A method and system for producing anhydrous hydrogen fluoride

Abstract

The present application relates to inorganic chemical industry and resource recycling technical field, specifically relates to a kind of preparation of anhydrous hydrogen fluoride process and system.The method includes that the raw material containing calcium fluoride is mixed with 55%~75% mass concentration dilute sulfuric acid reaction, control reaction temperature is 110-140 ℃, after reaction, material is separated by solid-liquid, obtain first filtrate and first calcium sulfate slurry, and first filtrate contains hydrogen fluoride;Anhydrous hydrogen fluoride is obtained by separation and extraction from first filtrate.A kind of system for preparing anhydrous hydrogen fluoride is also provided, including first reactor, for the raw material containing calcium fluoride is mixed with dilute sulfuric acid reaction, obtain after-reaction material;Solid-liquid separation device is connected with the outlet of first reactor, for after-reaction material solid-liquid separation, obtain first filtrate and first calcium sulfate slurry;Extraction device is connected with the liquid outlet of solid-liquid separation device, for anhydrous hydrogen fluoride is obtained by separation and extraction from first filtrate.Realize the high-value use of low-grade fluorine-containing resources.

Description

Technical Field

[0001] This invention relates to the field of inorganic chemical engineering and resource recycling technology, specifically to a process and system for preparing anhydrous hydrogen fluoride. Background Technology

[0002] Anhydrous hydrogen fluoride is an indispensable basic raw material in the modern fluorochemical industry chain, and is widely used in refrigerants, fluorinated polymer materials, fluorinated fine chemicals and new energy fields.

[0003] Currently, the mainstream industrial production process for anhydrous hydrogen fluoride both domestically and internationally is the fluorite-sulfuric acid process. This process uses high-grade fluorite concentrate (typically requiring a CaF2 content ≥97%) and high-concentration sulfuric acid (such as 98% fuming sulfuric acid) as raw materials. A gas-solid phase reaction occurs in a high-temperature rotary kiln or reactor at 200-300℃, directly generating gaseous hydrogen fluoride. After condensation and purification, the product is obtained. While this method is mature, it has extremely stringent requirements for raw material quality, leading to a strong dependence on high-quality fluorite resources and high beneficiation costs. Furthermore, the high-temperature, highly corrosive reaction environment places extremely high demands on equipment materials (requiring expensive nickel-based alloys), resulting in high energy consumption, high equipment investment and maintenance costs, and potential safety and environmental risks.

[0004] With the increasing depletion of high-quality fluorite resources, the utilization of large quantities of low-grade or complex fluorine-containing calcium resources (such as tailings from rare earth and beryllium ores flotation, and calcium fluoride sludge from the treatment of fluorine-containing wastewater in aluminum electrolysis or the photovoltaic industry) has become a focus of the industry. These resources typically contain 50% to 80% CaF2 and various impurities such as SiO2, Al2O3, and P2O5.

[0005] If the traditional fluorite-sulfuric acid process is used to treat such low-grade raw materials, the pretreatment cost is extremely high, requiring costly enrichment and purification, which is uneconomical. Therefore, developing a new process that can directly utilize low-grade fluorine-containing calcium resources, with mild reaction conditions, low cost, and the ability to achieve high-value utilization of waste has become an urgent need for the industry. Summary of the Invention

[0006] This invention aims to address the problems of the existing fluorite-sulfuric acid process for preparing anhydrous hydrogen fluoride, including high requirements for raw material grade, harsh reaction conditions, severe equipment corrosion, high energy consumption, and the difficulty in resource utilization of low-grade fluorine-containing calcium industrial solid waste. This invention provides a method and system for preparing anhydrous hydrogen fluoride that features strong raw material adaptability, a mild process, low cost, and the functional utilization of byproducts.

[0007] The specific technical solution of the present invention is as follows: In a first aspect, a method for preparing anhydrous hydrogen fluoride is provided, comprising the following steps: The raw material containing calcium fluoride is mixed with dilute sulfuric acid with a mass concentration of 55% to 75% and reacted. The reaction temperature is controlled at 110-140℃. After the reaction, the material is separated into solid and liquid to obtain a first filtrate and a first calcium sulfate slurry. The first filtrate contains hydrogen fluoride. Anhydrous hydrogen fluoride is separated and extracted from the first filtrate.

[0008] This invention, based on thermodynamic and kinetic analysis, synergistically optimizes the reaction temperature and sulfuric acid concentration to simultaneously achieve high yield (high calcium fluoride conversion rate) and high hydrogen fluoride liquid-phase distribution rate (minimal loss due to volatilization of generated hydrogen fluoride), i.e., "double high." The hydrogen fluoride liquid-phase distribution rate is defined as the proportion (95%~97%) of the total hydrogen fluoride actually generated from the hydrogen fluoride in the first filtrate plus the hydrogen fluoride in the first calcium sulfate slurry, thus forming a non-gas-phase reaction mode.

[0009] Specifically, the reaction temperature defined in this invention is 110℃~140℃. If the temperature is too low (<110℃), the reaction rate is slow and the yield will decrease significantly. If the temperature is too high (>140℃), the saturated vapor pressure of water increases, the solubility of hydrogen fluoride in the liquid phase decreases, and a large amount of it will vaporize, resulting in the hydrogen fluoride liquid phase partition rate not reaching 95%~97%. Therefore, 110~140℃ can ensure a sufficiently fast reaction rate, i.e., high yield, and also ensure sufficient water in the liquid phase and minimal hydrogen fluoride volatilization, i.e., high partition rate. At the same time, it significantly reduces energy consumption compared to the traditional high-temperature gas phase method (200~300℃), and is a non-gas phase reaction mode.

[0010] Meanwhile, the concentration of dilute sulfuric acid specified in this invention is 55%~75%. If the concentration is too low (<55%), there will be insufficient hydrogen ions, resulting in a slow reaction and low conversion rate; if the concentration is too high (>75%), the water content will decrease, and although the hydrogen ion concentration is high, there will be insufficient liquid water, leading to a large amount of hydrogen fluoride vaporization. Therefore, limiting the concentration of dilute sulfuric acid to 55%~75% provides sufficient hydrogen ions to drive the reaction while maintaining enough water to dissolve hydrogen fluoride and inhibit premature escape. Furthermore, the corrosiveness of sulfuric acid at this concentration is far lower than that of fuming sulfuric acid used in traditional processes, which can significantly reduce the requirements for equipment materials, directly reduce the equipment corrosion rate, and extend equipment life; at the same time, it greatly improves process safety and reduces the difficulty and risk of the process.

[0011] The temperature range of 110℃ to 140℃ specified in this invention, combined with a dilute sulfuric acid concentration of 55% to 75%, achieves a synergistic effect: at 110℃ to 140℃, the 55% to 75% dilute sulfuric acid can maintain a large amount of liquid water, efficiently dissolving the hydrogen fluoride generated in the reaction. If the temperature is too high and the concentration is too low, there is more water but the reaction rate is slow; if the temperature is too low and the concentration is too high, the reaction is fast but there is insufficient water. Only when both are within the specified range can a sufficiently fast reaction rate (high yield) and a sufficiently high liquid phase partition rate (≥95%) be simultaneously satisfied, while achieving a mild corrosive environment and low energy consumption.

[0012] In summary, this invention achieves both high yield and high hydrogen fluoride liquid phase partition rate by matching temperature with the mass concentration of dilute sulfuric acid, ultimately realizing a hydrogen fluoride liquid phase partition rate of 95%~97%, meaning that most of the hydrogen fluoride product remains in the liquid phase, facilitating subsequent extraction of anhydrous hydrogen fluoride.

[0013] Optionally, the calcium fluoride content in the raw material is 70% to 85% by mass.

