Ammonia Removal System

Abstract

To provide a technique capable of using an eliminator to the maximum ability thereof and also capable of reducing the replacement frequency of the eliminator.SOLUTION: An ammonia removal system includes: a sensor detecting the state of reformed gas flowing through a first reformed gas passage; a first valve provided in the first reformed gas passage; a first eliminator generating fuel gas by removing ammonia from reformed gas passing through the first reformed gas passage; and a control unit. The first valve is configured to be switchable between a first state where reformed gas is supplied to the first eliminator through the first reformed gas passage and a second state where reformed gas is not supplied to the first eliminator through the first reformed gas passage. The control unit switches the first valve from the first state to the second state when it is determined, based on the detection value of the sensor, that the amount of ammonia supplied to the first eliminator through the first reformed gas passage reaches a predetermined first reference amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed herein relates to an ammonia removal system. [Background technology]

[0002] Patent Document 1 discloses an ammonia removal system. The ammonia removal system of Patent Document 1 includes a reformed gas passage through which reformed gas flows, an on-off valve provided in the reformed gas passage, and a remover that removes ammonia from the reformed gas that has passed through the reformed gas passage. The ammonia removal system of Patent Document 1 also includes an ammonia concentration measuring device that measures the ammonia concentration in the treated gas after treatment in the remover, and closes the on-off valve when the ammonia concentration measured by the ammonia concentration measuring device exceeds a threshold value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6810910 Summary of the Invention [Problem to be solved by the invention]

[0004] In ammonia removal equipment, it is difficult to predict when the remover will break through, and the remover may not be able to be used to its full capacity, resulting in frequent replacement of the remover. In the ammonia removal equipment of Patent Document 1, the ammonia concentration in the treated gas after treatment by the remover is measured, so the ammonia concentration may be measured after the remover has broken through, resulting in the on-off valve being closed after the remover has broken through. To prevent this from happening, the remover must be replaced early, resulting in frequent replacement of the remover. Therefore, this specification provides a technology that enables the remover to be used to its full capacity and reduces the frequency of replacement of the remover. [Means for solving the problem]

[0005] The ammonia removal system disclosed in this specification includes a reformer that generates reformed gas by reforming a raw material gas, a first reformed gas passage through which the reformed gas generated by the reformer flows, a sensor that detects the state of the reformed gas flowing through the first reformed gas passage, a first valve provided in the first reformed gas passage, a first remover that generates fuel gas by removing ammonia from the reformed gas that has passed through the first reformed gas passage, and a control unit. The first valve is configured to be switchable between a first state in which reformed gas is supplied to the first remover through the first reformed gas passage and a second state in which reformed gas is not supplied to the first remover through the first reformed gas passage. The control unit switches the first valve from the first state to the second state when it determines, based on the detection value of the sensor, that the amount of ammonia supplied to the first remover through the first reformed gas passage has reached a predetermined first reference amount.

[0006] According to this configuration, when it is determined that the amount of ammonia supplied to the first eliminator has reached the first reference amount, the first valve is switched from the first state to the second state, so that the reformed gas can be supplied to the first eliminator until just before breakthrough of the first eliminator. This allows the first eliminator to be used to the limit of its capacity, and as a result, the frequency of replacement of the first eliminator can be reduced.

[0007] The sensors may include a temperature sensor that detects a temperature of the reformed gas flowing through the first reformed gas passage, and a pressure sensor that detects a pressure of the reformed gas flowing through the first reformed gas passage. The control unit may determine that the amount of ammonia supplied to the first remover through the first reformed gas passage has reached the first reference amount when an integral value obtained by integrating, over time, an ammonia concentration estimated from a detection value of the temperature sensor and a detection value of the pressure sensor reaches a predetermined first integral reference value.

[0008] According to this configuration, the amount of ammonia supplied to the first remover can be estimated with high accuracy by using the temperature sensor and the pressure sensor, thereby enabling the timing of switching the first valve from the first state to the second state to be controlled with high accuracy.

[0009] The ammonia removal system may further include a second reformed gas passage branching off from the first reformed gas passage via the first valve and through which the reformed gas generated by the reformer flows, and a second remover that produces fuel gas by removing ammonia from the reformed gas that has passed through the second reformed gas passage. The first valve may be configured to be switchable between the first state in which the reformed gas is supplied to the first remover through the first reformed gas passage but is not supplied to the second remover through the second reformed gas passage, and the second state in which the reformed gas is not supplied to the first remover through the first reformed gas passage but is supplied to the second remover through the second reformed gas passage.

[0010] According to this configuration, when the first remover has been used to its limit, the second remover can be used in place of the first remover, thereby enabling continuous and efficient use of the ammonia removal system.

[0011] The ammonia removal system may further include a second reformed gas passage branching from the first reformed gas passage upstream of the first valve and through which reformed gas generated by the reformer flows, a second valve provided in the second reformed gas passage, and a second remover that produces fuel gas by removing ammonia from the reformed gas that has passed through the second reformed gas passage. The second valve may be configured to be switchable between a first state in which reformed gas is supplied to the second remover through the second reformed gas passage and a second state in which reformed gas is not supplied to the second remover through the second reformed gas passage. When the control unit determines, based on the detection value of the sensor, that the amount of ammonia supplied to the first remover through the first reformed gas passage has reached a predetermined third reference amount that is less than the first reference amount, the control unit may switch the second valve from the second state to the first state and control an aperture of the second valve to an aperture less than that of the first valve.

[0012] This configuration allows a period during which the first and second eliminators are used in parallel, which allows for smooth switching from the first eliminator to the second eliminator without interrupting the flow of reformed gas.

[0013] The control unit may increase the opening of the second valve when, after controlling the opening of the second valve to an opening less than the opening of the first valve, it determines, based on the detection value of the sensor, that the amount of ammonia supplied to the first remover through the first reformed gas passage has reached the predetermined first reference amount.

[0014] According to this configuration, it is possible to smoothly switch to the second remover at the timing when the first remover has been used up to its capacity limit.

[0015] The ammonia removal system disclosed in this specification includes a reformer that generates reformed gas by reforming a raw material gas, a first reformed gas passage through which the reformed gas generated by the reformer flows, a sensor that detects the state of the reformed gas flowing through the first reformed gas passage, a first pump provided in the first reformed gas passage, a first remover that generates fuel gas by removing ammonia from the reformed gas that has passed through the first reformed gas passage, and a control unit. The first pump is configured to be switchable between an operating state in which the reformed gas is supplied to the first remover through the first reformed gas passage by pressure-feeding the reformed gas, and a stopped state in which the reformed gas is not supplied to the first remover through the first reformed gas passage. The control unit switches the first pump from the operating state to the stopped state when it determines, based on the detection value of the sensor, that the amount of ammonia supplied to the first remover through the first reformed gas passage has reached a predetermined first reference amount.

[0016] According to this configuration, similarly to the above, the first remover can be used to the limit of its capacity, and the frequency of replacement of the first remover can be reduced.

