JP6412187B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more particularly to failure detection of a rear stack and a fuel regeneration device in a multistage fuel cell system.

  For example, Patent Document 1 describes that in a multi-stage fuel cell system, the fuel utilization rate is improved by performing fuel regeneration by removing water vapor or water vapor and carbon dioxide from the anode off gas.

  By the way, in a multi-stage fuel cell system, when a multi-stage fuel cell stack deteriorates, it is particularly important to detect the deterioration of the previous fuel cell stack.

  The main reason is that if the composition and flow rate of the anode / cathode gas supplied to the subsequent fuel cell stack fluctuate and power generation is performed in this state, the subsequent fuel cell stack is also likely to deteriorate.

  The fuel cell stack may be deteriorated due to a heat cycle due to long-term operation or start / stop, or a load such as a change in gas pressure or a change in gas composition during operation.

  In particular, SOFC has a high operating temperature and high power generation efficiency. However, since the deterioration rate tends to increase with a high operating temperature, the upper limit temperature of the fuel cell stack is set as a countermeasure against the deterioration of the fuel cell stack. When the set upper limit temperature is exceeded, control for increasing the air flow rate is performed.

  As a means for detecting the deterioration of the fuel cell stack, a means for detecting the temperature during operation is generally used, and described in Patent Document 2 and Patent Document 3.

  In Patent Document 2, when the operating temperature of the SOFC is detected and the operating temperature becomes lower than a predetermined temperature, the operating temperature is lowered by reducing the output, and when the operating temperature becomes lower than the predetermined temperature, the output is returned to the rating. It is described that the control is performed.

  In Patent Document 3, the temperature of the power generation chamber is detected, a plurality of reference temperatures are set, a threshold value is provided for the temperature rise, and when the detected temperature exceeds the threshold value, the fuel cell module is It is described that it is determined that the fuel has deteriorated and control is performed to reduce the fuel flow rate and the rated output.

JP 2006-31989 JP 2007-273252 A JP 2011-103210 A

  By the way, in the fuel cell system, as a configuration for improving the energy utilization efficiency, a plurality of fuel cell stacks are provided, and unreacted fuel gas in the used fuel gas discharged from the previous fuel cell stack is replaced with the subsequent fuel cell stack. A multistage fuel cell system that is reused in a fuel cell stack is known.

  Multi-stage fuel cell systems are applied regardless of the type of fuel cell, and improvement of fuel utilization by multi-stage is being studied.

  As an example, high temperature operation type fuel cells (solid oxide fuel cells, molten carbonate fuel cells, etc.) are applied together with the fuel cell stacks at the front and rear stages. The solid oxide fuel cell (SOFC) may be either an oxide ion conductivity type or a pron conductivity type.

  As another example, a polymer electrolyte fuel cell or the like is applied only to the latter stage.

  Furthermore, if water vapor and carbon dioxide in the unreacted fuel gas can be removed between the front and rear fuel cell stacks, the concentration of hydrogen and carbon monoxide contributing to the reaction increases, and the recycled fuel gas is The performance of the used fuel cell stack can be improved.

  However, in the above fuel cell system, when determining the deterioration of the temperature of the fuel cell stack, if the conditions such as the power generation output (power generation load) change, the temperature change due to the change of the condition or the temperature change due to the deterioration of the fuel cell stack It is difficult to judge whether it is.

  Therefore, in the prior art including the Patent Document 2 and Patent Document 3, since deterioration is determined during power generation, the deterioration determination mode is set, and there is a problem that load tracking is impossible for several hours during the deterioration determination mode. .

  Further, the means for detecting deterioration during power generation cannot be detected at a time when the deterioration of the fuel cell stack is likely to proceed.

  An object of the present invention is to obtain a fuel cell system that can detect the deterioration of the fuel cell stack in advance in the power generation load following operation in consideration of the above facts.

  The present invention includes a vaporizer that vaporizes reformed water, a reformer that generates a fuel gas by reforming and reacting water vapor vaporized in the vaporizer and a raw material gas, and a first stage that receives the fuel gas from the reformer Fuel cell stack and a multi-stage power generation processing unit equipped with a subsequent fuel cell stack that generates power by receiving unreacted fuel gas after chemical reaction in the fuel cell stack provided in the previous stage, and fuel located in the second and subsequent stages An open circuit voltage detecting means for detecting an open circuit voltage of a cell constituting the battery stack or the fuel cell stack; an open circuit voltage detected by the open circuit voltage detecting means, which is executed before and after the generation load follow-up operation; and a reference A fuel cell system comprising: a determination means for comparing the voltage with each other to determine whether the operating state of the fuel cell stack positioned upstream of the fuel cell stack to be detected as an open circuit voltage is good or bad It is.

