Fuel cell system

Abstract

To provide a fuel cell system capable of eliminating constriction of a flow passage of raw fuel even if it occurs in a vaporization part.SOLUTION: The fuel cell system includes a vaporization part 5 for vaporizing water supplied from a water tank 19, a reforming part 6, and a cell stack 9 having a plurality of fuel cells 8 for generating power by using fuel gas. The fuel cell system includes a raw-fuel pump 3b for supplying raw-fuel, an air pump 22 for supplying air, a water tank 19, a water pump 21 for supplying water to a vaporization part 5, and a control device 26, wherein the control device 26 stops the raw-fuel pump 3b, the air pump 22, and the water pump 21 when a predetermined process executing condition is satisfied, and supplies a predetermined injection liquid to the vaporization part 5 by a predetermined amount while stopping power generation in a cell stack 9. A liquid injection process is executed in which the liquid for injection is not discharged from the vaporization part 5 at least during a predetermined standby time.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] The fuel cell system described in Patent Document 1 (JP 2013-191319 A) includes an evaporation section (evaporation section 2) that vaporizes water supplied from a water tank (4), a reforming section (3) that produces fuel gas by steam reforming a raw fuel using steam supplied from the evaporation section, and a cell stack (fuel cell 1) having a plurality of fuel cell units that generate electricity using the fuel gas produced in the reforming section. In addition, the fuel cell system includes a combustion section (105) that combusts off-gas discharged from the cell stack, and the water tank (4) that stores condensed water contained in exhaust gas that includes gas generated by combustion in the combustion section as water to be used for steam reforming. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-191319 Summary of the Invention [Problem to be solved by the invention]

[0004] In such a fuel cell system, when the water supplied to the vaporizer evaporates, substances contained in the water may precipitate inside the vaporizer. If such precipitates accumulate, the flow path of the raw fuel inside the vaporizer becomes narrowed, making it difficult for the raw fuel to flow.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a fuel cell system that can resolve narrowing of the raw fuel flow path in the vaporization section even if such narrowing occurs. [Means for solving the problem]

[0006] A characteristic configuration of the fuel cell system according to the present invention for achieving the above object is a system including, in an internal space within an internal container, a vaporization section that vaporizes water supplied from a water tank, a reforming section that generates fuel gas by steam reforming raw fuel using steam supplied from the vaporization section, a cell stack having a plurality of fuel cell units that generate electricity using the fuel gas generated in the reforming section, a combustion section that combusts off-gas discharged from the cell stack, and an igniter that ignites the off-gas, wherein the internal container is provided with an air inlet port used to supply air from the outside to the internal space, and an exhaust port used to exhaust exhaust gas including gas generated by combustion in the combustion section from the internal space to the outside, a raw fuel pump that supplies the raw fuel to the reforming section; an air pump that supplies air to the inner space through the air inlet; a water tank that stores condensed water produced by condensing water vapor contained in the exhaust gas discharged from the inner space through the exhaust port as water to be used for the steam reforming; a water pump that supplies the water stored in the water tank to the vaporization section; and a control device, When predetermined processing execution conditions are met, the control device stops the raw fuel pump, the air pump, and the water pump and stops power generation in the cell stack, while supplying a predetermined amount of a predetermined injection liquid to the vaporization section, and executes a liquid injection process in which the injection liquid is not discharged from the vaporization section for at least a predetermined waiting time.

[0007] According to the above characteristic configuration, the liquid injection process is performed, so that the interior of the vaporizer is continuously immersed in the injection liquid during the standby time. During this standby period, impurities that have precipitated inside the vaporizer dissolve in the injection liquid, and the liquid falls by gravity to the bottom of the vaporizer. In other words, even if impurities are attached to the interior of the vaporizer, the impurities are expected to dissolve in the injection liquid through the liquid injection process and collect at the bottom of the vaporizer. Furthermore, in the area where the impurities dissolved in the injection liquid were originally attached, the impurities move to other areas, forming a space through which the raw fuel can be flowed. Therefore, it is possible to provide a fuel cell system that can eliminate narrowing of the flow path of the raw fuel in the vaporizing section.

[0008] Another characteristic configuration of the fuel cell system of the present invention is that it comprises a liquid reservoir for storing the injection liquid and a liquid pump for supplying the injection liquid from the liquid reservoir to the vaporization section, and the control device supplies the injection liquid stored in the liquid reservoir to the vaporization section by operating the liquid pump during the liquid injection process.

[0009] According to the above characteristic configuration, the amount of injection liquid supplied to the vaporizing section per unit time can be freely adjusted by controlling the operation of the liquid pump.

[0010] Another characteristic configuration of the fuel cell system of the present invention is that the water tank is used as the liquid reservoir, the water pump is used as the liquid pump, and the water stored in the water tank is used as the injection liquid.

[0011] According to the above-mentioned characteristic configuration, the water stored in the water tank can be used as the injection liquid. Since the impurities precipitated inside the vaporizer were originally contained in the water supplied from the water tank, the impurities can be effectively dissolved by the water.

