JP2007012636A - Solid polymer fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid polymer fuel cell system with high reliability maintaining stable operation state by surely preventing dry-up of solid polymer electrolyte film without sacrificing reduction of size and weight of the system. <P>SOLUTION: A temperature sensor 19 for detecting the temperature of a fuel cell body 1 is mounted thereon. A temperature-humidity conversion device 2 for exchanging the temperature and humidity between not reacted air and reacted air is installed, and an air supply fan 5 is mounted on the temperature-humidity conversion device 2 through a not reacted air supply tube 6. A control unit 8 controlling the air supply fan 5 depending on the detected temperature is connected to the temperature sensor 19. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is an improvement of a polymer electrolyte fuel cell system for humidifying a reaction gas and preheating a fuel cell.

  A fuel cell has an anode electrode and a cathode electrode sandwiching an electrolyte, and causes an electrochemical reaction by supplying a reaction gas such as a fuel such as hydrogen to the anode electrode and an oxidant such as air to the cathode electrode. It is a device that converts chemical energy directly into electrical energy. There are various types of fuel cells due to differences in electrolytes, and in recent years, solid polymer fuel cells using a solid polymer electrolyte membrane as an electrolyte have attracted attention. Since the polymer electrolyte fuel cell can obtain a high output density with a simple structure, the system for performing the operation of the fuel cell can be simplified and made compact. Accordingly, there is a great interest as a power source for space and vehicles, and comprehensive development is progressing over the entire system.

  Here, the configuration of a general polymer electrolyte fuel cell will be described in detail with reference to FIG. The polymer electrolyte fuel cell is provided with a polymer electrolyte membrane 103 having ion conductivity and gas separation function. A pair of gas diffusion electrodes composed of an anode electrode 101a and a cathode electrode 101b are arranged so as to sandwich the electrolyte membrane 103. Catalyst layers 102 a and 102 b containing a catalyst made of a noble metal such as Pt are formed on the surfaces of the electrodes 101 a and 101 b that are in contact with the electrolyte membrane 103. A unit cell 104 is composed of these electrodes 101a, 101b, catalyst layers 102a, 102b, and electrolyte membrane 3. Further, a gas-impermeable separator 5 is disposed so as to sandwich the single cell 104. Grooves for supplying a reaction gas such as a fuel such as hydrogen or an oxidant such as air are formed on both surfaces or one surface of the separator 5.

  In the above polymer electrolyte fuel cell, a gas electrode which is an electrochemical reaction is supplied by supplying a fuel such as hydrogen to the anode electrode 101a and an oxidant such as air to the cathode electrode 101b through the groove of the separator 5, respectively. A reaction occurs, and an electromotive force is generated in the unit cell 104. However, the electromotive force per unit cell 104 is as low as about 1V. Therefore, actually, a plurality of unit cells 104 are stacked via the separator 105 and used as the battery stack 106. Further, since the electrochemical reaction is accompanied by heat generation, it is necessary to remove excess heat. Usually, the operating temperature of the polymer electrolyte fuel cell is set to 70 to 90 ° C. Therefore, a cooling plate 107 for circulating a cooling medium is inserted for each battery stack 106, and a desired operating temperature is maintained by supplying a cooling medium having a predetermined temperature and flow rate to the cooling plate 107. .

  Furthermore, gas leakage to the outside of the system may cause a decrease in gas utilization rate or an explosion due to a combustible gas such as hydrogen. Therefore, a sealing agent 108 is provided between the solid polymer electrolyte membrane 103 and the separator 105, and gas sealing is performed. The cathode electrode 101b generates water vapor along with the gas electrode reaction. However, when water is condensed in the electrode reaction part, the gas diffusibility is deteriorated. Therefore, this condensed water is discharged out of the battery together with the unreacted gas.

  By the way, as the solid polymer electrolyte membrane 103, a perfluorosulfonic acid membrane or the like which is a fluorine-based ion exchange membrane is representative, but these solid polymer electrolyte membranes 3 have hydrogen ion exchange groups in the molecule. It functions as an ion-conducting substance when saturated with water. On the contrary, when the solid polymer electrolyte membrane 103 is dried, the ionic conductivity is deteriorated and the battery performance is remarkably lowered.