[0014] Limiting the calcium fluoride content in the raw materials to 70%–85% lowers the requirements for raw material grade. Tailings with grades higher than this can be used directly without further enrichment, significantly reducing raw material costs and making it highly economical. Simultaneously, utilizing low-grade resources ensures the reactivity of the raw materials, guaranteeing the feasibility and stability of the process. This avoids problems such as excessively high impurity ratios due to excessively low grades, which could interfere with the main reaction, increase acid consumption, reduce product purity, and cause a surge in post-reaction solid waste.

[0015] By using high-grade ore with higher calcium fluoride content as raw material and mixing it with dilute sulfuric acid, and controlling the reaction temperature at 110-140℃, hydrogen fluoride can be retained in the reaction solution. In subsequent processes, anhydrous hydrogen fluoride can be separated and extracted from the first filtrate. The method for preparing anhydrous hydrogen fluoride adopted in this invention has low requirements for the grade of raw materials, and can effectively recycle and utilize low-grade raw materials such as rare earth flotation tailings powder (containing calcium fluoride) that were originally unusable, turning waste into treasure and improving production economic efficiency.

[0016] Optionally, the particle size of the raw material is greater than or equal to 500 mesh. When the reaction temperature and sulfuric acid concentration are low, the reaction kinetics may be insufficient. Pulverizing the raw material to an ultrafine state greatly increases its specific surface area, compensating for the insufficient reaction kinetics caused by the low reaction temperature. This achieves a high conversion rate of low-grade raw materials under mild conditions, promotes uniform reaction, reduces incomplete reaction or encapsulation caused by excessively large particles, and improves raw material utilization.

[0017] Optionally, the gauge pressure of the reaction is -20 kPa to 1 kPa. Limiting the pressure of the reaction system to the above range serves two main purposes: First, since the calcium fluoride content in the raw materials is relatively low, impurities are present, which may generate a small amount of air or impurity reaction gases. Controlling the reaction system within this pressure range can gently remove trace amounts of non-condensable gases generated during the reaction, preventing them from affecting the reaction equilibrium. Second, this pressure range can provide a slight suction force, which helps the subsequent directional flow of hydrogen fluoride vapor, but will not cause a large amount of hydrogen fluoride and water to be prematurely removed due to excessive vacuum, thus disrupting the liquid phase equilibrium.

[0018] Optionally, the amount of dilute sulfuric acid added is based on the mass ratio of sulfuric acid to calcium fluoride in the raw materials, wherein the mass ratio of sulfuric acid to calcium fluoride is 1.5-5:1. This invention, by precisely controlling the acid-to-material ratio, ensures a relatively high proportion of water in the reaction system, effectively maintaining the high liquid-phase solubility of hydrogen fluoride. This feed ratio balances reaction completeness and economy.

[0019] Optionally, it also includes reacting fluorosilicic acid with concentrated sulfuric acid to obtain a second liquid phase containing hydrogen fluoride, combining the second liquid phase with the first filtrate to obtain a mixed filtrate, separating and extracting anhydrous hydrogen fluoride from the mixed filtrate, and obtaining dilute sulfuric acid as a byproduct.

[0020] Optionally, the byproduct dilute sulfuric acid is recycled for reaction with the calcium fluoride-containing raw material.

[0021] The second liquid phase produced by the fluorosilicic acid process contains a high concentration of hydrogen fluoride. Combining it with the first filtrate avoids the loss of fluorine resources in the second liquid phase or the inconvenience of constructing a separate recovery line, achieving centralized recovery and efficient utilization of fluorine and improving the overall fluorine yield. By combining the filtrates from both processes for unified vacuum distillation extraction, the need for a separate extraction unit for the second liquid phase is eliminated, simplifying the process and reducing costs.

[0022] The by-product dilute sulfuric acid can be recycled as a raw material in the main reaction section, realizing the recycling of by-products. This closed-loop design not only solves the problem of handling by-product dilute sulfuric acid, but also reduces the need to purchase new sulfuric acid, lowers production costs, and has good economic and environmental benefits.

[0023] Optionally, the first calcium sulfate slurry contains hydrogen fluoride, and the first calcium sulfate slurry is combined with the second calcium sulfate slurry produced in the wet-process phosphoric acid stage for subsequent processing.

[0024] The first calcium sulfate slurry and the second calcium sulfate slurry are mixed and the mixed slurry is circulated into the scaling pipes of the phosphoric acid production system. The residual hydrogen fluoride in the second calcium sulfate slurry reacts with the silicon dioxide to remove scale from the pipes.

[0025] Specifically, the byproduct calcium sulfate slurry differs from ordinary gypsum in that it contains residual hydrogen fluoride. In the acidic environment of wet-process phosphoric acid production, this residual hydrogen fluoride reacts with silica in the phosphate rock to generate easily discharged volatile SiF4 or soluble fluorosilicic acid, thereby preventing or dissolving existing silicate scale layers and solving the long-standing problem of scaling and clogging in pipelines and equipment during wet-process phosphoric acid production. This achieves high-value utilization of solid waste, resulting in significant economic benefits.

[0026] Furthermore, the wet-process phosphoric acid production process is a slurry reaction system. Therefore, the first calcium sulfate slurry can be directly pumped into the sulfuric acid wet-process phosphoric acid system in slurry form. This allows for direct injection, requiring only adjustments to the piping connections in the actual process, without the need for large-scale modifications to existing phosphoric acid plants. The application method is simple, efficient, economical, and low-cost, achieving solid waste utilization.

[0027] Secondly, a system for preparing anhydrous hydrogen fluoride using the above method is provided, comprising: The first reactor is used to mix and react calcium fluoride raw materials with dilute sulfuric acid to obtain the reaction product; A solid-liquid separation device is used to process the reaction material to obtain a first filtrate and a first calcium sulfate slurry. An extraction device is used to separate and extract anhydrous hydrogen fluoride from the first filtrate.

[0028] An anhydrous hydrogen fluoride preparation system utilizing a mild reaction system of dilute sulfuric acid is provided. By combining a first reactor, solid-liquid separation, and extraction unit, the system effectively processes calcium fluoride-containing raw materials. The system has a simple and streamlined structure, avoids damage to equipment from high-temperature, highly corrosive gases, and reduces the requirements for equipment materials.

[0029] Optionally, the system further includes a second reactor for mixing and reacting fluorosilicic acid with concentrated sulfuric acid to generate fumed silicon tetrafluoride and a second liquid phase containing hydrogen fluoride; The second liquid phase and the first filtrate are combined and then separated and extracted by the extraction device to obtain anhydrous hydrogen fluoride.

[0030] This system, integrated with other industrial lines, achieves process coupling and by-product resource utilization. By adding a second reactor to the basic system, it gains the ability to co-process fluorosilicic acid. The hydrogen fluoride filtrate produced after the decomposition of fluorosilicic acid is combined with the first filtrate from the main process for extraction. This not only significantly improves the overall production efficiency of anhydrous hydrogen fluoride but also enables the recovery and utilization of fluorine resources, a by-product of phosphate chemical production. It expands the system's raw material adaptability, turning waste into treasure, and has good economic and environmental benefits.

[0031] Optionally, the system further includes a wet-process phosphoric acid unit, wherein the calcium sulfate slurry produced by the wet-process phosphoric acid unit is used as a second calcium sulfate slurry and is transported together with the first calcium sulfate slurry.

[0032] This system integrates with other industrial lines to achieve cross-process coupling. By combining the calcium sulfate slurry produced by both processes and using the residual hydrogen fluoride in the slurry to react with silica for pipeline descaling, the system achieves centralized collection and unified treatment of by-product gypsum.

[0033] Optionally, the fluorosilicic acid produced by the wet-process phosphoric acid unit is fed to the second reactor.

