JP2013069450A - Secondary battery type fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize degradation of battery performance when hydrogen gas leaks in a secondary battery type fuel cell system.SOLUTION: The secondary battery type fuel cell system comprises a first hydrogen generation member 1 capable of generating hydrogen by oxidation reaction with steam and renewable by reduction reaction with hydrogen, a power generation/electrolysis part (e.g., a fuel cell 2)having a power generation function for generating power by using the hydrogen supplied from the first hydrogen generation member 1 as fuel, and an electrolysis function for performing electrolysis of steam in order to produce hydrogen being supplied to the first hydrogen generation member 1, and a second hydrogen generation member 3 composed of a hydrogen-storage alloy into which hydrogen is taken in previously. When the system is generating power, the hydrogen partial pressure dependent on the equilibrium state of oxidation reduction reaction of the first hydrogen generation member 1 is equal to or lower than the hydrogen equilibrium pressure of the hydrogen-storage alloy.

Description

  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.

  A fuel cell typically includes a solid polymer electrolyte membrane using a solid polymer ion exchange membrane, a solid oxide electrolyte membrane using yttria-stabilized zirconia (YSZ), a fuel electrode (anode) and an oxidizer electrode. The one sandwiched from both sides by the (cathode) has a single cell configuration. A fuel gas flow path for supplying fuel gas (for example, hydrogen gas) to the fuel electrode and an oxidant gas flow path for supplying oxidant gas (for example, oxygen or air) to the oxidant electrode are provided. Power generation is performed by supplying fuel gas and oxidant gas to the fuel electrode and oxidant electrode through the passage.

  This fuel cell is designed to extract electric power when water is generated from hydrogen and oxygen. In principle, the efficiency of the electric power that can be extracted is high, which not only saves energy, but also generates only water when generating electricity. Therefore, it is an environmentally friendly power generation method, and is expected as a trump card for solving global energy and environmental problems.

International Publication No. 2011/030625

  Patent Document 1 discloses a hydrogen generation member that generates hydrogen by an oxidation reaction with water vapor and can be regenerated by a reduction reaction with hydrogen, a power generation function that generates power using hydrogen supplied from the hydrogen generation member as a fuel, and A power generation / electrolysis unit having an electrolysis function for electrolyzing water vapor to generate hydrogen to be supplied to the hydrogen generation member, and hydrogen between the hydrogen generation member and the power generation / electrolysis unit. A secondary battery type fuel cell system for circulating a mixed gas containing water vapor is disclosed.

  In the secondary battery type fuel cell system disclosed in Patent Document 1, hydrogen is a sealed space in which a part of the power generation / electrolysis unit (for example, the fuel electrode of the fuel cell unit) and the hydrogen generating member are sealed. Since it is stored inside and circulates between the said hydrogen generating member and the said electric power generation and electrolysis part, there is basically no need for addition.

  However, in the secondary battery type fuel cell system disclosed in Patent Document 1, when the hydrogen gas filled in the sealed space leaks due to a decrease in the sealing degree of the sealed space due to aged deterioration or the like, Since the amount of hydrogen supplied to the power generation / electrolysis section decreases, there is a problem that the battery performance is lowered, and in the worst case, it cannot be used as a battery.

  In view of the above situation, an object of the present invention is to provide a secondary battery type fuel cell system capable of suppressing a decrease in battery performance when hydrogen gas leaks.

  In order to achieve the above object, a secondary battery type fuel cell system according to the present invention includes a first hydrogen generating member that generates hydrogen by an oxidation reaction with water vapor and can be regenerated by a reduction reaction with hydrogen. Power generation / electricity having a power generation function for generating power using hydrogen supplied from one hydrogen generation member as fuel and an electrolysis function for electrolyzing water vapor to generate hydrogen supplied to the first hydrogen generation member A secondary battery type fuel cell system comprising a decomposition unit, wherein a mixed gas containing hydrogen and water vapor is circulated between the first hydrogen generation member and the power generation / electrolysis unit. A second hydrogen generation member made of a hydrogen storage alloy, and during power generation of the system, a hydrogen partial pressure determined by an equilibrium state of an oxidation-reduction reaction of the first hydrogen generation member is a hydrogen level of the hydrogen storage alloy. A configuration is pressure less (first configuration).

