JP2007018837A - Hydrogen gas dilution apparatus for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen gas dilution apparatus for a fuel cell which can prevent the hydrogen discharge of high concentration with a simple structure. <P>SOLUTION: This apparatus has a hydrogen lead-in pipe 3 for feeding the hydrogen discharged from a fuel cell and a reservoir tank 2 for storing the liquid L with gravity greater than that of water. The hydrogen lead-in pipe 3 is connected at the bottom of the reservoir tank 2, on the top of which the anode off-gas is fed as a hydrogen diluting gas. The hydrogen discharged through the hydrogen lead-in pipe 3 moves upwards in the liquid L in a dispersed state, while generating time delay with a baffle 2c. Water discharged together with the hydrogen floats up in the liquid L due to difference of the gravity with the liquid L, thereby being discharged out through a cathode off-gas pipe c2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrogen gas diluting device for a fuel cell that dilutes hydrogen discharged from the fuel cell during purging.

  A fuel cell mounted on a fuel cell vehicle, for example, sandwiches both surfaces of a solid polymer electrolyte membrane between an anode and a cathode, and supplies hydrogen to the anode and air (oxygen) to the cathode to cause a chemical reaction. As a result, electrical energy is extracted. By the way, in a system equipped with this type of fuel cell, unreacted hydrogen discharged from the fuel cell is returned to the fuel cell and circulated in order to avoid wasteful use of fuel. For this reason, nitrogen in the air supplied to the cathode electrode may permeate to the anode electrode side through the solid polymer electrolyte membrane, thereby reducing the hydrogen concentration on the anode electrode side and reducing the power generation performance. . Further, water is generated as a by-product due to a chemical reaction between hydrogen and oxygen, and this water is accumulated in the anode electrode, so that the power generation performance is lowered.

Therefore, as a technique for preventing the power generation performance from deteriorating, a branch path connected to the cathode offgas piping is provided in the circulation route for circulating hydrogen, and the anode offgas and the cathode offgas are mixed and introduced into the diluting device. (For example, refer to Patent Document 1).
JP 2002-289237 A (paragraphs 0133, 0134, FIG. 8)

  However, in the conventional diluting device, a retention chamber and a mixing chamber for temporarily retaining hydrogen discharged from the fuel cell are provided, and the hydrogen retained in the retention chamber and the mixing chamber is mixed with air. Branch piping for discharging the mixed hydrogen is required, and the structure becomes complicated.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a hydrogen gas diluting device for a fuel cell that can prevent high-concentration hydrogen from being discharged with a simple structure. .

  The present invention has a discharge hydrogen introduction path for introducing hydrogen discharged from a fuel cell, and a storage tank for storing liquid, the discharge hydrogen introduction path is connected to a lower part of the storage tank, and an upper part of the storage tank And a diluent gas for diluting the hydrogen is introduced.

  According to the present invention, by introducing hydrogen into the liquid, the rising speed of the hydrogen is suppressed while being dispersed by the liquid, so that the hydrogen can be mixed with the diluent gas with a time delay, Instantaneous increase in hydrogen concentration can be suppressed.

  Further, the liquid is preferably a liquid having a specific gravity greater than that of water. Thereby, the water discharged together with hydrogen from the fuel cell can float on the surface of the liquid due to the difference in specific gravity, and can be discharged together with the dilution gas.

  A baffle plate may be provided in the storage tank. As a result, it becomes possible to mix the hydrogen with the diluent gas with a further time delay, and the discharge of high-concentration hydrogen can be prevented.

  Moreover, it is preferable that the said liquid is non-freezing and a non-volatile thing in use environment. This makes it possible to withstand long-term use in a low temperature environment.

  According to the hydrogen gas dilution device for a fuel cell of the present invention, it is possible to prevent hydrogen from being discharged at a high concentration with a simple structure.

(First embodiment)
FIG. 1 is a configuration diagram showing a fuel cell system provided with the hydrogen gas dilution device of the first embodiment, and FIG. 2 is a diagram schematically showing the inside of the hydrogen gas dilution device.
As shown in FIG. 1, the fuel cell system F1 provided with the hydrogen gas diluting apparatus 1A of the first embodiment includes a fuel cell FC, an anode system 10, a cathode system 20, a control unit 30, and the like. .

