JP4731804B2 - Discharge method of fuel cell system - Google Patents

Description

  The present invention relates to a method for discharging a fuel cell system.

A fuel cell mounted on a fuel cell vehicle or the like includes an anode and a cathode on both sides of a solid polymer electrolyte membrane, a fuel gas (eg, hydrogen gas) is supplied to the anode, and an oxidant gas (eg, oxygen is supplied to the cathode). There is a type in which chemical energy related to the oxidation-reduction reaction of these gases is directly extracted as electric energy.
In this type of fuel cell, water is generated on the cathode side with power generation, and a part of the generated water permeates the solid polymer electrolyte membrane and enters the anode side. In addition, a small amount of nitrogen in the air supplied to the cathode permeates the solid polymer electrolyte membrane to the anode side and enters the hydrogen gas. These impurities such as moisture and nitrogen on the anode side may make power generation of the fuel cell unstable.

In particular, in a circulation type fuel cell system in which unreacted hydrogen discharged from a fuel cell is recycled to mix with fresh hydrogen gas and supplied to the fuel cell again in order to increase the fuel utilization rate, The impurity concentration tends to increase gradually.
Therefore, in this type of fuel cell, the hydrogen gas containing the impurities is discharged from the hydrogen circulation flow path periodically or according to the power generation status of the fuel cell to reduce the impurity concentration in the hydrogen gas (for example, , See Patent Document 1). Conventionally, the discharge of hydrogen gas containing impurities is performed by controlling the open valve holding time of the discharge valve to a fixed time regardless of the power generation state of the fuel cell.
JP 2000-243417 A

However, if the valve opening retention time of the discharge valve is controlled to a fixed time regardless of the power generation state of the fuel cell in this way, the amount of hydrogen gas discharged varies due to changes in the power generation state such as the temperature and pressure of the fuel cell, Various problems occur.
For example, if the discharge of hydrogen gas containing impurities is insufficient, the power generation stability of the fuel cell cannot be sufficiently recovered. On the other hand, if the discharge of hydrogen gas containing impurities is excessive, the apparent amount of hydrogen consumption increases and power generation efficiency deteriorates. In addition, when a system for diluting the hydrogen gas discharged from the hydrogen circulation flow path with the cathode off-gas discharged from the cathode is provided, it is difficult to stabilize the diluted hydrogen concentration.

  Therefore, the present invention provides a method for discharging a fuel cell system that can discharge an anode off-gas containing impurities without excess or deficiency even when the power generation state changes.

In order to solve the above problems, the invention according to claim 1 is directed to a cathode (for example, described later) by supplying a fuel gas (for example, hydrogen gas in an embodiment to be described later) to an anode (for example, an anode 3 in an embodiment to be described later). A fuel cell (for example, a fuel cell 1 in an embodiment to be described later) that is supplied with an oxidant gas (for example, air in an embodiment to be described later) to the cathode 4) in the embodiment, and an anode of the fuel cell A fuel gas circulation passage (for example, a fuel gas circulation passage 20 in an embodiment to be described later) for supplying the anode off-gas discharged again to the anode, and the anode off-gas can be discharged from the fuel gas circulation passage. A method for discharging a fuel cell system including a discharge valve (for example, a discharge valve 21 in an embodiment described later), the fuel gas When there is a request to discharge the anode off-gas from the annular flow path, a required discharge amount of anode off-gas to be discharged from the fuel gas circulation flow path according to the power generation state of the fuel cell (for example, required discharge in the embodiments described later) Amount VREQ) is calculated, and an anode off-gas discharge amount per unit time (for example, a discharge amount base in an embodiment described later) based on a pressure difference between the pressure in the fuel gas circulation passage and the pressure downstream of the discharge valve A value DVPGBS) is calculated, and the opening and closing of the discharge valve is controlled so that the integrated value of the anode offgas discharge amount is the same as the required discharge amount.
With this configuration , even when the pressure in the fuel gas circulation channel changes due to a change in the power generation state of the fuel cell, the anode offgas discharge amount per unit time can be accurately calculated, and the anode can be accurately The off-gas emission amount can be integrated. As a result, the amount of anode off-gas actually discharged from the discharge valve can be made the same as the required amount of discharge calculated according to the power generation state, so that the amount of anode off-gas required for impurity discharge can be reduced. Excess or deficiency does not occur, in other words, the discharge amount of anode off gas containing impurities can be optimized.

