JP5063619B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  2. Description of the Related Art A fuel cell, particularly a polymer electrolyte fuel cell, includes a membrane electrode assembly (hereinafter referred to as MEA) formed by joining an anode electrode to one surface of an electrolyte membrane and a cathode electrode to the other surface, and a reaction gas (fuel gas And a plate that circulates an oxidant) and a plate that circulates a heat medium such as cooling water, and a plurality of these are stacked and integrated to form a battery stack. Then, a fuel gas is supplied to the anode electrode side of the membrane electrode assembly and an oxidant such as air is supplied to the cathode electrode side to generate an electrochemical reaction through the electrolyte membrane to generate DC power. It is.

  In the polymer electrolyte fuel cell, the electrolyte membrane is required to be moistened in order to sufficiently exhibit proton permeability during power generation. For this reason, conventionally, the reaction gas is humidified with a humidifier and then supplied to the fuel cell, and the electrolyte membrane is wetted with water vapor contained in the reaction gas to maintain the wet state.

  However, when humidified reaction gas is supplied to the plate of the battery stack, it is cooled near the gas inlet of the plate and the dew point of the reaction gas decreases, and the water vapor in the reaction gas condenses and adheres in the gas flow path. Arise. If condensed water adheres to the gas flow path, the flow of the reaction gas is hindered, resulting in non-uniform gas distribution to multiple flow paths, and insufficient gas supply to the electrodes, leading to a decrease in power generation performance. It will be. As a means to prevent such deterioration in power generation performance due to condensed water, for example, a water absorbing material is provided in the gas channel, or unhumidified gas is supplied from an intermediate portion of the gas channel to remove the condensed water. Prior arts such as this are disclosed (for example, Patent Document 1).

  In the solid polymer fuel cell, the operation temperature is set to about 80 ° C. in order to continue normal operation. However, since the electrochemical reaction is an exothermic reaction, the temperature of the battery stack is raised. For this reason, conventionally, a heat medium such as cooling water is supplied to the plate of the battery stack to cool it, and the battery stack is maintained at an appropriate operating temperature. As a cooling water supply means as a heat medium, a cooling water circulation path in which a fuel cell and a water tank are connected to each other is configured and supplied from the water tank to the fuel cell via a pump (for example, Patent Document 2).

JP-A-6-89730 JP-A-10-55812

  According to the conventional condensate removing means, it is necessary to attach a water absorbing material in relation to the gas flow path, or to provide an unhumidified gas supply hole in the middle part of the gas flow path. There is a problem that it takes time to drill holes. Further, according to the conventional cooling water supply means, the structure is simple, but there is a problem that the heat of the cooling water discharged from the fuel cell at a high temperature (78 to 80 ° C.) cannot be effectively used.

  The present invention has been made to solve the above-described problems in the prior art, and is capable of taking measures against condensed water without performing any processing on the gas flow path, and can effectively use the heat of the heat medium discharged from the fuel cell. An object of the present invention is to provide a fuel cell and a fuel cell system.

As means for solving the above-mentioned object, claim 1 of the present invention is a bipolar plate having a fuel flow path on one side and an oxidant flow path on the other side, and a fuel flow path on one side. The anode cooling is provided with a heat medium flow path on the other surface, the fuel flow path side surface is opposed to the oxidant flow path side surface of the bipolar plate , and the membrane electrode assembly is sandwiched therebetween. A plate, and a cathode cooling plate that is provided with an oxidant flow path on one side and is positioned with the other flat side facing the surface on the heat medium flow path side of the anode cooling plate. In contrast, the surface on the fuel flow path side of the bipolar plate having the same configuration as that of the bipolar plate is opposed to the surface on the oxidant flow path side, and the same as the membrane electrode assembly in between. The bipolar plate is positioned by sandwiching the membrane electrode assembly of the construction, the fuel cell cell stack is constituted by stacking a plurality of combination thus each plate,
An air humidifier connected to the fuel cell and humidifying air as an oxidant supplied to the fuel cell and / or a fuel humidifier humidifying the fuel supplied to the fuel cell;
A total heat exchanger connected to the air humidifier for total heat exchange between the air discharged from the fuel cell and the reaction gas before being supplied to the air humidifier;
A heat medium circulation path connecting the fuel cell and the air humidifier and / or the fuel humidifier;
During operation of the fuel cell, in at least one reaction gas inlet region of the reaction gas (fuel gas and oxidant), the dew point of the reaction gas is set below the temperature of the heat medium, and The gist of the fuel cell system is characterized in that in the reaction gas outlet region, the dew point of the reaction gas is set to be equal to or higher than the temperature of the heat medium.

