Separation of hydrogen-hydrocarbon gas mixtures using closed-loop gas expander refrigeration

• US 6,560,989 B1
• Filed: 06/07/2002
• Issued: 05/13/2003
• Est. Priority Date: 06/07/2002
• Status: Active Grant

• Current Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Original Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Inventors: McNeil, Brian Alfred, Ott, Christopher Michael, Harris, Christopher Francis, Longhurst, Daniel Lewis, Rowles, Howard Charles, Roberts, Mark Julian
• Primary Examiner(s): Esquivel, Denise L.
• Assistant Examiner(s): Drake, Malik N.
• Application Number:
  US10/165,654
• Time in Patent Office: 340 Days
• Field of Search: 626/17, 626/18, 626/23, 629/12, 629/32
• US Class Current: 62/623
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/70 Refluxing the column with a condensed part of the feed stream, i.e. fractionator top is stripped or self-rectified
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2210/12 Refinery or petrochemical off-gas
• CPC Class Codes: F25J 2235/60 the fluid being (a mixture of) hydrocarbons
• CPC Class Codes: F25J 2270/02 Internal refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/12 External refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/14 External refrigeration with work-producing gas expansion loop
• CPC Class Codes: F25J 2270/16 with mutliple gas expansion loops of the same refrigerant
• CPC Class Codes: F25J 2270/40 Quasi-closed internal or closed external air refrigeration cycle
• CPC Class Codes: F25J 2270/42 Quasi-closed internal or closed external nitrogen refrigeration cycle
• CPC Class Codes: F25J 2270/60 Closed external refrigeration cycle with single component refrigerant [SCR], e.g. C1-, C2- or C3-hydrocarbons
• CPC Class Codes: F25J 2270/66 Closed external refrigeration cycle with multi component refrigerant [MCR], e.g. mixture of hydrocarbons
• CPC Class Codes: F25J 3/0219 Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
• CPC Class Codes: F25J 3/0233 separation of CnHm with 1 carbon atom or more
• CPC Class Codes: F25J 3/0238 separation of CnHm with 2 carbon atoms or more
• CPC Class Codes: F25J 3/0242 separation of CnHm with 3 carbon atoms or more
• CPC Class Codes: F25J 3/0252 separation of hydrogen production of hydrogen containing gas in general C01B3/00, e.g. separation of hydrogen or hydrogen containing gases form gaseous mixtures at low temperatures C01B3/506
• CPC Class Codes: Y10S 62/912 External refrigeration system
• CPC Class Codes: Y10S 62/932 From natural gas

Abstract

A method for the recovery of hydrogen and one or more hydrocarbons having one or more carbon atoms from a feed gas containing hydrogen and the one or more hydrocarbons, which process comprises cooling and partially condensing the feed gas to provide a partially condensed feed; separating the partially condensed feed to provide a first liquid stream enriched in the one or more hydrocarbons and a first vapor stream enriched in hydrogen; further cooling and partially condensing the first vapor stream to provide an intermediate two-phase stream; and separating the intermediate two-phase stream to yield a further-enriched hydrogen stream and a hydrogen-depleted residual hydrocarbon stream. Some or all of the cooling is provided by indirect heat exchange with cold gas refrigerant generated in a closed-loop gas expander refrigeration cycle.

Claims

1. A method for the recovery of hydrogen and one or more hydrocarbons having one or more carbon atoms from a feed gas containing hydrogen and the one or more hydrocarbons, which process comprises:

(a) cooling and partially condensing the feed gas to provide a partially condensed feed;

(b) separating the partially condensed feed to provide a first liquid stream enriched in the one or more hydrocarbons and a first vapor stream enriched in hydrogen;

(c) further cooling and partially condensing the first vapor stream to provide an intermediate two-phase stream; and

(d) separating the intermediate two-phase stream to yield a further-enriched hydrogen stream and a hydrogen-depleted residual hydrocarbon stream;

wherein some or all of the cooling in (a), or in (c), or in (a) and (c) is provided by indirect heat exchange with cold gas refrigerant generated in a closed-loop gas expander refrigeration cycle.

