Separation method of mixed gas of silicon tetrafluoride and hydrogen chloride

Abstract

The invention relates to the technical field of fluorine chemical industry, and particularly discloses a separation method of mixed gas of silicon tetrafluoride and hydrogen chloride. Comprising the following steps: step 1, gas absorption preparation: filling an alcohol absorbent into a gas absorption device, and connecting the gas absorption device with an activated carbon fiber membrane packed column in series; step 2, purification: enabling an intermediate product SiF4 / HCl mixed gas phase of anhydrous hydrogen fluoride produced by a fluosilicic acid method to pass through a gas absorption device to obtain purified SiF4 gas; and step 3, residual absorption: enabling the SiF4 gas purified in the step 2 to pass through an activated carbon fiber membrane packed column to obtain the SiF4 gas. The technical problem that in the prior art, due to the characteristic that SiF4 is dissolved in water and can react with alkali, common gas-phase dechlorination methods in industry are not suitable for a SiF4 / HCl system is solved. The blank of the current SiF4 and HCl separation technology block is filled, and a new thought is provided for separation and purification of SiF4.

Description

Technical Field

[0001] This application relates to the field of fluorochemical technology, and specifically discloses a method for separating a mixture of silicon tetrafluoride and hydrogen chloride gas. Background Technology

[0002] Currently, the main methods for producing anhydrous hydrogen fluoride in the industry are the fluorite process and the fluorosilicic acid process, with the fluorite process being the dominant one. However, fluorite is an unsustainable national strategic mineral resource, and its extraction has adverse environmental impacts, including soil and water pollution. In contrast, the fluorosilicic acid process for producing anhydrous hydrogen fluoride has greater development prospects. It not only provides an abundant source of fluorine resources but also offers an environmentally friendly method for disposing of fluorosilicic acid associated with phosphate rock. However, this method still faces many problems that urgently need to be solved.

[0003] In the production of anhydrous hydrogen fluoride via the fluorosilicic acid process, the raw material fluorosilicic acid contains 0.2-0.5% HCl impurities, which continuously accumulate during plant operation. Analysis revealed that the intermediate product SiF4 gas from the fluorosilicic acid process contains approximately 15% HCl. This HCl enters the downstream systems of the plant along with the SiF4 gas flow, severely impacting plant capacity, increasing energy consumption per unit, and resulting in a waste of resources and energy.

[0004] Industrial methods for gas-phase dechlorination are mainly divided into two types: water or saturated brine absorption and alkaline absorbent methods. Water or saturated brine absorption primarily utilizes the water solubility of HCl to separate it from the main gas. Therefore, it is necessary to ensure that the main gas is poorly soluble in water (such as Cl2, H2, O2, etc.). This method is mainly used in tail gas treatment. For example, patent application CN202121096458.3 discloses a hydrogen chloride tail gas treatment device for the synthesis of 3,4,5-trichlorotrifluorotoluene, which mentions pouring cold water into its absorption tank to absorb HCl gas. However, this method is not suitable for the SiF4 / HCl system because SiF4 itself is soluble in water. Using water or saturated brine absorption would result in the loss of SiF4 itself, and the dissolution of SiF4 in water is accompanied by a strong hydrolysis reaction. The hydrolysis product, fluorosilicic acid, is highly corrosive and harmful to personnel and equipment. Alkaline absorbent methods include various forms of wet, dry, and semi-dry methods, but their basic principle is the reaction between alkaline reagents and hydrogen chloride. However, this acid-base neutralization reaction method is not suitable for the SiF4 / HCl system because SiF4 is a Lewis acid and HCl is a typical Brønsted acid, both of which react with alkaline reagents, causing the loss of SiF4 itself.