  According to the present invention, in the determination means, the open circuit voltage of the cells constituting the fuel cell stack located in the second and subsequent stages is detected by the open circuit voltage detection means before and after the power generation load following operation. The open circuit voltage detected by the open circuit voltage detection means is compared with the reference voltage to determine whether the operating state of the fuel cell stack positioned upstream of the fuel cell stack that is the detection target of the open circuit voltage is good or bad. .

  The generation load follow-up operation is, for example, a period after the temperature rising process of the fuel cell system and the generation load follow-up operation is started, and the after power generation load follow-up operation is, for example, the generation load follow-up operation. This is a period until the temperature lowering process of the fuel cell system.

  Therefore, the quality of the fuel cell stack can be determined before and after the power generation load following operation.

  If it is before the power generation load following operation, the deterioration of the fuel cell stack can be detected in advance at the time of the power generation load following operation immediately after. Further, after the power generation load following operation, it is possible to detect the deterioration of the fuel cell stack in advance in the next power generation load following operation.

  In the present invention, the power generation processing of the multi-stage power generation processing unit is forcibly stopped when the determination unit determines a failure.

  The defect determination is a function deterioration of the fuel cell stack, and power generation itself may be possible. However, since it is not suitable for power generation with load fluctuations, it is determined that the functional degradation is a failure, and the power generation processing of the multistage power generation processing unit is immediately stopped.

  Thereby, for example, it is possible to avoid the worst situation that the load follow-up is interrupted until the deterioration is found and repaired.

  In the present invention, when supplying the unreacted fuel gas to the subsequent fuel cell stack, a fuel regeneration device for regenerating the fuel gas by removing at least one of carbon dioxide and water vapor, and the unreacted fuel gas And a switching means that is provided in a pipe line through which the fuel regeneration device can be switched between an applied state and a non-applied state, and in the state where the fuel regeneration device is applied, the determination means Is determined to be defective, the switching means is controlled to place the fuel regeneration device in a non-applied state, and the determination by the determination means is executed again.

  If the determination unit determines that the fuel regeneration device is being applied, the switching unit is controlled so that the fuel regeneration device is not applied, and the determination by the determination unit is executed again. For example, a solenoid valve (electromagnetic valve) or the like that can open and close the valve body by electrical control is applicable as the switching means. However, manual switching operations (such as opening and closing the valve body) are included in the category of control.

  Thereby, it is possible to specify whether the cause of the failure determination is the previous fuel cell stack or the fuel regeneration device.

  In the present invention, the reference value is a fixed value.

  If the reference voltage is a fixed value, it is possible to determine the quality of the open circuit voltage as an absolute amount.

  In the present invention, the reference value is an updated value of the latest open circuit voltage that has been determined to be good by the determination means.

  If the reference voltage is an updated value, whether the open circuit voltage is good or not can be determined as the rate of change (or amount of change) from the previous time. Of course, it is assumed that the previous determination is normal.

  As described above, the present invention has an excellent effect that the deterioration of the fuel cell stack can be detected in advance during the power generation load following operation.

It is a schematic block diagram of the fuel cell system which concerns on 1st Embodiment, (A) is a valve position of the application state (default) of a fuel regeneration apparatus, (B) is a valve position of the non-application state of a fuel regeneration apparatus. Show. It is a functional block diagram for SOFC stack soundness confirmation mode control performed in the control part which concerns on 1st Embodiment. It is a flowchart which shows the SOFC stack soundness confirmation mode control routine which concerns on 1st Embodiment. It is a flowchart which shows the SOFC stack soundness confirmation mode control routine which concerns on the modification (modification 1) of 1st Embodiment. It is a schematic block diagram of the fuel cell system which concerns on 2nd Embodiment. It is a flowchart which shows the SOFC stack soundness confirmation mode control routine which concerns on 2nd Embodiment. It is a flowchart which shows the SOFC stack soundness confirmation mode control routine which concerns on the modification (modification 2) of 2nd Embodiment.

  (First embodiment)

  The configuration of the fuel cell system 10 according to the first embodiment will be described together with the functions of the respective parts with reference to FIG.

