Systems and methods for regulating heating assembly operation through pressure swing adsorption purge control
View Patent ↗Pressure swing adsorption (PSA) assemblies with purge control systems, and hydrogen-generation assemblies and/or fuel cell systems containing the same. The PSA assemblies are operated according to a PSA cycle to produce a product hydrogen stream and a byproduct stream from a mixed gas stream. The byproduct stream may be delivered as a fuel stream to a heating assembly, which may heat the hydrogen-producing region that produces the mixed gas stream. The PSA assemblies may be adapted to regulate the flow of purge gas utilized therein, such as according to a predetermined, non-constant profile. In some embodiments, the flow- of purge gas is regulated to maintain the flow rate and/or fuel value of the byproduct stream at or within a determined range of a threshold value, and/or to regulate the flow of purge gas to limit the concentration of carbon monoxide in a heated exhaust stream produced from the byproduct stream.
1. A method for regulating the temperature of a hydrogen-producing region of a fuel processing system adapted to produce a mixed gas stream containing hydrogen gas and other gases, the method comprising:
producing a mixed gas stream containing hydrogen gas and other gases in a heated hydrogen-producing region of a fuel processing system;
delivering the mixed gas stream to a pressure swing adsorption assembly having a plurality of adsorbent beds containing adsorbent and adapted to produce a byproduct stream containing at least a substantial portion of the other gases and a product hydrogen stream containing a greater concentration of hydrogen gas than the mixed gas stream;
adsorbing the other gases from the mixed gas stream to produce a product hydrogen stream containing a greater concentration of hydrogen gas than the mixed gas stream;
depressurizing the adsorbent beds to facilitate desorption of the other gases from the adsorbent;
purging the adsorbent beds with a flow of purge gas to further facilitate desorption of the other gases, wherein the depressurizing and purging steps produce gas streams from which the byproduct stream is formed;
combusting the byproduct stream with air in a heating assembly adapted to produce a heated exhaust stream;
heating the hydrogen-producing region of the fuel processing system with the heated exhaust stream; and
regulating the flow rate of purge gas to the adsorbent beds to produce a sufficient flow of byproduct gas to maintain the hydrogen-producing region within a determined temperature range for producing the mixed gas stream, the regulating including one or more of selectively increasing and decreasing over a time period the flow rate of the purge gas.
2. The method of claim 1 , wherein the regulating includes ramping the flow rate of purge gas to the adsorbent beds.
3. The method of claim 1 , wherein the method includes regulating the foxy of purge gas to the adsorbent beds to produce a continuous flow of the byproduct stream.
4. The method of claim 1 , wherein the regulating includes delivering the flow rate of purge gas at an initial flow rate of purge gas that is less than 75% of an average flow rate of purge gas and thereafter increasing the flow rate of purge gas.
5. The method of claim 1 , wherein the regulating includes controlling the fuel value of the byproduct stream.
6. The method of claim 1 , wherein the hydrogen-producing region includes a reforming region adapted to produce the mixed gas stream.
7. The method of claim 6 , wherein the hydrogen-producing region includes a stream reforming region adapted to produce the mixed gas stream from water and an alcohol and further wherein the determined temperature range is 350-450° C.
8. The method of claim 6 , wherein the hydrogen-producing region includes a stream reforming region adapted to produce the mixed gas stream from water and a hydrocarbon and further: wherein the determined temperature range is 700-800° C.
9. The method of claim 6 , wherein the hydrogen-producing region includes a stream reforming region adapted to produce the mixed gas stream from water and an alcohol and further wherein the determined temperature range is 375-450° C.
10. The method of claim 6 , wherein the hydrogen-producing region includes a stream reforming region adapted to produce the mixed gas stream from water and a hydrocarbon and further wherein the determined temperature range is 725-825° C.
11. The method of claim 1 , wherein the determined temperature range is 350-450° C.
12. The method of claim 1 , wherein tie determined temperature range is 700-800° C.
13. The method of claim 1 , wherein the determined temperature range is 725-825° C.
14. The method of claim 1 , wherein the regulating includes regulating the flow rate of purge gas to the adsorbent beds of a pressure swing adsorption assembly to maintain the concentration of carbon monoxide in the heated exhaust stream below 50 ppm.
