JP2010251219A - Fuel cell system and method of operating the fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve power generation performance of a fuel cell using a nonaqueous electrolyte attaining generating operation in a moderate temperature range. <P>SOLUTION: A fuel cell system 20 includes a fuel cell stack 30 on which a plurality of fuel cells 31 are laminated. The fuel cell 31 is a fuel cell using an ionic liquid in an electrolyte membrane. When a voltage V of the fuel cell 31 drops to a value lower than a predetermined value Th, the fuel cell system 20 flows a current larger than an output request 95, starts a heater 75 to supply an oxidation gas which is higher than 100°C to the fuel cell stack 30, switches the supply route of the oxidation gas from a route via bypass pining 77 to a route via a dehydrating device 74 to supply dry air to the fuel cell stack 30, and increases the flow velocity of the oxidation gas to be supplied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system having an anhydrous electrolyte having proton conductivity under anhydrous conditions, an anode, and a cathode.

  In recent years, various types of fuel cells have been developed. One of them is a fuel cell using an anhydrous electrolyte having proton conductivity under anhydrous conditions. As such an electrolyte, an ionic liquid can be mentioned, for example. The ionic liquid has the property of being a liquid at room temperature while being an ionic substance, is non-volatile, has high thermal stability, and does not need to be humidified. Therefore, the ionic liquid has a medium temperature range (for example, 100 to 150 ° C. ) Is attracting attention as an electrolyte for fuel cells that perform highly efficient power generation.

  However, a fuel cell that uses an ionic liquid as an electrolyte has a relatively short history of development compared to other types of fuel cells, and further improvements have been desired. Such a problem is not limited to fuel cells that use an ionic liquid as an electrolyte, but is a problem that is common to fuel cells that use an anhydrous electrolyte capable of generating operation in an intermediate temperature range.

JP 2007-311297 A

  In consideration of at least a part of the above-mentioned problems, the problem to be solved by the present invention is to improve the power generation performance of a fuel cell using an anhydrous electrolyte capable of generating power in a middle temperature range.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1] A fuel cell system, a fuel cell comprising an anhydrous electrolyte having proton conductivity under anhydrous conditions, an anode, and a cathode, and water present around the cathode is removed to remove the cathode A fuel cell system comprising water removal means for performing poisoning suppression processing for suppressing poisoning due to water.

  The fuel cell system having such a configuration can suppress moisture poisoning of the cathode by the poisoning suppression treatment in the fuel cell including the anhydrous electrolyte having proton conductivity under anhydrous conditions, thereby suppressing the decrease in the activity of the cathode and generating power. Can be suppressed. It should be noted that the moisture poisoning of the cathode means that when a predetermined amount of moisture adheres to the cathode, the activity of the cathode rapidly decreases, and this knowledge has been obtained together with the present invention.

[Application Example 2] The fuel cell system according to Application Example 1, further comprising monitoring means for monitoring the activity of the cathode, wherein the water removal means is configured such that the monitoring means reduces the activity of the cathode to a predetermined value or less. A fuel cell system that performs the poisoning suppression process when it is detected.

  In the fuel cell system having such a configuration, when the activity of the cathode decreases, the poisoning suppression treatment can be performed to recover the activity, so that moisture poisoning of the cathode can be efficiently suppressed.

[Application Example 3] The fuel cell according to Application Example 1 or Application Example 2, wherein the moisture removing means includes a dehydrating means for reducing the amount of moisture contained in the oxidizing gas supplied to the cathode, and the poisoning As one of the suppression processes, a fuel cell system that supplies the cathode with an oxidizing gas whose water content has been reduced by the dehydrating means.

  The fuel cell system having such a configuration suppresses moisture poisoning of the cathode by supplying the oxidizing gas whose moisture content has been reduced by the dehydrating means to the cathode, thereby drying and removing the moisture present around the cathode. Can do.

[Application Example 4] The fuel cell according to any one of Application Example 1 to Application Example 3, wherein the moisture removing means includes a heating means for heating an oxidizing gas supplied to the cathode, One is a fuel cell system that supplies an oxidizing gas heated by the heating means to the cathode.

  The fuel cell system having such a configuration can suppress moisture poisoning of the cathode by supplying the oxidizing gas heated by the heating means to the cathode, thereby drying and removing moisture present around the cathode.

Application Example 5 The fuel cell system according to any one of Application Examples 1 to 4, wherein the moisture removing unit increases the flow rate of the oxidizing gas supplied to the cathode as one of the poisoning suppression processes.

  In the fuel cell system having such a configuration, by increasing the flow rate of the oxidizing gas supplied to the cathode, moisture existing in the vicinity of the cathode can be dried and removed, and moisture poisoning of the cathode can be suppressed.

Application Example 6 In the application examples 1 to 5, the moisture removing unit generates, as one of the poisoning suppression processes, a current larger than the current required for output from the fuel cell system. Any one of the fuel cells.

  The fuel cell system configured as described above generates a current larger than the current required for the output of the fuel cell system in the fuel cell, and dries and removes moisture existing around the cathode by self-heating due to a power generation reaction. Can prevent water poisoning.

Application Example 7 The fuel cell system according to Application Example 3 or Application Example 4, wherein the moisture removing unit performs the poisoning suppression process before starting the power generation operation of the fuel cell system.

  The fuel cell system configured as described above supplies the oxidizing gas with reduced moisture content to the cathode and / or the heated oxidizing gas to the cathode before starting the power generation operation. Moisture remaining on the cathode during operation can be dried and removed in advance before the power generation operation, thereby suppressing water poisoning of the cathode and performing a suitable power generation operation.

