JPH1179748A - Continuous production of high-purity vanadium electrolyte solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an economical and continuous production method of tervalent, quadrivalent and tervalent/quadrivalent mixture vanadium electrolytic solns. SOLUTION: Ammonium trivanadate is crystallized from a sulfuric acid soln. of ammonium methavanadate containing impurities, and the obtd. slurry is concentrated, subjected to centrifugal separation 10 and dried 11 to collect ammonium trivanadate. The collected material is heated in an oxidative atmosphere in a sealed rotary kiln 15 to remove ammonia to produce vanadium pentoxide, while ammonium trivanadate is reduced in the presence of hydrogen to produce vanadium trioxide. By dissolving the obtd. vanadium trioxide and vanadium pentoxide (or, only vanadium trioxide) in sulfuric acid and water and by controlling the mixing proportions of vanadium trioxide and vanadium pentoxide, tervalent, quadrivalent and tervalent/quadrivalent mixture vanadium electrolytic solns. can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a redox battery electrolyte, in particular, a high-purity trivalent, tetravalent, and trivalent / tetravalent mixed vanadium electrolyte.

[0002]

2. Description of the Related Art In recent years, acid rain, destruction of the ozone layer of CFCs,
Global environmental issues, such as greenhouse phenomena due to an increase in atmospheric carbon dioxide, have been highlighted as problems for all humankind. Despite these circumstances, the world's population continues to increase, especially in the third world, and it is expected that the demand for energy will continue to increase. To cope with this, inexhaustible use of solar energy,
For example, it is necessary to reduce the power consumption of existing power generation facilities such as solar cells, power generation and heat recovery using solar heat, wind power generation, and wave power generation (power generation using wave energy and seawater temperature difference).

Further, electric power can be easily converted into various kinds of energy and easily controlled, and there is no environmental pollution at the time of consumption. Therefore, the ratio of electric power to energy consumption is increasing year by year. The unique point of power supply is that production and consumption are performed simultaneously and storage is not possible. For this reason, small-scale thermal power generation, which is suitable for operating high-efficiency nuclear power generation and advanced thermal power generation with the highest efficiency rating as much as possible and for generating a large increase in daytime power demand in response to fluctuations in power consumption, At present, surplus power is generated at night due to hydropower generation. The development of technology for storing the surplus power at night and making it available efficiently during the day is also a longing for the power industry.

[0004] From the above situation, there is no environmental pollution,
In addition, various secondary batteries have been studied as a method of storing electric power, which is a highly versatile energy.
A redox battery, which is a large-capacity stationary battery that can be operated at normal pressure, is attracting attention. Redox batteries are liquid positive,
The battery active material of the negative electrode is passed through a liquid permeation type electrolytic cell to charge and discharge using an oxidation-reduction reaction, and has a longer life, less self-discharge, and reliability compared to conventional secondary batteries. It has the advantage that the battery cell that performs the oxidation-reduction reaction and the tank that stores electricity are separated, so that the electric capacity can be freely changed.In particular, both the positive and negative electrodes have vanadium. Vanadium redox flow batteries that use high power, and can be easily regenerated in the battery even with the mutual mixing of positive and negative electrolytes through an ion exchange membrane, attracting attention as the closest to practical use I have.

[0005] However, vanadium as a raw material is expensive, and a method of reducing pentavalent vanadium to tetravalent and trivalent vanadium, particularly a method of reducing trivalent vanadium, is performed only by a small-scale electrolytic reduction method. As a result, economic production of a vanadium electrolyte was not possible, and this was a major bottleneck in the practical application of vanadium redox flow batteries.

[0006] Therefore, the present inventors, starting from a vanadium compound containing a large amount of impurities, which is inexpensive and contains a large amount of impurities, which is recovered from a combustion medium generated when heavy oil fuel is burned earlier.
A basic method (JP-A-8-148177) has been proposed in which a vanadium ion is polymerized and precipitated in the presence of sulfuric acid, purified, and subjected to a hydrogen reduction operation, thereby producing a vanadium electrolyte at low cost. The present invention relates to a continuous vanadium electrolyte production process based on this method. According to the present invention, the production cost of the vanadium electrolyte solution has been greatly reduced, and this has made a great step toward the practical use of the vanadium redox flow battery.

[0007]

In the industrialization of vanadium redox flow batteries, it is a major problem to reduce the cost of the electrolyte, which accounts for a large part of the cost of vanadium batteries. The present inventors have developed a process for producing a mixed vanadium electrolytic solution in which a raw material refining step, a solid-liquid separation / drying step, a deammonification and reduction step, and a dissolving step are continuously performed using inexpensive recovered vanadium as a raw material. Allows economical production of liquids.

