JP2012052208A - Method of operating water electrolysis system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To successfully dilute a gas component to be discharged, and to reduce electric consumption and noise.SOLUTION: A method of operating a water electrolysis system 10 includes: a step of calculating the flow rates of permeated hydrogen and oxygen to be discharged from a high-pressure water electrolysis unit 12 to a gas-liquid separator 16; a step of calculating the dilution flow rate for the permeated hydrogen, required for diluting the permeated hydrogen, based on the flow rates of the permeated hydrogen and the oxygen, with regard to the production volume of hydrogen in operation; a step of calculating the dilution flow rate for the oxygen, required for diluting the oxygen, based on the flow rates of the permeated hydrogen and the oxygen, with regard to the production volume of hydrogen in operation; and a step of supplying air for dilution in the gas-liquid separator 16 by comparing the dilution flow rate for the permeated hydrogen with the dilution flow rate for the oxygen and selecting whichever is larger in flow rate as the air flow rate for dilution.

Description

  The present invention provides a high-pressure water electrolysis apparatus, a water circulation apparatus that circulates water to the high-pressure water electrolysis apparatus, and a gas-liquid separation that separates a gas component discharged from the high-pressure water electrolysis apparatus from the water in the water circulation apparatus. The present invention relates to a method for operating a water electrolysis system including the apparatus.

  For example, hydrogen gas is used as a fuel gas to generate power in a fuel cell. In general, a water electrolysis apparatus is employed when producing this hydrogen gas. This 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. On both sides of the electrolyte membrane / electrode structure, an anode-side feeder and a cathode-side feeder A unit is configured by arranging

  Therefore, in a state where a plurality of units are stacked, a voltage is applied to 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 produced together with hydrogen ions (protons) is discharged from the unit with excess water.

  As this type of water electrolysis system, for example, a water circulation device (water electrolysis system) of a water electrolysis device disclosed in Patent Document 1 is known. As shown in FIG. 7, in the water electrolysis system, the oxygen-side water tank 1 and the hydrogen-side water tank 2 are installed above the water electrolysis tank 3, and water electrolysis is naturally performed through the water supply pipes 4a and 4b by the force of gravity. Water is distributed to the tank 3. The power supply 5 can be turned on and off by a thyristor, whereby the amount of gas generated by electrolysis and the generation interval can be arbitrarily selected.

  The oxygen-side water tank 1 and the hydrogen-side water tank 2 are provided with systems 6a and 6b for replenishing consumed water. Water is lifted up in the discharge pipes 7a and 7b by the generated gas.

  Since gas is generated intermittently by the power source 5, water is effectively sandwiched between the gases, and a large amount of water can be lifted up. In order to supplement the lifted water, the water is supplied from the water supply pipes 4a and 4b by the force of gravity.

JP-A-9-291385

  By the way, in said water electrolysis system, while high concentration oxygen stays in the oxygen side water tank 1, the hydrogen which permeate | transmitted by the discharge pipe 7a side may stay depending on the case. In particular, in a high-pressure water electrolysis apparatus that generates hydrogen at a pressure higher than oxygen, hydrogen tends to stay in the oxygen-side water tank 1.

  However, the oxygen-side water tank 1 is not devised to dilute high-concentration oxygen or hydrogen, and is directly discharged. For this reason, for example, it is conceivable to supply dilution air into the oxygen-side water tank 1 using a blower. However, there is a problem that power consumption of the blower increases and noise is easily generated.

  The present invention solves this type of problem, and provides a method for operating a water electrolysis system capable of diluting a discharged gas component well and reducing power consumption and noise. With the goal.

  The present invention provides a high-pressure water electrolysis apparatus provided with power feeding bodies on both sides of an electrolyte membrane, electrolyzing water to generate oxygen on the anode side, and generating hydrogen at a higher pressure than oxygen on the cathode side, A water circulation device that circulates water to the high pressure water electrolysis device, and a gas component discharged from the anode side of the high pressure water electrolysis device is separated from the water in the water circulation device, and the gas component is diluted with air. It is related with the operating method of a water electrolysis system provided with the gas-liquid separation apparatus diluted by this.

