KR102286709B1 - Apparatus for producing vanadium electrolyte - Google Patents

Abstract

The present invention provides an apparatus for manufacturing a vanadium electrolyte, comprising: an agitation tank in which a first solution in which a vanadium compound is dissolved is manufactured by sequentially mixing a pentavalent vanadium compound, water, and a hydrazine-based reducing agent, and a second solution manufactured by accommodating the first solution as a vanadium electrolyte starting material or adding sulfuric acid to the first solution is accommodated as the vanadium electrolyte starting material; and a circulation filtering device for filtering the first solution or the second solution.

Description

Vanadium electrolyte manufacturing apparatus {APPARATUS FOR PRODUCING VANADIUM ELECTROLYTE}

The present invention relates to an apparatus for producing a vanadium electrolyte solution, and more particularly, by producing a 3.5-valent vanadium from a pentavalent vanadium using only a hydrazine compound as a reducing agent in the production of a vanadium electrolyte, the production cost is low, the process is simple, and a high-purity electrolyte is produced By using a single reactor, facility investment cost is low, maintenance and management are easy, mass production is possible, and by applying non-catalytic electroless reaction conditions, reaction time is shortened, reaction efficiency is maximized, and high-quality vanadium electrolyte is manufactured. It relates to an apparatus for producing a vanadium electrolyte that can achieve

Energy storage system (ESS) business is in the spotlight as a way to solve global energy problems such as depletion of petroleum energy, dangers of nuclear energy, and increasing energy shortages. Among them, the vanadium battery is attracting attention as a battery that can replace lithium ESS because of its excellent performance and stability.

Since vanadium electrolytes account for most of the price of vanadium batteries, if a high-purity electrolyte can be obtained while simplifying the manufacturing process of this electrolyte, the business viability of the vanadium ESS can be improved.

In a vanadium redox flow battery, charging and discharging of electrical energy is performed by repeating the oxidation-reduction reaction of a vanadium tetravalent electrolyte at the positive electrode and a vanadium trivalent electrolyte at the negative electrode. In the initial stage of development, vanadium trivalent electrolyte and tetravalent electrolyte were _{prepared from V 2} O ₃ and VOSO ₄ , respectively, but in order to overcome the disadvantage of using expensive raw materials, improved manufacturing methods using _{V 2} O _{5 as a raw material are} has been proposed

In the conventional production of a vanadium tetravalent electrolyte using a reducing agent, V ₂ O ₅ , a raw material, is usually dissolved in a sulfuric acid solution to form vanadium pentavalent ions (VO ₂ ) ⁺ , and this is used as a reducing agent to form vanadium tetravalent ions (VO ^{2 ). +} ) to prepare a tetravalent electrolyte. The types of reducing agents proposed in the existing process include oxalic acid and methanol.

The oxalic acid is a typically used reducing agent. When preparing 1 L of a tetravalent electrolyte of vanadium 1.6M sulfuric acid 4.0M, when using oxalic acid, vanadium, sulfuric acid, and water are mixed in consideration of heat generation, and then oxalic acid is added and stirred. proceed with In this process, if the temperature of the reactor is maintained at 90° C., a reaction time of 4 hours is required. Since the reaction rate of methanol is much slower than that of oxalic acid, its use is limited.

The reducing agent only proceeds from pentavalent to tetravalent reaction, and has a characteristic that does not participate in tetravalent to trivalent reaction, and side-reactants generated by the oxidation reaction of unreacted reducing agent or reducing agent seriously deteriorate electrolyte properties. cause it to deteriorate. Therefore, as a reducing agent for producing a vanadium electrolyte, a reducing agent that does not generate any side reactants or produces a side reactant that can be easily removed from the prepared electrolyte solution is suitable as in the case of carbon dioxide or nitrogen.

Conventional sulfur dioxide (SO ₂ ) satisfies the above reducing agent conditions and thus vanadium 4 can be effectively used for the preparation of the electrolyte, but because it exists as a gas under the general conditions of room temperature and normal pressure, the absorption rate into the electrolyte is low, so an excess of reducing agent must be used. The process is complicated and inefficient. In addition, due to toxicity, a separate process is required for detoxifying the excess sulfur dioxide remaining after the electrolyte is prepared, thereby increasing the cost of the process.

A vanadium trivalent electrolyte, which is an electrolyte for a negative electrode of a vanadium redox flow battery, is generally prepared from the above-described vanadium tetravalent electrolyte. In the conventional preparation (electrolysis method) of a vanadium tetravalent electrolyte using electrolysis, a voltage is applied to the vanadium tetravalent to produce pentavalent and trivalent valence at an anode and a cathode, respectively. At this time, the pentavalent electrolyte prepared at the anode must be converted back to a vanadium tetravalent electrolyte. In addition, due to the characteristics of the method using electrolysis, periodic replacement of electrodes and membranes is required, which also causes an increase in manufacturing cost.

In the conventional manufacturing of a vanadium electrolyte using a metal reducing agent (metal reducing method), there is a method using a metal such as Zn when reducing from tetravalent to trivalent. However, this method requires a subsequent process to filter out metal ions generated after the reaction, thereby increasing the manufacturing cost of the electrolyte and has disadvantages in that its performance is inferior to that of the electrolyte prepared by electrolysis.

A recent trend for electrolytes in vanadium redox flow batteries is to use the same vanadium 3.5-valent electrolyte for the first positive and negative electrodes. Vanadium 3.5 valence electrolyte refers to an electrolyte containing the same vanadium tetravalent and trivalent ions, and after the initial charging process, it is converted to a state in which vanadium tetravalent electrolyte is present at the positive electrode and vanadium trivalent electrolyte solution exists at the negative electrode.

In the conventional preparation of a 3.5-valent vanadium electrolyte (electrolysis method) using electrolysis, a voltage is applied to vanadium tetravalent to prepare a 4.5-valent and 3.5-valent electrolyte in the anode and the cathode, respectively. When the 3.5-valent electrolyte is prepared in this way, a process of reducing the 4.5-valent electrolyte prepared in the positive electrode again is required.

Finally, the conventional preparation of a vanadium 3.5 valence electrolyte using a catalyst and an organic reducing agent is a method of using a noble metal catalyst such as Ru, Pd, Pt, etc. in an organic reducing agent such as formic acid when reducing from tetravalent to trivalent. A general organic reducing agent cannot make tetravalent to trivalent, but among them, formic acid, an organic reducing agent, is added to vanadium tetravalent ions and catalyzed thereto to prepare a 3.5-valent electrolyte. However, this method has a risk that some of the noble metal catalyst in the electrolyte may remain, and the fact that most of the catalysts used are rare metals also greatly reduces price competitiveness.

(1) Korean Patent Registration No. 10-1415538 (2) Korean Patent Registration No. 10-1653765 (3) Korean Patent Application No. 10-2018-0023014

In order to solve the problems of the prior art as described above, the present invention is to prepare a 3.5-valent vanadium from pentavalent vanadium using only a hydrazine compound as a reducing agent in the production of a vanadium electrolyte, thereby producing a high-purity electrolyte with a low manufacturing cost and a simple process. By using a single reactor, facility investment cost is low, maintenance and management are easy, and mass production is possible. An object of the present invention is to provide an apparatus for producing a vanadium electrolyte that can be achieved.

