SOUR GAS TREATMENT PROCESS

• US 20120240617A1
• Filed: 06/25/2010
• Published: 09/27/2012
• Est. Priority Date: 06/26/2009
• Status: Active Grant

• Current Assignee: Total SA (Cook Composites and Polymers)
• Original Assignee: Total SA (Cook Composites and Polymers)
• Inventors: Weiss, Claire, Cadours, Renaud, Bouzalmata, Kamal
• Granted Patent: US 8,821,615 B2
• Time in Patent Office: Days
• US Class Current: 62/611
• CPC Class Codes: B01D 2256/24 Hydrocarbons
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2257/80 Water
• CPC Class Codes: B01D 2258/06 Polluted air
• CPC Class Codes: B01D 53/1425 Regeneration of liquid absorbents
• CPC Class Codes: B01D 53/1462 Removing mixtures of hydrogen sulfide and carbon dioxide
• CPC Class Codes: B01D 53/526 Mixtures of hydrogen sulfide and carbon dioxide
• CPC Class Codes: C01B 17/0408 Pretreatment of the hydrogen sulfide containing gases
• CPC Class Codes: C10L 3/10 Working-up natural gas or synthetic natural gas
• CPC Class Codes: C10L 3/102 of acid contaminants
• CPC Class Codes: Y02P 20/151 Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Abstract

The disclosure relates to a process for treating a gas mixture containing carbon dioxide and hydrogen sulphide, including the following steps: deacidificating the gas mixture by bringing the gas mixture into contact with a first lean absorbent solution stream, delivering a deacidified gas mixture, and a first rich absorbent solution stream; regenerating the first rich absorbent solution stream, delivering the first lean absorbent solution stream and a sour gas stream; distillating the sour gas stream, delivering a first carbon-dioxide-rich stream and a hydrogen-sulphide-rich stream; purifying the first carbon-dioxide-rich stream by bringing the first carbon-dioxide-rich stream into contact with a second lean absorbent solution stream, delivering a second carbon-dioxide-rich stream and a second rich absorbent solution stream, the molar concentration of carbon dioxide in the second carbon-dioxide-rich stream being greater than the molar concentration of carbon dioxide in the first carbon-dioxide-rich stream. The disclosure also relates to an installation designed to implement this process.

Claims

1. A method for treating a gas mixture containing carbon dioxide and hydrogen sulfide, comprising:

deacidificating the gas mixture by putting the gas mixture in contact with a first lean absorbent solution stream, delivering a deacidified gas mixture and a first rich absorbent solution stream;

regenerating the first rich absorbent solution, delivering the first lean absorbent solution stream and a stream of sour gases;

distillating the stream of sour gases, delivering a first carbon-dioxide-rich stream and a rich-hydrogen-sulfide stream; and

purifying the first carbon-dioxide-rich stream by putting the first carbon-dioxide-rich stream in contact with a second lean absorbent solution stream, delivering a second carbon-dioxide-rich stream and a second carbon-dioxide-rich stream and a second rich absorbent solution stream, the molar concentration of carbon dioxide in the second carbon-dioxide-rich stream being greater than a molar concentration of carbon dioxide in the first carbon-dioxide-rich stream.

2. The method according to claim 1, wherein the first lean absorbent solution stream and the second lean absorbent solution stream have the same composition.

3. The method according to claim 2, wherein:

the regeneration step also comprises regenerating the second rich absorbent solution stream, the regeneration step delivering the first lean absorbent solution stream and the second lean absorbent solution stream;

or

the deacidification step also comprises the putting of the gas mixture in contact with the second rich absorbent solution stream, delivering the deacidified gas mixture and the first rich absorbent solution stream.

4. The method according to claim 1, wherein the gas mixture containing carbon dioxide and hydrogen sulfide is based on hydrocarbons, and is natural gas.

5. The method according to claim 1, wherein the molar concentration ratio between carbon dioxide and hydrogen sulfide in the gas mixture comprising carbon dioxide and hydrogen sulfide is less than or equal to 1.

6. The method according to claim 1, wherein the molar concentration of carbon dioxide in the first carbon-dioxide-rich stream is comprised between 80 and 99%.

7. The method according to claim 1, wherein at least one of:

the carbon dioxide concentration in the hydrogen-sulfide-rich stream is less than or equal to 5,000 ppmv; and

the hydrogen sulfide concentration in the second carbon-dioxide-rich stream is less than or equal to 5,000 ppmv.

8. The method according to claim 1, further comprising:

dehydrating the deacidified gas mixture.

9. The method according to claim 1, not comprising any step for dehydrating the stream of sour gases by a molecular sieve or by contact with a solvent, prior to the distillation step.

