Method for preparing anhydrous hydrogen fluoride by comprehensive utilization of by-products

Abstract

The present application relates to a kind of byproduct comprehensive utilization preparation anhydrous hydrogen fluoride method, the fluorosilicic acid solution with the concentration of 12%-18% in the byproduct of wet-process phosphoric acid production process and the unqualified product in the production process of Mannheim potassium sulfate are reacted, then vacuum filtration is separated to obtain potassium fluosilicate filter cake and dilute sulfuric acid solution containing KCl, K2SO4 Such salt substances.Fluorosilicate potassium filter cake is added in more than 95% hot concentrated sulfuric acid and is decomposed, vacuum distillation and stirring are carried out during reaction process, SiF4, HF gas and potassium sulfate-containing solution are obtained, and the potassium sulfate-containing solution is recycled after cooling and returns to the first step.The raw materials used in the whole process are byproducts, and the cost is low.The byproduct of Mannheim potassium sulfate used not only can improve the fluorine yield of process system, but also can alleviate the situation that silicon dioxide is converted into silicon gel to block the process system.All substances in the process, waste water, waste gas and waste residue are recycled, and the whole process is safe and energy-saving.

Description

Technical Field

[0001] This invention relates to the field of hydrogen fluoride production technology, and in particular to a method for preparing anhydrous hydrogen fluoride through comprehensive utilization of by-products. Background Technology

[0002] Anhydrous hydrogen fluoride, as a fundamental raw material in the fluorochemical industry chain, is experiencing increasing market demand and rising prices. Many domestic companies, recognizing the considerable profits from anhydrous hydrogen fluoride products, have invested in the research and development of its production processes. In general, there are two main production methods for anhydrous hydrogen fluoride: the traditional fluorite process and the decomposition of fluorosilicic acid, a byproduct of wet-process phosphoric acid production from phosphate rock. The second method has become the preferred approach for domestic companies and a key step for wet-process phosphoric acid producers to expand their industry chain. Currently, numerous methods for producing anhydrous hydrogen fluoride from fluorosilicic acid have emerged in China's wet-process phosphoric acid industry, but the processes are largely similar, each with its own advantages and disadvantages. Very few processes are actually suitable for industrial-scale production. The processes for producing anhydrous hydrogen fluoride from fluorosilicic acid can be categorized as follows: one involves decomposing fluorosilicic acid with sulfuric acid; another involves converting fluorosilicic acid into related salts before decomposing it with sulfuric acid; one involves direct decomposition of fluorosilicic acid; and another involves converting fluorosilicic acid into related salts before direct decomposition.

[0003] For example, patent CN101948114A discloses a method for preparing silicon tetrafluoride and anhydrous hydrogen fluoride by acidifying sodium fluorosilicate with sulfuric acid, but the process is too simple and difficult to put into actual production.

[0004] For example, patent CN102275877A discloses a method for producing anhydrous hydrogen fluoride and silicon tetrafluoride using fluorosilicic acid. However, the process uses a rotary kiln, which is used in the fluorite process, and has high energy consumption and is difficult to operate.

[0005] For example, patent CN108439340A discloses a method for preparing anhydrous hydrogen fluoride, but it does not describe the process flow, making it difficult to implement. Furthermore, the dilute sulfuric acid produced in the process is not effectively utilized but instead used to produce phosphogypsum, which has no added value and wastes resources.

[0006] For example, patent CN112897466A discloses a method for producing anhydrous hydrogen fluoride using fluorosilicic acid in phosphoric acid. It describes the process flow, but the entire process is not optimized enough. Some materials are not fully utilized, the yield of anhydrous hydrogen fluoride cannot reach the maximum, and the raw material used is fluorophosphoric acid, which has a high impurity content, which is detrimental to the entire process.

[0007] All of these processes have various drawbacks, such as high production costs, high energy consumption, and difficult operation; ineffective utilization of by-products during production; or difficulty in industrialization. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, this invention combines the characteristics of wet-process phosphoric acid production and Mannheim furnace potassium sulfate production processes to provide a method for preparing anhydrous hydrogen fluoride by comprehensively utilizing by-products. The method for preparing anhydrous hydrogen fluoride using fluorosilicic acid by-product from wet-process phosphoric acid production and substandard products from Mannheim furnace potassium sulfate production can reduce production costs, comprehensively utilize by-product resources, is safe and efficient, economical and environmentally friendly, simple to operate, and can achieve a product purity of over 99.8%, and can realize industrial production.

[0009] To achieve the objectives of this invention, the technical solution is as follows:

[0010] A method for preparing anhydrous hydrogen fluoride through comprehensive utilization of byproducts, the method comprising the following steps:

[0011] 1) Add the substandard product from the potassium Mannheim sulfate production process to a 12%-18% fluorosilicic acid solution, which is a byproduct of the wet-process phosphoric acid production process, to obtain a reaction slurry;

[0012] 2) The reaction slurry obtained in step 1) is separated by vacuum filtration to obtain potassium fluorosilicate filter cake and dilute sulfuric acid solution;

[0013] 3) The dilute sulfuric acid solution obtained in step 2) is vacuum concentrated to obtain hot concentrated sulfuric acid of more than 95% for subsequent thermal decomposition reaction and washing with SiF4 and HF gas. After the potassium sulfate crystal obtained by vacuum concentration is naturally cooled, it is returned to step 1) for reaction. The acidic water produced by vacuum concentration can be discharged into the wet process phosphoric acid production system.

