A method and device for producing anhydrous hydrogen fluoride and co-producing ammonium sulfate using a solution containing ammonium fluoride

Abstract

The present application relates to the field of fluorine chemical technology, especially to a method and device for producing anhydrous hydrogen fluoride and co-producing ammonium sulfate by using ammonium fluoride solution, wherein ammonia gas-water vapor mixed gas produced by concentrating ammonium fluoride solution in a flash evaporation concentration tower is mixed with high-temperature acidolysis residual liquid produced by acidolysis of ammonium bifluoride with sulfuric acid, so as to fully utilize the heat energy between materials, ensure that the ammonium sulfate component in the acidolysis residual liquid is in a high-temperature flow state, and guarantee the concentration preparation of ammonium sulfate crystals; meanwhile, the ammonia in the ammonia gas-water vapor mixed gas is absorbed by hydrogen sulfate for utilization, the residual amount of hydrogen sulfate in the ammonium sulfate is reduced, the quality of the ammonium sulfate is improved, and the temperature of the waste liquid after the ammonium sulfate is crystallized and filtered is reduced, thereby reducing the waste liquid treatment cost.

Description

Technical Field

[0001] This invention relates to the field of fluorochemical technology, and in particular to a method and apparatus for producing anhydrous hydrogen fluoride and co-producing ammonium sulfate using an ammonium fluoride-containing solution. Background Technology

[0002] Fluorite-sulfuric acid leaching is the main process for producing anhydrous hydrogen fluoride. It involves reacting a metered mixture of fluorite concentrate and sulfuric acid to produce hydrogen fluoride gas. The gas is then passed through a crude distillation column to remove acid and dust, followed by condensation and recovery, or further processed through a degassing and rectification column. However, with the continuous depletion of fluorite concentrate, the complex process, high cost, and high energy consumption of the fluorite-sulfuric acid leaching method have become apparent, leading to a shift in research direction for anhydrous hydrogen fluoride production. For example, the use of fluorosilicic acid as a raw material to produce anhydrous hydrogen fluoride has spurred the rapid development of fluorosilicic acid-based anhydrous hydrogen fluoride production technology.

[0003] Currently, the production of anhydrous hydrogen fluoride using fluorosilicic acid mainly focuses on processes such as the artificial calcium hydrogen fluoride method, the sodium hydrofluoride thermal decomposition method, the fluorosilicic acid ammonification sulfuric acid decomposition method, and the fluorosilicic acid sulfuric acid decomposition method. Among these, the fluorosilicic acid ammonification sulfuric acid decomposition method has been studied the most and is gradually becoming the main process flow for the production of anhydrous hydrogen fluoride.

[0004] For example, the technical content disclosed in patent number 202011484304.1, the decomposition method of fluorosilicic acid ammoniated with sulfuric acid mainly involves the following reactions:

[0005] 2H2O(l)+H2SiF6+6NH3(g)=6NH4F(l)+SiO2↓ (1)

[0006] 2NH4F+H2O(l)=NH3(g)+ NH4HF2(l)+H2O(g) (2)

[0007] NH4HF2(l)= NH4HF2(s) (3)

[0008] NH4HF2(s)+H2SO4=NH4HSO4+2HF(g) (4)

[0009] NH4HF2(s)+NH4HSO4=(NH4)2SO4+2HF(g) (5)

[0010] It is evident that in this production process, when liquid ammonium bifluoride is concentrated to form solid ammonium bifluoride, NH3(g) and H2O(g) escape, forming a mixed gas containing ammonia, fluorine, and water vapor, and the exhaust temperature of this gas is typically ≤80℃. Simultaneously, in this process, when ammonium bifluoride is acid-hydrolyzed with sulfuric acid to prepare hydrogen fluoride gas, improper control of the raw materials often leads to the formation of impurity ions such as bisulfate, fluoride, and sulfate in the reaction mixture, resulting in low purity and poor quality of the obtained ammonium bifluoride product. Furthermore, the waste liquid obtained from the solid separation of ammonium sulfate contains a large amount of bisulfate ions, and the temperature in the waste liquid typically reaches above 140℃, making the treatment of the waste liquid after sulfuric acid acid hydrolysis difficult and energy-intensive.

[0011] Therefore, how to reduce energy consumption, reduce the escape rate of ammonia and fluorine-containing components, and ensure the purity of ammonium sulfate and the quality of anhydrous hydrogen fluoride have become urgent technical problems to be solved in the preparation of anhydrous hydrogen fluoride and ammonium sulfate products by the fluorosilicic acid-ammoniation-sulfuric acid decomposition method.

[0012] Although existing technologies have studied the recovery and utilization of mixed gases containing ammonia, fluorine, and water vapor generated during the concentration of liquid ammonium fluoride into solid ammonium fluoride, for example, returning the mixed gas to fluorosilicic acid absorption to achieve fluorosilicic acid pre-ammoniation, this method results in a high temperature of the mixed gas itself, causing the solution of the entire reaction system to be preheated, which increases the gas escape rate when concentrating to form solid ammonium fluoride, and the fluorine component in the mixed gas is difficult to be effectively absorbed, causing the vaporized fluorine component to escape. Another example is to send it to the phosphate fertilizer system for absorption or to other ammonia-based recovery processes after condensation to achieve ammonia recovery, but the fluorine recovery effect is not good.

