JP2008147076A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system that cools compressed air with simple construction to make it possible to prevent a fuel cell from being damaged, and has no possibility to lead to malfunction due to a difference in thermal expansion between constituent members. <P>SOLUTION: Thermal exchange is carried out via a humidifier 23 between at least a part of an air supply pipework section 20 for supplying high-temperature compressed air to a cathode side of a fuel cell 1 and a tank 17 reserving produced water on an anode side of the fuel cell 1, and thereby cooling of the compressed air supplied to a fuel cell 1 is carried out. Therefore, by thermal exchanging between non-driven parts, it is possible to cool compressed air with simple construction to prevent the fuel cell from being damaged as compared with a conventional complicated construction, and furthermore not to lead to malfunction due to a difference in thermal expansion between constituent members or constituent materials as in the conventional manner. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system that generates power using an electrochemical reaction between hydrogen and oxygen.

  Conventionally, a fuel cell system mounted on a vehicle supplies compressed air (oxygen) to the cathode side (oxygen electrode side) and hydrogen to the anode side (hydrogen electrode side), for example, a polymer electrolyte membrane type A fuel cell such as a fuel cell that generates electricity using an electrochemical reaction between hydrogen and oxygen gas is known.

  By the way, in the fuel cell system described above, in the reaction process, the generated water generated on the cathode side (oxygen electrode side) is back-diffused and mixed into the anode side (hydrogen electrode side) through the polymer electrolyte membrane. If the mixed product water is left on the anode side of the fuel cell, the product water accumulates and the hydrogen concentration gradually decreases. As a result, the power generation efficiency of the fuel cell decreases. Causes damage.

  Therefore, in this type of fuel cell, how to discharge the generated water on the anode side is one of the important issues. Therefore, in order to solve this problem, the applicant of the present application has proposed a technique described below with reference to FIG. 3 in the application of Japanese Patent Application No. 2006-074825.

  FIG. 3 is a block diagram of a conventional fuel cell system. In FIG. 3, 4 is a fuel tank, 5 is its main stop valve, 6, 7 and 8 are regulators provided in the fuel gas supply piping section 9 upstream from the fuel tank 4 to the fuel cell (FC) 1, A supply valve for hydrogen as a fuel and a pressure sensor.

  Reference numeral 15 denotes a fuel gas discharge pipe section downstream of the anode from the fuel cell 1 to the normally closed discharge valve 16, and 170 denotes a rectangular box or cylindrical body of an appropriate size provided in the fuel gas discharge pipe section 15. It is a tank. In addition, the valves 5, 7, 16 and the regulator 6 show a state in which white is opened, and show a state in which black painting is closed.

  Further, 22 is a compressor, 20 is an air supply piping section provided upstream of the cathode side for supplying compressed air compressed by the compressor 20 to the cathode side of the fuel cell 1, and 21 is a cathode side for discharging air from the fuel cell 1. It is the air discharge piping part provided in the downstream.

  Then, the high-pressure hydrogen gas that has passed through the main stop valve 5 of the fuel tank 4 is depressurized and adjusted by the regulator 6, and then passes through the supply valve 7 and the pressure sensor 8 from the anode side upstream to the downstream side of the fuel cell 1. In the meantime, an electrochemical reaction occurs between the hydrogen and oxygen (compressed air) supplied to the cathode side of the fuel cell 1 through the polymer electrolyte membrane to generate electric power.

  At this time, in this fuel cell system, the supply valve 7 is provided upstream of the anode side of the fuel cell 1, the tank 170 and the discharge valve 16 are provided downstream of the anode side, and when the generated water on the anode side is discharged, the supply valve 7 The discharge valve 16 is closed and the fuel cell 1 generates power, and then the supply valve 7 is opened to discharge the generated water.

  Further, the discharge timing of the produced water is determined from the wet state on the anode side of the fuel cell 1, in other words, the accumulated state of the produced water on the anode side of the fuel cell 1, and the set wet state on the anode side of the fuel cell 1 is determined. When detected, the supply valve 7 and the discharge valve 16 are closed, and the fuel cell 1 generates power.

