Storage device and method for producing hydrogen

Abstract

To provide a storage device and a method for producing hydrogen, capable of reducing breakdown of cells containing a solid oxide electrolyte.SOLUTION: A storage device comprises: a stack with a plurality of cells containing a solid oxide electrolyte that separates a fuel electrode and an air electrode; a storage tank for storing hydrogen gas produced by the stack; a pressure booster connected to a gas pipe that connects the stack and the storage tank, and pressurizes the hydrogen gas and sends it to the storage tank; and a first pressure gauge that detects the pressure of hydrogen gas between the stack and the pressure booster. A method for producing hydrogen uses the first pressure gauge to detect the pressure of hydrogen gas between the stack and the pressure booster, which pressurizes hydrogen gas produced by the stack and sends it to the storage tank, and controls an operating state of the pressure booster based on the detection result of the first pressure gauge.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen gas storage device and a method for producing hydrogen. [Background technology]

[0002] In a storage device that electrolyzes water using a stack of multiple cells containing an ion-conductive electrolyte and stores the generated hydrogen gas in a storage tank, the cells may be damaged by the pressure of the hydrogen gas filled in the storage tank. To reduce cell damage, the prior art disclosed in Patent Document 1 places a stack containing a solid polymer electrolyte inside the hydrogen storage tank and stores water in the hydrogen storage tank. The device further includes an oxygen storage tank that stores the oxygen gas and water generated by the stack, a pipe connecting the hydrogen storage tank and the oxygen storage tank, and a valve disposed in the pipe. The valve opens and closes so that the difference in pressure between the hydrogen storage tank and the oxygen storage tank is within a range that will not damage the cells, and the pipe is used to move water back and forth between the hydrogen storage tank and the oxygen storage tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-342773 Summary of the Invention [Problem to be solved by the invention]

[0004] The operating temperature of prior art stacks containing solid polymer electrolytes is around 60 to 80°C, making it possible to place the stack inside a hydrogen storage tank containing water. However, when using stacks containing solid oxide electrolytes, the operating temperature is higher than that of solid polymer electrolytes, and heating the stack to the operating temperature would vaporize the water contained in the hydrogen storage tank, making the prior art unusable. Furthermore, cells containing solid oxide electrolytes have lower toughness than cells containing solid polymer electrolytes, making them more susceptible to damage due to the pressure difference between the anode and cathode.

[0005] The present invention has been made to solve this problem, and has as its object to provide a storage device and a method for producing hydrogen that can reduce the damage to cells containing solid oxide electrolytes. [Means for solving the problem]

[0006] A first aspect for achieving this object is a hydrogen gas storage device comprising: a stack having a plurality of cells each including a solid oxide electrolyte that separates an anode from an cathode; a storage tank for storing hydrogen gas generated by the stack; a pressure booster connected to a gas pipe connecting the stack and the storage tank for pressurizing the hydrogen gas and sending it to the storage tank; and a first pressure gauge for detecting the pressure of the hydrogen gas between the stack and the pressure booster.

[0007] In a second aspect, the first aspect further includes a buffer tank connected to a gas pipe between the stack and the pressure booster, and a first pressure gauge detects the pressure of hydrogen gas in the buffer tank.

[0008] The third aspect is a hydrogen gas storage device that includes a stack having a plurality of cells each including a solid oxide electrolyte that separates an anode and an cathode, a pressure booster connected to a gas pipe leading to the stack and that boosts the hydrogen gas generated by the stack, and a first pressure gauge that detects the pressure of the hydrogen gas between the stack and the pressure booster.

[0009] A fourth aspect is the device according to any one of the first to third aspects, further comprising a control device that controls the operating state of the pressure booster based on the detection result of the first pressure gauge.

[0010] In a fifth aspect, in the first or second aspect, a second pressure gauge is provided to detect the pressure of the hydrogen gas in the storage tank.

[0011] A sixth aspect is the fifth aspect, further comprising a control device that controls the operating state of the pressure booster based on the detection result of the second pressure gauge.

[0012] A seventh aspect is any of the first to sixth aspects, further comprising a heat exchanger for cooling the hydrogen gas connected to the gas pipe between the stack and the pressure booster, and a thermometer for detecting the temperature of the hydrogen gas arranged in the gas pipe downstream of the heat exchanger.