[0017] The ammonia removal system may further include a second reformed gas passage branching from the first reformed gas passage upstream of the first pump and through which the reformed gas generated by the reformer flows, a second pump provided in the second reformed gas passage, and a second remover that produces fuel gas by removing ammonia from the reformed gas that has passed through the second reformed gas passage. The second pump may be configured to be switchable between an operating state in which the reformed gas is supplied to the second remover through the second reformed gas passage by pressure-feeding the reformed gas, and a stopped state in which the reformed gas is not supplied to the second remover through the second reformed gas passage. When the control unit determines, based on the detection value of the sensor, that the amount of ammonia supplied to the first remover through the first reformed gas passage has reached a predetermined third reference amount that is less than a predetermined first reference amount, the control unit may switch the second pump from the stopped state to the operating state and control the output of the second pump to be less than the output of the first pump.

[0018] According to this configuration, similar to the above, when switching from the first remover to the second remover, the switching can be performed smoothly without interrupting the flow of the reformed gas.

[0019] A fuel cell system may include the above-described ammonia removal system and a fuel cell that generates power using the fuel gas produced by the first remover.

[0020] According to this configuration, it is possible to prevent ammonia contained in the reformed gas from being supplied to the fuel cell due to breakthrough of the first remover while using the first remover to the limit of its capacity. The above-described ammonia removal system is particularly effective in a configuration including a fuel cell. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram schematically illustrating a fuel cell system according to a first embodiment. [Figure 2] 10 is a table showing an example of ammonia concentration related information. [Figure 3] 4 is a flowchart of a three-way valve control process according to the first embodiment. [Figure 4] FIG. 10 is a diagram showing an example of the time integral of the ammonia concentration. [Figure 5] FIG. 10 is a diagram schematically illustrating a fuel cell system according to a second embodiment. [Figure 6] 10 is a flowchart of an on-off valve control process according to a second embodiment. [Figure 7] FIG. 4 is a diagram showing an example of opening degree control of an on-off valve. [Figure 8] FIG. 10 is a diagram showing a schematic diagram of a fuel cell system according to a third embodiment. [Figure 9] 10 is a flowchart of a pump control process according to a third embodiment. [Figure 10] FIG. 4 is a diagram showing an example of pump output control. [Figure 11] FIG. 10 is a diagram showing a schematic diagram of a fuel cell system according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] (First Example) A fuel cell system 2 equipped with an ammonia removal system according to a first embodiment will be described with reference to the drawings. As shown in Fig. 1, the fuel cell system 2 includes a raw material tank 10, a vaporizer 12, a reformer 14, a first remover 16, a second remover 18, a fuel cell 20, and a controller 50.

[0023] Raw material tank 10 stores liquid ammonia as a raw material. A liquid passage 32 through which liquid ammonia flows is connected to raw material tank 10. An upstream end of liquid passage 32 is connected to raw material tank 10, and a downstream end of liquid passage 32 is connected to vaporizer 12. Liquid ammonia is supplied from raw material tank 10 to vaporizer 12 through liquid passage 32. A pump 22 is provided in liquid passage 32 to pump liquid ammonia from the upstream side to the downstream side of liquid passage 32.

[0024] The vaporizer 12 heats and vaporizes liquid ammonia supplied through the liquid passage 32. This generates gaseous ammonia as a raw material gas. A raw material gas passage 34 through which the raw material gas (gaseous ammonia) flows is connected to the vaporizer 12. The upstream end of the raw material gas passage 34 is connected to the vaporizer 12, and the downstream end is connected to the reformer 14. The raw material gas is supplied from the vaporizer 12 to the reformer 14 through the raw material gas passage 34.

[0025] The reformer 14 generates reformed gas by reforming the raw material gas (gaseous ammonia) supplied through the raw material gas passage 34. Catalysts used for reforming the raw material gas include, for example, copper, nickel, and ruthenium. The reformed gas contains hydrogen produced by reforming the raw material gas. The reformed gas also contains ammonia, a by-product of the reforming, and undecomposed ammonia. The reformer 14 includes a heater 15 that heats the raw material gas during reforming of the raw material gas. The heater 15 is, for example, an electric or gas type.

[0026] A first reformed gas passage 36, through which the generated reformed gas flows, is connected to the reformer 14. The upstream end of the first reformed gas passage 36 is connected to the reformer 14, and the downstream end is connected to the first remover 16. The reformed gas is supplied from the reformer 14 to the first remover 16 through the first reformed gas passage 36.

[0027] The first reformed gas passage 36 is provided with a temperature sensor 28, a pressure sensor 30, a heat exchanger 31, and a first three-way valve 24. The temperature sensor 28 is provided in the first reformed gas passage 36 upstream of the first three-way valve 24 and the heat exchanger 31. The temperature sensor 28 detects the temperature of the reformed gas flowing through the first reformed gas passage 36 upstream of the first three-way valve 24 and the heat exchanger 31. The temperature sensor 28 detects the temperature of the reformed gas before it is heat exchanged by the heat exchanger 31. Information on the temperature detected by the temperature sensor 28 is transmitted to the controller 50 at predetermined time intervals (for example, every 5 seconds).

[0028] The pressure sensor 30 is provided in the first reformed gas passage 36 upstream of the first three-way valve 24 and the heat exchanger 31. The pressure sensor 30 detects the pressure of the reformed gas flowing through the first reformed gas passage 36 upstream of the first three-way valve 24 and the heat exchanger 31. The pressure sensor 30 detects the pressure of the reformed gas before it is heat exchanged by the heat exchanger 31. Information on the detected pressure by the pressure sensor 30 is transmitted to the controller 50 at predetermined time intervals (for example, every 5 seconds).

[0029] The heat exchanger 31 is provided in the first reformed gas passage 36 upstream of the first three-way valve 24. The heat exchanger 31 cools the reformed gas flowing through the first reformed gas passage 36 upstream of the first three-way valve 24 to lower the temperature of the reformed gas. The heat exchanger 31 lowers the temperature of the reformed gas by exchanging heat between the reformed gas and an external fluid. The structure of the heat exchanger 31 is not particularly limited, but may include, for example, fins for heat exchange.

[0030] The first three-way valve 24 is provided in the first reformed gas passage 36 downstream of the temperature sensor 28, the pressure sensor 30, and the heat exchanger 31. A second reformed gas passage 38 is connected to the first three-way valve 24. The upstream end of the second reformed gas passage 38 is connected to the first three-way valve 24, and the downstream end is connected to the second remover 18. The second reformed gas passage 38 branches off from the first reformed gas passage 36 via the first three-way valve 24. The second reformed gas passage 38 is arranged in parallel with the first reformed gas passage 36 downstream of the first three-way valve 24.

[0031] The first three-way valve 24 opens and closes the first reformed gas passage 36 and the second reformed gas passage 38. The first three-way valve 24 is configured to be switchable between a first state and a second state. When the first three-way valve 24 is in the first state, the reformed gas generated in the reformer 14 is supplied to the first remover 16 through the first reformed gas passage 36. When the first three-way valve 24 is in the first state, the reformed gas generated in the reformer 14 is not supplied to the second remover 18 through the second reformed gas passage 38. On the other hand, when the first three-way valve 24 is in the second state, the reformed gas generated in the reformer 14 is supplied to the second remover 18 through the first reformed gas passage 36 and the second reformed gas passage 38, which are upstream of the first three-way valve 24. When the first three-way valve 24 is in the second state, the reformed gas produced in the reformer 14 is not supplied to the first remover 16 through the first reformed gas passage 36 .

