JP2005158553A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of alleviating poisoning by catalyst-carrying carbon on an electrolyte film at the start-up and stoppage of the system. <P>SOLUTION: At the start-up of the fuel cell system, a controller 30 supplies hydrogen from a hydrogen tank 2 to an anode 1a with air flow to a cathode 1b in an interrupted state and with an ejector 5 and a circulation function of a hydrogen circulating pump 8 in a stopped state, and makes it consume oxygen left in the cathode 1b due to power generation and power taking-out by the fuel cell 1. After the cathode oxygen is consumed, a normal power generating state is resumed by the fuel gas circulation by the ejector 5 and the hydrogen circulating pump 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system having an electrode catalyst using carbon as a carrier, and more particularly to a fuel cell system in which control at the time of starting and stopping is improved to prevent catalyst deterioration.

  In a fuel cell, a fuel gas such as hydrogen gas and an oxidant gas containing oxygen are electrochemically reacted through an electrolyte, and electric energy is directly taken out between electrodes provided on both surfaces of the electrolyte. In particular, solid polymer fuel cells using solid polymer electrolytes are attracting attention as power sources for electric vehicles because of their low operating temperature and easy handling. That is, a fuel cell vehicle is equipped with a hydrogen storage device such as a high-pressure hydrogen tank, a liquid hydrogen tank, or a hydrogen storage alloy tank in the vehicle, and reacts by supplying hydrogen supplied therefrom and air containing oxygen to the fuel cell. This is the ultimate clean vehicle that drives the motor connected to the drive wheels with the electric energy extracted from the fuel cell, and the only exhaust material is water.

  In general, a cell which is a constituent unit of a polymer electrolyte fuel cell supplies a membrane electrode structure (MEA) in which electrode catalyst layers are formed on both sides of a polymer electrolyte membrane and hydrogen as a fuel gas to the fuel electrode side. The separator includes a separator and a separator that supplies air as an oxidant gas to the oxidant electrode side. These electrode catalyst layers usually use a catalyst such as platinum and carbon as a catalyst carrier (for example, Patent Document 1).

  In a polymer electrolyte fuel cell, hydrogen gas is supplied to the anode and air (or oxygen) is supplied to the cathode, and the electrode reaction shown below proceeds to generate electric power.

(Chemical formula 1)
Anode (hydrogen electrode): H ₂ → 2H ⁺ + 2e ⁻ (1)
Cathode (oxygen electrode): 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O (2)
The electrolyte membrane of the fuel cell is coated with platinum fine particles as a reaction catalyst. Since platinum is expensive, it is generally applied to the surface of carbon using carbon as a carrier.
JP 2002-373664 A (5th page, FIG. 1)

  However, in the electrolyte membrane of the conventional polymer electrolyte fuel cell, when the fuel cell system is stopped, left standing, or started, carbon and water on the electrolyte membrane react at the cathode to cause carbon poisoning. As a result, the electrolyte membrane and the electrode catalyst deteriorated.

  This phenomenon will be described in more detail with reference to FIG. FIG. 1A is a schematic diagram for explaining a state in a cell when the fuel cell is started / stopped. The left side of FIG. 1 (b) is a table for explaining the conditions under which carbon poisoning occurs during start / stop.

  When the fuel cell system is shut down, when the load is disconnected and left with oxygen and hydrogen remaining on the cathode and anode, respectively, or when hydrogen starts to be supplied to the anode at start-up, the anode Will be mixed.

At this time, protons (H ⁺ ) move from the anode to the cathode, and the transferred proton and the oxygen at the cathode react to generate water. In this reaction, electrons (e ⁻ ) are required. However, since the load is not connected, the load current stops and electrons cannot move from the anode to the cathode through the load. Therefore, the water present on the cathode reacts with the catalyst-supporting carbon on the electrolyte membrane to generate carbon dioxide, protons, and electrons. The generated electrons are used for the cathodic water generation reaction. At this time, carbon on the electrolyte membrane is deprived and the electrolyte membrane deteriorates.

