JPH09180743A - Solid polymeric fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polymeric fuel cell having the capability of properly humidifying reaction gas fed to a fuel cell body under th application of a simple configuration. SOLUTION: This fuel cell is formed to have the recirculation passage where almost all of hydrogen discharge gas delivered from the fuel electrode 12 of a fuel cell body 11, and oxygen discharge gas delivered from the air electrode 13 thereof are respectively made to joint externally supplied hydrogen or oxygen in pumps 14A and 14B after circulation through condensers 25A and 25B, and again supplied to the fuel electrode 12 and the air electrode 13. Also, the temperature of the condensers 25A and 25B is controlled with temperature controllers 20A and 20B, thereby controlling the moisture of gases supplied to the fuel electrode 12 and the air electrode 13.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polymer electrolyte fuel cell using a polymer electrolyte membrane as an electrolyte layer,
In particular, it relates to a configuration for humidifying a reaction gas supplied to the fuel cell main body.

[0002]

2. Description of the Related Art FIG. 5 is a schematic cross-sectional view showing a general structure of a single cell which is a basic constituent element of a polymer electrolyte fuel cell. A fuel electrode 2 and an air electrode 3 are arranged on both main surfaces of an ion-conductive polymer film 1 serving as an electrolyte layer.
A current collector 4 having a fuel gas channel 6 is provided on the outer main surface of the
A current collector 5 having an air flow path 7 is disposed on the outer main surface of the air electrode 3, and gas separators 8 and 9 separate the adjacent single cells. In this configuration, when a fuel gas such as hydrogen and air or oxygen are passed through the fuel gas flow path 6 and the air flow path 7, respectively, electricity is generated at the interface between the polymer membrane 1, the fuel electrode 2 and the air electrode 3. A chemical reaction occurs and electricity is generated.

In this polymer electrolyte fuel cell, since the ion conductive polymer membrane 1 used as the electrolyte layer has a high ionic conductivity, it is different from conventional phosphoric acid fuel cells and molten carbonate fuel cells. It is possible to obtain high power density.
In addition, in this solid polymer electrolyte fuel cell, the steady-state operating temperature is generally about 60 to 100 ℃, but the ionic conductivity near room temperature is higher than other fuel cells, and it is possible to operate under load from room temperature. There is. Further, when hydrogen is used as the fuel gas and oxygen is used as the oxidant gas, a particularly high output density can be obtained, so that it is extremely effective not only as a stationary fuel cell but also as a mobile fuel cell.

In the polymer electrolyte fuel cell using hydrogen and oxygen, in order to effectively use hydrogen and oxygen, a majority of the exhaust gas discharged from the cell body is supplied with hydrogen or oxygen supplied from the outside. A recirculation method is generally used in which the recirculation method is used by mixing with, and supplying again to the battery body. On the other hand, the conductivity of the polymer film is greatly affected by the wettability of the film, and when exposed to a dry gas, the water content of the polymer film evaporates, the film dries and the conductivity decreases. That is, when a reactant gas such as fuel gas or oxygen, or an oxidant gas such as air is supplied in a dry state, the polymer membrane dries and the ionic conductivity decreases, and the internal resistance increases accordingly, and the fuel The battery characteristics will deteriorate. Further, when the dry state is promoted, the volume of the polymer film is reduced, so that the air between the polymer film 1 and the fuel electrode 2 or the air electrode 3, between the fuel electrode 2 and the current collector 4, and the air. The contact between the electrode 3 and the current collector 5 deteriorates, causing poor electrode reaction and poor current collection.
It will no longer function as a fuel cell. Therefore,
In the conventional polymer electrolyte fuel cell, in order to prevent such a situation from occurring, a method of incorporating a humidifier in a reaction gas supply circuit and humidifying and supplying it is adopted.

FIG. 6 is a flow chart showing an example of the basic structure of a reaction gas supply circuit of a conventional polymer electrolyte fuel cell. In this configuration, the fuel electrode 12 of the fuel cell body 11 is
The majority of the exhaust gas discharged from the exhaust gas is sent to the condenser 15A to remove excess water, and then combined with hydrogen supplied by being humidified by the humidifier 16A in the pump 14A and supplied again to the fuel cell main body 11 Is sent to the fuel electrode 12.
Similarly, the majority of the exhaust gas discharged from the air electrode 13 is
After being sent to the condenser 15B to remove excess water, the pump 14B joins with the oxygen supplied by the humidifier 16B and then sent to the air electrode 13 of the fuel cell main body 11 again. Humidifier 1 used in this configuration
As 6A and 16B, a humidifier of a type in which a reaction gas is caused to flow through water to humidify it, a humidifier of a type in which water is sprayed to the reaction gas to humidify it, and the like are used.

