JP2011222315A - Fuel cell system and membrane humidifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system implementing heating and humidification of oxygen-containing gas supplied to a fuel cell stack with a simple structure.SOLUTION: In the fuel cell system, oxygen-containing gas and cooling water passes a membrane humidifier 5 in the form of parallel flows, and heat and moisture of the cooling water are thereby moved to the hydrogen-containing gas through the membrane humidifier 5. The temperature and humidity of the oxygen-containing gas rise by receiving heat and moisture. The cooling water and the oxygen-containing gas can have a temperature almost equal to each other and a dew point temperature can be made almost same as the temperature in the oxygen-containing gas by providing the membrane humidifier 5 in this manner and letting the oxygen-containing gas and the cooling water pass in the form of the parallel flows, and the fuel cell system thereby can have a simple structure requiring no complicated devices such as a heat exchanger and a humidifier.

Description

  The present invention relates to a fuel cell system and a membrane humidifier.

  In the conventional fuel cell system, a hydrogen-containing gas containing hydrogen and an oxygen-containing gas are supplied to the fuel cell stack, and power is generated by the fuel cell stack. In this battery stack, a plurality of cells including an anode, an electrolyte, and a cathode are stacked. A hydrogen-containing gas is supplied to the anode, and an oxygen-containing gas is supplied to the cathode. The fuel cell stack is supplied with cooling water for cooling the anode and the cathode.

  In such a fuel cell system, for example, an oxygen-containing gas humidified to a humidity of 90% or more is supplied to the cathode of the fuel cell stack. Also, from the viewpoint of durability and stability of the fuel cell stack, it is necessary to prevent electrode drying and condensation in the fuel cell stack. In order to prevent this drying and condensation, it is necessary to keep the temperature difference between the oxygen-containing gas supplied to the fuel cell stack and the cooling water small, for example, a temperature difference of plus or minus 3 ° C. or less. For this reason, for example, in Patent Document 1, a humidifier for humidifying an oxygen-containing gas and a temperature difference between the cooling water and the oxygen-containing gas (temperature difference between the cooling water and the oxygen-containing gas at the entrance of the fuel cell stack). Describes a fuel cell system including a heat exchange device for keeping the temperature within a predetermined range.

JP 2005-011563 A

  However, in the conventional fuel cell system, it is necessary to provide a humidifier for humidifying the oxygen-containing gas and a heat exchange device for keeping the temperature difference between the cooling water and the oxygen-containing gas within a predetermined range. There is a problem that the device configuration of the battery system and the control of these devices are complicated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel cell system and a membrane humidifier that can realize heating and humidification of an oxygen-containing gas supplied to a fuel cell stack with a simple configuration.

  The present invention relates to a fuel cell stack having an anode into which a hydrogen-containing gas containing hydrogen is introduced, a cathode into which an oxygen-containing gas is introduced, an oxygen-containing gas introduction line for supplying the oxygen-containing gas to the cathode side, and a fuel A cooling water supply line that supplies cooling water for cooling the battery stack to the fuel cell stack, a cooling water supply line, and an oxygen-containing gas introduction line, and a membrane that allows the cooling water and the oxygen-containing gas to pass through in parallel flow And a humidifier.

  In the present invention, the oxygen-containing gas and the cooling water pass through the membrane humidifier in parallel flow, whereby the heat and moisture of the cooling water move to the oxygen-containing gas side via the membrane humidifier. The oxygen-containing gas increases in temperature and humidity by receiving heat and moisture. By providing the membrane humidifier and passing the oxygen-containing gas and the cooling water in parallel flow, the cooling water and the oxygen-containing gas are at the same temperature at the outlet side of the membrane humidifier and the dew point at the oxygen-containing gas. Since the temperature can be approximately the same as the temperature, a simple configuration that does not require complicated devices such as a heat exchange device and a humidifying device can be achieved. In addition, heat and moisture are exchanged using cooling water with a large heat capacity, and the oxygen-containing gas supplied to the cathode during startup is efficiently added to a temperature equivalent to that of cooling water while suppressing a decrease in cooling water temperature. The temperature and humidity can be increased, and the cathode electrode is not dried in the fuel cell stack, so that the durability of the fuel cell stack can be improved.

