Patent ID: 7871514
Filing Date: 2011-01-18
Classification: B01D,C10G

Abstract:
1. An extractive distillation process, whereby a polar hydrocarbon selective, water-soluble solvent is recovered from a solvent-rich stream containing the selective solvent, and measurable amounts of heavy hydrocarbons and sludge, which comprises the steps of: (a) introducing a feed containing a polar hydrocarbon and a less polar hydrocarbon into a middle portion of an extractive distillation column (EDC) and introducing a selective solvent feed stream into an upper portion of the EDC; (b) recovering a water-containing, less polar hydrocarbon-rich stream from the top of the EDC and withdrawing a first solvent-rich stream containing water-soluble solvent and polar hydrocarbon from the bottom of the EDC; (c) introducing the first solvent-rich stream into a middle portion of a solvent recovery column (SRC) and recovering a polar hydrocarbon-rich stream, that is substantially free of water-soluble solvent and less polar hydrocarbon, from the top of SRC, and removing a second solvent-rich stream from the bottom of the SRC; (d) introducing a greater portion of the second solvent-rich stream into the upper portion of the EDC in step (a) as the selective solvent feed stream and introducing a minor portion of the second solvent-rich stream into a heavy hydrocarbon removal zone; (e) separating a first water stream from the water-containing less polar hydrocarbon-rich stream that is recovered from the top of the EDC in step (b) and separating a second water stream from the polar hydrocarbon-rich stream that is recovered from the top of the SRC in step (c); (f) introducing at least a portion of the first stream of water and at least a portion of the second stream of water into the heavy hydrocarbon removal zone and recovering water-soluble solvent in an aqueous phase and rejecting heavy hydrocarbons into an oil phase; (g) withdrawing an accumulated oil phase containing the heavy hydrocarbons from the heavy hydrocarbon removal zone and recovering an aqueous phase containing the water-soluble solvent from the heavy hydrocarbon removal zone; (h) separating water from the water-containing less polar hydrocarbon-rich stream in step (b) to generate a less polar hydrocarbon-rich stream that is introduced into a solvent removal zone and introducing a portion of the first stream of water, or a portion of the second stream of water, or a portion of both the first and second streams of water from step (e) into a solvent removal zone thereby extracting entrained water-soluble solvent and rejecting the less polar hydrocarbons; (i) withdrawing an accumulated oil phase containing the less polar hydrocarbons from the solvent removal zone and recovering an aqueous phase containing water-soluble solvent from the solvent removal zone; (j) removing tramp iron and polymeric sludge from the aqueous phase from step (g) to yield a solids-free aqueous phase; and (k) introducing the aqueous phase from step (h) and the solids-free aqueous phase from step (j) into a steam generator and vaporizing water to form stripping steam which is introduced into the lower portion of the SRC in step (c).