[0013] In view of this, this researcher addresses the aforementioned technical problems in the fluorosilicic acid-ammoniation-sulfuric acid decomposition process by combining the fluorosilicic acid-ammoniation-sulfuric acid decomposition process for the production of anhydrous hydrogen fluoride with the ammonium sulfate production process. This approach achieves full utilization of thermal energy and waste gas recovery, thereby reducing the overall energy consumption of the fluorosilicic acid-ammoniation-sulfuric acid decomposition process and providing a new process for the co-production of anhydrous hydrogen fluoride and ammonium sulfate. Summary of the Invention

[0014] In order to solve the above-mentioned technical problems in the prior art, the present invention provides a method and apparatus for producing anhydrous hydrogen fluoride and co-producing ammonium sulfate using ammonium fluoride solution.

[0015] Specifically, this is achieved through the following technical solutions:

[0016] One of the objectives of this invention is to provide a method for producing anhydrous hydrogen fluoride and co-producing ammonium sulfate using an ammonium fluoride-containing solution, comprising the following steps:

[0017] S1: The ammonium fluoride solution is fed into the flash concentration tower for flash concentration to obtain a mixed gas of NH3-H2O and liquid and solid of NH4F-NH4HF2; solid-liquid separation is performed to obtain solid of NH4F-NH4HF2, and the filtrate is recycled back into the flash concentration tower.

[0018] 3NH4F+H2O(l)=NH3(g)+NH4F-NH4HF2(l)+H2O(g)

[0019] NH4F-NH4HF2(l)=NH4F-NH4HF2(s)

[0020] At this time, ammonia and water vapor escape from the flash concentration tower. In order to promote the low temperature of the mixed gas produced when NH4F is converted into NH4HF2 and to ensure that NH4HF2 is easily formed, the pressure during flash concentration in the flash concentration tower is 70-90 kPa and the temperature is 50-70℃.

[0021] S2: Mix solid NH4F-NH4HF2 with sulfuric acid and acid hydrolyze to obtain crude HF and acid hydrolysis residue;

[0022] NH4HF2(s)+H2SO4=NH4HSO4+2HF(g)

[0023] An acidolysis residue containing ammonium bisulfate was obtained. In order to make the acidolysis more thorough, ensure the conversion rate of NH4HF2 solid and sulfuric acid during acidolysis, and improve the HF yield, the acidolysis temperature was 140-179℃, and the amount of sulfuric acid added was 110-137.5% of the theoretical amount. This resulted in a high temperature of the acidolysis residue, and the excess sulfuric acid in the acidolysis residue easily formed ammonium bisulfate.

[0024] S3: Mix the NH3-H2O mixed gas and the acid hydrolysis residue, concentrate, filter, and obtain ammonium sulfate solid and filtrate. The filtrate is recycled and mixed with the NH3-H2O mixed gas.

[0025] NH3(g)+H2O(g)+NH4HSO4=(NH4)2SO4+H2O(l)

[0026] After concentration, ammonium sulfate crystals can be obtained directly. After filtration, the filtrate and ammonium sulfate crystals are obtained. At this time, the concentration is carried out in a flash concentration tower at a concentration pressure of 70-90 kPa, which helps to ensure the quality of ammonium sulfate.

[0027] S4: Crude HF is purified by acid washing with concentrated sulfuric acid, condensed, and distilled to obtain anhydrous hydrogen fluoride. The purified liquid is then mixed with solid NH4F-NH4HF2.

[0028] The ammonia-water vapor mixture generated from the concentration of ammonium fluoride solution in the flash concentration tower is mixed with the high-temperature acid hydrolysis residue produced from the acid hydrolysis of ammonium fluoride to produce hydrogen fluoride. This process ensures full utilization of the heat energy between the materials, guarantees that the ammonium sulfate component in the acid hydrolysis residue is in a high-temperature flowing state, and ensures the concentration and preparation of ammonium sulfate crystals. At the same time, the ammonia in the ammonia-water vapor mixture is absorbed and utilized by the bisulfate ions, reducing the residual amount of bisulfate ions in the ammonium sulfate, improving the quality of ammonium sulfate, and lowering the temperature of the waste liquid after ammonium sulfate crystallization filtration, thus reducing waste liquid treatment costs.

[0029] Preferably, the flash concentration pressure is 80 kPa and the temperature is 60°C.

[0030] Preferably, in step S2, the acidolysis temperature is 160°C, and the amount of sulfuric acid added is 120% of the theoretical amount.

