JP2021130863A - Method for separating vanadium, method for producing electrolyte for redox flow battery, apparatus for separating vanadium, and apparatus for producing electrolyte for redox flow battery - Google Patents

Abstract

To provide a method for separating vanadium having a high recovery rate at low cost, a method for producing an electrolyte for a redox flow battery, an apparatus for separating vanadium, and an apparatus for producing an electrolyte for a redox flow battery.SOLUTION: There is provided a method for separating vanadium from a vanadium-containing material containing at least a tetravalent and/or pentavalent vanadium compound and ammonium sulfate ((NH4)2SO4) and/or ammonium hydrogen sulfate (NH4HSO4). The method comprises a thermal decomposition step, in which the vanadium-containing material is heated to 450°C or higher to volatilize ammonia gas (NH3) and sulfate gas (SO3 and/or SO2) and to produce at least one kind of Vanadium(IV) Oxide Sulfate (VOSO4), Vanadium (V) Oxide (V2O5) and Vanadium (IV) Oxide (V2O4).SELECTED DRAWING: Figure 2

Description

The present invention relates to a vanadium separation method for separating vanadium from a metal mixture such as waste containing ammonium sulfate and / or ammonium hydrogen sulfate, a method for producing an electrolytic solution for a redox flow battery, a vanadium separation device, and redox. -Regarding the equipment for manufacturing electrolytes for flow batteries. Further, the present invention uses vanadium when ammonium sulfate and / or ammonium hydrogensulfate is generated in the process of separating vanadium from a metal mixture such as combustion ash and waste such as waste catalyst that does not contain ammonium sulfate and / or ammonium hydrogensulfate. The present invention relates to a vanadium separation method for separation, a method for producing an electrolytic solution for a redox flow battery, a vanadium separation device, and an apparatus for producing an electrolytic solution for a redox flow battery.

Vanadium (V) and nickel (Ni) are included in the combustion ash 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, and oil sand. , Iron (Fe), magnesium (Mg) and other multiple metals are included. Of these, vanadium, which is a valuable metal, has recently been desired to be supplied in large quantities as a main component of redox flow batteries, which are large batteries, and establishment of an efficient recovery method is desired. As the electrolytic solution of the redox flow battery, vanadium oxide sulfate (IV) is used on the positive electrode side and vanadium sulfate (III) is used on the negative electrode side.

The present inventor describes a method for separating vanadium from a metal mixture containing at least one or more divalent or trivalent metals selected from nickel, cobalt, manganese, palladium, platinum, copper and zinc and vanadium. It is being developed (see, for example, Patent Document 1). In this method, the metal mixture is leached with an acid to obtain a leachate, and an aqueous ammoniacal solution is added thereto to adjust the pH to 10 to 12 to form an ammine complex of metal ions and an anion complex of vanadium ions. Then, a carrier is added to the alkaline aqueous solution produced by the ammine complex and the anion complex to selectively adsorb and recover the metal ions, and vanadium is recovered from the tetravalent vanadium anion complex contained in the recovered alkaline aqueous solution. .. Examples of the carrier include lignite.

The tetravalent vanadium anion complex is adjusted to be acidic by adding an acidic solution such as sulfuric acid, and a mixture of vanadium sulfate and ammonium hydrogensulfate obtained from the anion complex is crystallized and precipitated. Subsequently, this precipitate is heat-calcinated (oxidized) at around 500 ° C. to obtain vanadyl sulfate (IV) (VOSO ₄ ). Further, it is recovered as _{vanadium pentoxide (V 2} O ₅ ) by performing a heating firing (oxidation) treatment at around 600 ° C. Vanadium pentoxide is reacted with ammonia to form ammonium metavanadate, which is decomposed at a high temperature in a nitrogen gas atmosphere to form an oxide (V ₂ O ₃ ). Then, by reacting this oxide with concentrated sulfuric acid to obtain vanadium sulfate (III), it can be used as a negative electrode material for an electrolytic solution for a redox flow battery.

By the way, petroleum-based combustion ash such as heavy oil contains not only valuable metals contained in catalysts but also oils, and therefore contains many elements such as carbon, hydrogen, sulfur, and nitrogen. Normally, heavy oil is burned in a boiler or the like, but the waste gas includes nitrogen (N ₂ ), oxygen (O ₂ ), carbon dioxide (CO ₂ ), sulfur oxides (SO _x ), and nitrogen oxides. a volatile gas such as an object (NO _x), are included and ash (ash), including carbon of the metal compound and unburned such V ₂ O 5, NiO.

Of these, SO _x and NO _x are air pollutants, and their release into the atmosphere is regulated by law in Japan, so it is necessary to decompose and remove these gases after combustion treatment. Normally, NO _x is decomposed into nitrogen and water and discarded by adding a catalyst and ammonia (NH ₃ ) as a reducing agent to a volatile gas and heating the gas to about 400 ° C. However, ammonia easily reacts with sulfur oxides (SO _x ), resulting in the formation of reactants ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) and ammonium hydrogen sulfate (NH ₄ HSO ₄ ). Therefore, the heavy oil combustion ash contains not only valuable metal compounds but also ammonium sulfate and ammonium hydrogen sulfate. Ammonium sulfate and ammonium hydrogensulfate contained in the raw material remain as ammonium hydrogensulfate until the final stage of vanadium recovery. In foreign countries, the release of air pollutants such as SOx and NOx to the atmosphere is often not regulated. In this case, ammonium sulfate and ammonium hydrogensulfate are not contained in the raw material, but ammonium hydrogensulfate is produced and remains from the vanadium anion complex as described above. Therefore, in the end, it becomes necessary to separate vanadium and ammonium hydrogensulfate.

Conventionally, as a method for separating vanadium from vanadium-containing waste, an oxidizing gas is supplied to the vanadium-containing slurry to prepare an ammonium metavanadate-containing slurry, and ammonium metavanadate (NH ₄ VO ₃ ) is precipitated. The method is known (see, for example, Patent Document 2).

