Preparation method of hydrogen fluoride, hydrogen fluoride and battery material

Abstract

The invention discloses a preparation method of hydrogen fluoride, hydrogen fluoride and a battery material. The preparation method comprises the following steps: reacting a fluosilicic acid solution with a sulfuric acid solution to obtain mixed gas and fluorine-containing sulfuric acid; the content of hydrogen fluoride in the mixed gas is 10%-20%, and the content of hydrogen fluoride in the fluorine-containing sulfuric acid is 90%-80%; treating the mixed gas with concentrated sulfuric acid to obtain absorbed sulfuric acid; performing falling film evaporation treatment on fluorine-containing sulfuric acid to obtain a hydrogen fluoride-containing gas phase; and absorbing sulfuric acid to wash the hydrogen fluoride-containing gas phase to obtain hydrogen fluoride gas. The preparation method of hydrogen fluoride provided by the invention is beneficial to improving the recovery rate of hydrogen fluoride.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine chemical industry, and specifically relates to a method for preparing hydrogen fluoride, hydrogen fluoride and battery materials. 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 and small investment, accounting for more than 80% of the total domestic output, but with high production costs and great environmental pressure. The fluosilicic acid method is relatively mature in technology and has good economic benefits.

[0003] At present, anhydrous hydrogen fluoride is prepared from fluorosilicic acid by reacting 98% sulfuric acid with 40% fluorosilicic acid. However, the overall yield of hydrogen fluoride is not high and 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 method for preparing hydrogen fluoride, hydrogen fluoride and battery materials. The method for preparing hydrogen fluoride is conducive to improving the recovery rate of hydrogen fluoride.

[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 the steps of:

[0006] The fluorosilicic acid solution is reacted with the sulfuric acid solution to obtain a mixed gas and fluorine-containing sulfuric acid; the content of hydrogen fluoride in the mixed gas is 10% to 20%, and the content of hydrogen fluoride in the fluorine-containing sulfuric acid is 90% to 80%;

[0007] The mixed gas is treated with concentrated sulfuric acid to obtain absorbed sulfuric acid, wherein the absorbed sulfuric acid is concentrated sulfuric acid after absorbing hydrogen fluoride;

[0008] Fluorine-containing sulfuric acid is treated by falling film evaporation to obtain a hydrogen fluoride-containing gas phase;

[0009] The hydrogen fluoride-containing gas phase is washed by absorbing sulfuric acid to obtain hydrogen fluoride gas.

[0010] In the embodiment of the present application, fluorosilicic acid reacts with a sulfuric acid solution to obtain a gas phase (i.e., a mixed gas) and a liquid phase (i.e., fluorine-containing sulfuric acid). Both the gas phase and the liquid phase contain hydrogen fluoride. By controlling the content of hydrogen fluoride in the gas phase and the content of hydrogen fluoride in the liquid phase, the yield of hydrogen fluoride can be increased.

[0011] In the embodiment of the present application, the content of hydrogen fluoride in the mixed gas is controlled to be 10% to 20%, which is beneficial to ensure that when the mixed gas is treated with concentrated sulfuric acid, the hydrogen fluoride in the mixed gas can be repeatedly absorbed, thereby increasing the yield of hydrogen fluoride in the gas phase. The increased yield of hydrogen fluoride is also beneficial to reducing the unit consumption of sulfuric acid; by controlling the content of hydrogen fluoride in the fluorine-containing sulfuric acid to be 90% to 80%, the yield of hydrogen fluoride in the liquid phase can be increased by falling film evaporation treatment, while avoiding excessive hydrogen fluoride content in the liquid phase, increasing the unit consumption of sulfuric acid, and increasing the raw material cost and treatment cost of sulfuric acid.

[0012] In some embodiments of the present application, the content of hydrogen fluoride in the mixed gas is 15% to 19%; the content of hydrogen fluoride in the fluorine-containing sulfuric acid is 85% to 81%.

[0013] In some embodiments of the present application, the mass concentration C1 of fluorosilicic acid in the fluorosilicic acid solution is 18% to 55%, and the mass concentration of sulfuric acid in the sulfuric acid solution is above 90%.

[0014] In some embodiments of the present application, in the reaction of the fluosilicic acid solution and the sulfuric acid solution, the mass ratio of the fluosilicic acid solution to the sulfuric acid solution is 1:1 to 1:4.

[0015] In some embodiments of the present application, the following one is satisfied during the reaction of the fluorosilicic acid solution with the sulfuric acid solution:

[0016] (i) the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 18%≤C1<30%, and the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:2 to 1:4;

[0017] (ii) the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 30%≤C1<40%, and the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:2 to 1:3;

[0018] (iii) The mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 40%≤C1≤55%, and the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:1 to 1:2.

[0019] In some embodiments of the present application, absorbing sulfuric acid to wash the hydrogen fluoride-containing gas phase further includes obtaining recycled sulfuric acid; the recycled sulfuric acid satisfies at least one of the following:

[0020] (a) recovering sulfuric acid as the source of sulfuric acid solution and reacting with fluosilicic acid solution;

[0021] (b) Calculated by mass percentage, the recovered sulfuric acid component includes 91% to 95% sulfuric acid and 1% to 5% hydrogen fluoride.

[0022] In some embodiments of the present application, when the fluosilicic acid solution and the sulfuric acid solution are reacted, the reaction temperature is controlled to be 80°C to 120°C.

[0023] In some embodiments of the present application, when the fluosilicic acid solution and the sulfuric acid solution are reacted, the reaction temperature is controlled to be 80°C to 100°C.

[0024] In some embodiments of the present application, the preparation method further comprises:

[0025] The hydrogen fluoride gas is condensed to obtain crude anhydrous hydrogen fluoride;

[0026] The crude anhydrous hydrogen fluoride is subjected to distillation treatment and degassing treatment to obtain the finished anhydrous hydrogen fluoride.

[0027] In some embodiments of the present application, the fluorine-containing sulfuric acid is treated by falling film evaporation to obtain a hydrogen fluoride-containing liquid phase;

[0028] The liquid phase containing hydrogen fluoride is subjected to air stripping treatment to obtain dilute sulfuric acid and stripping mixed gas;

[0029] The stripping mixed gas is treated by water absorption to obtain hydrofluoric acid.

[0030] In some embodiments of the present application, the mixed gas also includes silicon tetrafluoride, and the mixed gas is treated with concentrated sulfuric acid to obtain silicon tetrafluoride gas absorbed by concentrated sulfuric acid; the silicon tetrafluoride gas absorbed by concentrated sulfuric acid is subjected to fluorosilicic acid absorption treatment, filtration treatment, and washing treatment to obtain by-product silicon dioxide.

[0031] In a second aspect, the present application provides hydrogen fluoride obtained by the above-mentioned preparation method.

[0032] The third aspect of the present application proposes a battery material, including lithium hexafluorophosphate; the raw materials for preparing the battery material include the above-mentioned hydrogen fluoride, or include the above-mentioned hydrogen fluoride.

