JP2009009762A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely separate offgas from liquid independently of environment temperature. <P>SOLUTION: The fuel cell system 100 is provided with a fuel cell stack 50, a stack case 62 housing the fuel cell stack 50, a fuel gas exhaust channel 54 exhausting offgas of fuel gas from the fuel cell stack 50, and a gas liquid separator 56 communicated with the fuel gas exhaust channel 54 for separating flowing-in offgas from liquid. The gas liquid separator 56, installed outside the stack case 62, restrains moisture from freezing inside it 56, by introducing at least a part of a cooling medium into a coolant guide-in channel 72 in the vicinity of it 56 at cold times. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system that reuses discharged off-gas.

  An outline of a configuration of a general unit cell (also referred to as a fuel cell unit cell) corresponding to the minimum unit of the fuel cell, in particular, a main part including an electrode portion will be described. As illustrated in FIG. 2, a cathode catalyst layer 12 (also referred to as an oxidation electrode or a cathode electrode) and an anode catalyst layer 14 (also referred to as a fuel electrode or an anode electrode) are provided so as to face each other with the electrolyte membrane 10 interposed therebetween. A so-called membrane electrode assembly (MEA) 30 is configured. A cathode diffusion layer 16 is provided outside the cathode catalyst layer 12, and an anode diffusion layer 18 is provided outside the anode catalyst layer 14. Further, a cathode-side separator 26 in which an oxidizing gas flow path 20 and a cell refrigerant flow path 22 are formed is formed outside the cathode diffusion layer 16, and a fuel gas flow path 24 and a cell refrigerant flow are formed outside the anode diffusion layer 18. Anode separators 28 with passages 22 formed therein are provided, and these are integrated by, for example, adhesion or pressure bonding to form a single cell 40.

  Fuel cell stacks (also referred to as FC stacks) in which a plurality of obtained single cells 40 are stacked so as to obtain a desired electromotive force are applied in various fields. In general, the fuel cell stack generates electricity by supplying an oxidation gas such as oxygen or air to the cathode catalyst layer 12 and a fuel gas such as hydrogen to the anode catalyst layer 14. Such a fuel cell is usually controlled to have a predetermined temperature range of, for example, about 60 ° C. to 100 ° C. during power generation, but generates heat associated with a chemical reaction during power generation. A cooling medium (refrigerant) is circulated through the cell refrigerant flow path 22 provided in each single cell to prevent overheating of the fuel cell.

  In this way, a chemical reaction occurs at the fuel electrode and the oxidation electrode, and charges are generated to function as a battery. This fuel cell has various studies as a clean energy source because it has abundant raw material gas and liquid fuel used for power generation, and because of the principle of power generation, the discharged substance is water. Has been.

  In general, in order for a fuel cell to generate electric power satisfactorily, a predetermined amount of water (water content) is maintained with respect to the electrolyte membrane 10 in which, for example, a fluorine-based ion exchange resin such as perfluoro-based or perfluorosulfonic acid is used. Thus, it is preferable to exhibit the function as a proton permeable membrane. For example, moisture adjustment of the electrolyte membrane 10 is performed by humidifying one or both of the reaction gases supplied into the fuel cell. On the other hand, moisture may freeze when it is cold, and depending on the frozen part, it may be a cause of blockage of the flow path and functional degradation, so it is also used for humidification of generated water and reaction gas, for example in the gas flow path It is also necessary to consider the prevention of freezing of moisture.

  On the other hand, the fuel gas and the oxidizing gas supplied into the single cell are consumed by reacting with each other across the MEA (the fuel gas and the oxidizing gas are also called reactive gases), but a part of them is unreacted The exhaust gas remains in the exhaust gas (this is also referred to as off-gas). A method for further improving energy utilization efficiency by reusing such an unreacted reactive raw material such as hydrogen or oxygen or off-gas containing moisture has been studied.

  Patent Document 1 describes a fuel cell system provided with a cooling means in order to improve the recovery amount of liquid moisture (also referred to as liquid water) from exhaust gas in a gas-liquid separator.

  Patent Document 2 describes a technique for preventing freezing of generated water during cold using a cooling medium heated by discharged off-gas or heat exchange.

