A method for preparing high-purity VOSO4 electrolyte

Abstract

The application relates to a high-purity VOSO4 electrolyte preparation method and relates to the technical field of vanadium compound production. The short-process technology of medium-temperature ignition, low-temperature chlorination, rectification and acidification reduction is used to efficiently extract vanadium from vanadium-containing stone coal, and the technical effect of low energy consumption and almost no pollution is realized; the process also has the characteristics of simple separation method, no need of complex extraction, high product purity, good electrolyte performance and the like, and has the advantages of short process, low energy consumption and near-zero pollution, and opens up a new way for clean production of vanadium resources.

Description

Technical Field

[0001] This invention relates to the field of vanadium compound production technology, and in particular to a method for preparing high-purity VOSO4 electrolyte. Background Technology

[0002] Vanadium redox flow batteries (VRFBs), with their advantages of high safety, long cycle life, and independent design of power and capacity, have become one of the core technologies supporting large-scale grid connection and long-term energy storage of renewable energy sources such as wind and solar power. Vanadium electrolyte, as the active material of VRFBs, directly determines the battery's energy efficiency, cycle life, and operational reliability due to its purity, concentration, and stability. Currently, vanadium oxysulfate (VOSO4) electrolyte is commonly used in industry. The traditional preparation route involves first producing high-purity vanadium pentoxide (V2O5) from vanadium-containing resources (such as coal shale and vanadium slag), then dissolving V2O5 in sulfuric acid and obtaining a VOSO4 solution through chemical reduction or electrolytic reduction. This process is lengthy, energy-intensive, and highly polluting, severely restricting the cost reduction, efficiency improvement, and large-scale application of VRFBs.

[0003] Vanadium-bearing coal is a unique low-grade vanadium resource in my country, with a V2O5 content typically less than 1%, and containing a large amount of complex components such as silicon, aluminum, iron, and carbon. Extracting vanadium from coal shale and preparing high-purity electrolytes faces three major technical challenges: First, vanadium is encased in a stable aluminosilicate mineral lattice, which is difficult to dissociate using traditional physical beneficiation methods. High-temperature roasting is required to break the lattice, but conventional sodium or calcination roasting produces toxic and harmful gases such as hydrogen chloride, chlorine, and sulfur dioxide, and consumes extremely high amounts of energy. Second, coal shale contains a wide variety and high concentration of impurities. During leaching, vanadium enters the solution simultaneously with elements such as iron, aluminum, and phosphorus. Subsequent purification requires multi-stage extraction, ion exchange, or chemical precipitation, which is not only complex but also generates large amounts of acidic wastewater, waste residue, and organic extractant losses. Third, there is a serious contradiction between vanadium extraction rate and product purity—increasing the extraction rate often means extracting more impurities, while pursuing high purity requires sacrificing the extraction rate or adding purification steps, resulting in high overall recovery costs.

[0004] To address the aforementioned issues, several improvements have been proposed in existing technologies. For example, Chinese patent application CN201010105798 employs bioleaching technology, using bacterial oxidation to dissolve vanadium from the ore, thus avoiding waste gas pollution from roasting. However, the bioleaching cycle can take several days or even weeks and is extremely sensitive to conditions such as the sulfur content, particle size, and slurry concentration of the ore. When processing low-sulfur coal, the leaching efficiency drops sharply, failing to meet the efficiency and stability requirements of industrial production. Another example is Chinese patent application CN202510109635, which discloses a short-process method for preparing high-purity vanadium oxysulfate solution. This method directly obtains VOSO4 solution through a combination of aging leaching and two-stage extraction, eliminating the need for neutralization and vanadium precipitation steps. However, this method still cannot eliminate the use of strong acids (sulfuric acid, hydrochloric acid), and the leaching process generates a large amount of acidic wastewater. The extraction section relies on organic extractants (such as P2O4, TBP, etc.), and although a washing and recovery process is set up, organic phase loss is still unavoidable, which not only increases operating costs, but also brings additional environmental pressure and safety risks to the treatment of organic waste liquid. In addition, although the high-temperature chlorination method (using chlorine gas at temperatures above 400°C to convert vanadium into volatile vanadium trichloride oxychloride VOCl3) can achieve gas phase separation, chlorine gas is a highly toxic and corrosive gas, which places extremely high demands on the equipment materials. Moreover, at high temperatures, impurities such as iron, aluminum, and silicon in coal shale will also generate volatile chlorides, leading to a decrease in the purity of VOCl3 product. The exhaust gas treatment system is complex and large, and the investment and operating costs are unacceptable.

