CN116555791A - Electrochemical reaction device and electrochemical reaction method - Google Patents
Electrochemical reaction device and electrochemical reaction method Download PDFInfo
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- CN116555791A CN116555791A CN202211089298.9A CN202211089298A CN116555791A CN 116555791 A CN116555791 A CN 116555791A CN 202211089298 A CN202211089298 A CN 202211089298A CN 116555791 A CN116555791 A CN 116555791A
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- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 1
- 229920003934 Aciplex® Polymers 0.000 description 1
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- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
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- 229910001252 Pd alloy Inorganic materials 0.000 description 1
- 229910002837 PtCo Inorganic materials 0.000 description 1
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- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
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- 150000002739 metals Chemical class 0.000 description 1
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- 229910052758 niobium Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
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- 238000007254 oxidation reaction Methods 0.000 description 1
- IYDGMDWEHDFVQI-UHFFFAOYSA-N phosphoric acid;trioxotungsten Chemical compound O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.OP(O)(O)=O IYDGMDWEHDFVQI-UHFFFAOYSA-N 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
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- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
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- 238000007789 sealing Methods 0.000 description 1
- VSZWPYCFIRKVQL-UHFFFAOYSA-N selanylidenegallium;selenium Chemical compound [Se].[Se]=[Ga].[Se]=[Ga] VSZWPYCFIRKVQL-UHFFFAOYSA-N 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000006277 sulfonation reaction Methods 0.000 description 1
- 125000000542 sulfonic acid group Chemical group 0.000 description 1
- 239000008400 supply water Substances 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- JBQYATWDVHIOAR-UHFFFAOYSA-N tellanylidenegermanium Chemical compound [Te]=[Ge] JBQYATWDVHIOAR-UHFFFAOYSA-N 0.000 description 1
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 description 1
- CMPGARWFYBADJI-UHFFFAOYSA-L tungstic acid Chemical compound O[W](O)(=O)=O CMPGARWFYBADJI-UHFFFAOYSA-L 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
- C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B15/00—Operating or servicing cells
- C25B15/02—Process control or regulation
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B15/00—Operating or servicing cells
- C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/60—Constructional parts of cells
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Automation & Control Theory (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Abstract
The invention provides an electrochemical reaction device and an electrochemical reaction method. An electrochemical reaction device according to an embodiment includes: an electrochemical reaction cell including a 1 st electrode having a 1 st flow path, a 2 nd electrode having a 2 nd flow path, and a separator sandwiched between the 1 st electrode and the 2 nd electrode; a liquid tank for storing the liquid to be treated in the 2 nd flow path supplied to the 2 nd electrode; a 1 st piping connecting the inlet of the 2 nd flow path and the liquid tank; a 2 nd piping connecting the outlet of the 2 nd flow path and the liquid tank; and a reverse flow suppressing means provided in the 2 nd pipe for preventing reverse flow of the liquid to be treated flowing in the 2 nd pipe or reducing the reverse flow rate.
Description
The present application is based on Japanese patent application 2022-01964 (application day: 01/28/2022) and Japanese patent application 2022-118767 (application day: 07/26/2022), from which priority is given. The present application is incorporated by reference in its entirety into the above application.
Technical Field
Embodiments of the present invention relate to an electrochemical reaction apparatus and an electrochemical reaction method.
Background
As a typical example of an electrochemical reaction apparatus such as an electrolyzer, an electrochemical reaction apparatus is known in which a reaction system is operated by a reaction system of water (H 2 O) is electrolyzed to generate hydrogen (H) 2 ) And oxygen (O) 2 ) Is a water electrolysis apparatus. The water electrolyzer includes, for example, an electrolyzer having an anode, a cathode, a solid polymer electrolyte membrane (Polymer Electrolyte Membrane: PEM) sandwiched between the anode and the cathode, and other separators. In the water electrolysis apparatus, the water (H 2 O) is electrolyzed to generate hydrogen (H) at the cathode 2 ) Oxygen (O) is generated at the anode 2 ). A water electrolyzer (PEM-type water electrolyzer) using such a solid Polymer Electrolyte Membrane (PEM) as a membrane has characteristics of low operating temperature, high hydrogen purity, and the like. However, a water electrolyzer provided with a diaphragm such as a PEM-type water electrolyzer has a problem that the performance of the water electrolyzer is easily degraded if a start-stop operation is performed. Such problems are notLimited to water baths, electrolytic cells having a diaphragm and electrolytic devices (electrochemical reaction devices) are also problematic.
Disclosure of Invention
The present invention provides an electrochemical reaction apparatus and an electrochemical reaction method capable of suppressing performance degradation when starting and stopping operations are performed.
An electrochemical reaction device according to an embodiment includes: an electrochemical reaction cell comprising a 1 st electrode having a 1 st flow path, a 2 nd electrode having a 2 nd flow path, and a separator sandwiched between the 1 st electrode and the 2 nd electrode; a liquid tank for storing the liquid to be treated in the 2 nd flow path supplied to the 2 nd electrode; a 1 st pipe that connects an inlet of the 2 nd flow path and the tank and supplies the liquid to be treated to the 2 nd flow path; a second piping that connects an outlet of the second flow path to the liquid tank and returns the liquid to be treated to the liquid tank; and a reverse flow suppressing means provided in the 2 nd pipe for preventing reverse flow of the liquid to be treated flowing in the 2 nd pipe or reducing a reverse flow rate.
Drawings
Fig. 1 is a diagram showing the structure of an electrochemical reaction cell and the connection structure of the electrochemical reaction cell and a power source in an electrochemical reaction device according to an embodiment.
Fig. 2 is a diagram showing an electrochemical reaction apparatus according to embodiment 1.
Fig. 3 is an enlarged view showing a part of the electrochemical reaction apparatus according to embodiment 1.
Fig. 4 is a graph showing the comparison of the specific resistance of water at the time of stopping the electrochemical reaction apparatus according to embodiment 1 and the specific resistance of water at the time of stopping the electrochemical reaction apparatus without a check valve.
Fig. 5 is a graph showing a comparison between a change in voltage with time in the electrochemical reaction apparatus according to embodiment 1 and a change in voltage with time in the electrochemical reaction apparatus without a check valve.
Fig. 6 is a diagram showing an electrochemical reaction apparatus according to embodiment 2.
Fig. 7 is a diagram showing a part of example 1 of the electrochemical reaction apparatus according to embodiment 2.
Fig. 8 is a diagram showing a part of example 2 of the electrochemical reaction apparatus according to embodiment 2.
Fig. 9 is a diagram showing an electrochemical reaction apparatus according to embodiment 3.
Fig. 10 is a diagram showing an electrochemical reaction apparatus according to embodiment 4.
Fig. 11 is a diagram showing an electrochemical reaction apparatus according to embodiment 5.
FIG. 12 is a view showing an electrochemical reaction apparatus according to embodiment 6.
Fig. 13 is a diagram showing a modification of the electrochemical reaction apparatus shown in fig. 12.
Fig. 14 is a diagram showing an example of the electrochemical reaction apparatus according to embodiment 7.
FIG. 15 is a view showing another example of the electrochemical reaction apparatus according to embodiment 7.
(symbol description)
1: electrochemical reaction cell (electrolyzer), 2: 1 st electrode, 3: electrode 2, 4: a separator, 12: 1 st flow path, 13: flow passage 2, 20: electrochemical reaction device (electrolyzer), 22: water tank, 23: pure water production apparatus, 24: 1 st piping, 25: 2 nd pipe, 26: pump, 27: ultrapure water production device, 28: check valve, 29: liquid level sensor, 31: u-shaped piping, 32: gas supply unit, 33: long piping, 41: electrochemical reactor (electrochemical reaction cell stack), 46: overflow wall, 47: water tank with overflow structure, 51: gas-liquid separation tank (2 nd water tank), 53: and a valve.
