Fuel cell system

Abstract

To provide a fuel cell system capable of effectively eliminating clogging caused by particulate matter.SOLUTION: The fuel cell system (A) includes: a housing container (9) for accommodating a cell stack (6) and a combustion unit (8) in an internal space (9s); an air supply passage (13) having an air filter (21), an air blower (7), and the housing container (9) connected in series, a flow meter (22) being disposed in the passage; and a control unit (10). The control unit (10) acquires an air flow rate of air passing through the air supply passage (13) and controls the flow rate by adjusting the duty ratio of power supply to the air blower (7). The control unit (10) calculates the degree of blockage of an air supply system (23) including the air filter (21), the air blower (7), and the air supply passage (13), on the basis of the duty ratio and the air flow rate, and also acquires the outside air temperature. The control unit (10) initiates air flow improvement operation on the basis of the degree of blockage, and determines the amount of water vapor to be supplied to the air supply system (23) on the basis of both the degree of blockage and the outside air temperature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system. [Background technology]

[0002] In the fuel cell system described in Patent Document 1, power is generated in a plurality of cells provided in a cell stack by a power-generating reaction between hydrogen-containing gas supplied from a reformer and air supplied from an air blower. In the combustion section, combustible components in the anode exhaust gas discharged through the gas outlet edge of each cell are combusted with oxygen in the cathode exhaust gas also discharged through the gas outlet edge of each cell, and the resulting combustion heat heats the reformer and evaporator. The reformer, which reforms raw fuel supplied from a raw fuel pump into hydrogen-containing gas, the evaporator, which evaporates reforming water supplied from a reforming water pump to generate steam for the reforming process, the combustion section, which heats the reformer and evaporator, and the cell stack are all housed in the internal space of a storage container.

[0003] The hydrogen-containing gas produced in the reformer is supplied to a manifold through a hydrogen-containing gas passage, and is then distributed from the manifold to the fuel electrodes of the multiple cells in the cell stack. Meanwhile, air is supplied by an air blower through an air supply passage into the internal space of the storage container, and the air supplied to the internal space of the storage container is then supplied to the oxygen electrodes of each cell via the air inlet of each of the multiple cells in the cell stack. The fuel cell system has a control unit, and the operation of the fuel cell system is controlled by the control unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-155333 Summary of the Invention [Problem to be solved by the invention]

[0005] The outside air supplied to the interior space of the container by the air blower through the air supply passage contains fine particulate matter such as dust, PM2.5, and yellow sand. Therefore, the air supply system including the air blower and the air supply passage includes an air filter that purifies the air sent out by the air blower. The air filter is located upstream of the air blower.

[0006] As the fuel cell system continues to operate, particulate matter may adhere to the air supply system, such as the air filter and air blower, causing clogging. If clogging occurs, the pressure loss in the air supply system increases over the course of the fuel cell system's operation, causing the air flow condition in the air supply system to deteriorate. The air flow condition is determined by the control unit by constantly detecting the air flow rate using an air flow meter installed in the air supply path.

[0007] When the control unit determines that the pressure loss has increased and the air flow condition of the air supply system has deteriorated, it increases the duty ratio of the voltage applied to the air blower to increase the flow rate of air supplied to the internal space of the storage container. However, if a large amount of particulate matter has adhered, it is necessary to remove the adhered particulate matter to clear the blockage. In the fuel cell system described in Patent Document 1, the raw fuel pump and the air blower are stopped, and the reforming water pump is operated to supply an appropriate amount of steam to the air supply system. The steam dissolves and removes deposits (e.g., deposits containing ammonium sulfate) that have adhered to the air supply path, air blower, air filter, etc., thereby clearing the blockage. However, there was a concern that if an appropriate amount of steam was not supplied to the air supply system, the deposits might not be sufficiently dissolved.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel cell system that can effectively eliminate clogging caused by particulate matter. [Means for solving the problem]

