WO2016114214A1 - Fuel cell system, power generation method, and power generation device - Google Patents

Abstract

A fuel cell system 1 equipped with: a reformer 2 for generating a fuel gas by introducing air and reforming ammonia; a fuel cell 3 for generating power by using the air and the fuel gas; an ammonia tank 5 for storing the ammonia in a liquid state; a pump 6 for pumping the liquid ammonia toward the reformer 2; a vaporizer 7 for vaporizing the liquid ammonia and positioned between the pump 6 and the reformer 2; an air supply device 8 for sending air to the reformer 2 and the fuel cell 3; a heat exchanger 9 for preheating the air by performing a heat exchange, and positioned between the air supply device 8 and the fuel cell 3; a first exhaust gas supply unit 16 for supplying exhaust gas discharged by the fuel cell 3 to the vaporizer 7; and a second exhaust gas supply unit 17 for supplying exhaust gas to the heat exchanger 9. In addition, the vaporizer 7 vaporizes the liquid ammonia using the waste heat from the exhaust gas, and the heat exchanger 9 preheats the air by performing a heat exchange using the waste heat from the exhaust gas.

Description

Fuel cell system, power generation method, and power generation apparatus

The present invention relates to a fuel cell system, a power generation method, and a power generation apparatus.

As a conventional fuel cell system, for example, a technique described in Patent Document 1 is known. The fuel cell system described in Patent Document 1 includes a solid polymer fuel cell that generates power using a hydrogen-containing gas as a fuel gas, a reformer that generates ammonia by reforming ammonia, and a liquid state fuel cell system. A storage tank for storing ammonia, a pump provided between the storage tank and the reformer, for supplying liquid ammonia to the reformer, a pump for supplying air to the reformer, and air for the fuel cell And a pump for supplying

JP2011-146174A

In the above prior art, liquid ammonia is vaporized by a heat exchanger provided in the reformer. Specifically, power is supplied to the heater by the secondary battery, and heat exchange is performed between the liquid ammonia and the heat of the heater by the heat exchanger, thereby heating and vaporizing the liquid ammonia. Thus, since the heater and the secondary battery are used to vaporize ammonia, the system efficiency is poor.

An object of the present invention is to provide a fuel cell system, a power generation method, and a power generation apparatus that can improve system efficiency.

A fuel cell system according to one aspect of the present invention includes a reformer that generates a fuel gas by introducing an oxidant gas to reform ammonia, and a fuel gas and an oxidant gas generated by the reformer. Between the pump and the reformer, a fuel cell that generates electricity using a fuel, an ammonia tank that stores ammonia in a liquid state, a pump that sends liquid ammonia stored in the ammonia tank toward the reformer, The vaporizer for vaporizing ammonia in a liquid state, the insufflator for sending the oxidant gas to the reformer and the fuel cell, and between the insufflator and the fuel cell to heat the oxidant gas A heat exchanger that exchanges and preheats, a first exhaust gas supply unit that supplies exhaust gas discharged from the fuel cell to the vaporizer, and a second exhaust gas supply unit that supplies exhaust gas to the heat exchanger, , Liquid due to exhaust heat of exhaust gas The state of the ammonia is vaporized, the heat exchanger is preheated oxidant gas heat exchanger by the exhaust gas waste heat.

Thus, in the fuel cell system of the present invention, the exhaust gas discharged from the fuel cell is supplied to the vaporizer by the first exhaust gas supply unit, and the liquid ammonia is vaporized by the exhaust heat of the exhaust gas in the vaporizer. Further, the exhaust gas discharged from the fuel cell is supplied to the heat exchanger by the second exhaust gas supply unit, and the oxidant gas is heat-exchanged by the exhaust heat of the exhaust gas and preheated in the heat exchanger. Thus, the exhaust heat of exhaust gas is effectively used for the vaporization of ammonia and the heat exchange of the oxidant gas. Thereby, the system efficiency of a fuel cell system can be improved.

The oxidant gas is air, and further includes a control unit that controls the air-fuel ratio of the reformer. The control unit sets the air-fuel ratio of the reformer during start-up operation to be higher than the air-fuel ratio of the reformer during normal operation. May be controlled to be higher. With such a configuration, the amount of air introduced into the reformer increases during start-up operation compared to during normal operation. Accordingly, since the decomposition temperature of ammonia in the reformer increases, the temperature of the fuel gas generated in the reformer and introduced into the fuel cell increases. Thereby, a fuel cell can be warmed up early at the time of start-up operation.

The controller may perform control so that the air-fuel ratio of the reformer during start-up operation is 1.0 or more. In this case, the decomposition temperature of ammonia in the reformer becomes sufficiently high. As a result, it is possible to reliably warm the fuel cell early during start-up operation.

A valve that adjusts the flow rate of the air supplied from the insufflator to the reformer is disposed between the insufflator and the reformer, and the control unit controls the opening degree of the valve. The air-fuel ratio of the reformer may be controlled. By using the valve for adjusting the air flow rate in this way, the air-fuel ratio of the reformer can be easily controlled.

The apparatus further includes a combustor that combusts the exhaust gas discharged from the fuel cell, the first exhaust gas supply unit supplies the exhaust gas burned by the combustor to the vaporizer, and the second exhaust gas supply unit is combusted by the combustor. Exhaust gas may be supplied to the heat exchanger. When the exhaust gas discharged from the fuel cell is burned by the combustor, the temperature of the exhaust gas increases. Therefore, it is possible to effectively perform ammonia vaporization and heat exchange of the oxidant gas using exhaust heat of exhaust gas.

Here, the power generation device generally includes a solid oxide fuel cell and a reactor including a gas line for storing the solid oxide fuel cell and supplying fuel gas and oxidant gas. (For example, Japanese Patent Application Laid-Open Nos. 2013-2111117 and 2013-211118). The solid oxide fuel cell is generally composed of a fuel electrode formed on one surface of a solid oxide electrolyte and an air electrode that is spaced apart from the fuel electrode. During power generation, air is supplied to the air electrode side and hydrogen is supplied to the fuel electrode side, and the following reaction proceeds at about 800 to 1000 ° C. on each electrode.
Combustion electrode: H ₂ + O ²⁻ → H ₂ O + 2e ⁻
Air electrode: O ₂ + 4e ⁻ → 2O ²⁻

The oxygen ions generated at the air electrode move from the air electrode side to the fuel electrode side in the solid oxide electrolyte. At the same time, power generation is achieved by electrons flowing from the fuel electrode side to the air electrode side.

The solid oxide fuel cell cannot perform efficient power generation unless it is at a certain high temperature. Therefore, normally, the solid oxide fuel cell is heated with a heater or the like before power generation, and the power generation is started after the temperature of the solid oxide fuel cell is raised to about 600 to 1000 ° C. However, since the power generation cannot be started until the temperature of the solid oxide fuel cell is raised to about 600 to 1000 ° C., there is a problem that it takes time until the power generation is started after the apparatus is started.

Therefore, it is required to start power generation in a solid oxide fuel cell in a shorter time than conventional.

Therefore, the reformer uses a catalyst for ammonia decomposition to burn part of the ammonia with oxygen, and uses the heat of combustion to decompose the ammonia into hydrogen, and the fuel cell uses a plurality of ammonia decomposition devices. The fuel cell is constituted by a solid oxide fuel cell that is operated using a hydrogen-containing gas generated by at least one of the devices as a fuel.

The ammonia decomposition apparatus is used after the first ammonia decomposition apparatus and the solid oxide fuel cell used to generate a hydrogen-containing gas until the solid oxide fuel cell reaches a predetermined temperature. A second ammonia decomposition apparatus used as an apparatus for generating a hydrogen-containing gas may be included.

The ammonia decomposition catalysts provided in the first ammonia decomposition apparatus and the second ammonia decomposition apparatus may each contain at least one element selected from iron, cobalt, and nickel as a catalytic active component.

The content of the catalytically active component in the ammonia decomposition catalyst of the second ammonia decomposition apparatus may be higher than the content of the catalytically active component in the ammonia decomposition catalyst of the first ammonia decomposition apparatus.

