Natural Gas Processing Plant

• US 20130186133A1
• Filed: 07/23/2012
• Published: 07/25/2013
• Est. Priority Date: 08/02/2011
• Status: Active Grant

• Current Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Original Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Inventors: Golden, Timothy Christopher, Hufton, Jeffrey Raymond, Palamara, John Eugene, Ploeger, Jason Michael
• Granted Patent: US 9,945,608 B2
• Time in Patent Office: Days
• US Class Current: 62/636
• CPC Class Codes: C10L 3/10 Working-up natural gas or synthetic natural gas
• CPC Class Codes: C10L 3/101 Removal of contaminants
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/70 Refluxing the column with a condensed part of the feed stream, i.e. fractionator top is stripped or self-rectified
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2205/40 using hybrid system, i.e. combining cryogenic and non-cryogenic separation techniques
• CPC Class Codes: F25J 2205/60 using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end
• CPC Class Codes: F25J 2205/64 by pressure-swing adsorption [PSA] at the hot end
• CPC Class Codes: F25J 2210/04 Mixing or blending of fluids with the feed stream
• CPC Class Codes: F25J 2210/06 Splitting of the feed stream, e.g. for treating or cooling in different ways
• CPC Class Codes: F25J 2240/02 Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
• CPC Class Codes: F25J 2245/02 Recycle of a stream in general, e.g. a by-pass stream
• CPC Class Codes: F25J 2290/80 Retrofitting, revamping or debottlenecking of existing plant
• CPC Class Codes: F25J 3/0209 Natural gas or substitute natural gas
• CPC Class Codes: F25J 3/0233 separation of CnHm with 1 carbon atom or more
• CPC Class Codes: F25J 3/0238 separation of CnHm with 2 carbon atoms or more
• CPC Class Codes: F25J 3/08 Separating gaseous impurities from gases or gaseous mixtures or from liquefied gases or liquefied gaseous mixturescold traps B01D8/00

Abstract

The invention provides systems and methods for separating ethane and heavier hydrocarbons from a natural gas stream. In aspects of the invention, an adsorption unit is integrated with a cryogenic gas processing plant in order to overcome methane recovery limitations by sending the tail gas from the adsorption unit to the cryogenic gas processing plant to recover methane that would otherwise be lost.

Claims

1. A system for removing natural gas liquids from raw natural gas comprising:

(i) an adsorption unit configured to receive a raw natural gas stream and remove natural gas liquids from the raw natural gas stream to produce a first stream comprising methane and enriched in natural gas liquids and a second stream comprising methane and depleted in natural gas liquids;

(ii) a compressor or pump configured to receive and increase the pressure of the first stream; and

(iii) a demethanizer configured to remove at least a portion of the methane from the first stream, wherein the bottom product of the demethanizer comprises natural gas liquids;

wherein the second stream has a higher heating value less than 1100 BTU/SCF.

2. The system of claim 1, further comprising a heat exchanger configured to receive and cool the first stream.

3. The system of claim 1, wherein the raw natural gas stream comprises at least 60% methane by volume.

4. The system of claim 1, wherein the raw natural gas stream comprises less than 2% carbon dioxide by volume.

5. The system of claim 1, wherein the raw natural gas stream comprises less than 100 ppm water vapor by volume.

6. The system of claim 1, wherein the pressure of the raw natural gas stream is greater than 700 psia.

7. The system of claim 1, wherein the adsorption unit is a pressure swing adsorption unit.

8. The system of claim 6, wherein the lowest pressure in the pressure swing adsorption unit during any single cycle is 1 atm.

9. The system of claim 1, wherein the adsorption unit is a vacuum swing adsorption unit.

10. The system of claim 9, wherein the lowest pressure in the vacuum swing adsorption unit during any single cycle is 0.05 atm.

11. The system of claim 1, wherein the beds of the adsorption unit have a length to diameter ratio less than 1.5.

12. The system of claim 1, wherein a portion of the compressed first stream is compressed to the pressure of the raw natural gas stream, recycled, and fed to the adsorption unit.