[0008]

According to the present invention, (1) sulfuric acid is added to an aqueous solution of ammonium metavanadate containing impurities to adjust its pH to 1.5 to 2.0,
Depositing ammonium trivanadate by allowing the solution to stay at a temperature of 80 to 100 ° C for 0.5 to 3 hours to polymerize vanadium ions in the solution; (2) concentrating the obtained slurry, followed by centrifugation; Drying and recovering ammonium trivanadate; (3) using one closed rotary kiln furnace, ammonium trivanadate is removed under an oxidizing atmosphere for 400-
A step of producing vanadium pentoxide by heating to 690 ° C. to remove ammonia and reducing vanadium trivanadate at a temperature of 450 to 750 ° C. in the presence of hydrogen to produce vanadium trioxide; (4) obtaining The obtained vanadium trioxide and vanadium pentoxide (or only vanadium trioxide), sulfuric acid and water are supplied to an electrolytic solution preparation tank and dissolved in the vanadium oxide,
At this time, by adjusting the mixing ratio of vanadium trioxide and vanadium pentoxide to produce a mixed trivalent, tetravalent and trivalent / 4-valent vanadium electrolyte solution, a high-purity vanadium electrolyte solution comprising: A continuous manufacturing method is provided.

[0009]

FIG. 1 shows one embodiment of a method for producing an electrolytic solution according to the present invention. The present invention will be described with reference to FIG. The raw material vanadium (vanadium pentoxide or ammonium metavanadate) is put into the raw material storage hopper 1. When the raw material is vanadium pentoxide (V ₂ O ₅ ), the raw material is quantitatively supplied from the lower part of the hopper 1 to the dissolving tank 3 by the quantitative feeder 2. Ammonia and water (or aqueous ammonia) are supplied to the dissolution tank 3 to dissolve the raw material V ₂ O ₅ as ammonium metavanadate. At that time, the concentration of vanadium
Preferably, the dissolution temperature is 3 to 5% by volume and the residence time is 0.5 to 2 hours. The obtained ammonium metavanadate solution is continuously withdrawn from the dissolution tank 3 by the pump 4, solids are removed by the filter 5, and transferred to the purification reaction tank 6.

The starting material is ammonium metavanadate (NH
_In the case of ₄ VO ₃ ), the raw material ammonium metavanadate and water are quantitatively supplied from the lower part of the hopper 1 by the quantitative feeder 2 to the dissolving tank 3 for dissolution, and the pump 4 continuously removes the raw material from the dissolving tank 3. The solid is removed by the filter 5 and transferred to the purification reaction tank 6.

The ammonium metavanadate solution sent from the dissolving tank 3 to the refining reaction tank 6 is added with sulfuric acid to adjust the pH.
Adjust the pH to 1.5-2 with meter A. In the purification reaction tank 6, a temperature of 80 to 100 ° C., 0.5 to 3
The polymerization reaction proceeds during the residence time, and ammonium trivanadate (NH ₄ V ₃ O ₈ ) precipitates, whereby a slurry containing ammonium trivanadate is obtained. At this time, the impurities contained in the raw material are dissolved and exist in the liquid portion of the slurry. Next, the slurry was continuously withdrawn by the pump 7 and cooled by the cooler 8, and then settled in the settling tank 9
Transfer to The slurry concentration at this time is usually 5 to 10%.
Since this is a very dilute slurry, it is allowed to stand in the settling tank 9 to concentrate the ammonium trivanadate slurry. The supernatant liquid containing impurities is discharged out of the tank, and the concentrated slurry is separated into a solid and a liquid by the centrifugal separator 10.

Next, the obtained cake containing ammonium trivanadate is dried. Drying of the cake can be carried out using a conventional dryer 11, but as an alternative, the cake can be dried through an extruder 12 and formed into granules. The dried ammonium trivanadate is once stored in a hopper 13, then weighed by a load cell (not shown), and quantitatively supplied to a closed rotary kiln 15 by a screw feeder 14.

In the method of the present invention, V ₂ O ₅ and V ₂ O ₃ are produced from ammonium trivanadate using one closed rotary kiln furnace 15. When V ₂ O ₅ is produced by removing ammonia from ammonium trivanadate, 400 to 690 ° C. while flowing air.
At a temperature of 0.5 to 6 hours to obtain V ₂ O ₅
To manufacture. The reaction formula is shown below. 4NH ₄ V ₃ O ₈ + 3O ₂ = 6V ₂ O ₅ + 2N ₂ + 8H ₂ O When most of ammonia is desorbed from ammonium trivanadate, it reacts with oxygen in vanadium to become nitrogen in the following reaction. . 2NH ₄ V ₃ O ₈ = 3V ₂ O ₄ + N ₂ + 4H ₂ O 2V ₂ O ₄ + O ₂ = 2V ₂ O _{5 The} generated V ₂ O ₄ is oxidized to V ₂ O ₅ . Since the amount of ammonia in the waste gas is very small, waste gas treatment becomes very simple.