The above and other objects of the present invention can all be achieved by the present invention described below.

In order to achieve the above object, the present invention

A first solution in which the vanadium compound is dissolved is prepared by sequentially mixing a pentavalent vanadium compound, water, and a hydrazine-based reducing agent, and the first solution is accommodated as a vanadium electrolyte starting material, or sulfuric acid is added to the first solution a stirring tank for accommodating the second solution as a vanadium electrolyte starting material; and

It provides a vanadium electrolyte manufacturing apparatus, characterized in that it comprises a circulation filtration device for filtering the first solution or the second solution.

The stirring tank and the circulation filtering device may be each independently made of at least one material selected from the group consisting of glass, polyethylene resin, and Teflon resin.

The circulation filtering device may be provided with a filter made of PTFE, PE, PET or PP material and having a pore size of 0.2 to 5 μm.

The circulation filtering device may be installed in an electrolyte discharge pipe connected to an electrolyte outlet for discharging the electrolyte generated in the stirring tank, or a circulation pipe extending from one side of the discharge pipe and connected to the upper part of the stirring tank.

There may be one or more circulation filtering devices installed in the electrolyte discharge pipe, and one or more circulation filtering devices installed in the circulation pipe.

It may further include an open reflux condenser connected to the upper part of the stirring tank to cool and recover water and sulfuric acid vaporized during the reaction and discharge nitrogen gas.

The electrolytic solution manufacturing apparatus may be a catalyst-free electroless reaction apparatus.

As the hydrazine-based reducing agent, one or more hydrazine compounds selected from the group consisting of hydrazine anhydride, hydrates thereof and salts thereof are added in an amount of 0.3 to 0.375 moles based on 1 mole of the pentavalent vanadium compound, and a pentavalent vanadium compound in the first solution to form a tetravalent vanadium compound, wherein the pentavalent vanadium compound may be _{V 2} O ₅ , and the tetravalent vanadium compound _{may be VOSO 4 .}

The sulfuric acid is added in an amount of 2 to 3 moles based on 1 mole of the pentavalent vanadium compound, and the tetravalent vanadium compound is reduced in the second solution under a temperature condition of 70 to 110° C. to form a 3.3 to 3.7 vanadium compound, wherein The tetravalent vanadium compound may be VOSO ₄ , and the 3.3 to 3.7 vanadium compounds may be a mixture of VOSO ₄ and V ₂ (SO ₄ ) ₃ .

The water may be added in an amount of 400 to 700 parts by weight based on 100 parts by weight of the pentavalent vanadium compound.

The manufacturing apparatus may further include a filtration device in which the vanadium electrolyte generated in the stirring tank is discharged through the electrolyte outlet to remove impurities and to obtain a ^{3.5-valent vanadium compound (V 3.5+ electrolyte product) as a final electrolyte product.} .

The pentavalent vanadium compound used in the manufacturing apparatus may be a compound using 99% or more of a vanadium raw material.

The 3.5-valent vanadium compound produced in the manufacturing apparatus may be a compound capable of providing performance equivalent to that of a vanadium compound prepared using a 99.9% level of a vanadium raw material.

The stirring tank is a single reactor, and may further include a temperature control device for controlling the reaction temperature of the stirring tank.

According to the present invention, by using only a hydrazine compound as a reducing agent in the production of a vanadium electrolyte, 3.5-valent vanadium is produced from pentavalent vanadium, so that the production cost is low and the process is simple and high-purity electrolyte can be produced. A vanadium electrolyte manufacturing device with low investment cost, easy maintenance and management, mass production possible, and reduction of reaction time, maximization of reaction efficiency, and production of high-quality vanadium electrolyte by applying non-catalytic electroless reaction conditions. has the effect of providing.

In addition, the manufacturing apparatus of the present invention can provide the effect of generating a high-quality electrolyte from a low-purity raw material.

In addition, since the electroless process can be performed, it has the advantage of sufficiently performing the manufacturing process with a single reactor.

1 is a diagram schematically showing the configuration of an apparatus for manufacturing an electrolyte solution according to the present invention.
FIG. 2 is a view illustrating a structure in which a filter is mounted in a circulation filtration device among devices for preparing an electrolyte solution of the present invention.
3 is a view schematically showing an open reflux capacitor among the apparatus for preparing an electrolyte of the present invention.
4 is a diagram schematically illustrating a process flow diagram for preparing an electrolyte solution according to the present invention.
5 is a photograph taken by arranging the result of mixing the reaction raw material according to the input sequence of the present invention (Example) and the result of mixing the reaction raw material without following the input sequence of the present invention (Comparative Example).
6 is a graph showing the experimental results of the temperature change with time when the flow rate of sulfuric acid as an example is 240 ml/hr.
7 is a graph showing the temperature change with time when the flow rate of sulfuric acid is 240ml/hr and 480ml/hr as an embodiment.
8 is a graph showing the relationship between vanadium tetravalent and trivalent according to the amount of reducing agent confirmed by UV absorbance in Examples.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In the case of using a hydrazine compound as a reducing agent as a reducing agent as a non-catalytic chemical reaction in a single reactor in the production of a vanadium electrolyte solution and limiting reaction conditions such as the order of input of raw materials or reaction temperature, the manufacturing cost is low and the process is reduced and high purity It was confirmed that high-quality electrolytes can be produced in large quantities, the production, maintenance and management of the reaction device is easy, the reaction time is greatly shortened and the reaction efficiency is maximized, and based on this, further research is completed and the present invention is completed. did it

In the vanadium electrolyte production apparatus of the present invention, a first solution in which the vanadium compound is dissolved is prepared by sequentially mixing a pentavalent vanadium compound, water, and a hydrazine-based reducing agent, and the first solution is received as a vanadium electrolyte starting material, or sulfuric acid is added to the a stirring tank accommodating the second solution prepared by adding the first solution as a vanadium electrolyte starting material; and a circulation filtration device for filtering the first solution or the second solution. In this case, in the production of a vanadium electrolyte, only a hydrazine compound is used as a reducing agent to prepare 3.5-valent vanadium from pentavalent vanadium. Low unit cost and simple process, high-purity electrolyte can be produced, mass production is possible through a non-catalytic chemical reaction process, and reaction time is shortened, reaction efficiency is maximized, and high-quality electrolyte is manufactured by applying predetermined reaction conditions to a single reactor has the effect of achieving

1 is a diagram schematically showing the configuration of an apparatus for preparing an electrolyte solution according to the present invention.

Referring to FIG. 1 below, in the apparatus for preparing an electrolyte solution according to the present disclosure, a first solution in which the vanadium compound is dissolved is prepared by sequentially mixing a pentavalent vanadium compound, water, and a hydrazine-based reducing agent, and the first solution is used as a vanadium electrolyte starting material or a stirring tank 10 for receiving a second solution prepared by adding sulfuric acid to the first solution as a vanadium electrolyte starting material; and a circulation filtration device 20 for filtering the first solution or the second solution.

