JP2008097835A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system which suppresses the degradation of an electrolyte membrane by suppressing the generation of radicals. <P>SOLUTION: A control part 100 estimates the gas amount transmitting per unit time from a fuel electrode to an oxidant electrode or from the oxidant electrode to the fuel electrode through the electrolyte membrane of a fuel cell 100. The control part 100 makes oxygen in the oxidant electrode consumed when the transmitting gas amount is the prescribed amount or more. The fuel cell system 1 can reduce the generating amount of radicals caused by the reaction of oxygen and hydrogen since consume oxygen in the oxidant electrode is consumed when the gas amount transmitting through the electrolyte membrane is increased. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

In the fuel cell system, a crossover in which the fuel gas passes from the fuel electrode side to the oxidant electrode side occurs. The amount of fuel gas permeated by this crossover tends to increase when the fuel cell system is operated for a long time. The increase in the fuel gas permeation amount is considered to be caused by the decomposition of the electrolyte membrane in the fuel cell. When the fuel gas is hydrogen and the oxidant gas is oxygen, the electrolyte membrane is decomposed by the hydrogen peroxide generated in the fuel cell. That is, oxygen permeates from the oxidant electrode side, and in the catalyst layer on the fuel electrode side,
O ₂ + 2H ⁺ + 2e ⁻ = H ₂ O ₂ (1)
The following reaction occurs. Here, the hydrogen peroxide solution generates hydroxyl radicals (OH), and these radicals decompose the electrolyte membrane. Further, when the electrolyte membrane is decomposed, the amount of oxygen crossover increases, so that more hydrogen peroxide water is generated and the decomposition of the electrolyte membrane is further promoted.

Therefore, a fuel cell has been proposed in which a new catalyst layer is provided between the fuel electrode and the oxidant electrode, and the reaction between hydrogen and oxygen is promoted in this catalyst layer. In this fuel cell, a catalyst layer that is electrically conductively insulated from the oxidant electrode and the fuel electrode is formed in the electrolyte membrane, and hydrogen and oxygen are reacted in the catalyst layer to generate water. 1), the decomposition of the electrolyte membrane can be suppressed (see, for example, Patent Document 1).
JP-A-6-103992

  However, generally, the potential in the electrolyte membrane is low, and when the potential is lower than 0.68 [V], the reaction of the above formula (1) occurs in the newly provided catalyst layer. For this reason, in the conventional fuel cell system, the electrolyte membrane is decomposed by the generation of the hydrogen peroxide solution. As the decomposition proceeds, the amount of oxygen crossover increases, and more hydrogen peroxide solution is generated. The decomposition of the electrolyte membrane is further promoted. This problem is not limited to the case where the fuel gas is hydrogen and the oxidant gas is oxygen, but is common in the case where a reaction such as the equation (1) occurs and radicals are generated.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a fuel cell system capable of suppressing the generation of radicals and suppressing the decomposition of the electrolyte membrane. There is to do.

  The fuel cell system of the present invention includes a fuel cell, fuel gas supply means, oxidant gas supply means, permeated gas amount estimation means, oxidant gas consumption means, and control means. A fuel cell has a fuel electrode supplied with fuel gas, an oxidant electrode supplied with oxidant gas, and an electrolyte membrane sandwiched between the two electrodes, and generates power by reacting the fuel gas and oxidant gas. Do. The fuel gas supply means supplies fuel gas to the fuel electrode side of the fuel cell. The oxidant gas supply means supplies oxidant gas to the oxidant electrode side of the fuel cell. The permeated gas amount estimating means estimates the permeated gas amount permeating from the fuel electrode side to the oxidant electrode side or from the oxidant electrode side to the fuel electrode side per unit time through the electrolyte membrane. The oxidant gas consumption means consumes the oxidant gas on the oxidant electrode side. The control means consumes the oxidant gas on the oxidant electrode side by the oxidant gas consumption means when the permeate gas amount estimated by the permeate gas amount estimation means is a predetermined amount or more.

