JP2010135287A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system in which the amount of gas flowing into a fuel gas flow passage in a fuel cell is reduced by more than conventionally, when a gas flowing into a combustor is processed, after the supply of a reaction gas to a hydrogen generating device is stopped. <P>SOLUTION: The fuel cell system is equipped with a first route through which a gas delivered by the hydrogen generating device 1 is supplied to the combustor 2 via the fuel cell 4; a second route through which the gas delivered by the hydrogen generating device 1 bypasses the fuel cell 4 and is supplied to the combustor 2; a first valve to communicate and cut-off between the first routes; a second valve to communicate and cut-off between the second routes; and a controller 17. In the fuel cell system, communication among the first routes is carried out by the first valve, and power generation operation is executed in a state of cutting-off the second route by the second valve. The controller 17 is constituted so that combustion treatment or dilution treatment of gas flowing into the combustor, after stopping the supply of reaction gas from a reaction gas feeding is executed, in a state of cutting-off the first route by the first valve, and communication conducted among the second routes by the second valve. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control technique for processing a combustible gas flowing into a combustor after stopping supply of a reaction gas to a hydrogen generator in a stop operation of a power generation operation in a fuel cell system.

  As a fuel cell system, a hydrogen generation device that generates a fuel gas mainly composed of hydrogen by reforming a raw material gas such as city gas, and electricity between the fuel gas supplied from the hydrogen generation device and oxygen in the air What is provided with the fuel cell which produces electric power by a chemical reaction is known.

  By the way, when stopping the power generation operation of the fuel cell system, the supply of the reaction gas necessary for the reforming reaction (for example, in the case of the steam reforming reaction, the raw material gas and the steam) is stopped as the stopping process. Here, for some time after the supply of the reaction gas is stopped, the steam reforming reaction proceeds due to the reaction gas remaining in the hydrogen generation apparatus due to the retained heat of the hydrogen generation apparatus or remains in the hydrogen generation apparatus. It is known that the gas in the hydrogen generator expands by the evaporation of water.

  Therefore, after stopping the supply of the reaction gas to the hydrogen generator, a fuel cell system that combusts a gas containing a combustible gas such as hydrogen or a raw material gas flowing into the combustor along with the volume expansion has been proposed for a while. Yes. Here, even after the supply of the reaction gas to the hydrogen generator is stopped, the gas sent from the hydrogen generator with the volume expansion is supplied to the fuel cell as in the power generation operation.

JP 2006-147264 A

  By the way, in the fuel cell system of patent document 1, although the gas sent from a hydrogen generator is combusted with the said volume expansion, since supply of the reactive gas to a hydrogen generator is stopped, a combustor The amount of combustible gas that flows into the combustion chamber (that is, the combustion amount of the combustor) is smaller than that during power generation operation. Furthermore, considering that the reforming reaction is an endothermic reaction, the reforming reaction that proceeds in the hydrogen generator after stopping the supply of the reaction gas proceeds at a lower temperature than during the power generation operation, so that it is difficult to generate hydrogen. Therefore, there is a possibility that a fuel gas richer in steam than in the power generation operation may be generated.

  Therefore, when the combustion process is performed in a state where the hydrogen generator and the fuel cell are communicated as in the conventional fuel cell system, the water-rich gas sent from the hydrogen generator is a fuel gas flow path in the fuel cell. Flow into. Then, during the stop period of the fuel cell system, the water vapor flowing into the fuel gas flow path in the fuel cell is condensed, and the fuel gas flow path is clogged (flooding), and stable during the next power generation operation. There is a possibility that the amount of power generation cannot be obtained.

The present invention has been made in view of the above problems, and when processing (combustion processing, dilution processing, etc.) the gas flowing into the combustor after the supply of the reactive gas to the hydrogen generator is stopped, An object of the present invention is to provide a fuel cell system in which the amount of gas flowing into the fuel gas flow path is reduced as compared with the prior art.

