Hybrid membrane—PSA system for separating oxygen from air
A portable, non-cryogenic, oxygen generation system capable of delivering oxygen gas at purities greater than 98% and flow rates of 15 L/min or more is described. The system consists of two major components. The first component is a high efficiency membrane capable of separating argon and a portion of the nitrogen content from air, yielding an oxygen-enriched permeate flow. This is then fed to the second component, a pressure swing adsorption (PSA) unit utilizing a commercially available, but specifically formulated zeolite compound to remove the remainder of the nitrogen from the flow. The system is a unique gas separation system that can operate at ambient temperatures, for producing high purity oxygen for various applications (medical, refining, chemical production, enhanced combustion, fuel cells, etc . . . ) and represents a significant advance compared to current technologies.
1. A method of generating high-purity oxygen gas from air with the aid of a hybrid membrane/PSA system, comprising:
a) feeding an input stream of air to a compressor;
b) compressing the input air stream to a high pressure with a compressor;
c) feeding the compressed air to a membrane separation unit, thereby generating an oxygen-rich permeate stream of enriched oxygen with most of the argon removed, and generating a nitrogen-rich retentate stream of enriched nitrogen and argon;
d) feeding the permeate stream to a turbine;
e) re-compressing the permeate stream to a medium pressure with the turbine;
f) feeding the re-compressed permeate stream to a PSA unit, thereby generating an output oxygen stream with high purity;
g) generating a purge and vent stream from the PSA unit; and
h) using the nitrogen-rich retentate stream to power the turbine, thereby reducing total system power use;
whereby the purity of the output oxygen stream is greater than about 98%.
2. The method of claim 1 , wherein the temperature of the streams is at ambient temperature.
3. The method of claim 1 , wherein the membrane has a membrane selectivity greater than or equal to 2.
4. The method of claim 1 , wherein the membrane has a N 2 /Ar selectivity greater than or equal to 2.
5. The method of claim 1 , wherein the input air stream is compressed to a high pressure greater than or equal to 100 psig in step b).
6. The method of claim 1 , wherein the permeate stream is compressed to a medium pressure greater than or equal to 30 psig in step e).
7. The method of claim 1 , wherein the membrane has a membrane efficiency for recovering O 2 from air greater than or equal to 90%.
8. The method of claim 1 , wherein the PSA system has a N 2 removal efficiency greater than or equal to 99.87%.
9. The method of claim 1 , wherein the fraction of O 2 for PSA regeneration step is less than or equal to 60%.
10. The method of claim 1 , wherein the system generates a high purity oxygen output stream of at least 98.6% O 2 purity at 15 L/min and 15 psig pressure, with an overall O 2 recovery efficiency of at least 36%, for an input air stream of 318 L/min at 0 psig.
11. The method of claim 1 , wherein:
the input stream consists of 21.0% O 2 , 78.0% N 2 and 1.0% Ar;
the permeate stream consists of 34.7% O 2 , 64.9% N 2 and 0.4% Ar;
the retentate stream consists of 4.6% O 2 , 93.7% N 2 and 1.7% Ar;
the purge and vent stream consists of 24.2% O 2 , 75.5% N 2 and 0.3% Ar; and
the output stream consists of 98.6% O 2 , 0.2% N 2 and 1.2% Ar.
12. The method of claim 1 , further comprising recycling the purge and vent stream back to feed into the input stream going to the membrane separation unit.
13. A method of generating high-purity oxygen gas from air with the aid of a hybrid membrane/PSA system, comprising:
a) feeding an input stream of air to a compressor;
b) compressing the input air stream to a high pressure with a compressor;
c) feeding the compressed air to a membrane separation unit, thereby generating an oxygen-rich permeate stream of enriched oxygen with most of the argon removed, and generating a nitrogen-rich retentate stream of enriched nitrogen and argon;
d) feeding the permeate stream to a turbine;
e) re-compressing the permeate stream to a medium pressure with the turbine;
f) feeding the re-compressed permeate stream to a PSA unit, thereby generating an output oxygen stream with high purity;
g) generating a purge and vent stream from the PSA unit; and
h) using the nitrogen-rich retentate stream to power the turbine, thereby reducing total system power use;
whereby the purity of the output oxygen stream is greater than 98%;
wherein the temperature of the streams is at ambient temperature;
wherein the membrane has a membrane selectivity greater than or equal to 2;
wherein the membrane has a N 2 /Ar selectivity greater than or equal to 2;
wherein the input air stream is compressed to a high pressure greater than or equal to 100 psig in step b);
wherein the permeate stream is compressed to a medium pressure greater than or equal to 30 psig in step e);
wherein the membrane has a membrane efficiency for recovering O 2 from air greater than or equal to 90%;
wherein the PSA system has a N 2 removal efficiency greater than or equal to 99.87%;
wherein the fraction of O 2 for PSA regeneration step is less than or equal to 60%;
wherein the system generates a high purity oxygen output stream of at least 98.6% O 2 purity at 15 L/min and 15 psig pressure, with an overall O 2 recovery efficiency of at least 36%, for an input air stream of 318 L/min at 0 psig; and
wherein:
the input stream consists of 21.0% O 2 , 78.0% N 2 and 1.0% Ar;
the permeate stream consists of 34.7% O 2 , 64.9% N 2 and 0.4% Ar;
the retentate stream consists of 4.6% O 2 , 93.7% N 2 and 1.7% Ar;
the purge and vent stream consists of 24.2% O 2 , 75.5% N 2 and 0.3% Ar; and
the output stream consists of 98.6% O 2 , 0.2% N 2 and 1.2% Ar.
