JP6909826B2 - A method for producing a vanadium compound, a method for producing an electrolytic solution for a redox flow battery, an apparatus for producing a vanadium compound, and an apparatus for producing an electrolytic solution for a redox flow battery. - Google Patents

Description

The present invention relates to a method for producing a vanadium compound for separating a vanadium compound from combustion ash and the like, a method for producing an electrolytic solution for a redox flow battery, an apparatus for producing a vanadium compound, and a method for producing an electrolytic solution for a redox flow battery. Regarding the device.

Vanadium is used as a raw material for an electrolytic solution, which is a main component of a redox flow battery, which is a large storage battery. In redox flow batteries containing vanadium (vanadium redox flow batteries), inexpensive high-purity components that do not contain contaminant metal compounds such as nickel (Ni), iron (Fe), and magnesium (Mg) as constituents of the electrolytic solution. Vanadium is sought after. However, the vanadium products that are generally distributed are ferrovanadium for adding steel materials, and have the disadvantages that they coexist with iron and have low purity, and that they are mainly for steel materials and cannot be supplied in large quantities.

An alternative vanadium source is combustion ash containing vanadium. Combustion ash is obtained by burning heavy oil such as crude oil under atmospheric pressure distillation residue oil, vacuum distillation residual oil obtained by vacuum distillation, oil coke, oil sands, etc., and is vanadium (V), nickel. A plurality of metals such as (Ni), iron (Fe), and magnesium (Mg) are included. However, since the combustion ash has a low vanadium content (concentration), the wet method of extracting and purifying with an acid alkali has a drawback that the amount of chemicals used is large and the production cost is high.

As a technique for recovering vanadium from combustion ash, for example, the method of Patent Document 1 is known. In this method, the incineration ash is immersed in an alkaline solution, and vanadium is leached from the incineration ash into the alkaline solution to obtain a leachate slurry, and the leachate slurry obtained in the alkali leaching step is solid-liquid separated and insoluble. A solid-liquid separation step of removing substances to obtain a leachate, a pH adjustment step of adding an acid to the leachate after solid-liquid separation to make it acidic, and a aging step of aging until precipitates are deposited in the leachate after pH adjustment. And a separation step of separating the precipitate from the leachate after the aging step. According to this method, it is said that a vanadium compound having a low content of iron element can be obtained.

Further, in Patent Document 2, the first step of separating the washing residue by adjusting the pH by adding an alkaline solution while washing the dust collector ash with water, and the first step of adding an alkaline solution to the washing residue and heating it are described. 1 The second step of separating the filtrate, the third step of precipitating alkaline vanadate crystals from the first filtrate and separating them as the second filtration residue, and the second step of neutralizing the second filtration residue with acid and the first step. Describes a method for producing an electrolytic solution, which comprises a fourth step of mixing the washing waste water obtained in (1) to generate vanadium pentoxide and separating it as a third filtration residue.

In the first step of this document, it is said that by adjusting the pH of the suspension to preferably 6 to 8, it is possible to prevent the dissolution of metal impurities such as iron and nickel in the suspension. Further, in the second step, the heating temperature is preferably 50 to 100 ° C., and it is described that vanadium is contained in the first filtered solution in the form of a solution and solid-liquid separated from the first filtered residue. ing. Further, in the third step, the method for precipitating the alkali vanadate is not particularly limited, and a method for selectively separating according to the difference in solubility can be used, and sodium vanadate (NaVO _{3) can be used as crystals of the alkali vanadate.} ) Is precipitated. Further, the second filtered solution obtained in the third step is reused as an alkaline solution in the second step, and the second filtered solution is replenished with an alkaline solution for concentration recovery because the alkaline concentration is reduced. It is described that after making an alkaline solution having a predetermined concentration, it is reused as an alkaline solution in the second step and added to the cleaning residue.

International Publication No. 2017/208471 (summary, paragraph 0024, etc.) JP-A-2019-46723 (summary, claim 1, claim 3, paragraph 0025, paragraphs 0028-0032, etc.)

In a method of leaching vanadium into a liquid such as the method of Patent Document 1, it is necessary to add an alkaline solution at a certain ratio or more with respect to the solid content in order to increase the recovery rate of the leached liquid. Therefore, in order to recover vanadium from combustion ash having a low vanadium content, a relatively large amount of alkaline solution is required as compared with a raw material having a high vanadium content, and it is possible to achieve a practical and inexpensive processing cost. It was difficult.

Further, in the method of this document, it is _{necessary to add an acid (H 2} SO ₄ or the like) to the leachate after the alkali leaching to make it acidic, so that the cost of the acidifying agent and the time and effort of addition are required. Furthermore, as described above, since the vanadium content in the incinerator ash is low, a relatively large amount of alkali is added, which requires a large amount of acid to be added, which further increases the cost of acidifying agents. It is connected.

Furthermore, since the leachate from which the precipitate is separated after the aging step contains vanadium that could not be completely precipitated, it is preferable to recycle it and perform alkaline leaching again. However, in the method of the present document, since the leachate is acidic, it is necessary to add an alkaline solution again to leach the alkaline solution, which also causes a problem that a great deal of cost and labor are required.

In Patent Document 2, an alkaline solution is added to the washing residue to obtain a first filtrate. Since the dust collector ash contains a large amount of sulfate roots, the washing residue contains sulfate ions, and when an alkaline solution is added to this, alkali sulfate such as sodium sulfate (Glauber's salt) is generated. Since alkali sulfate is difficult to separate in the process of purifying vanadium, alkali sulfate tends to remain as a contaminant in the finally obtained purified vanadium product. In this document, since the treatment for separating the alkali sulfate is not performed, it is considered that the alkali sulfate remains as a contaminant in the purified vanadium product.

Further, in this document, it is described that a method of selectively separating by the difference in solubility can be used in the third step, but no specific method is described. Since the alkali concentration of the second filtrate obtained in the third step is lower than that of the first filtrate, it can be seen that the solution is not concentrated in the crystallization of the third step. Therefore, it is necessary to process a large amount of solution, which makes the device large and costly. Further, since it is necessary to add a large amount of high-concentration alkali when recycling the second filtrate to the second step, it is costly from this point as well.

