JP2016039059A - Solid oxide type fuel battery device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide type fuel battery having an exhaust manifold that can prevent oxidation of a fuel electrode of a fuel battery cell while executing shutdown stop.SOLUTION: A solid oxide type fuel battery device 1 has plural fuel battery cells 16, an exhaust gas aggregation chamber 18 which surrounds the end portions of the plural fuel battery cells 16 and stores fuel off-gas, and a cell housing container 8 in which the fuel battery cells 16 and the exhaust gas aggregation chamber 18 are mounted. The exhaust gas aggregation chamber 18 has an exhaust nozzle 18d for exhausting fuel off-gas, and oxygen adsorption members 130a to 130d are arranged in a flow passage between the openings of the end portions of the plural fuel battery cells 16 and the exhaust nozzle 18d, in the exhaust manifold.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a solid oxide fuel cell device, and more particularly to a solid oxide fuel cell device that generates power by reacting a fuel gas and an oxidant gas.

  A solid oxide fuel cell (hereinafter also referred to as “SOFC”) uses an oxide ion conductive solid electrolyte as an electrolyte, attaches electrodes on both sides thereof, and supplies fuel gas on one side, The fuel cell operates at a relatively high temperature by supplying an oxidant gas (air, oxygen, etc.) to the other side.

  Japanese Unexamined Patent Publication No. 3-34258 (Patent Document 1) discloses a solid oxide fuel cell provided with a fuel discharge chamber (exhaust manifold). The exhaust manifold surrounds the upper end portions (downstream end portions) of the plurality of fuel cells, and temporarily stores unreacted fuel off-gas that has not been used for the power generation reaction. Then, the fuel off-gas stored in the exhaust manifold is discharged from its outlet, where it is mixed with air, burned and exhausted.

  Japanese Patent No. 5316830 (Patent Document 2) discloses a solid oxide fuel cell in which a shutdown stop is performed to stop power generation and fuel supply simultaneously when stopping a fuel cell in operation. . In the shutdown stop, the supply of fuel is stopped almost simultaneously with the end of power generation, so that fuel that does not contribute to power generation is not supplied, and waste of fuel can be avoided.

  However, if the shutdown stop is executed and the supply of fuel is stopped almost simultaneously with the stop of the power generation, the supply of fuel is stopped while the fuel cell remains in a high temperature state. Therefore, when shutdown shutdown is performed, generally, an oxidant gas such as air enters the fuel electrode from the air electrode side of the fuel cell, and contacts the fuel electrode that is still in a high temperature state to oxidize the fuel electrode. There is a risk. In general, it takes several hours or more for a stack of fuel cells operating at a high temperature to be lowered to a temperature at which there is no risk of oxidation of the fuel electrode after shutdown. Therefore, if the fuel supply is continued until the temperature of the fuel cell is sufficiently lowered without shutting down in order to avoid the risk of fuel electrode oxidation, it does not contribute to power generation for several hours or more. It is necessary to continue to supply fuel, and a great deal of fuel is wasted.

  In the solid oxide fuel cell described in Patent Document 2, a thin tube having a predetermined flow path resistance is attached to the upper end portion of each fuel cell in order to execute shutdown stop, and a structure in which air does not easily enter mechanically This reduces the risk of fuel electrode oxidation. Further, in the solid oxide fuel cell described in Patent Document 2, air is introduced to the air electrode side during a period when the pressure on the fuel electrode side of each fuel cell immediately after shutdown is high and no air enters. By executing the temperature drop control, it has succeeded in sufficiently reducing the risk of anode oxidation.

JP-A-3-34258 Japanese Patent No. 5316830

  However, the configuration in which the thin tubes are attached to the upper ends of each of the plurality of fuel cells as described in Patent Document 2 is time-consuming to manufacture and increases the manufacturing cost. A configuration having an exhaust manifold surrounding the upper end portion of the fuel cell is preferable. On the other hand, in a fuel cell having an exhaust manifold, if a shutdown stop is executed, the fuel gas held in the exhaust manifold and the fuel cells flows out of the exhaust manifold and the internal pressure decreases with time. Then, the pressure difference between the exhaust manifold and the air electrode side of the fuel cell gradually decreases. In this state, air on the air electrode side or air that has flowed back from the outside through the downstream pipe may enter the exhaust manifold due to diffusion or the like. When such an intrusion of air occurs during a period in which the fuel electrode of the fuel cell is still in a temperature range where the fuel electrode is oxidized, the fuel electrode of the fuel cell is oxidized by the entered air.

  In addition, when the air enters the tube of the fuel cell in such a stop process, the present inventor causes an oxidation reaction due to the following two different mechanisms, and a micro crack is formed in the electrolyte due to the oxidation reaction. To find out.

  First, the first oxidation reaction (atmosphere oxidation reaction) is the oxidation of the fuel electrode caused by the contact of air with the high temperature fuel electrode. This atmospheric oxidation occurs when a substance capable of oxidation reaction (for example, nickel) contained in the fuel electrode comes into contact with air in a high-temperature atmosphere that is higher than the minimum oxidation temperature (about 300 ° C. in the case of nickel). In the SOFC, if the atmospheric oxidation of the fuel electrode proceeds rapidly at a time during the stop process, there is a risk that microcracks may be generated in the fuel cells only after one stop process. When a slight amount of air enters the fuel cell at a high temperature, the fuel electrode is slightly oxidized even if a micro crack does not occur in the fuel cell. For this reason, it is necessary to prevent the ingress of air into the fuel cell so that the fuel electrode is not exposed to air in a high temperature state.

Next, the second oxidation reaction (electrochemical oxidation reaction) is generally considered to occur in a temperature range lower than atmospheric oxidation, and the generation mechanism is as follows.
First, the electrolyte of the fuel battery cell can transmit oxygen ions from the air electrode to the fuel electrode in an active state. The active state of the electrolyte has a temperature characteristic, and this temperature characteristic has a lower limit temperature value. That is, the electrolyte becomes active when the temperature is lower than the lower limit temperature, and allows oxygen ions to pass from the air electrode to the fuel electrode. On the other hand, in the active state, the fuel electrode reacts the fuel (hydrogen) with oxygen ions that have permeated through the electrolyte, thereby generating water and releasing electrons. The catalytic activity of the fuel electrode that causes such a reaction also has a temperature characteristic, and this temperature characteristic also has a lower limit temperature value. That is, the fuel electrode is activated when the temperature is lower than the lower limit temperature, and deactivated when the temperature is lower than the lower temperature. In the deactivated state, the fuel electrode cannot act to react with the fuel even if oxygen ions are supplied.

  Generally, there is a temperature difference between the minimum activity temperature of the electrolyte and the minimum activity temperature of the fuel electrode. Therefore, when the lower active temperature limit of the fuel electrode is higher than the lower active temperature limit of the electrolyte, the electrolyte is in an active state while the temperature is decreasing after the shutdown is stopped, while the fuel electrode is in an inactive state. It will pass through the temperature zone. When the air electrode is in an active state, oxygen ions are provided from the electrolyte to the fuel electrode in this temperature range, but the provided oxygen ions cannot react with the fuel.

  Here, the fuel electrode contains a substance (for example, nickel) that can electrochemically react with oxygen ions, and this substance reacts with oxygen ions that cannot react with the fuel to form oxides (for example, nickel oxide). Is generated. Electrons are emitted by this electrochemical oxidation reaction, and an electromotive force is generated.

  As described above, the electrochemical oxidation reaction of the fuel electrode is performed in such a temperature range that the electrolyte is in an active state and the fuel electrode is in an inactive state, and the oxygen component is present on the fuel electrode side and the air electrode (oxidant gas electrode) side. Generated by the presence of a pressure difference. Here, the oxygen partial pressure difference between the fuel electrode side and the air electrode side also occurs in one fuel cell. That is, the oxygen partial pressure difference is small near one end of the fuel cell into which the air that has entered flows in, and the oxygen partial pressure difference increases because no air has yet entered near the other end. As described above, a hydrogen concentration gradient is generated in one of the fuel cells as air enters, so that a large electromotive force is generated in a portion where the oxygen partial pressure difference of the fuel cell is large, whereas a portion where the oxygen partial pressure difference is small. Then, electromotive force is not generated much.

  As a result, an internal battery phenomenon occurs in which electrons move from a large electromotive force portion to a small portion (current flows) inside one fuel cell. When electrons move due to this internal cell phenomenon, the flow of oxygen ions that permeate the electrolyte that has not lost its activity is promoted, and the electrochemical oxidation reaction of the fuel electrode is promoted. In particular, in one fuel battery cell, the flow of oxygen ions is concentrated in a portion where the difference in oxygen partial pressure is large, and many electrochemical oxidation reactions occur in this portion. Although the current due to such an internal battery phenomenon is weak, as described above, the cooling time is several hours, so the time for the fuel cell to pass through the temperature band is long, and the accumulated current amount (ie, , The amount of oxide generated) increases. As described above, when a spatial gradient of hydrogen concentration occurs in the fuel cell due to the ingress of air, the fuel electrode undergoes an electrochemical oxidation reaction due to the internal battery phenomenon.

  Then, after the stop process is completed while the two kinds of oxidation reactions as described above are occurring, when the fuel cell is restarted, fuel (hydrogen) is supplied to the fuel electrode. Oxides generated at the fuel electrode by the electrochemical oxidation reaction undergo a reducing action. As described above, when the fuel cell is stopped and started and the subsequent operation is performed, the oxidation / reduction reaction repeatedly occurs in the fuel electrode. When changes in the microstructure and volume of the fuel electrode repeatedly occur, not only fatigue is accumulated in the electrolyte, but also microstructural changes and volume expansion are accumulated, and eventually microcracks occur in the electrolyte. A fuel cell in which microcracks have occurred cannot maintain power generation efficiency suitable for practical use.

  As described above, in the SOFC, when the temperature of the fuel cell decreases to a non-oxidizable temperature range in which neither of the two types of oxidation reactions occurs in the stop step, air enters the fuel cell. Either or both of the oxidation reactions occur at the fuel electrode, and as a result, there is a possibility that microcracks may occur in the electrolyte. In particular, when a shutdown stop is executed in a fuel cell having an exhaust manifold as described in Patent Document 1 and air enters the exhaust manifold during the stop process, the entered air easily enters the fuel cell. There was a risk of doing so. In addition, even if shutdown is not performed, if blackout is stopped due to a power failure or the like, it is impossible to execute anti-oxidation measures by control such as continuous supply of fuel gas during the stop process. Become. Therefore, in a fuel cell equipped with an exhaust manifold, the timing of air entry into the fuel cell via the exhaust manifold until the temperature of the fuel cell decreases to a non-oxidizable temperature zone where no oxidation reaction occurs at the fuel electrode. Antioxidation measures that can delay structurally were necessary.

  Accordingly, the present invention provides a solid oxide fuel cell device having an exhaust manifold capable of preventing oxidation of the fuel electrode of the fuel cell while executing shutdown stop. The purpose is to do.

  In order to solve the above-described problems, the present invention provides a solid oxide fuel cell device that surrounds a plurality of fuel cells and ends of the plurality of fuel cells, and An exhaust manifold having an internal space for storing fuel off-gas flowing out from the opening, and a module case for housing the plurality of fuel cells and the exhaust manifold, wherein the exhaust manifold is configured to exhaust the stored fuel off-gas. It has an exhaust port, and an oxygen adsorbent is disposed in a flow path between the opening of the end of the plurality of fuel cells and the off-gas exhaust port in the exhaust manifold.

The present invention configured as described above is configured to store the fuel off-gas flowing out from the ends of the plurality of fuel cells by providing an exhaust manifold. For this reason, the exhaust manifold surrounds the ends of the plurality of fuel cells, and is configured to eject the stored fuel off-gas from the off-gas exhaust port.
As described above, the shutdown stop has advantages such as prevention of wasteful fuel consumption and quick stop, but, as in the prior art, unless additional parts such as thin tubes are arranged in each fuel cell, the temperature At the same time, the air flows backward from the air electrode side of the fuel cell to the exhaust manifold and the fuel electrode side, and the fuel electrode is oxidized. This problem can be solved by implementing control means such as fuel supply and air supply. However, in a situation such as a blackout stop, the control means cannot be executed, so that the oxidation of the fuel electrode cannot be suppressed. Therefore, an antioxidation measure is desired not by a control means but by a structural means. If structural means can suppress at least oxidation in the high temperature zone where oxidation of the fuel electrode is likely to occur, fatal damage such as damage to the fuel cell can be avoided. It is very effective.