On the other hand, when V ₂ O ₃ is produced by a reduction reaction of ammonium trivanadate, hydrogen or a mixed gas of hydrogen and nitrogen is passed while quantitatively supplying ammonium trivanadate to the rotary kiln 15.
In the furnace, a reduction reaction and a desorption reaction of ammonia occur. The reduction temperature is preferably from 450 to 750 ° C, and the residence time is preferably from about 1 to 4 hours. The reaction formula is as follows. 2NH ₄ V ₃ O ₈ + 6H ₂ = 3V ₂ O ₃ + 2NH ₃ + 7H ₂ O The sealed rotary kiln used in the present invention has a completely sealed rotary bearing. Can be used for
The equipment cost is reduced, which is very economical. V
At the time of switching between the production of ₂ O _{5 and} the production of V ₂ O ₃ , the inside of the furnace is purged with nitrogen, and if there are any undesired deposits or residues in the furnace in the next reaction, these are removed.

The obtained V ₂ O ₅ and V ₂ O ₃ are cooled in a cooler 16 and then transferred to hoppers 17 and 18 and stored. V ₂ O ₅ and V ₂ O ₅ and V _{2 are} fed from the V ₂ O ₅ and V ₂ O ₃ hoppers 17 and 18 to the electrolytic solution preparation tank 21 by the constant-rate feeders 19 and 20.
While supplying O ₃ quantitatively, sulfuric acid and water are added to dissolve the vanadium oxide to form an electrolyte. The heat of dilution of the sulfuric acid generated at this time can be used for heating the reaction solution. The reaction is carried out in a temperature range of 100 to 150 ° C. for 2 to 8 hours with good stirring.

The electrolyte solution for a vanadium redox battery using vanadium as the positive and negative electrode active materials includes a case where a tetravalent vanadium solution is applied to the positive electrode and a case where a trivalent vanadium solution is applied to the negative electrode, and a case where trivalent and tetravalent are applied to the positive and negative electrodes. There is a case where a mixed electrolyte having a valence of 1: 1 is applied. From the viewpoint of the production of an electrolyte, it is preferable to produce a mixed electrolyte of 1: 1 of trivalent and tetravalent, since only one tank is required, but in a battery, trivalent vanadium is converted to tetravalent in the positive electrode. In the negative electrode, on the other hand, tetravalent vanadium is all converted to trivalent, so that there is no problem in either method. In an industrial production method of an electrolytic solution, if the ratio between trivalent and tetravalent is exactly constant, the process becomes complicated and the productivity is reduced. Therefore, usually, the mixing ratio of V ₂ O ₃ and V ₂ O ₅ is adjusted to a molar ratio of 2.9: 1.1 to 3.2: 0.8 to make a trivalent of 45 to 55 mol%. Of vanadium and 55-
A mixed vanadium electrolyte comprising 45 mol% of tetravalent vanadium is obtained. Equivalent electrolytic solution of trivalent and tetravalent (V ³⁺ / V
^{4 +} = 1/1) can be obtained by the following reaction. 3V ₂ O ₃ + V ₂ O ₅ + 10H ₂ SO ₄ = 4VOSO ₄ + 2V ₂
(SO ₄ ) ₃ + 6H ₂ SO ₄ + 10H ₂ O

The mixing ratio of vanadium trioxide and vanadium pentoxide is from 0.9: 1.1 to 1.1: 0.
By adjusting the value to 9, a mixed vanadium electrolyte comprising 90 to 100 mol% of tetravalent vanadium and 0 to 10 mol% of trivalent vanadium can be produced. Furthermore, a trivalent vanadium electrolyte can be produced by dissolving only vanadium trioxide in water.