  The fuel cell system of the present invention includes a hydrogen generator that generates a fuel gas containing hydrogen by a reforming reaction using a raw material gas, a reaction gas supplier that supplies the hydrogen generator with a reactive gas, and the hydrogen generator A combustor that burns gas sent from the apparatus, a fuel cell that generates electricity using the fuel gas sent from the hydrogen generator, and a gas sent from the hydrogen generator passes through the fuel cell. The first path supplied to the combustor, the gas sent from the hydrogen generator bypasses the fuel cell, and communicates with the second path supplied to the combustor and the first path. A first valve for shutting off / blocking, a second valve for communicating / blocking the second path, and a controller, the first valve communicating with the first path, and the second valve serving as the second path. The power generation operation is performed with the In the fuel cell system, the controller shuts off the first path by the first valve and communicates the second path by the second valve, and the reaction gas from the reaction gas supply unit. After the supply of gas is stopped, the combustion process or dilution process of the gas flowing into the combustor is executed.

  According to the present invention, when the gas flowing into the combustor with the volume expansion of the gas in the hydrogen generator after the supply of the reactive gas to the hydrogen generator is processed (combustion process, dilution process, etc.) The amount of gas containing more water vapor into the fuel gas flow path in the fuel cell is reduced than before. Therefore, the possibility that flooding occurs in the fuel gas flow path in the fuel cell during the next power generation operation and the power generation amount decreases is reduced.

The schematic diagram which shows the structure of the fuel cell system concerning embodiment of this invention. The flowchart which shows the combustion process after the supply of the reactive gas to the hydrogen generator in the stop process of the power generation operation of the fuel cell system according to Embodiment 1 of the present invention is stopped. The flowchart which shows the dilution process after the supply of the reactive gas to the hydrogen generator in the stop process of the power generation operation of the fuel cell system according to the second embodiment of the present invention.

  The fuel cell system of the present invention will be described below.

  The fuel cell system of the present invention includes a hydrogen generator that generates a fuel gas containing hydrogen by a reforming reaction using a raw material gas, a reaction gas supplier that supplies the hydrogen generator with a reactive gas, and a hydrogen generator. A combustor that burns the supplied gas, a fuel cell that generates power using the fuel gas delivered from the hydrogen generator, and a gas that is delivered from the hydrogen generator are supplied to the combustor via the fuel cell. The first path, the gas sent from the hydrogen generator bypasses the fuel cell, is supplied to the combustor, the first valve communicates / blocks the first path, and the second path A fuel cell system comprising: a second valve for communicating / blocking the valve; and a controller, wherein the first valve communicates with the first path and the second valve blocks the second path. And the controller controls the first valve by the first valve. And the combustion process or the dilution process of the gas flowing into the combustor after the supply of the reaction gas from the reaction gas supplier is stopped in a state where the second valve communicates with the second valve. It is characterized by.

  As a result, the fuel gas in the fuel cell is processed when the gas flowing into the combustor (combustion process, dilution process, etc.) due to the volume expansion of the gas in the hydrogen generator after the supply of the reaction gas to the hydrogen generator is stopped. The amount of inflow of gas containing more water vapor than in the power generation operation in the flow path is suppressed as compared with the conventional case. Therefore, the possibility that flooding occurs in the fuel gas flow path in the fuel cell during the next power generation operation and the power generation amount decreases is reduced.

  Here, the “reforming reaction” includes any of steam reforming reaction, autothermal reaction, and partial reforming reaction.

  Here, the “reaction gas supply device” corresponds to the raw material gas supply device and the water supply device in the case of the steam reforming reaction, and in the case of the autothermal reaction, the raw material gas supply device, the water supply device and the air supply device. This corresponds to this, and in the case of a partial oxidation reaction, a raw material gas supply device and an air supply device correspond to this.

  In addition, the “combustor that burns the gas sent from the hydrogen generator” does not mean that the gas sent from the hydrogen generator directly burns by bypassing the fuel cell. Thus, a mode in which the gas flowing into the combustor is burned is also included.

  Further, “after the supply of the reaction gas is stopped” refers to after all the supply of the reaction gas is stopped. For example, in the case of the steam reforming reaction, it corresponds after the supply of the raw material gas and water is stopped. In the case of the autothermal method, it corresponds after the supply of the raw material gas, water and air is stopped. It should be noted that the above fluids (source gas, water, air, etc.) do not have to be stopped at the same time, and their timing may be somewhat different. When the stop timing of each fluid comes and goes, it means after the supply of the reactive gas that is stopped last is stopped.

  In addition, the “dilution process” increases the operation amount of the combustion air supply unit that supplies combustion air to the combustor compared to the time of the power generation operation, and after the supply of the reaction gas to the hydrogen generation device is stopped, It is defined as a process for diluting a gas containing a combustible gas such as raw material gas or hydrogen flowing into the combustor with volume expansion. The operation amount after the increase is preferably controlled so that the power generation amount of the fuel cell is larger than the operation amount at the maximum output.

