Methods of removing contaminants from hydrocarbon stream by swing adsorption and related apparatus and systems

• US 9,034,079 B2
• Filed: 02/27/2012
• Issued: 05/19/2015
• Est. Priority Date: 03/01/2011
• Status: Active Grant

• Current Assignee: Exxonmobil Upstream Research Company (Exxon Mobil Corporation)
• Original Assignee: Exxonmobil Upstream Research Company (Exxon Mobil Corporation)
• Inventors: Deckman, Harry W., Johnson, Robert A., Kelley, Bruce T., Ravikovitch, Peter I., Anderson, Thomas N.
• Primary Examiner(s): LAWRENCE JR, FRANK M
• Application Number:
  US13/984,911
• Publication Number:
  US 20140033919A1
• Time in Patent Office: 1,177 Days
• Field of Search: 95/96, 95/98, 951/00, 951/03, 951/36, 951/39
• US Class Current: 95/96
• CPC Class Codes: B01D 2256/245 Methane
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 2257/502 Carbon monoxide
• CPC Class Codes: B01D 2259/40041 with more than three sub-steps
• CPC Class Codes: B01D 2259/40049 with more than three sub-steps
• CPC Class Codes: B01D 2259/4063 using seven beds
• CPC Class Codes: B01D 53/02 by adsorption, e.g. preparative gas chromatography solid sorbent compositions B01J20/00, preparation of inorganic compounds or elements C01
• CPC Class Codes: B01D 53/047 Pressure swing adsorption
• CPC Class Codes: B01D 53/0473 Rapid pressure swing adsorption
• CPC Class Codes: C10L 3/104 Carbon dioxide
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

A pressure swing adsorption process for removal of CO2 from natural gas streams through a combination of a selective adsorbent material containing an effective amount of a non-adsorbent filler, adsorbent contactor design, and adsorption cycle design. The removal of contaminants from gas streams, preferably natural gas streams, using rapid-cycle swing adsorption processes, such as rapid-cycle pressure swing adsorption (RC-PSA). Separations at high pressure with high product recovery and/or high product purity are provided through a combination of judicious choices of adsorbent material, gas-solid contactor, system configuration, and cycle designs. For example, cycle designs that include steps of purge and staged blow-down as well as the inclusion of a mesopore filler in the adsorbent material significantly improves product (e.g., methane) recovery. An RC-PSA product with less than 10 ppm H2S can be produced from a natural gas feed stream that contains less than 1 mole percent H2S.

Claims

1. A swing adsorption process for removing CO₂ from natural gas streams, which process comprising:

a) subjecting a natural gas stream comprising methane and CO₂ to an adsorption step by introducing it into the feed input end of an adsorbent bed comprised of an adsorbent material selective for adsorbing CO₂, which adsorbent bed having a feed input end and a product output end and which adsorbent bed is operated at a first pressure and at a first temperature wherein at least a portion of said CO₂ is adsorbed by the adsorbent bed and wherein a gaseous product rich in methane and depleted in CO₂ exits the product output end of said adsorbent bed, wherein said adsorbent material is porous and contains an effective amount of non-adsorbent mesopore filler material, and wherein the adsorption step is performed for a period of less than 10 seconds;

b) stopping the introduction of said natural gas stream to said adsorbent bed before breakthrough of said target species from the product output end of said adsorbent bed;

c) subjecting said adsorption bed to successive 1 to 10 equalization steps wherein the pressure of said bed is reduced by a predetermined amount with each successive step;

d) conducting a high pressure gaseous stream rich in CO₂ through said adsorbent bed to remove hydrocarbons from the bed;

e) subjecting the purged adsorbent bed to multiple successive blow-down steps wherein the pressure of the bed is reduced by a predetermined amount with each successive blow-down step;

f) subjecting said adsorption bed to successive 1 to 10 equalization steps wherein the pressure of said bed is increased by a predetermined amount with each successive step; and

g) repressurizing said adsorbent bed to feed pressure using feed.