  According to the present invention, the amount of permeated gas permeating from the fuel electrode side to the oxidant electrode side per unit time through the electrolyte membrane is estimated, and when the estimated permeated gas amount is a predetermined amount or more, the oxidation on the oxidant electrode side is estimated. The agent gas is consumed. In this way, when the amount of permeated gas that permeates through the electrolyte membrane becomes large, the oxidant gas on the oxidant electrode side is consumed, so the amount of radicals generated by the reaction between the oxidant gas and the fuel gas is reduced. Can do. Therefore, generation of radicals can be suppressed and decomposition of the electrolyte membrane can be suppressed.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. As shown in the figure, a fuel cell system 1 includes a fuel cell 10, a fuel gas supply system 20 (fuel gas supply means), a fuel gas discharge system 30, a fuel gas circulation system 40, and an oxidant gas supply system. (Oxidant gas supply means) 50, an oxidant gas discharge system 60, a combustion catalyst 70, and a load system 80 are provided.

  The fuel cell 10 includes a fuel electrode 11 that receives supply of fuel gas (hydrogen gas) and an oxidant electrode 12 that receives supply of oxidant gas (oxygen (specifically, air containing oxygen)). The generated fuel gas and oxidant gas are reacted to generate electric power. Further, the fuel electrode 11 and the oxidant electrode 12 are overlapped with an electrolyte membrane interposed therebetween to constitute a power generation cell, and the fuel cell 10 has a stack structure in which a plurality of power generation cells are stacked.

  FIG. 2 is a detailed configuration diagram of a unit cell of the fuel cell 10 shown in FIG. As shown in FIG. 2, the fuel cell 10 has a solid polymer electrolyte membrane 13 (hereinafter simply referred to as an electrolyte membrane). An electrolyte membrane 13 is sandwiched between the electrodes 11 and 12. The fuel electrode 11 was laminated on the fuel electrode catalyst layer 11a and a fuel electrode catalyst layer 11a made of a mixture of a catalyst in which noble metal such as platinum is supported on porous carbon and a polymer electrolyte having hydrogen ion conductivity. A gas diffusion layer 11b having air permeability and electronic conductivity. Similarly, the oxidant electrode 12 includes an oxidant electrode catalyst layer 12a made of a mixture of a catalyst and a polymer electrolyte, and a gas diffusion layer having air permeability and electronic conductivity laminated on the oxidant electrode catalyst layer 12a. 12b. The two electrodes 11 and 12 are sandwiched between separators 14 and 15 having fuel gas and oxidant gas flow paths 14a and 15a.

  Reference is again made to FIG. The fuel gas supply system 20 supplies hydrogen to the fuel electrode side of the fuel cell, and includes a hydrogen tank 21, a hydrogen supply pipe 22, a pressure reducing valve 23, and a flow rate controller 24. The hydrogen tank 21 stores hydrogen gas supplied to the fuel electrode 11 of the fuel cell 10. The hydrogen supply pipe 22 connects the hydrogen tank 21 and the fuel electrode side inlet of the fuel cell 10 and guides hydrogen gas from the hydrogen tank 21 to the fuel electrode side inlet. The pressure reducing valve 23 mechanically reduces the high-pressure hydrogen gas in the hydrogen tank 21 to a predetermined pressure. The flow rate controller 24 controls the flow rate of hydrogen supplied to the fuel electrode 11 of the fuel cell 10.

  The fuel gas discharge system 30 discharges gas discharged from the fuel electrode side of the fuel cell 10 to the outside, and includes a gas discharge pipe 31. The gas discharge pipe 31 connects the fuel electrode side outlet of the fuel cell 10 and the combustion catalyst 70, and guides off-gas discharged from the fuel electrode side of the fuel cell 10 to the outside through the combustion catalyst 70. It becomes a flow path. The fuel gas discharge system 30 has a purge valve (not shown). The purge valve is controlled to be freely opened and closed, and controls the discharge of gas to the outside by closing and opening the flow path by opening and closing. The combustion catalyst 70 performs combustion treatment on the exhausted hydrogen from the fuel electrode side of the fuel cell 10 and the exhausted air from the oxidant electrode side.

