JP6498582B2 - Fuel cell system - Google Patents

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 A heat exchanger that performs heat exchange with hot water and cools the exhaust gas, and a water recovery tank that collects and stores water obtained by condensing water vapor in the exhaust gas cooled by the heat exchanger And a water supply path for supplying water stored in the water recovery tank to the fuel cell module and a path for supplying hot water flowing through the hot water circulation path. A reverse osmosis membrane, a water supply path for supplying water that has passed through the reverse osmosis membrane to the water recovery tank, a flow rate adjusting unit that adjusts at least the flow rate of hot water in the water supply path, and the water cycle Determination means for determining whether or not the amount of water stored in the collection tank is insufficient, and the determination means is insufficient in the amount of water stored in the water recovery tank A fuel cell system that, when determined, adjusts the flow rate adjusting unit so that hot water is supplied to the water supply path, and supplies water that has passed through the reverse osmosis membrane to the water recovery tank.

  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 a 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 collected hot water 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. And when the determination means determines that the amount of water stored in the water recovery tank is insufficient, the flow rate adjustment unit is adjusted so that hot water is supplied to the water supply path, and the reverse osmosis membrane is permeated. Supply water to the water recovery tank.

  As described above, even when the condensed water cannot be recovered from the exhaust gas, the water that has permeated the reverse osmosis membrane is supplied to the water recovery tank, so that the water used for steam reforming is insufficient. Is eliminated and the system can be operated continuously.

  Further, in the fuel cell system according to the present embodiment, the fuel cell system can be continuously operated even at the time of full storage without providing a radiator or a heat radiating pipe for cooling the hot water storage circulation path. 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 fuel cell system according to <1>, further including a drainage supply path that supplies drainage discharged from the water supply path without passing through the reverse osmosis membrane to the hot water storage circulation path.

  By supplying hot water to the reverse osmosis membrane, high-purity water that has passed through the reverse osmosis membrane and drainage that has not passed through the reverse osmosis membrane can be obtained. The fuel cell system according to this embodiment supplies wastewater that has not permeated through the reverse osmosis membrane to the hot water storage circulation path through the drainage supply path. Therefore, it can be recovered in a hot water storage tank without discharging the wastewater outside the system, and the wastewater can be effectively used and the installation cost of the system can be greatly reduced.

  <3> A 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. Judging by the detected water level of the water recovery tank, and when the water level of the water recovery tank detected by the water level detection means falls below a threshold value, the flow rate adjusting unit is configured to supply hot water to the water supply path. The fuel cell system according to <1> or <2>, wherein the fuel cell system is adjusted.

  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 less than the threshold value, the flow rate adjustment unit is adjusted so that hot water is supplied to the water supply path. To do. 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.

  <4> At least one of a predetermined position upstream of the heat exchanger in the hot water circulation path and a predetermined position of the hot water storage tank is further provided with temperature detection means, and the determination means is stored in the water recovery tank. It is determined whether the amount of water is insufficient 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 water supply The fuel cell system according to any one of <1> to <3>, wherein the flow rate adjusting unit is adjusted so that hot water is supplied to the 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, the flow rate adjustment unit is adjusted so that the hot water is supplied to the water supply path. I have to. Therefore, even if the detected temperature of the hot water is equal to or higher than the threshold value, the cooling efficiency of the exhaust gas is reduced and the condensed water cannot be suitably recovered from the exhaust gas, so that the hot 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.

  <5> The fuel cell system according to any one of <1> to <4>, wherein the reverse osmosis membrane has a heat resistant temperature of 60 ° C. or higher.

  By using a reverse osmosis membrane having a heat resistant temperature of 60 ° C. or more and excellent heat resistance, the reverse osmosis membrane has excellent durability when hot hot water is supplied to the reverse osmosis membrane for a long time.

  <6> The water treatment apparatus according to any one of <1> to <5>, 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 disposed between the heat exchanger and the water recovery tank, the water that has permeated the reverse osmosis membrane is not treated with water, and is supplied to the fuel cell module. Will be adversely affected on 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.