  According to such a configuration, when hydrogen leaks from the sealed space in which the mixed gas containing hydrogen and water vapor circulates, and the hydrogen partial pressure in the sealed space is lower than the hydrogen equilibrium pressure of the hydrogen storage alloy, Hydrogen is supplied from the hydrogen storage alloy to the power generation / electrolysis section, and the hydrogen partial pressure in the sealed space is restored to the hydrogen equilibrium pressure of the hydrogen storage alloy. Thereby, when hydrogen gas leaks, it can suppress that battery performance falls.

  Further, in order to generate water vapor on the fuel electrode side during power generation, in the secondary battery type fuel cell system of the first configuration, the power generation / electrolysis section is a solid oxide fuel cell (second It is desirable that

  In addition, when hydrogen is filled at atmospheric pressure at room temperature during production, the hydrogen equilibrium pressure of the hydrogen storage alloy is reduced to a hydrogen partial pressure determined from the equilibrium state of the oxidation-reduction reaction of the first hydrogen generating member at 500 ° C. to 800 ° C. In the secondary battery type fuel cell system having the second configuration, the hydrogen storage alloy may be uranium, titanium, or any of these alloys (third configuration). It is desirable.

  Further, in order to suppress deterioration of the hydrogen storage alloy, in the secondary battery type fuel cell system having any one of the first to third configurations, the hydrogen storage alloy allows hydrogen to pass through and prevents hydrogen from passing through. It is desirable to adopt a configuration (fourth configuration) covered with a permeable material.

  Further, in order to prevent the hydrogen storage alloy from releasing hydrogen when hydrogen is not leaking, in the secondary battery type fuel cell system having any one of the first to fourth configurations, the hydrogen storage alloy includes: Hydrogen is taken in to the maximum and the hydrogen partial pressure determined by the equilibrium state of the oxidation-reduction reaction of the first hydrogen generating member is smaller than the hydrogen equilibrium pressure of the hydrogen storage alloy at the time of power generation of the system. Is desirable.

  According to the secondary battery type fuel cell system of the present invention, hydrogen leaks from the sealed space in which the mixed gas containing hydrogen and water vapor circulates, and the hydrogen partial pressure in the sealed space is equal to the hydrogen equilibrium pressure of the hydrogen storage alloy. If the pressure is lower than the hydrogen storage alloy, hydrogen is supplied from the hydrogen storage alloy to the power generation / electrolysis section, and the hydrogen partial pressure in the sealed space is restored to the hydrogen equilibrium pressure of the hydrogen storage alloy, so that hydrogen gas leaks. In this case, the battery performance can be prevented from deteriorating.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematic structure of the secondary battery type fuel cell system which concerns on 1st Embodiment of this invention. It is a figure which shows the hydrogen partial pressure ratio in the sealed space which sealed the fuel electrode and the 1st hydrogen generating member. It is a figure which shows the hydrogen partial pressure in the sealed space which sealed the fuel electrode and the 1st hydrogen generating member. It is a figure which shows the modification of the secondary battery type fuel cell system which concerns on 1st Embodiment of this invention. It is a figure which shows the hydrogen equilibrium pressure characteristic of the hydrogen storage alloy in an environment with constant temperature. It is a figure which shows the change by the temperature of the hydrogen equilibrium pressure of a hydrogen storage alloy. It is a figure which shows the example of a time change of the hydrogen partial pressure in sealed space. It is a figure which shows the other time change example of the hydrogen partial pressure in sealed space. It is a figure which shows schematic structure of the secondary battery type fuel cell system which concerns on 2nd Embodiment of this invention. It is a figure which shows schematic structure of the secondary battery type fuel cell system which concerns on 3rd Embodiment of this invention. It is a figure which shows schematic structure of the secondary battery type fuel cell system which concerns on 4th Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not restricted to embodiment mentioned later.