Further, in this document, a sodium vanadate salt (NaVO ₃ ) is produced in the fourth step. Therefore, the pH after the addition of alkali in the second step is estimated to be about pH 7 to 9, judging from the known phase diagram of vanadium. Further, FIG. 4 shows changes in the leachate rate depending on the temperature and pH of various metals, where (a) is vanadium, (b) is nickel, (c) is iron, and (d) is magnesium. From this figure, it can be seen that the leaching rate of nickel and magnesium increases in the region where the pH is 11.5 or less. For this reason, also in this document, since alkali leaching occurs in a low pH range of 7 to 9, a large amount of metal impurities such as nickel and magnesium are leached, and the vanadium refined product also contains these metal impurities. Become.

An object of the present invention is a method for producing a vanadium compound which can be carried out at low cost with high purity of the obtained vanadium compound, a method for producing an electrolytic solution for a redox flow battery, an apparatus for producing a vanadium compound, and a redox. The purpose of the present invention is to provide an apparatus for producing an electrolytic solution for a flow battery.

The present inventors have different solubility of vanadium compounds such as sodium orthovanazine (V) and alkali sulfate such as sodium sulfate depending on the conditions of temperature and alkali concentration, and further, the alkali sulfate is dissolved and orthovanazine (V) acid. The present invention has been completed by finding the conditions of the optimum temperature and alkali concentration at which alkali is precipitated.

The present invention separates vanadium from raw material ash containing at least ammonium sulfate and / or ammonium hydrogensulfate, sulfuric acid, vanadium, and at least one other metal selected from nickel, iron and magnesium. A method for producing a vanadium compound, which comprises adding an alkali and water or an alkaline solution to the raw material ash so that the pH becomes 13 or higher, and leaching vanadium into the liquid phase to obtain an alkaline leachate, and the alkali. A solid-liquid separation step in which the leachate is solid-liquid separated to remove insoluble substances as solids and the alkaline leachate containing vanadium is obtained as a leachate, and an evaporative concentration step in which the leachate is evaporated and concentrated to obtain a concentrated solution. The concentrated solution comprises a crystallization / solid-liquid separation step of cooling the concentrated solution to a predetermined cooling temperature for crystallization and recovering the precipitate containing the vanadium compound as a solid content. The method for producing a vanadium compound is characterized in that the vanadium compound has a saturation concentration or more and the alkali sulfate has a saturation concentration or less.

In the present invention, the pH is set to 13 or higher in the alkali extraction step, and the leachate containing vanadium is recovered in the solid-liquid separation step. Subsequently, the leachate is evaporated and concentrated in the evaporation concentration step so that the alkali has a predetermined concentration, and the precipitate containing vanadium is recovered in the crystallization / solid-liquid separation step. The concentrate is adjusted so that the vanadium compound has a saturated concentration or more and the alkali sulfate has a saturated concentration or less at the cooling temperature. Therefore, the alkali sulfate can be selectively removed, and the vanadium compound can be efficiently recovered. As described above, in the present invention, it is not necessary to add an acid as in the conventional case, and the vanadium compound is selectively precipitated and recovered depending on the difference in solubility under the conditions of the temperature and the alkali concentration of the vanadium compound and the alkali sulfate. .. Therefore, as compared with the conventional case, vanadium can be separated inexpensively, easily and selectively.
Further, since leaching is performed in a pH region as high as pH 13 in the alkali extraction step, impurities such as nickel are less likely to leached out, and the purity of the finally obtained vanadium compound can be increased.
Furthermore, since the crystallization filtrate from which the solid content containing the vanadium compound was separated in the crystallization / solid-liquid separation step contains alkali in addition to the vanadium compound that did not precipitate, the alkali extraction step is performed again if necessary. Can be recycled. Further, in the present invention, since the leachate filtrate is evaporated and concentrated, the alkali concentration of the obtained concentrate is high, and it is not necessary to add alkali for recovering the alkali concentration at the time of recycling to the alkali extraction step. Since it requires only a small amount, it can be recycled at low cost.

That is, in the present invention, the vanadium compound can be carried out at low cost because the purity of the vanadium compound obtained is high because alkali sulfate and metal impurities can be selectively removed, and the amount of alkali used is small without the need for a large device. Manufacturing method can be provided.

Here, when the alkali is sodium hydroxide, it is preferable that the evaporation concentration step concentrates so that the concentration of sodium hydroxide in the concentrate is 10 to 25%.
Further, it is preferable that the evaporative concentration step evaporates and concentrates the leachate at 70 to 130 ° C., and the crystallization / solid-liquid separation step cools the concentrated solution to 0 to 20 ° C.

In this case, it is preferable to further include a raw material ash cleaning step for cleaning the raw material ash before the alkali extraction step.

In this way, by washing the raw material ash before the alkali extraction step, the ammonium sulfate content and sulfuric acid are considerably reduced, and even if evaporation concentration and cooling crystallization are performed, sulfate such as sodium sulfate (Glauber's salt) in the liquid is used. The concentration of alkali can be maintained below the saturation concentration. Therefore, the solid content obtained in the crystallization / solid-liquid separation step contains almost no ammonium sulfate or alkali sulfate, and a high-quality vanadium compound can be obtained.

Further, in a subsequent stage of the crystallization / solid-liquid separation step, a recycling step of reusing the crystallization filtrate separated from the solid content in the crystallization / solid-liquid separation step in the alkali extraction step may be further included. preferable.

As described above, by reusing the alkali contained in the filtrate from which the solid content has been separated in the crystallization / solid-liquid separation step in the alkali extraction step, vanadium can be produced at low cost and with a high recovery rate.

In this case, the sum of the sulfate roots brought in by the crystallization filtrate and the sulfate roots brought in from the raw material ash in the alkali extraction step is the saturation of alkali sulfate after cooling in the crystallization / solid-liquid separation step. It is preferable to further include a crystallization filtrate amount adjusting step for adjusting the amount of the crystallization filtrate to be recycled so as to be equal to or less than the sulfuric acid equivalent in the concentration.

By doing so, a high-purity vanadium compound containing no crystals of alkali sulfate can be recovered.

Furthermore, it is preferable to further include an oxidation step of oxidizing the raw material ash in the stage prior to the alkali extraction step.

In this way, the vanadium compound having a large valence is produced by oxidizing the raw material ash in the pre-stage of the alkali extraction step. Thereby, the extraction recovery rate of vanadium can be improved.

Further, in a subsequent stage of the alkali extraction step, a solid content cleaning step may be further provided in which the solid content is washed to recover the cleaning liquid containing vanadium, and the cleaning liquid is transferred to the evaporation concentration step together with the leaching filtrate. preferable.

By washing the solid content and recovering the cleaning liquid containing vanadium in this way, vanadium contained in the solid content can be recovered, so that the recovery rate of vanadium can be increased.

