JP2006216383A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of quickly detecting leak of fuel gas or oxidant gas with accuracy in a simple structure, even during an operation of a fuel cell. <P>SOLUTION: The fuel cell system is provided with a fuel cell 1 equipped with a fuel gas flow channel 1D and an oxidant gas flow channel 1E, a fuel gas supply device 2, an oxidant gas supply device 3, a fuel gas supply flow channel 6, an oxidant gas supply flow channel 7, a fuel gas exhaust flow channel 8, an oxidant gas exhaust flow channel 9, an exhaust-side carbon dioxide density detecting device 4, and a control device 10. The control device 10 obtains a detected value of the exhaust-side carbon dioxide density detecting device 4, and detects leakage if any of the fuel gas based on the detected value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system used for a portable power source, a power source for an electric vehicle, a cogeneration system, and the like. In particular, the present invention relates to a fuel cell system using a fuel cell having a polymer electrolyte membrane.

  The fuel cell generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air. One type of fuel cell is a polymer electrolyte fuel cell, the structure of which is as follows.

  A catalyst layer mainly composed of carbon powder carrying a platinum-based metal catalyst is formed on both surfaces of a polymer electrolyte membrane that selectively transports hydrogen ions. On the outer surface of the catalyst layer, a gas diffusion layer is formed of, for example, carbon paper or carbon cloth, which has both fuel gas permeability and electronic conductivity. The gas diffusion layer and the catalyst layer are combined to form a membrane electrode assembly.

  This membrane electrode assembly is sandwiched between a pair of separators made of a conductive material such as glassy carbon or metal for current collection. On the inner surface of the separator, a flow channel configured to expose a fuel gas or an oxidant gas to the membrane electrode assembly is formed. Therefore, the channel groove is partitioned by the membrane electrode assembly, and a fuel gas channel and an oxidant gas channel are formed on both surfaces of the membrane electrode assembly, respectively. In general, a gas seal material or a gasket for preventing the supplied fuel gas or oxidant gas from leaking from the channel groove is disposed between the membrane electrode assembly and the separator.

  A membrane electrode assembly sandwiched between such separators is a basic unit, and this is laminated in a number corresponding to the design output of electricity or heat of the polymer electrolyte fuel cell to form a polymer electrolyte fuel cell. Yes.

  In the fuel cell system, a fuel gas supply device and an oxidant gas supply device for supplying a fuel gas and an oxidant gas are connected to the polymer electrolyte fuel cell (hereinafter abbreviated as PEFC), and the generated heat is further reduced. An exhaust heat recovery device for recovery and a power conversion device that adjusts so that electricity generated by PEFC can be used are provided as necessary, and a control device that controls these devices is provided.

  The fuel gas supply device is generally a hydrogen gas supply device or a hydrogen generation device that generates a hydrogen-rich reformed gas by reforming a hydrocarbon-based fuel such as natural gas, propane gas, or gasoline. And supply hydrogen gas or reformed gas to PEFC as fuel gas. The oxidant gas supply device includes, for example, a blower such as a blower or a fan, and supplies oxygen gas or air as an oxidant gas to the PEFC. Inside the PEFC, a fuel gas or an oxidant gas flows in a channel groove formed by components such as a gasket, a polymer electrolyte membrane, and a separator. However, due to deterioration of these constituent members, for example, leakage of fuel gas and oxidant gas, that is, leakage from one gas to the other gas occurs due to damage to the polymer electrolyte membrane. The mixing of the fuel gas and the oxidant gas causes the polarization resistance of the electrode reaction when the supply of the fuel gas or the oxidant gas to the catalyst layer is insufficient, that is, when the exposure to the membrane electrode assembly is insufficient. Increases, causing a decrease in PEFC output. Therefore, in order to prevent the performance degradation of the fuel cell of PEFC, a fuel cell system or a detection method capable of detecting gas leakage into the fuel gas channel or the oxidant gas channel is required.

  Here, in a general pressure vessel, a leak rate inspection is generally performed in which a pressurized gas is sealed inside the vessel and a time required for the pressure drop or a pressure drop in a predetermined time is detected. It has been broken. However, since the fuel cell system is a system that is operated at any time, it is necessary to detect the leakage of the PEFC fuel gas or oxidant gas so as not to hinder the operation of the PEFC. A detection method in which gas is pressurized and sealed, and the pressure drop is observed is not practically suitable. On the other hand, several fuel cell systems for detecting leakage of fuel gas or oxidant gas in the fuel cell or methods for detecting leakage have already been disclosed, and the main fuel cell system or detection method is as follows.

  For example, the fuel cell system disclosed in Patent Document 1 calculates the amount of fuel gas consumed based on the output current value of the fuel cell, and further calculates the fuel gas pressure in the fuel gas cylinder from this amount. Then, the leakage of the fuel gas is determined by comparing the calculated pressure value with the detected pressure value actually detected by the pressure sensor.

  Further, the fuel cell diagnosis method disclosed in Patent Document 2 supplies a hydrogen-containing gas and an oxygen-containing gas to the fuel electrode and the oxidant electrode of the fuel cell, respectively, and a fuel accompanying a decrease in the supply amount of the oxygen-containing gas. A sudden change in the generated voltage of the battery is detected, and the amount of hydrogen leakage in the fuel cell is calculated from the correspondence between the oxygen-containing gas and the generated voltage.