  The fuel cell system 10 includes a carburetor 12, a reformer 14, a combustor 15, a first fuel cell stack 16, a second fuel cell stack 18, a fuel regeneration device 20, and a control unit 22 as main components. Yes.

  The first fuel cell stack 16 is a solid oxide fuel cell stack, and has a plurality of stacked fuel cells. The first fuel cell stack 16 may be composed of a plurality of stack modules that receive fuel gas and air under the same conditions. The first fuel cell stack 16 is not limited to the solid oxide form.

  The second fuel cell stack 18 is a solid oxide fuel cell stack, and has a plurality of stacked fuel cells. The second fuel cell stack 18 may be composed of a plurality of stack modules that receive fuel gas and air under the same conditions. The second fuel cell stack 18 is not limited to the solid oxide form.

  That is, the fuel cell system 10 according to the first embodiment is configured as a multi-stage fuel cell system 10 in which the fuel cell stack has two stages of the first fuel cell stack 16 and the second fuel cell stack 18. Yes. Note that the number of stages is not limited to two, and may be three or more.

  One end of the source gas pipe P1 is connected to the vaporizer 12, and the other end of the source gas pipe P1 is connected to a gas source (not shown). A gas (for example, methane) is sent from the gas source to the vaporizer 12 by the blower B. Further, the water supply pipe P <b> 2 is connected to the vaporizer 12, and reformed water (liquid phase) is sent to the vaporizer 12.

  In the first embodiment, methane is used as the source gas. However, the gas is not particularly limited as long as it can be reformed, and a hydrocarbon fuel can be used. Examples of the hydrocarbon fuel include natural gas, LP gas (liquefied petroleum gas), coal reformed gas, lower hydrocarbon gas, and the like.

  In the vaporizer 12, the supplied methane and water are mixed and heated, and the water is vaporized to become water vapor.

  Methane and water vapor are sent from the vaporizer 12 to the reformer 14 via the pipe P3. In the reformer 14, a fuel gas containing hydrogen is generated by a reforming reaction dependent on heating by the combustor 15. The fuel gas is supplied to the anode 16A of the first fuel cell stack 16 through the fuel gas pipe P4.

  For example, the oxidizing gas is supplied to the cathode 16B of the first fuel cell stack 16 from a pipe P5 via the fuel regeneration device 20. Thereby, in the first fuel cell stack 16, heat is generated by a chemical reaction, and electric power is generated. With this power generation, the anode off gas is discharged from the anode 16A of the fuel cell stack 16 to the fuel regeneration device 20 through the anode off gas pipe P6. Further, the cathode off gas is discharged from the cathode 16B, and the cathode off gas is supplied to the cathode 18B of the second fuel cell stack 18 through the cathode off gas pipe P7.

  From the anode off gas discharged from the anode 16A, the regenerated fuel gas is generated by the fuel regeneration device 20, and is supplied to the anode 18A of the second fuel cell stack 18 through the regenerated fuel gas pipe P8. In the second fuel cell stack 18, power generation is performed by a chemical reaction.

  Although details are omitted, the fuel regeneration device 20 has a function of separating at least one of carbon dioxide and water vapor from the anode off gas. As an example, the fuel regeneration device 20 includes a plurality of heat exchange units and separation units, and includes a regenerated fuel. When the gas is generated, processing such as heat exchange with air (oxidizing gas) supplied from the air supply unit is performed.

  Spent gas at the anode 18A and the cathode 18B is sent to the combustor 15 through the pipe P9 and the cathode off combustion introduction pipe P10, and is used for combustion in the combustor 15.

  The combustion exhaust gas from the combustor 15 is used as a heat source for evaporating the reformed water in the vaporizer 12 through, for example, a heat exchange unit (not shown).

  The multi-stage fuel cell system 10 according to the first embodiment shifts to load following operation after preparation for start-up (start-up process) for generating power is executed when a start instruction is issued.

  The load following operation is an operation for controlling the power generation amount according to the power consumption of the load.

  Here, if the fuel cell stacks 16 and 18 are deteriorated before generating the multistage fuel cell system 10 and performing the load following operation, the generated power may not follow the power consumption of the load. .

  Therefore, in the first embodiment, the multi-stage fuel cell system 10 is started and the operational state, that is, the soundness of the fuel cell stack is confirmed before shifting to the power generation load following state.