A power generation method according to one aspect of the present invention is a power generation method using the above-described fuel cell system, wherein the first ammonia decomposition apparatus has a mixed gas in which the volume ratio of oxygen to ammonia is 0.19 or more. A first step of supplying hydrogen, a second step of switching the device for generating a hydrogen-containing gas from the first ammonia decomposition device to the second ammonia decomposition device, and a volume ratio of oxygen to ammonia in the second ammonia decomposition device And a third step of supplying a mixed gas having 0.17 or less, and the second step is performed when the solid oxide fuel cell reaches a predetermined temperature.

A power generation device according to one aspect of the present invention includes a plurality of ammonia decomposition apparatuses that use an ammonia decomposition catalyst to burn a part of ammonia with oxygen and decompose the ammonia into hydrogen using the combustion heat; And a solid oxide fuel cell that is operated by using a hydrogen-containing gas generated by at least one of the ammonia decomposing apparatuses.

According to the above-described power generation apparatus, a power generation apparatus including a plurality of ammonia decomposition apparatuses is used, and an outlet gas of the ammonia decomposition apparatus (hydrogen-containing gas generated by decomposing ammonia) is used as a fuel gas. Also, power generation in the solid oxide fuel cell can be started in a short time.

According to the present invention, a fuel cell system, a power generation method, and a power generation apparatus that can improve system efficiency are provided.

It is a system configuration figure showing a fuel cell system concerning one embodiment. It is a flowchart which shows the procedure of the control processing performed by a control apparatus at the time of starting operation of a fuel cell system.

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

FIG. 1 is a system configuration diagram showing a fuel cell system according to an embodiment. In FIG. 1, a fuel cell system 1 of the present embodiment includes an ATR (Auto Thermal Reforming) type reformer 2 and a solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell) 3.

The reformer 2 introduces air to reform ammonia (NH ₃ ), thereby generating a fuel gas containing hydrogen. The reformer 2 includes an NH ₃ oxidation unit 2a and an NH ₃ decomposition unit 2b arranged on the downstream side of the NH ₃ oxidation unit 2a. The NH ₃ oxidation unit 2a generates heat by oxidizing ammonia. The NH ₃ decomposition unit 2b generates hydrogen by decomposing ammonia by heat generated in the NH ₃ oxidation unit 2a. The reforming unit 2 uses air as the oxidant gas, but any gas may be used as long as it oxidizes ammonia.

Here, however reformer 2 has a NH ₃ oxidation unit 2a and NH ₃ decomposition section 2b, when using the active catalyst in both the reaction of oxidation and decomposition of NH ₃ is NH ₃ An integrated reformer 2 having both functions of oxidizing and decomposing NH ₃ may be used without separating the oxidizing unit and the NH ₃ decomposing unit. In this case, since the oxidation reaction generally takes place earlier than the decomposition reaction, the same reaction as described above occurs.

The fuel cell 3 is connected to the reformer 2 via a fuel gas supply pipe 4. The fuel cell 3 generates power using the fuel gas and air generated by the reformer 2. The fuel cell 3 has a stack structure in which a plurality of single cells are stacked. The single cell includes an anode (fuel electrode) 3a, a cathode (air electrode) 3b, and an electrolyte (not shown) disposed between the anode 3a and the cathode 3b. The fuel gas supply pipe 4 is connected to the anode 3a. Fuel gas is introduced into the anode 3a. Air is introduced into the cathode 3b. The electrolyte is made of a ceramic such as stabilized zirconia.

The fuel cell system 1 includes a liquid NH ₃ tank 5, a pump 6, a vaporizer 7, an air blower 8, a heat exchanger 9, and a combustor 10.

The liquid NH ₃ tank 5 is an ammonia tank that stores ammonia in a liquid state. The liquid NH ₃ tank 5 stores ammonia at, for example, room temperature (20 ° C. to 25 ° C.) and several atmospheres (8 atmospheres to 10 atmospheres). Since the liquid NH ₃ tank 5 stores ammonia in a liquid state instead of a gas, the ammonia storage efficiency is good, and the operating time of the fuel cell system 1 can be extended. In addition, ammonia can be easily supplied to the liquid NH ₃ tank 5.

The pump 6 is connected to the reformer 2 via an ammonia supply pipe 11. The pump 6 sends out liquid ammonia (hereinafter, liquid ammonia) stored in the liquid NH ₃ tank 5 toward the reformer 2.

The vaporizer 7 is disposed in the ammonia supply pipe 11. That is, the vaporizer 7 is disposed between the pump 6 and the reformer 2. The vaporizer 7 vaporizes liquid ammonia.

The air blower 8 is connected to the reformer 2 and the fuel cell 3 via air supply pipes 12 and 13. One end of the air supply pipe 13 is branched and connected to the air supply pipe 12, and the other end of the air supply pipe 13 is connected to the cathode 3 b of the fuel cell 3. The air blower 8 is an air supply device that blows out air and sends it to the reformer 2 and the fuel cell 3.

The air supply pipe 12 is provided with a valve 14. That is, the valve 14 is disposed between the air blower 8 and the reformer 2. The valve 14 is an electromagnetic flow rate adjusting valve that adjusts the flow rate of air supplied from the air blower 8 to the reformer 2.

The heat exchanger 9 is disposed in the air supply pipe 13. That is, the heat exchanger 9 is disposed between the air blower 8 and the fuel cell 3. The heat exchanger 9 preheats the air sent to the fuel cell 3 by exchanging heat.

The combustor 10 is connected to the anode 3 a and the cathode 3 b of the fuel cell 3 through the exhaust pipe 15. In the exhaust pipe 15, a mixed gas of unreacted fuel gas discharged from the anode 3a and unreacted air discharged from the cathode 3b flows as exhaust gas (off gas). The combustor 10 burns exhaust gas. Specifically, the combustor 10 burns unburned fuel gas remaining in the exhaust gas. When exhaust gas is burned by the combustor 10, the temperature of the exhaust gas rises.

In addition, the fuel cell system 1 includes an exhaust gas supply pipe 16 that constitutes a first exhaust gas supply unit that supplies exhaust gas burned by the combustor 10 to the carburetor 7, and the exhaust gas burned by the combustor 10 as a heat exchanger 9. And an exhaust gas supply pipe 17 constituting a second exhaust gas supply unit for supplying to the exhaust gas.

The vaporizer 7 vaporizes liquid ammonia by exhaust heat of the exhaust gas flowing through the exhaust gas supply pipe 16. The exhaust gas flowing through the exhaust gas supply pipe 16 is released to the atmosphere. The heat exchanger 9 preheats the heat by exchanging air with the exhaust heat of the exhaust gas flowing through the exhaust gas supply pipe 17. The exhaust gas flowing through the exhaust gas supply pipe 17 is released to the atmosphere.

Furthermore, the fuel cell system 1 detects the temperature of the fuel cell 3 and the electric heater 18 for starting to heat the reformer 2 during the starting operation, the electric heater 19 for starting to heat the fuel cell 3 during the starting operation. The temperature sensor 20 which performs and the control apparatus 21 (control part) are provided. The temperature sensor 20 detects, for example, the temperature near the outlet where unreacted fuel gas in the fuel cell 3 is discharged.

The control device 21 controls the entire system during operation of the fuel cell system 1. Specifically, the control device 21 controls the pump 6, the air blower 8, the valve 14, and the electric heaters 18 and 19 based on the detection value of the temperature sensor 20.

During normal operation of the fuel cell system 1 as described above, when liquid ammonia stored in the liquid NH ₃ tank 5 is discharged from the pump 6, the liquid ammonia is sent to the vaporizer 7 through the ammonia supply pipe 11. It is done. In the vaporizer 7, the liquid ammonia is heated and vaporized by the exhaust heat of the exhaust gas flowing through the exhaust gas supply pipe 16. The vaporized ammonia is supplied to the reformer 2 through the ammonia supply pipe 11. On the other hand, air is supplied to the reformer 2 through the air supply pipe 12 by the air blower 8.

