JP2010287483A - Solid electrolyte type fuel battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolyte type fuel battery that prevents a fuel battery cell from being inactivated by carrying out a cleaning mode operation for removing sulfur adherent to a fuel battery cell under a predetermined condition during a power generation operation by a fuel battery module. <P>SOLUTION: The battery includes a desulfurizer 36 for removing sulfur contained in a fuel gas, a fuel flow adjustment unit 38 for supplying the fuel gas to a reformer 20, an air flow adjustment unit 45 for power generation which supplies air for power generation to a fuel battery cell assembly 12, a hydrogen flow adjustment unit 48 for adjusting a proportion of hydrogen to be supplied to the fuel battery cell assembly 12, a control section for increasing a proportion of hydrogen to be supplied to the fuel battery cell assembly 12 when reaching a predetermined condition, so as to carry out the cleaning mode operation for removing sulfur adherent to the fuel battery cell assembly 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

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 and / 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.

Conventional SOFCs are generally operated with power generation output kept constant. However, SOFCs can be used for facilities where there is almost no electricity demand at night or where there is a significant change in electricity demand during the day and night. When installing, it is necessary to change the power generation output value according to the required power generation amount.
For example, in the conventional SOFC described in Patent Document 1, two types of operating temperatures of the power generation unit are set depending on the amount of power usage, and the operation of the power generation unit is performed in a time zone where the power usage is low. By setting the temperature low, the amount of fuel gas used to maintain the operating temperature of the power generation unit is reduced, reducing costs and reducing CO ₂ emissions.

  In such a conventional SOFC, since city gas and kerosene used as fuel gas contain sulfur, the sulfur contained in the fuel gas adheres to the fuel battery cell, and the activity of the fuel battery cell ( There is a problem that the power generation capacity) decreases.

JP 2005-216618 A

Further, in the conventional SOFC, a fuel gas before reforming is provided by providing a desulfurizer that removes sulfur contained in the fuel gas upstream of the reformer that reforms the fuel gas and supplies the fuel cell. What removes sulfur from the is also known as a well-known technique.
However, in such a desulfurizer, it is difficult to desulfurize even a very small amount of sulfur in the fuel gas. Therefore, as the power generation operation is performed for a long period of time, these small amounts of sulfur that cannot be completely desulfurized gradually become fuel cells. There is a problem in that the activity (power generation capacity) of the fuel battery cell is remarkably reduced as compared with the beginning of the power generation operation.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and removes sulfur adhering to the fuel cell based on predetermined conditions during the power generation operation by the fuel cell module. An object of the present invention is to provide a solid oxide fuel cell capable of preventing the inactivation of the fuel cell by performing the operation (hereinafter referred to as “cleaning mode operation”).

In order to achieve the above object, the present invention provides a solid oxide fuel cell that generates electricity by reacting fuel gas and air, and is disposed in a power generation chamber in a fuel cell module, and a plurality of solid electrolyte fuels A fuel battery cell assembly including battery cells, a desulfurizer for removing sulfur contained in the fuel gas, fuel gas supply means for supplying fuel gas desulfurized by the desulfurizer, and the fuel gas supply means A reformer for reforming the supplied fuel gas and supplying the fuel cell assembly to the fuel cell assembly, power generation air supply means for supplying power generation air to the fuel cell assembly, and supply to the fuel cell assembly A hydrogen supply ratio adjusting means for adjusting a supply ratio of the generated hydrogen, and by increasing the supply ratio of hydrogen supplied to the fuel cell assembly when a predetermined condition is reached, It is characterized by having a control unit for executing a cleaning mode operation for removing sulfur attached to.
In the present invention configured as described above, when a predetermined condition is reached, the control unit attaches to the fuel cell assembly by increasing the supply ratio of hydrogen supplied to the fuel cell assembly. In this mode, the sulfur that has not been desulfurized by the desulfurizer can be removed and the fuel cell can be deactivated by the adhesion of sulfur. Can be prevented.

In the present invention, it is preferable that the predetermined condition for the control unit to execute the cleaning mode operation is when a predetermined power generation operation time has elapsed.
In the present invention configured as described above, since the control unit performs the cleaning mode operation when a predetermined power generation operation time has elapsed, the sulfur adhering to the fuel cell assembly without being completely desulfurized by the desulfurizer. And the inactivation of the fuel battery cell due to the adhesion of sulfur can be prevented. Since a predetermined condition for executing the cleaning mode operation is a condition that a predetermined power generation operation time elapses, it is not necessary to carry out the cleaning mode operation unnecessarily, and smooth steady power generation can be maintained. At the same time, it is possible to cope with the malfunction of the fuel battery cell due to the adhesion of sulfur.

In the present invention, preferably, the predetermined condition for the control unit to execute the cleaning mode operation may be a time when a power generation operation time has elapsed when the voltage of the fuel cell reaches a predetermined voltage. .
In the present invention configured as described above, the control unit performs the cleaning mode operation when the voltage of the fuel cell reaches a predetermined voltage, so that the control unit adheres to the fuel cell assembly without being completely desulfurized by the desulfurizer. Sulfur contained can be removed, and inactivation of the fuel battery cell due to the adhesion of sulfur can be prevented. Since the cleaning operation is performed while checking the voltage of the fuel cell itself, cleaning can be performed at an appropriate timing even when more than expected sulfur is attached to the fuel cell due to some problem.

In the present invention, preferably, the hydrogen supply ratio adjusting means is hydrogen supply means for supplying hydrogen to the fuel cell assembly, and the control unit supplies hydrogen to be supplied to the fuel cell assembly. The hydrogen supply means is controlled so as to increase the ratio to a hydrogen supply ratio higher than a hydrogen supply ratio region in which steady power generation operation by the fuel cell module is possible, and the cleaning mode operation is executed.
In the present invention configured as described above, when the cleaning mode operation is executed by the control unit, the supply ratio of the hydrogen supplied to the fuel cell assembly allows a steady power generation operation by the fuel cell module. Since the hydrogen supply rate rises to a higher hydrogen supply rate than the region of the hydrogen supply rate, the removal amount of sulfur adhering to the fuel cell assembly is increased, which effectively inactivates the fuel cell due to sulfur adhesion. Can be prevented.

