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WO2010056224A1 - Homogenous gas in shut down fuel cells - Google Patents

Homogenous gas in shut down fuel cells Download PDF

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Publication number
WO2010056224A1
WO2010056224A1 PCT/US2008/012750 US2008012750W WO2010056224A1 WO 2010056224 A1 WO2010056224 A1 WO 2010056224A1 US 2008012750 W US2008012750 W US 2008012750W WO 2010056224 A1 WO2010056224 A1 WO 2010056224A1
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WO
WIPO (PCT)
Prior art keywords
fuel cell
power plant
cell power
recycle
fuel
Prior art date
Application number
PCT/US2008/012750
Other languages
French (fr)
Inventor
Carl A. Reiser
Original Assignee
Utc Power Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Utc Power Corporation filed Critical Utc Power Corporation
Priority to PCT/US2008/012750 priority Critical patent/WO2010056224A1/en
Publication of WO2010056224A1 publication Critical patent/WO2010056224A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • H01M8/04097—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with recycling of the reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H01M8/04302—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during start-up
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H01M8/04303—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during shut-down
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • anode recycle and cathode recycle homogenizes the gas concentration in all of the fuel cells of the stack, thereby mitigating carbon and catalyst corrosion in and around the catalyst layers.
  • the process seeks to avoid, during shutdown, the presence of oxygen in the reactant gas compartments.
  • the desired result is to extend the time that the stack can maintain a fuel-rich (such as greater than a 2: 1 fuel to air stoichiometry) environment.
  • the process disconnects the main load, connects an auxiliary load or shorting resistor, blocks the 'entry of oxygen from the source, such as air, while flowing hydrogen into the anodes with fuel recycling, and while recycling cathode exhaust to the cathode inlets.
  • the aforementioned procedure may include a rapid hydrogen fuel purge just prior to restarting the fuel cell power plant.
  • the aforementioned procedures, or variants thereof, have been shown to be inadequate in that power plants still experience performance degradations due to carbon and catalyst corrosion in and around the catalyst layers.
  • the decay is very irreproducible from substack to substack (e.g., substacks of 10 fuel cells in an overall stack of 250 cells). In fact, variations in substack performance of as much as 50% have been observed.
  • the air at a point of intrusion where the oxygen concentration is high enough to cause corrosion, is spread throughout the stack by homogenization, thereby reducing the concentration of air at any and all points to a lower, average concentration of all the cells which will not cause corrosion.
  • the lower oxygen concentration at any cell mitigates the carbon and catalyst corrosion in and around catalyst layers and the consequent reduction in performance which would occur if local high O 2 concentrations were allowed to exist.
  • the homogenization of gases during shutdown (inoperation) of the fuel cell power plant can be effected with either or both of the fuel recycle system and the aforementioned cathode recycle system. Homogenization may occur immediately after the final step of a shutdown procedure that is, at the time of turning off the hydrogen flow when the recycle pumps would otherwise be shut down. Or, the homogenization may take place either intermittently or continuously throughout the period that the fuel cell power plant is inoperative. Another alterative is to perform the homogenization just before the first step in a start up procedure for restoring the fuel cell power plant to operation. [0013] The homogenization may preferably begin immediately after shutdown of the power plant is complete, and continue, either intermittently or continuously, until just prior to the first step of a start up procedure.
  • Fig. 1 is a simplified, schematic diagram of an exemplary fuel cell power plant which has cathode recycle and which will benefit from the present embodiments.
  • Fig. 2 is a simplified process diagram illustrating one of the embodiments of gas homogenization.
  • a fuel cell power plant 5 includes a stack of fuel cells 6, each fuel cell having an anode catalyst layer, a cathode catalyst layer and a proton exchange membrane disposed between said layers. Each fuel cell also has fuel reactant gas flow field channels adjacent the anode catalyst layer, with or without an additional layer between the fuel flow field channels and the catalyst layer. Each fuel cell also has oxidant reactant gas flow field channels adjacent the cathode catalyst layer, with or without an additional layer between the oxidant reactant gas flow field channels and the cathode catalyst layer. These are known and are not shown in the drawing.
  • the anodes 9 and cathodes 10 are separated by proton exchange membranes 11.
  • the anodes 9 receive fuel from a source 14 which passes through a pressure regulator 15 and a flow control valve 16, which is adjusted by a controller 17.
  • the fuel inlets 19 of the anodes also receive recycle fuel in a conduit 20 from a recycle pump 21 that is connected by a conduit 22 to the anode fuel outlets 23.
  • the controller 17 also operates a purge valve 25 to periodically or continuously release a small portion of the anode exhaust in order to rid the fuel cells of contaminants and inerts such as nitrogen.
