JP2007005170A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of completely consuming fuel gas at stoppage of operation, and capable of supplying oxidant gas from a buffer tank. <P>SOLUTION: The fuel cell system 1 is provided with a buffer tank 70. A controller 100 supplies air in the buffer tank 70 to an oxidant electrode 12 when the fuel cell system 1 is stopped. In this embodiment, a capacity of the buffer tank 70 is variable to enable to supply an appropriate amount of air to the oxidant electrode 12. Here, the capacity is decided by pressure of a fuel electrode 11, temperature of fuel gas, temperature of the oxidant gas, and fuel gas density in the fuel electrode 11 or the like. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

Conventionally, a buffer tank having a certain capacity is provided on the air supply pipe of the fuel cell stack, and air is supplied from the buffer tank into the stack so that all the gas in the fuel cell stack has a nitrogen atmosphere when the operation is stopped. Fuel cell systems that attempt to completely consume the remaining hydrogen are known. In this fuel cell system, the buffer tank has a capacity capable of storing the amount of air having the number of oxygen molecules that can completely consume hydrogen in the fuel cell stack (see, for example, Patent Document 1).
JP 2004-27310 A

  However, in the conventional fuel cell system, since the capacity of the buffer tank is fixed, the number of oxygen molecules in the buffer tank decreases when the air temperature is high and increases when the air temperature is low. For this reason, even if the air in the buffer tank is supplied to the fuel cell when the operation is stopped, the number of oxygen molecules is insufficient when the air temperature is high, and the hydrogen gas cannot be completely consumed. That is, in the conventional fuel cell system, there is a possibility that it is not possible to provide oxygen enough to completely consume hydrogen gas. Further, when the air temperature is low, the number of oxygen molecules becomes excessive, and there is a possibility that all the gases in the stack cannot be made into a nitrogen atmosphere.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to supply an oxidant gas from the buffer tank that can completely consume the fuel gas when the operation is stopped. An object of the present invention is to provide a fuel cell system in which all the gases in the stack can be in a nitrogen atmosphere.

  The fuel cell system of the present invention includes a fuel cell, an oxidant gas supply system, a buffer tank, and control means. A fuel cell has a fuel electrode supplied with a fuel gas and an oxidant electrode supplied with an oxidant gas, and generates electricity by reacting the fuel gas with the oxidant gas. The oxidant gas supply system supplies oxidant gas to the oxidant electrode of the fuel cell during normal operation. The buffer tank can supply an oxidant gas to the oxidant electrode of the fuel cell, and the storage capacity of the oxidant gas is variable. The control means does not supply the oxidant gas to the oxidant electrode of the fuel cell by the oxidant gas supply system when stopping the operation, but supplies the oxidant gas in the buffer tank to the oxidant electrode of the fuel cell. The fuel gas remaining in the fuel electrode is consumed. The control means calculates the amount of oxidant gas having the number of molecules sufficient to consume the fuel gas remaining in the fuel electrode of the fuel cell based on the temperature of the oxidant gas, and stores the calculated amount of oxidant gas. The capacity of the buffer tank is changed to the capacity to be performed.

  According to the present invention, the amount of oxidant gas having the number of molecules sufficient to consume the fuel gas remaining in the fuel electrode of the fuel cell is calculated, and the capacity of the buffer tank is changed to a capacity for storing the calculated amount of oxidant gas. To do. For this reason, even in a situation where the number of molecules of oxidant gas per unit volume changes due to factors such as temperature conditions, the amount of oxidant gas including the required number of molecules is obtained and the buffer is stored so that the amount is stored. The capacity of the tank is changed. Therefore, the buffer tank appropriately stores the oxidant gas having the number of molecules sufficient to consume the fuel gas. Therefore, the oxidant gas that can completely consume the fuel gas when the operation is stopped can be supplied from the buffer tank. Further, all the gas in the stack can be in a nitrogen atmosphere.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. A fuel cell system 1 shown in FIG. 1 is used as a driving power source for a vehicle, and includes a fuel cell 10, a fuel gas supply system 20, a fuel gas discharge system 30, a fuel gas circulation system 40, an oxidation system. An agent gas supply system 50 and an oxidant gas discharge system 60 are provided.

  The fuel cell 10 includes a fuel electrode 11 that receives supply of fuel gas and an oxidant electrode 12 that receives supply of oxidant gas, and generates power by reacting the fuel gas and oxidant gas. Here, in this embodiment, hydrogen gas is used as the fuel gas, and oxygen is used as the oxidant gas.

