Device for removing hydrogen fluoride in fluorine gas

Abstract

The utility model discloses a device for removing hydrogen fluoride in fluorine gas, which comprises a hydrogen fluoride condensing tower, the upper part of the hydrogen fluoride condensing tower is provided with a nitrogen back-blowing gas inlet pipeline and an F2 gas outlet pipeline, and the lower part of the hydrogen fluoride condensing tower is provided with an F2 gas inlet pipeline and a nitrogen gas outlet pipeline; the F2 gas inlet pipeline is used for enabling F2 to be treated to enter the hydrogen fluoride condensing tower; a blow-off pipeline is arranged at the bottom of the hydrogen fluoride condensing tower; a jacket is arranged on the outer wall of the hydrogen fluoride condensing tower, a refrigerating fluid filling port is formed in the upper part of the jacket, a refrigerating fluid discharging port is formed in the lower part of the jacket, and refrigerating fluid is filled in the jacket; the hydrogen fluoride condensation temperature control device can well control the hydrogen fluoride condensation temperature, avoids overlarge temperature fluctuation caused by direct liquid nitrogen cooling and difficulty in stable control of the hydrogen fluoride condensation temperature, and simultaneously avoids the safety problem caused by fluorine liquefaction due to overlow hydrogen fluoride condensation temperature caused by difficulty in temperature control.

Description

Technical Field

[0001] This utility model belongs to the field of fluorochemical technology, specifically relating to a device for removing hydrogen fluoride from fluorine gas. Background Technology

[0002] High-purity fluorine (F2) is a highly reactive gas with strong oxidizing properties. Due to its reactive characteristics, it is used in the semiconductor industry as an etching or cleaning gas in the manufacture of photovoltaic cells and TFTs (thin-film transistors) for liquid crystal displays. Simultaneously, as a gas in excimer lasers, fluorine lasers are also widely used in the semiconductor industry. F2 is also used as a cleaning agent in chemical vapor deposition (CVD) reaction chambers; compared to NF3, F2 has stronger reactivity and does not contribute to the greenhouse effect. With the booming development of the domestic semiconductor industry, the demand for fluorine gas used for these purposes is increasing significantly. To meet the needs of the electronics and photovoltaic industries, a high-purity fluorine gas is required. For example, in the semiconductor industry, a purity of 99.9% or higher, even 99.99%, is required. Specifically, the requirements for impurities such as hydrogen fluoride are becoming increasingly stringent; the hydrogen fluoride content in 99.9% fluorine gas must be at least below 200 ppm, placing higher demands on hydrogen fluoride removal.

[0003] Industrially, the method for producing fluorine gas by electrolysis is as follows: KF·2 hydrogen fluoride (a mixture of potassium hydroxide and hydrogen fluoride) is electrolyzed at 80~100℃, with compacted graphite as the anode and a steel electrolytic cell body as the cathode (or the anode is a carbon plate or nickel plate and the cathode is carbon steel), and potassium hydrogen fluoride is used as the electrolyte to electrolyze anhydrous hydrofluoric acid, which is then purified to obtain the fluorine gas.

[0004] Hydrogen fluoride has a boiling point of 19°C. Therefore, during electrolysis, the fluorine gas produced contains a large amount of hydrogen fluoride, approximately 5% to 10%. Chinese patent CN115571859A discloses a method for reducing the hydrogen fluoride content in fluorine gas, comprising the following steps: conveying fluorine gas containing hydrogen fluoride to an adsorption tower containing sodium fluoride balls; after the sodium fluoride balls adsorb the hydrogen fluoride, purified fluorine gas is obtained. The technical solution of this invention, by conveying fluorine gas containing hydrogen fluoride to an adsorption tower containing sodium fluoride balls, utilizes the reaction between the sodium fluoride balls and hydrogen fluoride to generate NaHF2, thereby adsorbing the hydrogen fluoride in the fluorine gas. This solves the problem in existing medium-temperature electrolytic fluorine production processes where the presence of hydrogen fluoride in the fluorine gas leads to low product quality and rapid corrosion of downstream equipment. It effectively reduces the hydrogen fluoride content in the fluorine gas, ensures the quality of the fluorine product, and extends the service life of downstream equipment. The activated spherical sodium fluoride is used for adsorption and purification. The hydrogen fluoride content in the adsorbed fluoride gas is greater than 1%. At the same time, after the spherical sodium fluoride adsorbs hydrogen fluoride, it will dissolve and pulverize, clogging the pipeline. In severe cases, it may even cause the electrolytic cell to explode. Utility Model Content