In the present invention, it is preferable that the control unit supply the predetermined hydrogen in a region where the supply ratio of hydrogen supplied to the fuel cell assembly is a hydrogen supply ratio in which steady power generation operation by the fuel cell module is possible. When a low load power generation operation that is less than the ratio is performed, the supply ratio of hydrogen supplied to the fuel cell assembly is set to a predetermined hydrogen in a hydrogen supply ratio region where the steady power generation operation is possible. The above cleaning mode operation is executed by increasing the supply rate to a value equal to or higher than the supply rate.
In the present invention configured as described above, the supply ratio of hydrogen supplied to the fuel cell assembly is less than a predetermined hydrogen supply ratio in a hydrogen supply ratio region in which steady power generation operation by the fuel cell module is possible. When the low load power generation operation is performed, the hydrogen supply ratio supplied to the fuel cell assembly is equal to or higher than a predetermined hydrogen supply ratio in the hydrogen supply ratio region where steady power generation operation is possible. Since the cleaning mode operation is performed by raising the temperature, it is possible to perform a steady power generation operation and remove sulfur adhering to the fuel cell even during the cleaning mode operation. In addition, since the cleaning mode operation is executed by increasing the supply ratio of hydrogen supplied to the fuel cell assembly within the range of the hydrogen supply ratio where steady power generation operation is possible, the hydrogen supply ratio is increased. The burden on the accompanying fuel cell can also be minimized.

In the present invention, it is preferable that the control unit changes the predetermined power generation operation time for executing the cleaning mode operation based on a history of operation by the fuel cell module.
In the present invention configured as described above, the amount of sulfur actually attached to the fuel cell varies depending on the operation history of the fuel cell module, but the predetermined power generation operation which is a condition for executing the cleaning mode operation Since the time is changed based on the operation history of the fuel cell module, the time interval between the cleaning mode operations according to the actual sulfur adhesion amount can be set appropriately. Further, the burden on the fuel cells due to the increase in the hydrogen supply ratio and the power generation chamber temperature can be minimized.
be able to.

In the present invention, it is preferable that the control unit sets the predetermined power generation operation time for performing the cleaning mode operation so that the supply ratio of hydrogen supplied to the fuel cell assembly is constant by the fuel cell module. Change to a shorter time as the ratio of low-load power generation operation in the operation history by the fuel cell module is lower when the power supply operation is less than a predetermined hydrogen supply ratio within the range of hydrogen supply ratio To do.
In the present invention configured as described above, the higher the ratio of the low load power generation operation in the operation history of the fuel cell module, the shorter the time during which the fuel cell assembly is exposed to a high hydrogen supply ratio or high temperature. Therefore, the amount of sulfur adhered to the fuel cell also increases, but the predetermined time until the next cleaning mode operation is executed after the execution of the cleaning mode operation is changed to a short time, and the next cleaning mode operation is performed. By accelerating the execution, it is possible to perform an appropriate operation according to the actual amount of sulfur attached to the fuel cell.

In the present invention, preferably, the control unit performs the cleaning mode operation for a predetermined duration, and when the voltage of the fuel cell reaches a predetermined voltage during the execution of the cleaning mode operation, the predetermined duration time. Even within, the cleaning mode operation is forcibly terminated.
In the present invention configured as described above, if the voltage of the fuel cell module reaches a predetermined voltage even if the cleaning mode operation is continued, the cleaning mode operation is forcibly performed even within the predetermined duration. Since it is made to complete | finish, it can prevent exposing a fuel cell to a high hydrogen supply ratio or high temperature wastefully, and can prevent deterioration of a fuel cell.

In the present invention, it is preferable that the control unit sets the predetermined power generation operation time, which is a condition for executing the cleaning mode operation, to be shorter as the aging time during which the power generation operation is performed by the fuel cell module is longer. Set to.
In the present invention configured as described above, in consideration of the fact that sulfur easily adheres to the fuel cell as the aging time of the fuel cell of the fuel cell module elapses, the predetermined power generation operation time is generated by the fuel cell module. The longer the operating time, the shorter the execution time of the cleaning mode operation can be set by setting it to a shorter time, and it is possible to perform an appropriate operation according to the actual amount of sulfur adhered to the fuel cell. it can.

In the present invention, it is preferable that the predetermined condition for the control unit to execute the cleaning mode operation is a manual operation, and the control unit forcibly executes the cleaning mode operation by the manual operation.
In the present invention configured as described above, even if a failure occurs in the desulfurization process of the fuel gas, such as failure of the desulfurizer, the cleaning mode operation is forcibly executed by manual operation. Therefore, sulfur adhering to the fuel battery cell can be surely removed.

  According to the fuel cell of the present invention, during the power generation operation by the fuel cell module, the fuel cell is inactivated by performing a cleaning mode operation for removing sulfur adhering to the fuel cell based on a predetermined condition. Can be prevented.

1 is an overall configuration diagram showing 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 operation stop 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 cleaning mode driving | operation of the 1st example of the solid oxide fuel cell (SOFC) by one Embodiment of this invention. It is a time chart which shows the comparative example of FIG. It is a time chart which shows the operation | movement at the time of the cleaning mode driving | operation of the 2nd example 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 cleaning mode driving | operation of the 3rd example 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 cleaning mode driving | operation of the 4th example 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 cleaning mode driving | operation of the 5th example of the solid oxide fuel cell (SOFC) by one Embodiment of this invention.

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 a plurality of fuel cell stacks 14, and the fuel cell stack 14 includes a plurality of fuel cell units 16. Thus, the fuel cell assembly 12 has a plurality of fuel cell units 16, and all of these fuel cell units 16 are connected in series.
Each fuel cell unit 16 is a bottomed cylindrical member made of a ceramic material, and forms a multilayer structure of an air electrode, a solid oxide electrolyte, and a fuel electrode from the inside to the outside. .
Further, when the air contacts the inner wall (air electrode) of the fuel cell unit 16 and the fuel gas contacts the outer wall (fuel electrode) of the fuel cell unit 16, O ²⁻ ions are ^generated in the fuel cell unit 16. It moves, and an electrochemical reaction takes place, and a potential difference is generated between the air electrode and the fuel electrode, so that power generation is performed.

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.
In the combustion chamber 18, a power generation air header 19 that supplies power generation air to the air electrode of each fuel cell unit 16 of the fuel cell assembly 12 is disposed.

Next, 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. is doing.
Further, a preheater 21 for preheating the fuel gas and the reforming air before being supplied to the reformer 20 is disposed above the reformer 20.
Further, an evaporator 22 is disposed above the preheater 21, and water necessary for reforming in the reformer 20 is vaporized and supplied to the reformer 20 by the evaporator 22. Yes.
In addition, a fuel gas dispersion chamber 23 is disposed below the power generation chamber 10, and the fuel gas reformed by the reformer 20 is uniformly dispersed in the fuel gas dispersion chamber 23, and is formed in the fuel cell assembly 12. It comes to be supplied.