15. The method of claim 1 , wherein the regulating includes selectively delivering a purge stream to the adsorbent beds according to a variable flow profile.
16. The method of claim 1 , wherein the regulating includes selectively delivering purge stream to the adsorbent beds according to a linear foxy profile.
17. The method of claim 1 , wherein the regulating includes selectively delivering a purge stream to the adsorbent beds according to a non-linear flow profile.
18. The method of claim 1 , wherein the regulating includes delivering the flow rate of purge gas at an initial flow rate of purge gas that is greater than 25% and less than 75% of an average fox rate of purge gas and thereafter increasing the flow rate of purge gas.
19. The method of claim 1 , wherein the regulating includes delivering the flow rate of purge gas at an initial flow rate of purge gas that is greater than 25% and less than 50% of an average flow rate of purge gas and thereafter increasing the flow rate of purge gas.
20. The method of claim 1 , wherein the regulating includes delivering the flow rate of purge gas at an initial flow rate of purge gas that is 25-75% of an average flow rate of the purge gas during a purge stage of a PSA cycle, and further wherein the initial flow rate is maintained for at least 10% of the purge stage.
21. A method for regulating the temperature of a hydrogen-producing region of a fuel processing system adapted to produce a mixed gas stream containing hydrogen gas and other gases, the method comprising:
producing a mixed gas stream containing hydrogen gas and other gases in a heated hydrogen-producing region of a fuel processing system;
delivering the mixed gas stream to a pressure swing adsorption assembly having a plurality of adsorbent beds containing adsorbent and adapted to produce a byproduct stream containing at least a substantial portion of the other gases and a product hydrogen stream containing a greater concentration of hydrogen gas than the mixed gas stream;
adsorbing the other gases from the mixed gas stream to produce a product hydrogen stream containing a greater concentration of hydrogen gas than the mixed gas stream;
depressurizing the adsorbent beds to facilitate desorption of the other gases from the adsorbent;
purging the adsorbent beds with a flow of purge gas to further facilitate desorption of the other gases, wherein the depressuriuing and purging steps produce gas streams from which the byproduct stream is formed;
combusting the byproduct stream with air in a heating assembly adapted to produce a heated exhaust stream;
heating the hydrogen-producing region of the fuel processing system with the heated exhaust stream; and
regulating the flow rate of purge gas to the adsorbent beds to produce a sufficient flow of byproduct gas to maintain the hydrogen-producing region within a determined temperature range for producing the mixed gas stream, the regulating including maintaining the fuel value of the byproduct stream within a predetermined range of a determined fuel value.
22. The method of claim 21 , wherein the regulating includes ramping the flow rate of purge gas to the adsorbent beds.
23. The method of claim 21 , wherein the regulating includes delivering the flow rate of purge gas at an initial flow rate of purge gas that is less than 75% of an average flow rate of purge gas and thereafter increasing the flow rate of purge gas.
24. The method of claim 21 , wherein the hydrogen producing region includes a reforming region adapted to produce the mixed gas stream.
25. The method of claim 24 , wherein the hydrogen-producing region includes a stream reforming region adapted to produce the mixed gas stream from water and an alcohol and further wherein the determined temperature range is 350-450° C.
26. The method of claim 24 , wherein the hydrogen-producing region includes a stream reforming region adapted to produce the mixed gas stream from water and a hydrocarbon and further wherein the determined temperature range is 700-800° C.
27. The method of claim 21 , wherein the determined temperature range is 350-450° C.
28. The method of claim 21 , wherein the determined temperature range is 700-800° C.
29. The method of claim 21 , wherein the determined temperature range is 725-825° C.
30. The method of claim 21 , wherein the regulating includes delivering the flow rate of purge gas at an initial flow rate of purge gas that is greater than 25% and less than 75% of an average flow rate of purge gas and thereafter increasing the flow rate of purge gas.
31. The method of claim 21 , wherein the regulating includes delivering the flow rate of purge gas at an initial flow rate of purge gas that is greater than 25% and less than 50% of an average flow rate of purge gas and thereafter increasing the how rate of purge gas.