[0005] Therefore, a method for removing hydrogen chloride from the SiF4 / HCl system is urgently needed in the process of producing anhydrous hydrogen fluoride using the fluorosilicic acid method. Summary of the Invention

[0006] The purpose of this invention is to provide a method for separating a mixture of silicon tetrafluoride and hydrogen chloride gas, in order to solve the technical problem mentioned above that, due to the characteristics of SiF4 itself being soluble in water and reacting with alkali, common industrial gas-phase dechlorination methods are not applicable to the SiF4 / HCl system.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows: a method for separating a mixture of silicon tetrafluoride and hydrogen chloride gas, comprising the following steps: Step 1, Gas Absorption Preparation: Fill the gas absorption device with alcohol absorbent and connect the gas absorption device and the activated carbon fiber membrane packing column in series; Step 2, Purification: The intermediate product SiF4 / HCl gas phase from the production of anhydrous hydrogen fluoride by the fluorosilicic acid method is passed through a gas absorption device to obtain purified SiF4 gas. Step 3, Residual Absorption: The purified SiF4 gas from Step 2 is passed through an activated carbon fiber membrane-packed column to obtain SiF4 gas.

[0008] The beneficial effects of this implementation plan are as follows: 1. Due to the water-soluble and alkali-reactive properties of SiF4, existing industrial gas-phase dechlorination methods are unsuitable for SiF4 / HCl systems. This application, however, utilizes a series process combining an alcohol absorbent and an activated carbon fiber membrane-packed column to achieve efficient and low-consumption separation of the SiF4 / HCl mixed gas phase from the intermediate product of anhydrous hydrogen fluoride production via the fluorosilicic acid method; this method is highly suitable for SiF4 / HCl systems. Specifically, in step 1, filling with an alcohol absorbent (such as terpineol or 1,4-butanediol) and combining it with an activated carbon fiber membrane device significantly improves the selectivity and rate of HCl absorption, increasing absorption efficiency by more than 30% compared to traditional water washing methods. Furthermore, this application reduces side reactions associated with water washing, such as SiF4 loss due to hydrolysis, and avoids corrosion of the separation equipment by fluorosilicic acid generated from SiF4 hydrolysis.

[0009] 2. The residual HCl content of the SiF4 gas separated in this application is already less than 4%. Furthermore, the microporous adsorption characteristics of the activated carbon fiber membrane further remove trace impurities (such as moisture or volatile organic compounds), ensuring the purity of the final SiF4 product. This method is very suitable for the separated SiF4 product in the anhydrous hydrogen fluoride production system of fluorosilicic acid process.

[0010] 3. In the anhydrous hydrogen fluoride production process using the fluorosilicic acid method, the raw material fluorosilicic acid contains 0.2-0.5% HCl impurities, which continuously accumulate during equipment operation. Analysis revealed that the SiF4 gas, an intermediate product of the fluorosilicic acid method, contains approximately 15% HCl. This HCl enters the subsequent systems along with the SiF4 gas stream, severely impacting equipment capacity and increasing unit energy consumption. While technicians sought to remove HCl from the SiF4 gas stream, the primary process is anhydrous hydrogen fluoride production, and excessively high HCl removal costs would increase the overall production cost of anhydrous hydrogen fluoride, making it unprofitable. This application utilizes recyclable alcohol-based absorbents and activated carbon fiber membranes, reducing operating costs (approximately 20% reduction in operating energy consumption) and environmental impact (no wastewater discharge). Overall, this application simplifies the operation process (integrated series design reduces equipment investment) and enhances industrial applicability, particularly suitable for large-scale anhydrous hydrogen fluoride production using the fluorosilicic acid method.

[0011] Furthermore, the gas absorption device includes a first-stage gas absorption device and a second-stage gas absorption device connected in series.

[0012] Furthermore, the method also includes a recycling method for alcohol absorbents, which includes the following steps: Step 201: When the HCl content in the SiF4 gas obtained in Step 3 is greater than or equal to 4%, the flow of the SiF4 / HCl mixed gas phase into the gas absorption device is stopped; Step 202: After stopping the flow of the SiF4 / HCl mixed gas phase into the gas absorption device, the alcohol absorbent in the gas absorption device is transported to a neutralization reactor; and an organic base is added dropwise to the alcohol absorbent in the neutralization reactor until the alcohol absorbent is neutral and the titration is completed; Step 203: The alcohol absorbent after the titration in Step 202 is filtered, and the filtered alcohol absorbent is reused in the gas absorption device of Step 1.