  With such a configuration, first, in a normal power generation state, the supply valve 7 is opened, and fuel hydrogen is supplied from the fuel tank 4 to the anode side of the fuel cell 1 via the regulator 6, the supply valve 7, and the pressure sensor 8. Gas is supplied. Then, the generated water that accompanies the power generation stays on the anode side of the fuel cell 1, the wet state on the anode side progresses, and the power generation capacity gradually decreases.

  Therefore, the wet state on the anode side of the fuel cell 1 is estimated or detected from a state value such as an integrated value, voltage, or power generation time of the current of the fuel cell 1, and the state value is set to a predetermined value set by an experiment or the like. When the required timing is reached and the generated water needs to be discharged, the supply valve 7 is closed, and the power generation of the fuel cell 1 is continued with the supply valve 7 and the discharge valve 16 closed.

  At this time, the fuel cell 1 generates power in a state where supply of hydrogen gas as fuel is stopped, and the tank 170 connected to the fuel cell 1 and the fuel cell 1 is decompressed by this power generation.

  When the inside of the fuel cell 1 drops to a predetermined pressure or the current amount (integrated value) from the start of the pressure reduction of the fuel cell 1 reaches a set value, the supply valve 7 is opened and the fuel cell 1 in the pressure-reduced state is opened. By injecting the hydrogen gas, the generated water on the anode side of the fuel cell 1 is pushed out to the tank 170 by the hydrogen gas flow from the fuel cell 1 to the tank 170 through the fuel gas discharge pipe portion 15 and reliably outside the cell. Can be discharged.

  By the way, the compressed air supplied to the cathode side of the fuel cell 1 becomes very high by being compressed to a high pressure by the compressor 22. Therefore, in order to prevent the fuel cell from being damaged by supplying high-temperature compressed air to the fuel cell 1, it is necessary to cool the compressed air. Various other techniques have been proposed for cooling the compressed air in this way (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-99996 ([0031]-[0036], FIG. 3, abstract)

  The fuel cell system described in Patent Document 1 includes a fuel cell that generates electricity by receiving supply of compressed hydrogen stored in a fuel tank and compressed air compressed by a compressor, and circulates exhaust hydrogen discharged from the fuel cell. A hydrogen circulation pump for supplying the fuel cell again is provided. The compressor and the hydrogen circulation pump are disposed in a housing in which a first space that takes in air and compresses the air and a second space into which hydrogen that has been decompressed and lowered in temperature flows are formed. In other words, a motor unit including a compressor motor and a hydrogen circulation motor is disposed in the housing, and heat is generated between the high-temperature compressed air compressed in the first space and the low-temperature hydrogen flowing into the second space. The compressed air is cooled by replacement.

  However, in the above-described method, since the motor part which is a driving component is arranged in the housing, the configuration of the apparatus becomes complicated. In addition, the temperature difference between the first space where the air is compressed and the high temperature and the second space where the low-temperature hydrogen is supplied causes a portion having different thermal expansion between the materials constituting the housing. There is a risk that the unit may malfunction. In addition, it has been proposed to configure the housing corresponding to the first space and the second space as separate materials so that the thermal expansion can be absorbed. However, in this case, the configuration is further complicated and the manufacturing cost is increased. I will invite you.

  The present invention provides a fuel cell system that can prevent the fuel cell from being damaged by cooling the compressed air with a simple configuration, and that does not cause a malfunction due to a difference in thermal expansion between the constituent members. For the purpose.

  In order to achieve the above-described object, the fuel cell system of the present invention is a fuel cell system that generates power by supplying hydrogen to the anode side of the fuel cell and supplying compressed air to the cathode side of the fuel cell. Heat that exchanges heat between an air supply piping section that supplies compressed air, a water storage section that stores the generated water on the anode side of the fuel cell, and at least a portion of the air supply piping section and the water storage section. And an exchange unit (claim 1).

  In the fuel cell system of the present invention, the heat exchanging unit includes a humidifying unit that humidifies the compressed air supplied by the air supply pipe unit, and the tank and the humidifying unit that constitute the water pool unit are heated. It is characterized by being arranged in contact with each other so as to be exchangeable (claim 2).