  The fuel gas supply system 20 supplies hydrogen gas, which is a fuel gas, to the fuel cell 10 and is connected to a hydrogen tank (not shown) and supplies the hydrogen gas from the hydrogen tank to the fuel electrode 11 of the fuel cell 10. Is. The fuel gas supply system 20 includes a hydrogen gas supply pipe 21 and a hydrogen humidifier 22. The hydrogen gas supply pipe 21 serves as a flow path for connecting the hydrogen tank and the fuel electrode 11 of the fuel cell 10 and guiding the hydrogen gas from the hydrogen tank to the fuel electrode 11 of the fuel cell 10. The hydrogen humidifier 22 humidifies the air supplied to the fuel cell 10 in order to keep the electrolyte membrane of the fuel cell 10 moist. The hydrogen humidifier 22 has a water storage part inside, and hydrogen gas is generated by water stored in the water storage part. It comes to humidify.

  The fuel gas supply system 20 includes a hydrogen gas flow rate adjustment valve 23, a hydrogen gas supply valve 24, a first branch pipe 25, a second branch pipe 26, a hydrogen humidifier inlet valve 27, and a hydrogen humidifier outlet. A valve 28 and a fuel electrode inlet valve 29 are provided. The hydrogen gas flow rate adjustment valve 23 is provided in the hydrogen gas supply pipe 21 and controls the amount of hydrogen gas supplied from the hydrogen tank to the fuel electrode 11 of the fuel cell 10 by adjusting the opening degree. The hydrogen gas supply valve 24 is provided in the hydrogen gas supply pipe 21 between the hydrogen gas flow rate adjustment valve 23 and the fuel electrode 11, and shuts or opens the flow path in the hydrogen gas supply pipe 21 by opening and closing. It is something to do.

  One end of the first branch pipe 25 is connected to a hydrogen gas supply pipe 21 (connection point A in FIG. 1) between the hydrogen gas flow rate adjustment valve 23 and the hydrogen gas supply valve 24, and the other end is a hydrogen humidifier 22. It is connected to the. The other end of the first branch pipe 25 extends to the water storage part of the hydrogen humidifier 22 and is immersed in water stored in the water storage part. The second branch pipe 26 has one end connected to the hydrogen humidifier 22 and the other end connected to a hydrogen gas supply pipe 21 (connection point B in FIG. 1) between the hydrogen gas supply valve 24 and the fuel electrode 11. ing. In addition, although the end of the 2nd branch pipe 26 is extended to the water storage part of the hydrogen humidifier 22, it is not immersed in the water stored in a water storage part.

  The hydrogen humidifier inlet valve 27 is provided in the first branch pipe 25 and shuts or opens the flow path in the first branch pipe 25 by opening and closing. The hydrogen humidifier outlet valve 28 is provided in the second branch pipe 26 and shuts or opens the flow path in the second branch pipe 26 by opening and closing. The fuel electrode inlet valve 29 is provided in the hydrogen gas supply pipe 21 between the connection point B and the fuel electrode 11, and shuts or opens the flow path in the hydrogen gas supply pipe 21 by opening and closing. It is.

  With this configuration, when the fuel electrode inlet valve 29 is opened, hydrogen gas is supplied to the fuel electrode 11 of the fuel cell 10 according to the opening degree of the hydrogen gas flow rate adjustment valve 23. Further, when the hydrogen gas supply valve 24 is closed and the hydrogen humidifier inlet valve 27 and the hydrogen humidifier outlet valve 28 are opened, the hydrogen gas flowing through the hydrogen gas flow rate adjusting valve 23 passes through the first branch. It flows into the hydrogen humidifier 22 through the pipe 25, is humidified in the process of passing through the water reservoir, passes through the second branch pipe 26, and is supplied to the fuel electrode 11 of the fuel cell 10. On the other hand, when the hydrogen gas supply valve 24 is opened and the hydrogen humidifier inlet valve 27 and the hydrogen humidifier outlet valve 28 are closed, the hydrogen gas is supplied to the fuel electrode 11 without passing through the hydrogen humidifier 22. The

  The fuel gas discharge system 30 includes a hydrogen gas discharge pipe 31 and a fuel electrode outlet valve 32. The hydrogen gas discharge pipe 31 connects the fuel electrode 11 of the fuel cell 10 and the outside, and guides the off gas discharged from the fuel electrode 11 to the outside. The fuel electrode outlet valve 32 is provided in the hydrogen gas discharge pipe 31, and controls the discharge of off-gas by opening and closing the flow path of the hydrogen gas discharge pipe 31.