[0031] To ensure the quality of the ammonium fluoride solution entering the flash concentration tower, preferably, the ammonium fluoride solution is obtained by first-stage ammoniation of fluorosilicic acid with ammonia gas in a primary reaction tank to adjust the pH to 4-5, then overflowing into a secondary reaction tank where ammonia gas is introduced for secondary ammoniation to adjust the pH to 6.5-7.5, and finally overflowing into a tertiary reaction tank where ammonia gas is introduced for tertiary ammoniation to adjust the pH to 8.0-9.0. The material in the tertiary reaction tank is then filtered. More preferably, the ammonium fluoride solution is obtained by first-stage ammoniation of fluorosilicic acid with ammonia gas in a primary reaction tank to adjust the pH to 4.3-4.7, then overflowing into a secondary reaction tank where ammonia gas is introduced for secondary ammoniation to adjust the pH to 6.7-7.0, and finally overflowing into a tertiary reaction tank where ammonia gas is introduced for tertiary ammoniation to adjust the pH to 8.4-8.8. The material in the tertiary reaction tank is then filtered.

[0032] The second objective of this invention is to provide a device for producing anhydrous hydrogen fluoride and co-producing ammonium sulfate using an ammonium fluoride solution, comprising a flash concentration tower, wherein the flash concentration tower is provided with an NH4F solution inlet, a mixed gas outlet, a liquid circulation port, and a slurry discharge port; the bottom of the slurry discharge port is connected to an NH4F dehydration component via a pipe, the NH4F dehydration component is provided with a liquid discharge port and a slag discharge port, the liquid discharge port being connected to the liquid circulation port via a liquid circulation pipe; the slag discharge port is connected to an acid hydrolysis tank, and the slag discharge port is capable of sending the solid NH4F-NH4HF2 generated in the NH4F dehydration component into the acid hydrolysis tank; the acid hydrolysis tank is provided with an HF gas outlet, an acid inlet, and an acid hydrolysis residue outlet. The HF gas outlet is connected to an acid washing and purification tank, and the HF gas outlet can send the generated crude HF gas into the acid washing and purification tank; the acid washing and purification tank is provided with an acid liquid outlet, a concentrated sulfuric acid inlet, and an exhaust port. The acid liquid outlet is connected to the acid liquid inlet, the concentrated sulfuric acid inlet is connected to a concentrated sulfuric acid tank, and the exhaust port is connected to a condenser distillation tower; the acid hydrolysis residue outlet is connected to a reaction tank via a pipeline, the mixed gas outlet is connected to the reaction tank via a pipeline, and the reaction tank is provided with a wastewater outlet and an ammonium sulfate solid outlet. The ammonium sulfate solid outlet is connected to an ammonium sulfate storage tank, the wastewater outlet is connected to a wastewater treatment assembly, and the condenser distillation tower is connected to an anhydrous HF tank.

[0033] By introducing a flash concentration tower, the NH4F solution is concentrated at low temperature to form a concentrated liquid and mixed gas containing NH4HF2, with the temperature of the mixed gas below 70℃. Simultaneously, the acid hydrolysis residue produced by the acid hydrolysis tank is sent to the reaction tank for reaction. Combined with the connection of the mixed gas into the reaction tank, the low-temperature mixed gas enters the acid hydrolysis residue, converting the hydrogen sulfate ions in the acid hydrolysis residue into sulfate ions, improving the quality of the ammonium sulfate product. At the same time, it reduces the temperature of the waste liquid discharged from the reaction tank after the reaction, reduces the difficulty of waste liquid treatment, and reduces costs.

[0034] To enable the direct production of ammonium sulfate and anhydrous HF products from NH4F solution using the fluorosilicic acid method, preferably, the NH4F solution inlet is connected to a silica preparation assembly. This silica preparation assembly comprises equipment capable of ammonolyzing fluorosilicic acid to prepare NH4F solution and SiO2 precipitate, followed by filtration and washing to obtain the SiO2 product.

[0035] Specifically, the silica preparation assembly for precipitated silica includes an ammonolysis tank with an ammonia inlet and a fluorosilicic acid inlet. The ammonia inlet is connected to an ammonia storage tank via a pipeline, and the fluorosilicic acid inlet is connected to a fluorosilicic acid tank via a pipeline. The ammonolysis tank also has an outlet, which is equipped with a filtration and washing assembly. The filtration and washing assembly is connected to a drying chamber and an NH4F liquid outlet. The drying chamber is connected to a silica tank, and the NH4F liquid outlet is connected to the NH4F solution inlet via a pipeline. This allows fluorosilicic acid and ammonia to be ammonolycated in the ammonolysis tank to form an NH4F solution and a SiO2 precipitate. After treatment by the filtration and washing assembly, the SiO2 precipitate is separated to obtain the NH4F solution. The SiO2 precipitate is dried in the drying chamber to prepare the silica product. The NH4F solution is sent to a flash concentration tower for flash concentration to form NH4HF2 and a mixed gas.

[0036] The ammonia hydrolysis tank 3 described in this invention is essentially an ammonium fluoride solution preparation assembly, comprising a primary reaction tank, a secondary reaction tank, and a tertiary reaction tank. These three tanks are interconnected via an overflow connection. Each of the three tanks has a slurry discharge pipe at its bottom, equipped with a valve. A fluorosilicic acid pipe is located on the primary reaction tank and connected to a fluorosilicic acid tank. Ammonia gas pipe extending to the bottom of each of the three tanks is located at the top and connected to an ammonia gas tank. This enables multi-stage continuous production of ammonium fluoride solution.