[0032] The first remover 16 removes ammonia from the reformed gas supplied through the first reformed gas passage 36 by using an adsorbent to adsorb the ammonia contained in the reformed gas. This produces a fuel gas with a reduced ammonia concentration. Examples of adsorbents used to adsorb ammonia include activated carbon, zeolite, and MOF (Metal Organic Framework). For example, the container of the first remover 16 is filled with an adsorbent. The first remover 16 can be replaced with a new first remover 16 after use. Alternatively, the adsorbent inside the first remover 16 may be replaced.

[0033] A first fuel gas passage 40, through which the generated fuel gas flows, is connected to the first remover 16. The upstream end of the first fuel gas passage 40 is connected to the first remover 16, and the downstream end is connected to the fuel cell 20. The fuel gas is supplied from the first remover 16 to the fuel cell 20 through the first fuel gas passage 40. A second three-way valve 26 is provided in the first fuel gas passage 40.

[0034] The second remover 18 is disposed in parallel with the first remover 16. The second remover 18 removes ammonia from the reformed gas supplied through the second reformed gas passage 38 by using an adsorbent to adsorb the ammonia contained in the reformed gas. This produces a fuel gas with a reduced ammonia concentration. Examples of adsorbents used to adsorb ammonia include activated carbon, zeolite, and MOF (Metal Organic Framework). For example, the container of the second remover 18 is filled with an adsorbent. The second remover 18 can be replaced with a new second remover 18 after use. Alternatively, the adsorbent inside the second remover 18 may be replaced.

[0035] A second fuel gas passage 42, through which the generated fuel gas flows, is connected to the second remover 18. The upstream end of the second fuel gas passage 42 is connected to the second remover 18, and the downstream end is connected to the second three-way valve 26. The second fuel gas passage 42 merges with the first fuel gas passage 40 via the second three-way valve 26. The second fuel gas passage 42 is arranged in parallel with the first fuel gas passage 40 upstream of the second three-way valve 26.

[0036] The second three-way valve 26 opens and closes the first fuel gas passage 40 and the second fuel gas passage 42. The second three-way valve 26 is configured to be switchable between a first state and a second state. When the second three-way valve 26 is in the first state, the fuel gas generated in the first eliminator 16 is supplied to the fuel cell 20 through the first fuel gas passage 40. When the second three-way valve 26 is in the first state, the fuel gas generated in the second eliminator 18 is not supplied to the fuel cell 20 through the second fuel gas passage 42. On the other hand, when the second three-way valve 26 is in the second state, the fuel gas generated in the second eliminator 18 is supplied to the fuel cell 20 through the second fuel gas passage 42 and the first fuel gas passage 40 downstream of the second three-way valve 26. When the second three-way valve 26 is in the second state, the fuel gas generated in the first eliminator 16 is not supplied to the fuel cell 20 through the first fuel gas passage 40.

[0037] The fuel cell 20 will now be described. In addition to the first fuel gas passage 40, an air passage 44 through which air flows is connected to the fuel cell 20. The upstream end of the air passage 44 is connected to an air supply source (not shown), and the downstream end is connected to the fuel cell 20. Air is supplied from the air supply source to the fuel cell 20 through the air passage 44. The upstream end of the air passage 44 may be open to the outside air.

[0038] The fuel cell 20 generates electricity using fuel gas supplied through the first fuel gas passage 40 and air supplied through the air passage 44. The fuel cell 20 includes, for example, a plurality of battery cells (not shown) stacked inside a container, and each battery cell generates electricity 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) or polymer electrolyte fuel cells (PEFCs), but are not limited to these. In the fuel cell 20 that generates electricity using fuel gas, unreacted fuel gas is discharged as exhaust gas during power generation.

[0039] An exhaust gas passage 46 through which exhaust gas flows is connected to the fuel cell 20. The upstream end of the exhaust gas passage 46 is connected to the fuel cell 20, and the downstream end is connected to a discharge destination (not shown). The exhaust gas is discharged from the fuel cell 20 through the exhaust gas passage 46 to the discharge destination. The discharge destination may be, for example, the reformer 14, the first removal device 16, the second removal device 18, etc.

[0040] The controller 50 includes, for example, a CPU (not shown) and a storage unit 52 (for example, a 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.

[0041] Ammonia concentration relationship information is stored in the memory unit 52 of the controller 50. FIG. 2 is a table showing an example of the ammonia concentration relationship information. As shown in FIG. 2, the ammonia concentration relationship information indicates the relationship between temperature (horizontal axis) and 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 28 provided in the first reformed gas passage 36. 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 30 provided in the first reformed gas passage 36. The ammonia concentration (e.g., 80%, 25%, . . .) in the ammonia concentration relationship information corresponds to the concentration of ammonia contained in the reformed gas flowing through the first reformed gas passage 36. The ammonia concentration relationship information is created in advance based on, for example, experiments or analyses. The ammonia concentration relationship information is not limited to the table shown in Fig. 2 and may be represented, for example, as a graph or a function. The controller 50 estimates the concentration of ammonia contained in the reformed gas flowing through the first reformed gas passage 36 based on the temperature detected by the temperature sensor 28, the pressure detected by the pressure sensor 30, and the ammonia concentration relationship information. For example, if the temperature detected by the temperature sensor 28 is 100°C and the pressure detected by the pressure sensor 30 is 0 kPa, the controller 50 estimates the concentration of ammonia contained in the reformed gas to be 80% based on the ammonia concentration relationship information.

[0042] (Three-way valve control process; Figure 3) Next, the three-way valve control process of the first embodiment will be described. The three-way valve control process of the first embodiment is started, for example, when a used first removal device 16 is replaced with a new, unused first removal device 16. At the time when the three-way valve control process of the first embodiment is started, the first three-way valve 24 and the second three-way valve 26 are assumed to be in a first state. When the first three-way valve 24 is in the first state, the reformed gas generated in the reformer 14 is supplied to the first removal device 16 through the first reformed gas passage 36. When the first three-way valve 24 is in the first state, the reformed gas generated in the reformer 14 is not supplied to the second removal device 18 through the second reformed gas passage 38. Furthermore, when the second three-way valve 26 is in the first state, the fuel gas generated in the first removal device 16 is supplied to the fuel cell 20 through the first fuel gas passage 40. When the second three-way valve 26 is in the first state, the fuel gas produced in the second eliminator 18 is not supplied to the fuel cell 20 through the second fuel gas passage 42. It is assumed that the used second eliminator 18 is replaced with a new, unused second eliminator 18 while the first three-way valve 24 and the second three-way valve 26 are in the first state.

[0043] In the fuel cell system 2, the controller 50 acquires detected temperature information from the temperature sensor 28 at predetermined time intervals (e.g., every 5 seconds). The controller 50 also acquires detected pressure information from the pressure sensor 30 at predetermined time intervals (e.g., every 5 seconds). The controller 50 determines the ammonia concentration at predetermined time intervals (e.g., every 5 seconds) based on the detected temperature information acquired from the temperature sensor 28, the detected pressure information acquired from the pressure sensor 30, and ammonia concentration relationship information (see FIG. 2) stored in the storage unit 52. For example, when the temperature detected by the temperature sensor 28 is 100°C and the pressure detected by the pressure sensor 30 is 0 kPa, the controller 50 estimates that the concentration of ammonia contained in the reformed gas flowing through the first reformed gas passage 36 is 80% based on the ammonia concentration relationship information.

