JP2006299322A - Water electrolytic device, power plant and power generating system provided with hot water storage tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power generating system in which the energy efficiency of a water electrolytic device is high in the start-up. <P>SOLUTION: The power generating system is provided with a power plant using hydrogen produced by the water electrolytic device and a hot water storage tank storing hot water heated by heat recovered from the power plant, wherein a first heat exchange means for supplying the heat of the hot water in the hot water storage tank to a replenishing water for the water electrolytic device is included in the power generating system. The power plant can keep high energy efficiency not only in the start-up but in the steady operation by effectively using heat energy generated inside the system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a water electrolysis device, a fuel cell using hydrogen generated from the water electrolysis device, a power generation device such as a gas engine, and a hot water storage tank for storing hot water produced by heat recovered from the power generation device And a power generation system.

  In recent years, the difference in power demand between day and night has increased, and there has been a demand for leveling the power load. As one of the means for leveling the electric power load, there is a system in which hydrogen is produced and stored by water electrolysis using nighttime electric power, and electric power is generated and hot water is produced by a power generation device using the stored hydrogen at the peak of electric power demand.

  For example, Patent Document 1 discloses an energy storage system including a water electrolysis device that performs water electrolysis with nighttime electric power at night to generate hydrogen and oxygen, a fuel cell, a hydrogen storage device, and an oxygen storage device. It is disclosed. The invention according to Patent Document 1 is an energy storage device including a water electrolysis device, a fuel cell, a hydrogen storage means, and a refrigerant supply means, and exchanges a part of the heat generated in the water electrolysis device. An apparatus for collecting by a vessel is disclosed. This apparatus can further be provided with a heat exchanger for recovering a part of the heat generated in the fuel cell, and supplied to the hydrogen storage means.

  Further, by using a reversible fuel cell that generates electricity as a fuel cell during the daytime and operates as a hydrogen generator at night, a fuel cell system that has a low power generation cost and that has a power load leveling function is disclosed in Patent Literature 2 is disclosed.

  In order to make a water electrolysis / fuel cell system economically feasible, it is essential to improve the efficiency of water electrolysis and fuel cells. Water electrolysis is performed by applying a predetermined current under a predetermined voltage, and it is preferable to increase energy efficiency (voltage efficiency × current efficiency) in order to reduce power consumption during water electrolysis. Here, the current efficiency is independent of the temperature and is in the range of about 90 to 98%. On the other hand, the voltage efficiency is indicated by the theoretical operating voltage / actual electrolysis voltage, and is temperature-dependent, comparing the electrolysis temperature. Otherwise, the voltage efficiency will decrease.

  However, if a heater for heating electrolyzed water is used in order to increase the efficiency of water electrolysis, energy dedicated to heating is required separately, which is not preferable from the viewpoint of energy saving.

  In particular, when the temperature is low in winter, etc., even if the water electrolysis device and the water supply piping are insulated to minimize heat dissipation, it takes a long time to increase the temperature after starting the water electrolysis device, or the predetermined temperature cannot be reached. In addition, there may be a problem that the electrolytic efficiency is lowered.

Patent Document 3 discloses a water electrolysis apparatus in which a heat exchanger is provided in the hydrogen side discharge line of a water electrolysis apparatus to exchange heat with make-up water to an oxygen separation tank as an invention for solving the problem of heating of the makeup water. Has been. By installing this heat exchanger, the water supplied to the water electrolysis device can be heated by the heat energy generated from the water electrolysis device without using energy dedicated to heating.
JP 2002-57222 A JP 2002-142386 A JP 2001-152378 A

  However, in the energy storage device disclosed in Patent Document 1, the heat generated in the water electrolysis device is used for cooling the refrigerant for cooling the hydrogen storage device, and a device for keeping the temperature of the electrolysis water at a high temperature has been made. Absent.

  Further, in the power supply system disclosed in Patent Document 2, the heat generated in the reversible fuel cell during power generation is recovered by circulating the heat recovery water and used as hot water in the home. However, no attempt has been made to keep the electrolyzed water temperature of the reversible fuel cell at a high temperature during water electrolysis.

