Fuel Cell Systems

Abstract

To provide a technique that can reduce the concentration of ammonia included in reformed gas while reducing the amount of heating in a reformer.SOLUTION: A fuel cell system comprises: a reformer that reforms raw material gas to generate reformed gas; a heating part that heats the raw material gas in the reformer; a gas passage through which the reformed gas generated by the reformer passes; a temperature sensor that detects the temperature of the reformed gas passing through the gas passage; a fuel cell that generates electric power using fuel gas generated by removing ammonia from the reformed gas passing through the gas passage; and a control part that controls the amount of heating by the heating part in accordance with the concentration of ammonia included in the reformed gas estimated from a detected temperature from the temperature sensor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a fuel cell system. [Background technology]

[0002] Patent Document 1 discloses a fuel cell system. The fuel cell system of Patent Document 1 includes a reformer that generates reformed gas (hydrogen-containing gas) by reforming a raw material gas, a combustor that heats the reformer, an ammonia remover that removes ammonia contained in the reformed gas generated by the reformer, a fuel cell that generates power using the reformed gas discharged from the ammonia remover, and a temperature detector sensor that detects the temperature of the reformed gas after the ammonia has been removed by the ammonia remover. The combustor heats the reformer by combusting the gas discharged from the ammonia remover and the off-gas discharged from the fuel cell. In the fuel cell system of Patent Document 1, a controller starts supplying the reformed gas from the reformer to the fuel cell when the temperature of the reformed gas detected by the temperature sensor is equal to or higher than a predetermined threshold value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2011 / 158495 Summary of the Invention [Problem to be solved by the invention]

[0004] In a fuel cell system, if the concentration of ammonia contained in the reformed gas is high, the power generation efficiency of the fuel cell may decrease. Also, if the amount of heat generated in the reformer is large, energy consumption increases and the efficiency of the entire system may decrease. Therefore, this specification provides a technology that can suppress the concentration of ammonia contained in the reformed gas while suppressing the amount of heat generated in the reformer. [Means for solving the problem]

[0005] The fuel cell system disclosed in this specification includes a reformer that generates a reformed gas by reforming a raw material gas, a heating unit that heats the raw material gas in the reformer, a gas passage through which the reformed gas generated by the reformer passes, a temperature sensor that detects the temperature of the reformed gas passing through the gas passage, a fuel cell that generates electricity using a fuel gas generated by removing ammonia from the reformed gas that has passed through the gas passage, and a control unit that controls the amount of heat generated by the heating unit in accordance with the concentration of ammonia contained in the reformed gas estimated from the temperature detected by the temperature sensor.

[0006] According to the above configuration, it is possible to suppress the concentration of ammonia contained in the reformed gas while suppressing the amount of heat in the reformer. For example, when the concentration of ammonia estimated from the temperature detected by the temperature sensor is high, it is estimated that the decomposition of ammonia is not promoted in the reformer. In this case, the amount of heat generated by the heating unit can be increased to promote the decomposition of ammonia, and the concentration of ammonia contained in the reformed gas can be suppressed. Also, when the concentration of ammonia estimated from the temperature detected by the temperature sensor is low, it is estimated that the decomposition of ammonia is promoted in the reformer. In this case, the amount of heat generated by the heating unit can be reduced. Since it is necessary to increase the amount of heat only when the decomposition of ammonia is not promoted, the amount of heat generated in the reformer can be suppressed.

[0007] The fuel cell system may further include a pressure sensor that detects a pressure of the reformed gas passing through the gas passage. The control unit may control an amount of heating by the heating unit in response to a concentration of ammonia contained in the reformed gas estimated from a temperature detected by the temperature sensor and a pressure detected by the pressure sensor.

[0008] According to this configuration, the concentration of ammonia contained in the reformed gas is estimated from the temperature detected by the temperature sensor and the pressure detected by the pressure sensor, so that the estimation accuracy is improved, and the amount of heat applied by the heating unit can be controlled with high accuracy.

[0009] The control unit may increase an amount of heating by the heating unit when a concentration of ammonia contained in the reformed gas is estimated to be equal to or higher than a predetermined first threshold value.

[0010] According to this configuration, by increasing the amount of heat when the concentration of ammonia is high, it is possible to promote the decomposition of ammonia and reduce the concentration of ammonia.

[0011] The control unit may reduce an amount of heat applied by the heating unit when a concentration of ammonia contained in the reformed gas is estimated to be less than a predetermined second threshold value. The second threshold value may be a value less than the first threshold value.