As described above, according to the first aspect of the present invention, the bipolar plate having the fuel flow path on one side and the oxidant flow path on the other side, the fuel flow path on the one side, and the other side. A battery stack is stacked by combining an anode cooling plate with a heat medium flow path on the surface, an oxidant flow path on one surface, and a flat cathode cooling plate on the other surface via a membrane electrode assembly. In the fuel cell of the integrated configuration, the reaction gas dew point is set to be equal to or lower than the temperature of the heat medium in the reaction gas inlet region, and the reaction gas dew point is set to be equal to or higher than the temperature of the heat medium in the reaction gas outlet region. In the reaction gas inlet region, condensation of water vapor in the reaction gas can be prevented, which makes it possible to take measures against condensed water without applying any processing to the reaction gas flow path. Steam The condensation forcing can be carried out, by leveling the pressure loss can be made uniform gas distribution, thereby to improve the power generation performance of the well in to the fuel cell to flow of the reaction gas.
In addition, since an air humidifier and / or a fuel humidifier is connected to the fuel cell, and the heat medium discharged from the fuel cell is introduced into these humidifiers to exchange heat, the heat of the heat medium discharged from the fuel cell Can be used effectively.

Further, a total heat exchanger is connected to the fuel cell so that total heat is exchanged between the air discharged from the fuel cell and the reaction gas before being supplied to the air humidifier. The heat of the reaction oxidant (air) can be used effectively.

It is a schematic sectional drawing which shows a one part component of the battery stack in the fuel cell system which concerns on this invention. The bipolar plate integrated in the battery stack is shown, (a) is a plan view on the fuel flow path side, and (b) is a plan view on the oxidant flow path side. FIG. 2 shows an anode cooling plate incorporated in a battery stack, where (a) is a plan view on the fuel flow path side, and (b) is a plan view on the water flow path side. 2A and 2B show a cathode cooling plate incorporated in a battery stack, in which FIG. 3A is a plan view on the side of an oxidant flow path, and FIG. 1 is a configuration diagram showing an embodiment of a fuel cell system according to the present invention.

  Next, an embodiment of a fuel cell system according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing some components of a fuel cell stack. In FIG. 1, reference numeral 1 denotes a bipolar plate, which has a groove-shaped fuel flow path 1a arranged in a straight line on one surface, and a groove-shaped oxidant flow path 1b arranged in a straight line on the other surface. Has been.

  FIG. 2 (a) is a plan view of the bipolar plate 1 on the fuel flow path side. A concave inlet header portion 1c communicating with each fuel flow path 1a is provided at the inlet of the fuel flow path 1a. The part 1c is connected to the fuel supply manifold 1d. The outlet of the fuel channel 1a is provided with a concave outlet header portion 1e communicating with each fuel channel 1a. The outlet header portion 1e is connected to the fuel discharge manifold 1f. Furthermore, a nozzle-shaped flow path resistance generating portion 1g is attached to the inlet region of the fuel flow path 1a to reduce the cross-sectional area of each fuel flow path 1a. As a result, the fuel gas flows into the inlet header portion 1c from the fuel supply manifold 1d, is accelerated by the flow passage resistance generating portion 1g, flows into each fuel flow passage 1a, and flows from the outlet of the fuel flow passage 1a to the outlet header portion 1e. It is discharged and merged, and discharged to the fuel discharge manifold 1f.

  FIG. 2B is a plan view of the bipolar plate 1 on the side of the oxidant flow path, and the inlet of the oxidant flow path 1b is provided with a recessed inlet header portion 1h communicating with each oxidant flow path 1b. The outlet of the oxidant channel 1b is provided with a concave outlet header portion 1i communicating with each oxidant channel 1b. A nozzle-like flow resistance generating portion 1j is attached to the inlet region of the oxidant flow path 1b to reduce the cross-sectional area of each oxidant flow path 1b. As a result, air as an oxidant flows into the inlet header portion 1h, is accelerated by the flow path resistance generating portion 1j, flows into each oxidant flow channel 1b, and is discharged from the outlet of the oxidant flow channel 1b to the outlet header portion 1i. Exhausted to the outside. 2A and 2B, 1k is a water supply manifold, and 1m is a water discharge manifold.