[0012] Another characteristic feature of the fuel cell system according to the present invention is that an acidic liquid is stored in the liquid reservoir, and the acidic liquid stored in the liquid reservoir is used as the injection liquid.

[0013] According to the above characteristic configuration, impurities can be quickly dissolved by supplying an acidic liquid to the vaporizing section in the liquid injection process.

[0014] Another characteristic configuration of the fuel cell system of the present invention is that it is equipped with a vibration generator that can impart vibrations to the vaporization section, and the control device uses the vibration generator to impart vibrations to the vaporization section at least either during the standby time or after the standby time has elapsed.

[0015] According to the above characteristic configuration, by vibrating the vaporization section at least either during the waiting time or after the waiting time has elapsed, i.e., after supplying the injection liquid to the vaporization section, the liquid in which impurities are dissolved becomes more likely to move to the bottom of the vaporization section.

[0016] Another characteristic feature of the fuel cell system according to the present invention is that, after the waiting time has elapsed, the control device operates the raw fuel pump and ignites the igniter, thereby performing a combustion process to combust the off-gas discharged from the cell stack.

[0017] According to the above-described characteristic configuration, the liquid collected at the bottom of the vaporizer due to the liquid injection process is heated by the combustion process. Then, in the vaporizer, the injected liquid is vaporized by heating, so that only the dissolved impurities remain at the bottom of the vaporizer. As a result, the vaporizer, which has a good flow of raw fuel, can be used to continue power generation in the fuel cell system.

[0018] Another characteristic feature of the fuel cell system of the present invention is that it is provided with a discharge mechanism capable of discharging the liquid and gas present inside the vaporization section, and the control device operates the discharge mechanism to discharge the liquid and gas present inside the vaporization section after the waiting time has elapsed.

[0019] According to the above-described characteristic configuration, the liquid containing dissolved impurities is quickly discharged by the discharge mechanism, which prevents impurities from being precipitated again from the liquid inside the vaporizer.

[0020] Another characteristic feature of the fuel cell system of the present invention is that the control device determines that the processing execution condition is satisfied each time a stop timing occurs to stop the raw fuel pump, the air pump, and the water pump and to stop power generation in the cell stack, or each time the stop timing occurs a predetermined number of times.

[0021] According to the above characteristic configuration, by periodically performing the liquid injection process, it is possible to prevent narrowing of the flow path of the raw fuel in the vaporization section, and even if narrowing of the flow path of the raw fuel does occur, it is possible to quickly resolve the narrowing.

[0022] Another characteristic configuration of the fuel cell system according to the present invention is that it includes a raw fuel flow meter that measures the flow rate per unit time of the raw fuel supplied to the reforming section by the raw fuel pump, and the raw fuel is configured to be supplied to the reforming section via the vaporization section, and the control device determines that the processing execution condition is satisfied when there is a deviation of more than a reference value in the correlation between the output of the raw fuel pump and the measurement value of the raw fuel flow meter.

[0023] For example, the raw fuel pump increases or decreases the output of the raw fuel pump (e.g., the duty ratio of the PWM control of the raw fuel pump) so that the flow rate per unit time of the raw fuel measured by the raw fuel flow meter becomes the target raw fuel flow rate. Therefore, if there is no constriction of the raw fuel flow path in the vaporizer, it is considered that there is only a deviation less than the reference value in the correlation between the output of the raw fuel pump and the measurement value of the raw fuel flow meter. On the other hand, if there is a constriction of the raw fuel flow path in the vaporizer, the pressure loss of the raw fuel increases, and it is considered that there is a deviation greater than the reference value in the correlation between the output of the raw fuel pump and the measurement value of the raw fuel flow meter. Therefore, in this characteristic configuration, when there is a deviation of a reference value or more in the correlation between the output of the raw fuel pump and the measurement value of the raw fuel flow meter, the control device determines that the above-mentioned processing execution condition is satisfied and executes the liquid injection processing, thereby eliminating the narrowing of the raw fuel flow path in the vaporization unit.

[0024] Another characteristic feature of the fuel cell system according to the present invention is that it includes a temperature adjusting section that adjusts the temperature of the injection liquid supplied to the vaporizing section.

[0025] According to the above-mentioned characteristic configuration, the injection liquid whose temperature has been adjusted by the temperature adjustment unit can be supplied to the vaporization unit, thereby allowing impurities that have precipitated inside the vaporization unit to be effectively dissolved in the injection liquid. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a diagram showing the configuration of a fuel cell system according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing a schematic configuration of the inside of a vaporizing section and a reforming section. [Figure 3] FIG. 4 is a diagram showing the configuration of a fuel cell system according to a second embodiment. [Figure 4] FIG. 10 is a diagram showing the configuration of a fuel cell system according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0027] First Embodiment A fuel cell system according to a first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing the configuration of the fuel cell system according to the first embodiment.

