WO2012165097A1

WO2012165097A1 - Secondary battery type fuel cell system

Info

Publication number: WO2012165097A1
Application number: PCT/JP2012/061596
Authority: WO
Inventors: 寛子大森; 誉之岡野
Original assignee: コニカミノルタホールディングス株式会社
Priority date: 2011-06-01
Filing date: 2012-05-02
Publication date: 2012-12-06
Also published as: JPWO2012165097A1

Abstract

A secondary battery type fuel cell system comprises: a hydrogen generating agent that generates hydrogen by an oxidation reaction with water and that is capable of regeneration by a reduction reaction with hydrogen; a generator/electrolysis section having a generating function that generates electricity by using as fuel hydrogen that is supplied from the hydrogen generating agent and an electrolytic function that performs electrolysis of water vapour for generating hydrogen that is supplied to the hydrogen generating agent; and a control section, wherein mixed gas containing hydrogen and water vapour is circulated between the hydrogen generating agent and the generator/electrolysis section. The control section performs temperature control of the generator/electrolysis section or control of the water vapour partial pressure ratio of the mixed gas, so that the water vapour partial pressure of the mixed gas is lower than the saturation water vapour partial pressure, after stopping of operation of at least either power generation operation or charging operation.

Description

Secondary battery type fuel cell system

The present invention relates to a secondary battery type fuel cell system capable of performing not only a power generation operation but also a charging operation.

In recent years, development of fuel cells that take out electricity by directly converting chemical energy generated when a reducing substance (fuel) and an oxidizing substance react into electric energy has been actively conducted. Fuel cells, for example, do not emit carbon dioxide in principle when hydrogen is used as the fuel, so they are not only attracting attention as a clean energy source, but also have a high efficiency of power energy that can be extracted in principle, so energy saving Furthermore, by recovering the heat generated during power generation, it has the feature that it can also use thermal energy, and is expected as a trump card for solving global energy and environmental problems.

Such a fuel cell includes, for example, a solid polymer electrolyte membrane using a solid polymer ion exchange membrane, a solid oxide electrolyte membrane using yttria-stabilized zirconia (YSZ) (see, for example, Patent Document 1) as a fuel electrode ( A single cell structure is sandwiched between the anode and the oxidant electrode (cathode). In the cell having such a configuration, a fuel gas flow path for supplying a fuel gas (for example, hydrogen gas) to the fuel electrode, and an oxidant gas flow for supplying an oxidant gas (for example, oxygen or air) to the oxidant electrode. The fuel gas and the oxidant gas are supplied to the fuel electrode and the oxidant electrode through these flow paths, respectively, and electricity is generated.

Fuel cells can be used in various forms, one of which is mounted on an EV (electric vehicle) and used as a power source for the EV. In such a usage mode, since the EV is a moving body, it is necessary to make the fuel cell not a type to which fuel is supplied from the outside but a type (secondary battery type) to which a renewable fuel generator is attached. is there.

Examples of the renewable fuel generator include a fuel generator that generates a fuel which is a reducing substance by a chemical reaction and can be regenerated by a reverse reaction of the chemical reaction. Then, a fuel that is a reducing substance is generated by a chemical reaction, and a hydrogen generator that is an example of a fuel generator that can be regenerated by a reverse reaction of the chemical reaction, that is, hydrogen is generated by a chemical reaction, Examples of a hydrogen generator that can be regenerated by a reverse reaction include a hydrogen generator that has a base material (main component) of iron, generates hydrogen by an oxidation reaction with water, and can regenerate by a reduction reaction with hydrogen. (For example, refer to Patent Document 2).

A hydrogen generator whose base material (main component) is iron can generate hydrogen by an oxidation reaction represented by the following formula (1).
4H ₂ O + 3Fe → 4H ₂ + Fe ₃ O ₄ (1)

Moreover, the hydrogen generator whose base material (main component) is iron can be regenerated by the reduction reaction shown in the following formula (2).
4H ₂ + Fe ₃ O ₄ → 3Fe + 4H ₂ O (2)

A hydrogen generator that generates hydrogen by the chemical reaction as described above and can be regenerated by a reverse reaction of the chemical reaction, a power generation function that generates power using hydrogen supplied from the hydrogen generator, and the hydrogen generator Secondary battery type fuel by having a structure in which a gas containing hydrogen and water vapor is circulated between a power generation / electrolysis unit having an electrolysis function for electrolyzing water for generating hydrogen to be supplied to A battery system can be realized.

As the power generation / electrolysis part, for example, a solid having an MEA (Membrane Electrode Assembly) structure in which a solid electrolyte that permeates O ²⁻ is sandwiched and an oxidant electrode and a fuel electrode are formed on both sides, respectively. An oxide fuel cell can be used. In the solid oxide fuel cell, the following reaction (3) occurs at the fuel electrode during the power generation operation.
H ₂ + O ²⁻ → H ₂ O + 2e (3)

The electrons generated by the reaction of the above formula (3) pass through the external load and reach the oxidant electrode, and the following reaction of the formula (4) occurs at the oxidant electrode.
(1/2) O ₂ + 2e → O ²⁻ (4)

And the oxygen ion produced | generated by reaction of said (4) Formula reaches | attains a fuel electrode through a solid electrolyte. By repeating the above series of reactions, the solid oxide fuel cell performs a power generation operation. Further, as can be seen from the above equation (3), during the power generation operation, H ₂ is consumed and H ₂ O is generated on the fuel electrode side.

