JP5428865B2 - High pressure hydrogen production system - Google Patents

Description

  The present invention relates to a system for producing high-pressure hydrogen by water electrolysis.

  For example, a high-pressure hydrogen production system is known as one that produces high-pressure hydrogen of 0.5 MPa or more used as fuel to be supplied to a fuel cell. As shown in FIG. 1, a general high-pressure hydrogen production system 3 includes a cell 10 that performs water electrolysis, a hydrogen-side storage tank 11 that stores hydrogen gas generated in the cell 10, and oxygen gas generated in the cell 10. An oxygen-side storage tank 12 is provided for storage. The cell 10 is, for example, a solid polymer type reversible cell or a water electrolysis cell. The inside of the cell 10 is separated into an anode side and a cathode side by a diaphragm, and oxygen gas is introduced into the anode side by electrolyzing pure water. To generate hydrogen gas on the cathode side. The system flow for water electrolysis operation and the system flow for water electrolysis dedicated machine in the reversible cell that can be operated by arbitrarily switching the operation mode by integrating the polymer electrolyte water electrolysis cell and the fuel cell Therefore, the following explanation will be made with the system flow of the water electrolysis dedicated machine.

  By controlling the pressure of oxygen gas or hydrogen gas generated from the cell 10 during water electrolysis operation or in a water electrolysis dedicated machine, hydrogen gas and oxygen of several MPa to several tens of MPa can be used without using a booster such as a compressor. Gas can be generated. However, the diaphragm separating hydrogen gas and oxygen gas in the cell 10 is a polymer thin film and has low mechanical strength. For this reason, when an excessive differential pressure is generated between the two electrodes, there is a problem that a seal breakage occurs due to damage to the diaphragm and the like. When such a phenomenon occurs, the gas between the two electrodes is mixed, so that a combustion reaction occurs on the catalyst, and in the worst case, the cell is burnt out, and there is a problem that the operation cannot be continued. In order to prevent this, control is performed to keep the differential pressure between the two electrodes below a certain value (usually several tens of MPa or less). This control of the differential pressure between the electrodes plays a role in preventing the loss of airtightness between the two electrodes, and is very important for safe operation of the high pressure operation of water electrolysis. However, the higher the pressure, the more difficult the control becomes, and a high degree of management and control accuracy are required.

  To solve this problem, increase the mechanical strength of the diaphragm or improve the cell structure by devising the cell structure, and devise parts other than the cell structure to improve the current range of pressure differential resistance. There is a way to manage within. Since it is difficult to ensure the differential pressure resistance only by the former method, the latter method is usually taken. As a method to devise parts other than the cell structure, in general, a pressure regulating valve that opens when the pressure in the system reaches the set pressure is provided on both sides of the generated gas or near the outlet of only the hydrogen side (cathode side). A method of keeping the pressure in the system at a predetermined pressure is used.

  In water electrolysis operation, if the gas layer capacity of each storage tank is strictly 2: 1 in the hydrogen storage tank: oxygen storage tank, theoretically no differential pressure will be generated. The water level constantly changes because of the occurrence of water in and out of the storage tank, and as a result, the air volume of the storage tank constantly changes. During water electrolysis operation, a differential pressure is generated between the two electrodes mainly due to the change in the volume of the air layer and various other factors. A method of eliminating the pressure difference between the two electrodes by exhausting the gas in the gas layer on the gas side to the outside of the trace amount system. When the air volume is small, since only the differential pressure becomes severe due to duplication of operations such as water supply to the storage tank, drainage from the storage tank, exhaust for pressure adjustment, etc., more accurate and highly accurate followability and control Sex is required.

  Conventionally, with respect to these problems, as in Patent Document 1 and Patent Document 2, the hydrogen gas system and the oxygen gas system are each provided with two valves, a pressure regulating valve and a leak valve, on one or both sides, and the pressure regulating valve provides hydrogen and oxygen. The hydrogen pressure and oxygen pressure are adjusted by the leak valve, and the direct current output to the water electrolysis cell is automatically controlled by the direct current power source to equalize the hydrogen system internal pressure and the oxygen system internal pressure. In general, this method is adopted, but the tank itself becomes excessive.

  Further, as in Patent Document 3, a separate gas tank is provided downstream of the pure water storage and gas-liquid separation tanks on both sides, and the volume ratio of the tanks is set to hydrogen 1.9 to 2.1: oxygen 1. A system has been proposed in which the pressure difference between the electrodes is reduced by reducing the pressure difference between the electrodes and by acting as a buffer for the change in the air volume due to the change in the tank water level. This method is the same as making the volume of the water layer volume of the conventional pure water storage / gas / liquid separation tank larger than the change in water layer volume that can generate the ratio and approaching 2: 1. . Therefore, the tank capacity is increased, and the pressure control itself including the differential pressure control is not significantly different from Patent Document 1 and Patent Document 2.

  Furthermore, as in Patent Document 4, the liquid layers of the pure water storage / gas / liquid separator of both electrodes are connected by piping, and when a differential pressure is generated, the differential pressure is reduced by moving the pure water between the two electrodes. There was a way to eliminate it. In addition, by setting the gas layer volume of the oxygen side tank to 4% or less of the hydrogen side gas layer volume, even if the gas between the two tanks is mixed, it is possible to prevent the generation of squealing gas. With this method, the detection mechanism of the differential pressure between the electrodes is complicated and it is necessary to strictly control a very small amount of water, and there is a possibility of gas mixing because the electrodes are connected by piping. By controlling the ratio of the air volume, the explosion limit value is not reached when viewed as an overall average, but gas movement occurs extremely suddenly if any problem occurs, so if considered locally, it will explode on the catalyst. The possibility of reaching the limit value is fully considered, and the control robustness is low and it is difficult to say that the system is safe.

