JP2008177058A - Reformer system, fuel cell system, and operation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reformer system, a fuel cell system, and an operation method thereof capable of avoiding damage to a fuel cell with a simple configuration when power generation in a solid oxide fuel cell is stopped. I will provide a.
In the fuel cell system 1, when the power generation in the fuel cell 3 is stopped, the amount of raw fuel introduced into the reforming catalyst 2a of the reformer 2 is reduced. Before the temperature of 2a falls to the unreformed gas generation temperature, the temperature of the reforming catalyst 2a is raised by heating the reforming catalyst 2a. As a result, when power generation in the fuel cell 3 is stopped, generation of unreformed gas can be prevented with a simple configuration, and damage to the fuel cell 3 can be avoided. .
[Selection] Figure 1

Description

  The present invention relates to a reformer system including a reformer that generates a reformed gas by reforming raw fuel with a reforming catalyst, and a fuel cell further including a solid oxide fuel cell using the reformed gas as a fuel. The present invention relates to a system and an operation method thereof.

As a conventional fuel cell system, there is known a fuel cell nitrogen supply facility that supplies nitrogen stored in a liquid nitrogen storage tank to the fuel electrode of the fuel cell when power generation in the solid oxide fuel cell is stopped. (For example, refer to Patent Document 1). According to such a fuel cell system, when power generation in the solid oxide fuel cell is stopped, in the fuel cell, nickel used for the fuel electrode can be prevented from being oxidized and expanded, As a result, it is possible to avoid damage to the electrolyte made of yttria-stabilized zirconia or the like.
JP 2004-220942 A

  However, in the conventional fuel cell system as described above, it is necessary to provide a liquid nitrogen storage tank and a fuel electrode nitrogen supply facility, which complicates the structure.

  Therefore, the present invention has been made in view of such circumstances, and avoids damaging the fuel cell with a simple configuration when stopping power generation in the solid oxide fuel cell. An object of the present invention is to provide a reformer system, a fuel cell system, and an operation method thereof.

  In order to achieve the above object, a reformer system according to the present invention reforms raw fuel with a reforming catalyst to produce reformed gas used as fuel for a solid oxide fuel cell. A reformer system comprising a reformer, a raw fuel introduction means for introducing raw fuel into the reforming catalyst, a heating means for raising the temperature of the reforming catalyst by heating the reforming catalyst, a reforming catalyst The temperature detection means for detecting the temperature and when the power generation in the fuel cell is stopped, the introduction amount of the raw fuel is reduced with respect to the raw fuel introduction means, and the temperature detected by the temperature detection means generates unreformed gas. And a control unit that raises the temperature of the reforming catalyst by heating the reforming catalyst with respect to the heating unit before the temperature is lowered.

  The fuel cell system according to the present invention includes a reformer that generates reformed gas by reforming raw fuel with a reforming catalyst, and a solid oxide fuel cell that uses the reformed gas as fuel. A fuel cell system comprising: raw fuel introduction means for introducing raw fuel into the reforming catalyst; heating means for raising the temperature of the reforming catalyst by heating the reforming catalyst; and detecting the temperature of the reforming catalyst When detecting the temperature detecting means and the power generation in the fuel cell, the introduction amount of the raw fuel is decreased with respect to the raw fuel introducing means, and the temperature detected by the temperature detecting means falls to the unreformed gas generation temperature. And a control means for raising the temperature of the reforming catalyst by heating the reforming catalyst with respect to the heating means.

  Furthermore, the operation method of the fuel cell system according to the present invention includes a reformer that generates reformed gas by reforming raw fuel with a reforming catalyst, and a solid oxide fuel cell that uses the reformed gas as fuel. A method of operating a fuel cell system comprising: reducing the amount of raw fuel introduced to the reforming catalyst when generating power in the fuel cell is stopped, and the temperature of the reforming catalyst generates unreformed gas Before the temperature drops, the temperature of the reforming catalyst is raised by heating the reforming catalyst.

  In these reformer systems, fuel cell systems, and operating methods thereof, the amount of raw fuel introduced into the reforming catalyst of the reformer is reduced when power generation in the solid oxide fuel cell is stopped. However, at this time, the temperature of the reforming catalyst is raised by heating the reforming catalyst before the temperature of the reforming catalyst falls to the unreformed gas generation temperature. As a result, when power generation in the solid oxide fuel cell is stopped, generation of unreformed gas is prevented and the reformed gas is supplied to the fuel cell. Therefore, when stopping power generation in a solid oxide fuel cell, it is possible to damage the fuel cell with a simple configuration without providing a liquid nitrogen storage tank and a fuel electrode nitrogen supply facility as in the prior art. It can be avoided.

