JP2017069104A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of being continuously operated without increasing a system size.SOLUTION: A fuel cell system comprises: a fuel cell module including a fuel cell; a hot-water storage tank for storing hot water; a hot-water circulation passage for circulating hot water in the hot-water storage tank; a first heat exchanger for cooling the exhaust gas from the fuel cell module; a water recovery tank for recovering and storing the water obtained by condensing water vapor in the cooled exhaust gas; a water supply passage for supplying the water stored in the water recover tank to the fuel cell module; a water supply passage provided with a reverse osmosis membrane and for supplying the water transmitted through the reverse osmosis membrane to the water recovery tank; a second heat exchanger for cooling the hot water circulating in the hot-water circulation passage; and determining means. When the determining means determines that an amount of water stored in the water recovery tank is insufficient, the fuel cell system supplies water to the water supply passage and supplies the water transmitted through the reverse osmosis membrane to the water recovery tank.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system.

  In a fuel cell system equipped with a fuel cell, the steam contained in the exhaust gas of the fuel cell system is condensed and recovered, and the steam obtained by vaporizing the recovered condensed water is used for steam reforming of the raw material gas. Sometimes used.

  Furthermore, in the fuel cell system, it is preferable to recover the heat generated during power generation from the viewpoint of waste heat utilization. For example, when condensing water vapor contained in the exhaust gas, the heat of the exhaust gas is heated using a heat exchanger. It is preferable that the hot water stored and stored in the hot water storage tank can be used for hot water supply, heating or the like.

  Here, when the temperature of the water stored in the hot water storage tank rises and the hot water storage tank is thermally filled (full storage state), the exhaust gas cannot be cooled by heat exchange. As a result, condensed water cannot be recovered from the exhaust gas.

  Therefore, from the viewpoint of effectively using the water vapor in the exhaust gas, it is necessary to stop the power generation in the fuel cell system at the time of full storage, and restart the power generation after the full storage is eliminated. However, high temperature operation fuel cells such as solid oxide fuel cells and molten carbonate fuel cells that operate at a temperature of 600 ° C. or higher require a large amount of energy, operation time, and the like for start / stop and restart. Therefore, continuous operation for a long time is required, and it is not realistic to start and stop each time the battery is full.

  In order to enable continuous operation of the fuel cell system for a long time, for example, a hot water circulation path for circulating hot water in a hot water storage tank is cooled by a radiator, and hot water supplied to a heat exchanger used for cooling exhaust gas. It has been proposed to lower the temperature (see, for example, Patent Document 1).

  In addition, there has been proposed a technique that enables continuous operation of the system even at the time of full storage without providing a radiator. For example, it has been proposed to dissipate heat by disposing a heat radiating pipe in a heat recovery water circuit from a hot water tank to a heat exchanger for heat recovery (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 2015-2093 Japanese Patent No. 4497396

  However, in the technique of Patent Document 1, since a radiator is used, problems such as an increase in size of the system and generation of noise occur. Moreover, in the technique of patent document 2, it is necessary to ensure the installation space of a heat sink, and there exists a problem that it receives to the influence of temperature.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell system capable of continuous operation even at full storage without increasing the system size.

The above problem is solved by, for example, the following means.
<1> A fuel cell module having a fuel cell, a hot water storage tank for storing hot water, a hot water storage circulation path for circulating hot water in the hot water storage tank, an exhaust gas discharged from the fuel cell module, and a hot water storage circulation path The first heat exchanger that performs heat exchange with hot water and cools the exhaust gas, and collects and stores water obtained by condensing water vapor in the exhaust gas cooled by the first heat exchanger. A water recovery tank, a water supply path for supplying water stored in the water recovery tank to the fuel cell module, and a reverse osmosis membrane are provided, and the water that has passed through the reverse osmosis membrane is recovered in the water. A water supply path for supplying to the tank, a hot water that is provided upstream of the first heat exchanger, and drainage discharged from the water supply path without passing through the reverse osmosis membrane. Heat exchange between A second heat exchanger that cools the hot water flowing through the hot water storage circulation path; and a determination unit that determines whether or not an amount of water stored in the water recovery tank is insufficient. When it is determined that the amount of water stored in the water recovery tank is insufficient, the fuel cell supplies water to the water supply path and supplies water that has passed through the reverse osmosis membrane to the water recovery tank system.

  The fuel cell system according to the present embodiment is a system that condenses and collects water vapor contained in the exhaust gas discharged from the fuel cell module, and supplies the recovered water to the fuel cell module. Here, the fuel cell system according to the present embodiment uses the first heat exchanger to condense the water vapor contained in the exhaust gas, and to recover the heat of the exhaust gas in the hot water circulating in the hot water storage circulation path. The hot water recovered from the heat is stored in a hot water tank.

  Normally, when the fuel cell system is operated continuously, the hot water circulating in the hot water circulation path continuously recovers heat from the exhaust gas, so the temperature of the hot water stored in the hot water tank rises and a certain amount of hot water is discharged. If there is not, it will be in the state filled up thermally (full storage state). As a result, the exhaust gas cannot be cooled, so that the condensed water cannot be recovered from the exhaust gas, resulting in a problem that the water used for steam reforming is insufficient.

  On the other hand, the fuel cell system according to the present embodiment is provided with a reverse osmosis membrane, a water supply path for supplying water that has permeated the reverse osmosis membrane to the water recovery tank, and an amount of water stored in the water recovery tank. Determining means for determining whether or not it is insufficient. When the determination unit determines that the amount of water stored in the water recovery tank is insufficient, water is supplied to the water supply path, and water that has passed through the reverse osmosis membrane is supplied to the water recovery tank.

  As described above, even when it is fully stored and the condensed water cannot be recovered from the exhaust gas, the water that has passed through the reverse osmosis membrane is supplied to the water recovery tank. Therefore, the problem that the water used for steam reforming is insufficient is solved, and the continuous operation of the system becomes possible.

  Moreover, since the hot water which distribute | circulates a hot water storage circulation path | route collect | recovers heat | fever continuously from waste gas in a 1st heat exchanger, it is higher temperature than the waste_water | drain discharged | emitted from the water supply path | route. Here, the fuel cell system according to this embodiment includes a second heat exchanger that exchanges heat between the hot water flowing through the hot water storage circulation path and the drainage discharged from the water supply path without passing through the reverse osmosis membrane. doing. Since the hot water flowing through the hot water storage circulation path is cooled by the second heat exchanger and the cooled hot water is supplied to the first heat exchanger, the exhaust gas can be cooled by the first heat exchanger. The condensed water can be recovered.