International Publication No. 2017/010437 Japanese Unexamined Patent Publication No. 2005-200231

However, in the method of Patent Document 2, it is difficult to recover vanadium at low cost because the introduction of an oxidizing gas or the like is costly. Further, in the method of this document, it is necessary to convert ammonium metavanadate to vanadium sulfate in order to use it as a negative electrode material for an electrolytic solution for a redox flow battery. Therefore, the method of the present document has an inconvenience that it is costly and the recovery rate is low, particularly for the purpose of providing a negative electrode material for an electrolytic solution for a redox flow battery.

An object of the present invention is to provide a vanadium separation method having a high recovery rate at low cost, a method for producing an electrolytic solution for a redox flow battery, a vanadium separation device, and an apparatus for producing an electrolytic solution for a redox flow battery. be.

The present invention comprises vanadium from a vanadium-containing material containing at least a tetravalent and / or pentavalent vanadium compound and ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) and / or ammonium hydrogen sulfate (NH ₄ HSO _4). A vanadium separation method for separation, in which the vanadium-containing material is heated to 450 ° C. or higher _{to volatilize ammonia gas (NH 3} ) and sulfate gas (SO ₃ and / or SO ₂ ), and vanadium oxide sulfate (IV) ( A vanadium separation method comprising: a thermal decomposition step of producing at least one of VOSO ₄ ), vanadium pentoxide (V ₂ O ₅ ) and divanadium tetroxide (V ₂ O _4).

In the present invention, the vanadium compound can be separated by heating the vanadium-containing material to 450 ° C. or higher to volatilize the gas. That is, by volatilizing the gas by heat treatment, vanadium oxide sulfate (IV) (VOSO ₄ ), which is a direct positive electrode material for the electrolytic solution for redox flow batteries, and vanadium pentoxide (V), which is a raw material for the negative electrode material, are used. ₂ O ₅ ) and / or divanadium tetroxide (V ₂ O ₄ ) can be separated efficiently.

In this case, the thermal decomposition step is carried out by heating at 450 to 550 ° C. to produce vanadium (IV) oxide sulfate (VOSO ₄ ) as the main product, or by heating at over 550 ° C. It is preferable to produce vanadium oxide (V ₂ O ₅ ) and / or divanadium tetraoxide (V ₂ O ₄ ) as the main product.

By adjusting the heating temperature in this way, vanadium oxide sulfate (IV) (VOSO ₄ ), which is a direct positive electrode material for the electrolyte for redox flow batteries, and vanadium pentoxide (V), which is a raw material for the negative electrode material, are used. ₂ O ₅ ) and / or divanadium tetroxide (V ₂ O ₄ ) can be selectively produced.

Further, in the pre-step of the thermal decomposition step, it is preferable to further include a pH adjusting step of adding sulfuric acid to the vanadium-containing material to adjust the pH to 2-4.

In this way, by adding inexpensive sulfuric acid as a raw material to generate vanadium sulfate before the thermal decomposition step, vanadium is converted into vanadium oxide sulfate (IV) (VOSO ₄ ) and vanadium pentoxide (V) in the next thermal decomposition step. It can be efficiently separated as ₂ O ₅ ) and divanadium tetroxide (V ₂ O _4).

Further, in the pre-step of the pH adjusting step, it is preferable to further include a neutralization crystallization step of precipitating ammonium sulfate and / or ammonium hydrogen sulfate crystals at pH 5 to 7.

As described above, when the content of ammonium sulfate or the like is high, the amount of ammonium sulfate can be reduced in advance by precipitating and separating the crystals of ammonium sulfate and / or ammonium hydrogen sulfate before adjusting the pH.

In this case, in the step before the thermal decomposition step, a part of the oxide of the divalent or trivalent metal is adjusted by adding an aqueous ammoniacal alkali to the vanadium-containing material to adjust the pH to 10 to 12. The step of adding an alkali to form the sludge of the hydroxide of the oxide of the divalent or trivalent metal, the ammine complex of the divalent nickel and / or cobalt ion, and the anion complex of the tetravalent vanadium ion. It is preferable to include an ion adsorption separation step of selectively adsorbing the divalent nickel and / or cobalt ammine complex with a carrier having a carboxyl group, and a sludge separation step of separating the sludge.

In this way, by adding an ammoniacal alkaline aqueous solution to the vanadium-containing material to adjust the pH to 10 to 12, a sludge of hydroxide, an ammine complex of nickel and / or cobalt, and an anion complex of vanadium are generated, and sludge is generated. Separation and selective ion adsorption separation of the ammine complex are performed. In this way, it is possible to form an anion complex of vanadium by a simple step of adding alkali.

Further, the present invention is characterized by having an electrolytic solution manufacturing process for producing an electrolytic solution for a redox flow battery using the vanadium recovered by the vanadium separation method according to any one of the above as a raw material. This is a method for producing an electrolytic solution.

Thus, in the present invention, is a starting material oxide sulfate vanadium redox flow battery electrolyte solution (IV) (VOSO _4), five vanadium oxide _(V 2 _{O 5)} and tetroxide, vanadium _{(V 2 O} 4) At least one of the above can be efficiently separated from the mixed solution to prepare the electrolytic solution.

The present invention comprises vanadium from a vanadium-containing material containing at least a tetravalent and / or pentavalent vanadium compound and ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) and / or ammonium hydrogen sulfate (NH ₄ HSO _4). A vanadium separator for separation, in which the vanadium-containing material is heated to 450 ° C. or higher _{to volatilize ammonia gas (NH 3} ) and sulfate gas (SO ₃ and / or SO ₂ ), and vanadium oxide sulfate (IV) ( The vanadium separator is characterized by comprising a thermal decomposition means for producing at least one of _{VOSO 4} ), vanadium pentoxide (V ₂ O ₅ ) and divanadium tetroxide (V ₂ O _4).

