JP2014137960A - Fuel cell power generation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell power generation device capable of supplying moisture to an oxidant gas without using a device for humidification and needing the running costs.SOLUTION: A fuel cell stack 10 is provided with a communication pipeline 21 for connecting an oxidant gas supply pipeline 14, which supplies an oxidant gas, with the side of a cooling plate of a coolant circulation pipeline 19, in which a coolant to be supplied to a fuel cell circulates, to add the coolant recovering reaction heat of the fuel cell to the oxidant gas. The structure eliminates the need of a humidifier and energy for humidification and is able to add moisture needed for power generation reaction to the oxidant gas.

Description

  The present invention relates to a fuel cell power generator using a metal compound as an electrolyte, and more particularly to a fuel cell power generator equipped with a fuel cell using a hydroxide ion conductive electrolyte.

  Electrochemical devices such as fuel cells, primary and secondary batteries, water electrolysis and sensors require an electrolyte that is an ionic conductor between the electrodes.

  For example, fuel cells are classified according to the type of electrolyte used, and phosphoric acid fuel cells (PAFC) using liquid phosphoric acid, polymer electrolytes (perfluorosulfonic acid, etc.) that operate at 100 ° C or lower are used. There are solid polymer fuel cells (PEFC) and solid oxide fuel cells (SOFC) using ion conductive ceramics that operate at high temperatures of 600 ° C or higher.

  In recent years, research on electrochemical devices using an anion conductive metal compound different from the fuel cell electrolyte described above as an electrolyte has been underway. Since these electrolytes are hydroxide ions (anions) and the cathode reaction is fast, these electrolytes have the advantage that they operate without using expensive Pt or the like as in the catalyst such as PEFC and PAFC. In addition, since it has ionic conductivity at 300 ° C. or lower rather than at a high temperature as in a conventional solid oxide fuel cell (SOFC), it is advantageous for reducing the cost of the system and has attracted attention.

In Patent Document 1, an anode and a cathode are sandwiched between a solid electrolyte layer made of a sintered metal oxide selected from NaCo ₂ O ₄ , LaSr ₃ Fe ₃ O ₁₀ and Bi ₄ Sr ₁₄ Fe ₂₄ O _56. Are arranged to constitute a fuel cell.

This electrolyte uses hydroxide ions (OH ⁻ ) as an ionic conductor, and the following reaction proceeds at the anode and the cathode.

Anode: H ₂ + 2OH ⁻ + 2e ⁻ → 2H ₂ O
Cathode: 1 / 2O ₂ + H ₂ O + 2e ⁻ → 2OH ⁻
Thus, water is necessary for the reaction on the cathode side, and humidified oxygen or humidified air needs to be supplied to the cathode side.

  On the other hand, as described in Patent Documents 2 and 3, in a polymer electrolyte fuel cell, in order to maintain the polymer electrolyte in a wet state, each reaction gas supplied to the cathode or anode is humidified and supplied. Had to do.

International Publication No. 2010/007949 Pamphlet JP 2011-49131 A JP 2008-243540 A

  However, in the conventional polymer electrolyte fuel cell, water is not required for the power generation reaction, and it is sufficient to humidify the reaction gas to such an extent that the electrolyte membrane does not dry. In the fuel cell using, water is consumed for the cathode reaction, so it is necessary to supply an amount of water necessary for power generation. Therefore, it is difficult to supply the cathode with sufficient water necessary for power generation by directly applying the humidification method performed in the conventional polymer electrolyte fuel cells described in Patent Documents 2 and 3. Moreover, in order to perform sufficient humidification, there existed a subject that an apparatus enlarged and the energy consumed with a humidification apparatus also became large.

  In order to solve the above problems, in the present invention, a fuel cell stack in which a plurality of fuel cells each including an electrolyte layer containing a hydroxide ion conductive metal compound and a cooling plate are laminated between an anode and a cathode. And a cooling water tank, and a cooling water circulation pipe through which the cooling water circulating through the cooling water tank and the cooling plate flows, and the fuel cell stack is supplied with fuel gas and oxidant gas to generate power In the fuel cell power generation device, the fuel cell power generator includes a communication pipe that communicates an oxidant gas supply pipe that supplies an oxidant gas to the fuel cell stack, and a cooling water outlet side of the cooling plate of the cooling water circulation pipe. The cooling water that has recovered the reaction heat is added to the oxidant gas via the communication pipe.

  Further, the communication pipe is provided with an orifice.

  Further, instead of providing the orifice, a flow meter is provided in the communication pipe, and a three-way valve is provided at a branch between the communication pipe and the cooling water circulation pipe. The opening degree of the three-way valve may be controlled so as to have a value set in advance according to the power generation load.

  Furthermore, a heat exchanger for exchanging heat between the anode exhaust gas discharged from the fuel cell stack and the oxidant gas supplied to the fuel cell stack is disposed upstream of the connection portion of the oxidant gas supply pipe with the communication pipe. It is preferable to arrange.

  By adopting the configuration of the present invention, the humidifier and the energy for humidification are unnecessary, and moisture necessary for the power generation reaction can be added to the oxidant gas.