  Patent Document 3 describes supplying an antifreeze liquid in order to prevent problems associated with freezing of produced water during cold weather.

JP 2002-313383 A JP 2006-147440 A JP 2006-286544 A

  By the way, among the offgas discharged from the fuel cell stack, the fuel gas offgas discharged particularly from the fuel electrode side contains moisture derived from the generated water accompanying the cell reaction as described above. On the other hand, the generated water contained in the offgas may contain an acidic substance due to the electrolyte membrane, and generally shows strong acidity. For this reason, in order to reuse the off-gas of the fuel gas as a hydrogen supply source, at least the acidic substance derived from the electrolyte membrane should be removed to prevent or suppress deterioration of the pump, piping, single cell, fuel cell stack, etc. desirable.

  On the other hand, in order to further reduce the cost of the fuel cell system, the miniaturization of components and devices to be used and the simplification of the configuration have been studied.

  The present invention provides a fuel cell system capable of gas-liquid separation of off-gas reliably without depending on environmental temperature, for example, below freezing.

  The configuration of the present invention is as follows.

  (1) A fuel cell stack in which single cells using a reaction gas of a fuel gas and an oxidizing gas are stacked, a housing for housing the fuel cell stack, and a reaction for discharging off-gas of the reaction gas from the fuel cell stack A gas discharge channel; and a gas-liquid separation unit that communicates with the reaction gas discharge channel and separates the inflowing off-gas, and the gas-liquid separation unit is provided outside the casing. And a fuel cell system for condensing moisture in the off-gas flowing from the fuel cell stack through the reaction gas discharge channel.

  (2) In the fuel cell system according to the above (1), the reaction gas discharge channel is a fuel gas discharge channel that discharges off-gas of the fuel gas, and the gas-liquid separation unit removes the fuel gas from the off-gas of the fuel gas. A fuel cell system, further comprising a regeneration gas supply flow path for supplying the regeneration gas from which moisture separated by gas-liquid separation has been removed into the fuel cell stack.

  (3) In the fuel cell system according to the above (1) or (2), introduction of a refrigerant capable of introducing at least a part of a cooling medium used for cooling the fuel cell stack in the vicinity of the gas-liquid separation unit. A fuel cell, further comprising: a flow path; and a refrigerant introduction control unit that controls introduction of the cooling medium, wherein the refrigerant introduction control unit controls introduction of the cooling medium based on a temperature of the gas-liquid separation unit. system.

  According to the present invention, off-gas can be reliably gas-liquid separated.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 schematically shows the configuration of a fuel cell system according to an embodiment of the present invention.

  In FIG. 1, a fuel cell system 100 includes a fuel cell stack 50 in which a plurality of single cells 40 as illustrated in FIG. 2 are stacked using a fuel gas and an oxidizing gas as a reaction gas, and a stack case that accommodates the fuel cell stack 50. 62, a gas-liquid separator 56 provided outside the stack case 62, and a radiator 68.

  Further, a fuel gas supply channel 52 and an oxidizing gas supply channel 64 are provided as reaction gas supply channels to be supplied to the fuel cell stack 50, respectively, and discharge of off-gas of the reaction gas discharged from the fuel cell stack 50 is performed. As the flow paths, a fuel gas discharge flow path 54 and an oxidizing gas discharge flow path 66 are provided. On the other hand, refrigerant flow paths 70a and 70b for circulating a cooling medium are provided between the fuel cell stack 50 and the radiator 68. The heat generated in the fuel cell stack 50 and the refrigerant flow paths 70a and 70b are provided. The internal temperature of the fuel cell stack 50 is maintained within a predetermined range by heat exchange with the cooling medium flowing through the inside.

  In the present embodiment, for example, fuel gas such as hydrogen gas is supplied from a fuel gas supply source (not shown) capable of supplying fuel gas such as pure hydrogen gas or reformed gas via the fuel gas supply channel 52. 50. On the other hand, an oxidizing gas such as air or oxygen is supplied from an oxidizing gas supply source (not shown) capable of supplying an oxidizing gas such as air by an oxidizing gas supply mechanism such as an air compressor or pure oxygen gas from an oxygen cylinder. The fuel cell stack 50 is supplied via the flow path 64. When the reaction gas is supplied into the fuel cell stack 50, hydrogen in the fuel gas and oxygen in the oxidation gas are consumed in each single cell, and then the off-gas of each reaction gas is supplied to the fuel gas discharge channel 54. Are discharged from the fuel cell stack 50 through the oxidizing gas discharge flow channel 66, respectively.

