JP2024001560A - Manufacturing method and manufacturing apparatus of electrolyte for vanadium redox flow battery - Google Patents

Abstract

To provide a manufacturing method and a manufacturing apparatus of an electrolyte for a simple and convenient vanadium redox flow battery in a low cost.SOLUTION: A manufacturing method includes steps of: preparing a solution containing an original powder containing pentavalent vanadium and less than tetravalent vanadium; obtaining a vanadium containing solution by mixing this original powder and the solution; and obtaining an electrolyte by performing an electrolytic reduction of the vanadium content solution. In this manufacturing method, a part of the electrolytes is used as a solution. A manufacturing apparatus comprises: an electrolyte tank; an accumulation tank of the electrolyte; a solvent tank of the original powder; an original supply line that supplies the original powder containing the pentavalent vanadium in the solvent tank; and a solution supply line that supplies one part of the electrolytes to the solvent tank.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a method and apparatus for producing an electrolyte for a redox flow battery. Specifically, the present disclosure relates to a method and apparatus for producing an electrolyte for a redox flow battery using vanadium as an active material.

Vanadium is used as a raw material for electrolyte, which is the main component of redox flow batteries, which are large storage batteries. In a redox flow battery (vanadium redox flow battery) that uses a sulfuric acid solution containing vanadium as an electrolyte, divalent vanadium ions (V ²⁺ ) are converted to trivalent vanadium ions (V ³⁺ ) on the negative electrode side during discharge. An oxidation reaction occurs, and on the positive electrode side, a reduction reaction occurs from pentavalent vanadyl ions (VO ₂ ⁺ ) to tetravalent vanadyl ions (VO ²⁺ ), and during charging, a reverse reaction occurs, making it difficult to use repeatedly. It is possible.

Conventionally, a sulfuric acid solution containing vanadium with an average valence of 3.5 has been used as an electrolyte for a vanadium redox flow battery. As a raw material for this electrolytic solution, a powder containing pentavalent vanadium (V ₂ O ₅ ) purified from vanadium-containing ore is used. An electrolytic solution can be obtained by dissolving this vanadium powder in sulfuric acid or the like and electrolytically reducing pentavalent vanadium ions (V ⁵⁺ ) in the solution to a desired valence. However, V ₂ O ₅ is usually slightly soluble in sulfuric acid solution, and its dissolution rate in sulfuric acid solution is extremely slow. Therefore, it takes a lot of time to produce an electrolytic solution by directly electrolytically reducing a solution containing pentavalent vanadium (V ⁵⁺ ). There is a need for a method for rapidly dissolving V ₂ O ₅ in a sulfuric acid solution.

Generally, after reducing V ₂ O ₅ using a chemical and dissolving it in a sulfuric acid solution, the resulting solution containing tetravalent vanadium (V ⁴⁺ ) is electrolytically reduced to an average valence of 3.5. A method for producing an electrolyte is known. Furthermore, a method is known in which V ₂ O ₅ is calcined in a reducing atmosphere to be reduced to a vanadium compound having a valence of 4 or less, and then dissolved in a sulfuric acid solution and electrolytically reduced.

Specifically, in Patent Document 1 (CA2635487A1), vanadyl sulfate solution (VOSO ₄ ) obtained by reacting V ₂ O ₅ and oxalic acid under predetermined reaction conditions is electrolyzed on the cathode side of an electrolytic cell. A technique for producing an electrolytic solution is disclosed. Patent Document 2 (WO02/04353A2) describes a technique for obtaining a vanadyl sulfate solution (VOSO ₄ ) by adding a sulfuric acid solution to a mixture of vanadium pentoxide (V ₂ O ₅ ) and vanadium trioxide (V ₂ O ₃ ). is disclosed.

Canadian Patent Application Publication No. 2635487 International Publication No. 2002/04353

A method of reducing and dissolving V ₂ O ₅ by adding a chemical such as oxalic acid disclosed in Patent Document 1, and a method of mixing and dissolving V ₂ O ₅ and V ₂ O ₃ disclosed in Patent Document 2 According to , manufacturing time is shortened due to improved dissolution rate. However, the chemicals used for reductive dissolution are expensive, and the production of V ₂ O ₃ is also expensive. Therefore, there is a problem that an increase in product cost as an electrolytic solution is unavoidable.

