JP2008269983A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the generation of steam white smoke by an efficient method which decreases use of electricity. <P>SOLUTION: A fuel cell system is equipped with a fuel cell unit 1; a decision means 15 deciding whether steam contained in offgas is condensed or not when offgas exhausted from the fuel cell unit 1 is exhausted to the outside air; and a moisture decreasing means decreasing moisture contained in the offgas. The fuel cell system is furthermore equipped with a gas exhaust passage 6 through which offgas exhausted from the fuel cell unit flows, and the moisture decreasing means is installed in the gas exhaust passage 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system that generates water during power generation.

The off gas discharged from the fuel cell contains generated water generated by the fuel cell. The off gas is discharged to the outside air in a state where the produced water is contained as water vapor. Since the temperature of the off-gas decreases before being discharged to the outside air, the off-gas is saturated with water vapor, and steam white smoke may be generated. There is a problem that water vapor white smoke hinders visibility. In addition, there is a problem that the steam white smoke does not look good. In order to prevent the generation of steam white smoke, there is a method in which off-gas is heated by an electric heater and then discharged to the outside air.
JP 2005-299853 A

  However, after exhaust gas is heated with an electric heater, the method of discharging to the outside air uses electricity. For this reason, there is a demand for a method for suppressing the generation of steam white smoke by an efficient method that reduces the use of electricity. An object of the present invention is to suppress the generation of steam white smoke by an efficient method with reduced use of electricity.

  The present invention employs the following means in order to solve the above-described problems. That is, the fuel cell system of the present invention includes a fuel cell main body, and determination means for determining whether or not condensation of water vapor contained in the off gas occurs when the off gas discharged from the fuel cell main body is discharged to the outside air. And a moisture reducing means for reducing the moisture contained in the off-gas. According to the fuel cell system of the present invention, when the water vapor contained in the off gas discharged from the fuel cell main body condenses, the moisture contained in the off gas can be reduced by the moisture reducing means. Therefore, it is possible to suppress the generation of white smoke that occurs when off-gas is discharged to the outside air.

  The fuel cell system of the present invention may further include a gas discharge passage through which off-gas discharged from the fuel cell main body passes, and the moisture reducing means may be provided in the gas discharge passage. According to the fuel cell system of the present invention, when water vapor contained in the off gas discharged from the fuel cell main body condenses, the moisture contained in the off gas passing through the gas discharge passage can be reduced by the moisture reducing means. Therefore, it is possible to suppress the generation of white smoke that occurs when off-gas passing through the gas discharge passage is discharged to the outside air.

  The fuel cell system of the present invention further includes a switching means for connecting the gas discharge passage and one of the branch passages, wherein the gas discharge passage includes a branch passage that is divided into at least two portions in the middle. A reducing means is provided in one of the branch passages, and when the determining means determines that condensation of the water vapor occurs, the switching means is controlled, and the gas discharge passage and the moisture reducing means are provided. The off-gas may be supplied to the moisture reducing means by connecting the branch passage. According to the fuel cell system of the present invention, the switching means can be controlled to connect the gas discharge passage and the branch passage provided with the moisture reducing means. Therefore, the generation of white smoke that occurs when off-gas passing through the gas discharge passage is discharged to the outside air by flowing the off gas into the branch passage and supplying the off gas to the moisture reducing means provided in the branch passage is suppressed. Is possible.

  Further, in the fuel cell system of the present invention, the moisture reducing means absorbs moisture contained in the supplied off gas and releases the absorbed moisture by supplying a high temperature and dry off gas. The determination means determines whether or not the off-gas is hot and dry, and if it is determined that the off-gas is hot and dry, the switching means controls the gas discharge passage and the moisture. The off-gas may be supplied to the moisture reducing means by connecting to the branch passage provided with the reducing means. According to the fuel cell system of the present invention, the switching means can be controlled to connect the gas discharge passage and the branch passage provided with the moisture reducing means. Therefore, the off-gas that is hot and dry flows into the branch passage, and the off-gas that is hot and dry is supplied to the moisture reducing means provided in the branch passage to release the moisture absorbed by the moisture reducing means. Can be made. As a result, the water absorption capacity of the water reducing means can be regenerated.

  The fuel cell system of the present invention further includes a gas supply passage through which the gas supplied to the fuel cell main body passes, and the water contained in the off-gas passing through the gas discharge passage is driven by the moisture reducing means. When the determination means determines that condensation of the water vapor occurs, the moisture reduction means is driven when a part of the gas is passed through the gas supply passage to reduce the moisture contained in the off-gas. You may let them. According to the fuel cell system of the present invention, when it is determined that condensation of water vapor occurs, the determination means drives the moisture reduction means, and part of the moisture contained in the off-gas passing through the gas discharge passage is supplied to the gas supply passage. Move to gas through. Therefore, it is possible to reduce moisture contained in the off gas passing through the gas discharge passage, and to suppress the generation of white smoke that occurs when the off gas passing through the gas discharge passage is discharged to the outside air.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that water vapor | steam white smoke generate | occur | produces with the efficient method which reduced use of electricity.

  Hereinafter, a fuel cell system according to the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings. The configuration of the following embodiment is an exemplification, and the present invention is not limited to the configuration of the embodiment.

<First Embodiment>
A fuel cell system according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating a configuration example of a fuel cell system according to the first embodiment.

  1, the fuel cell system according to the first embodiment includes a fuel cell stack 1, an anode gas passage 2, an anode off gas passage 3, an anode off gas circulation passage 4, a cathode gas passage 5, a cathode off gas passage 6A, and a cathode off gas passage 6B. , Hydrogen tank 7, hydrogen pump 8, pump 9, pressure regulating valve 10, filter 11, gas-liquid separator 12, drain tank 13, exhaust / drain valve 14, electronic control unit (ECU) 15, branch passage 16A, branch passage 16B, It has a three-way valve 17A, a three-way valve 17B, a moisture reducer 18, a temperature sensor 19, an external sensor 20, and a stack sensor 21. The electronic control unit 15 corresponds to the determination unit of the present invention. The moisture reducer 18 corresponds to the moisture reducing means of the present invention.