<First Embodiment>
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 includes a first hydrogen generating member 1 that generates hydrogen by an oxidation reaction with water vapor and can be regenerated by a reduction reaction with hydrogen, and power generation of the system. A fuel cell unit 2 that generates electricity by using hydrogen supplied from the first hydrogen generating member 1 as fuel, and performs electrolysis of water vapor to generate hydrogen supplied to the first hydrogen generating member 1 when the system is charged A second hydrogen generating member 3 made of a hydrogen storage alloy, a heater 4 for adjusting the temperatures of the first hydrogen generating member 1, the fuel cell unit 2, and the second hydrogen generating member 3, and a first hydrogen A generation member 1, a fuel cell unit 2, a second hydrogen generation member 3, and a container 5 that houses a heater 4 are provided. The container 5 is preferably a heat insulating container.

As the first hydrogen generating member 1, for example, a material in which a metal is used as a base material, a metal or a metal oxide is added to the surface, and hydrogen is generated by an oxidation reaction with water vapor can be used. Examples of the base metal include Ni, Fe, Pd, V, Mg, and alloys based on these, and Fe is particularly preferable because it is inexpensive and easy to process. Examples of the added metal include Al, Rd, Pd, Cr, Ni, Cu, Co, V, and Mo. Examples of the added metal oxide include SiO ₂ and TiO ₂ . However, the metal used as a base material and the added metal are not the same material. In the present embodiment, a hydrogen generation member mainly composed of Fe is used as the first hydrogen generation member 1.

  Further, in the first hydrogen generating member 1, 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 first hydrogen generating member 1, for example, the main body of the first hydrogen generating member 1 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. In addition, the first hydrogen generating member 1 may be one in which fine particles are solidified leaving a space that allows gas to pass through, or formed into pellet-shaped particles and filled with a large number of these particles in the space. It may be a form.

  As shown in FIG. 1, the fuel cell unit 2 has an MEA structure (membrane / electrode assembly) in which an electrolyte membrane 6 is sandwiched and a fuel electrode 7 and an oxidant electrode 8 are formed on both sides thereof. . Although FIG. 1 illustrates a structure in which only one MEA is provided, a plurality of MEAs may be provided, or a plurality of MEAs may be stacked.

  As the material of the electrolyte membrane 6, for example, a solid oxide electrolyte using yttria-stabilized zirconia (YSZ) can be used. For example, Nafion (trademark of DuPont), cationic conductive polymer, anionic conductive polymer Solid polymer electrolytes such as, but not limited to, those that pass hydrogen ions, those that pass oxygen ions, and those that pass hydroxide ions can be used as fuel cell electrolytes. Any material satisfying the characteristics may be used. In this embodiment, an electrolyte that passes oxygen ions or hydroxide ions, for example, a solid oxide electrolyte using yttria-stabilized zirconia (YSZ) is used as the electrolyte membrane 6, and the fuel electrode 7 side is used when generating power in the system. Water (water vapor) is generated in the water. In this case, hydrogen can be generated from the first hydrogen generating member 1 by an oxidation reaction between water vapor generated on the fuel electrode 7 side during power generation of the system and the first hydrogen generating member 1.

  In the case of a solid oxide electrolyte, the electrolyte membrane 6 can be formed using an electrochemical vapor deposition method (CVD-EVD method; Chemical Vapor Deposition-Electrochemical Vapor Deposition) or the like, and in the case of a solid polymer electrolyte. If there is, it can be formed using a coating method or the like.

  Each of the fuel electrode 7 and the oxidant electrode 8 can be configured by, for example, a catalyst layer in contact with the electrolyte membrane 6 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. Moreover, as a material of the diffusion electrode of the fuel electrode 7, for example, carbon paper, Ni—Fe cermet, Ni—YSZ cermet or the like can be used. Moreover, as a material of the diffusion electrode of the oxidizer electrode 8, for example, carbon paper, La—Mn—O-based compound, La—Co—Ce-based compound, or the like can be used.

  Each of the fuel electrode 7 and the oxidant electrode 8 can be formed using, for example, a vapor deposition method.

When the system generates power, the fuel cell unit 2 is connected to an external load, and the reaction of the following formula (1) occurs at the fuel electrode 7.
H ₂ + O ²⁻ → H ₂ O + 2e ⁻ (1)

The electrons generated by the reaction of the above formula (1) pass through the external load and reach the oxidant electrode 8, and the reaction of the following formula (2) occurs at the oxidant electrode 8.
1 / 2O ₂ + 2e ⁻ → O ²⁻ (2)

The oxygen ions generated by the reaction of the above formula (2) reach the fuel electrode 7 through the electrolyte membrane 6. By repeating the above series of reactions, the fuel cell unit 2 performs a power generation operation. Further, as can be seen from the above equation (1), during the power generation operation, H ₂ is consumed and H ₂ O is generated on the fuel electrode 7 side.

