JP2008140577A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress that impurities penetrate into a polymer electrolyte membrane and an electrode or the like to constitute a fuel cell. <P>SOLUTION: In the fuel cell in which power generation is carried out by reacting a fuel gas and an oxidation gas via the polymer electrolyte membrane 23, a water repellent layer 21c is installed at a surface of an oxygen electrode 21 contacting the polymer electrolyte membrane 23. On the other hand, by spraying fog like water to the air supplied to the oxygen electrode 21 from a nozzle 55, the impurities d in the air is made to be contained into water drops w, and the water drops dw containing the impurities d contact the oxygen electrode. Since the oxygen electrode 21 has the water repellent layer 21c on the surface, it repels the water drops dw and suppresses penetration of the impurities into the oxygen electrode 21 and the electrolyte membrane 23. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system in which entry of impurities into an electrode of a fuel cell is suppressed.

Conventionally, in a fuel cell system including a fuel cell stack using a polymer electrolyte membrane, a fuel chamber and an oxygen chamber exist on both sides of the electrolyte membrane, and the fuel gas in the fuel chamber passes through the fuel electrode or oxygen Oxidizing gas (mainly oxygen in the air) in the chamber is ionized through the oxygen electrode, and the ions are taken out through the electrolyte membrane to obtain electric power.
In such a fuel cell system, as shown in Patent Document 1, in a type in which outside air is introduced as an oxidizing gas, dust or the like contained in the outside air stays in the fuel cell or in the air duct. In order to suppress this, a filter is provided at the inlet of the air introduction fan.
JP-A-2005-44665

However, the conventional fuel cell system can prevent the entry of impurities larger than the pore diameter of the filter provided at the intake port of the air introduction fan, but prevents the entry of metal ions contained in dust and sea salt in the air. It cannot be prevented.
When such metal ions enter and stay in the fuel cell, they are combined with the polymer electrolyte membrane and the ion exchange resin constituting the electrode to lower the ionic conductivity and reduce the power generation performance of the fuel cell itself. There was a problem.
In order to solve this problem, it is conceivable to periodically clean the ion exchange resin to remove impurities, but the apparatus becomes large and is not practical.

  Accordingly, an object of the present invention has been made in view of the above-described facts, and it is an object of the present invention to provide a fuel cell system in which impurity metal ions are prevented from entering the fuel cell through outside air.

The present invention for solving the above problems has the following configuration.
(1) a fuel cell having a fuel electrode on one side of the electrolyte layer and an oxygen electrode on the other side;
An oxidizing gas supply means for supplying an oxidizing gas to the oxygen electrode;
Liquid contact means for bringing a liquid into contact with the oxidizing gas supplied to the fuel cell;
A water repellent layer formed on the surface of the oxidation electrode,
The water repellent layer is formed with a plurality of pores through which the oxidizing gas passes but not through the liquid.

  (2) The fuel cell system according to (1), wherein the liquid contact means is a spray device that injects the liquid into an oxidizing gas in the form of a mist.

  (3) A fuel cell system having an impurity recovery device that recovers impurities from the liquid in the exhaust gas of the fuel cell in addition to the configuration described in (1) or (2) above.

  According to the first aspect of the present invention, the oxidizing gas sent to the fuel cell by the supply means comes into contact with the liquid by the liquid contact means, so that impurities contained in the gas are trapped in the liquid. The liquid that trapped the impurities is repelled by the water-repellent layer of the oxidation electrode, and the pores do not pass the liquid. Therefore, the liquid that traps the impurities does not enter the oxidation electrode and goes out of the fuel cell. Discharged. This suppresses impurities from entering or remaining in the fuel cell, so that the performance of the fuel cell can be maintained for a longer period than before.

According to the second aspect of the present invention, by spraying the liquid in the oxidizing gas in the form of a mist, the chance of contact between the oxidizing gas and the liquid increases, and more impurities can be trapped in the liquid.
According to the invention described in claim 3, by separating the impurities from the recovered liquid, the recovered liquid can be reused as a spraying liquid.

Next, a preferred embodiment of the present invention will be described. This embodiment is a fuel cell system mounted on an electric vehicle. FIG. 1 is a block diagram showing a configuration of a fuel cell system 1 of the present invention. As shown in FIG. 1, the fuel cell system 1 is roughly configured by a fuel cell stack 100, a fuel supply system 10 including a hydrogen storage tank 11, an air supply system 12, a water supply system 50, and a load system 7. .
The configuration of the fuel cell stack 100 will be described with reference to FIGS. 2 and 3. 2 is a partial sectional side view of the fuel cell stack 10, and FIG. 3 is a partial sectional perspective view of the fuel cell stack. The fuel cell stack 100 includes a unit cell 2 as a fuel cell and a separator 3. The unit cell 2 has a configuration in which a solid polymer electrolyte membrane 23 is sandwiched between an oxygen electrode 21 that is an air electrode and a fuel electrode 22.
The separator 3 is inserted between the current collecting member 31 and the unit cell 2 for contacting the oxygen electrode 21 and the fuel electrode 22 and taking out current to the outside. It has the insertion member 33 overlapped with an edge part.