On the other hand, when the solid oxide fuel cell operates as an electrolyzer, the reverse reactions of the above formulas (3) and (4) occur, and H ₂ O is consumed and H ₂ is generated on the fuel electrode side.

Japanese Patent No. 3113340 JP 2008-94645 A

When a mixed gas of hydrogen gas and water vapor gas exists in the hydrogen generator in a state where iron (Fe) and iron oxide (Fe ₃ O ₄ ) are mixed in the hydrogen generator whose base material (main component) is iron The reaction rate of the iron oxidation reaction (the above formula (1)) is stable in an equilibrium state where the reaction rate of the iron oxide reduction reaction (the above formula (2)) coincides. A characteristic line T1 shown in FIGS. 8 and 9 indicates this equilibrium state.

8 and 9 show the relationship between the temperature of the mixed gas and the water vapor partial pressure ratio, and the temperature and pressure of the mixed gas. FIG. 9 shows the temperature range from 0 ° C. to 100 ° C. extracted from the temperature range shown in FIG. 8 (0 ° C. to 400 ° C.). When the pressure in the fuel cell device is 1 atm, that is, 101325 pascals, for example, in FIG. 8, if the water vapor partial pressure ratio on the right vertical axis is 10%, the pressure on the left vertical axis corresponds to 10132.5 pascals.

The water vapor partial pressure ratio in the above-mentioned equilibrium state depends on the temperature. As shown in FIG. 8, for example, if the temperature is 400 ° C., the water vapor partial pressure ratio is about 9%.

Also, the characteristic line T2 shown in FIGS. 8 and 9 indicates the saturated water vapor pressure, and the saturated water vapor pressure also depends on the temperature.

For example, it is assumed that the secondary battery type fuel cell system ends the power generation operation at 400 ° C. After the completion, when the temperature of the fuel cell device decreases according to the environmental temperature, if the temperature decreases to the operating temperature of the fuel cell device (for example, room temperature 25 ° C.) while the temperature drop rate is fast and the steam partial pressure ratio remains 9% Since the water vapor partial pressure exceeds the saturated water vapor pressure at room temperature (see FIG. 8), dew condensation occurs at room temperature to produce water. When the temperature drops below freezing point, the condensation turns into ice. If water generated by condensation enters the porous structure electrode of the fuel cell device and becomes ice below freezing point, the fuel cell device may be stressed by volume expansion, which may cause deterioration or damage of the fuel cell device. . The use environment temperature (hereinafter, representatively referred to as room temperature) is a certain temperature that is appropriately selected from a range of about 0 ° C. to 40 ° C., specifically. In addition, when the temperature decrease rate of the fuel cell device is high after the secondary battery type fuel cell system has finished the charging operation, similarly, condensation may occur and the fuel cell device may be deteriorated or damaged.

On the other hand, after the power generation operation or the charging operation of the secondary battery type fuel cell system is finished, the more the temperature drop rate of the fuel cell device is slower, the lower the water vapor partial pressure ratio is along a line closer to the characteristic line T1. Conceivable. Therefore, as shown in FIGS. 8 and 9, even if the fuel cell device is lowered to room temperature, the water vapor partial pressure ratio does not exceed the saturated water vapor pressure, and as a result, neither condensation nor freezing occurs.

In view of the above situation, an object of the present invention is to provide a secondary battery type fuel cell system capable of preventing deterioration and breakage due to condensation.

In order to achieve the above object, a secondary battery type fuel cell system according to one configuration of the present invention generates hydrogen by an oxidation reaction with water vapor and regenerates the hydrogen by a reduction reaction with hydrogen, and the hydrogen A power generation / electrolysis unit having a power generation function for generating power using hydrogen supplied from the generating agent as fuel and an electrolysis function for electrolyzing water vapor to generate hydrogen supplied to the hydrogen generating agent; A secondary battery type fuel cell system in which a mixed gas containing hydrogen and water vapor is circulated between the hydrogen generating agent and the power generation / electrolysis unit, and after stopping at least one of the power generation operation and the charging operation, Provided with a control unit that controls the temperature of the power generation / electrolysis unit or the water vapor partial pressure ratio of the mixed gas so that the water vapor partial pressure of the mixed gas is lower than the saturated water vapor partial pressureThe power generation / electrolysis unit electrolyzes, for example, a power generation operation that generates power using hydrogen supplied from the hydrogen generator and water vapor supplied from the hydrogen generator during regeneration of the hydrogen generator. For example, the fuel cell may be configured to switch between the electrolysis operation to be performed and, for example, a fuel cell that generates power using hydrogen supplied from the hydrogen generator, and the hydrogen at the time of regeneration of the hydrogen generator The structure separately provided with the electrolyzer which electrolyzes the water vapor | steam supplied from a generating agent may be sufficient.

