JP2007073455A - Abnormality detection method of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect a system abnormality such as abnormal combustion of a catalytic burner while preventing ignition delay and occurrence of misfire due to condensation water in the passage of the catalytic burner. <P>SOLUTION: An anode off-gas exhausted from a fuel cell 1 through an anode off-gas piping 17 is supplied to an inner cylinder 37 arranged in a housing 27 of a catalytic burner 25 and a cathode off-gas exhausted through a cathode off-gas piping 11 is supplied to the housing 27 of the catalytic burner 25. A catalyst 31 is installed in the inner cylinder 37 and a catalyst 29 is installed in the housing 27 at the downstream, respectively, and the anode off-gas is burnt by each catalyst 31, 29. A first and a second temperature sensors A, B are installed, respectively, at the downstream of the catalyst 31, 29, and abnormality of the system is detected by the detected temperature of each temperature sensor A, B. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an abnormality detection method for a fuel cell system including a catalytic combustor that introduces an anode off-gas and a cathode off-gas discharged from an anode electrode of a fuel cell and performs combustion processing.

As a system using catalytic combustion, for example, a system described in Patent Document 1 below is known. This is because gas phase combustion may occur when the fuel concentration in the catalytic combustor rises, and abnormal combustion is detected by providing a temperature sensor upstream of the combustor.
Japanese Patent Laid-Open No. 11-118115

  However, in the above-described abnormality detection method in the conventional catalytic combustor, there is one flow path in the catalytic combustor. Condensed water or the like flows into this single flow path. Since misfire occurs, there is a problem that abnormal combustion detection cannot be performed with high accuracy.

  Therefore, the present invention aims to accurately detect system abnormalities such as abnormal combustion of the catalytic combustor after preventing the occurrence of ignition delay and misfire due to the influence of condensed water in the flow path in the catalytic combustor. Yes.

  The present invention relates to an abnormality detection method for a fuel cell system including a catalytic combustor that introduces an anode off-gas discharged from an anode electrode of a fuel cell and performs a combustion process, and each of the housings of the catalytic combustor includes a catalyst. The temperature is divided into a plurality of flow paths, and the temperature downstream of at least one of the flow path for introducing the anode off gas and the flow path for not introducing the anode off gas among the plurality of flow paths is detected. The most important feature is to detect an abnormality based on the detected temperature.

  According to the present invention, since the inside of the catalyst combustor housing is divided into a plurality of flow paths each having a catalyst, it is possible to prevent the occurrence of ignition delay and misfire due to the influence of condensed water or the like in the flow path in the catalyst combustor. In addition, the temperature downstream of at least one of the flow path for introducing the anode off gas and the flow path for not introducing the anode off gas among the plurality of flow paths in the catalyst combustor is detected, and based on the detected temperature Therefore, the system abnormality such as the abnormal combustion of the catalytic combustor can be accurately detected.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Configuration of the entire fuel cell system]
First, the overall configuration of the fuel cell system will be described based on the schematic configuration diagram of the fuel cell system shown in FIG.

  The fuel cell 1 is provided with a cathode electrode 3 and an anode electrode 5 and accommodated in a stack case 7. An air supply pipe 9 and a cathode offgas pipe 11 are connected to the cathode electrode 3, and a humidifier 13 is installed in the middle of the pipes 9 and 11. The air supply pipe 9 on the upstream side of the humidifier 13 and the inside of the stack case 7 are connected by a ventilation air supply pipe 14.

  On the other hand, a hydrogen supply pipe 15 and an anode offgas pipe 17 are connected to the anode electrode 5, respectively. Further, the anode offgas pipe 17 and the hydrogen supply pipe 15 are connected by a hydrogen circulation pipe 19, and a hydrogen circulation pump 21 is installed at a connection portion between the hydrogen circulation pipe 19 and the anode offgas pipe 17. An anode purge valve 23 is installed in the anode off-gas pipe 17 downstream from the hydrogen circulation pump 21. Instead of the hydrogen circulation pump 21 for circulating the anode off gas, other known ones such as an ejector can be used.

  Then, the cathode offgas pipe 11 and the anode offgas pipe 17 described above are connected to the catalytic combustor 25. The catalyst combustor 25 is connected to the other end of a ventilation air discharge pipe 26 having one end connected to the inside of the stack case 7.

  The catalytic combustor 25 has a housing 27, and the cathode offgas pipe 11, the anode offgas pipe 17, and the ventilation air discharge pipe 26 are connected to one end or the center of the housing 27, respectively. As shown in FIG. 2, which will be described later, two catalysts 29 and 31 for burning the anode off-gas are installed in the housing 27 on the downstream side of the unit.

  As the catalysts 29 and 31, a conventionally known catalyst in which a noble metal such as platinum is supported on a carrier such as a metal honeycomb or a ceramic honeycomb is used. Further, an exhaust pipe 33 for discharging combustion gas generated in the catalyst 29 to the outside is connected to an end portion of the housing 27 further downstream than the downstream catalyst 29.

  The gas flow path 35 immediately upstream of the catalyst 29 in the housing 27 is divided into two flow paths, an internal flow path 39 and an external flow path 41, by an inner cylinder 37 as shown in FIG.

  In the above configuration, external air is supplied through the air supply pipe 9 by, for example, a compressor which is a conventionally known air supply device (not shown), and the supplied external air is the cathode offgas flowing through the cathode offgas pipe 11 in the humidifier 13. It is humidified using a part of the water in it.

  The humidified air supplied to the cathode electrode 3 of the fuel cell 1 is discharged from the cathode electrode 3 as cathode offgas after being used for power generation. The discharged cathode off gas passes through the cathode off gas pipe 11 and is supplied to the catalytic combustor 25 after a part of the water is taken away by the humidifier 13 on the way.

  On the other hand, when the fuel is hydrogen, the hydrogen is supplied to the anode electrode 5 of the fuel cell 1 through a hydrogen supply pipe 15 from a hydrogen supply source (not shown). In addition, when hydrocarbon is used as the fuel, the reformed gas passes through the hydrogen supply pipe 15 in the same manner from the system that supplies the hydrogen-rich reformed gas generated by the reformer. 5 is supplied.

