JP2007066918A - Power generation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power generation method reducing the generation amount of hydrogen gas, hardly producing problems of exhaust gas treatment or gas discharge, and stably, continuously, efficiently conducting power generation. <P>SOLUTION: In the power generation method conducting power generation by supplying hydrogen gas and oxygen-containing gas to a single unit cell or a plurality of unit cells UC each comprising a plate-shaped solid polymer electrolyte 1, a cathode side electrode plate 2, an anode side electrode plate 3, an oxygen-containing gas supply part supplying oxygen-containing gas to the cathode side electrode plate 2, and a hydrogen gas passage part supplying hydrogen gas to the anode side electrode plate, and in the unit cell UC which forms the final stage of the hydrogen supply, impurity gas is concentrated in the vicinity of exhaust port by flowing of the hydrogen gas, the small amount of concentrated impurity gas is exhausted from the unit cell UC so that the amount of the concentrated impurity gas becomes a certain value or less and in this state, power generation is conducted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power generation method for generating power by supplying hydrogen gas and oxygen-containing gas to a unit cell (including natural supply), and is particularly useful for portable devices.

  Polymer fuel cells that use solid polymer electrolytes such as polymer electrolytes have high energy conversion efficiency, are thin, small, and lightweight, and are therefore being actively developed for household cogeneration systems and automobiles . As a conventional structure of such a fuel cell, one shown in FIG. 9 is known (see, for example, Non-Patent Document 1).

  That is, as shown in FIG. 9, the anode 101 and the cathode 102 are disposed with the solid polymer electrolyte membrane 100 interposed therebetween. Further, the unit cell 105 is configured by being sandwiched by a pair of separators 104 via a gasket 103. Each separator 104 is formed with a gas flow path groove. A flow path for reducing gas (for example, hydrogen gas) is formed by contact with the anode 101, and an oxidizing gas (for example, for example, hydrogen gas) is contacted with the cathode 102. Oxygen gas) flow paths are formed. Each gas is supplied to the electrode reaction (chemical reaction at the electrode) by the action of the catalyst supported in the anode 101 or the cathode 102 while flowing through each flow path in the unit cell 105, and the generation of current and ions Conduction occurs.

  A large number of the unit cells 105 are stacked, and the unit cells 105 are electrically connected in series to constitute the fuel cell N, and the electrode 106 can be taken out from the unit cells 105 at both ends. Such a fuel cell N is attracting attention as a power source for electric vehicles and a distributed power source for home use in various applications because of its clean and high efficiency.

  On the other hand, with the recent activation of IT technology, mobile devices such as mobile phones, notebook computers, and digital cameras tend to be frequently used, but most of these power sources use lithium ion secondary batteries. However, as mobile devices become more sophisticated, power consumption has increased and clean and highly efficient fuel cells have been attracting attention as power sources.

  For this reason, as a fuel cell capable of further miniaturization, a solid polymer electrolyte membrane / electrode assembly, a cathode side metal plate in which a flow path for oxidant gas is formed, and an anode side metal in which a flow path for fuel gas is formed There has been proposed a fuel cell having a structure in which a metal plate on both sides is fastened with fixing pins and sealed with a gas packing around the inside (see, for example, Patent Document 1).

  However, in any of the above fuel cells, after supplying fuel gas such as hydrogen gas, 50 to 80% of the fuel cell is consumed by reaction, and the remaining fuel gas is discharged from the unit cell in the final stage. ing. For this reason, when hydrogen gas is used as the fuel, the amount of hydrogen gas discharged increases, and the problem of exhaust gas treatment and gas emission arises. Therefore, it is not suitable for portable device applications from the viewpoint of cost, device size, etc. It was.

  On the other hand, in Patent Document 2 below, when pure hydrogen gas is supplied to the anode side of the unit cell and power generation is performed, the concentration of the impurity gas on the anode side is detected, and when the concentration is above a certain level, the anode A fuel cell system for purging (discharging) gas from the side is disclosed.

  However, since this fuel cell system uses general fuel cells, for example, when the concentration of impurity gas in the exhaust gas from the anode side is 50% or more, the power generation efficiency is less than 50%. There is a problem that it cannot be used for normal power supply. Further, even if the concentration of hydrogen gas in the exhaust gas is reduced to less than 50%, the purge gas discharge amount increases, and there is a problem that the absolute amount of hydrogen gas discharged increases.

  Furthermore, in the fuel cell system described above, the concentration detection and purge control based on the concentration detection are complicated and expensive, and are difficult to apply to small and lightweight fuel cells for portable devices. In the method in which all hydrogen gas is consumed in the unit cell without being discharged from the unit cell, the impurity gas is concentrated in the hydrogen gas flow path in the unit cell, and the battery output decreases in a short time from the start of power generation.

Nikkei Mechanical separate volume "Fuel Cell Development Frontline" Date of issue: June 29, 2001, Publisher: Nikkei BP, Chapter 3, PEFC, 3.1 Principles and Features p46 JP-A-8-162145 Japanese Patent Laid-Open No. 2003-243020

  Accordingly, an object of the present invention is that a complicated control mechanism is not required, the amount of hydrogen gas discharged is small, and problems of exhaust gas treatment and gas release are unlikely to occur, and power generation can be performed stably and continuously efficiently. It is to provide a power generation method.