From the above equations (1) and (2), the reaction in the fuel cell unit 2 during the power generation operation is as shown in the following equation (3).
H ₂ + 1 / 2O ₂ → H ₂ O (3)

On the other hand, the first hydrogen generating member 1, the oxidation reaction shown in (4) below, and H ₂ consumes of H _{2 O} that is generated at the anode 7 side of the fuel cell unit 2 during the power generation system Can be generated.
3Fe + 4H ₂ O → Fe ₃ O ₄ + 4H ₂ (4)

  At this time, the hydrogen partial pressure ratio (hydrogen partial pressure and hydrogen partial pressure ratio) in the sealed space (the space surrounded by the electrolyte membrane 6 and the inner wall of the container 5) in which the fuel electrode 7 of the fuel cell unit 2 and the first hydrogen generating member 1 are sealed. The ratio of the hydrogen partial pressure to the sum of the water vapor partial pressures is a value as shown in FIG. For example, when the secondary battery type fuel cell system according to the first embodiment of the present invention is manufactured in an environment at a temperature of 20 ° C. and the sealed space is filled with hydrogen at 1 atm, the hydrogen content in the sealed space is reduced. The pressure has a value as shown in FIG.

  When the oxidation reaction of iron shown in the above formula (4) proceeds, the change from iron to iron oxide proceeds and the remaining amount of iron decreases, but by the reverse reaction (reduction reaction) of the above formula (4), The hydrogen generator 1 can be regenerated and the system can be charged.

When the system is charged, the fuel cell unit 2 is connected to an external power source, and an electrolysis reaction shown in the following equation (5), which is a reverse reaction of the above equation (3), occurs, and H ₂ O is consumed on the fuel electrode 7 side. is is H ₂ is generated, the first hydrogen generating member 1, reduction reaction occurs as shown in the reverse reaction is the following (6) of the oxidation reaction shown in above (4) equation, the fuel cell unit 2 fuel electrode H ₂ produced on the 7 side is consumed and H ₂ O is produced.
H ₂ O → H ₂ + 1 / 2O ₂ (5)
Fe ₃ O ₄ + 4H ₂ → 3Fe + 4H ₂ O (6)

  The second hydrogen generating member 3 made of a hydrogen storage alloy is accommodated in the container 5 in a state in which hydrogen is stored in advance when the secondary battery type fuel cell system according to the first embodiment of the present invention is manufactured. The fuel electrode 7 of the part 2 and the first hydrogen generating member 1 are disposed in a sealed space. Since the first hydrogen generating member 1 and the second hydrogen generating member 3 do not necessarily need to be arranged separately, instead of arranging the first hydrogen generating member 1 and the second hydrogen generating member 3. As shown in FIG. 4, a mixture 9 of the first hydrogen generating member and the second hydrogen generating member may be disposed. Examples of the mixture 9 of the first hydrogen generation member and the second hydrogen generation member include, for example, a mixture of Fe powder and hydrogen storage alloy powder, or Fe on the surface of the hydrogen storage alloy powder. The one arranged is mentioned.

  The hydrogen storage alloy has a hydrogen equilibrium pressure characteristic as shown in FIG. 5 under a constant temperature (T1) environment when hydrogen is stored beforehand. The hydrogen equilibrium pressure of the hydrogen storage alloy is determined by the amount of hydrogen held by the hydrogen storage alloy, that is, the hydrogen concentration of the hydrogen storage alloy. As shown in FIG. 5, there is a hydrogen concentration region R1 in which the hydrogen equilibrium pressure shows a substantially constant value (P1) with respect to the change in the hydrogen concentration of the hydrogen storage alloy. Further, the hydrogen equilibrium pressure of a hydrogen storage alloy that stores hydrogen and has a certain hydrogen concentration (for example, D1) in the hydrogen concentration region R1 shown in the figure varies depending on the temperature as shown in FIG.