<7> The fuel cell system according to any one of <1> to <6>, further including a dechlorination unit that removes chlorine in the hot water flowing through the water supply path upstream of the reverse osmosis membrane.
<8> The fuel cell system according to any one of <1> to <7>, further including a dechlorination unit that removes chlorine in water supplied to the hot water tank upstream of the hot water tank.

  By arranging the dechlorination section as described above, chlorine in hot water flowing through the water supply path or chlorine in the water supplied to the hot water storage tank is removed, so that a reverse osmosis membrane that is not chlorine resistant should also be used suitably. Can do.

  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.

  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.

[Fuel cell system]
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. The fuel cell system 10 according to the present embodiment includes a fuel cell module 1, a 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. . 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 hot water stored in the hot water storage tank 6. Is further provided with a hot water circulation path 16 that circulates water and a water supply path 15 that is supplied with hot water flowing through the hot water circulation path 16 and that supplies water that has permeated through the reverse osmosis membrane 5 to the water recovery tank 4.

  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. When it is determined that the amount is insufficient, the on-off valves A and B (flow rate adjusting units) are adjusted so that hot water is supplied to the water supply path 15, and the water that has permeated the reverse osmosis membrane 5 is transferred to the water recovery tank 4. It is a supply system.

  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 heat exchanger 2 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 16 to recover the heat. The hot water is stored in the hot water storage tank 6.

  As described above, 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 the hot water is kept constant. If it is not performed in an amount, it will be in a state of full heat (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, hot water is supplied to the water supply path 15 to perform reverse osmosis. In this system, water that has permeated 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, 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 heat radiating 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.

  Further, as in the fuel cell system 10 according to the present embodiment, a drainage supply path 19 for supplying drainage discharged from the water supply path 15 without passing through the reverse osmosis membrane 5 to the hot water storage circulation path 16 is further provided. Is preferred. Further, the drainage supply path 19 may be provided with an on-off valve C that adjusts the flow rate of drainage flowing through the drainage supply path 19 and prevents the inflow of hot water flowing through the hot water storage circulation path 16. In the present invention, the drainage supply path may not be provided, and the drainage that has not permeated through the reverse osmosis membrane may be discharged out of the system.

  By supplying hot water to the reverse osmosis membrane 5, high-purity water that has permeated the reverse osmosis membrane 5 and waste water that has not permeated the reverse osmosis membrane 5 are obtained. The fuel cell system 10 supplies the wastewater that has not permeated the reverse osmosis membrane 5 to the hot water storage circulation path 16 through the drainage supply path 19. Therefore, it is possible to collect in the hot water storage tank 6 without discharging the wastewater outside the system, and it is possible to effectively use the wastewater and greatly reduce the installation cost of the system.

  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 a source gas supply path 11, an oxygen supply path 12 and a reformed water supply path 14, and source 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 Connected to the fuel cell 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 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 condensed water obtained by condensing water vapor in the heat exchanger 2. Is an apparatus for removing impurities contained in water and impurities contained in water that has permeated 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 B and a reverse osmosis membrane 5 in order from the upstream side. Since the water supply path 15 is connected to the hot water storage circulation path 16 for circulating hot water, hot water flows through the water supply path 15 by opening the on-off valve B while driving the pump 25, and hot water is supplied to the reverse osmosis membrane 5. Supplied. In addition, as the on-off valve B, an electromagnetic valve, a motor 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 25 and supplying hot water to the reverse osmosis membrane 5, high-purity water that has permeated 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.

  Moreover, by supplying hot water to the reverse osmosis membrane 5, high-purity water that has permeated the reverse osmosis membrane 5 and waste water that has not permeated the reverse osmosis membrane 5 (water with many impurities) can be obtained. The drainage is discharged from the water supply path 15 and supplied to the hot water storage circulation path 16 through the drainage supply 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. .

  Furthermore, the reverse osmosis membrane 5 preferably has a heat resistant temperature of 60 ° C. or higher, more preferably 70 ° C. or higher, further preferably 80 ° C. or higher, and particularly preferably 90 ° C. or higher. By using a reverse osmosis membrane having a heat resistant temperature of 60 ° C. or more and excellent heat resistance, the reverse osmosis membrane has excellent durability when hot hot water is supplied to the reverse osmosis membrane for a long time.