  The present invention also includes a fuel cell stack having an anode into which a hydrogen-containing gas containing hydrogen is introduced, a cathode into which an oxygen-containing gas is introduced, and an oxygen-containing gas introduction line that supplies the oxygen-containing gas to the cathode side. The cooling water supply line for supplying the cooling water for cooling the fuel cell stack to the fuel cell stack, the cooling water supply line, and the oxygen-containing gas introduction line, and the cooling water and the oxygen-containing gas are passed in a counter flow. A film humidifier.

  In this invention, when the cooling water passes through the membrane humidifier, the temperature difference with the oxygen-containing gas increases toward the outlet side of the membrane humidifier, thereby increasing the heat exchange efficiency and passing in parallel flow. Compared with the case where the temperature of the cooling water at the outlet of the membrane humidifier is compared with the temperature of the oxygen-containing gas at the outlet of the membrane humidifier, the temperature of the oxygen-containing gas and the dew point temperature are approximately the same as the cooling water temperature or It becomes possible to make it higher. With this configuration, it is possible to efficiently heat the oxygen-containing gas while expecting a temperature decrease such as heat radiation from the pipe until the oxygen-containing gas is supplied to the fuel cell stack. In addition, this configuration may be applied when the movement of heat and moisture in the film humidifier is small.

  Moreover, it is preferable to further include a temperature raising means for raising the temperature of the cooling water on the cooling water supply line and on the upstream side of the membrane humidifier.

  In this case, the temperature of the cooling water is raised by the temperature raising means, and the oxygen-containing gas can be efficiently heated in the membrane humidifier.

  Further, it is preferable that the temperature raising means raises the temperature of the cooling water in advance before the oxygen-containing gas is supplied to the cathode.

  In this case, since the cooling water has been heated in advance, the oxygen-containing gas can be quickly heated and humidified by the cooling water that has been heated in advance at the start of power generation of the fuel cell stack. Efficiency can be improved.

  The present invention also includes a fuel cell stack having an anode into which a hydrogen-containing gas containing hydrogen is introduced, a cathode into which an oxygen-containing gas is introduced, and an oxygen-containing gas introduction line that supplies the oxygen-containing gas to the cathode side. The cooling water discharge line for discharging the cooling water supplied to cool the fuel cell stack from the fuel cell stack, the cooling water discharge line and the oxygen-containing gas introduction line, and the cooling water and the oxygen-containing gas are parallel to each other. A membrane humidifier that is passed in a flow or counterflow.

  In the present invention, the temperature and humidity of the oxygen-containing gas can be increased in the membrane humidifier using the cooling water having a temperature higher than that of the cooling water discharged from the fuel cell stack and supplied to the fuel cell stack. it can. Thereby, it is possible to efficiently heat the oxygen-containing gas while expecting a temperature drop such as heat radiation from the pipe until the oxygen-containing gas is supplied to the fuel cell stack. In addition, this configuration may be applied when the movement of heat and moisture in the film humidifier is small.

  The present invention includes a first flow path and a second flow path, and heat and moisture between a first fluid flowing through the first flow path and a second fluid flowing through the second flow path. The membrane humidifier performs the exchange of the above, wherein the first fluid is a liquid and the second fluid is a gas.

  In the present invention, heat and moisture are exchanged between the liquid and gas passing through the membrane humidifier. In this way, heat exchange and moisture exchange can be performed by the membrane humidifier, so the configuration is simplified compared to the case where heat exchange and moisture exchange are performed by separate devices. can do.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which implement | achieves heating and humidification of the oxygen containing gas supplied to a fuel cell stack with a simple structure, and a membrane humidifier can be provided.

1 is a schematic configuration diagram of an embodiment of a fuel cell system according to the present invention.

  Hereinafter, preferred embodiments of a fuel cell system according to the present invention will be described in detail with reference to the drawings.

