High-purity vanadyl sulfate electrolyte as well as preparation method and application thereof

Abstract

The invention provides a method for preparing a high-purity vanadyl sulfate electrolyte based on carbonaceous slate type stone coal vanadium ore. The method is characterized in that mixed acid of 10% sulfuric acid and 10% hydrochloric acid is used for soaking the carbonaceous slate type vanadium ore to obtain ash obtained through decarburization power generation, a leaching solution obtained after solid-liquid separation is reduced through SO2 generated in the decarburization power generation process, a tetravalent vanadium leaching solution is obtained, and the pH range is 1.8-2.6. Carrying out multi-stage counter-current extraction on the leachate by using a P204 / P507 / Cyanex272: TBP: sulfonated kerosene system, and after two phases are separated, carrying out multi-stage counter-current counter-extraction on a vanadium-loaded organic phase by using a 1-5mol / L sulfuric acid solution to obtain a high-purity vanadyl sulfate solution; and the vanadyl sulfate solution is electrolyzed to obtain a 3.5-valence vanadium electrolyte. According to the method, the vanadium recovery rate can exceed 90%, the prepared vanadium electrolyte is low in impurity content, the technological process is short, emission of waste gas and waste water is reduced, and energy conservation and environment protection are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of processing and manufacturing of vanadium electrolyte, and in particular relates to a method for preparing high-purity vanadyl sulfate electrolyte by utilizing stone coal vanadium ore. Background Art

[0002] All-vanadium ion flow batteries have the advantages of being clean, efficient, safe, and having a long life. They have been partially industrially applied in wind energy, photovoltaic power generation, distributed power stations, communication base stations, electric buses, military power storage, solar energy storage, and power station peak regulation. The concentration of vanadium in the electrolyte of all-vanadium batteries and the amount of electrolyte determine the capacity of the battery. The quality of the vanadium electrolyte has a direct impact on the energy density, battery performance, and cycle life. At present, the mainstream process for the preparation of vanadium electrolytes is to use high-purity solid vanadium pentoxide as a raw material, and to reduce V2O5 to vanadium sulfate through chemical reducing agents such as SO2, oxalic acid, V2O3, or by electrolysis, but high-purity vanadium pentoxide will result in high preparation costs.

[0003] Vanadium resources are widely distributed on the earth, mainly including magmatic vanadium-titanium magnetite and sedimentary vanadium ore. Sedimentary vanadium ore is mainly vanadium-containing stone coal, also known as stone coal vanadium ore. The proven reserves of stone coal in my country are 6.188×10 10 t, its V2O5 grade is mostly between 0.3% and 1.3%, accounting for 87% of the total vanadium reserves in my country's ores, and is an important vanadium resource. 3+ and V 4+ Composition, currently vanadium is extracted from stone coal by oxidation to V 5+ Afterwards, vanadium is leached out and then extracted or extracted with ion exchange resin. The ammonia salt or ammonia water used for vanadium precipitation is prone to produce ammonia nitrogen wastewater pollution.

[0004] Under the existing technical conditions of all-vanadium liquid flow batteries, in order to ensure the comprehensive performance of the battery, the vanadium concentration in the vanadyl sulfate electrolyte is required to be ≥1.5 mol / L, the sodium, potassium, and chlorine in the electrolyte are required to be less than 100 mg / L, iron, aluminum <50 mg / L, magnesium, calcium <30 mg / L, chromium, nickel, and molybdenum <15 mg / L, silicon, manganese <10 mg / L, and copper, arsenic, lead, gold, etc. are required to be less than 1 mg / L respectively.