Detailed Description
An electrochemical reaction device according to an embodiment will be described below with reference to the drawings. In the embodiments shown below, substantially the same constituent parts are denoted by the same reference numerals, and the description thereof may be partially omitted. The drawings are schematic, and the relationship between the thickness and the planar dimension, the ratio of the thickness of each portion, and the like may be different from actual ones. In the following description, the symbols of "to" represent ranges between the upper limit value and the lower limit value, respectively. In this case, each range includes an upper limit value and a lower limit value.
The structure of an electrochemical reaction cell and the connection structure between the electrochemical reaction cell and a power supply in the electrochemical reaction device according to the embodiment will be described with reference to fig. 1. The electrochemical reaction cell 1 shown in fig. 1 includes a 1 st electrode 2, a 2 nd electrode 3, and a separator 4 sandwiched between the 1 st electrode 2 and the 2 nd electrode 3. The separator 4 has, for example, a solid Polymer Electrolyte Membrane (PEM). When the electrochemical reaction cell 1 is used as a water electrolysis cell, the 1 st electrode 2 is a cathode (reduction electrode/hydrogen electrode), and the 2 nd electrode 3 is an anode (oxidation electrode/oxygen electrode). Hereinafter, the case of using the electrochemical reaction cell 1 as a water electrolysis cell will be mainly described, but the present invention is not limited thereto. As the solid polymer electrolyte membrane of the separator 4, a proton conductive membrane can be used.
As a constituent material of the proton conductive PEM, for example, a fluororesin having a sulfonic acid group can be used. Specific examples of such materials include Nafion (registered trademark) which is a fluororesin obtained by sulfonation polymerization of tetrafluoroethylene by dupont, aciplex (registered trademark) manufactured by asahi chemical company, feverline (registered trademark) manufactured by AGC company, and the like. The separator 4 is not limited to the solid polymer electrolyte membrane, and may be an electrolyte membrane such as a hydrocarbon membrane containing an electrolyte component or a membrane containing an inorganic substance such as tungstic acid or phosphotungstic acid.
The anode, namely, the 2 nd electrode 3, reacts with water (H 2 O) is electrolyzed to generate hydrogen ions (H) + ) And oxygen (O) 2 ). The cathode 1 st electrode 2 is formed by reacting hydrogen ions (H + ) Reduction is carried out to generate hydrogen (H) 2 ). The cathode 1 st electrode 2 has a 1 st catalyst layer 5 and a 1 st power feeding layer 6. The 1 st catalyst layer 5 is disposed in contact with the separator 4. The anode, i.e., the 2 nd electrode 3, has a 2 nd catalyst layer 7 and a 2 nd power feed layer 8. The 2 nd catalyst layer 7 is disposed in contact with the separator 4. The membrane electrode assembly (Membrane Electrode Assembly: MEA) 9 is constituted by sandwiching a membrane 4 such as a PEM between the 1 st electrode 2 and the 2 nd electrode 3.
As the 1 st catalyst layer 5 of the 1 st electrode 2 serving as the cathode, for example, metals such as platinum (Pt), silver (Ag), and palladium (Pd), and alloys (Pt alloy, ag alloy, pd alloy) containing at least 1 of Pt, ag, and Pd are used. Pt alloys such as Pt and PtCo, ptFe, ptNi, ptPd, ptIr, ptRu, ptSn are more preferably used for the 1 st catalyst layer 5. As the 2 nd catalyst layer 7 of the 2 nd electrode 3 which is the anode, for example, iridium (Ir) oxide, ruthenium (Ru) oxide, palladium (Pd) oxide, ir composite oxide, ru composite oxide, pd composite oxide, or the like can be used. Examples of the composite metal constituting the Ir composite oxide and the Ru composite oxide include titanium (Ti), niobium (Nb), vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), zinc (Zn), zirconium (Zr), molybdenum (Mo), tantalum (Ta), ru, ir, pd, and the like. As the 2 nd catalyst layer 7, ir oxide, ir composite oxide, and the like are more preferably used.
As the 1 st power feeding layer 6 of the 1 st electrode 2 and the 2 nd power feeding layer 8 of the 2 nd electrode 3, materials having gas diffusivity and conductivity can be used. Specifically, porous conductive members and the like are suitably used for the 1 st power feeding layer 6 and the 2 nd power feeding layer 8. As the 1 st power feeding layer 6 and the 2 nd power feeding layer 8, porous metal members such as Ti, ta, SUS, ni, pt, metal felt, metal nonwoven fabric wound with metal fibers, carbon paper, carbon cloth, and the like can be used. As the 1 st power feeding layer 6 and the 2 nd power feeding layer 8, ti excellent in corrosion resistance is preferably used, whereby durability can be improved. Further, by plating these materials with gold, platinum, or the like, durability can be further improved.
The MEA9 is sandwiched by a cathode separator 10 and an anode separator 11, thereby constituting the electrochemical reaction cell 1. The cathode separator 10 is provided with a 1 st flow path 12 through which the reaction substance and the product substance flow. The anode separator 11 is provided with a 2 nd flow path 13 through which the reaction substance and the product substance flow. Sealing members 14 are disposed on the side surfaces of the 1 st catalyst layer 5 and the 1 st power feeding layer 6 and the side surfaces of the 2 nd catalyst layer 7 and the 2 nd power feeding layer 8 to prevent leakage of gas or liquid from the MEA9 and the electrochemical reaction chamber 1.
The electrochemical reaction cell 1 is not limited to a single cell structure, and may have a stacked cell structure in which a plurality of electrochemical reaction cells 1 are stacked. The structure of the stacking groove is not particularly limited, and may be appropriately selected according to a desired voltage, reaction amount, and the like. When a plurality of electrochemical reaction cells 1 are used, the structure is not limited to the stacked cell structure, and may be a structure in which a plurality of electrochemical reaction cells 1 are arranged in a plane. The grooves arranged in a plane may be stacked. The number of the single cells included in the electrochemical reaction cell 1 is not particularly limited and may be appropriately selected.
As the reaction substance to be supplied to the electrochemical reaction tank 1, for example, an aqueous solution containing at least 1 of water, hydrogen, a modifying gas, methanol, ethanol, formic acid, and the like can be used. When the electrochemical reaction tank 1 according to the embodiment is a water electrolyzer, the water electrolyzer is preferably pure water (e.g., pure water having a specific resistance of 0.01mΩ·cm or more and 5mΩ·cm or less), and more preferably ultrapure water (e.g., ultrapure water having a specific resistance of 17mΩ·cm or more). The electrochemical reaction cell 1 in the embodiment is not limited to an electrolytic cell for water electrolysis, and can be applied to various electrolytic cells if it is an electrochemical reaction cell using an oxide as a catalyst, such as an electrolytic cell for carbon dioxide. The electrochemical reaction cell 1 is not limited to an electrolytic cell, and may be a fuel cell or the like.
The 1 st electrode 2 and the 2 nd electrode 3 of the electrochemical reaction cell 1 are electrically connected to a voltage applying mechanism (power supply) 15. A voltage measuring unit 16 and a current measuring unit 17 are provided in a circuit electrically connecting the power supply 15 and the 1 st electrode 2 and the 2 nd electrode 3. The power supply 15 is controlled to operate by a control unit 18. The control unit 18 controls the power supply 15 to apply a voltage to the electrochemical reaction cell 1. The voltage measuring unit 16 is electrically connected to the 1 st electrode 2 and the 2 nd electrode 3, and measures the voltage applied to the electrochemical reaction cell 1. The measurement information is sent to the control unit 18. The current measuring unit 17 is inserted into a voltage applying circuit for the electrochemical reaction cell 1, and measures the current flowing in the electrochemical reaction cell 1. The measurement information is sent to the control unit 18.
