JP2010238379A - Fuel cell system and stopping method of this fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to alleviate a combustible gas component in fuel gas to prevent ignition to it, or carbon monoxide poisoning at stoppage of power generation of a fuel cell, and to aim at size reduction. <P>SOLUTION: The system provided with a fuel cell, and a first temperature acquiring part S4 for acquiring temperature at a site showing the lowest temperature in a flow channel of fuel gas is further provided with a lowest temperature determination means 60a for determining whether a temperature acquired by the first temperature acquisition part S4 is above the water condensation temperature at stoppage of power generation of the fuel cell; and a circulation section closing means 60b for closing circulation of fuel gas in the circulation section of the fuel gas, including a fuel electrode, when the lowest temperature determination means 60a determines that the temperature acquired by the first temperature acquisition part S4 is above the water condensation temperature, as well as, a gas concentration lowering means 60c for lowering gas concentration in the closed circulation section. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell system and a method for stopping the fuel cell system.

As this type of fuel cell system, there is a configuration disclosed in Patent Document 1 under the name of a solid oxide fuel cell system.
The fuel cell system described in Patent Document 1 is an electrochemistry of a fuel gas, which is formed of an ion conductive ceramic, in an electrolyte of a battery cell, and oxygen supplied to an air electrode of the battery cell. A solid oxide fuel cell main body that generates DC power by reaction, and oxygen obtained by separating air into nitrogen and oxygen during operation of the solid oxide fuel cell main body is supplied to the air electrode of the battery cell An air separating device, a liquid nitrogen storage tank for storing nitrogen separated by the air separating device as liquid nitrogen, and the battery cell by nitrogen separated by the air separating device during operation of the solid oxide fuel cell A battery cell cooling facility for cooling the fuel cell and a fuel for supplying nitrogen stored in the liquid nitrogen storage tank to the fuel electrode of the battery cell when the solid oxide fuel cell is shut down It is of the structure that includes a polar nitrogen supply equipment.

JP 2004-220942 A

  However, the fuel cell system described in Patent Document 1 attempts to prevent oxidation of the fuel electrode by purging with a gas obtained by adding a reducing gas to an inert gas when the system is stopped. However, since N2 generated by the air separation device is used to supply the fuel electrode when the system is stopped, the problem that the increase in size of the system cannot be avoided remains unsolved.

  Therefore, the present invention reduces the combustible gas component contained in the fuel gas when stopping the power generation operation of the fuel cell to prevent the ignition of the fuel gas and the carbon monoxide leakage at the time of the stop, and to reduce the size. It is an object of the present invention to provide a fuel cell system that can be used and a method for stopping the fuel cell system.

  In order to achieve the above object, a fuel cell system according to the present invention includes a fuel cell that generates power by flowing fuel gas and air separately from each other through an air electrode and a fuel electrode stacked on both sides of an electrolyte. And a first temperature acquisition unit for acquiring a temperature at a portion showing the lowest temperature in the flow path of the fuel gas, and when the power generation operation of the fuel cell is stopped, the first temperature The minimum temperature determining means for determining whether or not the temperature acquired by the acquiring section is equal to or higher than the water condensation temperature, and the temperature acquired by the first temperature acquiring section is equal to or higher than the water condensation temperature by the minimum temperature determining means. Is determined, the flow section closing means for closing the flow of the fuel gas in the flow path section of the fuel gas including the fuel electrode and the gas concentration for reducing the gas concentration in the closed flow path section. And a density reducing means.

  In order to achieve the above object, the fuel cell system stopping method according to the present invention generates power by separating fuel gas and air from the air electrode and fuel electrode stacked on both sides of the electrolyte. When the operation of the fuel cell is stopped in the configuration including the fuel cell to perform, it is determined whether or not the temperature at the portion showing the lowest temperature in the flow path of the fuel gas is equal to or higher than the water condensation temperature, and the fuel gas When it is determined that the temperature at the portion showing the lowest temperature in the flow path is equal to or higher than the water condensation temperature, the gas concentration in the fuel gas flow path is reduced.

  According to the present invention, the combustible gas component contained in the fuel gas can be reduced while reducing the size of the fuel gas, thereby preventing the fuel gas from being ignited and carbon monoxide leakage at the time of stopping.