  In the reformer system according to the present invention, the control means changes the heating amount to the reforming catalyst with respect to the heating means in accordance with a decrease in the introduction amount of the raw fuel introduced by the raw fuel introduction means. Is preferred. Thereby, the temperature of the reforming catalyst can be raised and the generation of unreformed gas can be reliably prevented.

  In the reformer system according to the present invention, the heating means is preferably a heater, a burner or a burner off gas. According to the heater, the burner, or the burner off gas, the temperature of the reforming catalyst can be reliably and easily increased by heating the reforming catalyst.

  In the reformer system according to the present invention, the temperature detection means preferably detects the temperature of the reforming catalyst on the central axis of the flow path of the raw fuel introduced by the raw fuel introduction means. Thereby, the temperature of the portion where the reforming reaction of the raw fuel mainly occurs in the reforming catalyst can be accurately detected.

  According to the present invention, when power generation in a solid oxide fuel cell is stopped, damage to the fuel cell can be avoided with a simple configuration.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIGS. 1 and 2, a fuel cell system 1 includes a reformer 2 that generates reformed gas by reforming raw fuel with a reforming catalyst 2a, and solid oxidation that uses the reformed gas as fuel. A physical fuel cell 3.

  The reformer 2 generates a reformed gas containing hydrogen by subjecting the raw fuel and steam (water) to a steam reforming reaction with the reforming catalyst 2a. Since the steam reforming reaction is an endothermic reaction, the reformer 2 uses the exhaust heat of the fuel cell 3 for the steam reforming reaction. The raw fuel is a hydrocarbon fuel known in the field of solid oxide fuel cells as a raw material for reformed gas, that is, a compound containing carbon and hydrogen in its molecule (containing other elements such as oxygen). Or a mixture thereof may be used as appropriate. For example, it is a compound containing carbon and hydrogen in the molecule, such as hydrocarbons, alcohols and ethers. More specifically, methane, ethane, propane, butane, natural gas, LPG (liquefied petroleum gas), city gas, hydrocarbons such as gasoline, naphtha, kerosene and light oil, alcohols such as methanol and ethanol, dimethyl ether, etc. Ethers and the like. Of these, kerosene and LPG are preferable because they are easily available. Moreover, since kerosene and LPG can be stored independently, they are useful in areas where city gas lines are not widespread. Furthermore, a solid oxide fuel cell using kerosene or LPG is useful as an emergency power source. As the reforming catalyst 2a, a known catalyst can be used as a steam reforming catalyst or an autothermal reforming (autothermal reforming) catalyst. Examples of the partial oxidation reforming catalyst include a platinum-based catalyst, examples of the steam reforming catalyst include a ruthenium-based catalyst and a nickel-based catalyst, and examples of the autothermal reforming catalyst include a rhodium-based catalyst.

  The fuel cell 3 generates power using a plurality of cells called SOFC (Solid Oxide Fuel Cells). The cell is configured by disposing an electrolyte that is a solid oxide between a fuel electrode and an air electrode. The electrolyte is made of, for example, yttria stabilized zirconia (YSZ), and conducts oxide ions at a temperature of 800 ° C. to 1000 ° C. The fuel electrode is made of, for example, a mixture of nickel and YSZ, and generates electrons and water by reacting oxide ions with hydrogen in the reformed gas. The air electrode is made of lanthanum strontium manganite, for example, and reacts oxygen in the air with electrons to generate oxide ions.

  The fuel cell system 1 also includes a raw fuel introduction device (raw fuel introduction means) 4 for introducing raw fuel and water vapor (water) into the reforming catalyst 2a, and the reforming catalyst 2a by heating the reforming catalyst 2a. A plurality of heaters (heating means) 5 for raising the temperature and a cathode air introduction device (cathode air introduction means) (not shown) for introducing air into the cathode (air electrode) are provided. The raw fuel introduction device 4 includes a raw fuel introduction pipe for introducing the raw fuel and water vapor, an introduction amount adjusting valve for adjusting the introduction amounts of the raw fuel and water vapor, and the like. The cathode air introduction device has an air introduction pipe for introducing air, an introduction amount adjusting valve for adjusting the introduction amount of air, and the like. The heater 5 is a ceramic heater embedded in the reforming catalyst 2a, for example.

  Further, the fuel cell system 1 controls a plurality of temperature detectors (temperature detecting means) 6 for detecting the temperature of the reforming catalyst 2a, a temperature detector 7 for detecting the temperature of the cells of the fuel cell 3, and the entire system. And a control device (control means) 8. The temperature detectors 6 and 7 are, for example, thermocouples. A temperature measuring contact of each temperature detector 6 is installed so as to correspond to each heater 5 on the central axis L1 of the flow path of the raw fuel introduced by the raw fuel introduction device 4.