  The fuel gas circulation system 40 is for reusing hydrogen gas discharged without contributing to power generation, and includes a circulation pipe 41, a hydrogen pump 42, a first three-way valve 43, and a second three-way valve. 44. One end of the circulation pipe 41 is connected to the gas discharge pipe 31, and the other end is connected to the hydrogen supply pipe 22, and the off-gas discharged from the fuel electrode side of the fuel cell 10 is circulated so It becomes a flow path which sends in to. The hydrogen pump 42 is provided on the circulation pipe 41 and serves as a power source for circulating the gas discharged from the fuel electrode side of the fuel cell 10 and sending it again to the fuel electrode side of the fuel cell 10. The first three-way valve 43 is connected to one end side of the circulation pipe 41 and switches whether the gas discharged from the fuel electrode side of the fuel cell 10 is guided to the combustion catalyst 70 or introduced into the circulation pipe 41. The second three-way valve 44 is connected to the other end of the circulation pipe 41 and guides the hydrogen gas from the hydrogen tank 21 to the fuel electrode side of the fuel cell 10 or the gas circulated through the circulation pipe 41 to the fuel cell 10. This switches whether to lead to the fuel electrode side.

  The oxidant gas supply system 50 supplies oxygen to the oxidant electrode side of the fuel cell 10, and includes an air supply pipe 51, a compressor 52, and a filter 53. The air supply pipe 51 connects the outside and the oxidant electrode side inlet of the fuel cell 10 and serves as a flow path for guiding air to the oxidant electrode 12 of the fuel cell 10. The compressor 52 is provided on the air supply pipe 51, takes in outside air, compresses it, and sends it to the oxidant electrode 12 of the fuel cell 10. The filter 53 removes dust that flows in along with the outside air by the operation of the compressor 52.

  The oxidant gas discharge system 60 includes an air discharge pipe 61. The air discharge pipe 61 connects the oxidant electrode side outlet of the fuel cell 10 and the combustion catalyst 70, and has a flow path for guiding the gas discharged from the oxidant electrode side of the fuel cell 10 to the outside. It will be. The oxidant gas discharge system 60 has a pressure regulating valve (not shown). The pressure regulating valve is provided on the air discharge pipe 61 and controls the amount of gas discharged to the outside. Further, the pressure regulating valve can regulate the pressure on the oxidant electrode side of the fuel cell 10 by controlling the gas discharge amount.

  The load system 80 includes a load 81, a battery 82, a switch 83, and a relay 84. For example, when the fuel cell system 1 is mounted on a vehicle, the load 81 is a drive motor or the like serving as a drive power source for the vehicle, and operates with the generated power of the fuel cell 10. The battery 82 supplies the load 81 with an insufficient amount of power that cannot be supplied from the fuel cell 10 out of the requested amount of power. The battery 82 stores power when the power generated by the fuel cell 10 becomes surplus, and stores regenerative power by the drive motor when the load 81 is a drive motor. The switch 83 and the relay 84 are controlled according to the power supply from the fuel cell 10 to the load 81, the power supply from the battery 82 to the load, and the charging operation from the load 81 to the battery 82.

  Further, the fuel cell system 1 includes various sensors 91 to 94 and a control unit (permeated gas amount estimation means, oxidant gas consumption means, control means, current control means) 100. Of the various sensors 91 to 94, the first pressure sensor 91 measures the hydrogen pressure on the fuel electrode side of the fuel cell 10, and the second pressure sensor 92 measures the oxygen pressure on the oxidant electrode side of the fuel cell 10. Measure. The current sensor 93 detects the current of the fuel cell 10. The voltage sensor (voltage detection means) 94 detects the voltage of the fuel cell 10. The voltage sensor 94 is configured to be able to measure the voltage for each unit cell.

  The control unit 100 includes, for example, a central processing unit (CPU), a random access memory (RAM), a read-on memory (ROM), and an input / output interface (I / O interface). It has a gas consumption function, a control function, and a current control function.

