JP6861548B2 - Fuel cell system and how to operate the fuel cell system - Google Patents

Description

In the present invention, a reforming unit that reforms raw fuel to generate fuel gas, an anode to which the fuel gas generated in the reforming unit is supplied, and a cathode to which oxygen gas for power generation is supplied are provided. A fuel cell unit having a fuel cell unit, a combustion unit that burns a fuel component in the discharged fuel gas discharged from the anode after being used in a power generation reaction in the fuel cell unit, and an oxygen gas for power generation are supplied to the cathode. The present invention relates to a fuel cell system including a blower for generating oxygen for the purpose and an operation control unit. The present invention also relates to a method of operating a fuel cell system.

In the above fuel cell system, oxygen gas for power generation is supplied to the cathode of the fuel cell unit from a blower for power generation oxygen through a gas supply path, and the gas supply path is opened in the middle of the gas supply path. An on-off valve that can be switched to a closed state is provided (see, for example, Patent Document 1).

There is no problem when the blower and on-off valve are operating normally, but if an abnormality occurs in the blower or on-off valve due to the use of the fuel cell, oxygen gas for power generation is satisfactorily supplied to the cathode of the fuel cell. It may not be possible. Therefore, in order to detect the occurrence of such an abnormality, the following configuration has been proposed.

That is, another on-off valve is provided on the lower side of the on-off valve to be diagnosed in the gas supply path in the air flow direction, and the internal pressure is measured on each of the upper and lower air flow directions of the on-off valve to be diagnosed. It is equipped with a pressure sensor to determine the operation abnormality of the on-off valve based on the fluctuation of the internal pressure accompanying the start of operation of the fuel cell, the fluctuation of the internal pressure before and after the opening and closing of another on-off valve, and the like (for example,). See Patent Document 2).

Japanese Unexamined Patent Publication No. 2015-185249 Japanese Unexamined Patent Publication No. 2004-95425

The above-mentioned conventional configuration requires a plurality of separate devices that are not originally required, such as another on-off valve and a plurality of pressure sensors, and has disadvantages such as an increase in the number of parts and an increase in cost. Moreover, in the above-mentioned conventional configuration, although it is possible to determine the operation abnormality of the on-off valve, there is a disadvantage that it is not possible to determine the operation abnormality of the blower for power generation oxygen.

If the blower operation abnormality is added, it is easy to determine that the blower is abnormal when the blower is out of order and the blowing operation is not performed at all. On the other hand, for example, when an abnormality such as water entering the inside of the blower occurs, the operation of the blower can be continued, and if the output of the fuel cell is low, the output of the blower can be continued. It is possible to continue operation that is almost the same as normal operation. However, if the operation is continued with water invading the inside of the blower in this way, the blower may be significantly damaged in a short period of time.

The intrusion of water into the blower will be described.
Conventionally, some fuel cells have a configuration in which water is supplied to the inside of the fuel cell to moisten the anode and cathode. In this configuration, a large amount of water exists inside the fuel cell when the operation is stopped. Will be done.

Then, during the shutdown, the raw fuel gas is supplied via the reformer to prevent the cathode from being oxidized by the oxidant gas remaining inside the fuel cell, and the pressure inside the fuel cell is increased. The pressure holding process may be performed to set the value higher.

Further, when power generation is started from an operation stopped state, combustion air may be supplied via a reformer in order to discharge unburned gas or the like remaining in the combustion portion. At this time as well, the pressure inside the fuel cell may change to a higher level.

As a result, if the on-off valve provided in the gas supply path through which oxygen gas for power generation passes is out of order, the pressure inside the fuel cell changes to a higher level when the operation is stopped or when the operation is started. Therefore, some of the water existing inside the fuel cell may enter the blower through the gas supply path.

The present invention has been made in view of the above problems, and an object of the present invention is to prevent the supply of oxygen gas for power generation to the fuel cell unit without complicating the structure such as providing a separate device. The point is to be able to determine what has occurred.