  The fuel gas that has not been used for power generation in the fuel cell 1 is circulated from the anode off-gas pipe 17 through the hydrogen circulation pump 21 to the hydrogen circulation pipe 19 to the hydrogen supply pipe 15 and again to the anode electrode 5 as anode ingas. Supplied. Alternatively, the fuel gas that has not been used for power generation in the fuel cell 1 is discharged from the anode purge valve 23 as the anode off-gas, and is supplied to the catalytic combustor 25 through the anode off-gas pipe 17 downstream thereof.

  The anode off gas supplied to the catalytic combustor 25 and the cathode off gas supplied to the catalytic combustor 25 in the same manner are mixed in the housing 27 to reach the catalysts 31 and 29, and the anode off gas combustion is performed. After the combustion in which oxygen is consumed as the oxidizer for combustion, the combustion gas is discharged out of the system through the exhaust pipe 33.

  A part of the air supplied to the air supply pipe 9 upstream of the humidifier 13 is supplied as ventilation air into the stack case 7 outside the fuel cell 1 through the ventilation air supply pipe 14. This ventilation air is diluted with permeated hydrogen from the fuel cell 1 and then supplied to the catalytic combustor 27 through the ventilation air discharge pipe 26, and a small amount of hydrogen is combusted in the catalysts 29 and 31 in the same manner as described above. Process.

  By the way, the fuel cell 1 generates power using an electrochemical reaction using hydrogen at the anode electrode 5 and oxygen at the cathode electrode 3. By this power generation operation, hydrogen and oxygen react, and water / water vapor is generated in the cathode electrode 3. However, the moisture generated at the cathode electrode 3 and the nitrogen component contained in the air supplied to the cathode electrode 3 diffuse to the anode electrode 5 side over time due to the partial pressure difference between the electrodes. If moisture or nitrogen gas accumulates in the anode electrode 5, the power generation efficiency decreases due to a decrease in the hydrogen partial pressure in the anode electrode 5 or the film on the anode electrode 5 side being covered with moisture.

  As a method for preventing the power generation efficiency from decreasing in this way, when the hydrogen partial pressure decreases, the anode purge valve 23 is opened, and impurity gas and the like are discharged therefrom. At this time, since unused hydrogen is also discharged together with the impurity gas, it is discharged after combustion treatment in the catalytic combustor 25.

  The opening and closing of the anode purge valve 23 is controlled according to the operating state of the fuel cell system. As a control method, there are an intermittent purge that opens and closes intermittently, and a continuous purge that always opens the anode purge valve 23 but controls its opening and controls the purge discharge amount per unit time. According to the catalytic combustor 25 in the present embodiment, effective combustion is possible as will be described later, and it is possible to cope with either purge method. However, in some controls, when intermittently purging is performed. Limited.

  Next, the configuration of the catalytic combustor will be described in detail.

[First configuration of catalytic combustor]
FIG. 2 is a schematic side sectional view showing a first configuration of the catalytic combustor 25.

  The catalyst combustor 25 having the first configuration has a cylindrical housing 27 and houses the inner cylinder 37 in the upper part of the housing 27, so that the gas flow path 35 immediately upstream of the catalyst 29 is formed as described above. It is divided into two channels, an internal channel 39 and an external channel 41.

  The two flow paths described above are positioned vertically above and below, and by providing a partition plate at a substantially central position in the vertical direction within the housing 27, an upper flow path replacing the internal flow path 39 and an external flow path are provided. You may divide | segment into the lower flow path replaced with the path | route 41. FIG.

  In the inner cylinder 37, one end portion on the right side in FIG. 2 is substantially in contact with the catalyst 29, and the other end portion on the left side is located near the left end portion of the housing 27. An exhaust side inner cylinder 43 similar to the inner cylinder 37 is also provided on the exhaust pipe 33 side of the catalyst 29.

  As shown in FIG. 1, the cathode offgas pipe 11 and the anode offgas pipe 17 are connected to the upstream side of the catalyst combustor 25. Here, the cathode offgas pipe 11 is connected to the end face of the housing 27. A cathode offgas inlet 41 is opened in the housing 27.

  On the other hand, the anode off-gas pipe 17 is connected to the side surface of the housing 27 and passes through the inner cylinder 37, and the anode off-gas inlet 47 is opened in the inner cylinder 37. The anode off-gas introduction port 47 has a fuel injection pipe shape for injecting the anode off-gas into the inside. For example, the anode off-gas introduction port 47 is a stainless pipe having a diameter of about ¼ inch with a hole at the tip, and a fuel for injecting the anode off-gas to the pipe end surface. A jet hole is provided. One or more fuel ejection holes are provided at the center of the pipe end face.

  A gas mixing unit 49 for mixing the cathode off gas containing oxygen as an oxidant and the ejected anode off gas is provided in the internal flow path 39 downstream from the anode off gas introduction port 47 described above, and mixing is performed in the gas mixing unit 49. The gas burns in the downstream catalyst 31. The gas mixing unit 49 may simply form a space, but may use a conventionally known gas mixing technique such as a swirler or a plurality of perforated plates.

  The downstream catalyst 29 is ignited and combusted by activating the entire catalyst 29 when the heat of combustion of the upstream catalyst 31 is transmitted to the entire catalyst. A first temperature sensor A is installed in the internal flow path 39 between the catalyst 29 and the catalyst 31, and a second temperature sensor B is installed in the flow path downstream of the catalyst 31. The first and second temperature sensors A and B described above constitute temperature detecting means for detecting the gas temperature after combustion.

  Note that the ventilation air discharge pipe 26 is omitted in FIG.

  In the catalytic combustor 25 shown in FIG. 2, a part of the cathode offgas introduced into the housing 27 from the cathode offgas pipe 11 flows into the internal flow path 39 in the inner cylinder 37, and the rest flows outside the inner cylinder 37 in the housing. 27 flows into the external flow path 41 in the flow path.

