JP2006134741A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of a catalyst caused by a reaction between a fuel gas and an oxidizer gas in storage after fuel cell stop. <P>SOLUTION: This fuel cell is so controlled that supply of either of the fuel gas and the oxidizer gas is stopped in stopping the operation of the fuel cell; a power consumption means 2 is connected thereto; and, after the gas remaining in the fuel cell by the supply stop is consumed by a reaction with the other-side gas, the supply of the other-side gas is stopped. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to fuel cell stop control.

  The fuel cell has a fuel electrode and an oxidant electrode, and generates electricity by a chemical reaction between a fuel gas containing hydrogen supplied to the fuel electrode and an oxidant gas supplied to the oxidant electrode. . For example, in a molten carbonate fuel cell, carbon dioxide is required for the reaction on the oxidizer electrode side, so the exhaust gas on the fuel electrode side is combusted by the fuel processing device and heat is recovered, and then water is discharged by the condenser. After separation, the carbon dioxide gas is supplied to the oxidizer electrode side.

  As a result, the pressure on the oxidizer electrode side rapidly decreases when the fuel cell is stopped, whereas the pressure on the fuel electrode side does not decrease rapidly because the pressure of the fuel gas is released after passing through the fuel processing device and the condenser. . Therefore, a differential pressure is generated between the pressure on the fuel electrode side and the pressure on the oxidant electrode side, and this differential pressure may exceed an allowable value.

Therefore, a technique that can suppress the differential pressure between the fuel electrode side and the oxidant electrode side to an allowable value or less by supplying an oxidant gas to the oxidant electrode side for a certain period of time after the fuel cell is stopped is disclosed in Patent Literature 1.
JP-A-8-45527

  However, in the above conventional technique, the oxidant gas is supplied to the oxidant electrode side for a certain period of time after the fuel cell is stopped for the purpose of suppressing the differential pressure between the fuel electrode side and the oxidant electrode side below the allowable value. The catalyst may deteriorate due to the reaction between the fuel gas remaining on the fuel electrode side and the oxidant gas during storage after stopping the fuel cell.

  The present invention has been made paying attention to such conventional problems, and can prevent deterioration of the catalyst caused by the reaction between the fuel gas and the oxidant gas during storage after stopping the fuel cell. The purpose is to provide.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention provides a fuel cell having a fuel electrode supplied with a fuel gas containing hydrogen and an oxidant electrode supplied with an oxidant gas containing oxygen, and connecting the fuel electrode and the oxidant electrode. Thus, the power consumption means (2) that consumes the power generated by the reaction between the fuel gas and the oxidant gas and the supply of either the fuel gas or the oxidant gas are stopped when the operation of the fuel cell is stopped. In addition, the power consumption means (2) is connected to the stop control means (S103) for controlling the supply of the other gas to be stopped after the gas remaining in the fuel cell due to the supply stop is consumed by the reaction with the other gas. To S110).

  According to the present invention, it is possible to suppress the reaction between the fuel gas remaining in the fuel electrode and the oxidant gas mixed in the fuel electrode during storage after the fuel cell is stopped. Durability and reliability can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an overall configuration diagram showing a fuel cell in the present embodiment. The fuel cell in the present embodiment includes a fuel cell stack 1, a discharge device 2, and a controller 3.

  The fuel cell stack 1 is configured by assembling cells having a fuel electrode and an oxidant electrode. In the fuel cell stack 1, a fuel inlet pipe 4 for supplying fuel gas and a fuel outlet pipe 5 for discharging the reacted gas are connected to the fuel electrode side, and an oxidant inlet pipe 6 for supplying an oxidant gas and a post-reaction. An oxidant outlet pipe 7 for discharging the gas is connected to the oxidant electrode side. A fuel blower 8 for supplying fuel is connected to the fuel inlet pipe 4, and a shutoff valve 9 for shutting off the fuel supply is provided between the fuel inlet pipe 4 and the fuel cell stack 1. Further, the fuel outlet pipe 5 is provided with a shutoff valve 10 for shutting off fuel discharge. Similarly, an oxidant blower 11 for supplying an oxidant is connected to the oxidant inlet pipe 6, and a shutoff valve 12 for blocking the supply of the oxidant is provided between the oxidant inlet pipe 6 and the fuel cell stack 1. The oxidant outlet pipe 7 is provided with a shutoff valve 13 for shutting off the oxidant. As described above, the fuel cell stack 1 generates power by causing a chemical reaction between the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the oxidant electrode.