It is a block diagram which shows the structure of the electric power generation unit to which the fuel cell system which concerns on one Embodiment of this invention is applied. It is a block diagram which shows the structure of a fuel cell system same as the above. It is a block diagram which shows the function of the control unit which makes a part of fuel cell system same as the above. It is a flowchart when a power generation stop command is input. It is a flowchart of the atmosphere control of a circulation path. It is a flowchart which shows the control content of water condensation. (A) shows a configuration in which a water adsorber having a water adsorbent is provided in place of the water condenser described above, and is an enlarged view corresponding to a portion indicated by an enclosing line α in FIG. ) Shows a configuration in which a water permeator having a water permeable membrane is provided in place of the water condenser described above, and is an enlarged view corresponding to a portion indicated by an enclosing line α in FIG. 2.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated with reference to drawings. FIG. 1 is a block diagram showing a configuration of a power generation apparatus to which a fuel cell system according to an embodiment of the present invention is applied, FIG. 2 is a block diagram showing a configuration of the fuel cell system, and FIG. It is a block diagram which shows the function of the control unit which makes a part of system.

A power generator B to which a fuel cell system according to an embodiment of the present invention is applied supplies power to an external load 10 such as a motor shown in FIG. 1, and the configuration thereof is as follows.
That is, the first to third relays 20A to 20C, the voltmeter 23, the ammeter 24, the DC / DC converter 25, the battery 26, the inverter 27, and the control unit 28 together with the fuel cell system A1 according to the embodiment of the present invention. Etc. are configured.

  First, the fuel cell system A1 includes a fuel cell 30, fuel pumps 31 to 33, a fuel evaporator 34, a stack heating heat exchanger 35, a circulation blower 36, branch valves 37 and 53, a mixer 38, a fuel reformer 39, a reformer. Heat exchanger 40, combustors 41, 42, cathode air heater 43, air blowers 44-46, 47, shutoff valves 48, 49, water condenser 50, concentration sensors S1, S2 and first and second Temperature sensors S4, S3 and the like.

The fuel cell 30 is a case in which a single cell stack in which a plurality of cell units 51 are stacked on each other is accommodated in a case (all not shown). FIG. 2 shows only one cell unit 51 for the sake of simplicity.
The cell stack is provided with the second temperature sensor S3 (shown in FIG. 3) for measuring the temperature of the cell stack.

  The cell unit 51 includes a solid electrolyte cell 52... In which a fuel electrode 52 a and an air electrode 52 b are provided on both sides of an electrolyte 52 c. The fuel electrode 52 a and the air electrode 52 b include fuel gas and air. The power is generated by separating and flowing them together.

The fuel pump 31 supplies fuel necessary for power generation of the fuel cell 30 to the fuel evaporator 34, and a supply pipe 31 a is connected between the fuel pump 31 and the fuel evaporator 34. .
The fuel pump 31 is connected to the output port side of a control unit (hereinafter referred to as “C / U”) 28 and is appropriately driven.

The fuel evaporator 34 evaporates the fuel supplied by the fuel pump 31, and a supply pipe 34 a is connected between the fuel evaporator 34 and the mixer 38.
The mixer 38 has a function of selectively switching raw fuel, exhaust fuel gas or air supplied from the fuel evaporator 34, the branch valve 37 and the air blower 47, and is connected to the fuel reformer 39. Between the air blower 47 and the branch valve 37, feed pipes 38a, 47a and 37a are connected, respectively.
The “air blower 47” is an air feeder for feeding air to the fuel electrode 52a.

  The shut-off valve 48 is disposed on the feed pipe 47a and shuts off the air blower 47 and the mixer 38, and is connected to the output port side of the C / U 28 and is appropriately driven.

The fuel reformer 39 reforms the vaporized raw fuel into a hydrogen-rich fuel gas, and a feed pipe 39a is connected between the fuel reformer 39 and the fuel cell 30, and the fuel gas is supplied to the fuel reformer 39. The fuel is supplied to the fuel electrode 52a.
The fuel reformer 39 shown in this embodiment has a CO shift reaction function.

The gas concentration sensors S1 and S2 are for measuring the gas concentration in the flow path section of the fuel gas including the closed fuel electrode 52a, and among them, the gas concentration sensor S1 is the fuel flowing through the supply pipe 39a. The gas carbon monoxide and the concentration sensor S2 are for measuring each concentration of oxygen in the fuel gas.
A branch valve 53 is disposed in the middle of the feed pipe 39 a, and the branch pipe 53 a is connected to the water condenser 50.

The branch valve 53 is also connected to the output port side of the C / U 28 and is appropriately driven.
That is, the reformed fuel gas sent from the fuel reformer 39 is switched to the fuel electrode 52a or the water condenser 50 to be circulated.
The water condenser 50 has a function of condensing water vapor contained in the reformed fuel gas sent from the fuel reformer 39.

  A feed pipe 52e is connected between the above-described fuel electrode 52a and the above-described branch valve 37, and the exhaust fuel gas discharged from the fuel electrode 52a is circulated in the middle of the feed pipe 52e. A circulation blower 36 is provided.

The feed pipes 52e, 37a, 38a are return flow paths for returning the exhaust fuel gas discharged from the fuel electrode 52a to the fuel reformer 39.
The circulation blower 36 is also connected to the output port side of the C / U 28 and is appropriately driven.