  The hydrogen storage alloy stores hydrogen if the hydrogen pressure around the hydrogen storage alloy is higher than the hydrogen equilibrium pressure, and releases hydrogen if the hydrogen pressure around the hydrogen storage alloy is lower than the hydrogen equilibrium pressure. When the hydrogen pressure around the hydrogen storage alloy matches the hydrogen equilibrium pressure, the hydrogen storage alloy is in an equilibrium state, and it appears that no hydrogen enters or exits the hydrogen storage alloy.

  In the secondary battery type fuel cell system according to the first embodiment of the present invention, the hydrogen equilibrium pressure of the hydrogen storage alloy used as the second hydrogen generating member 3 is the first hydrogen generating member 1 during the power generation of the system. The hydrogen partial pressure determined from the equilibrium state of the oxidation-reduction reaction of Fe used is set to be lower than the partial pressure of hydrogen. Thus, normally, hydrogen is supplied from the first hydrogen generating member 1 to the fuel cell unit 2, and the fuel cell unit 2 generates electric power using the hydrogen to generate water (steam), and the steam is It is possible to perform a circulation in which the first hydrogen generating member 1 reacts with one hydrogen generating member 1 to generate hydrogen again. On the other hand, hydrogen leaks from the sealed space in which the fuel electrode 7 of the fuel cell unit 2 and the first hydrogen generating member 1 are sealed, and the hydrogen storage alloy in which the hydrogen partial pressure in the sealed space is used as the second hydrogen generating member 3. Is lower than the hydrogen equilibrium pressure, hydrogen is supplied from the hydrogen storage alloy used as the second hydrogen generating member 3 to the fuel cell unit 2, and the hydrogen partial pressure in the sealed space is the second hydrogen generating member 3. It recovers to the hydrogen equilibrium pressure of the hydrogen storage alloy used. Since it is not necessary to individually control the temperature of the first hydrogen generating member 1 and the second hydrogen generating member 3, temperature control can be simplified.

  The material of the hydrogen storage alloy used as the second hydrogen generating member 3 is not particularly limited, but when a solid oxide fuel cell is used as the fuel cell unit 2, for example, uranium, titanium, sodium, magnesium, or these Any of the alloys can be used. When any one of uranium, titanium, or each of these alloys is used, the hydrogen equilibrium pressure of the hydrogen storage alloy is reduced from 500 ° C. to 800 ° C. when the hydrogen is filled in the enclosed space at room temperature at the time of manufacture. Since the hydrogen partial pressure determined from the equilibrium state of the oxidation-reduction reaction can be reduced, it is preferable to use uranium, titanium, or any of these alloys. Further, from the viewpoint of suppressing the deterioration of the hydrogen storage alloy, it is more preferable that the hydrogen storage alloy used as the second hydrogen generating member 3 is covered with a hydrogen permeable material that transmits hydrogen and prevents water vapor transmission. Examples of the hydrogen permeable material that transmits hydrogen and prevents water vapor transmission include, for example, an inorganic porous film such as a ceramic thin film and a zeolite thin film, and at least one of palladium, vanadium, titanium, zirconium, nickel, ruthenium, niobium, and tantalum. A metal or alloy thin film made of a kind of material can be used. More specific examples include amorphous silica films, palladium alloy films such as palladium metal films and AgPd, vanadium, tantalum, niobium thin films as non-palladium, and vanadium as their alloy films with nickel, cobalt, and molybdenum added. And Vb alloys, Nb alloys obtained by adding palladium, titanium, nickel, ruthenium, tungsten and molybdenum to niobium, and alloys containing zirconium and nickel as main components.

  Next, as a first setting example of the hydrogen equilibrium pressure of the hydrogen storage alloy and the hydrogen partial pressure in the sealed space, the hydrogen concentration of the hydrogen storage alloy used as the second hydrogen generation member 3 is D1 (see FIG. 5). As described above, the hydrogen storage alloy used as the second hydrogen generating member 3 is preliminarily stored with hydrogen, and the environment during power generation of the system is set as the temperature T1 and the hydrogen partial pressure P1 in the sealed space as a hydrogen storage alloy. Let us consider a case where power generation is performed at a hydrogen equilibrium pressure of P1 (see FIG. 5). When power generation is performed at the temperature T1, the hydrogen partial pressure P1 in the sealed space is the same as the hydrogen equilibrium pressure P1 of the hydrogen storage alloy used as the second hydrogen generating member 3, so that the second hydrogen generation apparently appears. It seems that hydrogen does not enter and exit from the hydrogen storage alloy used as the member 3. On the other hand, Fe used as the first hydrogen generating member 1 supplies hydrogen to the fuel cell unit 2 by an oxidation reaction with water vapor generated by the fuel cell unit 2, and the fuel cell unit 2 generates power using the hydrogen. Water vapor again. Thereby, power generation is stably performed.

