A method for producing low-arsenic anhydrous hydrogen fluoride

Abstract

This invention provides a method for preparing low-arsenic anhydrous hydrogen fluoride, relating to the field of hydrogen fluoride preparation technology. The preparation method includes the following steps: (1) crude hydrogen fluoride from a storage tank is passed through a primary distillation column to obtain anhydrous hydrogen fluoride. The anhydrous hydrogen fluoride is then introduced into a pretreatment tank, and potassium permanganate solution is added for stirring and reaction to obtain a mixture; (2) the mixture is sequentially passed into a secondary distillation column and a tertiary distillation column for distillation to obtain low-arsenic anhydrous hydrogen fluoride. This invention changes the non-acid-discharge method of the primary distillation column to an acid-discharge method, and sets a pretreatment process between the original primary and secondary distillations to effectively utilize potassium permanganate solution for arsenic removal. Then, the arsenic compounds in the product are oxidized and carried away through the distillation column, thereby effectively purifying the product without generating new hazardous waste. This method can increase the continuous production capability of existing hydrogen fluoride production systems without major modifications.

Description

Technical Field

[0001] This invention relates to the field of hydrogen fluoride preparation technology, and in particular to a method for preparing low-arsenic anhydrous hydrogen fluoride. Background Technology

[0002] Electronic-grade hydrofluoric acid is an aqueous solution of anhydrous hydrogen fluoride. It is a colorless, transparent, and volatile liquid at room temperature, with a pungent odor and extremely strong corrosiveness. It is mainly used in liquid crystal displays, very large-scale integrated circuits, solar photovoltaic panels, etc., and can also be used for high-purity chemical analysis. It has a wide range of applications.

[0003] The preparation process of electronic-grade hydrofluoric acid mainly involves pretreatment and purification by distillation of industrial-grade hydrofluoric acid, followed by mixing with high-purity water. The main methods for preparing hydrogen fluoride are the fluorite-sulfuric acid method and the fluorosilicic acid method. During the preparation process, sulfuric acid, fluorosilicic acid, sulfur dioxide, and aspartic acid are often present. 3+ Fe 2+ NO 3- Cl - Impurities, including As 3+ Arsenic exists in the form of arsenic trioxide and can form an azeotropic reaction with hydrogen fluoride, making it difficult to remove by distillation. Therefore, arsenic removal is necessary before distillation. However, traditional arsenic removal methods generate a large amount of arsenic-containing waste residue. Although some processes can reduce the arsenic content in hydrogen fluoride products, they are not suitable for continuous industrial production and increase the possibility of contamination of low-arsenic products, making large-scale application difficult. In addition, unreasonable process parameter settings during the preparation process also affect the arsenic removal effect of hydrogen fluoride during preparation. Summary of the Invention

[0004] In view of this, the present invention proposes a method for preparing low-arsenic anhydrous hydrogen fluoride.

[0005] The technical solution of this invention is implemented as follows: A method for preparing low-arsenic anhydrous hydrogen fluoride includes the following steps: (1) The crude hydrogen fluoride from the storage tank is passed through a primary distillation column to obtain anhydrous hydrogen fluoride. The flow rate of the mixture into the primary distillation column is 2~6 m³ / s. 3 / h, reflux ratio of 4~5:1, pressure of 0.2~0.4MPa, bottom temperature of 60~90℃, top temperature of 35~45℃, anhydrous hydrogen fluoride is introduced into the pretreatment tank, and then potassium permanganate solution is added and stirred to obtain a mixture. (2) The mixture is sequentially fed into a two-stage distillation column and a three-stage distillation column for distillation to obtain low-arsenic anhydrous hydrogen fluoride; the flow rate of the mixture fed into the two-stage distillation column is 2~5 m³ / h. 3The reflux ratio is 4~6:1, the top pressure is depressurized every 12~15 minutes, the pressure is 0.2~0.5MPa, the bottom temperature is 60~80℃, and the top temperature is 35~40℃.

[0006] Furthermore, the gas phase discharged from the bottom of the first-stage distillation column, the gas phase discharged from the bottom of the second-stage distillation column, and the waste acid discharged from the third-stage distillation column are recovered through a mixer.

[0007] Furthermore, the mass concentration of the potassium permanganate solution is 3-8%.

[0008] Furthermore, the amount of potassium permanganate solution added is 0.03% to 0.06% of the mass of anhydrous hydrogen fluoride.