The invention according to claim 2, A node (e.g., an anode 3 in the embodiment) fuel gas (e.g., hydrogen gas in the embodiment) cathode is supplied (e.g., a cathode 4 in the embodiment) An oxidant gas (for example, air in the embodiment described later) is supplied to the fuel cell (for example, the fuel cell 1 in the embodiment described later) and the anode off-gas discharged from the anode of the fuel cell again. A fuel gas circulation passage (for example, a fuel gas circulation passage 20 in an embodiment to be described later) for supplying the anode, and a discharge valve (for example, described later) that enables the anode off-gas to be discharged from the fuel gas circulation passage. A discharge method for a fuel cell system comprising a discharge valve 21) in the embodiment, wherein the anode gas is discharged from the fuel gas circulation passage. When a request for discharging the fuel is made, a discharge time for opening the discharge valve (for example, a basic discharge time TMONBS in an embodiment to be described later) according to the power generation state of the fuel cell is calculated. Based on the pressure difference between the pressure in the gas circulation passage and the pressure downstream of the discharge valve, the discharge time is corrected so that the discharge time becomes shorter as the pressure difference is larger, and the corrected discharge time (for example, an embodiment described later) The discharge method of the fuel cell system is characterized in that the opening and closing of the discharge valve is controlled to be opened only during the required discharge time TMONREQ).
With this configuration, Ru can be set appropriately to the discharge time in accordance with the operating state of the fuel cell.

According to the first aspect of the present invention, even when the pressure in the fuel gas circulation flow path changes due to a change in the power generation state of the fuel cell, the anode off-gas discharge amount per unit time can be accurately calculated. As a result, the amount of anode off-gas actually discharged from the discharge valve can be made the same as the required emission calculated according to the power generation state. The amount of anode off-gas required for exhaust gas does not become excessive or deficient, in other words, the amount of anode off-gas containing impurities can be optimized, and as a result, the fuel cell can maintain a good power generation state. It is possible to improve the power generation efficiency.

According to the invention of claim 2, since the discharge time can be set appropriately according to the operating state of the fuel cell, there is no excess or deficiency in the discharge amount of the anode off-gas necessary for discharging impurities, in other words, For example, the discharge amount of the anode off gas containing impurities can be optimized, and as a result, the power generation efficiency can be improved.

  Hereinafter, an embodiment of a fuel cell system discharging method according to the present invention will be described with reference to the drawings of FIGS.

First, a first embodiment of a fuel cell system discharging method according to the present invention will be described with reference to the drawings of FIGS.
FIG. 1 is a schematic configuration diagram of a fuel cell system mounted on a fuel cell vehicle.
The fuel cell 1 is configured by stacking a plurality of cells formed by sandwiching a solid polymer electrolyte membrane 2 made of, for example, a solid polymer ion exchange membrane between an anode 3 and a cathode 4 from both sides (FIG. 1). Shows only a single cell), hydrogen gas is supplied as a fuel gas to the reaction gas channel 5 of the anode 3, and air containing oxygen as an oxidant gas is supplied to the reaction gas channel 6 of the cathode 4. Hydrogen ions generated by the catalytic reaction pass through the solid polymer electrolyte membrane 2 and move to the cathode 4 to cause an electrochemical reaction with oxygen at the cathode 4 to generate electric power, thereby generating water. Since part of the generated water generated on the cathode side permeates the solid polymer electrolyte membrane 2 and back diffuses to the anode side, the generated water also exists on the anode side.

  The air is pressurized to a predetermined pressure by a compressor 7 such as a supercharger (S / C) and supplied to the reaction gas passage 6 of the cathode 4 of the fuel cell 1 through the air supply passage 8. After the air supplied to the fuel cell 1 is used for power generation, it is discharged from the fuel cell 1 together with the produced water on the cathode side into the air discharge passage 9 and introduced into the diluting device 11 via the pressure control valve 10. Hereinafter, the air supplied to the fuel cell 1 is distinguished as supply air, and the air discharged from the fuel cell 1 is distinguished as exhaust air. An air flow rate detection sensor 12 that detects a weight flow rate (hereinafter abbreviated as air flow rate) QA of air supplied to the fuel cell 1 is provided upstream of the compressor 7 in the air supply flow path 8. A cathode inlet pressure sensor 13 that detects the pressure (hereinafter referred to as cathode inlet pressure) PA of the supply air immediately before flowing into the reaction gas passage 6 of the cathode 4 in the air supply passage 8 downstream of the compressor 7. Is provided. An air temperature sensor that detects the temperature of exhaust air immediately after being discharged from the reaction gas flow path 6 of the cathode 4 (hereinafter referred to as cathode outlet temperature) TAO upstream of the pressure control valve 10 in the air discharge flow path 9. 14 is provided.

