JP2005100846A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing the deterioration of a fuel cell during stoppage. <P>SOLUTION: The fuel cell system comprises an exhaust oxidant gas circulation system 42 for circulating oxidant gas exhausted from an oxygen electrode 1b when stopping an operation of the fuel cell 1, and a gas tank 13 for storing the exhausted oxidant gas having increased concentration of inert gas as the exhausted oxidant gas circulates. The fuel cell system comprises an inert gas supply system 43 for supplying the inert gas to a hydrogen electrode 1 from the gas tank 13. Depending of the condition of power generation of the fuel cell 1, the exhaust oxidant gas circulation system 42 and the inert gas supply system 43 are selectively switched by opening and closing flow control valves 15 and 16 and an inert gas flow control valve 14 to fill the inert gas to a hydrogen electrode 1a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to prevention of deterioration of a fuel cell.

Conventionally, in order to prevent deterioration of the hydrogen electrode when the fuel cell is stopped, exhaust hydrogen and supply hydrogen are mixed with an oxidant gas, burned by a combustor, and the generated inert gas is filled into the hydrogen electrode. Patent Document 1 discloses this.
US Patent Application Publication No. 2002/0098393

  However, in the above invention, exhaust hydrogen is mixed with an oxidant gas in order to purge hydrogen when the fuel cell is stopped, burns, and the inert gas generated thereby is supplied to the hydrogen electrode. Since the combustor is provided to burn the gas and the oxidant gas, there are problems such as an increase in weight and an increase in cost.

  The present invention was devised to solve such problems, and it is possible to prevent deterioration of the fuel cell by filling with an inert gas, and to reduce the size of the fuel cell system without requiring a combustor. And

  In the present invention, when performing stop processing of the fuel cell in the fuel cell system, the channel blocking means for blocking the discharge channel of the hydrogen electrode and the oxygen electrode, and the exhaust gas discharged from the oxygen electrode to the oxygen electrode Circulating circulation path, gas accumulation means connected to the circulation flow path, gas introduction means for introducing gas accumulation means for storing exhaust gas having a high concentration of inert gas, and supply from the gas accumulation means to the hydrogen electrode The exhaust gas supply flow path through which the exhaust oxidant gas flows, the flow path switching means for switching the circulation flow path and the exhaust gas supply flow path to be cut off, and the fuel cell after the fuel supply to the fuel cell is stopped. Based on the power generation state estimation means for estimating the power generation state, the gas delivery means for sending the inert gas from the gas storage means to the hydrogen electrode based on the power generation state, and the power generation amount of the fuel cell estimated by the power generation state estimation means Switching the circulation flow path and the discharge oxidizing gas passage, and a discharge gas filling control means for filling the hydrogen electrode exhaust gas by a gas delivery means.

  According to the present invention, when the fuel cell is stopped, the exhaust gas is circulated to the oxygen electrode to consume oxygen in the exhaust gas, to increase the concentration of the inert gas in the exhaust gas, and to store the inert gas in the gas When the hydrogen is accumulated in the means and the hydrogen at the hydrogen electrode almost disappears, the gas can be supplied to the hydrogen electrode and filled to prevent deterioration of the hydrogen electrode. In addition, since the combustor or the like is not used, the system can be downsized.

  The configuration of the first embodiment of the present invention will be described with reference to the configuration diagram of FIG.

  The first embodiment of the present invention includes a fuel cell 1 that generates electric power using hydrogen supplied to the hydrogen electrode 1a and oxidant gas supplied to the oxygen electrode 1b. In addition, a voltage detection device 17 is provided as voltage detection means for detecting the power generation amount of the fuel cell 1.

  The fuel system 40 includes a hydrogen supply valve 3 that controls the flow rate of hydrogen supplied from a hydrogen cylinder (not shown), and a hydrogen supply that serves as a flow path for supplying hydrogen whose flow rate is controlled by the hydrogen supply valve 3 to the hydrogen electrode 1a. A flow path 2 is provided. Furthermore, a hydrogen discharge flow path 4 which is a flow path when discharging exhaust oxidant gas discharged from the hydrogen electrode 1a to the outside, and a hydrogen discharge valve 5 which is a flow path shut-off means for controlling the flow rate of the exhaust gas are provided. .

  The oxidant system 41 includes an oxidant gas supply valve 7 that controls the flow rate of an oxidant gas, such as air, supplied from a compressor (not shown), and an oxidant whose flow rate is controlled by the oxidant gas supply valve 7. An oxidant gas supply channel 6 serving as a channel for supplying gas to the oxygen electrode 1b is provided. Furthermore, an oxidant gas discharge flow path 8 serving as a flow path for discharged oxidant gas discharged from the oxygen electrode 1b, and an oxidant gas discharge valve 9 serving as flow path blocking means for controlling the flow rate of the discharged oxidant gas are provided. .

