A refining and purification device and method for preparing high-purity fluorine gas

Abstract

The present invention relates to the technical field of electrolytic fluorine production, and provides a refining and purification device and method for preparing high-purity fluorine gas. The equipment provided by the present invention includes a fluorine production electrolytic cell, a slag removal device, a low-pressure tank, an HF low-temperature condensation system, a fluorine gas compressor, a fluorine gas precooler and a fluorine gas distillation tower; the top of the fluorine gas distillation tower is provided with a tower top condenser, the tower bottom is provided with a tower bottom reboiler, the outlet of the tower top condenser is connected to the fluorine gas storage tank, and the outlet of the tower bottom reboiler is connected to the hydrofluoric acid recovery device; the HF low-temperature condensation system includes a plurality of HF low-temperature condensers connected in series, and the bottom of the HF low-temperature condenser is provided with an HF liquid outlet, and the HF liquid outlet is connected to the HF recovery device. The equipment provided by the present invention can purify the crude fluorine gas by the mode of condensation + distillation, with high purification efficiency, and the equipment structure is simple, suitable for industrial and continuous production, and the purity of the obtained fluorine gas can reach more than 4N, which can meet the use requirements of the semiconductor industry.

Description

Technical Field

[0001] The invention relates to the technical field of electrolytic fluorine production, and in particular to a refining and purification device and method for preparing high-purity fluorine gas. Background Art

[0002] Fluorine (F 2 ), with a relative molecular weight of 38.00 and a boiling point of -188°C. It is a strongly oxidizing light yellow toxic gas with a pungent odor. Fluorine gas has extremely active chemical properties and can react with almost all elements. It is known as the most active substance in nature and is widely used in electronics, laser technology, medicine, plastics, petrochemicals, aerospace and other fields. It is an important raw material in the chemical industry. High-purity fluorine gas, as a cleaning agent for chemical vapor deposition reaction chambers, has strong reactivity and does not cause a greenhouse effect. It has great market potential in the semiconductor field.

[0003] At present, the conventional method for preparing fluorine gas known in the art is electrolysis, which is divided into three processes: low-temperature electrolysis, high-temperature electrolysis and medium-temperature electrolysis. The medium-temperature electrolysis process is commonly used in industry. The fluorine gas prepared by the medium-temperature electrolysis contains 1-15% hydrogen fluoride (HF) gas and about 1-5% carbon tetrafluoride (CF 4 ), 1-10% nitrogen (N 2 ) and trace amounts of oxygen (O 2 ) and oxyfluoride (OF 2 ) and other impurity gases. The purity of fluorine gas is only about 80-95%, and it must be purified before it can be used in the semiconductor field.

[0004] There are two common methods for fluorine gas purification: cryogenic freezing and fluoride salt adsorption. The cryogenic freezing method mainly involves cooling the fluorine gas to below -65°C. At this temperature, the fluorine gas is a gas, and most of the hydrogen fluoride gas is converted into a liquid phase, so that the two are separated. However, since hydrogen fluoride molecules form aggregates at low temperatures, the freezing method can only reduce the hydrogen fluoride content to below 4%. Even when the temperature drops below -120°C, the hydrogen fluoride content is still around 1%.

[0005] The fluoride salt adsorption method mainly uses alkali metal fluorides, such as sodium fluoride (NaF), potassium fluoride (KF), lithium fluoride (LiF), etc. to adsorb hydrogen fluoride gas at room temperature to generate alkali metal hydrofluorides, such as sodium hydrofluoride (NaHF 2 ), potassium bifluoride (KHF 2 ), lithium fluoride (LiHF 2) etc., and the produced alkali metal fluoride can decompose the adsorbed hydrogen fluoride gas at a high temperature above 200°C and turn it back into alkali metal fluoride. In this way, fluorine gas can be purified and alkali metal fluoride can be reused. The fluoride salt adsorption method can reduce the hydrogen fluoride gas in fluorine gas to less than 0.5%.

