Process to produce liquid cryogen

• US 4,778,497 A
• Filed: 06/02/1987
• Issued: 10/18/1988
• Est. Priority Date: 06/02/1987
• Status: Expired due to Fees

• Current Assignee: Praxair Technology Incorporated (Linde Plc)
• Original Assignee: Union Carbide Corporation (Dow, Inc.)
• Inventors: Hanson, Thomas C., Kun, Leslie C.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/056,702
• Time in Patent Office: 504 Days
• Field of Search: 62/9, 62/11, 62/23, 62/24, 62/25, 62/26, 62/29, 62/30, 62/36, 62/38, 62/41, 62/42, 62/43, 62/44
• US Class Current: 62/613
• CPC Class Codes: F25J 1/0007 Helium
• CPC Class Codes: F25J 1/001 Hydrogen
• CPC Class Codes: F25J 1/0012 Primary atmospheric gases, e.g. air
• CPC Class Codes: F25J 1/0015 Nitrogen
• CPC Class Codes: F25J 1/0017 Oxygen
• 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 1/0037 of a return stream
• 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 1/0202 in a quasi-closed internal refrigeration loop F25J1/0208, F25J1/0219, F25J1/0224 take precedence
• 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 1/0294 Multiple compressor casings/strings in parallel, e.g. split arrangement
• 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 2270/06 with multiple gas expansion loops
• CPC Class Codes: F25J 2290/34 Details about subcooling of liquids

Abstract

A process to produce liquid cryogen wherein subcooled supercritical liquid is expanded without vaporization and a portion thereof is used to carry out the subcooling by vaporization under reduced pressure.

Claims

1. A process for the production of liquid cryogen comprising:

(A) compressing feed gas to a pressure at least equal to its critical pressure;

(B) cooling the compressed gas to produce cold supercritical fluid;

(C) subcooling the cold supercritical fluid to produce cold supercritical liquid;

(D) expanding the cold supercritical liquid to produce liquid cryogen essentially without formation of vapor land thereafter further expanding a first portion of the expanded liquid cryogen to a lower pressure;

(E) vaporizing said further expanded first portion by indirect heat exchange with subcooling cold supercritical fluid of step (C); and

(F) recovering the remaining second portion of liquid cryogen as liquid product.

2. The process of claim 1 wherein the first portion comprises from 5 to 20 percent of the liquid cryogen.

3. The process of claim 1 wherein the feed gas is nitrogen.

4. The process of claim 1 wherein the feed gas is taken from a cryogenic air separation plant.

5. The process of claim 1 wherein the vaporized first portion is warmed by indirect heat exchange against cooling compressed gas of step (B).

6. The process of claim 5 wherein the warmed first portion is combined with feed gas and recycled through the process.

7. The process of claim 6 wherein the warmed first portion is compressed, prior to combination with feed gas, by compressor means powered by the expansion of step (D).

8. The process of claim 1 wherein the feed gas is compressed by compressor means powered by expansion of some of the compressed gas through expander means.

9. The process of claim 8 wherein feed gas in divided into two portions, each portion separately compressed by separate compressor means powered by expansion of some of the compressed gas through expander means, and the compressd portions recombined prior to the cooling of step (B).

10. The process of claim 8 wherein output from the expander means is warmed by indirect heat exchange against cooling compressed gas of step (B).

11. The process of claim 10 wherein the warmed expander means output is combined with feed gas and recycled through the process.

12. A process for the production of liquid cryogen comprising:

(A) compressing feed gas to a pressure at least equal to its critical pressure;

(B) cooling the compressed gas to produce cold supercritical fluid;

(C) expanding the cold supercritical fluid to produce lower pressure fluid;

(D) cooling lower pressure fluid to produce liquid cryogen and thereafter expanding a first portion of the liquid cryogen to a lower pressure;

(E) vaporizing said expanded first portion by indirect heat exchange with the cooling lower pressure fluid of step (D); and

(F) recovering the remaining second portion of liquid cryogen as liquid product.

13. The process of claim 12 wherein the first portion comprises from 5 to 20 percent of the liquid cryogen.

14. The process of claim 12 wherein the feed gas is nitrogen.

15. The process of claim 12 wherein the feed gas is taken from a cryogenic air separation plant.

16. The process of claim 12 wherein the vaporized first portion is warmed by indirect heat exchange against cooling compressed gas of step (B).

17. The process of claim 16 wherein the warmed first portion is combined with feed gas and recycled through the process.

18. The process of claim 17 wherein the warmed first portion is compressed, prior to combination with feed gas, by compressor means powered by the expansion of step (C).

19. The process of claim 12 wherein feed gas is compressed by compressor means powered by expansion of some of the compressed gas through expander means.

20. The process of claim 19 wherein feed gas is divided into two portions, each portion separately compressed by separate compressor means powered by expansion of some of the compressed gas through expander means, and the compressed portions recombined prior to the cooling of step (B).

21. The process of claim 19 wherein output from the expander means is warmed by indirect heat exchange against cooling compressed gas of step (B).

22. The process of claim 21 wherein the warmed expander means output is combined with feed gas and recycled through the process.

23. A process for the production of liquid cryogen comprising:

(A) dividing feed gas into two portions, compressing each portion separately to a pressure at least equal to its critical pressure by separate compressor means powered by expansion of some of the compressed gas through expander means, and recombining the compressed portions to form compressed gas;

(B) cooling the compressed gas to produce cold supercritical fluid;

(C) subcooling the cold supercritical fluid to produce cold supercritical liquid;

(D) expanding the cold supercritical liquid to produce liquid cryogen essentially without formation of vapor;

(E) vaporizing a first portion of the expanded liquid cryogen by indirect heat exchange with subcooling cold supercritical fluid of step (C); and

(F) recovering a second portion of liquid cryogen as product.

24. A process for the production of liquid cryogen comprising:

(A) dividing feed gas into two portions, compressing each portion separately to a pressure at least equal to its critical pressure by separate compressor means powered by expansion of some of the compressed gas through expander means, and recombining the compressed portions to form compressd gas;

(B) cooling the compressed gas to produce cold supercritical fluid;

(C) expanding the cold supercritical fluid to produce lower pressure fluid;

(D) cooling lower pressure fluid to produce liquid cryogen;

(E) vaporizing a first portion of the liquid cryogen by indirect heat exchange with the cooling lower pressure fluid of step (D); and

(F) recovering a second portion of liquid cryogen as product.