  Therefore, in the polymer electrolyte fuel cell system, measures for preventing the drying of the polymer electrolyte membrane 103 are generally taken. For example, in order to increase the relative humidity of the reaction gas, the reaction gas supplied to both the anode and cathode electrodes 101a and 101b is circulated so as to oppose each other, and the operation temperature is lowered from the usual 70 to 90 ° C. The technique of making it below ℃ is known. However, in such a technique, there is a problem in the long-term stability of the solid polymer electrolyte membrane 103 and the battery characteristics, and the CO poisoning of the catalyst layer 102a on the anode electrode 101a side is severe in operation at a low temperature of 60 ° C. or less. As a result, the anode polarization may increase and the battery characteristics may deteriorate.

  In order to solve the above problems, it is desirable to prevent the solid polymer electrolyte membrane 103 from drying by humidifying the reaction gas in advance with a humidifier and supplying it to the fuel cell. Specifically, a system has been proposed in which a humidifier having a structure in which water and a reactive gas are circulated on both sides is utilized utilizing the fact that the solid polymer electrolyte membrane 103 is a water vapor permeable membrane.

  Further, as described in Non-Patent Document 1, a gas chamber in which an already reacted gas discharged from a fuel cell and a reaction gas supplied to the fuel cell, that is, an unreacted gas, are separated by a water vapor permeable membrane. There is known a method of humidifying unreacted gas by introducing each of the above. As described above, since the water vapor is generated on the cathode electrode 101b side in association with the gas electrode reaction, the existing reaction gas contains a large amount of water vapor that is saturated or close thereto. On the other hand, the unreacted gas contains only a small amount of water vapor, and a water vapor partial pressure difference occurs between the gases. Using this partial pressure difference as a driving force, the concentration of water vapor can be diffused to humidify the unreacted gas. As described in the above-mentioned document, this method is characterized in that it does not cause a phase change. The technique described in Patent Document 1 also adopts the same concept.

Further, the polymer electrolyte fuel cell is provided with catalyst layers on the anode side and the cathode side, which are electrodes, and hydrogen and oxygen are supplied to each side during power generation. When power generation is stopped, the supply of reactive gas is shut off, but if it is shut off as it is, air diffuses to the anode side, causing hydrogen and oxygen to react with the catalyst on the anode side, resulting in an exothermic reaction. In severe cases, the electrolyte membrane may be damaged. Therefore, when the operation of the fuel cell is stopped, purging by flowing an inert gas such as nitrogen on the catalyst surface is generally performed in order to prevent diffusion of air to the anode side.
JFMcElroy and LJNuttall, "Status of Solid Polymer Electrolyte Technology and Potential for Transportation Applications," 17th IECEC, 1982, pp.667-671. 1968 USA JP-A-6-132038

  However, the above prior art has the following problems. First, when the reaction gas is humidified by a humidifier or exchanging humidity, the system becomes complicated and it is difficult to make it compact. Further, in a humidifier having a structure in which water and a reactive gas are circulated on both surfaces of a water vapor permeable membrane, when the outside air temperature becomes 0 ° C. or lower, freezing occurs on the water channel side, and the membrane is caused by blockage of the channel by ice and volume expansion of ice This causes problems such as breakage of the separator and deformation of the separator. Furthermore, in a low temperature environment where frozen ice must be melted at the time of startup, it takes a very long time to start up, and there has been a strong demand for a significant reduction in startup time.

  On the other hand, when the unreacted gas is humidified by introducing the reacted gas and the unreacted gas into the gas chambers separated by the water vapor permeable membrane, there is no problem due to the presence of the water flow path, but only the water vapor partial pressure difference between the gases. Therefore, when sufficient humidification is performed, a large humidifier is required, resulting in an increase in size and weight of the system. This is because the diffusion resistance of water vapor becomes very large, such as the diffusion resistance due to the water vapor concentration gradient on the already reacted gas side, the diffusion resistance in the water vapor permeable membrane, and the diffusion resistance on the unreacted gas side. Further, when the inside of the battery is purged with nitrogen gas when the operation of the fuel cell is stopped, a high-pressure cylinder for supplying nitrogen gas is indispensable, and there is a problem that the system is increased in size and weight.