Furthermore, the electrolytic solution for a redox flow battery is desired to have high purity in order to avoid gas generation due to side reactions caused by impurities in the electrolytic solution and adhesion of precipitates to the electrodes. If inexpensive industrial grade chemicals are used for reductive dissolution, contamination from the chemicals may occur.

A technique for inexpensively and easily producing a high-purity vanadium-containing electrolyte solution applicable to redox flow batteries has not yet been proposed. An object of the present disclosure is to provide a manufacturing method and a manufacturing apparatus for efficiently obtaining an electrolyte for a vanadium redox flow battery without using chemicals such as oxalic acid.

The method for producing an electrolyte for a vanadium redox flow battery of the present disclosure includes:
(1) Preparing a raw material powder containing pentavalent vanadium and a solution containing less than tetravalent vanadium (2) Mixing the raw material powder and the solution to obtain a vanadium-containing solution; 3) It includes electrolytically reducing this vanadium-containing solution to obtain an electrolyte. In this manufacturing method, a part of the electrolytic solution obtained by electrolytic reduction is used as a solution for the raw material powder.

An apparatus for manufacturing an electrolyte for a vanadium redox flow battery according to the present disclosure includes an electrolytic cell for obtaining an electrolyte by electrolytically reducing a vanadium-containing solution, an electrolyte storage tank provided to be able to circulate with this electrolytic cell, and this storage tank. A dissolving tank is provided to be able to supply a vanadium-containing solution to the electrolytic tank, a raw material supply line that supplies raw material powder containing pentavalent vanadium to the dissolving tank, and a part of the electrolytic solution is dissolved as a dissolving solution. It is equipped with a solution supply line that supplies the solution to the tank.

According to the manufacturing method and manufacturing apparatus according to the present disclosure, a highly purified vanadium redox flow battery electrolyte can be efficiently manufactured at low cost.

FIG. 1 is a conceptual diagram for explaining an apparatus for producing an electrolyte for a vanadium redox flow battery according to an embodiment.

Hereinafter, the present disclosure will be described in detail based on preferred embodiments, with appropriate reference to the drawings. The present disclosure is not limited to the following embodiments, and additions, deletions, and changes can be made without departing from the spirit of the present disclosure.

[Vanadium redox flow battery electrolyte manufacturing equipment]
An apparatus for manufacturing an electrolyte for a vanadium redox flow battery (hereinafter referred to as an "electrolyte manufacturing apparatus" or "manufacturing apparatus") is used in a method for manufacturing an electrolyte, which will be described later. This electrolytic solution manufacturing device includes an electrolytic cell that obtains an electrolytic solution by electrolytically reducing a vanadium-containing solution, an electrolytic solution storage tank that is provided to be able to circulate with this electrolytic cell, and a vanadium-containing electrolytic solution that is supplied to the electrolytic cell via this storage tank. A dissolution tank provided to be able to supply a solution, a raw material supply line that supplies raw material powder containing pentavalent vanadium to the dissolution tank, and a solution supply that supplies at least a portion of the electrolyte as a solution to the dissolution tank. It has a line. A preferred example of this manufacturing apparatus will be described below with reference to FIG.

The manufacturing apparatus shown in FIG. 1 includes an electrolytic cell (1), a storage tank (2), a dissolution tank (3), and an anolyte tank (4). As shown, in this embodiment, the electrolytic cell (1), the storage tank (2), the dissolution tank (3), and the anolyte tank (4) are provided with pipes (10, 12, 14, 16, 18, 20, 22 and 23) are connected.

The electrolytic cell (1) is divided into a cathode cell (1a) and an anode cell (1b) by a diaphragm (1c). A cathode and an anode are installed in the cathode cell (1a) and the anode cell (1b), respectively. A known ion exchange membrane or the like is used as the diaphragm. A carbon electrode or the like may be used as the cathode. As the anode, an oxygen generating anode such as IrO ₂ suitable for oxygen generation may be used. By supplying current to the cathode and anode from a power source, a reduction reaction can be carried out in the cathode cell, and an oxidation reaction can be carried out in the anode cell. In this electrolytic cell (1), a vanadium-containing solution is electrolytically reduced in a cathode cell (1a), and an anolyte is electrolytically oxidized in an anode cell (1b) to generate oxygen gas. A sulfuric acid solution can usually be used as the anolyte. Water consumed by electrolytic oxidation is replenished to the anode cell (1b) via piping (22).

The storage tank (2) is connected via a first circulation line (14) to the cathode cell (1a) of the electrolytic cell (1). A circulation pump indicated by the symbol P is installed in the first circulation line (14). By the operation of this circulation pump, the vanadium-containing solution is supplied from the storage tank (2) to the cathode cell (1a) as a crude electrolyte for electrolytic reduction, and the vanadium-containing solution electrolytically reduced in the cathode cell (1a) is It is returned to the storage tank (2). Through this circulation, an electrolytic solution containing vanadium of a predetermined valence is stored in the storage tank (2). A product extraction line (20) may be connected to the first circulation line (14) via a switching valve. When an electrolytic solution containing vanadium with an average valence of 3.5 is stored in the storage tank (2), this electrolytic solution may be collected from the product extraction line (20) and used as a product by switching a valve.

A raw material supply line (10), a solution supply line (12), and a vanadium-containing solution supply line (16) are connected to the dissolution tank (3) by piping. In this dissolution tank (3), the raw material powder containing pentavalent vanadium supplied from the raw material supply line (10) is mixed with the solution supplied from the solution supply line (12) to form a vanadium-containing solution. prepared. This solution supply line (12) is connected to the first circulation line (14) via a switching valve. In this manufacturing apparatus, the electrolytic solution stored in the storage tank (2) is supplied as a solution by switching the valve.

This dissolution tank (3) is connected to the storage tank (2) via a vanadium-containing solution supply line (16). A circulation pump designated by the symbol P is installed in the vanadium-containing solution supply line (16). By operating this circulation pump, the vanadium-containing solution prepared in the dissolution tank (3) is supplied to the storage tank (2). In this manufacturing apparatus, the vanadium-containing solution is transferred to the storage tank (2) by operating the circulation pump provided in the vanadium-containing solution supply line (16) and the circulation pump provided in the first circulation line (14) ) to the cathode cell (1a) of the electrolytic cell (1).

An anolyte supply line (22) and a second circulation line (18) are connected to the anolyte tank (4). Anolyte is supplied from the anolyte supply line (22) to the anolyte tank (3). The anolyte tank (4) is pipe-connected to the anode cell (1b) of the electrolytic cell (1) by a second circulation line (18). A circulation pump indicated by the symbol P is installed in the second circulation line (18). By operating this circulation pump, the anolyte is supplied from the anolyte tank (4) to the anode cell (1b), and the anolyte electrolytically oxidized in the anode cell (1b) is returned to the anolyte tank (4). A gas-liquid separator (5) is installed in the second circulation line (18). Oxygen gas generated during anodization is separated by a gas-liquid separator (5) and discharged to the outside of the system from an oxygen extraction line (23).

In this electrolyte manufacturing apparatus, a vanadium-containing solution electrolytically reduced to a valence of less than 4 in an electrolytic tank (1) is supplied as a solution to a dissolving tank (3). In the dissolution tank (3), the raw material powder containing pentavalent vanadium is rapidly reduced and dissolved by being mixed with a solution containing low valence vanadium. This manufacturing apparatus does not require expensive chemicals to dissolve raw material powder containing pentavalent vanadium. Furthermore, contamination with impurities due to the addition of drugs can also be avoided. According to this manufacturing apparatus, a high-purity electrolytic solution that can be applied to an electrolytic solution for a redox flow battery can be efficiently produced at low cost.

[Method for producing electrolyte for vanadium redox flow batteries]
A method for manufacturing an electrolyte for a vanadium redox flow battery (hereinafter referred to as an "electrolyte manufacturing method" or "manufacturing method") can be performed using the electrolyte manufacturing apparatus described above. This electrolyte manufacturing method involves preparing a raw material powder containing pentavalent vanadium and a solution containing less than tetravalent vanadium, and mixing the raw material powder and the solution to obtain a vanadium-containing solution. and electrolytically reducing the obtained vanadium-containing solution to obtain an electrolyte. In this manufacturing method, a part of the electrolytic solution that has been electrolytically reduced is used as a solution for the raw material powder. If necessary, the entire electrolytic solution that has been electrolytically reduced may be used as a solution for the raw material powder.