  In the fuel cell system of the present invention, in the stop operation of the power generation operation, the controller communicates the first path with the first valve and blocks the first path with the first valve from the state where the second path is blocked with the second valve. When switching to the state where the second path is communicated with the second valve, the first path is controlled after the first valve and the second valve are controlled and the first path and the second path are communicated together. A switching operation for shutting off and bringing the second path into communication is performed.

  This is because when the first path and the second valve are switched from the state in which the first path during power generation operation is communicated and the second path is blocked to the state in which the first path is blocked and the second path is communicated. When the control is performed so that the switching of the open / close state is performed at the same time, the second valve opens after the first valve and the second valve are simultaneously closed by the arrival timing of the control signal to the first valve and the second valve. There is. In such a case, when the first valve and the second valve are closed, the internal pressure rises due to the progress of the reforming reaction by the reaction gas remaining in the hydrogen generator or the evaporation of the residual water, and then the second valve When opened, when the gas suddenly flows into the combustor from the hydrogen generator and is being burned, the flame is blown out, and the gas containing combustible gas and carbon monoxide is discharged into the combustion exhaust gas path and the exhaust port. May be discharged to the outside of the fuel cell system. Further, when the dilution process is performed instead of the combustion process, there is a possibility that the dilution level of the gas containing the combustible gas or carbon monoxide is lowered and discharged to the outside of the fuel cell system.

  Here, after controlling the 1st valve and the 2nd valve as mentioned above, after passing through the state where the 1st course and the 2nd course were connected together, the 1st course cuts off and it makes the state where the 2nd course connected. By executing the switching operation, the transient internal pressure excess increase accompanying the volume expansion of the gas in the hydrogen generator is suppressed, and the gas flowing into the combustor during the switching operation is rapidly increased, and the combustion process and the dilution process are performed. The possibility of being exhausted outside the fuel cell system while being insufficient is reduced.

The fuel cell system of the present invention includes a raw material gas path through which raw material gas flows, a deodorizer that adsorbs odorous components contained in the raw material gas, and a third valve provided in a raw material gas path downstream of the deodorizer. And the controller closes the third valve before performing the switching operation.

  According to this configuration, in the power generation operation stop process, the third valve is closed before the switching operation of the first path and the second path. Therefore, the first valve and the second valve are simultaneously closed due to control failure, and the internal pressure is reduced. Even if it rises, the gas containing water vapor in the hydrogen generator is prevented from flowing back to the deodorizer.

  In the fuel cell system of the present invention, in the state where the first path and the second path are in communication with each other, the controller distributes the fuel gas during the next power generation operation by condensation of water vapor flowing into the fuel cell from the first path. The first route is blocked and the second route is in communication with a communication time threshold value that is not hindered.

  This is because the reforming reaction that proceeds after stopping the supply of the reaction gas has a lower conversion rate than during the power generation operation, so that a gas containing a large amount of water vapor is sent from the hydrogen generator, but like the fuel cell system of the present invention described above By restricting the communication time between the hydrogen generator and the fuel cell, it is possible to prevent the fuel gas from being blocked by the condensed water during the next power generation operation.

  The fuel cell system according to the present invention includes an igniter provided in a combustor, and the controller operates the igniter in a state where at least the first path and the second path are in communication with each other. .

  According to this configuration, the pressure loss of the path downstream of the hydrogen generator varies due to the change from the state in which only the first path communicates to the state in which the first path and the second path communicate, and the combustor Since the amount of inflowing gas tends to fluctuate, combustion stability is further improved by operating the igniter to suppress misfire.

(Embodiment 1)
The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

[Configuration of fuel cell system]
FIG. 1 is a schematic diagram showing a configuration of a fuel cell system according to an embodiment of the present invention.

