JP2012219276A - Water electrolysis system and method for controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably detect a failure in a back pressure valve provided in a water drainage line in a gas-liquid separator with a simple, economical structure through a simple, economical step.SOLUTION: A water electrolysis system 10 includes: a water electrolysis apparatus 12 that electrolyzes water to generate oxygen and high-pressure hydrogen having a pressure higher than the oxygen; the gas-liquid separator 22 that is provided in a high-pressure hydrogen pipe 20 for discharging the high-pressure hydrogen from the water electrolysis apparatus 12 and separates the water from the high-pressure hydrogen; and the water drainage line 26 for discharging the water from the gas-liquid separator 22. The water drainage line 26 is provided with the back pressure valve 94, a pressure-reducing valve 96, a pressure-detecting sensor 100 and a solenoid valve 98. The water electrolysis system 10 includes a failure detector 102 that detects a failure in the back pressure valve 94 by detecting pressure in the water drainage line 26 when performing decompression by opening the solenoid valve 98 after stopping the electrolysis.

Description

  The present invention is provided in a water electrolysis apparatus that electrolyzes water to generate oxygen and high-pressure hydrogen having a pressure higher than that of oxygen, and a hydrogen pipe that discharges the high-pressure hydrogen from the water electrolysis apparatus, A gas-liquid separator that separates water contained in the gas, a high-pressure hydrogen lead-out line that leads out the high-pressure hydrogen from which water has been separated from the gas-liquid separator, and a drainage line that discharges water from the gas-liquid separator The present invention relates to a water electrolysis system provided and a control method thereof.

  Generally, hydrogen is used as a fuel gas used for a power generation reaction of a fuel cell. This hydrogen is produced by, for example, a water electrolysis device. The water electrolysis apparatus uses a solid polymer electrolyte membrane (ion exchange membrane) in order to decompose water and generate hydrogen (and oxygen). Electrode catalyst layers are provided on both sides of the solid polymer electrolyte membrane to form an electrolyte membrane / electrode structure, and power supply bodies are disposed on both sides of the electrolyte membrane / electrode structure to provide unit cells. Is configured.

  Therefore, a cell unit in which a plurality of unit cells are stacked is supplied with voltage at both ends in the stacking direction, and water is supplied to the anode-side power feeding body. For this reason, water is decomposed and hydrogen ions (protons) are generated on the anode side of the electrolyte membrane / electrode structure, and the hydrogen ions permeate the solid polymer electrolyte membrane and move to the cathode side to bond with electrons. Thus, hydrogen is produced. On the other hand, on the anode side, oxygen generated together with hydrogen is discharged from the cell unit together with excess water.

  In the above water electrolysis apparatus, moisture-containing hydrogen is produced, and it is necessary to remove moisture from the hydrogen in order to obtain a dry state, for example, hydrogen having a moisture content of 5 ppm or less (hereinafter also referred to as dry hydrogen). There is.

  At that time, in a high-pressure hydrogen production apparatus in which hydrogen at a pressure higher than oxygen (for example, 1 MPa or more) is obtained on the cathode side, there is a problem that a gas-liquid separation apparatus for removing moisture from the high-pressure hydrogen becomes large.

  Therefore, for example, a hydrogen generation system disclosed in Patent Document 1 is known. As shown in FIG. 5, this hydrogen generation system includes a water electrolysis apparatus 1 that produces high-pressure hydrogen by electrolyzing water, and a gas-liquid separation apparatus 2 that removes water contained in the high-pressure hydrogen. ing.

  A drain line 4 is connected to the first gas-liquid separator 3 constituting the gas-liquid separator 2, and a pressure reducing valve 5, an electromagnetic valve 6, and a throttle 7 are connected to the drain line 4 in the drain flow direction. Are arranged sequentially.

  High-pressure hydrogen containing water vapor generated by the water electrolysis apparatus 1 is sent to the first gas-liquid separator 3 via the hydrogen lead-out path 8. In the first gas-liquid separator 3, water vapor contained in hydrogen is separated from the hydrogen and returned to the drain line 4, while the hydrogen can be supplied to the hydrogen line 9.