[0005] As an important vanadium source in China, carbonaceous slate-type vanadium ore has a metamorphic mudstone structure, plate-like structure and micro-stratification structure. The metal minerals of the ore are mainly pyrite, containing trace magnetite; the gangue minerals are mainly carbonaceous, muddy, quartz, calcite, etc., and the altered minerals sericite, chalcanthite, etc. are formed. The main chemical components of the ore are SiO2, C, Al2O3, Fe2O3, FeS2, etc., and their total content is greater than 80%, among which the general content of SiO2 is 40% to 80%, the content of Al2O3 is 6% to 10%, the content of Fe2O3 is 6% to 10%, and the content of C is 3% to 22%. The acidic vanadium-rich solution obtained by direct acid leaching is mainly V (IV), accompanied by the leaching and enrichment of impurities such as iron and aluminum. It has the characteristics of high vanadium and many impurities, which brings the difficulty of deep impurity removal and enrichment for the subsequent preparation of vanadium electrolyte. At present, in the process of extracting vanadium from vanadium-containing stone coal, the mass ratio of vanadium oxysulfate to total metal impurities (VOSO4 / ∑Me) in leaching, stripping or resin analysis solution (vanadium content 1.0-10.0 g / L) is less than 80. This vanadium oxysulfate solution cannot meet the technical requirements of vanadium battery electrolyte.

[0006] In view of the characteristics of the structural composition of carbonaceous slate-type vanadium ore coal, vanadium in carbonaceous slate-type vanadium ore coal is extracted to prepare electrolyte under the premise of saving costs and protecting the environment as much as possible. This patent proposes a method for preparing vanadium ore by decarbonization, power generation, leaching, reduction extraction, stripping and vanadium electrolyte mother liquor. Summary of the invention

[0007] The purpose of the present invention is to provide a method for extracting vanadium from stone coal and preparing vanadium electrolyte with short process, environmental friendliness, simple process, low cost and strong raw material adaptability for carbonaceous slate-type stone coal vanadium ore. The characteristics of carbonaceous slate-type stone coal vanadium ore are Pu-type hardness f=4-6, and the metal minerals of the ore are mainly pyrite, containing trace magnetite. The main chemical components of the ore are SiO2, C, Al2O3, Fe2O3, FeS2, etc., among which the general content of SiO2 is 40%-80%, the content of Al2O3 is 6%-10%, the content of Fe2O3 is 6%-10%, and the content of C is 3%-22%. The main mineral components of the ore are quartz, carbonaceous and sericite, and the average grade of V2O5 is 0.75%.

[0008] In order to achieve the above object, the specific technical solution adopted by the present invention is:

[0009] Step 1, ore pretreatment, decarbonization and power generation: In order to facilitate the leaching of vanadium, the ore is decarbonized and burned for 3 hours in a non-oxidizing atmosphere, which also promotes the conversion of V(III) into V(IV). The generated SO2 (Equations 1 and 2) is used as a reducing agent for the vanadium ore leachate. The heat generated by decarbonization is used to generate electricity for subsequent production processes, saving energy.

[0010] 2As2S3+9O2=2As2O3+6SO2↑ (1)

[0011] 2MeS+3O2=2MeO+2SO2↑ (2)

[0012] (Me is a metal element such as Fe, Ca, Mg, Cu, Ni, Zn, etc.)

[0013] In particular, the equipment used for decarbonizing stone coal for power generation is one of a tubular furnace, a circulating fluidized bed or a boiling furnace.

[0014] Step 2, leaching: using stone coal ash residue from decarbonization power generation as the solid phase, with a liquid-to-solid ratio of 2:1, adding 10% sulfuric acid + 10% hydrochloric acid, the leaching time is about 3 hours, at room temperature, continuous leaching, the purpose of which is to transfer the vanadium in the ore into the aqueous solution, to separate the vanadium from most of the gangue impurities, such a leachate will not form silica gel and agglomerate.

[0015] Particularly, in step (2), the vanadium leaching rate is greater than 90%, containing vanadium 1.0-5 g / L, Al 2.0-6 g / L, Fe 0.5-5 g / L, Si 0.5-1.5 g / L, and other metal impurities less than 1.0 g / L.

