JP2010177166A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing breakage of a fuel cell even when a sealing valve on the cathode inlet side has stopped closing during operation of the system. <P>SOLUTION: The fuel cell system 1A includes a first sealing valve 20 shutting off air supply piping 22a, 22b, a second sealing valved 21 shutting off air offgas piping 22c, 22d, and an ejector 30 arranged in hydrogen supply piping 31a, 31b and adjusting the pressure of hydrogen supplied to a fuel cell 10 by adjusting an opening based on the pressure in air supply piping 22a, 22b, and seals a cathode of the fuel cell 10 by closing the first sealing valve 20 and the second sealing valve 21 when power generation of the fuel cell 10 is stopped. In the fuel cell system 1A, the pressure in the air supply piping is gotten from a branch part S arranged between the fuel cell 10 and the first sealing valve 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a valve that seals the inlet / outlet of a cathode of a fuel cell.

  In the fuel cell system, when the power generation of the fuel cell is stopped, hydrogen on the anode side moves through the membrane (ion exchange membrane) to the cathode, and conversely, cathode air moves through the membrane to the anode. As a result, hydrogen and oxygen chemically react with each other at the cathode and the anode to generate OH radicals (hydroxy radicals). The OH radicals oxidize the electrodes, which significantly reduces the durability of the fuel cell. is there. As a countermeasure for solving such a problem, there has been proposed a technique for providing a sealing valve that seals the cathode-side inlet / outlet of the fuel cell to contain the cathode (see Patent Documents 1 to 3).

JP 2002-216823 A (FIG. 1) JP 2007-66831 A (FIG. 1) JP 2008-4337 A (FIG. 1)

  However, if the sealing valve abnormally closes due to some malfunction during the operation of the fuel cell system, it is expected that the fuel supply function to the fuel cell and the operation control function will be disturbed. It has not been studied until. In particular, when the valve on the inlet side of the fuel cell fails to close during system operation, the cathode side air (oxygen) in the fuel cell reacts with the hydrogen on the anode side to release the pressure on the cathode side first, Since the pressure on the anode side is maintained as it is, there is a possibility that the inter-electrode differential pressure (anode pressure-cathode pressure) becomes excessive in the fuel cell and the fuel cell may be damaged.

  An object of the present invention is to solve the above-described conventional problems, and to provide a fuel cell system capable of avoiding damage to the fuel cell even if the sealing valve on the cathode inlet side fails during the system operation. To do.

  The invention according to claim 1 is a fuel cell in which fuel is supplied to an anode and an oxidant is supplied to a cathode to generate power, a fuel flow path for supplying the fuel to the fuel cell, and the oxidation to the fuel cell. An oxidant flow path for supplying the oxidant, an oxidant discharge flow path for the oxidant discharged from the fuel cell, a first sealing valve for closing the oxidant flow path, and the oxidant discharge flow path. A fuel cell system including a second sealing valve to be closed, which is disposed in the fuel flow path and is supplied to the fuel cell by adjusting an opening degree based on a pressure in the oxidant flow path A pressure adjusting unit that adjusts the pressure of the fuel; and when the power generation of the fuel cell is stopped, the first sealing valve and the second sealing valve are closed to seal the cathode of the fuel cell. And a cathode sealing means, wherein the pressure of the oxidant flow path is Characterized in that it is obtained from the arranged bifurcation between the battery first sealing valve.

  According to this, even if the first sealing valve is closed due to a failure during operation of the fuel cell system, the acquisition position of the signal pressure applied to the pressure regulator of the fuel system is determined by the first sealing valve and the fuel cell. Therefore, even if the cathode side oxidant in the fuel cell is consumed and the cathode internal pressure decreases, the anode pressure also decreases in conjunction with the decrease in cathode internal pressure, and the differential pressure between the electrodes is constant. Thus, the fuel cell can be prevented from being damaged (problem).

  The invention according to claim 2 is provided with a humidifier that is disposed in the oxidant flow path and supplies moisture to the oxidant supplied to the fuel cell, and the humidifier is disposed downstream of the first sealing valve. It is characterized by being arranged.

  According to this, in addition to avoiding the above problems, water in the humidifier flows into the first sealing valve even when power generation is stopped even when the fuel cell system is used in a low-temperature environment that reaches below freezing point. As a result, the first sealing valve can be prevented from freezing, and damage or malfunction of the system can be avoided. For example, it is possible to prevent the first sealing valve from being frozen with water flowing out of the humidifier and preventing the first sealing valve from opening when the fuel cell system is started.

