Purification of argon through liquid phase cryogenic adsorption

Patent metadata

Field	Value
Publication number	US-9772139-B2
Application number	US-201514948959-A
Country	US
Kind code	B2
Filing date	Nov 23, 2015
Priority date	Mar 1, 2013
Publication date	Sep 26, 2017
Grant date	Sep 26, 2017

Abstract

The invention relates to a process for removing oxygen from liquid argon using a TSA (temperature swing adsorption) cyclical process that includes cooling an adsorbent bed to sustain argon in a liquid phase; supplying the adsorbent bed with a liquid argon feed that is contaminated with oxygen and purifying the liquid argon thereby producing an argon product with less oxygen contaminant than is in the initial liquid argon feed; draining the purified residual liquid argon product and sending purified argon out of the adsorbent bed. Regeneration of specially prepared adsorbent allows the adsorbent bed to warm up to temperatures that preclude the use of requiring either vacuum or evacuation of adsorbent from the bed.

First claim

What is claimed is:

1. An adsorption process for purifying a feed stream containing primarily liquid argon and oxygen employing an adsorbent exhibiting a faster rate of adsorption of oxygen and a slower rate of argon under the liquid argon feed conditions, comprising the following cycle of process steps:
a) supplying from the inlet of an adsorbent bed said liquid argon feed that contains oxygen in an amount of more than 10 parts per million and less or equal to 10,000 parts per million, adsorbing at least part of the oxygen on the adsorbent, at or below cryogenic temperatures, thereby producing a purified liquid argon product leaving said adsorbent bed from the outlet with less than or equal to 10 parts per million oxygen present in said purified liquid argon product;
b) draining from said adsorbent bed purified residual liquid argon by introducing a displacement purge gas;
c) allowing said adsorbent bed containing said adsorbent to warm to a temperature, desorbing at least part of the adsorbed oxygen and removing said adsorbed oxygen from the adsorbent bed such that the liquid argon feed may be supplied for purposes of repeating the cycle;
d) indirectly cooling said adsorbent bed having an inlet and an outlet and containing an adsorbent such that said adsorbent bed is indirectly cooled to a temperature below the boiling point of argon;
e) wherein said process steps (a)-(d) are repeated in a cyclical manner.

2. The process of claim 1 , wherein the liquid argon feed for step (a) contains oxygen in the concentration range of about 10 parts per million and wherein removal of said oxygen from said liquid argon feed results in a purified liquid argon product with less than or equal to 1 parts per million of oxygen.

3. The process of claim 1 , wherein the liquid argon feed temperature for step (a) is less than the boiling point of argon and the feed pressure is greater than or equal to 20 psig.

4. The process of claim 1 , wherein the purified residual liquid argon is drained from the adsorbent bed in step (b) using a nitrogen purge.

5. The process of claim 1 , wherein the purified residual liquid argon is drained from the adsorbent bed in step (b) using an argon purge.

6. The process of claim 1 , wherein the warming of the adsorbent bed in step (c) is carried out by first removing the liquid nitrogen used for indirect cooling and subsequently by purging the adsorbent bed with gaseous nitrogen having a temperature of at least 200 degrees Kelvin and a pressure of at least 2 psig.

7. The process of claim 6 , wherein the warming of the adsorbent bed in step (c) is continued until the adsorbent bed reaches a temperature of at least 200 degrees Kelvin.

8. The process of claim 7 , wherein following the warming of the adsorbent bed, a gaseous argon purge having a temperature of at least 200 degrees Kelvin and a pressure of at least 2 psig is carried out until the effluent from the bed is predominantly argon.

9. The process of claim 1 , wherein the warming of the adsorbent bed in step (c) is carried out by first removing the liquid nitrogen used for indirect cooling and subsequently by purging the adsorbent bed with gaseous argon having a temperature of at least 200 degrees Kelvin and a pressure of at least 2 psig.

10. The process of claim 9 , wherein the warming of the adsorbent bed in step (c) is continued until the adsorbent bed reaches a temperature of at least 200 degrees Kelvin.

11. The process of claim 1 , wherein cooling step (d) is carried out firstly by indirect cooling using liquid nitrogen until the adsorbent bed reaches a temperature of less than about 150 degrees Kelvin and subsequently by direct cooling using liquid argon wherein the cooling step is complete when the adsorbent bed, containing adsorbent, sustains the argon feed in a liquid phase.

12. The process of claim 11 , wherein the liquid argon for use in cooling step (d) is at least partially recovered from said adsorbent bed during the purification step (a).

13. The process of claim 1 , wherein the dynamic capacity of the adsorbent for oxygen to 1 part per million of oxygen of step (a) of subsequent adsorption cycles is at least 80 percent of said dynamic capacity of the adsorbent for oxygen for step (a) of the first adsorption process cycle.

14. The process of claim 1 , further comprising a second adsorbent bed wherein said second adsorbent bed is operated such that it is purifying liquid argon feed in step (a) while the first adsorbent bed is being regenerated by steps (b), (c) and cooled by step (d) and correspondingly the second adsorbed bed is regenerated by steps (b), (c) and cooled by step (d) while said first adsorbent bed is purifying the liquid argon feed in step (a), so as to produce a purified liquid argon product stream continuously.

Assignees

• Praxair Technology Inc

Inventors

• Kechagia Persefoni E
• Stephenson Neil A
• Barrett Philip A
• Du Hai
• Pontonio Steven J

Classifications

• C01B23/0068

  Zeolites · CPC title

• C01B2210/0034

  Argon · CPC title

• C01B23/0078

  Temperature swing adsorption · CPC title

• C01B2210/0021

  Temperature swing adsorption · CPC title

• C01B2210/0045

  Oxygen · CPC title