  Therefore, in the present invention, in the exhaust manifold, the oxygen adsorbent is disposed in the flow path from the end of the fuel cell to the off-gas exhaust port. The oxygen adsorbent is a member that takes in oxygen from the air and oxidizes itself by coming into contact with the air. Therefore, in the stop process, even if the air flows backward through the off-gas exhaust port from the outside of the exhaust manifold, the oxygen adsorbent is disposed before the air reaches the opening of the fuel cell in the exhaust manifold. Must pass through the flow path. Therefore, in the present invention, in the exhaust manifold, the oxygen adsorbent first takes in oxygen from the incoming air and is oxidized, so that only air with a very low oxygen concentration that hardly contains oxygen can reach the opening of the fuel cell. Become. As a result, the oxidation of the fuel electrode of the fuel cell can be delayed in time and the degree of oxidation can be greatly reduced.

In the present invention, preferably, the oxygen adsorbent is a metal material that is oxidized when exposed to air and reduced when exposed to fuel offgas at a temperature equal to or higher than the oxidation lower limit temperature of at least a plurality of fuel cells.
According to the present invention configured as described above, air enters the exhaust manifold in the temperature range where the fuel cell is oxidized during the stop process in consideration of the operating temperature characteristics of the solid oxide fuel cell device. Even if the oxygen adsorbent is oxidized instead of the fuel cell, the oxygen adsorbent is reduced by utilizing the fact that the oxygen adsorbent is placed in a fuel off-gas atmosphere during the power generation operation. be able to. In this way, by using a metal material that performs oxidation and reduction as an oxygen adsorbent in accordance with changes in the temperature and atmosphere in the exhaust manifold accompanying changes in operating conditions, replacement of the oxygen adsorbent is unnecessary and optional. Therefore, it is possible to facilitate the miniaturization and mounting of the member.

In the present invention, preferably, the oxidizing adsorbent includes nickel and titanium.
According to the present invention configured as described above, a metal material that is easy to obtain, process and handle can be used as the oxygen adsorbing material, so that safety and good oxygen adsorbing properties are ensured while suppressing manufacturing costs. In addition, the oxidation of the fuel electrode can be suppressed or delayed.

In the present invention, preferably, an oxygen adsorbent is disposed in the exhaust manifold, and a sub tank chamber for storing fuel off-gas flowing out from the openings at the ends of the plurality of fuel cells is provided.
According to the present invention configured as described above, in addition to the oxygen adsorbent being disposed, the sub-tank chamber for temporarily storing the fuel off-gas is provided in the exhaust manifold. As a result, the oxygen adsorbent can remove oxygen from the air that has entered the exhaust manifold to reduce the risk of oxidation of the fuel electrode, and even if air enters the exhaust manifold, the incoming air further stores fuel off-gas. If the sub tank chamber does not enter, the fuel cell cannot be reached, and the risk that air enters the fuel electrode of the fuel cell can be further reduced. Furthermore, since the oxidation of the fuel electrode can be suppressed by a combination of structural measures to prevent oxidation such as the arrangement of the oxygen adsorbent and the sub tank chamber, the capacity of the exhaust manifold itself can be reduced to prevent the oxidation of the fuel electrode. There is no need to increase the size, and the apparatus can be miniaturized.

In the present invention, preferably, the sub tank chamber is provided with a communication port at a lower end portion that communicates with the communication space that communicates the sub tank chamber and the off-gas exhaust port, and the oxygen adsorbent includes a plurality of fuels in the sub tank chamber. It arrange | positions between the electrical power collector which connects the edge part of a battery cell, and a communicating port.
According to the present invention configured as described above, the exhaust manifold has the sub tank chamber and the communication space, and the sub tank chamber and the communication space are communicated with each other through the communication port. And this communication port is provided in the lower end part of the sub tank chamber. Therefore, when air enters from the off-gas exhaust port in the stop step, the air enters the sub tank chamber through the communication space, through the communication port arranged at the lower end of the sub tank chamber, and further into the sub tank chamber. In this case, the fuel electrode cannot be reached unless it rises to the end of the fuel cell located above the communication port.

  Since air has a lower specific gravity than the fuel off-gas, even if it enters the sub-tank chamber filled with the fuel off-gas through the communication port, it accumulates at the bottom of the sub-tank chamber and is restricted from moving upward. Therefore, in order for the air to reach the end of the fuel cell, the fuel off-gas below the end of the fuel cell is expelled from the sub tank chamber, and the interface between the air layer and the fuel off-gas layer is the end of the fuel cell. Must reach the height. Thus, in the present invention, it is possible to extend the time from when the air starts to enter the exhaust manifold until it actually reaches the end of the fuel cell. In addition, since the communication port is located below the current collector, the time until the current contacts with the current collector can also be delayed, so that the current collector can be prevented from being oxidized. . Furthermore, since the communication port is formed at the lower end of the sub tank chamber, the vertical distance between the communication port and the end of the fuel cell can be increased, so that the air volume can be increased without increasing the capacity of the sub tank chamber. It is possible to prolong the time for the fuel to reach the end of the fuel cell.

In the present invention, preferably, the sub tank chamber communicates with the communication space that communicates the sub tank chamber with the off-gas exhaust port through the communication port, and the oxygen adsorbent is disposed in the communication space.
According to the present invention configured as described above, the exhaust manifold has the sub tank chamber and the communication space, and the sub tank chamber and the communication space are communicated with each other through the communication port. An oxygen adsorbent is disposed in the communication space. Therefore, even if air enters the exhaust manifold through the off-gas exhaust port in the stop process, oxygen is removed from the entered air by the oxygen adsorbent in the communication space. Furthermore, in order for the air from which oxygen has been removed to reach the end of the fuel cell, it is necessary to enter the sub tank chamber through the communication port. Therefore, in the present invention, it is possible to suppress the entry of oxygen-containing air into the sub tank chamber and to delay the time of entry.

In the present invention, preferably, the oxygen adsorbent is disposed in the sub tank chamber and in a communication space that communicates the sub tank chamber with the off-gas exhaust port.
According to the present invention configured as described above, the oxygen adsorbent is disposed in the communication space and the sub tank chamber, so that the air that has entered the exhaust manifold is first deprived of oxygen in the communication space, and then In addition, after further entering the sub tank chamber, oxygen is deprived in the sub tank chamber. Thereby, oxygen can be more reliably removed from the incoming air. In addition, the exhaust manifold has a double structure including the sub-tank chamber inside, so that the oxidation of the fuel electrode can be more reliably suppressed.

In the present invention, preferably, the oxygen adsorbent is a metal plate fixed to the electrolyte layers of a plurality of fuel cells.
According to the present invention configured as described above, the oxygen adsorbent can be easily manufactured by the metal plate. Moreover, by attaching to the electrolyte layer of the fuel cell, it is easy to assemble, and it is possible to hold the oxygen adsorbent in a fixed state, which may cause a short circuit between the fuel cells. It can be avoided.

In the present invention, the sub tank chamber is preferably provided with a top plate of the sub tank chamber adjacent to the off-gas exhaust port of the exhaust manifold, and the oxygen adsorbent is disposed on the top plate of the sub tank chamber in the exhaust manifold. Yes.
According to the present invention configured as described above, since the oxygen adsorbent is disposed close to the off-gas exhaust port, it is held at a higher temperature than the other parts by the fuel off-gas combustion heat during the power generation operation. The Therefore, even in the stopping step, the other portions are maintained at a relatively high temperature, so that oxidation with air is likely to occur. Further, when air enters from the off-gas exhaust port during the stop process, the oxygen adsorbing material is disposed in the vicinity of the off-gas exhaust port, so that the air that has entered easily comes into contact with the oxygen adsorbing material. Therefore, in the present invention, oxygen can be efficiently removed from the air that has entered by the oxygen adsorbent, and oxidation of the fuel electrode can be suppressed.

  According to the solid oxide fuel cell device of the present invention, in the solid oxide fuel cell device having an exhaust manifold, it is possible to prevent oxidation of the fuel electrode of the fuel cell while executing shutdown stop.

1 is an overall configuration diagram illustrating a solid oxide fuel cell apparatus (SOFC) including a fuel cell module according to an embodiment of the present invention. It is sectional drawing of the fuel cell storage container incorporated in the fuel cell module by one Embodiment of this invention. It is sectional drawing which decomposed | disassembled and showed the main member of the fuel cell storage container incorporated in the fuel cell module by one Embodiment of this invention. It is sectional drawing which expands and shows the part of the exhaust collection chamber incorporated in the fuel cell module by one Embodiment of this invention. It is a VV cross section in FIG. (A) It is sectional drawing which expands and shows the lower end part of the fuel cell by which the lower end is made into the cathode, (b) It is sectional drawing which expands and shows the lower end part of the fuel cell by which the lower end is made into the anode is there. 3 is a time chart schematically showing an example of a stop behavior in a solid oxide fuel cell device according to an embodiment of the present invention in time series. 6 is an enlarged time chart showing a state immediately after shutdown stop in a stop behavior of a solid oxide fuel cell device according to an embodiment of the present invention. It is explanatory drawing which shows typically the relationship between the activation temperature of the fuel electrode which comprises the fuel battery cell by one Embodiment of this invention, an electrolyte, and an air electrode, and a stop process. It is explanatory drawing of the effect | action in the stop process of the exhaust concentration chamber by one Embodiment of this invention.

Next, a solid oxide fuel cell device (SOFC) including a fuel cell module according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram illustrating a solid oxide fuel cell apparatus (SOFC) including a fuel cell module according to an embodiment of the present invention. As shown in FIG. 1, a solid oxide fuel cell apparatus (SOFC) 1 includes a fuel cell module 2 and an auxiliary unit 4 according to an embodiment of the present invention.

  The fuel cell module 2 includes a housing 6, and a fuel cell storage container 8 is disposed inside the housing 6 via an outer heat insulating material 7. A power generation chamber 10 is configured inside the fuel cell storage container 8, and a plurality of fuel cell cells 16 are concentrically arranged in the power generation chamber 10. With these fuel cell cells 16, A power generation reaction of air, which is fuel gas and oxidant gas, is performed.

  An exhaust collecting chamber 18 is attached to the upper end of each fuel cell 16. The remaining fuel (off-gas) that is not used in the power generation reaction in each fuel cell 16 is collected in an exhaust collection chamber 18 attached to the upper end, and a plurality of fuel cells 16 provided above the exhaust collection chamber 18 are collected. It flows out from the spout. The fuel that has flowed out is burned by the air remaining in the power generation chamber 10 without being used for power generation, and exhaust gas is generated.

  Next, the auxiliary unit 4 stores a water from a water supply source 24 such as a tap water and uses a filter to obtain pure water, and a water for adjusting the flow rate of the water supplied from the pure water tank. A water flow rate adjustment unit 28 (such as a “water pump” driven by a motor) as a supply device is provided. The auxiliary unit 4 also has a fuel blower 38 (a “fuel pump” driven by a motor) that is a fuel supply device that adjusts the flow rate of a hydrocarbon-based raw fuel gas supplied from a fuel supply source 30 such as city gas. Etc.).

  The raw fuel gas that has passed through the fuel blower 38 is supplied to the fuel gas supply channel 20 (FIG. 2) via the desulfurizer 36 disposed in the fuel cell module 2. Further, in the desulfurizer 36, the sulfur component in the raw fuel gas can be removed by adding hydrogen gas to the raw fuel gas. For this reason, the auxiliary unit 4 includes a condenser 33, an orifice 34, and a solenoid valve 35 for adding hydrogen gas to the raw fuel gas.

  The auxiliary unit 4 includes an air flow rate adjustment unit 45 (such as an “air blower” driven by a motor) that is an oxidant gas supply device that adjusts the flow rate of air supplied from the air supply source 40, and fuel gas. An air flow rate adjusting unit 46 (also “air blower” or the like) for purging the flow path is provided.