  At this time, although the cathode off gas contains moisture, the moisture flows downward due to gravity and mainly flows into the external channel 41, and a dry cathode off gas with little moisture flows into the internal channel 37. . The dried cathode off gas is mixed with the anode off gas introduced from the anode off gas introduction port 47 into the internal flow path 37 by the gas mixing unit 49, reaches the catalyst 31 downstream thereof, and burns.

  The combustion in the catalyst 31 uses dry cathode off gas as an oxidant, so that moisture hardly adheres to the catalyst 31 and ignites and burns efficiently. For this reason, it is possible to prevent the occurrence of ignition delay or misfire due to the influence of condensed water or the like.

  This combustion raises the gas temperature downstream of the catalyst 31, warms the portion 29 a of the catalyst 29 corresponding to the internal flow path 39, and transfers the heat to the entire catalyst 29. As a result, the entire catalyst 29 is sufficiently activated, and even at the portion 29b corresponding to the external flow path 41 through which a large amount of moisture flows, the temperature rises to ensure ignition and improve the combustion efficiency. The combustion gas burned by the catalyst 29 is discharged from the exhaust pipe 33 to the outside of the combustor.

  Thus, in the catalyst 29, the anode off-gas is efficiently burned starting from the portion 29a corresponding to the internal flow path 39, so that when the inside of the anode electrode 3 of the fuel cell 1 is purged, a large amount of condensed water is generated. Even when it is supplied by cathode off-gas or when so-called crossover hydrogen is generated where hydrogen passes from the anode 5 to the cathode 3, unburned hydrogen is discharged outside the combustor. Can be suppressed.

  Further, in the catalytic combustor 25 according to the first configuration described above, the anode off gas is supplied to the internal flow path 39 in the inner cylinder 37, and a part of the cathode off gas is introduced into the internal flow path 39. The fuel concentration of the mixed gas can be kept high to some extent, and the combustion characteristics can be improved.

  Here, the first temperature sensor A detects the combustion gas temperature downstream of the catalyst 31, and the second temperature sensor B detects the combustion gas temperature downstream of the catalyst 29, thereby determining combustion abnormality of the catalysts 31 and 29, etc. It can be used for various abnormality determination controls described later.

  Further, when the present fuel cell system is mounted on a moving body such as a vehicle, the inner cylinder 37 accommodated in the housing 27 is arranged not only in consideration of only the vertical direction but also in the front and rear in the vehicle traveling direction. It is desirable to make the arrangement.

  Condensed water in the cathode off-gas is more affected by gravity and acceleration / deceleration G of the vehicle than by gas flow. Usually, a vehicle or the like needs more output when accelerating, so that the amount of condensed water generated during acceleration is larger. Conversely, when the vehicle is decelerated, the amount of condensed water generated is small because the output is small. Therefore, the effect of the condensed water on the catalyst is greater during acceleration than during deceleration.

  Therefore, the condensed water accumulates not only on the lower side in the housing 27 but also on the vehicle rear side under the influence of the acceleration G. Therefore, when the gas flow path 35 in the housing 27 is divided, the division is performed in consideration of the movement of the condensed water during acceleration.

  For this reason, the housing 27 is installed in the vehicle so that the gas flow path 35 in the interior thereof extends in a direction intersecting the vehicle traveling direction, for example, the vehicle width direction, and the internal flow path 39 positioned at the upper part in the vertical direction is disposed in the housing. 27 is arranged close to the vehicle front side so that moisture does not easily flow into the internal flow path 39.

  Thereby, the combustion characteristic of the catalytic combustor 25 when the fuel cell system is mounted on a moving body such as a vehicle can be further improved.

  The housing 27 and the inner cylinder 37 of the catalytic combustor 25 are made of a material that can withstand the internal environment (combustion temperature, pressure, mixed gas, etc.), for example, a stainless alloy, and the gas flow rate and heat generation required for the combustion system. Other materials may be used as long as the design satisfies the requirements such as quantity. Further, the housing 27 of the catalytic combustor 25 is not necessarily cylindrical.

[Second configuration of catalytic combustor]
FIG. 3 is a side sectional view showing a second configuration of the catalytic combustor 25. In the second configuration of the catalytic combustor 25, the description of the same components as those of the first configuration shown in FIG. 2 is omitted, and the same components as those of the first configuration are omitted. The same reference numerals shall be attached.

  In the second configuration, the inner cylinder 37 in the catalytic combustor 25 of the first configuration shown in FIG. 2 is arranged at the center position of the housing 27, and the ventilation shown in FIG. The air discharge pipe 26 is connected, and the end on the upstream side of the inner cylinder 37 is closed with an end plate 55. Other configurations are substantially the same as the first configuration.

  The ventilation air discharge pipe 26 penetrates the housing 27 on the upstream side of the anode off-gas pipe 17 and protrudes into the internal flow path 39, and is provided with a ventilation air introduction port 57 directed toward the downstream side at the tip.

  That is, hydrogen that permeates in the vicinity of the fuel cell 1 is diluted in the stack case 7 using a part of the air supplied from the ventilation air supply pipe 14 shown in FIG. 1, and this diluted gas is ventilated. The air is supplied to the internal flow path 39 of the catalytic combustor 25 through the air discharge pipe 26. The ventilation air introduction port 57 can be designed using the same design concept as the anode off gas introduction port 47.

  The ventilation air introduced into the catalyst combustor 25 from within the stack case 7 does not contain moisture generated by the power generation of the fuel cell 1 unlike the cathode offgas, and is relatively dry (similar to the outside air). Therefore, more reliable and efficient combustion becomes possible by burning with the catalyst 31 using this dry ventilation air. Further, since the hydrogen contained in a minute amount in the ventilation air has a low concentration, combustion with the ventilation air alone is difficult, but since it is supplied to the catalyst 31 together with the anode off-gas, the combustion treatment can be reliably and effectively performed.

  The end plate 55 that closes the internal flow path 39 may be configured to be openable and closable using, for example, a butterfly valve instead of being fixed to the inner cylinder 37 in a closed state. As a result, the upstream end of the internal flow path 39 can be opened and closed according to the operating state of the fuel cell 1, and the combustion state of the catalyst 31 in the internal flow path 39 at that time (first temperature sensor). The flow rate of the cathode off-gas supplied to the internal flow path 39 can be adjusted according to (detected by A), and the combustion temperature in the internal flow path 39 can be controlled accordingly.