[0034] The waste fluorosilicic acid from the wet-process phosphoric acid unit is converted into a raw material and fed back to the second reactor as a raw material for the preparation of hydrogen fluoride. This realizes the internal circulation of materials in the system and forms a closed-loop system with deep coupling of phosphorus and fluorine resources. It significantly reduces the dependence on primary fluorite resources and improves the comprehensive utilization rate of resources.

[0035] Compared with the prior art, the advantages of the present invention are as follows: 1. The method for preparing anhydrous hydrogen fluoride provided by the present invention has low raw material requirements and can directly utilize low-grade and complex fluorine-containing calcium resources such as rare earth flotation tailings and calcium fluoride mud recovered from fluorine-containing wastewater, thereby achieving the substitution of concentrate, reducing the dependence on high-grade fluorite ore, and realizing the high-value utilization of industrial waste such as tailings.

[0036] This invention achieves both high yield and high hydrogen fluoride liquid phase partition rate by matching temperature with the mass concentration of dilute sulfuric acid, ultimately realizing a hydrogen fluoride liquid phase partition rate of 95%~97%, meaning that most of the hydrogen fluoride product remains in the liquid phase, facilitating subsequent extraction of anhydrous hydrogen fluoride.

[0037] This method features a simple process flow, low equipment requirements, low energy consumption, and low production costs. The raw materials have low corrosivity to the equipment, and the reaction conditions are mild, avoiding the harsh environment of high temperature and fuming sulfuric acid, thus significantly reducing investment and maintenance costs.

[0038] This method can be integrated with other industrial lines, achieving process coupling and resource utilization of by-products. For example, the calcium sulfate slurry obtained from the reaction, due to its residual hydrogen fluoride content, can effectively eliminate silica scale in pipelines and can be transported to other process sections for pipeline descaling, realizing the resource utilization of waste.

[0039] 2. The system for preparing anhydrous hydrogen fluoride provided by this invention achieves effective processing of calcium fluoride-containing raw materials by combining a first reactor, a solid-liquid separation and extraction unit. The system has a simple and streamlined structure, avoids damage to equipment caused by high-temperature and highly corrosive gases, reduces the requirements for equipment materials, and has low investment and production costs. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the method for preparing anhydrous hydrogen fluoride according to the present invention. Figure 1 .

[0041] Figure 2 This is a schematic diagram of the method for preparing anhydrous hydrogen fluoride according to the present invention. Figure 2 .

[0042] Figure 3 This is a schematic diagram of the method for preparing anhydrous hydrogen fluoride according to the present invention. Figure 3 . Specific Implementation

[0043] To enable those skilled in the art to better understand the technical solution of the invention, the invention will be further described in detail below with reference to specific embodiments.

[0044] Firstly, embodiments of the present invention provide a method for preparing anhydrous hydrogen fluoride, please refer to [the following text is also provided]. Figure 1 This includes the following steps: The raw material containing calcium fluoride is mixed with dilute sulfuric acid with a mass concentration of 55% to 75% and reacted. The reaction temperature is controlled at 110-140℃. After the reaction, the material is separated into solid and liquid to obtain a first filtrate and a first calcium sulfate slurry. The first filtrate contains hydrogen fluoride (the amount of hydrogen fluoride in the first calcium sulfate slurry is controlled according to the solid-liquid separation efficiency as needed). Anhydrous hydrogen fluoride is separated and extracted from the first filtrate.

[0045] This invention, based on thermodynamic and kinetic analysis, synergistically optimizes the reaction temperature and sulfuric acid concentration to simultaneously achieve high yield (high calcium fluoride conversion rate) and high hydrogen fluoride liquid-phase partitioning rate (minimal loss due to volatilization of generated hydrogen fluoride), i.e., "double high". The hydrogen fluoride liquid-phase partitioning rate is defined as the proportion (95%~97%) of the total hydrogen fluoride actually generated, consisting of hydrogen fluoride in the filtrate plus hydrogen fluoride in the slurry, thus forming a non-gas-phase reaction mode.

[0046] Specifically, the reaction temperature defined in this invention is 110℃~140℃. If the temperature is too low (<110℃), the reaction rate is slow and the yield will decrease significantly. If the temperature is too high (>140℃), the saturated vapor pressure of water increases, the solubility of hydrogen fluoride in the liquid phase decreases, and a large amount of it will vaporize, resulting in the hydrogen fluoride liquid phase partition rate not reaching 95%~97%. Therefore, 110~140℃ can ensure a sufficiently fast reaction rate, i.e., high yield, and also ensure sufficient water in the liquid phase and minimal hydrogen fluoride volatilization, i.e., high partition rate. At the same time, it significantly reduces energy consumption compared to the traditional high-temperature gas phase method (200~300℃), and is a non-gas phase reaction mode.

[0047] Meanwhile, the concentration of dilute sulfuric acid specified in this invention is 55%~75%. If the concentration is too low (<55%), there will be insufficient hydrogen ions, resulting in a slow reaction and low conversion rate; if the concentration is too high (>75%), the water content will decrease, and although the hydrogen ion concentration is high, there will be insufficient liquid water, leading to a large amount of hydrogen fluoride vaporization. Therefore, limiting the concentration of dilute sulfuric acid to 55%~75% provides sufficient hydrogen ions to drive the reaction while maintaining enough water to dissolve hydrogen fluoride and inhibit premature escape. Furthermore, the corrosiveness of sulfuric acid at this concentration is far lower than that of fuming sulfuric acid used in traditional processes, which can significantly reduce the requirements for equipment materials, directly reduce the equipment corrosion rate, and extend equipment life; at the same time, it greatly improves process safety and reduces the difficulty and risk of the process.

[0048] The temperature range of 110℃ to 140℃ specified in this invention, combined with a dilute sulfuric acid concentration of 55% to 75%, achieves a synergistic effect: at 110℃ to 140℃, the 55% to 75% dilute sulfuric acid can maintain a large amount of liquid water, efficiently dissolving the hydrogen fluoride generated in the reaction. If the temperature is too high and the concentration is too low, there is more water but the reaction rate is slow; if the temperature is too low and the concentration is too high, the reaction is fast but there is insufficient water. Only when both are within the specified range can a sufficiently fast reaction rate (high yield) and a sufficiently high liquid phase partition rate (≥95%) be simultaneously satisfied, while achieving a mild corrosive environment and low energy consumption.

[0049] In summary, this invention achieves both high yield and high hydrogen fluoride liquid phase partition rate by matching temperature with the mass concentration of dilute sulfuric acid, ultimately realizing a hydrogen fluoride liquid phase partition rate of 95%~97%, meaning that most of the hydrogen fluoride product remains in the liquid phase, facilitating subsequent extraction of anhydrous hydrogen fluoride.

[0050] In some embodiments of the present invention, the calcium fluoride content in the raw material is 70%–85% by mass. Limiting the calcium fluoride content to 70%–85% lowers the requirement for raw material grade; tailings with grades higher than this can be used directly without further enrichment, significantly reducing raw material costs and resulting in higher economic efficiency. Simultaneously, utilizing low-grade resources ensures the reactivity of the raw material, guaranteeing the feasibility and stability of the process and avoiding problems such as excessively high impurity ratios due to excessively low grades, which could interfere with the main reaction, increase acid consumption, reduce product purity, and cause a surge in post-reaction solid waste.

[0051] By using high-grade ore with higher calcium fluoride content as raw material and mixing it with dilute sulfuric acid, and controlling the reaction temperature at 110-140℃, hydrogen fluoride can be retained in the reaction solution. In subsequent processes, anhydrous hydrogen fluoride can be separated and extracted from the first filtrate. The method for preparing anhydrous hydrogen fluoride adopted in this invention has low requirements for the grade of raw materials, and can effectively recycle and utilize low-grade raw materials such as rare earth flotation tailings powder (containing calcium fluoride) that were originally unusable, turning waste into treasure and improving production economic efficiency.