In the present invention, the vanadium compound can be separated by heating the vanadium-containing material to 450 ° C. or higher to volatilize the gas. That is, by volatilizing the gas by heat treatment, and vanadium sulfate is a direct positive electrode material for electrolytic solution for redox flow battery, a vanadium pentoxide, which is a raw material of the negative electrode material (V 2 _{O 5)} and / or tetrafunctional Divanadium oxide (V ₂ O ₄ ) can be separated efficiently.

In this case, the pyrolysis means produces vanadyl oxide sulfate (IV) (VOSO ₄ ) as a main product by heating at 450 to 550 ° C, or by heating at more than 550 ° C. It is preferable to produce vanadium oxide (V ₂ O ₅ ) and / or divanadium tetraoxide (V ₂ O ₄ ) as the main product.

By adjusting the heating temperature in this way, vanadium oxide sulfate (IV) (VOSO ₄ ), which is a direct positive electrode material for the electrolyte for redox flow batteries, and vanadium pentoxide (V), which is a raw material for the negative electrode material, are used. ₂ O ₅ ) and / or divanadium tetroxide (V ₂ O ₄ ) can be selectively produced.

Further, it is preferable to further provide a pH adjusting means for adding sulfuric acid to the vanadium-containing material to adjust the pH to 2 to 4 in the stage prior to the thermal decomposition means.

In this way, by adding inexpensive sulfuric acid as a raw material before the thermal decomposition means to generate vanadium sulfate, vanadium is converted into vanadium oxide sulfate (IV) (VOSO ₄ ) and vanadium pentoxide (V) in the next thermal decomposition means. It can be efficiently separated as ₂ O ₅ ) and divanadium tetroxide (V ₂ O _4).

Further, it is preferable to further provide a neutralization crystallization means for precipitating ammonium sulfate and / or ammonium hydrogen sulfate crystals at a pH of 5 to 7 in the previous step of the pH adjusting means.

As described above, when the content of ammonium sulfate or the like is high, the amount of ammonium sulfate can be reduced in advance by precipitating and separating the crystals of ammonium sulfate and / or ammonium hydrogen sulfate before adjusting the pH.

In this case, in a step after the thermal decomposition means, a part of the oxide of the divalent or trivalent metal is formed by adding an aqueous ammoniacal alkali to the vanadium-containing material to adjust the pH to 10 to 12. As an alkali adding means for producing the sludge of the hydroxide of the oxide of the divalent or trivalent metal, the ammine complex of the divalent nickel and / or cobalt ion, and the anion complex of the tetravalent vanadium ion. It is preferable to provide an ion adsorption separation means for selectively adsorbing the divalent nickel and / or cobalt ammine complex with a carrier having a carboxyl group, and a sludge separation means for separating the sludge.

In this way, by adding an ammoniacal alkaline aqueous solution to the vanadium-containing material to adjust the pH to 10 to 12, a sludge of hydroxide, an ammine complex of nickel and / or cobalt, and an anion complex of vanadium are generated, and sludge is generated. Separation and selective ion adsorption separation of the ammine complex are performed. In this way, it is possible to form an anion complex of vanadium by a simple step of adding alkali.

Further, the present invention is characterized by having an electrolytic solution manufacturing means for producing an electrolytic solution for a redox flow battery using the vanadium recovered by the vanadium separator according to any one of the above as a raw material. It is an electrolytic solution manufacturing device.

Thus, in the present invention, is a starting material oxide sulfate vanadium redox flow battery electrolyte solution (IV) (VOSO _4), five vanadium oxide _(V 2 _{O 5)} and tetroxide, vanadium _{(V 2 O} 4) At least one of the above can be efficiently separated from the mixed solution to prepare the electrolytic solution.

According to the present invention, it is possible to provide a vanadium separation method having a high recovery rate at a low cost, a method for producing an electrolytic solution for a redox flow battery, a vanadium separation device, and an apparatus for producing an electrolytic solution for a redox flow battery. can.

It is a processing flow diagram which shows the vanadium separation method which concerns on one Embodiment of this invention, and the manufacturing method of the electrolytic solution for a redox flow battery. It is a processing flow diagram which shows the vanadium separation method which concerns on one Embodiment of this invention, and the manufacturing method of the electrolytic solution for a redox flow battery.

Hereinafter, the vanadium separation method of the present invention, the method for producing an electrolytic solution for a redox flow battery, the vanadium separation apparatus, and the apparatus for producing an electrolytic solution for a redox flow battery will be described in detail with reference to the drawings.

1. 1. Vanadium Separation Method FIGS. 1 and 2 are processing flow charts showing a vanadium separation method according to an embodiment of the present invention and a method for producing an electrolytic solution for a redox flow battery.

The vanadium separation method of the present invention can be suitably applied to waste containing vanadium and / or vanadium compounds. Examples of such waste 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 sand, vanadium slag, and the like. Examples include waste catalysts, industrial wastes, and waste liquids of various chemical reaction catalysts. Further, the waste can also include washing water obtained by washing these ash with water or the like. In particular, it can be suitably applied to wastes containing ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) and ammonium hydrogen sulfate (NH ₄ HSO ₄ ) (hereinafter sometimes referred to as "ammonium sulfate, etc." and "ammonium sulfate"). However, it can also be applied to waste that does not contain ammonium sulfate or the like. Examples of the waste containing a large amount of ammonium sulfate and the like include petroleum-based combustion ash and its washing water.

Waste catalysts from petroleum refining include, for example, vanadium, nickel, cobalt, molybdenum, copper, zinc, palladium, platinum, iron, phosphorus, sulfur and the like. Generally, these metals are abundantly contained as sulfides.

Vanadium slag is slag produced when magnetite is fired, and contains a metal mixture such as vanadium, manganese, aluminum, iron, titanium, silicon, calcium, and phosphorus. Generally, these metals are abundantly contained as oxides.