[Third configuration of catalytic combustor]
FIG. 4 is a side sectional view showing a third configuration of the catalytic combustor 25. The catalytic combustor 25 of the third configuration divides the inside of the housing 27 into three flow paths according to the characteristics of the supplied gas. That is, the inner cylinder 37 substantially the same as that in the first configuration shown in FIG. 2 is installed in the housing 27 to form the internal flow path 39. The upper end of the inner cylinder 37 and the upper inner wall of the housing 27 In addition, another upper inner cylinder 59 is installed to form the uppermost channel 61.

  The anode off-gas pipe 17 is connected to the internal flow path 39, and the ventilation air discharge pipe 26 is connected to the uppermost flow path 61. The upstream end of the uppermost flow path 61 is closed by the end plate 63. Therefore, here, a part of the cathode offgas introduced from the upstream end of the housing 27 to the gas flow path 35 via the cathode offgas pipe 11 is in the internal flow path 39 and the rest is in the external flow path 41. Flow into.

  As in FIG. 2, the catalyst 31 is installed in the internal flow path 39 in the vicinity of the catalyst 29, and the upstream side of the catalyst 31 is a gas mixing section (not shown) in which the anode off gas and the cathode off gas are mixed.

  Therefore, also in this example, as in the first configuration shown in FIG. 2, the anode off gas and the cathode off gas with less moisture are mixed in the internal flow path 39, and the mixed gas is efficiently used in the catalyst 31. The catalyst 29 that burns and is supplied to the downstream catalyst 29 is supplied with a high-temperature gas that has been heated by the combustion. The temperature of the catalyst 29 that receives the heat of the high-temperature gas rises, and the combustion efficiency of the entire catalyst 29 rises.

  At this time, the catalyst 29 is also supplied with the ventilation air introduced from the ventilation air discharge pipe 26 into the uppermost flow path 61, and the hydrogen contained in a minute amount in the ventilation air also warms the catalyst 29 sufficiently so that the catalyst activity is increased. Therefore, combustion processing is possible even at extremely low concentrations.

  Further, in the third configuration shown in FIG. 4, the exhaust side inner cylinder 65 is disposed on the downstream side of the catalyst 29 corresponding to the upper inner cylinder 59, and the temperature detection means is provided in the exhaust side inner cylinder 65. By providing the third temperature sensor C and detecting the combustion gas temperature in the exhaust side inner cylinder 63 downstream of the catalyst 29, it can be used for various abnormality determination control described later, such as combustion abnormality determination of the catalyst 29.

[Example of control]
Hereinafter, typical control examples for the configurations of the catalytic combustors 25 will be described.

5 to 8 show flowcharts of control examples in the catalytic combustor 25 having the first configuration shown in FIG. 2, and Table 1 shows purge methods, gas temperatures, and abnormal contents at that time.

  This control is performed as an abnormal process control separately from the control of the entire system. For example, when the system is operating, it is always carried out for several to several thousand cycles per second, and when an abnormality is detected, the determination result is communicated to the host control to encourage appropriate measures to be taken. Note that this control is only an abnormality determination, and the system control after the abnormality determination is out of the scope of this patent, so the description is omitted.

  FIG. 5 shows a first control example (first embodiment) in the catalytic combustor 25 having the first configuration shown in FIG. The first control example corresponds to the abnormality determination examples 1a and 1b in Table 1, and the purge method is continuous. First, the control is started upon receiving an abnormality determination instruction from the host control (step S100). Here, the temperature Ta detected by the first temperature sensor A (expressed as anode + cathode temperature in Table 1) is measured, and the temperature Ta is compared with the upper limit temperature Tha determined by the operating state of the system (step S101). The upper limit temperature Tha at this time is set in advance according to the operating conditions. For example, it is possible to use a combustion temperature calculated from the purge hydrogen concentration of the anode off gas expected from the operating state of the fuel cell 1.

  Here, when the temperature Ta is higher than the upper limit temperature Tha, the temperature Ta has increased too much, but the cause is determined to be that the amount of unused fuel such as hydrogen contained in the anode off gas is large (concentration is high). (Step S102). This determination result is an abnormality determination example 1a in Table 1, which is transmitted to the upper control (step S107), and appropriate processing is performed by the upper control.

  Conversely, when the temperature Ta is equal to or lower than the upper limit temperature Tha, the temperature Tb detected by the second temperature sensor B is measured, and the temperature Tb is compared with the upper limit temperature Thb determined by the operating state of the system (step S103). . The upper limit temperature Thb at this time is set in advance according to the operating conditions. For example, a temperature that is inversely proportional to the cathode offgas flow rate calculated from the power generation amount of the fuel cell 1 can be used.

  Here, when the temperature Tb is higher than the upper limit temperature Thb, the temperature Tb has risen too much, but it is determined that the cause is that hydrogen or the like that is not originally included in the cathode offgas is mixed due to crossover or the like. (Step S104). This determination result is the abnormality determination example 1b in Table 1, and is transmitted to the upper control in step S107 described above, and appropriate processing is performed by the upper control.

  On the other hand, when the temperature Tb is equal to or lower than the upper limit temperature Thb, it is determined that there is no problem such as system abnormality (step S105), and the abnormality determination control returns to the upper control, or the process returns to step S100 and the abnormality determination control is performed again. Is started (step S106).

  Thus, in the first control example, when the temperature Ta of the internal flow path 39 downstream of the catalyst 31 for introducing the anode off-gas or the temperature Tb downstream of the catalyst 29 of the external flow path 41 for introducing the cathode off-gas is high, Abnormalities such as an increase in the concentration of hydrogen contained in the anode off-gas and an increase in the amount of hydrogen mixed in the cathode off-gas can be detected, so that necessary measures can be taken early before abnormal combustion occurs.

  FIG. 6 is a modification of the first control example shown in FIG. 5, in which only steps S101 and S102 and steps S103 and S104 in FIG. 5 are replaced, and the basic control is the first control. Since it is the same as the example and the abnormality determination example is 1a and 1b in Table 1, details are omitted.