[0012] According to this configuration, by reducing the amount of heat when the concentration of ammonia is low, unnecessary heating can be suppressed.

[0013] The heating unit may include a first heater for heating the source gas by Joule heat. With this configuration, the amount of heat applied by the heating unit can be controlled with high precision.

[0014] The heating unit may include a second heater that heats the raw material gas with heat of the reformed gas generated by the reformer. With this configuration, the raw material gas can be heated by effectively utilizing the heat of the reformed gas.

[0015] The heating unit may include a third heater that heats the raw material gas with heat of exhaust gas discharged from the fuel cell. With this configuration, the raw material gas can be heated by effectively utilizing the heat of the exhaust gas from the fuel cell.

[0016] The fuel cell system may further include a remover that removes ammonia from the reformed gas that has passed through the gas passage, thereby producing the fuel gas.

[0017] According to this configuration, it is possible to supply a high-quality fuel gas with a low ammonia concentration to the fuel cell. Also, if the configuration can suppress the concentration of ammonia contained in the reformed gas, it is possible to suppress the amount of ammonia removed by the remover, thereby reducing the load on the remover. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of a fuel cell system according to a first embodiment. [Diagram 2] 4 is a table showing ammonia concentration related information in the first embodiment. [Diagram 3] 4 is a flowchart of a heat amount control process according to the first embodiment. [Figure 4] 4 is a time chart of the heat amount control process in the first embodiment. [Diagram 5] FIG. 13 is a schematic diagram showing a fuel cell system according to a second embodiment. [Figure 6] 10 is a flowchart of a heat amount control process according to a second embodiment. [Figure 7] 13 is a table showing ammonia concentration relationship information according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Example 1 A fuel cell system 2 of Example 1 will be described with reference to the drawings. As shown in Fig. 1, the fuel cell system 2 of Example 1 includes a raw material tank 10, a vaporizer 20, a reformer 12, a remover 14, a fuel cell 16, and a control unit 50.

[0020] The raw material tank 10 stores liquid ammonia as a raw material. A liquid supply path 70 through which the liquid ammonia flows is connected to the raw material tank 10. The upstream end of the liquid supply path 70 is connected to the raw material tank 10, and the downstream end is connected to the vaporizer 20. Liquid ammonia is supplied from the raw material tank 10 to the vaporizer 20 through the liquid supply path 70. A pump 72 that pumps liquid ammonia from the upstream side to the downstream side of the liquid supply path 70 is provided in the liquid supply path 70.

[0021] The vaporizer 20 heats and vaporizes liquid ammonia supplied through a liquid supply path 70. This generates gaseous ammonia as a raw material gas. A raw material gas supply path 60 through which a raw material gas (gaseous ammonia) flows is connected to the vaporizer 20. An upstream end of the raw material gas supply path 60 is connected to the vaporizer 20, and a downstream end of the raw material gas supply path 60 is connected to the reformer 12. The raw material gas is supplied from the vaporizer 20 to the reformer 12 through the raw material gas supply path 60.

[0022] The reformer 12 generates reformed gas by reforming the raw gas (gaseous ammonia) supplied through the raw gas supply passage 60. The catalyst used for reforming the raw gas is, for example, copper, nickel, ruthenium, or the like. The reformed gas contains hydrogen generated by reforming the raw gas. The reformed gas also contains undecomposed ammonia. The concentration of ammonia contained in the reformed gas varies depending on the progress of the reforming.

[0023] The reformer 12 is equipped with a first heater 40 (an example of a heating unit) that heats the raw material gas during reforming of the raw material gas. The first heater 40 increases the temperature of the raw material gas in the reformer 12. The first heater 40 is, for example, an electric or gas type. The first heater 40 in this embodiment is an electric heater that generates heat when electricity is applied. The first heater 40 (electric heater) heats the heating target by Joule heat when the power is on, and does not heat the heating target when the power is off. The amount of heat by the first heater 40 is controlled by the control unit 50. In a modified example, the first heater 40 may be a gas burner that heats the heating target by the combustion heat of gas.

[0024] A reformed gas supply passage 62 (an example of a gas passage) through which the reformed gas flows is connected to the reformer 12. The upstream end of the reformed gas supply passage 62 is connected to the reformer 12, and the downstream end is connected to the remover 14. The reformed gas is supplied from the reformer 12 to the remover 14 through the reformed gas supply passage 62.

