Process and device for preparing hydrogen fluoride by fluosilicic acid complexing method

Abstract

The invention discloses a process and a device for preparing hydrogen fluoride by a fluosilicic acid complexing method. The process comprises the following steps: mixing a fluosilicic acid solution, a complexing solution and a cross-linking agent to generate a complexing reaction to obtain a first mixed material containing a metastable state complex; raising the temperature of the first mixed material to be stable, so as to obtain a second mixed material containing a solid-phase steady-state complex; and carrying out solid-liquid separation on the second mixed material, drying the solid, and carrying out thermal decomposition to obtain hydrogen fluoride gas, silicon tetrafluoride gas and a liquid material. The device comprises complex reaction equipment, cross-linking reaction equipment, first solid-liquid separation equipment, a drying machine and complex decomposition equipment. The complexing agent can be recycled for a long period and has the advantages of being high in separation efficiency, small in fluosilicic acid loss, high in hydrogen fluoride yield, low in material consumption and energy consumption and the like, and on the basis that a hydrogen fluoride product reaches superior product indexes, the fluosilicic acid complexing rate reaches 98% or above, the complex decomposition rate reaches 95% or above, and the total hydrogen fluoride yield reaches 90% or above.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a process and apparatus for producing hydrogen fluoride by complexation of fluorosilicic acid. Background Technology

[0002] The phosphate fertilizer industry generates fluorosilicic acid as a byproduct during production. With the increasing scarcity of fluorite resources, the process of producing hydrofluoric acid from fluorosilicic acid has gradually become the industry mainstream. This successfully transforms the waste byproduct (fluorosilicic acid) of the phosphate fertilizer industry into a high-value fluorochemical cornerstone (anhydrous hydrogen fluoride), while simultaneously solving environmental problems and forming a circular economy. The processes for producing hydrogen fluoride from fluorosilicic acid are divided into direct and indirect methods. The direct method includes sulfuric acid decomposition and thermal decomposition, while the indirect method includes fluoride conversion and potassium fluorosilicate recycling. In the direct method, the sulfuric acid decomposition of fluorosilicic acid involves adding sulfuric acid to a concentrated fluorosilicic acid solution, which decomposes to produce hydrogen fluoride (HF) and silicon tetrafluoride (SiF4). The hydrogen fluoride is absorbed by the sulfuric acid to form fluorosulfonic acid, and the silicon tetrafluoride, after purification, is hydrolyzed at high temperature to produce silica and hydrogen fluoride, which are then recycled. The thermal decomposition of fluorosilicic acid involves heating fluorosilicic acid to directly decompose it into hydrogen fluoride, silicon tetrafluoride, or silicon dioxide. The hydrogen fluoride is purified by polyether extraction and distillation, and the silicon tetrafluoride can be returned to the system for recycling. In the indirect method, the fluoride conversion method converts fluorosilicic acid into fluorides such as sodium hydrofluoride and potassium hydrofluoride, which are then thermally decomposed or acidically hydrolyzed to produce hydrogen fluoride. For example, fluorosilicic acid can be used to produce synthetic fluorite, followed by hydrogen fluoride production using the fluorite process. The potassium fluorosilicate recycling method involves reacting fluorosilicic acid with potassium sulfate to produce potassium fluorosilicate, which is then hydrolyzed in hot water to produce hydrogen fluoride and silicic acid. The sulfuric acid and potassium sulfate can be recycled.

[0003] Currently, the mainstream industrial process for producing hydrogen fluoride from fluorosilicic acid is the sulfuric acid decomposition method. This process has been validated through decades of industrial practice and is technically mature. However, the biggest problem with this process has always been the environmental and economic challenges posed by the large amount of 70% concentrated sulfuric acid produced. Furthermore, concentrated sulfuric acid is highly corrosive, requiring sophisticated equipment and resulting in high investment costs. In recent years, with the increasing scarcity of fluorite resources and ever-increasing environmental requirements, it has become urgent to update and iterate this process to address the issue of large quantities of dilute sulfuric acid. Against this backdrop, the production of hydrogen fluoride from fluorosilicic acid has become a research hotspot.

[0004] Patent specification CN106865500A discloses a cyclic production process for preparing hydrogen fluoride from fluorosilicic acid. The process involves mixing and reacting fluorosilicic acid with alkaline earth metal fluorides or alkali metal fluorides to obtain a mixed solution of hydrogen fluoride and fluorosilicates. This solution further yields hydrogen fluoride gas and solid fluorosilicates. The solid fluorosilicates are then heated to decompose, yielding solid fluoride and silicon tetrafluoride gas. The silicon tetrafluoride gas is absorbed by a fluorosilicic acid solution, thus completing one production cycle. While the fluoride in this process can theoretically be recycled, the high-temperature heating of the solid fluorosilicates consumes a large amount of heat, resulting in excessively high energy costs and limiting its industrial application.

[0005] The patent specification with publication number CN113816340A discloses a method for preparing anhydrous hydrogen fluoride and co-producing silicon tetrafluoride from sodium fluorosilicate. This method involves a fluidized bed gas-solid reaction between sodium fluorosilicate and hydrogen chloride gas to obtain crude anhydrous hydrogen fluoride, which is then purified to obtain pure anhydrous hydrogen fluoride. The main disadvantage of this process is the high temperature of the gas-solid reaction, resulting in high energy consumption and costs.

[0006] The patent specification with publication number CN117208912A discloses a process for purifying and concentrating dilute fluorosilicic acid solution using chemical extraction. This process utilizes an organic base or modified organic base as the extractant and an inorganic acid as the back-extraction agent. The dilute fluorosilicic acid is concentrated through chemical extraction and chemical back-extraction. The auxiliary agent is recovered by vacuum distillation, and the extractant is recovered by vacuum heating decomposition. This process, based on the fact that fluorosilicic acid is a strong acid, uses base and acid for extraction and back-extraction, which inevitably leads to acid-base neutralization reactions. This not only consumes fluorosilicic acid, resulting in low fluorine conversion, but also introduces new separation problems and disadvantages due to the formation of new substances by the neutralization reaction.