  In the present embodiment, the fuel gas discharge channel 54 communicates with the gas-liquid separator 56. The gas-liquid separator 56 condenses at least a part of the water contained in the off-gas of the fuel gas discharged from the fuel cell stack 50 and flowing in through the fuel gas discharge flow path 54 into a gas phase and a liquid phase. Separate. At this time, since the gas-liquid separator 56 is provided outside the stack case 62, the temperature of the inflowing off-gas and the gas-liquid are substantially not affected by the heat generated in the fuel cell stack 50. Based on the difference between the ambient temperature of the separator 56 and the water content corresponding to the water content in the off-gas can be condensed.

  Here, the water contained in the off-gas of the fuel gas includes generated water generated by the electrode reaction in the fuel cell stack 50. The acidic substance contained in the off gas of the fuel gas together with the generated water and derived from the electrolyte membrane 10 shown in FIG. 2 is generally water-soluble. For this reason, most of it can be removed from the gas phase by dissolving this acidic substance in the liquid phase obtained by condensing the water in the off-gas using the gas-liquid separator 56.

  In this way, the fuel gas discharge channel 54 is communicated with the gas-liquid separator 56 to separate and remove impurities such as water-soluble acidic substances from off-gas containing hydrogen gas or water vapor derived from the fuel gas. The gas phase obtained can be reused as a regeneration gas that is part of the fuel gas. More specifically, as shown in FIG. 1, the gas-liquid separator is provided from the off-gas of the fuel gas by providing a regenerative gas supply channel 58 between the gas-liquid separator 56 and the fuel cell stack 50 so as to communicate therewith. The regenerated gas from which the moisture separated from the gas and liquid by 56 is removed can be supplied into the fuel cell stack 50 and reused. At this time, it is preferable to connect the regeneration gas supply flow path 58 to the upper part of the gas-liquid separator 56 so that components in the liquid phase separated by the gas-liquid separator 56 do not enter.

  In the embodiment shown in FIG. 1, the regeneration gas supply channel 58 is provided separately from the fuel gas supply channel 52. However, as another embodiment, the regeneration gas supply channel 58 is provided as a fuel. It is also possible to supply the fuel cell stack 50 after joining the gas supply flow path 52. Further, the flow rate and / or flow rate of the regeneration gas supplied from the regeneration gas supply channel 58 to the fuel cell stack 50 can be appropriately adjusted as necessary.

  On the other hand, the water phase stored in the lower part of the gas-liquid separator 56 is discharged to the outside of the fuel cell system 100 through the drainage flow channel 76 due to condensation. It is also suitable to discard or reuse the aqueous phase discharged at this time after performing neutralization treatment, ion removal treatment or the like, if necessary.

  In the embodiment of the present invention, any gas-liquid separator 56 shown in FIG. 1 may be used as long as gas-liquid separation can be performed according to the environmental temperature. A cooling type gas-liquid separator can be mentioned. The air-cooled gas / liquid separator performs condensation with air according to the environmental temperature, and has advantages such as a simple structure and easy maintenance. Further, the gas-liquid separator 56 is not limited to one, and a plurality of gas-liquid separators 56 may be used as necessary. Further, depending on the environmental temperature, a refrigerant cooling method using a cooling medium introduced into the refrigerant introduction flow path 72 (so-called water cooling method when the cooling medium is water) can be used in combination. Further, the gas-liquid separator 56 may be a separate member including a condenser that condenses off-gas and a storage unit that stores water condensed by the condenser.

  In the present embodiment, the material constituting the gas-liquid separator 56 is preferably a material having high thermal conductivity. However, since it is assumed that the water phase is retained for a predetermined period of time, a material having acid resistance is used. For example, stainless steel (SUS) or the like can be used, but is not limited thereto.

