Method and apparatus for argon recovery in a cryogenic air separation unit integrated with a pressure swing adsorption system

Patent metadata

Field	Value
Publication number	US-10012437-B2
Application number	US-201615057152-A
Country	US
Kind code	B2
Filing date	Mar 1, 2016
Priority date	Jul 31, 2015
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

A method and apparatus for argon recovery in which an impure argon stream is separated from air within a cryogenic air separation unit having a divided wall argon rejection/rectification column. The resulting argon stream is subsequently recovered and purified within an integrated pressure swing adsorption system to produce product grade argon.

First claim

What is claimed is:

1. A method of producing a purified argon product stream in a cryogenic air separation unit, the method comprising the steps of:
separating argon from an oxygen-argon containing stream within a lower pressure column of the cryogenic air separation unit using an argon rectification column arrangement disposed within the lower pressure column, the separation of the argon from the oxygen-argon containing stream producing an impure argon stream having between about and 4% and 25% of oxygen impurities;
warming the impure argon stream via indirect heat exchange in an argon recovery heat exchanger against a purified argon stream from the pressure swing adsorption system, a waste gas stream from the pressure swing adsorption system, and against a balancing air stream of purified, compressed air from an incoming air purification and compression train or a main heat exchanger of the cryogenic air separation unit;
pressurizing the warmed impure argon stream; and
purifying the warmed, pressurized, impure argon stream by introducing the warmed, pressurized impure argon stream into a pressure swing adsorption system to produce the purified argon product stream and the waste gas stream;
wherein the impure argon stream is an impure gaseous argon stream diverted from an upper location of the argon rectification column arrangement disposed within the lower pressure column.

2. The method of claim 1 , further comprising the steps of condensing and subcooling the purified argon product stream via indirect heat exchange with a liquid nitrogen stream from the cryogenic air separation unit to produce a purified liquid argon product stream.

3. The method of claim 1 , further comprising the steps of removing nitrogen impurities from the purified argon product stream via a high ratio column to produce a nitrogen impurity free purified argon product stream.

4. The method of claim 1 , further comprising the step of recycling the waste gas stream to the argon rectification column arrangement after exit from the argon recovery heat exchanger.

5. The method of claim 1 , further comprising the step of combining or recycling the waste gas stream with the impure argon stream upstream of the pressure swing adsorption system after the impure argon stream exits from the argon recovery heat exchanger.

6. The method of claim 1 , wherein the balancing air stream is returned to a location upstream of a lower column turbine system of the cryogenic air separation unit after warming the impure argon stream.

7. The method of claim 1 , wherein the balancing air stream is returned to the higher pressure column of the cryogenic air separation unit after warming the impure argon stream.

8. The method of claim 7 , wherein the balancing air stream is an elevated pressure stream that is withdrawn from an intermediate location of the main heat exchanger of the cryogenic air separation unit and introduced to the argon recovery heat exchanger where it warms the impure argon stream and then is returned to a location upstream of the higher pressure column of the cryogenic air separation unit as a liquid air stream.

9. An apparatus for producing a purified argon product comprising:
a cryogenic air separation unit having a higher pressure column and a lower pressure column, and an argon rectification column arrangement disposed within the lower pressure column, the cryogenic air separation unit configured to produce an impure argon stream having between about and 4% and 25% of oxygen impurities from an oxygen-argon containing stream introduced from the lower pressure column to the argon rectification column arrangement;
an argon recovery heat exchanger configured to warm the impure argon stream to a temperature between about 200K and 300K against a stream of the purified argon stream from the pressure swing adsorption system, a waste gas stream from the pressure swing adsorption system, and a balancing air stream of purified, compressed air of the cryogenic air separation unit;
an argon compressor or pump configured for pressurizing the impure argon stream;
a pressure swing adsorption system configured for purifying the pressurized impure argon stream, the pressure swing adsorption system comprising an adsorbent bed having an adsorbent configured for adsorbing the oxygen impurities to produce the purified argon stream and the waste gas stream.

10. The apparatus of claim 9 , further comprising an argon condensing assembly disposed within the lower pressure column at a location above the argon rectification column arrangement and wherein the impure argon stream is an impure gaseous argon stream diverted from an upper location of the argon rectification column arrangement or upstream of an argon condensing assembly.

11. The apparatus of claim 9 further comprising a recycle conduit disposed between the pressure swing adsorption system and the argon rectification column arrangement configured for recycling the waste gas stream to the argon rectification column arrangement disposed within the lower pressure column after exit from the argon recovery heat exchanger.

12. The apparatus of claim 9 , further comprising a recycle conduit disposed between the pressure swing adsorption system and the argon rectification column arrangement and configured for recycling the waste gas stream and combining the recycled waste gas with the impure argon stream upstream of the pressure swing adsorption system after the impure argon stream exits from the argon recovery heat exchanger.

13. The apparatus of claim 10 , further comprising a warm air balancing circuit configured to supply the balancing air stream from an incoming air purification and compression train of the cryogenic air separation unit to the heat exchanger argon recovery where it warms the impure argon stream and return the balancing air stream to a location upstream of a lower column turbine system of the cryogenic air separation unit.

14. The apparatus of claim 10 , further comprising a warm air balancing circuit configured to supply the balancing air stream from an incoming air purification and compression train of the cryogenic air separation unit to the heat exchanger argon recovery where it warms the impure argon stream and return the balancing air stream to the higher pressure column of the cryogenic air separation unit.

15. A method of producing a purified argon product stream in a cryogenic air separation unit, the method comprising the steps of:
separating argon from an oxygen-argon containing stream within a lower pressure column of the cryogenic air separation unit using an argon rectification column arrangement disposed within the lower pressure column, the separation of the argon from the oxygen-argon containing stream producing an impure argon stream having between about and 4% and 25% of oxygen impurities;
warming the impure argon stream against the purified argon product stream and against a balancing air stream of purified, compressed air;
pressurizing the warm impure argon stream; and
purifying the warm, pressurized, impure argon stream by introducing the warm, pressurized impure argon stream into a pressure swing adsorption system to produce the purified argon product stream and a waste gas stream
wherein the balancing air stream is returned to a location upstream of a lower column turbine system of the cryogenic air separation unit after warming the impure argon stream.

16. The method of claim 15 , further comprising the steps of removing nitrogen impurities from the purified argon product stream via a high ratio column to produce a nitrogen impurity free purified argon prod

Assignees

• Du Hai
• Prosser Neil M
• Luo Yang
• Stephenson Neil A
• Praxair Technology Inc

Inventors

• Du Hai
• Prosser Neil M
• Luo Yang
• Stephenson Neil A

Classifications

• F25J3/04103

  using solely hydrostatic liquid head · CPC title

• B01D2256/18

  Noble gases · CPC title

• F25J3/04412 Primary

  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 title

• C01B2210/0034

  Argon · CPC title

• B01D53/047

  Pressure swing adsorption · CPC title