  The fuel cell stack 1 is configured by stacking a plurality of cells. Each cell includes an electrolyte membrane, an anode (fuel electrode), a cathode (air electrode), and a separator. Between the anode and the cathode, a flow path for hydrogen and air is formed.

The anode gas passage 2 is a passage for supplying an anode gas containing hydrogen to the anode of the fuel cell stack 1. The cathode gas passage 5 is a passage for supplying cathode gas containing air to the cathode of the fuel cell stack 1.

  The hydrogen tank 7 supplies anode gas to the anode gas passage 2. The anode gas supplied from the hydrogen tank 7 is adjusted to a predetermined pressure by the pressure regulating valve 10. The anode gas is supplied from the anode gas passage 2 to the anode of the fuel cell stack 1. Further, the air sucked through the air filter 11 is driven by a pump 9 (also referred to as an air compressor), whereby cathode gas supplied from outside the fuel cell system is supplied to the cathode of the fuel cell stack 1.

  When the anode gas is supplied to the anode of the fuel cell stack 1, hydrogen ions are generated from the hydrogen contained in the anode gas. Further, oxygen contained in the air is supplied to the cathode of the fuel cell stack 1. In the fuel cell stack 1, an electrochemical reaction between hydrogen and oxygen occurs, and electric energy is generated. Further, at the cathode of the fuel cell stack 1, water is generated by combining hydrogen ions generated from hydrogen and oxygen.

  Of the anode gas supplied to the anode, a gas containing unreacted hydrogen and nitrogen permeating from the cathode (hereinafter referred to as anode off gas) is sent from the fuel cell stack 1 to the anode off gas passage 3.

  Further, unreacted gas (hereinafter referred to as “cathode off gas”) of the cathode gas supplied to the cathode is discharged from the fuel cell stack 1 to the cathode off gas passage 6A. The cathode off gas contains water generated by the fuel cell stack 1 as water vapor. The cathode offgas discharged from the cathode flows through the cathode offgas passage 6A and the cathode offgas passage 6B and is discharged to the outside air.

  The anode off-gas discharged from the anode of the fuel cell stack 1 flows through the anode off-gas passage 3 and the anode off-gas circulation passage 4, and is supplied again to the anode of the fuel cell stack 1 together with the anode gas from the hydrogen tank 7. The anode off gas passage 3 supplies the anode off gas discharged from the anode of the fuel cell stack 1 to the gas-liquid separator 12.

  The gas-liquid separator 12 separates moisture (liquid) and hydrogen (gas) contained in the anode off-gas discharged from the anode of the fuel cell stack 1. Hydrogen from which water has been separated by the gas-liquid separator 12 is supplied as an anode gas by the hydrogen pump 8 to the anode gas passage 2 through the anode off-gas circulation passage 4. The anode off-gas circulation passage 4 is a passage for supplying the anode gas sent from the hydrogen pump 8 to the anode gas passage 2. The anode off gas circulation passage 4 constitutes a circulation path on the anode side.

The drain tank 13 stores the water separated by the gas-liquid separator 12. By opening and closing the exhaust drain valve 14, the water stored in the drain tank 13 is sent to the cathode offgas passage 6A, and impurities (N ₂ ) in the anode offgas can be discharged from the circulation path. is there. The water sent to the cathode offgas passage 6A passes through the cathode offgas passage 6A and the cathode offgas passage 6B and is discharged to the outside air. The exhaust drain valve 14 is opened and closed appropriately so that the water stored in the drain tank 13 does not overflow or the concentration of impurities does not increase.

The electronic control unit 15 is electrically connected to the temperature sensor 19 and the external sensor 20 respectively. The electronic control unit 15 acquires cathode offgas temperature data measured by the temperature sensor 19. The electronic control unit 15 acquires the outside air temperature and outside air humidity data measured by the external sensor 20. The electronic control unit 15 is electrically connected to the stack sensor 21. The electronic control unit 15 acquires operating temperature data of the fuel cell stack 1 measured by the stack sensor 21. The electronic control unit 15 includes a CPU, a ROM, and the like inside, and the CPU executes various processes according to a control program recorded in the ROM.

  The temperature sensor 19 measures the temperature of the cathode offgas discharged to the outside air via the cathode offgas passage 6B. The temperature sensor 19 can be provided at an arbitrary position. For example, the temperature sensor 19 may be provided so that the temperature of the cathode off gas immediately before being discharged to the outside air can be measured. In this case, the temperature sensor 19 can measure the temperature of the cathode off gas immediately before being discharged to the outside air. The external sensor 20 measures the outside air temperature and the outside air humidity. The stack sensor 21 measures the operating temperature of the fuel cell stack 1.

  The cathode offgas passage 6A is branched into two branch passages 16A and 16B along the way. A moisture reducer 18 is provided in the branch passage 16A. The moisture reducer 18 reduces the moisture contained in the cathode offgas flowing through the branch passage 16A. That is, the moisture reducer 18 reduces the moisture contained in the cathode offgas when the cathode offgas is supplied.

  A three-way valve 17A is provided at a location where the cathode offgas passage 6A branches into a branch passage 16A and a branch passage 16B. A three-way valve 17B is provided at a location where the branch passage 16A and the branch passage 16B merge. The three-way valve 17A and the three-way valve 17B are electrically connected to the electronic control unit 15. The three-way valve 17 </ b> A and the three-way valve 17 </ b> B perform an operation of allowing the cathode off gas to flow into either the branch passage 16 </ b> A or the branch passage 16 </ b> B according to a command (control) from the electronic control unit 15. That is, the three-way valve 17A serves to connect the cathode offgas passage 6A and the branch passage 16A, and serves to connect the cathode offgas passage 6A and the branch passage 16B. The three-way valve 17B serves to connect the branch passage 16A and the cathode offgas passage 6B, and serves to connect the branch passage 16B and the cathode offgas passage 6B.