  • the valve 25 is connected by a conduit 27 to a conduit 29 where the anode exhaust is mixed with cathode exhaust in conduit 29.
  • the outflow of the conduit 29 may be to ambient or to a controlled confinement of some sort.
  • the cathodes 10 receive air at inlets 34 from an air blower 35. Air is applied to the input 37 of a filter 38, the output of which in the conduit 39 is passed through an air control valve 40 that is regulated by the controller 17.
  • the cathode outlets 42 are connected through a recycle conduit 44, a valve 45 and a conduit 46 to the inlet 47 of the air blower 35, which is also connected to the valve 40 by a conduit 48.
  • the recycle control valve 45 is operated by the controller 17 so as to control the amount, if any, of recycle air which is returned over a conduit 46 to the inlet 47 of the blower 35 and the cathode air inlets 34.
  • the cathode outlets 42 are also connected by a conduit 50 through a check valve 51 to the conduit 29, thereby diluting any hydrogen which may remain in the anode exhaust.
  • the fuel cell stack electrical power output 54 from the anode end of the stack, indicated by a minus sign, is connectable through a switch 55 to a conventional power conditioner 56, which is shown only schematically in the drawing.
  • the output 57 of the power conditioner 56 is connected to an actual load 59, which may be a vehicle or other electrical utilization apparatus.
  • the switch is shown connected to an auxiliary load 60, such as that described hereinbefore with respect to a hydrogen-stabilizing shutdown procedure.
  • the loads are connected by a return line 62 to the cathode end of the stack, indicated by a plus sign.
  • a signal 67 provided by the load 68 indicates that the stack should be shut down.
  • the shut down signal could alternatively come from the power conditioner 56, such as when it senses a problem with the load.
  • the controller will operate the switch 55 to shift the output of the fuel cell stack from the main load 59 to the auxiliary load 60.
  • the valve 40 is closed to block fresh air, the valve 45 is opened to recycle cathode exhaust to the cathode inlets, and fuel continues to be provided to the anodes with fuel recycle on.
  • an exemplary process 101 for homogenizing gases in a fuel cell power plant, while the power plant is inoperative may be entered at a point 102.
  • a first test 104 determines if the power plant is operating. If it is, homogenization is not required so an affirmative result of test 104 will allow other functions to be performed, through a return point 107. If the power plant is not operating, then a test 109 may be performed to determine if a start up routine is in process. If the power plant is in the process of starting up, an affirmative result of test 109 will end this process through the return point 107. [0025] If start up is not in process, then it should be determined at a test 111 whether shutdown of the power plant is complete or not. If it is not, then homogenization is not required.
  • step 114 in the process to initiate a run timer, indicative of how long recycle should be running before it shuts down again, in an embodiment in which the recycling is periodic or intermittent.
  • step 116 in the process starts the recycle to operate, which might include starting only the fuel recycle pump, or it may comprise starting only the cathode blower or pump with the cathode recycle valve open, or the step may comprise starting both of the recycle systems.
  • the timer is continuously monitored at a test 119. When timeout occurs, the recycle is stopped in a step 121.
  • a test 123 determines if start up of the fuel cell power plant is impending. This may be a small fraction of a minute before a start up procedure actually begins. If start up is not impending, a negative result reaches a step 126 which initiates a dwell timer, indicative of the amount of time between periods of operation of recycle. Then the dwell timer is monitored in a process test 128 to determine when the recycle should once again be started. An affirmative result of test 128 reverts the process back to the process step 114 to initiate the run timer and start recycle, as before. This will continue passing through a positive result of test 119, a negative result of test 123 and an affirmative result of test 128 during the time that the fuel cell power plant is inoperative.
  • the test 123 When start up is impending, the test 123 will be affirmative reaching a process step 131 which initiates a start up timer and a process step 133 which starts the recycle function. Then the timer is monitored in a process test 135 to determine when the recycle process has been operated its desired length of time. When the time is up, an affirmative result reaches a process step 138 to stop the recycle process, and this procedure is vacated through the return point 107.
  • the recycle could either be turned on or remain on at the completion of the shutdown process, and allowed to remain on until a start up is in process.
  • the homogenization may simply take place when start up is indicated and run for a time determined by a start up timer, or allowed to run until a start up procedure is in process.
  • the gases be homogenized so that, particularly at start up, there will not be wide variations in gas compositions in the various cells which could result in some cell voltages being excessive, leading to carbon corrosion in and around the catalyst layers.
  • the particular manner of performing homogenization by means of one or both of the fuel and air recycle functions will be selected in dependence upon the overall characteristics of a fuel cell power plant in which it is to be implemented.

