JP4600720B2 - Hydrogen discharge device for vehicles equipped with fuel cell system - Google Patents

Description

  The present invention relates to a hydrogen discharge device for a vehicle equipped with a fuel cell system, and more particularly to a hydrogen discharge device for a vehicle equipped with a fuel cell system for diluting hydrogen gas discharged to the atmosphere.

  In a fuel cell system for a vehicle, a fuel comprising a combination of a plurality of fuel cells each having an anode side electrode (hydrogen electrode) and a cathode side electrode (air electrode) facing each other across a solid polymer electrolyte membrane A battery stack is provided, and hydrogen gas (anode gas) is supplied to the anode side electrode (hydrogen electrode) by a hydrogen circulation pump (fuel pump), and oxidizing gas (air) is supplied to the cathode side electrode (air electrode) by a compressor. In the fuel cell stack, power is generated by the supplied hydrogen gas and oxidizing gas, and the hydrogen gas (hydrogen offgas) and oxygen gas (oxygen offgas) used for power generation when the fuel cell system is stopped. ) And are discharged.

2. Description of the Related Art Conventionally, hydrogen gas discharge devices in a fuel cell system include a hydrogen catalyst in a hydrogen gas discharge path mixed with oxygen gas in an oxygen gas discharge path and diluted, and the mixed gas is provided with a platinum catalyst. Some of them are sent to a combustor, and the hydrogen concentration contained in the mixed gas is reduced by this combustor, and thus hydrogen gas having a reduced hydrogen concentration is discharged to the atmosphere.
JP 2002-289237 A

  By the way, in the conventional hydrogen gas discharge device of the fuel cell system, the hydrogen concentration of the hydrogen gas discharged to the atmosphere must be less than the flammable limit (4%), but the hydrogen gas discharged to the atmosphere is diluted. It is difficult to reduce the hydrogen concentration to an appropriate value when the hydrogen concentration of the hydrogen gas discharged from the fuel cell stack is high. There was an inconvenience.

This invention generates hydrogen by supplying hydrogen gas and oxidizing gas, and discharges hydrogen from a vehicle equipped with a fuel cell system equipped with a fuel cell stack that discharges the hydrogen gas and oxygen gas used in this power generation. In the apparatus, a first discharge path for discharging oxygen gas is provided connected to the oxygen gas discharge port of the fuel cell stack, the upstream side is connected to the hydrogen gas discharge port of the fuel cell stack, and the downstream side is the first discharge A second discharge passage connected to the passage to discharge hydrogen gas is provided, and a purge valve for opening and closing the second discharge passage is provided in the second discharge passage, and a merging portion connected to the first discharge passage and an air discharge provided by connecting the third discharge path that connects the outlet, wherein the oxygen gas muffler provided on the upstream side of the merging portion of the first discharge channel, at the time of stopping the fuel cell system, Not, the supply of hydrogen gas to the fuel cell stack is stopped, then, after the small amount generated by the residual hydrogen gas, characterized in that a control means for opening controlling the purge valve.

  The hydrogen discharge device for a vehicle equipped with the fuel cell system according to the present invention first stops the supply of hydrogen gas to the fuel cell stack when the fuel cell system is stopped, and then performs micro-power generation using the residual hydrogen gas. After the purge valve is opened, the amount of hydrogen gas discharged from the fuel cell stack is reduced, and then the hydrogen gas from the fuel cell stack is mixed with oxygen gas, and the hydrogen gas from the fuel cell stack is Diluted to an appropriate hydrogen concentration below the flammable limit (4%) and then discharged to the atmosphere.

The purpose of this invention is to dilute the hydrogen gas discharged from the fuel cell stack to an appropriate hydrogen concentration below the flammable limit (4%) and discharge it to the atmosphere. After the reduction, the hydrogen gas from the fuel cell stack is mixed with oxygen gas.
Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

  1 to 3 show an embodiment of the present invention.

  In FIG. 1, reference numeral 2 denotes a fuel cell system mounted on a vehicle (not shown).

  The fuel cell system 2 includes a fuel cell stack configured by combining a plurality of fuel cell cells (not shown) each including an anode side electrode (hydrogen electrode), a cathode side electrode (air electrode), and a solid polymer electrolyte membrane. 4 is provided. The fuel cell stack 4 generates power by supplying hydrogen gas and oxidizing gas, and discharges hydrogen gas (hydrogen offgas) and oxygen gas (oxygen offgas) used for the power generation.