  FIG. 2 is a flowchart for explaining the operation of the fuel cell system according to the first embodiment. While the cathode off gas discharged from the fuel cell stack 1 is discharged to the outside air (for example, during power generation of the fuel cell), the fuel cell system according to the first embodiment operates.

  First, the electronic control unit 15 acquires data on the outside air temperature, the outside air humidity, and the cathode off-gas temperature (S201). Specifically, the electronic control unit 15 acquires data on the outside air temperature measured by the external sensor 20. In the first embodiment, the outside temperature measured by the external sensor 20 is referred to as a measured outside temperature. In addition, the electronic control unit 15 acquires the outside air humidity data measured by the external sensor 20. In the first embodiment, the outside air humidity measured by the external sensor 20 is referred to as measured outside air humidity. Furthermore, the electronic control unit 15 acquires the cathode offgas temperature data measured by the temperature sensor 19.

  Next, the electronic control unit 15 determines whether white smoke is generated based on the measured outside air temperature data, the measured outside air humidity data, and the cathode off gas temperature data (S202).

The water vapor contained in the cathode offgas discharged from the cathode offgas passage 6B to the outside air is cooled by the outside air. If the amount of water vapor of the water cooled by the outside air is larger than the amount of saturated water vapor at the cooled temperature, the water vapor discharged to the outside air condenses. When water vapor condenses, it initially becomes fine droplets. Water vapor containing water droplets appears white due to diffuse reflection of light. In the first embodiment, it is said that white smoke is generated when water vapor contained in the cathode off-gas exhausted to the outside air becomes visible in white.

  The relationship between the cathode off-gas temperature, the outside air temperature, the outside air humidity, and the generation of white smoke may be obtained by experiments or simulations. For example, a map (table) as shown in FIG. 3 is created in advance by experiment or simulation. Then, the electronic control unit 15 may determine whether white smoke is generated from the map.

  ΔT shown in FIG. 3 is a difference between the cathode off-gas temperature and the outside air temperature. The humidity shown in FIG. 3 is the outside air humidity. The circles in FIG. 3 indicate that white smoke is generated. In FIG. 3, “X” indicates that white smoke is not generated. When determining whether white smoke is generated using the map of FIG. 3, the electronic control unit 15 calculates ΔT1 which is the difference between the temperature of the cathode offgas and the measured outside air temperature. Then, the electronic control unit 15 refers to the map shown in FIG. 3 and determines whether white smoke is generated based on ΔT1 and the measured outside air humidity.

  Returning to the description of FIG. When it is determined that white smoke is generated (if the result of S202 is affirmative), the electronic control unit 15 controls the three-way valve 17A and the three-way valve 17B to cause the cathode offgas flowing through the cathode offgas passage 6A to flow into the branch passage 16A. (S203). That is, the three-way valve 17A and the three-way valve 17B are switched so that the cathode offgas flowing through the cathode offgas passage 6A flows into the branch passage 16A. The cathode offgas flowing into the branch passage 16A passes through the moisture reducer 18 provided in the branch passage 16A and flows into the cathode offgas passage 6B.

  FIG. 4 is a diagram illustrating the moisture reducer 18 according to the first embodiment in detail. As shown in FIG. 4, the moisture reducer 18 is provided in the branch passage 16A. Therefore, the cathode off gas flowing into the branch passage 16 </ b> A passes through the moisture reducer 18. In the first embodiment, a desiccant such as silica is used as the moisture reducer 18. The moisture reducer 18 absorbs part of the moisture contained in the cathode offgas flowing into the branch passage 16A. That is, when the cathode offgas is supplied, the moisture reducer 18 absorbs part of the moisture contained in the cathode offgas. When the moisture reducer 18 absorbs a predetermined amount of moisture, the moisture reducer 18 does not absorb moisture any more. In addition, when a high-temperature and dry cathode offgas is supplied to the moisture reducer 18 that has absorbed moisture, the moisture reducer 18 releases the absorbed moisture. By supplying a high temperature and dry cathode off gas, the moisture reducing device 18 can release moisture, and the moisture absorbing capacity of the moisture reducing device 18 can be regenerated. In the first embodiment, the case where a desiccant such as silica is used as the moisture reducer 18 has been described, but the present invention is not limited to this. For example, the moisture reducer 18 may be capable of absorbing moisture contained in the cathode offgas, and releasing moisture absorbed by heating to a high temperature to regenerate the moisture absorption capability. .

  Here, when it is determined that white smoke is generated, flowing the cathode off gas flowing through the cathode off gas passage 6A into the branch passage 16A provided with the moisture reducing device 18 is referred to as white smoke reduction processing in the first embodiment. .

  When the white smoke reduction process is performed, the electronic control unit 15 measures the time during which the cathode offgas flowing through the cathode offgas passage 6A is caused to flow into the branch passage 16A using a timer (not shown). In the first embodiment, the time during which the cathode off-gas flows into the branch passage 16A is referred to as the inflow time. Then, the electronic control unit 15 holds the measured inflow time. When the white smoke reduction process is repeatedly performed, the electronic control unit 15 integrates the measured inflow time. In the first embodiment, the time obtained by integrating the measured inflow time is referred to as the inflow integration time. The electronic control unit 15 holds the inflow integration time.

When it is determined that white smoke is generated, the amount of water vapor contained in the cathode off gas flowing through the cathode off gas passage 6A is saturated (or close to saturation). Therefore, when the cathode offgas passes through the moisture reducer 18 provided in the branch passage 16A, a part of the moisture contained in the cathode offgas is absorbed by the moisture reducer 18. The cathode offgas that has passed through the moisture reducer 18 provided in the branch passage 16A flows into the cathode offgas passage 6B. The cathode off gas flowing into the cathode off gas passage 6B is discharged to the outside air.