  The permeated gas amount estimation function is a function for estimating the permeated gas amount permeating from the fuel electrode side to the oxidant electrode side or from the oxidant electrode side to the fuel electrode side per unit time through the electrolyte membrane 13. The oxidant gas consumption function is a function of consuming oxygen on the oxidant electrode side. The control function is a function for performing control so that the oxidant gas on the oxidant electrode side is consumed by the oxidant gas consumption function when the permeate gas amount estimated by the permeate gas amount estimation function is a predetermined amount or more. The current control function is a function of flowing current through the cells of the fuel cell 10.

  During the operation of the fuel cell system, the permeate gas amount estimation function checks whether the amount of permeate gas that crosses over due to deterioration of the electrolyte membrane 13 of the fuel cell 10 is large. When the amount of crossover gas is large, that is, when the permeate gas amount estimated by the permeate gas amount estimation function is greater than or equal to a predetermined amount, the control function is Of oxidant gas. This suppresses the reaction of the above formula (1) to suppress the generation of hydroxyl radicals (OH).

  FIG. 3 is a flowchart showing the operation of the fuel cell system 1 according to the present embodiment, from start of the fuel cell system 1, confirmation of deterioration of the electrolyte membrane, operation operation at the time of deterioration, and system stop operation at the time of deterioration. A series of flows is shown.

  First, as shown in FIG. 3, the control unit 100 controls the fuel gas supply system 20 to start hydrogen supply (ST1). Next, the control part 100 starts the compressor 52 (ST2), and starts air supply. Next, control unit 100 determines whether or not a certain time has passed (ST3). If it is determined that a certain time has not elapsed (ST3: NO), this process is repeated until it is determined that a certain time has elapsed.

  On the other hand, when it is determined that a certain time has elapsed (ST3: YES), the permeate gas amount estimation function of the control unit 100 decreases the hydrogen utilization rate (ST4). At this time, the permeated gas amount estimation function decreases the hydrogen utilization rate by increasing the flow rate of hydrogen supplied to the fuel electrode side. As a result, the pressure on the fuel electrode side is increased, and the flow rate of the crossover gas is increased. The permeated gas amount estimation function may reduce the oxygen utilization rate instead of reducing the hydrogen utilization rate.

  Next, the control function of the control unit 100 obtains the current density of the fuel cell from the current value detected by the current sensor 93, and determines whether or not this current density exceeds a predetermined current density I1 (ST5). Here, when the amount of gas flowing between the two electrodes through the electrolyte membrane 13 increases, normal power generation is not performed and the voltage of the fuel cell 10 decreases and the current tends to increase at the same time. Therefore, in step ST5, the control function determines whether the crossover amount is large by comparing the current density obtained from the detection value of the current sensor 93 with the predetermined current density I1.

  The control function may determine whether or not the voltage of the fuel cell 10 is equal to or lower than a specified voltage value instead of determining whether or not the current density exceeds the predetermined current density I1. . In this case, the current control function causes a predetermined current to flow through the cells of the fuel cell 10. The voltage sensor 94 detects the voltage of the cell through which the current flows. The control function may determine whether the detected voltage is equal to or lower than a specified voltage value V0 and determine whether the current density exceeds a predetermined current density I1.

  Furthermore, the control function desirably sets the predetermined current to “0” amperes. That is, it is desirable for the control function to determine whether or not the current density exceeds a predetermined current density I1 based on the open circuit voltage. Thus, it is not necessary to pass a current when determining whether or not the current density exceeds the predetermined current density I1, and it can be determined whether or not the current density exceeds the predetermined current density I1.

  The predetermined current density I1 is determined as follows. Assuming that the amount of gas flowing per unit time through the electrolyte membrane 13 of the fuel cell 10 in the initial state is A, the predetermined current density I1 is set based on a gas amount three times that of A. As a result, a value that can be considered to be a significant increase even if changes and errors due to temperature and humidity are included can be used as a reference.

  When it is determined that the current density does not exceed the predetermined current density I1 (ST5: NO), the permeated gas amount estimation function of the control unit 100 increases the hydrogen utilization rate (ST6). That is, the permeated gas amount estimation function controls to return the hydrogen utilization rate decreased in step ST4. Thereafter, the process proceeds to step ST3.