  The invention according to claim 3 is characterized in that the humidifier obtains moisture from the oxidant at a position upstream of the second sealing valve in the oxidant discharge flow path.

  According to this, since the oxidant after moisture is removed flows into the second sealing valve when power generation is stopped, in addition to avoiding the above-described problem, the second sealing valve is prevented from freezing, System damage and problems can be avoided.

  The invention according to claim 4 is characterized in that the pressure adjusting unit is an ejector that adjusts an output by a differential pressure between the pressure of the fuel and the pressure of the oxidant.

  According to this, since the pressure is automatically adjusted with a simple configuration without performing electrical control, in addition to avoiding the above problems, the system is simplified and the cost can be reduced.

  According to the present invention, it is possible to provide a fuel cell system capable of avoiding damage to the fuel cell even when the sealing valve on the cathode inlet side malfunctions during system operation.

It is a whole lineblock diagram showing the fuel cell system of a 1st embodiment. The time chart which shows the change of the pressure when the 1st sealing valve has failed to close is shown, (a) is the case where the branching part is provided downstream of the first sealing valve, (b) This is a case where it is provided upstream of one sealing valve. It is a whole block diagram which shows the fuel cell system of 2nd Embodiment. It is a whole block diagram which shows the fuel cell system of 3rd Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, fuel cell system 1A-1C of this embodiment is applicable to all things which require electricity, such as mobile bodies, such as a fuel cell vehicle, a ship, and an aircraft, and a stationary thing for home use and business.

(First embodiment)
As shown in FIG. 1, the fuel cell system 1A of the first embodiment includes a fuel cell 10, a first sealing valve 20, a second sealing valve 21, air supply pipes (oxidant channels) 22a and 22b, air Off gas pipes (oxidant discharge flow paths) 22c, 22d, signal pressure pipe 23, ejector 30, hydrogen supply pipes (fuel flow paths) 31a, 31b, hydrogen off gas pipes 31c, 31d, 31e, a purge valve 32, and the like. Yes.

  The fuel cell 10 is, for example, a polymer electrolyte fuel cell (PEFC), and a MEA (Membrane Electrode Assembly) is sandwiched between a pair of conductive separators (not shown). A plurality of unit cells are stacked. The MEA is configured by sandwiching an electrolyte membrane (solid polymer membrane) between an anode including a catalyst, a cathode, and the like. A cathode channel 11 through which air flows is formed in the separator facing the cathode, and an anode channel 12 through which hydrogen flows is formed in the separator facing the anode.

  In such a fuel cell 10, hydrogen (fuel) is supplied to the anode, and oxygen-containing air (oxidant) is supplied to the cathode, so that power generation is possible. The fuel cell 10 and an external load (not shown) (such as a travel motor, a battery, and an air pump in the case of a vehicle) are electrically connected to generate power.

  In the cathode system of the fuel cell system 1 </ b> A, the first sealing valve 20 is connected to the air supply pipe 22 a on the upstream side, connected to the air supply pipe 22 b on the downstream side, and the air supply pipe 22 b is connected to the cathode flow path 11. It is connected to the inlet 10a.

  The second sealing valve 21 is connected to the air off-gas pipe 22c on the upstream side, the air off-gas pipe 22c is connected to the outlet 10b of the cathode channel 11, and communicates with the outside via the air off-gas pipe 22d on the downstream side. is doing. Although not shown, an air pump that sends compressed air to the cathode, a humidifier that humidifies the compressed air, and the like are provided upstream of the first sealing valve 20.

  In the anode system of the fuel cell system 1A, the ejector 30 is connected to the hydrogen supply pipe 31a on the upstream side, the hydrogen supply pipe 31b is connected to the downstream side, and the hydrogen supply pipe 31b is connected to the inlet 10c of the anode flow path 12. Has been.

  Further, the outlet 10d of the anode channel 12 is connected to the purge valve 32 via the hydrogen offgas pipe 31c, and is connected to the return port (not connected) of the ejector 30 via the hydrogen offgas pipe 31d formed by branching to the hydrogen offgas pipe 31c. Connected). Further, the purge valve 32 communicates with the outside via a hydrogen off gas pipe 31e and the like.