  The exhaust oxidant gas circulation system 42 connects the oxidant gas discharge channel 8 and the oxidant gas supply channel 6 and is an oxidant that is a circulation channel through which the exhaust oxidant gas circulating through the oxygen electrode 1b passes. A gas circulation channel 10, a flow rate control valve 15 for controlling the inflow of exhausted oxidant gas to the oxidant gas circulation channel 10, a pump 11 for circulating the oxidant gas, and an exhaust oxidant supplied to the oxygen electrode 1b And a flow control valve 16 for controlling the gas.

  Further, a gas tank 13 is provided as a gas storage means for storing exhaust oxidant gas in which oxygen is consumed by circulating oxygen electrode 1b to reduce oxygen concentration and to increase inert gas concentration. The gas tank 13 has a gas storage chamber 13b partitioned by a piston 13a inside, and the piston rod 13c connected to the piston 13a is driven by a motor 29 so that the piston 13a is interlocked with the movement of the motor 29. The volume of the gas storage chamber 13 b is changed, and the exhaust oxidant gas is sucked into the gas tank 13 or discharged from the gas tank 13. For example, a rack is formed on the piston rod 13c, a pinion is provided on the rotation shaft of the motor 29, and the rack and the pinion are engaged to form a power mechanism for the piston 13a. In this case, the piston 13a sucks or pushes the exhaust oxidant gas into the gas tank 13 as a gas suction means when sucking the exhaust oxidant gas and as a gas delivery means when discharging.

  The inert gas supply system 43 is an inert gas supply channel that is an exhaust gas supply channel for supplying exhaust oxidant gas having a high inert gas concentration from the gas storage chamber 13b of the gas tank 13 to the hydrogen electrode 1a. 12 and an inert gas flow rate control valve 14 which is a flow rate control means for controlling the exhaust oxidant gas flow rate.

  Moreover, the controller 30 is provided as a control means which controls the fuel cell system of this invention. The controller 30 controls the operation and stop of the fuel cell 1 in principle as follows.

  During normal operation, the hydrogen whose flow rate is controlled by the hydrogen supply valve 3 is supplied to the hydrogen electrode 1a of the fuel cell 1 through the hydrogen supply flow path 2, and the exhausted hydrogen consumed by the power generation of the fuel cell 1 is the hydrogen discharge valve. The flow rate is adjusted by 5 and discharged to the outside.

  The oxidant gas whose flow rate is controlled by the oxidant gas supply valve 7 is supplied to the oxygen electrode 1b of the fuel cell 1 through the oxidant gas supply flow path 6, and is discharged after the reaction in the fuel cell 1. Normally, the gas passes through the oxidant gas discharge passage 8, the flow rate is adjusted by the oxidant gas discharge valve 9, and the gas is discharged to the outside.

  On the other hand, in the stop process performed when the fuel cell 1 is stopped, the oxidant gas discharge valve 9 is closed, the flow rate control valves 15 and 16 are opened, and the pump 11 is started to discharge from the oxygen electrode 1b. The discharged oxidant gas passes through the oxidant gas circulation passage 10 and is circulated through the oxygen electrode 1b. By circulating the exhaust oxidant gas to the oxygen electrode 1b, the fuel cell 1 reduces the amount of power generation, but oxygen in the exhaust oxidant gas is consumed, so the oxygen concentration becomes low and is not consumed by the oxygen electrode 1b. The inert gas concentration becomes high. When the oxygen concentration becomes sufficiently low, the motor 29 moves the piston 13a to increase the volume of the gas storage chamber 13b of the gas tank 13, and the exhausted oxidant gas (hereinafter referred to as the gas tank 13) having a high inert gas concentration in the gas storage chamber 13b. The stored oxidant gas having a high inert gas concentration is used as the inert gas). Here, the inert gas is nitrogen contained in the air.

  When the power generation amount in the fuel cell 1 becomes smaller than a predetermined value, the flow control valves 15 and 16 are closed, the pump 11 is stopped, and the inert gas flow control valve 14 is opened (the flow control valves 15 and 16 and the inert gas flow). The gas flow rate control valve 14 forms a flow path switching means). Then, the piston 29a is moved by the motor 29 to reduce the volume of the gas storage chamber 13b of the gas tank 13, the inert gas stored in the gas storage chamber 13b is supplied to the hydrogen electrode 1a, the residual hydrogen is discharged, and the hydrogen electrode 1a is discharged. Is filled with an inert gas.

  Next, the control operation of the controller 30 will be described in detail according to the time chart of FIG. Note that the oxygen concentration and the inert gas concentration are predicted from control by the controller 30.

