JP2011009136A - Solid oxide fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell (SOFC) capable of safely stopping operation, by moving to fail safe operation through steam reforming reaction (SR) operation, even during suspension of water supply.SOLUTION: The solid oxide fuel cell includes water storage tanks 26a, 26b for storing water to be fed to a reformer 20; water amount detecting means 136a, 136b, 136c, 136d; a water supply means 28 including a feed water means 152 which supplies water to the water tanks; and a control means 110. The control means includes a normal stopping operation mode stopping operation through the steam reforming reaction (SR) operation; and a first fail safe operation mode controlling feed water means 152, 154, 158 so that water exceeding the prescribed amount is stored in the water storage tanks when an abnormality arises on the feed water side of the water supply means, and moving to the fail safe operation which stops operation through the steam reforming reaction (SR) operation using the stored water.

Description

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

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

  In this SOFC, water vapor or carbon dioxide is generated by the reaction between oxygen ions that have passed through the oxide ion conductive solid electrolyte and fuel, and electric energy and thermal energy are generated. Electric energy is taken out of the SOFC and used for various electrical applications. On the other hand, thermal energy is transmitted to fuel, SOFC, oxidant, etc., and used to increase their temperature.

Here, as one of conventional fuel cells, there is known a fuel cell system that enables so-called water independence without water replenishment from the outside (see, for example, Patent Document 1). The fuel cell system includes a condenser that recovers water from water vapor contained in the exhaust gas of the fuel cell and the exhaust gas of the fuel reformer, and a recovered water tank that temporarily stores the condensed water obtained by the condenser. The water in the recovered water tank can be reused as reforming steam.
However, in such a fuel cell system, when water breakage occurs in a state where water independence is difficult, such as immediately after startup, sufficient water condensed by the condenser cannot be obtained, and water independence is possible. There is a problem that is extremely difficult.

Furthermore, as a conventional fuel cell, a fuel cell power generation system that collects heat generated in the fuel cell and stores it in a hot water storage tank is also known (see, for example, Patent Document 2). In the fuel cell power generation system, when water breakage occurs during power generation, the power generation operation is stopped and the hot water storage pump circulates between the heat exchange means and the hot water storage tank until the low temperature water in the hot water storage tank is heated and disappears. As a result, the fuel cell can be rapidly cooled.
However, such a fuel cell power generation system has a problem that, when water is cut off, low-temperature water in the hot water storage tank is reduced, and the cooling effect is also lowered. In addition, this fuel cell power generation system can be stably and without adversely affecting the cells of the solid oxide fuel cell by stopping the operation through the steam reforming reaction (SR) operation when stopping the power generation operation. The basic structure of the technology to stop operation safely is fundamentally different.

  Furthermore, as a conventional fuel cell, there is also known a fuel cell device capable of stably generating power continuously by supplying water from a water storage tank to a water supply means at the time of water outage (for example, And Patent Document 3).

JP 2008-234869 A JP 2008-152999 A JP 2008-53209 A

Here, as will be described in detail later, in a conventional solid oxide fuel cell (SOFC), first, at start-up, fuel gas and reforming air are supplied into the reformer to perform partial oxidation reforming reaction (POX). Next, fuel and water are supplied into the reformer to perform a steam reforming reaction (SR) operation, and a power generation operation by the fuel cell module is performed.
On the other hand, when stopping the operation of this fuel cell module, the supply amount of fuel gas and water vapor to the reformer is decreased, and at the same time, the supply amount of power generation air into the fuel cell module is increased, The fuel cell assembly and the reformer are cooled with air to lower their temperatures. Thereafter, when the temperature of the power generation chamber decreases to a predetermined temperature, the supply of fuel gas and steam to the reformer is stopped, the steam reforming reaction (SR) operation in the reformer is terminated, and the fuel cell module is operated. To stop.

However, in such a solid oxide fuel cell (SOFC), when the supply of water to the reformer is stopped instantaneously, the steam reforming reaction (SR) operation in the reformer cannot be performed. Therefore, when an emergency stop is performed in a high temperature state, there is a problem that the fuel cell is oxidized and receives a large damage.
In addition, in order to be able to stop the operation through the steam reforming reaction (SR) operation even when the water is shut down, a device for always ensuring a certain amount or more of the water required for the steam reforming reaction (SR) operation. Although necessary, conventional fuel cells, including the fuel cells described in Patent Documents 1 to 3 described above, do not disclose or suggest such a device.

  Therefore, the present invention has been made to solve the above-described problems of the prior art, and even in the event of a water outage, a transition to fail-safe operation is performed and the operation is safely stopped through a steam reforming reaction (SR) operation. It is an object of the present invention to provide a solid oxide fuel cell (SOFC) that can be used.

To achieve the above object, the present invention provides a solid oxide fuel cell that generates power by reacting fuel gas and air, and includes a fuel cell assembly including a plurality of solid electrolyte fuel cells. A reformer for steam reforming the fuel gas and supplying it to the fuel cell assembly; a fuel gas supply means for supplying the reformer with fuel gas; and generating pure water to the reformer A water supply means for supplying water, a water storage tank for storing water supplied to the reformer, a water amount detection means for detecting the amount of water in the water storage tank, and a water supply means for supplying water to the water storage tank The water supply means comprising: reforming air supply means for supplying reforming air to the reformer; power generation air supply means for supplying power generation air to the fuel cell assembly; and startup Sometimes, fuel gas and reforming air are supplied into the reformer. A partial oxidation reforming reaction (POX) operation is performed, then a fuel and water are supplied into the reformer, a steam reforming reaction (SR) operation is performed, and then a power generation operation by the fuel cell assembly is performed. Control means, and the control means has a normal stop operation mode in which the operation is stopped through the steam reforming reaction (SR) operation and a predetermined amount in the water storage tank when the water supply side of the water supply means is abnormal. The above-mentioned water supply means is controlled so that the above water is stored, and the operation is shifted to a fail-safe operation in which the operation is stopped through a steam reforming reaction (SR) operation using the stored water. And a first fail-safe operation mode.
In the present invention configured as described above, even if an abnormality on the water supply side of the water supply means (such as water outage) occurs in a state where water independence is difficult (such as during startup), the control means performs the first fail-safe operation. The water supply means is controlled so that a predetermined amount or more of water is stored in the water storage tank of the water supply means, and a steam reforming reaction (SR) using the stored water. Since the operation can be shifted to the fail-safe operation that stops the operation, the operation can be safely stopped through the steam reforming reaction (SR) operation. In addition, even when there is a water outage, the steam reforming (SR) operation using the stored water can stop the operation while maintaining a stable cooling state. By performing an emergency stop at a high temperature without performing the reaction (SR) operation, it is possible to prevent the fuel cell from being oxidized and receive a large damage, and to reliably prevent a decrease in the durability of the fuel cell.

The control means is further configured such that when the water supply side of the water supply means is abnormal, a predetermined amount or more of water is not stored in the water storage tank, or a water supply side abnormality causes the water storage tank to exceed a predetermined amount. A second fail-safe operation mode in which the fuel gas supply means is controlled so as to stop the supply of the fuel gas when it is determined that water cannot be stored to shift to the fail-safe operation, and the first fail-safe operation is provided Control is performed so that the operation period in the mode is longer than the operation period in the second fail-safe operation mode.
In the present invention configured as described above, the operation in the first fail-safe operation mode is performed in response to water supply abnormality such as water interruption that may occur at a high frequency. For a period longer than the second fail-safe operation mode in which an instantaneous stop (emergency stop) is performed when it is determined that the water storage tank cannot store a predetermined amount or more of water due to an abnormality on the water supply side. Therefore, fail-safe operation can be performed while maintaining a stable cooling state, and it is possible to prevent the fuel cell from being oxidized and receive a great deal of damage, and to reliably reduce the durability of the fuel cell. Can be prevented.