[0009] Furthermore, the stirring reaction temperature is 15~25℃, the stirring speed is 200~300rpm, and the time is 8~12h.

[0010] Furthermore, the primary distillation column is subjected to acid removal every 30-40 minutes.

[0011] Furthermore, the flow rate of the mixture introduced into the primary distillation column is 5 m³ / s. 3 The flow rate is 1 / h, the reflux ratio is 3:1, the pressure is 0.4 MPa, the bottom temperature is 80℃, and the top temperature is 45℃.

[0012] Furthermore, the flow rate of the mixture introduced into the secondary distillation column is 4 m³ / s. 3 The flow rate is 1 h, the reflux ratio is 5:1, the top pressure is depressurized every 12 min, the pressure is 0.4 MPa, the bottom temperature is 70℃, and the top temperature is 40℃.

[0013] Furthermore, the flow rate of the three-stage distillation column is 2~5m³. 3 The reflux ratio is 3~5:1, the top pressure is depressurized 100~160min / time, the pressure is 0.05~0.1MPa, the bottom temperature is 40~50℃, and the top temperature is 19~21℃.

[0014] Furthermore, the flow rate introduced into the three-stage distillation column is 5m³. 3 The reflux ratio is 4:1, the top pressure is depressurized every 120 min, the pressure is 0.09 MPa, the bottom temperature is 50℃, and the top temperature is 19.6℃.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention modifies the primary distillation column from a non-acid-discharge method to an acid-discharge method, and incorporates a pretreatment process between the primary and secondary distillations to effectively remove arsenic using potassium permanganate solution. The arsenic compounds in the product are then oxidized and carried away by the distillation column, thus effectively purifying the product without generating new hazardous waste. This method can enable continuous production in existing hydrogen fluoride production systems without major modifications.

[0016] The method of this invention is simple in process and low in investment cost, improves product quality, increases the added value of hydrogen fluoride, and achieves the goal of reducing costs and increasing efficiency.

[0017] The preparation method of the present invention does not require the introduction of other chemical reagents during the efficient removal of arsenic, thus avoiding the introduction of other new impurities and effectively reducing the risk of secondary pollution of hydrogen fluoride products. Attached Figure Description

[0018] Figure 1 The flowcharts show the preparation process of low-arsenic anhydrous hydrogen fluoride in Examples 1-4 of this invention.

[0019] Figure 2 The process flow diagram for preparing low-arsenic anhydrous hydrogen fluoride is shown in Comparative Example 4.

[0020] In the diagram, 1-storage tank, 2-first-stage distillation column, 3-pretreatment tank, 4-second-stage distillation column, and 5-third-stage distillation column. Detailed Implementation

[0021] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0022] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0023] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0024] Example 1 A method for preparing low-arsenic anhydrous hydrogen fluoride includes the following steps: (1) The crude hydrogen fluoride from storage tank 1 is passed through a primary distillation column 2 to obtain anhydrous hydrogen fluoride. The flow rate of the mixture into the primary distillation column 2 is 2 m³ / s. 3 / h, reflux ratio of 3:1, pressure of 0.2MPa, bottom temperature of 60℃, top temperature of 35℃, acid discharge every 30min; (2) Anhydrous hydrogen fluoride is introduced into pretreatment tank 3, and then potassium permanganate solution with a mass concentration of 3% is added in three portions according to 0.03% of the mass of anhydrous hydrogen fluoride in pretreatment tank 3. The mixture is stirred and reacted for 8 hours at a temperature of 15℃ and a stirring speed of 200rpm to obtain a mixture. (3) The mixture is sequentially fed into a secondary distillation column 4 and a tertiary distillation column 5 for distillation to obtain low-arsenic anhydrous hydrogen fluoride; the flow rate of the mixture fed into the secondary distillation column 4 is 2 m³ / s. 3 The flow rate is 2 m³ / h, the reflux ratio is 3:1, the top pressure is depressurized every 12 minutes, the pressure is 0.2 MPa, the bottom temperature is 60℃, and the top temperature is 35℃; the flow rate of the three-stage distillation column 5 is 2 m³ / h. 3 / h, reflux ratio of 3:1, top depressurization every 100min / time, pressure of 0.05MPa, bottom temperature of 45℃, top temperature of 20℃; (4) The gas phase discharged from the bottom of the first-stage distillation column 2, the gas phase discharged from the bottom of the second-stage distillation column 4, and the waste acid discharged from the third-stage distillation column 5 are recovered by passing them through a mixer.

