JP2006331870A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system preventing freezing of moisture contained in cathode off-gas exhausted from a fuel cell and effectively separating the moisture in a fuel cell system provided with the fuel cell obtaining electrical energy by electrochemical reaction of hydrogen gas and oxygen gas. <P>SOLUTION: The fuel cell system has a heating medium of a flow amount based on at least one of the temperatures of the cathode off-gas or the heating medium circulate between a hydrogen supply path 21 supplying from a hydrogen tank 11 storing liquid hydrogen or high pressure hydrogen and a cathode off-gas path 24 in which the cathode off-gas exhausted from the cathode side of the fuel cell 10 and the heating medium made to carry out heat exchange with the hydrogen gas in the hydrogen supply path 21 is made to carry out heat exchange with the cathode off-gas in the cathode off-gas path 24. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system that generates electrical energy through an electrochemical reaction.

  In the fuel cell system, a fuel gas such as hydrogen and an oxidizing gas are supplied to the fuel cell, and electric energy is obtained by an electrochemical reaction between hydrogen and oxygen. It is desirable that the fuel gas can be stored in as much space as possible. For example, when hydrogen is used as the fuel gas, a large amount of hydrogen is stored in a space using a liquid hydrogen tank or a high-pressure hydrogen tank. .

  As a conventional fuel cell system, in a fuel cell system using hydrogen gas supplied from a high-pressure hydrogen tank as a fuel, a hydrogen supply passage for supplying hydrogen gas to the fuel cell, and an anode off-gas passage discharged from the anode side of the fuel cell And a condenser that is provided on the anode off-gas passage and condenses moisture in the anode off-gas, and the refrigerant passage of the condenser constitutes a part of the hydrogen supply passage. (For example, refer to Patent Document 1).

In the fuel cell system, when the hydrogen gas supplied from the high-pressure hydrogen tank is released from the high-pressure hydrogen tank due to heat absorption by the heat of vaporization, the temperature thereof decreases. In the fuel cell system, since the refrigerant passage of the condenser that condenses the moisture in the anode off gas forms part of the hydrogen supply passage, the fuel cell system discharges from the fuel cell with the low-temperature hydrogen gas supplied from the high-pressure hydrogen tank. The anode offgas thus formed can be heat exchanged in the condenser, and as a result, the anode offgas can be cooled and moisture in the anode offgas can be condensed and separated.
JP 2002-313376 A JP 2003-185096 A Japanese Patent Laid-Open No. 9-219209 JP 2003-184767 A Japanese Patent No. 3561659 JP 2002-313404 A

  In the conventional fuel cell system, the condenser is cooled by the hydrogen gas released from the high-pressure hydrogen tank, but if the hydrogen necessary for power generation of the fuel cell is continuously supplied from the high-pressure hydrogen tank, the condenser is overcooled. This may cause the water in the condenser to freeze.

  The present invention has been made in view of the above problems, and in a fuel cell system including a fuel cell that obtains electric energy by an electrochemical reaction between hydrogen gas and an oxidizing gas, the cathode off-gas discharged from the fuel cell is used. An object of the present invention is to provide a fuel cell system capable of effectively separating moisture contained therein while preventing the contained moisture from freezing.

In the present invention, a hydrogen tank storing liquid hydrogen or high-pressure hydrogen, and an anode and a cathode are joined to both surfaces of an electrolyte layer, and electric power is obtained by an electrochemical reaction between hydrogen gas and oxidizing gas supplied from the hydrogen tank. A fuel cell; a hydrogen supply passage for supplying hydrogen gas from the hydrogen tank to the anode side of the fuel cell; a cathode offgas passage through which a cathode offgas discharged from the cathode side of the fuel cell; the hydrogen supply passage and the cathode A heat exchanging means for exchanging heat with the hydrogen gas in the hydrogen supply passage to exchange heat with the cathode offgas in the cathode offgas passage by circulating a heat medium between the cathode offgas and the heat medium; Temperature detecting means for detecting at least one of the temperatures, and the temperature detected by the temperature detecting means Based on a fuel cell system and a heat medium control means for controlling the flow rate of the heat medium to be circulated by the heat exchange means.