2. The method of claim 1 wherein the cooling in (a) is effected in a first heat exchange zone and the further cooling in (c) is effected in a second heat exchange zone.

3. The method of claim 2 which further comprises introducing the first liquid stream into a stripping column, and withdrawing therefrom a liquid stream further enriched in the one or more hydrocarbons and a residual vapor stream comprising hydrogen and portions of the one or more hydrocarbons.

4. The method of claim 3 which further comprises reducing the pressure of the hydrogen-depleted residual hydrocarbon stream of (d) to yield a reduced-pressure residual hydrocarbon stream and warming the reduced-pressure residual hydrocarbon stream in the second heat exchange zone by indirect heat exchange with the first vapor stream enriched in hydrogen to provide a portion of the cooling in (c), thereby providing a warmed residual hydrocarbon stream.

5. The method of claim 4 which further comprises combining the residual vapor stream from the stripping column and the warmed residual hydrocarbon stream from the second heat exchange zone to provide a combined residual stream, and warming the combined residual stream by indirect heat exchange with the feed gas in the first heat exchange zone, thereby providing a portion of the cooling of the feed gas in (a).

6. The method of claim 2 wherein the cold gas refrigerant generated in the closed-loop gas expander refrigeration cycle provides cooling in the first and second heat exchange zones by the steps of

(1) compressing and cooling a refrigerant gas to provide a cooled compressed refrigerant gas and dividing the cooled compressed refrigerant gas into a first and a second cooled refrigerant gas stream;

(2) work expanding the first cooled refrigerant gas stream to provided a cooled work-expanded refrigerant gas stream;

(3) further cooling and reducing the pressure of the second cooled refrigerant gas stream to provide a cooled reduced-pressure refrigerant gas stream, wherein reducing the pressure is effected by either work expansion or Joule-Thomson expansion across a throttling valve;

(4) warming the cooled reduced-pressure refrigerant gas stream in the second heat exchange zone to provide at least a portion of the cooling of the first vapor stream in (c), thereby providing a warmed reduced-pressure refrigerant gas stream; and

(5) combining the cooled work-expanded refrigerant gas stream of (2) and the warmed reduced-pressure refrigerant gas stream of (4) to provide a combined reduced-pressure refrigerant gas stream and warming the combined reduced-pressure refrigerant gas stream in the first heat exchange zone to provide at least a portion of the cooling of the feed gas in (a), thereby warming the combined reduced-pressure refrigerant gas stream to provide the refrigerant gas of (1).

7. The method of claim 6 wherein the refrigerant gas is selected from the group consisting of nitrogen, methane, a mixture of nitrogen and methane, and air.

8. The method of claim 2 which further comprises warming the further-enriched hydrogen stream of (d) in the first and second heat exchange zones to provide by indirect heat exchange a portion of the cooling of the feed gas in (a) and a portion of the cooling of the first vapor stream in (c).

9. The method of claim 1 wherein the cooling in (a) and (c) is effected in a first heat exchange zone and wherein the method further comprises introducing the first liquid stream of (b) into a distillation column, and withdrawing therefrom a liquid stream enriched in hydrocarbons containing two or more carbon atoms and a residual vapor stream enriched in methane.

10. The method of claim 9 which further comprises introducing the intermediate two-phase stream of (c) into the distillation column.

11. The method of claim 9 which further comprises warming the residual vapor stream in the first heat exchange zone to provide by indirect heat exchange at least a portion of the cooling of the feed gas in (a).

12. The method of claim 9 which further comprises cooling and partially condensing the further-enriched hydrogen stream of (d) in a second heat exchange zone to provide an additional intermediate two-phase stream, and separating the additional intermediate two-phase stream to yield a hydrogen product stream and an additional hydrogen-depleted residual hydrocarbon stream.