  Although not shown, a hydrogen tank compressed and filled with high-purity hydrogen, an electromagnetically operated shut-off valve, a pressure reducing valve, and the like are provided upstream of the ejector 30 so that the hydrogen supplied from the hydrogen tank is predetermined. After being depressurized to this pressure, it is supplied to the ejector 30. The hydrogen off-gas pipe 31e and the air off-gas pipe 22d are connected to a diluter, and the hydrogen discharged from the anode system is diluted with the cathode air off-gas and discharged to the outside.

  The first sealing valve 20 is, for example, an electromagnetically operated on / off valve, and has a function of closing (sealing) the air supply pipes 22 a and 22 b on the air supply side of the fuel cell 10. The second sealing valve 21 is a similar electromagnetically operated on-off valve, and has a function of closing (sealing) the air off-gas pipes 22 c and 22 d on the air discharge side of the fuel cell 10. Therefore, the cathode (cathode channel 11) of the fuel cell 10 is sealed by closing the first sealing valve 20 and the second sealing valve 21, respectively.

  The first sealing valve 20 and the second sealing valve 21 may be a normally closed valve or a normally open valve, and may be a fuel cell system 1A (hereinafter referred to as fuel cell system 1B). , 1C can be selected as appropriate.

  The signal pressure pipe 23 is a flow path for applying a signal pressure (pilot pressure) to an ejector 30 described later by the pressure of air supplied to the fuel cell 10, and one end is between the first sealing valve 20 and the fuel cell 10. The other end is connected to the signal pressure input port of the ejector 30. A connecting portion between one end of the signal pressure pipe 23 and the air supply pipe 22b corresponds to the branch portion S.

  The ejector 30 sucks unreacted hydrogen discharged from the outlet 10d of the anode flow path 12 through the hydrogen offgas pipes 31c and 31d, mixes it with hydrogen from the hydrogen tank, and returns it to the inlet 10c of the fuel cell 10 again. And has the function of recirculating.

  The ejector 30 is of a variable flow type, and has a mechanism capable of controlling the pressure (output) of hydrogen supplied from the ejector 30 to the fuel cell 10 by inputting the cathode air pressure as a signal pressure. is there.

  That is, when the cathode air pressure increases, the hydrogen pressure output from the ejector 30 increases in conjunction with the air pressure, and conversely, when the air pressure decreases, the hydrogen pressure decreases automatically. To be controlled.

  As an ejector for changing the discharge pressure from the ejector 30 by air pressure, for example, a known technique in which two diaphragms are combined with a diffuser, a nozzle, a needle, and a needle holding guide can be applied (Japanese Patent Laid-Open No. 2002-227799). No. publication).

  According to such an ejector 30, a needle (not shown) from a nozzle (not shown) is generated by a differential pressure between the pressure of hydrogen supplied from a hydrogen tank (not shown) and the pressure of air inputted as a signal pressure. The pressure (output) discharged from the nozzle can be made variable by adjusting the flow path cross section (opening degree) by changing the protruding amount of.

  The purge valve 32 is an electromagnetically operated type. For example, by periodically opening the valve during power generation, impurities accumulated in the anode flow path 12, the hydrogen supply pipe 31b, and the hydrogen offgas pipe 31c (permeate the electrolyte membrane). Produced water, nitrogen contained in the air, etc.).

  The first sealing valve 20, the second sealing valve 21, and the purge valve 32 are appropriately controlled to be opened and closed by a control unit (ECU: Electronic Control Unit) not shown. The control unit includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like, and includes a cathode sealing unit.

  The cathode sealing means closes the first sealing valve 20 and the second sealing valve 21 when the operation of the fuel cell system 1A is stopped (when the power generation of the fuel cell 10 is stopped), and the cathode flow path 11 of the fuel cell 10 Is a means for preventing oxidation of electrodes (anode and cathode) in the fuel cell 10.

  Next, the operation of the fuel cell system 1A of the first embodiment will be described. First, when the ignition switch is turned on and the fuel cell system 1A is in operation (system operation), in the state where the first sealing valve 20 and the second sealing valve 21 are opened, the air pump ( Air supplied from a humidifier (not shown) is supplied to the cathode, and the hydrogen supplied from the hydrogen tank (not shown) is adjusted to the anode after the discharge pressure is adjusted by the ejector 30. Supplied.