  The gas component includes oxygen generated on the anode side and permeated hydrogen generated on the cathode side and permeated through the electrolyte membrane.

  In this operation method, based on the permeated hydrogen flow rate and the oxygen flow rate, the step of calculating the permeated hydrogen flow rate and the oxygen flow rate discharged from the high pressure water electrolysis device to the gas-liquid separation device, and the hydrogen production amount in operation. A step of calculating a dilute flow rate for permeate hydrogen necessary for diluting the permeate hydrogen, and oxygen necessary for diluting oxygen based on the permeate hydrogen flow rate and the oxygen flow rate with respect to the hydrogen production amount during operation; The process for calculating the dilution flow rate is compared with the permeated hydrogen dilution flow rate and the oxygen dilution flow rate, and the higher flow rate is selected as the dilution air flow rate and the dilution air is supplied into the gas-liquid separator. Process.

  Further, this operation method includes a step of calculating a permeated hydrogen flow rate that has permeated the electrolyte membrane from the cathode side to the anode side based on the operating temperature of the high-pressure water electrolysis apparatus and the pressure of hydrogen generated on the cathode side. Is preferred.

  Further, in this operation method, the dilution air is preferably supplied by controlling a blower connected to the gas-liquid separator.

  According to the present invention, the permeate hydrogen dilution flow rate required for diluting permeate hydrogen and the oxygen dilution flow rate required for diluting oxygen are calculated. Next, the higher flow rate of the permeate hydrogen dilution flow rate and the oxygen dilution flow rate is selected as the dilution air flow rate, and dilution air is supplied into the gas-liquid separator.

  Accordingly, since the optimum amount of dilution air is supplied based on the permeated hydrogen flow rate and oxygen flow rate actually discharged from the high-pressure water electrolyzer, the permeated hydrogen and oxygen dilution process is performed efficiently and reliably. .

  In addition, for example, a blower that supplies dilution air is not always driven with a constant output corresponding to the maximum hydrogen concentration, and supply of excessive dilution air can be suppressed. As a result, the blower is efficiently controlled, and the discharged gas component can be diluted well, and the power consumption and noise of the blower can be reduced.

It is a schematic structure explanatory view of a water electrolysis system to which an operation method concerning an embodiment of the present invention is applied. It is a disassembled perspective explanatory drawing of the unit cell which comprises the said water electrolysis system. It is a flowchart explaining the said driving | running method. It is relationship explanatory drawing of the pressure of hydrogen and the hydrogen permeation amount which are manufactured. It is explanatory drawing of the relationship between the dilution flow rate for permeated hydrogen and the dilution flow rate for oxygen with respect to the hydrogen production amount. It is explanatory drawing of the relationship between the dilution flow rate for permeated hydrogen and the dilution flow rate for oxygen with respect to the hydrogen production amount at the time of low temperature operation. 1 is a schematic explanatory diagram of a water electrolysis system disclosed in Patent Document 1. FIG.

  As shown in FIG. 1, the water electrolysis system 10 to which the operation method according to the embodiment of the present invention is applied is configured to electrolyze water (pure water) to generate oxygen and high-pressure hydrogen (hydrogen higher than oxygen). The high pressure water electrolyzer 12 to be manufactured, the water circulator 14 for circulating the water to the high pressure water electrolyzer 12, and the gas components (oxygen gas and hydrogen gas) discharged from the high pressure water electrolyzer 12 are converted into the water circulator. 14 is provided with a gas-liquid separation device 16 that separates from the water in 14 and stores the water, a water supply device 18 that supplies pure water generated from city water to the gas-liquid separation device 16, and a controller 20.

  The high-pressure water electrolysis apparatus 12 is configured by stacking a plurality of unit cells 24. 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 a power source (DC power source) 38 via wirings 36a and 36b.

  As shown in FIG. 2, the unit cell 24 includes a disk-shaped electrolyte membrane / electrode structure 42, and an anode separator 44 and a cathode separator 46 that sandwich the electrolyte membrane / electrode structure 42. The anode-side separator 44 and the cathode-side separator 46 have a disc shape and are made of, for example, a carbon member or a metal plate.