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  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Fuel Cell (AREA)

Abstract

To mitigate corrosion of carbon in and around the catalysts of a fuel cell power plant (5), the gases in the anodes (6) and/or cathodes (10) are homogenized when the fuel cell plant is not in operation, by operating either or both of the anode gas recycle function (19-23) or the cathode gas recycle function (34, 35, 42, 44-47), either continuously, and/or intermittently (126, 128), and/or immediately (131-138) before start up of the fuel cell power plant.

Description

Homogenous Gas in Shut Down Fuel Cells Technical Field
[0001] While a fuel cell power plant is shut down, either immediately after becoming shut down, or continuously and/or intermittently during the entire shut down period, and/or just before restart of the fuel cell power plant, either or both of anode recycle and cathode recycle homogenizes the gas concentration in all of the fuel cells of the stack, thereby mitigating carbon and catalyst corrosion in and around the catalyst layers.
Background Art
[0002] An exemplary fuel cell shutdown process is set forth in US
7,141 ,324. The process seeks to avoid, during shutdown, the presence of oxygen in the reactant gas compartments. The desired result is to extend the time that the stack can maintain a fuel-rich (such as greater than a 2: 1 fuel to air stoichiometry) environment.
[0003] The process disconnects the main load, connects an auxiliary load or shorting resistor, blocks the 'entry of oxygen from the source, such as air, while flowing hydrogen into the anodes with fuel recycling, and while recycling cathode exhaust to the cathode inlets.
[0004] When the cell voltage drops to 0.2 volts per cell, the process in the aforementioned patent assumes that substantially all of the oxygen within the cathode recycle system (flow fields, manifolds and associated plumbing), and any oxygen that has diffused across the electrolyte to the anode flow field will have been consumed. Once the voltage per cell reaches 0.2 volts, both the anode and the cathode receive fresh hydrogen, with both the anode and cathode recycle operative.
[0005] This has the effect of not only reducing the amount of oxygen in the cathodes by electrochemical reaction, but also eventually stabilizing the cathodes and the anodes with approximately the same partial pressure of hydrogen, along with inerts, mostly nitrogen, and traces of other gases, as the oxygen is consumed.
[0006] In the aforesaid patent, the process is continued until the cathode and anode have hydrogen concentrations greater than 90% as determined by hydrogen concentration sensors for the anodes and cathodes. Other processes may measure the oxygen and continue the process until the oxygen is a fractional percent.
[0007] The aforementioned procedure may include a rapid hydrogen fuel purge just prior to restarting the fuel cell power plant. [0008] The aforementioned procedures, or variants thereof, have been shown to be inadequate in that power plants still experience performance degradations due to carbon and catalyst corrosion in and around the catalyst layers. The decay is very irreproducible from substack to substack (e.g., substacks of 10 fuel cells in an overall stack of 250 cells). In fact, variations in substack performance of as much as 50% have been observed.
Summary
[0009] The variations in performance, between cells or substacks of cells, are believed to be due to variations in the air intrusion patterns (through leaks and the like) during shutdown. During shutdown, ambient air is drawn into the reactant gas chambers both by condensation of the water vapor in the stacks and by shrinking of the reactant gases due to cool down. This ambient air intrusion contains oxygen which is reacted with the hydrogen remaining in the reactant chambers further reducing the hydrogen inventory. With time, if the fuel cell power plant is shut down for more than about one day, the reactant chambers typically fill with air; however, during the transition (from hydrogen to air), the oxygen, nitrogen and hydrogen compositions vary from one cell to another and from one substack to another.
[0010] It has been discovered that this variation in gas compositions from cell to cell causes some cells to experience high voltages which lead to carbon and catalyst corrosion in and around the catalyst layers of those cells, which results in decay and reduced performance caused by the decay.