  In the anode, a region where hydrogen is present and a region where air is present are mixed. In the region where anode hydrogen exists, hydrogen dissociates and protons and electrons are generated. In the region where the air of the anode exists, oxygen, protons moved from the cathode, and electrons generated by protonation of hydrogen react to generate water.

  When the open-circuit voltage of the fuel cell is high, the movement of electrons easily occurs, and these chemical reactions are promoted, and the carbon poisoning of the electrolyte membrane becomes intense.

  In summary, when the fuel cell is stopped and left after it is stopped, air (oxygen) remains at the cathode, hydrogen remains at the anode and air (oxygen) flows from the outside, The condition that the carbon of the electrolyte membrane-like platinum catalyst carrier is poisoned is established by the fact that the extraction is stopped and the open-circuit voltage is high.

  In addition, when the fuel cell is started, air (oxygen) enters the cathode from the outside, hydrogen supply to the anode is started, air (oxygen) and hydrogen are mixed, and the anode is filled with hydrogen. The condition that the carbon of the electrolyte membrane-like platinum catalyst carrier is poisoned is established by the fact that the electric power extraction is stopped until the open-circuit voltage is high.

  The poisoning of the catalyst-supported carbon in the electrolyte membrane affects the IV characteristics of the fuel cell output. That is, when the same output current is taken out, the carbon poisoned one has a lower output voltage than the one that is not poisoned, and a large generated power cannot be obtained.

  In view of the above problems, an object of the present invention is to prevent deterioration of a fuel cell by preventing a high open-circuit voltage from being generated between an anode and a cathode when the fuel cell system is started and stopped.

In order to solve the above problems, the first invention of the present application relates to a fuel gas supply means for supplying fuel gas to the anode of the fuel cell, an air supply means for supplying air to the cathode of the fuel cell, and the operating state of the fuel cell. An operating state detecting means for detecting, a fuel cell deterioration preventing control means for causing the fuel cell to consume cathode oxygen in a state where air supply from the air supplying means is stopped, and a cathode oxygen based on the output of the operating state detecting means Cathode oxygen consumption determination means for determining whether or not consumption exceeds a predetermined level, a fuel gas circulation device for circulating unreacted fuel gas discharged from the anode to the anode again, and a fuel gas for controlling the fuel gas circulation device Circulation control means;
A fuel cell system comprising: a fuel cell system comprising: a fuel cell supply unit that starts supplying fuel gas to the anode when the fuel cell system is started up, and the operation state detection unit detects a predetermined operation state; The gist is that the control by the prevention control means is started, and the fuel gas circulation control device controls the fuel gas circulation device so that the fuel cell does not deteriorate during the control.

  In order to solve the above problems, the second invention of the present application includes a fuel gas supply means for supplying fuel gas to the anode of the fuel cell, an air supply means for supplying air to the cathode of the fuel cell, and the operating state of the fuel cell. Based on the output of the operating state detecting means, the fuel cell deterioration preventing control means for consuming oxygen of the cathode while the air supply from the air supplying means to the fuel cell is stopped, and the cathode based on the output of the operating state detecting means Cathode oxygen consumption determination means for determining whether or not the oxygen consumption exceeds a predetermined level, a fuel gas circulation device for recirculating unreacted fuel gas discharged from the anode to the anode, and a fuel for controlling the fuel gas circulation device A gas circulation control means, wherein when the fuel cell system is stopped, air supply to the card is stopped by the air supply means. Thereafter, control by the fuel cell deterioration prevention control means is started, and after the cathode oxygen consumption determination means determines that the cathode oxygen has been consumed, the fuel gas circulation control means stops the fuel gas circulation device. Is the gist.

  According to the present invention, there is an effect that the fuel cell system can be started and stopped without deteriorating the fuel cell.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. The embodiment described below is a fuel cell system suitable for a fuel cell vehicle.

