JP2007012388A - Fuel cell system and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system which eliminates the need of additives for lowering a melting point and which is capable of coping with plugging of an exhaust passage due to various causes, and to provide its operation method. <P>SOLUTION: The fuel cell system comprises a supply piping 13 for supplying air to the fuel cell 10 and an exhaust piping 14 for discharging air off-gas exhausted from the fuel cell 10, and is provided with a communicating piping 30 to be communicated with the exhaust piping 14 and the supply piping 13 and a relief valve 32 which restricts flow of gas from the supply piping 13 to the exhaust piping 14 and permits flow of gas from the exhaust piping 14 to the supply piping 13 in the communicating piping 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system and a method for operating the fuel cell system, and more particularly to measures against freezing of the flow path.

  In the fuel cell system, generated water is generated by an electrochemical reaction. This generated water, for example, when the operation of the fuel cell is stopped, the temperature of the discharge path of the reaction off-gas decreases and the generated water is saturated. As the water vapor pressure decreases, it will condense in the discharge path. If the system is left with the condensed water remaining in the discharge channel in this way, the discharge channel is narrowed by freezing of the generated water when the discharge temperature is cooled because the outside air temperature is below freezing. Or may be blocked.

For this reason, in order to suppress such clogging of the discharge path due to freezing of generated water, for example, a technique of adding reforming methanol to condensed water as an additive for lowering the melting point of condensed water is disclosed ( For example, see Patent Document 1).
JP-A-10-223249

  However, as described above, if an additive such as methanol is added to the condensed water in order to lower the melting point of the condensed water, the additive such as methanol is naturally consumed wastefully. End up. Further, the cause of the clogging of the discharge path is not necessarily the freezing of the generated water, but it becomes impossible to cope with the clogging caused by the cause other than the freezing of the generated water. As a cause other than the freezing of the generated water, for example, a case where foreign matter enters the discharge path from the outside through the discharge port can be cited.

  Accordingly, an object of the present invention is to provide a fuel cell system and an operation method thereof that do not require an additive for lowering the melting point and can cope with clogging of the discharge path due to various causes.

  In order to achieve the above object, a fuel cell system of the present invention has a supply path for supplying a reaction gas to a fuel cell, and a discharge path for discharging a reaction off-gas discharged from the fuel cell, A communication path that connects the discharge path and the supply path, and restricts a gas flow from the supply path to the discharge path in the communication path, while allowing a gas flow from the discharge path to the supply path. And a valve.

  According to this configuration, the communication path that connects the supply path and the discharge path is provided with a valve that restricts the gas flow from the supply path to the discharge path while allowing the gas flow from the discharge path to the supply path. Therefore, when the discharge passage is clogged, the reaction off gas flows from the discharge passage to the supply passage by this valve. As a result, the operating state can be maintained. Thereby, it becomes unnecessary to use an additive etc., and it becomes possible to cope with clogging caused by causes other than freezing of generated water.

  In this case, it is preferable that the valve allows the gas flow from the discharge path to the supply path only when the pressure in the discharge path exceeds a predetermined value.

  According to this configuration, since the gas flow from the discharge path to the supply path is allowed only when the pressure in the discharge path exceeds a predetermined value, that is, when the clogging occurs on the discharge path side, the operation efficiency is improved during normal operation. There is no lowering.

  The fuel cell system of the present invention includes a supply path for supplying a reaction gas to the fuel cell, and a discharge path for discharging a reaction off-gas discharged from the fuel cell, wherein the discharge path and the supply It is good also as a structure which has a communicating path which connects a path | route, an electromagnetic valve which opens and closes this communicating path, and a control means which controls the open / close state of the said electromagnetic valve.

  According to this configuration, in a situation where the control means can determine that the discharge path is clogged, for example, according to the outside air temperature or the pressure of the discharge path, the electromagnetic means provided in the communication path that connects the supply path and the discharge path. The valve is opened and the reaction off gas flows from the discharge path to the supply path via the communication path. As a result, the operating state can be maintained. This also eliminates the need for using additives and the like, and makes it possible to cope with clogging caused by causes other than freezing of the produced water.

  Furthermore, when a silencer is provided in the discharge path, the communication path preferably communicates with the upstream side of the silencer in the discharge path.

  According to this configuration, the fuel cell system has a very high reaction off-gas flow rate, and a synthetic resin silencer is used. Therefore, when the discharge path is clogged, the silencer is damaged by high pressure. Etc. can be prevented.