[0028] The fuel cell system includes various components inside an outer vessel 1. A hot module 31 is provided inside the outer vessel 1. The hot module 31 has an inner vessel 2 that houses devices such as a cell stack 9 that operate in a high-temperature environment. The hot module 31 houses a vaporization section 5, a reforming section 6, a manifold 7, the cell stack 9, a combustion section 11, an igniter 10, and the like in an inner space 28 inside the inner vessel 2.

[0029] As will be described later, the fuel cell system includes a raw fuel pump 3b that supplies raw fuel to the reforming section 6, an air pump 22 that supplies air to the inner space 28 via the air inlet 12, a water tank 19 that stores condensed water produced by condensing water vapor contained in the exhaust gas discharged from the inner space 28 via the exhaust port 13 as water to be used for steam reforming, a water pump 21 that supplies the water stored in the water tank 19 to the vaporizing section 5, and a control device 26. In this embodiment, the raw fuel is supplied to the reforming section 6 via the vaporizing section 5.

[0030] The raw fuel is supplied to the vaporization unit 5 via a raw fuel supply path L1. In the example shown in FIG. 1 , a raw fuel supply unit 3 and a desulfurization unit 4 are provided along the raw fuel supply path L1. The desulfurization unit 4 removes sulfur compounds and other contaminants contained in the raw fuel. The raw fuel supply unit 3 flows a predetermined target amount of raw fuel through the raw fuel supply path L1. For example, the raw fuel supply unit 3 includes a raw fuel flow meter 3a that measures the flow rate per unit time of the raw fuel flowing through the raw fuel supply path L1, and a raw fuel pump 3b that flows the raw fuel through the raw fuel supply path L1 so that the flow rate per unit time of the raw fuel measured by the raw fuel flow meter 3a becomes the target amount of raw fuel. The control device 26 that controls the operation of the fuel cell system operates the raw fuel pump 3b so that the flow rate per unit time of the raw fuel measured by the raw fuel flow meter 3a becomes the target amount of raw fuel. For example, the raw fuel pump 3b increases or decreases the output of the raw fuel pump 3b (for example, the duty ratio of the PWM control of the raw fuel pump 3b) so that the flow rate per unit time of the raw fuel measured by the raw fuel flow meter 3a (i.e., the flow rate per unit time of the raw fuel supplied to the vaporization section 5) becomes the target raw fuel flow rate.

[0031] The vaporization unit 5 vaporizes water supplied from the water tank 19 via the water supply passage L6 to generate steam, and supplies the steam to the reforming unit 6. The water tank 19 is provided with a heater 29 that can heat the water stored in the water tank 19. In other words, the fuel cell system includes the heater 29 as a temperature adjustment unit that adjusts the temperature of the water as an injection liquid to be supplied to the vaporization unit 5. The operation of the heater 29 is controlled by the control device 26.

[0032] The reforming unit 6 generates fuel gas by steam reforming the hydrocarbon-containing raw fuel (such as city gas) supplied via the raw fuel supply line L1 using steam supplied from the vaporizing unit 5. That is, water stored in the water tank 19 is used for steam reforming of the raw fuel in the reforming unit 6. The reforming unit 6 is provided with a temperature measuring device T1 that measures the temperature of the reforming unit 6. The measurement result of this temperature measuring device T1 is transmitted to the control device 26.

[0033] 2 is a diagram showing a schematic configuration of the interior of the vaporizer 5 and the reformer 6. As shown in the figure, a raw fuel supply channel L1 and a water supply channel L6 are connected to the vaporizer 5. The cylindrical vaporizer 5 contains particles 5a such as alumina. The cylindrical reformer 6 contains a carrier 6a carrying a reforming catalyst on its surface.

[0034] The cell stack 9 is configured to have a plurality of fuel cell units 8 that generate electricity using the fuel gas produced in the reforming unit 6. For example, the fuel cell units 8 are solid oxide cells with a solid electrolyte provided between an anode and a cathode. The fuel gas produced in the reforming unit 6 passes through a fuel gas supply path L3 to reach the manifold 7, where the fuel gas is distributed to the anodes of the fuel cell units 8. A power conversion circuit unit 25 that extracts current from the cell stack 9 is connected to the cell stack 9. The operation of the power conversion circuit unit 25 is controlled by a control device 26. For example, the control device 26 can control the operation of the power conversion circuit unit 25 to start and stop power generation in the cell stack 9.

[0035] The space above the cell stack 9 serves as a combustion section 11 that combusts off-gas (i.e., gas discharged from the anode) discharged from the cell stack 9, which has a plurality of fuel cell cells 8. An igniter 10 ignites the off-gas. The combustion heat generated in the combustion section 11 is transferred to the vaporization section 5, reforming section 6, and other sections inside the inner vessel 2, and is used for water vaporization by the vaporization section 5 and steam reforming by the reforming section 6.