15. The method according to claim 1 applied in an installation comprising:

a conduit for supplying the gas mixture;

a first conduit for supplying a lean absorbent solution;

an absorption column, fed by the gas mixture supply conduit and by the first lean absorbent solution supply conduit;

a conduit for drawing off the deacidified gas mixture stemming from the absorption column;

a first conduit for drawing off the rich absorbent solution stemming from the absorption column;

a regenerator, fed by the first conduit for drawing of the rich absorbent solution;

a conduit for drawing off the lean absorbent solution stemming from the regenerator;

a conduit for drawing off the sour gases stemming from the regenerator;

a distillation unit fed by the conduit for drawing off the sour gases;

a conduit for drawing off the hydrogen-sulfide-rich stream stemming from the distillation unit;

a first conduit for drawing off the carbon-dioxide-rich stream stemming from the distillation unit;

a second lean absorbent solution supply conduit;

a contacter fed by the first conduit for drawing off the carbon-dioxide-rich stream and by the second lean absorbent solution supply conduit;

a second conduit for drawing off the carbon-dioxide-rich stream stemming from the contacter; and

a second conduit for drawing off the rich absorbent solution stemming from the contacter.

17. The method according to claim 5, wherein the molar concentration ratio between carbon dioxide and hydrogen sulfide in the gas mixture comprising carbon dioxide and hydrogen sulfide is less than or equal to 0.75.

18. The method according to claim 17, wherein the molar concentration ratio between carbon dioxide and hydrogen sulfide in the gas mixture comprising carbon dioxide and hydrogen sulfide is less than or equal to 0.5

19. The method according to claim 6, wherein the molar concentration of carbon dioxide in the first carbon-dioxide-rich stream is comprised between 85 and 98%.

20. The method according to claim 7, wherein at least one of:

the carbon dioxide concentration in the hydrogen-sulfide-rich stream is less than or equal to 2,000 ppmv; and

the hydrogen sulfide concentration in the second carbon-dioxide-rich stream is less than or equal to 1,000 ppmv.

10. An installation for treating a gas mixture containing sour gases, comprising:

a conduit for supplying a gas mixture;

a first conduit for supplying a lean absorbent solution;

an absorption column, fed by the gas mixture supply conduit and by the first lean absorbent solution supply conduit;

a conduit for drawing off a deacidified gas mixture stemming from the absorption column;

a first conduit for drawing off a rich absorbent solution stemming from the absorption column;

a regenerator, fed by the first conduit for drawing of a rich absorbent solution;

a conduit for drawing off a lean absorbent solution stemming from the regenerator;

a conduit for drawing off sour gases stemming from the regenerator;

a distillation unit fed by the conduit for drawing off sour gases;

a conduit for drawing off a hydrogen-sulfide-rich stream stemming from the distillation unit;

a first conduit for drawing off a carbon-dioxide-rich stream stemming from the distillation unit;

a second lean absorbent solution supply conduit;

a contacter fed by the first conduit for drawing off a carbon-dioxide-rich stream and by the second lean absorbent solution supply conduit;

a second conduit for drawing off a carbon-dioxide-rich stream stemming from the contacter; and

a second conduit for drawing off a rich absorbent solution stemming from the contacter.

11. The installation according to claim 10, wherein the first lean absorbent solution supply conduit and the second lean absorbent solution supply conduit stem from a same tank of lean absorbent solution.

12. The installation according to claim 11, wherein:

the second conduit for drawing off a rich absorbent solution feeds the regenerator;

or

the second conduit for drawing off a rich absorbent solution feeds the absorption column.

13. The installation according to claim 10, wherein the contacter is an absorption column or an injection mixer or a static mixer.

14. The installation according to claim 10, which is without any unit for dehydration by a solvent or by a molecular sieve between the regenerator and the distillation unit.

16. A method for producing liquefied natural gas, comprising:

(a) the treatment of natural gas containing sour gases comprising;

deacidificating the gas mixture by putting the gas mixture in contact with a first lean absorbent solution stream, delivering a deacidified gas mixture and a first rich absorbent solution stream;

regenerating the first rich absorbent solution, delivering the first lean absorbent solution stream and a stream of sour gases;

distillating the stream of sour gases, delivering a first carbon-dioxide-rich stream and a rich-hydrogen-sulfide stream; and

purifying the first carbon-dioxide-rich stream by putting the first carbon-dioxide-rich stream in contact with a second lean absorbent solution stream, delivering a second carbon-dioxide-rich stream and a second carbon-dioxide-rich stream and a second rich absorbent solution stream, the molar concentration of carbon dioxide in the second carbon-dioxide-rich stream being greater than a molar concentration of carbon dioxide in the first carbon-dioxide-rich stream; and

(b) liquefaction of the liquid natural gas.