  Therefore, when the water level of the first gas-liquid separator 3 reaches the highest water level, the electromagnetic valve 6 is opened, so that the water in the gas-liquid separator 3 is discharged from the drain line 4 to the pure water supply device. ing. At that time, the pressure reducing valve 5 is set so that the secondary pressure is maintained at atmospheric pressure, and water discharged from the first gas-liquid separator 3 at a high pressure is normal pressure by the pressure reducing valve 5. The pressure is reduced until it is discharged.

JP 2009-191333 A

  By the way, in the above hydrogen generation system, the drain line 4 is provided with a pressure reducing valve 5 in order to reduce the pressure of 35 MPa to 0.5 MPa, for example. Therefore, if the pressure reducing valve 5 fails, the pressure of the high-pressure first gas-liquid separator 3 may not be stably maintained.

  The present invention solves this type of problem, and it is possible to reliably detect a failure of the back pressure valve disposed in the drain line of the gas-liquid separator with a simple and economical configuration and process. An object of the present invention is to provide a water electrolysis system and a control method thereof.

  The present invention is provided in a water electrolysis apparatus that electrolyzes water to generate oxygen and high-pressure hydrogen having a pressure higher than that of oxygen, and a hydrogen pipe that discharges the high-pressure hydrogen from the water electrolysis apparatus, A gas-liquid separator that separates water contained in the gas, a high-pressure hydrogen lead-out line that leads out the high-pressure hydrogen from which water has been separated from the gas-liquid separator, and a drainage line that discharges water from the gas-liquid separator The present invention relates to a water electrolysis system provided and a control method thereof.

  In this water electrolysis system, a back pressure valve, a pressure reducing valve, a pressure sensor, and a solenoid valve are sequentially arranged in the drainage line from upstream to downstream, and the water electrolysis system opens the solenoid valve after electrolysis is stopped. When performing depressurization, a failure detection device is provided for detecting a failure of the back pressure valve by detecting the pressure of the drainage line.

  In this water electrolysis system, it is preferable that the failure detection device detects the failure of the back pressure valve by detecting the pressure of the drainage line in a state where the electromagnetic valve is closed after depressurization.

  Furthermore, this control method generates high-pressure hydrogen by a water electrolysis device, and also performs an electrolysis step of separating moisture contained in the high-pressure hydrogen by a gas-liquid separation device, and opens a solenoid valve after electrolysis is stopped to release pressure. And a step of detecting the pressure of the drainage line, and a step of determining that the back pressure valve is faulty when the pressure of the drainage line does not decrease within a set time.

  Furthermore, this control method includes a step of closing the solenoid valve when the pressure of the drain line falls within a set time, and a back pressure valve when the pressure of the drain line is increased after the solenoid valve is closed. It is preferable to have a step of determining that it is a failure.

  According to the present invention, when the depressurization is performed by opening the solenoid valve after the electrolysis is stopped, the pressure of the drain line is detected. At that time, since the solenoid valve is opened, if the back pressure valve maintains the pressure on the gas-liquid separator side well, the pressure in the drain line downstream of the back pressure valve decreases. .

  Therefore, when the pressure in the drainage line does not decrease within the set time, it is determined that drainage leakage (pressure leak) is caused from the back pressure valve, and a failure of the back pressure valve is detected. This makes it possible to reliably detect a failure of the back pressure valve disposed in the drain line of the gas-liquid separator with a simple and economical configuration and process.

It is a schematic structure explanatory view of a water electrolysis system concerning an embodiment of the present invention. It is a flowchart explaining the control method which concerns on embodiment of this invention. It is explanatory drawing of the mass leak detection of a back pressure valve in the said control method. In the control method, it is the explanation drawing of the minute leak detection of the back pressure valve. 2 is an explanatory diagram of a hydrogen generation system disclosed in Patent Document 1. FIG.

