JP6090862B2 - Starting method of water electrolyzer - Google Patents

Description

  In the present invention, a power feeding body is provided on both sides of the electrolyte membrane, and by applying an electrolytic current between the power feeding bodies, water is electrolyzed to generate oxygen on the anode side, while the cathode side has more oxygen than the oxygen. The present invention relates to a method for starting a water electrolysis apparatus that generates high-pressure hydrogen.

  In general, hydrogen gas is used as a fuel gas for generating power from a fuel cell. Hydrogen gas is manufactured by, for example, a water electrolysis system incorporating a water electrolysis device. The water electrolysis apparatus uses a solid polymer electrolyte membrane (ion exchange membrane) in order to electrolyze water and generate hydrogen (and oxygen). Electrode catalyst layers are provided on both sides of the electrolyte membrane to form an electrolyte membrane / electrode structure, and a power cell is provided on each side of the electrolyte membrane / electrode structure to form a unit cell. Has been.

  In a state where a plurality of unit cells are stacked, a voltage is applied to both ends in the stacking direction, and water is supplied to the anode side. For this reason, on the anode side of the electrolyte membrane / electrode structure, water is decomposed to generate hydrogen ions (protons). The hydrogen ions permeate the electrolyte membrane and move to the cathode side, and combine with electrons to form hydrogen. Is manufactured. On the other hand, on the anode side, oxygen produced together with hydrogen ions is discharged from the unit with excess water.

  In the water electrolysis apparatus, a high-pressure hydrogen production apparatus (differential pressure type water electrolysis apparatus) that generates high-pressure (generally 1 MPa or more) hydrogen on the cathode side may be employed. In this high-pressure hydrogen production apparatus, high-pressure hydrogen is filled in the fluid passage of the cathode-side separator across the electrolyte membrane, while atmospheric water and oxygen are present in the fluid passage of the anode-side separator. Therefore, when the operation is stopped (end of supply of generated hydrogen), it is necessary to remove the pressure difference between both sides of the electrolyte membrane in order to protect the electrolyte membrane.

  Therefore, for example, a method for stopping the operation of a water electrolysis apparatus disclosed in Patent Document 1 is known. This operation stopping method includes a step of applying a voltage after the supply of hydrogen from the cathode-side electrolysis chamber is stopped, and a step of depressurizing at least the cathode-side electrolysis chamber in a state where the voltage is applied. ing. Thereby, since the hydrogen leaked from the cathode side to the anode side is returned to the cathode side by the hydrogen film pump effect, the retention of the leaked high-pressure hydrogen can be suppressed, and the deterioration of the catalyst electrode due to hydrogen can be prevented. It is said.

JP 2010-236089 A

  By the way, in the above-described high-pressure hydrogen production apparatus, it may be difficult to apply an electrolytic current when an abnormality occurs and an emergency stop occurs. At that time, when the reduced pressure treatment (hereinafter also referred to as electroless reduced pressure treatment) is performed without applying the electrolytic current, the moisture content of the electrolyte membrane is larger than that when the electrolytic current is applied (hereinafter also referred to as electrolytic reduced pressure treatment). The state will be different. Specifically, in the electroless decompression process, there is a problem that the electrolyte membrane is easily dried and the electrolyte membrane is deteriorated at the next start-up.

  The present invention solves this type of problem, and even when an electroless decompression process is performed, the electrolyte membrane is not activated in a dry state, and the deterioration of the electrolyte membrane is prevented. An object of the present invention is to provide a method for starting up a water electrolysis apparatus capable of performing differential pressure water electrolysis.

  In the water electrolysis apparatus to which the starting method according to the present invention is applied, a power feeding body is provided on both sides of the electrolyte membrane, and by applying an electrolysis current between the power feeding bodies, water is electrolyzed and oxygen is supplied to the anode side. Is generated. On the other hand, hydrogen having a pressure higher than that of oxygen is generated on the cathode side.

  This activation method includes a step of determining whether or not at least the cathode side pressure reduction has been performed while applying the pressure reducing electrolytic current when the water electrolysis apparatus was stopped last time. This starting method has a step of circulating water through the water electrolysis device before starting application of the electrolysis current at the time of starting.