  The reformer 2, the raw fuel introduction device 4, the heater 5, the temperature detector 6 and the control device 8 constitute a reformer system 9.

Next, an operation method of the fuel cell system 1 will be described.
[When entering cold standby]

  A method of operating the fuel cell system 1 when entering cold standby will be described with reference to FIG. Note that the cold standby means that the operation of the fuel cell system 1 is completely stopped and the fuel cell system 1 stands by while the temperature of the cells of the fuel cell 3 is at room temperature. Cold standby is used when the fuel cell system 1 takes a long time to start, and is therefore used when the power generation stop time of the fuel cell 3 is relatively long.

  As shown in FIG. 3, first, a cold standby command is issued by the control device 8 (step S11), and the current sweep from the fuel cell 3 is stopped (step S12). That is, the fuel cell 3 is controlled by the control device 8, and the power generation in the fuel cell 3 is stopped. Subsequently, the raw fuel introduction device 4 is controlled by the control device 8, and the amount of raw fuel and water vapor introduced into the reforming catalyst 2a is reduced (step S13). Here, the introduction of raw fuel and water vapor is gradually reduced. Thereby, the temperature of the cell of the fuel cell 3 and the temperature of the reforming catalyst 2a begin to drop.

When decreasing the introduction amount of the raw fuel and steam is started, the temperature of the reforming catalyst 2a detected by each temperature detector 6 is equal to or less than T _R is determined by the control device 8 (step S14 ). T _R is the temperature between the temperature of the non-reformed gas generation temperature and the rated operation reforming catalyst 2a, for example, if the raw fuel is kerosene, at a temperature of 400 ° C. to 700 ° C.. T _R is suitably set for each temperature detector 6, if the case of same in the temperature detector 6, there is a case to be different from. The unreformed gas generation temperature is such that the raw fuel is not completely reformed by the reforming catalyst 2a, and a hydrocarbon gas having 2 or more carbon atoms (unreformed gas) that can damage the cells of the fuel cell 3 is generated. It means the temperature at which it starts to be introduced into the reformed gas, and is preset according to the amount of fuel introduced. Incidentally, carbon monoxide in the reformed gas reacts with oxide ions at the fuel electrode to become electrons and carbon dioxide.

Then, the temperature of the reforming catalyst 2a detected by each temperature detector 6 is not more than T _R, the following heater output processing is executed by the controller 8 (step S15).

That is, the heater 5 corresponding to the temperature detector 6 that detects a temperature below T _R is controlled by the control unit 8, the temperature of the reforming catalyst 2a by the heater 5 is heated by the reforming catalyst 2a is raised. When heating of the reforming catalyst 2a is started, it is determined by the control device 8 whether or not the temperature of the reforming catalyst 2a detected by the temperature detector 6 is equal to or lower than a predetermined temperature, and the temperature of the reforming catalyst 2a is determined. Is equal to or lower than a predetermined temperature, the output of the heater 5 is increased by the control device 8. A plurality of predetermined temperatures are set as a temperature higher than the temperature at which unreformed gas can be generated according to the amount of raw fuel and water vapor that are gradually reduced, and the output of the heater 5 is controlled each time the temperature falls below the predetermined temperature. It is changed by the device 8. As described above, the control device 8 changes the amount of heating of the reforming catalyst 2a with respect to the heater 5 in accordance with a decrease in the amount of raw fuel introduced by the raw fuel introduction device 4. Thereby, the temperature of the reforming catalyst 2a can be raised, and generation | occurrence | production of unreformed gas can be prevented reliably.

While the above heater output process is being executed, the control device 8 determines whether or not the temperature of the fuel cell 3 detected by the temperature detector 7 is equal to or lower than T _C 1 (step S16). T _C 1 is a temperature at which the fuel cell 3 does not require a reformed gas as a reducing gas for the fuel electrode, and the temperature is 100 ° C. to 500 ° C., preferably 100 ° C. to 300 ° C., more preferably 100 ° C. ~ 200 ° C. If the temperature of the cell detected by the temperature detector 7 is equal to or lower than T _C 1, the control device 8 controls the raw fuel introduction device 4 and the heater 5, and the raw fuel introduction device 4 supplies the reforming catalyst 2 a to the reforming catalyst 2 a. The introduction of raw fuel and water vapor is stopped, and the output of the heater 5 is stopped (step S17).