  First, the overall configuration of the fuel cell system according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of a fuel cell system 1. As shown in FIG. 1, a fuel cell system 1 includes a reformer 2 that generates a reformed gas as a hydrogen-containing gas from a gas fuel such as city gas, LPG, or a liquid fuel such as kerosene. And a fuel cell stack 3 that generates power using the reformed gas generated by the quality device 2. The fuel cell system 1 is used as, for example, a household power supply source, and kerosene is used as a liquid fuel from the viewpoint that it can be easily obtained and stored independently. Yes.

  The reformer 2 is for reforming liquid fuel to generate a reformed gas, and has a reformer 21 and a burner 22. The reformer 21 performs a steam reforming reaction between liquid fuel and steam with a reforming catalyst to generate a reformed gas containing hydrogen. The burner 22 supplies the amount of heat necessary for the steam reforming reaction by heating the reforming catalyst of the reformer 21. Note that the liquid fuel supplied to the reformer 2 is desulfurized by a desulfurizer (not shown).

  The fuel cell stack 3 is configured by stacking a plurality of battery cells 30 and generates power using the reformed gas obtained by the reformer 2 to output a direct current. The battery cell 30 includes an anode 31, a cathode 32, and an electrolyte (not shown) that is a solid polymer disposed between the anode 31 and the cathode 32, and introduces a reformed gas into the anode 31. By introducing an oxygen-containing gas (for example, air) into the cathode 32, an electrochemical power generation reaction is performed in each battery cell 30. In FIG. 1, only one battery cell 30 among the battery cells 30 to be stacked is illustrated. The fuel cell stack 3 has a cooling water flow path 33 through which cooling water for cooling the anode 31 and the cathode 32 flows.

  Further, the fuel cell system 1 includes an oxygen-containing gas introduction line L12 through which an oxygen-containing gas introduced into the cathode 32 is circulated, and a gas lead-out line L11 through which the gas led out from the cathode 32 is circulated. The oxygen-containing gas introduction line L12 is provided with an air blower A1 for introducing an oxygen-containing gas to the cathode 32.

  The fuel cell system 1 also includes a reformed gas introduction line L22 for circulating the reformed gas introduced into the anode 31, and a gas outlet line L21 for circulating the gas derived from the anode 31. The upstream side of the reformed gas introduction line L22 is connected to the reformer 21, and the reformed gas generated by the reformer 21 is introduced to the anode 31 through the reformed gas introduction line L22. The gas lead-out line L21 is for discharging a gas containing hydrogen that has not contributed to power generation in the fuel cell stack 3 from the reformed gas supplied to the anode 31 through the reformed gas introduction line L22. . The downstream side of the gas lead-out line L21 is connected to the burner 22, and the gas led out from the anode 31 can be used as fuel for the burner 22.

  In the fuel cell system 1, the cooling water supply line L <b> 32 through which the cooling water introduced into the cooling water flow path 33 for cooling the anode 31 and the cathode 32 circulates, and the cooling water derived from the cooling water flow path 33 circulates. Cooling water discharge line L31. The cooling water supply line L32 is provided with a pump WP1 for introducing the cooling water into the fuel cell stack 3.

  The fuel cell system 1 also includes a heat exchanger 6 (temperature raising means) that performs heat exchange between the reformed gas flowing in the reformed gas introduction line L22 and the cooling water flowing in the cooling water supply line L32. The reformed gas has a higher temperature than the cooling water, and heat is transferred to the cooling water through the heat exchanger 6.

  In addition, the fuel cell system 1 allows the fluid flowing through the first flow path 51 and the fluid flowing through the second flow path 52 to pass in parallel flow (flow in the same direction), and heat and moisture between both fluids. A membrane humidifier 5 is provided. The first flow path 51 of the membrane humidifier 5 is connected to the cooling water supply line L32, and the second flow path 52 is connected to the oxygen-containing gas introduction line L12. Accordingly, the cooling water supplied to the fuel cell stack 3 flows through the first flow path 51 of the membrane humidifier 5, and the oxygen-containing gas supplied to the cathode 32 flows through the second flow path 52.