[0025] The reformed gas supply passage 62 is provided with a heat exchanger 22. The heat exchanger 22 is provided between the reformer 12 and the remover 14. The heat exchanger 22 cools the reformed gas by exchanging heat between the reformed gas passing through the reformed gas supply passage 62 and an external fluid. The heat exchanger 22 lowers the temperature of the reformed gas supplied from the reformer 12 to the remover 14. The structure of the heat exchanger 22 is not particularly limited, and may include, for example, fins for heat exchange.

[0026] A temperature sensor 30 is provided in the reformed gas supply passage 62. The temperature sensor 30 is provided between the reformer 12 and the heat exchanger 22. The temperature sensor 30 detects the temperature of the reformed gas discharged from the reformer 12. The temperature sensor 30 detects the temperature of the reformed gas passing through the reformed gas supply passage 62 upstream of the heat exchanger 22. The temperature sensor 30 detects the temperature of the reformed gas before the ammonia is removed by the remover 14 and before the reformed gas is heat exchanged by the heat exchanger 22. Information on the detected temperature by the temperature sensor 30 is transmitted to the control unit 50.

[0027] Further, the reformed gas supply passage 62 is provided with a pressure sensor 32. The pressure sensor 32 is provided between the reformer 12 and the heat exchanger 22. The pressure sensor 32 detects the pressure of the reformed gas discharged from the reformer 12. The pressure sensor 32 detects the pressure of the reformed gas passing through the reformed gas supply passage 62 upstream of the heat exchanger 22. The pressure sensor 32 detects the pressure of the reformed gas before the ammonia is removed by the remover 14 and before the reformed gas is heat exchanged by the heat exchanger 22. Information on the detected pressure by the pressure sensor 32 is transmitted to the control unit 50.

[0028] The remover 14 removes ammonia from the reformed gas by adsorbing the ammonia contained in the reformed gas supplied through the reformed gas supply passage 62 with an adsorbent. In this way, a fuel gas with a reduced ammonia concentration is generated. Examples of the adsorbent used for adsorbing ammonia include activated carbon, zeolite, and MOF (Metal Organic Framework). For example, the inside of a container of the remover 14 is filled with the adsorbent.

[0029] A fuel gas supply path 64, through which fuel gas flows, is connected to the remover 14. The upstream end of the fuel gas supply path 64 is connected to the remover 14, and the downstream end is connected to the fuel cell 16. Fuel gas is supplied from the remover 14 to the fuel cell 16 through the fuel gas supply path 64.

[0030] In addition to the fuel gas supply path 64, an air supply path 68 through which air flows is connected to the fuel cell 16. The upstream end of the air supply path 68 is connected to an air supply source (not shown), and the downstream end is connected to the fuel cell 16. Air is supplied from the air supply source to the fuel cell 16 through the air supply path 68. The upstream end of the air supply path 68 may be open to the outside air.

[0031] The fuel cell 16 generates power using fuel gas supplied through a fuel gas supply channel 64 and air supplied through an air supply channel 68. The fuel cell 16 includes, for example, a plurality of battery cells (not shown) stacked inside a container, and each battery cell generates power through a chemical reaction between hydrogen contained in the fuel gas and oxygen contained in the air. The battery cells are, for example, solid oxide fuel cells (SOFCs) and polymer electrolyte fuel cells (PEFCs), but are not limited to these. In the fuel cell 16 that generates power using fuel gas, unreacted fuel gas is discharged as exhaust gas during power generation.

[0032] An exhaust gas passage 66 through which exhaust gas flows is connected to the fuel cell 16. The upstream end of the exhaust gas passage 66 is connected to the fuel cell 16, and the downstream end is connected to an external discharge destination (not shown). Exhaust gas is discharged from the fuel cell 16 through the exhaust gas passage 66 to the discharge destination.

[0033] The control unit 50 includes, for example, a CPU (not shown) and a storage unit 52 (for example, ROM or RAM), and executes various controls and processes related to the fuel cell system 2 according to the programs stored in the storage unit 52.

