Hydrogen fluoride-containing sulfuric acid solution negative pressure coupling resolution method and system

Abstract

The present application relates to the field of fluorinated industrial resource recycling, in particular to a negative pressure coupled resolution method and system for a sulfuric acid solution containing hydrogen fluoride. The sulfuric acid solution containing hydrogen fluoride generated by the reaction of fluosilicic acid and concentrated sulfuric acid is introduced into a negative pressure coupled resolution tower, coupled extraction is carried out, and separation is carried out under the condition of low temperature and negative pressure, the crude hydrogen fluoride is obtained at the top of the tower, and anhydrous hydrogen fluoride product is obtained through rectification and condensation; the sulfuric acid solution is obtained at the bottom of the tower. The present application can reduce the boiling point of each component, improve the resolution rate, and solve the problems of incomplete separation and resource waste caused by unreasonable proportion of the extraction agent. The process flow is simple and continuous, the flow is compact, and the effective resolution and separation of the sulfuric acid solution containing hydrogen fluoride are realized under mild conditions.

Description

Technical Field

[0001] This invention relates to the field of fluorochemical resource recycling, specifically a negative pressure coupling analysis method and system for sulfuric acid solutions containing hydrogen fluoride. Background Technology

[0002] During the acidolysis reaction in fluorochemicals, a sulfuric acid solution containing hydrogen fluoride remains. In this solution, hydrogen fluoride, sulfuric acid, and water form stable hydrogen-bonded compounds and exhibit multiple azeotropic phenomena, making it difficult to separate the three. Existing processes not only fail to achieve efficient resource recovery but also suffer from prominent problems such as complex processes, high energy consumption, and a single desorption and separation mechanism. Summary of the Invention

[0003] The purpose of this invention is to provide a negative pressure coupled desorption method and system for sulfuric acid solutions containing hydrogen fluoride. Addressing the shortcomings in the desorption of hydrogen fluoride-sulfuric acid-water ternary mixtures, this invention utilizes a synergistic process of coupled extraction and negative pressure desorption, multi-stage distillation technology, and the dehydration effect of concentrated sulfuric acid to achieve coupled negative pressure desorption of sulfuric acid solutions containing hydrogen fluoride. This efficiently separates anhydrous hydrogen fluoride and concentrated sulfuric acid for the production of anhydrous hydrogen fluoride and concentrated sulfuric acid products, enabling the recovery of fluorine and sulfur resources. Furthermore, the closed-loop process allows for the recycling of the coupled extractant.

[0004] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a negative pressure coupling analysis method for sulfuric acid solutions containing hydrogen fluoride, comprising the following steps: Step S1: The concentrated sulfuric acid solution containing hydrogen fluoride after the acidolysis reaction is passed into a negative pressure coupled desorption tower. The coupling extractant is sprayed at the top of the tower, and the material in the bottom of the tower is recycled and desorbed. Crude hydrogen fluoride is collected at the top of the tower, and sulfuric acid is collected in the bottom of the tower. Step S2: The collected crude hydrogen fluoride is subjected to primary distillation. The top product of the primary distillation column is dried, and the coupling extractant in the bottom of the column is collected and reused. Step S3: The dried primary distillation column top material is subjected to secondary distillation. The secondary distillation column top material is condensed to obtain anhydrous hydrogen fluoride product. The secondary distillation column bottom material is recycled to the negative pressure coupling desorption column for recycling desorption.

[0005] As a preferred embodiment, step S4 is also included: a portion of the sulfuric acid collected in step S1 is compounded with fuming sulfuric acid and reused for acidolysis, and the remainder is reused for phosphoric acid extraction.

[0006] As a preferred embodiment, in step S1, the concentrated sulfuric acid solution containing hydrogen fluoride is the residue after the acidolysis reaction of fluorosilicic acid and sulfuric acid, wherein the concentration of hydrogen fluoride is 1~9%, the concentration of sulfuric acid is 70~76%, the water content is 15~21%, and the concentration of fluorosilicic acid is 0.03~0.07%.

[0007] As a preferred embodiment, in step S1, the vacuum degree inside the negative pressure coupling desorption column is 2~5 kPa; the desorption temperature is 180~210℃; the desorption time is 20~25 min; the bottom material is circulated and desorbed through a reboiler; the bottom reboiler temperature is 150~180℃; and the ratio of feed liquid entering the reboiler to bottom distillate is 1:1~0.5:1.

[0008] As a preferred embodiment, in step S1, the concentration of crude hydrogen fluoride at the top of the column is 30-37%, the water content is 60-66%, the concentration of silicon tetrafluoride is 0.5-0.9%, and the concentration of sulfuric acid is 0.2-0.5%; the concentration of dilute sulfuric acid at the bottom of the column is 80-86%, and the water content is 15-21%.

[0009] As a preferred option, in step S1, the coupling extractant is cyclohexanol, and the volume ratio of cyclohexanol to liquid is 5:1 to 1:1, with a cyclohexanol concentration of 90 to 95%.

[0010] As a preferred option, in step S2, the first-stage distillation conditions are 165~168℃, the top product is hydrogen fluoride containing 8~11% water, which is dried with concentrated sulfuric acid, and the amount of concentrated sulfuric acid introduced is 5~11% of the material mass; the coupling extractant containing 8~10% water is drawn from the bottom of the column and reused in step S1.