2. A cyclical swing adsorption process for removing contaminants from a gaseous feed stream, the process comprising:

a) passing a gaseous feed stream at a feed pressure through an adsorbent bed for an adsorption time interval greater than 1 second and less than 60 seconds to separate one or more contaminants from the gaseous feed stream to form a product stream;

b) interrupting the flow of the gaseous feed stream;

c) performing a plurality of depressurization steps, wherein each depressurization step reduces the pressure within the adsorbent bed from a depressurization initial pressure to a depressurization final pressure;

d) passing a purge stream into the adsorbent bed to remove hydrocarbons from the adsorbent bed;

e) subjecting the purged adsorbent bed to one or more blow-down steps, wherein each blow-down step reduces the pressure within the adsorbent bed from a blow-down initial pressure to a blow-down final pressure;

f) performing a plurality of re-pressurization steps, wherein each re-pressurization step increases the pressure within the swing adsorption bed from re-pressurization initial pressure to a re-pressurization final pressure; and

g) repeating the steps a) to f) for at least one additional cycle.

3. The cyclical swing adsorption process of claim 2, wherein the feed stream is a hydrocarbon containing stream having >

1 volume percent hydrocarbons based on the total volume of the feed stream.

4. The cyclical swing adsorption process of claim 2, wherein the feed stream comprises hydrocarbons and CO₂, wherein the CO₂ is in the range of 1 to 80 mole % and the hydrocarbons are in the range of 20 to 99 mole %.

5. The cyclical swing adsorption process of claim 2, wherein the adsorbent bed comprises an adsorbent material contains a mesopore filler that reduces the non-sweepable void space between adsorbent particles to less than 30% by volume in pores with diameters greater than 20 angstroms and less than 1 micron.

6. The cyclical swing adsorption process of claim 2, wherein the adsorbent bed comprises an adsorbent material contains a mesopore filler that reduces the non-sweepable void space between adsorbent particles to less than 20% by volume in pores with diameters greater than 20 angstroms and less than 1 micron.

7. The cyclical swing adsorption process of claim 2, wherein the adsorbent bed comprises an adsorbent material contains a mesopore filler that reduces the non-sweepable void space between adsorbent particles to less than 10% by volume in pores with diameters greater than 20 angstroms and less than 1 micron.

8. The cyclical swing adsorption process of claim 2, wherein the adsorption bed comprises a first adsorbent material selective to CO₂ and a second adsorbent material selective to H₂S.

9. The cyclical swing adsorption process of claim 2, wherein the adsorption time interval is greater than 2 seconds and less than 50 seconds.

10. The cyclical swing adsorption process of claim 2, wherein the adsorption time interval is greater than 2 seconds and less than 10 seconds.

11. The cyclical swing adsorption process of claim 2, wherein the purge stream comprises less than 40 mole percent methane.

12. The cyclical swing adsorption process of claim 2, wherein the adsorbent bed comprises an adsorbent material having a ratio of single component diffusion coefficients of CO₂ and methane is greater than 10.

13. The cyclical swing adsorption process of claim 2, wherein the adsorbent bed comprises an adsorbent material having a ratio of single component diffusion coefficients of CO₂ and methane is greater than 100.

14. The cyclical swing adsorption process of claim 2, wherein the adsorbent bed comprises a structured contactor having a plurality of channels through the structured contactor.

15. The cyclical swing adsorption process of claim 2, wherein the feed pressure is greater than 350 psig.

16. The cyclical swing adsorption process of claim 2, wherein the feed pressure is greater than 500 psig.

17. The cyclical swing adsorption process of claim 2, wherein the process recovers greater than 90% of the desired product based on a ratio of the desired product in the product stream divided by the desired product in the gaseous feed stream.

18. The cyclical swing adsorption process of claim 2, wherein the process recovers greater than 95% of the desired product based on a ratio of the desired product in the product stream divided by the desired product in the gaseous feed stream.

19. The cyclical swing adsorption process of claim 2, wherein the process recovers greater than 97% of the desired product based on a ratio of the desired product in the product stream divided by the desired product in the gaseous feed stream.