  FIG. 2 is a diagram showing a basic configuration of the fuel cell system according to the present invention. In the figure, 101 is a fuel gas supply means for supplying fuel gas to the fuel cell system, 102 is an operating state detecting means for detecting the operating state of the fuel cell system, and 103 is a fuel based on the outputs of 101 and 102. This is fuel cell deterioration prevention control means for consuming oxygen at the cathode while the supply of air from the air supply means to the battery is stopped. Reference numeral 104 denotes cathode oxygen consumption determining means for determining that oxygen has been consumed at the cathode based on the output of 102, and reference numeral 105 denotes fuel gas circulation control for controlling the fuel gas circulation device based on the outputs of 101 and 104. Means.

  FIG. 3 is a system configuration diagram showing an embodiment of the fuel cell system according to the present invention. The correspondence between the components in FIG. 3 and FIG. 2 is that the hydrogen tank 2, the hydrogen tank main valve 3, the pressure reducing valve 301, the hydrogen supply valve 4 and the ejector 5 correspond to the fuel gas supply means 101.

  The voltage sensor 21 corresponds to the operating state detection unit 102, and the cathode oxygen consumption control unit 26 corresponds to the fuel cell deterioration prevention control unit 103, the air electrode oxygen consumption control unit 104, and the fuel gas circulation control unit 105.

  In FIG. 3, a fuel cell (fuel cell main body) 1 is an internal humidification type, although not particularly limited, and humidifies a reaction gas with an anode 1a, a cathode 1b, an electrolyte membrane 1c, porous separators 1d and 1e, and pure water. For this purpose, a pure water electrode 1f, 1g, a separator 1h for separating the pure water electrode 1g and the cooling water channel 1i, and a cooling water channel 1i are provided.

  Hydrogen is supplied to the anode 1 a from the hydrogen tank 2 through the hydrogen tank main valve 3, the pressure reducing valve 301, and the hydrogen supply valve 4. The high-pressure hydrogen supplied from the hydrogen tank 2 is mechanically reduced to a predetermined intermediate pressure by the pressure reducing valve 301, and the intermediate pressure is controlled to be reduced to a desired hydrogen pressure by the hydrogen supply valve 4 and supplied to the anode 1a.

  The control of the entire fuel cell system is performed under the sequence controller 30 for controlling the sequence of the entire system, the air pressure control means 22 for controlling the air pressure of the cathode 1b, the hydrogen pressure control means 23 for controlling the hydrogen pressure of the anode 1a, Cooling water temperature control means 24 for controlling the cooling water temperature, pure water recovery control means 25 for controlling the recovery of the pure water to the pure water tank 13 when the fuel cell is stopped in a low temperature environment, and starting and stopping the fuel cell Cathode oxygen consumption control means 26 for controlling the oxygen consumption of the cathode is sometimes provided.

  The ejector 5 and the hydrogen circulation pump 8 serve as a fuel gas circulation device for mixing the new hydrogen supplied from the hydrogen supply valve 4 and the hydrogen that has not been consumed by the anode 1a and performing the recirculation supplied to the anode 1a. is set up. The hydrogen circulation pump 8 is installed to supplement the hydrogen circulation function in the hydrogen flow rate region where the ejector 5 does not operate.

  According to the present embodiment, since the hydrogen circulation pump is used as the fuel gas circulation device, precise hydrogen flow rate control can be performed. For applications where the operating state of the fuel cell does not fluctuate significantly, the system configuration can be simplified by using only the ejector as the fuel gas circulation device.

  The ejector 5 and the hydrogen circulation pump 8 are fuel gas circulation devices whose circulation / stop is controlled by the fuel gas circulation control means 105 of FIG. The ejector 5 incorporates a shut valve that opens and closes a suction port for sucking in the anode off gas discharged from the anode 1a in order to receive the circulation / stop control from the fuel gas circulation control means 105.

  The hydrogen pressure of the anode 1a is controlled by driving the hydrogen supply valve 4 by feeding back the pressure detected by the hydrogen pressure control means 23 with the pressure sensor 6a. By controlling the hydrogen pressure to be constant, the hydrogen consumed by the fuel cell is automatically compensated.