  In FIG. 1, reference numeral 2 denotes an anode cooling plate, which has a groove-shaped fuel flow path 2a arranged in a straight line on one surface, and a groove-shaped heat medium flow path 2b arranged in a straight line on the other surface. It is installed.

  FIG. 3A is a plan view of the anode cooling plate 2 on the fuel flow path side, and a concave inlet header portion 2c communicating with each fuel flow path 2a is provided at the inlet of the fuel flow path 2a. The header portion 2c is connected to the fuel supply manifold 2d. The outlet of the fuel channel 2a is provided with a concave outlet header portion 2e communicating with each fuel channel 2a. The outlet header portion 2e is connected to the fuel discharge manifold 2f. Further, a nozzle-like flow resistance generating portion 2g is attached to the inlet region of the fuel flow path 2a to reduce the cross-sectional area of each fuel flow path 2a. As a result, the fuel gas flows into the inlet header 2c from the fuel supply manifold 2d, is accelerated by the flow path resistance generating section 2g and flows into each fuel flow path 2a, and from the outlet of the fuel flow path 2a to the outlet header section 2e. It is discharged and merged, and discharged to the fuel discharge manifold 2f.

  FIG. 3B is a plan view of the anode cooling plate 2 on the heat medium flow path side, and a concave inlet header portion 2h communicating with each heat medium flow path 2b is provided at the inlet of the heat medium flow path 2b. The inlet header portion 2h is connected to the heat medium supply manifold 2k. The outlet of the heat medium passage 2b is provided with a concave outlet header portion 2i communicating with each heat medium passage 2b. The outlet header portion 2i is connected to the heat medium discharge manifold 2m. Thus, water as the heat medium flows from the heat medium supply manifold 2k into the inlet header portion 2h, flows into each heat medium flow channel 2b, and is discharged from the outlet of the heat medium flow channel 2b to the outlet header portion 2i to join. And discharged to the heat medium discharge manifold 2m.

  The anode cooling plate 2 configured in this way is positioned with the surface on the fuel flow path 2a side facing the surface on the oxidant flow path 1b side of the bipolar plate 1 with the MEA interposed therebetween. A gasket G is disposed so as to surround the outer periphery of the MEA.

  In FIG. 1, reference numeral 3 denotes a cathode cooling plate, and a groove-like oxidant passage 3b is arranged in a straight line on one surface.

  FIG. 4A is a plan view of the cathode cooling plate 3 on the side of the oxidant flow path 3b. At the inlet of the oxidant flow path 3b, a concave inlet header portion 3h communicating with each oxidant flow path 3b is provided. Provided at the outlet of the oxidant flow path 3b is a recessed outlet header portion 3i communicating with each oxidant flow path 3b. A nozzle-like flow resistance generating portion 3g is attached to the inlet region of the oxidant flow path 3b to reduce the cross-sectional area of each oxidant flow path 3b. As a result, air as an oxidant flows into the inlet header portion 3h, is accelerated by the flow path resistance generating portion 3g, flows into each oxidant flow channel 3b, and is discharged from the outlet of the oxidant flow channel 3b to the outlet header portion 3i. Exhausted to the outside. FIG. 4B is a plan view of the cathode cooling plate 3 on the side where the oxidant flow path 3b is not formed. 4A and 4B, 3d is a fuel supply manifold, 3f is a fuel discharge manifold, 3k is a heat medium supply manifold, and 3m is a heat medium discharge manifold.

  The cathode cooling plate 3 is positioned such that the surface side where the oxidant flow path 3b is not formed faces the surface of the anode cooling plate 2 on the heat medium flow path 2b side. Further, the surface on the fuel flow path 1a side of the bipolar plate 1 having the same configuration as that of the bipolar plate 1 is opposed to the surface on the oxidant flow path 3b side with respect to the cathode cooling plate 3, and the MEA is sandwiched therebetween. The bipolar plate 1 is positioned. Also in this case, the gasket G is attached so as to surround the outer peripheral portion of the MEA.

  A battery stack is configured by combining a plurality of plates in such an order, stacking a plurality of plates, disposing end plates (not shown) at both ends, and fastening and integrating them with a rod or the like. The fuel supply manifold, the fuel discharge manifold, the heat medium supply manifold, and the heat medium discharge manifold in each of the plates constitute a communication hole that communicates in the stacking direction of the battery stack.