[0009] In order to achieve the above object, the fuel cell system according to the present invention includes an evaporator that evaporates reforming water supplied by a reforming water pump, a reformer that generates hydrogen-containing gas by a reforming reaction between raw fuel supplied by a raw fuel pump and steam supplied from the evaporator, an air blower that takes in air from the outside and sends it out, an air filter that purifies the air taken in by the air blower, a fuel electrode and an oxygen electrode, and a cell stack in which a plurality of cells are stacked to generate electricity when the hydrogen-containing gas is supplied from the reformer to the fuel electrode and the air sent out by the air blower is supplied to the oxygen electrode, a combustion unit that burns combustible components in the fuel electrode exhaust gas discharged from the fuel electrode with oxygen in the oxygen electrode exhaust gas discharged from the oxygen electrode and heats the reformer and the evaporator with the combustion heat, a storage container that houses the evaporator, the reformer, the cell stack and the combustion unit in its internal space, and a storage container that connects the air blower to the storage container and converts the air sent out from the air blower into a fuel cell stack. the control unit controls the supply of electricity to the air blower by controlling a duty ratio, acquires the flow rate of the air sent out from the air blower when the air blower is energized at the duty ratio and detected by the flow meter, calculates the degree of blockage of the air supply system including the air filter, the air blower, and the air supply line based on the duty ratio and the flow rate of the air, acquires an outside air temperature, stops the raw fuel pump and the air blower based on the degree of blockage, and starts an air flow improvement operation in which the reforming water pump is operated, and determines the amount of the reforming water to be supplied by the reforming water pump to generate the steam to be supplied to the air supply system based on the degree of blockage and the outside air temperature during the air flow improvement operation.

[0010] The ease with which particulate matter containing ammonium sulfate adhering to the air supply passage, air blower, air filter, etc. dissolves varies depending on the outside air temperature (the temperature of the location where the matter is adhering). Therefore, according to the above-described characteristic configuration, the air flow improvement operation is performed based on the degree of blockage, and the amount of reforming water supplied by the reforming water pump to generate steam that improves the degree of blockage during the air flow improvement operation is determined based on the degree of blockage and the outside air temperature, making it possible to effectively eliminate clogging caused by particulate matter.

[0011] A further characteristic feature of the fuel cell system according to the present invention is that the control unit reduces the amount of the reforming water supplied by the reforming water pump as the outside air temperature increases.

[0012] Particulate matter containing ammonium sulfate adhering to the air supply passage, air blower, air filter, etc. dissolves more easily at higher outside temperatures, so less water vapor is required. According to the above-described characteristic configuration, the amount of reforming water that generates water vapor decreases as the outside temperature increases, making it possible to more effectively eliminate clogging caused by particulate matter.

[0013] A further characteristic feature of the fuel cell system of the present invention is that, if the degree of blockage does not decrease below the reference value even after the air flow improvement operation, the control unit determines the amount of reforming water to be supplied by the reforming water pump so that the amount of water vapor generated is increased by a predetermined percentage, and performs the air flow improvement operation again using the water vapor generated in the predetermined percentage increase.

[0014] According to the above characteristic configuration, by increasing the amount of water vapor generated and performing the air flow improvement operation again, the particulate matter that could not be sufficiently dissolved during the initial air flow improvement operation can be dissolved, thereby more effectively eliminating blockages caused by particulate matter. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a block diagram showing the flow state of fluids in the fuel cell system according to the first embodiment during normal operation. [Figure 2] 10 is a graph showing the degree of blockage based on the air flow rate in a fuel cell system and the duty ratio of the voltage applied to the air blower. [Figure 3] 10 is a graph showing the relationship between the outside air temperature and the amount of water vapor at each degree of blockage. [Figure 4] FIG. 10 is a flowchart showing a control operation. [Figure 5] FIG. 2 is a block diagram showing the fluid flow state during air flow improvement operation of the fuel cell system according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] [First embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, a fuel cell system A according to an embodiment of the present invention is configured to include an evaporator 2, a raw fuel pump 3, a reformer 4, a cell stack 6, an air blower 7, a combustion unit 8, a storage container 9, and a control unit 10. The evaporator 2 evaporates reforming water supplied by a reforming water pump 1. The reformer 4 generates a hydrogen-containing gas by a reforming reaction between the raw fuel gas (e.g., natural gas-based city gas such as 13A) supplied by the raw fuel pump 3 and the steam supplied from the evaporator 2. The cell stack 6 is configured by stacking a plurality of cells 5, each of which generates electricity by supplying the hydrogen-containing gas from the reformer 4 to the fuel electrode 5a and air from the air blower 7 to the oxygen electrode 5c. The combustion unit 8 combusts combustible components in the fuel electrode exhaust gas discharged from the fuel electrode 5a with oxygen in the oxygen electrode exhaust gas discharged from the oxygen electrode 5c, and heats the reformer 4 and the evaporator 2 with the resulting combustion heat. The storage container 9 accommodates the evaporator 2, the reformer 4, the cell stack 6, and the combustion section 8 in an internal space 9s. The control section 10 controls the operation of the fuel cell system A.