The characteristic configuration of the fuel cell system according to the present invention is
A reformer that reforms raw fuel to generate fuel gas,
A fuel cell unit having an anode to which the fuel gas generated in the reforming unit is supplied and a cathode to which oxygen gas for power generation is supplied.
A combustion unit that burns fuel components in the exhaust fuel gas discharged from the anode after being used in a power generation reaction in the fuel cell unit.
A blower for power generation oxygen for supplying the oxygen gas for power generation to the cathode,
A fuel cell system equipped with an operation control unit.
A voltage detection unit that detects the output voltage of the fuel cell unit,
A power detection unit that detects the output power of the fuel cell unit is provided.
The operation control unit
The output of the power generation oxygen blower is adjusted so that the flow rate of the power generation oxygen gas per unit time becomes a target flow rate commensurate with the output power of the fuel cell unit.
Supply of the oxygen gas for power generation to the cathode when the output voltage detected by the voltage detection unit shows a fluctuation of a predetermined allowable range or more while the output power detected by the power detection unit is constant. Judging that there is a problem with
The operation control unit
It is determined that a problem has occurred in the supply of the power generation oxygen gas to the cathode, and the current output of the power generation oxygen blower determines the flow rate of the power generation oxygen gas per unit time of the fuel cell. When the target flow rate is greater than the set value when the target flow rate is set to match the output power of the unit, there is a problem with the supply of the oxygen gas for power generation due to an increase in the flow path resistance of the oxygen gas for power generation. Judge that it is occurring and
When it is determined that a problem has occurred in the supply of the oxygen gas for power generation to the cathode, and the current output of the blower for power generation oxygen is not larger than the set value by the set value or more, the power generation is performed. failure of the supply of the power generation oxygen gas caused by oxygen for blower is in point you determined to be occurring.

The operation control unit adjusts the output of the blower for power generation oxygen so that the target flow rate is commensurate with the output power of the fuel cell unit. In some cases, a turbulence peculiar to the flow rate of the air sent out from the blower may occur, and the output voltage of the fuel cell unit may fluctuate greatly up and down due to this turbulence.

Therefore, taking advantage of this, if the output voltage of the fuel cell unit fluctuates beyond the permissible range under the condition that the output power of the fuel cell unit is constant, a problem occurs in the supply of oxygen gas for power generation to the cathode. It can be determined that the fuel cell is used. The voltage detection unit and the power detection unit are originally required to detect the operating state of the fuel cell.

As a result, by using the originally required device, it is possible to determine that a failure in supplying oxygen gas for power generation to the fuel cell section has occurred without inviting complication of the structure such as providing a separate device. It became a thing.
By the way, even if there is a problem in the supply of oxygen gas for power generation, the cause of the problem is not only the one caused by the blower for power generation oxygen, but also the gas supply path through which the oxygen gas for power generation passes. It is also possible that the flow path resistance is increasing due to the blockage due to the above factors.
If the cause is an increase in the flow path resistance, even if the output of the generated oxygen blower is adjusted to the reference output corresponding to the target flow rate, the power generation oxygen gas of the target flow rate cannot be supplied. As a result, when the operation control unit adjusts the output of the generated oxygen blower so as to reach the target flow rate, the output of the generated oxygen blower becomes an output larger than the set amount by a set amount or more. On the other hand, if the cause is a blower for generated oxygen, the output of the blower for generated oxygen is unlikely to fluctuate significantly from the reference output.
Therefore, in the above characteristic configuration, when it is determined that a problem has occurred in the supply of oxygen gas for power generation by utilizing this, the cause is an increase in the flow path resistance, or the blower for power generation oxygen is the cause. It becomes possible to determine whether or not.

Another characteristic configuration of the fuel cell system according to the present invention is that when the operation control unit determines that a problem has occurred in the supply of the oxygen gas for power generation to the cathode, the output power of the fuel cell unit is determined. The point is that the low output operation is performed for a predetermined period to bring the unit into a predetermined low output state.

For example, even if there is an abnormality in the operation of the blower for power generation oxygen due to the intrusion of water, etc., when the fuel cell unit is operating in a low output state, it is almost the same as normal operation. It is possible to continue stable operation with little fluctuation in output voltage. Therefore, when it is determined that a problem has occurred, it is possible to avoid disadvantages such as early damage due to an unreasonable force applied to the generated oxygen blower by performing low output operation. As a result of determining that a problem has occurred, it is possible to take some measures while the predetermined time elapses. Therefore, the low output operation is performed for a predetermined period and continues unnecessarily for a long time. You can avoid that.

Yet another characteristic configuration of the fuel cell system according to the present invention is
The operation control unit
When it is determined that a problem has occurred in the supply of the oxygen gas for power generation to the cathode, and the current output of the blower for power generation oxygen is not larger than the set value by the set value or more, the power generation is performed. The point is that it is determined that a defect in the supply of the oxygen gas for power generation due to the intrusion of water into the oxygen blower has occurred.

