Method for converting sulfur hexafluoride into hydrofluoric acid

Abstract

The invention discloses a method for converting sulfur hexafluoride into hydrofluoric acid, which comprises the following steps: placing water and sulfur hexafluoride gas in a reaction container, and irradiating by gamma rays to obtain the hydrofluoric acid. According to the method for directly converting sulfur hexafluoride into hydrofluoric acid by gamma rays, SF6 is easily dissociated by gamma rays, generated active substances react with water, and the product is stable and has high value. The gamma ray penetrating power is high, and the device is suitable for large-capacity and even high-pressure reaction. The radiation energy is low in cost and clean, the half-life period of a common 60Co radioactive source is 5.23 years, the method is suitable for large-scale conversion of SF6, harmless treatment of SF6 is achieved in a high-efficiency and low-carbon mode through an ionizing radiation method, the cost is effectively reduced, and the conversion efficiency of SF6 is improved.

Description

Technical Field

[0001] The invention relates to the technical field of sulfur hexafluoride degradation and conversion, and in particular to a method for converting sulfur hexafluoride into hydrofluoric acid. Background Art

[0002] Sulfur hexafluoride (SF6) gas is a greenhouse gas that needs to be reduced according to the Kyoto Protocol. Its global warming potential is 25,200 times that of carbon dioxide. However, it is used in large quantities in power equipment as an insulating and arc-extinguishing medium. Currently, the amount used in my country's power industry is close to 100,000 tons. According to the State Grid Corporation's plan, the use of SF6 gas will reach a peak between 2025 and 2028, and then more than 2,000 tons of SF6 gas will be retired each year. The harmless treatment and resource utilization of existing SF6 gas is an urgent issue that must be studied.

[0003] SF6 molecules are extremely stable and difficult to degrade naturally. The main degradation treatment technologies currently include thermal decomposition, catalytic oxidation, discharge, photoreduction, ionizing radiation treatment, etc. At the same time, SF6 contains abundant fluorine elements, and it is of great significance to convert the F atoms in it into hydrofluoric acid, an important industrial raw material.

[0004] The Chinese patent application document with publication number CN105873857A proposes a harmless treatment scheme for SF6, which specifically involves irradiating the gas phase after mixing SF6 with hydrogen, and directly liquefying the product hydrogen fluoride or absorbing it with metal ion salt to produce fluorinated salt. The use of hydrogen increases equipment design and processing costs, and poses a safety hazard. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to degrade SF6 at low cost and high efficiency and convert it into high-value products.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] A method for converting sulfur hexafluoride into hydrofluoric acid comprises the following steps: placing water and sulfur hexafluoride gas in a reaction container, and obtaining the hydrofluoric acid by irradiating with gamma rays.

[0008] Beneficial effects: The method provided by the present invention for directly converting sulfur hexafluoride into hydrofluoric acid by gamma rays, gamma rays can easily dissociate SF6, produce active substances that react with water, and the products are stable and of high value. Gamma rays have strong penetrating power and are suitable for large-capacity and even high-pressure reactions. Radiation energy is cheap and clean, and is commonly used 60The half-life of the Co radioactive source is 5.23 years, which is suitable for the large-scale conversion of SF6. The ionizing radiation method is used to achieve efficient and low-carbon harmless treatment of SF6, effectively reducing costs and improving SF6 conversion efficiency.

[0009] Preferably, the purity of the sulfur hexafluoride gas is >99%.

[0010] Preferably, the reaction container is a fluorine-resistant reaction container.

[0011] Preferably, the material of the fluorine-resistant reaction container is Monel 400 alloy.

[0012] Preferably, the method for converting sulfur hexafluoride into hydrofluoric acid comprises the following steps: adding water into a reaction container, then introducing sulfur hexafluoride gas, and obtaining the hydrofluoric acid by gamma ray irradiation.

[0013] Preferably, the volume of SF6 gas introduced into the reaction container accounts for 20-98% of the volume of the reaction container.

[0014] Preferably, the volume of SF6 gas introduced into the reaction container accounts for 40-98% of the volume of the reaction container.

[0015] Preferably, the volume of SF6 gas introduced into the reaction container accounts for 60-98% of the volume of the reaction container.

[0016] Preferably, the pressure of the reaction system after the sulfur hexafluoride gas is introduced is 0.1-2 MPa.

[0017] Preferably, the irradiation is carried out at a temperature of 0-100°C.

[0018] Preferably, the irradiation is carried out at a temperature of 10-50°C.

[0019] Preferably, the irradiation is carried out at a temperature of 20-30°C.

[0020] Preferably, the irradiation is carried out at room temperature.

[0021] Preferably, during the irradiation process, the gamma ray dose rate ranges from 5 to 150 Gy / min.

[0022] Preferably, the gamma ray dose rate ranges from 20-100 Gy / min.

[0023] Preferably, the gamma ray dose rate ranges from 30-50 Gy / min.

[0024] Preferably, during the irradiation process, the total absorbed radiation dose of the reaction system is 20-200 kGy.

[0025] Preferably, during the irradiation process, the total absorbed radiation dose of the reaction system is 80-100 kGy.

[0026] Preferably, during the irradiation process, the total absorbed radiation dose of the reaction system is 50-150 kGy.