[0014] 4) Add the potassium fluorosilicate filter cake obtained in step 2) to hot concentrated sulfuric acid of 95% or higher for thermal decomposition reaction. If the amount of hot concentrated sulfuric acid is insufficient, 98% concentrated sulfuric acid can be added. During the reaction, vacuum distillation and stirring are carried out. The thermal decomposition reaction yields a solution containing SiF4 and HF gas and a solution containing potassium sulfate. After cooling, the solution containing potassium sulfate is returned to step 1) for further reaction.

[0015] 5) The gas containing SiF4 and HF obtained in step 4) is washed and dehydrated with concentrated sulfuric acid of 95% or higher that has been cooled in step 3), and the resulting washing liquid is returned to step 4) for thermal decomposition reaction;

[0016] 6) The SiF4 and HF gases washed in step 5) are condensed to obtain liquid HF and SiF4 gases;

[0017] 7) The liquid HF obtained in step 6) is purified and distilled to obtain anhydrous hydrogen fluoride product with a purity of over 99.8%. The remaining liquid obtained from distillation is returned to step 4) for further reaction.

[0018] 8) The SiF4 gas obtained in step 6) is passed into the dilute sulfuric acid solution from step 2) for hydrolysis to obtain a hydrolyzed slurry and a gas mainly composed of HF. The gas mainly composed of HF is discharged into step 5) by a vacuum pump for washing and dehydration to recover HF. The hydrolyzed slurry is filtered and separated to obtain an acidic solution containing KF, K2SO4, and KCl and silicon dioxide. The acidic solution containing KF, K2SO4, and KCl is returned to step 1) to continue the reaction to improve the yield of fluorine. The silicon dioxide is recycled to prepare silica.

[0019] Complete the preparation of anhydrous hydrogen fluoride by comprehensive utilization of by-products.

[0020] Preferably, in step 1), the ratio of the amount of potassium oxide in the substandard Mannheim potassium sulfate to the amount of fluorosilicic acid in the 12%-18% fluorosilicic acid solution is (1~2):1, the reaction temperature is controlled at 10℃~40℃, and the reaction time is controlled at 10min~60min.

[0021] Preferably, the main components of the substandard Mannheim potassium sulfate in step 1) are as follows: water-soluble K2O: 45%-50%, Cl... - ≤2%, H2O≤1.5%, free acid (calculated as sulfuric acid)≤1.5%, pH3-5. Non-conforming products can provide H2SO4 to the process system, thereby increasing the yield of fluorine.

[0022] Preferably, the vacuum filtration described in step 2) has a vacuum level controlled between -20 kPa and -80 kPa.

[0023] Preferably, the vacuum concentration temperature of the dilute sulfuric acid solution in step 3) is controlled at 100~180℃, the vacuum degree is controlled at -20KPa~-80KPa, the concentration of the obtained hot concentrated sulfuric acid is controlled at above 95%, and the temperature of the hot concentrated sulfuric acid is controlled at 100℃-180℃.

[0024] Preferably, in step 4), the vacuum distillation temperature is controlled at 100~180℃, the vacuum degree is controlled at -20KPa~-80KPa, the stirring rate is controlled at 200-400r / min, the ratio of the amount of potassium fluorosilicate in the potassium fluorosilicate filter cake added for the thermal decomposition reaction to the amount of sulfuric acid in the total concentrated sulfuric acid added in the reaction is controlled at 1:1, and the reaction time is controlled at 10-300min; the concentrated sulfuric acid is added first for the thermal decomposition reaction, and then the potassium fluorosilicate filter cake is added.

[0025] Preferably, the concentrated sulfuric acid washing temperature in step 5) is controlled at 10°C to 45°C.

[0026] The condensation temperature mentioned in step 6) is controlled at -5℃ to 10℃.

[0027] Preferably, the SiF4 gas obtained in step 6) is hydrolyzed using the dilute sulfuric acid solution obtained in step 2).

[0028] The beneficial effects of this invention are as follows:

[0029] 1) Using fluorosilicic acid, a byproduct of wet-process phosphoric acid production, and substandard products from Mannheim furnace potassium sulfate production as raw materials can save production costs and achieve the goal of comprehensive utilization of byproducts.

[0030] 2) The entire process does not involve the treatment of wastewater, waste gas, or waste residue, making it relatively economical and environmentally friendly.

[0031] 3) All by-products generated during the entire process are recycled, which can save resources and improve production efficiency.

[0032] 4) The entire process is carried out under negative pressure to prevent the leakage of toxic gases and to reduce operating temperature and heat loss. Low-pressure steam or waste gas can be used in the production process, resulting in lower energy consumption.

[0033] 5) The substandard potassium sulfate contains KCl and K2SO4, and the pH is between 3 and 5. When the ratio of the amount of potassium oxide in the substandard product to the amount of fluorosilicic acid in the 12%-18% fluorosilicic acid solution is (1~2):1, it can not only improve the yield of fluorine, but also the dilute sulfuric acid solution also contains salts such as KCl and K2SO4. Using it to hydrolyze the SiF4 gas generated later can disperse the SiO2 colloidal particles generated by the hydrolysis of silicon tetrafluoride, reduce the agglomeration effect, and produce finer silica particles. At the same time, it can alleviate the situation where SiO2 colloidal particles turn into silica gel and block the production system. Attached Figure Description

[0034] Figure 1 A schematic diagram of the process flow of this invention. Detailed Implementation

[0035] The present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited to the scope described in the embodiments.