The control unit 18 is configured by a computer such as a PC or a microcomputer, for example, and performs arithmetic processing on the data signals output from the respective units to output necessary control signals to the respective components. The control unit 18 further includes a memory, and controls the output of the power supply 15 based on the measurement information according to a program stored in the memory, thereby controlling the application of voltage, the change of load, and the like to the electrochemical reaction tank 1. When the electrochemical reaction cell 1 is used for a cell reaction, the electrochemical reaction cell 1 is subjected to a voltage. When the electrochemical reaction tank 1 is used for a reaction other than a battery reaction, for example, a hydrogen generation reaction by water electrolysis, an electrolysis reaction of carbon dioxide, or the like, a voltage is applied to the electrochemical reaction tank 1. The electrochemical reaction device according to the embodiment is configured such that, for example, a voltage is applied between the 1 st electrode 2 and the 2 nd electrode 3 to cause an electrochemical reaction.
(embodiment 1)
Next, an electrochemical reaction apparatus 20 according to embodiment 1 provided with the electrochemical reaction cell 1 shown in fig. 1 will be described with reference to fig. 2. The configuration of the electrochemical reaction apparatus 20 when applied to a water electrolysis apparatus for electrolyzing water will be mainly described here, but the electrochemical reaction apparatus of the embodiment is not limited to this, and may be an electrolysis apparatus for carbon dioxide or the like. The electrochemical reaction apparatus (electrolyzer) 20 shown in fig. 2 is provided with a water supply system (treatment target liquid supply system) 21 for supplying water as the treatment target liquid to the 2 nd electrode 3 of the electrochemical reaction tank (electrolyzer) 1.
The water supply system 21 includes a water tank 22 as a liquid tank for storing the liquid to be treated supplied to the 2 nd flow path 13 of the 2 nd electrode 3. The water tank 22 is connected to a pure water producing device 23, and pure water as a processing stock solution can be supplied from the pure water producing device 23 to the water tank 22. As the pure water production apparatus 23, for example, a reverse osmosis membrane (RO membrane) apparatus can be used. Tap water W or the like may be supplied as raw water to the pure water producing apparatus 23. When such water W is treated by a pure water production apparatus 23 such as an RO membrane apparatus, pure water (treatment stock solution) having a specific resistance of about 0.01 to 5 M.OMEGA.cm@25deg.C can be produced, wherein the specific resistance of the tap water W is about 0.01 M.OMEGA.cm@25deg.C or less. Such pure water may be supplied into the water tank 22.
The 1 st pipe 24 and the 2 nd pipe 25 are connected to the water tank 22. The 1 st pipe 24 is a supply pipe for supplying water to the 2 nd electrode 3 of the electrochemical reaction tank 1, and is connected to the water tank 22 and the inlet IN of the 2 nd channel 13. The 1 st pipe 24, which is a supply pipe, is provided with a pump 26 and an ultrapure water production device 27. As the ultrapure water production device 27, for example, an ultrapure water device using an ion exchange resin can be used. The pure water contained in the water tank 22 is sent to the ultrapure water production device 27 via the pump 26. When pure water having a specific resistance in the range of 0.01 to 5 M.OMEGA.cm@25deg.C is treated by the ultrapure water production apparatus 27 such as an ion exchange resin apparatus, ultrapure water having a specific resistance of 17 M.OMEGA.cm@25deg.C or more, such as 18.24 M.OMEGA.cm@25deg.C, can be produced as the liquid to be treated. The ultrapure water is supplied as the treatment target liquid to the inlet IN of the 2 nd flow path 13 of the 2 nd electrode 3, and electrolysis of water is performed by the 2 nd electrode 3 serving as the anode while flowing through the 2 nd flow path 13.
An outlet OUT of the 2 nd flow path 13 of the 2 nd electrode 3 is connected to an outlet of the oxygen (O 2 ) And the remaining water is returned to the 2 nd pipe 25 in the water tank 22. The 2 nd pipe 25 is a pipe for decomposing water to generate oxygen (O 2 ) And a return pipe (also referred to as an oxygen pipe) for returning the surplus water to the water tank 22, and is connected to the outlet OUT of the 2 nd flow path 13 and the water tank 22. The water tank 22 has a gas-liquid separation function, and oxygen (O) separated in the water tank 22 can be recovered as needed 2 ). The water stored in the water tank 22 circulates through the 1 st pipe 24, the pump 26, the ultrapure water production device 27, the 2 nd flow path 13, and the 2 nd pipe 25. The 2 nd pipe 25 is provided with a check valve 28 as a backflow suppressing means, as will be described later.
In the electrolysis of water by the 2 nd electrode 3, oxygen (O 2 ) And hydrogen ions (protons/H) + ). Proton (H) is transported from electrode 2 to electrode 1 of electrochemical reaction cell 1 through membrane 4 + ). Since water is also fed from the 2 nd electrode 3 to the 1 st electrode 2 through the diaphragm 4, a water tank having a gas-liquid separation function can be connected to the outlet of the 1 st flow path 12 of the 1 st electrode 2 as needed. Protons (H) transported to the 1 st electrode 2 + ) And electrons (e) reaching the 1 st electrode 2 through an external circuit - ) Reaction to produce hydrogen (H) 2 ). Hydrogen (H) generated in the 1 st electrode 2 2 ) Is discharged to the outside directly from the 1 st electrode 2 or via the water tank and recovered.
Next, the operation of the electrochemical reaction apparatus 20 shown in fig. 2 will be described. When electrolysis of water is performed, if a voltage is applied from an external power source to the 2 nd electrode 3 as an anode, water (H 2 O) is electrolyzed, taking placeThe reaction of formula (1) shown below.
2H 2 O→O 2 +4H + +4e - (1)
Protons (H) generated at this time + ) Is supplied to the 1 st electrode 2 as a cathode through the separator 4. Furthermore, the electron (e - ) The 1 st electrode 2 is reached through an external circuit. Hydrogen is generated in the 1 st electrode 2 as a cathode by a reaction of the following formula (2).
4H + +4e - →2H 2 (2)
By the reaction of the above-mentioned formula (1) and formula (2), hydrogen and oxygen can be produced.
As described above, the outlet OUT of the 2 nd flow path 13 of the 2 nd electrode 3 and the water tank 22 are connected via the 2 nd pipe 25. In such a configuration, when the backflow suppressing means such as the check valve 28 is not provided in the 2 nd pipe 25, there is a concern that the pure water in the water tank 22 supplied from the pure water producing device 23 flows back to the 2 nd electrode 3 through the 2 nd pipe 25 and the 2 nd flow path 13 or impurities are diffused in a concentration gradient when the operation of the electrolytic device 20 is stopped. If pure water flows into the 2 nd electrode 3, the 2 nd electrode 3 is porous, so that pure water having a specific resistance in the range of 0.1 to 5mΩ·cm contained in the water tank 22 reaches the separator 4 and the 1 st electrode 2. The small amount of anionic component and cationic component contained in such pure water, siO 2 The particles enter the separator 4, and thus have adverse effects such as a decrease in ionic conductivity, or an extreme decrease in the reaction area of electrochemical reactions such as electrolysis due to adsorption onto the catalyst on the 1 st electrode 2 and the 2 nd electrode 3. Such a reverse flow of pure water from the water tank 22 to the electrochemical reaction tank 1 is a factor that decreases the performance of the electrochemical reaction tank 1.