  At time t0, the fuel cell 1 is in operation. At this time, the hydrogen supply valve 3 and the hydrogen discharge valve 5, and the oxidant gas supply valve 7 and the oxidant gas discharge valve 9 are open, and are necessary for power generation in the fuel cell 1. The flow rates of hydrogen and oxidant gas are controlled by the opening of each supply valve. The flow control valves 15 and 16 and the inert gas flow control valve 14 are closed. Thereby, each exhaust gas containing surplus hydrogen and oxidant after power generation discharged from the hydrogen electrode 1a and the oxygen electrode 1b of the fuel cell 1 is discharged to the outside.

  The stop process of the fuel cell 1 is started at t1. Here, first, the oxidant gas discharge valve 9 is closed, the flow control valves 15 and 16 are opened, and the pump 11 is started. As a result, the discharged oxidant gas discharged from the oxygen electrode 1b flows into the oxidant gas circulation passage 10 and circulates through the oxygen electrode 1b.

  At t2, when the rotational speed of the pump 11 becomes sufficiently high and stable, the piston 29a is moved by the motor 29 to gradually increase the volume of the gas storage chamber 13b of the gas tank 13, and the inert gas is accumulated in the gas storage chamber 13b. . Since the volume of the gas storage chamber 13b increases, the volume of the oxidant gas that circulates including the oxidant gas circulation channel 10 increases, and the oxygen concentration temporarily increases. Thereafter, as the circulation is repeated, oxygen in the exhaust oxidant gas is consumed by the oxygen electrode 1b, and the oxygen concentration gradually decreases. Further, since the oxygen concentration is lowered, the generated power in the fuel cell 1 is reduced, and the voltage detected by the voltage detection device 17 is gradually lowered. In this case, by slowing down the moving speed of the piston 13a by the motor 29, the volume of the gas storage chamber 13b is gradually increased, the pressure fluctuation in the oxygen electrode 1b is reduced, and damage to the oxygen electrode 1b due to pressure fluctuation is prevented. To. Further, in order to prevent the deterioration of the oxygen electrode 1b due to the pressure drop of the oxygen electrode 1b, an oxidant gas is supplied from the outside, and the pressure of the oxygen electrode 1b is adjusted to a pressure range in which the oxygen electrode 1b does not deteriorate. The pressure of the oxygen electrode 1b is detected by a pressure gauge (not shown).

  When the oxygen in the circulating exhaust oxidant gas is consumed and the oxygen concentration becomes low, the reaction of the fuel cell 1 becomes small. When the voltage detected by the voltage detection device 17 becomes lower than the hydrogen supply stop voltage V1 at t3, it is determined that it is not necessary to supply new hydrogen to the hydrogen electrode 1a, and the hydrogen supply valve 3 is closed to supply the hydrogen electrode 1a. Stop the hydrogen supply. Here, the hydrogen supply stop voltage V1 is a voltage obtained in advance by experiments or the like. Further, the oxidant gas supply valve 7 is closed to stop the oxidant gas supply from the outside. Thereafter, the hydrogen used for power generation uses the residual hydrogen in the hydrogen electrode 1a. Thus, hydrogen can be consumed without remaining in the hydrogen electrode 1a.

  When the amount of oxygen in the exhaust oxidant gas is further reduced, the voltage detected by the voltage detection device 17 is further reduced, and when the inert gas supply start voltage V2 is reached at t4, residual hydrogen in the hydrogen electrode 1a is consumed. Further, it is determined that oxygen in the exhaust oxidant gas is sufficiently consumed and that the inert gas is sufficiently accumulated in the gas storage chamber 13b, the flow control valves 15 and 16 are closed, the pump 11 is stopped, Stop circulation of exhaust oxidant gas. Further, the inert gas flow control valve 14 is opened, the piston 29a is pushed by the motor 29, and the supply of the inert gas accumulated in the gas storage chamber 13b to the hydrogen electrode 1a is started. Here, the inert gas supply start voltage V2 is a value obtained in advance by experiments or the like.

  Thereafter, at t5, the hydrogen electrode 1a discharges almost no remaining hydrogen, and instead is sufficiently filled with inert gas, so the hydrogen discharge valve 5 and the inert gas flow control valve 14 are closed to complete the stop process. (T4 to t5 constitute exhaust gas filling control means).

  In this embodiment, the voltage detection device 17 is used to measure the power generation state of the fuel cell 1, but a device that measures the degree of variation in cell voltage may be used instead.

  Further, the maximum volume Vt of the gas storage chamber 13b is, as shown in FIG. 3, the volume of the hydrogen electrode 1a, the flow volume from the gas storage chamber 13b to the hydrogen electrode 1a, and from the fuel cell 1 to the hydrogen discharge valve 5. It is the same as or more than the hydrogen electrode side volume Vh, which is the total volume of the hydrogen discharge flow path 4 and the flow path volume. Thereby, the hydrogen electrode 1a can be filled with the inert gas stored in the gas storage chamber 13b. At this time, if the maximum volume Vt of the gas storage chamber 13b and the hydrogen electrode side volume Vh are the same, air may flow backward from the hydrogen discharge side, so the timing of closing the hydrogen discharge valve 5 may be closed before t4. Is possible.

