JP2012048939A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of appropriately exhausting a water product from a gas passage on the cathode side of power generation cells to achieve high generating efficiency.SOLUTION: An oxidation off-gas exhausting case 39 is provided so as to cover the downstream opening of an oxidation off-gas passage 28 in power generation cells 12 constituting a fuel cell stack 11. A water holding body 40 is installed in the oxidation off-gas exhausting case 39. A water product heating case 46 is integrally formed at the lower portion of the exhausting case 39. A water product produced at the time of power generation, flows into the oxidation off-gas exhausting case 39 through the oxidation off-gas passage 28, and is absorbed in the water holding body 40. The water product absorbed in the water holding body 40 is heated to evaporate by a hot coolant which is heated while being used for cooling and is flowing in the water product heating case 46. Therefore the water product efficiently evaporates to be exhausted to the outside.

Description

  The present invention relates to a fuel cell in which a plurality of solid electrolyte type power generation cells are stacked, and more particularly to a fuel cell capable of appropriately treating generated water generated by power generation.

  Conventionally, in this type of fuel cell, hydrogen gas is supplied from the gas flow path to the gas diffusion electrode on the anode side of the solid electrolyte membrane constituting the electrode structure of each power generation cell, and the gas flow to the gas diffusion electrode on the cathode side. Air containing oxygen is supplied from the road, and an electrochemical reaction between hydrogen and oxygen is performed to generate electricity. When water is generated in the gas flow path on the cathode side during this power generation, and this generated water remains as water droplets on the surface of the gas diffusion electrode on the cathode side, the effective surface area of the gas diffusion electrode is reduced, and oxygen supply The amount is reduced by water droplets, the electrochemical reaction between hydrogen and oxygen is inhibited, and the power generation efficiency is lowered. For this reason, it is required to properly discharge the generated water from the gas flow path on the cathode side of the power generation cell. In order to cope with this, the capacity of the compressor of the supply device for supplying the oxidizing gas is increased to increase the flow rate of the oxidizing gas in the gas flow path on the cathode side and increase the flow rate to efficiently generate the generated water with the oxidizing gas. The method of discharging was adopted.

  However, the conventional fuel cell has a problem in that since the flow rate of the oxidizing gas is increased, the capacity of the compressor has to be increased, so that the power consumption increases and the power generation efficiency decreases accordingly.

  On the other hand, a fuel cell disclosed in Patent Document 1 has also been proposed. In this fuel cell, a water absorbing material is provided inside the oxidizing off gas case, and the generated water is efficiently discharged to the outside by the water absorbing material. That is, almost the entire amount of gas passes through the water absorbing material without bypassing the water absorbing material, so that the water absorbing material absorbs and sucks out water, moves in the water absorbing material, and drains efficiently.

JP 2006-228507 A (see paragraphs 0015 and 0020 and FIGS. 2 and 3 of the specification)

  However, in the fuel cell disclosed in Patent Document 1, since the water absorbing material is disposed so as to block the flow path of the oxidizing off gas case, the flow resistance of the oxidizing off gas increases, and the compressor of the oxidizing gas supply device Therefore, there is a problem in that the power consumption of the compressor increases and the power generation efficiency decreases accordingly.

  The present invention eliminates the problems in the prior art and can properly discharge the generated water in the gas flow path on the cathode side of the power generation cell, thereby improving the power generation efficiency. It is to provide.

  In order to solve the above problems, the invention according to claim 1 is characterized in that an end plate is joined to the outermost power generation cell among the plurality of stacked power generation cells, and fuel gas and oxidizing gas are connected to the end plate. Are provided with a fuel gas supply port and an oxidizing gas supply port for supplying each of the power generation cells, a fuel offgas discharge port and an oxidation offgas discharge port generated by power generation, and a cooling water supply port and a cooling water for cooling the power generation cell. In a fuel cell provided with a discharge port, an oxidation off gas discharge case is joined to the surface of the end plate so as to cover the oxidation off gas discharge port, and generated water generated by power generation is temporarily placed on the inner bottom portion of the case. It is necessary that a water retaining body made of a porous material for retaining water be accommodated in the case, and that the case be provided with heating means for heating and evaporating the water impregnated in the water retaining body. To.

  According to a second aspect of the present invention, in the first aspect, the heating means is configured by joining a cooling water discharge pipe connected to a cooling water discharge port formed in the end plate to the oxidizing off gas discharge case. It is a summary.

  A gist of a third aspect of the present invention is that, in the second aspect, a generated water heating case connected to a cooling water discharge pipe is integrally formed at a lower portion of the oxidizing off gas discharge case.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, a water retention layer made of a porous material is provided at the bottom of the oxidizing off gas passage formed in each of the power generation cells. Is the gist.

The gist of a fifth aspect of the present invention is that, in the fourth aspect, the porosity of the water retaining body is set to be smaller than the porosity of the water retaining layer.
(Function)
In the present invention, the generated water generated in the oxidizing gas passage of the power generation cell by power generation is temporarily retained by the water retaining body accommodated at the bottom of the oxidizing off gas discharge case. The generated water held in the water retaining body by the heating means is heated and evaporated. For this reason, the generated water is properly absorbed and evaporated by the water holding body, and the generated water remains in the oxidizing gas passage of the power generation cell and can be prevented from adhering to the membrane electrode assembly. The amount of oxidizing gas supplied to the body is reduced, and power generation efficiency is prevented from being reduced.

  According to the present invention, the generated water in the oxidizing gas passage on the cathode side of the power generation cell can be properly discharged, and the power generation efficiency can be improved.

FIG. 1 is a cross-sectional view taken along line 1-1 of FIG. 3 showing a first embodiment of the fuel cell according to the present invention. The perspective view of the electric power generation cell and end plate of a fuel cell. FIG. 3 is a perspective view of a state in which a hydrogen gas supply pipe, a fuel gas discharge pipe, an oxidizing gas supply case, an oxidizing off gas discharge case, a cooling water supply case, a cooling water discharge case, and a generated water heating case are mounted on the end plate. The longitudinal cross-sectional view which shows 2nd Embodiment of the fuel cell of this invention. The longitudinal cross-sectional view which shows 3rd Embodiment of the fuel cell of this invention. The fragmentary longitudinal cross-section which shows another embodiment of the heating means of produced water.

(First embodiment)
Hereinafter, an embodiment of a fuel cell embodying the present invention will be described with reference to FIGS.
A fuel cell stack 11 of the fuel cell system shown in FIG. 1 has a plurality of power generation cells 12 that generate power by an electrochemical reaction between hydrogen and oxygen. End plates 13 and 14 are stacked on both ends of the stacked power generation cells 12 via current collector plates and insulating plates (not shown).

  As shown in FIG. 1, the power generation cell 12 includes a seal gasket-integrated MEA 17 in which a seal gasket 16 is disposed around a membrane electrode assembly 15 (MEB: Electron Assembly, MEA), and the seal gasket-integrated MEA 17. The anode-side separator 18 and the cathode-side separator 19 sandwich both surfaces. On both surfaces of a solid electrolyte membrane 20 made of a fluorine-based polymer membrane constituting the membrane electrode assembly 15, an anode-side metal porous body layer 21 and a cathode-side metal that have conductivity and function as gas diffusion electrodes. Each porous body layer 22 is disposed. The anode separator 18 is formed with a fuel gas passage 23 for supplying fuel (hydrogen) gas to the anode metal porous body layer 21. A fuel gas flow path 23 of each power generation cell 12 has a fuel gas from a common fuel gas supply passage 24 (see FIG. 2) provided in the end plate 13, the seal gasket 16, the anode side separator 18 and the cathode side separator 19. Is distributed. The fuel off-gas used for power generation is a common fuel off-gas passage 25 (see FIG. 2) provided from each fuel gas passage 23 to the end plate 13, the seal gasket 16, the anode side separator 18, and the cathode side separator 19. It is designed to be discharged to the outside.

  The cathode side separator 19 is formed with an oxidizing gas passage 26 for supplying an oxidizing (oxygen) gas to the cathode side metal porous body layer 22. As shown in the lower part of FIG. 1, the oxidizing gas passage 26 of each power generation cell 12 has a common oxidizing gas supply passage formed in the end plate 13, the seal gasket 16, the anode side separator 18 and the cathode side separator 19. The oxidizing (oxygen) gas is distributed and supplied from 27 upward. As shown in the upper part of FIG. 1, the end plate 13, the seal gasket 16, the anode-side separator 18 and the cathode-side separator 19 are joined together with the oxidizing off-gas in each oxidizing gas flow path 26 used for power generation. A common oxidant off-gas passage 28 is formed to discharge the gas.

  As shown in FIG. 1, a cooling water passage 31 for cooling each power generation cell 12 is formed on the back surface of the anode side separator 18 and the cathode side separator 19. As shown in FIG. 2, each of the power generation cells 12 and the end plate 13 is formed with a common cooling water supply passage 32 for distributing and supplying cooling water to the cooling water passage 31. The power generation cell 12 and the end plate 13 are formed with a common cooling water discharge passage 33 for discharging cooling water in the cooling water passage 31 used for cooling the fuel cell to the outside. In FIG. 2, the fuel gas supply passage 24, the fuel off gas passage 25, the oxidizing gas supply passage 27, the oxidizing off gas passage 28, the cooling water passage 31, the cooling water discharge passage 33, and the like are simplified.

  Next, based on FIG. 3, the fuel gas supply passage 24, the fuel off-gas passage 25, the oxidizing gas supply passage 27, the oxidizing off-gas passage 28, the cooling water supply passage 32, and the cooling water discharge passage 33 are formed on the surface of the end plate 13. A description will be given of piping and a case to be mounted corresponding to each opening.

  On the surface of the end plate 13, a hydrogen gas supply pipe 35 for supplying hydrogen gas at a predetermined pressure from a hydrogen gas cylinder (not shown) to the fuel gas supply passage 24 is attached. A fuel off-gas discharge pipe 36 for discharging the fuel off-gas from the fuel off-gas passage 25 to a hydrogen dilution device (not shown) is attached to the surface of the end plate 13.

  An oxidant gas supply case 37 for supplying an oxidant gas to the oxidant gas supply passage 27 is mounted on the surface of the end plate 13 by a bolt (not shown). The oxidizing gas supply case 37 is supplied with compressed air from an unillustrated compressor via an oxidizing gas supply pipe 38. An oxidation off gas discharge case 39 for discharging the oxidation off gas in the oxidation off gas passage 28 to the outside is mounted on the surface of the end plate 13 by a bolt (not shown). As shown in FIGS. 1 and 2, a water retaining body 40 made of a porous material formed of a sintered body such as copper or aluminum is accommodated in the oxidizing off gas discharge case 39. The water generated in the oxidant gas passage 26 on the cathode side during power generation by the water retaining body 40 is carried by the oxidant offgas into the oxidant offgas discharge case 39 through the oxidant offgas passage 28. Thereafter, the generated water is impregnated in the water retaining body 40 by the capillary action of the water retaining body 40. An oxidizing off gas discharge pipe 41 is connected to the oxidizing off gas discharge case 39 so that the oxidizing off gas is discharged to the outside.

  A cooling water supply case 42 for supplying cooling water to the cooling water supply passage 32 is mounted on the surface of the end plate 13 by a bolt (not shown), and the case is supplied from a pump (not shown) via a first circulation pipe 43. Cooling water is supplied to 42. A cooling water discharge case 44 for discharging high-temperature cooling water used for cooling in the cooling water discharge passage 33 to the outside is mounted on the surface of the end plate 13 by bolts (not shown). A radiator (not shown) is connected to the cooling water discharge case 44 via a second circulation pipe 45, and the cooling water cooled by the radiator is circulated and supplied to the fuel cell stack 11 via the first circulation pipe 43. It has become so. A generated water heating case 46 as a heating means for heating and evaporating the generated water permeated into the water retaining body 40 in the oxidized off gas discharge case 39 is integrally formed at the lower part of the oxidized off gas discharge case 39. Yes. A second circulation pipe 45 connected to the cooling water discharge case 44 is connected to the inlet (right end in FIG. 3) of the generated water heating case 46. The second circulation pipe 45 is also connected to the outlet of the generated water heating case 46 (left end in FIG. 3).

Next, the operation of the fuel cell configured as described above will be described.
In the fuel cell shown in FIG. 1, the fuel cell stack 11 is operated by a control signal from a control unit (not shown). When hydrogen gas is supplied from a hydrogen tank (not shown) to the fuel cell stack 11 through the hydrogen gas supply pipe 35 and the fuel gas supply passage 24, the hydrogen gas is supplied to the fuel gas passage 23 of the power generation cell 12 shown in FIG. To be supplied. On the other hand, when a compressor (not shown) is operated and air (oxygen) is supplied to the oxidizing gas supply case 37 of the power generation cell 12 shown in FIGS. 1 and 3 through the oxidizing gas supply pipe 38, this air is supplied to the oxidizing gas supply. The gas is distributed and supplied to the oxidizing gas flow path 26 of each power generation cell 12 through the passage 27. Hydrogen supplied to the fuel gas channel 23 is supplied to the anode-side metal porous body layer 21. The air supplied to the oxidizing gas flow path 26 of the cathode side separator is supplied to the cathode side metal porous body layer 22. Through the solid electrolyte membrane 20 of the MEA 17, the hydrogen and oxygen as an oxidant gas contained in the air are reacted by an electrochemical reaction to generate power.

  The hydrogen subjected to the electrochemical reaction is discharged as fuel offgas from the fuel gas passage 23, the fuel offgas passage 25, and the fuel offgas discharge pipe 36 to the outside, and is sent to a hydrogen diluter (not shown) and collected. Hydrogen is reused. On the other hand, oxygen that has been subjected to the electrochemical reaction is discharged outside as an oxidizing off gas from the oxidizing gas flow channel 26 through the oxidizing off gas passage 28 and the oxidizing off gas discharge case 39.

  Generated water is generated in the oxidizing gas flow path 26 of the cathode side metal porous body layer 22 of the power generation cell 12 by the power generation by the fuel cell stack 11 described above. A part of this generated water permeates the solid electrolyte membrane 20 and enters the anode-side metal porous body layer 21 as permeated water. The water droplets of the permeated water are discharged to the outside together with the fuel off-gas through the fuel off-gas discharge pipe 36 formed in the fuel cell stack 11.

  When a pump (not shown) is operated, the cooling water cooled by the radiator is supplied from the cooling water supply case 42 of the first circulation pipe 43 and the fuel cell stack 11 to the cooling water flow path 31 and the anode of the cathode separator 19 of each power generation cell 12. The heat generated by the power generation supplied to the cooling water flow path 31 of the side separator 18 is absorbed by the cooling water, and the power generation cell 12 is cooled. The cooling water flows from the cooling water discharge case 44 of the fuel cell stack 11 to the radiator through the second circulation pipe 45 and the generated water heating case 46, where it is cooled and reused for cooling the fuel cell stack 11.

According to the fuel cell stack 11 of the above embodiment, the following effects can be obtained.
(1) In the first embodiment, the water retaining body 40 is accommodated inside the oxidizing off gas discharge case 39, and the generated water heating case 46 is provided below the oxidizing off gas discharge case 39. Further, the water retaining body 40 absorbs the produced water contained in the oxidized off gas flowing from the oxidized off gas passage 28 into the oxidized off gas discharge case 39 by capillary action, and the high temperature cooling water flowing inside the generated water heating case 46 is used. The water retaining body 40 was heated to evaporate the cooling water. For this reason, the generated water can be properly discharged from the oxidizing off gas passage 28, and the generated water adheres to the membrane electrode assembly 15, thereby preventing a decrease in power generation efficiency due to insufficient supply of the oxidizing gas.

