A method for preparing an electrolyte for an iron-chromium flow battery

Abstract

The present invention relates to the technical field of energy storage battery electrolytes, and specifically discloses a method for preparing an iron-chromium flow battery electrolyte. The method uses high-purity iron powder, hydrochloric acid and chromic anhydride as raw materials, and generates ferric chloride and chromium trichloride through chemical reactions under specified conditions. After the reaction is completed, high-purity iron powder is continued to be added to convert all trivalent iron into divalent iron, and finally the required chromium chloride and hydrochloric acid remainder are supplemented, so as to directly prepare the required qualified iron-chromium flow battery electrolyte. The present invention can simply and efficiently prepare the required iron-chromium flow battery electrolyte, and simplifies the production process and reduces the production cost compared to the traditional chloride salt compounding process. The preparation method of the present invention has a simple process, saves time and labor, and has no emissions, which is more environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of energy storage battery electrolyte, and in particular to a method for preparing an iron-chromium liquid flow battery electrolyte. Background Art

[0002] In recent years, the proportion of renewable energy power generation such as wind and light in my country has increased rapidly, but the problems of consumption, transmission and distribution, and fluctuations have become increasingly prominent, and a large number of rigid demands for energy storage have emerged. Therefore, long-term and large-scale energy storage technology has gradually begun to move to the forefront, among which flow battery energy storage technology has quickly become one of the best solutions. The iron-chromium flow battery has been widely praised for its high safety, flexible design, low cost, and long cycle life. As a key component of the iron-chromium flow battery, the electrolyte of the iron-chromium flow battery accounts for about one-third of its total cost, and its importance is self-evident.

[0003] In the preparation of traditional iron-chromium flow battery electrolyte, the chloride salt compounding method is generally used, that is, ferrous chloride, chromium chloride and hydrochloric acid are prepared in a specified proportion. Its characteristics are mature formula, simple process, no emission and no pollution, but the production cost is relatively high. Alloy production electrolyte is an emerging process. Its advantage is that it can minimize the cost of electrolyte, but its process is complicated, the impurity removal effect is not ideal, and chromium slag is generated during the production process, which does not belong to the green circular production model.

[0004] Therefore, there is an urgent need for a new method for preparing electrolyte that can effectively avoid the occurrence of the above-mentioned situation, has the advantages of reducing costs and increasing efficiency, is simple and practical, and is green and environmentally friendly, and has the potential for large-scale promotion. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for preparing an iron-chromium liquid flow battery electrolyte, which adopts a streamlined process of chromium anhydride iron powder raw material to prepare the iron-chromium liquid flow battery electrolyte, has the advantages of no emissions and low cost, and avoids the chromium pollution problem in the traditional production process, solving the problems mentioned in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing an electrolyte for an iron-chromium liquid flow battery, comprising the following steps:

[0007] S1. Add chromic anhydride, high-purity iron powder, hydrochloric acid and water into a reaction container to generate a mixture A of ferric chloride and chromium chloride through a chemical reaction;

[0008] S2. Continue to add high-purity iron powder to the mixture A until the trivalent iron is completely reduced to divalent iron, thereby obtaining a mixture B of divalent iron and trivalent chromium;

[0009] S3. Titrate the mixture B solution, continue to add chromium chloride, hydrochloric acid and water to the solution according to the standard electrolyte index, keep stirring the reaction container for 30 minutes, and obtain a standard electrolyte.

[0010] Preferably, in the reaction vessel, a large amount of heat is generated during the chemical reaction of hydrochloric acid, high-purity iron powder and chromic anhydride, resulting in a rapid rise in temperature. Therefore, temperature control is very important, so the temperature range of the entire preparation process must be strictly controlled between 20 and 40° C. The entire preparation process is protected by an inert gas, otherwise the required electrolyte product cannot be produced, and the inert gas is nitrogen or argon.

[0011] Preferably, in step S1, the process specifically includes: dissolving chromic anhydride in water to obtain a chromic anhydride solution; adding high-purity iron powder, and then adding hydrochloric acid at a uniform rate, stirring and reacting for 1 to 2 hours to obtain a mixture A of chromium trichloride and ferric chloride in the solution.