When ammonia and air are introduced into the reformer 2, in the NH ₃ oxidation section 2a of the reformer 2, a part of ammonia and oxygen in the air chemically react as shown in the following formula, and the oxidation of the ammonia Heat is generated by the reaction (exothermic reaction).
NH ₃ + 3 / 4O ₂ → 1 / 2N ₂ + 3 / 2H ₂ O

Then, in the NH ₃ decomposition section 2b of the reformer 2, the remaining ammonia is decomposed by the heat generated in the NH ₃ oxidation section 2a as shown in the following formula (endothermic reaction), and the fuel gas is rich in hydrogen. Is generated. The fuel gas is supplied to the anode 3 a of the fuel cell 3 through the fuel gas supply pipe 4. The temperature of the fuel gas at this time is about 600 ° C., for example.
NH ₃ → 3 / 2H ₂ + 1 / 2N ₂

Also, air at room temperature is sent to the heat exchanger 9 through the air supply pipes 12 and 13 by the air blower 8. In the heat exchanger 9, air at normal temperature is heat-exchanged by the exhaust heat of the exhaust gas flowing through the exhaust gas supply pipe 17 and preheated. The preheated air is supplied to the cathode 3 b of the fuel cell 3 through the air supply pipe 13. Note that the temperature of the air at this time is approximately the same as the temperature of the fuel gas, for example.

When the fuel gas and air are introduced into the fuel cell 3, in the fuel cell 3, hydrogen in the fuel gas and oxygen in the air chemically react to generate water and generate DC power. The DC power generated in the fuel cell 3 is converted into AC power by the inverter 22. Then, AC power is supplied to the power load 23.

Also, exhaust gas (off-gas) is discharged from the fuel cell 3. The temperature of the exhaust gas at this time is, for example, about 700 ° C. to 800 ° C. The exhaust gas is supplied to the combustor 10 through the exhaust pipe 15 and burned by the combustor 10. The temperature of the exhaust gas after combustion is, for example, about 1000 ° C. to 1100 ° C.

The exhaust gas combusted in the combustor 10 is supplied to the vaporizer 7 through the exhaust gas supply pipe 16. The exhaust heat of the exhaust gas is used for vaporizing liquid ammonia by the vaporizer 7. Further, the exhaust gas combusted by the combustor 10 is supplied to the heat exchanger 9 through the exhaust gas supply pipe 17. The exhaust heat of the exhaust gas is used for heat exchange of air by the heat exchanger 9.

FIG. 2 is a flowchart showing the procedure of the control process executed by the control device 21 during the start-up operation of the fuel cell system 1. When a power switch (not shown) of the fuel cell system 1 is turned on, execution of this process is started.

In the initial state when the execution of this process is started, the opening degree of the valve 14 is an opening degree that ensures the air-fuel ratio (A / F) of the reformer 2 during normal operation. . The air-fuel ratio of the reformer 2 is a ratio between the amount of air present in the reformer 2 and the amount of fuel gas. The air-fuel ratio of the reformer 2 during normal operation is, for example, 0.75 (the amount of air is 75% with respect to the amount of fuel gas of 100%).

Here, the normal operation is an operation performed when the temperature of the fuel cell 3 reaches the operating temperature (for example, about 700 ° C.). The start-up operation is an operation that is performed before the temperature of the fuel cell 3 reaches the operating temperature.

In FIG. 2, the control device 21 first controls the starting electric heaters 18 and 19 to be turned on (step S101). Then, the temperature of the reformer 2 rises and the temperature of the fuel cell 3 rises.

Subsequently, the control device 21 controls the pump 6 so that a small amount of liquid ammonia is sent out toward the reformer 2 by the pump 6 (step S102). When a small amount of liquid ammonia is discharged from the pump 6, the supply pressure of the liquid ammonia decreases to, for example, normal pressure (atmospheric pressure). For this reason, even if liquid ammonia is in a normal temperature state, liquid ammonia is vaporized by the vaporizer 7. The vaporized ammonia is supplied to the reformer 2.

Subsequently, the control device 21 controls the air blower 8 so that air is blown out by the air blower 8 (step S103). Then, air is supplied to the reformer 2 and the fuel cell 3.

Subsequently, the control device 21 controls the air-fuel ratio of the reformer 2 to be higher than that during normal operation by controlling the opening of the valve 14 to be larger than that during normal operation (step S104). ). Specifically, the control device 21 performs control so that the air-fuel ratio of the reformer 2 is 1.0 or more (A / F ≧ 1.0), for example. By increasing the air-fuel ratio of the reformer 2 in this way, the amount of air supplied to the reformer 2 becomes larger than during normal operation.

When ammonia and air are supplied to the reformer 2, fuel gas is generated by the reformer 2. Thereafter, when fuel gas and air are supplied to the fuel cell 3, power generation is performed by the fuel cell 3. Then, the exhaust gas discharged from the fuel cell 3 is combusted by the combustor 10, and the exhaust gas after combustion is supplied to the vaporizer 7 and the heat exchanger 9. Thereby, the normal temperature air sent by the air blower 8 is preheated by the exhaust heat of the exhaust gas in the heat exchanger 9.

Subsequently, the control device 21 acquires the detection value of the temperature sensor 20 (step S105). Then, the control device 21 determines whether or not the temperature of the fuel cell 3 has reached the operating temperature (step S106). When the temperature of the fuel cell 3 has not reached the operating temperature, step S105 is repeatedly executed.

When the temperature of the fuel cell 3 reaches the operating temperature, the control device 21 performs control so that the electric heaters 18 and 19 for starting are turned off (step S107).

Subsequently, the control device 21 controls the pump 6 so that a certain amount of liquid ammonia is sent out toward the reformer 2 by the pump 6 (step S108). The amount of liquid ammonia sent out at this time is sufficiently larger than that during execution of the above-described procedure S102. A certain amount of liquid ammonia is vaporized by the exhaust heat of the exhaust gas in the vaporizer 7.

Subsequently, the control device 21 controls the opening degree of the valve 14 to return to the opening degree in the initial state (during normal operation), so that the air-fuel ratio of the reformer 2 is returned to the air-fuel ratio in the initial state. Control (step S109). As described above, the normal operation of the fuel cell system 1 described above is performed.

As described above, in the present embodiment, the exhaust gas discharged from the fuel cell 3 is supplied to the vaporizer 7 through the exhaust gas supply pipe 16. Then, the liquid ammonia sent out by the pump 6 is vaporized by the exhaust heat of the exhaust gas in the vaporizer 7. The exhaust gas discharged from the fuel cell 3 is supplied to the heat exchanger 9 through the exhaust gas supply pipe 17. And the air sent by the air blower 8 is heat-exchanged by the exhaust heat of exhaust gas in the heat exchanger 9, and is preheated. Thus, exhaust heat of exhaust gas is effectively used for vaporization of liquid ammonia and heat exchange of air. Therefore, an electric heater for vaporizing liquid ammonia, an electric heater for exchanging heat of air, and a power source for supplying electric power to these electric heaters are not required. Thereby, the system efficiency of the fuel cell system 1 can be improved.

Further, since the heat exchanger 9 preheats the air using the exhaust heat of the exhaust gas, there is a temperature difference between the fuel gas introduced into the anode 3a of the fuel cell 3 and the air introduced into the cathode 3b of the fuel cell 3. Get smaller. Therefore, since the temperature difference between the anode 3a and the cathode 3b becomes small, it becomes difficult for heat stress distribution to occur in the electrolyte (not shown) disposed between the anode 3a and the cathode 3b. As a result, the performance and reliability of the fuel cell 3 can be increased.

Further, the control device 21 controls the air-fuel ratio of the reformer 2 during the start-up operation to be higher than the air-fuel ratio of the reformer 2 during the normal operation. For this reason, at the start-up operation, the amount of air introduced into the reformer 2 is increased compared to the normal operation. Accordingly, since the decomposition temperature of ammonia in the reformer 2 is increased, the temperature of the fuel gas generated in the reformer 2 and introduced into the fuel cell 3 is increased. Thereby, the fuel cell 3 can be warmed up early at the time of starting operation.