[0007] Patent CN116835597A discloses a multi-stage extraction and concentration process for dilute fluorosilicic acid. This process uses alcohol-based organic compounds as extractants to extract and concentrate the dilute fluorosilicic acid, and adds polar or non-polar organic compounds as auxiliaries to the extractant. The extractant is then recovered using vacuum distillation. This patent employs a multi-stage liquid-liquid extraction method for fluorosilicic acid extraction. The biggest problems in the extraction process are emulsification, difficulty in layering, and effective separation of the two liquid phases. This results in low extraction efficiency, significant extractant loss, and even failure to operate during continuous multi-stage extraction, making industrial application difficult.

[0008] In summary, existing processes for producing hydrogen fluoride from fluorosilicic acid, whether direct, indirect, or other novel methods such as chemical extraction, all have limitations restricting their industrial application. On the one hand, while the sulfuric acid decomposition method is relatively mature and stable, the increasing scarcity of fluorite resources and growing environmental pressures on enterprises necessitate a fundamental solution to the problem of large quantities of dilute sulfuric acid. Developing new, efficient processes for producing hydrogen fluoride from fluorosilicic acid is crucial for protecting fluorite resources and achieving sustainable development in the phosphorus and fluorochemical industries. Summary of the Invention

[0009] To address the aforementioned technical problems and shortcomings in this field, this invention provides a process and apparatus for producing hydrogen fluoride via fluorosilicic acid complexation. This process differs from the traditional sulfuric acid decomposition method for producing hydrogen fluoride, completely eliminating the use of concentrated sulfuric acid and fundamentally solving the environmental problem of generating large amounts of dilute sulfuric acid. It also differs from general extraction and back-extraction processes involving liquid-liquid phases and liquid-liquid phase separation. The entire process involves liquid-solid and gas-liquid-solid phases and corresponding separation processes, and the complexing agent can be recycled over a long period. It boasts advantages such as high separation efficiency, low fluorosilicic acid loss, high hydrogen fluoride yield, and low material and energy consumption. Based on achieving superior-grade hydrogen fluoride product indicators, the fluorosilicic acid complexation rate reaches over 98%, the complex decomposition rate reaches over 95%, and the total hydrogen fluoride yield reaches over 90%.

[0010] The specific technical solution is as follows: In a first aspect, the present invention provides a process for preparing hydrogen fluoride by a fluorosilicic acid complexation method, comprising the steps of: (1) A complexing reaction occurs when fluorosilicic acid solution, complexing solution and crosslinking agent are mixed to obtain a first mixture containing metastable complexes; The complexing solution contains a complexing agent and an auxiliary agent; the complexing agent includes one or more of N-alkyl-substituted aromatic amine compounds, P-alkyl-substituted aromatic phosphorus compounds, N-alkyl-substituted aromatic phosphorus compounds, and alkyl-substituted aromatic sulfur compounds; the auxiliary agent is a substance that can provide a hydrogen bond donor, is insoluble in water, and is miscible with the complexing agent. (2) The first mixture is heated to a stable temperature to obtain a second mixture containing a solid-phase stable complex; (3) The second mixture is separated into solid and liquid components. After the solid is dried, it is thermally decomposed to obtain hydrogen fluoride gas, silicon tetrafluoride gas and liquid material.

[0011] The principle of the complexation reaction in this invention is based on fluorosilicate (SiF6) ions. 2- [SiF6] is a strong ligand and complexes with the complexing agent described in this invention to form a complex containing [SiF6]. 2-The multinuclear complex structure of the unit contains both NH···F, SH···F, or PH···F hydrogen bond networks and weaker CH··F hydrogen bonds formed by the CH groups of the cyclic compound. In principle, the complex can be liquid or solid depending on the molecular structure of the complexing agent and the structure of the complex itself; the complex described in this invention should be solid. Furthermore, when screening complexes for industrial applications, not only the complexing ability of the complexing agent must be considered, but also the dissociation ability of the formed coordinate bonds. That is, the complex must be able to decompose under mild and suitable conditions to achieve the technical effect of recycling. Therefore, this invention screens complexing agents that can rapidly complex with fluorosilicic acid to produce stable solid complexes and can easily and completely decompose without chemical degradation, realizing a closed-loop process for the production of hydrogen fluoride by fluorosilicic acid complexation.

[0012] The working principle of the crosslinking agent in this invention is to build bridges between two or more molecules, thereby connecting these molecules into a more stable structural network, thus obtaining a mixture of a stable complex and water. At this time, the stable complex is a terminal solid complex.

[0013] The liquid obtained from the solid-liquid separation of the second mixture is the residual water after the extraction of fluorosilicic acid by the complexation reaction, as well as trace amounts of complexing agents, auxiliaries, and / or crosslinking agents. It can be discharged as wastewater. The solid obtained from the solid-liquid separation of the second mixture, i.e., the solid complex, is dried to a water content of less than 0.5% and then introduced into the decomposition equipment for thermal decomposition.

[0014] In step (1), the source of the fluorosilicic acid solution and the concentration of fluorosilicic acid therein are not limited in principle. In some embodiments, in step (1), the mass concentration of fluorosilicic acid in the fluorosilicic acid solution is 10% to 40%, such as the standard commercial concentration of purified by-products from phosphate fertilizer plants of 30% to 34% or the concentration of intermediate products from phosphate fertilizer by-products of 10% to 20%.

[0015] In step (1), the molar ratio of fluorosilicic acid in the fluorosilicic acid solution to the complexing agent is preferably 15:1 to 1:15, and more preferably 5:1 to 1:5.

[0016] The N-alkyl-substituted aromatic amine compound preferably includes one or more of N-methylaniline, N-ethylaniline, N-n-butylaniline, N,N-dimethylaniline, N,N-diethylaniline, N-ethyl-N-methylaniline, N-isopropylaniline, N-tert-butylaniline, and N-pyrrolidinylaniline.

[0017] The p-alkyl-substituted aromatic phosphorus compound preferably includes one or more of triphenylphosphine, methylphenylphosphine, phenyl tert-butylphosphine, phenyl dicyclohexylphosphine, p,p-dimethylphenylphosphine, p,p-dibutylphenylphosphine, p,p-diphenylbutylphosphine, p,p-diethylphenylphosphine, phenyl dicyclohexylphosphine, and diethyl phenyl phosphite.

[0018] The N-alkyl-substituted aromatic phosphorus compound preferably includes one or more of diphenyl(N,N-dimethylamino)phosphine, di-tert-butyl(N,N-diethylamino)phosphine, phosphodiamid, hexamethylphosphoric triamine, phenylbis(dimethylamino)phosphine, and hexamethylphosphoric triamine (HMPA).