[0011] As a preferred option, in step S3, the secondary distillation conditions are 70~75℃, the top product is refined hydrogen fluoride, which is condensed at a low temperature of 4~9℃ to obtain anhydrous hydrogen fluoride; the bottom product is a hydrogen fluoride-water binary azeotrope, which is recycled to step S1 for analytical separation.

[0012] As a preferred option, in step S4, the amount of fuming sulfuric acid used in the sulfuric acid compounding process is 1.25 to 1.5 times the mass of dilute sulfuric acid, the compounding temperature is 110 to 115°C, and the compounding time is 60 to 90 minutes.

[0013] Secondly, the present invention also provides a negative pressure coupled analysis system for sulfuric acid solution containing hydrogen fluoride, which is applicable to the above-mentioned negative pressure coupled analysis method for sulfuric acid solution containing hydrogen fluoride, comprising: a negative pressure coupled analysis tower, a reboiler, a primary distillation tower and a secondary distillation tower; The concentrated sulfuric acid solution containing hydrogen fluoride from the acidolysis process is fed into the inlet of a negative pressure coupled analysis tower. The top of the negative pressure coupled analysis tower is connected to the inlet of a primary distillation tower, and the bottom of the tower is connected to a reboiler. The reboiler is also connected to the inlet of the negative pressure coupled analysis tower to form a cycle. The bottom of the tower is also connected to a phosphoric acid extraction tank and a compounding tank. The compounding tank is connected to the reactor of the acidolysis process. The top of the primary distillation column is connected to the inlet of the secondary distillation column via a drying device, and the bottom of the column is connected to the inlet of the spray unit at the top of the negative pressure coupling desorption column. The top of the secondary distillation column is connected to the condenser, and the bottom is connected to the inlet of the negative pressure coupling analysis column. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of one specific embodiment of the present invention; Figure 2 This is a schematic diagram of the system structure according to one specific embodiment of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased.

[0016] Unless otherwise stated, all percentages in this invention represent mass fractions. Ratios are mass percentages, and concentrations are mass concentrations.

[0017] Unless otherwise specified, all materials, instruments, and equipment used below are conventional materials, instruments, and equipment or obtained through commercial channels; all testing methods used are existing methods unless otherwise specified.

[0018] Existing technologies disclose a process for separating fluorinated sulfuric acid by continuously introducing steam to separate hydrogen fluoride and sulfuric acid. However, this method is highly corrosive to equipment and involves high process temperatures. Furthermore, the continuous steam supply results in excessively low sulfuric acid concentrations, necessitating an additional concentration stage, which increases energy consumption and costs. Existing technologies also employ the introduction of inert gases to reduce gas partial pressure, but this still fails to overcome the limitations of traditional distillation and desorption, and also suffers from drawbacks such as high reaction temperatures and stringent equipment corrosion resistance requirements. While some existing technologies introduce benzyl alcohol as an extractant, this is only applicable to the hydrogen fluoride-water binary system, essentially representing a single-mechanism desorption separation with limited application scenarios. Moreover, the extractant is expensive, and the extractant ratio has not been optimized, resulting in low desorption separation efficiency and hindering industrial application.

[0019] It is evident that most current industry processes for treating this type of hydrogen fluoride-sulfuric acid solution system employ only single-mechanism analysis techniques, and there is still a lack of solutions for multi-mechanism coupled analysis. Furthermore, the separation effect of extractants on the hydrogen fluoride-sulfuric acid-water ternary association system has not received sufficient attention from the industry. Even when a few companies attempt to use extraction methods, they fail to achieve efficient separation due to unreasonable selection of extractant dosage ratios and types.

[0020] Furthermore, in a first aspect, the present invention provides a negative pressure coupling analysis method for sulfuric acid solution containing hydrogen fluoride, comprising the following steps: Step S1: The concentrated sulfuric acid solution containing hydrogen fluoride after the acidolysis reaction is passed into a negative pressure coupled desorption tower. The coupling extractant is sprayed at the top of the tower, and the material in the bottom of the tower is recycled and desorbed. Crude hydrogen fluoride is collected at the top of the tower, and sulfuric acid is collected in the bottom of the tower. Step S2: The collected crude hydrogen fluoride is subjected to primary distillation. The top material of the primary distillation column is dried and the coupling extractant is collected for reuse. Step S3: The dried overhead material from the primary distillation column is subjected to secondary distillation, and the overhead material from the secondary distillation column is condensed to obtain anhydrous hydrogen fluoride product.

[0021] This invention innovatively employs a process combining concentrated sulfuric acid dehydration effect, coupled extraction, and negative pressure circulation analysis, possessing the following significant core advantages: (1) Negative pressure desorption can lower the boiling point of each component and improve the desorption rate.

[0022] (2) Coupled analysis can selectively extract hydrogen fluoride, which solves the problems of incomplete separation and waste of resources caused by unreasonable extractant ratio.

[0023] (3) The process is simple and continuous, the process is compact, the conditions are mild, and it can be adapted to sulfuric acid solutions containing hydrogen fluoride of different concentrations. Compared with the traditional analysis process, it can not only reduce energy consumption, but also avoid equipment corrosion caused by excessive hydrogen fluoride residue. At the same time, it can realize continuous operation, adapt to the needs of large-scale industrial production, and effectively solve the problems of dispersed and incomplete analysis in the traditional analysis process.