In the present invention, preferably, the control means performs control so that an operation period in the first fail-safe operation mode is shorter than an operation period in the normal stop operation mode.
In the present invention configured as described above, the control means controls the operation period in the first fail-safe operation mode to be shorter than the operation period in the normal stop operation mode. The fuel tank can be stably shifted to the fail-safe operation by the first fail-safe operation mode without increasing the capacity of the water storage tank and without damaging the fuel cell due to oxidation.

In the present invention, preferably, the control means operates after performing a steam reforming reaction (SR) operation in a state in which the supply of fuel gas is maintained in the first fail-safe operation mode and the normal stop operation mode. The fuel gas supply means is controlled to stop the operation.
In the present invention configured as described above, when an abnormality requiring an instantaneous stop is required, the second fail-safe operation mode can be used to shift to the fail-safe operation to stop the supply of fuel gas instantaneously. At the time of abnormality or normal stop, the first fail-safe operation mode or the normal stop operation mode is used to shift to the fail-safe operation while maintaining the fuel supply by the fuel gas supply means without instantaneously stopping the fuel gas supply. The operation can be stopped through a steam reforming reaction (SR) operation. Therefore, when water supply is abnormal, such as when water is cut off, or during a normal stop, the fuel gas supply stops instantaneously, the steam reforming reaction (SR) operation cannot be performed, and an emergency stop occurs at a high temperature, causing the fuel cell to oxidize and cause significant damage. It is possible to prevent the deterioration of the durability of the fuel cell.

In the present invention, preferably, the water supply means includes a first water storage tank and a second water storage tank, and the control means includes a first storage tank and a second storage amount. The water supply means is controlled so that the total amount of water stored in the water storage tank is equal to or greater than a predetermined amount.
In the present invention configured as described above, the first water storage volume is secured by securing the water volume so that the total volume of the water storage volume of the first water storage tank and the water storage volume of the second water storage tank is equal to or greater than a predetermined amount. Water management of the tank and the second water storage tank can be unified and simplified.

In the present invention, preferably, the water supply means is arranged such that the first water storage tank is disposed on the upstream side of the second water storage tank and on the downstream side of the water supply means. After water supply by the water supply means is performed from the first water storage tank to the second water storage tank, water supply by the water supply means is controlled so that the first water storage tank becomes full.
In the present invention configured as described above, the first storage tank disposed on the upstream side of the second storage tank is simply controlled to supply water by the water supply means so that the first storage tank is filled with water. The amount of water required for the steam reforming reaction (SR) operation in the 1 fail-safe operation mode can be reliably maintained.

In the present invention, preferably, the water supply means includes a first water amount detection means for detecting a predetermined upper limit water storage amount of the first water storage tank and a predetermined amount of the second water storage tank. Second water amount detection means for detecting a lower limit water storage amount, and the control means detects the first water amount when the second water amount detection means detects a predetermined lower limit water storage amount of the second water storage tank. The water supply means is controlled so that water is supplied from the water storage tank to the second water storage tank and water is supplied up to a predetermined upper limit water storage amount of the first water storage tank.
In the present invention configured as described above, when the second water amount detecting means detects the predetermined lower limit water storage amount of the second water storage tank, water is supplied from the first water storage tank to the second water storage tank. By the simple control of supplying water by the water supply means so that the first water storage tank has a predetermined upper limit water storage amount (full water), the water vapor correction in the first fail-safe operation mode can be performed even when the water supply side of the water supply means is abnormal. The amount of water required for quality reaction (SR) operation can be reliably maintained.

In the present invention, preferably, the control means is a steam reforming reaction (SR) operation in which the steam reforming reaction (SR) operation performed in the first failsafe operation mode is performed in the normal stop operation mode. Control differently.
In the present invention configured as described above, it is difficult to store the amount of water necessary for the steam reforming reaction (SR) operation in the normal stop operation mode in the event of an abnormality on the water supply side of the water supply means. Since the steam reforming reaction (SR) operation performed in the first fail-safe operation mode is controlled differently from the steam reforming reaction (SR) operation performed in the normal stop operation mode, the fuel cell is oxidized. Thus, it is possible to prevent a large amount of water from being used and to save the amount of water used in the steam reforming reaction (SR) operation performed in the first fail-safe operation mode.

In the present invention, preferably, the control means uses the steam reforming performed in the normal stop operation mode to the amount of fuel gas used in the steam reforming reaction (SR) operation performed in the first failsafe operation mode. The fuel gas supply means is controlled so as to be lower than the amount of fuel gas used for the reaction (SR) operation.
In the present invention configured as above, when the operation is stopped through the steam reforming reaction (SR) operation in the first fail-safe operation mode, the amount of fuel gas is reformed in the normal stop operation mode. Since the temperature of the fuel cell is lowered by lowering the amount of fuel gas used in the reaction (SR) operation, the steam reforming reaction (SR) operation in the first fail-safe operation mode is started. The time until the fuel gas is consumed and stops can be shortened compared to the normal stop operation mode. Therefore, the amount of water used for the steam reforming reaction (SR) operation performed in the first fail-safe operation mode can be saved.

In the present invention, preferably, the control means further controls the amount of water used for the steam reforming reaction (SR) operation performed in the first failsafe operation mode to the steam reforming performed in the normal stop operation mode. The water supply means is controlled so as to be lower than the amount of water used for quality reaction (SR) operation.
In the present invention configured as above, when the operation is stopped through the steam reforming reaction (SR) operation in the first fail-safe operation mode, the amount of fuel gas is reformed in the normal stop operation mode. While reducing the amount of fuel gas used in the reaction (SR) operation, the amount of water is also actively reduced from the amount of water used in the steam reforming reaction (SR) operation performed in the normal stop operation mode. Therefore, even if there is an abnormality such as water outage, operation can be stopped safely with the amount of stored water.

In the present invention, preferably, the control means further performs the amount of power generation air used for the steam reforming reaction (SR) operation performed in the first fail-safe operation mode in the normal stop operation mode. The power generation air supply means is controlled so as to be lower than the amount of power generation air used in the steam reforming reaction (SR) operation.
In the present invention configured as above, when the operation is stopped through the steam reforming reaction (SR) operation in the first fail-safe operation mode, the amount of fuel gas is reformed in the normal stop operation mode. The temperature of the fuel cell is lowered by lowering the amount of the fuel gas used for the reaction (SR) operation. If the temperature of the fuel cell is rapidly reduced, the cell Since it also affects itself, when the operation is stopped through the steam reforming reaction (SR) operation by shifting to the fail safe operation in the first fail safe operation mode, the amount of power generation air is reduced. Thereby, the temperature fall of a fuel cell can be suppressed and the influence on cell itself can be relieved.

  According to the solid oxide fuel cell (SOFC) of the present invention, the operation can be safely stopped through the steam reforming reaction (SR) operation by shifting to the fail-safe operation even when the water is shut off.