  Further, in the water electrolysis apparatus disclosed in Patent Document 3, high-temperature pure water (about 85 to 120 ° C.) and wet hydrogen gas (about 85 to 120 ° C.) in the oxygen separation tank and the hydrogen separation tank are kept during operation. However, immediately after the water electrolyzer is activated, the temperature of the electrolyzed water is low, so that the energy efficiency is low.

  An object of the present invention is to provide a power generation system including a water electrolysis device and a power generation device, which overcomes the disadvantage of the prior art that energy efficiency immediately after startup is low.

  As a result of intensive studies to solve the above problems, the present inventor has found that a water electrolysis device, a power generation device such as a fuel cell using hydrogen generated from the water electrolysis device, a gas engine, and the power generated by the power generation device or Combined with a hot water storage tank that stores hot water heated by the thermal energy recovered from the power generator, and using the thermal energy of the hot water in the hot water tank, the electrolyzed water is maintained at a high temperature even when the water electrolysis device is started. The inventors have invented a power generation system with high energy efficiency.

  Specifically, the present invention includes a water electrolysis device, a power generation device using hydrogen generated from the water electrolysis device, and a hot water storage tank for storing hot water heated using heat recovered from the power generation device. It is an electric power generation system, Comprising: It is related with an electric power generation system provided with the 1st heat exchange means for performing heat exchange between the warm water in the said hot water storage tank, and the said water electrolysis apparatus (Claim 1). With such a configuration, when the water electrolysis apparatus is started, it becomes possible to make the electrolyzed water of the water electrolysis apparatus high temperature by using the heat of hot water in the hot water tank, and the energy efficiency of the water electrolysis apparatus Can be kept high immediately after startup.

  The present invention also provides a power generation system comprising a water electrolysis device, a power generation device using hydrogen generated from the water electrolysis device, and a hot water storage tank for storing hot water heated using heat recovered from the power generation device. The hot water in the hot water storage tank is used as raw water for producing makeup water (electrolyzed water) for the water electrolysis device (claim 2). Even when the hot water in the hot water tank is directly mixed with tap water or used directly as raw water for producing make-up water, the electrolyzed water can be heated to a high temperature when the water electrolysis device is started. Therefore, the energy efficiency of the water electrolysis device can be maintained high before reaching the steady operation.

  It is preferable to provide a second heat exchange means for supplying heat of the released hydrogen to the makeup water in the hydrogen discharge line of the water electrolysis device. By adopting such a configuration, the heat energy of hydrogen gas released from the water electrolysis device to the outside is recovered as a heat source for heating makeup water (electrolysis water), so that the water electrolysis device can be operated in a steady state. The hot water in the hot water tank is not consumed.

  It is also preferable to provide a third heat exchange means for supplying heat of the released oxygen to the makeup water in the oxygen release line of the water electrolysis device. Even with such a configuration, by recovering the thermal energy of the oxygen gas released from the water electrolysis device to the outside as a heat source for heating the makeup water (electrolysis water), the water electrolysis device can be operated in a steady state. Does not consume hot water in the hot water tank.

  It is preferable that the apparatus further includes fourth heat exchange means for supplying heat of the electrolyzed water discharged from the hydrogen separation tank of the water electrolysis apparatus to the makeup water. By adopting such a configuration, by recovering the thermal energy of the high-temperature pure water discharged from the water electrolysis device as a heat source for heating the makeup water (electrolysis water), during the steady operation of the water electrolysis device, It is not necessary to consume hot water in the hot water tank.

  The water electrolysis device is preferably a fuel cell that generates power using hydrogen gas and oxygen gas generated from the water electrolysis device.

  In the power generation system of the present invention, the energy efficiency of the water electrolysis apparatus is high immediately after startup by effectively using the thermal energy of the hot water in the hot water tank. Also, by installing heat exchange means, the thermal energy of the high temperature gas or high temperature electrolyzed water released from the gas separation tank of the water electrolysis device should be effectively used for heating the electrolyzed water supplied to the oxygen separation tank. Can do. As a result, the makeup water heated using the hot water in the hot water tank can be further heated to a temperature preferable for water electrolysis.