[0027] The advantages of the present invention are:

[0028] (1) The present invention uses high-energy gamma rays to activate SF6, commonly used cobalt-60 ( 60 The half-life of the Co) radioisotope source is 5.23 years, and the average energy of its γ photons is 1.25 MeV, which is much higher than the bond energy of SF6 (3.5-4 eV). Therefore, it is easy to dissociate the inert SF6 to generate two active products, F2 and SF4, which are further converted into a stable product with high added value, hydrofluoric acid, in the presence of water. Compared with electron beam technology, γ rays have high energy, low cost, strong penetration, and can react in a pressure-resistant metal container, so the treatment efficiency is high and the cost is low, which is suitable for large-scale degradation and conversion of SF6.

[0029] (2) The present invention does not require the use of hydrogen, but uses water as a source of hydrogen atoms to directly irradiate SF6. Water participates in the irradiation degradation and transformation of SF6 gas, absorbs active free radicals or active intermediates generated by SF6 under ionizing radiation, reacts rapidly and has high activity, and can generate stable hydrofluoric acid, saving the process equipment and steps of liquefied hydrogen fluoride.

[0030] (3) Water, as a low-cost absorbent, can also generate active intermediate transient products under radiation conditions, which can further accelerate the reaction and improve the conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the ion chromatogram of the liquid product after irradiation in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0034] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0035] Example 1

[0036] A method for converting sulfur hexafluoride into hydrofluoric acid, the specific steps are as follows:

[0037] First, add 20 mL of deionized water to a 500 mL reaction vessel (a nickel pressure vessel resistant to HF acid corrosion, i.e., a Monel 400 alloy pressure vessel), then fill the reaction vessel with pure SF6 gas from a gas cylinder through the inlet valve, ventilate for 20 minutes to exhaust the air, then close the inlet valve and outlet valve, and the reaction system pressure is 0.1 MPa. Place the reaction vessel at room temperature 60 The irradiation was carried out under Co gamma rays, the irradiation absorbed dose rate was 30 Gy / min, and the total irradiation absorbed dose was 180 kGy. After the reaction, the anions in the liquid were tested by ion chromatography.

[0038] Experimental test analysis

[0039] Figure 1 This is the ion chromatogram of the liquid product after irradiation in Example 1. A peak appears in the retention time interval of 3.75-6.8 min, and the peak center is about 4.5 min. The anion corresponding to the peak here is fluoride ion, and it is delayed compared to the standard peak (3.8 min). This is because HF will associate under strong acid conditions, the ion radius increases, and the elution time is delayed. According to the standard curve, the peak area is integrated and calculated, and the corresponding HF concentration is 10.78 g / L.

[0040] Example 2

[0041] A method for converting sulfur hexafluoride into hydrofluoric acid, the specific steps are as follows:

[0042] First, add 200 mL of deionized water to a 500 mL reaction vessel (a nickel pressure vessel resistant to HF acid corrosion, i.e., a Monel 400 alloy pressure vessel), and then fill the reaction vessel with pure SF6 gas from a gas cylinder through the inlet valve. After the air is exhausted, close the outlet valve, and continue to add SF6 gas until the pressure gauge of the pressure vessel shows 2 MPa. Place the reaction vessel at room temperature. 60 The irradiation was carried out under Co gamma rays, the irradiation absorbed dose rate was 30 Gy / min, the total irradiation absorbed dose was 180 kGy, and after the reaction was completed, the hydrofluoric acid concentration in the aqueous solution was tested by ion chromatography and was 36.3 g / L.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for converting sulfur hexafluoride into hydrofluoric acid, characterized in that: The method comprises the following steps: placing water and sulfur hexafluoride gas in a reaction container, and obtaining the hydrofluoric acid by irradiating with gamma rays.

2. The method for converting sulfur hexafluoride into hydrofluoric acid according to claim 1, characterized in that: The purity of the sulfur hexafluoride gas is >99%.

3. The method for converting sulfur hexafluoride into hydrofluoric acid according to claim 1, characterized in that: The reaction container is a fluorine-resistant reaction container.

4. The method for converting sulfur hexafluoride into hydrofluoric acid according to claim 3, characterized in that: The material of the fluorine-resistant reaction container is Monel 400 alloy.

5. The method for converting sulfur hexafluoride into hydrofluoric acid according to claim 1, characterized in that: The method comprises the following steps: adding water into a reaction container, then introducing sulfur hexafluoride gas, and obtaining the hydrofluoric acid by irradiating with gamma rays.

6. The method for converting sulfur hexafluoride into hydrofluoric acid according to claim 5, characterized in that: The volume of SF6 gas introduced into the reaction container accounts for 20-98% of the volume of the reaction container.

7. The method for converting sulfur hexafluoride into hydrofluoric acid according to claim 5, characterized in that: After sulfur hexafluoride gas is introduced, the pressure of the reaction system is 0.1-2MPa.

8. The method for converting sulfur hexafluoride into hydrofluoric acid according to claim 1, characterized in that: The irradiation is carried out at a temperature of 0-100°C.

9. The method for converting sulfur hexafluoride into hydrofluoric acid according to claim 1, characterized in that: During the irradiation process, the gamma ray dose rate ranged from 5-150Gy / min.

10. The method for converting sulfur hexafluoride into hydrofluoric acid according to any one of claims 1 to 9, characterized in that: During the irradiation process, the total absorbed radiation dose of the reaction system is 20-200 kGy.

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