Method and system for comprehensively recycling thionyl fluoride synthesis waste gas

Abstract

The invention belongs to a tail gas resource utilization technology, and particularly provides a method and a system for comprehensively reutilizing thionyl fluoride synthesis waste gas. The method comprises the following steps: S1, tail gas extraction: extracting tail gas generated in a thionyl fluoride synthesis reaction process, wherein the tail gas contains hydrogen chloride, hydrogen fluoride, unreacted chlorinated raw materials and intermediate byproducts; s2, condensation treatment: negative pressure is controlled, the tail gas is guided into a condensation unit for cooling, and the cooling temperature is controlled within the range of 0-10 DEG C for removing high-boiling-point impurities; s3, waste gas absorption: introducing the condensed tail gas into an absorption tower, and fully absorbing hydrogen chloride and hydrogen fluoride in the tail gas to form mixed acid; s4, chemical precipitation: adding lime milk into the mixed acid to convert hydrogen fluoride into insoluble calcium fluoride precipitate, converting hydrogen chloride into calcium chloride, and then filtering to obtain a calcium fluoride filter cake and a calcium chloride solution; s5, concentrating and crystallizing: concentrating and crystallizing the calcium chloride solution to obtain calcium chloride crystals.

Description

Technical Field

[0001] The present invention relates to a technology for resource utilization of tail gas, and specifically provides a method and system for comprehensive recycling of thionyl fluoride synthesis waste gas. Background Art

[0002] With the continuous development of the semiconductor industry, high-end chip technology has made continuous breakthroughs, among which dry etching technology has been widely used. As the key etching electronic gas and cleaning electronic gas, higher demands have also been put forward. Fluorine-based electronic gas has ushered in rapid development.

[0003] Typical fluorine-based electronic gases currently include sulfur hexafluoride (SF6), carbon tetrafluoride (CF4) and fluorocarbon gases (such as CH3F, CH2F2, CHF3, C2F6, C3F8, etc.). Their GWP values ​​are relatively high and have a large potential impact on the environment. The development of etching and cleaning gases with low GWP values ​​has become the key to the development of the semiconductor industry. Thionyl fluoride (SOF2) is easier to dispose of and more environmentally friendly while ensuring etching and cleaning effects.

[0004] The industrial synthesis of thionyl fluoride (SOF2) typically involves a one-step reaction between anhydrous hydrogen fluoride (AHF) and thionyl chloride (SOCl2). However, this reaction produces a large amount of hydrogen chloride (HCl) gas as a by-product. If discharged without treatment, this HCl can cause severe environmental pollution and potentially corrode equipment and piping, posing a safety hazard.

[0005] At present, the treatment of hydrogen chloride mostly relies on alkaline solution absorption and purification, which has problems such as low recovery rate, high energy consumption, poor product purity, and heavy post-processing burden. It is difficult to meet the demand for the reuse of high-purity hydrogen chloride gas in the fields of electronic chemistry, pharmaceutical intermediates, etc.

[0006] Therefore, there is an urgent need to provide a technical solution with simple process, high energy efficiency, and the ability to achieve high-purity and high-yield recovery of by-product hydrogen chloride, which can not only effectively solve the problem of by-gas disposal in the synthesis process of thionyl fluoride, but also realize resource utilization and improve the overall economy and green level of the system. Summary of the Invention

[0007] In view of the above problems, the present invention aims to provide a method for comprehensive recycling of thionyl fluoride synthesis waste gas, comprising the following steps: S1, tail gas extraction: the tail gas generated during the thionyl fluoride synthesis reaction is extracted, wherein the tail gas contains hydrogen chloride, hydrogen fluoride, unreacted chlorinated raw materials and intermediate by-products; S2, condensation treatment: controlling the negative pressure to introduce the tail gas into the condensation unit for cooling, and the cooling temperature is controlled in the range of 0°C to 10°C to remove high-boiling-point impurities; S3, exhaust gas absorption: the condensed exhaust gas is introduced into the absorption tower to fully absorb the hydrogen chloride and hydrogen fluoride in the exhaust gas to form mixed acid; S4. Chemical precipitation: adding lime milk to the mixed acid to convert hydrogen fluoride into insoluble calcium fluoride precipitate and hydrogen chloride into calcium chloride, followed by filtration to obtain a calcium fluoride filter cake and a calcium chloride solution. The calcium fluoride filter cake and the calcium chloride solution are obtained by filtration using a Gore membrane or a ceramic filter, and a diatomaceous earth filter aid layer is pre-coated on the surface of the Gore membrane or the ceramic filter; S5, concentration and crystallization: concentrating and crystallizing the calcium chloride solution to obtain calcium chloride crystals.