[0033] The fourth aspect of the present application provides a system for preparing hydrogen fluoride, comprising:

[0034] A decomposition tower, wherein the decomposition tower is provided with a liquid phase input end for a fluorosilicic acid solution and a sulfuric acid solution;

[0035] An absorption tower, wherein the absorption tower is provided with a liquid phase input end of concentrated sulfuric acid, and a gas phase input end of the absorption tower is connected to a gas phase output end of the decomposition tower;

[0036] A falling film evaporator, wherein the liquid phase input end of the falling film evaporator is connected to the liquid phase output end of the decomposition tower;

[0037] The washing tower has a gas phase input end connected to the gas phase output end of the falling film evaporator, a liquid phase input end connected to the liquid phase output end of the absorption tower, and the washing tower is also provided with a gas phase output end of hydrogen fluoride gas.

[0038] The system provided in the present application can be used to prepare the above-mentioned hydrogen fluoride, which is beneficial to improving the recovery rate of hydrogen fluoride.

[0039] In some embodiments of the present application, the liquid phase output end of the washing tower is connected to the liquid phase input end of the decomposition tower.

[0040] 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

[0041] Figure 1 is a schematic diagram of a system for preparing hydrogen fluoride provided in some embodiments of the present application.

[0042] Figure 2 is a schematic diagram of a system for preparing hydrogen fluoride provided in some embodiments of the present application.

[0043] Figure 3 It is a schematic diagram of a system for preparing hydrogen fluoride used in the specific embodiment of the present application.

[0044] Figure 4 It is a schematic diagram of the process flow of the method for preparing hydrogen fluoride adopted in the specific embodiment of the present application. DETAILED DESCRIPTION

[0045] 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.

[0046] 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 and small investment, accounting for more than 80% of the total domestic output, but with high production costs and great environmental pressure. The fluosilicic acid method is relatively mature in technology and has good economic benefits.

[0047] At present, when preparing anhydrous hydrogen fluoride from fluorosilicic acid, 98% sulfuric acid and 40% fluorosilicic acid are reacted to produce a portion of hydrogen fluoride that remains in the liquid phase for the next step of extraction, while the other portion of hydrogen fluoride overflows with the silicon tetrafluoride gas, resulting in hydrogen fluoride loss. However, the overall yield of hydrogen fluoride is not high and needs to be further improved.

[0048] To this end, the first aspect of the embodiment of the present application proposes a method for preparing hydrogen fluoride, comprising:

[0049] The fluorosilicic acid solution is reacted with the sulfuric acid solution to obtain a mixed gas and fluorine-containing sulfuric acid; the content of hydrogen fluoride in the mixed gas is 10% to 20%, and the content of hydrogen fluoride in the fluorine-containing sulfuric acid is 90% to 80%;

[0050] The mixed gas is treated with concentrated sulfuric acid to obtain absorbed sulfuric acid, which is concentrated sulfuric acid after absorbing hydrogen fluoride;

[0051] Fluorine-containing sulfuric acid is treated by falling film evaporation to obtain a hydrogen fluoride-containing gas phase;

[0052] The hydrogen fluoride-containing gas phase is washed by absorbing sulfuric acid to obtain hydrogen fluoride gas.

[0053] In the embodiment of the present application, fluorosilicic acid reacts with a sulfuric acid solution to obtain a gas phase (i.e., a mixed gas) and a liquid phase (i.e., fluorine-containing sulfuric acid). Both the gas phase and the liquid phase contain hydrogen fluoride. By controlling the content of hydrogen fluoride in the gas phase and the content of hydrogen fluoride in the liquid phase, the yield of hydrogen fluoride can be increased.

[0054] In the embodiment of the present application, the content of hydrogen fluoride in the mixed gas is controlled to be 10% to 20%, which is beneficial to ensure that when concentrated sulfuric acid is used to treat the mixed gas, the hydrogen fluoride in the mixed gas can be repeatedly absorbed, and the yield of hydrogen fluoride in the gas phase is increased. The increase in the yield of hydrogen fluoride is also beneficial to reducing the unit consumption of sulfuric acid; by controlling the content of hydrogen fluoride in fluorine-containing sulfuric acid to be 90% to 80%, the yield of hydrogen fluoride in the liquid phase can be increased by falling film evaporation. In addition, it is beneficial to avoid excessive hydrogen fluoride content in the liquid phase, increase the unit consumption of sulfuric acid, and increase the raw material cost and processing cost of sulfuric acid. This is because the unit consumption of sulfuric acid = sulfuric acid feed mass / anhydrous hydrogen fluoride product mass, so the hydrogen fluoride produced by the reaction of silicofluoric acid solution and sulfuric acid solution is too much dissolved in sulfuric acid, and the falling film evaporator is difficult to precipitate all hydrogen fluoride, which will result in more hydrofluoric acid by-products and a decrease in the output of anhydrous hydrogen fluoride products. In order to improve the yield, the amount of sulfuric acid solution and silicofluoric acid solution will be further increased, resulting in an increase in sulfuric acid unit consumption.

[0055] The sum of the content of hydrogen fluoride in the mixed gas and the content of hydrogen fluoride in the fluorine-containing sulfuric acid is 100%. As an example, the content of hydrogen fluoride in the mixed gas is 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, etc.; the corresponding content of hydrogen fluoride in fluorine-containing sulfuric acid is 90%, 89.5%, 89%, 88.5%, 88%, 87.5%, 87%, 86.5%, 86%, 85.5%, 85%, 84.5%, 84%, 83.5%, 83%, 82.5%, 82%, 81.5%, 81%, 80.5%, 80%, etc.

[0056] In the embodiment of the present application, fluorosilicic acid is reacted with a sulfuric acid solution. The sulfuric acid solution acts as a catalyst to promote the decomposition of fluorosilicic acid to produce silicon tetrafluoride and hydrogen fluoride. The decomposition principle of fluorosilicic acid is: H2SiF6=HF+SiF4.

[0057] The mixed gas is treated by concentrated sulfuric acid absorption, and part of the hydrogen fluoride in the mixed gas is dissolved in the concentrated sulfuric acid; another part of the hydrogen fluoride reacts with the concentrated sulfuric acid to generate fluorosulfonic acid, so that the sulfuric acid obtained after the concentrated sulfuric acid absorption includes sulfuric acid, water, hydrogen fluoride and fluorosulfonic acid.

[0058] The sulfuric acid after the concentrated sulfuric acid absorption washes the hydrogen fluoride-containing gas phase, and the sulfuric acid after the concentrated sulfuric acid absorption contacts with moisture and hydrogen fluoride gas. On the one hand, the fluorosulfonic acid in the sulfuric acid after the concentrated sulfuric acid absorption is hydrolyzed into hydrogen fluoride and sulfuric acid, releasing hydrogen fluoride gas; on the other hand, the sulfuric acid after the concentrated sulfuric acid absorption is diluted with water to release heat to release the hydrogen fluoride dissolved in the sulfuric acid after the concentrated sulfuric acid absorption; finally, the three mixed gases of hydrogen fluoride in the hydrogen fluoride-containing gas phase, hydrogen fluoride gas hydrolyzed and released in the sulfuric acid after the concentrated sulfuric acid absorption, and hydrogen fluoride gas dissolved and released are used as the washed hydrogen fluoride gas, which can be further purified to obtain anhydrous hydrogen fluoride. During the washing process, the hydrolysis reaction mechanism of fluorosulfonic acid is: HSO3F+H2O=H2SO4+HF.