  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. The anode-side power supply body 50 and the cathode-side power supply body 52 are made of, for example, a sintered body (porous conductor) of spherical atomized titanium powder.

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

  A surface 44 a of the anode separator 44 facing the electrolyte membrane / electrode structure 42 is provided with a supply passage 62 a that communicates with the water supply communication hole 56 and a discharge passage 62 b that communicates with the discharge communication hole 58. A first flow path 64 that communicates with the supply passage 62a and the discharge passage 62b is provided on the surface 44a. The first flow path 64 is provided within a range corresponding to the surface area of the anode-side power supply body 50 and is configured by a plurality of flow path grooves, a plurality of embosses, and the like.

  A hydrogen discharge passage 66 communicating with the hydrogen communication hole 60 is provided on the surface 46 a of the cathode separator 46 facing the electrolyte membrane / electrode structure 42. A second flow path 68 communicating with the hydrogen discharge passage 66 is formed on the surface 46a. The second flow path 68 is provided in a range corresponding to the surface area of the cathode-side power feeder 52, and includes a plurality of flow path grooves, a plurality of embosses, and the like.

  The seal members 70a and 70b are integrated with each other around the outer peripheral ends of the anode side separator 44 and the cathode side separator 46. The seal members 70a and 70b include, for example, EPDM, NBR, fluorine rubber, silicone rubber, fluorosilicone rubber, butyl rubber, natural rubber, styrene rubber, chloroplane, acrylic rubber, or other seal materials, cushion materials, or packing materials. Used.

  As shown in FIG. 1, the water circulation device 14 includes a circulation pipe 72 that communicates with the water supply communication hole 56 of the high-pressure water electrolysis device 12. The circulation pipe 72 is provided with a circulation pump 74 and an ion exchanger 76, and is connected to a lead-out port 78 a provided at the bottom of a reservoir 78 constituting the gas-liquid separation device 16. One end of a return pipe 80 communicates with an introduction port 78 b provided at the bottom of the reservoir 78, while the other end of the return pipe 80 communicates with a discharge communication hole 58 of the high-pressure water electrolysis apparatus 12.

  The reservoir 78 includes a pure water supply pipe 84 connected to the water supply device 18, a blower pipe 87 connected to a blower (blowing unit) 86 that supplies dilution air, and pure water in the reservoir 78. An oxygen exhaust pipe 88 for discharging the separated gas components (oxygen gas and hydrogen gas) is connected.

  One end of a high-pressure hydrogen pipe 90 is connected to the hydrogen communication hole 60 of the high-pressure water electrolysis apparatus 12. The other end of the high-pressure hydrogen pipe 90 is connected to a high-pressure hydrogen supply unit (fuel tank, fuel cell vehicle, etc.) not shown.

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

  At the time of starting the water electrolysis system 10, pure water generated from city water is supplied to the reservoir 78 constituting the gas-liquid separation device 16 via the water supply device 18. On the other hand, in the water circulation device 14, the water in the reservoir 78 is supplied to the water supply communication hole 56 of the high-pressure water electrolysis device 12 through the circulation pipe 72 under the action of the circulation pump 74. Further, a voltage is applied to the terminal portions 34a and 34b of the terminal plates 26a and 26b through a power supply 38 that is electrically connected.

  Therefore, as shown in FIG. 2, 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 flows along the anode-side power feeder 50. Moving.

  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 pressure higher than that of the water supply communication hole 56, and can flow through the hydrogen communication hole 60 and be taken out of the high-pressure water electrolysis apparatus 12 through the high-pressure hydrogen pipe 90.

  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 14 along the discharge communication hole 58. (See FIG. 1). Further, the hydrogen in the second flow path 68 is maintained at a higher pressure than the mixed fluid in the first flow path 64, and a part of the hydrogen permeates the solid polymer electrolyte membrane 48 and the first flow path 64. To leak.

  After the unreacted gas water and gas components (oxygen gas and permeated hydrogen gas) are introduced into the reservoir 78 and separated into gas and liquid, the water is exchanged from the circulation pipe 72 via the circulation pump 74 to the ion exchanger 76. Through the water supply communication hole 56. The gas component separated from the water is diluted by dilution air supplied from the blower 86 and then discharged to the outside from the oxygen exhaust pipe 88.