In addition to nickel and vanadium, the residual ash contains a metal mixture such as iron, magnesium, molybdenum, cobalt, manganese, and titanium.

When ammonium sulfate or the like is contained in the waste, it is preferable that ammonium sulfate or the like is contained in an amount of 1% or more, preferably 5% or more, more preferably 10% or more by weight. Further, the present invention can be preferably used in these wastes containing vanadium in an amount of 1% or more, preferably 3% or more, more preferably 5% or more by weight. Further, in the present invention, divalent or trivalent metals such as nickel, iron or magnesium are all 0.1% or more, preferably 0.5% or more, more preferably 1% or more and 10% or less by weight. It can be preferably used for those contained.

In the following embodiments, the vanadium separation method for separating vanadium from heavy oil combustion ash containing vanadium and one or more divalent or trivalent metals selected from nickel, iron and magnesium as waste. explain. More specifically, the decomposition / removal of NOx air pollutants will be described as a representative of the raw material combustion ash generated in a system that decomposes NOx air pollutants into water and nitrogen by reaction with ammonia gas at about 400 ° C. in the presence of a catalyst. In this embodiment, metals (impurities) such as nickel other than vanadium are separated and removed by the flow shown in FIG. 1, and then thermally decomposed by the flow shown in FIG. 2. However, depending on the target product, this is performed. Not limited to. For example, if there is no problem even if these impurities are contained in the product, a part or all of the flow shown in FIG. 1 may be omitted or another treatment may be performed.

(Preparation of raw material slurry)
Hereinafter, the step of separating vanadium using a carrier will be described with reference to FIG. First, an acid (sulfuric acid or the like) is added to the combustion ash to prepare a raw material slurry. The amount of the acid added to the combustion ash can be appropriately set, but is preferably about 1 to 50% by mass with respect to the combustion ash.

(PH adjustment: alkali addition process)
Next, by adding an aqueous ammoniacal alkali solution to the raw material slurry obtained in the above step to adjust the pH, iron hydroxide, magnesium hydroxide, and complexes of nickel and vanadium are formed (step 31). ). Examples of the ammoniacal alkaline aqueous solution include aqueous ammonia (ammonium hydroxide (NH ₄ OH)). The concentration of the ammonia water to be added is not particularly limited as long as the complex described later is sufficiently formed, but is preferably in the range of 15 to 35% by mass, and more preferably in the range of 20 to 30% by mass. Further, in this step, the pH is adjusted in the range of 10.5 to 12, but it is more preferable to adjust the pH in the range of 10 to 11.

(Solid-liquid separation: sludge separation process)
Next, the alkaline aqueous solution obtained in step 31 is filtered and separated, and the filtered precipitate (sludge) and the filtrate are separated (step 32). Sludge is a hydroxide such as iron hydroxide and magnesium hydroxide and is separated as a colloidal solid component (step 33). In this step, iron and magnesium are separated from the metal mixture.

On the other hand, the filtrate obtained in step 32 is an alkaline aqueous solution and contains a divalent nickel ion ammine complex and a tetravalent and / or pentavalent vanadium ion anion complex. Examples of divalent nickel ion ammine complexes include (NH ₄ ) ₂ Ni (SO ₄ ) _2, and examples of tetravalent vanadium ion anion complexes include (NH ₄ ) ₂ V. ₂ (OH) ₆ (SO ₄ ) _{2 and the} like can be mentioned.

(Lignite ion exchange reaction)
A carrier having a carboxyl group is added to this alkaline aqueous solution, and the mixture is stirred for a predetermined time, and the nickel ions are selectively adsorbed by an ion adsorption (ion exchange) reaction between the nickel ions in the ammine complex and the carboxyl groups in the carrier (step). 34: Ion adsorption separation step). The carrier having a carboxyl group is not particularly limited as long as it undergoes an ion adsorption reaction with nickel in the ammine complex. Examples of the carrier include natural coal and the like. Further, as the coal, low-grade coal having a relatively low carbon content is preferable from the viewpoint of being inexpensive and easily available. Examples of low-grade coal include subbituminous coal, lignite, lignite, and peat.

The pH of the alkaline aqueous solution is preferably in the range of 10 to 12, more preferably in the range of 10.5 to 11. When the above pH is in the range of 10 to 12, the adsorption of nickel ions to brown coal occurs preferentially over the adsorption of vanadium, and nickel ions are overwhelmingly selectively recovered from the mixed solution of vanadium and nickel. can do.

(Solid-liquid separation)
Next, the alkaline aqueous solution is filtered and separated (step 35). The carrier adsorbed with nickel ions as a precipitate is washed and dried (step 36). To recover nickel from a carrier that has adsorbed nickel ions, the carrier can be burned together and nickel can be recovered as _{nickel oxide (NiO / NiO 2).}

The filtrate obtained in step 35 is a mixed solution containing an anion complex of tetravalent vanadium ion and ammonium sulfate or the like. For details of the steps (steps 31 to 36) of FIG. 1, Patent Document 1 (International Publication No. 2017/010437) can be referred to.

(Ammonium sulfate crystallization)
Next, with reference to FIG. 2, a step of separating vanadium from a mixed solution (vanadium-containing substance) containing an anion complex of tetravalent vanadium ions and ammonium sulfate or the like will be described. First, sulfuric acid is added to the mixed solution obtained in step 35 to adjust the pH to 5 to 7 (neutralization crystallization step: step 41). The pH in this step is in the range of 5 to 7, preferably in the range of 5.5 to 6.5, and particularly preferably approximately 6. The temperature in this step is preferably in the range of 50 to 60 ° C. The amount of vanadium contained in the mixed solution is usually 0.01% or more, preferably 0.1% or more, and more preferably 1% or more by weight. The amount of ammonium sulfate or the like contained in the mixed solution is usually 0.1% or more, preferably 1% or more, and more preferably 5% or more in terms of weight ratio.