  If hydrogen leaks from the sealed space due to aging and the hydrogen partial pressure in the sealed space starts to decrease, the secondary battery type fuel cell system does not include the second hydrogen generating member 3 made of a hydrogen storage alloy. In this case, as shown by the alternate long and short dash line in FIG. 7, the hydrogen partial pressure in the sealed space is gradually lowered from the time t1 when hydrogen starts to leak, and the battery performance is deteriorated. When the secondary battery type fuel cell system includes the second hydrogen generation member 3 made of a hydrogen storage alloy as described above, hydrogen is released from the second hydrogen generation member 3 made of a hydrogen storage alloy, Since the hydrogen partial pressure in the sealed space immediately returns to P1, which is the original state, as indicated by the solid line in FIG. 7, it is possible to suppress a decrease in battery performance.

  Next, as a second setting example of the hydrogen equilibrium pressure of the hydrogen storage alloy and the hydrogen partial pressure in the sealed space, the hydrogen concentration of the hydrogen storage alloy used as the second hydrogen generating member 3 is D1 (see FIG. 5). As described above, the hydrogen storage alloy used as the second hydrogen generating member 3 is made to store the maximum amount of hydrogen beforehand, and the environment during power generation of the system is defined as the temperature T1 and the hydrogen partial pressure P2 (> P1) in the sealed space. Consider a case where power generation is performed at a hydrogen equilibrium pressure of P1 (see FIG. 5) of the hydrogen storage alloy. During power generation at the temperature T1, the hydrogen partial pressure P2 in the sealed space is higher than the hydrogen equilibrium pressure P1 of the hydrogen storage alloy used as the second hydrogen generating member 3, but as the second hydrogen generating member 3, Since the hydrogen storage alloy to be used has already stored the maximum amount of hydrogen (100% of the allowable value), it cannot store any more hydrogen, and the hydrogen equilibrium of the hydrogen storage alloy used as the second hydrogen generating member 3 The pressure stabilizes at P1. For this reason, it appears that hydrogen does not enter or exit from the hydrogen storage alloy used as the second hydrogen generating member 3 in appearance. On the other hand, Fe used as the first hydrogen generating member 1 supplies hydrogen to the fuel cell unit 2 by an oxidation reaction with water vapor generated by the fuel cell unit 2, and the fuel cell unit 2 generates power using the hydrogen. Water vapor again. Thereby, power generation is stably performed.

  If hydrogen leaks from the sealed space due to aging and the hydrogen partial pressure in the sealed space starts to decrease, the secondary battery type fuel cell system does not include the second hydrogen generating member 3 made of a hydrogen storage alloy. In this case, as shown by the alternate long and short dash line in FIG. 8, the hydrogen partial pressure in the sealed space gradually decreases from the time t1 when hydrogen starts to leak, and the battery performance deteriorates. In the case where the secondary battery type fuel cell system includes the second hydrogen generating member 3 made of a hydrogen storage alloy as shown in FIG. 8, the above-mentioned time t1 when hydrogen starts to leak as shown by the solid line in FIG. The hydrogen partial pressure in the sealed space decreases until time t2 when the hydrogen partial pressure in the sealed space reaches P1, and hydrogen is released from the second hydrogen generating member 3 made of a hydrogen storage alloy after time t2. In the enclosed space Since oxygen partial pressure is maintained at P1 it is possible to suppress deterioration in battery performance.

Second Embodiment
FIG. 9 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. 9 includes the second hydrogen generating member 3, the sealed space surrounded by the inner wall of the container 5 and the electrolyte membrane 6, and the second hydrogen. The secondary battery type fuel cell system according to the first embodiment of the present invention shown in FIG. 1 is the same as that shown in FIG. 1 except that a pipe communicating with the generating member 3 is provided inside the wall of the container 5.