  Examples of the reverse osmosis membrane having a heat resistant temperature of 60 ° C. or higher include aromatic polyamide membranes and polysulfone membranes, and commercially available membranes may be used. For example, Duratherm series reverse osmosis membranes such as Duratherm STD, Duratherm PRO, Duratherm Excel, Duratherm Elite, etc. manufactured by GE Water Technologies, Inc., SU-710T, SU-720TS, SUL-G20TS, SUL-G20TS manufactured by Toray Industries, Inc. TS series reverse osmosis membranes such as SUL-G20 FTS may be used.

  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 heat exchanger 2 and the water recovery tank 4, the water that has passed through the reverse osmosis membrane 5 is not treated with water. It will be supplied to the fuel cell module 1, which 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 the exhaust gas discharged from the fuel cell module 1 by the 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 a hot water storage circulation path 16, and the hot water storage circulation path 16 is provided with a pump 25, an on-off valve A and a heat exchanger 2 in order from the upstream side. By opening the on-off valve A and driving the pump 25, the hot water stored in the hot water storage tank 6 flows through the hot water storage circulation path 16. Further, by opening the on-off valve B and driving the pump 25, the hot water stored in the hot water storage tank 6 flows through the water supply path 15, and hot water is supplied to the reverse osmosis membrane 5.

  In the fuel cell system 10 according to the present embodiment, a pump 25 is disposed upstream of the connecting portion between the hot water storage circulation path 16 and the water supply path 15 and the on-off valve A. Therefore, by switching the on-off valves A and B, hot water circulation in the hot water storage circulation path 16 and hot water supply to the water supply path 15 and the reverse osmosis membrane 5 can be performed by one pump, and another pump is provided in the water supply path 15. There is no need to provide.

  Here, if hot water is supplied to the water supply path 15 by opening the on-off valve B and driving the pump 25, the wastewater that has not permeated the reverse osmosis membrane 5 is discharged from the water supply path 15. At this time, by opening the on-off valve C, the wastewater is supplied to the hot water storage circulation path 16 through the drainage supply path 19. Therefore, it is possible to collect in the hot water storage tank 6 without discharging the wastewater outside the system, and it is possible to effectively use the wastewater and greatly reduce the installation cost of the system.

  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, hot 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.

  Furthermore, as described above, by supplying water to the water supply path 15, the drainage is supplied to the hot water storage circulation path 16 through the drainage supply path 19. Therefore, it is possible to collect in the hot water storage tank 6 without discharging the wastewater outside the system, and it is possible to effectively use the wastewater and greatly reduce the installation cost of the system.

  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, after the system is started, the on-off valve A is opened and the on-off valves B and C are closed to drive the pump 25 to circulate hot water in the hot water storage circulation path 16. ing. When time elapses after the system is activated and the determination means 40 determines that the water level in the water recovery tank 4 detected by the water level sensor 41 is equal to or lower than the threshold (first threshold), the on-off valve A is closed and opened / closed. Hot water is supplied to the water supply path 15 by opening the valves B and C. Thereby, water that has passed through the reverse osmosis membrane 5 is supplied to the water recovery tank 4, and waste water that has not passed through the reverse osmosis membrane 5 is supplied to the hot water storage circulation path 16. 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, when the amount of water permeated through the reverse osmosis membrane 5 and supplied to the water recovery tank 4 (ml / min) is larger than the amount of water required for steam reforming (ml / min), water recovery The water level in the tank 4 gradually increases. Therefore, when the determination means 40 determines that the water level in 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 A is opened and the on-off valves B and C are closed. Accordingly, the supply of hot water to the water supply path 15 may be stopped. Thereby, it can adjust so that water may not drain drain by overflow from the water collection tank 4, and since hot hot water is no longer supplied to the reverse osmosis membrane 5, the burden of the reverse osmosis membrane 5 is reduced.

