Fuel cell system

Abstract

To provide a fuel cell system that can continue to operate even when inert gas is mixed into fuel gas.SOLUTION: A fuel cell system according to an embodiment includes a fuel cell that generates electricity when fuel gas is supplied to it, a determination unit that determines the proportion of inert gas mixed in the fuel gas supplied to the fuel cell, and an operation control unit that changes the operating conditions of the fuel cell system on the basis of the proportion of inert gas mixed in determined by the determination unit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This embodiment relates to a fuel cell system.

Background Art

[0002] A fuel cell system includes a fuel cell in which an electrolyte membrane is interposed between a fuel electrode and an oxidant electrode. In the fuel cell, the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the oxidant electrode react electrochemically through the electrolyte membrane. Thus, the fuel cell is a power generation device that converts chemical energy into electrical energy. The fuel gas is, for example, hydrogen gas, and the oxidant gas is, for example, air.

[0003] A fuel tank for storing the fuel gas supplied to the fuel electrode is connected to the fuel cell system. During normal operation, the fuel gas is supplied from the fuel tank to the fuel electrode, and the fuel cell generates electricity. The fuel tank stores high-pressure hydrogen gas or liquid hydrogen.

[0004] When refueling the fuel tank, a separate refueling tank is connected to the fuel tank through a refueling flow path such as a pipe. The refueling flow path is purged with an inert gas such as nitrogen gas or helium gas, and then the fuel is supplied from the refueling tank to the fuel tank in a gaseous state or a liquid state.

[0005] In this way, an inert gas can be mixed into the fuel stored in the fuel tank. When the fuel gas containing the inert gas is supplied to the fuel electrode, it becomes easier for the inert gas to accumulate inside the fuel electrode in the fuel cell system. Also, during normal operation of the fuel cell, the inert gas contained in the oxidant electrode can move through the electrolyte membrane to the fuel electrode inside the fuel cell.

[0006] When the inert gas accumulates inside the fuel electrode in this way, the fuel gas concentration inside the fuel electrode can decrease. For this reason, the performance of the fuel cell may decrease, and the operation of the fuel cell may stop.

[0007] Fuel cell systems may include a fuel gas circulation channel that returns fuel gas discharged from the fuel cell back to the fuel cell. In this case, a degassing line, including a degassing valve, is connected to the fuel gas circulation channel. In such fuel cell systems, inert gas can be released from the degassing valve into the fuel electrode, allowing for a recovery of the fuel gas concentration. However, if more inert gas is supplied to the fuel electrode than can be released by normal degassing, the concentration of inert gas in the fuel electrode may increase. This can lead to a decrease in fuel cell performance and potentially cause the fuel cell to shut down. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2016 / 165824 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The embodiment aims to provide a fuel cell system that can continue operating even when an inert gas is mixed in with the fuel gas. [Means for solving the problem]

[0010] The fuel cell system according to this embodiment includes a fuel cell that generates electricity when fuel gas is supplied to it, a determination unit that determines the proportion of inert gas mixed into the fuel gas supplied to the fuel cell, and an operation control unit that changes the operating conditions of the fuel cell system based on the proportion of inert gas mixed in determined by the determination unit.

[0011] The fuel cell system according to this embodiment includes a fuel cell that generates electricity when fuel gas is supplied, a fuel gas circulation channel that returns the fuel gas discharged from the fuel cell to the fuel cell, a third pressure gauge that measures the pressure value of the fuel gas in the fuel gas circulation channel, a degassing channel that discharges the fuel gas from the fuel gas circulation channel to the outside, a degassing valve provided in the degassing channel, and an operation control unit that changes the operating conditions of the fuel cell system based on the pressure value measured by the third pressure gauge.

[0012] The fuel cell system according to this embodiment includes a fuel cell that generates electricity when supplied with fuel gas, and an operation control unit that changes the operating conditions of the fuel cell system based on information stored in a higher-level control system of the fuel cell system. [Effects of the Invention]

[0013] According to this embodiment, operation can be continued even when an inert gas is mixed in with the fuel gas. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 shows a fuel cell system according to the first embodiment. [Figure 2] Figure 2 is a diagram illustrating the opening and closing time interval of the degassing valve shown in Figure 1. [Figure 3] Figure 3 shows a fuel cell system according to the second embodiment. [Figure 4] Figure 4 is a diagram illustrating a modified example of the opening and closing time interval of the degassing valve shown in Figure 3. [Figure 5] Figure 5 shows a fuel cell system according to the third embodiment. [Modes for carrying out the invention]

[0015] The embodiments will be described below with reference to the drawings.

[0016] (First Embodiment) First, the fuel cell system 1 according to the first embodiment will be described using FIG. 1. The fuel cell system 1 according to this embodiment may be installed in a building, for example, or may be mounted on a moving body. Examples of buildings include condominiums, office buildings, factories, commercial facilities, etc. In this case, the generated electric power of the fuel cell system 1 may be used for driving an elevator, lighting, air conditioning, etc. inside the building. Examples of moving bodies include ships, automobiles, railway vehicles, etc. In this case, the generated electric power of the fuel cell system 1 may be used for driving the moving body, lighting, air conditioning, etc. inside the moving body.