[0052] In some embodiments of the present invention, the particle size of the raw material is greater than or equal to 500 mesh. When the reaction temperature and sulfuric acid concentration are low, the reaction kinetics are insufficient. Pulverizing the raw material to an ultrafine state greatly increases its specific surface area, compensating for the insufficient reaction kinetics caused by the low reaction temperature. This achieves a high conversion rate of low-grade raw materials under mild conditions, promotes uniform reaction, reduces incomplete reaction or encapsulation caused by excessively large particles, and improves raw material utilization.

[0053] In some embodiments of the present invention, the gauge pressure of the reaction is -20 kPa to 1 kPa. Limiting the pressure of the reaction system to the above range serves two main purposes: First, since the calcium fluoride content in the raw materials is relatively low, impurities are present, which may generate a small amount of air or impurity reaction gases. Controlling the reaction system within this pressure range can gently remove trace amounts of non-condensable gases generated during the reaction, preventing them from affecting the reaction equilibrium. Second, this pressure range can provide a slight suction force, which helps the subsequent directional flow of hydrogen fluoride vapor, but without causing a large amount of hydrogen fluoride and water to be prematurely removed due to excessive vacuum, thus disrupting the liquid phase equilibrium.

[0054] In some embodiments of the present invention, the amount of dilute sulfuric acid added is calculated based on the mass ratio of sulfuric acid contained therein to calcium fluoride in the raw materials, wherein the mass ratio of sulfuric acid to calcium fluoride is 1.5-5:1. The present invention, by precisely controlling the acid-to-material ratio, ensures a relatively high proportion of water in the reaction system, effectively maintaining the high liquid-phase solubility of hydrogen fluoride. This feed ratio balances reaction completeness and economy.

[0055] In some embodiments of the present invention, please refer to the relevant references. Figure 2 The method also includes reacting fluorosilicic acid with concentrated sulfuric acid, where the fluorosilicic acid decomposes in the concentrated sulfuric acid to produce silicon tetrafluoride and hydrogen fluoride. Silicon tetrafluoride is released as a gas from the reaction solution, while most of the hydrogen fluoride remains in the reaction solution, thus obtaining a second liquid phase containing hydrogen fluoride. The second liquid phase is combined with the first filtrate to obtain a mixed filtrate, and anhydrous hydrogen fluoride and dilute sulfuric acid as a byproduct are separated and extracted from the mixed filtrate.

[0056] In some embodiments of the present invention, please continue to refer to Figure 2 The byproduct dilute sulfuric acid is recycled for reaction with the calcium fluoride-containing raw material.

[0057] The second liquid phase produced by the fluorosilicic acid process contains a high concentration of hydrogen fluoride. Combining it with the first filtrate avoids the loss of fluorine resources in the second liquid phase or the inconvenience of constructing a separate recovery line, achieving centralized recovery and efficient utilization of fluorine and improving the overall fluorine yield. By combining the filtrates from both processes for unified vacuum distillation extraction, the need for a separate extraction unit for the second liquid phase is eliminated, simplifying the process and reducing costs.

[0058] Dilute sulfuric acid, a byproduct of the fluorosilicic acid process, can be recycled as a raw material in the main reaction stage, achieving the recycling of byproducts. This closed-loop design not only solves the problem of disposing of byproduct dilute sulfuric acid but also reduces the need to purchase new sulfuric acid, lowers production costs, and has good economic and environmental benefits.

[0059] In some embodiments of the present invention, please refer to the relevant references. Figure 3It also includes the following: the first calcium sulfate slurry contains hydrogen fluoride, and the first calcium sulfate slurry is combined with the second calcium sulfate slurry produced in the wet-process phosphoric acid section for subsequent processing. The first calcium sulfate slurry and the second calcium sulfate slurry are mixed, and the mixed slurry is circulated into the scaling pipes of the phosphoric acid production system. The residual hydrogen fluoride in the first calcium sulfate slurry reacts with the silica to remove scale from the pipes.

[0060] Specifically, the first calcium sulfate slurry differs from ordinary gypsum in that it contains residual hydrogen fluoride. In the acidic environment of wet-process phosphoric acid production, this residual hydrogen fluoride reacts with silica in the phosphate rock to generate easily discharged volatile SiF4 or soluble fluorosilicic acid, thereby preventing or dissolving existing silicate scale layers and solving the long-standing problem of scaling and clogging in pipelines and equipment during wet-process phosphoric acid production. This achieves high-value utilization of solid waste, resulting in significant economic benefits.

[0061] Furthermore, the wet-process phosphoric acid production process is a slurry reaction system. Therefore, the first calcium sulfate slurry can be directly pumped into the sulfuric acid wet-process phosphoric acid system in slurry form. This allows for direct injection, requiring only adjustments to the piping connections in the actual process, without the need for large-scale modifications to existing phosphoric acid plants. The application method is simple, efficient, economical, and low-cost, achieving solid waste utilization.

[0062] Secondly, a system for preparing anhydrous hydrogen fluoride using the above method is provided, comprising: The first reactor is used to mix and react calcium fluoride raw materials with dilute sulfuric acid to obtain the reaction product; A solid-liquid separation device is used to process the reaction material to obtain a first filtrate and a first calcium sulfate slurry. An extraction device is used to separate and extract anhydrous hydrogen fluoride from the first filtrate.

[0063] Understandably, an anhydrous hydrogen fluoride preparation system utilizing a mild reaction system of dilute sulfuric acid has been provided. By combining a first reactor, solid-liquid separation, and extraction unit, the system effectively processes calcium fluoride-containing raw materials. The system has a simple and streamlined structure, avoids damage to the equipment from high-temperature, highly corrosive gases, and reduces the requirements for equipment materials.

[0064] In some embodiments of the present invention, the system further includes a second reactor for mixing and reacting fluorosilicic acid with concentrated sulfuric acid to generate gaseous silicon tetrafluoride and a second liquid phase containing hydrogen fluoride; The second liquid phase and the first filtrate are combined and then separated and extracted by the extraction device to obtain anhydrous hydrogen fluoride.

[0065] By integrating the main reaction system with the fluorosilicic acid co-production unit and / or the wet-process phosphoric acid co-production unit, the co-production units share the extraction and purification units of the main system, reducing redundant equipment investment and lowering construction and operating costs. The byproduct dilute sulfuric acid from the fluorosilicic acid co-production unit is recycled for further reaction, reducing production costs. The calcium sulfate slurry from the wet-process phosphoric acid co-production unit is mixed for descaling, solving the problem of pipeline scaling and reducing waste emissions. The system boasts high adaptability and low production costs.

[0066] In some embodiments of the present invention, the system further includes a wet-process phosphoric acid unit, wherein the calcium sulfate slurry produced by the wet-process phosphoric acid unit is used as a second calcium sulfate slurry and is transported together with the first calcium sulfate slurry.

[0067] This system integrates with other industrial lines to achieve cross-process coupling. By combining the calcium sulfate slurry produced by both processes and using the residual hydrogen fluoride in the slurry to react with silica for pipeline descaling, the system achieves centralized collection and unified treatment of by-product gypsum.

[0068] In some embodiments of the present invention, the fluorosilicic acid produced by the wet-process phosphoric acid unit is fed to the second reactor.

[0069] The waste fluorosilicic acid from the wet-process phosphoric acid unit is converted into a raw material and fed back to the second reactor as a raw material for the preparation of hydrogen fluoride. This realizes the internal circulation of materials in the system and forms a closed-loop system with deep coupling of phosphorus and fluorine resources. It significantly reduces the dependence on primary fluorite resources and improves the comprehensive utilization rate of resources. Example 1

[0070] This embodiment provides a method for preparing anhydrous hydrogen fluoride; please refer to the following reference. Figure 1 The specific steps are as follows: Preparation of raw materials containing calcium fluoride: Select a rare earth flotation tailings, whose main mineral component is fluorite (CaF2 content of about 75%), and dry and ultrafine grind it to a particle size ≥500 mesh. Prepare a 65% dilute sulfuric acid solution.

