JP6189190B2 - Fuel cell reduction device and fuel cell reduction method - Google Patents

Description

  The present invention relates to a fuel cell reduction device and a fuel cell reduction method.

  As one of the fuel cells, a solid oxide fuel cell (SOFC) is known. The SOFC has a fuel cell composed of a solid electrolyte, fuel electrodes formed on both sides thereof, and an air electrode. The SOFC supplies fuel gas to the fuel electrode, oxidant gas to the air electrode, and causes electric power by chemically reacting the fuel contained in the fuel gas and the oxygen contained in the oxidant gas via the solid electrolyte. (For example, Patent Documents 1 to 4).

  SOFC fuel cells are formed by firing. Firing of fuel cells is performed in an electric furnace or a gas furnace. Ni is used for the material of the fuel cell. The Ni is present as NiO in the fuel cell after firing. In the state of NiO, SOFC cannot generate electricity. In order to make the SOFC ready for power generation, it is necessary to reduce NiO to Ni.

Conventionally, the reduction of NiO has been performed by placing the fuel cell in a high temperature state and ventilating H ₂ to the fuel electrode side. In the reduction processing apparatus, a metal material is used for some parts constituting the reduction processing chamber. If a part made of a metal material becomes too hot, it causes a problem in structural strength, and also oxidizes and shortens its life. Therefore, when reducing NiO, the temperature of the component part made of a metal material must be suppressed, and the fuel cell must be in a high temperature state. The high temperature state refers to, for example, 600 ° C. at both ends of the fuel cell and 700 ° C. to 900 ° C. of the power generation unit.

JP 2004-119298 A JP 2008-21597 A JP-A-9-70540 JP 2012-59505 A

  As a method for increasing the temperature of the fuel cell, it is preferable that a gas furnace can be used as in the case of firing the fuel cell. However, when the gas furnace is used, it is difficult to partially raise the temperature of the fuel battery cell, and the entire reduction treatment chamber and the SOFC become hot. Therefore, a gas furnace cannot be used.

  As another method of raising the temperature of the fuel cell, there is a method of partially heating the fuel cell using an electric heater.

  However, when an electric heater is used, there is a concern that the electricity cost will increase during mass production.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the fuel cell reduction | restoration apparatus and fuel cell reduction | restoration method which can advance a reductive reaction, suppressing reduction processing cost.

In order to solve the above problems, the fuel cell reduction device and the fuel cell reduction method of the present invention employ the following means.
The present invention is a fuel cell reduction device for reducing a cell stack including a plurality of fuel cells formed by laminating a fuel electrode, a solid electrolyte, and an air electrode having an oxidation catalyst ability, A storage chamber for storing the cell stack; a fuel electrode side fluid supply path for supplying a first fluid containing a reducing agent to the fuel electrode side of the cell stack stored in the storage chamber; and the storage chamber. An air electrode side fluid supply path for supplying a second fluid containing an oxidant to the air electrode side of the cell stack, and an oxidant delivery section for sending a fluid containing an oxidant into the air electrode side fluid supply path; A preheating part for preheating the fluid containing the oxidant sent into the air electrode side fluid supply path, and a second fluid containing the oxidant sent into the air electrode side fluid supply path with a flammability limit concentration or less. Add fluid containing flammable fuel That a fuel addition unit includes a cathode-side fluid discharge path is a tubular member, wherein the air electrode-side fluid supply path, a second fluid containing the oxidizing agent toward the surface of the air electrode side of the cell stack A plurality of supply ports, the plurality of supply ports are arranged at predetermined intervals in the axial direction of the cell stack, and the air electrode side fluid discharge path is concentric with the side wall of the storage chamber. The fuel cell reduction device is disposed at the center of the storage chamber, and the cell stack is disposed between a side wall of the storage chamber and the air electrode side fluid discharge path .

  The combustible fuel can be catalytically combusted by an oxidation catalyst contained in the air electrode. Catalytic combustion is a flameless combustion method using a catalytic oxidation reaction on the catalyst surface. The flameless combustion method can allow complete oxidation of a lean fuel having a flammable limit concentration or less to proceed stably at a relatively low temperature.