  The present invention is a fuel cell system that obtains electric power by an electrochemical reaction between a hydrogen gas supplied from a hydrogen tank storing liquid hydrogen or high-pressure hydrogen and an oxidizing gas. The hydrogen tank stores liquid hydrogen or high-pressure hydrogen, and the temperature of the hydrogen gas supplied from the hydrogen tank decreases when it is released from the hydrogen tank due to heat of vaporization or heat absorption due to adiabatic expansion.

  The temperature of the cathode offgas discharged from the cathode side of the fuel cell rises due to the electrochemical reaction of the fuel cell. Also, due to the electrochemical reaction of the fuel cell, the cathode off gas contains a large amount of water in the form of water vapor.

  Here, the fuel cell system according to the present invention circulates a heat medium between a hydrogen supply passage through which a low-temperature hydrogen gas passes and a cathode off-gas passage through which a cathode off-gas heated by the fuel cell passes, and the hydrogen supply passage And heat exchange means for exchanging heat with the cathode offgas in the cathode offgas passage. By the heat exchange means, heat exchange can be performed between the low temperature hydrogen gas and the high temperature cathode off gas. As a result, the heat energy is transferred from the heat medium to the hydrogen gas to heat the hydrogen gas, and the heat energy is transferred from the cathode off gas to the heat medium to cool the cathode off gas. The heat exchange on the cathode offgas passage side by the heat exchange means in the present invention includes not only direct heat exchange between the heat medium and the cathode offgas, but also indirect heat exchange via another medium. It is a waste.

  By heating the hydrogen gas by the heat exchange means, a relatively high temperature hydrogen gas can be supplied to the fuel cell. Thereby, the fall of the power generation efficiency accompanying the cooling of the fuel cell by supplying low temperature hydrogen gas can be prevented. Some fuel cell systems include a vaporizer, a heater, a decompressor, and the like in the hydrogen supply passage in order to adjust the temperature and pressure of hydrogen supplied from the hydrogen tank. According to the fuel cell system of the present invention, it is possible to reduce the load on the vaporizer, the heater, and the pressure reducer, and it is also possible to dispense with the device depending on the usage mode.

  Moreover, the fuel cell system according to the present invention can effectively remove moisture contained in the cathode offgas by cooling the cathode offgas. Depending on the type of the fuel cell, the cathode off gas may contain harmful ions such as fluorine ions. When the harmful ions pass through the cathode offgas passage, the cathode offgas passage may corrode. However, by cooling the cathode offgas and separating the water, harmful ions contained in the cathode offgas can be separated together with the water. Furthermore, it is possible to prevent the generation of white smoke in a low temperature environment by removing the moisture of the cathode off gas.

  The cathode offgas discharged from the fuel cell is substantially proportional to the supplied hydrogen gas, and as the supplied hydrogen gas increases, the discharged cathode offgas also increases. In the present invention, heat exchange is performed between the hydrogen gas and the cathode offgas, and since the supplied hydrogen gas and the discharged cathode offgas increase and decrease in proportion, the balance of heat exchange is maintained and the efficiency is increased. It is possible to perform heat exchange well.

  Furthermore, the fuel cell system according to the present invention includes the temperature detection unit and the heat medium control unit, and controls the flow rate of the heat medium based on the temperature detected by the temperature detection unit. It is possible to control the amount of heat exchanged with each other almost uniformly. The fuel cell system performs heat exchange by circulating a heat medium between the hydrogen supply passage and the cathode offgas passage. For example, when the temperature of the fuel cell is low, such as immediately after the start of the fuel cell, the fuel cell system is discharged from the fuel cell. The temperature of the cathode offgas produced is low, and the cathode offgas may be supercooled due to heat exchange with hydrogen gas. However, by controlling the flow rate of the heat medium, it is possible to prevent the cathode offgas from being overcooled and to prevent the moisture contained in the cathode offgas from freezing.

