Hydrogen fluoride, preparation method thereof and battery material

Abstract

The invention discloses hydrogen fluoride, a preparation method thereof and a battery material. The preparation method of hydrogen fluoride comprises the steps that fluosilicic acid and first sulfuric acid react to generate mixed gas and first mixed sulfuric acid, the first mixed sulfuric acid is a sulfuric acid solution containing hydrogen fluoride, and the mixed gas comprises silicon tetrafluoride gas and hydrogen fluoride gas; washing the mixed gas with second sulfuric acid to obtain second mixed sulfuric acid and washed silicon tetrafluoride gas; the second mixed sulfuric acid is obtained by absorbing the hydrogen fluoride gas by second sulfuric acid; washing the water-containing hydrogen fluoride with second mixed sulfuric acid to obtain crude hydrogen fluoride gas; and purifying the crude hydrogen fluoride gas to obtain anhydrous hydrogen fluoride. According to the preparation method of the hydrogen fluoride, through washing treatment of the second sulfuric acid and washing treatment of the second mixed sulfuric acid, the recovery rate of the hydrogen fluoride is remarkably increased.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine chemical industry, and specifically relates to hydrogen fluoride and a preparation method thereof and a battery material. Background Art

[0002] At present, the main processes for preparing anhydrous hydrogen fluoride are: fluorite method and fluosilicic acid method. The fluorite method uses fluorite and sulfuric acid to react to produce anhydrous hydrogen fluoride. It is the mainstream process on the market, with mature technology, small investment, and high total output, but high production costs and great environmental pressure. The fluosilicic acid method is relatively mature in technology and has good economic benefits, but it has high investment costs, complex process flow, and a large amount of fluorine-containing dilute sulfuric acid needs to rely on phosphorus chemical equipment for nitration, which has certain limitations, and the silicon dioxide produced in the process is easy to clog the pipeline.

[0003] At present, in the method of preparing anhydrous hydrogen fluoride using fluorosilicic acid, 98% sulfuric acid and 40% fluorosilicic acid are used to react to prepare anhydrous hydrogen fluoride, but the overall yield of hydrogen fluoride is about 75%, and the yield of hydrogen fluoride needs to be further improved. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, one object of the present invention is to provide a hydrogen fluoride and a preparation method thereof and a battery material. The hydrogen fluoride preparation method is conducive to improving the hydrogen fluoride yield.

[0005] The first aspect of the present application provides a method for preparing hydrogen fluoride. According to an embodiment of the present application, the preparation method comprises:

[0006] reacting fluorosilicic acid with first sulfuric acid to produce a mixed gas and first mixed sulfuric acid, wherein the first mixed sulfuric acid is a sulfuric acid solution containing hydrogen fluoride, and the mixed gas includes silicon tetrafluoride gas and hydrogen fluoride gas;

[0007] The mixed gas is washed with a second sulfuric acid to obtain a second mixed sulfuric acid and washed silicon tetrafluoride gas; the second mixed sulfuric acid is obtained by absorbing hydrogen fluoride gas with the second sulfuric acid;

[0008] washing the aqueous hydrogen fluoride with a second mixed sulfuric acid to obtain a crude hydrogen fluoride gas;

[0009] Purify the crude hydrogen fluoride gas to obtain anhydrous hydrogen fluoride.

[0010] In the present application, fluorosilicic acid is reacted with a first sulfuric acid, and the first sulfuric acid, that is, a sulfuric acid solution, is used as a catalyst to promote the decomposition of fluorosilicic acid to produce silicon tetrafluoride and hydrogen fluoride. The decomposition principle of fluorosilicic acid is: H 2 SiF 6 =HF+SiF 4 .

[0011] In the present application, the mixed gas is washed with a second sulfuric acid (such as concentrated sulfuric acid), and part of the hydrogen fluoride gas in the mixed gas is dissolved in the second sulfuric acid; another part of the hydrogen fluoride gas reacts with the second sulfuric acid to generate fluorosulfonic acid, and the obtained second mixed sulfuric acid includes sulfuric acid, water, hydrogen fluoride and fluorosulfonic acid.

[0012] The second mixed sulfuric acid washes the aqueous hydrogen fluoride, and the second mixed sulfuric acid contacts with water and hydrogen fluoride gas. On the one hand, the fluorosulfonic acid in the second mixed sulfuric acid is hydrolyzed into hydrogen fluoride and sulfuric acid, releasing hydrogen fluoride gas; on the other hand, the second mixed sulfuric acid is diluted with water to release heat to release the hydrogen fluoride dissolved in the second mixed sulfuric acid; finally, the three mixed gases of hydrogen fluoride in the aqueous hydrogen fluoride, hydrogen fluoride gas released by hydrolysis in the second mixed sulfuric acid, and hydrogen fluoride gas released by dissolution are used as crude hydrogen fluoride gas, which can be further purified to obtain anhydrous hydrogen fluoride. The preparation method provided by the present application improves the yield of hydrogen fluoride in the mixed gas obtained by the main reaction, thereby facilitating the improvement of the overall yield of hydrogen fluoride, which can reach more than 80%, and more preferably, more than 90%.

[0013] In some embodiments of the present application, the mass ratio of water to hydrogen fluoride in aqueous hydrogen fluoride is 1:5 to 1:19; and / or, aqueous hydrogen fluoride includes at least one of hydrofluoric acid output from a fluorite process tail gas absorber, hydrofluoric acid output from an electronic grade hydrofluoric acid tail gas absorber, and hydrofluoric acid output from a phosphorus chemical tail gas absorber.

[0014] In some embodiments of the present application, the first mixed sulfuric acid is treated by falling film evaporation to obtain liquid dilute sulfuric acid and gaseous hydrogen fluoride, and the gaseous hydrogen fluoride serves as a source of aqueous hydrogen fluoride.

[0015] In some embodiments of the present application, based on the total mass of aqueous hydrogen fluoride, the mass percentage of hydrogen fluoride in aqueous hydrogen fluoride is 40% to 95%.

[0016] In some embodiments of the present application, the second mixed sulfuric acid is used to wash the aqueous hydrogen fluoride to obtain a third mixed sulfuric acid; the third mixed sulfuric acid is used as a source of the first sulfuric acid to react with fluorosilicic acid.

[0017] In some embodiments of the present application, the preparation method further comprises: treating the washed silicon tetrafluoride gas, comprising the steps of:

[0018] The washed silicon tetrafluoride gas is absorbed by the first fluorosilicic acid solution to obtain a fluorosilicic acid mixed solution containing silicon dioxide precipitate, and the solid-liquid separation is performed to obtain a second fluorosilicic acid solution and silicon dioxide precipitate;

[0019] The silica precipitate is washed to obtain a third fluorosilicic acid solution and silica solid.