The present invention is for a redox flow battery, which comprises an electrolytic solution manufacturing process for producing an electrolytic solution for a redox flow battery using the vanadium produced by the method for producing a vanadium compound according to any one of the above as a raw material. This is a method for producing an electrolytic solution.

By separating vanadium inexpensively, easily and selectively in this way, an electrolytic solution for a redox flow battery can be produced inexpensively and easily.

The present invention separates vanadium from raw material ash containing at least ammonium sulfate and / or ammonium hydrogensulfate, sulfuric acid, vanadium, and at least one other metal selected from nickel, iron and magnesium. An alkali extraction means for obtaining an alkaline leachate by adding alkali and water or an alkaline solution to the raw material ash so as to have a pH of 13 or higher and leaching vanadium into the liquid phase, and the alkali. A solid-liquid separation means for solid-liquid separating the leachate to remove insoluble matter as a solid content and obtaining the alkaline leachate containing vanadium as a leachate, and an evaporative concentration means for evaporating and concentrating the leachate to obtain a concentrated solution. And the crystallization / solid-liquid separation step of cooling the concentrated solution to a predetermined cooling temperature for crystallization and recovering the precipitate containing vanadium as a solid content, the concentrated solution is prepared at the cooling temperature. It is an apparatus for producing a vanadium compound, characterized in that the vanadium compound has a saturation concentration or more and the alkali sulfate has a saturation concentration or less.

In the present invention, the pH is set to 13 or higher by the alkaline extraction means , and the leachate containing vanadium is recovered by the solid-liquid separation means. Subsequently, the leachate is evaporated and concentrated by the evaporative concentration means so that the alkali has a predetermined concentration, and the precipitate containing vanadium is recovered by the crystallization / solid-liquid separation means. As described above, in the present invention, it is not necessary to add an acid as in the conventional case, and the vanadium compound is selectively precipitated and recovered depending on the difference in solubility under the conditions of the temperature and the alkali concentration of the vanadium compound and the alkali sulfate. .. Therefore, as compared with the conventional case, vanadium can be separated inexpensively, easily and selectively. Further, since the crystallization filtrate obtained by separating the solid content containing the vanadium compound by the crystallization / solid-liquid separation means contains alkali in addition to the vanadium compound that did not precipitate, the alkali extraction means is re-extracted as necessary. Can be recycled.

Here, when the alkali is sodium hydroxide, the evaporation concentration means preferably concentrates so that the concentration of sodium hydroxide in the concentrate is 10 to 25%.
Further, it is preferable that the evaporative concentration means evaporates and concentrates the leachate at 70 to 130 ° C., and the crystallization / solid-liquid separation means cools the concentrated liquid to 0 to 20 ° C.

In this case, it is preferable to further provide a raw material ash cleaning means for cleaning the raw material ash in the stage prior to the alkaline extraction means.

In this way, by washing the raw material ash before the alkaline extraction means, the ammonium sulfate content and sulfuric acid are considerably reduced, and even if evaporation concentration and cooling crystallization are performed, sulfuric acid such as sodium sulfate (Glauber's salt) in the liquid is used. The concentration of alkali can be maintained below the saturation concentration. Therefore, the solid content obtained by the crystallization / solid-liquid separation means contains almost no ammonium sulfate or alkali sulfate, and a high-quality vanadium compound can be obtained.

Further, in a later stage of the crystallization / solid-liquid separation means, a recycling means for reusing the crystallization filtrate separated from the solid content by the crystallization / solid-liquid separation means by the alkali extraction means may be further included. preferable.

In this way, by reusing the alkali contained in the filtrate from which the solid content has been separated by the crystallization / solid-liquid separation means by the alkali extraction means, vanadium can be separated at low cost and with a high recovery rate.

In this case, in the alkali extraction means, the total of the sulfate roots brought in by the crystallization filtrate and the sulfate roots brought in from the raw material ash is the amount equivalent to the saturation concentration after cooling in the crystallization / solid-liquid separation means. It is preferable to further include a crystallization filtrate amount adjusting means for adjusting the amount of the crystallization filtrate to be recycled as follows.

By doing so, a high-purity vanadium compound containing no crystals of alkali sulfate can be recovered.

Furthermore, it is preferable to further provide an oxidizing means for oxidizing the raw material ash in the stage prior to the alkaline extraction means.

In this way, the vanadium compound having a large valence is produced by oxidizing the raw material ash in the stage prior to the alkaline extraction means. Thereby, the extraction recovery rate of vanadium can be improved.

Further, in a subsequent stage of the alkali extraction means , a solid content cleaning means for washing the solid content to recover the cleaning liquid containing vanadium and transferring the cleaning liquid together with the leaching filtrate to the evaporation concentration means may be further provided. preferable.

By washing the solid content and recovering the cleaning liquid containing vanadium in this way, vanadium contained in the solid content can be recovered, so that the recovery rate of vanadium can be increased.

The present invention is for a redox flow battery, which comprises an electrolytic solution manufacturing means for producing an electrolytic solution for a redox flow battery using the vanadium separated by the vanadium compound manufacturing apparatus according to any one of the above as a raw material. It is an electrolytic solution manufacturing device.

By separating vanadium inexpensively, easily and selectively in this way, an electrolytic solution for a redox flow battery can be produced inexpensively and easily.

According to the present invention, a method for producing a vanadium compound, which can be carried out at low cost with high purity of the obtained vanadium compound, a method for producing an electrolytic solution for a redox flow battery, an apparatus for producing a vanadium compound, and a redox. An apparatus for producing an electrolytic solution for a flow battery can be provided.

It is a processing flow diagram which shows the manufacturing method of the vanadium compound which concerns on 1st Embodiment of this invention, and the manufacturing method of the electrolytic solution for a redox flow battery. It is a graph which shows the solubility curve of sodium orthovanadate and sodium sulfate at different temperature and alkali concentration. It is a processing flow diagram which shows the manufacturing method of the vanadium compound which concerns on the 2nd Embodiment of this invention, and the manufacturing method of the electrolytic solution for a redox flow battery. It is a graph which shows the change of the leachation rate by pH of vanadium, nickel, iron, and magnesium. It is a graph which shows the amount of the cleaning liquid recovered by the solid content washing step, and the recovery rate of a vanadium compound. It is a Pourbaix diagram showing the state change due to the pH of vanadium and the redox potential, and the graph showing the change in the ratio of the washing loss of vanadium due to the pH adjustment at the time of washing with water.

Hereinafter, the configuration of the embodiment of the present invention will be described. The present invention can be carried out with appropriate modifications without changing the gist thereof.