Japanese Patent No. 34002829 JP 2007-31739 A JP 2004-84042 A JP 2003-342773 A

  The object of the present invention is to easily eliminate the differential pressure between the two electrodes, which is a problem during high-pressure hydrogen generation operation during water electrolysis operation of a reversible cell integrating water electrolysis and a fuel cell, or in hydrogen production using a water electrolysis dedicated machine. And to make the system more compact.

To achieve the above object, according to the present invention, a cell for performing water electrolysis, an oxygen side storage tank for storing oxygen gas generated in the cell, and a hydrogen side storage for storing hydrogen gas generated in the cell. A high-pressure hydrogen production system comprising a tank, wherein a deformable pressure absorber comprising a sealed container in which a predetermined gas is sealed in the oxygen-side storage tank and a gas layer portion in the hydrogen-side storage tank. A high-pressure hydrogen production system is provided. In the present invention, by providing pressure absorbers in the hydrogen side storage tank and the oxygen side storage tank, the generation of the differential pressure is prevented or alleviated without controlling the differential pressure between the two electrodes.

  According to the present invention, the high-pressure hydrogen comprising a cell for performing water electrolysis, an oxygen-side storage tank for storing oxygen gas generated in the cell, and a hydrogen-side storage tank for storing hydrogen gas generated in the cell. In the manufacturing system, a deformable pressure absorber filled with a predetermined gas is provided in the oxygen side storage tank and the hydrogen side storage tank, and the pressure absorption provided in the oxygen side storage tank. A high-pressure hydrogen production system characterized in that a flow path is provided for communicating a body and a pressure absorber provided in the hydrogen-side storage tank. Is provided.

  Further, in this high-pressure hydrogen production system, the pressure absorber provided in the hydrogen-side storage tank occupies a volume of 90% or more of the gas layer portion in the hydrogen-side storage tank in a normal pressure no-load state. Is desirable. Further, it is desirable that the pressure absorber provided in the oxygen side storage tank occupies a volume of 90% or more of the gas layer portion in the oxygen side storage tank in a normal pressure no-load state. Furthermore, when the differential pressure between the hydrogen side storage tank and the oxygen side storage tank is 0, the hydrogen side storage tank has a capacity larger than the volume of the pressure absorber provided in the oxygen side storage tank. It is desirable that the volume of the provided pressure absorber is 1.6 to 2 times.

  The pressure absorber provided in the hydrogen side storage tank and the pressure absorber provided in the oxygen side storage tank may be formed of a metal bellows or a polymer film. In this case, the predetermined gas sealed in the pressure absorber provided in the hydrogen side storage tank and the pressure absorber provided in the oxygen side storage tank is, for example, nitrogen gas.

  The pressure absorber provided in the hydrogen side storage tank and the pressure absorber provided in the oxygen side storage tank are formed of a polymer film, and the pressure absorber provided in the hydrogen side storage tank. The predetermined gas sealed in the pressure absorber provided in the oxygen-side storage tank may be oxygen gas in the oxygen-side storage tank.

  According to the present invention, the pressure absorbers provided in the hydrogen side storage tank and the oxygen side storage tank are deformed to prevent or alleviate the occurrence of the differential pressure without controlling the differential pressure between the two electrodes. Even when a differential pressure occurs due to some abnormality, the differential pressure value and the differential pressure increase rate can be reduced. The high-pressure hydrogen production system of the present invention automatically eliminates the differential pressure without performing the differential pressure control in each process of step-up, steady operation, and step-down. Further, since the gas volume formed in the hydrogen side storage tank and the oxygen side storage tank can be made smaller than before, the hydrogen side storage tank and the oxygen side storage tank can be made compact.

  In particular, by connecting the pressure absorber in the hydrogen-side storage tank and the pressure absorber in the oxygen-side storage tank through the flow path, gas is immediately generated between the pressure absorbers connected in the flow path even when a differential pressure occurs. Movement occurs. Since the gas movement directly becomes an indirect gas layer volume change between the two tanks, “the gas layer pressure of the hydrogen side storage tank = the pressure of the pressure absorber in the hydrogen side storage tank = the pressure absorption in the oxygen side storage tank” The volume of the pressure absorber quickly changes so that the pressure of the body = the gas layer pressure of the oxygen-side storage tank ”, and the differential pressure between the two electrodes can be eliminated directly on the spot without using an electrical signal. Therefore, compared to the conventional method of eliminating the differential pressure by receiving the differential pressure signal between the two poles and transferring the received signal to the control device to operate the pressure control device, there is no time delay or high accuracy. Reliable handling is possible without control. Further, by insulating between the two electrodes, there is no possibility of mixing the bipolar gas at portions other than the cell diaphragm as in the conventional method. In addition, there is no waste of electrolyzed gas because no exhaust for adjusting the differential pressure is required. In addition, since the fluctuation is also dispersed in each pressure absorber as described above and the fluctuation is absorbed as described above, it changes compared to the conventional method in which only one container (for example, a conventional oxygen side air layer) is used. The pressure value itself can also be reduced. As a result, the air volume and the water volume can be reduced, and even if the diaphragm is broken, the energy stored in the entire system is small, so that the damage can be minimized.