[0036] Example 1

[0037] 1) Add 12% fluorosilicic acid solution (density 1.12 g / cm³), a byproduct of wet-process phosphoric acid production, to 500 mL of the solution. 3The addition of substandard products (48% water-soluble K₂O, Cl₂) during the production of potassium Mannheim sulfate resulted in the addition of these products. - The content is 2%, the moisture content is 1.5%, the free acid (calculated as sulfuric acid) content is 1.5%, and the pH is 3.5. The ratio of the amount of potassium oxide in the unqualified product to the amount of fluorosilicic acid in the fluorosilicic acid solution is controlled at 1:1 to obtain the reaction slurry.

[0038] 2) The reaction slurry obtained in step 1) is vacuum filtered, and the vacuum degree is controlled at -45KPa to separate potassium fluorosilicate filter cake and dilute sulfuric acid solution.

[0039] 3) The dilute sulfuric acid solution obtained in step 2) is concentrated under vacuum, with the temperature controlled at 150℃ and the vacuum degree controlled at -45KPa, to obtain 95% hot concentrated sulfuric acid for subsequent thermal decomposition reaction and for washing with SiF4 and HF gas after cooling. The potassium sulfate crystals obtained by vacuum concentration are naturally cooled and returned to step 1) for reaction. The acidic water produced by concentration can be discharged into the wet process phosphoric acid production system.

[0040] 4) The potassium fluorosilicate filter cake obtained in step 2) is added to 95% hot concentrated sulfuric acid obtained from vacuum concentration for thermal decomposition. The ratio of potassium fluorosilicate in the filter cake to sulfuric acid in the total concentrated sulfuric acid is controlled at 1:1. Vacuum distillation is performed during the reaction, with the temperature controlled at 150℃, the vacuum degree controlled at -45KPa, the stirring rate controlled at 300r / min, and the reaction time controlled at 60min. The thermal decomposition reaction yields a solution containing SiF4 and HF gas and a solution containing potassium sulfate. The potassium sulfate solution is cooled and returned to step 1) for further reaction.

[0041] 5) The SiF4 and HF gas obtained in step 4) is washed and dehydrated with the cooled concentrated sulfuric acid obtained in step 3). The washing temperature is controlled at 25°C. The resulting washing solution is returned to step 4) for reaction.

[0042] 6) The SiF4 and HF-containing gas washed in step 5) is condensed at a temperature of 5°C to obtain liquid HF and SiF4 gas.

[0043] 7) The liquid HF obtained in step 6) is purified and distilled to obtain anhydrous hydrogen fluoride product. The remaining liquid obtained from distillation is returned to step 4) for reaction.

[0044] 8) The SiF4 gas obtained in step 6) is hydrolyzed with the dilute sulfuric acid solution obtained in step 2) to obtain a hydrolyzed slurry and gases such as HF. The gases such as HF are discharged into step 5) for washing and dehydration via a vacuum pump. The hydrolyzed slurry is filtered and separated to obtain an acidic solution and silicon dioxide. The acidic solution is returned to step 1) to continue to participate in the reaction. The silicon dioxide can be recycled to prepare silica.

[0045] Experimental results: 51.8 g of anhydrous hydrogen fluoride was obtained, with a hydrogen fluoride content of 99.85%. The yield of fluorine was m. 无水氟化氢成品 *w 氟化氢 *144 / (ρ 氟硅酸 *v 氟硅酸 *w 氟硅酸 *120) = 92.36%. Where m 无水氟化氢成品 To determine the quality of the obtained anhydrous hydrogen fluoride product, w 氟化氢 The content of hydrogen fluoride in anhydrous hydrogen fluoride, ρ 氟硅酸 v is the density of the fluorosilicic acid solution. 氟硅酸 w is the volume of the fluorosilicic acid solution. 氟硅酸 This represents the mass fraction of the fluorosilicic acid solution.

[0046] Example 2

[0047] 1) Add 12% fluorosilicic acid solution (density 1.12 g / cm³), a byproduct of wet-process phosphoric acid production, to 500 mL of the solution. 3 The addition of substandard products (48% water-soluble K₂O, Cl₂) during the production of potassium Mannheim sulfate resulted in the addition of these products. - The content is 2%, the moisture content is 1.5%, the free acid (calculated as sulfuric acid) content is 1.5%, and the pH is 3.5. The ratio of the amount of potassium oxide in the unqualified product to the amount of fluorosilicic acid in the fluorosilicic acid solution is controlled at 1.2:1 to obtain the reaction slurry.

[0048] 2) The reaction slurry obtained in step 1) is vacuum filtered, and the vacuum degree is controlled at -45KPa to separate potassium fluorosilicate filter cake and dilute sulfuric acid solution.

[0049] 3) The dilute sulfuric acid solution obtained in step 2) is concentrated under vacuum, with the temperature controlled at 150℃ and the vacuum degree controlled at -45KPa, to obtain 95% hot concentrated sulfuric acid for subsequent thermal decomposition reaction and for washing with SiF4 and HF gas after cooling. The potassium sulfate crystals obtained by vacuum concentration are naturally cooled and returned to step 1) for reaction. The acidic water produced by concentration can be discharged into the wet process phosphoric acid production system.