  In addition, when the water electrolysis device has been operating for a long time after reaching a steady state, it is necessary to continuously supply makeup water to the water electrolysis device, but heat exchange is performed on low-temperature makeup water produced from tap water. Since it can be heated inside the water electrolysis device by means, rapid temperature change of the electrolyzed water is unlikely to occur without using hot water in the hot water tank. In this case, it is not necessary to use the hot water in the hot water tank for heating the electrolyzed water except at the time of start-up, so the hot water in the hot water tank can be freely used for general purposes.

  Furthermore, since the heat recovered by the heat exchange means can be used to heat the hot water in the hot water storage tank, the temperature of the hot water produced using only the exhaust heat from the power generator (about 60 ° C) Further, it can be heated to a higher temperature (about 80 ° C.).

  Embodiments of the present invention will be described below with reference to the drawings as appropriate. The present invention is not limited to these.

  FIG. 1 is a schematic configuration diagram of a power generation system according to Example 1 which is an embodiment of the present invention. The concept of the power generation system of Example 1 will be described with reference to FIG.

This power generation system includes a hot water tank 1, a water electrolysis device 2, a fuel cell 6, and a heat recovery path 11. The fuel cell 6 uses hydrogen gas (H ₂ ) and oxygen gas (O ₂ ) obtained by electrolyzing electrolyzed water (pure water) in the electrolysis cell 4 of the water electrolysis apparatus 2, and the fuel cell 6 generates power. I do. At this time, heat generated during operation of the fuel cell 6 is recovered using the cooling water 10. The cooling water 10 that has become hot water is stored in the hot water storage tank 1 via the heat recovery path 11.

  Further, in this power generation system, when the water electrolysis device 2 is activated, the hot water in the hot water tank 1 and the make-up water 8 to the water electrolysis device 2 are heat-exchanged using the first heat exchanger 7 to make the make-up water 8 Can be heated.

  FIG. 2 is a schematic configuration diagram of a power generation system according to Example 2, which is an embodiment of the present invention. The concept of the power generation system of Example 2 will be described with reference to FIG.

  The basic configuration of the power generation system of the second embodiment is also the same as that of the first embodiment, but the first heat exchanger 7 is not provided. In this power generation system, the hot water 9 in the hot water tank 1 is mixed with the tap water 12 or supplied directly to the pure water device 13 without mixing. The raw water supplied to the pure water device 13 is heated by mixing the hot water 9 and the tap water 12 or supplying the hot water 9 directly to the pure water device 13, and the pure water device 13 produces pure water having a high temperature. It becomes possible to do. By supplying this high-temperature pure water as make-up water 8 to the oxygen separation tank 3, the temperature of the electrolyzed water is high even immediately after the water electrolysis apparatus 2 is started, so that energy efficiency is high.

  The pure water device 13 is a device that manufactures pure water by using a reverse osmosis membrane (RO membrane), an ion exchange resin, or a combination thereof.

  As the water electrolysis apparatus 2 in Example 1 or 2, an apparatus having a configuration as shown in FIG. 3 can also be used. Next, the function of each component of the water electrolysis apparatus shown in FIG. 3 will be specifically described.

  In FIG. 3, 21 is a pre-filter, 22 is a booster pump, 23 is a first reverse osmosis membrane, and 24 is a second reverse osmosis membrane. The pure water supply line 25 from the prefilter 21 to the oxygen separation tank 30 passes through the second heat exchanger 28 installed in the hydrogen discharge line 27 of the hydrogen separation tank 26 and further passes through the fourth heat exchanger 29. The oxygen separation tank 30 is reached. The pure water circulation line 31 connected to the bottom of the oxygen separation tank 30 passes through the pump 32, the first heat exchanger 33, the temperature indicating controller 34, the ion exchange resin 35, the final filter 36, and the electrolytic cell 37, and again to the oxygen separation tank. It is configured to return to 30.

  A hydrogen supply line 38 for carrying hydrogen generated from the electrolysis cell 37 reaches the hydrogen separation tank 26.

  A dehumidifier 42 is disposed downstream of the second heat exchanger 28 in the hydrogen discharge line 27 connected to the hydrogen separation tank 26.

  46 and 47 installed in each line indicate a flow control valve and an on / off valve, respectively.

