A method for preparing vanadium electrolyte by extracting vanadium without ammonium and liquid circulation, and vanadium electrolyte

Abstract

The present invention provides a method and use of preparing vanadium electrolyte by extracting vanadium without ammonium and liquid circulation, and the method of preparing vanadium electrolyte by extracting vanadium without ammonium and liquid circulation comprises the following steps: step 1, sodium roasting; step 2, leaching and filtration; step 3, acidification and impurity removal; step 4, reduction; step 5, extraction-stripping and vanadium extraction; step 6, cooling and crystallization; step 7, valence state adjustment of vanadium electrolyte. The vanadium-containing raw materials of the present invention include but are not limited to stone coal, vanadium slag, and vanadium-titanium magnetite. The method of preparing vanadium electrolyte by extracting vanadium without ammonium and liquid circulation of the present invention has the advantages of short production process, low energy consumption, and no wastewater discharge, and can achieve the effect of green and efficient vanadium extraction, providing support for China's goal of achieving carbon neutrality.

Description

Technical Field

[0001] The invention relates to vanadium electrolyte technology, and in particular to a method for preparing vanadium electrolyte by extracting vanadium without ammonium through liquid circulation, and the vanadium electrolyte. Background Art

[0002] Currently, vanadium-titanium magnetite is the main source of vanadium, and its original content is less than 1%. After the steelmaking process, iron is refined and vanadium is enriched in the slag. The V2O5 content is increased to more than 8%, which can be used as a source of vanadium in the vanadium chemical industry. Petroleum contains a small amount of vanadium. After combustion or gasification decarbonization, vanadium is enriched. Usually, the vanadium content in the combustion ash can reach more than 5%.

[0003] The traditional vanadium extraction process is sodium roasting, neutralization and impurity removal, ammonium salt precipitation to obtain ammonium vanadate, and then high-temperature calcination or melt casting to obtain vanadium pentoxide or flake vanadium. Ammonium salts are required in this process, so a large amount of wastewater containing ammonium and sodium is generated during the vanadium extraction process. It needs to be deammonized by adding alkali at high temperature, and then evaporated and dried at high temperature to obtain sodium sulfate crystals. A large amount of flake caustic soda and steam are consumed during ammonium evaporation, which is costly and causes serious environmental pollution. A large amount of energy is consumed during the evaporation and crystallization of sodium sulfate solution.

[0004] At present, the main process of vanadium electrolyte is to prepare raw materials with high impurity content such as ammonium metavanadate, red vanadium, and ammonium polyvanadate from raw materials, then dissolve them with alkali, remove impurities, add ammonium salt to precipitate vanadium, obtain high-purity vanadium compounds, and then obtain vanadium oxides through high-temperature calcination, and further obtain vanadium electrolyte through dissolution-reduction. Obviously, this method has many processes, is time-consuming, consumes a lot of energy, and puts great pressure on the environment. In order to meet the demand for vanadium electrolyte, it is urgent to find a simple and low-cost electrolyte production process. Summary of the invention

[0005] The purpose of the present invention is to propose a method for preparing vanadium electrolyte by ammonium-free, liquid circulation vanadium extraction, in response to the problems existing in the current production of vanadium electrolyte. This method has the advantages of short production process, low energy consumption, and no wastewater discharge. It can achieve the effect of green and efficient vanadium extraction, and provide support for China's goal of achieving carbon neutrality.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing vanadium electrolyte by ammonium-free, liquid circulation vanadium extraction, comprising the following steps:

[0007] Step 1: Sodium roasting

[0008] Mix sodium carbonate and vanadium-containing raw materials (such as crushed steel slag) evenly, put them into a furnace, and oxidize and calcine them at high temperature to convert vanadium into water-soluble sodium vanadate;

[0009] Step 2: Leaching and filtration

[0010] The material obtained by calcining in step 1 is dissolved in water or the crystallization mother liquor in step 6 for leaching, and filtered to obtain sodium vanadate leaching solution and waste residue;