[0050] 4) The potassium fluorosilicate filter cake obtained in step 2) is added to 95% hot concentrated sulfuric acid obtained from vacuum concentration for thermal decomposition. The ratio of potassium fluorosilicate in the filter cake to sulfuric acid in the total concentrated sulfuric acid is controlled at 1:1. Vacuum distillation is performed during the reaction, with the temperature controlled at 150℃, the vacuum degree controlled at -45KPa, the stirring rate controlled at 300r / min, and the reaction time controlled at 60min. The thermal decomposition reaction yields a solution containing SiF4 and HF gas and a solution containing potassium sulfate. The potassium sulfate solution is cooled and returned to step 1) for further reaction.

[0051] 5) The SiF4 and HF gas obtained in step 4) is washed and dehydrated with the cooled concentrated sulfuric acid obtained in step 3). The washing temperature is controlled at 25°C. The resulting washing solution is returned to step 4) for reaction.

[0052] 6) The SiF4 and HF-containing gas washed in step 5) is condensed at a temperature of 5°C to obtain liquid HF and SiF4 gas.

[0053] 7) The liquid HF obtained in step 6) is purified and distilled to obtain anhydrous hydrogen fluoride product. The remaining liquid obtained from distillation is returned to step 4) for reaction.

[0054] 8) The SiF4 gas obtained in step 6) is hydrolyzed with the dilute sulfuric acid solution obtained in step 2) to obtain a hydrolyzed slurry and gases such as HF. The gases such as HF are discharged into step 5) for washing and dehydration via a vacuum pump. The hydrolyzed slurry is filtered and separated to obtain an acidic solution and silicon dioxide. The acidic solution is returned to step 1) to continue to participate in the reaction. The silicon dioxide can be recycled to prepare silica.

[0055] Experimental results: 52.11 g of anhydrous hydrogen fluoride was obtained, with a hydrogen fluoride content of 99.85%. The fluorine yield was m. 无水氟化氢成品 *w 氟化氢 *144 / (ρ 氟硅酸 *v 氟硅酸 *w 氟硅酸 *120) = 92.91%. Where m 无水氟化氢成品 To determine the quality of the obtained anhydrous hydrogen fluoride product, w 氟化氢 The content of hydrogen fluoride in anhydrous hydrogen fluoride, ρ 氟硅酸 v is the density of the fluorosilicic acid solution. 氟硅酸 w is the volume of the fluorosilicic acid solution. 氟硅酸 This represents the mass fraction of the fluorosilicic acid solution.

[0056] Example 3

[0057] 1) Add 12% fluorosilicic acid solution (density 1.12 g / cm³), a byproduct of wet-process phosphoric acid production, to 500 mL of the solution.3 The addition of substandard products (48% water-soluble K₂O, Cl₂) during the production of potassium Mannheim sulfate resulted in the addition of these products. - The content is 2%, the moisture content is 1.5%, the free acid (calculated as sulfuric acid) content is 1.5%, and the pH is 3.5. The ratio of the amount of potassium oxide in the unqualified product to the amount of fluorosilicic acid in the fluorosilicic acid solution is controlled at 1.4:1 to obtain the reaction slurry.

[0058] 2) The reaction slurry obtained in step 1) is vacuum filtered, and the vacuum degree is controlled at -45KPa to separate potassium fluorosilicate filter cake and dilute sulfuric acid solution.

[0059] 3) The dilute sulfuric acid solution obtained in step 2) is concentrated under vacuum, with the temperature controlled at 150℃ and the vacuum degree controlled at -45KPa, to obtain 95% hot concentrated sulfuric acid for subsequent thermal decomposition reaction and for washing with SiF4 and HF gas after cooling. The potassium sulfate crystals obtained by vacuum concentration are naturally cooled and returned to step 1) for reaction. The acidic water produced by concentration can be discharged into the wet process phosphoric acid production system.

[0060] 4) The potassium fluorosilicate filter cake obtained in step 2) is added to 95% hot concentrated sulfuric acid obtained from vacuum concentration for thermal decomposition. The ratio of potassium fluorosilicate in the filter cake to sulfuric acid in the total concentrated sulfuric acid is controlled at 1:1. Vacuum distillation is performed during the reaction, with the temperature controlled at 150℃, the vacuum degree controlled at -45KPa, the stirring rate controlled at 300r / min, and the reaction time controlled at 60min. The thermal decomposition reaction yields a solution containing SiF4 and HF gas and a solution containing potassium sulfate. The potassium sulfate solution is cooled and returned to step 1) for further reaction.

[0061] 5) The SiF4 and HF gas obtained in step 4) is washed and dehydrated with the cooled concentrated sulfuric acid obtained in step 3). The washing temperature is controlled at 25°C. The resulting washing solution is returned to step 4) for reaction.

[0062] 6) The SiF4 and HF-containing gas washed in step 5) is condensed at a temperature of 5°C to obtain liquid HF and SiF4 gas.

[0063] 7) The liquid HF obtained in step 6) is purified and distilled to obtain anhydrous hydrogen fluoride product. The remaining liquid obtained from distillation is returned to step 4) for reaction.

[0064] 8) The SiF4 gas obtained in step 6) is hydrolyzed with the dilute sulfuric acid solution obtained in step 2) to obtain a hydrolyzed slurry and gases such as HF. The gases such as HF are discharged into step 5) for washing and dehydration via a vacuum pump. The hydrolyzed slurry is filtered and separated to obtain an acidic solution and silicon dioxide. The acidic solution is returned to step 1) to continue to participate in the reaction. The silicon dioxide can be recycled to prepare silica.