[0017] As shown in FIG. 1, the fuel cell system 1 includes a fuel cell 2, a fuel tank 3, a fuel gas supply passage 4, an oxidant gas supply unit 5, an oxidant gas supply passage 6, an oxidant gas discharge passage 8, a fuel gas circulation passage 9, a degassing passage 10, a power conversion device 11, and a control device 30.

[0018] The fuel cell 2 is configured to be able to generate electricity. The fuel cell 2 is a power generation device that generates electricity using the fuel gas supplied from the fuel tank 3 and the oxidant gas supplied from the oxidant gas supply unit 5. Examples of the fuel gas include hydrogen gas, a mixed gas containing hydrogen gas, etc. Examples of the oxidant gas include air, etc. More specifically, although not shown, the fuel cell 2 includes a fuel electrode (anode), an oxidant electrode (cathode), and an electrolyte membrane interposed between the fuel electrode and the oxidant electrode. The fuel gas supplied to the fuel electrode and the oxidant gas supplied to the oxidant electrode react electrochemically through the electrolyte membrane. In this way, chemical energy is converted into electrical energy, and the fuel cell 2 can generate electricity.

[0019] The fuel tank 3 is an example of a fuel supply unit. The fuel tank 3 is configured to store the fuel gas for supplying to the fuel electrode. High-pressure hydrogen gas or liquid hydrogen is stored in the fuel tank 3.

[0020] The fuel gas supply passage 4 supplies the fuel gas stored in the fuel tank 3 to the fuel electrode of the fuel cell 2. A fuel gas supply valve 12, a flow rate adjustment valve 13, a first pressure gauge 14, and a second pressure gauge 15 may be provided in the fuel gas supply passage 4. The fuel gas supply valve 12 is a valve that controls the supply of fuel gas from the fuel tank 3 to the fuel electrode. The fuel gas supply valve 12 opens during the operation of the fuel cell system 1 to supply fuel gas to the fuel electrode. The fuel gas supply valve 12 may be controlled by the control device 30.

[0021] The flow rate adjustment valve 13 is a valve for adjusting the supply flow rate of fuel gas to the fuel electrode of the fuel cell 2. The opening degree of the flow rate adjustment valve 13 is adjusted based on a command from the control device 30. The opening degree command value by the control device 30 is stored in the control device 30. The flow rate adjustment valve 13 may be provided on the downstream side of the fuel gas supply valve 12. An injector, a proportional solenoid valve, a proportional motor valve, or the like capable of controlling the opening degree may be used for the flow rate adjustment valve 13.

[0022] The first pressure gauge 14 is configured to measure the pressure value P1 of the fuel gas flowing into the flow rate adjustment valve 13 in the fuel gas supply passage 4. The pressure value P1 corresponds to the inlet pressure value of the flow rate adjustment valve 13. The first pressure gauge 14 is provided on the upstream side of the flow rate adjustment valve 13 in the fuel gas supply passage 4. The first pressure gauge 14 may be provided between the fuel gas supply valve 12 and the flow rate adjustment valve 13. The pressure value P1 measured by the first pressure gauge 14 is transmitted to the control device 30.

[0023] The second pressure gauge 15 is configured to measure the pressure value P2 of the fuel gas flowing out of the flow rate adjustment valve 13 in the fuel gas supply passage 4. The pressure value P2 corresponds to the outlet pressure value of the flow rate adjustment valve 13. The second pressure gauge 15 is provided on the downstream side of the flow rate adjustment valve 13 in the fuel gas supply passage 4. The second pressure gauge 15 may be provided between the flow rate adjustment valve 13 and the fuel cell 2. The pressure value P2 measured by the second pressure gauge 15 is transmitted to the control device 30.

[0024] The oxidizing gas supply unit 5 is configured to supply oxidizing gas to the oxidizing electrode. The oxidizing gas supply unit 5 may consist of, for example, a blower or a compressor.

[0025] The oxidant gas supply channel 6 supplies oxidant gas from the oxidant gas supply unit 5 to the oxidant electrode of the fuel cell 2. An oxidant gas supply valve 16 may be provided in the oxidant gas supply channel 6. The oxidant gas supply valve 16 is a valve that controls the supply of oxidant gas from the oxidant gas supply unit 5 to the oxidant electrode. The oxidant gas supply valve 16 opens when the fuel cell system 1 is in operation to supply oxidant gas to the oxidant electrode. The oxidant gas supply valve 16 may be controlled by the control device 30.

[0026] The oxidant gas discharge channel 8 discharges the oxidant gas emitted from the oxidant electrode of the fuel cell 2 to the outside. An oxidant gas discharge valve 18 may be provided in the oxidant gas discharge channel 8. The oxidant gas discharge valve 18 is a valve that controls the discharge of oxidant gas from the oxidant electrode to the outside. The oxidant gas discharge valve 18 opens when the fuel cell system 1 is in operation to discharge oxidant gas from the oxidant electrode. The oxidant gas discharge valve 18 may be controlled by the control device 30.