[0036] The inner container 2 is provided with an air inlet 12 used to supply air from the outside to the inner space 28, and an exhaust port 13 used to exhaust exhaust gas including gas (combustion exhaust gas) generated by combustion in the combustion section 11 from the inner space 28 to the outside, An air supply path L2 is connected to the air inlet 12 of the inner container 2, and air (oxygen) is supplied into the inner container 2. An air pump 22 serving as an air supply unit is provided midway along the air supply path L2. For example, the control device 26 operates the air pump 22 so that the flow rate of air per unit time becomes a target flow rate. The air supplied into the inner container 2 is supplied to the cathode and used for power generation, and is also used for combustion in the combustion unit 11.

[0037] Gas present inside the inner container 2 is discharged to the outside of the inner container 2 through the exhaust port 13 of the inner container 2 .

[0038] The exhaust gas discharged from the exhaust port 13 to the outside of the inner container 2 flows through the exhaust gas flow path L4 and is supplied to the heat exchanger 16. In the heat exchanger 16, heat is exchanged between the exhaust gas and hot water flowing through the hot water circulation path L9 as a heat medium for exhaust heat recovery, i.e., the exhaust gas is cooled, and the moisture contained in the exhaust gas is condensed.

[0039] The fuel cell system includes a heat recovery device H that recovers heat from the combustion exhaust gas discharged from the combustion unit 11. Specifically, the heat recovery device H includes a heat exchange unit 16 to which exhaust gas discharged from the inner container 2, including the combustion exhaust gas generated in the combustion unit 11, a hot water storage tank 23 that stores hot water, a hot water circulation path L9 through which hot water circulates between the heat exchange unit 16 and the hot water storage tank 23, and a hot water pump 24 that pumps hot water through the hot water circulation path L9, and is configured to supply hot water taken out from the bottom of the hot water storage tank 23 to the heat exchange unit 16 and return the hot water that has flowed through the heat exchange unit 16 to the top of the hot water storage tank 23, thereby circulating the hot water, so that the heat of the combustion exhaust gas recovered by the heat exchange unit 16 is stored in the hot water storage tank 23.

[0040] A branching section 17 serving as a gas-liquid separator is provided in the exhaust gas flow path L4 downstream of the heat exchanger 16, and a water recovery path L5 branches off from the exhaust gas flow path L4. Gas-phase components in the exhaust gas are discharged to the outside of the outer container 1 through the exhaust gas flow path L4, and liquid-phase components (condensed water) in the exhaust gas pass through the water recovery path L5 and reach the water tank 19, where they are stored. A water purifier 15 containing an ion exchange resin or the like is provided between the branching section 17 and the water tank 19, and removes impurities from the water that flows from the exhaust gas flow path L4 into the water recovery path L5. In this way, the water tank 19 is configured to store recovered water recovered from the combustion exhaust gas by cooling the combustion exhaust gas in the heat recovery device H.

[0041] Condensed water recovered using the water recovery line L5 is supplied to the water tank 19. The water stored in the water tank 19 is supplied to the vaporization unit 5 via the water supply line L6. A water pump 21 serving as a water supply unit is provided midway along the water supply line L6. The control device 26 operates the water pump 21 so that the amount of water per unit time supplied to the vaporization unit 5 becomes a target flow rate. For example, the water pump 21 operates at a target output determined according to the target water volume, causing a predetermined target volume of water to flow through the water supply line L6. The control device 26 can supply water to the vaporization unit 5 by rotating the water pump 21 forward, and can also discharge water or gas from the vaporization unit 5 toward the water tank 19 by rotating the water pump 21 backward.

[0042] As described above, in the heat exchanger 16, heat exchange takes place between the exhaust gas and hot water, which serves as a heat medium for exhaust heat recovery and flows through the hot water circulation path L9. The hot water is stored in the hot water storage tank 23 and circulates between the hot water storage tank 23 and the heat exchanger 16 via the hot water circulation path L9. A hot water pump 24 is provided in the hot water circulation path L9 from the hot water storage tank 23 to the heat exchanger 16.

[0043] With this configuration, hot water supplied from the bottom of the hot water storage tank 23 to the heat exchanger 16 via the hot water circulation path L9 is heated in the heat exchanger 16, and the heated hot water is supplied via the hot water circulation path L9 to the top of the hot water storage tank 23. In this way, hot water is stored in the hot water storage tank 23 in a state that forms temperature stratification, i.e., heat is stored, such that relatively high temperature hot water exists in the top of the hot water storage tank 23 and relatively low temperature hot water exists in the bottom of the hot water storage tank 23.

[0044] A water supply line L7 for supplying water (clean water) to the hot water storage tank 23 is connected to the bottom of the hot water storage tank 23, and a hot water outlet line L8 for discharging the hot water stored in the hot water storage tank 23 to the outside is connected to the top of the hot water storage tank 23. A predetermined water supply pressure is also applied to the hot water inside the hot water storage tank 23 by the water supply line L7 to which water supply pressure is applied. With this configuration, in the hot water storage tank 23, for example, when a water faucet (not shown) connected to the hot water outlet line L8 is opened, hot water is discharged from the hot water storage tank 23 to the hot water outlet line L8, and in response, water is supplied into the hot water storage tank 23 from the water supply line L7.