[0024] One implementation method also includes step S4: A portion of the sulfuric acid collected in step S1 is compounded with fuming sulfuric acid and reused in the acidolysis reaction, while the remainder is reused in phosphoric acid extraction. This achieves a closed-loop resource system within the process flow, maximizing recycling.

[0025] In one embodiment, in step S1, the concentrated sulfuric acid solution containing hydrogen fluoride is the residue after the acidolysis reaction of fluorosilicic acid and sulfuric acid, wherein the concentration of hydrogen fluoride is 1-9%, the concentration of sulfuric acid is 70-76%, the water content is 15-21%, and the concentration of fluorosilicic acid is 0.03-0.07%. In step S1, the resolution rate is 95-99%.

[0026] The raw material entering the negative pressure coupled analysis tower is the reaction liquid from the acidolysis section of the preceding concentrated sulfuric acid and fluorosilicic acid reaction. The limited concentration and water content can ensure that the pressure inside the negative pressure coupled analysis tower remains constant and reduce the fluctuation of negative pressure inside the tower.

[0027] In one implementation method, in step S1, the vacuum degree inside the negative pressure coupling desorption column is 2~5 kPa; the desorption temperature is 180~210℃; the desorption time is 20~25 min; the bottom material is circulated and desorbed through a reboiler; the bottom reboiler temperature is 150~180℃; and the ratio of the feed liquid entering the reboiler to the bottom distillate is 1:1~0.5:1.

[0028] Negative pressure desorption lowers the boiling points of each component. Combined with reboiler heating, it ensures the feed liquid can be circulated for desorption, improving the desorption rate. Under negative pressure, the boiling points of each component decrease, and the binding force of sulfuric acid on hydrogen fluoride and water decreases, increasing the relative volatility of hydrogen fluoride and promoting its volatilization. By limiting the above process parameters, effective desorption and separation of materials can be ensured in the negative pressure coupled desorption tower, with a desorption rate ≥95%. At the same time, limiting the feed liquid entering the reboiler and the distillate from the bottom of the tower ensures continuous operation of the process and avoids excessive positive pressure from gas inside the negative pressure coupled desorption tower.

[0029] In one embodiment, the crude hydrogen fluoride concentration in step S1 is 30-37%, the water content is 60-66%, the concentration of silicon tetrafluoride generated by the high-temperature decomposition of fluorosilicic acid impurities in the raw material is 0.5-0.9%, and the sulfuric acid concentration is 0.2-0.5%; the concentration of dilute sulfuric acid in the bottom of the tower is 80-86%, and the water content is 15-21%.

[0030] The above-mentioned concentration and water content limits are to constrain the material resolution of the negative pressure coupled desorption tower. If the concentration is too high, the material may undergo ineffective circulation and desorption in the negative pressure coupled desorption tower; if the concentration is too low, the desorption will be incomplete, making it difficult to recover the coupling extractant in step S2 and difficult to control the hydrogen fluoride distillation in step S3.

[0031] In one embodiment, in step S1, the coupling extractant is cyclohexanol, and the volume ratio of cyclohexanol to liquid is 5:1 to 1:1, with a cyclohexanol concentration of 90 to 95%.

[0032] Compared to benzyl alcohol and other extractants, cyclohexanol exhibits better thermal stability and is less prone to decomposition under low-temperature conditions during negative pressure desorption. It is also more affordable (industrial benzyl alcohol costs 9000 RMB / ton, while industrial cyclohexanol costs 7000 RMB / ton). The resulting cycloethanol-hydrogen fluoride mixture is easier to separate. Furthermore, optimizing the cyclohexanol dosage ratio and recycling process solves problems such as incomplete separation and resource waste caused by improper extractant ratios. The coupling effect of cyclohexanol effectively breaks the stable hydrogen bond association system and azeotropic barrier formed by sulfuric acid, hydrogen fluoride, and water, significantly improving the separation efficiency of hydrogen fluoride and further enhancing its reuse feasibility. This fundamentally solves the core problem of the difficulty in completely separating the three components, reducing production costs.

[0033] In one implementation method, in step S2, the first-stage distillation conditions are 165~168℃, the top product is hydrogen fluoride containing 8~10% water, which is dried with concentrated sulfuric acid, and the amount of concentrated sulfuric acid introduced is 5~10% of the material mass; the coupling extractant containing 8~11% water is drawn from the bottom of the column and reused in step S1.

[0034] After analysis, the extractant can be recovered through primary distillation, achieving a purity of over 90% and a reuse rate of over 95%, thus realizing the internal recycling of extractant resources. By limiting the above process parameters, hydrogen fluoride and the coupling extractant can be effectively separated, while ensuring that the concentration of cyclohexanol after separation is ≥90%, achieving the goal of reusing the coupling extractant. Drying the separated hydrogen fluoride with sulfuric acid further concentrates it, reducing the difficulty of the subsequent secondary distillation separation in step S3.

[0035] In one implementation method, in step S3, the secondary distillation conditions are 70~75℃, the top product is refined hydrogen fluoride, which is condensed at a low temperature of 4~9℃ to obtain anhydrous hydrogen fluoride; the bottom product is a hydrogen fluoride-water binary azeotrope, which is recycled to step S1 for analysis and separation.