  FIG. 5 is a configuration diagram showing an embodiment of the fuel cell system according to the present invention. An air humidifier 5 is connected to the heat medium outlet 4 a of the fuel cell 4, and the fuel humidifier 6 is connected to the air humidifier 5. The heat exchanger 7 is connected to the fuel humidifier 6, and the heat medium supply port 4 b of the fuel cell 4 is connected to the heat exchanger 7, thereby forming a water circulation path 8 of water as a heat medium. .

  Also, a total heat exchanger 9 is connected to the oxidant discharge port 4 c of the fuel cell 4, the air humidifier 5 is connected to the total heat exchanger 9, and the oxidant of the fuel cell 4 is supplied to the air humidifier 5. By connecting the opening 4d, an air supply path 10 for air as an oxidizing agent is formed. The oxidant supply port 4d is provided in an oxidant supply external manifold (not shown) attached to the upper part of the battery stack, and air as an oxidant is distributed and supplied from the external manifold to the oxidant flow path of each plate. The oxidant discharge port 4c is provided in an external manifold (not shown) for oxidant discharge attached to the lower part of the battery stack, and oxidant as the oxidant discharged from the oxidant flow path of each plate is joined. It is configured to discharge from the discharge port 4c.

  Further, a fuel reformer 11 is connected to the fuel humidifier 6, and a hydrogen-based reformed gas is generated from the raw fuel such as city gas by the fuel reformer 11, and this reformed gas is used as the fuel humidifier 6. Then, the fuel cell 4 is supplied to the fuel supply port 4e. Water is stored inside the fuel humidifier 6, and the reformed gas is humidified by bubbling the reformed gas into the water. The humidified fuel gas supplied to the fuel supply port 4e of the fuel cell 4 flows through the communication hole formed in the stacking direction in the cell stack by the fuel supply manifold, and is distributed and supplied to the fuel inlet header portion of each plate. The fuel gas that flows along each fuel flow path and is discharged from the fuel flow path (fuel gas that has not reacted) joins at the outlet header, and passes through the communication holes formed in the stacking direction in the cell stack. It flows and is discharged outside. The unreacted fuel gas discharged to the outside is generally sent to the reformer burner of the fuel reformer from the fuel discharge port 4f and burned.

  The air taken from the outside as the oxidant is supplied to the oxidant supply port 4d of the fuel cell (specifically, the oxidant supply port of the external manifold) after exchanging heat and moisture in the total heat exchanger 9. Water is stored inside the air humidifier 5, and the air is humidified by bubbling air into the water. The humidified air supplied to the oxidant supply port 4d of the fuel cell 4 is distributed and supplied to the inlet header portion of each plate, circulates along each oxidant flow path, and is discharged from the oxidant flow path. The air after the reaction) joins at the outlet header and is discharged from the oxidant discharge port 4c of the fuel cell 4 (specifically, the oxidant discharge port of the external manifold). The discharged unreacted air is exhausted to the outside through the total heat exchanger 7.

  In this way, the fuel gas and the oxidant are supplied to the fuel cell 4 and an electrochemical reaction occurs through the MEA electrolyte membrane to generate DC power. On the other hand, water in the water circulation path 8 is supplied to the heat medium supply port 4b of the fuel cell 4 and flows through the communication holes formed in the stacking direction in the cell stack to the inlet header portion of each anode cooling plate 2. The water that is distributed and distributed along each heat medium flow path and discharged from the heat medium flow path is merged at the outlet header portion, and flows through the communication holes formed in the stacking direction in the battery stack. It is discharged from the discharge port 4a.

  The anode cooling plate 2 can cool the anode cooling plate 2 because the heat medium flow path 2b is provided back-to-back with the fuel flow path 2a as described above. Further, since the heat medium flow path 2b of the anode cooling plate 2 is in contact with the surface of the cathode cooling plate 3 where the oxidant flow path is not formed as described above, the cathode cooling plate 3 is also cooled. Can do. As a result, the fuel cell 4 during power generation is cooled and maintained at a normal operating temperature (about 80 ° C.).

  By the way, the temperature of water as a heat medium discharged from the fuel cell 4 is raised to about 78 ° C. When this high temperature water is introduced into the air humidifier 5, the temperature of the internal water can be increased. . The water temperature that has passed through the air humidifier 5 drops to about 76 ° C., and this medium temperature water is introduced into the fuel humidifier 6. As described above, the high temperature (100 to 150 ° C.) reformed gas from the fuel reformer 11 is introduced into the fuel humidifier 6 and bubbled, so that the heat of evaporation is lost, but the internal water is 75 to 76. Maintained at ℃.