[0016] Step 3, reduction extraction: the flue gas (containing SO2) generated during decarbonization and power generation in step 1 is introduced into the vanadium-containing leaching solution of step 2, and V(V) therein is reduced to V(IV) to obtain an extractant solution with a pH value of 1.8-2.6, and an extractant organic phase composition of 15% P204 (bis(2-ethylhexyl) phosphate) / P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) / Cyanex272 (bis(2,4,4-trimethylpentyl)phosphonic acid) + 5% TBP + 80% sulfonated kerosene, O / A = 1-5:4, extraction is carried out at 25-50°C for 4-10 minutes, and the aqueous phase is subjected to 5-7 levels of countercurrent extraction to obtain a loaded organic phase and a raffinate.

[0017] Step 4, back extraction: the concentration of the back extraction agent H2SO4 solution is 1-5 mol / L, the back extraction phase ratio O / A=3:1-5, and the back extraction time is 10-20 min. The loaded organic phase is subjected to 3-5 levels of countercurrent back extraction at room temperature to obtain an unloaded organic phase and back water.

[0018] Step 5: electrolyze the stripped vanadium-containing aqueous solution of step 4 to obtain a 3.5-valent vanadium electrolyte after electrolysis for a set time.

[0019] The beneficial effects of the technical solution of the present invention are: the overall preparation process is environmentally friendly and energy-saving, and the process is short. Step 1 decarbonization generates electricity, which fully utilizes the thermal energy of stone coal, and at the same time converts trivalent vanadium into tetravalent vanadium, which is beneficial to leaching; adding dilute hydrochloric acid in step 2 is conducive to the leaching of vanadium, and the vanadium leaching rate is high, which can reach 90-98%, containing 1.0-5.0g / L of vanadium, less other impurities, and the concentration of other metals is 0.5-10g / L; in step 3, the flue gas (including SO2) released by the decarbonization of stone coal vanadium ore is passed into the leaching solution to reduce pentavalent vanadium, reducing the emission of waste gas during the vanadium extraction process of carbonaceous stone coal vanadium ore; the added extractant can make the vanadium extraction rate 97-99%, while the impurity metal cations are not extracted; step 4 uses sulfuric acid to extract high-purity vanadium-containing sulfuric acid solution, and the vanadium stripping rate is 93-99%. The vanadium-containing electrolyte prepared by the method of the present invention meets the national standard (GB / T 37204-2018) for first-grade all-vanadium liquid flow battery electrolyte, wherein the total vanadium concentration is above 1.5 mol / L, the aluminum concentration is less than 50 mg / L, the iron concentration is less than 30 mg / L, the Si concentration is less than 10 mg / L, and the concentrations of magnesium, manganese, molybdenum, nickel, etc. are below 1 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 : Process diagram for preparing vanadium electrolyte mother liquor from carbonaceous slate-type vanadium ore coal through decarbonization power generation - leaching - reduction extraction - stripping - electrolysis - vanadium electrolyte mother liquor. DETAILED DESCRIPTION

[0021] The present invention is used to prepare a vanadium battery electrolyte by extracting vanadium from stone coal, a preparation method thereof, and a redox battery including the electrolyte. Those skilled in the art should understand that the following specific description is for the purpose of facilitating the understanding of the present invention. The technical solution of the present invention is not limited to the specific implementation methods listed below, but also includes any combination of the specific methods.

[0022] Example 1

[0023] A vanadium-extracting electrolyte for stone coal and a preparation method thereof. The specific steps of the preparation method described in this embodiment are:

[0024] In a non-oxidizing atmosphere, a boiling furnace is used to decarbonize the carbonaceous slate vanadium ore for power generation, and then the ash after stone coal decarbonization power generation is used as the leaching ore, 10% sulfuric acid + 10% hydrochloric acid are added, the liquid-solid ratio is 2:1, and the flue gas (including SO2) produced by the decarbonization combustion of the vanadium ore is introduced. The pH value of the leaching mother liquor is 2.0, V is 2.62g / L; Al is 4.62g / L; Si is 1.48g / L; Fe is 0.89g / L; Mg is 0.92g / L; K is 0.96g / L; Na is 0.90g / L; Ca is 0.87g / L; Mn is 0.03g / L; As is 0.03g / L.