[0059] In addition, the embodiment of the present application adopts a falling film evaporation method to evaporate sulfuric acid containing hydrogen fluoride. 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. And the overall temperature of falling film evaporation is low, which is conducive to reducing steam loss. The hydrogen fluoride-containing gas phase evaporated from the falling film is directly washed with sulfuric acid after absorption by concentrated sulfuric acid. The hydrogen fluoride-containing gas phase usually carries water, which promotes the release of hydrogen fluoride by sulfuric acid after absorption by concentrated sulfuric acid, which is conducive to effectively recovering the main reaction (i.e., the reaction of fluorosilicic acid with sulfuric acid solution) to obtain hydrogen fluoride, improve the hydrogen fluoride yield, and also help reduce the unit consumption of sulfuric acid.

[0060] In some embodiments of the present application, the composition of the hydrogen fluoride-containing gas phase is: sulfuric acid, 60% to 70%; hydrogen fluoride, 3% to 6%; water, 25% to 40%.

[0061] In some embodiments of the present application, the content of hydrogen fluoride in the mixed gas is 15% to 19%; the content of hydrogen fluoride in the fluorine-containing sulfuric acid is 85% to 81%.

[0062] The embodiment of the present application satisfies the above conditions by controlling the content of hydrogen fluoride in the mixed gas and the content of hydrogen fluoride in the fluorine-containing sulfuric acid, which is conducive to improving the overall yield of hydrogen fluoride and reducing the unit consumption of sulfuric acid. Further, the content of hydrogen fluoride in the mixed gas is 16% to 18%; the content of hydrogen fluoride in the fluorine-containing sulfuric acid is 84% ​​to 82%.

[0063] In some embodiments of the present application, the mass concentration C1 of fluorosilicic acid in the fluorosilicic acid solution is 18% to 55%, and the mass concentration of sulfuric acid in the sulfuric acid solution is above 90%.

[0064] In the embodiments of the present application, the mass concentration of fluorosilicic acid and the mass concentration of sulfuric acid solution meet the above conditions, which are sufficient to achieve a decomposition reaction between fluorosilicic acid and sulfuric acid solution.

[0065] As an example, the mass concentration of fluorosilicic acid in the fluorosilicic acid solution is 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, etc.

[0066] As an example, the mass concentration of sulfuric acid in the sulfuric acid solution is 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0067] Furthermore, the mass concentration of fluorosilicic acid in the fluorosilicic acid solution is 50% to 55%, and the mass concentration of sulfuric acid in the sulfuric acid solution is above 98%.

[0068] The embodiment of the present application limits the mass concentration of the fluorosilicic acid solution to 50% to 55%, which is conducive to reducing the amount of sulfuric acid used and reducing the overall sulfuric acid unit consumption. This is because during the reaction of the fluorosilicic acid solution and the sulfuric acid solution, the sulfuric acid absorbs water to promote the decomposition reaction. If a higher concentration of fluorosilicic acid solution is used, its water content is relatively low, the amount of sulfuric acid absorbed is small, and the amount of sulfuric acid used is also reduced, which is conducive to reducing the amount of sulfuric acid used and reducing the overall sulfuric acid unit consumption.

[0069] In addition, the concentration of the sulfuric acid solution increases and the water content decreases, which helps reduce the by-product of dilute sulfuric acid.

[0070] Furthermore, the mixed gas also includes silicon tetrafluoride. In the embodiment of the present application, the source of the fluorosilicic acid solution includes the fluorosilicic acid solution produced by treating silicon tetrafluoride, and the resources are recycled.

[0071] Furthermore, in the embodiment of the present application, the source of the sulfuric acid solution includes washed sulfuric acid obtained by washing the hydrogen fluoride-containing gas phase by absorbing sulfuric acid.

[0072] In some embodiments of the present application, in the reaction of the fluosilicic acid solution and the sulfuric acid solution, the mass ratio of the fluosilicic acid solution to the sulfuric acid solution is 1:1 to 1:4.

[0073] In the embodiments of the present application, by controlling the mass ratio of fluorosilicic acid to sulfuric acid solution in the main reaction, it is beneficial to regulate the content of hydrogen fluoride in the mixed gas and the content of hydrogen fluoride in the fluorine-containing sulfuric acid to meet the specified conditions, thereby facilitating the improvement of the hydrogen fluoride yield and the reduction of sulfuric acid consumption.

[0074] As an example, the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4, etc.

[0075] In some embodiments of the present application, the following one is satisfied during the reaction of the fluorosilicic acid solution with the sulfuric acid solution:

[0076] (i) the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 18%≤C1<30%, and the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:2 to 1:4;

[0077] (ii) the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 30%≤C1<40%, and the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:2 to 1:3;

[0078] (iii) The mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 40%≤C1≤55%, and the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:1 to 1:2.

[0079] In the embodiments of the present application, the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 18%≤C1<30%, the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:2~1:4, and more than 90% of the hydrogen fluoride produced by the reaction is soluble in the sulfuric acid solution, and only less than 10% of the hydrogen fluoride enters the gas phase and is output in the form of a mixed gas and is absorbed by concentrated sulfuric acid. The absorption amount of concentrated sulfuric acid is relatively low, and hydrogen fluoride will continue to be absorbed in the subsequent washing treatment. Therefore, the yield of hydrogen fluoride is improved, but there is still much room for improvement.

[0080] In the embodiments of the present application, the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 30%≤C1<40%, the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:2-1:3, 10%-13% of the hydrogen fluoride produced by the reaction enters the gas phase, and the amount absorbed by the concentrated sulfuric acid increases relatively, but is not saturated. A small amount of hydrogen fluoride can also be absorbed during the washing treatment, and the hydrogen fluoride yield will be further improved.

[0081] In the embodiments of the present application, the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 40%≤C1≤55%, the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:1-1:2, 10%-20% of the hydrogen fluoride produced by the reaction enters the gas phase, and the amount absorbed by the concentrated sulfuric acid increases, which may be nearly saturated or reach a saturated state. After entering the washing treatment, a large amount of hydrogen fluoride can be released, thereby promoting a better improvement in the yield of hydrogen fluoride.

[0082] In some embodiments of the present application, absorbing sulfuric acid to wash the hydrogen fluoride-containing gas phase further includes obtaining recycled sulfuric acid; the recycled sulfuric acid satisfies at least one of the following:

[0083] (a) recovering sulfuric acid as the source of sulfuric acid solution and reacting with fluosilicic acid solution;

[0084] (b) Calculated by mass percentage, the recovered sulfuric acid component includes 91% to 95% sulfuric acid and 1% to 5% hydrogen fluoride.