  The discharge device 2 (power consuming means) is a discharge resistor electrically connected between the fuel electrode and the oxidant electrode via the switch 14 and the electric conductor 15. The discharge device 2 consumes electric power generated by the reaction between the fuel gas remaining in the fuel electrode and the oxidant gas supplied to the oxidant electrode by closing the switch 14 when the fuel cell is stopped.

  The controller 3 predicts the stop time of the fuel cell when the operation of the fuel cell is stopped, and based on the predicted stop time, the switch 14, the fuel blower 8, the oxidant blower 11, the shut-off valves 9, 10, 12 and 13 are controlled via a signal cable 16.

  Next, the control performed by the controller 3 will be described with reference to FIG. FIG. 2 is a flowchart showing the control when the fuel cell is stopped in the present embodiment.

  In step S101, the stop time of the fuel cell is predicted. The stop time is the time from when the fuel cell is stopped to when it is next started, and is predicted based on, for example, a time zone. Note that when the operation of the fuel cell is stopped, for example, the state of the vehicle on which the fuel cell is mounted is changed from the driving state to the stopped state by the driver's key operation.

  In step S102, it is determined whether or not the predicted stop time is equal to or longer than a predetermined time. If the predicted stop time is equal to or longer than the predetermined time, the process proceeds to step S103, and if the predicted time is less than the predetermined time, the process proceeds to step S107. The predetermined time is set to a time required for the oxidant gas to enter the fuel electrode side pipe when the fuel cell is stopped and the concentration of the oxidant gas reaches a predetermined concentration (eg, 3%). Accordingly, when the stop time is longer than the predetermined time and the concentration of the oxidant gas may reach the predetermined concentration, the process proceeds to step S103, and when there is no possibility that the predetermined concentration is reached, the process proceeds to step S107. become. The predetermined time varies depending on the seal of the fuel cell stack 1 and the seal of the valve. Therefore, the predetermined time is obtained in advance by experiments or the like according to the fuel cell used.

  In step S103 and subsequent steps executed when it is determined that the predicted stop time is equal to or longer than the predetermined time, processing for consuming the fuel gas in the fuel cell is performed. This lowers the concentration of the fuel gas in the fuel cell so that the concentration of the oxidant gas mixed into the fuel electrode after the fuel cell stops increases and the catalyst does not deteriorate due to the reaction between the remaining fuel gas and the oxidant gas. Because.

  The process after step S103 will be described. In step S103, the supply of fuel gas is stopped. The supply of the fuel gas is stopped by closing the shutoff valves 9 and 10 after the fuel blower 8 is stopped and the flow rate becomes zero.

  In step S104, the switch of the discharge device 2 is closed. As a result, the electric power generated between the fuel electrode and the oxidant electrode is consumed by the reaction between the fuel gas remaining in the fuel electrode and the oxidant gas supplied to the oxidant electrode.

  In step S105, it is determined whether the voltage of the fuel cell stack 1 is smaller than a predetermined voltage. If the voltage of the discharge device 2 is smaller than the predetermined voltage, the process proceeds to step S106, and if the voltage of the discharge device 2 is equal to or higher than the predetermined voltage, the process proceeds to step S105 again. Here, the predetermined voltage is a voltage of the fuel cell stack 1 when the fuel gas inside the fuel cell stack 1 is almost completely consumed, and is obtained in advance by an experiment or the like. The voltage of the fuel cell stack 1 may be detected by a voltage sensor provided in the fuel cell stack 1 or may be detected as a voltage applied to the discharge device 2.

  In step S106, the supply of the oxidant gas is stopped. The supply of the oxidant gas is stopped by closing the shutoff valves 12 and 13 after the oxidant blower 11 is stopped and the flow rate becomes zero.