  In addition, when the impurity removal part is provided in the supply path, it is preferable that the communication path communicates with the upstream side of the impurity removal part in the supply path.

  According to this configuration, when dust, fuel cells, and exfoliation from piping elements communicating with the reaction off gas flowing from the discharge path to the supply path via the communication path are mixed, it can be removed. .

  The fuel cell system of the present invention includes a supply path for supplying a reaction gas to the fuel cell and a discharge path for discharging a reaction off-gas discharged from the fuel cell, and is branched from the discharge path. And a branch discharge passage that opens to the outside, and a valve that restricts the flow of gas from the outside to the discharge passage in the branch discharge passage and allows the gas flow from the discharge passage to the outside. good.

  According to this configuration, there is provided a valve that restricts the gas flow from the outside to the discharge path in the branch discharge path that branches from the discharge path and opens to the outside, while allowing the gas flow from the discharge path to the outside. Therefore, when the discharge passage is clogged, the reaction off-gas flows from the discharge passage to the outside through the branch discharge passage by this valve. As a result, the operating state can be maintained. This also eliminates the need for using additives and the like, and makes it possible to cope with clogging caused by causes other than freezing of the produced water.

  Also in this case, it is preferable that the valve allows the gas flow from the discharge passage to the outside through the branch discharge passage only when the pressure in the discharge passage exceeds a predetermined value.

  According to this configuration, in order to allow the gas flow from the discharge path to the outside through the branch discharge path only when the pressure in the discharge path exceeds a predetermined value, that is, when the discharge path side is clogged. During normal operation, gas discharge through the branch discharge path can be regulated.

  Also in this case, when a silencer is provided in the discharge path, the branch discharge path is preferably branched from the upstream side of the silencer in the discharge path.

  According to this configuration, particularly when a silencer made of a synthetic resin is used, it is possible to prevent the silencer from being damaged due to high pressure.

  The operating method of the fuel cell system of the present invention is an operating method of a fuel cell system having a supply path for supplying a reaction gas to the fuel cell and an exhaust path for discharging a reaction off gas discharged from the fuel cell. Then, when the gas pressure in the exhaust passage becomes equal to or higher than a predetermined pressure, a part of the reaction off gas is exhausted from the exhaust passage to the outside.

  In this case, it is preferable that at least a part of the reaction off gas exhausted to the outside from the discharge path is supplied to the supply path.

  According to the present invention, an additive for lowering the melting point becomes unnecessary, and it becomes possible to cope with clogging of the discharge path due to various causes.

  First, a preferred first embodiment for carrying out the present invention will be described with reference to FIG. Hereinafter, the case where the present invention is applied to an in-vehicle power generation system of a fuel cell vehicle will be described. However, the present invention is not limited to such an application example, and may be applied to any moving body such as a ship, an aircraft, a walking robot, Application to a stationary power generation system in which a fuel cell is used as a power generation facility for a building (house, building, etc.) is also possible.

  FIG. 1 shows a system configuration diagram of the main part of the fuel cell system. As shown in this figure, the fuel cell system includes a pipe 11 for supplying hydrogen gas as a fuel gas to the fuel cell 10, a pipe 12 for guiding hydrogen off-gas after passing through the fuel cell 10, and an oxidizing gas (reactive gas). A supply pipe (supply path) 13 for supplying air, a discharge pipe (discharge path) 14 for discharging air off-gas after passing through the fuel cell 10, and a cooling system pipe (not shown) for cooling the fuel cell 10 are provided. Configured.

  Although not shown, the fuel cell 10 has a stack structure in which a plurality of cells each composed of a separator having a flow path of hydrogen gas, air, and cooling water and a MEA (Membrane Electrode Assembly) sandwiched between a pair of separators are stacked. It has.

  An air cleaner (impurity removal unit) 21 is provided in the supply pipe 13 for supplying air as an oxidizing gas to the fuel cell 10 at a position between the suction port 20 opened to the outside and the fuel cell 10. An air compressor 22 is provided between the air cleaner 21 and the fuel cell 10. Accordingly, when the air compressor 22 is driven, the supply pipe 13 sucks air from the suction port 20 and captures dust and the like with the air cleaner 21 and then introduces the dust into the fuel cell 10.

  Here, the supply pipe 13 is provided with the suction port 20 facing the outside of the vehicle body 24, but at least the fuel cell 10 side than the air cleaner 21 is provided in the vehicle body 24 that is not easily affected by outside air. .