The current collecting member 31 is made of a material having conductivity and corrosion resistance. The current collecting member 31 is made of a material such as carbon or metal, for example. In the case of being made of metal, for example, a material such as stainless steel, nickel alloy, titanium alloy or the like that has been subjected to corrosion-resistant conductive treatment can be used. Here, the corrosion-resistant conductive treatment includes, for example, gold plating.
On the surface of the current collecting member 31 that is in contact with the fuel electrode 22, a plurality of convex portions 311 bulging continuously in a straight line are formed at equal intervals, and grooves 312 are formed between the convex portions 311. The That is, the convex part 311 and the groove | channel 312 are the shapes arrange | positioned alternately. The convex portion 311 is a contact portion 313 in which the flat portion of the peak that protrudes most is in contact with the fuel electrode 22, and the fuel electrode 22 can be energized through the contact portion 313. The groove 312 and the surface of the fuel electrode 22 form a fuel gas flow passage 315 through which hydrogen gas as fuel gas flows.

Grooves 314 and 314 are formed at both ends of the convex portion 311 in a direction orthogonal to the convex portion 311, and a fuel gas flow path 316 is formed by the groove 314 and the surface of the fuel electrode 22. The plurality of fuel gas flow paths 315 communicate with the fuel gas flow path 316 at both ends, and the plurality of fuel gas flow paths 315 and the pair of fuel gas flow paths 316 provide hydrogen to the fuel electrode 22. A fuel gas holding unit 30 for supplying gas is configured.
A fuel gas supply hole 318 and a fuel gas discharge hole 317 are formed in the fuel gas holding part 30, and hydrogen gas flows into the fuel gas holding part 30 from the fuel gas supply hole 318 and supplies hydrogen to the fuel electrode 22. However, it flows out from the fuel gas discharge hole 317. In this embodiment, the current collecting member 31 has a rectangular shape, and the fuel gas supply hole 318 and the fuel gas discharge hole 317 are positioned symmetrically with respect to the centroid in a plan view of the current collecting member 31 (in the diagonal direction). Are arranged respectively. FIG. 2 shows a fuel gas supply hole 318. As described above, the fuel gas holding unit 30 is formed between each separator 3 and the unit cell 2.

  The fuel gas supply hole 318 of each fuel gas holding unit 30 communicates with a fuel gas supply passage 319a formed in the stacking direction of the current collector 31 at one end in the fuel cell stack 100, The fuel gas discharge holes 317 communicate with the fuel gas discharge passages 319b formed in the stacking direction of the current collecting members 31 at the other end in the fuel cell stack 100, respectively. A fuel gas manifold 34 that distributes the fuel gas to the fuel gas holding portions 30 is configured by the fuel gas supply passage 319 a and the fuel gas supply holes 318. One of the pair of fuel gas discharge passages 319a and 319b is connected to the fuel gas supply channel 201B, and the other is connected to the gas circulation channel 202.

  On the surface of the current collecting member 31 that comes into contact with the oxygen electrode 21, a plurality of convex portions 321 bulging continuously in a straight line are formed at equal intervals, and grooves 322 are formed between the convex portions 321. The That is, the convex part 321 and the groove | channel 322 become the shape arrange | positioned alternately. The convex portion 321 is a contact portion 323 in which the flat portion of the peak that protrudes most is in contact with the oxygen electrode 21, and the oxygen electrode 21 can be energized through the contact portion 323. An air flow passage 325 through which air as an oxidizing gas flows is formed by the groove 322 and the surface of the oxygen electrode 21. The groove 322 reaches both ends of the current collecting member 31, and the upper and lower ends of the air flow passage 325 communicate with an opening that communicates with the outside of the fuel cell stack 100. One of the opening portions at both ends forms an air inflow portion 326 through which air flows, and the other opening forms an air outflow portion 327 through which air flows out. The air flowing in from the air inflow portion 326 is guided to the air outflow portion 327 while contacting the oxygen electrode 21 in the air flow passage 325 and supplying oxygen to the oxygen electrode. An air manifold 54 is provided on the vertically upper side of the fuel cell stack 100 configured as described above. The inlet 43 is constituted by the aggregate of the air inflow portions 326, and the outlet 44 is constituted by the air outflow portions 327.