[0011] During periods of inoperation in these embodiments, the air at a point of intrusion, where the oxygen concentration is high enough to cause corrosion, is spread throughout the stack by homogenization, thereby reducing the concentration of air at any and all points to a lower, average concentration of all the cells which will not cause corrosion. The lower oxygen concentration at any cell mitigates the carbon and catalyst corrosion in and around catalyst layers and the consequent reduction in performance which would occur if local high O2 concentrations were allowed to exist.
[0012] The homogenization of gases during shutdown (inoperation) of the fuel cell power plant can be effected with either or both of the fuel recycle system and the aforementioned cathode recycle system. Homogenization may occur immediately after the final step of a shutdown procedure that is, at the time of turning off the hydrogen flow when the recycle pumps would otherwise be shut down. Or, the homogenization may take place either intermittently or continuously throughout the period that the fuel cell power plant is inoperative. Another alterative is to perform the homogenization just before the first step in a start up procedure for restoring the fuel cell power plant to operation. [0013] The homogenization may preferably begin immediately after shutdown of the power plant is complete, and continue, either intermittently or continuously, until just prior to the first step of a start up procedure.
[0014] The aforementioned irreproducible decay, resulting from gas composition variation from cell to cell, is currently the life-limiting mechanism for fuel cell power plants used in transportation. Homogenization of the gases during the time that a fuel cell power plant is inoperative will significantly extend the life of fuel cell power plants. [0015] Other variations will become more apparent in the light of the following detailed description of exemplary embodiments, as illustrated in the accompanying drawings.
Brief Description of the Drawings
[0016] Fig. 1 is a simplified, schematic diagram of an exemplary fuel cell power plant which has cathode recycle and which will benefit from the present embodiments. [0017] Fig. 2 is a simplified process diagram illustrating one of the embodiments of gas homogenization.
Mode(s) of Implementation
[0018] Referring to Fig. 1 , a fuel cell power plant 5 includes a stack of fuel cells 6, each fuel cell having an anode catalyst layer, a cathode catalyst layer and a proton exchange membrane disposed between said layers. Each fuel cell also has fuel reactant gas flow field channels adjacent the anode catalyst layer, with or without an additional layer between the fuel flow field channels and the catalyst layer. Each fuel cell also has oxidant reactant gas flow field channels adjacent the cathode catalyst layer, with or without an additional layer between the oxidant reactant gas flow field channels and the cathode catalyst layer. These are known and are not shown in the drawing.
[0019] The anodes 9 and cathodes 10 are separated by proton exchange membranes 11. The anodes 9 receive fuel from a source 14 which passes through a pressure regulator 15 and a flow control valve 16, which is adjusted by a controller 17. The fuel inlets 19 of the anodes also receive recycle fuel in a conduit 20 from a recycle pump 21 that is connected by a conduit 22 to the anode fuel outlets 23. The controller 17 also operates a purge valve 25 to periodically or continuously release a small portion of the anode exhaust in order to rid the fuel cells of contaminants and inerts such as nitrogen. The valve 25 is connected by a conduit 27 to a conduit 29 where the anode exhaust is mixed with cathode exhaust in conduit 29. The outflow of the conduit 29 may be to ambient or to a controlled confinement of some sort.
[0020] The cathodes 10 receive air at inlets 34 from an air blower 35. Air is applied to the input 37 of a filter 38, the output of which in the conduit 39 is passed through an air control valve 40 that is regulated by the controller 17. The cathode outlets 42 are connected through a recycle conduit 44, a valve 45 and a conduit 46 to the inlet 47 of the air blower 35, which is also connected to the valve 40 by a conduit 48. The recycle control valve 45 is operated by the controller 17 so as to control the amount, if any, of recycle air which is returned over a conduit 46 to the inlet 47 of the blower 35 and the cathode air inlets 34. [0021] The cathode outlets 42 are also connected by a conduit 50 through a check valve 51 to the conduit 29, thereby diluting any hydrogen which may remain in the anode exhaust.