[0013] Furthermore, the organic base is any one of aniline, triethylamine, N,N-diethylaniline, N-methylaniline, and benzylamine.

[0014] Furthermore, the organic base is aniline, and the temperature of the alcohol absorbent is maintained at 20-25°C during titration.

[0015] Furthermore, the alcohol absorbent is any one or a mixture of tert-butanol, cyclohexanol, terpineol, tert-amyl alcohol, n-butanol, and 1,4-butanediol.

[0016] Furthermore, the alcohol absorbent is 1,4-butanediol, and the operating temperature of the gas absorption device is 25-30℃, with a gas flow rate of 1.5L / min for the SiF4 / HCl mixed gas phase.

[0017] Furthermore, it also includes a method for regenerating and reusing the activated carbon fiber membrane in the activated carbon fiber membrane packed column. The method for regenerating and reusing the activated carbon fiber membrane includes the following steps: Step 301, when the HCl content in the SiF4 gas obtained in step 3 is greater than or equal to 4%, stop introducing purified SiF4 gas into the activated carbon fiber membrane packed column; Step 302, heat the activated carbon fiber membrane packed column to above 75-150℃, and continuously introduce air into the activated carbon fiber membrane packed column for more than 4 hours, with an air flow rate greater than 70-150L / min.

[0018] Furthermore, in step 302, the heating temperature of the activated carbon fiber membrane-filled column is 90-100℃.

[0019] Furthermore, the air flow rate is 70 L / min. Attached Figure Description

[0020] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0021] The following detailed description illustrates the specific implementation method: Implementation, for example, attached Figure 1 As shown: General Overview of the Program Step 1, Gas Absorption Preparation: Fill the gas absorption device with alcohol absorbent and connect the gas absorption device and the activated carbon fiber membrane packing column in series; Step 2, Purification: The intermediate product SiF4 / HCl gas phase from the production of anhydrous hydrogen fluoride by the fluorosilicic acid method is passed through a gas absorption device to obtain purified SiF4 gas. Step 3, Residual Absorption: The purified SiF4 gas in Step 2 is passed through an activated carbon fiber membrane to obtain SiF4 gas. Step 201: When the HCl content in the SiF4 gas obtained in step 3 is greater than or equal to 4%, stop feeding the SiF4 / HCl mixed gas phase into the gas absorption device. Step 202: After stopping the flow of SiF4 / HCl mixed gas phase into the gas absorption device, transfer the alcohol absorbent in the gas absorption device to the neutralization reactor; and add organic base dropwise to the alcohol absorbent in the neutralization reactor until the alcohol absorbent is neutral and the titration is completed. Step 203: Filter the alcohol absorbent after the titration in step 202, and reuse the filtered alcohol absorbent in the gas absorption device of step 1.

[0022] Example 1 (1) Preparation of gas absorption device: The first stage gas absorption device is a 20L stirred reactor. 10Kg of 1,4-butanediol is added to the stirred reactor. The temperature is controlled at 25-30℃ and the stirring speed is 15r / min. The second stage gas absorption device is also a 20L stirred reactor. 10Kg of 1,4-butanediol is added to the stirred reactor. The temperature is controlled at 25-30℃ and the stirring speed is 15r / min. Activated carbon fiber membrane packed column (r=5cm, d=50cm).

[0023] (2) SiF4 / HCl gas (average HCl content 15.7%) is passed sequentially through the first-stage gas absorption device, the second-stage gas absorption device, and the activated carbon fiber membrane packed column at a flow rate of 30L / min. After dechlorination and purification, it enters the subsequent production system of AHF by fluorosilicic acid method.

[0024] (3) After continuous dechlorination for 8 hours, the HCl content of SiF4 after purification was 4.01%, and purification was stopped.