  When a lean fuel having a flammable limit concentration or less is supplied to the air electrode side of the cell stack, the combustible fuel undergoes catalytic combustion only on the surface of the air electrode. The temperature of the fuel cell can be raised by the heat generated during combustion. In normal flame combustion, a lean fuel below the flammable limit concentration does not self-ignite. Therefore, no heat is generated by combustion in the portion of the cell stack that does not include the fuel cells. According to the present invention, the temperature of the fuel cell can be raised only without using an external high-temperature heat source such as an electric heater. Even if an external high-temperature heat source is used, it is sufficient to use it supplementarily, so that the electricity bill can be saved.

  The oxidation catalyst is a component contained in the air electrode. Since it is not necessary to add a new configuration to the fuel cell, the temperature rise using catalytic combustion is suitable as a temperature raising means in the design of a large fuel cell reduction device.

  In the fuel battery cell that has reached a high temperature due to catalytic combustion, the reducing agent reacts with the oxide contained in the fuel battery cell, and the oxide can be reduced.

  In patent document 4, the fluid containing a combustible fuel is supplied from the one end part side of a cell stack to the direction along the air electrode side surface of a fuel cell. In the method described in Patent Document 4, the temperature of the lower part of the cell stack is higher than that of the upper part, and a temperature distribution is generated in the axial direction. When reducing from the lower part of the high temperature cell stack, fuel deficiency occurs at the lower part when the upper part of the later generation is reduced.

  In the present invention, the fluid containing the combustible fuel is supplied toward the air electrode side surface of the fuel battery cell. Thereby, it is possible to suppress the occurrence of temperature distribution bias in the axial direction of the cell stack. By avoiding the temperature distribution, unreacted NiO can be prevented from remaining.

  The oxidation catalyst contained in the air electrode acts as a catalyst in a predetermined temperature range. By supplying the second fluid containing the preheated oxidant to the air electrode side of the cell stack, the temperature of the fuel cell can be raised to a temperature range where catalytic combustion is possible.

  1 aspect of the said invention WHEREIN: The said fuel addition part adjusts the addition amount of the fluid containing the said combustible fuel and the measurement means which measures the temperature of the said fuel cell, and control which controls the temperature of the said fuel cell It is preferable to provide the part.

  It is not preferable to make the temperature of the fuel cell too high because the fuel cell may be damaged. On the other hand, it is not preferable to make the temperature of the fuel battery cell too low because the reduction reaction may be delayed. According to one aspect of the invention, the temperature environment suitable for the reduction treatment of the cell stack can be maintained by adjusting the amount of fluid containing combustible fuel and changing the amount of heat generated by catalytic combustion.

  1 aspect of the said invention WHEREIN: With respect to the flow direction of the 2nd fluid supplied from the said air electrode side fluid supply path, these cell stacks are each arrange | positioned so that a position may be shifted, respectively. It is preferable to provide a support portion for supporting the.

  It is desirable that the second fluid is supplied to all the fuel cells of all cell stacks accommodated in the accommodation chamber without any deviation. According to one embodiment of the present invention, the plurality of cell stacks can be reduced in a well-balanced manner by shifting the position of the cell stacks regardless of the accommodated positions.

The present invention provides a fluid containing a preheated oxidant on the air electrode side of a cell stack provided with a plurality of fuel cells formed by laminating a fuel electrode, a solid electrolyte, and an air electrode having oxidation catalytic ability. A first temperature raising step for supplying and raising the temperature of the fuel cell; and a plurality of supply ports arranged at predetermined intervals in the axial direction of the cell stack on the air electrode side of the cell stack. A fluid containing an oxidant to which a fluid containing a flammable fuel having a flammable limit concentration or less is added is supplied toward the air electrode side surface of the stack, and the flammable fuel is catalytically burned to raise the fuel cell. A second temperature raising step for heating and a reduction step for supplying a fluid containing a reducing agent to the fuel electrode side of the cell stack, and the cell stack accommodates an air electrode side fluid discharge path that is a tubular member. Will be concentric with the side walls of the containment chamber Disposed in the center of the storage chamber, the cell stack is disposed between a side wall of the storage chamber and the air electrode side fluid discharge path, and the fluid containing the supplied oxidant is supplied to the air electrode side fluid. A fuel cell reduction method for discharging from a discharge path is provided.

  When a lean fuel having a flammable limit concentration or less is supplied to the air electrode side of the cell stack, the combustible fuel undergoes catalytic combustion only on the surface of the air electrode. The temperature of the fuel cell can be raised by the heat generated during combustion. According to the present invention, the temperature of the fuel cell can be raised only without using an external high-temperature heat source such as an electric heater.