It is explanatory drawing of the conventional high pressure hydrogen production system. It is explanatory drawing of the high pressure hydrogen production system concerning embodiment of this invention. It is explanatory drawing of the high pressure hydrogen production system concerning another embodiment of this invention. It is the graph which compared the high pressure hydrogen production system of the Example of this invention, and the differential pressure generation by a prior art example. (Hydrogen side storage tank) It is the graph which compared the high pressure hydrogen production system of the Example of this invention, and the differential pressure generation by a prior art example. (Oxygen side storage tank)

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol. As shown in FIG. 2, the high-pressure hydrogen production system 1 according to the embodiment of the present invention includes a cell 10 that performs water electrolysis, a hydrogen-side storage tank 11 that stores hydrogen gas generated in the cell 10, and a cell 10. An oxygen-side storage tank 12 for storing the generated oxygen gas is provided.

  The cell 10 is, for example, a solid polymer type reversible cell or a water electrolysis cell. The inside of the cell 10 is separated into an anode side and a cathode side by a diaphragm (not shown), and the pure water W introduced into the cell 10 is electrolyzed to generate hydrogen gas on the cathode side and oxygen gas on the anode side. Is generated. The power supply to the cell 10 is performed by the DC power supply 14 after being calculated by the calculator 13. A hydrogen side storage tank 11 is connected to the cathode side of the cell 10 via a pipe 15, and an oxygen side storage tank 12 is connected to the anode side of the cell 10 via a pipe 16.

  Pure water W is stored in the lower part of the hydrogen-side storage tank 11. A pipe 21 communicating with the makeup water tank 20 is connected to the bottom of the hydrogen-side storage tank 11, and a flow rate adjusting valve 22 and an electromagnetic valve 23 are provided in the pipe 21. The water level of the pure water W in the hydrogen side storage tank 11 is monitored by a float type water level gauge 24, and the opening and closing of the electromagnetic valve 23 is controlled by an electric signal from the water level gauge 24, and the hydrogen side storage tank 11 The level of the pure water W is kept within a certain range.

  Similarly, pure water W is also stored in the lower part of the oxygen-side storage tank 12. An extraction pipe 25 communicating with the cell 10 is connected to the bottom of the oxygen-side storage tank 12, and a circulation for supplying the pure water W in the oxygen-side storage tank 12 to the cell 10 is connected to the extraction pipe 25. A pump 26 is provided. By the operation of the circulation pump 26, the pure water W in the oxygen side storage tank 12 is supplied to the cell 10, and the pure water W is electrolyzed in the cell 10 to generate hydrogen gas on the cathode side. Oxygen gas is generated.

  Further, a supplementary water pipe 30 communicating from the supplementary water tank 20 is connected to the bottom of the oxygen side storage tank 12, and the pure water W in the supplementary water tank 20 is stored in the supplementary water pipe 30 on the oxygen side. A replenishing water pump 31 for replenishing the tank 12, a flow rate adjusting valve 32, and an electromagnetic valve 33 are provided. The water level of the pure water W in the oxygen side storage tank 12 is monitored by a float type water level gauge 34, and the pure water W in the oxygen side storage tank 12 is supplied to the cell 10 by the operation of the circulation pump 26. When the water level of the pure water W in the oxygen-side storage tank 12 is lowered, the opening and closing of the electromagnetic valve 33 is controlled by an electric signal from the water level gauge 34, and the supply water tank 20 passes through the makeup water tank 20 to the oxygen-side storage tank 12. Is supplied with pure water W, and the water level of the pure water W in the oxygen-side storage tank 12 is kept within a certain range.

  A return pipe 35 for returning the pure water W in the makeup water pipe 30 to the makeup water tank 20 is connected to the makeup water pipe 30 downstream of the makeup water pump 31. The return pipe 35 is provided with a flow rate adjusting valve 36, a heat exchanger 37, an ion exchange resin 38, and a filter 39. While the water in the make-up water tank 20 is not supplied into the oxygen-side storage tank 12, it is circulated through the return pipe 35, whereby the purity of the pure water W in the system is maintained.

  On the downstream side of the circulation pump 26 in the extraction pipe 25, a bypass pipe 40 for extracting a part of the pure water W from the extraction pipe 25 and returning it to the makeup water tank 20 is connected. The bypass pipe 40 is provided with a flow rate adjustment valve 41 and an electromagnetic valve 42.

  In the hydrogen side storage tank 11, the part above the liquid level of the pure water W is a gas layer part 11a in which hydrogen gas is stored, and the hydrogen gas separated in the hydrogen side storage tank 11 is hydrogen side. The gas is stored in the gas layer portion 11 a in the storage tank 11. The pressure in the air layer portion 11 a is detected by the barometer 45.

  Also, an electrolyzed hydrogen gas extraction pipe 46 is connected to the gas layer portion 11a of the hydrogen-side storage tank 11, and the gas filter 47 and the pressure in the system are set to the set pressure. There are provided a pressure regulating valve 48 which is opened when the pressure reaches a pressure measuring device 49 for detecting the pressure in the system. The take-out pipe 46 includes a leak pipe 51 having a safety valve 50 for releasing the pressure when the system pressure abnormally increases, a pressure release pipe 54 having a solenoid valve 52 and a regulating valve 53, hydrogen A hydrogen concentration meter 55 for measuring the hydrogen concentration in the gas and a concentration measuring pipe 57 provided with a regulating valve 56 are connected.