[0036] Limiting the above process parameters can effectively separate the remaining water in hydrogen fluoride, allowing for further purification and concentration, and improving the purity of hydrogen fluoride. Hydrogen fluoride has a boiling point of 19℃, and condensation at 4~9℃ ensures complete liquefaction of the hydrogen fluoride to obtain anhydrous hydrogen fluoride with a purity ≥99.99%.

[0037] In one embodiment, in step S4, the amount of fuming sulfuric acid used in the sulfuric acid compounding process is 1.25 to 1.5 times the mass of dilute sulfuric acid, the compounding temperature is 110 to 115°C, and the compounding time is 60 to 90 minutes. The amount of sulfuric acid in the compounded portion is 5 to 8%.

[0038] By limiting the above process parameters, partial internal circulation of sulfuric acid can be achieved, with the remaining dilute sulfuric acid being recycled into a phosphoric acid extraction tank. This method relies on fuming sulfuric acid to concentrate dilute sulfuric acid through compounding, simplifying the conventional dilute sulfuric acid concentration process and reducing energy consumption.

[0039] Secondly, such as Figure 1 , 2 As shown, the present invention also provides a negative pressure coupled analysis system for sulfuric acid solution containing hydrogen fluoride, which is applicable to the above-mentioned negative pressure coupled analysis method for sulfuric acid solution containing hydrogen fluoride, comprising: a negative pressure coupled analysis tower, a reboiler, a primary distillation tower and a secondary distillation tower; The feed pipe of the acid hydrolysis process is connected to the inlet of the negative pressure coupling analysis tower. The top of the negative pressure coupling analysis tower is connected to the inlet of the first-stage distillation tower, and the bottom of the tower is connected to the reboiler. The reboiler is connected to the inlet of the negative pressure coupling analysis tower via a pump. The bottom of the tower is also connected to the phosphoric acid extraction tank and the compounding tank. The compounding tank is connected to the reactor of the acid hydrolysis process. The top of the primary distillation column is connected to the inlet of the secondary distillation column via a drying device, and the bottom of the column is connected to the inlet of the spray unit at the top of the negative pressure coupling desorption column. The top of the secondary distillation column is connected to the condenser, and the bottom is connected to the inlet of the negative pressure coupling analysis column. The negative pressure coupling analysis column is preferably made of Hastelloy alloy and uses PTFE packing. All piping is made of 316L stainless steel with an internal PTFE coating, and the interface gaskets are flexible graphite gaskets.

[0040] Compared with existing single separation processes, this invention uses three processes in synergy: dehydration effect, coupled extraction, and negative pressure desorption, and is equipped with corresponding equipment to break the hydrogen bond association of the sulfuric acid-hydrogen fluoride-water ternary mixture, which greatly improves the desorption rate. Moreover, the coupled extractant achieves resource closed loop in the process flow, maximizing recycling.

[0041] The system of this invention can be seamlessly integrated with existing fluorochemical production processes, facilitating large-scale industrial application. It can effectively solve the core dilemmas of difficult separation, strong corrosion, high cost, and heavy environmental pressure in the treatment of sulfuric acid solutions containing hydrogen fluoride, realize the recycling of fluorine and sulfur resources, and combine technological advancement, economic feasibility, and green environmental protection. It is one of the optimal process routes for the treatment of sulfuric acid solutions containing hydrogen fluoride in the fluorochemical industry.

[0042] The following describes in detail a negative pressure coupling analytical method and system for sulfuric acid solutions containing hydrogen fluoride, with reference to specific embodiments.

[0043] The equipment involved in the embodiments: Negative pressure coupled desorption tower: HF-sulfuric acid negative pressure desorption tower (commercially available product) Reboiler: Commercially available product Primary Distillation Column: Explosion-proof Stainless Steel Distillation Column EX QYSJL-25L Secondary distillation column: Explosion-proof stainless steel distillation column EX QYSJL-25L Condensation equipment: GLC3-6 shell and tube cooler.

[0044] Drying equipment: Sulfuric acid drying tower (commercially available product) An example of a negative pressure coupling analysis method for sulfuric acid solution containing hydrogen fluoride includes the following steps: Step S1: Collect the concentrated sulfuric acid residue containing hydrogen fluoride after the reaction of sulfuric acid and fluorosilicic acid and pass it into a negative pressure coupled desorption tower, wherein the concentration of hydrogen fluoride is 1~9%, the concentration of sulfuric acid is 70~76%, the water content is 15~21%, and the concentration of fluorosilicic acid is 0.03~0.07%.

[0045] The vacuum degree inside the column is 2~5 kPa, the desorption temperature is 180~210℃, the desorption time is 20~25 min, and cyclohexanol is sprayed from the top of the column as a coupling extractant. The feed rate is cyclohexanol: feed liquid = 1:1~5:1 (volume ratio), and the concentration of cyclohexanol is 90~95%. The temperature of the reboiler at the bottom of the column is 150~180℃, and the ratio of the feed liquid entering the reboiler to the distillate at the bottom of the column is 1:1~0.5:1.

[0046] Crude hydrogen fluoride is collected at the top of the tower, with a hydrogen fluoride concentration of 30-37% and a water content of 60-66%, a silicon tetrafluoride concentration of 0.5-0.9%, and a sulfuric acid concentration of 0.2-0.5%. Sulfuric acid is collected at the bottom of the tower, with a sulfuric acid concentration of 80-86% and a water content of 15-21%.