Subsequently, the control device 8 determines whether or not the temperature of the cell of the fuel cell 3 detected by the temperature detector 7 is equal to or lower than T _C 2 (step S18). T _C 2 is the temperature the fuel cell 3 is to eliminate the introduction of air into the cathode, the temperature is preferably 50 ° C. to 200 DEG ° C., more preferably 50 ° C. to 100 ° C.. Then, if the temperature of the cell detected by the temperature detector 7 is T _{C 2} or less, the operation of the entire system by the control unit 8 is stopped (step S19), the fuel cell system 1 enters the cold standby.
[When entering hot standby]

  An operation method of the fuel cell system 1 when entering the hot standby will be described with reference to FIG. The hot standby means that the power generation in the fuel cell 3 is stopped and the fuel cell system 1 stands by while the temperature of the cell of the fuel cell 3 is at the operating temperature. The hot standby is employed when the stop time of power generation in the fuel cell 3 is relatively short because it does not require a long time to start the fuel cell system 1.

  As shown in FIG. 4, first, a hot standby command is issued by the control device 8 (step S21), and the current sweep from the fuel cell 3 is stopped (step S22). That is, the fuel cell 3 is controlled by the control device 8, and the power generation in the fuel cell 3 is stopped. Subsequently, the raw fuel introduction device 4 is controlled by the control device 8, and the amount of raw fuel and water vapor introduced into the reforming catalyst 2a is reduced (step S23). Here, the amounts of raw fuel and water vapor introduced are reduced by a predetermined amount.

Then, the temperature of the reforming catalyst 2a detected by each temperature detector 6 is not more than T _R, and the temperature of the cell of the fuel cell 3 detected by the temperature detector 7 is a condition that is T _{C 3} or more It is judged by the control apparatus 8 whether it satisfy | fills (step S24). T _C 3 is the operating temperature of the cell. For example, when the electrolyte is made of YSZ, Y C is a temperature of 800 ° C. to 1000 ° C. at which YSZ conducts oxide ions.

As a result of the determination process in step S24, when the condition is satisfied, the heater output process described above is executed by the control device 8 in order to prevent generation of unreformed gas in the reformer 2 (step S25). ), The process returns to step S24. On the other hand, if the condition is not satisfied as a result of the determination processing in step S24, the control device 8 determines whether or not the temperature of the cell of the fuel cell 3 detected by the temperature detector 7 is less than T _C 3. (Step S26).

If the cell temperature of the fuel cell 3 is less than T _C 3 as a result of the determination process in step S26, the control unit 8 controls the raw fuel introduction device 4 to maintain the cell temperature at the operating temperature. Then, the amount of raw fuel and steam introduced into the reforming catalyst 2a is increased by the raw fuel introduction device 4 (step S27), and the process returns to the determination process of step S24. Here, the introduction amounts of the raw fuel and the water vapor are increased by a predetermined amount smaller than the predetermined amount decreased in the process of step S23. On the other hand, when the temperature of the cell of the fuel cell 3 is equal to or higher than T _{C3 as} a result of the determination process in step S26, the process returns to the determination process in step S24.

  In this way, the reformed gas supplied from the reformer 2 to the fuel cell 3 is burned in the combustion chamber of the fuel cell 3, and the fuel cell system 1 enters a hot standby.

  As described above, in the reformer system 9, the fuel cell system 1, and the operation method thereof, when the power generation in the fuel cell 3 is stopped, the raw fuel is introduced into the reforming catalyst 2 a of the reformer 2. At this time, the temperature of the reforming catalyst 2a is raised by heating the reforming catalyst 2a before the temperature of the reforming catalyst 2a falls to the unreformed gas generation temperature. As a result, when power generation in the fuel cell 3 is stopped, generation of unreformed gas is prevented and the reformed gas is supplied to the fuel cell 3. Therefore, when power generation in the fuel cell 3 is stopped, damage to the fuel cell 3 can be avoided with a simple configuration.

  Further, the temperature detector 6 detects the temperature of the reforming catalyst 2a on the central axis L1. Thereby, the temperature of the portion where the reforming reaction mainly occurs in the reforming catalyst 2a can be accurately detected.

  The present invention is not limited to the embodiment described above.

  For example, as shown in FIG. 5, the number of heaters 5 may be one. Further, by adopting a burner or a burner off gas pipe instead of the heater 5, the temperature of the reforming catalyst 2a may be raised by heating the reforming catalyst 2a. Even with the burner or the burner off gas, similarly to the heater 5, the temperature of the reforming catalyst 2a can be reliably and easily raised by heating the reforming catalyst 2a.