At this time, the control device 21 controls the air-fuel ratio of the reformer 2 to be 1.0 or more, so that the decomposition temperature of ammonia in the reformer 2 becomes sufficiently high. Accordingly, it is possible to reliably warm the fuel cell 3 early during the start-up operation.

Further, the control device 21 controls the opening degree of the valve 14 that adjusts the flow rate of the air supplied from the air blower 8 to the reformer 2. Thereby, the air-fuel ratio of the reformer 2 can be easily controlled.

Furthermore, the exhaust gas after being combusted by the combustor 10 is supplied to the vaporizer 7 and the heat exchanger 9. When the exhaust gas discharged from the fuel cell 3 is combusted by the combustor 10, the temperature of the exhaust gas increases. Therefore, the vaporization of liquid ammonia and the heat exchange of air using the exhaust heat of exhaust gas can be performed effectively.

Note that the present invention is not limited to the above embodiment. For example, in the above embodiment, the control device 21 controls the air-fuel ratio of the reformer 2 by controlling the opening of the valve 14 that adjusts the flow rate of air supplied from the air blower 8 to the reformer 2. However, the form is not particularly limited. For example, the fuel cell system 1 may include two air blowers with different air blowing amounts per unit time. In such a configuration, the control device 21 operates an air blower with a large amount of blown out air during start-up operation, and operates an air blower with a small amount of blown out air during normal operation, so that the control device 21 operates during start-up operation and normal operation. The air-fuel ratio of the reformer 2 is controlled. In this case, the valve 14 becomes unnecessary.

In the above embodiment, the control device 21 controls the air-fuel ratio of the reformer 2 by controlling the flow rate of the air supplied to the reformer 2. However, the control device 21 is not particularly limited to this configuration, and may control the air-fuel ratio of the reformer 2 by controlling the flow rate of ammonia supplied to the reformer 2. In this case, a valve for adjusting the flow rate of ammonia supplied to the reformer 2 is disposed in the ammonia supply pipe 11.

Moreover, in the said embodiment, although the control apparatus 21 is controlling so that the air fuel ratio of the reformer 2 at the time of starting operation is made higher than the air fuel ratio of the reformer 2 at the time of normal operation, especially the form It is not limited to. When the early warm-up of the fuel cell 3 is not required, the control device 21 may make the air-fuel ratio of the reformer 2 during start-up operation equal to the air-fuel ratio of the reformer 2 during normal operation. In this case, the control process executed by the control device 21 can be simplified.

Furthermore, in the above embodiment, the fuel cell system 1 includes the combustor 10 that combusts the exhaust gas discharged from the fuel cell 3. However, the combustor 10 may be omitted if the exhaust heat of the exhaust gas immediately after being discharged from the fuel cell 3 can be used as it is for the vaporization of liquid ammonia and the heat exchange of air. In this case, the configuration of the fuel cell system 1 can be simplified.

Moreover, in the said embodiment, although the control apparatus 21 determines whether it switches from starting operation to normal operation based on the detected value of the temperature sensor 20 which detects the temperature of the fuel cell 3, especially in that form. Is not limited. For example, the power generation amount of the fuel cell 3 increases as the temperature of the fuel cell 3 increases. Therefore, the fuel cell system 1 may include a sensor that detects the amount of power generated by the fuel cell 3 instead of the temperature sensor 20. In such a configuration, the control device 21 determines whether to switch from the startup operation to the normal operation based on the power generation amount of the fuel cell 3.

Further, the following configuration may be adopted as a fuel cell system according to another embodiment. That is, the reformer may be provided with a plurality of ammonia decomposing apparatuses that use a catalyst for decomposing ammonia to burn a part of ammonia with oxygen and decompose the ammonia into hydrogen using the heat of combustion. The fuel cell may be constituted by a solid oxide fuel cell (hereinafter referred to as SOFC) that is operated using a hydrogen-containing gas generated by at least one of a plurality of ammonia decomposing apparatuses.

The power generation apparatus of the present embodiment includes a plurality of ammonia decomposition apparatuses that use an ammonia decomposition catalyst to burn part of ammonia with oxygen and decompose the ammonia into hydrogen using the heat of combustion, and the plurality of ammonia decomposition apparatuses. And a solid oxide fuel cell operated using at least one hydrogen-containing gas produced as a fuel.

In the ammonia decomposition apparatus, a combustion reaction (exothermic reaction) in which a part of ammonia is combusted with oxygen and a decomposition reaction (endothermic reaction) in which ammonia is decomposed into hydrogen using the combustion heat are performed. As long as there are two or more ammonia decomposition apparatuses, any number of ammonia decomposition apparatuses may be provided. However, in the ammonia decomposition apparatus, the first ammonia decomposition apparatus (hereinafter referred to as a temperature raising apparatus) used as an apparatus for generating a hydrogen-containing gas until the SOFC reaches a predetermined temperature, and the SOFC has reached the predetermined temperature. It is preferable to provide at least two ammonia decomposing apparatuses including a second ammonia decomposing apparatus (hereinafter referred to as “operating apparatus”) used as an apparatus for generating the hydrogen-containing gas later.

The temperature of the SOFC rises as the hydrogen-containing gas generated by the heating device continues to be supplied to the SOFC. In order to raise the temperature of the solid oxide fuel cell in a shorter time, the SOFC may be further heated by a heater or the like.

When the SOFC reaches a predetermined temperature, it is preferable to switch the device that generates the hydrogen-containing gas from the temperature raising device to the operation device. The predetermined temperature may be any temperature that enables power generation using SOFC, and is, for example, 600 to 1000 ° C. If the SOFC has reached a predetermined temperature, power generation is started without switching from the temperature raising device to the driving device. However, the ammonia decomposition catalyst is deactivated by making the ammonia decomposition apparatus used until the temperature of the SOFC cell rises to the operating temperature and the ammonia decomposition apparatus used when generating power with SOFC after the temperature increase as separate apparatuses. It is possible to prevent the power generation efficiency from being lowered. Switching from the temperature raising device to the operation device may be performed at any time after the SOFC reaches a predetermined temperature. However, from the viewpoint of preventing the deactivation, it is preferable to switch quickly when the SOFC reaches a predetermined temperature. The switching means between the temperature raising device and the operation device is not particularly limited, and can be performed using, for example, a manual valve, an automatic valve, or the like.

The temperature raising device is not limited to one, and a plurality of temperature raising devices of two or more may be used. The driving device is not limited to one, and a plurality of driving devices of two or more may be used. Even when three or more ammonia decomposing apparatuses are provided, it is preferable to use a temperature raising apparatus as an apparatus for generating a hydrogen-containing gas until the SOFC reaches a predetermined temperature. In addition, after the SOFC reaches a predetermined temperature, it is preferable to use an operation device as a device for generating a hydrogen-containing gas. When a plurality of temperature raising devices are provided, the temperature may be switched from one temperature raising device to another temperature raising device until the SOFC reaches a predetermined temperature. In the case where the apparatus is provided, switching from one operating apparatus to another operating apparatus may be performed during power generation after the SOFC reaches a predetermined temperature.

In addition, a hydrogen-containing gas may be generated using a plurality of temperature raising devices at the same time until the SOFC reaches a predetermined temperature. During power generation after the SOFC reaches a predetermined temperature, The hydrogen-containing gas may be generated using the operating device at the same time.

<Elevation device>
The temperature raising device is provided with an ammonia decomposition catalyst. By supplying a gas containing ammonia and oxygen to the temperature raising device, a part of the ammonia is burned with oxygen. By using the combustion heat, an autothermal reforming reaction that decomposes ammonia into hydrogen and nitrogen proceeds. As a form of the catalyst for decomposing ammonia, a pellet-shaped or ring-shaped catalyst can be filled and used, but a honeycomb-shaped catalyst is preferable from the viewpoint of low pressure loss.