  The oxidation catalyst is a component contained in the air electrode. Since it is not necessary to add a new configuration to the fuel cell, the temperature rise using catalytic combustion is suitable as a temperature raising means in the design of a large fuel cell reduction device.

  In the fuel battery cell that has reached a high temperature due to catalytic combustion, the reducing agent reacts with the oxide contained in the fuel battery cell, and the oxide can be reduced.

  In the present invention, the fluid containing the combustible fuel is supplied toward the air electrode side surface of the fuel battery cell. Thereby, it is possible to suppress the occurrence of temperature distribution bias in the axial direction of the cell stack. By preventing the temperature distribution in the axial direction, unreacted NiO can be prevented from remaining.

  The oxidation catalyst contained in the air electrode acts as a catalyst in a predetermined temperature range. By supplying the second fluid containing the preheated oxidant to the air electrode side of the cell stack, the temperature of the fuel cell can be raised to a temperature range where catalytic combustion is possible.

  In one aspect of the invention, the method includes a step of measuring the temperature of the fuel cell, and a temperature control step of controlling the temperature of the fuel cell by adjusting the amount of fluid containing the combustible fuel. Preferably it is.

  1 aspect of the said invention WHEREIN: The said temperature control process adds the fluid containing the combustible fuel of a combustible limit density | concentration to the fluid containing the said oxidizing agent until the temperature of the said fuel cell reaches 700 degreeC. And after the first control step, after the second control step, the second control step of adjusting the amount of fluid containing the combustible fuel so that the temperature of the fuel cell does not exceed 900 ° C., And a third control step of adjusting the amount of the combustible fuel added so that the temperature of the fuel battery cell is maintained at 700 ° C. or higher and 900 ° C. or lower.

  By controlling the amount of flammable fuel added, a temperature environment suitable for the reduction treatment of the cell stack can be maintained.

  1 aspect of the said invention WHEREIN: The fluid containing the said combustible fuel is the gas or hydrogen gas which has methane as a main component, The said combustible limit density | concentration may be 3 volume%.

  By doing so, the temperature of the fuel cell can be raised more safely.

  In the present invention, a catalytic reaction of combustible fuel is performed to raise the temperature of the fuel cell, whereby the reduction reaction can be advanced while suppressing the reduction treatment cost of the cell stack.

It is a partial expanded longitudinal cross-sectional view which shows the one aspect | mode of the cell stack processed by reduction. It is a schematic diagram explaining the structure of a fuel cell reduction apparatus. It is a fragmentary longitudinal cross-sectional view of a fuel cell reduction device. It is a cross-sectional view of a storage chamber in which a plurality of cell stacks are stored. It is a timing chart explaining the process of the fuel cell reduction method which concerns on one Embodiment of this invention. It is a schematic diagram explaining the reduction process of NiO.

  The present invention relates to a fuel cell reduction device and a fuel cell reduction for reducing a cell stack including a plurality of fuel cells formed by stacking a fuel electrode, a solid electrolyte, and an air electrode having an oxidation catalyst ability. Regarding the method.

  Hereinafter, an embodiment of a fuel cell reduction device and a fuel cell reduction method according to the present invention will be described with reference to the drawings.

  In the following, for convenience of explanation, the positional relationship of each component is specified using the expressions “upper” and “lower” on the basis of the paper surface, but this is not necessarily limited to the vertical direction. For example, the upward direction on the paper surface may correspond to the downward direction in the vertical direction. Moreover, you may respond | correspond to the horizontal direction where the up-down direction in a paper surface goes orthogonally to a perpendicular direction.

  In the following description, a cylindrical shape is described as an example of a cell stack of a solid oxide fuel cell (SOFC). However, the cell stack is not necessarily limited to this, and may be a flat cell stack, for example.

FIG. 1 shows one mode of a cell stack to be reduced.
The cell stack 101 includes a cylindrical base tube 103, a plurality of fuel cells 105 formed on the outer peripheral surface of the base tube 103, and an interconnector 107 formed between adjacent fuel cells 105. The fuel cell 105 is formed by stacking a fuel electrode 109, a solid electrolyte 111, and an air electrode 113. The cell stack 101 is connected to the air electrode 113 of the fuel cell 105 formed at the end in the axial direction of the base tube 103 among the plurality of fuel cells 105 formed on the outer peripheral surface of the base tube 103. The lead film 115 is electrically connected through the via. The cell stack 101 has supported parts at both ends.