  As shown in FIG. 1, the water electrolysis system 10 according to the first embodiment of the present invention electrolyzes water (pure water) to generate oxygen and high-pressure hydrogen (higher than normal-pressure oxygen pressure, for example, 1 to 70 MPa hydrogen) and a water reservoir for separating the oxygen and excess water discharged from the water electrolyzer 12 and storing the water An apparatus 14, a water circulation apparatus 16 for circulating the water stored in the water storage apparatus 14 to the water electrolysis apparatus 12, and a water supply apparatus for supplying pure water generated from city water to the water storage apparatus 14 18, a gas-liquid separator 22 that removes moisture contained in the high-pressure hydrogen led out from the water electrolyzer 12 to the high-pressure hydrogen pipe 20, and the high-pressure hydrogen from which water has been separated from the gas-liquid separator 22 High pressure to derive It comprises a hydrogen outlet line 24, a drain line 26 for discharging a high-pressure water from the gas-liquid separator 22, a controller (control unit) 28.

  The water electrolysis apparatus 12 includes a cell unit in which a plurality of unit cells 30 are stacked. At one end in the stacking direction of the unit cells 30, a terminal plate 32a, an insulating plate 34a, and an end plate 36a are sequentially arranged outward. Similarly, a terminal plate 32b, an insulating plate 34b, and an end plate 36b are sequentially disposed on the other end in the stacking direction of the unit cells 30 toward the outside. The end plates 36a and 36b are integrally clamped and held.

  Terminal portions 38a and 38b are provided on the side portions of the terminal plates 32a and 32b so as to protrude outward. The terminal portions 38a and 38b are electrically connected to the electrolytic power source 40 via the wirings 39a and 39b.

  The unit cell 30 includes a disk-shaped electrolyte membrane / electrode structure 42, and an anode-side separator 44 and a cathode-side separator 46 that sandwich the electrolyte membrane / electrode structure 42. The anode side separator 44 and the cathode side separator 46 have a disk shape.

  The electrolyte membrane / electrode structure 42 includes, for example, a solid polymer electrolyte membrane 48 in which a perfluorosulfonic acid thin film is impregnated with water, and an anode-side power feeder 50 and a cathode provided on both surfaces of the solid polymer electrolyte membrane 48. Side power supply body 52.

  An anode electrode catalyst layer 50 a and a cathode electrode catalyst layer 52 a are formed on both surfaces of the solid polymer electrolyte membrane 48. The anode electrode catalyst layer 50a uses, for example, a Ru (ruthenium) -based catalyst, while the cathode electrode catalyst layer 52a uses, for example, a platinum catalyst.

  A water supply communication hole 56 for supplying water (pure water) to each other in the stacking direction, and oxygen generated by the reaction and unreacted water are discharged to the outer peripheral edge of the unit cell 30. The discharge communication hole 58 and the hydrogen communication hole 60 for flowing hydrogen generated by the reaction are provided.

  The water circulation device 16 includes a circulation pipe 72 that communicates with the water supply communication hole 56 of the water electrolysis device 12, and the circulation pipe 72 includes a circulation pump 74 and an ion exchanger 76 that constitute a water storage device 14. Connected to the bottom of section 78.

  One end portion of the return pipe 80 communicates with the upper portion of the tank portion 78, and the other end of the return pipe 80 communicates with the discharge communication hole 58 of the water electrolysis apparatus 12. One end of the return pipe 80 is set to a position that always opens in the water stored in the tank portion 78.

  A pure water supply pipe 84 connected to the water supply device 18 and an oxygen exhaust pipe 86 for discharging oxygen separated from the pure water in the tank section 78 are connected to the tank section 78.

  One end of the high-pressure hydrogen pipe 20 is connected to the hydrogen communication hole 60 of the water electrolysis apparatus 12, and the other end of the high-pressure hydrogen pipe 20 is connected to the gas-liquid separator 22 via a check valve 87. . The high-pressure hydrogen from which moisture has been removed by the gas-liquid separator 22 is led out to the high-pressure hydrogen lead-out line 24 as dry hydrogen. The high-pressure hydrogen lead-out line 24 is provided with a first back pressure valve 88 set at a first set pressure value (for example, 35 MPa).