[0008] The present invention also provides a comprehensive recycling system for thionyl fluoride synthesis waste gas for implementing the method, comprising: Reaction tail gas guiding assembly, condensation assembly, absorption assembly, precipitation assembly, filtration assembly and concentration crystallization assembly; The reaction tail gas guiding assembly is connected to the tail gas outlet of the synthesis reactor and is provided with a buffer chamber and a pressure reducing valve; The condensation assembly includes a shell and tube condenser, a drainage collection tank, a vacuum pump and a cooling circulation pump; The absorption assembly includes an absorption tower body, a spray device, an absorption liquid circulation pump, a pH adjustment control system and a temperature adjustment circuit; The precipitation component is provided with a reaction kettle, a stirring device, and a lime milk spraying device; The filter is gradually provided with a Gore membrane or a ceramic filter, wherein a diatomaceous earth filter aid layer is pre-coated on the surface of the Gore membrane or the ceramic filter; and The concentration crystallization component is equipped with a vacuum pump, a liquid level regulator and a temperature control heating jacket.

[0009] Beneficial effects: The present invention provides a method for the comprehensive reuse of thionyl fluoride synthesis waste gas. The method effectively improves the recovery and reuse of hydrogen fluoride and hydrogen chloride in the tail gas through continuous steps such as tail gas extraction, condensation and cooling, waste gas absorption, chemical precipitation, and concentrated crystallization, reduces the waste gas emission load, and has strong practical value. Furthermore, a "dynamic membrane" is formed on the surface of the Gore membrane or ceramic filter by pre-coating a diatomaceous earth filter aid layer to significantly improve the flux. This is because colloids are easily formed during the chemical precipitation process, and the colloids easily cause the surface of the Gore membrane or ceramic filter to become clogged. Diatomaceous earth particles have a porous and rigid structure, forming a loose, low-compressibility filter cake layer on the membrane surface, which effectively blocks suspended matter, colloids, and organic pollutants from directly contacting the membrane surface, avoiding clogging of membrane pores and irreversible pollution. During filtration, the flux attenuation of the diatomaceous earth pre-coated dynamic membrane is reduced by about 75% compared with the non-pre-coated group, and the pure water flux recovery rate is increased by 30%.

[0010] Regarding tail gas treatment, this method utilizes a buffer section and controlled extraction rate to ensure a stable tail gas flow into subsequent units and maintain the hydrogen chloride volume fraction within the effective extraction range. The condensation step utilizes a combination of pre-cooling and main cooling sections to control the cooling rate and impurity precipitation process, improving condensation efficiency and preventing pipeline blockage. The absorption section incorporates a multi-stage spray and countercurrent contact system to fully dissolve the hydrogen chloride in the absorption liquid, enhancing gas-liquid transfer efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of the method of the present invention. DETAILED DESCRIPTION

[0012] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the examples. The examples are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0013] Example 1 according to Figure 1 As shown, this embodiment provides a method for the comprehensive reuse of thionyl fluoride synthesis waste gas, which is suitable for the efficient utilization of hydrogen chloride-containing tail gas generated in the thionyl fluoride production process. The method includes the following steps, and combines system integration and process optimization with the preferred embodiment.