[0012] Preferably, the mass ratio of the chromic anhydride, high-purity iron powder, hydrochloric acid and water is 100:56-60:220-260:60.

[0013] Preferably, the CrO3 content in the chromic anhydride is 98% to 99.9%.

[0014] Preferably, in step S1, the Fe content in the high-purity iron powder is 99% to 99.9%, and the particle size is greater than 200 mesh; the addition rate of the high-purity iron powder is 2 to 3 g / min.

[0015] Preferably, in step S1, the amount of hydrochloric acid added is controlled at 10-20 g / min, and the mass concentration of hydrochloric acid is 32%-36%.

[0016] The addition speed of high-purity iron powder and hydrochloric acid must be strictly controlled to avoid the generation of hydrogen or even chlorine due to too fast or too slow addition speed.

[0017] Preferably, in step S3, the purpose of titrating the solution is to check whether the electrolyte index meets the theoretical value according to the reaction equation, and chromium chloride, hydrochloric acid and water are continuously added to the solution according to the standard electrolyte index, the molar number of the added chromium is 1 / 3 to 1 / 2 of the added iron, the molar number of the added hydrochloric acid is 2 to 4 times the added iron, and the mass of the added water is 10% to 35% of the mass of the mixed solution.

[0018] Preferably, in step S3, the standard electrolyte index range includes: divalent iron ion concentration of 1-3 mol / L, trivalent iron ion concentration of less than 0.05 mol / L, trivalent chromium ion concentration of 1-3 mol / L, and hydrogen ion concentration of 2-4 mol / L.

[0019] Preferably, the reaction formula of the present invention is as follows:

[0020] CrO3+Fe+6HCl=CrCl3+FeCl3+3H2O

[0021] Fe+2FeCl3=3FeCl2

[0022] The beneficial effects of the present invention are:

[0023] 1) The preparation method of the iron-chromium flow battery electrolyte of the present invention uses chromic anhydride, high-purity iron powder, hydrochloric acid and water as raw materials. After the reaction is completed, chromium chloride, hydrochloric acid and water are appropriately added according to demand to prepare the required electrolyte. The preparation method is safe and reliable, simple in process, low in environmental requirements, sufficient in supply, and significantly reduces costs and increases efficiency. It is a green, circular and pollution-free process with sustainable development.

[0024] 2) The preparation method of the present invention uses chromic anhydride and iron powder as raw materials to simply and quickly prepare iron-chromium liquid flow battery electrolyte. The process is clean and pollution-free, and there is no need to add an impurity remover for the impurity removal procedure. A high-purity electrolyte product is finally obtained by using a dissolution reaction and then adding chromium salts and acids, without generating any by-products. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] Example 1

[0027] A method for preparing an electrolyte for an iron-chromium liquid flow battery comprises the following steps:

[0028] (1) adding 100 g of chromic anhydride to 60 g of deionized water, and stirring the mixture in a reaction vessel for 30 minutes to completely dissolve the chromic anhydride;

[0029] (2) Add 56 g of high-purity iron powder at a uniform rate of 3 g / min and 220 g of 32% hydrochloric acid at a rate of 20 g / min. After the addition is completed, continue to stir and react at 20 to 40° C. for 1 to 2 hours;

[0030] (3) Continue to add 28g of high-purity iron powder and stir until fully dissolved;

[0031] (4) Add 133 g of chromium trichloride hexahydrate and stir to dissolve;

[0032] (5) Add 285 g of 32% hydrochloric acid and mix thoroughly;

[0033] (6) Accurately determine the volume to 1L;

[0034] (7) The electrolyte test results after titration were: ferrous iron ion concentration 1.5 mol / L, ferric iron ion concentration 0.03 mol / L, trivalent chromium ion concentration 1.5 mol / L, and hydrogen ion concentration 2.5 mol / L.

