SYSTEMS AND METHODS FOR REMOVAL OF NITROGEN FROM LNG

• US 20170370641A1
• Filed: 06/23/2016
• Published: 12/28/2017
• Est. Priority Date: 06/23/2016
• Status: Abandoned Application

• Current Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Original Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Inventors: Mak, John, Thomas, Jacob, Graham, Curt
• Application Number:
  US15/191,251
• Publication Number:
  US 20170370641A1
• Time in Patent Office: Days
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/40 Features relating to the provision of boil-up in the bottom of a column
• 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 2200/94 Details relating to the withdrawal point
• CPC Class Codes: F25J 2210/62 Liquefied natural gas [LNG]; Natural gas liquids [NGL]; Liquefied petroleum gas [LPG]
• CPC Class Codes: F25J 2215/04 Recovery of liquid products
• CPC Class Codes: F25J 2240/40 Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
• CPC Class Codes: F25J 2270/02 Internal refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/88 Quasi-closed internal refrigeration or heat pump cycle, if not otherwise provided
• CPC Class Codes: F25J 2290/12 Particular process parameters like pressure, temperature, ratios
• CPC Class Codes: F25J 2290/40 Vertical layout or arrangement of cold equipments within in the cold box, e.g. columns, condensers, heat exchangers etc.
• CPC Class Codes: F25J 3/0209 Natural gas or substitute natural gas
• CPC Class Codes: F25J 3/0214 Liquefied natural gas
• CPC Class Codes: F25J 3/0233 separation of CnHm with 1 carbon atom or more
• CPC Class Codes: F25J 3/0257 separation of nitrogen from air F25J3/04, production of nitrogen in general C01B21/00
• CPC Class Codes: F25J 3/0295 Start-up or control of the process; Details of the apparatus used, e.g. sieve plates, packings

Abstract

A system for the removal of nitrogen from a liquid natural gas (LNG) stream. The system. comprises a feed heat changer and a stripper column. The heat receives the LNG stream and cools the LNG stream via heat exchange with a stripper column side-draw stream to yield a cooled LNG stream and a heated side-draw stream. The stripper column receives the cooled LNG stream at a first tray and the heated side-draw stream. The stripper column produces the stripper column side-draw stream, a stripper column overhead stream, and a stripper column bottom stream. The stripper column side-draw stream is taken from the stripper column at a second tray. The second tray is at least about 15 feet higher than the feed heat exchanger.

Claims

1. A system for the removal of nitrogen from a liquid natural gas (LNG) stream, the system comprising:

a feed heat exchanger, wherein the heat is configured to receive the LNG stream and to cool the LNG stream via heat exchange with a stripper column side-draw stream to yield a cooled LNG stream and a heated side-draw stream; and

a stripper column, wherein the stripper column is configured to receive the cooled LNG stream at a first tray and the heated side-draw stream, and wherein the stripper column is configured to produce the stripper column side-draw stream, a stripper column overhead stream, and a stripper column bottom stream,

wherein the stripper column is configured such that the stripper column side-draw stream is taken from the stripper column at a second tray, wherein the second tray is at least about 15 feet higher than the feed heat exchanger.

2. The system of claim 1, further comprising a pressure reduction device, wherein the pressure reduction device is configured to reduce the pressure of the stripper column side-draw stream prior to introduction into the feed heat exchanger.

3. The system of claim 2, wherein the pressure reduction device is a valve.

4. The system of claim 2, further comprising a control device, wherein the control device is configured to control the flow of the heated side-draw stream prior to introduction into the feed heat exchanger

5. The system of claim 4, wherein the control device is a flow control valve.

6. The system of claim 1, wherein the system is configured to receive the LNG stream from a LNG liquefaction plant.

7. The system of claim 1, wherein the LNG stream is characterized as a relatively-high nitrogen content LNG stream.

8. The system of claim 7, wherein the stripper column bottom stream has less than about 0.9 mole % nitrogen.

9. The system of claim 1, wherein the cooled LNG stream has a temperature of from about 256°

F. to −

275°

F.

10. The system of claim 1, wherein the second tray is at least about 20 feet higher than the feed heat exchanger.

11. A method for the removal of nitrogen from a liquid natural gas (LNG) stream, the method comprising:

receiving, at a feed heat exchanger, the LNG stream;

cooling the LNG stream via heat exchange with a stripper column side-draw stream to yield a cooled LNG stream and a heated side-draw stream;

receiving, at a stripper column, the cooled LNG stream at a first tray and the heated side-draw stream;

producing the stripper column side-draw stream from the stripper column at a second tray that is at least about 15 feet higher than the feed heat exchanger; and

producing a stripper column overhead stream and a stripper column bottom stream.

12. The method of claim 11, further comprising controlling the flow of the stripper column side-draw stream prior to introducing the stripper column side-draw stream into the feed heat exchanger.

13. The method of claim 12, wherein controlling the flow of the stripper column side-draw stream comprises passing the stripper column side-draw stream through a first valve.

14. The method of claim 11, further comprising controlling the flow of the heated side-draw stream prior to introducing the heated side-draw stream into the feed heat exchanger.

15. The method of claim 14, wherein controlling the flow of the heated side-draw stream comprising passing the heated side-draw stream through a second valve.

16. The method of claim 11, wherein receiving the LNG stream comprises receiving the LNG stream from a LNG liquefaction plant.

17. The method of claim 11, wherein the LNG stream is characterized as a relatively-high nitrogen content LNG stream.

18. The method of claim 17, wherein the s column bottom stream has less than about 0.9 mole % nitrogen.

19. The method of claim 11, wherein cooling the LNG stream comprises cooling the LNG stream to a temperature of from about −

256°

F. to −

275°

F.

20. The method of claim 11, wherein the second tray is at least about 20 feet higher than the feed heat exchanger.