  A deformable pressure absorber 60 is provided in the gas layer portion 11 a in the hydrogen-side storage tank 11. As will be described later, the pressure absorber 60 is a deformable hermetic container formed of, for example, a metal bellows or a polymer film, and a gas such as nitrogen gas or oxygen gas is sealed therein. For this reason, when the pressure of the gas layer portion 11a in the hydrogen side storage tank 11 changes, the pressure absorber 60 expands or contracts and the volume of the pressure absorber 60 itself changes, and the gas layer portion in the hydrogen side storage tank 11 changes. The pressure change of 11a is absorbed and relaxed. The pressure absorber 60 occupies a volume of 90% or more of the gas layer portion 11a in the hydrogen-side storage tank 11 in a no-load state where the pressure of the gas layer portion 11a is normal pressure.

  Similarly, in the oxygen side storage tank 12, the part above the liquid level of the pure water W is a gas layer part 12a in which oxygen gas is stored, and the oxygen gas separated from the liquid in the oxygen side storage tank 12 is It is stored in the gas layer portion 12 a in the oxygen side storage tank 12. The pressure in the air layer portion 12 a is detected by the barometer 65.

  Further, a gas extraction portion 66 for electrolyzed oxygen gas is connected to the gas layer portion 12 a of the oxygen-side storage tank 12, and a gas filter 67 and a pressure in the system are set to the set pressure in the extraction piping 66. There is provided a pressure regulating valve 68 that is opened when the value becomes. Further, a leakage pipe 71 provided with a safety valve 70 for releasing the pressure when the system pressure abnormally rises and a pressure release pipe 74 provided with an electromagnetic valve 72 and a regulating valve 73 are connected to the take-out pipe 66. ing.

  In addition, a deformable pressure absorber 80 is provided in the gas layer portion 12 a in the oxygen-side storage tank 12. As will be described later, the pressure absorber 80 is a deformable hermetic container formed of, for example, a metal bellows or a polymer film, and a gas such as nitrogen gas or oxygen gas is sealed therein. For this reason, when the pressure of the gas layer portion 12a in the oxygen side storage tank 12 changes, the pressure absorber 80 expands or contracts and the pressure absorber 80 itself changes in volume, and the gas layer portion in the oxygen side storage tank 12 changes. The pressure change of 12a is absorbed and relaxed. The pressure absorber 80 occupies a volume of 90% or more of the gas layer portion 12a in the oxygen-side storage tank 12 in a no-load state where the pressure of the gas layer portion 12a is normal pressure.

  The pressure absorber 60 provided in the gas layer portion 11 a in the hydrogen side storage tank 11 and the pressure absorber 80 provided in the gas layer portion 12 a in the oxygen side storage tank 12 are communicated by a flow path 81. . For this reason, the gas sealed in the two pressure absorbers 60 and 80 can freely move between the two pressure absorbers 60 and 80, and thereby, the two pressure absorbers 60 and 80 can be moved back and forth. The internal pressure is always kept equal.

  Here, the volume obtained by subtracting the volume of pure water W from the total volume in the hydrogen-side storage tank 11 is the pure volume from the total volume V11 of the gas layer portion 11 a in the hydrogen-side storage tank 11 and the total volume in the oxygen-side storage tank 12. When the volume obtained by subtracting the volume of the water W is defined as the total volume V12 of the gas layer portion 12a in the oxygen side storage tank 12, when the pressure in the hydrogen side storage tank 11 and the pressure in the oxygen side storage tank 12 are equal, In the hydrogen side storage tank 11, the total volume V11 of the gas layer portion 11 a in the hydrogen side storage tank 11 is 1.6 to 2 times the total volume V12 of the gas layer portion 12 a in the oxygen side storage tank 12. And the water level WL1 of the pure water W, the volume in the oxygen-side storage tank 12, and the water level WL2 of the pure water W are designed.

  Now, in the high-pressure hydrogen production system 1 according to the embodiment of the present invention configured as described above, pure water W in the oxygen-side storage tank 12 is supplied to the cell 10. When it is confirmed that the pure water W having a predetermined flow rate or more is stably supplied into the cell 10 and that the predetermined water level is secured, power is supplied from the DC power supply device 14 and the load is gradually increased. Is raised. Thereby, in the cell 10, the pure water W is electrolyzed, hydrogen gas is generated on the cathode side, and oxygen gas is generated on the anode side.

  In this high-pressure hydrogen production system 1, since the pressure regulating valve 48 is provided in the hydrogen gas extraction pipe 46, the load of the DC power supply 14 is monitored while the pressure in the system is monitored by the pressure measuring device 49. By controlling with, hydrogen production according to the load on the demand side is performed. Further, the makeup water pump 31 provided in the makeup water pipe 30 may be operated only when the water quality is lowered or when the oxygen-side storage tank 12 needs to be replenished, but it may be operated constantly. The control method for hydrogen production in accordance with the demand-side load described here is an example of a known technique, and is not limited to this control method, and a simpler control system that is known may be configured.