[0019] The alkyl-substituted aromatic sulfur compound preferably includes one or more of the following: 2-methylbenzylthiophenol, 4-tert-butylbenzylthiophenol, 2-ethylphenylmethyl sulfide, 4-isopropyldiphenyl sulfide, 4-methylphenylmethyl sulfoxide, 2,4,6-trimethylphenylphenyl sulfone, methyl 4-ethylbenzenesulfonate, methylphenyl sulfide, ethylphenyl sulfide, butylphenyl sulfide, methylphenyl sulfoxide, methylphenyl sulfone, and methyl benzenesulfonate.

[0020] The additives preferably include one or more of long-chain fatty alcohols, long-chain fatty acids, and long-chain alkylamines, and more preferably include one or more of n-hexanol, n-octanol, nonylphenol, n-hexylamine, n-octylamine, dodecylamine, N-dodecylaniline, N-n-octylacetamide, n-decanoic acid, stearic acid, and lauric acid.

[0021] In step (1), the mass ratio of the complexing agent to the adjuvant is preferably 100:1 to 1:1, and more preferably 50:1 to 2:1.

[0022] In step (1), the temperature of the complexation reaction is preferably 5~60℃, and more preferably 5~35℃. Step (1) needs to be carried out under appropriately low temperature conditions, which can ensure the complexation reaction rate and maximize the reduction of fluorosilicic acid decomposition rate. At this temperature, the molecular thermal motion is not ideal, and primary cross-linking products are generated. That is, under the complexation reaction conditions, only a mixture of metastable complex and water can be obtained. The cross-linking reaction requires an appropriate increase in temperature, because at this time the fluorosilicic acid molecules have already undergone a complexation reaction, and there is no need to consider the problem of their decomposition affecting the efficiency of the complexation reaction. Therefore, appropriately increasing the reaction temperature can, on the one hand, accelerate the thermal motion speed of complex molecules or reactive groups, greatly increase the frequency and energy of mutual collisions, and on the other hand, the increase in temperature can reduce the viscosity of the material, thereby increasing the fluidity of the molecular chain, making it easier for the functional groups that need to be cross-linked to contact and diffuse with each other, creating good conditions for the cross-linking reaction, and forming a mixture of stable complex and water.

[0023] In step (1), the pressure of the complexation reaction is preferably atmospheric pressure ~ 1.0 MPa, and more preferably atmospheric pressure ~ 0.15 MPa.

[0024] In step (1), the complexation reaction time is preferably 5 to 120 min, and more preferably 10 to 40 min.

[0025] The crosslinking agent preferably includes one or more of 1,4-diiodobutane, 1,6-dibromohexane, 1,4-dichlorobutane, glutaraldehyde, adipic acid chloride, and diisocyanate.

[0026] In step (1), based on the total mass of fluorosilicic acid solution, complexing solution and crosslinking agent as 100%, the mass percentage of the crosslinking agent is preferably 0.01% to 5%, and more preferably 0.05% to 0.5%.

[0027] In step (2), the temperature at which the first mixture is heated to a stable temperature is preferably 10~85℃, and more preferably 15~60℃.

[0028] In step (2), the pressure at which the first mixture is heated and stabilized is preferably atmospheric pressure ~ 1.0 MPa, and more preferably atmospheric pressure ~ 0.15 MPa.

[0029] Preferably, the temperature at which the first mixture stabilizes in step (2) is 5-30°C higher than the temperature of the complexation reaction in step (1). More preferably, the temperature at which the first mixture stabilizes in step (2) is 10-20°C higher than the temperature of the complexation reaction in step (1).

[0030] In step (3), the thermal decomposition temperature is preferably 120~450℃, and more preferably 150~320℃.

[0031] In step (3), the pressure of thermal decomposition is preferably 0.1~1.0 MPa, and more preferably 0.12~0.20 MPa.

[0032] In step (3), the thermal decomposition time is preferably 20-180 min, and more preferably 30-120 min.

[0033] Preferably, the process for preparing hydrogen fluoride by the fluorosilicic acid complexation method further includes: Hydrogen fluoride gas and silicon tetrafluoride gas are separated by a first distillation; after the first distillation separation, the crude hydrogen fluoride obtained is purified by a second distillation to obtain anhydrous hydrogen fluoride, and the obtained silicon tetrafluoride is used for hydrolysis to prepare fluorosilicic acid solution; The liquid material circulation sleeve is used for the complexation reaction in step (1).

[0034] The liquid material contains a complexing solution and a small amount of crosslinking agent. After being cooled to the complexing reaction temperature, it is recycled to complete one operating cycle. Additionally, during operation, a small amount of the complexing solution and crosslinking agent can be replenished to compensate for any losses.

[0035] Secondly, the present invention provides an apparatus for producing hydrogen fluoride by a fluorosilicic acid complexation method, comprising: A complexation reaction apparatus is used to mix fluorosilicic acid solution, complexation solution and crosslinking agent to undergo a complexation reaction, and obtain a first mixture containing metastable complexes; Crosslinking reaction equipment is used to heat and stabilize a first mixture to obtain a second mixture containing a solid-phase stable complex. The first solid-liquid separation device is used to separate the second mixture of materials into solid and liquid components. A dryer is used to dry the solids obtained from the second solid-liquid separation process in the first solid-liquid separation device. Complex decomposition equipment is used to decompose solids dried by a thermal decomposition dryer to obtain hydrogen fluoride gas, silicon tetrafluoride gas, and liquid materials.

[0036] The complexation reaction process in the complexation reaction equipment includes: material clarification - generation of suspended solids - increase in suspended solids - no further change in suspended solids - termination of the complexation reaction. The final state of the complexation reaction is a semi-transparent, homogeneous mixture of metastable complex and water containing suspended solids. The complexation reaction equipment can be any device with dispersion and mixing functions, such as a stirred tank, homogenizer, plow mixer, ribbon mixer, V-type mixer, double-helix conical mixer, planetary power mixer, etc.