FIG. 7 is a flow chart showing another example of the basic configuration of the reaction gas supply circuit of the conventional polymer electrolyte fuel cell. In the present configuration, a majority of the exhaust gas discharged from the fuel electrode 12 is combined with the trace amount of hydrogen sent from the outside in the pump 14A after the excess water is removed by the condenser 15A, and the humidifier is then supplied. It is humidified by 16 A and sent to the fuel electrode 12 again. Similarly, a majority of the exhaust gas discharged from the air electrode 13 joins with a small amount of oxygen having a water content supplied from the outside in the pump 14B, and then is humidified by the humidifier 16B and sent to the air electrode 13. Since the humidifiers 16A and 16B used in this configuration are required to have a small pressure loss, water is allowed to flow through one side of a membrane that permeates moisture, and a reaction gas is sent to the opposite side to humidify the membrane. The method is commonly used.

In these configurations, the humidifier 16A,
A method of controlling the humidification amount by controlling the temperature of the water of 16B and humidifying the supplied reaction gas to near the saturated steam pressure is adopted.

[0008]

As described above, in the conventional polymer electrolyte fuel cell, a humidifier is installed in the reaction gas supply circuit to humidify and supply the reaction gas to form a polymer membrane. A method of keeping it wet and maintaining a predetermined ionic conductivity is adopted. However, in these methods, since it is necessary to incorporate a humidifier in the device, there is a problem that the entire device becomes large and the weight becomes heavy. Although the reaction water is usually used as the humidification water supplied to the built-in humidifier, it is necessary to incorporate a reaction water return pipe and control the flow rate of the humidification water, which complicates the piping system configuration. There is a drawback that it ends up.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a polymer electrolyte fuel cell in which the reaction gas supplied to the fuel cell body is accurately humidified with a simple structure. To do.

[0010]

In order to achieve the above object, in the present invention, (1) a solid polymer fuel cell using a solid polymer membrane as an electrolyte layer is discharged from a fuel cell main body. At least a part of the exhaust gas is passed through a condenser that removes excess water, then merged with a reaction gas supplied from the outside, and a recirculation circuit is supplied again to the fuel cell main body. , The condenser is provided with a temperature adjustment function for controlling the temperature of the flowing gas, and at least one of a fuel gas system supplied to the fuel electrode and an oxidant gas system supplied to the air electrode is provided. One system is provided with a recirculation circuit including the condenser having the above-mentioned temperature adjusting function.

(2) In the polymer electrolyte fuel cell described above, the recirculation circuit has a function of heating the exhaust gas after flowing through the condenser having a temperature adjusting function and keeping the exhaust gas above the dew point. A heat exchanger is provided, and for example, a heat exchanger configured by using exhaust gas discharged from the fuel cell main body as a heating source is provided. (3) Further, in the above-described polymer electrolyte fuel cell, the condenser is constituted by using a reaction gas supplied from the outside to the fuel cell main body as a refrigerant.

According to the above (1), by controlling the temperature, the moisture content of the gas flowing through the condenser is controlled,
Since the moisture content of the gas supplied to the fuel cell main body is controlled by joining with the reaction gas supplied from the outside, a predetermined moist gas can be supplied to the fuel cell main body without using a humidifier as in the conventional case. Can be supplied to. In addition, as in (2), the gas flowing through the condenser is heated, and the dew point of the gas rises, so there is no risk of the water content of the supplied gas condensing, and a stable, moist gas is obtained. Can be supplied to the fuel cell body.

Further, according to (3), the exhaust gas can be cooled without separately supplying cooling water to the refrigerant circuit of the condenser.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow chart showing the basic constitution of a reaction gas supply system of a first embodiment of a polymer electrolyte fuel cell of the present invention. This configuration is a reaction gas supply system for a polymer electrolyte fuel cell that uses hydrogen and oxygen as reaction gases, and the fuel cell body 11 is used at an operating temperature of 75 ° C.
Of the hydrogen-based exhaust gas discharged from the fuel electrode 12 and the oxygen-based exhaust gas discharged from the air electrode 13 of
After passing through the condensers 25A and 25B whose temperatures are controlled by the temperature controllers 20A and 20B, respectively, the pumps 14A and 14B are combined with a minute amount of hydrogen or oxygen having a water content supplied from the outside, and then the fuel electrodes are recombined. 1
2 and the air electrode 13 are provided with a recirculation circuit.