Then, when the vacuum while applying a previous stop at reduced pressure for electrolysis current water electrolysis apparatus is judged to have been carried out, the electrolyte were allowed to start the circulation of water to the water electrolysis device to the current startup If setting the first waiting time until it starts applying current, previous the decompression during the pressure reducing electrolysis current has an applied to stop the water electrolysis apparatus is determined to have been performed, the current is set to be longer than the water electrolysis device said circulation of water to initiate the electroless the first waiting time and the second waiting time until it starts applying current from the startup.

In addition, this activation method preferably includes a step of storing the time required for depressurization when the water electrolysis apparatus was stopped last time. At this time, it is preferable to set the second waiting time until the application of the electrolytic current is started longer as the time required for depressurization is longer.

  Furthermore, this starting method preferably includes a step of gradually increasing the electrolytic current applied at the time of starting. At that time, when it is determined that the application of the electrolysis current for decompression is not performed during decompression, the time for increasing the electrolysis current to the rated current value is set to the time when the electrolysis current for decompression is applied during decompression. It is preferable to set the electrolytic current longer than the time for raising the electrolytic current to the rated current value.

Furthermore, this starting method preferably includes a step of measuring the impedance value of the electrolyte membrane. At that time, the higher the measured impedance value, the longer the second waiting time until the application of the electrolytic current starts.

According to the present invention, when the electrolytic reduced pressure treatment is performed, a first waiting time from to initiate the circulation of water to the water electrolysis device until it starts to apply the electrolytic current is set. Meanwhile, when the electroless decompression process is performed, a second waiting time has to start circulation of water into the water electrolysis device until it starts to apply the electrolytic current is set. The second standby time is set longer than the first standby time. For this reason, the electrolyte membrane in which moisture tends to be insufficient due to the electroless decompression process has a longer water circulation time than after the electrolytic decompression process, and is well humidified (hydrated).

  Therefore, even when the electroless decompression process is performed, the electrolyte membrane is not activated in a dry state. Thereby, deterioration of the electrolyte membrane can be prevented and good differential water electrolysis can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS It is schematic structure explanatory drawing of the water electrolysis apparatus to which the starting method which concerns on the 1st Embodiment of this invention is applied. In the said starting method, it is explanatory drawing of each waiting time when the last pressure reduction process is an electrolytic pressure reduction process and an electroless pressure reduction process. In the starting method, it is an explanatory view of the relationship between the decompression time and the standby time. It is explanatory drawing when the application rate of an electrolysis current is changed in the said starting method. It is schematic structure explanatory drawing of the water electrolysis apparatus to which the starting method which concerns on the 2nd Embodiment of this invention is applied.

  As shown in FIG. 1, the water electrolysis apparatus 10 to which the start-up method according to the first embodiment of the present invention is applied has oxygen (normal pressure) and higher pressure than oxygen by electrolyzing water (pure water). A differential pressure type water electrolysis mechanism 12 for producing pure hydrogen (high pressure hydrogen) is provided.

  The water electrolysis apparatus 10 is supplied with water (pure water) generated from city water via a pure water supply mechanism 14, and supplies the water to the differential pressure water electrolysis mechanism 12, and the differential pressure water electrolysis mechanism 12. A water circulation mechanism 16 that circulates and supplies the excess water discharged from the water to the differential pressure water electrolysis mechanism 12. The water electrolysis apparatus 10 includes a high-pressure hydrogen pipe 18 that leads high-pressure hydrogen from the differential-pressure water electrolysis mechanism 12 and a controller (control unit) 20.

  The differential pressure type water electrolysis mechanism 12 constitutes a differential pressure type high pressure hydrogen production apparatus (cathode side pressure> anode side pressure), and a plurality of unit cells 24 are stacked. At one end of the unit cells 24 in the stacking direction, a terminal plate 26a, an insulating plate 28a, and an end plate 30a are sequentially disposed outward. Similarly, a terminal plate 26b, an insulating plate 28b, and an end plate 30b are sequentially disposed on the other end in the stacking direction of the unit cells 24 toward the outside. The end plates 30a and 30b are integrally clamped and held.

  Terminal portions 34a and 34b are provided on the side portions of the terminal plates 26a and 26b so as to protrude outward. The terminal portions 34a and 34b are electrically connected to the electrolytic power source 38 via the wirings 36a and 36b. The terminal part 34 a on the anode (anode) side is connected to the positive electrode of the electrolytic power supply 38, while the terminal part 34 b on the cathode (cathode) side is connected to the negative electrode of the electrolytic power supply 38.