  The inventors of the present invention have intensively studied to achieve the above object. As a result, a unit cell having a sufficiently small channel cross-sectional area of the anode-side hydrogen gas channel portion is used, and 0% of hydrogen gas supplied to the unit cell is measured. It has been found that power generation can be performed stably and continuously by discharging power while discharging 0.02 to 4% by volume of gas, and the present invention has been completed.

  That is, the power generation method of the present invention includes a plate-shaped solid polymer electrolyte, a cathode-side electrode plate disposed on one side of the solid polymer electrolyte, an anode-side electrode plate disposed on the other side, and the cathode Hydrogen gas and oxygen are provided in one or more unit cells formed by an oxygen-containing gas supply unit that supplies an oxygen-containing gas to the side electrode plate and a hydrogen gas flow path unit that supplies hydrogen gas to the anode-side electrode plate. In the power generation method of generating power by supplying the contained gas, the amount of the impurity gas concentrated while concentrating the impurity gas near the outlet by the flow of hydrogen gas in the unit cell that is the final stage of hydrogen gas supply Is characterized in that power generation is performed while discharging a small amount of gas from the unit cell so that is less than a certain value.

  According to the power generation method of the present invention, since the power generation is performed while the impurity gas is concentrated in the vicinity of the discharge port by the flow of hydrogen gas, the concentration of the impurity gas is increased only in the vicinity of the discharge port. Moreover, since there is almost no impurity gas, the power generation efficiency can be kept high. Also, even if the impurity gas is concentrated near the discharge port, if the discharge is not performed, the amount of impurity gas increases and power generation stops, but the amount of impurity gas must be kept below a certain level by discharging a small amount of gas. Can do. As a result, a complicated control mechanism is not required, the amount of hydrogen gas discharged is small, the problem of exhaust gas treatment and gas release is less likely to occur, and power generation can be performed stably and continuously.

  In the above, as the unit cell that is the final stage of hydrogen gas supply, a hydrogen gas flow channel section having a flow path cross-sectional area of 1% or less of the area of the anode side electrode plate is used. It is preferable that 0.02 to 4% by volume of gas is discharged from the unit cell with respect to the hydrogen gas supplied to the unit cell as the final stage.

  According to this configuration, since the unit cell having a sufficiently small channel cross-sectional area with respect to the electrode area is used, the linear velocity of the hydrogen gas supply increases, and the hydrogen gas is almost entirely contained in the solid polymer electrolyte. When consumed, the impurity gas is concentrated on the downstream side without diffusing to the upstream side. Therefore, the accumulation of the impurity gas in the unit cell can be prevented only by discharging a minute amount of gas. At this time, since the concentration of the impurity gas is increased only in the vicinity of the discharge port, since the impurity gas is hardly present when viewed in the entire unit cell, the power generation efficiency can be maintained high.

  In addition, the linear velocity of the supply gas calculated on the basis of the cross-sectional area of the hydrogen gas flow path is 0.1 m / sec or more for the unit cell that is the final stage of hydrogen gas supply. It is preferable to supply hydrogen gas. As a result, the impurity gas can be more reliably concentrated downstream without diffusing upstream.

  Moreover, it is preferable that the density | concentration of the hydrogen gas contained in the gas discharged | emitted from the said unit cell is less than 50 volume%. Thereby, impurity gas can be efficiently discharged | emitted out of the system with high concentration.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an assembled perspective view showing an example of a unit cell of a fuel cell according to the present invention, and FIG. 2 is a longitudinal sectional view showing an example of a unit cell of the fuel cell according to the present invention. FIG. 3 is a schematic configuration diagram showing an example of a fuel cell according to the present invention configured by a plurality of unit cells.

  As shown in FIGS. 1 to 3, the fuel cell according to the present invention includes a plate-shaped solid polymer electrolyte 1, a cathode-side electrode plate 2 disposed on one side of the solid polymer electrolyte 1, and the other side. The anode-side electrode plate 3 is arranged, an oxygen-containing gas supply unit that supplies an oxygen-containing gas to the cathode-side electrode plate 2, and a hydrogen gas flow path unit that supplies hydrogen gas to the anode-side electrode plate 3. Singular or plural unit cells UC. In the present embodiment, as shown in FIG. 3, an example in which a fuel cell is configured by a plurality of unit cells UC is shown.

  First, the unit cell UC will be described. In this embodiment, as shown in FIGS. 1 to 2, a hydrogen gas flow channel 9 is formed in the anode side metal plate 5 by etching to form a hydrogen gas flow channel, and the cathode side metal plate 4 has air. An example of using a unit cell UC in which an opening 4c for naturally supplying gas is formed and an oxygen-containing gas supply unit is configured will be described. As described above, the gas supply unit is configured by the metal plates 4 and 5, thereby making it possible to reduce the thickness and weight of the fuel cell.

  The solid polymer electrolyte 1 may be any solid polymer membrane battery as long as it is used in conventional solid polymer membrane batteries. From the viewpoint of chemical stability and conductivity, a perfluorocarbon having a sulfonic acid group which is a super strong acid. A cation exchange membrane made of a polymer is preferably used. Nafion (registered trademark) is preferably used as such a cation exchange membrane.

  In addition, for example, a porous film made of a fluororesin such as polytetrafluoroethylene impregnated with the above Nafion or other ion conductive material, a porous film made of a polyolefin resin such as polyethylene or polypropylene, or a non-woven fabric. A material carrying Nafion or another ion conductive material may be used.

  The thinner the solid polymer electrolyte 1 is, the more effective it is to make the whole thinner. However, in consideration of ion conduction function, strength, handling property, etc., 10 to 300 μm can be used, but 25 to 50 μm is preferable. .