[0034] The storage unit 52 of the control unit 50 stores ammonia concentration relationship information. FIG. 2 is a table showing an example of the ammonia concentration relationship information. As shown in FIG. 2, the ammonia concentration relationship information shows the relationship between the temperature (horizontal axis) and the pressure (vertical axis), and the ammonia concentration (e.g., 80%, 25%, . . .). The temperature (horizontal axis (e.g., 100° C., 200° C., . . .)) in the ammonia concentration relationship information corresponds to the temperature of the reformed gas detected by the temperature sensor 30 provided in the reformed gas supply passage 62. The pressure (vertical axis (e.g., 0 kPa, 100 kPa, . . .)) in the ammonia concentration relationship information corresponds to the pressure of the reformed gas detected by the pressure sensor 32 provided in the reformed gas supply passage 62. The ammonia concentration (e.g., 80%, 25%, . . .) in the ammonia concentration relationship information corresponds to the concentration of ammonia contained in the reformed gas passing through the reformed gas supply passage 62. The ammonia concentration relationship information is created in advance, for example, based on an experiment or an analysis. The ammonia concentration relationship information is not limited to the table shown in Fig. 2, and may be represented, for example, by a graph or a function. The control unit 50 estimates the concentration of ammonia contained in the reformed gas passing through the reformed gas supply path 62 based on the temperature detected by the temperature sensor 30, the pressure detected by the pressure sensor 32, and the ammonia concentration relationship information. For example, when the temperature detected by the temperature sensor 30 is 100°C and the pressure detected by the pressure sensor 32 is 0 kPa, the control unit 50 estimates the concentration of ammonia contained in the reformed gas to be 80% based on the ammonia concentration relationship information.

[0035] (Heat amount control process; Fig. 3, Fig. 4) Next, the heating amount control process of the first embodiment will be described. The heating amount control process is started, for example, when there is an instruction to start the reformer 12. At the time when the heating amount control process is started, the first heater 40 (electric heater) provided in the reformer 12 is in an off state. As shown in FIG. 3, in S10 of the heating amount control process, the control unit 50 judges whether or not the concentration of ammonia contained in the reformed gas estimated by the ammonia concentration relationship information (see FIG. 2) is equal to or higher than a predetermined first threshold value Th1 (for example, 50%). The ammonia concentration in S10 is specified based on the detected temperature of the temperature sensor 30, the detected pressure of the pressure sensor 32, and the ammonia concentration relationship information (see FIG. 2). The predetermined first threshold value Th1 is a value less than a predetermined concentration allowable value Ta (for example, 60%) (see FIG. 4). The predetermined concentration allowable value Ta is set, for example, according to the ammonia removal capacity of the remover 14. If it is determined in S10 that the ammonia concentration is equal to or higher than the first threshold value Th1 (in the case of YES), the process proceeds to S12. If it is determined in S10 that the concentration of ammonia is less than the first threshold value Th1 (if NO), the process waits.

[0036] In S12 after YES in S10, the control unit 50 turns on the power supply to the first heater 40 (electric heater) provided in the reformer 12 (see FIG. 4). When the power supply to the first heater 40 is turned on, the first heater 40 generates heat and heats the raw material gas inside the reformer 12. This increases the temperature of the raw material gas and promotes reforming of the raw material gas. As a result, the decomposition of ammonia is promoted and the concentration of ammonia contained in the reformed gas decreases. The temperature of the reformed gas increases.

[0037] In the next S14, the control unit 50 judges whether the ammonia concentration contained in the reformed gas estimated by the ammonia concentration relation information (see FIG. 2) is less than a predetermined second threshold value Th2 (for example, 10%). The ammonia concentration in S14 is specified based on the temperature detected by the temperature sensor 30, the pressure detected by the pressure sensor 32, and the ammonia concentration relation information (see FIG. 2). The predetermined second threshold value Th2 is a value less than the above-mentioned first threshold value Th1 (see FIG. 4). If it is judged in S14 that the ammonia concentration is less than the second threshold value Th2 (YES), the process proceeds to S16. If it is judged in S14 that the ammonia concentration is equal to or greater than the second threshold value Th2 (NO), the process returns to S12. In S12, the power supply of the first heater 40 (electric heater) is kept on, and the heating of the raw material gas by the first heater 40 is kept.

[0038] In S16 after YES in S14, the control unit 50 turns off the power supply to the first heater 40 (electric heater) (see FIG. 4). When the power supply to the first heater 40 is turned off, the heating of the raw material gas by the first heater 40 stops. As a result, the concentration of ammonia contained in the reformed gas increases, and the temperature of the reformed gas decreases.

[0039] In the next S18, the control unit 50 judges whether or not there is an instruction to stop the reformer 12. If it is judged that there is an instruction to stop the reformer 12 (if YES), the heating amount control process ends. If it is judged that there is no instruction to stop the reformer 12 (if NO), the process returns to S10. The control unit 50 repeats the above process.