[0014] S1, exhaust gas extraction: During the thionyl fluoride synthesis reaction, a gas phase outlet is provided at the top of the reactor to draw out the by-product tail gas. Specifically, by controlling the opening state of the gas phase outlet valve at the top of the reactor, the tail gas flow rate is controlled between 2.0 and 3.0 m / s to ensure that the tail gas can be stably delivered to the back-end processing unit. In order to reduce the pressure pulse caused by gas flow fluctuations, a buffer section is provided in the lead-out channel and an anti-corrosion material is provided to line the inner lining. The outlet pressure is controlled to be no higher than 0.1 MPa. Preferably, the outlet pressure is controlled to be around 50 kPa or below.

[0015] To ensure that the exhaust gas composition meets subsequent treatment requirements, an online sampling interface is installed in the middle of the exhaust gas channel. A multi-component gas analyzer monitors the volume fractions of hydrogen chloride, hydrogen fluoride, unreacted feed gas, and impurities in real time. The volume fraction of hydrogen chloride is controlled to be no less than 20%. The sampling frequency is once every 5 seconds, and the data is transmitted to the control system in real time.

[0016] The thionyl fluoride synthesis reaction specifically comprises: S11. Ratio and mixing of raw gas: First, industrial-grade thionyl chloride (SOCl2) and hydrogen fluoride (HF) are selected as the main raw materials. The thionyl chloride is stored in liquid form and vaporized by an electrically heated vaporizer installed on a low-pressure feed line. The vaporizer features a dual-temperature zone: the first zone is controlled at 40°C to 60°C for liquid preheating, and the second zone is set at 70°C to 90°C for complete vaporization. The vaporization pressure is maintained between atmospheric pressure and 0.2 MPa. Hydrogen fluoride is stored in high-pressure cylinders and regulated by a pressure reducing valve assembly for a stable supply to the reaction system. SOCl2 and HF are metered separately by mass flow meters, and the feed rates are precisely controlled before introduction into a mixer. In another embodiment, separated and recovered hydrogen fluoride is introduced through a compression pump via a parallel pipeline to replace the high-pressure cylinders in the supply of hydrogen fluoride gas.

[0017] The mixer adopts a tubular static mixer made of corrosion-resistant titanium alloy, with a tube diameter of 25 to 50 mm, an internal spiral turbulence structure, and a length controlled between 0.5 and 1.2 m. The structural design adopts a staggered modular turbulence combination, which can effectively control the flow rate of the gas channel and increase the contact surface area, ensuring that the mixed gas reaches the set component uniformity before entering the preheating system. The molar ratio of thionyl chloride to hydrogen fluoride is controlled between 1:2 and 1:4, and 1:3 is recommended as the initial setting ratio to meet the kinetic requirements of generating thionyl fluoride in the actual reaction tower.

[0018] S12. Temperature adjustment of mixed gas: The mixed gas is fed into a shell-and-tube heat exchanger via a heat exchange pipeline. This heat exchanger and temperature feedback module form a closed-loop control system, ensuring stable thermal conditions before the gas enters the tower. The heat exchange medium is saturated steam or high-temperature thermal oil, with an inlet and outlet temperature differential maintained between 15°C and 25°C. The heated gas temperature is controlled within a range of 50°C to 100°C. The feedback controller, connected to a thermocouple and a proportional-integral control device, offers rapid response to accommodate transient heat load changes caused by raw material flow fluctuations, maintaining a balanced heat input at the system's feed end.

[0019] S13, raw material gas introduction: The heated mixed gas is introduced into the base of the reactive distillation tower via a corrosion-resistant metal hose. The tower is a vertical cylindrical structure with a total height of 8 to 12 meters and a diameter of 150 to 300 mm. The tower is constructed of 316L stainless steel lined with polytetrafluoroethylene sheeting, offering excellent resistance to HF and SOCl2 corrosion. The tower is divided into five functional sections: the base, reaction section, packing section, reflux section, and top condensation zone. These sections are connected by flanges and equipped with guide tubes or liquid distributors. Multiple temperature sampling ports and pressure monitoring points are installed on the tower wall—located at the base, middle of the reaction section, lower part of the reflux section, and in the top pre-condensation zone—to monitor operating status.