[0037] The purpose of the slurry discharge pipe described in this invention is to discharge the sedimented slurry generated during the preparation of ammonium fluoride solution. Therefore, any operational scheme that can achieve this purpose and discharge the sedimented slurry settled in the primary, secondary, and tertiary reaction tanks is acceptable, not limited to the slurry discharge pipe described in this invention. Furthermore, the structure of the slurry discharge pipe in this invention should be able to discharge the sedimented slurry. The purpose of installing a valve on the slurry discharge pipe is to achieve intermittent discharge of the sedimented slurry. Therefore, as long as the sedimented slurry on the slurry discharge pipe can be controlled to flow out intermittently, thereby achieving continuous overflow production of ammonium fluoride solution, it is acceptable.

[0038] Compared with the prior art, the technical effects of this invention are reflected in:

[0039] The invention features a simple process flow, convenient operation, minimal modification to existing process equipment, few additional equipment requirements, low equipment cost, significant energy-saving and consumption-reducing effects, and is easy to promote and implement in the industrial sector.

[0040] This invention utilizes the NH3-H2O mixed gas discharged from the flash concentration tower to act on the acid hydrolysis residue, achieving heat energy exchange and purification of bisulfate ions. This improves the quality of ammonium sulfate products while reducing the amount of cooling water required for the cooling treatment of waste liquid after filtration of ammonium sulfate crystals, thus reducing treatment costs. It truly realizes the dual recovery and utilization of materials and energy. Attached Figure Description

[0041] Figure 1 A process flow diagram is provided for this invention.

[0042] Figure 2 A process flow diagram for another embodiment of the present invention is provided.

[0043] Figure 3 A process equipment connection diagram is provided for this invention.

[0044] Figure 4 Diagram showing the equipment connections for the overflow process of preparing ammonium fluoride solution by ammoniation of fluorosilicic acid.

[0045] 1-Fluorosilicic acid tank; 2-Ammonia storage tank; 3-Ammonium hydrolysis tank; 4-Filter and washing assembly; 5-Flash concentration tower; 6-Drying oven; 7-Silica tank; 8-NH4F dehydration assembly; 9-Reaction tank; 10-Ammonium sulfate storage tank; 11-Acid hydrolysis tank; 12-Wastewater treatment assembly; 13-Acid washing and purification tank; 14-Concentrated sulfuric acid tank; 15-Anhydrous HF tank; 16-Condensation distillation tower.

[0046] 3.1 - Primary reaction tank; 3.2 - Secondary reaction tank; 3.3 - Tertiary reaction tank; 3.4 - Ammonia gas pipe; 3.5 - Fluorosilicic acid pipe. Detailed Implementation

[0047] The technical solution of the present invention will be further defined below with reference to the accompanying drawings and specific embodiments, but the scope of protection is not limited to the description.

[0048] like Figure 1 As shown, in some embodiments, a method for producing anhydrous hydrogen fluoride and co-producing ammonium sulfate using an ammonium fluoride-containing solution includes the following steps:

[0049] S1: The ammonium fluoride solution is fed into the flash concentration tower for flash concentration to obtain a mixed gas of NH3-H2O and liquid and solid of NH4F-NH4HF2; solid-liquid separation is performed to obtain solid of NH4F-NH4HF2, and the filtrate is recycled back into the flash concentration tower.

[0050] S2: Mix solid NH4F-NH4HF2 with sulfuric acid and acid hydrolyze to obtain crude HF and acid hydrolysis residue;

[0051] S3: Mix the NH3-H2O mixed gas and the acid hydrolysis residue, concentrate, filter, and obtain ammonium sulfate solid and filtrate. The filtrate is recycled and mixed with the NH3-H2O mixed gas.

[0052] S4: Crude HF is purified by acid washing with concentrated sulfuric acid, condensed, and distilled to obtain anhydrous hydrogen fluoride. The purified liquid is then mixed with solid NH4F-NH4HF2.

[0053] This process involves mixing and interacting the mixed gas formed by flash concentration in a flash concentration tower with the acid hydrolysis residue produced by acid hydrolysis. This allows the ammonia and water vapor emitted during the conversion of ammonium fluoride to ammonium bifluoride to come into contact with the acid hydrolysis residue. This not only lowers the overall temperature of the acid hydrolysis residue but also causes the ammonia to react with bisulfate ions to generate sulfate ions. This significantly improves the purity of the prepared ammonium sulfate product. At the same time, it also reduces the temperature drop during the crystallization and precipitation of ammonium sulfate, resulting in a lower temperature of the discharged waste liquid, reduced energy consumption, and lower wastewater treatment costs.

[0054] In some embodiments, the flash concentration pressure is 70-90 kPa, for example: 70 kPa, 73 kPa, 75 kPa, 79 kPa, 80 kPa, 82 kPa, 85 kPa, 88 kPa or 90 kPa, etc., and the temperature is 50-70℃, for example: 50℃, 55℃, 58℃, 60℃, 63℃, 67℃, 70℃, etc.