In this structure, the flow rate of recirculation flowing through the hydrogen-based condenser 25A is set to 5 times the flow rate supplied from the outside, and the condenser 25A is controlled by the temperature controller 20A.
Assuming that the operation is controlled at ℃, the saturated steam pressure at 65 ℃ is 25.01 kPa, so the saturated steam pressure of the gas supplied to the fuel electrode 12 is 5/6, which is 20.84 kPa.
The dew point will be controlled at 62 ° C. Similarly, the recirculation flow rate flowing through the oxygen-based condenser 25B is set to four times the flow rate supplied from the outside, and the condenser 25B is connected to the temperature controller 2
If the operation is performed by controlling the temperature to 60 ° C. by 0B, the dew point of the gas supplied to the air electrode 13 will be controlled to 55 ° C.

FIG. 2 is a flow chart showing the basic constitution of the reaction gas supply system of the second embodiment of the polymer electrolyte fuel cell of the present invention. This structure is a reaction gas supply system for a polymer electrolyte fuel cell that uses hydrogen and air as reaction gases. Since the air system is a blow-by type, the humidification amount is large, so that the conventional humidifier is used. On the other hand, the hydrogen system is
Similar to the hydrogen system of the above embodiment, a majority of the exhaust gas is caused to flow through the condenser 25A, the temperature of the condenser 25A is controlled by the temperature controller 20A, and the condenser 25A is recirculated to control the amount of water.

In this structure, the fuel cell main body 11 is
When operating at an operating temperature of ℃, and when the recirculation flow rate through the hydrogen-based condenser 25A is 8 times the flow rate supplied from the outside, if the condenser 25A is operated at 70 ℃, the fuel electrode The saturated vapor pressure of the gas supplied to 12 is 27.70 kPa, and the dew point is controlled at 67 ° C. Also, if the operation is controlled at 60 ° C, the saturated vapor pressure of the gas supplied to the fuel electrode 12 becomes 17.25 kPa, and the dew point is controlled at 57 ° C. That is, by controlling the temperature of the condenser 25A by the temperature controller 20A, the dew point of the gas supplied to the fuel electrode 12 can be freely controlled, and the fuel cell main body 11
The required humidifying gas can be supplied by adjusting the humidifying dew point to the required operating temperature or less.

In this configuration, the air system is a blow-by type, but like the oxygen system of the first embodiment, after the majority of the exhaust gas discharged from the air electrode 13 is passed through the condenser. Alternatively, the pump may be configured to have a recirculation circuit that merges with air supplied from the outside and supplies the air to the air electrode 13 again, and the condenser may be temperature-controlled by a temperature controller to control the humidification amount. it can.

FIG. 3 is a flow chart showing the basic structure of the reaction gas supply system of the third embodiment of the polymer electrolyte fuel cell of the present invention. This configuration is a reaction gas supply system for a polymer electrolyte fuel cell that uses hydrogen and oxygen as reaction gases. The difference from the first embodiment shown in FIG. 1 lies in the hydrogen system recirculation circuit. A heat exchanger 17A for heating the exhaust gas cooled by the condenser 25A is provided, and further, a heat exchanger 17B for heating the exhaust gas cooled by the condenser 25B is provided in the oxygen-based recirculation circuit. In point.

With this structure, the temperature of the recirculated gas becomes higher than the dew point, so that the contained water is supplied without condensing in the system, and the humidified gas can be stably supplied. Further, in the configuration shown in the figure, the heat exchanger 1
Since 7A and 17B are of a type in which high-temperature exhaust gas discharged from the fuel electrode 12 and the air electrode 13 is used for heating, it is not necessary to install a special heating source and heating can be performed easily.

FIG. 4 is a flow chart showing the basic constitution of the reaction gas supply system of the fourth embodiment of the polymer electrolyte fuel cell of the present invention. This configuration is a reaction gas supply system for a polymer electrolyte fuel cell that uses hydrogen and oxygen as reaction gases, and its feature is that the hydrogen supplied from the outside is a condenser provided in a hydrogen recirculation circuit. After passing through as a cooling medium of 25 A, it is supplied to the fuel electrode 12, and similarly, oxygen supplied from the outside is supplied to the condenser 2 provided in the oxygen-based recirculation circuit.
The point is that the cooling medium of 5B flows through and then is supplied to the air electrode 13. Although the cooling efficiency by the gas is generally inferior to that by the liquid, the cooling capacity required for the condensers 25A and 25B in the present reaction gas supply system is small, and the required cooling can be performed by this configuration. If hydrogen or oxygen supplied from the outside is used as a cooling medium in this way, it is not necessary to supply a special refrigerant, and the required cooling can be obtained with a simple system.