[0020] In some embodiments of the present application, the treatment of the washed silicon tetrafluoride gas satisfies at least one of the following:

[0021] (i) the mass concentration of the first fluorosilicic acid solution is 25% to 30%;

[0022] (ii) the mass concentration of the second fluorosilicic acid solution is 40% to 55%;

[0023] (iii) the mass concentration of the third fluorosilicic acid solution is 11% to 18%;

[0024] (iv) the third fluorosilicic acid solution is concentrated to produce the first fluorosilicic acid solution;

[0025] (v) The second fluorosilicic acid solution is used as a source of fluorosilicic acid and reacts with the first sulfuric acid.

[0026] In some embodiments of the present application, purifying crude hydrogen fluoride gas to obtain anhydrous hydrogen fluoride comprises:

[0027] Condensing crude hydrogen fluoride gas to obtain crude anhydrous hydrogen fluoride;

[0028] The crude anhydrous hydrogen fluoride is sequentially subjected to rectification treatment and degassing treatment to obtain anhydrous hydrogen fluoride.

[0029] In some embodiments of the present application, liquid dilute sulfuric acid is subjected to air stripping treatment to obtain dilute sulfuric acid and a stripping mixed gas, wherein the stripping mixed gas includes air and stripping hydrogen fluoride;

[0030] The stripping mixed gas is treated by water absorption to obtain hydrofluoric acid.

[0031] In some embodiments of the present application, the first mixed sulfuric acid is treated by falling film evaporation, including at least one of the following:

[0032] (a) controlling the falling film evaporation temperature to be 130° C. to 160° C.; and / or the pressure to be -30 kPa to 0 kPa;

[0033] (b) The content of hydrogen fluoride in the liquid dilute sulfuric acid is less than 5‰.

[0034] In some embodiments of the present application, at least one of the following is satisfied during the reaction of fluorosilicic acid with the first sulfuric acid:

[0035] (α) controlling the reaction temperature to be 60°C to 140°C;

[0036] (β) Fluorosilicic acid uses a fluosilicic acid with a mass concentration of 40% to 50%;

[0037] (γ) The first sulfuric acid comprises: 91% to 95% sulfuric acid and 1% to 5% hydrogen fluoride.

[0038] In a second aspect, the present application provides hydrogen fluoride, which is obtained by the above-mentioned preparation method.

[0039] The present application adopts the above preparation method to obtain hydrogen fluoride with high yield and high purity.

[0040] The third aspect of the present application provides a battery material, and the raw materials for preparing the battery material include hydrogen fluoride obtained by the above-mentioned preparation method, or the above-mentioned hydrogen fluoride.

[0041] The hydrogen fluoride obtained by the above-mentioned preparation method in the present application can be used as a raw material for some battery materials, such as a raw material for lithium hexafluorophosphate.

[0042] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of the preparation method of hydrogen fluoride provided in the examples of the present application.

[0044] Figure 2 A step diagram of the method for preparing hydrogen fluoride provided in an embodiment of the present application.

[0045] Figure 3 A flow chart of a method for preparing hydrogen fluoride provided in a specific embodiment of the present application.

[0046] Figure 4 A schematic diagram of the system structure used in the method for preparing hydrogen fluoride provided in the specific embodiment of the present application. DETAILED DESCRIPTION

[0047] The embodiments of the present invention are described in detail below, which are intended to explain the present invention but should not be construed as limiting the present invention.

[0048] At present, anhydrous hydrogen fluoride is prepared from fluorosilicic acid by using 98% sulfuric acid and 40% fluorosilicic acid for a main decomposition reaction to prepare fluorine-containing sulfuric acid, and the fluorine-containing sulfuric acid is distilled to distill out anhydrous hydrogen fluoride, which is then washed, cooled, distilled, and degassed to obtain anhydrous hydrogen fluoride. However, the overall yield of hydrogen fluoride is about 75%, especially the recovery effect of hydrogen fluoride in the gas phase obtained by the main decomposition reaction is poor, resulting in the overall hydrogen fluoride yield to be further improved.

[0049] To this end, the first aspect of the embodiment of the present application proposes a method for preparing hydrogen fluoride. According to the embodiment of the present application, the preparation method comprises:

[0050] reacting fluorosilicic acid with first sulfuric acid to produce a mixed gas and first mixed sulfuric acid, wherein the first mixed sulfuric acid is a sulfuric acid solution containing hydrogen fluoride, and the mixed gas includes silicon tetrafluoride gas and hydrogen fluoride gas;

[0051] The mixed gas is washed with a second sulfuric acid to obtain a second mixed sulfuric acid and washed silicon tetrafluoride gas; the second mixed sulfuric acid is obtained by absorbing hydrogen fluoride gas with the second sulfuric acid;

[0052] washing the aqueous hydrogen fluoride with a second mixed sulfuric acid to obtain a crude hydrogen fluoride gas;

[0053] Purify the crude hydrogen fluoride gas to obtain anhydrous hydrogen fluoride.

[0054] In the embodiment of the present application, fluorosilicic acid is reacted with the first sulfuric acid, and the first sulfuric acid, that is, sulfuric acid solution, is used as a catalyst to promote the decomposition of fluorosilicic acid to produce silicon tetrafluoride and hydrogen fluoride. The decomposition principle of fluorosilicic acid is: H 2 SiF 6 =HF+SiF 4 .

[0055] In the embodiment of the present application, the mixed gas is washed with a second sulfuric acid (such as concentrated sulfuric acid), and part of the hydrogen fluoride gas in the mixed gas is dissolved in the second sulfuric acid; another part of the hydrogen fluoride gas reacts with the second sulfuric acid to generate fluorosulfonic acid, and the obtained second mixed sulfuric acid includes sulfuric acid, water, hydrogen fluoride and fluorosulfonic acid.

[0056] The second mixed sulfuric acid washes the aqueous hydrogen fluoride, and the second mixed sulfuric acid contacts with water and hydrogen fluoride gas. On the one hand, the fluorosulfonic acid in the second mixed sulfuric acid is hydrolyzed into hydrogen fluoride and sulfuric acid, releasing hydrogen fluoride gas; on the other hand, the second mixed sulfuric acid is diluted with water to release heat to release the hydrogen fluoride dissolved in the second mixed sulfuric acid; finally, the three mixed gases of hydrogen fluoride in the aqueous hydrogen fluoride, hydrogen fluoride gas released by hydrolysis in the second mixed sulfuric acid, and hydrogen fluoride gas released by dissolution are used as crude hydrogen fluoride gas, which can be further purified to obtain anhydrous hydrogen fluoride. The preparation method provided by the present application improves the yield of hydrogen fluoride in the mixed gas obtained by the main reaction, thereby facilitating the improvement of the overall yield of hydrogen fluoride, which can reach more than 80%, and more preferably, more than 90%.

[0057] In the second mixed washing process, the hydrolysis reaction mechanism of fluorosulfonic acid is: HSO 3 F+H 2 O=H 2 SO 4 +HF.