[0025] 15% P204+5% TBP+80% sulfonated kerosene was used as the extractant, O / A=1:4, and the extraction was performed at 25°C for 4 minutes. The aqueous phase was subjected to 5-stage countercurrent extraction to obtain a loaded organic phase and a raffinate, and the vanadium extraction rate was 97.25%. Further, 5mol / L H2SO4 was used as the stripping agent for stripping, the stripping phase ratio was O / A=3:5, the stripping time was 10 minutes, and the loaded organic phase was subjected to 5-stage countercurrent stripping at room temperature to obtain an unloaded organic phase and a stripping aqueous phase, and the vanadium stripping rate was 99.03%.

[0026] The stripping water phase is introduced into an electrolytic cell for electrolysis, and reduction electrolysis is performed for a certain period of time to obtain a 3.5-valent vanadium electrolyte.

[0027] The vanadium electrolyte prepared in this embodiment is measured by ICP: V concentration is about 2.0 mol / L; Al is 21 mg / L; Si is 3.3 mg / L; Fe is 19 mg / L; Mg is 2.2 mg / g / L; K is 5.2 mg / L; Na is 9.1 mg / L; Ca is 4.3 mg / L; other metal ions are less than 1 mg / L. The composition meets the requirements of the first-grade product of all-vanadium redox flow battery electrolyte in the national standard (GB / T-37204-2018).

[0028] The vanadium electrolyte in this embodiment is 40 mA / cm 2 The battery was tested for 50 cycles of charge and discharge at the current density: the average coulomb efficiency was 93.12%; the voltage efficiency was 91.23%; and the energy efficiency was 87.37%.

[0029] Example 2

[0030] A vanadium-extracting electrolyte for stone coal and a preparation method thereof. The specific steps of the preparation method described in this embodiment are:

[0031] In a non-oxidizing atmosphere, a boiling furnace is used to decarbonize the carbonaceous slate vanadium ore for power generation, and then the ash after stone coal decarbonization power generation is used as the leaching ore, 10% sulfuric acid + 10% hydrochloric acid are added, the liquid-solid ratio is 2:1, and the flue gas (including SO2) produced by the decarbonization combustion of the vanadium ore is introduced. The pH value of the leaching mother liquor is 1.8, V is 5.02g / L; Al is 7.97g / L; Si is 3.66g / L; Fe is 1.46g / L; Mg is 1.27g / L; K is 2.32g / L; Na is 1.38g / L; Ca is 2.67g / L; Mn is 0.05g / L; As is 0.05g / L.

[0032] 15% P507 + 5% TBP + 80% sulfonated kerosene was used as the extractant, O / A = 5:4, and the extraction was performed at 50°C for 10 minutes. The aqueous phase was subjected to 7-stage countercurrent extraction to obtain a loaded organic phase and a raffinate, and the vanadium extraction rate was 99.35%. Further stripping was performed with 2mol / L H2SO4 stripping agent, the stripping phase ratio O / A = 3:1, the stripping time was 20 minutes, and the loaded organic phase was subjected to 3-stage countercurrent stripping at room temperature to obtain an unloaded organic phase and a stripping aqueous phase, and the vanadium stripping rate was 98.76%.

[0033] The stripping water phase is introduced into an electrolytic cell for electrolysis, and reduction electrolysis is performed for a certain period of time to obtain a 3.5-valent vanadium electrolyte.

[0034] The vanadium electrolyte prepared in this embodiment is measured by ICP: V concentration is about 1.7 mol / L; Al is 26 mg / L; Si is 3.0 mg / L; Fe is 19 mg / L; Mg is 1.0 mg / L; K is 1.5 mg / L; Na is 1.1 mg / L; Ca is 1.6 mg / L; other metal ions are less than 1 mg / L. The composition meets the requirements of the first-grade product of all-vanadium redox flow battery electrolyte in the national standard (GB / T-37204-2018).