  Therefore, the control of the flow rate of the heat medium based on the temperature of the cathode offgas or the heat medium is adjustment of the flow rate of the heat medium so that the cathode offgas does not freeze. For example, when the temperature of the cathode offgas is low and it is better to suppress the cooling, the flow rate of the heat medium can be suppressed to prevent the moisture contained in the cathode offgas from freezing.

  The heat medium control means may be any means that can control the flow rate of the heat medium so as to prevent the cathode off gas from freezing. In a fuel cell system equipped with a gas-liquid separator described later, The temperature of the gas-liquid separator reflecting the temperature may be detected by the temperature detection means, and the flow rate of the heat medium may be controlled based on the detected temperature of the gas-liquid separator.

  In the fuel cell system according to the present invention, the heat medium is preferably a gas. The heat medium circulates between the hydrogen gas in the hydrogen supply passage and the cathode offgas passage, and performs heat exchange between the hydrogen gas and the cathode offgas. The hydrogen gas is below freezing depending on the storage state, and the heat medium may be cooled below below freezing. Therefore, it is desirable that the heat medium is a fluid that does not freeze by heat exchange with hydrogen gas. For example, when the heat medium is a gas, the heat medium itself can be effectively prevented from freezing.

  The fuel cell system according to the present invention further includes a gas-liquid separator that is provided on the cathode offgas passage and separates water contained in the cathode offgas, and heat exchange in the cathode offgas passage of the heat exchange means is performed. It may be performed in the gas-liquid separator.

  The gas-liquid separator is an apparatus that separates moisture in the cathode offgas by cooling, compressing, etc. the cathode offgas. By performing heat exchange in the cathode offgas passage of the heat exchange means in the gas-liquid separator, the cathode offgas from which moisture is separated or the gas-liquid separator is cooled, and the moisture in the cathode offgas by the gas-liquid separator is The separation effect can be promoted.

  In the fuel cell system according to the present invention, heat exchange in the cathode offgas passage of the heat exchanging means is performed immediately downstream of the cathode offgas discharge port of the fuel cell that discharges the cathode offgas to the cathode offgas passage. May be a feature.

  By performing the heat exchange immediately downstream of the cathode offgas discharge port of the fuel cell, the cathode offgas can be cooled immediately downstream of the cathode offgas discharge port to separate moisture in the cathode offgas. Therefore, the moisture content of the cathode offgas passing through the cathode offgas passage can be reduced at an early stage, and harmful ions such as fluorine ions contained in the cathode offgas are separated together with moisture, thereby more effectively corroding the cathode offgas passage. Can be prevented.

Furthermore, the fuel cell system according to the present invention is provided on the cathode offgas passage,
A gas-liquid separator that separates moisture contained in the cathode off-gas; and heat exchange in the cathode off-gas passage of the heat exchange means is performed on the cathode off-gas passage between the gas-liquid separator and the fuel cell. It may be a feature.

  By performing the heat exchange on the cathode offgas passage between the gas-liquid separator and the fuel cell, the cathode offgas can be cooled before the cathode offgas flows into the gas-liquid separator. Therefore, the moisture content in the cathode off gas flowing into the gas-liquid separator is reduced, and the moisture separation effect of the gas-liquid separator can be promoted. Further, as in the case of performing the heat exchange immediately downstream of the cathode offgas discharge port of the fuel cell, harmful ions of the cathode offgas passing through the cathode offgas passage are reduced as much as possible, and corrosion of the cathode offgas passage is prevented. It can be effectively prevented.

  The fuel cell system according to the present invention further includes a muffler that constitutes a part of the cathode offgas passage and discharges the cathode offgas that passes through the cathode offgas passage to the atmosphere. The heat exchange may be performed in the muffler.

  In recent years, miniaturization of fuel cell systems has been demanded. In particular, in an electric vehicle using fuel cells as fuel, various passages and devices such as the cathode offgas passage must be disposed in a space-saving manner. There may be restrictions. Also. The cathode offgas discharged from the fuel cell is separated into moisture by an air-liquid separator or the like as necessary, and then discharged from the muffler serving as an outlet of the cathode offgas passage to the atmosphere (outside the fuel cell system).