The fuel cell system 100 of the present embodiment includes a hydrogen generator 1 having a reformer (not shown) that generates a fuel gas containing hydrogen from a reforming reaction using a raw material gas, and a hydrogen generator 1 A raw material gas supply device 10 for supplying a raw material gas, a raw material gas supply passage 21 through which a raw material gas supplied to the hydrogen generator 1 by the raw material gas supply device 10 flows, and a raw material gas supply passage 21 are provided in the raw material gas. A deodorizer 9 for removing odor components contained therein, a third valve 11 provided downstream of the deodorizer 9, and a water supply device 12 for supplying reformed water used for the steam reforming reaction to the hydrogen generator. A water supply path 22 through which reformed water supplied to an evaporator (not shown) provided in the hydrogen generator 1 by the water supplier 12 flows, and a combustible gas (hydrogen) sent from the hydrogen generator , Gas including raw material gas) Combustor 2, igniter 3 for igniting a gas containing a combustible gas flowing into combustor 2, combustion air supplier 13 for supplying combustion air to combustor 2, and misfire of the combustor From the misfire detector 18 to be detected, the flue gas path 23 through which the flue gas discharged from the combustor 2 flows, the fuel cell 4 that generates power using the fuel gas sent from the hydrogen generator 1, and the hydrogen generator 1 A fuel gas supply path 5 for supplying the supplied fuel gas to the combustor 2 via the fuel cell 4, a first valve 6 provided in the fuel gas supply path 5 for opening and closing the fuel gas path, and a fuel cell 4 is a bypass path 7 that is bypassed 4 and supplied to the combustor 2, a second valve 8 that opens and closes the bypass path, and an off-fuel gas that is discharged from the fuel cell 4 and flows to the combustor 2. Route 16 and off-fuel gas route 16 A fourth valve 14 to be closed, an oxidant gas supplier 15 for supplying an oxidant gas to the fuel cell 4, a controller 17, at least the hydrogen generator 1, the fuel cell 4, the raw material gas supplier 10, and a combustor. 2 and a housing 20 that houses the controller 17. Here, the “first path” includes the fuel gas supply path 5, the fuel gas flow path 4 a, and the off-fuel gas path 16. The “second path” includes a fuel gas path 5, a bypass path 7, and an off fuel gas path 16. In the fuel cell system of the present embodiment, a form in which a part of the first path is shared with the second path is adopted, but it may be configured as a separate path without being shared.

  In the fuel cell system 100 of the present embodiment, the hydrogen generator 1 is configured to generate the fuel gas by the steam reforming reaction. However, the fuel gas is generated by the autothermal reaction or the partial oxidation reaction. May be adopted. In this case, in the case of steam reforming, the combustor 2 is configured to supply heat to the hydrogen generation device, but is not configured to supply heat to the hydrogen generation device. It is comprised so that it may function as a combustion treatment device of gas containing combustible gas sent out.

  In addition, the hydrogen generator is configured to have a reformer (not shown), and in order to further reduce the concentration of carbon monoxide in the gas sent from the reformer downstream of the reformer, You may employ | adopt the form further provided with the transformation device which performs shift reaction, and the CO removal device which performs oxidation reaction.

[Operation of fuel cell system]
In the fuel cell system 100 of the present embodiment, during the power generation operation, the raw material gas and water are supplied to the hydrogen generator 1 by the raw material gas supply device 10 and the water supply device 12, and the fuel contains hydrogen by the steam reforming reaction. Gas is generated. The fuel gas sent from the hydrogen generator 1 is supplied to the fuel cell 4 through the fuel gas supply path 5, flows through the fuel gas path 4 a in the fuel cell 4, and is not used for the power generation reaction of the fuel cell 4. Off-fuel gas containing hydrogen is discharged from the fuel cell 4. The off-fuel gas flows through the off-fuel gas path 16 and is introduced into the combustor 2 where it is burned. The flue gas sent from the combustor 2 flows through the flue gas passage 23 and is discharged from the exhaust port at the downstream end to the outside of the fuel cell system 100 (housing 20).

  During the power generation operation, the hydrogen generator 1 generates a fuel gas having a high hydrogen concentration, so that the reformer (not shown) is maintained at a high temperature of about 700 ° C. by supplying heat from the combustor 2. . During the power generation operation, the first valve 6 and the fourth valve 14 are opened, and the second valve is closed.

  Next, the stop process of the fuel cell system will be described. FIG. 2 shows an example of a flow for performing a combustion process on a gas containing a combustible gas sent from the hydrogen generator after the supply of the reaction gas to the hydrogen generator is stopped in the stop process of the fuel cell system of the present invention. explain about. The combustion process will be described based on this flowchart.