1. 1. First Embodiment Hereinafter, the first embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a method for producing a vanadium compound according to the first embodiment of the present invention, (a) is a flow chart showing a process of a method for producing a vanadium compound, and (b) is a flow chart of (a). It is a schematic diagram which shows the transition of the component contained in a raw material in each process of.

The method for producing a vanadium compound of the present invention can be suitably applied to a raw material ash containing vanadium and / or a vanadium compound. Examples of such raw material ash include petroleum-based combustion ash such as heavy oil, incineration boiler ash which becomes atmospheric pressure or vacuum distillation residual oil, partially oxidized ash, petroleum coke ash, residual ash of oil sands, and the like. Can be done.

The raw material ash in the present invention contains at least ammonium sulfate, sulfuric acid, vanadium, and other metals such as nickel, iron, and magnesium. Ammonium sulfate consists of ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) and / or ammonium hydrogen sulfate (NH ₄ HSO ₄ ). The ammonium sulfate content contained in the raw material ash is about 20 to 60% by weight, and more generally about 30 to 50%. Examples of waste containing a large amount of ammonium sulfate include petroleum-based combustion ash. The amount of sulfuric acid contained in the raw material ash is about 1 to 20% by mass (wt%), and more generally about 5 to 10% by mass.

Vanadium contained in the raw material ash takes the form of compounds having various valences of trivalent, tetravalent, and pentavalent. Specifically, NH ₄ V ₃ (OH) ₆ (SO ₄ ) ₂ , VOSO ₄・ 5H ₂ O, V ₂ O _5, etc. Generally, vanadium contained in the raw material ash is about 0.1 to 30% by mass, and more generally about 1 to 10% by mass.

The raw material ash contains a water-insoluble solid (SS content) containing unburned carbon as a main component as carbon content. The carbon content in the raw material ash is about 5 to 90% by mass per dry matter, and more generally about 30 to 70% by mass.

In addition to these, raw material ash contains other elements (metal impurities) other than vanadium, such as iron, magnesium, nickel, cobalt, molybdenum, manganese, titanium, copper, zinc, palladium, platinum, phosphorus, and sulfur. May occur. In general, these metal impurities are often contained as sulfates, oxides, and the like. Generally, these metal impurities contained in the raw material ash are about 0.1 to 20% by mass, and more generally about 1 to 10% by mass, although it depends on the type of the element.

(Raw material ash preparation process)
As shown in FIG. 1A, in the method for producing a vanadium compound of the present invention, first, combustion ash (raw material ash) is prepared (step 10). In this step, the above-mentioned raw material ash is used as it is, or a raw material ash slurry obtained by dissolving it in a solvent such as water is used as the raw material ash. The components contained in the raw material ash in this case are as shown in FIG. 1 (b) (step 10).

(Alkaline leaching process)
Next, an alkali is added to the raw material ash (raw material ash itself or the raw material ash slurry) to adjust the pH to 13 or higher to obtain an alkaline leachate containing vanadium (step 12). Examples of the alkali used in this step include sodium hydroxide (NaOH), lithium hydroxide (LiOH), potassium hydroxide (KOH), rubidium hydroxide (RbOH), cesium hydroxide (CsOH), and calcium hydroxide (Ca (Ca (). OH) ₂ ), strontium hydroxide (Sr (OH) ₂ ), barium hydroxide (Ba (OH) ₂ ) and the like can be mentioned. Of these, sodium hydroxide is preferable because it is easily available.

The temperature of the alkali leaching step is lower than the temperature of the evaporation concentration step described later, for example, about 10 to 40 ° C, preferably 20 to 30 ° C. The alkali leachate after addition of alkali has a pH of 12.5 to 15, preferably pH 13 to 14. When the pH of the alkaline leachate is 13 or more and 14 or less, vanadium can be easily selectively extracted into the alkaline leachate. The concentration of alkali contained in the alkali leachate depends on the concentration rate in the evaporation concentration step described later, and is preferably in the range of 10% by mass / concentration rate to 25% by mass / concentration rate. For example, when the concentration rate is 5 times (volume reduced to 1/5), the concentration of alkali contained in the alkali leachate is preferably 2 to 5% by mass.

(Solid-liquid separation process)
Next, the insoluble matter is removed from the alkaline leachate as a solid content, and a leachate containing vanadium is obtained (step 13). The separation method is not particularly limited, and examples thereof include precipitation separation, centrifugation, and suction filtration. As shown in FIG. 1 (b) (step 13), the components contained in the raw material ash after this step are those in which carbon is removed, and ammonium sulfate, sulfate ions, and vanadium are contained in the leachate. include.

(Solid content cleaning process)
After the solid-liquid separation step, it is preferable to perform a step of washing the solid content (cake) (solid content washing step). In this solid content cleaning step, water is added in an amount of 1 to 3 times the amount of water (solid content water content) contained in the solid content (cake) to perform cleaning. By this step, vanadium can be extracted and recovered from the solid water content. This is because the solid content after alkali leaching has a high pH, and the cake washing water also has a high pH of about 12 to 13, so that vanadium is in a solution state and can be easily recovered by washing. Further, the cleaning liquid (cleaning filtrate) obtained in the solid content cleaning step is collected and transferred to the next evaporation concentration step together with the leaching filtrate. As shown in FIG. 5, when the cleaning liquid was not recovered (cleaning filtrate volume 0 mL), the recovery rate was 88%, whereas when the cleaning liquid was recovered, the recovery rate was as high as 100% or more. It becomes. The amount of washing water may be controlled by monitoring the pH and electrical conductivity of the cake washing water.
On the other hand, in Patent Document 2, alkali leaching is performed at pH 9 or less, and cake washing is not described. In Patent Document 2, even if the cake is washed, the washing is performed at a pH near neutrality, and new extraction of vanadium cannot be expected. Rather, as shown in FIG. 4, a metal such as nickel is used. A lot of contaminants may seep out.

(Evaporation concentration process)
Next, the leachate filtrate is evaporated and concentrated to obtain a concentrated solution having an alkali concentration of 10 to 25% by mass (step 14). The method for evaporating and concentrating is not particularly limited, but it can be carried out using an evaporative concentrating can or the like. The evaporation concentration temperature is preferably 70 to 130 ° C., although it depends on the salt concentration of the leachate filtrate. If the evaporation concentration temperature is high, the amount of input energy required for concentration increases and the processing cost increases. Therefore, it is preferable to perform treatment at a temperature of 100 ° C. or lower, particularly 80 to 90 ° C., by evaporating under reduced pressure.