[0011] Step 3: Acidification and impurity removal

[0012] Adding acid to neutralize the sodium vanadate solution and remove the main impurities by precipitation, including but not limited to silicon, aluminum and chromium; continuing to add acid for acidification;

[0013] Step 4: Restore

[0014] Reducing vanadium to tetravalent vanadium to obtain a mixed solution of tetravalent vanadium (such as vanadyl sulfate) and sodium sulfate;

[0015] Step 5: Extraction-stripping of vanadium

[0016] A stabilizer is added to the mixed solution, and an organic phase is used as an extractant and an acid is used as a stripping agent to perform a liquid-liquid extraction-stripping method to obtain an acid solution of tetravalent vanadium and a raffinate containing sodium sulfate;

[0017] Step 6: Cooling and crystallization

[0018] The raffinate is cooled, stirred for crystallization, and filtered to obtain sodium sulfate crystals and a crystallization mother liquor, and the crystallization mother liquor is returned to step 2;

[0019] Step 7: Adjustment of valence state of vanadium electrolyte

[0020] Using a reducing agent or an electrolytic device, the acid solution of tetravalent vanadium (vanadium oxydichloride and / or vanadyl sulfate) obtained in step 5 is used to reduce the average valence state of vanadium to a desired valence state; the desired valence state is +3 to +4.

[0021] Furthermore, the vanadium-containing raw materials include but are not limited to stone coal, vanadium slag, and vanadium-titanium magnetite. The particle size of the vanadium-containing raw materials is less than 300um.

[0022] Furthermore, in step 1, the mass ratio of sodium carbonate to vanadium in the vanadium-containing raw material is 1-5:1, and the preferred mass ratio is 3-5:1.

[0023] Furthermore, the high temperature oxidation calcination in step 1 is carried out at 700-1000°C for 1-24 hours. The preferred high temperature oxidation calcination is carried out at 800-900°C in an air atmosphere for 6-12 hours.

[0024] Furthermore, the liquid-to-solid ratio of the leaching in step 2 is 1-10:1, and the preferred liquid-to-solid ratio is 3-8:1.

[0025] Furthermore, the acid in step 3 is a mixture of one or more of sulfuric acid, phosphoric acid and hydrochloric acid. The pH of the acid addition end point in step 3 is 1-4, and the stirring reaction time is 0.5-10h.

[0026] Furthermore, in step 4, the reduction electrolysis current is reduced or a reducing agent is added, and the reducing agent is one or a combination of several of sulfur dioxide, glucose, sucrose, citric acid, oxalic acid, iron powder, aluminum powder, zinc powder, hydrazine hydrate and VC.

[0027] Furthermore, the stabilizer described in step 5 is a mixture of one or more of phosphoric acid, monohydrogen phosphate, dihydrogen phosphate, metaphosphate, and pyrophosphate; after adding the stabilizer, the stability of the solution can be improved, precipitation can be prevented, and a third phase can be generated, which makes it difficult to separate the organic phase from the aqueous phase.

[0028] Furthermore, the extractant in step 5 is one or a mixture of bis(2-ethylhexyl) phosphate (P204), P507, N263, and N235. The stripping agent in step 5 is one or a mixture of sulfuric acid, phosphoric acid, hydrochloric acid, pyrophosphoric acid, metaphosphoric acid, methanesulfonic acid, and aminomethanesulfonic acid. The ratio of the amount of the stripping agent to the amount of vanadium is 1 to 5:1, and the preferred mass ratio is 3-5:1.

[0029] Furthermore, the cooling temperature in step 6 is <40°C.

[0030] Furthermore, the method for reducing the average valence of vanadium in step 7 is to reduce vanadium by electrolytic reduction; the other is to add a reducing agent, wherein the reducing agent is a mixture of one or more of glucose, citric acid, oxalic acid, sulfur dioxide, V2O3, vanadium sulfate or hydrazine hydrate.

[0031] Another object of the present invention is to disclose a vanadium electrolyte prepared by the above method.