  First, when a command to stop the power generation operation of the fuel cell system 100 is output from the controller 17, the operation of the igniter 3 is started (step S101). Next, the controller 17 stops the water supply device 12 and the raw material gas supply device 10, and stops the supply of water for steam reforming reaction (reformed water) and the raw material gas to the hydrogen generator 1. Further, the oxidant gas supply unit 15 is also stopped, and the supply of the oxidant gas to the fuel cell 4 is also stopped. Further, the third valve 11 is closed (step S102). On the other hand, the combustion air supply unit 13 performs an operation, and executes a combustion process of a gas containing a combustible gas that continuously flows into the combustor 2.

  Here, when the supply of the reaction gas (raw material gas, water vapor) to the hydrogen generator 1 is stopped in step S102, the amount of the gas including the combustible gas flowing into the combustor 2 is the residual reaction gas in the hydrogen generator 1. Only the volume expansion due to the progress of the reforming reaction and the evaporation of the residual water, which is lower than before the supply of the reaction gas is stopped, and the combustion stability of the combustor 2 is lowered. However, since the ignition operation is executed by the igniter 3 in the above step S101, even if a misfire occurs, the ignition is promptly re-ignited and the combustion stability is improved. In addition, the ignition operation is configured to be performed before the supply of the reactive gas to the hydrogen generator is stopped as in the present flow, but may be performed simultaneously with the supply of the reactive gas is stopped. It does not matter. However, it is more preferable to perform the ignition operation by the igniter 3 before stopping the supply of the reaction gas as in this flow, because it becomes possible to re-ignite against a misfire immediately after the stop of the supply of the reaction gas.

  Next, in a state where the first valve 6 and the fourth valve 14 are kept open, the controller 17 opens the second valve 8 so that the bypass path 7 is also communicated (step S103). By this step S103, “the first path is blocked by the first valve and the second path is communicated by the second valve” is entered. As a result, at least one of the first valve 6 and the fourth valve 14 and the second valve 8 are compared with the case where the closing of the first valve 6 and the fourth valve 14 and the opening of the second valve 8 are performed simultaneously. Are simultaneously closed (that is, the first path and the second path are simultaneously blocked). Accordingly, when the second valve 8 is opened after the internal pressure rises due to the progress of the reforming reaction by the reaction gas remaining in the hydrogen generator or the evaporation of residual water due to the simultaneous closing, the hydrogen generator is suddenly opened. The gas flows into the combustor, and the possibility that a combustible gas having a low dilution level or a gas containing carbon monoxide is discharged outside the fuel cell system is reduced. Further, the gas flowing into the combustor 2 is changed by changing the pressure loss in the downstream path of the hydrogen generator by changing the state in which only the first path is in communication to the state in which the first and second paths are in communication. Since the amount is likely to fluctuate, the combustibility of the combustor 2 becomes unstable. However, since the ignition operation of the igniter 3 is executed in this state, even if a misfire occurs, it is re-ignited promptly and combustion stability is improved.

  Next, after the state in which the first path and the second path are both communicated in step S103 is continued for the communication threshold time or longer, the first valve 6 and the fourth valve 8 are closed and the first path is blocked (step S104). ). Here, the communication time threshold is set as a time during which the flow of fuel gas is not hindered during the next power generation operation due to condensation of water vapor flowing into the fuel cell from the first path. In the above flow, both the first valve 6 and the fourth valve 8 are closed to shut off the first path, but either the first valve 6 or the fourth valve 8 is closed. May be. That is, “blocking the first path by the first valve” means that the valve provided on the first path may be closed as long as the first path can be blocked.

  Thereafter, it is determined whether misfire is detected by the misfire detector 18 and whether the duration of the ignition operation started in step S101 is equal to or greater than a predetermined ignition time threshold (step S105), and the misfire detector 18 detects misfire. Is detected, or when the duration of the ignition operation exceeds a predetermined ignition time threshold T1 (Yes in step S105), the ignition operation of the igniter 3 is stopped and the second valve 8 is closed. (Step 106). If no misfire is detected by the misfire detector 18 and the duration of the ignition operation started in step S101 is less than the predetermined ignition time threshold T1 (No in step S102), until Yes in step S102 The step S102 is repeatedly executed.

And after performing step S106, operation | movement of the combustion air supply device 13 is continued, and the gas inside the combustor 2 is scavenged (step S107: scavenging process). In this scavenging process, there is a possibility that combustible gas, carbon monoxide, etc. may remain in the combustor 2 immediately after executing step S106, so that these are diluted and discharged outside the fuel cell system. In addition, it is preferable to increase the operation amount of the combustion air supply device 13 as compared with the time of the combustion processing. For example, the amount of operation of the combustion air supply device in the scavenging process is preferably larger than the amount of operation during power generation operation, but the amount of power generated by the fuel cell is greater than the amount of operation during maximum output. Such control is more preferable from the viewpoint of improving the dilutability and shortening the scavenging time.