[0047] Step S2: The crude hydrogen fluoride at the top of the column is subjected to primary distillation at a temperature of 165-168°C. The top product is a light component containing 8-11% water, which is then dried by passing concentrated sulfuric acid through it. The amount of concentrated sulfuric acid passed through is 5-10% of the mass of the material. Cyclohexanol containing 8-11% water is drawn from the bottom of the column and reused as a coupling extractant in step S1.

[0048] Step S3: The top component of the primary distillation column is further distilled in a secondary distillation at a temperature of 70~75°C. The top product is a light component refined hydrogen fluoride, which is condensed at a low temperature of 4~9°C to obtain anhydrous hydrogen fluoride. The bottom product is a hydrogen fluoride-water binary azeotrope, which is recycled to step S1 for analysis and separation.

[0049] Step S4: Part of the sulfuric acid collected in the reboiler of Step S1 is recycled to the phosphoric acid extraction tank. The remaining portion is compounded with fuming sulfuric acid. The amount of sulfuric acid in the compounded portion is 5-8%, and the amount added is 1.25-1.5 times the mass of the dilute sulfuric acid. The compounding temperature is 110-115℃, and the compounding time is 60-90 minutes. The resulting concentrated sulfuric acid is recycled to the acidolysis process. The remaining portion is recycled to the phosphoric acid extraction tank. The overall resolution rate is 95-99%.

[0050] Example 1

[0051] The negative pressure coupling analytical method for sulfuric acid solution containing hydrogen fluoride in this embodiment: In step S1: the concentration of hydrogen fluoride is 1.03%, the concentration of sulfuric acid is 70.21%, the water content is 20.11%, and the concentration of fluorosilicic acid is 0.065%.

[0052] The vacuum level inside the column is 2 kPa; the desorption temperature is 180℃, the desorption time is 20 min, the feed rate is cyclohexanol: feed liquid = 3:1 (volume ratio), the cyclohexanol concentration is 90%; the reboiler temperature at the bottom of the column is 150℃, and the ratio of feed liquid entering the reboiler to distillate liquid at the bottom of the column is 0.5:1.

[0053] Crude hydrogen fluoride is collected at the top of the column, with a hydrogen fluoride concentration of 31.52%, a water content of 65.11%, a silicon tetrafluoride concentration of 0.526%, and a sulfuric acid concentration of 0.401%. Sulfuric acid is collected at the bottom of the column, with a sulfuric acid concentration of 80.39% and a water content of 20.24%.

[0054] In step S2: the crude hydrogen fluoride at the top of the column undergoes primary distillation at a temperature of 165°C. The top product is a light component containing 10.45% water, which is then dried by passing concentrated sulfuric acid through it at a rate of 5% of the material mass. Cyclohexanol containing 10.02% water is drawn from the bottom of the column and reused as a coupling extractant in step S1.

[0055] In step S3: the top component of the primary distillation column is further distilled in a secondary distillation at a temperature of 70°C. The top component is purified hydrogen fluoride, which is then condensed at a low temperature of 4°C to obtain anhydrous hydrogen fluoride.

[0056] In step S4: the sulfuric acid collected in the column in step S1 is partially recycled to the phosphoric acid extraction tank, and the remaining part is compounded with fuming sulfuric acid. The amount added is 1.25 times the mass of dilute sulfuric acid, the compounding temperature is 110℃, and the compounding time is 60 min, so that the concentrated sulfuric acid is recycled to the acidolysis process.

[0057] Example 2

[0058] The negative pressure coupling analytical method for sulfuric acid solution containing hydrogen fluoride in this embodiment: In step S1: the concentration of hydrogen fluoride is 5.36%, the concentration of sulfuric acid is 72.34%, the water content is 18.46%, and the concentration of fluorosilicic acid is 0.049%.

[0059] The vacuum degree inside the column was 3.5 kPa; the desorption temperature was 190℃; the desorption time was 23 min; cyclohexanol was sprayed from the top of the column as a coupling extractant, and the feed rate was cyclohexanol: feed liquid = 4:1 (volume ratio), with a cyclohexanol concentration of 92.5%.

[0060] The reboiler temperature at the bottom of the column is 170℃, and the ratio of feed liquid to distillate liquid entering the reboiler is 0.7:1. Crude hydrogen fluoride is collected at the top of the column, with a hydrogen fluoride concentration of 32.59%, a water content of 63.59%, a silicon tetrafluoride concentration of 0.605%, and a sulfuric acid concentration of 0.336%. Sulfuric acid is collected at the bottom of the column, with a sulfuric acid concentration of 82.43% and a water content of 17.15%.

[0061] In step S2: the crude hydrogen fluoride at the top of the column undergoes primary distillation at a temperature of 167°C. The top product is a light component containing 9.16% water, which is then dried by passing concentrated sulfuric acid through it at a rate of 8% of the material mass. Cyclohexanol containing 9.34% water is drawn from the bottom of the column and reused as a coupling extractant in step S1.

[0062] In step S3: the top component of the primary distillation column is further distilled in a secondary distillation at a temperature of 73°C. The top product is a light component refined hydrogen fluoride, which is condensed at a low temperature of 6°C to obtain anhydrous hydrogen fluoride. The bottom product is a hydrogen fluoride-water binary azeotrope, which is recycled to step S1 for analysis and separation.