Further, the auxiliary unit 4 is provided with a hot water production device 50 for recovering the heat of the exhaust gas from the fuel cell module 2. The hot water production apparatus 50 is supplied with tap water, and the tap water is heated by the heat of the exhaust gas and supplied to a hot water storage tank of an external hot water heater (not shown).
Furthermore, the fuel cell module 2 is connected to an inverter 54 that is a power extraction unit (power conversion unit) for supplying the power generated by the fuel cell module 2 to the outside.

Next, the internal structure of the fuel cell housing container built in the fuel cell module 2 according to the embodiment of the present invention will be described with reference to FIGS. 2 is a cross-sectional view of the fuel cell module 2, and FIG. 3 is an exploded cross-sectional view of the main members of the fuel cell storage container.
As shown in FIG. 2, a plurality of fuel cells 16 are concentrically arranged in a space in the fuel cell storage container 8, and a fuel gas supply channel 20 that is a fuel gas passage so as to surround the periphery thereof. An exhaust gas exhaust passage 21 and an oxidant gas supply passage 22 which are exhaust gas passages are formed concentrically in order.

  First, as shown in FIG. 2, the fuel cell storage container 8 is a substantially cylindrical hermetic container, and an oxidant gas introduction pipe serving as an oxidant gas inlet for supplying air for power generation is provided on the side surface thereof. An exhaust gas exhaust pipe 58 for exhaust gas exhaust is connected to the bottom surface.

  As shown in FIGS. 2 and 3, inside the fuel cell storage container 8, an inner cylindrical member 64, which is a power generation chamber constituting member, and an outer cylindrical member in order from the inside so as to surround the periphery of the fuel cell 16. 66, an inner cylindrical container 68 and an outer cylindrical container 70 are arranged. The above-described fuel gas supply flow path 20, exhaust gas discharge flow path 21, and oxidant gas supply flow path 22 are flow paths configured between these cylindrical members and cylindrical containers, respectively, and between adjacent flow paths. Heat exchange takes place at. That is, the fuel gas supply channel 20 is disposed so as to surround the power generation chamber 10, the exhaust gas discharge channel 21 is disposed so as to surround the fuel gas supply channel 20, and the oxidant gas supply channel 22 is configured as the exhaust gas discharge channel. 21 is arranged so as to surround 21. In addition, an exhaust gas chamber 23 into which the exhaust gas guided by the exhaust gas discharge passage 21 flows is provided in the space on the lower end side of the fuel cell storage container 8.

  The inner cylindrical member 64 is a substantially cylindrical hollow body, and its upper end and lower end are open. A circular first fixing member 63 that is a dispersion chamber forming plate is airtightly welded to the inner wall surface of the inner cylindrical member 64. A fuel gas dispersion chamber 76 is defined by the lower surface of the first fixing member 63, the inner wall surface of the inner cylindrical member 64, and the upper surface of the dispersion chamber bottom member 72. The first fixing member 63 is formed with a plurality of insertion holes 63a through which the fuel battery cells 16 are inserted, and each fuel battery cell 16 is inserted into each insertion hole 63a in the ceramic adhesive. Is bonded to the first fixing member 63. As described above, in the solid oxide fuel cell device 1 of the present embodiment, each member constituting the fuel cell module 2 is filled with the ceramic adhesive in the joint portion between the members constituting the fuel cell module 2 and cured. Are hermetically joined to each other.

  The outer cylindrical member 66 is a cylindrical tube disposed around the inner cylindrical member 64, and is generally similar to the inner cylindrical member 64 so that an annular flow path is formed between the outer cylindrical member 66 and the inner cylindrical member 64. It is formed into a shape. Further, an intermediate cylindrical member 65 is disposed between the inner cylindrical member 64 and the outer cylindrical member 66. The intermediate cylindrical member 65 is a cylindrical tube disposed between the inner cylindrical member 64 and the outer cylindrical member 66. A reforming portion 94 is formed in the upper portion of the space between the outer cylindrical member 66 of the inner cylindrical member 64. An annular space between the outer peripheral surface of the intermediate cylindrical member 65 and the inner peripheral surface of the outer cylindrical member 66 functions as the fuel gas supply channel 20. Therefore, the reforming unit 94 and the fuel gas supply channel 20 receive heat due to heat generation in the fuel cell 16 and combustion of residual fuel at the upper end of the exhaust collecting chamber 18. Further, the upper end portion of the inner cylindrical member 64 and the upper end portion of the outer cylindrical member 66 are hermetically joined by welding, and the upper end of the fuel gas supply channel 20 is closed. Furthermore, the lower end of the intermediate cylindrical member 65 and the outer peripheral surface of the inner cylindrical member 64 are hermetically joined by welding.

  The inner cylindrical container 68 is a cup-shaped member having a circular cross section disposed around the outer cylindrical member 66, and an annular flow path having a substantially constant width is formed between the inner cylindrical container 68 and the outer cylindrical member 66. The side surface is formed in a generally similar shape to the outer cylindrical member 66. The inner cylindrical container 68 is disposed so as to cover the open portion at the upper end of the inner cylindrical member 64. An annular space between the outer peripheral surface of the outer cylindrical member 66 and the inner peripheral surface of the inner cylindrical container 68 functions as the exhaust gas discharge passage 21 (FIG. 2). The exhaust gas discharge passage 21 communicates with the space inside the inner cylindrical member 64 through a plurality of small holes 64 a provided in the upper end portion of the inner cylindrical member 64. Further, an exhaust gas crossing passage 23 a is provided so as to connect the lower inner peripheral surface of the outer cylindrical member 66 and the lower outer peripheral surface of the inner cylindrical member 64. Through the exhaust gas crossing passage 23 a, the exhaust gas discharge passage 21 and the exhaust gas chamber 23 are communicated with each other across the fuel gas supply passage 20.

A combustion catalyst 60 and a sheath heater 61 that is a heater for heating the combustion catalyst 60 are disposed below the exhaust gas discharge passage 21.
The combustion catalyst 60 is a catalyst filled in an annular space between the outer peripheral surface of the outer cylindrical member 66 and the inner peripheral surface of the inner cylindrical container 68 above the exhaust gas crossing passage 23 a. The exhaust gas descending the exhaust gas discharge passage 21 passes through the combustion catalyst 60 to remove carbon monoxide and flows into the exhaust gas chamber 23 through the exhaust gas crossing passage 23a.
The sheath heater 61 is an electric heater attached so as to surround the outer peripheral surface of the outer cylindrical member 66 below the combustion catalyst 60. When the solid oxide fuel cell device 1 is started, the sheath heater 61 is energized, whereby the combustion catalyst 60 disposed in the vicinity thereof is heated to the activation temperature.

  The outer cylindrical container 70 is a cup-shaped member having a circular cross section disposed around the inner cylindrical container 68, and an annular channel having a substantially constant width is formed between the outer cylindrical container 70 and the inner cylindrical container 68. The side surface is formed in a substantially similar shape to the inner cylindrical container 68. An annular space between the outer peripheral surface of the inner cylindrical container 68 and the inner peripheral surface of the outer cylindrical container 70 functions as the oxidant gas supply channel 22. Further, an oxidant gas introduction pipe 56 is connected to the lower side surface of the outer cylindrical container 70, and the oxidant gas supply flow path 22 communicates with the oxidant gas introduction pipe 56.

  The dispersion chamber bottom member 72 is a substantially circular dish-like member, and is hermetically fixed to the inner wall surface of the inner cylindrical member 64 with a ceramic adhesive. Thereby, a fuel gas dispersion chamber 76 is formed between the first fixing member 63 and the dispersion chamber bottom member 72. Further, at the center of the dispersion chamber bottom member 72, an insertion tube 72a that is a bus bar passage for inserting the bus bar 80 (FIG. 2) is provided. The bus bar 80 electrically connected to each fuel cell 16 is drawn out of the fuel cell storage container 8 through the insertion tube 72a. Further, the insertion tube 72a is filled with a ceramic adhesive, whereby the bus bar 80 is fixed, and the airtightness of the fuel gas dispersion chamber 76 is secured. Further, since the ceramic adhesive has high heat insulating properties, heat loss from the fuel gas dispersion chamber 76 through the insertion tube 72a can be suppressed.

  Further, an annular space defined by the inner peripheral surface of the inner cylindrical member 64, the bottom surface of the dispersion chamber bottom member 72, and the outer peripheral surface of the insertion tube 72 a is used as the exhaust gas chamber 23. That is, the exhaust gas chamber 23 is provided inside the annular exhaust gas discharge passage 21 and the fuel gas supply passage 20 so as to be located on the opposite side of the power generation chamber 10 with respect to the fuel gas dispersion chamber 76. . In the present specification, “inside the exhaust gas discharge passage 21” means that at least a part of the exhaust gas chamber 23 exists in a projection plane obtained by projecting the annular exhaust gas discharge passage 21 in the axial direction. Means. The same applies to “the inside of the fuel gas supply channel 20”. The exhaust gas chamber 23 is connected to an exhaust gas crossing passage 23a at the upper part of the side surface, and exhaust gas is introduced. An exhaust gas discharge pipe 58 is connected to the bottom surface of the exhaust gas chamber 23, and the exhaust gas is discharged outside the fuel cell module 2 through the exhaust gas discharge pipe 58.

  As shown in FIG. 2, a heat insulating material is disposed in an annular space defined by the inner peripheral surface of the inner cylindrical member 64, the bottom surface of the dispersion chamber bottom member 72, and the outer peripheral surface of the insertion tube 72a. The heat insulating material surrounds the periphery of the insertion tube 72a from the heat insulating material plate-like portion 73a disposed along the fuel gas dispersion chamber 76 (the bottom surface of the dispersion chamber bottom member 72). It is comprised from the heat insulating material protrusion part 73b extended. For this reason, a space excluding the space occupied by the heat insulating material plate-like portion 73 a and the heat insulating material protrusion 73 b in the annular space functions as the exhaust gas chamber 23. These heat insulating material plate portion 73 a and heat insulating material protrusion 73 b are arranged so as to insulate between the fuel gas dispersion chamber 76 and the exhaust gas chamber 23. Since the dispersion chamber bottom member 72 is made of metal, the temperature of the entire dispersion chamber rises to the same level as the temperature in the fuel gas dispersion chamber 76, but a heat insulating material protrusion 73b is also arranged around the insertion tube 72a. Therefore, the outflow of heat to the exhaust gas chamber 23 via the dispersion chamber bottom member 72 is also suppressed.

Further, in the exhaust gas chamber 23, a desulfurizer 36, which is a hydrodesulfurizer, is disposed so as to surround the heat insulating material protrusion 73b. The desulfurizer 36 is heated to a temperature capable of catalysis by the exhaust gas introduced into the exhaust gas chamber 23.
As shown in FIG. 2, a hydrogen extraction pipe 92 is connected to the fuel gas dispersion chamber 76. The hydrogen extraction pipe 92 communicates with the inside of the fuel gas dispersion chamber 76, penetrates the heat insulating material plate-like portion 73 a, further penetrates the exhaust gas chamber 23, and extends to the outside of the fuel cell module 2. As shown in FIG. 1, the hydrogen extraction pipe 92 is connected to a condenser 33 built in the auxiliary machine unit 4. The fuel gas in the fuel gas dispersion chamber 76 contains a lot of water vapor together with hydrogen gas. In the condenser 33, the water vapor contained in the fuel gas is condensed and separated from the hydrogen gas. The hydrogen gas from which the water vapor has been separated is mixed with the raw fuel gas supplied from the fuel supply source 30 via the orifice 34 and the electromagnetic valve 35 on the upstream side of the fuel blower 38. The raw fuel gas to which the hydrogen gas is added is sent to the desulfurizer 36 by the fuel blower 38.

  Since the pressure in the fuel gas dispersion chamber 76 is higher than the pressure on the upstream side of the fuel blower 38, the reformed fuel gas is taken out from the fuel gas dispersion chamber 76 due to this pressure difference. The orifice 34 is adjusted so as to give an appropriate flow path resistance to the flow path returning from the fuel gas dispersion chamber 76 to the upstream side of the fuel blower 38 and an appropriate amount of hydrogen gas is added to the raw fuel gas. Further, when hydrogen is not added to the raw fuel gas, the electromagnetic valve 35 is closed. In addition, although water vapor is mixed in the fuel gas (hydrogen gas) taken out from the fuel gas dispersion chamber 76 through the hydrogen extraction pipe 92, the hydrogen extraction pipe 92 is drawn out through the exhaust gas chamber 23 having a relatively high temperature. Therefore, the extracted water vapor is not condensed in the pipe line before reaching the condenser 33. For this reason, hydrogen gas can be stably taken out from the fuel gas dispersion chamber 76.