  In the present embodiment, in order to enhance the cooling action in the gas-liquid separator 56 and improve the gas-liquid separation efficiency, for example, fins that increase the heat transfer area between the air and the air are provided on the outer surface of the gas-liquid separator. It is also suitable to apply or to use a fan for blowing air. Furthermore, on the inner wall surface of the gas-liquid separator 56, it promotes the aggregation of moisture, such as forming irregularities and groove shapes to adjust the surface roughness, adjusting the water contact angle, and making it hydrophobic or hydrophilic. It is also preferable to adopt the configuration.

  The fuel cell system according to the embodiment of the present invention is particularly suitable for use in a place where the temperature can be adjusted, such as indoors, where there is little change in the environmental temperature. On the other hand, the refrigerant introduction flow path 72 and the refrigerant introduction control unit 74 shown in FIG. 1 are further provided under conditions where the environmental temperature changes greatly, such as outdoors, for example, even in cold weather, as described below. By providing, it becomes possible to prevent or suppress problems associated with the freezing of the produced water in the gas-liquid separator 56 provided outside the stack case 62 and in the vicinity thereof.

  In FIG. 1, the refrigerant introduction control unit 74 is configured to be able to control the introduction of the cooling medium into the refrigerant introduction flow path 72 based on the temperature of the gas-liquid separator 56. On the other hand, the refrigerant introduction flow path 72 is configured to be able to introduce at least a part of the cooling medium used for cooling the fuel cell stack 50 in the vicinity of the gas-liquid separator 56. Here, “in the vicinity of the gas-liquid separator 56” indicates that the temperature can be changed with respect to the gas-liquid separator 56 as the cooling medium is introduced into the refrigerant introduction flow path 72. The specific distance may be appropriately set according to the material of the refrigerant introduction flow path 72, the temperature of the cooling medium to be introduced, and the like, and is not particularly limited. It is also preferable to adjust the flow rate and / or flow rate of the cooling medium introduced into the refrigerant introduction flow path 72 as necessary.

  In the present embodiment, when a temperature sensor (not shown) provided in the gas-liquid separator 56 detects that the temperature has decreased to a predetermined temperature, for example, 0 ° C., the refrigerant introduction control unit 74 opens the valves v1 and v2 to cool the cooling. Control to introduce the medium into the refrigerant introduction flow path 72 is performed. At this time, the temperature of the cooling medium has risen to a predetermined temperature, for example, about 30 ° C. to 60 ° C. due to circulation between the fuel cell stack 50 and the radiator 68, and therefore, by introduction of the cooling medium into the refrigerant introduction flow path 72. The temperature of the gas-liquid separator 56 gradually increases. When the temperature sensor provided in the gas-liquid separator 56 detects that the temperature has risen to a predetermined temperature, for example, 10 ° C., the refrigerant introduction control unit 74 closes the valves v1 and v2, and the cooling medium to the refrigerant introduction channel 72 Control to stop the introduction of. The temperature of the gas-liquid separator 56 detected by the temperature sensor can be the internal temperature, or can be the temperature of the members constituting the gas-liquid separator 56.

  The cooling medium introduction control as described above with respect to the refrigerant introduction flow path 72 shown in FIG. 1 can be suitably performed particularly immediately after the start of the start of the fuel cell stack 50, but other embodiments are possible. The temperature sensor provided in the gas-liquid separator 56 monitors the temperature of the gas-liquid separator 56 constantly or at predetermined intervals, and controls the introduction of the cooling medium according to the temperature change of the gas-liquid separator 56. It is also suitable. Further, the configuration of the valves v1 and v2 for adjusting the introduction of the cooling medium with respect to the refrigerant introduction flow path 72 is an example, and it is needless to say that the configuration is not limited to the configuration shown in FIG. It is also possible to control by opening and closing.