  Returning to the description of FIG. When it is determined that white smoke is not generated (No in the process of S202), the electronic control unit 15 determines whether the cathode offgas discharged from the fuel cell stack 1 is hot and dry (S204). Specifically, the electronic control unit 15 acquires data of the cathode offgas temperature measured by the temperature sensor 19 and determines whether the cathode offgas temperature is equal to or higher than a predetermined temperature. When the temperature of the cathode off gas is equal to or higher than the predetermined temperature, the electronic control unit 15 determines that the cathode off gas is high temperature. The predetermined temperature is a value that varies depending on the type of desiccant such as silica used as the moisture reducer 18. Further, the electronic control unit 15 acquires the cathode offgas humidity data measured by the humidity sensor 19 and determines whether the cathode offgas humidity is equal to or higher than a predetermined humidity. When the humidity of the cathode off gas is equal to or higher than the predetermined humidity, the electronic control unit 15 determines that the cathode off gas is dry. For example, the temperature sensor 19 may be provided so that the temperature of the cathode off gas flowing into the branch passage 16A can be measured. In this case, the temperature sensor 19 can measure the temperature of the cathode off gas immediately before flowing into the branch passage 16A.

  When it is determined that the cathode offgas discharged from the fuel cell stack 1 is high temperature and dry (in the case of affirmative in the process of S204), the electronic control unit 15 determines whether the moisture reducer 18 is absorbing moisture. (S205). Specifically, the electronic control unit 15 determines whether the held inflow time or accumulated inflow time is equal to or longer than a predetermined time. When the held inflow time or accumulated inflow time is equal to or longer than the predetermined time, the electronic control unit 15 determines that the moisture reducer 18 absorbs moisture.

  When it is determined that the moisture reducer 18 is absorbing moisture (in the case of affirmative in the process of S205), the electronic control unit 15 performs the process of S203. That is, the electronic control unit 15 controls the three-way valve 17A and the three-way valve 17B, and causes the cathode offgas flowing through the cathode offgas passage 6A to flow into the branch passage 16A. Since the cathode off gas flowing into the branch passage 16A is hot and dry, the moisture reducer 18 that absorbs moisture releases the absorbed moisture. In this way, the cathode offgas that is hot and dry is caused to flow into the branch passage 16A and the moisture absorbed by the moisture reducer 18 is released, thereby regenerating the moisture absorption capability of the moisture reducer 18.

  In the first embodiment, a high temperature and dry cathode off gas flowing into the branch passage 16A and a high temperature and dry cathode off gas passing through the moisture reducer 18 are referred to as a high temperature drying process. When the high temperature drying process is performed, the electronic control unit 15 initializes the timer.

  On the other hand, when it is determined that the cathode offgas discharged from the fuel cell stack 1 is high temperature and not dry (No in the process of S204), the electronic control unit 15 controls the three-way valve 17A and the three-way valve 17B, The cathode off gas flowing through the cathode off gas passage 6A is caused to flow into the branch passage 16B (S206). That is, the three-way valve 17A and the three-way valve 17B are switched so that the cathode offgas flowing through the cathode offgas passage 6A flows into the branch passage 16B. Since the moisture reducing device 18 is not provided in the branch passage 16B, the cathode offgas flowing into the branch passage 16B flows into the cathode offgas passage 6B as it is. The cathode off gas flowing into the cathode off gas passage 6B is discharged to the outside air.

Further, when it is determined that the moisture reducer 18 has not absorbed moisture (No in the process of S205), the process of S206 is performed. That is, the electronic control unit 15 controls the three-way valve 17A and the three-way valve 17B, and causes the cathode offgas flowing through the cathode offgas passage 6A to flow into the branch passage 16B. Since the moisture reducing device 18 is not provided in the branch passage 16B, the cathode offgas flowing into the branch passage 16B flows into the cathode offgas passage 6B as it is. The cathode off gas flowing into the cathode off gas passage 6B is discharged to the outside air.

  In the first embodiment, in the process of S205, the electronic control unit 15 determines whether the cathode offgas discharged from the fuel cell stack 1 is hot and dry, but the present invention is not limited to this. That is, in the process of S205, the electronic control unit 15 may determine whether the cathode offgas discharged from the fuel cell stack 1 satisfies either a high temperature or a dry condition. In the process of S205, the electronic control unit 15 may determine whether the cathode off gas discharged from the fuel cell stack 1 is at a high temperature. In the process of S205, the electronic control unit 15 may determine whether the cathode offgas discharged from the fuel cell stack 1 is dry.

<Effects of First Embodiment>
When the electronic control unit 15 determines that white smoke is generated, the cathode offgas discharged from the fuel cell stack 1 to the cathode offgas passage 6A flows into the branch passage 16A and passes through the moisture reducer 18. When the cathode off-gas discharged to the outside air passes through the moisture reducer 18, a part of the moisture contained in the cathode off-gas is absorbed by the moisture reducer 18, so that the moisture contained in the cathode off-gas decreases.

  When the cathode offgas is discharged to the outside air in a state where the moisture contained in the cathode offgas is reduced, the water vapor contained in the cathode offgas is not condensed immediately. That is, the water vapor contained in the cathode off-gas with reduced moisture is not saturated. As a result, before the water vapor contained in the cathode offgas discharged to the outside air condenses, the cathode offgas discharged to the outside air becomes discrete. Therefore, the water vapor contained in the cathode off gas discharged to the outside air is not in a state where it can be visually recognized as white.

  Therefore, according to the fuel cell system according to the first embodiment, it is possible to suppress the generation of white smoke caused by discharging the cathode off gas to the outside air. Furthermore, since it is not necessary to heat the cathode off gas with an electric heater or the like that consumes a large amount of electricity, the generation of white smoke can be suppressed by an efficient method that reduces the use of electricity.

Second Embodiment
A fuel cell system according to a second embodiment of the present invention will be described with reference to FIGS. In the first embodiment, the case where a desiccant such as silica is used as the moisture reducer 18 has been described. In the second embodiment, a case where a mechanical dehumidifier is used as the moisture reducer 18 will be described. Other configurations of the fuel cell system according to the second embodiment are the same as the configurations of the fuel cell system according to the first embodiment shown in FIG. Therefore, the same components are denoted by the same reference numerals as those in the first embodiment, and description thereof is omitted.

