said rectification column;
• (f) withdrawing from a point above the point of withdrawal of said liquid stream enriched in impurities having higher boiling point than ethanol, and below the top of the rectification column, a vapor stream and feeding the same to the boiler of the dehydration column wherein the vapor stream is partially condensed,
• returning the non-condensed portion of the vapor stream to the rectification column at a point above the point of vapor stream withdrawal,
• returning at least a portion of the condensed vapor to the rectification column at the point of vapor stream withdrawal, and at least a portion of the condensed vapor to the upper portion of the dehydration column;
• (g) withdrawing from the top of the rectification column, a vapor stream enriched in ethanol and containing an entrainer and impurities having a lower boiling point than ethanol, totally condensing said vapor stream enriched in ethanol and withdrawing a portion of an organic phase so-produced while recycling the remaining condensed phase to the top of the rectification column;
• (h) withdrawing a vapor stream from the top of said dehydration column, totally condensing said vapor stream, admixing an entrainer selected from the group consisting of a gasoline fraction, cyclohexane, benzene and n-hexane with said condensed vapor stream,
• separating said admixture into an aqueous phase and an organic phase,
• withdrawing a portion of said aqueous phase in an amount to balance the water input and output of the dehydration column and
• feeding said portion of said aqueous phase to the rectification column at a point above the feed point of the dilute aqueous solution of ethanol and below the withdrawal point of the liquid stream enriched in impurities having a higher boiling point than ethanol, and returning the remaining admixture of entrainer and condensed vapor stream to the top of the dehydration column;
• and
• (i) operating said dehydration column at a head pressure of 0.5-2 bar and withdrawing a sump product from said dehydration column comprising ethanol containing less than 0.1% by wt. water, based on ethanol.