[0044] As shown in Fig. 3, in S2 of the three-way valve control process, the controller 50 time-integrates the ammonia concentration determined based on the ammonia concentration relationship information (see Fig. 2). As shown in Fig. 4, the controller 50 sequentially adds up the ammonia concentration at predetermined time intervals (for example, every 5 seconds).

[0045] As shown in FIG. 3, in the next S4, the controller 50 determines whether the time integral value of the ammonia concentration has reached a predetermined first integral reference value. If the time integral value of the ammonia concentration has reached the first integral reference value (YES), the process proceeds to S6. If the time integral value of the ammonia concentration has reached the first integral reference value, the controller 50 determines that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has reached a predetermined first reference amount. If the amount of ammonia that the first remover 16 can remove is defined as a limit removal amount, the predetermined first reference amount is an amount equal to or less than the limit removal amount. The predetermined first integral reference value is set to a value corresponding to the first reference amount. The first integral reference value and the first reference amount are determined in advance, for example, based on experiments or analyses.

[0046] If the time integral value of the ammonia concentration does not reach the first integral reference value in S4 (NO), the process returns to S2. If the time integral value of the ammonia concentration does not reach the first integral reference value, the controller 50 determines that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 does not reach the predetermined first reference amount. The controller 50 repeatedly performs the time integration of the ammonia concentration until the time integral value of the ammonia concentration reaches the first integral reference value.

[0047] In S6 after YES in S4, the controller 50 switches the first three-way valve 24 and the second three-way valve 26 from the first state to the second state. When the first three-way valve 24 is switched to the second state, the reformed gas generated in the reformer 14 is supplied to the second remover 18 through the second reformed gas passage 38. When the first three-way valve 24 is switched to the second state, the reformed gas generated in the reformer 14 is not supplied to the first remover 16 through the first reformed gas passage 36. Furthermore, when the second three-way valve 26 is switched to the second state, the fuel gas generated in the second remover 18 is supplied to the fuel cell 20 through the second fuel gas passage 42. When the second three-way valve 26 is switched to the second state, the fuel gas generated in the first remover 16 is not supplied to the fuel cell 20 through the first fuel gas passage 40.

[0048] After the process of S6 is executed and before the process of S12, which will be described later, is executed, the used first remover 16 is replaced with a new, unused first remover 16. For example, the user of the fuel cell system 2 replaces the first remover 16.

[0049] In S8 following S6, the controller 50 integrates the ammonia concentration determined based on the ammonia concentration relationship information over time, similar to S2 described above. In S10, the controller 50 determines whether the time integral of the ammonia concentration has reached a predetermined second integral reference value. The predetermined second integral reference value may be the same as or different from the first integral reference value in S4 described above. If the time integral of the ammonia concentration has reached the second integral reference value (YES), the process proceeds to S12. If the time integral of the ammonia concentration has reached the second integral reference value, the controller 50 determines that the amount of ammonia supplied to the second remover 18 through the second reformed gas passage 38 has reached a predetermined second reference amount. If the amount of ammonia that the second remover 18 can remove is defined as a limit removal amount, the predetermined second reference amount is an amount equal to or less than the limit removal amount. The predetermined second integral reference value is set to a value corresponding to the second reference amount. The second integral reference value and the second reference amount are determined in advance, for example, based on experiments or analysis.

[0050] If the time integral value of the ammonia concentration does not reach the second integral reference value in S10 (NO), the process returns to S8. If the time integral value of the ammonia concentration does not reach the second integral reference value, the controller 50 determines that the amount of ammonia supplied to the second remover 18 through the second reformed gas passage 38 does not reach the predetermined second reference amount. The controller 50 repeatedly performs the time integration of the ammonia concentration until the time integral value of the ammonia concentration reaches the second integral reference value.

[0051] In S12 after YES in S10, the controller 50 switches the first three-way valve 24 and the second three-way valve 26 from the second state to the first state. When the first three-way valve 24 is switched to the first state, the reformed gas generated in the reformer 14 is supplied to the first remover 16 through the first reformed gas passage 36. When the second three-way valve 26 is switched to the first state, the fuel gas generated in the first remover 16 is supplied to the fuel cell 20 through the first fuel gas passage 40. After S12, the process returns to S2 described above, and the processes from S2 to S12 are repeatedly executed.

[0052] After the process of S12 is executed and before the process of S6 described above is executed, the used second remover 18 is replaced with a new, unused second remover 18. For example, the user of the fuel cell system 2 replaces the second remover 18. The three-way valve control process is terminated appropriately based on, for example, a predetermined termination instruction.

[0053] (effect) The above has described the fuel cell system 2 of the first embodiment. As described above, the fuel cell system 2 includes the temperature sensor 28 that detects the temperature of the reformed gas flowing through the first reformed gas passage 36, the pressure sensor 30 that detects the pressure of the reformed gas flowing through the first reformed gas passage 36, the first three-way valve 24 provided in the first reformed gas passage 36, and the first remover 16 that produces fuel gas by removing ammonia from the reformed gas that has passed through the first reformed gas passage 36. The first three-way valve 24 is configured to be switchable between a first state in which the reformed gas is supplied to the first remover 16 through the first reformed gas passage 36, and a second state in which the reformed gas is not supplied to the first remover 16 through the first reformed gas passage 36. The controller 50 switches the first three-way valve 24 from the first state to the second state when it determines, based on the detection values ​​of the sensors 28, 30, that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has reached a predetermined first reference amount (S4, S6). The controller 50 determines that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has reached the first reference amount when an integral value obtained by integrating over time the ammonia concentration estimated from the temperature detected by the temperature sensor 28 and the pressure detected by the pressure sensor 30 reaches a predetermined first integral reference value (S2, S4). The fuel cell system 2 also includes a fuel cell 20 that generates electricity using the fuel gas produced by the first remover 16.

[0054] According to this configuration, by switching the first three-way valve 24 from the first state to the second state when it is determined that the amount of ammonia supplied to the first eliminator 16 has reached the first reference amount, the reformed gas can be supplied to the first eliminator 16 until just before breakthrough of the first eliminator 16. The first reference amount is an amount according to the ammonia removal capacity of the first eliminator 16. This allows the first eliminator 16 to be used to its capacity limit, thereby reducing the frequency of replacement of the first eliminator 16. Breakthrough of the first eliminator 16 can also be prevented. Furthermore, the amount of ammonia supplied to the first eliminator 16 can be accurately estimated by using the temperature sensor 28 and the pressure sensor 30. This allows accurate control of the timing of switching the first three-way valve 24 from the first state to the second state. Furthermore, while using the first eliminator 16 to its capacity limit, it is possible to prevent ammonia contained in the reformed gas from being supplied to the fuel cell 20 due to breakthrough of the first eliminator 16.