It is preferable to add sulfuric acid to the mixed solution while stirring the mixed solution with a stirrer or the like. After adding sulfuric acid, let the mixed solution stand for about 10 minutes to 1 hour. In the evaporation and concentration step following this step, when the concentration of ammonium sulfate contained in the mixed solution is high, crystals of ammonium sulfate are precipitated due to the difference in solubility between the anion complex of tetravalent vanadium ion and ammonium sulfate.

By separating the precipitated ammonium sulfate with a centrifuge or the like, the amount of ammonium sulfate contained in the mixed solution can be reduced (step 42). The separation conditions by the centrifuge are preferably in the range of 100 to 1000 G and 1 to 30 minutes, for example. The centrifuge preferably has a function of washing and recovering the vanadium complex adhering to the surface of the separated ammonium sulfate crystals.

(Vanadyl sulfate / ammonium sulfate eutectic analysis)
Next, sulfuric acid is further added to the mixed solution containing the anion complex of tetravalent vanadium ions to adjust the pH to 2 to 4 (pH adjustment step: step 43). The pH in this step is in the range of 2 to 4, preferably in the range of 2.5 to 3.5, and particularly preferably approximately 3. The temperature in this step is preferably in the range of 50 to 60 ° C. It is preferable to add sulfuric acid to the mixed solution while stirring the mixed solution with a stirrer or the like. After adding sulfuric acid, let the mixed solution stand for about 10 minutes to 1 hour. By this step, vanadium (IV) oxide sulfate (vanadyl sulfate) and ammonium hydrogensulfate are produced by the following reaction, and these are eutectic-precipitated in the subsequent evaporation and concentration step.
(NH ₄ ) ₂ V ₂ (OH) ₆ (SO ₄ ) ₂ + H ₂ SO ₄ → _{2 VOSO 4} + _{2NH 4} HSO ₄ + 4H ₂ O

The vanadium compound contained in the mixed solution is not limited to the above-mentioned anion complex of tetravalent vanadium ion, and examples thereof include a tetravalent vanadium compound. Examples of the tetravalent vanadium compound include vanadyl sulfate (VOSO ₄ ) and vanadium dioxide (VO ₂ ). The amount of vanadium contained in the mixed solution is usually 0.01% or more, preferably 0.1% or more, and more preferably 1% or more by weight. The amount of ammonium sulfate or the like contained in the mixed solution is usually 0.1% or more, preferably 1% or more, and more preferably 5% or more in terms of weight ratio.

By separating this eutectic precipitate with a centrifuge or the like, vanadium (IV) oxide sulfate (vanadyl sulfate), ammonium sulfate and the like can be recovered as solids. The conditions for centrifugation are preferably, for example, 50 to 60 ° C., 100 to 1000 G, and 1 to 30 minutes.

(Pyrolysis in firing furnace: Pyrolysis process)
Next, the eutectic precipitate obtained in step 43 is thermally decomposed in the presence of oxygen (step 44). In this step, ammonium hydrogensulfate contained in the eutectic precipitation is volatilized as ammonia, sulfur trioxide and water vapor by the following reaction (step 45). This reaction proceeds above 450 ° C. Ammonium sulfate is converted to ammonium hydrogen sulfate in the process of raising the temperature (see the formula below).
NH ₄ HSO ₄ → NH ₃ + SO ₃ + H ₂ O

In this pyrolysis, the eutectic precipitate is heated at 450-550 ° C. to produce vanadyl sulphate (IV) (VOSO ₄ ) as the main product. Vanadium (IV) oxide sulfate (VOSO ₄ ) is useful as a direct raw material for the electrolyte on the positive electrode side of a redox flow battery.

On the other hand, by heating the eutectic precipitate at more than 550 ° C., vanadium (IV) oxide sulfate is oxidized to obtain vanadium pentoxide (V ₂ O ₅ ) and / or divanadium tetroxide (V ₂ O ₄ ). It can be produced as the main product. Vanadium pentoxide (V ₂ O ₅ ) and divanadium tetroxide (V ₂ O ₄ ) can generate a positive electrolyte by leaching dilute sulfuric acid and adding a reducing agent, or react with concentrated sulfuric acid to produce vanadium sulfate. (III) can be produced. This vanadium (III) sulfate is useful as a raw material for an electrolytic solution on the negative electrode side of a redox flow battery. That is, by adjusting the thermal decomposition temperature of the eutectic precipitate, the materials on the positive electrode side and the negative electrode side of the electrolytic solution of the redox flow battery can be selectively generated. In this case, the lower limit of the heating temperature is 400 ° C., which is the complete decomposition temperature of ammonium hydrogensulfate, and the upper limit is 650 ° C., which causes ammonia combustion.

Pyrolysis is performed by burning fuel using a firing furnace or the like. Examples of the fuel include LPG gas, which can be mixed with air and burned. The thermal decomposition is carried out by putting the eutectic precipitate into a firing furnace or the like, then raising the temperature to a predetermined temperature of 450 to 550 ° C. or more than 550 ° C., and maintaining the temperature for a predetermined time. The thermal decomposition time is about 10 minutes to 10 hours, preferably in the range of 30 minutes to 5 hours. It is preferable to raise the temperature stepwise at regular intervals up to a predetermined temperature. For example, after raising the temperature by 10 ° C., the temperature is maintained for about 1 hour, and by repeating this, the temperature can be raised to the above-mentioned predetermined temperature. preferable.

The amount of ammonium sulfate or the like contained in the eutectic precipitate subjected to the thermal decomposition step is not particularly limited as long as the above thermal decomposition proceeds, but is 5% by weight based on the total amount of the eutectic precipitate. The above is preferable, 10% by weight or more is more preferable, and 15% by weight or more is particularly preferable. The upper limit of the amount of ammonium sulfate contained in the eutectic precipitate is not particularly limited, but is preferably 80% by weight or less, more preferably 70% by weight or less, and particularly preferably 60% by weight or less.