  The fuel cell FC is a solid polymer type PEM (Proton Exchange Membrane) type fuel cell, and a membrane electrode assembly (MEA) having an anode electrode and a cathode electrode on both sides of an electrolyte membrane. And a plurality of unit cells each having a structure in which a cell is sandwiched between a pair of conductive separators (not shown).

  The anode system 10 supplies hydrogen to the anode electrode of the fuel cell FC and discharges hydrogen from the anode electrode. The anode gas pipe a1, the anode offgas pipe a2, the high-pressure hydrogen tank 11, the hydrogen circulation device 12, the purge A valve 13 and the like are provided.

  One end of the anode gas pipe a <b> 1 is connected to the inlet side of the anode electrode of the fuel cell FC, and the other end is connected to the high-pressure hydrogen tank 11. The anode off-gas pipe a2 has one end connected to the outlet side of the anode electrode of the fuel cell FC and the other end connected to the purge valve 13.

  The high-pressure hydrogen tank 11 includes, for example, a container capable of storing high-purity hydrogen at a very high pressure, and an electromagnetic shut-off valve (not shown). When the control unit 30 opens the shut-off valve, hydrogen is supplied toward the anode electrode of the fuel cell FC via the anode gas pipe a1.

  The hydrogen circulation device 12 is configured to recirculate the hydrogen discharged from the fuel cell FC back to the fuel cell FC, and includes an ejector 12a and a circulation pipe 12b. The ejector 12a is provided in the anode gas pipe a1, one end of the circulation pipe 12b is connected to the ejector 12a, and the other end is connected to the anode off-gas pipe a2. As described above, by providing the hydrogen circulation device 12 to circulate hydrogen, useless use of hydrogen can be prevented.

  The purge valve 13 is provided in the anode off-gas pipe a2 on the downstream side of the other end of the circulation pipe 12b. The purge valve 13 is controlled to be opened and closed periodically, for example, by a control unit 30 described later.

  The cathode system 20 supplies air (air) as an oxidant to the cathode electrode of the fuel cell FC and discharges air from the cathode electrode. The cathode gas pipe c1, the cathode offgas pipe c2, the compressor 21, the humidifier A device (not shown) is provided.

  One end of the cathode gas pipe c <b> 1 is connected to the inlet side of the cathode electrode of the fuel cell FC, and the other end is connected to the compressor 21. The cathode offgas pipe c2 has one end connected to the cathode electrode outlet side of the fuel cell FC and the other end connected to the outside of the fuel cell system F1 through the hydrogen gas diluter 1A.

  The compressor 21 is composed of a supercharger or the like driven by a motor, and air is introduced into the cathode gas pipe c1 through a filter (not shown). The humidifier is provided on the downstream side of the compressor 21 and humidifies the air from the compressor 21 to a humidity suitable for power generation in the fuel cell FC. This humidifier humidifies the dry air introduced from the compressor 21 with, for example, cathode offgas (humidified air + generated water) discharged from the cathode electrode of the fuel cell FC.

  The fuel cell system F1 is further provided with a cooling system including a radiator and a circulation pump (not shown), and the cooling system causes heat generated by the fuel cell FC to generate power in the atmosphere. Released.

  The control unit 30 includes a CPU, ROM, RAM, peripheral circuit, input / output interface, and the like (not shown), and is provided in the high-pressure hydrogen tank 11 based on various operation information detected by a sensor (not shown). The control valve controls the shutoff valve (not shown), the rotation output of the motor of the compressor 21, the opening / closing operation of the purge valve 13, and the like.

  The hydrogen gas diluting apparatus 1A of the first embodiment is provided on the downstream side of the fuel cell FC, and includes a storage tank 2 and a discharged hydrogen introduction pipe 3. This exhaust hydrogen introduction pipe 3 corresponds to the exhaust hydrogen introduction path in the present invention.

  As shown in FIG. 2, the storage tank 2 is formed in a cylindrical shape, for example, and the liquid L is stored therein so that a predetermined space is formed in the upper portion 2 a in the storage tank 2.