[0055] The fuel cell system 2 also includes a second reformed gas passage 38 branching off from the first reformed gas passage 36 via a first three-way valve 24, and a second remover 18 that produces fuel gas by removing ammonia from the reformed gas that has passed through the second reformed gas passage 38. The first three-way valve 24 is configured to be switchable between a first state in which the reformed gas is supplied to the first remover 16 through the first reformed gas passage 36 but is not supplied to the second remover 18 through the second reformed gas passage 38, and a second state in which the reformed gas is not supplied to the first remover 16 through the first reformed gas passage 36 but is supplied to the second remover 18 through the second reformed gas passage 38.

[0056] According to this configuration, when the first remover 16 has been used to its limit, the second remover 18 can be used in place of the first remover 16. This allows the fuel cell system 2 to be used continuously and efficiently.

[0057] Although one embodiment has been described above, the specific aspects are not limited to the above embodiment. In the following description, the same components as those in the above description will be assigned the same reference numerals and descriptions thereof will be omitted.

[0058] (Second Example) The fuel cell system 2 of the first embodiment described above includes the first three-way valve 24 and the second three-way valve 26, but is not limited to this configuration. As shown in Fig. 5, the fuel cell system 2 of the second embodiment includes a first on-off valve 60, a second on-off valve 62, a third on-off valve 64, and a fourth on-off valve 66 instead of the first three-way valve 24 and the second three-way valve 26.

[0059] The first on-off valve 60 is provided in the first reformed gas passage 36 and opens and closes the first reformed gas passage 36. The first on-off valve 60 is configured to be switchable between an open state (an example of a first state) and a closed state (an example of a second state). When the first on-off valve 60 is in the open state, the reformed gas generated in the reformer 14 is supplied to the first remover 16 through the first reformed gas passage 36. When the first on-off valve 60 is in the closed state, the reformed gas generated in the reformer 14 is not supplied to the first remover 16 through the first reformed gas passage 36. Furthermore, the opening degree of the first on-off valve 60 is controllable in the open state.

[0060] The second on-off valve 62 is provided in the second reformed gas passage 38 and opens and closes the second reformed gas passage 38. The upstream end of the second reformed gas passage 38 is connected to the first reformed gas passage 36 upstream of the first on-off valve 60, and the downstream end is connected to the second remover 18. The second reformed gas passage 38 branches off from the first reformed gas passage 36 upstream of the first on-off valve 60 and downstream of the temperature sensor 28, the pressure sensor 30, and the heat exchanger 31. The second on-off valve 62 is configured to be switchable between an open state (an example of a first state) and a closed state (an example of a second state). When the second on-off valve 62 is in the open state, the reformed gas generated in the reformer 14 is supplied to the second remover 18 through the first reformed gas passage 36 and the second reformed gas passage 38 upstream of the first on-off valve 60. When the second on-off valve 62 is in a closed state, the reformed gas generated in the reformer 14 is not supplied to the second remover 18 through the second reformed gas passage 38. In addition, the opening degree of the second on-off valve 62 can be controlled when it is in an open state.

[0061] The third on-off valve 64 is provided in the first fuel gas passage 40 and opens and closes the first fuel gas passage 40. The third on-off valve 64 is configured to be switchable between an open state and a closed state. When the third on-off valve 64 is in the open state, the fuel gas generated in the first remover 16 is supplied to the fuel cell 20 through the first fuel gas passage 40. When the third on-off valve 64 is in the closed state, the fuel gas generated in the first remover 16 is not supplied to the fuel cell 20 through the first fuel gas passage 40. Furthermore, the opening degree of the third on-off valve 64 is controllable in the open state.

[0062] The fourth on-off valve 66 is provided in the second fuel gas passage 42 and opens and closes the second fuel gas passage 42. The second fuel gas passage 42 has an upstream end connected to the second eliminator 18 and a downstream end connected to the first fuel gas passage 40 downstream of the third on-off valve 64. The second fuel gas passage 42 merges with the first fuel gas passage 40 downstream of the third on-off valve 64. The fourth on-off valve 66 is configured to be switchable between an open state and a closed state. When the fourth on-off valve 66 is in the open state, the fuel gas generated in the second eliminator 18 is supplied to the fuel cell 20 through the second fuel gas passage 42 and the first fuel gas passage 40 downstream of the third on-off valve 64. When the fourth on-off valve 66 is in the closed state, the fuel gas generated in the second eliminator 18 is not supplied to the fuel cell 20 through the second fuel gas passage 42. Furthermore, the fourth on-off valve 66 is configured to have an aperture controllable in the open state.

[0063] (Open / close valve control process; Figure 6) Next, the on-off valve control process of the second embodiment will be described. The on-off valve control process of the second embodiment is started, for example, when a used first removal device 16 is replaced with a new, unused first removal device 16. At the time when the on-off valve control process of the second embodiment is started, the first on-off valve 60 and the third on-off valve 64 are in an open state, and the second on-off valve 62 and the fourth on-off valve 66 are in a closed state. Also, the opening degrees of the first on-off valve 60 and the third on-off valve 64 are assumed to be X (see FIG. 7). When the first on-off valve 60 is in an open state, the reformed gas generated in the reformer 14 is supplied to the first removal device 16 through the first reformed gas passage 36. When the third on-off valve 64 is in an open state, the fuel gas generated in the first removal device 16 is supplied to the fuel cell 20 through the first fuel gas passage 40. Furthermore, when the second on-off valve 62 is in a closed state, the reformed gas generated in the reformer 14 is not supplied to the second remover 18 through the second reformed gas passage 38. When the fourth on-off valve 66 is in a closed state, the fuel gas generated in the second remover 18 is not supplied to the fuel cell 20 through the second fuel gas passage 42. It is assumed that the used second remover 18 is replaced with a new, unused second remover 18 while the second on-off valve 62 and the fourth on-off valve 66 are in a closed state.

[0064] As shown in FIG. 6, in S2 of the on-off valve control process, similar to S2 of the three-way valve control process of the first embodiment (see FIG. 3), the controller 50 time-integrates the ammonia concentration identified based on the ammonia concentration relationship information (see FIG. 2).

[0065] In the following S20, the controller 50 determines whether the time integral value of the ammonia concentration has reached a predetermined third integral reference value. If the time integral value of the ammonia concentration has reached the third integral reference value (YES), the process proceeds to S22. If the time integral value of the ammonia concentration has reached the third integral reference value, the controller 50 determines that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has reached a predetermined third reference amount. The predetermined third integral reference value in S20 is a value less than the first integral reference value in S4, which will be described later, and the predetermined third reference amount in S20 is an amount less than the first reference amount in S4. The third integral reference value and the third reference amount are determined in advance, for example, based on experiments or analyses.

[0066] If the time integral value of the ammonia concentration does not reach the third integral reference value in S20 (NO), the process returns to S2. If the time integral value of the ammonia concentration does not reach the third integral reference value, the controller 50 determines that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 does not reach the predetermined third reference amount. The controller 50 repeatedly performs the time integration of the ammonia concentration until the time integral value of the ammonia concentration reaches the third integral reference value.