[0005] In summary, existing technologies have consistently failed to resolve the fundamental contradiction in the efficient, clean, and streamlined preparation of high-purity vanadium electrolyte from complex vanadium-bearing coal: wet methods rely on strong acids and organic extractants, generating wastewater and waste residue; pyrometallurgical methods produce toxic gases or rely on highly toxic chlorine; and biological methods are too inefficient. Therefore, there is an urgent need to develop a novel vanadium extraction and electrolyte preparation technology that combines high extraction rate, high product purity, streamlined process, low energy consumption, and near-zero emissions. Summary of the Invention

[0006] This application provides a method for preparing high-purity VOSO4 electrolyte, which solves the problems existing in the prior art.

[0007] This application provides a method for preparing a high-purity VOSO4 electrolyte, including the following steps:

[0008] S1: After crushing and grinding the vanadium-containing coal ore, pass it through a 200-mesh sieve to obtain raw material powder, and dry it at 100℃-120℃;

[0009] S2: Mix the dried raw material powder with anthracite, control the calorific value of the mixture to be 2000 kcal / kg-4500 kcal / kg, and ignite it at 500℃-650℃ in air or oxygen atmosphere with an oxygen partial pressure of 12%-21% using electric heating wire or plasma ignition. After the system temperature reaches 700℃-900℃, keep it at that temperature for 3-5 hours.

[0010] S3: Grind the ignited clinker again, add anhydrous aluminum chloride and mix evenly. The mass ratio of vanadium-containing coal to anhydrous aluminum chloride is 5:1-30:1. Chlorinate and roast at 150℃-200℃ for 1-2 hours under nitrogen or argon protection to generate gaseous VOCl3.

[0011] S4: The generated mixed vapor is fed into a three-stage condensation unit. The first stage uses heat transfer oil to condense and remove high-boiling-point impurities at 150℃-180℃. The second stage uses a distillation column to condense and collect VOCl3 liquid at 65℃-90℃, controlling the reflux ratio to be 25:1-40:1. The third stage uses calcium chloride aqueous solution to condense and capture residual VOCl3 at -20℃. The tail gas is discharged after being absorbed by alkaline solution.

[0012] S5: Add 98% sulfuric acid to the collected VOCl3 liquid to adjust the pH to 1-3, then add oxalic acid and stir until the solution turns clear blue to obtain VOSO4 electrolyte.

[0013] Furthermore, the calorific value of the mixture in step S2 is 2500 kcal / kg-3500 kcal / kg.

[0014] Furthermore, in step S2, the initial ignition temperature is 600℃-650℃, and the heat preservation temperature is 800℃-900℃.

[0015] Furthermore, in step S3, anhydrous aluminum chloride is used as the chlorinating agent, and the chlorination roasting temperature is 150℃-180℃.

[0016] Furthermore, in step S3, the mass ratio of vanadium-containing coal to anhydrous aluminum chloride is 12:1-20:1.

[0017] Furthermore, the reflux ratio of the second-stage distillation in step S4 is 30:1-40:1.

[0018] Furthermore, the third-stage condensation temperature in step S4 is -20°C to -10°C.

[0019] Furthermore, in step S5, 98% sulfuric acid is used to ensure that the pH value of the system is between 1 and 3, and oxalic acid is used as a reducing agent to stir until it turns into a clear blue color.