Incidentally, the air blower 44 is an air feeder for feeding air to the air electrode 52b. That is, air necessary for power generation of the fuel cell 30 is supplied to the cathode air heater 43, and a supply pipe 44 a is connected between the air blower 44 and the cathode air heater 43. .
The air blower 44 is also connected to the output port side of the C / U 28 and is appropriately driven.

The cathode air heater 46 heats the air supplied to the air electrode 52b, and a supply pipe 43a is connected between the cathode air heater 46 and the air electrode 52b.
Further, a feed pipe 52d is connected between the air electrode 52a and the fuel evaporator 34 described above, and exhaust air discharged from the air electrode 52a is sent to the fuel evaporator 34 to be supplied to the fuel pump 31. Heat exchange with the fuel gas fed from the vehicle.

  The combustor 41 burns fuel and air fed by the fuel pump 32 and the air blower 45, and a feed pipe 41 a is interposed between the combustor 41 and the stack heating heat exchanger 35. It is connected.

  The stack heating heat exchanger 35 is disposed in close contact with a cell stack (not shown), and heats the cell stack with the heating gas delivered from the combustor 41 described above.

  A feed pipe 35a is connected between the stack heating heat exchanger 35 and the cathode air heater 43 described above, and the heated gas discharged from the stack heating heat exchanger 35 is supplied to the cathode air heater 43. To exchange heat with the air supplied to the air electrode 52b.

The combustor 42 burns fuel and air fed by the fuel pump 33 and the air blower 46, and a feed pipe 42 a is connected between the combustor 42 and the branch valve 37. Has been.
A shutoff valve 49 is provided in the middle of the feed pipe 42a.
The fuel pumps 32 and 33, the air blowers 45 and 46, and the shutoff valve 49 are also connected to the output port side of the C / U 28 and are appropriately driven.

The shutoff valves 48 and 49 are for shutting off the flow of the fuel gas in the fuel gas flow path including the fuel electrode 52a.
The “fuel gas flow path” shown in the present embodiment is composed of feed pipes 38a, 39a, 52e, and 37a.

  The reformer heating heat exchanger 40 is disposed in close contact with the fuel reformer 39, and a feed pipe 42a is connected between the reformer heating heat exchanger 40 and the combustor 42. The reformer heating heat exchanger 40 is discharged from the fuel electrode 52a and is combusted. Heat exchange is performed between the exhaust gas heated by 42 and the fuel gas reformed by the fuel reformer 40.

  The battery 26 shown in FIG. 1 supplies electric power for reduction for reducing the fuel electrode 52 a of the fuel cell 30, and also supplies electric power for driving to the external load 10 through the inverter 27 described below. It comes to pay.

The DC / DC converter 25 is for performing voltage conversion for the inverter 27 or the fuel cell 30.
The inverter 27 is for converting the DC power output from the fuel cell 30 into AC, and for converting the DC power supplied from the battery 26 into AC and supplying power to the external load 10.

  The first relay 20A is between the DC / DC converter 25 and the fuel cell 30, the second relay 20B is between the battery 26 and the inverter 27, and the third relay 20C is between the inverter 27 and Each is interposed between the fuel cells 30, and both are connected to the output port side of the C / U 28 to be connected and disconnected.

One of the output terminals 30a and 30b of the fuel cell 30 is provided with the above-described ammeter 24 for measuring the output current of the fuel cell 30, and between the output terminals 30a and 30b for measuring the output voltage. Voltmeters 23 are provided.
The ammeter 23 and the voltmeter 24 are connected to the input port side of the C / U 28, and each acquired measurement value is input.

  As shown in FIG. 3, the C / U 28 includes a central control unit 60 including a CPU (Central Processing Unit), an interface circuit and the like (all not shown), and a memory 61 including a hard disk and a semiconductor memory. is there.

By executing the program used for the fuel cell system A1 and the power generation apparatus B stored in the memory 61, the C / U 28 and therefore the central control unit 60 perform the following functions.
A function of determining whether or not the temperature at the portion showing the lowest temperature in the fuel gas flow path is equal to or higher than the water condensation temperature when the power generation operation of the fuel cell 30 is stopped. This function is referred to as “minimum temperature determination means 60a”.

The “part showing the lowest temperature in the flow path of the fuel gas” shown in the present embodiment is a position immediately after the fuel reformer 39 is discharged, specifically, the first temperature sensor disposed in the branch valve 53. Temperature measurement is performed by S4.
In other words, in the present embodiment, the first temperature sensor S4 is a first temperature acquisition unit for acquiring the temperature at the portion showing the lowest temperature in the flow path of the fuel gas.