  In the cell 10, the pure water W is electrolyzed into hydrogen ions and oxygen ions according to the output of the DC power supply 14. Among them, oxygen ions become oxygen gas on the catalyst and are discharged to the oxygen-side storage tank 12 together with the circulating water. Further, the hydrogen ions move to the hydrogen side with accompanying water, become hydrogen gas on the hydrogen side catalyst, and are discharged to the hydrogen side storage tank 11. The discharged oxygen and hydrogen are subjected to gas-liquid separation in the oxygen side storage tank 12 and the hydrogen side storage tank 11, respectively. The pure water W subjected to the gas-liquid separation is sent again to the cell 10, the hydrogen gas is discharged from the extraction pipe 46, and the oxygen gas is discharged from the extraction pipe 66. At this time, if the system pressure is equal to or lower than the rated pressure, hydrogen gas and oxygen gas stay in the hydrogen side storage tank 11 and the oxygen side storage tank 12 and contribute to an increase in pressure. When the internal pressure reaches a predetermined value, gas is discharged from the pressure regulating valves 48 and 68 and supplied to the demand side. As shown in the figure, when a pressure regulating valve 48 is provided in the take-out piping 46, the pressure detected by the pressure measuring device 49 is constantly monitored by the computing unit 13, and when the pressure drops below a predetermined value, the DC power supply By supplying electric power from the device 14 to the cell 10, hydrogen production is performed in accordance with the load on the demand side.

  The pure water W taken out to the bypass pipe 40 for the purpose of maintaining the quality of the pure water W from the take-out pipe 25 for supplying the pure water W to the cell 10 is returned to the makeup water tank 20. Since the water level in the oxygen-side storage tank 12 decreases due to the electrolysis in the cell 10 and the return to the make-up water tank 20, the operation of the make-up water pump 31 by the operation of the make-up water pump 31 by the detection of the water level gauge 34. Purified pure water W is supplied into the tank 12.

  The barometers 45 and 65 measure the pressure in the hydrogen side storage tank 11 and the oxygen side storage tank 12, and the differential pressure is constantly monitored by the calculator 13. When the pressure difference between the electrodes exceeds a predetermined value due to some abnormality, the power from the DC power supply 14 is immediately cut off, and the high-pressure hydrogen production system 1 is urgently stopped.

  When the high pressure hydrogen production system 1 is stopped, the power supply from the DC power supply device 14 is stopped. The solenoid valves 52 and 72 of the pressure release pipes 54 and 74 of both poles are opened, the gas in the system is exhausted, and the pressure is reduced to near normal pressure. Since this system is provided with a differential pressure elimination mechanism, it is not necessary to perform special differential pressure control in all steps from step-up to step-down as described above.

  In the case of operation in which the pressure in the system exceeds 0.9 MPa (G), the pressure absorber 60 provided in the gas layer portion 11a in the hydrogen side storage tank 11 and the gas in the oxygen side storage tank 12 are used. By providing a plurality of pressure absorbers 80 provided in the layer portion 12a and changing the pressure of the nitrogen gas filled in each pressure absorber 60, 80, it is possible to cope with any operating pressure. In that case, it is desirable that the magnification of the design upper limit pressure with respect to the initial sealed pressure of each of the pressure absorbers 60 and 80 (hereinafter referred to as pressure increase magnification) is 8 to 10 times or less. For example, when the initial pressure of the pressure absorbers 60 and 80 is 0 MPa (G) (= normal pressure, absolute pressure: 0.1 MPa), and the pressure increase ratio is 10 times, the maximum pressure is 0.9 MPa ( G) (= absolute pressure: 1.0 MPa). When the pressure is further increased, the tank is equipped with two pressure absorbers 60 and 80 having an initial pressure of the separation membrane container of 0 MPa (G) and pressure absorbers 60 and 80 having a pressure of 0.9 MPa (G). You can do it. As the pressure increase rate of each pressure absorber 60, 80 is decreased, the differential pressure elimination capability increases. However, the number of pressure absorbers 60, 80 increases accordingly, so that the number of pressure absorbers 60, 80 in accordance with the maximum operating pressure. And the pressure increase magnification of each pressure absorber 60, 80 may be selected. At that time, the pressure increase factor is decreased for the pressure absorbers 60 and 80 having a higher initial pressure.

  According to the high-pressure hydrogen production system 1, the pressure absorbers 60 and 80 provided in the hydrogen-side storage tank 11 and the oxygen-side storage tank 12 are deformed, so that the differential pressure can be controlled without controlling the differential pressure between the two electrodes. Can be prevented or alleviated in advance, and even when a differential pressure occurs due to some abnormality, the differential pressure value and the differential pressure increase rate can be reduced. Even if the differential pressure control is not performed in each process of step-up, steady operation, and step-down, the differential pressure is automatically eliminated. Further, since the volume of the gas layer portions 11a and 12a formed in the hydrogen side storage tank 11 and the oxygen side storage tank 12 can be made smaller than before, the hydrogen side storage tank 11 and the oxygen side storage tank 12 can be made compact. It becomes.

