A method for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid

Abstract

This application relates to the technical field of hydrogen fluoride preparation processes, and provides a method for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid, which includes the following steps: (1) preheating the fluorine-containing by-product sulfuric acid; (2) distilling the preheated fluorine-containing by-product sulfuric acid to obtain a gas-phase component and a liquid-phase component; (3) condensing the gas-phase component to obtain crude hydrogen fluoride; wherein, the components of the fluorine-containing by-product sulfuric acid include sulfuric acid and hydrofluoric acid, the concentration of the sulfuric acid is C, the temperature of the distillation is T, and C and T satisfy the following formula: 0.95 ≤ η ≤ 2.

Description

Technical Field

[0001] This application relates to the technical field of hydrogen fluoride preparation processes, and particularly to a method for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid. Background Art

[0002] Industrially, the sulfuric acid method is used to produce anhydrous hydrogen fluoride, that is, fluorosilicic acid reacts with concentrated sulfuric acid to obtain anhydrous hydrogen fluoride. The by-product of the phosphoric acid plant is low-concentration fluorosilicic acid. After filtering and concentrating it into high-concentration fluorosilicic acid, it reacts with 98% concentrated sulfuric acid to generate hydrogen fluoride, SiF4, and fluorine-containing by-product sulfuric acid. Among them, the fluorine-containing by-product sulfuric acid includes sulfuric acid, hydrogen fluoride, water, and fluorosulfonic acid. However, a large amount of hydrogen fluoride still remains in the fluorine-containing by-product sulfuric acid. In addition, other reaction by-products in the industry will also produce fluorine-containing by-product sulfuric acid.

[0003] The most direct method for industrially recovering hydrogen fluoride from fluorine-containing by-product sulfuric acid is the distillation method. However, in the actual production process, the distillation effect of hydrogen fluoride is very poor. If the temperature is increased for distillation, the energy consumption will increase and the cost will increase. Therefore, how to efficiently and low-energy recover hydrogen fluoride from fluorine-containing by-product sulfuric acid has become the key to the preparation of anhydrous hydrogen fluoride by the sulfuric acid method. Summary of the Invention

[0004] The purpose of this application is to provide a method for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid to improve the distillation efficiency and recovery rate of hydrogen fluoride. The specific technical solutions are as follows:

[0005] The first aspect of this application provides a method for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid, which includes the following steps:

[0006] (1) Preheat the fluorine-containing by-product sulfuric acid;

[0007] (2) Distill the preheated fluorine-containing by-product sulfuric acid to obtain a gas-phase component and a liquid-phase component;

[0008] (3) Condense the gas-phase component to obtain crude hydrogen fluoride;

[0009] Among them, the components of the fluorine-containing by-product sulfuric acid include sulfuric acid and hydrofluoric acid, the concentration of the sulfuric acid is C, the temperature of the distillation is T, and C and T satisfy the following formula:

[0010] , 0.95 ≤ η ≤ 2.

[0011] In some embodiments of this application, 0.98 ≤ η ≤ 1.2.

[0012] In some embodiments of this application, based on the total mass of the fluorine-containing by-product sulfuric acid, the concentration of the sulfuric acid is 50wt% - 75wt%.

[0013] In some embodiments of the present application, based on the total mass of the fluorine-containing by-product sulfuric acid, the concentration of the sulfuric acid is 60 wt% to 70 wt%.

[0014] In some embodiments of the present application, based on the total mass of the fluorine-containing by-product sulfuric acid, the concentration of the hydrofluoric acid is ≥ 3.5 wt%.

[0015] In some embodiments of the present application, the temperature of the preheating is 123 °C to 183 °C, preferably 140 °C to 166 °C.

[0016] In some embodiments of the present application, the temperature of the distillation is 123 °C to 183 °C, preferably 140 °C to 166 °C.

[0017] In some embodiments of the present application, the condensation temperature of the condensation is -20 °C to 19 °C.

