Method for preparing high-purity sulfur hexafluoride from sulfur recovered in a hydrofluoric acid production process
Fluorine-containing active ions are prepared by hydrofluoric acid electrolysis, directly generating sulfur hexafluoride gas, which is then purified by distillation. This solves the problem of sulfur deposition, improves product purity and production efficiency, reduces energy consumption, and is suitable for electrical equipment.
Patent Information
- Application Number
- CN202610229228.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-26
- Publication Date
- 2026-05-29
AI Technical Summary
Existing methods for preparing sulfur hexafluoride suffer from sulfur deposition problems, leading to corrosion of pipelines and equipment, blockage of production systems, and safety hazards. Furthermore, the product purity is low, energy consumption is high, and there is a lack of effective methods for treating exhaust gases and substandard products.
The method of preparing fluorine-containing active ions by hydrofluoric acid electrolysis directly utilizes sulfur-containing gas to generate sulfur hexafluoride gas, and then purifies it by distillation, which simplifies the process, avoids additional desulfurization treatment, and improves production efficiency and product purity.
It effectively solves the problem of sulfur deposition, reduces equipment corrosion and maintenance costs, improves the purity and production efficiency of sulfur hexafluoride, reduces energy consumption, and is suitable for the field of electrical equipment.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of high-purity sulfur hexafluoride preparation technology, and particularly relates to a method for preparing high-purity sulfur hexafluoride by recovering sulfur during the preparation of hydrofluoric acid. Background Technology
[0002] Sulfur hexafluoride (SF6) is a colorless, odorless, non-toxic, and non-flammable stable gas with excellent electrical insulation and arc-quenching properties. It is widely used in electrical equipment such as circuit breakers, converters, transformers, large-capacity cables, and surge arresters. Its preparation typically involves the reaction of fluorine gas with sulfur. The crude SF6 gas produced requires continuous purification to obtain a product that meets industrial production requirements.
[0003] However, during the preparation of hydrogen fluoride, the raw material for fluorine gas, a large amount of sulfur-containing gas is generated in the rotary reactor due to the presence of a large amount of elemental sulfur and small amounts of metal sulfides and sulfate metal compounds in the fluorite powder. If this gas directly enters equipment such as condensers, it will condense into solid elemental sulfur due to the low temperature of the pipes and equipment, and deposit on the inner walls. This sulfur deposition not only causes corrosion of pipes and equipment, increasing maintenance costs, but also causes blockages in the production system, posing safety hazards. Although the sulfur content in fluorite can be reduced during the hydrogen fluoride preparation process through physical removal, chemical removal, and enhanced mineral processing, these methods still cannot effectively solve the problem of sulfur deposition in the production system. In addition, existing methods for preparing sulfur hexafluoride suffer from problems such as high impurity content in the raw materials, the need for multi-stage distillation, high energy consumption, low product purity, and a lack of methods for handling tail gas and substandard products. Summary of the Invention
[0004] The purpose of this invention is to provide a method for recovering sulfur and preparing high-purity sulfur hexafluoride during the preparation of hydrofluoric acid. This method, which uses hydrofluoric acid electrolysis to prepare fluorine-containing active ions, eliminates the need for sulfur removal and directly utilizes the fluorine-containing active ions of elemental sulfur fluoride to generate sulfur hexafluoride gas. High-purity sulfur hexafluoride gas is then prepared through distillation purification, thereby achieving the recovery and utilization of sulfur resources, improving production efficiency and product purity. This method simultaneously reduces energy consumption and environmental pollution. It not only solves the sulfur deposition problem present in existing technologies but also avoids various byproducts and impurities generated by the strong fluorination properties of fluorine gas in traditional preparation methods, thus meeting the production requirements for high-purity sulfur hexafluoride gas.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for recovering sulfur to prepare high-purity sulfur hexafluoride during the preparation of hydrofluoric acid includes the following steps: S1. The HF gas produced from the hydrogen fluoride rotary reactor is fed into a scrubbing tower for preliminary treatment. The preliminary treatment of the HF gas in the scrubbing tower mainly removes fluorosulfonic acid, sulfuric acid mist, solid dust and high-boiling-point fluoride impurities. Then, the sulfur-containing HF gas is directly fed into the electrolytic fluorination unit.
[0006] S2. Fluoride ions are produced by electrolysis of sulfur-containing hydrogen fluoride gas at 85–103 °C; S3. Sulfur vapor is then introduced into step S2 to react and generate sulfur hexafluoride gas; S4. The sulfur hexafluoride gas prepared in step S3 is passed into a high-boiling recovery distillation column for preliminary separation and recovery of high-purity sulfur hexafluoride product. Then, the unpurified gas is passed into a low-boiling recovery distillation column for further separation and recovery of high-purity sulfur hexafluoride product.
[0007] Furthermore, the raw material for the production of hydrogen fluoride in step S1 is fluorite powder, with high-grade fluorite powder containing 0.05-0.5% S and low-grade fluorite powder containing 0.5-10% S.