[0067] In S22 after YES in S20, the controller 50 switches the second on-off valve 62 and the fourth on-off valve 66 from a closed state to an open state. Also, in S22, the controller 50 controls the aperture of the second on-off valve 62 to an aperture Y that is less than the aperture (X) of the first on-off valve 60 (see FIG. 7). Also, the controller 50 controls the aperture of the fourth on-off valve 66 to an aperture Y that is less than the aperture (X) of the third on-off valve 64 (see FIG. 7). Note that the apertures of the second on-off valve 62 and the fourth on-off valve 66 may be the same or different. When the second on-off valve 62 is switched to the open state, the reformed gas generated in the reformer 14 is supplied to the second remover 18 through the second reformed gas passage 38. When the fourth on-off valve 66 is switched to an open state, the fuel gas produced in the second remover is supplied to the fuel cell 20 through the second fuel gas passage .

[0068] In S24 following S22, the controller 50, similar to S2 described above, integrates the ammonia concentration determined based on the ammonia concentration relationship information (see FIG. 2) over time. In S4 following S24, similar to S4 in the three-way valve control process (see FIG. 3) of the first embodiment, the controller 50 determines whether the time integral value of the ammonia concentration has reached a predetermined first integral reference value. If the time integral value of the ammonia concentration has reached the first integral reference value (YES), the process proceeds to S26. If the time integral value of the ammonia concentration has reached the first integral reference value, the controller 50 determines that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has reached the predetermined first reference amount. On the other hand, if the time integral value of the ammonia concentration has not reached the first integral reference value (NO), the process returns to S24. If the time integral value of the ammonia concentration has not reached the first integral reference value, the controller 50 determines that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has not reached the predetermined first reference amount. The controller 50 repeatedly executes the time integration of the ammonia concentration until the time integration value of the ammonia concentration reaches the first integration reference value.

[0069] In S26 after YES in S4, the controller 50 increases the opening degrees of the second on-off valve 62 and the fourth on-off valve 66 (see FIG. 7). For example, the controller 50 sets the opening degrees of the second on-off valve 62 and the fourth on-off valve 66 to X. The opening degrees of the second on-off valve 62 and the fourth on-off valve 66 may be the same or different. In S26, the controller 50 also switches the first on-off valve 60 and the third on-off valve 64 from an open state to a closed state (see FIG. 7). When the first on-off valve 60 is switched to the closed state, the reformed gas generated in the reformer 14 is not supplied to the first remover 16 through the first reformed gas passage 36. When the third on-off valve 64 is switched to the closed state, the fuel gas generated in the first remover 16 is not supplied to the fuel cell 20 through the first fuel gas passage 40.

[0070] After the process of S26 is executed and before the process of S30, which will be described later, is executed, the used first remover 16 is replaced with a new, unused first remover 16. For example, the user of the fuel cell system 2 replaces the first remover 16.

[0071] In S8 following S26, the controller 50 integrates the ammonia concentration determined based on the ammonia concentration relationship information over time, similar to S2 described above. In the following S28, the controller 50 determines whether the time integral value of the ammonia concentration has reached a predetermined fourth integral reference value. If the time integral value of the ammonia concentration has reached the fourth integral reference value (YES), the process proceeds to S30. If the time integral value of the ammonia concentration has reached the fourth integral reference value, the controller 50 determines that the amount of ammonia supplied to the second remover 18 through the second reformed gas passage 38 has reached a predetermined fourth reference amount. The predetermined fourth integral reference value in S28 is a value less than the second integral reference value in S10 described below, and the predetermined fourth reference amount in S28 is an amount less than the second reference amount in S10. The fourth integral reference value and the fourth reference amount are determined in advance, for example, based on experiments or analysis.

[0072] If the time integral value of the ammonia concentration does not reach the fourth integral reference value in S28 (NO), the process returns to S8. If the time integral value of the ammonia concentration does not reach the fourth integral reference value, the controller 50 determines that the amount of ammonia supplied to the second remover 18 through the second reformed gas passage 38 does not reach the predetermined fourth reference amount. The controller 50 repeatedly performs the time integration of the ammonia concentration until the time integral value of the ammonia concentration reaches the fourth integral reference value.

[0073] In S30 after YES in S28, the controller 50 switches the first on-off valve 60 and the third on-off valve 64 from a closed state to an open state. Also, in S30, the controller 50 controls the opening degree of the first on-off valve 60 to an opening degree Y that is less than the opening degree (X) of the second on-off valve 62 (see FIG. 7). Also, the controller 50 controls the opening degree of the third on-off valve 64 to an opening degree Y that is less than the opening degree (X) of the fourth on-off valve 66. Note that the opening degrees of the first on-off valve 60 and the third on-off valve 64 may be the same or different. When the first on-off valve 60 is switched to the open state, the reformed gas generated in the reformer 14 is supplied to the first remover 16 through the first reformed gas passage 36. When the third on-off valve 64 is switched to the open state, the fuel gas generated in the first remover 16 is supplied to the fuel cell 20 through the first fuel gas passage 40.

[0074] In S32 following S30, the controller 50, similar to S8 described above, integrates the ammonia concentration determined based on the ammonia concentration relationship information (see FIG. 2) over time. In S10, similar to S10 in the three-way valve control process (see FIG. 3) of the first embodiment, the controller 50 determines whether the time integral value of the ammonia concentration has reached a predetermined second integral reference value. If the time integral value of the ammonia concentration has reached the second integral reference value (YES), the process proceeds to S34. If the time integral value of the ammonia concentration has reached the second integral reference value, the controller 50 determines that the amount of ammonia supplied to the second remover 18 through the second reformed gas passage 38 has reached the predetermined second reference amount. On the other hand, if the time integral value of the ammonia concentration has not reached the second integral reference value (NO), the process returns to S32. If the time integral value of the ammonia concentration has not reached the second integral reference value, the controller 50 determines that the amount of ammonia supplied to the second remover 18 through the second reformed gas passage 38 has not reached the predetermined second reference amount. The controller 50 repeatedly executes the time integration of the ammonia concentration until the time integration value of the ammonia concentration reaches the second integration reference value.

[0075] In S34 after YES in S10, the controller 50 increases the opening degrees of the first on-off valve 60 and the third on-off valve 64 (see FIG. 7). For example, the controller 50 sets the opening degrees of the first on-off valve 60 and the third on-off valve 64 to X. The opening degrees of the first on-off valve 60 and the third on-off valve 64 may be the same or different. In S34, the controller 50 also switches the second on-off valve 62 and the fourth on-off valve 66 from an open state to a closed state (see FIG. 7). When the second on-off valve 62 is switched to the closed state, the reformed gas generated in the reformer 14 is not supplied to the second remover 18 through the second reformed gas passage 38. When the fourth on-off valve 66 is switched to the closed state, the fuel gas generated in the second remover 18 is not supplied to the fuel cell 20 through the second fuel gas passage 42. After S34, the process returns to S2, and the processes from S2 to S34 are repeatedly executed.

[0076] After the process of S34 is executed and before the process of S22 described above is executed, the used second remover 18 is replaced with a new, unused second remover 18. For example, the user of the fuel cell system 2 replaces the second remover 18. The on-off valve control process is terminated appropriately based on, for example, a predetermined termination instruction.