  Further, if the extraction of the generated current (generated power) from the fuel cell 10 increases during operation, the rotational speed of the air pump motor (not shown) is increased and the cathode pressure (air pressure) is increased. As the signal pressure increases, the differential pressure between the hydrogen pressure (fuel pressure) from the hydrogen tank and the air pressure (oxidant pressure) as the signal pressure changes, causing the ejector 30 to change. The anode pressure (hydrogen pressure) discharged from the fuel is increased. Conversely, when the extraction of the generated current from the fuel cell 10 decreases, the anode pressure discharged from the ejector 30 decreases in conjunction with the decrease in the cathode pressure.

  By the way, when the acquisition position (branch part) of the signal pressure input to the ejector 30 is on the upstream side of the first sealing valve 20, as shown in FIG. 2B as a comparative example, the operation of the fuel cell system 1A is performed. When a malfunction occurs in the first sealing valve 20 and the valve is switched from the open state to the closed state, the upstream pressure of the first sealing valve 20 increases, and the ejector 30 discharges in conjunction with the increase in the upstream pressure. The flow rate of hydrogen to be increased increases, and the anode pressure (anode internal pressure) Pa rises. Further, the air on the downstream side of the first sealing valve 20 is consumed by the reaction with hydrogen in the fuel cell 10, and the downstream pressure (cathode internal pressure) Pc of the first sealing valve decreases. Since the anode internal pressure increases and the cathode internal pressure decreases in this way, the inter-electrode differential pressure (Pa−Pc) between the cathode internal pressure Pc and the anode internal pressure Pa becomes excessive, and the fuel cell 10 may be damaged. There is.

  Therefore, in the fuel cell system 1A of the first embodiment, the acquisition position (branch portion S) of the signal pressure input to the ejector 30 is set on the downstream side of the first sealing valve 20, so FIG. ), Even if the first sealing valve 20 is switched from the open state to the closed state due to some malfunction during the operation of the fuel cell system 1A, the downstream pressure Pc (cathode internal pressure) of the first sealing valve 20 The internal pressure of the anode also decreases in conjunction with the decrease in the pressure), and the inter-electrode differential pressure (Pa-Pc) remains constant. Thus, even when the cathode internal pressure suddenly decreases, the signal pressure also decreases suddenly in conjunction with it, so that the anode-side control pressure (anode internal pressure) can be lowered, and the fuel cell 10 is not likely to be damaged. .

  Further, according to the first embodiment, since the ejector 30 in which the anode pressure is adjusted using the cathode pressure as a signal pressure is used, the pressure is automatically adjusted with a simple configuration. In addition, the system becomes simple and the cost can be reduced.

(Second Embodiment)
The fuel cell system 1B of the second embodiment shown in FIG. 3 has a configuration in which a humidifier 40 is added to the fuel cell system 1A of the first embodiment, and the other components are denoted by the same reference numerals and are duplicated. Is omitted.

  The humidifier 40 shown in FIG. 3 is provided downstream of the first sealing valve 20 and downstream of the branch portion S on the air supply pipe 22b. The type of the humidifier 40 is not particularly limited as long as it can humidify compressed air from an air pump (not shown). For example, the humidifier 40 humidifies the air supplied from the air pump by spraying water. It may be a thing, or it may be a thing which bubbles air in water and humidifies.

  According to the second embodiment, since the humidifier 40 is provided downstream rather than upstream of the first sealing valve 20, it is possible to prevent water in the humidifier 40 from flowing into the first sealing valve 20. When the battery system 1B is used in a low temperature environment that reaches below freezing point, when the operation of the fuel cell system 1B is stopped, the first sealing valve 20 is frozen and cannot be opened and closed. It becomes possible to do. Therefore, it becomes possible to avoid damage and malfunction of the fuel cell system 1B due to freezing of the first sealing valve 20.

  Further, if the humidifier 40 is provided downstream of the branch portion S, it is possible to avoid the problem that the water remaining in the humidifier 40 flows into the signal pressure pipe 23 and the signal pressure pipe 23 is blocked by freezing. Become. In addition, the position of the branch part S is not limited between the 1st sealing valve 20 and the humidifier 40, What is necessary is just the downstream of the 1st sealing valve 20, and the humidifier 40 and the fuel cell 10 are sufficient. It may be between.