The secondary battery type fuel cell system according to the present invention prevents condensation at room temperature by temperature control or steam partial pressure ratio control, so that deterioration and breakage can be prevented.

1 is a schematic diagram showing a schematic configuration of a secondary battery type fuel cell system according to a first embodiment of the present invention. It is a flowchart which shows the operation | movement at the time of the electric power generation operation stop of the secondary battery type fuel cell system which concerns on 1st Embodiment of this invention. It is a figure which shows the step which can be substituted with step S40 in FIG. 2A. It is a flowchart which shows the operation | movement at the time of the charging operation stop of the secondary battery type fuel cell system which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows schematic structure of the secondary battery type fuel cell system which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the operation | movement at the time of the electric power generation operation stop of the secondary battery type fuel cell system concerning 2nd Embodiment of this invention. It is a schematic diagram which shows schematic structure of the secondary battery type fuel cell system which concerns on 3rd Embodiment of this invention. It is a flowchart which shows the operation | movement at the time of the electric power generation operation stop of the secondary battery type fuel cell system concerning 3rd Embodiment of this invention. It is a schematic diagram which shows schematic structure of the secondary battery type fuel cell system which concerns on 4th Embodiment of this invention. It is a figure which shows the temperature characteristic of the water vapor partial pressure in a hydrogen generator in a saturated water vapor pressure and an equilibrium state. It is a low temperature area | region enlarged view of FIG.

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments described later.

<Hydrogen generator>
The main body of the hydrogen generating agent used in the secondary battery type fuel cell system according to one configuration of the present invention may be anything as long as it can release hydrogen by a chemical reaction. For example, Ni, Fe, Pd, V Mg, each of these alloys, etc. are mentioned.

In addition, the main components of these hydrogen generators can be regenerated by releasing the hydrogen through a chemical reaction in which hydrogen is generated and then reversing the chemical reaction in which hydrogen is generated.

Also, it is desirable to increase the surface area per unit volume in order to increase the reactivity. As a measure for increasing the surface area per unit volume of the hydrogen generating agent, for example, the main component of the hydrogen generating agent may be made into fine particles and the fine particles may be molded. Examples of the fine particles include a method of crushing particles by crushing using a ball mill or the like. Further, the surface area of the fine particles may be further increased by generating cracks in the fine particles by a mechanical method or the like, and the surface area of the fine particles is further increased by roughening the surface of the fine particles by acid treatment, alkali treatment, blasting, etc. It may be increased.

Further, Ti, Zr, V, Nb, Cr, Mo, Al, Ga, Mg, Sc, Ni, Cu and Nd may be added as a catalyst.

The particle diameter of the fine particles is preferably 10 mm or less, more preferably 3 mm or less, and further preferably 150 μm or less from the viewpoint of reactivity. In addition, although the minimum of a particle size is not specifically limited, A 0.01 micrometer thing can also be used. Further, in order to obtain high reactivity with water vapor, it is particularly preferable that the average particle size of the fine particles is 0.05 to 0.5 μm.

<Method for producing hydrogen generator>
As an example of a method for producing a hydrogen generator used in the secondary battery type fuel cell system according to the present invention, a method for producing iron as a main component of the hydrogen generator will be described below.

First, iron or iron oxide fine particles are prepared using an iron compound such as pure iron, iron oxide, or iron nitrate as a raw material. Then, a specific metal is added by physical mixing or impregnation method, preferably coprecipitation method, before forming iron or iron oxide fine particles.

The specific metal added to the iron or iron oxide fine particles is at least one of the metals of Group 4, Group 5, Group 13 and Group 13 of the IUPAC periodic table, preferably Ti, Zr, V, It is selected from any of Nb, Cr, Mo, Al, and Ga. Alternatively, any of Mg, Sc, Ni, and Cu can be used as a specific metal added to iron or iron oxide fine particles.

The amount of the specific metal added to the fine particles of iron or iron oxide is preferably 0.5 to 30 mol%, more preferably 0.5 to 15 mol% of the total metal atoms, calculated by the number of moles of metal atoms. Prepare as follows.

Fine particles of iron or iron oxide to which a specific metal is added are formed into a shape with a large surface area suitable for chemical reaction, such as powder or pellets, cylinders, honeycombs, and nonwoven fabrics for efficient use. The

There are a method of molding fine particles of iron or iron oxide to which a specific metal is added, a method of firing a green sheet in which a slurry is formed into a layer, and a method of pressing a dried powder under pressure.

In addition, the molded body of iron oxide fine particles has the ability to generate hydrogen by being subjected to reduction treatment. The conditions for the reduction reaction are not particularly limited as long as iron oxide can be reduced. For example, carbon monoxide gas or hydrogen gas can be used.

When contacting the compact of iron oxide fine particles with carbon monoxide gas or hydrogen gas, it is heated in a carbon monoxide gas or hydrogen gas atmosphere, or carbon monoxide gas or hydrogen gas is pressurized inside the compact. It can also be distributed.