  Specifically, by detecting an electromotive force “OCV“ Open Circuit Voltage ”, which is an open circuit voltage of any cell of a multi-stage fuel cell stack, a fuel cell upstream (previous stage) from the detection position Check stack health. That is, in the first embodiment, since the fuel cell stacks 16 and 18 are provided in two stages, the OCV detection unit 36 is installed in the cell of the fuel cell stack 18 to detect the OCV of the cell, and the fuel cell The soundness of the stack 16 is confirmed (normal / abnormal determination).

  In a multistage fuel cell system, when a multistage fuel cell stack deteriorates, it is particularly important to detect the deterioration of the previous fuel cell stack (see the following reasons 1 to 3).

  (Reason 1) If the composition and flow rate of the anode / cathode gas supplied to the subsequent fuel cell stack fluctuate and power generation is performed in this state, the subsequent fuel cell stack is also likely to deteriorate.

  (Reason 2) The front fuel cell stack is more affected by pressure fluctuation due to water vaporization and pressure fluctuation due to pump pulsation than the fuel cell stack at the rear stage.

  (Reason 3) For example, a fuel cell stack of a fuel cell system capable of internal reforming is particularly likely to deteriorate in the preceding fuel cell stack.

  In the first embodiment, “deterioration” includes functional degradation, but actually, in view of the situation where power generation cannot follow the load, it is paraphrased as “failure”, which is the worst state of functional degradation. May be. Hereinafter, deterioration and failure are collectively referred to as “abnormal”.

  The OCV reference value (no leak) of the cells of the fuel cell stack 18 is known (as an example, 1.06 V), and this known reference value (if the reference value has a width, its lower limit level) is It is possible to determine whether it is normal or abnormal by storing the reference value at the OCV detection time and comparing it with the OCV detection value. Since the upper limit level of the reference value is not assumed to increase when the OCV is abnormal, the lower limit level of the reference value may be set. The setting of the upper limit level is not denied, and the reference value may be determined as a predetermined range.

  As an example of an abnormality, the fuel gas is methane (CH4), S / C = 2.5, the fuel cell stack temperature = 700 ° C., 50% of the fuel gas leaks from the inside of the cell, and the equivalent air is the anode. Assuming that the fuel regenerator 20 flows into the 18A side and is in an equilibrium state, when the carbon dioxide is removed by 50% and the water is removed by 80%, the abnormal value (with leakage) is 0.96V. Therefore, the state (normal or abnormal) of the fuel cell stack 16 can be confirmed by monitoring the OCV.

  By the way, since the multistage fuel cell system 10 of the first embodiment includes the fuel regeneration device 20, when the detected value of the OCV of the cell of the fuel cell stack 18 shows an abnormal value, In some cases, it cannot be determined that the fuel cell stack 16 has leaked.

  That is, an abnormality may occur due to a malfunction in the fuel regeneration device 20. Therefore, a bypass pipe P11 that short-passes the fuel regeneration device 20 interposed between the fuel cell stack 16 and the fuel cell stack 18 is provided, and the fuel regeneration device 20 is applied or not applied by valve switching control. Can be set.

  That is, as shown in FIG. 1, a bypass pipe that directly connects the anode off-gas pipe P6 and the regenerated fuel gas pipe P8 between the anode off-gas pipe P6 and the regenerated fuel gas pipe P8 without using the fuel regenerator 20. P11 is provided. A short pass valve 24 is interposed in the middle of the bypass pipe P11.

  In addition, a communication valve 26A is interposed on the fuel regeneration device 20 side of the anode offgas pipe P6 with respect to the connection portion with the bypass pipe P11. Further, a communication valve 26B is interposed on the fuel regeneration device 20 side from the connection portion of the regeneration fuel gas pipe P8 with the bypass pipe P11.

  Here, as shown in FIG. 1A, when the fuel regeneration device 20 is applied, the short pass valve 24 is closed and the communication valves 26A and 26B are opened. A state where the fuel regeneration device 20 is applied and a default state are set.

  On the other hand, as shown in FIG. 1B, when the fuel regeneration device 20 is not applied, the short pass valve 24 is opened and the communication valves 26A and 26B are closed.

  FIG. 2 is a functional block diagram specialized in confirmation mode control for the soundness of the fuel cell stack, which is executed in the control unit 22 according to the first embodiment. The blocks in FIG. 2 do not limit the hardware configuration of the control unit 22. For example, the control unit 22 includes a microcomputer having a CPU, a RAM, a ROM, an input / output port (I / O), and a bus such as a data bus and a control bus for connecting them as a hardware configuration. The soundness of the fuel cell stack executed by the CPU may be performed by the confirmation mode control program.