  On the other hand, the hydrogen gas supplied from the hydrogen tank 15 flows through the hydrogen gas supply flow path 17, and is depressurized to a predetermined pressure by the regulator 16 on the way, and is controlled to a predetermined flow rate by the flow control valve 27, and passes through the ejector 19. It is supplied to the reaction gas flow path 5 of the anode 3 of the fuel cell 1. The unreacted hydrogen gas that has not been consumed is discharged from the fuel cell 1 as an anode off-gas, sucked into the ejector 19 through the anode off-gas flow path 18, and joined with fresh hydrogen gas supplied from the hydrogen tank 15. Then, it is supplied again to the anode 3 of the fuel cell 1. That is, the anode off gas discharged from the fuel cell 1 circulates in the fuel cell 1 through the anode off gas passage 18 and the hydrogen gas supply passage 17 downstream of the ejector 19. In this embodiment, the hydrogen gas supply channel 17 and the anode off-gas channel 18 downstream from the ejector 19 constitute a fuel gas circulation channel 20.

An anode inlet pressure sensor 23 that detects the pressure (hereinafter referred to as anode inlet pressure) PH of the hydrogen gas immediately before flowing into the reaction gas passage 5 of the anode 3 is provided in the hydrogen gas supply passage 17 downstream of the ejector 19. And an anode inlet temperature sensor 24 for detecting the temperature (hereinafter referred to as anode inlet temperature) TH of the hydrogen gas. That is, in the first embodiment, the pressure in the fuel gas circulation passage 20 is detected by the anode inlet pressure sensor 23.
An anode offgas discharge channel 22 having a discharge valve 21 branches from the anode offgas channel 18, and the anode offgas discharge channel 22 is connected to the diluting device 11. In the diluting device 11, the anode off gas discharged from the anode off gas discharge flow path 22 is diluted with the discharged air discharged from the air discharge flow path 9 and discharged.

The electric power obtained by the power generation of the fuel cell 1 is supplied to a load such as a vehicle driving motor, and the generated current IFC at that time is detected by the ammeter 25.
The fuel cell 1 is controlled by an electronic control unit (hereinafter abbreviated as “ECU”) 30. Therefore, the ECU 30 includes an air flow rate detection sensor 12, a cathode inlet pressure sensor 13, an air temperature sensor 14, an anode inlet pressure sensor 23, and an anode inlet. Signals from the temperature sensor 24, the ammeter 25, and the atmospheric pressure sensor 26 are input to control the rotational speed of the compressor 7, the openings of the flow control valve 27 and the pressure control valve 10, and the opening and closing of the discharge valve 21.

In the fuel cell system configured as described above, when continuously operating, the concentration of impurities (such as moisture and nitrogen) in the hydrogen gas flowing through the fuel gas circulation passage 20 increases as described above. The power generation of the fuel cell 1 may become unstable.
Therefore, in this fuel cell system, every time the fuel cell system is operated continuously for a certain time and according to the power generation status of the fuel cell 1, the discharge valve 21 is opened, and the anode off-gas containing impurities is discharged from the fuel gas circulation passage 20 to the anode off-gas. By discharging to the diluting device 11 through the flow path 22 (hereinafter, this process is referred to as an impurity discharge process), the impurity concentration in the hydrogen gas flowing through the anode 3 of the fuel cell 1 is set to a predetermined value or less. The power generation of the fuel cell 1 is maintained in a stable state.

  In the fuel cell system according to this embodiment, the amount of anode off-gas to be discharged from the fuel gas circulation passage 20 according to the power generation state of the fuel cell 1 (hereinafter referred to as required discharge) when performing the impurity discharge process. The amount of anode off-gas actually discharged from the discharge valve 21 is controlled to open and close the discharge valve 21 so that the power generation state of the fuel cell 1 changes. In this case, the discharge amount of the anode off gas necessary for impurity discharge is optimized so that the discharge amount is optimized, thereby maintaining the good power generation state of the fuel cell 1 and improving the power generation efficiency. The stabilization of the dilution process by the diluting device 11 is achieved.