[0032] Another object of the present invention is to disclose a method for preparing vanadium electrolyte by extracting vanadium without ammonium and by circulating solution, and its application in the field of directly extracting vanadium from vanadium-containing raw materials to produce vanadium electrolyte.

[0033] The working principle of the method for preparing vanadium electrolyte by ammonium-free double-circulation vanadium extraction of the present invention is as follows:

[0034] (1) No ammonium means that no ammonium salt is used in the vanadium extraction process. The extraction method is used instead of the ammonium salt precipitation method, which can save the cost of ammonium salt and the evaporation cost of ammonium in wastewater;

[0035] (2) Solution circulation process refers to the circulation of sodium salt solution in the vanadium extraction process. The sodium salt is continuously enriched. After reaching a certain concentration, sodium sulfate crystals are obtained through cooling and crystallization. The energy consumption is significantly reduced compared with evaporation crystallization, and no wastewater is discharged during the vanadium extraction process.

[0036] (3) Acidification and reduction process to remove the main impurities in the solution to obtain a purified vanadyl sulfate / sodium sulfate solution;

[0037] (4) The reduction-liquid-liquid extraction process can produce a tetravalent vanadium solution in one step, which can be further reduced by chemical reduction or electrolytic reduction to obtain a vanadium electrolyte with a qualified valence state.

[0038] The method for preparing vanadium electrolyte by ammonium-free double-circulation vanadium extraction and its use in the present invention have the following advantages compared with the prior art:

[0039] 1) The liquid-liquid extraction method is used instead of the ammonium salt vanadium precipitation process to achieve impurity separation and vanadium purification, avoiding the use of ammonium salts and subsequent ammonium removal operations, significantly reducing costs and environmental pollution;

[0040] 2) Directly extract vanadium from the raw material leaching solution to make a tetravalent vanadium acid solution, and then obtain the electrolyte through electrolysis, which greatly simplifies the production process of the electrolyte, significantly reduces the cost and shortens the time;

[0041] 3) By adopting a solution circulation system, sodium is enriched during the vanadium extraction process. After reaching a certain concentration, sodium sulfate crystals are obtained through cooling and crystallization, which replaces the traditional evaporation crystallization process. This can significantly reduce energy consumption and there is no wastewater discharge during the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A process flow for preparing vanadium electrolyte for ammonium-free, liquid circulation vanadium extraction;

[0043] Figure 2 is the charge and discharge cycle curve of the electrolyte. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with embodiments:

[0045] Example 1

[0046] This embodiment discloses a method for preparing a vanadium electrolyte by extracting vanadium without ammonium and by liquid circulation, comprising the following steps:

[0047] 1. Use sodium carbonate and vanadium in vanadium slag (V 8.3%wt) in a ratio of 1:1, calcine at 850℃ for 12h in air atmosphere, and the calcined product is clinker;

[0048] 2. Leach the clinker with water or the crystallization mother liquor of step 6 at a liquid-to-solid ratio of 4:1 to obtain a vanadium slag leachate containing 31 g / L of V;

[0049] 3. Add sulfuric acid to acidify to pH 2, maintain the temperature at 80°C, and continue stirring;

[0050] 4. Add sulfur dioxide until the solution turns pure blue;

[0051] 5. Add 1g / L phosphoric acid as a stabilizer; use di(2-ethylhexyl) phosphate (P204) as an extractant, adjust the pH value with sodium hydroxide, and extract vanadium into the organic phase; use a mixture of dilute sulfuric acid and phosphoric acid as a stripping agent until the V2O5 concentration reaches 150g / L;

[0052] 6. Cool the raffinate to 25°C, crystallize to obtain sodium sulfate crystals, and return the crystallization mother liquor to step 2;

[0053] 7. Use an electrolytic device to reduce vanadium to a valence of 3.5 to obtain a sulfur-phosphorus mixed acid vanadium electrolyte.