[0077] (effect) The fuel cell system 2 of the second embodiment has been described above. As described above, the fuel cell system 2 includes the first reformed gas passage 36, the first on-off valve 60 provided in the first reformed gas passage 36, the second reformed gas passage 38 branching off from the first reformed gas passage 36 upstream of the first on-off valve 60, and the second on-off valve 62 provided in the second reformed gas passage 38. The first on-off valve 60 and the second on-off valve 62 are each configured to be switchable between an open state and a closed state. When the controller 50 determines, based on the detection values ​​of the sensors 28 and 30, that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has reached a predetermined third reference amount, the controller 50 switches the second on-off valve 62 from a closed state to an open state and controls the aperture of the second on-off valve 62 to an aperture less than that of the first on-off valve 60 (S20, S22). The controller 50 determines that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has reached the first reference amount when the integral value obtained by time-integrating the ammonia concentration estimated from the temperature detected by the temperature sensor 28 and the pressure detected by the pressure sensor 30 reaches a predetermined first integral reference value (S2, S20).

[0078] According to this configuration, it is possible to provide a period during which the first eliminator 16 and the second eliminator 18 are used in parallel. As a result, when switching from the first eliminator 16 to the second eliminator 18, the changeover can be performed smoothly without interrupting the flow of reformed gas.

[0079] The controller 50 controls the aperture of the second on-off valve 62 to an aperture less than that of the first on-off valve 60, and then, when it determines that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has reached a predetermined first reference amount based on the detection values ​​of the sensors 28, 30, increases the aperture of the second on-off valve 62 (S24, S4, S26). According to this configuration, it is possible to smoothly switch to the second remover 18 at a timing when the first remover 16 has been used to the limit of its capacity.

[0080] (Third Example) The fuel cell system 2 of the second embodiment described above includes the first on-off valve 60 and the second on-off valve 62, but is not limited to this configuration. As shown in Fig. 8, the fuel cell system 2 of the third embodiment includes a first pump 80 and a second pump 82 instead of the first on-off valve 60 and the second on-off valve 62.

[0081] The first pump 80 is provided in the first reformed gas passage 36, and pumps the reformed gas from the upstream side to the downstream side of the first reformed gas passage 36. The first pump 80 is configured to be switchable between an operating state and a stopped state. When the first pump 80 is in the operating state, the reformed gas generated in the reformer 14 is supplied to the first remover 16 through the first reformed gas passage 36. When the first pump 80 is in the stopped state, the reformed gas generated in the reformer 14 is not supplied to the first remover 16 through the first reformed gas passage 36. The first pump 80 is configured to be output controllable in the operating state.

[0082] The second pump 82 is provided in the second reformed gas passage 38, and pumps the reformed gas from the upstream side to the downstream side of the second reformed gas passage 38. The second pump 82 is configured to be switchable between an operating state and a stopped state. When the second pump 82 is in the operating state, the reformed gas generated in the reformer 14 is supplied to the second remover 18 through the second reformed gas passage 38. When the second pump 82 is in the stopped state, the reformed gas generated in the reformer 14 is not supplied to the second remover 18 through the second reformed gas passage 38. The second pump 82 is configured to be output controllable in the operating state.

[0083] (Pump control process; Figure 9) Next, the pump control process of the third embodiment will be described. As shown in Fig. 9, in the pump control process, instead of the processes of S22, S26, S30, and S34 of the on-off valve control process of the second embodiment (see Fig. 6), the processes of S42, S46, S50, and S54 are executed, respectively. When the pump control process of the third embodiment is started, it is assumed that the first pump 80 is in an operating state and the second pump 82 is in a stopped state. It is assumed that the output of the first pump 80 is V (see Fig. 10). In the following, a description of the processes in the pump control process that are the same as those in the on-off valve control process (see Fig. 6) will be omitted.

[0084] In S42 of the pump control processing, the controller 50 switches the second pump 82 from a stopped state to an operating state. Also in S42, the controller 50 controls the output of the second pump 82 to an output W that is less than the output (V) of the first pump 80 (see FIG. 10). When the second pump 82 is switched to the operating state, the reformed gas generated in the reformer 14 is supplied to the second remover 18 through the second reformed gas passage 38. Note that in S42, similar to S22 (see FIG. 6), the controller 50 switches the fourth on-off valve 66 from a closed state to an open state. Also, the controller 50 controls the aperture of the fourth on-off valve 66 to an aperture Y that is less than the aperture (X) of the third on-off valve 64 (see FIG. 7).

[0085] 9, the controller 50 increases the output of the second pump 82 (see FIG. 10). For example, the controller 50 sets the output of the second pump 82 to V. Also, in S46, the controller 50 switches the first pump 80 from an operating state to a stopped state (see FIG. 10). When the first pump 80 is switched to the stopped state, the reformed gas generated in the reformer 14 is not supplied to the first remover 16 through the first reformed gas passage 36. Note that, in S46, similarly to S26 (see FIG. 6), the controller 50 increases the opening degree of the fourth on-off valve 66 (see FIG. 7). Also, the controller 50 switches the third on-off valve 64 from an open state to a closed state.

[0086] 9, the controller 50 switches the first pump 80 from a stopped state to an operating state. Also, in S50, the controller 50 controls the output of the first pump 80 to an output W that is less than the output (V) of the second pump 82 (see FIG. 10). When the first pump 80 is switched to the operating state, the reformed gas generated in the reformer 14 is supplied to the first remover 16 through the first reformed gas passage 36. Note that, in S50, similarly to S30 (see FIG. 6), the controller 50 switches the third on-off valve 64 from a closed state to an open state. Also, the controller 50 controls the aperture of the third on-off valve 64 to an aperture Y that is less than the aperture (X) of the fourth on-off valve 66 (see FIG. 7).

[0087] 9, the controller 50 increases the output of the first pump 80 (see FIG. 10). For example, the controller 50 sets the output of the first pump 80 to V. Also, in S54, the controller 50 switches the second pump 82 from an operating state to a stopped state (see FIG. 10). When the second pump 82 is switched to the stopped state, the reformed gas generated in the reformer 14 is not supplied to the second remover 18 through the second reformed gas passage 38. Note that, in S54, similarly to S34 (see FIG. 6), the controller 50 increases the opening degree of the third on-off valve 64 (see FIG. 7). Also, the controller 50 switches the fourth on-off valve 66 from an open state to a closed state.

[0088] (effect) The fuel cell system 2 of the third embodiment has been described above. As described above, the fuel cell system 2 includes the first pump 80 provided in the first reformed gas passage 36. When the controller 50 determines, based on the detection values ​​of the sensors 28, 30, that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has reached a predetermined first reference amount, the controller 50 switches the first pump 80 from an operating state to a stopped state. According to this configuration, as with the fuel cell systems 2 of the first and second embodiments, the first remover 16 can be used to the limit of its capacity, and the frequency of replacement of the first remover 16 can be reduced.

[0089] The fuel cell system 2 also includes a second pump 82 provided in the second reformed gas passage 38. When the controller 50 determines, based on the detection values ​​of the sensors 28, 30, that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has reached a predetermined third reference amount, the controller 50 switches the second pump 82 from a stopped state to an operating state and controls the output of the second pump 82 to an output less than the output of the first pump 80. According to this configuration, similar to the fuel cell system 2 of the second embodiment, when switching from the first remover 16 to the second remover 18, the switch can be performed smoothly without interrupting the flow of reformed gas.