The base tube 103 is made of a porous material, for example, CaO stabilized ZrO ₂ (CSZ), Y ₂ O ₃ stabilized ZrO ₂ (YSZ), or MgAl ₂ O ₄ . The base tube 103 supports the fuel cell 105, the interconnector 107, and the lead film 115. The base tube is formed by an extrusion method.

  The fuel electrode 109 is made of a material containing Ni. The fuel electrode 109 is made of an oxide of a composite material of Ni and a zirconia-based electrolyte material. For example, Ni / YSZ is used.

  The solid electrolyte 111 is mainly made of YSZ having gas tightness that prevents gas from passing through and high oxygen ion conductivity at high temperatures.

The air electrode 113 is made of a material obtained by mixing a conductive perovskite oxide represented by La _1-x Sr _x MnO ₃ and a zirconia-based electrolyte material. Mn contained in the air electrode 113 acts as an oxidation catalyst. For example, the air electrode is LaCaMnO ₃ , SmSrMnO ₃ , SmCaMnO ₃ , PrSrMnO ₃ , PrCaMnO ₃ or the like.

The interconnector 107 is made of a conductive perovskite oxide represented by M _1-x L _x TiO ₃ (M is an alkaline earth metal element, L is a lanthanoid element) such as SrTiO ₃ system, and is disposed on the fuel electrode side. It is a dense film so that the supplied gas and the gas supplied to the air electrode side do not mix. The interconnector 107 has stable electrical conductivity in both an oxidizing atmosphere and a reducing atmosphere. The interconnector 107 electrically connects the air electrode 113 of one fuel battery cell 105 and the fuel electrode 111 of the other fuel battery cell 105 in adjacent fuel battery cells 105, and connects the adjacent fuel battery cells 105 to each other. They are connected in series.

  Since the lead film 115 needs to have electronic conductivity and a thermal expansion coefficient close to that of other materials constituting the cell stack 101, the lead film 115 is made of Ni such as Ni / YSZ and a zirconia-based electrolyte material. Composed of composite material. The lead film 115 leads direct current power generated by the plurality of fuel cells 105 connected in series by the interconnector to the vicinity of the end of the cell stack 101.

  The fuel electrode 109, the solid electrolyte 111, the air electrode 113, the interconnector 107, and the lead film 115 are each formed by appropriately forming a slurry made of powder as a material on the base tube 103 and baking it.

In FIG. 2, the schematic diagram explaining the structure of the fuel cell reduction apparatus which concerns on this embodiment is shown. FIG. 3 shows a partial longitudinal sectional view of the fuel cell reduction device.
The fuel cell reduction device 1 includes a storage chamber 2, a fuel electrode side fluid supply path 3, an air electrode side fluid supply path 4, a fuel electrode side fluid discharge path 5, an air electrode side fluid discharge path 6, and a support portion. .

The storage chamber 2 can store a plurality of cell stacks 101 therein. The storage chamber 2 is preferably cylindrical.
The storage chamber 2 has a heat insulating member 7. The heat insulating member 7 is formed from a material having heat insulating properties. The heat insulating member 7 divides the inside of the accommodation chamber into a reduction chamber 8 in which the fuel cell 105 of the cell stack 101 is disposed and a support chamber 10 in which the supported portion 9 of the cell stack 101 is disposed. The reduction chamber 8 and the support chamber 10 can be ventilated. The supported portion 9 of the cell stack 101 is a non-power generation portion provided at both ends of the cell stack 101.

The fuel electrode side supply path 3 can supply a first fluid containing a reducing agent to the fuel electrode side of the cell stack 101 accommodated in the accommodation chamber 2. The first fluid including the reducing agent is H ₂ gas, N ₂ gas, water vapor, city gas reformed gas, or the like. The first fluid containing the reducing agent may be a combination of H ₂ gas, N ₂ gas, and water vapor.

  The fuel electrode side fluid discharge path 5 can discharge the first fluid that is supplied from one end of the cell stack 101 to the fuel electrode and flows to the other end of the cell stack 101 to the outside of the storage chamber 2. The fuel electrode side fluid discharge path 5 passes through the lower wall surface of the storage chamber 2. The interface between the fuel electrode side fluid discharge path 5 and the lower wall surface is hermetically sealed.