  In the water electrolysis apparatus of FIG. 3 configured as described above, the tap water that has reached the prefilter 21 of the pure water supply line 25 is preliminarily filtered by the prefilter 21, and is opened by the booster pump 22 via the fully open on / off valve 44. After the pressure is increased and purified through the first reverse osmosis membrane 23 and the second reverse osmosis membrane 24 to a predetermined high purity, it is supplied to the oxygen separation tank 30. At that time, in the second heat exchanger 28, heat is indirectly exchanged with the high-temperature (about 60 to 100 ° C.) humidified hydrogen gas discharged from the hydrogen separation tank 26, so that makeup pure water is supplied. The temperature is raised by a certain temperature, and the temperature that was initially 10-25 ° C. is raised by several ° C.

  On the other hand, the wet hydrogen gas discharged from the hydrogen separation tank 26 is cooled by makeup pure water in the second heat exchanger 28 to generate condensed water. The wet hydrogen gas flows from the lower part to the upper part of the second heat exchanger 28, and the hydrogen discharge line 27 is formed so as to have a downward gradient from the second heat exchanger 28 toward the hydrogen separation tank 26. Thus, the produced condensed water flows down to the hydrogen separation tank 26. In this way, since the amount of moisture brought into the dehumidifier 42 is reduced, dehumidification in the dehumidifier 42 is facilitated. The hydrogen gas dehumidified in the dehumidifier 42 is appropriately adjusted in the opening degree of the flow control valve 43 provided in the hydrogen discharge line 27 in accordance with an instruction from a pressure instruction controller 46 that monitors the pressure in the hydrogen separation tank 26. However, high-purity hydrogen gas is supplied to the use point.

  On the other hand, the supplementary pure water that has been heated by a certain temperature in the second heat exchanger 28 is discharged at a high temperature (about 50 to 100 ° C.) through the second pure water discharge line 41 in the fourth heat exchanger 29. As a result of indirectly performing heat exchange with the pure water, the temperature is further raised to about 40 ° C. or higher (for example, 40 to 60 ° C.) and reaches the oxygen separation tank 30.

  The pure water supplied to the oxygen separation tank 30 passes through the pure water circulation line 31 and is supplied to the electrolysis cell 37. In the electrolysis cell 37, pure water is electrolyzed to generate oxygen on the anode side and hydrogen on the cathode side. The pure water that has not been electrolyzed with oxygen is gas-liquid separated in the oxygen separation tank 30, the oxygen gas is released out of the system, and the pure water is recirculated through the pure water circulation line 31.

  At this time, the deionized water flowing through the deionized water circulation line 31 is heated in the first heat exchanger 33 with hot water from the hot water storage tank 1 for storing hot water produced using exhaust heat obtained by the operation of the fuel cell 6. Heat exchanged.

  In the initial operation of the water electrolysis apparatus 2, since the temperatures of the pure water in the pure water circulation line 31 and the second pure water discharge line 41 and the hydrogen gas in the hydrogen discharge line 27 are low, the second heat exchanger 28 and the fourth The temperature of make-up water cannot be sufficiently increased only by heat exchange by the heat exchanger 29. For this reason, there is a risk that the energy efficiency of the water electrolysis apparatus in the initial operation is lowered if it is a conventional power generation system. However, in the power generation system of the present invention including the water electrolysis apparatus shown in FIG. Since the pure water in the pure water circulation line 31 is heated by using it, it is possible to increase the energy efficiency of the water electrolysis apparatus from the initial stage of operation.

  Further, in the water electrolysis apparatus shown in FIG. 3, since the pure water in the pure water circulation line 31 is heated before being supplied to the electrolysis cell 37, the heated pure water is directly cooled without being cooled. 37.

  On the other hand, normally, in a water electrolysis apparatus, it is necessary to keep the temperature of circulating pure water (pure water supplied to an electrolysis cell) at a predetermined temperature or lower (for example, 90 ° C.) for the reason described later. The hot water in the hot water tank obtained by using the exhaust heat from the fuel cell is generally around 60 ° C. Therefore, when the circulating pure water becomes a high temperature exceeding a predetermined temperature, the water electrolysis apparatus shown in FIG. Then, it is possible to cool the circulating pure water flowing through the pure water circulation line 31 using the first heat exchanger 33.