  The fuel gas circulation system 40 circulates the hydrogen gas discharged without contributing to power generation from the downstream side to the upstream side of the fuel electrode 11 of the fuel cell 10, and includes a hydrogen circulation pipe 41, a hydrogen circulation pump 42, , A hydrogen gas dehydrator (dehydrating means) 43, a hydrogen circulation pipe inlet valve 44, and a hydrogen circulation pipe outlet valve 45 are provided. The hydrogen circulation pipe 41 serves as a flow path for circulating the off-gas discharged from the fuel electrode 11 from the downstream side to the upstream side of the fuel electrode 11, and one end thereof is the fuel electrode 11 and the fuel electrode outlet valve of the fuel cell 10. 32 is connected to a hydrogen gas discharge pipe 31 (connection point C in FIG. 1), and the other end is connected to a hydrogen gas supply pipe 21 (shown in FIG. 1) between the fuel electrode inlet valve 29 and the fuel electrode 11 of the fuel cell 10. 1 is connected to a connection point D) in FIG. The hydrogen circulation pump 42 is provided in the hydrogen circulation pipe 41 and serves as a circulation power source for circulating off-gas discharged from the fuel electrode 11 of the fuel cell 10 and sending it to the fuel electrode 11 again.

  The hydrogen gas dehydrator 43 removes the produced water generated by the power generation of the fuel cell 10, and is configured to remove the produced water by condensing and removing moisture contained in the hydrogen gas, for example. . In addition, the hydrogen gas dehydrator 43 is configured to send moisture extracted by condensation to the hydrogen humidifier 22 through a pipe (not shown). The hydrogen circulation pipe inlet valve 44 is provided in the hydrogen circulation pipe 41 between the connection point C and the hydrogen gas dehydrator 43, and shuts or opens the flow path in the hydrogen circulation pipe 41 by opening and closing. Is. The hydrogen circulation pipe outlet valve 45 is provided in the hydrogen circulation pipe 41 between the hydrogen circulation pump 42 and the connection point D, and shuts or opens the flow path in the hydrogen circulation pipe 41 by opening and closing. is there.

  Due to such a configuration, the off-gas from the fuel electrode 11 is discharged to the outside when the fuel electrode outlet valve 32 is opened. On the other hand, when the fuel electrode outlet valve 32 is not opened, the hydrogen circulation pipe inlet valve 44 and the hydrogen circulation pipe outlet valve 45 are opened, and the off-gas from the fuel electrode 11 is upstream of the fuel electrode 11 by the hydrogen circulation pump 42. It will be returned to. At this time, the off-gas is dehydrated by the hydrogen gas dehydrator 43 to remove excess moisture.

  The oxidant gas supply system 50 supplies oxygen, which is an oxidant gas, to the fuel cell 10. The oxidant gas supply system 50 is connected to a compressor (not shown) and supplies air fed from the compressor to the oxidant electrode 12 of the fuel cell 10. To do. The oxidant gas supply system 50 includes an air supply pipe 51 and an air humidifier 52. The air supply pipe 51 connects the compressor and the oxidant electrode 12 of the fuel cell 10, and serves as a flow path for guiding the air pumped from the compressor to the oxidant electrode 12 of the fuel cell 10. The air humidifier 52 humidifies the air supplied to the fuel cell 10 in order to keep the electrolyte membrane of the fuel cell 10 moist. The air humidifier 52 has a water storage part inside, and the air is stored by water stored in the water storage part. It comes to humidify.

  The oxidant gas supply system 50 includes an air flow rate adjustment valve 53, an air supply valve 54, a third branch pipe 55, a fourth branch pipe 56, an air humidifier inlet valve 57, and an air humidifier outlet valve. 58 and an oxidant electrode inlet valve 59. The air flow rate adjusting valve 53 is provided in the air supply pipe 51 and controls the amount of air supplied from the compressor to the oxidant electrode 12 of the fuel cell 10 by adjusting the opening degree. The air supply valve 54 is provided in the air supply pipe 51 between the air flow rate adjustment valve 53 and the oxidant electrode 12, and shuts or opens the flow path in the air supply pipe 51 by opening and closing operation. It is.

  One end of the third branch pipe 55 is connected to an air supply pipe 51 (connection point E in FIG. 1) between the air flow rate adjustment valve 53 and the air supply valve 54, and the other end is connected to the air humidifier 52. ing. Further, the other end of the third branch pipe 55 extends to the water storage part of the air humidifier 52 and is immersed in water stored in the water storage part. The fourth branch pipe 56 has one end connected to the air humidifier 52 and the other end connected to an air supply pipe 51 (connection point F in FIG. 1) between the air supply valve 54 and the oxidant electrode 12. Yes. One end of the fourth branch pipe 56 extends to the water storage part of the air humidifier 52, but is not immersed in the water stored in the water storage part.