  The purge valve 7 provided between the anode 1a and the dilution blower 9 is opened in the following cases (1) to (3). (1) Discharge nitrogen accumulated in the hydrogen system in order to ensure the hydrogen circulation function. (2) In order to recover the cell voltage, the water clogged in the gas flow path is blown away. (3) In order to prevent deterioration of the fuel cell, the gas in the hydrogen system is replaced with hydrogen while performing cathode oxygen consumption control in which only the anode 1a is supplied at startup and oxygen in the cathode 1b is consumed. The cathode oxygen consumption control is also performed when the engine is stopped.

  The dilution blower 9 dilutes the hydrogen discharged from the purge valve 7 with air so that the hydrogen concentration is lower than the flammable concentration, and discharges the hydrogen outside the system.

  Air to the cathode 1b is supplied from the compressor 10. The air pressure of the cathode 1b is detected by a pressure sensor 6b provided at the cathode inlet. The air pressure control means 22 controls the cathode air pressure to a desired value by feedback-controlling the pressure detected by the pressure sensor 6b and driving the air pressure regulating valve 11.

  The pure water for humidification used by the pure water electrodes 1 f and 1 g is supplied from the pure water tank 13 by the pure water pump 12. The air pressure, hydrogen pressure, and pure water pressure are set in consideration of power generation efficiency and water balance, and are controlled to a predetermined differential pressure so as not to cause distortion in the electrolyte membrane 1c and the separators 1d and 1e. Part of the pure water supplied to the pure water electrodes 1f and 1g humidifies the hydrogen of the anode and the air of the cathode through the porous separators 1d and 1e, respectively. The remaining pure water returns to the pure water tank 13 via the pure water shut valve 14d.

  The pure water recovery control means 25 drives the pure water recovery valves 14a, 14b, 14c and the pure water shut valve 14d, thereby supplying the pure water electrodes 1f, 1g of the fuel cell 1 and the pure water in the pure water system pipe 10 to the compressor 10. Is recovered in the pure water tank 13 by the air pressure supplied to the cathode 1b. If the fuel cell system is stopped with the pure water remaining in the pure water electrodes 1f and 1g, the pure water may be frozen and expanded below freezing and the fuel cell 1 may be damaged. Collect into the tank 13. It should be noted that structural measures are taken so that the pure water tank 13 is not damaged even if the pure water freezes inside the pure water tank 13.

  The pure water shut valve 14d is an on-off valve that suppresses hydrogen leakage to the pure water pipe. By closing the pure water recovery valve 14b and the pure water shut valve 14d when hydrogen is supplied to the anode 1a in a state where pure water is not circulating to the pure water electrodes 1f and 1g when the fuel cell system is started and stopped. In addition, hydrogen leakage to the pure water pipe can be suppressed.

  Cooling water to the cooling water flow path 1 i inside the fuel cell 1 is supplied by a cooling water pump 15. The three-way valve 16 switches or diverts the flow path of the cooling water between the direction of the radiator 17 and the direction of the radiator bypass. When the radiator 17 is not sufficiently cooled by the traveling wind, the radiator fan 18 passes the wind to the radiator 17 and cools the cooling water. The temperature of the cooling water is adjusted by driving the three-way valve 16 and the radiator fan 18 by feeding back the cooling water temperature detected by the temperature sensor 19 by the cooling water temperature control means 24.

  The power manager 20 extracts power from the fuel cell 1 and supplies power to a load device such as a vehicle drive motor (not shown).

  The cathode oxygen consumption control means 26 stops the air supply in the compressor 10 at the start and stop of the fuel cell system, and the electric power is supplied from the fuel cell 1 according to the fuel cell voltage detected by the voltage sensor 21 and the elapsed time. Is taken out and used for cathode oxygen consumption control for consuming oxygen of the cathode 1b.