The reduction treatment is preferably performed at about 200 ° C. to about 600 ° C. from the viewpoint of reduction efficiency. In the reduction treatment, Fe ₃ O ₄ does not necessarily have to be reduced to Fe, and the reduction reaction can be stopped with FeO, which is a low-valent metal oxide. Moreover, it is more preferable to perform the said reduction reaction at 300 degreeC or more when vaporizing the organic type binder etc. which are contained in a molded object. The voids between the particles are preferably 30 to 70% with respect to the total volume of the molded body.

The hydrogen generator mainly composed of iron can generate H ₂ by consuming H ₂ O by the oxidation reaction shown in the above formula (1).

When the oxidation reaction of iron shown in the above formula (1) proceeds, the change from iron to iron oxide proceeds and the remaining amount of iron decreases, but the reverse reaction (reduction reaction) of the above formula (1), that is, the above The hydrogen generating agent can be regenerated by the reduction reaction shown in the formula (2). In addition, both the oxidation reaction of iron shown in the above formula (1) and the reduction reaction of the above formula (2) can be promoted at a temperature of less than 600 ° C.

<Secondary battery type fuel cell system according to the first embodiment of the present invention>
FIG. 1 shows a schematic configuration of a secondary battery type fuel cell system according to the first embodiment of the present invention. The secondary battery type fuel cell system according to the first embodiment of the present invention shown in FIG. 1 includes a hydrogen generating agent 1, a fuel cell unit 2, a heater 3 for adjusting temperature, and a temperature sensor 4 for detecting temperature. The voltage measuring unit 5, the temperature control unit 6, and the container 7 are provided. The hydrogen generating agent 1 and the fuel cell unit 2 are accommodated in the same container 7, and the heater 3 and the temperature sensor 4 are also provided in the container 7.

Further, the hydrogen generating agent 1 and the fuel cell unit 2 of the secondary battery type fuel cell system shown in FIG. 1 may be provided with a sensor for detecting leakage of the fuel gas, if necessary.

The hydrogen generating agent 1 is a hydrogen generating agent that can release hydrogen by a chemical reaction and can be regenerated by a reverse reaction of the chemical reaction in which hydrogen is generated.

The fuel cell unit 2 is a battery unit having an MEA (Membrane Electrode Assembly) structure in which an electrolyte 8 is sandwiched and an oxidant electrode 9 and a fuel electrode 10 are formed on both sides, respectively.

As the material of the electrolyte 8, a known material can be used. For example, ceria-based oxide (GDC) doped with samarium (Sm), gadolinium (Gd), strontium (Sr), or magnesium (Mg). Oxygen ion conductive ceramic materials such as doped lanthanum galide oxide, zirconia oxide (YSZ) containing scandium (Sc) and yttrium (Y) can be used, but are not limited thereto. Any material that conducts oxygen ions or hydrogen ions and satisfies the characteristics as an electrolyte of a fuel cell may be used.

In the case of a solid oxide electrolyte, the electrolyte 8 can be formed by using an electrochemical vapor deposition method (CVD-EVD method; Chemical Vapor Deposition-Electrochemical Vapor Deposition) or the like. For example, it can be formed using a coating method or the like.

Each of the oxidant electrode 9 and the fuel electrode 10 can be constituted by, for example, a catalyst layer in contact with the electrolyte 8 and a diffusion electrode laminated on the catalyst layer. As the catalyst layer, for example, platinum black or a platinum alloy supported on carbon black can be used. Further, as the material of the diffusion electrode of the oxidizer electrode 9, for example, carbon paper, La—Mn—O compound, La—Co—Ce compound, or the like can be used. Further, as the material of the diffusion electrode of the fuel electrode 10, for example, carbon paper, Ni—Fe cermet, Ni—YSZ cermet and the like can be used.

Each of the oxidizer electrode 9 and the fuel electrode 10 can be formed using, for example, a vapor deposition method.

The heater 3 heats the inside of the container 7, and the temperature sensor 4 detects the temperature in the container 7. The voltage measuring unit 5 measures the open circuit voltage of the fuel cell unit 2. The temperature control unit 6 controls the heater 3 while referring to the temperature detected by the temperature sensor 4.

When the power generation operation is stopped, the secondary battery type fuel cell system according to the first embodiment of the present invention having the above configuration starts the flow operation shown in FIG. 2A.

First, the internal temperature of the container 7 is measured by the temperature sensor 4 (step S10). Next, the temperature control unit 6 determines whether or not the internal temperature of the container 7 measured by the temperature sensor 4 is 100 ° C. or higher (step S20). Here, the reason why the threshold value is 100 ° C. is that when the pressure in the fuel cell device is 101325 Pascals, condensation does not occur at 100 ° C. or higher. Therefore, the internal temperature serving as the threshold value may be a lower limit value of the temperature at which dew condensation does not occur according to the pressure in the fuel cell device.

Here, if the internal temperature of the container 7 is not 100 ° C. or more (NO in step S20), the temperature controller 6 heats the inside of the container 7 by the heater 3 (step S50), and then returns to step S10. In addition, the heating by the heater 3 in step S50 is adjusted to a degree of heating slightly higher than 100 ° C. when the internal temperature of the vessel 7 is not 100 ° C. or higher, and the heating by the heater 3 increases the internal temperature of the vessel 7. ing. By keeping the internal temperature at 100 ° C. or higher in this way, the occurrence of condensation due to a rapid temperature drop is prevented.