  In the present embodiment, the temperature acquisition unit has been described as an example of the configuration in which the fuel cell 30 and the first and second temperature sensors S4 and S3 are disposed in order to grasp the temperature of the fuel flow path. In addition, for example, a temperature map of each part measured in advance corresponding to the operating state and the stop time may be stored in the memory 61, and the temperature obtained by appropriately referring to the temperature map of each part may be acquired. .

A function for closing the flow of the fuel gas in the flow path section of the fuel gas including the fuel electrode 52a when the minimum temperature determination means 60a determines that the temperature measured by the first temperature sensor S4 is equal to or higher than the water condensation temperature. . This function is referred to as “distribution section closing means 60b”.
The “fuel gas passage section including the fuel electrode 52a” is configured by the feed pipes 38a, 39a, 52e, and 37a as described above, and the fuel electrode 52a is included in the path.
In this embodiment, the flow passage section is closed by the shutoff valves 48 and 49 and the circulation blower 36 is stopped. However, at least the shutoff valve 48 may be closed and the circulation blower 36 may be stopped. .
The shutoff valves 48 and 49 are for shutting off the flow of the fuel gas in the fuel gas flow path including the fuel electrode 52a.

A function for reducing the gas concentration in the closed flow path section. This function is referred to as “gas concentration reducing means 60c”.
Based on the gas concentration measured by the gas concentration sensors S1 and S2, the gas concentration in the flow path section of the fuel gas including the closed fuel electrode 52a is reduced within a predetermined concentration range.
Specifically, the gas concentration in the flow path section is reduced so that the hydrogen amount falls within a predetermined concentration range of about 1 to 4%, for example.
In other words, in the present embodiment, the gas concentration sensor S1 is a gas concentration acquisition unit for acquiring the gas concentration in the flow path section of the fuel gas including the closed fuel electrode.

Specifically, the supply of fuel gas to the fuel electrode 52a is stopped, and the air blower 44 is driven to continue the supply of air to the air electrode 52b.
In addition, although the gas concentration acquisition part shown in this embodiment is measuring the combustible gas density | concentration with a gas concentration sensor, the combustible gas amount map of each site | part previously measured corresponding to the driving | running state and stop time is stored in the memory 61. You may make it memorize | store and acquire a gas concentration by referring the combustible gas amount map of each of those site | parts.
Further, a function of estimating the amount of combustible gas based on the amount of current generated by the fuel cell may be provided. That is, a configuration in which combustible gas amount estimation means is provided may be used.

When it is determined whether or not the temperature measured by the first temperature sensor S4 is equal to or higher than the water condensation temperature, the amount of water vapor in the fuel gas flow path section including the closed fuel electrode 52a is determined as the outside temperature saturated water vapor. Function to remove until the pressure falls below. This function is referred to as “water vapor removing means 60d”.
In the present embodiment, the amount of water vapor in the fuel gas flow path section including the fuel electrode 52a closed by the water condenser 50 is removed until it becomes equal to or lower than the outside air temperature saturated water vapor pressure.
When it is spread, the branch valve 53 is switched to the water condenser 50, and the water condenser 50 removes the amount of water vapor in the fuel gas flow path until it becomes equal to or lower than the ambient temperature saturated water vapor pressure.

A function for determining whether or not the temperature of the fuel cell 30 measured by the second temperature sensor S3 is equal to or higher than the operating temperature of the fuel cell 30. This function is referred to as “battery temperature determination means 60e”.
The temperature of the fuel cell 30 is acquired by a second temperature sensor S3 disposed in a cell stack (not shown).

A function of heating the fuel cell 30 by the cell heating device when it is determined that the temperature of the fuel cell 30 measured by the second temperature sensor S3 is equal to or higher than the operating temperature of the fuel cell 30. This function is referred to as “battery heating means 60f”.
In the present embodiment, the battery heating device is configured by the stack heating heat exchanger 35 and the combustor 41, but is not limited thereto.

When the battery temperature determination unit 60e determines that the temperature of the fuel cell 30 measured by the second temperature sensor S3 is equal to or higher than the operating temperature of the fuel cell 30, the battery 26 is connected to the fuel cell 30 to A function to increase the amount of hydrogen by causing electrolysis of water. This function is referred to as “hydrogen amount adjusting means 60 g”.

A function of supplying air to the fuel electrode 52a by the air blower (air feeder) 47 when it is determined that the temperature at the portion showing the lowest temperature in the flow path of the fuel gas is equal to or higher than the water condensation temperature. This function is referred to as “fuel electrode air feeding means 60h”.

A function of supplying fuel gas to the fuel reformer 39 when it is determined that the temperature of the fuel cell 30 is equal to or higher than its operating temperature. This function is referred to as “fuel gas feeding means 60i”.