Next, impurity discharge processing control in Embodiment 1 will be described with reference to the flowchart of FIG.
First, in step S101, it is determined whether there is an impurity discharge request. In the first embodiment, when the power generation operation of the fuel cell 1 is continued for a certain time, and when the lowest cell voltage among the cell voltages of the fuel cell 1 falls below a preset lower limit voltage, there is an impurity discharge request. It is determined.

If the determination result in step S101 is “NO” (no impurity discharge request), the process returns to step S101.
If the determination result in step S101 is “YES” (impurity emission requested), the process proceeds to step S102, and the required emission amount VREQ corresponding to the current power generation state is calculated. Here, the required emission amount VREQ can be calculated based on, for example, the generated current IFC of the fuel cell 1 or the anode inlet temperature TH. In this embodiment, the required emission amount VREQ is increased as the generated current IFC is increased, and the required emission amount VREQ is increased as the anode inlet temperature TH is lower.

After calculating the required discharge amount VREQ in step S102, the process proceeds to step S103, and the discharge valve 21 is opened.
Next, proceeding to step S104, the atmospheric pressure PO detected by the atmospheric pressure sensor 26 is set as the gas pressure (hereinafter referred to as the discharge valve outlet pressure) POUT in the anode off-gas discharge passage 22 downstream of the discharge valve 21. To do. This is a case where the discharge valve outlet pressure POUT can be regarded as almost the same as the atmospheric pressure PO. If it cannot be regarded as the same, for example, a pressure sensor is provided directly in the anode off-gas discharge passage 22 downstream of the discharge valve 21. The exhaust valve outlet pressure POUT is detected, or the exhaust air pressure downstream of the pressure control valve 10 is estimated as described in the second embodiment (steps S203 to S205), and this exhaust air pressure is calculated as the exhaust valve outlet pressure. It is preferable to obtain the discharge valve outlet pressure POUT by a method such as regarding POUT.

Next, the process proceeds to step S105, and the discharge amount base value is determined based on the anode inlet pressure PH detected by the anode inlet pressure sensor 23 and the discharge valve outlet pressure POUT with reference to the discharge amount base value map shown in FIG. (Anode off-gas discharge amount per unit time) DVPGBS is calculated. Here, the discharge amount base value DVPGBS is a base value of the discharge amount discharged per unit time with the control cycle for executing the series of steps S104 to S109 in the impurity discharge processing routine as a unit time.
In the discharge amount base value map, the larger the differential pressure upstream and downstream of the discharge valve 21, the larger the gas flow rate flowing through the discharge valve 21, so the discharge base value DVPGBS increases as the anode inlet pressure PH increases. The discharge amount base value DVPGBS is set to increase as the discharge valve outlet pressure POUT decreases.

  In step S106, the temperature correction coefficient KTH is calculated based on the anode inlet temperature TH detected by the anode inlet temperature sensor 24 with reference to the temperature correction coefficient table shown in FIG. The temperature correction coefficient table is set so that the temperature correction coefficient KTH decreases as the anode inlet temperature TH increases.

Next, the process proceeds to step S107, where the temperature correction is performed by multiplying the discharge amount base value DVPGBS calculated in step S105 by the temperature correction coefficient KTH calculated in step S106, and the corrected discharge amount base value DVPG is calculated (DVPG = DVPGBS x KTH).
Next, the process proceeds to step S108, and the integrated discharge amount VPG is calculated. In the method of calculating the integrated discharge amount VPG, the process of step S107 is performed on the integrated discharge amount (that is, the previous value VPG _{n-1 of} the integrated discharge amount) calculated when the series of processes of steps S104 to S109 was executed last time. The value obtained by adding the corrected discharge amount base value DVPG calculated and executed is set as the current value VPG _n of the integrated discharge amount (VPG _n = VPG _n-1 + DVPG). Note that the initial value of the integrated discharge amount VPG is zero.

