Floating liquefied natural gas pretreatment system

Patent metadata

Field	Value
Publication number	US-9791106-B2
Application number	US-201213707171-A
Country	US
Kind code	B2
Filing date	Dec 6, 2012
Priority date	Dec 6, 2011
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

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 CO 2 -depleted non-permeate streams. The first cooled CO 2 -depleted non-permeate stream is routed to additional pretreatment equipment, while the second cooled CO 2 -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 CO 2 -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:
passing an inlet natural gas stream through a membrane system to produce a cooled CO 2 -rich permeate stream and a cooled CO 2 -depleted non-permeate stream;
routing the cooled CO2-rich permeate stream and the cooled CO2-depleted non-permeate stream directly to a heat exchanger;
cross-exchanging heat in the heat exchanger between the cooled CO 2 -rich permeate stream and the cooled CO 2 -depleted non-permeate stream with a substantially water-free natural gas outlet stream of a gas dehydration unit to produce a heated CO 2 -rich permeate stream, a first cooled CO 2 -depleted non-permeate stream and a second cooled CO2-depleted non-permeate stream;
routing the first cooled CO 2 -depleted non-permeate stream to additional pretreatment equipment; and
directing the second cooled CO 2 -depleted non-permeate stream directly to a LNG train.

2. A pretreatment method according to claim 1 further comprising processing the inlet natural gas stream in a mercury removal system to form a substantially mercury-free natural gas stream.

3. A pretreatment method according to claim 2 wherein the mercury removal system is a mercury/H 2 S removal bed.

4. A pretreatment method according to claim 1 further comprising removing mercury to a level required to protect downstream equipment.

5. A pretreatment method according to claim 1 wherein the additional pretreatment equipment is chosen from the group consisting of a gas sweetening system and a gas dehydration system.

6. A pretreatment method according to claim 1 wherein the membrane system is a CO 2 removal membrane system.

7. A pretreatment method according to claim 2 wherein the mercury removal system is located after the additional pretreatment equipment.

Assignees

• Cameron Int Corp

Inventors

• Jariwala Ankur D
• Peters Richard D

Classifications

• F17C13/082 Primary

  for large sea-borne storage vessels (load-accommodating arrangements for ships or waterborne vessels B63B25/12) · CPC title

• F25J1/0259

  Modularity and arrangement of parts of the liquefaction unit and in particular of the cold box, e.g. pre-fabrication, assembling and erection, dimensions, horizontal layout "plot" · CPC title

• F25J1/0237

  integrating refrigeration provided for liquefaction and purification/treatment of the gas to be liquefied, e.g. heavy hydrocarbon removal from natural gas (details related to rectification F25J3/02; details related to partial condensation F25J3/06; working-up natural gas C10L3/10) · CPC title

• F25J2220/66

  Separating acid gases, e.g. CO2, SO2, H2S or RSH · CPC title

• B01D2257/602

  Mercury or mercury compounds · CPC title