  On the other hand, in step S107 and subsequent steps executed when the stop time predicted in step S102 is less than the predetermined time, a process for consuming the oxidant gas is performed. This is because when the predicted stop time is determined to be less than the predetermined time, the fuel cell is started before the concentration of the oxidant gas at the fuel electrode becomes equal to or higher than the predetermined concentration. However, there is a risk of catalyst deterioration due to direct reaction between the fuel gas and the oxidant gas at the fuel electrode at the next startup, and the oxidant gas is consumed so that the oxidant gas does not enter the fuel electrode. It is necessary.

  The process after step S107 will be described. In step S107, the supply of the oxidizing gas is stopped. The supply of the oxidant gas is stopped by closing the shutoff valves 12 and 13 after the oxidant blower 11 is stopped and the flow rate becomes zero.

  In step S108, the switch 14 of the discharge device 2 is closed. As a result, the electric power generated between the fuel electrode and the oxidant electrode is consumed by the reaction between the oxidant gas remaining in the oxidant electrode and the fuel gas supplied to the fuel electrode.

  In step S109, it is determined whether or not the voltage of the fuel cell stack 1 is smaller than a predetermined voltage. If the voltage of the fuel cell stack 1 is lower than the predetermined voltage, the process proceeds to step S110. If the voltage of the fuel cell stack 1 is equal to or higher than the predetermined voltage, the process proceeds to step S109 again. Here, the predetermined voltage is a voltage of the fuel cell stack 1 when the oxidant gas inside the fuel cell stack 1 is almost completely consumed, and is obtained in advance by an experiment or the like.

  In step S110, the supply of fuel gas is stopped. The supply of the fuel gas is stopped by closing the shutoff valves 9 and 10 after the fuel blower 8 is stopped and the flow rate becomes zero.

  In step S111, it is determined whether or not the actual stop time has exceeded a predetermined time. If the actual stop time has exceeded the predetermined time, the process proceeds to step S112, and if the actual stop time is less than the predetermined time, the process proceeds to step S101. The actual stop time is the time elapsed from when the fuel cell was stopped to the present time. The predetermined time is the predetermined time used in step S102. That is, it is a time when it is predicted that the concentration of the oxidant gas in the fuel electrode is equal to or higher than a predetermined concentration, and it is necessary to consume the oxidant gas in the fuel cell beforehand.

  In step S112, supply of oxidant gas is started. The supply of the oxidant gas is started by opening the shutoff valves 12 and 13 and operating the oxidant blower 11.

  In step S113, it is determined whether or not the voltage of the fuel cell stack 1 is smaller than a predetermined voltage. If the voltage of the fuel cell stack 1 is lower than the predetermined voltage, the process proceeds to step S114. If the voltage of the fuel cell stack 1 is equal to or higher than the predetermined voltage, the process proceeds to step S113 again. Here, the predetermined voltage is a voltage of the fuel cell stack 1 when the fuel gas inside the fuel cell stack 1 is almost completely consumed, and is obtained in advance by an experiment or the like.

  In step S114, the supply of the oxidant gas is stopped. The supply of the oxidant gas is stopped by closing the shutoff valves 12 and 13 after the oxidant blower 11 is stopped and the flow rate becomes zero.

  The operation will be described by summarizing the above control. In the fuel cell according to the present embodiment, the time from when the fuel cell is stopped to when it is next activated is predicted. If the predicted time is a predetermined time or more, the supply of the fuel gas is stopped, and the fuel gas remaining in the fuel electrode is consumed by reacting with the oxidant gas supplied to the oxidant electrode. At this time, the electric power generated between the fuel electrode and the oxidant electrode is consumed by the discharge device 2. Thus, when the fuel gas is consumed and the voltage of the fuel cell stack 1 becomes lower than a predetermined voltage, the supply of the oxidant gas is stopped. After the supply of the oxidant gas is stopped, the fuel pipe near the fuel electrode is at a lower pressure than the oxidant pipe near the oxidant electrode, so that the oxidant gas on the oxidant electrode side moves to the fuel electrode side. However, since the fuel gas is consumed, the oxidant gas and the fuel gas do not react, and both electrodes are filled with the oxidant gas.