  On the other hand, when it is determined that the current density exceeds the predetermined current density I1 (ST5: YES), the control function determines that the crossover amount is large. The oxidant gas consumption function increases the oxygen utilization rate (ST7). That is, the oxidant gas consumption function decreases the rotation speed of the compressor 52 and decreases the oxygen supply amount to the fuel cell 10. As a result, oxygen is insufficient in the fuel cell 10, and as a result, oxygen on the oxidizer electrode side is consumed. Note that when oxygen is insufficient in the fuel cell 10, the voltage of the fuel cell 10 decreases.

  Then, the control function determines whether the voltage of the unit cell detected by the voltage sensor 94 is equal to or lower than a predetermined voltage value V1 (ST8). That is, the control function determines whether or not the oxygen on the oxidizer electrode side is insufficient by determining whether the detected voltage is equal to or lower than the predetermined voltage value V1. Due to this oxygen deficiency, the generation of radicals can be suppressed even if the amount of crossover is increased due to deterioration of the electrolyte membrane 13.

  If it is determined that the detected voltage is not equal to or lower than the predetermined voltage value V1 (ST8: NO), the process proceeds to step ST7. On the other hand, when determining that the detected voltage is equal to or lower than the predetermined voltage value V1 (ST8: YES), the control unit 100 sets the operation mode to the emergency operation mode (ST9). When the operation mode is set to the emergency operation mode, in the subsequent operation control, the control function maintains the voltage detected by the voltage sensor 94 to be equal to or lower than the predetermined voltage value V1. Thereby, generation | occurrence | production of radicals can be suppressed continuously.

  After setting to the emergency operation mode, the control unit 100 determines whether or not a stop signal indicating that the fuel cell system 1 is stopped has been input (ST10). When the stop signal is not input (ST10: NO), this process is repeated until it is determined that the stop signal is input. On the other hand, when it is determined that the stop signal has been input (ST10: YES), the control function stops the compressor 52 and stops the supply of the oxidant gas (ST11).

  Thereafter, the control function controls the load system 80 to extract current from the fuel cell 10 (ST12). Then, the control function determines whether or not the cell voltage of the fuel cell 10 is “0.2” V or less (ST13). When it is determined that the cell voltage is not less than “0.2” V (ST13: NO), the process proceeds to step ST12.

  On the other hand, when it is determined that the cell voltage is “0.2” V or less (ST13: YES), the control function stops the hydrogen supply from the fuel gas supply system 20 (ST14). Then, the fuel cell system 1 stops and the process ends. As described above, the supply of oxygen is stopped in step ST11, the current is taken out in step ST12, and then the fuel cell system 1 is stopped. For this reason, after consuming oxygen, the fuel cell system 1 is stopped, and generation of radicals can be suppressed after the system is stopped. Note that the electrodes 11 and 12 may be short-circuited instead of taking out the current.

Next, the predetermined voltage value V1 in step ST8 will be described. FIG. 4 is a diagram showing the predetermined voltage value V1 in step ST8 of FIG. In FIG. 4, the load fluctuation is such that an operation in which a load of 1.2 A / cm ² is taken out from a state where current is not flowing (0 A / cm ² ) and returned to 0 A / cm ² is one cycle, and this cycle is performed a plurality of times. The test shows the results of measuring the open-circuit voltage at predetermined time intervals in each of the four control states.

  The four control states are: when the predetermined voltage value V1 in step ST8 is 0.9V and the voltage is maintained at 0.9V in the subsequent operation (method 1), the voltage is 0.88V, and the voltage is also applied in the subsequent operation. Is maintained at 0.88V (method 2), and 0.85V, and the voltage is maintained at 0.85V in the subsequent operation (method 3), and in the subsequent operation without performing the control of step ST8. The case where the voltage is not controlled (method 4).

  As shown in FIG. 4, in the case of Method 4 in which the control in step ST <b> 8 is not performed and the voltage is not controlled in the subsequent operation, the open-circuit voltage rapidly decreases in a specific time zone. This is presumably because the electrolyte membrane 13 deteriorates due to an increase in the amount of crossover, and the performance of the fuel cell 10 cannot be maintained.