[0020] Furthermore, the V2O5 content in the vanadium-bearing coal is 0.5%-1.5%.

[0021] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0022] By using medium-temperature ignition to disrupt the crystal structure of vanadium-containing minerals, the encapsulated vanadium is fully exposed and oxidized to V2O5. Combined with a low-temperature chlorination process, V2O5 is selectively converted into gaseous VOCl3, achieving a vanadium extraction rate of up to 88.39%, significantly higher than traditional processes.

[0023] Utilizing the characteristic that anhydrous aluminum chloride reacts only with V2O5 to generate gaseous VOCl3 at a low temperature of 150℃-180℃, efficient separation of vanadium from impurities such as iron, aluminum, silicon, and calcium is achieved. Combined with a three-stage condenser distillation unit, the different boiling points of each chloride are used to purify the product step by step. The collected VOCl3 has high purity, the molar ratio of V to Cl is close to 1:3, and the impurity content is negligible.

[0024] VOSO4 electrolyte, prepared by direct conversion of high-purity VOCl3, was tested at 50℃ and 80 mA / cm². 2 At current density, the coulombic efficiency reaches 95%, the voltage efficiency reaches 92%, and the energy efficiency reaches 87.4%, which are significantly better than the traditional V2O5-H2SO4 system (70.7%) and V2O5-HCl-H2SO4 system (74.0%), and the high temperature stability is excellent.

[0025] From vanadium-containing coal to VOSO4 electrolyte, the process eliminates the multiple stages of leaching, extraction, vanadium precipitation, calcination, and dissolution found in traditional processes. It utilizes the carbon combustion of the coal itself for heating, eliminating the need for a continuous external heat source. The chlorination temperature is only 150℃-180℃, resulting in a significant reduction in overall energy consumption.

[0026] The entire process does not use chlorine, strong acid leaching solution or organic extractant, and there is no wastewater or waste residue discharged. The chlorination tail gas is discharged in compliance with standards after being absorbed by alkaline solution. The reaction byproduct Al2O3 residue is non-toxic and harmless and easy to dispose of, achieving green production with near-zero emissions. Attached Figure Description

[0027] Figure 1 This is a flowchart of a method for preparing high-purity VOSO4 electrolyte according to the present invention. Detailed Implementation

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] The method of this invention is not only applicable to vanadium-bearing coal, but also to other secondary resources containing vanadium pentoxide or low-valent vanadium oxide (such as mineral processing tailings and smelting slag). The material ratio, reaction time, and reaction temperature of different materials in the whole process can be appropriately adjusted to adapt to the differences in their chemical composition and mineral structure, but the overall process flow remains consistent.

[0030] The present invention is described below based on embodiments, but the present invention is not limited to these embodiments. In the following detailed description of the present invention, some specific details are described in detail, but well-known methods, processes, procedures, and elements are not described in detail in order to avoid obscuring the essence of the present invention.

[0031] Furthermore, those skilled in the art should understand that the accompanying drawings provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0032] Unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as encompassing rather than being exclusive or exhaustive; that is, meaning "including but not limited to."

[0033] In the description of this invention, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0034] In the description of this invention, "content" refers to a percentage by mass.

[0035] To better explain and facilitate understanding of this invention, the following description is provided in conjunction with the appendix. Figure 1 The present invention will be further described in detail through specific embodiments.

[0036] Example 1:

[0037] The vanadium shale ore used in this experiment came from a mine in Ankang, Shaanxi Province. Its main chemical components were determined by conventional chemical analysis methods to be: SiO2, Al2O3, Fe2O3, CaO, V2O5, Na2O, MgO, Ba, S, P, and C, as shown in Table 1. Non-major components included: K2O, Zn, Co, Ni, W, Cu, Ag, and Au.