  Further, the exhaust pipe 14 for exhausting the air that has passed through the fuel cell 10 is provided with a muffler made of a synthetic resin (which suppresses the exhaust sound of the air off gas between the exhaust port 26 opened to the outside and the fuel cell 10 ( A muffler 27 is provided. Here, the discharge pipe 14 is provided with the discharge port 26 and the muffler 27 facing the outside of the vehicle body 24, but the fuel cell 10 side of the muffler 27 is provided in the vehicle body 24 that is not easily affected by outside air. Yes.

  In the first embodiment, a communication pipe (communication path) 30 that connects the supply pipe 13 and the discharge pipe 14 on the oxidizing gas supply side is provided. The communication pipe 30 has one end communicating with the upstream side of the air cleaner 21 in the supply pipe 13 and the other end communicating with the upstream side of the muffler 27 in the discharge pipe 14. The communication pipe 30 is also provided in the vehicle body 24 that is not easily affected by outside air.

  The communication pipe 30 restricts the gas flow from the supply pipe 13 to the discharge pipe 14 through the communication pipe 30, while the gas flow from the discharge pipe 14 to the supply pipe 13 through the communication pipe 30. A relief valve (valve) 32 is provided. The relief valve 32 opens only when the pressure in the discharge pipe 14 exceeds a predetermined value set in advance, and allows the gas to flow from the discharge pipe 14 to the supply pipe 13.

  The relief valve 32 is closed by an urging force of a spring (not shown). The pressure difference between the upstream side (discharge pipe 14 side) and the downstream side (supply pipe 13 side) is higher than the downstream side. When the pressure exceeds a predetermined value based on the urging force, the valve is mechanically opened. Since the supply pipe 13 side of the communication pipe 30 is connected to the suction port 20 with respect to the relief valve 32 and is basically always at atmospheric pressure, the relief valve 32 has a predetermined pressure in which the pressure in the discharge pipe 14 is set in advance. The valve is opened only when the value is exceeded.

  The predetermined value is set so that the relief valve 32 is kept closed even if the pressure in the discharge pipe 14 is slightly increased by the exhaust resistance by the muffler 27 during normal operation.

  With the above configuration, if the muffler 27 or the discharge port 26 is blocked by some external factor such as snow or freezing of the generated water of the fuel cell 10, the pressure in the discharge pipe 14 will increase. When the pressure exceeds a predetermined value, the relief valve 32 opens. As a result, the air off-gas flows to the supply pipe 13 side through the communication pipe 30 and is introduced into the fuel cell 10 in a state where dust and the like are removed by the air cleaner 21 and mixed with the outside air. Will continue to generate electricity.

  According to the first embodiment described above, the flow of gas from the supply pipe 13 to the discharge pipe 14 is restricted in the communication pipe 30 that connects the supply pipe 13 and the discharge pipe 14 on the oxidizing gas supply side, while the discharge pipe 14 is discharged. Since the relief valve 32 that allows the gas flow from the pipe 14 to the supply pipe 13 is provided, even if the discharge pipe 14 is clogged and a sudden pressure rise occurs, the relief pipe 32 and the relief valve 32 discharge. The air off gas can be instantaneously flowed from the pipe 14 to the supply pipe 13 to release the pressure.

  As a result, it is possible to maintain the driving state, and it is possible to avoid traveling on the shoulder of the moving body, and further, it is possible to travel to a nearby maintenance factory. Thereby, it is not necessary to use an additive or the like, and it is possible to cope with clogging caused by causes other than freezing of generated water (for example, snow).

  Further, the relief valve 32 allows the gas flow from the discharge pipe 14 to the supply pipe 13 only when the pressure in the discharge pipe 14 exceeds a predetermined value, that is, when the discharge pipe 14 is clogged. Even if the pressure in the discharge pipe 14 increases due to the exhaust resistance due to the muffler 27 at the normal time, the relief valve 32 does not open and the operating efficiency is not lowered.

  Furthermore, since the fuel cell system uses a muffler 27 made of a synthetic resin with a very high flow rate of air off gas and low pressure resistance, if the clogging occurs, a high pressure is applied to the muffler 27 to cause damage or the like. However, since the communication pipe 30 communicates with the upstream side of the muffler 27 in the discharge pipe 14 as described above, it is possible to prevent the muffler 27 from being damaged due to high pressure.

  In addition, since the communication pipe 30 communicates with the upstream side of the air cleaner 21 in the supply pipe 13, the off-gas flowing from the discharge pipe 14 through the communication pipe 30 to the supply pipe 13 communicates with dust, the fuel cell, and it. When the exfoliation from the piping element is mixed, it is possible to flow the air off gas to the fuel cell 10 side after removing it.

