JP2011181263A - Method of maintaining shutdown state of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for maintaining a shutdown state of a fuel cell system, capable of maintaining performance of at least part of the fuel cell system even if gas leak occurs. <P>SOLUTION: In a state where the operation of a fuel cell FC is maintained in a shutdown state, a first closure target region V1 is closed, a second closure target region V2 is closed, and a gas is allowed to flow between a fuel gas generator 1 and an anode 2a, at set pressure-holding timing when a shutdown state-maintaining process to store the fuel cell FC is performed, pressure-holding processing in a pressure-holding target region between the first closure target region V1 and the second closure target region V2 is performed and at the same time, when a gas leak from the pressure-holding target range is detected while the shutdown state-maintaining process is performed, the first closure target region V1 and a third closure target region V3 are closed and the gas flow between the fuel gas generator 1 and the anode 2a is shut off, and thereby, pressure-holding target range separation processing to separate the pressure-holding target range is performed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for maintaining a stopped state of a fuel cell system.

  At the stage where the stop transition process for shifting the operation of the fuel cell to the stop state where the output of power from the fuel cell is stopped is performed, air (oxygen) as the oxidant gas remains in the cathode. Therefore, as a method for maintaining the stopped state of the fuel cell system, the hydrogen-containing gas is supplied to the cathode and the stopped state is maintained until the next start of the fuel cell in order to prevent deterioration due to oxidation of the cathode. It has been proposed to perform a stopped state maintaining step (see, for example, Patent Document 1). Specifically, in the method described in Patent Document 1, in a system specially equipped with a gas conduction path connecting the gas flow paths of the anode and the cathode, the hydrogen-containing gas is supplied by supplying the hydrogen-containing gas to the anode. It is also supplied to the cathode through the gas conduction path. Then, after all or part of the oxidant gas remaining on the cathode is replaced with a hydrogen-containing gas, a stop state maintaining step of closing the shutoff valve and sealing the anode and the cathode is performed.

Japanese Patent Laying-Open No. 2005-93115 (Claims 1 to 4)

  In the method described in Patent Document 1, a hydrogen-containing gas is supplied from the anode to the cathode for the purpose of preventing the oxidation of the cathode by the remaining oxidant gas. Therefore, since special piping for supplying the hydrogen-containing gas to the cathode is required, there arises a problem that the configuration of the apparatus becomes complicated and the cost of the apparatus increases. In addition, if a special pipe that is not used during normal power generation operation is used to supply gas that is not used during normal power generation operation to the cathode, complicated procedures such as switching the gas flow path and replacing the gas are required. Is required.

In addition, in Japanese Patent Application No. 2008-225326 filed by the applicant of the present application, a fuel gas generator for generating fuel gas supplied to an anode using a reformer and an anode of a fuel cell are sealed together. A method for maintaining a stopped state of a fuel cell system that is stored in a stopped state is described. Specifically, this stopped state maintaining method maintains the operation of the fuel cell in a stopped state, and is a first closing target site upstream of the reformer of the gas distribution system leading from the fuel gas generator to the anode. The fuel cell is stored in a state in which the second closing target portion in the middle of the gas discharge path from the anode is closed and the gas flow between the fuel gas generating device and the anode is allowed. It is. When this stopped state maintenance method is adopted, the fuel gas generator and the anode of the fuel cell are sealed together using the reformed gas (hydrogen) that is present in the fuel gas generator when the operation is stopped. There is an advantage that you can.
As described above, the fuel gas generation device (particularly, the reforming catalyst of the reformer) is deteriorated while the fuel cell system is stopped by integrally sealing the fuel gas generation device and the anode of the fuel cell. And deterioration of the anode can be suppressed together.

  Further, Japanese Patent Application No. 2008-225326 discloses a pressure holding process for supplying gas into the fuel cell system to increase the pressure in the fuel cell system when a pressure drop occurs with a temperature drop in the fuel cell system. Is also described. By appropriately performing such a pressure holding process while the fuel gas generation device and the anode of the fuel cell are integrally sealed, intrusion of oxygen into the fuel cell system during that time can be avoided.

Note that a change in temperature and pressure in the fuel cell system may cause a gap in the seal portion between the fuel cell electrolyte and the anode and cathode, and gas leakage from the gap may occur. Further, the fuel gas generator is repeatedly exposed to a high temperature environment and a low temperature environment such that the temperature is high during operation and the temperature is as low as the surroundings when stopped. Therefore, if there is a weak part such as poor welding at the connection point of the internal pipe of the fuel gas generation device, there is a possibility that a crack or the like will occur in that part and gas leakage from the crack or the like may occur.
When a problem such as gas leakage occurs in the fuel cell system, it is preferable to stop the pressure holding process described above. This is because if a pressure holding process is performed to increase the pressure in the fuel cell system in spite of the occurrence of gas leakage, more gas (especially residual hydrogen or hydrocarbon gas) from the fuel cell system. This is because there is a risk of leakage.

  However, while the fuel cell system is stopped, the fuel gas generation device and the anode of the fuel cell are sealed together, and the fuel gas generation device and the anode of the fuel cell are integrally held with pressure. In the method for maintaining the stopped state of the fuel cell system, if the pressure holding process is stopped when a gas leak occurs, the pressure holding process for a normal part where no gas leak has occurred is also stopped at the same time. is there. For example, when a gas leak occurs due to a problem in the fuel cell, the fuel gas generation device is not subjected to the pressure holding process even though there is no problem in the fuel gas generation device. Therefore, there is a possibility that the catalyst (for example, the reforming catalyst) in the fuel gas generating apparatus that should be normal is oxidized or wetted by the remaining water vapor. Further, when the operation of the fuel cell system is resumed after performing maintenance for repairing gas leakage from the fuel cell, there is a possibility that a problem that the reformed gas is not sufficiently generated by the fuel gas generation device may occur. is there.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a stopped state maintaining method for a fuel cell system that can maintain at least a part of the performance of the fuel cell system even if a gas leak occurs. The point is to provide.