  Also, in relation to the determination of the deterioration of the fuel cell, the deterioration state of the fuel cell is determined by detecting the state of the fuel cell by various methods, and the result is fed back to the control mechanism of the fuel cell. There has been disclosed a fuel cell system that suppresses the progress, and as a result, achieves higher durability and longer life of the fuel cell and the fuel cell system.

  For example, in Patent Document 3, when impurity ions in water in fuel gas humidified water or the like are analyzed from PEFC, it is determined whether or not the operating state of PEFC is in a performance degradation region, and it is determined that it is in a performance degradation region. Discloses a PEFC operation method in which the PEFC operation state is avoided from the performance degradation region by stopping the PEFC operation or limiting the operation conditions.

In Patent Document 4, a fuel cell is operated in several basic operation patterns, and the life of the fuel cell fuel cell is predicted based on the relationship between the power generation time and the output voltage change rate in the basic operation pattern. Is disclosed.
Japanese Patent Application Laid-Open No. 11-224681 Japanese Patent Laid-Open No. 9-27336 JP 2004-127548 A JP-A-11-97049

  However, in the fuel cell, water vapor contained in the gas supplied to the fuel cell becomes condensed water in the path of the oxidant gas or the fuel gas, and this water stays in the oxidant gas flow path or the fuel gas flow path and becomes a gas. If the distribution of the fuel cell is obstructed, the output of the fuel cell is reduced. Therefore, during the start-up operation, the stop operation, or the operation operation of the fuel cell, a purge process for purging residual gas and moisture in the fuel cell is generally performed. As a method of this purge process, for example, there is a method in which dry fuel gas is supplied into the fuel cell and condensed water is pushed out of the fuel cell. Therefore, in the fuel cell system disclosed in Patent Document 1, when the fuel gas is used for the purge process for purging the residual gas and moisture of the fuel cell, the consumption of the fuel gas accompanying the purge process is included in the leakage amount. As a result, leakage detection of the fuel cell becomes inaccurate.

  Further, in the fuel cell diagnosis method disclosed in Patent Document 2, the generated voltage of the fuel cell is measured while gradually decreasing the supply amount of the oxygen-containing gas to the cathode. Since the change in the generated voltage is small, the detection accuracy is low. In addition, since fluctuations in the electric output of the fuel cell involve various factors such as electrode performance deterioration, the accuracy of the method for estimating the leakage of fuel gas based on the generated voltage is low.

  In PEFC, fluoride ions are generated when the polymer electrolyte membrane is decomposed. Further, fluoride ions have a property of corroding metals. Therefore, in the PEFC operation method disclosed in Patent Document 3, the deterioration of PEFC is determined by detecting ions such as metal ions in water such as generated water and humidified water. However, leakage of PEFC fuel gas or oxidant gas also occurs when the polymer electrolyte membrane is physically damaged. In the case of such breakage of the polymer electrolyte membrane, generation of metal ions or fluoride ions is unlikely to occur. Therefore, a method for judging deterioration of PEFC from detection of metal ions or fluoride ions is based on fuel gas or oxidant. Not suitable for gas leak detection.

  In addition, an electrode catalyst such as platinum of a fuel cell is determined depending on a load variation of the fuel cell, a gas component in the fuel cell, or a partial pressure of the gas component in the fuel cell, and a temperature / humidity condition during stoppage. Affected by performance. That is, since the electrode area of the fuel cell changes depending on the history of the fuel cell, it is difficult to accurately predict the life of the fuel cell only by the operation pattern of the fuel cell. Therefore, there has been a problem that the life prediction of the fuel cell approximated from the basic operation pattern of the fuel cell or a combination of a plurality of basic operation patterns becomes inaccurate.

  Thus, in order to quickly detect the leakage of the fuel gas or the oxidant gas of the fuel cell, the conventional technique is not accurate enough and tends to be inaccurate. In addition, regarding the determination of deterioration of the fuel cell, it takes time and labor to acquire data in the basic operation pattern of the fuel cell, and preparation of a detection device for metal ions or fluoride ions is costly.

  The present invention has been made in order to solve the above-described problems, and a fuel cell capable of quickly and accurately detecting leakage of fuel gas or oxidant gas even during operation of the fuel cell with a simple structure. The purpose is to provide a system.

  As a result of intensive studies to achieve the above object, the present inventors have paid attention to the difference in composition between the fuel gas and the oxidant gas and the difference in supply pressure between the two gases, and the composition in the oxidant gas. We came up with a method to detect leakage of fuel gas or oxidant gas by fluctuation. That is, when the fuel gas or the oxidant gas leaks, the gas leaks from the higher supply pressure side to the lower supply pressure, so that the gas composition on the lower supply pressure side varies. In PEFC, since fuel gas generally has a higher supply pressure than oxidant gas, leakage of fuel gas to oxidant gas can be detected by detecting composition variation of oxidant gas. .

  Here, hydrogen and oxygen are different in the composition of the fuel gas and the oxidant gas. However, the concentration of hydrogen, which is the main component of the fuel gas, varies because the hydrogen concentration fluctuates inside the fuel cell because hydrogen is involved in the cell chemical reaction of the fuel cell. Correlation with agent gas leakage is low. Similarly, since the concentration of oxygen, which is the main component of the oxidant gas, also participates in the cell chemical reaction of the fuel cell, the oxygen concentration fluctuates inside the fuel cell. Correlation with leakage of oxidant gas is low. As for the components contained in both the fuel gas and the oxidant gas, if the concentration difference is small, leakage cannot appear as a significant variation in the concentration difference.