  The present invention has been proposed to solve the above problems, and its main purpose is to reliably prevent the drying of the solid polymer electrolyte membrane without sacrificing the reduction in size and weight of the system. To provide a highly reliable polymer electrolyte fuel cell system that maintains a stable operation state.

  Another object of the present invention is to provide a polymer electrolyte fuel cell system that can be reliably started in a short time even in a low temperature environment. Furthermore, another object of the present invention is to provide a polymer electrolyte fuel cell system that can realize purging of an inert gas when the operation is stopped with a simple configuration.

  Therefore, in order to achieve the above object, the polymer electrolyte fuel cell system according to claim 1 is configured to maintain water retention between the existing reaction gas discharged from the fuel cell main body and the reaction gas supplied to the fuel cell main body. A temperature / humidity exchanger for exchanging temperature / humidity by contacting with a porous body; and a reformer for reforming hydrocarbon fuel to generate a reformed gas, downstream of the reformer A second burner for heating the cooling medium by burning the reformed gas on the side is provided. In the first aspect of the invention, the fuel cell body can be preheated by using the reformed gas downstream of the reformer as a heating source for the cooling medium, so that fuel can be saved and start-up time can be shortened. It becomes.

  According to a second aspect of the present invention, in the polymer electrolyte fuel cell system according to the first aspect, the second burner is a catalytic combustor. In the invention according to claim 2, by adopting the catalytic combustor, the inert gas component can be made cleaner, and a system with higher reliability can be realized.

  According to a third aspect of the present invention, in the polymer electrolyte fuel cell system according to the first or second aspect, the combustion gas of the second burner is supplied to the reaction gas supply path when the system is started or stopped. Yes. In the third aspect of the invention, the fuel cell main body can be preheated more efficiently by taking the combustion gas of the second burner into the reaction gas supply path when the system is started, and the startup time is reduced. It can be greatly shortened. In addition, since the combustion gas of the second burner can be used as an inert gas that covers the ambient atmosphere of the battery when the system is stopped, a high-pressure cylinder for supplying nitrogen gas is not necessary, and the system can be reduced in size and weight. Can do.

  According to a fourth aspect of the present invention, in the polymer electrolyte fuel cell system according to any one of the first to third aspects, the combustion gas of the second burner is supplied to the temperature / humidity exchanger. In this invention of Claim 4, preheating of a temperature-humidity exchanger and water retention porous humidification can be performed using the combustion gas of a 2nd burner.

  According to a fifth aspect of the invention, in the polymer electrolyte fuel cell system according to any one of the first to fourth aspects, the temperature of the reaction gas when the combustion gas from the second burner is supplied is detected. Gas temperature detection means is provided, and the temperature control means controls the temperature of the fuel cell main body according to the temperature of the reaction gas detected by the gas temperature detection means.

  In the invention of claim 5 as described above, since the temperature control means controls the temperature of the fuel cell main body based on the temperature detected by the gas temperature detecting means, the combustion gas from the second burner should be at a high temperature. For example, the temperature of the fuel cell main body can be lowered to prevent deterioration of the solid polymer electrolyte membrane.

  As described above, according to the present invention, the polymer electrolyte fuel cell having the temperature / humidity exchanger that humidifies the unreacted gas by bringing the unreacted gas into contact with the unreacted gas through the water-retaining porous body. In the system, the reaction gas is supplied under the optimal temperature or humidity conditions of the reaction gas required by the temperature / humidity exchanger, so that the system can be started, stopped, and operated in a steady state. It is not necessary to operate, and waste of energy can be saved, and a highly efficient system can be provided. Also, by supplying burner combustion gas for heating the cooling medium to the temperature / humidity exchanger and the gas supply pipe of the fuel cell body, the system can be preheated efficiently, saving fuel and shortening startup time. It was realized. Furthermore, by using the property that the combustion gas is inactive, the battery can be purged and the electrolyte membrane can be prevented from deteriorating while contributing to the system tonight.