[0058] In addition, as an example, concentrated sulfuric acid includes sulfuric acid having a mass concentration of 98%.

[0059] Further, the preparation process of hydrogen fluoride is as follows Figure 1 As shown:

[0060] Step a. reacting fluorosilicic acid with a first sulfuric acid to produce a mixed gas and a first mixed sulfuric acid, wherein the first mixed sulfuric acid is a sulfuric acid solution containing hydrogen fluoride, and the mixed gas includes silicon tetrafluoride gas and hydrogen fluoride gas;

[0061] Step b. washing the mixed gas with a second sulfuric acid to obtain a second mixed sulfuric acid and washed silicon tetrafluoride gas; the second mixed sulfuric acid is obtained by absorbing hydrogen fluoride gas in the second sulfuric acid;

[0062] Step c. washing the aqueous hydrogen fluoride with a second mixed sulfuric acid to obtain a crude hydrogen fluoride gas;

[0063] Step d. Purifying the crude hydrogen fluoride gas to obtain anhydrous hydrogen fluoride.

[0064] In some embodiments of the present application, the mass ratio of water to hydrogen fluoride in the aqueous hydrogen fluoride is 1:5 to 1:19; and / or the aqueous hydrogen fluoride includes at least one of hydrofluoric acid output from a fluorite process tail gas absorber, hydrofluoric acid output from an electronic grade hydrofluoric acid tail gas absorber, and hydrofluoric acid output from a phosphorus chemical tail gas absorber.

[0065] In the embodiment of the present application, the mass ratio of water to hydrogen fluoride in the aqueous hydrogen fluoride satisfies the above conditions, which can not only stabilize the sulfuric acid component of the washing tower, but also a small amount of water promotes the release of hydrogen fluoride in the washing tower, which is beneficial to promote the release of hydrogen fluoride gas in the second mixed sulfuric acid and improve the yield of hydrogen fluoride.

[0066] If the mass ratio of water to hydrogen fluoride is higher than 1:5, a large amount of water will enter the washing tower, causing the sulfuric acid concentration in the washing tower to be too low, which will subsequently affect the decomposition reaction; if the mass ratio of water to hydrogen fluoride is lower than 1:19, it can directly enter the distillation tower, and the entire process will change.

[0067] In specific examples, the mass ratio of water to hydrogen fluoride in aqueous hydrogen fluoride is 1:5, 1.6, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, and 1:19.

[0068] Furthermore, the mass ratio of water to hydrogen fluoride in aqueous hydrogen fluoride is 1:8 to 1:12.

[0069] In the embodiment of the present application, the mass ratio of water to hydrogen fluoride is controlled to be between 1:8 and 1:12, the yield of hydrogen fluoride is between 80% and 85%, and the amount of water introduced is moderate, so that the hydrogen fluoride in the second mixed sulfuric acid can be well released.

[0070] In some embodiments of the present application, the first mixed sulfuric acid is treated by falling film evaporation to obtain liquid dilute sulfuric acid and gaseous hydrogen fluoride, and the gaseous hydrogen fluoride serves as a source of aqueous hydrogen fluoride.

[0071] In the embodiment of the present application, the first mixed sulfuric acid is evaporated by a falling film evaporation method. Under negative pressure, hydrogen fluoride is more volatile, which can significantly improve the evaporation and extraction efficiency of hydrogen fluoride and reduce the unit consumption of sulfuric acid. In addition, the overall temperature of falling film evaporation is relatively low, which is conducive to reducing steam loss.

[0072] In the embodiment of the present application, the second mixed sulfuric acid can be used to directly wash the gas phase hydrogen fluoride evaporated by falling film. The gas phase usually carries water vapor, which promotes the release of hydrogen fluoride by the second mixed sulfuric acid, is beneficial to effectively recover the hydrogen fluoride produced by the main reaction (i.e., the reaction of fluorosilicic acid and the first sulfuric acid), improves the yield of hydrogen fluoride, and is also beneficial to reduce the unit consumption of sulfuric acid.

[0073] In some embodiments of the present application, based on the total mass of aqueous hydrogen fluoride, the mass percentage of hydrogen fluoride in aqueous hydrogen fluoride is 40% to 95%.

[0074] As an example, based on the total mass of aqueous hydrogen fluoride, the mass percentage of hydrogen fluoride in aqueous hydrogen fluoride is 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc.

[0075] In some embodiments of the present application, the aqueous hydrogen fluoride gas is washed with a second mixed sulfuric acid to obtain a third mixed sulfuric acid; the third mixed sulfuric acid is used as a source of the first sulfuric acid to react with fluorosilicic acid.

[0076] In the embodiment of the present application, some hydrogen fluoride still remains in the third mixed sulfuric acid. The third mixed sulfuric acid, i.e., sulfuric acid containing residual hydrogen fluoride, is returned again as a raw material for reacting with fluorosilicic acid, and the circulation operation is continued, which can further improve the yield of hydrogen fluoride and reduce the loss of hydrogen fluoride.

[0077] In some embodiments of the present application, the preparation method further comprises: The preparation method further comprises: treating the washed silicon tetrafluoride gas, comprising the steps of:

[0078] The washed silicon tetrafluoride gas is absorbed by the first fluorosilicic acid solution to obtain a fluorosilicic acid mixed solution containing silicon dioxide precipitate, and the solid-liquid separation is performed to obtain a second fluorosilicic acid solution and silicon dioxide precipitate;

[0079] The silica precipitate is washed to obtain a third fluorosilicic acid solution and silica solid.

[0080] In the embodiment of the present application, the first fluorosilicic acid solution is used to absorb the washed silicon tetrafluoride gas, and the first fluorosilicic acid provides an acidic environment to promote the hydrolysis reaction of silicon tetrafluoride as shown below: SiF 4 +H 2 O=H 2 SiF6 +SiO 2 , thereby obtaining a fluosilicic acid mixed solution containing silicon dioxide precipitate. Compared with the first fluosilicic acid solution, the mass concentration of fluosilicic acid in the fluosilicic acid mixed solution containing silicon dioxide precipitate increases. Therefore, the absorption treatment process is used to obtain silicon dioxide as a byproduct on the one hand, and to increase the concentration of fluosilicic acid on the other hand.

[0081] In an embodiment of the present application, a mixed fluorosilicic acid solution containing silica precipitate is subjected to solid-liquid separation (such as filtration treatment) to obtain a second fluorosilicic acid solution and silica precipitate. The silica is further extracted by solid-liquid separation, and a concentrated second fluorosilicic acid solution is obtained. The mass concentration of the second fluorosilicic acid solution is greater than the mass concentration of the first fluorosilicic acid solution.

[0082] In the embodiment of the present application, impurities in the silicon dioxide precipitate are further removed by washing treatment to obtain a silicon dioxide by-product with higher purity, and at the same time, a third fluorosilicic acid solution with lower mass concentration is obtained.