13. The system of claim 1, wherein the adsorption unit is portable.

31. A method for producing natural gas liquids and natural gas comprising:

(i) providing raw natural gas to a system according to claim 1; and

(ii) recovering natural gas liquids and natural gas, wherein the natural gas has a higher heating value less than 1100 BTU/SCF.

14. A system for treating raw natural gas comprising:

(i) an adsorption unit configured to receive a raw natural gas stream and produce a first stream comprising methane and enriched in natural gas liquids and a second stream comprising methane and depleted in natural gas liquids;

(ii) a compressor or pump configured to receive and increase the pressure of the first stream to produce a gas processing plant feed stream; and

(iii) a gas processing plant configured to receive the gas processing plant feed stream.

15. The system of claim 14, further comprising a heat exchanger configured to receive and cool the gas processing plant feed stream before the gas processing plant feed stream enters the gas processing plant.

16. The system of claim 14, wherein the raw natural gas stream comprises at least 60% methane by volume.

17. The system of claim 14, wherein the raw natural gas stream comprises less than 2% carbon dioxide by volume.

18. The system of claim 14, wherein the raw natural gas stream comprises less than 100 ppm water vapor by volume.

19. The system of claim 14, wherein the pressure of the raw natural gas stream is greater than 700 psia.

20. The system of claim 14, wherein the adsorption unit is a pressure swing adsorption unit.

21. The system of claim 20, wherein the lowest pressure in the pressure swing adsorption unit during any single cycle is 1 atm.

22. The system of claim 14, wherein the adsorption unit is a vacuum swing adsorption unit.

23. The system of claim 22, wherein the lowest pressure in the vacuum swing adsorption unit during any single cycle is 0.05 atm.

24. The system of claim 14, wherein the beds of the adsorption unit have a length to diameter ratio less than 1.5.

25. The system of claim 14, wherein a portion of the first stream is compressed to the pressure of the raw natural gas stream, recycled, and fed to the adsorption unit.

26. The system of claim 14, wherein the adsorption unit is portable.

27. The system of claim 14, wherein the gas processing plant comprises:

(a) a main raw natural gas feed stream;

(b) a first heat exchanger configured to receive and cool the main raw natural gas feed stream to produce a cooled feed stream;

(c) a separation unit configured to receive the cooled feed stream and separate it into a vapor feed stream and a liquid feed stream;

(d) an expander configured to receive and expand a portion of the vapor feed stream to form a main demethanizer feed stream;

(e) a second heat exchanger configured to receive and condense a portion of the vapor feed stream, a portion of the cooled feed stream, a portion of a demethanizer overhead stream, or any combination thereof to form a demethanizer reflux stream; and

(f) a demethanizer configured to receive the main demethanizer feed stream, the liquid feed stream, and the methanizer reflux stream and produce the demethanizer overhead stream comprising methane and a demethanizer bottoms stream comprising natural gas liquids.

28. The system of claim 27, wherein the gas processing plant feed stream is combined with the main raw natural gas feed stream and fed to the first heat exchanger.

29. The system of claim 27, wherein the gas processing plant feed stream is combined with the liquid feed stream and fed to the demethanizer.

32. A method for producing pipeline quality gas comprising:

(i) providing raw natural gas to a system according to claim 14; and

(ii) recovering natural gas having a higher heating value less than 1100 BTU/SCF.

30. A system for removing natural gas liquids from raw natural gas comprising:

(i) a membrane separation unit configured to receive a raw natural gas stream and remove natural gas liquids from the raw natural gas stream to produce a first stream comprising methane and enriched in natural gas liquids and a second stream comprising methane and depleted in natural gas liquids;

(ii) a compressor or pump configured to receive and increase the pressure of the first stream; and

(iii) a demethanizer system configured to remove at least a portion of the methane from the compressed first stream, wherein the bottom product of the demethanizer comprises natural gas liquids;

wherein the second stream has a higher heating value less than 1100 BTU/SCF.

33. A method for producing pipeline quality gas comprising:

(i) providing raw natural gas to a system according to claim 30; and

(ii) recovering natural gas having a higher heating value less than 1100 BTU/SCF.