According to the above characteristic configuration, if the output of the blower for power generation oxygen is not larger than the set value from the reference output even though the output voltage of the fuel cell unit fluctuates and a problem occurs, it is for power generation oxygen. Determine that the cause is water intrusion into the blower. That is, in such a case, there is no problem in the blowing capacity of the generated oxygen blower itself, and it can be assumed that the cause is the intrusion of water.

Therefore, it is possible to determine whether or not the cause is the intrusion of water based on the difference in the output magnitude of the generated oxygen blower.

The characteristics of the operation method of the fuel cell system according to the present invention are:
A fuel cell unit having a reforming unit that reforms raw fuel to generate fuel gas, an anode to which the fuel gas generated in the reforming unit is supplied, and a cathode to which oxygen gas for power generation is supplied. A combustion unit that burns a fuel component in the discharged fuel gas discharged from the anode after being used in a power generation reaction in the fuel cell unit, and generated oxygen for supplying the power generation oxygen gas to the cathode. A method of operating a fuel cell system equipped with a blower for
The fuel cell system includes a voltage detection unit that detects the output voltage of the fuel cell unit and a power detection unit that detects the output power of the fuel cell unit.
The output of the generated oxygen blower is adjusted so that the flow rate of the power generation oxygen gas per unit time becomes a target flow rate commensurate with the output power of the fuel cell unit, and the output power detected by the power detection unit. The voltage detection step of detecting the output voltage by the voltage detection unit while the voltage is constant,
When the output voltage detected in the voltage detection step shows a fluctuation of more than a predetermined allowable range, a defect determination step of determining that a defect has occurred in the supply of the oxygen gas for power generation to the cathode, and a defect determination step .
In the defect determination step, when it is determined that a defect has occurred in the supply of the power generation oxygen gas to the cathode, the current output of the power generation oxygen blower is per unit time of the power generation oxygen gas. If the flow rate is larger than the set value from the reference output when the target flow rate is set to match the output power of the fuel cell unit, the power generation oxygen gas is caused by an increase in the flow path resistance of the power generation oxygen gas. If the current output of the power generation oxygen blower is not larger than the set value by the set value or more, it is estimated that the power generation oxygen blower is the cause of the power generation oxygen. The point is that it has a defect cause estimation process for estimating that a gas supply defect has occurred.

The output of the blower for power generation oxygen is adjusted so that the target flow rate matches the output power of the fuel cell section. For example, if an abnormality occurs in the blower operation due to the intrusion of water, etc., the blower will start. A turbulence peculiar to the flow rate of the sent out air occurs, and the output voltage of the fuel cell unit may fluctuate greatly up and down due to this turbulence.

Therefore, in the voltage detection process, when the output power of the fuel cell unit is constant, the output voltage of the fuel cell unit is detected, and in the defect determination process, if the output voltage shows a fluctuation of more than a predetermined allowable range. , It can be determined that a problem has occurred in the supply of the oxygen gas for power generation to the cathode. The voltage detection unit and the power detection unit are originally required to detect the operating state of the fuel cell.

As a result, by using the originally required device, a problem in supplying oxygen gas for power generation to the fuel cell section occurred without inviting the structure of the fuel cell system to be complicated, such as providing a separate device. It became possible to distinguish that.
By the way, even if there is a problem in the supply of oxygen gas for power generation, the cause of the problem is not only the one caused by the blower for power generation oxygen, but also the gas supply path through which the oxygen gas for power generation passes. It is also possible that the flow path resistance is increasing due to the blockage due to the above factors.
If the cause is an increase in the flow path resistance, even if the output of the generated oxygen blower is adjusted to the reference output corresponding to the target flow rate, the power generation oxygen gas of the target flow rate cannot be supplied. As a result, when the operation control unit adjusts the output of the generated oxygen blower so as to reach the target flow rate, the output of the generated oxygen blower becomes an output larger than the set amount by a set amount or more. On the other hand, if the cause is a blower for generated oxygen, the output of the blower for generated oxygen is unlikely to fluctuate significantly from the reference output.
Therefore, in the above characteristics, when it is determined that a problem has occurred in the supply of oxygen gas for power generation by utilizing this, the cause is an increase in the flow path resistance, or the blower for power generation oxygen is the cause. It becomes possible to determine whether or not there is.

Another feature of the operating method of the fuel cell system according to the present invention is.
When it is determined in the defect determination step that a defect has occurred in the supply of the oxygen gas for power generation to the cathode, a low output operation for setting the output power of the fuel cell unit to a predetermined low output state is performed for a predetermined period. The point is that it has a countermeasure process to be taken.