[0025] Example 2 A method for preparing low-arsenic anhydrous hydrogen fluoride includes the following steps: (1) The crude hydrogen fluoride from storage tank 1 is passed through a primary distillation column 2 to obtain anhydrous hydrogen fluoride. The flow rate of the mixture into the primary distillation column 2 is 6 m³ / s. 3 The reflux ratio is 4:1, the pressure is 0.4MPa, the bottom temperature is 90℃, the top temperature is 45℃, and acid is discharged every 40 minutes. (2) Anhydrous hydrogen fluoride is introduced into pretreatment tank 3, and then potassium permanganate solution with a mass concentration of 8% is added in 4 portions according to 0.06% of the mass of anhydrous hydrogen fluoride in pretreatment tank 3. The mixture is stirred and reacted for 12 hours at a temperature of 25℃ and a stirring speed of 300rpm to obtain a mixture. (3) The mixture is sequentially fed into the secondary distillation column 4 and the tertiary distillation column 5 for distillation to obtain low-arsenic anhydrous hydrogen fluoride; the flow rate of the mixture fed into the secondary distillation column 4 is 5 m³ / s. 3 The flow rate is 5 m³ / h, the reflux ratio is 6:1, the top pressure is depressurized every 15 minutes, the pressure is 0.5 MPa, the bottom temperature is 80℃, and the top temperature is 40℃; the flow rate of the three-stage distillation column 5 is 5 m³ / h. 3 / h, reflux ratio of 5:1, top depressurization every 160 min / time, pressure of 0.1 MPa, bottom temperature of 50℃, top temperature of 20℃; (4) The gas phase discharged from the bottom of the first-stage distillation column 2, the gas phase discharged from the bottom of the second-stage distillation column 4, and the waste acid discharged from the third-stage distillation column 5 are recovered by passing them through a mixer.

[0026] Example 3 A method for preparing low-arsenic anhydrous hydrogen fluoride includes the following steps: (1) The crude hydrogen fluoride from storage tank 1 is passed through a primary distillation column 2 to obtain anhydrous hydrogen fluoride. The flow rate of the mixture into the primary distillation column 2 is 4 m³ / s. 3 / h, reflux ratio of 5:1, pressure of 0.3MPa, bottom temperature of 70℃, top temperature of 40℃, acid is discharged once every 32min; (2) Anhydrous hydrogen fluoride is introduced into pretreatment tank 3, and then potassium permanganate solution with a mass concentration of 7% is added in three portions according to 0.06% of the mass of anhydrous hydrogen fluoride in pretreatment tank 3. The mixture is stirred and reacted for 9 hours at a temperature of 20℃ and a stirring speed of 250rpm to obtain a mixture. (3) The mixture is sequentially fed into the secondary distillation column 4 and the tertiary distillation column 5 for distillation to obtain low-arsenic anhydrous hydrogen fluoride; the flow rate of the mixture fed into the secondary distillation column 4 is 5 m³ / s. 3 The flow rate is 4 m³ / h, the reflux ratio is 4:1, the top pressure is depressurized every 14 min / time, the pressure is 0.3 MPa, the bottom temperature is 70℃, and the top temperature is 35℃; the flow rate of the three-stage distillation column 5 is 4 m³ / h. 3 / h, reflux ratio of 5:1, top depressurization every 20 min, pressure of 0.06 MPa, bottom temperature of 45℃, top temperature of 21℃; (4) The gas phase discharged from the bottom of the first-stage distillation column 2, the gas phase discharged from the bottom of the second-stage distillation column 4, and the waste acid discharged from the third-stage distillation column 5 are recovered by passing them through a mixer.