In this electrolyte manufacturing method, pentavalent vanadium in the raw material powder is reduced by a solution containing less than tetravalent vanadium. On the other hand, less than tetravalent vanadium in the solution is oxidized by mixing with pentavalent vanadium. Through this oxidation reaction and reduction reaction, the average valence of vanadium in the liquid mixture decreases, and the raw material powder is reduced and dissolved. Further, in this manufacturing method, an electrolytic solution in which vanadium is electrolytically reduced to a valence of less than 4 is used as a solution for the raw material powder. This production method does not require expensive chemicals to dissolve the raw material powder containing pentavalent vanadium. Furthermore, contamination with impurities due to the addition of drugs can also be avoided. According to this manufacturing method, a high purity electrolyte solution applicable to an electrolyte solution for redox flow batteries can be efficiently produced at low cost. In addition, when installing and starting operation of the electrolyte production equipment, a solution containing less than tetravalent vanadium is prepared using a high-purity reagent. After the device starts operating, a portion of the obtained electrolyte can be used as a dissolving solution, so no expensive reagents are required.

The raw material powder is not particularly limited as long as it contains pentavalent vanadium. Pentavalent vanadium is typically vanadium pentoxide (V ₂ O ₅ ). For example, combustion ash of petroleum-based fuel or powder containing vanadium pentoxide recovered from waste catalysts may be used as the raw material powder. Commercially available vanadium pentoxide may be used as the raw material powder.

The average valence of vanadium contained in the solution may be less than 4, and may be more than or equal to 2 and less than 4, and may be more than or equal to 2 and less than or equal to 3. A sulfuric acid solution containing vanadium with an average valence of less than 4 can be preferably used. Here, the "average valence" means the average value of valences calculated based on the number of moles of vanadium. The solution may contain pentavalent vanadium as long as the effects of the present disclosure are not impaired.

As described above, in this embodiment, an electrolytic solution obtained by electrolytically reducing a vanadium-containing solution obtained by dissolving raw material powder containing pentavalent vanadium is used as the dissolving solution. For example, an electrolytic solution obtained by electrolytically reducing vanadium pentoxide in sulfuric acid may be used as the dissolving solution within the range where the effects of the present disclosure can _be obtained. The electrolytic solution obtained by doing this may be used as the dissolving solution.

The method and conditions for mixing the raw material powder and the solution are not particularly limited. For example, dissolution tanks equipped with known stirrers can be used. The dissolution temperature may be at least room temperature, may be about 50° C., and may be higher if reductive dissolution is possible. From the viewpoint of energy cost, the preferred melting temperature is room temperature. The dissolution time may be changed as appropriate depending on the type of raw material powder and dissolving liquid, the dissolution temperature, etc., but according to the method of the present disclosure, the dissolution rate is improved, so a uniform vanadium-containing solution can be obtained in a relatively short time. be able to.

From the viewpoint of improving solubility, it is preferable that a solution containing a mole of vanadium with an average valence of x and a raw material powder containing b moles of pentavalent vanadium are mixed under conditions that satisfy the following relational expression.
(4-x)×a≧b
(In the formula, a and b are real numbers greater than 0, and x is a real number greater than or equal to 2 and less than 4.)

As long as the effects of the present disclosure can be obtained, the vanadium concentration in the vanadium-containing solution obtained by mixing the raw material powder and the solution is not particularly limited. From the viewpoint of obtaining an electrolytic solution suitable for a vanadium redox flow battery, the vanadium concentration in the vanadium-containing solution may be 1.7 mol/L or more.

The sulfuric acid concentration in the vanadium-containing solution is not particularly limited, and is appropriately adjusted depending on the vanadium concentration. From the viewpoint of improving solubility, the sulfuric acid concentration of the vanadium-containing solution may be 4.3 mol/L or more, but if the vanadium compound (solid) to be added can be dissolved in its entirety, the sulfuric acid concentration is 4.3 mol/L. It may be less than

An electrolytic cell including a cathode cell and an anode cell can be used for electrolytic reduction of a vanadium-containing solution. The conditions for electrolytic reduction are not particularly limited, and are appropriately selected depending on the physical properties of the vanadium-containing solution and the desired physical properties of the electrolytic solution. For example, when electrolyzing under conditions that reduce vanadium in a vanadium-containing solution to an average valence of less than 4, the resulting electrolytic solution can be used as a solution for the raw material powder. Furthermore, when electrolyzing is carried out under conditions that reduce the average valence to 3.5, the resulting electrolytic solution can be used as it is as a product for an electrolytic solution for redox flow batteries. Further, an electrolytic solution electrolyzed under conditions that reduce the average valence to 3 or less, preferably to an average valence of 2, may be stored and used separately as a solution for the raw material powder.