A function of reducing the amount of air supplied by the air blower (air feeder) 44 when the battery temperature determination means 60e determines that the temperature of the fuel cell 30 is equal to or higher than the operating temperature thereof. This function is referred to as “air supply amount reducing means 60j”.

A function of increasing the amount of air supplied by the air blower (air feeder) 47 so as to increase the value of O ₂ / C of the fuel reformer 39. This function is referred to as “air supply amount increasing means 60k”.
Specifically, the amount of air corresponding to the remaining amount of combustible gas included in the fuel gas supplied toward the fuel reformer 39 is supplied.

When the temperature at the portion showing the lowest temperature in the fuel gas flow path is determined to be equal to or higher than the water condensation temperature by the minimum temperature determination means 60a, the temperature is discharged from the fuel electrode 52a by the circulation blower (returning feeder) 36. A function of returning the exhausted fuel gas to the fuel reformer 39. This function is referred to as “exhaust fuel gas return means 60l”.

  A method for stopping the fuel cell system A1 will be described with reference to FIGS. FIG. 4 is a flowchart when a power generation stop command is input, FIG. 5 is a flowchart of the circulation path atmosphere control, and FIG. 6 is a flowchart showing the contents of control of water condensation.

  First, the stopping method of the fuel cell system A1 determines whether or not the temperature at the portion showing the lowest temperature in the flow path of the fuel gas is equal to or higher than the water condensation temperature when the operation of the fuel cell 30 is stopped. When it is determined that the temperature at the portion showing the lowest temperature in the fuel gas flow path is equal to or higher than the water condensation temperature, the main content is to reduce the gas concentration in the fuel gas flow path. It is.

Step 1 (abbreviated as “S1” in the figure. The same applies hereinafter): Stop control of the fuel cell system A1 is performed in accordance with an instruction from the outside.
Step 2: First, control for reducing the amount of combustible gas is performed.

Step 3: That is, the shutoff valves 48 and 49 are closed to shut off the new fuel gas and the exhausted fuel gas, respectively, and the fuel pump 31 is stopped, whereby the new fuel gas and the exhausted fuel flowing into and out of the fuel electrode 52a are shut down. Shut off gas.
That is, the gas concentration in the flow path of the fuel gas is reduced.

  Step 4: Continue to supply air to the air electrode 52b to continue power generation. Further, the relay 20C is disconnected to disconnect the external load 10, and the charging of the battery 26 is started by connecting the relay 20A.

Step 5: Improve fuel removal efficiency as needed.
Specifically, it is determined whether or not the current value acquired by the ammeter 24 is equal to or less than a preset threshold value. If it is determined that the current value is equal to or less than a preset threshold value, the process proceeds to step 8; Otherwise, go to step 6.

Step 6: Determine whether to end the fuel removal operation (power generation operation).
That is, it is determined whether or not the temperature acquired by the second temperature sensor S3 installed in the cell stack is equal to or higher than a preset operating temperature. Return to step 4.

At this time, the reaction amount of the combustible material can be determined at the same time. For example, from the amount of charge read from the value of the ammeter 24, the amount of the remaining combustible material can be estimated by obtaining the difference between the combustible material amount immediately after the stop examined in advance and the measured reaction amount.
It is also possible to judge from the hydrogen concentration acquired by the concentration sensor S2 installed in the flow path and the numerical value acquired by the concentration sensor S1.

Step 7: End the power generation. The relay 20A is opened, and the fuel cell 30 is brought into an open circuit state.
Step 8: Start the control when the removal rate needs to be improved.
Specifically, the consumption efficiency of combustible gas is improved by raising the cell stack temperature. The rise in the temperature of the cell stack can be realized by, for example, reducing the amount of air introduced into the air electrode 52b and reducing the heat transfer amount of the gas discharged from the air electrode 52b.

  Alternatively, the operating temperature of the fuel cell 30 may be increased by temporarily operating the fuel pump 32 and the air pump 452 to introduce a high temperature gas into the stack heating heat exchanger 35 that heats the cell stack. .

Further, the shutoff valves 48 and 49 are temporarily opened to introduce air and raise the O2 / C of the fuel reformer 39, thereby raising the temperature of the discharge side of the fuel reformer 39 and the air electrode 52b. It can also be made.
In the unlikely event that the amount of oxygen introduced becomes excessive and the H ₂ concentration decreases, it is preferable to perform control to reduce H ₂ O using the battery 26 and increase the amount of H ₂ .

  Step 9: The concentration of the combustible material that has reacted is calculated from the amount of charge read from the current value obtained by the ammeter 24.