  Next, the start control and stop control of the fuel cell system in the present embodiment will be described with reference to a flowchart. FIG. 6 is a general flowchart of a start sequence and FIG. 7 is a stop sequence. These sequences are executed by the cooperation of the air pressure control means 22, the hydrogen pressure control means 23, the pure water recovery control means 25, and the cathode oxygen consumption control means 26 under the leadership of the sequence controller 30.

  In the fuel cell system startup sequence of FIG. 6, first, in step S10, the hydrogen supply pressure at the time of idling is designated to the hydrogen supply valve 4, and the hydrogen tank main valve 3 is opened, so that the anode of the fuel cell 1 from the hydrogen tank 2 is opened. The hydrogen supply to 1a is started. Next, in step S <b> 12, the cell group voltage or the total voltage of the fuel cell 1 is detected by the voltage sensor 21 and read into the sequence controller 30.

  In step S14, it is determined whether to start the deterioration prevention control based on the voltage detection result in step S12. In this determination, the detected voltage value is compared with a predetermined value, and if the detected voltage value is equal to or greater than the predetermined value, the process proceeds to step S16 in order to start the deterioration prevention control.

  Here, if the voltage sensor 21 detects the voltage of the cell group of the fuel cell 1, the maximum value of the detected cell group voltage is compared with a predetermined value as the voltage detection value.

  The predetermined value to be compared is set to a value smaller than the voltage at which deterioration of the fuel cell 1 is obtained in advance through experiments or the like. If the detected voltage value is less than the predetermined value in step S14, the process returns to step S12.

  In step S16, in order to prevent deterioration of the fuel cell, the supply of hydrogen to the anode 1a is continued while the supply of air to the cathode 1b is stopped, and the cathode oxygen consumption control means 26 sends the fuel for consumption of cathode oxygen to the power manager 20. An instruction to take out power from the battery 1 is given (corresponding to the fuel cell deterioration prevention control means 103 in FIG. 2). The deterioration prevention power extraction control in step S16 may be a method of extracting electric power (current) from the fuel cell 1 with a device such as the power manager 20 as in the case of normal power generation, or connecting an externally prepared resistor or the like. The method may be used.

  Next, in step S18, the oxygen amount of the cathode 1b is estimated, and in step S20, it is determined whether or not oxygen is consumed by a predetermined amount or more at the cathode b.

  The method for estimating the cathode oxygen amount in step S18 may be a method for detecting the maximum value of the voltage of the cell group composed of a plurality of cells, or a method for detecting the total voltage of the fuel cell. In step S20, it is determined that a predetermined amount or more of the cathode oxygen has been consumed when the maximum value or the total voltage value of the cell group voltage is equal to or less than a predetermined value.

  Further, when oxygen in the air is consumed at the cathode, hydrogen that has permeated (crossed over) the electrolyte membrane 1c from the anode to the cathode can no longer react with oxygen, and therefore from a part of the air system path such as the purge valve 7 or the like. A method of detecting that hydrogen has been discharged may be used, or a method of measuring an elapsed time after starting to take out power for preventing deterioration may be used. Moreover, these methods may be used alone or in combination.

  When it is determined that the oxygen of the cathode is consumed when it is detected that the fuel gas is discharged from a part of the cathode path of the fuel cell, it is possible to appropriately determine the oxygen consumption. It is possible to proceed to the next step after reliably detecting.

  When it is determined that the cathode oxygen has been consumed when the continuation time of the deterioration prevention control has passed the predetermined time, the control software can be easily created.

  If it is determined in step S20 that the cathode oxygen has not yet been consumed, the process returns to step S18, and if it is determined that oxygen has been consumed, the process proceeds to step S22.

  In this way, the hydrogen circulation pump and ejector, which are fuel gas circulation devices, are not activated until the cathode oxygen is consumed, so the hydrogen flow rate is low during this period, and the fuel cell voltage increases slowly. Therefore, it is easy to judge that the fuel cell voltage has exceeded the predetermined value (predetermined operating state), or that the oxygen in the cathode has been consumed (the oxygen concentration has decreased below the predetermined value), or that the battery has deteriorated. It is easy to start and stop prevention control.