[0006] In actual production, the purification process of fluorine gas usually uses a combination of low-temperature freezing method and fluoride salt adsorption method. First, a large amount of HF is removed by freezing method, and then the remaining HF is removed by adsorption method. Finally, the hydrogen fluoride gas in the fluorine gas is reduced to less than 0.5%. However, neither low-temperature freezing method nor fluoride salt adsorption method can remove carbon tetrafluoride (CF 4 ), nitrogen (N 2 ), oxygen (O 2 ) and oxyfluoride (OF 2 ) and other gases, the quality of fluorine gas is still not satisfactory. Summary of the invention

[0007] In view of this, the present invention provides a refining and purification device and method for preparing high-purity fluorine gas. The device provided by the present invention can achieve the purification of HF and carbon tetrafluoride (CF 4 ), nitrogen (N 2 ), oxygen (O 2 ) and oxyfluoride (OF 2 ) and other gases, the purification efficiency is high, and the purity of the obtained fluorine gas can reach above 4N.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] A refining and purification device for preparing high-purity fluorine gas, comprising:

[0010] A fluorine-producing electrolytic cell 1; the fluorine-producing electrolytic cell 1 is provided with an anode outlet and a cathode outlet;

[0011] A slag removal device 2 whose inlet is connected to the anode outlet of the fluorine-producing electrolytic cell 1;

[0012] A low-pressure tank 3 whose inlet is connected to the outlet of the slag removal device 2, and the low-pressure tank 3 is provided with a nitrogen automatic pressure replenishing device;

[0013] An HF cryogenic condensation system, the HF cryogenic condensation system comprising a plurality of HF cryogenic condensers 4 connected in series; a gas inlet of the first HF cryogenic condenser 4 of the HF cryogenic condensation system is connected to the outlet of the low-pressure tank 3; an HF liquid outlet is provided at the bottom of the HF cryogenic condenser 4, and the HF liquid outlet is connected to the HF recovery device 11;

[0014] A fluorine gas compressor 5 whose inlet is connected to the gas outlet of the last HF low-temperature condenser 4 of the HF condensation system; the fluorine gas compressor 5 is linked to the nitrogen automatic pressure replenishing device;

[0015] a fluorine gas precooler 6 whose inlet is connected to the outlet of the fluorine gas compressor 5;

[0016] A fluorine gas distillation tower 7 whose inlet is connected to the outlet of the fluorine gas precooler 6; a tower top condenser 8 is provided at the top of the fluorine gas distillation tower 7, and a tower bottom reboiler 9 is provided at the bottom of the tower;

[0017] a fluorine gas storage tank 10 whose inlet is connected to the outlet of the tower top condenser 8;

[0018] A hydrofluoric acid recovery device 12 whose inlet is connected to the outlet of the tower bottom reboiler 9.

[0019] Preferably, the number of the HF low-temperature condensers 4 is more than one.

[0020] Preferably, the HF low-temperature condenser 4 is provided with an inner coil or tube array inside and an outer jacket outside.

[0021] Preferably, the tower top condenser 8 is provided with an inner coil or tube array inside and an outer jacket outside; and a temperature measuring point, a pressure measuring point and a sampling point are provided at the top of the tower top condenser 8.

[0022] Preferably, a valve is provided on the pipeline at the cathode outlet of the fluorine-producing electrolytic cell 1; valves are provided at the inlet and outlet of the low-pressure tank 3; valves are provided at the gas inlet, gas outlet and HF liquid outlet of the HF low-temperature condenser 4; valves are provided at the inlet and outlet of the fluorine gas compressor 5; a valve is provided at the outlet of the tower kettle reboiler 9; a valve is provided at the inlet of the fluorine gas storage tank 10, and the fluorine gas storage tank 10 is also provided with a fluorine gas outlet, and a valve is provided at the fluorine gas outlet.

[0023] Preferably, according to the gas flow sequence, the materials of the pipelines and valves after the fluorine gas compressor 5 are all corrosion-resistant and oxidation-resistant metals; and the pipeline connections after the fluorine gas compressor 5 are all welded.

