JP2005222897A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To securely prevent generation of steam white smoke when an off-gas to be exhausted from a fuel cell is discharged into the air, regarding a fuel cell system. <P>SOLUTION: The fuel cell system is provided with a cooling means 6 in the off-gas discharge flow-path 4 to discharge into the air the off-gas to be exhausted from the fuel cell 2, and discharges into the air the off-gas which has been cooled below the atmospheric temperature by the cooling means 6. The off-gas discharge flow-path 4 is preferably provided with a plurality of discharge outlets 42, from each of which the off-gas is dispersedly discharged. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system, and relates to a technique for preventing the generation of water vapor white smoke when off-gas discharged from a fuel cell is released into the atmosphere.

  A fuel cell has a structure in which an anode and a cathode are arranged with an electrolyte membrane in between. A fuel gas containing hydrogen contacts the anode, and an oxidizing gas containing oxygen such as air contacts the cathode, and electricity is supplied to both electrodes. A chemical reaction occurs and an electromotive force is generated. At that time, at the cathode, hydrogen ions that have permeated through the electrolyte membrane from the anode side react with oxygen to generate water. The generated water becomes water vapor and is contained in an off gas (cathode off gas) discharged from the cathode and released into the atmosphere.

  By the way, since the fuel cell is usually operated at a high temperature (for example, about 80 ° C. even in a polymer electrolyte fuel cell having a relatively low operation temperature), the temperature of the cathode offgas is higher than the atmospheric temperature. For this reason, as soon as the cathode off-gas is released into the atmosphere, the water vapor contained in the cathode off-gas is condensed by rapid cooling, and steam white smoke is generated. In particular, the generation of steam white smoke becomes noticeable in winter when the temperature is low. Further, when a reformed gas reformed from a hydrocarbon raw material is used as the fuel gas, since the reformed gas contains water vapor, the off-gas discharged from the anode also contains water vapor. For this reason, steam white smoke may be generated even when the anode off-gas is released into the atmosphere.

  Water vapor white smoke is not preferable in appearance and in the image of the viewer. In particular, in recent years, an electric vehicle (fuel cell vehicle) equipped with a fuel cell has been developed. However, in order to put the fuel cell vehicle into practical use, measures against steam white smoke need to be fully studied. This is because a large amount of steam white smoke may cause discomfort to the driver of the succeeding vehicle and disturb the driver's view.

Conventionally, as a technique for preventing the generation of steam white smoke, for example, a technique described in Patent Document 1 is known. In this prior art, the water vapor in the off gas is condensed by pre-cooling with the air sucked in by a blower or the like before the off gas is released into the atmosphere, and the condensed water vapor is recovered and then released into the atmosphere. The generation of white smoke is prevented.
JP-A-9-223510 Japanese Utility Model Publication No. 6-60056

  However, it cannot be said that the above prior art is sufficient as a measure for preventing the generation of steam white smoke. When the offgas is cooled by air as in the above-described conventional technology, the temperature of the offgas after cooling does not become lower than the temperature of the air that is the refrigerant, that is, the atmospheric temperature. For this reason, even if water vapor in the off-gas is condensed and recovered by cooling before release, when the off-gas is released into the atmosphere, the water vapor remaining in the off-gas is condensed due to the temperature difference between the atmospheric temperature and the off-gas. Then, steam white smoke is generated.

  The present invention has been made to solve the above-described problems, and is a fuel cell that can more reliably prevent the generation of steam white smoke when off-gas discharged from the fuel cell is released into the atmosphere. The purpose is to provide a system.

In order to achieve the above object, a first invention includes a fuel cell that generates power by receiving supply of hydrogen and oxygen, and an off-gas discharge channel for releasing off-gas discharged from the fuel cell into the atmosphere. A fuel cell system having:
The off gas discharge flow path is provided with a cooling means for cooling the off gas to an atmospheric temperature or lower.

  A second invention is characterized in that, in the first invention, the off-gas discharge flow path is provided with a plurality of discharge ports.

  According to a third invention, in the first or second invention, the cooling means is a Peltier element.

  A fourth invention is characterized in that, in the first or second invention, the cooling means is a heat exchanging means for exchanging heat between hydrogen supplied from a high-pressure hydrogen tank to the fuel cell and off-gas. It is said.

  A fifth invention is characterized in that, in the first or second invention, the cooling means is a heat exchanging means for exchanging heat between the refrigerant of the air conditioner and the off-gas.

  A sixth invention is characterized in that, in any one of the first to fifth inventions, the off-gas discharge passage is a discharge passage for cathode off-gas discharged from the cathode of the fuel cell.