  Here, the fuel gas is generally a hydrogen gas or a reformed gas generated by reforming a hydrocarbon-based gas, and carbon dioxide having a concentration of about 20% to 40% in the reformed gas. It is included. In general, oxygen gas or air is used as the oxidant gas, and the air contains carbon dioxide having a concentration of about 300 ppm to 500 ppm. Accordingly, it has been found that carbon dioxide is contained in at least one of the fuel gas and the oxidant gas, and even if contained in both, the concentration difference between the carbon dioxide concentrations is large. Further, even when hydrogen gas is used as the fuel gas and oxygen gas is used as the oxidant gas, some carbon dioxide may be mixed into one by mixing air or the like. From the above, when a leak of fuel gas or oxidant gas occurs, it is thought that a significant fluctuation occurs in the carbon dioxide concentration of the gas on the lower supply pressure side, and the researcher The inventors have come up with the invention of a fuel cell system that detects leakage of fuel gas or oxidant gas based on concentration fluctuations. When monitoring the change in the concentration of carbon dioxide, it is necessary to consider the solubility of carbon dioxide in water (condensed water generated when humidifying at least one of battery reaction product water, oxidant gas, and fuel gas). In some cases, the amount can be determined by preliminary experiments.

  That is, in order to solve the above problems, a fuel cell system according to the present invention includes a fuel gas channel and an oxidant gas flow formed so as to be in contact with anodes and cathodes formed on both sides of a polymer electrolyte membrane, respectively. A fuel cell, a fuel gas supply device that supplies fuel gas to the fuel gas flow channel, an oxidant gas supply device that supplies oxidant gas to the oxidant gas flow channel, and the fuel gas flow A fuel gas supply channel that connects the fuel gas supply device to the channel, an oxidant gas supply channel that connects the oxidant gas supply device to the oxidant gas channel, and an exhaust gas from the fuel gas channel A fuel gas discharge channel through which excess fuel gas flows, an oxidant gas discharge channel through which excess oxidant gas discharged from the oxidant gas channel flows, the oxidant gas discharge channel, and the fuel Gas discharge flow path An exhaust-side carbon dioxide concentration detection device disposed in any one of the control devices, and the control device acquires a detection value of the exhaust-side carbon dioxide concentration detection device, Based on this, leakage of the fuel gas is detected. If comprised in this way, since the fuel cell system can detect the leakage of fuel gas or oxidant gas by the change of the carbon dioxide concentration in an oxidant gas discharge flow path or a fuel gas discharge flow path, it is simple. Due to the structure and operation, leakage of fuel gas or oxidant gas can be detected quickly and accurately even during the operation of the fuel cell.

  Further, from the viewpoint of obtaining the above-described effect of the present invention more reliably, the supply pressure of the oxidant gas supply device is lower than the supply pressure of the fuel gas supply device, and the exhaust-side carbon dioxide concentration detection device is the oxidant. The control device is disposed in the gas discharge flow path, acquires the detection value of the discharge-side carbon dioxide concentration detection device, and is supplied with the oxidant gas flow path to the carbon dioxide concentration of the oxidant gas. And a leakage value composed of numerical information indicating a difference in carbon dioxide concentration from the carbon dioxide concentration of the oxidant gas discharged from the oxidant gas flow path. Alternatively, the supply pressure of the fuel gas supply device is lower than the supply pressure of the oxidant gas supply device, the exhaust-side carbon dioxide concentration detection device is disposed in the fuel gas discharge flow path, and the control device is The detection value of the exhaust-side carbon dioxide concentration detection device is acquired, and the carbon dioxide concentration of the fuel gas supplied to the fuel gas flow channel and the carbon dioxide concentration of the fuel gas discharged from the fuel gas flow channel It is preferable to calculate a leakage value composed of numerical information indicating a difference in carbon dioxide concentration between the first and second carbon dioxide (claim 13).

  A supply-side carbon dioxide concentration detection device disposed in the oxidant gas supply flow path; and the control device detects the discharge-side carbon dioxide concentration detection device and the supply-side carbon dioxide concentration detection device. The difference between the carbon dioxide concentration of the oxidant gas supplied to the oxidant gas flow channel and the carbon dioxide concentration of the oxidant gas discharged from the oxidant gas flow channel is obtained. It is preferable to calculate a leakage value consisting of numerical information indicating the above (claim 3). Alternatively, a supply-side carbon dioxide concentration detection device disposed in the fuel gas supply flow path is provided, and the control device detects values of the discharge-side carbon dioxide concentration detection device and the supply-side carbon dioxide concentration detection device. From the numerical information indicating the difference in carbon dioxide concentration between the carbon dioxide concentration of the fuel gas supplied to the fuel gas flow channel and the carbon dioxide concentration of the fuel gas discharged from the fuel gas flow channel. It is good to calculate the leakage value which becomes (Claim 14). With this configuration, the carbon dioxide concentration of the oxidant gas supplied to the oxidant gas flow channel or the carbon dioxide concentration of the fuel gas supplied to the fuel gas flow channel, that is, the reference carbon dioxide concentration can be directly detected. Therefore, the detection accuracy can be improved.

  The said control apparatus is good to provide the output part which outputs the said leakage value outside (Claim 4). If comprised in this way, since the user of a fuel cell system can acquire the leak of fuel gas or oxidant gas quickly and accurately, damage and a performance fall of a fuel cell system can be prevented beforehand.