[0038] Table 1. Major elemental chemical composition (%) of vanadium-bearing shale ore

[0039]

[0040] Step 1: Grind and crush the raw materials, pass them through a 200-mesh sieve to obtain raw material powder, and then dry them at 100℃.

[0041] Step 2: Mix the processed raw materials with anthracite to prepare a mixed sample A with a calorific value of 3500 kcal / kg. Place sample A in a muffle furnace and ignite it using a heating wire at an ignition temperature of 600℃. Observe the temperature value of the K-type thermocouple. When the temperature reaches 880℃, maintain the temperature for 3 hours.

[0042] Step 3: Grind the oxidized sample A again and mix it with anhydrous aluminum chloride at a mass ratio of 20:1 to obtain sample B. Place sample B in a tube furnace at 165℃ and continuously purge with argon gas for chlorination treatment.

[0043] Step 4: Observe the volume of the yellow liquid in the gas collecting bottle of the second-stage condenser. Stop the experiment when the liquid volume no longer changes. Control the reflux ratio during distillation to 38:1 by adjusting the opening of the outlet valve and reflux valve of the reflux distributor.

[0044] The extraction rate of vanadium is calculated using the following formula:

[0045]

[0046] Where, x i Extraction rate of elements (%); m s The mass (g) of the solid sample used for extraction; w s The content (% or g / t) of the element in the solid sample used for extraction; m t The calculated mass (g) of the extract; w t The value represents the content (% or g / t) of elements in the extract. The final vanadium extraction rate was 88.39%.

[0047] The liquid in the gas collecting bottle was introduced into a beaker to obtain sample C. The concentration of VOCl3 in the sample C solution was quantitatively determined by inductively coupled plasma optical emission spectrometry (ICP-OES), and the purity reached 99.99%, with V and Cl accounting for 29.36% and 61.41%, respectively. The analytical results show that the molar ratio of V to Cl is very close to 3:1, and the content of other impurity elements is almost negligible.

[0048] Step 5: Slowly add concentrated H2SO4 to sample C to adjust the pH to 2-3, and then add oxalic acid and stir until the solution turns clear blue to obtain a 2M electrolyte solution containing VOSO4, which meets the requirements of "Electrolytes for Vanadium Redox Flow Batteries" (GB / T 37204-2018).

[0049] The electrolyte performance was tested, including coulombic efficiency (CE), voltage efficiency (VE), and battery current density at different temperatures (80 mA / cm²). 2 When the temperature increased from 10℃ to 25℃, all three efficiencies significantly improved, with EE increasing from 83% to 86.4%. When the temperature increased from 25℃ to 35℃, EE increased by 1.2%. When the temperature further increased to 50℃, EE increased by only 0.5%, as shown in Table 2.

[0050] Table 2 Electrolyte performance of different systems

[0051]

[0052] As shown in Table 2, the vanadium electrolyte of this research system meets the requirements of the "General Technical Conditions for Vanadium Redox Flow Batteries" (GB / T32509-2025), and its stability significantly surpasses that of traditional systems. Its unique advantage lies in maintaining excellent electrochemical performance even under harsh conditions such as high temperatures. This strong environmental adaptability highlights its advanced nature and reliability compared to traditional electrolytes, providing a solid foundation for it to become a key material for next-generation high-performance battery systems.

[0053] Example 2:

[0054] The raw material of vanadium shale used in this experimental group is the same as that in Example 1.

[0055] Step 1: Grind and crush the raw materials, pass them through a 200-mesh sieve to obtain raw material powder, and then dry them at 100℃.

[0056] Step 2: Mix the processed raw materials with anthracite to prepare a mixed sample A with a calorific value of 2700 kcal / kg. Place sample A in a muffle furnace and ignite it using a heating wire at an ignition temperature of 600℃. Observe the temperature value of the K-type thermocouple. When the temperature reaches 750℃, maintain the temperature for 3 hours.