  According to the first aspect of the present invention, the heat exchanging section is provided between at least a part of the air supply piping section that supplies the compressed air to the cathode side of the fuel cell and the water reservoir section that stores the generated water on the anode side of the fuel cell. By performing heat exchange, the high-temperature compressed air supplied to the fuel cell is cooled. Therefore, by exchanging heat between the non-driven components, it is possible to prevent the fuel cell from being damaged by cooling the compressed air with a very simple configuration as compared with the conventional complicated configuration. In addition, it is possible to provide a fuel cell system that does not cause a malfunction due to a difference in thermal expansion between constituent materials and constituent members.

  According to the second aspect of the present invention, the compressed air supplied from the air supply pipe section is humidified by the humidifying means, so that the compressed air can be cooled, and the humidifying means and the tank are arranged in contact with each other so as to allow heat exchange. Therefore, heat exchange can be performed between the compressed air and the tank, and the compressed air can be cooled more efficiently and easily.

  Next, in order to describe the present invention in more detail, the embodiment will be described in detail with reference to FIGS. 1 and 2.

  FIG. 1 is a block diagram of the fuel cell system, and FIG. 2 is an explanatory diagram of the generated water discharge process of the fuel cell system of FIG. 1. In these drawings, the same reference numerals as those in FIG. Is a fuel tank, 5 is its main stop valve, 6, 7 and 8 are regulators provided in the fuel gas supply piping section 9 upstream of the anode from the fuel tank 4 to the fuel cell (FC) 1, and hydrogen as a fuel Supply valve, pressure sensor. Reference numeral 15 denotes a fuel gas discharge pipe section downstream of the anode from the fuel cell 1 to the normally closed discharge valve 16, and 17 denotes an appropriately sized rectangular box or cylinder provided in the fuel gas discharge pipe section 15. It is a tank. The generated water discharged from the anode side of the fuel cell 1 flows into the tank 17 via the fuel gas discharge pipe section 15 and is accumulated in the tank 17. The tank 17 is a rectangular box or cylinder having an appropriate size, and forms the “water reservoir” of the present invention.

  Also, as shown in FIG. 1, an air supply piping section 20 that supplies compressed air compressed by the compressor 22 to the cathode side of the fuel cell 1, and an air discharge piping that discharges air remaining after the chemical reaction from the fuel cell 1. Portion 21 is piped. Then, the moisture contained in the residual air discharged from the fuel cell 1 through the air discharge pipe part 21 is supplied to the compressed air passing through the air supply pipe part 20 through a hollow fiber that can transmit only water molecules. Then, a humidifier (corresponding to “humidifying means” of the present invention) 23 for humidifying the compressed air is provided.

  As described above, the compressed air supplied to the cathode side of the fuel cell 1 through the air supply piping unit 20 is humidified by the humidifier 23, whereby the compressed air can be cooled. Further, when the humidified compressed air is supplied to the fuel cell 1, moisture is supplied to the polymer electrolyte membrane constituting the fuel cell 1, and a chemical reaction between hydrogen and oxygen of the fuel generated in the fuel cell 1 occurs. Can be promoted.

  Further, as shown in FIG. 1, the humidifier 23 and the tank 17 are arranged in contact with each other so as to be able to exchange heat. Therefore, heat exchange is performed between the compressed air passing through the air supply piping unit 20 and the tank 17 via the humidifier 23, and the high-temperature compressed air is cooled. Thus, the humidifier 23 functions as a “heat exchange part” of the present invention, and the tank 17 functions as a high-temperature compressed air and a heat sink of the humidifier 23.

  In FIGS. 1 and 2, the valves 5, 7, 16 and the regulator 6 are shown in a state in which white is opened and in a state in which black painting is closed.

  Further, in the fuel cell system of this embodiment, as in the fuel cell system of FIG. 3, when the produced water on the anode side is discharged, the supply valve 7 and the discharge valve 16 provided in the tank 17 are closed. After power generation of the fuel cell 1, the supply valve 7 is opened to discharge generated water. Then, the discharge timing of the produced water is determined from the wet state on the anode side of the fuel cell 1, that is, the accumulated state of the produced water on the anode side of the fuel cell 1, and the set wet state on the anode side of the fuel cell 1 is detected. Occasionally, the fuel cell 1 is generated with the supply valve 7 and the discharge valve 16 closed.

  Next, the generated water discharge process of the fuel cell system of FIG. 1 will be described with reference to FIG.