[0045] The fuel cell system also includes a control device 26 and a storage device 27 that stores information handled by the fuel cell system (for example, details of process execution conditions and details of liquid injection processes, which will be described later). The control device 26 controls the operations of various devices such as the igniter 10, the raw fuel pump 3b, the water pump 21, the air pump 22, and the hot and cold water pump 24.

[0046] In such a fuel cell system, if the water supplied to the vaporizer 5 contains impurities, the impurities may precipitate on the surfaces of the particles 5a when the water is vaporized in the vaporizer 5. Continuous precipitation of impurities on the surfaces of the particles 5a may result in a narrowing of the raw fuel flow path inside the vaporizer 5. For example, the exhaust gas flow path and the hot water flow path may communicate with each other in the heat exchanger 16, causing hot water containing a large amount of impurities to enter the exhaust gas flow path L4. Even in such a case, most of the impurities are removed by the water purifier 15, but impurities that cannot be removed by the water purifier 15 are stored in the water tank 19 and then supplied to the vaporizer 5. As a result, if the exhaust gas flow path and the hot water flow path communicate with each other in the heat exchanger 16, a large amount of impurities (e.g., sodium carbonate) will precipitate in the vaporizer 5, potentially narrowing the raw fuel flow path.

[0047] Therefore, when a predetermined process execution condition is satisfied, the control device 26 of the fuel cell system of this embodiment stops the raw fuel pump 3b, the air pump 22, and the water pump 21, and also stops power generation in the cell stack 9, while supplying a predetermined amount (e.g., 50 mL) of a predetermined injection liquid to the vaporization unit 5 and executing a liquid injection process that does not discharge the injection liquid from the vaporization unit 5 for at least a predetermined waiting time (e.g., 1 hour). Note that, in order to prevent the injection liquid supplied to the vaporization unit 5 from vaporizing, the control device 26 preferably executes the liquid injection process while, for example, the temperature of the vaporization unit 5 is below the boiling point of the injection liquid. In this embodiment, the temperature measured by a temperature measuring device T1 provided in the reforming unit 6 adjacent to the vaporization unit 5 may be referred to as the temperature of the vaporization unit 5.

[0048] Specifically, the fuel cell system includes a liquid reservoir T that stores a liquid to be injected and a liquid pump P that supplies the liquid to be injected from the liquid reservoir T to the vaporization unit 5. In the liquid injection process, the control device 26 supplies the liquid to be injected stored in the liquid reservoir T to the vaporization unit 5. In this embodiment, the water tank 19 is used as the liquid reservoir T, the water pump 21 is used as the liquid pump P, and the water stored in the water tank 19 is used as the liquid to be injected. That is, in the liquid injection process, the water (liquid to be injected) stored in the water tank 19 is supplied to the vaporization unit 5. The impurities that precipitate inside the vaporization unit 5 are substances that were originally contained in the water supplied from the water tank 19, and therefore the impurities can be effectively dissolved by the water. In addition, the control device 26 can freely adjust the amount of water supplied per unit time to the vaporization unit 5 by controlling the operation of the water pump 21 (liquid pump P).

[0049] Furthermore, in the liquid injection process, control device 26 may operate heater 29, which serves as a temperature control unit that adjusts the temperature of the water stored in water tank 19, to heat water heated to a predetermined temperature and supply it to vaporization unit 5. For example, if water heated to 40°C or higher is supplied to vaporization unit 5, sodium carbonate that has precipitated as an impurity inside vaporization unit 5 can be well dissolved in the water.

[0050] By carrying out such a liquid injection process, the state in which the inside of the vaporizer 5 is immersed in water (injection liquid) continues for the above-mentioned waiting time. Then, during this waiting period, impurities that have precipitated inside the vaporizer 5 dissolve in the water, and the solution falls by gravity to the bottom of the vaporizer 5. In other words, even if impurities are attached to the inside of the vaporizer 5, the impurities are expected to dissolve in water through the liquid injection process, and the solution will collect at the bottom of the vaporizer 5. Then, in the area where the impurities dissolved in water were originally attached, the impurities move to other areas, forming a space, through which the raw fuel can be flowed.

[0051] The above-mentioned processing execution conditions can be set as appropriate. For example, the control device 26 may determine that the processing execution conditions are satisfied each time a stop timing occurs to stop the raw fuel pump 3b, the air pump 22, and the water pump 21 and to stop power generation in the cell stack 9, or each time a predetermined number of stop timings occur. In other words, by periodically executing the liquid injection processing, it is possible to prevent narrowing of the raw fuel flow path in the vaporization unit 5, and even if narrowing of the raw fuel flow path does occur, it is possible to quickly resolve the narrowing.

[0052] Alternatively, the control device 26 may determine that the processing execution condition is satisfied when there is a deviation equal to or greater than a reference value in the correlation between the output of the raw fuel pump 3b and the measurement value of the raw fuel flow meter 3a.