[0037] The cross-linking process occurs in the cross-linking reaction equipment. Specifically, this process includes: mixing a metastable complex and water – heating for cross-linking – aggregation and growth of suspended matter – termination of cross-linking. At the end of cross-linking, the material is a semi-transparent, integral gel with thixotropic flowability, characterized by neatly arranged suspended matter and internally filled liquid. The cross-linking process generally requires slight mixing; otherwise, it will affect the cross-linking rate and damage the structure of the cross-linked product. Slight mixing here refers to slow fluctuations on the surface and inside the material, allowing the cross-linking agent in the upper and lower parts to slowly entrain the main body. This is in contrast to vigorous agitation. For example, a stirring speed of less than 20 rpm in a stirred tank can achieve this effect. The cross-linking reaction equipment can be any device with dispersion and mixing functions, such as a stirred tank, homogenizer, plow mixer, ribbon mixer, V-type mixer, double-helix conical mixer, planetary mixer, etc. It is only necessary to intermittently activate its mixing function or reduce its mixing capacity.

[0038] Since the materials in the complexation reaction equipment and crosslinking reaction equipment are slurries or gels containing suspended solids, it is preferred that both the complexation reaction equipment and the crosslinking reaction equipment adopt a conical or elliptical bottom to avoid flat bottoms and facilitate material discharge. In addition, the material conveying from the complexation reaction equipment to the crosslinking reaction equipment and from the crosslinking reaction equipment to the first solid-liquid separation equipment and other downstream equipment can adopt gravity discharge or pressure discharge, with pressure discharge being preferred. Furthermore, a short and thick pipeline should be installed between the discharge port and the receiving port to avoid horizontal pipes and 90° bends and prevent solid deposition.

[0039] The dryer can be any of the following: spray dryer, fluidized bed dryer, belt dryer, airflow dryer, drum dryer, vacuum rake dryer, etc.

[0040] Complex decomposition equipment can generally be equipment containing stirring or vibration components, and an outlet collector is installed inside the equipment at the front end of the liquid outlet pipeline at the bottom of the equipment. The outlet collector is a filter component composed of supporting steel bars and intercepting wire mesh, which is used to intercept solid complexes entrained in the liquid discharge.

[0041] Preferably, the apparatus for producing hydrogen fluoride by the fluorosilicic acid complexation method further includes: The first distillation column is used for the first distillation separation of hydrogen fluoride gas and silicon tetrafluoride gas produced by the complex decomposition equipment. The second distillation column is used for a second distillation to purify the crude hydrogen fluoride obtained from the first distillation, yielding anhydrous hydrogen fluoride.

[0042] Preferably, in the apparatus for producing hydrogen fluoride by fluorosilicic acid complexation, the liquid material outlet of the complex decomposition device is connected to the complexation reaction device, and the liquid material is circulated and used for complexation reaction in the complexation reaction device.

[0043] Preferably, the apparatus for producing hydrogen fluoride by complexation of fluorosilicic acid further includes a fluorosilicic acid raw material tank and a second solid-liquid separation device; the fluorosilicic acid raw material tank, the second solid-liquid separation device and the complexation reaction device are connected in sequence; The silicon tetrafluoride gas outlet of the first distillation column is connected to the fluorosilicic acid feed tank, which is used to receive fluorosilicic acid feed and silicon tetrafluoride gas, as well as the silicon tetrafluoride gas hydrolyzed to generate silicon dioxide and fluorosilicic acid. The second solid-liquid separation device is used to separate silicon dioxide to obtain a fluorosilicic acid solution.

[0044] The first and second solid-liquid separation devices can be filtration devices. Specifically, any device with filtration function to achieve solid-liquid separation can be used, not limited to any one of plate and frame filter press, chamber filter press, centrifugal filter, rotary drum vacuum filter, cartridge filter, membrane filter, etc.

[0045] The process for producing hydrogen fluoride by fluorosilicic acid complexation described in the first aspect can be carried out using the apparatus for producing hydrogen fluoride by fluorosilicic acid complexation described in the second aspect.

[0046] Thirdly, the present invention provides an apparatus for the production of hydrogen fluoride by fluorosilicic acid complexation as described in the second aspect for use in the production of hydrogen fluoride by fluorosilicic acid complexation.

[0047] Those skilled in the art should understand that among existing methods for producing hydrogen fluoride from fluorosilicic acid, the direct decomposition of sulfuric acid is the most traditional and mature industrial process for producing anhydrous hydrogen fluoride, and it is also the dominant production method globally. While the sulfuric acid decomposition method has withstood the test of long-term operational reliability, its inherent shortcomings in environmental protection, resource consumption, energy efficiency, and economic benefits are becoming increasingly prominent. These contradictions are exacerbated in the context of global green and low-carbon development. Therefore, research institutions and researchers in the phosphate and fluorochemical industries are actively exploring new and feasible alternative processes. Among these new processes, the most promising and suitable alternative for current development requirements is the fluorosilicic acid extraction process for producing hydrogen fluoride. Although this process can solve the environmental problem of producing large amounts of dilute sulfuric acid, the liquid-liquid extraction process suffers from numerous problems such as multiple extraction stages, low extraction rate, difficulty in liquid-liquid phase separation, and significant extractant loss, thus becoming a bottleneck restricting industrialization. This invention employs a novel fluorosilicic acid complexation process for producing hydrogen fluoride. While completely solving the environmental problem of generating large amounts of dilute sulfuric acid, the fluorosilicic acid complexation process is designed as a closed-loop process of solid-liquid separation, solid complex decomposition, and complex solution recycling. This is of great significance for promoting the sustainable development of the phosphorus chemical and fluorochemical industries.

[0048] Compared with the prior art, the beneficial effects of this invention are as follows: 1) This invention designs and constructs a new process route for the decomposition of fluorosilicic acid complexes to produce hydrogen fluoride, and realizes the recycling of the complex solution, so that the whole process can be continuously closed-loop. This not only eliminates the use of concentrated sulfuric acid in the traditional direct decomposition method of fluorosilicic acid, thus fundamentally solving the environmental problem of generating a large amount of dilute sulfuric acid in the industry, but also, based on the fact that the complexation method is completely different from the traditional extraction method, there are no bottleneck problems that restrict industrial application in the multi-stage extraction and liquid-liquid separation process, making it easier to implement in industry.

[0049] 2) In this invention, fluorosilicic acid is efficiently extracted through a complexation reaction and further cross-linked and stabilized by a cross-linking agent. The separation of the complexation product is a liquid-solid separation process, which is the key to high extraction efficiency, high complexation efficiency of fluorosilicic acid, and low loss of complexation solution, thus greatly improving the economic efficiency of producing hydrogen fluoride from fluorosilicic acid.