The hydrogen-containing gas generated by the temperature raising device is used for raising the temperature of the SOFC. For this reason, it is preferable that the hydrogen-containing gas be at a relatively high temperature of 600 to 800.degree. Since the ammonia decomposition catalyst is easily deactivated when used under high temperature conditions, when the SOFC reaches a predetermined temperature, the device that generates the hydrogen-containing gas is switched from the temperature raising device to the operation device. Is preferred. By separating the ammonia decomposing apparatus used until the SOFC is heated to a predetermined temperature and the ammonia decomposing apparatus used for generating power with the SOFC after the temperature rising, the ammonia decomposing catalyst is deactivated and the power generation efficiency is lowered. Can be prevented.

(Ammonia decomposition catalyst)
The catalyst for decomposing ammonia mounted in the temperature raising device preferably contains a catalytically active component and a heat-resistant oxide. However, when the volume per unit mass of the catalytically active component is large, the catalytically active component alone may be used. The catalytic active component having a small volume per unit mass of the catalytic active component is preferably used after being supported and / or diluted by a heat-resistant oxide. This is because the heat resistance of the catalyst component is expected to be improved by using it together with the heat resistant oxide, and the surface area involved in the activity of the catalyst component is expected to be increased by being dispersed on the heat resistant oxide.

It is preferable that the ammonia decomposition catalyst mounted on the temperature raising device contains at least one element selected from iron, cobalt, and nickel as a catalytically active component. The content of the catalytically active component in the catalyst is preferably 5 to 80% by mass, more preferably 10 to 70% by mass, and further preferably 20 to 60% by mass. When the content of the catalytically active component is less than 5% by mass, the amount of the catalytically active component is insufficient, and the amount of hydrogen supplied to the SOFC may be insufficient. On the other hand, when the amount is more than 80% by mass, the aggregation of the catalytically active component proceeds and the catalyst may be deteriorated.

As the heat-resistant oxide, a porous oxide generally used as a catalyst carrier can be used. For example, α-alumina, activated alumina, silica, zirconia, titania, zeolite, silica which is a composite oxide thereof. Alumina, silica titania, titania zirconia, or the like can be used, and the honeycomb can be coated with the remaining mass of the catalytically active component.

The catalyst preferably contains at least one metal selected from silver, copper, palladium and platinum as a promoter component. The content of the promoter active component in the catalyst is preferably 0.1 to 5% by mass, more preferably 1 to 3% by mass. When the content of the promoter component is less than 0.1% by mass, there is a possibility that a sufficient function as a promoter cannot be achieved. On the other hand, if it exceeds 5% by mass, the combustion activity of the catalyst may be excessively increased.

(Catalyst preparation method)
A known method can be used to prepare the catalyst. For example, (1) the catalyst is prepared by immersing the honeycomb in a slurry obtained by wet pulverizing the catalyst component, removing excess slurry, and drying and firing. Method, (2) Immerse the honeycomb in a slurry obtained by wet-grinding a heat-resistant oxide, remove excess slurry, dry or fire, then immerse in an aqueous catalyst active component solution, remove excess liquid, (3) A sol-like material that is a heat-resistant oxide precursor, and in some cases, the honeycomb is immersed in a liquid material containing an aqueous liquid of a catalytically active component, and excess liquid material is removed, followed by drying and firing. This is a method for preparing a catalyst. The drying temperature is preferably 50 to 300 ° C., and the firing temperature is preferably 300 to 700 ° C.

When obtaining a slurry by wet pulverization, an aqueous slurry is prepared in which the number fraction of catalyst component particles having a secondary particle size of 10 μm or more is 10% or less, preferably 5% or less, more preferably 1% or less, It is preferable that the ceramic molded body is applied, dried and / or fired. If it exceeds 10%, the thickness of the catalyst component layer becomes thick, and the diffusion of gas to the entire catalyst component layer becomes slow, so that the entire catalyst component layer may not be used effectively, and sufficient catalytic activity may not be obtained. There is.

The arithmetic average diameter of the slurry is preferably 5 μm or less, preferably 4 μm or less, and more preferably 3 μm or less. If the thickness exceeds 5 μm, the thickness of the catalyst component layer becomes thick and gas diffusion to the entire catalyst component layer becomes slow, so that the entire catalyst component layer may not be used effectively, and sufficient catalytic activity may not be obtained. is there.

As the particle size distribution of the slurry, a method used for usual slurry particle size distribution measurement can be used. For example, the particle size distribution of the slurry can be measured using a particle size distribution measuring apparatus using a laser diffraction method. From the particle size distribution measurement result of the slurry, the number fraction with respect to the particle diameter in the catalyst component slurry and the arithmetic average diameter can be calculated.

When the catalyst component is coated by the above procedure, the amount to be coated varies depending on the slurry composition, viscosity, and solid component concentration (solid component concentration with respect to the liquid amount). It is preferable to confirm that the thickness becomes. When the catalyst component is thinner than the target average thickness in one operation, the target thickness can be obtained by repeating the above preparation method a plurality of times.

Further, when the slurry viscosity is high, the honeycomb formed body can be coated after adjusting to a slurry preferable for coating by adding a surfactant and adjusting pH.

(Gas supplied to the temperature raising device)
In the temperature raising device, it is preferable to promote the temperature rise of the SOFC by increasing the gas temperature at the outlet of the temperature raising device, so that it is used for ammonia combustion reaction (exothermic reaction). The gas (supplied to the apparatus) preferably has a relatively high volume ratio of oxygen to ammonia (hereinafter referred to as oxygen / ammonia). Specifically, oxygen / ammonia is preferably 0.19 to 0.25, more preferably 0.195 to 0.23. If oxygen / ammonia is lower than 0.19, a high-temperature outlet gas cannot be obtained from the temperature-raising device, and the temperature rise of the SOFC may not be sufficiently promoted. Also, if oxygen / ammonia is higher than 0.25, the ammonia combustion reaction becomes excessive, and not only ammonia is consumed wastefully, but also the ammonia decomposition catalyst may be exposed to higher temperatures and deactivated. There is.

<Operation device>
Similar to the temperature raising device, the operating device is provided with an ammonia decomposition catalyst. The hydrogen-containing gas produced by the operating device is used for SOFC power generation. Therefore, the hydrogen-containing gas may be at a relatively low temperature of about 500 ° C. compared to the temperature raising device at the outlet of the operating device. Then, since the reaction temperature in the operating device is sufficient at a relatively low temperature of 500 to 600 ° C., the deactivation is moderate even if the ammonia decomposition catalyst used in the operating device is used for a long time.

(Ammonia decomposition catalyst)
As the ammonia decomposition catalyst mounted on the operation device, the same catalyst as the ammonia decomposition catalyst mounted on the temperature raising device may be used, but as described above, the gas temperature at the outlet of the operation device is Since it is preferably suppressed at a relatively low temperature, an ammonia decomposition catalyst having excellent decomposition activity at a relatively low temperature of about 500 to 600 ° C. is preferable.

It is preferable that the ammonia decomposition catalyst mounted on the operation apparatus also contains at least one element selected from iron, cobalt, and nickel as a catalytic active component. As described above, since the hydrogen-containing gas may be at a relatively low temperature at the outlet of the operating device, the ratio of ammonia used in the ammonia decomposition reaction (endothermic reaction) is relatively high (ammonia combustion reaction (exothermic reaction)). In order to promote the decomposition reaction in the operating device, the content of the catalytically active component in the ammonia decomposition catalyst of the operating device is It is preferable that the content of the catalytically active component in the ammonia decomposition catalyst is higher. The higher the content of the catalytically active component, the more easily the catalyst particles aggregate. However, the temperature of the hydrogen-containing gas at the outlet of the operating device may be lower than the temperature of the hydrogen-containing gas at the outlet of the temperature raising device. Absent. Therefore, even if the content rate of the said catalyst active component is high, aggregation of a catalyst particle can be suppressed. The content of the catalytically active component in the catalyst in the ammonia decomposition catalyst of the operating device is preferably 30 to 90% by mass, more preferably 45 to 85% by mass, and still more preferably 60 to 80% by mass.