1 is an overall configuration diagram showing a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. 1 is a front sectional view showing a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a fragmentary sectional view showing a fuel cell unit of a solid oxide fuel cell (SOFC) by one embodiment of the present invention. 1 is a perspective view showing a fuel cell stack of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. 1 is a block diagram illustrating a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. It is a time chart which shows the operation | movement at the time of starting of the solid oxide fuel cell (SOFC) by one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of the normal stop driving | operation by the normal stop operation mode of the solid oxide fuel cell (SOFC) by one Embodiment of this invention. It is the schematic which shows the water flow volume adjustment unit of the solid oxide fuel cell (SOFC) by one Embodiment of this invention. 4 is a flowchart showing control contents for controlling a fuel flow rate, a water flow rate, and a power generation air flow rate when the solid oxide fuel cell (SOFC) according to an embodiment of the present invention is operated in a fail-safe operation mode. . The control contents for controlling the respective water storage amounts of the first water storage tank and the second water storage tank when the solid oxide fuel cell (SOFC) according to the embodiment of the present invention is operated in the fail-safe operation mode. It is a flowchart to show.

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

  The fuel cell module 2 includes a housing 6, and a sealed space 8 is formed inside the housing 6 via a heat insulating material (not shown, but the heat insulating material is not an essential component and may not be necessary). Is formed. In addition, you may make it not provide a heat insulating material. A fuel cell assembly 12 that performs a power generation reaction with fuel gas and an oxidant (air) is disposed in a power generation chamber 10 that is a lower portion of the sealed space 8. The fuel cell assembly 12 includes ten fuel cell stacks 14 (see FIG. 5), and the fuel cell stack 14 includes 16 fuel cell unit 16 (see FIG. 4). Yes. Thus, the fuel cell assembly 12 has 160 fuel cell units 16, and all of these fuel cell units 16 are connected in series.

A combustion chamber 18 is formed above the above-described power generation chamber 10 in the sealed space 8 of the fuel cell module 2. In this combustion chamber 18, the remaining fuel gas that has not been used for the power generation reaction and the remaining oxidant (air) ) And combusted to generate exhaust gas.
Further, a reformer 20 for reforming the fuel gas is disposed above the combustion chamber 18, and the reformer 20 is heated to a temperature at which a reforming reaction can be performed by the combustion heat of the residual gas. ing. Further, an air heat exchanger 22 for receiving combustion heat and heating air is disposed above the reformer 20.

Next, the auxiliary unit 4 includes a first water storage tank 26a for storing water from a water supply source 24 such as a water supply, and water supplied from the first water storage tank 26a as pure water using a filter. And a water flow rate adjustment unit 28 including two water storage tanks (pure water tanks) 26b (details will be described later). The water flow rate adjustment unit 28 is supplied from the second water storage tank (pure water tank) 26b. The pure water is supplied to the reformer 20 by adjusting the flow rate of the pure water.
The auxiliary unit 4 also includes a gas shut-off valve 32 that shuts off the fuel gas supplied from a fuel supply source 30 such as city gas, a desulfurizer 36 for removing sulfur from the fuel gas, and a flow rate of the fuel gas. A fuel flow rate adjusting unit 38 (such as a “fuel pump” driven by a motor) is provided.
Further, the auxiliary unit 4 includes an electromagnetic valve 42 that shuts off air that is an oxidant supplied from the air supply source 40, a reforming air flow rate adjusting unit 44 that adjusts the flow rate of air, and a power generation air flow rate adjusting unit. 45 (such as an “air blower” driven by a motor), a first heater 46 for heating the reforming air supplied to the reformer 20, and a second for heating the power generating air supplied to the power generation chamber And a heater 48. The first heater 46 and the second heater 48 are provided in order to efficiently raise the temperature at startup, but may be omitted.

Next, a hot water production apparatus 50 to which exhaust gas is supplied is connected to the fuel cell module 2. The hot water production apparatus 50 is supplied with tap water from the water supply source 24, 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).
The fuel cell module 2 is provided with a control box 52 for controlling the amount of fuel gas supplied and the like.
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 to the outside.

Next, the internal structure of a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a side sectional view showing a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention, and FIG. 3 is a sectional view taken along line III-III in FIG.
As shown in FIGS. 2 and 3, in the sealed space 8 in the housing 6 of the fuel cell module 2, as described above, the fuel cell assembly 12, the reformer 20, and the air heat exchange are sequentially performed from below. A vessel 22 is arranged.

  The reformer 20 is provided with a pure water introduction pipe 60 for introducing pure water and a reformed gas introduction pipe 62 for introducing reformed fuel gas and reforming air to the upstream end side thereof. In addition, in the reformer 20, an evaporation unit 20a and a reforming unit 20b are formed in order from the upstream side, and the reforming unit 20b is filled with a reforming catalyst. The fuel gas and air mixed with the steam (pure water) introduced into the reformer 20 are reformed by the reforming catalyst filled in the reformer 20. As the reforming catalyst, a catalyst obtained by imparting nickel to the alumina sphere surface or a catalyst obtained by imparting ruthenium to the alumina sphere surface is appropriately used.

  A fuel gas supply pipe 64 is connected to the downstream end side of the reformer 20, and the fuel gas supply pipe 64 extends downward and further in an manifold 66 formed below the fuel cell assembly 12. It extends horizontally. A plurality of fuel supply holes 64 b are formed in the lower surface of the horizontal portion 64 a of the fuel gas supply pipe 64, and the reformed fuel gas is supplied into the manifold 66 from the fuel supply holes 64 b.

  A lower support plate 68 having a through hole for supporting the fuel cell stack 14 described above is attached above the manifold 66, and the fuel gas in the manifold 66 flows into the fuel cell unit 16. Supplied.

  Next, an air heat exchanger 22 is provided above the reformer 20. The air heat exchanger 22 includes an air aggregation chamber 70 on the upstream side and two air distribution chambers 72 on the downstream side. The air aggregation chamber 70 and the air distribution chamber 72 include six air flow path tubes 74. Connected by. Here, as shown in FIG. 3, three air flow path pipes 74 form a set (74a, 74b, 74c, 74d, 74e, 74f), and the air in the air collecting chamber 70 is in each set. It flows into each air distribution chamber 72 from the air flow path pipe 74.

The air flowing through the six air flow path pipes 74 of the air heat exchanger 22 is preheated by exhaust gas that burns and rises in the combustion chamber 18.
An air introduction pipe 76 is connected to each of the air distribution chambers 72, the air introduction pipe 76 extends downward, and the lower end side communicates with the lower space of the power generation chamber 10, and the air that has been preheated in the power generation chamber 10. Is introduced.

Next, an exhaust gas chamber 78 is formed below the manifold 66. Further, as shown in FIG. 3, an exhaust gas passage 80 extending in the vertical direction is formed inside the front surface 6 a and the rear surface 6 b which are surfaces along the longitudinal direction of the housing 6, and the upper end side of the exhaust gas passage 80 is formed. Is in communication with the space in which the air heat exchanger 22 is disposed, and the lower end side is in communication with the exhaust gas chamber 78. Further, an exhaust gas discharge pipe 82 is connected to substantially the center of the lower surface of the exhaust gas chamber 78, and the downstream end of the exhaust gas discharge pipe 82 is connected to the above-described hot water producing apparatus 50 shown in FIG.
As shown in FIG. 2, an ignition device 83 for starting combustion of fuel gas and air is provided in the combustion chamber 18.

Next, the fuel cell unit 16 will be described with reference to FIG. FIG. 4 is a partial cross-sectional view showing a fuel cell unit of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 4, the fuel cell unit 16 includes a fuel cell 84 and inner electrode terminals 86 respectively connected to the vertical ends of the fuel cell 84.
The fuel cell 84 is a tubular structure extending in the vertical direction, and includes a cylindrical inner electrode layer 90 that forms a fuel gas flow path 88 therein, a cylindrical outer electrode layer 92, an inner electrode layer 90, and an outer side. An electrolyte layer 94 is provided between the electrode layer 92 and the electrode layer 92. The inner electrode layer 90 is a fuel electrode through which fuel gas passes and becomes a (−) electrode, while the outer electrode layer 92 is an air electrode in contact with air and becomes a (+) electrode.