  On the other hand, in the case of methods 1 to 3 in which voltage control is performed, it can be seen that the rapid decrease of the open-circuit voltage is eliminated as in method 4, and the deterioration of the electrolyte membrane 13 is suppressed. In particular, in the case of Method 2 in which the control is performed at 0.88 V, a high voltage is maintained for the longest time. For this reason, it can be said that the predetermined voltage value V1 of step ST8 is desirably 0.88V. When the voltage sensor 94 detects not only the voltage of the unit cell but also the voltages of N cells (N is an integer of 2 or more) connected in series at a time, the predetermined voltage value V1 is N at 0.88 volts. It is desirable that the voltage multiplied by is taken.

  FIG. 5 is a flowchart showing the operation of the fuel cell system 1 according to the present embodiment, and shows processing when the system is activated when the emergency operation mode is set. As shown in FIG. 5, when the system is activated when the emergency operation mode is set, the control function controls the load system 80 to extract current from the fuel cell 10 (ST21). Next, the control function controls the fuel gas supply system 20 to start hydrogen supply (ST22). Next, the control function starts the compressor 52 (ST23) and starts air supply.

  Thereafter, the control function determines whether or not the cell voltage detected by the voltage sensor 94 is “0.5” V or more (ST24). When it is determined that the cell voltage is not “0.5” V or higher (ST24: NO), this process is repeated until it is determined that the cell voltage is “0.5” V or higher.

  On the other hand, when it is determined that the cell voltage is “0.5” V or more (ST24: YES), the start-up process shown in FIG. 5 is terminated. Here, once the gas is supplied and the current is taken out, the voltage of the fuel cell 10 may sometimes exceed a predetermined voltage value V1 (for example, 0.88V). That is, oxygen on the oxidizer electrode side cannot be deficient, and generation of radicals cannot be suppressed. However, as described above, by supplying gas while taking out current, the voltage of the fuel cell 10 can be suppressed to a predetermined voltage value V1 or less, and generation of radicals can be suppressed even at the time of startup.

  Thus, according to the fuel cell system 1 according to the present embodiment, the amount of permeated gas that permeates from the fuel electrode side to the oxidant electrode side or from the oxidant electrode side to the fuel electrode side per unit time through the electrolyte membrane 13. And the oxygen on the oxidizer electrode side is consumed when the estimated amount of permeated gas is a predetermined amount or more. Thus, since the oxygen on the oxidizer electrode side is consumed when the amount of permeated gas that permeates the electrolyte membrane 13 increases, the amount of radicals generated by the reaction between oxygen and hydrogen can be reduced. Therefore, generation of radicals can be suppressed and decomposition of the electrolyte membrane 13 can be suppressed.

  Further, when the amount of permeated gas is increased, normal power generation reaction is not performed, the voltage of the fuel cell 10 is decreased, and the current density is increased at the same time. For this reason, the amount of permeated gas that permeates the electrolyte membrane 13 is estimated from the current density of the fuel cell 10, and when the current density exceeds the predetermined current density I1, it is determined that the amount of permeated gas is equal to or greater than the predetermined amount. The oxidant gas on the electrode side is consumed. Accordingly, the amount of permeated gas can be obtained from the current state without directly measuring the amount of permeated gas, and the amount of permeated gas can be estimated easily.

  Further, after the oxidant gas on the oxidant electrode side is consumed, the voltage of the fuel cell 10 is maintained at a predetermined voltage or lower. As a result, the state in which the oxidant gas on the oxidant electrode side is consumed can be maintained, and the generation of radicals can be continuously suppressed to prevent decomposition of the electrolyte membrane 13.

  The predetermined current is 0 amperes. That is, it is determined whether or not the current density exceeds the predetermined current density I1 based on the open circuit voltage. Thus, it is not necessary to pass a current when determining whether or not the current density exceeds the predetermined current density I1, and it can be determined whether or not the current density exceeds the predetermined current density I1.