  The gas-liquid separator 22 includes a tank unit 90 for storing water. The tank unit 90 is provided with a water level detection unit, for example, a water level detection sensor 92 that detects whether or not the water level WS in the tank unit 90 is a set height. A detection signal from the water level detection sensor 92 is input to the controller 28.

  A drain line 26 is connected to the lower part of the gas-liquid separator 22. A drain valve 26 is connected to the drain line 26 by a second back pressure valve 94, a pressure reducing valve 96, and an electromagnetic valve 98 that opens and closes in response to an open / close signal from the controller 28. Arranged along the flow direction. A pressure detection sensor 100 is disposed in the drain line 26 between the pressure reducing valve 96 and the electromagnetic valve 98.

  The second back pressure valve 94 is set to a second set pressure (for example, 34 MPa) that is lower than the first set pressure (for example, 35 MPa) of the first back pressure valve 88. The pressure reducing valve 96 is set to reduce the primary pressure (for example, 34 MPa) to a predetermined secondary pressure (for example, 1.0 MPa).

  The controller 28 has a function as the failure detection device 102 that detects the failure of the second back pressure valve 94 by detecting the pressure of the drainage line 26 when the electromagnetic valve 98 is opened to release pressure after the electrolysis is stopped.

  The operation of the water electrolysis system 10 configured as described above will be described below along the flowchart shown in FIG. 2 in relation to the control method according to the present embodiment.

  First, electrolysis by the water electrolysis system 10 is started (step S1). As shown in FIG. 1, pure water generated from city water via the water supply device 18 is supplied to a tank unit 78 that constitutes the water storage device 14.

  In the water circulation device 16, the water in the tank unit 78 is supplied to the water supply communication hole 56 of the water electrolysis device 12 through the circulation pipe 72 under the action of the circulation pump 74. On the other hand, a voltage is applied to the terminal portions 38a and 38b of the terminal plates 32a and 32b via the electrolytic power supply 40 that is electrically connected.

  Therefore, in each unit cell 30, water is supplied from the water supply communication hole 56 to the first flow path 64 of the anode side separator 44, and this water moves along the anode side power supply body 50. Therefore, water is decomposed by electricity in the anode electrode catalyst layer 50a, and hydrogen ions, electrons, and oxygen are generated. Hydrogen ions generated by this anodic reaction permeate the solid polymer electrolyte membrane 48 and move to the cathode electrode catalyst layer 52a side, and combine with electrons to obtain hydrogen.

  Thereby, hydrogen flows along the second flow path 68 formed between the cathode-side separator 46 and the cathode-side power feeder 52. This hydrogen is maintained at a higher pressure than the water supply communication hole 56 and can flow out of the water electrolysis apparatus 12 through the hydrogen communication hole 60.

  On the other hand, oxygen generated by the reaction and unreacted water flow through the first flow path 64, and these mixed fluids are discharged to the return pipe 80 of the water circulation device 16 along the discharge communication hole 58. The After the unreacted water and oxygen are introduced into the tank section 78 and separated, the water is introduced from the circulation pipe 72 through the ion exchanger 76 into the water supply communication hole 56 via the circulation pump 74. . Oxygen separated from the water is discharged to the outside from the oxygen exhaust pipe 86.

  The hydrogen generated in the water electrolysis device 12 is sent to the gas-liquid separation device 22 via the high-pressure hydrogen pipe 20. In the gas-liquid separator 22, water vapor (water) contained in hydrogen is separated from the hydrogen and stored in the tank unit 90, while the hydrogen is led out to the high-pressure hydrogen lead line 24 (electrolysis step). .

  The tank unit 90 includes a water level detection sensor 92 for detecting whether or not the water level WS in the tank unit 90 is a set height. When the controller 28 determines through the water level detection sensor 92 that the water level WS has been lowered to the set lower position, the controller 28 instructs the stop of drainage from the tank unit 90 to the drainage line 26. That is, the electromagnetic valve 98 is closed. On the other hand, when the controller 28 determines that the water level WS has risen to the set upper position, the controller 28 opens the electromagnetic valve 98 and instructs the drainage line 26 to drain.