  The muffler is an outlet for discharging the cathode off gas to the outside of the fuel cell system, and its arrangement is not the center of the fuel cell system but the end portion. That is, the muffler is arranged at a position where arrangement restrictions are few in the fuel cell system, and arrangement restrictions of other passages, devices, etc. are eased by arranging heat exchange means on the muffler. It becomes possible.

  According to the present invention, in a fuel cell system including a fuel cell that obtains electric energy by an electrochemical reaction between hydrogen gas and an oxidizing gas, hydrogen gas supplied to the fuel cell and cathode off-gas discharged from the fuel cell are provided. Thus, heat exchange can be performed to effectively separate the moisture while preventing the moisture contained in the cathode offgas from freezing.

  An embodiment of a fuel cell system according to the invention will be described in detail based on the drawings.

  FIG. 1 is a system configuration diagram of a fuel cell system to which the present invention is applied. This fuel cell system includes a fuel cell 10 in which an anode and a cathode are joined to both surfaces of an electrolyte layer, a hydrogen tank 11 that stores hydrogen gas as a fuel, an air compressor 12 as an air supply device that supplies an oxidizing gas, Hydrogen supply passage 21 through which hydrogen gas supplied to fuel cell 10 passes, oxygen supply passage 22 through which oxidizing gas supplied to fuel cell 10 passes, and anode off-gas discharged from the anode side of fuel cell 10 are supplied with hydrogen A hydrogen circulation passage 23 that circulates in the passage 21, a cathode offgas passage 24 through which the cathode offgas discharged from the cathode side of the fuel cell 10 passes, a heat exchange system 30 that performs heat exchange between the hydrogen gas and the cathode offgas, It has.

The fuel cell 10 obtains electric energy by electrochemically reacting hydrogen and oxygen through an electrolyte. The fuel cell 10 according to the present embodiment is a solid polymer electrolyte fuel cell that is frequently used in an electric vehicle that runs using the fuel cell as a power source.

  The fuel cell 10 is configured to be supplied with hydrogen from a hydrogen tank 11 and supplied with an oxidizing gas containing oxygen from an air compressor 12. Liquid hydrogen is stored in the hydrogen tank 11. The liquid hydrogen is vaporized by the vaporizer 13 provided in the hydrogen supply passage 21 and supplied to the fuel cell 10. The humidifier 14 is provided in the oxygen supply passage 22, and the oxidizing gas supplied from the air compressor 12 is humidified by the humidifier 14 and supplied to the fuel cell 10.

  The hydrogen gas and the oxidizing gas supplied to the fuel cell 10 react electrochemically in the fuel cell 10, and a cathode off gas containing moisture is discharged from the cathode side of the fuel cell. Further, unreacted hydrogen gas in this electrochemical reaction is discharged as anode off gas from the anode side of the fuel cell, and is circulated through the hydrogen circulation passage 23 to the hydrogen supply passage 21. Thereby, the hydrogen gas discharged from the fuel cell 10 can be used again as the fuel of the fuel cell 10.

  In the present embodiment, the anode off gas is supplied to the hydrogen supply passage 21 as it is. However, when moisture is contained in the anode off gas, a gas-liquid separator is provided in the hydrogen circulation passage 23 so as to be contained in the anode off gas. It may be configured to supply the hydrogen supply passage 21 after removing the water.

  The cathode off-gas discharged from the cathode side of the fuel cell 10 contains moisture due to an electrochemical reaction in the fuel cell 10 and its temperature is rising. The cathode offgas passage 24 is provided with a gas-liquid separator 15 for separating moisture in the cathode offgas. The cathode offgas discharged from the fuel cell 10 is separated from the moisture by the gas-liquid separator 15 and is discharged to the atmosphere from the muffler 16 provided at the outlet of the cathode offgas passage 24.