Application Example 8 Application Example 3 or Application Example 4 in which the moisture removing unit performs the poisoning suppression process in a state where supply of fuel gas to the anode is stopped after the power generation operation of the fuel cell system is stopped. The fuel cell system described.

  In the fuel cell system configured as described above, after the power generation operation of the fuel cell system is stopped, the oxidizing gas with reduced moisture content is supplied to the cathode and / or the heated oxidizing gas is supplied to the cathode. Therefore, since moisture around the cathode is dried and removed and does not remain, at the start of the next power generation operation, moisture poisoning of the cathode can be suppressed and the power generation operation can be suitably performed.

[Application Example 9] A fuel cell system, a plurality of fuel cell stacks in which a plurality of fuel cells and fuel cells each having a proton conductivity under anhydrous conditions, an anode, and a cathode are stacked; Moisture removal means for performing poisoning suppression processing for removing moisture existing around the cathode and suppressing poisoning of the cathode by moisture for each of the plurality of fuel cell stacks, and the plurality of fuel cells Monitoring means for monitoring the activity of the cathode for each of the stacks, wherein the moisture removing means is configured to monitor the fuel cell stack in power generation operation among the plurality of fuel cell stacks. When it is detected that the activity of the cathode has fallen below a predetermined value, out of the plurality of fuel cell stacks, the power generation operation of the stopped fuel cell stack is started, The fuel cell stack decreases is detected in serial activity stops the power generation operation, the fuel cell system performs the poisoning suppression process.

  In the fuel cell system configured as described above, when the activity of the cathode decreases, the power generation operation of the fuel cell stack that is stopped is started, and the power generation operation is stopped for the fuel cell stack in which the decrease in activity is detected. At the same time, since the poisoning suppression process is performed, the system as a whole can be operated while suppressing a decrease in power generation performance due to a decrease in cathode activity. Further, since the power generation operation is stopped and the poisoning suppression process is performed, the effect of removing moisture is great, and the decrease in activity can be recovered reliably or in a short time.

Application Example 10 The fuel cell system according to any one of Application Examples 1 to 9, wherein the anhydrous electrolyte includes trifluoromethanesulfonic acid and diethylmethylamine.

  In the fuel cell system having such a configuration, when the anhydrous electrolyte contains trifluoromethanesulfonic acid and diethylmethylamine, high proton conductivity can be exhibited and suitable power generation performance can be exhibited.

Application Example 11 The fuel cell system according to any one of Application Examples 1 to 10, wherein the cathode includes at least platinum.

  If the fuel cell system having such a configuration is configured to include platinum in the cathode, it can exhibit high catalytic activity and exhibit suitable power generation performance.

In addition to the configuration as a fuel cell system, the present invention can also be realized as a fuel cell operation method according to Application Example 12, a program thereof, a storage medium storing the program, and the like.
[Application Example 12] A method of operating a fuel cell system comprising an anhydrous electrolyte having proton conductivity under anhydrous conditions, an anode, and a cathode, wherein the activity of the cathode is monitored, and the activity of the cathode is reduced to a predetermined value or less. A method of operating a fuel cell system, which removes moisture present around the cathode when it is lowered.

It is explanatory drawing which shows schematic structure of the fuel cell system 20 as 1st Example of this invention. 2 is an explanatory diagram showing a schematic configuration of a fuel cell stack 30. FIG. 4 is a flowchart showing a flow of cathode poisoning suppression processing in the fuel cell system 20. It is explanatory drawing which shows the relationship between the addition amount of the water to an ionic liquid, and oxygen reduction current density (at the time of voltage 0.8V) in the conventional fuel cell which used ionic liquid for electrolyte. It is explanatory drawing which shows schematic structure of the fuel cell system 20 as 2nd Example. It is a flowchart which shows the flow of the operation switching process in the fuel cell system 20 as 2nd Example. It is a flowchart which shows the flow of the starting / stopping process in the fuel cell system 20 as 3rd Example.

Examples of the present invention will be described.
A. First embodiment:
A-1. Schematic configuration of the fuel cell system 20:
FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system 20 as a first embodiment of the present invention. The fuel cell system 20 includes a fuel cell stack 30 that generates power by an electrochemical reaction, a fuel gas system device 60 that supplies and discharges fuel gas to the fuel cell stack 30, and an oxidizing gas that supplies and discharges oxidizing gas to and from the fuel cell stack 30. A system device 70, a cooling system device 80 for cooling the fuel cell stack 30, and a control unit 90 for controlling the fuel cell system 20 are provided.

  The fuel cell stack 30 is configured by stacking a plurality of fuel cells 31 including an anode, a cathode, an electrolyte membrane, a separator, and the like. Details of the configuration of the fuel cell stack 30 will be described later. The fuel cell stack 30 is provided with a voltmeter 35. The voltmeter 35 can measure the output voltage of each fuel cell 31 and the overall output voltage of the fuel cell stack 30.

  The fuel gas system device 60 includes a hydrogen tank 61, a shut valve 62, a regulator 63, a diluter 66, and pipes 64, 65 and 68. The high-pressure hydrogen stored in the hydrogen tank 61 is adjusted in pressure and supply amount by the shut valve 62 and the regulator 63 and supplied as fuel gas to the anode of the fuel cell stack 30 via the pipe 64. Exhaust gas from the anode (hereinafter also referred to as anode off gas) is guided to the diluter 66 via the pipe 65 and then discharged out of the fuel cell system 20 via the pipe 68.