  Hereinafter, controlling the supply of hot 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 of the water recovery tank 4 detected by the water level sensor 41 is equal to or less than the first threshold value, the on-off valve A is closed and the on-off valves B and C are opened in step 202 to enter the water supply path 15. Supply hot water. At this time, if the amount of water permeated through the reverse osmosis membrane 5 and supplied to the water recovery tank 4 (ml / min) is larger than the amount of water required for steam reforming (ml / min), water recovery The water level in the 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 supply of hot water 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 greater than or equal to the second threshold value, the supply of hot water to the water supply path 15 is stopped by opening the on-off valve A and closing the on-off valves B and C at step 204.

  When the supply of hot water to the water supply path 15 is stopped, the fully stored state is maintained, or the water level detected by the water level sensor 41 when the fully stored state is once cleared but becomes full again. 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 unit 40 determines that a predetermined time has elapsed since the system start-up, hot water is supplied to the water supply path 15 by closing the on-off valve A and opening the on-off valves B and C. Thereby, water that has passed through the reverse osmosis membrane 5 is supplied to the water recovery tank 4, and waste water that has not passed through the reverse osmosis membrane 5 is supplied to the hot water storage circulation path 16. 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 amount of water (ml / min) that permeates the reverse osmosis membrane 5 and is supplied to the water recovery tank 4 is larger than the amount of water required for steam reforming (ml / min). In this case, 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 elapsed since the hot water was supplied to the water supply path 15, the open / close valve A is opened and the open / close valves B and C are closed, thereby entering the water supply path 15. The hot water supply may be stopped.

  Further, when the supply of hot 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 hot water to the water supply path 15 is stopped, hot water may be supplied to the water supply path 15 again.

  Further, when the determination unit 40 determines that a predetermined time has elapsed since the hot water was supplied to the water supply path 15, the procedure for stopping the supply of hot 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 hot water to 15 is stopped, the procedure of supplying hot water to the water supply path 15 may be repeated in order.

  Hereinafter, control of hot water supply to the water supply path 15 according to the start-up 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 since the system was started, in step 302, hot water is supplied to the water supply path 15 by closing the on-off valve A and opening the on-off valves B, C. At this time, if the amount of water permeated through the reverse osmosis membrane 5 and supplied to the water recovery tank 4 (ml / min) is larger than the amount of water required for steam reforming (ml / min), water recovery The water level in the 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 hot water supply to the water supply path 15 is continued. If the predetermined time has elapsed since the water supply, the on-off valve A is opened and the on-off valve B, By closing C, the supply of hot water to the water supply path 15 is stopped.

  When the supply of hot 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.

  Next, in step 305, it is determined whether a predetermined time has passed since the hot water supply stop. If a predetermined time has elapsed since the stop of hot water supply, hot water is supplied to the water supply path 15 by closing the on-off valve A and opening the on-off valves B and C at step 306. 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 hot water was supplied. If the predetermined time has not elapsed since the hot water supply, the hot water supply to the water supply path 15 is continued. If the predetermined time has elapsed since the hot water supply, the on-off valve A is opened in step 308, and By closing the on-off valves B and C, the supply of hot 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 at least one of a predetermined position upstream of the heat exchanger 2 and a predetermined position of the hot water storage tank 6 in the hot water storage circulation path 16. Is further provided. The temperature detection means can be provided at any location as long as it is upstream of the heat exchanger 2 in the hot water circulation path 16. For example, in the hot water circulation path 16, the vicinity of the supply port of the hot water storage tank 6 can be cited. It is done. 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 on-off valve A is closed and the on-off valves B and C are opened. Thus, hot water is supplied to the water supply path 15. Thereby, even if it is a case where the cooling efficiency of waste gas falls and condensed water cannot be recovered suitably from waste gas, the water which permeate | transmitted the reverse osmosis membrane 5 is supplied to the water collection 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 hot 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, hot water may be supplied to the water supply path 15 when the temperature of the hot water at a predetermined location indicates a temperature of hot water when fully stored or a temperature lower than the temperature of hot water when fully stored. 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 hot 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 heat exchanger 2 in the hot water circulation path 16 and at a predetermined position of the hot water storage tank 6. The temperature detection means may be provided at positions having different heights.