Next, the auxiliary unit 4 evaporates by adjusting the flow rate of the water supplied from the pure water tank 26 that stores the water from the water supply source 24 such as a water supply and uses the filter to obtain pure water. A water flow rate adjusting unit 28 (such as a “water pump” driven by a motor) for supplying water at a predetermined flow rate to the vessel 23 is provided.
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). The air adjusted to a predetermined flow rate by the power generation air flow rate adjustment unit 45 is supplied to the power generation air header 19 in the fuel cell module 2.
Furthermore, the auxiliary unit 4 includes an electromagnetic valve 47 that shuts off hydrogen supplied from a hydrogen supply source 46 such as a hydrogen cylinder, and a hydrogen flow rate adjustment unit 48 that adjusts the flow rate of hydrogen. Hydrogen adjusted to a predetermined flow rate is supplied to the fuel gas dispersion chamber 23 in the middle of the path through which the fuel gas reformed by the reformer 20 is supplied to the fuel gas dispersion chamber 23.

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, 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. 2 is a block diagram illustrating a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 2, the solid oxide fuel cell 1 includes a control unit 60. The control unit 60 includes an operation button such as “ON” or “OFF” for operation by the user. A device 62, a display device 64 for displaying various data such as a power generation output value (wattage), and a notification device 66 for issuing a warning (warning) in an abnormal state are connected. In addition, this alerting | reporting apparatus 66 may be connected to the management center in a remote place, and may notify this management center of an abnormal state.

Next, signals from various sensors described below are input to the control unit 60.
First, the combustible gas detection sensor 70 is for detecting a gas leak, and is attached to the fuel cell module 2 and the auxiliary unit 4.
In the CO detection sensor 72, CO in the exhaust gas that is originally discharged to the outside through an exhaust gas passage (not shown) or the like leaks to an external housing (not shown) that covers the fuel cell module 2 and the accessory unit 4. This is to detect whether or not
The hot water storage state detection sensor 74 is for detecting the temperature and amount of hot water in a water heater (not shown).

The power state detection sensor 76 is for detecting the current and voltage of the inverter 54 and the distribution board (not shown). In addition, the power state detection sensor 76 can specifically detect the power (or current and voltage) generated in the fuel cell assembly 12 in the inverter 54.
The power generation air flow rate detection sensor 78 is for detecting the flow rate of the power generation air supplied to the power generation chamber 10.
The reforming air flow rate sensor 80 is for detecting the flow rate of the reforming air supplied to the reformer 20.
The fuel flow sensor 82 is for detecting the flow rate of the fuel gas supplied to the reformer 20.

The water flow rate sensor 84 is for detecting the flow rate of pure water (steam) supplied to the reformer 20.
The water level sensor 86 is for detecting the water level of the pure water tank 26.
The pressure sensor 88 is for detecting the pressure on the upstream side outside the reformer 20.
The exhaust temperature sensor 90 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 92 is provided on the front side and the rear side in the vicinity of the fuel cell assembly 12, and the temperature in the vicinity of the fuel cell stack 14 in the power generation chamber 10 (hereinafter referred to as “power generation”). The temperature of the fuel cell stack 14 (that is, the fuel cell unit 16 itself) is estimated by detecting the room temperature ").
The combustion chamber temperature sensor 94 is for detecting the temperature of the combustion chamber 18.
The exhaust gas chamber temperature sensor 96 is for detecting the temperature of the exhaust gas in the exhaust gas chamber 78.
The reformer temperature sensor 98 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 100 is for detecting the temperature of 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 60, and the control unit 60, based on data from 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 adjustment unit 45 and the hydrogen flow rate adjustment unit 48 to control each flow rate in these units.
Further, the control unit 60 sends a control signal to the inverter 54 to control the power supply amount.

Next, the operation at the time of starting by the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 3 is a time chart showing the operation at the time of start-up of the solid oxide fuel cell (SOFC) according to the 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 via the preheater 21 of the fuel cell module 2. At the same time, power generation air is supplied from the power generation air flow rate adjustment unit 45 to the power generation air header 19 of the fuel cell module 2.
Immediately after this, fuel gas is also supplied from the fuel flow rate adjusting unit 38, and the fuel gas mixed with the reforming air via the preheater 21 passes through the reformer 20 and the fuel gas dispersion chamber 23. It is supplied into the power generation chamber 10, passes through the fuel cell stack 14 and the fuel cell unit 16, and reaches the combustion chamber 18. Further, in the power generation chamber 10, the fuel gas introduced from the fuel gas dispersion chamber 23 comes into contact with the fuel electrode of each fuel cell unit 16, so that the air in each fuel cell unit 16 is generated from the power generation air header 19. Electricity is generated by an electrochemical reaction with the air for power generation supplied to the electrode.

Next, ignition is performed by an ignition device (not shown), and the fuel gas and air (reforming air and generating air) in the combustion chamber 18 are combusted. Exhaust gas is generated by the combustion of the fuel gas and air, and the exhaust gas warms the fuel gas containing the reforming air in the reformer 20 and is supplied to the hot water production apparatus 50.
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 from the fuel gas dispersion chamber 23 to the lower side of the fuel cell stack 14, 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 98 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. In addition, the reforming air flow rate adjusting unit 44 supplies a gas in which fuel gas, reforming air, and water vapor are mixed in advance to the reformer 20. 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 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.

  Thus, after the fuel cell module 2 is ignited by an ignition device (not shown), the partial oxidation reforming reaction POX, the autothermal reforming reaction ATR, and the steam reforming reaction SR proceed sequentially, The temperature in the power generation chamber 10 gradually increases. Next, when the temperature in the power generation chamber 10 and the fuel cell unit 16 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 module 16 is closed. Electricity generation by the battery module 2 is started, whereby current flows through the circuit. Due to the power generation of the fuel cell module 2, the fuel cell unit 16 itself also generates heat, and the temperature of the fuel cell unit 16 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, fuel gas and air larger than the amount of fuel gas and air consumed by the fuel cell unit 16 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 when the solid oxide fuel cell (SOFC) according to the present embodiment is stopped will be described with reference to FIG. FIG. 4 is a time chart showing the operation when the solid oxide fuel cell (SOFC) is stopped according to this embodiment.
As shown in FIG. 4, when the operation of the fuel cell module 2 is stopped, first, the fuel flow rate adjustment unit 38 and the water flow rate adjustment unit 28 are operated to supply fuel gas and water vapor to the reformer 20. Reduce the amount.

  Further, when the operation of the fuel cell module 2 is stopped, the amount of fuel gas and water vapor supplied to the reformer 20 is reduced, and at the same time, the fuel cell module for generating air by the reforming air flow rate adjusting unit 44 The supply amount into 2 is increased, the fuel cell assembly 12 and the reformer 20 are cooled by air, and these temperatures are lowered. Thereafter, when the temperature of the power generation chamber decreases to a predetermined temperature, for example, 400 ° C., the supply of fuel gas and steam to the reformer 20 is stopped, and the steam reforming reaction SR of the reformer 20 is ended. This supply of power generation air continues until the temperature of the reformer 20 decreases to a predetermined temperature, for example, 200 ° C., and when this temperature is reached, the power generation air from the power generation air flow rate adjustment unit 45 is supplied. Stop supplying.