Step 10: Estimate the amount of remaining combustible material from the difference between the amount of combustible material immediately after stopping examined in advance and the reaction amount measured in Step 9.
In other words, the remaining combustible material amount is calculated based on the combustible material amount and the reaction amount immediately after the operation is stopped.
It is determined whether or not the calculated amount of remaining combustible material is within a predetermined range. If it is determined here that the amount of remaining combustible material is within the predetermined range, the process proceeds to step 11; otherwise, the process returns to step 8.

Step 11: End the power generation.
By opening the relay 20A, the fuel cell 30 is brought into an open circuit state, and the process proceeds to Step 12.
Step 12: Shift to circulation path atmosphere operation control.

Hereinafter, a description will be given with reference to FIG.
Step 13: The circulation path atmosphere operation control is executed.
Step 14: The hydrogen concentration is detected by the concentration sensor S2 installed in the feed pipe 39a.
Step 15: Calculate the target amount of hydrogen.
In the present embodiment, the oxidizing component in the fuel electrode 52a is H ₂ O. At this time, when the ratio of H ₂ / H ₂ O becomes a certain value or less, the oxidation reaction of the fuel electrode component proceeds.
The lower limit value of H ₂ / H ₂ O at the electrode used is calculated as follows.
That is, the concentration of H ₂ O becomes equal to or lower than the saturated water vapor pressure by the control from step 20.
Since the current control was performed at a stop temperature of 15 ° C. and an operating pressure of 0.11 MPa, the H ₂ O concentration is 1.7 vol% or less.
In the electrode used this time, H ₂ / H ₂ O = 1/75. Therefore, the lower limit of the hydrogen concentration is 233 ppm. The upper limit value was set to 4% as a numerical value of the H ₂ concentration meter from the viewpoint of ignition when hydrogen leaked.

Step 16: Air is introduced so that the actual H ₂ concentration falls within the concentration range calculated in Step 15 with respect to the H ₂ concentration detected in Step 14. The reaction assumed at this time is 2H ₂ + O ₂ → H ₂ O.
If the H ₂ concentration is 4%, the H ₂ / H ₂ O ratio will not be 1/75 or less. Further, the oxidation reaction of hydrogen proceeds on the reforming catalyst.

Step 17: It is determined whether or not the oxidation reaction of hydrogen proceeds. In this catalyst, it is 120 ° C.
Step 18: It is determined whether or not the water condensation temperature is reached.
In the present embodiment, the saturated water vapor pressure at the temperature of the temperature sensor S4 attached to the branch valve 37 provided on the discharge side of the fuel reformer 39 where the temperature is lowest becomes equal to the operating pressure of the fuel cell 30. Temperature was taken as a threshold value. In this case, it is about 103 ° C.

Step 19: Shift to water condensation control.
Step 20: Execute water condensation control.
Step 21: Refer to the temperature acquired by the temperature sensor S3 installed in the cell stack having the highest temperature in the fuel cell system A1.
Note that a high-temperature profile of the cell stack measured in advance can be substituted.

Step 22: The branch valve 53 on the upstream side of the water condenser 50 is opened, and the gas in the circulation channel is introduced into the water condenser 50.
Step 23: It is determined whether or not the temperature acquired in Step 21 has become the outside air temperature. If it is determined that the temperature has become the outside air temperature, the process proceeds to Step 24. Otherwise, the process returns to Step 21.
Step 24: Stop the operation of the fuel cell system A1.

According to the power generation unit B according to the above-described embodiment, the following effects can be obtained.
-By reducing the amount of combustible gas in the shut-off fuel flow path, it is possible to prevent the ignition of fuel and carbon monoxide poisoning during stoppage.
-By controlling the amount of hydrogen to a predetermined value, oxidation of the fuel electrode during stoppage can be prevented, and electrode deterioration and structural breakdown due to oxidation during long-term stoppage can be avoided.
-Condensation of water and oxidation of the fuel electrode due to this can be avoided by reducing the amount of water vapor in the fuel flow path below the saturated water vapor amount.

・ It is difficult to design a valve with a substantially high sealing property at a high temperature part, but the shutoff valves 48 and 49 are arranged at the above-mentioned parts having a relatively low temperature so that the fuel gas can be easily discharged. It can be sealed.

When it is determined whether or not the temperature measured by the first temperature sensor S4 is equal to or higher than the water condensation temperature, the amount of water vapor in the fuel gas flow path section including the closed fuel electrode 52a is determined as the outside temperature saturated water vapor. By providing the water vapor removing means 60d that removes until the pressure becomes lower than the pressure, the temperature of the fuel cell system A1 decreases due to heat dissipation after the power generation is stopped. At this time, water vapor in the fuel gas is condensed. This water condensation is preferentially advanced by the water condenser 50.
This prevents the fuel gas from being introduced into the water condenser 50 at a high temperature near the operating temperature of the fuel cell, thereby preventing heat dissipation loss at this portion and preventing thermal deterioration of the water condenser 50. be able to.
Condensation of the amount of water vapor in the fuel flow path in the fuel flow path, particularly condensation in the fuel electrode, can be prevented, whereby oxidation of the fuel electrode can be avoided.