  Hereinafter, an example of an embodiment of the present invention will be specifically described with reference to the drawings. In addition, about the member same as a prior art example, the same code | symbol is described and description is abbreviate | omitted.

(1) First Embodiment [Configuration]
A first embodiment of the present invention will be described. FIG. 1 shows a system diagram of the first embodiment, and FIG. 2 is a conceptual diagram showing the principle of temperature / humidity exchange of the temperature / humidity exchanger of the present invention.

  First, the temperature / humidity exchanger 2 will be described with reference to FIG. The temperature / humidity exchanger 2 has a structure in which an unreacted gas and an already reacted gas are brought into contact with each other with a water-retaining porous body 50 interposed therebetween. As shown in this figure, the high-temperature and high-humidity already reacted gas discharged from the polymer electrolyte fuel cell main body 1 is led to the temperature / humidity exchanger 2 and discharged through the gas groove 52. Inside the humidity exchanger 2, it comes into contact with a low-temperature unreacted gas through the porous body 50. On the other hand, the unreacted gas is guided from the outside to the temperature / humidity exchanger 2 and supplied to the battery body 1 through the gas groove 51.

  In the porous body 50, heat exchange is performed by contacting the low-temperature unreacted gas and the high-temperature reacted gas at the same time, and at the same time, the vapor that has been contained is condensed because it is below the dew point on the reacted gas side. It is absorbed by the water-retaining porous body 50. Furthermore, the absorbed condensed water moves to the unreacted gas side and evaporates to the unreacted gas in a dry state. In this way, the temperature and humidity exchanger 2 exchanges the temperature and humidity at the same time. The unreacted gas and the already-reacted gas may be oxidant gas, fuel gas, or both gases, but here, only air is used as the reaction gas. This is because the air flow is overwhelmingly higher than the fuel flow rate, so that humidification of the air becomes dominant.

  Next, a polymer electrolyte fuel cell system having the temperature / humidity exchanger 2 as described above will be described with reference to FIG. In FIG. 1, 1 is a polymer electrolyte fuel cell body, 2 is a temperature / humidity exchanger, 3 is an inlet of unreacted gas to the polymer electrolyte fuel cell body 1, 4 is from the polymer electrolyte fuel cell body 1 The exit of the already reacted gas is shown. A fan 5 for supplying air is attached to the temperature / humidity exchanger 2 via an unreacted air supply pipe 6. The temperature / humidity exchanger 2 is provided with a previously reacted air discharge pipe 7. As described above, in the temperature / humidity exchanger 2, the unreacted air and the already reacted air exchange temperature and humidity, and further, the unreacted air having high temperature and high humidity is supplied to the fuel cell body 1. .

  On the other hand, on the fuel cell main body 1 side, 16 is a fuel supply pipe, 17 is a fuel discharge pipe, 20 is a fuel supply valve, and 18 is a cooling medium circulation path. In the fuel cell main body 1, power is generated by the reaction between the supplied unreacted air and the fuel gas, and heat generation due to power generation occurs in the fuel cell main body 1. The cooling medium circulation path 18 has a radiator 12 for dissipating heat generated in the battery body 1 as waste heat to the atmosphere, a heat dissipating fan 13 for sending air to the heat dissipator 12, and a pump for conveying the cooling medium. 9. A cooling medium heater 10 for heating the cooling medium at the start-up and a burner 11 for applying heat to the cooling medium heater 10 are incorporated, and these constitute a battery temperature control means for controlling the temperature of the fuel cell body 1. The

  Reference numeral 14 denotes a fuel pump for feeding fuel to the burner 11, and 15 denotes a combustion air supply fan. Reference numeral 19 denotes a temperature sensor for detecting the temperature of the fuel cell main body 1, and reference numeral 8 denotes a control unit that controls each device based on the temperature. The control unit 8 controls the air supply fan 5 to adjust the amount of air supplied to the temperature / humidity exchanger 2. In FIG. 1, the temperature / humidity exchange unit 2 and the fuel cell main body 1 are illustrated separately, but it goes without saying that they may be integrated.