On the other hand, if the internal temperature of the container 7 is 100 ° C. or higher (YES in step S20), the voltage measuring unit 5 determines that the open circuit voltage of the fuel cell unit 2 (when the fuel cell unit 2 is not connected to any load). The output voltage of the fuel cell unit 2 is measured (step S30).

When the fuel cell unit 2 is not connected to any load, the voltage (electromotive force) E of the fuel cell unit 2 is expressed by the following Nernst equation because there is no loss due to overvoltage.

E0 is the standard electromotive force, R is the gas constant, T is the absolute temperature, F is the Faraday constant, P _H2 and P _H2O are the hydrogen and water vapor partial pressures at the fuel electrode 10 of the fuel cell unit 2, and P _O2 is the fuel It is the partial pressure of oxygen at the oxidant electrode 9 of the battery unit 2, and ΔG0 is the standard Gibbs free energy in the power generation reaction (H ₂ + 1 / 2O ₂ → H ₂ O) of the fuel cell unit 2, and is unique if the temperature is determined It is a value determined by.

The temperature control unit 6 uses the internal temperature of the container 7 measured by the temperature sensor 4 and the open circuit voltage of the fuel cell unit 2 measured by the voltage measurement unit 5 to calculate the water vapor partial pressure ratio from the Nernst equation. Is obtained (step S30). For example, the water vapor partial pressure ratio can be obtained by setting the total pressure of the fuel electrode 10 of the fuel cell unit 2 to 101325 Pascal and the partial pressure of oxygen at the oxidant electrode 9 of the fuel cell unit 2 to 20265 Pascal.

After step S30, the temperature controller 6 determines whether or not the water vapor partial pressure ratio obtained in step S30 is 0.1% or less (step S40). Here, the reason why the threshold value is 0.1% will be described. As FIG. 9 shows, the water vapor partial pressure ratio corresponding to the saturated water vapor pressure at 0 ° C. is about 0.6%. That is, if the water vapor partial pressure ratio is 0.6% or less, no condensation occurs even if the temperature is rapidly lowered to room temperature. If the water vapor partial pressure ratio decreases as shown by the characteristic line T1 shown in FIG. 8, the water vapor partial pressure ratio at 100 ° C. is about 0.1%. Therefore, in this embodiment, the threshold is set to 0.1%. Yes. However, if it is 0.6% as described above, condensation does not occur regardless of the temperature drop rate, so the threshold used in step S40 may be any value as long as it is 0.6% or less. Therefore, step S40 in FIG. 2A can be replaced with, for example, step S40 shown in FIG. 2B.

Here, if the water vapor partial pressure ratio obtained in step S30 is not less than 0.1% (NO in step S40), the process returns to step S10. In addition, when it is planned to be used in an environment where the temperature change is abrupt, when the answer is NO in step S40, the process may proceed to step S50 and be heated by the heater 3. In this case, the heating by the heater 3 may be adjusted so that the internal temperature of the container 7 does not increase.

On the other hand, if the water vapor partial pressure ratio obtained in step S30 is 0.1% or less (YES in step S40), the temperature control after stopping the power generation operation is terminated. Further, for example, when the temperature at the end of the power generation operation is 400 ° C., there is no condensation unless the temperature is less than 50 ° C. (see FIG. 8), so a temperature lower than 100 ° C. (eg, 80 ° C.) is set in step S20. It is also possible to set a threshold value.

<Secondary Battery Type Fuel Cell System According to Second Embodiment of the Present Invention>
FIG. 3 shows a schematic configuration of a secondary battery type fuel cell system according to the second embodiment of the present invention. The secondary battery type fuel cell system according to the second embodiment of the present invention shown in FIG. 3 removes the voltage measuring unit 5 from the secondary battery type fuel cell system according to the first embodiment of the present invention shown in FIG. Instead, a dew point meter 11 is newly provided in the container 7.

The secondary battery type fuel cell system according to the second embodiment of the present invention configured as described above starts the flow operation shown in FIG. 4 when the power generation operation is stopped.

Since the flow operation shown in FIG. 4 is the same as the flow operation shown in FIG. 2A except that the process of step S35 is executed instead of step S30, only step S35 will be described.

In step S35, the temperature control unit 6 obtains a water vapor partial pressure ratio from the water vapor partial pressure in the container 7 measured by the dew point meter 11 (step S35). For example, the water vapor partial pressure ratio can be obtained by setting the total pressure of the fuel electrode 10 of the fuel cell unit 2 to 101325 Pascals. When HTT103 (manufactured by Toyo Technica), which is an example of a dew point meter having high temperature resistance, is used, the partial pressure of water vapor can be measured up to 150 ° C. As described above, when the dew point meter has an upper limit of the measurable temperature, it is preferable to provide a step of determining whether or not the temperature of the water vapor gas is equal to or lower than the upper limit. For example, in the case of the above-mentioned HTT103 (manufactured by Toyo Technica), the upper limit is 150 ° C. Therefore, a step of determining whether or not the temperature of the water vapor gas is 150 ° C. or lower is added before step S20. It is preferable to wait while measuring the temperature until the temperature becomes below, and to proceed to step S20 when the temperature becomes 150 ° C. or below. Alternatively, this flow may be started after the water vapor gas reaches 150 ° C. or lower and waits for 150 ° C. or lower.