The stirring tank 10 and the circulation filtering device 20 are each independently made of at least one material selected from the group consisting of glass, polyethylene resin, and Teflon resin. Reaction raw materials or reaction by-products requiring acid resistance or chemical resistance It is preferable because it can protect the device from

In addition, the stirring tank 10 and the circulation filtering device 20 may be each independently coated with one or more materials selected from the group consisting of glass, polyethylene resin, and Teflon resin.

The stirring tank 10 may be a flow reactor or a tubular reactor, and a structure such as a baffle that helps uniform mixing of reactants may be installed inside the reactor. In addition, an external jacket may be attached to control the temperature of the reactant, or an internal heat exchange coil may be installed.

The circulation filter 20 is made of PTFE, PE, PET or PP material and has a pore size of 0.2 to 5 μm, preferably 0.5 to 5 μm, more preferably 1 to 4 μm, even more preferably It is a device located in a support fixture structure with a hole so that the filter to be filtered can freely move while the filter layer of 1 to 3 μm can support the filter and a buffer layer such as an O-ring that prevents solution leakage in an acid-resistant case.

When the circulation filtration device is used, it is preferable to effectively remove impurities such as Si and Al contained in the electrolyte. The above-mentioned impurities may _{form a gel such as H 2} SiO ₃ or combine with free sulfate ions in the electrolyte to form a salt during the vanadium reduction process.

They penetrate between the electrodes during charging and discharging of a vanadium battery, and not only reduce the flow rate, but also cause physical/chemical damage to the passage of the ion exchange membrane, thereby lowering the movement of protons, thereby causing IR loss and capacity fading effects.

Reduction from a vanadium tetravalent compound to a 3.5-valent compound by performing circulation filtering on the vanadium tetravalent compound using the circulation filtration device of the present invention?? It is possible to pre-remove impurities that previously cause degradation of the electrolyte performance.

This prevents the formation of gels or impurity salts that may occur in the process of reducing vanadium 3.5 to a compound. As a result, as described above, the performance of the electrolyte using the circulation filtration device of the present disclosure can realize a charge/discharge capacity of 99.9% even when using 99% pure vanadium.

At this time, the circulation filtering device 20 may be provided in the form of a filter device structure commonly used in the related field.

For example, FIG. 2 is a diagram illustrating a structure in which the filter 21 in the circulation filtration device 20 is mounted among the devices for preparing an electrolyte solution of the present invention.

2 (a) below illustrates a mounting structure having a combination of a supporter fixture and a membrane filter, and FIG. 2 (b) illustrates a filter bag-type filtration system structure, these two examples Filtration devices including filtration concepts can be used without limitation.

It is preferable that the filtering device is made of an acid-resistant material and the buffer layer in the filtering device is formed of an O-ring, etc. to prevent the material to be filtered from flowing out in a direction other than the filter area. In consideration of the above, the filter in the filtering device may be supported and the filter may be supported as a supporter fixture in which a hole through which a material to be filtered can be moved is mounted. The filter is preferably in a form that is easy to detach, and a separate filter aid such as celite may be used together.

The circulation filtering device 20 extends from one side of the electrolyte discharge pipe 41 connected to the electrolyte discharge port 40 for discharging the electrolyte generated in the stirring tank 10, or the discharge pipe 41, and the It may be installed in the circulation pipe 42 connected to the upper part of the stirring tank 10 . In this case, there is an advantage in that a filtration device is naturally inserted into a single process system, so that a high-purity, high-quality electrolyte can be manufactured without enlarging the process system.

The circulation filtering device 20 installed in the circulation pipe 42 may be preferably one or more, more preferably one or two, and still more preferably one, within this range, a single process system. There is an advantage in that a high-purity, high-quality electrolyte can be manufactured without a large-scale process system as the circulation filtering device is naturally inserted into it.

The circulation filtering device 20 installed in the discharge pipe 41 may be preferably one or more, more preferably one to three, and still more preferably one or two, within this range. There is an advantage in that a high-purity, high-quality electrolyte can be manufactured without a large-scale process system as the circulation filtration device is naturally inserted in a single process system.

The total number of circulation filtration devices 20 installed in the vanadium electrolyte production apparatus may be preferably two or more, more preferably two or three, more preferably two, and within this range, a single There is an advantage in that a high-purity, high-quality electrolyte can be manufactured without enlarging the process system or greatly extending the process time by naturally inserting the circulation filter into the process system.

As a specific example, there may be one or more circulation filtering devices 20 installed in the electrolyte discharge pipe 41 , and there may be one or more circulation filtering devices 20 installed in the circulation pipe 42 .

In addition, the manufacturing apparatus 1 of the present base material is connected to the upper portion of the stirring tank 10 to include an open reflux condenser 30 that cools and recovers water and sulfuric acid vaporized during the reaction and discharges nitrogen gas. It is preferable because the circulation filtration effect can be maximized.

3 is a view schematically showing the open reflux capacitor 30 among the apparatus for preparing an electrolyte solution of the present invention.

As shown in FIG. 3 (a), the open reflux condenser 30 used in the present invention may be in the form of a dimroth in which a tube through which a cooling liquid flows is inserted in the condenser, and in FIG. As you can see, there may be an intercalated layer in the condenser that is filled with a chemically stable, cooling material (eg glass beads).

At this time, the nitrogen gas generated during the reaction is discharged through the upper layer of the open reflux condenser 30 , and the vaporized water vapor and sulfuric acid generated together are condensed and cooled to stay in the stirring tank 10 .

The electrolytic solution manufacturing apparatus 1 is a catalyst-free electroless reaction apparatus, which improves reaction efficiency and minimizes side reactions while simplifying and shortening the reaction process, and discharges nitrogen gas generated in the stirring tank 10 as described above, and , the vaporized water vapor and sulfuric acid produced together are condensed and cooled to stay in the stirring tank 10 and can be utilized to maintain a high temperature in the stirring tank 10, thereby maximizing the reaction efficiency and changing the composition in the stirring tank 10 at the same time. It can provide a blocking advantage.

The hydrazine-based reducing agent used in the present description may be, for example, at least one selected from the group consisting of hydrazine anhydride, hydrates thereof, and salts thereof.

The hydrazine-based reducing agent may be added, for example, in an amount of 0.3 to 0.375 moles based on 1 mole of the pentavalent vanadium compound, and reduce the pentavalent vanadium compound in the first solution to form a tetravalent vanadium compound.

In this case, the pentavalent vanadium compound may be _{V 2} O ₅ , and the tetravalent vanadium compound _{may be VOSO 4 .}

In addition, sulfuric acid used in the present description is added in an amount of, for example, 2 to 3 moles based on 1 mole of the pentavalent vanadium compound, and 3.3 to 3.7 by reducing the tetravalent vanadium compound in the second solution under a temperature condition of 70 to 110 ° C. can form vanadium compounds.

Here, the tetravalent vanadium compound may be VOSO ₄ , and the 3.3 to 3.7 vanadium compounds may be a mixture of VOSO ₄ and V ₂ (SO ₄ ) ₃ .