  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 this embodiment includes a dechlorination unit (not shown) that removes chlorine in hot water flowing through the water supply path 15 upstream of the reverse osmosis membrane 5 and the first water supply path 17 in the hot water storage tank 6. It is preferable to further include at least one of a dechlorination section (not shown) for removing chlorine in the supplied water.

  By disposing the dechlorination unit as described above, chlorine in hot 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. The choice of the reverse osmosis membrane 5 can be expanded.

  In this embodiment, the on-off valve B is closed when the on-off valve A is open, or the on-off valve A is closed when the on-off valve B is open. However, the present invention is not limited thereto. . For example, both the on-off valve A and the on-off valve B may be opened, and a portion of hot water flowing through the hot water storage circulation path 16 may be supplied to the water supply path 15 while flowing hot water through a location where the on-off valve A is provided. . Thereby, even if the drainage supply path 19 is not provided, the hot water can be circulated in the hot water storage circulation path 16.

  Further, without providing the on-off valves A and B, a flow rate adjusting unit such as a three-way valve is provided at the connecting portion between the hot water storage circulation path 16 and the water supply path 15, and hot water supplied to the water supply path 15 depending on the degree of opening and closing. It is good also as a structure which adjusts the quantity of. Thereby, the quantity of the hot water supplied to the reverse osmosis membrane 5 can be adjusted according to the quantity of the water which permeate | transmits the reverse osmosis membrane 5 and should be supplied to the water recovery tank 4, and the burden of the reverse osmosis membrane 5 is carried out. It is reduced.

  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 ... Fuel cell system, 1 ... Fuel cell module, 2 ... Heat exchanger, 3 ... Water treatment apparatus, 4 ... Water recovery tank, 5 ... Reverse osmosis membrane, 6 ... Hot water storage tank, 11 ... Raw material gas supply path, 12 ... Oxygen supply path, 13 ... exhaust path, 14 ... reformed water supply path, 15 ... water supply path, 16 ... hot water storage circulation path, 17 ... first water supply path, 18 ... second water supply path, 19 ... drainage supply path, 21, 22 ... Blower, 23, 25 ... Pump, 26 ... Mixing valve, 31 ... Hot water path, 40 ... Determination means, 41 ... Water level sensor

Claims (7)

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 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 heat exchanger;
A water supply path for supplying water stored in the water recovery tank to the fuel cell module;
The hot water circulation path is connected to the hot water circulation path, and is supplied with hot water flowing through the hot water circulation path, and is provided with a reverse osmosis membrane, and the water that has permeated the reverse osmosis membrane is supplied to the water recovery tank. A water supply route to supply,
A flow rate adjusting unit for adjusting the flow rate of hot water in at least the water supply path;
Determination means for determining whether or not the amount of water stored in the water recovery tank is insufficient;
Temperature detection means provided at at least one of a predetermined position upstream of the heat exchanger in the hot water circulation path and a predetermined position of the hot water storage tank;
With
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, and the hot water detected by the temperature detection means. A fuel cell system that adjusts the flow rate adjusting unit so that hot water is supplied to the water supply path and supplies water that has permeated the reverse osmosis membrane to the water recovery tank when the temperature of the water reaches a threshold value or more .   The fuel cell system according to claim 1, further comprising a drainage supply path that supplies drainage discharged from the water supply path without passing through the reverse osmosis membrane to the hot water storage circulation path. 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. 3. The fuel cell system according to claim 1, wherein when the water level of the water recovery tank is equal to or lower than a threshold value, the flow rate adjusting unit is adjusted so that hot water is supplied to the water supply path. The fuel cell system according to any one of claims 1 to 3 , wherein the reverse osmosis membrane has a heat resistant temperature of 60 ° C or higher. The fuel cell according to any one of claims 1 to 4 , 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 5 , further comprising a dechlorination unit that removes chlorine in the hot 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 6 , further comprising a dechlorination unit that removes chlorine in water supplied to the hot water tank upstream of the hot water tank.