  Next, how each device is controlled by the temperature sensor 19 will be described with reference to the control flowchart of FIG. At startup, when the temperature of the sensor 19 is lower than a certain set temperature Ta (step 1), the device is controlled so as to heat the fuel cell main body 1. Here, the set temperature Ta is a particularly important value in this system. That is, when the unreacted gas is humidified using the waste heat of the battery as in this system, the capacity of the temperature / humidity exchanger greatly depends on the operating temperature of the battery. Normally, the temperature is set to 70 ° C. or higher, which is close to the operating temperature of the battery, or to a temperature lower than this if the fuel is operable even if the temperature is sufficiently low, such as hydrogen fuel.

  When the fuel cell main body 1 is heated, the cooling medium pump 9 is first started (step 2). At this time, the heat dissipating fan 13 is OFF (step 3), and control is performed so as to eliminate preheating waste as much as possible. Then, the fuel pump 14, the combustion air supply fan 15, and the burner 11 of the cooling medium heater 10 are turned on (step 4), and the cooling medium heated to a high temperature is supplied from the temperature / humidity exchanger 2 to the fuel cell body 1. Then, the fuel cell body 1 is heated. At this time, if the heating amount and the cooling medium amount of the burner 11 are adjusted according to the temperature of the fuel cell main body 1, control without overshoot becomes possible.

  When the fuel cell body 1 reaches the set temperature Ta, the devices for heating these fuel cell bodies are turned off, the fuel valve 20 is turned on (step 5), the air supply fan 5 is turned on (step 6), and the reaction Gas is supplied to the battery and power generation is started. Then, the fuel pump 14, the combustion air supply fan 15, and the burner 11 of the cooling medium heater 10 are turned off (step 7), the heat dissipating fan is turned on (step 8), and the routine shifts to a steady operation. Note that the temperature control of the fuel cell main body 1 in a steady state is performed by controlling the heat dissipation amount so that the heat dissipation amount of the cooling medium matches the heat generation amount of the battery.

  FIG. 4 is a flowchart when the system is stopped. When the system stop is commanded (step 11), the air supply fan 5 is first turned off (step 12), and then the fuel valve 20 is turned off (step 13). Thereafter, if the temperature of the fuel cell main body 1 detected by the temperature sensor 19 is higher than the set temperature Tb (step 14), the cooling medium pump 9 is turned on (step 15), and the radiating fan 13 is turned on (step 16). The temperature of the battery body 1 is lowered, and when the set temperature Tb is reached, the entire system is stopped (step 17). The set temperature Tb is a case where the overshoot is higher than the normal operating temperature, and is set to a set value higher than the operating temperature.

[Function and effect]
As described above, in the first embodiment, the waste heat of the already-reacted gas discharged from the fuel cell main body 1 is reduced by the function of the temperature / humidity exchanger 2 for exchanging the unreacted gas and the already-reacted gas with temperature and humidity. The unreacted gas can be humidified by using it. At this time, based on the temperature of the fuel cell main body 1 detected by the temperature sensor 19, the control unit 8 controls the air supply fan 5 to adjust the amount of air supplied to the temperature / humidity exchanger 2. Therefore, the reaction gas can be supplied to the temperature / humidity exchanger 2 under the optimum temperature condition, and the temperature / humidity exchanger 2 can exhibit high performance. As a result, the unreacted gas (air) can be efficiently humidified to prevent the solid polymer electrolyte membrane 103 from being dried. As a result, stable operation can be maintained without increasing the size and weight of the system. Further, by detecting the temperature of the fuel cell main body 1, the operation of each device constituting the system can be accurately controlled. Therefore, it is not necessary to operate an extra device, and it is possible to provide a highly efficient system without wasting energy.

  Furthermore, in the first embodiment, since the reaction gas is only air, the configuration of the temperature / humidity exchanger 2 can be greatly simplified, and the system can be made compact, lighter, and lower in cost. It becomes possible. Moreover, since the cooling medium is heated using the burner 11, the fuel cell main body 1 can be preheated in a short time, and the startup time can be greatly shortened.