In order to achieve the above object, the fuel cell system stop state maintaining method according to the present invention is characterized in that an electrolyte is provided between an anode supplied with a fuel gas containing hydrogen and a cathode supplied with an oxidant gas. A fuel cell system comprising: a fuel cell configured to generate a fuel gas generating device for generating the fuel gas supplied to the anode using a reformer in a gas supply path to the anode; A state maintenance method,
A stop transition step of shifting the operation of the fuel cell to a stop state in which output of power from the fuel cell is stopped;
After the stop transition step, the first closing target portion upstream of the reformer of the gas distribution system that maintains the operation of the fuel cell in the stopped state and communicates from the fuel gas generation device to the anode. And the second closing target part in the middle of the gas discharge path from the anode is closed, and the flow of gas between the fuel gas generator and the anode is allowed. A stopped state maintaining step for storing the battery,
At the set pressure holding timing during the stop state maintaining step, the pressure holding process for the pressure holding target range is performed with the pressure holding target range between the first closing target part and the second closing target part. And when the gas leakage from the pressure holding target range is detected while the stop state maintaining step is being performed, the fuel gas generating device in the middle of the first closing target portion, the gas circulation system, and the A pressure holding target range separation process for separating the pressure holding target range is performed by closing a third closing target portion between the anodes and shutting off a gas flow between the fuel gas generation device and the anode. In the point.

According to the above characteristic configuration, by performing the pressure holding process in the pressure holding target range at the set pressure holding timing while the stop state maintaining step is being performed, the first closing target portion to the second closing target portion. The pressure in the pressure holding target range is maintained. That is, since the pressure in the pressure holding target range is maintained, even if there is a change in the internal temperature of the fuel cell during the stop state maintaining process, the gas to the reformer (for example, oxygen) Or gas (for example, oxygen) from the outside of the fuel cell or from the cathode to the anode is less likely to occur. Therefore, oxidation of the reformer catalyst and the anode is suppressed.
Further, when a gas leak from the pressure holding target range is detected during the stop state maintaining step, the first closing target portion and the third closing target portion are closed, and the fuel gas generating device and the anode are closed. A pressure holding target range separation process for separating the pressure holding target range by cutting off the gas flow is performed. That is, a range between the first closing target portion and the third closing target portion in the entire holding pressure range by the pressure holding target range separation process for closing the first closing target portion and the third closing target portion ( That is, the range including the reformer of the fuel gas generator can be selectively separated from the entire holding target range. As a result, even if a gas leak occurs between the third closing target part and the second closing target part (for example, a fuel cell between the third closing target part and the second closing target part). The pressure in the region between the first closing target site and the third closing target site (that is, the reformer of the fuel gas generating device between the first closing target site and the third closing target site) can be maintained. And since oxidation of the reformer etc. of the fuel gas generator can be suppressed, the maintenance of the fuel cell system is performed after performing maintenance for repairing the gas leakage generated between the third closing target part and the second closing target part. When the operation is resumed, there is no problem that the reformed gas is not sufficiently generated by the fuel gas generation device.
Therefore, it is possible to provide a method for maintaining the stopped state of the fuel cell system that can maintain the performance of at least a part of the fuel cell system even if a gas leak occurs.

  Another characteristic configuration of the stopped state maintaining method of the fuel cell system according to the present invention is that the second closing target portion is closed in the pressure holding target range separation process.

According to the above characteristic configuration, when the gas leakage from the pressure holding target range is detected during the stop state maintaining step, the first closing target site, the second closing target site, and the third closing target site are closed. Then, a pressure holding target range separation process is performed in which the pressure holding target range is separated by blocking the gas flow between the fuel gas generation device and the anode. That is, by the pressure holding target range separation process, the range between the first closing target part and the third closing target part in the entire pressure holding target range can be individually separated, and The range between the 3rd closure object part and the 2nd closure object part can be isolated individually.
As a result, the gas leakage ranges between the third closing target part including the anode and the second closing target part or between the first closing target part including the reformer and the third closing target part. Even if it occurs in any of the above ranges, it is possible to prevent the influence of gas leakage such as oxygen intrusion into the range where no gas leakage occurs.
Further, by continuing to close the first closing target site, the second closing target site, and the third closing target site even after the gas leak is detected, that is, the location where the gas leak has occurred By securely separating and sealing from a safe part that has not occurred, the gas leakage can proceed slowly.

  Still another characteristic configuration of the method for maintaining the stopped state of the fuel cell system according to the present invention is that the pressure-holding process is performed by opening the first closing target part and the pressure holding from the upstream side of the first closing target part. This is a process for increasing the pressure inside the pressure holding target range by supplying gas to the target range.

  According to the above characteristic configuration, the pressure inside the pressure holding target range is increased by opening the first closing target site and supplying the gas from the upstream side of the first closing target site to the pressure holding target range. Can do. As a result, it becomes difficult for oxygen or the like to enter the holding target range from the outside.

  Still another characteristic configuration of the method for maintaining the stopped state of the fuel cell system according to the present invention is that after the pressure holding target range separation processing is performed, the first closing target portion and the third closing target in the pressure holding target range. The point is that the pressure holding process is stopped when a gas leak from a range between the region to be closed is detected.