[0035] The vanadium electrolyte in this embodiment is 40 mA / cm 2 The battery was tested for 50 cycles of charge and discharge at the current density: the average coulomb efficiency was 90.46%; the voltage efficiency was 91.23%; and the energy efficiency was 86.07%.

[0036] Example 3

[0037] A vanadium-extracting electrolyte for stone coal and a preparation method thereof. The specific steps of the preparation method described in this embodiment are:

[0038] In a non-oxidizing atmosphere, a boiling furnace is used to decarbonize the carbonaceous slate vanadium ore for power generation, and then the ash after stone coal decarbonization power generation is used as the leaching ore, 10% sulfuric acid + 10% hydrochloric acid are added, the liquid-solid ratio is 2:1, and the flue gas (including SO2) produced by the decarbonization combustion of the vanadium ore is introduced. The pH value of the leaching mother liquor is 2.6, V is 1.13g / L; Al is 2.79g / L; Si is 1.00g / L; Fe is 0.98g / L; Mg is 0.67g / L; K is 0.90g / L; Na is 0.75g / L; Ca is 0.85g / L; Mn is 0.01g / L; As is 0.01g / L.

[0039] 15% Cyanex272 + 5% TBP + 80% sulfonated kerosene was used as the extractant, O / A = 3:4, and the extraction was performed at 40°C for 4 minutes. The aqueous phase was subjected to 7-stage countercurrent extraction to obtain a loaded organic phase and a raffinate, and the vanadium extraction rate was 99.43%. Further stripping was performed with 3 mol / L H2SO4 stripping agent, the stripping phase ratio O / A = 1:1, the stripping time was 15 minutes, and the loaded organic phase was subjected to 4-stage countercurrent stripping at room temperature to obtain an unloaded organic phase and a stripping aqueous phase, and the vanadium stripping rate was 99.06%.

[0040] The stripping water phase is introduced into an electrolytic cell for electrolysis, and reduction electrolysis is performed for a certain period of time to obtain a 3.5-valent vanadium electrolyte.

[0041] The vanadium electrolyte prepared in this embodiment is measured by ICP: V concentration is about 2.1 mol / L; Al is 28 mg / L; Si is 4.1 mg / L; Fe is 20 mg / L; Mg is 3.1 mg / L; K is 4.5 mg / L; Na is 7.1 mg / L; Ca is 3.2 mg / L; other metal ions are less than 1 mg / L. The composition meets the requirements of the first-grade product of all-vanadium redox flow battery electrolyte in the national standard (GB / T-37204-2018).

[0042] The vanadium electrolyte in this embodiment is 40 mA / cm 2 The battery was tested for 50 cycles of charge and discharge at the current density: the average coulomb efficiency was 92.24%; the voltage efficiency was 91.67%; and the energy efficiency was 87.65%.

[0043] Example 4

[0044] A vanadium-extracting electrolyte for stone coal and a preparation method thereof. The specific steps of the preparation method described in this embodiment are:

[0045] In a non-oxidizing atmosphere, a boiling furnace is used to decarbonize the carbonaceous slate vanadium ore for power generation, and then the ash after stone coal decarbonization power generation is used as the leaching ore, 10% sulfuric acid + 10% hydrochloric acid are added, the liquid-solid ratio is 2:1, and the flue gas (including SO2) produced by the decarbonization combustion of the vanadium ore is introduced. The pH value of the leaching mother liquor is 2.0, V is 3.62g / L; Al is 3.65g / L; Si is 1.65g / L; Fe is 1.79g / L; Mg is 1.23g / L; K is 1.08g / L; Na is 1.27g / L; Ca is 1.45g / L; Mn is 0.05g / L; As is 0.03g / L.