  As shown in FIG. 2, the hydrogen take-out pipe 92 communicates with the fuel gas dispersion chamber 76 at the bottom of the fuel gas dispersion chamber 76, that is, on the side close to the heat insulating material plate-like portion 73 a. Each fuel cell 16 communicates with the fuel gas dispersion chamber 76 on the ceiling surface of the fuel gas dispersion chamber 76, that is, on the side close to the power generation chamber 10. As described above, since the hydrogen extraction pipes 92 are communicated with positions sufficiently away from the respective fuel cells 16, the removal of the fuel gas by the hydrogen extraction pipes 92 is caused to flow into the fuel cells 16. There is no adverse effect. Therefore, even when the fuel gas is taken out by the hydrogen take-out pipe 92, the fuel gas flows evenly into each fuel battery cell 16, and the fuel supply unevenness does not occur.

  The desulfurizer 36 is a container having an annular cross section, and is filled with a desulfurization catalyst. An insertion tube 72a of the dispersion chamber bottom member 72 and a bus bar 80 extending therein are received in the hollow portion at the center of the desulfurizer 36 (FIG. 2). With this configuration, the exhaust gas flowing into the exhaust gas chamber 23 contacts the outer peripheral surface of the desulfurizer 36 and heats the desulfurizer 36. Further, since a gap is provided between the desulfurizer 36 and the heat insulating plate 73a (FIG. 2), exhaust gas flows into this gap, and the desulfurizer 36 is also heated from the upper end surface. . Accordingly, the desulfurizer 36 is heated to a temperature at which desulfurization can be performed early after the fuel cell module is started.

  The inside of the desulfurizer 36 is divided into three layers of a dispersion layer, a catalyst layer, and an aggregation layer by two donut-shaped partition plates. A desulfurizer inflow pipe 36c is connected to the dispersion layer, which is the space above the upper partition plate, and the raw fuel gas is sent by the fuel blower 38 (FIG. 1) through the desulfurizer inflow pipe 36c.

  The raw fuel gas introduced through the desulfurizer inflow pipe 36c is dispersed all around in the dispersion layer, and flows into the catalyst layer through a large number of small holes provided in the partition plate. The raw fuel gas that has flowed into the catalyst layer comes into contact with the desulfurization catalyst filled therein, and sulfur components mixed in the raw fuel gas are removed. Thus, in this embodiment, the flow path through which the raw fuel gas flows in contact with the desulfurization catalyst is lengthened by forming the desulfurizer 36 in an annular shape. As a result, the efficiency of removing sulfur components is improved, and the space inside the annular shape is not used as a dead space, but is effectively utilized as a space for inserting the insertion tube 72a. In the present embodiment, the desulfurizer 36 is a hydrodesulfurization type hydrodesulfurizer that reacts a sulfur component in the raw fuel gas with hydrogen using a catalyst.

  The raw fuel gas from which the sulfur component has been removed in the catalyst layer flows into the aggregation layer through a large number of small holes provided in the partition plate. The raw fuel gas flowing into the aggregated layer flows out of the desulfurizer 36 through the desulfurizer outflow pipe 36d connected to the aggregated layer. The desulfurizer outflow pipe 36d is connected to the fuel gas supply pipe 90 (FIG. 2), and the raw fuel gas that has passed through the desulfurizer 36 is introduced into the fuel gas supply flow path 20 through the fuel gas supply pipe 90. .

  On the other hand, an oxidant gas injection pipe 74 having a circular cross section for injecting air for power generation is attached so as to hang down from the ceiling surface of the inner cylindrical container 68. The oxidant gas injection pipe 74 extends in the vertical direction on the central axis of the inner cylindrical container 68, and each fuel cell 16 is disposed on a concentric circle around it. By attaching the upper end of the oxidant gas injection pipe 74 to the ceiling surface of the inner cylindrical container 68, the oxidant gas supply flow path 22 and the oxidant gas formed between the inner cylindrical container 68 and the outer cylindrical container 70 are formed. An injection pipe 74 is communicated. The air supplied through the oxidant gas supply channel 22 is injected downward from the tip of the oxidant gas injection pipe 74, hits the upper surface of the first fixing member 63, and spreads throughout the power generation chamber 10.

  The fuel gas dispersion chamber 76 is a cylindrical airtight chamber formed between the first fixing member 63 and the dispersion chamber bottom member 72, and each fuel cell 16 is forested on the upper surface thereof. Each fuel cell 16 attached to the upper surface of the first fixing member 63 has an inner fuel electrode communicating with the inside of the fuel gas dispersion chamber 76. The lower end portion of each fuel cell 16 penetrates the insertion hole 63a of the first fixing member 63 and protrudes into the fuel gas dispersion chamber 76, and each fuel cell 16 is fixed to the first fixing member 63 by adhesion. ing.

  As shown in FIG. 2, the inner cylindrical member 64 is provided with a plurality of small holes 64 b below the first fixing member 63. A space between the outer periphery of the inner cylindrical member 64 and the inner periphery of the intermediate cylindrical member 65 is communicated with the fuel gas dispersion chamber 76 through a plurality of small holes 64b. The supplied fuel once rises in the space between the inner circumference of the outer cylindrical member 66 and the outer circumference of the intermediate cylindrical member 65, and then descends in the space between the outer circumference of the inner cylindrical member 64 and the inner circumference of the intermediate cylindrical member 65. Then, it flows into the fuel gas dispersion chamber 76 through the plurality of small holes 64b. The fuel that has flowed into the fuel gas dispersion chamber 76 is distributed to the fuel electrode of each fuel cell 16 attached to the ceiling surface (first fixing member 63) of the fuel gas dispersion chamber 76.

  Further, the lower end portion of each fuel cell 16 projecting into the fuel gas dispersion chamber 76 is electrically connected to the bus bar 80 in the fuel gas dispersion chamber 76, and electric power is drawn out through the insertion tube 72a. The bus bar 80 is an elongated metal conductor for taking out the electric power generated by each fuel battery cell 16 to the outside of the fuel battery cell container 8, and is fixed to the insertion pipe 72 a of the dispersion chamber bottom member 72 via the insulator 78. Has been. The bus bar 80 is electrically connected to a current collector 82 attached to each fuel cell 16 inside the fuel gas dispersion chamber 76. The bus bar 80 is connected to the inverter 54 (FIG. 1) outside the fuel cell storage container 8. The current collector 82 is also attached to the upper end portion of each fuel cell 16 projecting into the exhaust collection chamber 18 (FIG. 4). The current collectors 82 at the upper end and the lower end connect the plurality of fuel cells 16 in parallel electrically, and connect the plurality of sets of fuel cells 16 connected in parallel electrically in series. The both ends of this series connection are connected to the bus bar 80, respectively.

  The current collector 82 is a substantially circular metal plate made of a conductive metal (for example, nickel, titanium, etc.), and through holes are formed corresponding to the arrangement positions of the fuel cells 16. Each fuel cell 16 can be attached to the current collector 82 by being inserted into the through hole.

Next, the configuration of the exhaust gas collecting chamber will be described with reference to FIGS. 4 and 5.
FIG. 4 is an enlarged cross-sectional view showing a portion of the exhaust collecting chamber, and FIG. 5 is a VV cross section in FIG.
As shown in FIG. 4, the exhaust concentration chamber 18 is a donut-shaped cross-section chamber attached to the upper end of each fuel cell 16, and an oxidant gas injection pipe 74 is provided at the center of the exhaust concentration chamber 18. Extends through.

  As shown in FIG. 5, three stays 64 c for supporting the exhaust collecting chamber 18 are attached to the inner wall surface of the inner cylindrical member 64 at equal intervals. As shown in FIG. 4, each stay 64 c is a small piece obtained by bending a thin metal plate. By placing the exhaust collection chamber 18 on each stay 64 c, the exhaust collection chamber 18 is concentric with the inner cylindrical member 64. Positioned above. As a result, the gap between the outer peripheral surface of the exhaust collecting chamber 18 and the inner peripheral surface of the inner cylindrical member 64 and the gap between the inner peripheral surface of the exhaust collecting chamber 18 and the outer peripheral surface of the oxidizing gas injection pipe 74 are as follows. , Uniform over the entire circumference (FIG. 5).

The exhaust collecting chamber 18 is configured by hermetically joining the collecting chamber upper member 18a and the collecting chamber lower member 18b.
The aggregation chamber lower member 18b is a circular dish-shaped member opened upward, and a cylindrical portion for allowing the oxidant gas injection pipe 74 to pass therethrough is provided at the center thereof.
The aggregation chamber upper member 18a is a stepped circular cup-shaped member that is open at the bottom, and an opening for penetrating the oxidant gas injection pipe 74 is provided at the center thereof. The lower part of the aggregation chamber upper member 18a is configured to be fitted into a donut-shaped cross-sectional area opened above the aggregation chamber lower member 18b.

  The gap between the inner peripheral surface of the wall around the aggregation chamber lower member 18b and the outer peripheral surface of the aggregation chamber upper member 18a is filled with a ceramic adhesive and cured, so that the airtightness of the joint is ensured. Yes. Further, a large-diameter seal ring 19a is disposed on the ceramic adhesive layer formed of the ceramic adhesive filled in the joint portion, and covers the ceramic adhesive layer. The large-diameter seal ring 19a is an annular thin plate, is disposed so as to cover the filled ceramic adhesive after being filled with the ceramic adhesive, and is fixed to the exhaust collecting chamber 18 by curing of the adhesive.

  On the other hand, the ceramic adhesive is also filled and hardened between the outer peripheral surface of the cylindrical portion at the center of the aggregation chamber lower member 18b and the edge of the opening at the center of the aggregation chamber upper member 18a. It is secured. Further, a small-diameter seal ring 19b is disposed on the ceramic adhesive layer formed of the ceramic adhesive filled in the joint portion, and covers the ceramic adhesive layer. The small-diameter seal ring 19b is an annular thin plate, is disposed so as to cover the filled ceramic adhesive after being filled with the ceramic adhesive, and is fixed to the exhaust collecting chamber 18 by curing of the adhesive.

  A plurality of circular insertion holes 18c are provided on the bottom surface of the aggregation chamber lower member 18b. The upper end portions of the fuel cells 16 are respectively inserted into the insertion holes 18c, and the fuel cells 16 extend through the insertion holes 18c. A ceramic adhesive is poured onto the bottom surface of the aggregation chamber lower member 18b through which each fuel cell 16 penetrates, and is cured, whereby a gap between the outer periphery of each fuel cell 16 and each insertion hole 18c. Are hermetically filled, and each fuel cell 16 is fixed to the aggregation chamber lower member 18b.

  Further, a circular thin plate-like cover member 19c is disposed on the ceramic adhesive poured on the bottom surface of the aggregation chamber lower member 18b, and is fixed to the aggregation chamber lower member 18b by hardening of the ceramic adhesive. The cover member 19c is provided with a plurality of insertion holes at positions similar to the insertion holes 18c of the aggregation chamber lower member 18b, and the upper end portion of each fuel cell 16 has a ceramic adhesive layer and the cover member 19c. It extends through.

  On the other hand, the upper side surface of the aggregation chamber upper member 18a is provided with a plurality of jet outlets 18d for ejecting the fuel gas concentrated in the exhaust aggregation chamber 18 (FIG. 4). The respective outlets 18d are arranged at equal intervals on the upper side surface of the aggregation chamber upper member 18a. As shown by arrows in FIG. 4, the remaining fuel that is not used for power generation flows into the exhaust collection chamber 18 from the upper end of each fuel cell 16, and the fuel collected in the exhaust collection chamber 18 It exits from the outlet 18d and is burned there.

