Hydrogen passivation shut down system for a fuel cell power plant
View Patent ↗The invention is a hydrogen passivation shut down system for a fuel cell power plant ( 10 ). An anode flow path ( 24 ) is in fluid communication with an anode catalyst ( 14 ) for directing hydrogen fuel to flow adjacent to the anode catalyst ( 14 ), and a cathode flow path ( 38 ) is in fluid communication with a cathode catalyst ( 16 ) for directing an oxidant to flow adjacent to the cathode catalyst ( 16 ) of a fuel cell ( 12 ). Hydrogen fuel is permitted to transfer between the anode flow path ( 24 ) and the cathode flow path ( 38 ). A hydrogen reservoir ( 66 ) is secured in fluid communication with the anode flow path ( 24 ) for receiving and storing hydrogen during fuel cell ( 12 ) operation, and for releasing the hydrogen into fuel cell ( 12 ) whenever the fuel cell ( 12 ) is shut down.
1. A method of shutting down a fuel cell power plant ( 10 ), the power plant comprising at least one fuel cell ( 12 ) for generating electrical current from hydrogen containing reducing fluid fuel and oxygen containing oxidant reactant streams, the fuel cell ( 12 ) including an anode catalyst ( 14 ) and a cathode catalyst ( 16 ) on opposed sides of an electrolyte ( 18 ), an anode flow path ( 24 ) in fluid communication with the anode catalyst ( 14 ) for directing the hydrogen fuel to flow through the fuel cell ( 12 ) and adjacent the anode catalyst ( 14 ), and a cathode flow path ( 38 ) in fluid communication with the cathode catalyst ( 16 ) for directing the oxidant stream to flow through the fuel cell ( 12 ) and adjacent the cathode catalyst ( 14 ), the method comprising the steps of:
a. disconnecting a primary load ( 90 ) from the fuel cell ( 12 );
b. terminating flow of the oxidant into the cathode flow path ( 24 ) from an oxidant source ( 58 );
c. connecting an auxiliary load ( 94 ) to the fuel cell ( 12 );
d. permitting transfer of the hydrogen fuel from the anode flow path ( 24 ) into the cathode flow path ( 38 );
e. terminating flow of the hydrogen fuel into the anode flow path ( 24 ) from a hydrogen fuel source ( 54 ) whenever the anode flow path ( 24 ) and cathode flow path ( 38 ) are filled with a hydrogen concentration of greater than ninety percent hydrogen; and,
f. permitting release into the anode flow path ( 24 ) and into the cathode flow path ( 38 ) of hydrogen stored within a hydrogen reservoir means for storing hydrogen secured in fluid communication with the anode flow path ( 24 ).
2. The method of claim 1 , wherein the step of permitting transfer of hydrogen fuel from the anode flow path ( 24 ) into the cathode flow path ( 38 ) includes directing the hydrogen fuel to pass through a hydrogen transfer valve ( 64 ) secured in fluid communication between the anode flow path ( 24 ) and the cathode flow path ( 38 ).
3. The method of claim 1 , wherein the step of permitting transfer of hydrogen fuel from the anode flow path ( 24 ) into the cathode flow path ( 38 ) includes electrochemically pumping the hydrogen from the anode flow path ( 24 ) into the cathode flow path ( 38 ) by passing a direct current to the fuel cell ( 12 ).
4. The method of claim 1 , wherein the step of permitting transfer of hydrogen fuel from the anode flow path ( 24 ) into the cathode flow path ( 38 ) includes securing a proton exchange membrane electrolyte ( 18 ) between the anode catalyst ( 14 ) and the cathode catalyst ( 16 ) so that the hydrogen may diffuse through the proton exchange membrane electrolyte ( 18 ) from the anode flow path ( 24 ) into the cathode flow path ( 38 ).
5. The method of claim 1 , comprising the further step of, after the permitting transfer of the hydrogen fuel step, and before the terminating flow of the hydrogen fuel step, accelerating flow of a cathode exhaust stream with one of an oxidant blower ( 60 ) or a cathode bypass blower ( 76 ) from a cathode exhaust ( 44 ) of the cathode flow path ( 38 ) through a cathode bypass line ( 74 ) to a cathode inlet ( 40 ) of the cathode flow path ( 38 ).
6. The method of claim 1 , comprising the further step of, after the step of permitting release of hydrogen into the anode flow path ( 24 ) from the hydrogen reservoir step, periodically sensing an amount of hydrogen within the anode flow path ( 24 ) or the cathode flow path ( 38 ) with a hydrogen sensor means for detecting a concentration of hydrogen within the anode flow path ( 24 ) or the cathode flow path ( 38 ), then admitting hydrogen into the anode flow path ( 24 ) to a concentration of greater than ninety percent hydrogen whenever the sensor means detects the concentration of hydrogen within the anode flow path ( 24 ) or the cathode flow path ( 38 ) is below a predetermined concentration.