  The oxidizing gas system device 70 includes an air cleaner 71, an air compressor 72, a three-way valve 73, a dehydrator 74, a heater 75, pipes 76 and 78, and a bypass pipe 77. Air sucked from the air cleaner 71 is compressed by the air compressor 72 and supplied as an oxidizing gas to the cathode of the fuel cell stack 30 via the three-way valve 73, the dehydrator 74, the heater 75 and the pipe 76. Further, the sucked air can be guided to the heater 75 via the bypass pipe 77, that is, bypass the dehydrator 74 by controlling the three-way valve 73. Exhaust gas from the cathode (hereinafter also referred to as “cathode off-gas”) is introduced into the diluter 66 via a pipe 78.

  The dehydrator 74 reduces the amount of water in the supply air. In this embodiment, an adsorption method is adopted. Specifically, moisture was adsorbed by passing air through a layer filled with activated carbon. However, the adsorptive member is not limited to activated carbon, and may be, for example, a water-absorbing polymer. Further, the dehydration method is not limited to the adsorption method, and may be a method of dehydrating by cooling or pressurization. The dehydrator 74 is used for the cathode poisoning suppression process described later, and is not used during normal power generation operation of the fuel cell system 20. That is, during normal operation, the three-way valve 73 is controlled so that supply air is guided to the heater 75 via the bypass pipe 77.

  In this embodiment, the heater 75 is an electric heater, and heats the supply air by a heater provided in the flow path of the supply air. In this embodiment, when the heater 75 is activated, the air can be heated to 100 ° C. or higher. The heater 75 is used for cathode poisoning suppression processing described later, and is not used during normal power generation operation of the fuel cell system 20. That is, during normal operation, the heater 75 is in a stopped (OFF) state. If the heater 75 is provided in the path between the dehydrator 74 and the fuel cell stack 30 as in the present embodiment, the air supplied through the route passing through the dehydrator 74 is heated by the heater 75. Since there is little moisture of supply air, it can heat efficiently. However, the arrangement order of the dehydrator 74 and the heater 75 may be reversed.

  The diluter 66 dilutes the concentration of hydrogen contained in the anode off gas by mixing the cathode off gas and the anode off gas. The exhaust gas discharged from the diluter 66 is discharged out of the fuel cell system 20 through the pipe 68. The fuel gas system device 60 may be configured such that the anode off-gas is guided again to the pipe 64 and circulated and used in the fuel cell stack 30. The fuel gas system device 60 may have a so-called anode dead end configuration that does not have an anode off-gas discharge path. Further, the fuel gas system device 60 and the oxidant gas system device 70 may individually include an off-gas discharge path.

  The cooling system device 80 includes a radiator 81, a circulation pump 82, and a pipe 83. The cooling water is circulated between the fuel cell stack 30 and the radiator 81 by the circulation pump 82 through the pipe 83. Thereby, the heat generated by the electrochemical reaction of the fuel cell stack 30 is absorbed and the heat is dissipated by the radiator 81, so that the temperature of the fuel cell stack 30 can be maintained appropriately.

  Each component described above is controlled by the control unit 90. The control unit 90 is configured as a microcomputer including a CPU, a RAM, and a ROM therein, and an output request 95 and various sensors of the fuel cell system 20 are executed by developing a program stored in the ROM and executing the program. In response to the signal from 97, a drive signal is output to the regulator 63, the air compressor 72, the heater 75, etc. and various actuators 96 of the fuel cell system 20 to control the overall operation of the fuel cell system 20. The control unit 90 also functions as a monitoring unit 91 and a moisture removal control unit 92. Details of the monitoring unit 91 and the moisture removal control unit 92 will be described later in “A-3. Cathode poisoning suppression process”.

A-2. General configuration of the fuel cell stack 30:
The configuration of the fuel cell stack 30 described above will be described with reference to FIG. In the fuel cell stack 30 of this embodiment, a plurality of fuel cells 31 including an electrolyte membrane / electrode assembly 41, a gas diffusion layer 46, and a separator 50 are stacked, and terminals, insulators, and end plates (not shown) are formed from both ends of the stacked body. It is configured to be sandwiched. In addition, the fuel cell stack 30 is not limited to a configuration in which a plurality of fuel cells 31 are stacked, and may be configured by a single fuel cell 31.

  The electrolyte membrane / electrode assembly 41 is a portion where an electrochemical reaction of the fuel cell is performed, and includes an anode 42, an electrolyte membrane 43, and a cathode 44. The electrolyte membrane 43 is an anhydrous electrolyte that uses ionic liquid and has proton conductivity under anhydrous conditions. In the present embodiment, the electrolyte membrane 43 is formed by gelling an ionic liquid. As such a gelling material, various polymer materials can be used. In this example, a cyclic dipeptide derivative (cyclo (L-Asp (OR) -L-Phe)) was used.

  The ionic liquid is a salt that becomes liquid at room temperature, and various known ones can be used. For example, it may be a hydrophilic ionic liquid containing an imidazolium derivative cation and a trifluoromethanesulfonate anion, or selected from the group consisting of an imidazolium derivative cation, a pyridinium derivative cation, a pyrrolidinium derivative cation, and an ammonium derivative cation. At least one molecular cation and at least one molecular anion selected from the group consisting of boron tetrafluoride anion, trifluoromethanesulfonate anion, hydrogen fluoride anion, monohydrogen sulfate anion and dihydrogen phosphate anion The ionic liquid containing these may be sufficient. In this example, an ionic liquid containing trifluoromethanesulfonic acid and diethylmethylamine having excellent proton conductivity was used.

  The anode 42 and the cathode 44 are formed by supporting a catalyst on a conductive carrier, and form a three-phase interface of a catalyst, an electrolyte, and a reactive gas (fuel gas or oxidizing gas). In this example, carbon particles carrying a platinum catalyst were immersed in the ionic liquid and fixed with an ionomer (here, polytetrafluoroethylene). In this example, platinum having high activity was used as the catalyst. However, the type of the catalyst is not particularly limited. For example, an alloy of platinum and nickel or cobalt may be used, or nickel or ruthenium may be used. It may be used.