  First, step S1 of FIG. 2 shows a normal power generation state. In this normal power generation state, the supply valve 7 is opened, and the high-pressure hydrogen gas stored in the fuel tank 4 is decompressed by the regulator 6. Thereafter, the fuel is supplied to the anode side of the fuel cell 1 through the supply valve 7 and the pressure sensor 8.

  Further, compressed air compressed by the compressor 22, humidified by the humidifier 23 and cooled is supplied to the cathode side of the fuel cell 1 by the air supply pipe unit 20. In addition, after the chemical reaction in the fuel cell 1, residual air containing moisture is discharged through the air discharge pipe portion 21. Note that, as described above, the humidifier 23 humidifies the compressed air supplied to the cathode side of the fuel cell 1 through the air supply piping unit 20 using the moisture contained in the residual air.

  Then, the generated water that accompanies the power generation stays on the anode side of the fuel cell 1, the wet state on the anode side progresses, and the power generation capacity gradually decreases. The hatched portions of the fuel cell 1, the tank 17, etc. in FIG. 2 are the generated water schematically shown.

  Therefore, the wet state on the anode side of the fuel cell 1 is estimated or detected from a state value such as an integrated value, voltage, or power generation time of the current of the fuel cell 1, and the state value is set to a predetermined value set by an experiment or the like. When it reaches the timing at which the generated water needs to be discharged, the process proceeds to step S2 in FIG. 2, the supply valve 7 is closed, and the power generation of the fuel cell 1 is continued with the supply valve 7 and the discharge valve 16 closed.

  At this time, the fuel cell 1 generates power in a state where supply of hydrogen gas as fuel is stopped, and gas is consumed by this power generation, and a tank (water reservoir) 17 communicated with the fuel cell 1 and the fuel cell 1. Is in a reduced pressure state.

  Then, when the inside of the fuel cell 1 falls to a predetermined pressure or the current amount (integrated value) from the start of depressurization of the fuel cell 1 reaches a set value, the process proceeds to step S3 in FIG. Hydrogen gas is injected into the fuel cell 1 in a decompressed state, and the generated water on the anode side of the fuel cell 1 is fed into the tank 17 by the hydrogen gas flow from the fuel cell 1 to the tank 17 through the fuel gas discharge pipe portion 15. Extrude and discharge reliably outside the battery.

  At this time, in order to prevent the generated water in the tank 17 from flowing back to the fuel cell 1, in this embodiment, the fuel gas discharge piping portion 15 between the fuel cell 1 and the tank 17 is connected to the upper portion of the tank 17 and discharged. A valve 16 is provided in the lower part of the tank 17, and generated water is dropped into the tank 17 and stored. Instead of providing a step between the connection position of the tank 7 to the fuel gas discharge pipe section 15 on the fuel cell 1 side and the position of the discharge valve 16, for example, the fuel gas between the fuel cell 1 and the tank 17. A check valve may be provided in the discharge pipe portion 15.

  Further, in order to surely discharge the generated water staying on the anode side of the fuel cell 1, the tank 17 is made larger than the space volume on the anode side of the fuel cell 1, and all the fuel and the like on the anode side are all put into the tank 17. The pressure may be reduced so as to be introduced, and the adjustment of the pressure reduction can be controlled by adjusting the generated power of the fuel cell 1. The pressure change ΔP and the generated current i are expressed as follows: ΔP = (R · T / V) × ((i / 96485) × (number of cells / 2)) where R, T, and V are gas multipliers, temperature, and volume. There is a relationship.

  In addition, hydrogen gas is injected into the fuel cell 1 in a decompressed state, and the generated water on the anode side of the fuel cell 1 is supplied to the tank 17 by the hydrogen gas flow from the fuel cell 1 to the tank 17 through the fuel gas discharge pipe portion 15. A part of the injected low-temperature hydrogen flows into the tank 17 when being pushed out. Therefore, since the tank 17 is cooled by the low-temperature hydrogen that has flowed in, the function of the tank 17 as a heat radiating plate for the high-temperature compressed air and the humidifier 23 that pass through the air supply pipe unit 20 is improved, and compression is performed more efficiently. Air and humidifier 23 are cooled.