  The air humidifier inlet valve 57 is provided in the third branch pipe 55, and shuts or opens the flow path in the third branch pipe 55 by opening and closing. The air humidifier outlet valve 58 is provided in the fourth branch pipe 56 and shuts or opens the flow path in the fourth branch pipe 56 by opening and closing. The oxidant electrode inlet valve 59 is provided in the air supply pipe 51 between the connection point F and the oxidant electrode 12, and opens and closes the flow path in the oxidant electrode inlet valve 59. To do.

  With this configuration, when the oxidant electrode inlet valve 59 is opened, air is supplied to the oxidant electrode 12 of the fuel cell 10 according to the opening of the air flow rate adjustment valve 53. In addition, there are two types of air supply paths. When the air supply valve 54 is closed and the air humidifier inlet valve 57 and the air humidifier outlet valve 58 are opened, the air flows through the air flow rate adjustment valve 53. The air flows into the air humidifier 52 through the third branch pipe 55, is humidified in the process of passing through the water storage unit, passes through the fourth branch pipe 56, and is supplied to the oxidant electrode 12 of the fuel cell 10. On the other hand, when the air supply valve 54 is opened and the air humidifier inlet valve 57 and the air humidifier outlet valve 58 are closed, air is supplied to the oxidizer electrode 12 without passing through the air humidifier 52. .

  The oxidant gas discharge system 60 includes an air discharge pipe 61 and an oxidant electrode outlet valve 62. The air discharge pipe 61 connects the oxidant electrode 12 of the fuel cell 10 and the outside, and guides offgas from the oxidant electrode 12 to the outside. The oxidant electrode outlet valve 62 is provided in the air discharge pipe 61, and controls the discharge of off-gas by opening and closing the flow path in the air discharge pipe 61. Because of such a configuration, the off-gas from the oxidant electrode 12 is discharged to the outside when the oxidant electrode outlet valve 62 is opened.

  Further, the fuel cell system 1 includes a buffer tank 70, a tank supply pipe 71, a tank capacity control valve 72, a tank discharge pipe 73, a capacity adjustment discharge valve 74, a first air supply line 80, And an air supply line valve 81.

  The buffer tank 70 is a tank in which the storage capacity of air, which is an oxidant gas, is variable, and has a capacity adjustment plate 70a that bisects the internal space. The capacity adjustment plate 70a is slidably provided in the buffer tank 70 so that the amount of air that can be stored in the buffer tank 70 can be changed. One end of the first air supply line 80 is connected to one space side of the buffer tank 70 that is separated by the capacity adjustment plate 70a. The other end of the first air supply line 80 is connected to an air supply pipe 51 (connection point G in FIG. 1) between the oxidant electrode inlet valve 59 and the oxidant electrode 12 of the fuel cell 10. This is a flow path for supplying the air inside the buffer tank 70 to the oxidant electrode 12. The first air supply line valve 81 is provided in the first air supply line 80 and shuts or opens the flow path in the first air supply line 80 by opening and closing.

  Since the first air supply line 80 and the first air supply line valve 81 are thus provided, the buffer tank 70 is configured to be able to supply the air in the buffer tank 70 to the oxidant electrode 12 of the fuel cell 10. Will be.

  The tank supply pipe 71 serves as a flow path for supplying air sent from the compressor or the like to the buffer tank 70. One end of the tank supply pipe 71 is connected to the compressor, for example, and the other end is separated by the capacity adjustment plate 70a. Connected to the space. The tank capacity control valve 72 is provided in the tank supply pipe 71, and controls the amount of air supplied from the compressor to the other side space of the buffer tank 70 by adjusting the opening degree.

  The tank discharge pipe 73 is a flow path for discharging the air in the buffer tank 70. One end of the tank discharge pipe 73 is connected to the space on the other side separated by the capacity adjustment plate 70a, and the other end is connected to the outside. linked. The capacity adjusting discharge valve 74 is provided in the tank discharge pipe 73, and opens and closes to block or open the flow path in the tank discharge pipe 73, and exists in the other side space of the buffer tank 70. It controls the discharge of air.

  With this configuration, air is supplied to the space on the other side of the buffer tank 70 in accordance with the opening of the tank capacity control valve 72. At this time, the capacity adjustment plate 70a slides to widen the space on the other side. Thereby, the capacity in the space on one side of the buffer tank 70 is reduced. In addition, the air pressure in the space on one side is increased. When the capacity adjusting discharge valve 74 is opened, the air in the buffer tank 70 is discharged to the outside. At this time, the capacity adjustment plate 70a slides to narrow the space on the other side. That is, the capacity in the space on one side of the buffer tank 70 is increased. In addition, the air pressure in the space on one side is lowered. Thus, the capacity of the buffer tank 70 is variable, and the air pressure is also variable.