(2) Second Embodiment [Configuration]
FIG. 5 shows a system diagram of the second embodiment of the present invention. Since the component parts of the system and their configurations are almost the same as those in the first embodiment, a detailed description thereof is omitted here. The second embodiment is characterized in that the humidity sensor 21 is provided at the air outlet of the fuel cell main body 1.

  The operating characteristics of the temperature / humidity exchanger 2 are greatly affected by the state of the already reacted air. That is, there is a characteristic that the higher the temperature and humidity of the reacted air, the more moisture the unreacted air receives. On the other hand, if the reacted air is low temperature and low humidity, the moisture received by the unreacted air decreases. In order to keep the humidity exchange amount at an appropriate value, there is of course an optimum humidity condition, and maintaining this is necessary for stable operation of the system. The experimentally determined condition is that when the operating temperature range of the polymer electrolyte fuel cell 1 is normally 60 ° C. to 100 ° C. or less, the humidity at the air outlet of the fuel cell main body 1 is between about 85% and 100%. If so, it is known to show good properties. The system is configured to maintain this value during operation.

  There are various methods for changing the condition of the already reacted air. In the second embodiment, the simplest method is to change the operating temperature of the fuel cell body 1. That is, when the temperature of the fuel cell main body is raised without changing the amount of reaction gas, the vapor pressure rises, so the relative humidity tends to decrease. On the other hand, when the temperature of the fuel cell body 1 is lowered, the relative humidity tends to increase. That is, the temperature of the fuel cell main body 1 is controlled by changing the temperature or flow rate of the cooling medium, thereby controlling the temperature of the fuel cell main body 1 so that the humidity becomes an optimum humidity.

[Function and effect]
The second embodiment has the following operational effects in addition to the first embodiment. The humidity of the air outlet of the fuel cell main body 1, that is, the inlet of the temperature / humidity exchanger 2 is detected, and the temperature of the fuel cell main body 1 is changed from the detected humidity so that the temperature / humidity exchanger 2 operates under optimum conditions. be able to. As a result, the humidity at the outlet of the fuel cell main body 1 can always be controlled to the optimum 85% to 100%, and the system can be operated stably.

(3) Third Embodiment [Configuration]
Next, a third embodiment of the present invention will be described. FIG. 6 shows a system diagram of the third embodiment. Since the component parts of the system and their configurations are almost the same as those in the first embodiment, a detailed description thereof is omitted here. In the present embodiment, the combustion gas outlet of the cooling medium heating burner 11 in the cooling medium circulation path 18 is connected to the unreacted air supply pipe 6 so that the combustion gas of the burner 11 is supplied with unreacted air when the system is started. A switching valve 25 is installed in the point configured to be supplied to the pipe 6 and the unreacted air supply pipe 6 so that the combustion gas of the burner 11 is supplied to the fuel cell main body 1 when the system is started. There is a feature in the point.

[Function and effect]
If heating of the cooling medium is required at system startup, the cooling medium heater 10 is heated by the hot combustion gas of the burner 11 and the cooling medium is heated by heat exchange, but this combustion gas is still sufficient at the burner outlet. The temperature is very high. For this reason, in the third embodiment, the combustion gas is guided to the temperature / humidity exchanger 2 and the fuel cell main body 1 through the unreacted air supply pipe 6 to turn the discarded heat into preheating, which is more efficient. You can preheat. In addition, since this combustion gas contains moisture, the moisture is given to the solid polymer electrolyte membrane 103 in the fuel cell main body 1 and the porous body 50 in the temperature / humidity exchanger 2 to be in a high humidity state. Can be started more smoothly.

  Further, since the combustion gas of the burner 11 is composed mainly of water vapor, CO 2 and nitrogen, it exhibits characteristics as an inert gas. By utilizing this characteristic, the switching valve 25 is switched when the system is stopped to guide the combustion gas into the fuel cell main body 1, and the gas surrounding the battery main body 1 can be purged by the combustion gas of the burner 11. Can be prevented. In addition, if the combustion gas of the burner 11 is used, it is not necessary to bother to incorporate a high-pressure cylinder for supplying nitrogen gas into the system, so that the system can be further reduced in size and weight. In this case, since the temperature of the fuel cell main body 1 rises, the fuel cell main body 1 is cooled using the cooling medium.