[0025] (4) Organic absorbent post-treatment and recycling: The absorbents in the I and II stage gas absorption devices are transferred to a 20L neutralization reactor, and N,N-diethylaniline is added dropwise to adjust the pH to neutral, forming a hydrochloride precipitate. After filtration, the precipitate is returned to the gas absorption device for recycling.

[0026] (5) Post-treatment regeneration of activated carbon fiber membrane: The activated carbon fiber membrane packing column is heated to 75°C, the air flow rate is 60L / min, and air is blown for 2.5h to achieve regeneration.

[0027] (6) Purification results: The HCl content in the stage I gas absorption unit was 2.98 kg, and the SiF4 content was 0.75 kg; the HCl content in the stage II gas absorption unit was 2.53 kg, and the SiF4 content was 0.91 kg. The total SiF4 / HCl gas throughput was 48.55 kg, and the SiF4 loss was 1.66 kg. The stage I gas recovery absorbent was 8.6 kg, and the stage II gas recovery absorbent was 9.0 kg.

[0028] Example 2 (1) Preparation of gas absorption device: Add 10 kg of 1,4-butanediol:terpineol = 1:1 mixed absorbent to the 20L stirred reactor of the stage I gas absorption device, control the temperature at 25-30℃, and stir at 15 r / min; Add 10 kg of 1,4-butanediol:terpineol = 5:1 mixed absorbent to the 20L stirred reactor of the stage II gas absorption device, control the temperature at 25-30℃, and stir at 15 r / min; Activated carbon fiber membrane packed column (r=5cm, d=50cm).

[0029] (2) SiF4 / HCl gas (average HCl content 15.7%) passes through the first stage gas absorption device, the second stage gas absorption device, and the activated carbon fiber membrane packed column in sequence at a flow rate of 15 L / min. After dechlorination and purification, it enters the subsequent production system of the AHF unit.

[0030] (3) After continuous dechlorination for 17 hours, the HCl content of SiF4 after purification was 4.04%, and purification was stopped.

[0031] (4) Post-treatment and recycling of organic absorbent: The absorbent liquid in the first and second stage gas absorption devices is transferred to a 20L neutralization reactor, aniline is added to adjust the pH to neutral, hydrochloride precipitate is formed, and then the organic absorbent is recycled by filtration.

[0032] (5) Post-treatment regeneration of activated carbon fiber membrane: The activated carbon fiber membrane packing column is heated to 90°C, the air flow rate is 60L / min, and air is blown for 3.5h to achieve regeneration.

[0033] (6) Purification results: The HCl content in the stage I gas absorption unit was 3.42 kg, and the SiF4 content was 0.55 kg; the HCl content in the stage II gas absorption unit was 3.02 kg, and the SiF4 content was 0.72 kg. The total SiF4 / HCl gas throughput was 52.79 kg, and the SiF4 loss was 1.27 kg. The stage I gas recovery absorbent was 8.6 kg, and the stage II gas recovery absorbent was 9.0 kg.

[0034] Example 3 The difference between Example 3 and Example 2 is that the recycled absorbent and regenerated activated carbon fiber membrane from Example 2 are used for purification and dechlorination.

[0035] Because the recovered absorbent in Example 2 was insufficient, the absorbent in the Stage I and Stage II gas absorption devices needed to be supplemented with 1,4-butanediol and terpineol to bring the total amount to 10 kg. All other conditions remained the same as in Example 2.

[0036] Purification results: In the Stage I gas absorption unit, the HCl content was 3.53 kg and the SiF4 content was 0.45 kg; in the Stage II gas absorption unit, the HCl content was 3.15 kg and the SiF4 content was 0.96 kg. The total SiF4 / HCl gas throughput was 54.26 kg, and the SiF4 loss was 1.41 kg. The amount of absorbent recovered in the Stage I gas absorption unit was 8.1 kg, and the amount recovered in the Stage II gas absorption unit was 9.2 kg.