  Further, on the bottom surface of the aggregation chamber lower member 18b, there is a cup-shaped surrounding member 120 having a cylindrical side surface portion 120b extending downward from a peripheral edge portion of a substantially circular upper surface portion (top plate) 120a. It is attached. The peripheral edge of the lower opening of the surrounding member 120 is airtightly connected to the bottom surface of the aggregation chamber lower member 18b by welding, ceramic adhesive, or the like. A substantially circular through hole 120c is formed at the center of the upper surface portion 120a. The cylindrical portion of the aggregation chamber lower member 18b is inserted into the through hole 120c, and the through hole 120c is airtightly connected to the cylindrical portion. ing. Furthermore, at the peripheral edge of the lower opening of the surrounding member 120, notched communication ports 120d are formed at several locations in the circumferential direction (four locations in the present embodiment).

  With such a configuration, the inside of the exhaust collecting chamber 18 is a communication space that communicates with the sub tank chamber 18A between the surrounding member 120 and the bottom surface of the collecting chamber lower member 18b and the outer space of the sub tank chamber 18A and communicates with the jet outlet 18d. 18B. The sub tank chamber 18A and the communication space 18B are communicated with each other through a communication port 120d. Therefore, after the fuel off gas flowing out from the upper end of the fuel cell 16 is once stored in the sub tank chamber 18A and then pushed out into the communication space 18B through the communication port 120d at the lower end of the sub tank chamber 18A. Then, it moves upward and flows out of the jet outlet 18d.

  Although the communication port 120d is formed at the lowermost portion of the sub tank chamber 18A, the communication port may be formed by providing a through hole in the side surface portion 120b or the upper surface portion 120a of the surrounding member 120. . However, it is preferable that the communication port 120d be positioned vertically below the opening at the upper end of the fuel cell 16 and further the current collector 82.

  In addition, the plurality of communication ports 120d are dimensioned so that the flow resistance of the plurality of communication ports 120d is larger than the flow resistance of the plurality of jet ports 18d. It is bigger than the loss. Therefore, the movement of the gas from the sub tank chamber 18A through the communication port 120d to the communication space 18B moves or flows out, rather than the movement of the gas from the communication space 18B through the jet outlet 18d into the power generation chamber 10. It is difficult (the same is true in the reverse direction).

  A current collector 82 is attached to the upper end of each fuel cell 16 in the sub tank chamber 18A. The current collector 82 is electrically connected to the electrode layer of the fuel battery cell 16. In this embodiment, this electrode layer is sequentially laminated on the surface of the tubular porous support that constitutes the fuel battery cell 16. Of the fuel electrode layer, the electrolyte layer, and the air electrode layer, the same material as that of the lowermost fuel electrode layer is formed. Further, a plurality of oxygen adsorbents 130 a are attached to the upper end portion of each fuel battery cell 16. The oxygen adsorbent 130a is oxidized in an oxidizing atmosphere at a high temperature (that is, adsorbs oxygen in the air) and is reduced by hydrogen in a reducing atmosphere (that is, reacts with hydrogen and releases oxygen). , And the same member as the current collector 82 (for example, nickel, titanium). However, the oxygen adsorbent 130a is attached to the electrolyte layer exposed by removing the air electrode layer at the upper end portion of the fuel battery cell 16.

Further, in the communication space 18B, cylindrical oxygen adsorbents 130b and 130c are attached to the inner side surface of the side wall of the aggregation chamber upper member 18a and the outer side surface of the side surface portion 120b of the surrounding member 120, respectively. Further, a substantially annular oxygen adsorbent 130d having a through hole formed in the center is disposed on the upper surface of the upper surface portion 120a of the surrounding member 120. The oxygen adsorbent 130d is arranged so as to be surrounded by the jet outlets 18d along the vicinity of the jet outlets 18d arranged in the circumferential direction. These oxygen adsorbents 130b, 130c, and 130d are also formed of the same material as the oxygen adsorbent 130a.
In addition, you may arrange | position an oxygen adsorption material in another position in 18 A of subtank chambers, and the communication space 18B. Further, the oxygen adsorbent may be a powder shape, a porous shape, or the like instead of a metal plate shape. In this case, it can be fixed to the side wall or the like with a ceramic adhesive or the like.

Next, a configuration for reforming the raw fuel gas supplied from the fuel supply source 30 will be described with reference to FIG.
First, an evaporating section 86 for generating steam for steam reforming is provided in the lower part of the fuel gas supply flow path 20 formed by a space between the inner cylindrical member 64 and the outer cylindrical member 66. . The evaporation unit 86 includes a ring-shaped inclined plate 86 a attached to the lower inner periphery of the outer cylindrical member 66 and a water supply pipe 88. The evaporation unit 86 is disposed between the sheath heater 61 disposed in the exhaust gas discharge passage 21 and the heat insulating material plate-shaped portion 73 a disposed in the exhaust gas chamber 23. The inclined plate 86 a is a metal thin plate formed in a ring shape, and its outer peripheral edge is attached to the inner wall surface of the outer cylindrical member 66. On the other hand, the inner peripheral edge of the inclined plate 86 a is positioned above the outer peripheral edge, and a gap is provided between the inner peripheral edge of the inclined plate 86 a and the outer wall surface of the inner cylindrical member 64.

  The water supply pipe 88 is a pipe that extends in the vertical direction from the lower end of the inner cylindrical member 64 into the fuel gas supply flow path 20, and the water for steam reforming supplied from the water flow rate adjustment unit 28 passes through the water supply pipe 88. To the evaporation unit 86. The upper end of the water supply pipe 88 passes through the inclined plate 86a and extends to the upper surface side of the inclined plate 86a, and the water supplied to the upper surface side of the inclined plate 86a is the upper surface of the inclined plate 86a and the inner wall surface of the outer cylindrical member 66. Stay between. The water supplied to the upper surface side of the inclined plate 86a is evaporated there to generate water vapor.

  A fuel gas introduction part for introducing the raw fuel gas into the fuel gas supply channel 20 is provided below the evaporation part 86. The raw fuel gas sent from the fuel blower 38 is introduced into the fuel gas supply passage 20 through the desulfurizer 36 and the fuel gas supply pipe 90. The fuel gas supply pipe 90 is a pipe extending vertically from the lower end of the inner cylindrical member 64 into the fuel gas supply flow path 20. Further, the upper end of the fuel gas supply pipe 90 is positioned below the inclined plate 86a. The raw fuel gas flowing out from the fuel gas supply pipe 90 is introduced to the lower side of the inclined plate 86a and rises to the upper side of the inclined plate 86a while the flow path is narrowed by the inclination of the inclined plate 86a. The raw fuel gas that has risen to the upper side of the inclined plate 86a is sufficiently mixed while rising together with the water vapor generated in the evaporation section 86.

  Furthermore, a reforming portion 94 is provided in the annular space on the upper, inner and outer peripheral sides of the intermediate cylindrical member 65. The reforming part 94 is arranged so as to surround the upper part of each fuel battery cell 16 and the periphery of the exhaust collecting chamber 18 above it. The reforming unit 94 includes a catalyst holding plate (not shown) attached to the outer wall surface of the inner cylindrical member 64 and the outer wall surface of the intermediate cylindrical member 65, and the reforming catalyst 96 held thereby.

The mixed gas of the raw fuel gas and the water vapor flows upward in the flow path between the outer periphery of the intermediate cylindrical member 65 and the inner periphery of the outer cylindrical member 66 and then turns back to return to the outer periphery of the inner cylindrical member 64 and the intermediate cylindrical member 65. Flows downward in the flow path between the inner peripheries. When the mixed raw fuel gas and water vapor come into contact with the reforming catalyst 96 filled in the reforming section 94, the steam reforming reaction SR shown in the formula (1) proceeds in the reforming section 94.
C _m H _n + xH ₂ O → aCO ₂ + bCO + cH ₂ (1)

  By this steam reforming reaction SR, the raw fuel gas is reformed into a fuel gas rich in hydrogen. The fuel gas reformed in the reforming section 94 flows downward in the space between the inner periphery of the intermediate cylindrical member 65 and the outer periphery of the inner cylindrical member 64, flows into the fuel gas dispersion chamber 76, and each fuel cell. 16 is supplied. Although the steam reforming reaction SR is an endothermic reaction, the heat required for the reaction is supplied by the combustion heat of off-gas flowing out from the exhaust collecting chamber 18 and the generated heat generated in each fuel cell 16.

Next, the fuel battery cell 16 will be described with reference to FIG.
In the fuel cell module 2 according to the embodiment of the present invention, a cylindrical horizontal stripe cell using a solid oxide is employed as the fuel cell 16. On each fuel cell 16, a plurality of single cells 16a are formed in a horizontal stripe shape, and one fuel cell 16 is configured by electrically connecting them in series. Each fuel cell 16 is configured such that one end thereof is an anode (anode) and the other end is a cathode (cathode), and half of the plurality of fuel cells 16 has an upper end as an anode and a lower end as a cathode. The other half are arranged so that the upper end is a cathode and the lower end is an anode.

  FIG. 6A is an enlarged cross-sectional view showing a lower end portion of the fuel battery cell 16 whose lower end is a cathode, and FIG. 6B is a cross-sectional view of the fuel battery cell 16 whose lower end is an anode. It is sectional drawing which expands and shows a lower end part.

  As shown in FIG. 6, the fuel cell 16 is formed of an elongated cylindrical porous support body 97 and a plurality of layers formed in a horizontal stripe pattern on the outside of the porous support body 97. Around the porous support 97, a fuel electrode layer 98, a reaction suppression layer 99, a solid electrolyte layer 100, and an air electrode layer 101 are formed in a horizontal stripe shape in order from the inside. For this reason, the fuel gas supplied through the fuel gas dispersion chamber 76 flows inside the porous support body 97 of each fuel battery cell 16, and the air injected from the oxidant gas injection pipe 74 is the air electrode. It flows outside the layer 101. Each single cell 16 a formed on the fuel cell 16 is composed of a set of fuel electrode layer 98, reaction suppression layer 99, solid electrolyte layer 100, and air electrode layer 101. The fuel electrode layer 98 of one single cell 16 a is electrically connected to the air electrode layer 101 of the adjacent single cell 16 a via the interconnector layer 102. Thereby, the several single cell 16a formed on the one fuel cell 16 is electrically connected in series.

  As shown in FIG. 6A, an electrode layer 103a is formed on the outer periphery of the porous support 97 at the cathode side end of the fuel battery cell 16, and a lead film layer 104a is formed outside the electrode layer 103a. Has been. At the cathode side end, the air electrode layer 101 and the electrode layer 103a of the single cell 16a located at the end are electrically connected by the interconnector layer 102. The electrode layer 103 a and the lead film layer 104 a are formed so as to penetrate the first fixing member 63 at the end portion of the fuel cell 16 and protrude downward from the first fixing member 63. The electrode layer 103a is formed below the lead film layer 104a, and the current collector 82 is electrically connected to the electrode layer 103a exposed to the outside. As a result, the air electrode layer 101 of the single cell 16a located at the end is connected to the current collector 82 via the interconnector layer 102 and the electrode layer 103a, and current flows as shown by the arrows in the figure. Further, a gap between the edge of the insertion hole 63a of the first fixing member 63 and the lead film layer 104a is filled with a ceramic adhesive, and the fuel cell 16 is fixed first on the outer periphery of the lead film layer 104a. It is fixed to the member 63.

  As shown in FIG. 6B, at the anode side end of the fuel battery cell 16, the fuel electrode layer 98 of the single cell 16a located at the end is extended, and the extension of the fuel electrode layer 98 is the electrode. It functions as the layer 103b. A lead film layer 104b is formed outside the electrode layer 103b. The electrode layer 103 b and the lead film layer 104 b are formed so as to penetrate the first fixing member 63 at the end portion of the fuel cell 16 and protrude downward from the first fixing member 63. The electrode layer 103b is formed below the lead film layer 104b, and the current collector 82 is electrically connected to the electrode layer 103b exposed to the outside. As a result, the fuel electrode layer 98 of the single cell 16a located at the end is connected to the current collector 82 via the electrode layer 103b formed integrally, and a current flows as shown by an arrow in the figure. Further, a gap between the edge of the insertion hole 63a of the first fixing member 63 and the lead film layer 104b is filled with a ceramic adhesive, and the fuel cell 16 is first fixed on the outer periphery of the lead film layer 104b. It is fixed to the member 63.