  The control device includes a storage unit in which an evaluation leakage value for evaluating the leakage value is stored in advance, and the control device compares the leakage value with the evaluation leakage value to thereby calculate the fuel cell. It is good to evaluate the deterioration state of (claim 5). If comprised in this way, since the fuel cell system can use the leak value for evaluation as a judgment standard, it can evaluate the deterioration state of a fuel cell appropriately.

  The said control apparatus is good to provide the output part which outputs the said evaluated leakage value or evaluation result outside (Claim 6). If comprised in this way, since the user of a fuel cell system can acquire evaluation of the deterioration state of a fuel cell, the countermeasure judgment of the damage of a fuel cell system and a performance fall can be performed more easily.

  The control device may adjust the operating condition of the fuel cell based on the evaluated leakage value. With this configuration, the fuel cell system can extend the life of the fuel cell substantially automatically using the evaluation leakage value as a criterion.

  The control device calculates the leakage value at every predetermined detection time interval, and the storage unit stores the leakage value corresponding to the operation time of the fuel cell. The transition line of the leakage value with respect to the operation time may be obtained by a statistical approximation method, and the progress of deterioration of the fuel cell may be predicted based on a comparison between the transition line and the leakage value for evaluation. . With this configuration, the fuel cell system detects the leakage of the fuel gas or the oxidant gas quickly and accurately even during the operation of the fuel cell with a simple structure and operation, and predicts the life of the fuel cell system. It can be carried out.

  The said control apparatus is good to change the said detection time interval according to the locus | trajectory of the said transition line (Claim 9). With this configuration, unnecessary detection leakage value acquisition operation can be omitted without affecting detection leak value transition line acquisition, so that the operation of the fuel cell system can be rationalized.

  The evaluation leakage value stored in the storage unit of the control device includes a limit leakage value at the end of the service life of the fuel cell, and the control device extrapolates the transition line to obtain the limit leakage value. The predicted remaining operation time of the fuel cell until it reaches may be acquired (claim 10). If comprised in this way, the fuel cell system can perform the lifetime prediction of a fuel cell system based on specific numerical information.

  The control device may include an output unit that outputs the predicted remaining operation time to the outside (claim 11). With this configuration, the user of the fuel cell system can obtain an evaluation of the remaining life of the fuel cell as specific numerical information. Therefore, preparations for measures for damage and performance degradation of the fuel cell system, It is possible to select an appropriate operation mode or to create a fuel cell operation plan.

  The control device may adjust operating conditions of the fuel cell based on the predicted remaining operating time. With this configuration, the fuel cell system automatically extends the life of the fuel cell, so that the operation management burden on the user of the fuel cell system can be reduced.

  As described above, the fuel cell system according to the present invention has an effect that the leakage of the fuel gas or the oxidant gas can be detected quickly and accurately even during the operation of the fuel cell with a simple structure.

  Hereinafter, preferred embodiments of a fuel cell system and an operation method of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram showing the basic configuration of the first embodiment of the fuel cell system of the present invention.

  First, the configuration of the fuel cell system 100 of the present embodiment will be described.

  The fuel cell system 100 includes a fuel gas supply device 2 and an oxidant gas supply device 3. A fuel gas supply channel 6 is connected to the fuel gas supply device 2, and an oxidant gas supply device 3 is oxidized. The agent gas supply channel 7 is connected. Here, the fuel gas supply device 2 includes a hydrogen generator that reforms a hydrocarbon-based fuel such as natural gas, propane gas, or gasoline to generate a hydrogen-rich reformed gas. Is supplied to PEFC1 as fuel gas. When producing a fuel gas by reforming a hydrocarbon gas such as natural gas, carbon dioxide is by-produced, so the carbon dioxide concentration is determined based on the composition of the hydrocarbon gas. Concentration becomes constant. The supply pressure of the fuel gas supply device 2 during the PEFC1 operation is 6.5 to 8.5 kPa, and the supply pressure can be adjusted by the gas flow rate. The oxidant gas supply device 3 includes a blower such as a blower or a fan, and supplies oxygen gas or air as an oxidant gas to the PEFC 1. The supply pressure of the oxidant gas supply device 3 during the PEFC1 operation is 5.0 to 7.0 kPa, and the supply pressure can be adjusted by the gas flow rate. Accordingly, the fuel gas supply pressure is configured to be higher than the oxidant gas supply pressure.

  The fuel gas supply channel 6 is connected to a polymer electrolyte fuel cell (hereinafter referred to as PEFC) 1, and the fuel gas is supplied from the fuel gas supply device 2 to the PEFC 1. The oxidant gas supply channel 7 is connected to the PEFC 1, and the oxidant gas is supplied from the oxidant gas supply device 3 to the PEFC 1.

  In this PEFC 1, a membrane electrode assembly 1A is sandwiched between a pair of separators, more precisely an anode separator 1B and a cathode separator 1C, and is formed by a groove formed on the surface of the membrane electrode assembly 1A and the anode separator 1B. A fuel gas flow path 1D is formed by partitioning. Similarly, an oxidant gas flow path 1E is formed by being partitioned by the membrane electrode assembly 1A and a groove formed on the surface of the cathode separator 1C. As a result, in the PEFC 1, the fuel gas channel 1D and the oxidant gas channel 1E are partitioned by the membrane electrode assembly 1A having a polymer electrolyte membrane.

  A fuel gas supply channel 6 is connected to one end of the fuel gas channel 1D so that the fuel gas is supplied to the fuel gas channel 1D. Further, an oxidant gas supply channel 7 is connected to one end of the oxidant gas channel 1E, and the oxidant gas is supplied to the oxidant gas channel 1E. The fuel gas and the oxidant gas supplied to the fuel gas channel 1D and the oxidant gas channel 1E chemically react at the anode and the cathode to generate electric power and heat.