  Next, the operation method according to the present embodiment will be described below along the flowchart shown in FIG.

  First, the operating conditions of the water electrolysis system 10 are set (step S1). Specifically, the operating temperature of the high-pressure water electrolyzer 12 and the pressure of hydrogen generated on the cathode side are set. As a result, as shown in FIG. 4, the permeated hydrogen flow rate that permeates the solid polymer electrolyte membrane 48 from the cathode side to the anode side is calculated (step S2). In addition, the operating temperature has a relationship of T1 ° C. <T2 ° C. <T3 ° C. in FIG. 4, and the higher the operating temperature and the higher the hydrogen pressure, the greater the permeated hydrogen flow rate.

  Next, when the hydrogen production amount X is set (step S3), the process proceeds to step S4, where the permeated hydrogen dilution flow rate M1 necessary for diluting permeated hydrogen and the oxygen dilution flow rate necessary for diluting oxygen are obtained. M2 is calculated.

  In this case, if the permeated hydrogen dilution flow rate M1 for reducing the permeated hydrogen concentration to V1 or less is n1 and (0.5X + M1 + n1) ≦ V1, where M1 ≧ ( 1-V1) n1 / V1-0.5X is obtained (first formula).

  On the other hand, the oxygen dilution flow rate M2 for setting the oxygen concentration to V2 or less is M2 ≧ (1−V2) X / 2 (from the relationship of (0.5X + M2 · 0.21) / (0.5X + M2 + n1) ≦ V2). V2-0.21) −V2 · n1 / (V2−0.21) is obtained (second formula). In addition, said 0.21 shows 21% which is the oxygen concentration in air.

  Therefore, for example, when the operating temperature is 60 ° C. and the hydrogen pressure is 35 MPa, if the hydrogen production amount X is 10 (L / min), the oxygen flow rate 0.5X is 5 (L / min) and the permeated hydrogen amount n1 is 0.5 (L / min).

  For this reason, the permeated hydrogen dilution flow rate M1 for setting the permeated hydrogen concentration V1 permeating to the anode side to, for example, 0.5% or less is about 95 (L / min) or more from the first equation. Further, the oxygen dilution flow rate M2 for setting the oxygen concentration V2 on the anode side to 25% or less, for example, is about 91 (L / min) or more from the second equation.

  Accordingly, in step S5, it is determined that the permeated hydrogen dilution flow rate M1> the oxygen dilution flow rate M2 (YES in step S5), and the process proceeds to step S6. In step S6, the permeated hydrogen dilution flow rate M1 is set to the dilution air flow rate M1, and the blower 86 is controlled via the controller 20 (step S7).

  The permeated hydrogen dilution flow rate M1 and the oxygen dilution flow rate M2 have the relationship shown in FIG. 5 when the hydrogen production amount X is changed when the operating temperature is 60 ° C. and the hydrogen pressure is 35 MPa, for example.

  As a result, when the hydrogen production amount X is increased, the relationship shifts to the permeated hydrogen dilution flow rate M1 <the oxygen dilution flow rate M2 (NO in step S5). In step S8, the oxygen dilution flow rate M2 is set to the dilution air flow rate M2. The above process is continuously performed until the operation of the water electrolysis system 10 is stopped (step S9).

  In addition, when the operating temperature is low, for example, when the operating temperature is 30 ° C. and the hydrogen pressure is 35 MPa, and the hydrogen production amount X is 10 (L / min), the oxygen flow rate 0.5X is 5 (L / min). min), the permeated hydrogen amount n1 is 0.18 (L / min).

  At that time, the permeated hydrogen dilution flow rate M1 for setting the permeated hydrogen concentration V1 permeating to the anode side to, for example, 0.5% or less is about 31 (L / min) or more from the first equation. On the other hand, the oxygen dilution flow rate M2 for setting the oxygen concentration V2 on the anode side to 25% or less, for example, is about 93 (L / min) or more from the second equation. The relationship between the permeated hydrogen dilution flow rate M1 and the oxygen dilution flow rate M2 during this low-temperature operation is shown in FIG.