  The heat exchange system 30 is a heat exchange means in the present invention, and includes a first heat exchanger 31 provided in the hydrogen supply passage 21, a second heat exchanger 32 provided in the gas-liquid separator 15, A heat medium circulation passage 33 through which a heat medium circulating between the first heat exchanger 31 and the second heat exchanger 32 passes, and a heat medium pump 34 that circulates the heat medium in the heat medium circulation passage 33. ing.

  The heat exchange system 30 circulates the heat medium in the heat medium circulation passage 33 by the heat medium pump 34, thereby exchanging heat between the hydrogen gas passing through the hydrogen supply passage 21 and the cathode off gas passing through the cathode off gas passage 24. It is a system to be performed. Specifically, when the liquid hydrogen stored in the hydrogen tank 11 is released to the outside of the hydrogen tank 11, the hydrogen gas is absorbed by the heat of vaporization accompanying the change of the hydrogen gas from the liquid to the gas and the heat absorption due to the adiabatic expansion action. The temperature is relatively low. Therefore, in the first heat exchanger 31, heat exchange is performed between the relatively low-temperature hydrogen gas and the heat medium, thereby increasing the temperature of the hydrogen gas and lowering the temperature of the heat medium. As a result, higher-temperature hydrogen gas can be supplied to the fuel cell 10 and power generation efficiency can be improved. The first heat exchanger 31 is disposed between the hydrogen tank 11 and the vaporizer 13. Therefore, since the hydrogen gas whose temperature has been raised by the first heat exchanger 31 is caused to flow into the vaporizer 13, the load on the vaporizer 13 can be reduced.

Next, the heat medium cooled by the first heat exchanger 31 is sent to the second heat exchanger 32 by the action of the heat medium pump 34. As a result, the relatively high temperature cathode off-gas discharged from the fuel cell 10 can be cooled. That is, by performing heat exchange between a relatively high temperature cathode offgas containing water (water vapor) generated by an electrochemical reaction in the fuel cell 10 and the cooled heat medium, the cathode offgas is cooled and the temperature of the heat medium is increased. A rise is planned. As a result of the cooling of the cathode offgas, it is possible to facilitate separation of moisture in the cathode offgas. In the present embodiment, the second heat exchanger 32 is disposed in the gas-liquid separator 15, and the gas-liquid separator 15 can be cooled together with the cathode off gas. It becomes possible to separate water in the cathode off gas.

  The heat medium whose temperature has been raised in the second heat exchanger 32 is circulated by the heat medium pump 34 and sent to the first heat exchanger 31 again, and is used for heat exchange in the first heat exchanger 31 described above. . As described above, the heat exchange system 30 performs heat exchange between the hydrogen gas passing through the hydrogen supply passage 21 and the cathode offgas passing through the cathode offgas passage 24, thereby improving the power generation efficiency of the fuel cell 10 due to the temperature rise of the hydrogen gas. And separation of moisture by cooling the cathode offgas.

  Here, when the load of the fuel cell 10 increases, it is necessary to increase the amount of power generated by the fuel cell 10 in order to cope with the load. At this time, the amount of hydrogen supplied from the hydrogen tank 11 increases, and the generated cathode offgas also increases. In other words, the heat of vaporization and heat absorption of the hydrogen gas accompanying the release of hydrogen from the hydrogen tank 11 increases, and the heat generation of the cathode off gas also increases. Thus, in the above fuel cell system, even if the load of the fuel cell 10 fluctuates, the balance between the amount of heat of vaporization and heat absorption of hydrogen gas and the amount of heat generated by the cathode offgas is maintained. Stable heat exchange can be performed regardless of the load.

  However, depending on the environment in which the fuel cell 10 is placed, there may be a problem that the cathode offgas is excessively cooled by the heat exchange described above. Therefore, the fuel cell system according to the present invention includes an outside air temperature sensor 19 that detects the outside air temperature around the fuel cell 10, a temperature sensor 20 that serves as a temperature detection unit that detects the temperature of the gas-liquid separator 15, and a heat medium. And an electronic control unit (ECU) 30 as heat medium control means for controlling the pump and the like. Each detected temperature by the outside air temperature sensor 19 and the temperature sensor 20 is configured to be input to the ECU 40.

