Fuel battery system

Abstract

To provide a fuel battery system having a high durability.SOLUTION: A fuel battery system 100 includes: a heat exchanger 51 that has a hot / water flow path 512 through which hot / water flows and exchanges heat between an exhaust gas discharged from a hot module 1 and hot / water; a hot / water circulation circuit L6 through which hot / water circulates; a hot / water circulation pump 62 that circulates hot / water in the hot / water circulation circuit L6; and a control part 10 that controls an operation of the hot / water circulation pump 62. The control part 10 executes blocking tendency confirmation processing of determining whether or not the hot / water flow path 512 has a blocking tendency. When it is determined in the blockage tendency checking processing that the hot / water flow path 512 has a blockage tendency, a blockage cancellation mode for cancelling the blockage tendency of the hot / water flow path 512 or a blockage reduction mode for reducing the blockage tendency of the hot / water flow path 512 is executed. The operation of the hot / water circulation pump 62 is controlled so that the output is different between the blockage cancellation mode and the blockage reduction mode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a power generation system including a power generation device that generates power with the generation of exhaust heat, a circulation path through which a heat exchange liquid circulates, a heat exchanger (a heat exchanger for exhaust heat treatment in Patent Document 1) that is incorporated in the circulation path and performs heat exchange between the exhaust heat and the heat exchange liquid, a tank that is incorporated in the circulation path, a liquid level detection sensor that detects the liquid level in the tank, and a determination unit that determines whether an abnormality has occurred in the exchanger based on the detection result of the liquid level in the tank. The determination unit disclosed in Patent Document 1 determines an abnormality in the heat exchanger based on the phenomenon in which chloride ions and the like contained in the heat exchange liquid precipitate and the liquid leaks from the heat exchanger due to corrosion caused by the precipitate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-73460 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the heat exchanger corrodes and breaks, it will need to be replaced or repaired, which increases costs. For this reason, there is a demand for a highly durable fuel cell system that can suppress the deposition of deposits, which is a precursor to corrosion.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a fuel cell system having high durability. [Means for solving the problem]

[0006] The fuel cell system according to the present invention, which achieves the above object, has the following characteristic configuration: a hot module having a fuel cell that generates electricity based on a fuel gas and an oxidant gas; a heat exchanger having a hot water flow path through which hot water flows and performing heat exchange between the hot water and the exhaust gas discharged from the hot module; a hot water circulation circuit to which the heat exchanger is connected and through which the hot water circulates; a hot water circulation pump that circulates the hot water through the hot water circulation circuit; A control unit that controls the operation of the hot water circulation pump; Equipped with The control unit Execute a clogging tendency confirmation process to determine whether the hot water / cold water flow path has a clogging tendency; In the clogging tendency confirmation process, when it is determined that the hot and cold water flow path has the clogging tendency, a clogging elimination mode for eliminating the clogging tendency of the hot and cold water flow path or a clogging reduction mode for reducing the clogging tendency of the hot and cold water flow path is executed, The hot water circulation pump is controlled so that its operation differs between the blockage elimination mode and the blockage alleviation mode.

[0007] According to the above characteristic configuration, by controlling the operation of the hot water circulation pump, the hot water flow path of the heat exchanger can be cleaned with hot water, thereby suppressing the adhesion of deposits to the heat exchanger and removing any deposited deposits, ensuring high durability. Furthermore, since the operation of the hot water circulation pump differs between the blockage elimination mode and the blockage reduction mode, the operating mode (cleaning method) can be changed depending on the degree of deposit adhesion, for example. This makes it possible to suppress unnecessary operation of the hot water circulation pump and optimize the fuel cell system.

[0008] Another characteristic configuration of the fuel cell system according to the present invention is: The control unit controls the hot water circulation pump so that the increase / decrease in the output of the hot water circulation pump in the blockage relief mode is greater than the increase / decrease in the output of the hot water circulation pump in the blockage reduction mode.

[0009] According to the above-mentioned characteristic configuration, the cleaning method can be changed depending on whether the blockage elimination mode or the blockage reduction mode is selected, thereby reducing unnecessary operation of the hot water circulation pump and optimizing the fuel cell system.

[0010] Another characteristic configuration of the fuel cell system according to the present invention is: a hot and cold water flow meter for measuring the flow rate of the hot and cold water circulating in the hot and cold water circulation circuit; The control unit In the clogging tendency confirmation process, when the actual flow rate measured by the hot and cold water flow meter is smaller than the commanded flow rate commanded as the flow rate of the hot and cold water circulating in the hot and cold water circulation circuit, a command actual deviation value, which is a value that deviates between the commanded flow rate and the actual flow rate, is determined to be equal to or greater than a first command actual deviation threshold value, and a first duration is determined to be equal to or greater than a first specified time; If it is determined that the first duration is equal to or greater than a first specified time, it is determined that there is a tendency toward blockage, and if it is determined that the first duration is not equal to or greater than the first specified time, it is determined that there is no tendency toward blockage.

[0011] According to the above characteristic configuration, it is possible to more reliably determine the tendency for clogging in the heat exchanger.

[0012] Another characteristic configuration of the fuel cell system according to the present invention is as follows: The control unit When it is determined that there is a tendency for clogging, execute a blockage degree determination process for determining whether the degree of the blockage tendency is a first degree or a second degree lower than the first degree; In the blockage degree determination process, it is determined whether the command actual deviation value is equal to or greater than a second command actual deviation threshold value, the second command actual deviation threshold value being set to a value greater than the first command actual deviation threshold value; If it is determined that the command actual deviation value is equal to or greater than the second command actual deviation threshold, it is determined that the deviation is at the first degree, and the blockage resolution mode is executed.

[0013] According to the above characteristic configuration, the degree of clogging can be determined, and if the degree of clogging is high (first degree), a clogging elimination mode can be executed to eliminate the clogging tendency, thereby suppressing the adhesion of deposits and removing the attached deposits.

[0014] Another characteristic configuration of the fuel cell system according to the present invention is as follows: a hot and cold water flow meter for measuring the flow rate of the hot and cold water circulating in the hot and cold water circulation circuit; The control unit In the clogging tendency confirmation process, a second duration is determined as to whether or not an assumed actual deviation value, which is the deviation value between the actual flow rate and the assumed flow rate when the actual flow rate measured by the hot and cold water flow meter is smaller than the assumed hot and cold water flow rate assumed when the output of the hot and cold water circulation pump is constant, is equal to or greater than a first assumed actual deviation threshold, or whether or not an assumed actual output deviation value, which is the duration of a state where the actual output of the hot and cold water circulation pump is greater than the assumed output of the hot and cold water circulation pump assumed when the actual flow rate measured by the hot and cold water flow meter is constant, is equal to or greater than a first assumed actual output deviation threshold, If it is determined that the second duration is equal to or greater than the second specified time, it is determined that there is a tendency toward blockage, and if it is determined that the second duration is not equal to or greater than the second specified time, it is determined that there is no tendency toward blockage.

[0015] According to the above characteristic configuration, it is possible to more reliably determine the tendency for clogging in the heat exchanger.

[0016] Another characteristic configuration of the fuel cell system according to the present invention is as follows: The control unit When it is determined that there is a tendency for clogging, execute a blockage degree determination process for determining whether the degree of the blockage tendency is a first degree or a second degree lower than the first degree; in the blockage degree determination process, determining whether the expected actual deviation value is equal to or greater than a second expected actual deviation threshold value, which is set to a value greater than the first expected actual deviation threshold value, or whether the expected actual output deviation value is equal to or greater than a second expected actual output deviation threshold value, which is set to a value greater than the first expected actual output deviation threshold value; If it is determined that the expected actual deviation value is equal to or greater than the second expected actual deviation threshold, or if the expected actual output deviation value is equal to or greater than the second expected actual output deviation threshold, it is determined that the deviation is at the first degree, and the blockage resolution mode is executed.