  FIG. 5 is a flowchart for explaining the operation of the fuel cell system according to the second embodiment. While the cathode off gas discharged from the fuel cell stack 1 is discharged to the outside air (for example, during power generation of the fuel cell), the fuel cell system according to the second embodiment operates.

  First, the electronic control unit 15 acquires data on the outside air temperature, the outside air humidity, and the cathode off-gas temperature (S501). The processing of S501 is the same as the processing of S201 described in the first embodiment, and detailed description thereof is omitted.

  Next, the electronic control unit 15 determines whether white smoke is generated based on the measured outside air temperature data, the measured outside air humidity data, and the cathode off gas temperature data (S502). The process of S502 is the same as the process of S202 described in the first embodiment, and detailed description thereof is omitted.

  When it is determined that white smoke is generated (when the result of S502 is affirmative), the electronic control unit 15 controls the three-way valve 17A and the three-way valve 17B to cause the cathode offgas flowing through the cathode offgas passage 6A to flow into the branch passage 16A. (S503). That is, the three-way valve 17A and the three-way valve 17B are switched so that the cathode offgas flowing through the cathode offgas passage 6A flows into the branch passage 16A. The cathode offgas flowing into the branch passage 16A passes through the moisture reducer 18 provided in the branch passage 16A and flows into the cathode offgas passage 6B.

  FIG. 6 is a diagram illustrating the moisture reducer 18 according to the second embodiment in detail. As shown in FIG. 6, the moisture reducer 18 is provided in the branch passage 16A. Therefore, the cathode off gas flowing into the branch passage 16 </ b> A passes through the moisture reducer 18. In the second embodiment, a dehumidifier is used as the moisture reducer 18. The electronic control unit 15 and the moisture reducer 18 are electrically connected, and the electronic control unit 15 controls the driving of the moisture reducer 18. When the moisture reducer 18 is driven, a part of the moisture contained in the cathode offgas flowing into the branch passage 16A is dehumidified (absorbed). The power source of the moisture reducer 18 may use the power generation of the fuel cell stack 1. The electronic control unit 15 controls the three-way valve 17A and the three-way valve 17B and drives the moisture reducer 18 to dehumidify a part of the moisture contained in the cathode offgas flowing into the branch passage 16A.

  In the second embodiment, the case where a dehumidifier is used as the moisture reducer 18 has been described, but the present invention is not limited to this. For example, a gas-liquid separator that separates the cathode offgas and the moisture contained in the cathode offgas may be used as the moisture reducer 18. When a gas-liquid separator is used as the moisture reducer 18, an outlet for discharging the moisture separated by the gas-liquid separator may be provided in the branch passage 16A. Moreover, you may provide further the drain tank which stores the water | moisture content isolate | separated by the gas-liquid separator. In this case, an outlet for discharging the water stored in the drain tank may be provided in the branch passage 16A.

  When it is determined that white smoke is generated, the amount of water vapor contained in the cathode off gas flowing through the cathode off gas passage 6A is saturated (or close to saturation). Therefore, when the cathode off gas passes through the moisture reducer 18 provided in the branch passage 16A, a part of the moisture contained in the cathode off gas is dehumidified by the moisture reducer 18. The cathode offgas that has passed through the moisture reducer 18 provided in the branch passage 16A flows into the cathode offgas passage 6B. The cathode off gas flowing into the cathode off gas passage 6B is discharged to the outside air.

  Returning to the description of FIG. When it is determined that white smoke does not occur (No in S502), the electronic control unit 15 controls the three-way valve 17A and the three-way valve 17B and flows the cathode off gas flowing through the cathode off gas passage 6A into the branch passage 16B. (S504). That is, the three-way valve 17A and the three-way valve 17B are switched so that the cathode offgas flowing through the cathode offgas passage 6A flows into the branch passage 16B. The cathode offgas flowing into the branch passage 16B flows into the cathode offgas passage 6B as it is. The cathode off gas flowing into the cathode off gas passage 6B is discharged to the outside air.

<Effects of Second Embodiment>
When the electronic control unit 15 determines that white smoke is generated, the cathode offgas discharged from the fuel cell stack 1 to the cathode offgas passage 6A flows into the branch passage 16A and passes through the moisture reducer 18. When the cathode offgas discharged to the outside air passes through the moisture reducer 18, a part of the moisture contained in the cathode offgas is dehumidified by the moisture reducer 18, so that the moisture contained in the cathode offgas decreases.

  When the cathode offgas is discharged to the outside air in a state where the moisture contained in the cathode offgas is reduced, the water vapor contained in the cathode offgas is not condensed immediately. That is, the water vapor contained in the cathode off-gas with reduced moisture is not saturated. As a result, before the water vapor contained in the cathode offgas discharged to the outside air condenses, the cathode offgas discharged to the outside air becomes discrete. Therefore, the water vapor contained in the cathode off gas discharged to the outside air is not in a state where it can be visually recognized as white.

  Therefore, according to the fuel cell system concerning a 2nd embodiment, it becomes possible to control generation of white smoke by discharging cathode off gas to outside air. Furthermore, since it is not necessary to heat the cathode off gas with an electric heater or the like that consumes a large amount of electricity, the generation of white smoke can be suppressed by an efficient method that reduces the use of electricity.

<Third Embodiment>
A fuel cell system according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a diagram illustrating a configuration example of a fuel cell system according to the third embodiment.

  As shown in FIG. 7, a cathode offgas passage 6C, a humidifier 50, a bypass passage 51, and a bypass valve 52 are added to the configuration of the fuel cell system described in the first embodiment. Other configurations of the fuel cell system according to the third embodiment are the same as the configurations of the fuel cell system according to the first embodiment shown in FIG. Therefore, the same components are denoted by the same reference numerals as those in the first embodiment, and description thereof is omitted. The humidifier 50 corresponds to the moisture reducing means of the present invention.