  In addition, hydrogen remaining in the fuel circulation path is prevented from flowing into the anode of the fuel cell, and the amount of hydrogen supplied to the fuel cell anode is stabilized, so that the rise of the fuel cell voltage becomes gradual.

  In step S22, control of the fuel gas circulation device is started, and in step S24, it is determined whether or not the hydrogen replacement of the anode 1a is completed.

  If it is determined in step S24 that the hydrogen replacement of the anode 1a has not been completed, the process stays in step S24. If it is determined that the hydrogen replacement of the anode 1a has been completed, the process proceeds to step S26 and normal power generation is performed. Start and end the startup control sequence.

  In the fuel cell system stop sequence of FIG. 7, first, in step S30, the power manager 20 is instructed to stop normal power extraction from the fuel cell 1, thereby stopping normal power extraction from the fuel cell 1, and in step S32. The compressor 10 is stopped and the air supply to the cathode 1b is stopped.

  Next, in step S34, the power manager 20 is instructed to start taking out power for preventing deterioration from the fuel cell 1 while supplying hydrogen to the anode 1a. The deterioration prevention power extraction control in step S34 may be a method of extracting power (current) from the fuel cell 1 with a device such as the power manager 20 as in the case of normal power generation, or a method of connecting a separately prepared resistor or the like. But you can.

  When taking out power to prevent deterioration during start-stop control of the fuel cell, when taking out power in the same way as during normal power generation by the power manager, it is possible to realize deterioration prevention control without adding a new device. .

  In addition, when taking out power to prevent deterioration during start-stop control of the fuel cell, when taking out power using a separately prepared resistor, etc., it is not necessary to consider the energy consumption method during deterioration prevention control, and it is easy to prevent deterioration. A control system can be constructed.

  Next, in step S36, the amount of oxygen at the cathode is estimated, and in step S38, it is determined whether or not a predetermined amount or more of oxygen has been consumed in the cathode 1b.

  The cathode oxygen amount estimation method in step S36 may be a method for detecting the maximum value of the voltage of a cell group composed of a plurality of cells, or a method for detecting the total voltage of the fuel cell. In step S38, it is determined that a predetermined amount or more of the cathode oxygen has been consumed when the maximum value or the total voltage value of the cell group voltage is equal to or less than a predetermined value.

  Further, when oxygen in the air is consumed at the cathode, hydrogen that has permeated (crossed over) the electrolyte membrane 1c from the anode to the cathode can no longer react with oxygen, and therefore from a part of the air system path such as the purge valve 7 or the like. A method of detecting that hydrogen has been discharged may be used, or a method of measuring an elapsed time after starting to take out power for preventing deterioration may be used. Moreover, these methods may be used alone or in combination.

  If it is determined in step S38 that oxygen is not consumed, the process returns to step S36. If it is determined that oxygen is consumed, the process proceeds to step S40.

  In step S <b> 40, the power manager 20 is instructed to stop taking out power for preventing deterioration from the fuel cell 1. In step S42, the hydrogen supply to the anode 1a is stopped by closing the hydrogen tank main valve 3. At this time, the hydrogen supply valve 4 may be closed at the same time.

  After stopping the hydrogen supply in S42, the control of the ejector 5 and the hydrogen circulation pump 8, which are fuel gas circulation devices, is stopped in Step S44. In step S46, it is determined whether or not to collect pure water by referring to the outside air temperature or the like. If pure water recovery is to be performed, the entire system is stopped after the pure water recovery is completed, and the stop sequence of the fuel cell system is ended. To do.

  Hereinafter, the effects of the present invention will be described with reference to comparative examples and time charts of the present example.

  FIG. 4 shows a comparative example, and FIG. 5 shows (a) hydrogen supply, (b) fuel cell cell group voltage or total voltage (fuel cell voltage), (c) deterioration prevention control, and (d) cathode oxygen. The amount and (e) hydrogen circulation are shown respectively.