  That is, in the water electrolysis apparatus of the present invention provided with the water electrolysis apparatus shown in FIG. 3, the hot water in the hot water tank 1 is used for heating circulating pure water in the initial operation of the water electrolysis apparatus 2. Since it is used for cooling the circulating pure water during the steady operation of No. 2, it is possible to obtain hot water having a temperature higher than that of normally obtained warm water (about 60 ° C.) obtained by using exhaust heat from the fuel cell.

  Here, when the temperature of the pure water circulating through the pure water circulation line 31 is 90 ° C. or more, the life of the O-ring or gasket of the sealing material, which is a module component of the electrolytic cell 37, is shortened, or the hydrogen embrittlement of the titanium electrode material. Therefore, the opening degree of the flow control valve 43 is appropriately set according to the instruction from the temperature indicator controller 34 so that the pure water temperature detected by the temperature indicator controller 34 is 90 ° C. or less. It is preferable to adjust the temperature of pure water circulating through the pure water circulation line 31 to 90 ° C. or less by supplying hot water from the hot water supply line 47 to the first heat exchanger 33. The final filter 36 in the pure water circulation line 31 is not necessarily required, and may be omitted if it is guaranteed that no foreign matter is mixed in the pure water circulation line 31.

  In FIG. 3, the hot water supply line 47 is connected only to the first heat exchanger 33, but another hot water supply line is connected to the second heat exchanger 28, a third heat exchanger (described later). (Not shown), further connected to the fourth heat exchanger 29, when the hot water or hot electrolyzed water discharged from the gas separation tank of the water electrolysis device is not heated, the hot water in the hot water storage tank is heated. It is also possible to adopt a configuration used for heating.

  The pressure in the oxygen separation tank 30 is detected by the pressure indicating controller 46, and when the pressure exceeds a certain level, the oxygen in the oxygen separation tank 30 is released to the atmosphere via the flow control valve 43, The pressure in the oxygen separation tank 30 can be controlled to be kept below a certain level.

  In the water electrolysis apparatus shown in FIG. 3, the hydrogen gas and the supplementary pure water are configured to exchange heat with the second heat exchanger 28, but the present invention is not limited thereto, and the oxygen gas and the supplemental pure water are exchanged with oxygen. It is good also as a structure which heat-exchanges with the 3rd heat exchanger (not shown) provided in the oxygen exhaust line connected to the separation tank 30. FIG. As described above, by exchanging heat between the oxygen gas and the supplemental pure water, the exhaust heat of the oxygen gas can be used effectively, and at the same time, the amount of pure water released outside the system accompanying the oxygen gas can be reduced. it can.

  The gas pipe of the oxygen discharge line is usually provided with a hydrogen concentration meter (detector) for measuring the hydrogen concentration in the oxygen gas from the viewpoint of quality control and safety of the gas (not shown). As described above, the oxygen gas is dehumidified by the condensation of moisture during heat exchange, so that moisture can be prevented from entering the hydrogen concentration meter.

  In the conventional water electrolysis apparatus, the pure water in the oxygen separation tank is discharged out of the system accompanying the oxygen gas as described above. In a system with an open atmosphere (atmospheric pressure) and a pure water temperature of 80 ° C in the oxygen separation tank during operation, the amount reaches about 44% of the pure water consumption of the water electrolyzer.

  However, in the power generation system of the present invention provided with a water electrolysis apparatus provided with a third heat exchanger in the oxygen discharge line, the amount of pure water released outside the system can be reduced, so the cost for producing pure water Can be reduced.

  In the water electrolysis apparatus shown in FIG. 3, the hot water in the hot water tank and the pure water in the pure water circulation line 31 are heated by a heat exchanger (first heat exchanger 33) provided in the pure water circulation line 31. Although it was set as the structure exchanged, it is not limited to this, For example, you may provide the heat exchanger for heat-exchanging the warm water and pure water of a hot water tank in the oxygen separation tank 30, and this and the 1st heat exchanger 33 May be combined.

  Alternatively, the hot water in the hot water tank may be directly supplied to the water electrolysis apparatus through the prefilter 21 without exchanging heat.

