Floating liquefied natural gas pretreatment system

Patent metadata

Field	Value
Publication number	US-11255487-B2
Application number	US-201715784870-A
Country	US
Kind code	B2
Filing date	Oct 16, 2017
Priority date	Dec 6, 2011
Publication date	Feb 22, 2022
Grant date	Feb 22, 2022

Abstract

A pretreatment system and method for a floating liquid natural gas (“FLNG”) facility are presented. The inlet natural gas stream flows through a membrane system to remove carbon dioxide and a heat exchanger, producing first and second cooled CO2-depleted non-permeate streams. The first cooled CO2-depleted non-permeate stream is routed to additional pretreatment equipment, while the second cooled CO2-depleted non-permeate stream is routed directly to a LNG train. Alternatively, the inlet natural gas stream may flow through a membrane system to produce a single cooled CO2-depleted non-permeate stream that is routed to the LNG train after sweetening and dehydration. Because the pretreatment system delivers the incoming gas stream to the LNG train at a lower temperature than conventional systems, less energy is needed to convert the gas stream to LNG. In addition, the pretreatment system has a smaller footprint than conventional pretreatment systems.

First claim

What is claimed is:

1. A pretreatment method for cooling and purifying a natural gas stream for processing into LNG, the method comprising:
separating an inlet natural gas stream using a membrane to produce a cooled permeate stream and a cooled non-permeate stream;
routing the cooled permeate and non-permeate streams directly to a heat exchanger;
cross-exchanging heat in the heat exchanger between the cooled permeate and non-permeate streams and a water-removed natural gas outlet stream to produce:
a first heated permeate stream,
a first cooled non-permeate stream, and
a second cooled non-permeate stream;

processing the first cooled non-permeate stream to form the water-removed natural gas outlet stream; and
routing the second cooled non-permeate stream directly to an LNG train.

2. A pretreatment method according to claim 1 further comprising:
removing mercury from the inlet natural gas stream.

3. A pretreatment method according to claim 2 further comprising removing H2S from the inlet natural gas stream.

4. A pretreatment method according to claim 2 further comprising removing mercury to a level required to protect downstream equipment.

5. A pretreatment method according to claim 1 , further comprising removing mercury from the water-removed natural gas outlet stream.

6. A pretreatment method according to claim 1 wherein the water-removed natural gas outlet stream is obtained by processing the first cooled non-permeate stream in a gas sweetening system, a gas dehydration system, or both.

7. A pretreatment method according to claim 1 wherein the membrane is an acid gas removal membrane.

8. A pretreatment method according to claim 1 wherein the cooled permeate and non-permeate streams differ in an amount of CO2 contained in said streams.

9. A pretreatment method for cooling and purifying a natural gas stream for processing into LNG, the method comprising:
separating an inlet natural gas stream using a membrane to produce a cooled permeate stream and a cooled non-permeate stream;
cross-exchanging heat in a heat exchanger between the cooled permeate and non-permeate streams and a water-removed natural gas outlet stream and to produce:
a first heated permeate stream,
a first cooled non-permeate stream, and
a second cooled non-permeate stream.

10. A pretreatment method according to claim 9 further comprising: removing hydrogen sulfide from the first cooled non-permeate stream to form the water-removed natural gas outlet stream.

11. A pretreatment method according to claim 9 further comprising routing the second cooled non-permeate stream directly to an LNG train.

12. A pretreatment method according to claim 9 further comprising:
removing mercury from the inlet natural gas stream.

13. A pretreatment method according to claim 12 further comprising removing H2S from the inlet natural gas stream.

14. A pretreatment method according to claim 12 further comprising removing mercury to a level required to protect downstream equipment.

15. A pretreatment method according to claim 9 , further comprising removing mercury from the first cooled non-permeate stream to form the water-removed natural gas outlet stream.

16. A pretreatment method according to claim 9 , wherein the water-removed natural gas outlet stream is obtained by processing the first cooled non-permeate stream in a gas sweetening system, a gas dehydration system, or both.

17. A pretreatment method according to claim 9 wherein the membrane is an acid gas removal membrane.

18. A pretreatment method according to claim 9 wherein the cooled permeate and non-permeate streams differ in an amount of CO2 contained in said streams.

Assignees

• Cameron Int Corp

Inventors

• Jariwala Ankur D
• Peters Richard D

Classifications

• F25J2220/68

  Separating water or hydrates · CPC title

• F25J2205/80

  using membrane, i.e. including a permeation step · CPC title

• F25J3/06

  by partial condensation (F25J3/08 takes precedence; by rectification F25J3/02 {; purification of hydrocarbons in general C07C7/00}) · CPC title

• B01D2256/245

  Methane · CPC title

• F25J1/0278

  Unit being stationary, e.g. on floating barge or fixed platform · CPC title