[0005] The purpose of this invention is to provide a device for removing hydrogen fluoride from fluorine gas, achieving stable control of the temperature of the hydrogen fluoride condenser. This device can effectively reduce the hydrogen fluoride content in the fluorine gas produced by electrolysis, while avoiding the problems of unstable condenser temperature control caused by directly using liquid nitrogen as a cold source, as well as the safety issues caused by local liquefaction of fluorine gas. The device has a simple structure and is easy to use.

[0006] The objective of this utility model is achieved through the following technical solution:

[0007] An apparatus for removing hydrogen fluoride from fluorine gas includes: a hydrogen fluoride condensation tower, an F2 inlet pipe, an F2 outlet pipe, a nitrogen backflushing inlet pipe, a nitrogen outlet pipe, a drain pipe, a refrigerant filling port, a refrigerant discharge port, a liquid nitrogen inlet, and a cold nitrogen outlet.

[0008] The upper part of the hydrogen fluoride condenser is equipped with a nitrogen backflush inlet pipe and an F2 outlet pipe. The nitrogen backflush inlet pipe is used to supply nitrogen to the hydrogen fluoride condenser for backflush, and the F2 outlet pipe is used to discharge the treated F2 gas.

[0009] The lower part of the hydrogen fluoride condenser is equipped with an F2 inlet pipe and a nitrogen outlet pipe; the F2 inlet pipe is used to supply the F2 to be treated into the hydrogen fluoride condenser; the nitrogen outlet pipe is used to supply nitrogen to the exhaust gas treatment device after discharge. A drain pipe is provided at the bottom of the hydrogen fluoride condenser.

[0010] The outer wall of the hydrogen fluoride condenser is equipped with a jacket, with a refrigerant filling port at the upper part of the jacket and a refrigerant discharge port at the lower part of the jacket. The jacket is filled with refrigerant. The refrigerant filling port and the refrigerant discharge port are used to replenish the refrigerant periodically and to discharge the refrigerant during maintenance.

[0011] The jacket also includes a coil with both ends extending out of the jacket. The upper end of the coil is connected to a liquid nitrogen inlet, and the lower end is connected to a cold nitrogen outlet. Liquid nitrogen flows within the coil. The liquid nitrogen inlet and the cold nitrogen outlet provide a cooling source for the refrigerant.

[0012] The jacket and coils are designed for cryogenic condensation to remove hydrogen fluoride from the F2 being treated. Liquid nitrogen flows into the coils within the hydrogen fluoride condenser jacket through the liquid nitrogen inlet to cool the refrigerant, and the refrigerant temperature is controlled by a jacket thermometer. The refrigerant is added to the jacket through the refrigerant filler port and stored for later use. Liquid nitrogen vaporizes as it flows within the coils, releasing its cooling capacity to cool the refrigerant and maintain it at its freezing point. Stable temperature control is achieved through the phase change of the refrigerant.

[0013] Preferably, valves are provided on the F2 intake pipe, F2 exhaust pipe, nitrogen backflushing intake pipe, nitrogen exhaust pipe, sewage pipe, coolant filling port, coolant discharge port, liquid nitrogen inlet and cold nitrogen outlet.

[0014] Preferably, the hydrogen fluoride condenser, F2 inlet pipe, F2 outlet pipe, nitrogen backflushing inlet pipe, nitrogen outlet pipe and sewage pipe are all made of carbon steel, stainless steel or Monel material, so as to resist hydrogen fluoride corrosion.

[0015] Preferably, the coolant filling port, coolant drain port, liquid nitrogen inlet port, and cold nitrogen outlet port are all made of stainless steel.

[0016] Preferably, a pressure gauge is connected to the top of the hydrogen fluoride condenser. The pressure gauge is used to maintain the pressure of the equipment, and the equipment operates at normal pressure.