Therefore, in the electrochemical reaction apparatus (electrolyzer) 20 of embodiment 1, a check valve 28 is provided as a backflow suppressing means in the 2 nd pipe 25 connecting the water tank 22 and the outlet OUT of the 2 nd flow path 13 of the 2 nd electrode 3. When the operation of the electrolyzer 20 is stopped, the pure water in the water tank 22 is prevented from flowing backward to the 2 nd electrode 3 via the 2 nd pipe 25 and the 2 nd flow path 13 by the check valve 28. By suppressing the backflow of pure water from the water tank 22 to the 2 nd electrode 3, the electrochemical reaction apparatus (electrolytic apparatus) 20 can be stopped in a state where the 2 nd flow path 13 and the 2 nd electrode 3 are filled with ultrapure water. Therefore, the performance of the electrochemical reaction chamber 1 at the time of stopping the electrochemical reaction apparatus (electrolyzer) 20 can be maintained.
The check valve 28 for suppressing the backflow of pure water in the water tank 22 to the 2 nd electrode 3 is preferably a value represented by the following formula (3) or more as the lowest reverse differential pressure P (kPa).
Δh×ρ×g(3)
Δh is "the height above the liquid in the water tank 22—the height of the check valve 28", ρ is the liquid density, g is the gravitational acceleration. By using the check valve 28 having the lowest non-return differential pressure P equal to or higher than the value represented by the formula (3), the backflow of pure water in the water tank 22 to the 2 nd electrode 3 when the operation of the electrolyzer 20 is stopped can be effectively prevented. The check valve 28 having such a configuration may be a lift check valve such as a swing check valve or a smolenky check valve (also referred to as a slow-closing check valve), a butt check valve, or a ball check valve. On the other hand, a valve (so-called tesla valve) having a plurality of tear-drop rings around which the liquid flowing in the tube flows is not suitable.
In the electrochemical reaction apparatus (electrolyzer) 20 of embodiment 1, the 2 nd pipe 25 provided with the check valve 28 is preferably connected to the water below the liquid surface of the water tank 22, that is, to the water. The pure water producing apparatus 23 is configured as shown in fig. 3, for example, to supply water W as raw water of water to be treated (water to be electrolyzed) to the water tank 22. The water tank 22 has a liquid level sensor 29 provided inside thereof. The liquid level sensor may be a laser type liquid level meter or the like provided outside the water tank 22. When the liquid level in the water tank 22 is lower than the lower limit value of the liquid level sensor 29, the water feed pump 30 for feeding water W from the pure water producing apparatus 23 to the water tank 22 is started to feed water into the water tank 22. Therefore, the 2 nd pipe 25 is preferably connected to a position lower than the liquid level in the water tank 22 set by the liquid level sensor 29.
By connecting the 2 nd pipe 25 to a position lower than the liquid surface set by the liquid surface sensor 29, the backflow of the pure water in the water tank 22 can be suppressed by the check valve 28 while maintaining the liquid-tight state by the 2 nd pipe 25. Even when the 2 nd pipe 25 is connected to a position higher than the liquid surface, the backflow of water in the 2 nd pipe 25 can be suppressed. However, if the stop time becomes long, the water remaining in the 2 nd pipe 25 evaporates, and the MEA9 dries. If dried, the separator 4 contracts and swells when water is supplied again, and the separator 4 is mechanically loaded by repeating the dry-wet cycle, so that the separator 4 is broken or deformed to cause clogging of the flow path, which is not preferable from the viewpoint of durability of the electrolytic cell 1.
Fig. 4 shows the specific resistance of water at the time of stopping (at the time of stopping the current) by the electrochemical reaction device (electrolytic device) 20, compared with the specific resistance of water at the time of stopping by the electrolytic device without a check valve. Fig. 5 shows a comparison between the change in voltage of the electrochemical reaction apparatus (electrolyzer) 20 with the change in voltage of the electrolyzer without check valve with time. As shown in fig. 4, by providing the check valve 28 in the 2 nd pipe 25, it is possible to suppress a decrease in specific resistance caused by the water in the water tank 22 flowing back to the 2 nd electrode 3. Further, as shown in fig. 5, by providing the check valve 28 in the 2 nd pipe 25, the degradation of the performance of the electrolytic cell 1 caused by the reverse flow of the water in the water tank 22 can be suppressed.
(embodiment 2)
The electrochemical reaction apparatus 20 according to embodiment 2 will be described with reference to fig. 6 to 8. In the electrochemical reaction apparatus 20 shown in fig. 6, the 2 nd pipe 25 connecting the water tank 22 and the outlet OUT of the 2 nd flow path 13 of the 2 nd electrode 3 has a U-shaped pipe 31 arranged in an inverted U-shape (arranged in a convex shape facing upward) as a reverse flow suppressing means. The other components are the same as those of the electrochemical reaction apparatus 20 of embodiment 1 shown in fig. 2. According to the U-shaped pipe 31 arranged in the inverted U-shape, when stopping the water flowing in the 2 nd pipe 25, as shown in fig. 7, oxygen (O 2 ) The gas and liquid are separated in the U-shaped pipe 31, and the gas is stored in the upper portion of the U-shaped pipe 31 to form a gas storage portion G. By forming such a gas storage portion G in the U-shaped pipe 31, the ultrapure water UW on the 2 nd electrode 3 side and the pure water PW on the water tank 22 side are separated. Therefore, the water tank 22 and the 2 nd electrode 3 are not formedThe liquids merge to prevent the pure water PW of the water tank 22 from flowing backward into the 2 nd electrode 3.
The U-shaped pipe 31 as the backflow suppressing means is an example of a backflow suppressing pipe, and the backflow suppressing pipe is not limited to the U-shaped pipe as long as it has a shape in which the gas storage portion G can be formed by gas-liquid separation. The backflow suppressing pipe is preferably formed so as to easily form the gas storage portion G inside the pipe and to prevent natural gas leakage from the gas storage portion G, and examples thereof include a U-shaped pipe 31, a V-shaped pipe, and the like. When the gas in the gas-liquid mixture flow discharged from the 2 nd electrode 3 remains in the U-shaped pipe 31, if the pump 26 is operated immediately after the electrolysis is stopped, the whole gas leaks out from the 2 nd pipe 25. In order to store the generated gas during electrolysis in the U-shaped pipe 31 as the gas storage portion G, it is preferable to stop the pump 26 immediately after the gas generation by electrolysis is stopped.
Instead of the above-mentioned method, the method may be performed by mixing the gas (e.g., O 2 ) The gas-liquid separation is performed to form the gas storage portion G, and, for example, as shown in fig. 8, gas is supplied from the external gas supply portion 32 to a portion where the gas storage portion G of the U-shaped pipe 31 is formed. The gas supplied from the gas supply unit 32 is not particularly limited, and may be oxygen (O 2 ) May be other than nitrogen (N) 2 ) Argon (Ar), air, etc. When the gas is supplied from the external gas supply unit 32, the pump 26 may be stopped within a range where the liquid surface of the gas-liquid mixture flow of the U-shaped pipe 31 does not drop.
When a backflow suppressing pipe such as a U-shaped pipe 31 is used, the 2 nd pipe 25 is preferably connected to a position lower than the liquid surface of the water tank 22. The liquid level of the water tank 22 is set by a liquid level sensor in the same manner as in embodiment 1. This makes it possible to suppress the backflow of pure water in the water tank 22 by the gas reserving portion G formed in the backflow suppressing piping such as the U-shaped piping 31 while maintaining the liquid-tight state by the 2 nd piping 25. This can suppress degradation in characteristics, durability, and the like of the electrolytic cell 1.