  The activation instruction receiving unit 28 receives an activation instruction for the multistage fuel cell system 10. The start instruction receiving unit 28 is connected to the valve operation control unit 30, and based on the start instruction, each valve (the short pass valve 24 and the communication valves 26A and 26B) is set to a default state (application state of the fuel regeneration device 20). To do. In the first embodiment, the application of the fuel regeneration device 20 is the default state, the short pass valve 24 is closed, and the communication valves 26A and 26B are open (see FIG. 1A).

  Further, when the valve operation control unit 30 receives a notification of abnormality determination under the default state from the determination unit 42 described later during the temperature rise immediately after the start instruction, the valve regeneration control unit 20 applies each valve to the non-application of the fuel regeneration device 20. State. That is, the short pass valve 24 is opened, and the communication valves 26A and 26B are closed (see FIG. 1B).

  The valve operation control unit 30 is connected to the activation execution unit 32, and notifies the activation execution instruction after the operation control of each valve.

  More specifically, the temperature raising process is executed after the start instruction. During this temperature raising process, the fuel regeneration device 20 is not applied, and after the temperature raising is sufficiently performed, the fuel regeneration device 20 is applied. State. This is to improve the temperature raising speed, and the valve operation control unit 30 controls the SHOPASS valve 24 and the communication valves 26A and 26B in synchronization with this temperature raising process, so that FIG. The temperature is raised in the state, and the state is shifted to the state shown in FIG.

  When the activation execution unit 32 receives the activation execution notification, the OCV detection unit 36 detects the post-stage fuel cell stack (that is, in the first embodiment, after the temperature increase is completed). An instruction is given to capture the OCV (VAocv, VBocv) of the cells of the fuel cell stack 18).

  The detection value VAocv is a voltage when the fuel regeneration device 20 is applied (default), and the detection value VBocv is a voltage when the fuel regeneration device 20 is not applied.

  The OCV capturing unit 34 is connected to the comparison unit 38. The comparison unit 38 is connected to the reference value memory 40.

  Therefore, the comparison unit 38 compares the OCV (VAocv, VBocv) of the cells of the fuel cell stack 18 taken in by the OCV taking-in unit 34 with the reference value.

  At the time of this comparison, the reference value memory 40 reads the reference value VSa when the fuel regeneration device 20 is applied (default time), and reads the reference value VSb when the fuel regeneration device 20 is not applied. The reference value VSb is set to a value slightly lower than the reference value VSa (VSb <VSa).

  The comparison result in the comparison unit 38 is sent to the determination unit 42.

  If the determination result in the determination unit 42 is determined to be abnormal by comparing the VAocv and the reference value VSa, the valve operation control unit 30 is instructed to perform valve switching control so that the fuel regeneration device 20 is not applied. To do. That is, the short pass valve 24 is opened, and the communication valves 26A and 26B are closed (see FIG. 1B).

  When the determination result in the determination unit 42 is determined to be normal by comparing the VAocv and the reference value VSa, and when it is determined to be normal or abnormal by comparing the VBocv and the reference value VSb, the processing selection unit 44 Notify normal or abnormal.

  When receiving a normal notification, the process selection unit 44 outputs an execution instruction to the normal processing unit 46 and shifts to load follow-up operation. When receiving the abnormality notification, the process selection unit 44 outputs an execution instruction to the abnormality processing unit 48. Then, abnormality notification and operation stop processing are executed.

  Note that the above-described determination process is executed after the temperature rise and before power generation.

  The operation of the first embodiment will be described below.

  (Power generation operation of multi-stage fuel cell stack)

  In the fuel cell system according to the first embodiment, first, methane is supplied from a gas source and water is supplied to the vaporizer 12 for the first fuel cell stack as the first stage. The supplied methane and water are mixed and heated by obtaining heat from the combustion exhaust gas, and the water is vaporized to become steam.

  Methane and water vapor are sent from the vaporizer 12 to the reformer 14. In the reformer 14, a fuel gas containing hydrogen is generated by the reforming reaction. The fuel gas is supplied to the anode 16 </ b> A of the first fuel cell stack 16. An oxidizing gas is supplied to the cathode 16B of the first fuel cell stack 16. Thereby, in the 1st fuel cell stack 16, electric power generation is performed by a chemical reaction.