13. The method of claim 12 which further comprises warming the hydrogen product stream in the first and second heat exchange zones to provide by indirect heat exchange a portion of the cooling of the feed gas in (a) and a portion of the cooling of the further-enriched hydrogen stream.

14. The method of claim 12 which further comprises reducing the pressure of the additional hydrogen-depleted residual hydrocarbon liquid stream to yield a reduced-pressure residual hydrocarbon liquid stream, warming the reduced-pressure residual hydrocarbon liquid stream in the second heat exchange zone to yield a two-phase residual hydrocarbon liquid stream, separating the two-phase residual hydrocarbon stream to yield a residual hydrocarbon vapor stream and an enriched hydrocarbon liquid stream, and introducing the enriched hydrocarbon liquid stream into the distillation column as reflux.

15. The method of claim 14 which further comprises warming the residual hydrocarbon vapor stream in the first heat exchange zone to provide a portion of the cooling of the feed gas in (a).

16. The method of claim 9 wherein a portion of the feed gas stream is cooled by indirect heat exchange with one or more hydrocarbon-rich liquid streams withdrawn from a lower part of the distillation column to provide a cooled feed stream and one or more vaporized hydrocarbon-rich streams, the one or more vaporized hydrocarbon-rich streams are returned to the distillation column to provide boil-up therein, and the cooled feed stream is combined with the partially condensed feed of (a).

17. The method of claim 12 wherein the cold gas refrigerant generated in the closed-loop work expander refrigeration cycle provides cooling in the first and second heat exchange zones by the steps of

(1) providing a compressed refrigerant gas, cooling the compressed refrigerant gas to provide a cooled compressed refrigerant gas, and dividing the cooled compressed refrigerant gas into a first and a second cooled refrigerant gas stream;

(2) work expanding the first cooled refrigerant gas stream to a first pressure to provided a cooled work-expanded refrigerant gas stream;

(3) further cooling and reducing the pressure of the second cooled refrigerant gas stream to a second pressure to provide a cooled reduced-pressure refrigerant gas stream, wherein reducing the pressure is effected by either work expansion or Joule-Thomson expansion across a throttling valve, and the second pressure is lower than the first pressure;

(4) warming the cooled reduced-pressure refrigerant gas stream in the second heat exchange zone to provide at least a portion of the cooling of the further-enriched hydrogen stream of (d), thereby providing a warmed reduced-pressure refrigerant gas stream;

(5) further warming the warmed reduced-pressure refrigerant gas stream in the first heat exchange zone to provide a portion of the cooling of the feed gas in (a), thereby providing a further-warmed reduced-pressure refrigerant gas;

(6) warming the cooled work-expanded refrigerant gas stream of (2) in the first heat exchange zone to provide at least a portion of the cooling of the feed gas in (a), thereby providing a warmed work-expanded refrigerant gas; and

(7) compressing the further-warmed reduced-pressure refrigerant gas of (5) and the warmed work-expanded refrigerant gas of (6) to provide the compressed refrigerant gas in (1).

18. The method of claim 17 wherein the refrigerant gas is selected from the group consisting of nitrogen, methane, a mixture of nitrogen and methane, and air.

19. The method of claim 1 wherein the cooling in (a) and (c) is effected in a first heat exchange zone and wherein the method further comprises introducing the first liquid stream of (b) into a stripping column and withdrawing therefrom a liquid stream enriched in hydrocarbons containing two or more carbon atoms and a residual vapor stream enriched in methane.

20. The method of claim 19 which further comprises cooling and partially condensing the further-enriched hydrogen stream of (d) in a second heat exchange zone to provide a two-phase stream and separating the two-phase stream to yield a hydrogen vapor product stream and an additional hydrocarbon-enriched liquid stream.