[0027] Example 4 A method for preparing low-arsenic anhydrous hydrogen fluoride includes the following steps: (1) The crude hydrogen fluoride from storage tank 1 is passed through a primary distillation column 2 to obtain anhydrous hydrogen fluoride. The flow rate of the mixture into the primary distillation column 2 is 5 m³ / s. 3 The reflux ratio is 3:1, the pressure is 0.4MPa, the bottom temperature is 80℃, the top temperature is 45℃, and acid is discharged every 35 minutes. (2) Anhydrous hydrogen fluoride is introduced into pretreatment tank 3, and then potassium permanganate solution with a mass concentration of 6% is added in 4 portions according to 0.05% of the mass of anhydrous hydrogen fluoride in pretreatment tank 3. The mixture is stirred and reacted for 10 hours at a temperature of 25℃ and a stirring speed of 280rpm to obtain a mixture. (3) The mixture is sequentially fed into the secondary distillation column 4 and the tertiary distillation column 5 for distillation to obtain low-arsenic anhydrous hydrogen fluoride; the flow rate of the mixture fed into the secondary distillation column 4 is 4 m³ / s. 3The flow rate is 5 m³ / h, the reflux ratio is 5:1, the top pressure is depressurized every 12 minutes, the pressure is 0.4 MPa, the bottom temperature is 70℃, and the top temperature is 40℃; the flow rate of the three-stage distillation column 5 is 5 m³ / h. 3 / h, reflux ratio of 4:1, top depressurization every 120 min / time, pressure of 0.08 MPa, bottom temperature of 50℃, top temperature of 19.6℃; (4) The gas phase discharged from the bottom of the first-stage distillation column 2, the gas phase discharged from the bottom of the second-stage distillation column 4, and the waste acid discharged from the third-stage distillation column 5 are recovered by passing them through a mixer.

[0028] Comparative Example 1 This comparative example is based on Example 4, but the operating conditions of the first-stage distillation column 2 are changed, while the rest remain the same.

[0029] A method for preparing low-arsenic anhydrous hydrogen fluoride includes the following steps: (1) The crude hydrogen fluoride from storage tank 1 is passed through a primary distillation column 2 to obtain anhydrous hydrogen fluoride. The flow rate of the mixture into the primary distillation column 2 is 10 m³ / s. 3 / h, reflux ratio of 3:1, pressure of 0.9MPa, bottom temperature of 60℃, top temperature of 45℃, acid is discharged once every 90min; (2) Anhydrous hydrogen fluoride is introduced into pretreatment tank 3, and then potassium permanganate solution with a mass concentration of 6% is added in 4 portions according to 0.05% of the mass of anhydrous hydrogen fluoride in pretreatment tank 3. The mixture is stirred and reacted for 10 hours at a temperature of 25℃ and a stirring speed of 280rpm to obtain a mixture. (3) The mixture is sequentially fed into the secondary distillation column 4 and the tertiary distillation column 5 for distillation to obtain low-arsenic anhydrous hydrogen fluoride; the flow rate of the mixture fed into the secondary distillation column 4 is 4 m³ / s. 3 The flow rate is 5 m³ / h, the reflux ratio is 5:1, the top pressure is depressurized every 12 minutes, the pressure is 0.4 MPa, the bottom temperature is 70℃, and the top temperature is 40℃; the flow rate of the three-stage distillation column 5 is 5 m³ / h. 3 / h, reflux ratio of 4:1, top depressurization every 150 min / time, pressure of 0.08 MPa, bottom temperature of 50℃, top temperature of 40℃; (4) The gas phase discharged from the bottom of the first-stage distillation column 2, the gas phase discharged from the bottom of the second-stage distillation column 4, and the waste acid discharged from the third-stage distillation column 5 are recovered by passing them through a mixer.

[0030] Comparative Example 2 This comparative example is based on Example 4, but the operating conditions of the secondary distillation column 4 are changed, while the rest remain the same.

[0031] A method for preparing low-arsenic anhydrous hydrogen fluoride includes the following steps: (1) The crude hydrogen fluoride from storage tank 1 is passed through a primary distillation column 2 to obtain anhydrous hydrogen fluoride. The flow rate of the mixture into the primary distillation column 2 is 5 m³ / s. 3 The reflux ratio is 3:1, the pressure is 0.4MPa, the bottom temperature is 80℃, the top temperature is 45℃, and acid is discharged every 35 minutes. (2) Anhydrous hydrogen fluoride is introduced into pretreatment tank 3, and then potassium permanganate solution with a mass concentration of 6% is added in 4 portions according to 0.05% of the mass of anhydrous hydrogen fluoride in pretreatment tank 3. The mixture is stirred and reacted for 10 hours at a temperature of 25℃ and a stirring speed of 280rpm to obtain a mixture. (3) The mixture is sequentially fed into the secondary distillation column 4 and the tertiary distillation column 5 for distillation to obtain low-arsenic anhydrous hydrogen fluoride; the flow rate of the mixture fed into the secondary distillation column 4 is 4 m³ / s. 3 The flow rate is 1.5 MPa, the reflux ratio is 2:1, the top pressure is depressurized every 60 minutes, the pressure is 1.5 MPa, the bottom temperature is 70°C, and the top temperature is 40°C; the flow rate of the three-stage distillation column 5 is 5 m³ / h. 3 / h, reflux ratio of 4:1, top depressurization every 150 min / time, pressure of 0.08 MPa, bottom temperature of 50℃, top temperature of 19.6℃; (4) The gas phase discharged from the bottom of the first-stage distillation column 2, the gas phase discharged from the bottom of the second-stage distillation column 4, and the waste acid discharged from the third-stage distillation column 5 are recovered by passing them through a mixer.