In addition, water used as a solvent in the present substrate may be added in an amount of 400 to 700 parts by weight based on 100 parts by weight of the pentavalent vanadium compound.

In particular, in the first solution of the present disclosure, the reduction of the hydrazine-based reducing agent can be induced at a low temperature without a separate heating and pressurization process when sulfuric acid is added, which will be described later, by adding a pentavalent vanadium compound and water and then sequentially adding the hydrazine-based reducing agent. It is relatively advantageous in terms of temperature rise, and as a result, it can provide the effect of shortening the overall process time.

For reference, if sulfuric acid is added before the hydrazine-based reducing agent, the temperature rises due to an exothermic reaction. Considering the reduction reaction performed by the hydrazine-based reducing agent under this heated high temperature, it is necessary to separately control the flow rate to prevent the rapid reaction. so it is not preferable That is, the hydrazine-based reducing agent is _{decomposed into NH 3 + N when the temperature is 180° C. or higher, and is decomposed into N 2} + H ₂ when the temperature is 350° C. or higher. When the hydrazine-based reducing agent is added under heating conditions with sulfuric acid The possibility of decomposition of the hydrazine-based reducing agent before performing the role of reduction is increased by the heat generated in the local part. It is necessary to put in to achieve the desired 3.5 value.

On the other hand, if the hydrazine-based reducing agent is first added and then sulfuric acid is sequentially added according to the present description, the possibility of consumption of the above-described hydrozine-based reducing agent can be reduced, so that an excess of about 0 to 3 wt% is added based on the stoichiometric ratio, It is also possible to achieve the desired 3.5 value.

In the manufacturing apparatus, the vanadium electrolyte generated in the stirring tank is discharged through the electrolyte outlet 50 for discharging the electrolyte prepared in the stirring tank 10 to remove impurities, and a 3.5-valent vanadium compound (V ^{3.5) as a final electrolyte product +} It may further include a filtration device 50 to obtain an electrolyte product).

At this time, various conventional removal devices can be used to remove impurities, and for example, a filter press, an ion exchange device, a centrifugal separator, a heat/pressure sublimation purification device, a wave energy device, etc. may be tried.

The pentavalent vanadium compound used in the manufacturing apparatus 1 of the present disclosure may be used as a reaction raw material having a purity of 99.9% or more, and as shown in Examples to be described later, a pentavalent vanadium compound having a purity of 99.99% is used. In this case, it can be seen that a high-quality 3.5-valent vanadium electrolyte solution equivalent to or similar to that in the case of using a pentavalent vanadium compound having a purity of 99.9% is prepared.

The 3.5-valent vanadium compound manufactured in the manufacturing apparatus 1 of the present invention may exhibit the same charge/discharge performance as the 3.5-valent vanadium compound manufactured using a vanadium raw material having a purity of 99.9% or more.

In particular, the agitation tank 10 used in the manufacturing apparatus 1 of the present invention can use a single reactor as opposed to using two or more conventionally known reactors as a vanadium manufacturing apparatus, so facility investment costs, maintenance costs, and equipment It is advantageous from a management point of view.

Furthermore, the manufacturing apparatus of the present disclosure may further include a temperature control device 60 for controlling the reaction temperature in the stirring tank 10 .

The temperature control device 60 is preferably a heat exchanger, more preferably a jacket type heat exchanger, in which case it is easy to control the reaction temperature, so that the reaction efficiency is excellent and a high-purity, high-quality vanadium electrolyte is produced. There is an advantage.

The jacket-type heat exchanger in the present invention is not particularly limited in the case of a jacket-type heat exchanger commonly used in the art to which the present invention belongs, and may be, for example, a jacket surrounding the stirring tank 10 and including a heat transfer medium. .

Hereinafter, a manufacturing method using the above-described manufacturing apparatus will be described in detail with reference to the accompanying drawings.

4 is a view briefly showing a process flow diagram for preparing an electrolyte according to the present invention.

4, a first step of reducing a pentavalent vanadium compound to a tetravalent vanadium compound; and a second step of reducing the tetravalent vanadium compound to a 3.3 to 3.7 vanadium compound, wherein at least one hydrazine compound selected from the group consisting of hydrazine anhydride, hydrates thereof, and salts thereof is added in the first step, It is characterized in that sulfuric acid is added in the second step.

The first and second steps may preferably be carried out in one reactor (corresponding to the stirring tank 10 of FIG. 1 ), in this case, the process and reaction time are shortened, mass production is possible, and the facility There are advantages in that investment cost is low, maintenance and management are easy, and reaction efficiency is maximized.

The reactor (agitation tank 10) preferably includes an open reflux condenser 30 to recover water vapor and vaporized sulfuric acid and discharge nitrogen gas. In this case, the reaction efficiency is maximized, and a separate inert gas The inside of the reactor becomes an inert environment naturally even without supply of the reactor, so side reactions such as oxidation are suppressed, and thus, there is an advantage in that a high-purity, high-quality vanadium electrolyte is manufactured.

The reaction is an oxidation-reduction reaction, and may be carried out as shown in Scheme 1 below, preferably in an acidic solution.

[Scheme 1]

N ₂ H ₅ ⁺ → N ₂ + 5H ⁺ +4e ^-

The nitrogen gas (N ₂ ) generated in Reaction Formula 1 is discharged by the open reflux condenser 30 .

_{In addition, the entire reaction in which V 2} O ₅ of the present invention is reduced to an electrolyte solution of 3.5 vanadium may preferably proceed as shown in Scheme 2 below.

[Scheme 2]

4V ₂ O ₅ + 10H ₂ SO ₄ + 3N ₂ H ₄ H ₂ O → 4VO(SO ₄ ) + 2V ₂ (SO ₄ ) ₃ + 19H ₂ O + 3N ₂

Similarly, the nitrogen gas (N ₂ ) generated in Reaction Equation 2 is discharged by the open reflux condenser 30 .

It may include the step of filtering using the circulation filtering device 20 after the first step or after the second step. Preferably, it may include a step of filtering using the circulation filtering device 20 between the first step and the second step, and more preferably, the circulation filtering device 20 between the first step and the second step. ) may include a step of primary filtration using the second step and then secondary filtration using the circulation filtration device 20 after the second step, and in this case, a high-purity, high-quality vanadium electrolyte solution without significantly extending the process time This has the advantage of being manufactured.

The circulation filtering device 20 may use a filtration means having a pore size of 0.2 to 5 μm as described above, more preferably 0.5 to 5 μm, more preferably 1 to 4 μm, even more preferably A filtration means having a diameter of 1 to 3 μm may be used, and the filtration means used in this case may be a filter, a tube, or the like.

The _{pentavalent vanadium compound is preferably V 2} O ₅ , the tetravalent vanadium compound is preferably VOSO ₄ , and the 3.3 to 3.7 vanadium compound is preferably VOSO ₄ and V ₂ (SO ₄ ) ₃ Mixing may be performed, and in this case, there is an advantage in that a high-purity, high-quality vanadium electrolyte is prepared.