  For this reason, the fuel cell system 2 is provided with an air-based air supply mechanism 6 that supplies air (cathode gas: oxidizing gas) to the fuel cell stack 4, and hydrogen gas (anode gas) is supplied to the fuel cell stack 4. ) Is provided, and a vehicle drive electric device, a vehicle drive motor (not shown), and the like are provided.

  In the air supply mechanism 6, the oxidizing gas supply port 10 of the fuel cell stack 4 and the air cleaner (filter) 12 are connected by an oxidizing gas supply path 14 that supplies the oxidizing gas to the fuel cell stack 4. In this oxidizing gas supply path 14, an oxidizing gas side flow meter 16 that measures the flow rate of oxidizing gas sequentially from the air cleaner 12 side, a compressor 18 that pumps the oxidizing gas to the fuel cell stack 4 side, and a compressor 18 An oxidizing gas silencer 20 that reduces the generated noise and an oxidizing gas heat exchanger 22 that reduces the temperature of the oxidizing gas are provided. Further, a first discharge path 26 that is an oxygen gas side discharge path for discharging oxygen gas is connected to the oxygen gas discharge port 24 of the fuel cell stack 4. The first exhaust path 26 is provided with an oxygen gas silencer 28 for reducing oxygen gas exhaust noise.

  In the hydrogen supply mechanism 8, a hydrogen gas supply path 32 that leads hydrogen gas from a hydrogen tank (not shown) is connected to the hydrogen gas supply port 30 of the fuel cell stack 4. Further, the upstream side of the second discharge path 36, which is a hydrogen gas discharge path for guiding the hydrogen gas discharged from the fuel cell stack 4, is connected to the hydrogen gas discharge port 34 of the fuel cell stack 4. The downstream side of the second discharge path 36 is connected to a junction 38 on the downstream side of the oxygen gas silencer 28 of the first discharge path 26. The supply side connection part 40 of the hydrogen gas supply path 32 and the discharge side connection part 42 of the second discharge path 36 are connected by a circulation path 44.

  The circulation path 44 circulates a part of the hydrogen gas as the unreacted gas discharged from the fuel cell stack 4 to the fuel cell stack 4. In this circulation path 44, the hydrogen gas from the hydrogen tank side and a part of the hydrogen gas as the unreacted gas discharged from the fuel cell stack 4 are sequentially transferred to the fuel cell stack 4 side from the discharge side connecting portion 42 side. A hydrogen circulation pump 46 for pumping and a hydrogen gas side flow meter 48 for measuring the flow rate of hydrogen gas as unreacted gas discharged from the fuel cell stack 4 are provided.

  Further, a purge valve 50 that opens and closes the second discharge path 36 is provided in the second discharge path 36 on the downstream side of the discharge side coupling portion 42. The purge valve 50 is disposed in the vicinity of a hydrogen circulation path 52 including a hydrogen circulation pump 46 that pumps hydrogen gas to the fuel cell stack 4. The second discharge path 36 is provided with a third discharge path 56 that connects the junction 38 to which the first discharge path 26 is connected and the atmospheric outlet 54. Although not shown, the third discharge path 56 is provided with a pressure adjustment valve.

  A hydrogen discharge path 60 is connected to a connection portion 58 of the second discharge path 36 between the discharge side coupling portion 42 and the purge valve 50. Although not shown, the hydrogen discharge path 60 is provided with a pressure regulating valve.

  The purge valve 50 is provided with a control means 62 in communication therewith. When the fuel cell system 2 is stopped, the control means 62 first stops the supply of hydrogen gas to the fuel cell stack 4, and then controls the opening of the purge valve 50 after performing a small amount of power generation using the residual hydrogen gas. To do. The control means 62 controls to open the purge valve 50 when the hydrogen pressure in the hydrogen supply mechanism 8 falls below a set value. The hydrogen pressure is measured by the hydrogen pressure sensor 64, for example.

  Further, on the downstream side of the compressor 18, a first discharge path 26 between the compressor 18 and the oxidizing gas silencer 20 is branched from the branching portion 66 and the first discharge on the fuel cell stack 4 side from the oxygen gas silencer 28. A bypass path 68 connected to the middle of the path 26 is connected. The bypass passage 68 is provided with an air amount adjustment valve 70 capable of adjusting the flow rate of air sent from the compressor 18 to the first discharge passage 26 side. The air supply mechanism 6 is provided with an air system pressure sensor 72 that measures the air system pressure.