  In estimating the amount of permeated gas, the pressure on the fuel electrode side or the pressure on the oxidant electrode side is increased. Thereby, the gas flow rate which crosses over can be enlarged, and the fall of the voltage of the fuel cell 10 can be made remarkable. Therefore, it is possible to improve the accuracy of determining whether or not the amount of permeated gas is greater than or equal to a predetermined amount.

  The oxidant gas consumption function consumes oxygen on the oxidant electrode side by increasing the utilization rate of oxygen. That is, the supply flow rate of oxygen to the fuel cell 10 is decreased to increase the utilization rate of oxygen, and oxygen is deficient to consume oxygen on the oxidizer electrode side. Thereby, oxygen can be consumed easily. In addition, when the supply flow rate of oxygen to the fuel cell 10 is decreased, the amount of water taken out from the electrolyte membrane 13 is reduced, so that the electrolyte membrane 13 can be moistened. Furthermore, since the electrolyte membrane 13 is moistened, the amount of gas that temporarily crosses over can be reduced.

  When the permeated gas amount is a predetermined amount or more and the system is to be stopped, after the oxygen supply is stopped, the fuel electrode 11 and the oxidant electrode 12 are short-circuited or a current is taken out from the fuel cell 10, and thereafter Stop the hydrogen supply. Here, hydrogen and oxygen can be consumed by short-circuiting the fuel electrode 11 and the oxidant electrode 12 or taking out a current from the fuel cell 10. Therefore, only oxygen is consumed by performing the above after stopping the oxygen supply. Then, in order to stop hydrogen supply, after consumption of oxygen advances, the fuel cell system 1 will be stopped. Therefore, generation of radicals can be suppressed even after the system is stopped.

  Further, when the system is started up when the permeated gas amount is a predetermined amount or more, the fuel electrode 11 and the oxidant electrode 12 are short-circuited or a current is taken out from the fuel cell 10, and then hydrogen supply is started. Thus, by performing a short circuit or taking out current in advance, the fuel cell system 1 is started after consuming oxygen as much as possible. Therefore, generation of radicals can be suppressed immediately after the system is started.

  The predetermined current density I1 is set on the basis of three times the amount of permeated gas of the initial fuel cell. For this reason, the amount of permeated hydrogen that can be considered to be a significant increase even if changes and errors due to temperature and humidity are included can be used as a reference.

  The predetermined voltage V1 is a voltage obtained by multiplying the number of cells connected in series by 0.88 volts. For this reason, as shown in FIG. 4, voltage degradation can be suppressed for the longest period.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment, and may be modified without departing from the gist of the present invention.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. It is a detailed block diagram of the unit cell of the fuel cell shown in FIG. It is a flowchart which shows operation | movement of the fuel cell system which concerns on this embodiment, and shows a series of flow from starting of a fuel cell system, confirmation of deterioration of an electrolyte membrane, operation operation at the time of deterioration, and system stop operation at the time of deterioration. Yes. It is a figure which shows the predetermined voltage value V1 of step ST8 of FIG. It is a flowchart which shows operation | movement of the fuel cell system which concerns on this embodiment, and has shown the process at the time of system start-up when it is set to emergency operation mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 10 ... Fuel cell 11 ... Fuel electrode 11a ... Fuel electrode catalyst layer 11b ... Gas diffusion layer 12 ... Oxidant electrode 12a ... Oxidant electrode catalyst layer 12b ... Gas diffusion layer 13 ... Electrolyte membranes 14, 15 ... Separator 14a, 15a ... flow path 20 ... fuel gas supply system (fuel gas supply means)
DESCRIPTION OF SYMBOLS 21 ... Hydrogen tank 22 ... Hydrogen supply piping 23 ... Pressure reducing valve 24 ... Flow rate controller 30 ... Fuel gas discharge system 31 ... Gas discharge piping 40 ... Fuel gas circulation system 41 ... Circulation piping 42 ... Hydrogen pump 43 ... First three-way valve 44 ... Second three-way valve 50 ... Oxidant gas supply system (oxidant gas supply means)
DESCRIPTION OF SYMBOLS 51 ... Air supply piping 52 ... Compressor 53 ... Filter 60 ... Oxidant gas discharge system 61 ... Air discharge piping 70 ... Combustion catalyst 80 ... Load system 81 ... Load 82 ... Battery 83 ... Switch 84 ... Relay 91 ... 1st pressure sensor 92 ... second pressure sensor 93 ... current sensor 94 ... voltage sensor (voltage detection means)
100: Control unit (permeate gas amount estimation means, oxidant gas consumption means, control means, current control means)