  Then, when the execution time of the scavenging process reaches or exceeds a predetermined scavenging time threshold necessary for scavenging, the operation of the combustion air supply device 13 is stopped (step S108), and a series of flows relating to the combustion process is completed.

  By performing the combustion process after stopping the supply of the reaction gas to the hydrogen generator as in the fuel cell system of the present embodiment described above, the fuel gas flow path in the fuel cell contains more water vapor than during power generation operation. The amount of gas flowing in is suppressed as compared with the prior art. Therefore, the possibility that flooding occurs in the fuel gas flow path in the fuel cell during the next power generation operation and the power generation amount decreases is reduced.

(Embodiment 2)
The fuel cell system according to Embodiment 2 of the present invention will be described below. The fuel cell system according to the present embodiment is substantially the same as the fuel cell system according to the first embodiment, but after the reaction gas supply to the hydrogen generator is stopped, the gas flowing into the combustor is diluted by the controller. However, this is a feature different from the first embodiment. The characteristic operation will be described in detail below.

[Operation of fuel cell system]
FIG. 3 shows an example of a flow for diluting a gas containing a combustible gas sent from the hydrogen generator after the supply of the reaction gas to the hydrogen generator is stopped in the stop process of the fuel cell system of the present invention. The dilution process will be described based on this flowchart.

  First, when a command for stopping the power generation operation of the fuel cell system 100 is output from the controller 17, the operation amount of the combustion air supply device 13 is increased more than the operation amount during the power generation operation (step S101). Next, the controller 17 stops the water supply device 12 and the raw material gas supply device 10, and stops the supply of the reforming water and the raw material gas to the hydrogen generator 1. Further, the oxidant gas supply unit 15 is also stopped, and the supply of the oxidant gas to the fuel cell 4 is also stopped. Further, the third valve 11 is closed (step S202).

  Here, when the supply of the reaction gas (raw material gas, water vapor) to the hydrogen generator 1 is stopped in step S202, the amount of the gas including the combustible gas flowing into the combustor 2 is the residual reaction gas in the hydrogen generator 1. As the reforming reaction progresses and the volume expands as the residual water evaporates, a gas containing a combustible gas is supplied to the combustor 2. In step S101, the amount of operation of the combustion air supply device 2 is increased. Therefore, this gas is diluted in the combustor 2 and discharged to the outside of the fuel cell system 100 through the combustion exhaust gas passage 23 and the exhaust port (dilution process). In this dilution process, in order to further improve the dilutability, it is more preferable to control the power generation amount of the fuel cell to be an operation amount larger than the operation amount at the maximum output. Further, in this flow, the increase in the operation amount of the combustion air supply unit 13 is performed before the supply of the reaction gas to the hydrogen generator is stopped, but at the same time as the supply of the reaction gas is stopped. It may be after that.

Next, the controller 17 opens the second valve 8 and allows the bypass path 7 to communicate with the first valve 6 and the fourth valve 14 being kept open (step S203). By this step S203, “the first path is blocked by the first valve and the second path is communicated by the second valve” is entered. As a result, at least one of the first valve 6 and the fourth valve 14 and the second valve 8 are compared with the case where the closing of the first valve 6 and the fourth valve 14 and the opening of the second valve 8 are performed simultaneously. Are simultaneously closed (that is, the first path and the second path are simultaneously blocked). Therefore, when the second valve 8 is opened after the internal pressure rises due to the progress of the reforming reaction by the reactive gas remaining in the hydrogen generator due to the simultaneous closing or the evaporation of residual water, the hydrogen generator is suddenly opened. The gas flows into the combustor, and the possibility that a combustible gas having a low dilution level or a gas containing carbon monoxide is discharged outside the fuel cell system is reduced.

  Next, as in the fuel cell system of the first embodiment, after the state in which the first path and the second path are both communicated in step S203 is continued for the communication threshold time or longer, the first valve 6 and the fourth valve 8 are changed. It is closed and the first path is blocked (step S204). In the above flow, both the first valve 6 and the fourth valve 8 are closed to block the first path, but either the first valve 6 or the fourth valve 8 is closed. May be. That is, “blocking the first path by the first valve” means that the valve provided on the first path may be closed as long as the first path can be blocked.