[0024] The present invention also provides a method for preparing high-purity fluorine gas using the equipment described in the above scheme, comprising the following steps:

[0025] Fluorine is produced by electrolysis in the fluorine production electrolytic cell 1, and crude fluorine gas is produced at the anode;

[0026] The crude fluorine gas is deslagging in the deslagging device 2, and the deslagging crude fluorine gas enters the low-pressure tank 3. The nitrogen pressure replenishing device of the low-pressure tank 3 is linked with the fluorine gas compressor 5 to control the pressure of the low-pressure tank 3 at -2000~-500Pa;

[0027] The crude fluorine gas after the slag removal enters the HF low-temperature condenser 4 from the low-pressure tank 3, HF is condensed, and enters the HF recovery device 11 from the HF liquid outlet, and the remaining gas is the preliminarily purified fluorine gas;

[0028] The preliminarily purified fluorine gas enters the fluorine gas compressor 5 for pressurization, and the pressurized fluorine gas enters the fluorine gas precooler 6 for precooling, and then enters the fluorine gas distillation tower 7 for distillation. During the distillation process, the heavy components are enriched in the bottom of the tower and discharged into the hydrofluoric acid recovery device 12, and the high-purity fluorine gas is introduced into the fluorine gas storage tank 10 from the top condenser 8 as the light component.

[0029] Preferably, the operating temperature of the slag removal device 2 is room temperature, and the operating pressure is -500 to 500 Pa;

[0030] The operating temperature of the low-pressure tank 3 is room temperature;

[0031] The operating temperature of the HF low temperature condenser 4 is -80 to -65°C, and the operating pressure is -2000 to -500Pa;

[0032] The preliminarily purified fluorine gas is pressurized to 1.5-3.5 MPa in a fluorine gas compressor 5; the pressurized fluorine gas is precooled to -100--80°C in a fluorine gas precooler 6;

[0033] The pressure of the fluorine gas distillation tower 7 is 1.5 to 3.5 MPa, and the distillation temperature is -180 to -140°C.

[0034] Preferably, in the HF cryogenic condenser 4, liquid nitrogen is used as a cold source, and the liquid nitrogen flows through the inner coil or tube and the outer jacket of the HF cryogenic condenser 4; the crude fluorine gas enters from the top of the HF cryogenic condenser 4 and is inserted below the middle of the condenser tank;

[0035] The tower top condenser 8 uses liquid nitrogen as a cold source, and the liquid nitrogen flows through the inner coil or tube and outer jacket of the tower top condenser 8;

[0036] The fluorine gas precooler 6 uses liquid nitrogen as a cooling source.

[0037] Preferably, the liquid nitrogen first passes through the tower top condenser 8, then flows to the fluorine gas precooler 6, then flows to the HF low temperature condenser 4, and then is vented.

[0038] The present invention provides a refining and purification device for preparing high-purity fluorine gas, comprising a fluorine production electrolytic cell 1, a slag removal device 2, a low-pressure tank 3, an HF low-temperature condensation system, a fluorine gas compressor 5, a fluorine gas precooler 6 and a fluorine gas distillation tower 7; the top of the fluorine gas distillation tower 7 is provided with a tower top condenser 8, the bottom of the tower is provided with a tower bottom reboiler 9, the outlet of the tower top condenser is connected to a fluorine gas storage tank 10, and the outlet of the tower bottom reboiler 9 is connected to a hydrofluoric acid recovery device 12; the HF low-temperature condensation system comprises a plurality of HF low-temperature condensers 4 connected in series, and the bottom of the HF low-temperature condenser 4 is provided with an HF liquid outlet, and the HF liquid outlet is connected to an HF recovery device 11. The device provided by the present invention comprises an HF low-temperature condenser 4, which can condense and remove most of the HF in the crude fluorine gas to achieve preliminary purification of the crude fluorine gas. At the same time, the device provided by the present invention also comprises a fluorine gas distillation tower 7, which can remove the remaining HF and carbon tetrafluoride (CF 4 ), nitrogen (N 2 ), oxygen (O 2 ) and oxyfluoride (OF 2 ) are removed by distillation, and high-purity fluorine gas is introduced into the fluorine gas storage tank 10 from the top condenser 8 as a light component. According to the characteristics of the crude fluorine gas and each impurity component, the present invention uses the condensation + distillation mode for purification and separation, with high purification efficiency and simple equipment structure, which is suitable for industrial and continuous production.

[0039] In addition, in the equipment provided by the present invention, the fluorine gas compressor 5 is linked with the nitrogen automatic pressure replenishing device of the low-pressure tank 3 to jointly coordinate the control and stabilize the pressure in the low-pressure tank, thereby ensuring the safe and stable operation of the fluorine-producing electrolytic cell 1.