[0017] The cell stack 6 is provided with a manifold 12 that can distribute and supply the hydrogen-containing gas supplied from the reformer 4 through a hydrogen-containing gas passage 11 to the fuel electrodes 5a of each cell 5. In addition, an air supply passage 13 that can supply air from an air blower 7 to the internal space 9s of the storage container 9 is connected to the storage container 9. Furthermore, in the internal space 9s of the storage container 9, the multiple cells 5 of the cell stack 6 are configured so that they can discharge the fuel electrode exhaust gas from the fuel electrode 5a of each cell 5 and the oxygen electrode exhaust gas from the oxygen electrode 5c of each cell 5 to the surrounding space through a gas discharge edge portion 5e that is part of the periphery of each cell 5, and can introduce air from the surrounding space to the oxygen electrode 5c of each cell 5 through an air inlet portion 5i that is separated from the gas discharge edge portion 5e of each cell 5.

[0018] Next, each component of the fuel cell system A will be described. The cells 5 and the cell stack 6 are well known, and therefore will be briefly described without detailed explanation or illustration. The cells 5 are configured as solid oxide cells with a solid electrolyte layer (not shown) between the fuel electrode 5a and the oxygen electrode 5c. The solid electrolyte layer is made of, for example, zirconium oxide. Each cell 5 of the cell stack 6 is configured as a roughly rectangular plate, allowing a hydrogen-containing gas to flow along the surface of the fuel electrode 5a and air to flow along the surface of the oxygen electrode 5c. One of a pair of opposing edge portions of each cell 5 is configured as a gas discharge edge portion 5e through which fuel electrode exhaust gas from the fuel electrode 5a and oxygen electrode exhaust gas from the oxygen electrode 5c are discharged, and the vicinity of the other edge portion is configured as an air inlet portion 5i through which air can be introduced into the oxygen electrode 5c. Although not shown, the edge portion of each cell 5 near which the air inlet portion 5i is configured is provided with a hydrogen-containing gas inlet through which a hydrogen-containing gas can be introduced into the fuel electrode 5a.

[0019] Then, a cell stack 6 is formed by assembling multiple cells 5 in a stacked state while electrically connected in series, with each cell 5 having its gas discharge edge 5e facing in the same direction and each edge having a hydrogen-containing gas inlet facing in the same direction.

[0020] The manifold 12 is disposed on the side surface of the cell stack 6 where the edge portion where the hydrogen-containing gas inlet of each cell 5 is provided is located, in a state where the hydrogen-containing gas inlet of each cell 5 is in communication with the manifold 12. In this way, in the cell stack 6 equipped with the manifold 12, the air inlet 5i of each cell 5 is exposed to the surrounding space and is configured so that the air inlet 5i of each cell 5 can receive air from the surrounding space.

[0021] The cell stack 6 configured in this manner is disposed in the storage container 9 in an orientation in which the manifold 12 is located below, the gas discharge edge 5e of each cell 5 faces upward, and the stacking direction of the multiple cells 5 is horizontal. In the internal space 9s of the storage container 9, an evaporator 2 and a reformer 4 are disposed side by side above the cell stack 6 at a distance from the cell stack 6.

[0022] A combustion space 14 between the cell stack 6 and the evaporator 2 and reformer 4 in the internal space 9s of the storage container 9 is configured so that the anode exhaust gas and oxygen electrode exhaust gas are discharged from the gas discharge edge 5e of each cell 5 and combustible components in the anode exhaust gas can be combusted with oxygen in the oxygen electrode exhaust gas, and this combustion space 14 is used as a combustion unit 8. The combustion unit 8 is provided with an ignition heater 15 that ignites the combustible components in the anode exhaust gas. The combustion unit 8 formed in the combustion space 14 is configured so that the combustible components in the anode exhaust gas can be combusted with oxygen in the oxygen electrode exhaust gas and the combustion heat generated by this combustion can heat the evaporator 2, reformer 4, and cell stack 6 disposed in the internal space 9s of the storage container 9.