  As described above, in the present embodiment, when the operation of the fuel cell module 2 is stopped, the steam reforming reaction SR by the reformer 20 and the cooling by the power generation air are used in combination. The operation of the fuel cell module can be stopped.

Next, the operation during the cleaning mode operation of the first example of the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIGS.
FIG. 5 is a time chart showing the operation during the cleaning mode operation of the first example of the solid oxide fuel cell (SOFC) according to the present embodiment, and FIG. 6 is a time chart showing a comparative example of FIG.

First, in FIG. 5, the vertical axis represents the hydrogen supply ratio, the power generation chamber temperature (T), the cell voltage (V) (the voltage of the fuel cell assembly 12), and the horizontal axis represents the time (t). Yes.
Here, in particular, the “hydrogen supply ratio” on the vertical axis in FIG. 5 is the ratio of the amount of hydrogen supplied from the fuel gas dispersion chamber 23 to the fuel cell assembly 12 and the amount of methane (H ₂ / CH ₄ ). Means. In particular, the hydrogen amount in the hydrogen supply ratio is supplied from the hydrogen flow rate adjustment unit 48 to the hydrogen amount reformed from the fuel gas in the reformer 20 and supplied to the fuel cell assembly 12 through the fuel gas dispersion chamber 23. The amount of hydrogen added to the amount of hydrogen generated is shown. The methane amount at the hydrogen supply ratio indicates the amount of methane that is reformed from the fuel gas in the reformer 20 and is supplied to the fuel gas dispersion chamber 23.
In the cleaning mode operation of the first example by the solid oxide fuel cell (SOFC) 1 of the present embodiment, the hydrogen supply ratio region (hereinafter referred to as the temperature region in which the power generation chamber temperature (T) is 850 ° C. or higher and 950 ° C. or lower) “Constant power generation operation region”), and the cell voltage (V) is larger than the lower limit voltage value V0 (= 0.76 V) and a constant power generation operation is performed under a predetermined condition. It is supposed to be executed in.

More specifically, first, after the start-up operation of the fuel cell module 2 described with reference to FIG. 3, the power generation operation is started at time t0.
Next, the power generation operation time τ1 (= 5000 hours) from the start of the power generation operation at time t0 to the start of the cleaning mode operation at time t1 and the lower limit voltage value V0 (= 0.76V) of the cell voltage (V). Is determined in advance as a reference value for determining whether or not to start the cleaning mode operation.
For example, as shown in FIG. 5, when the cell voltage (V) does not reach the lower limit voltage value V0 from time t0 to time t1 when the power generation operation time τ1 has elapsed, the control unit 60 supplies hydrogen at time t1. A signal is sent to the hydrogen flow rate adjustment unit 48 as the means, and the first cleaning mode operation is started regardless of the power generation amount by the power generation operation so far.
On the other hand, when the cell voltage (V) detected by the power state detection sensor 76 reaches the lower limit voltage value V0 by the time t1 when the power generation operation time τ1 has elapsed from the time t0, the power generation operation time from the time t0 at that time. Without waiting for the elapse of τ1, the first cleaning mode operation is forcibly started regardless of the amount of power generated by the previous power generation operation.

  Further, when the first cleaning mode operation is started at time t1, based on the signal sent from the control unit 60 to the hydrogen flow rate adjustment unit 48, the power generation chamber temperature (T) regardless of the power generation amount generated until then. Is supplied from the hydrogen flow rate adjustment unit 48 to the fuel gas dispersion chamber 23 so that the temperature is forcibly increased to a predetermined temperature (950 ° C. to 1000 ° C.) higher than the steady power generation operation region. The supply ratio of hydrogen supplied to the fuel cell assembly 12 in the power generation chamber 10 during the steady power generation operation performed until t1 increases.

In other words, in the cleaning mode operation, hydrogen supplied to the fuel cell assembly 12 in the power generation chamber 10 through the fuel gas dispersion chamber 23 is other than hydrogen contained in the fuel gas reformed by the reformer 20. In addition, hydrogen is also added to the fuel cell assembly 12 from the hydrogen flow rate adjustment unit 48. The hydrogen added from the hydrogen flow rate adjustment unit 48 to the fuel cell assembly 12 is subjected to a steam reforming reaction (endothermic reaction). Since it is directly supplied to the fuel cell assembly 12 without any reaction), the temperature of the fuel cell assembly 12 can be increased to increase the temperature.
As described above, in the cleaning mode operation, the ratio of hydrogen supplied to the fuel cell assembly 12 is increased to increase the temperature of the fuel cell assembly 12, and as a result, the fuel cell assembly 12 adheres to each fuel cell unit 16. Sulfur is removed.

Next, the time (t2-t1) during which the first cleaning mode operation is started at time t1 and the cleaning mode operation is continued until the first cleaning mode operation is completed at time t2 is 2 hours or more and 3 hours or less. The predetermined time is set in advance.
Further, as shown in FIG. 5, the cell voltage at the time when the initial cleaning mode is completed at time t2 is higher than the cell voltage at time t1 because sulfur adhering to each fuel cell unit 16 is removed. The voltage has recovered.
Furthermore, from time t2 to time t3, the steady power generation operation in which the supply ratio of hydrogen supplied to the fuel cell assembly 12 is within the steady power generation operation region is executed again.

  Here, in the n-th (n ≧ 2) cleaning mode operation, does the power generation operation time τn from the time when the previous cleaning mode operation ends to the time when the next cleaning mode operation starts reaches 5000 hours? Or, when the cell voltage reaches either one of the conditions until the power generation operation time τn reaches 5000 hours before the power generation operation time τn reaches 5000 hours, regardless of the power generation amount by the power generation operation so far The cleaning mode operation is set in advance so as to be executed immediately.

For example, at time t3 shown in FIG. 5, the cell voltage has not reached the lower limit voltage value V0, but since the power generation operation time τ2 after the completion of the first cleaning mode operation at time t2 has reached 5000 hours, Regardless of the amount of power generated by this power generation operation, the second cleaning mode operation is executed, and the supply ratio of hydrogen supplied to the fuel cell assembly 12 is higher than the steady operation region, as in the first cleaning mode operation. Forcibly increased to a predetermined hydrogen supply rate (power generation chamber temperature (T) is forcibly increased to a predetermined temperature (950 ° C. to 1000 ° C.) higher than the steady power generation operation region), and the second cleaning mode at time t4 The operation is terminated, and the steady power generation operation in which the supply ratio of hydrogen supplied to the fuel cell assembly 12 is within the steady power generation operation region is executed again.
Note that the operation continuation time (t4-t3) from the start to the end of the second cleaning mode operation is also set in advance to a predetermined time of 2 hours or more and 3 hours or less, as in the first cleaning mode operation. ing.