  Then, until a certain amount of generated water is accumulated in the tank 17, the process returns from step S3 to step S1 to perform normal power generation, and when the generated water needs to be discharged, the process proceeds to steps S2 and S3, and the above processing is repeated. return.

  Further, when a certain amount of generated water accumulates in the tank 17, the process proceeds from step S3 to S4 in FIG. 2, the discharge valve 16 is opened, the stored water in the tank 17 is discharged, and after the drainage is completed, the discharge valve 16 is closed. And it returns to process S1. The discharge valve 16 is formed of an electromagnetic valve similar to the supply valve 7 or the like, or a float type valve.

  As described above, in the fuel cell system of this embodiment, at least a part of the air supply piping unit 20 that supplies high-temperature compressed air to the cathode side of the fuel cell 1 and the generated water on the anode side of the fuel cell 1 are used. By performing heat exchange with the tank 17 to be stored through the humidifier 23, the compressed air supplied to the fuel cell 1 is cooled. Therefore, by exchanging heat between the non-driven components, it is possible to prevent the fuel cell from being damaged by cooling the compressed air with a very simple configuration as compared with the conventional complicated configuration. There is no risk of malfunction due to differences in thermal expansion between constituent materials and constituent members.

  Further, the compressed air supplied from the air supply pipe unit 20 is humidified by the humidifier 23, whereby the compressed air can be cooled, and the humidifier 23 and the tank 17 are arranged in contact with each other so as to be able to exchange heat. Therefore, heat exchange can be performed between the compressed air and the tank 17 via the humidifying means 23, and the compressed air can be cooled more efficiently and easily. As shown in FIG. 1, by placing the humidifier 23 having the same shape on the rectangular tank 17, the contact area between the tank 17 and the humidifier 23 is increased, and the humidifier by the tank 17 is used. 23 and the heat dissipation effect of compressed air is improved.

  In addition, as shown in FIG. 2, in the process of discharging generated water, low temperature hydrogen supplied from the fuel tank 4 to the fuel cell 1 flows into the tank 17, so that the tank 17 is cooled by the flowing hydrogen, The function as the heat radiating plate 17 is further improved, and the humidifier 23 and the compressed air are cooled more efficiently.

  In addition, compared with conventional technology for cooling compressed air, the compressed air can be cooled with a very simple and simple configuration, so the fuel cell system can be downsized, and in particular, it is limited to the space where the fuel cell system is placed, such as a light vehicle. It can be used for small equipment with

  The present invention is not limited to the above-described embodiments, and various modifications other than those described above can be made without departing from the gist of the present invention. The compressed air can be cooled without going through the humidifier 23 by arranging the air supply pipe 20 so as to penetrate the tank 17.

  Further, the hydrogen of the fuel may be configured such that hydrogen is generated from methanol or natural gas by a reformer and supplied to the fuel cell 1. Further, the number of cells of the fuel cell 1 may be whatever.

  Further, the fuel cell system of the present invention can be used as a power source for household electrical products of 1 kw to 10 kw and an emergency power source thereof, or a battery for vehicles. When the fuel cell system of the present invention is used as a vehicle battery, the fuel cell system can be made compact in the vehicle by utilizing the internal space of the hollow side member constituting the vehicle as the “water reservoir” of the present invention. It can be installed.

1 is a block diagram of a fuel cell system according to an embodiment of the present invention. It is explanatory drawing of the generated water discharge process of the fuel cell system of FIG. It is a block diagram of the conventional fuel cell system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 9 Fuel gas supply piping part 16 Discharge valve 17 Tank (reservoir part)
20 Air supply piping part 23 Humidifier (humidifying means, heat exchange part)

Claims (2)

In the fuel cell system for generating power by supplying hydrogen to the anode side of the fuel cell and supplying compressed air to the cathode side of the fuel cell,
An air supply pipe for supplying the compressed air;
A water reservoir for storing generated water on the anode side of the fuel cell;
A fuel cell system comprising: a heat exchanging unit that exchanges heat between at least a part of the air supply pipe unit and the water reservoir. The heat exchange part includes a humidifying means for humidifying the compressed air supplied by the air supply pipe part,
2. The fuel cell system according to claim 1, wherein a tank constituting the water reservoir and the humidifying means are arranged in contact with each other so as to be able to exchange heat.

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