[0023] A reforming water supply path 16, through which reforming water is pumped by a reforming water pump 1, is drawn from the outside of the storage container 9 and connected to the evaporator 2, and a raw fuel gas supply path 17, through which raw fuel gas is pumped by a raw fuel pump 3, is also drawn from the outside of the storage container 9 and connected to the evaporator 2. A raw fuel adjustment valve 18 is provided in the raw fuel gas supply path 17 to adjust the flow rate of the raw fuel gas.

[0024] The evaporator 2 is configured to heat and evaporate the reforming water supplied through the reforming water supply passage 16 using the combustion heat transmitted from the combustion section 8, and to mix the water vapor generated by the evaporation of the reforming water with the raw fuel gas supplied through the raw fuel gas supply passage 17.

[0025] The reformer 4 is filled with a reforming catalyst (not shown). The evaporator 2 and the reformer 4 are connected by a relay path 19 so that the raw fuel gas mixed with steam in the evaporator 2 is introduced into the reformer 4. The reformer 4 is configured to reform the raw fuel gas mixed with steam supplied from the evaporator 2 with steam using combustion heat transferred from the combustion section 8, thereby reforming the raw fuel gas into a reformed gas containing hydrogen, i.e., a hydrogen-containing gas.

[0026] The reformer 4 and the manifold 12 are connected by a hydrogen-containing gas passage 11 so as to supply the hydrogen-containing gas produced in the reformer 4 to the manifold 12. The hydrogen-containing gas supplied to the manifold 12 is distributed from the hydrogen-containing gas inlet of each of the plurality of cells 5 of the cell stack 6 to the fuel electrodes 5a of each cell 5, flows upward through the fuel electrodes 5a of each cell 5, and is used for the power generation reaction. After that, the gas is discharged from the gas discharge edge 5e of each cell 5 as fuel electrode exhaust gas into the combustion space 14 used as the combustion section 8.

[0027] An air inlet 20 is provided at the bottom of the storage container 9, and an air supply path 13 through which air is sent out by an air blower 7 is connected to the air inlet 20. An air filter 21 that purifies the air sent out by the air blower 7 is provided in a portion of the air supply path 13 upstream of the air blower 7. In addition, an air flow meter 22 (an example of a flow meter) that detects the flow rate of air supplied through the air supply path 13 is provided in a portion of the air supply path 13 downstream of the air blower 7. In other words, the air supply path 13, the air blower 7, the air filter 21, and the air flow meter 22 constitute an air supply system 23 that supplies air to the oxygen electrodes 5c of each of the multiple cells 5 in the cell stack 6.

[0028] Then, air is purified by the air blower 7 through the air filter 21 and then supplied to the internal space 9s of the storage container 9 through the air supply path 13. The air supplied to the internal space 9s of the storage container 9 in this manner is supplied to the oxygen electrodes 5c of each of the multiple cells 5 of the cell stack 6 from the air inlet portions 5i of each of the cells 5, flows upward through the oxygen electrodes 5c of each cell 5, and is used for the power generation reaction. After that, the air is discharged as oxygen electrode exhaust gas from the gas discharge edge portions 5e of each cell 5 into the combustion space 14 used as the combustion section 8. Then, in the combustion section 8, combustible components in the anode exhaust gas are combusted with the oxygen in the oxygen electrode exhaust gas.

[0029] Furthermore, the storage container 9 is formed with a combustion exhaust gas outlet 24 at the bottom or the like, which discharges the combustion exhaust gas generated in the combustion section 8 to the outside, and a carbon monoxide removal section 25 is provided near the opening of the combustion exhaust gas outlet 24 on the inner surface of the storage container 9, which contains a combustion catalyst (e.g., a platinum-based catalyst) that removes carbon monoxide gas from the combustion exhaust gas discharged to the outside from the combustion exhaust gas outlet 24.

[0030] Next, the control operation of the control unit 10 will be described. An operation unit 26 is provided which transmits various information, such as operation commands for the fuel cell system A, to the control unit 10, and this operation unit 26 is equipped with a display 27 which displays and outputs various information. The display 27 is configured as an LCD (liquid crystal display). A temperature sensor 32 is also connected to the control unit 10. The temperature sensor 32 acquires the outside air temperature, which is the temperature around the fuel cell system A, and transmits the outside air temperature data to the control unit 10.