[0055] In some embodiments, in step S2, the acidolysis temperature is 140-179°C, for example: 140°C, 146°C, 150°C, 153°C, 160°C, 168°C, 170°C, 172°C, 179°C, etc., and the amount of sulfuric acid added is 110-137.5% of the theoretical amount, for example: 110%, 120%, 130%, 135%, 137%, 137.5%, etc.

[0056] In some embodiments, in step S3, the concentration is carried out in an ammonium sulfate flash concentration tower at a controlled pressure of 70-90 kPa, such as 70 kPa, 73 kPa, 75 kPa, 79 kPa, 80 kPa, 82 kPa, 85 kPa, 88 kPa, or 90 kPa. This helps to fully utilize the material's own heat to achieve rapid concentration, allowing water to evaporate quickly and form ammonium sulfate crystals. At the same time, it avoids the drawback of high energy consumption in subsequent wastewater treatment due to heating, thus helping to reduce treatment costs.

[0057] like Figure 2 and Figure 4As shown, in some embodiments, the ammonium fluoride solution is obtained by first-stage ammoniation of fluorosilicic acid in a primary reaction tank 3.1 with ammonia gas to adjust the pH to 4-5, then overflowing into a secondary reaction tank 3.2 where ammonia gas is introduced for second-stage ammoniation to adjust the pH to 6.5-7.5, and finally overflowing into a tertiary reaction tank 3.3 where ammonia gas is introduced for third-stage ammoniation to adjust the pH to 8.0-9.0. The material in the tertiary reaction tank 3.3 is then filtered. This helps ensure the continuous preparation and acquisition of the ammonium fluoride solution and reduces the silicon content in the solution.

[0058] like Figure 3As shown, in some embodiments, a device for producing anhydrous hydrogen fluoride and co-producing ammonium sulfate using ammonium fluoride solution includes a flash concentration tower 5. The flash concentration tower 5 is equipped with an NH4F solution inlet, a mixed gas outlet, a liquid circulation port, and a slurry outlet. The bottom of the slurry outlet is connected to an NH4F dehydration assembly 8 via a pipe. The NH4F dehydration assembly is equipped with a liquid outlet and a slag outlet. The liquid outlet is connected to the liquid circulation port via a liquid circulation pipe. The slag outlet is connected to an acid hydrolysis tank 11, and the slag outlet can send the solid NH4F-NH4HF2 produced in the NH4F dehydration assembly 8 into the acid hydrolysis tank 11. The acid hydrolysis tank 11 is equipped with an HF gas outlet, an acid inlet, and an acid hydrolysis residue outlet. The HF gas outlet is connected to... The system is equipped with an acid washing purification tank 13, and the HF gas outlet is capable of sending the generated crude HF gas into the acid washing purification tank 13. The acid washing purification tank 13 is provided with an acid liquid outlet, a concentrated sulfuric acid inlet, and an exhaust port. The acid liquid outlet is connected to the acid liquid inlet, the concentrated sulfuric acid inlet is connected to a concentrated sulfuric acid tank 14, and the exhaust port is connected to a condenser distillation tower 16. The acid hydrolysis residue outlet is connected to a reaction tank 9 via a pipeline, and the mixed gas outlet is connected to the reaction tank 9 via a pipeline. The reaction tank 9 is provided with a wastewater outlet and an ammonium sulfate solid outlet. The ammonium sulfate solid outlet is connected to an ammonium sulfate storage tank 10, the wastewater outlet is connected to a wastewater treatment component 12, and the condenser distillation tower 16 is connected to an anhydrous HF tank 15. The ammonium fluoride solution is introduced into the flash concentration tower 5 through the NH4F solution inlet. The temperature and pressure inside the flash concentration tower 5 are controlled in an adjustable manner, so that the pressure is controlled at <90kPa and the temperature is below 70℃ for flash concentration. This causes the ammonium fluoride in the ammonium fluoride solution to decompose, forming ammonium hydrogen fluoride and ammonia. This results in a mixture of ammonia and water vapor, as well as ammonium hydrogen fluoride remaining in the liquid. The ammonium hydrogen fluoride is then converted into HF gas and escaped through a concentration-dehydration-acid hydrolysis process. At the same time, a mixed slurry of ammonium sulfate and ammonium hydrogen sulfate is formed, which is the acid hydrolysis residue. The interaction between the acid hydrolysis residue and the mixed gas in reaction tank 9 allows the overall temperature of the acid hydrolysis residue to be lowered after the mixed gas is introduced. At the same time, the low-temperature ammonia and other mixed gases react with bisulfate ions to convert them into sulfate ions, forming ammonium sulfate. This not only helps to improve the product quality and purity of ammonium sulfate, but also helps to overcome the high energy consumption caused by the large temperature drop during wastewater treatment, resulting in a significant reduction in wastewater treatment costs. The device has a simple structural improvement, low modification cost, and significant economic benefits. It is more suitable for introduction into the original process of anhydrous hydrogen fluoride production in fluorochemical enterprises to reduce costs.