  The effect of 1st Embodiment of this invention is demonstrated.

  The exhaust oxidant gas discharged from the oxygen electrode 1b when the fuel cell 1 is stopped is circulated to the oxygen electrode 1b by the oxidant gas circulation flow path 10, and the exhaust oxidant gas whose inert gas concentration increases as it circulates. Is stored in the gas storage chamber 13b, and then the inert gas is supplied and filled from the gas storage chamber 13b to the hydrogen electrode 1a, whereby deterioration of the fuel cell 1 while the fuel cell 1 is stopped can be prevented. Further, since the oxidant gas circulation passage 10 includes the gas tank 13 without using a combustor or the like, the hydrogen electrode 1a after the fuel cell 1 is stopped can be filled with an inert gas. The battery system can be reduced in size.

  When accumulating the inert gas in the gas storage chamber 13b, the pressure fluctuation of the oxygen electrode 1b is reduced by reducing the moving speed of the piston 13a, and even if oxygen of the exhaust oxidant gas is consumed, it is externally supplied. Since the oxidizing gas is supplied to adjust the pressure of the oxygen electrode 1b, the deterioration of the oxygen electrode 1b can be prevented.

  The configuration of the second embodiment of the present invention will be described with reference to FIG.

  The second embodiment will be described with a focus on differences from the first embodiment. In this embodiment, in addition to the configuration of the first embodiment, a pressure gauge 18 as pressure detection means is provided in the hydrogen supply flow path 2. The pressure gauge 18 detects the pressure of the hydrogen electrode 1a. The controller 30 also has an inert gas supply control function that adjusts the opening degree of the inert gas flow control valve 14 so that the pressure fluctuation of the hydrogen electrode 1a falls within a predetermined range based on the pressure detected by the pressure gauge 18. Have Thereby, pressure fluctuation of the hydrogen electrode 1a due to consumption of hydrogen or inflow of inert gas is regulated. As a control method, PI control or the like is used.

  The control operation by the controller 30 will be described with reference to the time chart of FIG.

  Here, the control from t0 to t2 is the same as that from t0 to t2 in the first embodiment, and a description thereof will be omitted.

  When the oxygen in the circulating exhaust oxidant gas is consumed and the oxygen concentration becomes low, the reaction of the fuel cell 1 becomes small. When the voltage detected by the voltage detection device 17 becomes lower than the hydrogen supply stop voltage V1 at t3, it is determined that it is not necessary to supply new hydrogen to the hydrogen electrode 1a, and the hydrogen supply valve 3 is closed to supply the hydrogen electrode 1a. Stop the hydrogen supply. Further, the oxidant gas supply valve 7 is closed to stop the oxidant gas supply from the outside. Here, the hydrogen supply stop voltage V1 is a voltage obtained in advance by experiments or the like. Thereafter, the hydrogen used for power generation uses the residual hydrogen in the hydrogen electrode 1a. Thus, hydrogen can be consumed without remaining in the hydrogen electrode 1a. When the residual hydrogen is consumed at the hydrogen electrode 1a, the pressure of the consumed hydrogen decreases, but the opening degree of the inert gas flow control valve 14 is adjusted according to the pressure of the hydrogen electrode 1a detected by the pressure gauge 18. Then, the exhaust oxidant gas is supplied to the hydrogen electrode 1a, and the pressure in the hydrogen electrode 1a is controlled to be within a predetermined range.

  When the voltage detected by the voltage detector 17 is further lowered and reaches the inert gas supply start voltage V2 at t4, the residual hydrogen in the hydrogen electrode 1a is further consumed, and the inert gas is contained in the gas storage chamber 13b. The flow control valves 15 and 16 are closed, the pump 11 is stopped, and the exhaust oxidant gas circulation is stopped. Further, the inert gas flow control valve 14 is further opened, the piston 13a is pushed by the motor 29, and the supply of the inert gas accumulated in the gas storage chamber 13b to the hydrogen electrode 1a is started. Thereby, the inert gas can be filled in the hydrogen electrode 1a. When an inert gas is supplied from the gas storage chamber 13b to the hydrogen electrode 1a, the pressure of the hydrogen electrode 1a increases. However, the pressure of the hydrogen electrode 1a is detected by the pressure gauge 18, and the inert gas flow control valve 14 is detected according to the pressure. Is controlled so that the pressure of the hydrogen electrode 1a does not rapidly increase. Thereby, damage to the hydrogen electrode 1a can be prevented.