  After executing step S204, it is determined whether the duration of the dilution process is equal to or greater than a predetermined duration threshold T2 (step S205). If the duration of the dilution process is equal to or greater than T2 (Yes in step S205), The second valve 8 is closed. And after performing step S206, operation | movement of the combustion air supply device 13 is continued similarly to the fuel cell system of Embodiment 1, and the gas inside the combustor 2 is scavenged (scavenging process: step S207). When the execution time of the scavenging process reaches or exceeds a predetermined scavenging time threshold necessary for scavenging, the operation of the combustion air supply device 13 is stopped (step S208), and a series of flows related to the combustion process is completed.

  A gas that contains more water vapor in the fuel gas flow path in the fuel cell than in the power generation operation by performing a dilution process after stopping the supply of the reaction gas to the hydrogen generator as in the fuel cell system of the present embodiment described above The amount of flowing in is controlled more than before. Therefore, the possibility that flooding occurs in the fuel gas flow path in the fuel cell during the next power generation operation and the power generation amount decreases is reduced.

  According to the fuel cell system of the present invention, when processing (combustion processing, dilution processing, etc.) the gas flowing into the combustor with the volume expansion of the gas in the hydrogen generation device after the supply of the reaction gas to the hydrogen generation device is stopped. In addition, the amount of gas containing more water vapor than that in the power generation operation into the fuel gas flow path in the fuel cell is reduced as compared with the prior art. Accordingly, flooding occurs in the fuel gas flow path in the fuel cell during the next power generation operation, and the possibility that the power generation amount decreases is reduced, which is useful as a cogeneration system or the like.

DESCRIPTION OF SYMBOLS 1 Hydrogen generator 2 Combustor 3 Igniter 4 Fuel cell 4a Fuel gas flow path 4b Oxidant gas flow path 5 Fuel gas supply path 6 1st valve 7 Bypass path 8 2nd valve 9 Deodorizer 10 Raw material gas supply 11 11th 3 valve 12 water supply device 13 combustion air supply device 14 fourth valve 15 oxidant gas supply device 16 off-fuel gas route 17 controller 21 raw material gas supply route 22 water supply route 23 combustion exhaust gas route

Claims (5)

From a hydrogen generator that generates a fuel gas containing hydrogen by a reforming reaction using a raw material gas, a reaction gas supplier that supplies the hydrogen generator with a gas necessary for the reforming reaction, and the hydrogen generator A combustor that burns the delivered gas, a fuel cell that generates electricity using the fuel gas delivered from the hydrogen generator, and a gas delivered from the hydrogen generator via the fuel cell. A first path supplied to the combustor, and a gas sent from the hydrogen generator bypasses the fuel cell, and communicates / blocks the second path supplied to the combustor and the first path. A first valve that communicates / blocks the second path, and a controller, the first valve communicates with the first path, and the second valve blocks the second path. Fuel cell system in which power generation operation is performed in the The controller is configured to supply the reaction gas from the reaction gas supply device in a state where the first path is blocked by the first valve and the second path is communicated by the second valve. The fuel cell system is configured to execute a combustion process or a dilution process of the gas flowing into the combustor after the operation is stopped. In the stop process of the power generation operation, the controller communicates the first path with the first valve and blocks the first path with the first valve from the state where the second path is blocked with the second valve. When switching to the state where the second path is communicated with the second valve, the first valve and the second valve are controlled to pass through the state where the first path and the second path are communicated together. 2. The fuel cell system according to claim 1, wherein a switching operation for shutting off the first path and connecting the second path is performed later. The control unit comprising the source gas path through which the source gas flows, a deodorizer that adsorbs odor components contained in the source gas, and a third valve provided in the source gas path downstream of the deodorizer, The fuel cell system according to claim 1, wherein the container closes the third valve before executing the switching operation. In the state where the first path and the second path are in communication with each other, the controller communicates such that the flow of the fuel gas is not hindered during the next power generation operation due to condensation of water vapor flowing into the fuel cell from the first path. 2. The fuel cell system according to claim 1, wherein the first path is cut off and the second path is in communication with a time threshold value or less. 2. The igniter provided in the combustor, wherein the controller operates the igniter in a state where at least the first path and the second path are in communication with each other. Fuel cell system.

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