  The gas diffusion layer 46 serves as a flow path for a reaction gas used for an electrochemical reaction in the electrolyte membrane / electrode assembly 41 and collects current. In general, the gas diffusion layer 46 can be formed of a conductive member having gas permeability, such as carbon paper, carbon cloth, or carbon nanotube. In this example, carbon cloth was used.

  In addition, a seal portion 47 is provided on the outer periphery of the electrolyte membrane / electrode assembly 41 and the gas diffusion layer 46 to ensure the sealing performance of the flow path of the reaction gas formed by the gas diffusion layer 46. Yes. As shown in the figure, the seal portion 47 is provided with several through holes. The through hole is provided in the separator 50 in the same manner, and will be described below together with the description of the separator 50.

  The separator 50 is a portion that forms the wall surface of the gas diffusion layer 46 that serves as a reaction gas flow path. In this embodiment, stainless steel is used, but a gas-impermeable conductive member, for example, dense carbon that has been made gas impermeable by compressing carbon, or calcined carbon, may be used. The separator 50 and the above-described seal portion 47 are provided with several through holes in the outer peripheral portion thereof. By connecting these through holes, as shown in the figure, a fuel gas supply manifold 51 and a fuel gas discharge manifold 52 as fuel gas flow paths, and an oxidant gas supply manifold 53 and oxidant gas discharge as oxidant gas flow paths. A manifold 54, a cooling water supply manifold 55 as a cooling water flow path, and a cooling water discharge manifold 56 are formed.

  The fuel gas supplied from the pipe 64 of the fuel gas system device 60 to the fuel gas supply manifold 51 passes through the flow path and the hole (not shown) formed in the separator 50 and the gas diffusion layer 46. And supplied from the gas diffusion layer 46 to the anode 42. Then, the anode off gas is discharged from the gas diffusion layer 46 to the fuel gas discharge manifold 52 through a hole portion of the separator 50 and a flow path (not shown) formed therein, and is connected to the pipe 65 of the fuel gas system device 60. Led to.

  In addition, the oxidizing gas supplied from the piping 76 of the oxidizing gas system device 70 to the oxidizing gas supply manifold 53 is diffused through a flow path and a hole (not shown) formed in the separator 50. The gas is supplied to the layer 46 and supplied from the gas diffusion layer 46 to the cathode 44. Then, the cathode off-gas is discharged from the gas diffusion layer 46 to the oxidizing gas discharge manifold 54 through the hole portion of the separator 50 and a flow path (not shown) formed therein, and is connected to the piping 78 of the oxidizing gas system device 70. Led to.

  Further, the cooling water supplied to the cooling water supply manifold 55 from the cooling system device 80 described above is discharged to the cooling water discharge manifold 56 through a flow path (not shown) formed in the separator 50. Again, it is guided to the cooling system device 80.

  The fuel cell system 20 described above can be operated at 100 ° C. or higher because the electrolyte membrane 43 has proton conductivity under anhydrous conditions. In this embodiment, the operating temperature of the fuel cell system 20 is 100 ° C. or higher, specifically 120 ° C. In this way, the operating temperature is set to be higher when platinum is used as the catalyst, because the ionic liquid is adsorbed on the catalyst and the oxygen reduction reaction may be hindered to increase the overvoltage. This is because it is possible to suppress an increase in the amount of. However, the temperature of the operation of the fuel cell system 20 may be an intermediate temperature range, and may be, for example, a range from room temperature to about 180 ° C.

A-3. Cathode poisoning suppression treatment:
The cathode poisoning suppression process in the fuel cell system 20 will be described with reference to FIG. The cathode poisoning suppression treatment here is that the cathode 44 is poisoned by the water contained in the oxidizing gas supplied to the cathode 44 or the generated water generated by the power generation reaction at the cathode 44, and the activity decreases. This is a process to suppress this. In the present embodiment, the cathode poisoning suppression process is started and repeated when the power generation operation of the fuel cell system 20 reaches a steady operation. Here, the steady operation refers to an operation performed after the start-up mode operation of the fuel cell system 20 is finished and before the stop-mode operation is started.

  When the cathode poisoning suppression process is started, the control unit 90 determines whether or not the voltage V detected by the voltmeter 35 is equal to or lower than a predetermined value Th as a process of the monitoring unit 91 (step S110). In the present embodiment, the voltage V is an output voltage of each fuel cell 31 constituting the fuel cell stack 30, and if the output voltage of any one of the fuel cells 31 is equal to or less than a predetermined value Th, the control unit 90 Determines that the voltage V has become equal to or lower than the predetermined value Th. This is because it is possible to detect a decrease in the output of the fuel cell stack 30 on the safer side. However, the voltage V may be the entire voltage of the fuel cell stack 30. Alternatively, the control unit 90 may determine that the voltage V has become equal to or less than the predetermined value Th when the output voltage of the predetermined number of fuel cells 31 has become equal to or less than the predetermined value Th.

  The determination in step S110 is to determine whether or not the activity of the cathode 44 has decreased. The control unit 90 determines that the activity of the cathode 44 is predetermined when the voltage V becomes equal to or lower than the predetermined value Th. Judged to have decreased to the following. However, the criterion for determining the decrease in the activity of the cathode 44 is not limited to such an example. In the fuel cell system 20 of the present embodiment, the main factors that decrease the output voltage of the fuel cell 31 are a decrease in the activity of the cathode 44 and a decrease in the operating temperature T of the fuel cell 31. Therefore, for example, the fuel cell stack 30 includes a temperature sensor that detects the operating temperature T, and the control unit 90 is configured only when the operating temperature T is equal to or higher than a predetermined value and the voltage V is equal to or lower than the predetermined value Th. It may be determined that the activity of the cathode 44 has decreased.