  When the pressure in the hydrogen electrode 1a is stabilized, the residual hydrogen is discharged and the inert gas is filled, the hydrogen discharge valve 5 and the inert gas flow control valve 14 are closed at t5, and the fuel cell stop process is terminated.

  The effect of 2nd Embodiment of this invention is demonstrated.

  By supplying the exhaust oxidant gas to the hydrogen electrode 1a in accordance with the pressure drop of the hydrogen electrode 1a after the hydrogen supply valve 3 is closed, the sudden pressure drop of the hydrogen electrode 1a can be prevented, and the gas storage chamber When the inert gas from 13b is charged into the hydrogen electrode 1a, the inert gas flow control valve 14 is gradually opened according to the pressure of the hydrogen electrode 1a, thereby preventing a rapid pressure increase of the hydrogen electrode 1a. Damage to the fuel cell 1 can be prevented.

  The configuration of the third embodiment of the present invention will be described with reference to FIG.

  The third embodiment will be described with a focus on differences from FIG. This embodiment includes a flow meter 19 as a hydrogen flow rate detecting means upstream of the hydrogen supply valve 3 in addition to the configuration of the first embodiment. The controller 30 calculates the amount of hydrogen necessary to consume oxygen contained in the exhaust oxidant gas when the exhaust oxidant gas is circulated. Further, the flow rate of hydrogen detected by the flow meter 19 is integrated. As a result, only hydrogen necessary for the stop process of the fuel cell 1 is accurately supplied to the hydrogen electrode 1a to prevent unnecessary hydrogen supply.

  Here, a method for calculating the hydrogen amount will be described.

As shown in FIG. 3, the volume of the oxygen electrode 1b, the flow volume of the exhaust oxidant gas circulation system 42 (the gas storage chamber 13b is the maximum volume), and the oxidant gas supply flow that passes when the exhaust oxidant gas circulates. Hydrogen required to consume oxygen in the oxygen-side volume V0, which is the total of the channel volumes of the passage 6 and the oxidant gas discharge channel 8, by power generation of the fuel cell 1, is the mole of oxygen in the oxygen-side volume V0. The number of moles is at least twice that of the number. First, the air mole number N (Air) of the oxygen side volume V0 is
N (Air) mol = V0 × P0 / (R × T0) (1)
However, P0: average pressure around the oxygen electrode, R: gas constant, T0: average temperature.
When the specific gravity of air is 28.96 g and the specific gravity of air is applied to the above (1), it becomes the air weight of exhausted oxidant gas, and the composition ratio of exhausted oxidant gas is 80% nitrogen and 20% oxygen, The number of moles of oxygen N (O2) in the exhausted oxidizing gas is
N (O2) mol = N (Air) × 28.96 × 0.2 / 32 (2)
It becomes. Since the number of moles of hydrogen N (H2) necessary for consuming this oxygen in the fuel cell 1 is twice that of the above equation (2),
N (H2) mol = 2N (O2) mol (3)
It becomes. This makes it possible to calculate the number of moles of hydrogen necessary for consuming oxygen in the exhausted oxidant gas. Here, the average pressure and the average temperature around the oxygen electrode 1b are measured by a pressure gauge and a thermometer (not shown).

  Next, the control operation by the controller 30 will be described with reference to the time chart of FIG.

  At time t0, the fuel cell 1 is in operation. At this time, the hydrogen supply valve 3, the hydrogen discharge valve 5, the oxidant gas supply valve 7, and the oxidant gas discharge valve 9 are open, and the flow control valves 15, 16 are not connected. The active gas flow control valve 14 is closed. As a result, each exhaust gas containing surplus hydrogen and oxidant after power generation discharged from the hydrogen electrode 1a and oxygen electrode 1b of the fuel cell 1 is discharged to the outside.

  The stop process of the fuel cell 1 is started at t1. Here, first, the oxidant gas discharge valve 9 is closed, the flow control valves 15 and 16 are opened, and the pump 11 is started. As a result, the discharged oxidant gas discharged from the oxygen electrode 1b flows into the oxidant gas circulation passage 10 and circulates through the oxygen electrode 1b. Also, the integration of the hydrogen flow rate measured by the flow meter 19 is started.