[0059] like Figure 2 and Figure 3As shown, in some embodiments, the NH4F solution inlet is connected to a silica preparation assembly. That is, ammonium fluoride solution is prepared using the ammonolysis of fluorosilicate to produce silica: 2H2O(l) + H2SiF6 + 6NH3(g) = 6NH4F(l) + SiO2↓. After filtering out the SiO2 precipitate, the silica product is prepared by drying. The filtered liquid is ammonium fluoride liquid, which is sent to a flash concentration tower 5 for temperature and pressure control for concentration. The silica preparation assembly is also connected according to conventional processes, for example: Figure 2 and Figure 3 As shown, it includes an ammonia hydrolysis tank 3, which has an ammonia inlet and a fluorosilicic acid inlet. The ammonia inlet is connected to an ammonia storage tank 2 via a pipeline, and the fluorosilicic acid inlet is connected to a fluorosilicic acid tank 1 via a pipeline. The ammonia hydrolysis tank 3 has an outlet, and a filter and washing assembly 4 is installed on the outlet. The filter and washing assembly 4 is connected to a drying chamber 6 and an NH4F liquid outlet. The drying chamber 6 is connected to a silica tank 7, and the NH4F liquid outlet is connected to the NH4F solution inlet via a pipeline. This allows for continuous and cyclical production of ammonium sulfate, and co-production of anhydrous HF.

[0060] For other matters not covered in this invention, those skilled in the art can refer to existing technology or common knowledge, conventional technical means, and habitual technical means known to them for understanding and implementation. For example, the term "connection" described in this invention refers to the various connection methods that those skilled in the art can select, such as pipeline connection and belt conveyor, based on the connection relationship between the corresponding equipment and components, to meet the requirements of... Figure 1 and Figure 2 and Figure 3 The overall process and the connections between process equipment shown are as follows: for liquids and slurries, pipe connections are usually used, and then pumping is used to achieve flow; for solids, belt conveyors are usually used; and for gases, sealed pipe connections are usually used.

[0061] The most significant technological improvement of this invention lies in its application to the traditional process of preparing anhydrous hydrogen fluoride from ammonium fluoride. For example, as disclosed in patent number 200310104113.8, solid ammonium fluoride is prepared by ammonolysis-silica reaction followed by concentration-drying. The ammonia gas generated during concentration is recycled and reused. Based on the process of preparing hydrogen fluoride and ammonium sulfate by acidolysis of solid ammonium fluoride, the concentration-drying process for preparing solid ammonium fluoride is introduced into a flash concentration tower for flash concentration. Under specific pressure and temperature, the flash concentration produces solid ammonium fluoride, ammonia gas, and water vapor. The ammonia gas and water vapor mixture escapes from the flash concentration tower. The solid ammonium fluoride is then used for acidolysis to prepare ammonium sulfate and hydrogen fluoride. This allows the acidolysis residue generated during the acidolysis process to be treated by contact with the mixed gas, thereby lowering the temperature of the acidolysis residue and promoting the precipitation of ammonium sulfate crystals. This achieves full utilization of the escaped material, reduces the difficulty of treating acidolysis residue and ammonium sulfate crystallization waste liquid, and lowers the treatment cost. For example, patent number 200610106974.3 discloses a process of preparing silicon dioxide and ammonium fluoride solution by ammonolysis of fluorosilicic acid, followed by high-temperature (130-200℃) decomposition of the ammonium fluoride solution and cooling to prepare ammonium bifluoride. Ammonia gas is recovered to prepare ammonia water for reuse. Based on the process of preparing anhydrous hydrogen fluoride by acidolysis of ammonium bifluoride, the process of high-temperature decomposition of ammonium fluoride solution is introduced into a flash concentration tower for flash concentration. The flash concentration is controlled at specific pressure and temperature to prepare solid ammonium bifluoride, ammonia gas, and water vapor. The mixed gas of ammonia gas and water vapor escapes from the flash concentration tower. The solid ammonium bifluoride is used for acidolysis to prepare ammonium sulfate and hydrogen fluoride. The acidolysis residue generated during the acidolysis process is treated by contact with the mixed gas to reduce the temperature of the acidolysis residue, promote the precipitation of ammonium sulfate crystals, and thus realize the full utilization of the escaped material, reduce the difficulty of treating acidolysis residue and ammonium sulfate crystallization waste liquid, and reduce treatment costs. The invention introduces a flash evaporation concentration process to prepare ammonium bifluoride solution, which fully ensures that ammonia and water vapor form a mixed gas, allowing ammonia and water vapor to mix evenly in a gaseous state, while also ensuring the conversion of ammonium bifluoride solution into solid ammonium bifluoride.

[0062] In order to verify the technical effect of the present invention, the research team carried out the following preparation of anhydrous hydrogen fluoride and ammonium sulfate samples, and performed quality analysis on the obtained samples.

[0063] In the sample preparation process described below, the ammonium fluoride solution used in Examples 1 and 2 was obtained by first-stage ammoniation of fluorosilicic acid with ammonia gas in a primary reaction tank 3.1, adjusting the pH value to between 4 and 5, then overflowing into a secondary reaction tank 3.2 and undergoing secondary ammoniation with ammonia gas, adjusting the pH value to between 6.5 and 7.5, then overflowing into a tertiary reaction tank 3.3 and undergoing tertiary ammoniation with ammonia gas, adjusting the pH value to between 8.0 and 9.0, and finally filtering the material in the tertiary reaction tank 3.3. In Example 3, the ammonium fluoride solution was obtained by directly mixing fluorosilicic acid with ammonia gas, adjusting the pH value to between 8.0 and 9.0, reacting for a certain period of time, and then filtering.