  Since the inner electrode terminal 86 attached to the upper end side and the lower end side of the fuel cell 16 has the same structure, the inner electrode terminal 86 attached to the upper end side will be specifically described here. The upper portion 90 a of the inner electrode layer 90 includes an outer peripheral surface 90 b and an upper end surface 90 c exposed to the electrolyte layer 94 and the outer electrode layer 92. The inner electrode terminal 86 is connected to the outer peripheral surface 90b of the inner electrode layer 90 through a conductive sealing material 96, and is further in direct contact with the upper end surface 90c of the inner electrode layer 90, thereby Electrically connected. A fuel gas passage 98 communicating with the fuel gas passage 88 of the inner electrode layer 90 is formed at the center of the inner electrode terminal 86.

  The inner electrode layer 90 includes, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, and Sc, and Ni and ceria doped with at least one selected from rare earth elements. The mixture is formed of at least one of Ni and a mixture of lanthanum garade doped with at least one selected from Sr, Mg, Co, Fe, and Cu.

  The electrolyte layer 94 is, for example, zirconia doped with at least one selected from rare earth elements such as Y and Sc, ceria doped with at least one selected from rare earth elements, lanthanum gallate doped with at least one selected from Sr and Mg, Formed from at least one of the following.

  The outer electrode layer 92 includes, for example, lanthanum manganite doped with at least one selected from Sr and Ca, lanthanum ferrite doped with at least one selected from Sr, Co, Ni and Cu, Sr, Fe, Ni and Cu. It is formed from at least one of lanthanum cobaltite doped with at least one selected from the group consisting of silver and silver.

Next, the fuel cell stack 14 will be described with reference to FIG. FIG. 5 is a perspective view showing a fuel cell stack of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 5, the fuel cell stack 14 includes 16 fuel cell units 16, and the lower end side and the upper end side of these fuel cell units 16 are a ceramic lower support plate 68 and an upper side, respectively. It is supported by the support plate 100. The lower support plate 68 and the upper support plate 100 are formed with through holes 68a and 100a through which the inner electrode terminal 86 can pass.

  Furthermore, a current collector 102 and an external terminal 104 are attached to the fuel cell unit 16. The current collector 102 includes a fuel electrode connection portion 102a that is electrically connected to an inner electrode terminal 86 attached to the inner electrode layer 90 that is a fuel electrode, and an entire outer peripheral surface of the outer electrode layer 92 that is an air electrode. And an air electrode connecting portion 102b electrically connected to each other. The air electrode connecting portion 102b is formed of a vertical portion 102c extending in the vertical direction on the surface of the outer electrode layer 92 and a plurality of horizontal portions 102d extending in a horizontal direction along the surface of the outer electrode layer 92 from the vertical portion 102c. Has been. The fuel electrode connection portion 102a is linearly directed obliquely upward or obliquely downward from the vertical portion 102c of the air electrode connection portion 102b toward the inner electrode terminal 86 positioned in the vertical direction of the fuel cell unit 16. It extends.

  Further, the inner electrode terminals 86 at the upper end and the lower end of the two fuel cell units 16 located at the ends of the fuel cell stack 14 (the far left side and the near side in FIG. 5) are external terminals, respectively. 104 is connected. These external terminals 104 are connected to the external terminals 104 (not shown) of the fuel cell unit 16 at the end of the adjacent fuel cell stack 14, and as described above, the 160 fuel cell units 16 Everything is connected in series.

Next, sensors and the like attached to the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 6 is a block diagram illustrating a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 6, the solid oxide fuel cell 1 includes a control unit 110, and the control unit 110 includes operation buttons such as “ON” and “OFF” for operation by the user. A device 112, a display device 114 for displaying various data such as a power generation output value (wattage), and a notification device 116 for issuing an alarm (warning) in an abnormal state are connected. The notification device 116 may be connected to a remote management center and notify the management center of an abnormal state.

Next, signals from various sensors described below are input to the control unit 110.
First, the combustible gas detection sensor 120 is for detecting a gas leak, and is attached to the fuel cell module 2 and the auxiliary unit 4.
The CO detection sensor 122 detects whether or not CO in the exhaust gas originally discharged to the outside through the exhaust gas passage 80 or the like leaks to an external housing (not shown) that covers the fuel cell module 2 and the auxiliary unit 4. Is to do.
The hot water storage state detection sensor 124 is for detecting the temperature and amount of hot water in a water heater (not shown).

The power state detection sensor 126 is for detecting the current and voltage of the inverter 54 and the distribution board (not shown).
The power generation air flow rate detection sensor 128 is for detecting the flow rate of power generation air supplied to the power generation chamber 10.
The reforming air flow sensor 130 is for detecting the flow rate of the reforming air supplied to the reformer 20.
The fuel flow sensor 132 is for detecting the flow rate of the fuel gas supplied to the reformer 20.

The water flow rate sensor 134 is for detecting the flow rate of pure water (steam) supplied to the reformer 20.
The water level sensor 136 (details will be described later) is for detecting the respective water levels of the first water storage tank 26a and the second water storage tank (pure water tank) 26b.
The pressure sensor 138 is for detecting the pressure on the upstream side outside the reformer 20.
The exhaust temperature sensor 140 is for detecting the temperature of the exhaust gas flowing into the hot water production apparatus 50.

As shown in FIG. 3, the power generation chamber temperature sensor 142 is provided on the front side and the back side in the vicinity of the fuel cell assembly 12, and detects the temperature in the vicinity of the fuel cell stack 14 to thereby detect the fuel cell stack. 14 (ie, the fuel cell 84 itself) is estimated.
The combustion chamber temperature sensor 144 is for detecting the temperature of the combustion chamber 18.
The exhaust gas chamber temperature sensor 146 is for detecting the temperature of the exhaust gas in the exhaust gas chamber 78.
The reformer temperature sensor 148 is for detecting the temperature of the reformer 20, and calculates the temperature of the reformer 20 from the inlet temperature and the outlet temperature of the reformer 20.
The outside air temperature sensor 150 is for detecting the temperature of the outside air when the solid oxide fuel cell (SOFC) is disposed outdoors. Further, a sensor for measuring the humidity or the like of the outside air may be provided.

Signals from these sensors are sent to the control unit 110, and the control unit 110, based on data based on these signals, the water flow rate adjustment unit 28, the fuel flow rate adjustment unit 38, the reforming air flow rate adjustment unit 44, A control signal is sent to the power generation air flow rate adjusting unit 45 to control each flow rate in these units.
Further, the control unit 110 sends a control signal to the inverter 54 to control the power supply amount.

Next, the operation at the time of start-up by the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 7 is a time chart showing the operation at the time of startup of the solid oxide fuel cell (SOFC) according to one embodiment of the present invention.
Initially, in order to warm the fuel cell module 2, the operation is started in a no-load state, that is, in a state where a circuit including the fuel cell module 2 is opened. At this time, since no current flows through the circuit, the fuel cell module 2 does not generate power.

First, reforming air is supplied from the reforming air flow rate adjustment unit 44 to the reformer 20 of the fuel cell module 2 via the first heater 46. At the same time, the power generation air is supplied from the power generation air flow rate adjustment unit 45 to the air heat exchanger 22 of the fuel cell module 2 via the second heater 48, and this power generation air is supplied to the power generation chamber 10 and the combustion chamber. Reach chamber 18.
Immediately after this, the fuel gas is also supplied from the fuel flow rate adjustment unit 38, and the fuel gas mixed with the reforming air passes through the reformer 20, the fuel cell stack 14, and the fuel cell unit 16, and It reaches the combustion chamber 18.