[0013] The eighth aspect is a hydrogen production method in which hydrogen gas generated by a stack having a plurality of cells each containing a solid oxide electrolyte that separates an anode and an cathode is stored in a storage tank, and the pressure of the hydrogen gas between the stack and a booster device that pressurizes the hydrogen gas generated by the stack and sends it to the storage tank is detected using a first pressure gauge, and the operating state of the booster device is controlled based on the detection result of the first pressure gauge.

[0014] In a ninth aspect, in the eighth aspect, the pressure of the hydrogen gas in the storage tank is detected using a second pressure gauge, and the operating state of the pressure booster is controlled based on the detection result of the second pressure gauge.

[0015] A tenth aspect is a method for producing hydrogen, in which a first pressure gauge is used to detect the pressure of hydrogen gas between a booster device that boosts the pressure of hydrogen gas generated by a stack having a plurality of cells each containing a solid oxide electrolyte that separates a fuel electrode and an air electrode, and the stack, and the operating state of the booster device is controlled based on the detection result of the first pressure gauge. [Effects of the Invention]

[0016] According to the present invention, hydrogen gas generated by a stack provided with cells containing a solid oxide electrolyte is stored in a storage tank. A pressure booster that pressurizes the hydrogen gas and sends it to the storage tank is connected to a gas pipe connecting the stack and the storage tank, and the pressure of the hydrogen gas between the stack and the pressure booster is detected by a first pressure gauge. In addition, a pressure booster that pressurizes the hydrogen gas generated by the stack is connected to a gas pipe connected to the stack provided with cells containing a solid oxide electrolyte, and the pressure of the hydrogen gas between the stack and the pressure booster is detected by the first pressure gauge.

[0017] By controlling the operation of the pressure booster based on the detection results of the first pressure gauge, the pressure of hydrogen gas between the stack and the pressure booster can be controlled, preventing excessive pressure from being applied to the cells and reducing the risk of cell damage. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is a block diagram of a storage device according to one embodiment. [Figure 2] FIG. 1 is a schematic diagram of a stack. [Figure 3] FIG. 2 is a schematic diagram showing an operating state of a booster device. DETAILED DESCRIPTION OF THE INVENTION

[0019] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Figure 1 is a block diagram of a storage device 10 according to one embodiment. The storage device 10 includes a stack 11 that generates hydrogen gas by electrolysis of water (steam), a storage tank 18 that stores the hydrogen gas generated by the stack 11, and a pressure booster 20 connected to a gas pipe 19 that connects the stack 11 and the storage tank 18.

[0020] The hydrogen gas stored in the storage tank 18 can be divided into small portions and packed into high-pressure containers (not shown) for storage or transportation as compressed hydrogen. The hydrogen gas stored in the storage tank 18 can also be divided into small portions, liquefied, packed into insulated containers (not shown), and stored or transportation as liquefied hydrogen. The hydrogen gas stored in the storage tank 18 can also be stored or transportation by being absorbed into a hydrogen storage material.

[0021] Figure 2 is a schematic diagram of the stack 11. The stack 11 is a device that generates hydrogen by electrolyzing water vapor. The stack 11 includes a fuel cell that generates electricity from fuel gases such as hydrogen, carbon monoxide, and hydrocarbons, and is capable of reversible operation between generating hydrogen and other fuels.

[0022] The stack 11 is provided with a plurality of cells 12. Each cell 12 includes an anode 13, an air electrode 14, and a solid oxide electrolyte 15 that separates the anode 13 and the air electrode 14. In this embodiment, the stack 11 is exemplified by stacking flat plate-shaped cells 12. The stack 11 is heated by a heater (not shown). There are no limitations on the heater as long as it heats the stack 11, and examples include a heat exchanger or a heating element that heats the stack 11 with high-temperature gas.

[0023] Examples of the material for the electrolyte 15 include stabilized zirconia, ceria-based solid solution, and a solid solution of alumina with one or more selected from stabilized zirconia and ceria-based solid solution. Examples of stabilizers for stabilized zirconia include CaO, MgO, YO, ScO, and YbO. Examples of elements that dissolve in ceria in the ceria-based solid solution include Gd, Sm, and Y.

[0024] Examples of the material for the fuel electrode 13 include a material containing a catalyst containing Ni and zirconia with Y dissolved therein, and a material containing a catalyst containing Ni and ceria with Gd dissolved therein. Examples of the catalyst include Ni, Ni-based alloys, and cermets, which are composites (sintered bodies) of NiO and oxides (solid electrolytes).

