GAS-TREATING PROCESS AND SYSTEM

• US 3,594,983 A
• Filed: 06/17/1969
• Issued: 07/27/1971
• Est. Priority Date: 06/17/1969
• Status: Expired due to Term

• Current Assignee: James D. Yearout
• Original Assignee: James D. Yearout
• Inventors: Yearout, James D.
• Application Number:
  US04/834,011
• Time in Patent Office: 770 Days
• US Class Current: 95/97
• CPC Class Codes: B01D 2253/108 Zeolites
• CPC Class Codes: B01D 2253/308 Pore size
• CPC Class Codes: B01D 2256/245 Methane
• CPC Class Codes: B01D 2257/302 Sulfur oxides
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2257/7022 Aliphatic hydrocarbons
• CPC Class Codes: B01D 2257/80 Water
• CPC Class Codes: B01D 2259/40052 Recycled product or process gas
• CPC Class Codes: B01D 2259/40056 Gases other than recycled product or process gas
• CPC Class Codes: B01D 2259/4006 Less than four
• CPC Class Codes: B01D 2259/40081 Counter-current
• CPC Class Codes: B01D 2259/4009 using hot gas
• CPC Class Codes: B01D 2259/40098 with other heating means
• CPC Class Codes: B01D 2259/403 using three beds
• CPC Class Codes: B01D 53/047 Pressure swing adsorption
• CPC Class Codes: B01D 53/0476 Vacuum pressure swing adsorption
• CPC Class Codes: B01D 53/261 by adsorption
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

Removal of certain components from gas mixtures such as hydrocarbon mixtures, particularly the removal of carbon dioxide and small quantities of other gases such as water vapor and hydrogen sulfide, from natural gas for production of natural gas of improved heating value, by an adsorption process and system, including according to one embodiment, passing natural gas containing a minor amount of carbon dioxide, and small amounts of water vapor and hydrogen sulfide, through a synthetic zeolite or molecular sieve in three separate adsorption zones to remove the carbon dioxide, hydrogen sulfide and water vapor by adsorption in such zones, recovering a purified natural gas stream, and regenerating the adsorbent in the three adsorption zones by a combination of pressure swing regeneration and thermal swing regeneration, the pressure swing regeneration occurring in relatively short periods of time of the order of about one-half hour for two of the adsorbent zones, employing a pressurized purge gas such as nitrogen, or a vacuum, so that one of the two last mentioned zones is undergoing pressure desorption for removal of the adsorbed carbon dioxide, while the other of such two zones is on stream, such one-half hour on stream-one-half hour pressure regeneration cycles being carried out for a substantial period, and concurrently therewith, the third adsorption zone, which had been previously on stream and previously subjected to such pressure swing regeneration for desorption of carbon dioxide, is subjected to thermal desorption during the period of on stream-pressure desorption cycling of the two first mentioned zones, to thereby desorb the more strongly adsorbed water vapor and hydrogen sulfide components.

Claims

2. A process as defined in claim 1, wherein said gas mixture is an essentially hydrocarbon mixture.

3. A process as defined in claim 1, wherein said third adsorption zone following said thermal desorption, is placed on stream alternately with said first of said two first mentioned adsorption zones, and said third and said first adsorption zones alternately subjected to said pressure swing regeneration, and wherein said second of said two first mentioned adsorption zones is subjected to said thermal desorption.

4. A process as defined in claim 1, wherein said gas mixture is an alternately hydrocarbon mixture, and wherein said third adsorption zone following said thermal desorption, is placed on stream altenately with said first of said two first meNtioned adsorption zones, and said third and said first adsorption zones alternately subjected to said pressure swing regeneration, and wherein said second of said two first mentioned adsorption zones is subjected to said thermal desorption.

5. A process as defined in claim 4, including three adsorption zones, said adsorbent employed in each of said adsorption zones being a zeolitic molecular sieve adsorbent of a selected pore size for adsorbing said components of said hydrocarbon mixture desired to be adsorbed.

6. A process as defined in claim 5, wherein said pressure desorption during pressure swing regeneration in each of said two first mentioned adsorption zones is carried out by passage of a compressed purge gas alternately through each of said two first mentioned zones.

7. A process as defined in claim 5, wherein said thermal desorption in said third adsorption zone is carried out by heating said third adsorption zone.

8. A process as defined in claim 5, wherein said pressure desorption during pressure swing regeneration in each of said first mentioned adsorption zones is carried out by passage of a compressed purge gas alternately through each of said two first mentioned zones, or by subjecting each of said two first mentioned zones alternately to a vacuum, and wherein said thermal desorption in said third adsorption zone is carried out by heating said third adsorption zone.

9. A process as defined in claim 5, wherein said gas mixture contains a minor portion of carbon dioxide, water vapor and a small amount of hydrogen sulfide, said carbon dioxide, water vapor and hydrogen sulfide being adsorbed by said zeolitic molecular sieve adsorbent in each of said adsorption zones, said carbon dioxide being desorbed from said zeolitic adsorbent in said two first mentioned adsorption zones during the pressure swing regeneration cycles therein, and said water vapor and hydrogen sulfide being desorbed from said zeolitic adsorbent in said third adsorption zone during said thermal desorption in said third adsorption zone, said pressure swing regeneration cycles for desorption of carbon dioxide being relatively rapid, and said thermal regeneration for desorption of said water vapor and hydrogen sulfide being a substantially longer cycle than each of said pressure swing regeneration cycles.

10. A process as defined in claim 9, wherein said desorption of carbon dioxide from said zeolitic adsorbent in said two first mentioned adsorption zones is carried out by passage therethrough of a compressed purge gas selected from the group consisting of compressed dry nitrogen and natural gas, and said thermal regeneration in said third zone is carried out by indirect heating of the zeolitic adsorbent in said zone.

11. A process as defined in claim 10, wherein each of said two first mentioned adsorption zones is subjected to a plurality of on-stream and pressure desorption cycles, the first adsorption zone being on stream for about one-half hour while the second adsorption zone is subjected to pressure desorption for one-half hour, each for a total period of 16 hours, and said thermal regeneration in said third adsorption zone is carried out for a period of about 8 hours.

12. A process as defined in claim 5, wherein said pressure desorption during pressure swing regeneration in each of said two first mentioned adsorption zones is carried out by subjecting each of said two first mentioned zones alternately to a vacuum.

13. A process as defined in claim 5, wherein said thermal desorption in said third adsorption zone is carried out by passage of a hot gas through said third adsorption zone.

14. A process as defined in claim 5, wherein said pressure desorption during pressure swing regeneration in each of said first mentioned adsorption zones is carried out by subjecting each of said two first mentioned zones alternately to a vacuum, and wherein said thermal desorption in said third adsorption zone is carried out by passage of a hot gas through said tHird adsorption zone.

15. A process as defined in claim 9, wherein said desorption of carbon dioxide from said zeolitic adsorbent in said two first mentioned adsorption zones is carried out by subjecting said adsorbent to reduced pressure, and said thermal regeneration in said third zone is carried out by passage of a minor portion of heated effluent hydrocarbon mixture product essentially free of hydrogen sulfide and water vapor from said process, through said third adsorption zone.