  Next, the ignition device 83 is ignited to burn the fuel gas and air (reforming air and power generation air) in the combustion chamber 18. Exhaust gas is generated by the combustion of the fuel gas and air, the power generation chamber 10 is warmed by the exhaust gas, and when the exhaust gas rises in the sealed space 8 of the fuel cell module 2, The fuel gas containing the reforming air is warmed, and the power generation air in the air heat exchanger 22 is also warmed.

  At this time, the fuel gas mixed with the reforming air is supplied to the reformer 20 by the fuel flow rate adjusting unit 38 and the reforming air flow rate adjusting unit 44. The partial oxidation reforming reaction POX shown in FIG. Since the partial oxidation reforming reaction POX is an exothermic reaction, the startability is good. Further, the heated fuel gas is supplied to the lower side of the fuel cell stack 14 through the fuel gas supply pipe 64, whereby the fuel cell stack 14 is heated from below, and the combustion chamber 18 also has the fuel gas and air. The fuel cell stack 14 is also heated from above, and as a result, the fuel cell stack 14 can be heated substantially uniformly in the vertical direction. Even if the partial oxidation reforming reaction POX proceeds, the combustion reaction between the fuel gas and air continues in the combustion chamber 18.

_{C m H n + xO 2 →} aCO 2 + bCO + cH 2 (1)

  When the reformer temperature sensor 148 detects that the reformer 20 has reached a predetermined temperature (for example, 600 ° C.) after the partial oxidation reforming reaction POX is started, the water flow rate adjustment unit 28 and the fuel flow rate adjustment unit 38 are detected. The reforming air flow rate adjusting unit 44 supplies the reformer 20 with a gas in which fuel gas, reforming air, and steam are mixed in advance. At this time, in the reformer 20, an autothermal reforming reaction ATR in which the partial oxidation reforming reaction POX described above and a steam reforming reaction SR described later are used together proceeds. Since the autothermal reforming reaction ATR is thermally balanced internally, the reaction proceeds in the reformer 20 in a thermally independent state. That is, when oxygen (air) is large, heat generation by the partial oxidation reforming reaction POX is dominant, and when there is much steam, an endothermic reaction by the steam reforming reaction SR is dominant. At this stage, the initial stage of startup has already passed, and the temperature inside the power generation chamber 10 has been raised to a certain temperature. Therefore, even if the endothermic reaction is dominant, no significant temperature drop is caused. Further, the combustion reaction continues in the combustion chamber 18 even while the autothermal reforming reaction ATR is in progress.

  When the reformer temperature sensor 146 detects that the reformer 20 has reached a predetermined temperature (for example, 700 ° C.) after the start of the autothermal reforming reaction ATR shown in Formula (2), the reforming air flow rate The supply of reforming air by the adjustment unit 44 is stopped, and the supply of water vapor by the water flow rate adjustment unit 28 is increased. As a result, the reformer 20 is supplied with a gas that does not contain air and contains only fuel gas and water vapor, and the steam reforming reaction SR of formula (3) proceeds in the reformer 20.

_{C m H n + xO 2 +} yH 2 O → aCO 2 + bCO + cH 2 (2)
C _m H _n + xH ₂ O → aCO ₂ + bCO + cH ₂ (3)

  Since the steam reforming reaction SR is an endothermic reaction, the reaction proceeds while maintaining a heat balance with the combustion heat from the combustion chamber 18. At this stage, since the fuel cell module 2 is in the final stage of start-up, the power generation chamber 10 is heated to a sufficiently high temperature. Therefore, even if the endothermic reaction proceeds, the power generation chamber 10 is greatly reduced in temperature. There is nothing. Even if the steam reforming reaction SR proceeds, the combustion reaction continues in the combustion chamber 18.

  In this way, after the fuel cell module 2 is ignited by the ignition device 83, the partial oxidation reforming reaction POX, the autothermal reforming reaction ATR, and the steam reforming reaction SR proceed in sequence, so that the inside of the power generation chamber 10 The temperature gradually increases. Next, when the temperature in the power generation chamber 10 and the fuel cell 84 reaches a predetermined power generation temperature lower than the rated temperature at which the fuel cell module 2 is stably operated, the circuit including the fuel cell module 2 is closed, and the fuel cell Power generation by the module 2 is started, so that a current flows in the circuit. Due to the power generation of the fuel cell module 2, the fuel cell 84 itself also generates heat, and the temperature of the fuel cell 84 also rises. As a result, the rated temperature at which the fuel cell module 2 is operated becomes, for example, 600 ° C. to 800 ° C.

  Thereafter, in order to maintain the rated temperature, more fuel gas and air than the amount of fuel gas and air consumed in the fuel cell 84 are supplied, and combustion in the combustion chamber 18 is continued. During power generation, power generation proceeds in a steam reforming reaction SR with high reforming efficiency.

Next, the operation during the normal stop operation in the normal stop operation mode of the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 8 is a time chart showing the operation during the normal stop operation in the normal stop operation mode of the solid oxide fuel cell (SOFC) according to the present embodiment.
As shown in FIG. 8, when the operation of the fuel cell module 2 is stopped, first, the control unit 110 selects the normal stop operation mode, operates the fuel flow rate adjustment unit 38 and the water flow rate adjustment unit 28, The amount of fuel gas and steam supplied to the reformer 20 is reduced.

  Further, when performing the normal stop operation of the fuel cell module 2 in the normal stop operation mode, the supply amount of the fuel gas and the steam to the reformer 20 is reduced, and at the same time, the power generation air flow rate adjustment unit 45 performs the power generation. The supply amount of air into the fuel cell module 2 is increased, the fuel cell assembly 12 and the reformer 20 are cooled by air, and these temperatures are lowered. Thereafter (for example, 5 hours after the start of the steam reforming reaction (SR) operation in the normal stop operation mode), when the temperature of the power generation chamber drops to a predetermined temperature, for example, 400 ° C., the fuel gas and the steam are improved. When the supply to the mass device 20 is stopped and the steam reforming reaction (SR) operation of the reformer 20 is ended, the operation period in the normal stop operation mode is ended. In addition, the supply of power generation air continues until the temperature of the reformer 20 (or the temperature of the power generation chamber) is lowered to a predetermined temperature, for example, 200 ° C., even after the operation period in the normal stop operation mode ends. When the predetermined temperature is reached, the supply of power generation air from the power generation air flow rate adjustment unit 45 is stopped.

  On the other hand, when the supply of water supplied from the water supply source 24 such as a water supply to the water flow rate adjustment unit 28 falls below a predetermined amount of water, or when no water is supplied and a so-called water outage state occurs, An operation different from the operation in the normal stop operation mode (hereinafter referred to as “operation in the fail-safe operation mode”) described in detail is performed.

Next, the water flow rate adjusting unit 28 according to this embodiment described above will be described in detail with reference to FIG. FIG. 9 is a schematic diagram showing a water flow rate adjustment unit of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 9, the water flow rate adjustment unit 28 that is a water supply unit that generates pure water and supplies it to the reformer 20 adjusts the flow rate of tap water from the water supply source 24 in order from the upstream side. A flow rate adjusting valve 152, a first water storage tank 26a for temporarily storing tap water from the water supply source 24, a pump 154 for supplying water in the first water storage tank 26a, and the supplied water RO membrane (reverse osmosis membrane) 156 for producing pure water by purifying water, a second water storage tank (pure water tank) 26b for temporarily storing the produced pure water, and this pure water as fuel A pulse pump 158 that intermittently supplies the reformer 20 of the battery module 2 by pulse control is provided.
Further, a heat exchanger 160 and a heater 162 for preventing water and pure water from freezing are also provided.