Further, at time t5 shown in FIG. 5, since the power generation operation time τ3 after the end of the second cleaning mode operation at time t4 reaches 5000 hours, the cell voltage has reached the lower limit voltage value V0. Regardless of the amount of power generated by the power generation operation up to, the third cleaning mode operation is executed, and the supply ratio of hydrogen supplied to the fuel cell assembly 12 is steady operation as in the first and second cleaning mode operations. The temperature is forcibly increased to a predetermined hydrogen supply rate higher than the region (the power generation chamber temperature (T) is forcibly increased to a predetermined temperature (950 ° C. to 1000 ° C.) higher than the steady power generation operation region), and 3 at time t6. The second cleaning mode operation is ended, and the steady power generation operation in which the supply ratio of hydrogen supplied to the fuel cell assembly 12 is within the steady power generation operation region is executed again.
Note that the operation continuation time (t6-t5) from the start to the end of the third cleaning mode operation is also set to a predetermined time of 2 hours or more and 3 hours or less as in the first and second cleaning mode operations. It is set in advance.

Similarly, at the time t7 shown in FIG. 5, the cell voltage has reached the lower limit voltage value V0 before the power generation operation time τ4 reaches 5000 hours after the third cleaning mode operation ends at the time t6. Regardless of the amount of power generated by the previous power generation operation, the fourth cleaning mode operation is executed, and the supply rate of hydrogen supplied to the fuel cell assembly 12 is a steady operation as in the third cleaning mode operation. Forcibly increases to a predetermined hydrogen supply rate higher than the region (the power generation chamber temperature (T) is forcibly increased to a predetermined temperature (950 ° C. to 1000 ° C.) higher than the steady power generation operation region), and 4 at time t8. The second cleaning mode operation is ended, and the steady power generation operation in which the supply ratio of hydrogen supplied to the fuel cell assembly 12 is within the steady power generation operation region is executed again.
Note that the operation continuation time (t8-t7) from the start to the end of the third cleaning mode operation is also set to a predetermined time of 2 hours or more and 3 hours or less, as in the first and second cleaning mode operations. It is set in advance.

On the other hand, FIG. 6 is a time chart when the cleaning mode operation is not executed at all as a comparative example of FIG.
As shown in FIG. 6, when the cleaning mode operation is not executed at time t1 when the power generation operation time τ1 has elapsed from time t0, the cell voltage (V) continues to decrease after time t1. Further, if the cleaning mode operation is not executed even when the cell voltage (V) reaches the lower limit voltage value V0 at time t9, the cell voltage (V) continues to decrease with a relatively large slope after time t9.

  According to the cleaning mode operation of the first example according to the present embodiment described above, regardless of the power generation amount by the fuel cell module 2, the power generation operation time after the start operation is ended and the power generation operation is started, and the previous time When the power generation operation time after the completion of the cleaning mode operation and restarting the power generation operation reaches a predetermined time (for example, 5000 hours) or the cell voltage during the power generation operation reaches a predetermined lower limit voltage value, the control is performed. The cleaning mode operation is executed by the unit 60, and the supply rate of hydrogen supplied to the fuel cell assembly 12 is forcibly increased to a predetermined hydrogen supply rate higher than the steady operation region (the power generation chamber temperature (T) is increased). Forcibly rising to a predetermined temperature (950 ° C. to 1000 ° C.) higher than the steady power generation operation region) to effectively remove sulfur adhering to the fuel cell assembly 12 It is possible. As a result, inactivation of the fuel battery cell due to sulfur adhesion can be prevented.

Next, the operation during the cleaning mode operation of the second example of 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 during the cleaning mode operation of the second example of the solid oxide fuel cell (SOFC) according to the present embodiment.

  As shown in FIG. 7, the cleaning mode operation of the second example by the solid oxide fuel cell (SOFC) 1 of the present embodiment is in the steady power generation operation region where the power generation chamber temperature (T) is 850 ° C. or more and 950 ° C. or less. Low load power generation operation with a cell supply voltage (V) greater than the lower limit voltage value V0 (= 0.74V) in the region of the hydrogen supply ratio corresponding to the region below the predetermined temperature (less than 900 ° C.) Is executed under a predetermined condition when the operation is performed.

More specifically, first, after the start-up operation of the fuel cell module 2 described with reference to FIG. 3, the power generation operation time τ1 from the start of the low load power generation operation at time t100 to the start of the cleaning mode operation at time t101. (= 5000 hours) and the lower limit voltage value V0 (= 0.74V) of the cell voltage (V) are set in advance as reference values for determining whether or not to start the cleaning mode operation.
For example, as shown in FIG. 7, when the cell voltage (V) does not reach the lower limit voltage value V0 from time t100 to time t101 when the power generation operation time τ1 has elapsed, at time t101, the control unit 60 performs the hydrogen flow rate. A signal is sent to the adjustment unit 48, and the first cleaning mode operation is started regardless of the amount of power generated by the previous power generation operation.
On the other hand, when the cell voltage (V) detected by the power state detection sensor 76 reaches the lower limit voltage value V0 from time t100 to time t101 when the power generation operation time τ1 has elapsed, the power generation operation time from time t100 to that time. The first cleaning mode operation is forcibly started without waiting for the elapse of τ1, and after the predetermined time (2 to 3 hours) operation, the first cleaning mode operation is terminated at time t102, and the low load power generation operation is executed again. The

  Further, when the first cleaning mode operation is started at time t101, the low load power generation operation is performed based on the signal sent from the control unit 60 to the hydrogen flow rate adjustment unit 48 regardless of the power generation amount by the power generation operation so far. Up to a predetermined hydrogen supply rate (for example, the power generation chamber temperature (T) corresponds to 950 ° C.) in the range of the hydrogen supply rate (corresponding to the steady power generation operation range (850 ° C. to 950 ° C.) of the power generation chamber temperature (T)) By forcibly increasing the temperature, the temperature of the fuel cell assembly 12 can be increased and the temperature can be increased.

That is, by this cleaning mode operation, the temperature of the fuel cell assembly 12 can be kept high, and the sulfur adhering to each fuel cell unit 16 can be removed.
Also, in the n-th (n ≧ 2) cleaning mode operation, whether the power generation operation time τn from the time when the previous cleaning mode operation ends to the time when the next cleaning mode operation starts reaches 5000 hours, Alternatively, when the cell voltage reaches the lower limit voltage value V0 before the power generation operation time τn reaches 5000 hours, the cleaning mode operation is performed regardless of the power generation amount by the power generation operation so far.