  FIG. 7 shows a second control example (second embodiment) in the catalytic combustor 25 having the first configuration shown in FIG. The second control example corresponds to the abnormality determination examples 2a, 2b, and 2c in Table 1, and the purge method is intermittent.

  The second control example is performed when the temperature Tb is equal to or lower than the upper limit temperature Thb and there is no problem such as a system abnormality in step S103 in the first control example shown in FIG. Steps S100 to S107 are the same as those in the first control example, and a description thereof will be omitted.

  After the temperature Tb becomes equal to or lower than the upper limit temperature Thb in step S103, the temperature Ta detected by the first temperature sensor A is measured, and the temperature Ta fluctuates according to the system operation (anode off gas purge control). (Step S111A).

  Here, when the temperature Ta varies, the process proceeds to step S112A, and when the temperature Ta does not vary, the control proceeds to step S112B. The step with the same step number followed by an alphabet identification code is the same control logic, but the downstream step is different.

  In the above steps S112A and B, the temperature Tb detected by the second temperature sensor B is measured, and it is confirmed whether the temperature Tb varies according to the system operation (anode off-gas purge control). At this time, the process proceeds to each downstream step depending on whether the temperature Tb is fluctuating or not.

  If the temperature Tb varies in step S112A, the process proceeds to step S106 through step S105 similar to that shown in FIG. That is, here, since the temperature Ta downstream of the catalyst 31 and the temperature Tb downstream of the catalyst 29 both fluctuate corresponding to the intermittent purge, it is determined that there is no problem such as system abnormality (step S105). The process returns from the abnormality determination control to the higher control, or returns to step S100 and starts the abnormality determination control again.

  If the temperature Tb does not fluctuate in step S112A despite the intermittent purging, it is determined that the second temperature sensor B is abnormal (step S114). This is determination example 2b. In step S107 described above, the information is transmitted to the upper control, and appropriate processing is performed by the upper control.

  If the temperature Tb varies in step S112B, it is determined that there is an abnormality in the first temperature sensor A (step S113), and the determination result is the abnormality determination example 2a in Table 1, and thereafter the second temperature. In the same manner as when the sensor B is abnormal, the process proceeds to step S107.

  If the temperature Tb does not fluctuate in step S112B, that is, if neither the temperature Ta nor Tb fluctuates despite the intermittent purge being performed, it is determined that the anode off gas purge control is abnormal ( In step S115), the determination result is the abnormality determination example 2c in Table 1. In the next step S107, the determination result is transmitted to the upper control, and appropriate processing is performed by the upper control.

  As described above, in the second control example, when intermittent purge is performed, the temperature Ta of the internal flow path 39 downstream of the catalyst 31 for introducing the anode off gas and the downstream of the catalyst 29 of the external flow path 41 for introducing the cathode off gas are provided. When the temperature Tb does not fluctuate, an abnormality in the first temperature sensor A or the second temperature sensor B can be detected, so that a diagnosis failure due to a sensor detection abnormality can be prevented in advance.

  Further, when there is no change in any of the temperatures Ta and Tb, it is determined that there is an abnormality in the purge control of the anode off gas, so that appropriate processing can be performed in advance before abnormal combustion occurs.

  FIG. 8 shows a modification of the second control example shown in FIG. Here, step S111B is used instead of step S111A in FIG. In step S11B, as in step S111A, the temperature Ta detected by the first temperature sensor A is measured, and it is confirmed whether the temperature fluctuates in accordance with system operation (anode off-gas purge control). .

  Here, when the temperature Ta does not fluctuate, after setting the “first temperature sensor A abnormality” flag (step S121), the temperature Tb detected by the second temperature sensor B is measured, and the temperature is the system operation. It is confirmed whether the temperature fluctuates according to (anode off-gas purge control) (step S112C). Moreover, also when temperature Ta is fluctuating in step S111B, it transfers to above-mentioned step S112C.

  In step S112C, when the temperature Tb does not change, after setting the “second temperature sensor B abnormality” flag (step S122), or when the temperature Tb is changing in the step S112C, the state of each flag is changed. Confirmation (step S123), and control is shifted to the downstream step according to the result.

  For example, the “first temperature sensor A abnormality” flag is the first digit, the “second temperature sensor B abnormality” flag is the second digit, the flag when there is an abnormality is “1”, and the flag when there is no abnormality is “0”. In the case of the binary number of “00”, “01”, “10”, and “11”, the downstream steps S105 (no abnormality), S114 (second temperature sensor B abnormality), S113 are obtained, respectively. Either (first temperature sensor A abnormality) or S115 (purge control abnormality) is determined, and the process proceeds to that step.

  After shifting to the downstream step designated for each combination of flags, the determination result is returned to the upper control based on each determination result.

FIG. 9 shows a third control example (third embodiment) in the catalytic combustor 25 having the third configuration shown in FIG. The third control example corresponds to the abnormality determination examples 3a and 3b in Table 2, and the purge method is continuous.

  The third control example is performed when the temperature Tb is equal to or lower than the upper limit temperature Thb and there is no problem such as a system abnormality in step S103 in the first control example shown in FIG. Steps S100 to S107 are the same as those in the first control example, and a description thereof will be omitted.

  In step S103, after the temperature Tb becomes equal to or lower than the upper limit temperature Thb, the temperature Tc detected by the third temperature sensor C is measured, and the temperature Tc is compared with the upper limit temperature Thc determined by the operating state of the system ( Step S201A). The temperature Thc at this time is set in advance depending on the operating conditions, but may be a constant temperature.

  Here, when the temperature Tc is higher than the upper limit temperature Thc, the pressure Pc of the ventilation air is obtained by a pressure sensor (not shown) and compared with the operation lower limit pressure Pl (step S202). The pressure Pc at this time may be a pressure proportional to the flow rate of the air ventilating the periphery of the fuel cell 1, such as an air supply pressure or an air discharge pressure, depending on the system. The operation lower limit pressure Pl can be, for example, a constant value or a value that varies in proportion to the output of the fuel cell 1.