[0090] (Variation) (1) In some embodiments, the temperature sensor 28 may be provided between the heat exchanger 31 and the first three-way valve 24. The temperature sensor 28 may detect the temperature of the reformed gas flowing through the first reformed gas passage 36 downstream of the heat exchanger 31 and upstream of the first three-way valve 24. In other words, the temperature sensor 28 may detect the temperature of the reformed gas after heat exchange by the heat exchanger 31.

[0091] (2) In some embodiments, the pressure sensor 30 may be provided between the heat exchanger 31 and the first three-way valve 24. The pressure sensor 30 may detect the pressure of the reformed gas flowing through the first reformed gas passage 36 downstream of the heat exchanger 31 and upstream of the first three-way valve 24. In other words, the pressure sensor 30 may detect the pressure of the reformed gas after heat exchange by the heat exchanger 31.

[0092] (Fourth Example) Although the above-described fuel cell system 2 includes a temperature sensor 28 and a pressure sensor 30, the present invention is not limited to this configuration. Furthermore, although the above-described fuel cell system 2 integrates the ammonia concentration over time, the present invention is not limited to this configuration. As shown in FIG. 11 , the fuel cell system 2 of the fourth embodiment includes a flow rate sensor 70. The flow rate sensor 70 is provided in the first reformed gas passage 36 upstream of the first three-way valve 24 and detects the flow rate of the reformed gas flowing through the first reformed gas passage 36 upstream of the first three-way valve 24. When the time integral value of the flow rate detected by the flow rate sensor 70 reaches a predetermined integral reference value, the controller 50 switches the first three-way valve 24 from the first state to the second state. When the time integral value of the flow rate detected by the flow rate sensor 70 reaches the predetermined integral reference value, the controller 50 determines that the amount of ammonia supplied to the first remover 16 through the first reformed gas passage 36 has reached the first reference amount (see S4 and S6 in FIG. 3 ). The same applies to the second, third, and fourth reference amounts. The same applies to a configuration in which the fuel cell system 2 is provided with a first on-off valve 60 and a second on-off valve 62 instead of the first three-way valve 24. The same applies to a configuration in which the fuel cell system 2 is provided with a first pump and a second pump. Note that the distinctions between first, second, third, and fourth in the specification are made for convenience's sake.

[0093] Although specific examples of the present invention have been described in detail above, 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. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0094] 2: fuel cell system, 10: raw material tank, 12: vaporizer, 14: reformer, 15: heater, 16: first remover, 18: second remover, 20: fuel cell, 22: pump, 24: first three-way valve, 26: second three-way valve, 28: temperature sensor, 30: pressure sensor, 32: liquid passage, 34: raw material gas passage, 36: first reformed gas passage, 38: second reformed gas passage, 40: first fuel gas passage, 42: second fuel gas passage, 44: air passage, 46: exhaust gas passage, 50: controller, 52: memory unit, 60: first on-off valve, 62: second on-off valve, 64: third on-off valve, 66: fourth on-off valve, 70: flow rate sensor, 80: first pump, 82: second pump

Claims

1. a reformer that generates a reformed gas by reforming a raw material gas; a first reformed gas passage through which the reformed gas generated by the reformer flows; a sensor for detecting a state of the reformed gas flowing through the first reformed gas passage; a first valve provided in the first reformed gas passage; a first remover that removes ammonia from the reformed gas that has passed through the first reformed gas passage to produce a fuel gas; a second reformed gas passage branching from the first reformed gas passage upstream of the first valve, through which the reformed gas generated by the reformer flows; a second valve provided in the second reformed gas passage; a second remover that removes ammonia from the reformed gas that has passed through the second reformed gas passage to produce a fuel gas; a control unit, the first valve is configured to be switchable between a first state in which the reformed gas is supplied to the first remover through the first reformed gas passage and a second state in which the reformed gas is not supplied to the first remover through the first reformed gas passage, and the control unit switches the first valve from the first state to the second state when it determines, based on a detection value of the sensor, that an amount of ammonia supplied to the first remover through the first reformed gas passage has reached a predetermined first reference amount; the second valve is configured to be switchable between a first state in which the reformed gas is supplied to the second remover through the second reformed gas passage and a second state in which the reformed gas is not supplied to the second remover through the second reformed gas passage, when the control unit determines, based on the detection value of the sensor, that the amount of ammonia supplied to the first remover through the first reformed gas passage has reached a predetermined third reference amount that is less than the first reference amount, the control unit switches the second valve from the second state to the first state and controls the opening degree of the second valve to an opening degree that is less than the opening degree of the first valve.

2. 10. The ammonia removal system of claim 1, the sensor includes a temperature sensor that detects a temperature of the reformed gas flowing through the first reformed gas passage, and a pressure sensor that detects a pressure of the reformed gas flowing through the first reformed gas passage; the control unit determines that the amount of ammonia supplied to the first remover through the first reformed gas passage has reached the first reference amount when an integral value obtained by integrating the ammonia concentration over time, the integral value being estimated from the detection value of the temperature sensor and the detection value of the pressure sensor, reaches a predetermined first integral reference value.

3. 3. The ammonia removal system according to claim 1 or 2, the control unit controls the opening of the second valve to an opening less than the opening of the first valve, and then increases the opening of the second valve when it determines, based on the detection value of the sensor, that the amount of ammonia supplied to the first remover through the first reformed gas passage has reached the predetermined first reference amount.

4. a reformer that generates a reformed gas by reforming a raw material gas; a first reformed gas passage through which the reformed gas generated by the reformer flows; a sensor for detecting a state of the reformed gas flowing through the first reformed gas passage; a first pump provided in the first reformed gas passage; a first remover that removes ammonia from the reformed gas that has passed through the first reformed gas passage to produce a fuel gas; a second reformed gas passage branching from the first reformed gas passage upstream of the first pump, through which the reformed gas generated by the reformer flows; a second pump provided in the second reformed gas passage; a second remover that removes ammonia from the reformed gas that has passed through the second reformed gas passage to produce a fuel gas; a control unit, the first pump is configured to be switchable between an operating state in which the reformed gas is supplied to the first remover through the first reformed gas passage by pressure-feeding the reformed gas, and a stop state in which the reformed gas is not supplied to the first remover through the first reformed gas passage, the control unit switches the first pump from the operating state to the stopped state when it determines, based on the detection value of the sensor, that the amount of ammonia supplied to the first remover through the first reformed gas passage has reached a predetermined first reference amount; the second pump is configured to be switchable between an operating state in which the reformed gas is supplied to the second remover through the second reformed gas passage by pressure-feeding the reformed gas, and a stop state in which the reformed gas is not supplied to the second remover through the second reformed gas passage, when the control unit determines, based on the detection value of the sensor, that the amount of ammonia supplied to the first remover through the first reformed gas passage has reached a predetermined third reference amount that is less than a predetermined first reference amount, the control unit switches the second pump from the stopped state to the operating state and controls the output of the second pump to an output that is less than the output of the first pump.

5. An ammonia removal system according to any one of claims 1 to 4; a fuel cell that generates electricity using the fuel gas produced by the first remover.

Images