[0065] Experimental results: 52.35 g of anhydrous hydrogen fluoride was obtained, with a hydrogen fluoride content of 99.85%. The fluorine yield was m. 无水氟化氢成品 *w 氟化氢 *144 / (ρ 氟硅酸 *v 氟硅酸 *w 氟硅酸 *120) = 93.34%. Where m 无水氟化氢成品 To determine the quality of the obtained anhydrous hydrogen fluoride product, w 氟化氢 The content of hydrogen fluoride in anhydrous hydrogen fluoride, ρ 氟硅酸 v is the density of the fluorosilicic acid solution. 氟硅酸 w is the volume of the fluorosilicic acid solution. 氟硅酸 This represents the mass fraction of the fluorosilicic acid solution.

[0066] Example 4

[0067] 1) Add 12% fluorosilicic acid solution (density 1.12 g / cm³), a byproduct of wet-process phosphoric acid production, to 500 mL of the solution. 3 The addition of substandard products (48% water-soluble K₂O, Cl₂) during the production of potassium Mannheim sulfate resulted in the addition of these products. - The content is 2%, the moisture content is 1.5%, the free acid (calculated as sulfuric acid) content is 1.5%, and the pH is 3.5. The ratio of the amount of potassium oxide in the unqualified product to the amount of fluorosilicic acid in the fluorosilicic acid solution is controlled at 1.6:1 to obtain the reaction slurry.

[0068] 2) The reaction slurry obtained in step 1) is vacuum filtered, and the vacuum degree is controlled at -45KPa to separate potassium fluorosilicate filter cake and dilute sulfuric acid solution.

[0069] 3) The dilute sulfuric acid solution obtained in step 2) is concentrated under vacuum, with the temperature controlled at 150℃ and the vacuum degree controlled at -45KPa, to obtain 95% hot concentrated sulfuric acid for subsequent thermal decomposition reaction and for washing with SiF4 and HF gas after cooling. The potassium sulfate crystals obtained by vacuum concentration are naturally cooled and returned to step 1) for reaction. The acidic water produced by concentration can be discharged into the wet process phosphoric acid production system.

[0070] 4) The potassium fluorosilicate filter cake obtained in step 2) is added to 95% hot concentrated sulfuric acid obtained from vacuum concentration for thermal decomposition. The ratio of potassium fluorosilicate in the filter cake to sulfuric acid in the total concentrated sulfuric acid is controlled at 1:1. Vacuum distillation is performed during the reaction, with the temperature controlled at 150℃, the vacuum degree controlled at -45KPa, the stirring rate controlled at 300r / min, and the reaction time controlled at 60min. The thermal decomposition reaction yields a solution containing SiF4 and HF gas and a solution containing potassium sulfate. The potassium sulfate solution is cooled and returned to step 1) for further reaction.

[0071] 5) The SiF4 and HF gas obtained in step 4) is washed and dehydrated with the cooled concentrated sulfuric acid obtained in step 3). The washing temperature is controlled at 25°C. The resulting washing solution is returned to step 4) for reaction.

[0072] 6) The SiF4 and HF-containing gas washed in step 5) is condensed at a temperature of 5°C to obtain liquid HF and SiF4 gas.

[0073] 7) The liquid HF obtained in step 6) is purified and distilled to obtain anhydrous hydrogen fluoride product. The remaining liquid obtained from distillation is returned to step 4) for reaction.

[0074] 8) The SiF4 gas obtained in step 6) is hydrolyzed with the dilute sulfuric acid solution obtained in step 2) to obtain a hydrolyzed slurry and gases such as HF. The gases such as HF are discharged into step 5) for washing and dehydration via a vacuum pump. The hydrolyzed slurry is filtered and separated to obtain an acidic solution and silicon dioxide. The acidic solution is returned to step 1) to continue to participate in the reaction. The silicon dioxide can be recycled to prepare silica.

[0075] Experimental results: 52.52 g of anhydrous hydrogen fluoride was obtained, with a hydrogen fluoride content of 99.85%. The fluorine yield was m. 无水氟化氢成品 *w 氟化氢 *144 / (ρ 氟硅酸 *v 氟硅酸 *w 氟硅酸 *120) = 93.64%. Where m 无水氟化氢成品 To determine the quality of the obtained anhydrous hydrogen fluoride product, w 氟化氢 The content of hydrogen fluoride in anhydrous hydrogen fluoride, ρ 氟硅酸 v is the density of the fluorosilicic acid solution. 氟硅酸 w is the volume of the fluorosilicic acid solution. 氟硅酸 This represents the mass fraction of the fluorosilicic acid solution.

[0076] Example 5

[0077] 1) Add 12% fluorosilicic acid solution (density 1.12 g / cm³), a byproduct of wet-process phosphoric acid production, to 500 mL of the solution.3 The addition of substandard products (48% water-soluble K₂O, Cl₂) during the production of potassium Mannheim sulfate resulted in the addition of these products. - The content is 2%, the moisture content is 1.5%, the free acid (calculated as sulfuric acid) content is 1.5%, and the pH is 3.5. The ratio of the amount of potassium oxide in the unqualified product to the amount of fluorosilicic acid in the fluorosilicic acid solution is controlled at 1.8:1 to obtain the reaction slurry.