  Next, when the electrolysis operation by the water electrolysis apparatus 12 is stopped (YES in step S2), the process proceeds to step S3, and the electromagnetic valve 98 is opened. For this reason, the water in the tank part 90 is drained through the drainage line 26, so that the pressure on the cathode side, which is the high-pressure side of the water electrolysis device 12, is released.

  At that time, the controller 28 detects the drain pressure on the downstream side of the pressure reducing valve 96 via the pressure detection sensor 100 disposed in the drain line 26 at a position downstream of the pressure reducing valve 96. When it is determined that the detected pressure is maintained at a constant pressure without being reduced (NO in step S4), the process proceeds to step S5. If it is determined in step S5 that the pressure is maintained for a predetermined time T or longer (YES in step S5), the process proceeds to step S6.

  In step S6, as shown in FIG. 3, no pressure drop is caused over a predetermined time T although the electromagnetic valve 98 is opened. For this reason, it is determined that a failure has occurred in the second back pressure valve 94, and an alarm is displayed.

  If the pressure on the gas-liquid separator 22 side is maintained by the second back pressure valve 94, the waste water is sent to the downstream side of the second back pressure valve 94 at a pressure of the second set pressure (for example, 34 MPa), Further, the pressure is reduced to, for example, 1.0 MPa by the pressure reducing valve 96 and drained. That is, if the second back pressure valve 94 is functioning normally, the pressure on the downstream side of the second back pressure valve 94 is reduced from 34 MPa by the pressure reducing valve 96, and the pressure detected by the pressure detection sensor 100 decreases. appear.

  Therefore, if the pressure in the drainage line 26 does not decrease within the predetermined time T, it is determined that drainage leakage (pressure leakage) is caused from the second back pressure valve 94, and a relatively large amount of drainage leakage occurs. May occur. For this reason, after the back pressure valve failure alarm is made (step S6), the process proceeds to step S7, and the system is completely stopped with the electromagnetic valve kept open (step S8).

  In step S7, the electromagnetic valve 98 is maintained in the open state because a large amount of drainage leakage may be caused from the second back pressure valve 94, and it is necessary to protect the electromagnetic valve 98. is there.

  On the other hand, if it is determined in step S3 that the pressure drop in the drainage line 26 is caused after the solenoid valve 98 is opened (YES in step S4), the process proceeds to step S9, where the solenoid valve 98 is turned on. Blocked. Further, after the system is stopped (step S10), it is determined whether or not the pressure in the drain line 26 has increased during the system stop period (step S11).

  As shown in FIG. 4, if the pressure in the drainage line 26 increases during the system stop period (YES in step S11), it is determined that a slight drainage leak is caused from the second back pressure valve 94. Therefore, after the back pressure valve failure alarm is made (step S12), the process proceeds to step S8, where the system is completely stopped.

  If it is determined that there is no pressure increase during the system stop period (NO in step S11), the process proceeds to step S13 to determine whether or not an instruction to start the system is given. When the system is activated (YES in step S13), the process returns to step S1 to start electrolysis. On the other hand, when the system is not activated (NO in step S13), the control process is terminated.

  In this case, in this embodiment, after the electrolysis is stopped, when the electromagnetic valve 98 is opened and the water electrolysis apparatus 12 is depressurized, the pressure detection disposed in the drain line 26 downstream of the pressure reducing valve 96. The pressure of the drain line 26 is detected via the sensor 100. At that time, if the pressure of the drain line 26 does not decrease within a predetermined time T, it is determined that the drainage of the drainage is caused from the second back pressure valve 94, and the failure of the second back pressure valve 94 is detected. Has been.

  Thereby, the failure of the second back pressure valve 94 arranged in the drain line 26 of the gas-liquid separator 22 can be reliably detected using an existing device without using a dedicated facility. For this reason, there is an effect that the quality of the second back pressure valve 94 can be accurately determined with a simple and economical configuration and process.