The schematic structure figure of the fuel cell used for the fuel cell power generator of the present invention. The schematic diagram which shows embodiment of the fuel cell electric power generating apparatus of this invention. The schematic diagram which shows different embodiment of the fuel cell electric power generating apparatus of this invention.

FIG. 1 is a sectional structural view of a fuel cell (single cell) 1 used in the fuel cell power generator of the present invention. The fuel cell 1 includes a catalyst layer 3 (an anode side catalyst layer 3a and a cathode side catalyst layer 3c) and a gas diffusion layer on both principal surfaces of an electrolyte layer 2 made of hydroxide ion (OH ⁻ ) conductive metal oxide. 4 is provided with an electrode 5 (anode 5a and cathode 5c), and a separator 6 is disposed outside the electrodes 5a and 5c. A gas flow path 7 is formed in the separator 6. The peripheral edge of the separator 6 is sealed with a sealing material 8.

For the electrolyte layer 2, a hydroxide ion conductive metal compound sintered body such as NaCo ₂ O ₄ , LaSr ₃ Fe ₃ O ₁₀ and Bi ₄ Sr ₁₄ Fe ₂₄ O ₅₆ described in Patent Document 1 is used. Can do.

  For the catalyst layer 3, for example, a conventionally known catalyst metal or alloy such as Pd or Pt can be used, and the catalyst layer 3 may be provided only on the anode side.

  As the gas diffusion layer 4, carbon paper or a metal mesh can be used. As the separator 6, a gas-impermeable carbon plate, a metal plate, or the like can be used.

  Specifically, the fuel cell 1 of the present embodiment was manufactured as follows.

The electrolyte layer 2 was prepared by first mixing a mixture of NaCo ₂ O ₄ powder and PTFE dispersion at a composition ratio of 100: 5 by stirring and mixing with ethylene glycol as a solvent while applying ultrasonic waves. This paste was applied to a polyimide film by a screen printing method, and this was heat-treated in an air atmosphere at 280 ° C. to obtain an electrolyte layer 2.

The anode catalyst layer 3a is formed by applying a mixture of NaCo ₂ O ₄ powder supporting 15 wt% Pd with ethylene glycol to one surface of the electrolyte layer 2 by a screen printing method and then performing a heat treatment. did.

The cathode catalyst layer 3c was formed by applying NaCo ₂ O ₄ powder mixed with ethylene glycol to the other surface of the electrolyte layer 2 by a screen printing method and then performing heat treatment.

  For the gas diffusion layer 4, carbon paper (TGPH60) manufactured by Toray was used. The separator 6 was formed by molding a gas flow path 7 by molding a material made of flake graphite powder and a phenol resin.

  Next, the fuel cell power generator of this embodiment using the fuel cell 1 produced as described above will be described.

  FIG. 2 is an explanatory diagram of the fuel cell power generator according to this embodiment. The fuel cell stack 10 is formed by stacking a plurality of fuel cells 1 and a cooling plate 11. In FIG. 2, one each of the fuel cell 1 and the cooling plate 11 is schematically illustrated.

  The fuel cell stack 10 includes a fuel gas supply pipe 12 that supplies fuel gas to the anode 5a of the fuel cell 1, a fuel gas discharge pipe 13 through which the anode exhaust gas discharged from the anode 5a flows, and a cathode 5c of the fuel cell 1 to the cathode 5c. An oxidant gas supply pipe 14 for supplying oxidant gas (air in the present embodiment) and an oxidant gas discharge pipe 15 through which the cathode exhaust gas discharged from the cathode 5c flows are connected.

  Connected to the upstream side of the fuel gas supply pipe 12 is a fuel reformer 16 for reforming raw fuel such as city gas or methane fermentation gas to generate a fuel gas composed of hydrogen. An air blower 17 is connected to the upstream side as oxidant gas supply means.

  The cooling water stored in the cooling water tank 18 is supplied to the cooling plate 11 of the fuel cell stack 10 via the cooling water circulation pipe 19 by the pump 20, and the cooling water heated by flowing through the cooling plate 11 is cooled. The water is returned to the water tank 18.

  The cooling water circulation pipe 19 on the cooling water outlet side of the cooling plate 11 and the oxidant gas supply pipe 14 are connected by a communication pipe 21, and an orifice 22 is provided in the communication pipe 21.

  A heat exchanger 23 is provided in the piping path of the fuel gas discharge pipe 13, and the anode exhaust gas is cooled by the cooling water flowing through the exhaust heat recovery water pipe 24 of the heat exchanger 23. Thereby, the water vapor generated by the cell reaction in the anode exhaust gas becomes condensed water and is collected in the cooling water tank 18. The anode exhaust gas after being introduced into the cooling water tank 18 and collecting the condensed water is used as a part of fuel by the burner (not shown) of the reformer 16 through the exhaust pipe 25.

  A cooling water circulation pipe 19 is also connected to the heat exchanger 23 downstream from the branch with the communication pipe 21, and the exhaust heat of the fuel cell stack 10 is recovered.