[0031] The control unit 10 includes a communication unit 30 and a judgment and instruction unit 31. The communication unit 30 communicates with a host computer 29 in a management center (not shown) via a communication network 28 such as the Internet. The management center is installed at a city gas supply company or the like, and the host computer 29 is configured to be able to communicate with the communication units 30 of multiple fuel cell systems A. The communication unit 30 is configured to communicate operating information of the fuel cell system A, such as the consumption amount of raw fuel gas, the output power value, the flow rate of air flowing through the air supply path 13, the voltage applied to the air blower 7, and abnormality information, to the host computer 29 via the communication network 28. The fuel cell system A can also be operated from the host computer 29 via the communication network 28.

[0032] The judgment instruction unit 31 is configured to control the operation of the reforming water pump 1, the raw fuel pump 3, the raw fuel regulating valve 18, the air blower 7, the ignition heater 15, etc., based on commands from the operation unit 26, including commands for the output power value output from the fuel cell system A, and detection information from the air flow meter 22, etc.

[0033] An explanation will now be given of the control of the voltage applied to the air blower 7 to adjust the flow rate of air flowing through the air supply path 13. The judgment instruction unit 31 controls the voltage value applied to the air blower 7 by changing the duty ratio using PWM (Pulse Width Modulation) control, which controls the voltage applied to the air blower 7 through duty control.

[0034] Normal operation will now be described. During normal operation, the judgment and instruction unit 31 operates the raw fuel pump 3, the reforming water pump 1, and the air blower 7 based on the predetermined power setting, which is the predetermined output power of the fuel cell system A set by the operation unit 26. The predetermined power is, for example, rated power. At this time, the judgment and instruction unit 31 operates the raw fuel regulating valve 18 so that the flow rate of the raw fuel gas corresponds to the predetermined power output from the cell stack 6. The judgment and instruction unit 31 also controls the output of the reforming water pump 1 so that the flow rate of the reforming water corresponds to the flow rate of the raw fuel gas. The fuel cell system A has a memory unit (not shown) that stores a data table relating to the flow rates of the raw fuel gas and the reforming water corresponding to the predetermined power. The judgment and instruction unit 31 reads data relating to the flow rates of the raw fuel gas and the reforming water corresponding to the set predetermined power from the memory unit, and controls the aperture of the raw fuel regulating valve 18 and the output of the reforming water pump 1. In addition, the judgment instruction unit 31 controls the duty ratio of the voltage applied to the air blower 7 (hereinafter simply referred to as the duty ratio of the air blower 7) so that the flow rate of air flowing through the air supply path 13 detected by the air flow meter 22 corresponds to the flow rate of the raw fuel gas.

[0035] In normal operation of the fuel cell system A when outputting a predetermined power in a state where the air supply system 23 is not clogged with particulate matter, a predetermined duty ratio is applied to the air blower 7, and a predetermined flow rate, which is the flow rate of air flowing through the air supply path 13, is detected by the air flow meter 22. The judgment instruction unit 31 continuously acquires this predetermined flow rate and duty ratio.

[0036] In this embodiment, during normal operation, the judgment and instruction unit 31 acquires the air flow rate detected by the air flow meter 22 and controls the duty ratio of the air blower 7. However, as the operation time of the fuel cell system A passes, particulate matter such as dust, PM2.5, and yellow sand contained in the outside air adheres to the air supply system 23, causing clogging. When clogging occurs, the pressure loss in the air supply system 23 increases, deteriorating the air flow condition of the air supply system 23. Specifically, the air flow rate detected by the air flow meter 22 decreases. When the air flow condition deteriorates, the judgment and instruction unit 31 increases the duty ratio of the air blower 7 to maintain a predetermined power, thereby controlling the air flow rate corresponding to the predetermined power. In other words, when the air supply system 23 is clogged, a higher duty ratio is applied to the air blower 7 than when the air supply system 23 is not clogged, in order to ensure the same air flow rate.

