CONFIGURATIONS AND METHODS FOR SMALL SCALE LNG PRODUCTION

• US 20180003429A1
• Filed: 07/01/2016
• Published: 01/04/2018
• Est. Priority Date: 07/01/2016
• Status: Active Grant

• Current Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Original Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Inventors: Mak, John
• Granted Patent: US 11,112,173 B2
• Time in Patent Office: Days
• CPC Class Codes: F25J 1/0022 Hydrocarbons, e.g. natural gas
• CPC Class Codes: F25J 1/004 by flash gas recovery F25J1/0267 takes precedence
• CPC Class Codes: F25J 1/005 by expansion of a gaseous refrigerant stream with extraction of work
• CPC Class Codes: F25J 1/0052 by vaporising a liquid refrigerant stream
• CPC Class Codes: F25J 1/0072 Nitrogen
• CPC Class Codes: F25J 1/0208 in combination with an internal quasi-closed refrigeration loop, e.g. with deep flash recycle loop F25J1/021 takes precedence
• CPC Class Codes: F25J 1/0245 Different modes, i.e. 'runs', of operation; Process control
• CPC Class Codes: F25J 1/0275 adapted for special use of the liquefaction unit, e.g. portable or transportable devices
• CPC Class Codes: F25J 1/0288 using work extraction by mechanical coupling of compression and expansion of the refrigerant, so-called companders
• CPC Class Codes: F25J 2210/60 Natural gas or synthetic natural gas [SNG]
• CPC Class Codes: F25J 2220/66 Separating acid gases, e.g. CO2, SO2, H2S or RSH
• CPC Class Codes: F25J 2220/68 Separating water or hydrates
• CPC Class Codes: F25J 2230/60 the fluid being hydrocarbons or a mixture of hydrocarbons
• 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 2245/90 the recycled stream being boil-off gas from storage
• CPC Class Codes: F25J 2270/16 with mutliple gas expansion loops of the same refrigerant
• CPC Class Codes: F25J 2290/12 Particular process parameters like pressure, temperature, ratios
• CPC Class Codes: F25J 2290/60 Details about pipelines, i.e. network, for feed or product distribution
• CPC Class Codes: F25J 2290/62 Details of storing a fluid in a tank
• CPC Class Codes: F25J 5/00 Arrangements of cold exchangers or cold accumulators in separation or liquefaction plants heat exchangers F28C, F28D, F28F

Abstract

An LNG plant comprises a cold box and a refrigeration unit fluidly coupled with a plurality of heat exchanger passes in the cold box. The refrigeration unit is configured to provide a first refrigerant stream to a first heat exchanger pass of the plurality of heat exchanger passes at a first pressure, a second refrigerant stream to a second heat exchanger pass at a second pressure, and a third refrigerant stream to a third heat exchanger pass at a third pressure. The second refrigerant stream comprises a first portion of the first refrigerant stream, and the third refrigerant stream comprises a second portion of the first refrigerant stream. The second pressure and the third pressure are both below the first pressure. The cold box is configured to produce LNG from a natural gas feed stream to the cold box using a refrigeration content from the refrigeration unit.

Claims

1. An LNG plant comprising:

a cold box comprising a plurality of heat exchanger passes; and

a refrigeration unit comprising a closed refrigeration cycle, wherein the cold box is fluidly coupled with the refrigeration unit, wherein the cold box is configured to receive a natural gas feed stream and produce LNG from the feed stream using a refrigeration content from the refrigeration unit, wherein the refrigeration unit comprises;

a first compressor unit configured to compress a refrigerant to produce a compressed refrigerant at a first pressure;

a first heat exchanger pass of the plurality of heat exchanger passes, wherein the first heat exchanger pass is configured to pass the compressed refrigerant through the cold box to cool the compressed refrigerant;

a splitter configured to separate the cooled, compressed refrigerant into a first portion and a second portion;

a first expander configured to receive the first portion from the splitter and expand the first portion to a second pressure, wherein the second pressure is less than the first pressure;

a second expander configured to receive the second portion from the splitter and expand the second portion to a third pressure, wherein the third pressure is less than the second pressure;

a second heat exchanger pass of the plurality of heat exchanger passes configured to pass the first portion at the second pressure through the cold box;

a third heat exchanger pass of the plurality of heat exchanger passes configured to pass the second portion at the third pressure through the cold box to provide at least a portion of the refrigeration content in the cold box;

at least one second compressor, wherein the at least one second compressor is configured to receive the second portion downstream of the third heat exchanger pass and compress the second portion to the second pressure; and

a mixer, wherein the mixer is configured to combine the compressed second portion downstream of the at least one second compressor and the first portion downstream of the second heat exchanger pass to form the refrigerant upstream of the first compressor.