  As a result, if the voltage V is larger than the predetermined value Th (step S110: NO), it means that the activity of the cathode 44 has not decreased, and the control unit 90 returns the process to the original. On the other hand, if the voltage V is equal to or less than the predetermined value Th (step S110: YES), this means that the activity of the cathode 44 has decreased, and the control unit 90 outputs the output request 95 as a process of the moisture removal control unit 92. Is controlled to flow a larger current (step S120). Specifically, the shut valve 62, the regulator 63 and the air compressor 72 are controlled to supply a larger amount of reaction gas to the fuel cell stack 30 than the supply amount of reaction gas corresponding to the output request 95. The reason why such a large current flows is to increase the amount of heat generated by the power generation reaction of the fuel cell stack 30 and to dry and remove moisture existing around the cathode 44 by self-heating.

  When a current larger than the output request 95 is supplied, the control unit 90 determines whether or not the voltage V is equal to or lower than a predetermined value Th after a predetermined period has elapsed (step S130). The predetermined value Th here is the same value as the predetermined value Th in step S110 described above. The same applies to a predetermined value Th in step S150 and step S170 described later. As a result, if the voltage V is equal to or lower than the predetermined value Th (step S130: YES), the activity of the cathode 44 has not recovered, so the control unit 90 further switches the heater 75 on as a process of the moisture removal control unit 92. Activation (ON) is performed, and an oxidizing gas of 100 ° C. or higher (hereinafter also referred to as a high-temperature oxidizing gas) is supplied to the fuel cell stack 30 (step S140). In this embodiment, the oxidizing gas is heated to 110 ° C. by the heater 75.

  As described above, the high-temperature oxidizing gas is supplied to dry and remove moisture existing around the cathode 44. The oxidizing gas is dried at a temperature higher than the boiling point (100 ° C.) of water. The removal effect is increased. However, the heating temperature of the oxidizing gas may be 100 ° C. or less. This is because even when the temperature is 100 ° C. or lower, the saturated vapor pressure of water becomes larger than when heating is not performed, and moisture drying and removal effects can be expected to some extent.

  Further, as the power source of the heater 75, surplus power when generating power with an output larger than the output request 95 in step S120 can be used. That is, an efficient process is realizable by combining the process of step S120 and the process of step S140. However, the power of the battery provided in the fuel cell system 20 may be used as the power source of the heater 75.

  When the heater 75 is activated, the control unit 90 determines whether or not the voltage V is equal to or lower than a predetermined value Th after a predetermined period has elapsed (step S150). As a result, if the voltage V is equal to or lower than the predetermined value Th (step S150: YES), the activity of the cathode 44 has not recovered, so that the control unit 90 further performs a three-way valve 73 as a process of the moisture removal control unit 92. Is controlled to switch the supply route of the oxidizing gas from the route via the bypass pipe 77 to the route via the dehydrator 74 (step S160). As a result, the dehydrating device 74 supplies an oxidizing gas (hereinafter also referred to as dry air) having a reduced water content to the fuel cell stack 30.

  When the dry air is supplied, the control unit 90 determines whether or not the voltage V is equal to or lower than the predetermined value Th after the elapse of the predetermined period (step S170). As a result, if the voltage V is less than or equal to the predetermined value Th (step S170: YES), the activity of the cathode 44 has not recovered, and the control unit 90 further performs the processing of the moisture removal control unit 92 as the air compressor 72. Is controlled to increase the flow rate of the supplied oxidizing gas (step S180).

  When the flow rate of the oxidizing gas is increased, the control unit 90 determines whether or not the voltage V is equal to or lower than the predetermined value Th after the predetermined period has elapsed (step S190). As a result, if the voltage V is equal to or lower than the predetermined value Th (step S190: YES), the activity of the cathode 44 is not recovered, so that the control unit 90 performs the above-described steps S120, S140, S160, The process of S180 is continued.

  On the other hand, if the voltage V is greater than the predetermined value Th (step S190: NO), or if the voltage V is greater than the predetermined value Th in steps S130, S150, S170 (any of steps S130, S150, S170: NO). Since the activity of the cathode 44 has been recovered, the control unit 90 stops the processes of steps S120, S140, S160, and S180 as the process of the moisture removal control unit 92, and returns the operation of the fuel cell stack 30 to the normal operation. (Step S200). Thus, the cathode poisoning suppression process is completed.

  In the above-described cathode poisoning suppression process, the control unit 90 is configured to execute the four processes of steps S120, S140, S160, and S180 step by step in a predetermined order after a predetermined elapsed period. The processing order of the four processes is not particularly limited, and may be arbitrarily changed. The control unit 90 may be configured to simultaneously execute at least two of the four processes when the voltage V is equal to or lower than the predetermined value Th. The control unit 90 need not execute all four processes, and may be configured to execute at least one of these processes. Further, the predetermined value Th that is a criterion for determining whether or not the four processes can be executed does not have to be the same value as described above, and may be different values. In addition, the control unit 90 may select a process to be executed from among the processes of steps S120, S140, S160, and S180 according to the value of the voltage V.