[0085] In some embodiments of the present application, when the fluosilicic acid solution and the sulfuric acid solution are reacted, the reaction temperature is controlled to be 80°C to 120°C.

[0086] In the embodiment of the present application, under the condition of relatively low reaction temperature, it is beneficial to increase the content of hydrogen fluoride in fluorine-containing sulfuric acid and reduce the content of hydrogen fluoride in the mixed gas. By controlling the reaction temperature of the fluosilicic acid solution and the sulfuric acid solution to react at 80°C to 120°C, it is beneficial to regulate the content of hydrogen fluoride in the mixed gas and the content of hydrogen fluoride in the fluorine-containing sulfuric acid to meet the specified conditions. As an example, the reaction temperature is controlled to be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, etc.

[0087] In some embodiments of the present application, when the fluosilicic acid solution and the sulfuric acid solution are reacted, the reaction temperature is controlled to be 80°C to 100°C.

[0088] In the embodiment of the present application, by controlling the reaction temperature of the fluorosilicic acid solution and the sulfuric acid solution to be kept in a relatively low temperature range, it is beneficial to control the content of hydrogen fluoride in the mixed gas and the content of hydrogen fluoride in the fluorine-containing sulfuric acid to meet the specified conditions and reduce energy consumption. As an example, the reaction temperature is controlled to be 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, 94°C, 96°C, 98°C, 100°C, etc.

[0089] In some embodiments of the present application, the preparation method further comprises:

[0090] The hydrogen fluoride gas is condensed to obtain crude anhydrous hydrogen fluoride;

[0091] The crude anhydrous hydrogen fluoride is subjected to distillation treatment and degassing treatment to obtain the finished anhydrous hydrogen fluoride.

[0092] In the embodiment of the present application, the washed 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 and degassing treatments in sequence to obtain a finished anhydrous hydrogen fluoride product, i.e., the target product anhydrous hydrogen fluoride.

[0093] In some embodiments of the present application, the fluorine-containing sulfuric acid is treated by falling film evaporation to obtain a hydrogen fluoride-containing liquid phase;

[0094] The liquid phase containing hydrogen fluoride is subjected to air stripping treatment to obtain dilute sulfuric acid and stripping mixed gas;

[0095] The stripping mixed gas is treated by water absorption to obtain hydrofluoric acid.

[0096] In the embodiment of the present application, the liquid phase containing hydrogen fluoride is stripped with hot air, which can reduce steam loss and reduce the production of by-product sulfuric acid. Dilute sulfuric acid and stripping mixed gas can be obtained by stripping; hot air and hydrogen fluoride are absorbed by water to obtain hydrofluoric acid, thereby obtaining two by-products; and the stripping mixed gas contains hot air, which carries a high amount of heat into the water absorption device, which is beneficial to reducing the heating energy consumption of the water absorption device and improving the resource utilization effect.

[0097] In some embodiments of the present application, the mixed gas also includes silicon tetrafluoride, and the mixed gas is treated with concentrated sulfuric acid to obtain silicon tetrafluoride gas absorbed by concentrated sulfuric acid; the silicon tetrafluoride gas absorbed by concentrated sulfuric acid is subjected to fluorosilicic acid absorption treatment, filtration treatment, and washing treatment to obtain by-product silicon dioxide.

[0098] In some embodiments of the present application, the first fluorosilicic acid solution is used to absorb the silicon tetrafluoride gas absorbed by concentrated sulfuric acid to obtain a silicic acid solution containing silicon dioxide;

[0099] The silicofluoric acid solution containing silicon dioxide is filtered to obtain a second silicofluoric acid solution and a solid phase containing silicon dioxide;

[0100] The silicon dioxide-containing solid phase is washed to obtain a third fluorosilicic acid solution and silicon dioxide as a byproduct.

[0101] In the embodiment of the present application, the first fluorosilicic acid solution is used to absorb the silicon tetrafluoride gas after the concentrated sulfuric acid is absorbed. The fluorosilicic acid provides an acidic environment to promote the hydrolysis reaction of silicon tetrafluoride as follows: SiF4+H2O=H2SiF6+SiO2, thereby obtaining a silicofluoric acid solution containing silicon dioxide. Compared with the first fluorosilicic acid solution, the mass concentration of fluorosilicic acid in the silicofluoric acid solution containing silicon dioxide increases. Therefore, the absorption process is used to obtain silicon dioxide as a byproduct on the one hand, and on the other hand, it plays a role in increasing the concentration of fluorosilicic acid.

[0102] In an embodiment of the present application, a silicofluoric acid solution containing silicon dioxide is filtered to obtain a second silicofluoric acid solution and a solid phase containing silicon dioxide. The solid-liquid separation is achieved through filtering, and silicon dioxide is further extracted. At the same time, a concentrated second silicofluoric acid solution is obtained. The mass concentration of the second silicofluoric acid solution is greater than the mass concentration of the first silicofluoric acid solution.

[0103] In the embodiment of the present application, impurities in the silicon dioxide solid phase 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.

[0104] In some embodiments of the present application, Figure 1 As shown, the preparation method of hydrogen fluoride includes the steps of:

[0105] S1000. Decompose fluorosilicic acid and sulfuric acid solution to produce mixed gas and sulfuric acid containing hydrogen fluoride; the mixed gas includes silicon tetrafluoride and hydrogen fluoride. The content of hydrogen fluoride in the mixed gas is 10% to 20%, and the content of hydrogen fluoride in the fluorine-containing sulfuric acid is 90% to 80%.

[0106] S2000. Use concentrated sulfuric acid to absorb hydrogen fluoride in the mixed gas to obtain sulfuric acid absorbed by concentrated sulfuric acid and silicon tetrafluoride gas absorbed by concentrated sulfuric acid.

[0107] S3000. The sulfuric acid containing hydrogen fluoride is treated by falling film evaporation to produce a liquid phase containing hydrogen fluoride and a gas phase containing hydrogen fluoride;

[0108] S6000. The hydrogen fluoride-containing gas phase is washed with sulfuric acid after absorption with concentrated sulfuric acid to obtain washed hydrogen fluoride gas and washed sulfuric acid.

[0109] S4000. The washed hydrogen fluoride gas is condensed to obtain anhydrous hydrogen fluoride crude product; the anhydrous hydrogen fluoride crude product is further distilled and degassed to obtain anhydrous hydrogen fluoride finished product.

[0110] S5000. The liquid phase containing hydrogen fluoride is treated by air stripping 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 treated by water absorption to obtain a by-product hydrofluoric acid.