[0083] In some embodiments of the present application, the treatment of the washed silicon tetrafluoride gas satisfies at least one of the following:

[0084] (i) the mass concentration of the first fluorosilicic acid solution is 25% to 30%;

[0085] (ii) the mass concentration of the second fluorosilicic acid solution is 40% to 55%;

[0086] (iii) the mass concentration of the third fluorosilicic acid solution is 11% to 18%;

[0087] (iv) the third fluorosilicic acid solution is concentrated to produce the first fluorosilicic acid solution;

[0088] (v) The second fluorosilicic acid solution is used as a source of fluorosilicic acid and reacts with the first sulfuric acid.

[0089] In an embodiment of the present application, the mass concentration of the first fluorosilicic acid solution is 25% to 30%. In specific examples, the mass concentration is 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, etc.

[0090] In an embodiment of the present application, the mass concentration of the second fluorosilicic acid solution is 40% to 50%. In specific examples, the mass concentration is 40%, 40.5%, 41%, 41.5%, 42%, 42.5%, 43%, 43.5%, 44%, 44.5%, 45%, 45.5%, 46%, 46.5%, 47%, 47.5%, 48%, 48.5%, 49%, 49.5%, 50%, etc.

[0091] In an embodiment of the present application, the mass concentration of the third fluorosilicic acid solution is 11% to 18%. In specific examples, the mass concentration is 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, etc.

[0092] In the embodiment of the present application, the third fluorosilicic acid solution is concentrated to produce the first fluorosilicic acid solution, and the concentration of the third fluorosilicic acid solution can be increased by vacuum concentration, for example.

[0093] In the embodiment of the present application, the second fluorosilicic acid solution with a higher concentration can be used as the source of fluorosilicic acid in the main reaction to react with the first sulfuric acid. The mass concentration of fluorosilicic acid is relatively high. In a specific example, the mass concentration reaches 40% to 50%, which is conducive to reducing the amount of the first sulfuric acid and reducing the unit consumption of sulfuric acid. In addition, the fluorosilicic acid can be recycled to improve resource utilization.

[0094] According to the embodiment of the present application, after absorbing the washed silicon tetrafluoride gas with a first fluorosilicic acid having a mass concentration of 25% to 30%, the silicon tetrafluoride decomposes to produce fluorosilicic acid, which can increase the concentration of the silicic acid solution; after filtering, a second fluorosilicic acid solution having a mass concentration of 40% to 50% can be obtained, and the second fluorosilicic acid solution is used for decomposition reaction with the first sulfuric acid. In addition, after washing the silicon dioxide precipitate, by-product silicon dioxide and a third fluorosilicic acid solution having a mass concentration of 11% to 18% are obtained, and the third fluorosilicic acid solution is vacuum concentrated to obtain a first fluorosilicic acid solution having a mass concentration of 25% to 30%, thereby realizing the recycling of the by-product fluorosilicic acid.

[0095] In some embodiments of the present application, purifying crude hydrogen fluoride gas to obtain anhydrous hydrogen fluoride comprises:

[0096] The crude hydrogen fluoride gas is condensed to obtain crude anhydrous hydrogen fluoride; the crude anhydrous hydrogen fluoride is sequentially subjected to rectification treatment and degassing treatment to obtain anhydrous hydrogen fluoride.

[0097] In the embodiment of the present application, the crude hydrogen fluoride gas is subjected to condensation treatment to obtain a crude anhydrous hydrogen fluoride product; the crude anhydrous hydrogen fluoride product is then subjected to distillation treatment and degassing treatment in sequence to obtain a finished anhydrous hydrogen fluoride product, i.e., the target product anhydrous hydrogen fluoride.

[0098] In some embodiments of the present application, liquid dilute sulfuric acid is subjected to air stripping treatment to obtain dilute sulfuric acid and a stripping mixed gas, wherein the stripping mixed gas includes air and stripping hydrogen fluoride; the stripping mixed gas is subjected to water absorption treatment to obtain hydrofluoric acid.

[0099] In the embodiment of the present application, the liquid phase dilute sulfuric acid is stripped with hot air, which can reduce steam loss and reduce the generation of by-product sulfuric acid. The stripping can obtain by-product dilute sulfuric acid and stripping mixed gas; the hot air and hydrogen fluoride are absorbed by water to obtain by-product hydrofluoric acid, thereby obtaining two by-products; and the stripping mixed gas contains hot air, which carries a high heat into the water absorption device, which is conducive to reducing the heating energy consumption of the water absorption device and improving the resource utilization effect.

[0100] In some embodiments of the present application, the first mixed sulfuric acid is treated by falling film evaporation, including at least one of the following:

[0101] (a) controlling the falling film evaporation temperature to be 130° C. to 160° C.; and / or the pressure to be -30 kPa to 0 kPa;

[0102] (b) The content of hydrogen fluoride in the liquid dilute sulfuric acid is less than 5‰.

[0103] In the embodiment of the present application, in the step of falling film evaporation of the first mixed sulfuric acid, the temperature and / or pressure parameters are controlled to meet the above conditions, which is conducive to improving the evaporation effect, improving the recovery rate of hydrogen fluoride, and avoiding excessive water and sulfuric acid in the hydrogen fluoride gas, thereby helping to reduce the unit consumption of sulfuric acid. In a specific example, the temperature is 130°C, 135°C, 140°C, 145°C, 150°C, 155°C or 160°C, etc. In a specific example, the pressure is -30kpa, -25kpa, -20kpa, -15kpa, -10kpa, -5kpa, -1kpa, etc.

[0104] Further, the falling film evaporation temperature is 135° C. to 145° C. In specific examples, the falling film evaporation temperature is 135° C., 136° C., 137° C., 138° C., 139° C., 140° C., 141° C., 142° C., 143° C., 144° C., 145° C., and the like.

[0105] Furthermore, the falling film evaporation pressure is -15 kPa to -5 kPa. In a specific example, the falling film evaporation pressure is -15 kPa, -14 kPa, -13 kPa, -12 kPa, -11 kPa, -10 kPa, -9 kPa, -8 kPa, -7 kPa, -6 kPa, -5 kPa, etc.

[0106] In the embodiment of the present application, sulfuric acid containing hydrogen fluoride is treated by falling film evaporation to control the content of hydrogen fluoride in the liquid phase dilute sulfuric acid to be less than 5‰, thereby ensuring that most of the hydrogen fluoride is separated from the sulfuric acid, which is beneficial to improving the recovery rate of hydrogen fluoride. In specific examples, the content of hydrogen fluoride is less than 5‰, less than 4.5‰, less than 4‰, less than 3.5‰, less than 3‰, less than 2.5‰, less than 2‰, less than 1.5‰, less than 1‰, etc.

[0107] In some embodiments of the present application, at least one of the following is satisfied during the reaction of fluorosilicic acid with the first sulfuric acid:

[0108] (α) controlling the reaction temperature to be 60°C to 140°C;

[0109] (β) Fluorosilicic acid uses a fluosilicic acid with a mass concentration of 40% to 50%;

[0110] (γ) The first sulfuric acid comprises: 91% to 95% sulfuric acid and 1% to 5% hydrogen fluoride.

[0111] In the embodiment of the present application, in the step of decomposing fluorosilicic acid and the first sulfuric acid, the reaction temperature is 60°C to 140°C. In a specific example, the reaction temperature is 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 92°C, 94°C, 96°C, 98°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, etc. Further, the reaction temperature is 90°C to 100°C, and in a specific example, the reaction temperature is 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, etc.

[0112] In the embodiment of the present application, in the embodiment of the present application, fluorosilicic acid is used as a raw material to decompose and produce hydrogen fluoride and silicon tetrafluoride. The mass concentration of fluorosilicic acid meets the above conditions, which is conducive to improving the reaction efficiency, reducing the amount of the first sulfuric acid, increasing the hydrogen fluoride yield, and further reducing the unit consumption of sulfuric acid. In the specific example, the mass concentration of fluorosilicic acid is 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50%, etc.

[0113] In the embodiment of the present application, the composition of the first sulfuric acid is as described above, and a by-product sulfuric acid solution may be used, such as a third mixed sulfuric acid. In a specific example, in the composition of the first sulfuric acid, the content of sulfuric acid may be 91%, 92%, 93%, 94%, or 95%, etc.; the content of hydrogen fluoride may be 1%, 2%, 3%, 4%, 5%, etc.

[0114] In some embodiments of the present application, in the decomposition reaction of fluorosilicic acid and the first sulfuric acid, the silicon content in the first mixed sulfuric acid is controlled to meet the above conditions, so that the fluorosilicic acid can be fully decomposed. In specific examples, the silicon content is less than 2‰, less than 1.8‰, less than 1.6‰, less than 1.4‰, less than 1.2‰, less than 1.0‰, less than 0.8‰, less than 0.6‰, less than 0.4‰, less than 0.2‰, less than 0.1‰, etc.

[0115] In some embodiments of the present application, after the fluorosilicic acid is reacted with the third mixed sulfuric acid, the composition of the obtained first mixed sulfuric acid is: sulfuric acid, 60% to 70%; hydrogen fluoride, 3% to 6%; water, 25% to 40%.

[0116] In some embodiments of the present application, in the step of washing the mixed gas with a second sulfuric acid, the temperature of the sulfuric acid absorption tower is 20°C to 80°C; the temperature of the silicon tetrafluoride gas after washing is 20°C to 60°C.

[0117] In some embodiments of the present application, after the mixed gas is washed with a second sulfuric acid, the composition of the obtained second mixed sulfuric acid is: sulfuric acid, 94% to 96%; hydrogen fluoride, 1% to 3%; water: 2% to 4%.

[0118] In some embodiments of the present application, the first mixed sulfuric acid is subjected to falling film evaporation treatment to produce a liquid phase of dilute sulfuric acid having the following composition: sulfuric acid, 60% to 70%; hydrogen fluoride, 0% to 1%; water, 30% to 40%. Furthermore, the content of hydrogen fluoride is less than 5‰.

[0119] In some embodiments of the present application, in the step of washing the aqueous hydrogen fluoride with the second mixed sulfuric acid, the temperature of the washing tower is 80° C. to 140° C., and the pressure is -3 kpa to 0 kpa.

[0120] In some embodiments of the present application, Figure 2 As shown, the method for preparing hydrogen fluoride comprises the steps of:

[0121] Step a. Decomposing fluorosilicic acid and a first sulfuric acid to generate a mixed gas and a first mixed sulfuric acid; the mixed gas includes silicon tetrafluoride gas and hydrogen fluoride gas.

[0122] Step b. washing the mixed gas with a second sulfuric acid to obtain a second mixed sulfuric acid and washed silicon tetrafluoride gas; the second mixed sulfuric acid is obtained by absorbing hydrogen fluoride gas with the second sulfuric acid.

[0123] Step c. using the first fluorosilicic acid solution to absorb the washed silicon tetrafluoride gas to obtain a fluorosilicic acid mixed solution containing silicon dioxide precipitate;

[0124] Step d. The fluorosilicic acid mixed solution containing silicon dioxide precipitate is filtered to obtain a second fluorosilicic acid solution and silicon dioxide precipitate; the filtered second fluorosilicic acid solution is circulated back to step a and decomposed with the first sulfuric acid as fluorosilicic acid or as a raw material of fluorosilicic acid. The silicon dioxide precipitate is washed and the obtained solid phase is dried to obtain by-product silicon dioxide; the liquid phase obtained by washing is the third fluorosilicic acid solution, which is used as the raw material of the first fluorosilicic acid solution.

[0125] Step e. The first mixed sulfuric acid is treated by falling film evaporation to produce liquid dilute sulfuric acid and gaseous hydrogen fluoride;

[0126] Step f. Using the second mixed sulfuric acid to wash the gaseous hydrogen fluoride to obtain crude hydrogen fluoride gas and a third mixed sulfuric acid. The third mixed sulfuric acid is recycled back to step a and used as the first sulfuric acid or as a raw material for the first sulfuric acid to undergo a decomposition reaction with fluorosilicic acid.

[0127] Step g. The crude hydrogen fluoride gas is condensed to obtain a crude anhydrous hydrogen fluoride product; the crude anhydrous hydrogen fluoride product is further distilled and degassed to obtain a finished anhydrous hydrogen fluoride product.

[0128] Step h. The liquid phase dilute sulfuric acid is subjected to air stripping treatment to obtain by-product dilute sulfuric acid and a stripping mixed gas; the stripping mixed gas includes air and stripping hydrogen fluoride; the stripping mixed gas is subjected to water absorption treatment to obtain a by-product hydrofluoric acid.

[0129] In some embodiments of the present application, Figure 3 As shown, the method for preparing hydrogen fluoride comprises the steps of:

[0130] Step a. 40% to 50% of fluorosilicic acid and the third mixed sulfuric acid enter a decomposition tower and react in the decomposition tower to produce silicon tetrafluoride gas, hydrogen fluoride gas and the first mixed sulfuric acid. The decomposition reaction carried out in the decomposition tower is as follows:

[0131] H 2 SiF 6 =HF+SiF 4 .

[0132] Reaction temperature: 60°C to 140°C, preferably 90°C to 100°C.

[0133] The composition of the third mixed sulfuric acid: sulfuric acid, 91% to 95%; hydrogen fluoride, 1% to 5%; water, 2% to 6%.

[0134] The first mixed sulfuric acid comprises: sulfuric acid, 60% to 70%; hydrogen fluoride, 3% to 6%; and water, 25% to 40%.