  A fuel gas discharge channel 8 is connected to the other end of the fuel gas channel 1D, and excess fuel gas that has not chemically reacted at the anode flows from the other end of the fuel gas channel 1D to the fuel gas discharge channel 8. Discharged. Further, an oxidant gas discharge channel 9 is connected to the other end of the oxidant gas channel 1E, and excess oxidant gas that has not chemically reacted at the cathode is oxidized from the other end of the oxidant gas channel 1E. It is discharged to the agent gas discharge channel 9.

The oxidant gas discharge channel 9 is provided with a discharge side carbon dioxide concentration detection device (hereinafter referred to as a discharge side CO ₂ detection device) 4, and the carbon dioxide concentration of the fluid flowing through the oxidant gas discharge channel 9 Is detected. As the discharge-side CO ₂ detection device 4, for example, a CO ₂ detection device that utilizes absorption of infrared rays in a specific wavelength band by carbon dioxide can be used.

In addition, the fuel cell system 100 includes a control device 10. The control device 10 includes a control unit 10A configured by a CPU, a microcomputer, a storage unit 10B configured by a memory, an input unit 10C configured by a keyboard, and an output configured by a monitor device, a printer, and the like. Part 10D. Then, the control device 10 controls the operation of the fuel cell system 100. In particular, the control device 10 acquires a detection value (for example, a current signal value, a voltage signal value, etc.) of the discharge-side CO ₂ detection device 4, and is discharged from the oxidant gas flow path 1E from the detection value in the control unit 10A. The carbon dioxide concentration R ₁ of the oxidant gas is calculated, and the difference is compared with the carbon dioxide concentration of the oxidant gas supplied to the oxidant gas flow path 1E, that is, the reference carbon dioxide concentration R _0. The detection leakage value Q = | R ₁ −R ₀ | consisting of numerical information indicating the above is calculated. The reference carbon dioxide concentration R ₀ is obtained in advance from the composition of the oxidant gas, input as the reference carbon dioxide concentration R ₀ from the input unit 10C, and stored in 10A. Alternatively, when the oxidant gas is air, the carbon dioxide concentration in the atmosphere is measured in advance, and the measured concentration is input as the reference carbon dioxide concentration R ₀ from the input unit 10C and stored in the control unit 10A. You may keep it. When air is used as the oxidant gas, the carbon dioxide concentration of air is generally about 300 ppm to 500 ppm. In determining the reference carbon dioxide concentration R ₀ , the solubility of carbon dioxide in water (condensed water generated when at least one of battery reaction product water, oxidant gas, and fuel gas is humidified) is taken into consideration. If necessary, the amount may be grasped in advance by a preliminary experiment or the like and reflected in R ₀ .

The storage unit 10B stores an evaluation leakage value for evaluating leakage of fuel gas or oxidant gas. For example, the initial leakage value Q _{100 at} the beginning of service of the PEFC ₁ , the time when the functional failure of the PEFC ₁ occurs, that is, the limit leakage value Q ₀ of the PEFC 1 at the end of its service life, and the intermediate between the initial leakage value Q ₁₀₀ and the limiting leakage value Q ₀ Intermediate leakage values Q ₈₀ , Q ₆₀ , Q ₄₀ , and Q _{20 that} are values are previously input from the input unit 10D and stored. These evaluation leakage values Q _{100 to} Q ₀ can be obtained in advance by an endurance test using the same model as the PEFC 1.

  Here, the control device means not only a single control device but also a control device group in which a plurality of control devices cooperate to execute control. Therefore, the control device 10 does not need to be composed of a single control device, and a plurality of control devices are distributed and configured to control the operation of the fuel cell system 100 in cooperation with each other. May be. For example, the output unit 10D can be configured to be transmitted by the information terminal and displayed on the mobile device.

  Next, the leakage value detection operation of the fuel cell system 100, which is a feature of the present invention, will be described. This leakage value detection operation is performed by being controlled by the control device 10.

First, the control device 10 acquires the detection value of the discharge side CO ₂ detection device 4 in the operation operation state of the PEFC 1, that is, in the flow state of the fuel gas and the oxidant gas.

The control device 10 acquires the detection leakage value Q based on the detection value of the discharge side CO ₂ detection device 4.

  Here, when there is no leakage of the fuel gas or the oxidant gas, the detected leakage value Q is almost zero.

  However, when there is leakage of fuel gas or oxidant gas, for example, when the polymer electrolyte membrane of the membrane electrode assembly 1A is damaged, the supply pressure of the fuel gas is higher than the supply pressure of the oxidant gas. Therefore, the fuel gas leaks from the fuel gas channel 1D to the oxidant gas channel 1E side. As the damage to the polymer electrolyte membrane increases, this leakage also increases and the detection leakage value Q increases. When the reformed gas generated by the reforming of hydrocarbon gas is used as the fuel gas, the carbon dioxide concentration in the fuel gas is about 20% to 30%. The increase of carbon dioxide in the oxidant gas flow path 1E appears remarkably.

  As a result, the fuel cell system 100 can detect the leakage of the fuel gas or the oxidant gas based on the change in the carbon dioxide concentration in the oxidant gas discharge passage 9. Even during operation, leakage of fuel gas or oxidant gas can be detected quickly and accurately.