In a situation where gas leakage occurs, if the pressure holding process is performed to increase the pressure inside the pressure holding target range, gas leakage may be promoted.
However, in this feature configuration, after the pressure holding target range separation processing is performed, the pressure holding pressure is detected when a gas leak from the range between the first closing target portion and the third closing target portion within the pressure holding target range is detected. Since the process is stopped, gas leakage to the outside of the pressure holding target range is suppressed.

  Still another characteristic configuration of the method for maintaining the stopped state of the fuel cell system according to the present invention is that the first closing target portion and the third closing target after the set determination time has elapsed since the pressure holding target range separation processing has been performed. When a gas leak from the part is detected, the gas leak detected before the pressure holding target range separation process is a gas leak from between the first closing target part and the third closing target part. And when no gas leak is detected, the gas leak detected before the pressure holding target range separation process is from between the third closing target part and the second closing target part. The point is that it is determined that the gas has leaked.

  According to the above characteristic configuration, when gas leakage from between the first closing target part and the third closing target part is detected after a set determination time has elapsed since the pressure holding target range separation process has been performed. The gas leakage that occurred before the pressure holding target range separation process is between the first closing target part and the third closing target part (that is, between the first closing target part and the third closing target part). When it is determined that the gas leak has occurred from the fuel gas generation device or the like, and the gas leak is not detected, the gas leak generated before the pressure holding target range separation process is the second closing target portion and the second closing target portion. It can be determined that the gas leaked from the part to be closed (that is, a fuel cell or the like between the third part to be closed and the second part to be closed). Thereby, it is specified whether the part which should perform maintenance is between the 1st closure object part and the 3rd closure object part, or between the 3rd closure object part and the 2nd closure object part. Is possible.

Still another characteristic configuration of the stopped state maintaining method of the fuel cell system according to the present invention is:
The fuel cell system is provided with a pressure gauge capable of detecting the pressure inside the gas distribution system between the first closing target part and the third closing target part,
The set holding pressure timing is a timing at which the pressure inside the holding pressure range detected by the pressure gauge falls below the set holding pressure.

While the stop state maintaining process is being performed, the internal temperature of the fuel cell or the fuel gas generator may change. When a change in the internal temperature of the fuel cell or the fuel gas generator occurs, the internal pressure in the pressure holding target range including the anode of the fuel cell or the fuel gas generator changes. When the internal pressure in the pressure holding target range is reduced, oxygen (air) may enter the pressure holding target range.
In this characteristic configuration, when the pressure inside the pressure holding target range detected by the pressure gauge provided between the first closing target part and the third closing target part falls below the set holding pressure, the pressure holding process is performed. Therefore, the possibility that oxygen (air) enters the pressure holding target range can be reduced. Furthermore, since a pressure gauge for detecting the pressure in the pressure holding target range is provided between the first closing target portion and the third closing target portion, the pressure holding target range separation processing is performed after the pressure holding target range separation processing is performed. Even when the area between the first closing target part and the third closing target part is set as the pressure holding target range, the pressure in the pressure holding target range between the first closing target part and the third closing target part is measured with a pressure gauge. The pressure holding process can be executed upon detection.

  Still another characteristic configuration of the method for maintaining the stopped state of the fuel cell system according to the present invention is that when the pressure holding process is frequently performed or when gas is supplied to the pressure holding target range in the pressure holding process. Gas leak occurred when the time required to increase the pressure inside the pressure holding target range is equal to or longer than the set required time, or when the pressure decreasing rate inside the pressure holding target range is equal to or higher than the set decreasing speed. It is in the point to judge.

The fact that the pressure holding process is performed more frequently than the normal frequency (reference frequency) can be regarded as a large pressure drop in the pressure holding target range (for example, gas outflow from the pressure holding target range). In addition, when the gas is supplied to the pressure holding target range during the pressure holding process, the time required for the pressure inside the pressure holding target range to rise is equal to or longer than the set required time. Therefore, it can be considered that it takes a long time to increase the pressure inside the pressure holding target range. Alternatively, the fact that the pressure decrease rate within the pressure holding target range is equal to or higher than the set pressure reducing rate can be regarded as a large outflow amount of gas from the pressure holding target range.
Therefore, as in this feature configuration, the control means needs to increase the pressure inside the pressure holding target range when the pressure holding process is performed or when gas is supplied to the pressure holding target range in the pressure holding process. By monitoring the time or the rate of pressure decrease within the pressure holding target range, the possibility of gas leakage from the pressure holding target range can be quickly detected.
Furthermore, since a pressure gauge for detecting the pressure in the pressure holding target range is provided between the first closing target site and the third closing target site, after the pressure holding target range separation processing is performed, The pressure in the pressure holding target range between the first closing target part and the third closing target part can be selectively detected. That is, after the pressure holding target range separation process is performed, gas leakage from the pressure holding target range between the first closing target site and the third closing target site can be selectively detected.

  Still another characteristic configuration of the method for maintaining the stopped state of the fuel cell system according to the present invention is that a gas leak occurs when the gas detection sensor capable of detecting the monitoring target gas detects the monitoring target gas having a concentration equal to or higher than the set concentration. It is in the point to judge.

  According to the above characteristic configuration, the gas leakage of the monitoring target gas can be accurately detected by using the gas detection sensor.

It is a figure explaining the structure of the fuel cell system with which the stop state maintenance method of the fuel cell system of 1st Embodiment is implemented. It is a timing diagram explaining the operating state of a fuel cell system. It is a flowchart of control including a pressure holding object range separation process. It is a figure explaining the structure of the fuel cell system with which the stop state maintenance method of the fuel cell system of 2nd Embodiment is implemented.