Next, the process proceeds to step S109, and it is determined whether or not the integrated discharge amount VPG calculated in step S108 is smaller than the required discharge amount VREQ calculated in step S102.
If the determination result in step S109 is “YES” (VREQ> VPG), since the integrated discharge amount VPG has not yet reached the required discharge amount VREQ, the process returns to step S104, and a series of processing of steps S104 to S109 is performed. The process is executed again, and the discharge of the anode off gas from the discharge valve 21 is continued.
On the other hand, if the determination result in step S109 is “NO” (VREQ ≦ VPG), since the accumulated discharge amount VPG has reached the required discharge amount VREQ, the process proceeds to step S110, the discharge valve 21 is closed, and the impurity discharge process is performed. Exit.

  According to the impurity discharge processing control of the first embodiment, when there is an impurity discharge request, first, the required discharge amount VREQ corresponding to the power generation state of the fuel cell 1 is calculated and actually discharged from the discharge valve 21. Since the opening / closing of the discharge valve 21 is controlled so that the integrated amount of anode off gas becomes the same as the required discharge amount VREQ, there is no excess or deficiency in the discharge amount of the anode off gas necessary for impurity discharge. It is possible to optimize the discharge amount of the anode off-gas containing.

  In particular, in the first embodiment, the anode inlet pressure PH (that is, the pressure in the fuel gas circulation passage 20) detected by the anode inlet pressure sensor 23 and the discharge valve outlet pressure POUT (that is, downstream of the discharge valve 21). Since the discharge amount base value DVPGBS per unit time with the control cycle as a unit time is calculated based on the differential pressure with respect to the pressure), even if the power generation state of the fuel cell 1 changes, the accumulated discharge amount VPG is accurately calculated. Can be calculated, and the optimization of the emission amount can be made effective.

  As a result, not only can the stability of power generation of the fuel cell 1 be sufficiently restored, but also the amount of hydrogen gas that is not used for power generation and discharged together with impurities can be minimized. improves. Furthermore, since the amount of hydrogen gas flowing into the diluting device 11 is optimized, the hydrogen concentration after dilution can be stabilized.

  In the first embodiment, the temperature correction of the discharge amount based on the anode inlet temperature TH is performed on the discharge amount base value DVPGBS, but instead, the anode inlet temperature TH with respect to the required discharge amount VREQ. You may perform temperature correction based on.

Next, a second embodiment of the discharge method of the fuel cell system according to the present invention will be described with reference to the drawings of FIGS. Note that the configuration of the fuel cell system is the same as that of the first embodiment, and thus the description thereof is omitted.
In the first embodiment, the integrated discharge amount VPG of the anode off-gas actually discharged from the discharge valve 21 is calculated, and the opening / closing of the discharge valve 21 is controlled so that the integrated discharge amount VPG is the same as the required discharge amount VREQ. In the second embodiment, the discharge time corresponding to the required discharge amount VREQ is calculated, and the discharge valve 21 is closed when the elapsed time after the discharge valve 21 is opened reaches the discharge time. The discharge amount of anode off-gas containing the gas is optimized.

Next, impurity discharge processing control in the second embodiment will be described with reference to the flowchart of FIG.
First, in step S201, it is determined whether there is an impurity discharge request. The determination as to whether or not there is an impurity discharge request is the same as in the first embodiment. That is, when the power generation operation of the fuel cell 1 is continued for a certain period of time, and when the lowest cell voltage among the cell voltages of the fuel cell 1 falls below a preset lower limit voltage, it is determined that there is an impurity discharge request. .

If the determination result in step S201 is “NO” (no impurity discharge request), the process returns to step S201.
When the determination result in step S201 is “YES” (impurity discharge request is present), the process proceeds to step S202, and the basic discharge time TMONBS corresponding to the current power generation state is calculated. This basic discharge time TMONBS corresponds to the required discharge amount VREQ in the first embodiment, and can be calculated based on the power generation current IFC of the fuel cell 1 and the anode inlet temperature TH. In this embodiment, the basic discharge time TMONBS is increased as the generated current IFC is increased, and the basic discharge time TMONBS is increased as the anode inlet temperature TH is decreased.

  Next, the process proceeds to step S203. A series of processes of steps S203 to S205 is a process for calculating the discharge valve outlet pressure POUT downstream of the discharge valve 21. Therefore, when the discharge valve outlet pressure POUT can be approximated by the atmospheric pressure PO as in the first embodiment, the processes in steps S203 to S205 can be replaced with steps corresponding to step S104 in the first embodiment. In addition, when a pressure sensor is provided in the anode off-gas discharge flow path 22 downstream of the discharge valve 21 to directly detect the discharge valve outlet pressure POUT, the processes of steps S203 to S205 are detected by the pressure sensor. This pressure value can be replaced with the step of setting the discharge valve outlet pressure POUT.