  The humidifier 50 humidifies the cathode gas flowing through the cathode gas passage 5. The humidifier 50 humidifies the cathode offgas flowing through the cathode offgas passage 6A and discharges it to the cathode offgas passage 6C. Further, the humidifier 50 moves a part of the moisture contained in the cathode offgas flowing through the cathode offgas passage 6 </ b> A to the cathode gas flowing through the cathode gas passage 5. That is, a part of the water contained in the cathode off gas discharged from the fuel cell stack 1 returns to the fuel cell stack 1 again via the humidifier 50.

  The bypass passage 51 is provided in the cathode gas passage 5. A bypass valve 52 is provided in the bypass passage 51. When the bypass valve 52 is open, the cathode gas flowing through the cathode gas passage 5 is supplied to the fuel cell stack 1 via the bypass passage 51. Since the humidifier 50 has a large resistance, when the bypass valve 52 is open, the cathode gas flowing through the cathode passage 5 hardly passes through the humidifier 50. On the other hand, when the bypass valve 52 is closed, the cathode gas flowing through the cathode gas passage 5 passes through the humidifier 50 and is supplied to the fuel cell stack 1.

  The electronic control unit 15 and the humidifier 50 are electrically connected, and the electronic control unit 15 controls the driving of the humidifier 50. The electronic control unit 15 and the bypass valve 52 are electrically connected, and the electronic control unit 15 controls the opening and closing of the bypass valve 52.

  FIG. 8 is a flowchart for explaining the operation of the fuel cell system according to the third embodiment. While the cathode off gas discharged from the fuel cell stack 1 is discharged to the outside air (for example, during power generation of the fuel cell), the fuel cell system according to the third embodiment operates.

  Normally, the electronic control unit 15 stops the driving of the humidifier 50 by controlling the driving of the humidifier 50 and keeps the bypass valve 52 open by controlling the bypass valve 52 ( S801). That is, the water content in the fuel cell stack 1 is kept low. When the bypass valve 52 is open, the cathode gas flowing through the cathode gas passage 5 is supplied to the fuel cell stack 1 via the bypass passage 51. Therefore, the cathode gas flowing through the cathode passage 5 hardly passes through the humidifier 50, so that the water content in the fuel cell stack 1 is low. Further, the electronic control unit 15 controls the three-way valve 17A and the three-way valve 17B to cause the cathode offgas flowing through the cathode offgas passage 6C to flow into the branch passage 16B. The cathode offgas flowing into the branch passage 16B flows into the cathode offgas passage 6B and is discharged to the outside air. Further, a shut valve may be provided in the cathode gas passage 5 immediately before the humidifier 50. When the driving of the humidifier 50 is stopped and the bypass valve 52 is open, the cathode gas flowing through the cathode passage 5 can be prevented from passing through the humidifier 50 by closing the shut valve.

  Next, the electronic control unit 15 acquires the outside air temperature, the outside air humidity, and the cathode off-gas temperature (S802). The processing of S802 is the same as the processing of S201 described in the first embodiment, and detailed description thereof is omitted.

  Next, the electronic control unit 15 determines whether white smoke is generated based on the measured outside air temperature data, the measured outside air humidity data, and the cathode off gas temperature data (S803). The processing of S803 is the same as the processing of S202 described in the first embodiment, and detailed description thereof is omitted.

  When it is determined that white smoke is generated (in the case of positive determination in step S803), the electronic control unit 15 starts driving the humidifier 50 by controlling the driving of the humidifier 50, and controls the bypass valve 52. By doing so, the bypass valve 52 is closed (S804). When the humidifier 50 is driven and the bypass valve 52 is closed, a part of the cathode off-gas that is discharged from the fuel cell stack 1 and flows through the cathode off-gas passage 6 </ b> A flows into the cathode gas passage 5 through the humidifier 50. Move to. Therefore, the water content of the cathode off gas flowing through the cathode gas passage 6C is smaller than the water content of the cathode off gas flowing through the cathode off gas passage 6A. In the third embodiment, the process of starting the driving of the humidifier 50 by controlling the driving of the humidifier 50 by the electronic control unit 15 and closing the bypass valve 52 by controlling the bypass valve 52 is referred to as a moisture movement process. .

  On the other hand, if it is determined that white smoke does not occur (No in step S803), the electronic control unit 15 controls the driving of the humidifier 50 so that the driving of the humidifier 50 remains in a stopped state and bypasses. By controlling the valve 52, the bypass valve 52 is left open (S805). The cathode offgas flows through the cathode offgas passage 6C, the branch passage 16B, and the cathode offgas passage 6B and is discharged to the outside air without moving the moisture of the cathode offgas flowing through the cathode offgas passage 6A.

  Further, when the cathode gas is insufficiently humidified, such as at a high temperature, that is, when the cathode gas supplied to the fuel cell stack needs to be humidified, the moisture transfer process may be performed. By performing the moisture transfer process, the cathode gas flowing through the cathode gas passage 5 is supplied to the fuel cell stack 1 in a humidified state.

A cathode offgas passage 6C, a humidifier 50, a bypass passage 51, and a bypass valve 52 are added to the fuel cell system including the branch passage 16A, the branch passage 16B, the three-way valve 17A, the three-way valve 17B, and the moisture reducer 18. Three embodiments have been described. Instead of this, a fuel cell system that does not include the branch passage 16A, the branch passage 16B, the three-way valve 17A, the three-way valve 17B, and the moisture reducer 18 is added to the cathode offgas passage 6C, the humidifier 50, the bypass passage 51, and the bypass valve 52. The third embodiment may be realized by adding.

  In addition, the cathode off-gas passage 6C, the humidifier 50, the bypass passage 51, and the bypass valve 52 are added to the configuration of the fuel cell system described in the first embodiment, and the third embodiment has been described. Instead, the third embodiment may be realized by adding the cathode offgas passage 6C, the humidifier 50, the bypass passage 51, and the bypass valve 52 to the configuration of the fuel cell system described in the second embodiment. .