<First Embodiment>
A method for maintaining a stopped state of the fuel cell system according to the first embodiment will be described below with reference to the drawings. This stop state maintaining method is a method of performing a stop state maintaining step described below.
FIG. 1 is a diagram illustrating the configuration of a fuel cell system S1 (S) in which the method for maintaining a stopped state of the fuel cell system according to the first embodiment is implemented. The fuel cell system S1 includes a fuel gas generation device 1 and a fuel cell FC. The operation control of the fuel cell system S1 to be described later is performed by the control means C unless otherwise specified. The fuel gas generator 1 steam-reforms a raw material gas containing a hydrocarbon such as methane in a reformer 1a to generate a fuel gas mainly containing hydrogen. In addition to the reformer 1a shown in FIG. 1, the fuel gas generator 1 includes a desulfurizer, a steam generator, and a gas obtained by steam reforming for removing sulfur compounds contained in the raw material gas. The carbon monoxide remover etc. which remove the carbon monoxide contained in are provided, but those descriptions are omitted. The reformer 1a is provided with a pressure sensor P1 for detecting the pressure of the reformer 1a and a temperature sensor T1 for detecting the temperature of the reformer 1a. The pressure sensor P1 may be provided in another part of the fuel gas generator 1, or may be provided anywhere on the pipe between the valve V1 and the valve V3.
The reformed gas (gas containing hydrogen as a main component) generated by the fuel gas generator 1 is supplied to the anode 2 a via the gas supply path 3.

The fuel cell FC includes a fuel cell 2 that generates power. The fuel battery cell 2 is configured by providing an electrolyte 2c between an anode 2a to which a fuel gas containing hydrogen is supplied and a cathode 2b to which an oxidant gas is supplied. A fuel gas generator 1 is connected to the gas supply path 3 to the anode 2a. The fuel gas generated by the fuel gas generation device 1 is supplied via the gas supply path 3. The anode 2a is provided with a pressure sensor P2 for detecting the pressure of the anode 2a and a temperature sensor T2 for detecting the temperature of the anode 2a.
The “gas distribution system” of the present invention includes a gas flow path through which raw material gas is supplied to the fuel gas generation apparatus 1, a gas flow path inside the fuel gas generation apparatus 1, and the fuel gas generation apparatus 1 to the anode 2a. A gas flow path (gas supply path 3), a gas flow path inside the anode 2a, and a gas flow path discharged from the anode 2a are included.

In the middle of the gas supply path 3 to the anode 2a, a fuel gas humidifier 4 having a fuel gas storage water tank 4a is provided. In the fuel gas humidifier 4, the fuel gas is supplied from the fuel gas generating device 1 through the gas supply path 3 into the stored water stored in the fuel gas storage water tank 4 a and is supplied to the surface of the stored water. While coming out, humidify the fuel gas in contact with the stored water. The space on the surface of the stored water inside the fuel gas storage water tank 4a is connected to the anode 2a. In the middle of the gas supply path 3 from the fuel gas generating device 1 to the anode 2a, a valve V3 for blocking or allowing the gas flow in the gas supply path 3 is provided.
The gas used for the power generation reaction in the anode 2a is discharged to the outside of the fuel cell FC through the gas discharge path 7. The exhausted gas is recovered in exhaust heat in a heat exchanger (not shown) and then provided to an exhaust process such as burning in a burner (not shown). In the middle of the gas discharge path 7, a valve V <b> 2 that blocks or allows the gas flow in the gas discharge path 7 is provided.

Air as an oxidant gas is supplied to the cathode 2 b through the gas supply path 5 by the blower 9. In the middle of the gas supply path 5, an oxidant gas humidifier 6 having an oxidant gas storage water tank 6a is provided. The oxidant gas humidifier 6 is configured such that the air supplied from the blower 9 is supplied to the stored water stored in the oxidant gas storage water tank 6a through the gas supply path 5, and the surface of the stored water. While coming out, the oxidant gas is brought into contact with the stored water and humidified. The space on the surface of the stored water inside the oxidant gas storage water tank 6a is connected to the cathode 2b. In the middle of the gas supply path 5 from the blower 9 to the cathode 2b, a valve V4 for blocking or allowing the gas flow in the gas supply path 5 is provided.
The gas used for the power generation reaction at the cathode 2b is discharged to the outside of the fuel cell FC via the gas discharge path 8. The exhausted gas is recovered as exhaust heat by a heat exchanger (not shown). Since the exhausted gas is originally air present in the surroundings, no special exhaust treatment is required.

Below, the operation process of the fuel cell FC (during power generation), the stop transition process for shifting the operation of the fuel cell FC to a stop state in which the output of power from the fuel cell FC is stopped, and the stop after the stop transition process Each of the stop state maintaining steps for maintaining the state will be described with reference to a timing diagram illustrating the operating state of the fuel cell system S1 shown in FIG. 2 represents the reforming catalyst temperature (° C.), the battery temperature (° C.), the cathode air flow rate (liter / min), the cell voltage (V), the raw material gas flow rate (liter / min), and the reformer pressure ( kPa), but the meanings for each are different. Specifically, the reforming catalyst temperature (° C.) is represented by the numerical value on the vertical axis in FIG. 2, and the value obtained by multiplying the battery temperature (° C.) by 10 is represented by the numerical value on the vertical axis in FIG. A value obtained by multiplying (liter / min) by 10 is represented by a numerical value on the vertical axis in FIG. 2, a value obtained by multiplying the cell voltage (V) by 10 is represented by a numerical value on the vertical axis in FIG. The value obtained by multiplying min) by 10 ² is represented by the numerical value on the vertical axis in FIG. 2, and the value obtained by multiplying the reformer pressure (kPa) by 10 is represented by the numerical value on the vertical axis in FIG.