[0050] 3) In this invention, the thermal decomposition process of the steady-state complex is completed under relatively mild conditions, which is safe and reliable. The phase change is from solid to gas and liquid. The gas obtained is hydrogen fluoride and silicon tetrafluoride gas, and the liquid obtained is complexation solution and crosslinking agent. Based on the fact that these liquid compounds are high-boiling-point liquid compounds, not only is the volatilization loss small and they are not easily deteriorated, but they can also be used for a long period of time. The process of producing hydrogen fluoride by complexation of fluorosilicic acid achieves the technical effect of extremely low consumption of complexation solution and crosslinking agent under the premise of continuous operation.

[0051] 4) This invention is based on a complexation (metastable complex) - cross-linking (stable complex) process, which is not affected by the concentration of fluorosilicic acid. Therefore, it has a wide applicability to the concentration of fluorosilicic acid raw materials. In principle, as long as the raw material contains fluorosilicic acid, it can be accurately complexed and extracted. This invention is of great significance to the overall rigor and flexibility of the phosphorus chemical and fluorochemical industries. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the apparatus structure and process flow for producing hydrogen fluoride by fluorosilicic acid complexation according to the present invention. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0054] Example 1: See Figure 1 An apparatus for producing hydrogen fluoride by complexation of fluorosilicic acid includes a fluorosilicic acid raw material tank 3, a second solid-liquid separation device 6, a complexation reaction device 12, a cross-linking reaction device 17, a first solid-liquid separation device 22, a dryer 25, a complex decomposition device 27, a first distillation column 34, and a second distillation column 37.

[0055] Fluorosilicic acid raw material tank 3 is used to receive fluorosilicic acid raw material 1 and silicon tetrafluoride gas 2, and to hydrolyze silicon tetrafluoride gas 2 to generate silicon dioxide and fluorosilicic acid. The fluorosilicic acid raw material outlet 4 from the fluorosilicic acid raw material tank 3 enters the second solid-liquid separation device 6 via the fluorosilicic acid outlet pump 5. The second solid-liquid separation device 6 is a filter used to separate silicon dioxide to obtain a fluorosilicic acid solution 8.

[0056] The complexation reaction device 12 is a reaction vessel with a complexation reaction stirring paddle 14 connected to an external complexation reaction stirring motor 13. It is used to mix fluorosilicic acid solution 8, complexation solution 10 and crosslinking agent 11 to carry out a complexation reaction and obtain a first mixture containing metastable complexes.

[0057] The complexation reaction device 12 is connected to the crosslinking reaction device 17 via a complexation reaction discharge pipe 15 equipped with a complexation reaction discharge valve 16.

[0058] The crosslinking reaction equipment 17 is a reaction vessel with a built-in crosslinking reaction stirring paddle 19 connected to an external crosslinking reaction stirring motor 18, which is used to heat and stabilize the first mixture to obtain a second mixture containing a solid-phase stable complex.

[0059] The crosslinking reaction device 17 is connected to the first solid-liquid separation device 22 via a crosslinking reaction discharge pipe 20 equipped with an AC reaction discharge valve 21.

[0060] The first solid-liquid separation device 22 is a filter used to separate the second mixture of materials into solid complex 24 and filtrate 23.

[0061] Dryer 25 is used to dry the solid complex 24 obtained by the first solid-liquid separation device 22 from the second mixture.

[0062] The dryer 25 is connected to the complex decomposition device 27 through the dryer discharge pipe 26.

[0063] The complex decomposition device 27 has a built-in complex decomposition stirring paddle 29 connected to an external complex decomposition stirring motor 28. This paddle is used to decompose the solid complex after drying in the thermal decomposition dryer 25, yielding hydrogen fluoride gas, silicon tetrafluoride gas, and liquid material 31. Liquid material 31 is collected through the outlet collector 30 of the complex decomposition device 27 and transported by the liquid material discharge pump 32. It is then mixed with the fluorosilicic acid solution 8 as circulating material 7 to form a mixture 9, which is then fed into the complexation reaction device 12. The first distillation column 34 is used to separate the mixed gas 33 of hydrogen fluoride and silicon tetrafluoride produced by the complex decomposition device 27 in the first distillation, to obtain silicon tetrafluoride gas 2 and crude hydrogen fluoride 35.

[0064] The second distillation column 37 is used for a second distillation to purify the crude hydrogen fluoride 35 obtained from the first distillation separation, yielding anhydrous hydrogen fluoride 36.

[0065] The apparatus described above for the production of hydrogen fluoride by fluorosilicic acid complexation can be used for the production of hydrogen fluoride by fluorosilicic acid complexation.

[0066] A process for producing hydrogen fluoride by fluorosilicic acid complexation, using the aforementioned apparatus for producing hydrogen fluoride by fluorosilicic acid complexation, comprising: Fluorosilicic acid raw material 1 and silicon tetrafluoride gas 2 are concentrated in fluorosilicic acid raw material tank 3. The resulting fluorosilicic acid raw material discharge 4 is sent to the second solid-liquid separation device 6 for filtration via fluorosilicic acid discharge pump 5. The resulting fluorosilicic acid solution 8 is mixed with circulating material 7 to form a mixture 9, which enters the complexing reaction device 12. Complexation occurs under stirring. After a certain residence time, a metastable mixture of complex and water is obtained. This mixture enters the crosslinking reaction device 17 via the complexing reaction discharge pipe 15 and the complexing reaction discharge valve 16. After appropriate heating, crosslinking occurs. After the crosslinking reaction is completed, a stable mixture of complex and water is obtained. This mixture enters the first solid-liquid separation device 22 via the crosslinking reaction discharge pipe 20 and the crosslinking reaction discharge valve 21. After filtration, a filtrate 23 containing almost water and a solid complex 24 are obtained. The solid complex 24 is then sent to the dryer 25 for further drying and dehydration to a water content of less than 0.5%, resulting in a dried solid complex. The dried solid complex is introduced into the complex decomposition device 27, where it undergoes thermal decomposition under suitable temperature, pressure, and stirring. The gaseous product collected at the top of the complex decomposition device 27 is a mixture of hydrogen fluoride and silicon tetrafluoride gas 33, while the liquid material 31 from the decomposition at the bottom of the device consists of a complex solution and a crosslinking agent liquid. An outlet collector 30 is installed at the bottom of the complex decomposition device 27 to prevent undecomposed solid complex from being carried away by the liquid at the bottom of the tank, thus preventing blockage of subsequent equipment and pipelines. The hydrogen fluoride and silicon tetrafluoride gas 33 is first separated by distillation in the first distillation column 34. The silicon tetrafluoride gas 2 obtained at the top of the column is recycled to the fluorosilicic acid raw material tank 3 for concentration, while the crude hydrogen fluoride 35 obtained at the bottom of the column enters the second distillation column 37 for purification, ultimately yielding anhydrous hydrogen fluoride 36.