[0040] (effect) The above has described the fuel cell system 2 of Example 1. As described above, the fuel cell system 2 includes the reformer 12 that generates reformed gas by reforming a raw material gas, the first heater 40 that heats the raw material gas in the reformer 12, the reformed gas supply passage 62 through which the reformed gas generated by the reformer 12 passes, the temperature sensor 30 that detects the temperature of the reformed gas passing through the reformed gas supply passage 62, the fuel cell 16 that generates power using the fuel gas generated by removing ammonia from the reformed gas that has passed through the reformed gas supply passage 62, and the control unit 50 that controls the amount of heat generated by the first heater 40 depending on the concentration of ammonia contained in the reformed gas estimated from the temperature detected by the temperature sensor 30.

[0041] According to the above configuration, it is possible to suppress the concentration of ammonia contained in the reformed gas while suppressing the amount of heat in the reformer 12. For example, when the concentration of ammonia estimated from the temperature detected by the temperature sensor 30 is high, it is estimated that the decomposition of ammonia is not promoted in the reformer 12. In this case, by increasing the amount of heat by the first heater 40, it is possible to promote the decomposition of ammonia, and it is possible to suppress the concentration of ammonia contained in the reformed gas. In addition, when the concentration of ammonia estimated from the temperature detected by the temperature sensor 30 is low, it is estimated that the decomposition of ammonia is promoted in the reformer 12. In this case, it is possible to reduce the amount of heat by the first heater 40. Since it is only necessary to increase the amount of heat when the decomposition of ammonia is not promoted, it is possible to suppress the amount of heat in the reformer 12.

[0042] The fuel cell system 2 also includes a pressure sensor 32 that detects the pressure of the reformed gas passing through the reformed gas supply passage 62. The control unit 50 controls the amount of heat generated by the first heater 40 in accordance with the concentration of ammonia contained in the reformed gas estimated from the temperature detected by the temperature sensor 30 and the pressure detected by the pressure sensor 32. With this configuration, the concentration of ammonia contained in the reformed gas is estimated from the temperature detected by the temperature sensor 30 and the pressure detected by the pressure sensor 32, improving the estimation accuracy. This allows the amount of heat generated by the first heater 40 to be controlled with high accuracy.

[0043] When it is estimated that the concentration of ammonia contained in the reformed gas is equal to or higher than a predetermined first threshold value Th1, the control unit 50 increases the amount of heating by the first heater 40. According to this configuration, by increasing the amount of heating when the concentration of ammonia is high, it is possible to promote decomposition of ammonia and reduce the concentration of ammonia.

[0044] When it is estimated that the concentration of ammonia contained in the reformed gas is less than a predetermined second threshold value Th2 which is less than the first threshold value Th1, the control unit 50 reduces the amount of heating by the first heater 40. According to this configuration, by reducing the amount of heating when the concentration of ammonia is low, unnecessary heating can be suppressed.

[0045] The first heater 40 heats the source gas by Joule heat. With this configuration, the amount of heat applied by the first heater 40 can be controlled with high precision.

[0046] The fuel cell system 2 includes a remover 14 that generates fuel gas by removing ammonia from the reformed gas that has passed through the reformed gas supply passage 62. With this configuration, it is possible to supply high-quality fuel gas with a low concentration of ammonia to the fuel cell 16. Furthermore, if the configuration is such that the concentration of ammonia contained in the reformed gas can be suppressed, it is possible to suppress the amount of ammonia removed by the remover 14, thereby reducing the load on the remover 14.

[0047] Example 2 Next, a fuel cell system 2 of Example 2 will be described. In the following, the description of the same configuration as that of Example 1 may be omitted. As shown in Fig. 5, the fuel cell system 2 of Example 2 includes a second heater 42 (another example of a heating section) and a third heater 44 (another example of a heating section) provided in the reformer 12. In addition, the fuel cell system 2 of Example 2 includes a reformed gas branch passage 80 connected to the reformed gas supply passage 62, and an exhaust gas branch passage 90 connected to the exhaust gas passage 66.

[0048] The upstream end of the reformed gas branch passage 80 is connected to the reformed gas supply passage 62 downstream of the temperature sensor 30 and the pressure sensor 32 and upstream of the heat exchanger 22. In a modified example, the upstream end of the reformed gas branch passage 80 may be connected to the reformed gas supply passage 62 upstream of the temperature sensor 30 and the pressure sensor 32. The downstream end of the reformed gas branch passage 80 is connected to the second heater 42 provided in the reformer 12. The reformed gas is supplied from the reformed gas supply passage 62 to the second heater 42 through the reformed gas branch passage 80. The reformed gas discharged from the reformer 12 is supplied to the second heater 42.