[0017] According to the above characteristic configuration, the degree of clogging can be determined, and if the degree of clogging is high (first degree), a clogging elimination mode can be executed to eliminate the clogging tendency, thereby suppressing the adhesion of deposits and removing the attached deposits.

[0018] Another characteristic configuration of the fuel cell system according to the present invention is as follows: A first hot water temperature detection unit that detects the inflow temperature of the hot water flowing into the heat exchanger; A second hot water temperature detection unit that detects the outflow temperature of the hot water flowing out from the heat exchanger; Further provided with The control unit In the clogging tendency confirmation process, when the output of the hot water circulation pump and the outflow temperature are constant, and when the outflow temperature is higher than the inflow temperature, it is determined whether a third duration, which is the duration of a state in which an inflow / outflow temperature deviation value indicating a deviation value between the outflow temperature and the inflow temperature is equal to or less than a first inflow / outflow temperature deviation threshold, is equal to or greater than a third specified time; If it is determined that the third duration is equal to or greater than the third specified time, it is determined that there is a tendency toward blockage, and if it is determined that the third duration is not equal to or greater than the third specified time, it is determined that there is no tendency toward blockage.

[0019] According to the above characteristic configuration, it is possible to more reliably determine the tendency for clogging in the heat exchanger.

[0020] Another characteristic configuration of the fuel cell system according to the present invention is as follows: The control unit When it is determined that there is a tendency for clogging, execute a blockage degree determination process for determining whether the degree of the blockage tendency is a first degree or a second degree lower than the first degree; In the blockage degree determination process, it is determined whether the inlet / outlet temperature deviation value is equal to or less than a second inlet / outlet temperature deviation threshold value, which is set to a value smaller than the first inlet / outlet temperature deviation threshold value; If it is determined that the inlet / outlet temperature deviation value is equal to or less than the second inlet / outlet temperature deviation threshold, it is determined that the deviation is at the first degree, and the blockage resolution mode is executed.

[0021] According to the above characteristic configuration, the degree of clogging can be determined, and if the degree of clogging is high (first degree), a clogging elimination mode can be executed to eliminate the clogging tendency, thereby suppressing the adhesion of deposits and removing the attached deposits.

[0022] Another characteristic configuration of the fuel cell system according to the present invention is as follows: When the control unit determines that the degree of clogging tendency is the second degree, it determines whether or not exhaust heat recovery is necessary to perform heat exchange between the exhaust gas and the hot water, When it is determined that the exhaust heat recovery is necessary, the blockage mitigation mode is executed; If it is determined that the exhaust heat recovery is not necessary, the blockage elimination mode is executed.

[0023] According to the above characteristic configuration, the blockage mitigation mode or the blockage resolution mode can be executed depending on whether or not exhaust heat recovery is required, so that a decrease in convenience for users of the fuel cell system can be suppressed.

[0024] Another characteristic configuration of the fuel cell system according to the present invention is as follows: When the control unit determines that the degree of clogging tendency is the second degree, it determines whether or not exhaust heat recovery is necessary to perform heat exchange between the exhaust gas and the hot water, When it is determined that the exhaust heat recovery is necessary, the blockage mitigation mode is executed; If it is determined that the exhaust heat recovery is not necessary, it is further determined whether or not power generation in the fuel cell can be stopped, and if it is determined that power generation in the fuel cell can be stopped, the blockage resolution mode is executed, and if it is determined that power generation in the fuel cell cannot be stopped, the blockage alleviation mode is executed.

[0025] According to the above characteristic configuration, when it is determined that exhaust heat recovery is unnecessary, the blockage resolution mode or the blockage mitigation mode can be executed depending on whether or not power generation can be stopped.

[0026] Another characteristic configuration of the fuel cell system according to the present invention is as follows: The control unit issues error information indicating a malfunction when the number of times the blockage resolution mode has been executed reaches a predetermined cumulative number.

[0027] According to the above characteristic configuration, when the blockage resolution mode is executed a predetermined cumulative number of times, error information is notified, thereby making it possible to avoid the risk of a serious malfunction.

[0028] Another characteristic configuration of the fuel cell system according to the present invention is as follows: Further provided is a hot water tank connected to the hot water circulation circuit and storing the hot water, The control unit determines whether a fourth duration, which is a duration of a state in which hot water is not dispensed from the hot water tank, is equal to or longer than a fourth specified time, When it is determined that the fourth duration is equal to or longer than a fourth specified time, it is determined that the exhaust heat recovery is unnecessary, If it is determined that the fourth duration is not equal to or longer than a fourth specified time, it is determined that the exhaust heat recovery is necessary.

[0029] According to the above characteristic configuration, it is possible to more reliably determine whether or not exhaust heat recovery is required.

[0030] Another characteristic configuration of the fuel cell system according to the present invention is as follows: a hot water tank connected to the hot water circulation circuit and storing the hot water; A temperature detection unit that detects at least one of the temperature of the hot water stored in the hot water tank and the temperature of the hot water in the hot water circulation circuit from the hot water tank to the heat exchanger, The control unit determines whether a fifth duration, which is a duration of a state in which the temperature of the hot water detected by the temperature detection unit is equal to or higher than a hot water temperature threshold, is equal to or longer than a fifth specified time, If it is determined that the fifth duration is equal to or longer than the fifth specified time, it is determined that the exhaust heat recovery is unnecessary, If it is determined that the fifth duration is not equal to or longer than the fifth specified time, it is determined that the exhaust heat recovery is necessary.

[0031] According to the above characteristic configuration, it is possible to more reliably determine whether or not exhaust heat recovery is required.

[0032] Another characteristic configuration of the fuel cell system according to the present invention is as follows: The hot water circulation circuit further includes a heat dissipation fan disposed upstream of the heat exchanger in the direction of flow of the hot water, and configured to dissipate heat from the hot water. determining whether a sixth duration, which is a duration of a state in which the output of the heat dissipation fan is equal to or greater than a fan threshold, is equal to or greater than a sixth specified time; If it is determined that the sixth duration is equal to or longer than a sixth specified time, it is determined that the exhaust heat recovery is unnecessary, If it is determined that the sixth duration is not equal to or longer than a sixth specified time, it is determined that the exhaust heat recovery is necessary.

[0033] According to the above characteristic configuration, it is possible to more reliably determine whether or not exhaust heat recovery is required. [Brief explanation of the drawings]

[0034] [Figure 1]1 is a schematic diagram showing the configuration of a fuel cell system according to an embodiment; [Figure 2] 10 is a flowchart illustrating a process for determining a tendency for blockage according to the embodiment. [Figure 3] 10 is a diagram showing an example of the output of the hot water circulation pump in the blockage elimination mode according to the embodiment. FIG. [Figure 4] 10 is a diagram showing an example of the output of the hot water circulation pump in the blockage reduction mode according to the embodiment. FIG. [Figure 5] 10 is a diagram showing an example of the output of the hot water circulation pump in the blockage reduction mode according to the embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0035] A fuel cell system 100 (solid oxide fuel cell system) according to an embodiment of the present invention will be described below with reference to the drawings. FIG.