[0111] Furthermore, the method further comprises the steps of:

[0112] The first fluorosilicic acid solution is used to absorb the silicon tetrafluoride gas absorbed by the concentrated sulfuric acid to obtain a silicic acid solution containing silicon dioxide;

[0113] The fluorosilicic acid solution containing silicon dioxide is filtered to obtain a second fluorosilicic acid solution and a solid phase containing silicon dioxide;

[0114] The silicon dioxide-containing solid phase is washed and the obtained solid phase is dried to obtain by-product silicon dioxide.

[0115] In some embodiments of the present application, Figure 2 As shown, the method for preparing hydrogen fluoride comprises the steps of:

[0116] S1000. Decompose fluorosilicic acid and sulfuric acid solution to produce mixed gas and sulfuric acid containing hydrogen fluoride; the mixed gas includes silicon tetrafluoride and hydrogen fluoride. The content of hydrogen fluoride in the mixed gas is 10% to 20%, and the content of hydrogen fluoride in the fluorine-containing sulfuric acid is 90% to 80%.

[0117] S2000. Use concentrated sulfuric acid to absorb hydrogen fluoride in the mixed gas to obtain sulfuric acid absorbed by concentrated sulfuric acid and silicon tetrafluoride gas absorbed by concentrated sulfuric acid.

[0118] S3000. Using a first fluorosilicic acid solution to absorb the silicon tetrafluoride gas after the concentrated sulfuric acid is absorbed to obtain a silicic acid solution containing silicon dioxide;

[0119] S4000. The fluorosilicic acid solution containing silicon dioxide is filtered to obtain a second fluorosilicic acid solution and a solid phase containing silicon dioxide; the filtered second fluorosilicic acid solution is circulated back to step S1000 and decomposed with sulfuric acid solution as fluorosilicic acid or as a raw material of fluorosilicic acid. The solid phase containing silicon dioxide is washed and 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.

[0120] S5000. The sulfuric acid containing hydrogen fluoride is treated by falling film evaporation to produce a hydrogen fluoride-containing liquid phase and a hydrogen fluoride-containing gas phase;

[0121] S6000. The hydrogen fluoride-containing gas phase is washed with sulfuric acid after absorption with concentrated sulfuric acid to obtain washed hydrogen fluoride gas and washed sulfuric acid. The washed sulfuric acid is circulated back to step S1000 as a sulfuric acid solution or as a raw material for a sulfuric acid solution to undergo a decomposition reaction with fluorosilicic acid.

[0122] S7000. The washed hydrogen fluoride gas is condensed to obtain anhydrous hydrogen fluoride crude product; the anhydrous hydrogen fluoride crude product is further distilled and degassed to obtain anhydrous hydrogen fluoride finished product.

[0123] S8000. The liquid phase containing hydrogen fluoride is treated by air stripping 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 treated by water absorption to obtain a by-product hydrofluoric acid.

[0124] In some embodiments of the present application, Figure 3 As shown, the method for preparing hydrogen fluoride comprises the steps of:

[0125] S1000. Fluorosilicic acid with a mass concentration of 18% to 55% and sulfuric acid with a mass concentration of 90% to 98% are introduced into a decomposition tower, and the mass ratio of fluosilicic acid to sulfuric acid is 1:1 to 1:4, and reacts in the decomposition tower to produce a mixed gas including silicon tetrafluoride gas and hydrogen fluoride gas, and produce sulfuric acid containing hydrogen fluoride. The decomposition reaction carried out in the decomposition tower is as follows:

[0126] H2SiF6=HF+SiF4.

[0127] Reaction temperature: 80°C to 120°C, preferably 80°C to 100°C.

[0128] The composition of sulfuric acid from the scrubbing tower: sulfuric acid, 91% to 95%; hydrogen fluoride, 1% to 5%; water, 2% to 6%.

[0129] The composition of sulfuric acid containing hydrogen fluoride: sulfuric acid, 60% to 70%; hydrogen fluoride, 3% to 6%; water, 25% to 40%.

[0130] S2000. The silicon tetrafluoride gas and hydrogen fluoride gas produced in step S1000 are passed through a sulfuric acid absorption tower. 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, while the 98% sulfuric acid has a cooling effect on the mixed gas.

[0131] The composition of sulfuric acid after absorption in the sulfuric acid absorption tower: sulfuric acid, 94% to 96%; hydrogen fluoride, 1% to 3%; water: 2% to 4%.

[0132] The temperature of the sulfuric acid absorption tower: 20℃~80℃.

[0133] S3000. The silicon tetrafluoride gas absorbed by the absorption tower in step S2000 enters the silicon tetrafluoride absorption tower, and 25% to 30% fluorosilicic acid is used to absorb the silicon tetrafluoride gas to form a fluorosilicic acid solution containing silicon dioxide. The hydrolysis reaction carried out in the silicon tetrafluoride absorption tower is as follows:

[0134] SiF4+H2O=H2SiF6+SiO2.

[0135] Then, the fluorosilicic acid solution containing silicon dioxide is filtered through a filter, and the fluorosilicic acid solution obtained by filtration enters a 40% to 55% fluorosilicic acid storage tank, and returns to the decomposition tower to perform step S1000. The silicon dioxide obtained by filtration is washed, and the solid phase and washing liquid obtained by washing are obtained. 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.

[0136] The concentration of fluorosilicic acid in the washing liquid is 3% to 10%.

[0137] The temperature of silicon tetrafluoride absorption tower: 20℃~50℃.

[0138] S4000. The sulfuric acid containing hydrogen fluoride produced in step S1000 enters a falling film evaporator for heating and evaporation to produce gaseous hydrogen fluoride and liquid dilute sulfuric acid.

[0139] Falling film evaporator temperature: 130℃~170℃; pressure: -3kpa~0kpa.

[0140] The composition of gaseous hydrogen fluoride: hydrogen fluoride, 80% to 99%; water, 1% to 20%.

[0141] The composition of liquid dilute sulfuric acid: sulfuric acid, 60% to 70%; hydrogen fluoride, 0% to 1%; water, 30% to 40%.

[0142] S5000. The gaseous hydrogen fluoride (containing sulfuric acid and water) produced in step S4000 enters a washing tower and is washed with sulfuric acid absorbed by the sulfuric acid absorption tower in step 2. The hydrogen fluoride in the sulfuric acid absorbed by the sulfuric acid absorption tower is released.

[0143] The temperature of the washing tower is 80℃~140℃, and the pressure is -3kpa~0kpa.

[0144] The composition of the washing liquid after washing: sulfuric acid, 91% to 95%; hydrogen fluoride, 1% to 5%; water, 2% to 6%.

[0145] S6000. The washed hydrogen fluoride gas obtained in step S3000 enters a condenser and is condensed into anhydrous hydrogen fluoride crude product (i.e., crude AHF).

[0146] The composition of the crude anhydrous hydrogen fluoride: hydrogen fluoride, 97% to 99%; sulfuric acid, 0% to 1%; water, 0 to 1%.

[0147] Condenser temperature: 5℃~18℃.

[0148] S7000. The crude anhydrous hydrogen fluoride enters the distillation tower for distillation, and then enters the degassing tower for degassing to obtain pure hydrogen fluoride as the finished anhydrous hydrogen fluoride (i.e., finished product AHF). The liquid in the bottom of the distillation tower is returned to the washing process.