For example, even if there is an abnormality in the operation of the blower for power generation oxygen due to the intrusion of water, etc., when the fuel cell unit is operating in a low output state, it is almost the same as normal operation. It is possible to continue stable operation with little fluctuation in output voltage. Therefore, when it is determined that a problem has occurred, it is possible to avoid disadvantages such as early damage due to an unreasonable force applied to the generated oxygen blower by performing low output operation. As a result of determining that a problem has occurred, it is possible to take some measures while the predetermined time elapses. Therefore, the low output operation is performed for a predetermined period and continues unnecessarily for a long time. You can avoid that.

Yet another feature of the operating method of the fuel cell system according to the present invention is.
When it is estimated in the defect cause estimation step that a defect in the supply of the oxygen gas for power generation caused by the blower for power generation has occurred, the output power of the fuel cell unit is brought into a predetermined low output state. The point is that it has a countermeasure process for performing low-power operation for a predetermined period.

According to the above method, when it is estimated that a malfunction in the supply of oxygen gas for power generation due to the blower for power generation oxygen has occurred, the output power of the fuel cell unit is set to a predetermined low output state. If it is assumed that the cause is, another measure will be taken.

Therefore, appropriate measures can be taken only when the blower for generated oxygen is the cause.

Yet another feature of the operating method of the fuel cell system according to the present invention is.
In the defect cause estimation step, when it is estimated that a defect in the supply of the oxygen gas for power generation caused by the blower for power generation has occurred, the fuel cell unit is not generated at a predetermined timing. The point is to operate the power generation oxygen blower to flow the power generation oxygen gas from the power generation oxygen blower toward the cathode.

According to the above method, a large amount of water is present on the cathode side by flowing the oxygen gas for power generation from the blower for power generation oxygen toward the cathode at an appropriate timing while the fuel cell unit is not generating power. However, it is possible to prevent water from entering the blower for power generation oxygen.

Yet another feature of the operating method of the fuel cell system according to the present invention is.
It is preferable that the predetermined timing is the timing at which the pressure from the cathode to the generated oxygen blower is applied while the fuel cell unit is not generated.

According to the above method, water invades the power generation oxygen blower by flowing the power generation oxygen gas from the power generation oxygen blower toward the cathode at the timing when the pressure from the cathode to the power generation oxygen blower is applied. Can be prevented more accurately.

It is a schematic block diagram of a fuel cell system. It is a structure explanatory drawing of a cell. It is a flowchart explaining the driving method. It is a figure which shows the actual measurement data of the stable operation state. It is a figure which shows the actual measurement data of the abnormal operation state.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
The fuel cell system according to the present invention and its operation method will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a fuel cell system. The fuel cell system uses a fuel gas generator 1 that reforms a raw fuel gas as a raw material (for example, a city gas containing methane) to generate a fuel gas, and a fuel gas supplied from the fuel gas generator 1. It includes a fuel cell power generation device 2 that generates power by using it as fuel, and an operation control unit 3 that controls the operation of the fuel gas generation device 1 and the fuel cell power generation device 2.

The fuel gas generator 1 includes a reforming unit 4 that reforms the raw fuel gas to generate a fuel gas containing hydrogen as a main component, and a combustion unit 5 that burns the fuel component to heat the reforming unit 4. , A raw fuel blower 6 for supplying raw fuel gas to the reforming unit 4 through the raw material fuel supply path L1, and a combustion oxygen blower 7 for supplying combustion oxygen gas to the combustion unit 5 through the combustion oxygen supply path L2. A first on-off valve 8 that can open and close the raw material and fuel supply path L1 and a second on-off valve 9 that can open and close the combustion oxygen supply path L2 are provided. Further, the raw material fuel supply path L1 is provided with a raw material fuel flow meter 10 for measuring the flow rate of the raw material fuel gas supplied by the raw material blower 6, and the combustion oxygen supply path L2 is supplied by the combustion oxygen blower 7. A combustion oxygen flow meter 11 for measuring the flow rate of the combustion oxygen to be produced is provided.

The reforming unit 4 reforms the raw material fuel gas in the presence of water vapor to generate a fuel gas containing hydrogen as a main component. Specifically, in the reforming section 4, the raw fuel gas is steam reformed using the heat generated in the combustion section 5 provided adjacent to the reforming section 4, and hydrogen is the main component as a by-product. Produces a reformed gas containing carbon monoxide and carbon dioxide. Although not shown, the reforming unit 4 also performs a process of removing carbon monoxide contained in the reformed gas after reforming. The fuel gas generated by the reforming unit 4 is supplied to the fuel cell power generation device 2 through the fuel gas supply path L3.

The supply amount of the raw fuel gas supplied through the raw fuel supply path L1 is measured by the raw material flow meter 10, and the operation control unit 3 performs the raw fuel so that the measured flow rate becomes a preset target flow rate. Adjust the output of the blower 6 for. When the raw material blower 6 is not operating when the operation is stopped or the like, the first on-off valve 8 is closed.

The combustion unit 5 burns a flammable gas to generate heat. As the flammable gas, as will be described later, an exhaust gas containing hydrogen that has not been consumed in the power generation reaction in the fuel cell power generation device 2, a raw fuel gas, or a mixture thereof can be used. Further, combustion air (oxygen) for the combustible gas is supplied to the combustion unit 5 via the combustion oxygen supply path L2.

The amount of combustion oxygen gas supplied through the combustion oxygen supply path L2 is measured by the combustion oxygen flow meter 11, and the operation control unit 3 so that the measured flow rate becomes a preset target flow rate. Adjusts the output of the combustion oxygen blower 7. When the combustion oxygen blower 7 is not operating, such as when the operation is stopped, the second on-off valve 9 is closed.

The fuel cell power generation device 2 is supplied with the fuel gas and oxygen gas for power generation as described above to perform power generation, and the oxygen gas for power generation is supplied to the fuel cell unit 12 through the oxygen supply path L4 for power generation. A blower 13 for power generation oxygen, a third on-off valve 14 capable of opening and closing the oxygen supply path L4 for power generation, a water tank 15 for storing cooling water for cooling the fuel cell unit 12, and oxygen gas for power generation. A fourth on-off valve 16 that can open and close the power generation oxygen discharge path L5 through which unconsumed gas passes, a pump 17 for circulating and supplying cooling water, and a voltage that detects the output voltage of the fuel cell unit 12. A detection unit 18 and a power detection unit 19 for detecting the output power of the fuel cell unit 12 are provided. Further, the power generation oxygen supply path L4 is provided with a power generation oxygen flow meter 20 for measuring the flow rate of the power generation oxygen gas supplied by the power generation oxygen blower 13.

The fuel cell unit 12 is a solid polymer fuel cell, and as shown in FIG. 2, one fuel cell unit 12 has an electrolyte membrane 22 made of a solid polymer sandwiched between an anode (fuel electrode) 23 and a cathode (oxygen electrode) 24. Cell C is configured, and a plurality of cells C are stacked.

The anode 23 includes a gas diffusion layer 23a and a catalyst layer 23b, and the fuel gas supplied to the fuel gas flow path 26a formed on one surface of the first separator 26 on the side facing the gas diffusion layer 23a is the gas diffusion layer 23a. It reaches the catalyst layer 23b through. Similarly, the cathode 24 includes a gas diffusion layer 24a and a catalyst layer 24b, and oxygen (air) supplied to the air flow path 27a formed on one surface of the second separator 27 on the side facing the gas diffusion layer 24a is supplied. It reaches the catalyst layer 24b through the gas diffusion layer 24a. The catalyst layers 23b and 24b are composed of a carrier carrying a metal catalyst and promote a chemical reaction.

A cooling water flow path 27b through which cooling water flows is formed between the second separator 27 and the first separator 26 of the adjacent cell C. The cooling water flow path 27b and the separators 26 and 27 constitute a cooling unit 28 (see FIG. 1) for cooling the fuel cell unit 12. The cooling water circulation path 29 connected to the cooling water flow path 27b is provided with a water tank 15 and a pump 17, and when the pump 17 operates, the cooling water stored in the water tank 15 is collected by the fuel cell unit 12. After passing through the cooling water flow path 27b, the water is circulated and supplied so as to return to the water tank 15.

In the fuel cell unit 12, reformed fuel gas is supplied to the anode 23, oxygen (air) is supplied to the cathode 24, and a power generation reaction is performed. The output power of the fuel cell unit 12 (that is, the amount of power generation reaction) is adjusted by the operation control unit 3 using an inverter (not shown), and the power is supplied to the power consuming device (not shown).

Of the hydrogen contained in the fuel gas supplied to the anode 23, excess hydrogen not consumed in the power generation reaction in the fuel cell unit 12 is discharged from the anode 23 and passes through the anode exhaust gas flow path L6 to the combustion unit 5. It is supplied and burned as a flammable gas. A combustion oxygen supply path L2 is connected to the anode exhaust gas flow path L6.