[0067] Example 2: The apparatus and process for preparing hydrogen fluoride by the fluorosilicic acid complexation method in Example 1 were used to prepare a superior grade of hydrogen fluoride (anhydrous hydrogen fluoride).

[0068] The complexed solutions are designated as specific complexed solution A and specific complexed solution B, respectively, and their components and contents are shown in Table 1.

[0069] Table 1

[0070] The process includes the following steps: (1) A fluorosilicic acid solution, a specific complexing solution, and a crosslinking agent are added to a complexing reaction device to undergo a complexing reaction. The complexing reaction device uses a conventional preparation kettle. After a period of time, a mixture of metastable complex and water is obtained. (2) The mixture from step (1) is pressed into a crosslinking reaction device and further heated to stabilize it, resulting in a mixture of stable complex and water. (3) The mixture from step (2) is filtered to obtain a solid complex. After further drying, it is introduced into a complex decomposition device to decompose into hydrogen fluoride gas, silicon tetrafluoride gas, and liquid materials such as complexing agent under a certain temperature and pressure. (4) The hydrogen fluoride gas from step (3) is purified by distillation to obtain anhydrous hydrogen fluoride. The silicon tetrafluoride gas is returned to the fluorosilicic acid raw material part for concentration. The liquid materials such as complexing agent are recycled.

[0071] The mass concentration of fluorosilicic acid in fluorosilicic acid raw material 1 is 11.6%. The complexation process uses a specific complexing solution A; The complexation reaction conditions are as follows: temperature 35℃, pressure at atmospheric pressure; molar ratio of fluorosilicic acid to complexing agent 2.15:1; complexation time 30 min. Crosslinking agent: glutaraldehyde; The crosslinking reaction conditions are as follows: the stable temperature is 45℃, and the pressure is atmospheric pressure; the mass of the crosslinking agent added accounts for 0.08% of the total mass of the fluorosilicic acid solution, the specific complexing solution and the crosslinking agent in step (1); Fluorosilicic acid complexation rate: 98.2%; The thermal decomposition conditions for the solid complex were: temperature 220~225℃; pressure 0.12~0.18MPa; residence time 90min. Complex decomposition rate: over 95.6%.

[0072] After the above process, the total yield of hydrogen fluoride reached 90.2%, and the quality of the hydrogen fluoride product reached the superior grade (the key indicators are: hydrogen fluoride content ≥99.99%, moisture content ≤0.003%, fluorosilicic acid content ≤0.003%, sulfur dioxide (SO2) ≤0.003%, and non-volatile acid (calculated as H2SO4) ≤0.003%).

[0073] Example 3: The apparatus and process for producing hydrogen fluoride using the fluorosilicic acid complexation method of Example 1 are similar to those in Example 2.

[0074] The mass concentration of fluorosilicic acid in fluorosilicic acid raw material 1 is 19.8%. The complexation process uses a specific complexing solution A; The complexation reaction conditions are as follows: temperature 25℃, pressure at atmospheric pressure; molar ratio of fluorosilicic acid to complexing agent 2.15:1; complexation time 60 min. Crosslinking agent: glutaraldehyde; The crosslinking reaction conditions are as follows: the stable temperature is 35℃, and the pressure is atmospheric pressure; the mass of the crosslinking agent added accounts for 0.08% of the total mass of the fluorosilicic acid solution, the specific complexing solution and the crosslinking agent in step (1); Fluorosilicic acid complexation rate: 98.4%; The thermal decomposition conditions for the solid complex were: temperature 220~225℃; pressure 0.12~0.18MPa; residence time 90min. Complex decomposition rate: 95.7%.

[0075] After the above process, the total yield of hydrogen fluoride reached 90.6%, and the quality of the hydrogen fluoride product reached the superior grade (the key indicators are: hydrogen fluoride content ≥99.99%, moisture content ≤0.003%, fluorosilicic acid content ≤0.003%, sulfur dioxide (SO2) ≤0.003%, and non-volatile acid (calculated as H2SO4) ≤0.003%).

[0076] Example 4: The apparatus and process for preparing hydrogen fluoride using the fluorosilicic acid complexation method of Example 1 are similar to those in Example 2.

[0077] Fluorosilicic acid raw material 1: 35% (mass concentration of fluorosilicic acid); The complexation process uses a specific complexing solution A; The complexation reaction conditions are as follows: temperature 20℃, pressure at atmospheric pressure; molar ratio of fluorosilicic acid to complexing agent 2.15:1; complexation time 80 min; Crosslinking agent: glutaraldehyde; The crosslinking reaction conditions are as follows: the stable temperature is 30℃, and the pressure is atmospheric pressure; the mass of the crosslinking agent added accounts for 0.08% of the total mass of the fluorosilicic acid solution, the specific complexing solution and the crosslinking agent in step (1); Fluorosilicic acid complexation rate: 98.7%; The thermal decomposition conditions for the solid complex were: temperature 220~225℃; pressure 0.12~0.18MPa; residence time 90min. Complex decomposition rate: 95.8%.

[0078] After the above process, the total yield of hydrogen fluoride reached 90.8%, and the quality of the hydrogen fluoride product reached the superior grade (the key indicators are: hydrogen fluoride content ≥99.99%, moisture content ≤0.003%, fluorosilicic acid content ≤0.003%, sulfur dioxide (SO2) ≤0.003%, and non-volatile acid (calculated as H2SO4) ≤0.003%).

[0079] Example 5: The apparatus and process for preparing hydrogen fluoride using the fluorosilicic acid complexation method of Example 1 are similar to those in Example 2.