[0025] The material of the cathode 14 is a perovskite oxide, La 1-XSr X MnO 3-δ ,La 1-X Sr X CoO 3-δ ,La 1-X Sr X Co 1-Y Fe Y O 3-δ ,Pr 1-X Sr X MnO 3-δ is exemplified.

[0026] The stack 11 is heated by a heater (not shown) to the operating temperature of the cell 12 (approximately 600°C to 1000°C). When the positive terminal of a power source (not shown) is connected to the air electrode 14 of the stack 11 and the negative terminal of the power source is connected to the fuel electrode 13, electrons flow toward the fuel electrode 13. Water vapor supplied to the stack 11 is reduced at the fuel electrode 13, generating hydrogen at the fuel electrode 13. Electrons are removed at the air electrode 14, causing oxide ions to migrate to the air electrode 14 via the electrolyte 15 and be oxidized at the air electrode 14, generating oxygen at the air electrode 14. Separators 16 and 17 separate the fuel electrode 13 and the air electrode 14, preventing the hydrogen generated at the fuel electrode 13 from mixing with the oxygen generated at the air electrode 14.

[0027] Returning to Figure 1, the explanation will be made. The hydrogen gas generated by the stack 11 is supplied to a gas pipe 19. There are no restrictions on the pressure booster 20 placed in the gas pipe 19, as long as it is a device that boosts the hydrogen gas and sends it to the storage tank 18. Examples of the pressure booster 20 include a compressor and a blower. The discharge amount (capacity) of the pressure booster 20 is greater than the amount of hydrogen gas generated by the stack 11.

[0028] A buffer tank 21 is connected to the gas pipe 19 between the stack 11 and the booster device 20. The buffer tank 21 is a tank that temporarily stores hydrogen gas. The capacity of the buffer tank 21 is set appropriately depending on the discharge rate of the booster device 20. The capacity of the buffer tank 21 is smaller than the capacity of the storage tank 18, for example. The hydrogen gas stored in the buffer tank 21 upstream of the booster device 20 can reduce the frequency of the booster device 20 switching between operating and stopped, thereby reducing the occurrence of breakdowns in the booster device 20.

[0029] A heat exchanger 22 is connected to the gas pipe 19 between the stack 11 and the buffer tank 21. The heat exchanger 22 transfers heat from the high-temperature hydrogen gas generated by the stack 11, which is heated to approximately 600°C to 1000°C, to a low-temperature heat medium, thereby cooling the hydrogen gas. For example, the temperature of the hydrogen gas discharged from the stack 11 is close to 100°C, but the heat exchanger 22 can lower the temperature of the hydrogen gas to approximately 20°C.

[0030] Because the temperature of the hydrogen gas is lowered by the heat exchanger 22, the heat resistance requirements for the buffer tank 21, pressure booster 20, storage tank 18, first pressure gauge 23, and second pressure gauge 24, which are arranged downstream of the heat exchanger 22, are reduced. This allows for a wider range of choices for tank materials and equipment. Furthermore, because the lower the temperature of a gas, the smaller its volume, so when the temperature of the hydrogen gas is lowered by the heat exchanger 22, the amount of hydrogen gas filled into the buffer tank 21 and storage tank 18 can be increased.

[0031] There are no limitations on the heat medium to which the heat of the hydrogen gas is transferred in the heat exchanger 22. An example of the heat medium is water (a raw material for hydrogen gas) supplied to the stack 11. When the heat of the hydrogen gas is transferred to the water (heat medium) supplied to the stack 11 in the heat exchanger 22, the energy required to vaporize the water can be reduced, thereby improving the energy efficiency of the storage device 10.

[0032] The storage device 10 is equipped with a first pressure gauge 23, a second pressure gauge 24, and a thermometer 25. The first pressure gauge 23 detects the pressure of hydrogen gas in the buffer tank 21. In order to reduce damage to the cell 12, the first pressure gauge 23 is preferably a measuring instrument that can detect a pressure (gauge pressure) of 1 kPa or more and 100 kPa or less.

[0033] The second pressure gauge 24 detects the pressure of the hydrogen gas in the storage tank 18. It is preferable that the second pressure gauge 24 is a measuring instrument that can detect a maximum pressure (gauge pressure) of 1 MPa. This is because the pressure is controlled to be less than 1 MPa based on the detection result of the second pressure gauge 24 so that the hydrogen gas in the storage tank 18 does not fall under the category of high-pressure gas as defined by the High-Pressure Gas Safety Act.