[0008] Furthermore, in step S2, the inter-electrode voltage of the electrolytic cell is 5–6.9V, and the cathode and anode gas pressure is 0.01MPa ± 800Pa. This refers to the pressure of the electrolytic cell, which is generally a slightly positive pressure environment. Furthermore, in step S3, the reaction temperature is 150–200°C and the pressure is 0.2–0.4 MPa, which is the pressure of the reactor during the preparation of hydrofluoric acid.
[0009] Furthermore, in step S4, the top temperature of the high-boiling recovery distillation column is 65–75°C and the pressure is 0.3–0.4 MPa; the top temperature of the low-boiling recovery distillation column is 25–35°C and the pressure is 0.1–0.2 MPa. This pressure is the pressure of the distillation column.
[0010] The advantages of this invention are: 1. The present invention provides a method for preparing fluorine-active ions by electrolysis of hydrofluoric acid, which eliminates the need for additional desulfurization treatment and allows for the direct use of sulfur-containing gas to prepare sulfur hexafluoride, thereby simplifying the process, improving production efficiency, and reducing production costs. 2. This invention uses an electrolytic method to prepare fluorine active ions, avoiding the problems of difficult-to-control reaction temperature and increased byproducts that increase the burden of post-processing in the traditional direct fluorination method, and overcoming the disadvantage that the direct fluorination method is not suitable for industrial production; 3. This invention uses fluorine-active ions prepared by electrolysis to directly fluorinate elemental sulfur and generate sulfur hexafluoride gas, avoiding the problem of sulfur vapor condensing and depositing on the inner wall of equipment in the traditional preparation method of hydrofluoric acid, effectively solving the Fe~S corrosion problem of pipelines and equipment, and reducing maintenance costs; 4. The sulfur hexafluoride gas prepared by the method of the present invention has high purity and good quality, and can be widely used in electrical equipment such as circuit breakers, converters, transformers, large container cables, surge arresters, etc., and has good market application prospects. Detailed Implementation
[0011] Example 1: This invention provides a method for recovering sulfur to prepare high-purity sulfur hexafluoride during the preparation of hydrofluoric acid, the specific steps of which are as follows: 1) The crude HF gas from the hydrogen fluoride rotary reactor enters a scrubbing tower for preliminary treatment, mainly to remove fluorosulfonic acid, sulfuric acid mist, solid dust, and high-boiling-point fluoride impurities. Then, the sulfur-containing HF gas is directly fed into the electrolytic fluorination unit. 2) The sulfur-containing hydrogen fluoride gas is electrolyzed at 85–103°C to produce fluoride ions. The inter-electrode voltage of the electrolytic cell is controlled between 5–6.9V, and the gas pressure at the cathode and anode is kept stable within ±800Pa, with a pressure difference not exceeding 800Pa. This reduces the risk of over-electrolysis due to high voltage and temperature, which could lead to the generation of fluoride gas and other fluoride impurities. The electrolytic cell volume is 100–200L. A nickel plate anode is used, completely immersed in the hydrofluoric acid electrolyte. The electrolytic gas flow rate is controlled at 0.5–1 m³ / h. The current and voltage of this electrolytic cell change continuously as the electrolytic fluorination proceeds; they are not fixed values. Initially, the voltage is set at around 1V, and then it is increased by 0.2-0.5V at regular intervals. When the voltage reaches 5V, the current is about 0.1A, and electrolysis begins. The voltage and current continue to rise, and electrolysis continues until the voltage reaches a maximum of 6.9V and the current reaches a maximum of 6.3A, at which point it stops. The amount of charge has reached the theoretical value, and most of the substance has been electrolyzed. The voltage will then slowly drop to 0V, and the electrolysis will end once the current gradually decreases to below 1A.
[0012] 3) Sulfur vapor is introduced into the above gas to mix and react. The reaction temperature is controlled at 150-200℃ and the pressure is controlled at 0.2-0.4MPa to ensure that the reaction proceeds fully and sulfur hexafluoride gas is generated. The amount of sulfur vapor introduced is 6:1-8:1 molar ratio of sulfur-containing hydrogen fluoride gas to sulfur. The reaction time is controlled at 12-24h. The temperature and pressure are kept constant during the reaction. After the reaction is completed, the temperature is quickly cooled to room temperature and the pressure is reduced to atmospheric pressure.
[0013] 4) Sulfur hexafluoride (SF6) mixed with high-boiling-point and low-boiling-point impurities is recovered using high-boiling-point and low-boiling-point recovery distillation columns. SF6 gas is initially separated in the high-boiling-point recovery distillation column, with the top temperature controlled at 65–75°C and the pressure at 0.3–0.4 MPa, achieving a recovery rate of 90–95%. The unpurified gas is then further separated in the low-boiling-point recovery distillation column, with the top temperature controlled at 25–35°C and the pressure at 0.1–0.2 MPa, achieving a recovery rate of 98–99%. The high-purity SF6 product from the bottom of the low-boiling-point recovery distillation column is collected, with a purity exceeding 99.9995%.