[0017] Preferably, a condenser thermometer is connected to the upper part of the hydrogen fluoride condenser.

[0018] Preferably, the jacket is equipped with a jacket thermometer.

[0019] Preferably, the freezing point of the refrigerant is -90 to -120°C.

[0020] A method for removing hydrogen fluoride from fluorine gas includes the following steps:

[0021] Step 1: Add a freezing liquid with a freezing point of -90 to -120°C into the jacket;

[0022] Step 2: Liquid nitrogen flows into the coil inside the jacket to cool the refrigerant and control the refrigerant temperature between -90 and -120°C, thereby controlling the temperature of the hydrogen fluoride condenser tower between -80 and -90°C.

[0023] Step 3: The fluorine gas containing hydrogen fluoride generated by electrolysis enters the hydrogen fluoride condenser from the bottom of the F2 inlet pipe. After being condensed at low temperature to remove hydrogen fluoride, the gas flows out from the F2 outlet pipe into the subsequent pipe, thus obtaining the purified F2 gas.

[0024] Step 4: The liquid hydrogen fluoride in the hydrogen fluoride condensation tower is discharged through the drain pipe.

[0025] Preferably, in step 2, the fluorine gas enters from the bottom of the hydrogen fluoride condenser through the F2 inlet pipe, and the flow rate in the condenser is 0.2–4 m³ / s. 3 / h.

[0026] The fluorine gas containing hydrogen fluoride produced by electrolysis in step 3 can be obtained by those skilled in the art through existing conventional methods for producing fluorine gas by electrolysis. The fluorine gas produced by electrolysis usually contains a large amount of hydrogen fluoride, as explained in the background section of this utility model. Therefore, it will not be described in detail here.

[0027] The beneficial effects of this utility model are:

[0028] The device of this invention purifies the fluorine gas generated by electrolysis. It uses a hydrogen fluoride condenser with an internal cooling coil to condense the hydrogen fluoride. The condenser temperature is controlled between -80 and -90°C by a cryogenic refrigerant. Because the refrigerant absorbs and releases a large amount of heat during phase change, the temperature control is stable. At the same time, the temperature of each step is much higher than the boiling point of fluorine gas -188°C. Therefore, this device solves the problem of unstable temperature and local temperature drop leading to fluorine liquefaction in the prior art when using liquid nitrogen for direct condensation, and is less likely to cause safety accidents.

[0029] This invention utilizes a novel hydrogen fluoride condensation tower. The condenser has an internal jacket containing a coil. Liquid nitrogen flows inside the coil, while the jacket is filled with refrigerant. The refrigerant's freezing point is selected to be between -90°C and -120°C. By using the liquid nitrogen inside the coil as a cold source, and taking advantage of the refrigerant's ability to absorb and release a large amount of heat during the freezing and liquefaction phase change, the hydrogen fluoride condensation equipment can be kept stable at -80°C to -90°C for an extended period. The condensed hydrogen fluoride is discharged through a drain pipe. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of this utility model.

[0031] Figure 2 This is a schematic diagram of the structure of the jacket and coil of this utility model.

[0032] Among them, 1-hydrogen fluoride condenser, 2-F2 inlet pipe, 3-F2 outlet pipe, 4-nitrogen backflushing inlet pipe, 5-nitrogen outlet pipe, 6-sewage pipe, 7-condenser thermometer, 8-jacket thermometer, 9-refrigerant filling port, 10-refrigerant discharge port, 11-liquid nitrogen inlet, 12-cold nitrogen outlet, 13-jacket, 14-coil. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; and the experimental materials, unless otherwise specified, are all commercially available.