  Furthermore, in this embodiment, as shown in FIG. 4, when the pressure of the drainage line 26 drops after the solenoid valve 98 is opened, the solenoid valve 98 is closed and the system is stopped. During this system stop period, the pressure of the drainage line 26 is detected, and when the pressure of the drainage line 26 increases, it is determined that the second back pressure valve 94 is in failure. Therefore, a slight leak from the second back pressure valve 94 can be reliably detected with a simple and economical configuration and process.

DESCRIPTION OF SYMBOLS 10 ... Water electrolysis system 12 ... Water electrolysis apparatus 14 ... Water storage apparatus 16 ... Water circulation apparatus 18 ... Water supply apparatus 20 ... High-pressure hydrogen piping 22 ... Gas-liquid separation apparatus 24 ... High-pressure hydrogen derivation line 26 ... Drain line 28 ... Controller 30 ... Unit cell 42 ... electrolyte membrane / electrode structure 44 ... anode side separator 46 ... cathode side separator 48 ... solid polymer electrolyte membrane 50 ... anode side power supply body 52 ... cathode side power supply body 56 ... water supply communication hole 58 ... discharge communication hole DESCRIPTION OF SYMBOLS 60 ... Hydrogen communication hole 88, 94 ... Back pressure valve 90 ... Tank part 92 ... Water level detection sensor 96 ... Pressure reducing valve 98 ... Solenoid valve 100 ... Pressure detection sensor 102 ... Failure detection apparatus

Claims (4)

A water electrolysis device that electrolyzes water to generate oxygen and high-pressure hydrogen that is higher in pressure than the oxygen;
A gas-liquid separator that is disposed in a hydrogen pipe that discharges the high-pressure hydrogen from the water electrolyzer and separates water contained in the high-pressure hydrogen;
A high-pressure hydrogen outlet line for extracting the high-pressure hydrogen from which water has been separated from the gas-liquid separator;
A drain line for discharging water from the gas-liquid separator;
A water electrolysis system comprising:
In the drainage line, a back pressure valve, a pressure reducing valve, a pressure sensor and a solenoid valve are sequentially arranged from upstream to downstream,
The water electrolysis system includes a failure detection device that detects a failure of the back pressure valve by detecting the pressure of the drainage line when the solenoid valve is opened to release pressure after electrolysis is stopped. Water electrolysis system.   The water electrolysis system according to claim 1, wherein the failure detection device detects a failure of the back pressure valve by detecting a pressure of the drainage line in a state in which the electromagnetic valve is closed after depressurization. Water electrolysis system. A water electrolysis device that electrolyzes water to generate oxygen and high-pressure hydrogen that is higher in pressure than the oxygen;
A gas-liquid separator that is disposed in a hydrogen pipe that discharges the high-pressure hydrogen from the water electrolyzer and separates water contained in the high-pressure hydrogen;
A high-pressure hydrogen outlet line for extracting the high-pressure hydrogen from which water has been separated from the gas-liquid separator;
A drain line for discharging water from the gas-liquid separator;
With
The drainage line is a control method for a water electrolysis system in which a back pressure valve, a pressure reducing valve, a pressure sensor and a solenoid valve are sequentially arranged from upstream to downstream,
An electrolysis step of generating high-pressure hydrogen by the water electrolyzer, and separating water contained in the high-pressure hydrogen by the gas-liquid separator;
Opening the solenoid valve after the electrolysis is stopped, and depressurizing;
Detecting the pressure of the drain line;
Determining that the back pressure valve is faulty when the pressure in the drain line does not decrease within a set time;
A method for controlling a water electrolysis system comprising: The control method according to claim 3, wherein when the pressure of the drainage line falls within a set time, the electromagnetic valve is closed.
Determining that the back pressure valve is faulty when the pressure in the drainage line is increased after the solenoid valve is closed;
A method for controlling a water electrolysis system comprising:

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