[0135] Step b. The silicon tetrafluoride gas and hydrogen fluoride gas produced in step a are passed through a sulfuric acid absorption tower. A second sulfuric acid, i.e., 98% sulfuric acid, is used to absorb the mixed gas of silicon tetrafluoride and hydrogen fluoride, and the hydrogen fluoride gas is absorbed into the 98% sulfuric acid to obtain a second mixed sulfuric acid, and the 98% sulfuric acid cools the mixed gas.

[0136] The second mixed sulfuric acid comprises: sulfuric acid, 94% to 96%; hydrogen fluoride, 1% to 3%; and water, 2% to 4%.

[0137] The temperature of the sulfuric acid absorption tower: 20℃~80℃; the temperature of silicon tetrafluoride gas: 20℃~60℃.

[0138] Step c. The silicon tetrafluoride gas absorbed by the absorption tower in step b enters the silicon tetrafluoride absorption tower, and the first fluorosilicic acid solution, i.e., 25% to 30% fluorosilicic acid, is used to absorb the silicon tetrafluoride gas to form a fluorosilicic acid solution containing silicon dioxide precipitation. The hydrolysis reaction carried out in the silicon tetrafluoride absorption tower is as follows:

[0139] SiF 4 +H 2 O=H 2 SiF 6 +SiO 2 .

[0140] Then, the fluorosilicic acid solution containing silicon dioxide precipitate is filtered through a filter, and the second fluorosilicic acid solution obtained by filtration enters a 40% to 50% fluorosilicic acid storage tank, and returns to the decomposition tower to perform step a. The silicon dioxide precipitate obtained by filtration is washed, and the solid phase and washing liquid obtained by washing are the third fluorosilicic acid solution. The solid phase is dried to obtain by-product silicon dioxide and sold as a by-product. The washing liquid enters a 11% to 18% fluorosilicic acid solution storage tank, and the 11% to 18% fluorosilicic acid is vacuum concentrated to increase the concentration to 25% to 30% fluorosilicic acid, and enters a silicon tetrafluoride absorption tower.

[0141] The concentration of fluorosilicic acid in the third fluorosilicic acid solution is 3% to 10%.

[0142] The temperature of silicon tetrafluoride absorption tower: 20℃~50℃.

[0143] Step d. The first mixed sulfuric acid produced in step a is heated and evaporated in a falling film evaporator to produce gaseous hydrogen fluoride and liquid dilute sulfuric acid.

[0144] Falling film evaporator temperature: 130℃~160℃; pressure: -3kpa~0kpa.

[0145] The composition of liquid dilute sulfuric acid: sulfuric acid, 60% to 70%; hydrogen fluoride, 0% to 1%; water, 30% to 40%.

[0146] Step e. The gaseous hydrogen fluoride (containing sulfuric acid and water) produced in step d enters a washing tower and is washed with the second mixed sulfuric acid in step b. The hydrogen fluoride in the second mixed sulfuric acid is released to obtain crude hydrogen fluoride gas and a third mixed sulfuric acid.

[0147] The temperature of the washing tower is 80℃~140℃, and the pressure is -3kpa~0kpa.

[0148] The composition of the third mixed sulfuric acid: sulfuric acid, 91% to 95%; hydrogen fluoride, 1% to 5%; water, 2% to 6%.

[0149] Step f. The crude hydrogen fluoride gas obtained in step e enters a condenser and is condensed into anhydrous crude hydrogen fluoride (ie, crude AHF).

[0150] The composition of the crude anhydrous hydrogen fluoride: hydrogen fluoride, 97% to 99%; sulfuric acid, 0% to 1%; water, 0 to 1%.

[0151] Condenser temperature: 5℃~18℃.

[0152] Step g. The crude anhydrous hydrogen fluoride enters a distillation tower for distillation, and then enters a degassing tower for degassing to obtain pure hydrogen fluoride as anhydrous hydrogen fluoride finished product (i.e., finished product AHF). The liquid in the bottom of the distillation tower is returned to the washing process. After distillation, there is a small amount of sulfuric acid in the bottom of the tower. With continuous distillation, the boiling point of the system becomes higher and higher, and the residue needs to be discharged in time to the sulfuric acid washing tower used for washing the mixed gas to control the temperature of the distillation tower system.

[0153] Purity of anhydrous hydrogen fluoride product: ≥99.97%, hydrogen fluoride yield: 80% to 90%.

[0154] The composition of the distillation bottom liquid is: hydrogen fluoride, 90% to 95%; sulfuric acid, 1% to 5%; water 0 to 1%.

[0155] The temperature of the distillation tower kettle is 21℃~28℃, and the temperature of the distillation tower top is 17℃~19.5℃.

[0156] The temperature of the degassing tower bottom is 19.5℃~21℃, and the temperature of the degassing tower top is 17℃~19.5℃.

[0157] Step h. The liquid dilute sulfuric acid produced in step d enters a stripping tower, and is stripped with hot air to strip hydrogen fluoride from the liquid dilute sulfuric acid. The hydrogen fluoride and the hot air enter an absorption tower to obtain byproduct hydrofluoric acid. The stripped sulfuric acid is cooled to obtain 60% to 70% dilute sulfuric acid.

[0158] Temperature of stripping tower: 100℃~120℃.

[0159] Temperature of absorption tower: 20℃~40℃.

[0160] A second aspect of the embodiments of the present application provides hydrogen fluoride, which is obtained by the above-mentioned preparation method.

[0161] The examples of the present application adopt the above-mentioned preparation method to obtain hydrogen fluoride with a high yield and high purity.

[0162] A third aspect of an embodiment of the present application proposes a battery material, and the raw materials for preparing the battery material include hydrogen fluoride obtained by the preparation method proposed in the first aspect, or the hydrogen fluoride proposed in the second aspect.

[0163] The hydrogen fluoride obtained by the above-mentioned preparation method in the embodiment of the present application can be used as a raw material for some battery materials, such as a raw material for lithium hexafluorophosphate, sodium hexafluorophosphate, potassium hexafluorophosphate, lithium bis(fluorosulfonate)imide, lithium fluorosulfonate, etc.

[0164] The present invention is described below with reference to specific examples. It should be noted that these examples are merely illustrative and do not limit the present invention in any way. The reagents used in the examples are all from Aladdin Biochemical Technology Co., Ltd.

[0165] Example 1

[0166] Step A: 50% fluorosilicic acid and the third mixed sulfuric acid enter the decomposition tower and react in the decomposition tower to produce silicon tetrafluoride gas, hydrogen fluoride gas and the first mixed sulfuric acid. The decomposition reaction carried out in the decomposition tower is as follows:

[0167] H 2 SiF 6 =HF+SiF 4 .

[0168] Reaction temperature: 90℃.

[0169] The composition of the third mixed sulfuric acid: sulfuric acid, 94%; hydrogen fluoride, 2%; water, 4%.

[0170] The composition of the first mixed sulfuric acid: sulfuric acid, 67%; hydrogen fluoride, 3.5%; water, 29.5%.