[0027] The fuel gas circulation channel 9 is configured to return the fuel gas discharged from the fuel electrode of the fuel cell 2 back to the fuel cell 2. The upstream end of the fuel gas circulation channel 9 may be connected to the fuel electrode of the fuel cell 2 as described above, and the downstream end of the fuel gas circulation channel 9 may be connected to the fuel gas supply channel 4 as described above. In this case, the fuel gas discharged from the fuel electrode can be supplied to the fuel gas supply channel 4, and the fuel gas can be recycled. A circulation blower 19 may be provided in the fuel gas circulation channel 9. The circulation blower 19 draws fuel gas from the fuel electrode and sends the fuel gas to the fuel gas supply channel 4.

[0028] The degassing passage 10 is configured to discharge fuel gas from the fuel gas circulation passage 9 to the outside. A degassing valve 20 may be provided in the degassing passage 10.

[0029] The degassing valve 20 is provided in the fuel gas circulation passage 9 and is a valve that controls the discharge of fuel gas from the fuel gas circulation passage 9 to the outside. As shown in Figure 2, the degassing valve 20 may repeatedly be in a closed state maintained at a predetermined time interval t1 and an open state maintained at a predetermined time interval t2.

[0030] As shown in Figure 1, the power converter 11 is a device for converting the voltage and current of the power generated by the fuel cell 2. The power converted by the power converter 11 is supplied to an external load. The power converter 11 may be a DC / DC converter or an inverter. The power converter 11 is connected to the fuel cell 2 via an output line 21. An ammeter 22 is provided on the output line 21. The ammeter 22 is configured to measure the current value of the power generated and output from the fuel cell 2.

[0031] The control device 30 may include a determination unit 31 and an operation control unit 32. The control device 30 is configured to control the fuel gas supply valve 12, flow rate control valve 13, oxidizer gas supply valve 16, oxidizer gas discharge valve 18, degassing valve 20, and power converter 11 as described above.

[0032] The determination unit 31 is configured to determine the proportion of inert gas mixed into the fuel gas supplied to the fuel cell 2. In this embodiment, the determination unit 31 determines the proportion of inert gas mixed in based on the amount of fuel gas supplied to the fuel cell 2 and the amount of fuel gas consumed in the fuel cell 2.

[0033] More specifically, the determination unit 31 calculates the amount of fuel gas supplied to the fuel electrode and the amount of fuel gas consumed by the fuel cell 2. The amount of fuel gas supplied is calculated based on the pressure value P1 measured by the first pressure gauge 14, the pressure value P2 measured by the second pressure gauge 15, and the opening degree θ of the flow control valve 13. Fuel gas supply amount Q in Here, G is the specific gravity of the fuel gas, T is the temperature of the fuel gas, and C is the capacity coefficient of the flow control valve 13. v Therefore, it may also be calculated using the following formula (1).

number

[0034] Fuel gas consumption is calculated based on the current value measured by the ammeter 22. Fuel gas consumption is proportional to the current value of the generated power. Fuel gas consumption Q co The power can be calculated using the following equation (2), where I is the power generation current of fuel cell 2, N is the number of cells in the cell stack of fuel cell 2, and F is the Faraday number.

number

[0035] The determination unit 31 calculates the difference between the fuel gas supply amount and the fuel gas consumption amount calculated as described above. If this difference is greater than a predetermined threshold, it may be determined that the proportion of inert gas mixed in has increased.

[0036] As the proportion of inert gas mixed into the fuel gas increases, the fuel gas supply rate may increase. More specifically, the molecular weight of inert gases such as nitrogen or helium is greater than that of hydrogen gas. As a result, as the proportion of inert gas mixed into the fuel gas increases, the specific gravity of the fuel gas increases. In this case, the pressure loss of the fuel gas increases, the flow rate of fuel gas passing through the flow control valve 13 decreases, and the pressure value P1 decreases. When the control device 30 detects a decrease in the pressure value P1, it increases the opening of the flow control valve 13 in order to increase the flow rate of the fuel gas. As a result, the fuel gas supply rate Q shown in equation (1) is increased. in It increases.

[0037] In this way, the difference between the fuel gas supply amount and the fuel gas consumption amount increases, and based on this difference, the proportion of inert gas mixed into the fuel gas can be determined. Based on this determination by the determination unit 31, the operating conditions of the fuel cell system 1 are changed, and the operation of the fuel cell system 1 is continued.

[0038] The operation control unit 32 changes the operating conditions of the fuel cell system 1 based on the inert gas mixing ratio determined by the determination unit 31. For example, the operation control unit 32 may adjust the upper limit of the power generation current of the fuel cell 2 and the fuel supply amount based on the inert gas mixing ratio. The operation control unit 32 may lower the upper limit of the power generation current of the fuel cell 2 when the inert gas mixing ratio increases by controlling the power conversion device 11 described above. In addition, the operation control unit 32 may lower the fuel gas supply amount when the inert gas mixing ratio increases by controlling the flow control valve 13.

[0039] Next, a method for operating the fuel cell system 1 according to this embodiment, which has the above configuration, will be described.