  Therefore, the problem that the water used for steam reforming is insufficient is solved more suitably, and the burden on the reverse osmosis membrane is reduced by effectively using the wastewater that has not permeated the reverse osmosis membrane.

  Furthermore, in the fuel cell system according to the present embodiment, the hot water flowing through the hot water storage circulation path can be cooled without providing a radiator or a heat radiating pipe for cooling the hot water storage circulation path. Can be operated continuously. Furthermore, since it is not necessary to provide a radiator or a heat radiating pipe, an increase in system size can be suppressed.

  <2> The water level detection means for detecting the water level of the water recovery tank is further provided, and the determination means determines whether or not the amount of water stored in the water recovery tank is insufficient by the water level detection means. The fuel according to <1>, wherein the fuel is determined based on the detected water level of the water recovery tank, and supplies water to the water supply path when the water level of the water recovery tank detected by the water level detection unit becomes a threshold value or less. Battery system.

  In the fuel cell system according to the present embodiment, when the determination unit determines that the water level of the water recovery tank detected by the water level detection unit is equal to or lower than the threshold value, water is supplied to the water supply path and the water that has permeated the reverse osmosis membrane. Is supplied to the water recovery tank. Therefore, the problem that the water used for steam reforming is insufficient is suppressed, and the continuous operation of the system is possible even at full storage.

  <3> Temperature detection means is further provided at at least one of a predetermined position upstream of the first heat exchanger and a predetermined position of the hot water storage tank in the hot water circulation path, and the determination means is provided in the water recovery tank. Whether or not the amount of stored water is insufficient is determined based on the temperature of the hot water detected by the temperature detection means, and when the temperature of the hot water detected by the temperature detection means exceeds a threshold value, The fuel cell system according to <1> or <2>, wherein water is supplied to the water supply path.

  In the fuel cell system according to the present embodiment, when the determination unit determines that the temperature of the hot water detected by the temperature detection unit is equal to or higher than the threshold value, water is supplied to the water supply path, and the water that has passed through the reverse osmosis membrane is discharged. It is made to supply to a collection tank. Therefore, even if the temperature of the detected hot water is equal to or higher than the threshold value, the cooling efficiency of the exhaust gas is reduced, and condensed water cannot be suitably recovered from the exhaust gas, so that water is supplied from the water supply path. Thus, a sufficient amount of water can be stored in the water recovery tank. Therefore, the problem that the water used for steam reforming is insufficient is suppressed, and the continuous operation of the system is possible even at the time of full storage.

  <4> The water treatment apparatus according to any one of <1> to <3>, further including a water treatment device disposed downstream of the water recovery tank and between the water recovery tank and the fuel cell module. Fuel cell system.

  Water that has permeated through the reverse osmosis membrane has increased purity, but if the purity does not reach the level required for water for steam reforming, a reverse osmosis membrane that can achieve the level may be adopted. It may not be reasonable. In such a case, for example, when the water treatment device is arranged between the first heat exchanger and the water recovery tank, the water that has passed through the reverse osmosis membrane is not treated with water, and the fuel cell It will be supplied to the module, adversely affecting each component in the module.

  On the other hand, in the fuel cell system according to the present embodiment, since the water treatment device is provided between the water recovery tank and the fuel cell module, the water that has passed through the reverse osmosis membrane is treated by the water treatment device. Therefore, high-purity water is supplied to the fuel cell module, and adverse effects on each component in the module are suppressed.

<5> The fuel cell system according to any one of <1> to <4>, further including a dechlorination unit that removes chlorine in water flowing through the water supply path upstream of the reverse osmosis membrane.
<6> The fuel cell system according to any one of <1> to <5>, further including a dechlorination unit that removes chlorine in water supplied to the hot water tank upstream of the hot water tank.

  By disposing the dechlorination unit as described above, chlorine in water flowing through the water supply path or chlorine in water supplied to the hot water storage tank is removed, so that a reverse osmosis membrane that is not chlorine resistant can also be suitably used. it can.

  According to the present invention, it is possible to provide a fuel cell system capable of continuous operation even when fully stored without increasing the system size.

1 is a schematic configuration diagram showing a fuel cell system according to an embodiment of the present invention. It is a flowchart which shows the control process 1 of the water supply in the fuel cell system which concerns on one Embodiment of this invention. It is a flowchart which shows the control process 2 of the water supply in the fuel cell system which concerns on one Embodiment of this invention. It is a schematic block diagram which shows the fuel cell system used as the comparison object of this invention.

  In this specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  First, a fuel cell system to be compared with the fuel cell system of the present invention will be described with reference to FIG. FIG. 4 is a schematic configuration diagram showing a fuel cell system to be compared with the present invention.

  In FIG. 4, a fuel cell system 100 to be compared includes a fuel cell module 101, a heat exchanger 102, water treatment devices 103 and 108, a water recovery tank 104, a hot water storage tank 106, and a radiator 109. Prepare. Further, the fuel cell system 100 supplies the water collected in the water recovery tank 104 to the fuel cell module 101 and the water treated by the water treatment device 108 to the water recovery tank 4. A water supply path 115 and a hot water circulation path 116 for circulating hot water stored in the hot water storage tank 106 are further provided.

  Further, the fuel cell system 100 condenses and collects water vapor contained in the exhaust gas discharged from the fuel cell module 101, and supplies the recovered water to the fuel cell module 101 as reformed water, thereby supplying the fuel cell. This system provides the necessary reforming water. Here, the fuel cell system 100 uses the heat exchanger 102 to condense the water vapor contained in the exhaust gas and to recover the heat of the exhaust gas in the hot water circulating through the hot water storage circulation path 116.

  When the fuel cell system is operated continuously, the hot water circulating in the hot water circulation path continuously recovers heat from the exhaust gas, so the temperature of the hot water stored in the hot water tank rises and a certain amount of hot water is not discharged. It will be in the state (full storage state) that was filled up thermally. As a result, the exhaust gas cannot be cooled, so that the condensed water cannot be recovered from the exhaust gas, resulting in a problem that the water used for steam reforming is insufficient.

  Therefore, the fuel cell system 100 includes a radiator 109 for cooling the hot water flowing through the hot water storage circulation path 116, and cools the hot water flowing through the hot water storage circulation path 116 by supplying air to the radiator 109 through the air supply path 119. It is the composition to do. As a result, the exhaust gas can be cooled even at full storage, and condensed water can be recovered from the exhaust gas. This eliminates the problem of insufficient water used for steam reforming and enables continuous operation of the system. .

