Refrigeration system

• US 5,483,806 A
• Filed: 05/12/1995
• Issued: 01/16/1996
• Est. Priority Date: 05/16/1994
• Status: Expired due to Term

• Current Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Original Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Inventors: Allam, Rodney J., Smith, Colin D., Miller, Jeremy P., Topham, Anthony K. J.
• Primary Examiner(s): KILNER, CHRISTOPHER B
• Application Number:
  US08/439,802
• Time in Patent Office: 249 Days
• Field of Search: 62/40, 62/402, 62/401
• US Class Current: 62/402
• CPC Class Codes: F25B 9/004 the refrigerant being air
• CPC Class Codes: F25J 1/005 by expansion of a gaseous refrigerant stream with extraction of work
• CPC Class Codes: F25J 1/007 Primary atmospheric gases, mixtures thereof
• 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 1/0265 comprising cores associated exclusively with the cooling of a refrigerant stream, e.g. for auto-refrigeration or economizer
• CPC Class Codes: F25J 1/0284 Electrical motor as the prime mechanical driver
• 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 2230/20 Integrated compressor and process expander; Gear box arrangement; Multiple compressors on a common shaft
• CPC Class Codes: F25J 2270/912 Liquefaction cycle of a low-boiling (feed) gas in a cryocooler, i.e. in a closed-loop refrigerator

Abstract

A refrigeration system using air as the refrigerant comprises a compressor which compresses air to 84 bar g. The compressed air is cooled first by cooling water and then by returning air in a plate-fin heat exchanger before being expanded to 59 bar g in an expander. The expanded air at -61° C. is passed through indirect cooling coils in a cold store which it leaves at -45° C. This air is then passed through the plate-fin heat exchanger before being recycled to the compressor. The refrigeration delivered is about 1.05 kw refrigeration/kw power input.

Claims

1. A refrigeration system comprising:

(i) a compressor for compressing air, nitrogen or nitrogen enriched air to a pressure of from 20 bar g to 140 bar g;

(ii) a heat exchanger for cooling said compressed air, nitrogen or nitrogen enriched air;

(iii) an expander for expanding said cooled compressed air, nitrogen or nitrogen enriched air to a pressure in the range of from 15 bar g to 110 bar g;

(iv) a cooling device for receiving cold expanded air, nitrogen or nitrogen enriched air; and

(v) means for conveying air, nitrogen or nitrogen enriched air from said cooling device at a temperature of from -20°

C. to -120°

C. to said heat exchanger for cooling said air, nitrogen or nitrogen enriched air.

2. A refrigeration system as claimed in claim 1, further comprising means to recycle said air, nitrogen or nitrogen enriched air to said compressor.

3. A refrigeration system as claimed in claim 1, wherein said heat exchanger is a plate fin heat exchanger.

4. A refrigeration system as claimed in claim 1, wherein said compressor is connected to said expander via a gear system so that, in use, the speed of rotation of the expander is in a fixed ratio to the speed of rotation of the compressor.

5. A method of operating a refrigeration system, which method comprises the steps of:

(i) compressing air, nitrogen or nitrogen enriched air to a pressure from 20 bar g to 140 bar g in a compressor;

(ii) cooling said compressed air, nitrogen or nitrogen enriched air in a heat exchanger;

(iii) expanding said compressed air, nitrogen or nitrogen enriched air in an expander to a pressure in the range of from 15 bar g to 110 bar g;

(iv) using said expanded air, nitrogen or nitrogen enriched air to cool a refrigerated space;

(v) withdrawing said expanded air, nitrogen or nitrogen enriched air from said refrigerated space at a temperature of from -20°

C. to -120°

C.; and

(vi) introducing said expanded air, nitrogen or nitrogen enriched air withdrawn from said refrigerated system into said heat exchanger for at least partially cooling said compressed air, nitrogen or nitrogen enriched air prior to expansion thereof.

6. A method according to claim 5, wherein said expanded air, nitrogen or nitrogen enriched air is withdrawn from said refrigerated space at a temperature of from -20°

C. to -100°

C.

7. A method according to claim 5, wherein the pressure of the expanded air, nitrogen or nitrogen enriched air from step (iii) is from 0.6 to 0.85 the pressure of the compressed air from step (i).

8. A method according to claim 5, including the step of recycling air, nitrogen or nitrogen enriched from step (vi) for recompression.

9. A method according to claim 5, wherein said air, nitrogen or nitrogen enriched air is compressed to a pressure of from 70 bar g to 100 bar g.

10. A method according to claim 9, wherein said air, nitrogen or nitrogen enriched air is compressed to a pressure of from 80 bar g to 90 bar g.

11. A method according to claim 8, wherein said air, nitrogen or nitrogen enriched air is expanded to a pressure of from 50 bar g to 80 bar g.

12. A method according to claim 11, wherein said air, nitrogen or nitrogen enriched air is expanded to a pressure of from 50 bar g to 70 bar g.

13. A method according to claim 8, wherein said expanded air, nitrogen or nitrogen enriched air is withdrawn from said refrigerated space at a temperature of from -30°

C. to -100°

C.

14. A method according to claim 13, where said expanded air, nitrogen or nitrogen enriched air is withdrawn from said refrigerated system at a temperature of from -30°

C. to -50°

C.

15. A method according to claim 14, wherein said expanded air, nitrogen or nitrogen enriched air is withdrawn from said refrigerated space at a temperature of -35°

C. to -45°

C.

16. A method according to claim 15, wherein said expanded air, nitrogen or nitrogen enriched air is withdrawn from said refrigerated space at a temperature of from -70°

C. to -90°

C.

17. A method according to claim 16, wherein said expanded air, nitrogen or nitrogen enriched air is withdrawn from said refrigerated space at a temperature of from -75°

C. to -85°

C.

20. A method according to claim 5, wherein said air, nitrogen or nitrogen enriched air is compressed to a pressure of from 70 bar g to 100 bar g.

18. A method of operating a refrigeration system, which method comprises the steps of:

(i) compressing air, nitrogen or nitrogen enriched air to a pressure from 20 bar g to 140 bar g in a compressor;

(ii) cooling said compressed air, nitrogen or nitrogen enriched air in a heat exchanger;

(iii) expanding said compressed air, nitrogen or nitrogen enriched air in an expander to a pressure which is in the range of from 15 bar g to 110 bar g and is also in the range of from 0.6 to 0.85 the pressure of the compressed air, nitrogen or nitrogen enriched air from step (i);

(iv) using said expanded air, nitrogen or nitrogen enriched air to cool a refrigerated space;

(v) withdrawing said expanded air, nitrogen or nitrogen enriched air from said refrigerated space at a temperature of from -20°

C. to -120°

C.;

(vi) introducing said expanded air, nitrogen or nitrogen enriched air withdrawn from said refrigerated system into said heat exchanger for at least partially cooling said compressed air, nitrogen or nitrogen enriched air prior to expansion thereof; and

(vii) recycling air, nitrogen or nitrogen enriched from step (vi) for recompression.

19. A method according to claim 18, wherein said expanded air, nitrogen or nitrogen enriched air is withdrawn from said refrigerated space at a temperature of from -20°

C. to -100°

C.

21. A method according to claim 18, wherein said expanded air, nitrogen or nitrogen enriched air is withdrawn from said refrigerated space at a temperature of from -30°

C. to -100°

C.