[0036] [Fuel cell system] 1, the fuel cell system 100 includes a hot module 1, a reforming water supply unit 2, a raw fuel supply unit 3, an oxidizing gas supply unit 4, a heat exchange unit 5, a hot water circulation unit 6, an input / output unit 9, a control unit 10, and an external container 100H. The external container 100H houses the hot module 1, the reforming water supply unit 2, the raw fuel supply unit 3, the oxidizing gas supply unit 4, the heat exchange unit 5, the hot water circulation unit 6, the input / output unit 9, and the control unit 10.

[0037] [Hot Module] The hot module 1 is a fuel cell module that generates electricity by reacting hydrogen and oxygen. The hot module 1 has an inner vessel 11, a vaporization section 12, a reforming section 13, a fuel cell section 14, a combustion section 15, and a combustion catalyst section 16.

[0038] The inner container 11 has heat insulating properties and houses the vaporization section 12, the reforming section 13, the fuel cell section 14, the combustion section 15, and the combustion catalyst section 16. The inner container 11 has an exhaust port 111 formed therein.

[0039] A reforming water supply unit 2, a raw fuel supply unit 3, and an oxidizing gas supply unit 4 are connected to the hot module 1, and reforming water, raw fuel, and oxidizing gas (oxidizer) are supplied to the hot module 1. In this embodiment, the reforming water and raw fuel are supplied to the vaporization unit 12, and the oxidizing gas is supplied to the fuel cell unit 14.

[0040] [Vaporization section] In addition to the reforming water and raw fuel, combustion heat generated in the combustion section 15 is supplied to the vaporization section 12. The vaporization section 12 vaporizes the reforming water by utilizing the combustion heat to generate steam. In this embodiment, the vaporization section 12 supplies a mixed gas obtained by mixing the raw fuel with steam vaporized from the reforming water to the reforming section 13.

[0041] [Modification section] The reforming section 13 is supplied with the mixed gas from the vaporizing section 12. Note that the raw fuel may be supplied directly to the reforming section 13 from the raw fuel supply section 3 without passing through the vaporizing section 12.

[0042] In addition to the mixed gas, combustion heat generated in the combustion section 15 is supplied to the reforming section 13. The reforming section 13 generates fuel gas by steam reforming the mixed gas (raw fuel) by utilizing the combustion heat. The fuel gas generated in the reforming section 13 is supplied to the fuel cell section 14.

[0043] [Fuel cell department] The fuel cell section 14 is a cell stack made up of a plurality of cells C (an example of a fuel cell). In this embodiment, the cells C are solid oxide fuel cells, and are made up of an anode (combustion electrode), a cathode (air electrode), and an electrolyte. Note that the cells C may be fuel cells other than solid oxide fuel cells.

[0044] Fuel gas and oxidant gas are supplied to cell C. Cell C generates electricity based on the fuel gas and oxidant gas. Specifically, cell C generates electricity by chemically reacting hydrogen contained in the fuel gas with oxygen contained in the oxidant gas. The fuel gas and oxidant gas not used for power generation are discharged as off-gas (excess gas).

[0045] [Combustion section] The combustion section 15 is supplied with off-gas discharged from the fuel cell section 14 and burns the off-gas to generate combustion heat. The combustion section 15 is disposed between the vaporization section 12 and the reforming section 13 and the fuel cell section 14, and the combustion heat generated in the combustion section 15 increases the temperature of the internal space of the internal container 11. The combustion section 15 discharges combustion exhaust gas (an example of exhaust gas) along with the fuel of the off-gas. The combustion exhaust gas is discharged to the outside of the internal container 11 via the combustion catalyst section 16 disposed in the exhaust port 111.

[0046] [Combustion catalyst section] The combustion catalyst section 16 uses oxygen to catalytically combust hydrogen, carbon monoxide, and the like contained in the combustion exhaust gas. The catalytically combusted combustion exhaust gas is discharged to the outside of the inner vessel 11.

[0047] [Reformed Water Supply Department] The reforming water supply unit 2 supplies reforming water to the hot module 1. The reforming water is, for example, tap water from which impurities have been removed. The reforming water supply unit 2 includes a reforming water supply passage L1, an ion exchange resin 20, a water tank 21, and a pump 22.

[0048] The ion exchange resin 20 removes impurities from the reforming water (purifying the reforming water) and supplies it to the water tank 21. The water tank 21 stores the reforming water. The pump 22 pumps the reforming water stored in the water tank 21. As a result, the reforming water is supplied to the hot module 1 via the reforming water supply path L1. In this embodiment, the pump 22 circulates the reforming water used in the hot module 1 between the hot module 1 and the water tank 21. The amount of reforming water supplied to the hot module 1 per unit time is adjusted by controlling the operation of the pump 22.

[0049] [Raw and fuel supply department] The raw fuel supply unit 3 supplies a raw fuel (raw fuel gas) containing hydrocarbons to the hot module 1. The raw fuel is, for example, city gas, LP gas, or the like.

[0050] The raw fuel supply unit 3 includes a raw fuel supply line L2, a solenoid valve 31, a fuel flow meter 32, a gas blower 33, and a desulfurization unit 34. The solenoid valve 31 can adjust the flow rate of the raw fuel flowing through the raw fuel supply line L2. The fuel flow meter 32 measures the flow rate of the raw fuel flowing through the raw fuel supply line L2. The gas blower 33 supplies the raw fuel to the hot module 1 via the raw fuel supply line L2. In other words, the amount of raw fuel supplied to the hot module 1 per unit time is adjusted by controlling the operation of the solenoid valve 31 and / or the gas blower 33. The desulfurization unit 34 is disposed upstream of the hot module 1 in the flow direction of the raw fuel and removes sulfur from the raw fuel. As a result, the raw fuel from which the sulfur has been removed is supplied to the hot module 1.

[0051] [Oxidant gas supply unit] The oxidant gas supply unit 4 supplies an oxidant gas containing oxygen (e.g., air) to the hot module 1. The oxidant gas supply unit 4 has an oxidant gas supply path L3, an oxidant gas blower 41, and an oxidant gas flow meter 42. The oxidant gas blower 41 supplies the oxidant gas to the hot module 1 via the oxidant gas supply path L3. The oxidant gas flow meter 42 measures the flow rate of the oxidant gas flowing through the oxidant gas supply path L3. The amount of oxidant gas supplied to the hot module 1 per unit time is adjusted by controlling the operation of the oxidant gas blower 41.

[0052] [Heat exchange section] The heat exchange section 5 condenses and recovers water contained in the combustion exhaust gas supplied from the combustion catalyst section 16. The heat exchange section 5 has a combustion exhaust gas passage L4, a heat exchanger 51, and a water recovery passage L5.

[0053] The combustion exhaust gas passage L4 is connected to the combustion catalyst section 16 and the heat exchanger 51. The combustion exhaust gas is supplied from the combustion catalyst section 16 to the heat exchanger 51 via the combustion exhaust gas passage L4.

[0054] The heat exchanger 51 has a gas flow path 511 through which the combustion exhaust gas flows, and a hot and cold water flow path 512 through which hot and cold water circulating through the hot and cold water circulation unit 6 flows. Inside the heat exchanger 51, each of the gas flow path 511 and the hot and cold water flow path 512 is branched into multiple paths, and heat exchange occurs between the combustion exhaust gas flowing through each of the multiple gas flow paths 511 and the hot and cold water flowing through each of the multiple hot and cold water flow paths 512. This cools the combustion exhaust gas and heats the hot water. When the combustion exhaust gas is cooled, the water contained in the combustion exhaust gas condenses and becomes a liquid (liquid phase). The gas phase components in the combustion exhaust gas are discharged to the outside of the outer container 100H via the combustion exhaust gas path L4, and the liquid phase components (condensed water) in the combustion exhaust gas are led to the water recovery path L5.