[0022] As an example, in the embodiment disclosed, the fuel cell stack electrical power output 54 from the anode end of the stack, indicated by a minus sign, is connectable through a switch 55 to a conventional power conditioner 56, which is shown only schematically in the drawing. The output 57 of the power conditioner 56 is connected to an actual load 59, which may be a vehicle or other electrical utilization apparatus. The switch is shown connected to an auxiliary load 60, such as that described hereinbefore with respect to a hydrogen-stabilizing shutdown procedure. As shown schematically in the drawing, the loads are connected by a return line 62 to the cathode end of the stack, indicated by a plus sign. [0023] In the embodiment described herein, a signal 67 provided by the load 68 indicates that the stack should be shut down. The shut down signal could alternatively come from the power conditioner 56, such as when it senses a problem with the load. The controller will operate the switch 55 to shift the output of the fuel cell stack from the main load 59 to the auxiliary load 60. The valve 40 is closed to block fresh air, the valve 45 is opened to recycle cathode exhaust to the cathode inlets, and fuel continues to be provided to the anodes with fuel recycle on. [0024] Referring now to Fig. 2, an exemplary process 101 for homogenizing gases in a fuel cell power plant, while the power plant is inoperative, may be entered at a point 102. A first test 104 determines if the power plant is operating. If it is, homogenization is not required so an affirmative result of test 104 will allow other functions to be performed, through a return point 107. If the power plant is not operating, then a test 109 may be performed to determine if a start up routine is in process. If the power plant is in the process of starting up, an affirmative result of test 109 will end this process through the return point 107. [0025] If start up is not in process, then it should be determined at a test 111 whether shutdown of the power plant is complete or not. If it is not, then homogenization is not required. But if it is, an affirmative result will reach a step 114 in the process to initiate a run timer, indicative of how long recycle should be running before it shuts down again, in an embodiment in which the recycling is periodic or intermittent. A following step 116 in the process starts the recycle to operate, which might include starting only the fuel recycle pump, or it may comprise starting only the cathode blower or pump with the cathode recycle valve open, or the step may comprise starting both of the recycle systems. Then the timer is continuously monitored at a test 119. When timeout occurs, the recycle is stopped in a step 121.
[0026] A test 123 determines if start up of the fuel cell power plant is impending. This may be a small fraction of a minute before a start up procedure actually begins. If start up is not impending, a negative result reaches a step 126 which initiates a dwell timer, indicative of the amount of time between periods of operation of recycle. Then the dwell timer is monitored in a process test 128 to determine when the recycle should once again be started. An affirmative result of test 128 reverts the process back to the process step 114 to initiate the run timer and start recycle, as before. This will continue passing through a positive result of test 119, a negative result of test 123 and an affirmative result of test 128 during the time that the fuel cell power plant is inoperative. [0027] When start up is impending, the test 123 will be affirmative reaching a process step 131 which initiates a start up timer and a process step 133 which starts the recycle function. Then the timer is monitored in a process test 135 to determine when the recycle process has been operated its desired length of time. When the time is up, an affirmative result reaches a process step 138 to stop the recycle process, and this procedure is vacated through the return point 107. [0028] In other embodiments, the recycle could either be turned on or remain on at the completion of the shutdown process, and allowed to remain on until a start up is in process.
[0029] Or, in suitable cases, the homogenization may simply take place when start up is indicated and run for a time determined by a start up timer, or allowed to run until a start up procedure is in process. [0030] The important thing is that the gases be homogenized so that, particularly at start up, there will not be wide variations in gas compositions in the various cells which could result in some cell voltages being excessive, leading to carbon corrosion in and around the catalyst layers. The particular manner of performing homogenization by means of one or both of the fuel and air recycle functions will be selected in dependence upon the overall characteristics of a fuel cell power plant in which it is to be implemented.