  The fuel cell system 1 includes a second air supply line 90 and a second air supply line valve 91. The second air supply line 90 serves as a flow path for supplying air inside the buffer tank 70 to the fuel electrode 11, and one end of the second air supply line 90 is between the buffer tank 70 and the first air supply line valve 81. 1 is connected to an air supply line 80 (connection point H in FIG. 1), and the other end is connected to a hydrogen gas supply pipe 21 (connection point I in FIG. 1) between the connection point D and the fuel electrode 11 of the fuel cell 10. It is connected. The second air supply line valve 91 is provided in the second air supply line 90 and shuts or opens the flow path in the second air supply line 90 by opening and closing.

  Since the second air supply line 90 and the second air supply line valve 91 are thus provided, the buffer tank 70 can supply not only the oxidant electrode 12 but also the internal gas to the fuel electrode 11. Will be.

  Furthermore, the fuel cell system 1 includes a controller (control means) 100 and an oxidant gas circulation system 110. The controller 100 controls the entire fuel cell system 1. The controller 100 can perform normal operation control and stop operation control.

  The normal operation control is control that performs power generation according to the amount of current required from the load side. In this normal operation control, the controller 100 controls the fuel gas supply system 20 to supply an appropriate amount of hydrogen gas to the fuel electrode 11 of the fuel cell 10. The controller 100 also controls the oxidant gas supply system 50 to supply an appropriate amount of hydrogen gas to the oxidant electrode 12 of the fuel cell 10.

  The stop operation control is control for stopping the fuel cell system 1 and is control for consuming as much hydrogen gas and oxygen in the fuel cell 10 as possible so as not to deteriorate the catalyst of the fuel cell 10. is there. In this stop operation control, the controller 100 closes the fuel electrode inlet valve 29, the fuel electrode outlet valve 32, the oxidant electrode inlet valve 59, and the oxidant electrode outlet valve 62. In addition, the controller 100 opens the first air supply line valve 81 and supplies the air in the buffer tank 70 to the oxidant electrode 12 of the fuel cell 10. As a result, the controller 100 consumes the hydrogen gas present in the fuel electrode 11 of the fuel cell 10.

  The oxidant gas circulation system 110 circulates gas from the downstream of the oxidant electrode 12 of the fuel cell 10 to the upstream of the oxidant electrode 12 through the buffer tank 70, and is used in the stop operation control. Is. The oxidant gas circulation system 110 includes an air circulation pipe 111, an air circulation pump 112, an air dehydrator (dehydration means) 113, an air circulation pipe inlet valve 114, and an air circulation pipe outlet valve 115.

  The air circulation pipe 111 serves as a flow path for sending off gas to the buffer tank 70 in order to circulate off gas discharged from the oxidant electrode 12 from downstream to upstream of the oxidant electrode 12. One end of the air circulation pipe 111 is connected to an air discharge pipe 61 (connection point J in FIG. 1) between the oxidant electrode 12 and the oxidant electrode outlet valve 62 of the fuel cell 10, and the other end is a buffer tank. It is connected to the space on one side of 70. The air circulation pump 112 is provided in the air circulation pipe 111 and serves as a power source for feeding the buffer tank 70 to circulate off-gas discharged from the oxidant electrode 12 of the fuel cell 10.

  The air dehydrator 113 removes the produced water generated by the power generation of the fuel cell 10 and is configured to remove the produced water by condensing and taking out moisture contained in the air, for example. The air dehydrator 113 is configured to send moisture condensed and taken out to the air humidifier 52 through a pipe (not shown). The air circulation pipe inlet valve 114 is provided in the air circulation pipe 111 between the connection point J and the air dehydrator 113, and shuts or opens the flow path in the air circulation pipe 111 by opening and closing operation. It is. The air circulation pipe outlet valve 115 is provided in the air circulation pipe 111 between the air circulation pump 112 and the buffer tank 70, and shuts or opens the flow path in the air circulation pipe 111 by opening and closing. is there.

  Due to such a configuration, the off-gas from the oxidant electrode 12 is discharged to the outside when the oxidant electrode outlet valve 62 is opened. However, in the stop operation control, the oxidant electrode outlet valve 62 is discharged. Is closed and the air circulation pipe inlet valve 114 and the air circulation pipe outlet valve 115 are opened. Then, the air circulation pump 112 is driven, and the off-gas from the oxidant electrode 12 is dehydrated by the air dehydrator 113 and then returned to the buffer tank 70. In the stop operation control, the air in the buffer tank 70 is supplied to the oxidant electrode 12 of the fuel cell 10, so that the air in the buffer tank 70 passes through the first air supply line 80 and the air circulation pipe 111. Will circulate through.