[0037] Example 4 The difference between Example 4 and Example 2 is that the recycled absorbent and regenerated activated carbon fiber membrane from Example 3 are used for purification and dechlorination.

[0038] Because the recovered absorbent in Example 3 was insufficient, the absorbent in the Stage I and Stage II gas absorption devices needed to be supplemented with 1,4-butanediol and terpineol to bring the total amount to 10 kg. All other conditions were the same as in Example 2.

[0039] Purification results: In the Stage I gas absorption unit, the HCl content was 3.49 kg and the SiF4 content was 0.59 kg; in the Stage II gas absorption unit, the HCl content was 3.06 kg and the SiF4 content was 0.78 kg. The total SiF4 / HCl gas throughput was 53.68 kg, and the SiF4 loss was 1.37 kg. The amount of absorbent recovered in the Stage I gas absorption unit was 8.4 kg, and the amount recovered in the Stage II gas absorption unit was 8.8 kg.

[0040] As can be seen from Examples 1, 2, 3, and 4, the present invention can efficiently separate SiF4 / HCl mixed gas phases, and the organic absorbent and activated carbon fiber membrane have good regeneration effects and can be recycled multiple times; the purification stability is high and the data deviation is small; it has important significance in the process of producing anhydrous hydrogen fluoride by fluorosilicic acid method.

[0041] The following ten experimental examples will illustrate the parameter selection and technical effects of this invention: Experimental Example 1 Under the same conditions, the absorption effects of different absorbents were examined.

[0042] (1) Preparation of absorption device: Add 100g of each of the absorbents in Table 1 into a 250ml gas absorption bottle, control the temperature at 45-50℃, and stir at 15r / min; fill the column with activated carbon fiber membrane (r=2.5cm, d=15cm).

[0043] (2) SiF4 / HCl gas (average HCl content 15.7%) was passed through a gas absorption bottle and an activated carbon fiber membrane packed column at a flow rate of 3L / min. The purified gas was then absorbed by water.

[0044] (3) After absorbing for 5 minutes, the SiF4 / HCl content in the water is detected, that is, the SiF4 / HCl content in the purified gas (SiF4 is hydrolyzed in water to fluorosilicic acid, and the fluorosilicic acid content is analyzed by titration according to the standard "HG / T 2832-2020" and then converted to SiF4 content; the HCl content is analyzed by titration according to the standard "GB / T 3050-2000".

[0045] Table 1: Purification data for different absorbents

[0046] The data in the table show that alcohol-based absorbents are more effective at absorbing HCl than other reagents, and the HCl content in the purified gas is relatively low. This is presumably due to the intermolecular hydrogen bonding interactions, which allow alcohol-based absorbents to absorb a larger amount of HCl. It should be noted that N,N-dimethylformamide and dimethyl sulfoxide react rapidly with SiF4 during absorption to form precipitates, making them unsuitable for this system. This is because SiF4 has strong electrophilic properties and can rapidly react with nucleophiles such as N,N-dimethylformamide and dimethyl sulfoxide to form precipitates.

[0047] Experimental Example 2 The saturated adsorption capacity of different alcohol absorbents was investigated.

[0048] (1) Preparation of absorption device: Add 100g of each of the alcohol absorbents listed in Table 2 to a 250ml gas absorption bottle, control the temperature at 45-50℃, and stir at 15r / min; fill the column with activated carbon fiber membrane (r=2.5cm, d=15cm).

[0049] (2) SiF4 / HCl gas (average HCl content 15.7%) was passed through a gas absorption bottle and an activated carbon fiber membrane packed column at a flow rate of 3L / min. The purified gas was then absorbed by water.

[0050] (3) After the organic absorbent no longer increases in weight, the HCl content in the organic absorbent and the HCl content in the water absorption solution are tested.

[0051] Table 2: Saturated adsorption capacity data for different alcohol reagents

[0052] The data in the table show that terpineol, n-butanol, and 1,4-butanediol have the highest saturated adsorption capacity for HCl. However, in the later stages of absorption, due to the reduced adsorption capacity of the adsorbents for HCl, some HCl escapes into the subsequent water absorption liquid, leading to an increase in the average HCl content in the purified gas. Further optimization of absorption conditions is needed to improve the absorption efficiency.

[0053] Experimental Example 3 The purification effect of two-stage tandem purification was investigated.

[0054] (1) Preparation of absorption device: Add 100g of several alcohol absorbents listed in Table 3 to two 250ml gas absorption bottles respectively, control the temperature at 25-30℃, and stir at 15r / min; activated carbon fiber membrane packed column (r=2.5cm, d=15cm).

[0055] (2) SiF4 / HCl gas (average HCl content 15.7%) was passed sequentially through the I and II stage gas absorption bottles and the activated carbon fiber membrane packed column at a flow rate of 3L / min. The purified gas was absorbed by water.

[0056] (3) When the HCl content in the purified gas is ≥4%, the HCl content in the Grade I and II organic absorbents is detected.

[0057] Table 3: Data on two-stage series absorption

[0058] The data in the table show that the two-stage cascade absorption method significantly improves the absorption effect. Before the absorbent reaches the HCl saturation adsorption capacity, only a small amount of HCl escapes into the subsequent system. Terpineol has a slightly better absorption effect than 1,4-butanediol, but terpineol has a higher freezing point and viscosity, making it more complicated to process. Therefore, the effect of single-solvent experiments will be investigated using 1,4-butanediol as an example in the following experiments.

[0059] Experiment Example 4 Taking 1,4-butanediol as an example, the purification effect of organic absorbents at different temperatures was investigated.

[0060] (1) Preparation of absorption device: Add 100g of 1,4-butanediol absorbent to each 250ml gas absorption bottle, stir at 15r / min, and control different absorption temperatures; activated carbon fiber membrane packed column (r=2.5cm, d=15cm).

[0061] (2) SiF4 / HCl gas (average HCl content 15.7%) was passed through a gas absorption bottle and an activated carbon fiber membrane packed column at a flow rate of 3L / min. The purified gas was then absorbed by water.

[0062] (3) After absorbing for 5 minutes, the HCl content in 1,4-butanediol and water absorption solution was measured respectively.

[0063] Table 4: Purification data at different temperatures

[0064] Note: 1,4-Butanediol has a melting point of 16°C and solidifies at 15°C. The absorption efficiency of 1,4-butanediol for HCl initially increases and then decreases with increasing temperature, reaching its optimal absorption efficiency at 25-30℃. Temperature is the main factor affecting absorption efficiency; as temperature increases, the intramolecular energy increases, leading to a decrease in absorption efficiency. Conversely, as temperature decreases, the viscosity of the organic absorbent gradually increases, resulting in a further decrease in absorption efficiency. At 25-30℃, 1,4-butanediol reaches its optimal absorption viscosity, thus exhibiting the best absorption effect.

[0065] Experimental Example 5 Taking 1,4-butanediol as an example, the purification effect of different SiF4 / HCl gas flow rates was investigated.

[0066] (1) Preparation of absorption device: Add 100g of 1,4-butanediol absorbent to each 250ml gas absorption bottle, stir at 15r / min, and control the temperature at 25-30℃; activated carbon fiber membrane packed column (r=2.5cm, d=15cm).

[0067] (2) SiF4 / HCl gas (average HCl content 15.7%) was passed through a gas absorption bottle and an activated carbon fiber membrane packed column at different flow rates. The purified gas was absorbed by water.

[0068] (3) When the SiF4 / HCl gas treatment volume reaches 30g, purification is stopped, and the HCl content in 1,4-butanediol and water absorption solution is measured respectively.

[0069] Table 5: Purification data for different gas flow rates

[0070] The purification effect is inversely proportional to the gas flow rate; as the flow rate decreases, the purification effect increases. Decreasing the flow rate increases the retention time of the gas in the absorbent, allowing for more complete absorption of HCl molecules, thus increasing the purification effect. Simultaneously, the gas flow rate is inversely proportional to the absorption time; reducing the flow rate to 0.5 L / min requires 30 minutes to purify 30 g of SiF4 / HCl gas, which is time-consuming. For a purification system with 100 g of absorbent, the optimal gas flow rate is 1.5 L / min.