  According to the first to sixth inventions, the offgas can be released to the atmosphere after the dew point of the offgas is lowered to the atmospheric temperature or lower by cooling the offgas to the atmospheric temperature or lower in the offgas discharge flow path. . Thereby, generation | occurrence | production of water vapor | steam white smoke can be prevented even when atmospheric temperature is low like winter.

  In particular, according to the second invention, off-gas is dispersed from a plurality of discharge ports and released into the atmosphere, so that even if white steam is generated, it can be made difficult to recognize.

Embodiment 1 FIG.
The first embodiment of the present invention will be described below with reference to FIG.
FIG. 1 is a schematic configuration diagram of a fuel cell system as Embodiment 1 of the present invention. This fuel cell system is configured as a vehicle fuel cell system mounted on a fuel cell vehicle. A fuel cell vehicle is equipped with a motor (not shown) as a prime mover, and a fuel cell stack 2 is mounted as a power source for driving the motor.

  The fuel cell stack 2 is configured by stacking a plurality of single cells of a fuel cell. Although not shown, the single cell is configured such that both sides of a proton conductive electrolyte membrane are sandwiched between an anode and a cathode as catalyst electrodes, and both sides are sandwiched between conductive separators. In each single cell, an anode gas flow path through which fuel gas containing hydrogen flows is formed between the anode and the separator, and a cathode gas flow path through which oxidizing gas containing oxygen flows between the cathode and the separator. Is formed.

  The fuel cell stack 2 is connected to a tail pipe (off-gas discharge channel) 4 for discharging the cathode off-gas discharged from the cathode gas channel into the atmosphere. In each single cell of the fuel cell stack 2, when an electromotive force is generated by an electrochemical reaction, hydrogen ions and oxygen that have permeated the electrolyte membrane from the anode side react to generate water at the cathode. Since the fuel cell stack 2 is operated at a high temperature, the generated water becomes steam, and the steam is contained in the cathode off gas and is discharged from the cathode gas flow path to the tail pipe 4.

  The fuel cell system according to the present embodiment is characterized by the configuration of the tail pipe 4 for releasing the cathode off-gas into the atmosphere. A cooling device 6 is attached to the tail pipe 4, and a gas-liquid separator 8 is attached downstream of the cooling device 6 and upstream of the muffler 10. The downstream end of the tail pipe 4 is bifurcated, and two discharge ports 42 through which the cathode off gas is discharged into the atmosphere are provided.

  The cooling device 6 is configured by winding a Peltier element 62 around the tail pipe 4, and cools the cathode off-gas flowing in the tail pipe 4 by supplying power from the control device 64 to the Peltier element 62. Yes. The cooling temperature of the cathode offgas by the Peltier element 62 is controlled by the control device 64, and the control device 64 controls the cooling temperature of the Peltier element 62 so as to cool the cathode offgas to the atmospheric temperature or lower. By being cooled by the cooling device 6, the water vapor contained in the cathode off-gas is condensed into droplets. The droplets are collected by a gas-liquid separator 8 attached downstream of the cooling device 6, and only the cathode off-gas passes through the muffler 10 arranged downstream of the gas-liquid separator 8 and enters the atmosphere from each discharge port 42. To be released.

  According to the fuel cell system according to the present embodiment, the cathode offgas is cooled to the atmospheric temperature or lower by the cooling device 6, and therefore, when the cathode offgas is released into the atmosphere, the cathode offgas is caused by the temperature difference between the atmospheric temperature and the offgas. It is prevented that the water vapor | steam which remains in it condenses and water vapor | steam white smoke is generated. In addition, once the cathode off-gas dew point is cooled to the atmospheric temperature or lower, the dew point of the cathode off gas is lowered to the atmospheric temperature or lower. The droplets in which the water vapor in the cathode off gas is condensed by cooling are collected by the gas-liquid separator 8, so that even if the temperature of the cathode off gas increases after cooling, the amount of water vapor in the cathode off gas increases and the dew point is increased. Is prevented from becoming higher than the atmospheric temperature again. Therefore, even if the cathode offgas temperature rises above the atmospheric temperature before being released into the atmosphere, steam white smoke is not generated due to the temperature difference from the atmospheric temperature.

  Further, according to the fuel cell system according to the present embodiment, the cathode off-gas is dispersed and discharged from the two discharge ports 42, so that it is difficult to recognize even when steam white smoke is generated. Water vapor white smoke is recognized from the outside when moisture in the air blocks light transmission. However, water vapor white smoke is quickly diffused into the air by being dispersed and emitted from the two discharge ports 42. This makes it easier for light to pass through and is difficult to recognize from the outside.