  The electrode plates 2 and 3 can function as a gas diffusion layer, and can supply and discharge fuel gas, oxidizing gas, and water vapor, and at the same time can exhibit a current collecting function. As the electrode plates 2 and 3, the same or different ones can be used, and it is preferable to support a catalyst having an electrode catalytic action on the base material. The catalyst is preferably supported at least on the inner surfaces 2 b and 3 b in contact with the solid polymer electrolyte 1.

  As the electrode base material, for example, conductive carbon materials such as carbon paper, fibrous carbon such as carbon fiber nonwoven fabric, and aggregates of conductive polymer fibers can be used. In general, the electrode plates 2 and 3 are prepared by adding a water-repellent substance such as a fluororesin to such a conductive porous material. When the catalyst is supported, a catalyst such as platinum fine particles and fluorine It is formed by mixing a water-repellent substance such as a resin, mixing it with a solvent to form a paste or ink, and then applying this to one side of an electrode substrate that should face the solid polymer electrolyte membrane. The

  In general, the electrode plates 2 and 3 and the solid polymer electrolyte 1 are designed according to the reducing gas and the oxidizing gas supplied to the fuel cell. In the present invention, an oxygen-containing gas such as air or pure oxygen is used as the oxidizing gas, and hydrogen gas is used as the reducing gas (fuel). In the present invention, the cathode-side electrode plate 2 on the side where air is naturally supplied causes a reaction between oxygen and hydrogen ions to generate water, and therefore it is preferable to design the cathode-side electrode plate 2 according to the electrode reaction.

  Hydrogen gas preferably has a purity of 95% or more, more preferably 99% or more, and a purity of 99.9% because hydrogen gas discharge is reduced and power generation is performed stably and continuously efficiently. The above is more preferable.

  As the catalyst, at least one metal selected from platinum, palladium, ruthenium, rhodium, silver, nickel, iron, copper, cobalt and molybdenum, or an oxide thereof can be used. A supported one can also be used.

  The thickness of the electrode plates 2 and 3 is more effective for reducing the overall thickness as the thickness is reduced, but is preferably 50 to 500 μm in view of electrode reaction, strength, handling properties, and the like.

  The electrode plates 2 and 3 and the solid polymer electrolyte 1 may be laminated and integrated in advance by adhesion, fusion, or the like, or may simply be arranged in a stacked manner. Such a laminated body can also be obtained as a thin film electrode assembly (MEA), and may be used.

  In the present embodiment, the cathode side metal plate 4 is disposed on the surface of the cathode side electrode plate 2, and the anode side metal plate 5 is disposed on the surface of the anode side electrode plate 3. Further, the anode side metal plate 5 is provided with an inlet 5c and an outlet 5d for hydrogen gas, and a flow channel 9 is provided therebetween.

  In the present invention, the oxygen-containing gas supply unit is preferably provided with a diffusion suppression mechanism that suppresses diffusion of moisture from the cathode side to the outside. In this embodiment, the cathode side metal plate 4 is provided with an opening 4c for naturally supplying oxygen in the air, which corresponds to a diffusion suppression plate that functions as a diffusion suppression mechanism. It is constituted so that air can be supplied naturally through the air.

  The cathode side metal plate 4 that is a diffusion suppressing plate is preferably provided with an opening 4 c with an aperture ratio of 10 to 30% with respect to the area of the cathode side electrode plate 2. In the case of such an aperture ratio, the number, shape, size, formation position, etc. of the opening 4c may be any as long as they are within the range of the aperture ratio. In addition, if it is in the range of said aperture ratio, the current collection from the cathode side electrode plate 2 can also fully be performed. The opening 4c of the cathode side metal plate 4 can be provided with a plurality of circular holes, slits or the like, for example, regularly or randomly.

  As the metal plates 4 and 5, any metal can be used as long as it does not adversely affect the electrode reaction, and examples thereof include stainless steel plates, nickel, copper, and copper alloys. However, from the viewpoint of elongation, weight, elastic modulus, strength, corrosion resistance, press workability, etching workability and the like, a stainless steel plate, nickel and the like are preferable. The metal plates 4 and 5 are preferably subjected to noble metal plating such as gold plating in order to reduce contact resistance with the electrode plates 2 and 3.

  In the present invention, from the viewpoint of concentrating the impurity gas to the downstream side without diffusing to the upstream side, for the unit cell UC that is the final stage of the hydrogen gas supply, the channel cross-sectional area of the hydrogen gas channel part is set to the anode side electrode plate 3% or less of 3 area. This ratio is preferably 0.5% or less, more preferably 0.2% or less, and still more preferably 0.001 to 0.1%. In the present invention, the channel cross-sectional area of the hydrogen gas channel portion refers to the area of a cross section perpendicular to the channel direction of the space formed as a channel when the electrode plate 3 is assumed to be completely flat. Even if this area is almost zero, power can be generated by flowing hydrogen gas through the porous voids of the electrode plate 3. Moreover, the area of the anode side electrode plate 3 refers to the entire area of the anode side electrode plate 3 regardless of the presence or absence of an electrode reaction.

  Thus, in order to reduce the channel cross-sectional area, it is effective to reduce the depth of the channel groove or to increase the length of the channel to reduce the width of the channel.