[0064] Example 1

[0065] An ammonium fluoride solution was prepared and concentrated in a flash concentrator at a pressure of 70 kPa and a temperature of 50 °C, yielding a mixed gas of NH3-H2O, a liquid of NH4F-NH4HF2, and a solid of NH4F-NH4HF2. Solid-liquid separation was performed, yielding the solid NH4F-NH4HF2, and the filtrate was recycled back into the flash concentrator. The solid NH4F-NH4HF2 was then acid-hydrolyzed with sulfuric acid at 120 °C, with the sulfuric acid added at 100% of the theoretical amount, yielding crude HF and acid hydrolysis residue. The mixed gas of NH3-H2O was directly introduced into the acid hydrolysis residue through a pipeline for mixing and reaction, followed by concentration and filtration to obtain solid ammonium sulfate and filtrate. The filtrate was recycled and mixed with the mixed gas of NH3-H2O. The solid ammonium sulfate was dried to obtain the final product. The crude HF was purified by acid washing with concentrated sulfuric acid, condensed, and distilled to obtain anhydrous hydrogen fluoride. The purified liquid was then mixed with the solid NH4F-NH4HF2.

[0066] Example 2

[0067] An ammonium fluoride solution was prepared and concentrated in a flash concentrator at a pressure of 90 kPa and a temperature of 70 °C, yielding a mixed gas of NH3-H2O, a liquid of NH4F-NH4HF2, and a solid of NH4F-NH4HF2. Solid-liquid separation was performed, yielding the solid NH4F-NH4HF2, and the filtrate was recycled back into the flash concentrator. The solid NH4F-NH4HF2 was then acid-hydrolyzed with sulfuric acid at 220 °C, with the sulfuric acid added at 150% of the theoretical amount, yielding crude HF and acid hydrolysis residue. The mixed gas of NH3-H2O was directly introduced into the acid hydrolysis residue through a pipeline for mixing and reaction, followed by concentration and filtration to obtain solid ammonium sulfate and filtrate. The filtrate was recycled and mixed with the mixed gas of NH3-H2O. The solid ammonium sulfate was dried to obtain the final product. The crude HF was purified by acid washing with concentrated sulfuric acid, condensed, and distilled to obtain anhydrous hydrogen fluoride. The purified liquid was then mixed with the solid NH4F-NH4HF2.

[0068] Example 3

[0069] An ammonium fluoride solution was prepared and concentrated in a flash concentrator at a pressure of 80 kPa and a temperature of 60 °C, yielding a mixed gas of NH3-H2O, a liquid of NH4F-NH4HF2, and a solid of NH4F-NH4HF2. Solid-liquid separation was performed, yielding the solid NH4F-NH4HF2, and the filtrate was recycled back into the flash concentrator. The solid NH4F-NH4HF2 was then acid-hydrolyzed with sulfuric acid at 180 °C, with the sulfuric acid added at 130% of the theoretical amount, yielding crude HF and acid hydrolysis residue. The mixed gas of NH3-H2O was directly introduced into the acid hydrolysis residue through a pipeline for mixing and reaction, followed by concentration and filtration to obtain solid ammonium sulfate and filtrate. The filtrate was recycled and mixed with the mixed gas of NH3-H2O. The solid ammonium sulfate was dried to obtain the final product. The crude HF was purified by acid washing with concentrated sulfuric acid, condensed, and distilled to obtain anhydrous hydrogen fluoride. The purified liquid was then mixed with the solid NH4F-NH4HF2.

[0070] The anhydrous hydrogen fluoride and ammonium sulfate obtained in Examples 1-3 were subjected to quality analysis, and the results are shown in Tables 1 and 2 below.

[0071] Table 1. Quality Analysis Results of Anhydrous Hydrogen Fluoride Products

[0072]

[0073] As shown in Table 1, the anhydrous hydrogen fluoride obtained by this invention has an HF content of over 99.93%, and the mass contents of fluorosilicic acid and non-volatile acids are reduced to below 0.01%.

[0074] Table 2. Quality Analysis Results of Ammonium Sulfate Products

[0075]

[0076] As shown in Table 2, the ammonium sulfate produced by this invention has high purity, with a nitrogen content of over 21.6% and low free acid content, thus ensuring the quality of the ammonium sulfate product.

[0077] This invention utilizes the mixed gas generated in a flash concentration tower to directly react with the high-temperature acid hydrolysis residue, reducing subsequent waste liquid treatment costs and ensuring the quality of ammonium sulfate. Other matters not covered in this invention can be implemented using existing technology or common knowledge well-known to those skilled in the art, and conventional technical means.