  Along with this power generation, anode off-gas is discharged from the anode 16A of the fuel cell stack 16. Further, the cathode off gas is discharged from the cathode 16B, and the cathode off gas is supplied to the cathode 18B of the second fuel cell stack 18.

  From the anode off-gas discharged from the anode 16 </ b> A, a regenerated fuel gas is generated by the fuel regeneration device 20 and supplied to the anode 18 </ b> A of the second fuel cell stack 18. In the second fuel cell stack 18, power generation is performed by a chemical reaction.

  (Checking the soundness of the fuel cell stack)

  If the fuel cell stacks 16 and 18 are deteriorated before generating the multistage fuel cell system 10 and performing the load following operation, the power generation may not be able to follow the load. Therefore, in the first embodiment, the multi-stage fuel cell system 10 is started and the operational state, that is, the soundness of the fuel cell stack is confirmed before shifting to the power generation load following state.

  FIG. 3 is a flowchart showing a soundness confirmation mode control routine of the fuel cell stack according to the first embodiment.

  In step 100, it is determined whether or not an activation instruction has been issued. If a negative determination is made, this routine ends. If an affirmative determination is made in step 100, the routine proceeds to step 101 where valve control is executed.

  In step 101, valve control is executed so that the fuel regeneration device 20 is not applied. That is, in this step 114, the short pass valve 24 is opened and the communication valves 26A and 26B are closed (see FIG. 1B).

  In the next step 102, the temperature raising process is executed. When the temperature raising process in step 102 is completed, the routine proceeds to step 103.

  In step 103, the short pass valve 24 is closed and the communication valves 26A, 26B are opened (see FIG. 1 (A)) in a default state (the fuel regeneration device 20 is applied).

  In the next step 104, an activation process is executed, and the process proceeds to step 106. For example, supply of raw material gas and reforming water.

  In step 106, the OCV (VAocv) of the fuel cell stack 18 at the subsequent stage is detected, and then the routine proceeds to step 108 where the reference value OCV (VSa) in the application state (with regeneration) of the fuel regeneration device 20 is read out. 110.

  In step 110, the OCV detection value VAocv is compared with the OCV reference value VSa. As a result of the comparison in step 110, if it is determined that VAocv ≧ VSa, it is determined that the operation is normal, the process proceeds to step 112, SOFC power generation is started, and then the process proceeds to step 113. In step 113, the routine proceeds to SOFC power generation load following operation processing, and this routine ends.

  On the other hand, if it is determined that VAocv <VSa as a result of the comparison in step 110, it is determined that there is an abnormality, and the process proceeds to step 114.

  The abnormality determination in this step 110 is not limited to the leak of the fuel cell stack 16 in the previous stage, but may be caused by the fuel regeneration device 20. Therefore, in step 114, valve control is executed so that the fuel regeneration device 20 is not applied. That is, in this step 114, the short pass valve 24 is opened and the communication valves 26A and 26B are closed (see FIG. 1B).

  In the next step 116, the OCV (VBocv) of the subsequent fuel cell stack 18 is detected, and then the routine proceeds to step 118, where the OCV reference value (VSb) in the non-applied state (no regeneration) of the fuel regeneration device 20 is obtained. Read and move to step 120.

  In step 120, the OCV detection value VBocv is compared with the OCV reference value VSb. If it is determined as a result of the comparison in step 120 that VBocv ≧ VSb, it is determined that the operation is normal, the process proceeds to step 112, and the process proceeds to the SOFC power generation load follow-up operation process with the fuel regeneration device 20 disconnected. Then, this routine ends. Here, the process is shifted to the load follow-up operation process in a state where the fuel regeneration device 20 is disconnected. However, it is desirable to notify some warning that prompts the inspection of the fuel regeneration device 20. Further, it is determined whether or not there is a margin that can be delayed in the shift to the load operation process. If there is a margin, the shift to the load operation process is delayed and the maintenance of the regenerative fuel device 20 is performed. May be.

  As a result of the comparison in step 120, if it is determined that VBocv <VSb, it is determined that the fuel cell stack 16 in the previous stage is abnormal, and the process proceeds to step 122 to notify the abnormality.

  In the next step 124, the activation of the SOFC is stopped, and this routine ends.

  As described above, in the present embodiment, the state (normal or abnormal) of the fuel cell stack 16 in the preceding stage is detected by detecting the OCV of the cells in the fuel cell stack 18 in the subsequent stage and comparing it with a known reference value in advance. Can be judged. For this reason, it is possible to detect an abnormality caused by the activation in which the deterioration of the fuel cell stack is likely to proceed before the activation.