  Except for the above-mentioned channel cross-sectional area, the channel groove 9 provided in the anode side metal plate 5 may have any planar shape or cross section as long as a channel such as hydrogen gas can be formed by contact with the electrode plate 3. Shape may be sufficient. However, in consideration of the channel density, the lamination density at the time of lamination, the flexibility, etc., it is preferable to mainly form the vertical groove 9a parallel to one side of the metal plate 5 and the vertical groove 9b. In this embodiment, a plurality of (three in the illustrated example) vertical grooves 9a are connected in series to the horizontal grooves 9b to balance the flow path density and the flow path length.

  A part of the channel groove 9 (for example, the lateral groove 9b) of the metal plate 5 may be formed on the outer surface of the electrode plate 3. As a method of forming the flow channel groove on the outer surface of the electrode plate 3, a mechanical method such as heating press or cutting may be used. However, it is preferable to perform groove processing by laser irradiation in order to perform fine processing suitably. From the viewpoint of performing laser irradiation, the base material for the electrode plates 2 and 3 is preferably an aggregate of fibrous carbon.

  One or a plurality of injection ports 5 c communicating with the flow channel groove 9 of the metal plate 5 can be formed. It is preferable to form only one discharge port 5d, and it is preferable to provide it at the downstream end of the flow channel groove 9. As the discharge port 5d approaches the downstream end of the flow channel groove 9, the impurity gas concentrated to a higher concentration can be efficiently discharged.

  In addition, although the thickness of the metal plates 4 and 5 is more effective for reducing the overall thickness as the thickness is reduced, 0.1 to 1 mm is preferable in consideration of strength, elongation, weight, elastic modulus, handling property, and the like.

  Etching is preferable as a method of forming the flow channel 9 in the metal plate 5 in view of processing accuracy and ease. For example, in the channel groove 9 by etching, a width of 0.1 to 10 mm and a depth of 0.05 to 1 mm are preferable. The cross-sectional shape of the channel groove 9 is preferably substantially square, substantially trapezoidal, substantially semicircular, V-shaped or the like.

  Etching is also preferably used for forming the opening 4 c in the metal plate 4, thinning the outer edge of the metal plates 4, 5, and forming the inlet 5 c to the metal plate 5.

  Etching can be performed using, for example, a dry film resist or the like, after forming an etching resist having a predetermined shape on the metal surface, and then using an etching solution corresponding to the type of the metal plates 4 and 5. Further, by using two or more kinds of metal laminated plates and selectively etching each metal, the cross-sectional shape of the flow channel 9 and the thickness of the thinned outer edge can be controlled with higher accuracy. it can.

  The embodiment shown in FIG. 2 is an example in which the caulking portions (outer edge portions) of the metal plates 4 and 5 are thinned by etching. In this way, the caulking portion is etched to have an appropriate thickness, whereby sealing by caulking can be performed more easily. From this viewpoint, the thickness of the crimped portion is preferably 0.05 to 0.3 mm.

  In the present invention, if an oxygen-containing gas supply unit that supplies an oxygen-containing gas to the cathode-side electrode plate 2 and a hydrogen gas channel unit that supplies hydrogen gas to the anode-side electrode plate 3 are formed, the channel unit Any formation structure may be used. In the case where the flow path portion or the like is formed by the metal plates 4 and 5, it is preferable that the peripheral edges of the metal plates 4 and 5 are sealed by a bending press in an electrically insulated state. In the present embodiment, an example of sealing with caulking is shown.

  Electrical insulation can be performed by interposing the insulating material 6, the peripheral edge of the solid polymer electrolyte 1, or both. When the insulating material 6 is used, the thickness is preferably 0.1 mm or less from the viewpoint of thinning. In addition, it is possible to further reduce the thickness by coating the insulating material (for example, the insulating material 6 can have a thickness of 1 μm).

  As the insulating material 6, a sheet-like resin, rubber, thermoplastic elastomer, ceramics, and the like can be used. However, in order to improve the sealing performance, resin, rubber, thermoplastic elastomer, and the like are preferable, and in particular, polypropylene, polyethylene, polyester, fluorine Resin and polyimide are preferable. The insulating material 6 can be integrated with the metal plates 4 and 5 in advance by sticking or coating the peripheral edges of the metal plates 4 and 5 directly or via an adhesive.

  As the caulking structure, the structure shown in FIG. 2 is preferable from the viewpoint of sealing performance, ease of manufacture, thickness, and the like. That is, the outer edge portion 5a of one metal plate 5 is made larger than the other outer edge portion 4a, and the insulating material 6 is interposed, while the outer edge portion 5a of one metal plate 5 is changed to the outer edge portion 4a of the other metal plate 4. A caulking structure that is folded back so as to sandwich pressure is preferable. In this caulking structure, it is preferable to provide a step in the outer edge portion 4a of the metal plate 4 by pressing or the like. Such a caulking structure itself is known as metal processing, and can be formed by a known caulking device.

  As shown in FIGS. 1 to 3, the fuel cell according to the present invention has a unit cell UC of the final stage Sn in the discharge port 5 d of the hydrogen gas flow path unit for the unit cell UC that is the final stage Sn of hydrogen gas supply. A discharge control mechanism for controlling the amount of gas discharged from the engine is provided. In the present embodiment, an example is shown in which a pressure control valve 10 is provided as a discharge control mechanism to discharge gas so that the primary pressure is below a certain level.

  The discharge of the gas from the discharge control mechanism in the present invention may be intermittent or continuous, and the discharge amount may be changed even at a constant amount. However, from the viewpoint of stabilizing the concentration state of the impurity gas and maintaining high power generation efficiency, it is preferable to discharge the gas in a substantially constant amount.

