Process for purification of vent streams

Patent metadata

Field	Value
Publication number	US-2017335084-A1
Application number	US-201515535801-A
Country	US
Kind code	A1
Filing date	Nov 9, 2015
Priority date	Dec 18, 2014
Publication date	Nov 23, 2017
Grant date	—

Abstract

Disclosed herein is a system for recovering olefins from a vent stream comprising an absorber; and a stripper; where the absorber and the stripper are in a recycle loop; and where the absorber is operative to treat a vent stream with a solvent to remove more than 99 wt % of a halogenated by-product contained in the vent stream and to recover 90 to 95 wt % of olefin molecules present in the vent stream; and where the stripper is operative to remove more than 99 wt % of the halogenated by-products present in the solvent; and where the solvent is recycled to the absorber.

First claim

1 . A system for recovering olefins from a vent stream comprising:
an absorber; and a stripper; where the absorber and the stripper are in a recycle loop; and where the absorber is operative to treat a vent stream with a solvent to remove more than 99 wt % of a halogenated by-product contained in the vent stream and to recover 90 to 95 wt % of olefin molecules present in the vent stream; and where the stripper is operative to remove more than 99 wt % of the halogenated by-products present in the solvent; and where the solvent is recycled to the absorber.

2 . The system of claim 1 , further comprising a heat exchanger that lies downstream of the absorber and upstream of the stripper; where the heat exchanger is operative to transfer heat from a halogen concentrated stream discharged from the absorber to a solvent rich stream discharged from the stripper.

3 . The system of claim 1 , where the absorber functions at a lower pressure than a pressure in the vent stream.

4 . The system of claim 1 , further comprising a condenser and a reboiler, where the condenser and the reboiler are located downstream of the stripper and are operative to discharge a liquid stream and a gaseous stream respectively to an incinerator; where the liquid stream and the gaseous stream together contain a substantial portion of the halogenated by-products present in the vent stream.

5 . The system of claim 1 , where the system is operative to convert the vent stream comprising 90 to 95 wt % of olefin molecules, 5 to 7 wt % of alkanes and 1.0×10 −2 to 2×10 −2 wt % of the halogenated by-product, based on the total weight of the vent stream, to produce an olefin rich stream 214 that comprises 90 to 95 wt % of olefin molecules, 5 to 7 wt % of alkanes and 1.0×10 −4 to 2×10 −4 wt % of the halogenated by-product, based on a total weight of the olefin rich stream.

6 . The system of claim 1 , where the olefin molecule comprises ethylene and where the halogenated by-product is pentafluoro-benzene.

7 . The system of claim 1 , where the solvent comprises toluene, diesel, isoparaffinic solvents or a combination thereof.

8 . A method comprising:
charging a vent stream that comprises 90 to 95 wt % of olefin molecules, 5 to 7 wt % of alkanes and 1.0×10 −2 to 2×10 −2 wt % of a halogenated by-product, based on the total weight of the vent stream to an absorber; discharging from the absorber an olefin rich stream that comprises 90 to 95 wt % of olefin molecules, 5 to 7 wt % of alkanes and 1.0×10 −4 to 2×10 −4 wt % of the halogenated by-product, based on a total weight of the olefin rich stream; charging a stripper with a halogen concentrated stream received from the absorber; discharging from the stripper a solvent rich stream that is recycled to the absorber; and discharging from the stripper to an incinerator a waste stream that contains a substantial portion of the halogenated by-products present in the vent stream.

9 . The method of claim 8 , further comprising transferring heat from the halogen concentrated stream to the solvent rich stream.

10 . A composition comprising:
an olefin rich stream that comprises:
90 to 95 wt % of olefin molecules:
5 to 7 wt % of alkanes; and
1.0×10 −4 to 2×10 −4 wt % of the halogenated by-product, based on a total weight of the olefin rich stream.

11 . The composition of claim 10 , where the olefin molecules comprise ethylene and where the halogenated by-product is pentafluoro-benzene.

Assignees

• Dow Global Technologies Llc

Inventors

• Pendergast Jr John G
• Masey Johnny W
• Swindoll Robert D
• Liu Yujun

Classifications

• C07C7/11 Primary

  by absorption, i.e. purification or separation of gaseous hydrocarbons with the aid of liquids · CPC title

• B01D53/1425

  Regeneration of liquid absorbents · CPC title

• C08J11/02 Primary

  of solvents, plasticisers or unreacted monomers · CPC title

• B01D53/1487

  Removing organic compounds · CPC title

• B01D53/1493

  Selection of liquid materials for use as absorbents · CPC title