  When the rotational speed of the pump 11 becomes sufficiently high and stable at t2, the piston 29a is moved by the motor 29 to gradually increase the volume of the gas storage chamber 13b, and the inert gas is accumulated in the gas storage chamber 13b. Since the volume of the gas storage chamber 13b increases, the volume of the oxidant gas that circulates including the oxidant gas circulation channel 10 increases, and the oxygen concentration temporarily increases. Thereafter, as the circulation is repeated, oxygen in the exhaust oxidant gas is consumed by the oxygen electrode 1b, and the oxygen concentration gradually decreases. Further, since the oxygen concentration is lowered, the generated power in the fuel cell 1 is reduced, and the voltage detected by the voltage detection device 17 is gradually lowered. In this case, by slowing down the moving speed of the piston 13a by the motor 29, the volume of the gas storage chamber 13b is gradually increased, the pressure fluctuation in the oxygen electrode 1b is reduced, and damage to the oxygen electrode 1b due to pressure fluctuation is prevented. To. Further, in order to prevent the deterioration of the oxygen electrode 1b due to the pressure drop of the oxygen electrode 1b, an oxidant gas is supplied from the outside, and the pressure of the oxygen electrode 1b is adjusted to a pressure range in which the oxygen electrode 1b does not deteriorate. The pressure of the oxygen electrode 1b is detected by a pressure gauge (not shown).

  Next, at t3, when the amount of hydrogen obtained by integrating the hydrogen flow rate detected by the flow meter 19 from time t1 to time t3 reaches the amount of hydrogen calculated by the equation (3), oxygen in the exhausted oxidant gas It is determined that the hydrogen necessary to consume the hydrogen has been supplied to the hydrogen electrode 1a, the hydrogen supply valve 3 is closed, and the supply of hydrogen to the hydrogen electrode 1a of the fuel cell 1 is stopped. Further, the oxidant gas supply valve 7 is closed to stop the oxidant gas supply from the outside. Thereafter, the hydrogen used for power generation uses the residual hydrogen in the hydrogen electrode 1a. Thus, hydrogen can be consumed without remaining in the hydrogen electrode 1a.

  Subsequent control after t4 is the same as in the first embodiment, and a description thereof is omitted here.

  The effect of the third embodiment of the present invention will be described.

  The amount of hydrogen necessary for the stop process of the fuel cell 1 is calculated according to the amount of oxygen in the exhausted oxidant gas, and the hydrogen flow rate detected by the flow meter 19 is integrated, and the integrated hydrogen flow rate reaches the calculated hydrogen amount. Then, the supply of hydrogen to the hydrogen electrode 1a is stopped, and only the necessary amount of hydrogen is supplied to the hydrogen electrode 1a, so that the shortage or surplus of hydrogen when the fuel cell 1 is stopped can be reduced. Deterioration can be further prevented.

  The configuration of the fourth embodiment of the present invention will be described with reference to FIG.

  The fourth embodiment will be described with a focus on differences from FIG. In this embodiment, in addition to the configuration of the first embodiment, the oxidant gas circulation passage 10 is provided with an oxygen concentration sensor 20 as oxygen concentration detection means for measuring the oxygen concentration in the exhausted oxidant gas. Further, the controller 30 has an inert gas supply control function for determining the supply of the inert gas to the hydrogen electrode 1 a based on the oxygen concentration sensor 20 and controlling the inert gas supply control valve 14. As a result, the oxygen concentration in the exhaust oxidant gas is accurately measured, and the hydrogen electrode 1a is filled with an inert gas having a sufficiently low oxygen concentration.

  Next, the control operation by the controller 30 will be described with reference to the time chart of FIG.

  Here, since t0 to t2 are the same as those in the first embodiment, description thereof is omitted here.

  At t3, when the volume of the gas storage chamber 13b becomes maximum, the oxygen concentration determination process is started. In this process, the oxygen concentration in the exhaust oxidant gas is detected by the oxygen concentration sensor 20, and it is determined whether the oxygen in the exhaust oxidant gas is consumed by circulation to the oxygen electrode 1b and the inert gas concentration is increased. .

  When the oxygen in the exhaust oxidant gas circulating in the oxygen electrode 1b is consumed and the oxygen concentration becomes low, the reaction of the fuel cell 1 becomes small, and the voltage detected by the voltage detector 17 at t4 is higher than the hydrogen supply stop voltage V1. When it becomes low, it is determined that it is not necessary to supply hydrogen to the hydrogen electrode 1a, and the hydrogen supply valve 3 is closed to stop supplying hydrogen to the hydrogen electrode 1a. Further, the oxidant gas supply valve 7 is closed to stop the oxidant gas supply from the outside. Here, the hydrogen supply stop voltage voltage V1 is a voltage obtained in advance through experiments or the like. Thereafter, the hydrogen used for power generation uses the residual hydrogen in the hydrogen electrode 1a. Thus, hydrogen can be consumed without remaining in the hydrogen electrode 1a.

  When the oxygen concentration detected by the oxygen concentration sensor 20 becomes lower than the inert gas supply concentration N1 at t5, it is determined that the inert gas that has sufficiently consumed oxygen is accumulated in the gas storage chamber 13b. The control valves 15 and 16 are closed, the pump 11 is stopped, and the circulation of the exhaust oxidant gas is stopped. Further, the inert gas flow control valve 14 is opened, and the piston 29a is pushed by the motor 29 to start supplying the inert gas accumulated in the gas storage chamber 13b to the hydrogen electrode 1a. Thereby, the hydrogen electrode 1a can be filled with an inert gas. Here, the inert gas supply concentration N1 is an oxygen concentration obtained by an experiment or the like in advance.