2. Method for producing electrolytic solution for redox flow battery In the method for producing electrolytic solution for redox flow battery of the present invention, in addition to the vanadium separation method described above, vanadium recovered by the method is used as an electrolytic solution for redox flow battery. Used as a raw material (electrolyte solution manufacturing process). As the electrolytic solution for the redox flow battery, vanadium oxide sulfate (IV) can be used on the positive electrode side and vanadium sulfate (III) can be used on the negative electrode side. The concentration of vanadium contained in the electrolytic solution 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.

As a method for producing vanadyl oxide sulfate (IV), which is a raw material for the electrolytic solution on the positive electrode side, VOSO ₄ obtained in step 44 can be used as it is. When vanadyl pentoxide (V ₂ O ₅ ) or _{divanadium tetroxide (V 2} O _{4 ) is mixed, VOSO 4} can be produced by adding sulfuric acid and a reducing agent. In this case, the material of the positive electrode electrolytic solution can be produced by adding sulfuric acid to the solidified product obtained by the thermal decomposition in step 44 (step 46).

Further, as a method for producing vanadium (III) sulfate, which is a raw material for the electrolytic solution on the negative electrode side, for example, the following method can be mentioned. _{First, ammonium metavanadate is produced from powdery substances such as vanadium pentoxide (V 2} O ₅ ) and divanadium tetraoxide (V ₂ O ₄ ) obtained in step 44, and decomposed at a high temperature in a nitrogen gas atmosphere. The oxide (V ₂ O ₃ ) is obtained (step 47). Next, vanadium (III) sulfate is obtained from the obtained oxide by a high-pressure reaction method or an atmospheric pressure method. The high-pressure reaction method is, for example, a method in which 5 to 40% concentrated sulfuric acid is _{added to V 2} O ₃ under the conditions of 250 ° C. and 40 atm to dissolve and precipitate vanadium (III) sulfate. On the other hand, in the atmospheric pressure method, for example, 80% concentrated sulfuric acid is _{added to V 2} O ₃ under the conditions of 250 ° C. and atmospheric pressure to dissolve and precipitate, and then dissolved in less than 50% dilute sulfuric acid to dissolve vanadium sulfate. This is a method for obtaining (III).

3. 3. Vanadium Separation Device The vanadium separation device of the present invention can be configured as a device for carrying out the vanadium separation method described above. As an example, the vanadium separation device of the present invention can be configured as a vanadium separation system (plant or the like) including a complex generation tank, a nickel recovery tank, a sulfur crystallization tank, a eutectic crystallization tank, and a thermal decomposition device.

In the complex generation tank, an ammoniacal alkaline aqueous solution is added to the raw material slurry to adjust the pH to 10 to 12, and the divalent nickel ion ammine complex and the tetravalent and / or pentavalent vanadium ion anion complex are combined with the alkaline aqueous solution. It is a means (ion adsorption separation means) for generating inside. In the complex formation tank, a part of the oxide of the divalent or trivalent metal becomes sludge of the hydroxide of the oxide of the divalent or trivalent metal (corresponding to the alkali addition means of the present invention), and subsequently, this By separating sludge (corresponding to the sludge separating means of the present invention), divalent or trivalent metals are removed. In the complex formation tank, a complex is formed by the method described in steps 31 to 33 described above.

The nickel recovery tank is a means for recovering nickel ions by adding a carrier having a carboxyl group to an alkaline aqueous solution formed by an ammine complex and an anion complex and selectively adsorbing nickel ions in the ammine complex on the carrier. In the nickel recovery tank, nickel is recovered by the method described in steps 34 to 36 described above.

The ammonium sulfate crystallization tank is a means for precipitating ammonium sulfate crystals by adding sulfuric acid to the mixed solution after nickel recovery to adjust the pH to 5 to 7, and corresponds to the neutralization crystallization means of the present invention. In the ammonium sulfate crystallization tank, ammonium sulfate is removed by the methods described in steps 41 and 42 described above.

The eutectic crystallization tank is a means for adding sulfuric acid to a mixed solution (vanadium-containing substance) after ammonium sulfate crystallization to adjust the pH to 2 to 4, and corresponds to the pH adjusting means of the present invention. In the eutectic tank, eutectic analysis is performed between vanadium (IV) oxide sulfate (vanadyl sulfate) and ammonium sulfate or the like by the method described in step 43 described above.

The thermal decomposition apparatus heats the vanadium-containing material to 450 ° C. or higher _{to volatilize ammonia gas (NH 3} ) and sulfuric acid gas (SO ₃ and / or SO ₂ ), and vanadium oxide sulfate (IV) (VOSO ₄ ), 5. It is an apparatus for producing at least one kind of vanadium oxide (V ₂ O ₅ ) and divanadium tetraoxide (V ₂ O _4). The pyrolysis apparatus corresponds to the pyrolysis means of the present invention. In the thermal decomposition apparatus, thermal decomposition is performed by the methods described in steps 44 and 45 described above.

4. Equipment for producing electrolyte for redox flow batteries The equipment for producing electrolytes for redox flow batteries of the present invention uses vanadium obtained by the above-mentioned vanadium separator as a raw material for electrolytes for redox flow batteries. That is, the manufacturing apparatus of the present invention has an electrolytic solution manufacturing means for producing an electrolytic solution from vanadium recovered by the vanadium recovery device by the method described in the above "2. Method for producing an electrolytic solution for a redox flow battery". The electrolytic solution manufacturing means manufactures the electrolytic solution by the method described in step 46 and step 47 described above.

5. Modification example (modification example 1)
Hereinafter, a modified example of the present embodiment will be described. In the above embodiment, nickel is selectively adsorbed on the carrier by an ion exchange reaction using lignite to separate it from vanadium in step 34, but the present invention is not limited to this, and separation is performed by another method. It is also possible.

