Patent ID: 8263815

Claim:
A process for recovering an organic solvent from a solvent/water mixture, comprising: (a) subjecting the mixture to a distillation step comprising a stripping step performed in a stripping section and a rectification step performed in a rectification section, to produce a rectified vapor stream, enriched in organic solvent compared with the mixture, and a bottoms stream; (b) compressing at least a portion of the rectified vapor stream to form a compressed overhead vapor stream; (c) 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 compressed 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 a first residue vapor stream enriched in solvent compared with the first compressed overhead vapor stream; (v) withdrawing from the first permeate side a first permeate stream enriched in water compared with the first compressed overhead vapor stream; (d) performing a second membrane separation step, comprising: (i) providing a second membrane having a second feed side and a second permeate side, the membrane being selective in favor of water over solvent; (ii) passing at least a portion of the first residue vapor stream at a second feed pressure across the second feed side; (iii) maintaining a second permeate pressure on the second permeate side that is lower than the second feed pressure; (iv) withdrawing from the second feed side a dehydrated solvent product; (v) withdrawing from the second permeate side a second permeate stream enriched in water compared with the first residue vapor stream; (e) recovering latent heat of condensation from the first permeate stream by returning the first permeate stream as a vapor to the stripping section.