(4) Fourth Embodiment [Configuration]
Next, a fourth embodiment of the present invention will be described. FIG. 7 is a system diagram of the fourth embodiment. Although the basic configuration of the fourth embodiment is the same as that of the first embodiment, the hydrogen obtained from the hydrocarbon fuel by the reformer 30 on the fuel cell main body 1 side is supplied from the fuel supply pipe 16 to the fuel. It is different in that it is supplied to the inside of the battery body 1 and is characterized in that a catalyst burner 31 is provided as a second burner for heating the cooling medium by burning the reformed gas downstream of the reformer 30. . Hereinafter, equipment installed in the reformer 30 will be described. Reference numeral 33 denotes a pump for supplying fuel to the reformer 30. When methanol is normally used, it is supplied in a state containing moisture. Further, 32 is a fan for supplying combustion air to the burner 31, and 34 is a preheating burner for the reformer 30.

[Function and effect]
With the above configuration, in the fourth embodiment, hydrogen in the reformed gas can be fueled by the burner 31 provided on the downstream side of the reformer 30, and the cooling medium can be heated by the heat. When the hydrogen generated in the reformer 30 at the time of start-up is used for power generation, since the temperature has not yet risen, the efficiency is low and CO is also included in many cases, leading to deterioration of the fuel cell body 1 There is. However, in the present embodiment, the gas of the reformer 30 is burned by the burner 31, so that more heat can be used for preheating the fuel cell main body 1. Moreover, the combustion gas of the burner 31 can be supplied into the fuel cell body 1 to heat the fuel cell body 1. Accordingly, since the combustion gas can be directly supplied into the fuel cell main body 1, the combustion gas is heated in addition to the cooling medium, and the fuel cell main body 1 can be preheated with more heat. Further, since the combustion gas contains water vapor, the solid polymer electrolyte membrane 3 inside the fuel cell main body 1 can be brought into a high humidity state, and the start-up can be made smoother. Furthermore, since the burner 31 employs a catalyst burner, clean combustion gas can be supplied. Further, it is possible to purge the fuel cell main body by burning the burner at start-up and stop using the fact that the combustion gas is an inert gas.

(5) Fifth Embodiment [Configuration]
Next, a fifth embodiment of the present invention will be described. FIG. 8 is a system diagram of a polymer electrolyte fuel cell showing the present embodiment. Since the component parts of the system and their configurations are almost the same as those of the fourth embodiment, detailed description thereof is omitted here. In the present embodiment, the combustion gas of the burner 31 provided on the downstream side of the reformer 30 is connected to the fuel gas supply side of the fuel cell main body 1 and to the unreacted gas supply pipe 5 of the temperature / humidity exchanger 2. It is a feature.

[Function and effect]
In the system configured as described above, the combustion gas of the burner 31 is supplied to the temperature / humidity exchanger 2 via the unreacted gas supply pipe 5 in addition to the effect of shortening the startup time by preheating the temperature / humidity exchanger 2. Can be supplied to the porous body 50 inside the temperature / humidity exchanger 2, and the porous body 50 can be humidified. Therefore, even if preheating is completed and dried unreacted gas is supplied, it is possible to start up more smoothly.

(6) Sixth Embodiment [Configuration]
FIG. 9 is a system diagram of the sixth embodiment of the present invention. Since the component parts of the system and their configurations are almost the same as those in the fourth embodiment, a detailed description is omitted here. The present embodiment is characterized in that the temperature detection means 37 is provided at the fuel gas inlet of the fuel cell main body 1 and the flow rate of the cooling medium is controlled according to the temperature detected by the control unit 8. is there.