As another method, for example, the ammonium metavanadate precipitation method can be mentioned. In this method, ammonia is added to a slurry containing at least vanadium and ammonium sulfate and reacted with vanadium to produce ammonium metavanadate (NH ₄ VO ₃ ). The reaction temperature is usually in the range of 20-60 ° C, preferably in the range of 30-40 ° C. The reaction time is usually in the range of 10 minutes to 10 hours, preferably in the range of 1 to 5 hours. The pH at the time of reaction is usually pH 8 or higher, preferably in the range of pH 9 to pH 12. Since vanadium precipitates as ammonium vanadate, it is separated and recovered by an appropriate separation method such as centrifugation. This ammonium metavanadate precipitation method separates nickel and vanadium particularly efficiently when the amount of nickel contained in the slurry is significantly lower than the amount of vanadium (for example, V / Ni = 100 or more). be able to.

(Modification 2)
As the other method described above, for example, an ion exchange resin separation method can be mentioned. Examples of the ion exchange resin used in this method include those that selectively adsorb vanadium. Such ion exchange resins, for example, a polyamine type chelating resin "DIAION CR20 (H ₂ SO ₄ form)" can be exemplified (Mitsubishi Chemical). The pH of the slurry is usually in the range of pH 3-7, preferably in the range of pH 4-6. Also in this method, only vanadium can be selectively separated from the slurry containing nickel and vanadium.

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. 1. Separation of vanadium from vanadium-containing mixture (1) Preparation of simulated liquid The reagents in the raw material composition table shown in the table below were weighed. Next, 250 ml / 300 ml of distilled water was placed in a 500 ml beaker, and the powdered reagent was dissolved while stirring with a stirrer. After dissolving the reagent, aqueous ammonia was slowly added to obtain a simulated solution having a pH of 11.

The simulated solution obtained using a stirrer was stirred at 300 mp for 30 minutes and then allowed to stand for 30 minutes. Subsequently, the simulated liquid after standing was 500 G with a swing rotor, and the precipitate was removed in 10 minutes to obtain a supernatant liquid.

(2) Recovery of Ni with lignite 3 g of lignite (particle size <45 μm) was added to the obtained supernatant. The lignite used was crushed, passed through a 45 μm sieve, and passed through a sieve mesh. The supernatant liquid to which lignite was added was stirred slowly overnight (16 hours) at room temperature (25 ° C.) using a stirrer (rotation speed 100 rpm) so that the lignite did not stand still. The supernatant liquid after stirring was centrifuged to recover Ni-supported lignite. The Ni-supported lignite was recovered by precipitating at 500 G for 10 minutes using a swing rotor.

(3) Neutralization Crystallization The supernatant liquid after recovering the Ni-supported lignite is slowly stirred at room temperature (25 ° C.) using a stirrer, and the supernatant liquid is adjusted to pH 6.0 using concentrated sulfuric acid (36N). It was adjusted. When the supernatant reached pH 6.0, the mixture was stirred at 100 rpm for 30 minutes using a stirrer and then allowed to stand for 30 minutes to precipitate an ammonium sulfate precipitate. After standing, the precipitate of ammonium sulfate was recovered at 500 G for 10 minutes using a swing rotor.

(4) Oxidation Crystallization While slowly stirring the supernatant after collecting the precipitate with a stirrer, concentrated sulfuric acid (36N) was added at room temperature (25 ° C.) to adjust the pH to 3.0. When the pH reached 3.0, the mixture was stirred with a stirrer at 100 rpm for 30 minutes and then allowed to stand for 30 minutes. After standing, the precipitate was collected at 500 G for 10 minutes using a swing rotor.

(5) Evaporation to dryness The supernatant was placed in an evaporating dish and allowed to stand at 80 ° C. for drying. A large evaporating dish was used, and the residual liquid of the supernatant was added little by little and dried. The dried product contained sulfuric acid and did not become solid, but was gum-like.

(6) Heat decomposition The dried product was placed in a crucible and heated in an electric furnace. As shown in the temperature chart below, the temperature rise is repeated by repeating the steps of raising the temperature by 10 ° C. and holding for 1 hour, then raising the temperature by 20 ° C. and holding for 1 hour, and finally 400 ° C. (Comparative Example 1) and 500 ° C. (implemented). Three samples were prepared in Example 1) and heated to 600 ° C. (Example 2). During the temperature rise, the furnace of the electric furnace was opened a little for ventilation, and the thermocouple was set from the inside of the crucible to the bottom, and the temperature of the sample was measured. The sample temperature and the temperature inside the furnace were recorded with a data logger. In addition, the sample adhering to the inside of the crucible was scraped off with a stick at the timing of holding at a constant temperature and stirred so that the entire sample was heated at a uniform temperature.
<Temperature temperature chart>
● Comparative Example 1: Hold at 90 ° C for 1 hour → Temperature rise → Hold at 100 ° C for 1 hour → Temperature rise → Hold at 120 ° C for 1 hour → Temperature rise → Hold at 130 ° C for 1 hour → Temperature rise → Hold at 150 ° C for 1 hour Retention → ... → Hold at 400 ° C for 1 hour ● Example 1: Hold at 90 ° C for 1 hour → Temperature rise → Hold at 100 ° C for 1 hour → Temperature rise → Hold at 120 ° C for 1 hour → Temperature rise → At 130 ° C 1 hour holding → temperature rise → 150 ° C for 1 hour → ・ ・ ・ → 500 ° C for 3 hours ● Example 2: 90 ° C for 1 hour → temperature rise → 100 ° C for 1 hour → temperature rise → 120 Hold at ° C for 1 hour → Temperature rise → Hold at 130 ° C for 1 hour → Temperature rise → Hold at 150 ° C for 1 hour → ・ ・ ・ → Hold at 600 ° C for 1 hour

(7) Sample Analysis Elemental analysis was performed on each of the samples of Example 1, Example 2, and Comparative Example 1 using "2400II" (manufactured by PerkinElmer Japan). In addition, as controls, _{three samples of NH 4} VO 3 (control 1), VOSO ₄ xH ₂ O (control 2), and V ₂ O ₅ (control 3) were also subjected to elemental analysis in the same manner. The results are shown in the table below.