[0053] Specifically, as described above, the raw fuel pump 3b increases or decreases the output of the raw fuel pump 3b (e.g., the duty ratio of the PWM control of the raw fuel pump 3b) so that the flow rate per unit time of the raw fuel measured by the raw fuel flow meter 3a becomes the target raw fuel flow rate. Therefore, when no constriction of the raw fuel flow path occurs in the vaporization unit 5 (i.e., when the raw fuel pump 3b is supplying the raw fuel normally), the correlation between the output of the raw fuel pump 3b and the measurement value of the raw fuel flow meter 3a deviates by less than a reference value. For example, when a standard measurement value of the raw fuel flow meter 3a is determined for each output of the raw fuel pump 3b (e.g., 30%), it is considered that, when no constriction of the raw fuel flow path occurs in the vaporization unit 5, the actual measurement value of the raw fuel flow meter 3a deviates from the standard measurement value by less than the reference value (e.g., less than ±30%).

[0054] On the other hand, if a narrowing occurs in the flow path of the raw fuel in the vaporizing section 5, the pressure loss of the raw fuel increases, and it is therefore considered that a deviation of more than the reference value exists in the correlation between the output of the raw fuel pump 3b and the measurement value of the raw fuel flow meter 3a. For example, if a standard measurement value of the raw fuel flow meter 3a is determined for each output (e.g., 30%) of the raw fuel pump 3b, if a narrowing occurs in the flow path of the raw fuel in the vaporizing section 5, it is considered that the actual measurement value of the raw fuel flow meter 3a will deviate from the standard measurement value to the smaller side by more than the reference value.

[0055] Therefore, when there is a deviation equal to or greater than a reference value in the correlation between the output of the raw fuel pump 3b and the measurement value of the raw fuel flow meter 3a, the control device 26 determines that the above-mentioned processing execution condition is satisfied and executes the liquid injection processing. As a result, even if a narrowing of the raw fuel flow path in the vaporization unit 5 has occurred, the narrowing can be resolved.

[0056] In this way, in the liquid injection process, the control device 26 operates the water pump 21 to supply water stored in the water tank 19 as the injection liquid to the vaporization unit 5. As a result, it is expected that the impurities precipitated on the surfaces of the particles 5a will dissolve in the water during the waiting time. Then, it is expected that the liquid with the dissolved impurities will accumulate at the bottom of the vaporization unit 5.

[0057] Then, after the standby time has elapsed, the control device 26 operates the raw fuel pump 3b and ignites the igniter 10, thereby performing a combustion process to combust the off-gas discharged from the cell stack 9. That is, by operating the raw fuel pump 3b, the raw fuel passes through the vaporization section 5, the reforming section 6, the manifold 7, and the cell stack 9 and reaches the combustion section 11, where it is combusted. As a result, the liquid accumulated at the bottom of the vaporization section 5 is heated and vaporized, and the original impurities precipitate at the bottom of the vaporization section 5. That is, the impurities that had adhered to the surfaces of the particles 5a and narrowed the gas flow path move to the bottom of the vaporization section 5, and the narrowing of the raw fuel flow path is resolved.

[0058] Alternatively, the fuel cell system may be provided with a discharge mechanism capable of discharging the liquid and gas present inside the vaporization unit 5, and the control device 26 may operate the discharge mechanism after a standby time has elapsed to discharge the liquid and gas present inside the vaporization unit 5, rather than or in addition to performing combustion in the combustion unit 11 as described above. For example, the water pump 21 provided in the fuel cell system may be used as a discharge mechanism by operating it in reverse rotation.

[0059] Second Embodiment The fuel cell system of the second embodiment differs from the first embodiment in that it includes a liquid reservoir T separate from the water tank 19. The fuel cell system of the second embodiment will be described below, but a description of the same configuration as in the above embodiment will be omitted.

[0060] 3 is a diagram showing the configuration of a fuel cell system according to a second embodiment. As shown in the figure, a liquid reservoir T, separate from a water tank 19, is provided inside an outer container 1. The liquid reservoir T and the vaporization unit 5 are connected by a liquid supply path Lp through which the liquid flows. A liquid pump P is provided midway along the liquid supply path Lp. In the liquid injection process, the control device 26 operates the liquid pump P (forward rotation operation) to supply the injection liquid stored in the liquid reservoir T to the vaporization unit 5.

[0061] Furthermore, the liquid reservoir T is provided with a heater 32 that can heat the injection liquid stored in the liquid reservoir T. In other words, the fuel cell system is provided with the heater 32 as a temperature adjustment unit that adjusts the temperature of the injection liquid to be supplied to the vaporization unit 5. The operation of the heater 32 is controlled by the control device 26. As described in the above embodiment, by adjusting the temperature of the injection liquid to be supplied to the vaporization unit 5, impurities that have precipitated inside the vaporization unit 5 can be effectively dissolved in the injection liquid.