[0149] Purity of anhydrous hydrogen fluoride product: ≥99.97%, hydrogen fluoride yield: 80% to 90%.

[0150] The composition of the distillation bottom liquid is: hydrogen fluoride, 90% to 95%; sulfuric acid, 1% to 5%; water 0 to 1%.

[0151] The temperature of the distillation tower kettle is 21℃~28℃, and the temperature of the distillation tower top is 17℃~19.5℃.

[0152] The temperature of the degassing tower bottom is 19.5℃~21℃, and the temperature of the degassing tower top is 17℃~19.5℃.

[0153] S8000. The liquid dilute sulfuric acid produced in step S4000 enters a stripping tower, where hot air is used for stripping to remove hydrogen fluoride from the liquid dilute sulfuric acid. The hydrogen fluoride and 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.

[0154] The temperature of the stripping tower: 100℃~140℃.

[0155] Temperature of absorption tower: 20℃~40℃.

[0156] A second aspect of an embodiment of the present application provides hydrogen fluoride, which is obtained by the above-mentioned preparation method, or includes the above-mentioned hydrogen fluoride.

[0157] The hydrogen fluoride provided in the embodiments of the present application is obtained by the above-mentioned preparation method, with low energy consumption and high hydrogen fluoride yield.

[0158] A third aspect of an embodiment of the present application provides a battery material, including lithium hexafluorophosphate; the raw materials for preparing the battery material include the above-mentioned hydrogen fluoride.

[0159] A third aspect of the present application provides a system for preparing hydrogen fluoride, comprising:

[0160] A decomposition tower, wherein the decomposition tower is provided with a liquid phase input end for a fluorosilicic acid solution and a sulfuric acid solution;

[0161] An absorption tower, wherein the absorption tower is provided with a liquid phase input end of concentrated sulfuric acid, and a gas phase input end of the absorption tower is connected to a gas phase output end of the decomposition tower;

[0162] A falling film evaporator, wherein the liquid phase input end of the falling film evaporator is connected to the liquid phase output end of the decomposition tower;

[0163] The washing tower has a gas phase input end connected to the gas phase output end of the falling film evaporator, a liquid phase input end connected to the liquid phase output end of the absorption tower, and the washing tower is also provided with a gas phase output end of hydrogen fluoride gas.

[0164] The preparation system provided in the embodiments of the present application can be used to prepare the above-mentioned hydrogen fluoride, or to prepare hydrogen fluoride using the above-mentioned preparation method.

[0165] In some embodiments of the present application, the liquid phase output end of the washing tower is connected to the liquid phase input end of the fluorosilicic acid solution and the sulfuric acid solution of the decomposition tower, which is conducive to the recovery and utilization of sulfuric acid.

[0166] 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.

[0167] Example 1

[0168] Step 1: Fluorosilicic acid with a mass concentration of 55% and sulfuric acid with a mass concentration of 98% are introduced into a decomposition tower, and the mass ratio of fluosilicic acid to sulfuric acid is 1:2, and a reaction is carried out in the decomposition tower to generate a mixed gas including silicon tetrafluoride gas and hydrogen fluoride gas, and generate sulfuric acid containing hydrogen fluoride.

[0169] The reaction temperature is: 100°C.

[0170] The composition of the sulfuric acid solution containing hydrogen fluoride: 66% sulfuric acid, 4% hydrogen fluoride, and 30% water.

[0171] Step 2: Use concentrated sulfuric acid to absorb the mixed gas entering the sulfuric acid absorption tower; part of the hydrogen fluoride is dissolved in the concentrated sulfuric acid, and part of the hydrogen fluoride reacts with the concentrated sulfuric acid to generate fluorosulfonic acid, thereby obtaining fluorine-containing sulfuric acid and silicon tetrafluoride gas.

[0172] The temperature of the sulfuric acid absorption tower is: below 80°C.

[0173] Concentration of concentrated sulfuric acid: 98%

[0174] The composition of fluorine-containing sulfuric acid: 93% sulfuric acid, 2% hydrogen fluoride, 3% fluorosulfonic acid, and 2% water.

[0175] Step 3: Take 500g of sulfuric acid solution containing hydrogen fluoride and add it into 1000ml PFA (perfluoroalkoxy vinyl ether copolymer) decomposition kettle to obtain gas phase through decomposition treatment.

[0176] The analysis temperature is: 140℃, the pressure is -10kpa.

[0177] Composition of the gas phase: 95% sulfuric acid, 1% hydrogen fluoride, 4% water.

[0178] Step 4: 150 g of fluorine-containing sulfuric acid is used to wash the gas phase entering the washing tower; fluorosulfonic acid reacts with water to generate sulfuric acid and hydrogen fluoride, and the hydrogen fluoride in the fluorine-containing sulfuric acid is resolved to obtain a washed sulfuric acid solution and hydrogen fluoride gas.

[0179] The reaction mechanism of fluorosulfonic acid and water to generate sulfuric acid and hydrogen fluoride is: HSO3F+H2O=H2SO4+HF.

[0180] Scrubber tower temperature: 50°C.

[0181] Scrubber gas phase temperature: 80℃~140℃,

[0182] The composition of the sulfuric acid solution after washing: 91% sulfuric acid, 2% hydrogen fluoride, 3% fluorosulfonic acid, and 4% water.

[0183] Step 5: The hydrogen fluoride gas from the scrubbing tower in step 4 is condensed in a condenser, rectified in a distillation tower, and degassed in a degassing tower to obtain anhydrous hydrogen fluoride.

[0184] Condenser temperature: 50℃.

[0185] Distillation tower temperature: 23°C.

[0186] Degassing tower temperature: 21°C.

[0187] Example 2-Example 26

[0188] The specific preparation methods of hydrogen fluoride provided in Examples 2 to 26 are as shown in Example 1, and the specific parameter values ​​are shown in Table 1.

[0189] Table 1

[0190]

[0191] Performance Testing

[0192] 1. Test method:

[0193] 1. Detection of the yield of hydrogen fluoride: According to the national standard GB / T 7746-2023; the calculation formula is as follows:

[0194] Yield of hydrogen fluoride: in:

[0195] m(AHF) represents the weight of the product anhydrous hydrogen fluoride, in g;

[0196] m(H2SiF6) represents the weight of fluorosilicic acid reacted with the first sulfuric acid, in g;

[0197] w(H2SiF6) represents the mass fraction of fluorosilicic acid reacted with the first sulfuric acid;

[0198] "2" represents the molar ratio of hydrofluoric acid to produce hydrogen fluoride; "20" represents the molar mass of HF; and "144" represents the molar mass of H2SiF6.

[0199] 2. Sulfuric acid unit consumption: unit consumption (H2SO4) = m(H2SO4) / m(anhydrous hydrogen fluoride), dimensionless; where:

[0200] m(H2SO4) represents the weight of all sulfuric acid added during the preparation process, in g;

[0201] m (anhydrous hydrogen fluoride) represents the weight of the product anhydrous hydrogen fluoride, in g.