[0049] The reformed gas branch path 80 is provided with a reformed gas valve 82 that opens and closes the reformed gas branch path 80. When the reformed gas valve 82 is opened, the reformed gas is supplied to the second heater 42, and when the reformed gas valve 82 is closed, the reformed gas is no longer supplied to the second heater 42.

[0050] The second heater 42 is a heat exchanger, and heats the raw material gas and cools the reformed gas by heat exchange between the reformed gas supplied from the reformed gas branch path 80 and the raw material gas inside the reformer 12. The second heater 42 (heat exchanger) increases the temperature of the raw material gas by the heat of the reformed gas discharged from the reformer 12.

[0051] An upstream end of a reformed gas return path 84 is connected to the second heater 42. A downstream end of the reformed gas return path 84 is connected to the reformed gas supply path 62 downstream of the temperature sensor 30 and the pressure sensor 32 and upstream of the heat exchanger 22. In a modified example, the downstream end of the reformed gas return path 84 may be connected to the reformed gas supply path 62 downstream of the heat exchanger 22. The reformed gas is supplied (returned) from the second heater 42 to the reformed gas supply path 62 through the reformed gas return path 84.

[0052] The exhaust gas branch passage 90 has an upstream end connected to the exhaust gas passage 66 and a downstream end connected to the third heater 44. Exhaust gas is supplied from the exhaust gas passage 66 to the third heater 44 through the exhaust gas branch passage 90. Exhaust gas discharged from the fuel cell 16 is supplied to the third heater 44.

[0053] The exhaust gas branch passage 90 is provided with an exhaust gas valve 92 that opens and closes the exhaust gas branch passage 90. When the exhaust gas valve 92 is opened, exhaust gas is supplied to the third heater 44, and when the exhaust gas valve 92 is closed, exhaust gas is no longer supplied to the third heater 44.

[0054] The third heater 44 is a heat exchanger, and heats the raw material gas and cools the exhaust gas by heat exchange between the exhaust gas supplied from the exhaust gas branch passage 90 and the raw material gas inside the reformer 12. The third heater 44 (heat exchanger) uses the heat of the exhaust gas discharged from the fuel cell 16 to increase the temperature of the raw material gas.

[0055] The upstream end of a second exhaust gas passage 94 is connected to the third heater 44. The downstream end of the second exhaust gas passage 94 is connected to an external discharge destination (not shown), and the exhaust gas is discharged through the second exhaust gas passage 94 to the discharge destination.

[0056] (Heat amount control process; Fig. 6) Next, a description will be given of the heat amount control process of the second embodiment. When the heat amount control process of the second embodiment is started, the first heater 40 (electric heater) provided in the reformer 12 is in an off state. When the heat amount control process of the second embodiment is started, the reformed gas valve 82 provided in the reformed gas branch path 80 is closed, and the exhaust gas valve 92 provided in the exhaust gas branch path 90 is also closed.

[0057] 6, in S12 of the heating amount control process of the second embodiment, the control unit 50 turns on the power supply of the first heater 40 (electric heater). Also, in S12, the control unit 50 opens the reformed gas valve 82 provided in the reformed gas branch path 80 and opens the exhaust gas valve 92 provided in the exhaust gas branch path 90.

[0058] When the power supply of the first heater 40 is turned on, the first heater 40 generates heat, and the raw material gas inside the reformer 12 is heated. When the reformed gas valve 82 is opened, the reformed gas is supplied to the second heater 42 through the reformed gas branch path 80, and the raw material gas inside the reformer 12 is heated by the heat of the reformed gas. When the exhaust gas valve 92 is opened, the exhaust gas is supplied to the second heater 42 through the exhaust gas branch path 90, and the raw material gas inside the reformer 12 is heated by the heat of the exhaust gas. This increases the temperature of the raw material gas, and promotes the reforming of the raw material gas. As a result, the decomposition of ammonia is promoted, and the concentration of ammonia contained in the reformed gas decreases.

[0059] 6, in S16 of the heating amount control process of the second embodiment, the control unit 50 turns off the power supply to the first heater 40 (electric heater). Also, in S16, the control unit 50 closes the reformed gas valve 82 provided in the reformed gas branch path 80 and closes the exhaust gas valve 92 provided in the exhaust gas branch path 90.