  FIG. 4 is a cross-sectional view of the fuel cell schematically showing the configuration of the oxygen electrode 21 that is an oxidation electrode. The oxygen electrode 21 has layers in the order of the catalyst layer 21a, the diffusion layer 21b, and the water repellent layer 21c from the solid polymer electrolyte membrane 23 side, and the surface in contact with the oxygen gas is the same as the water repellent layer 21c. It has become. Although not shown, the water repellent layer 21c has a large number of pores. The diameter of the pores is smaller than the minimum diameter of water droplets that water forms in the air. Water droplets containing impurities such as metal ions are bounced off by the water repellent layer 21c and cannot easily enter the inside of the water repellent layer 21c, and the impurities enter the diffusion layer 21b, the catalyst layer 21a, and thus the electrolyte membrane 23. Is suppressed. In addition, oxygen is supplied through the pores. In this way, the impurities trapped in the water are suppressed from entering the unit cell 2.

  Next, the configuration of the fuel cell system shown in FIG. 1 will be described. The configuration of the fuel supply system 10 will be described. A hydrogen storage tank 11 that is a fuel gas cylinder is connected to a gas intake port of the fuel cell stack 100 via fuel gas supply channels 201A and 201B. The fuel gas supply passage 201A includes a hydrogen source valve 18, a primary pressure sensor S0, a regulator 19, a secondary pressure sensor S1, a first gas supply valve 20, a hydrogen pressure regulating valve 28, a second gas supply valve 29, and a tertiary pressure sensor. S2 is sequentially provided, and the fuel gas supply channel 201A is connected to one end of the fuel gas supply channel 201B. The other end of the fuel gas supply channel 201B is connected to the IN of the gas inlet 201B of the fuel cell stack 100. One end of a gas discharge channel 202 is connected to the gas discharge port of the fuel cell stack 100, and the other end is connected to the fuel gas supply channel 201B to constitute a fuel gas circulation channel. In the gas discharge channel 202, a trap 24, a circulation pump 25, and a circulation electromagnetic valve 26 are arranged in this order from the gas discharge port side of the fuel cell stack 100. A water level sensor S10 is attached to the trap 24, and one end of the gas outlet path 203 is connected to the trap 24. The other end of the gas outlet path 203 is connected to the air duct 124. An exhaust solenoid valve 27 is provided in the gas outlet passage 203.

Next, the air supply system 12 will be described. The air supply system 12 includes an air fan 122 that is an oxidizing gas supply means, an air introduction path 123, an air manifold 54, an air duct 124 that is an air discharge path, and the like. In the air introduction path 123, a filter 121, an air fan 122, and an air manifold 54 are provided in this order along the inflow direction.
In the air introduction path 123, a nozzle 55 that injects water toward the air introduction path 123 is provided at a position immediately before the air manifold 54. The nozzle 55 which is a spray device as the liquid contact means may be provided in the air manifold 54. The nozzle 55 injects water made into mist. The sprayed mist water is sprayed so as to fill the entire cross section of the air introduction path 123. Moreover, water is injected so that it may be as fine as possible. By configuring in this way, the frequency of contact between the oxidizing gas air and water increases, and the amount of impurities trapped in water (taken into water) by the water contact increases. Such trapping of impurities in water tends to occur easily in a state where the gas is stirred. For example, a nozzle 55 is provided immediately before the inlet of the air fan 122, and a mist-like state is formed together with air. The water may be stirred in the air fan 122 and guided to the fuel cell stack 100.

The air manifold 54 divides and flows the air into the inlet 43 of the fuel cell stack 100.
An exhaust manifold 53A1 is connected to the air outlet of the fuel cell stack 100, and the air discharged from the outlet 44 is merged by the exhaust manifold 53A1 and sent to the air duct 124. Further, the exhaust manifold 53A1 collects water dripping from the outlet 44.

The air duct 124 guides the air flowing out from the outlet 44 to the outside via the condenser 51. A condenser 51 to which a fan is attached is provided at the end of the air duct 124, and a filter 125 is subsequently connected. The condenser 51 extracts moisture from the air. Further, the water evaporated in the fuel cell stack 100 in the water supplied from the nozzle 55 is also collected here. The water collected by the exhaust manifold 53A1 and the water collected by the condenser 51 are collected in the water tank 531 as will be described later. The air duct 124 is provided with an exhaust temperature sensor S9, and the temperature in the fuel cell stack 100 is indirectly detected.