  In particular, by connecting the pressure absorber 60 in the hydrogen side storage tank 11 and the pressure absorber 80 in the oxygen side storage tank 12 through the flow path 81, the pressure absorption connected by the flow path 81 even when a differential pressure is generated. Immediate gas transfer occurs between the bodies 60,80. Since the gas movement becomes an indirect gas layer volume change between the two tanks as it is, “the gas layer pressure of the hydrogen side storage tank 11 = the pressure of the pressure absorber 60 in the hydrogen side storage tank 11 = the oxygen side storage tank 12”. The volume of the pressure absorbers 60 and 80 quickly changes so that the pressure of the pressure absorber 80 in the inside = the gas layer pressure of the oxygen-side storage tank 12, and the differential pressure between the two electrodes can be obtained without using an electric signal. Can be solved directly on the spot. Therefore, compared to the conventional method of eliminating the differential pressure by receiving the differential pressure signal between the two poles and transferring the received signal to the control device to operate the pressure control device, there is no time delay or high accuracy. Reliable handling is possible without control. Further, by insulating between the two electrodes, there is no possibility of mixing the bipolar gas at portions other than the cell diaphragm as in the conventional method. In addition, there is no waste of electrolyzed gas because no exhaust for adjusting the differential pressure is required. In addition, since the fluctuation is also dispersed in each pressure absorber as described above and the fluctuation is absorbed as described above, it changes compared to the conventional method in which only one container (for example, a conventional oxygen side air layer) is used. The pressure value itself can also be reduced. As a result, the air volume and the water volume can be reduced, and even if the diaphragm is broken, the energy stored in the entire system is small, so that the damage can be minimized.

  In addition, the separation membrane container used with the accumulator currently used for the automobile suspension etc. can be diverted to the pressure absorbers 60 and 80 used as a differential pressure cancellation mechanism by this invention. The pressure absorbers 60 and 80 can be broadly classified into a metal bellows type and a polymer film type depending on the material used. Both types normally enclose a gas such as nitrogen in the pressure absorbers 60 and 80, and when the external pressure fluctuations occur, the volume changes itself by utilizing the compressibility of the nitrogen gas enclosed inside. , Absorb and mitigate pressure fluctuations. Since the pressure absorbers 60 and 80 are excellent in high-frequency response, they have followability to pressure fluctuation during water electrolysis operation. In the metal bellows type, since the separation membrane is made of metal, there is no permeation of the enclosed gas and there is no need for maintenance (gas re-encapsulation).

  In FIG. 2, the system flow when the metal film type pressure absorbers 60 and 80 are used has been described. As the pressure absorbers 60 and 80 inserted into the tanks of the respective poles increase the volume ratio of the pressure absorbers 60 and 80 in the total volume of the tank gas layer, the greater the differential pressure elimination effect is obtained. For this reason, when the tank internal pressure of each electrode is a normal pressure state before the operation, it is preferable to set the capacity to occupy 90% or more of the tank gas layer. Here, the actual gas volume in the hydrogen-side storage tank 11 (the volume of the gas layer portion 11 a in the hydrogen-side storage tank 11 -the volume of the pressure absorber 60 in the hydrogen-side storage tank 11) and the actual gas in the oxygen-side storage tank 12. The ratio of the gas volume (the volume of the gas layer portion 12a formed in the oxygen side storage tank 12-the volume of the pressure absorber 80 of the oxygen side storage tank 12) is such that the volume of the pressure absorbers 60 and 80 is maximized. 1.6 to 2 times (based on the volume of the pressure absorber 80 of the oxygen-side storage tank 12) in both the normal pressure state during loading and the maximum pressure state in which the volume of the pressure absorbers 60 and 80 is minimized. It is preferable to do this. For this purpose, the volume of the pressure absorbers 60 and 80 is 1.6 to 2 times (in reference to the actual gas volume standard of the oxygen-side storage tank 12) even in a situation where the volume changes greatly, such as the pressure increasing process at the start and the pressure decreasing process at the stop. The pressure absorbers 60 and 80 may be designed so as to maintain the ratio of Specifically, using a tank having the same diameter on both the hydrogen side and the oxygen side, the ratio of the initial lengths of the pressure absorbers 60 and 80 (at the time of no-load normal pressure) is 1.6 to 2 times (on the oxygen side) The length of the pressure absorbers 60 and 80 is the same for both poles, and the ratio of the cross-sectional area of the container is 1.6 to 2 times (oxygen) Side cross-sectional area standard). Even if it is other than this, when the pressure difference between the electrodes is 0, the volume ratio of the pressure absorbers 60 and 80 between the two electrodes may be designed to be 1.6 to 2 times. In consideration of the theoretical generation amount, the total volume V11 of the gas layer portion 11a in the hydrogen side storage tank 11 is strictly set to the total volume V12 of the gas layer portion 12a in the oxygen side storage tank 12 = 2: 1. Although it is ideal, in reality it is impossible to make it strictly 2: 1, and since the tank water level during water electrolysis operation constantly fluctuates with water supply and drainage, Differential pressure is always generated in all the steady processes. However, in this system incorporating the differential pressure canceling mechanism, the volume ratio needs only to be 1.6 to 2 times, and there is sufficient tolerance in consideration of manufacturing and various other constraints and operating conditions. doing. Even if the volume of the pressure absorbers 60 and 80 does not reach a predetermined volume ratio (for example, hydrogen 2: oxygen 1 in the case of a double design) due to the differential pressure generated in the pressurization process, if the rated pressure is reached. A substantially predetermined volume ratio is obtained by the elastic force of the pressure absorbers 60 and 80 themselves.

  In addition, in the step-down process when the system is shut down, it is only necessary to step down the pressure by exhausting a small amount of gas in the system after shutting off the power as before, but the relationship between the amount of exhaust from both poles at that time is The amount may be 0.4 to 1 times the hydrogen side displacement. Since this system can tolerate such a wide flow rate range, there is no need to use highly accurate equipment or control even in the decompression process. In addition, since the storage amount is small, the system can be quickly returned to normal pressure.