<Secondary Battery Type Fuel Cell System According to Third Embodiment of the Present Invention>
FIG. 5 shows a schematic configuration of a secondary battery type fuel cell system according to the third embodiment of the present invention. The secondary battery type fuel cell system according to the third embodiment of the present invention shown in FIG. 5 is similar to the secondary battery type fuel cell system according to the first embodiment of the present invention shown in FIG. 13 is newly provided.

The voltage application unit 12 applies a reverse voltage to the fuel cell unit 2 so that the fuel cell unit 2 electrolyzes water vapor. The selection unit 13 selects the voltage measurement unit 5 when the process of step S30 shown in FIG. 6 is executed, and electrically connects the voltage measurement unit 5 and the fuel cell unit 2, and when the process of step S55 shown in FIG. 6 is executed. The voltage application unit 12 is selected to electrically connect the voltage application unit 12 and the fuel cell unit 2.

The secondary battery type fuel cell system according to the third embodiment of the present invention having the above configuration starts the flow operation shown in FIG. 6 when the power generation operation is stopped.

Since the flow operation shown in FIG. 6 is the same as the flow operation shown in FIG. 2A except that the process of step S55 is added, only step S55 will be described.

If the water vapor partial pressure ratio obtained by the temperature control unit 6 in step S30 is not less than 0.1% (NO in step S40), the temperature control unit 6 applies a reverse voltage to the fuel cell unit 2 to the voltage application unit 12. Then, the fuel cell unit 2 electrolyzes the water vapor in the container 7 to generate hydrogen (step S55). Specifically, when the voltage application unit 12 applies a voltage between the oxidant electrode 9 and the fuel electrode 10 of the fuel cell unit 2 and energizes, the fuel electrode 10 energizes with water vapor (H ₂ O) in the mixed gas. The reaction shown in the following formula (5) occurs with the electrons (e) supplied by the above, and hydrogen is generated by electrolysis. Thus, the water vapor partial pressure ratio is lowered by electrolysis.

H ₂ O + 2e → H ₂ + O ²⁻ (5)
Thereafter, the process returns to step S10.

<Secondary Battery Type Fuel Cell System According to Fourth Embodiment of the Present Invention>
FIG. 7 shows a schematic configuration of a secondary battery type fuel cell system according to the fourth embodiment of the present invention. The secondary battery type fuel cell system according to the fourth embodiment of the present invention shown in FIG. 7 removes the voltage measuring unit 5 from the secondary battery type fuel cell system according to the first embodiment of the present invention shown in FIG. The double wall container 14 is used instead of the container 7.

The double-walled container 14 has an inner wall 15 and an outer wall 16, and enhances heat insulation performance by making the inside of the double wall have a low thermal conductivity. The double wall container 14 also has a support portion 17 that supports the inner wall 15 in order to fix the double wall structure.

As a method of making the inside of the double wall have a low thermal conductivity, the space inside the double wall is made an airtight space to make a vacuum state, the space inside the double wall is made an airtight space and the heat conductivity is low. Examples thereof include a method of filling a gas and a method of filling a space in the double wall with a member having low thermal conductivity such as glass wool. From the viewpoint of making the thermal conductivity as low as possible, a method of making the space in the double wall an airtight space and making it in a vacuum state is preferable.

As the material of the inner wall 15 and the outer wall 16, glass or metal, which is a high temperature resistant material, may be used. Further, as the material of the support portion 17, it is preferable to use glass or the like, which is a material that has high temperature resistance and low thermal conductivity.

Heat transfer from the inner wall 15 to the outer wall 16 mainly occurs via the support portion 17. In order to improve the heat insulation performance of the double-walled container 14, a material having a low thermal conductivity is used as the material of the support part 17, the cross-sectional area of the support part 17 is reduced, and the length of the support part 17 (inner wall 15 and outer wall There is a method of increasing the distance to 16).

Furthermore, the double wall container 14 also has a bimetal 18 in the double wall. The bimetal 18 is fixed to the inner wall 15, but is not fixed to the outer wall 16. In the double wall container 14, when the bimetal 18 is less than 300 ° C., the bimetal 18 and the outer wall 16 are in a non-contact state, and when the inside of the container is hot and the bimetal 18 is 300 ° C. or higher, The shape of the bimetal 18 is designed so that the bimetal 18 and the outer wall 16 are brought into contact with each other due to the deformation of the bimetal 18. Examples of the shape of the bimetal 18 include a cube, a U-shape, and a spiral shape. When the bimetal 18 and the outer wall 16 are in contact with each other, that is, at a high temperature of 300 ° C. or higher, heat is transferred from the inner wall 15 to the outer wall 16 via the bimetal 18, and the rate of decrease in the internal temperature is increased. On the other hand, when the bimetal 18 and the outer wall 16 are in a non-contact state, that is, when the temperature is lower than 300 ° C., the inside of the double-walled container 14 is thermally insulated, and the rate of decrease in the internal temperature becomes slow.