[0080] The mass concentration of fluorosilicic acid in fluorosilicic acid raw material 1 is 11.6%. The complexation process uses a specific complexing solution B; The complexation reaction conditions are as follows: temperature 20℃, pressure at atmospheric pressure; molar ratio of fluorosilicic acid to complexing agent 1.12:1; complexation time 55 min; Crosslinking agent: diisocyanate; The crosslinking reaction conditions are as follows: the stable temperature is 25℃, the pressure is atmospheric pressure, and the mass of the crosslinking agent added accounts for 0.25% of the total mass of the fluorosilicic acid solution, the specific complexing solution and the crosslinking agent in step (1); Fluorosilicic acid complexation rate: 98.3%; The thermal decomposition conditions for the solid complex were: temperature 200~208℃; pressure 0.15~0.2MPa; residence time 30min. Complex decomposition rate: 95.7%.

[0081] After the above process, the total yield of hydrogen fluoride reached 90.6%, and the quality of the hydrogen fluoride product reached the superior grade (the key indicators are: hydrogen fluoride content ≥99.99%, moisture content ≤0.003%, fluorosilicic acid content ≤0.003%, sulfur dioxide (SO2) ≤0.003%, and non-volatile acid (calculated as H2SO4) ≤0.003%).

[0082] Example 6: The apparatus and process for preparing hydrogen fluoride using the fluorosilicic acid complexation method of Example 1 are similar to those in Example 2.

[0083] The mass concentration of fluorosilicic acid in fluorosilicic acid raw material 1 is 19.8%. The complexation process uses a specific complexing solution B; The complexation reaction conditions are as follows: temperature 15℃, pressure at atmospheric pressure; molar ratio of fluorosilicic acid to complexing agent 1.18:1; complexation time 25 min; Crosslinking agent: diisocyanate; The crosslinking reaction conditions are as follows: the stable temperature is 26℃, the pressure is atmospheric pressure, and the mass of the crosslinking agent added accounts for 0.25% of the total mass of the fluorosilicic acid solution, the specific complexing solution and the crosslinking agent in step (1); Fluorosilicic acid complexation rate: 98.5%; The thermal decomposition conditions for the solid complex were: temperature 200~208℃; pressure 0.15~0.2MPa; residence time 30min. Complex decomposition rate: 95.7%.

[0084] After the above process, the total yield of hydrogen fluoride reached 90.9%, and the quality of the hydrogen fluoride product reached the superior grade (the key indicators are: hydrogen fluoride content ≥99.99%, moisture content ≤0.003%, fluorosilicic acid content ≤0.003%, sulfur dioxide (SO2) ≤0.003%, and non-volatile acid (calculated as H2SO4) ≤0.003%).

[0085] Example 7: The apparatus and process for preparing hydrogen fluoride using the fluorosilicic acid complexation method of Example 1 are similar to those in Example 2.

[0086] Fluorosilicic acid raw material 1: 35% (mass concentration of fluorosilicic acid); The complexation process uses a specific complexing solution B; The complexation reaction conditions are as follows: temperature 10℃, pressure at atmospheric pressure; molar ratio of fluorosilicic acid to complexing agent 1.1:1; complexation time 25 min; Crosslinking agent: diisocyanate; The crosslinking reaction conditions are as follows: the temperature for stabilization is 15℃, the pressure is atmospheric pressure, and the mass of the crosslinking agent added accounts for 0.25% of the total mass of the fluorosilicic acid solution, the specific complexing solution and the crosslinking agent in step (1); Fluorosilicic acid complexation rate: 98.8%; The thermal decomposition conditions for the solid complex were: temperature 200~208℃; pressure 0.15~0.2MPa; residence time 40min. Complex decomposition rate: 95.0%.

[0087] After the above process, the total yield of hydrogen fluoride reached 90.1%, and the quality of the hydrogen fluoride product reached the superior grade (the key indicators are: hydrogen fluoride content ≥99.99%, moisture content ≤0.003%, fluorosilicic acid content ≤0.003%, sulfur dioxide (SO2) ≤0.003%, and non-volatile acid (calculated as H2SO4) ≤0.003%).

[0088] Examples 2-7 illustrate the apparatus and process for producing hydrogen fluoride using the fluorosilicic acid complexation method of this invention. The main design involves the formation of a metastable complex from fluorosilicic acid and a specific complexing solution, followed by the formation of a stable complex through the action of a crosslinking agent. Since this complex is a solid complex, liquid-liquid extraction is not involved. The solid complex is simply decomposed into hydrogen fluoride gas and a liquid complexing solution, allowing for the continuous generation of hydrogen fluoride while the complexing solution and crosslinking agent are recycled. This makes the method more easily implemented industrially and completely solves the environmental problem of generating large amounts of dilute sulfuric acid. The method of this invention has advantages such as high separation efficiency, low fluorosilicic acid loss, high hydrogen fluoride yield, and low material and energy consumption. While achieving superior quality standards for hydrogen fluoride products, the fluorosilicic acid complexation rate is over 98%, the complex decomposition rate is over 95%, and the total hydrogen fluoride yield is over 90%.

[0089] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A process for the production of hydrogen fluoride by fluosilicic acid complexation, characterized in that, The method comprises the steps of: (1) mixing a fluosilicic acid solution, a complexing solution and a cross-linking agent to generate a complexing reaction to obtain a first mixture containing metastable complexes; The complexing solution contains a complexing agent and an auxiliary agent; the complexing agent includes one or more than two of N-alkyl-substituted aromatic amine compounds, P-alkyl-substituted aromatic phosphorus compounds, N-alkyl-substituted aromatic phosphorus compounds and alkyl-substituted aromatic sulfur compounds; the auxiliary agent is a substance capable of providing a hydrogen bond donor, insoluble in water and capable of being miscible with the complexing agent; (2) stabilizing the first mixture at a high temperature to obtain a second mixture containing solid stable complexes; (3) performing solid-liquid separation on the second mixture to obtain solid, drying the solid and performing thermal decomposition to obtain hydrogen fluoride gas, silicon tetrafluoride gas and a liquid material.