  The air electrode side fluid supply path 4 can supply a second fluid containing an oxidant to the air electrode side of the cell stack 101 toward the air electrode side of the cell stack 101 accommodated in the accommodation chamber 2. The second fluid containing an oxidant is a fluid containing an oxidizer to which a fluid containing an oxidizer or a fluid containing a flammable fuel having a flammable limit concentration or less is added.

  The air electrode side fluid supply path 4 has a plurality of supply ports 15. The supply port 15 opens toward the outer peripheral surface of the cell stack 101 (the surface on which the air electrode is provided). In the present embodiment, the supply port 15 is provided on the side wall surface in the reduction chamber 8 of the storage chamber 2. A part of the supply port 15 is provided on the side wall surface in the support chamber 10. The plurality of supply ports 15 are preferably arranged so that the second fluid can be supplied to the fuel cells 105 of all the cell stacks 101 accommodated in the accommodation chamber 2 without deviation. For example, the supply port is a magnetic tube having an outer diameter of about 5 mm and an inner diameter of about 3 mm. The interval between adjacent supply ports is preferably about 200 mm or more and 300 mm or less. The supply port is preferably arranged in a circular shape.

  The air electrode side fluid supply path 4 is connected to an oxidant delivery unit 11, a fuel addition unit 12, and a preheating unit (13, 14). The fuel addition unit 12 and the preheating unit (13, 14) are connected between the oxidant delivery unit 11 and the supply port 15 in the middle of the air electrode side fluid supply path 4. In this embodiment, the preheating part (13, 14) is connected to the downstream side of the fuel addition part 12.

  The oxidant delivery unit 11 can deliver a fluid containing an oxidant toward the storage chamber 2. The oxidant delivery unit 11 is a compressor or the like. The fluid containing the delivered oxidant becomes the base of the second fluid.

  The fuel addition unit 12 is located at the rear stage of the oxidant delivery unit 11. The fuel addition unit 12 can add a fluid containing a flammable fuel having a flammability limit concentration or less to a fluid containing an oxidant before being supplied to the storage chamber 2. The fuel addition unit 12 preferably includes a control unit (not shown) that controls the temperature of the fuel cell by adjusting the amount of fluid containing the combustible fuel. In that case, the fuel addition part 12 is provided with the measurement means which measures the temperature of a fuel cell. The control part can adjust the addition amount of the fluid containing the combustible fuel according to the temperature of the fuel cell measured by the measuring means.

  The preheating unit (13, 14) can raise the temperature of the second fluid containing the oxidizing agent to about 400 ° C. to 600 ° C. before being supplied to the storage chamber 2. The preheating unit is an electric heater 14, a heat exchanger 13, and the like. Only the electric heater 14 may be sufficient as a preheating part.

The air electrode side fluid discharge path 6 can discharge the second fluid containing the oxidant supplied into the storage chamber to the outside of the storage chamber. The air electrode side fluid discharge path 6 is a tubular member provided with a vent hole 16 on a side surface. In FIG. 3, the tubular member passes through the central portion of the lower wall surface of the storage chamber 2. The interface between the tubular member and the lower wall surface is hermetically sealed. The ventilation hole 16 is disposed in the reduction chamber 8. A part of the vent hole 16 may be disposed in the support chamber 10.
The air electrode side fluid discharge path 6 may be routed through the heat exchanger 13.

  The support portion supports the plurality of cell stacks 101 in the accommodation chamber. The support portion is made of a metal material having high temperature durability such as Inconel.

  Each support portion is configured so that the plurality of cell stacks are arranged at different positions with respect to the flow direction of the second fluid supplied from the supply port 15 of the air electrode side fluid supply path 6. I can support it. The flow direction of the second fluid is a direction perpendicular to the opening surface of the supply port 15. Shifting the position with respect to the flow direction of the second fluid indicates that the flow direction of the second fluid is represented by a line and that the axis points of two or more cell stacks are not placed on the line. The line extends to a range where the second fluid can flow.

  With reference to FIG. 4, an aspect of the arrangement of the cell stack will be described. FIG. 4 is a cross-sectional view of the storage chamber 2 in which a plurality of cell stacks 101 are stored. In the figure, the storage chamber 2 is cylindrical and has a structure in which the side wall can be divided. Line A indicates a dividing line. A plurality of supply ports are provided on the side wall of the storage chamber 2 (not shown). An air electrode side fluid discharge path 6 is disposed in the center of the storage chamber. The side wall of the storage chamber 2 and the tubular member of the air electrode side fluid discharge path 6 are arranged concentrically.