(embodiment 3)
An electrochemical reaction apparatus 20 according to embodiment 3 will be described with reference to fig. 9. In the electrochemical reaction apparatus 20 shown in fig. 9, a long pipe 33 is provided as a backflow suppressing pipe in the 2 nd pipe 25 connecting the water tank 22 and the outlet OUT of the 2 nd flow path 13 of the 2 nd electrode 3. During operation of the apparatus, the generated oxygen and ultrapure water move into the water tank 22 through the 2 nd pipe 25 including the long pipe 33. When the operation of the electrochemical reaction apparatus 20 is stopped, pure water flows back from the water tank 22 to the 2 nd electrode 3. In contrast, by sufficiently extending the length of the 2 nd pipe 25 including the long pipe 33 (for example, the shortest distance to the 2 nd pipe 25 is about several tens times), the time for pure water to reach the 2 nd electrode 3 from the water tank 22 can be extended.
The appropriate length of the 2 nd pipe 25 can be calculated by using the philosophy from the impurity concentration of the water contained in the water tank 22 and the pipe diameter. That is, since the length of the 2 nd pipe 25 in which the impurity in the water diffuses to the 2 nd electrode 3 can be calculated by using the philter's law, the length of the 2 nd pipe 25 including the long pipe 33 can be set so that the specific resistance of the water reaching the 2 nd electrode 3 is not lower than 5mΩ·cm by taking into consideration the time for stopping the electrochemical reaction apparatus 20, for example. When the operation stop period is long, it is preferable to further lengthen the pipe length. In this way, by sufficiently extending the length of the 2 nd pipe 25 by the long pipe 33, the time for pure water to reach the 2 nd electrode 3 from the water tank 22 can be prolonged, and the 2 nd flow path 13 and the 2 nd electrode 3 can be maintained in a state filled with ultrapure water for a long period of time. Therefore, deterioration of the electrolytic cell 1 and the electrolytic device 20 can be suppressed.
(embodiment 4)
An electrochemical reaction apparatus 20 according to embodiment 4 will be described with reference to fig. 10. Fig. 10 shows an electrochemical reactor 41 in which a plurality of electrochemical reaction cells shown in fig. 1 are stacked. The basic constitution other than this is substantially the same as that of the electrochemical reaction apparatus 20 shown in FIG. 2. The differences between the electrochemical reaction apparatus 20 shown in fig. 2 and the electrochemical reaction apparatus 20 shown in fig. 10 will be mainly described below. The electrochemical reaction apparatus 20 shown in fig. 10 has a water tank 22 as a liquid tank for storing the liquid to be treated in the 2 nd flow path for supplying the liquid to the 2 nd electrode, similarly to the electrochemical reaction apparatus 20 shown in fig. 2. A reverse osmosis membrane (RO membrane) device 42 and a carbon filter device 43 are connected to the water tank 22 as a pure water production device. On the upstream side of the carbon filter device 43, a solenoid valve 44 electrically connected to the liquid level sensor 29 provided in the water tank 22 is provided. When the liquid level in the water tank 22 measured by the liquid level sensor 29 is lower than the lower limit value, the solenoid valve 44 is opened, and pure water is supplied to the water tank 22 through the carbon filter device 43 and the RO membrane device 42.
The 1 st pipe 24, which is a water supply pipe to the tank stack 41, is provided with a pump 26 and an ion exchange resin device 45 as an ultrapure water production device. Ultrapure water having a specific resistance of 17 M.OMEGA.cm@25deg.C or higher, such as 18.24 M.OMEGA.cm@25deg.C, can be supplied from the ion exchange resin device 45 to the 2 nd electrode of the cell stack 41. An outlet of the 2 nd flow path of the 2 nd electrode in the cell stack 41 is connected to oxygen (O) generated by decomposing water in the cell stack 41 2 ) And the remaining ultrapure water is returned to the 2 nd pipe 25 in the water tank 22. The 2 nd pipe 25 is connected to a position higher than the liquid level in the water tank 22 set by the liquid level sensor 29. Thus, when the operation of the tank stack 41 is stopped, the water in the 2 nd pipe 25 is prevented from flowing back into the tank stack 41.
However, if the stop time of the stack 41 becomes longer, the water remaining in the 2 nd pipe 25 evaporates, and the MEA is dried. If the membrane shrinks when dried, swelling may occur when water is supplied again, and mechanical load is applied to the membrane by repeating the dry-wet cycle, so that there is a concern that the flow path is blocked by rupture or deformation of the membrane, or durability of the cell stack 41 is lowered. From such a viewpoint, it is preferable that the 2 nd pipe 25 is connected to a position lower than the liquid surface in the water tank 22 set by the liquid surface sensor 29. However, the light cannot suppress the backflow of the water in the 2 nd pipe 25 into the tank stack 41. In this regard, the following configurations of embodiment 5 or 6 or other embodiments are preferably adopted.
(embodiment 5)
The electrochemical reaction device 20 according to embodiment 5 will be described with reference to fig. 11. The differences between the electrochemical reaction apparatus 20 shown in fig. 11 and the electrochemical reaction apparatus 20 of embodiment 4 shown in fig. 10 will be mainly described. The electrochemical reaction apparatus 20 shown in fig. 11 includes a water tank 47 having an overflow structure separated into two tanks, i.e., a low water level tank portion L and a high water level tank portion H, by an overflow wall 46. In the water tank 47 having the overflow wall 46, one of the two tanks partitioned by the overflow wall 46 is a high water level tank portion H on the water inlet side, and the other is a low water level tank portion L on the water outlet side. The water supply pipe 48 of the RO membrane device 42 is connected to the low water level tank L. Pure water (process stock solution) produced in the RO membrane device 42 is supplied to the low water level tank L. The 1 st pipe 24, which is a water supply pipe to the tank stack 41, is connected to the low water level tank L. The 2 nd pipe 25, which is a drain pipe from the tank stack 41, is connected to the high water level tank H. The ultrapure water (treatment target liquid) treated in the tank stack 41 is returned to the high water level tank section H. The 2 nd pipe 25 is connected to water below the liquid surface set by the overflow wall 46 of the high water level tank H. Thereby, the water seal of the 2 nd pipe 25 is maintained.
In the water tank 47 having the double tank structure, water fed into the high water level tank portion H exceeds the overflow wall 46 and is fed into the low water level tank portion L. Therefore, the water fed into the high water level groove portion H is not mixed with the water remaining in the low water level groove portion L. As described above, since the 2 nd pipe 25 is connected below the liquid surface of the high water level tank H, the water returned from the tank stack 41 (ultrapure water having a specific resistance of 17mΩ·cm or more) does not mix with the water remaining in the low water level tank L (pure water having a specific resistance in the range of 0.1 to 5mΩ·cm). Therefore, even if the ultrapure water stored in the high water level tank section H and the ultrapure water in the 2 nd pipe 25 flow back into the tank stack 41 when the operation of the tank stack 41 is stopped, the performance of the tank stack 41 is not degraded. That is, the pure water produced in the RO membrane apparatus 42 contains little anion component, cation component, and SiO 2 And (3) particles. The ionic conductivity is reduced by the introduction of the ionic molecules into the separator, or the ionic molecules are adsorbed on the catalyst on the 1 st electrode and the 2 nd electrode, so that the reaction area of electrochemical reactions such as electrolysis is reduced. However, the ultrapure water is merely flowed back into the tank stack 41. That is, the liquid to be treated (ultrapure water) containing pure water as the treatment stock solution does not flow back into the tank stack 41. Therefore, the performance of the cell stack 41 is not degraded. Degradation of the cell stack 41 and the electrolysis device 20 can be suppressed.