  (Modification 1)

  In the first embodiment, the reference value is set as a fixed value, but the soundness of the previous fuel cell stack may be set as a comparison value as a detection value by the OCV detection unit 36 in the confirmation mode control. In this case, a reference value update unit 39 is added to the post-stage fuel cell stack OCV capturing unit 34, as indicated by the dotted line block in FIG. The reference value update unit 39 is connected to the reference value memory 40, and the detection value obtained by the OCV detection unit 36 that is taken in by the post-stage fuel cell stack OCV taking unit 34 is stored in the reference value memory 40. Each of them is updated and stored as VSa and VSb.

  FIG. 4 is a flowchart showing a fuel cell stack soundness confirmation mode control routine according to the first modification. In the flowchart of FIG. 4, the same steps as those in the flowchart of FIG. 3 described above are denoted by “A” at the end of the same step numbers, and description thereof is omitted.

  In this modified example 1, as shown in FIG. 4, in step 110A, the OCV detection value VAocv is compared with the OCV reference value VSa, and if normality is determined (VAocv ≧ VSa), in step 111, the reference value VSa is updated to the current detection value VAocv (VSa ← VAocv), the process proceeds to step 112A, SOFC power generation is started, and then the process proceeds to step 113A. In step 113A, the routine proceeds to SOFC power generation load follow-up operation processing, and this routine ends.

  In the first modification, as shown in FIG. 4, in step 120A, the OCV detection value VBocv is compared with the OCV reference value VSb, and when normality is determined (VBocv ≧ VSb), in step 121, The reference value VSb is updated to the current detection value VBocv (VSb ← VBocv), the process proceeds to step 112A, the process proceeds to the SOFC power generation load follow-up operation process, and this routine ends.

  (Second Embodiment)

  The second embodiment of the present invention will be described below. In addition, about the same component as 1st Embodiment, the same code | symbol is attached | subjected and description of the structure is abbreviate | omitted.

  The feature of the second embodiment is a configuration in which the fuel regeneration device 20 (see FIG. 1) mounted in the first embodiment does not exist. That is, as shown in FIG. 5, a pipe P <b> 12 is provided in which the anode off gas is directly supplied as the regenerated fuel gas to the anode 18 </ b> A of the fuel cell stack 18.

  In other words, the pipe P12 has a structure in which the anode off-gas pipe P6, the bypass pipe P11, and the regenerated fuel gas pipe P8 of FIG. 1 are connected in series with a single pipe.

  In the fuel cell system 10A of the second embodiment, it is determined that the OCV abnormal value of the cells in the subsequent fuel cell stack 18 is caused by the abnormality in the previous fuel cell stack 16.

  The operation of the second embodiment will be described below with reference to the flowchart of FIG.

  In step 150, it is determined whether an activation instruction has been issued. If a negative determination is made, this routine ends. Further, when an affirmative determination is made at step 150, the routine proceeds to step 151, where the temperature raising process is executed, and the routine proceeds to step 152. In step 152, an activation process is executed, and the process proceeds to step 154.

  In step 154, the OCV (Vocv) of the subsequent fuel cell stack 18 is detected, and then the process proceeds to step 156 to read the reference value OCV (VS) in the application state (with regeneration) of the fuel regeneration device 20, and step Move to 158.

  In step 158, the OCV detection value Vocv is compared with the OCV reference value VS. As a result of the comparison in step 158, when it is determined that Vocv ≧ VS, it is determined that the operation is normal, the process proceeds to step 160, power generation of SOFC is started, and then the process proceeds to step 161. In step 161, the routine proceeds to SOFC power generation load follow-up operation processing, and this routine ends.

  As a result of the comparison in step 158, if it is determined that Vocv <VS, it is determined that there is an abnormality, and the process proceeds to step 162 to notify the abnormality.

  In the next step 164, the activation of the SOFC is stopped, and this routine ends.

  (Modification 2)

  In the second embodiment, the reference value is a fixed value, but the soundness of the previous fuel cell stack may be used as a comparison value as a detection value by the OCV detection unit 36 in the confirmation mode control.

  FIG. 7 is a flowchart showing a fuel cell stack soundness confirmation mode control routine according to the second modification. In the flowchart of FIG. 7, the same steps as those in the flowchart of FIG. 6 are denoted by “A” at the end of the same step number, and the description thereof is omitted.