[0057] Step 3: Grind the oxidized sample A again and mix it with anhydrous aluminum chloride at a mass ratio of 20:1 to obtain sample B. Place sample B in a tube furnace at 165℃ and continuously purge with argon gas for chlorination treatment.

[0058] Step 4: Control the reflux ratio during distillation to 38:1. The final vanadium extraction rate was 72.11%. The purity of the solution was 99.98%.

[0059] Step 5: Slowly add concentrated H2SO4 to sample C to adjust the pH to 2-3, then add oxalic acid and stir until the solution turns clear blue, thus obtaining a 2M electrolyte solution containing VOSO4.

[0060] The final measured electrolyte energy efficiency was 86.5%. Specific parameters are shown in Table 3.

[0061] Table 3 Electrolyte performance of Example 2

[0062]

[0063] Example 3:

[0064] The raw material of vanadium shale used in this experimental group is the same as that in Example 1.

[0065] Step 1: Grind and crush the raw materials, pass them through a 200-mesh sieve to obtain raw material powder, and then dry them at 100℃.

[0066] Step 2: Mix the processed raw materials with anthracite to prepare a mixed sample A with a calorific value of 3500 kcal / kg. Place sample A in a muffle furnace and ignite it using a heating wire at an ignition temperature of 600℃. Observe the temperature value of the K-type thermocouple. When the temperature reaches 880℃, maintain the temperature for 3 hours.

[0067] Step 3: Grind the oxidized sample A again and mix it with anhydrous aluminum chloride at a mass ratio of 20:1 to obtain sample B. Place sample B in a tube furnace at 165℃ and continuously purge with argon gas for chlorination treatment.

[0068] Step 4: Control the reflux ratio during distillation to 28:1.

[0069] The final vanadium extraction rate was 84.92%. The purity of the solution was 99.96%.

[0070] Step 5: Slowly add concentrated H2SO4 to sample C to adjust the pH to 2-3, then add oxalic acid and stir until the solution turns clear blue, thus obtaining a 2M electrolyte solution containing VOSO4.

[0071] The final measured electrolyte energy efficiency was 85.6%. Specific parameters are shown in Table 4.

[0072] Table 4 Electrolyte performance of Example 3

[0073]

[0074] Example 4:

[0075] The vanadium shale ore used in this experiment came from a mine in Huaihua, Hunan Province. Its main chemical components were determined by conventional chemical analysis methods to be: SiO2, Al2O3, CaO, Fe2O3, K2O, Na2O, MgO, Ba, and V, with percentage contents shown in Table 5. Non-main components included: Ti, P, Cr, Cu, Zn, etc.

[0076] Table 5. Major elemental chemical composition (%) of vanadium-bearing shale ore

[0077]

[0078] Step 1: Grind and crush the raw materials, pass them through a 200-mesh sieve to obtain raw material powder, and then dry them at 100℃.

[0079] Step 2: Mix the processed raw materials with anthracite to prepare a mixed sample A with a calorific value of 3500 kcal / kg. Place sample A in a muffle furnace and ignite it using a heating wire at an ignition temperature of 600℃. Observe the temperature value of the K-type thermocouple. When the temperature reaches 880℃, maintain the temperature for 3 hours.

[0080] Step 3: Take the oxidized sample A, grind it again, and mix it with anhydrous aluminum chloride at a mass ratio of 12:1 to obtain sample B. Place sample B in a tube furnace at 165℃ and continuously purge it with argon gas for chlorination treatment.

[0081] Step 4: Control the reflux ratio during distillation to 38:1.

[0082] The final vanadium extraction rate was 74.6%. The purity of the solution was 99.98%.

[0083] Step 5: Slowly add concentrated H2SO4 to sample C to adjust the pH to 2-3, then add oxalic acid and stir until the solution turns clear blue, thus obtaining a 2M electrolyte solution containing VOSO4.

[0084] The final measured electrolyte energy efficiency was 86.5%. Specific parameters are shown in Table 6.