The first step may preferably be carried out by including 100 parts by weight of a pentavalent vanadium compound, 400 to 700 parts by weight of water, 100 to 400 parts by weight of sulfuric acid, and 8 to 30 parts by weight of a hydrazine compound, and more preferably a pentavalent vanadium compound. 100 parts by weight of a vanadium compound, 500 to 700 parts by weight of water, 200 to 400 parts by weight of sulfuric acid, and 12 to 30 parts by weight of a hydrazine compound, and more preferably 100 parts by weight of a pentavalent vanadium compound, 500 to 600 parts by weight of water parts by weight, 200 to 300 parts by weight of sulfuric acid, and 15 to 25 parts by weight of a hydrazine compound, and more preferably 100 parts by weight of a pentavalent vanadium compound, 500 to 550 parts by weight of water, 250 to 300 parts by weight of sulfuric acid and 12 to 20 parts by weight of the hydrazine compound. Within this range, the reaction time is shortened, the reaction efficiency is excellent, and a high-purity, high-quality vanadium electrolyte is prepared.

The ratio of the molar concentrations (M; mol/L) of the pentavalent vanadium compound, sulfuric acid, and hydrazine compound input in the first step may be preferably 1: 2 to 3: 0.3 to 0.4, and more preferably 1 : 2.2 to 2.8: 0.35 to 0.4, more preferably 1: 2.3 to 2.7: 0.36 to 0.39, even more preferably 1: 2.4 to 2.6: 0.37 to 0.38, within this range, the reaction time is shortened and the reaction efficiency This is excellent and has the advantage of producing a high-purity, high-quality vanadium electrolyte.

Preferably, the first step may include i) adding a pentavalent vanadium compound and water, ii) adding a reducing agent thereafter, and iii) adding sulfuric acid thereafter. In this case, the process time may be reduced It is shortened, the reaction efficiency is excellent, and the decomposition of the reducing agent is minimized, and there is an advantage of producing a high-purity, high-quality vanadium electrolyte.

The second step may preferably be a step of reducing a tetravalent vanadium compound to a 3.3 to 3.7 vanadium compound, more preferably a 3.4 to 3.6 vanadium compound, and most preferably a 3.5 valent vanadium compound. step, and in this case, there is an advantage in that a high-purity, high-quality vanadium electrolyte is prepared.

In the second step, the heating time may preferably be from 10 hours to 50 hours, more preferably from 10 hours to 40 hours, still more preferably from 10 hours to 30 hours, even more preferably from 10 hours to 20 hours. , most preferably from 10 hours to 15 hours, and in this case, there is an advantage in that a high-purity, high-quality vanadium electrolyte solution with excellent reaction efficiency is prepared.

The second step may preferably be heated to 80 to 110 ° C, more preferably from 90 to 110 ° C, more preferably from 100 to 110 ° C, even more preferably from 105 to 110 ° C, In this case, the reaction time is shortened and the reaction efficiency is excellent, but there is an advantage in that a high-purity, high-quality vanadium electrolyte is prepared.

The first step and the second step may be performed under atmospheric pressure, for example, but may be pressurized or reduced as necessary within a range satisfying the above-described reaction conditions.

In a preferred embodiment, the entire amount of the hydrazine compound may be added in the first step with respect to the total weight of the hydrazine compound added to the vanadium electrolyte preparation. 60 to 80% by weight may be added in, and the remaining 20 to 40% by weight may be added in the second step, and in a more preferred embodiment, 60 to 70% by weight is added in the first step, and the remaining 20 in the second step to 30% by weight may be added, and in this case, there is an advantage in that a high-purity, high-quality vanadium electrolyte is prepared while decomposition of the hydrazine compound is minimized.

The hydrazine compound may be preferably added in an aqueous solution state, more preferably 50 to 90 wt% aqueous hydrazine compound solution, more preferably 60 to 90 wt% aqueous hydrazine compound solution, even more preferably is added as 70 to 90% by weight aqueous hydrazine compound aqueous solution, particularly preferably 75 to 85% by weight aqueous hydrazine compound solution, and within this range, the reaction proceeds stably, and high-purity, high-quality vanadium electrolyte solution with excellent reaction efficiency is prepared There is an advantage to be

The hydrazine hydrate is preferably hydrazine monohydrate, and the hydrazine salt is preferably hydrazine sulfate.

In the first step, for example, a Pt catalyst may be further included, and in this case, there is an effect of further accelerating the reduction reaction.

In the present description, the Pt catalyst is not particularly limited if it is a Pt catalyst commonly used in the art to which the present invention belongs.

Hereinafter, preferred examples are presented to aid the understanding of the present invention, but the following examples are merely illustrative of the present invention and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, It goes without saying that such variations and modifications fall within the scope of the appended claims.

[Example]

The composition of the vanadium electrolyte, which will be described below as an example, is 1.7 moles of a vanadium compound and 4.3 moles of sulfuric acid, and the ionic value of the vanadium electrolyte is 3.5, and is an electrolyte in which vanadium tetravalent ions and vanadium trivalent ions are mixed in a 1:1 ratio.

Materials required for preparing the electrolyte solution of the examples are as follows: 155 g of a vanadium compound, 435 g of sulfuric acid, 765 g of water, 39.8 g of an 80 wt% aqueous solution of hydrazine monohydrate.

Here, hydrazine monohydrate is required as much as the number of moles corresponding to the value obtained by multiplying the number of moles of vanadium by 0.375, and in the case of 1.7 moles of vanadium, as much as 0.6375 M is required. In the case of hydrazine, an 80 wt% aqueous solution of hydrazine monohydrate was used.

In this description, M means the number of moles (mol/L) of the solute dissolved in 1L of the solution.

The configuration of the apparatus for preparing the electrolyte solution of the embodiment is shown in FIG. 1 below. Referring to FIG. 1 , a stirring tank 10 capable of reacting 1L or more, a jacketed heat exchanger 60 provided outside of the stirring tank 10, and an open reflux condenser with purging and cooling functions ( 30), provided at the bottom of the stirring tank 10 and extending from one side of the electrolyte discharge port 40 through which the manufactured electrolyte is discharged, the electrolyte discharge pipe 41 connected to the electrolyte discharge port 40, and the stirring tank (10) is installed in the circulation pipe 42 connected to the upper part, the material is PTFE and the filter having a pore size of 0.45 μm is provided in a form capable of circulation filtration, and the circulation filtration device 20 coated with Teflon therein, And it is composed of a filtration device 50 installed on one side of the electrolyte discharge pipe 41, and the surface in contact with the electrolyte of the manufacturing device 1 has acid resistance and chemical resistance such as glass, PTFE, PE, Teflon, etc. It was used by having a material or coating it with the material.

At this time, as the circulation filtering device 20, the filter bag (b) structure of the structure shown in FIG. 2 was used, and as the open reflux condenser 30, a pipe through which the cooling liquid flows in the structure shown in FIG. 3 was used. The structure (a) in the form of an inserted dimroth was used.

A process flow chart for preparing the electrolyte of the embodiment using the above-described manufacturing apparatus 1 is shown in FIG. 4 below. 4, in the stirring tank 10, deionized water (DIW), a vanadium compound having a purity of 99.9 wt% (V ₂ O ₅ ), hydrazine monohydrate (N ₂ H ₄ ·H ₂ O) and sulfuric acid (H ₂ SO ₄ ) is introduced through the raw material inlet in the order, and the input reaction raw material is stirred while starting the first-step reduction reaction.