In the secondary battery type fuel cell system according to the fourth embodiment of the present invention shown in FIG. 7, the internal temperature of the double-walled container 14 is maintained at 300 ° C. or higher by the temperature control of the temperature control unit 6 during the power generation operation. Yes. Therefore, during the power generation operation, the bimetal 18 and the outer wall 16 are in contact with each other to prevent overheating in the double-walled container 14.

In the secondary battery type fuel cell system according to the fourth embodiment of the present invention shown in FIG. 7, when the power generation operation is stopped, the temperature control of the temperature control unit 6 is also stopped. Thereby, when the internal temperature of the double-walled container 14 falls and becomes less than 300 ° C., the bimetal 18 and the outer wall 16 are brought into a non-contact state. Thereby, the inside of the double-walled container 14 is insulated, and the rate of decrease in the internal temperature of the double-walled container 14 is slowed, so that it is possible to prevent dew condensation at room temperature and generation of water.

The bimetal 18 has a structure in which two types of conductive materials having different linear expansion coefficients are joined. For example, a bimetal having a structure in which a stainless material having a linear expansion coefficient of 17 × 10 ⁻⁶ / ° C. and a titanium alloy having a linear expansion coefficient of 9 × 10 ⁻⁶ / ° C. can be used. When heated, a bimetal having a structure in which two types of conductive materials having different linear expansion coefficients are joined is curved in a convex shape toward the metal material having a large linear expansion coefficient.

Here, reference values of the linear expansion coefficient of the metal material are shown in ascending order. In order to satisfy the design conditions described above, two types having different linear expansion coefficients may be selected from the metals listed below or other metals.
^{^{Cr: 6.5 × 10 -6 /℃,Ti:8.9×10 -6}} /℃,Pt:9.0×10 -6 /℃,SUS430:10.4×10 -6 / ℃, Co: ^{^{^{12.5 × 10 -6 /℃,Ni:13.3×10 -6 /℃,Au:14.1×10 -6}}} /℃,SUS310:15.8×10 -6 / ℃, Mo: 16. ^{^{^{0 × 10 -6 /℃,SUS316:16.0×10 -6 /℃,SUS301:16.9×10 -6}}} /℃,Cu:17.0×10 -6 /℃,SUS304:17.3× ^{^{^{^{10 -6 /℃,Ag:19.1×10 -6 /℃,Mn:23.0×10 -6 /℃,Pb:29.0×10 -6}}}} / ℃

Instead of the bimetal 18, a shape changing member (for example, a shape memory alloy) whose shape changes depending on the temperature other than the bimetal may be used.

<Evaluation method>
The secondary battery type fuel cell system according to the first embodiment of the present invention is a comparative example in which the temperature control after power generation is stopped is not executed.

After stopping the power generation operation, the water vapor pressure partial pressure ratio at the time when the internal temperature of the container (container 7 or double-walled container 14) was reduced to 100 ° C. was determined. In the secondary battery type fuel cell systems according to the first to fourth embodiments of the present invention, all were 0.1%. In the secondary battery type fuel cell system according to the fourth embodiment of the present invention, a dew point meter was provided in the double wall container 14 to determine the water vapor pressure partial pressure ratio.

In the secondary battery type fuel cell system according to the first, second, and fourth embodiments of the present invention, the time required for the internal temperature of the container to drop from 300 ° C. to 100 ° C. after the power generation operation is stopped is a comparative example. It became 10 times.

In addition, the comparative example and the secondary battery type fuel cell system according to the first to fourth embodiments of the present invention were allowed to stand at an environmental temperature of −5 ° C. for 24 hours after the power generation operation was stopped. Thereafter, each fuel cell unit 2 was observed, and whether or not ice was generated inside the fuel cell unit and whether or not a crack occurred in the fuel cell unit was investigated. The survey results are shown in Table 1. From the results shown in Table 1, it was confirmed that the present invention can prevent the generation of ice inside the fuel cell unit and the generation of cracks in the fuel cell unit. That is, it has been confirmed that the present invention can prevent deterioration and breakage of the fuel cell unit.

<Modification>
In the fuel cell system according to each of the embodiments described above, a structure in which only one MEA that is the fuel cell unit 2 and one hydrogen generation member 1 are provided is illustrated. For example, a plurality of MEAs may be provided on the same plane, Furthermore, a multi-unit configuration in which a plurality of units each composed of an MEA and a hydrogen generating member are stacked may be employed.

Moreover, in each embodiment mentioned above, although the structure which accommodated the hydrogen generating agent 1 and the fuel cell unit 2 in the same container is illustrated, the hydrogen generating agent 1 and the fuel cell unit 2 are accommodated in a separate container. However, a structure may be provided in which a circulation path for circulating gas between the hydrogen generating agent 1 and the fuel cell unit 2 is provided. In this case, a pump for circulating the gas in the circulation path may be provided.

Further, a plurality of at least one of the hydrogen generating agent 1 and the fuel cell unit 2 may be provided. In this case, for example, an arrangement in which one of the hydrogen generating agent 1 and the fuel cell unit 2 is radially surrounded by the other may be considered.