In the present configuration, the case of the reaction gas supply system having the heat exchangers 17A and 17B in the hydrogen-based and oxygen-based recirculation circuits is shown as an example.
It is obvious that the same effect can be obtained even when 7B is not provided, and it is also effective if it is used only in one of the hydrogen-based and oxygen-based recirculation circuits.

[0023]

As described above, according to the present invention, (1) in a polymer electrolyte fuel cell using a polymer electrolyte membrane as an electrolyte layer, at least a part of the exhaust gas discharged from the fuel cell body is It is equipped with a recirculation circuit that is passed through a condenser that removes excess water, then merges with a reaction gas that is supplied from the outside, and is then fed back to the fuel cell main body. Since it is equipped with a temperature adjustment function to control the temperature of the gas to be used, the reaction gas supplied to the fuel cell body can be accurately humidified with a simple structure without the use of a humidifier as in the past. Form fuel cell can be obtained.

(2) Further, the recirculation circuit is provided with a heat exchanger having a function of heating the exhaust gas after passing through the condenser having a temperature adjusting function and keeping the exhaust gas at a temperature above the dew point. If a heat exchanger configured with the exhaust gas discharged from the fuel cell body as a heating source is provided,
This is more preferable because the water content of the gas is stably supplied to the fuel cell body without condensing.

(3) Further, if the condenser is constituted by the reaction gas supplied from the outside to the fuel cell main body as a refrigerant, it is not necessary to separately supply the cooling water to the refrigerant circuit,
A simpler structure can be achieved.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a basic configuration of a reaction gas supply system of a first embodiment of a polymer electrolyte fuel cell of the present invention.

FIG. 2 is a flow chart showing the basic configuration of a reaction gas supply system of a second embodiment of the polymer electrolyte fuel cell of the present invention.

FIG. 3 is a flow diagram showing the basic configuration of a reaction gas supply system of a third embodiment of the polymer electrolyte fuel cell of the present invention.

FIG. 4 is a flowchart showing the basic structure of a reaction gas supply system of a fourth embodiment of the polymer electrolyte fuel cell of the present invention.

FIG. 5 is a schematic sectional view showing a general configuration of a single cell of a polymer electrolyte fuel cell.

FIG. 6 is a flowchart showing an example of a basic configuration of a gas supply system of a conventional polymer electrolyte fuel cell.

FIG. 7 is a flowchart showing another example of the basic configuration of the gas supply system of the conventional polymer electrolyte fuel cell.

[Explanation of symbols]

 1 Polymer Membrane 2 Fuel Electrode 3 Air Electrode 4 Current Collector 5 Current Collector 6 Fuel Gas Channel 7 Air Channel 8 Gas Separator 9 Gas Separator 11 Fuel Cell Main Body 12 Fuel Electrode 13 Air Electrode 14A, 14B Pump 15A, 15B Condenser 16 Humidifier 16A, 16B Humidifier 17A, 17B Heat exchanger 20A, 20B Temperature controller 25A, 25B Condenser

Claims (5)

[Claims] 1. A fuel electrode and an air electrode are disposed on both main surfaces of an electrolyte layer made of a solid polymer membrane, and a fuel gas is passed through the fuel electrode and an oxidant gas is passed through the air electrode to cause an electrochemical reaction. In a polymer electrolyte fuel cell that obtains electric energy, at least a part of the exhaust gas discharged from the fuel cell main body is passed through a condenser that removes excess water, and then a reaction gas supplied from the outside A solid polymer type having a recirculation circuit that is merged and supplied again to the fuel cell main body, and the condenser has a temperature adjusting function for controlling the temperature of the flowing gas. Fuel cell. 2. The polymer electrolyte fuel cell according to claim 1, wherein at least one of a fuel gas system supplied to the fuel electrode and an oxidant gas system supplied to the air electrode. However, the solid polymer fuel cell is characterized in that the recirculation circuit is provided with the condenser having the temperature adjusting function. 3. The polymer electrolyte fuel cell according to claim 1 or 2, wherein the recirculation circuit heats the exhaust gas after passing through the condenser having a temperature adjusting function and keeps it above the dew point. A polymer electrolyte fuel cell comprising a heat exchanger having a function. 4. The polymer electrolyte fuel cell according to claim 3, wherein the heat exchanger provided in the recirculation circuit is constituted by using exhaust gas discharged from the fuel cell body as a heating source. Polymer electrolyte fuel cell. 5. The polymer electrolyte fuel cell according to claim 1, 2, 3 or 4, wherein the condenser is constituted by using a reaction gas supplied to the fuel cell main body from the outside as a refrigerant. A polymer electrolyte fuel cell characterized by: