US20230227986A1

US20230227986A1 - Sodium hydroxide production device and sodium hypochlorite production device including the same

Info

Publication number: US20230227986A1
Application number: US18/186,790
Authority: US
Inventors: Boong Ik Jung; Jung Sik Kim; Tae Shin CHO; Dong Hyuck CHOI; Tae Woo Kim
Original assignee: Techwin Co Ltd
Current assignee: Techwin Co Ltd
Priority date: 2020-10-13
Filing date: 2023-03-20
Publication date: 2023-07-20
Also published as: KR102433195B1; WO2022080793A1; KR20220048590A

Abstract

One aspect of the present invention provides a sodium hydroxide production device, which includes: a first tank configured to store a sodium salt including two or more sodium ions in a molecule; a first electrolysis unit including a first anode chamber and a first cathode chamber which are partitioned by a first separator; and a water supply unit configured to supply water to the first tank and the first cathode chamber, wherein the first tank, a pipe configured to supply an aqueous sodium salt solution produced in the first tank to the first anode chamber, the first anode chamber, and a pipe configured to supply a material produced in the first anode chamber to the first tank constitute a closed loop, and a sodium hypochlorite production device including the same.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/KR2021/013973, filed on Oct. 12, 2021, which claims priority to and the benefit of Korean Patent Application No. 10-2020-0131650, filed on Oct. 13, 2020, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a sodium hydroxide production device and a sodium hypochlorite production device including the same.

BACKGROUND ART

Sodium hypochlorite (NaOCl) is being applied in various fields such as water supply and sewage, wastewater treatment, seawater electrolysis, ballast water treatment, agricultural food and food material sterilization, and the like.
Sodium hypochlorite is manufactured using a low-concentration sodium hypochlorite manufacturing system and a high-concentration sodium hypochlorite manufacturing system according to a concentration thereof.
Low-concentration sodium hypochlorite having a concentration of 0.4 to 1.0% is obtained by passing salt water through a separator-free electrolysis bath in which a contact-type electrode reaction takes place. High-concentration sodium hypochlorite having a concentration of 2% or more is obtained by reacting chlorine gas produced in a separator-containing electrolysis bath, in which a anode and a cathode are partitioned by a separator, with sodium hydroxide in a separate reaction unit.
FIG. 1 is a schematic diagram of a conventional system of manufacturing high-concentration sodium hypochlorite. Referring to FIG. 1 , a conventional sodium hypochlorite manufacturing system may include: a raw water treatment unit 10 configured to treat raw water to obtain purified water; and a salt water treatment unit 22 configured to treat saturated salt water prepared from some of purified water and salt stored in a salt tank 21, and the purified saturated salt water and residual purified water obtained in the salt water treatment unit 22 may be transferred to a anode chamber and a cathode chamber constituting an electrolysis unit 40, respectively.
The electrolysis unit 40 is a separator-containing electrolysis bath and may include a anode chamber, a cathode chamber, and a separator that partitions the anode chamber and the cathode chamber. The anode chamber and the cathode chamber includes a anode bath 50 and a cathode bath 60 that allow a anodic product and a cathodic product to be circulated, respectively, and in the anode bath, anodic water may be desalinated with hydrochloric acid, sodium hydroxide, or the like and then discharged to the outside or circulated to the salt tank 21 for reuse.
In addition, chlorine gas and sodium hydroxide, which are produced in the anode chamber and the cathode chamber, respectively, are reacted after passing through the anode bath 50 and the cathode bath 60 and moving to a reaction unit 70, and as a result, sodium hypochlorite is produced.
Additionally, when the pH of the produced aqueous sodium hypochlorite solution is decreased below 12, the concentration of ClO₃ ⁻, which is a disinfection by-product in the aqueous solution, is increased. Therefore, to stably store sodium hypochlorite by maintaining a pH of the aqueous solution above 12, equipment for injecting sodium hydroxide into the reaction unit 70 and/or a sodium hypochlorite tank (not shown) may be additionally provided.
As such, the conventional sodium hypochlorite manufacturing system has a problem in which the surrounding environment is contaminated due to anodic water discharged from a anode bath required for circulation of anodic water, a problem in which transportation, storage, and handling burdens are increased due to an increase in freezing point (in the case of a concentration of 30 wt % or more, a freezing point is increased to up to 15° C.) according to a toxicity and concentration increase of sodium hydroxide used to stably store the produced high-concentration sodium hypochlorite, and a problem in which a maintenance burden caused by a complicated configuration of various types of equipment (tanks, pipes, and the like) for supplying sodium hydroxide from the outside is increased.