It is preferable that the catalyst for decomposing ammonia mounted in the operation device contains, for example, an alkali metal or an alkaline earth metal as a promoter component. Since these metals improve the decomposition reaction activity of the catalyst, they are effective in increasing the amount of hydrogen generation and extending the life of the catalyst. The content of the cocatalyst component is about 1 to 5% by mass of the entire catalyst. If it is too small, the effect of activating the decomposition reaction cannot be obtained, and if it is too large, the combustion activity may be reduced.

(Catalyst preparation method)
The ammonia decomposition catalyst mounted on the operation apparatus can be prepared in the same manner as the ammonia decomposition catalyst mounted on the temperature raising apparatus.

(Gas supplied to the operating device)
Since the hydrogen-containing gas generated in the operating device is used for SOFC power generation, the hydrogen concentration at the outlet of the operating device is preferably relatively high. Therefore, it is preferable that the ratio of ammonia used for ammonia decomposition reaction (endothermic reaction) is relatively high (the ratio of ammonia used for ammonia combustion reaction (exothermic reaction) is relatively low). That is, it is preferable that the gas supplied to the operating device has a relatively low ratio of oxygen / ammonia. Specifically, oxygen / ammonia is preferably 0.08 to 0.17, more preferably 0.09 to 0.165. If the oxygen / ammonia is lower than 0.08, there is a risk that the amount of heat necessary for autothermal reforming cannot be obtained sufficiently. If the oxygen / ammonia is higher than 0.17, the combustion reaction of ammonia increases, resulting in SOFC. The ratio of hydrogen in the supplied hydrogen-containing gas decreases, and the ammonia decomposition catalyst may be deactivated.

<SOFC>
The form of the SOFC used in the present invention will be described. Usually, a SOFC cell has a solid oxide electrolyte and a fuel electrode on one surface of the electrolyte and an air electrode on the other surface.

(Fuel electrode)
The fuel electrode is a pole for reacting the fuel gas and oxygen ions generated at the air electrode and moving to the fuel electrode via the solid oxide electrolyte, and exhausts the fuel exhaust gas after the reaction. As the fuel electrode, a fuel electrode material usually used in SOFC used for fuel gas can be used, and it is generally formed by a fuel electrode catalyst and solid electrolyte particles.

The material of the fuel electrode electrode catalyst is not particularly limited in the practice of the present invention, and an electrode catalyst for a fuel electrode generally used in SOFC can be selected according to the fuel gas used. For this, a metal such as cobalt or nickel, or an alloy thereof is selected.

The solid electrolyte particles diffuse oxygen ions that have moved through the solid oxide electrolyte into the fuel electrode. The material is not particularly limited, and for example, a material (described later) that can be used for a solid oxide electrolyte is used. If necessary, two or more kinds of solid electrolyte particles may be mixed and used.

Solid electrolyte particles having a specific surface area in the range of 1 to 20 m ² / g are preferred for forming pores in the fuel electrode, and those in the range of 3 to 15 m ² / g are particularly preferred. When the specific surface area is less than 1 m <2> / g, large pores are likely to be locally formed in the fuel electrode, and the problem of non-uniform fuel gas flow tends to occur. On the other hand, if the specific surface area exceeds 20 m ² / g, the sinterability increases, the amount of pores decreases, and the problem of insufficient fuel gas flow tends to occur.

The mixing ratio of the fuel electrode electrode catalyst and the solid electrolyte particles may be within the range normally used in SOFC. For example, the ratio of the fuel electrode electrode catalyst / solid electrolyte particles is 20/80 to 60/40 by mass ratio. Can be used.

The thickness of the fuel electrode can be changed in various ways, but is usually about 20 to 200 μm in the case of an electrolyte-supported cell (ESC), an air-electrode-supported cell (CSC) and a single chamber type, preferably About 30 to 120 μm. On the other hand, when the anode supporting substrate and the anode active layer are regarded as one anode, as in the anode supporting cell (ASC), the thickness is usually 200 to 2000 μm, preferably 300 to 1000 μm. If the fuel electrode is too thin, the original function of the fuel electrode cannot be obtained. On the other hand, if the fuel electrode is too thick, gas diffusion is insufficient and cell performance is degraded.

The fuel electrode may further contain a reforming catalyst in order to reduce unused fuel gas contained in the fuel exhaust gas. A known catalyst can be used as the reforming catalyst.

(Method of forming fuel electrode)
The anode can be formed using any technique commonly used for forming thin films, films, and the like. For example, it can be easily formed by applying a paste containing an electrode material in a predetermined pattern on the surface of a solid oxide electrolyte that has already been formed, and baking it after drying. For the application of the paste, for example, a printing method such as a screen printing method can be advantageously used. The firing temperature can be varied in a wide range depending on the characteristics of the material used, but is usually in the range of about 900 to 1500 ° C. Of course, other methods may be used if necessary.

(Air electrode)
The air electrode is an electrode into which oxygen or a gas containing oxygen is introduced in addition to air. In the electrode, oxygen becomes oxygen ions and moves to the fuel electrode via the solid oxide electrolyte. As the material, an air electrode material usually used for SOFC can be used, and it is generally formed of an air electrode electrode catalyst and solid electrolyte particles.

As the air electrode catalyst, a known one can be used. For example, an oxide having a manganese-based, ferrite-based, cobalt-based or nickel-based perovskite structure is preferable. For example, a group 2 of the periodic table such as strontium (Sr) is used. lanthanum strontium manganite element is added _{(La X S r1-X MnO} 3), lanthanum strontium cobaltite _{(La X Sr 1-X CoO} 3), lanthanum strontium cobalt ferrite _{(La X Sr 1-X Co} Y Fe 1 _-Y O ₃ ), lanthanum nickel ferrite (LaNi _Y Fe _{1 -Y} O ₃ ) and the like.

The solid electrolyte particles contained in the air electrode can be the same material as the solid electrolyte particles that can be used in the fuel electrode.

The thickness of the air electrode can be variously changed, but is usually about 20 to 200 μm, preferably about 30 to 120 μm. If the air electrode is too thin, the original function of the air electrode cannot be obtained, the air electrode reaction becomes insufficient, and the output decreases.

The air electrode can be formed by the same formation method as the fuel electrode. The formation method of the fuel electrode and the air electrode may be the same or different.

(Solid oxide electrolyte)
When the fuel electrode is installed on one side of the solid oxide electrolyte and the air electrode is installed on the other side, the oxygen ions generated in the air electrode move into the fuel electrode. Pass through.

As a material for the solid oxide electrolyte, those known as SOFC solid oxide electrolytes can be used. For example, YSZ (yttria stabilized zirconia), ScSZ (scandia stabilized zirconia), and zirconia in addition to Ce. Oxygen ion conductivity such as zirconia powder doped with Al, etc., doped ceria powder such as SDC (Samaria doped ceria), GDC (gadria doped ceria), LSGM (lanthanum gallate) powder, bismuth oxide powder, etc. Ceramic materials can be used. These solid oxide electrolytes may be used in combination of two or more if necessary.

The shape of the solid oxide electrolyte depends on the shape of the cell, but is not specified. The shape of the cell generally includes a flat plate cell, a cylindrical cell, a segmented cell, etc., and the solid oxide electrolyte is directly formed according to each shape, or screen printing method, spin coating method on the support. It is formed using any technique conventionally used for forming a sheet, a thin film, a film, and the like. For example, when forming using a green sheet process, the solid oxide electrolyte material paste is applied in a predetermined pattern, dried to form a green sheet, and then the green sheet is fired at a high temperature to obtain a flat plate. Type solid oxide electrolyte can be formed easily. For the application of the paste, for example, a printing method such as a screen printing method can be advantageously used. Specifically, a solid oxide electrolyte material can be formed by printing a paste of a solid oxide electrolyte material in a predetermined pattern on one side of a flat temporary support, and drying and firing. The firing temperature can be varied in a wide range depending on the characteristics of the solid oxide electrolyte material used, but is usually in the range of about 1200 to 1500 ° C.