  Further, the control device 10 displays the detected leakage value Q on the output unit 10D. Thereby, since the user of the fuel cell system 100 can quickly and accurately acquire the leakage of the fuel gas or the oxidant gas, it is possible to prevent the fuel cell system 100 from being damaged and the performance from being deteriorated in advance.

Further, the control unit 10 causes the control unit 10A, and comparing the detected leakage values evaluation leaking values stored in Q the storage unit 10B Q ₁₀₀ to Q _0, and displays the evaluated state of deterioration of PEFC1. Specifically, the evaluation leakage values Q _{100 to} Q ₀ with the closest detected leakage value Q and the difference amounts between the evaluation leakage values Q _{100 to} Q ₀ are acquired and displayed on the output unit 10D. Furthermore, according to the difference amount, the control unit 10A may rank about several levels, and the rank may be displayed in color or level in the output unit 10D. By performing the evaluation in this way, the fuel cell system 100 can use the evaluation leakage values Q _{100 to} Q ₀ as the determination criteria, and thus can appropriately evaluate the deterioration state of the fuel cell. In addition, since the evaluation result is displayed, the user of the fuel cell system 100 can obtain an evaluation of the deterioration state of the PEFC 1, so that measures against damage and performance degradation of the fuel cell system 100 can be performed more easily. be able to.

Further, the control unit 10, in accordance with the comparison evaluation between the detected leakage values Q and evaluation leakage value Q ₁₀₀ to Q _0, adjusting the operating conditions of the fuel cell system 100. For example, every time the detected leakage value Q reaches the intermediate leakage values Q ₈₀ , Q ₆₀ , Q ₄₀ , Q ₂₀ starting from the initial leakage value Q ₁₀₀ , the control device 10 is in the operation of the fuel cell system 100. The oxidant gas supply device 3 and the fuel gas supply device 2 are controlled so as to operate with the pressure loss suppressed by lowering the upper limit of the pressure loss of the oxidant gas and fuel gas supply pressure between the inlets and outlets of the PEFC 1 To do. As a result, the fuel cell system 100 can extend the life of the PEFC 1 almost automatically using the evaluation leakage values Q _{100 to} Q ₀ as threshold values, that is, judgment criteria.

  Next, the life prediction operation of the fuel cell system 100 using the detected leakage value Q will be described.

  First, the control unit 10A of the control device 10 controls the fuel cell system 100 to perform a leakage value detection operation at every predetermined detection time interval Δt using a built-in clock. The predetermined detection time interval Δt is a time interval based on the operation time of the PEFC 1. And the control apparatus 10 memorize | stores and accumulate | stores the detection leak value Q in the memory | storage part 10B so as to correspond with the driving | running time T of PEFC1 until the time of performing leak value detection operation.

  Then, the control unit 10A acquires a transition line of the detected leakage value Q with respect to the operation time T based on the accumulated detected leakage value Q by a statistical approximation method. For example, the transition line can be acquired by a statistical process such as a least square method. Then, the control unit 10A predicts future changes in the detected leakage value Q. For example, the transition line can be extrapolated and predicted.

  Here, FIG. 2A to FIG. 2C are graphs conceptually showing transition lines of the detected leakage value with respect to the PEFC operation time, and FIG. 2A is a ratio at which the detected leakage value is constant. FIG. 2B is a graph when the detected leakage value changes so as to be stabilized gradually, and FIG. 2C is a graph when the change of the detected leakage value gradually increases. .

As shown in FIG. 2 (a) to FIG. 2 (c), the control section 10A, by comparing the the estimated line and limit leakage value Q _0, the prediction residual to PEFC1 reaches the limit leakage value Q ₀ The operation time ΔT ₀ is calculated.

As a result, the fuel cell system 100 can detect the leakage of the fuel gas or the oxidant gas based on the change in the carbon dioxide concentration R _{1 in} the oxidant gas discharge channel 9. Even during the operation, the leakage of fuel gas or oxidant gas can be detected quickly and accurately, and the life of the fuel cell system 100 can be predicted.

In addition, the control device 10 displays the predicted remaining operation time ΔT ₀ on the output unit 10D. Accordingly, the user of the fuel cell system 100 can obtain the evaluation of the remaining life of the PEFC 1 as specific numerical information, so that preparations for measures against damage and performance degradation of the fuel cell system 100 and an appropriate operation mode of the PEFC 1 can be obtained. Or the operation plan of PEFC1 can be made.

Further, the control unit 10A of the control device 10 adjusts the operation condition of the PEFC ₁ based on the predicted remaining operation time ΔT ₀ . Specifically, the life extension operation mode is selected, and the output power and the like of the oxidant gas supply device 3, the fuel gas supply device 2, and the PEFC 1 are controlled. For example, in the life extension operation mode, the pressure loss of the oxidant gas and the pressure loss of the fuel gas between the inlets and outlets of the PEFC 1 are made uniform, or the supply pressure of the oxidant gas and the fuel gas is suppressed to reduce the pressure between the inlets and outlets of the PEFC 1. The control unit 10A controls the oxidant gas supply device 3 and the fuel gas supply device 2 so as to suppress these pressure losses. As a result, the fuel cell system 100 extends the life of the PEFC 1 almost automatically, so that the operation management burden on the user of the fuel cell system 100 can be reduced.