  The ECU 40 controls the heat medium pump 34 according to a program set in advance based on the detected temperatures of the outside air temperature sensor 19 and the temperature sensor 20, and the flow rate of the heat medium so that the cathode off gas is not excessively cooled. Adjust. The heat exchange control in the fuel cell system having the above-described configuration for controlling the flow rate of the heat medium will be described based on the flowchart shown in FIG. The heat exchange control is a routine that is repeatedly executed by the ECU 40 at regular intervals.

  In S101, the outside air temperature sensor 19 detects the outside air temperature around the fuel cell 10 and the temperature sensor 20 detects the temperature of the gas-liquid separator 15 respectively. When the process of S101 ends, the process proceeds to S102.

  In S102, it is determined whether the outside air temperature detected in S101 is lower than a preset set temperature T1, or whether the temperature of the gas-liquid separator 15 detected in S101 is lower than a preset set temperature T2. The Here, the set temperatures T1 and T2 are the threshold values of the outside air temperature and the gas-liquid when there is a possibility that the cathode off-gas may be excessively cooled and frozen when the heat medium is circulated by the heat exchange system 30 and the heat exchange is performed. This is the temperature threshold of the separator 15. That is, when heat exchange is performed by the heat exchange system 30 in a state where the outside air temperature is lower than the set temperature T1 or in the state where the temperature of the gas-liquid separator 15 is lower than the set temperature T2, the cathode offgas generated by the second heat exchanger 32 is changed. There is a possibility that moisture in the cathode off-gas may be frozen by cooling. Therefore, in S102, it is determined based on the outside air temperature or the temperature of the gas-liquid separator 15 whether or not there is a possibility of moisture freezing of the cathode off gas.

  Therefore, if either the outside air temperature is lower than the set temperature T1 or the temperature of the gas-liquid separator 15 is lower than the set temperature T2, it is determined that the moisture in the cathode offgas may be frozen. The process proceeds to S103. On the other hand, if any other determination is made, it is determined that there is no possibility that the moisture in the cathode off gas will freeze, and the process proceeds to S104.

  In S103, the operation of the heat medium pump 34 is stopped. Thereby, the circulation of the heat medium in the heat medium circulation passage 33 is stopped, and the cathode offgas is not cooled by the heat exchange system 30. After the process of S103, this control is terminated.

  In S104, it is determined whether or not the temperature of the gas-liquid separator 15 detected in S101 is higher than a preset temperature T3. The preset temperature T3 is higher than the preset temperature T2, and the temperature of the gas-liquid separator 15 when it is determined that the cathode off gas needs to be cooled, that is, when the temperature rises due to the cathode off gas that needs to be cooled. This is the temperature of the gas-liquid separator 15.

  If it is determined that the temperature of the gas-liquid separator 15 is higher than the set temperature T3, the process proceeds to S105, the output of the heat medium pump 34 is increased, and the flow rate of the heat medium flowing through the heat medium circulation passage 33 is increased. Thereby, cooling of the cathode off gas flowing through the cathode off gas passage 24 is promoted. If it is determined that the temperature of the gas-liquid separator 15 is not higher than the set temperature T3, the process proceeds to S106, the output of the heat medium pump 34 is lowered, and the flow rate of the heat medium flowing through the heat medium circulation passage 33 is decreased. Thereby, cooling of the cathode off gas flowing through the cathode off gas passage 24 is suppressed, and excessive cooling is avoided. After the process of S105 or after the process of S106, this control is terminated.

  According to this control, in the fuel cell system shown in FIG. 1, the strength of the cooling of the cathode offgas by the heat medium is controlled based on the temperature of the gas-liquid separator 15 or the outside air temperature reflecting the cathode offgas temperature. As a result, it is possible to avoid the moisture in the cathode offgas from freezing due to supercooling.