[0037] In the fuel cell system A of this embodiment, as shown in FIG. 2, a table of the degree of blockage (degree of blockage of the air supply system 23) based on the relationship between the air flow rate and the duty ratio of the air blower 7 instructed by the judgment and instruction unit 31 is stored in the memory unit. Specifically, a state in which the air supply system 23 is not clogged with particulate matter is considered to be the normal state. At this time, a predetermined duty ratio is applied to the air blower 7, a predetermined flow rate flows through the air supply path 13, and a predetermined power is output. The judgment and instruction unit 31 determines that the degree of blockage has increased as the air flow rate decreases from the normal state and the duty ratio increases. The degree of blockage is a continuous or discrete value depending on its magnitude.

[0038] As shown in Fig. 3, the determination and instruction unit 31 also stores in the storage unit a table showing the relationship between the outside temperature and the amount of water vapor supplied to the air supply system 23 according to each degree of blockage. Specifically, when the outside temperature is high, the amount of water vapor is reduced, and when the outside temperature is low, the amount of water vapor is increased. Below, the procedure for determining the amount of water vapor to be supplied to the air supply system 23 and removing particulate matter to clear blockages will be described with reference to Fig. 4.

[0039] During normal operation of the fuel cell system A when outputting a predetermined power when the air supply system 23 is not clogged with particulate matter, a predetermined duty ratio is applied to the air blower 7, and a predetermined flow rate, which is the flow rate of air flowing through the air supply path 13, is detected by the air flow meter 22. The judgment instruction unit 31 continuously acquires this air flow rate and duty ratio. The judgment instruction unit 31 calculates the degree of blockage based on the acquired air flow rate and duty ratio (step S1). A data table showing the relationship between the predetermined flow rate and the predetermined duty ratio is stored in the memory unit. Thereafter, if normal operation continues and the air supply system 23 becomes clogged with particulate matter, the duty ratio that needs to be applied to the air blower 7 to ensure the predetermined flow rate increases. The judgment instruction unit 31 applies a voltage with a high duty ratio to the air blower 7. At this time, the calculated degree of blockage increases.

[0040] If the degree of blockage exceeds a predetermined value (Yes in step S2) and continues for a predetermined period (e.g., one day) or more (Yes in step S3), the judgment and instruction unit 31 determines to switch from normal operation to airflow improvement operation in order to eliminate the blockage caused by particulate matter (step S4). Hereinafter, the timing to switch from normal operation to airflow improvement operation will be referred to as the timing requiring improvement.

[0041] Examples of timing when improvement is necessary include when the judgment instruction unit 31 judges that (1) the air flow rate detected by the air flow meter 22 is a sign of failure due to a "low reading" that is lower than the actual air flow rate, (2) when the low reading becomes severer than a certain level and judges that an alarm should be issued, or (3) when the degree of blockage becomes greater than a predetermined value and judges that a flow abnormality error should be issued. A flow abnormality is an abnormality that, if left unchecked, will completely clog the air supply system 23 and prevent air from flowing.

[0042] The determination and instruction unit 31 determines the amount of water vapor to be supplied to the air supply system 23 based on the degree of blockage and the outside air temperature at the timing when improvement is required, and executes the air flow improving operation (step S5).

[0043] As shown in FIG. 5, during air flow improved operation, the raw fuel pump 3 and the air blower 7 are stopped, and the reforming water pump 1 is operated to supply reforming water to the evaporator 2 through the reforming water supply path 16. At this time, the reforming water pump 1 operates to supply reforming water in an amount corresponding to the amount of steam supplied to the air supply system 23. The evaporator 2 then evaporates the reforming water using the residual heat of the evaporator 2 itself, the residual heat of the combustion section 8, and the residual heat in the storage container 9. The high-temperature steam generated by the evaporation of the reforming water is supplied to the reformer 4 through the relay path 19, heated by the residual heat of the reformer 4, and further supplied to the manifold 12 through the hydrogen-containing gas path 11. The high-temperature steam supplied to the manifold 12 is distributed and supplied to the fuel electrodes 5a of the multiple cells 5 of the cell stack 6, flows upward through the fuel electrodes 5a of each cell 5, and is discharged from the gas discharge edge 5e of each cell 5 into the combustion space 14 formed in the combustion section 8.