The amount of oxygen gas for power generation supplied to the cathode 24 through the oxygen supply path L4 for power generation is measured by the oxygen flow meter 20 for power generation, and the operation is performed so that the measured flow rate becomes a preset target flow rate. The control unit 3 adjusts the output of the generated oxygen blower 13 (specifically, the rotation speed of the blower fan, etc.). When the blower 13 for power generation oxygen is not operating, such as when the operation is stopped, the third on-off valve 14 is closed.

The surplus oxygen gas for power generation discharged from the fuel cell unit 12 is exhausted to the outside after passing through the water tank 15 through the oxygen discharge path L5 for power generation. Since the excess oxygen gas for power generation may contain a large amount of water existing in the cathode 24, the water is recovered in the water tank 15. To add an explanation, in the fuel cell of the present embodiment, when the operation is stopped, the entire fuel cell covered with the casing is filled with water to prevent oxygen from entering and the electrode deteriorates due to oxidation. We are taking measures such as preventing.

Then, the operation control unit 3 adjusts the output of the power generation oxygen blower 13 so that the flow rate of the power generation oxygen gas per unit time becomes a target flow rate commensurate with the output power of the fuel cell unit 12, and the power generation detection unit 3 While the output power detected in 19 was constant, the output voltage of the fuel cell unit 12, specifically the output voltage of the cell C, detected by the voltage detection unit 18 showed fluctuations exceeding a predetermined allowable range. At this time, it is determined that a problem has occurred in the supply of the oxygen gas for power generation to the cathode 24.

As shown in FIG. 3, the operation control unit 3 includes a voltage detection process (step # 1), a defect determination process (step # 2), a defect cause estimation process (step # 3), and countermeasures. The step (step # 4) is executed.

In the voltage detection step (# 1), the voltage detection unit 18 detects the output voltage while the output power of the fuel cell unit 12 detected by the power detection unit 19 is constant. The voltage detection unit 18 detects the voltage generated by the plurality of cells C in the fuel cell unit 12 and obtains the average value (referred to as the average cell voltage). FIG. 4 shows the data of the measured values measured by the applicant. FIG. 4 is data on the operating state of the fuel cell unit 12 in a stable operation. In this example, when the output is stable, the output power is about 700 W and the average cell voltage is about 730 mV.

In the defect determination step (# 2), when the output voltage detected in the voltage detection step shows a fluctuation of more than a predetermined allowable range, it is determined that a defect has occurred in the supply of oxygen gas for power generation to the cathode 24. To do. Specifically, the standard deviation of the output voltage of a single cell C is obtained, and if the standard deviation is smaller than the threshold value as compared with the preset threshold value, the operation is normal. If the standard deviation is larger than the threshold value, it is determined that a problem has occurred in the supply of oxygen gas for power generation to the cathode 24. For the standard deviation, the voltage data of the average value of the output voltage of the cell C for 5 seconds is obtained, and the standard deviations of 12 pieces of the voltage data are calculated. Since the fluctuation range of the output voltage fluctuates depending on the magnitude of the output power, it is preferable to set the threshold value to a different value according to the magnitude of the output power of the fuel cell unit 12 at that time. For example, when the output power is 250 W or more and less than 400 W, the threshold value is set to 4 mV, when the output power is 400 W or more and less than 600 W, the threshold value is set to 5 mV, and when the output power is 600 W or more and 700 W or less, the threshold value is set to 6 mV. be able to.

In the failure cause estimation step (# 3), the current output of the power generation oxygen blower 13 is the reference output when the flow rate of the power generation oxygen gas per unit time is set to the target flow rate commensurate with the output power of the fuel cell unit 12. If it is larger than the set value, it is estimated that a problem in the supply of power generation oxygen gas has occurred due to an increase in the flow path resistance of the power generation oxygen gas, and the current output of the power generation oxygen blower 13 is estimated. If is not larger than the set value from the reference output, it is presumed that the power generation oxygen gas supply failure caused by the power generation oxygen blower 13 has occurred.

That is, the change characteristics between the output power of the fuel cell unit 12 and the corresponding flow rate (reference output) of the oxygen gas for power generation per unit time are determined and determined in advance by experiments and the like. If the current output of the power generation oxygen blower 13 is larger than the set value from the reference output, the flow of the power generation oxygen gas is smaller than the current output size of the power generation oxygen blower 13, that is, for power generation. It can be assumed that the flow path resistance of oxygen gas is increasing.

However, if it is determined that the supply of oxygen gas for power generation of the cathode 24 has a problem, but the current output of the oxygen generator 13 for power generation is not larger than the set value by more than the set value, power generation is performed. It is determined that a defect caused by the oxygen blower 13, specifically, a defect caused by water entering the generated oxygen blower 13 has occurred.