14. A method of generating high-purity oxygen gas from air with the aid of a hybrid membrane/PSA system, comprising:
a) feeding an input stream of air to a compressor;
b) compressing the input air stream to a high pressure with a compressor;
c) feeding the compressed air to a membrane separation unit, thereby generating an oxygen-rich permeate stream of enriched oxygen with most of the argon removed, and generating a nitrogen-rich retentate stream of enriched nitrogen and argon;
d) feeding the permeate stream to a turbine;
e) re-compressing the permeate stream to a medium pressure with the turbine;
f) feeding the re-compressed permeate stream to a PSA unit, thereby generating an output oxygen stream with high purity;
g) generating a purge and vent stream from the PSA unit;
h) using the nitrogen-rich retentate stream to power the turbine, thereby reducing total system power use; and
i) recycling the purge and vent stream back to feed into the input stream going to the membrane separation unit;
whereby the purity of the output oxygen stream is greater than about 98%.
15. The method of claim 14 , wherein the temperature of the streams is at ambient temperature.
16. The method of claim 14 , wherein the membrane has a membrane selectivity greater than or equal to 2.
17. The method of claim 14 , wherein the membrane has a N 2 /Ar selectivity greater than or equal to 2.
18. The method of claim 14 , wherein the input air stream is compressed to a high pressure greater than or equal to 100 psig in step b).
19. The method of claim 14 , wherein the permeate stream is compressed to a medium pressure greater than or equal to 30 psig in step e).
20. The method of claim 14 , wherein the membrane has a membrane efficiency for recovering O 2 from air greater than or equal to 90%.
21. The method of claim 14 , wherein the PSA system has a N 2 removal efficiency greater than or equal to 99.87%.
22. The method of claim 14 , wherein the fraction of O 2 for PSA regeneration step is less than or equal to 60%.
23. The method of claim 14 , wherein the system generates a high purity oxygen output stream of at least 99.2% O 2 purity at 15 L/min and 15 psig pressure, with an overall O 2 recovery efficiency of at least 78.3%, for an input air stream of 183 L/min at 0 psig.
24. The method of claim 14 , wherein:
the input stream consists of 21.0% O 2 , 78.0% N 2 and 1.0% Ar;
the permeate stream consists of 38.9% O 2 , 60.8% N 2 and 0.2% Ar,
the retentate stream consists of 5.5% O 2 , 93.7% N 2 and 0.07% Ar;
the purge and vent stream consists of 27.7% O 2 , 72.1% N 2 and 0.2% Ar; and
the output stream consists of 99.2% O 2 , 0.2% N 2 and 0.6% Ar.
25. A method of generating high-purity oxygen gas from air with the aid of a hybrid membrane/PSA system, comprising:
a) feeding an input stream of air to a compressor;
b) compressing the input air stream to a high pressure with a compressor;
c) feeding the compressed air to a membrane separation unit, thereby generating an oxygen-rich permeate stream of enriched oxygen with most of the argon removed, and generating a nitrogen-rich retentate stream of enriched nitrogen and argon;
d) feeding the permeate stream to a turbine;
e) re-compressing the permeate stream to a medium pressure with the turbine;
f) feeding the re-compressed permeate stream to a PSA unit, thereby generating an output oxygen stream with high purity;
g) generating a purge and vent stream from the PSA unit; and
h) using the nitrogen-rich retentate stream to power the turbine, thereby reducing total system power use; and
i) recycling the purge and vent stream back to feed into the input stream going to the membrane separation unit;
whereby the purity of the output oxygen stream is greater than 98%;
wherein the temperature of the streams is at ambient temperature;
wherein the membrane has a membrane selectivity greater than or equal to 2;
wherein the membrane has a N 2 /Ar selectivity greater than or equal to 2;
wherein the input air stream is compressed to a high pressure greater than or equal to 100 psig in step b);
wherein the permeate stream is compressed to a medium pressure greater than or equal to 30 psig in step e);
wherein the membrane has a membrane efficiency for recovering O 2 from air greater than or equal to 90%;
wherein the PSA system has a N 2 removal efficiency greater than or equal to 99.87%;
wherein the fraction of O 2 for PSA regeneration step is less than or equal to 60%;
wherein the system generates a high purity oxygen output stream of at least 99.2% O 2 purity at 15 L/min and 15 psig pressure, with an overall O 2 recovery efficiency of at least 78.3%, for an input air stream of 183 L/min at 0 psig.; and
wherein:
the input stream consists of 21.0% O 2 , 78.0% N 2 and 1.0% Ar;
the permeate stream consists of 38.9% O 2 , 60.8% N 2 and 0.2% Ar;
the retentate stream consists of 5.5% O 2 , 93.7% N 2 and 0.07% Ar;
the purge and vent stream consists of 27.7% O 2 , 72.1% N 2 and 0.2% Ar; and
the output stream consists of 99.2% O 2 , 0.2% N 2 and 0.6% Ar.