The thickness of the solid oxide electrolyte is generally in the range of 5 to 500 μm. In the case of an electrolyte-supported cell (ESC), the thickness is 50 to 500 μm, preferably 100 to 400 μm. The fuel electrode-supported cell (ASC) or air electrode In the case of a support type cell (CSC), the thickness is 5 to 100 μm, preferably 10 to 50 μm.

(Formation of SOFC cell)
The SOFC cell is formed on the surface opposite to the fuel electrode with the solid oxide electrolyte and the fuel electrode formed on one surface of the solid oxide electrolyte, for example, as in the conventional fuel cell. Configured as a cell including the air electrode formed.

The shape of the SOFC cell may be a generally used shape such as a flat plate cell, a cylindrical cell, or a segment cell. For example, ESC, ASC, and CSC are mentioned as a flat cell. In addition, it is preferable that the fuel electrode and the air electrode be a two-chamber fuel cell in which a solid oxide electrolyte is sandwiched, but both the fuel electrode and the air electrode are formed on one surface of the solid oxide electrolyte. The single-chamber fuel cell may be used. When configured as a single chamber type cell, it is configured as a cell in which one or more pairs of a fuel electrode and an air electrode are formed on at least one surface of the solid oxide electrolyte. Examples of the cylindrical cell include a cylindrical vertical stripe cell and a cylindrical horizontal stripe cell, and a cylindrical flat plate cell can be included therein. In short, in the implementation of the present embodiment, the SOFC can have various structures including structures known in publications and structures currently implemented.

The fuel electrode and the air electrode are formed to be porous so that the fuel gas can be sufficiently diffused therein and sufficient electric conductivity can be maintained. The porosity can be changed in various ways, but is usually preferably about 10 to 60%.

In this embodiment, an intermediate layer such as a barrier layer may be provided between the fuel electrode and / or the air electrode and the solid oxide electrolyte.

<Fuel gas>
As the fuel gas, an outlet gas of an ammonia decomposing apparatus (a hydrogen-containing gas generated by decomposing ammonia) is used. Therefore, in addition to nitrogen and hydrogen generated by the ammonia decomposition reaction in the apparatus, the fuel gas may contain ammonia, water vapor, or the like remaining without reacting in the ammonia decomposition apparatus. Further, an inert gas such as a rare gas may be included to such an extent that the power generation efficiency does not decrease.

<Oxidant gas>
The oxidant gas is not particularly limited as long as it has an ability to oxidize fuel gas, but air or the like can be used in addition to a gas mainly containing oxygen.

<Reaction of each electrode>
Electric power can be generated by introducing fuel gas into the fuel electrode and introducing oxidant gas into the air electrode. The power generation itself as a fuel cell proceeds at about 800 to 1000 ° C. on each electrode by the following reaction formula.
Combustion electrode: H ₂ + O ²⁻ → H ₂ O + 2e ⁻
Air electrode: O ₂ + 4e ⁻ → 2O ²⁻

<Power generation method>
An example of a power generation method using the fuel cell system and the power generation apparatus of the present embodiment will be described below. Here, it was provided with one device for temperature increase, one device for operation, and an SOFC operated with hydrogen-containing gas generated by either the temperature increase device or the operation device as fuel. Power generation is performed using a power generation device.

The power generation method includes a first step of supplying a gas mixture having a volume ratio of oxygen to ammonia (hereinafter referred to as oxygen / ammonia) of 0.19 or more to a temperature raising device, and raising the temperature of the device that generates a hydrogen-containing gas. The second step of switching from the operating device to the operating device and the third step of supplying the operating device with a mixed gas having oxygen / ammonia of 0.17 or less are included. When the temperature of is reached.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and the present invention is implemented with modifications within a range that can be adapted to the purpose described above and below. All of which are within the scope of the present invention.

<Ammonia decomposition device 1>
(Preparation of ammonia decomposition catalyst A)
Cobalt nitrate hexahydrate 131.0 g, manganese nitrate hexahydrate 34.1 g and silver nitrate 7.56 g were weighed and dissolved in 200 mL of pure water. Into the obtained metal nitrate solution, 51.6 g of γ-alumina was added and heated to 100 ° C. in a water bath to evaporate to dryness. The obtained solid was calcined at 500 ° C. for 3 hours in an air atmosphere to obtain a catalyst component. After roughly pulverizing the catalyst component in an alumina mortar, 100 g of the catalyst component powder, 100 g of pure water, and 10 g of colloidal silica sol were mixed and wet pulverized with a ball mill for 6 hours. A hexagonal cell cordierite honeycomb molded body having 600 cells per square inch is coated with the obtained catalyst component slurry by a wash coat method, excess slurry is blown off by air blow, and the process is dried at 120 ° C. six times. Thereafter, firing was performed at 500 ° C. for 1 hour to obtain a honeycomb-shaped ammonia decomposition catalyst A coated with a catalyst component. The amount of catalyst supported on the obtained ammonia decomposition catalyst A was 300 g per liter of the honeycomb formed body. Moreover, the catalyst active component content rate was 35 mass%, and the promoter component content rate was 5 mass%.

(Preparation of ammonia decomposition apparatus 1)
The ammonia decomposing apparatus 1 was prepared such that the volume of the ammonia decomposing catalyst A was 20 mL.

<Ammonia decomposition device 2>
(Preparation of ammonia decomposition catalyst B)
291.0 g of cobalt nitrate hexahydrate, 43.4 g of cerium nitrate hexahydrate, and 49.3 g of zirconia sol (25 mass% concentration in terms of ZrO ₂ ) suspension were weighed and dissolved in 1 L of pure water, A nitrate aqueous solution was prepared. 147.6 g of potassium hydroxide was dissolved in 2 L of pure water to prepare an aqueous potassium hydroxide solution. While stirring the potassium hydroxide aqueous solution, the metal nitrate aqueous solution was added dropwise. After completion of dropping, the obtained suspension was subjected to suction filtration, and washed with pure water 5 times to obtain a precipitate. The obtained precipitate was dried overnight at 120 ° C. and then calcined at 450 ° C. for 3 hours in an air atmosphere to obtain a catalyst component. After roughly pulverizing the catalyst component in an alumina mortar, 100 g of catalyst component powder, 100 g of pure water, 5.0 g of cesium hydroxide, and 10 g of colloidal silica sol were mixed, and wet pulverized with a ball mill for 6 hours. A hexagonal cell cordierite honeycomb molded body having 600 cells per square inch is coated with the obtained catalyst component slurry by a wash coat method, excess slurry is blown off by air blow, and the process is dried at 120 ° C. six times. Thereafter, firing was performed at 500 ° C. for 1 hour to obtain a honeycomb-shaped ammonia decomposition catalyst B coated with a catalyst component. The amount of catalyst supported on the obtained ammonia decomposition catalyst B was 280 g per liter of the honeycomb formed body. Further, the catalytic active component content was 73%.

(Preparation of ammonia decomposition apparatus 2)
The ammonia decomposing apparatus 2 was prepared such that the volume of the ammonia decomposing catalyst B was 20 mL.

<Ammonia decomposition device 2 '>
It was produced by exactly the same method as the ammonia decomposition apparatus 2.

<Example 1>
(Ammonia decomposition reaction)
Ammonia was supplied to the ammonia decomposition apparatus 1 at a flow rate of 3.32 L / min and air at a flow rate of 3.66 L / min. The supplied gas was heated to 200 ° C. with an electric heater to start an autothermal reforming reaction on the ammonia decomposition catalyst. At this time, oxygen / ammonia in the supply gas was 0.23. Further, the outlet gas (hydrogen-containing gas) of the ammonia decomposing apparatus 1 was a flow rate of 9.54 L / min and the temperature was 750 ° C.

(At SOFC startup temperature rise)
While supplying the outlet gas of the ammonia decomposing apparatus 1 directly to the SOFC (cell size: 50 mm × 50 mm), the SOFC cell was simultaneously heated to the operating temperature (650 ° C.) with the SOFC heater. It took 8 minutes to raise the temperature from room temperature to the operating temperature.