The cause of water entering the power generation oxygen blower 13 is that the third on-off valve 14 and the fourth on-off valve 16 open and fail, and the water sealed inside the fuel cell unit 12 is the power generation oxygen supply path L4. It is conceivable that the water flows into the generated oxygen blower 13 through the blower 13. For example, when the fuel gas is supplied through the reforming unit 4 in order to avoid deterioration due to oxidation of the electrodes when the operation is stopped, or in order to remove the exhaust gas in the combustion unit 5 when the operation is started. When operating the combustion oxygen blower 7, water may enter.

FIG. 5 shows data of measured values when water invades the generated oxygen blower 13. As is clear from this figure, it can be seen that the output voltage of the fuel cell unit 12 fluctuates greatly and the standard deviation becomes large. In the one shown in FIG. 5, when the output voltage of the fuel cell unit 12 decreases, the output power of the fuel cell unit 12 also decreases, and the output power also decreases according to the change of the output voltage. It is fluctuating. When water enters the generated oxygen blower 13 in this way, the output voltage fluctuates greatly. Therefore, the fluctuation should be discriminated by comparing the standard deviation with the threshold value (for example, 6 mV in the examples shown in FIGS. 4 and 5). Can be done. Even in this case, it is better to execute the voltage detection step while the output power of the fuel cell unit 12 is constant. That is, in the example shown in FIG. 5, it is preferable to perform the operation during a specific period (such as the period indicated by Q in FIG. 5) in which the output power is constant.

In the countermeasure step (# 4), the operation control unit 3 determines in the defect determination step (# 2) that a defect has occurred in the supply of the oxygen gas for power generation to the cathode 24, and the defect cause estimation step. In (# 3), when it is estimated that a problem caused by the generated oxygen blower 13 has occurred, a low output operation for bringing the output power of the fuel cell unit 12 into a predetermined low output state is performed for a predetermined period.

For example, the output of the fuel cell unit 12 is set to a low output (for example, 250 W) lower than the maximum output (700 W), and the low output operation is performed. Then, the low output operation is continued until a state in which water is considered to have been discharged from the generated oxygen blower 13, that is, no defect is determined in the defect determination step. In the low output operation, the output of the generated oxygen blower 13 can be suppressed to a low level, and the generated oxygen blower 13 is less likely to be damaged.

Further, when the operation is stopped and the fuel gas is supplied through the reforming unit 4, the generated oxygen blower 13 is operated in a low output state. That is, power is generated at the timing when the pressure from the cathode 24 toward the generated oxygen blower 13 is applied while the fuel cell unit 12 is not generating power, for example, when the exhaust gas treatment of the combustion unit 5 at the start of operation of the fuel cell unit 12 is performed. The oxygen blower 13 is operated in a low output state.

By operating in such a low output state, water can be discharged from the generated oxygen blower 13 while avoiding the early failure of the generated oxygen blower 13.

[Another Embodiment]
(1) In the above embodiment, low output operation is performed as a countermeasure step, but instead of this configuration, the operation of the fuel cell unit may be stopped.

(2) In the above embodiment, in the defect determination step, the standard deviation of the output voltage is obtained, and the standard deviation is compared with the threshold value to determine the defect. However, the amount of fluctuation of the output voltage per unit time The defect may be determined based on the above, or the defect may be determined based on the rate of change of the output voltage.

The configuration disclosed in the above embodiment (including another embodiment, the same shall apply hereinafter) can be applied in combination with the configuration disclosed in other embodiments as long as there is no contradiction. The embodiments disclosed in the present specification are examples, and the embodiments of the present invention are not limited thereto, and can be appropriately modified without departing from the object of the present invention.

The present invention can be applied to fuel cell systems.

3 Operation control unit 4 Remodeling unit 5 Combustion unit 12 Fuel cell unit 13 Blower for power generation oxygen 18 Voltage detection unit 19 Power detection unit 23 Anode 24 Cathode

Claims (7)