2. The LNG plant of claim 1, wherein the first compressor unit comprises a plurality of compressors arranged in series and an intercooler disposed between consecutive compressors.

3. The LNG plant of claim 1, wherein the at least one second compressor comprises a plurality of second compressors, and wherein at least one second compressor of the plurality of second compressors is mechanically coupled to the first expander or the second expander.

4. The LNG plant of claim 1, wherein the second pressure is between about 20% and about 50% of the first pressure on an absolute scale.

5. The LNG plant of claim 1, wherein the third pressure is between about 3% and about 20% of the first pressure on an absolute scale.

6. The LNG plant of claim 1, further comprising a heat exchanger fluidly coupled between the first compressor and the first heat exchanger pass, wherein the heat exchanger is configured to cool the compressed refrigerant prior to the compressed refrigerant passing to the first heat exchanger pass.

7. An LNG plant comprising:

a cold box comprising a heat exchanger, wherein the heat exchanger comprises a plurality of heat exchanger passes;

a refrigeration unit fluidly coupled with the plurality of heat exchanger passes, wherein the refrigeration unit is configured to provide;

a first refrigerant stream to a first heat exchanger pass of the plurality of heat exchanger passes, wherein the first refrigerant stream is at a first pressure;

a second refrigerant stream to a second heat exchanger pass of the plurality of heat exchanger passes, wherein the second refrigerant stream comprises a first portion of the first refrigerant stream downstream of the first heat exchanger pass, and wherein the second refrigerant stream is at a second pressure; and

a third refrigerant stream to a third heat exchanger pass of the plurality of heat exchanger passes, wherein the third refrigerant stream comprises a second portion of the first refrigerant stream downstream of the first heat exchanger pass, and wherein the third refrigerant stream is at a third pressure, wherein the second pressure and the third pressure are both below the first pressure,

wherein the cold box is configured to receive a natural gas feed stream and produce LNG from the natural gas feed stream using a refrigeration content from the refrigeration unit in the plurality of heat exchanger passes.

8. The LNG plant of claim 7, wherein the first pressure is between about 1,000 psia and 2,000 psia.

9. The LNG plant of claim 7, wherein the second pressure is between about 20% and about 50% of the first pressure on an absolute scale.

10. The LNG plant of claim 7, wherein the third pressure is between about 3% and about 20% of the first pressure on an absolute scale.

11. The LNG plant of claim 7, wherein a ratio of the second pressure to the third pressure is between about 10:

1 and about 2;

1.

12. The LNG plant of claim 7, wherein a molar ratio of a flowrate of the second refrigerant stream to a flowrate of the first refrigerant stream is between about 0.5 and about 0.75.

13. The LNG plant of claim 7, wherein the refrigeration unit is configured to provide the LNG at an energy of between about 320 kW/ton and about 425 kW/ton.

14. A method of generating LNG from a natural gas feed comprising:

passing a first refrigerant stream through a first heat exchanger pass of a plurality of heat exchanger passes in a cold box, wherein the first refrigerant stream is at a first pressure;

separating the first refrigerant stream into a second refrigerant stream and a third refrigerant stream downstream of the cold box;

passing the second refrigerant stream through a second heat exchanger pass of the plurality of heat exchanger passes, wherein the second refrigerant stream is at a second pressure;

passing the third refrigerant stream through a third heat exchanger pass of the plurality of heat exchanger passes, wherein the third refrigerant stream is at a third pressure, wherein the second pressure and the third pressure are both below the first pressure;

passing a natural gas feed stream through at least a fourth heat exchanger pass of the plurality of heat exchanger passes; and

liquefying at least a portion of the natural gas stream in the cold box using a refrigeration content provided by at least one of the second refrigerant stream or the third refrigerant stream to form an LNG stream.

15. The method of claim 14, further comprising:

combining the second refrigerant stream and the third refrigerant stream downstream of the cold box to form a recycle stream; and

compressing the recycle stream to form the first refrigerant stream.

16. The method of claim 15, wherein compressing the recycle stream comprises compressing the recycle stream in a two-stage compressor.

17. The method of claim 15, further comprising:

expanding the second refrigerant stream to the second pressure in a first expander;

expanding the third refrigerant stream to the third pressure in a second expander, wherein the second pressure is between about 20% and about 50% of the first pressure on an absolute scale; and

compressing the third refrigerant stream prior to combining the second refrigerant stream and the third refrigerant stream.

18. The method of claim 16, wherein at least one of the first expander or the second expander is coupled to a compressor, wherein compressing the third refrigerant stream prior to combining the second refrigerant stream and the third refrigerant stream comprises using the compressor to compress the third refrigerant stream.

19. The method of claim 14, wherein the second pressure is between about 20% and about 50% of the first pressure on an absolute scale.

20. The method of claim 14, wherein the third pressure is between about 3% and about 20% of the first pressure on an absolute scale.