  In addition, as a countermeasure against some abnormality, it is safer if a conventionally performed control for detecting the differential pressure and adjusting the pressure is incorporated. Even in this case, the differential pressure generated in this system with a built-in differential pressure canceling device becomes slower than the differential pressure generated in a device without it, so an inexpensive pressure adjustment method should be adopted. Can do.

  In this method, in order to eliminate the differential pressure of 100 KPa or more that occurs when there is no differential pressure elimination mechanism, for example, in the process of pressure reduction after the end of operation, for example, due to clogging of the throttle valve or the filter in the preceding stage, etc. Even if the exhaust is not performed as prescribed, the pressure difference is eliminated to some extent due to the volume change between the pressure absorbers 60 and 80, so that the abnormality may not be detected early. Even in such an emergency situation, a circuit that detects the differential pressure and urgently stops the system without incorporating any special measures is built in the calculator 13, but this detection delay is prevented by an inexpensive method. For this purpose, the step-down process may be managed by time. Specifically, if the pressure does not drop to a predetermined pressure within a predetermined time, a circuit that determines that there is an abnormality, stops the exhaust, and urgently stops the system may be incorporated in the calculator 13. After that, it is dealt with by exhausting manually from the preliminary control valve provided separately. As a result, a precursor such as clogging of the filter can be detected at an early stage, and an abnormal situation can be prevented. This is the same in the step-up process. If the pressure does not rise to a predetermined pressure within a predetermined time, it is determined that there is an abnormality, and a circuit that cuts off the power from the DC power supply 14 and urgently stops the system is incorporated in the arithmetic unit 13. It ’s fine.

  Moreover, since the mechanical strength of the membrane made of a polymer membrane is low as described above, it is necessary to assume that the membrane is damaged in designing the system. Minimizing the amount of fuel and combustion aids (hydrogen gas, oxygen gas, water) present in the system is an effective way to minimize damage even if the diaphragm is damaged. Reduction is essential. In this system, the volume of the gas layer, which is also the pressure buffer, can be much smaller than that of the conventional method due to the effect of the differential pressure canceling mechanism. In this respect as well, compared to the pure water storage and gas-liquid separation tank of the conventional method, It can be reduced to a few tenths.

  Here, even if the material of the pressure absorbers 60 and 80 is a polymer film, the above-described effect can be obtained. However, when the polymer film type is adopted, the gas permeation from the polymer film is different from the metal bellows type. Therefore, the pressure absorbers 60 and 80 need to be replenished regularly. FIG. 3 shows the high-pressure hydrogen production system 2 according to the embodiment when the polymer membrane type pressure absorbers 60 and 80 are used. In the case of using a polymer film for the pressure absorbers 60, 80, oxygen is enclosed in the pressure absorbers 60, 80 instead of nitrogen, and oxygen gas generated during operation is used, and the pressure absorbers 60, 80 are used. What is necessary is just to re-enclose the gas permeated from the inside periodically.

  In the high-pressure hydrogen production system 2 shown in FIG. 3, an oxygen gas flow path 85 for introducing oxygen gas from the gas layer portion 12 a in the oxygen side storage tank 12 to the flow path 81 is connected. A pressure regulating valve 86 is provided in the oxygen gas flow path 85. In the high-pressure hydrogen production system 2 shown in FIG. 3, a small amount of oxygen permeates from the pressure absorbers 60 and 80 not only to the oxygen side but also to the hydrogen side. Since the amount of permeation through the diaphragm is much higher, there is no safety problem. Further, since the hydrogen gas generated as described above originally contains a small amount of oxygen, the hydrogen supply piping system is generally provided with a catalyst tower for burning oxygen for the purpose of increasing the purity of the hydrogen gas. (Not shown). By using oxygen gas as the sealing gas, oxygen permeated from the pressure absorbers 60 and 80 is also combusted in the catalyst tower, so that the permeation from the pressure absorbers 60 and 80 does not occur without lowering the purity of the generated hydrogen gas. There is no need to install new removal equipment for the gas.

  In the high-pressure hydrogen production system 2 shown in FIG. 3, the equipment necessary for regassing the pressure absorbers 60 and 80 is an oxygen gas flow that connects the gas layer portion 12 a in the oxygen-side storage tank 12 and the flow path 81. Only the passage 85 and the pressure regulating valve 86 are added, and the configuration is very simple and no control is required. This pressure regulating valve 86 can always keep the pressure after the pressure regulating valve (the pressure absorbers 60 and 80 side) constant regardless of the pressure in the oxygen side storage tank 12, and the internal pressure of the pressure absorbers 60 and 80 becomes high. Also, this is a general-purpose pressure regulating valve that does not cause a back flow from the pressure absorbers 60 and 80 into the oxygen-side storage tank 12.