  In the membrane humidifier 5, heat and moisture are exchanged between the cooling water flowing through the first flow path 51 and the oxygen-containing gas flowing through the second flow path 52. Specifically, heat and moisture are transferred from the cooling water to the oxygen-containing gas, and the oxygen-containing gas is heated and humidified. Note that the channel lengths of the first channel 51 and the second channel 52 are set so that the oxygen-containing gas has a desired temperature and humidity. By exchanging heat and moisture between the cooling water and the oxygen-containing gas by the membrane humidifier 5, the temperature of the cooling water and the oxygen-containing gas introduced from the membrane humidifier 5 to the fuel cell stack 3 is changed. The difference is within a predetermined range (for example, plus or minus 3 ° C. or less), and the oxygen-containing gas is humidified to a desired humidity.

  Further, the fuel cell system 1 includes a control unit 4 that controls the pump WP1. The control unit 4 operates the pump WP1 in advance before the start of power generation by the fuel cell stack 3 (before the oxygen-containing gas is supplied to the cathode 32). The heat exchange is performed in step 1, and the temperature of the cooling water is raised in advance. Although not shown, the cooling water is a circulation system, and the temperature of the whole cooling water rises by exchanging heat with the reformed gas and continuously receiving heat. Thus, when power generation by the fuel cell stack 3 is started, the oxygen-containing gas can be quickly heated and humidified in the membrane humidifier 5 using the cooling water that has been heated in advance. While the temperature of the cooling water is raised in advance using the reformed gas, the reformed gas is circulated by an unillustrated solenoid valve or the like so that the reformed gas is not introduced into the anode 31 through the reformed gas introduction line L22. Is blocked.

  Then, the effect | action and effect of the fuel cell system 1 concerning this embodiment are demonstrated. According to the fuel cell system 1 of the present embodiment, when the oxygen-containing gas and the cooling water pass through the membrane humidifier 5 in parallel flow, the heat and moisture of the cooling water are converted into the oxygen-containing gas via the membrane humidifier 5. Move to the side. The oxygen-containing gas increases in temperature and humidity by receiving heat and moisture. Thus, by providing the membrane humidifier 5 and allowing the oxygen-containing gas and the cooling water to pass in parallel flow, the cooling water and the oxygen-containing gas are at substantially the same temperature and oxygen-containing gas at the outlet side of the membrane humidifier 5. Since the dew point temperature can be approximately the same as the temperature, a simple configuration that does not require complicated devices such as a heat exchange device and a humidifying device can be achieved. Furthermore, by exchanging heat and moisture using cooling water having a large heat capacity, the oxygen-containing gas supplied to the cathode 32 at startup can be efficiently reduced to a temperature equivalent to that of the cooling water while suppressing a decrease in cooling water temperature. Heating and humidification can be performed, the electrode of the cathode 32 is not dried in the fuel cell stack 3, and the durability of the fuel cell stack 3 can be improved.

  Moreover, since the temperature of the cooling water is raised by the heat of the reformed gas in the heat exchanger 6, the oxygen-containing gas can be efficiently heated in the membrane humidifier 5.

  In addition, by raising the temperature of the cooling water in advance, the oxygen-containing gas can be quickly heated at the start of power generation of the fuel cell stack 3, and the power generation efficiency of the fuel cell stack 3 can be improved.

  Further, heat and moisture are exchanged between the liquid and gas passing through the membrane humidifier 5. As described above, since the heat exchange and the moisture exchange can be performed by the membrane humidifier 5, the configuration is simplified as compared with the case where the heat exchange and the moisture exchange are performed by individual devices. Can be

  The present invention is not limited to the above embodiment. For example, in the membrane humidifier 5, the cooling water and the oxygen-containing gas are passed in parallel flow (flow in the same direction) (see FIG. 1). Gas can also be passed in counterflow (reverse flow). In this case, when the cooling water passes through the membrane humidifier 5, the temperature difference from the oxygen-containing gas increases toward the outlet side of the membrane humidifier, so that the heat exchange efficiency is increased, and the cooling water is allowed to pass in parallel flow. When compared with the temperature of the cooling water at the outlet of the membrane humidifier and the temperature of the oxygen-containing gas at the outlet of the membrane humidifier, the temperature of the oxygen-containing gas and the dew point temperature are approximately the same or higher than the cooling water temperature. It becomes possible to do. With this configuration, it is possible to efficiently heat the oxygen-containing gas while expecting a temperature decrease such as heat radiation from the pipe until the oxygen-containing gas is supplied to the fuel cell stack 3. Moreover, when the movement of heat and moisture in the film humidifier 5 is small, this configuration may be applied.

