Temperature swing adsorption

• US 5,846,295 A
• Filed: 03/07/1997
• Issued: 12/08/1998
• Est. Priority Date: 03/07/1997
• Status: Expired due to Term

• Current Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Original Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Inventors: Golden, Timothy Christopher, Allam, Rodney John, Kalbassi, Mohammed Ali
• Primary Examiner(s): SPITZER, ROBERT H
• Application Number:
  US08/812,564
• Time in Patent Office: 641 Days
• Field of Search: 95/104-106, 95/114, 95/115, 95/117-126, 95/139, 95/145
• US Class Current: 95/105
• CPC Class Codes: B01D 2253/104 Alumina
• CPC Class Codes: B01D 2253/108 Zeolites
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2257/702 Hydrocarbons
• CPC Class Codes: B01D 2257/80 Water
• CPC Class Codes: B01D 2259/40052 Recycled product or process gas
• CPC Class Codes: B01D 2259/402 using two beds
• CPC Class Codes: B01D 53/0407 Constructional details of adsorbing systems
• CPC Class Codes: B01D 53/0462 Temperature swing adsorption
• CPC Class Codes: F25J 2205/70 Heating the adsorption vessel
• CPC Class Codes: F25J 2230/04 Compressor cooling arrangement, e.g. inter- or after-stage cooling or condensate removal
• CPC Class Codes: F25J 3/04157 Afterstage cooling and so-called "pre-cooling" of the feed air upstream the air purification unit and main heat exchange line F25J3/04618 takes precedence
• CPC Class Codes: F25J 3/04169 by adsorption of the impurities adsorption in general B01D53/02
• CPC Class Codes: F25J 3/04181 Regenerating the adsorbents
• CPC Class Codes: F25J 3/04775 Air purification and pre-cooling
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

Temperature swing adsorption to remove CO₂ from a gas stream is conducted using alumina to adsorb all the water and at least most of the carbon dioxide from the gas stream. Optionally a downstream zone of zeolite may be provided to remove further carbon dioxide and hydrocarbons.

Claims

1. A process for the temperature swing adsorption of at least carbon dioxide and water from a feed gas to form a purified gas for subsequent cryogenic treatment, comprising contacting the feed gas at a first temperature with a solid adsorbent comprising agglomerates of activated alumina, impregnated with an adsorption enhancing impregnant of a basic solution having a pH of 9 or more, to adsorb all of said water and substantially all of said carbon dioxide so as to produce a dry, purified gas from which at least most of the carbon dioxide has been removed, and periodically regenerating the adsorbent by contacting the adsorbent with a regenerating gas at a second temperature in excess of said first temperature but below a calcining temperature of the impregnant to desorb said carbon dioxide and water from said adsorbent by said regenerating gas at said second temperature.

2. A process as claimed in claim 1, wherein the feed gas is air, natural gas or synthesis gas.

3. A process as claimed in claim 2, further comprising the subsequent cryogenic separation of said air.

4. A process as claimed in claim 1, wherein the pH of the impregnating solution is at least 10.

5. A process as claimed in claim 1, wherein the pH of the impregnating solution is from 10 to 12.

6. A process as claimed in claim 1, wherein the pH of the impregnating solution is about 11.

7. A process as claimed in claim 1, wherein the pH of the impregnating solution is related to the zero point charge of the alumina according to the formula:

space="preserve" listing-type="equation">pH≧

zpc-1.4

8. A process as claimed in claim 7, wherein the pH of the impregnating solution is related to the zero point charge of the alumina by the formula:

space="preserve" listing-type="equation">zpc+2≧

pH≧

zpc-1.4

9.

9. A process as claimed in claim 7, wherein the pH of the impregnating solution is related to the zero point charge of the alumina by the formula:

space="preserve" listing-type="equation">zpc+1≧

pH≧

zpc-1.

10. A process as claimed in claim 1, wherein said basic solution is a solution of an alkali metal or ammonium compound.

11. A process as claimed in claim 10, wherein said compound is selected from the group consisting of hydroxides, carbonates, bicarbonates, phosphates, and organic acid salts.

12. A process as claimed in claim 1, wherein the feed gas is supplied at a pressure of from 2 to 20 bara.

13. A process as claimed in claim 1, wherein the feed gas is supplied at a pressure of from 2 to 15 bara.

14. A process as claimed in claim 1, wherein the feed gas is supplied at a temperature of from 5°

to 50°

C.

15. A process as claimed in claim 1, wherein the feed gas is supplied at a temperature of from 10°

to 40°

C.

16. A process as claimed in claim 1, which is operated at a P/A ratio of from 0.1 to 0.8.

17. A process as claimed in claim 1, which is operated at a P/A ratio of from 0.2 to 0.5.

18. A process as claimed in claim 1, wherein feed gas is fed to the adsorbent for a period of from 60 to 600 minutes prior to regeneration of the adsorbent.

19. A process as claimed in claim 1, wherein feed gas is fed to the adsorbent for a period of from 70 to 300 minutes prior to regeneration of the adsorbent.

20. A process as claimed in claim 1, wherein the gas for regenerating the adsorbent is fed at a temperature of from 30°

to 150°

C. which exceeds the temperature of the feed gas supplied to the adsorbent by from 25°

to 110°

C.

21. A process as claimed in claim 1, wherein the regenerating gas is fed to the adsorbent at a pressure of from 0.5 to 8 bara.

22. A process as claimed in claim 1, wherein the regenerating gas is fed to the adsorbent at a pressure of from 1 to 3 bara.

23. A process as claimed in claim 1, wherein said adsorbent further includes a body of zeolite downstream (in the direction of feed gas flow) from the alumina adsorbent for adsorbing residual carbon dioxide and/or hydrocarbons.

24. A process as claimed in claim 23, wherein the zeolite adsorbent makes up from 5 to 30% v/v of the total adsorbent.

25. A process as claimed in claim 23, wherein at least 70 percent of the carbon dioxide is adsorbed in the alumina adsorbent.

26. A process as claimed in claim 23, wherein at least 80 percent of the carbon dioxide is adsorbed in the alumina adsorbent.