DISCLOSURE

Technical Problem

The present invention is designed to solve the above-described problems of the related art and directed to providing a sodium hydroxide production device, which is environmentally friendly and has easy maintenance, and a sodium hypochlorite production device including the same.

Technical Solution

One aspect of the present invention provides a sodium hydroxide production device, which includes: a first tank configured to store a sodium salt including two or more sodium ions in a molecule; a first electrolysis unit including a first anode chamber and a first cathode chamber which are partitioned by a first separator; and a water supply unit configured to supply water to the first tank and the first cathode chamber, wherein the first tank, a pipe configured to supply an aqueous sodium salt solution produced in the first tank to the first anode chamber, the first anode chamber, and a pipe configured to supply a material produced in the first anode chamber to the first tank constitute a closed loop.
In an embodiment, the sodium salt may have a structure represented by the following Chemical Formula.
Na_xA_y <Chemical Formula>
In Chemical Formula, x is an integer of 2 or more, A is an anionic material capable of bonding to a sodium ion, and y is an integer satisfying the Chemical Formula.
In an embodiment, the sodium salt may be one selected from the group consisting of sodium carbonate, sodium sulfate, sodium persulfate, sodium phosphate dibasic, sodium phosphate tribasic, and a combination of two or more thereof.
In an embodiment, the first separator may be a cation-exchange membrane.
Another aspect of present invention provides a sodium hypochlorite production device, which includes the above sodium hydroxide production device and further includes: a second tank configured to store salt; a second electrolysis unit including a second anode chamber and a second cathode chamber which are partitioned by a second separator; and a reaction unit configured to react a anodic product produced in the second anode chamber and a cathodic product produced in the first and second cathode chambers to obtain sodium hypochlorite, wherein the water supply unit supplies water to the second tank and the second cathode chamber, and saturated salt water produced in the second tank is supplied to the second anode chamber.
In an embodiment, the sodium hypochlorite production device may not include equipment for injecting sodium hydroxide into the reaction unit from the outside of the sodium hypochlorite production device.
In an embodiment, the second separator may be a cation-exchange membrane.
In an embodiment, the first and second electrolysis units may be connected in parallel.
In an embodiment, at least one of the first and second electrolysis units may be automatically controlled according to the pH of sodium hypochlorite obtained in the reaction unit.

Advantageous Effects

A sodium hydroxide production device according to one aspect of the present invention can obtain sodium hydroxide in an environmentally friendly way using a sodium salt, which is substantially not harmful or toxic, as a raw material.
In addition, since the sodium hydroxide production device has a closed loop so that materials are circulated between a tank in which the sodium salt is stored and a anode chamber of a first electrolysis unit in which sodium hydroxide is produced, it can be combined with a second electrolysis unit for producing sodium hypochlorite. In this case, since sodium hydroxide produced in the first electrolysis unit can be used as a raw material for producing sodium hypochlorite in the second electrolysis unit or as a buffer for adjusting the pH of produced sodium hypochlorite, burdens caused by transportation, storage, handling, and use of sodium hydroxide can be significantly reduced.
Additionally, since the second electrolysis unit of a sodium hypochlorite production device includes a anode chamber, a cathode chamber, and a separator and, as necessary, does not include a cathode bath for circulating a cathodic product obtained in the cathode chamber and/or a anode bath for circulating a anodic product obtained in the anode chamber, a conventional problem in which the surrounding environment is deteriorated as anodic water containing a large amount of by-products is discharged from the anode bath can be solved.
However, it is to be understood that the effects of the present invention are not limited to the above-described effects and include all effects deducible from the configuration of the invention described in the detailed description of the present invention or in the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a conventional sodium hypochlorite production device.