The evaporation concentration step is preferably carried out under reduced pressure. The ratio (concentration rate) of the volume of the leachate before the evaporation concentration step to the volume of the leachate after the evaporation concentration step is usually about 2 to 8 times, more preferably 4 to 6 times. As shown in FIG. 1 (b) (step 14), the volume of the leachate is reduced in this step, and the leachate contains ammonium sulfate, sulfate ions, and vanadium. The evaporated water may be used as the adjusting water in the alkali extraction step, or may be used as the washing water in the raw material ash washing step in the second embodiment described later.

(Cryptography / solid-liquid separation process)
Next, the concentrate is cooled and crystallized, and the precipitate containing vanadium is recovered as a solid (step 15). The cooling temperature is preferably 0 to 20 ° C. Examples of the crystallization method include a water tank having a cooling function, a cooling crystallization tank, and a poor solvent crystallization tank to which an organic poor solvent such as methanol is added. After crystallization, solid-liquid separation is performed. Examples of the solid-liquid separation method include a method using a thickener, a decanter, a basket centrifugal vacuum belt filter, and the like. As shown in FIG. 1 (b), after this step, each of ammonium sulfate, alkali sulfate (in this embodiment, sodium sulfate (Na ₂ SO ₄ : Glauber's salt)), and vanadium compound (Na ₃ VO _4, etc.) A part of it is precipitated as solid content, and the rest of these and alkali (NaOH) are contained in the crystallization filtrate.

The solid content is recovered as a purified vanadium raw material containing a vanadium compound as a main component (step 17), and is used for the production of a redox flow electrolytic solution and the like. Since the crystallization filtrate in this step contains alkali and unrecovered vanadium, it is returned to the alkali extraction step (step 12) and recycled as needed.

Here, the mechanism by which the vanadium compound is selectively separated in the evaporation concentration step and the crystallization / solid-liquid separation step will be described. FIG. 2 is a graph showing the solubility curves of _{sodium orthovanadate (Na 3} VO ₄ ) and sodium sulfate (Na ₂ SO ₄ : Glauber's salt) at different temperatures and alkali concentrations. In this figure, (a) shows the solubility curve of sodium orthovanadate, and (b) shows the solubility curve of sodium sulfate.

As shown in this figure, the higher the temperature, the higher the solubility of each compound. Further, the solubility of each compound depends on the alkali concentration (NaOH concentration), and as the alkali concentration increases, the solubility decreases and becomes substantially constant.

_{In FIG. 2, the compositions of Na 3} VO ₄ and Na ₂ SO ₄ contained in the alkaline leachate (in the case of 30 ° C.) are shown by “filter solution @ 30 ° C.” in each graph. When this alkaline leachate is evaporated and concentrated at 80 ° C., Na ₃ VO ₄ and Na ₂ SO ₄ and alkali (NaOH) remain in the liquid, so that the concentration change is represented by a straight line passing through the origin. The concentrated solution after concentration is at 80 ° C., and _{the composition of Na 3} VO ₄ and Na ₂ SO ₄ contained therein is shown by “after concentration @ 80 ° C.” in each graph. FIG. 2 is an example when concentrated 5 times. If this concentration is lower than the saturated solubility at 80 ° C. (below the solubility curve), no solid matter precipitates at that time. Next, in the crystallization / solid-liquid separation step, when this concentrated solution is cooled to 10 ° C., the concentrated solution reaches the composition of the saturated solution at 10 ° C., and the components exceeding the saturated concentration are precipitated and the solid content (solid content ( It is collected as a cake). _{The composition of Na 3} VO ₄ and Na ₂ SO ₄ contained therein is shown by "filter solution @ 10 ° C." in each graph.

Here, the concentration equivalent to the concentrated solution calculated from the component concentration of the alkaline extract is at least the saturated concentration of _{Na 3} VO _{4 and saturated of Na 2} SO _{4 at the} temperature (for example, 10 ° C.) in the crystallization / solid-liquid separation step. If the concentration is below the concentration, a high-purity Na ₃ VO _{4 precipitate containing no Na 2} SO ₄ crystals can be recovered.
Further, in the above-mentioned, if the Na ₃ VO ₄ saturation concentration gradually approaches zero and the crystallization treatment is performed in the region near the lower limit, the vanadium compound can be recovered in high yield, and the Na ₂ SO ₄ saturation concentration becomes zero. Stable recovery of high-purity vanadium compounds is possible by crystallization in a region showing high solubility without gradual approach.
_{Under such conditions, SO 4} in the alkaline extract is set to 0.6% by mass or less and concentrated 2 to 7 times, so that the alkali concentration of the concentrated solution is 10 to 25% by mass and the Na ₂ SO ₄ saturation concentration is 4. It is preferably ~ 7% by mass and Na ₃ VO ₄ saturation concentration 0 to 2% by mass.

(Modification example)
An oxidation step for oxidizing the raw material ash may be further provided in the stage prior to the alkali extraction step. Examples of the oxidation step include a method of adding an oxidizing gas and / or an oxidizing agent to the raw material ash. Examples of the oxidizing gas include air, oxygen, ozone, nitrous oxide, nitric oxide, nitrogen dioxide and chlorine. Examples of the oxidizing agent include hydrogen peroxide and hypochlorous acid. In the raw material ash, vanadium takes the form of compounds having various valences of trivalent, tetravalent, and pentavalent, but in the alkali extraction step, approximately pentavalent vanadium is selectively dissolved in the alkaline leachate. Trivalent and tetravalent vanadium and metal impurities are hardly dissolved. Therefore, by adding an oxidation step, it is possible to convert trivalent or tetravalent vanadium into pentavalent vanadium and improve the recovery rate of vanadium.

(Manufacturing method of electrolyte for redox flow batteries)
The method for producing an electrolytic solution for a redox flow battery of the present invention is a method for using a vanadium compound produced by the method for producing a vanadium compound as a stock solution for an electrolytic solution for a redox flow battery. The method for producing an electrolytic solution for a redox flow battery includes an electrolytic solution manufacturing process which is a step of producing an electrolytic solution for a redox flow battery based on the vanadium raw material produced by the above-mentioned method for producing a vanadium compound.