  In this case, in this embodiment, the operating temperature of the high-pressure water electrolyzer 12 and the pressure of hydrogen generated on the cathode side are set, and the hydrogen production amount X is set. Thus, the permeated hydrogen dilution flow rate M1 necessary for diluting the permeated hydrogen and the oxygen dilution flow rate M2 necessary for diluting oxygen are calculated.

  Next, the higher flow rate of the permeated hydrogen dilution flow rate M1 and the oxygen dilution flow rate M2 is selected as the dilution air flow rate, and the blower 86 is controlled under the action of the controller 20 to be used for dilution in the gas-liquid separator 16. Air is being supplied.

  Therefore, since the optimum amount of dilution air is supplied based on the permeated hydrogen flow rate and the oxygen flow rate actually discharged from the high-pressure water electrolyzer 12 to the return pipe 80, the permeated hydrogen and oxygen dilution process is efficient and Surely fulfilled.

  In addition, the blower 86 for supplying dilution air is not always driven with a constant output corresponding to the maximum hydrogen concentration, and can suppress excessive supply of dilution air. For this reason, the blower 86 is efficiently controlled, and it is possible to effectively dilute the discharged gas component, and to reduce the power consumption and noise of the blower 86.

DESCRIPTION OF SYMBOLS 10 ... Water electrolysis system 12 ... High pressure water electrolysis apparatus 14 ... Water circulation apparatus 16 ... Gas-liquid separation apparatus 18 ... Water supply apparatus 20 ... Controller 24 ... Unit cell 38 ... Power supply 42 ... Electrolyte membrane and electrode structure 44 ... Anode side separator 46 ... cathode separator 48 ... solid polymer electrolyte membrane 50 ... anode side feeder 52 ... cathode side feeder 56 ... water supply communication hole 58 ... discharge communication hole 60 ... hydrogen communication hole 64, 68 ... channel 66 ... hydrogen discharge passage 72 ... circulation pipe 74 ... circulation pump 76 ... ion exchanger 78 ... reservoir 80 ... return pipe 84 ... pure water supply pipe 86 ... blower 88 ... oxygen exhaust pipe 90 ... high pressure hydrogen pipe

Claims (3)

A power feeder provided on both sides of the electrolyte membrane, electrolyzing water to generate oxygen on the anode side, and generating high-pressure hydrogen on the cathode side than the oxygen; and
A water circulation device for circulating the water to the high-pressure water electrolysis device;
A gas-liquid separation device for separating the gas component discharged from the anode side of the high-pressure water electrolysis device from the water in the water circulation device, and diluting the gas component with dilution air;
A method for operating a water electrolysis system comprising:
The gas component includes the oxygen generated on the anode side and permeated hydrogen generated on the cathode side and permeated through the electrolyte membrane,
Calculating a permeated hydrogen flow rate and an oxygen flow rate discharged from the high-pressure water electrolyzer to the gas-liquid separator;
Calculating a permeated hydrogen dilution flow rate for diluting the permeated hydrogen based on the permeated hydrogen flow rate and the oxygen flow rate with respect to the hydrogen production amount during operation;
Calculating a dilution flow rate for oxygen necessary for diluting the oxygen based on the permeated hydrogen flow rate and the oxygen flow rate with respect to the hydrogen production amount in operation;
Comparing the dilution flow rate for permeated hydrogen and the dilution flow rate for oxygen, selecting the higher flow rate as the dilution air flow rate, and supplying the dilution air into the gas-liquid separator;
A method for operating a water electrolysis system, comprising:   2. The operation method according to claim 1, wherein the permeated hydrogen that permeates the electrolyte membrane from the cathode side to the anode side based on an operating temperature of the high-pressure water electrolyzer and a pressure of the hydrogen generated on the cathode side. A method for operating a water electrolysis system comprising a step of calculating a flow rate.   The operation method according to claim 1 or 2, wherein the dilution air is supplied by controlling a blower connected to the gas-liquid separator.

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