  In the above-described embodiment, the Peltier element 62 is wound around the tail pipe 4, but it is also possible to adopt a configuration as shown in FIGS. 2A, 2B, and 2C. In the configuration shown in FIG. 2A, a Peltier element 65 is wound around the tail pipe 4 and a heat transfer metal plate 66 is provided inside the tail pipe 4 in order to efficiently transfer the heat of the cathode off gas to the Peltier element 65. It is attached. In the configuration shown in FIG. 2B, the Peltier element 67 is attached along the inner surface of the tail pipe 4 so that heat can be directly absorbed from the cathode off gas. Further, in the configuration shown in FIG. 2C, a large contact area is obtained between the cathode off-gas and the Peltier element 68 by attaching a plurality of Peltier elements 68 formed in a wave shape inside the tail pipe 4.

  Further, in the above-described embodiment, the downstream end of the tail pipe 4 is formed in a bifurcated manner and the two discharge ports 42 are provided. However, the configuration shown in FIGS. 3A and 3B can be adopted. In the configuration shown in FIG. 3A, a plurality of discharge ports 45 are opened on the side surface of the tail pipe 4 separately from the discharge ports 44 provided at the downstream end of the tail pipe 4, for example, by punching. The off-gas can be dispersed and released. In the configuration shown in FIG. 3B, by attaching a plurality of branch pipes 46 to the side surface of the tail pipe 4, the cathode off-gas is emitted from the discharge port 44 provided at the downstream end of the tail pipe 4 and the discharge port 47 at the tip of the branch pipe 46. Can be dispersed and released.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
In the first embodiment described above, the cathode offgas is cooled using the Peltier element. However, in this embodiment, the cathode offgas is conventionally cooled using the configuration provided in the fuel cell system. Yes. FIG. 4 is a schematic diagram showing a main part of a fuel cell system as Embodiment 2 of the present invention. In FIG. 4, the same parts as those in the first embodiment are denoted by the same reference numerals.

  In the fuel cell system according to the present embodiment, the fuel gas is supplied to the fuel cell stack from the hydrogen tank 12 mounted on the vehicle. Hydrogen is stored in the hydrogen tank 12 in a compressed state. The hydrogen tank 12 is connected to the anode gas flow path of the fuel cell stack by a hydrogen pipe 14, and hydrogen having a flow rate corresponding to the power generation load of the fuel cell stack 2 is supplied from the hydrogen tank 12.

  Although hydrogen stored in the hydrogen tank 12 is extremely low in temperature, it needs to be heated to a certain temperature before being supplied to the fuel cell stack. Therefore, in the fuel cell system according to the present embodiment, by passing a part 14 a of the hydrogen pipe 14 through the tail pipe 4, heat is generated between the cathode off-gas flowing through the tail pipe 4 and the hydrogen pipe flowing through the hydrogen pipe 14. The exchange is made to be performed. A portion 14a passing through the tail pipe 4 of the hydrogen pipe 14 serves as a heat exchanging portion, and the heat exchange at the heat exchanging portion 14a heats the hydrogen and raises the temperature.

  As described above, according to the fuel cell system of the present embodiment, it is possible to efficiently raise the temperature of hydrogen and cool the cathode offgas. In addition, in order to prevent generation | occurrence | production of water vapor | steam white smoke, it is necessary to cool cathode offgas to below atmospheric temperature. In the fuel cell system of the present embodiment, the cathode offgas cooling temperature can be adjusted by changing the surface area of the heat exchange part 14a of the hydrogen pipe 14. The specific surface area of the heat exchange unit 14a may be determined in consideration of the use environment of the fuel cell vehicle on which the fuel cell system is mounted.

  In the above-described embodiment, a part 14 a of the hydrogen pipe 14 is passed through the tail pipe 4, but the hydrogen pipe 14 may be in close contact with the side surface of the tail pipe 14. However, also in this case, it is necessary to determine the contact area between the hydrogen pipe 14 and the tail pipe 4 in consideration of the use environment of the fuel cell vehicle so that the cathode off gas can be cooled to the atmospheric temperature or lower.

  In the above-described embodiment, the description of the configuration other than the cooling system for cooling the cathode off gas is omitted, but the configuration described in the first embodiment may be adopted for the configuration other than the cooling system. it can. That is, a gas-liquid separator can be attached downstream of the heat exchange part 14a of the tail pipe 4, or a plurality of discharge ports can be provided in the tail pipe 4.

Embodiment 3 FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
In the present embodiment, the cathode offgas is cooled using a configuration conventionally provided in an automobile. FIG. 5 is a schematic diagram showing a main part of a fuel cell system as Embodiment 3 of the present invention. In FIG. 5, the same parts as those in the first embodiment are denoted by the same reference numerals.