[0171] Step B: The silicon tetrafluoride gas and hydrogen fluoride gas produced in step A are passed through a sulfuric acid absorption tower. A second sulfuric acid, i.e., 98% sulfuric acid, is used to absorb the mixed gas of silicon tetrafluoride gas and hydrogen fluoride gas, and the hydrogen fluoride gas is absorbed into the 98% sulfuric acid to obtain a second mixed sulfuric acid, while the 98% sulfuric acid has a cooling effect on the mixed gas.

[0172] The composition of the second mixed sulfuric acid: sulfuric acid, 96%; hydrogen fluoride, 2%; water: 2%.

[0173] The temperature of the sulfuric acid absorption tower: 40°C; the temperature of the silicon tetrafluoride gas: 80°C.

[0174] Step C: The silicon tetrafluoride gas absorbed by the absorption tower in step B enters the silicon tetrafluoride absorption tower, and the first fluorosilicic acid solution, i.e., 30% fluorosilicic acid, is used to absorb the silicon tetrafluoride gas to form a fluorosilicic acid solution containing silicon dioxide precipitation. The hydrolysis reaction carried out in the silicon tetrafluoride absorption tower is as follows:

[0175] SiF 4 +H 2 O=H 2 SiF 6 +SiO2 .

[0176] Then, the fluorosilicic acid solution containing silicon dioxide precipitate is filtered through a filter, and the second fluorosilicic acid solution obtained by filtration enters a 50% fluorosilicic acid storage tank and returns to the decomposition tower to perform step A. The silicon dioxide precipitate obtained by filtration is washed, and the solid phase and washing liquid obtained by washing are the third fluorosilicic acid solution. The solid phase is dried to obtain by-product silicon dioxide and sold as a by-product. The washing liquid enters a 18% fluorosilicic acid solution storage tank, and the 18% fluorosilicic acid is vacuum concentrated to increase the concentration to 30% fluorosilicic acid and enters a silicon tetrafluoride absorption tower.

[0177] The concentration of fluorosilicic acid in the third fluorosilicic acid solution is 10%.

[0178] Temperature of silicon tetrafluoride absorption tower: 30°C.

[0179] Step D: The first mixed sulfuric acid produced in step A enters a falling film evaporator for heating and evaporation to produce gaseous hydrogen fluoride and liquid dilute sulfuric acid.

[0180] Falling film evaporator temperature: 150℃; pressure: -3kpa.

[0181] The composition of liquid dilute sulfuric acid: sulfuric acid, 68%; hydrogen fluoride, 0.3%; water, 32%.

[0182] Step E: The gaseous hydrogen fluoride (containing sulfuric acid and water) produced in step D enters a washing tower and is washed with the second mixed sulfuric acid in step B. The hydrogen fluoride in the second mixed sulfuric acid is released to obtain crude hydrogen fluoride gas and a third mixed sulfuric acid.

[0183] The temperature of the washing tower is 100℃, and the pressure is -3kpa.

[0184] The composition of the third mixed sulfuric acid: sulfuric acid, 94%; hydrogen fluoride, 2%; water, 4%.

[0185] Step F: The crude hydrogen fluoride gas obtained in step E enters a condenser and is condensed into anhydrous crude hydrogen fluoride (i.e., crude AHF).

[0186] The composition of the crude anhydrous hydrogen fluoride: hydrogen fluoride, 99%; sulfuric acid, 0.6%; water, 0.4%.

[0187] Condenser temperature: 8°C.

[0188] Step G: The crude anhydrous hydrogen fluoride enters a distillation tower for distillation, and then enters a degassing tower for degassing to obtain pure hydrogen fluoride as anhydrous hydrogen fluoride product (i.e., finished product AHF). The distillation tower bottom liquid is returned to the sulfuric acid washing tower for washing the mixed gas.

[0189] Purity of anhydrous hydrogen fluoride product: ≥99.97%, hydrogen fluoride yield: 85%.

[0190] The composition of the distillation tower bottom liquid is: hydrogen fluoride, 96%; sulfuric acid, 2%; water 2%.

[0191] The temperature of the distillation tower kettle is 23℃ and the temperature of the distillation tower top is 19℃.

[0192] The temperature of the degassing tower bottom is 21°C, and the temperature of the degassing tower top is 19°C.

[0193] Step H: The liquid dilute sulfuric acid produced in step D enters a stripping tower, and is stripped with hot air to strip hydrogen fluoride from the liquid dilute sulfuric acid. The hydrogen fluoride and the hot air enter an absorption tower to obtain by-product hydrofluoric acid. The stripped sulfuric acid is cooled to obtain: 70% dilute sulfuric acid.

[0194] Temperature of stripping tower: 120℃.

[0195] Temperature of absorption tower: 30℃.

[0196] Example 2-Example 23

[0197] The specific preparation methods of hydrogen fluoride provided in Examples 2 to 23 are as shown in Example 1, and the specific parameter values ​​are shown in Table 1.

[0198] Table 1

[0199]

[0200] Performance Testing

[0201] 1. Test method:

[0202] 1. Yield of hydrogen fluoride: in:

[0203] m(AHF) represents the weight of the product anhydrous hydrogen fluoride, in g;

[0204] m(H 2 SiF 6 ) represents the weight of fluorosilicic acid reacted with the first sulfuric acid, in g;

[0205] w(H 2 SiF 6 ) represents the mass fraction of fluorosilicic acid reacting with the first sulfuric acid;

[0206] "2" indicates the molar ratio of hydrofluoric acid to hydrogen fluoride; "20" indicates the molar mass of HF; "144" indicates H 2 SiF 6 The molar mass of .

[0207] 2. Purity of hydrogen fluoride: The purity of anhydrous hydrogen fluoride is tested according to the national standard GB / T 7746-2023.

[0208] 3. Sulfuric acid unit consumption: unit consumption (H 2 SO 4 )=m(H 2 SO 4 ) / m(anhydrous hydrogen fluoride), dimensionless; where:

[0209] m(H 2 SO 4 ) represents the weight of all sulfuric acid added during the preparation process, in g;

[0210] m (anhydrous hydrogen fluoride) represents the weight of the product anhydrous hydrogen fluoride, in g.

[0211] 2. Test results:

[0212] Examples 1-23 were tested, and the results are shown in Table 2.