[0055] The water recovery line L5 branches off from the combustion exhaust gas line L4 downstream of the heat exchanger 51 in the flow direction of the combustion exhaust gas, and is connected to the reforming water supply unit 2. The condensed water introduced into the water recovery line L5 is supplied to the water tank 21 of the reforming water supply unit 2 via the ion exchange resin 20 arranged between the water recovery line L5 and the water tank 21, and is stored in the water tank 21 as reforming water.

[0056] [Hot water circulation section] The hot water circulation unit 6 has a hot water circulation circuit L6, a hot water tank 61, a hot water circulation pump 62, a hot water cooling unit 63, a hot water flow meter 64, a hot water temperature detection unit 65, and a hot water supply channel L7.

[0057] The hot water tank 61 stores hot water. The bottom and top of the hot water tank 61 are connected to the hot water circulation circuit L6. The hot water circulation pump 62 circulates hot water between the hot water tank 61 and the heat exchange unit 5 via the hot water circulation circuit L6. More specifically, the hot water circulation pump 62 pumps hot water from the bottom of the hot water tank 61 through the heat exchanger 51 to the top of the hot water tank 61. In other words, hot water flows out from the bottom of the hot water tank 61 into the hot water circulation circuit L6, and hot water heated in the heat exchange unit 5 flows back to the hot water tank 61 from the top. The hot water cooling unit 63 cools the hot water upstream of the heat exchange unit 5 in the direction of hot water flow. The hot water cooling unit 63 includes, for example, a radiator 631 and a heat dissipation fan 632. In this embodiment, the hot and cold water flow meter 64 is arranged downstream of the heat exchanger 51 and upstream of the hot and cold water tank 61 in the flow direction of hot and cold water flowing through the hot and cold water circulation circuit L6. The hot and cold water flow meter 64 measures the flow rate of hot and cold water flowing through the hot and cold water circulation circuit L6.

[0058] The hot water temperature detection unit 65 measures the temperature of the hot water flowing through the hot water circulation circuit L6. In this embodiment, the hot water temperature detection unit 65 includes a first hot water temperature detection unit 651 and a second hot water temperature detection unit 652. The first hot water temperature detection unit 651 is arranged upstream of the heat exchanger 51 (downstream of the hot water tank 61) in the direction of hot water flowing through the hot water circulation circuit L6, and detects the temperature of the hot water flowing into the heat exchanger 51 (hereinafter referred to as the inflow temperature T1). The second hot water temperature detection unit 652 is arranged downstream of the heat exchanger 51 (upstream of the hot water tank 61) in the direction of hot water flowing through the hot water circulation circuit L6, and detects the temperature of the hot water flowing out of the heat exchanger 51 (hereinafter referred to as the outflow temperature T2). The hot water circulation pump 62 controls the flow rate of the hot water flowing through the hot water circulation circuit L6 so that the outflow temperature T2 (i.e., the temperature of the hot water after heat recovery, which is the temperature detected by the second hot water temperature detection unit 652) becomes a predetermined target temperature (e.g., 65 degrees). The target temperature is set arbitrarily by the designer of the fuel cell system 100, etc.

[0059] [Control Unit] The control unit 10 is composed of a microcontroller including a processor, semiconductor memory, etc. The control unit 10 controls the operation of each of the hot module 1, the reforming water supply unit 2, the raw fuel supply unit 3, the oxidant gas supply unit 4, the heat exchange unit 5, the hot water circulation unit 6, and the input / output unit 9. The control unit 10 has a memory unit 101 composed of semiconductor memory. The memory unit 101 stores data indicating the target temperature, etc., and program data for executing the processing described below.

[0060] In this embodiment, the control unit 10 executes a blockage tendency determination process to determine whether the hot and cold water flow path 512 is prone to blockage. In the blockage tendency determination process, if the control unit 10 determines that the hot and cold water flow path 512 is prone to blockage, the control unit 10 executes a blockage elimination mode M1 or a blockage reduction mode M2. The control unit 10 controls the operation of the hot and cold water circulation pump 62 so that the output of the hot and cold water circulation pump 62 differs between the blockage elimination mode M1 and the blockage reduction mode M2. More specifically, the control unit 10 executes the blockage elimination mode M1 or the blockage reduction mode M2 ​​by controlling the output (rotation speed) of the hot and cold water circulation pump 62 and the operating time of the hot and cold water circulation pump 62. The control unit 10 controls the operation of the hot and cold water circulation pump 62 so that the amplification width of the output of the hot and cold water circulation pump 62 in the blockage elimination mode M1 is greater than the amplification width of the output of the hot and cold water circulation pump 62 in the blockage reduction mode M2.

[0061] [Occupation tendency determination processing] The clogging tendency determination process will be described in detail below with reference to Fig. 2. Fig. 2 is a flowchart showing the clogging tendency determination process. The clogging tendency determination process is executed, for example, every time the operating time of the fuel cell system 100 (hot module 1) reaches a predetermined specified operating time (for example, 1000 hours). The specified operating time is arbitrarily set by a designer or the like.

[0062] As shown in FIG. 2, in the clogging tendency determination process, the control unit 10 determines whether or not the hot and cold water flow path 512 of the heat exchanger 51 is clogging tendency (step S101).

[0063] The control unit 10 determines whether or not there is a tendency toward blockage based on at least one of the following first trend determination condition TK1, second trend determination condition TK2, and third trend determination condition TK3.

[0064] The first trend determination condition TK1 is a condition that, when the hot and cold water circulation pump 62 is operated to achieve the target flow rate, the time during which a command-actual deviation value R3, which is the deviation between the command flow rate R1 and the actual flow rate R2, continues to be equal to or greater than a first command-actual deviation threshold TR1 (e.g., 10% of the command flow rate R1), is equal to or greater than a first specified time Hk1 (e.g., 1 hour) (hereinafter referred to as the first duration H1). Note that, in the first trend determination condition TK1, the command flow rate R1 is the flow rate (target flow rate) commanded by the control unit 10 as the flow rate of hot and cold water flowing through the hot and cold water circulation circuit L6, and the actual flow rate R2 is the flow rate measured by the hot and cold water flow meter 64, and the actual flow rate R2 is smaller than the command flow rate R1.

[0065] In other words, when determining whether or not there is a tendency toward blockage based solely on the first tendency determination condition TK1, the control unit 10 determines whether or not the first duration H1 is equal to or greater than the first specified time Hk1, and if it determines that the first duration H1 is equal to or greater than the first specified time Hk1, it determines that there is a tendency toward blockage, and if it determines that the first duration H1 is not equal to or greater than the first specified time Hk1 (is less than the first specified time Hk1), it determines that there is no tendency toward blockage.

[0066] The second trend judgment condition TK2 is a condition that, when the hot water / cold water circulation pump 62 is operated to achieve the target flow rate, the time (hereinafter referred to as the second duration H2) during which the estimated actual deviation value R5, which is the deviation value between the actual flow rate R2 and the estimated flow rate R4, is greater than or equal to the first estimated actual deviation threshold TS1 (e.g., 10% of the estimated flow rate R4), or the time during which the estimated actual output deviation value S3, which is the deviation between the actual output S2 and the estimated output S1, is greater than or equal to the first estimated actual output deviation threshold TJ1 (e.g., 10% of the estimated output S1), continues is greater than or equal to a second specified time Hk2 (e.g., 1 hour). In addition, in the second trend judgment condition TK2, the estimated flow rate R4 (target flow rate) is the flow rate of hot and cold water (actual flow rate R2) estimated when the output of the hot and cold water circulation pump 62 is constant, and the actual flow rate R2 is smaller than the estimated flow rate R4, and the estimated output S1 is the output of the hot and cold water circulation pump 62 estimated when the actual flow rate R2 is constant, and the actual flow rate R2 is greater than the estimated output S1.