  However, since the fuel cell system 100 is provided with the radiator 109, there is a problem that the system size is increased and noise is generated. Therefore, it is desirable to provide a fuel cell system that can suppress an increase in system size and noise generation and can be continuously operated even at full storage.

  On the other hand, the fuel cell system 10 according to an embodiment of the present invention described below is a system that can be continuously operated even at full storage, while increasing the system size and suppressing noise generation. Hereinafter, an embodiment of a fuel cell system of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram showing a fuel cell system according to an embodiment of the present invention.

[Fuel cell system]
A fuel cell system 10 according to the present embodiment includes a fuel cell module 1, a first heat exchanger 2, a water treatment device 3, a water recovery tank 4 (water recovery tank), a reverse osmosis membrane 5, and a hot water storage tank. 6 and the second heat exchanger 7. The fuel cell system 10 according to the present embodiment includes a reformed water supply path 14 (water supply path) for supplying water stored in the water recovery tank 4 to the fuel cell module 1 and water that has passed through the reverse osmosis membrane 5. Is further provided with a water supply path 15 for supplying water to the water recovery tank 4 and a hot water circulation path 16 for circulating hot water stored in the hot water storage tank 6.

  Further, the fuel cell system 10 includes a determination unit 40 that determines whether or not the water stored in the water recovery tank 4 is insufficient, and the determination unit 40 includes the water stored in the water recovery tank 4. In this system, when it is determined that the amount is insufficient, water is supplied to the water supply path 15 and water that has permeated the reverse osmosis membrane 5 is supplied to the water recovery tank 4.

  Further, the fuel cell system 10 according to the present embodiment condenses and collects water vapor contained in the exhaust gas discharged from the fuel cell module 1, and supplies the recovered water to the fuel cell module 1 as reformed water. In this system, the reformed water necessary for the fuel cell is provided. Here, the fuel cell system 10 uses the first heat exchanger 2 to condense the water vapor contained in the exhaust gas and recover the heat of the exhaust gas to the hot water circulating in the hot water circulation path 16. The hot water collected is stored in the hot water storage tank 6.

  As described above, when the fuel cell system is continuously operated, the hot water circulating in the hot water circulation path continuously recovers heat from the exhaust gas, so the temperature of the hot water stored in the hot water tank rises and It becomes a full state (full storage state). As a result, the exhaust gas cannot be cooled, so that the condensed water cannot be recovered from the exhaust gas, resulting in a problem that the water used for steam reforming is insufficient.

  On the other hand, in the fuel cell system 10 according to the present embodiment, when the determination unit 40 determines that the amount of water stored in the water recovery tank 4 is insufficient, water is supplied to the water supply path 15 to perform reverse osmosis. Water that has passed through the membrane 5 is supplied to the water recovery tank 4.

  As described above, even when the condensate cannot be recovered from the exhaust gas due to full storage, the water that has passed through the reverse osmosis membrane 5 is supplied to the water recovery tank 4, so that the water used for steam reforming is insufficient. This eliminates the problem and enables continuous operation of the system. Furthermore, since the purity of the water that has passed through the reverse osmosis membrane 5 is increased, the burden of water treatment is reduced as compared with the case where hot water or clean water is directly mixed with condensed water for steam reforming, for example.

  Moreover, since the hot water flowing through the hot water storage circulation path 16 continuously recovers heat from the exhaust gas in the first heat exchanger 2, the temperature is higher than the waste water discharged from the water supply path 15. Here, in the fuel cell system 10 according to the present embodiment, the second heat exchange is performed between the hot water flowing through the hot water storage circulation path 16 and the drainage discharged from the water supply path 15 without passing through the reverse osmosis membrane 5. The hot water flowing through the hot water storage circulation path 16 is cooled by the heat exchanger 7, and the cooled hot water is supplied to the first heat exchanger 2, so that the exhaust gas can be cooled in the first heat exchanger 2, The condensed water can be recovered from the exhaust gas.

  Therefore, the problem that the water used for steam reforming is insufficient is solved more suitably, and the burden on the reverse osmosis membrane 5 is reduced by effectively using the wastewater that has not permeated the reverse osmosis membrane 5.

  Furthermore, in the fuel cell system 10 according to the present embodiment, the fuel cell system 10 can be continuously operated without providing a radiator or a radiator pipe for cooling the hot water storage circulation path 16. Further, the fuel cell system 10 is useful because it is not necessary to provide a radiator or a heat radiating pipe, so that an increase in system size can be suppressed and noise due to the provision of the radiator does not occur.

  Hereinafter, each component of the fuel cell system 10 according to the present embodiment will be described in detail.

  A fuel cell system 10 according to the present embodiment includes a fuel cell module 1 including a fuel cell (not shown). The fuel cell module 1 has a function of generating power by supplying fuel, and further includes a vaporizer and a reformer described later in addition to the fuel cell.

  The fuel cell module 1 is connected to the raw material gas supply path 11, the oxygen supply path 12 and the reformed water supply path 14, and the raw material gas, oxygen and reformed water are supplied to the fuel cell module 1 from the respective paths. . A blower 21 that circulates the source gas is installed in the source gas supply path 11, a blower 22 that circulates oxygen is installed in the oxygen supply path 12, and the reformed water supply path 14 is modified. A pump 23 for circulating quality water is installed.

  The raw material gas flowing through the raw material gas supply path 11 is not particularly limited as long as it contains a hydrocarbon gas that can be steam reformed. For example, natural gas, LP gas (liquefied petroleum gas), coal reformed gas And lower hydrocarbon gas. Examples of the lower hydrocarbon gas include lower hydrocarbons having 4 or less carbon atoms such as methane, ethane, ethylene, propane, butane, and methane is particularly preferable. In addition, as hydrocarbon gas, what mixed the lower hydrocarbon gas mentioned above may be used.

  The reformed water flowing through the reformed water supply path 14 is vaporized by a vaporizer (not shown) provided in the fuel cell module 1, and the vapor generated by the vaporization passes through the steam supply path (not shown). It is supplied to a reformer (not shown).

  The fuel cell system 10 has a reformer that generates reformed gas by steam reforming a raw material gas outside the fuel cell. The reformer includes, for example, a combustion section in which a burner or a combustion catalyst is disposed, and a reforming section that includes a reforming catalyst, and a raw material gas supply path 11 and a steam supply path on the upstream side of the reforming section The fuel cell is connected via a reformed gas supply path (not shown) downstream of the reforming unit.