  If the predicted time is less than the predetermined time, the supply of the oxidant gas is stopped, and the oxidant gas remaining on the oxidant electrode is consumed by reacting with the fuel gas supplied to the fuel electrode. At this time, the electric power generated between the fuel electrode and the oxidant electrode is consumed by the discharge device 2. As a result, when the oxidant gas is consumed and the voltage of the discharge device 2 becomes lower than the predetermined voltage, the supply of the fuel gas is stopped. Since there is no oxidant gas moving to the fuel electrode after the supply of fuel gas is stopped, it is possible to prevent the fuel gas and oxidant gas from reacting directly at the fuel electrode when the fuel cell is next started. In this state, when the actual stop time becomes equal to or longer than the predetermined time, supply of the stopped oxidant gas is started. Thus, when the fuel gas is consumed and the voltage of the fuel cell stack 1 becomes lower than a predetermined voltage, the supply of the oxidant gas is stopped.

  As described above, in the present embodiment, when the stop time predicted when the fuel cell is stopped is equal to or longer than the predetermined time, the supply of the fuel gas is stopped and the electric power generated between the fuel electrode and the oxidant electrode is discharged. The fuel gas remaining in the fuel electrode is consumed by consuming the fuel by 2. As a result, it is possible to prevent the deterioration of the catalyst layer by suppressing the reaction between the oxidant gas mixed into the fuel electrode and the fuel gas when the fuel cell is stopped and during storage after the stop. Therefore, durability and reliability of the fuel cell can be improved.

  Further, when the stop time predicted when the fuel cell is stopped is less than a predetermined time, the oxidant gas is stopped and the electric power generated between the fuel electrode and the oxidant electrode is consumed by the discharge device 2, whereby the oxidant The oxidant gas remaining at the pole is consumed. Thereby, it is possible to prevent the catalyst from deteriorating by suppressing the direct reaction between the fuel gas and the oxidant gas at the fuel electrode at the next start-up.

  Furthermore, the stop time predicted when the fuel cell was stopped was less than the predetermined time. However, when a predetermined time or more has passed after that, the oxidant gas is supplied with the fuel gas stopped to oxidize the fuel electrode. The electric power generated with the agent electrode is consumed by the discharge device 2 to consume the fuel gas remaining in the fuel electrode. As a result, even when the actual stop time of the fuel cell exceeds the stop time predicted at the time of stop, the reaction between the oxidant gas and the fuel gas mixed in the fuel electrode during storage after the stop of the fuel cell is suppressed, thereby reducing the catalyst. Deterioration of the layer can be prevented. Therefore, durability and reliability of the fuel cell can be improved.

  Furthermore, since the supply of the oxidant gas or the fuel gas is stopped after determining that the fuel gas or the oxidant gas has been consumed based on the voltage of the fuel cell stack 1, the fuel gas or the oxidant gas is reliably supplied. It can be consumed, and the reaction between the oxidant gas and the fuel gas during storage of the fuel cell can be more reliably suppressed to prevent the catalyst layer from deteriorating.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

  In this embodiment, the stop time of the fuel cell is predicted based on the time zone. However, the present invention is not limited to this. For example, the distance from the parking lot set in advance is determined by information from the GPS navigation system. If it is a stop near a parking lot, the stop time may be predicted to be long. Furthermore, it may be predicted that the stop time is long based on the position information that stops on a daily basis by installing a learning function. Furthermore, a switch input by the driver may be provided, and when the stop time is long, the driver may determine that the stop time is long by turning on the switch. Furthermore, it may be predicted that the stop time is long by combining these determination means. By using these various determination means, the stop time can be determined with higher accuracy, so that the deterioration of the catalyst can be prevented and the durability and reliability of the fuel cell can be further improved.

  Further, in this embodiment, the fuel blower 8 and the shutoff valve 9 and the oxidant blower 11 and the shutoff valve 12 are provided separately, but the function of the shutoff valve 9 is provided in the fuel blower 8 and the oxidant blower. 11 may have the function of the shutoff valve 12. Thereby, the apparatus can be further simplified.

  Further, in the present embodiment, it is determined whether or not the stop time predicted when the fuel cell is stopped is equal to or longer than a predetermined time, and the type of gas to be consumed is changed according to the determination result. Therefore, the fuel gas may be always consumed when the fuel cell is stopped without determining the stop time (steps S103 to S106), and the oxidant gas is always consumed similarly (steps S107 to S110). It may be.