  Furthermore, the liquid L is, for example, a nonpolar liquid having a specific gravity greater than that of water. By using a liquid having such characteristics, water introduced together with hydrogen can be floated in the liquid L due to a difference in specific gravity between the liquid and water.

  The liquid L here is not particularly limited as long as it has the above-described characteristics, and examples thereof include glycols such as ethylene glycol and alcohols such as glycerin. In addition, various additives, such as a rust preventive agent, can be used in the range which does not impair the effect of this invention.

  Note that the liquid L may be non-freezing and non-volatile under the usage environment of the system. By using a liquid having such characteristics, it can withstand long-term use in a low-temperature environment such as a cold region or winter.

  The storage tank 2 is connected to the storage tank 2 so that the cathode offgas pipe c2 passes above the upper portion 2a of the storage tank 2, that is, the surface of the liquid L in the storage tank 2.

  In the storage tank 2, a plurality of baffle plates 2c, 2c, 2c are provided. Each baffle plate 2c does not completely block the upper part and the lower part, but has a shape and an arrangement such that the upper part and the lower part partially communicate with each other. Note that the number, size, inclination, interval, and the like of the baffle plates 2c can be appropriately changed within a range not impairing the effects of the present embodiment.

  The exhaust hydrogen introduction pipe 3 connects the storage tank 2 and the purge valve 13, and its tip protrudes into the storage tank 2 on the side near the bottom 2 b of the storage tank 2, that is, the bottom of the storage tank 2. So connected.

Next, operation | movement of 1 A of hydrogen gas dilution apparatuses of 1st Embodiment is demonstrated.
When hydrogen is supplied from the high-pressure hydrogen tank 11 to the anode electrode of the fuel cell FC and the compressor 21 is operated and air is supplied to the cathode electrode, hydrogen and oxygen in the air undergo an electrochemical reaction to generate power. Is called. For example, if the fuel cell system F1 is mounted on a vehicle, the generated power (generated current) is supplied to a load such as a travel motor or an auxiliary machine (not shown). By the way, since the hydrogen circulation device 12 circulates hydrogen at the anode electrode of the fuel cell FC, when the power generation of the fuel cell FC is continued, nitrogen contained in the air supplied to the cathode electrode is reduced. Water that permeates through the electrolyte membrane to the anode electrode and is generated along with power generation at the cathode electrode passes through the electrolyte membrane to the anode electrode, and the hydrogen concentration in the anode electrode decreases. As a result, the power generation performance of the fuel cell FC may deteriorate. Therefore, while supplying hydrogen from the high-pressure hydrogen tank 11, impurities such as nitrogen accumulated in the anode electrode are discharged by opening and closing the purge valve 13, for example, periodically (every predetermined time) under the control of the control unit 30. In addition, by introducing new hydrogen, the power generation performance of the fuel cell FC is prevented from deteriorating.

  When the purge valve 13 is opened under the control of the control unit 30, hydrogen and water in the anode system 10 are introduced into the storage tank 2 through the discharged hydrogen introduction pipe 3 together with impurities such as nitrogen. When hydrogen is introduced into the storage tank 2, the hydrogen floats up in the storage tank 2 toward the cathode offgas pipe c2. At this time, the liquid L in the storage tank 2 obstructs the floating of the hydrogen and raises the storage tank 2 while causing a time delay with respect to the hydrogen. Furthermore, since the path of the hydrogen introduced into the storage tank 2 is hindered by the plurality of baffle plates 2c, the hydrogen is lifted up with a further time delay. The hydrogen that has reached the surface (upper surface) of the liquid L jumps out of the liquid L, is diluted by the cathode offgas (diluted gas) flowing through the cathode offgas pipe c2, and then is discharged into the atmosphere. In this way, it is possible to prevent high-concentration hydrogen from being released all at once by circulating the hydrogen discharged during the purge of the fuel cell FC to the liquid L. The baffle plate 2c may be configured not to be installed. After the purge is completed, the introduction of hydrogen or water into the storage tank 2 is stopped by closing the purge valve 13.

  In addition, by making the liquid L nonpolar and having a specific gravity greater than that of water, water introduced into the storage tank 2 can also float in the liquid L with a specific gravity difference. It can be discharged into the atmosphere via the pipe c2.