[0032] Comparative Example 3 This comparative example is based on Example 4, but the operating conditions of the three-stage distillation column 5 are changed, while the rest remain the same.

[0033] A method for preparing low-arsenic anhydrous hydrogen fluoride includes the following steps: (1) The crude hydrogen fluoride from storage tank 1 is passed through a primary distillation column 2 to obtain anhydrous hydrogen fluoride. The flow rate of the mixture into the primary distillation column 2 is 5 m³ / s. 3 The reflux ratio is 3:1, the pressure is 0.4MPa, the bottom temperature is 80℃, the top temperature is 45℃, and acid is discharged every 35 minutes. (2) Anhydrous hydrogen fluoride is introduced into pretreatment tank 3, and then potassium permanganate solution with a mass concentration of 6% is added in 4 portions according to 0.05% of the mass of anhydrous hydrogen fluoride in pretreatment tank 3. The mixture is stirred and reacted for 10 hours at a temperature of 25℃ and a stirring speed of 280rpm to obtain a mixture. (3) The mixture is sequentially fed into the secondary distillation column 4 and the tertiary distillation column 5 for distillation to obtain low-arsenic anhydrous hydrogen fluoride; the flow rate of the mixture fed into the secondary distillation column 4 is 4 m³ / s. 3The flow rate is 8 m³ / h, the reflux ratio is 5:1, the top pressure is depressurized every 12 minutes, the pressure is 0.4 MPa, the bottom temperature is 70℃, and the top temperature is 40℃; the flow rate of the three-stage distillation column 5 is 8 m³ / h. 3 / h, reflux ratio of 2:1, top depressurization every 120 min / time, pressure of 2.0 MPa, bottom temperature of 50℃, top temperature of 25℃; (4) The gas phase discharged from the bottom of the first-stage distillation column 2, the gas phase discharged from the bottom of the second-stage distillation column 4, and the waste acid discharged from the third-stage distillation column 5 are recovered by passing them through a mixer.

[0034] Comparative Example 4 Based on the process of Example 4, the operation of the first-stage distillation column 2 is omitted; otherwise, it remains the same as Example 4. Its process flow diagram is as follows: Figure 2 As shown.

[0035] A method for preparing low-arsenic anhydrous hydrogen fluoride includes the following steps: (1) The crude hydrogen fluoride from the storage tank 1 is introduced into the pretreatment tank 3. Then, according to the amount of 0.05% of the mass of anhydrous hydrogen fluoride in the pretreatment tank 3, a 6% potassium permanganate solution is added in 4 portions. The mixture is stirred and reacted for 10 hours at a temperature of 25°C and a stirring speed of 280 rpm to obtain a mixture. (2) The mixture is sequentially fed into a secondary distillation column 4 and a tertiary distillation column 5 for distillation to obtain low-arsenic anhydrous hydrogen fluoride; the flow rate of the mixture fed into the secondary distillation column 4 is 4 m³ / s. 3 The flow rate is 5 m³ / h, the reflux ratio is 5:1, the top pressure is depressurized every 12 minutes, the pressure is 0.4 MPa, the bottom temperature is 70℃, and the top temperature is 40℃; the flow rate of the three-stage distillation column 5 is 5 m³ / h. 3 / h, reflux ratio of 4:1, top depressurization every 120 min / time, pressure of 0.08 MPa, bottom temperature of 50℃, top temperature of 19.6℃; (3) The gas phase discharged from the bottom of the first-stage distillation column 2, the gas phase discharged from the bottom of the second-stage distillation column 4, and the waste acid discharged from the third-stage distillation column 5 are recovered by a mixer.

