Process for removing oxygen from a hydrogen stream
An adsorption process is provided to remove oxygen from a hydrogen stream through the use of a copper material in combination with layers of adsorbent to remove water and nitrogen from a hydrogen stream. This process is particularly useful for purification of hydrogen product gas from water electrolyzers with the hydrogen product gas having greater than 99.9 mol % purity.
1. A process for producing a high-purity hydrogen gas stream from a gaseous feed stream comprising hydrogen and oxygen and at least one of water and nitrogen, said process comprising sending said feed stream through an adsorbent bed comprising a catalyst material selected from copper, palladium or platinum, and then purging said adsorbent bed in a counter-current direction with a purge stream comprising a hydrogen-rich gas that is substantially free of oxygen.
2. The process of claim 1 wherein said gaseous feed stream comprises from about 97 mol % to about 99.9 mol % hydrogen, from about 10 ppmv to about 2,000 ppmv oxygen, and water from about 50% to 100% of saturation.
3. The process of claim 1 wherein said gaseous feed stream comprises from about 100 ppmv to about 2000 ppmv nitrogen.
4. The process of claim 1 , wherein said product stream comprises more than 99.9 mol % hydrogen, less than about 5 ppmv oxygen, and less than about 10 ppmv water.
5. The process of claim 1 wherein said product stream comprises less than about 300 ppmv nitrogen.
6. The process of claim 1 , wherein said adsorbent bed is in a pressure swing adsorption unit and comprises three layers of adsorbent material comprising a first dehydration adsorbent layer, a copper material layer and a second dehydration adsorbent layer.
7. The process of claim 1 , wherein said adsorbent bed is in a pressure swing adsorption unit and comprises four layers of adsorbent material comprising a dehydration adsorbent layer, a copper material layer, a second dehydration adsorbent layer and a nitrogen removal adsorbent.
8. The process of claim 6 wherein said first dehydration adsorbent layer and said second dehydration layer comprise silica gel, activated alumina or sodium X zeolite.
9. The process of claim 7 wherein said first dehydration adsorbent layer and said second dehydration layer comprise silica gel, activated alumina or sodium X zeolite and said nitrogen removal adsorbent comprises a calcium X zeolite or a calcium A zeolite.
10. The process of claim 1 wherein said adsorbent bed is in a pressure swing adsorption unit comprising three or more adsorption beds wherein said feed stream is at a pressure greater than about 10 bar(g), at a temperature less than about 60° C. and said purge stream is at a pressure less than about 1 bar(g).
11. The process of claim 1 wherein said adsorbent bed is in a temperature swing adsorption unit wherein said feed stream is at a temperature less than about 60° C. and said purge stream is at a temperature greater than about 180° C.
12. The process of claim 6 wherein said layer of copper material comprises about 10% to about 40% of said adsorbent bed by volume and each of said desiccant layers comprise about 10% to about 40% by volume of said adsorbent bed.
13. The process of claim 7 wherein said layer of copper material comprises about 10% to about 30% of said adsorbent bed by volume, each of said desiccant layers comprise about 10% to about 40% by volume of said adsorbent bed and said nitrogen removal adsorbent comprises about 20% to about 50% of said adsorbent bed by volume.
14. The process of claim 1 wherein said catalyst material comprises more than about 10 wt % copper on an activated alumina support.
15. A system for treating a gaseous feed stream wherein said system comprises at least two adsorbent beds, a gas inlet and a gas outlet wherein said adsorbent beds comprise at least three layers of adsorbent material wherein a first layer adjacent to said inlet comprises a dehydration adsorbent, a second layer comprises a catalyst comprising a copper material and a third layer comprises a dehydration adsorbent.
16. The system of claim 15 further comprising a nitrogen removal adsorbent between said gas outlet and said third layer.
17. The system of claim 15 wherein said dehydration adsorbent is selected from silica gel, activated alumina and sodium X zeolite.
18. The system of claim 16 wherein said nitrogen removal adsorbent is calcium X zeolite or calcium A zeolite.
19. The system of claim 15 wherein said layer of copper material comprises about 10% to about 40% of said adsorbent bed by volume and each of said dehydration layers comprise about 10% to about 40% by volume of said adsorbent bed.
20. The system of claim 16 wherein said layer of copper material comprises about 10% to about 30% of said adsorbent bed by volume, each of said dehydration layers comprise about 10% to about 40% by volume of said adsorbent bed and said nitrogen removal adsorbent comprises about 20% to about 50% of said adsorbent bed by volume.