[0071] Reaction: One ton of the aforementioned tailings powder is added to a reactor equipped with a stirrer and a reflux condenser. The amount of dilute sulfuric acid added is based on the mass ratio of sulfuric acid to calcium fluoride in the raw material, with a sulfuric acid to calcium fluoride mass ratio of 3:1. The metered-up 65% dilute sulfuric acid is slowly added. Stirring is started, and the speed is controlled at 300 r / min. The reaction temperature is controlled at 125℃. The system is maintained under a slight negative pressure (-2 kPa).

[0072] Solid-liquid separation: After the reaction continues for 2 hours, the reaction slurry is transferred to a filter press for solid-liquid separation to obtain the first filtrate and the first calcium sulfate slurry. The first filtrate contains hydrogen fluoride.

[0073] Hydrogen fluoride extraction and purification: The first filtrate is fed into a distillation column for vacuum distillation, with the bottom temperature controlled at 85-95℃. Crude hydrogen fluoride gas is distilled off at the top of the column. This crude hydrogen fluoride gas is then passed sequentially through a concentrated sulfuric acid drying column and a pre-cooling purification column to remove most of the moisture and sulfuric acid mist. Finally, it enters a rectification column for purification. The distillation temperature at the top of the rectification column is approximately 19.5℃, yielding anhydrous hydrogen fluoride product with a purity ≥99.9%, which is collected in a storage tank after condensation. Example 2

[0074] The remaining steps and parameters are the same as in Example 1, except that the concentration of dilute sulfuric acid is 60%. Example 3

[0075] The remaining steps and parameters are the same as in Example 1, except that the concentration of dilute sulfuric acid is 70%. Example 4

[0076] The remaining steps and parameters are the same as in Example 1, except that the concentration of dilute sulfuric acid is 55%. Example 5

[0077] The remaining steps and parameters are the same as in Example 1, except that the concentration of dilute sulfuric acid is 75%. Example 6

[0078] The remaining steps and parameters are the same as in Example 1, except that the reaction temperature is 110°C. Example 7

[0079] The remaining steps and parameters are the same as in Example 1, except that the reaction temperature is 140°C. Example 8

[0080] The remaining steps and parameters are the same as in Example 1, except that the mass ratio of sulfuric acid to calcium fluoride is 1.5:1. Example 9

[0081] The remaining steps and parameters are the same as in Example 1, except that the mass ratio of sulfuric acid to calcium fluoride is 5:1. Example 10

[0082] In this embodiment, a method for preparing anhydrous hydrogen fluoride by combining it with the fluorosilicic acid method, based on Example 1, is provided. Please refer to the relevant documentation. Figure 2 The specific steps are as follows: Preparation of raw materials containing calcium fluoride: Select a rare earth flotation tailings, whose main mineral component is fluorite (CaF2 content of about 75%), and dry and ultrafine grind it to a particle size ≥500 mesh. Prepare a 65% dilute sulfuric acid solution.

[0083] Reaction: One ton of the aforementioned tailings powder is added to a reactor equipped with a stirrer and a reflux condenser. The amount of dilute sulfuric acid added is based on the mass ratio of sulfuric acid to calcium fluoride in the raw material, with a sulfuric acid to calcium fluoride mass ratio of 3:1. The metered-up 65% dilute sulfuric acid is slowly added. Stirring is started, and the speed is controlled at 300 r / min. The reaction temperature is controlled at 125℃. The system is maintained under a slight negative pressure (-2 kPa).

[0084] Solid-liquid separation: After the reaction continues for 2 hours, the reaction slurry is transferred to a filter press for solid-liquid separation to obtain the first filtrate and the first calcium sulfate slurry. The first filtrate contains hydrogen fluoride.

[0085] Combined with the fluorosilicic acid method: Fluorosilicic acid is placed in another fluoropolymer-lined reactor with a stirrer. 98% concentrated sulfuric acid is slowly added at a mass ratio of fluorosilicic acid to concentrated sulfuric acid of 1:1.2. The reaction temperature is controlled at 80-90℃, and the reaction is carried out at atmospheric pressure for 1 hour to obtain silicon tetrafluoride gas and a second liquid phase rich in hydrogen fluoride. The second liquid phase obtained in the above steps is combined with the first filtrate to obtain a mixed filtrate.

[0086] Hydrogen fluoride extraction and purification: The mixed filtrate is fed into a distillation column for vacuum distillation, with the bottom temperature controlled at 85-95℃. Crude hydrogen fluoride gas is distilled off from the top of the column. The crude hydrogen fluoride gas is then passed sequentially through a concentrated sulfuric acid drying column and a pre-cooling purification column to remove most of the moisture and sulfuric acid mist, and finally enters a rectification column for purification. The distillation temperature at the top of the rectification column is approximately 19.5℃, yielding anhydrous hydrogen fluoride product with a purity ≥99.9%. After condensation, it is collected in a storage tank, yielding dilute sulfuric acid as a byproduct.

[0087] The byproduct, dilute sulfuric acid, was tested and found to have a sulfuric acid concentration of approximately 45% to 55%. After the concentration was adjusted to 55% to 75%, it was reused in the reaction with calcium fluoride-containing raw materials, thus realizing the recycling of sulfuric acid. Example 11

[0088] In this embodiment, a method for preparing anhydrous hydrogen fluoride by combining it with the wet phosphoric acid method, based on Example 1, is provided. The specific steps are as follows: Similar to Example 1, the preparation of the calcium fluoride-containing raw material is as follows: Select a rare earth flotation tailings, whose main mineral component is fluorite (CaF2 content of about 75%), and dry and ultrafine grind it to a particle size ≥500 mesh. Prepare a 65% dilute sulfuric acid solution.

[0089] Reaction: One ton of the aforementioned tailings powder is added to a reactor equipped with a stirrer and a reflux condenser. The amount of dilute sulfuric acid added is based on the mass ratio of sulfuric acid to calcium fluoride in the raw material, with a sulfuric acid to calcium fluoride mass ratio of 3:1. The metered-up 65% dilute sulfuric acid is slowly added. Stirring is started, and the speed is controlled at 300 r / min. The reaction temperature is controlled at 125℃. The system is maintained under a slight negative pressure (-2 kPa).

[0090] Solid-liquid separation: After the reaction continues for 2 hours, the reaction slurry is transferred to a filter press for solid-liquid separation to obtain the first filtrate and the first calcium sulfate slurry. Both the first filtrate and the first calcium sulfate slurry contain hydrogen fluoride.

[0091] Hydrogen fluoride extraction and purification: The first filtrate is fed into a distillation column for vacuum distillation, with the bottom temperature controlled at 85-95℃. Crude hydrogen fluoride gas is distilled off at the top of the column. This crude hydrogen fluoride gas is then passed sequentially through a concentrated sulfuric acid drying column and a pre-cooling purification column to remove most of the moisture and sulfuric acid mist. Finally, it enters a rectification column for purification. The distillation temperature at the top of the rectification column is approximately 19.5℃, yielding anhydrous hydrogen fluoride product with a purity ≥99.9%, which is collected in a storage tank after condensation.

[0092] Co-production with wet-process phosphoric acid: Phosphoric acid is prepared using the traditional dihydrate wet-process phosphoric acid production method. Phosphate rock slurry and sulfuric acid are added to an extraction tank, and the reaction temperature is controlled at 75-85℃ for 4-6 hours. The reaction yields silicon tetrafluoride gas and a reaction solution. The reaction solution is then subjected to solid-liquid separation to obtain phosphoric acid product and the byproduct calcium sulfate slurry (i.e., phosphogypsum slurry).