[Operation process (during power generation)]
When the power generation operation of the fuel cell FC is performed, the fuel gas generation device 1 also needs to be operated. Therefore, the valve V1 is opened so that the raw material gas can be supplied to the fuel gas generator 1. In the reformer 1a, a reforming reaction for reforming the hydrocarbon, which is the raw material gas, into hydrogen is performed, thereby generating a fuel gas containing hydrogen. The valve V3 provided in the gas supply path 3 is opened. Therefore, the fuel gas generated by the fuel gas generation device 1 is supplied to the anode 2 a via the fuel gas humidifier 4. The valve V2 is opened, and the exhaust gas from the anode 2a is discharged outside the fuel cell FC.
The valve V4 provided in the gas supply path 5 is opened so that the air (oxidant gas) supplied by the blower 9 reaches the cathode 2b.
Although not shown, an electric load or an inverter is electrically connected to the fuel cell 2.
As described above, the fuel gas is supplied to the anode 2a and the air is supplied to the cathode 2b, whereby a power generation reaction is performed in the fuel cell 2 and a current flows to the electric load or the inverter.

[Stop transition process]
In the stop transition process for stopping the operation of the fuel cell FC, the electrical connection between the electric load or the inverter and the fuel cell 2 of the fuel cell FC is released, and the power output obtained by the power generation in the fuel cell FC is output. Is a step of stopping the process. Therefore, before the output of the electric power obtained by the power generation in the fuel cell FC is stopped, the supply amount of the raw material gas and the supply amount of the oxidant gas (cathode air) to the fuel cell FC are decreased. As a result, the amount of gas (including water vapor) generated inside the reformer 1a decreases, and the pressure of the reformer 1a also decreases. Further, the temperature of the fuel cell FC (that is, the temperature of the anode 2a and the cathode 2b) gradually decreases.

  Thereafter, the blower 9 is stopped, the valve V4 provided in the gas supply path 5 to the cathode 2b is closed, and the supply of air to the cathode 2b is stopped. At this time, the raw material gas is supplied to the fuel gas generator 1, and the supply of the fuel gas from the fuel gas generator 1 to the anode 2a is continued. Therefore, in the fuel battery cell 2, the supply amount of air is very small compared to the supply amount of fuel gas, and the cell voltage rapidly decreases. That is, here, the air (oxygen) remaining on the cathode 2b reacts with the fuel gas (hydrogen) remaining on the anode 2a in a state where the supply of air to the cathode 2b is stopped. Then, the electrical connection between the electric load or the inverter and the fuel cell 2 of the fuel cell FC is released, and the output of the electric power obtained by the power generation in the fuel cell FC is stopped.

[Stop state maintenance process]
After the stop transition step, a stop state maintaining step described later is performed. However, as shown in FIG. 2, the temperature of the reforming catalyst inside the reformer 1a has not yet decreased at the time when the stop transition process is completed, and is due to the generation of hydrogen by the reforming reaction or the generation of steam. An increase in the pressure of the reformer 1a is observed. Therefore, when the valve V3 is opened while the temperature of the reforming catalyst is high, the gas or water vapor is supplied to the anode 2a, the pressure of the anode 2a is increased, and the cathode 2b in which the supply of air is stopped There is a possibility that the pressure difference will increase and the electrolyte 2c may be damaged. Therefore, the fuel gas generator isolation process is performed in which the valve V1 is closed and the valve V3 is closed until the temperature of the reforming catalyst becomes equal to or lower than the set temperature (650 ° C. in the example shown in FIG. 2).

  Specifically, an increase in the pressure of the reformer 1a due to the generation of hydrogen by the reforming reaction or the generation of water vapor is observed while the fuel gas generator isolating process is being performed. Therefore, when the pressure between the valve V1 and the valve V3 exceeds the set pressure, a pressure reduction process for reducing the pressure between the valve V1 and the valve V3 is performed. Specifically, when the pressure of the reformer 1a existing between the valve V1 and the valve V3 exceeds a set pressure (for example, 6 kPa), the valve V3 is opened and gas is supplied from the fuel gas generator 1 to the anode 2a. To reduce the pressure between the valve V1 and the valve V3. As shown in FIG. 2, the temperature of the reforming catalyst gradually decreases while the pressure reduction process repeatedly increases and decreases the pressure in the reformer 1 a (referred to as “pressure release process” in FIG. 2). To do. When the temperature of the reformer 1a (that is, the temperature of the reforming catalyst) becomes equal to or lower than the set temperature (250 ° C. in the example shown in FIG. 2), the fuel gas generator isolating process is terminated. Then, the valve V1 upstream of the reformer 1a of the gas distribution system leading from the fuel gas generator 1 to the anode 2a (an example of the “first closing target portion” of the present invention) is closed, and the anode 2a The valve V2 in the middle of the gas discharge path 7 (an example of the “second closing target portion” of the present invention) is closed, and the gas flow between the fuel gas generator 1 and the anode 2a is allowed ( A stop state maintaining step is performed in which the valve V3 is opened). That is, the pressure holding target range is defined between the valve V1 (first closing target part) and the valve V2 (second closing target part).