[0020] S14, reaction zone condition setting and gas phase reaction: After entering the reaction zone, the gas mixture flows upward along the packing layer, forming countercurrent contact with the reflux liquid. The packing layer in the reaction zone is filled with ball rings or polytetrafluoroethylene structured packing, with a packing layer height of 1.5 to 4.0 m. The reaction zone is maintained at a temperature range of 80°C to 120°C, and the pressure within the tower is stabilized between 0.15 and 0.3 MPa. A stable temperature and pressure field is maintained through the combined regulation of the bottom reboiler and the top condensation load.

[0021] Under the reaction conditions, thionyl chloride and hydrogen fluoride react in the gas phase as follows:

[0022] The continuous separation interface formed by the gas-liquid flow in the tower provides mass transfer support for the reaction, forming a gas phase mainstream channel and a liquid film reaction zone inside the packing. The generated thionyl fluoride rises to the condensation area at the top of the tower, and the by-product hydrogen chloride is carried out with the airflow.

[0023] S2. Condensation treatment: The exhaust gas is conveyed to the condensation module under controlled negative pressure. It initially passes through a pre-cooling zone to reduce its temperature to no higher than 25°C before being directed to the main condensation zone for precise temperature control, maintaining a cooling temperature between 0°C and 10°C. The negative pressure is maintained below 50 kPa, keeping the boiling point of hydrogen fluoride below 10°C, thereby primarily separating unreacted thionyl chloride. Controlling the cooling temperature can reduce both the vacuum level and the load on the vacuum pump. The condensation module utilizes a double-jacket cooling structure, using an ethylene glycol-water mixture as the cooling medium. The coolant temperature is controlled by an independent chiller. The condensation section boasts a heat exchange area exceeding 1.5 m², ensuring sufficient separation of high-boiling-point components in the exhaust gas (such as intermediate byproducts and some unreacted raw materials). The condensate is collected and collected through a drain outlet for the waste treatment system.

[0024] S3, exhaust gas absorption: The tail gas after condensation treatment is introduced into the absorption tower for absorption of hydrogen chloride and hydrogen fluoride gas. Three layers of liquid spray plates are arranged in the absorption tower, and a multi-stage spray structure from top to bottom is adopted. The density of nozzles on each layer is not less than 36 / m². The tail gas enters from the bottom of the tower and forms a countercurrent contact with the water continuously flowing in from the top of the tower from bottom to top, which significantly improves the gas-liquid contact efficiency. The water at the top of the tower comes from the liquid storage tank. After uninterrupted repeated absorption, when the concentration of the mixed acid reaches the set value, it is pumped into the next step for precipitation. Preferably, the overall concentration of the mixed acid is 10-20 wt% and is pumped into the next step for precipitation to prevent penetration. During the exhaust gas absorption process, the dissolution of hydrogen chloride and hydrogen fluoride gases in water will produce a release of heat, causing the reaction temperature to slowly rise.

[0025] S4. Chemical precipitation: The mixed acid in the storage tank is pumped into the reactor, and the lime milk is sprayed into the mixed acid at a theoretical molar excess of 0.01-0.5%. The mixture is stirred vigorously to form a precipitate at a stirring speed of at least 100 rpm. During the chemical precipitation process, the hydrofluoric acid and calcium hydroxide undergo an acid-base neutralization reaction, generating a secondary exotherm that further increases the reaction temperature.

[0026] Preferably, the concentration of the lime milk is 1-10 wt%, and intermittent spraying is the primary spraying method. This prevents localized over-alkalinity from causing Ca(OH)2 colloids and CaF2 particles to intertwine and form colloidal precipitates. The atomized lime milk droplet size can be 50-500 μm, with a spray frequency of 20-60 seconds per spray, and each spray volume is one-fiftieth to one-hundredth of the total volume of the lime milk. Preferably, the stirring speed is approximately 250-350 rpm to ensure growth of the CaF2 particles rather than forming a colloidal suspension, which would hinder subsequent filtration. A speed too low (less than 100 rpm) can easily produce colloids, making subsequent solid-liquid separation impossible. The lime milk is preferably prepared using wet grinding combined with ultrasonic dispersion to produce micron-sized (1-10 μm) lime milk with a specific surface area >40 m² / g, which can increase the reaction rate by 40%.