FIG. 2 is a schematic diagram of a sodium hydroxide production device according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a first electrolysis unit according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of a sodium hypochlorite production device according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a second electrolysis unit according to an embodiment of the present invention.

FIG. 6 is a schematic diagram of a combination of first and second electrolysis units according to an embodiment of the present invention.

MODES OF THE INVENTION

Hereinafter, the present invention will be described in detail with reference to accompanying drawings. However, it should be understood that the present invention can be implemented in various forms, and that it is not intended to limit the present invention to the exemplary embodiments. Also, in the drawings, descriptions of parts unrelated to the detailed description are omitted to clearly describe the present invention. Throughout the specification, like numbers refer to like elements.
Throughout the specification, a certain part being “connected” to another part means that the certain part is “directly connected” to the other part or that the certain part is “indirectly connected” to the other part through another member interposed between the two parts. Also, a certain part “including” a certain element signifies that the certain part may further include, instead of excluding, another element unless particularly indicated otherwise.
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Sodium Hydroxide Production Device
FIG. 2 is a schematic diagram of a sodium hydroxide production device according to an embodiment of the present invention, and FIG. 3 is a schematic diagram of a first electrolysis unit according to an embodiment of the present invention.
Referring to FIGS. 2 and 3 , a sodium hydroxide production device according to one aspect of the present invention includes: a first tank configured to store a sodium salt including two or more sodium ions in a molecule; a first electrolysis unit including a first anode chamber and a first cathode chamber which are partitioned by a first separator; and a water supply unit configured to supply water to the first tank and the first cathode chamber, wherein the first tank, a pipe configured to supply an aqueous sodium salt solution produced in the first tank to the first anode chamber, the first anode chamber, and a pipe configured to supply a material produced in the first anode chamber to the first tank constitute a closed loop.
A first tank 200 may store a sodium salt including two or more sodium ions in a molecule. The sodium salt including two or more sodium ions in a molecule may be dissolved in water provided by a water supply unit 100 and supplied in an aqueous solution to a first anode chamber 310 of a first electrolysis unit 300.
The first tank 200 may store the sodium salt supplied from the outside, may be provided with purified water from the water supply unit 100 to produce an aqueous solution in which the sodium salt is dissolved, preferably, a saturated aqueous solution, and may supply the aqueous solution to the first anode chamber 310 of the first electrolysis unit 300.
The first tank 200 may include: a sodium salt supply portion through which the sodium salt is introduced in a solid state from the outside; a purified water inlet through which purified water is supplied from the water supply unit 100; and a saturated aqueous sodium salt solution outlet through which the saturated aqueous solution is discharged.
When a predetermined voltage is applied to the first electrolysis unit 300, the following materials may be produced in a first anode chamber 310 and a first cathode chamber 320.
First, sodium ions (Nat), carbon dioxide gas (CO₂) (only in a case where the sodium salt is sodium carbonate), and oxygen gas (O₂) may be produced in the first anode chamber 310, and hydrogen gas (H₂) and hydroxide ions (OH⁻) may be produced in the first cathode chamber 320. The sodium ions produced in the first anode chamber 310 may move to the first cathode chamber 320 through a first separator 330 and react with hydroxide ions produced in advance in the first cathode chamber 320 to produce sodium hydroxide.
The sodium hydroxide obtained in the sodium hydroxide production device may be used as a raw material for producing sodium hypochlorite along with sodium hydroxide produced in a second cathode chamber of a second electrolysis unit constituting a sodium hypochlorite production device to be described below, and as necessary, may be used as a buffer for adjusting the pH of produced sodium hypochlorite to increase storage stability.
The sodium salt may have a structure represented by the following Chemical Formula.
Na_xA_y <Chemical Formula>
In Chemical Formula, x is an integer of 2 or more, A is an anionic material capable of bonding to a sodium ion, and y is an integer satisfying the Chemical Formula.
The anionic material may be one selected from the group consisting of a carbonate ion (CO₃ ²⁻), a sulfate ion (SO₄ ²⁻), a persulfate ion ((S₂O₈)²⁻)), a phosphate ion (PO₄ ³⁻), a hydrogen phosphate ion (HPO₄ ²⁻), and a combination of two or more thereof and is preferably a carbonate ion, but the present invention is not limited thereto. Also, the sodium salt produced by bonding between the sodium ion and the anionic material may be one selected from the group consisting of sodium carbonate (Na₂CO₃), sodium sulfate (Na₂SO₄), sodium persulfate (Na₂S₂O₈), sodium phosphate tribasic (Na₃PO₄), sodium phosphate dibasic (Na₂HPO₄), and a combination of two or more thereof and is preferably sodium carbonate, but the present invention is not limited thereto.