[0040] Before starting operation of the fuel cell system 1, fuel is supplied to the fuel tank 3. For example, first, as shown in Figure 1, one end of a supply passage 40, such as a pipe, is connected to the fuel tank 3. Subsequently, the supply passage 40 is purged with an inert gas such as nitrogen gas. Then, a supply tank 41 is connected to the other end of the supply passage 40, and fuel is supplied from the supply tank 41 to the fuel tank 3. Inert gas may remain in the fuel supplied to the fuel tank 3. The fuel supplied from the supply tank 41 to the fuel tank 3 may be in liquid or gaseous form. After the fuel supply is complete, the supply passage 40 and the supply tank 41 are removed from the fuel tank 3.

[0041] After refueling is complete, the fuel cell system 1 will be started.

[0042] First, the fuel gas supply valve 12 and the oxidizer gas supply valve 16 are opened, and the oxidizer gas supply unit 5 and the circulation blower 19 are driven. As a result, fuel gas is supplied from the fuel tank 3 to the fuel electrode of the fuel cell 2, and oxidizer gas is supplied from the oxidizer gas supply unit 5 to the oxidizer electrode of the fuel cell 2. The supply flow rate of the oxidizer gas is adjusted by the oxidizer gas supply unit 5 based on a command from the control device 30. The fuel gas supplied to the fuel electrode and the oxidizer gas supplied to the oxidizer electrode react electrochemically through the electrolyte membrane. As a result, chemical energy is converted into electrical energy, and the fuel cell 2 generates electricity. The generated electricity is output from the fuel cell 2, and the voltage and current are converted in the power converter 11. The generated electricity is supplied to the load from the power converter 11.

[0043] The fuel gas that has passed through the fuel electrode is drawn into the fuel gas circulation channel 9. The oxidizer gas that has passed through the oxidizer electrode is discharged to the outside through the oxidizer gas discharge channel 8 because the oxidizer gas discharge valve 18 is open.

[0044] The fuel gas that flows into the fuel gas circulation channel 9 is sent to the fuel gas supply channel 4 by the circulation blower 19 and supplied back to the fuel electrode. In this way, the fuel gas is circulated and recycled during the operation of the fuel cell system 1.

[0045] During operation of the fuel cell system 1, the determination unit 31 of the control device 30 determines the proportion of inert gas mixed into the fuel gas, and the power control unit 24 changes the operating conditions of the fuel cell system 1 based on the determination of the proportion of inert gas.

[0046] More specifically, the first pressure gauge 14 and the second pressure gauge 15 measure the pressure values ​​P1 and P2 of the fuel gas in the fuel gas supply passage 4, and the measured pressure values ​​are transmitted to the control device 30. The ammeter 22 measures the current value of the power generated from the fuel cell 2, and the measured current value is transmitted to the control device 30. The judgment unit 31 of the control device 30 calculates the fuel gas supply amount based on the pressure value P1 measured by the first pressure gauge 14, the pressure value P2 measured by the second pressure gauge 15, and the stored opening degree of the flow control valve 13. The judgment unit 31 also calculates the fuel gas consumption amount based on the current value measured by the ammeter 22. If the difference between the fuel gas supply amount and the fuel gas consumption amount is greater than a predetermined threshold, it is determined that the proportion of inert gas mixed into the fuel gas is large.

[0047] If the determination unit 31 determines that the proportion of inert gas mixed in is large, the operation control unit 32 lowers the upper limit of the power generation current of the fuel cell 2 and also lowers the fuel gas supply amount. For example, the operation control unit 32 controls the power converter 11 to lower the upper limit of the power generation current and controls the flow control valve 13 to lower the fuel gas supply amount. As a result, the supply flow rate of fuel gas supplied to the fuel electrode of the fuel cell system 1 is reduced, which reduces the rate at which inert gas accumulates in the fuel electrode and prevents a decrease in the performance of the fuel cell.

[0048] Subsequently, if the proportion of inert gas mixed into the fuel gas decreases, the determination unit 31 may determine that the proportion of inert gas mixed in is not large. More specifically, if the difference between the fuel gas supply amount and the fuel gas consumption amount is below a predetermined threshold, the determination unit 31 may determine that the proportion of inert gas mixed into the fuel gas is not large. In this case, the operation control unit may restore the upper limit of the power generation current of the fuel cell 2 and the fuel gas supply amount to their original values.

[0049] As described above, according to this embodiment, the operating conditions of the fuel cell system 1 are changed based on the proportion of inert gas mixed into the fuel gas supplied to the fuel cell 2. This allows the fuel cell system 1 to be operated appropriately even when the proportion of inert gas mixed into the fuel gas is high. Therefore, operation can be continued even when inert gas is mixed into the fuel gas.

[0050] Furthermore, according to this embodiment, the determination unit 31 determines the inert gas mixing ratio based on the amount of fuel gas supplied to the fuel cell 2 and the amount of fuel gas consumed in the fuel cell 2. This makes it possible to accurately determine the inert gas mixing ratio in the fuel gas.