[0085] Table 6 Electrolyte performance of Example 4

[0086]

[0087] Subsequent investigations revealed that operating in high-altitude permafrost regions presents several core challenges for vanadium-bearing garnet-type coal mines. These challenges include extremely low calorific value (<1200 kcal / kg), high lattice energy making crystal destruction difficult, high calcium impurities consuming chlorinating agents, low temperatures causing all wet processes to freeze and fail, and unacceptable energy consumption and severe pollution from traditional roasting methods. The solutions employed included replacing the combustion aid with thermite-grade aluminum powder and nitrates, increasing the ignition oxygen partial pressure to 25%, and raising the peak temperature to 1000℃ to achieve irreversible garnet lattice collapse. Simultaneously, the mass ratio of chlorinating agent (AlCl3) to clinker was adjusted to 10:1, and the chlorination temperature was increased to 180℃ to preferentially consume CaO and fully convert V. By combining the adaptation improvements of adjusting the distillation temperature to 55℃ and increasing the reflux ratio to 45:1 under low pressure, it was finally achieved that the system could start up and operate without any liquid medium or external heat source at -40℃, achieving a vanadium extraction rate of 86.7%, a VOCl3 purity of 99.97%, zero wastewater discharge, and a battery energy efficiency of 88.1% (50℃). This achieved a green, efficient, and short-process vanadium extraction effect that existing technologies (acid leaching, high-temperature chlorination, biological methods, etc.) could not achieve under this extreme scenario.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-purity VOSO4 electrolyte, characterized in that, Includes the following steps: S1: After crushing and grinding the vanadium-containing coal ore, pass it through a 200-mesh sieve to obtain raw material powder, and dry it at 100℃-120℃; S2: Mix the dried raw material powder with anthracite, control the calorific value of the mixture to be 2000 kcal / kg-4500 kcal / kg, and ignite it at 500℃-650℃ in air or oxygen atmosphere with an oxygen partial pressure of 12%-21% using electric heating wire or plasma ignition. After the system temperature reaches 700℃-900℃, keep it at that temperature for 3-5 hours. S3: Grind the ignited clinker again, add anhydrous aluminum chloride and mix evenly. The mass ratio of vanadium-containing coal to anhydrous aluminum chloride is 5:1-30:

1. Chlorinate and roast at 140℃-190℃ for 1-2 hours under nitrogen or argon protection to generate gaseous VOCl3. S4: The generated mixed vapor is fed into a three-stage condensation unit. The first stage uses heat transfer oil to condense and remove high-boiling-point impurities at 150℃-180℃. The second stage uses a distillation column to condense and collect VOCl3 liquid at 65℃-90℃, controlling the reflux ratio to be 25:1-40:

1. The third stage uses calcium chloride aqueous solution to condense and capture residual VOCl3 at -20℃. The tail gas is discharged after being absorbed by alkaline solution. S5: Add 98% sulfuric acid to the collected VOCl3 liquid to adjust the pH to 1-3, then add oxalic acid and stir until the solution turns clear blue to obtain VOSO4 electrolyte.

2. The method according to claim 1, characterized in that, The calorific value of the mixture in step S2 is 2500 kcal / kg-3500 kcal / kg.

3. The method according to claim 1, characterized in that, In step S2, the initial ignition temperature is 600℃-650℃, and the heat preservation temperature is 800℃-900℃.

4. The method according to claim 1, characterized in that, In step S3, anhydrous aluminum chloride is used as the chlorinating agent, and the chlorination roasting temperature is 150℃-180℃.

5. The method according to claim 1, characterized in that, In step S3, the mass ratio of vanadium-containing coal to anhydrous aluminum chloride is 12:1-20:

1.

6. The method according to claim 1, characterized in that, The reflux ratio of the second-stage distillation in step S4 is 30:1-40:

1.

7. The method according to claim 1, characterized in that, The vanadium-bearing coal contains 0.5%-1.5% V2O5 by mass.

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