The first electrolysis unit 300 may include the first anode chamber 310 and the first cathode chamber 320 which are partitioned by the first separator 330. The first anode chamber 310 may include a anode and may be loaded with anodic water including a material produced by an electrolysis reaction at the anode and a gas-phase material. Also, the first cathode chamber 320 may include a cathode and may be loaded with cathodic water including a material produced by an electrolysis reaction at the cathode and a gas-phase material.
Descriptions of electrolysis reactions in the first anode chamber 310 and the first cathode chamber 320, which constitute the first electrolysis unit 300, and the resulting products are described above.
The first separator 330 may be an ion-exchange membrane, for example, preferably, a cation-exchange membrane. The cation-exchange membrane may allow sodium ions (Na⁺) produced in the first anode chamber 310 to permeate and move to the first cathode chamber 320 and, as necessary, may include an additional layer and/or functional group capable of preventing hydroxide ions (OH⁻) produced in the first cathode chamber 320 from permeating and moving to the first anode chamber 310.
The water supply unit 100 may supply water to the first tank 200 and the first cathode chamber 320. Specifically, the water supply unit 100 may be a raw water treatment unit that treats raw water to produce purified water and supplies the purified water to the first tank 200 and the first cathode chamber 320.
The raw water treatment unit may produce purified water by removing impurities such as calcium, magnesium, and the like from raw water. The raw water treatment unit may use one selected from the group consisting of a water softener, a reverse osmosis membrane process, a nano-membrane process, an electrodialysis process, an electrosorption deionization process, and a combination of two or more thereof and preferably uses a water softener and/or a reverse osmosis membrane process, but the present invention is not limited thereto.
In the sodium hydroxide production device, the first tank 200, a pipe configured to supply an aqueous sodium salt solution produced in the first tank 200 to the first anode chamber 310, the first anode chamber 310, and a pipe configured to supply a material produced in the first anode chamber 310 to the first tank 200 may constitute a closed loop. As used herein, the term “closed loop” refers to a system controlled so that any material is not introduced from the outside or not discharged to the outside in the transfer and circulation of the material through the first tank 200, a pipe configured to supply an aqueous sodium salt solution produced in the first tank 200 to the first anode chamber 310, the first anode chamber 310, and a pipe configured to supply a material produced in the first anode chamber 310 to the first tank 200.
Particularly, the pipe configured to supply an aqueous sodium salt solution produced in the first tank 200 to the first anode chamber 310 and the pipe configured to supply a material produced in the first anode chamber 310 to the first tank 200 may not include a channel through which any material may flow in or out. However, when the sodium salt stored in the first tank 200 is consumed within a predetermined range, a required amount of sodium salt may be replenished in the first tank 200 so that an aqueous sodium salt solution having a required concentration is continuously supplied to the first anode chamber 310.
The closed loop may allow sodium hydroxide to be continuously and stably produced in the first cathode chamber 320 of the first electrolysis unit 300, and the produced sodium hydroxide may be used as a raw material for producing sodium hypochlorite along with sodium hydroxide produced in a second cathode chamber of a second electrolysis unit constituting a sodium hypochlorite production device to be described below, and as necessary, may be used as a buffer for adjusting the pH of produced sodium hypochlorite to increase storage stability.
When the sodium hydroxide production device is combined with a sodium hypochlorite production device to be described below, since separate equipment for injecting sodium hydroxide (equipment required for storage and injection of sodium hydroxide), which is essentially included in a conventional sodium hypochlorite production device, can be omitted, burdens caused by transportation, storage, handling, and use of sodium hydroxide can be significantly reduced.
Sodium Hypochlorite Production Device
FIG. 4 is a schematic diagram of a sodium hypochlorite production device according to an embodiment of the present invention, and FIG. 5 is a schematic diagram of a second electrolysis unit according to an embodiment of the present invention.
Referring to FIGS. 4 and 5 , a sodium hypochlorite production device according to another aspect of the present invention includes the above sodium hydroxide production device and further includes: a second tank 210 configured to store salt; a second electrolysis unit 400 including a second anode chamber 410 and a second cathode chamber 420 which are partitioned by a second separator 430; and a reaction unit (not shown) configured to react a anodic product produced in the second anode chamber 410 and a cathodic product produced in the first and second cathode chambers 320 and 420 to obtain sodium hypochlorite.