[0035] An apparatus for removing hydrogen fluoride from fluorine gas, such as Figure 1and Figure 2 As shown, the system includes: a hydrogen fluoride condenser tower 1, an F2 inlet pipe 2, an F2 outlet pipe 3, a nitrogen backflush inlet pipe 4, a nitrogen outlet pipe 5, a drain pipe 6, a condenser tower thermometer 7, a jacket thermometer 8, a refrigerant filling port 9, a refrigerant discharge port 10, a liquid nitrogen inlet 11, and a cold nitrogen outlet 12. Valves are installed on the F2 inlet pipe 2, F2 outlet pipe 3, nitrogen backflush inlet pipe 4, nitrogen outlet pipe 5, drain pipe 6, refrigerant filling port 9, refrigerant discharge port 10, liquid nitrogen inlet 11, and cold nitrogen outlet 12. The hydrogen fluoride condenser tower 1, F2 inlet pipe 2, F2 outlet pipe 3, nitrogen backflush inlet pipe 4, nitrogen outlet pipe 5, and drain pipe 6 are made of carbon steel, stainless steel, or Monel material to resist hydrogen fluoride corrosion. The cryogenic filling port 9, cryogenic discharge port 10, liquid nitrogen inlet 11, and cold nitrogen outlet 12 are all made of stainless steel.

[0036] A pressure gauge is connected to the top of the hydrogen fluoride condenser 1. The pressure gauge is used to maintain the pressure of the equipment, which operates at normal pressure.

[0037] A nitrogen backflush inlet pipe 4 and an F2 outlet pipe 3 are installed above the hydrogen fluoride condenser 1, and an F2 inlet pipe 2 and a nitrogen outlet pipe 5 are installed below the hydrogen fluoride condenser 1. A drain pipe 6 is installed at the bottom of the hydrogen fluoride condenser, through which liquid hydrogen fluoride is discharged. A pressure gauge and a condenser thermometer 7 are also connected to the top of the hydrogen fluoride condenser.

[0038] The outer wall of the hydrogen fluoride condenser 1 is provided with a jacket 13. A refrigerant filling port 9 is provided at the upper part of the jacket 13, and a refrigerant discharge port 10 is provided at the lower part of the jacket 13. The jacket 13 is filled with refrigerant, and the freezing point of the refrigerant is -90~-120℃. A coil 14 is also provided inside the jacket 13. The two ends of the coil 14 extend out of the jacket 13 respectively. The upper end of the coil 14 is connected to the liquid nitrogen inlet 11, and the lower end of the coil 14 is connected to the cold nitrogen outlet 12. Liquid nitrogen flows in the coil 14. A jacket thermometer 8 is provided on the jacket 13. The refrigerant is added into the jacket 13 through the refrigerant filling port 9 and discharged through the refrigerant discharge port 10 during maintenance.

[0039] F2 inlet pipe 2 is used to supply F2 to be treated into the hydrogen fluoride condenser 1; nitrogen outlet pipe 5 is used to supply nitrogen for purging and replacement, which is then discharged into the waste gas treatment device; nitrogen backflushing inlet pipe 4 is used to supply nitrogen into the hydrogen fluoride condenser 1 for backflushing and replacement; F2 outlet pipe 3 is used to discharge the treated F2 gas; sewage pipe 6 is used to discharge the condensed hydrogen fluoride to the waste gas treatment tower; condenser tower thermometer 7 is used to measure the temperature of the condenser tower; jacket thermometer 8 is used to control the temperature of the refrigerant in the jacket 13; refrigerant filling port 9 is used to add refrigerant; refrigerant discharge port 10 is used to vent the refrigerant during maintenance; liquid nitrogen inlet 11 is used to add liquid nitrogen; cold nitrogen discharge port 12 is used to discharge the cold nitrogen gas after the liquid nitrogen has vaporized.

[0040] The work process includes the following steps:

[0041] Step 1: A specific coolant is added to the jacket 13 of the hydrogen fluoride condenser 1 through the coolant filling port 9 for later use. Liquid nitrogen flows into the coil 14 through the liquid nitrogen inlet 11 to cool the coolant in the jacket 13. Cold nitrogen gas is discharged from the cold nitrogen outlet 12.

[0042] Step 2: By controlling the jacket thermometer 8 between -90 and -120°C and the hydrogen fluoride condenser thermometer 7 between -80 and -90°C, stable temperature control is achieved by utilizing the phase change of liquefaction and solidification of the refrigerant.