[0093] Calcium sulfate slurry mixing and pipeline descaling: First and second calcium sulfate slurries are mixed evenly in a mixing tank at a mass ratio of 1:2. The residual hydrogen fluoride in the mixed slurry is periodically or continuously circulated through easily scaled pipelines (such as the return gas pipe of the phosphoric acid concentration section and the gypsum discharge pipe) for cleaning. The hydrogen fluoride reacts with the silica scale deposited on the inner wall of the pipeline to generate volatile silicon tetrafluoride, thereby dissolving and removing the scale. Example 12

[0094] In this embodiment, a method for preparing anhydrous hydrogen fluoride is provided, based on Example 1, by simultaneously combining the fluorosilicic acid method and the wet phosphoric acid method. Please refer to the relevant documentation. Figure 3 The method includes: (1) Reaction of calcium fluoride raw material (same as in Example 1) Preparation of raw materials containing calcium fluoride: Select a rare earth flotation tailings, whose main mineral component is fluorite (CaF2 content of about 75%), and dry and ultrafine grind it to a particle size ≥500 mesh. Prepare a 65% dilute sulfuric acid solution.

[0095] Reaction: One ton of the aforementioned tailings powder is added to a reactor equipped with a stirrer and a reflux condenser. The amount of dilute sulfuric acid added is based on the mass ratio of sulfuric acid to calcium fluoride in the raw material, with a sulfuric acid to calcium fluoride mass ratio of 3:1. The metered-up 65% dilute sulfuric acid is slowly added. Stirring is started, and the speed is controlled at 300 r / min. The reaction temperature is controlled at 125℃. The system is maintained under a slight negative pressure (-2 kPa).

[0096] After the reaction continued for 2 hours, the reaction slurry was transferred to a filter press for solid-liquid separation to obtain the first filtrate and the first calcium sulfate slurry. Both the first filtrate and the first calcium sulfate slurry contained hydrogen fluoride.

[0097] (2) Combined with the fluorosilicic acid method (same as Example 10) Fluorosilicic acid was placed in a fluorinated reactor with a stirrer. 98% concentrated sulfuric acid was slowly added at a mass ratio of fluorosilicic acid to concentrated sulfuric acid of 1:1.2. The reaction temperature was controlled at 80-90℃, and the reaction was carried out at atmospheric pressure for 1 hour to obtain silicon tetrafluoride gas and a second liquid phase rich in hydrogen fluoride.

[0098] (3) Filtrate combination and purification The first filtrate and the second liquid phase were combined to obtain a mixed filtrate. This mixed filtrate was then fed into a distillation column for vacuum distillation, with the bottom temperature controlled at 85-95℃. Crude hydrogen fluoride gas was distilled off at the top of the column. This crude hydrogen fluoride gas was then passed sequentially through a concentrated sulfuric acid drying column and a pre-cooling purification column to remove most of the moisture and sulfuric acid mist, before finally entering a rectification column for further purification. The distillation temperature at the top of the rectification column was approximately 19.5℃, yielding anhydrous hydrogen fluoride with a purity ≥99.9%, which was condensed and collected in a storage tank. Dilute sulfuric acid was also obtained as a byproduct.

[0099] (4) Reuse of byproduct dilute sulfuric acid The byproduct dilute sulfuric acid (concentration of about 45%~55%) is adjusted to a concentration of 55%~75% and then reused in the reaction with calcium fluoride-containing raw materials to achieve the recycling of sulfuric acid.

[0100] (5) Co-production with wet-process phosphoric acid (same as Example 11) Phosphoric acid is prepared using a traditional dihydrate wet phosphoric acid process. Phosphate rock slurry and sulfuric acid are added to an extraction tank, and the reaction temperature is controlled at 75-85℃ for 4-6 hours to obtain silicon tetrafluoride gas and a reaction solution. The reaction solution is then subjected to solid-liquid separation to obtain phosphoric acid product and the byproduct calcium sulfate slurry (i.e., phosphogypsum slurry).

[0101] (6) Recycling of fluorosilicic acid The fluorosilicic acid solution generated by the tail gas scrubbing system in the wet phosphoric acid process is transported to the fluorosilicic acid process in step (2) for reuse.

[0102] Specifically, the silicon tetrafluoride gas phase obtained from the reaction of phosphate rock slurry and sulfuric acid is washed in a spray tower to obtain a fluorosilicic acid solution, which is then returned to the fluorosilicic acid process. Furthermore, the phosphoric acid product obtained in the wet-process phosphoric acid step generates a gaseous product containing silicon tetrafluoride gas during concentration. This gaseous product is combined with the silicon tetrafluoride gas phase obtained from the reaction of phosphate rock slurry and sulfuric acid, and then washed in a spray tower.

[0103] (7) Calcium sulfate slurry mixing and pipeline descaling The first calcium sulfate slurry obtained in step (1) and the second calcium sulfate slurry obtained in step (5) are mixed evenly in a mixing tank at a mass ratio of 1:2. The residual hydrogen fluoride in the mixed slurry is periodically or continuously circulated through easily scaled pipelines (such as the return gas pipe of the phosphoric acid concentration section and the gypsum discharge pipe) for cleaning. The hydrogen fluoride reacts with the silica scale deposited on the inner wall of the pipeline to generate volatile silicon tetrafluoride, thereby dissolving and removing the scale.

[0104] The remaining steps and parameters of Comparative Example 1 are the same as those of Example 1, except that the reaction temperature is 100°C.

[0105] The remaining steps and parameters of Comparative Example 2 are the same as those of Example 1, except that the reaction temperature is 150°C.

[0106] The remaining steps and parameters of Comparative Example 3 are the same as those of Example 1, except that the concentration of dilute sulfuric acid is 50%.

[0107] The remaining steps and parameters of Comparative Example 4 are the same as those of Example 1, except that the concentration of dilute sulfuric acid is 80%.

[0108] The remaining steps and parameters of Comparative Example 5 are the same as those of Example 1, except that the concentration of dilute sulfuric acid is 50% and the reaction temperature is 100°C.

[0109] The remaining steps and parameters of Comparative Example 6 are the same as those of Example 1, except that the concentration of dilute sulfuric acid is 50% and the reaction temperature is 150°C.

[0110] The remaining steps and parameters of Comparative Example 7 are the same as those of Example 1, except that the concentration of dilute sulfuric acid is 80% and the reaction temperature is 100°C.

[0111] The remaining steps and parameters of Comparative Example 8 are the same as those of Example 1, except that the concentration of dilute sulfuric acid is 80% and the reaction temperature is 150°C.

[0112] The remaining steps and parameters of Comparative Example 9 are the same as those of Example 1, except that the mass ratio of sulfuric acid to calcium fluoride is 1.2:1.

[0113] The remaining steps and parameters of Comparative Example 10 are the same as those of Example 1, except that the mass ratio of sulfuric acid to calcium fluoride is 6:1.

[0114] Experimental Example 1: Effect of dilute sulfuric acid concentration and reaction temperature on the liquid phase partition rate of hydrogen fluoride 1.1 Experimental Setup Examples 1-7 are identical in experimental setup, raw materials, and operating procedures, except for differences in the concentration of dilute sulfuric acid and temperature. Similarly, Comparative Examples 1-8 are identical in experimental setup, raw materials, and operating procedures to Example 1, except for differences in the concentration of dilute sulfuric acid and temperature.

[0115] 1.2 Measurement Indicators and Methods 1.2.1 Yield Calculation Sample collection: In the method used in this application, the raw material containing calcium fluoride reacts with dilute sulfuric acid to obtain a reaction solution and a small amount of reaction tail gas. After condensation, the reaction tail gas still contains a small amount of hydrogen fluoride, which is passed into a two-stage alkaline scrubbing tower (containing 10% NaOH solution) for absorption. The reaction solution is separated into a first filtrate and a first calcium sulfate slurry by solid-liquid separation.