  In the discharge control mechanism of the present invention, 0.02 to 4% by volume, preferably 0.05 to 3% by volume, based on the hydrogen gas (strictly, the total amount including impurity gas) supplied to the unit cell UC of the final stage Sn. %, More preferably 0.1 to 2% by volume of gas (including impurity gas) is controlled. Here, when the gas discharge amount changes, the average value is obtained. If the amount of gas discharged is less than 0.02% by volume, the concentrated impurity gas cannot be discharged sufficiently, the output of the fuel cell decreases with time, and power generation stops in a short time. Further, if the amount of gas discharged exceeds 4% by volume, the amount of hydrogen gas discharged increases, resulting in problems of exhaust gas treatment and gas release.

  When a certain amount or more of hydrogen gas is supplied from the hydrogen gas inlet 5c, the pressure in the inner surface side space increases, and the pressure in the inner surface side space (that is, hydrogen gas) can be controlled to a predetermined value by the pressure control valve 10. it can. Thereby, it is also possible to prevent leakage from the sealing portion and poor contact between the metal plate 5 and the electrode plate 3.

  The pressure control valve 10 may be of any type as long as the pressure in the inner surface space can be controlled to a predetermined value. However, in order to simplify the structure, a self-control valve is preferable, and the internal detection type is more preferable than the external detection type. Is more preferable.

  In the present embodiment, as shown in FIG. 4, an urging means 13 for urging the valve body 12 to the valve seat 11, an adjusting mechanism 14 for adjusting the urging force of the urging means 13, and the valve seat 11 are provided. A valve seat space 15 that accommodates the valve body 12, an introduction passage 16 that communicates with the valve seat space 15 and can be blocked by the valve body 12, and a discharge passage 17 that communicates from the valve seat space 15 to the outside. An example using the pressure control valve 10 is shown.

  The pressure control valve 10 is connected in an airtight manner by inserting the connecting portion 18a of the cylindrical main body 18 forming the valve seat space 15 into the discharge port 5d of the anode side metal plate 5 and caulking the end portion. It is. Further, the male screw portion 14a of the adjusting mechanism 14 is screwed to the female screw portion 18b of the cylindrical main body 18, and the length of the spring as the biasing means 13 is adjusted by the screwing amount, thereby The biasing force can be adjusted. The valve body 12 is formed of, for example, a laminated body of a metal plate 12b and silicone rubber 12a.

  In this pressure control valve 10, when the pressure of the hydrogen gas with respect to the valve body 12 blocking the introduction flow path 16 becomes a certain level or more, the pressure control valve 10 is placed between the valve body 12 and the valve seat 11 against the urging force of the urging means 13. Since a gap is generated and hydrogen gas is discharged to the outside through the valve seat space 15 and the discharge flow path 17, the internal pressure can be maintained substantially constant. Moreover, since the adjustment mechanism 14 which adjusts the urging | biasing force of the urging means 13 which urges | biases the valve body 12 is provided, the setting value of internal pressure control can be changed.

  According to this pressure control valve 10, since the pressure control valve can be configured with the simplest configuration, the pressure control valve can be reduced in size and thickness (for example, a diameter of 4 mm and a height of 5 mm is possible), and the fuel cell as a whole can be reduced in thickness. It becomes easy.

  In the present invention, one or a plurality of unit cells UC can be used, and when one unit cell UC is used, this is the final stage of hydrogen gas supply, and therefore the unit cell UC has a discharge control mechanism. Provided. When a plurality of unit cells UC are used, the configuration is as follows.

  Electrically, the unit cells UC are usually connected in series, but may be connected in parallel with priority given to the current value. When the voltage is insufficient, a boot-up circuit (DC-DC converter) is connected as necessary.

  As for hydrogen gas, each unit cell UC from the first stage S1 to the last stage Sn is connected in series, or a plurality of unit cell UC groups connected in series are configured, and hydrogen gas is supplied to each unit cell UC group in parallel. It can also be supplied. In the latter case, a discharge control mechanism is provided at the last stage of each unit cell UC group. In the present invention, from the viewpoint of efficiently concentrating the impurity gas to the unit cell UC of the final stage Sn, a mode in which hydrogen gas is supplied in series is preferable.

  In the example shown in FIG. 3, the unit cells UC from the first stage S1 to the last stage Sn are connected in series by the hydrogen supply pipe 25, and the unit cell of the first stage S1 from the hydrogen gas generation cell 20 which is a hydrogen gas supply means. Hydrogen gas is supplied to the UC. The supplied hydrogen gas flows to the final stage side while being consumed in each unit cell UC, and is discharged from the discharge control mechanism of the unit cell UC of the final stage Sn.

  When the unit cell UC is used, a hydrogen gas supply tube can be directly joined to the hydrogen gas inlet 5c and outlet 5d of the metal plate 5, but the fuel cell is made thinner. Above, it is preferable to provide a tube joint having a small thickness and a pipe parallel to the surface of the metal plate 5.

  As a method for supplying hydrogen gas, a method using a hydrogen generator that generates hydrogen gas by a chemical reaction is preferable in order to suitably control the pressure in the inner surface side space using the pressure control valve 10 as described above. Examples of such a hydrogen generator include those in which nano iron particles, aluminum powder, a reaction catalyst, or a porous material thereof is accommodated in a container, and further provided with heating means and moisture supply means.