(embodiment 6)
An electrochemical reaction apparatus 20 according to embodiment 6 will be described with reference to fig. 12. The differences between the electrochemical reaction apparatus 20 shown in fig. 12 and the electrochemical reaction apparatus 20 of the 4 th and 5 th embodiments shown in fig. 10 and 11 will be mainly described. In the electrochemical reaction apparatus 20 shown in fig. 12, the RO membrane device 42 is directly connected to the 1 st pipe 24 which is a water supply pipe to the tank stack 41. The 1 st pipe 24 is provided with a pump 26 and an ion exchange resin device 45. Therefore, the pure water as the treatment stock solution produced by the RO membrane device 42 is directly supplied to the ion exchange resin device 45 for producing the ultrapure water as the treatment target solution through the 1 st pipe 24. The water tank 22 is connected to the 2 nd pipe 25 which is a drain pipe from the tank stack 41. The pipe 49 on the outlet side of the water tank 22 is connected to the upstream side of the pump 26 of the 2 nd pipe 25. The pipe 49 is provided with a check valve 50.
In the electrochemical reaction apparatus 20 having such a configuration, pure water produced by the RO membrane apparatus 42 is directly fed to the ion exchange resin apparatus 45 without passing through the water tank 22. Ultrapure water produced by the ion exchange resin device 45 is fed into the tank stack 41. The water (ultrapure water) discharged from the tank stack 41 is fed into the water tank 22, and then fed into the tank stack 41 through the pipe 49 and the ion exchange resin device 45. At this time, since the pure water produced by the RO membrane device 42 is not fed into the water tank 22, the water remaining in the water tank 22 is basically only ultrapure water passing through the tank stack 41. Therefore, even if the ultrapure water stored in the water tank 22 and the ultrapure water in the 2 nd pipe 25 flow back into the tank 41 when the operation of the tank 41 is stopped, the ultrapure water as the treatment target liquid containing the pure water as the treatment stock solution does not flow back into the tank 41, and therefore, the performance of the tank 41 is not lowered as in the electrochemical reaction apparatus 20 of embodiment 5.
The electrochemical reaction apparatus 20 of embodiment 6 may have a configuration shown in fig. 13. Fig. 13 is a diagram showing a modification of the electrochemical reaction device 20 shown in fig. 12. In the electrochemical reaction apparatus 20 shown in fig. 13, the RO membrane device 42 is connected to the 1 st piping 24 in the same manner as the electrochemical reaction apparatus 20 shown in fig. 12. Not only the RO membrane device 42 but also a pipe 56 from the RO membrane device 42 is connected to the 1 st pipe 24, and an ejector 55 provided in the 2 nd pipe 24 connected to the outlet of the water tank 22 is connected thereto. The 2 nd pipe 24 has a pump 26, a check valve 54, and an ejector 55, which are provided in this order on the upstream side of the ion exchange resin device 45. The ejector 55 is connected to the ion exchange resin device 45 via the 1 st pipe 24. In fig. 12, a pump 26 is disposed downstream of the connection portion between the 2 nd piping 24 and the piping 56 of the RO membrane device 42, whereas in fig. 13, the piping 56 of the RO membrane device 42 is connected downstream of the pump 26 in the 2 nd piping 24.
The ejector 55 is a jet pump having two inlets of a relatively high-pressure water inlet (1 st inlet) 55a and a relatively low-pressure water inlet (2 nd inlet) 55b, and 1 outlet 55c. A water feed port of the pump 26 for ejecting water having a relatively high pressure is connected to the 1 st inlet 55 a. The 2 nd inlet 55b is connected to a water supply port of the RO membrane device 42 for discharging water having a relatively low pressure. Inside the ejector 55, water having a relatively high pressure (water ejected from the pump 26/water in the water tank 22) is ejected from the nozzle, and the water having a relatively low pressure (water ejected from the RO membrane device 42) is ejected by the impact force so as to be entrained, whereby the water having a relatively low pressure ejected from the RO membrane device 42 is easily supplied to the ion exchange resin device 45. In addition, the ejector 55 also has an effect of mixing water having a relatively high pressure and water having a relatively low pressure. Thus, the pressure of the water supply port of the RO membrane apparatus 42 is maintained at a low pressure favorable for RO membrane treatment, and water (RO water) discharged from the RO membrane apparatus 42 can be supplied to the pipe having a high pressure, so that ultrapure water treatment can be performed immediately. Therefore, the retention of the RO water of relatively low purity in the system can be suppressed to the minimum, and thus the contamination of the electrochemical device 1 can be effectively suppressed.
(embodiment 7)
The electrochemical reaction device 20 according to embodiment 7 will be described with reference to fig. 13 and 14. The differences between the electrochemical reaction apparatus 20 shown in fig. 13 and 14 and the electrochemical reaction apparatus 20 of the 4 th and 5 th embodiments shown in fig. 10 and 11 will be mainly described. In FIG. 13 and the drawings14, a 2 nd water tank (gas-liquid separation tank) 51 having a gas-liquid separation function is connected to the outlet of the 1 st flow path of the 1 st electrode of the cell stack 41. Hydrogen (H) generated by water decomposition is extracted from the 1 st electrode of the cell stack 41 2 ) And the remaining water is fed into a 2 nd water tank (gas-liquid separation tank) 51. The configuration of the water tank (1 st water tank) 22 and the like are the same as those of the 4 th electrochemical reaction apparatus 20 shown in fig. 10, except that the 2 nd pipe 25 is connected below the water surface of the 1 st water tank 22.
However, when the operation of the tank stack 41 is stopped, the following is considered as a factor of the backflow of the water remaining in the water tank 22 and the water in the 2 nd pipe 25 into the tank stack 41. That is, when the operation of the cell stack 41 is stopped, water flows from the 2 nd electrode into the 1 st electrode via the separator. Thus, when the operation of the tank stack 41 is stopped, it is considered that the water remaining in the water tank 22 and the water in the 2 nd pipe 25 flow back into the tank stack 41. In order to prevent the water in the water tank 22 and the 2 nd pipe 25 from flowing back into the cell stack 41, the water may be prevented from flowing from the 2 nd electrode to the 1 st electrode through the separator when the operation of the cell stack 41 is stopped.
Therefore, in the electrochemical reaction apparatus 20 shown in fig. 13, the 2 nd water tank 51 is provided so that the liquid surface of the 2 nd water tank (gas-liquid separation tank) 51 is higher than the liquid surface of the 1 st water tank 22. Since the internal pressure of the 2 nd water tank 51 is made higher than the internal pressure of the 1 st water tank 22 based on the rest positions of the 2 nd water tank 51 and the 1 st water tank 22, the backflow of water in the 1 st water tank 22 and the 2 nd pipe 25 into the tank stack 41 at the time of stopping the operation of the tank stack 41 can be suppressed. Since the internal pressure of the 2 nd water tank 51 is higher than the internal pressure of the 1 st water tank 22, in the electrochemical reaction apparatus 20 shown in fig. 14, a valve 53 is provided in the gas discharge pipe 52 of the 2 nd water tank 51, and the opening and closing operations of the valve 53 are controlled. By adopting such a constitution, the internal pressure P of the 1 st water tank 22 is increased O2 Increasing the internal pressure P of the 2 nd water tank 51 H2 The backflow of water in the 1 st water tank 22 and the 2 nd pipe 25 into the tank stack 41 can be suppressed when the operation of the tank stack 41 is stopped.
Examples
Next, examples and evaluation results thereof will be described.