When the sodium hydroxide production device and the sodium hypochlorite production device are combined, the water supply unit 100 may supply water to the first tank 200, the second tank 210, and the second cathode chamber 420, and saturated salt water produced in the second tank 210 may be supplied to the second anode chamber.
The second tank 210 may store solid-phase salt. The salt may be dissolved in water provided by the water supply unit 100 and supplied in an aqueous solution to the second anode chamber 410 of the second electrolysis unit 400.
The second tank 210 may store the salt supplied from the outside. The second tank may be supplied with purified water from the water supply unit 100 to produce an aqueous solution in which the salt is dissolved, preferably, saturated salt water, and may supply the aqueous solution to the second anode chamber 410 of the second electrolysis unit 400.
The second tank 210 may include: a salt supply portion through which the salt is introduced in a solid state from the outside; a purified water inlet through which purified water is supplied from the water supply unit 100; and a saturated salt water outlet through which the saturated salt water is discharged.
In addition, a salt water treatment unit 220 may be provided between the second tank 210 and the second anode chamber 410. Since the salt water treatment unit 220 prevents contamination of the second separator 430 of the second electrolysis unit 400 by removing impurities such as calcium, magnesium, and the like included in saturated salt water discharged from the second tank 210, it may serve to increase electrolysis efficiency and the lifespan of the second separator 430.
The salt water treatment unit 220 may include a heating portion provided with a heater in a bath having a predetermined size and a water softening unit provided with a chelating resin capable of adsorbing and removing impurities in salt water passing through the heating portion. The heating portion may improve the adsorption efficiency of the water softening unit by appropriately maintaining the temperature and pH of unpurified saturated salt water. For example, the appropriate temperature and pH of saturated salt water may be 50 to 80° C. and 9 or more, respectively, but the present invention is not limited thereto.
The second electrolysis unit 400 may include the second anode chamber 410 and the second cathode chamber 420 which are partitioned by the second separator 430. The second anode chamber 410 may include a anode and may be loaded with anodic water including a material produced by an electrolysis reaction at the anode and a gas-phase material. Also, the second cathode chamber 420 may include a cathode and may be loaded with cathodic water including a material produced by an electrolysis reaction at the cathode and a gas-phase material.
When a predetermined voltage is applied to the second electrolysis unit 400, the following materials may be produced in the second anode chamber 410 and the second cathode chamber 420.
First, sodium ions (Nat), chlorine gas (Cl₂), and chlorine ions (Cl⁻) may be produced in the second anode chamber 410, and hydrogen gas (H₂) and hydroxide ions (OH⁻) may be produced in the second cathode chamber 420. The sodium ions produced in the second anode chamber 410 may move to the second cathode chamber 420 through the second separator 430 and react with hydroxide ions produced in advance in the second cathode chamber 420 to produce sodium hydroxide.
The sodium hydroxide produced in the second cathode chamber 420 may be used as a raw material for producing sodium hypochlorite along with sodium hydroxide obtained in the first cathode chamber 320 of the sodium hydroxide production device, and as necessary, may be used as a buffer for adjusting the pH of produced sodium hypochlorite to increase storage stability.
Since the sodium hypochlorite production device is combined with the sodium hydroxide production device and substantially uses sodium hydroxide obtained by the sodium hydroxide production device in an in-situ manner without controlling a material balance in the electrolysis unit and/or reaction unit and/or separately injecting sodium hydroxide, which is required for stably storing produced sodium hypochlorite, from the outside, separate equipment for injecting sodium hydroxide (equipment required for storage and injection of sodium hydroxide), which is essentially included in a conventional sodium hypochlorite production device, can be omitted, and accordingly, burdens caused by transportation, storage, handling, and use of sodium hydroxide can be significantly reduced.
The reaction unit may allow a cathodic product, specifically, sodium hydroxide, produced in the first cathode chamber 320 of the first electrolysis unit 300 and the second cathode chamber 420 of the second electrolysis unit 400 to react with a anodic product, specifically, chlorine gas, produced in the second anode chamber 410 of the second electrolysis unit 400 to produce sodium hypochlorite.