[0063] In step S4: the sulfuric acid collected in the column in step S1 is partially recycled to the phosphoric acid extraction tank, and the remaining part is compounded with fuming sulfuric acid. The amount added is 1.4 times the mass of dilute sulfuric acid, the compounding temperature is 112℃, and the compounding time is 70 min, so that the concentrated sulfuric acid is recycled to the acidolysis process.

[0064] Example 3

[0065] The negative pressure coupling analytical method for sulfuric acid solution containing hydrogen fluoride in this embodiment: In step S1: the concentration of hydrogen fluoride is 8.02%, the concentration of sulfuric acid is 75.04%, the water content is 15.65%, and the concentration of fluorosilicic acid is 0.034%.

[0066] The vacuum degree inside the column is 5 kPa; the desorption temperature is 210℃; the desorption time is 25 min; cyclohexanol is sprayed from the top of the column as a coupling extractant, and the feed rate is cyclohexanol: feed liquid = 5:1 (volume ratio), and the concentration of cyclohexanol is 95%.

[0067] The reboiler temperature at the bottom of the column is 180℃, and the ratio of feed liquid to distillate liquid entering the reboiler is 1:1. Crude hydrogen fluoride is collected at the top of the column, with a hydrogen fluoride concentration of 36.06%, a water content of 60.02%, a silicon tetrafluoride concentration of 0.811%, and a sulfuric acid concentration of 0.202%. Sulfuric acid is collected at the bottom of the column, with a sulfuric acid concentration of 85.16% and a water content of 15.11%.

[0068] In step S2: the crude hydrogen fluoride at the top of the column undergoes primary distillation at a temperature of 168°C. The top product is a light component containing 8.08% water, which is then dried by passing concentrated sulfuric acid through it. The amount of concentrated sulfuric acid passed through is 10% of the mass of the material. Cyclohexanol containing 7.98% water is drawn from the bottom of the column and reused as a coupling extractant in step S1.

[0069] In step S3: the top component of the primary distillation column is further distilled in a secondary distillation at a temperature of 75°C. The top product is a light component refined hydrogen fluoride, which is condensed at a low temperature of 9°C to obtain anhydrous hydrogen fluoride. The bottom product is a hydrogen fluoride-water binary azeotrope, which is recycled to step S1 for analysis and separation.

[0070] Step S4: Part of the sulfuric acid collected in the column in step S1 is recycled to the phosphoric acid extraction tank. The remaining part is mixed with fuming sulfuric acid at a ratio of 1.5 times the mass of dilute sulfuric acid. The mixing temperature is 115℃ and the mixing time is 90 min to obtain concentrated sulfuric acid which is recycled to the front-end acidolysis process.

[0071] Comparative Example 1 (Analysis of Pressure Anomaly): In step S1: the pressure inside the tower is 3 kPa (positive pressure). The rest is the same as in Example 2.

[0072] Crude hydrogen fluoride is collected at the top of the column, with a hydrogen fluoride concentration of 28.23%, a water content of 70.77%, a silicon tetrafluoride concentration of 0.614%, and a sulfuric acid concentration of 0.38%. Sulfuric acid is collected at the bottom of the column, with a sulfuric acid concentration of 86.28% and a water content of 13.71%.

[0073] Comparative Example 2 (Analysis of Temperature Anomalies) In step S1: the analysis temperature is 170℃. The rest is the same as in Example 2.

[0074] Crude hydrogen fluoride is collected at the top of the tower, with a hydrogen fluoride concentration of 25.16%, a water content of 73.89%, a silicon tetrafluoride concentration of 0.708%, and a sulfuric acid concentration of 0.238%. Sulfuric acid is collected at the bottom of the tower, with a sulfuric acid concentration of 90.36% and a water content of 9.58%.

[0075] Comparative Example 3 (Abnormal Reboiler Circulation Ratio) In step S1, the ratio of feed liquid to bottom distillate in the reboiler is 0.4:1. The rest is the same as in Example 2.

[0076] Crude hydrogen fluoride is collected at the top of the column, with a hydrogen fluoride concentration of 27.67%, a water content of 71.38%, a silicon tetrafluoride concentration of 0.668%, and a sulfuric acid concentration of 0.277%. Sulfuric acid is collected at the bottom of the column, with a sulfuric acid concentration of 88.29% and a water content of 11.68%.

[0077] Comparative Example 4 (abnormal ratio of fuming sulfuric acid) Step S4: Part of the sulfuric acid collected in the column bottom of step S1 is recycled to the phosphoric acid extraction tank. The remaining part is compounded with fuming sulfuric acid, the amount added is 1 times the mass of the dilute sulfuric acid, the compounding temperature is 100℃, and the compounding time is 30 min, to obtain concentrated sulfuric acid which is recycled to the front-end acidolysis process. The rest is the same as in Example 2.

[0078] Comparative Example 5 (Benzyl alcohol as extractant) In step S1: the concentration of hydrogen fluoride is 5.47%, the concentration of sulfuric acid is 72.53%, the water content is 18.64%, and the concentration of fluorosilicic acid is 0.042%.