[0018] In some embodiments of the present application, the equipment for the distillation is selected from at least one of a vacuum falling film evaporator, a vacuum rising film evaporator, a distillation kettle, a flash tank, and a rectifying column.

[0019] Advantages of the present application:

[0020] The present application provides a method for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid, which comprises the following steps:

[0021] (1) Preheating the fluorine-containing by-product sulfuric acid; (2) Distilling the preheated fluorine-containing by-product sulfuric acid to obtain a gas-phase component and a liquid-phase component; (3) Condensing the gas-phase component to obtain crude hydrogen fluoride; wherein, the components of the fluorine-containing by-product sulfuric acid include sulfuric acid and hydrofluoric acid, the concentration of the sulfuric acid is C, the temperature of the distillation is T, and C and T satisfy the following formula:

[0022] , 0.95 ≤ η ≤ 2.

[0023] When 0.95 ≤ η ≤ 2, hydrogen fluoride is easily distilled out, while the distillation of sulfuric acid is reduced, the yield of hydrogen fluoride is relatively high, and the concentration of the crude hydrogen fluoride is higher than that when η > 2. When η > 2, the larger η is, the more hydrogen fluoride is distilled out, and at the same time, a large amount of sulfuric acid will also be distilled out, which is not conducive to subsequent separation and purification, and increases the energy consumption. The yield of the distilled hydrogen fluoride is relatively high, but the purity is low. When η < 0.95, the smaller η is, the less easily hydrogen fluoride is distilled out, and the yield of hydrogen fluoride is low. Therefore, by controlling the concentration C of sulfuric acid and the temperature T of distillation so that 0.95 ≤ η ≤ 2, it is easier to extract hydrogen fluoride from fluorine-containing by-product sulfuric acid while reducing the distillation of sulfuric acid, reducing the required distillation temperature, improving the distillation efficiency, reducing energy consumption, and the purity of hydrogen fluoride in the distilled gas-phase component is higher, and the yield of hydrogen fluoride increases.

[0024] Of course, it is not necessary for any product or method implementing the present application to simultaneously achieve all the advantages described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and those of ordinary skill in the art can also obtain other embodiments based on these drawings.

[0026] Figure 1 is a process flow diagram for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid;

[0027] Figure 2 is a structural diagram of the device for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid, where each label is: 1. fluorine-containing by-product sulfuric acid storage tank; 2. preheater; 3. vacuum falling film evaporator; 4. hydrogen fluoride condenser; 5. crude hydrogen fluoride collection tank; 6. distillation buffer tank. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following will clearly and completely describe the technical solutions in the present application in conjunction with the embodiments of the present application and the drawings. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the present application belong to the scope of protection of the present application.

[0029] The first aspect of the present application provides a method for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid, which includes the following steps:

[0030] (1) Preheat the fluorine-containing by-product sulfuric acid;

[0031] (2) Distill the preheated fluorine-containing by-product sulfuric acid to obtain a gas-phase component and a liquid-phase component;

[0032] (3) Condense the gas-phase component to obtain hydrogen fluoride product; wherein, the components of the fluorine-containing by-product sulfuric acid include sulfuric acid and hydrofluoric acid, the concentration of the sulfuric acid is C, the temperature of the distillation is T, and C and T satisfy the following formula:

[0033] , 0.95 ≤ η ≤ 2.