  The comparative example shows a case where the hydrogen circulation device is started simultaneously with the start of the fuel cell system. At time t0, the fuel gas (hydrogen) is controlled to a predetermined pressure (or flow rate) and the supply to the anode is started, and at the same time, the hydrogen circulation device is started. As a result, hydrogen is rapidly supplied to the anode, and the fuel cell voltage in (b) starts to rise rapidly.

  When the fuel cell voltage exceeds the deterioration prevention control threshold value Vp (this is time t1), the deterioration prevention control is started. As a result, electric power is taken out (power generation) from the fuel cell, and oxygen in the cathode The amount decreases.

  However, in this case, since the fuel gas supply start control and the hydrogen circulation device circulation start control are simultaneously performed, the fuel cell voltage rises quickly, and the deterioration prevention control is started at the same deterioration prevention control voltage threshold Vp. Even after (t1), depending on the amount of hydrogen present in the hydrogen circulation path, the voltage after the start of the deterioration prevention control exceeds the deterioration threshold value Vd, resulting in a slight deterioration of the fuel cell. There is a problem that it may end up.

  Therefore, in this embodiment, as shown in FIG. 5, even if the fuel gas (hydrogen) is controlled to a predetermined pressure (or flow rate) at time t0, the hydrogen circulation device does not start, and the cell voltage or total voltage of the fuel cell is not activated. The increase is dependent only on the amount of hydrogen supplied from the hydrogen supply means to reduce the variation in the voltage increase rate.

  Further, by suppressing the amount of hydrogen supplied to the fuel cell, the voltage increase rate is also suppressed to a small value, and when the fuel cell voltage reaches the deterioration prevention control threshold value Vp as shown in FIG. 5B (t1 ′> t1). ), The fuel cell voltage does not exceed the deterioration threshold value Vd even if the deterioration prevention control is started. Thereafter, when the oxygen amount of the cathode is reduced to a predetermined amount (t2> t1 ′), the hydrogen circulation device is activated to perform hydrogen replacement in the circulation path, so that the system can be activated without deteriorating the fuel cell. it can.

  Further, in the comparative example, when there is no hydrogen in the anode of the fuel cell at the time of start-up and hydrogen remains in a part of the fuel gas circulation system, the residual hydrogen reaches the anode when the hydrogen circulation pump is moved. This is the same as a sudden increase in hydrogen supply. In such a state with oxygen in the cathode, the voltage may increase rapidly. On the other hand, in this embodiment, a rapid increase in voltage can be prevented by moving the circulation pump after oxygen is exhausted from the cathode.

(A) It is a schematic diagram of the fuel cell at the time of starting / stopping. (B) It is a table | surface which shows the carbon poisoning condition at the time of starting / stopping, and its solution. It is a principal part block diagram of the fuel cell system which concerns on this invention. 1 is a system configuration diagram illustrating a configuration of an embodiment of a fuel cell system according to the present invention. It is a time chart explaining the mode at the time of fuel cell system starting in a comparative example. It is a time chart explaining the mode at the time of the fuel cell system starting in an Example. It is a flowchart explaining the starting sequence in the fuel cell system of an Example. It is a flowchart explaining the stop sequence in the fuel cell system of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell 2 ... Hydrogen tank 3 ... Hydrogen tank main valve 4 ... Hydrogen supply valve 5 ... Ejector 6a, 6b ... Pressure sensor 7 ... Purge valve 8 ... Hydrogen circulation pump 9 ... Dilution blower 10 ... Compressor 11 ... Air pressure regulating valve 12 ... Pure water pump 13 ... Pure water tanks 14a, 14b, 14c ... Pure water recovery valve 14d ... Pure water shut valve 15 ... Cooling water pump 16 ... Three-way valve 17 ... Radiator 18 ... Radiator fan 19 ... Temperature sensor 20 ... Power manager 21 ... Voltage sensor 22 ... Air pressure control means 23 ... Hydrogen pressure control means 24 ... Cooling water temperature control means 25 ... Pure water recovery control means 26 ... Cathode oxygen consumption control means 30 ... Sequence controller

Claims (11)