  According to the cleaning mode operation of the second example according to the present embodiment described above, the temperature of the power generation chamber is low at a temperature lower than a predetermined hydrogen supply rate in the region of the hydrogen supply rate in which steady power generation operation by the fuel cell module is possible. Even when the load power generation operation is performed, regardless of the amount of power generated by the fuel cell module 2, the low load power generation operation time from the start of the start operation and the start of the low load power generation operation, and the previous time When the cleaning mode operation is finished and the low load power generation operation is restarted, the power generation operation time reaches a predetermined time (for example, 5000 hours), or the cell voltage during the power generation operation reaches a predetermined lower limit voltage value. The control unit 60 causes the power generation chamber temperature (T) to be higher than a hydrogen supply rate at which the low-load power generation operation is performed within the region of the hydrogen supply rate in the steady power generation operation (for example, Cleaning mode operation is performed forcibly raised to correspond) to the collector chamber temperature 950 ° C.. For this reason, even when the cleaning mode operation is being performed, it is possible to perform a steady power generation operation and to effectively remove sulfur adhering to the fuel cell assembly 12. Inactivation of the battery cell can be prevented. In addition, since the hydrogen supply rate is increased and the cleaning mode operation is executed within the region of the hydrogen supply rate in which steady power generation operation is possible (corresponding to the power generation chamber temperature of 850 ° C. to 950 ° C.), the hydrogen supply rate and The burden on the fuel cell unit 16 due to heating or the like accompanying an increase in the temperature of the power generation chamber can be minimized.

Next, the operation during the cleaning mode operation of the third example 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 cleaning mode operation of the third example of the solid oxide fuel cell (SOFC) according to the present embodiment.

  As shown in FIG. 8, the cleaning mode operation of the third example by the solid oxide fuel cell (SOFC) 1 of the present embodiment is in the steady power generation operation region where the power generation chamber temperature (T) is 850 ° C. or more and 950 ° C. or less. And a predetermined condition when a steady power generation operation is performed at a cell voltage (V) larger than the lower limit voltage value V0 (= 0.74 V). It is supposed to be executed below.

More specifically, first, after the start-up operation of the fuel cell module 2 described with reference to FIG. 3, the power generation operation time τ1 (=) from the start of the power generation operation at time t200 to the start of the cleaning mode operation at time t201. 5000 hours) and the lower limit voltage value V0 (= 0.74V) of the cell voltage (V) are set in advance as reference values for determining whether or not to start the cleaning mode operation.
In addition, when the power generation operation time τ1 from when the power generation operation is started at time t200 to when the first cleaning mode operation is started at time t201 and when the nth (n ≧ 2) cleaning mode operation is executed, the previous time The power generation operation is restarted from the time when the cleaning mode operation is completed, and the power generation operation time τn from the time when the next cleaning mode operation is started is changed according to the state of the power generation operation.

  More specifically, in order to grasp the power generation operation state, the power generation chamber temperature detected by the power generation chamber temperature sensor 92 during the power generation operation and the integrated value based on the operation time, or the power generation chamber temperature (T) is 850 ° C. or more and 950 Typically, the accumulated time during which the power generation operation is performed under the low load condition in the region of the hydrogen supply ratio corresponding to the region of less than the predetermined temperature (less than 900 ° C) in the steady power generation operation region that is below ℃ Based on the quantitative value indicating the operation history of the fuel cell module 2, the power generation operation state is quantified by a specific amount. Based on these quantified values, the power generation operation time τ1 from the start of the power generation operation to the start of the first cleaning mode operation or the nth (n ≧ 2) cleaning mode operation is executed. In this case, it is determined whether or not to change the power generation operation time τn from the end of the previous cleaning mode operation to the start of the next cleaning mode operation.

  As an example, FIG. 8 shows an example in which the first cleaning mode operation is started at time t201, the initial cleaning mode operation ends at time t202 after a predetermined time, and again at time t202 when the power generation operation time τ2 (= 5000 hours) has elapsed. The executed steady power generation operation is executed in a state where the hydrogen supply ratio and the power generation chamber temperature are higher than the steady power generation operation from time t200 to t201. As a result, the sulfur adhering to the fuel cell assembly 12 is more effective when the second cleaning mode operation is completed at time t204 than when the first cleaning mode operation is completed at time t202. Therefore, the power generation operation time τ3 from the end of the second cleaning mode operation at time t204 to the start of the third cleaning mode operation at time t205 is changed from a predetermined 5000 hours to 7000 hours. It has changed.

  According to the cleaning mode operation of the third example according to the present embodiment described above, the amount of sulfur actually attached to the fuel cell assembly 12 varies depending on the history of the power generation operation of the fuel cell module 2, but the nth cleaning is performed. Since the power generation operation time τn before the mode operation can be changed based on the operation history (power generation operation time, hydrogen supply ratio, power generation chamber temperature) in which the power generation operation by the fuel cell module 2 is performed, actual sulfur adhesion The time interval between cleaning mode operations according to the amount can be set appropriately. In addition, the burden on the fuel cell unit 16 due to heating accompanying the increase in the hydrogen supply ratio and the power generation chamber temperature can be minimized.

Next, the operation of the fourth example of the solid oxide fuel cell (SOFC) according to the present embodiment during the cleaning mode operation will be described with reference to FIG.
FIG. 8 is a time chart showing the operation during the cleaning mode operation of the fourth example of the solid oxide fuel cell (SOFC) according to the present embodiment.

As shown in FIG. 9, in the cleaning mode operation of the fourth example by the solid oxide fuel cell (SOFC) 1 of this embodiment, first, after the start-up operation of the fuel cell module 2 described with reference to FIG. The region of the hydrogen supply ratio corresponding to the region below the predetermined temperature (T1) in the steady power generation operation region where the power generation chamber temperature (T) is 850 ° C. or more and 950 ° C. or less from the start of the low load power generation operation to time t301. In addition, the low load power generation operation is performed with the cell voltage (V) being larger than the lower limit voltage value V0 (= 0.74V).
Next, from time t301 to time t302, the steady power generation operation is executed in a predetermined region (T1 <T ≦ T2) in which the hydrogen supply ratio and the power generation chamber temperature are higher than the low load power generation operation from time t300 to t301. The first cleaning mode operation is executed at time t302.
Here, the power generation operation time τ1 from the start of the low load power generation operation at time t300 to the execution of the first cleaning mode operation is predetermined as 5000 hours before the operation, but from time t300 to t301. Since the low load power generation operation is executed, the predetermined time (5000 hours) is changed to a shorter time (4000 hours) in order to accelerate the initial cleaning mode operation.