[0036] The performance of the low-arsenic anhydrous hydrogen fluoride products obtained by the preparation processes of Examples 1-4 and Comparative Examples 1-4 were measured respectively. The arsenic ion content was determined by inductively coupled plasma mass spectrometry (ICP-MS), and the contents of fluorosilicic acid, sulfur dioxide, and non-volatile acid were determined according to GB / T7746—2023 Industrial Anhydrous Hydrogen Fluoride. The measurement results are shown in Table 1 below.

[0037] Table 1

[0038] As can be seen from Table 1 above, compared with Examples 1-4, the arsenic content in the products of Comparative Examples 1-4 is generally higher. This indicates that an unsuitable process cannot achieve deep arsenic removal, and also increases the content of fluorosilicic acid, sulfur dioxide, and non-volatile acids in the anhydrous hydrogen fluoride product. This invention changes the non-acid discharge method of the primary distillation column to an acid discharge method, and sets up a pretreatment process between the original primary and secondary distillations. This effectively utilizes potassium permanganate solution to remove arsenic, then oxidizes the arsenic compounds in the product and carries them away through the distillation column, thereby effectively purifying the product without introducing new hazardous waste. It also effectively removes other impurities, improves the purity of anhydrous hydrogen fluoride, and effectively improves product quality.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing low-arsenic anhydrous hydrogen fluoride, characterized in that, Includes the following steps: (1) The crude hydrogen fluoride from the storage tank is passed through a primary distillation column to obtain anhydrous hydrogen fluoride. The flow rate of the mixture into the primary distillation column is 2~6 m³ / s. 3 / h, reflux ratio of 4~5:1, pressure of 0.2~0.4MPa, bottom temperature of 60~90℃, top temperature of 35~45℃, anhydrous hydrogen fluoride is introduced into the pretreatment tank, and then potassium permanganate solution is added and stirred to obtain a mixture. (2) The mixture is sequentially fed into a two-stage distillation column and a three-stage distillation column for distillation to obtain low-arsenic anhydrous hydrogen fluoride; the flow rate of the mixture fed into the two-stage distillation column is 2~5 m³ / h. 3 The reflux ratio is 4~6:1, the top pressure is depressurized every 12~15 minutes, the pressure is 0.2~0.5MPa, the bottom temperature is 60~80℃, and the top temperature is 35~40℃.

2. The method for preparing low-arsenic anhydrous hydrogen fluoride according to claim 1, characterized in that, The mass concentration of the potassium permanganate solution is 3-8%.

3. The method for preparing low-arsenic anhydrous hydrogen fluoride according to claim 1, characterized in that, The amount of potassium permanganate solution added is 0.03% to 0.06% of the mass of anhydrous hydrogen fluoride.

4. The method for preparing low-arsenic anhydrous hydrogen fluoride according to claim 1, characterized in that, The stirring reaction temperature is 15~25℃, the stirring speed is 200~300rpm, and the time is 8~12h.

5. The method for preparing low-arsenic anhydrous hydrogen fluoride according to claim 1, characterized in that, The primary distillation column is deaerated every 30-40 minutes.

6. The method for preparing low-arsenic anhydrous hydrogen fluoride according to claim 1, characterized in that, The flow rate of the mixture fed into the first-stage distillation column is 5 m³ / s. 3 The flow rate is 1 / h, the reflux ratio is 3:1, the pressure is 0.4 MPa, the bottom temperature is 80℃, and the top temperature is 45℃.

7. The method for preparing low-arsenic anhydrous hydrogen fluoride according to claim 1, characterized in that, The flow rate of the mixture fed into the secondary distillation column is 4 m³ / s. 3 The flow rate is 1 h, the reflux ratio is 5:1, the top pressure is depressurized every 12 min, the pressure is 0.4 MPa, the bottom temperature is 70℃, and the top temperature is 40℃.

8. The method for preparing low-arsenic anhydrous hydrogen fluoride according to claim 1, characterized in that, The flow rate introduced into the three-stage distillation column is 2~5m³. 3 The reflux ratio is 3~5:1, the top pressure is depressurized 100~160min / time, the pressure is 0.05~0.1MPa, the bottom temperature is 40~50℃, and the top temperature is 19~21℃.

9. The method for preparing low-arsenic anhydrous hydrogen fluoride according to any one of claims 1 or 8, characterized in that, The flow rate introduced into the three-stage distillation column is 5m³. 3 The reflux ratio is 4:1, the top pressure is depressurized every 120 min, the pressure is 0.09 MPa, the bottom temperature is 50℃, and the top temperature is 19.6℃.

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