Example 1 had a high content of sulfur (S), but a small amount of other elements, and the results were similar to those of Control 2. From this, it was found that in Example 1, a _{large amount of VOSO 4} xH _{2 O was contained as the main product.} In Example 2, the amount of each element was small, and the results were similar to those of Control 3. From this, it was found that in Example 2, a _{large amount of V 2} O _{5 was contained as the main product.} From these facts, it was found that when the sample was heated at a temperature of about 500 ° C., VOSO ₄ xH ₂ O became the main product, and when it was heated at a temperature of about 600 ° C., V ₂ O _{5 became the main product.} ..

On the other hand, Comparative Example 1 contains a large amount of nitrogen (N), sulfur (S), and hydrogen (H). From this, it is considered that NH ₄ VO ₃ , VOSO ₄ xH ₂ O, (NH ₄ ) ₂ SO _{4 and the} like are the main products in Comparative Example 1. That is, when the heating temperature is as low as 400 ° C., it is considered that ammonium sulfate and the like contained in the sample remain without being decomposed.

Claims (12)

Vanadium separation to separate vanadium from vanadium-containing compounds containing at least tetravalent and / or pentavalent vanadium compounds and ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) and / or ammonium hydrogen sulfate (NH ₄ HSO _4). It ’s a method,
The vanadium-containing material is heated to 450 ° C. or higher _{to volatilize ammonia gas (NH 3} ) and sulfuric acid gas (SO ₃ and / or SO ₂ ), and vanadium oxide sulfate (IV) (VOSO ₄ ) and vanadium pentoxide (V) are volatilized. A thermal decomposition step that produces at least one of ₂ O ₅ ) and divanadium tetroxide (V ₂ O _4).
A vanadium separation method comprising. In the pyrolysis step, vanadyl oxide sulfate (IV) (VOSO ₄ ) is produced as a main product by heating at 450 to 550 ° C., or
The vanadium according to claim 1, wherein vanadium pentoxide (V ₂ O ₅ ) and / or divanadium tetraoxide (V ₂ O ₄ ) is produced as a main product by heating at a temperature higher than 550 ° C. Separation method. The vanadium separation method according to claim 1, further comprising a pH adjusting step of adding sulfuric acid to the vanadium-containing material to adjust the pH to 2 to 4 in the pre-step of the thermal decomposition step. The vanadium separation method according to claim 3, further comprising a neutralization crystallization step of precipitating ammonium sulfate and / or ammonium hydrogensulfate crystals at pH 5 to 7 in the pre-step of the pH adjusting step. In the stage before the thermal decomposition step
By adjusting the pH to 10 to 12 by adding an aqueous ammoniacal alkali to the vanadium-containing material, a part of the oxide of the divalent or trivalent metal is hydroxylated by the oxide of the divalent or trivalent metal. An alkali addition step of producing sludge of a substance, an ammine complex of divalent nickel and / or cobalt ion, and an anion complex of the tetravalent vanadium ion.
An ion adsorption separation step of selectively adsorbing the divalent nickel and / or cobalt ammine complex with a carrier having a carboxyl group.
The vanadium separation method according to claim 1, further comprising a sludge separation step for separating the sludge. 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 recovered by the vanadium separation method according to any one of claims 1 to 5 as a raw material. Method for producing electrolyte. Vanadium separation to separate vanadium from vanadium-containing compounds containing at least tetravalent and / or pentavalent vanadium compounds and ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) and / or ammonium hydrogen sulfate (NH ₄ HSO _4). It ’s a device,
The vanadium-containing material is heated to 450 ° C. or higher _{to volatilize ammonia gas (NH 3} ) and sulfuric acid gas (SO ₃ and / or SO ₂ ), and vanadium oxide sulfate (IV) (VOSO ₄ ) and vanadium pentoxide (V) are volatilized. A thermal decomposition means for producing at least one of ₂ O ₅ ) and divanadium tetroxide (V ₂ O _{4), and}
A vanadium separator comprising. The pyrolysis means either produces vanadyl sulfate (IV) (VOSO ₄ ) as the main product by heating at 450 to 550 ° C.
_{The vanadium according to claim 7, wherein vanadium pentoxide (V 2} O ₅ ) and / or divanadium tetraoxide (V ₂ O ₄ ) is produced as a main product by heating at a temperature higher than 550 ° C. Separator. The vanadium separation apparatus according to claim 7, further comprising a pH adjusting means for adding sulfuric acid to the vanadium-containing material to adjust the pH to 2 to 4 in the stage prior to the thermal decomposition means. The vanadium separation apparatus according to claim 7, further comprising a neutralization crystallization means for precipitating ammonium sulfate and / or ammonium hydrogensulfate crystals at a pH of 5 to 7 in the preceding step of the pH adjusting means. In the stage before the thermal decomposition means
By adjusting the pH to 10 to 12 by adding an aqueous ammoniacal alkali to the vanadium-containing material, a part of the oxide of the divalent or trivalent metal is hydroxylated by the oxide of the divalent or trivalent metal. An alkali-adding means for producing sludge of a substance, an ammine complex of divalent nickel and / or cobalt ion, and an anion complex of the tetravalent vanadium ion.
An ion adsorption separation means for selectively adsorbing the divalent nickel and / or cobalt ammine complex with a carrier having a carboxyl group.
The vanadium separating device according to claim 7, further comprising a sludge separating means for separating the sludge. 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 recovered by the vanadium separator according to any one of claims 7 to 11 as a raw material. Electrolyte manufacturing equipment.

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