  Note that the control unit 10A of the control device 10 changes the detection time interval Δt according to the locus of the transition line of the detected leakage value Q with respect to the operation time T. For example, as shown in FIG. 2A, when the detected leakage value Q changes at a constant pace, Δt is kept constant. However, as shown in FIG. 2B, when the detected leakage value Q changes so as to be gradually stabilized, Δt is changed so as to gradually increase. Further, as shown in FIG. 2C, when the change in the detection leakage value Q gradually increases, Δt is changed so as to gradually decrease. As a result, an unnecessary leakage value detection operation can be omitted without affecting the acquisition of the transition line of the detection leakage value Q, so that the operation of the fuel cell system 100 can be rationalized.

(Second Embodiment)
FIG. 3 is a schematic diagram showing the basic configuration of the second embodiment of the fuel cell system of the present invention. In FIG. 3, the same or corresponding parts as in FIG.

The configuration of the fuel cell system 101 of the present embodiment is the same as that of the fuel cell system 101 except that a supply-side carbon dioxide concentration detection device (hereinafter referred to as supply-side CO ₂ detection device) 5 is disposed in the oxidant gas supply flow path 7. The configuration is the same as that of the fuel cell system 100 of one embodiment. As a result, the reference carbon dioxide concentration R ₀ is detected by the supply-side CO ₂ detection device 5. That is, the control device 11 acquires the detection values of the discharge-side CO ₂ detection device 4 and the supply-side CO ₂ detection device 5, and the oxidant gas discharged from the reference carbon dioxide concentration R ₀ and the oxidant gas flow path 1E. The detection leakage value Q = | R ₁ −R ₀ | composed of numerical information indicating the difference in carbon dioxide concentration from the carbon dioxide concentration R ₁ is calculated. Based on the detected leakage value Q, the control device 11 controls the fuel cell system 101 to perform the leakage value detection operation and the life prediction operation in the same manner as in the first embodiment.

As a result, the fuel cell system 101 can directly detect the reference carbon dioxide concentration R ₀ , so that the detection accuracy can be improved.

The supply-side CO ₂ detection device 5 is the same type of detection device as the discharge-side CO ₂ detection device 4. Thereby, the comparison and the difference calculation of the detection values of the discharge side CO ₂ detection device 4 and the supply side CO ₂ detection device 5 can be facilitated.

(Third embodiment)
FIG. 4 is a schematic diagram showing the basic configuration of the third embodiment of the fuel cell system of the present invention. 4, parts that are the same as or correspond to those in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted.

The configuration of the fuel cell system 102 of the present embodiment is such that the supply pressure of the oxidant gas supply device 3 is set to be higher than the supply pressure of the fuel gas supply device 2 and the exhaust side CO ₂ The configuration is the same as that of the fuel cell system 100 of the first embodiment except that the detection device 4 is provided. That is, since the concentration of carbon dioxide in the fuel gas varies due to the oxidant gas leaking to the fuel gas flow path 1D side, the first variation is detected by detecting the concentration variation by the exhaust-side CO ₂ detector 4. The same effect as the embodiment can be obtained.

(Fourth embodiment)
FIG. 5 is a schematic diagram showing the basic configuration of the fourth embodiment of the fuel cell system of the present invention. In FIG. 5, the same or corresponding parts as in FIG.

The configuration of the fuel cell system 103 of the present embodiment is such that the supply pressure of the oxidant gas supply device 3 is set to be higher than the supply pressure of the fuel gas supply device 2, and the discharge side CO _{2 is} detected in the fuel gas discharge flow path 7. The configuration of the fuel cell system 101 of the second embodiment is the same as the configuration of the fuel cell system 101 of the second embodiment except that the device 4 is provided and the supply side CO ₂ detection device 5 is provided in the fuel gas supply flow path 6. . That is, since the concentration of carbon dioxide in the fuel gas varies due to the oxidant gas leaking to the fuel gas flow path 1D side, this variation in concentration is detected by the exhaust side CO ₂ detector 4 and the supply side CO ₂ detector 5. By detecting by this, the same effect as in the second embodiment can be obtained.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments. For example, oxygen gas may be used as the oxidant gas. Further, hydrogen gas may be used as the fuel gas. In this case, in the first embodiment and the second embodiment, the carbon dioxide concentration R ₁ detected by the exhaust side CO ₂ detection device 4 decreases in accordance with the leakage. In the third embodiment and the fourth embodiment, the carbon dioxide concentration R ₁ detected by the discharge-side CO ₂ detection device 4 is increased and detected in accordance with the leakage. Furthermore, when oxygen gas is used as the oxidant gas and hydrogen gas is used as the fuel gas, some carbon dioxide may be mixed into one of the gases, for example, by mixing air.

  INDUSTRIAL APPLICABILITY The present invention is useful as a fuel cell system that can quickly and accurately detect leakage of fuel gas or oxidant gas even during operation of the fuel cell with a simple structure.

It is a schematic diagram which shows the basic composition of 1st Embodiment of the fuel cell system of this invention. 2 (a) to 2 (c) are graphs conceptually showing transition lines of detected leakage values with respect to PEFC operation time, and FIG. 2 (a) shows a case where the detected leakage values change at a constant pace. 2B, FIG. 2B is a graph when the detected leakage value changes so as to be gradually stabilized, and FIG. 2C is a graph when the change of the detected leakage value gradually increases. It is a schematic diagram which shows the basic composition of 2nd Embodiment of the fuel cell system of this invention. It is a schematic diagram which shows the basic composition of 3rd Embodiment of the fuel cell system of this invention. It is a schematic diagram which shows the basic composition of 4th Embodiment of the fuel cell system of this invention.