[0202] 2. Test results:

[0203] The performance tests of Examples 1-26 were carried out, and the results are shown in Table 2.

[0204] Table 2

[0205]

[0206] Performance test result analysis description:

[0207] 1. As shown in Examples 16-22, the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 18%≤C1<30%, the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:2-1:4, and most of the hydrogen fluoride produced by the reaction is dissolved in the sulfuric acid solution. Only a small amount (less than 10%) of the hydrogen fluoride enters the gas phase and is output as a mixed gas and absorbed by concentrated sulfuric acid. The absorption amount of concentrated sulfuric acid is relatively low, and hydrogen fluoride will continue to be absorbed during the subsequent washing treatment. Therefore, the yield of hydrogen fluoride is improved, but there is still much room for improvement.

[0208] (1) Specifically, the yield of hydrogen fluoride and the unit consumption of sulfuric acid were investigated under the same mass concentration of fluorosilicic acid and different mass ratios of fluorosilicic acid solution and sulfuric acid solution. As shown in Examples 16-20, the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies C1=20% as an example: ① As the mass ratio of fluorosilicic acid solution and sulfuric acid solution decreases and the amount of sulfuric acid solution increases, the content of hydrogen fluoride in the liquid phase shows an increasing trend, the content of hydrogen fluoride in the gas phase shows a decreasing trend, and the yield of hydrogen fluoride shows a trend of gradually decreasing first. The method for preparing hydrogen fluoride provided in Example 9 (i.e., the mass ratio of fluorosilicic acid solution and sulfuric acid solution is 1:2) obtains a higher yield of hydrogen fluoride. This is because, when the mass ratio of fluorosilicic acid solution and sulfuric acid solution exceeds 1:2 (i.e., the ratio is lower than the ratio of 1:2), the amount of sulfuric acid used is relatively large, the boiling point of the system increases, and at the same temperature, the amount of hydrogen fluoride that can be evaporated from the liquid phase decreases, which will cause the yield of hydrogen fluoride to show a decreasing trend. ② With the decrease of the mass ratio of fluorosilicic acid solution to sulfuric acid solution and the increase of the amount of sulfuric acid solution, the unit consumption of sulfuric acid shows an increasing trend.

[0209] (2) Specifically, the yield of hydrogen fluoride and the unit consumption of sulfuric acid were also investigated under the same mass ratio of fluosilicic acid solution to sulfuric acid solution and different mass concentrations of fluosilicic acid. As shown in Example 16 and Examples 21-22, taking the mass ratio of fluosilicic acid solution to sulfuric acid solution as 1:2 as an example: ① With the increase of the mass concentration of fluosilicic acid, the content of hydrogen fluoride in the liquid phase showed a decreasing trend, the content of hydrogen fluoride in the gas phase showed an increasing trend, and the yield of hydrogen fluoride showed an increasing trend. ② With the increase of the mass concentration of fluosilicic acid, the unit consumption of sulfuric acid showed a decreasing trend.

[0210] 2. As shown in Examples 9-15, the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 30%≤C1<40%, the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:2-1:3, more hydrogen fluoride produced by the reaction enters the gas phase, and the amount absorbed by the concentrated sulfuric acid is relatively increased, but it is not saturated, and a small amount of hydrogen fluoride can be absorbed during the washing treatment, and the hydrogen fluoride yield will be further improved.

[0211] (1) Specifically, the yield of hydrogen fluoride and the unit consumption of sulfuric acid were investigated under the same mass concentration of fluorosilicic acid and different mass ratios of fluorosilicic acid solution and sulfuric acid solution. As shown in Examples 9-13, the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies C1=35% as an example: ① As the mass ratio of fluorosilicic acid solution and sulfuric acid solution decreases and the amount of sulfuric acid solution increases, the content of hydrogen fluoride in the liquid phase shows an increasing trend, the content of hydrogen fluoride in the gas phase shows a decreasing trend, and the yield of hydrogen fluoride shows a trend of gradually decreasing first. The method for preparing hydrogen fluoride provided in Example 9 (i.e., the mass ratio of fluorosilicic acid solution and sulfuric acid solution is 1:2) obtains a higher yield of hydrogen fluoride. This is because, when the mass ratio of fluorosilicic acid solution and sulfuric acid solution exceeds 1:2 (i.e., the ratio is lower than the ratio of 1:2), the amount of sulfuric acid used is relatively large, the boiling point of the system increases, and at the same temperature, the amount of hydrogen fluoride that can be evaporated from the liquid phase decreases, which will cause the yield of hydrogen fluoride to show a decreasing trend. ② With the decrease of the mass ratio of fluorosilicic acid solution to sulfuric acid solution and the increase of the amount of sulfuric acid solution, the unit consumption of sulfuric acid shows an increasing trend.

[0212] (2) Specifically, the yield of hydrogen fluoride and the unit consumption of sulfuric acid were also investigated under the same mass ratio of fluosilicic acid solution to sulfuric acid solution and different mass concentrations of fluosilicic acid. As shown in Example 9 and Examples 14-15, taking the mass ratio of fluosilicic acid solution to sulfuric acid solution as 1:2 as an example: ① With the increase of the mass concentration of fluosilicic acid, the content of hydrogen fluoride in the liquid phase showed a decreasing trend, the content of hydrogen fluoride in the gas phase showed an increasing trend, and the yield of hydrogen fluoride showed an increasing trend. ② With the increase of the mass concentration of fluosilicic acid, the unit consumption of sulfuric acid showed a decreasing trend.

[0213] 3. As shown in Examples 1-8, the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies 40%≤C1≤55%, the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:1-1:2, more hydrogen fluoride among the hydrogen fluoride produced by the reaction enters the gas phase, and the amount absorbed by the concentrated sulfuric acid increases, which can be nearly saturated or reach a saturated state. After entering the washing treatment, a large amount of hydrogen fluoride can be released, which promotes a better improvement in the yield of hydrogen fluoride.

[0214] (1) Specifically, the yield of hydrogen fluoride and the unit consumption of sulfuric acid were investigated under the same mass concentration of fluorosilicic acid and different mass ratios of fluorosilicic acid solution and sulfuric acid solution. As shown in Examples 1-6, the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies C1=55% as an example: ① As the mass ratio of fluorosilicic acid solution and sulfuric acid solution decreases and the amount of sulfuric acid solution increases, the content of hydrogen fluoride in the liquid phase shows an increasing trend, the content of hydrogen fluoride in the gas phase shows a decreasing trend, and the yield of hydrogen fluoride shows a trend of first increasing and then decreasing. The method for preparing hydrogen fluoride provided in Example 3 (i.e., the mass ratio of fluorosilicic acid solution and sulfuric acid solution is 1:1.2) obtains a higher yield of hydrogen fluoride. This is because, when the mass ratio of fluorosilicic acid solution and sulfuric acid solution exceeds 1:1.2 (i.e., the ratio is lower than the ratio of 1:1.2), the amount of sulfuric acid used is relatively large, the boiling point of the system increases, and at the same temperature, the amount of hydrogen fluoride that can be evaporated from the liquid phase decreases, which will cause the yield of hydrogen fluoride to show a decreasing trend. ② With the decrease of the mass ratio of fluorosilicic acid solution to sulfuric acid solution and the increase of the amount of sulfuric acid solution, the unit consumption of sulfuric acid shows an increasing trend.