  The cell stacks 101 are arranged in two rows so as to draw a first circle and a second circle between the storage chamber 2 and the air electrode side fluid discharge path 6. The second circle has a smaller diameter than the first circle. The first circle and the second circle are concentric with the accommodation chamber. The cell stacks 101b arranged in the second circle are arranged so that the axial points are shifted in the radial direction from the cell stacks 101a arranged in the first circle.

  The support section has a plurality of pairs of support tools including an upper support tool that supports one end of the cell stack 101 and a lower support tool that supports the other end of the cell stack. The pair of supports can support one cell stack 101 such that the axial direction of the cell stack 101 is substantially parallel to the side wall surface of the storage chamber 2.

  The upper support has a hollow structure through which fluid can flow. The upper support tool penetrates the upper wall surface of the storage chamber 2.

  One end of the upper support is located outside the storage chamber 2. One end of the upper support is a flange structure 26 or the like, and is connected to the fuel electrode side fluid supply path 3 outside the storage chamber 2. The other end of the upper support is located in the support chamber 10 of the storage chamber 2. A female support member 17 is provided at the other end of the upper support. The female support member 17 can be fitted to one end of the cell stack 101 (supported portion 9). The interface between the upper support and the upper wall surface is hermetically sealed.

  The lower support has a hollow structure through which fluid can flow. The lower support is provided in the support chamber 10 of the storage chamber 2. The lower support has a female support member 18 at one end. The other end of the lower support has a flange structure 19 or the like and is connected to the fuel electrode side fluid discharge path 5. The female support member 18 can be fitted to the other end portion (supported portion 9) of the cell stack 101.

  An electric heater 20 may be provided inside the side wall surface of the storage chamber 2. The electric heater 20 can supplement the inside of the accommodation chamber as an auxiliary.

  In the present embodiment, the fuel electrode side fluid supply path 4 is provided on the side wall surface of the storage chamber 2 and the fuel electrode side fluid discharge path 5 is provided in the central portion of the storage chamber 2. May be. That is, the fuel electrode side fluid discharge path 5 may be provided in the side wall surface of the storage chamber 2, and the fuel electrode side fluid supply path 4 may be provided in the center of the storage chamber 2.

  Next, the fuel cell reduction method according to the present embodiment will be described with reference to FIG. FIG. 5 is a timing chart illustrating the steps of the fuel cell reduction method according to this embodiment. In the figure, the upper graph shows the temperature history of the fuel cell, and the lower graph shows the transition of the amount of combustible fuel added.

  The fuel cell reduction method according to the present embodiment includes a first temperature raising step, a second temperature raising step, and a reduction step.

  First, a plurality of cell stacks are accommodated in the accommodation chamber. In that case, a fuel cell is arrange | positioned in the reduction | restoration chamber of a storage chamber. Specifically, the female support member of the upper support is fitted to one end of the cell stack. The female support member of the lower support is fitted to the other end of the cell stack. The lower support is connected to the fuel electrode side fluid discharge path. Connect the reducing agent supply path to the upper support.

(First temperature raising step)
A fluid containing an oxidizing agent is preheated to about 400 ° C. to 600 ° C. A fluid containing a preheated oxidant is supplied to the air electrode side of the cell stack housed in the housing chamber. The supply flow rate is preferably 0.2 to 0.8 Nm ³ / h as the air flow rate per cell stack.

  The fluid containing the oxidant is oxidant gas. The oxidant gas is a gas containing approximately 15% to 30% oxygen. As the oxidant gas, air is typically suitable, but other than air, a mixed gas of fuel exhaust gas and air, a mixed gas of oxygen and air, or the like may be used.

  When the fluid containing the preheated oxidant is supplied to the storage chamber, the temperature of the storage chamber and the temperature of the fuel battery cell are raised to 400 ° C. or higher.

(Second temperature raising step)
When the temperature of the fuel cell reaches 400 ° C., the addition of the fluid containing the combustible fuel is started. The fluid containing the combustible fuel is added to the fluid containing the oxidizer in an amount below the flammable limit concentration. In the second temperature raising step, the amount of the fluid containing the combustible fuel is preferably set to the combustible limit concentration. As the fluid containing the combustible fuel, a gas mainly composed of methane such as city gas, hydrogen gas, or the like can be used. The combustible limit concentration of the combustible fuel is 3% by volume.