[0027] After precipitation, the product is filtered through a filtration assembly, such as a Gore membrane or ceramic filter. During the filtration process, the filtration temperature can be controlled to prevent precipitation of calcium chloride. Preferably, after two exotherms, the temperature should reach above 40°C. In the present invention, the temperature during the filtration process is controlled to approximately 38-42°C. This is because the solubility of calcium chloride changes most between 30 and 40°C (100 g / L → 128 g / L), and its solubility changes less significantly with increasing temperature (from 40 to 60°C, its solubility increases by approximately 10 g). In contrast, calcium fluoride exhibits a slight solubility change at 40°C, but increases significantly after the temperature reaches 50°C. Therefore, controlling the filtration temperature can increase the solubility of calcium chloride and ensure sufficient precipitation of calcium fluoride, thereby improving the purity of both. The resulting CaF2 filter cake is washed to remove entrained chlorides and other impurities. The washing solution, containing chloride salts, can be returned to the chemical precipitation process. After washing and drying, the high-purity CaF2 can be sold as metallurgical-grade fluorspar (calcium fluoride content >97%) to steel mills (as a flux) or fluorine chemical companies (as a raw material for HF production). Preferably, a 50-100 μm diatomaceous earth filter layer pre-coated on the surface of the Gore membrane or ceramic filter can be used to form a "dynamic membrane" to significantly increase flux. This is because colloids are easily formed during the chemical precipitation process, which can easily clog the Gore membrane or ceramic filter surface. Diatomaceous earth particles have a porous and rigid structure, forming a loose, low-compressibility filter cake layer on the membrane surface. This effectively blocks suspended matter, colloids, and organic pollutants from directly contacting the membrane surface, preventing pore clogging and irreversible contamination. During filtration, the diatomaceous earth pre-coated dynamic membrane shows approximately 75% lower flux attenuation than the uncoated group, and a 30% increase in pure water flux recovery. The dynamic membrane acts as a "sacrificial layer," allowing pollutants to preferentially deposit on the diatomaceous earth layer rather than on the membrane itself, significantly reducing the membrane's effective filtration resistance. Since the diatomaceous earth particle size is much larger than the membrane pore size, a surface filtration mechanism is formed (rather than deep blockage), and the transmembrane pressure (TMP) is significantly reduced.

[0028] S5, concentrated crystallization: Calcium chloride crystals (CaCl2·2H2O or anhydrous CaCl2) are obtained by applying a vacuum pump and heating to accelerate evaporation and concentration. Calcium chloride has a wide range of uses, such as deicing agents, desiccants, concrete additives, and in the food industry.

[0029] Through the above steps, the comprehensive recycling method for thionyl fluoride synthesis waste gas provided in this embodiment realizes the continuous steps of tail gas extraction, condensation and cooling, waste gas absorption, chemical precipitation, and concentrated crystallization, effectively improving the recovery and reuse of hydrogen fluoride and hydrogen chloride in the tail gas, reducing the waste gas emission load, and having strong practical value. Furthermore, this method improves resource utilization efficiency, reduces tail gas emission pressure, and improves the safety of system operation and engineering adaptability. This method is suitable for continuous industrial production scenarios and has good promotion value.

[0030] Example 2 This embodiment provides a comprehensive recycling system for thionyl fluoride synthesis waste gas, suitable for the targeted recovery and reuse of by-product tail gas during the industrial synthesis of thionyl fluoride. The system has modular components, controllable operation, and is suitable for continuous operation.