  Next, a second embodiment of the fuel cell system according to the present invention will be described with reference to FIG. The difference between the fuel cell system of the present embodiment and the fuel cell system according to the first embodiment described above is a place where the second heat exchanger is disposed. Since the other configuration is the same as that of the first embodiment, the same reference numeral is assigned to the same configuration, and the detailed description thereof is omitted.

  The heat exchange system 50 in the fuel cell system according to the present embodiment includes a first heat exchanger 31, a second heat exchanger 52, a heat medium circulation passage 53, and a heat medium pump 34. The second heat exchanger 52 is provided on the cathode offgas passage 24 between the fuel cell 10 and the humidifier 14 immediately downstream of the cathode offgas discharge port of the fuel cell 10. The heat medium circulation passage 53 is a passage through which the heat medium is circulated between the first heat exchanger 31 and the second heat exchanger 52.

With the heat exchange system 50 configured as described above, the cathode gas flowing through the cathode off-gas passage 24 can be cooled as in the first embodiment, and moisture contained in the gas can be effectively separated. . Here, since the second heat exchanger 52 is provided immediately downstream of the cathode offgas discharge port of the fuel cell 10, in order to separate moisture in the cathode offgas at an early stage, fluorine ions contained in the gas It is possible to separate harmful ions such as from the gas together with moisture. As a result, the amount of harmful ions contained in the cathode offgas flowing through the cathode offgas passage 24 can be reduced, the release of the harmful ions to the outside is prevented, and corrosion of the cathode offgas passage 24 due to the harmful ions is prevented. Can do.

  Further, the second heat exchanger 52 is provided immediately downstream of the cathode offgas discharge port of the fuel cell 10 and on the cathode offgas passage 24 between the fuel cell 10 and the humidifier 14. The separated water can be circulated through the humidifier 14, and the efficiency of the system can be improved.

  Also in the fuel cell system according to the present embodiment, it is possible to execute the heat exchange control shown in FIG. 2, thereby preventing overcooling of the cathode offgas.

  Next, a third embodiment of the fuel cell system according to the present invention will be described with reference to FIG. The difference between the fuel cell system of the present embodiment and the fuel cell system according to the first embodiment described above is a place where the second heat exchanger is disposed. Since the other configuration is the same as that of the first embodiment, the same reference numeral is assigned to the same configuration, and the detailed description thereof is omitted.

  The heat exchange system 60 in the fuel cell system according to the present embodiment includes a first heat exchanger 31, a second heat exchanger 62, a heat medium circulation passage 63, and a heat medium pump 34. The second heat exchanger 62 is provided on the cathode offgas passage 24 between the humidifier 14 and the gas-liquid separator 15. The heat medium circulation passage 63 is a passage through which the heat medium is circulated between the first heat exchanger 31 and the second heat exchanger 62.

  With the heat exchange system 60 configured as described above, the cathode gas flowing through the cathode off-gas passage 24 can be cooled as in the first embodiment, and moisture contained in the gas can be effectively separated. . Here, by providing the second heat exchanger 62 between the humidifier 14 and the gas-liquid separator 15, the water content in the cathode offgas flowing into the gas-liquid separator 15 is reduced, It is possible to reduce the burden on the moisture separation effect by the gas-liquid separator 15. Further, by providing the second heat exchanger 62 on the more upstream side, similarly to the second embodiment, the release of harmful ions contained in the cathode offgas to the outside and the cathode offgas due to the harmful ions are suppressed. Corrosion of the passage 24 can be prevented as much as possible.

  Also in the fuel cell system according to the present embodiment, it is possible to execute the heat exchange control shown in FIG. 2, thereby preventing overcooling of the cathode offgas.

  Next, a fourth embodiment of the fuel cell system according to the present invention will be described with reference to FIG. The difference between the fuel cell system of the present embodiment and the fuel cell system according to the first embodiment described above is a place where the second heat exchanger is disposed. Since the other configuration is the same as that of the first embodiment, the same reference numeral is assigned to the same configuration, and the detailed description thereof is omitted.