[0034] The thermometer 25 is disposed in the gas pipe 19 downstream of the heat exchanger 22 and detects the temperature of the hydrogen gas in the gas pipe 19. The first pressure gauge 23, the second pressure gauge 24, and the thermometer 25 each input their detection results (current values) to the control device 26.

[0035] The control device 26 includes a central processing unit (CPU), a non-volatile memory (ROM), and a volatile memory (RAM) (none of which are shown). The control device 26 controls the operating state of the pressure booster 20 based on the detection results input by the first pressure gauge 23, the second pressure gauge 24, and the thermometer 25.

[0036] Fig. 3 is a schematic diagram showing the operating state of the pressure booster 20. Fig. 3 shows the pressure 27 in the buffer tank 21 detected by the first pressure gauge 23 and the operating (ON) and stopped (OFF) states of the pressure booster 20 on the time axis.

[0037] At time T0, with the booster device 20 stopped, current is passed through the cell 12 (see FIG. 2) to supply steam to the stack 11. As the stack 11 generates hydrogen gas, the pressure 27 in the buffer tank 21 gradually increases from pressure P1. When the pressure 27 reaches pressure P2 at time T1, the control device 26 (see FIG. 1) operates the booster device 20. As a result, the hydrogen gas in the buffer tank 21 moves to the storage tank 18. Because the discharge rate of the booster device 20 is greater than the amount of hydrogen gas generated by the stack 11, the hydrogen gas in the buffer tank 21 gradually decreases, and the pressure 27 drops. The pressure P2 is set within an allowable range that will not damage the cell 12 (see FIG. 2) due to pressurization, and is stored in the ROM of the control device 26. This reduces the risk of damage to the cell 12.

[0038] When the pressure 27 reaches the pressure P1 at time T2, the control device 26 (see FIG. 1) stops the pressure booster 20. As a result, the hydrogen gas generated by the stack 11 starts to accumulate in the buffer tank 21, causing the pressure 27 to rise. The pressure P1 is preset based on the capacity of the buffer tank 21 and is stored in the ROM of the control device 26. This prevents the cell 12 (see FIG. 2) from being destroyed by the pressure reduction caused by the suction of the pressure booster 20.

[0039] When pressure 27 reaches pressure P2 at time T3, control device 26 (see FIG. 1) operates pressure booster 20 to transfer the hydrogen gas in buffer tank 21 to storage tank 18. By repeatedly operating and stopping pressure booster 20 in accordance with pressure 27, hydrogen gas can be stored in storage tank 18 while reducing damage to cell 12.

[0040] When the pressure of the hydrogen gas in the storage tank 18 detected by the second pressure gauge 24 exceeds a predetermined pressure P3, the control device 26 stops the pressure booster 20 and stops the operation of the stack 11. The pressure P3 is set in advance according to the discharge rate (capacity) of the pressure booster 20 and is stored in the ROM of the control device 26. This prevents the pressure booster 20 from becoming insufficient in capacity relative to the storage tank 18.

[0041] The control device 26 adjusts the amount of heat medium supplied to the heat exchanger 22 and the amount of electricity and steam supplied to the stack 11 according to the temperature of the hydrogen gas detected by a thermometer 25 arranged downstream of the heat exchanger 22. This keeps the temperature of the hydrogen gas downstream of the heat exchanger 22 within an appropriate range. As a result, damage to the first pressure gauge 23 and the second pressure gauge 24 due to overheating can be reduced.

[0042] The control device 26 stops the operation of the stack 11 when the temperature of the hydrogen gas detected by the thermometer 25 exceeds a predetermined temperature T1. The temperature T1 is preset according to the heat resistance temperature of the first pressure gauge 23 and is stored in the ROM of the control device 26. This makes it possible to prevent damage to the first pressure gauge 23.

[0043] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0044] In the embodiment, the stack 11 has been described as having a flat cell design. The flat cell 12 may be an electrode-supported type or an electrolyte-supported type. It may also be a metal-supported type (metal-supported flat type) in which the fuel electrode 13, the air electrode 14, and the electrolyte 15 are supported by a porous body of a metal such as an Fe-Cr-based metal. Furthermore, the stack 11 is not limited to one including flat cell 12, but may be a stack 11 including cylindrical horizontal stripe or cylindrical vertical stripe cells 12. However, stack 11 including flat cell 12 tends to be more easily damaged by hydrogen gas pressure than stack 11 including cylindrical cell 12, and therefore the effect of the embodiment is greater.