[0034] Among them, the preferred range of η is 0.98 ≤ η ≤ 1.2. For example, the value of η can be 0.95, 0.98, 1, 1.1, 1.2, 1.4, 1.6, 1.8, 2, or a range composed of any two of these numerical values. The inventors have found through research that when 0.95 ≤ η ≤ 2, hydrogen fluoride is easily vaporized, while the evaporation of sulfuric acid is reduced, the yield of hydrogen fluoride is relatively high, and the concentration of crude hydrogen fluoride is higher than that of the crude hydrogen fluoride prepared when η > 2; when η > 2, the larger η is, while hydrogen fluoride is vaporized, a large amount of sulfuric acid will also be vaporized, which is not conducive to subsequent separation and purification, increases energy consumption, the yield of the vaporized hydrogen fluoride is relatively high, but the purity is low; when η < 0.95, the smaller η is, the less easily hydrogen fluoride is vaporized, and the yield of hydrogen fluoride is low. Therefore, by controlling the concentration C of sulfuric acid and the distillation temperature T to make 0.95 ≤ η ≤ 2, it is easier to extract hydrogen fluoride from fluorine-containing by-product sulfuric acid, while reducing the evaporation of sulfuric acid, lowering the required distillation temperature, improving the distillation efficiency, reducing energy consumption, and the purity of hydrogen fluoride in the distilled gas-phase component is higher, and the yield of hydrogen fluoride increases. The above effects are better within the preferred range of 0.98 ≤ η ≤ 1.2.

[0035] In some embodiments of the present application, based on the total mass of the fluorine-containing by-product sulfuric acid, the concentration of the sulfuric acid is 50 wt% - 75 wt%, preferably 60 wt% - 70 wt%. For example, the concentration of the sulfuric acid can be 50 wt%, 52 wt%, 54 wt%, 56 wt%, 58 wt%, 60 wt%, 62 wt%, 64 wt%, 66 wt%, 68 wt%, 70 wt%, 72 wt%, 74 wt%, 75 wt%, or a range composed of any two of these numerical values. Selecting the concentration of sulfuric acid within the scope of the present application can make the hydrofluoric acid in the fluorine-containing by-product sulfuric acid easily vaporized while minimizing the evaporation of sulfuric acid as much as possible, improving the distillation efficiency and reducing energy consumption.

[0036] In some embodiments of the present application, based on the total mass of the fluorine-containing by-product sulfuric acid, the concentration of the hydrofluoric acid ≥ 3.5 wt%. The concentration of the hydrofluoric acid is related to the source of the fluorine-containing by-product sulfuric acid. For example, when preparing hydrogen fluoride by reacting fluorosilicic acid and concentrated sulfuric acid, different concentrations of fluorosilicic acid and concentrated sulfuric acid react or their molar ratios are different, and the concentration of hydrofluoric acid in the by-product sulfuric acid obtained is different. When the molar ratio of fluorosilicic acid (30% concentration) and concentrated sulfuric acid (98% concentration) is 1.1:8.22, the concentration of hydrofluoric acid is 3.74%; when the molar ratio of fluorosilicic acid (50% concentration) and sulfuric acid (98% concentration) is 1:7, the concentration of hydrofluoric acid is 4.38%.

[0037] In some embodiments of the present application, the temperature of the preheating is 123°C to 183°C, preferably 140°C to 166°C. For example, the temperature of the preheating can be 123°C, 130°C, 140°C, 150°C, 160°C, 166°C, 170°C, 180°C, 183°C or a range composed of any two of these values. Heating the fluorine-containing by-product sulfuric acid in advance within the range of the present application is beneficial to improving the distillation efficiency.

[0038] In some embodiments of the present application, the condensation temperature of the condensation is -20°C to 19°C. For example, the temperature of the condensation can be -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C, 15°C, 19°C or a range composed of any two of these values. Controlling the condensation temperature within the range of the present application is beneficial to improving the condensation efficiency of the gas-phase components and increasing the recovery rate of hydrogen fluoride.

[0039] The present application does not particularly limit the method of condensation, as long as the purpose of the present application is satisfied. For example, brine with a temperature of -20°C to 19°C can be used for condensation.

[0040] In some embodiments of the present application, the temperature of the distillation is 123°C to 183°C, preferably 140°C to 166°C. For example, the temperature of the evaporation can be 123°C, 130°C, 140°C, 150°C, 160°C, 166°C, 170°C, 180°C, 183°C or a range composed of any two of these values. Within the range of the present application, the temperature of the distillation can, on the premise of ensuring that hydrogen fluoride in the fluorine-containing by-product sulfuric acid is distilled out and sulfuric acid is less distilled out, minimize energy consumption as much as possible.