[0044] The high-temperature water vapor discharged into the combustion space 14 fills the internal space 9s of the storage container 9, and most of the high-temperature water vapor that has filled the internal space 9s is discharged to the outside of the storage container 9 through the air inlet 20, flows into the air supply path 13, and flows back through the air supply path 13 while passing through the air flow meter 22 and the air filter 21. The water vapor remaining in the internal space 9s is discharged to the outside of the storage container 9 through the combustion exhaust gas outlet 24. Incidentally, since the water vapor discharged to the outside of the storage container 9 from the combustion exhaust gas outlet 24 passes through the carbon monoxide removal section 25, the pressure loss of the water vapor passing through the combustion exhaust gas outlet 24 is significantly greater than the pressure loss of the water vapor flowing back through the air supply path 13. Therefore, the water vapor that has filled the internal space 9s is preferentially discharged back through the air supply path 13.

[0045] Then, as the high-temperature water vapor passes through the air flow meter 22 and the air filter 21 and flows back through the air supply line 13, deposits including ammonium sulfate and the like adhering to the air filter 21, the air flow meter 22, etc. are dissolved and removed by the water vapor, improving the air flow condition of the air supply system 23.

[0046] Returning to FIG. 4, the air flow improvement operation is performed for a predetermined time. After the air flow improvement operation is completed, an improvement confirmation operation is performed to confirm the air flow state (step S6). The improvement confirmation operation is, for example, an operation in which a predetermined power output is changed in a short period of time. During the improvement confirmation operation, the judgment instruction unit 31 acquires the air flow rate and duty ratio at each output and calculates the degree of blockage. If the calculated degree of blockage during this improvement confirmation operation has decreased to a reference value or below (Yes in step S7), it is considered that the air flow state of the air supply system 23 has been appropriately improved, and the judgment instruction unit 31 switches from the improvement confirmation operation to normal operation (step S8).

[0047] On the other hand, if the degree of blockage is still greater than the reference value during the improvement confirmation operation (No in step S7), the judgment and instruction unit 31 determines that the air flow state of the air supply system 23 has not yet been appropriately improved, and switches back to the air flow improvement operation. During this second air flow improvement operation, the judgment and instruction unit 31 controls the amount of reforming water supplied to the evaporator 2 so that the amount of water vapor supplied to the air supply system 23 is greater than the initial amount of water vapor by a predetermined percentage (for example, 30%). Then, the second air flow improvement operation is executed (step S9). The second air flow improvement operation is similar to the first air flow improvement operation, and therefore a detailed description thereof will be omitted.

[0048] After the second air flow improvement operation is completed, a second improvement confirmation operation is performed (step S10). If the degree of blockage is reduced to the reference value or less during this improvement confirmation operation (Yes in step S11), it is considered that the air flow condition of the air supply system 23 has been appropriately improved, and the judgment instructing unit 31 switches from the improvement confirmation operation to normal operation (step S8).

[0049] On the other hand, if the degree of blockage is greater than the reference value despite two improvement check runs (No in step S11), the judgment and instruction unit 31 determines that the cause of the blockage in the air supply system 23 is not an attachment containing ammonium sulfate or the like, but rather the attachment of inorganic foreign matter that is not dissolved in high-temperature steam, or a malfunction of the air flow meter 22, and notifies the host computer 29 of this fact from the communication unit 30 via the communication network 28 (step S12). Specifically, the cause of the blockage in the air supply system 23 is displayed on a display (not shown) of the host computer 29.

[0050] In this way, by determining the amount of water vapor to be supplied to the air supply system 23 based on the degree of blockage and the outside air temperature, clogging of the air supply system 23 due to particulate matter can be effectively eliminated.

[0051] Other Embodiments (1) In the first embodiment, the operation mode is switched to the airflow improvement operation mode when the degree of blockage exceeds a predetermined value and continues for a predetermined period (one day) or longer. However, this is not limited to this. The predetermined period may be a period other than one day, or no predetermined period may be set. In the latter case, the operation mode is switched to the airflow improvement operation mode when the degree of blockage exceeds a predetermined value.

[0052] (2) In the first embodiment, the amount of water vapor in the second airflow improving operation is increased by 30% compared to the amount of water vapor in the first operation, but the predetermined percentage increase may be other than 30%.

[0053] (3) In the first embodiment, the airflow improving operation is performed a second time when the degree of blockage does not fall below the reference value. However, the airflow improving operation may be performed three or more times.