[0078] 2) The reaction slurry obtained in step 1) is vacuum filtered, and the vacuum degree is controlled at -45KPa to separate potassium fluorosilicate filter cake and dilute sulfuric acid solution.

[0079] 3) The dilute sulfuric acid solution obtained in step 2) is concentrated under vacuum, with the temperature controlled at 150℃ and the vacuum degree controlled at -45KPa, to obtain 95% hot concentrated sulfuric acid for subsequent thermal decomposition reaction and for washing with SiF4 and HF gas after cooling. The potassium sulfate crystals obtained by vacuum concentration are naturally cooled and returned to step 1) for reaction. The acidic water produced by concentration can be discharged into the wet process phosphoric acid production system.

[0080] 4) The potassium fluorosilicate filter cake obtained in step 2) is added to 95% hot concentrated sulfuric acid obtained from vacuum concentration for thermal decomposition. The ratio of potassium fluorosilicate in the filter cake to sulfuric acid in the total concentrated sulfuric acid is controlled at 1:1. Vacuum distillation is performed during the reaction, with the temperature controlled at 150℃, the vacuum degree controlled at -45KPa, the stirring rate controlled at 300r / min, and the reaction time controlled at 60min. The thermal decomposition reaction yields a solution containing SiF4 and HF gas and a solution containing potassium sulfate. The potassium sulfate solution is cooled and returned to step 1) for further reaction.

[0081] 5) The SiF4 and HF gas obtained in step 4) is washed and dehydrated with the cooled concentrated sulfuric acid obtained in step 3). The washing temperature is controlled at 25°C. The resulting washing solution is returned to step 4) for reaction.

[0082] 6) The SiF4 and HF-containing gas washed in step 5) is condensed at a temperature of 5°C to obtain liquid HF and SiF4 gas.

[0083] 7) The liquid HF obtained in step 6) is purified and distilled to obtain anhydrous hydrogen fluoride product. The remaining liquid obtained from distillation is returned to step 4) for reaction.

[0084] 8) The SiF4 gas obtained in step 6) is hydrolyzed with the dilute sulfuric acid solution obtained in step 2) to obtain a hydrolyzed slurry and gases such as HF. The gases such as HF are discharged into step 5) for washing and dehydration via a vacuum pump. The hydrolyzed slurry is filtered and separated to obtain an acidic solution and silicon dioxide. The acidic solution is returned to step 1) to continue to participate in the reaction. The silicon dioxide can be recycled to prepare silica.

[0085] Experimental results: 52.62 g of anhydrous hydrogen fluoride was obtained, with a hydrogen fluoride content of 99.85%. The fluorine yield was m. 无水氟化氢成品 *w 氟化氢 *144 / (ρ 氟硅酸 *v 氟硅酸 *w 氟硅酸 *120) = 93.82%. Where m 无水氟化氢成品 To determine the quality of the obtained anhydrous hydrogen fluoride product, w 氟化氢 The content of hydrogen fluoride in anhydrous hydrogen fluoride, ρ 氟硅酸 v is the density of the fluorosilicic acid solution. 氟硅酸 w is the volume of the fluorosilicic acid solution. 氟硅酸 This represents the mass fraction of the fluorosilicic acid solution.

[0086] Example 6

[0087] 1) Add 12% fluorosilicic acid solution (density 1.12 g / cm³), a byproduct of wet-process phosphoric acid production, to 500 mL of the solution. 3 The addition of substandard products (48% water-soluble K₂O, Cl₂) during the production of potassium Mannheim sulfate resulted in the addition of these products. - The content is 2%, the moisture content is 1.5%, the free acid (calculated as sulfuric acid) content is 1.5%, and the pH is 3.5. The ratio of the amount of potassium oxide in the unqualified product to the amount of fluorosilicic acid in the fluorosilicic acid solution is controlled at 2:1 to obtain the reaction slurry.

[0088] 2) The reaction slurry obtained in step 1) is vacuum filtered, and the vacuum degree is controlled at -45KPa to separate potassium fluorosilicate filter cake and dilute sulfuric acid solution.

[0089] 3) The dilute sulfuric acid solution obtained in step 2) is concentrated under vacuum, with the temperature controlled at 150℃ and the vacuum degree controlled at -45KPa, to obtain 95% hot concentrated sulfuric acid for subsequent thermal decomposition reaction and for washing with SiF4 and HF gas after cooling. The potassium sulfate crystals obtained by vacuum concentration are naturally cooled and returned to step 1) for reaction. The acidic water produced by concentration can be discharged into the wet process phosphoric acid production system.

[0090] 4) The potassium fluorosilicate filter cake obtained in step 2) is added to 95% hot concentrated sulfuric acid obtained from vacuum concentration for thermal decomposition. The ratio of potassium fluorosilicate in the filter cake to sulfuric acid in the total concentrated sulfuric acid is controlled at 1:1. Vacuum distillation is performed during the reaction, with the temperature controlled at 150℃, the vacuum degree controlled at -45KPa, the stirring rate controlled at 300r / min, and the reaction time controlled at 60min. The thermal decomposition reaction yields a solution containing SiF4 and HF gas and a solution containing potassium sulfate. The potassium sulfate solution is cooled and returned to step 1) for further reaction.

[0091] 5) The SiF4 and HF gas obtained in step 4) is washed and dehydrated with the cooled concentrated sulfuric acid obtained in step 3). The washing temperature is controlled at 25°C. The resulting washing solution is returned to step 4) for reaction.