  A source gas containing a hydrocarbon gas such as methane is supplied to the reforming section through the source gas supply path 11, and steam is supplied to the reforming section through the steam supply path. Then, after the hydrocarbon gas is steam reformed in the reforming section, the generated reformed gas is supplied to the fuel cell through the reformed gas supply path.

  The combustion section heats the reforming section with combustion heat. For example, the combustion section causes a combustion reaction between oxygen and a raw material gas containing a hydrocarbon gas, or unreacted in the cathode offgas discharged from the fuel cell. The reforming part is heated by causing a combustion reaction of oxygen and unreacted hydrogen in the anode off gas. The exhaust gas generated by the combustion reaction is supplied to the exhaust path 13 and is discharged to the outside of the fuel cell module 1.

When methane, which is an example of hydrocarbon gas, is steam reformed, carbon monoxide and hydrogen are generated by the reaction of the following formula (a) in the reforming section.
CH ₄ + H ₂ O → CO + 3H ₂ ... (A)

  The reforming catalyst installed in the reforming section is not particularly limited as long as it is a catalyst for the steam reforming reaction, but Ni, Rh, Ru, Ir, Pd, Pt, Re, Co, Fe and Mo. A steam reforming catalyst containing at least one of the above as a catalyst metal is preferred.

  The steam carbon ratio S / C, which is the ratio between the number S of water vapor molecules per unit time supplied to the reforming section and the number of carbon atoms C of hydrocarbon gas per unit time supplied to the reforming section, It is preferably 1.5 to 3.5, more preferably 2.0 to 3.0, and even more preferably 2.0 to 2.5. When the steam carbon ratio S / C is within this range, the hydrocarbon gas is efficiently steam reformed, and a reformed gas containing hydrogen and carbon monoxide is generated. Furthermore, carbon deposition in the fuel cell module 1 can be suppressed, and the reliability of the fuel cell module 1 can be improved.

  Moreover, it is preferable that a combustion part heats a reforming part to 600 to 800 degreeC from a viewpoint of performing steam reforming efficiently, and it is more preferable to heat to 600 to 700 degreeC.

  The fuel cell system 10 according to the present embodiment includes a fuel cell that generates power using the reformed gas supplied from the reformer through the reformed gas supply path. The fuel cell may be, for example, a fuel cell including an air electrode (cathode), an electrolyte, and a fuel electrode (anode), or a fuel cell stack in which a plurality of fuel cells are stacked. As the fuel cell, a low-temperature fuel cell that operates at a temperature of 200 ° C. or lower, for example, a polymer electrolyte fuel cell that operates at about 60 ° C. to 100 ° C., phosphoric acid that operates at about 150 ° C. to 200 ° C. Type fuel cells, high-temperature fuel cells operating at about 600 ° C. to 800 ° C., for example, solid oxide fuel cells operating at about 700 ° C. to 800 ° C., molten carbonates operating at about 600 ° C. to 700 ° C. Type fuel cell.

  A reformed gas is supplied to the anode of the fuel cell through a reformed gas supply path, and a gas containing oxygen is supplied to the cathode of the fuel cell through an oxygen supply path 12. Then, mainly water vapor (mainly water vapor and carbon dioxide in the molten carbonate fuel cell) is generated by an electrochemical reaction between the reformed gas and oxygen. Further, the electrons generated at the anode move to the cathode through an external circuit. As the electrons move from the anode to the cathode in this way, power is generated in the fuel cell.

  Here, the off-gas discharged from the anode and the cathode is supplied to the combustion part of the reformer as described above, and after unreacted hydrogen and oxygen are used for the combustion reaction, the fuel cell module 1 is passed through the exhaust path 13. May be discharged from the fuel cell module 1 through the exhaust path 13 without being supplied to the combustion section.

  In a fuel cell system including a high-temperature fuel cell, the reformer does not need to be attached to the outside of the fuel cell, and the raw material gas and water vapor are supplied directly to the fuel cell, and the water vapor reforming is performed inside the fuel cell. The structure which performs quality (internal reforming) may be sufficient. Since the reaction temperature inside the fuel cell stack is as high as 600 ° C. to 800 ° C., it is possible to perform steam reforming in the fuel cell stack.

  The exhaust gas discharged from the fuel cell module 1 and flowing through the exhaust path 13 exchanges heat with the hot water flowing through the hot water storage circulation path 16 in the first heat exchanger 2. Thereby, the exhaust gas flowing through the exhaust path 13 is cooled, the water vapor contained in the exhaust gas is condensed, and the hot water circulating through the hot water storage circulation path 16 recovers the heat of the exhaust gas. The condensed water obtained by condensing the water vapor is supplied to the water recovery tank 4, and the hot water from which the heat of the exhaust gas has been recovered is supplied to the hot water storage tank 6. Moreover, the exhaust gas which distribute | circulates the exhaust path 13 is exhausted outside.

  The water recovery tank 4 is a container that recovers and stores water obtained by condensing water vapor contained in the exhaust gas flowing through the exhaust passage 13. In the water recovery tank 4, when a predetermined amount or more of water is stored, drainage is performed by overflow, for example.

  The water recovery tank 4 is connected to the reforming water supply path 14, and the reforming water supply path 14 is provided with a water treatment device 3 and a pump 23. By driving the pump 23, the water stored in the water recovery tank 4 is processed by the water treatment device 3 and then supplied to the fuel cell module 1 through the reformed water supply path 14.

  The water treatment device 3 is disposed downstream of the water recovery tank 4 and between the water recovery tank 4 and the fuel cell module 1, and is obtained by condensing water vapor in the first heat exchanger 2. This is an apparatus for removing impurities contained in condensed water and impurities contained in water that has passed through the reverse osmosis membrane 5. Examples of the water treatment apparatus include a water treatment apparatus having an ion exchange resin that needs to be replaced or regenerated with chemicals, and an electrodeionization type water treatment apparatus that can electrically regenerate the ion exchange resin.

  The water recovery tank 4 is connected to a water supply path 15, and the water supply path 15 is provided with an on-off valve 27, a pump 24, and a reverse osmosis membrane 5 in order from the upstream. Since the water supply path 15 is connected to the first water supply path 17 that is a path for supplying water to the hot water storage tank 6, the water flows through the water supply path 15 by opening the on-off valve 27 and driving the pump 24. Then, water is supplied to the reverse osmosis membrane 5. In addition, as the on-off valve 27, an electromagnetic valve, an electrically operated valve, etc. are mentioned, for example.