[0018]

【Example】

Example 1 Production of V ³⁺ / V ⁴⁺ = ^1/1 Electrolyte Approximately 800 kg of recovered ammonium metavanadate manufactured by Kashima Kita Kyodo was supplied to the storage tank 1. 60 kg / hr of ammonium metavanadate and 1.5 m of pure water by the fixed quantity feeder 2
The solution was supplied to the 2 m ³ dissolving tank 3 at a supply speed of ³ / hr. The dissolution tank was heated to a temperature of 85-97 ° C. with low pressure steam to completely dissolve ammonium metavanadate. The ammonium metavanadate solution was withdrawn from the lower part of the dissolution tank by the pump 4 at a rate of 1.5 m ³ / hr. The residence time in the dissolution tank was about 1.3 hours. The solution was sent to a purification reaction tank 6 after removing solids with a filter 5. The purified reaction vessel was heated to a temperature of 85 to 97 ° C. with low-pressure steam, and sulfuric acid and pure water were added so that the pH became about 1.8 while monitoring with a pH meter A. 1.5 m ³ / hr from the bottom of the purification reactor
The slurry liquid of ammonium trivanadate was taken out at the speed of, cooled in the cooler 8 and sent to the sedimentation tank 9. Ammonium trivanadate was settled in the settling tank, and the supernatant was sent to a waste acid treatment facility. The slurry of ammonium trivanadate concentrated to about 25% was sent to the centrifuge 10. Separate the water in a centrifuge,
After forming a cake of ammonium trivanadate having a water content of about%, the cake was sent to the dryer 11. After the water content was adjusted to about 0 to 5% in the dryer, it was sent to the hopper 13. Feeder 14 is used to remove ammonium trivanadate
While supplying the air to the closed rotary kiln furnace 15 at a speed of 0 kg / hr and flowing air at a speed of 6 Nm ³ / hr,
V ₂ O ₅ was produced at a temperature of 50 ° C. and a residence time of 2 hours, cooled by a cooler 16 and sent to a hopper 17. When the hopper became full, the supply of ammonium trivanadate was stopped, and the inside of the rotary kiln furnace was completely purged with nitrogen.

A mixed gas of hydrogen and nitrogen (7: 3) is
The mixture was supplied at a flow rate of m ³ / hr, and ammonium trivanadate was supplied again to the rotary kiln furnace at a rate of 50 kg / hr. V ₂ O ₃ at a reduction temperature of 650 ° C. and a residence time of 4 hours
After cooling with the cooler 16, the hopper 1
8 and stored. After some extent accumulated V ₂ O ₃ in the hopper, pure water 24 to the pressure type electrolyte preparation tank 21 3m ³
83.4kg was loaded and V ₂ O _{5 was} supplied from feeders 19 and 20.
122.9 kg and 303.8 kg of V ₂ O ₃ were supplied and stirred well. Then, 1260 kg of concentrated sulfuric acid was supplied over about 1 hour. When the temperature became 100 ° C. due to the heat of dilution, the valve was opened, the steam in the preparation tank was purged, and the air in the dead space was removed. After the addition of concentrated sulfuric acid, the mixture was heated with steam to raise the temperature to about 135 ° C. After reacting at that temperature for 1 hour, the heated steam was stopped and water was flowed through the jacket to cool. After cooling, 0.
After fine filtration with a 45 μm cartridge type membrane filter, the solution was sent to the product tank 24. The analysis results of the obtained electrolytic solution are as follows. Total V concentration V ³⁺ V ⁴⁺ SO ₄ ^2- 1.8 0.95 0.85 4.27 (52.8%) (47.2%)

Example 2 Production of V ^{4 +} Vanadium Electrolyte Solution 2335 kg of pure water was charged into a 3 m ³ pressurized discharge control tank 21, and V ₂ O ₅ 245.7 k was supplied from feeders 19 and 20.
g, V ₂ O ₃ 310 kg and concentrated sulfuric acid 1260 kg were supplied in the same manner as in Example 1. The analysis results of the obtained electrolytic solution are as follows. Total V concentration V ⁴⁺ V ³⁺ SO ₄ ^2- 1.81 1.76 0.05 4.26 (97.2%) (2.8%)

Example 3 Production of V ^{3 +} Vanadium Electrolyte 2300 kg of pure water was poured into a 3 m ³ pressurized discharge adjusting tank 21, and 450 kg of V ₂ O ₅ and concentrated sulfuric acid 1 were supplied from a feeder 20.
Except supplying 260 kg, it carried out similarly to Example 1. The analysis results of the obtained electrolytic solution are as follows. Total V concentration V ³⁺ V ⁴⁺ SO ₄ ^2- 1.81 1.77 0.04 4.26 (98.0%) (2.0%)

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of the method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Raw material storage hopper 2,19,20 Quantitative feeder 3 Dissolution tank 4,7,22 Pump 5 Filter 6 Purification reaction tank 8,16,23 Cooler 9 Sedimentation tank 10 Centrifuge 11 Dryer 12 Extruder 13 Trivanazine Ammonium hopper 14 Feeder 15 Closed rotary kiln furnace 17, 18 V ₂ O ₅ , V ₂ O ₃ hopper 21 Electrolyte preparation tank 24 Product tank