In addition, after the first cleaning mode operation is executed for a predetermined time (2 to 3 hours) at time t302, the cleaning mode operation is ended at time t303, and the temperature is again below the predetermined temperature (T1) within the steady power generation operation temperature region. A low load power generation operation is performed in the region.
At time t304, the second cleaning mode operation is executed. At times t303 to 304, only the low load power generation operation is executed. Therefore, in order to accelerate the start of the second cleaning mode operation, the first cleaning mode operation is performed. The power generation operation time τ2 from the end to the start of the second cleaning mode operation is changed from a predetermined time (5000 hours) to a shorter time (3000 hours).

Further, after the second cleaning mode operation is performed for a predetermined time (2 to 3 hours) at time t304, the cleaning mode operation is terminated at time t305, and the power generation chamber temperature (T) from time t305 to t306 is constant power generation operation. The steady power generation operation is executed at a predetermined temperature T3 (≧ T2) in the temperature region, and the third cleaning mode operation is executed at time t306.
Here, at times t305 to 306, since the steady power generation operation is performed in a state where the hydrogen supply ratio and the power generation chamber temperature are higher than those at times t300 to t302 and t303 to t304, the second cleaning mode operation is completed. The power generation operation time τ3 from the start to the third cleaning mode operation is longer than the time τ1 and τ2 until the first and second cleaning mode operations are executed.

  That is, in the cleaning mode operation of the fourth example according to the present embodiment, in the power generation operation in which the hydrogen supply ratio and the power generation chamber temperature other than the cleaning mode operation are executed in the steady power generation operation region, the hydrogen supply ratio and the power generation chamber temperature are The higher the proportion of low-load power generation operation performed in a relatively low region within the steady power generation operation region in the operation history of the fuel cell module 2, the first cleaning mode operation starts after the power generation operation starts. Power generation operation time τ1 and time τn from the end of the previous cleaning mode operation to the start of the nth (n ≧ 2) cleaning mode operation are shorter than a predetermined time (5000 hours). It can be changed.

  According to the cleaning mode operation of the fourth example according to this embodiment described above, the time during which the fuel cell assembly 12 is exposed to a higher temperature as the ratio of the low load power generation operation to the operation history by the fuel cell module 2 is higher. However, the amount of sulfur attached to the fuel cell unit 16 also increases, but the power generation operation time τ1 from the start of the power generation operation to the start of the first cleaning mode operation or the previous cleaning mode operation ends. The time τn until the nth (n ≧ 2) cleaning mode operation starts is changed to a shorter time than the predetermined time (5000 hours), and the execution of the cleaning mode operation is accelerated. Therefore, it is possible to perform an appropriate operation in accordance with the actual sulfur adhesion amount of the fuel cell unit 16.

Next, the operation during the cleaning mode operation of the fifth example 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 cleaning mode operation of the fifth example of the solid oxide fuel cell (SOFC) according to the present embodiment.

  As shown in FIG. 10, in the cleaning mode operation of the fifth example by the solid oxide fuel cell (SOFC) 1 of this embodiment, first, after the start-up operation of the fuel cell module 2 described with reference to FIG. The power generation operation is started, and the power generation operation time τn (= 5000 hours) and the lower limit voltage value V0 (= 0.76 V) of the cell voltage (V) before starting the n-th (n ≧ 1) cleaning mode operation at time tn. ) Is determined in advance as a reference value for determining whether or not to start the cleaning mode operation.

Furthermore, the duration of continuing the nth cleaning mode operation from the start of the nth (n ≧ 1) cleaning mode operation at time tn until the end of the nth cleaning mode operation at time t (n + 1). Is determined in advance for a predetermined time (2 to 3 hours).
On the other hand, when the cell voltage has increased to the predetermined voltage (V1) at time t (n + 1) during the n-th cleaning mode operation, the control unit 60 sends a signal from the power state detection sensor 76. It is received and judged that sulfur adhering to the fuel cell assembly 12 has been removed and the cell voltage has been recovered, regardless of a predetermined duration (2 to 3 hours) of operation in a predetermined cleaning mode. The nth cleaning mode operation is forcibly terminated.

  According to the cleaning mode operation of the fifth example according to this embodiment described above, when the voltage of the fuel cell module reaches a predetermined voltage even if the cleaning mode operation is continued, a predetermined continuation of the predetermined cleaning mode operation is performed. Regardless of the time, the cleaning mode operation is forcibly terminated, so that it is possible to prevent the fuel cell assembly 12 from being unnecessarily exposed to a high temperature and to prevent deterioration of the fuel cell unit 16.

  In the present embodiment in which the cleaning mode operation of the first to fifth examples described above is executed, is the power generation time τn before the n-th (n ≧ 1) cleaning mode operation reaches a predetermined time? Alternatively, as a means for forcibly increasing the hydrogen supply rate supplied from the fuel gas dispersion chamber 23 to the fuel cell assembly 12 in order to execute the cleaning mode operation when the cell voltage reaches a predetermined voltage, The embodiment has been described in which the amount of hydrogen supplied from the hydrogen flow rate adjustment unit 48 to the fuel gas dispersion chamber 23 is increased by a signal sent from the control unit 60 to the hydrogen supply means (hydrogen flow rate adjustment unit 48). The present invention is not limited and can be applied to other forms.

  For example, when performing the cleaning mode operation, instead of the fuel gas supplied from the fuel flow rate adjustment unit 38 to the fuel gas dispersion chamber 23 via the reformer 20, the fuel gas dispersion unit 48 distributes the fuel gas accordingly. Hydrogen may be directly supplied to the fuel cell assembly 12 through the chamber 23. However, when hydrogen is directly supplied to the fuel cell assembly 12 instead of the fuel gas in this way, the temperature of the cell (power generation chamber temperature) is equivalent to the amount that the fuel cell unit 16 does not undergo the reforming reaction. May rise rapidly, or the cell may deteriorate due to high temperature. Therefore, in order to suppress such a temperature rise of the cell, by increasing the amount of power generation air supplied from the power generation air flow rate adjustment unit 45 to the power generation air header 19 and cooling the fuel cell unit 16, The cleaning mode operation can be executed by increasing only the hydrogen supply ratio without changing the temperature of the fuel cell assembly 12.

  Further, the temperature of the reformer 20 is increased as a hydrogen supply ratio adjusting means for forcibly increasing the hydrogen supply ratio supplied from the fuel gas dispersion chamber 23 to the fuel cell assembly 12 in order to execute the cleaning mode operation. By increasing the reforming rate in the reformer 20, the ratio of supplying hydrogen reformed from the fuel gas may be increased. In this case, it can be realized by separately providing a heating means for heating the reformer 20 itself, or a heating means such as a heater or a burner for heating the fuel gas or reforming air supplied to the reformer 20. is there.