In each of the above-described embodiments, an electrolyte that conducts oxygen ions is used as the electrolyte 8 to generate water on the fuel electrode 10 side during power generation. According to this configuration, water is generated on the electrode side (fuel electrode 10 side) connected to the hydrogen generating agent 1 by the gas flow path for supplying hydrogen from the hydrogen generating agent 1 to the fuel cell unit 2. This is advantageous for simplification and downsizing. On the other hand, as a fuel cell disclosed in Japanese Patent Application Laid-Open No. 2009-99491, a solid polymer electrolyte that allows hydrogen ions to pass through can be used as the electrolyte of the fuel cell unit 2. However, in this case, since water is generated on the oxidant electrode 9 side during power generation, a flow path for propagating this water to the hydrogen generating agent 1 may be provided.

Further, as described above, the charging operation (reduction treatment) is preferably performed at a high temperature of 200 ° C. to 600 ° C. from the viewpoint of reduction efficiency. Therefore, after the charging operation is stopped, the temperature of the fuel cell device rapidly decreases and condensation occurs. A similar problem occurs. Therefore, it is desirable to perform temperature control or water vapor partial pressure ratio control similar to that after stopping the power generation operation after stopping the charging operation. For example, in FIG. 2A showing the flow operation started after the stop of the power generation operation, “power generation” may be replaced with “charge” and read (see FIG. 2C).

DESCRIPTION OF SYMBOLS 1 Hydrogen generating agent 2 Fuel cell unit 3 Heater 4 Temperature sensor 5 Voltage measurement part 6 Temperature control part 7 Container 8 Electrolyte 9 Oxidant electrode 10 Fuel electrode 11 Dew point meter 12 Voltage application part 13 Selection part 14 Double wall container 15 Inner wall 16 Outer wall 17 Support 18 Bimetal

Claims

A hydrogen generating agent that generates hydrogen by an oxidation reaction with water vapor and can be regenerated by a reduction reaction with hydrogen;
A power generation / electrolysis unit having a power generation function for generating power using hydrogen supplied from the hydrogen generation agent as fuel and an electrolysis function for electrolyzing water vapor for generating hydrogen supplied to the hydrogen generation agent; Prepared,
A secondary battery type fuel cell system for circulating a mixed gas containing hydrogen and water vapor between the hydrogen generating agent and the power generation / electrolysis unit,
After stopping at least one of the power generation operation and the charging operation, the temperature control of the power generation / electrolysis unit or the water vapor partial pressure ratio of the mixed gas is set so that the water vapor partial pressure of the mixed gas becomes lower than the saturated water vapor partial pressure. A secondary battery type fuel cell system comprising a control unit for performing control.
2. The secondary battery type fuel cell system according to claim 1, wherein a water vapor partial pressure ratio of the mixed gas at the end of control of the control unit is 0.6% or less.
After the stop of at least one of the power generation operation and the charging operation, the control unit has a temperature of the power generation / electrolysis unit of 100 ° C. or higher until a water vapor partial pressure ratio of the mixed gas is 0.6% or less. The secondary battery type fuel cell system according to claim 2, wherein the temperature is controlled as described above.
The secondary battery type fuel cell system further includes a temperature sensor and a voltage measurement unit,
The water vapor partial pressure ratio is calculated from the temperature of the power generation / electrolysis unit detected by the temperature sensor and the open circuit voltage of the power generation / electrolysis unit measured by the voltage measurement unit. Item 4. The secondary battery type fuel cell system according to any one of Items 1 to 3.
The secondary battery type fuel cell system further includes a dew point meter,
The secondary battery type fuel cell system according to any one of claims 1 to 3, wherein the water vapor partial pressure ratio is calculated from a water vapor partial pressure measured by the dew point meter.
The secondary battery type fuel cell system further includes a voltage application unit,
The water vapor partial pressure ratio is controlled by electrolyzing water vapor in the mixed gas by applying a voltage to the power generation / electrolysis unit by the voltage application unit. The secondary battery type fuel cell system according to any one of the above.
A hydrogen generating agent that generates hydrogen by an oxidation reaction with water vapor and can be regenerated by a reduction reaction with hydrogen;
A power generation / electrolysis unit having a power generation function of generating power using hydrogen supplied from the hydrogen generator as an fuel and an electrolysis function of electrolyzing water vapor for generating hydrogen supplied to the hydrogen generator;
A container containing the hydrogen generating agent and the power generation / electrolysis unit;
A secondary battery type fuel cell system for circulating a mixed gas containing hydrogen and water vapor between the hydrogen generating agent and the power generation / electrolysis unit,
A secondary battery type fuel cell system comprising a member for controlling the temperature in the container by changing the thermal conductivity from the inside to the outside of the container.
The container is a double-walled container having an outer wall and an inner wall,
The member is disposed between the outer wall and the inner wall, and is a shape deforming member whose shape changes due to a temperature change,
The secondary battery type fuel cell system according to claim 7, wherein the thermal conductivity from the inside of the container to the outside is switched by contact or non-contact of the member with the outer wall and the inner wall.
The secondary battery type fuel cell system according to any one of claims 1 to 8, wherein the power generation / electrolysis unit is a solid oxide fuel cell.