20. The cyclical swing adsorption process of claim 2, wherein each of the depressurization steps comprising passing a portion of the feed stream in the adsorbent bed to an equalization tank and then during one of the re-pressurization steps passing at least a fraction of the portion to the adsorbent bed from the equalization tank.

21. The cyclical swing adsorption process of claim 2, further comprising passing a second purge through the adsorbent bed after the one or more blow-down steps and prior to the repeating the steps a-f.

22. The cyclical swing adsorption process of claim 2, wherein the gaseous feed stream comprising one or more contaminants above a contaminant threshold, wherein the one or more contaminants comprise one or more of 1 to 80 mole percent CO₂, less than 1 mole percent H₂S, and any combination thereof, and wherein the contaminant threshold comprises one or more of less than 10 parts per million H₂S;

less than 4 mole percent CO₂, and any combination thereof; and

the product stream has contaminants less than the contaminant threshold.

23. A cyclical pressure swing adsorption process for removing contaminant from a gaseous feed stream, the process comprising:

introducing a gaseous feed stream comprising a desired product and one or more contaminants above a contaminant threshold, wherein the one or more contaminants comprise one or more of 1 to 80 mole percent CO₂, less than 1 mole percent H₂S, and any combination thereof, and wherein the contaminant threshold comprises one or more of less than 10 parts per million H₂S;

less than 4 mole percent CO₂, and any combination thereof;

subjecting the gaseous feed stream to a pressure swing adsorption process within an adsorbent bed for an adsorption time interval greater than 1 second and less than 60 seconds to separate the one or more contaminants from the gaseous feed stream to form a product stream, wherein the pressure swing adsorption process recovers greater than 90% of the desired product based on a ratio of the desired product in the product stream divided by the desired product in the gaseous feed stream;

conducting away from the adsorbent bed a product stream having contaminants below the contaminant threshold.

24. The cyclical pressure swing adsorption process of claim 23, wherein the adsorbent bed comprises two or more adsorbent materials, wherein each adsorbent material is configured to target a different one of the one or more contaminants.

25. The cyclical pressure swing adsorption process of claim 23, wherein the swing adsorption process comprising the steps of:

a) passing a gaseous feed stream at a feed pressure through an adsorbent bed;

b) interrupting the flow of the gaseous feed stream;

c) performing a plurality of depressurization steps, wherein each depressurization step reduces the pressure within the absorbent bed from a depressurization initial pressure to a depressurization final pressure;

d) performing a plurality of re-pressurization steps, wherein each re-pressurization step increases the pressure within the absorbent bed from re-pressurization initial pressure to a re-pressurization final pressure; and

e) repeating the steps a) to d) for at least one additional cycle.

26. The cyclical pressure swing adsorption process of claim 25, wherein the swing adsorption process comprising the further steps between steps c) and d) of passing a purge stream into the adsorbent bed to purge the desired product along with one or more contaminants from the adsorbent bed.

27. The cyclical pressure swing adsorption process of claim 26, wherein the additional purge stream comprises greater than 80 vol. % CO₂ based on the total volume of the purge stream.

28. The cyclical pressure swing adsorption process of claim 26, wherein the additional purge stream comprises greater than 80 vol. % N₂ based on the total volume of the purge stream.

29. The cyclical pressure swing adsorption process of claim 24, wherein the swing adsorption process comprising the further steps between steps c) and d) of:

performing a plurality of blow-down steps to produce an exhaust stream, where each blow-down step reduces the pressure that the adsorbent bed is exposed to from the blow-down initial pressure to the blow-down final pressure; and

passing an additional purge stream into the adsorbent bed to purge the one or more contaminants.

30. The cyclical pressure swing adsorption process of claim 29, wherein the additional purge stream comprises greater than 80 vol. % desired product based on the total volume of the additional purge stream.

31. The cyclical pressure swing adsorption process of claim 29, wherein the additional purge stream comprises greater than 80 vol. % N₂ based on the total volume of the additional purge stream.

32. The cyclical pressure swing adsorption process of claim 29, wherein the performing the plurality of blow-down steps comprises flowing the exhaust stream in a first direction during one of the plurality of blow-down steps;

and flowing the exhaust stream in a second direction during another of the plurality of blow-down steps.