[0067] In other words, when determining whether or not there is a tendency toward blockage based solely on the second tendency determination condition TK2, the control unit 10 determines whether or not the second duration H2 is equal to or greater than the second specified time Hk2, and if it determines that the second duration H2 is equal to or greater than the second specified time Hk2, it determines that there is a tendency toward blockage, and if it determines that the second duration H2 is not equal to or greater than the second specified time Hk2 (is less than the second specified time Hk2), it determines that there is no tendency toward blockage.

[0068] The third trend determination condition TK3 is a condition that, when the output of the hot water circulation pump 62 is operated at a constant level so that the temperature of the outflow temperature T2 (high-temperature hot water) is constant, the time during which the inflow / outflow temperature deviation value T3, which is the deviation value between the outflow temperature T2 and the inflow temperature T1, continues to be equal to or less than the first inflow / outflow temperature deviation threshold TT1 (e.g., 30% of the expected temperature difference) (hereinafter referred to as the third duration H3) is equal to or greater than a third specified time Hk3 (e.g., 1 hour). Note that in the third trend determination condition TK3, the outflow temperature T2 is higher than the inflow temperature T1.

[0069] In other words, when determining whether or not there is a tendency toward blockage based solely on the third tendency determination condition TK3, the control unit 10 determines whether or not the third duration H3 is equal to or greater than the third specified time Hk3, and if it determines that the third duration H3 is equal to or greater than the third specified time Hk3, it determines that there is a tendency toward blockage, and if it determines that the third duration H3 is not equal to or greater than the third specified time Hk3 (is less than the third specified time Hk3), it determines that there is no tendency toward blockage.

[0070] When the control unit 10 determines that there is no tendency toward blockage (step S101; No), the control unit 10 repeats the process of step S101.

[0071] On the other hand, when the control unit 10 determines that there is a tendency for blockage (step S101; Yes), it executes a blockage degree determination process to determine whether the degree of blockage is a first degree (high degree) or a second degree (low degree) (step S103).

[0072] The control unit 10 determines whether the degree of blockage is the first degree (high degree) or the second degree (low degree) based on at least one of the following first degree determination condition TD1, second degree determination condition TD2, and third degree determination condition TD3.

[0073] The first degree determination condition TD1 is a condition that the command actual deviation value R3 is equal to or greater than a second command actual deviation threshold TR2 (for example, 30% of the command flow rate R1) that is set to a value greater than the first command actual deviation threshold TR1.

[0074] That is, when determining the degree of blockage based only on the first degree determination condition TD1, the control unit 10 determines whether the actual command deviation value R3 is equal to or greater than the second actual command deviation threshold TR2, and if it determines that the actual command deviation value R3 is equal to or greater than the second actual command deviation threshold TR2, it determines that the blockage is at the first degree. Note that in this embodiment, the control unit 10 determines whether the time (first duration H1) during which the actual command deviation value R3 is equal to or greater than the second actual command deviation threshold TR2 continues is equal to or greater than the first specified time Hk1, and if it determines that the first duration H1 is equal to or greater than the first specified time Hk1, it determines that the blockage is at the first degree, and if it determines that the first duration H1 is not equal to or greater than the first specified time Hk1 (the first duration H1 is shorter than the first specified time Hk1), it determines that the blockage is at the second degree.

[0075] The second degree determination condition TD2 is a condition in which the assumed actual deviation value R5 is greater than or equal to a second assumed actual deviation threshold TS2 (for example, 30% of the assumed flow rate R4) which is set to a value greater than the first assumed actual deviation threshold TS1, or the assumed actual output deviation value S3 is greater than or equal to a second assumed actual output deviation threshold TJ2 (for example, 30% of the assumed output S1) which is set to a value greater than the first assumed actual output deviation threshold TJ1.

[0076] In other words, when determining the degree of blockage based only on the second degree determination condition TD2, the control unit 10 determines whether the expected actual deviation value R5 is greater than or equal to the second expected actual deviation threshold TS2, or whether the expected actual output deviation value S3 is greater than or equal to the second expected actual output deviation threshold TJ2, and if it determines that the expected actual deviation value R5 is greater than or equal to the second expected actual output deviation threshold TS2, or that the expected actual output deviation value S3 is greater than or equal to the second expected actual output deviation threshold TJ2, it determines that the blockage is at the first degree. In this embodiment, the control unit 10 determines whether the time (second duration H2) during which the expected actual deviation value R5 is equal to or greater than the second expected actual deviation threshold TS2 or the expected actual output deviation value S3 is equal to or greater than the second expected actual output deviation threshold TJ2 continues is equal to or greater than the second specified time Hk2, and if it determines that the second duration H2 is equal to or greater than the second specified time Hk2, it determines that the first degree exists, and if it determines that the second duration H2 is not equal to or greater than the second specified time Hk2 (the second duration H2 is shorter than the second specified time Hk2), it determines that the second degree exists.

[0077] The third degree determination condition TD3 is a condition that the inlet / outlet temperature deviation value T3 is equal to or less than a second inlet / outlet temperature deviation threshold TT2 (for example, 50% of the expected temperature difference) that is set to a value smaller than the first inlet / outlet temperature deviation threshold TT1.

[0078] That is, when determining the degree of blockage based only on the third degree determination condition TD3, the control unit 10 determines whether the inlet / outlet temperature deviation value T3 is equal to or less than the second inlet / outlet temperature deviation threshold TT2, and if it determines that the inlet / outlet temperature deviation value T3 is equal to or less than the second inlet / outlet temperature deviation threshold TT2, it determines that the degree is the first. Note that in this embodiment, the control unit 10 determines whether the time during which the inlet / outlet temperature deviation value T3 is equal to or less than the second inlet / outlet temperature deviation threshold TT2 continues (third duration H3) is equal to or greater than a third specified time Hk3, and if it determines that the third duration H3 is equal to or greater than the third specified time Hk3, it determines that the degree is the first, and if it determines that the third duration H3 is not equal to or greater than the third specified time Hk3 (the third duration H3 is shorter than the third specified time Hk3), it determines that the degree is the second.

[0079] When the control unit 10 determines that the degree of blockage is the first degree (step S103; Yes), it executes the blockage resolution mode M1 (step S111).

[0080] On the other hand, when the control unit 10 determines that the degree of blockage is the second degree (not the first degree) (step S103; No), it executes a process for determining whether or not exhaust heat recovery is necessary, which determines whether or not exhaust heat recovery is necessary by exchanging heat between the exhaust gas and hot water (step S105), and executes the blockage elimination mode M1 or the blockage reduction mode M2 ​​depending on whether or not exhaust heat recovery is necessary.