  When the temperature Pc is higher than the operation lower limit pressure Pl, it is determined that the hydrogen permeation amount from the fuel cell 1 to the ventilation air around the fuel cell 1 is increasing (step S204: abnormality in Table 2). (Corresponding to the determination example 3a), the process proceeds to higher control from step S107.

  On the other hand, when the pressure Pc is equal to or lower than the operation lower limit pressure Pl, it is determined that there is an abnormality in which the flow rate of the ventilation air around the fuel cell 1 is reduced (step S203: corresponding to the abnormality determination example 3b in Table 2). The process proceeds to higher-order control from S107.

  On the other hand, if the temperature Tc is equal to or lower than the upper limit temperature Thc in step 201A, the process proceeds to step S106 through step S105 corresponding to the absence of abnormality similar to that shown in FIG.

  Thus, in the third control example, when the temperature Tc downstream of the catalyst 29 in the uppermost flow path 61 for introducing the ventilation air is high and the pressure Pc of the ventilation air is high, the hydrogen from the fuel cell 1 to the ventilation air An increase in permeation amount can be detected, and necessary measures can be taken early before the hydrogen permeation amount becomes excessive. On the other hand, when the temperature Tc is high and the pressure Pc is low, an abnormality in insufficient ventilation air flow can be detected at an early stage, and an excessive increase in the hydrogen concentration in the ventilation air can be detected in advance.

Further, in the case of the third control example, since abnormality is detected using not only temperature but also pressure, reliability is improved as an abnormality detection system. FIG. 10 shows the third example shown in FIG. In a modified example of the control example, steps S101, S102, S103, and S104 in FIG. 9 and steps S201A, S202, S203, and S204 are simply replaced within a range where there is no problem in terms of control. 3 is the same as the control example 3 and the abnormality determination example is also 3a and 3b in Table 2, and the details are omitted.

  FIGS. 11, 12A, and 12B are flowcharts in which abnormality detection control in intermittent purge is further added to the third control example in FIG. 9, and the abnormality determination examples 3c to 3f in Table 2 are added. It corresponds. 12A and 12B are continued from FIG.

  In this control example, when the temperature Tc is equal to or lower than the upper limit temperature Thc in step S201A after starting in step S100 and in step S201A, the same as in steps S111A (FIG. 7) and S111B (FIG. 8) described above. That is, it is confirmed whether the temperature Ta fluctuates according to the system operation (anode off gas purge control) (step S111C).

  After that, according to the result, the same control as the above-described steps S112A (FIG. 7), S112B (FIG. 7), S112C (FIG. 8), that is, the temperature Tb depends on the system operation (anode off gas purge control). It is confirmed whether it has fluctuated (steps S112D and S112E).

  Thereafter, the process proceeds to one of steps S205A to S205 depending on the result. In each step of step S205, it is measured whether the temperature Tc of the third temperature sensor C varies. As a result, the process proceeds to any of steps S105, S113 to S115, and S206 to S209 described above, and the result is returned to the upper control.

  At this time, in step S206 (FIG. 11), the temperature Tc does not vary regardless of the intermittent purge, and therefore it is determined that the third temperature sensor C is abnormal (corresponding to the abnormality determination example 3e in Table 2). . In step S207 (FIG. 12 (a)), the temperatures Ta and Tc do not vary regardless of the intermittent purge, so it is determined that the first and third temperature sensors A and C are abnormal (see Table 2). In step S208 (FIG. 11), it is determined that the second and third temperature sensors B and C are abnormal because the temperatures Tb and Tc do not change regardless of the intermittent purge. Corresponding to the abnormal control example 3h in Table 2), in step S209 (FIG. 12B), the temperature Ta and Tb do not change regardless of the intermittent purge, so the first and second temperature sensors A and B are abnormal. (Corresponding to abnormality control example 3i in Table 2).

  Further, as shown in FIG. 13, when there is no change in each temperature based on the determination results of each determination step S111D (whether there is Ta fluctuation), S112G (whether there is Tb fluctuation), and S205E (whether there is Tc fluctuation). In steps S121, S122 and S211, a "first temperature sensor A abnormality" flag, a "second temperature sensor B abnormality" flag and a "third temperature sensor C abnormality" flag are set, respectively.

  Thereafter, the contents of the flag are confirmed (step S210). The process proceeds to any of steps S105, S113 to S115, and S206 to S209 according to the flag contents, and the result is returned to the upper control. The flag content at this time can be, for example, a 3-digit binary number. That is, the “first temperature sensor A abnormality” flag is the first digit, the “second temperature sensor B abnormality” flag is the second digit, and the “third temperature sensor C abnormality” flag is the third digit. When the flag is “1” and the flag when there is no flag is “0”, “000”, “100”, “010”, “111”, “001”, “101”, “011”, “ 110 ”determination results are obtained.

  As described above, when intermittent control is performed on the third control example, the internal flow path downstream of the catalyst 31 for introducing the anode off-gas when performing intermittent purge, as in the second control example described above. If the temperature Ta of 39, the temperature Tb downstream of the catalyst 29 in the external flow channel 41 for introducing the cathode off-gas, and the temperature Tc of the uppermost flow channel 61 downstream of the catalyst 29 for introducing the ventilation air do not fluctuate, Since the abnormality of the temperature sensor A, the second temperature sensor B, and further the third temperature sensor C can be detected, a diagnosis omission due to the sensor detection abnormality can be prevented in advance.

FIG. 14 shows a fourth control example (fourth embodiment) in the catalytic combustor 25 having the second configuration shown in FIG. The fourth control example corresponds to the abnormality determination examples 4a to 4d in Table 3, and the purge method is continuous.

  In the fourth control example, the abnormality determination control started in step S100 measures the temperature Tb detected by the second temperature sensor B in step S103, and the temperature Tb is determined by the operating state of the system. Compare with Thb. The temperature Thb at this time is a temperature set in advance according to operating conditions as described above, and varies according to the operating state of the system.

  Here, when the temperature Tb is higher than the upper limit temperature Thb, it is determined that hydrogen having a higher concentration than expected has flowed into the cathode off gas (step S104), and this information is transmitted from the step S107 to the upper control, and the upper control is performed. To perform appropriate processing (corresponding to abnormality determination example 4a in Table 3).

