Patent ID: 8128787

Claim:
A process for recovering an organic solvent from a solvent and water mixture, comprising: (a) subjecting at least a first portion of the mixture to a first distillation step, carried out by passing a first feed stream of the mixture, at a first pressure, into a first column having a first reboiler system, to produce a solvent-enriched, first overhead vapor stream and a first bottoms stream, wherein the first bottoms stream consists essentially of water; (b) condensing the first overhead vapor stream to form a condensed overhead stream; (c) pumping at least a portion of the condensed overhead stream to a second distillation step, carried out under a second pressure that is higher than the first pressure in a second column having a second reboiler system and a reflux condenser system, to produce a solvent-enriched, second overhead vapor stream and a second bottoms stream; (d) performing a membrane separation step, comprising: (i) providing a membrane having a feed side and a permeate side, the membrane being selective in favor of water over solvent; (ii) passing at least a portion of the second overhead vapor stream at a feed pressure across the feed side; (iii) maintaining a permeate pressure on the permeate side that is lower than the feed pressure; (iv) withdrawing from the feed side, as a residue stream, a dehydrated product stream; (v) withdrawing from the permeate side a permeate stream enriched in water compared with the second overhead vapor stream; (e) recovering heat by: (i) providing a heat exchanger that forms at least part of the first reboiler system; (ii) passing through the heat exchanger as a heating stream at least one stream selected from the group consisting of (I) the dehydrated product stream, (II) a reflux stream withdrawn from the second column, and (III) the second bottoms stream; (iii) passing a reboil stream withdrawn from the first column through the heat exchanger in heat exchanging relationship with the heating stream; and (f) recirculating the permeate stream within the process.