After the fuel gas generator isolating process is completed in the stop state maintaining step, the pressure increase in the reformer 1a is not observed, and conversely, the pressure decrease in the pressure holding target range is observed due to the temperature decrease of the reforming catalyst. Therefore, after the fuel gas generation device isolation process described above, the pressure holding process for the pressure holding target range is performed at the set pressure holding timing while the stop state maintaining process is continuously performed. Further, when gas leakage from the pressure holding target range is detected during the stop state maintaining process, the valve V1 (first closing target portion), the fuel gas generator 1 and the anode 2a in the middle of the gas distribution system are detected. The pressure holding target range is separated by closing the valve V3 (an example of the “third closing target portion” of the present invention) between the two and shutting off the gas flow between the fuel gas generating device 1 and the anode 2a. The pressure holding target range separation process is performed.
Hereinafter, the pressure holding process and the pressure holding target range separation process will be described.

[Pressure holding treatment]
In the present embodiment, as shown in FIG. 2, the control means C is configured such that the pressure of the reformer 1a (an example of “a predetermined part of the gas distribution system leading to the anode 2a inside the fuel gas generator 1)” The pressure drop due to the temperature drop of the gas generator 1 and the pressure rise due to opening the valve V1 and allowing the raw material gas to flow in are repeated. That is, when the pressure of the reformer 1a detected by the pressure sensor P1 tends to decrease, if the pressure falls below the set holding pressure (4 kPa in the example shown in FIG. 2), it is determined that the set holding pressure timing has come. . Then, the valve V1 is opened for a set time, and the raw material gas flows into the fuel gas generator 1 during that time. That is, the pressure holding process is repeatedly performed at an appropriate set pressure holding timing. By the pressure holding process, the pressure in the pressure holding target range is maintained by the source gas and the remaining reformed gas (hydrogen). As a result, intrusion of air from the outside to the reformer 1a and the anode 2a can be suppressed. In addition, even if oxygen enters the anode 2a from the cathode 2b, the invaded oxygen reacts with hydrogen (remaining reformed gas) supplied to the anode 2a and is consumed, resulting in a low oxygen concentration. Therefore, the oxidation of the anode 2a by the oxygen can be suppressed.

[Pressurization target range separation processing]
In addition, when the control means C detects a gas leak from the pressure holding target range during the stop state maintaining process, the control means C and the gas V1 (an example of the “first closing target portion” of the present invention) and the gas Gas between the fuel gas generating device 1 and the anode 2a by closing the valve V3 (an example of the “third closing target portion” of the present invention) between the fuel gas generating device 1 and the anode 2a in the middle of the distribution system The pressure holding target range separation process for separating the pressure holding target range is performed by blocking the distribution of the pressure. That is, initially, the pressure holding target range configured between the valve V1 and the valve V2 is changed between the pressure holding target range configured between the valve V1 and the valve V3, and the valve V3 and the valve V2. Separated into the pressure holding target range. And the control means C performs the said pressure holding process continuously with respect to the pressure holding object range comprised between the valve V1 and the valve V3, after performing the pressure holding object range isolation | separation process. In this embodiment, since the pressure sensor P1 is provided between the valve V1 and the valve V3, the pressure holding target range is defined as the pressure holding target range after the pressure holding target range separation processing is performed. Even in this case, the pressure holding process can be performed by detecting the pressure in the pressure holding target range between the valve V1 and the valve V3 with the pressure sensor P1.

That is, by this pressure holding target range separation processing, a range between the valve V1 and the valve V3 in the entire pressure holding target range (that is, a range including the reformer 1a of the fuel gas generation device 1) is selectively selected. Can be isolated. As a result, even if a gas leak occurs between the valve V3 and the valve V2 (for example, the fuel cell 2 between the valve V3 and the valve V2), the gas leakage between the valve V1 and the valve V3 ( That is, the pressure of the reformer of the fuel gas generation device between the valve V1 and the valve V3 can be maintained. And oxidation of the reformer 1a etc. of the fuel gas generator 1 can be suppressed.
In addition, the pressure holding target range initially configured between the valve V1 and the valve V2 is the same as the pressure holding target range configured between the valve V1 and the valve V3, and between the valve V3 and the valve V2. The gas leakage is separated into the pressure holding target range constituted by the range between the valve V3 and the valve V2 including the anode 2a or the like, or the valve V1 and the valve V3 including the reformer 1a and the like. Can be prevented from being affected by gas leakage such as oxygen intrusion into the range where no gas leakage occurs. Furthermore, by continuing to close the valve V1, the valve V3, and the valve V2 even after the gas leak is detected, that is, by continuing to seal the portion where the gas leak has occurred, the gas leak gradually proceeds. Therefore, even if a gas leak occurs, the performance of at least a part of the fuel cell system S1 can be maintained.

  In the present embodiment, the control means C is required to increase the pressure inside the pressure holding target range when the frequency of the pressure holding processing is high or when gas is supplied to the pressure holding target range in the pressure holding processing. When the time is equal to or longer than the set required time, or when the pressure decrease rate inside the pressure holding target range is equal to or higher than the set pressure decreasing speed, it is determined that a gas leak from the pressure holding target range has occurred.

In other words, the fact that the pressure holding process is performed more frequently than the normal frequency (reference frequency) can be regarded as a large pressure drop in the pressure holding target range (for example, outflow of gas from the pressure holding target range). . In addition, when the gas is supplied to the pressure holding target range during the pressure holding process, the time required for the pressure inside the pressure holding target range to rise is equal to or longer than the set required time. Therefore, it can be considered that it takes a long time to increase the pressure inside the pressure holding target range. Alternatively, the fact that the pressure decrease rate within the pressure holding target range is equal to or higher than the set pressure reducing rate can be regarded as a large outflow amount of gas from the pressure holding target range.
As described above, the control unit C performs the above-described holding pressure processing time, or the time required to increase the pressure inside the holding pressure target range when the gas is supplied to the holding pressure range in the holding pressure process, or The possibility of gas leakage from the pressure holding target range can be quickly detected by monitoring the rate of pressure drop within the pressure holding target range. In particular, in this embodiment, the pressure sensor P1 for detecting the pressure in the pressure holding target range is provided between the valve V1 and the valve V3 (between the first closing target site and the third closing target site). Therefore, after the pressure holding target range separation process is performed, the pressure in the pressure holding target range between the valve V1 and the valve V3 can be selectively detected. That is, after the pressure holding target range separation process is performed, gas leakage from the pressure holding target range between the valve V1 and the valve V3 can be selectively detected.