[0045] In the embodiment, the buffer tank 21 is disposed in the gas pipe 19 between the stack 11 and the pressurizing device 20, but this is not necessarily limited to this. It is naturally possible to omit the buffer tank 21. This is because, if the length of the gas pipe 19 between the stack 11 and the pressurizing device 20 is increased or the cross-sectional area of ​​the gas pipe 19 is increased, it is possible to store hydrogen gas in the gas pipe 19 in the same way as the buffer tank 21, although this depends on the capacity of the buffer tank 21. When the buffer tank 21 is omitted, the first pressure gauge 23 is disposed in the gas pipe 19 between the stack 11 and the pressurizing device 20.

[0046] Although not described in the embodiment, it is of course possible to dispose a control valve in the gas pipe 19 between the storage tank 18 and the pressure booster 20, and for the control device 26 to adjust the opening of the control valve based on the pressure detected by the first pressure gauge 23. Furthermore, instead of the control device 26 turning on and off the operation of the pressure booster 20 based on the pressure detected by the first pressure gauge 23, it is of course possible for the control device 26 to control the operating state of the pressure booster 20 based on the pressure detected by the first pressure gauge 23 so that the discharge rate of the pressure booster 20 changes continuously. [Explanation of symbols]

[0047] 10 Storage Device 11 Stack 12 cells 13 Fuel electrode 14 Air electrode 15 Electrolytes 18 Storage Tank 19 Gas Pipe 20 Booster 21 Buffer Tank 22 Heat exchanger 23 First pressure gauge 24 Second pressure gauge 25 Thermometer 26 Control device

Claims

1. a stack including a plurality of cells each including a solid oxide electrolyte separating an anode from a cathode; A storage tank that stores the hydrogen gas generated by the stack, a pressure booster connected to a gas pipe connecting the stack and the storage tank, for boosting the pressure of hydrogen gas and sending it to the storage tank; a first pressure gauge that detects the pressure of hydrogen gas between the stack and the pressure booster.

2. a buffer tank connected to the gas pipe between the stack and the pressure booster; 2. The storage device according to claim 1, wherein the first pressure gauge detects the pressure of hydrogen gas in the buffer tank.

3. a stack including a plurality of cells each including a solid oxide electrolyte separating an anode from a cathode; a pressure booster connected to a gas pipe leading to the stack and configured to boost the pressure of hydrogen gas generated by the stack; a first pressure gauge that detects the pressure of hydrogen gas between the stack and the pressure booster.

4. The storage device according to any one of claims 1 to 3, further comprising a control device that controls the operating state of the pressure boosting device based on the detection result of the first pressure gauge.

5. 3. The storage device according to claim 1, further comprising a second pressure gauge for detecting the pressure of hydrogen gas in the storage tank.

6. The storage device according to claim 5, further comprising a control device that controls the operating state of the pressure booster based on the detection result of the second pressure gauge.

7. a heat exchanger for cooling hydrogen gas, the heat exchanger being connected to the gas pipe between the stack and the pressure booster; 4. The storage device according to claim 1, further comprising: a thermometer disposed in the gas pipe downstream of the heat exchanger for detecting the temperature of the hydrogen gas.

8. A method for producing hydrogen in which a stack is provided with a plurality of cells each including a solid oxide electrolyte that separates a fuel electrode from a cathode, and hydrogen gas generated by the stack is stored in a storage tank, A hydrogen production method in which the pressure of hydrogen gas between the stack and a pressure booster device that pressurizes the hydrogen gas generated by the stack and sends it to the storage tank is detected using a first pressure gauge, and the operating state of the pressure booster device is controlled based on the detection result of the first pressure gauge.

9. 9. The method for producing hydrogen according to claim 8, wherein the pressure of the hydrogen gas in the storage tank is detected using a second pressure gauge, and the operating state of the pressure booster is controlled based on the detection result of the second pressure gauge.

10. A method for producing hydrogen, comprising: detecting, using a first pressure gauge, the pressure of hydrogen gas between a stack having a plurality of cells each containing a solid oxide electrolyte that separates an anode and an cathode, and a booster device that boosts the pressure of hydrogen gas generated by the stack; and controlling the operating state of the booster device based on the detection result of the first pressure gauge.

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