  In addition, when the fuel cell system 1 enters the cold standby, after the output is reduced to an arbitrary partial load before the current sweep stop process (step S12), the fuel cell system 1 executes the current sweep stop process (step S12). The cold standby stop process described with reference to FIG. 3 may be executed. In that case, the electric power generated until the current sweep stop process (step S12) is executed may be stored in a capacitor or consumed by a loader, for example.

  Further, ATR or partial oxidation reforming reaction may be realized by the reformer 2 during rated operation of the fuel cell 3. In these cases, the amount of raw fuel introduced into the reforming catalyst 2a of the reformer 2 is decreased, and the reforming catalyst 2a is removed before the temperature of the reforming catalyst 2a drops to the unreformed gas generation temperature. If the temperature of the reforming catalyst 2a is raised by heating, the generation of unreformed gas can be prevented with a simple configuration when power generation in the fuel cell 3 is stopped. It is possible to avoid giving damage.

  In the fuel cell system 1, known components of the indirect internal SOFC can be appropriately provided as necessary. Specific examples include a vaporizer for vaporizing liquid, a pump for pressurizing various fluids, a pressure increasing means such as a compressor, a blower, etc., a valve for adjusting the flow rate of the fluid, or for blocking / switching the fluid flow Such as flow control means, flow path blocking / switching means, heat exchanger for heat exchange / recovery, condenser for condensing gas, heating / heat retaining means for externally heating various devices with steam, etc., hydrocarbon system These include fuel and combustible storage means, instrument air and electrical systems, control signal systems, control devices, output and power electrical systems, and the like.

1 is a front view of an embodiment of a fuel cell system according to the present invention. FIG. 2 is a plan view of the fuel cell system shown in FIG. 1. 2 is a flowchart showing an operation method when the fuel cell system shown in FIG. 1 enters a cold standby. 2 is a flowchart showing an operation method when the fuel cell system shown in FIG. 1 enters a hot standby. It is a top view of other embodiments of a fuel cell system concerning the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Reformer, 2a ... Reforming catalyst, 3 ... Fuel cell, 4 ... Raw fuel introduction apparatus (raw fuel introduction means), 5 ... Heater (heating means), 6 ... Temperature detector ( Temperature detecting means), 7 ... Cell temperature detector (cell temperature detecting means), 8 ... Control device (control means), 9 ... Reformer system, L1 ... Center axis of raw fuel flow path.

Claims (6)

A reformer system including a reformer that generates a reformed gas used as a fuel for a solid oxide fuel cell by reforming raw fuel with a reforming catalyst,
Raw fuel introduction means for introducing the raw fuel into the reforming catalyst;
Heating means for raising the temperature of the reforming catalyst by heating the reforming catalyst;
Temperature detecting means for detecting the temperature of the reforming catalyst;
When power generation in the fuel cell is stopped, the amount of the raw fuel introduced is reduced with respect to the raw fuel introduction unit, and the temperature detected by the temperature detection unit is reduced to the unreformed gas generation temperature. And a control means for raising the temperature of the reforming catalyst by heating the reforming catalyst with respect to the heating means.   The control means changes a heating amount of the reforming catalyst with respect to the heating means in accordance with a decrease in the introduction amount of the raw fuel introduced by the raw fuel introduction means. The reformer system according to claim 1.   The reformer system according to claim 1, wherein the heating unit is a heater, a burner, or a burner off gas.   The temperature detection means detects the temperature of the reforming catalyst on a central axis of a flow path of the raw fuel introduced by the raw fuel introduction means. The described reformer system. A fuel cell system comprising a reformer that generates reformed gas by reforming raw fuel with a reforming catalyst, and a solid oxide fuel cell that uses the reformed gas as fuel,
Raw fuel introduction means for introducing the raw fuel into the reforming catalyst;
Heating means for raising the temperature of the reforming catalyst by heating the reforming catalyst;
Temperature detecting means for detecting the temperature of the reforming catalyst;
When power generation in the fuel cell is stopped, the amount of the raw fuel introduced is reduced with respect to the raw fuel introduction unit, and the temperature detected by the temperature detection unit is reduced to the unreformed gas generation temperature. And a control means for raising the temperature of the reforming catalyst by heating the reforming catalyst with respect to the heating means. An operation method of a fuel cell system comprising: a reformer that generates reformed gas by reforming raw fuel with a reforming catalyst; and a solid oxide fuel cell that uses the reformed gas as fuel. ,
When the power generation in the fuel cell is stopped, the amount of the raw fuel introduced into the reforming catalyst is decreased, and the reforming catalyst is cooled before the reforming catalyst temperature falls to the unreformed gas generation temperature. A method of operating a fuel cell system, wherein the temperature of the reforming catalyst is raised by heating the catalyst.

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