[0079] The vacuum level inside the column was 3.5 kPa; the desorption temperature was 190℃, and the desorption time was 25 min. Cyclohexanol was sprayed from the top of the column as a coupling extractant, with a benzyl alcohol:feed ratio of 4:1 (volume ratio) and a benzyl alcohol concentration of 95%. The reboiler temperature at the bottom of the column was 170℃, and the ratio of feed to distillate entering the reboiler was 0.7:1. Crude hydrogen fluoride was collected at the top of the column, with a hydrogen fluoride concentration of 23.35% and a water content of 66.17%, a silicon tetrafluoride concentration of 0.821%, and a sulfuric acid concentration of 0.517%. Sulfuric acid was collected at the bottom of the column, with a sulfuric acid concentration of 78.55% and a water content of 20.28%.

[0080] Step S2: The crude hydrogen fluoride at the top of the column is subjected to primary distillation at a temperature of 167°C. The top product is a light component containing 11.46% water, which is then dried by passing concentrated sulfuric acid through it at a rate of 8% of the material mass. Benzyl alcohol containing 9.75% water is drawn from the bottom of the column and reused as a coupling extractant in step S1.

[0081] Step S3: The top component of the primary distillation column is further distilled in a secondary distillation at a temperature of 75°C. The top product is a light component refined hydrogen fluoride, which is condensed at a low temperature of 6°C to obtain anhydrous hydrogen fluoride. The bottom product is a hydrogen fluoride-water binary azeotrope, which is recycled to step S1 for analysis and separation.

[0082] Step S4: Part of the sulfuric acid collected in the column in step S1 is recycled to the phosphoric acid extraction tank. The remaining part is compounded with fuming sulfuric acid at a ratio of 1.4 times the mass of dilute sulfuric acid. The compounding temperature is 115℃ and the compounding time is 75 min to obtain concentrated sulfuric acid which is recycled to the front-end acidolysis process.

[0083] Comparative Example 6 (Single analytical process, without the addition of coupling extractant) In step S1: The residual sulfuric acid solution containing hydrogen fluoride after the reaction of sulfuric acid and fluorosilicic acid (where the concentration of hydrogen fluoride is 8.02%, the concentration of sulfuric acid is 75.04%, the water content is 15.65%, and the concentration of fluorosilicic acid is 0.034%) is collected and passed into a negative pressure coupling analysis tower.

[0084] The vacuum degree inside the column is 5 kPa; the desorption temperature is 210℃, the desorption time is 25 min; the temperature of the reboiler at the bottom of the column is 180℃, and the ratio of feed liquid entering the reboiler to distillate liquid at the bottom of the column is 1:1.

[0085] Crude hydrogen fluoride is collected at the top of the column, with a hydrogen fluoride concentration of 36.06%, a water content of 60.02%, a silicon tetrafluoride concentration of 0.811%, and a sulfuric acid concentration of 0.202%. Sulfuric acid is collected at the bottom of the column, with a sulfuric acid concentration of 85.16% and a water content of 15.11%.

[0086] Step S2: The crude hydrogen fluoride at the top of the column undergoes primary distillation at a temperature of 168°C. The top product is a light component containing 8.08% water, which is then dried by passing concentrated sulfuric acid through it. The amount of concentrated sulfuric acid passed through is 10% of the mass of the material. The bottom effluent is recycled to step S1.

[0087] Step S3: The top component of the primary distillation column is further distilled in a secondary distillation at a temperature of 75°C. The top product is a light component refined hydrogen fluoride, which is condensed at a low temperature of 9°C to obtain anhydrous hydrogen fluoride. The bottom product is a hydrogen fluoride-water binary azeotrope, which is recycled to step S1 for analysis and separation.

[0088] Step S4: Part of the sulfuric acid collected in the column in step S1 is recycled to the phosphoric acid extraction tank. The remaining part is mixed with fuming sulfuric acid. The amount added is 1.5 times the mass of dilute sulfuric acid. The mixing temperature is 115℃ and the mixing time is 90 min. The resulting concentrated sulfuric acid is recycled to the acidolysis process.

[0089] The relevant data for the above embodiments and comparative examples are shown in Table 1: Table 1. Relevant parameters and effects of the embodiments and comparative examples. The overall resolution rate in the table is calculated as the ratio of the total amount of hydrogen fluoride at the top of the desorption column to the total amount of hydrogen fluoride in the feedstock; the cyclohexanol recovery rate is the ratio of the mass of the recycled cyclohexanol to the total mass of the added cyclohexanol. Testing was conducted according to GB / T 7746-2023 "Industrial Anhydrous Hydrogen Fluoride". As shown in Table 1, within the conditions of the examples, the anhydrous hydrogen fluoride product meets the requirements for first-class products in GB / T 7746-2023 "Industrial Anhydrous Hydrogen Fluoride". Furthermore, the cyclohexanol recovery rate is ≥95%, and the resolution rate is ≥95%. The cyclohexanol concentration was analyzed by gas chromatography according to HG / T 4121-2023. The sulfuric acid reuse concentration was analyzed using the sodium hydroxide standard titration method according to GB / T 534-2024 "Industrial Sulfuric Acid".