[0081] [Waste heat recovery necessity determination process] In the exhaust heat recovery necessity determination process, the control unit 10 determines whether exhaust heat recovery is necessary based on at least one of the following first exhaust heat recovery necessity determination condition TH1, second exhaust heat recovery necessity determination condition TH2, and third exhaust heat recovery necessity determination condition TH3. Note that a case where exhaust heat recovery is necessary refers to a case where the flow rate of hot water (hot water circulation pump 62) flowing through the hot water circulation circuit L6 (see FIG. 1) needs to be controlled so that the temperature of hot water after heat recovery reaches a target temperature, and a case where exhaust heat recovery is not necessary refers to a case where the flow rate of hot water (hot water circulation pump 62) flowing through the hot water circulation circuit L6 does not need to be controlled so that the target temperature is reached (for example, when it is acceptable for the temperature of hot water after heat recovery to be below the target temperature, or when the temperature of hot water has already reached the target temperature).

[0082] The first exhaust heat recovery necessity determination condition TH1 is a condition that the time during which no hot water flows out of the hot water tank 61 (hereinafter referred to as the fourth duration H4) continues is equal to or longer than the fourth specified time Hk4 (e.g., 1 hour).

[0083] In other words, when determining whether or not exhaust heat recovery is necessary based only on the first exhaust heat recovery necessity determination condition TH1, the control unit 10 determines whether the fourth duration H4 is equal to or greater than the fourth specified time Hk4, and if it determines that the fourth duration H4 is equal to or greater than the fourth specified time Hk4, it determines that exhaust heat recovery is unnecessary, and if it determines that the fourth duration H4 is not equal to or greater than the fourth specified time Hk4 (the fourth duration H4 is less than the fourth specified time Hk4), it determines that exhaust heat recovery is necessary.

[0084] The second exhaust heat recovery necessity determination condition TH2 is a condition that the time (hereinafter referred to as the fifth duration H5) during which the hot water temperature detected by the second hot water temperature detection unit 652 remains above the hot water temperature threshold value TW (e.g., 50°C) is greater than or equal to the fifth specified time Hk5 (e.g., 1 hour).

[0085] In other words, when determining whether or not exhaust heat recovery is necessary based only on the second exhaust heat recovery necessity determination condition TH2, the control unit 10 determines whether the fifth duration H5 is equal to or greater than the fifth specified time Hk5, and if it determines that the fifth duration H5 is equal to or greater than the fifth specified time Hk5, it determines that exhaust heat recovery is unnecessary, and if it determines that the fifth duration H5 is not equal to or greater than the fifth specified time Hk5 (the fifth duration H5 is less than the fifth specified time Hk5), it determines that exhaust heat recovery is necessary.

[0086] The third exhaust heat recovery necessity determination condition TH3 is a condition that the time during which the output (rotation speed) of the heat dissipation fan 632 continues to be equal to or greater than the fan threshold value TF (50% of the fan output during exhaust heat recovery) (hereinafter referred to as the sixth duration time H6) is equal to or greater than the sixth specified time Hk6 (e.g., 1 hour).

[0087] The control unit 10 determines whether the sixth duration H6 is equal to or greater than the sixth specified time Hk6, and if it determines that the sixth duration H6 is equal to or greater than the sixth specified time Hk6, it determines that exhaust heat recovery is unnecessary, and if it determines that the sixth duration H6 is not equal to or greater than the sixth specified time Hk6 (the sixth duration H6 is less than the sixth specified time Hk6), it determines that exhaust heat recovery is necessary.

[0088] When the control unit 10 determines that exhaust heat recovery is unnecessary (step S105; Yes), it determines whether the fuel cell unit 14 can stop power generation (step S107). For example, the control unit 10 determines that power generation can be stopped if the period until a scheduled shutdown of the fuel cell system 100 is less than a threshold period, and determines that power generation cannot be stopped if the period until the scheduled shutdown is equal to or greater than the threshold period. Alternatively, the control unit 10 determines that power generation can be stopped if it determines that the benefit of continued operation is small, and determines that power generation cannot be stopped if it determines that the benefit of continued operation is large. Alternatively, the control unit 10 determines that power generation can be stopped if the user of the fuel cell system 100 permits shutdown, and determines that power generation cannot be stopped if the user does not permit shutdown. Note that scheduled shutdown is a period preset by a designer or the like, e.g., 27 days. The magnitude of the benefit of continued operation is determined based on, for example, heat demand determined by a flow meter, a thermometer, or the like, and power demand determined by an ammeter, a voltmeter, or the like, not shown.

[0089] When the control unit 10 determines that power generation can be stopped (step S107; Yes), it stops power generation by the fuel cell system 100 (hot module 1) (step S109) and executes blockage elimination mode M1 (step S111). When the control unit 10 executes blockage elimination mode M1, it counts up the number of executions. Information indicating the number of executions is stored in the memory unit 101. Note that the number of executions at the start of operation of the fuel cell system 100 (i.e., the initial value) is zero, and the number of executions is reset (set to zero), for example, when the heat exchanger 51 is inspected or replaced.

[0090] Next, the control unit 10 determines whether the number of times the blockage resolution mode M1 has been executed is equal to or greater than a specified number (an example of a predetermined cumulative number) (step S113). If the control unit 10 determines that the number of times the blockage resolution mode M1 has been executed is not equal to or greater than the specified number, that is, that the number of times the blockage resolution mode M1 has been executed is less than the specified number (step S113; No), the process returns to step S101.

[0091] On the other hand, when the control unit 10 determines that the blockage resolution mode M1 has been executed a specified number of times or more (step S113; Yes), it notifies (notifies) error information indicating a malfunction (step S115) and ends the process. The error information is output, for example, via the input / output unit 9 (see FIG. 1) provided in the fuel cell system 100. The input / output unit 9 is configured, for example, with a display, a touch sensor, a button, etc.

[0092] If the control unit 10 determines that exhaust heat recovery is necessary (step S105; No), or if it determines that exhaust heat recovery is necessary (step S105; Yes) but power generation cannot be stopped (step S107; No), it executes blockage alleviation mode M2 ​​(step S117), and the processing returns to step S101.

[0093] [Blockage resolution mode and blockage mitigation mode] Next, blockage resolution mode M1 and blockage alleviation mode M2 ​​will be described with reference to Figures 3 to 5. Figure 3 is a diagram showing an example of the output PV of the hot and cold water circulation pump 62 in blockage resolution mode M1. Figure 4 is a diagram showing an example of the output PV of the hot and cold water circulation pump 62 in blockage alleviation mode M2. Figure 5 is a diagram showing another example of the output PV of the hot and cold water circulation pump 62 in blockage alleviation mode M2. Note that the vertical axis in Figures 3 to 5 represents the output PV of the hot and cold water circulation pump 62, and the horizontal axis represents time (t).

[0094] As shown in FIG. 3, in blockage elimination mode M1, the control unit 10 switches the output (rotation speed) of the hot and cold water circulation pump 62 between a maximum value and a minimum value. That is, the control unit 10 switches the output (rotation speed) of the hot and cold water circulation pump 62 between a maximum value and a minimum value so that the flow rate of hot and cold water flowing through the hot and cold water circulation circuit L6 is maximized or minimized. Specifically, the control unit 10 controls the output of the hot and cold water circulation pump 62 so that the maximum value and the minimum value occur at the same time interval (referred to as the first switching time interval). In blockage elimination mode M1, the control unit 10 repeats switching the hot and cold water circulation pump 62 between the maximum value (once) and the minimum value (once) at the first switching time interval multiple times, which constitutes one cycle. For example, the control unit 10 operates the hot and cold water circulation pump 62 at the maximum flow rate for 10 to 30 seconds and at the minimum flow rate for 10 to 30 seconds three to ten times. Note that this also includes cases where the hot and cold water circulation pump 62 is stopped when the output (rotation speed) of the hot and cold water circulation pump 62 is at its minimum value. The first switching time interval and the number of cycles executed in the blockage elimination mode M1 can each be set arbitrarily by a designer or the like. The first switching time interval is, for example, at least 10 seconds but less than 30 seconds, and the number of cycles is, for example, at least 3 times (3 cycles) but less than 10 times (10 cycles). The interval between the maximum value and the minimum value is not limited to the same time interval, and may be different time intervals. The control unit 10 ends the blockage elimination mode M1 when the number of cycles set by the designer has been executed.