(During SOFC steady operation)
After raising the temperature of the SOFC cell to the operating temperature (650 ° C.), the ammonia decomposition apparatus 1 was switched to the ammonia decomposition apparatus 2. At the same time, the supply gas was changed to a flow rate of 3.32 L / min for ammonia and a flow rate of 2.49 L / min for air. At this time, oxygen / ammonia was 0.16. Further, the ammonia conversion rate by the decomposition catalyst reaction was 83%.

<Example 2>
Ammonia was supplied to the ammonia decomposition apparatus 2 at a flow rate of 3.32 L / min and air at a flow rate of 3.36 L / min. The supplied gas was heated to 200 ° C. with an electric heater to start an autothermal reforming reaction on the ammonia decomposition catalyst. At this time, oxygen / ammonia in the supply gas was 0.21. Further, the outlet gas (hydrogen-containing gas) of the ammonia decomposing apparatus 2 had a flow rate of 9.28 L / min, and the temperature was 650 ° C.

(At SOFC startup temperature rise)
While supplying the outlet gas of the ammonia decomposing apparatus 2 directly to the SOFC (cell size: 50 mm × 50 mm), the SOFC cell was heated to the operating temperature (650 ° C.) with the heater for SOFC heating. It took 10 minutes to raise the temperature from room temperature to the operating temperature.

(During SOFC steady operation)
After raising the temperature of the SOFC cell to the operating temperature (650 ° C.), the ammonia decomposition apparatus 2 was switched to the ammonia decomposition apparatus 2 ′. At the same time, the supply gas was changed to a flow rate of 3.32 L / min for ammonia and a flow rate of 2.49 L / min for air. At this time, oxygen / ammonia was 0.16. Further, the ammonia conversion rate by the decomposition catalyst reaction was 83%.

<Comparative Example 1>
In Example 2, power generation was performed in the same manner as in Example 2 except that the ammonia decomposition apparatus 2 was continuously used even after the temperature of the SOFC cell was raised to the operating temperature (650 ° C.). The time required for raising the temperature from room temperature to the operating temperature of 650 ° C. was 10 minutes, and the ammonia conversion rate by the decomposition catalyst reaction was 78%.

<Comparative example 2>
In Example 2, power generation was performed in the same manner as in Example 2 except that air was supplied to the ammonia decomposition apparatus 2 at a flow rate of 2.49 L / min (oxygen / ammonia in the supply gas was 0.16). As a result, the flow rate of the outlet gas during the SOFC temperature increase was 8.06 L / min, and the temperature was 480 ° C. In addition, the time required for raising the temperature from room temperature to the operating temperature of 650 ° C. was 14 minutes.

<Comparative Example 3>
When the temperature of the SOFC cell was raised only by the heater for SOFC heating, it took 20 minutes to raise the temperature from room temperature to the operating temperature of 650 ° C.

The power generation device of the present invention is excellent in power generation efficiency and can start power generation with a solid oxide fuel cell in a short time, and thus can be operated at a low cost. Therefore, the fuel cell of the present invention can be advantageously used in various fields such as automobile power generation, commercial power generation, and household power generation. Further, by downsizing, for example, it can be advantageously used for driving LEDs, LCD displays, portable radios, portable information devices, and the like.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Reformer, 3 ... Fuel cell, 5 ... Liquid NH3 tank (ammonia tank), 6 ... Pump, 7 ... Vaporizer, 8 ... Air blower (air supply device), 9 ... Heat exchange , 10 ... combustor, 16 ... exhaust gas supply pipe (first exhaust gas supply part), 17 ... exhaust gas supply pipe (second exhaust gas supply part), 21 ... control device (control part).

Claims (11)

1. A reformer that generates fuel gas by introducing oxidant gas to reform ammonia; and
   A fuel cell that generates power using the fuel gas and the oxidant gas generated by the reformer;
   An ammonia tank for storing the ammonia in a liquid state;
   A pump for feeding the liquid ammonia stored in the ammonia tank toward the reformer;
   A vaporizer disposed between the pump and the reformer to vaporize the liquid ammonia;
   An insufflator for sending the oxidant gas to the reformer and the fuel cell;
   A heat exchanger that is disposed between the air supply device and the fuel cell and preheats the oxidant gas by heat exchange;
   A first exhaust gas supply unit configured to supply exhaust gas discharged from the fuel cell to the vaporizer;
   A second exhaust gas supply unit for supplying the exhaust gas to the heat exchanger,
   The vaporizer vaporizes the liquid ammonia by exhaust heat of the exhaust gas,
   The heat exchanger is a fuel cell system that preheats the oxidant gas by exchanging heat with exhaust heat of the exhaust gas.
2. The oxidant gas is air,
   A control unit for controlling the air-fuel ratio of the reformer;
   The fuel cell system according to claim 1, wherein the control unit controls the air-fuel ratio of the reformer during start-up operation to be higher than the air-fuel ratio of the reformer during normal operation.
3. The fuel cell system according to claim 2, wherein the control unit controls the air-fuel ratio of the reformer during the start-up operation to be 1.0 or more.
4. Between the insufflator and the reformer, a valve for adjusting the flow rate of the air supplied from the insufflator to the reformer is disposed,
   The fuel cell system according to claim 2 or 3, wherein the control unit controls an air-fuel ratio of the reformer by controlling an opening degree of the valve.
5. Further comprising a combustor for combusting the exhaust gas discharged from the fuel cell;
   The first exhaust gas supply unit supplies the exhaust gas burned by the combustor to the vaporizer,
   The fuel cell system according to any one of claims 1 to 4, wherein the second exhaust gas supply unit supplies the exhaust gas burned by the combustor to the heat exchanger.
6. The reformer includes a plurality of ammonia decomposing devices that burn a part of ammonia with oxygen using an ammonia decomposing catalyst, and decompose the ammonia into hydrogen using the heat of combustion.
   The fuel cell according to any one of claims 1 to 5, wherein the fuel cell is configured by a solid oxide fuel cell that is operated by using a hydrogen-containing gas generated by at least one of the plurality of ammonia decomposition apparatuses as a fuel. The fuel cell system described.
7. The ammonia decomposition apparatus includes a first ammonia decomposition apparatus and a solid oxide fuel cell that are used as an apparatus for generating the hydrogen-containing gas until the solid oxide fuel cell reaches a predetermined temperature. The fuel cell system according to claim 6, further comprising a second ammonia decomposition apparatus used as an apparatus for generating the hydrogen-containing gas after reaching the temperature.
8. The ammonia decomposing catalyst provided in the first ammonia decomposing apparatus and the second ammonia decomposing apparatus comprises at least one element selected from iron, cobalt, and nickel, respectively, as a catalytically active component. Item 8. The fuel cell system according to Item 7.
9. The content rate of the catalytically active component in the ammonia decomposition catalyst of the second ammonia decomposing apparatus is higher than the content rate of the catalytically active component in the ammonia decomposing catalyst of the first ammonia decomposing apparatus. Fuel cell system.
10. A power generation method using the fuel cell system according to any one of claims 7 to 9,
    A first step of supplying the first ammonia decomposition apparatus with a mixed gas having a volume ratio of oxygen to ammonia of 0.19 or more;
    A second step of switching the device for generating the hydrogen-containing gas from the first ammonia decomposition device to the second ammonia decomposition device;
    A third step of supplying the second ammonia decomposition apparatus with a mixed gas having a volume ratio of oxygen to ammonia of 0.17 or less;
    The second step is a power generation method performed when the solid oxide fuel cell reaches a predetermined temperature.
11. A plurality of ammonia decomposing apparatuses for burning a part of ammonia with oxygen by the catalyst for decomposing ammonia and decomposing ammonia into hydrogen using the combustion heat;
    A power generator comprising: a solid oxide fuel cell that is operated using a hydrogen-containing gas generated by at least one of the plurality of ammonia decomposition apparatuses as a fuel.

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