Fuel gas supply means for supplying fuel gas to the anode of the fuel cell;
Air supply means for supplying air to the cathode of the fuel cell;
An operating state detecting means for detecting the operating state of the fuel cell;
Fuel cell deterioration prevention control means for consuming oxygen in the cathode in a state where the air supply from the air supply means is stopped in the fuel cell;
Cathode oxygen consumption determination means for determining whether or not the cathode oxygen consumption is equal to or higher than a predetermined value based on the output of the operating state detection means;
A fuel gas circulation device for circulating unreacted fuel gas discharged from the anode to the anode again;
Fuel gas circulation control means for controlling the fuel gas circulation device;
A fuel cell system comprising:
At the start of the fuel cell system, after the fuel gas supply means starts to supply fuel gas to the anode, the operation state detection means starts control by the fuel cell deterioration prevention control means after detecting a predetermined operation state,
A fuel cell system, wherein the fuel gas circulation control device controls the fuel gas circulation device so that the fuel cell does not deteriorate during the control.   2. The fuel cell system according to claim 1, wherein the fuel gas circulation control unit activates the fuel gas circulation device after the cathode oxygen consumption determination unit determines that the cathode oxygen is consumed. Fuel gas supply means for supplying fuel gas to the anode of the fuel cell;
Air supply means for supplying air to the cathode of the fuel cell;
An operating state detecting means for detecting the operating state of the fuel cell;
Fuel cell deterioration prevention control means for consuming oxygen at the cathode in a state where the air supply from the air supply means to the fuel cell is stopped;
Cathode oxygen consumption determination means for determining whether or not the cathode oxygen consumption is equal to or higher than a predetermined value based on the output of the operating state detection means;
A fuel gas circulation device for circulating unreacted fuel gas discharged from the anode to the anode again;
Fuel gas circulation control means for controlling the fuel gas circulation device;
A fuel cell system comprising:
When the fuel cell system is stopped,
After stopping the air supply to the card by the air supply means, start the control by the fuel cell deterioration prevention control means,
A fuel cell system, wherein the fuel gas circulation control means stops the fuel gas circulation device after the cathode oxygen consumption judgment means judges that the cathode oxygen has been consumed. The operating state detecting means is a voltage sensor that detects a voltage of a cell group composed of a plurality of cells of a fuel cell,
2. The cathode oxygen consumption determining means determines that the oxygen of the cathode is consumed when the maximum value of the voltage of the cell group detected by the voltage sensor falls below a predetermined value. 4. The fuel cell system according to any one of items 3. The operating state detection means is a voltage sensor that detects the total voltage of the fuel cell,
4. The cathode oxygen consumption determining means determines that the cathode oxygen has been consumed when the total voltage value detected by the voltage sensor falls below a predetermined value. The fuel cell system according to claim 1. The operating state detecting means is a fuel gas detecting means for detecting that the fuel gas is discharged from a part of the air system path of the fuel cell,
6. The cathode oxygen consumption determining means determines that the cathode oxygen has been consumed when the fuel gas detecting means detects the discharge of fuel gas. The fuel cell system described in 1.   The said cathode oxygen consumption judgment means judges that the oxygen of the cathode was consumed when the continuation time of deterioration prevention control passed predetermined time, The one of Claims 1 thru | or 6 characterized by the above-mentioned. The fuel cell system described.   The fuel cell deterioration prevention control means prevents the voltage of the fuel cell from rising more than a predetermined value by taking out a predetermined power by the power take-off device in the start / stop control as in the case of normal power generation. The fuel cell system according to any one of claims 1 to 7.   The fuel cell deterioration prevention control means connects a predetermined resistance to the output terminal of the fuel cell during start / stop control so that the voltage of the fuel cell does not rise above a predetermined level. 8. The fuel cell system according to any one of 7 above.   The fuel cell system according to any one of claims 1 to 9, wherein the fuel gas circulation device is a circulation pump.   The fuel cell system according to any one of claims 1 to 9, wherein the fuel gas circulation device is an ejector.

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