[0095] As shown in FIG. 4, in blockage alleviation mode M2, the control unit 10 switches the output (rotation speed) of the hot and cold water circulation pump 62 between a first output value and a second output value. Specifically, the control unit 10 controls the output of the hot and cold water circulation pump 62 so that the first output value and the second output value are at the same time interval or at different time intervals. The first output value is a value smaller than the maximum value and larger than the command value during normal operation, and is set arbitrarily by a designer, etc. The second output value is a value larger than the minimum value and smaller than the command value during normal operation, and is set arbitrarily by a designer, etc. In blockage alleviation mode M2, the control unit 10 switches between the first output value (at least two times but less than three times) and the second output value (at least one time but less than three times) of the hot and cold water circulation pump 62 at the same time interval or at different time intervals, and repeats this cycle multiple times. For example, only when the flow rate of hot and cold water flowing through the hot and cold water circulation circuit L6 remains constant for 1 to 10 minutes or more, the control unit 10 repeats 3 to 10 cycles of operation, with a flow rate equal to or greater than the command value for normal operation for 1 to 10 seconds and a flow rate equal to or less than the command value for normal operation for 1 to 10 seconds, and ends the blockage alleviation mode M2 ​​1 to 3 hours after the start of the mode. The number of cycles executed in the blockage alleviation mode M2 ​​can be arbitrarily set by a designer or the like. The number of cycles executed in the blockage alleviation mode M2 ​​is, for example, 3 or more (3 cycles) and less than 10 (10 cycles). The control unit 10 ends the blockage alleviation mode M2 ​​after the number of cycles set by the designer has been executed. The first output value may be smaller than the command value for normal operation, and the second output value may be larger than the command value for normal operation. As shown in FIG. 5, the control unit 10 may switch the output (rotation speed) of the hot and cold water circulation pump 62 between the first output value and the second output value in the blockage alleviation mode M2. Specifically, the control unit 10 may repeat an operation of 1 to 10 seconds at a flow rate equal to or greater than the command value during normal operation, and 1 to 10 seconds at a flow rate equal to or less than the command value during normal operation, with 3 to 10 cycles of operation being considered as one operation, and may perform this operation 3 to 10 times at intervals of 10 to 30 seconds.

[0096] <Another embodiment> In the above embodiment, a specific example of the configuration of the fuel cell system has been described, but the configuration can be changed as appropriate.

[0097] In the above embodiment, the fuel cell system of the present invention has been described using specific numerical examples, but these numerical values ​​are given for illustrative purposes only and can be changed as appropriate.

[0098] 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.

[0099] (1) The control unit 10 may omit the blockage degree determination process. In other words, if the control unit 10 determines that there is a blockage tendency in the blockage tendency determination process, the control unit 10 may execute the blockage resolution mode M1 or the blockage alleviation mode M2 ​​without executing the blockage degree determination process.

[0100] (2) Furthermore, when the control unit 10 determines that the degree of blockage is the second degree (step S103 in FIG. 2; No), or when it determines that exhaust heat recovery is unnecessary (step S105; Yes), it determines whether or not it is possible to stop power generation (step S107). However, the processing of step S107 may be omitted. That is, when the control unit 10 determines that exhaust heat recovery is unnecessary (step S105; Yes), it may execute the blockage resolution mode M1 (step S111), and when it determines that exhaust heat recovery is necessary (step S105; No), it may execute the blockage mitigation mode M2 ​​(step S117).

[0101] (3) Furthermore, when the control unit 10 determines that the degree of blockage is the first degree (step S103; Yes), the control unit 10 may stop power generation and then execute the blockage resolution mode M1 (step S111).

[0102] (4) In the process for determining whether or not the hot water / cold water flow path 512 is clogged, the control unit 10 may determine that the hot water / cold water flow path 512 is clogged if any one, two, or all of the first trend determination condition TK1, the second trend determination condition TK2, and the third trend determination condition TK3 are satisfied. The same applies to the process for determining the degree of clogged water flow path 512 and the process for determining whether or not the exhaust heat recovery is necessary. [Industrial Applicability]

[0103] The present invention can be used in a fuel cell system. [Explanation of symbols]

[0104] 1: Hot module 10: Control section 51:Heat exchanger 61: Hot and cold water tank 62: Hot and cold water circulation pump 64: Hot water flow meter 65: Hot and cold water temperature detector 100: Fuel cell system 512: Hot water flow path 632: Heat dissipation fan 651: First hot water temperature detector 652: Second hot water temperature detector C: Cell (fuel cell) H1: First duration H2: Second duration H3: Third duration H4: Fourth duration H5: 5th duration H6: 6th duration Hk1: First regulation time Hk2: Second regulation time Hk3: 3rd regulation time Hk4: 4th regulation time Hk5: 5th regulation time Hk6: 6th regulation time L6: Hot water circulation circuit M1: Blockage resolution mode M2: Blockage reduction mode R1: Command flow rate R2: Actual flow rate R3: Deviation value between command and actual value R4: Expected flow rate R5: Estimated actual deviation value S1: Estimated output S2: Actual output S3: Estimated actual output deviation value T1:Inflow temperature T2:Outflow temperature T3: Inlet / outlet temperature deviation value TF: Fan Threshold TJ1: First expected actual output deviation threshold TJ2: Second expected actual output deviation threshold TR1: First command / actual deviation threshold TR2: Second command / actual deviation threshold TS1: First expected-actual deviation threshold TS2: Second expected-actual deviation threshold TT1: First inlet / outlet temperature deviation threshold TT2: Second inlet / outlet temperature deviation threshold TW: Water temperature threshold

Claims

1. a hot module having a fuel cell that generates electricity based on a fuel gas and an oxidant gas; a heat exchanger having a hot water flow path through which hot water flows and performing heat exchange between the hot water and the exhaust gas discharged from the hot module; a hot water circulation circuit to which the heat exchanger is connected and through which the hot water circulates; a hot water circulation pump that circulates the hot water through the hot water circulation circuit; A control unit that controls the operation of the hot water circulation pump; Equipped with The control unit Execute a clogging tendency confirmation process to determine whether the hot water / cold water flow path has a clogging tendency; In the clogging tendency confirmation process, when it is determined that the hot and cold water flow path has the clogging tendency, a clogging elimination mode for eliminating the clogging tendency of the hot and cold water flow path or a clogging reduction mode for reducing the clogging tendency of the hot and cold water flow path is executed, The fuel cell system controls the hot and cold water circulation pump so that it operates differently in the blockage elimination mode and the blockage mitigation mode.

2. The fuel cell system of claim 1, wherein the control unit controls the hot water circulation pump so that the increase / decrease in the output of the hot water circulation pump in the blockage resolution mode is greater than the increase / decrease in the output of the hot water circulation pump in the blockage reduction mode.