  The exhaust air discharged from the cathode and the anode off-gas flowing into the diluting device 11 through the exhaust valve 21 merge in the diluting device 11 and become equal pressure. Therefore, the air pressure downstream of the pressure control valve 10 The anode offgas pressure downstream of the exhaust valve 21 can be regarded as almost equal. Therefore, in the second embodiment, the pressure downstream of the pressure control valve 10 is calculated, and the pressure value is regarded as the anode off-gas pressure downstream of the exhaust valve 21 (exhaust valve outlet pressure POUT).

In step S203, the exhaust pressure loss DPOUT is calculated based on the air flow rate QA detected by the air flow rate detection sensor 12 with reference to the exhaust pressure loss table shown in FIG. Here, the exhaust pressure loss DPOUT is the pressure loss of the exhaust air in the dilution device 11. The exhaust pressure loss table is set so that the exhaust pressure loss DPOUT increases as the air flow rate QA increases.
In the second embodiment, the air flow rate QA is used as a parameter for calculating the exhaust pressure loss DPOUT. However, as the parameters for calculating the exhaust pressure loss DPOUT, the air flow rate QA, the generated current IFC, the target power generation amount Any of IREQ or a combination of these can be used as a parameter. Further, correction may be made based on the cathode outlet temperature TAO or the refrigerant temperature TW of the fuel cell 1 as necessary.

In step S204, the pressure loss correction coefficient KTAO is calculated based on the cathode outlet temperature TAO detected by the air temperature sensor 14 with reference to the pressure loss correction coefficient table shown in FIG. The pressure loss correction coefficient table is set so that the pressure loss correction coefficient KTAO increases as the cathode outlet temperature TAO increases.
In step S205, the product of the exhaust pressure loss DPOUT and the pressure loss correction coefficient KTAO is added to the atmospheric pressure PO detected by the atmospheric pressure sensor 26 to calculate the exhaust valve outlet pressure POUT (POUT = DPOUT × KTAO). + PO).

In step S206, the discharge valve 21 is opened and the discharge timer starts counting.
Next, the process proceeds to step S207, and the discharge time pressure is determined based on the anode inlet pressure PH detected by the anode inlet pressure sensor 23 and the discharge valve outlet pressure POUT with reference to the discharge time pressure correction coefficient map shown in FIG. A correction coefficient KPON is calculated.
In the discharge time pressure correction coefficient map, the larger the pressure difference between the upstream and downstream of the discharge valve 21, the larger the gas flow rate through the discharge valve 21 and the shorter the discharge time. Therefore, the higher the anode inlet pressure PH, the longer the discharge time. The discharge time pressure correction coefficient KPON is set to be smaller as the pressure correction coefficient KPON is smaller and the discharge valve outlet pressure POUT is lower.

Next, proceeding to step S208, the discharge time temperature correction coefficient KTON is calculated based on the anode inlet temperature TH detected by the anode inlet temperature sensor 24 with reference to the discharge time temperature correction coefficient table shown in FIG. Discharge time temperature correction coefficient table is set as the anode inlet temperature TH lower the temperature correction coefficient KTON increases.
Next, the process proceeds to step S209, where the basic discharge time TMONBS calculated in step S202 is multiplied by the discharge time pressure correction coefficient KPON calculated in step S207 and the discharge time temperature correction coefficient KTON calculated in step S208 to perform pressure correction and temperature correction. And the required discharge time TMONREQ is calculated (TMONREQ = TMONBS × KPON × KTON).

Next, the process proceeds to step S210, and it is determined whether or not the requested discharge time TMONREQ has elapsed since the discharge valve 21 was opened. That is, it is determined whether or not the count value of the discharge timer has reached the required discharge time TMONREQ.
If the determination result in step S210 is “NO” (time has not elapsed), the process returns to step S210, the open state of the discharge valve 21 is maintained, and the discharge of the anode off gas from the discharge valve 21 is continued. .
On the other hand, if the determination result in step S210 is “YES” (time has elapsed), the process proceeds to step S211, the discharge valve 21 is closed, the discharge timer is reset, and the impurity discharge process is terminated.

