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

Patent metadata

Field	Value
Publication number	US-10145609-B2
Application number	US-201816009635-A
Country	US
Kind code	B2
Filing date	Jun 15, 2018
Priority date	Jul 31, 2015
Publication date	Dec 4, 2018
Grant date	Dec 4, 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 an argon rejection column and a reflux type argon condenser disposed internally within the lower pressure column. An impure argon stream is subsequently recovered from the argon rejection column and purified within an integrated adsorbent based argon refining and purification subsystem to produce product grade argon. The waste stream from the adsorbent based argon refining and purification subsystem is recycled back to the argon rejection column so as to improve the argon recovery.

First claim

What is claimed is:

1. A method of producing a purified argon product stream in a cryogenic air separation unit having a higher pressure column, a lower pressure column, an argon column, and an argon condenser, the method comprising the steps of:
extracting an oxygen-argon containing stream from an intermediate location of the lower pressure column of the cryogenic air separation unit;
separating argon from the oxygen-argon containing stream within the argon column to produce an argon-rich overhead vapor stream and an oxygen rich liquid bottoms stream;
condensing at least a portion of the argon-rich overhead vapor stream from the argon column against an oxygen enriched liquid stream to produce the argon-rich reflux stream;
directing at least a portion of the oxygen rich liquid bottoms stream to the lower pressure column at a location below the intermediate location;
directing at least a portion of the produce the argon-rich reflux stream to the argon column as reflux;
producing an impure argon stream by diverting another portion of the argon-rich overhead vapor stream as the impure argon stream from the argon column or diverting a portion of the argon-rich reflux stream as the impure argon stream from argon condenser, the impure argon stream having between about and 4% and 25% of oxygen impurities;
warming the impure argon stream;
pressurizing the warmed, impure argon stream;
purifying the warm, pressurized, impure argon stream in a pressure swing adsorption system to produce a purified argon product stream and a waste gas stream; and
recycling the waste gas stream from the pressure swing adsorption system to the argon column or the lower pressure column;
wherein the impure argon stream is warmed against the purified argon product stream, the waste gas stream from the pressure swing adsorption system, and a balancing air stream of purified, compressed air.

2. The method of claim 1 , further comprising the steps of subcooling the purified argon product stream via indirect heat 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 , 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.

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

5. The method of claim 1 , wherein the argon condenser is disposed within the lower pressure column above the intermediate location.

6. The method of claim 5 , wherein the argon column and the lower pressure column are disposed within a lower pressure column shell and form a divided wall column arrangement.

7. An air separation system for producing a purified argon product stream comprising:
an incoming air purification and compression train or subsystem configured for receiving a feed air stream and producing a compressed and pre-purified air stream;
a main heat exchange subsystem coupled to the incoming air purification and compression train or subsystem and configured to cool the compressed and pre-purified feed air stream to temperatures suitable for rectification;
a distillation column subsystem having a higher pressure column, a lower pressure column, an argon column and an argon condenser configured to separate the cooled, compressed and pre-purified feed air stream into oxygen-rich product stream, one or more nitrogen-rich streams, and an impure argon stream having between about and 4% and 25% of oxygen impurities;
an auxiliary heat exchanger configured to warm the impure argon stream against a stream of a purified argon product stream from a pressure swing adsorption system, a waste gas stream from the pressure swing adsorption system, and a balancing air stream of purified, compressed air;
an argon compressor or pump disposed downstream of the argon column and configured for pressurizing the warmed, impure argon stream;
the pressure swing adsorption system is disposed downstream of the argon compressor or pump and configured for purifying the warmed, pressurized impure argon stream and produce the purified argon product stream and the waste gas stream; and
a recycling circuit connecting the pressure swing adsorption system with the argon column and configured to direct the waste gas stream from the pressure swing adsorption system to the argon column;
wherein the argon column is configured for separating argon from an oxygen-argon containing stream extracted from the lower pressure column at an intermediate location and to produce an argon-rich overhead vapor stream and an oxygen rich liquid bottoms stream, and wherein the oxygen rich liquid bottoms stream is returned to the lower pressure column at a location below the intermediate location;
wherein the argon condenser is configured for condensing at least a portion of the argon-rich overhead vapor stream from the argon column against an oxygen enriched liquid stream to produce an argon-rich reflux stream and wherein at least a portion of the argon-rich reflux stream is returned to the argon column as reflux; and
wherein the impure argon stream comprises another portion of the argon-rich overhead vapor stream from the argon column or a portion of the argon-rich reflux stream from argon condenser.

8. The air separation system of claim 7 , wherein the auxiliary heat exchanger is further configured to subcool the purified argon product stream via indirect heat with a nitrogen rich liquid stream from the distillation column subsystem to produce a purified liquid argon product stream.

9. The air separation system of claim 7 , further comprising a subcooler fluidically coupled to the auxiliary heat exchanger and the distillation column subsystem, the subcooler being configured to subcool the purified argon product stream via indirect heat with a nitrogen rich liquid stream from the distillation column subsystem to produce a purified liquid argon product stream.

10. The air separation system of claim 7 , further comprising a balancing air return conduit coupled to the auxiliary heat exchanger and configured for recycling the cooled balancing air stream exiting the auxiliary heat exchanger to a location upstream of a lower column turbine system of the incoming air purification and compression train or subsystem.

11. The air separation system of claim 7 , further comprising a balancing air return conduit coupled to the auxiliary heat exchanger and configured for recycling the cooled balancing air stream exiting the auxiliary heat exchanger to a location upstream of the higher pressure column of the distillation column subsystem.

12. The air separation system of claim 7 , wherein the argon condenser is disposed within the lower pressure column above the intermediate location.

13. The air separation system of claim 7 , wherein the argon column and the lower pressure column are disposed within a lower pressure column shell and form a divided wall column arrangement.

Assignees

• Prosser Neil M
• Luo Yang
• Praxair Technology Inc

Inventors

• Prosser Neil M
• Luo Yang

Classifications

• F25J3/04739

  in combination with an auxiliary pure argon column · CPC title

• F25J2205/02

  using simple phase separation in a vessel or drum · CPC title

• B01D2257/102

  Nitrogen · CPC title

• F25J2200/80

  using integrated mass and heat exchange, i.e. non-adiabatic rectification in a reflux exchanger or dephlegmator · CPC title

• F25J3/04296

  Claude expansion, i.e. expanded into the main or high pressure column · CPC title