  In addition, the load apparatus 120, the secondary battery 121, and the voltage measuring device 122 are connected to the fuel cell 10 shown in FIG. The load device 120 is a device such as a motor serving as a drive source of the fuel cell vehicle. The secondary battery 121 is an auxiliary battery, and stores the surplus power that is not consumed by the load device 120. When the fuel cell 10 cannot generate power or the power generation amount is insufficient, the load device 120 is used. It supplies power to The voltage measuring device 122 measures the generated voltage of the fuel cell 10.

  Next, an outline of the operation of the fuel cell system 1 according to the present embodiment will be described. During normal operation, the fuel cell system 1 controls the fuel gas supply system 20 and the oxidant gas supply system 50 to supply appropriate amounts of hydrogen gas and oxygen to the fuel cell 10 in order to generate power according to the demand of the load device 120. To supply. When the fuel cell system 1 is stopped, such as when the vehicle is stopped, the controller 100 executes stop operation control. At this time, the controller 100 closes the valves 29, 32, 59, 62, opens the first air supply line valve 81, and supplies the air in the buffer tank 70 to the oxidant electrode 12 of the fuel cell 10. Here, conventionally, since the buffer tank 70 can store only a certain amount of air, when the oxidant gas expands due to a temperature change, etc., it is supplied to the oxidant electrode 12 of the fuel cell 10 in the stop operation control. The number of air molecules decreased and the hydrogen gas of the fuel cell 10 could not be consumed.

  However, in this embodiment, the capacity of the buffer tank 70 is variable. For this reason, an appropriate amount of air can be provided to the oxidant electrode 12 of the fuel cell 10 in the stop operation control. More specifically, the controller 100 determines the fuel based on at least one of the pressure of the fuel electrode 11 immediately before the fuel cell 10 is stopped, the temperature of hydrogen gas, the temperature of air, and the concentration of hydrogen gas in the fuel electrode 11. An oxygen amount (air amount) capable of having a molecular number sufficient to consume the hydrogen gas remaining in the fuel electrode 11 of the battery 10 is calculated. Then, the controller 100 changes the capacity of the buffer tank 70 to a capacity for storing the calculated oxygen amount. Thereby, oxygen that can completely consume the hydrogen gas in the fuel cell 10 when the operation is stopped can be supplied from the buffer tank 70.

  Next, detailed operation of the fuel cell system 1 according to the present embodiment will be described. FIG. 2 is a flowchart showing a detailed operation of the fuel cell system 1 according to the present embodiment. Note that the processing shown in FIG. 2 indicates the stop operation control, and it is assumed that the normal operation control is performed before the stop operation control is performed.

  As shown in the figure, in the stop operation control, the controller 100 first opens the hydrogen gas supply valve 24 and the air supply valve 54, and then the hydrogen humidifier inlet valve 27, the hydrogen humidifier outlet valve 28, and the air humidifier inlet valve. 57 and the air humidifier outlet valve 58 are closed (ST1). Then, the controller 100 opens the first air supply line valve 81, the air circulation pipe inlet valve 114, and the air circulation pipe outlet valve 115 (ST2).

  Thereafter, the controller 100 remains in the fuel electrode 11 of the fuel cell 10 based on the pressure of the fuel electrode 11 immediately before the fuel cell 10 is stopped, the temperature of hydrogen gas, the temperature of air, and the hydrogen gas concentration in the fuel electrode 11. The amount of oxygen (the amount of air) having the number of molecules sufficient to consume the hydrogen gas to be consumed is calculated (ST3). Next, the controller 100 activates the air circulation pump 112 (ST4).

  Then, the controller 100 controls the tank capacity control valve 72 and the capacity adjustment discharge valve 74 to change the capacity of the buffer tank 70 so that the calculated oxygen amount can be taken in, and the oxygen amount (air amount) is changed. The sample is taken into the buffer tank 70 (ST5). As a result, an appropriate amount of air is taken into the buffer tank 70.

  Thereafter, the controller 100 closes the air flow rate adjustment valve 53, the oxidant electrode inlet valve 59, and the oxidant electrode outlet valve 62, and circulates the gas (ST6). Next, the controller 100 closes the hydrogen gas flow rate adjustment valve 23, the fuel electrode inlet valve 29 and the fuel electrode outlet valve 32, opens the hydrogen circulation pipe inlet valve 44 and the hydrogen circulation pipe outlet valve 45, and activates the hydrogen circulation pump 42. Then, the gas is circulated (ST7). In this way, by circulating the gas, the electrochemical reaction between the hydrogen gas and oxygen is promoted, the hydrogen gas is consumed quickly, and the operation of the fuel cell system 1 is stopped early.

  Thereafter, the controller 100 operates both the dehydrators 43 and 113 (ST8). That is, the controller 100 operates the air dehydrator 113 to remove the generated water generated during the shutdown process, and operates the hydrogen gas dehydrator 43 to cross the oxidizer electrode 12 due to cross leak. Remove the water that has moved. This prevents water from blocking the flow path of the oxidant electrode 12 and causing a delay in the electrochemical reaction.