7. The method of claim 6 , wherein the admitting hydrogen into the anode flow path ( 24 ) further comprises admitting hydrogen into the anode flow path ( 24 ) to a concentration of about one hundred percent hydrogen within the anode flow path ( 24 ).
8. The method of claim 1 , comprising the further step of, after the step of permitting release of hydrogen into the anode flow path ( 24 ) from the hydrogen reservoir step, periodically sensing an amount of hydrogen within the anode flow path ( 24 ) or the cathode flow path ( 38 ) with a hydrogen sensor means for detecting a concentration of hydrogen within the anode flow path ( 24 ) or the cathode flow path ( 38 ), then admitting hydrogen into the anode flow path ( 24 ) in a concentration that is inversely proportional to the detected concentration of hydrogen within the anode flow path ( 24 ) or the cathode flow path ( 38 ).
9. The method of claim 1 , comprising the further steps of, after the step of permitting release of hydrogen into the anode flow path ( 24 ) from the hydrogen reservoir step, sensing an amount of hydrogen within the anode flow path ( 24 ) or the cathode flow path ( 38 ) with a hydrogen sensor means for detecting a concentration of hydrogen within the anode flow path ( 24 ) or the cathode flow path ( 38 ), then whenever the detected hydrogen concentration is less than 0.0001 percent, performing a rapid hydrogen fuel purge step wherein hydrogen fuel is directed to traverse the anode flow field ( 28 ) of the fuel cell ( 12 ) between an anode inlet ( 26 ) and an anode exhaust ( 30 ) in less than 1.0 seconds, then starting up the fuel cell ( 12 ).
10. The method of claim 9 , wherein the rapid hydrogen fuel purge step further comprises directing the hydrogen fuel to traverse the anode flow field ( 28 ) of the fuel cell ( 12 ) between the anode inlet ( 26 ) and the anode exhaust ( 30 ) in less than 0.2 seconds.
11. The method of claim 9 , wherein the rapid hydrogen fuel purge step further comprises directing the hydrogen fuel to traverse the anode flow field ( 28 ) of the fuel cell ( 12 ) between the anode inlet ( 26 ) and the anode exhaust ( 30 ) in less than 0.05 seconds.
12. The method of claim 1 , wherein the step of terminating the flow of hydrogen fuel into the anode flow path ( 24 ) further includes terminating the flow of hydrogen fuel into the into the anode flow path ( 24 ) from the hydrogen fuel source ( 54 ) whenever the anode flow path ( 24 ) and cathode flow path ( 38 ) are filled with a hydrogen concentration of about one hundred percent hydrogen.
13. A method of operating a fuel cell power plant ( 10 ), the power plant comprising at least one fuel cell ( 12 ) including an anode catalyst ( 14 ) and a cathode catalyst ( 16 ) disposed on opposed sides of an electrolyte ( 18 ), an anode flow path ( 24 ) in fluid communication between the anode catalyst ( 14 ) and a fuel source ( 54 ), a cathode flow path ( 38 ) in fluid communication between the cathode catalyst ( 16 ) and an oxygen source ( 58 ), the cathode flow path ( 38 ) including a cathode bypass line ( 74 ) disposed between a cathode inlet ( 40 ) and a cathode exhaust ( 44 ) of the cathode flow path ( 38 ); the method comprising the steps of:
a. terminating flow of a hydrogen fuel from the fuel source ( 54 ) to the anode catalyst ( 14 );
b. recycling reactant fluid disposed in said cathode flow path ( 38 ) through the cathode by-pass line ( 74 );
c. introducing fuel into the cathode flow path ( 38 ) from the anode flow path ( 24 );
d. reacting the fuel with the recycled reactant fluid within the cathode flow path ( 38 ) until the hydrogen concentration of the recycled reactant fluid becomes greater than ninety percent.
14. A method of operating a fuel cell power plant ( 10 ), the power plant comprising at least one fuel cell ( 12 ) including an anode catalyst ( 14 ) and a cathode catalyst ( 16 ) disposed on opposed sides of an electrolyte ( 18 ), an anode flow path ( 24 ) in fluid communication between the anode catalyst ( 14 ) and a fuel source ( 54 ), a cathode flow path ( 38 ) in fluid communication between the cathode catalyst ( 16 ) and an oxygen source ( 58 ), the cathode flow path ( 38 ) including a cathode bypass line ( 74 ) disposed between a cathode inlet ( 40 ) and a cathode exhaust ( 44 ) of the cathode flow path ( 38 ); the method comprising the steps of: the method comprising the steps of:
a. securing a hydrogen transfer valve ( 64 ) in fluid communication between the anode flow path ( 24 ) and the cathode flow path ( 38 );
b. introducing fuel from the fuel source ( 54 ) into the cathode flow path ( 38 ) from the anode flow path ( 24 );
c. recycling reactant fluid disposed in said cathode flow path ( 38 ) through the cathode by-pass line ( 74 );
d. reacting the fuel with the recycled reactant fluid within the cathode flow path ( 38 ) until the hydrogen concentration of the recycled reactant fluid becomes greater than ninety percent.