Further, the first water storage tank 26a includes water level sensors 136a and 136b for detecting the predetermined upper limit water level and the lower limit water level, respectively, and the water level sensors 136a and 136b detect the respective water levels. Can be detected (for example, the full water amount of the first water storage tank 26a, etc.).
The water storage amount of the first water storage tank 26a only needs to be able to detect at least the water storage amount when the water is full, and the water level sensor 136b that detects the predetermined lower limit water level of the first water storage tank 26a is omitted. May be.
Similarly, the second water storage tank 26b also includes water level sensors 136c and 136d that respectively detect the predetermined upper limit water level and lower limit water level, and these water level sensors 136c and 136d detect the respective water levels, thereby The water storage amount corresponding to the water level (for example, the lower limit water storage amount of the second water storage tank 26b, etc.) can be detected.
The water storage amount of the second water storage tank 26b only needs to be able to detect at least the lower limit water storage amount, and the water level sensor 136c that detects the predetermined upper water level of the second water storage tank 26b is omitted. Also good.

  Next, the contents of control for performing the operation in the fail-safe operation mode of the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIGS. FIG. 10 is a flowchart showing the control contents for controlling the fuel flow rate, the water flow rate, and the power generation air flow rate when the solid oxide fuel cell (SOFC) according to the present embodiment is operated in the fail-safe operation mode. is there. FIG. 11 shows the control contents for controlling the respective water storage amounts of the first water storage tank and the second water storage tank when the solid oxide fuel cell (SOFC) according to the present embodiment is operated in the fail-safe operation mode. It is a flowchart which shows. 10 and 11, S indicates each step.

First, as shown in FIG. 10, in S1, the supply of water supplied from the water supply source 24 such as a water supply to the water flow rate adjustment unit 28 falls below a predetermined amount of water, or no water is supplied, so-called water cutoff. It is determined whether or not an abnormality has occurred in the water supply such as being in a state. If it is determined that there is an abnormality in the water supply, the process proceeds to S2, and the control unit 110 selects the first fail-safe operation mode.
Next, in S3, the total amount of both the water storage amounts of the first water storage tank 26a and the second water storage tank (pure water tank) 26b is a predetermined amount or more (for example, the first water storage tank 26a and the second water storage tank). It is determined whether or not at least one of the (pure water tank) 26b is equal to or greater than the amount of water that is full. And if the total amount of both the water storage amount of both the water storage tanks 26a and 26b is more than predetermined amount, it will progress to S4.

Next, in S4, the control unit 110 uses the steam reforming reaction (SR) in the normal stop operation mode for the flow rate of the fuel gas used in the steam reforming reaction (SR) operation performed in the first failsafe operation mode. ) The fuel flow rate adjusting unit 38 is controlled so as to be set to a value reduced by 30% of the flow rate of the fuel gas used in the operation.
At the same time, the flow rate of water used in the steam reforming reaction (SR) operation performed in the first fail-safe operation mode is 30% of the flow rate of water used in the steam reforming reaction (SR) operation in the normal stop operation mode. The water flow rate adjusting unit 28 is controlled so as to set the reduced value.
Further, at the same time, the power generation air flow rate adjustment unit 45 is controlled so that the flow rate of the power generation air is set to a value reduced by 15% of the flow rate of the power generation air in the normal stop operation mode.

In S4, when the flow rate of fuel gas, the flow rate of water, and the flow rate of power generation air are set, the process proceeds to S5, the abnormal stop control is executed, and the operation in the first fail-safe operation mode is performed.
Here, with respect to the operation in the first fail-safe operation mode, after performing the steam reforming reaction (SR) operation while maintaining the supply of fuel gas and water at a lower flow rate than in the normal stop operation mode for a predetermined time, The operation is stopped by stopping the supply of gas and water, but the operation period from the start of the operation in the first fail-safe operation mode to the stop (the steam reforming reaction in the first fail-safe operation mode) (SR) corresponds to the time from when the operation is started until it is stopped) is the operation period in the normal stop operation mode (the time from the start of the steam reforming reaction (SR) operation in the normal stop operation mode to the stop) Equivalent to).

On the other hand, in S3, the total amount of both the water storage tanks 26a, 26b is less than a predetermined amount, and the water storage tanks 26a, 26b are not in a state where water of a predetermined amount or more is stored. If it is determined that a predetermined amount or more of water cannot be stored in both the water storage tanks 26a and 26b due to an abnormality on the water supply side such as the supply source 24, the process proceeds to S6 and the control unit 110 selects the second fail-safe operation mode. .
Next, in S7, the controller 110 determines the flow rate of the fuel gas used in the steam reforming reaction (SR) operation in the normal stop operation mode for the flow rate of the fuel gas used in the operation in the second fail-safe operation mode. The fuel flow rate adjustment unit 38 is controlled so as to set the value reduced by 100% (flow rate 0).
At the same time, the flow rate of water used in the operation in the second fail-safe operation mode is set to a value (flow rate 0) obtained by reducing 100% of the flow rate of water used in the steam reforming reaction (SR) operation in the normal stop operation mode. Thus, the water flow rate adjustment unit 28 is controlled.
Further, at the same time, the power generation air flow rate adjustment unit 45 is controlled so that the flow rate of the power generation air is set to a value (flow rate 0) that is reduced by 100% of the flow rate of power generation air in the normal stop operation mode.
When the fuel gas flow rate, the water flow rate, and the power generation air flow rate are all set to zero in S7, the process proceeds to S5, the abnormal stop control is executed, and the operation in the second fail-safe operation mode is performed. Is called.

  That is, for the operation in the second fail-safe operation mode, when the total amount of both water storage tanks 26a, 26b is less than a predetermined amount at the time of abnormality related to water supply, fuel gas, water, and The supply of power generation air is stopped instantaneously, and the steam reforming reaction (SR) operation is not performed. Therefore, it is different from the operation in the normal stop operation mode and the first fail-safe operation mode described above, and the operation period in the second fail-safe operation mode is the shortest as compared with the operation periods in the other operation modes. ing.

Next, in the first fail-safe operation mode described above, the respective water storage amounts of the first water storage tank 26a and the second water storage tank (pure water tank) 26b are controlled according to the control content shown in FIG. Allows safe shutdown via reforming reaction (SR) operation.
First, as shown in FIG. 11, in S101, based on the information detected by the water level sensor 136d of the second water storage tank (pure water tank) 26b by the control unit 110, the second water storage tank (pure water tank) 26b. Is less than or equal to a predetermined lower limit water storage amount. When it is determined that the second water storage tank (pure water tank) 26b is equal to or less than a predetermined lower limit water storage amount, the process proceeds to S102.

  Next, in S102, based on information detected by the water level sensor 136a of the first water storage tank 26a by the control unit 110, the first water storage tank 26a reaches a predetermined upper limit water storage amount (for example, full water amount). It is determined whether or not. When it is determined that the first water storage tank 26a has not reached a predetermined upper limit water storage amount (for example, full water amount), the process proceeds to S103, and further water is supplied from the water supply source 24 to the first water storage tank 26a. The flow rate adjustment valve 152 is controlled as shown in FIG.