[0035] Example 2

[0036] A method for preparing an electrolyte for an iron-chromium liquid flow battery comprises the following steps:

[0037] (1) 80 g of chromic anhydride was added to 50 g of deionized water and stirred in a reactor for 30 minutes to completely dissolve the chromic anhydride;

[0038] (2) Add 45 g of high-purity iron powder at a uniform rate of 2 g / min and 260 g of 32% hydrochloric acid at a rate of 15 g / min. After the addition is completed, continue to stir and react at 20-40° C. for 1-2 hours;

[0039] (3) Continue to add 23 g of high-purity iron powder and stir until fully dissolved;

[0040] (4) Add 160 g of chromium chloride hexahydrate and stir to dissolve;

[0041] (5) Add 300 g of 32% hydrochloric acid and mix thoroughly;

[0042] (6) Accurately determine the volume to 1L;

[0043] (7) The electrolyte test results after titration were: ferrous iron ion concentration 1.2 mol / L, ferric iron ion concentration 0.02 mol / L, trivalent chromium ion concentration 1.4 mol / L, and hydrogen ion concentration 2.6 mol / L.

[0044] The preparation method provided by the present invention adopts chromic anhydride and iron powder as raw materials to simply and quickly prepare an iron-chromium liquid flow battery electrolyte. The chromic anhydride used in the present invention belongs to hexavalent chromium. The present invention uses it as a raw material in the process of producing the electrolyte and finally completely converts it into trivalent chromium. The process is clean and pollution-free, and there is no need to add an impurity remover to perform an impurity removal procedure. A high-purity electrolyte product is finally obtained by adopting a dissolution reaction and then adding chromium salts and acids, without generating any by-products.

[0045] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an electrolyte for an iron-chromium flow battery, characterized in that: The steps include: S1. Add chromic anhydride, high-purity iron powder, hydrochloric acid and water into a reaction container to generate a mixture A of ferric chloride and chromium chloride through a chemical reaction; S2. Continue to add high-purity iron powder to the mixture A until the trivalent iron is completely reduced to divalent iron, thereby obtaining a mixture B of divalent iron and trivalent chromium; S3, titrating the mixture B solution, continuing to add chromium chloride, hydrochloric acid and water to the solution according to the standard electrolyte index, and keeping the reaction container stirring for 30 minutes to obtain a standard electrolyte; In the reaction vessel, the temperature range of the whole preparation process is controlled between 20 and 40° C. The whole preparation process is protected by an inert gas, which is nitrogen or argon; In step S1, the Fe content in the high-purity iron powder is 99% to 99.9%, and the particle size is greater than 200 mesh; the addition rate of the high-purity iron powder is 2 to 3 g / min; and the CrO3 content in the chromic anhydride is 98% to 99.9%.

2. The method for preparing an electrolyte for an iron-chromium flow battery according to claim 1, characterized in that: In step S1, it specifically includes: dissolving chromic anhydride in water to obtain a chromic anhydride solution; adding high-purity iron powder, and then adding hydrochloric acid at a uniform rate, stirring and reacting for 1 to 2 hours, to obtain a mixture A of chromium trichloride and ferric chloride in the solution.

3. The method for preparing an electrolyte for an iron-chromium flow battery according to claim 1, characterized in that: In step S1, the mass ratio of the chromic anhydride, high-purity iron powder, hydrochloric acid and water is 100:56-60:220-260:

60.

4. The method for preparing an electrolyte for an iron-chromium flow battery according to claim 1, characterized in that: In step S1, the amount of hydrochloric acid added is controlled at 10-20 g / min, and the mass concentration of hydrochloric acid is 32%-36%.

5. The method for preparing an electrolyte for an iron-chromium flow battery according to claim 1, characterized in that: In step S3, chromium chloride, hydrochloric acid and water are continuously added to the solution according to the standard electrolyte index, the molar number of the added chromium is 1 / 3 to 1 / 2 of the added iron, the molar number of the added hydrochloric acid is 2 to 4 times of the added iron, and the mass of the added water is 10% to 35% of the mass of the mixed solution.

6. The method for preparing an electrolyte for an iron-chromium flow battery according to claim 1, characterized in that: In step S3, the standard electrolyte index range includes: divalent iron ion concentration of 1 to 3 mol / L, trivalent iron ion concentration less than 0.05 mol / L, trivalent chromium ion concentration of 1 to 3 mol / L, and hydrogen ion concentration of 2 to 4 mol / L.