Patent ID: 8114255

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at least part of the reflux condenser system and at least part of the reboiler system; (ii) passing a reflux stream withdrawn from the second column through the heat exchanger; (iii) passing a reboil stream withdrawn from the first column through the heat exchanger in heat exchanging relationship with the reflux stream; and (f) recirculating the first permeate stream within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