  The high-temperature water that has passed through the fuel humidifier 6 is introduced into the heat exchanger 7, where heat is exchanged with water from a hot water storage tank (not shown), and this water becomes hot water and is returned to the hot water storage tank. It is. The water temperature that has passed through the heat exchanger 7 falls to about 74 ° C., and this low-temperature water is supplied to the heat medium supply port 4 b of the fuel cell 4. Therefore, by circulating the water discharged from the fuel cell 4 along the water circulation path 8, the heat of the water as the heat medium can be effectively used.

  In the present invention, in the reaction gas inlet region, the dew point of the reaction gas is set below the temperature of the heat medium, and in the reaction gas outlet region, the dew point of the reaction gas is set above the temperature of the heat medium.

  If the dew point of the reaction gas is set lower than the temperature of the heat medium in the reaction gas inlet region, the reaction gas is heated by the heat medium in the inlet region. Condensation can be prevented. Accordingly, the condensed water does not adhere to the flow path in the reaction gas inlet region, and the reaction gas starts to flow smoothly.

  If the dew point of the reaction gas is set to be higher than the temperature of the heat medium in the reaction gas outlet region, the reaction gas may be cooled by the heat medium in the outlet region, and water vapor in the reaction gas may be condensed. However, if condensed water adheres to the heat medium flow path in the outlet area, pressure is uniformly applied to each heat medium flow path, making it easy to blow off water droplets. can do. If condensate adheres to some of the flow paths as in the past, the gas distribution in each flow path becomes uneven and power generation performance becomes unstable, and the reaction gas escapes to other flow paths. It becomes difficult to blow water drops. In the present invention, by forcibly condensing in each flow path in the reaction gas outlet region as described above, pressure loss can be leveled and gas distribution can be made uniform.

  In the above embodiment, the fuel gas and the oxidant are in parallel flow and flow from the top to the bottom in the direction of gravity, and the heat medium is counterflow with the reaction gas, but the heat medium should be performed in parallel with the reaction gas. Is also possible.

DESCRIPTION OF SYMBOLS 1 ... Bipolar plate 1a ... Fuel flow path 1b ... Oxidant flow path 2 ... Anode cooling plate 2a ... Fuel flow path 2b ... Heat medium flow path 3 ... Cathode cooling plate 3b ... Oxidant flow path 4 ... Fuel cell 5 ... Air humidification 6 ... Fuel humidifier 7 ... Heat exchanger 8 ... Water circulation path 9 ... Total heat exchanger 10 ... Air supply path 11 ... Fuel reformer

Claims (1)

A bipolar plate having a fuel channel on one side and an oxidant channel on the other side, a fuel channel on one side, and a heat medium channel on the other side. Is opposed to the surface of the bipolar plate on the side of the oxidant flow path, and is opposed to the anode cooling plate positioned with the membrane electrode assembly interposed therebetween, and the oxidant flow path is provided on one side, and the other plane side A cathode cooling plate positioned opposite the surface of the anode cooling plate on the heat medium flow path side, and the bipolar plate having the same configuration as the bipolar plate on the surface of the oxidant flow path with respect to the cathode cooling plate The surface of the fuel flow path side of the plate is opposed to each other, and a membrane electrode assembly having the same configuration as the membrane electrode assembly is sandwiched therebetween, so that the bipolar plate is positioned. Lighted, and thus the fuel cell cell stack by stacking a plurality of a combination of each plate is formed,
An air humidifier connected to the fuel cell and humidifying air as an oxidant supplied to the fuel cell and / or a fuel humidifier humidifying the fuel supplied to the fuel cell, and connected to the air humidifier A total heat exchanger for exchanging total heat between the air discharged from the fuel cell and the reaction gas before being supplied to the air humidifier, the fuel cell, the air humidifier and / or the fuel A heat medium circulation path connected to a humidifier,
During operation of the fuel cell, in at least one reaction gas inlet region of the reaction gas (fuel gas and oxidant), the dew point of the reaction gas is set below the temperature of the heat medium, and In the reaction gas outlet region, the dew point of the reaction gas is set to be equal to or higher than the temperature of the heat medium.

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