33. The cyclical pressure swing adsorption process of claim 29, wherein the performing the plurality of blow-down steps comprises flowing the exhaust stream in a first direction and a second direction during at least one of the plurality of blow-down steps.

34. The cyclical pressure swing adsorption process of claim 23, wherein the cycle of steps a) through d) is performed in a time interval less than about 20 seconds.

35. The cyclical pressure swing adsorption process of claim 23, wherein the pressure during the adsorption of the one or more contaminants is greater than 350 psig (2413 kPag).

36. The cyclical pressure swing adsorption process of claim 23, wherein the pressure during the adsorption of the one or more contaminants is greater than 500 psig (3447 kPag).

37. The cyclical pressure swing adsorption process of claim 23, wherein subjecting the gaseous feed stream to the pressure swing adsorption process is a single pass process.

38. The cyclical pressure swing adsorption process of claim 23, wherein subjecting the gaseous feed stream to the pressure swing adsorption process comprises recycling one or more the contaminants through the pressure swing adsorption vessel.

39. The cyclical pressure swing adsorption process of claim 23, wherein the pressure swing adsorption bed comprises two or more adsorbent materials, wherein each adsorbent material is configured to target a different one of the one or more contaminants.

40. The cyclical pressure swing adsorption process of claim 23, wherein the pressure prior to step d) for the cycle is in the range of 0.25 bar a and 10 bar a.

41. The cyclical pressure swing adsorption process of claim 23, wherein the adsorbent bed comprises an adsorbent material formed into a layer.

42. The cyclical swing adsorption process of claim 23, wherein the process recovers greater than 95% of the desired product based on a ratio of the desired product in the product stream divided by the desired product in the gaseous feed stream.

43. The cyclical swing adsorption process of claim 23 wherein the process recovers greater than 97% of the desired product based on a ratio of the desired product in the product stream divided by the desired product in the gaseous feed stream.

44. The cyclical swing adsorption process of claim 23, wherein the total cycle time for completing all of the steps in the cycle is less than 30 seconds.

45. The cyclical swing adsorption process of claim 23, wherein the total cycle time for completing all of the steps in the cycle is less than 15 seconds.

46. The cyclical swing adsorption process of claim 23, wherein contaminant threshold comprises less than 4 parts per million H₂S.

47. The cyclical swing adsorption process of claim 23, wherein contaminant threshold comprises less than 2 mole percent CO₂.

48. The cyclical swing adsorption process of claim 23, wherein the adsorbent bed comprises an adsorbent material having a ratio of single component diffusion coefficients of CO₂ and methane is greater than 10.

49. The cyclical swing adsorption process of claim 23, wherein the adsorbent bed comprises an adsorbent material having a ratio of single component diffusion coefficients of CO₂ and methane is greater than 100.

50. The cyclical swing adsorption process of claim 23, wherein the adsorbent bed comprises an adsorbent material contains a mesopore filler that reduces the non-sweepable void space between adsorbent particles to less than 30% by volume in pores with diameters greater than 20 angstroms and less than 1 micron.

51. The cyclical swing adsorption process of claim 23, wherein the adsorbent bed comprises an adsorbent material contains a mesopore filler that reduces the non-sweepable void space between adsorbent particles to less than 20% by volume in pores with diameters greater than 20 angstroms and less than 1 micron.

52. the cyclical swing adsorption process of claim 23, further comprising passing the stream from one or more of the blow-down steps and depressurization steps through an adsorbent bed of a second pressure swing adsorption process to remove hydrocarbons from the stream.

53. The cyclical swing adsorption process of claim 23, wherein the adsorbent bed comprises a structured contactor having a plurality of channels through the structured contactor.

54. The cyclical swing adsorption process of claim 25, wherein each of the depressurization steps comprising passing a portion of the feed stream in the adsorbent bed to an equalization tank and then during one of the re-pressurization steps passing at least a fraction of the portion to the adsorbent bed from the equalization tank.