[0062] Furthermore, the control device 26 can cause the liquid pump P to function as a discharge mechanism capable of discharging the liquid and gas present inside the vaporizing section 5 by causing the liquid pump P to operate in the reverse direction.

[0063] The injection liquid stored in the liquid reservoir T and supplied to the vaporization unit 5 can be selected as appropriate. For example, the injection liquid may be water or an acidic liquid. For example, when an acidic liquid (such as hydrochloric acid) is used as the injection liquid, impurities adhering to the surfaces of the particles 5a in the vaporization unit 5 can be quickly dissolved by the acidic liquid.

[0064] 3, the water pump 21 and the water tank 19 may be used together in the liquid injection process. For example, the control device 26 may operate (in a forward rotation direction) at least one of the water pump 21 and the liquid pump P in the liquid injection process. When discharging the injection liquid from the vaporization unit 5, the control device 26 may operate (in a reverse rotation direction) at least one of the water pump 21 and the liquid pump P.

[0065] <Third embodiment> The fuel cell system of the third embodiment differs from the above-described embodiments in that it includes a vibration generator 30. The fuel cell system of the third embodiment will be described below, but a description of the same configuration as in the above-described embodiments will be omitted.

[0066] 4 is a diagram showing the configuration of a fuel cell system according to a third embodiment. As shown in the figure, the fuel cell system includes a vibration generator 30 that can apply vibrations to the vaporization unit 5. For example, the vibration generator 30 is installed so as to be able to apply vibrations to at least one of the piping that constitutes the raw fuel supply path L1 and the piping that constitutes the water supply path L6. When the control device 26 starts the operation of the vibration generator 30, the vibrations generated by the vibration generator 30 are transmitted to the vaporization unit 5, and when the control device 26 stops the operation of the vibration generator 30, the vibrations are no longer transmitted to the vaporization unit 5.

[0067] The vibration generator 30 can be realized using a dedicated device designed solely for generating physical vibrations, or various pumps that generate physical vibrations when in operation. For example, when a pump provided in a fuel cell system is used as the vibration generator 30, the pump can be connected to the raw fuel supply line L1 or the water supply line L6 by a metal band or the like.

[0068] Alternatively, vibration generator 30 may be a device (e.g., raw fuel pump 3b, air pump 22, etc.) that generates pressure fluctuations in gas to impart vibrations to vaporizer 5. For example, control device 26 can impart pressure fluctuations to the gas inside or outside vaporizer 5 by alternately operating and stopping at least one of raw fuel pump 3b and air pump 22, thereby imparting vibrations to vaporizer 5.

[0069] Then, after supplying a predetermined amount of the injection liquid to the vaporizer 5, the control device 26 vibrates the vaporizer 5 using the vibration generator 30 at least during the standby time or after the standby time has elapsed. As a result, the liquid in which impurities are dissolved in the injection liquid is more likely to move to the bottom of the vaporizer 5.

[0070] <Another embodiment> In the above embodiment, the configuration of the fuel cell system has been specifically described, but the configuration can be changed as appropriate.

[0071] In the above embodiment, an example has been described in which the control device 26 automatically performs the liquid injection process. However, the liquid injection process may also be performed by a person, such as a user of the fuel cell system or a maintenance worker. For example, a syringe filled with an injection liquid such as water or an acidic liquid is prepared, and a tube connected to the syringe is inserted into a hole provided midway through the raw fuel supply path L1 or the water supply path L6, with the tip of the tube positioned inside the vaporizer 5. In this state, the injection liquid is discharged from the syringe, thereby supplying the injection liquid into the vaporizer 5. The syringe can also be used as the discharge mechanism to discharge the liquid and gas present inside the vaporizer 5 after the waiting time has elapsed.

[0072] In the third embodiment, an example has been described in which control device 26 operates vibration generator 30 to apply vibration to vaporizer 5, but a person such as a user of the fuel cell system or a maintenance worker may also apply vibration to vaporizer 5. For example, a user or worker may connect vibration generator 30 to the raw fuel supply path L1 or the water supply path L6 outside inner container 2 and operate it to apply the vibration to vaporizer 5. In this case, vibration generator 30 may be any of various pumps provided in the fuel cell system. Alternatively, a metal rod or metal wire, etc., one end of which is connected to the vibration generator 30, may be inserted into a hole provided in the raw fuel supply path L1 or the water supply path L6, and the other end of the metal rod or metal wire, etc., may be placed inside the vaporizer 5. In this state, the vibration generator 30 may be operated to apply vibrations to the vaporizer 5 via the metal rod or metal wire, etc.

[0073] In the above embodiment, an example has been described in which water pump 21 and liquid pump P are rotated in reverse to cause them to function as a discharge mechanism, but a discharge mechanism with a different configuration can also be used. For example, a pipe communicating with the interior of vaporizer 5 can be connected to the bottom of vaporizer 5, and an on-off valve can be installed midway along the pipe. When controller 26 opens the on-off valve, the liquid and gas present inside vaporizer 5 are discharged from the pipe, and when controller 26 closes the on-off valve, the liquid and gas present inside vaporizer 5 are not discharged from the pipe. In other words, the pipe and on-off valve can function as a discharge mechanism.