  After that, at t6, the residual hydrogen that hardly remains at the hydrogen electrode 1a was discharged, and instead the inert gas was sufficiently filled. Therefore, the hydrogen discharge valve 4 and the inert gas flow control valve 14 were closed to complete the stop process. To do.

  The effect of 4th Embodiment of this invention is demonstrated.

  Since the oxygen concentration in the exhaust oxidant gas is detected by the oxygen concentration sensor 20, the oxygen consumption in the oxygen electrode 1b is accurately detected, and an inert gas is supplied from the gas storage chamber 13b to the hydrogen electrode 1a based on the concentration. Since the filling is started, an inert gas having an accurate concentration can be quickly supplied, and the time until the filling is started can be shortened.

  The configuration of the fifth embodiment of the present invention will be described with reference to FIG.

  The fifth embodiment will be described with a focus on differences from FIG. In this embodiment, in addition to the configuration of the first embodiment, a pump 23 that circulates discharged hydrogen from the hydrogen electrode 1a, a hydrogen circulation passage 24 that serves as a passage for discharged hydrogen circulated by the pump 23, and a hydrogen circulation passage. The flow rate control valve 22 that controls the flow rate of discharged hydrogen to 24 and the flow rate control valve 21 that controls the flow rate of discharged hydrogen from the pump 23 to the hydrogen supply flow path 2 are provided. Thereby, when the stop process of the fuel cell 1 is performed, the exhausted hydrogen discharged from the hydrogen electrode 1a is circulated to the hydrogen electrode 1a to consume residual hydrogen.

  Next, the control operation by the controller 30 will be described according to the time chart of FIG.

  At time t0, the fuel cell 1 is in operation. At this time, the hydrogen supply valve 3 and the hydrogen discharge valve 5, the oxidant gas supply valve 7 and the oxidant gas discharge valve 9 are open, and the flow control valves 15 and 16 are not connected. The active gas flow control valve 14 is closed. Moreover, the flow control valves 21 and 22 are open, and the pump 23 is operating. As a result, the exhaust oxidant gas discharged from the oxygen electrode 1b of the fuel cell 1 is discharged to the outside, and part of the discharged hydrogen discharged from the hydrogen electrode 1a passes through the hydrogen circulation passage 24 to the hydrogen electrode 1a. Resupplied and consumed.

  From t1 to before t4, the flow control valves 21, 22 and the pump 23 continue the control at t0. Since other controls are the same as those in the first embodiment, a description thereof is omitted here.

  Further, when the amount of oxygen in the exhaust oxidant gas is further reduced, the voltage detected by the voltage detector 17 is further reduced, and the inert gas supply start voltage V2 set in advance at t4 is reached, the inside of the hydrogen electrode 1a. Residual hydrogen is consumed, oxygen in the oxidant gas is also consumed, and it is determined that the inert gas is sufficiently accumulated in the gas tank 13, the flow control valves 15 and 16 are closed, and the pump 11 is stopped. , Stop circulating the exhaust oxidant gas. Further, the flow control valves 21 and 22 are closed, and the pump 23 is stopped. Further, the inert gas flow control valve 14 is opened, the piston 29a is pushed by the motor 29, and the supply of the inert gas accumulated in the gas storage chamber 13b to the hydrogen electrode 1a is started. Thereby, the hydrogen electrode 1a can be filled with an inert gas.

  After that, at t5, the residual hydrogen that hardly remains in the hydrogen electrode 1a is discharged, and instead, the inert gas is sufficiently filled. Therefore, the hydrogen discharge valve 5 and the inert gas flow control valve 14 are closed to complete the stop process. To do.

  The effect of 5th Embodiment of this invention is demonstrated.

  When the fuel cell 1 is stopped, the residual hydrogen is circulated through the hydrogen circulation passage 24, and the hydrogen concentration is reduced like the oxidant gas, and then the inert gas is filled into the hydrogen electrode 1a. Degradation of the fuel cell 1 can be prevented while minimizing the amount of discharge.

  It goes without saying that the present invention is not limited to the above-described embodiments, and includes various modifications and improvements that can be made within the scope of the technical idea.

  The present invention can be used in various fields where fuel cells are used. In particular, it can be used in fuel cell vehicles that are frequently started and stopped.