[0060] When the power supply to the first heater 40 is turned off, the heating of the raw material gas by the first heater 40 stops. Furthermore, when the reformed gas valve 82 is closed, the reformed gas is no longer supplied to the second heater 42, and the heating of the raw material gas by the heat of the reformed gas stops. Furthermore, when the exhaust gas valve 92 is closed, the exhaust gas is no longer supplied to the second heater 42, and the heating of the raw material gas by the heat of the exhaust gas stops. As a result, the heating of the raw material gas by the second heater 42 stops.

[0061] (effect) The fuel cell system 2 of the second embodiment has been described above. As described above, the fuel cell system 2 includes the second heater 42 that heats the raw material gas with the heat of the reformed gas generated by the reformer 12. The fuel cell system 2 also includes the third heater 44 that heats the raw material gas with the heat of the exhaust gas discharged from the fuel cell 16. The control unit 50 controls the amount of heat in the reformer 12 by controlling the opening and closing of the reformed gas valve 82 provided in the reformed gas branch path 80. The control unit 50 also controls the amount of heat in the reformer 12 by controlling the opening and closing of the exhaust gas valve 92 provided in the exhaust gas branch path 90.

[0062] According to this configuration, the raw material gas can be heated by effectively utilizing the heat of the reformed gas. Also, the raw material gas can be heated by effectively utilizing the heat of the exhaust gas of the fuel cell 16. With this configuration, as in the first embodiment, the concentration of ammonia contained in the reformed gas can be suppressed while suppressing the amount of heat in the reformer 12.

[0063] Moreover, according to the above configuration, the temperature of the reformed gas can be lowered by increasing the temperature of the raw material gas. This makes it possible to lower the temperature of the reformed gas supplied to the remover 14, and facilitates the removal of ammonia in the remover 14. Furthermore, the temperature of the exhaust gas can be lowered by increasing the temperature of the raw material gas. This makes it possible to lower the temperature of the exhaust gas discharged to the outside, and thus makes it possible to safely discharge the exhaust gas.

[0064] (Modification) (1) In the above-mentioned first and second embodiments, the ammonia concentration relationship information (see FIG. 2) for estimating the concentration of ammonia contained in the reformed gas is information indicating the relationship between the temperature and pressure and the concentration of ammonia, but is not limited thereto. In a modified example, as shown in FIG. 7, the ammonia concentration relationship information may be information indicating the relationship between the temperature and the concentration of ammonia. The temperature (horizontal axis (e.g., 100° C., 200° C., . . .)) in the ammonia concentration relationship information in the modified example corresponds to the temperature of the reformed gas detected by the temperature sensor 30 provided in the reformed gas supply passage 62. The ammonia concentration (e.g., 80%, 25%, . . .) in the ammonia concentration relationship information corresponds to the concentration of ammonia contained in the reformed gas passing through the reformed gas supply passage 62. The control unit 50 estimates the concentration of ammonia contained in the reformed gas passing through the reformed gas supply passage 62 based on the temperature detected by the temperature sensor 30 and the ammonia concentration relationship information. In the modified example, the pressure sensor 32 can be omitted.

[0065] (2) In a modified example, the control unit 50 may be configured to control the amount of heating by adjusting the amount of electricity supplied to the first heater 40 (electric heater). For example, the control unit 50 may reduce the amount of electricity supplied to the first heater 40 to reduce the amount of heating, and increase the amount of electricity supplied to the first heater 40 to increase the amount of heating. The control unit 50 does not necessarily have to turn the power of the first heater 40 on and off.

[0066] (3) In a modified example, the control unit 50 may be configured to control the amount of heating by adjusting the opening of the reformed gas valve 82 provided in the reformed gas branch path 80. For example, the control unit 50 may reduce the amount of heating by reducing the opening of the reformed gas valve 82, and increase the amount of heating by increasing the opening of the reformed gas valve 82. The control unit 50 does not necessarily have to open / close the reformed gas valve 82.

[0067] (4) In a modified example, the control unit 50 may be configured to control the amount of heating by adjusting the opening of the exhaust gas valve 92 provided in the exhaust gas branch passage 90. For example, the control unit 50 may reduce the amount of heating by reducing the opening of the exhaust gas valve 92, and may increase the amount of heating by increasing the opening of the exhaust gas valve 92. The control unit 50 does not necessarily have to open / close the exhaust gas valve 92.

