Process for operating a heat exchanger

• US 5,233,839 A
• Filed: 07/02/1992
• Issued: 08/10/1993
• Est. Priority Date: 03/13/1991
• Status: Expired due to Fees

• Current Assignee: L'Air Liquide Societe Anonyme Pour L'Etude et L'Exploitation Des Procedes Georges Claude (L'Air Liquide SA)
• Original Assignee: L'Air Liquide Societe Anonyme Pour L'Etude et L'Exploitation Des Procedes Georges Claude (L'Air Liquide SA)
• Inventors: Greter, Lucien, Venet, Francois
• Primary Examiner(s): Ford, John K.
• Application Number:
  US07/907,707
• Time in Patent Office: 404 Days
• Field of Search: 62/36, 62/40, 165/166, 165/167
• US Class Current: 165/166
• CPC Class Codes: F25J 2210/42 Nitrogen
• CPC Class Codes: F25J 2245/90 the recycled stream being boil-off gas from storage
• CPC Class Codes: F25J 2280/20 Control for stopping, deriming or defrosting after an emergency shut-down of the installation or for back up system
• CPC Class Codes: F25J 2280/30 Control of a discontinuous or intermittent ("batch") process
• CPC Class Codes: F25J 2290/42 Modularity, pre-fabrication of modules, assembling and erection, horizontal layout, i.e. plot plan, and vertical arrangement of parts of the cryogenic unit, e.g. of the cold box
• CPC Class Codes: F25J 3/04787 Heat exchange, e.g. main heat exchange line; Subcooler, external reboiler-condenser F25J3/04793 and F25J3/0486 take precedence
• CPC Class Codes: F25J 3/04824 Stopping of the process, e.g. defrosting or deriming; Back-up procedures
• CPC Class Codes: F25J 3/04842 Intermittent process, so-called batch process
• CPC Class Codes: F25J 5/002 for continuously recuperating cold, i.e. in a so-called recuperative heat exchanger
• CPC Class Codes: Y10S 62/903 Heat exchange structure

Abstract

The invention aims at preventing the risks of deformation and breaking down of the heat exchanger which is part of a plant for the batch treatment of fluids, of the type in which, during active periods which are separated from one another by rest periods, at least one refrigerating fluid is allowed to circulate in first ducts of the exchanger, from the cold end to the hot end of the latter, and at least one calorigenic fluid is circulated in second ducts of the exchanger, from the hot end to the cold end of the latter, characterized in that, during rest periods, heat is introduced at the hot end and cold is introduced at the cold end of the exchanger so as to maintain these two ends at temperatures which are relatively close to those corresponding to the active periods, at least one of these two inputs being supplied by means of a reserve fluid of the plant.

Claims

1. Process for operating a heat exchanger which is part of a plant for the batch treatment of fluids, in which during active periods which are separated from one another by rest periods, at least one refrigerating fluid is allowed to circulate in first ducts of the exchanger, from the cold end to the hot end of the latter, and at least one calorigenic fluid circulates in second ducts of the exchanger, from the hot end to the cold end of the latter, wherein during rest periods, heat is introduced at the hot end and cold is introduced at the cold end of the exchanger so as to keep these two ends at temperatures which are relatively close to those corresponding to the active periods, at least one of these two inputs being supplied by means of a reserve fluid of the plant.

2. Process according to claim 1, wherein at the end of each rest period, said quantities of heat and/or cold are progressively increased to progressively bring the temperatures of the two ends of the exchanger to temperatures corresponding to the active periods.

3. Process according to claim 1, in which, during the active periods, one of the two ends of the exchanger is at a temperature near room temperature, wherein this end of the exchanger is placed in heat exchange relationship with outer atmosphere during the rest periods.

4. Process according to claim 1, for a cryogenic plant, wherein the hot end is placed in heat exchange relationship with outside atmosphere, by conduction, and the cold end is placed in heat exchange relationship with evaporations from a reserve cryogenic fluid of the plant.

5. Process according to claim 4, wherein during the rest periods, an additional quantity of heat is brought to the hot end.

6. Process according to claim 5, wherein said additional quantity of heat is constant, and the circulation of said evaporations is carried out when the temperature at the hot end exceeds an upper limit and is interrupted when it becomes below a lower limit.

7. Process according to claim 5, which comprises circulating said evaporations from the cold end to the hot end of the exchanger, through said second ducts of the exchanger.

8. Process according to claim 5, wherein said additional quantity of heat is provided by the Joule effect.

9. Process according to claim 5, which comprises circulating said evaporations from the cold end to the hot end of the heat exchanger through ducts especially provided for this purpose.