[0031] The system includes the following components: Reaction exhaust gas guide components: This component, located at the tail gas outlet of the synthesis reactor, is used to stabilize the exhaust gas discharge and control its flow. It comprises an exhaust gas outlet pipe, a buffer chamber, and a pressure-reducing valve. The buffer chamber regulates outlet pressure fluctuations and features an online gas sampling port and a hydrogen chloride volume fraction analyzer for real-time monitoring of exhaust gas composition. The pressure-reducing valve is pneumatically adjustable with a response time of less than 1 second. It coordinates with the exhaust gas flow control system to adjust the exhaust gas discharge rate.

[0032] Condensation components: The tail gas is guided into the condensation component for temperature degradation and impurity pre-separation. The condensation component includes a shell and tube condenser, a drainage collection tank, a vacuum pump and a cooling circulation pump. The shell and tube condenser is made of 316L stainless steel, and the internal fluid is an ethanol-water mixed cooling medium. The cooling temperature is controlled within the range of 0°C to 5°C. The cooling circulation pump is equipped with a temperature control feedback loop to automatically adjust the flow rate to maintain a stable condensation temperature difference. The liquid impurities generated by condensation enter the drainage collection tank and are discharged into the waste liquid treatment unit by an independent conveying system. The main function of the vacuum pump is to work with the cooling circulation pump to provide a negative pressure below 40kPa.

[0033] The condensation component and the absorption component are connected by a corrosion-resistant and pressure-resistant flexible connecting pipe. The hose has a three-layer structure, with an outer layer as a reinforcement layer, an elastomer in the middle, and an inner layer coated with polytetrafluoroethylene. The pipe diameter is DN50 to DN80 and is equipped with a quick interface shut-off valve and a sampling interface for gas segmented sampling and sealed switching of post-stage maintenance operations.

[0034] Absorption components: The condensed exhaust gas enters the absorption assembly for liquid-phase absorption of hydrogen fluoride and hydrogen chloride. The absorption assembly comprises the absorption tower, a spray system, an absorption liquid circulation pump, a pH control system, and a temperature regulation circuit. The absorption tower is a vertical cylindrical structure equipped with three layers of cross-flow spray trays with evenly spaced nozzles. The absorption liquid is sprayed from the top of the tower, while the exhaust gas is introduced from the bottom, achieving countercurrent contact.

[0035] The temperature control circuit is equipped with an external cooling water jacket to maintain the liquid temperature below 25°C.

[0036] Sedimentation components: After the mixed acid is pumped into the reactor in the precipitation component, it is rapidly stirred by a stirring device, and lime milk is intermittently pumped into it through a lime milk spray device. When the pH value is finally controlled within the range of 6-9, the reaction is completed.

[0037] Filter components: The CaF2 filter cake is obtained by filtering through a filter element such as a Gore membrane or a ceramic filter.

[0038] Concentrated crystallization components: Evacuate the solution with a vacuum pump and heat to accelerate evaporation and concentration to obtain calcium chloride crystals (CaCl2·2H2O or anhydrous CaCl2).

[0039] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for comprehensive recycling of thionyl fluoride synthesis waste gas, characterized in that: The following steps are involved: S1, tail gas extraction: the tail gas generated during the thionyl fluoride synthesis reaction is extracted, wherein the tail gas contains hydrogen chloride, hydrogen fluoride, unreacted chlorinated raw materials and intermediate by-products; S2, condensation treatment: controlling the negative pressure to introduce the tail gas into the condensation unit for cooling, and the cooling temperature is controlled in the range of 0°C to 10°C to remove high-boiling-point impurities; S3, exhaust gas absorption: the condensed exhaust gas is introduced into the absorption tower to fully absorb the hydrogen chloride and hydrogen fluoride in the exhaust gas to form mixed acid; S4. Chemical precipitation: adding lime milk to the mixed acid to convert hydrogen fluoride into insoluble calcium fluoride precipitate and hydrogen chloride into calcium chloride, followed by filtration to obtain a calcium fluoride filter cake and a calcium chloride solution. The calcium fluoride filter cake and the calcium chloride solution are obtained by filtration using a Gore membrane or a ceramic filter, and a diatomaceous earth filter aid layer is pre-coated on the surface of the Gore membrane or the ceramic filter; S5, concentration and crystallization: concentrating and crystallizing the calcium chloride solution to obtain calcium chloride crystals.