Claims

Claims
1. A method (101), characterized by: during the time that a fuel cell power plant is not in operation (104), homogenizing the gas within the fuel cells by operating (116, 133) a recycle function selected from either or both of (a) an anode gas recycle function (21) and (b) a cathode gas recycle function (45-47).
2. A method (101) according to claim 1 further characterized in that said recycle function (19-23; 34, 42, 44-47) is operated continuously during the time that a fuel cell power plant is not in operation.
3. A method (101) according to claim 1 further characterized in that said recycle function (19-23; 34, 42, 44-47) is operated intermittently (126, 128) during the time that a fuel cell power plant is not in operation.
4. A method (101) according to claim 1 further characterized in that said recycle function (19-23; 34, 42, 44-47) is operated immediately (131-138) before start up of the fuel cell power plant.
5. A method (101) according to claim 1 further characterized in that said recycle function (19-23; 34, 42, 44-47) is operated (114, 116) immediately after the fuel cell power plant is shut down.
6. A method (101) according to claim 1 further characterized in that said recycle function (19-23; 34, 42, 44-47) is operated intermittently (126, 128) during the time that a fuel cell power plant is not in operation and immediately (131-138) before start up of the fuel cell power plant.
7. A method (101) according to claim 1 further characterized in that said recycle function (19-23; 34, 42, 44-47) comprises solely an anode gas recycle function (19-23), continuously and/or intermittently (126, 128) during the time that a fuel cell power plant is not in operation, and/or immediately (131-138) before start up of the fuel cell power plant.
8. A method (101) according to claim 1 further characterized in that said recycle function (19-23; 34, 42, 44-47) comprises solely a cathode gas recycle function (34, 42; 44-47), continuously and/or intermittently (126, 128) during the time that a fuel cell power plant is not in operation, and/or immediately (131-138) before start up of the fuel cell power plant.
PCT/US2008/012750 2008-11-12 2008-11-12 Homogenous gas in shut down fuel cells WO2010056224A1 (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130196240A1 (en) * 2012-01-23 2013-08-01 Honda Motor Co., Ltd. Fuel cell system and method for stopping operation of fuel cell system
CN103579643A (en) * 2012-07-25 2014-02-12 中国科学院大连化学物理研究所 Fuel cell system, parking discharge control method and use of fuel cell system
EP2840636A1 (en) * 2013-08-20 2015-02-25 Siemens Aktiengesellschaft Method for operating a fuel cell stack and fuel cell stack and fuel cell system

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6514635B2 (en) * 2001-01-25 2003-02-04 Utc Fuel Cells, Llc Procedure for shutting down a fuel cell system having an anode exhaust recycle loop
WO2006024933A2 (en) * 2004-09-03 2006-03-09 Nissan Motor Co., Ltd. Fuel cell system
US20080038602A1 (en) * 2006-08-10 2008-02-14 Gm Global Technology Operations, Inc. Method for mitigating cell degradation due to startup and shutdown via cathode re-circulation combined with electrical shorting of stack
WO2008093147A2 (en) * 2006-12-27 2008-08-07 Nissan Motor Co., Ltd. Fuel cell system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6514635B2 (en) * 2001-01-25 2003-02-04 Utc Fuel Cells, Llc Procedure for shutting down a fuel cell system having an anode exhaust recycle loop
WO2006024933A2 (en) * 2004-09-03 2006-03-09 Nissan Motor Co., Ltd. Fuel cell system
US20080038602A1 (en) * 2006-08-10 2008-02-14 Gm Global Technology Operations, Inc. Method for mitigating cell degradation due to startup and shutdown via cathode re-circulation combined with electrical shorting of stack
WO2008093147A2 (en) * 2006-12-27 2008-08-07 Nissan Motor Co., Ltd. Fuel cell system

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130196240A1 (en) * 2012-01-23 2013-08-01 Honda Motor Co., Ltd. Fuel cell system and method for stopping operation of fuel cell system
US9401520B2 (en) * 2012-01-23 2016-07-26 Honda Motor Co., Ltd. Fuel cell system and method for stopping operation of fuel cell system
CN103579643A (en) * 2012-07-25 2014-02-12 中国科学院大连化学物理研究所 Fuel cell system, parking discharge control method and use of fuel cell system
EP2840636A1 (en) * 2013-08-20 2015-02-25 Siemens Aktiengesellschaft Method for operating a fuel cell stack and fuel cell stack and fuel cell system
WO2015024785A1 (en) * 2013-08-20 2015-02-26 Siemens Aktiengesellschaft Method for operating a fuel cell stack, fuel cell stack and fuel cell system
KR20160032233A (en) * 2013-08-20 2016-03-23 지멘스 악티엔게젤샤프트 Method for operating a fuel cell stack, fuel cell stack and fuel cell system
AU2014310784B2 (en) * 2013-08-20 2016-07-28 Siemens Energy Global GmbH & Co. KG Method for operating a fuel cell stack, fuel cell stack and fuel cell system
KR101909796B1 (en) 2013-08-20 2018-10-18 지멘스 악티엔게젤샤프트 Method for operating a fuel cell stack

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