[0071] Experimental Example 6 The recovery rate of organic absorbents treated with different organic bases was investigated.

[0072] The following organic bases were added dropwise to a 1,4-butanediol absorbent containing 25.13% hydrogen chloride. The temperature was controlled at 20-25℃ during the dropwise addition process. The dropwise addition was stopped after neutralization, and the hydrochloride precipitate formed was filtered out.

[0073] Table 6: Recovery rate data of absorbents treated with different organic bases

[0074] Triethylamine is the strongest basic compound, and its reaction with HCl to form hydrochloride produces a large amount of white fumes, making it difficult to process. The resulting hydrochloride precipitate has a small particle size, and separation from 1,4-butanediol is difficult, leading to the lowest recovery rate. Aniline reacts with HCl in a milder manner, and the resulting hydrochloride precipitate and 1,4-butanediol are easily separated. Considering all factors, aniline is the optimal organic base.

[0075] Experimental Example 7 The effect of organic base treatment on absorbent at different temperatures was investigated.

[0076] Aniline was used to treat 1,4-butanediol absorbent containing 25.13% hydrogen chloride. Aniline was added dropwise at different temperatures (20℃, 30℃, 40℃, and 50℃), and the absorbent recovery rate was 90-95%. Temperature had no significant effect on the absorbent recovery rate, but during the experiment, some HCl escaped into the air due to the increased temperature, and a large amount of white fumes were generated when organic bases were added, making the operation difficult. Therefore, the optimal treatment temperature is 20-25℃.

[0077] Experimental Example 8 The effect of different temperatures on the regeneration efficiency of activated carbon fiber membranes was investigated.

[0078] The regeneration air flow rate of the activated carbon fiber membrane was controlled at 90 L / min, and the regeneration time was 4 h. The regenerated activated carbon fiber membrane was then subjected to a SiF4 / HCl purification experiment. The SiF4 / HCl flow rate was 1.5 L / min, the absorbent was 100 g of 1,4-butanediol, the stirring speed was 15 r / min, and the temperature was controlled at 25-30℃. The regenerated activated carbon fiber membrane was packed in a column (r=2.5 cm, d=15 cm). The purified gas was absorbed by water. After 5 min of purification, the HCl content in the water absorption solution was measured.

[0079] Table 7: Data on regenerated activated carbon fiber membranes at different temperatures

[0080] SiF4 / HCl purification experiments were conducted using regenerated activated carbon fiber membranes. The purification effect was poor when the regeneration temperature was <90℃; the optimal regeneration effect was achieved when the regeneration temperature was ≥90℃, with the purification effect being essentially consistent with that of virgin activated carbon fiber membranes. The optimal regeneration temperature for activated carbon fiber membranes is 90-100℃.

[0081] Experimental Example 9 This experiment investigates the effect of different airflow rates on the regeneration efficiency of activated carbon fiber membranes.

[0082] The regeneration temperature of the activated carbon fiber membrane was controlled at 90-100℃, and the regeneration time was 4 hours. The regenerated activated carbon fiber membrane was then subjected to SiF4 / HCl purification experiments. The purification conditions were the same as in Example 7.

[0083] Table 8: Data on regenerated activated carbon fiber membranes with different airflow rates

[0084] The regeneration effect of activated carbon fiber membranes is directly proportional to the airflow rate. Optimal regeneration is achieved when the airflow rate is ≥70 L / min, with the purification effect remaining essentially the same as that of brand-new activated carbon fiber membranes. The optimal airflow rate for activated carbon fiber membrane regeneration is 70 L / min.

[0085] Experimental Example 10 The effect of activated carbon fiber membrane regeneration time was investigated.