  The unit cell 24 includes an 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 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 is formed on one surface of the solid polymer electrolyte membrane 48, and a cathode electrode catalyst layer is formed on the other surface of the solid polymer electrolyte membrane.

  A water supply communication hole 56 for supplying water (pure water) to each other in the stacking direction is provided at the outer peripheral edge of the unit cell 24. A discharge communication hole 58 for discharging oxygen generated by the reaction and unreacted water (mixed fluid) and a hydrogen communication hole 60 for flowing hydrogen generated by the reaction are provided at the outer peripheral edge of the unit cell 24. And are provided.

  A surface of the anode separator 44 facing the electrolyte membrane / electrode structure 42 is provided with a first flow path (anode side electrolytic chamber) 64 communicating with the water supply communication hole 56 and the discharge communication hole 58. In the first flow path 64, oxygen generated by the reaction and unreacted water flow. A second flow path (cathode side electrolytic chamber) 68 communicating with the hydrogen communication hole 60 is formed on the surface of the cathode side separator 46 facing the electrolyte membrane / electrode structure 42. High-pressure hydrogen generated by the reaction flows through the second flow path 68.

  The water circulation mechanism 16 includes a circulation pipe 72 that communicates with the water supply communication hole 56 of the differential pressure type water electrolysis mechanism 12, and a circulation pump 74, an ion exchanger 76, and a gas-liquid separator 78 are disposed in the circulation pipe 72. Is done.

  One end portion of the return pipe 80 communicates with the upper portion of the gas-liquid separator 78, and the other end portion of the return pipe 80 communicates with the discharge communication hole 58 of the differential pressure water electrolysis mechanism 12. The gas / liquid separator 78 is connected to a pure water supply pipe 82 connected to the pure water supply mechanism 14 and an oxygen exhaust pipe 84 for discharging oxygen separated from the pure water by the gas / liquid separator 78. Is done.

  A high-pressure hydrogen pipe 18 is connected to the hydrogen communication hole 60 of the differential pressure water electrolysis mechanism 12, and the high-pressure hydrogen pipe 18 is connected to a hydrogen supply unit (for example, via a check valve 86 and a back pressure valve (not shown)). Connected to a hydrogen tank). A decompression pipe 88 branches from the high-pressure hydrogen pipe 18, and a decompression valve 90 and a variable valve 92 are provided in the decompression pipe 88.

  The operation of the water electrolysis apparatus 10 configured as described above will be described below.

  First, during the start-up operation of the water electrolysis apparatus 10, pure water generated from city water (hereinafter simply referred to as water) is supplied to the gas-liquid separator 78 constituting the water circulation mechanism 16 through the pure water supply mechanism 14. The In the water circulation mechanism 16, water is supplied to the water supply communication hole 56 of the differential pressure type water electrolysis mechanism 12 through the circulation pipe 72 under the action of the circulation pump 74. On the other hand, an electrolytic current (electrolytic voltage) is applied to the terminal portions 34a and 34b of the terminal plates 26a and 26b through an electrically connected electrolytic power source 38.

  For this reason, in each unit cell 24, 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 to generate hydrogen ions, electrons and oxygen. Hydrogen ions generated by this anodic reaction permeate the solid polymer electrolyte membrane 48 and move to the cathode 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 pressure higher than that of the water supply communication hole 56, and can flow out of the differential pressure type water electrolysis mechanism 12 through the hydrogen communication hole 60 and through the high-pressure hydrogen pipe 18.

  On the other hand, oxygen generated by the reaction and used water flow through the first flow path 64, and these mixed fluids are discharged to the return pipe 80 of the water circulation mechanism 16 along the discharge communication hole 58. The After this used water and oxygen are introduced into the gas-liquid separator 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. Is done. Oxygen separated from the water is discharged to the outside from the oxygen exhaust pipe 84.

  Next, when the electrolysis operation of the water electrolysis apparatus 10 is stopped, the controller 20 starts the depressurization process of the differential pressure type water electrolysis mechanism 12. Specifically, the pressure release valve 90 is opened, and the pressure release pipe 88 communicates with the hydrogen communication hole 60. For this reason, the high-pressure hydrogen filled in the cathode-side second flow path 68 is gradually decompressed by adjusting the opening of the variable valve 92.