Further, when the control means C detects a gas leak after the set determination time has elapsed after performing the pressure holding target range separation process (as described above, from the pressure holding target range between the valve V1 and the valve V3). Gas leakage detected before the pressure holding target range separation process is performed between the valve V1 (first closing target part) and the valve V3 (third closing target part) (that is, When it is determined that the gas has leaked from the fuel gas generation device between the valve V1 and the valve V3), and when no gas leak is detected, the valve V3 (third closing target site) and the valve V2 (first valve) 2) (ie, a fuel cell located between the valve V3 and the valve V2).
Then, after performing the pressure holding target range separation process, the control means C detects the gas leakage from the range between the first closing target portion and the third closing target portion within the pressure holding target range. Cancel processing.

FIG. 3 is a flowchart of control including the above-described pressure holding target range separation processing, which will be described in detail below.
In step # 10 of FIG. 3, the control means determines whether or not the valve V3 is closed. That is, the control means determines whether or not the pressure holding target range separation process has already been performed. When the valve V3 has not been closed yet (in the case of “No” in step # 10 of FIG. 3), the pressure holding process is being performed with the range between the valve V1 and the valve V2 as the pressure holding target range. is there. On the other hand, when the valve V3 is already closed (in the case of “Yes” in step # 10 of FIG. 3), the pressure holding target range configured between the valve V1 and the valve V3, and the valve V3 The pressure holding process is performed only on the pressure holding target range constituted between the valve V1 and the valve V3 (the valve V3 and the valve V2). The range between V2 is a situation where a simple sealing process is performed).

When it is determined in step # 10 that the valve V3 is not yet closed, the control unit determines whether or not a gas leak has occurred in step # 12. If it is determined in step # 12 that a gas leak has occurred, the control means closes the valve V3 in step # 14 to perform the pressure holding target range separation process, and is configured between the valve V1 and the valve V3. The pressure holding process is performed only on the target pressure holding range. That is, even if a gas leak occurs between the valve V3 and the valve V2 (for example, the fuel battery cell 2 between the valve V3 and the valve V2), the gas leak occurs between the valve V1 and the valve V3 (that is, , The pressure of the reformer 1a, etc. of the fuel gas generator 1 between the valve V1 and the valve V3 can be maintained. And oxidation of the reformer 1a etc. of the fuel gas generator 1 can be suppressed.
On the other hand, if it is determined in step # 12 that no gas leak has occurred, the control means continues the pressure holding process with the pressure holding range between the valve V1 and the valve V2.

When it is determined in step # 10 that the valve V3 has already been closed, the control means determines in step # 16 whether or not a gas leak has occurred. When it is determined in step # 16 that a gas leak has occurred (that is, when it is determined that a gas leak has occurred from the pressure holding target range configured between the valve V1 and the valve V3). ), The pressure holding process is stopped in step # 18. That is, if the pressure inside the pressure holding target range is increased in a situation where gas leakage from the pressure holding target range occurs, the gas leakage may be promoted, but the pressure holding process is performed in step # 18. By stopping, gas leakage to the outside of the pressure holding target range is suppressed.
On the other hand, when it is determined in step # 16 that no gas leak has occurred, the control means continues the pressure holding process in the pressure holding target range configured between the valve V1 and the valve V3.

Second Embodiment
The method for maintaining the stopped state of the fuel cell system according to the second embodiment is different from the first embodiment in the gas leak detection method. Hereinafter, the method for maintaining the stopped state of the fuel cell system according to the second embodiment will be described, but the description of the same configuration as that of the first embodiment will be omitted.

  FIG. 4 is a diagram for explaining the configuration of a fuel cell system S2 (S) in which the fuel cell system stop state maintaining method of the second embodiment is implemented. The fuel cell system S2 does not include the fuel gas humidifier 4 and the oxidant gas humidifier 6. In addition, the fuel cell system S2 includes a gas sensor (gas detection sensor) 10 capable of detecting a raw material gas such as methane and a combustible gas such as hydrogen (that is, a monitoring target gas) used in the system. And a control means determines with the gas leak having generate | occur | produced, when the monitoring object gas more than a setting density | concentration is detected by the gas sensor 10. FIG. That is, in the present embodiment, by using the gas sensor 10, it is possible to accurately detect a gas leak of the monitoring target gas. The gas sensor 10 is provided, for example, in a portion of the fuel cell system S immediately before the ventilation air for ventilating the inside of the fuel cell system S comes out of the fuel cell system S.

<Another embodiment>
<1>
In the above-described embodiment, as the set holding pressure timing for performing the holding pressure processing, the timing when the set holding pressure is reached when the pressure of the reformer 1a tends to decrease is illustrated, but other timings are set as the set holding pressure. It can also be a timing. For example, the control means C measures the elapsed time after the fuel gas generating device isolation process ends, and every time the elapsed time reaches a set time (for example, the elapsed time after the fuel gas generating device isolation process ends) May be modified so that it is determined that the set pressure holding timing has been reached (every 10 minutes, 30 minutes, 60 minutes, 120 minutes, ...).