  The reverse osmosis membrane 5 is a membrane that selectively permeates water by applying pressure to water containing impurities and does not permeate impurities other than water such as ions and salts (suppresses permeation of impurities). Therefore, by driving the pump 24 and supplying water to the reverse osmosis membrane 5, high-purity water that has passed through the reverse osmosis membrane 5 can be obtained. The high-purity water is supplied to the water recovery tank 4 through the water supply path 15.

  In addition, by supplying water to the reverse osmosis membrane 5, high-purity water that has permeated through the reverse osmosis membrane 5 and water with a large amount of impurities that have not permeated through the reverse osmosis membrane 5 can be obtained. Water with a large amount of impurities is discharged from the water supply path 15 and supplied to the second heat exchanger 7 through the drainage path 19.

  The reverse osmosis membrane 5 is not particularly limited as long as it selectively permeates water and does not permeate impurities other than water such as ions and salts, and a commercially available one can be used. Moreover, examples of the structure of the reverse osmosis membrane include a hollow fiber membrane, a spiral membrane, and a tubular membrane. Examples of the material of the reverse osmosis membrane include cellulose acetate, aromatic polyamide, polyvinyl alcohol, and polysulfone. .

  By the way, although the purity of the water that has permeated through the reverse osmosis membrane 5 is increased, if the purity does not reach the level required for water for steam reforming, a reverse osmosis membrane that can achieve the level is adopted. Sometimes it is not reasonable to do. In such a case, for example, when the water treatment device 3 is disposed between the first heat exchanger 2 and the water recovery tank 4, the water that has permeated the reverse osmosis membrane 5 is treated with water. However, the fuel cell module 1 is supplied to the fuel cell module 1 and may adversely affect each component (for example, the reforming unit) in the module.

  On the other hand, in the fuel cell system 10 according to the present embodiment, the water treatment device 3 is provided in the reformed water supply path 14 between the water recovery tank 4 and the fuel cell module 1, so that the reverse osmosis membrane 5 is permeated. The treated water is treated by the water treatment device 3. Therefore, high-purity water is supplied to the fuel cell module 1, and adverse effects on each component in the module are suppressed.

  Next, the hot water storage tank 6 is a container for storing hot water recovered from the heat of exhaust gas discharged from the fuel cell module 1 by the first heat exchanger 2. Further, water is supplied to the hot water storage tank 6 through the first water supply path 17, and hot water is supplied from the hot water storage tank 6 to the outside of the system through the hot water supply path 31. Hot water supplied to the outside of the system through the hot water supply path 31 is mixed with water supplied through the second water supply path 18 at an appropriate temperature by the mixing valve 26, and used for hot water supply or heating, for example.

  The hot water storage tank 6 is connected to the hot water storage circulation path 16, and the hot water storage circulation path 16 is provided with the second heat exchanger 7, the pump 25, and the first heat exchanger 2 in order from the upstream. By driving the pump 25, hot water stored in the hot water storage tank 6 flows through the hot water storage circulation path 16.

  The second heat exchanger 7 exchanges heat between the hot water flowing through the hot water circulation path 16 and the waste water flowing through the drainage path 19 to cool the hot water flowing through the hot water circulation path 16. Therefore, heat exchange is performed when the drainage is flowing through the drainage path 19, but heat exchange is not performed when the drainage is not flowing through the drainage path 19.

  The hot water flowing through the hot water storage circulation path 16 continuously collects heat from the exhaust gas in the first heat exchanger 2, and therefore has a higher temperature than the drainage discharged from the water supply path 15. Therefore, the hot water flowing through the hot water storage circulation path 16 is cooled by heat exchange between the hot water flowing through the hot water storage circulation path 16 and the drainage flowing through the drainage path 19 in the second heat exchanger 7. The cooled hot water is supplied to the first heat exchanger 2. And since the exhaust gas can be cooled in the first heat exchanger 2 and condensed water can be recovered from the exhaust gas, the problem of lack of water used for steam reforming is more preferably solved. In addition, the burden on the reverse osmosis membrane 5 is reduced by effectively using the wastewater that has not permeated the reverse osmosis membrane 5. Furthermore, the fuel cell system 10 according to the present embodiment can cool the hot water flowing through the hot water storage circulation path 16 without providing a radiator, and is useful in terms of space saving and suppression of noise generation.

  If water is not supplied to the water supply path 15, water with a large amount of impurities that has not permeated the reverse osmosis membrane 5 is not discharged from the water supply path 15, so that the wastewater does not flow through the drainage path 19, Heat exchange in the heat exchanger 7 is not performed.

  The hot water after passing through the second heat exchanger 7 exchanges heat with the exhaust gas flowing through the exhaust path 13 in the first heat exchanger 2, and the hot water recovered from the heat of the exhaust gas passes through the hot water storage circulation path 16. It is distributed and stored in the hot water storage tank 6.

  Here, since the hot water flowing through the hot water storage circulation path 16 downstream from the first heat exchanger 2 is hotter than the waste water flowing through the drainage path 19, the second heat is further downstream from the first heat exchanger 2. When the exchanger 7 is installed, the hot water supplied to the hot water storage tank 6 is cooled, which affects the temperature stratification of the hot water storage tank 6. On the other hand, when the second heat exchanger 7 is installed upstream of the first heat exchanger 2 as in the fuel cell system 10 according to the present embodiment, the temperature stratification of the hot water storage tank 6 is not affected. Therefore, it is preferable that the place where the second heat exchanger 7 is installed is upstream of the first heat exchanger 2.

  The hot water storage tank 6 supplies hot water to the hot water storage circulation path 16 from the lower part near the supply port connected to the first water supply path 17 and circulates hot water at the upper part near the hot water outlet connected to the hot water supply path 31. The hot water flowing through the path 16 is collected. Therefore, a temperature gradient is generated in the hot water stored in the hot water storage tank 6, and the temperature of the hot water stored from the lower part toward the upper part increases.