A-4. effect:
Before describing the effects of this embodiment, problems in a conventional fuel cell using an ionic liquid as an electrolyte (hereinafter referred to as a conventional fuel cell) will be described. FIG. 4 is a diagram in which water is added to an ionic liquid as an electrolyte in a conventional fuel cell, and the relationship between the amount of water added and the oxygen reduction current density (at a voltage of 0.8 V) is plotted. As shown in the figure, the oxygen reduction current density of the conventional fuel cell is in the range of 0.15 to 0.16 mA / cm ² until the water addition amount is 1000 ppm, whereas the water addition amount is about In 10000 ppm, in about 0.04mA / cm ^2, 100000ppm, is approximately 0 mA / cm ^2.

  That is, when the amount of water added increases more than a predetermined amount, the oxygen reduction current density rapidly decreases. This indicates that in conventional fuel cells, if the moisture contained in the oxidizing gas or the water generated by the power generation reaction remains on the cathode more than a predetermined amount, the activity of the cathode is drastically lowered (moisture poisoning of the cathode). ing. Such knowledge has been obtained together with the present invention.

In light of this problem, the fuel cell system 20 of the above-described embodiment detects the cathode voltage V decreasing, that is, detects that the activity of the cathode 44 has decreased due to moisture poisoning. A process for drying and removing moisture existing around 44, specifically, the following four processes are executed.
(1) A current larger than the output request 95 is passed.
(2) Supply high-temperature oxidizing gas to the fuel cell 31.
(3) Supply dry air to the fuel cell 31.
(4) Increase the flow rate of the oxidizing gas.
By such treatment, the fuel cell system 20 can dry and remove moisture present around the cathode 44, recover poisoning of the cathode 44 due to moisture, and suppress deterioration in power generation performance.

  Further, since the above-described four processes are executed in stages, the contents of the processes do not become excessive and are efficient. Moreover, since the above-mentioned four processes are executed only when the activity of the cathode 44 is lowered, it is efficient.

B. Second embodiment:
The second embodiment of the present invention will be described for differences from the first embodiment. A schematic configuration of a fuel cell system 20 as a second embodiment is shown in FIG. As illustrated, the fuel cell system 20 as the second embodiment includes a first system 20a, a second system 20b, and a control unit 90. The first system 20a includes a fuel cell stack 30a, a fuel gas system device 60a, an oxidizing gas system device 70a, and a cooling system device 80a. The configuration of each of the fuel cell stack 30a, the fuel gas system device 60a, the oxidizing gas system device 70a, and the cooling system device 80a is the same as that of the fuel cell stack 30, the fuel gas system device 60, and the oxidizing gas system device 70 of the first embodiment described above. This is the same as the cooling system device 80, and the illustration is simplified. The configuration of the second system 20b is the same as that of the first system 20a. That is, the fuel cell system 20 includes two series of fuel cell stacks. Hereinafter, the components of the first system 20a and the second system 20b are expressed by adding “a” and “b” to the end of the reference numerals of the components used in the first embodiment.

  The configuration of the control unit 90 is basically the same as that of the first embodiment. However, the control unit 90 receives the output request 95 and signals from the various sensors 97a and 97b of the first system 20a and the second system 20b. Drive signals are output to the various actuators 96a and 96b of the first system 20a and the second system 20b, and the overall operation of both the first system 20a and the second system 20b is controlled. In the present embodiment, the control unit 90 performs a power generation operation using either one of the first system 20a and the second system 20b. That is, one of the first system 20a and the second system 20b functions as a spare machine. The control unit 90 may be individually provided for each system.

  The operation switching process in the fuel cell system 20 will be described with reference to FIG. The operation switching process is a process for switching and controlling the power generation operation between the first system 20a and the second system 20b while suppressing moisture poisoning of the cathodes 44a and 44b. This process is started when the power generation operation of one of the first system 20a and the second system 20b is started and reaches a steady operation. Here, the description will be made assuming that the first system 20a has reached steady operation. The second system 20b is in a stopped state.

  When the operation switching process is started, the control unit 90 causes the voltage V detected by the voltmeter 35a of the first system 20a during the power generation operation to be equal to or less than a predetermined value Th as a process of the monitoring unit 91 as shown in FIG. It is determined whether or not (step S310). As a result, if the voltage V is greater than the predetermined value Th (step S310: NO), the activity of the cathode 44a has not decreased, and the control unit 90 continues the steady operation.

  On the other hand, if the voltage V is equal to or lower than the predetermined value Th (step S310: YES), the activity of the cathode 44a is reduced, so that the control unit 90 performs the second operation during the operation stop as the process of the moisture removal control unit 92. The power generation operation of the system 20b is activated (step S320), and the system waits until the activated power generation operation of the second system 20b reaches a steady operation (step S330).

  Then, when the power generation operation of the activated second system 20b reaches a steady operation (step S330: YES), the control unit 90 initially performs the power generation operation as the process of the moisture removal control unit 92. The generator 75 is stopped, the heater 75a is started (ON), and the oxidizing gas supply route is switched from the route via the bypass pipe 77 to the route via the dehydrator 74, so that dry air of 100 ° C. or higher is predetermined. The fuel cell stack 30a is supplied for a period (step S340). The treatment here may be either dry air supply or high-temperature oxidizing gas supply.

  When the supply of the dry air at 100 ° C. or higher is completed, the control unit 90 stops the operation of the first system 20a that was initially performing the power generation operation (step S350). Thus, the operation switching process ends. In the next operation switching process, the first system 20a is started in step S320, and the second system 20b is stopped in step S350.

  In the above-described example, in step S340, in a state where the power generation operation is stopped, dry air of 100 ° C. or higher is supplied to the first system 20a for a predetermined period, but while performing the power generation operation of the first system 20a, When the dry air is supplied and the voltage V becomes larger than a predetermined value, the supply may be stopped. In this way, the first system 20a can be stopped after confirming that the cathode 44a has recovered. The fuel cell system 20 may include three or more fuel cell stacks. If at least one of the systems functions as a spare machine, the same control as in the above example is possible.