  In the second modification, as shown in FIG. 7, in step 158A, the OCV detection value Vocv is compared with the OCV reference value VS. VS is updated to the current detection value Vocv (VS ← Vocv), the process proceeds to step 160A, SOFC power generation is started, and then the process proceeds to step 161A. In step 161A, the routine proceeds to SOFC power generation load follow-up operation processing, and this routine ends.

  In the first embodiment and the second embodiment (including each of Modification 1 and Modification 2), the fuel cell stack is a two-stage system, and the fuel cell stack 18 at the rear stage is used as the fuel at the front stage. The state of the battery stack 16 is discriminated. However, in the case of a multi-stage fuel cell stack of three or more stages, it is placed in any of the fuel cell stacks on the upper (upstream) side of the fuel cell stack that detects the OCV of the cell. Since it is determined that an abnormality has occurred, the OCV detection unit 36 may be installed for each fuel cell stack in each stage after the second stage.

  Further, in the first embodiment and the second embodiment (including the respective modifications 1 and 2), the open circuit voltage (OCV) of any cell of the fuel cell stack that is multi-stage is set. Although detected, the open circuit voltage (OCV) of the fuel cell stack 18 and the fuel cell stack at a later stage may be detected.

  Furthermore, in the first embodiment and the second embodiment (including the respective modifications 1 and 2), the open circuit voltage is detected after the start and before the power generation load operation. You may make it detect an open circuit voltage after a stop. In other words, the process may be executed in the order of power generation stop → recognizing the subsequent stack voltage and determining failure → temperature decreasing process.

B Blower P1 Raw material gas pipe P2 Water supply pipe P3 Pipe P4 Fuel gas pipe P5 Pipe P6 Anode offgas pipe P7 Cathode offgas pipe P8 Regenerated fuel gas pipe P9 Pipe P10 Cathode off combustion introduction pipe P11 Bypass pipe 10 Fuel cell system 12 Vaporizer ( Multistage power generation processing unit)
14 Reformer (Multi-stage power generation processing unit)
15 Combustor (Multi-stage power generation processing unit)
16 First fuel cell stack (multi-stage power generation processing unit)
16A Anode 16B Cathode 18 Second fuel cell stack (multistage power generation processing unit)
18A Anode 18B Cathode 20 Fuel regeneration device 22 Control unit (determination means)
24 short pass valve 26A, 26B communication valve 28 activation instruction receiving unit 30 valve operation control unit 32 activation execution unit 34 OCV taking-in unit 36 OCV detection unit (voltage detection means)
38 Comparison Unit 40 Reference Value Memory 42 Judgment Unit 44 Process Selection Unit 46 Normal Processing Unit

Claims (5)

A vaporizer that vaporizes reformed water, a reformer that generates a fuel gas by reforming the steam vaporized by the vaporizer and a raw material gas, and a first-stage fuel cell stack that receives the fuel gas from the reformer And a multi-stage power generation processing unit including a subsequent fuel cell stack that generates power by receiving unreacted fuel gas after chemical reaction in the fuel cell stack provided in the previous stage, and
An open circuit voltage detecting means for detecting an open circuit voltage of a fuel cell stack positioned after the second stage, or cells constituting the fuel cell stack;
A fuel cell that is executed before and after the power generation load follow-up operation and that is positioned upstream of the fuel cell stack that is the detection target of the open circuit voltage by comparing the open circuit voltage detected by the open circuit voltage detection means with a reference voltage Determining means for determining whether the operating state of the stack is good or bad;
A fuel cell system.   2. The fuel cell system according to claim 1, wherein when the determination unit determines a failure, the power generation processing of the multistage power generation processing unit is forcibly stopped. A fuel regenerator that regenerates the fuel gas by removing at least one of carbon dioxide and water vapor when supplying the unreacted fuel gas to the subsequent fuel cell stack;
Switching means provided in a pipeline through which the unreacted fuel gas flows, and capable of switching the fuel regeneration device to either an applied state or a non-applied state;
When the determination unit determines that the fuel regeneration device is applied, the switching unit is controlled so that the fuel regeneration device is not applied, and the determination by the determination unit is executed again. The fuel cell system according to claim 1 or 2, wherein   The fuel cell system according to any one of claims 1 to 3, wherein the reference voltage is a fixed value.   4. The fuel cell system according to claim 1, wherein the reference voltage is an updated value of a latest open circuit voltage that is determined to be good by the determination unit. 5.