  Further, in the present embodiment, by separately providing a heating means such as a heater or a burner for heating the fuel gas supplied to the reformer 20 and the power generation air supplied to the power generation air header 19, a cleaning mode is provided. You may devise so that a hydrogen supply rate and a power generation room temperature may be raised more effectively at the time of operation.

  Further, in addition to the cleaning mode operation of the first to fifth examples according to the present embodiment, the fuel cell module 2 generates power for a long period of time, and a predetermined aging time of the fuel cell unit 16 (for example, 40000 hours). In consideration of the fact that sulfur tends to adhere to the fuel cell unit 16 over time, the longer the aging time during which the power generation operation by the fuel cell module 2 is performed, the longer the previous cleaning mode operation ends. The cleaning mode operation may be executed by setting the power generation time interval until the next cleaning mode operation is started. Thus, the fuel cell assembly 12 that has passed over time can be appropriately operated according to the amount of sulfur adhering to the actual fuel cell unit 16 by advancing the execution of the cleaning mode operation. .

  Furthermore, in addition to the cleaning mode operations of the first to fifth examples according to the present embodiment, the cleaning mode operation may be forcibly executed by manually operating the controller 60 as appropriate. Thereby, even if a failure occurs in the desulfurization process of the fuel gas, such as a failure of the desulfurizer 36, the sulfur adhering to the fuel cell assembly 12 can be reliably removed as appropriate.

  In the above-described embodiment, an example in which the desulfurizer 36 is provided on the upstream side of the fuel flow rate adjustment unit 38 has been described as an example. However, the present invention is not limited to such a configuration. It may be provided on the downstream side of the unit 38.

DESCRIPTION OF SYMBOLS 1 Solid oxide type fuel cell 2 Fuel cell module 4 Auxiliary unit 8 Sealed space 10 Power generation chamber 12 Fuel cell assembly 14 Fuel cell stack 16 Fuel cell unit (solid oxide fuel cell)
DESCRIPTION OF SYMBOLS 18 Combustion chamber 19 Power generation air header 20 Reformer 21 Preheater 22 Evaporator 23 Fuel gas dispersion chamber 24 Water supply source 26 Pure water tank 28 Water flow rate adjustment unit 30 Fuel supply source 36 Desulfurizer 38 Fuel flow rate adjustment unit (fuel) Gas supply means)
40 Air supply source 44 Reforming air flow rate adjustment unit 45 Power generation air flow rate adjustment unit (power generation air supply means)
46 Hydrogen supply source 47 Solenoid valve 48 Hydrogen flow rate adjustment unit (hydrogen supply means)
DESCRIPTION OF SYMBOLS 50 Hot water manufacturing apparatus 52 Control box 54 Inverter 60 Control part 62 Operation apparatus 64 Display apparatus 66 Alarm apparatus 76 Electric power state detection sensor 92 Power generation room temperature sensor 100 Outside temperature sensor

Claims (10)

A solid oxide fuel cell that generates electricity by reacting fuel gas and air,
A fuel cell assembly that is disposed in a power generation chamber in the fuel cell module and includes a plurality of solid electrolyte fuel cells;
A desulfurizer for removing sulfur contained in the fuel gas;
A reformer for reforming fuel gas and supplying the fuel cell assembly to the reformer;
Fuel gas supply means for supplying fuel gas to the reformer;
Power generation air supply means for supplying power generation air to the fuel cell assembly;
A hydrogen supply rate adjusting means for adjusting a supply rate of hydrogen supplied to the fuel cell assembly;
Control that executes a cleaning mode operation for removing sulfur adhering to the fuel cell assembly by increasing a supply ratio of hydrogen supplied to the fuel cell assembly when a predetermined condition is reached. And
A solid oxide fuel cell comprising:   2. The solid oxide fuel cell according to claim 1, wherein the predetermined condition for the control unit to execute the cleaning mode operation is when a predetermined power generation operation time has elapsed.   2. The solid oxide fuel cell according to claim 1, wherein the predetermined condition for the control unit to execute the cleaning mode operation is when the voltage of the fuel cell reaches a predetermined voltage.   The hydrogen supply rate adjusting means is hydrogen supply means for supplying hydrogen to the fuel cell assembly, and the control unit determines a supply rate of hydrogen supplied to the fuel cell assembly by the fuel cell module. 4. The cleaning mode operation according to claim 1, wherein the hydrogen supply unit is controlled so as to increase to a hydrogen supply rate higher than a hydrogen supply rate range in which steady power generation operation is possible, and the cleaning mode operation is executed. The solid oxide fuel cell as described.   The control unit is a low-load power generation in which a supply ratio of hydrogen supplied to the fuel cell assembly is less than a predetermined hydrogen supply ratio in a hydrogen supply ratio region in which steady power generation operation by the fuel cell module is possible When the operation is performed, the hydrogen supply ratio supplied to the fuel cell assembly is increased to a predetermined hydrogen supply ratio or more in the hydrogen supply ratio region where the steady power generation operation is possible. The solid oxide fuel cell according to any one of claims 1 to 3, wherein the cleaning mode operation is executed.   The solid oxide fuel cell according to claim 2, wherein the control unit changes the predetermined power generation operation time for executing the cleaning mode operation based on a history of operation by the fuel cell module.   The control unit is configured to supply the predetermined power generation operation time for performing the cleaning mode operation, a hydrogen supply rate at which a supply ratio of hydrogen supplied to the fuel cell assembly allows a steady power generation operation by the fuel cell module. 3. The solid according to claim 2, wherein the shorter the time is, the higher the ratio of the low-load power generation operation performed in the operation history by the fuel cell module performed when the ratio is less than the predetermined hydrogen supply ratio in the ratio area. Electrolytic fuel cell.   The control unit executes the cleaning mode operation for a predetermined duration, and when the voltage of the fuel cell reaches a predetermined voltage during the execution of the cleaning mode operation, The solid oxide fuel cell according to claim 1, wherein the cleaning mode operation is forcibly terminated.   The control unit sets the predetermined power generation operation time, which is a condition for executing the cleaning mode operation, to a shorter time as the aging time during which the power generation operation by the fuel cell module is performed is longer. 9. The solid oxide fuel cell according to any one of 8 above.   2. The solid electrolyte according to claim 1, wherein the predetermined condition for the control unit to execute the cleaning mode operation is a manual operation, and the control unit forcibly executes the cleaning mode operation by the manual operation. Type fuel cell.

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