  Next, the process proceeds to S104, and based on the information detected by the water level sensor 136a of the first water storage tank 26a by the control unit 110, it is determined again whether or not the first water storage tank 26a has reached a predetermined upper limit water storage amount. judge. When it is determined that the first water storage tank 26a has reached a predetermined upper limit water storage amount (for example, full water amount), the process proceeds to S105, the pump 154 is operated, and the water in the first water storage tank 26a is discharged. It supplies to RO membrane (reverse osmosis membrane) 156, produces | generates a pure water, and supplies this pure water to the 2nd water storage tank (pure water tank) 26b.

  Next, the process proceeds to S106, and based on the information detected by the control unit 110 by the water level sensor 136c of the second water storage tank (pure water tank) 26b, the second water storage tank (pure water tank) 26b has a predetermined upper limit. It is determined whether or not the amount of stored water has been reached. When it is determined that the second water storage tank (pure water tank) 26b has reached the predetermined upper limit water storage amount, the process proceeds to S107, and further water is supplied from the water supply source 24 to the first water storage tank 26a. Thus, the flow rate adjustment valve 152 is controlled. At the same time, the pump 154 is stopped and the supply of water from the first water storage tank 26a to the second water storage tank (pure water tank) 26b is stopped.

  Next, the process proceeds to S108, and the first water storage tank 26a reaches a predetermined upper limit water storage amount (for example, full water amount) based on information detected by the control unit 110 by the water level sensor 136a of the first water storage tank 26a. It is determined again whether or not. When it is determined that the first water storage tank 26a has reached a predetermined upper limit water storage amount (for example, full water amount), the process proceeds to S109, the flow rate adjustment valve 152 is closed, and the first water storage tank 26a is moved to. Stop water supply.

According to the solid oxide fuel cell (SOFC) according to the above-described embodiment of the present invention, for example, in a state where water independence is difficult at the time of start-up or the like, the water is supplied from the water supply source 24 such as tap water to the water flow rate adjustment unit 28. Even if there is an abnormality in the supply of water, such as when the supply of water falls below a predetermined amount of water or the water is not supplied and is in a so-called water shut-off state, the control unit 110 performs the first fail-safe operation. The mode is executed, and the total amount of both the first and second water storage tanks 26a and 26b (pure water tank) 26b is equal to or larger than a predetermined amount (for example, the first water storage tank 26a and the second water storage tank ( Since the flow rate adjustment valve 152 is controlled so that at least one of the pure water tanks 26b is more than the amount of water that is full), the steam reforming reaction (SR) using this stored water. luck It can be carried out safely shutdown via the.
In addition, even in the event of a water outage, the steam reforming reaction (SR) operation using this stored water can perform a fail safe operation while maintaining a stable cooling state. SR) The emergency stop at a high temperature without performing the operation can prevent the fuel cell unit 16 from being oxidized and suffering a great damage, and reliably prevent the durability of the fuel cell unit 16 from being lowered. it can.

  Further, according to the solid oxide fuel cell (SOFC) according to the present embodiment, the operation in the first fail-safe operation mode is performed in response to a water supply abnormality such as water interruption that may occur at a high frequency. The total amount of water stored in both the water storage tank 26a and the second water storage tank (pure water tank) 26b is not in a state where water is stored in a predetermined amount or more, or the first water supply is abnormal due to an abnormality on the water supply side such as the water supply source 24. When it is determined that a predetermined amount or more of water cannot be stored in the water storage tank 26a and the second water storage tank (pure water tank) 26b, the period is longer than the second fail-safe operation mode in which an emergency stop (instantaneous stop) is performed. Therefore, fail-safe operation can be performed while maintaining a stable cooling state, and it is possible to prevent the fuel cell unit 16 from being oxidized and receiving great damage. Can, a reduction in the durability of the fuel cell units 16 can be reliably prevented.

  Furthermore, according to the solid oxide fuel cell (SOFC) according to the present embodiment, the operation stop via the steam reforming reaction (SR) operation using the stored water in the first fail-safe operation mode causes the operation to stop from the normal stop operation mode. Since the operation can be stopped in a short period of time, the capacity of the first water storage tank 26a and the second water storage tank 26b is not increased in preparation for an abnormal water supply, and the fuel cell unit 16 is also oxidized. The operation can be stopped by stably shifting to the fail-safe operation in the first fail-safe operation mode without causing damage.

  Further, according to the solid oxide fuel cell (SOFC) according to the present embodiment, the supply of fuel gas can be stopped instantaneously by the second fail-safe operation mode in the event of an abnormality that requires an instantaneous stop. When the supply is abnormal or during a normal stop, steam reforming is performed in a state where the fuel supply by the fuel flow rate adjustment unit 38 is maintained without instantaneously stopping the supply of fuel gas in the first fail-safe operation mode or the normal stop operation mode. The operation can be stopped through the reaction (SR) operation. Therefore, when the water supply is abnormal, such as when water is shut down, or during a normal stop, the fuel gas supply stops instantaneously and the steam reforming reaction (SR) operation cannot be performed, and an emergency stop occurs at a high temperature, and the fuel cell is oxidized. Thus, it is possible to prevent a large amount of damage and to reliably prevent a decrease in the durability of the fuel cell.

  Furthermore, according to the solid oxide fuel cell (SOFC) according to the present embodiment, the total amount of the water stored in the first water storage tank 26a and the water stored in the second water storage tank (pure water tank) 26b is a predetermined amount or more ( For example, by securing the amount of water so that at least one of the first water storage tank 26a and the second water storage tank (pure water tank) 26b is equal to or greater than the amount of water that is full), the first water storage tank 26a and The water management of the second water storage tank (pure water tank) 26b can be unified and simplified.

  Further, according to the solid oxide fuel cell (SOFC) according to the present embodiment, the flow rate is adjusted so that the first water storage tank 26a disposed upstream of the second water storage tank (pure water tank) 26b is full. By simple control for supplying water by the valve 152, the supply of water supplied from the water supply source 24 such as tap water to the water flow rate adjustment unit 28 is less than a predetermined amount of water, or no water is supplied, and so-called water outage state. Even if an abnormality occurs in the supply of water, such as, the amount of water necessary for the steam reforming reaction (SR) operation in the first fail-safe operation mode can be reliably maintained.

  Furthermore, according to the solid oxide fuel cell (SOFC) according to the present embodiment, when the water level sensor 136d detects the predetermined lower limit water storage amount of the second water storage tank 26b, the second water storage from the first water storage tank 26a. Water is supplied from the water supply source 24 such as tap water by simple control in which water is supplied to the tank 26b and water is supplied by the flow rate adjustment valve 152 so that the first water storage tank 26a reaches a predetermined upper limit water storage amount (full water). Even if there is an abnormality in the supply of water, such as when the supply of water supplied to the adjustment unit 28 falls below a predetermined amount of water, or the water is not supplied and is in a so-called water shut-off state, the first fail The amount of water required for the steam reforming reaction (SR) operation in the safe operation mode can be reliably maintained.

  Further, according to the solid oxide fuel cell (SOFC) according to the present embodiment, it is possible to store the amount of water necessary for the steam reforming reaction (SR) operation performed in the normal stop operation mode when the water supply is abnormal. Although it is serious, since the steam reforming reaction (SR) operation performed in the first fail-safe operation mode is controlled differently from the steam reforming reaction (SR) operation performed in the normal stop operation mode, It is possible to prevent the fuel cell unit 16 from being oxidized and receive great damage, and to save the amount of water used for the steam reforming reaction (SR) operation performed in the first fail-safe operation mode.