  The heat exchange system 70 in the fuel cell system according to the present embodiment includes a first heat exchanger 31, a second heat exchanger 72, a heat medium circulation passage 73, and a heat medium pump 34. The second heat exchanger 72 is provided in the muffler 16. The heat medium circulation passage 73 is a passage through which the heat medium is circulated between the first heat exchanger 31 and the second heat exchanger 62.

With the heat exchange system 70 configured as described above, the cathode off-gas flowing through the muffler 16 that is also a part of the cathode off-gas passage 24 is cooled as in the first embodiment, and moisture contained in the gas is effectively removed. It becomes possible to separate. Here, the second heat exchanger 72 is provided in the muffler 16 having a relatively small size, thereby reducing the space volume required for the heat exchange system 70 constituting the fuel cell system as much as possible. It becomes possible, and it becomes possible to ease restrictions on arrangement of other components excluding the second heat exchanger 72. This is particularly useful when the fuel cell system is used under severe space volume restrictions, for example, when the vehicle on which the fuel cell system is mounted is relatively small.

  Also in the fuel cell system according to the present embodiment, it is possible to execute the heat exchange control shown in FIG. 2, thereby preventing overcooling of the cathode offgas.

1 is a configuration diagram of a fuel cell system according to a first embodiment of the present invention. It is a flowchart which shows the process in the fuel cell system based on the Example of this invention. It is a block diagram of the fuel cell system which concerns on the 2nd Example of this invention. It is a block diagram of the fuel cell system which concerns on the 3rd Example of this invention. It is a block diagram of the fuel cell system which concerns on the 4th Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 11 ... Hydrogen tank 15 ... Gas-liquid separator 16 ... Muffler 19 ... Outside temperature sensor 20 ... Temperature sensor 21 ... Hydrogen Supply passage 22 ... Oxygen supply passage 24 ... Cathode off-gas passage 30, 50, 60, 70 ... Heat exchange system 31 ... First heat exchanger 32, 52, 62, 72 ... Second heat exchanger 33, 53, 63, 73 ... Heat medium circulation passage 34 ... Heat medium pump 40 ... ECU

Claims (6)

A hydrogen tank storing liquid hydrogen or high-pressure hydrogen;
A fuel cell in which an anode and a cathode are joined to both surfaces of an electrolyte layer, and electric power is obtained by an electrochemical reaction between hydrogen gas and an oxidizing gas supplied from the hydrogen tank;
A hydrogen supply passage for supplying hydrogen gas from the hydrogen tank to the anode side of the fuel cell;
A cathode offgas passage through which a cathode offgas discharged from the cathode side of the fuel cell passes;
Heat exchange means for circulating heat between the hydrogen supply passage and the cathode offgas passage so that the heat medium exchanged with the hydrogen gas in the hydrogen supply passage exchanges heat with the cathode offgas in the cathode offgas passage;
Temperature detecting means for detecting the temperature of at least one of the cathode offgas and the heat medium;
A fuel cell system comprising: a heat medium control means for controlling a flow rate of the heat medium circulated by the heat exchange means based on the temperature detected by the temperature detection means.   The fuel cell system according to claim 1, wherein the heat medium is a gas. A gas-liquid separator provided on the cathode offgas passage for separating water contained in the cathode offgas;
The fuel cell system according to claim 1 or 2, wherein heat exchange in the cathode off-gas passage of the heat exchange means is performed in the gas-liquid separator.   The heat exchange in the cathode offgas passage of the heat exchange means is performed immediately downstream of a cathode offgas discharge port of a fuel cell that discharges the cathode offgas to the cathode offgas passage. The fuel cell system described in 1. A gas-liquid separator provided on the cathode offgas passage for separating water contained in the cathode offgas;
The fuel cell system according to claim 1 or 2, wherein heat exchange in the cathode offgas passage of the heat exchange means is performed on a cathode offgas passage between the gas-liquid separator and the fuel cell. . Further comprising a muffler that constitutes a part of the cathode offgas passage and discharges the cathode offgas passing through the cathode offgas passage to the atmosphere;
The fuel cell system according to claim 1 or 2, wherein heat exchange in the cathode offgas passage of the heat exchange means is performed in the muffler.

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