[0092] 6) The SiF4 and HF-containing gas washed in step 5) is condensed at a temperature of 5°C to obtain liquid HF and SiF4 gas.

[0093] 7) The liquid HF obtained in step 6) is purified and distilled to obtain anhydrous hydrogen fluoride product. The remaining liquid obtained from distillation is returned to step 4) for reaction.

[0094] 8) The SiF4 gas obtained in step 6) is hydrolyzed with the dilute sulfuric acid solution obtained in step 2) to obtain a hydrolyzed slurry and gases such as HF. The gases such as HF are discharged into step 5) for washing and dehydration via a vacuum pump. The hydrolyzed slurry is filtered and separated to obtain an acidic solution and silicon dioxide. The acidic solution is returned to step 1) to continue to participate in the reaction. The silicon dioxide can be recycled to prepare silica.

[0095] Experimental results: 52.65 g of anhydrous hydrogen fluoride was obtained, with a hydrogen fluoride content of 99.85%. The fluorine yield was m. 无水氟化氢成品 *w 氟化氢 *144 / (ρ 氟硅酸 *v 氟硅酸 *w 氟硅酸 *120) = 93.87%. Where m 无水氟化氢成品 To determine the quality of the obtained anhydrous hydrogen fluoride product, w 氟化氢 The content of hydrogen fluoride in anhydrous hydrogen fluoride, ρ 氟硅酸 v is the density of the fluorosilicic acid solution. 氟硅酸 w is the volume of the fluorosilicic acid solution. 氟硅酸 This represents the mass fraction of the fluorosilicic acid solution.

[0096] Comparative Example 1

[0097] 1) Add 12% fluorosilicic acid solution (density 1.12 g / cm³), a byproduct of wet-process phosphoric acid production, to 500 mL of the solution.3 Analytical grade potassium sulfate is added to the solution, and the ratio of potassium oxide in the potassium sulfate to fluorosilicic acid in the fluorosilicic acid solution is controlled at 1:1 to obtain a reaction slurry.

[0098] 2) The reaction slurry obtained in step 1) is vacuum filtered, and the vacuum degree is controlled at -45KPa to separate potassium fluorosilicate filter cake and dilute sulfuric acid solution.

[0099] 3) The dilute sulfuric acid solution obtained in step 2) is concentrated under vacuum, with the temperature controlled at 150℃ and the vacuum degree controlled at -45KPa, to obtain 95% hot concentrated sulfuric acid for subsequent thermal decomposition reaction and for washing with SiF4 and HF gas after cooling. The potassium sulfate crystals obtained by vacuum concentration are naturally cooled and returned to step 1) for reaction. The acidic water produced by concentration can be discharged into the wet process phosphoric acid production system.

[0100] 4) The potassium fluorosilicate filter cake obtained in step 2) is added to 95% hot concentrated sulfuric acid obtained from vacuum concentration for thermal decomposition. The ratio of potassium fluorosilicate in the filter cake to sulfuric acid in the total concentrated sulfuric acid is controlled at 1:1. Vacuum distillation is performed during the reaction, with the temperature controlled at 150℃, the vacuum degree controlled at -45KPa, the stirring rate controlled at 300r / min, and the reaction time controlled at 60min. The thermal decomposition reaction yields a solution containing SiF4 and HF gas and a solution containing potassium sulfate. The potassium sulfate solution is cooled and returned to step 1) for further reaction.

[0101] 5) The SiF4 and HF gas obtained in step 4) is washed and dehydrated with the cooled concentrated sulfuric acid obtained in step 3). The washing temperature is controlled at 25°C. The resulting washing solution is returned to step 4) for reaction.

[0102] 6) The SiF4 and HF-containing gas washed in step 5) is condensed at a temperature of 5°C to obtain liquid HF and SiF4 gas.

[0103] 7) The liquid HF obtained in step 6) is purified and distilled to obtain anhydrous hydrogen fluoride product. The remaining liquid obtained from distillation is returned to step 4) for reaction.

[0104] 8) The SiF4 gas obtained in step 6) is hydrolyzed with the dilute sulfuric acid solution obtained in step 2) to obtain a hydrolyzed slurry and gases such as HF. The gases such as HF are discharged into step 5) for washing and dehydration via a vacuum pump. The hydrolyzed slurry is filtered and separated to obtain an acidic solution and silicon dioxide. The acidic solution is returned to step 1) to continue to participate in the reaction. The silicon dioxide can be recycled to prepare silica.

[0105] Experimental results: 50.25 g of anhydrous hydrogen fluoride was obtained, with a hydrogen fluoride content of 99.85%. The fluorine yield was m. 无水氟化氢成品 *w 氟化氢 *144 / (ρ 氟硅酸 *v 氟硅酸 *w 氟硅酸 *120) = 89.6%. Where m 无水氟化氢成品 To determine the quality of the obtained anhydrous hydrogen fluoride product, w 氟化氢 The content of hydrogen fluoride in anhydrous hydrogen fluoride, ρ 氟硅酸 v is the density of the fluorosilicic acid solution. 氟硅酸 w is the volume of the fluorosilicic acid solution. 氟硅酸 This represents the mass fraction of the fluorosilicic acid solution.