  The fuel cell system 20 having such a configuration causes one of the first system 20a and the second system 20b to perform a power generation operation. And if the activity of the cathode of the system | strain in power generation operation falls, while switching the system | strain which performs power generation operation, high temperature dry air is supplied with respect to the system | strain with which activity fell, and activity is recovered. That is, it is possible to recover the activity of the cathode of the fuel cell stack whose activity has decreased while performing suitable power generation with the fuel cell stack whose activity has not decreased. Therefore, it is possible to suppress a decrease in power generation performance as the entire system. In addition, the newly activated system can start the power generation operation in a state where the activity has been recovered. Moreover, since the poisoning suppression process is performed in a state where the power generation operation is stopped, that is, in a state where generated water is not generated at the cathode 44, the moisture removal effect is large, and the decrease in activity can be reliably recovered. Or the fall of activity can be recovered in a short time. Further, even after the power generation operation is stopped, the residual hydrogen can be completely consumed (power generation) with the high temperature dry air. In addition to the moisture removal effect of the cathode 44 by the high temperature dry air, the water removal effect by the self-heating due to the power generation is also achieved. I can expect.

C. Third embodiment:
A difference of the third embodiment of the present invention from the first embodiment will be described. The configuration of the fuel cell system 20 as the third embodiment is the same as that of the first embodiment, and is different from the first embodiment in that start / stop processing described later is performed. Hereinafter, the start / stop processing will be described with reference to FIG. The start / stop process is a process for performing start / stop control of the fuel cell system 20 for suppressing a decrease in the activity of the cathode 44. In the present embodiment, the start / stop process is started when the power of the fuel cell system 20 is turned on.

  When the start / stop process is started, the control unit 90 waits for an instruction to start the power generation operation of the fuel cell system 20 as shown in FIG. 7 (step S410). Such an instruction may be received from a user interface included in the fuel cell system 20, or may be received from a CPU or the like of a vehicle or device in which the fuel cell system 20 is mounted.

  Then, upon receiving an instruction to start the power generation operation of the fuel cell system 20 (step S410: YES), the control unit 90 supplies dry air to the fuel cell 31 for a predetermined period as a process of the moisture removal control unit 92, and the previous power generation. The water remaining around the cathode 44 at the end of the operation is dried and removed (step S420). When the dry air is supplied, the control unit 90 starts the power generation operation of the fuel cell system 20 (step S430).

  When the power generation operation is started, the control unit 90 waits for an instruction to stop the power generation operation of the fuel cell system 20 (step S440). And if the stop instruction | indication of electric power generation driving | operation is received (step S440: YES), the control unit 90 will supply dry air to the fuel cell 31 after stopping supply of fuel gas as a process of the water | moisture-content removal control part 92, Hydrogen remaining in the fuel cell 31 is completely consumed (power generation) (step S450). In steps S420 and S450, a high-temperature oxidizing gas may be supplied instead of or in addition to the supply of dry air. Further, the above-described processing may be executed either before starting the power generation operation or after stopping the power generation operation.

  The fuel cell system 20 having such a configuration dries and removes moisture existing around the cathode 44 by supplying dry air before or after the power generation operation of the fuel cell system 20 is started. In addition, moisture poisoning of the cathode 44 at the next start-up can be suppressed, and a decrease in power generation performance can be suppressed. In addition, since the residual hydrogen is completely consumed by dry air after the power generation operation is stopped, in addition to the moisture removal effect of the cathode 44 by dry air, a moisture removal effect by self-heating due to power generation can be expected. In addition, since the poisoning suppression process is performed in a state where the power generation operation is stopped, the water removal effect is large, and the decrease in activity can be reliably recovered. Or the fall of activity can be recovered in a short time.

D. Variation:
A modification of the above-described embodiment will be described.
D-1. Modification 1:
In the first and second embodiments described above, when the control unit 90 determines that the activity of the cathode 44 has decreased, the control unit 90 executes a process of suppressing moisture poisoning of the cathode 44 such as supply of dry air. Although configured, such processing may be performed at all times regardless of the activity of the cathode 44. In this way, moisture poisoning of the cathode 44 can be more reliably suppressed. When such processing is always performed, there may be a difference in the degree and number of processing between the normal time and the detection of the decrease in the activity of the cathode 44. For example, when the control unit 90 always heats the oxidizing gas using the heater 75, the oxidizing unit normally heats the oxidizing gas to 50 ° C., and when the activity of the cathode 44 decreases, the oxidizing gas reaches 100 ° C. or more. You may control so that it may become. In this way, efficient processing can be performed according to the situation.

  Alternatively, the control unit 90 may execute a process for suppressing moisture poisoning of the cathode 44 intermittently at a predetermined timing. The predetermined timing can be, for example, every predetermined period. Such a period can be, for example, when the power generation operation time reaches a predetermined time or when the total output reaches a predetermined value. In this way, the processing can be made efficient.

  Further, in the third embodiment, for the system that switches the power generation operation of the first system 20a and the second system 20b at a predetermined timing, for example, every predetermined period, and stops the power generation operation, Dry air may be supplied. In each of the above-described configurations, the voltmeter 35 is not essential when the detection of the decrease in the activity of the cathode 44 by the voltmeter 35 is not triggered by the execution of the processing.