  According to the impurity discharge processing control of the second embodiment, when there is an impurity discharge request, first, the basic discharge time TMONBS corresponding to the required discharge amount VREQ is calculated according to the power generation state of the fuel cell 1, and The required discharge time TMONREQ is calculated by performing pressure correction and temperature correction, and the opening / closing of the discharge valve 21 is controlled so that the discharge valve 21 is open only during the required discharge time TMONREQ. Excess or deficiency in the discharge amount of the anode off gas does not occur, in other words, the discharge amount of the anode off gas containing impurities can be optimized.

  In particular, in the second embodiment, the anode inlet pressure PH (that is, the pressure in the fuel gas circulation passage 20) detected by the anode inlet pressure sensor 23 and the discharge valve outlet pressure POUT (that is, downstream of the discharge valve 21). Since the basic discharge time TMONBS is corrected and the required discharge time TMONREQ is calculated based on the differential pressure with respect to the pressure), the discharge time can be appropriately corrected according to the operating state of the fuel cell 1, and the anode off gas Effective optimization of emissions can be achieved.

  As a result, not only can the stability of power generation of the fuel cell 1 be sufficiently restored, but also the amount of hydrogen gas that is not used for power generation and discharged together with impurities can be minimized. improves. Furthermore, since the amount of hydrogen gas flowing into the diluting device 11 is optimized, the hydrogen concentration after dilution can be stabilized.

In the second embodiment, the temperature correction of the basic discharge time TMONBS is performed based on the anode inlet temperature TH. However, the present invention can be realized without performing this correction.
In the present invention, the fuel gas of the fuel cell is not limited to pure hydrogen gas, and may be a hydrogen-rich gas generated by reforming a fuel containing hydrocarbons.
The fuel cell system according to the present invention is not limited to the one mounted on the fuel cell vehicle as in the above-described embodiments, and may be a stationary fuel cell system.

It is an example of the block diagram of the fuel cell system suitable for implementation of this invention. It is a flowchart which shows the impurity discharge process control routine in Example 1 of this invention. It is a figure which shows an example of the discharge | emission amount base value map used in the said Example 1. FIG. It is a figure which shows an example of the temperature correction coefficient table used in the said Example 1. FIG. It is a flowchart which shows the impurity discharge process control routine in Example 2 of this invention. It is a figure which shows an example of the exhaust pressure loss table used in the said Example 2. FIG. It is a figure which shows an example of the pressure loss correction coefficient table used in the said Example 2. FIG. It is a figure which shows an example of the discharge time pressure correction coefficient map used in the said Example 2. FIG. It is a figure which shows an example of the discharge time temperature correction coefficient table used in the said Example 2. FIG.

Explanation of symbols

1 Fuel Cell 3 Anode 4 Cathode 20 Fuel Gas Circulation Channel 21 Discharge Valve

Claims (2)

A fuel cell in which fuel gas is supplied to the anode and oxidant gas is supplied to the cathode to generate power; a fuel gas circulation channel for supplying anode off-gas discharged from the anode of the fuel cell to the anode again; A discharge method of a fuel cell system comprising a discharge valve that enables discharge of anode off gas from the fuel gas circulation flow path,
Calculating a required discharge amount of the anode off gas to be discharged from the fuel gas circulation flow path according to a power generation state of the fuel cell when there is a request to discharge the anode off gas from the fuel gas circulation flow path;
Based on the pressure difference between the pressure in the fuel gas circulation flow path and the pressure downstream of the exhaust valve, the anode off-gas discharge amount per unit time is calculated,
An exhaust method for a fuel cell system, wherein opening and closing of the exhaust valve is controlled so that an integrated value of the anode off-gas discharge amount is the same as the required exhaust amount. A fuel cell in which fuel gas is supplied to the anode and oxidant gas is supplied to the cathode to generate power; a fuel gas circulation channel for supplying anode off-gas discharged from the anode of the fuel cell to the anode again; A discharge method of a fuel cell system comprising a discharge valve that enables discharge of anode off gas from the fuel gas circulation flow path,
When there is a request to discharge the anode off-gas from the fuel gas circulation flow path, a discharge time for opening the discharge valve according to the power generation state of the fuel cell is calculated, and further, the fuel gas circulation flow path Based on the pressure difference between the internal pressure and the pressure downstream of the discharge valve, the discharge time is corrected to be shorter as the pressure difference is larger, and the discharge valve is opened only during the corrected discharge time. A method for discharging a fuel cell system, wherein opening and closing is controlled.

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