3. a hot and cold water flow meter for measuring the flow rate of the hot and cold water circulating in the hot and cold water circulation circuit; The control unit In the clogging tendency confirmation process, when the actual flow rate measured by the hot and cold water flow meter is smaller than the commanded flow rate commanded as the flow rate of the hot and cold water circulating in the hot and cold water circulation circuit, a command actual deviation value, which is the value of deviation between the commanded flow rate and the actual flow rate, is determined to be equal to or greater than a first command actual deviation threshold value, and a first duration is determined to be equal to or greater than a first specified time, 2. The fuel cell system of claim 1, wherein if the first duration is determined to be equal to or greater than a first specified time, it is determined that there is a tendency toward clogging, and if the first duration is determined to be less than the first specified time, it is determined that there is no tendency toward clogging.

4. The control unit When it is determined that there is a tendency for clogging, executes a blockage degree determination process for determining whether the degree of the blockage tendency is a first degree or a second degree lower than the first degree; In the blockage degree determination process, it is determined whether the command actual deviation value is equal to or greater than a second command actual deviation threshold value, the second command actual deviation threshold value being set to a value greater than the first command actual deviation threshold value; 4. The fuel cell system according to claim 3, wherein when it is determined that the command actual deviation value is equal to or greater than the second command actual deviation threshold, it is determined that the deviation is at the first degree, and the blockage elimination mode is executed.

5. a hot and cold water flow meter for measuring the flow rate of the hot and cold water circulating in the hot and cold water circulation circuit; The control unit In the clogging tendency confirmation process, a second duration is determined as to whether or not an assumed actual deviation value, which is the deviation value between the actual flow rate measured by the hot and cold water flow meter and the assumed flow rate when the actual flow rate is smaller than the assumed hot and cold water flow rate assumed when the output of the hot and cold water circulation pump is constant, is equal to or greater than a first assumed actual deviation threshold, or whether or not an assumed actual output deviation value, which is the duration of a state where an assumed actual output deviation value, which is the deviation value between the actual output and the assumed output when the actual output of the hot and cold water circulation pump is greater than the assumed output of the hot and cold water circulation pump assumed when the actual flow rate measured by the hot and cold water flow meter is constant, is equal to or greater than a second specified time; 2. The fuel cell system of claim 1, wherein if the second duration is determined to be equal to or greater than the second specified time, it is determined that there is a tendency toward clogging, and if the second duration is determined to be less than the second specified time, it is determined that there is no tendency toward clogging.

6. The control unit When it is determined that there is a tendency for clogging, executes a blockage degree determination process for determining whether the degree of the blockage tendency is a first degree or a second degree lower than the first degree; in the blockage degree determination process, determining whether the expected actual deviation value is equal to or greater than a second expected actual deviation threshold, which is set to a value greater than the first expected actual deviation threshold, or whether the expected actual output deviation value is equal to or greater than a second expected actual output deviation threshold, which is set to a value greater than the first expected actual output deviation threshold; 6. The fuel cell system of claim 5, wherein when it is determined that the expected actual deviation value is equal to or greater than the second expected actual deviation threshold, or when it is determined that the expected actual output deviation value is equal to or greater than the second expected actual output deviation threshold, it is determined that the degree is the first degree and the blockage resolution mode is executed.

7. A first hot water temperature detection unit that detects an inflow temperature of the hot water flowing into the heat exchanger; A second hot water temperature detection unit that detects the outflow temperature of the hot water flowing out from the heat exchanger; Further provided with The control unit In the clogging tendency confirmation process, when the output of the hot water circulation pump and the outflow temperature are constant, and when the outflow temperature is higher than the inflow temperature, it is determined whether a third duration, which is the duration of a state in which an inflow / outflow temperature deviation value indicating a deviation value between the outflow temperature and the inflow temperature is equal to or less than a first inflow / outflow temperature deviation threshold, is equal to or greater than a third specified time; 2. The fuel cell system of claim 1, wherein if the third duration is determined to be equal to or greater than the third specified time, it is determined that there is a tendency toward clogging, and if the third duration is determined not to be equal to or greater than the third specified time, it is determined that there is no tendency toward clogging.

8. The control unit When it is determined that there is a tendency for clogging, executes a blockage degree determination process for determining whether the degree of the blockage tendency is a first degree or a second degree lower than the first degree; In the blockage degree determination process, it is determined whether the inlet / outlet temperature deviation value is equal to or less than a second inlet / outlet temperature deviation threshold value, which is set to a value smaller than the first inlet / outlet temperature deviation threshold value; 8. The fuel cell system according to claim 7, wherein when it is determined that the inlet / outlet temperature deviation value is equal to or less than the second inlet / outlet temperature deviation threshold, it is determined that the degree is the first degree, and the blockage elimination mode is executed.

9. When the control unit determines that the degree of clogging tendency is the second degree, it determines whether or not exhaust heat recovery is necessary to perform heat exchange between the exhaust gas and the hot water, When it is determined that the exhaust heat recovery is necessary, the blockage mitigation mode is executed; 9. The fuel cell system according to claim 4, wherein the blockage elimination mode is executed when it is determined that the exhaust heat recovery is unnecessary.

10. When the control unit determines that the degree of clogging tendency is the second degree, it determines whether or not exhaust heat recovery is necessary to perform heat exchange between the exhaust gas and the hot water, When it is determined that the exhaust heat recovery is necessary, the blockage mitigation mode is executed; 9. A fuel cell system as described in any one of claims 4, 6, and 8, wherein, when it is determined that the exhaust heat recovery is unnecessary, it further determines whether power generation in the fuel cell can be stopped, and when it is determined that power generation in the fuel cell can be stopped, it executes the blockage resolution mode, and when it is determined that power generation in the fuel cell cannot be stopped, it executes the blockage reduction mode.

11. 2. The fuel cell system according to claim 1, wherein the control unit issues error information indicating a malfunction when the number of times the blockage elimination mode has been executed reaches a predetermined cumulative number.

12. Further provided is a hot water tank connected to the hot water circulation circuit and storing the hot water, The control unit determines whether a fourth duration, which is a duration of a state in which hot water is not dispensed from the hot water tank, is equal to or longer than a fourth specified time, When it is determined that the fourth duration is equal to or longer than a fourth specified time, it is determined that the exhaust heat recovery is unnecessary, 10. The fuel cell system according to claim 9, wherein when it is determined that the fourth duration is not equal to or longer than a fourth specified time, it is determined that the exhaust heat recovery is necessary.

13. a hot water tank connected to the hot water circulation circuit and storing the hot water; A temperature detection unit that detects at least one of the temperature of the hot water stored in the hot water tank and the temperature of the hot water in the hot water circulation circuit from the hot water tank to the heat exchanger, The control unit determines whether a fifth duration, which is a duration of a state in which the temperature of the hot water detected by the temperature detection unit is equal to or higher than a hot water temperature threshold, is equal to or longer than a fifth specified time, If it is determined that the fifth duration is equal to or longer than the fifth specified time, it is determined that the exhaust heat recovery is unnecessary, 10. The fuel cell system according to claim 9, wherein when it is determined that the fifth duration is not equal to or longer than the fifth specified time, it is determined that the exhaust heat recovery is necessary.

14. The hot water circulation circuit further includes a heat dissipation fan disposed upstream of the heat exchanger in the direction of flow of the hot water, and configured to dissipate heat from the hot water. determining whether a sixth duration, which is a duration of a state in which the output of the heat dissipation fan is equal to or greater than a fan threshold, is equal to or greater than a sixth specified time; If it is determined that the sixth duration is equal to or longer than a sixth specified time, it is determined that the exhaust heat recovery is unnecessary, 10. The fuel cell system according to claim 9, wherein when it is determined that the sixth duration is not equal to or longer than a sixth specified time, it is determined that the exhaust heat recovery is necessary.

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