As for the electrolytic solution for redox flow batteries, it is preferable that there are few impurities mixed in. According to this manufacturing method, in the process of electrolytically reducing a vanadium-containing solution to reduce it to an average valence of 2, impurities such as Ni are deposited on the cathode and removed from the solution. By using the thus obtained electrolytic solution containing vanadium with an average valence of 2 as a solution for the raw material powder, a highly pure electrolytic solution can be obtained. Note that the average valence of vanadium in the electrolytic solution and the vanadium-containing solution can be measured by a known method. Examples include a method of detecting the potential of the electrolytic solution and the solution using a voltmeter or the like, and a method of measuring the hue or absorbance of the electrolytic solution and the solution using a spectrophotometer or the like.

Hereinafter, the effects of the present disclosure will be clarified through Examples, but the present disclosure should not be interpreted in a limited manner based on the description of the Examples.

[Example 1]
An electrolytic solution for a vanadium redox flow battery was manufactured using a manufacturing facility having the basic configuration shown in FIG. First, raw material powder vanadium pentoxide (V ₂ O ₅ ), a sulfuric acid solution whose concentration was adjusted in advance, and a solution containing trivalent vanadium (vanadium concentration 1.7 mol/L) were put into a dissolution tank. By mixing and stirring at 60° C. for 6 hours, a vanadium-containing solution containing tetravalent vanadium (vanadium concentration 1.7 mol/L, sulfuric acid concentration 4.3 mol/L) was obtained. The amount charged into the dissolution tank was adjusted so that the molar ratio of vanadium (V ⁵⁺ ) in vanadium pentoxide to vanadium (V ³⁺ ) in the solution was 1:1. This vanadium-containing solution was electrolytically reduced in an electrolytic cell under conditions of 50 mA/cm ² to obtain an electrolytic solution containing vanadium with an average valence of 3.5. After a part of this electrolytic solution is collected as a product from the product extraction line, electrolytic reduction is further continued to produce an electrolytic solution containing vanadium with an average valence of 3 (vanadium concentration 1.7 mol/L, sulfuric acid concentration 4.0 mol/L). 3 mol/L) was obtained. This electrolytic solution and vanadium pentoxide are poured into a dissolution tank so that the molar ratio of vanadium (V ⁵⁺ ) to vanadium (V ³⁺ ) in the solution is 1:1, and electrolytic reduction is repeated. In this manner, the vanadium redox flow battery electrolyte of Example 1 was continuously produced.

[Example 2]
Example 1 was repeated, except that the amount charged into the dissolution tank was adjusted so that the molar ratio of vanadium (V ⁵⁺ ) in vanadium pentoxide to vanadium (V ³⁺ ) in the solution was 1:2. In the same manner, the electrolytic solution of Example 2 was continuously produced.

[Example 3]
Example 1 was repeated, except that the amount charged into the dissolution tank was adjusted so that the molar ratio of vanadium (V ⁵⁺ ) in vanadium pentoxide to vanadium (V ³⁺ ) in the solution was 1:3. In the same manner, the electrolytic solution of Example 3 was continuously produced.

[Example 4]
In Example 4, after obtaining the electrolytic solution containing vanadium with an average valence of 3.5 in Example 1, electrolytic reduction was further continued to prepare a solution containing vanadium with an average valence of 2. Due to this electrolytic reduction, a small amount of deposits were observed on the cathode. The obtained solution containing vanadium with an average valence of 2 (vanadium concentration 1.6 mol/L, sulfuric acid concentration 4.3 mol/L) and vanadium pentoxide are combined with vanadium (V ⁵⁺ ) and vanadium in the solution. The vanadium redox flow battery electrolyte of Example ⁴ ( An average valence of 3.5, a vanadium concentration of 1.6 mol/L, and a sulfuric acid concentration of 4.3 mol/L were obtained.