  The compressor 18, the hydrogen circulation pump 46, and the air amount adjustment valve 70 communicate with the control means 62 and are controlled by the control means 62. Further, detection signals from the hydrogen pressure sensor 64 and the air pressure sensor 72 are input to the control means 62.

  Then, the control means 62 controls the operation of the compressor 18 and the air amount adjustment valve 70 during startup of the fuel cell system, and the hydrogen concentration of the hydrogen gas from the fuel cell stack 4 is determined by the amount of air from the compressor 18 side. To be adjusted.

  Next, the operation of this embodiment will be described.

  In the fuel cell system 2, as shown in FIG. 1, in the air supply mechanism 6, when the compressor 18 is driven, the oxidizing gas from the air cleaner 12 side is supplied from the oxidizing gas supply path 14 to the fuel cell stack 4, The oxygen gas from the fuel cell stack 4 is discharged from the first discharge path 26, and in the hydrogen supply mechanism 8, the hydrogen circulation pump 46 is driven so that the hydrogen gas in the hydrogen tank is supplied from the hydrogen gas supply path 32 to the fuel. While being supplied to the battery stack 4, the hydrogen gas from the fuel cell stack 4 is discharged from the second discharge path 36.

  Then, when the fuel cell system 2 is started or stopped when the vehicle is stopped or the like, as shown in FIG. 2, when the program of the control means 62 is started (step 102), the fuel cell system 2 (Step 104). If this step 104 is NO, this determination is continued. On the other hand, if this step 104 is YES, after the supply of hydrogen gas is stopped, (Step 106). This micro power generation is a power generation performed to consume only hydrogen gas remaining in the fuel cell stack 4 for a predetermined time (for example, within about 1 minute) without supplying hydrogen gas from the hydrogen tank side.

  Next, it is determined whether the hydrogen pressure (PH2) is equal to or lower than the hydrogen pressure set value (P1) and the air pressure (PO2) is equal to or lower than the air pressure set value (P2) (step 108). In this case, hydrogen system set value (P1) = air system set value (P2), and this hydrogen system set value (P1) and air system set value (P2) are, for example, 110 to 120 (KPa).

  If step 108 is NO, this determination is continued. On the other hand, if this step 108 is YES, the purge valve 50 is controlled to be opened (step 110), and the amount of mixed air is adjusted, that is, the fuel. The compressor 18 and the air amount adjustment valve 70 are controlled to operate so that the hydrogen concentration of the hydrogen gas discharged from the battery stack 4 becomes an appropriate hydrogen concentration (2 to 4% or less) (step 112), and the purge valve 50 And the mixed gas is discharged from the third discharge path 56 to the atmosphere (step 114), and the program is ended (step 116).

  Further, when the fuel cell system 2 is being started up, for example, during the start of the vehicle, as shown in FIG. 3, when the program of the control means 62 is started (step 202), the hydrogen gas in the hydrogen system It is determined whether or not the hydrogen concentration (CH2) is equal to or lower than the set hydrogen concentration (C1) (step 204). If this step 204 is NO, this determination is continued. The hydrogen concentration (CH2) in the hydrogen system is calculated from a predetermined map based on the operation time of the fuel cell system 2, the amount of power generation, and the like, not by detection means such as a sensor. During startup, the hydrogen concentration of the hydrogen gas in the fuel cell stack 4 gradually decreases due to air permeation through the membrane. In order to prevent this, the hydrogen gas used for power generation is appropriately diluted using the discharge method during start-up shown in FIG. 3, discharged into the atmosphere, and supplied to the fuel cell stack 4. It is necessary to keep the concentration above a certain value.

  On the other hand, if step 204 is YES, the purge valve 50 is controlled to open (step 206), and the amount of mixed air is adjusted, that is, the hydrogen concentration of the hydrogen gas discharged from the fuel cell stack 4 is appropriate. The compressor 18 and the air amount adjustment valve 70 are controlled to be 2 to 4% or less (step 208), the purge valve 50 is appropriately opened, and the mixed gas is discharged to the atmosphere (step 210). The program is ended (step 212).