When the first-step reduction reaction is completed, the reactant is passed through the circulation pipe 42 in which the circulation filtering device 20 is installed to remove impurities that may contain components such as Si, Al, Fe, and then surrounds the reaction tank. A two-step reduction reaction is performed by heating the reactants with the jacketed heat exchanger 60 .

The water vapor generated during the two-step reduction reaction and the water vapor in the nitrogen gas (N ₂ ) are cooled by the reflux condenser (3) and returned to the reactor, and the nitrogen gas (N ₂ ) is discharged to the outside through the open reflux condenser (3). can be discharged

When the two-step reduction reaction is completed, the electrolyte is discharged through the discharge pipe 41 in which the filtering device 50 is installed, and then impurities are removed once more using the above-described purification device, and the final electrolyte product (V ^3.5+ electrolyte product) was obtained.

As described above, the vanadium electrolyte manufacturing apparatus and process according to the present invention, unlike the known vanadium electrolyte manufacturing apparatus and process, it is possible to produce a 3.5-valent electrolyte with one reactor, and there is a significant advantage in process equipment and maintenance compared to the existing ones. .

Hereinafter, the electrolyte preparation step of the embodiment will be described in detail by dividing it into a total of five steps.

Step 1: Putting vanadium, water, and hydrazine monohydrate into the reactor

There may be several mixing methods for the mixing order in step 1, but the most preferable method is to administer to the stirring tank 10 in the order of water → vanadium → hydrazine monohydrate under the operation of the stirrer. A certain amount of water may be added in this process. For example, it is possible to administer by mixing a part of water with hydrazine monohydrate and diluting it. Also, after adding water and a vanadium compound, to treat the vanadium compound attached to the inside of the raw material inlet, water is flowed to wash it into the reactor. method is also possible. However, if there is water in the reactor before adding the vanadium compound, it may be more advantageous in dispersing the vanadium compound in the stirring tank 10 . When water is added after adding the vanadium compound, the isolation of the vanadium compound between the bottom of the stirring tank 10 and the vanadium compound-water interface occurs more easily, and the isolated and aggregated vanadium compound has room to generate unnecessary load.

The most undesirable mixing method in step 1 is mixing the vanadium compound and hydrazine monohydrate directly. When a vanadium compound and hydrazine monohydrate are mixed, water is added, and sulfuric acid is administered in step 2 to make an electrolyte, a part of the vanadium compound, a raw material, is not dissolved in the sulfuric acid, and precipitation occurs. When the two raw materials are mixed without water, smoke and heat are generated under a vigorous reaction, and the vanadium compound turns black. Due to this phenomenon, it is estimated that a part of the hydrazine compound is decomposed by the instantaneous heat of reaction, and the reduction function is not performed after the sulfuric acid is added, resulting in precipitation of the vanadium compound. In this step, 26.6 g of hydrazine monohydrate is first added out of the total 39.8 g. In this input process, the temperature in the stirring tank 10 may rise to within 10 °C.

5 is a photograph taken together with the case where the mixture was normally mixed and the case where the vanadium compound precipitation occurred. Referring to FIG. 5 , it can be seen that the vanadium compound, which is a raw material, is precipitated under the right beaker.

In step 1, it is important to accurately inject a predetermined amount into the container without having to worry about controlling the flow rate of the input of the raw material.

Step 2: Addition of sulfuric acid

Unlike step 1, step 2 is a step that requires input considering the flow rate. In consideration of the exotherm of the reaction solution formulated in step 1, the amount of sulfuric acid input is determined. Sulfuric acid is introduced slowly to prevent the reaction solution from splashing on the wall surface of the stirring tank 10 as much as possible, and in this case, it is preferable that the exothermic temperature does not exceed 110°C. In this process, a cooling device such as the open reflux condenser 30 or a heating device such as the heat exchanger 60 may be used if necessary.

For reference, the exothermic temperature of 110° C. is a temperature under experimental conditions according to an embodiment of the present invention, and when a vacuum scrubber is installed in the reactor, the atmospheric pressure in the reactor is somewhat lowered, and the boiling point of the electrolyte may be lowered. As an example, an experiment in which a scrubber was installed was conducted to confirm the boiling point at 105°C.

On the other hand, in the case of using a high-pressure reactor, the boiling point of the electrolyte may be higher than 110° C. conversely. Accordingly, the exothermic temperature of 110° C. may be interpreted differently as referring to a temperature near the boiling point of the electrolyte.

6 is a graph showing the experimental results for the temperature change according to the input time at a flow rate of 240ml/hr. Referring to FIG. 6 , there was no separate heating in this process and the capacitor was operated. Although there is a deviation, it can be seen that the temperature rises sharply before 25 minutes when about 100 ml is injected, and then gradually decreases after 25 minutes. The sudden temperature change before 25 minutes is exotherm generated in the process of dissolving 1.7M of vanadium in 1.7M of sulfuric acid (about 100ml) and converting it into a vanadium pentavalent ion, and at the same time the pentavalent ion is changed to a tetravalent ion by hydrazine monohydrate. it is by

7 is a graph showing the temperature change according to time when the flow rate is 240ml/hr and 480ml/hr compared to the graph. Referring to FIG. 7 , at 480 ml/hr, it reached 106° C. in 13 minutes and 107° C. in 15 minutes, and then maintained at 107° C. until the completion of the sulfuric acid input. At 13 minutes, the equilibrium point was almost reached, and if we look back, it also coincides with the time when 1.7M sulfuric acid was added. If sulfuric acid is added faster than 480 ml/hr, it may be difficult to apply in this embodiment.

In the case of step 2, since conditions may be different for each experiment, it is necessary to find an appropriate flow rate, however, the flow rate can be determined in consideration of the rapid temperature rise in the first half and the gentle temperature change in the second half. In the case of this embodiment, in the first half, 200 to 300ml/h, preferably 220 to 260ml/h, specifically 240ml/h, and in the second half, 430 to 530ml/h, preferably 460 to 500ml/h, specifically It can be set to 480ml/h.

The process (water → vanadium compound → hydrazine monohydrate → sulfuric acid) (hereinafter referred to as 'Example 1') of step 1 and 2 tested in this example is water → vanadium compound → sulfuric acid → hydrazine monohydrate. It has two advantages compared to the input method (hereinafter referred to as 'Comparative Example 1').

First, the reaction time is short, and secondly, the reduction efficiency of the reducing agent is high.

If sulfuric acid is administered to water + vanadium compound over 50 to 70 minutes, more specifically 60 minutes, prior to hydrazine monohydrate, the temperature rises from 26°C to 81°C. Then, when 26.6 g of hydrazine monohydrate is diluted in 100 g of water and the inflow rate is 250 ml/hr, it takes about 30 minutes, and the final temperature was 105°C. Here, hydrazine monohydrate is preferably used by mixing 20 to 30 parts by weight with 100 parts by weight of water and diluting it.

