Process for liquefying a gas, notably a natural gas or air, comprising a medium pressure drain and application

• US 6,105,391 A
• Filed: 12/21/1998
• Issued: 08/22/2000
• Est. Priority Date: 12/22/1997
• Status: Expired due to Term

• Current Assignee: Institut Francais Du Petrole
• Original Assignee: Institut Francais Du Petrole
• Inventors: Capron, Pierre
• Primary Examiner(s): CAPOSSELA, RONALD C
• Application Number:
  US09/216,968
• Time in Patent Office: 610 Days
• Field of Search: 62/613, 62/619, 62/621, 62/910
• US Class Current: 62/613
• CPC Class Codes: F25J 1/0022 Hydrocarbons, e.g. natural gas
• CPC Class Codes: F25J 1/0035 by gas expansion with extraction of work
• CPC Class Codes: F25J 1/004 by flash gas recovery F25J1/0267 takes precedence
• CPC Class Codes: F25J 1/0042 by liquid expansion with extraction of work
• CPC Class Codes: F25J 1/0045 by vaporising a liquid return stream
• CPC Class Codes: F25J 1/0052 by vaporising a liquid refrigerant stream
• CPC Class Codes: F25J 1/0219 in combination with an internal quasi-closed refrigeration loop, e.g. using a deep flash recycle loop
• CPC Class Codes: F25J 1/0231 for the working-up of the hydrocarbon feed, e.g. reinjection of heavier hydrocarbons into the liquefied gas
• CPC Class Codes: F25J 1/0238 Purification or treatment step is integrated within one refrigeration cycle only, i.e. the same or single refrigeration cycle provides feed gas cooling (if present) and overhead gas cooling
• CPC Class Codes: F25J 1/025 Details related to the refrigerant production or treatment, e.g. make-up supply from feed gas itself
• CPC Class Codes: F25J 1/0292 Refrigerant compression by cold or cryogenic suction of the refrigerant gas
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/04 in a dual pressure main column system
• CPC Class Codes: F25J 2200/72 Refluxing the column with at least a part of the totally condensed overhead gas
• CPC Class Codes: F25J 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2200/78 Refluxing the column with a liquid stream originating from an upstream or downstream fractionator column
• CPC Class Codes: F25J 2200/80 using integrated mass and heat exchange, i.e. non-adiabatic rectification in a reflux exchanger or dephlegmator
• CPC Class Codes: F25J 2205/02 using simple phase separation in a vessel or drum
• CPC Class Codes: F25J 2215/04 Recovery of liquid products
• CPC Class Codes: F25J 2215/62 Ethane or ethylene
• CPC Class Codes: F25J 2215/64 : Propane or propylene
• CPC Class Codes: F25J 2215/66 : Butane or mixed butanes
• CPC Class Codes: F25J 2230/08 : Cold compressor, i.e. suction of the gas at cryogenic temperature and generally without afterstage-cooler
• CPC Class Codes: F25J 2230/30 : Compression of the feed stream
• 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 2240/30 : Dynamic liquid or hydraulic expansion with extraction of work, e.g. single phase or two-phase turbine
• CPC Class Codes: F25J 2245/90 : the recycled stream being boil-off gas from storage
• CPC Class Codes: F25J 2270/02 : Internal refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/12 : External refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/66 : Closed external refrigeration cycle with multi component refrigerant [MCR], e.g. mixture of hydrocarbons
• CPC Class Codes: F25J 2290/12 : Particular process parameters like pressure, temperature, ratios
• 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 3/0242 : separation of CnHm with 3 carbon atoms or more
• CPC Class Codes: F25J 3/0247 : separation of CnHm with 4 carbon atoms 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 3/029 : of helium
• CPC Class Codes: Y10S 62/91 : Expander

Abstract

The invention is a process for liquefying a compound A from a mixture comprising at least compound A and at least one compound B. The mixture is available at a pressure P1 with separation of the at least one compounds B and/or of compound A being performed by distillation at a pressure substantially close to pressure P2 in order to produce at least a stream mainly comprising the compound A and at least a stream F4 comprising most of the at least one compound B. The invention has an application of methane and/or helium extraction during liquefaction of a natural gas.