  FIG. 9 shows the moisture content of the cathode off-gas at the point A of the cathode off-gas passage 6A and the point B of the cathode off-gas passage 6C in the normal state and the state where the moisture movement process is performed. The normal state is a state where the driving of the humidifier 50 is stopped and the bypass valve 52 is opened. The moisture content of the cathode offgas is the relative humidity of the cathode offgas.

  The upper part of FIG. 9 shows a normal state or a state (moisture transfer state) in which moisture transfer processing is performed. The middle part of FIG. 9 shows the moisture content of the cathode offgas at point A of the cathode offgas passage 6A. The lower part of FIG. 9 shows the moisture content of the cathode offgas at point B in the cathode offgas passage 6C.

  In the normal state (A), the moisture content of the cathode offgas at point A of the cathode offgas passage 6A and the moisture content of the cathode offgas at point B of the cathode offgas passage 6C are both constant. In the normal state (A), the moisture content of the cathode offgas at the point A of the cathode offgas passage 6A and the moisture content of the cathode offgas at the point B of the cathode offgas passage 6C are the same. This is because in the normal state (A), since the driving of the humidifier 50 is stopped, there is no movement of moisture in the cathode offgas flowing through the cathode offgas passage 6A.

  In the moisture movement state (B), the moisture content of the cathode offgas at the point A of the cathode offgas passage 6A gradually increases. The moisture movement state (B) is a case where moisture movement processing is performed when it is determined that white smoke is generated. When the moisture transfer process is performed, the cathode gas flowing through the cathode gas passage 5 is humidified and supplied to the fuel cell stack 1. Then, a certain amount of moisture contained in the humidified cathode gas is stored in the fuel cell stack 1 and gradually discharged to the cathode offgas passage 6A. Therefore, in the moisture movement state (B), the moisture content of the cathode offgas at the point A of the cathode offgas passage 6A gradually increases.

  In the moisture movement state (B), the moisture content of the cathode offgas at the point B of the cathode offgas passage 6C decreases rapidly and gradually increases. The moisture content of the cathode off gas at point B in the cathode off gas passage 6C is constant. When the moisture movement process is performed, a part of the moisture contained in the cathode offgas flowing through the cathode offgas passage 6 </ b> A moves to the cathode gas flowing through the cathode passage 5. Immediately after the moisture transfer process is performed, most of the moisture contained in the cathode offgas flowing through the cathode offgas passage 6A moves to the cathode gas flowing through the cathode passage 5, so that the amount of moisture in the cathode offgas at point B in the cathode offgas passage 6C is , Decrease rapidly. The cathode gas flowing through the cathode gas passage 5 is humidified and supplied to the fuel cell stack 1. Therefore, the amount of moisture contained in the cathode offgas passing through the humidifier 50 exceeds the amount of moisture moved by the humidifier 50, and the amount of moisture in the cathode offgas at point B in the cathode offgas passage 6C gradually increases.

In the normal state (C), the moisture content of the cathode offgas at the point A of the cathode offgas passage 6A gradually decreases. In the normal state (C), the cathode gas flowing through the cathode gas passage 5 is supplied to the fuel cell stack 1 without being humidified. Then, the cathode offgas is gradually discharged from the fuel cell stack 1 to the cathode offgas passage 6A. Therefore, in the normal state (C), the moisture content of the cathode offgas at the point A of the cathode offgas passage 6A gradually decreases.

  In the normal state (C), the moisture content of the cathode offgas at point B of the cathode offgas passage 6C increases rapidly and gradually decreases. In the normal state (C), since the driving of the humidifier 50 is stopped, the movement of moisture contained in the cathode offgas flowing through the cathode offgas passage 6A is eliminated. Therefore, immediately after the moisture transfer state (B) is changed to the normal state (C), the cathode offgas moisture amount at point B of the cathode offgas passage 6C increases rapidly. In the normal state (C), since the cathode gas flowing through the cathode gas passage 5 is not humidified, the moisture content of the cathode off gas gradually decreases at the point B of the cathode off gas passage 6C.

  In the moisture movement state (D), the moisture content of the cathode offgas at the point A of the cathode offgas passage 6A gradually increases. The moisture movement state (D) is a case where the moisture movement treatment is performed when humidification of the cathode gas is insufficient, such as at a high temperature. When the moisture transfer process is performed, the cathode gas flowing through the cathode gas passage 5 is humidified and supplied to the fuel cell stack 1. Then, a certain amount of moisture contained in the humidified cathode gas is stored in the fuel cell stack 1 and gradually discharged to the cathode offgas passage 6A. Therefore, in the moisture movement state (B), the moisture content of the cathode offgas at the point A of the cathode offgas passage 6A gradually increases.

  In the moisture movement state (D), the cathode offgas moisture amount at the point B of the cathode offgas passage 6C rapidly decreases and gradually increases. The moisture content of the cathode off gas at point B in the cathode off gas passage 6C is constant. When the moisture movement process is performed, a part of the moisture contained in the cathode offgas flowing through the cathode offgas passage 6 </ b> A moves to the cathode gas flowing through the cathode passage 5. Immediately after performing the moisture transfer process, most of the moisture contained in the cathode offgas flowing through the cathode offgas passage 6A moves to the cathode gas flowing through the cathode passage 5, so that the amount of moisture in the cathode offgas at point B of the cathode offgas passage 6C is , Decrease rapidly. The cathode gas flowing through the cathode gas passage 5 is humidified and supplied to the fuel cell stack 1. Therefore, the amount of moisture contained in the cathode offgas passing through the humidifier 50 exceeds the amount of moisture moved by the humidifier 50, and the amount of moisture in the cathode offgas at point B in the cathode offgas passage 6C gradually increases.