As shown in Examples 1-4, according to the production method and production apparatus of the present disclosure, it was possible to efficiently produce an electrolyte for a vanadium redox flow battery without using expensive chemicals. From this result, the superiority of the present disclosure is clear.

[Disclosure items]
Each of the following items discloses preferred embodiments.

[Item 1]
Preparing a raw material powder containing pentavalent vanadium and a solution containing less than tetravalent vanadium; Mixing the raw material powder and the solution to obtain a vanadium-containing solution; and Electrolytically reducing this vanadium-containing solution. and obtaining an electrolyte;
A method for producing an electrolyte for a vanadium redox flow battery, using a portion of this electrolyte as a solution for a raw material powder.

[Item 2]
When the average valence of vanadium contained in the solution is x, the number of moles of this vanadium is a, and the number of moles of pentavalent vanadium contained in the raw material powder is b, then this raw material powder and the solution The method for producing an electrolytic solution for a vanadium redox flow battery according to item 1, wherein the electrolyte solution for a vanadium redox flow battery is mixed under conditions that satisfy the following relational expression. In the formula, a and b are real numbers greater than 0, and x is a real number greater than or equal to 2 and less than 4.
(4-x)×a≧b

[Item 3]
The method for producing an electrolyte for a vanadium redox flow battery according to item 1 or 2, further comprising storing a part of the electrolyte as a solution.

[Item 4]
The method for producing an electrolytic solution for a vanadium redox flow battery according to item 3, wherein the electrolytic solution to be stored contains vanadium with an average valence of 2.

[Item 5]
An electrolytic cell that obtains an electrolytic solution by electrolytically reducing a vanadium-containing solution, an electrolytic solution storage tank that is provided to be able to circulate with this electrolytic cell, and a vanadium-containing solution that can be supplied to the electrolytic cell via this storage tank. A dissolving tank provided, a raw material supply line that supplies a raw material powder containing pentavalent vanadium to the dissolving tank, and a solution supply line that supplies a part of the electrolyte as a solution to the dissolving tank. Manufacturing equipment for electrolyte for vanadium redox flow batteries.

The method and equipment described above can be applied to uses other than electrolytes for redox flow batteries.

1... Electrolytic cell 1a... Cathode cell 1b... Anode cell 1c... Diaphragm 2... Storage tank 3... Dissolution tank 4... Anolyte tank 5... Gas-liquid separator 10... Raw material supply line 12... Solution supply line 14... First circulation line 16... Vanadium-containing solution supply line 18... Second circulation line 20... Product extraction line 22...・Anolyte supply line 23...Oxygen extraction line

Claims (5)

preparing a raw material powder containing pentavalent vanadium and a solution containing less than tetravalent vanadium; mixing the raw material powder and the solution to obtain a vanadium-containing solution; and electrolyzing the vanadium-containing solution. reducing to obtain an electrolyte;
A method for producing an electrolytic solution for a vanadium redox flow battery, using a part of the electrolytic solution as the dissolving solution. When the valence of vanadium contained in the solution is x, the number of moles of this vanadium is a, and the number of moles of pentavalent vanadium contained in the raw material powder is b, this raw material powder and the solution The method for producing an electrolytic solution for a vanadium redox flow battery according to claim 1, wherein the following are mixed under conditions that satisfy the following relational expression.
(4-x)×a≧b
(In the formula, a and b are real numbers greater than 0, and x is a real number greater than or equal to 2 and less than 4.) The method for producing an electrolyte for a vanadium redox flow battery according to claim 1 or 2, further comprising storing a part of the electrolyte as the solution. The method for producing an electrolytic solution for a vanadium redox flow battery according to claim 3, wherein the electrolytic solution to be stored contains vanadium with an average valence of 2. An electrolytic cell that obtains an electrolytic solution by electrolytically reducing a vanadium-containing solution, an electrolytic solution storage tank that is provided to be able to circulate with this electrolytic cell, and a vanadium-containing solution that can be supplied to the electrolytic cell via this storage tank. a dissolution tank provided in the dissolution tank, a raw material supply line that supplies raw material powder containing pentavalent vanadium to the dissolution tank, and a solution supply line that supplies a part of the electrolyte as a solution to the dissolution tank; A manufacturing device for electrolyte for vanadium redox flow batteries.

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