Claims

1. A process for liquefying a compound A from a mixture comprising at least compound A and at least one compound B, each one of the at least one compound B having a lower boiling point than the compound A and the mixture being at a pressure P1, the liquefaction process comprising:

producing by expansion a gaseous effluent at a pressure P2 lower than P1 of a majority of the at least one compound B and a liquefied effluent at a pressure P3 lower than P2 of a majority of the compound A and substantially depleted of the at least one compound B; and

separating by distillation at least one of the at least one compound B and compound A at a pressure close to pressure P2 which produces at least a stream substantially comprising the compound A and a stream comprising a majority of the at least one compound B.

2. A process in accordance with claim 1 wherein:

separation is performed of each of the compound A and at least one of the compound B.

3. A process is claimed in claim 2, wherein:

the distillation is performed in a column which provides a condensed stream comprising at least one compound B and a part of the compound A and producing another stream including compound A and a majority of the at least one compound B with at least part of the another stream being used as reflux.

4. A process as claimed in claim 3, wherein:

the distillation is performed in a distillation column and;

the reflux is generated by heat exchange between a stream from the distillation column and at least one cold fluid is recovered after an expansion involved with the liquefied effluent.

5. A process as claimed in claim 4, wherein:

the at least one cold fluid recovered after expansion occurs in a liquid form at a bubble point.

6. A process as claimed in claim 2, wherein:

a value of the pressure before a first expansion ranges between 3 and 15 MPa and between 1 and 5 MPa after the first expansion.

7. A process as claimed in claim 2, wherein:

the first expansion is performed at a temperature ranging between -100°

C. and 0°

C.

8. A process as claimed in claim 2, further comprising:

using turbo-expanders to provide the expansion.

9. A process is claimed in claim 1, wherein:

the distillation is performed in a column which provides a condensed stream comprising at least one compound B and a part of the compound A and producing another stream including compound A and a majority of the at least one compound B with at least part of the another stream being used as reflux.

10. A process as claimed in claim 9, wherein:

the distillation is performed in a distillation column and;

the reflux is generated by heat exchange between a stream from the distillation column and at least one cold fluid is recovered after an expansion involved with the liquefied effluent.

11. A process as claimed in claim 10, wherein:

the at least one cold fluid recovered after expansion occurs in a liquid form at a bubble point.

12. A process as claimed in claim 10, wherein:

a value of the pressure before a first expansion ranges between 3 and 15 MPa and between 1 and 5 MPa after the first expansion.

13. A process as claimed in claim 10, wherein:

the first expansion is performed at a temperature ranging between -100°

C. and 0°

C.

14. A process as claimed in claim 9, wherein:

a value of the pressure before a first expansion ranges between 3 and 15 MPa and between 1 and 5 MPa after the first expansion.

15. A process as claimed in claim 9, wherein:

the first expansion is performed at a temperature ranging between -100°

C. and 0°

C.

16. A process as claimed in claim 1, wherein:

a value of the pressure before a first expansion ranges between 3 and 15 MPa and between 1 and 5 MPa after the first expansion.

17. A process as claimed in claim 1, wherein:

the first expansion is performed at a temperature ranging between -100°

C. and 0°

C.

18. A process as claimed in claim 1, wherein:

the mixture is refrigerated by using an external coolant before the expansion.

19. A process as claimed in claim 1 wherein:

the mixture is refrigerated by using an external coolant after the expansion.

20. A process as claimed in claim 1 wherein:

at least part of the separated stream comprising a majority of at least one compound B is used as a refrigeration agent for the liquified effluent.

21. A process as claimed in claim 1 wherein:

methane is compound A and one of nitrogen or helium are the at least one compound B.

22. An application of the process of claim 1 comprising:

extracting at least one of argon or nitrogen during liquefying air.