  As a result, a first discharge path 26 for discharging oxygen gas is provided connected to the oxygen gas discharge port 24 of the fuel cell stack 4, the upstream side is connected to the hydrogen gas discharge port 34 of the fuel cell stack 4, and the downstream side is the first. A second discharge path 36 that discharges hydrogen gas is connected to the first discharge path 26, and a purge valve 50 that opens and closes the second discharge path 36 is provided in the second discharge path 36. When the fuel cell system 2 is stopped, first, supply of hydrogen gas to the fuel cell stack 4 is stopped when the fuel cell system 2 is stopped. Then, after performing a small amount of power generation with the residual hydrogen gas, the purge valve 50 is controlled to open, so that after the amount of hydrogen gas discharged from the fuel cell stack 4 is reduced, Since the hydrogen gas from the stack 4 is mixed with oxygen gas and discharged to the atmosphere, the hydrogen gas from the fuel cell stack 4 is diluted to an appropriate hydrogen concentration (2 to 4% or less) and discharged to the atmosphere. Can do.

  Further, since the control means 62 controls the opening of the purge valve 50 when the hydrogen system pressure (PH2) falls below the hydrogen system set value (P1), the purge valve 50 is operated after the hydrogen gas falls to an appropriate pressure value. Therefore, high concentration hydrogen gas is not released to the atmosphere.

  Further, since the purge valve 50 is disposed in the vicinity of the hydrogen circulation path 52 including the hydrogen circulation pump 46 that pumps the hydrogen gas to the fuel cell stack 4, the hydrogen gas is prevented from collecting in the hydrogen gas system path. Thus, the amount of residual hydrogen gas can be reduced.

  Furthermore, the fuel cell system 2 includes an oxidizing gas supply path 14 that supplies an oxidizing gas to the fuel cell stack 4, and this oxidizing gas supply path 14 is branched from the downstream side of the compressor 18 that pumps the oxidizing gas. 1 is provided with a bypass passage 68 connected to the discharge passage 26, and the bypass passage 68 is provided with an air amount adjusting valve 70 capable of adjusting the air flow rate. Therefore, the bypass passage 68 and the compressor 18 as an auxiliary machine are provided in the air system. By adjusting the air flow rate to the first discharge path 26, the hydrogen gas released to the atmosphere can be diluted to an appropriate hydrogen concentration even when the hydrogen gas concentration is high.

  Further, the control means 62 controls the compressor 18 and the air amount adjustment valve 70 during the startup of the fuel cell system 2 to control the concentration of hydrogen gas discharged into the atmosphere. Even during startup, the amount of air in the air system is controlled by the compressor 18 and the air amount adjusting valve 70 so as to be mixed with oxygen gas and discharged to the atmosphere, so that the hydrogen gas can be diluted to an appropriate hydrogen concentration. Therefore, it is possible to release appropriately diluted hydrogen gas during startup of the fuel cell system 2, and to maintain the power generation performance of the fuel cell stack 4 at a high level.

  That is, in this embodiment, when the fuel cell system 4 is stopped, before the hydrogen gas is released outside the vehicle, the supply of the hydrogen gas to the fuel cell stack 4 is stopped, and remains in the hydrogen system by micro-power generation. After the hydrogen gas is consumed and the pressure of the hydrogen gas is sufficiently reduced, the purge valve 50 is controlled to be opened, and a small amount of the remaining hydrogen gas is mixed with the air supplied to the fuel cell stack 4, so that the hydrogen gas The hydrogen gas is discharged from the air outlet 54 of the air system at a hydrogen concentration of 2 to 4% or less. Further, the air system includes a bypass passage 68 and an air amount adjustment valve 70 from the compressor 18 to the air discharge port 54, and the air amount to the air discharge port 54 side can be arbitrarily adjusted. Furthermore, the confluence portion 38 of the second discharge path 36 and the first discharge path 26, which is a confluence portion of hydrogen gas and air, is laid out in the vicinity of the atmospheric discharge port 54, and thus the hydrogen gas pipe portion is shortened, Parts that use special materials such as prevention of hydrogen gas leakage and measures against hydrogen embrittlement can be reduced, and hydrogen gas can be discharged to the atmosphere.