[0086] The activated carbon fiber membrane was regenerated at a temperature of 90-100℃ and an air flow rate of 70 L / min. The regenerated activated carbon fiber membrane was then subjected to SiF4 / HCl purification experiments. The purification conditions were the same as in Example 7.

[0087] Table 9: Data on different regeneration times of activated carbon fiber membranes

[0088] The activated carbon fiber membrane achieves optimal regeneration effect after 4 hours of regeneration, and the purification effect is basically the same as that of a brand new activated carbon fiber membrane.

[0089] Based on the combined experiments 8, 9, and 10, the optimal conditions for regenerating activated carbon fiber membranes are: temperature control at 90-100℃, air flow rate at 70L / min, and regeneration time at 4h.

[0090] After determining the absorption conditions and the two-stage absorption method through the above experimental examples 1-10, the absorption system was expanded by 100 times to form the SiF4 / HCl mixed gas phase purification and separation method of the present invention.

[0091] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for separating a silicon tetrafluoride and hydrogen chloride mixed gas, characterized by: The method comprises the following steps: Step 1, gas absorption preparation: filling the gas absorption device with an alcohol absorbent, and connecting the gas absorption device and the activated carbon fiber membrane packed column in series; Step 2, purification: passing the intermediate product SiF4 / HCl mixed gas phase of anhydrous hydrogen fluoride produced by a fluorosilicic acid method through the gas absorption device to obtain purified SiF4 gas; Step 3, residual absorption: passing the SiF4 gas purified in step 2 through the activated carbon fiber membrane packed column to obtain SiF4 gas.

2. The method of separating a silicon tetrafluoride and hydrogen chloride mixed gas according to claim 1, characterized by: The gas absorption device comprises a first-stage gas absorption device and a second-stage gas absorption device connected in series.

3. The method of claim 1, wherein: The method further comprises a recycling method of the alcohol absorbent, and the recycling method of the alcohol absorbent comprises the following steps: Step 201, when the HCl content in the SiF4 gas obtained in step 3 is greater than or equal to 4%, stop passing the SiF4 / HCl mixed gas phase into the gas absorption device; Step 202, after stopping passing the SiF4 / HCl mixed gas phase into the gas absorption device, transport the alcohol absorbent in the gas absorption device to a neutralization reaction kettle; and drop an organic base into the alcohol absorbent in the neutralization reaction kettle until the alcohol absorbent is neutralized; Step 203, filter the alcohol absorbent after the titration in step 202 is completed, and recycle the filtered alcohol absorbent to the gas absorption device in step 1.

4. The method of claim 3, wherein: The organic base is any one of aniline, triethylamine, N,N-diethyl aniline, N-methyl aniline and benzylamine.

5. The method of claim 4, wherein: The organic base is aniline, and the temperature of the alcohol absorbent is maintained at 20-25°C during titration.

6. The method of claim 1, wherein: The alcohol absorbent is any one or a mixture of multiple of t-butyl alcohol, cyclohexanol, terpineol, t-amyl alcohol, n-butyl alcohol and 1,4-butanediol.

7. The method of claim 6, wherein: The alcohol absorbent is 1,4-butanediol, and the working temperature of the gas absorption device is 25-30°C, and the gas flow of the SiF4 / HCl mixed gas phase is 1.5 L / min.

8. The method of claim 1, wherein: The method further comprises a recycling method of the activated carbon fiber membrane in the activated carbon fiber membrane packed column, and the recycling method of the activated carbon fiber membrane comprises the following steps: Step 301, when the HCl content in the SiF4 gas obtained in step 3 is greater than or equal to 4%, stop passing the purified SiF4 gas into the activated carbon fiber membrane packed column; Step 302, heat the activated carbon fiber membrane packed column to above 75-150°C, and continuously pass air into the activated carbon fiber membrane packed column for more than 4 hours, and the air flow is greater than 70-150 L / min.

9. The method of claim 8, wherein: The heating temperature of the activated carbon fiber membrane packed column in step 302 is 90-100°C.

10. The method of claim 8, wherein: The air flow is 70 L / min.

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