2. The process for the production of hydrogen fluoride by fluosilicic acid complexation according to claim 1, characterized in that, In step (1): The mass concentration of fluosilicic acid in the fluosilicic acid solution is 10% to 40%; The molar ratio of fluosilicic acid in the fluosilicic acid solution to the complexing agent is 15:1 to 1:15, and further 5:1 to 1:5; The N-alkyl-substituted aromatic amine compounds include one or more than two of N-methylaniline, N-ethylaniline, N-n-butylaniline, N,N-dimethylaniline, N,N-diethylaniline, N-ethyl-N-methylaniline, N-isopropylaniline, N-tert-butylaniline and N-pyrrolidinylaniline; The P-alkyl-substituted aromatic phosphorus compounds include one or more than two of triphenylphosphine, methylphenylphosphine, phenyl-tert-butylphosphine, phenyl-dicyclohexylphosphine, P,P-dimethylphenylphosphine, P,P-dibutylphenylphosphine, P,P-diphenylbutylphosphine, P,P-diethylphenylphosphine, phenyl-dicyclohexylphosphine and phenyl diethyl phosphite; The N-alkyl-substituted aromatic phosphorus compounds include one or more than two of diphenyl(N,N-dimethylamino)phosphine, di-tert-butyl(N,N-diethylamino)phosphine, phosphoric acid diamide, hexamethylphosphoramide, phenylbis(dimethylamino)phosphine and hexamethylphosphoramide; The alkyl-substituted aromatic sulfur compounds include one or more than two of 2-methylphenyl mercaptan, 4-tert-butylphenyl mercaptan, 2-ethylphenyl methyl sulfide, 4-isopropyl diphenyl sulfide, 4-methylphenyl methyl sulfoxide, 2,4,6-trimethylphenyl phenyl sulfone, 4-ethylbenzenesulfonic acid methyl ester, methylphenyl sulfide, ethylphenyl sulfide, butylphenyl sulfide, methylphenyl sulfoxide, methylphenyl sulfone and methyl benzenesulfonate; The auxiliary agent includes one or more than two of long-chain fatty alcohols, long-chain fatty acids and long-chain alkyl amines, and further includes one or more than two of n-hexanol, n-octanol, nonyl phenol, n-hexylamine, n-octylamine, dodecylamine, N-dodecyl aniline, N-n-octyl acetamide, n-decanoic acid, stearic acid and lauric acid; The mass ratio of the complexing agent to the auxiliary agent is 100:1 to 1:1, and further 50:1 to 2:1; The temperature of the complexing reaction is 5 to 60°C, and further 5 to 35°C; The pressure of the complexing reaction is normal pressure to 1.0 MPa, and further normal pressure to 0.15 MPa; The time of the complexing reaction is 5-120 min, and further 10-40 min; The cross-linking agent includes one or two or more of 1,4-diiodobutane, 1,6-dibromohexane, 1,4-dichlorobutane, glutaraldehyde, adipoyl chloride, and diisocyanate; The mass percentage of the cross-linking agent in the total mass of the fluosilicic acid solution, the complexing solution, and the cross-linking agent is 0.01%-5%, and further 0.05%-0.5%.

3. The process for the production of hydrogen fluoride by fluosilicic acid complexation according to claim 1, characterized in that, In step (2): The temperature at which the first mixture is stably heated is 10-85°C, and further 15-60°C; The pressure at which the first mixture is stably heated is normal pressure-1.0 MPa, and further normal pressure-0.15 MPa.

4. The process for the production of hydrogen fluoride by fluosilicic acid complexation according to claim 1, characterized in that, The temperature at which the first mixture is stably heated in step (2) is 5-30°C higher than the temperature of the complexing reaction in step (1), and further, the temperature at which the first mixture is stably heated in step (2) is 10-20°C higher than the temperature of the complexing reaction in step (1).

5. The process for the production of hydrogen fluoride by fluosilicic acid complexation according to claim 1, characterized in that, In step (3): The temperature of the thermal decomposition is 120-450°C, and further 150-320°C; The pressure of the thermal decomposition is 0.1-1.0 MPa, and further 0.12-0.20 MPa; The time of the thermal decomposition is 20-180 min, and further 30-120 min.

6. The process for the production of hydrogen fluoride by fluosilicic acid complexation according to claim 1, characterized in that, The process for preparing hydrogen fluoride by the fluosilicic acid complexing method further includes: The hydrogen fluoride gas and the silicon tetrafluoride gas are first rectified and separated; after the first rectification and separation, the obtained crude hydrogen fluoride is secondly rectified and purified to obtain anhydrous hydrogen fluoride, and the obtained silicon tetrafluoride is used for hydrolysis to prepare a fluosilicic acid solution; A liquid material circulation jacket is used for the complexing reaction in step (1).

7. An apparatus for producing hydrogen fluoride by a fluosilicic acid complex method, characterized by comprising: It includes: A complexing reaction device for mixing a fluosilicic acid solution, a complexing solution, and a cross-linking agent to perform a complexing reaction and obtain a first mixture containing a metastable complex; A cross-linking reaction device for stably heating the first mixture to obtain a second mixture containing a solid stable complex; A first solid-liquid separation device for solid-liquid separation of the second mixture; A dryer for drying the solid obtained by the solid-liquid separation of the second mixture by the first solid-liquid separation device; A complex decomposition device for thermally decomposing the solid dried by the dryer to obtain hydrogen fluoride gas, silicon tetrafluoride gas, and liquid material.

8. The apparatus for producing hydrogen fluoride by fluosilicic acid complexation method according to claim 7, wherein The device for preparing hydrogen fluoride by the fluosilicic acid complexing method further includes: A first rectifying column for first rectifying and separating the hydrogen fluoride gas and the silicon tetrafluoride gas generated by the complex decomposition device; A second rectifying column for second rectifying and purifying the crude hydrogen fluoride obtained by the first rectification and separation to obtain anhydrous hydrogen fluoride.

9. The apparatus for producing hydrogen fluoride by fluosilicic acid complexation method according to claim 8, characterized by The liquid material outlet of the complex decomposition device is connected to the complexing reaction device, and the liquid material circulation jacket is used for the complexing reaction in the complexing reaction device; The device for preparing hydrogen fluoride by the fluosilicic acid complexing method further includes a fluosilicic acid raw material tank and a second solid-liquid separation device; the fluosilicic acid raw material tank, the second solid-liquid separation device, and the complexing reaction device are connected in sequence; The silicon tetrafluoride gas outlet of the first rectifying column is connected to the fluosilicic acid raw material tank, and the fluosilicic acid raw material tank is used for receiving fluosilicic acid raw material and silicon tetrafluoride gas and hydrolyzing the silicon tetrafluoride gas to generate silicon dioxide and fluosilicic acid; The second solid-liquid separation device is used for separating out the silicon dioxide to obtain the fluosilicic acid solution.

10. Use of the apparatus for producing hydrogen fluoride by fluosilicic acid complex method according to any one of claims 7-9 for producing hydrogen fluoride by fluosilicic acid complex method.

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