  Here, during startup of the fuel cell system 10, hot water is continuously circulated through the hot water storage circulation path 16 in order to cool the exhaust gas flowing through the exhaust path 13 and condense the water vapor. Therefore, when the fuel cell system 10 is operated continuously for a long time, the temperature of the hot water stored in the hot water storage tank 6 rises, and if a certain amount of hot water is not discharged at that time, a state where it is thermally filled (full storage state) )become. When full storage is reached, there is almost no temperature gradient in the hot water stored in the hot water storage tank 6, and there is almost no temperature difference between the upper side and the lower side of the hot water stored in the hot water storage tank 6. Therefore, at the time of full storage, the exhaust gas cannot be cooled by heat recovery from the exhaust gas flowing through the exhaust path 13, and as a result, the condensed water cannot be recovered from the exhaust gas, and the water stored in the water recovery tank 4 May be insufficient.

  However, in the fuel cell system 10 according to the present embodiment, when the determination unit 40 determines that the amount of water stored in the water recovery tank 4 is insufficient, water is supplied to the water supply path 15 and vice versa. The water that has passed through the osmotic membrane 5 is supplied to the water recovery tank 4. Therefore, the problem that water is insufficient in the water recovery tank 4 is solved even at the time of full storage, and the system can be continuously operated.

  Further, as described above, by supplying water to the water supply path 15, heat exchange is performed between the hot water flowing through the hot water storage circulation path 16 and the drainage flowing through the drainage path 19 in the second heat exchanger 7. Therefore, the hot water flowing through the hot water storage circulation path 16 is cooled. As a result, the cooled hot water is supplied to the first heat exchanger 2 so that the exhaust gas can be cooled and the condensed water can be recovered from the exhaust gas, so that the water used for steam reforming is insufficient. The problem is solved more suitably, and the burden on the reverse osmosis membrane 5 is further reduced.

  Hereinafter, specific example 1 in the case where the determination unit 40 determines that the amount of water stored in the water recovery tank 4 is insufficient will be described. First, the determination means 40 may determine whether or not the amount of water stored in the water recovery tank 4 is insufficient based on the water level of the water recovery tank 4 detected by the water level detection means.

  At this time, the fuel cell system 10 according to the present embodiment further includes a water level sensor 41 which is a water level detecting means for detecting the water level of the water recovery tank 4. As the water level sensor 41, a conventionally known sensor such as a float sensor or an electrode sensor can be appropriately selected and used.

  In the fuel cell system 10 according to the present embodiment, when the determination unit 40 determines that the water level of the water recovery tank 4 detected by the water level sensor 41 is equal to or lower than the threshold value (first threshold value), the on-off valve 27 is opened. And by supplying the pump 24, water is supplied to the water supply path 15. As a result, the water that has passed through the reverse osmosis membrane 5 is supplied to the water recovery tank 4 and the hot water is cooled in the second heat exchanger 7, so that the water vapor in the exhaust gas is discharged in the first heat exchanger 2. Condensed water obtained by condensation is recovered in the water recovery tank 4. Therefore, the problem that the water used for steam reforming is insufficient is suppressed, and the continuous operation of the system is possible even at full storage. In addition, as a water level of the water collection tank 4 used as a threshold value (first threshold value), for example, an amount of water that can be supplied to the fuel cell module 1 until water is supplied from the water supply path 15. That is all you need.

  Here, the water that permeates through the reverse osmosis membrane 5 and is supplied to the water recovery tank 4, and the condensed water that is recovered in the water recovery tank 4 is condensed with water vapor in the exhaust gas in the first heat exchanger 2. When the total amount (ml / min) is larger than the amount of water (ml / min) required for steam reforming, the water level in the water recovery tank 4 gradually increases. Therefore, when the determination means 40 determines that the water level of the water recovery tank 4 detected by the water level sensor 41 is equal to or higher than the threshold (second threshold), the on-off valve 27 is closed and the pump 24 is stopped. The supply of water to the water supply path 15 may be stopped. Thereby, the burden of the reverse osmosis membrane 5 can be reduced, and adjustment can be made so that water is not drained from the water recovery tank 4 due to overflow.

  Hereinafter, controlling the supply of water to the water supply path 15 in accordance with the water level of the water recovery tank 4 will be described with reference to FIG. FIG. 2 is a flowchart showing the water supply control process 1 in the fuel cell system according to the embodiment of the present invention.

  As shown in FIG. 2, in step 200, the fuel cell system 10 is activated. At this time, water supplied to the fuel cell module 1 is stored in the water recovery tank 4, and this water is used for steam reforming of the raw material gas.

  When the fuel cell system 10 is started and continuously operated, as described above, the temperature of the hot water stored in the hot water storage tank 6 rises, and the fuel cell system 10 is in a thermally filled state (full storage state). At the time of full storage, the condensed water cannot be recovered from the exhaust gas, so that the water level in the water recovery tank 4 gradually decreases.

  In step 201, it is determined whether or not the water level in the water recovery tank 4 detected by the water level sensor 41 is equal to or less than a first threshold value. If the water level in the water recovery tank 4 detected by the water level sensor 41 is equal to or less than the first threshold value, the open / close valve 27 is opened and the pump 24 is driven in step 202 to supply water to the water supply path 15. . At this time, the water that permeates the reverse osmosis membrane 5 and is supplied to the water recovery tank 4, the water vapor in the exhaust gas is condensed in the first heat exchanger 2, and the condensed water that is recovered in the water recovery tank 4 When the total amount (ml / min) is larger than the amount of water (ml / min) required for steam reforming, the water level in the water recovery tank 4 gradually increases.

  Next, in step 203, it is determined whether or not the water level in the water recovery tank 4 detected by the water level sensor 41 is equal to or greater than a second threshold value. If the water level of the water recovery tank 4 detected by the water level sensor 41 is not greater than or equal to the second threshold value, the water supply to the water supply path 15 is continued, and the water level of the water recovery tank 4 detected by the water level sensor 41 Is equal to or greater than the second threshold value, in step 204, the on-off valve 27 is closed and the pump 24 is stopped to stop water supply to the water supply path 15.

  Then, when the supply of water to the water supply path 15 is stopped, the fully-stored state is maintained, or once the fully-stored state has been canceled but becomes fully-stored again, the water detected by the water level sensor 41 is detected. The water level in the recovery tank 4 falls again.

  Therefore, if there is no system operation stop request in step 205, steps 201 to 204 may be repeated. If there is a system stop request in step 205, the operation of the fuel cell system 10 is stopped. The operation of the system may be stopped at any timing between steps 200 to 205.

  Hereinafter, specific example 2 in the case where the determination unit 40 determines that the amount of water stored in the water recovery tank 4 is insufficient will be described. The determination means 40 may determine whether or not the amount of water stored in the water recovery tank 4 is insufficient based on the startup time of the fuel cell system.