[0106] As can be seen from Example 1 and Comparative Example 1, adding Mannheim potassium sulfate instead of analytical grade potassium sulfate to the system can introduce substances such as sulfuric acid and hydrochloric acid, which can not only improve the yield of fluorine in the whole system, but also alleviate the problem of silica converting into silica gel and clogging the system during the hydrolysis of SiF4.

[0107] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in these embodiments can be arbitrarily combined without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for preparing anhydrous hydrogen fluoride through comprehensive utilization of by-products, characterized in that, The method includes the following steps: 1) Add the substandard product from the potassium Mannheim sulfate production process to a 12%-18% fluorosilicic acid solution, which is a byproduct of the wet-process phosphoric acid production process, to obtain a reaction slurry; 2) The reaction slurry obtained in step 1) is separated by vacuum filtration to obtain potassium fluorosilicate filter cake and dilute sulfuric acid solution; 3) The dilute sulfuric acid solution obtained in step 2) is vacuum concentrated to obtain hot concentrated sulfuric acid of more than 95% for subsequent thermal decomposition reaction and washing with SiF4 and HF gas. The potassium sulfate crystals obtained by vacuum concentration are naturally cooled and returned to step 1) for reaction. The acidic water generated by vacuum concentration is discharged into the wet process phosphoric acid production system. 4) The potassium fluorosilicate filter cake obtained in step 2) is added to concentrated sulfuric acid at a temperature of 95% or higher for thermal decomposition reaction. During the reaction, vacuum distillation and stirring are carried out. The thermal decomposition reaction yields a solution containing SiF4 and HF gas and a solution containing potassium sulfate. The solution containing potassium sulfate is cooled and returned to step 1) for further reaction. 5) The gas containing SiF4 and HF obtained in step 4) is washed and dehydrated with concentrated sulfuric acid of 95% or higher that has been cooled in step 3), and the resulting washing liquid is returned to step 4) for thermal decomposition reaction; 6) The SiF4 and HF gases washed in step 5) are condensed to obtain liquid HF and SiF4 gases; 7) The liquid HF obtained in step 6) is purified and distilled to obtain anhydrous hydrogen fluoride product with a purity of over 99.8%. The remaining liquid obtained from distillation is returned to step 4) for further reaction. 8) The SiF4 gas obtained in step 6) is passed into the dilute sulfuric acid solution from step 2) for hydrolysis to obtain a hydrolyzed slurry and a gas mainly composed of HF. The gas mainly composed of HF is discharged into step 5) by a vacuum pump for washing and dehydration to recover HF. The hydrolyzed slurry is filtered and separated to obtain an acidic solution containing KF, K2SO4, and KCl and silicon dioxide. The acidic solution containing KF, K2SO4, and KCl is returned to step 1) to continue the reaction to improve the yield of fluorine. The silicon dioxide is recycled to prepare silica. Complete the preparation of anhydrous hydrogen fluoride by comprehensive utilization of by-products.

2. The method for preparing anhydrous hydrogen fluoride by comprehensive utilization of byproducts according to claim 1, characterized in that: In step 1), the ratio of the amount of potassium oxide in the substandard Mannheim potassium sulfate to the amount of fluorosilicic acid in the 12%-18% fluorosilicic acid solution is (1~2):

1. The reaction temperature is controlled at 10℃~40℃ and the reaction time is controlled at 10min~60min.

3. The method for preparing anhydrous hydrogen fluoride by comprehensive utilization of byproducts according to claim 1, characterized in that: The main components of the substandard Mannheim potassium sulfate in step 1) are as follows: water-soluble K2O: 45%-50%, Cl... - ≤2%, H2O≤1.5%, free acid≤1.5%, pH3-5. Non-conforming products can provide H2SO4 to the process system, thereby increasing the yield of fluorine.

4. The method for preparing anhydrous hydrogen fluoride through comprehensive utilization of by-products according to claim 1, characterized in that: The vacuum filtration described in step 2) has a vacuum level controlled between -20 kPa and -80 kPa.

5. The method for preparing anhydrous hydrogen fluoride through comprehensive utilization of by-products according to claim 1, characterized in that: In step 3), the vacuum concentration temperature of the dilute sulfuric acid solution is controlled at 100~180℃, the vacuum degree is controlled at -20kPa~-80kPa, the concentration of the obtained hot concentrated sulfuric acid is controlled at above 95%, and the temperature of the hot concentrated sulfuric acid is controlled at 100℃-180℃.

6. The method for preparing anhydrous hydrogen fluoride through comprehensive utilization of by-products according to claim 1, characterized in that: In step 4), the vacuum distillation temperature is controlled at 100-180℃, the vacuum degree is controlled at -20kPa--80kPa, the stirring rate is controlled at 200-400r / min, the ratio of potassium fluorosilicate in the potassium fluorosilicate filter cake added for the thermal decomposition reaction to sulfuric acid in the total concentrated sulfuric acid added in the reaction is controlled at 1:1, and the reaction time is controlled at 10-300min; concentrated sulfuric acid is added first for the thermal decomposition reaction, followed by potassium fluorosilicate filter cake.

7. The method for preparing anhydrous hydrogen fluoride through comprehensive utilization of by-products according to claim 1, characterized in that: The concentrated sulfuric acid washing temperature described in step 5) is controlled at 10℃~45℃.

8. The method for preparing anhydrous hydrogen fluoride through comprehensive utilization of by-products according to claim 1, characterized in that: The condensation temperature mentioned in step 6) is controlled at -5℃ to 10℃.

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