  On the other hand, the power generation method of the present invention can be suitably performed using the fuel cell as described above. That is, the power generation method of the present invention includes a plate-shaped solid polymer electrolyte, a cathode-side electrode plate disposed on one side of the solid polymer electrolyte, an anode-side electrode plate disposed on the other side, and the cathode Hydrogen gas and oxygen are provided in one or more unit cells formed by an oxygen-containing gas supply unit that supplies an oxygen-containing gas to the side electrode plate and a hydrogen gas flow path unit that supplies hydrogen gas to the anode-side electrode plate. In the power generation method of generating power by supplying the contained gas, the amount of the impurity gas concentrated while concentrating the impurity gas near the outlet by the flow of hydrogen gas in the unit cell that is the final stage of hydrogen gas supply Is characterized in that power generation is performed while discharging a small amount of gas from the unit cell so that is less than a certain value.

  At that time, as the unit cell serving as the final stage of the hydrogen gas supply, a unit gas whose cross-sectional area of the hydrogen gas flow path portion is 1% or less of the area of the anode side electrode plate is used. It is preferable to generate electric power while discharging 0.02 to 4% by volume of the gas from the unit cell to the hydrogen gas supplied to the final unit cell.

  At this time, from the viewpoint of efficiently concentrating the impurity gas downstream, the supply gas calculated with respect to the cross-sectional area of the hydrogen gas flow path section for the unit cell that is the final stage of hydrogen gas supply It is preferable to supply hydrogen gas so that the linear flow velocity of the gas is 0.1 m / second or more. More preferably, the linear velocity of the supply gas is 0.5 m / second or more and 1 m / second or more.

  Further, the concentration of hydrogen gas contained in the gas discharged from the unit cell UC as the final stage is preferably less than 50% by volume, more preferably less than 40% by volume, and less than 30% by volume. More preferably.

  In the present invention, the pressure of the hydrogen gas flow path portion at the position where the discharge control mechanism is provided is preferably 7 KPa or more. Thereby, the permeation of the impurity gas from the cathode side can be suppressed, and the power generation efficiency can be kept high even if the gas discharge amount from the discharge control mechanism is smaller.

  The fuel cell according to the present invention has a small amount of hydrogen gas emission, hardly causes problems of exhaust gas treatment and gas release, and can stably and continuously generate power efficiently. It can be suitably used for mobile devices.

  However, since the problem of exhaust gas treatment and power generation efficiency as described above is not limited to portable devices, the present invention can be widely applied to power generation devices such as fuel cells for automobiles and cogeneration.

[Other Embodiments]
(1) In the above-described embodiment, an example of using a pressure control valve that discharges gas so that the pressure on the primary side becomes a certain level or less is used as the discharge control mechanism. However, as the discharge control mechanism in the present invention, Any gas can be used as long as it can discharge 0.02 to 4% by volume of gas on average with respect to the hydrogen gas supplied to the unit cell.

  For example, a valve that can be manually adjusted in opening, or an orifice or a pore that cannot be adjusted in opening may be used. When these are used, the gas is continuously discharged, but a discharge control mechanism that discharges gas intermittently may be used. Further, a discharge control mechanism that periodically discharges gas for a fixed time may be provided, and the gas may be discharged intermittently from the unit cell regardless of the change in pressure.

  (2) In the above-described embodiment, an oxygen-containing gas is formed by disposing a diffusion suppression plate (metal plate) having openings at a constant opening ratio with respect to the area of the cathode side electrode plate on the surface of the cathode side electrode plate. Although an example in which the supply unit is formed has been shown, the oxygen-containing gas supply unit may be configured by a flow channel for oxygen-containing gas, similarly to the anode side. In that case, as with the anode side metal plate, the channel groove, the inlet, and the exhaust port for oxygen-containing gas such as air are formed by etching or pressing, and the cathode side metal plate is formed as with the anode side metal plate. Power generation can be performed while supplying air or the like from the inlet. In this case, as a method for suppressing the diffusion of moisture from the cathode side to the outside, for example, a method of supplying an oxygen-containing gas containing moisture can be mentioned.

  (3) In the above-described embodiment, an example in which the metal plate is disposed on the surfaces of the cathode side electrode plate and the anode side electrode plate to form the oxygen-containing gas supply unit and the hydrogen gas flow path unit has been described. Instead of the metal plate, other materials or various separators conventionally used can be used.

  In the above-described embodiment, an example in which the channel groove is formed in the anode side metal plate by etching has been shown. However, in the present invention, the channel is formed in the anode side metal plate by a mechanical method such as press working or cutting. A groove may be formed.

  (4) In the above-described embodiment, the cathode side electrode plate is exposed as it is from the opening of the cathode side metal plate. However, in the present invention, the cathode side metal plate is hydrophobic so as to cover the opening. A porous polymer porous membrane may be laminated. The polymer porous membrane may be laminated on the inside or outside of the cathode side metal plate.

  (5) In the above-described embodiment, an example in which a pressure control valve that discharges gas so that the pressure on the primary side becomes a certain level or less is used as the discharge control mechanism. It is also possible to provide a discharge control mechanism for controlling the gas flow rate to be substantially constant. In that case, it is preferable to detect the flow rate of the exhaust gas and feedback control the opening of the valve.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below.