[0078] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A process for the production of anhydrous hydrogen fluoride co-product ammonium sulfate using a solution containing ammonium fluoride, characterized in that, The method comprises the following steps: S1: sending the ammonium fluoride solution into a flash concentration tower for flash concentration to obtain NH3-H2O mixed gas, NH4F-NH4HF2 liquid and NH4F-NH4HF2 solid; solid-liquid separation is performed to obtain NH4F-NH4HF2 solid, and the filtrate is recycled into the flash concentration tower; the flash concentration pressure is 70-90 kPa, and the temperature is 50-70℃; S2: mixing the NH4F-NH4HF2 solid with sulfuric acid for acidolysis, the acidolysis temperature is 140-179℃, the sulfuric acid is added in an amount of 110-137.5% of the theoretical amount, and crude HF and acidolysis residual liquid are obtained; S3: mixing the NH3-H2O mixed gas and the acidolysis residual liquid, concentrating, filtering to obtain ammonium sulfate solid and filtrate, and the filtrate is recycled and mixed with the NH3-H2O mixed gas; the concentration is a concentration treatment under the control of a pressure of 70-90 kPa; S4: purifying the crude HF through sulfuric acid washing, condensing, rectifying to obtain anhydrous hydrogen fluoride, and sending the liquid after the acid washing purification into the NH4F-NH4HF2 solid mixing.

2. The method of claim 1, wherein, In the step S1, the flash concentration pressure is 80 kPa, and the temperature is 60℃.

3. The method of claim 1, wherein, In the step S2, the acidolysis temperature is 160℃, and the sulfuric acid is added in an amount of 120% of the theoretical amount.

4. The method of claim 1, wherein, In the step S3, the concentration is a concentration treatment in an ammonium sulfate flash concentration tower under the control of a pressure of 70-90 kPa.

5. The method of claim 1, wherein, The ammonium fluoride solution is obtained by adjusting the pH value of fluorosilicic acid to 4-5 through primary ammonia in a primary reaction tank (3.1), adjusting the pH value to 6.5-7.5 through secondary ammonia in a secondary reaction tank (3.2) overflowed from the primary reaction tank, adjusting the pH value to 8.0-9.0 through tertiary ammonia in a tertiary reaction tank (3.3) overflowed from the secondary reaction tank, and filtering the material in the tertiary reaction tank.

6. The method of claim 1 or 5, wherein, The ammonium fluoride solution is obtained by adjusting the pH value of fluorosilicic acid to 4.3-4.7 through primary ammonia in a primary reaction tank (3.1), adjusting the pH value to 6.7-7.0 through secondary ammonia in a secondary reaction tank (3.2) overflowed from the primary reaction tank, adjusting the pH value to 8.4-8.8 through tertiary ammonia in a tertiary reaction tank (3.3) overflowed from the secondary reaction tank, and filtering the material in the tertiary reaction tank.

7. An apparatus for producing anhydrous hydrogen fluoride co-producing ammonium sulfate using a solution containing ammonium fluoride, characterized by comprising: The flash concentration tower (5) is provided with an NH4F solution inlet, a mixed gas outlet, a liquid circulation port and a slurry discharge port; the bottom of the slurry discharge port is connected with an NH4F dehydration assembly (8) through a pipeline, the NH4F dehydration assembly is provided with a liquid discharge port and a residue discharge port, the liquid discharge port is connected with the liquid circulation port through a liquid circulation pipeline; the residue discharge port is connected with an acidolysis tank (11), and the residue discharge port can send the solid NH4F-NH4HF2 generated in the NH4F dehydration assembly (8) into the acidolysis tank (11); the acidolysis tank (11) is provided with an HF gas outlet, an acid liquid inlet and an acidolysis residual liquid outlet, the HF gas outlet is connected with an acid washing and purifying tank (13), and the HF gas outlet can send the generated crude HF gas into the acid washing and purifying tank (13); the acid washing and purifying tank (13) is provided with an acid liquid outlet, a concentrated sulfuric acid inlet and an exhaust port, the acid liquid outlet is in communication with the acid liquid inlet, the concentrated sulfuric acid inlet is connected with a concentrated sulfuric acid tank (14), and the exhaust port is connected with a condensing rectification tower (16); the acidolysis residual liquid outlet is connected with a reaction tank (9) through a pipeline, the mixed gas outlet is in communication with the reaction tank (9) through a pipeline, and the reaction tank (9) is provided with a sewage outlet and an ammonium sulfate solid outlet, the ammonium sulfate solid outlet is connected with an ammonium sulfate storage tank (10), the sewage outlet is connected with a waste water treatment assembly (12), and the condensing rectification tower (16) is connected with a anhydrous HF tank (15); When the flash concentration tower (5) is in flash concentration, the flash concentration pressure is 70-90kPa, and the temperature is 50-70℃; when the acidolysis tank (11) is in acidolysis, the acidolysis temperature is 140-179℃; the mixed-concentration-filtration reaction is carried out in the reaction tank (9), and the concentration is a concentration treatment under the control of a pressure of 70-90kPa.

8. The apparatus of claim 7 wherein, The NH4F solution inlet is connected with a silicon preparation assembly. The NH4F solution inlet is connected with a silicon preparation assembly.

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