[0090] By comparing with the comparative examples, it is clear that the negative pressure coupled desorption process is significantly superior to the single separation process. Cyclohexanol extractant shows significantly better separation effect for hydrogen fluoride than other extractants, and is also more economical and environmentally friendly. Abnormalities in desorption pressure, desorption temperature, reboiler circulation ratio, and the formulation of fuming sulfuric acid all resulted in inferior results compared to Examples 1-3.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A negative pressure coupled analytical method for sulfuric acid solution containing hydrogen fluoride, characterized in that: Includes the following steps: Step S1: The concentrated sulfuric acid solution containing hydrogen fluoride after the acidolysis reaction is passed into a negative pressure coupled desorption tower. The coupling extractant is sprayed at the top of the tower, and the material in the bottom of the tower is recycled and desorbed. Crude hydrogen fluoride is collected at the top of the tower, and sulfuric acid is collected in the bottom of the tower. Step S2: The collected crude hydrogen fluoride is subjected to primary distillation. The top product of the primary distillation column is dried, and the coupling extractant in the bottom of the column is collected and reused. Step S3: The dried primary distillation column top material is subjected to secondary distillation. The secondary distillation column top material is condensed to obtain anhydrous hydrogen fluoride product. The secondary distillation column bottom material is recycled to the negative pressure coupling desorption column for recycling desorption.

2. The negative pressure coupling desorption method for sulfuric acid solution containing hydrogen fluoride according to claim 1, characterized in that: It also includes step S4: part of the sulfuric acid collected in step S1 is compounded with fuming sulfuric acid and reused for acidolysis reaction, and the remainder is reused for phosphoric acid extraction.

3. The negative pressure coupling desorption method for sulfuric acid solution containing hydrogen fluoride according to claim 1, characterized in that: In step S1, the concentrated sulfuric acid solution containing hydrogen fluoride is the residue after the acidolysis reaction of fluorosilicic acid and sulfuric acid, wherein the concentration of hydrogen fluoride is 1~9%, the concentration of sulfuric acid is 70~76%, the water content is 15~21%, and the concentration of fluorosilicic acid is 0.03~0.07%.

4. The negative pressure coupling desorption method for sulfuric acid solution containing hydrogen fluoride according to claim 1, characterized in that: In step S1, the vacuum degree inside the negative pressure coupling desorption column is 2~5 kPa; the desorption temperature is 180~210℃; the desorption time is 20~25 min; the bottom material is circulated and desorbed through a reboiler; the bottom reboiler temperature is 150~180℃; and the ratio of feed liquid entering the reboiler to bottom distillate is 1:1~0.5:

1.

5. The negative pressure coupling desorption method for sulfuric acid solution containing hydrogen fluoride according to claim 1, characterized in that: In step S1, the concentration of crude hydrogen fluoride at the top of the column is 30-37%, the water content is 60-66%, the concentration of silicon tetrafluoride is 0.5-0.9%, and the concentration of sulfuric acid is 0.2-0.5%; the concentration of dilute sulfuric acid at the bottom of the column is 80-86%, and the water content is 15-21%.

6. The negative pressure coupling desorption method for sulfuric acid solution containing hydrogen fluoride according to claim 1, characterized in that: In step S1, the coupling extractant is cyclohexanol, and the volume ratio of cyclohexanol to liquid is 5:1 to 1:1, with a cyclohexanol concentration of 90 to 95%.

7. The negative pressure coupling desorption method for sulfuric acid solution containing hydrogen fluoride according to claim 1, characterized in that: In step S2, the first-stage distillation conditions are 165~168℃, and the top product is hydrogen fluoride containing 8~11% water, which is dried with concentrated sulfuric acid, with the amount of concentrated sulfuric acid introduced being 5~11% of the material mass; the coupling extractant containing 8~10% water is drawn from the bottom of the column and reused in step S1.

8. The negative pressure coupling desorption method for sulfuric acid solution containing hydrogen fluoride according to claim 1, characterized in that: In step S3, the secondary distillation conditions are 70~75℃. The top product is refined hydrogen fluoride, which is condensed at a low temperature of 4~9℃ to obtain anhydrous hydrogen fluoride. The bottom product is a hydrogen fluoride-water binary azeotrope, which is recycled to step S1 for analysis and separation.

9. The negative pressure coupling desorption method for sulfuric acid solution containing hydrogen fluoride according to claim 2, characterized in that: In step S4, the amount of fuming sulfuric acid used in the sulfuric acid compounding process is 1.25 to 1.5 times the mass of dilute sulfuric acid, the compounding temperature is 110 to 115°C, and the compounding time is 60 to 90 minutes.

10. A negative pressure coupled analytical system for sulfuric acid solution containing hydrogen fluoride, characterized in that: The negative pressure coupled desorption method for sulfuric acid solution containing hydrogen fluoride according to any one of claims 1 to 9 includes: a negative pressure coupled desorption column, a reboiler, a primary distillation column and a secondary distillation column; The concentrated sulfuric acid solution containing hydrogen fluoride from the acidolysis process is fed into the inlet of a negative pressure coupled analysis tower. The top of the negative pressure coupled analysis tower is connected to the inlet of a primary distillation tower, and the bottom of the tower is connected to a reboiler. The reboiler is also connected to the inlet of the negative pressure coupled analysis tower to form a cycle. The bottom of the tower is also connected to a phosphoric acid extraction tank and a compounding tank. The compounding tank is connected to the reactor of the acidolysis process. The top of the primary distillation column is connected to the inlet of the secondary distillation column via a drying device, and the bottom of the column is connected to the inlet of the spray unit at the top of the negative pressure coupling desorption column. The top of the secondary distillation column is connected to the condenser, and the bottom is connected to the inlet of the negative pressure coupling analysis column.

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