As the electrolytic solution for the redox flow battery, vanadium (V) or vanadium (IV) is used on the positive electrode side, and vanadium (III) or vanadium (II) is used on the negative electrode side. In the method of the present invention, vanadium is mainly _{recovered as vanadium (V) such as sodium orthovanadate (Na 3} VO ₄ ), and therefore can be particularly suitably used for producing an electrolytic solution on the negative electrode side. However, the present invention is not limited to this, and for example, the recovered vanadium (V) may be reduced to vanadium (III) or vanadium (II) to be used in the production of an electrolytic solution on the positive electrode side. .. The concentration of vanadium contained in the electrolyte for a redox flow battery is not particularly limited, but both the positive electrode side and the negative electrode side are, for example, in the range of 0.1 mol / l to 10 mol / l, preferably 1 to 3 mol / l. It can be within the range of l.

(Vanadium compound manufacturing equipment)
The vanadium compound production apparatus of the present invention can be configured as an apparatus for carrying out the vanadium compound production method of the first embodiment described above. The vanadium compound production apparatus of the present embodiment includes an alkali extraction means, a solid-liquid separation means, an evaporation concentration means, and a crystallization / solid-liquid separation means.

The alkali extraction means is a means for carrying out the alkali extraction step of the first embodiment, and alkali is added to the raw material ash so that the pH is 13 or more and 14 or less to obtain an alkali leachate containing vanadium. Examples of the alkaline extraction means include a stirring and mixing tank for mixing an alkaline solution and boiler combustion ash.

The solid-liquid separation means is a means for carrying out the solid-liquid separation step of the first embodiment, and solid-liquid separates the alkaline leachate, removes the insoluble matter as a solid content, and obtains a leachate containing vanadium. Examples of the solid-liquid separation means include a dehydrator that separates the alkaline leachate and the solid content.

The solid content cleaning means is a means for carrying out the solid content cleaning step of the first embodiment, and cleans the solid content (cake) after the solid-liquid separation. Examples of the solid content cleaning means include a combination of a water tank for adding water, a vacuum belt filter for solid-liquid separation, a basket-type centrifuge, a dehydrator such as a decanter, and the like. Further, the solid content cleaning means may be a means of sprinkling water on the vacuum belt filter without using a water tank for adding water.

The evaporative concentration means is a means for carrying out the evaporative concentration step of the first embodiment, and evaporates and concentrates the leachate at 70 to 100 ° C. to obtain a concentrated solution having an alkali concentration of 10 to 25% by mass. Examples of the solid-liquid separation means include an evaporation concentration can and an RO membrane separation device.

The crystallization / solid-liquid separation means is a means for carrying out the crystallization / solid-liquid separation step of the first embodiment. Collect as solids. The crystallization / solid-liquid separation means is composed of a crystallization means and a solid-liquid separation means. Examples of the crystallization means include a water tank having a cooling function, a cooling crystallization tank, and a poor solvent crystallization tank to which an organic poor solvent such as methanol is added. Examples of the solid-liquid separation means include thickeners, decanters, basket centrifugal vacuum belt filters, and the like.

The vanadium compound production apparatus may further include an oxidizing means for oxidizing the raw material ash before the alkaline extraction means. Examples of the oxidizing means include an air diffuser for aerating the oxidizing gas.

(Manufacturing equipment for electrolyte for redox flow batteries)
The apparatus for producing an electrolytic solution for a redox flow battery of the present invention is an apparatus for using a vanadium compound produced by the apparatus for producing a vanadium compound as a stock solution for an electrolytic solution for a redox flow battery. The apparatus for producing the electrolytic solution for the redox flow battery includes an electrolytic solution manufacturing means which is a step of producing the electrolytic solution for the redox flow battery based on the vanadium raw material produced by the above-mentioned equipment for producing the vanadium compound. For details of the apparatus for producing the electrolytic solution for the redox flow battery, the above-described method for producing the electrolytic solution for the redox flow battery can be referred to.

2. Second Embodiment Hereinafter, the second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows a method for producing a vanadium compound according to a second embodiment of the present invention, (a) is a flow chart of a method for producing a vanadium compound, and (b) is a transition of components contained in a raw material. It is a schematic diagram which shows.

The method for producing the vanadium compound of the present embodiment includes a raw material ash preparation step (step 20), a raw material ash cleaning step (step 21), an alkali leaching step (step 22), a solid-liquid separation step (step 23), and an evaporation concentration step (step 23). Step 24), a crystallization / solid-liquid separation step (step 25), and a recycling step (step 26) are provided. Of these steps, the steps other than the raw material ash washing step (step 21) and the recycling step (step 26) are the same as those in the first embodiment described above, and thus the description thereof will be omitted or simplified.

(Raw material ash cleaning process)
In the present embodiment, after the raw material ash preparation step (step 20), the raw material ash cleaning step (step 21) for cleaning the raw material ash is performed. In this step, soluble metal impurities (iron, nickel, magnesium, etc.) are removed from the raw material ash, and soluble salts (ammonium sulfate, sulfuric acid, etc.) that hinder the reuse of alkali are removed. Examples of the solvent used for cleaning the raw material ash include water or an alkaline solution. In the raw material ash cleaning step, it is preferable to perform cleaning with a solvent having a weight ratio of 2 to 20 times that of the raw material ash.

Examples of the cleaning method include a batch method and a continuous method. Specifically, a combination of a water tank for adding water, a vacuum belt filter for solid-liquid separation, a basket-type centrifuge, a dehydrator such as a decanter, etc. is used. The method etc. can be mentioned. Further, as a cleaning method, a method of sprinkling water on the vacuum belt filter without using a water tank for adding water may be used. The cleaning temperature is 10 to 40 ° C, preferably 20 to 30 ° C. The cleaning time varies depending on the batch method, the continuous method, or the like, but is generally about 1 second to 60 minutes, preferably about 1 to 30 minutes.

Further, in the raw material ash washing step, the pH of the raw material ash aqueous solution during washing is set to 4 to 7, preferably 5 to 6 in order to prevent vanadium from being eluted during washing with water. Hereinafter, it will be described that this pH is preferable. FIG. 6 (a) is a pool diagram showing a state change due to the pH of vanadium and a redox potential, and FIG. 6 (b) is a graph showing a change in the ratio of vanadium washing loss due to pH adjustment during washing. From the Pourbaix diagram of FIG. 6 (a), in the region where the pH is as low as 3 or less, the stable state of vanadium is ^ions such as VO 2+, whereas in the region where the pH is as high as 4 to 7, the stable state is ions. The stable state of vanadium is a solid such as _{V 2} O _4. Therefore, by setting the pH to 4 to 7 in the raw material ash cleaning step, it is possible to efficiently remove contaminants by making vanadium a solid and making it difficult to elute vanadium in the cleaning liquid. In fact, as shown in FIG. 6B, if the pH of the raw material ash aqueous solution is not adjusted during washing, the pH becomes as low as 3, and the vanadium loss becomes large. On the other hand, it can be seen that when the pH of the raw material ash aqueous solution is adjusted to 4, 5 and 6, the vanadium loss is smaller than that when the pH is not adjusted.