Example 1
As shown in fig. 2, an electrochemical reaction apparatus (electrolyzer) 20 is configured by connecting a water tank 22 and a 2 nd flow path 12 of a 2 nd electrode 3 in an electrochemical reaction tank (electrolyzer) 1 with a 2 nd pipe 25 provided with a check valve 28. During operation of the apparatus, oxygen and ultrapure water generated in the 2 nd electrode 3 are supplied to the water tank 22 through the 2 nd pipe 25. On the other hand, when the device is stopped, the water in the water tank 22 does not flow back to the 2 nd electrode 3 through the check valve 28. At this time, the height difference of the check valve 28 provided below the liquid surface of the water tank 22 is 30cm, and the minimum operating pressure of the check valve 28 based on the formula (3) is preferably set to 3kPa or more. Thus, in example 1, a ball check valve having a minimum operating pressure of 5kPa was used.
In the electrochemical reaction apparatus 20 having such a configuration, a specific resistance meter was provided at a portion between the check valve 28 of the 2 nd pipe 25 and the 2 nd flow path 13, and it was confirmed that the water quality did not significantly decrease from 18.24mΩ·cm when the apparatus was stopped. With such an apparatus, the procedure of running for 1 hour at 50A and then stopping for 24 hours was repeated 300 times as 1 time. At the beginning of the operation of the device, the voltage was 1.85V and the current density was 2A/cm 2 . On the other hand, after repeating 300 times, it was confirmed that the sustain voltage was 1.87V and the current density was 2A/cm 2 Is a value of (2).
Example 2
As shown in fig. 6, a U-shaped pipe 31 is provided in the 2 nd pipe 25 between the water tank 22 and the 2 nd flow path 13 in the electrochemical reaction cell (electrolytic cell) 1 so as to be convex upward. During operation of the apparatus, oxygen and ultrapure water generated in the 2 nd electrode 3 are supplied to the water tank 22 through the 2 nd pipe 25. On the other hand, when the apparatus is stopped, the pump 26 is stopped immediately after the electrolysis is stopped, and the generated gas is formed in the U-shaped pipe 31, thereby causing gas to remain. Thus, the water in the water tank 22 is caused to flow together and shut off by the gas, so that the water does not flow back to the 2 nd electrode 3.
In the electrochemical reaction apparatus 20 having such a configuration, the gas in the U-shaped pipe 31 is stored closer to the 2 nd electrode 3 side than the water in the 2 nd pipe 25A specific resistance meter was provided, and it was confirmed that the water quality did not significantly decrease from 18.24 M.OMEGA.cm when the apparatus was stopped. With such an apparatus, the procedure of running for 1 hour at 50A and then stopping for 24 hours was repeated 300 times as 1 time. At the beginning of the operation of the device, the voltage was 1.85V and the current density was 2A/cm 2 . On the other hand, after repeating 300 times, it was confirmed that the sustain voltage was 1.87V and the current density was 2A/cm 2 Is a value of (2).
Example 3
As shown in fig. 6 and 8, a U-shaped pipe 31 is provided in the 2 nd pipe 25 between the water tank 22 and the 2 nd flow path 13 in the electrochemical reaction cell (electrolytic cell) 1 so as to be convex upward. The gas supply unit 32 is connected to the upper portion of the U-shaped pipe 31, and is configured to be able to supply gas from the outside to the U-shaped pipe 31. During operation of the apparatus, oxygen and ultrapure water generated in the 2 nd electrode 3 are supplied to the water tank 22 through the 2 nd pipe 25. On the other hand, when the apparatus is stopped, the pump 26 is temporarily operated immediately after the stop of electrolysis, and then gas is injected from the outside into the U-shaped pipe 31 to form gas storage. Thus, the water in the water tank 22 is caused to flow together and shut off by the gas, and thus does not flow back to the 2 nd electrode 3.
In the electrochemical reaction apparatus 20 having such a configuration, it was confirmed that the water quality was not greatly lowered from 18.24mΩ·cm when the apparatus was stopped by providing a specific resistance meter at the portion where the water in the 2 nd pipe 25 was stored on the 2 nd electrode 3 side of the gas stored in the U-shaped pipe 31. With such an apparatus, the procedure of running for 1 hour at 50A and then stopping for 24 hours was repeated 300 times as 1 time. At the beginning of the operation of the device, the voltage was 1.85V and the current density was 2A/cm 2 . On the other hand, after repeating 300 times, it was confirmed that the sustain voltage was 1.87V and the current density was 2A/cm 2 Is a value of (2).
Example 4
As shown in fig. 9, a long pipe 33 is provided in the 2 nd pipe 25 between the water tank 22 and the 2 nd flow path 13 in the electrochemical reaction cell (electrolytic cell) 1. Assuming that the impurity concentration of water in the water tank 22 is 2ppm, the necessary piping length when the piping diameter is 1 inch is calculated from the philter's law. In example 4, the pipe length of the 2 nd pipe 25 including the long pipe 33 was set to 2m as a sufficient length that the 24-hour specific resistance did not decrease.
In the electrochemical reaction apparatus 20 having such a configuration, a specific resistance meter was provided near the 2 nd channel 13 of the 2 nd pipe 25, specifically, at a position 5cm away from the 2 nd channel 13, and it was confirmed that the water quality was 15mΩ·cm at 3 hours, 10mΩ·cm at 12 hours, and 7mΩ·cm at 24 hours after the apparatus was stopped, and the water quality of the water tank 24 did not drop to 0.1mΩ·cm. With such an apparatus, the procedure of running for 1 hour at 50A and then stopping for 24 hours was repeated 300 times as 1 time. At the beginning of the operation of the device, the voltage was 1.85V and the current density was 2A/cm 2 . On the other hand, after repeating 300 times, it was confirmed that the sustain voltage was 1.89V and the current density was 2A/cm 2 Is a value of (2).
Comparative example 1
In fig. 2, 6, and 9, the electrochemical reaction apparatus 20 is constituted by connecting the water tank 22 to the 2 nd channel 13 at the shortest distance by the 2 nd pipe 25 without the backflow suppressing means. In the electrochemical reaction apparatus 20 having such a configuration, a specific resistance of water after the apparatus is stopped is measured by providing a specific resistance meter between the water tank 22 and the 2 nd flow path 13 when the apparatus is stopped. As a result, it was found that the specific resistance of water was reduced to about 1 M.OMEGA.cm for about 3 hours and to 0.1 M.OMEGA.cm for about 12 hours. This indicates that the water of the water tank 22 is flowing back into the MEA 9. With this apparatus, the operation was repeated 300 times under the same conditions as in example 1. At the beginning of the operation of the device, the voltage was 1.85V and the current density was 2A/cm 2 . In contrast, after repeating 300 times, the voltage was increased to 2.25V and the current density was 2A/cm 2 . From the above results, it was confirmed that the degradation of the electrolytic cell 1 proceeds due to the reverse flow of the water tank 22 when the apparatus is stopped.
The configurations of the above embodiments can be applied in combination, and partial substitution can be performed. Although several embodiments of the present invention have been described herein, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other modes, and various omissions, substitutions, modifications, and the like can be made without departing from the spirit of the invention. These embodiments and modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and their equivalents.
Claims (20)
1. An electrochemical reaction device, comprising:
an electrochemical reaction cell comprising a 1 st electrode having a 1 st flow path, a 2 nd electrode having a 2 nd flow path, and a separator sandwiched between the 1 st electrode and the 2 nd electrode;
a liquid tank that accommodates a liquid to be treated in the 2 nd flow path for supplying the liquid to the 2 nd electrode;
a 1 st pipe that connects an inlet of the 2 nd flow path and the tank and supplies the liquid to be treated to the 2 nd flow path;
a second piping that connects an outlet of the second flow path to the liquid tank and returns the liquid to be treated to the liquid tank; and
and a reverse flow suppressing means provided in the 2 nd pipe for preventing reverse flow of the liquid to be treated flowing in the 2 nd pipe or reducing a reverse flow rate.