The present invention is not limited to the above-described embodiments, and the following modifications can be made.
In the above-described embodiment, the example in which the water vapor amount in the fuel gas flow path is removed by the water condenser until the water temperature is equal to or lower than the outside air temperature saturated water vapor pressure has been described, but as shown in FIGS. It may be configured.
FIG. 7 (A) shows a configuration in which a water adsorber having a water adsorbent is disposed instead of the water condenser described above, and is an enlarged view corresponding to a portion indicated by an envelope α in FIG. (B) shows a configuration in which a water permeator provided with a water permeable membrane is provided in place of the water condenser described above, and is an enlarged view corresponding to a portion indicated by an encircling line α in FIG. .

FIG. 7A shows a configuration in which a water adsorber 55 having a water adsorbent 55a is provided in place of the water condenser 50 described above.
The water adsorbent 55a of the water adsorber 55 circulates the fuel gas only for a required time at the next start-up of the fuel cell system, and the moisture adsorbed when the fuel cell system is stopped. It is made to evaporate.
As the water adsorbent, for example, a porous material such as silica gel can be used.

FIG. 7B shows a configuration in which a water permeator 56 including a water permeable membrane 56 a is provided in place of the water condenser 50.
In the water permeator 56, a branch valve 53 is disposed on one side of the water permeable membrane 56a, and an air blower 57 is disposed on the other side.
Simultaneously with the switching of the branch valve 53, the air blower 57 is driven to release the permeated moisture out of the path.

26 Battery 30 Fuel Cell 31 Feed Pump 35, 41 Battery Heating Device 36 Return Feeder 37a, 38a, 52e Return Channel 38a, 39a, 52e, 37a Fuel Gas Channel Section 39 Fuel Reformer 44 Air Supply (Air blower)
47 Air feeder (Air blower)
48, 49 Shut-off valve 50 Water condenser 52c Electrolyte 52b Air electrode 52a Fuel electrode 53 Branch valve 55 Water adsorber 56 Water permeator 60a Minimum temperature judging means 60b Flow section closing means 60c Gas concentration reducing means 60d Water vapor removing means 60e Battery temperature Determination means 60f Battery heating means 60g Hydrogen amount adjustment means 60h Fuel electrode air supply means 60i Fuel gas supply means 60j Air supply amount reduction means 60k Air supply amount increase means 60l Exhaust fuel gas return means S1, S2 Gas concentration sensor (Gas concentration acquisition unit)
S3 Second temperature sensor S4 First temperature sensor (first temperature acquisition unit)

Claims (20)