  6A and 6B, the configuration of the lower end portion of each fuel cell 16 has been described, but the configuration of the upper end portion of each fuel cell 16 is also the same. In the upper end portion, each fuel cell 16 is fixed to the aggregation chamber lower member 18b of the exhaust aggregation chamber 18, but the configuration of the fixed portion is the same as the fixing to the first fixing member 63 in the lower end portion. .

Next, the structure of the porous support body 97 and each layer is demonstrated.
In the present embodiment, the porous support body 97 is formed by extruding and sintering a mixture of forsterite powder and a binder.
In this embodiment, the fuel electrode layer 98 is a conductive thin film composed of a mixture of NiO powder and 10YSZ (10 mol% Y ₂ O ₃ -90 mol% ZrO ₂ ) powder.

In the present embodiment, the reaction suppression layer 99 is a thin film composed of a cerium-based composite oxide (LDC 40, that is, 40 mol% La ₂ O ₃ -60 mol% CeO ₂ ). The chemical reaction between the layer 98 and the solid electrolyte layer 100 is suppressed.
In the present embodiment, the solid electrolyte layer 100 is a thin film made of LSGM powder having a composition of La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O ₃ . Electric energy is generated by the reaction between oxide ions and hydrogen or carbon monoxide through the solid electrolyte layer 100.

In this embodiment, the air electrode layer 101 is a conductive thin film made of powder having a composition of La _0.6 Sr _0.4 Co _0.8 Fe _0.2 O ₃ .
In this embodiment, the interconnector layer 102 is a conductive thin film made of SLT (lanthanum-doped strontium titanate). Adjacent single cells 16 a on the fuel cell 16 are connected via the interconnector layer 102.
The electrode layers 103a and 103b are formed of the same material as the fuel electrode layer 98 in the present embodiment.
In this embodiment, the lead film layers 104a and 104b are made of the same material as that of the solid electrolyte layer 100.

Next, with reference to FIG.1 and FIG.2, the effect | action of the solid oxide fuel cell apparatus 1 is demonstrated.
First, in the starting process of the solid oxide fuel cell device 1, the fuel blower 38 is started, fuel supply is started, and energization to the sheath heater 61 is started. When energization of the sheath heater 61 is started, the combustion catalyst 60 disposed above the sheath heater 61 is heated, and the evaporator 86 disposed inside is also heated. The fuel supplied by the fuel blower 38 flows into the fuel gas supply channel 20 from the fuel gas supply pipe 90 via the desulfurizer 36. The inflowed fuel ascends in the fuel gas supply flow path 20 to reach the reforming portion 94, then descends in the reforming portion 94, and passes through a number of small holes 64b provided in the lower portion of the inner cylindrical member 64. It flows into the fuel gas dispersion chamber 76. Immediately after the solid oxide fuel cell device 1 is started, the temperature of the reforming catalyst 96 in the reforming unit 94 has not risen sufficiently, so that fuel reforming is not performed.

  The fuel gas that has flowed into the fuel gas dispersion chamber 76 flows into the exhaust collection chamber 18 through the inside (fuel electrode side) of each fuel cell 16 attached to the first fixing member 63 of the fuel gas dispersion chamber 76. Immediately after the start of the solid oxide fuel cell device 1, the temperature of each fuel cell 16 has not risen sufficiently, and power is not taken out to the inverter 54. Does not occur.

  The fuel that has flowed into the exhaust aggregation chamber 18 is ejected from the ejection port 18 d of the exhaust aggregation chamber 18. The fuel ejected from the ejection port 18d is ignited by an ignition heater (not shown) and burned there. Due to this combustion, the reforming section 94 disposed around the exhaust aggregation chamber 18 is heated. Further, the exhaust gas generated by the combustion flows into the exhaust gas discharge passage 21 through the small hole 64 a provided in the upper part of the inner cylindrical member 64. The high-temperature exhaust gas descends in the exhaust gas discharge passage 21 and is used for power generation that flows in the fuel gas supply passage 20 provided on the inside and the oxidant gas supply passage 22 provided on the outside. Heat the air. Further, the carbon monoxide is removed from the exhaust gas by passing through the combustion catalyst device 60 disposed in the exhaust gas discharge passage 21. The exhaust gas from which the carbon monoxide has been removed flows radially inward through the exhaust gas crossing passage 23 a and flows into the exhaust gas chamber 23. The exhaust gas flowing into the exhaust gas chamber 23 heats the desulfurizer 36 disposed in the exhaust gas chamber 23 and is discharged from the fuel cell module through the exhaust gas discharge pipe 58.

When the evaporation section 86 is heated by the exhaust gas and the sheath heater 61, the water for steam reforming supplied to the evaporation section 86 is evaporated and steam is generated. The water for steam reforming is supplied by the water flow rate adjusting unit 28 to the evaporation unit 86 in the fuel cell storage container 8 through the water supply pipe 88. The water vapor generated by the evaporator 86 and the raw fuel gas supplied via the fuel gas supply pipe 90 are sufficiently mixed in the fuel gas supply flow path 20.
In addition, since the evaporation part 86 is arrange | positioned adjacent to the sheath heater 61, it will be in the state which temperature rises early after starting and can produce | generate water vapor | steam. Moreover, since the evaporation part 86 is arrange | positioned between the sheath heater 61 and the heat insulating plate-shaped part 73a, the heat | fever of the sheath heater 61 cannot escape easily and temperature rises early. Further, since the exhaust gas crossing passage 23a is provided below and in the vicinity of the evaporation unit 86, the evaporation unit 86 is also heated by the heat of the exhaust gas flowing in the exhaust gas crossing passage 23a.

  The mixed raw fuel gas and water vapor rise in the fuel gas supply channel 20 and flow into the reforming unit 94. In a state where the reforming catalyst 96 of the reforming section 94 has risen to a temperature at which reforming is possible, when the mixture of raw fuel gas and steam passes through the reforming section 94, a steam reforming reaction occurs, The air-fuel mixture is reformed to a fuel gas containing a large amount of hydrogen. The reformed fuel gas flows into the fuel gas dispersion chamber 76 through the small hole 64b. The fuel gas containing abundant hydrogen that has flowed into the fuel gas dispersion chamber 76 flows into each fuel cell 16, while a part thereof is taken out of the fuel cell module 2 through the hydrogen extraction pipe 92.

  The taken-out fuel gas (hydrogen) is introduced into the condenser 33 of the auxiliary unit 4 where the mixed water vapor is removed. The fuel gas (hydrogen) from which the water vapor has been removed passes through the orifice 34 and the electromagnetic valve 35 and is added to the raw fuel gas upstream of the fuel blower 38. The raw fuel gas to which hydrogen is added is sent to the desulfurizer 36 by the fuel blower 38. In a state where the desulfurizer 36 in the exhaust gas chamber 23 is heated to a predetermined temperature by the exhaust gas, the sulfur component in the raw fuel gas is reacted with the added hydrogen and the desulfurization catalyst and removed. In the present embodiment, the desulfurization catalyst in the desulfurizer 36 catalyzes when heated to about 200 to 300 ° C. The raw fuel gas from which the sulfur component has been removed in the desulfurizer 36 flows into the fuel gas supply channel 20 through the fuel gas supply pipe 90 as described above.

  On the other hand, the reformed fuel gas flowing into each fuel cell 16 from the fuel gas dispersion chamber 76 rises inside each fuel cell 16 (fuel electrode side). The small holes 64 b of the fuel gas dispersion chamber 76 are provided around the periphery, and a sufficient volume is secured as the fuel gas dispersion chamber 76, so that the reformed fuel protrudes into the fuel gas dispersion chamber 76. Evenly flows into each fuel cell 16.

  On the other hand, the air, which is the oxidant gas supplied by the air flow rate adjusting unit 45, flows into the oxidant gas supply passage 22 through the oxidant gas introduction pipe 56. The air flowing into the oxidant gas supply channel 22 rises in the oxidant gas supply channel 22 while being heated by the exhaust gas flowing inside. The air rising in the oxidant gas supply passage 22 is collected at the center at the upper end portion in the fuel cell storage container 8 and flows into the oxidant gas injection pipe 74 communicated with the oxidant gas supply passage 22. To do. The air flowing into the oxidant gas injection pipe 74 is injected into the power generation chamber 10 from the lower end, and the injected air hits the upper surface of the first fixing member 63 and spreads throughout the power generation chamber 10. The air that has flowed into the power generation chamber 10 flows into the gap between the outer peripheral wall of the exhaust collecting chamber 18 and the inner peripheral wall of the inner cylindrical member 64, and between the inner peripheral wall of the exhaust collecting chamber 18 and the outer peripheral surface of the oxidizing gas injection pipe 74. Ascend through the gaps in between.

  At this time, a part of the air flowing through the outside (air electrode side) of each fuel cell 16 is used for the power generation reaction. Further, a part of the air that has risen above the exhaust aggregation chamber 18 is used for the combustion of fuel ejected from the ejection port 18d of the exhaust aggregation chamber 18. Exhaust gas generated by the combustion and air remaining without being used for power generation and combustion flow into the exhaust gas discharge passage 21 through the small hole 64a. The exhaust gas and air that have flowed into the exhaust gas discharge passage 21 are discharged after carbon monoxide is removed by the combustion catalyst 60.

  In this way, the temperature rises to about 650 ° C., which is the temperature at which each fuel cell 16 can generate electricity, and the reformed fuel flows inside each fuel cell 16 (fuel electrode side) and outside (air electrode side). When air flows through the chamber, an electromotive force is generated by a chemical reaction. In this state, when the inverter 54 is connected to the bus bar 80 drawn out from the fuel cell storage container 8, electric power is taken out from each fuel cell 16 to generate power.

Next, with reference to FIG. 7 and FIG. 8, the stop process in the solid oxide fuel cell device 1 will be described in time series.
FIG. 7 is a time chart schematically showing an example of the stop behavior when the shutdown stop is executed in the solid oxide fuel cell device 1 according to the embodiment of the present invention. FIG. 8 is an enlarged time chart showing a state immediately after the shutdown stop in FIG.

  In the example of the time chart shown in FIG. 8, the stop switch is operated by the user at time t101, and the pre-stop control is started. The control unit (pre-stop processing circuit) of the solid oxide fuel cell device 1 executes the following pre-stop control. In the pre-stop control, first, output to the outside by the fuel cell module 2 is stopped. As a result, as indicated by a thin one-dot chain line in FIG. 8, the current and power taken out from the fuel cell module 2 rapidly decrease. In the pre-stop control, the current output from the fuel cell module 2 to the outside is stopped, but a certain weak current (about 1 A) for operating the auxiliary unit 4 of the solid oxide fuel cell device 1 is stopped. ) Is continued for a predetermined period. For this reason, a weak current is taken out from the fuel cell module 2 during the pre-stop control even after the generated current significantly decreases at time t101. Further, as indicated by a broken line in FIG. 8, the output voltage of the fuel cell module 2 increases with a decrease in the extracted current. In this way, during the pre-stop control, by limiting the amount of power to be extracted and continuing the power generation with a predetermined power while extracting a weak current, a part of the supplied fuel is used for power generation. Thus, a significant increase in surplus fuel that remains unused is avoided, and the temperature in the fuel cell module 2 is lowered.

  Further, in the pre-stop control, after time t101, the fuel supply amount indicated by the dotted line in FIG. 8 and the supply amount of reforming water indicated by the thin solid line are linearly reduced. On the other hand, the air supply amount for power generation indicated by a thick dashed line is increased linearly. Therefore, during the pre-stop control, more air is supplied than the amount corresponding to the electric power extracted from the fuel cell module 2. In this way, by increasing the air supply amount, heat is taken from the reforming unit 94 and the temperature rise in the fuel cell module 2 is suppressed. Subsequently, in the example shown in FIG. 8, at time t <b> 102 about 20 seconds after time t <b> 101, the fuel supply amount and the water supply amount are reduced to the supply amount corresponding to the weak current extracted from the fuel cell module 2. And then the reduced supply is maintained. As described above, as the pre-stop control, by reducing the fuel supply amount and the water supply amount, the air flow in the fuel cell module 2 caused by the rapid stop of the large flow rate of fuel when the fuel supply is completely stopped. It prevents turbulence and a large amount of fuel remaining in the reforming section 94 and the fuel gas dispersion chamber 76 after the fuel supply is completely stopped. After time t101, the temperature of the air on the air electrode side in the fuel cell module 2 indicated by the thick solid line in FIG. 8 is lowered by decreasing the fuel supply amount and increasing the air supply amount. However, a large amount of heat is still accumulated in the heat insulating material 7 and the like surrounding the fuel cell module 2. In addition, during the pre-stop control, the current output to the outside is stopped, but the supply of fuel and water is continued. Thus, air does not enter the fuel electrode inside each fuel cell 16. Therefore, the supply of air can be continued safely.