As such, when hydrazine monohydrate is added later, if there is no separate cooling process, it enters at a high temperature raised by the addition of sulfuric acid. The high temperature conditions have to control the flow rate due to the rather rapid reaction.

On the other hand, when hydrazine monohydrate is added first and sulfuric acid is added later, since the reduction of hydrazine monohydrate starts from a low temperature, there are relatively few side effects on temperature increase, so the overall process time can be shortened. That is, when the input sequence of this example is followed, the flow control raw material is one sulfuric acid, but in the comparative example above, the flow control raw material becomes two of sulfuric acid and hydrazine monohydrate, so processing time or processing difficulties follow.

Hydrazine monohydrate is decomposed _{into NH 3} + NH when the temperature is above 180℃ _{, and into N 2} + 2H ₂ when the temperature is above 350℃. The possibility of decomposition of hydrazine by heat without playing a reducing role increases. Due to this side reaction, a part of hydrazine is consumed without participating in the reduction reaction, so contrary to the actual theory, experimentally, an excess of about 4-7% of stoichiometric ratio can be added to achieve 3.5 value. On the other hand, when hydrazine monohydrate is added first and sulfuric acid is added later, the possibility of the side reaction described in the former is relatively low, and it is economical because it is possible to achieve 3.5 value by experimentally adding an excess of about 0 to 3%.

The end time of step 2 may be the time when sulfuric acid input is completed, or additional stirring may be performed at 110° C. or less within 2 hours.

In step 2, the open reflux condenser 30 discharges the gas by-product (N ₂ ) from the reduction process of pentavalent vanadium ions out of the vessel, and vaporized H ₂ O and H ₂ SO ₄ are condensed and cooled to cool the stirring tank (10). By allowing it to stay inside, it is possible to maintain a high temperature (around 110° C.), thereby maximizing the reaction efficiency and preventing a change in the composition in the stirring tank 10 .

Step 3: Circulation Filtration Process

The circulation filtration process is a work in which the electrolyte in the reactor is filtered using a circulation system to filter out impurities. The application time of the circulation filtration process can be carried out immediately after sulfuric acid is added in step 2, and in addition, it can be carried out between 'the time when the amount of vanadium moles is added' and 'at the time when all the sulfuric acid is introduced and about 2 hours have elapsed'. The filter used in the circulation filtration process may have hydrophilic, hydrophobic, amphiphilic or amphiphilic properties, and the material should be at least one selected from the group consisting of PTFE, PE, PET and PP with acid resistance, and the pore size The size may be between 0.2 and 5 um. Here, the time required for filtration may be controlled by the size of the filter, that is, the diameter and the pore size.

In this embodiment, the electrolyte solution to which the circulation filtration process is applied to the same raw material is superior in cycle-to-cycle discharge capacity, Coulomb efficiency, energy efficiency, etc. (hereinafter, charge/discharge characteristics) compared to the electrolyte solution not applied. When the circulation filtration process uses 99.9% of vanadium purity as a raw material, the charging and discharging characteristics show a slight improvement compared to the non-applied process. In addition, when the circulation filtration process is applied to a 99.5% pure vanadium raw material or a 99% pure vanadium raw material, it appears at the same level as the charge/discharge characteristics of an electrolyte prepared using a 99.9% pure vanadium raw material. From this, it was confirmed that even using low-purity vanadium, it is possible to manufacture an electrolyte that has the charging/discharging performance level of an electrolyte prepared using high-purity vanadium.

This effect comes from the following reasons.

First, in vanadium pentavalent ions and tetravalent compounds, impurities that were not dissolved in the compound react with free sulfuric acid in the compound during the preparation of the vanadium 3.5 valence compound to form impurity salts, thereby degrading the performance of the vanadium electrolyte. In particular, the charge and discharge capacity cannot be maintained, and as the cycle progresses, the charge/discharge capacity decreases when the circulation filtration process is not applied. The cost of inserting the filtration process is only insignificant compared to the benefits of using low-purity vanadium.

Second, replacing the filter is not a difficult task.

Third, filter price is relatively cheap and price volatility is stable, while vanadium price is expensive but price volatility is unstable.

When the analysis of the electrolyte sample without/applying the circulation filtration process was performed, it was confirmed that the Si content was reduced by 35.9% when the circulation filtration process was applied. In addition, it was confirmed that Fe and Al also decreased by 5% or more. This means that the impurities are filtered better at tetravalent or 3.5 is dissolved in the electrolyte during the manufacturing process and changed to a poorly filtered form.

Impurity Si easily forms a precipitate on the electrode and ion exchange membrane during charging and discharging, and this precipitate affects the durability and lifespan of the battery. When Al and Fe are contained in the electrolyte in more than a certain amount, they cause a capacity fading effect, which leads to a decrease in performance.

It was confirmed that the electrolyte performance was improved by removing impurities that adversely affect the electrolyte charge/discharge performance compared to the same number of filters through the process. For example, there is a difference of about 3.5% in the charge/discharge capacity in 5 cycles, and it can be seen that the gap gradually widens in subsequent cycles.

Step 4: Manufacturing Process of 3.5-valent Electrolyte

After the circulation filtration process is finished, the temperature of the stirring tank 10 is adjusted to 110° C. using the heat exchange device 60 . Then, 13.2 g of hydrazine monohydrate is placed in the stirring tank (10). Although hydrazine monohydrate can be added even if the temperature of the stirring tank 10 does not reach 110° C., when hydrazine monohydrate is added to the tetravalent electrolyte at a temperature of 90° C. or less, particularly 70° C. or less, sulfuric acid-hydrazine salt is formed. Therefore, there is a possibility that the reducing function of hydrazine may be lowered.

In step 4, the open reflux condenser 30 discharges gas by-products (N ₂ ) from the reduction process of tetravalent vanadium ions out of the vessel, and vaporized H ₂ O and H ₂ SO ₄ are condensed and cooled to stay in the reactor to high temperature. By enabling maintenance (around 110° C.), there is an advantage in that it is possible to prevent a change in the composition in the stirring tank 10 while maximizing the reaction efficiency. The time required for the four-step process is less than about 15 hours.

Since the side reaction effect due to the instantaneous high temperature of the reducing agent mentioned in step 2 is insignificant in step 4, an excess of reducing agent is not required to prepare 3.5 valence. Taking advantage of the fact that the production of tetravalent to trivalent vanadium electrolytes follows a stoichiometric ratio, although the value may decrease as a vanadium electrolyte, it can be manufactured by adjusting the ratio of tetravalent ions to trivalent ions in the vanadium electrolyte as desired. there is a characteristic

8 is a graph showing the relationship between the oxidation number of vanadium and the reaction time measured through UV absorbance in the four-step reaction. Here, the reaction time for 3.5 to reach the vanadium compound was approximately 10 hours.

Step 5: Final Filtering Process

When the vanadium 3.5 compound is completed, the temperature is lowered and the final filtration process is performed. Since many impurities are filtered out in the circulation filtration process, there are almost no impurities caught in the filter in the process, so the filtration time is quite short.