[0014] Example 2: This invention provides a method for recovering sulfur to prepare high-purity sulfur hexafluoride during the preparation of hydrofluoric acid, the specific steps of which are as follows: 1) The crude HF gas from the hydrogen fluoride rotary reactor is pre-treated by a scrubbing tower, a crude cooler and other equipment. The crude HF gas and sulfur-containing gas components are separated by compressed air purging. The compressed air flow rate is 8-12 L / min and the purging time is 20-25 min. 2) The sulfur-containing hydrogen fluoride gas is electrolyzed at a temperature of 90-100℃ to produce fluoride ions. The inter-electrode voltage of the electrolytic cell is controlled between 5 and 6.9V, and the gas pressure at the cathode and anode is kept stable within ±700Pa, with a pressure difference not exceeding 700Pa, in order to reduce the generation of fluoride gas due to excessive electrolysis caused by high voltage and high temperature, thereby generating other fluoride impurities. The volume of the electrolytic cell is 150-180L. Nickel plate anodes are used, and the nickel anodes are completely immersed in the hydrofluoric acid electrolyte. The electrolytic gas flow rate is controlled at 0.8m³ / h.
[0015] 3) Sulfur vapor is introduced into the above gas to mix and react. The reaction temperature is controlled at 170-190℃ and the pressure is 0.3MPa to ensure that the reaction proceeds fully and sulfur hexafluoride gas is generated. The amount of sulfur vapor introduced is 7:1 molar ratio of sulfur-containing hydrogen fluoride gas to sulfur. The reaction time is controlled at 18h. The temperature and pressure are kept constant during the reaction. After the reaction is completed, the temperature is quickly cooled to room temperature and the pressure is reduced to atmospheric pressure.
[0016] 4) Sulfur hexafluoride (SF6) mixed with high-boiling-point and low-boiling-point impurities is recovered using high-boiling-point and low-boiling-point recovery distillation columns. SF6 gas is initially separated in the high-boiling-point recovery distillation column, with the top temperature controlled at 70°C and the pressure at 0.35 MPa, achieving a recovery rate of 92%. The unpurified gas is then further separated in the low-boiling-point recovery distillation column, with the top temperature controlled at 30°C and the pressure at 0.15 MPa, achieving a recovery rate of 99%. The high-purity SF6 product from the bottom of the low-boiling-point recovery distillation column is collected, achieving a purity of 99.9998%.
[0017] This patent mainly eliminates the need for treatment of the sulfur generated during the hydrogen fluoride preparation process, directly generating sulfur hexafluoride gas. This reduces the safety risks in the hydrogen fluoride production process while utilizing the generated sulfur, reducing production steps, and achieving high efficiency and energy saving.
Claims
1. A method for recovering sulfur to prepare high-purity sulfur hexafluoride during the preparation of hydrofluoric acid, characterized in that, Includes the following steps: S1. The HF gas produced from the hydrogen fluoride rotary reactor enters the scrubbing tower for preliminary treatment; S2. Fluoride ions are produced by electrolysis of sulfur-containing hydrogen fluoride gas at 85–103 °C; S3. Sulfur vapor is then introduced into step S2 to react and generate sulfur hexafluoride gas; S4. The sulfur hexafluoride gas prepared in step S3 is passed into a high-boiling recovery distillation column for preliminary separation and recovery of high-purity sulfur hexafluoride product. Then, the unpurified gas is passed into a low-boiling recovery distillation column for further separation and recovery of high-purity sulfur hexafluoride product.
2. The method for preparing high-purity sulfur hexafluoride by recovering sulfur during the preparation of hydrofluoric acid as described in claim 1, characterized in that: In step S1, the raw material for producing hydrogen fluoride is fluorite powder. The S content in high-grade fluorite powder is 0.05-0.5%, and the S content in low-grade fluorite powder is 0.5-10%.
3. The method for preparing high-purity sulfur hexafluoride by recovering sulfur during the preparation of hydrofluoric acid as described in claim 1, characterized in that: In step S2, the inter-electrode voltage of the electrolytic cell is 5–6.9V, and the cathode and anode gas pressures are 0.01MPa ± 800Pa.
4. The method for preparing high-purity sulfur hexafluoride by recovering sulfur during the preparation of hydrofluoric acid as described in claim 1, characterized in that: In step S3, the reaction temperature is 150–200°C and the pressure is 0.2–0.4 MPa.
5. The method for preparing high-purity sulfur hexafluoride by recovering sulfur during the preparation of hydrofluoric acid as described in claim 1, characterized in that: In step S4, the top temperature of the high-boiling recovery distillation column is 65–75°C, and the pressure is 0.3–0.4 MPa; the top temperature of the low-boiling recovery distillation column is 25–35°C, and the pressure is 0.1–0.2 MPa.