  In the present embodiment shown in FIG. 1, the cooling medium introduced into the refrigerant introduction flow path 72 is configured to flow through the fuel cell stack 50 and introduce a temperature rise from the refrigerant flow path 70b. For example, the cooling medium cooled by heat exchange in the radiator 68 may be introduced from the refrigerant flow path 70a. According to this configuration, for example, gas-liquid separation can be performed under a temperature condition lower than the environmental temperature, and accordingly, it is assumed that the amount of liquid phase obtained by condensation of moisture increases. By applying this configuration to, for example, gas-liquid separation of off-gas of oxidant gas instead of off-gas of fuel gas, water that is a liquid phase obtained by gas-liquid separation is not directly discharged together with off-gas, for example, without oxidation. Although it is possible to re-use as a gas humidifying material, this configuration is particularly suitable for a fuel cell system mounted on a moving body such as a vehicle.

  As shown in FIG. 1, in the fuel cell system 100 according to the embodiment of the present invention, the fuel gas system circulation mechanism excluding the gas-liquid separator 56 is substantially in the stack case 62 except for a part of the piping portion. All are housed. In the portion accommodated in the stack case 62, it is possible to prevent or suppress problems such as freezing of moisture accompanying a decrease in environmental temperature. In particular, by including the pump (or injector) 60 that contributes to the supply of the regeneration gas to the fuel cell stack 50 in the stack case 62, noise (abnormal noise) caused by high-speed rotation of the motor, etc. Since vibration can be reduced and suppressed, it is preferable. On the other hand, the gas-liquid separator 56 is provided outside the stack case 62. This makes it possible to gas-liquid-separate off-gas of the fuel gas reliably regardless of the internal temperature of the stack case 62 associated with the operation of the fuel cell stack 50. On the other hand, at the time of cold, By introducing the refrigerant into the refrigerant introduction flow path 72 in the vicinity of the liquid separator 56, it becomes possible to suppress freezing of moisture inside the gas-liquid separator 56.

  Thus, according to the embodiment of the present invention, it is possible to gas-liquid-separate offgas reliably without depending on the environmental temperature.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used in a fuel cell system that recycles the reaction gas off-gas by gas-liquid separation.

It is a figure which shows the outline of a structure of the fuel cell system in embodiment of this invention. It is a figure which illustrates the outline of a structure of a single cell.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Electrolyte membrane, 12 Cathode catalyst layer, 14 Anode catalyst layer, 16 Cathode diffusion layer, 18 Anode diffusion layer, 20 Oxidation gas flow path, 22 Cell refrigerant flow path, 24 Fuel gas flow path, 26 Cathode side separator, 28 Anode side Separator, 30 membrane electrode assembly (MEA), 40 single cell, 50 fuel cell stack, 52 fuel gas supply flow path, 54 fuel gas discharge flow path, 56 gas-liquid separator, 58 regenerative gas supply flow path, 60 pump, 62 Stack case, 64 Oxidizing gas supply channel, 66 Oxidizing gas discharge channel, 68 Radiator, 70a, 70b Refrigerant channel, 72 Refrigerant introduction channel, 74 Refrigerant introduction controller, 76 Drain channel, 100 Fuel cell system.

Claims (3)

A fuel cell stack in which unit cells using fuel gas and oxidizing gas as reaction gases are stacked;
A housing for housing the fuel cell stack;
A reaction gas discharge channel for discharging the off gas of the reaction gas from the fuel cell stack;
A gas-liquid separation means that communicates with the reaction gas discharge flow path and separates the off-gas flowing into the gas-liquid;
With
The gas-liquid separation means is provided outside the casing and condenses moisture in off-gas flowing from the fuel cell stack through the reaction gas discharge channel. The fuel cell system according to claim 1,
The reaction gas discharge flow path is a fuel gas discharge flow path for discharging off-gas of the fuel gas,
A fuel cell system, further comprising a regeneration gas supply channel for supplying regeneration gas from the fuel gas off-gas separated from the fuel gas off-gas by the gas-liquid separation means into the fuel cell stack. The fuel cell system according to claim 1 or 2,
A refrigerant introduction passage capable of introducing at least a part of a cooling medium provided for cooling the fuel cell stack in the vicinity of the gas-liquid separation unit;
A refrigerant introduction control unit for controlling introduction of the cooling medium;
Further comprising
The refrigerant introduction control unit controls introduction of the cooling medium based on a temperature of the gas-liquid separation unit.

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