[0046] 15% P507 + 5% TBP + 80% sulfonated kerosene was used as the extractant, O / A = 1:2, and the extraction was performed at 25°C for 10 minutes. The aqueous phase was subjected to 5-stage countercurrent extraction to obtain a loaded organic phase and a raffinate, and the vanadium extraction rate was 98.85%. Further, 4 mol / L H2SO4 was used as the stripping agent, the stripping phase ratio was O / A = 1:1, the stripping time was 20 minutes, and the loaded organic phase was subjected to 5-stage countercurrent stripping at room temperature to obtain an unloaded organic phase and a stripping aqueous phase, and the vanadium stripping rate was 99.15%.

[0047] The stripping water phase is introduced into an electrolytic cell for electrolysis, and reduction electrolysis is performed for a certain period of time to obtain a 3.5-valent vanadium electrolyte.

[0048] The vanadium electrolyte prepared in this embodiment is measured by ICP: V concentration is about 1.8 mol / L; Al is 21 mg / L; Si is 2.8 mg / L; Fe is 16 mg / L; Mg is 1.3 mg / L; K is 4.2 mg / L; Na is 7.8 mg / L; Ca is 3.1 mg / L; other metal ions are less than 1 mg / L. The composition meets the requirements of the first-grade product of all-vanadium redox flow battery electrolyte in the national standard (GB / T-37204-2018).

[0049] The vanadium electrolyte in this embodiment is 40 mA / cm 2 The battery was tested for 40 cycles of charge and discharge at the current density: the average coulomb efficiency was 92.35%; the voltage efficiency was 92.57%; and the energy efficiency was 88.27%.

[0050] Example 5

[0051] A vanadium-extracting electrolyte for stone coal and a preparation method thereof. The specific steps of the preparation method described in this embodiment are:

[0052] In a non-oxidizing atmosphere, a boiling furnace is used to decarbonize the carbonaceous slate vanadium ore for power generation, and then the ash after stone coal decarbonization power generation is used as the leaching ore, 10% sulfuric acid + 10% hydrochloric acid are added, the liquid-solid ratio is 2:1, and the flue gas (including SO2) produced by the decarbonization combustion of the vanadium ore is introduced. The pH value of the leaching mother liquor is 2.0, V is 1.95g / L; Al is 4.73g / L; Si is 1.86g / L; Fe is 1.28g / L; Mg is 1.07g / L; K is 1.24g / L; Na is 0.84g / L; Ca is 0.57g / L; Mn is 0.03g / L; As is 0.03g / L.

[0053] 15% P204+5% TBP+80% sulfonated kerosene was used as the extractant, O / A=1:2, and the extraction was performed at 35℃ for 4min. The aqueous phase was subjected to 7-stage countercurrent extraction to obtain a loaded organic phase and a raffinate, and the vanadium extraction rate was 99.45%. Further, 1mol / L H2SO4 was used as the stripping agent for stripping, the stripping phase ratio was O / A=3:4, the stripping time was 10min, and the loaded organic phase was subjected to 3-stage countercurrent stripping at room temperature to obtain an unloaded organic phase and a stripping aqueous phase, and the vanadium stripping rate was 97.65%.

[0054] The stripping water phase is introduced into an electrolytic cell for electrolysis, and reduction electrolysis is performed for a certain period of time to obtain a 3.5-valent vanadium electrolyte.

[0055] The vanadium electrolyte prepared in this embodiment is measured by ICP: V concentration is about 1.9 mol / L; Al is 30 mg / L; Si is 5.0 mg / L; Fe is 19 mg / L; Mg is 3.4 mg / L; K is 3.6 mg / L; Na is 9.0 mg / L; Ca is 5.3 mg / L; other metal ions are less than 1 mg / L. The composition meets the requirements of the first-class all-vanadium redox flow battery electrolyte in the national standard (GB / T-37204-2018).

