Treatment of nitrogen-rich natural gas streams

Patent metadata

Field	Value
Publication number	US-10215488-B2
Application number	US-201615041359-A
Country	US
Kind code	B2
Filing date	Feb 11, 2016
Priority date	Feb 11, 2016
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

Helium can be recovered from nitrogen-rich natural gas at high pressure with low helium loss by cryogenic distillation of the natural gas after pre-treatment of the gas to remove incompatible impurities and then recovery of natural gas liquid (NGL) from the pre-treated gas by distillation. Overall power consumption may be reduced, particularly if the feed to the helium recovery column system is at least substantially condensed by indirect heat exchange against a first portion of nitrogen-enriched bottoms liquid at first pressure, and a second portion of nitrogen-enriched bottoms liquid at a second pressure that is different from the first pressure.

First claim

The invention claimed is:

1. A process for recovering helium and natural gas liquid (NGL) from pressurized natural gas comprising methane, C 2+ hydrocarbons, helium and at least 70% nitrogen, said process comprising:
pre-treating said pressurized nitrogen-rich natural gas to remove one or more impurities incompatible with the process and produce pre-treated natural gas;
cooling said pre-treated natural gas to produce cooled pre-treated natural gas;
separating said cooled pre-treated natural gas by distillation in an NGL recovery column system comprising one or more distillation columns, to produce NGL and C 2+ hydrocarbon-depleted natural gas comprising helium and methane; and
separating said C 2+ hydrocarbon-depleted natural gas by distillation in a helium recovery column system to produce helium-enriched overhead vapor and nitrogen-enriched bottoms liquid comprising methane.

2. The process of claim 1 comprising separating said nitrogen-enriched bottoms liquid by distillation in a methane recovery column system to produce nitrogen-enriched overhead vapor and methane-enriched bottoms liquid.

3. The process of claim 2 , wherein at least a portion of said nitrogen-enriched bottoms liquid is heated and partially vaporized prior to being fed as feed to said methane recovery column system.

4. The process of claim 2 , wherein a portion said nitrogen-enriched bottoms liquid is cooled prior to being fed as reflux to said methane recovery column system.

5. The process of claim 2 , wherein said methane recovery column system operates at a pressure from more than 1 bar to 35 bar.

6. The process of claim 2 , wherein said nitrogen-enriched bottoms liquid is reduced in pressure prior to being fed to said methane recovery column system.

7. The process of claim 2 , wherein methane-enriched bottoms liquid is removed from the process without vaporization.

8. The process of claim 2 , wherein a portion of said methane-enriched bottoms liquid is vaporized to produce fuel gas.

9. The process of claim 2 , wherein said methane-enriched bottoms liquid comprises at least 90% methane.

10. The process of claim 2 , wherein said methane-enriched bottoms liquid comprises at least 90% methane.

11. The process of claim 2 , wherein at least a portion of said nitrogen in said nitrogen-enriched overhead vapor is condensed and removed as liquid nitrogen.

12. The process of claim 11 , wherein said liquid nitrogen comprises at least 99% nitrogen.

13. The process of claim 11 , wherein said helium-enriched overhead vapor is purified to produce purified helium and at least a portion of said liquid nitrogen is used as a refrigerant in a process to liquefy said purified helium.

14. The process of claim 13 , wherein said purified helium comprises at least 99% helium.

15. The process of claim 1 , wherein said helium-enriched overhead vapor comprises at least 50% helium.

16. The process of claim 1 , wherein said pressurized natural gas is at a pressure in the range from 2 bar to 200 bar.

17. The process of claim 1 , wherein said pressurized natural gas undergoes said pre-treatment without pressure adjustment.

18. The process of claim 1 , wherein said NGL recovery column system operates at a pressure from 2 bar to 35 bar.

19. The process of claim 1 , wherein said cooled pre-treated natural gas is reduced in pressure prior to being fed to said NGL recovery column system.

20. The process of claim 1 , wherein said helium recovery column system operates at a pressure from 2 bar to 35 bar.

21. The process of claim 1 , wherein said C 2+ hydrocarbon-depleted natural gas is reduced in pressure prior to being fed to said helium recovery column system.

22. The process of claim 1 , wherein said pressurized natural gas comprises at least 80% nitrogen.

23. The process of claim 1 , wherein said pressurized natural gas comprises at least 90% nitrogen.

24. The process of claim 1 , wherein said pressurized natural gas comprises from 0.01% to 10% helium.

25. The process of claim 1 , wherein said pressurized natural gas comprises from 0.01% to 5% helium.

26. The process of claim 1 , wherein said pressurized natural gas comprises from 0.1% to 30% methane.

27. The process of claim 1 , wherein said pressurized natural gas comprises from 0.1% to 20% methane.

28. The process of claim 1 , wherein said pressurized natural gas comprises from 0.1% to 10% methane.

29. The process of claim 1 , wherein said pressurized natural gas comprises from 0.01% to 5% C 2+ hydrocarbons.

30. The process of claim 1 , wherein the source of the pressurized natural gas is a field of natural gas at a pressure from 2 bar to 200 bar comprising at least 70% nitrogen; from 0.01% to 10% helium; from 0.1% to 30% methane; and from 0.01% to 5% C 2+ hydrocarbons.

31. The process of claim 1 , wherein said C 2+ hydrocarbon-depleted natural gas is cooled and at least partially condensed prior to being fed to said helium recovery column system.

32. The process of claim 31 , wherein said cooling of said C 2+ hydrocarbon-depleted natural gas is achieved by indirect heat exchange against at least a first portion of said nitrogen-enriched bottoms liquid at a first elevated pressure and a second portion of said nitrogen-enriched bottoms liquid at a second elevated pressure that is different from said first elevated pressure.

Assignees

• Air Prod & Chem

Inventors

• White Vincent
• Higginbotham Paul
• Palamara John Eugene
• Berger Alan

Classifications

• F25J3/029

  of helium · CPC title

• F25J3/0209 Primary

  Natural gas or substitute natural gas · CPC title

• F25J2290/34

  Details about subcooling of liquids · CPC title

• F25J2270/04

  Internal refrigeration with work-producing gas expansion loop · CPC title

• F25J2270/02

  Internal refrigeration with liquid vaporising loop · CPC title