A reformer that reforms raw fuel to generate fuel gas,
A fuel cell unit having an anode to which the fuel gas generated in the reforming unit is supplied and a cathode to which oxygen gas for power generation is supplied.
A combustion unit that burns fuel components in the exhaust fuel gas discharged from the anode after being used in a power generation reaction in the fuel cell unit.
A blower for power generation oxygen for supplying the oxygen gas for power generation to the cathode,
A fuel cell system equipped with an operation control unit.
A voltage detection unit that detects the output voltage of the fuel cell unit,
A power detection unit that detects the output power of the fuel cell unit is provided.
The operation control unit
The output of the power generation oxygen blower is adjusted so that the flow rate of the power generation oxygen gas per unit time becomes a target flow rate commensurate with the output power of the fuel cell unit.
Supply of the oxygen gas for power generation to the cathode when the output voltage detected by the voltage detection unit shows a fluctuation of a predetermined allowable range or more while the output power detected by the power detection unit is constant. Judging that there is a problem with
The operation control unit
It is determined that a problem has occurred in the supply of the power generation oxygen gas to the cathode, and the current output of the power generation oxygen blower determines the flow rate of the power generation oxygen gas per unit time of the fuel cell. When the target flow rate is greater than the set value when the target flow rate is set to match the output power of the unit, there is a problem with the supply of the oxygen gas for power generation due to an increase in the flow path resistance of the oxygen gas for power generation. Judge that it is occurring and
When it is determined that a problem has occurred in the supply of the oxygen gas for power generation to the cathode, and the current output of the blower for power generation oxygen is not larger than the set value by the set value or more, the power generation is performed. the fuel cell system wherein you determine that a malfunction of the supply of the power generation oxygen gas is generated caused by oxygen for blower. When the operation control unit determines that a problem has occurred in the supply of the oxygen gas for power generation to the cathode, the operation control unit performs a low output operation for a predetermined period of time to bring the output power of the fuel cell unit into a predetermined low output state. The fuel cell system according to claim 1. The operation control unit
When it is determined that a problem has occurred in the supply of the oxygen gas for power generation to the cathode, and the current output of the blower for power generation oxygen is not larger than the set value by the set value or more, the power generation is performed. The fuel cell system according to claim 1 or 2 , wherein it is determined that a defect in the supply of oxygen gas for power generation has occurred due to the intrusion of water into the oxygen blower. A fuel cell unit having a reforming unit that reforms raw fuel to generate fuel gas, an anode to which the fuel gas generated in the reforming unit is supplied, and a cathode to which oxygen gas for power generation is supplied. A combustion unit that burns a fuel component in the discharged fuel gas discharged from the anode after being used in a power generation reaction in the fuel cell unit, and generated oxygen for supplying the power generation oxygen gas to the cathode. A method of operating a fuel cell system equipped with a blower for
The fuel cell system includes a voltage detection unit that detects the output voltage of the fuel cell unit and a power detection unit that detects the output power of the fuel cell unit.
The output of the generated oxygen blower is adjusted so that the flow rate of the power generation oxygen gas per unit time becomes a target flow rate commensurate with the output power of the fuel cell unit, and the output power detected by the power detection unit. The voltage detection step of detecting the output voltage by the voltage detection unit while the voltage is constant,
When the output voltage detected in the voltage detection step shows a fluctuation of more than a predetermined allowable range, a defect determination step of determining that a defect has occurred in the supply of the oxygen gas for power generation to the cathode, and a defect determination step .
In the defect determination step, when it is determined that a defect has occurred in the supply of the power generation oxygen gas to the cathode, the current output of the power generation oxygen blower is per unit time of the power generation oxygen gas. If the flow rate is larger than the set value from the reference output when the target flow rate is set to match the output power of the fuel cell unit, the power generation oxygen gas is caused by an increase in the flow path resistance of the power generation oxygen gas. If the current output of the power generation oxygen blower is not larger than the set value by the set value or more, it is estimated that the power generation oxygen blower is the cause of the power generation oxygen. A method of operating a fuel cell system , which comprises a defect cause estimation process for presuming that a gas supply defect has occurred. In the defect cause estimation step, when it is estimated that a defect in the supply of the oxygen gas for power generation caused by the blower for power generation has occurred, the output power of the fuel cell unit is brought into a predetermined low output state. The method of operating a fuel cell system according to claim 4 , further comprising a countermeasure step of performing low-power operation for a predetermined period. In the defect cause estimation step, when it is estimated that a defect in the supply of the oxygen gas for power generation caused by the blower for power generation has occurred, the fuel cell unit is not generated at a predetermined timing. The method for operating a fuel cell system according to claim 4 or 5 , wherein the power generation oxygen blower is operated to flow the power generation oxygen gas from the power generation oxygen blower toward the cathode. The method for operating a fuel cell system according to claim 6 , wherein the predetermined timing is a timing at which a pressure from the cathode toward the generated oxygen blower is applied while the fuel cell unit is not generated.

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