Example 1
Corrosion-resistant SUS (50 mm x 26 mm x 0.3 mm thick) with grooves (width 0.8 mm, depth 0.2 mm, spacing 1.6 mm, number 21), peripheral caulking part, gas introduction and discharge holes are chlorinated This was provided by etching with a ferric aqueous solution, and this was used as the anode side metal plate. At this time, the channel cross-sectional area of the hydrogen gas channel provided in the anode side metal plate was 0.16 mm ³ . Similarly, SUS (50 mm × 26 mm × 0.3 mm thickness) having corrosion resistance has through holes (0.6 mmφ, pitch 1.5 mm, number 357, contact area opening ratio 13%), peripheral caulking portion, gas introduction The discharge hole was formed by etching with a ferric chloride aqueous solution, and this was used as a cathode side metal plate. Then, an insulating sheet (50 mm × 26 mm × 2 mm width, thickness 80 μm) was bonded to SUS.

A thin film electrode assembly (49.3 mm × 25.3 mm) was prepared as follows. As the platinum catalyst, a 20% platinum-supported carbon catalyst (EC-20-PTC) manufactured by US Electrochem Co., Ltd. was used. This platinum catalyst, carbon black (Akzo Ketjen Black EC), and polyvinylidene fluoride (Kayner) were mixed at a ratio of 75% by weight, 15% by weight, and 10% by weight, respectively, and dimethylformamide was added by 2.5% by weight. The catalyst paste was prepared by adding to the mixture of the platinum catalyst, carbon black, and polyvinylidene fluoride in such a ratio as to give a% polyvinylidene fluoride solution, and dissolving and mixing in a mortar. Carbon paper (TGP-H-90 manufactured by Toray, thickness 370 μm) is cut into 20 mm × 43 mm, and about 20 mg of the catalyst paste prepared as described above is applied with a spatula and heated at 80 ° C. Dried in the dryer. Thus, a carbon paper carrying 4 mg of the catalyst composition was produced. The amount of platinum supported is 0.6 mg / cm ² .

  Using both the platinum catalyst-supported carbon paper produced as described above and a Nafion film (Nafion 112 manufactured by DuPont, 25.3 mm × 49.3 mm, thickness 50 μm) as a solid polymer electrolyte (cation exchange membrane), both surfaces thereof Then, hot pressing was performed for 2 minutes at 135 ° C. and 2 MPa using a mold. The thin-film electrode assembly thus obtained is sandwiched between the two SUS plates in the center and crimped as shown in FIG. 2 to obtain a thin and small micro fuel cell having an outer dimension of 50 mm × 26 mm × 1.4 mm. I was able to. The flow path cross-sectional area of the hydrogen gas flow path portion of this unit cell was 0.019% with respect to the area of the anode side electrode plate. This was used as a unit cell, and as shown in FIG. 3, a fuel cell was constructed by connecting three unit cells in series (gas and electricity).

The battery characteristics of this micro fuel cell were evaluated. The fuel cell characteristics were measured using a fuel cell evaluation system manufactured by Toyo Technica, flowing hydrogen gas (purity 100%) to the anode side at room temperature, opening the cathode side to the atmosphere, and a current of 1.0 A (current density 120 mA / cm ² ). Measured at constant operation. At that time, the supply gas flow rate of hydrogen gas was 22.8 mL / min for the most upstream unit cell and 7.6 mL / min for the final unit cell. Further, a pressure control valve was provided at the discharge port of the unit cell in the final stage, and this was adjusted (set pressure 10 KPa), so that the average gas discharge amount was 0.1 mL / min. That is, 1.3% by volume of gas was set to be discharged with respect to the hydrogen gas supplied to the final unit cell.

  FIG. 5 shows the change with time in voltage. From this result, it was found that substantially the same output voltage value can be maintained over a long period of time.

Comparative Example 1
In Example 1, a fuel cell was produced in the same manner as in Example 1 except that no gas was discharged from the final unit cell without providing a pressure control valve, and the fuel cell characteristics were evaluated. The result is shown in FIG. As shown in this result, it was found that when the gas was not discharged from the unit cell, the output voltage of the fuel cell became half or less in about 20 minutes, and the power generation stopped early.

Reference example 1
In Example 1, the discharge amount of the average gas from the unit cell of the final stage was 4.56 mL / min (20 vol% of the total supply amount) without providing a pressure control valve while performing a constant operation at a current of 1.0 A. Except for the above, a fuel cell was produced in the same manner as in Example 1, and the fuel cell characteristics were evaluated. The result is shown in FIG. As shown by this result, it was found that in Reference Example 1, although the voltage slightly increased compared to Example 1, there was almost no difference from Example 1.

Example 2
In Example 1, while performing a constant operation at a current of 0.5 A (supplying 3.8 mL / min to the final unit cell), 1.3 volumes with respect to the hydrogen gas supplied to the final unit cell. A fuel cell was produced in the same manner as in Example 1 except that% gas was discharged, and the fuel cell characteristics were evaluated. The result is shown in FIG. As this result shows, it was found that substantially the same output voltage value can be maintained over a long period of time.

Comparative Example 2
In Comparative Example 1, a comparison was made except that gas was not discharged from the final unit cell while performing a constant operation at a current of 0.5 A (supplying 3.8 mL / min to the final unit cell). A fuel cell was produced in the same manner as in Example 1, and the fuel cell characteristics were evaluated. The result is shown in FIG. As shown by this result, it was found that when the gas was not discharged from the unit cell, the output voltage of the fuel cell became less than half in about 15 minutes, and the power generation stopped early.