By appropriately adjusting a material balance in the reaction unit, the residual sodium hydroxide, which is not involved in production of sodium hypochlorite in sodium hydroxide produced in the first and second cathode chambers 320, 420, may be allowed to serve as a buffer that adjusts the pH of produced sodium hypochlorite within a predetermined range. In this case, the sodium hypochlorite production device may not include equipment for injecting sodium hydroxide into the reaction unit from the outside of the sodium hypochlorite production device.
The second separator 430 may be an ion-exchange membrane, for example, preferably, a cation-exchange membrane. The cation-exchange membrane may allow sodium ions (Nat) produced in the second anode chamber 410 to permeate and move to the second cathode chamber 420 and, as necessary, may include an additional layer and/or functional group capable of preventing hydroxide ions (OH⁻) produced in the second cathode chamber 420 from permeating and moving to the second anode chamber 410.
FIG. 6 is a schematic diagram of a combination of first and second electrolysis units according to an embodiment of the present invention. Referring to FIG. 6 , the first electrolysis unit 300 of the sodium hydroxide production device and the second electrolysis unit 400 of the sodium hypochlorite production device may be connected in parallel.
As used herein, the term “connected in parallel” means that the first and second electrolysis units 300 and 400 are connected so that the raw material injection and product discharge thereof are independently performed without any material movement and exchange between the first and second electrolysis units 300 and 400 such as injection of a product of the first electrolysis unit 300 into the second electrolysis unit 400 as a raw material or injection of a product of the second electrolysis unit 400 into the first electrolysis unit 300 as a raw material. However, as necessary, pipes for injecting, discharging, and transferring the same material may be integrated into a single pipe.
FIG. 6 shows a sodium hypochlorite production device in which a single first electrolysis unit 300 and a plurality of second electrolysis units 400 are sequentially and continuously disposed, but the present invention is not limited thereto. In the sodium hypochlorite production device, a plurality of first electrolysis units 300 may be provided, the first and second electrolysis units 300 and 400 may be alternately disposed, or a first electrolysis unit 300 may be disposed between a plurality of continuously disposed second electrolysis units 400.
A saturated aqueous sodium salt solution in the first electrolysis unit 300 may circulate through the first anode chamber 310 and the first tank 200, and the first cathode chamber 320 may allow water provided by the water supply unit 100 to be converted into sodium hydroxide and discharge the sodium hydroxide to the outside of the first electrolysis unit 300.
The second anode chamber 410 in the second electrolysis unit 400 may allow saturated salt water provided from the second tank 210 to be converted into chlorine gas and discharge the chlorine gas to the outside of the second electrolysis unit 400, and the second cathode chamber 420 may allow water provided by the water supply unit 100 to be converted into sodium hydroxide and discharge the sodium hydroxide to the outside of the first electrolysis unit 300.
A pipe for supplying water to the first and second cathode chambers 320 and 420 and a pipe for supplying saturated salt water to a plurality of second anode chambers 410 may each be branched from a single pipe. Also, a pipe for transferring sodium hydroxide produced in the first and second cathode chambers 320 and 420 and chlorine gas produced in a plurality of second anode chambers 410 to the reaction unit may be integrated into a single pipe.
According to the pH of sodium hypochlorite obtained in the reaction unit, at least one of the first and second electrolysis units may be automatically controlled.
For example, when the pH of sodium hypochlorite obtained in the reaction unit is below a predetermined range, the first electrolysis unit 300 may be further activated so that an excessive amount of sodium hydroxide relative to chlorine gas is produced. On the other hand, when the pH of sodium hypochlorite obtained in the reaction unit is above a predetermined range, an amount of produced sodium hydroxide may be reduced by delaying an electrolysis reaction of the first electrolysis unit 300 or lowering electrolysis efficiency. The amount of sodium hydroxide produced according to the pH of sodium hypochlorite obtained in the reaction unit may be automatically controlled by sensors, controllers, valves, pumps, and the like that are electrically connected to each other.
The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art to which the present invention pertains that the present invention can be easily modified and implemented in various other forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are only exemplary in all aspects and not limiting. For example, each of the constituents described as being one combined entity may be implemented separately, and similarly, constituents described as being separate entities may be implemented in a combined form.
It should be understood that the scope of the present invention is defined by the following claims and that all changes or modifications derived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention.