<Third Embodiment>
FIG. 10 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. 10 includes two containers 10 and 11 instead of the container 5, the fuel cell unit 2 is arranged inside the container 10, and the container 11, the first hydrogen generating member 1, the second hydrogen generating member 3, and the heater 4 are disposed, and further, enclosed by an inner wall of the container 10 and the electrolyte membrane 6, and an inner wall of the container 11. The secondary battery type fuel cell system according to the first embodiment of the present invention shown in FIG. 1 is the same as that shown in FIG. Similar to the modification shown in FIG. 4, in the secondary battery type fuel cell system according to the third embodiment of the present invention shown in FIG. 10, the first hydrogen generating member 1 and the second hydrogen generating member 3 Instead, a mixture of the first hydrogen generating member and the second hydrogen generating member may be provided.

<Fourth embodiment>
FIG. 10 shows a schematic configuration of a secondary battery type fuel cell system according to the fourth embodiment of the present invention. In the secondary battery type fuel cell system according to the third embodiment of the present invention shown in FIG. 10, a partition wall 12 is provided in the container 5, and fuel is provided in one of the internal spaces of the container 5 divided into two by the partition wall 12. 1 except that the battery part 2 and the second hydrogen generating member 3 are provided, the other one is provided with the first hydrogen generating member 1 and the heater 4, and the two internal spaces of the container 5 are communicated with each other. This is the same as the secondary battery type fuel cell system according to the first embodiment.

<Example>
Three examples of the secondary battery type fuel cell system according to the first embodiment of the present invention shown in FIG. 1 will be described below.

Example 1
Uranium is used for the second hydrogen generating member 3 made of a hydrogen storage alloy, and hydrogen is stored at 1 atm and 20 ° C. in a sealed space in which the fuel electrode 7 of the fuel cell unit 2 and the first hydrogen generating member 1 are sealed at the time of manufacture. Fill with. When the system is operated at 540 ° C. during power generation, the hydrogen partial pressure determined from the equilibrium state of the oxidation-reduction reaction of Fe used as the first hydrogen generation member 1 and the hydrogen storage used as the second hydrogen generation member 3 Both the hydrogen equilibrium pressure of the alloy is 2.22 atm. That is, during power generation of the system, the hydrogen partial pressure determined from the equilibrium state of the oxidation-reduction reaction of Fe used as the first hydrogen generation member 1 and the hydrogen equilibrium pressure of the hydrogen storage alloy used as the second hydrogen generation member 3 Can be combined.

  Thus, even when hydrogen leaks from the sealed space, while the hydrogen storage alloy used as the second hydrogen generating member 3 is sufficiently stored in the hydrogen storage alloy, the hydrogen content in the sealed space can be reduced during system power generation. The pressure is maintained at 2.22 atm, and stable power generation can be performed.

(Example 2)
Uranium is used for the second hydrogen generating member 3 made of a hydrogen storage alloy, and hydrogen is stored at 1 atm and 20 ° C. in a sealed space in which the fuel electrode 7 of the fuel cell unit 2 and the first hydrogen generating member 1 are sealed at the time of manufacture. Fill with. When the system is operated at 500 ° C. during power generation, the hydrogen partial pressure determined from the equilibrium state of the oxidation-reduction reaction of Fe used as the first hydrogen generating member 1 becomes 2.20 atm. The hydrogen equilibrium pressure of the hydrogen storage alloy used is 2 atm. That is, during power generation of the system, the hydrogen equilibrium pressure of the hydrogen storage alloy used as the second hydrogen generation member 3 is determined from the hydrogen partial pressure determined from the equilibrium state of the Fe redox reaction used as the first hydrogen generation member 1. Get smaller.

  Thus, even when hydrogen leaks from the sealed space, while the hydrogen storage alloy used as the second hydrogen generating member 3 is sufficiently stored in the hydrogen storage alloy, the hydrogen content in the sealed space can be reduced during system power generation. The pressure is maintained at 2.0 atm, and stable power generation can be performed.