(Third embodiment)
The fuel cell system 1C of the third embodiment shown in FIG. 4 is configured as a humidifier 50 instead of the humidifier 40 of the fuel cell system 1B of the second embodiment, and the other components are denoted by the same reference numerals. Therefore, the duplicate description is omitted.

  In the humidifier 50, air (low wet gas) supplied from an air pump (not shown) through the air supply pipes 22a and 22b is discharged from the cathode of the fuel cell 10 to the air off gas pipe 22c (high off gas). Humidified gas). The humidifier 50 is, for example, a dry air inlet / outlet from an air pump (not shown) in a case (not shown) in which a hollow fiber membrane bundle in which a plurality of hollow fiber membranes (water exchange membranes) are bundled is accommodated. In addition, a known technique in which an air off-gas inlet / outlet is provided can be employed.

  According to such a humidifier 50, the air (low wet gas) supplied from the air pump circulates on one side of the hollow fiber membrane of the humidifier 50 and is discharged from the fuel cell 10 (high wet gas). ) Circulates on the other surface side of the hollow fiber membrane, so that air (low wet gas) is humidified.

  According to the third embodiment, in addition to the effects obtained by the second embodiment, the humidifier 50 is provided upstream of the second sealing valve 21, so that, for example, the outlet 10b of the cathode channel 11 of the fuel cell 10 is provided. The flow of the generated water discharged from the air is blocked by the humidifier 50, and the generated water can be prevented from flowing into the second sealing valve 21.

  In addition, since the air off-gas (oxidant) after moisture is absorbed by passing through the humidifier 50 flows into the second sealing valve 21, the problem that the second sealing valve 21 is frozen is avoided. Is possible. Therefore, damage or malfunction of the fuel cell system 1C due to freezing of the second sealing valve 21 can be avoided.

  In addition, in the humidifier 50 of 3rd Embodiment, although the example using the hollow fiber membrane was mentioned as an example, it is not limited to this, If it performs a water exchange through a membrane, It may be a moisture exchange membrane having another shape such as a flat membrane shape or a spiral shape.

  In addition, the present invention is not limited to the above-described embodiments, and the ejector has been described as an example of the pressure adjusting unit. However, for example, the present invention is an ejector whose pressure is electrically controlled using a solenoid as a drive source. May be. Moreover, although the case where it applied to the ejector of variable flow rate was mentioned as an example as a pressure regulation part, it may apply to the pressure-reduction valve (regulator) which makes a cathode pressure a signal pressure.

1A to 1C Fuel cell system 10 Fuel cell 20 First sealing valve 21 Second sealing valve 22a, 22b Air supply pipe (oxidant flow path)
22c, 22d Air off-gas piping (oxidant discharge flow path)
30 Ejector (Pressure adjustment unit)
31a, 31b Hydrogen supply pipe (fuel flow path)
40, 50 Humidifier S Branch

Claims (4)

A fuel cell in which fuel is supplied to the anode and oxidant is supplied to the cathode to generate electricity;
A fuel flow path for supplying the fuel to the fuel cell;
An oxidant flow path for supplying the oxidant to the fuel cell;
An oxidant discharge passage through which the oxidant discharged from the fuel cell flows;
A first sealing valve that shuts off the oxidant flow path;
A second sealing valve that shuts off the oxidant discharge channel, and a fuel cell system comprising:
A pressure adjusting unit that is disposed in the fuel flow path and adjusts the pressure of the fuel supplied to the fuel cell by adjusting the opening degree based on the pressure of the oxidant flow path;
A cathode sealing means for closing the first sealing valve and the second sealing valve when the power generation of the fuel cell is stopped, and sealing the cathode of the fuel cell;
The fuel cell system according to claim 1, wherein the pressure of the oxidant flow path is obtained from a branch portion disposed between the fuel cell and the first sealing valve. A humidifier disposed in the oxidant flow path and providing moisture to the oxidant supplied to the fuel cell;
The fuel cell system according to claim 1, wherein the humidifier is disposed downstream of the first sealing valve.   The fuel cell system according to claim 2, wherein the humidifier obtains moisture from the oxidant at a position upstream of the second sealing valve in the oxidant discharge flow path.   4. The fuel cell according to claim 1, wherein the pressure adjusting unit is an ejector that adjusts an output based on a differential pressure between the pressure of the fuel and the pressure of the oxidant. 5. system.

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