[0056] The vanadium electrolyte in this embodiment is 40 mA / cm 2 The battery was tested for 50 cycles of charge and discharge at the current density: the average coulomb efficiency was 90.78%; the voltage efficiency was 89.85%; and the energy efficiency was 85.93%.

Claims

1. A high-purity vanadyl sulfate electrolyte and its preparation method and use, characterized in that: A high-purity vanadium sulphate electrolyte is obtained from vanadium-containing stone coal ore through decarbonization, power generation, leaching, reduction extraction, stripping and electrolysis.

2. A high-purity vanadyl sulfate electrolyte, its preparation method and use according to claim 1, characterized in that: The stone coal used is a carbonaceous slate-type vanadium ore. The main chemical components of the ore are SiO2, C, Al2O3, Fe2O3, FeS2, etc., and their total content is greater than 80%. Among them, the general content of SiO2 is 40% to 80%, the content of Al2O3 is 6% to 10%, the content of Fe2O3 is 6% to 10%, and the content of C is 3% to 22%.

3. A high-purity vanadyl sulfate electrolyte, its preparation method and use according to claim 1, characterized in that: Pretreatment of ore, decarbonization and power generation: While making full use of the thermal energy of high-carbon stone coal, the ore is decarbonized and burned in a non-oxidizing atmosphere, which also promotes the conversion of V(III) into V(IV) and facilitates the leaching of vanadium; the generated SO2 is used to reduce V(V) to V(IV).

4. A high-purity vanadyl sulfate electrolyte, its preparation method and use according to claim 1, characterized in that: The stone coal ash residue from decarbonization power generation is used as the solid phase. The liquid-solid ratio selected for the leaching process is 2:

1. 10% sulfuric acid + 10% hydrochloric acid are added. The leaching time is about 3 hours. Under normal temperature conditions, continuous leaching is carried out to control the vanadium leaching rate to be greater than 90%.

5. A high-purity vanadyl sulfate electrolyte, its preparation method and use according to claim 1, characterized in that: In the extraction process, the decarbonized power generation stone coal mixed acid leaching liquid is reduced by the flue gas (containing SO2) produced in the decarbonization process to obtain an extractant with a pH value of 1.8 to 2.6, containing 1.0 to 5 g / L vanadium, 2.0 to 4 g / L Al, 0.5 to 5 g / L Fe, 0.5 to 1.5 g / L Si, and other metal impurities less than 1.0 g / L.

6. A high-purity vanadyl sulfate electrolyte, its preparation method and use according to claim 5, characterized in that: The extractant of the extraction process is one of P204 (bis(2-ethylhexyl) phosphate) / P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) / Cyanex272 (bis(2,4,4-trimethylpentyl)phosphonic acid), the additive is tributyl phosphate (TBP), and the diluent is sulfonated kerosene.

7. A high-purity vanadyl sulfate electrolyte, its preparation method and use according to claim 5, characterized in that: The composition of the extractant organic phase is 15% P204 (bis (2-ethylhexyl) phosphate) / P507 (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) / Cyanex272 (bis (2,4,4-trimethylpentyl) phosphonic acid) + 5% TBP + 80% sulfonated kerosene, O / A = 1-5:4, extraction is carried out at 25-50°C for 4-10 minutes, and the aqueous phase is subjected to 5-7 levels of countercurrent extraction to obtain a loaded organic phase and a raffinate.

8. A high-purity vanadyl sulfate electrolyte, its preparation method and use according to claim 1, characterized in that: The concentration of the stripping agent H2SO4 solution is 1-5 mol / L, the stripping phase ratio O / A=3:1-5, and the stripping time is 10-20 min. The loaded organic phase is subjected to 3-5 stages of countercurrent stripping at room temperature to obtain an unloaded organic phase and stripping water.

9. A high-purity vanadyl sulfate electrolyte, its preparation method and use according to claim 1, characterized in that: The vanadium-containing aqueous solution obtained by direct electrolysis stripping is subjected to a specific period of time to obtain a 3.5-valent vanadium electrolyte.

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