  When the time elapses after the fuel cell system 10 is started, the hot water stored in the hot water storage tank 6 is fully stored, and it becomes impossible to collect condensed water from the exhaust gas. The water stored in the collection tank 4 will be insufficient. Therefore, when the determination means 40 determines that a predetermined time has elapsed since the system activation, the opening / closing valve 27 is opened and the pump 24 is driven to supply water to the water supply path 15. As a result, the water that has passed through the reverse osmosis membrane 5 is supplied to the water recovery tank 4 and the hot water is cooled in the second heat exchanger 7, so that the water vapor in the exhaust gas is discharged in the first heat exchanger 2. Condensed water obtained by condensation is recovered in the water recovery tank 4. Therefore, the problem that the water used for steam reforming is insufficient is suppressed, and the continuous operation of the system is possible even at full storage.

  Further, as described above, the water that has passed through the reverse osmosis membrane 5 and supplied to the water recovery tank 4 and the water vapor in the exhaust gas are condensed in the first heat exchanger 2 and recovered in the water recovery tank 4. When the total amount of condensed water (ml / min) is larger than the amount of water required for steam reforming (ml / min), the water level in the water recovery tank 4 gradually increases at a constant rate. Therefore, when the determination means 40 determines that a predetermined time has passed since the water was supplied to the water supply path 15, the water to the water supply path 15 is closed by closing the on-off valve 27 and stopping the pump 24. May be stopped.

  Furthermore, when the supply of water to the water supply path 15 is stopped, the water level of the water recovery tank 4 is lowered again at a constant rate if the full storage state is maintained. Therefore, when the determination unit 40 determines that a predetermined time has elapsed since the supply of water to the water supply path 15 is stopped, water may be supplied to the water supply path 15 again.

  In addition, when the determination unit 40 determines that a predetermined time has elapsed since the supply of water to the water supply path 15, the procedure for stopping the supply of water to the water supply path 15, and the determination unit 40 includes the water supply path When it is determined that a predetermined time has elapsed since the supply of water to 15 is stopped, a procedure for supplying water to the water supply path 15 may be repeated in order.

  Hereinafter, controlling the supply of water to the water supply path 15 in accordance with the start time, the water supply time, and the water supply stop time of the fuel cell system will be described with reference to FIG. FIG. 3 is a flowchart showing the water supply control process 2 in the fuel cell system according to the embodiment of the present invention.

  As shown in FIG. 3, in step 300, the fuel cell system 10 is activated. At this time, water supplied to the fuel cell module 1 is stored in the water recovery tank 4, and this water is used for steam reforming of the raw material gas.

  When the fuel cell system 10 is started and continuously operated to reach a fully stored state, the condensed water cannot be recovered from the exhaust gas, so that the water level in the water recovery tank 4 gradually decreases.

  In step 301, it is determined whether a predetermined time has elapsed since the start of the fuel cell system 10. If a predetermined time has elapsed from the start of the system, in step 302, the on-off valve 27 is opened and the pump 24 is driven to supply water to the water supply path 15. At this time, the water that permeates the reverse osmosis membrane 5 and is supplied to the water recovery tank 4, the water vapor in the exhaust gas is condensed in the first heat exchanger 2, and the condensed water that is recovered in the water recovery tank 4 When the total amount (ml / min) is larger than the amount of water (ml / min) required for steam reforming, the water level in the water recovery tank 4 gradually increases.

  Next, in step 303, it is determined whether a predetermined time has passed since the water supply. If the predetermined time has not elapsed since the water supply, the water supply to the water supply path 15 is continued. If the predetermined time has elapsed since the water supply, in step 304, the on-off valve 27 is closed and the pump 24 is stopped. Thus, the supply of water to the water supply path 15 is stopped.

  When the supply of water to the water supply path 15 is stopped, the water level in the water recovery tank 4 is lowered again at a constant rate if the fully stored state is maintained.

  Next, in step 305, it is determined whether a predetermined time has elapsed since the water supply was stopped. If a predetermined time has elapsed since the water supply was stopped, in step 306, the on-off valve 27 is opened and the pump 24 is driven to supply water again to the water supply path 15. At this time, as in step 302, the water level in the water recovery tank 4 gradually increases at a constant rate even at the time of full storage.

  In step 307, it is determined whether a predetermined time has elapsed since the supply of water. If the predetermined time has not elapsed since the water supply, the water supply to the water supply path 15 is continued. If the predetermined time has elapsed since the water supply, in step 308, the on-off valve 27 is closed, and The pump 24 is stopped and the supply of water to the water supply path 15 is stopped.

  If there is no system stop request in step 309, steps 305 to 308 may be repeated. If there is a system operation stop request in step 309, the operation of the fuel cell system 10 is stopped. Note that the system operation may be stopped at any timing between steps 300 to 209.

  Hereinafter, specific example 3 in the case where the determination unit 40 determines that the amount of water stored in the water recovery tank 4 is insufficient will be described. The determination means 40 may determine whether or not the amount of water stored in the water recovery tank 4 is insufficient based on the temperature of the hot water detected by the temperature detection means.

  At this time, the fuel cell system 10 according to the present embodiment has temperature detection means (not shown) at least one of a predetermined position upstream of the first heat exchanger 2 and a predetermined position of the hot water storage tank 6 in the hot water circulation path 16. )). The temperature detection means can be provided at any position as long as it is upstream of the first heat exchanger 2 in the hot water circulation path 16. For example, in the hot water circulation path 16, in the vicinity of the supply port of the hot water storage tank 6, Examples include between the hot water storage tank 6 and the second heat exchanger 7, between the second heat exchanger 7 and the first heat exchanger 2, and the like. Further, the temperature detection means can be provided at an arbitrary location of the hot water storage tank 6, and examples thereof include a vicinity of a supply port connected to the hot water storage circulation path 16, an arbitrary position in the hot water storage circulation path 16, and the like.

  In the fuel cell system 10 according to the present embodiment, when the determination unit 40 determines that the temperature of the hot water detected by the temperature detection unit is equal to or higher than the threshold value, the open / close valve 27 is opened and the pump 24 is driven. Then, water is supplied to the water supply path 15. As a result, even if the cooling efficiency of the exhaust gas is reduced and condensed water cannot be recovered from the exhaust gas, the water that has passed through the reverse osmosis membrane 5 is supplied to the water recovery tank 4 and the second heat Since the hot water is cooled in the exchanger 7, the condensed water obtained by condensing the water vapor in the exhaust gas in the first heat exchanger 2 is recovered in the water recovery tank 4. Therefore, the problem that the water used for steam reforming is insufficient is suppressed, and the continuous operation of the system is possible even at full storage.