[0041] In some embodiments of the present application, the equipment for distillation is selected from at least one of a vacuum falling-film evaporator, a vacuum rising-film evaporator, a distillation kettle, a flash tank, and a rectification column. The material of the distillation kettle is not limited and can be selected from common distillation kettles on the market. For example, a polytetrafluoroethylene distillation kettle can be selected. Selecting the vacuum falling-film evaporator can accurately control the temperature of the distillation for extracting hydrogen fluoride from the fluorine-containing by-product sulfuric acid and strengthen mass transfer and heat transfer.

[0042] In some embodiments of the present application, the equipment for distillation is selected from a vacuum falling-film evaporator, and the pressure of the vacuum falling-film evaporator is -13 kPa to 0 kPa. For example, the pressure of the vacuum falling-film evaporator can be -13 kPa, -10 kPa, -7 kPa, -4 kPa, 0 kPa or a range composed of any two of these values. Within the range of the present application, the pressure of the vacuum falling-film evaporator is beneficial to reducing the boiling point of the by-product sulfuric acid, thereby reducing the temperature required for distillation and improving the distillation efficiency of hydrogen fluoride.

[0043] In the present application, the gas-phase components include water vapor, hydrogen fluoride, and sulfuric acid vapor; the liquid-phase components include concentrated sulfuric acid and residual hydrofluoric acid.

[0044] The present application places no restrictions on the source of the fluorine-containing by-product sulfuric acid. Depending on the source of the fluorine-containing by-product sulfuric acid, the liquid-phase components may further include other substances. For example, when the fluorine-containing by-product sulfuric acid is a by-product of the reaction of fluosilicic acid with concentrated sulfuric acid to prepare hydrogen fluoride, the liquid-phase components further include fluorosulfonic acid.

[0045] In some embodiments of the present application, a device for implementing a method for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid is used. The device includes a fluorine-containing by-product sulfuric acid storage tank 1, a preheater 2, a vacuum falling-film evaporator 3, a hydrogen fluoride condenser 4, a crude hydrogen fluoride collection tank 5, and a distillation buffer tank 6; the fluorine-containing by-product sulfuric acid storage tank 1 is connected to the preheater 2, the preheater 2 is connected to the vacuum falling-film evaporator 3, the vacuum falling-film evaporator 3 is connected to the hydrogen fluoride condenser 4 and the distillation buffer tank 6, and the hydrogen fluoride condenser 4 is connected to the crude hydrogen fluoride collection tank 5.

[0046] In the present application, the rate at which the fluorine-containing by-product sulfuric acid is fed into the preheater is 10 kg / h to 600 kg / h. For example, the rate at which the fluorine-containing by-product sulfuric acid is fed into the preheater can be 10 kg / h, 50 kg / h, 100 kg / h, 200 kg / h, 300 kg / h, 400 kg / h, 500 kg / h, 600 kg / h, or any range composed of any two of these values. After being preheated by the preheater, the fluorine-containing by-product sulfuric acid enters the vacuum falling-film evaporator from the top, and a liquid film or liquid droplets are formed on the inner wall of the vertical tube of the vacuum falling-film evaporator through a liquid distributor. At the same time, low-pressure steam is introduced into the shell side of the vacuum falling-film evaporator to heat the outer wall of the vertical tube. When the liquid film or liquid droplets are heated to a certain temperature, the hydrogen fluoride escaping from the by-product sulfuric acid enters the gas-phase pipeline under the action of negative pressure, and crude hydrogen fluoride is obtained by condensation. The remaining components flow down along the vertical tube wall and enter the liquid-phase pipeline to obtain the liquid-phase components.