[0043] Step 3: Discharge the fluorine gas produced by electrolysis, which has a hydrogen fluoride content of 5%~10%, at a rate of 0.5m... 3 / h~4 m 3 The gas flows through F2 inlet pipe 2 from the bottom of hydrogen fluoride condenser 1. After being condensed at low temperature to remove hydrogen fluoride, the gas enters the subsequent pipeline through F2 outlet pipe 3, thus obtaining purified F2 gas. The hydrogen fluoride content in the gas is 0.8% as detected by infrared spectroscopy.

[0044] Step 4: A small amount of liquid hydrogen fluoride in the hydrogen fluoride condensation tower 1 is discharged through the drain pipe 6.

[0045] Step 5: During equipment inspection and maintenance, the fluorine gas in the equipment is replaced and purged by using nitrogen backflushing inlet pipe 4 and nitrogen outlet 5. The refrigeration is discharged through refrigerant outlet 10 before inspection and maintenance.

[0046] The refrigerant used in this embodiment is dichloromethane. The method of this invention is used to purify the fluorine gas generated by electrolysis. The outer wall of the hydrogen fluoride condenser 1 is equipped with a jacket and coil. The temperature of the hydrogen fluoride condenser 1 is controlled between -80 and -90°C by the low-temperature refrigerant, and the temperature control is stable. At the same time, the temperature of each step is much higher than the boiling point of fluorine gas -188°C. Therefore, this method solves the problem of unstable temperature and local temperature drop leading to fluorine liquefaction in the prior art when using liquid nitrogen for direct condensation, and is less likely to cause safety accidents.

[0047] In summary, the above are merely preferred embodiments of this utility model and are not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. An apparatus for removing hydrogen fluoride from fluorine gas, characterized by comprising: include: Hydrogen fluoride condenser (1); The upper part of the hydrogen fluoride condenser (1) is provided with a nitrogen backflush inlet pipe (4) and an F2 outlet pipe (3). The lower part of the hydrogen fluoride condenser (1) is provided with an F2 inlet pipe (2) and a nitrogen outlet pipe (5); the bottom of the hydrogen fluoride condenser (1) is provided with a sewage discharge pipe (6). The outer wall of the hydrogen fluoride condenser (1) is provided with a jacket (13), the upper part of the jacket (13) is provided with a refrigerant inlet (9), the lower part of the jacket (13) is provided with a refrigerant outlet (10), and the jacket (13) is filled with refrigerant. The jacket (13) is also provided with a coil (14), with both ends of the coil (14) extending out of the jacket (13). The upper end of the coil (14) is connected to the liquid nitrogen inlet (11), and the lower end of the coil (14) is connected to the cold nitrogen outlet (12). Liquid nitrogen flows in the coil (14).

2. The apparatus for removing hydrogen fluoride from fluorine gas according to claim 1, wherein Valves are installed on the F2 intake pipe (2), F2 exhaust pipe (3), nitrogen backflushing intake pipe (4), nitrogen exhaust pipe (5), sewage pipe (6), coolant filling port (9), coolant discharge port (10), liquid nitrogen inlet (11) and cold nitrogen outlet (12).

3. The apparatus for removing hydrogen fluoride from fluorine gas according to claim 1, wherein The hydrogen fluoride condenser (1), F2 inlet pipe (2), F2 outlet pipe (3), nitrogen backflushing inlet pipe (4), nitrogen outlet pipe (5) and sewage pipe (6) are all made of carbon steel, stainless steel or Monel.

4. The apparatus for removing hydrogen fluoride from fluorine gas according to claim 1, wherein The refrigerant filling port (9), refrigerant discharge port (10), liquid nitrogen inlet (11), and cold nitrogen outlet (12) are all made of stainless steel.

5. The apparatus for removing hydrogen fluoride from fluorine gas according to claim 1, wherein A pressure gauge is connected to the top of the hydrogen fluoride condenser (1).

6. The apparatus for removing hydrogen fluoride from fluorine gas according to claim 1, wherein A condenser thermometer (7) is connected to the upper part of the hydrogen fluoride condenser (1).

7. The apparatus for removing hydrogen fluoride from fluorine gas according to claim 1, wherein A jacket thermometer (8) is provided on the jacket (13).

8. The apparatus for removing hydrogen fluoride from fluorine gas according to claim 1, wherein The freezing point of the refrigerant is -90 to -120°C.

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