[0051] Furthermore, according to this embodiment, the determination unit 31 can calculate the fuel gas supply amount based on the pressure value P1 measured by the first pressure gauge 14, the pressure value P2 measured by the second pressure gauge 15, and the opening degree of the flow control valve 13. The determination unit 31 can also calculate the fuel gas consumption amount based on the power generation current value measured by the ammeter 22. Based on the calculated fuel gas supply amount and fuel gas consumption amount, the mixing ratio of inert gas can be determined. This improves the accuracy of determining the mixing ratio of inert gas.

[0052] Furthermore, according to this embodiment, the operation control unit 32 adjusts the upper limit of the power generation current of the fuel cell 2 and the fuel gas supply amount based on the inert gas mixing ratio determined by the determination unit 31. As a result, when the inert gas mixing ratio increases, the upper limit of the power generation current of the fuel cell 2 can be lowered and the fuel gas supply amount can be lowered. Therefore, by reducing the rate at which inert gas accumulates in the fuel electrode, a decrease in the performance of the fuel cell can be prevented, and operation can be continued even when inert gas is mixed in the fuel gas.

[0053] In this case, the mixing of inert gas with the fuel gas increases the specific gravity of the fuel gas, which can lead to a greater pressure loss of the fuel gas. In this case, the adjustment range of the fuel gas in the flow control valve 13 is reduced, and the maximum adjustable flow rate may be decreased. In contrast, according to this embodiment, the operation control unit 32 lowers the upper limit of the power generation current of the fuel cell 2 and reduces the fuel gas supply amount based on the mixing ratio of inert gas determined by the determination unit 31. This reduces the fuel gas supply flow rate and expands the adjustment range of the fuel gas in the flow control valve 13.

[0054] Furthermore, when fuel gas mixed with inert gas is supplied, the rate of accumulation of inert gas in the anode system, including the fuel gas supply channel 4 and the fuel gas circulation channel 9, may increase. In this case, even if the degassing valve 20 is opened and the fuel gas is discharged to the outside, it may be difficult to reduce the proportion of inert gas mixed in and maintain the hydrogen concentration in the fuel gas at a predetermined concentration. In contrast, according to this embodiment, the upper limit of the power generation current of the fuel cell 2 is reduced and the fuel gas supply amount is reduced based on the proportion of inert gas mixed in determined by the determination unit 31. As the fuel gas supply amount is reduced, the rate of accumulation of inert gas in the anode system can be reduced, and the hydrogen concentration in the fuel gas can be maintained at a predetermined concentration by the degassing treatment in the degassing channel 10.

[0055] In the above-described embodiment, the operation control unit 32 was shown to reduce the upper limit of the power generation current of the fuel cell 2 and to reduce the fuel supply amount based on the inert gas mixing ratio. However, this embodiment is not limited to this. For example, the operation control unit 32 may adjust the time interval t1 (see Figure 2) in which the degassing valve 20 is closed based on the inert gas mixing ratio determined by the determination unit 31.

[0056] For example, if the judgment unit 31 determines that the proportion of inert gas mixed in is large, the operation control unit 32 may shorten the time interval t1 during which the degassing valve 20 is closed. This increases the proportion of time during which the degassing valve 20 is open, allowing fuel gas to be efficiently released to the outside from the degassing passage 10. As a result, the proportion of inert gas mixed in the fuel gas can be reduced. Subsequently, if the proportion of inert gas mixed in the fuel gas decreases, the time interval t1 during which the degassing valve 20 is closed may be returned to its original value.

[0057] Furthermore, for example, the operation control unit 32 may adjust the time interval t2 in which the degassing valve 20 is open based on the proportion of inert gas contamination determined by the judgment unit 31. For example, the time interval t2 in which the degassing valve 20 is open may be increased. This increases the proportion of time in which the degassing valve 20 is open, allowing fuel gas to be efficiently released to the outside from the degassing passage 10. As a result, the proportion of inert gas contamination in the fuel gas can be reduced. Subsequently, if the proportion of inert gas contamination in the fuel gas decreases, the time interval t2 in which the degassing valve 20 is open may be returned to its original value.

[0058] (Second Embodiment) Next, the fuel cell system in the second embodiment will be described with reference to Figures 3 and 4.

[0059] In the second embodiment shown in Figures 3 and 4, the main difference is that the time interval in which the vent valve is closed or open is adjusted based on the pressure value measured by the third pressure gauge; other configurations are substantially the same as those of the first embodiment shown in Figures 1 and 2. In Figures 3 and 4, the same reference numerals are used for parts identical to those in the first embodiment shown in Figures 1 and 2, and detailed descriptions are omitted.

[0060] As shown in Figure 3, the fuel cell system 1 according to this embodiment is equipped with a third pressure gauge 50. The fuel cell system 1 according to this embodiment does not necessarily have to be equipped with the judgment unit 31 described above.

[0061] The third pressure gauge 50 is configured to measure the pressure value of the fuel gas in the fuel gas circulation passage 9. The third pressure gauge 50 is located downstream of the circulation blower 19 in the fuel gas circulation passage 9. The third pressure gauge 50 may also be located between the circulation blower 19 and the branching point of the degassing passage 10. The pressure value measured by the third pressure gauge 50 is transmitted to the control device 30. The third pressure gauge 50 may also be located upstream of the circulation blower 19.