  Conversely, when the temperature Tb is equal to or lower than the upper limit temperature Thb, the temperature Td detected by the second temperature sensor D is measured, and the temperature Td is compared with the upper limit temperature Thd determined by the operating state of the system (step S301). . The upper limit temperature Thd at this time is a control parameter that varies depending on the operating state of the system, for example, similar to the above Tha.

  Here, when the temperature Td is equal to or lower than the upper limit Thd, the process proceeds from step S105 to S106, and it is notified to the upper control that there is no abnormality in particular, or the process returns to step S100 and the abnormality detection control is resumed.

  If the temperature Td is higher than the upper limit temperature Thd in step S301, the operating pressure Pc of the ventilation air around the fuel cell 1 is changed to a pressure sensor (not shown) in step S202, as in the control in FIG. And the pressure Pc is compared with the operation lower limit pressure Pl. The operation lower limit pressure Pl may be a constant value as described above, or may be a value that varies depending on the operation state of the system.

  Here, when the operation pressure Pc is equal to or lower than the operation lower limit pressure Pl, it is determined in step S203 that there is an abnormality due to a decrease in the flow rate of the ventilation air in the fuel cell 1 (corresponding to the abnormality determination example 4b in Table 3). Then, control is transferred from step S107 to higher control.

  Conversely, when the operating pressure Pc is higher than the operating lower limit pressure Pl, it is an abnormal increase in the purge hydrogen concentration of the anode gas, an abnormal increase in the anode purge hydrogen flow rate, or an abnormality due to hydrogen leakage from the fuel cell 1 to the surrounding ventilation air. (Step S302: Corresponding to the abnormality determination examples 4c and 4d), the control is transferred from Step S107 to the upper control.

  As described above, in the fourth control example, when the temperature Tb downstream of the catalyst 29 is high, it is possible to detect that a hydrogen concentration higher than expected has flowed into the cathode offgas. Increase abnormality can be detected early and necessary countermeasures can be taken early.

  Further, when the temperature Td of the internal flow path 39 downstream of the catalyst 39 is high and the pressure Pc of the ventilation air is low, an abnormality in the insufficient flow rate of the ventilation air can be detected at an early stage, and the hydrogen concentration in the ventilation air increases excessively. Can be detected in advance.

  Further, when the temperature Td downstream of the catalyst 39 is high and the pressure Pc of the ventilation air is high, abnormal increase in the purge hydrogen concentration of the anode gas, abnormal increase in the anode purge hydrogen flow rate, or hydrogen from the fuel cell 1 to the surrounding ventilation air Abnormalities due to leakage can be detected in advance, and necessary measures can be taken early before abnormal combustion occurs.

  FIG. 15 is a modified example of the fourth control example shown in FIG. 14 above. Steps S103 and S104 in FIG. 14 and steps S301, S202, S302, and S203 are simply replaced within a range where there is no problem in control. The basic control is the same as in the fourth control example, and the abnormality determination example is also 4a to 4d in Table 3, so the details are omitted.

  Finally, FIG. 16 shows a control example in which abnormality detection control in intermittent purge is further added to the fourth control example in FIG. This control example corresponds to the abnormality determination examples 4e to 4g in Table 2.

  Starting from step S100, after step S103 in FIG. 15, that is, the detected temperature Td of the first temperature sensor D is not more than the upper limit temperature Thd (step S301), and the detected temperature Tb of the second temperature sensor B is not more than the upper limit temperature Thb. In the case of (Step S103), it is confirmed whether the temperature Td varies according to the intermittent purge of the anode off gas (Step S303).

  Here, when the temperature Td does not fluctuate, a “first temperature sensor D abnormality” flag is set (step S304). If the temperature Td fluctuates according to the anode off-gas purge after step S304 and in step S303, does the detected temperature Tb of the second temperature sensor B fluctuate according to the anode off-gas purge? Confirm (step S112F).

  Here, when the temperature Tb does not fluctuate, a “second temperature sensor B abnormality” flag is set (step S122B). After step S122B and when the temperature Tb varies in step S112F, the presence / absence of a temperature sensor abnormality flag is confirmed (step S305).

  In this control example, similarly to the example of FIG. 8 described above, for example, the “first temperature sensor D abnormality” flag is set to the first digit and the “second temperature sensor B abnormality” flag is set to the second digit. When the case flag is “1” and the case flag is “0”, four types of determination results “00”, “01”, “10”, and “11” are obtained.

  Then, depending on the content of the flag, the above-described steps S105 (no abnormality), S114 (abnormality in the second temperature sensor B: corresponding to the abnormality determination example 4f in Table 3), S306, S115 (abnormality in purge: abnormality in Table 3) Control is transferred to (corresponding to determination example 4g).

  In step S306, it is determined that there is an abnormality in the first temperature sensor D (corresponding to the abnormality determination example 4e in Table 3), and in the same manner as in steps S114 and S115, the control is transmitted to the upper control from step S107. Further, after step S105 with no abnormality, step S106 is continued.

  As described above, when intermittent purge is performed for the fourth control example, as in the above-described second control example, when the intermittent purge is performed, the anode off-gas and the ventilation air downstream of the catalyst 31 are introduced. When the temperature Td of the internal flow path 39 or the temperature Tb downstream of the catalyst 29 of the external flow path 41 for introducing the cathode off gas does not fluctuate, an abnormality in the first temperature sensor D or the second temperature sensor B can be detected. Diagnosis omission due to detection abnormality can be prevented in advance.

  Although specific embodiments to which the present invention is applied have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.