  The water electrolysis apparatus shown in FIG. 3 has been described above.

  In Examples 1 and 2, the fuel cell 6 is selected as an example of a power generation device that uses hydrogen gas. However, instead of the fuel cell 6, a gas engine that uses hydrogen gas is used as the power generation device. You can also

  In the water electrolysis apparatus shown in FIG. 3, the pressure in the oxygen separation tank is maintained, but the present invention is not limited to this, and only the hydrogen side (hydrogen separation tank and hydrogen discharge line) holds the pressure. The oxygen side (oxygen separation tank and oxygen discharge line) may be opened to atmospheric pressure.

  By opening the oxygen side to atmospheric pressure, the capacity of the makeup water pump 22 may be small, and may be unnecessary depending on circumstances. In addition, since pressure control (differential pressure control) is simplified, machinery and piping can be reduced, and the size of the apparatus can be reduced. Conventionally, in order to perform differential pressure control, an oxygen separation tank of a certain size is required, and because of the incidental equipment, piping, etc., the oxygen separation tank (including the pure water circulation line etc.) There was also a lot of water. As a result, the total amount of heat required for heating pure water was large, but by reducing the size of the device as described above, the amount of pure water can be reduced, and the total amount of heat required for heating pure water can also be reduced. Is possible.

  As described above, the power generation system of the present invention is characterized by high energy efficiency even immediately after startup by effectively using the thermal energy of hot water in the hot water tank. Moreover, the electrolysis temperature can be maintained at an appropriate temperature by using the water electrolysis apparatus shown in FIG.

  The power generation system of the present invention is useful as a clean and high energy efficiency power generation system.

1 is a schematic configuration diagram of a power generation system according to Embodiment 1. FIG. FIG. 3 is a schematic configuration diagram of a power generation system according to a second embodiment. It is a whole flowchart of an example of the water electrolysis apparatus which can be used for this invention.

Explanation of symbols

1: Hot water storage tank 2: Water electrolysis device 3: Oxygen separation tank 4: Electrolysis module 5: Pure water circulation path 6: Fuel cell 7: First heat exchanger 8: Makeup water 9: Hot water 10: Cooling water 11: Heat recovery Path 12: Tap water 13: Pure water device 21: Prefilter 22: Booster pump 23: First reverse osmosis membrane 24: Second reverse osmosis membrane 25: Pure water supply line 26: Hydrogen separation tank 27: Hydrogen discharge line 28: Second heat exchanger 29: Fourth heat exchanger 30: Oxygen separation tank 31: Pure water circulation line 32: Pump 33: First heat exchanger 34: Temperature indication controller 35: Ion exchange resin 36: Final filter 37: Electrolysis cell 38: Hydrogen supply line 39: First pure water discharge line 40: Flow rate indicating controller 41: Second pure water discharge line 42: Dehumidifier 43: Flow control valve 44: On / off valve 45: Water level gauge 46: Pressure gauge 47: Hot water storage Supply line

Claims (6)

A power generation system comprising a water electrolysis device, a power generation device using hydrogen generated from the water electrolysis device, and a hot water storage tank for storing hot water heated using heat recovered from the power generation device,
A power generation system comprising first heat exchanging means for exchanging heat between the hot water in the hot water storage tank and the water electrolysis apparatus. A power generation system comprising a water electrolysis device, a power generation device using hydrogen generated from the water electrolysis device, and a hot water storage tank for storing hot water heated using heat recovered from the power generation device,
A power generation system using hot water in the hot water tank as raw water for makeup water of the water electrolysis device.   3. The power generation system according to claim 1, further comprising second heat exchange means for supplying heat of released hydrogen to the makeup water in a hydrogen release line of the water electrolysis apparatus.   The power generation system according to any one of claims 1 to 3, further comprising third heat exchange means for supplying heat of released oxygen to the makeup water in an oxygen release line of the water electrolysis apparatus.   5. The fourth heat exchange means according to claim 1, further comprising fourth heat exchange means for supplying heat of the electrolyzed water discharged from the hydrogen separation tank of the water electrolysis apparatus to the makeup water. Power generation system.   The power generation system according to any one of claims 1 to 5, wherein the power generation device is a fuel cell.

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