  Next, a second preferred embodiment for carrying out the present invention will be described with a focus on differences from the first embodiment with reference to FIG. In addition, the same code | symbol is attached | subjected to the part similar to 1st Embodiment, and the description is abbreviate | omitted.

  In the second embodiment, the communication pipe 30 of the first embodiment is not provided, but a branch discharge pipe (branch discharge path) 34 branched from the discharge pipe 14 and opened to the outside is provided. While the flow of gas from the outside to the discharge pipe 14 is restricted at 34, a relief valve 32 similar to that of the first embodiment that allows the flow of gas from the discharge pipe 14 to the outside is the discharge pipe 14 of the branch discharge pipe 34. And the branch outlet 35 opened to the outside.

  Here, the branch discharge pipe 34 branches from the upstream side of the muffler 27 in the discharge pipe 14, that is, from between the muffler 27 and the fuel cell 10.

  The relief valve 32 of the second embodiment is the same as that of the first embodiment as described above. That is, the relief valve 32 opens only when the pressure in the discharge pipe 14 exceeds a predetermined value set in advance, and allows the gas flow from the discharge pipe 14 to the outside through the branch discharge pipe 34. It is allowed, and when the pressure difference between the upstream side (exhaust pipe 14 side) and the downstream side (outside air side) is higher than the downstream side by a predetermined value based on the biasing force of the spring, it opens mechanically. I speak.

  Since the branch discharge port 35 downstream of the relief valve 32 of the branch discharge pipe 34 opens to the atmosphere and is always at atmospheric pressure, the relief valve 32 has a predetermined pressure in which the pressure in the discharge pipe 14 is set in advance. The valve is opened only when the value is exceeded.

  In this case as well, the above-described predetermined value is set so that the relief valve 32 remains in the closed state even if the pressure in the exhaust pipe 14 slightly increases due to the exhaust resistance by the muffler 27 during normal operation. .

  With the above configuration, when the muffler 27 or the discharge port 26 of the discharge pipe 14 is blocked by some external factor such as snow or freezing of the generated water of the fuel cell 10, the pressure in the discharge pipe 14 increases. Therefore, when the pressure exceeds a predetermined value, the relief valve 32 is opened. As a result, the air off-gas is discharged to the outside through the branch discharge pipe 34, so that the fuel cell 10 can continue the normal power generation state.

  According to the second embodiment described above, the flow of gas from the outside to the discharge pipe 14 is restricted in the branch discharge pipe 34 branched from the discharge pipe 14 on the oxidizing gas supply side, while the flow from the discharge pipe 14 to the outside is limited. Since the relief valve 32 that allows the gas flow is provided, even if the discharge pipe 14 is clogged and a sudden pressure rise occurs, the branch discharge pipe 34 and the relief valve 32 instantaneously move from the discharge pipe 14 to the outside. Air off gas can be flowed to relieve pressure.

  As a result, the driving state can be maintained, and the traveling of the moving body becomes possible as usual. Thereby, it is not necessary to use an additive or the like, and it is possible to cope with clogging caused by causes other than freezing of generated water (for example, snow).

  The relief valve 32 allows the gas flow from the discharge pipe 14 to the branch discharge pipe 34 only when the pressure in the discharge pipe 14 exceeds a predetermined value, that is, when the discharge pipe 14 is clogged. Therefore, even if the pressure in the exhaust pipe 14 is increased due to the exhaust resistance due to the muffler 27 at the normal time, the relief valve 32 does not open, and the exhaust of gas through the branch exhaust pipe 34 can be regulated.

  Further, since the branch discharge pipe 34 is branched from the upstream side of the muffler 27 in the discharge pipe 14, it is possible to prevent the muffler 27 from being damaged due to high pressure.

  Next, a preferred third embodiment for carrying out the present invention will be described with a focus on differences from the first embodiment with reference to FIG. In addition, the same code | symbol is attached | subjected to the part similar to 1st Embodiment, and the description is abbreviate | omitted.

  In the third embodiment, the mechanical relief valve 32 of the first embodiment is not provided in the communication pipe 30, and an electromagnetic open / close electromagnetic valve 37 is provided instead. An outside air temperature sensor 38 is provided for detection. The ECU (control means) 39 controls the open / close state of the electromagnetic valve 37 based on the detection result of the outside air temperature sensor 38, that is, the outside air temperature.