  In the example shown in FIG. 8, the fuel supply amount and the water supply amount for reforming are made zero at time t103 about 2 minutes after the time t101 when the pre-stop control is started, and the current taken out from the fuel cell module 2 It is also zeroed and shutdown is stopped.

  Further, in the example shown in FIG. 8, after the shutdown is stopped at time t103, the supply of power generation air (however, the power generation is completely stopped) is continued as the temperature drop control (exhaust heat, exhaust air blow). control). As a result, the air in the fuel cell module 2 (air electrode side of the fuel cell 16) and the fuel off-gas that has flowed out of the exhaust collecting chamber 18 after the shutdown is stopped are discharged, so that the temperature drop control functions as an exhaust process.

  In the present embodiment, after the fuel supply is completely stopped at time t103, a large amount of power generation air is continuously supplied for a predetermined period until time t104. In the present embodiment, the air supply amount for power generation is increased to the maximum air supply amount during the pre-stop control, and this air supply amount is maintained thereafter. During the period in which the temperature drop control is performed, fuel remains in the exhaust aggregation chamber 18, the fuel electrode side of the fuel cell 16 and the reforming portion 94, and the exhaust aggregation chamber 18 and the fuel electrode side (each The pressure inside the fuel cell 16 is still sufficiently high. Therefore, in the predetermined period in which the temperature drop control is performed, even if the power generation air is supplied in a state where the fuel supply is stopped, the air does not enter the exhaust collecting chamber 18 and the fuel electrode side.

  Next, at time t105 when the temperature in the fuel cell module 2 is lowered to about 300 ° C. (the lower limit temperature for oxidation due to atmospheric oxidation of the fuel electrode), the control unit (shutdown stop circuit) of the solid oxide fuel cell device 1 is cooled. Start operation control. Therefore, between time t104 and time t105, the fuel cell module 2 is naturally cooled. On the other hand, in the cooling operation control, the air flow rate adjustment unit 45 is continuously operated at a large flow rate. At this point, several hours (about 5 to 6 hours) have passed since the shutdown stopped, and the exhaust concentration chamber 18 and the fuel electrode side and the air electrode side of each fuel battery cell 16 are reduced to almost atmospheric pressure, The air on the air electrode side can diffuse to the fuel electrode side through the exhaust collecting chamber 18. In the cooling operation control, the fuel cell 16 is rapidly cooled by sending a large amount of air into the fuel cell module 2. By cooling the fuel cell 16, the temperature of the electrolyte layer of each fuel cell 16 is lowered. When the electrolyte layer is cooled to a deactivated state, oxygen ions do not permeate the electrolyte layer and there is no risk of electrochemical oxidation of the fuel electrode. In addition, when air is continuously fed at a large flow rate to the air electrode side of the fuel cell 16, air may enter the fuel electrode side of the fuel cell 16 through the exhaust collecting chamber 18. However, when the air enters, the oxygen partial pressures on the air electrode side and the fuel electrode side become substantially equal, so the risk of electrochemical oxidation of the fuel electrode is greatly reduced.

  Further, at time t106 when the temperature in the fuel cell module 2 has decreased to about 150 ° C., the control unit (shutdown stop circuit) operates the purge air flow rate adjustment unit 46. By operating the air flow rate adjusting unit 46, air is supplied to the fuel electrode side (inside each fuel cell 16) and the exhaust collecting chamber 18 of the fuel cell 16 via the reforming unit 94 and the fuel gas dispersion chamber 76. Is supplied directly. Further, the supply of air by the air flow rate adjusting unit 45 is continued as it is. By operating the purge air flow rate adjusting unit 46 and supplying air directly to the fuel electrode side, the fuel remaining in the reforming portion 94, the fuel gas dispersion chamber 76, the inside of each fuel cell 16, etc., Water vapor is discharged. As a result, the oxygen partial pressures on the air electrode side and the fuel electrode side are completely equal, so that even if the temperature of the fuel cell 16 is locally high, the risk of electrochemical oxidation of the fuel electrode is substantial. As a result, safety can be ensured. The supply of air to the fuel electrode side by the purge air flow rate adjustment unit 46 starts from a temperature in the fuel cell module 2 of about 300 ° C., similarly to the forced air cooling in the power generation chamber 10 by the air flow rate adjustment unit 45. You may do it. In addition to performing the purge by the purge air flow rate adjusting unit 46 during the stop process, or not performing it during the stop process, it is performed in the next start-up process, particularly at the initial stage or at the start. You may make it do.

Next, with reference to FIG. 9, the relationship between the stop process in the solid oxide fuel cell device 1 and the temperature of the fuel cell 16 will be described.
In the solid oxide fuel cell device 1 of the present embodiment, the fuel cell 16 is held at about 650 ° C. or higher during power generation in normal operation. When the stop switch is operated in this state, shutdown stop is executed after pre-stop processing is performed.

  In the present embodiment, the fuel electrode of the fuel battery cell 16 contains nickel, and the margin is set higher than the lower limit oxidation temperature (300 ° C.) that is the lowest temperature at which nickel atmosphere oxidation can occur. An oxidation suppression temperature Te (350 ° C.) is set. The oxidation suppression temperature means a temperature at which the risk that the fuel electrode is oxidized in the atmosphere is sufficiently reduced. The risk of the anode being oxidized gradually decreases with decreasing temperature and eventually becomes zero. For this reason, even if it is the oxidation suppression temperature of a temperature range a little higher than the oxidation minimum temperature of a fuel electrode, the risk of fuel electrode oxidation can fully be reduced.

  In the present embodiment, the lower limit temperature Ta of the fuel electrode, which is the lower limit temperature at which the catalyst of the fuel electrode of the fuel cell 16 is activated, is about 290 ° C., which is lower than the oxidation suppression temperature Te. The fuel electrode receives oxygen ions from the electrolyte layer and reacts the received oxygen ions with fuel (hydrogen) until the temperature decreases from the power generation operating temperature range to the activation lower limit temperature Ta, thereby generating water and generating electrons. Can be released. However, when the temperature of the fuel electrode is lower than the activation lower limit temperature Ta, even if oxygen ions are received, the fuel electrode cannot react with the fuel and cause a power generation reaction.

On the other hand, the minimum active temperature Tb of the electrolyte in which the electrolyte layer is in an active state capable of transmitting oxygen ions from the air electrode to the fuel electrode is about 200 ° C., which is lower than the minimum active temperature Ta of the fuel electrode. The electrolyte layer can transmit oxygen ions received from the air electrode to the fuel electrode until the electrolyte layer falls from the power generation operating temperature range to the activation lower limit temperature Tb. However, when the temperature of the electrolyte layer is lower than the lower limit activation temperature Tb, oxygen ions cannot be transmitted to the fuel electrode even if oxygen ions are received from the air electrode.
Note that the air electrode is in an active state capable of converting oxygen in the air into oxygen ions at the activation lower limit temperature Tb or higher of the electrolyte layer.

  As shown in FIG. 9, in the temperature zone Tc between the activation lower limit temperature Ta of the fuel electrode and the activation lower limit temperature Tb of the electrolyte, the electrolyte layer is in an active state capable of transmitting oxygen ions to the fuel electrode. It is in a deactivated state in which the catalytic activity is lost. Therefore, after the shutdown is stopped, when the fuel cell 16 is in this temperature zone Tc, oxygen ions are supplied to the fuel electrode through the electrolyte layer.

  In the temperature zone Tc, the electrolyte layer and the air electrode are in an active state, and oxygen ions can pass through the air electrode and the electrolyte layer to the fuel electrode, but the fuel electrode has a deactivated catalyst activity. Therefore, the fuel electrode cannot cause a normal power generation reaction that causes the supplied oxygen ions to react with the fuel (hydrogen).

On the other hand, the fuel electrode contains nickel, and nickel is likely to react with oxygen in the air to form nickel oxide in a high temperature atmosphere at or above the oxidation suppression temperature Te (about 350 ° C.), but lower than the oxidation suppression temperature Te. In the temperature zone Tc, nickel is in a state of hardly reacting with oxygen in the air.
However, when oxygen ions that have passed through the electrolyte layer are supplied to the fuel electrode in the temperature zone Tc, nickel in the fuel electrode can be combined with oxygen ions to become nickel oxide by an electrochemical oxidation reaction. When this reaction occurs, electrons are emitted. Therefore, when the above electrochemical oxidation reaction occurs, a charge is generated by a mechanism different from that of a normal power generation reaction.
When the fuel electrode is in an active state, it is considered that only a normal power generation reaction in which oxygen ions are combined with fuel occurs, and an abnormal reaction in which oxygen ions are combined with nickel does not occur substantially.

  On the other hand, after the shutdown is stopped, the extraction of electric power from the fuel cell module 2 is stopped, so that it is considered that no current flows even if charges are generated by the electrochemical oxidation reaction. . However, the present inventor has found that even if the extraction of electric power is stopped and the fuel electrode and the air electrode are electrically non-conductive (open circuit), a weak current can flow locally. I found it.

  That is, the electrochemical oxidation reaction occurs based on the difference in oxygen partial pressure between the fuel electrode side and the air electrode side. Therefore, when a large amount of hydrogen remains on the fuel electrode side, the oxygen partial pressure on the fuel electrode side is low, and the difference in oxygen partial pressure on the air electrode side is large. Therefore, oxygen ions easily flow through the electrolyte layer. Become. Therefore, for example, when air enters the vicinity of the upper end portion of the fuel cell 16, the difference in oxygen partial pressure near the upper end portion of the fuel cell 16 is reduced.

  For this reason, many electrochemical oxidation reactions occur in the vicinity of the lower end portion of the fuel battery cell 16 to generate a large amount of charge, and relatively less charge is generated in the vicinity of the upper end portion. As a result, a potential difference is generated in the fuel electrode of one fuel battery cell 16, and local charge movement (weak current) occurs. When a weak current due to such a local battery phenomenon flows, the electrochemical oxidation reaction of nickel further proceeds. In particular, the flow of oxygen ions concentrates near the lower end of each fuel cell 16 where the difference in oxygen partial pressure between the fuel electrode side and the air electrode side is large, and many electrochemical oxidation reactions occur in this portion.

Nickel oxide generated by the electrochemical oxidation reaction is reduced by the fuel (hydrogen) supplied to the fuel electrode during the power generation operation. As described above, when the nickel contained in the fuel electrode undergoes an electrochemical oxidation / reduction reaction by stopping and starting and subsequent operation, the fuel electrode changes in the microstructure and volume.
Furthermore, in addition to the frequent stopping and starting of the fuel cell module, the electrochemical oxidation reaction of nickel occurs for a relatively long time in the stopping and starting process, particularly in the stopping process that requires a long time.

Thus, when a change in the microstructure and volume of the fuel electrode occurs, tensile stress is applied to the electrolyte layer. Each fuel cell where the flow of oxygen ions due to local battery phenomenon concentrates as the cumulative amount of nickel that undergoes electrochemical oxidation / reduction reactions increases many times due to long-term use. In the vicinity of the lower end of 16, a minute crack is finally generated in the electrolyte layer.
Thus, the present inventors are in a state where nickel, which is a specific substance contained in the fuel electrode, is subjected to electrochemical oxidation in the temperature zone Tc, and is electrochemically oxidized and reduced during the subsequent operation. Upon receipt, it was discovered that the microstructure and volume of the fuel electrode changed, gave tensile stress to the electrolyte layer, and finally caused minute cracks in the electrolyte layer to damage the fuel cell.