In this step, after the solid-liquid separation step, it is desirable that the weight ratio of soluble components including ammonium sulfate, sulfuric acid, etc. to the weight of the raw material ash is 5% or less. In the present embodiment, since the raw material ash cleaning step is provided before the alkali extraction step, the ammonium sulfate content and sulfuric acid contained in the raw material ash can be significantly reduced as shown in FIG. 3 (b).

Next, the alkali leaching step (step 22), the solid-liquid separation step (step 23), the evaporation concentration step (step 24), and the crystallization / solid-liquid separation step (step 25) are sequentially performed. Here, as shown in FIG. 3B, in the present embodiment, ammonium sulfate, sulfuric acid, and the like are significantly reduced from the raw material ash by the raw material ash washing step, so that the alkaline leachate and the leachate filtrate are used in the subsequent steps. The amount of ammonium sulfate and sulfuric acid remaining in the concentrate is low. The precipitate obtained in the crystallization / solid-liquid separation step contains almost no of these impurities, and is almost exclusively a vanadium compound and an alkali.

(Recycling process)
In the subsequent stage of the crystallization / solid-liquid separation step, the crystallization filtrate obtained in the crystallization / solid-liquid separation step is preferably recycled to the alkaline extraction step. The recycling process may be performed by a return pump, an overflow tank, or the like. In this case, the entire amount of the crystallization filtrate may be reused as an alkaline solution in the alkaline extraction step, but in order to suppress the accumulation of sulfate roots in the system, it is discharged to the outside of the system in the range of 1 to 30% by mass, and the rest. May be used.

In the present embodiment, since impurities such as ammonium sulfate and sulfuric acid are removed in the raw material ash washing step, most of these impurities are contained in the precipitate obtained in the crystallization / solid-liquid separation step (step 25). Not done. Therefore, a high quality vanadium raw material can be obtained as compared with the method of the first embodiment.

Further, in order to remove these impurities in the raw material ash washing step, the boiling point of the alkaline extract is lower than that in the case where the impurities are contained as in the first embodiment. Therefore, the evaporation and concentration can be performed at a low temperature in the evaporation and concentration step. Therefore, as compared with the first embodiment, the evaporation and concentration step does not require a large amount of input energy, and the production cost of the vanadium raw material can be reduced.

Further, the crystallization filtrate obtained in the crystallization / solid-liquid separation step (step 25) also contains almost no impurities, and is almost exclusively a vanadium compound and an alkali. Therefore, as compared with the method of the first embodiment, the amount of alkali to be added can be reduced and the vanadium recovery rate from the raw material ash can be increased.

By performing the raw material ash cleaning step in this way, a high-quality vanadium raw material can be obtained. _{Specifically, the content of the vanadium compound (Na 3} VO _4, etc.) contained in the precipitate (solid content) obtained in the crystallization / separation step can be set to 30 to 40% by mass. Further, in the case of a dry matter base in which the solid content is dried, Na ₃ VO ₄ can be 70 to 80% by mass, Na ₂ SO ₄ can be 2 to 5% by mass, and NaOH can be 20 to 25% by mass. Further, if a solid content washing step of washing the solid content with water or the like is provided after the crystallization / separation step, _{it is possible to increase the Na 3} VO ₄ to 90% by mass or more on a dry matter basis.

Further, the salt concentration contained in the crystallization filtrate in the crystallization / separation step can be as low as 15 to 20% by mass, and the amount of energy required in the evaporation concentration step is 14000 kcal or less per 1 kg of pure vanadium recovered. can do.

(Amount adjustment process for crystallization filtrate)
Further, in the recycling step, the total of the sulfate roots brought in by the crystallization filtrate and the sulfate roots brought in from the raw material ash in the alkali extraction step is equal to or less than the saturation concentration after cooling in the crystallization / solid-liquid separation step. It is preferable to adjust the amount of the crystallization filtrate to be recycled so as to be.

(Vanadium compound manufacturing equipment)
The vanadium compound production apparatus of the present invention can be configured as an apparatus for carrying out the vanadium compound production method of the second embodiment described above. The vanadium compound production apparatus of the present embodiment includes raw material ash cleaning means, alkali extraction means, solid-liquid separation means, evaporation concentration means, crystallization / solid-liquid separation means, recycling means, and crystallization filtrate amount adjusting means. Of these, the alkali extraction means, the solid-liquid separation means, the evaporation concentration means, and the crystallization / solid-liquid separation means are described in the first embodiment described above, and thus the description thereof will be omitted.

The raw material ash cleaning means is a means for carrying out the raw material ash cleaning step of the second embodiment, and the raw material ash cleaning means for cleaning the raw material ash is, for example, a water tank for adding water and a vacuum for solid-liquid separation. Examples include a combination of a belt filter, a basket-type centrifuge, a dehydrator such as a decanter, and the like. Further, the raw material ash cleaning means may be a means of sprinkling water on the vacuum belt filter without using a water tank for adding water.

The recycling means is a means for carrying out the recycling step of the second embodiment, and the crystallization filtrate separated from the solid content by the crystallization / solid-liquid separating means is reused by the alkaline extraction means. Examples of the recycling means include a return pump and an overflow tank.

In the recycling step, the crystallization filtrate amount adjusting means is such that the total of the sulfate roots brought in by the crystallization filtrate and the sulfate roots brought in from the raw material ash in the alkali extraction step is cooled in the crystallization / solid-liquid separation step. Adjust the amount of crystallization filtrate to be recycled so that it is equal to or less than the amount equivalent to the saturation concentration.

Hereinafter, the present invention will be specifically described based on examples, but these do not limit the object of the present invention, and the present invention is not limited to these examples.

(1) Washing step Using 5 kg of boiler combustion ash (moisture content 14.9%, vanadium (V) content 2.3%) as a raw material, add 10 kg of water, stir for 60 minutes, and then use a centrifugal dehydrator. Solid-liquid separation was performed. The obtained residue was 4.5 kg (moisture content 33 wt%). In this washing step, 16.6 wt% of vanadium (V) contained in the raw material ash was eluted in the filtrate.