  Although it does not specifically limit as a threshold value used as the object which determines whether water is supplied to the water supply path | route 15, For example, from the temperature (for example, 90 degreeC) of the hot water at the time of full storage, the temperature of the hot water at the time of full storage Lower temperature (for example, 60 ° C. or more and less than 90 ° C.). That is, water may be supplied to the water supply path 15 when the temperature of the hot water at the predetermined location indicates that the temperature of the hot water at the time of full storage or a temperature lower than the temperature of the hot water at the time of full storage. In particular, when it is shown that the temperature is lower than the temperature of hot water at the time of full storage, a sufficient amount of water is stored in the water recovery tank 4 by supplying water to the water supply path 15. This is preferable.

  Further, the temperature detecting means can be provided at an arbitrary location of the hot water storage tank 6. In the hot water storage tank 6, the hot water stored in the hot water storage tank 6 has almost the same temperature in the entire region in the fully stored state, but when it is not in the fully stored state, the hot water stored in the hot water storage tank 6 is along the height direction. The temperature rises. Therefore, it is preferable to provide the temperature detection means at the lower part of the hot water storage circulation path 16 and at the upper part of the supply port connected to the hot water storage circulation path 16. At this time, if the temperature detection means indicates the temperature of the hot water at the time of full storage, it can be seen that the hot water stored in the hot water storage tank 6 is immediately before full storage. Therefore, it is preferable because water can be supplied to the water supply path 15 immediately before the water is fully stored, and a sufficient amount of water can be stored in the water recovery tank 4.

  A plurality of temperature detection means may be provided. For example, the temperature detection means may be provided both at a predetermined position upstream of the first heat exchanger 2 in the hot water circulation path 16 and at a predetermined position of the hot water storage tank 6. You may provide a temperature detection means in the position where the height of the tank 6 differs, respectively.

  The configuration of specific example 3 in which the temperature detecting means is provided may be combined with the configuration of specific examples 1 and 2 described above.

  The fuel cell system 10 according to the present embodiment supplies the hot water tank 6 to the dechlorination section (not shown) for removing chlorine in the water flowing through the water supply path 15 upstream of the reverse osmosis membrane 5 and the first water supply path 17. It is preferable to further include at least one of a dechlorination section (not shown) for removing chlorine in the water to be discharged.

  By disposing the dechlorination unit as described above, chlorine in the water flowing through the water supply path 15 or chlorine in the water supplied to the hot water storage tank 6 is removed, so the reverse osmosis membrane 5 that is not chlorine resistant is also suitable. It can be used, and the options of the reverse osmosis membrane 5 can be expanded.

  Although the embodiments of the present invention have been described with reference to the embodiments, these embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. Further, it goes without saying that the scope of rights of the present invention is not limited to these embodiments and can be implemented in various modes without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10,100 ... Fuel cell system, 1, 101 ... Fuel cell module, 2 ... 1st heat exchanger, 3, 103, 108 ... Water treatment apparatus, 4, 104 ... Water recovery tank, 5 ... Reverse osmosis membrane, 6, 106 ... Hot water storage tank, 7 ... Second heat exchanger, 11, 111 ... Raw material gas supply path, 12, 112 ... Oxygen supply path, 13, 113 ... Exhaust path, 14, 114 ... Reformed water supply path, 15, 115 ... water supply path, 16, 116 ... hot water storage circulation path, 17, 117 ... first water supply path, 18, 118 ... second water supply path, 19 ... drainage path, 21, 22, 121, 122, 124 ... blower, 23, 24 25, 123, 125 ... Pump, 26, 126 ... Mixing valve, 27, 127 ... Open / close valve, 31, 131 ... Hot water path, 40 ... Determination means, 41 ... Water level sensor, 102 ... Heat exchanger, 109 ... Radiator, 11 ... air supply route

Claims (6)

A fuel cell module comprising a fuel cell;
A hot water storage tank for storing hot water,
A hot water circulation path for circulating hot water in the hot water tank;
A first heat exchanger that performs heat exchange between the exhaust gas discharged from the fuel cell module and hot water flowing through the hot water storage circulation path, and cools the exhaust gas;
A water recovery tank for recovering and storing water obtained by condensing water vapor in the exhaust gas cooled by the first heat exchanger;
A water supply path for supplying water stored in the water recovery tank to the fuel cell module;
A reverse osmosis membrane is provided, and a water supply path for supplying water that has passed through the reverse osmosis membrane to the water recovery tank,
Provided upstream of the first heat exchanger, and performs heat exchange between hot water flowing through the hot water storage circulation path and drainage discharged from the water supply path without passing through the reverse osmosis membrane, A second heat exchanger for cooling the hot water flowing through the hot water storage circulation path;
Determination means for determining whether or not the amount of water stored in the water recovery tank is insufficient;
With
When the determination means determines that the amount of water stored in the water recovery tank is insufficient, water is supplied to the water supply path, and the water that has passed through the reverse osmosis membrane is supplied to the water recovery tank. Fuel cell system to supply. A water level detection means for detecting the water level of the water recovery tank;
The determination means determines whether or not the amount of water stored in the water recovery tank is insufficient based on the water level of the water recovery tank detected by the water level detection means, and is detected by the water level detection means. The fuel cell system according to claim 1, wherein water is supplied to the water supply path when the water level of the water recovery tank thus obtained is equal to or less than a threshold value. A temperature detection means is further provided at at least one of a predetermined position upstream of the first heat exchanger in the hot water circulation path and a predetermined position of the hot water storage tank;
The determination means determines whether or not the amount of water stored in the water recovery tank is insufficient based on the temperature of the hot water detected by the temperature detection means,
3. The fuel cell system according to claim 1, wherein water is supplied to the water supply path when the temperature of the hot water detected by the temperature detection means is equal to or higher than a threshold value.   The fuel cell according to any one of claims 1 to 3, further comprising a water treatment device that is disposed downstream of the water recovery tank and between the water recovery tank and the fuel cell module. system.   The fuel cell system according to any one of claims 1 to 4, further comprising a dechlorination unit that removes chlorine in water flowing through the water supply path upstream of the reverse osmosis membrane.   The fuel cell system according to any one of claims 1 to 5, further comprising a dechlorination unit that removes chlorine in water supplied to the hot water tank upstream of the hot water tank.