  In the shutdown stop according to the present embodiment, the temperature measured by the power generation chamber temperature sensor that measures the temperature of the fuel battery cell 16 or the power generation chamber 10 is lower than the oxidation suppression temperature Te of the fuel electrode after the end of the temperature drop control. It is allowed to stand naturally until it drops to a certain 300 ° C. (the minimum oxidation temperature of the fuel electrode). Further, when the temperature of the power generation chamber 10 reaches 300 ° C., there is no possibility of atmospheric oxidation of the fuel electrode, so that air cooling can be performed. Therefore, the temperature in the fuel cell module 2 can be rapidly lowered by performing air cooling by operating the air flow rate adjusting units 45 and 46. In this temperature lowering process, the fuel cell 16 is rapidly cooled to below the activation lower limit temperature Tb of the electrolyte, so that the occurrence of electrochemical oxidation is extremely suppressed.

Next, with reference to FIG. 10, the operation of the exhaust concentration chamber 18 after the shutdown of the solid oxide fuel cell device 1 is stopped will be described.
Immediately after the shutdown is stopped, the pressure on the fuel electrode side inside the exhaust collecting chamber 18 and each fuel cell is maintained higher than the pressure on the air electrode outside the fuel cell. For this reason, the fuel gas existing in the exhaust collecting chamber 18 and each fuel cell 16 is gradually ejected to the air electrode side based on the pressure difference from the external air electrode side. Therefore, the fuel gas is jetted through the jet outlet 18d of the exhaust collecting chamber 18.

  Further, the air (and the fuel gas ejected from the ejection port 18d) existing on the air electrode side of each fuel battery cell 16 is based on the pressure difference between the pressure on the air electrode side (pressure in the power generation chamber) and the atmospheric pressure. And discharged outside the fuel cell module. Therefore, after the shutdown is stopped, the pressure on the fuel electrode side and the air electrode side of each fuel cell and the pressure in the exhaust collecting chamber 18 naturally decrease.

  However, since the exhaust collecting chamber 18 includes a plurality of jet outlets 18d having a predetermined flow path resistance and a communication port 120d having a larger flow path resistance, the fuel after the fuel supply and power generation are stopped. The pressure drop on the pole side is made more gradual than the pressure drop on the air electrode side, and the fuel remains for a long time after shutdown.

  Further, in the present embodiment, the pressure loss due to the communication port 120d is set to be larger than the pressure loss due to the jet port 18d, so that after the shutdown is stopped, the sub tank chamber 18A is more than the communication space 18B in the exhaust collecting chamber 18. However, the internal pressure is configured to be maintained high.

Thus, in the present embodiment, during the natural standing period after the shutdown is stopped, the fuel gas is left on the fuel electrode side until the fuel cell 16 is at least lowered to the oxidation suppression temperature or less, so that atmospheric oxidation is performed at the fuel electrode. The resulting risk is suppressed.
In this embodiment, when the temperature of the fuel cell 16 reaches 300 ° C., air cooling by the air flow rate adjustment unit 45 is started, so that the fuel cell 16 is forcibly cooled and the fuel electrode is electrochemically oxidized. Can be reduced to a restartable temperature which is a temperature range in which any oxidation reaction does not occur.

  However, during the stop process, especially during natural standing, the internal pressure on the air electrode side may be higher than the internal pressure of the exhaust collecting chamber 18, or both internal pressures may become equal pressure earlier than a predetermined period. There is. For example, a case where the atmospheric pressure increases due to a change in external weather, or a case where the temperature in the power generation chamber 10 is maintained higher than the fuel supply flow path for some reason is assumed. In this case, air on the air electrode side may enter the fuel electrode side through the exhaust collecting chamber 18 by diffusion or the like, and atmosphere oxidation may occur.

  As described above, when air enters the exhaust collection chamber 18 from the air electrode side, as shown in FIG. 10, the air first enters the communication space 18B through the jet outlet 18d, It moves downward in the communication space 18B, enters the sub tank chamber 18A through the communication port 120d provided at the lower end of the surrounding member 120, moves upward in the sub tank chamber 18A, and moves to the upper end of the fuel cell 16. To reach.

  In the present embodiment, the surrounding member 120 is provided in the exhaust collecting chamber 18 so that the air entry path from the jet outlet 18d to the upper end portion of the fuel cell 16 is not linear but is detoured. Thereby, the air entry path can be lengthened, and the time for the air that has entered from the jet outlet 18d to reach the upper end of the fuel cell 16 can be delayed.

  In the present embodiment, even if air enters the sub tank chamber 18A filled with fuel gas (hydrogen) having a specific gravity lighter than air through the communication port 120d, the air enters the bottom of the sub tank chamber 18A. Accumulation and upward movement are restricted. As the amount of entered air increases, the air layer in the sub tank chamber 18A gradually increases, and the boundary surface between the air layer and the fuel gas layer rises. Therefore, in the present embodiment, it is possible to extend in time that the air enters the fuel electrode in the fuel cell 16 until the interface between the air and the fuel gas reaches the upper end opening of the fuel cell 16. it can.

  In the present embodiment, since the communication port 120d is disposed vertically below the current collector 82, the time when the air that has entered comes into contact with the current collector 82 containing a substance capable of oxidation reaction such as nickel is determined. Can be delayed. Furthermore, in this embodiment, since the electrode layer of the fuel battery cell 16 to which the current collector 82 is attached also contains a substance capable of oxidation reaction such as nickel, the time when the air that has entered the exposed electrode layer comes into contact with the electrode layer. Can be delayed. Thereby, in the high temperature state in the stop process, it is possible to suppress performance deterioration due to atmospheric oxidation of the current collector 82 and the electrode layer. Furthermore, since it is not necessary to apply a protective coating for blocking air to the electrode layer to prevent atmospheric oxidation of the electrode layer, the manufacturing cost can be reduced.

  In the present embodiment, since the communication port 120d is provided at the lower end of the surrounding member 120, the air that has entered through the communication port 120d can be easily stored in the bottom of the sub tank chamber 18A. Thereby, even if the volume of the sub tank chamber 18A is not increased more than necessary, the arrival time of the air to the upper end of the fuel cell 16 can be sufficiently delayed, so that the surrounding member 120 can be made relatively small and compact. This contributes to the miniaturization of the entire apparatus.

  In the present embodiment, oxygen adsorbents 130b to 130d are arranged in the communication space 18B, and an oxygen adsorbent 130a is arranged in the sub tank chamber 18A. Thereby, the air that has entered from the jet port 18d is first adsorbed by the oxygen adsorbent 130d disposed on the upper surface portion 120a of the surrounding member 120. Since the oxygen adsorbent 130d is provided in the vicinity of the plurality of jet outlets 18d, the oxygen adsorbent 130d is maintained at a higher temperature than other parts during power generation by the combustion heat of the fuel off-gas at the jet outlet 18d. Is done. For this reason, since the oxygen adsorbent 130d can be maintained in a state where it can be oxidized in the atmosphere for a long period of time, it is possible to easily take in oxygen by the oxygen adsorbent 130d when the entering air passes in the vicinity of the oxygen adsorbent 130d. .

  Next, the air that has entered comes into contact with the oxygen adsorbents 130b and 130c disposed upstream of the oxygen adsorbent 130a (with respect to the flow direction of the fuel gas) in the communication space 18B, and oxygen is thereby absorbed. Adsorbed. Further, the air that has entered the sub tank chamber 18A through the communication port 120d comes into contact with a plurality of metal disk-like oxygen adsorbents 130a arranged vertically below the current collector 82, and thereby adsorbs oxygen. Is done. Furthermore, oxygen can also be adsorbed by the current collector 82. Note that the oxygen adsorbents 130a to 130d that have been oxidized by adsorbing oxygen are reduced in a reducing atmosphere by the fuel gas after the activation after the stop process, and oxygen is released.

  Thus, in this embodiment, by providing the sub tank chamber 18A in the exhaust gas collecting chamber 18, the entry of air from the jet outlet 18d to the upper end (downstream end) of the fuel cell 16 is delayed in time. be able to. As a result, in the stopping step, the air until the temperature of the fuel battery cell 16 is lowered below the oxidation lower limit temperature or the oxidation suppression temperature of the fuel electrode, and further below the temperature range where the electrochemical oxidation reaction occurs. Can be prevented from entering the fuel cell 16, and oxidation of the fuel electrode and damage to the fuel cell 16 associated therewith can be suppressed.

Further, in the present embodiment, the oxygen adsorbents 130a to 130d are arranged in the path from the jet outlet 18d to the upper end of the fuel cell 16, so that oxygen is removed from the entering air and oxygen is not included. Alternatively, only air with a reduced oxygen concentration can enter the fuel electrode side. Thereby, even if air contacts the fuel electrode, the degree of oxidation of the fuel electrode can be greatly reduced.
In the present embodiment, the exhaust electrode collecting chamber 18 is provided with a structural anti-oxidation measure such as the sub tank chamber 18A and / or the oxygen adsorbents 130a to 130d. The risk of breakage of the fuel battery cell 16 due to the oxidation of can be greatly reduced.

DESCRIPTION OF SYMBOLS 1 Solid oxide fuel cell apparatus 2 Fuel cell module 4 Auxiliary machine unit 8 Fuel cell storage container (module case)
10 Power generation chamber 16 Fuel cell 18 Exhaust concentration chamber (exhaust manifold)
18A Sub tank chamber 18B Communication space 18d Spout (off-gas exhaust)
18a Aggregation chamber upper member 18b Aggregation chamber lower member 18d Spout 20 Fuel gas supply channel 21 Exhaust gas discharge channel 22 Oxidant gas supply channel 56 Oxidant gas introduction pipe 58 Exhaust gas discharge pipe 74 Oxidant gas injection pipe 76 Fuel Gas dispersion chamber 82 Current collector 94 Reforming part 120 Enclosing member 120a Upper surface part (top plate)
120b Side surface portion 120d Communication port 130a-130d Oxygen adsorbent

Claims (9)

In the solid oxide fuel cell device,
A plurality of fuel cells;
An exhaust manifold that surrounds the ends of the plurality of fuel cells and has an internal space for storing fuel offgas flowing out from the openings at the ends of the plurality of fuel cells;
A module case for accommodating the plurality of fuel cells and the exhaust manifold,
The exhaust manifold has an off-gas exhaust port for exhausting the stored fuel off-gas,
A solid oxide fuel cell, wherein an oxygen adsorbent is disposed in a flow path between the opening of the end portions of the plurality of fuel cells and the off-gas exhaust port in the exhaust manifold. apparatus.   The oxygen adsorbent is a metal material that is oxidized when exposed to air and reduced when exposed to fuel off-gas at least at a temperature equal to or higher than an oxidation lower limit temperature of the plurality of fuel cells. The solid oxide fuel cell device described.   The solid oxide fuel cell device according to claim 2, wherein the oxidation adsorbent contains nickel and titanium.   The sub-chamber chamber is provided in the exhaust manifold, and the sub-tank chamber for storing the fuel off-gas flowing out from the openings at the ends of the plurality of fuel cells is provided in the exhaust manifold. 4. The solid oxide fuel cell device according to 3. In the sub tank chamber, a communication port that communicates with a communication space that communicates the sub tank chamber and the off-gas exhaust port is provided at a lower end portion.
5. The solid according to claim 4, wherein the oxygen adsorbent is disposed in the sub tank chamber between a current collector that connects end portions of the plurality of fuel cells and the communication port. Oxide fuel cell device. The sub tank chamber is communicated with a communication space that communicates the sub tank chamber and the off-gas exhaust port through a communication port.
The solid oxide fuel cell device according to claim 4, wherein the oxygen adsorbent is disposed in the communication space.   5. The solid oxide fuel cell device according to claim 4, wherein the oxygen adsorbent is disposed in the subtank chamber and a communication space that communicates the subtank chamber and the off-gas exhaust port. 6.   4. The solid oxide fuel cell device according to claim 3, wherein the oxygen adsorbent is a metal plate fixed to an electrolyte layer of the plurality of fuel cells. The sub tank chamber is provided near the off gas exhaust port of the exhaust manifold, and a top plate of the sub tank chamber is provided.
5. The solid oxide fuel cell device according to claim 4, wherein the oxygen adsorbent is disposed on a top plate of the sub tank chamber in the exhaust manifold.

Images