<Effect of the third embodiment>
When it is determined by the electronic control unit 15 that white smoke is generated, the humidifier 50 is driven by the electronic control unit 15 and the bypass valve 52 is closed. A part of the moisture contained in the cathode offgas flowing through the cathode offgas passage 6 </ b> A moves to the cathode gas flowing through the cathode gas passage 5 by the humidifier 50. Therefore, moisture contained in the cathode offgas flowing through the cathode offgas passage 6C is reduced. When the cathode offgas is discharged to the outside air in a state where the moisture contained in the cathode offgas is reduced, the water vapor contained in the cathode offgas is not condensed immediately. That is, the water vapor contained in the cathode off-gas with reduced moisture is not saturated. As a result, before the water vapor contained in the cathode offgas discharged to the outside air condenses, the cathode offgas discharged to the outside air becomes discrete. Therefore, the water vapor contained in the cathode off gas discharged to the outside air is not in a state where it can be visually recognized as white.

  Therefore, according to the fuel cell system according to the third embodiment, it is possible to suppress the generation of white smoke caused by discharging the cathode off gas to the outside air. Furthermore, since it is not necessary to heat the cathode off gas with an electric heater or the like that consumes a large amount of electricity, the generation of white smoke can be suppressed by an efficient method that reduces the use of electricity.

<Modification>
In the first embodiment, the second embodiment, and the third embodiment, whether the electronic control unit 15 generates white smoke based on the cathode offgas temperature data, the measured outside air temperature data, and the measured outside air humidity data. Judgment was made. In this modification, the electronic control unit 15 is modified so as to determine whether white smoke is generated based on the measured outside air temperature data, the measured outside air humidity data, and the operating temperature data of the fuel cell stack 1. Also good.

  Specifically, in the process of S201 described in FIG. 2, the process of S501 described in FIG. 5, and the process of S802 described in FIG. 8, the electronic control unit 15 performs measurement outside air temperature data and measurement outside air humidity data. And the data of the operating temperature of the fuel cell stack 1 are acquired.

  Further, in the process of S202 described in FIG. 2, the process of S502 described in FIG. 5, and the process of S803 described in FIG. 8, the electronic control unit 15 performs measurement outside air temperature data, measured outside air humidity data, and fuel cell. It is determined whether white smoke is generated based on the operating temperature data of the stack 1. The relationship between the outside air temperature, the outside air humidity, the operating temperature of the fuel cell stack 1 and the generation of white smoke is obtained through experiments or simulations. For example, a map is created in advance by experiment or simulation. In this case, a map similar to the map described in FIG. 3 may be created. Then, the electronic control unit 15 determines whether white smoke is generated from the map. When determining whether white smoke is generated using a map similar to the map described in FIG. 3, the electronic control unit 15 calculates ΔT2 which is the difference between the operating temperature of the fuel cell stack 1 and the measured outside air temperature. calculate. Then, the battery control unit 15 refers to a map similar to the map described in FIG. 3 and determines whether white mist is generated based on ΔT2 and the measured outside air humidity.

  By modifying the processing of S201 and S202 described in FIG. 2, the processing of S501 and S502 described in FIG. 5, and the processing of S802 and S803 described in FIG. It is possible to determine whether white smoke is generated based on the measured outside air temperature data, the measured outside air humidity data, and the operating temperature data of the fuel cell stack 1.

It is a figure which shows the structural example of the fuel cell system which concerns on 1st Embodiment. It is a flowchart explaining operation | movement of the fuel cell system which concerns on 1st Embodiment. It is the figure which showed the example of the map (table) of the fuel cell system which concerns on 1st Embodiment. It is the figure explaining the moisture reducing device 18 of 1st Embodiment in detail. It is a flowchart explaining operation | movement of the fuel cell system which concerns on 2nd Embodiment. It is the figure explaining the moisture reducing device 18 of 2nd Embodiment in detail. It is a figure which shows the structural example of the fuel cell system which concerns on 3rd Embodiment. It is a flowchart explaining operation | movement of the fuel cell system which concerns on 3rd Embodiment. It is the figure which showed the moisture content of the cathode off gas in the point A of 6 A of cathode off gas passages, and the B point of cathode off gas passage 6C.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 2 Anode gas passage 3 Anode off gas passage 4 Anode off gas circulation passage 5 Cathode gas passage 6 Cathode off gas passage 7 Hydrogen tank 8 Hydrogen pump 9 Pump 10 Pressure regulating valve 11 Filter 12 Gas-liquid separator 13 Drain tank 14 Exhaust drain valve 15 Electronic control unit (ECU)
16A, 16B Branch passages 17A, 17B Three-way valve 18 Moisture reducer 19 Temperature sensor 20 External sensor 21 Stack sensor 50 Humidifier 51 Bypass passage 52 Bypass valve

Claims (5)

A fuel cell body;
Determining means for determining whether or not condensation of water vapor contained in the off gas occurs when the off gas discharged from the fuel cell body is discharged to the outside air;
A fuel cell system comprising: a moisture reducing unit that reduces moisture contained in the off gas. A gas discharge passage through which off-gas discharged from the fuel cell body passes;
The fuel cell system according to claim 1, wherein the moisture reducing means is provided in the gas discharge passage. The gas discharge passage includes a branch passage that is divided into at least two from the middle,
A switching means for connecting the gas discharge passage and one of the branch passages;
The moisture reducing means is provided in one of the branch passages,
When it is determined that condensation of the water vapor occurs, the determination means controls the switching means, and connects the gas discharge passage and the branch passage provided with the moisture reduction means, thereby The fuel cell system according to claim 2, wherein the off gas is supplied to a reducing unit. The moisture reducing means absorbs moisture contained in the supplied off gas, and releases the absorbed moisture by being supplied with a high temperature and dry off gas,
The determination means determines whether or not the off-gas is high temperature and dry. When it is determined that the off-gas is high temperature and dry, the determination means controls the switching means, and the gas discharge passage and the moisture reduction are controlled. The fuel cell system according to claim 3, wherein the off gas is supplied to the moisture reducing means by connecting the branch passage provided with the means. A gas supply passage through which the gas supplied to the fuel cell body passes;
The moisture reducing means is driven to reduce the moisture contained in the off gas by moving a part of the moisture contained in the off gas passing through the gas discharge passage to the gas passing through the gas supply passage.
The fuel cell system according to claim 2, wherein the determination unit drives the moisture reduction unit when it is determined that condensation of the water vapor occurs.

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