  Then, controller 100 determines whether or not the cell voltage has become a certain value or less (ST9). That is, the controller 100 determines whether or not the hydrogen gas and oxygen are consumed and the cell voltage is reduced. Here, since the gas of the fuel cell 10 is desirably consumed completely, the constant value is set to approximately “0V”. The constant value is not limited to “0V”.

  If it is determined that the cell voltage is not lower than the predetermined value (ST9: NO), the controller 100 repeats this process until it is determined that the cell voltage is lower than the predetermined value. On the other hand, when it is determined that the cell voltage has become equal to or lower than a certain value (ST9: YES), the controller 100 determines that the hydrogen gas and oxygen in the fuel cell 10 are almost consumed. That is, at this time, the fuel cell 10 is almost occupied by nitrogen gas.

  Then, the controller 100 closes the first air supply line valve 81 and opens the second air supply line valve 91 (ST10). As a result, the controller 100 sends nitrogen gas to the fuel electrode 11 of the fuel cell 10. Thereafter, the controller 100 determines whether or not the fuel electrode 11 and the oxidant electrode 12 have the same pressure (ST11). That is, the controller 100 determines whether or not the stop processing of the fuel cell system 1 can be completed by setting both the electrodes 11 and 12 to the same pressure.

  When it is determined that the fuel electrode 11 and the oxidant electrode 12 are not at the same pressure (ST11: NO), the controller 100 determines this until the fuel electrode 11 and the oxidant electrode 12 are at the same pressure. Repeat the process. On the other hand, when it is determined that the fuel electrode 11 and the oxidant electrode 12 have the same pressure (ST11: YES), the stop process of the fuel cell system 1 is completed.

  In this way, according to the fuel cell system 1 according to the present embodiment, the oxygen amount (air amount) having the number of molecules sufficient to consume the hydrogen gas remaining in the fuel electrode 11 of the fuel cell 10 is calculated, and the calculation is performed. The capacity of the buffer tank 70 is changed to a capacity for storing the oxygen amount. For this reason, even in a situation where the number of oxygen molecules per unit volume changes due to factors such as temperature conditions, the amount of oxygen including the necessary number of molecules is obtained, and the capacity of the buffer tank 70 is set so that the amount is stored. Be changed. Therefore, oxygen having a molecular number sufficient to consume hydrogen gas is appropriately stored in the buffer tank 70. Therefore, oxygen capable of completely consuming hydrogen gas when the operation is stopped can be supplied from the buffer tank, and all the gas in the stack can be made a nitrogen atmosphere.

  Further, after the air in the buffer tank 70 is supplied to the oxidant electrode 12 of the fuel cell 10 to consume the hydrogen gas remaining in the fuel electrode 11 of the fuel cell 10, the gas in the buffer tank 70 is changed to the fuel cell 10. The fuel electrode 11 is supplied to make the fuel electrode 11 and the oxidant electrode 12 have the same pressure. For this reason, the fuel electrode 11 and the oxidant electrode 12 can be quickly made to have equal pressure, and the operation of the fuel cell system 1 can be stopped early.

  Further, when the air in the buffer tank 70 is supplied to the oxidant electrode 12 of the fuel cell 10 and the hydrogen gas remaining in the fuel electrode 11 of the fuel cell 10 is consumed, the oxidant gas circulation system 110 (first air supply line) 80) and the fuel gas circulation system 40 circulates each gas. For this reason, the electrochemical reaction between hydrogen gas and oxygen can be promoted to quickly consume the hydrogen gas, and the fuel cell system 1 can be shut down early.

  In addition, when the air in the buffer tank 70 is supplied to the oxidant electrode 12 of the fuel cell 10 and the hydrogen gas remaining in the fuel electrode 11 of the fuel cell 10 is consumed, both dehydrators 43 and 113 are operated to generate water. Therefore, it is possible to prevent the generated water generated during the operation stop process from blocking the flow path of the oxidant electrode 12 and the like. Thereby, delay of an electrochemical reaction can be prevented and the operation of the fuel cell system 1 can be stopped early.

  Further, the hydrogen gas remaining in the fuel electrode 11 of the fuel cell 10 is only consumed based on at least one of the pressure of the fuel electrode 11, the temperature of hydrogen gas, the temperature of air, and the hydrogen gas concentration in the fuel electrode 11. Therefore, the capacity of the buffer tank 70 can be calculated accurately.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment, and may be modified without departing from the gist of the present invention. For example, in the present embodiment, the fuel gas is hydrogen gas and the oxidant gas is oxygen. However, the present invention is not limited to this, and other gases may be used.