[0062] In this embodiment, the operation control unit 32 adjusts the time interval t1 (see Figure 2) during which the vent valve 20 is closed based on the pressure value P3 measured by the third pressure gauge 50. Alternatively, the operation control unit 32 may also adjust the time interval t2 (see Figure 2) during which the vent valve 20 is open based on the pressure value P3 measured by the third pressure gauge 50.

[0063] For example, the operation control unit 32 may adjust the time interval t1 for closing the degassing valve 20 based on the rate of increase of the pressure value P3 measured by the third pressure gauge 50. If the rate of increase of the pressure value P3 is greater than a predetermined threshold, the time interval t1 for closing the degassing valve 20 may be shortened.

[0064] Furthermore, the operation control unit 32 may adjust the time interval t2 for opening the degassing valve 20 if the rate of increase of the pressure value P3 measured by the third pressure gauge 50 is greater than a predetermined threshold. If the rate of increase of the pressure value P3 is greater than a predetermined threshold, the time interval t2 for opening the degassing valve 20 may be increased.

[0065] Here, if the fuel gas is not mixed with inert gas, nitrogen gas from the oxidizer gas moves from the cathode system, including the oxidizer gas supply channel 6, to the anode system. This can increase the proportion of inert gas mixed into the fuel gas. In this case, the rate of increase in the proportion of inert gas is relatively low. On the other hand, if the fuel gas is mixed with inert gas, in addition to the movement of nitrogen gas from the cathode system to the anode system, fuel gas mixed with inert gas is supplied. Therefore, the rate of increase in the proportion of inert gas mixed into the fuel gas in the anode system is relatively high. In this case, the rate of increase of the pressure value P3 measured by the third pressure gauge 50 increases, and the proportion of inert gas mixed into the fuel gas increases. Monitoring the rate of increase of the pressure value P3 measured by the third pressure gauge 50 is effective in determining the proportion of inert gas mixed in.

[0066] As described above, according to this embodiment, the operating conditions of the fuel cell system 1 are changed based on the pressure value P3 measured by the third pressure gauge 50 installed in the fuel gas circulation path 9. This allows the fuel cell system 1 to be operated appropriately even when the proportion of inert gas mixed in the fuel gas is high. Therefore, operation can be continued even when inert gas is mixed in the fuel gas.

[0067] Furthermore, according to this embodiment, the time interval t1 in which the degassing valve 20 is closed is adjusted based on the rate of increase of the pressure value P3 measured by the third pressure gauge 50. By using the rate of increase of the pressure value P3, the proportion of inert gas mixed in the oxidizer gas can be determined separately from the nitrogen gas that has moved from the cathode system to the anode system. Therefore, degassing by the degassing valve 20 can effectively reduce the proportion of inert gas mixed in the fuel gas, and operation can be continued even if inert gas is mixed in the fuel gas.

[0068] Furthermore, according to this embodiment, the time interval t2 for opening the degassing valve 20 is adjusted based on the rate of increase of the pressure value P3 measured by the third pressure gauge 50. By using the rate of increase of the pressure value P3, the proportion of inert gas contained in the oxidizer gas can be determined separately from the nitrogen gas that has moved from the cathode system to the anode system. Therefore, degassing by the degassing valve 20 can effectively reduce the proportion of inert gas contained in the fuel gas, and operation can be continued even if inert gas is mixed in the fuel gas.

[0069] In the above-described embodiment, the operation control unit 32 adjusted the time interval t1 for closing the degassing valve 20 and the time interval t2 for opening the degassing valve 20 based on the rate of increase of the fuel gas pressure value P3 in the fuel gas circulation passage 9. However, this embodiment is not limited to this. The operation control unit 32 may open and close the degassing valve 20 based on the fuel gas pressure value P3 in the fuel gas circulation passage 9. For example, as shown in Figure 4, when the pressure value P3 measured by the third pressure gauge 50 reaches a desired upper limit value Pa, the degassing valve 20 is opened. This allows fuel gas with a high proportion of inert gas to be discharged to the outside from the degassing passage 10. Fuel gas supplied from the fuel tank 3 is supplied to the fuel gas circulation passage 9, and the proportion of inert gas in the fuel gas circulation passage 9 can be reduced. When the proportion of inert gas is reduced, the pressure loss of the fuel gas is reduced, and the pressure value P3 decreases. The operation control unit 32 may close the degassing valve 20 when the pressure value P3 reaches a desired lower limit value Pb. This prevents fuel gas with a low inert gas content from being discharged to the outside through the degassing passage 10. In this way, the pressure value P3 can be adjusted between the upper limit value Pa and the lower limit value Pb, allowing the fuel cell system 1 to be operated properly and continuously.

[0070] (Third embodiment) Next, the fuel cell system in the third embodiment will be described using Figure 5.

[0071] In the third embodiment shown in Figure 5, the main difference is that the operating conditions of the fuel cell system are changed based on information stored in the higher-level control system of the fuel cell system; other configurations are substantially the same as those of the first embodiment shown in Figures 1 and 2. In Figure 5, the same reference numerals are used for parts identical to those of the first embodiment shown in Figures 1 and 2, and detailed descriptions are omitted.