[0054] Compared with the traditional process of extracting vanadium to prepare electrolyte, in this embodiment, water circulates in the system without evaporation and crystallization, avoiding the addition of ammonium sulfate and the liquid alkali and steam required for deammoniation of wastewater. A rough calculation shows that the cost saved is about 28,000 yuan / tV2O5, which is equivalent to a saving of 4,200 yuan / m³ per cubic meter of electrolyte.

[0055] The comparison of the cycle efficiency of the sulfur-phosphorus mixed acid vanadium electrolyte of the present invention and the control electrolyte is shown in the figure Figure 2 As shown in the figure, CE is current efficiency, EE is energy efficiency, and VE is voltage efficiency; it can be seen from the figure that the performance of the sulfur-phosphorus mixed acid vanadium electrolyte of the present invention is not significantly different from that of the control standard electrolyte, and the performance is excellent. The standard electrolyte is processed by conventional process: ammonium metavanadate raw material---removal of impurities (complexation to remove impurities)---1000 degrees calcination---generation of V2O5---processing and preparation of electrolyte, and the electrolyte parameters are 1.6mol / L vanadium ion and 4.2mol / L sulfuric acid.

[0056] Example 2

[0057] This embodiment discloses a method for preparing a vanadium electrolyte by extracting vanadium without ammonium and by liquid circulation, comprising the following steps:

[0058] 1. Using sodium carbonate and vanadium in petroleum fly ash (V 16.6%wt) in a ratio of 2:1, calcining at 900°C for 6h in air atmosphere, the calcined product is clinker;

[0059] 2. Leach the clinker with water at a liquid-to-solid ratio of 4:1 to obtain a vanadium slag leachate containing 40 g / L of V;

[0060] 3. Add sulfuric acid to acidify to pH 1.5, maintain the temperature at 90°C, and continue stirring;

[0061] 4. According to the amount of vanadium, add citric acid with the amount of 1 / 16 vanadium, and continue to stir the reaction until the solution turns pure blue;

[0062] 5. Add 2g / L metaphosphoric acid as a stabilizer; use 2-ethylhexyl phosphate (P507) as an extractant, adjust the pH value with sodium hydroxide, and extract vanadium into the organic phase; use a mixed solution of 8mol / L hydrochloric acid and 0.1mol / L phosphoric acid as a stripping agent, and repeatedly strip until the V2O5 concentration reaches 100g / L;

[0063] 6. Cool the raffinate to 10°C, crystallize to obtain sodium sulfate crystals, and return the crystallization mother liquor to step 2;

[0064] 7. Add V2O3 to adjust the average valence of vanadium in the stripping solution obtained in step 5 to 3.5, and obtain a vanadium hydrochloride electrolyte.

[0065] Example 3

[0066] This embodiment discloses a method for preparing a vanadium electrolyte by extracting vanadium without ammonium and by liquid circulation, comprising the following steps:

[0067] The ratio of sodium carbonate to vanadium in petroleum gasification coke slag (V 3.2%) is 5:1, calcined at 700℃ for 24h in air atmosphere, and the calcined product is clinker;

[0068] The clinker was leached with water at a liquid-to-solid ratio of 2:1 to obtain a vanadium slag leaching solution containing 70 g / L of V;

[0069] Add sulfuric acid to acidify to pH 2, maintain the temperature at 90°C, and continue stirring;

[0070] Add zinc powder according to the amount of vanadium, continue stirring the reaction until the solution turns pure blue, and filter out the residual zinc powder;

[0071] 3.5 g of sodium dihydrogen phosphate was added as a stabilizer; di(2-ethylhexyl) phosphate (P204) was used as an extractant, and the pH value was adjusted with sodium hydroxide to extract the vanadium into the organic phase; methanesulfonic acid was used as a stripping agent, and the extraction was repeated until the vanadium concentration reached 100 g / L;

[0072] Cool the raffinate to 20°C, crystallize to obtain sodium sulfate crystals, and return the crystallization mother liquor to step 2;

