Pressure swing adsorption process operation and optimization

• US 6,605,136 B1
• Filed: 07/10/2002
• Issued: 08/12/2003
• Est. Priority Date: 07/10/2002
• Status: Expired due to Term

• Current Assignee: Inogen Incorporated
• Original Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Inventors: Labuda, Matthew James, Golden, Timothy Christopher, Whitley, Roger Dean, Weist, Edward Landis Jr., Chiang, Robert Ling, Graham, David Ross
• Primary Examiner(s): Spitzer, Robert H.
• Application Number:
  US10/192,360
• Time in Patent Office: 398 Days
• Field of Search: 95/96--98, 951/00--05, 951/30, 951/40
• US Class Current: 95/98
• CPC Class Codes: B01D 2253/102 Carbon
• CPC Class Codes: B01D 2253/104 Alumina
• CPC Class Codes: B01D 2253/108 Zeolites
• CPC Class Codes: B01D 2253/25 Coated, impregnated or composite adsorbents
• CPC Class Codes: B01D 2253/304 Linear dimensions, e.g. particle shape, diameter
• CPC Class Codes: B01D 2256/12 Oxygen
• CPC Class Codes: B01D 2256/16 Hydrogen
• CPC Class Codes: B01D 2257/102 Nitrogen
• CPC Class Codes: B01D 2257/502 Carbon monoxide
• CPC Class Codes: B01D 2257/80 Water
• CPC Class Codes: B01D 2259/40007 Controlling pressure or temperature swing adsorption
• CPC Class Codes: B01D 2259/40062 Four
• CPC Class Codes: B01D 2259/4146 Contiguous multilayered adsorbents
• CPC Class Codes: B01D 53/047 Pressure swing adsorption
• CPC Class Codes: B01D 53/261 by adsorption

Abstract

A pressure swing adsorption process which comprises introducing a feed gas mixture into an inlet of an adsorber vessel during a feed period, wherein the feed gas mixture contains a more strongly adsorbable component and a less strongly adsorbable component and the adsorber vessel contains a bed of adsorbent material which selectively adsorbs the more strongly adsorbable component, and withdrawing a product gas enriched in the less strongly adsorbable component from an outlet of the adsorber vessel during at least a portion of the feed period, wherein a dimensionless cycle-compensated mass transfer coefficient defined as K t_feedV_ads/V_feed is maintained in the range of about 23 to about 250.

Claims

1. A pressure swing adsorption process which comprises introducing a feed gas mixture into an inlet of an adsorber vessel during a feed period, wherein the feed gas mixture contains a more strongly adsorbable component and a less strongly adsorbable component and the adsorber vessel contains a bed of adsorbent material which selectively adsorbs the more strongly adsorbable component, and withdrawing a product gas enriched in the less strongly adsorbable component from an outlet of the adsorber vessel during at least a portion of the feed period, wherein a dimensionless cycle-compensated mass transfer coefficient defined as K t_feedV_ads/V_feed is maintained in the range of about 23 to about 250, where K is the linear driving force mass transfer coefficient for diffusion of the more strongly adsorbable component in the adsorbent closest to a product end of the bed of adsorbent material, t_feed is the duration of the feed period, V_ads is the empty volume of a section of the adsorber vessel which contains the bed of adsorbent material, and V_feed is the volume of the feed gas mixture introduced into the inlet of the adsorber vessel during the feed period, and wherein V_feed is defined as NRT/P_ads, where N is the number of moles of the feed gas mixture introduced into the inlet of the adsorber vessel during the feed period t_feed, R is the universal gas constant, T is the average absolute temperature of the feed gas mixture at the inlet of the adsorber vessel, and P_ads is the absolute pressure of the feed gas at the inlet of the adsorber vessel.

2. The process of claim 1 wherein the more strongly adsorbed component is nitrogen and the less strongly adsorbed component is oxygen.

3. The process of claim 2 wherein K t_feedV_ads/V_feed is maintained in the range of about 23 to about 100.

4. The process of claim 2 wherein the adsorbent material comprises one or more zeolites, with or without binder material, selected from the group consisting of CaA, NaX, CaX, BaX, LiX, NaLSX, CaLSX, BaLSX, and LiLSX zeolites.

5. The process of claim 1 wherein the more strongly adsorbed component is carbon monoxide and the less strongly adsorbed component is hydrogen.

6. The process of claim 5 wherein K t_feedV_ads/V_feed is maintained in the range of about 66 to about 250.

7. The process of claim 5 wherein the adsorbent material comprises one or more zeolites, with or without binder material, selected from the group consisting of CaA, NaX, CaX, BaX, LiX, NaLSX, CaLSX, BaLSX, and LiLSX zeolites.