[0068] (5) In a modified example, the fuel cell system 2 may be configured to include one or two of the first heater 40, the second heater 42, and the third heater 44. One or two of the first heater 40, the second heater 42, and the third heater 44 may be omitted.

[0069] (6) In a modified example, the control unit 50 may energize the first heater 40 (electric heater) with the power generated by the fuel cell 16.

[0070] (7) In a modified example, the vaporizer 20 may be omitted. In this case, the fuel cell system 2 may include a gas cylinder (not shown) instead of the raw material tank 10. The gas cylinder stores a raw material gas (e.g., ammonia gas, hydrocarbon gas, formic acid gas, hydrazine gas, etc.). A raw material gas supply path 60 is connected to the gas cylinder. When a raw material gas other than ammonia gas is used, ammonia is generated as a by-product in the reformer 12.

[0071] (8) In a modified example, the remover 14 may be configured to remove ammonia by passing the reformed gas through water.

[0072] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0073] 2: fuel cell system, 10: raw material tank, 12: reformer, 14: remover, 16: fuel cell, 20: vaporizer, 22: heat exchanger, 30: temperature sensor, 32: pressure sensor, 40: first heater, 42: second heater, 44: third heater, 50: control unit, 52: memory unit, 60: raw material gas supply channel, 62: reformed gas supply channel, 64: fuel gas supply channel, 66: exhaust gas channel, 68: air supply channel, 70: liquid supply channel, 72: pump, 80: reformed gas branch channel, 82: reformed gas valve, 84: reformed gas return channel, 90: exhaust gas branch channel, 92: exhaust gas valve, 94: second exhaust gas channel

Claims

1. a reformer that generates a reformed gas by reforming a raw material gas; a heating unit that heats the raw material gas in the reformer; a gas passage through which the reformed gas generated by the reformer passes; a temperature sensor for detecting a temperature of the reformed gas passing through the gas passage; a pressure sensor for detecting a pressure of the reformed gas passing through the gas passage; a fuel cell that generates power using a fuel gas produced by removing ammonia from the reformed gas that has passed through the gas passage; a control unit that controls the amount of heat generated by the heating unit in accordance with a concentration of ammonia contained in the reformed gas estimated from the temperature detected by the temperature sensor and the pressure detected by the pressure sensor.

2. A reformer for generating a reformed gas by reforming a raw material gas; a heating unit that heats the raw material gas in the reformer; a gas passage through which the reformed gas generated by the reformer passes; a temperature sensor for detecting a temperature of the reformed gas passing through the gas passage; a fuel cell that generates power using a fuel gas produced by removing ammonia from the reformed gas that has passed through the gas passage; a control unit that controls an amount of heat generated by the heating unit in response to a concentration of ammonia contained in the reformed gas estimated from a temperature detected by the temperature sensor; The control unit increases an amount of heat applied by the heating unit when a concentration of ammonia contained in the reformed gas is estimated to be equal to or higher than a predetermined first threshold value.

3. A fuel cell system as claimed in claim 2, The control unit reduces an amount of heating by the heating unit when a concentration of ammonia contained in the reformed gas is estimated to be less than a predetermined second threshold value.

4. A fuel cell system as claimed in claim 3, A fuel cell system, wherein the second threshold value is less than the first threshold value.

5. A reformer for generating a reformed gas by reforming a raw material gas; a heating unit that heats the raw material gas in the reformer; a gas passage through which the reformed gas generated by the reformer passes; a temperature sensor for detecting a temperature of the reformed gas passing through the gas passage; a fuel cell that generates power using a fuel gas produced by removing ammonia from the reformed gas that has passed through the gas passage; a control unit that controls an amount of heat generated by the heating unit in response to a concentration of ammonia contained in the reformed gas estimated from a temperature detected by the temperature sensor; The control unit reduces an amount of heating by the heating unit when a concentration of ammonia contained in the reformed gas is estimated to be less than a predetermined second threshold value.

6. 6. A fuel cell system according to claim 1, The heating unit includes a first heater that heats the raw material gas by Joule heat.

7. 7. A fuel cell system according to claim 1, a second heater configured to heat the raw material gas by heat of the reformed gas generated by the reformer;

8. 8. A fuel cell system according to claim 1, The heating unit includes a third heater that heats the raw material gas with heat of exhaust gas discharged from the fuel cell.

9. 9. A fuel cell system according to claim 1, The fuel cell system further comprises a remover that removes ammonia from the reformed gas that has passed through the gas passage, thereby producing the fuel gas.

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