A fuel cell that generates power by flowing fuel gas and air separately from each other on an air electrode and a fuel electrode stacked on both sides of the electrolyte, and a temperature at a portion showing the lowest temperature in the flow path of the fuel gas. A fuel cell system comprising a first temperature acquisition unit for acquiring,
When stopping the power generation operation of the fuel cell, minimum temperature determination means for determining whether the temperature acquired by the first temperature acquisition unit is equal to or higher than the water condensation temperature;
When the minimum temperature determination means determines that the temperature acquired by the first temperature acquisition unit is equal to or higher than the water condensing temperature, the flow section closing that closes the fuel gas flow in the fuel gas flow path including the fuel electrode is closed. And a gas concentration reducing means for reducing the gas concentration in the closed flow passage section. A shut-off valve for closing the flow path section of the fuel gas including the fuel electrode,
The fuel cell system according to claim 1, wherein the flow path closing means closes the flow path section by the shut-off valve. It has a gas concentration acquisition unit for acquiring the gas concentration of the fuel gas passage section including the closed fuel electrode,
The gas concentration reduction means reduces the gas concentration in the flow path section of the fuel gas including the closed fuel electrode based on the gas concentration acquired by the gas concentration acquisition unit so as to be within a predetermined concentration range. The fuel cell system according to claim 1 or 2. A feed pump for feeding fuel gas toward the fuel electrode, and an air blower for feeding air to the air electrode;
The fuel cell system according to any one of claims 1 to 3, wherein the gas concentration reduction means stops driving the feed pump and continues driving the air blower. A fuel reformer for reforming the fuel gas flowing toward the fuel cell is disposed in the flow path of the fuel gas, and the first temperature acquisition unit is the first temperature sensor,
The fuel cell system according to any one of claims 1 to 4, wherein the first temperature sensor is disposed in a flow path on the discharge side of the fuel reformer.   When it is determined that the temperature acquired by the first temperature acquisition unit is lower than the water condensation temperature, the amount of water vapor in the flow path section of the fuel gas including the closed fuel electrode is equal to or lower than the outside air temperature saturated water vapor pressure. The fuel cell system according to any one of claims 1 to 5, further comprising a water vapor removing unit for removing the water vapor. A battery heating device for heating the fuel cell, and a second temperature acquisition unit for acquiring the temperature of the fuel cell,
Battery temperature determination means for determining whether or not the temperature of the fuel cell acquired by the second temperature acquisition unit is equal to or higher than the operating temperature of the fuel cell;
A battery heating means is provided for heating the fuel cell by the battery heating device when it is determined that the temperature of the fuel cell acquired by the second temperature acquisition unit is equal to or higher than the operating temperature of the fuel cell. Item 7. The fuel cell system according to any one of Items 1 to 6. It has a battery that can be connected to the fuel cell,
When the battery temperature determination means determines that the temperature of the fuel cell acquired by the second temperature acquisition unit is equal to or higher than the operating temperature of the fuel cell, the battery is connected to the fuel cell and the water is electrolyzed. 8. A fuel cell system according to claim 7, further comprising hydrogen amount adjusting means for increasing the hydrogen amount. An air feeder for supplying air to the fuel electrode is disposed,
An anode air feeding means is provided for feeding air to the fuel electrode by an air feeder when it is determined that the temperature at the lowest temperature portion in the fuel gas flow path is equal to or higher than the water condensation temperature. The fuel cell system according to any one of claims 1 to 8, wherein The fuel reformer has a CO shift reaction function,
When it is determined that the temperature of the fuel cell is above its operating temperature,
The fuel cell system according to any one of claims 1 to 8, further comprising fuel gas supply means for supplying fuel gas to the fuel reformer.   The fuel cell system according to any one of claims 1 to 10, further comprising a return flow path for returning the exhaust fuel gas discharged from the fuel electrode to the fuel reformer. An air feeder for supplying air to the air electrode is provided,
When the battery temperature determination means determines that the temperature of the fuel cell is equal to or higher than the operating temperature, an air supply amount reduction means for reducing the amount of air supplied by the air feeder is provided. The fuel cell system according to any one of claims 1 to 11. An air feeder for supplying air to the fuel reformer is provided,
The air supply amount increasing means for increasing the amount of air supplied by the air supply unit is provided so as to increase the value of O ₂ / C of the fuel reformer. The fuel cell system according to any one of claims.   14. The fuel according to claim 13, wherein the air supply amount increasing means supplies an air amount corresponding to the remaining amount of combustible gas contained in the fuel gas supplied to the fuel reformer. Battery system. A return flow path is provided for returning the exhaust fuel gas discharged from the fuel electrode to the fuel reformer, and the exhaust fuel gas is returned to the fuel reformer through the return path. A return feeder is provided to
When it is determined by the minimum temperature determination means that the temperature at the lowest temperature portion in the fuel gas flow path is equal to or higher than the water condensation temperature, the fuel reformed from the exhaust gas discharged from the fuel electrode by the return feeder The fuel cell system according to any one of claims 1 to 14, further comprising exhaust fuel gas return means for returning the gas to the vessel. A water condenser is installed,
When it is determined that the temperature at the portion showing the lowest temperature in the fuel gas flow path is equal to or lower than the water condensation temperature,
The fuel cell according to any one of claims 1 to 15, wherein the water vapor removing means removes the amount of water vapor in the flow path of the fuel gas by the water condenser until the water temperature is equal to or lower than a saturated water vapor pressure at the outside temperature. system. A branch valve for branching the fuel gas toward the fuel cell so as to flow toward the water condenser is disposed in the discharge-side flow path of the fuel reformer,
The water vapor removing means removes the branch valve with a water condenser until the amount of water vapor in the flow path of the fuel gas becomes equal to or lower than the outside air temperature saturated water vapor pressure. Fuel cell system.   The fuel cell system according to claim 16 or 17, wherein a water adsorber having a water adsorbent is disposed in place of the water condenser.   The fuel cell system according to claim 16 or 17, wherein a water permeator having a water permeable membrane is disposed in place of the water condenser. A method of stopping a fuel cell system including a fuel cell that generates power by flowing fuel gas and air separately from each other on an air electrode and a fuel electrode stacked on both sides of an electrolyte,
When stopping the operation of the fuel cell, it is determined whether the temperature at the portion showing the lowest temperature in the fuel gas flow path is equal to or higher than the water condensation temperature,
Stopping the fuel cell system, comprising: reducing the gas concentration in the fuel gas flow path when it is determined that the temperature at the portion showing the lowest temperature in the flow path of the fuel gas is equal to or higher than the water condensation temperature Method.

Images