  That is, the ECU 39 normally closes the electromagnetic valve 37 and opens the electromagnetic valve 37 when it is detected from the detection result of the outside air temperature sensor 38 that the generated water of the fuel cell 10 is in a freezing temperature condition. is there.

  According to the third embodiment described above, the ECU 39 causes the muffler 27 or the discharge port 26 to freeze the generated water of the fuel cell 10 according to the detection result of the outside air temperature sensor 38, that is, the outside air temperature. In a situation where it can be determined that there is a possibility of being blocked, the electromagnetic valve 37 provided in the communication pipe 30 that connects the supply pipe 13 and the discharge pipe 14 is opened, and the communication pipe 30 is connected from the discharge pipe 14 to the supply pipe 13. Air off gas will flow through.

  As a result, the operating state can be maintained. This also eliminates the need to use an additive or the like, and can deal with, for example, snow clogging other than freezing of the generated water. In the case of this configuration, when the outside air temperature is low, for example, there is a possibility that the air cleaner 21 may be frozen, this freezing is prevented by flowing air off gas having a relatively high temperature through the communication pipe 30 to the air cleaner 21. You can also.

  In the third embodiment, a pressure sensor may be provided in the discharge pipe 14, and the solenoid valve 37 may be opened when the pressure detected by the ECU 39 exceeds the predetermined value. Furthermore, the opening / closing of the electromagnetic valve 37 may be controlled from the detection results of both the outside air temperature sensor 38 and the pressure sensor.

1 is a block diagram schematically showing a system configuration of a fuel cell system according to a first embodiment of the present invention. It is a block diagram which shows roughly the system configuration | structure of the fuel cell system which concerns on 2nd Embodiment of this invention. It is a block diagram which shows roughly the system configuration | structure of the fuel cell system which concerns on 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 13 ... Supply pipe (supply path), 14 ... Discharge pipe (discharge path), 21 ... Air cleaner (impurity removal part), 27 ... Muffler (silencer), 30 ... Communication pipe (communication path), 32 ... Relief valve (valve), 34 ... Branch discharge pipe (branch discharge path), 37 ... Solenoid valve, 39 ... ECU (control means)

Claims (10)

A fuel cell system having a supply path for supplying a reaction gas to a fuel cell and a discharge path for discharging a reaction off gas discharged from the fuel cell,
A communication passage communicating the discharge passage and the supply passage;
A fuel cell system comprising: a valve that restricts a gas flow from the supply path to the discharge path in the communication path, and permits a gas flow from the discharge path to the supply path.   2. The fuel cell system according to claim 1, wherein the valve allows a gas flow from the discharge path to the supply path only when a pressure in the discharge path exceeds a predetermined value. A fuel cell system having a supply path for supplying a reaction gas to a fuel cell and a discharge path for discharging a reaction off gas discharged from the fuel cell,
A communication passage communicating the discharge passage and the supply passage;
A solenoid valve for opening and closing the communication path;
And a control means for controlling an open / close state of the electromagnetic valve. A silencer is provided in the discharge path,
4. The fuel cell system according to claim 1, wherein the communication path communicates with the upstream side of the silencer in the discharge path. 5. The supply path is provided with an impurity removal unit,
The fuel cell system according to any one of claims 1 to 4, wherein the communication path communicates with an upstream side of the impurity removal portion in the supply path. A fuel cell system having a supply path for supplying a reaction gas to a fuel cell and a discharge path for discharging a reaction off gas discharged from the fuel cell,
A branch discharge passage that branches off from the discharge passage and opens to the outside;
A fuel cell system comprising: a valve that restricts the flow of gas from the outside to the discharge path in the branch discharge path, but permits the flow of gas from the discharge path to the outside.   7. The valve according to claim 6, wherein the valve allows a gas flow from the discharge path to the outside through the branch discharge path only when a pressure in the discharge path exceeds a predetermined value. Fuel cell system. A silencer is provided in the discharge path,
The fuel cell system according to claim 6 or 7, wherein the branch discharge path branches from the upstream side of the silencer in the discharge path. A method for operating a fuel cell system, comprising: a supply path for supplying a reaction gas to a fuel cell; and a discharge path for discharging a reaction off gas discharged from the fuel cell,
A method for operating a fuel cell system, comprising: exhausting a part of the reaction off-gas from the exhaust passage to the outside when the gas pressure in the exhaust passage becomes equal to or higher than a predetermined pressure.   The operation method of the fuel cell system according to claim 9, wherein at least a part of the reaction off gas exhausted to the outside from the discharge path is supplied to the supply path.