  Examples of the present invention will be described below. 4 and 5 show the difference in the generated differential pressure between the high-pressure hydrogen production system of the present invention and the conventional example. At this time, the volume ratio between the hydrogen side and the oxygen side is twice the maximum value, and the volume of the pressure absorber is 90% of the volume of the gas layer portion of the hydrogen side storage tank and the oxygen side storage tank. FIG. 4 shows the effect when the hydrogen side pressure decreases from the rated pressure state, and FIG. 5 shows the effect when the oxygen side pressure decreases from the rated pressure state. Both figures show the effect of the differential pressure canceling mechanism when the pressure increase magnification is 4 times (0.3 MPa (G)), 7 times (0.6 MPa (G)), 10 times (0.9 MPa (G)). Is shown. The lower the pressure increase ratio, the lower the differential pressure cancellation effect (the differential pressure decreases when the differential pressure cancellation mechanism is incorporated into the differential pressure generated when there is no differential pressure cancellation mechanism (conventional example)). It can be seen from this figure that the effect is large. It can also be seen that a much greater differential pressure elimination effect can be obtained when the pressure on the oxygen side drops than when the pressure on the hydrogen side drops. Since the volume ratio is doubled, there is a big difference in the effect of eliminating the differential pressure between the oxygen side and the hydrogen side. However, the volume ratio is gradually averaged by lowering the volume ratio. The effect on the side pressure drop is greater. The tank water level change, which is the variation factor of the air volume, is more noticeable on the oxygen side, and compared to the hydrogen side, the oxygen side controls the water level by controlling multiple devices. Is likely to occur. Considering this point, it is ideal that the effect of eliminating the differential pressure against the pressure fluctuation on the oxygen side is high, and this system is suitable for this. Each numerical value given here is a value when the allowable inter-electrode differential pressure is ± 50 kPa. Therefore, if the value increases, the allowable range increases accordingly.

  The present invention is useful, for example, for the production of hydrogen used as fuel for fuel cells.

W pure water 1, 2 high pressure hydrogen production system (embodiment of the present invention)
3 High-pressure hydrogen production system (prior art)
DESCRIPTION OF SYMBOLS 10 Cell 11 Hydrogen side storage tank 11a Gas layer part 12 Oxygen side storage tank 12a Gas layer part 13 Calculator 14 DC power supply device 15, 16, 21 Pipe 20 Supply water tank 22 Flow control valve 23 Electromagnetic valve 24 Water level gauge 25 Extraction pipe 26 Circulation pump 30 Supply water piping 31 Supply water pump 32 Flow rate adjustment valve 33 Solenoid valve 34 Water level gauge 35 Return piping 36 Flow rate adjustment valve 37 Heat exchanger 38 Ion exchange resin 39 Filter 40 Bypass piping 41 Flow rate adjustment valve 42 Electromagnetic valve 45 Atmospheric pressure Total 46 Extraction piping 47 Gas filter 48 Pressure regulating valve 49 Pressure measuring instrument 50 Safety valve 51 Leak piping 52 Solenoid valve 53 Adjustment valve 54 Pressure release piping 55 Hydrogen concentration meter 56 Adjustment valve 57 Concentration measurement piping 60 Pressure absorber 66 Extraction piping 67 Gas Filter 68 Pressure regulating valve 70 Safety valve 71 Leak pipe 72 Electric Magnetic valve 73 Adjustment valve 74 Pressure release pipe 80 Pressure absorber 81 Flow path 85 Oxygen gas flow path 86 Pressure control valve

Claims (8)

A high-pressure hydrogen production system comprising a cell that performs water electrolysis, an oxygen-side storage tank that stores oxygen gas generated in the cell, and a hydrogen-side storage tank that stores hydrogen gas generated in the cell,
A high-pressure hydrogen production, characterized in that a deformable pressure absorber comprising a sealed container filled with a predetermined gas is provided in a gas layer portion in the oxygen-side storage tank and in the hydrogen-side storage tank. system. A high-pressure hydrogen production system comprising a cell that performs water electrolysis, an oxygen-side storage tank that stores oxygen gas generated in the cell, and a hydrogen-side storage tank that stores hydrogen gas generated in the cell,
In the oxygen side storage tank and the hydrogen side storage tank, a deformable pressure absorber filled with a predetermined gas is provided,
A high-pressure hydrogen production system, characterized in that a flow path is provided for communicating a pressure absorber provided in the oxygen-side storage tank and a pressure absorber provided in the hydrogen-side storage tank.   The pressure absorber provided in the oxygen side storage tank occupies a volume of 90% or more of a gas layer portion in the oxygen side storage tank in a normal pressure no-load state. 2. The high-pressure hydrogen production system according to 2.   The pressure absorber provided in the hydrogen side storage tank occupies a volume of 90% or more of a gas layer portion in the hydrogen side storage tank in a normal pressure no-load state. 4. The high-pressure hydrogen production system according to any one of 3.   When the differential pressure between the oxygen side storage tank and the hydrogen side storage tank is 0, the pressure is provided in the hydrogen side storage tank compared to the volume of the pressure absorber provided in the oxygen side storage tank. The high-pressure hydrogen production system according to claim 1, wherein the pressure absorber has a volume of 1.6 to 2 times.   The pressure absorber provided in the oxygen-side storage tank and the pressure absorber provided in the hydrogen-side storage tank are formed of a metal bellows or a polymer film. The high-pressure hydrogen production system according to any one of the above.   The predetermined gas sealed in the pressure absorber provided in the oxygen-side storage tank and the pressure absorber provided in the hydrogen-side storage tank is nitrogen gas. The high-pressure hydrogen production system according to any one of the above. The pressure absorber provided in the oxygen side storage tank and the pressure absorber provided in the hydrogen side storage tank are formed of a polymer film,
The predetermined gas sealed in the pressure absorber provided in the oxygen side storage tank and the pressure absorber provided in the hydrogen side storage tank is oxygen gas in the oxygen side storage tank. The high-pressure hydrogen production system according to any one of claims 1 to 5.

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