  Next, the water supply system will be described. The water supply system 50 includes a water tank 531 serving as a water storage means, a water conduit 57 that guides water collected by the exhaust manifold 53A1 and the condenser 51 to the water tank 531, and a water supply passage 56 that guides water from the water tank 531 to the nozzle 55. And an impurity recovery device for removing impurities from the recovered water. A collection pump 62 is provided in the water conduit 57. The recovery pump 62 sends the water extracted from the exhaust gas by the condenser 51 to the water tank 531. In the water supply channel 56, a filter 64 as an impurity recovery device and a supply pump 61 as a water supply means are provided in this order. The water tank 531 is provided with a water level sensor S5 and a tank water level sensor S7 which is a storage amount detection means.

  The filter 64 is made of a material that separates impurities by an adsorption action such as activated carbon, a material that filters impurities like a hollow fiber membrane, or an ion exchange resin. The impurity recovery apparatus having these components may be accommodated in the water tank 531, for example. The water from which impurities have been removed by the impurity recovery device is again sprayed in a mist form from the nozzle 55 to trap the impurities from the air.

  A load system 7 is connected to the fuel cell stack 100, and electric power output from the fuel cell stack 100 is supplied to the load system 7. The electrode of the fuel cell stack 100 is connected to an inverter 73 via a wiring 71, and electric power is supplied from the inverter 73 to a load such as a motor. An auxiliary power source 76 is connected to the inverter 73 via a bidirectional converter 75 that is a switching circuit. The auxiliary power source 76 can be constituted by, for example, a battery or a capacitor. The load system 7 is provided with a voltage sensor S4 for detecting the output voltage of the fuel cell stack 100 and a current sensor S3 for detecting the output current.

As shown in FIG. 4, in the above configuration, when the air that is the oxidizing gas is sucked by the air fan 122, relatively large impurities d (large dust or the like) are separated by the filter 121, and further the fuel. It is sent to the battery stack 100. Mist-like water is sprayed from the nozzle 55 to the guided air, and impurities such as metal ions are trapped in the water droplets w.
The water droplet dw trapping the impurity d that has passed through the filter 121 is rebounded together with the impurity d by the water repellent layer 21c of the oxygen electrode 21, and the entry of the impurity d into the electrode is suppressed. The water dw repelled by the water repellent layer 21c is discharged to the outside of the fuel cell stack 100 together with air. On the other hand, oxygen in the air passes through the water repellent layer 21 c through the pores of the water repellent layer 21 c and reacts with the electrolyte membrane 23.

In addition to the configuration described above, the diameter of the pores formed in the water-repellent layer 21c is set to a predetermined size so that the diameter of the water droplets ejected from the nose 55 is larger than the diameter of the pores. The nozzle structure may be adjusted.
In addition, as a liquid contact means, it is good also as a structure which bubbles air in the water tank filled with water other than the spraying apparatus (nozzle 55). In this case, in order to increase the contact frequency between water and air, it is preferable to make air fine.
Moreover, although the said structure mentioned the structure in an oxygen electrode, also in a hydrogen electrode, it is good also as a structure which provided the spraying device as a contact means to provide a water-repellent layer on the surface and to contact water in a fuel gas introduction path. Good. By adopting such a configuration, it is possible to suppress impurities contained in the fuel gas from entering and staying in the fuel cell.

Furthermore, in the present embodiment, the case where water is used as a liquid for collecting metal ions has been described. However, the liquid may be one obtained by adding an additive such as a surfactant in addition to pure water or tap water. Or alcohol.
Although the present embodiment is applied to a fuel cell system including a fuel cell stack in which a large number of fuel cells are stacked, it may be applied to a fuel cell assembly in which fuel cells are connected in a plane direction. Needless to say.

1 is a block diagram showing a fuel cell system 1 of the present invention. It is a partial cross section side view of a fuel cell stack. It is a partial cross section perspective view of a fuel cell stack. It is a model diagram which shows the structure and air supply system of a fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 100 Fuel cell stack 122 Air fan 123 Air introduction path 21 Oxygen electrode 21a Catalyst layer 21b Diffusion layer 21c Water repellent layer 531 Water tank 53A1 Exhaust manifold 54 Air manifold 55 Nozzle 61 Supply pump

Claims (3)

A fuel cell having a fuel electrode on one side of the electrolyte layer and an oxygen electrode on the other side;
An oxidizing gas supply means for supplying an oxidizing gas to the oxygen electrode;
Liquid contact means for bringing a liquid into contact with the oxidizing gas supplied to the fuel cell;
A water repellent layer formed on the surface of the oxidation electrode,
The water repellent layer is formed with a plurality of pores through which the oxidizing gas passes but not through the liquid.   2. The fuel cell system according to claim 1, wherein the liquid contact unit is a spraying device that sprays the liquid into an oxidizing gas in a mist form. 3.   A fuel cell system having an impurity recovery device that recovers impurities from a liquid in exhaust gas of the fuel cell in addition to the configuration according to claim 1 or 2.

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