It is a schematic block diagram of the fuel cell system of this invention. FIG. 2 is a schematic side sectional view showing a first configuration of a catalytic combustor in the fuel cell system of FIG. 1. FIG. 3 is a schematic side sectional view showing a second configuration of the catalytic combustor in the fuel cell system of FIG. 1. FIG. 5 is a schematic side sectional view showing a third configuration of the catalytic combustor in the fuel cell system of FIG. 1. It is a flowchart which shows the 1st example of control in the catalytic combustor of a 1st structure. It is a flowchart which shows the modification of the 1st control example in FIG. FIG. 3 is a flowchart showing a second control example in the catalytic combustor having the first configuration shown in FIG. 2. FIG. It is a flowchart which shows the modification of the 2nd control example in FIG. 6 is a flowchart showing a third control example in the catalytic combustor having the third configuration shown in FIG. 4. It is a flowchart which shows the modification of the 3rd control example in FIG. 10 is a flowchart in which abnormality detection control in intermittent purge is added to the third control example in FIG. 9. 10 is a flowchart in which abnormality detection control in intermittent purge is added to the third control example in FIG. 9. 13 is a flowchart showing a modification of the third control example in FIGS. It is a flowchart which shows the 4th example of control in the catalytic combustor of the 2nd structure shown in FIG. It is a flowchart which shows the modification of the 4th control example in FIG. 16 is a flowchart in which abnormality detection control in intermittent purge is added to the fourth control example in FIG. 15.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 3 Anode electrode 5 Cathode electrode 7 Stack case which accommodates a fuel cell 25 Catalytic combustor 27 Catalytic combustor housing 29, 31 Catalyst 35 Gas flow path 39 Internal flow path (flow path for introducing anode off gas)
41 External channel (channel without introducing anode off gas)
61 Uppermost channel (channel without introducing anode off gas)
A, D First temperature sensor (temperature detection means)
B Second temperature sensor (temperature detection means)
C Third temperature sensor (temperature detection means)

Claims (12)

  In a fuel cell system abnormality detection method including a catalytic combustor that introduces and burns an anode off gas discharged from an anode electrode of a fuel cell, a plurality of flow paths each having a catalyst are disposed in the housing of the catalytic combustor. The temperature of the downstream side of at least one of the flow path for introducing the anode off gas and the flow path for not introducing the anode off gas among the plurality of flow paths is detected, and the detected temperature is set to the detected temperature. An abnormality detection method for a fuel cell system that detects an abnormality based on the above.   2. The abnormality detection method for a fuel cell system according to claim 1, wherein when the temperature downstream of the catalyst in the flow path for introducing the anode off gas is higher than a reference temperature set in advance from operating conditions of the fuel cell, An abnormality detection method for a fuel cell system, characterized in that an abnormality is determined due to an increase in the flow rate of the introduced anode off gas.   2. The abnormality detection method for a fuel cell system according to claim 1, wherein the flow path not introducing the anode off gas is a flow path for introducing the cathode off gas discharged from the cathode electrode of the fuel cell, and introduces the anode off gas. When the temperature downstream of the catalyst in the non-flow channel is higher than a reference temperature set in advance from the operating conditions of the fuel cell, it is determined that there is an abnormality due to mixing of the anode gas into the cathode offgas. Anomaly detection method.   2. The abnormality detection method for a fuel cell system according to claim 1, wherein when the anode off gas is intermittently introduced into the catalytic combustor, based on temperature fluctuations downstream of the catalysts provided in the plurality of flow paths. An abnormality detection method for a fuel cell system, characterized by detecting an abnormality.   5. The abnormality detection method for a fuel cell system according to claim 4, wherein a temperature fluctuation downstream of the catalyst in a flow path not introducing the anode off gas is larger than a temperature fluctuation downstream of the catalyst in the flow path introducing the anode off gas. In this case, it is determined that there is an abnormality in the temperature detection means provided downstream of the catalyst in the flow path for introducing the anode off gas.   5. The abnormality detection method for a fuel cell system according to claim 4, wherein a temperature fluctuation downstream of the catalyst in a flow path not introducing the anode off gas is smaller than a temperature fluctuation downstream of the catalyst in the flow path introducing the anode off gas. In this case, it is determined that there is an abnormality in the temperature detection means provided downstream of the catalyst in the flow path not introducing the anode off gas.   5. The abnormality detection method for a fuel cell system according to claim 4, wherein each of the temperatures downstream of the catalyst in the flow path for introducing the anode off gas and downstream of the catalyst in the flow path for not introducing the assodic off gas are both. An abnormality detection method for a fuel cell system, wherein when there is no fluctuation, it is determined that there is an abnormality in the control for introducing the assode off gas into the catalytic combustor.   The abnormality detection method for a fuel cell system according to any one of claims 1, 2, 4, 5, 6, and 7, wherein the flow path not introducing the anode off gas is provided in a stack case that houses the fuel cell. An abnormality detection method for a fuel cell system, characterized by being a flow path for introducing ventilation air alone.   The abnormality detection method for a fuel cell system according to any one of claims 1 to 7, wherein the flow path not introducing the anode off gas is a flow path for introducing the cathode off gas discharged from the cathode electrode of the fuel cell. A method for detecting an abnormality in a fuel cell system, comprising: introducing ventilation air in a stack case housing the fuel cell into a flow path for introducing the anode off gas.   10. The abnormality detection method for a fuel cell system according to claim 8 or 9, wherein a pressure of ventilation air in a stack case housing the fuel cell is detected, and an abnormality is detected based on the detected pressure value. An abnormality detection method for a fuel cell system.   The abnormality detection method for a fuel cell system according to claim 10, wherein the temperature downstream of the catalyst in the flow path for introducing the ventilation air in the stack case is higher than a reference temperature assumed in advance from operating conditions, and When the pressure of the flow path for introducing the ventilation air in the stack case is higher than the pressure assumed in advance from the operating conditions of the fuel cell, the amount of anode gas leakage to the flow path for introducing the ventilation air in the stack case An abnormality detection method for a fuel cell system, characterized in that it is determined that an abnormality is caused by an excess.   11. The abnormality detection method for a fuel cell system according to claim 10, wherein a temperature downstream of the catalyst in a flow path for introducing ventilation air in the stack case is higher than a reference temperature assumed in advance from operating conditions, and the stack. When the pressure of the flow path for introducing the ventilation air in the case is lower than the pressure assumed in advance from the operating condition of the fuel cell, it is determined that the abnormality is caused by the insufficient flow rate of the ventilation air into the stack case. An abnormality detection method for a fuel cell system.

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