[0116] The first calcium sulfate slurry (filter cake) was washed three times with deionized water (500 mL each time), and the washing liquids were combined to obtain the washing solution of the first calcium sulfate slurry. Assuming a washing efficiency of 100%, the mass of hydrogen fluoride in the washing solution is equal to the mass of hydrogen fluoride entrained / adsorbed in the slurry.

[0117] Determination of the total mass of hydrogen fluoride actually generated: Combine all the above-mentioned fluoride-containing solutions (tail gas absorption liquid, first filtrate, and washing liquid of the first calcium sulfate slurry), and determine the total fluoride mass using the fluoride ion selective electrode method. This mass is recorded as the total mass of hydrogen fluoride actually generated.

[0118] Calculation of theoretical total hydrogen fluoride mass: Based on the mass of calcium fluoride added, the theoretical total hydrogen fluoride mass = mass of CaF2 added × 0.512 (where 0.512 is the mass coefficient for complete conversion of CaF2 into hydrogen fluoride, i.e. 2 × 20.01 / 78.07).

[0119] Yield calculation: Yield = (Actual total mass of hydrogen fluoride produced / Theoretical total mass of hydrogen fluoride) × 100%.

[0120] 1.2.2 Determination of the liquid-phase partition ratio of hydrogen fluoride The generated hydrogen fluoride is divided into three parts: hydrogen fluoride in the gas phase, hydrogen fluoride in the first filtrate, and hydrogen fluoride in the first calcium sulfate slurry. The liquid phase distribution rate of hydrogen fluoride is defined as the proportion of the hydrogen fluoride in the first filtrate plus the hydrogen fluoride in the first calcium sulfate slurry to the total amount of hydrogen fluoride actually generated.

[0121] The mass of hydrogen fluoride in the liquid phase = the mass of hydrogen fluoride in the first filtrate + the mass of hydrogen fluoride in the first calcium sulfate slurry washing solution (the first calcium sulfate slurry is washed 3 times with deionized water, 500 mL each time, and the washing solutions are combined; assuming the washing efficiency is 100%, the mass of hydrogen fluoride in the washing solution is equal to the mass of hydrogen fluoride entrained / adsorbed in the slurry).

[0122] The actual total mass of hydrogen fluoride generated is the same as the actual total fluorine mass in 1.2.1.

[0123] Hydrogen fluoride liquid phase distribution rate = (mass of liquid hydrogen fluoride / total mass of actual generated hydrogen fluoride) × 100%.

[0124] 1.3 Results and Analysis The yields and liquid phase distributions of hydrogen fluoride for each group are shown in Table 1.

[0125] Table 1. Yields and liquid-phase partition ratios of hydrogen fluoride at different dilute sulfuric acid concentrations and reaction temperatures.

[0126] As shown in Table 1, in Examples 1 to 7, which are within the reaction temperature range of 110 to 140°C and the dilute sulfuric acid concentration range of 55% to 75% as defined in this invention, the yield can reach 88% to 98% and the liquid phase partition rate of hydrogen fluoride can reach 95% to 99%, achieving both high yield and high liquid phase partition rate.

[0127] While Comparative Examples 1, 5, and 7 achieved high liquid phase partition rates due to temperatures below 110℃, and Comparative Example 3 achieved high yields due to concentrations below 55%, their yields decreased significantly, ranging from only 30% to 65%.

[0128] Comparative Examples 2, 4, 6, and 8, due to temperatures above 140℃ or concentrations above 75%, achieved higher yields, but the liquid phase partition rate of hydrogen fluoride decreased significantly, ranging from only 40% to 78%, resulting in severe losses due to hydrogen fluoride volatilization.

[0129] This indicates that only by controlling the temperature between 110 and 140°C and the sulfuric acid concentration between 55% and 75% can a high reaction rate (i.e., high yield) and a high hydrogen fluoride liquid-phase partition rate (high hydrogen fluoride liquid-phase retention) be simultaneously achieved. Optimal results can only be achieved when both the dilute sulfuric acid concentration and the reaction temperature meet the ranges defined in this invention; neither is dispensable. Any deviation from a single parameter or both parameters will lead to a significant decrease in the partition rate.

[0130] Experimental Example 2: Effect of the mass ratio of sulfuric acid to calcium fluoride In this experimental example, the concentration of dilute sulfuric acid was fixed at 65%, the reaction temperature was 125°C, and the mass ratio of sulfuric acid (calculated as pure H2SO4) to calcium fluoride in the raw materials (hereinafter referred to as acid-mineral ratio) was changed. The other conditions were the same as in Example 1. Specifically, Examples 8 (acid-mineral ratio 1.5:1), 9 (acid-mineral ratio 5:1), Comparative Example 9 (acid-mineral ratio 1.2:1), and Comparative Example 10 (acid-mineral ratio 6:1) were provided.

[0131] Following the same determination method as in Experiment Example 1, the yield and liquid phase partition ratio of hydrogen fluoride after each reaction were determined, and the results are shown in Table 2.

[0132] Table 2 Yields and liquid phase partition rates of hydrogen fluoride at different acid-to-ore ratios Example 1 3:1 96 97 Example 8 1.5:1 85 95 Example 9 5:1 98 96 Comparative Example 9 1.2:1 50 81 Comparative Example 10 6:1 99 68 As shown in Table 2, when the mass ratio of sulfuric acid to calcium fluoride (acid-to-ore ratio) is within the range of 1.5-5:1 as defined in this invention, such as in Examples 1, 8, and 9, the yield is ≥85% and the liquid phase partition rate of hydrogen fluoride is ≥95%.

[0133] When the mass ratio of sulfuric acid to calcium fluoride (acid-to-ore ratio) is less than 1.5:1, such as 1.2:1 in Comparative Example 9, the sulfuric acid is severely insufficient, the yield is only 50%, and the system water is insufficient due to the low acid content, the distribution rate also drops to 81%.

[0134] When the mass ratio of sulfuric acid to calcium fluoride (acid-to-ore ratio) is higher than 5:1, such as 6:1 in Comparative Example 10, the yield reaches 99%, but the excess sulfuric acid increases the viscosity of the system and the release of hydrogen fluoride, reducing the distribution rate to 68%.

[0135] Therefore, the preferred sulfuric acid to calcium fluoride mass ratio of 1.5:1 to 5:1 in this invention has advantages. The technical solution of this invention achieves both high liquid-phase distribution rate and high yield of hydrogen fluoride by controlling the mass ratio of sulfuric acid to calcium fluoride within a specific range. However, comparative examples 9 and 10, which do not use the sulfuric acid to calcium fluoride mass ratio specified in this invention, do not achieve the same effect as the embodiments and cannot achieve the same high liquid-phase distribution rate and high yield of hydrogen fluoride.

[0136] Experimental Example 3: Determination and Statistical Analysis of the Partition Coefficient of Hydrogen Fluoride Filtrate In this experimental example, the mass of hydrogen fluoride in the first filtrate and the first calcium sulfate slurry washing liquid was determined by the fluoride ion selective electrode method, and the hydrogen fluoride filtrate partition coefficients of Examples 1 to 12 were calculated respectively.

[0137] The hydrogen fluoride filtrate distribution coefficient is defined as the proportion of hydrogen fluoride in the filtrate to the total liquid-phase hydrogen fluoride (hydrogen fluoride in the first filtrate plus hydrogen fluoride in the first calcium sulfate slurry), i.e.: Hydrogen fluoride filtrate distribution coefficient = mass of hydrogen fluoride in the filtrate ÷ (mass of hydrogen fluoride in the filtrate + mass of hydrogen fluoride in the slurry) × 100%. Data for each group are shown in Table 3.