2. The method for comprehensive recycling of thionyl fluoride synthesis waste gas according to claim 1, characterized in that: Step S1 includes the following sub-steps: S11, open the gas phase outlet at the top of the reactor and control the tail gas outlet velocity between 2.0 and 3.0 m / s; S12. Set a buffer section in the outlet channel to balance pressure fluctuations and maintain the outlet pressure no higher than 0.1 MPa; S13. The exhaust gas sampling point is located in the middle of the channel to monitor the gas composition and ensure that the volume fraction of hydrogen chloride is not less than 20%.

3. The method for comprehensive recycling of thionyl fluoride synthesis waste gas according to claim 1, characterized in that: The condensing unit in step S2 adopts a circulating cooling mode. The tail gas passes through a pre-cooling zone before entering the main condensing zone to initially reduce the gas temperature to no higher than 25°C, and then enters the main condensing zone for precise temperature control.

4. The method for comprehensive recycling of thionyl fluoride synthesis waste gas according to claim 1, characterized in that: In step S3, a multi-stage liquid spray structure is set in the absorption tower, the tail gas enters the absorption section from bottom to top, the absorption liquid is continuously distributed from top to bottom, the tail gas and the liquid undergo at least two stages of countercurrent contact process, and the absorption liquid flow rate is controlled at 0.5-1.5 L / min.

5. The method for comprehensive recycling of thionyl fluoride synthesis waste gas according to claim 1, characterized in that: In step S4, adding lime milk to the mixed acid to convert hydrogen fluoride into insoluble calcium fluoride precipitate and converting hydrogen chloride into calcium chloride specifically includes: Prepare lime milk with a concentration of 1-10 wt%; spraying the lime milk into the mixed acid in an excess of 0.1% to 3% according to the theoretical molar ratio, while vigorously stirring to form a precipitate; The pH value is finally controlled within the range of 6-9, and the reaction is completed.

6. The method for comprehensive recycling of thionyl fluoride synthesis waste gas according to claim 5, characterized in that: In step S4, the step of spraying the lime milk into the mixed acid in an excess of 0.1% to 3% according to the theoretical molar ratio specifically comprises: The particle size of lime milk atomized droplets is 50–500 μm, the spray frequency is 20–60 s / time, and the amount of each spray is one fiftieth to one hundredth of the total volume of lime milk.

7. A comprehensive recycling system for thionyl fluoride synthesis waste gas for implementing the method according to any one of claims 1 to 6, characterized in that: include: Reaction tail gas guiding assembly, condensation assembly, absorption assembly, precipitation assembly, filtration assembly and concentration crystallization assembly; The reaction tail gas guiding assembly is connected to the tail gas outlet of the synthesis reactor and is provided with a buffer chamber and a pressure reducing valve; The condensation assembly includes a shell and tube condenser, a drainage collection tank, a vacuum pump and a cooling circulation pump; The absorption assembly includes an absorption tower body, a spray device, an absorption liquid circulation pump, a pH adjustment control system and a temperature adjustment circuit; The precipitation component is provided with a reaction kettle, a stirring device, and a lime milk spraying device; The filter assembly is provided with a Gore membrane or a ceramic filter, wherein a pre-coated diatomaceous earth filter aid layer is provided on the surface of the Gore membrane or the ceramic filter; and The concentration crystallization component is equipped with a vacuum pump, a liquid level regulator and a temperature control heating jacket.

8. The comprehensive recycling system for thionyl fluoride synthesis waste gas according to claim 7, characterized in that: The condensation component and the absorption component are connected by a corrosion-resistant and pressure-resistant flexible connecting pipe. The inner wall of the pipe is coated with polytetrafluoroethylene. The pipe diameter is DN50 to DN80 and is equipped with a stop valve and a sampling interface for gas segmented sampling and sealed switching operations.

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