[0073] Vanadium sulfate (V2(SO4)3) is added to adjust the average valence of vanadium in the stripping solution obtained in step 4 to 3.5 to obtain a vanadium electrolyte.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing vanadium electrolyte by ammonium-free, liquid circulation vanadium extraction, characterized in that: The following steps are involved: Step 1: Sodium roasting The sodium carbonate and the vanadium-containing raw material are mixed evenly, put into a furnace, and subjected to high-temperature oxidation calcination to convert the vanadium into water-soluble sodium vanadate; the mass ratio of the sodium carbonate to the vanadium in the vanadium-containing raw material is 1-5:1; the conditions of the high-temperature oxidation calcination are 700-1000°C and the time is 1-24h; the vanadium-containing raw material is stone coal, vanadium slag or vanadium-titanium magnetite, and the particle size of the vanadium-containing raw material is less than 300μm; Step 2: Leaching and filtration The material obtained by calcining in step 1 is dissolved in water or the crystallization mother liquor in step 6 for leaching, and filtered to obtain sodium vanadate leaching solution and waste residue; Step 3: Acidification and impurity removal Add acid to neutralize the sodium vanadate solution and remove the main impurity precipitation, and continue to add acid for acidification; Step 4: Restore Reducing vanadium to tetravalent vanadium to obtain a mixed solution of tetravalent vanadium and sodium sulfate; the reduction is electrolytic current reduction or adding a reducing agent, and the reducing agent is one or a combination of sulfur dioxide, glucose, sucrose, citric acid, oxalic acid, iron powder, aluminum powder, zinc powder, hydrazine hydrate and VC; Step 5: Extraction-stripping of vanadium A stabilizer is added to the mixed solution, and an organic phase is used as an extractant and an acid is used as a stripping agent to perform a liquid-liquid extraction-stripping method to obtain a tetravalent vanadium acid solution and a raffinate containing sodium sulfate; the stabilizer is a mixture of one or more of phosphoric acid, monohydrogen phosphate, dihydrogen phosphate, metaphosphate, and pyrophosphate; Step 6: Cooling and crystallization The raffinate is cooled, stirred for crystallization, and filtered to obtain sodium sulfate crystals and a crystallization mother liquor, and the crystallization mother liquor is returned to step 2; Step 7: Adjustment of valence state of vanadium electrolyte Using a reducing agent or an electrolytic device, the acid solution of the tetravalent vanadium obtained in step 5 is used to reduce the average valence of vanadium to a desired valence; the desired valence is +3~+4; the method for reducing the average valence of vanadium is to reduce vanadium by electrolytic reduction; the other method is to add a reducing agent, wherein the reducing agent is a mixture of one or more of glucose, citric acid, oxalic acid, sulfur dioxide, V2O3, vanadium sulfate or hydrazine hydrate.

2. The method for preparing vanadium electrolyte by ammonium-free and liquid circulation vanadium extraction according to claim 1, characterized in that: The vanadium-containing raw material is a mixture of one or more of stone coal, vanadium slag and vanadium-titanium magnetite.

3. The method for preparing vanadium electrolyte by ammonium-free and liquid circulation vanadium extraction according to claim 1, characterized in that: The acid in step 3 is a mixture of one or more of sulfuric acid, phosphoric acid and hydrochloric acid.

4. The method for preparing vanadium electrolyte by ammonium-free and liquid circulation vanadium extraction according to claim 1, characterized in that: In step 5, the extractant is one of bis(2-ethylhexyl) phosphate, P507, N263, and N235; the stripping agent is one of sulfuric acid, phosphoric acid, hydrochloric acid, pyrophosphoric acid, metaphosphoric acid, methanesulfonic acid, and aminomethanesulfonic acid, or a mixture thereof, and the ratio of the amount of the stripping agent to the amount of vanadium is 1 to 5:

1.

5. Use of the method for preparing vanadium electrolyte by extracting vanadium without ammonium and by solution circulation as claimed in any one of claims 1 to 4 in the field of directly extracting vanadium from vanadium-containing raw materials to produce vanadium electrolyte.

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