  The exhaust heat recovered by the exhaust heat recovery system pipe 24 is recovered in a hot water storage tank (not shown) and effectively used for hot water supply or the like.

  A replenishment water pipe 26 is connected to the cooling water tank 18. When the value of a water level meter (not shown) provided in the cooling water tank 18 falls below a predetermined value, the water is passed through the ion exchange resin cylinder 27. Of tap water.

  In the operation of the fuel cell power generator in the present embodiment having the above-described configuration, the set value of the operating temperature of the fuel cell stack 10 is set to 150 ° C., and the control device 28 sets the detected value of the temperature sensor 29 to the set value of 150. The number of rotations of the pump 20 is controlled so that the cooling water flow rate flowing through the cooling water circulation pipe 19 is adjusted so that the temperature becomes ° C.

  Then, the cooling water supplied to the cooling plate 11 by the cooling water circulation pipe 19 is heated by the reaction heat of the fuel cell 1 and becomes steam. A part of this steam is introduced into the oxidant gas supply pipe 14 via the communication pipe 21 and the orifice 22. The orifice 22 is adjusted so that the dew point of the oxidant gas supplied to the fuel cell stack 10 during rated operation is 62 ° C. Thereby, water vapor | steam can be supplied to the cathode 5c of the fuel cell 1 with oxidizing agent gas, and it is not necessary to provide a humidifier separately.

  In addition, adjustment of the said dew point can set a dew point in the range of 50-150 degreeC according to the humidification dependence characteristic of the ionic conduction of the electrolyte to be used.

  FIG. 3 is a fuel cell power generation device showing a different embodiment of the present invention. About the structure which is common in embodiment of FIG. 2, the same part number is attached | subjected and description is abbreviate | omitted.

  In the fuel cell power generator of this embodiment, a three-way valve 31 and a flow meter 32 are provided at a branch point between the communication pipe 21 and the cooling water circulation pipe 19. Further, a heat exchanger 33 for exchanging heat between the anode exhaust gas and the oxidant gas is provided on the paths of the fuel gas discharge pipe 13 and the oxidant gas supply pipe 14.

  In the present embodiment, the steam discharged from the cooling plate 11 is introduced into the communication pipe 21 via the three-way valve 31. The control device 28 controls the opening degree of the three-way valve 31 so that the flow rate detection value of the flow meter 21 provided in the communication pipe 21 becomes a flow rate set in advance according to the power generation load of the fuel cell stack 10. Do.

  Thereby, a required amount of moisture can be supplied together with the oxidant gas according to the output current. In addition, since the heat exchanger 33 is provided and the steam from the communication pipe 21 is supplied to the oxidant gas heated by the high-temperature anode exhaust gas discharged from the stack 10, the oxidant supplied to the cathode 5c is supplied. The dew point of gas can be raised and the amount of humidification can be increased.

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Electrolyte layer 3 Catalyst layer 4 Gas diffusion layer 5a Anode 5c Cathode 6 Separator 7 Gas flow path 8 Sealing material 10 Fuel cell stack 11 Cooling plate 12 Fuel gas supply piping 13 Fuel gas discharge piping 14 Oxidant gas supply piping 15 Oxidant gas discharge piping 16 Fuel reformer 17 Air blower 18 Cooling water tank 19 Cooling water circulation piping 20 Pump 21 Communication piping 22 Orifice 23, 33, 34 Heat exchanger 24 Waste heat recovery system piping 25 Exhaust piping 26 Supplementary water piping 27 Ion exchange resin cylinder 28 Controller 29 Temperature sensor 31 Three-way valve 32 Flow meter

Claims (4)

A fuel cell stack in which a fuel cell having an electrolyte layer containing a hydroxide ion conductive metal compound between an anode and a cathode and a cooling plate are stacked; a cooling water tank; the cooling water tank; In a fuel cell power generator comprising a cooling water circulation pipe through which cooling water circulating through the cooling plate flows, and supplying the fuel cell stack with fuel gas and oxidant gas to generate power,
An oxidant gas supply pipe that supplies an oxidant gas to the fuel cell stack, and a communication pipe that communicates with the cooling water outlet side of the cooling plate of the cooling water circulation pipe;
The fuel cell power generator according to claim 1, wherein the cooling water recovered from the reaction heat of the fuel cell is added to the oxidant gas via the communication pipe.   The fuel cell power generator according to claim 1, wherein the communication pipe includes an orifice. The communication pipe is provided with a flow meter,
A three-way valve is provided at a branch between the communication pipe and the cooling water circulation pipe.
2. The fuel according to claim 1, wherein the opening degree of the three-way valve is controlled so that a detection value of the flow meter becomes a value set in advance according to a power generation load of the fuel cell stack. Battery power generator. A heat exchanger for exchanging heat between the anode exhaust gas discharged from the fuel cell stack and the oxidant gas;
4. The fuel cell power generator according to claim 1, wherein the heat exchanger is disposed upstream of a connection portion between the oxidant gas supply pipe and the communication pipe. 5.

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