21. The method of claim 20 which further comprises reducing the pressure of the additional hydrocarbon-enriched liquid stream to yield a reduced-pressure hydrocarbon-enriched liquid stream, warming the reduced-pressure hydrocarbon-enriched liquid stream in the second heat exchange zone to provide an additional two-phase stream, separating the additional two-phase stream to provide a vapor stream containing hydrocarbons and residual hydrogen and a liquid stream further enriched in hydrocarbons, and introducing the liquid stream further enriched in hydrocarbons into the top of the stripping column.

22. The method of claim 21 which further comprises warming the vapor stream containing hydrocarbons and residual hydrogen in the first heat exchange zone to provide a portion of the cooling of the feed gas in (a).

23. The method of claim 20 which further comprises warming the hydrogen vapor product stream in the second heat exchange zone to provide by indirect heat exchange a portion of the cooling of the further-enriched hydrogen stream and further warming the hydrogen product stream in the first heat exchange zone to provide by indirect heat exchange a portion of the cooling of the feed gas in (a).

24. The method of claim 20 which further comprises warming the residual vapor stream in the first heat exchange zone to provide by indirect heat exchange a portion of the cooling of the feed gas in (a).

25. The method of claim 20 wherein a portion of the feed gas stream is cooled by indirect heat exchange with one or more hydrocarbon-rich liquid streams withdrawn from a lower part of the stripping column to provide a cooled feed stream and one or more vaporized hydrocarbon-rich streams, the one or more vaporized hydrocarbon-rich streams are returned to the stripping column to provide boil-up therein, and the cooled feed stream is combined with the partially condensed feed of (a).

26. The method of claim 20 wherein the cold gas refrigerant generated in the closed-loop gas expander refrigeration cycle provides cooling in the first and second heat exchange zones by the steps of

(1) providing a compressed refrigerant gas, dividing the compressed refrigerant gas into a first compressed refrigerant gas stream and a second compressed refrigerant gas stream, and work expanding the first compressed refrigerant gas stream to a first pressure to provided a first cooled work-expanded refrigerant gas stream;

(2) cooling the second compressed refrigerant gas stream in the first heat exchange zone to provide a cooled second compressed refrigerant gas stream;

(3) dividing the cooled second compressed refrigerant gas stream into a first portion and a second portion, work expanding the first portion to the first pressure to provide a second cooled work-expanded refrigerant gas stream, and further cooling the second portion in the first heat exchange zone to provide an intermediate cooled compressed refrigerant gas stream;

(4) warming the second cooled work-expanded refrigerant gas stream in the first heat exchange zone to provide a partially-warmed second work-expanded refrigerant gas stream and provide by indirect heat exchange a portion of the cooling of the feed stream in (a), and combining the partially-warmed second work-expanded refrigerant gas stream with the first cooled work-expanded refrigerant gas stream of (1) to provide a combined cooled work-expanded refrigerant gas stream;

(5) warming the combined cooled work-expanded refrigerant gas stream in the first heat exchange zone to provide by indirect heat exchange a portion of the cooling of the feed gas in (a), thereby providing a first warmed refrigerant gas stream;

(6) further cooling the intermediate cooled compressed refrigerant gas stream of (3) to provide a cold compressed refrigerant gas stream, reducing the pressure of the cold compressed refrigerant gas stream to a second pressure by either work expansion or Joule-Thomson expansion across a throttling valve, wherein the second pressure is lower than the first pressure, to provide a cold reduced-pressure refrigerant gas stream;

(7) warming the cold reduced-pressure refrigerant gas stream to provide by indirect heat exchange a portion of the cooling of the further-enriched hydrogen stream of (d) in the second heat exchange zone and a portion of the cooling of the feed gas of (a) in the first heat exchange zone, thereby providing a second warmed refrigerant gas stream; and

(8) compressing the first and second warmed refrigerant gas streams to provide the compressed refrigerant gas in (1).

27. The method of claim 26 wherein the refrigerant gas is selected from the group consisting of nitrogen, methane, a mixture of nitrogen and methane, and air.