(Example 3)
Titanium is used for the second hydrogen generation member 3 made of a hydrogen storage alloy, and hydrogen is 0.6 atm in a sealed space in which the fuel electrode 7 of the fuel cell unit 2 and the first hydrogen generation member 1 are sealed at the time of manufacture. Fill at 20 ° C. When the system is operated at 700 ° C. during power generation, the hydrogen partial pressure determined from the equilibrium state of the oxidation-reduction reaction of Fe used as the first hydrogen generating member 1 becomes 1.13 atm. The hydrogen equilibrium pressure of the hydrogen storage alloy used is 1.0 atm. That is, during power generation of the system, the hydrogen equilibrium pressure of the hydrogen storage alloy used as the second hydrogen generation member 3 is determined from the hydrogen partial pressure determined from the equilibrium state of the Fe redox reaction used as the first hydrogen generation member 1. Get smaller.

  Thus, even when hydrogen leaks from the sealed space, while the hydrogen storage alloy used as the second hydrogen generating member 3 is sufficiently stored in the hydrogen storage alloy, the hydrogen content in the sealed space can be reduced during system power generation. The pressure is maintained at 1.0 atm, and stable power generation can be performed.

<Modification>
In each of the embodiments described above, a solid oxide electrolyte is used as the electrolyte membrane 6 of the fuel cell 2 so that water (water vapor) is generated on the fuel electrode 7 side during power generation. According to this configuration, since the water vapor is generated on the side where the first hydrogen generating member 1 or the mixture 9 of the first hydrogen generating member and the second hydrogen generating member is provided, the apparatus can be simplified and reduced in size. It is advantageous to make. 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 may be used as the electrolyte membrane 6 of the fuel cell unit 2. However, in this case, since water vapor is generated on the oxidant electrode 8 side of the fuel cell unit 2 during power generation, this water vapor is combined with the first hydrogen generating member 1 or the first hydrogen generating member. What is necessary is just to provide the flow path which propagates to the mixture 9 with a 2nd hydrogen generating member.

  In the above-described embodiment, one fuel cell unit 2 performs both power generation and water electrolysis. However, a fuel cell (for example, a solid oxide fuel cell dedicated to power generation) and a water electrolyzer (for example, water) A solid oxide fuel cell dedicated for electrolysis may be connected to the fuel generating member 1 in parallel on the gas flow path.

DESCRIPTION OF SYMBOLS 1 1st hydrogen generating member 2 Fuel cell part 3 2nd hydrogen generating member 4 Heater 5, 10, 11 Container 6 Electrolyte membrane 7 Fuel electrode 8 Oxidant electrode 9 1st hydrogen generating member and 2nd hydrogen generating member Mixture with 12 partition wall

Claims (5)

A first hydrogen generating member that generates hydrogen by an oxidation reaction with water vapor and can be regenerated by a reduction reaction with hydrogen;
Power generation function having power generation function using hydrogen supplied from the first hydrogen generation member as fuel and electrolysis function performing electrolysis of water vapor for generating hydrogen to be supplied to the first hydrogen generation member・ Equipped with an electrolysis unit,
A secondary battery type fuel cell system for circulating a mixed gas containing hydrogen and water vapor between the first hydrogen generating member and the power generation / electrolysis unit,
A second hydrogen generating member made of a hydrogen storage alloy that has previously taken in hydrogen;
A secondary battery type fuel cell system characterized in that a hydrogen partial pressure determined by an equilibrium state of an oxidation-reduction reaction of the first hydrogen generating member is equal to or less than a hydrogen equilibrium pressure of the hydrogen storage alloy during power generation of the system. .   The secondary battery type fuel cell system according to claim 1, wherein the power generation / electrolysis unit is a solid oxide fuel cell.   The secondary battery type fuel cell system according to claim 2, wherein the hydrogen storage alloy is uranium, titanium, or any of these alloys.   The secondary battery type fuel cell system according to any one of claims 1 to 3, wherein the hydrogen storage alloy is covered with a hydrogen permeable material that permeates hydrogen and prevents permeation of water vapor. The hydrogen storage alloy has taken in hydrogen to the maximum extent,
5. The hydrogen partial pressure determined by the equilibrium state of the oxidation-reduction reaction of the first hydrogen generation member during power generation of the system is smaller than the hydrogen equilibrium pressure of the hydrogen storage alloy. One item is a secondary battery type fuel cell system.