[0072] As shown in Figure 5, a higher-level control system 60 is connected to the control device 30. The control system 60 issues various commands, such as operation commands, to the control device 30. Based on these commands, the control device 30 controls the operation of the fuel cell 2. The control system 60 also stores various information, and the control device 30 obtains the information necessary for controlling the operation of the fuel cell 2 from the control system 60. The fuel cell system 1 according to this embodiment does not necessarily have to include the judgment unit 31 described above.

[0073] In this embodiment, the operation control unit 32 changes the operating conditions of the fuel cell system 1 based on information stored in the control system 60. The information stored in the control system 60 includes the purge completion time of the purge process performed when refueling the fuel tank 3 described above. The control device 30 acquires this purge completion time, and the operation control unit 32 may change the operating conditions of the fuel cell system 1 based on the purge completion time. For example, the operation control unit 32 may assume that the proportion of inert gas mixed in is high until a predetermined elapsed period has elapsed from the purge completion time, and change the operating conditions of the fuel cell system 1. This elapsed period may be adjusted arbitrarily. For example, the elapsed period may be adjusted as the period during which power generation by the fuel cell 2 continues, or it may be the period until the amount of power generated by the fuel cell 2 reaches a predetermined amount of power. For example, the elapsed period may be adjusted arbitrarily based on the type of gas used in the purge process, or it may be adjusted arbitrarily based on the number of replacements with purge gas.

[0074] In this case, the operation control unit 32 may lower the upper limit of the power generation current of the fuel cell 2 and the fuel gas supply amount from the end of the purge time until the above-mentioned elapsed period has elapsed. This reduces the rate at which inert gas accumulates in the fuel electrode of the fuel cell 2, thereby preventing a decrease in the performance of the fuel cell. The rate at which the upper limit of the power generation current is reduced and the rate at which the fuel gas supply amount is reduced may be adjusted arbitrarily. For example, the rate at which the upper limit of the power generation current is reduced and the rate at which the fuel gas supply amount is reduced may be adjusted arbitrarily based on the type of gas used for the purge process or the number of times the gas is replaced by the purge gas. After the above-mentioned elapsed period has elapsed from the end of the purge time, the operation control unit 32 may restore the upper limit of the power generation current and the fuel gas supply amount to their original values.

[0075] Alternatively, the operation control unit 32 may shorten the time interval t1 (see Figure 2) during which the degassing valve 20 is closed from the end of the purge time until the aforementioned elapsed period has elapsed. This increases the proportion of time during which the degassing valve 20 is open, allowing fuel gas to be efficiently released to the outside from the degassing passage 10. As a result, the proportion of inert gas mixed into the fuel gas can be reduced. Furthermore, the operation control unit 32 may lengthen the time interval t2 (see Figure 2) during which the degassing valve 20 is open from the end of the purge time until the aforementioned elapsed period has elapsed. After the aforementioned elapsed period has elapsed from the end of the purge time, the operation control unit 32 may return the time interval t1 and the time interval t2 of the degassing valve 20 to their original values.

[0076] As described above, according to this embodiment, the operation of the fuel cell system 1 is controlled based on information stored in the higher-level control system 60 of the fuel cell system 1. This allows the fuel cell system 1 to be operated appropriately even when the proportion of inert gas mixed in the fuel gas is high. Therefore, operation can be continued even when inert gas is mixed in the fuel gas.

[0077] In the above-described embodiment, an example was given in which the fuel cell system 1 does not include a determination unit 31. However, this embodiment is not limited to this. For example, the fuel cell system 1 may include a determination unit 31.

[0078] Generally, a fuel cell system 1 monitors the difference between the amount of fuel gas supplied to the fuel electrode and the amount of fuel gas consumed, calculated from the power generation current of the fuel cell 2, in order to detect fuel gas leaks. Since the molecular weight of inert gas is larger than that of fuel gas, the amount of fuel gas supplied to the fuel electrode is overestimated when inert gas is mixed in. In this case, the difference between the amount of fuel gas supplied and the amount of fuel gas consumed is likely to be overestimated, and fuel gas leaks are likely to be falsely detected.

[0079] To address this, the determination unit 31 may determine that the proportion of inert gas has increased if the difference between the fuel gas supply amount and the fuel gas consumption amount is greater than the first threshold during the period from the end of the purge until the above-mentioned elapsed time has elapsed. The operation control unit 32 may change the operating conditions of the fuel cell system 1 in the same manner as described above based on the proportion of inert gas determined by the determination unit 31. If the determination unit 31 determines that the proportion of inert gas in the fuel gas is not large, the operation control unit 32 may return the operating conditions of the fuel cell system 1 to their original state. After the above-mentioned elapsed time has elapsed, the determination unit 31 may determine that the proportion of inert gas has increased if the difference between the fuel gas supply amount and the fuel gas consumption amount is greater than the second threshold. In this case, the operation control unit 32 may similarly change the operating conditions of the fuel cell system 1. The second threshold may be smaller than the first threshold. Even after the above-mentioned elapsed time has elapsed, if the determination unit 31 determines that the proportion of inert gas in the fuel gas is not large, the operation control unit 32 may return the operating conditions of the fuel cell system 1 to their original state. In this way, by increasing the first threshold used by the determination unit 31 from the end of the purge time until the above-mentioned elapsed period has elapsed, operation can be continued.