  Furthermore, according to the solid oxide fuel cell (SOFC) according to the present embodiment, when the operation is stopped through the steam reforming reaction (SR) operation in the first fail-safe operation mode, the amount of the fuel gas is normally stopped. The temperature of the fuel cell unit 16 is lowered by reducing the amount of fuel gas used in the steam reforming reaction (SR) operation performed in the mode, and the steam reforming reaction in the first fail-safe operation mode. (SR) The time from the start of operation until the fuel gas is consumed and stopped (the operation period in the first fail-safe operation mode) can be made shorter than the operation period in the normal stop operation mode. Therefore, the amount of water used for the steam reforming reaction (SR) operation performed in the first fail-safe operation mode can be saved.

  Further, according to the solid oxide fuel cell (SOFC) according to the present embodiment, when the operation is stopped through the steam reforming reaction (SR) operation in the first fail-safe operation mode, the amount of the fuel gas is normally stopped. The amount of water used in the steam reforming reaction (SR) operation performed in the normal stop operation mode while the amount of water is reduced from the amount of fuel gas used in the steam reforming reaction (SR) operation performed in the mode. Therefore, even if there is an abnormality such as water outage, the operation can be safely stopped with the amount of water stored in the first water storage tank 26a and the second water storage tank 26b.

  Furthermore, according to the solid oxide fuel cell (SOFC) according to the present embodiment, when the operation is stopped through the steam reforming reaction (SR) operation in the first fail-safe operation mode, the amount of the fuel gas is normally stopped. The temperature of the fuel cell unit 16 is reduced by reducing the amount of the fuel gas used in the steam reforming reaction (SR) operation performed in the mode, but the temperature of the fuel cell unit 16 is decreased. When the operation is rapidly performed, the cell itself is also affected. Therefore, when the operation is stopped through the steam reforming reaction (SR) operation in the first fail-safe operation mode, the amount of power generation air By reducing the amount, the temperature drop of the fuel cell unit 16 can be suppressed, and the influence on the cell itself can be mitigated.

DESCRIPTION OF SYMBOLS 1 Solid oxide type fuel cell 2 Fuel cell module 4 Auxiliary machine unit 8 Sealed space 10 Power generation chamber 12 Fuel cell assembly 14 Fuel cell stack 16 Fuel cell unit 18 Combustion chamber 20 Reformer 22 Air heat exchanger 24 Water supply source 26a First water tank 26b Second water tank (pure water tank)
28 Water flow rate adjustment unit 30 Fuel supply source 38 Fuel flow rate adjustment unit 40 Air supply source 44 Reforming air flow rate adjustment unit 45 Power generation air flow rate adjustment unit 50 Hot water production device 52 Control box 54 Inverter 83 Ignition device 84 Fuel cell 110 Control unit 112 Operating device 114 Display device 116 Alarm device 126 Power state detection sensors 136a, 136b, 136c, 136d Water level sensor 142 Power generation chamber temperature sensor 150 Outside air temperature sensor 152 Flow rate adjustment valve 154 Pump 156 RO membrane (reverse osmosis membrane)
158 Pulse pump 160 Heat exchanger 162 Heater

Claims (11)

A solid oxide fuel cell that generates electricity by reacting fuel gas and air,
A fuel cell assembly comprising a plurality of solid electrolyte fuel cells,
A reformer for steam reforming the fuel gas and supplying the fuel cell assembly to the fuel cell assembly;
Fuel gas supply means for supplying fuel gas to the reformer;
Water supply means for generating pure water and supplying it to the reformer, a water storage tank for storing the water supplied to the reformer, a water amount detection means for detecting the amount of water in the water storage tank, and The water supply means comprising water supply means for supplying water to the water storage tank;
Reforming air supply means for supplying reforming air to the reformer;
Power generation air supply means for supplying power generation air to the fuel cell assembly;
At start-up, fuel gas and reforming air are supplied into the reformer for partial oxidation reforming reaction (POX) operation, and fuel and water are supplied into the reformer for steam reforming reaction (SR) Control means for performing the operation and thereafter performing the power generation operation by the fuel cell assembly,
The control means includes a normal stop operation mode in which operation is stopped through the steam reforming reaction (SR) operation, and a state where water of a predetermined amount or more is stored in the water storage tank when an abnormality occurs on the water supply side of the water supply means. A first fail-safe operation mode for controlling the water supply means so as to be shifted to a fail-safe operation for stopping the operation through a steam reforming reaction (SR) operation using the stored water. And a solid oxide fuel cell.   The control means is further configured such that when the water supply side of the water supply means is abnormal, a predetermined amount or more of water is not stored in the water storage tank, or a water supply side abnormality causes the water storage tank to exceed a predetermined amount. A second fail-safe operation mode in which the fuel gas supply means is controlled so as to stop the supply of the fuel gas when it is determined that water cannot be stored to shift to the fail-safe operation, and the first fail-safe operation is provided 2. The solid oxide fuel cell according to claim 1, wherein the operation period according to the mode is controlled to be longer than the operation period according to the second fail-safe operation mode.   3. The solid oxide fuel cell according to claim 2, wherein the control means controls the operation period in the first fail-safe operation mode to be shorter than the operation period in the normal stop operation mode.   In the first fail-safe operation mode and the normal stop operation mode, the control means performs the steam reforming reaction (SR) operation while maintaining the supply of fuel gas, and then stops the operation. The solid oxide fuel cell according to claim 3, wherein the gas supply means is controlled. In the water supply means, the water storage tank includes a first water storage tank and a second water storage tank,
2. The solid oxide fuel according to claim 1, wherein the control means controls the water supply means so that a total amount of the water storage amount of the first water storage tank and the water storage amount of the second water storage tank becomes a predetermined amount or more. battery.   The water supply means is arranged such that the first water storage tank is arranged on the upstream side of the second water storage tank and on the downstream side of the water supply means, and the control means is connected to the water tank from the first water storage tank. 6. The solid oxide fuel cell according to claim 5, wherein the water supply by the water supply means is controlled so that the first water storage tank becomes full after the water supply by the water supply means is performed on the second water storage tank.   The water supply means includes a first water amount detection means for detecting a predetermined upper limit water storage amount of the first water storage tank and a first lower limit water storage amount of the second water storage tank. 2, and when the second water amount detection means detects a predetermined lower limit water storage amount of the second water storage tank, the control means detects the second water amount detection means from the first water storage tank. 7. The solid oxide fuel cell according to claim 6, wherein the water supply means is controlled such that water is supplied to the water storage tank and water is supplied up to a predetermined upper limit water storage amount of the first water storage tank.   The control means controls the steam reforming reaction (SR) operation performed in the first fail-safe operation mode to be different from the steam reforming reaction (SR) operation performed in the normal stop operation mode. 2. The solid oxide fuel cell according to 1.   The control means uses the amount of fuel gas used for the steam reforming reaction (SR) operation performed in the first fail-safe operation mode for the steam reforming reaction (SR) operation performed in the normal stop operation mode. 9. The solid oxide fuel cell according to claim 8, wherein the fuel gas supply means is controlled so as to be lower than the amount of fuel gas produced.   The control means further converts the amount of water used in the steam reforming reaction (SR) operation performed in the first fail-safe operation mode into the steam reforming reaction (SR) operation performed in the normal stop operation mode. The solid oxide fuel cell according to claim 9, wherein the water supply means is controlled so as to be lower than the amount of water used.   The control means further uses the steam reforming reaction (SR) performed in the normal stop operation mode to determine the amount of power generation air used in the steam reforming reaction (SR) operation performed in the first fail-safe operation mode. The solid oxide fuel cell according to claim 9 or 10, wherein the power generation air supply means is controlled so as to be lower than the amount of power generation air used for operation.

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