It is a block diagram of 1st Embodiment of this invention. It is a time chart of 1st Embodiment of this invention. It is a figure which shows the relationship between the gas tank volume of 1st Embodiment of this invention, and the volume of a hydrogen flow path, and the relationship between the oxygen electrode circulation flow path and hydrogen flow volume of 3rd Embodiment. It is a block diagram of 2nd Embodiment of this invention. It is a time chart of 2nd Embodiment of this invention. It is a block diagram of 3rd Embodiment of this invention. It is a time chart of 3rd Embodiment of this invention. It is a block diagram of 4th Embodiment of this invention. It is a time chart of 4th Embodiment of this invention. It is a block diagram of 5th Embodiment of this invention. It is a time chart of 5th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Hydrogen supply flow path 3 Hydrogen supply valve 5 Hydrogen discharge valve (flow path cutoff means)
9 Oxidant discharge valve (channel blocking means)
10 Oxidant gas circulation channel (circulation channel)
11 Pump 12 Inert gas supply flow path 13 Gas tank (gas accumulation means)
13a Piston 13b Gas storage chamber 14 Inert gas flow control valve (flow control means)
17 Voltage detector (power generation state estimation means)
18 Pressure gauge (pressure detection means)
19 Flow meter (hydrogen flow rate detection means)
20 Oxygen concentration sensor (oxygen concentration detection means)
24 Hydrogen circulation flow path 29 Motor

Claims (9)

In a fuel cell system comprising a fuel cell that generates electricity by a reaction between hydrogen supplied to a hydrogen electrode and an oxidant supplied to an oxygen electrode,
A flow path blocking means for blocking each discharge flow path of the hydrogen electrode and the oxygen electrode during the stop process of the fuel cell;
A circulation flow path for circulating exhaust gas containing an inert gas exhausted from the oxygen electrode to the oxygen electrode during a stop process of the fuel cell;
Gas accumulating means connected to the circulation channel;
A gas introduction means for circulating the circulation passage and introducing the exhaust gas having a high inert gas concentration into the gas accumulation means;
An exhaust gas supply passage connecting the gas storage means and the hydrogen electrode;
Channel switching means for switching between the circulation channel and the exhaust gas supply channel so that they can be blocked;
Power generation state estimation means for estimating the power generation state of the fuel cell after stopping the supply of the hydrogen and the oxidant to the fuel cell;
Gas delivery means for delivering the exhaust gas from the gas accumulation means to the hydrogen electrode;
When the power generation amount of the fuel cell estimated by the power generation state estimation means becomes a predetermined value or less, the flow path switching means shuts off the circulation flow path and makes the exhaust gas supply flow path conductive, and the gas delivery A fuel cell system comprising: exhaust gas filling control means for sending and filling the exhaust gas from the gas storage means to the hydrogen electrode. Voltage detecting means for detecting the power generation voltage of the fuel cell;
2. The fuel cell system according to claim 1, wherein the power generation state estimation unit estimates a power generation state of the fuel cell based on the voltage of the fuel cell detected by the voltage detection unit. Comprising oxygen concentration detection means for detecting the oxygen concentration of the exhaust gas;
2. The fuel cell system according to claim 1, wherein the power generation state detection unit estimates a power generation state of the fuel cell based on an oxygen concentration of the exhaust gas detected by the oxygen concentration detection unit.   The volume of the gas accumulating means is at least the total amount of the volume of the hydrogen electrode and the flow volume of the exhaust gas supply flow path. Fuel cell system. The gas storage means is a gas tank capable of changing the volume of the gas storage chamber;
The fuel cell system according to any one of claims 1 to 4, wherein the gas introduction unit enlarges the volume of the gas storage chamber, and the gas delivery unit also reduces the volume. A slidable piston that is housed in the gas tank and defines the gas storage chamber;
A motor for moving the piston via a feed mechanism,
6. The fuel cell system according to claim 5, wherein the gas storage chamber is enlarged or reduced by the piston that is moved by the motor. Pressure detecting means for detecting the pressure of the hydrogen electrode;
Flow rate control means for controlling the flow rate of the exhaust gas supplied from the gas storage means to the hydrogen electrode,
7. The flow rate of the exhaust gas by the flow rate control unit is controlled according to the pressure detected by the pressure detection unit when the exhaust gas is filled in the hydrogen electrode. The fuel cell system according to any one of the above. A hydrogen flow rate detecting means for detecting a hydrogen flow rate to the hydrogen electrode;
The hydrogen flow rate at which the integrated value of the hydrogen flow rate detected by the hydrogen flow rate detection means after the transition to the fuel cell stop process reduces the oxygen concentration in the exhaust gas flowing through the circulation flow path to a predetermined value or less. The fuel cell system according to any one of claims 1 to 7, wherein the supply of hydrogen to the hydrogen electrode is stopped when reaching the value. A hydrogen circulation passage for circulating hydrogen discharged from the hydrogen electrode to the hydrogen electrode;
9. The fuel cell system according to claim 1, wherein when supplying the exhaust gas from the gas storage unit to the hydrogen electrode, the hydrogen circulation passage is closed.

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