[0080] Another example of a fuel cell system 1 equipped with a determination unit 31 will be described. In this case, the information stored in the control system 60 includes the concentration of inert gas in the fuel gas. The control device 30 may acquire this inert gas concentration, and based on the inert gas concentration, the determination unit 31 may determine whether the proportion of inert gas mixed into the fuel gas supplied to the fuel cell 2 is large or not. For example, the determination unit 31 may determine that the proportion of inert gas mixed in has increased if the concentration of inert gas stored in the control system 60 is greater than a predetermined threshold. The operation control unit 32 may change the operating conditions of the fuel cell system 1 based on the proportion of inert gas mixed in determined by the determination unit 31. If the determination unit 31 determines that the concentration of inert gas stored in the control system 60 is not greater than a predetermined threshold, the operation control unit 32 may return the operating conditions of the fuel cell system 1 to their original state.

[0081] According to the embodiments described above, operation can be continued even when an inert gas is mixed in with the fuel gas.

[0082] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. Naturally, these embodiments can also be combined in part as appropriate within the scope of the spirit of the invention. [Explanation of Symbols]

[0083] 1: Fuel cell system, 2: Fuel cell, 9: Fuel gas circulation channel, 10: Degassing channel, 13: Flow control valve, 14: First pressure gauge, 15: Second pressure gauge, 20: Degassing valve, 22: Ammeter, 30: Control device, 31: Decision unit, 32: Operation control unit, 50: Third pressure gauge, 60: Control system

Claims

1. A fuel cell system, Fuel supply unit, A fuel cell that generates electricity by receiving fuel gas from the fuel supply unit, A determination unit for determining the proportion of inert gas mixed into the fuel gas supplied from the fuel supply unit to the fuel cell, An operation control unit that changes the operating conditions of the fuel cell system based on the mixing ratio of the inert gas determined by the determination unit, A fuel cell system equipped with [a specific feature / feature].

2. The determination unit determines the mixing ratio of the inert gas based on the amount of fuel gas supplied from the fuel supply unit to the fuel cell and the amount of fuel gas consumed in the fuel cell. The fuel cell system according to claim 1.

3. A flow control valve for adjusting the flow rate of the fuel gas supplied from the fuel supply unit to the fuel cell, A first pressure gauge for measuring the pressure value of the fuel gas flowing into the flow control valve, A second pressure gauge for measuring the pressure value of the fuel gas flowing out from the flow control valve, An ammeter for measuring the current value of the power generated from the fuel cell, Equipped with, The determination unit calculates the fuel gas supply amount based on the pressure value measured by the first pressure gauge, the pressure value measured by the second pressure gauge, and the opening degree of the flow control valve, and calculates the fuel gas consumption amount based on the power generation current value measured by the ammeter. The fuel cell system according to claim 2.

4. The operation control unit adjusts the upper limit of the power generation current of the fuel cell and the amount of fuel gas supplied based on the mixing ratio of the inert gas determined by the determination unit. The fuel cell system according to claim 2 or 3.

5. A fuel gas circulation channel for returning the fuel gas discharged from the fuel cell back to the fuel cell, A degassing passage for discharging the fuel gas from the fuel gas circulation passage to the outside, A degassing valve is provided in the aforementioned degassing passage, Equipped with, The operation control unit adjusts the time interval during which the degassing valve is closed or the time interval during which the degassing valve is open based on the mixing ratio of the inert gas determined by the determination unit. The fuel cell system according to claim 1.

6. The operation control unit changes the operating conditions of the fuel cell system based on information stored in a higher-level control system of the fuel cell system. The fuel cell system according to claim 1.

7. The information of the control system includes the end time of the purge process performed when refueling the fuel supply unit. The operation control unit changes the operating conditions of the fuel cell system during a predetermined period from the end of the purge time. The fuel cell system according to claim 6.

8. The determination unit determines, based on the information of the control system, the proportion of inert gas mixed in the fuel gas supplied from the fuel supply unit to the fuel cell. The fuel cell system according to claim 6.

9. The information of the control system includes the end time of the purge process performed when refueling the fuel supply unit. The determination unit determines that the proportion of inert gas mixed in has increased if, during the period from the end of the purge time until a predetermined elapsed time has elapsed, the difference between the amount of fuel gas supplied from the fuel supply unit to the fuel cell and the amount of fuel gas consumed in the fuel cell is greater than a first threshold, and after the elapsed period has elapsed, if the difference between the amount of fuel gas supplied and the amount of fuel gas consumed is greater than a second threshold, the determination unit determines that the proportion of inert gas mixed in has increased. The second threshold is smaller than the first threshold. The fuel cell system according to claim 8.

10. The information of the control system includes the concentration of the inert gas in the fuel gas. The determination unit determines, based on the concentration of the inert gas, the proportion of inert gas mixed into the fuel gas supplied from the fuel supply unit to the fuel cell. The fuel cell system according to claim 8.

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