  In other words, the hydrogen gas supply is stopped after the vehicle starts and stops, and the hydrogen gas is consumed by a small amount of power generation. Therefore, the hydrogen gas remaining in the hydrogen system can be consumed, and the pressure of the piping in the hydrogen system Can be lowered. Further, since the purge valve 50 is provided on the hydrogen-based discharge side and the hydrogen gas is joined to the air-based atmospheric discharge port 54, an air blower or the like for diluting the hydrogen gas can be dispensed with separately. Further, by providing the bypass passage 68 and the air amount adjusting valve 70 in the air system, the air flow rate can be adjusted when the hydrogen gas is diluted, and an appropriate hydrogen concentration can be obtained. Furthermore, since the merge part 8 of hydrogen and air is disposed in the vicinity of the atmospheric discharge port 54, the hydrogen gas piping can be shortened. Further, since the purge valve 50 for controlling the flow rate of the hydrogen gas is disposed in the vicinity of the hydrogen circulation path 52, the remaining amount of the hydrogen gas can be reduced. Furthermore, by strictly controlling the compressor 18 and the air amount adjustment valve 70, the hydrogen gas during the startup of the vehicle can be appropriately diluted and discharged to the atmosphere.

  Note that by laying out the purge valve closer to the hydrogen-based circulation portion than the air discharge port of air, the capacity of the hydrogen gas to be retained can be reduced. Further, the hydrogen gas being started can be diluted by strictly controlling the air amount adjusting valve.

  In the present invention, after the supply of hydrogen gas to the fuel cell stack is stopped, the hydrogen circulation pump can be continuously driven, and the residual hydrogen gas can be actively used for micro power generation to effectively use the hydrogen gas. It is. In addition, a gas storage tank is provided in the circulation path, and after the supply of hydrogen gas to the fuel cell stack is stopped, the residual hydrogen gas is stored in the gas storage tank, and the hydrogen gas in the gas storage tank is stored in the fuel cell at the time of restart. It is also possible to eliminate the waste of hydrogen gas by supplying it to the stack.

  A structure in which hydrogen gas is mixed with oxygen gas after the amount of discharged hydrogen gas is reduced can be applied to a fuel cell system and a fuel cell vehicle.

1 is a system configuration diagram of a fuel cell system. It is a flowchart of the discharge method of the hydrogen gas at the time of starting stop. It is a flowchart of the discharge method of the hydrogen gas during starting.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Fuel cell system 4 Fuel cell stack 6 Air supply mechanism 8 Hydrogen supply mechanism 14 Oxygen gas supply path 18 Compressor 26 1st discharge path 36 2nd discharge path 38 Merge part 44 Circulation path 46 Hydrogen circulation pump 50 Purge valve 52 Hydrogen circulation path 54 Air outlet 56 Third exhaust passage 62 Control means 68 Bypass passage 70 Air amount adjustment valve

Claims (4)

In a hydrogen discharge device for a vehicle equipped with a fuel cell system equipped with a fuel cell stack that generates power by supplying hydrogen gas and oxidizing gas and discharges the hydrogen gas and oxygen gas used in the power generation, A first discharge path for discharging oxygen gas is provided by being connected to an oxygen gas discharge port of the fuel cell stack, and an upstream side is connected to a hydrogen gas discharge port of the fuel cell stack and a downstream side is connected to the first discharge path. A second discharge path for discharging hydrogen gas is provided, and a purge valve for opening and closing the second discharge path is provided in the second discharge path, and a confluence portion connected to the first discharge path is connected to the atmospheric discharge port. to provided by connecting the third discharge path, the oxygen gas muffler provided on the upstream side of the merging portion of the first discharge channel, at the time of stopping the fuel cell system, first of all, the fuel A vehicle equipped with a fuel cell system is provided with a control means for controlling the opening of the purge valve after stopping the supply of hydrogen gas to the battery stack, and then performing a slight amount of power generation with residual hydrogen gas. Hydrogen discharger.   2. The hydrogen discharge apparatus for a vehicle equipped with a fuel cell system according to claim 1, wherein the control means controls the opening of the purge valve when the hydrogen system pressure falls below a set value.   The fuel cell system is provided with an oxidant gas supply path for supplying an oxidant gas to the fuel cell stack, and the oxidant gas supply path branches from the downstream side of the compressor for pumping the oxidant gas to the first discharge path. The fuel cell system according to claim 1, wherein a bypass passage connected to the first exhaust passage is provided in the bypass passage, and an air amount adjustment valve capable of adjusting an air flow rate to the first discharge passage is provided in the bypass passage. Vehicle hydrogen discharger. Wherein, during startup of the fuel cells system, according to claim 3 which operates controlling said air control valve and the compressor, and adjusting the hydrogen concentration of the hydrogen gas discharged into the atmosphere A hydrogen discharger for a vehicle equipped with the fuel cell system described in 1.

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