Claims (11)

A fuel cell having a fuel gas supply, an oxidant electrode receiving an oxidant gas supply, and an electrolyte membrane sandwiched between the two electrodes, and generating a power by reacting the fuel gas and the oxidant gas; ,
Fuel gas supply means for supplying fuel gas to the fuel electrode side of the fuel cell;
An oxidant gas supply means for supplying an oxidant gas to the oxidant electrode side of the fuel cell;
A permeate gas amount estimating means for estimating a permeate gas amount per unit time passing from the fuel electrode side to the oxidant electrode side or from the oxidant electrode to the fuel electrode side through the electrolyte membrane;
Oxidant gas consuming means for consuming the oxidant gas on the oxidant electrode side;
Control means for consuming the oxidant gas on the oxidant electrode side by the oxidant gas consumption means when the permeate gas amount estimated by the permeate gas amount estimation means is a predetermined amount or more;
A fuel cell system comprising: The permeate gas amount estimation means estimates the permeate gas amount from the current density of the fuel cell,
When the current density exceeds a predetermined current density, the control means determines that the amount of permeated gas is equal to or greater than a predetermined amount, and consumes the oxidant gas on the oxidant electrode side by the oxidant gas consumption means. The fuel cell system according to claim 1, wherein: Further comprising voltage detection means for detecting the voltage of the fuel cell;
The control means maintains the voltage detected by the voltage detection means at a predetermined voltage or lower after oxidant gas on the oxidant electrode side is consumed by the oxidant gas consumption means. A fuel cell system according to claim 1 or claim 2. Current control means for causing current to flow through the cells of the fuel cell;
Voltage detection means for detecting a voltage of a cell that is supplied with current by the current control means, and
The control means determines whether or not the current density of the fuel cell exceeds a predetermined current density based on a voltage value detected by the voltage detection means when a predetermined current is passed by the current control means. The fuel cell system according to claim 2. The fuel cell system according to claim 4, wherein the predetermined current passed by the current control means is 0 amperes. 6. The permeated gas amount estimating means increases the pressure on the fuel electrode side or the pressure on the oxidant electrode side when estimating the permeated gas amount. The fuel cell system described. The said oxidant gas consumption means consumes the oxidant gas by the side of the said oxidant electrode by raising the utilization factor of oxidant gas. The any one of Claims 1-6 characterized by the above-mentioned. Fuel cell system. The control means is for stopping the system from a state in which the gas is supplied by the fuel gas supply means and the oxidant gas supply means when the permeate gas amount estimated by the permeate gas amount estimation means is a predetermined amount or more. After the supply of the oxidant gas by the oxidant gas supply means is stopped, the fuel electrode and the oxidant electrode are short-circuited or a current is taken out from the fuel cell, and then the fuel gas supply by the fuel gas supply means The fuel cell system according to any one of claims 1 to 7, wherein the fuel cell system is stopped. In the case where the permeated gas amount estimated by the permeated gas amount estimating unit is equal to or greater than a predetermined amount and the system is started, the control unit short-circuits the fuel electrode and the oxidant electrode or generates a current from the fuel cell. 9. The fuel according to any one of claims 1 to 8, wherein the fuel gas is supplied by the fuel gas supply means and thereafter the oxidant gas supply is started by the oxidant gas supply means. Battery system. 3. The fuel cell system according to claim 2, wherein the predetermined current density is set based on three times the amount of permeated gas per unit time permeating through the electrolyte membrane for the fuel cell in an initial state. The fuel cell system according to claim 3, wherein the predetermined voltage is a voltage obtained by multiplying the number of cells connected in series by 0.88 volts.

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