A fluid containing an oxidizer to which a fluid containing a combustible fuel having a flammable limit concentration or less is added is supplied toward the air electrode side of the cell stack toward the air electrode side of the cell stack. The supply flow rate is preferably 0.2 to 0.8 Nm ³ / h as the air flow rate per cell stack.

  When the fuel cell temperature becomes 400 ° C. or higher, the oxidation catalyst contained in the air electrode acts, and catalytic combustion of the supplied combustible fuel is started. Heat is generated by catalytic combustion, and the temperature of the fuel cell further rises.

(Reduction process)
After the second temperature raising step, when the temperature of the fuel battery cell reaches 700 ° C., the supply of the fluid containing the reducing agent to the fuel electrode side of the cell stack accommodated in the accommodation chamber is started. The supply flow rate of the fluid containing the reducing agent is set to 0.5 to 1.5 Nm ³ / h per cell stack.

  FIG. 6 is a schematic diagram illustrating the NiO reduction process. In the same figure, (a) is an image before reduction, (b) is an initial reduction, and (c) is an image after reduction. Ni contained in the material of the fuel cell is present in the fuel cell as NiO before reduction. When a fluid containing a reducing agent is supplied to the fuel electrode side of the cell stack, NiO and the reducing agent react, and NiO is reduced from the surface layer (outside) (b). The temperature of the fuel cell rises due to heat generated by the reduction reaction. In the initial stage of reduction, a short circuit current (a black arrow in the horizontal direction in (b)) is generated through Ni on the NiO surface layer. At that time, heat is generated to raise the temperature of the fuel cell. Therefore, at the initial stage of the reduction reaction, the amount of heat generated in the fuel cell is large. At the completion of the reduction process, almost all of the NiO has been reduced to Ni.

The fuel cell reduction method according to this embodiment preferably includes a temperature control step.
In the temperature control step, the temperature of the fuel cell is controlled by adjusting the amount of fluid containing the combustible fuel. The temperature control process includes a first control process, a second control process, and a third control process.

  During the temperature control step, the temperature of the fuel battery cell is measured, and the amount of fluid containing combustible fuel added may be adjusted according to the measured temperature. The temperature of the fuel battery cell is a temperature obtained by measuring the surface temperature of the air electrode with a thermocouple or the like. Alternatively, the air temperature in the reduction chamber may be measured.

  The first control process is performed in parallel with the second temperature raising process. That is, until the temperature of the fuel cell reaches 700 ° C., the fluid containing the flammable limit concentration of the flammable fuel is continuously added to the fluid containing the oxidizer. Thereby, the temperature rising time of the fuel cell can be shortened.

  The second control process is performed at the initial stage of the reduction process. The cell stack is preferably subjected to reduction treatment at a temperature not exceeding 900 ° C. due to limitations such as the heat resistant temperature of the base tube. In the initial stage of reduction, there is heat generation due to the reduction reaction and heat generation due to the occurrence of a short-circuit current, so the amount of heat generated in the fuel cell increases. Therefore, the amount of fluid containing combustible fuel is reduced, and control is performed so that the temperature of the fuel cell does not exceed 900 ° C. The amount of the combustible fuel added to the fluid containing the oxidizer is gradually reduced from about 3% by volume to about 1% by volume.

  As the reduction of NiO proceeds, the generation of short-circuit current stops, so the amount of heat generation decreases and the temperature of the fuel cell starts to decrease. If the temperature of the fuel cell becomes too low, the reduction reaction is delayed. Therefore, the third control step is performed when the temperature of the fuel cell starts to decrease. In the third control step, the addition amount of the fluid containing the combustible fuel is appropriately adjusted so that the temperature of the fuel battery cell is maintained at 700 ° C. or higher and 900 ° C. or lower. The amount of the fluid containing the combustible fuel may be appropriately increased from 1% by volume with respect to the fluid containing the oxidant.