[0215] (2) Specifically, the yield of hydrogen fluoride and the unit consumption of sulfuric acid were also investigated under the same mass ratio of fluosilicic acid solution to sulfuric acid solution and different mass concentrations of fluosilicic acid. As shown in Example 3 and Examples 7-8, taking the mass ratio of fluosilicic acid solution to sulfuric acid solution as 1:1.2 as an example: ① With the increase of the mass concentration of fluosilicic acid, the content of hydrogen fluoride in the liquid phase showed a decreasing trend, the content of hydrogen fluoride in the gas phase showed an increasing trend, and the yield of hydrogen fluoride showed an increasing trend. ② With the increase of the mass concentration of fluosilicic acid, the unit consumption of sulfuric acid showed a decreasing trend.

[0216] 4. As shown in Example 3 and Examples 23-26, in the reaction between the fluorosilicic acid solution and the sulfuric acid solution, the reaction temperature is controlled to be 80°C to 120°C, and the mass concentration of fluorosilicic acid in the fluorosilicic acid solution satisfies C1=55%, and the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is more than 1:1.2. As an example, the yield trend of hydrogen fluoride at different reaction temperatures is explored. As the reaction temperature increases, the change in the content of hydrogen fluoride in the liquid phase and the gas phase is relatively small, and the change in the yield of hydrogen fluoride is relatively small. In Example 3, the yield of hydrogen fluoride is relatively high at a reaction temperature of 100°C.

[0217] 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.

[0218] 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: The hydrofluorosilicic acid solution is reacted with the sulfuric acid solution to obtain a mixed gas and fluorine-containing sulfuric acid; the content of hydrogen fluoride in the mixed gas is 10% to 20%, and the content of hydrogen fluoride in the fluorine-containing sulfuric acid is 90% to 80%; The mixed gas is treated with concentrated sulfuric acid to obtain absorbed sulfuric acid, wherein the absorbed sulfuric acid is concentrated sulfuric acid after absorbing hydrogen fluoride; The fluorine-containing sulfuric acid is subjected to falling film evaporation to obtain a hydrogen fluoride-containing gas phase; The absorbing sulfuric acid washes the hydrogen fluoride-containing gas phase to obtain hydrogen fluoride gas.

2. The preparation method according to claim 1, characterized in that: The mass concentration C1 of fluorosilicic acid in the fluorosilicic acid solution is 18% to 55%, and the mass concentration of sulfuric acid in the sulfuric acid solution is above 90%.

3. The preparation method according to claim 2, characterized in that: In the reaction of the fluorosilicic acid solution and the sulfuric acid solution, the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:1 to 1:

4.

4. The preparation method according to claim 3, characterized in that: The hydrosilicic acid solution and the sulfuric acid solution are reacted to satisfy one of the following conditions: (i) the mass concentration of the fluorosilicic acid in the fluorosilicic acid solution satisfies 18%≤C1<30%, and the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:2 to 1:4; (ii) the mass concentration of the fluorosilicic acid in the fluorosilicic acid solution satisfies 30%≤C1<40%, and the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:2 to 1:3; (iii) The mass concentration of the fluorosilicic acid in the fluorosilicic acid solution satisfies 40%≤C1≤55%, and the mass ratio of the fluorosilicic acid solution to the sulfuric acid solution is 1:1 to 1:

2.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The absorbing sulfuric acid to wash the hydrogen fluoride-containing gas phase also includes obtaining recovered sulfuric acid; the recovered sulfuric acid satisfies at least one of the following: (a) the recovered sulfuric acid is used as the source of the sulfuric acid solution to react with the hydrosilicic acid solution; (b) Calculated by mass percentage, the recovered sulfuric acid component includes 91% to 95% sulfuric acid and 1% to 5% hydrogen fluoride.

6. The preparation method according to any one of claims 1 to 4, characterized in that: In the reaction of the fluorosilicic acid solution and the sulfuric acid solution, the reaction temperature is controlled to be 80°C to 120°C.

7. The preparation method according to any one of claims 1 to 4, characterized in that: Also includes: The hydrogen fluoride gas is condensed to obtain crude anhydrous hydrogen fluoride; The crude anhydrous hydrogen fluoride is subjected to rectification treatment and degassing treatment to obtain finished anhydrous hydrogen fluoride.

8. The preparation method according to any one of claims 1 to 4, characterized in that: The fluorine-containing sulfuric acid is subjected to falling film evaporation treatment to obtain a hydrogen fluoride-containing liquid phase; The hydrogen fluoride-containing liquid phase is subjected to air stripping treatment to obtain dilute sulfuric acid and stripping mixed gas; The stripping mixed gas is treated by water absorption to obtain hydrofluoric acid.

9. The preparation method according to any one of claims 1 to 4, characterized in that: The mixed gas also includes silicon tetrafluoride. After the mixed gas is treated with concentrated sulfuric acid, silicon tetrafluoride gas absorbed by concentrated sulfuric acid is obtained. The silicon tetrafluoride gas absorbed by concentrated sulfuric acid is subjected to fluorosilicic acid absorption treatment, filtration treatment, and washing treatment to obtain by-product silicon dioxide.

10. A hydrogen fluoride, characterized in that: The hydrogen fluoride is obtained by the preparation method according to any one of claims 1 to 9.

11. A battery material, characterized in that: Including lithium hexafluorophosphate; the raw material for preparing the battery material includes hydrogen fluoride obtained by the preparation method described in any one of claims 1 to 9, or includes hydrogen fluoride described in claim 10.

12. A system for preparing hydrogen fluoride, characterized in that: include: A decomposition tower, wherein the decomposition tower is provided with a liquid phase input end for a fluorosilicic acid solution and a sulfuric acid solution; An absorption tower, wherein the absorption tower is provided with a liquid phase input end of concentrated sulfuric acid, and a gas phase input end of the absorption tower is connected to a gas phase output end of the decomposition tower; A falling film evaporator, wherein the liquid phase input end of the falling film evaporator is connected to the liquid phase output end of the decomposition tower; A washing tower, wherein the gas phase input end of the washing tower is connected to the gas phase output end of the falling film evaporator, the liquid phase input end of the washing tower is connected to the liquid phase output end of the absorption tower, and the washing tower is also provided with a gas phase output end of hydrogen fluoride gas.

13. The system according to claim 12, characterized in that The liquid phase output end of the washing tower is connected to the liquid phase input end of the decomposition tower.

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