  Moreover, although the 1st flow path 51 of the membrane humidifier 5 shall be connected to the cooling water supply line L32, you may connect the 1st flow path 51 to the cooling water discharge line L31. In this case, the temperature and humidity of the oxygen-containing gas can be increased in the membrane humidifier 5 using cooling water having a temperature higher than that of the cooling water flowing through the cooling water supply line L32. As a result, the oxygen-containing gas can be efficiently heated in anticipation of a temperature decrease such as pipe heat dissipation until the oxygen-containing gas is supplied to the fuel cell stack 3. Moreover, when the movement of heat and moisture in the film humidifier 5 is small, this configuration may be applied.

  Further, the temperature of the cooling water is raised using the reformed gas, but other than this, for example, exhaust gas discharged from the reformer 2 is used, or the fuel cell system 1 is discharged. In the case where hot water generated using heat is stored, the temperature of the cooling water can be raised using the heat of the hot water. Further, the temperature of the cooling water can be raised by the heater.

  Further, when pure hydrogen is supplied to the anode 31 of the fuel cell stack 3 from a gas tank or the like, the reformer 2 may not be provided.

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 3 ... Fuel cell stack, 31 ... Anode, 32 ... Cathode, 5 ... Membrane humidifier, 6 ... Heat exchanger, L12 ... Oxygen containing gas introduction line, L31 ... Cooling water discharge line, L32 ... Cooling Water supply line.

Claims (6)

A fuel cell stack having an anode into which a hydrogen-containing gas containing hydrogen is introduced, and a cathode into which an oxygen-containing gas is introduced;
An oxygen-containing gas introduction line for supplying an oxygen-containing gas to the cathode side;
A cooling water supply line for supplying cooling water for cooling the fuel cell stack to the fuel cell stack;
In the cooling water supply line and the oxygen-containing gas introduction line, a membrane humidifier that allows the cooling water and the oxygen-containing gas to pass in parallel flow;
A fuel cell system comprising: A fuel cell stack having an anode into which a hydrogen-containing gas containing hydrogen is introduced, and a cathode into which an oxygen-containing gas is introduced;
An oxygen-containing gas introduction line for supplying an oxygen-containing gas to the cathode side;
A cooling water supply line for supplying cooling water for cooling the fuel cell stack to the fuel cell stack;
A membrane humidifier in the cooling water supply line and the oxygen-containing gas introduction line, which allows the cooling water and the oxygen-containing gas to pass through in a counter flow
A fuel cell system comprising:   3. The fuel cell system according to claim 1, further comprising a temperature raising unit configured to raise the temperature of the cooling water on the cooling water supply line and on the upstream side of the membrane humidifier.   The fuel cell system according to claim 3, wherein the temperature raising means raises the temperature of the cooling water in advance before the oxygen-containing gas is supplied to the cathode. A fuel cell stack having an anode into which a hydrogen-containing gas containing hydrogen is introduced, and a cathode into which an oxygen-containing gas is introduced;
An oxygen-containing gas introduction line for supplying an oxygen-containing gas to the cathode side;
A cooling water discharge line for discharging cooling water supplied to cool the fuel cell stack from the fuel cell stack;
A membrane humidifier in the cooling water discharge line and the oxygen-containing gas introduction line that allows the cooling water and the oxygen-containing gas to pass through in parallel flow or counterflow,
A fuel cell system comprising: Heat and moisture exchange between a first fluid that flows through the first channel and a second fluid that flows through the second channel, the first channel having a first channel and a second channel A membrane humidifier that performs
The membrane humidifier, wherein the first fluid is a liquid and the second fluid is a gas.

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