  At that time, an electrolysis current lower than the above electrolysis current (hereinafter, also referred to as an electrolysis pressure reducing pressure) is applied by the electrolysis power supply 38 (electrolytic pressure reduction treatment). The electrolytic current for decompression is set to, for example, the minimum current value that can obtain the membrane pump effect.

  When the hydrogen pressure in the second flow path 68 becomes the same as the pressure (normal pressure) in the first flow path 64, voltage application by the electrolytic power supply 38 is stopped. Thereby, the operation of the water electrolysis apparatus 10 is stopped.

  Next, a starting method for the water electrolysis apparatus 10 according to the first embodiment of the present invention will be described.

  First, when a start signal (for example, an ignition switch) is input (turned on), the controller 20 before the start operation (startup) of the water electrolysis apparatus 10, that is, before starting application of the electrolysis current, A process of circulating water through the differential pressure type water electrolysis mechanism 12 is performed. Specifically, the circulation pump 74 constituting the water circulation mechanism 16 is driven, and water is circulated and supplied to the differential pressure water electrolysis mechanism 12 via the circulation pipe 72.

  Here, the controller 20 determines whether the electrolytic depressurization process or the electroless depressurization process was performed when the water electrolysis apparatus 10 was stopped last time. The electroless depressurization process refers to a process of depressurizing without applying an electrolysis current when an abnormality occurs during operation of the water electrolysis apparatus 10 and the water electrolysis apparatus 10 is emergency stopped.

  When the controller 20 determines that the electrolytic depressurization process has been performed at the previous stop of the water electrolysis apparatus 10, the controller 20 quickly starts application of the electrolysis current after water is circulated and supplied to the differential pressure water electrolysis mechanism 12. As shown in FIG. 2, the electrolysis current An is applied at a time T2 that is set for a short waiting time ΔTa from the time T1 at which the supply of circulating water is started. The electrolysis current An is gradually increased to the rated current value As. Therefore, the water electrolysis operation by the water electrolysis apparatus 10 is started.

  On the other hand, when the controller 20 determines that the electroless decompression process has been performed when the water electrolysis apparatus 10 was stopped last time, the controller 20 has the standby time ΔTb longer than the standby time ΔTa, and the electrolytic current Aa is applied from the time T3. Is done. The electrolytic current Aa is gradually increased to the rated current value As. Thereby, the water electrolysis operation by the water electrolysis apparatus 10 is started.

  In this case, in the first embodiment, when the electrolytic pressure reduction process is performed at the previous stop, the standby time ΔTa from when the water circulation to the differential pressure type water electrolysis mechanism 12 is started until the electrolytic current An is applied. Is set. On the other hand, when the electroless pressure reduction process is performed at the previous stop, the waiting time ΔTb is set from the start of the water circulation to the differential pressure water electrolysis mechanism 12 until the electrolysis current Aa is applied. The standby time ΔTb is set longer than the standby time ΔTa.

  For this reason, by performing the electroless decompression process at the previous stop, the solid polymer electrolyte membrane 48 that is likely to be deficient in water has a longer water circulation time than when the electrolytic decompression process was performed at the previous stop. It is well humidified (containing water).

  Therefore, the solid polymer electrolyte membrane 48 is not activated in the dry state even when the electroless decompression process is performed at the previous stop. As a result, it is possible to obtain an effect of preventing the deterioration of the solid polymer electrolyte membrane 48 and performing a good differential pressure water electrolysis process.

  Further, the controller 20 can have a step of storing the time required for depressurization when the water electrolysis apparatus 10 was stopped last time. At this time, as shown in FIG. 3, the longer the time T required for depressurization, the longer the time for circulating water before starting application of the electrolysis current, that is, the standby time ΔT is set longer. For this reason, water can be circulated and fed well in accordance with the amount of water in the solid polymer electrolyte membrane 48, and quality can be improved.

  Furthermore, the controller 20 has a step of gradually increasing the electrolytic current applied at the time of startup. At that time, as shown in FIG. 4, when the electroless decompression process is performed at the previous decompression, the time during which the electrolytic current Aaa is increased to the rated current value As is equal to the electrolytic current An when the electrolytic decompression process is performed. Is set longer than the time required to increase the current to the rated current value As. That is, the rising angle of the electrolysis current Aaa is set smaller than the rising angle of the electrolysis current An.