[0138] Table 3 Example 1 92 Example 2 95 Example 3 91 Example 4 90 Example 5 90 Example 6 89 Example 7 85 Example 8 86 Example 9 95 Example 10 93 Example 11: Combined with wet phosphoric acid process 75 Example 12: Simultaneous use with fluorosilicic acid method and wet phosphoric acid method 71 It should be noted that the present invention can control the hydrogen fluoride filtrate distribution coefficient through solid-liquid separation efficiency. The filtrate distribution coefficients in Examples 1 to 12 and the range of filtrate distribution coefficients in the present invention are only preferred options, but not mandatory. They are optimizations based on different examples to balance descaling effect, production capacity and other factors.

[0139] Firstly, for Examples 1-9 of this invention, since there is no coupling with other processes and fewer downstream processes, there are fewer pipelines. Although Example 10 is used in conjunction with the fluorosilicic acid process, it is not coupled with the wet phosphoric acid process, and there is no need to retain excessive hydrogen fluoride in the slurry. Therefore, the hydrogen fluoride filtrate distribution coefficient in Examples 1-10 is controlled at a relatively high level, between 80% and 95%, allowing more liquid-phase hydrogen fluoride to enter the first filtrate, resulting in a higher concentration of hydrogen fluoride in the first filtrate and thus improving the production capacity and efficiency of hydrogen fluoride. A smaller portion enters the first calcium sulfate slurry, which already contains a certain amount of hydrogen fluoride. Its delivery to the downstream pipelines achieves the same pipeline descaling effect as Examples 1-9. This effectively balances yield and pipeline descaling effect.

[0140] Furthermore, for Embodiments 11 and 12 of this invention, please refer to... Figure 3 This is a coupled process used in conjunction with the wet-process phosphoric acid process. Therefore, the first and second calcium sulfate slurries are combined and transported to the downstream stage. In this case, an excessively high filtrate distribution coefficient is not pursued; instead, a suitable amount of hydrogen fluoride is intentionally retained in the calcium sulfate slurry, controlling the hydrogen fluoride filtrate distribution coefficient between 65% and 80%. Approximately 65% ​​to 80% of the liquid-phase hydrogen fluoride enters the filtrate, while the remaining approximately 20% to 35% is retained in the calcium sulfate slurry. After the first calcium sulfate slurry and the second calcium sulfate slurry produced in the wet-process phosphoric acid process are combined, the residual hydrogen fluoride in the slurry reacts with silica, effectively removing silicate scale in the wet-process phosphoric acid production system. This effectively solves the scaling and clogging problems present in the original wet-process phosphoric acid process.

[0141] In summary, the filtrate distribution coefficient ranges in Examples 1-12 are preferred options, but not mandatory. They are optimizations based on various factors such as different descaling effects and production capacity requirements. This invention, while ensuring a high hydrogen fluoride liquid-phase distribution rate, achieves a balance between fluoride resource recovery and the functional utilization of by-product gypsum by appropriately controlling the filtrate distribution coefficient. The hydrogen fluoride retained in the slurry is not lost, but rather recycled as an effective component for pipeline descaling, significantly improving the economic and environmental benefits of the process.

[0142] Experiment Example 4: Recording and Statistics of the Impact of Co-production Example 10 was used in conjunction with the fluorosilicic acid process. Example 11 was used in conjunction with the wet phosphoric acid process. Example 12 was used in conjunction with both the fluorosilicic acid process and the wet phosphoric acid process. Based on engineering accounting under the same production scale, the energy consumption, process equipment cost input, etc. of Examples 1, 10, 11, and 12 were statistically compared, and the results are as follows: In Example 10 of this invention, the purification energy consumption is reduced by 30% compared to Example 1 by combining it with the fluorosilicic acid method.

[0143] The present invention, in combination with the wet phosphoric acid process, can effectively reduce the number of process steps and reduce equipment and labor input by 25% compared with Example 1.

[0144] In addition, Embodiment 12 of the present invention is used in combination with the fluorosilicic acid method and the wet phosphoric acid method, resulting in a decrease in overall energy saving (purification energy consumption) and equipment investment.

[0145] In summary, the method of this invention can be integrated with other industrial production lines, achieving process coupling and by-product resource utilization. It effectively reduces purification energy consumption, streamlines process steps, and minimizes equipment and labor input, thus achieving energy conservation. It possesses superior economic benefits and industrial application value.

[0146] The present invention provides a detailed description of a method and system for preparing anhydrous hydrogen fluoride. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing anhydrous hydrogen fluoride, characterized in that, Includes the following steps: The raw material containing calcium fluoride is mixed with dilute sulfuric acid with a mass concentration of 55% to 75% and reacted. The reaction temperature is controlled at 110-140℃. After the reaction, the material is separated into solid and liquid to obtain a first filtrate and a first calcium sulfate slurry. The first filtrate contains hydrogen fluoride. Anhydrous hydrogen fluoride is separated and extracted from the first filtrate.

2. The method for preparing anhydrous hydrogen fluoride according to claim 1, characterized in that, The raw material contains 70% to 85% calcium fluoride by mass.

3. The method for preparing anhydrous hydrogen fluoride according to claim 1, characterized in that, The particle size of the raw material is greater than or equal to 500 mesh.

4. The method for preparing anhydrous hydrogen fluoride according to claim 1, characterized in that, The gauge pressure of the reaction is -20 kPa to 1 kPa.

5. The method for preparing anhydrous hydrogen fluoride according to claim 1, characterized in that, The amount of dilute sulfuric acid added is calculated based on the mass ratio of the sulfuric acid contained therein to the calcium fluoride in the raw material, and the mass ratio of sulfuric acid to calcium fluoride is 1.5-5:

1.

6. The method for preparing anhydrous hydrogen fluoride according to claim 1, characterized in that, It also includes reacting fluorosilicic acid with concentrated sulfuric acid to obtain a second liquid phase containing hydrogen fluoride, combining the second liquid phase with the first filtrate to obtain a mixed filtrate, and separating and extracting anhydrous hydrogen fluoride and dilute sulfuric acid as a byproduct from the mixed filtrate.

7. The method for preparing anhydrous hydrogen fluoride according to claim 6, characterized in that, The byproduct, dilute sulfuric acid, is recycled for reaction with the calcium fluoride-containing raw material.

8. The method for preparing anhydrous hydrogen fluoride according to claim 1, characterized in that, It also includes the fact that the first calcium sulfate slurry contains hydrogen fluoride, and the first calcium sulfate slurry is combined with the second calcium sulfate slurry produced in the wet-process phosphoric acid section for subsequent processing.

9. A system for preparing anhydrous hydrogen fluoride using the method according to any one of claims 1 to 8, characterized in that, include: The first reactor is used to mix and react calcium fluoride raw materials with dilute sulfuric acid to obtain the reaction product; A solid-liquid separation device is used to process the reaction material to obtain a first filtrate and a first calcium sulfate slurry. An extraction device is used to separate and extract anhydrous hydrogen fluoride from the first filtrate.

10. The system for preparing anhydrous hydrogen fluoride according to claim 9, characterized in that, The system also includes a second reactor for mixing and reacting fluorosilicic acid with concentrated sulfuric acid to generate gaseous silicon tetrafluoride and a second liquid phase containing hydrogen fluoride. The second liquid phase is combined with the first filtrate and then separated and extracted by the extraction device to obtain anhydrous hydrogen fluoride and dilute sulfuric acid as a byproduct. The dilute sulfuric acid byproduct is returned to the first reactor.

11. The system for preparing anhydrous hydrogen fluoride according to claim 9, characterized in that, The system also includes a wet-process phosphoric acid unit, wherein the calcium sulfate slurry produced by the wet-process phosphoric acid unit is used as a second calcium sulfate slurry and is transported together with the first calcium sulfate slurry.

12. The system for preparing anhydrous hydrogen fluoride according to claim 11, characterized in that, The fluorosilicic acid produced by the wet-process phosphoric acid unit is transported to the second reactor.

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