2. The electrochemical reaction apparatus according to claim 1, wherein,
the liquid tank is provided with a liquid level sensor,
the 2 nd pipe is connected to a position lower than the liquid level in the liquid tank set by the liquid level sensor.
3. The electrochemical reaction apparatus according to claim 1, wherein the reverse flow suppressing mechanism is provided with a check valve.
4. The electrochemical reaction apparatus of claim 3, wherein the check valve has a swing check valve, a lift check valve, a butt check valve, or a ball check valve.
5. The electrochemical reaction apparatus according to claim 1, wherein the backflow suppressing mechanism comprises a backflow suppressing pipe having a shape capable of forming a gas storage section.
6. The electrochemical reaction apparatus according to claim 5, wherein the backflow suppressing mechanism includes a gas supply portion for supplying a gas to the gas storage portion of the backflow suppressing piping.
7. The electrochemical reaction apparatus according to claim 1, wherein,
the liquid tank is provided with a liquid level sensor,
the 2 nd pipe is connected to a position higher than the liquid level in the liquid tank set by the liquid level sensor.
8. The electrochemical reaction apparatus according to claim 1, wherein,
further comprises a gas-liquid separation tank connected to the outlet of the 1 st flow path,
the gas-liquid separation tank is disposed such that the liquid level in the tank is higher than the liquid level in the tank set by a liquid level sensor provided in the tank.
9. The electrochemical reaction apparatus according to claim 1, further comprising:
a gas-liquid separation tank connected to the outlet of the 1 st flow path, and
a valve provided in a gas discharge pipe of the gas-liquid separation tank;
The valve is controlled so that the internal pressure of the gas-liquid separation tank is higher than the internal pressure of the liquid tank.
10. The electrochemical reaction apparatus according to claim 1, further comprising:
a pure water producing part connected to the liquid tank and supplying pure water to the liquid tank, and
an ultrapure water producing section provided in the 1 st pipe and supplying ultrapure water to the 2 nd flow path of the 2 nd electrode;
the electrochemical reaction tank is configured to electrolyze the ultrapure water.
11. An electrochemical reaction device, comprising:
an electrochemical reaction cell comprising a 1 st electrode having a 1 st flow path, a 2 nd electrode having a 2 nd flow path, and a separator sandwiched between the 1 st electrode and the 2 nd electrode,
a target liquid supply system including a pure water producing section for producing pure water, and an ultrapure water producing section for producing ultrapure water by treating pure water supplied from the pure water producing section, the ultrapure water being supplied as a target liquid to the electrochemical reaction tank, and
a liquid tank for storing the liquid to be treated which is supplied to the electrochemical reaction tank and is treated;
the liquid to be treated supply system is provided with a pure water backflow suppressing means for suppressing backflow of the liquid to be treated containing the pure water from the liquid tank into the electrochemical reaction tank.
12. The electrochemical reaction apparatus according to claim 11, wherein,
the liquid tank is provided with an overflow structure which is separated into a low water level groove part and a high water level groove part through an overflow wall,
a pipe for supplying the deionized water from the deionized water producing portion to the ultrapure water producing portion is connected to the low water level tank portion of the liquid tank, and the deionized water is supplied to the ultrapure water producing portion via the low water level tank portion of the liquid tank,
and a pipe for returning the liquid to be treated from the electrochemical reaction tank to the liquid tank is connected to the high water level tank portion of the liquid tank.
13. The electrochemical reaction apparatus according to claim 11, wherein,
a supply pipe for supplying the pure water from the pure water producing section to the ultrapure water producing section is directly connected to the ultrapure water producing section,
a pipe for returning the liquid to be treated from the electrochemical reaction tank to the liquid tank is connected to the liquid tank, and a pipe for supplying the liquid to be treated from the liquid tank to the electrochemical reaction tank is connected to an upstream side of the ultrapure water production section of the supply pipe via a check valve.
14. The electrochemical reaction apparatus according to claim 11, wherein,
A pipe for supplying the liquid to be treated from the liquid tank to the electrochemical reaction tank is connected to the ultrapure water production section via a pump and an ejector,
a water supply port for supplying the pure water from the pure water producing section is connected to the ejector.
15. An electrochemical reaction method comprising the steps of:
a step of preparing a liquid to be treated by treating the raw liquid to be treated;
a step of supplying the liquid to be treated to a 2 nd flow path of an electrochemical reaction tank, and causing an electrochemical reaction in the electrochemical reaction tank, wherein the electrochemical reaction tank includes a 1 st electrode having a 1 st flow path, a 2 nd electrode having a 2 nd flow path, and a separator sandwiched between the 1 st electrode and the 2 nd electrode; and
and a step of suppressing backflow of the liquid to be treated containing the raw liquid to the 2 nd flow path while stopping the electrochemical reaction of the liquid to be treated.
16. The electrochemical reaction process of claim 15, wherein,
the stock solution is temporarily stored in a tank, and then treated to prepare the solution to be treated,
the liquid to be treated in the electrochemical reaction tank is returned to the liquid tank through a pipe provided with a check valve.
17. The electrochemical reaction process of claim 15, wherein,
the stock solution is temporarily stored in a tank, and then treated to prepare the solution to be treated,
the liquid to be treated in the electrochemical reaction tank is returned to the liquid tank through a backflow suppressing pipe having a shape capable of forming a gas storage portion.
18. The electrochemical reaction process of claim 15, wherein,
the stock solution is treated to prepare the solution to be treated after being temporarily stored in the low water level tank portion of a liquid tank having an overflow structure separated into two tanks, a low water level tank portion and a high water level tank portion by an overflow wall,
the liquid to be treated in the electrochemical reaction tank is returned to the high water level tank portion of the liquid tank.
19. The electrochemical reaction process of claim 15, wherein,
the stock solution is temporarily stored in a tank, and then treated to prepare the solution to be treated,
the liquid to be treated by the electrochemical reaction tank is returned to the liquid tank,
the electrochemical reaction tank includes a gas-liquid separation tank connected to the outlet of the 1 st flow path, and is controlled so that the internal pressure of the gas-liquid separation tank is higher than the internal pressure of the liquid tank.
20. The electrochemical reaction process of claim 15, wherein,
the treatment stock solution is pure water produced by a pure water producing section,
the pure water is directly sent to an ultrapure water production section to produce ultrapure water as the liquid to be treated,
the ultrapure water is sent to the electrochemical reaction tank via a pipe for treatment,
the ultrapure water treated by the electrochemical reaction tank is sent to a liquid tank,
the ultrapure water stored in the liquid tank is sent to a position upstream of the ultrapure water production section of the piping via a check valve.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2022-011964 | 2022-01-28 | ||
| JP2022118767A JP2023110824A (en) | 2022-01-28 | 2022-07-26 | Electrochemical reaction apparatus and electrochemical reaction method |
| JP2022-118767 | 2022-07-26 |
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| Publication Number | Publication Date |
|---|---|
| CN116555791A true CN116555791A (en) | 2023-08-08 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202211089298.9A Pending CN116555791A (en) | 2022-01-28 | 2022-09-07 | Electrochemical reaction device and electrochemical reaction method |
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| CN (1) | CN116555791A (en) |
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- 2022-09-07 CN CN202211089298.9A patent/CN116555791A/en active Pending
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