  In addition, after the operation of the fuel cell system F1 is stopped, the fuel cell system F1 should be sufficiently drained and stopped in preparation for freezing of the water remaining in the storage tank 2 so as to cope with the operation stop in a low temperature environment. Is preferred.

(Second Embodiment)
FIG. 3 is a configuration diagram showing a fuel cell system provided with the hydrogen gas dilution device of the second embodiment.
The hydrogen gas diluting apparatus 1B of the second embodiment is configured such that a dry gas before being supplied to the fuel cell FC as a diluting gas is supplied to the cathode offgas pipe c2. That is, the hydrogen gas dilution device 1B in the second embodiment has a configuration in which a bypass pipe 4 and on-off valves 5 and 6 are added to the fuel cell system F1. The configuration of the hydrogen gas dilution device 1B is the same as that of the hydrogen gas dilution device 1A, and the other components are denoted by the same reference numerals and description thereof is omitted.

  One end of the bypass pipe 4 is connected to the cathode gas pipe c1 on the upstream side of the fuel cell FC, and the other end is connected to the cathode offgas pipe c2 on the downstream side of the fuel cell FC. When the humidifier described above is provided in the cathode gas pipe c1, the cathode gas pipe c1 and the bypass pipe 4 are connected on the upstream side of the humidifier.

  The on-off valve 5 is provided on the downstream side of the connection portion of the cathode gas pipe c1 with the bypass pipe 4, and the on-off valve 6 is provided on the bypass pipe 4. The on / off valves 5 and 6 are controlled to open and close by the control unit 30.

  In the hydrogen gas dilution device 1B configured as described above, during the power generation of the fuel cell FC, the control unit 30 controls the open / close valve 5 to open and the open / close valve 6 to close. The hydrogen introduced into the storage tank 2 at the time of purging is discharged to the cathode offgas pipe c2 with a time delay, and high concentration hydrogen can be prevented from being discharged.

  In the hydrogen gas dilution device 1B, when the power generation of the fuel cell FC is stopped, the on-off valve 5 is controlled to be closed and the on-off valve 6 is opened before the compressor 21 is stopped. The water discharged together with hydrogen to the cathode offgas pipe c2 through the storage tank 2 is diluted with a dilution gas (cathode offgas) flowing through the cathode offgas pipe c2. The dilution gas at this time is a dry gas (air) that is directly introduced into the cathode offgas pipe c2 without passing through the fuel cell FC, so that the water remaining in the storage tank 2 is vaporized. It becomes possible to discharge reliably. Therefore, when the fuel cell system F1 is used in a low-temperature environment such as a cold region or winter, it is possible to avoid the inconvenience that the water remaining in the storage tank 2 is frozen and the device is damaged.

It is a block diagram which shows the fuel cell system provided with the hydrogen gas dilution apparatus of 1st Embodiment. It is a figure which shows typically the inside of the hydrogen gas dilution apparatus of 1st Embodiment. It is a block diagram which shows the fuel cell system provided with the hydrogen gas dilution apparatus of 2nd Embodiment.

Explanation of symbols

1A, 1B Hydrogen gas diluting device 2 Storage tank 2c Baffle plate 3 Discharge hydrogen introduction pipe (discharge hydrogen introduction path)
FC fuel cell L Liquid

Claims (4)

  A discharge hydrogen introduction passage for introducing hydrogen discharged from the fuel cell; and a storage tank for storing a liquid, the discharge hydrogen introduction passage is connected to a lower portion of the storage tank, and the hydrogen is supplied to an upper portion of the storage tank. A hydrogen gas diluting apparatus for a fuel cell, wherein a diluting gas to be diluted is introduced.   2. The hydrogen gas dilution device for a fuel cell according to claim 1, wherein the liquid is a liquid having a specific gravity greater than that of water.   3. The hydrogen gas dilution device for a fuel cell according to claim 1, wherein a baffle plate is provided in the storage tank.   4. The hydrogen gas dilution device for a fuel cell according to claim 1, wherein the liquid is non-freezing and non-volatile in a use environment. 5.

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