[0047] In the present application, "low-pressure steam" refers to steam with a relatively low pressure and a certain degree of superheat, and its function is to heat the outer wall of the vertical tube of the vacuum falling-film evaporator. The present application does not make special limitations on the pressure and temperature of the low-pressure steam, as long as the purpose of the present application can be satisfied. For example, the pressure range of the low-pressure steam is 0.1 Mpa to 1.0 Mpa, and the temperature is 100 °C to 185 °C.

[0048] In the present application, Figure 1Process flow chart for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid: First, the fluorine-containing by-product sulfuric acid is pumped from the fluorine-containing by-product sulfuric acid storage tank into a preheater for preheating. Then, the preheated fluorine-containing by-product sulfuric acid is introduced into a vacuum falling film evaporator for distillation to obtain a gas-phase component and a liquid-phase component. Finally, the gas-phase component is introduced into a hydrogen fluoride condenser for condensation to obtain crude hydrogen fluoride; the liquid-phase component is cooled and then enters a distillation buffer tank to obtain by-product sulfuric acid (trace HF).

[0049] In this application, Figure 2 Structural diagram of the device for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid, where each label is: 1. Fluorine-containing by-product sulfuric acid storage tank; 2. Preheater; 3. Vacuum falling film evaporator; 4. Hydrogen fluoride condenser; 5. Crude hydrogen fluoride collection tank; 6. Distillation buffer tank.

[0050] Example

[0051] Hereinafter, examples and comparative examples are given to illustrate the embodiments of this application more specifically. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0052] Testing methods and equipment:

[0053] Testing method for the content of hydrogen fluoride in the liquid to be tested: Refer to the determination of the content of hydrogen fluoride in the national standard GB / T 7744-2023 "Industrial Hydrofluoric Acid".

[0054] Testing method for the content of sulfuric acid in the liquid to be tested: Refer to the determination of the content of non-volatile acids in the national standard GB / T 7744-2023 "Industrial Hydrofluoric Acid".

[0055] Calculation of hydrogen fluoride recovery

[0056] The calculation formula for hydrogen fluoride is as follows:

[0057]

[0058] Y is the recovery rate of hydrogen fluoride, M1 is the mass of the fluorine-containing by-product sulfuric acid before evaporation, M2 is the mass of the distilled crude hydrogen fluoride, C1 is the mass concentration of hydrofluoric acid in the fluorine-containing by-product sulfuric acid before evaporation, and C2 is the mass concentration of the distilled crude hydrogen fluoride.

[0059] Example 1

[0060] Based on the total mass of the fluorine-containing by-product sulfuric acid, the concentration C of the sulfuric acid is 50 wt%, and the concentration of hydrofluoric acid is 3.86 wt%. Prepare 100 kg of the fluorine-containing by-product sulfuric acid, and feed the fluorine-containing by-product sulfuric acid into the preheater at a rate of 120 kg / h. The preheating temperature is 123 °C, and then it enters from the top of the vacuum falling-film evaporator. The distillation temperature T is 123 °C, the pressure of the vacuum falling-film evaporator is -10 kPa, the length of the vertical tube in the vacuum falling-film evaporator is 1 m. The gas-phase components after vacuum falling-film evaporation enter the condenser and are condensed with brine at -15 °C to obtain crude hydrogen fluoride. The liquid-phase components are cooled and enter the distillation buffer tank. After 50 minutes of feeding the material, a sample is taken for testing.

[0061] Substitute C and T into the formula: , and calculate to obtain η = 1.056.

[0062] Examples 2 to 12

[0063] Except for adjusting the concentration C of sulfuric acid, the distillation temperature T to satisfy 0.95 ≤ η ≤ 2, and the concentration of hydrofluoric acid and the preheating temperature are changed, the rest are the same as in Example 1.

[0064] Example 13

[0065] Add 100 kg of the fluorine-containing by-product sulfuric acid to a polytetrafluoroethylene distillation kettle. The concentration C of sulfuric acid in the fluorine-containing by-product sulfuric acid is 60.42 wt%, and the concentration of hydrofluoric acid is 4.21 wt%. Control the distillation temperature at 140.1 °C, maintain the system pressure at -10 kPa, control the stirring rate at 100 rpm, and condense the distilled gas phase with frozen brine at -15 °C to obtain crude hydrogen fluoride. After 10 h of distillation time, a sample is taken for analysis.