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Furusato V-Battery Development Office, Kashima Kita Kyodo Co., Ltd. 8-3-1 Chuo, Ami-cho, Inashiki-gun, Ibaraki Prefecture (72) Inventor Kanji Sato Inashiki-gun, Ibaraki 8-3 Chuo Amicho Kashima Kita Kyodo Co., Ltd. V Battery Development Room

Claims (4)

[Claims] (1) Sulfuric acid is added to an aqueous solution of ammonium metavanadate containing impurities to adjust the pH to 1.5 to 2.
0, and allowed to stay at a temperature of 80 to 100 ° C. for 0.5 to 3 hours to polymerize vanadium ions in the solution to precipitate ammonium trivanadate; (2) concentrating the obtained slurry Thereafter, a step of recovering ammonium trivanadate by centrifugation and drying; (3) ammonium trivanadate is oxidized in an oxidizing atmosphere by using one closed rotary kiln furnace under an oxidizing atmosphere.
A step of producing vanadium pentoxide by heating to 690 ° C. to remove ammonia and reducing vanadium trivanadate at a temperature of 450 to 750 ° C. in the presence of hydrogen to produce vanadium trioxide; (4) obtaining The obtained vanadium trioxide and vanadium pentoxide, and sulfuric acid and water were supplied to an electrolytic solution preparation tank and dissolved in the vanadium oxide. At this time, the mixing ratio of vanadium trioxide and vanadium pentoxide was 2.9 by molar ratio. : 1.1
To 3.2: 0.8 to produce a mixed vanadium electrolyte comprising 45 to 55 mol% of trivalent vanadium and 55 to 45 mol% of tetravalent vanadium. Continuous production method of mixed vanadium / tetravalent electrolyte. (1) Sulfuric acid is added to an aqueous solution of ammonium metavanadate containing impurities to adjust the pH to 1.5 to 2.
0, and allowed to stay at a temperature of 80 to 100 ° C. for 0.5 to 3 hours to polymerize vanadium ions in the solution to precipitate ammonium trivanadate; (2) concentrating the obtained slurry Thereafter, a step of recovering ammonia trivanadate by centrifugation and drying; (3) ammonia trivanadate in an oxidizing atmosphere using an enclosed rotary kiln furnace in an oxidizing atmosphere for 400 to 6;
A step of producing vanadium pentoxide by heating to 90 ° C. to remove ammonia and reducing vanadium trivanadate at a temperature of 450 to 750 ° C. in the presence of hydrogen to produce vanadium trioxide; (4) obtaining The obtained vanadium trioxide and vanadium pentoxide, and sulfuric acid and water were supplied to an electrolytic solution preparation tank and dissolved in the vanadium oxide, and at this time, the mixing ratio of vanadium trioxide and vanadium pentoxide was 0.9 in molar ratio. : 1.1-
1.1: producing a mixed vanadium electrolyte solution consisting of 90 to 100 mol% of tetravalent vanadium and 0 to 10 mol% of trivalent vanadium by adjusting to 0.9. A continuous method for producing a mixed tetravalent vanadium electrolyte. (1) Sulfuric acid is added to an aqueous solution of ammonium metavanadate containing impurities to adjust the pH to 1.5 to 2.
0, and allowed to stay at a temperature of 80 to 100 ° C. for 0.5 to 3 hours to polymerize vanadium ions in the solution to precipitate ammonium trivanadate; (2) concentrating the obtained slurry Thereafter, a step of recovering ammonium trivanadate by centrifugation and drying; (3) ammonium trivanadate is oxidized in an oxidizing atmosphere by using one closed rotary kiln furnace under an oxidizing atmosphere.
A step of producing vanadium pentoxide by heating to 690 ° C. to remove ammonia and producing vanadium trioxide by reduction at a temperature of 450 to 750 ° C. in the presence of ammonium hydrogen trivanadate; Supplying vanadium trioxide, sulfuric acid, and water to an electrolytic solution preparation tank to dissolve the vanadium oxide in the vanadium oxide to produce a trivalent vanadium electrolytic solution. . 4. An aqueous solution of ammonium metavanadate in the step (1) is prepared by adding vanadium pentoxide containing impurities, ammonia and water at a temperature of 60 to 100 ° C. for 0.5 hour.
The method according to any one of claims 1 to 3, which is obtained by reacting for 2 to 2 hours.