<2>
In the above embodiment, if it is not necessary to detect the pressure and temperature of the anode 2a, the pressure sensor P2 for detecting the pressure of the anode 2a and the temperature sensor T2 for detecting the temperature of the anode 2a may not be provided.
Or in the said 1st Embodiment, the control means C uses the pressure sensor P1 which detects the pressure of the inside (reformer 1a) of a gas distribution system, and the pressure inside the pressure retention object range is set pressure holding pressure. Although the example of determining whether or not the pressure is lower than the above is described, the pressure inside the holding pressure range is lower than the set holding pressure by using the pressure sensor P2 that detects the pressure of the anode 2a as the inside of the gas distribution system. You may modify | change so that it may determine whether it was.

<3>
In the above embodiment, the valve V4 is provided in the gas supply path 5 to the cathode 2b, but this valve V4 may not be provided.

<4>
In the above embodiment, an example of performing a pressure holding target range separation process that closes all of the valves V1, V2, and V3 when a gas leakage is detected while the pressure holding range is between the valve V1 and the valve V2. However, the pressure holding target range separation processing of another form, for example, the pressure holding target range separation processing such as closing the valve V1 and the valve V3 and opening the valve V2 may be performed. That is, the pressure holding target range separation process may be performed so that only the space between the valve V1 and the valve V3 is set as the pressure holding target range. For example, when there is a gas leak from the fuel cell FC, there is a system in which maintenance is required to replace the fuel cell FC with a new one. In such a case, it is not necessary to close the valve V2 because air may enter the fuel cell FC that has been leaked and is waiting to be replaced. As a result, no electric power is required to keep the valve V2 closed.

  The present invention can be used to maintain the performance of at least a part of the fuel cell system even when a gas leak or the like occurs.

DESCRIPTION OF SYMBOLS 1 Fuel gas production | generation apparatus 1a Reformer 2 Fuel cell 2a Anode 2b Cathode 3 Gas supply path (gas distribution system)
7 Gas exhaust passage 10 Gas sensor (gas detection sensor)
C Control means FC Fuel cell P1 Pressure sensor (pressure gauge)
S (S1, S2) Fuel cell system V1 valve (first part to be closed)
V2 valve (second closing target)
V3 valve (third closing target)

Claims (8)

A fuel cell comprising an electrolyte provided between an anode to which a fuel gas containing hydrogen is supplied and a cathode to which an oxidant gas is supplied, is supplied to the anode through a gas supply path to the anode A method for maintaining a stopped state of a fuel cell system to which a fuel gas generation device that generates the fuel gas using a reformer is connected,
A stop transition step of shifting the operation of the fuel cell to a stop state in which output of power from the fuel cell is stopped;
After the stop transition step, the first closing target portion upstream of the reformer of the gas distribution system that maintains the operation of the fuel cell in the stopped state and communicates from the fuel gas generation device to the anode. And the second closing target part in the middle of the gas discharge path from the anode is closed, and the flow of gas between the fuel gas generator and the anode is allowed. A stopped state maintaining step for storing the battery,
At the set pressure holding timing during the stop state maintaining step, the pressure holding process for the pressure holding target range is performed with the pressure holding target range between the first closing target part and the second closing target part. And when the gas leakage from the pressure holding target range is detected while the stop state maintaining step is being performed, the fuel gas generating device in the middle of the first closing target portion, the gas circulation system, and the A pressure holding target range separation process for separating the pressure holding target range is performed by closing a third closing target portion between the anodes and shutting off a gas flow between the fuel gas generation device and the anode. A method for maintaining a stopped state of a fuel cell system.   The method for maintaining a stopped state of a fuel cell system according to claim 1, wherein the second closing target part is closed in the pressure holding target range separation process.   The pressure holding process increases the pressure inside the pressure holding target range by opening the first closing target site and supplying gas from the upstream side of the first closing target site to the pressure holding target range. The method for maintaining a stopped state of a fuel cell system according to claim 1 or 2, wherein   After performing the pressure holding target range separation process, if a gas leak from a range between the first closing target part and the third closing target part in the pressure holding target range is detected, the pressure holding process is performed. The stop state maintaining method for a fuel cell system according to any one of claims 1 to 3, wherein the stop state is maintained.   When a gas leakage from between the first closing target part and the third closing target part is detected after a set determination time has elapsed since the pressure holding target range separation process has been performed, the pressure holding target range When it is determined that the gas leak detected before the separation process is a gas leak from between the first closing target part and the third closing target part, and the gas leakage is not detected, the pressure holding The gas leak detected before the target range separation process is determined to be a gas leak from between the third closing target part and the second closing target part. A method for maintaining a stopped state of a fuel cell system. The fuel cell system is provided with a pressure gauge capable of detecting the pressure inside the gas distribution system between the first closing target part and the third closing target part,
The fuel cell system according to any one of claims 1 to 5, wherein the set pressure holding timing is a timing at which a pressure inside the pressure holding target range detected by the pressure gauge falls below a set pressure holding pressure. How to maintain the stopped state.   When the pressure holding process is frequently performed or when gas is supplied to the pressure holding target range in the pressure holding process, the time required to increase the pressure inside the pressure holding target range is equal to or longer than the set required time. The method for maintaining a stopped state of a fuel cell system according to claim 6, wherein it is determined that a gas leak has occurred at a certain time or when the rate of pressure decrease within the pressure holding target range is equal to or greater than a set rate of decrease.   The stop of the fuel cell system according to any one of claims 1 to 5, wherein a gas detection sensor capable of detecting a monitoring target gas determines that a gas leak has occurred when the monitoring target gas having a set concentration or more is detected. State maintenance method.

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