1 is a configuration diagram of a fuel cell system according to a first embodiment of the present invention. It is explanatory drawing which shows the control content of a control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 10 ... Fuel cell 11 ... Fuel electrode 12 ... Oxidant electrode 20 ... Fuel gas supply system 21 ... Hydrogen gas supply piping 22 ... Hydrogen humidifier 23 ... Hydrogen gas flow control valve 24 ... Hydrogen gas supply valve 25 ... 1st branch pipe 26 ... 2nd branch pipe 27 ... Hydrogen humidifier inlet valve 28 ... Hydrogen humidifier outlet valve 29 ... Fuel electrode inlet valve 30 ... Fuel gas discharge system 31 ... Hydrogen gas discharge pipe 32 ... Fuel electrode outlet valve 40 ... Fuel gas circulation system 41 ... Hydrogen circulation pipe 42 ... Hydrogen circulation pump 43 ... Hydrogen gas dehydrator (dehydration means)
44 ... Hydrogen circulation pipe inlet valve 45 ... Hydrogen circulation pipe outlet valve 50 ... Oxidant gas supply system 51 ... Air supply pipe 52 ... Air humidifier 53 ... Air flow rate adjustment valve 54 ... Air supply valve 55 ... Third branch pipe 56 ... Fourth branch pipe 57 ... Air humidifier inlet valve 58 ... Air humidifier outlet valve 59 ... Oxidant electrode inlet valve 60 ... Oxidant gas discharge system 61 ... Air discharge pipe 62 ... Oxidant electrode outlet valve 70 ... Buffer tank 70a ... Capacity adjustment plate 71 ... Tank supply pipe 72 ... Tank capacity control valve 73 ... Tank discharge pipe 74 ... Capacity adjustment discharge valve 80 ... First air supply line 81 ... First air supply line valve 90 ... Second air supply line 91 ... Second air supply line valve 100... Controller (control means)
110 ... oxidant gas circulation system 111 ... air circulation pipe 112 ... air circulation pump 113 ... air dehydrator (dehydration means)
114 ... Air circulation piping inlet valve 115 ... Air circulation piping outlet valve 120 ... Load device 121 ... Secondary battery 122 ... Voltage measuring instrument

Claims (4)

A fuel cell having a fuel electrode supplied with a fuel gas and an oxidizer electrode supplied with an oxidant gas, and reacting the fuel gas with the oxidant gas to generate electric power;
An oxidant gas supply system for supplying an oxidant gas to the oxidant electrode of the fuel cell during normal operation;
A buffer tank capable of supplying an oxidant gas to the oxidant electrode of the fuel cell;
When the operation is stopped, the oxidant gas supply system does not supply the oxidant gas to the oxidant electrode of the fuel cell, but the oxidant gas in the buffer tank is supplied to the oxidant electrode of the fuel cell. Control means for consuming fuel gas remaining in the fuel electrode of the battery,
The buffer tank has a variable oxidant gas storage capacity,
The control means consumes the fuel gas remaining in the fuel electrode of the fuel cell based on at least one of the pressure of the fuel electrode, the temperature of the fuel gas, the temperature of the oxidant gas, and the fuel gas concentration in the fuel electrode. A fuel cell system, comprising: calculating an amount of oxidant gas having a number of molecules sufficient to allow the buffer tank to have a capacity for storing the calculated amount of oxidant gas. The buffer tank is capable of supplying an oxidant gas to the fuel electrode of the fuel cell,
The control means supplies the oxidant gas in the buffer tank to the oxidant electrode of the fuel cell and consumes the fuel gas remaining in the fuel electrode of the fuel cell, and then converts the gas in the buffer tank to the fuel The fuel cell system according to claim 1, wherein the fuel electrode and the oxidant electrode are supplied with an equal pressure by being supplied to the fuel electrode of the battery. An oxidant gas circulation system for circulating gas from the oxidant electrode downstream of the fuel cell through the buffer tank to the oxidant electrode upstream;
A fuel gas circulation system for circulating gas from downstream to upstream of the fuel electrode of the fuel cell,
The control means supplies the oxidant gas in the buffer tank to the oxidant electrode of the fuel cell and consumes the fuel gas remaining in the fuel electrode of the fuel cell. The fuel cell system according to claim 1, wherein the gas is circulated in the gas circulation system. Further comprising dehydrating means for removing generated water generated by power generation in the fuel cell;
The control means operates the dehydration means to supply the oxidant gas in the buffer tank to the oxidant electrode of the fuel cell and consume the fuel gas remaining in the fuel electrode of the fuel cell. The fuel cell system according to any one of claims 1 to 3, wherein the fuel cell system is removed.

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