LIST OF REFERENCE NUMERALS

- 10: raw water treatment unit
- 21, 210: salt tank (second tank)
- 22, 220: salt water treatment unit
- 40: electrolysis unit
- 50: anode bath
- 51: primary desalination unit
- 52: secondary desalination unit
- 60: cathode bath
- 70: reaction unit
- 100: water supply unit
- 200: first tank
- 300: first electrolysis unit
- 310: first anode (first anode chamber)
- 320: first cathode (first cathode chamber)
- 330: first separator
- 400: second electrolysis unit
- 410: second anode (second anode chamber)
- 420: second cathode (second cathode chamber)
- 430: second separator

Claims

1. A sodium hydroxide production device comprising:

a first tank configured to store a sodium salt including two or more sodium ions in a molecule;

a first electrolysis unit including a first anode chamber and a first cathode chamber which are partitioned by a first separator; and

a water supply unit configured to supply water to the first tank and the first cathode chamber,

wherein the first tank, a pipe configured to supply an aqueous sodium salt solution produced in the first tank to the first anode chamber, the first anode chamber, and a pipe configured to supply a material produced in the first anode chamber to the first tank constitute a closed loop.

2. The sodium hydroxide production device of claim 1, wherein the sodium salt has a structure represented by the following Chemical Formula:

Na_xA_y <Chemical Formula>

in Chemical Formula,

x is an integer of 2 or more,

A is an anionic material capable of bonding to a sodium ion, and

y is an integer satisfying the Chemical Formula.

3. The sodium hydroxide production device of claim 2, wherein the sodium salt is one selected from the group consisting of sodium carbonate, sodium sulfate, sodium persulfate, sodium phosphate dibasic, sodium phosphate tribasic, and a combination of two or more thereof.

4. The sodium hydroxide production device of claim 1, wherein the first separator is a cation-exchange membrane.

5. A sodium hypochlorite production device comprising the sodium hydroxide production device according to claim 1, the device further comprising:

a second tank configured to store salt;

a second electrolysis unit including a second anode chamber and a second cathode chamber which are partitioned by a second separator; and

a reaction unit configured to react a anodic product produced in the second anode chamber and a cathodic product produced in the first and second cathode chambers to obtain sodium hypochlorite,

wherein the water supply unit supplies water to the second tank and the second cathode chamber, and

saturated salt water produced in the second tank is supplied to the second anode chamber.

6. The sodium hypochlorite production device of claim 5, wherein the sodium hypochlorite production device does not include equipment for injecting sodium hydroxide into the reaction unit from the outside of the sodium hypochlorite production device.

7. The sodium hypochlorite production device of claim 5, wherein the second separator is a cation-exchange membrane.

8. The sodium hypochlorite production device of claim 5, wherein the first and second electrolysis units are connected in parallel.

9. The sodium hypochlorite production device of claim 5, wherein at least one of the first and second electrolysis units is automatically controlled according to a pH of sodium hypochlorite obtained in the reaction unit.