  Furthermore, in this embodiment, after the stop time predicted when the fuel cell is stopped is less than a predetermined time and the oxidant gas is consumed, the actual stop time from the stop of the operation of the fuel cell becomes a predetermined time or more. At this time, control is performed so that the fuel gas is consumed. However, in order to simplify the control, the control after the actual stop time from the stop of the operation of the fuel cell becomes a predetermined time or more (steps S111 to S114). May be omitted.

1 is an overall configuration diagram showing a fuel cell according to the present invention. It is a flowchart which shows the control at the time of the fuel cell stop in this invention.

Explanation of symbols

1 Fuel Cell Stack 2 Discharge Device (Power Consumption Means)
3 Controller 4 Fuel Inlet Piping 5 Fuel Outlet Piping 6 Oxidant Inlet Piping 7 Oxidant Outlet Piping 8 Fuel Blower 9 Shutoff Valve 10 Shutoff Valve 11 Oxidant Blower 12 Shutoff Valve 13 Shutoff Valve 14 Switch 15 Electrical Conductor 16 Signal Cable

Claims (8)

In a fuel cell having a fuel electrode supplied with a fuel gas containing hydrogen and an oxidant electrode supplied with an oxidant gas containing oxygen,
Power consuming means for consuming electric power generated by a reaction between the fuel gas and the oxidant gas by connecting between the fuel electrode and the oxidant electrode;
When the operation of the fuel cell is stopped, the supply of either the fuel gas or the oxidant gas is stopped and the power consuming means is connected, and the gas remaining in the fuel cell by the supply stop is the other gas A stop control means for controlling to stop the supply of the other gas after being consumed by the reaction with the gas;
A fuel cell comprising: The stop control means stops the supply of the fuel gas when the operation of the fuel cell is stopped and connects the power consumption means, and the fuel gas remaining in the fuel cell is consumed by a reaction with the oxidant gas. And control to stop the supply of the oxidant gas after being
The fuel cell according to claim 1. The stop control means stops the supply of the oxidant gas when the voltage of the fuel cell becomes a predetermined voltage or lower.
The fuel cell according to claim 2. The stop control means stops the supply of the oxidant gas when the fuel cell is stopped and connects the power consuming means, and the oxidant gas remaining in the fuel cell reacts with the fuel gas. Control to stop the supply of the fuel gas after being consumed,
The fuel cell according to claim 1. The stop control means stops the supply of the fuel gas when the voltage of the fuel cell becomes a predetermined voltage or less;
The fuel cell according to claim 4. A stop time determination means for determining whether or not a stop time predicted when the fuel cell is stopped is equal to or longer than a predetermined time;
The stop control means, when the stop time predicted when the fuel cell is stopped is a predetermined time or longer, stops the supply of the fuel gas when the fuel cell is stopped and connects the power consumption means, Control is performed to stop the supply of the oxidant gas after the fuel gas remaining in the fuel cell is consumed by the reaction with the oxidant gas, and a stop time predicted when the operation of the fuel cell is stopped When it is less than a predetermined time, the supply of the oxidant gas is stopped when the operation of the fuel cell is stopped, and the power consuming means is connected, and the oxidant gas remaining in the fuel cell reacts with the fuel gas. Control to stop the supply of the fuel gas after being consumed by
The fuel cell according to claim 1. Actual stop time determination for determining whether or not the actual stop time from the stop of operation of the fuel cell is equal to or longer than the predetermined time after the stop time predicted when the fuel cell is stopped is less than a predetermined time With means,
When the actual stop time from the stop of the operation of the fuel cell is equal to or longer than the predetermined time, the stop control unit is configured to stop the oxidation in a state where the supply of the fuel gas is stopped and the power consumption unit is connected. Controlling the supply of the oxidant gas after the oxidant gas is supplied and the fuel gas remaining in the fuel cell is consumed by the reaction with the oxidant gas;
The fuel cell according to claim 6. The stop control means stops the supply of the oxidant gas when the voltage of the fuel cell becomes a predetermined voltage or less;
The fuel cell according to claim 7.

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