Explanation of symbols

1 Polymer electrolyte fuel cell (PEFC)
DESCRIPTION OF SYMBOLS 1A Membrane electrode assembly 1B Anode separator 1C Cathode separator 1D Fuel gas flow path 1E Oxidant gas flow path 2 Fuel gas supply device 3 Oxidant gas supply device 4 Emission side CO ₂ detection device 5 Supply side CO ₂ detection device 6 Fuel gas Supply channel 7 Oxidant gas supply channel 8 Fuel gas discharge channel 9 Oxidant gas discharge channel 10, 11 Control device 10A Control unit 10B Storage unit 10C Input unit 10D Output unit 100, 101, 102, 103 Fuel cell system T Operation time Q Detection leak value Δt Detection time interval ΔT ₀ Expected remaining operation time Q ₀ Limit leak value Q ₁₀₀ Initial leak value

Claims (14)

A fuel cell having a fuel gas channel and an oxidant gas channel formed so as to be in contact with an anode and a cathode formed on both sides of the polymer electrolyte membrane,
A fuel gas supply device for supplying fuel gas to the fuel gas flow path;
An oxidant gas supply device for supplying an oxidant gas to the oxidant gas flow path;
A fuel gas supply channel connecting the fuel gas supply device to the fuel gas channel;
An oxidant gas supply channel connecting the oxidant gas supply device to the oxidant gas channel;
A fuel gas discharge channel through which excess fuel gas discharged from the fuel gas channel flows;
An oxidant gas discharge channel through which excess oxidant gas discharged from the oxidant gas channel flows;
An exhaust-side carbon dioxide concentration detecting device disposed in any of the oxidant gas discharge channel and the fuel gas discharge channel;
A control device,
The said control apparatus is a fuel cell system which acquires the detection value of the said discharge side carbon dioxide concentration detection apparatus, and detects the leakage of the said fuel gas based on this detection value. The supply pressure of the oxidant gas supply device is lower than the supply pressure of the fuel gas supply device,
The discharge-side carbon dioxide concentration detection device is disposed in the oxidant gas discharge flow path;
The control device acquires a detection value of the discharge-side carbon dioxide concentration detection device and discharges the carbon dioxide concentration of the oxidant gas supplied to the oxidant gas flow channel and the oxidant gas flow channel. 2. The fuel cell system according to claim 1, wherein a leakage value including numerical information indicating a difference in carbon dioxide concentration from a carbon dioxide concentration of the oxidant gas is calculated. A supply-side carbon dioxide concentration detection device disposed in the oxidant gas supply flow path;
The control device acquires detection values of the discharge-side carbon dioxide concentration detection device and the supply-side carbon dioxide concentration detection device, and the carbon dioxide concentration of the oxidant gas supplied to the oxidant gas flow path and the The fuel cell system according to claim 2, wherein a leakage value comprising numerical information indicating a difference in carbon dioxide concentration from a carbon dioxide concentration of the oxidant gas discharged from the oxidant gas flow path is calculated.   The fuel cell system according to claim 2, wherein the control device includes an output unit that outputs the leakage value to the outside. The control device includes a storage unit in which an evaluation leakage value for evaluating the leakage value is stored in advance.
The fuel cell system according to claim 2, wherein the control device evaluates a deterioration state of the fuel cell by comparing the leakage value and the evaluation leakage value.   The fuel cell system according to claim 5, wherein the control device includes an output unit that outputs the evaluated leakage value or evaluation result to the outside.   The fuel cell system according to claim 5, wherein the control device adjusts operating conditions of the fuel cell based on the evaluated leakage value. The control device calculates the leakage value at every predetermined detection time interval, and the storage unit stores the leakage value corresponding to the operation time of the fuel cell,
The control device acquires a transition line of the leakage value with respect to the operation time by a statistical approximation method, and predicts the progress of deterioration of the fuel cell based on a comparison between the transition line and the leakage value for evaluation. The fuel cell system according to claim 5.   The fuel cell system according to claim 8, wherein the control device changes the detection time interval according to a locus of the transition line. The evaluation leakage value stored in the storage unit of the control device includes a limit leakage value at the end of the service life of the fuel cell,
9. The fuel cell system according to claim 8, wherein the control device extrapolates the transition line and obtains a predicted remaining operation time of the fuel cell until the limit leakage value is reached.   The fuel cell system according to claim 10, wherein the control device includes an output unit that outputs the predicted remaining operation time to the outside.   The fuel cell system according to claim 10, wherein the control device adjusts an operation condition of the fuel cell based on the predicted remaining operation time. The supply pressure of the fuel gas supply device is lower than the supply pressure of the oxidant gas supply device,
The discharge-side carbon dioxide concentration detection device is disposed in the fuel gas discharge flow path;
The control device acquires a detection value of the exhaust-side carbon dioxide concentration detection device, and the carbon dioxide concentration of the fuel gas supplied to the fuel gas flow channel and the fuel gas discharged from the fuel gas flow channel The fuel cell system which calculates the leak value which consists of numerical information which shows the difference of the carbon dioxide concentration with the carbon dioxide concentration of. A supply-side carbon dioxide concentration detection device disposed in the fuel gas supply flow path;
The control device acquires detection values of the exhaust-side carbon dioxide concentration detection device and the supply-side carbon dioxide concentration detection device, and the carbon dioxide concentration of the fuel gas supplied to the fuel gas flow path and the fuel gas The fuel cell system according to claim 13, wherein a leakage value comprising numerical information indicating a difference in carbon dioxide concentration from the carbon dioxide concentration of the fuel gas discharged from the flow path is calculated.

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