If the circulation filtration process is not applied, it may take more time to filter out impurities in the final filtration process, and a re-filtration process may be required to check whether the impurities are removed by re-filtering the filter once again. In this case, the first filtration process among the two filtration processes performed after the completion of the vanadium electrolyte solution is the same as applying the circulation filtration process in a different order. Therefore, in this embodiment, impurities contained in the raw material of vanadium are primarily filtered through the circulation filtration process to prevent various side reactions that may occur during the manufacturing process of the 3.5 electrolytic solution in advance, thereby improving the performance of the electrolytic solution, while reducing the overall process time. It can be said that there is an advantage that it does not affect. In addition to the effect of simply shortening the process time, there is an advantage that a high-purity vanadium electrolyte can be manufactured using a low-purity vanadium raw material.

A vanadium electrolyte solution prepared using the 99.9% purity shown in Example 1 (hereinafter, Example 1), and an electrolyte solution prepared by applying the process in Example 1 to 99% purity vanadium (hereinafter, Comparative Example 2-A) ) and 99% purity of vanadium in 50 cycles of specific charge/discharge conditions of the electrolyte solution (hereinafter, Comparative Example 2-B) prepared without performing the cycle filtration step corresponding to step 3 in the process in Example 1 The discharging capacity for each was compared under the charging/discharging evaluation system.

As a result, when the average discharge capacity of Example 1 was 100%, the average discharge capacity of Comparative Example 2-A was about 99.8%, and the average discharge capacity of Comparative Example 2-B was 97.2%, which Although it was carried out under specific charging/discharging conditions, the characteristics of improving the charging/discharging performance are interpreted as very effective results even if the charging/discharging conditions such as current density, flow rate, voltage range, and number of cycles change.

Experiment result

In conclusion, it was confirmed that the vanadium electrolyte manufacturing method and manufacturing apparatus according to the present invention have the following excellent effects compared to the comparative examples or the prior art through the above-described examples.

First, the present invention is prepared using only hydrazine monohydrate, so that the process is simple and high-purity vanadium electrolyte can be prepared compared to the conventional reducing agent + electrolysis manufacturing method or reducing agent + (reducing agent + catalyst) method.

Second, in the present invention, by using a single reactor, the facility investment cost is significantly lower compared to the conventional use of two or more reactors, and subsequent maintenance and management are greatly facilitated.

Third, the present invention is greatly advantageous in terms of mass production compared to the conventional electrolysis or catalyst-using process by using a non-catalytic chemical reaction.

The electrolysis method may require periodic replacement of membranes and electrodes, and also the size of the membrane and electrodes should be considered in order to improve the hourly output. Therefore, the electrolysis method is a process that requires more cost and facilities for mass production. In addition, although the catalyst using process has an advantage over the electrolysis method in that it uses a reducing agent, a catalyst recovery process from the electrolyte must be added, the problem of periodic replacement of the catalyst, and the dissolution of some catalysts in the vanadium electrolyte There is a problem of performance degradation.

Fourth, the present invention achieves process optimization by controlling the input sequence in the raw material mixing process, and through this, it is possible to shorten the process time and manufacture a high-quality vanadium electrolyte solution by improving the reducing agent efficiency at the same time.

Fifth, the present invention uses an open reflux capacitor to create an inert environment inside the reactor and fundamentally block side reactions to maximize reaction efficiency, and at the same time to obtain the vanadium electrolyte composition as originally designed.

Sixth, according to the present invention, the quality of the vanadium electrolyte can be improved without a significant change in the total process time by changing the filtration order in consideration of the reaction between impurities and the electrolyte in some cases.

Seventh, according to the present invention, it is possible to manufacture a vanadium electrolyte that exhibits the same level of charge/discharge performance as that of a high-quality vanadium electrolyte even if low-purity vanadium is used through the filtration means in the reactor.

1: Manufacturing device
10: stirring tank
20: circulation filter
21: filter
30: open reflux capacitor
40: electrolyte outlet
41: exhaust pipe
42: circulation pipe
50: filter

Claims (13)

A first solution in which water, a pentavalent vanadium compound, and a hydrazine-based reducing agent are sequentially mixed and reacted is prepared, and the first solution is received as a vanadium electrolyte starting material, or sulfuric acid is added to the first solution and reacted with a second solution A stirring tank for accommodating the vanadium electrolyte as a starting material; and
A circulation filtration device for filtering the first solution or the second solution,
An apparatus for producing a vanadium electrolyte solution, characterized in that an open reflux condenser is provided at an upper portion of the stirring tank to cool the water and sulfuric acid vaporized during the reaction, recover it to the stirring tank, and discharge nitrogen gas. According to claim 1,
The agitation tank and the circulation filtration device are each independently made of at least one material selected from the group consisting of glass, polyethylene resin, and Teflon resin. According to claim 1,
The circulation filtering device is a vanadium electrolyte production device, characterized in that it is equipped with a filter made of PTFE, PE, PET or PP material and having a pore size of 0.2 to 5 μm. According to claim 1,
The circulation filtering device is installed in an electrolyte discharge pipe connected to an electrolyte outlet for discharging the electrolyte generated in the stirring tank, or a circulation pipe extending from one side of the discharge pipe and connected to the upper part of the stirring tank, characterized in that Vanadium electrolyte manufacturing device. 5. The method of claim 4,
Vanadium electrolyte production apparatus, characterized in that at least one circulation filtering device installed in the electrolyte discharge pipe, and at least one circulation filtering device installed in the circulation pipe. According to claim 1,
The circulation filtering device is a vanadium electrolyte production device, characterized in that it has a structure in which a filter is mounted. According to claim 1,
The apparatus for producing an electrolyte solution is a vanadium electrolyte production apparatus, characterized in that it is a catalyst-free electroless reaction apparatus. According to claim 1,
The hydrazine-based reducing agent is at least one hydrazine compound selected from the group consisting of hydrazine anhydride, hydrates thereof, and salts thereof,
The hydrazine-based reducing agent is in the range of 0.3 to 0.4 moles based on 1 mole of the pentavalent vanadium compound,
The pentavalent vanadium compound is V ₂ O ₅ Vanadium electrolyte production apparatus, characterized in that. According to claim 1,
The sulfuric acid is added in an amount of 2 to 3 moles based on 1 mole of the pentavalent vanadium compound. According to claim 1,
The water is added in an amount of 400 to 700 parts by weight based on 100 parts by weight of the pentavalent vanadium compound. According to claim 1,
The manufacturing apparatus further includes a filtering device in which the vanadium electrolyte generated in the stirring tank is discharged through the electrolyte outlet to remove impurities including Si and ^{to obtain a 3.5-valent vanadium compound (V 3.5+ electrolyte product) as a final electrolyte product.} Vanadium electrolyte manufacturing apparatus, characterized in that. According to claim 1,
A vanadium electrolyte manufacturing apparatus, characterized in that the pentavalent vanadium compound used as a reaction raw material in the manufacturing apparatus has a purity of 99% or more. According to claim 1,
The stirring tank is a single reactor,
Vanadium electrolyte manufacturing apparatus, characterized in that it further comprises an external jacket heat exchanger or an internal thermal coil as a temperature control device for controlling the reaction temperature of the stirring tank to 70 to 110 ℃.

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