8. The process of claim 1 wherein the duration of the feed period is in the range of about 7 to about 120 seconds and the adsorbent material comprises particles with an average particle diameter in the range of about 1.2 to about 1.6 mm.

9. The process of claim 1 wherein the duration of the feed period is in the range of about 3 to about 60 seconds and the adsorbent material comprises particles with an average particle diameter in the range of about 0.8 to about 1.2 mm.

10. The process of claim 1 wherein the duration of the feed period is in the range of about 0.25 to about 30 seconds and the adsorbent material comprises particles with an average particle diameter in the range of about 0.3 to about 0.8 mm.

11. The process of claim 1 which further comprises a purge period during which a purge gas is introduced into the adsorber vessel and passed through the bed of adsorbent material to desorb the more strongly adsorbed component, wherein the value of (Δ

P/P)_purge is maintained below about 0.3, where Δ

P is the pressure drop across the bed of adsorbent material at the end of the purge period and P is the minimum absolute pressure in the bed of adsorbent material at the end of the purge period.

12. The process of claim 1 wherein the bed of adsorbent material comprises two or more adsorbents.

13. A method of operating a pressure swing adsorption process which comprises:

(a) introducing a feed gas mixture at a feed gas flow rate into an inlet of an adsorber vessel during a feed period, t_feed, wherein the feed gas mixture comprises a more strongly adsorbable component and a less strongly adsorbable component and the adsorber vessel contains a bed of adsorbent material which selectively adsorbs the more strongly adsorbable component, and withdrawing a product gas enriched in the less strongly adsorbable component from an outlet of the adsorber vessel during at least a portion of the feed period;

(b) depressurizing the adsorber vessel by withdrawing a depressurization gas therefrom;

(c) purging the bed of adsorbent material during a purge period in which a purge gas is introduced at a purge gas flow rate into the adsorber vessel and passed through the bed of adsorbent material to desorb the more strongly adsorbed component; and

(d) repeating (a) through (c) in a cyclic manner;

wherein the operation of the pressure swing adsorption process is controlled by selecting a desired value of a dimensionless cycle-compensated mass transfer coefficient defined as K t_feedV_ads/V_feed and adjusting the feed gas flow rate, the duration of the feed period, or both the feed gas flow rate and the duration of the feed period to maintain the desired value of K t_feedV_ads/V_feed, where K is the linear driving force mass transfer coefficient for diffusion of the more strongly adsorbable component in the adsorbent closest to a product end of the bed of adsorbent material, t_feed is the duration of the feed period, V_ads is the empty volume of a section of the adsorber vessel which contains the bed of adsorbent material, and V_feed is the volume of the feed gas mixture introduced into the inlet of the adsorber vessel during the feed period, and wherein V_feed is defined as NRT/P_ads, where N is the number of moles of the feed gas mixture introduced into the inlet of the adsorber vessel during the feed period t_feed, R is the universal gas constant, T is the average absolute temperature of the feed gas mixture at the inlet of the adsorber vessel, and P_ads is the absolute pressure of the feed gas at the inlet of the adsorber vessel.

14. The method of claim 13 wherein the desired value of K t_feedV_ads/V_feed is in the range of about 23 to about 250.

15. The method of claim 14 wherein the more strongly adsorbed component is nitrogen and the less strongly adsorbed component is oxygen.

16. The method of claim 15 wherein the desired value of K t_feedV_ads/V_feed is in between about 23 and about 100.

17. The method of claim 15 wherein the adsorbent material comprises one or more zeolites, with or without binder material, selected from the group consisting of CaA, NaX, CaX, BaX, LiX, NaLSX, CaLSX, BaLSX, and LiLSX zeolites.

18. The method of claim 14 wherein the more strongly adsorbed component is carbon monoxide and the less strongly adsorbed component is hydrogen.

19. The method of claim 18 wherein the desired value of K t_feedV_ads/V_feed is between about 66 and about 250.

20. The method of claim 18 wherein the adsorbent material comprises one or more zeolites, with or without binder material, selected from the group consisting of CaA, NaX, CaX, BaX, LiX, NaLSX, CaLSX, BaLSX, and LiLSX zeolites.

21. The method of claim 13 wherein the purge gas flow rate is controlled such that (Δ

P/P)_purge is maintained below about 0.3, where Δ

P is the pressure drop across the bed of adsorbent material at the end of the purge period and P is the minimum absolute pressure in the bed of adsorbent material at the end of the purge period.

22. The method of claim 13 wherein the bed of adsorbent material comprises two or more adsorbents.