  Therefore, the solid polymer electrolyte membrane 48 can be more reliably transferred from the dry state to the desired wet state, and the effect that the performance degradation of the differential pressure type water electrolysis mechanism 12 can be reliably suppressed can be obtained. It is done.

  FIG. 5 is a schematic configuration explanatory diagram of the water electrolysis apparatus 100 to which the activation method according to the second embodiment of the present invention is applied. In addition, the same referential mark is attached | subjected to the component same as the water electrolysis apparatus 10 which concerns on 1st Embodiment, and the detailed description is abbreviate | omitted.

  In the water electrolysis apparatus 100, the differential pressure type water electrolysis mechanism 12 is provided with an impedance measurement unit 102 that measures the moisture content of the electrolyte membrane / electrode structure 42 (solid polymer electrolyte membrane 48). The impedance measuring unit 102 measures the resistance value of the electrolyte membrane / electrode structure 42, and it is detected that the water content of the solid polymer electrolyte membrane 48 decreases as the measured resistance value increases. The

  In the second embodiment, the impedance measuring unit 102 measures the resistance value of the electrolyte membrane / electrode structure 42, and the resistance value is sent to the controller 20. In the controller 20, the longer the measured resistance value is, the longer the time for circulating water in the differential pressure water electrolysis mechanism 12, that is, the standby time is set. As a result, the dry state of the solid polymer electrolyte membrane 48 can be accurately detected, and the deterioration of the solid polymer electrolyte membrane 48 can be suppressed as much as possible economically and reliably.

DESCRIPTION OF SYMBOLS 10,100 ... Water electrolysis apparatus 12 ... Differential pressure type water electrolysis mechanism 14 ... Pure water supply mechanism 16 ... Water circulation mechanism 18 ... High pressure hydrogen piping 20 ... Controller 24 ... Unit cell 42 ... Electrolyte membrane and electrode structure 48 ... Solid polymer electrolyte Membrane 50 ... Anode-side power supply 52 ... Cathode-side power supply 56 ... Water supply communication hole 58 ... Discharge communication hole 60 ... Hydrogen communication holes 64, 68 ... Flow path 72 ... Circulation pipe 74 ... Circulation pump 80 ... Return pipe

Claims (4)

A power feeder is provided on both sides of the electrolyte membrane, and by applying an electrolysis current between the power feeders, water is electrolyzed to generate oxygen on the anode side, while hydrogen having a pressure higher than that of oxygen on the cathode side. A method for starting a water electrolysis device to be generated,
Determining whether or not at least the cathode side depressurization was performed while applying a depressurizing electrolysis current when the water electrolysis apparatus was stopped last time;
Circulating the water through the water electrolysis device before starting application of the electrolysis current at startup; and
Have
If it is determined that the pressure reduction has been performed while applying the electrolytic current for pressure reduction when the water electrolysis device is stopped last time, the water electrolysis is started after the water circulation to the water electrolysis device is started at the time of the current start-up. Set the first waiting time until the start of current application,
If the last of the pressure reducing time of the pressure reducing electrolysis current has an applied to stop the water electrolysis apparatus is judged to have been done, since the circulation of the water to the water electrolysis device to the current startup is initiated starting the water electrolysis apparatus characterized by setting longer than the second waiting time the first waiting time until it starts the application of the electrolysis current. The starting method according to claim 1, further comprising a step of storing a time required for depressurization when the water electrolysis apparatus is stopped last time.
The method of starting a water electrolysis apparatus, wherein the second waiting time until the application of the electrolysis current is started is set longer as the time required for depressurization is longer. The starting method according to claim 1 or 2, further comprising a step of gradually increasing the electrolytic current applied at the time of starting,
When it is determined that the application of the electrolysis current for decompression is not performed during decompression, the time for increasing the electrolysis current to the rated current value is set to the time when the electrolysis current for decompression is applied during decompression. A method for starting a water electrolysis apparatus, characterized in that the current is set to be longer than the time required to increase the rated current value. The starting method according to any one of claims 1 to 3, further comprising a step of measuring an impedance value of the electrolyte membrane,
The method of starting a water electrolysis apparatus, wherein the second waiting time until the application of the electrolysis current is started is set longer as the measured impedance value is higher.

Images