[0074] In the above embodiment, the fuel cell system of the present invention has been described using specific numerical examples and material examples, but these numerical values ​​and materials are given for illustrative purposes only and can be changed as appropriate.

[0075] In the above embodiment, an example has been described in which the heaters 29, 32 serving as temperature adjustment units are provided in the water tank 19 and the liquid reservoir T, but the heaters 29, 32 may be provided in other locations. For example, the heaters 29, 32 may be provided midway along the water supply path L6 or the liquid supply path Lp to adjust the temperature of the injection liquid. The temperature control unit may be realized using a device other than the heater described above. For example, the temperature control unit may be realized using a Peltier element or the like.

[0076] 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 contradictions arise. 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]

[0077] The present invention can be used in a fuel cell system that can eliminate narrowing of the flow path of the raw fuel in the vaporizing section. [Explanation of symbols]

[0078] 1:Fuel cell 2: Inner container 3a: Raw fuel flow meter 3b: Raw fuel pump 5: Vaporization section 6: Modification section 8: Fuel cell 9: Cell stack 10:Igniter 11: Combustion section 12: Air supply port 13: Exhaust port 19: Water tank 21: Water pump 22: Air pump 26: Control device 28: Inner space 29: Heater (temperature control unit) 30: Vibration generator 32: Heater (temperature control unit) P: Liquid pump (discharge mechanism) T:Liquid reservoir

Claims

1. an internal space within the inner container comprising: a vaporization section that vaporizes water supplied from a water tank; a reforming section that generates fuel gas by steam reforming raw fuel using steam supplied from the vaporization section; a cell stack having a plurality of fuel cell units that generates electricity using the fuel gas generated in the reforming section; a combustion section that combusts off-gas discharged from the cell stack; and an igniter that ignites the off-gas; and the inner container is provided with an air inlet used to supply air from the outside to the internal space and an exhaust port used to exhaust exhaust gas including gas generated by combustion in the combustion section from the internal space to the outside. a raw fuel pump that supplies the raw fuel to the reforming section; an air pump that supplies air to the inner space through the air inlet; a water tank that stores condensed water produced by condensing water vapor contained in the exhaust gas discharged from the inner space through the exhaust port as water to be used for the steam reforming; a water pump that supplies the water stored in the water tank to the vaporization section; and a control device, The control device, when a predetermined processing execution condition is satisfied, stops the raw fuel pump, the air pump, and the water pump, and stops power generation in the cell stack, while supplying a predetermined amount of a predetermined injection liquid to the vaporization section, and performs a liquid injection process without discharging the injection liquid from the vaporization section for at least a predetermined waiting time.

2. a liquid reservoir that stores the injection liquid; and a liquid pump that supplies the injection liquid from the liquid reservoir to the vaporizing unit, 2. The fuel cell system according to claim 1, wherein the control device supplies the injection liquid stored in the liquid reservoir to the vaporization section by operating the liquid pump in the liquid injection process.

3. 3. The fuel cell system according to claim 2, wherein the water tank is used as the liquid reservoir, the water pump is used as the liquid pump, and the water stored in the water tank is used as the injection liquid.

4. 3. The fuel cell system according to claim 2, wherein an acidic liquid is stored in the liquid reservoir, and the acidic liquid stored in the liquid reservoir is used as the injection liquid.

5. a vibration generator capable of applying vibration to the vaporizing unit; 2. The fuel cell system according to claim 1, wherein the control device applies vibration to the vaporizing unit using the vibration generator at least one of during the standby time and after the standby time has elapsed.

6. 6. The fuel cell system according to claim 1, wherein the control device, after the waiting time has elapsed, operates the raw fuel pump and ignites the igniter, thereby performing a combustion process to combust the off-gas discharged from the cell stack.

7. a discharge mechanism capable of discharging liquid and gas present inside the vaporizing unit; 6. The fuel cell system according to claim 1, wherein the control device operates the discharge mechanism to discharge liquid and gas present inside the vaporization section after the waiting time has elapsed.

8. The fuel cell system according to any one of claims 1 to 5, wherein the control device determines that the processing execution condition is satisfied each time a stop timing occurs to stop the raw fuel pump, the air pump, and the water pump and to stop power generation in the cell stack, or each time the stop timing occurs a predetermined number of times.

9. a raw fuel flow meter for measuring a flow rate per unit time of the raw fuel supplied to the reforming section by the raw fuel pump; The raw fuel is supplied to the reforming unit via the vaporizing unit, 6. The fuel cell system according to claim 1, wherein the control device determines that the processing execution condition is satisfied when there is a deviation of a reference value or more in the correlation between the output of the raw fuel pump and the measurement value of the raw fuel flow meter.

10. 6. The fuel cell system according to claim 1, further comprising a temperature adjusting section that adjusts the temperature of the injection liquid supplied to the vaporizing section.

Images