(2) In the first embodiment, since the oxidizing off gas discharge case 39 and the generated water heating case 46 are integrally formed, the heat of the cooling water can be transmitted to the water holding body 40 through one partition wall, and the cooling water Can be efficiently heated. In addition, a dedicated part for attaching the generated water heating case 46 can be omitted, and manufacturing and assembly can be easily performed to reduce cost.
(Second Embodiment)
Next, a second embodiment of the fuel cell according to the present invention will be described with reference to FIG. In the following embodiments, description of the same configuration as that of the first embodiment is omitted.

In this embodiment, in the configuration of the first embodiment, a water retention layer 51 made of a porous material is accommodated in the oxidizing off gas passage 28.
In this embodiment, since the water retention layer 51 is disposed on the inner bottom portion of the oxidation off gas passage 28, the generated water contained in the oxidation off gas flowing into the oxidation off gas passage 28 from each of the oxidation gas passages 26 is retained in the water retention layer. 51. The trapped product water is caused to flow toward the water holding body 40 by the flow pressure of the oxidizing off gas flowing in the upper part of the oxidation off gas passage 28 and heated by the high-temperature cooling water in the product water heating case 46 inside the water holding body 40. And evaporated. For this reason, produced water can be efficiently discharged outside.
(Third embodiment)
Next, a third embodiment of the fuel cell according to the present invention will be described with reference to FIG.

  As shown in FIG. 5, a water retention layer 51 made of a porous material is disposed throughout the oxidation off gas passage 28 over the entire area. The porosity of the water retaining body 40 is set smaller than the porosity of the water retaining layer 51.

In this embodiment, since the porosity of the water retaining body 40 is set smaller than the porosity of the water retaining layer 51, the generated water inside the water retaining layer 51 easily flows into the water retaining body 40, and the generated water The flow is done properly.
(Example of change)
It should be noted that the embodiments described above can be modified and embodied as follows.

As shown in FIG. 6, the second circulation pipe 45 may be brought into contact with the lower surface of the oxidizing off gas discharge case 39 instead of the generated water heating case 46.
-Although not shown in figure, you may arrange | position the electric heater as a heating means in the lower part of the said water holding body 40. FIG.

  DESCRIPTION OF SYMBOLS 12 ... Electric power generation cell, 13, 14 ... End plate, 28 ... Oxidation off gas passage, 39 ... Oxidation off gas discharge case, 40 ... Water retention body, 42 ... Case, 46 ... Production water heating case, 51 ... Water retention layer.

Claims (5)

An end plate is joined to the outermost power generation cell among the plurality of stacked power generation cells, and the end plate is provided with a fuel gas supply port and an oxidation gas supply port for supplying fuel gas and oxidizing gas to each power generation cell. And a fuel cell provided with a cooling water supply port and a cooling water discharge port for cooling the power generation cell, provided with a fuel off gas discharge port and an oxidation off gas discharge port generated by power generation,
A water retention body made of a porous material that joins an oxidation offgas discharge case to the surface of the end plate so as to cover the oxidation offgas discharge port, and temporarily retains generated water generated by power generation at the inner bottom of the case And a heating means for heating and evaporating the water impregnated in the water holding body. 2. The fuel according to claim 1, wherein the heating means is constituted by joining a cooling water discharge pipe connected to a cooling water discharge port formed in the end plate to the oxidizing off gas discharge case. battery. 3. The fuel cell according to claim 2, wherein a generated water heating case connected to a cooling water discharge pipe is integrally formed at a lower portion of the oxidizing off gas discharge case. The fuel cell according to any one of claims 1 to 3, wherein a water retention layer made of a porous material is provided at a bottom portion of the oxidizing off gas passage formed in each of the power generation cells. 5. The fuel cell according to claim 4, wherein the porosity of the water retention body is set smaller than the porosity of the water retention layer.

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