D-2. Modification 2:
In the above-described embodiment, the electrolyte membrane 43 formed by gelling an ionic liquid with a polymer material is used as a method for holding the ionic liquid in the electrolyte membrane 43. However, the ionic liquid holding method is limited to such an example. It is not something that can be done. For example, the matrix layer formed of fine particles such as silicon carbide may be impregnated with an ionic liquid to hold the ionic liquid in the matrix layer, or may be formed by a diaphragm film between the anode 42 and the cathode 44. It is good also as a free electrolyte type which circulates an ionic liquid in the made electrolyte chamber. These methods are generally used in alkaline fuel cells and phosphoric acid fuel cells.

  The embodiment of the present invention has been described above, but among the components of the present invention in the above-described embodiment, elements other than the elements described in the independent claims are additional elements and can be omitted as appropriate. Moreover, although the embodiment of the present invention has been described, the present invention is not limited to such an example, and it is needless to say that the present invention can be implemented in various modes without departing from the gist of the present invention. For example, the present invention can be applied not only to a fuel cell using an ionic liquid as an electrolyte but also to various fuel cell systems using an anhydrous electrolyte having proton conductivity under anhydrous conditions. In addition to the configuration as a fuel cell system, the present invention can be realized as a fuel cell operating method, a computer program thereof, a storage medium storing the program, and the like.

DESCRIPTION OF SYMBOLS 20 ... Fuel cell system 20a ... 1st system 20b ... 2nd system 30, 30a, 30b ... Fuel cell stack 31 ... Fuel cell 35 ... Voltmeter 41 ... Electrolyte membrane electrode assembly 42 ... Anode 43 ... Electrolyte membrane 44 ... Cathode 46 ... Gas diffusion layer 47 ... Seal part 50 ... Separator 51 ... Fuel gas supply manifold 52 ... Fuel gas discharge manifold 53 ... Oxidation gas supply manifold 54 ... Oxidation gas discharge manifold 55 ... Cooling water supply manifold 56 ... Cooling water discharge manifold 60, 60a, 60b ... fuel gas system equipment 61 ... hydrogen tank 62 ... shut valve 63 ... regulator 64, 65, 68 ... piping 66 ... diluter 70, 70a, 70b ... oxidizing gas system equipment 71 ... air cleaner 72 ... air compressor 73 ... three-way Valve 74 ... Dehydrator 75 ... Heater 76, 78 ... Piping 77 ... Bypass piping 80, 80a, 80b ... Cooling system equipment 81 ... Radiator 82 ... Circulation pump 83 ... Piping 90 ... Control unit 91 ... Monitoring unit 92 ... Moisture removal control unit 95 ... Output request 96, 96a, 96b ... Various actuators 97, 97a, 97b ... Various sensors

Claims (12)

A fuel cell system,
A fuel cell comprising an anhydrous electrolyte having proton conductivity under anhydrous conditions, an anode, and a cathode;
A fuel cell system comprising: a moisture removing unit that removes moisture present around the cathode and performs poisoning suppression processing that suppresses poisoning of the cathode due to moisture. The fuel cell system according to claim 1, wherein
And further comprising monitoring means for monitoring the activity of the cathode,
The water removal means performs the poisoning suppression process when the monitoring means detects that the activity of the cathode has dropped below a predetermined value. Fuel cell system. The fuel cell system according to claim 1 or 2, wherein
The moisture removing means includes
Comprising dehydrating means for reducing the amount of water contained in the oxidizing gas supplied to the cathode;
As one of the poisoning suppression processes, a fuel cell system that supplies an oxidant gas whose water content has been reduced by the dehydrating means to the cathode. A fuel cell system according to any one of claims 1 to 3,
The moisture removing means includes
A heating means for heating the oxidizing gas supplied to the cathode;
As one of the poisoning suppression processes, a fuel cell system that supplies the cathode with the oxidizing gas heated by the heating means.   The fuel cell system according to any one of claims 1 to 4, wherein the moisture removing means increases the flow rate of the oxidizing gas supplied to the cathode as one of the poisoning suppression processes.   The fuel according to any one of claims 1 to 5, wherein the moisture removing means causes the fuel cell to generate a current larger than a current required for the fuel cell system as one of the poisoning suppression processes. Battery system.   5. The fuel cell system according to claim 3, wherein the moisture removing unit performs the poisoning suppression process before starting the power generation operation of the fuel cell system.   5. The fuel cell system according to claim 3, wherein the moisture removing unit performs the poisoning suppression process in a state where supply of fuel gas to the anode is stopped after the power generation operation of the fuel cell system is stopped. . A fuel cell system,
A plurality of fuel cell stacks in which a plurality of fuel cells including an anhydrous electrolyte having proton conductivity under anhydrous conditions, an anode, and a cathode are stacked;
Moisture removal means for performing a poisoning suppression process for removing moisture present around the cathode and suppressing poisoning due to moisture of the cathode for each of the plurality of fuel cell stacks;
Monitoring means for monitoring the activity of the cathode for each of the plurality of fuel cell stacks;
The moisture removing unit is configured to detect the plurality of fuels when the monitoring unit detects that the activity of the cathode of the fuel cell stack in the power generation operation of the plurality of fuel cell stacks falls below a predetermined value. A fuel cell stack that is out of operation is started to generate power, and the power generation operation is stopped and the poisoning suppression process is performed on the fuel cell stack in which the decrease in activity is detected. Battery system.   The fuel cell system according to any one of claims 1 to 9, wherein the anhydrous electrolyte contains trifluoromethanesulfonic acid and diethylmethylamine.   The fuel cell system according to claim 1, wherein the cathode contains at least platinum. A method of operating a fuel cell system comprising an anhydrous electrolyte having proton conductivity under anhydrous conditions, an anode, and a cathode,
Monitoring the activity of the cathode;
A method of operating a fuel cell system, wherein water existing around the cathode is removed when the activity of the cathode falls below a predetermined level.

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