[0213] Table 2

[0214] sample Hydrogen fluoride yield Purity of hydrogen fluoride Sulfuric acid consumption Example 1 81.41％ 99.97％ 8.55 Example 2 82.15％ 99.99％ 8.55 Example 3 82.75％ 99.97％ 8.55 Example 4 83.15％ 99.99％ 8.55 Example 5 84.42％ 99.98％ 13.88 Example 6 84.96％ 99.98％ 12.03 Example 7 85.32％ 99.99％ 10.24 Example 8 86.31％ 99.98％ 8.55 Example 9 82.76％ 99.96％ 8.55 Example 10 83.01％ 99.97％ 8.55 Embodiment 11 83.23％ 99.99％ 8.55 Example 12 86.31％ 99.97％ 8.55 Embodiment 13 65.43％ 99.99％ 8.55 Embodiment 14 72.54％ 99.96％ 8.55 Embodiment 15 84.54％ 99.99％ 8.55 Example 16 88.54％ 99.98％ 8.55 Embodiment 17 91.21％ 99.96％ 8.55 Embodiment 18 92.10％ 99.99％ 8.55 Embodiment 19 90.54％ 99.97％ 8.55 Embodiment 20 87.67％ 99.97％ 8.55 Embodiment 21 86.31％ 99.98％ 8.55 Embodiment 22 73.43％ 99.99％ 8.55 Embodiment 23 68.32％ 99.99％ 8.55

[0215] The preparation method of anhydrous hydrogen fluoride provided in the embodiment of the present application has a high yield and purity of hydrogen fluoride obtained, and reduces the unit consumption of sulfuric acid. As shown in Examples 1-4, with the increase of the content of hydrogen fluoride in gas phase hydrogen fluoride, the yield of anhydrous hydrogen fluoride shows an increasing trend; as shown in Examples 5-8, with the increase of the concentration of fluorosilicic acid, the yield of anhydrous hydrogen fluoride shows an increasing trend; as in Examples 9-12, the lower the content of hydrogen fluoride in the third mixed sulfuric acid, the higher the hydrogen fluoride released by the scrubber, and the higher the yield of hydrogen fluoride; as in Examples 13-18, with the increase of the falling film evaporation temperature, the more hydrogen fluoride is distilled, the more conducive to improving the yield of hydrogen fluoride; as in Examples 19-23, with the decrease of the falling film evaporation pressure, it is conducive to evaporating more hydrogen fluoride, and the yield of hydrogen fluoride shows an increasing trend.

[0216] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0217] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing hydrogen fluoride, characterized in that: include: reacting fluorosilicic acid with a first sulfuric acid to produce a mixed gas and a first mixed sulfuric acid, wherein the first mixed sulfuric acid is a sulfuric acid solution containing hydrogen fluoride, and the mixed gas includes silicon tetrafluoride gas and hydrogen fluoride gas; The mixed gas is washed with a second sulfuric acid to obtain a second mixed sulfuric acid and washed silicon tetrafluoride gas; the second mixed sulfuric acid is obtained by absorbing the hydrogen fluoride gas with the second sulfuric acid; washing the aqueous hydrogen fluoride with the second mixed sulfuric acid to obtain crude hydrogen fluoride gas; The crude hydrogen fluoride gas is purified to obtain anhydrous hydrogen fluoride.

2. The preparation method according to claim 1, characterized in that: The mass ratio of water to hydrogen fluoride in the aqueous hydrogen fluoride is 1:5 to 1:19; and / or the aqueous hydrogen fluoride includes at least one of hydrofluoric acid output from a fluorite process tail gas absorber, hydrofluoric acid output from an electronic grade hydrofluoric acid tail gas absorber, and hydrofluoric acid output from a phosphorus chemical tail gas absorber.

3. The preparation method according to claim 1 or 2, characterized in that: The first mixed sulfuric acid is treated by falling film evaporation to obtain liquid dilute sulfuric acid and gaseous hydrogen fluoride, and the gaseous hydrogen fluoride serves as the source of the aqueous hydrogen fluoride.

4. The preparation method according to claim 3, characterized in that: Based on the total mass of the aqueous hydrogen fluoride, the mass percentage of hydrogen fluoride in the aqueous hydrogen fluoride is 40% to 95%.

5. The preparation method according to claim 1, characterized in that: The step of washing the aqueous hydrogen fluoride with the second mixed sulfuric acid also produces a third mixed sulfuric acid; The third mixed sulfuric acid serves as a source of the first sulfuric acid and reacts with the fluorosilicic acid.

6. The preparation method according to claim 1, characterized in that: Also includes: Treating the washed silicon tetrafluoride gas comprises the steps of: The washed silicon tetrafluoride gas is absorbed by a first fluorosilicic acid solution to obtain a fluorosilicic acid mixed solution containing silicon dioxide precipitate, and solid-liquid separation is performed to obtain a second fluorosilicic acid solution and the silicon dioxide precipitate; The silica precipitate is washed to obtain a third fluorosilicic acid solution and silica solid.

7. The preparation method according to claim 6, characterized in that: The treatment of the washed silicon tetrafluoride gas satisfies at least one of the following: (i) the mass concentration of the first fluorosilicic acid solution is 25% to 30%; (ii) the mass concentration of the second fluorosilicic acid solution is 40% to 55%; (iii) the mass concentration of the third fluorosilicic acid solution is 11% to 18%; (iv) the third fluorosilicic acid solution is concentrated to produce a first fluorosilicic acid solution; (v) The second fluorosilicic acid solution, as the source of the fluorosilicic acid, reacts with the first sulfuric acid.

8. The preparation method according to claim 1, characterized in that: The step of purifying the crude hydrogen fluoride gas to obtain anhydrous hydrogen fluoride comprises: Condensing the crude hydrogen fluoride gas to obtain crude anhydrous hydrogen fluoride; The crude anhydrous hydrogen fluoride is sequentially subjected to distillation treatment and degassing treatment to obtain anhydrous hydrogen fluoride.

9. The preparation method according to claim 3, characterized in that: The liquid phase dilute sulfuric acid is subjected to air stripping treatment to obtain dilute sulfuric acid and stripping mixed gas, wherein the stripping mixed gas includes air and stripping hydrogen fluoride; The stripping mixed gas is treated by water absorption to obtain hydrofluoric acid.

10. The preparation method according to claim 3, characterized in that: The first mixed sulfuric acid is treated by falling film evaporation, comprising at least one of the following: (a) controlling the falling film evaporation temperature to be 130° C. to 160° C.; and / or the pressure to be -30 kPa to 0 kPa; (b) The content of hydrogen fluoride in the liquid phase dilute sulfuric acid is less than 5‰.

11. The preparation method according to claim 1, characterized in that: The step of reacting fluorosilicic acid with the first sulfuric acid at least satisfies one of the following conditions: (α) controlling the reaction temperature to be 60°C to 140°C; (β) the fluorosilicic acid has a mass concentration of 40% to 50%; (γ) The first sulfuric acid comprises: 91% to 95% sulfuric acid and 1% to 5% hydrogen fluoride.

12. A hydrogen fluoride, characterized in that: The hydrogen fluoride is obtained by the preparation method according to any one of claims 1 to 11.

13. A battery material, characterized in that: The raw material for preparing the battery material includes hydrogen fluoride obtained by the preparation method according to any one of claims 1 to 11, or includes hydrogen fluoride according to claim 12.

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