  When the combustion gas is directly supplied to the fuel cell main body 1 and preheating is performed, the combustion gas contacts the reaction surface in the fuel cell main body 1 and cannot be supplied at a very high temperature. Usually, it is 120 ° C. or less, which is the heat resistant temperature of the polymer electrolyte membrane. In the present embodiment, the temperature detecting means 37 detects the temperature of the inlet portion of the fuel cell main body 1 for the combustion gas, and the control unit 8 controls the flow rate of the cooling medium so that this temperature becomes 120 ° C. or less. It has become. In the present embodiment, the temperature detection is used as the fuel gas inlet, but it may of course be on the unreacted gas inlet side of the temperature and humidity exchanger 2 to which the combustion gas from the burner 31 is supplied. It may be both.

[Function and effect]
In the system configured as described above, in addition to the action obtained in the fourth embodiment, the temperature of the combustion gas at the inlet of the fuel cell main body 1 is detected, and the flow rate of the cooling medium is adjusted according to this temperature. By controlling, the temperature of the combustion gas for preheating the fuel cell main body 1 can be kept at 120 ° C. or lower and maintained at an appropriate temperature so as not to deteriorate the polymer electrolyte membrane 3. Therefore, the reliability of the system is further improved.

System diagram of the first embodiment of the present invention Conceptual diagram of a humidity exchanging unit in the form of the first embodiment Control flow chart at the time of system startup according to the first embodiment of this invention Control flow chart at the time of system stop according to the first embodiment of the present invention System diagram of the second embodiment of the present invention System diagram of the third embodiment of the present invention System diagram of the fourth embodiment of the present invention System diagram of the fifth embodiment of the present invention System diagram of the sixth embodiment of the present invention System diagram of conventional polymer electrolyte fuel cell system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Solid polymer fuel cell main body 2 ... Temperature / humidity exchanger 3 ... Battery inlet 4 of unreacted air ... Battery outlet 5 of unreacted air ... Unreacted air supply fan 6 ... Unreacted air supply pipe 7 ... Reacted air Discharge pipe 8 ... Control unit 9 ... Cooling medium supply pump 10 ... Cooling medium heater 11 ... Cooling medium heating burner 12 ... Radiator 13 ... Radiating fan 14 ... Burner fuel supply pump 15 ... Combustion air supply fan 16 ... Fuel gas Supply pipe 17 ... Fuel gas discharge pipe 18 ... Cooling medium circulation path 19, 37 ... Temperature sensor 20 ... Fuel gas valve cooling fan 21 ... Humidity sensor 25, 36 ... Switch valve 30 for combustion gas / unreacted air ... Reformer 31 ... Reformed gas burner 32 ... air supply fan 33 ... fuel pump 34 ... reformer preheating burner 35 ... air switching valve 50 ... water-retaining porous body 51 ... unreacted gas supply groove 52 ... already reacted gas supply groove 5 ... The end plate 55 ... separator

Claims (5)

A fuel cell main body having a solid polymer electrolyte membrane and discharging a reaction gas containing a large amount of water vapor, and a reformer for reforming a hydrocarbon fuel to generate a reformed gas; A temperature / humidity exchanger having a water-retaining porous body and taking the reaction gas and the reaction gas into contact with each other through the porous body to exchange heat and moisture between the two gases; In the polymer electrolyte fuel cell system provided with temperature control means for controlling the temperature of the fuel cell main body,
A solid polymer fuel cell system comprising a second burner for heating the cooling medium by burning a reformed gas downstream of the reformer.   2. The polymer electrolyte fuel cell system according to claim 1, wherein the second burner is a catalytic combustor.   3. The polymer electrolyte fuel cell system according to claim 1, wherein the combustion gas of the second burner is supplied to the reaction gas supply path when the system is started or stopped. .   The solid polymer fuel cell system according to any one of claims 1 to 3, wherein combustion gas of the second burner is configured to be supplied to the temperature and humidity exchanger. Gas temperature detection means for detecting the temperature of the reaction gas when combustion gas is supplied from the second burner is provided;
The temperature control unit is configured to control the temperature of the fuel cell main body according to the temperature of the reaction gas detected by the gas temperature detection unit. Solid polymer fuel cell system.

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