(2) Alkali leaching step To 1 kg of the residue obtained in the water washing step, 1.0 kg of slurryed water: 2.1 kg and 30 wt% caustic soda (NaOH) was added, and the mixture was stirred at pH 13.8 for 60 minutes and then pressurized. Filtration was carried out to obtain 2.8 kg of filtrate. The residue was washed with 2.1 kg of water, and the washing liquid at that time was also recovered to obtain a total of 4.8 kg of alkaline leachate.

(3) Evaporation and Concentration Step 4.8 kg of the filtrate (pre-concentration liquid) obtained in the alkali leaching step was concentrated under reduced pressure at 80 to 85 ° C. and −70 kPa to obtain 1.0 kg of the concentrate.

(4) Cooling Crystallization Step 1.0 kg of the concentrated solution obtained in the evaporation concentration step was taken, cooled gradually, and stirred at 5 ° C. for 5 hours to precipitate crystals. Solid-liquid separation was performed by suction filtration using a 1.0 μm membrane. As a result, 157 g of solid cake I (of which _{vanadium (V) as Na 3} VO ₄ : 64 g: 18 g) was obtained. The composition ratio of this cake I in the dry matter was 85 _{wt% for Na 3} VO _{4 , 0.1 wt% for Na 2} SO ₄ , and 15 wt% for NaOH. Since most of the NaOH is mixed with the adhering water, the mixing rate can be significantly reduced by improving the solid-liquid separability. The input energy required for the evaporation concentration step was 13950 kcal per 1.0 kg of pure vanadium recovered.

Claims (14)

A vanadium compound that separates vanadium from raw material ash containing at least ammonium sulfate and / or ammonium hydrogensulfate, sulfuric acid, vanadium, and at least one other metal selected from nickel, iron, and magnesium. It ’s a manufacturing method,
An alkali extraction step of adding alkali and water or an alkaline solution to the raw material ash so that the pH becomes 13 or higher and leaching vanadium into the liquid phase to obtain an alkaline leachate.
A solid-liquid separation step in which the alkaline leachate is solid-liquid separated, insoluble matter is removed as a solid content, and the alkaline leachate containing vanadium is obtained as a leachate.
The evaporative concentration step of evaporating and concentrating the leachate to obtain a concentrated solution, and
It includes a crystallization / solid-liquid separation step of cooling the concentrated solution to a predetermined cooling temperature for crystallization and recovering the vanadium-containing precipitate as a solid content.
The concentrated solution is a method for producing a vanadium compound, characterized in that the vanadium compound has a saturated concentration or more and the alkali sulfate has a saturated concentration or less at the cooling temperature. The method for producing a vanadium compound according to claim 1, further comprising a raw material ash cleaning step for cleaning the raw material ash in a step prior to the alkali extraction step. In the subsequent stage of the crystallization / solid-liquid separation step, a recycling step of reusing the crystallization filtrate separated from the solid content in the crystallization / solid-liquid separation step in the alkali extraction step is further included. The method for producing a vanadium compound according to claim 1. In the alkali extraction step, the total of the sulfate roots brought in by the crystallization filtrate and the sulfate roots brought in from the raw material ash is equal to or less than the saturation concentration after cooling in the crystallization / solid-liquid separation step. The method for producing a vanadium compound according to claim 3, further comprising a step of adjusting the amount of the crystallization filtrate to adjust the amount of the crystallization filtrate to be recycled. The method for producing a vanadium compound according to claim 1, further comprising an oxidation step of oxidizing the raw material ash in a step prior to the alkali extraction step. It is characterized by further comprising a solid content cleaning step in which the solid content is washed to recover the vanadium-containing cleaning liquid in a subsequent stage of the alkali extraction step, and the cleaning liquid is transferred to the evaporation concentration step together with the leachate filtrate. The method for producing a vanadium compound according to claim 1. A redox flow characterized by having an electrolytic solution manufacturing process for producing an electrolytic solution for a redox flow battery using the vanadium separated by the method for producing a vanadium compound according to any one of claims 1 to 6 as a raw material. A method for manufacturing an electrolytic solution for a battery. A vanadium compound that separates vanadium from raw material ash containing at least ammonium sulfate and / or ammonium hydrogensulfate, sulfuric acid, vanadium, and at least one other metal selected from nickel, iron, and magnesium. It ’s a manufacturing device,
An alkali extraction means for obtaining an alkaline leachate by adding alkali and water or an alkaline solution to the raw material ash so as to have a pH of 13 or higher and leaching vanadium into the liquid phase.
A solid-liquid separation means for solid-liquid separating the alkaline leachate, removing insoluble matter as a solid content, and obtaining an alkaline leachate containing vanadium as a leaching solution.
An evaporative concentration means for obtaining a concentrated solution by evaporating and concentrating the leachate filtrate,
Includes a crystallization / solid-liquid separation means for cooling the concentrated solution to a predetermined cooling temperature for crystallization and recovering the vanadium-containing precipitate as a solid content.
The concentrated liquid is an apparatus for producing a vanadium compound, characterized in that the vanadium compound has a saturated concentration or more and the alkali sulfate has a saturated concentration or less at the cooling temperature. The apparatus for producing a vanadium compound according to claim 8, further comprising a raw material ash cleaning means for cleaning the raw material ash in a stage prior to the alkaline extraction means. It is characterized by further including a recycling means for reusing the crystallization filtrate separated from the solid content by the crystallization / solid-liquid separation means in the alkali extraction means in a subsequent stage of the crystallization / solid-liquid separation means. 8. The apparatus for producing a vanadium compound according to claim 8. In the alkali extraction means, the total of the sulfate roots brought in by the crystallization filtrate and the sulfate roots brought in from the raw material ash is equal to or less than the saturation concentration after cooling in the crystallization / solid-liquid separation means. The vanadium compound production apparatus according to claim 8, further comprising a crystallization filtrate amount adjusting means for adjusting the amount of the crystallization filtrate to be recycled. The apparatus for producing a vanadium compound according to claim 8, further comprising an oxidizing means for oxidizing the raw material ash in the stage prior to the alkaline extraction means. A feature of the solid content cleaning means is that, in a subsequent stage of the alkali extraction means, the solid content is washed to recover the cleaning liquid containing vanadium, and the cleaning liquid is transferred to the evaporation concentration means together with the leaching filtrate. 8. The apparatus for producing a vanadium compound according to claim 8. Redox flow, which comprises an electrolytic solution manufacturing means for producing an electrolytic solution for a redox flow battery using the vanadium separated by the vanadium compound manufacturing apparatus according to any one of claims 8 to 13 as a raw material. A device for manufacturing electrolytes for batteries.

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