Cryogenic air separation system for producing gaseous oxygen

• US 5,265,429 A
• Filed: 02/21/1992
• Issued: 11/30/1993
• Est. Priority Date: 02/21/1992
• Status: Expired due to Fees

• Current Assignee: Praxair Technology Incorporated (Linde Plc)
• Original Assignee: Praxair Technology Incorporated (Linde Plc)
• Inventors: Dray, James R.
• Primary Examiner(s): Bennett, Henry A.
• Assistant Examiner(s): KILNER, CHRISTOPHER B
• Application Number:
  US07/838,894
• Time in Patent Office: 648 Days
• Field of Search: 62/22, 62/24, 62/13, 62/25, 62/37, 62/38, 62/40, 62/41, 62/42
• US Class Current: 62/646
• CPC Class Codes: F25J 2205/02 using simple phase separation in a vessel or drum
• CPC Class Codes: F25J 2250/40 One fluid being air
• CPC Class Codes: F25J 2250/50 One fluid being oxygen
• CPC Class Codes: F25J 2250/58 One fluid being argon or crude argon
• CPC Class Codes: F25J 3/0409 of oxygen
• CPC Class Codes: F25J 3/04206 including a so-called "auxiliary vaporiser" for vaporising and producing a gaseous product
• CPC Class Codes: F25J 3/0423 Subcooling of liquid process streams
• CPC Class Codes: F25J 3/04296 Claude expansion, i.e. expanded into the main or high pressure column
• CPC Class Codes: F25J 3/04412 in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
• CPC Class Codes: F25J 3/04515 Simultaneously changing air feed and products output
• CPC Class Codes: F25J 3/04678 cooled by oxygen enriched liquid from high pressure column bottoms
• CPC Class Codes: Y10S 62/924 Argon
• CPC Class Codes: Y10S 62/94 High pressure column

Abstract

A cryogenic air separation system employing a product boiler coupled with a liquid air supply whereby liquid oxygen is effectively vaporized to produce gaseous oxygen product while providing for steady state operation of the cryogenic air separation plant without significant refrigeration loss.

Claims

1. A method for producing gaseous oxygen by the cryogenic rectification of feed air comprising:

(A) passing a fraction of the feed air into a product boiler and condensing feed air by indirect heat exchange with liquid oxygen in the product boiler;

(B) passing condensed feed air into a cryogenic rectification plant comprising a higher pressure column and a lower pressure column and producing liquid oxygen therein;

(C) passing liquid oxygen produced in the cryogenic rectification plant to the product boiler to carry out the condensation of the feed air, and recovering gaseous oxygen from the product boiler as product;

(D) pumping liquid oxygen produced in the cryogenic rectification plant and thereafter passing the pumped liquid oxygen into a liquid oxygen tank to produce a supply of liquid oxygen;

(E) increasing the flow of liquid oxygen to the product boiler by passing liquid oxygen from the liquid oxygen supply to the product boiler and commensurately increasing the flow of feed air to the product boiler to produce excess condensed feed air;

(F) passing excess condensed feed air produced in the product boiler into a liquid air tank to produce a supply of liquid air while continuing to pass condensed feed air into the cryogenic rectification plant without passing through the liquid air tank; and

(G) turboexpanding another fraction of the feed air and passing the turboexpanded feed air fraction into the higher pressure column.

2. The method of claim 1 further comprising passing an argon-containing fluid from the cryogenic rectification plant into an argon column and recovering an argon fluid having an argon concentration of at least 95 percent from the argon column.

5. The method of claim 1 further comprising cooling condensed feed air by indirect heat exchange with liquid oxygen prior to passing the condensed feed air into the cryogenic rectification plant.

3. A cryogenic air separation plant for producing gaseous oxygen comprising:

(A) a product boiler, means for supplying feed air to the product boiler, and means for passing liquid from the product boiler to a cryogenic rectification plant comprising a higher pressure column and a lower pressure column;

(B) means for passing liquid from the cryogenic rectification plant into the product boiler and means for recovering gaseous product from the product boiler;

(C) a liquid oxygen tank, a pump, means for passing liquid from the cryogenic rectification plant to the pump and from the pump into the liquid oxygen tank, and means for passing liquid from the liquid oxygen tank into the product boiler;

(D) a liquid air tank, means for passing liquid from the product boiler into the liquid air tank, and means for passing liquid from the liquid air tank into the cryogenic rectification plant and wherein the said means for passing liquid from the product boiler to the cryogenic rectification plant in clause (A) does not include the liquid air tank; and

(E) a turboexpander, means for passing feed air into the turboexpander, and means for passing feed air from the turboexpander into the higher pressure column.

4. The cryogenic air separation plant of claim 3 further comprising an argon column, means for passing fluid from the cryogenic rectification plant into the argon column, and means for recovering fluid from the argon column.

6. The cryogenic air separation plant of claim 3 further comprising a heat exchanger, means for passing liquid from the product boiler to the heat exchanger, and means for passing liquid from the heat exchanger into the cryogenic rectification plant.