[0066] Comparative Examples 1 to 3

[0067] Except for adjusting the concentration C of sulfuric acid, the distillation temperature T and the preheating temperature to satisfy 0 < η < 0.95, and the concentration of hydrofluoric acid is changed, the rest are the same as in Example 1.

[0068] Comparative Example 4

[0069] Except for adjusting the concentration C of sulfuric acid, the distillation temperature T and the preheating temperature to satisfy η = 5, and the concentration of hydrofluoric acid is changed, the rest are the same as in Example 1.

[0070] Table 1

[0071]

[0072] Among them, M2 is the mass of the crude hydrogen fluoride distilled out, C1 is the mass concentration of hydrofluoric acid in the fluorine-containing by-product sulfuric acid before evaporation, and C2 is the mass concentration of the crude hydrogen fluoride distilled out.

[0073] It can be seen from Examples 1 to 13 that when 0.95 ≤ η ≤ 2, hydrogen fluoride is easily distilled out, while the distillation of sulfuric acid is reduced. The yield of hydrogen fluoride is relatively high, and the concentration of crude hydrogen fluoride is higher than that of the crude hydrogen fluoride prepared when η > 2. It can be seen from Comparative Examples 1 to 3 that when η < 0.95, the smaller η is, the less easily hydrogen fluoride is distilled out. When η = 0.472, the yield of hydrogen fluoride is only 20.56%. It can be seen from Comparative Example 4 that when η = 5, although the yield of hydrogen fluoride reaches 94.77%, the concentration of crude hydrogen fluoride is only 35.98%. When hydrogen fluoride is distilled out, a large amount of sulfuric acid is also distilled out, which is not conducive to subsequent separation and purification and increases the energy consumption.

[0074] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for extracting hydrogen fluoride from fluorine-containing by-product sulfuric acid, characterized in that, It includes the following steps: (1) Preheat the fluorine-containing by-product sulfuric acid; (2) Distill the preheated fluorine-containing by-product sulfuric acid to obtain a gas-phase component and a liquid-phase component; (3) Condense the gas-phase component to obtain crude hydrogen fluoride; Wherein, the components of the fluorine-containing by-product sulfuric acid include sulfuric acid and hydrofluoric acid, the concentration of the sulfuric acid is C, the temperature of the distillation is T, and C and T satisfy the following formula: , 0.95 ≤ η ≤ 2.

2. The method according to claim 1, wherein 0.98 ≤ η ≤ 1.

2.

3. The method according to claim 1, wherein Based on the total mass of the fluorine-containing by-product sulfuric acid, the concentration of the sulfuric acid is 50wt% - 75wt%.

4. The method according to claim 3, characterized in that Based on the total mass of the fluorine-containing by-product sulfuric acid, the concentration of the sulfuric acid is 60wt% - 70wt%.

5. The method according to claim 1, characterized in that, Based on the total mass of the fluorine-containing by-product sulfuric acid, the concentration of the hydrofluoric acid ≥ 3.5wt%.

6. The method according to claim 1, wherein The temperature of the preheating is 123°C - 183°C.

7. The method according to claim 6, wherein The temperature of the preheating is 140°C - 166°C.

8. The method according to claim 1, wherein The temperature of the distillation is 123°C - 183°C.

9. The method according to claim 8, wherein The temperature of the distillation is 140°C - 166°C.

10. The method according to claim 1, wherein The condensation temperature of the condensation is -20°C - 19°C.

11. The method according to claim 1, wherein The equipment for the distillation is selected from at least one of a vacuum falling-film evaporator, a vacuum rising-film evaporator, a distillation kettle, a flash tank, and a rectifying column.

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