  The automobile is provided with an air conditioner for air conditioning in the passenger compartment. The same applies to a fuel cell vehicle, in which an air conditioner indoor unit is arranged in the passenger compartment and a compressor is arranged outside the passenger compartment. The refrigerant circulates between the compressor and the indoor unit. However, in the fuel cell system according to the present embodiment, heat exchange is performed between the refrigerant and the cathode off gas. Specifically, as shown in FIG. 5, a cylindrical tube 16 is provided so as to wrap around the tail pipe 4, and the refrigerant of the air conditioner is passed through the cylindrical tube 16. The cylindrical tube 16 serves as a heat exchanger, and the cathode offgas is cooled by the heat exchange in the cylindrical tube 16 and the temperature is lowered. In addition, in order to prevent generation | occurrence | production of water vapor | steam white smoke, it is necessary to cool cathode offgas to below atmospheric temperature. In the fuel cell system of this embodiment, the cooling temperature of the cathode offgas can be adjusted by changing the length of the cylindrical tube 16. The specific length of the cylindrical tube 16 may be determined in consideration of the use environment of the fuel cell vehicle on which the fuel cell system is mounted.

  In the above-described embodiment, the cathode offgas is cooled from the outside of the tail pipe 4, but the cathode offgas is passed inside the tail pipe 4 by passing a part of the refrigerant pipe through which the refrigerant flows into the tail pipe 4. You may make it cool. However, also in this case, it is necessary to determine the length of the refrigerant pipe passing through the tail pipe 4 in consideration of the use environment of the fuel cell vehicle so that the cathode off gas can be cooled to the atmospheric temperature or lower.

  In the above-described embodiment, the description of the configuration other than the cooling system for cooling the cathode off gas is omitted, but the configuration described in the first embodiment may be adopted for the configuration other than the cooling system. it can. That is, a gas-liquid separator can be attached downstream of the cylindrical tube 16, or a plurality of discharge ports can be provided in the tail pipe 4.

Others.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the means for cooling the cathode offgas is not limited to Peltier elements, hydrogen from a hydrogen tank, and air conditioner refrigerant, as long as the cathode offgas can be cooled to an atmospheric temperature or lower. Not.

  Further, in the above-described embodiment, the present invention is used as a means for preventing the generation of white water vapor when the cathode off gas is released into the atmosphere, but the application of the present invention is limited to this. is not. In some cases, water generated at the cathode permeates the electrolyte membrane and moves to the anode, so that the anode off-gas discharged from the anode may also contain water vapor. When hydrogen is obtained by reforming a hydrocarbon raw material with a reformer, since the reformed gas contains water vapor, the off-gas discharged from the anode also contains water vapor. Even in such a case, by applying the present invention, it becomes possible to prevent generation of water vapor white smoke when the anode off-gas is discharged into the atmosphere.

It is a figure which shows schematic structure of the fuel cell system as Embodiment 1 of this invention. It is a figure which shows the modification of the cooling device using a Peltier device. It is a figure which shows the modification of the cooling device using a Peltier device. It is a figure which shows the modification of the cooling device using a Peltier device. It is a figure which shows the modification of the discharge port provided in a tail pipe. It is a figure which shows the modification of the discharge port provided in a tail pipe. It is a figure which shows schematic structure of the principal part of the fuel cell system as Embodiment 2 of this invention. It is a figure which shows schematic structure of the principal part of the fuel cell system as Embodiment 3 of this invention.

Explanation of symbols

2 Fuel cell stack 4 Tail pipes 42, 44, 45, 47 Discharge port 46 Branch pipe 6 Cooling devices 62, 65, 67, 68 Peltier device 64 Control device 66 Metal plate for heat transfer 8 Gas-liquid separator 10 Muffler 12 Hydrogen tank 14 Hydrogen pipe 14a Heat exchange part 16 Cylindrical pipe

Claims (6)

In a fuel cell system having a fuel cell that generates power by receiving supply of hydrogen and oxygen, and an off-gas discharge channel for releasing off-gas discharged from the fuel cell into the atmosphere,
A fuel cell system, characterized in that a cooling means for cooling off-gas to an atmospheric temperature or lower is provided in the off-gas discharge channel.   The fuel cell system according to claim 1, wherein the off-gas discharge channel is provided with a plurality of discharge ports.   The fuel cell system according to claim 1 or 2, wherein the cooling means is a Peltier element.   3. The fuel cell system according to claim 1, wherein the cooling unit is a heat exchange unit that exchanges heat between hydrogen and off-gas supplied from the high-pressure hydrogen tank to the fuel cell. 4.   3. The fuel cell system according to claim 1, wherein the cooling unit is a heat exchange unit that exchanges heat between a refrigerant of an air conditioner and off-gas. 6. The fuel cell system according to claim 1, wherein the off-gas discharge channel is a discharge channel of a cathode off-gas discharged from a cathode of the fuel cell.

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