[0054] (4) In the first embodiment described above, if the degree of obstruction does not fall below the reference value even after repeating the air flow operation twice, the communication unit 30 notifies the host computer 29 via the communication network 28. However, instead of notifying the host computer 29, or in addition to notifying the host computer 29, the display 27 of the operation unit 26 may be configured to notify the host computer 29.

[0055] (5) In the first embodiment, the control unit 10 of the fuel cell system A determines the timing for switching from normal operation to air flow improved operation, but this is not limited to this. The host computer 29 may determine the timing for improvement and execute the air flow improved operation instead of the control unit 10.

[0056] (6) In the first embodiment, the air flow improvement operation is immediately switched from normal operation to the air flow improvement operation when an improvement is required, but this is not limited to this. During normal operation, the temperature of the fuel cell system A is high, so if the air flow improvement operation is continued and high-temperature steam is supplied to the air supply system 23, there is a concern that this may affect the durability of the fuel cell system A. Therefore, as a control method that reduces the impact on durability, a shutdown process that stops normal operation may be performed for a certain period of time, and the temperature of the power generation unit may be lowered to a level that does not affect durability, before the air flow improvement operation is executed.

[0057] (7) In the first embodiment, the air flow improvement operation is performed when improvement is required during normal operation, but this is not limited to this. As an example of control that has little impact on the durability of the fuel cell system A, the air flow improvement operation may be performed at the timing of the shutdown process on a microcomputer meter shutdown day, which occurs periodically, regardless of the degree of blockage.

[0058] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0059] The present invention can be used in a fuel cell system. [Explanation of symbols]

[0060] 1: Reformed water pump 2: Evaporator 3: Raw fuel pump 4: Reformer 5: Cell 5a: Fuel electrode 5c: Oxygen electrode 6: Cell stack 7: Air blower 8: Combustion section 9: Storage container 9s :Internal space 10: Control section 13: Air supply channel 21: Air filter 22: Air flow meter (flow meter) 23: Air supply system A: Fuel cell system

Claims

1. an evaporator that evaporates reforming water supplied by a reforming water pump; a reformer that generates a hydrogen-containing gas by causing a reforming reaction between the raw fuel supplied by the raw fuel pump and the steam supplied from the evaporator; An air blower that takes in air from the outside and sends it out; an air filter for cleaning the air taken into the air blower; a cell stack including a plurality of stacked cells each having a fuel electrode and an oxygen electrode, the hydrogen-containing gas being supplied from the reformer to the fuel electrode and the air delivered by the air blower being supplied to the oxygen electrode to generate electricity; a combustion unit that burns combustible components in the anode exhaust gas discharged from the anode with oxygen in the cathode exhaust gas discharged from the cathode, and heats the reformer and the evaporator with the resulting combustion heat; a storage container that houses the evaporator, the reformer, the cell stack, and the combustion unit in its internal space; an air supply path connecting the air blower and the storage container and supplying the air blown out from the air blower to the internal space of the storage container; a flow meter disposed in the air supply path and configured to detect the flow rate of the air blown by the air blower; a control unit that controls the operation, The control unit controlling the duty ratio to control energization of the air blower, and acquiring the flow rate of the air sent from the air blower when energized at the duty ratio and detected by the flow meter; calculating a degree of blockage of the air supply system including the air filter, the air blower, and the air supply path based on the duty ratio and the air flow rate, and acquiring an outside air temperature; stopping the raw fuel pump and the air blower based on the degree of blockage and starting an air flow improvement operation in which the reforming water pump is operated; a fuel cell system that, during the air flow improvement operation, determines the amount of reforming water to be supplied by the reforming water pump to generate the steam to be supplied to the air supply system based on the degree of blockage and the outside air temperature.

2. 2. The fuel cell system according to claim 1, wherein the control unit reduces the amount of the reforming water supplied by the reforming water pump as the outside air temperature increases.

3. 3. The fuel cell system of claim 1, wherein, when the degree of blockage does not decrease to below the reference value even after the air flow improvement operation, the control unit determines the amount of reforming water supplied by the reforming water pump so that the amount of steam generated is increased by a predetermined percentage, and performs the air flow improvement operation again using the water steam generated in the predetermined percentage increase.

Images