Example 3
In Example 1, while performing a constant operation at a current of 1.5 A (supplying 11.4 mL / min to the unit cell of the final stage), 1.3 volumes of hydrogen gas supplied to the unit cell of the final stage A fuel cell was produced in the same manner as in Example 1 except that% gas was discharged, and the fuel cell characteristics were evaluated. The result is shown in FIG. As this result shows, it was found that substantially the same output voltage value can be maintained over a long period of time.

Comparative Example 3
In Comparative Example 1, a comparison was made except that gas was not discharged from the final unit cell while performing a constant operation at a current of 1.5 A (11.4 mL / min supplied to the final unit cell). A fuel cell was produced in the same manner as in Example 1, and the fuel cell characteristics were evaluated. The result is shown in FIG. As shown by this result, it was found that when the gas was not discharged from the unit cell, the output voltage of the fuel cell became less than half in about 30 minutes, and the power generation stopped early.

Example 4
In Example 1, while performing a constant operation at a current of 1.0 A (supplying 7.6 mL / min to the unit cell of the final stage), the gas discharge rate from the unit cell of the final stage is 0 to 12 cc / h. Except for the change, a fuel cell was produced in the same manner as in Example 1, and the fuel cell characteristics were evaluated. The result is shown in FIG. As shown in this result, at 0.6 cc / h (discharge amount 0.13% by volume) or more, substantially the same output voltage value can be maintained over a long period of time, and it is critical between 0 cc / h (0% by volume). It turns out that there is a value.

Example 5
In Example 1, the pressure control valve provided at the discharge port was set to a pressure of 5 KPa, and while the constant operation at a current of 1.0 A (7.6 mL / min supply to the unit cell of the final stage) was performed, the final stage A fuel cell was produced in the same manner as in Example 1 except that the amount of gas discharged from the unit cell was changed to 4.0 to 8.0 cc / h, and the fuel cell characteristics were evaluated. The result is shown in FIG. As shown by this result, when the output voltage is 7.7 cc / h (discharging amount 1.7% by volume) or more, substantially the same output voltage value can be maintained over a long period of time, and 5.4 cc / h (1.2% by volume). It was found that there was a critical value between.

Example 6
In Example 1, the pressure control valve provided at the discharge port was set to a pressure of 5 KPa, and while the constant operation at a current of 1.0 A (7.6 mL / min supply to the unit cell of the final stage) was performed, the final stage A fuel cell was prepared in the same manner as in Example 1 except that the amount of gas discharged from the unit cell was changed to 5 to 15 cc / h, and the composition of the exhaust gas was measured by gas chromatography. The result is shown in FIG. As shown by this result, it was found that when the gas discharge amount is 5 cc / h to 10 cc / h, the concentration of hydrogen gas in the exhaust gas is less than 50% by volume. From the comparison between this result and Example 1 and Reference Example 1, it can be seen that the impurity gas is concentrated only in the vicinity of the pressure control valve, and thus the power generation efficiency is high.

Assembly perspective view showing an example of a unit cell of a fuel cell in the present invention The longitudinal cross-sectional view which shows an example of the unit cell of the fuel cell in this invention Schematic configuration diagram showing an example of a fuel cell according to the present invention composed of a plurality of unit cells Sectional drawing which shows an example of the pressure control valve used for the fuel cell (unit cell) in this invention The graph which shows the time-dependent change of the voltage in Examples 1-3, Comparative Examples 1-3, and Reference Example 1. The graph which shows the time-dependent change of the voltage at the time of changing the discharge amount of gas in Example 4. The graph which shows the time-dependent change of the voltage at the time of changing the discharge amount of gas in Example 5. The graph which shows the change of the gas composition at the time of changing the discharge amount of gas in Example 6. Assembly perspective view showing an example of a conventional fuel cell

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solid polymer electrolyte 2 Cathode side electrode plate 3 Anode side electrode plate 4 Cathode side metal plate 4c Opening part 5 Anode side metal plate 5c Inlet 5d Outlet 9 Channel groove 10 Pressure control valve (discharge control mechanism)
Sn Last stage UC Unit cell

Claims (4)

A plate-shaped solid polymer electrolyte, a cathode-side electrode plate disposed on one side of the solid polymer electrolyte, an anode-side electrode plate disposed on the other side, and an oxygen-containing gas supplied to the cathode-side electrode plate To generate power by supplying hydrogen gas and oxygen-containing gas to one or a plurality of unit cells formed by the oxygen-containing gas supply section and the hydrogen gas flow path section for supplying hydrogen gas to the anode-side electrode plate. In the power generation method to be performed,
For the unit cell that is the final stage of hydrogen gas supply, a small amount of gas is discharged from the unit cell so that the amount of the concentrated impurity gas is below a certain level while the impurity gas is concentrated near the discharge port by the flow of hydrogen gas. A power generation method characterized in that power generation is performed.   As the unit cell serving as the final stage of hydrogen gas supply, a unit gas whose cross-sectional area of the hydrogen gas flow path portion is 1% or less of the area of the anode-side electrode plate is used. The power generation method according to claim 1, wherein 0.02 to 4% by volume of gas is discharged from the unit cell with respect to the hydrogen gas supplied to the unit cell.   Hydrogen gas so that the linear velocity of the supply gas calculated on the basis of the channel cross-sectional area of the hydrogen gas channel part is 0.1 m / sec or more with respect to the unit cell that is the final stage of hydrogen gas supply The power generation method according to claim 1 or 2, wherein the power is supplied.   The power generation method according to any one of claims 1 to 3, wherein the concentration of hydrogen gas contained in the gas discharged from the unit cell is less than 50% by volume.

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