DESCRIPTION OF SYMBOLS 1 Fuel cell reduction apparatus 2 Storage chamber 3 Fuel electrode side fluid supply path 4 Air electrode side fluid supply path 5 Fuel electrode side fluid discharge path 6 Air electrode side fluid discharge path 7 Heat insulation member 8 Reduction chamber 9 Supported part (non-power generation part) )
DESCRIPTION OF SYMBOLS 10 Support chamber 11 Oxidant delivery part 12 Fuel addition part 13 Preheater (heat exchanger)
14 Preheater (electric heater)
15 Supply port 16 Ventilation hole 17 Female support member (the other end portion of the upper support, support portion)
18 Female support member (lower support, support part)
19 Flange structure (lower support, support part)
20 Electric heater (auxiliary)
26 Flange structure (one end of upper support, support part)
101, 101a, 101b Cell stack 103 Base tube 105 Fuel cell 107 Interconnector 109 Fuel electrode 111 Solid electrolyte 113 Air electrode

Claims (7)

A fuel cell reduction device for reducing a cell stack including a plurality of fuel cells formed by laminating a fuel electrode, a solid electrolyte, and an air electrode having an oxidation catalyst ability,
A storage chamber for storing a plurality of the cell stacks;
A fuel electrode side fluid supply path for supplying a first fluid containing a reducing agent to the fuel electrode side of the cell stack stored in the storage chamber;
An air electrode side fluid supply path for supplying a second fluid containing an oxidant to the air electrode side of the cell stack stored in the storage chamber;
An oxidant delivery section for delivering a fluid containing an oxidant into the air electrode side fluid supply path;
A preheating unit for preheating a fluid containing an oxidant sent into the air electrode side fluid supply path;
A fuel addition unit for adding a fluid containing a flammable fuel having a flammable limit concentration or less to a fluid containing an oxidant sent into the air electrode side fluid supply path;
An air electrode side fluid discharge path which is a tubular member;
With
The air electrode side fluid supply path has a plurality of supply ports for supplying a second fluid containing an oxidant toward the air electrode side surface of the cell stack;
The plurality of supply ports are arranged at predetermined intervals in the axial direction of the cell stack ,
The air electrode side fluid discharge path is disposed in the center of the storage chamber so as to be concentric with the side wall of the storage chamber,
The fuel cell reduction device , wherein the cell stack is disposed between a side wall of the storage chamber and the air electrode side fluid discharge path . The fuel addition part is
Measuring means for measuring the temperature of the fuel cell;
The fuel cell reduction device according to claim 1, further comprising a control unit that adjusts an amount of fluid containing the combustible fuel to control a temperature of the fuel cell.   A support portion that supports the plurality of cell stacks is provided so that the plurality of cell stacks are arranged at different positions with respect to the flow direction of the second fluid supplied from the air electrode side fluid supply path. The fuel cell reduction device according to claim 1 or 2. Supplying a fluid containing a preheated oxidant to the air electrode side of a cell stack including a plurality of fuel cells formed by laminating a fuel electrode, a solid electrolyte, and an air electrode having an oxidation catalyst ability; A first temperature raising step for raising the temperature of the fuel cell;
From the plurality of supply ports arranged at predetermined intervals in the axial direction of the cell stack on the air electrode side of the cell stack, toward the air electrode side surface of the cell stack, flammability below the flammability limit concentration Supplying a fluid containing an oxidant to which a fluid containing fuel is added; catalytically burning the combustible fuel to raise the temperature of the fuel cell; and
A reduction step of supplying a fluid containing a reducing agent to the fuel electrode side of the cell stack;
Equipped with a,
An air electrode side fluid discharge path that is a tubular member is disposed in the center of the storage chamber so as to be concentric with the side wall of the storage chamber in which the cell stack is stored,
The cell stack is disposed between a side wall of the storage chamber and the air electrode side fluid discharge path,
A fuel cell reduction method for discharging a fluid containing the supplied oxidant from the air electrode side fluid discharge path . Measuring the temperature of the fuel cell; and
Adjusting the amount of fluid containing the combustible fuel and controlling the temperature of the fuel cell; and
The fuel cell reduction method according to claim 4 , comprising: The temperature control step includes
A first control step of adding a fluid containing a flammable fuel at a flammable limit concentration to the fluid containing the oxidant until the temperature of the fuel cell reaches 700 ° C .;
After the first control step, a second control step of adjusting the amount of fluid containing the combustible fuel so that the temperature of the fuel cell does not exceed 900 ° C .;
After the second control step, a third control step of adjusting the amount of the combustible fuel added so that the temperature of the fuel cell is maintained at 700 ° C. or higher and 900 ° C. or lower;
The fuel cell reduction method according to claim 5 comprising: The fluid containing the combustible fuel is a gas mainly containing methane or hydrogen gas,
The fuel cell reduction method according to any one of claims 4 to 6 , wherein the flammable limit concentration is 3% by volume.

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