[0040] Furthermore, in the device provided by the present invention, the HF low-temperature condenser 4 and the tower top condenser 8 adopt a cooling method of an outer jacket, an inner coil or a tube array, so that the cold capacity of liquid nitrogen is more fully utilized, waste is reduced, and the cooling effect is better.

[0041] The present invention also provides a method for preparing high-purity fluorine gas using the equipment described in the above scheme. The purity of the fluorine gas prepared by the method provided by the present invention can reach above 4N, which can meet the use requirements of the semiconductor industry. In addition, there is no need to use a fluoride salt adsorption process during the preparation process, and the adsorption and regeneration of fluoride salts are omitted. The process is more consistent and the system has better sealing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The refining and purification equipment for preparing high-purity fluorine gas provided by the present invention, Figure 1Middle: 1-fluorine production electrolytic cell, 2-slag removal device, 3-low-pressure tank, 4-HF low-temperature condenser, 5-fluorine gas compressor, 6-fluorine gas precooler, 7-fluorine gas distillation tower, 8-tower top condenser, 9-tower kettle reboiler, 10-fluorine gas storage tank, 11-HF recovery device, 12-hydrofluoric acid recovery device;

[0043] Figure 2 This is the structural diagram of the HF low-temperature condenser. Figure 2 Middle: 13-condenser tank, 14-outer jacket, 15-cooling inner tubes. DETAILED DESCRIPTION

[0044] The present invention provides a refining and purification device for preparing high-purity fluorine gas, comprising:

[0045] A fluorine-producing electrolytic cell 1; the fluorine-producing electrolytic cell 1 is provided with an anode outlet and a cathode outlet;

[0046] A slag removal device 2 whose inlet is connected to the anode outlet of the fluorine-producing electrolytic cell 1;

[0047] A low-pressure tank 3 whose inlet is connected to the outlet of the slag removal device 2, and the low-pressure tank 3 is also provided with a nitrogen automatic pressure replenishing device;

[0048] An HF cryogenic condensation system, the HF cryogenic condensation system comprising a plurality of HF cryogenic condensers 4 connected in series; a gas inlet of the first HF cryogenic condenser 4 of the HF cryogenic condensation system is connected to the outlet of the low-pressure tank 3; an HF liquid outlet is provided at the bottom of the HF cryogenic condenser 4, and the HF liquid outlet is connected to the HF recovery device 11;

[0049] A fluorine gas compressor 5 whose inlet is connected to the gas outlet of the last HF low-temperature condenser 4 of the HF condensation system; the fluorine gas compressor 5 is linked to the nitrogen automatic pressure replenishing device;

[0050] a fluorine gas precooler 6 whose inlet is connected to the outlet of the fluorine gas compressor 5;

[0051] A fluorine gas distillation tower 7 whose inlet is connected to the outlet of the fluorine gas precooler 6; a tower top condenser 8 is provided at the top of the fluorine gas distillation tower 7, and a tower bottom reboiler 9 is provided at the bottom of the tower;

[0052] a fluorine gas storage tank 10 whose inlet is connected to the outlet of the tower top condenser 8;

[0053] A hydrofluoric acid recovery device 12 whose inlet is connected to the outlet of the tower bottom reboiler 9.

[0054] The structural schematic diagram of the refining and purification equipment for preparing high-purity fluorine gas provided by the present invention is as follows Figure 1 As shown below, combined Figure 1 For detailed explanation:

[0055] The refining and purification equipment for preparing high-purity fluorine gas provided by the present invention comprises a fluorine-producing electrolytic cell 1; the fluorine-producing electrolytic cell 1 is provided with an anode outlet and a cathode outlet; the cathode outlet of the fluorine-producing electrolytic cell 1 is H 2 The outlet of the cathode outlet is preferably provided with a valve, and the anode outlet of the fluorine-producing electrolytic cell 1 is the outlet of crude fluorine gas. The present invention has no special requirements on the structure of the fluorine-producing electrolytic cell 1, and a fluorine-producing electrolytic cell well known to those skilled in the art can be used.

[0056] The refining and purification equipment for preparing high-purity fluorine gas provided by the present invention comprises a slag removal device 2 whose inlet is connected to the anode outlet of the fluorine production electrolytic cell 1. In the present invention, the slag removal device 2 is used to remove impurities such as solid or liquid electrolytes in the crude fluorine gas; the material of the slag removal device 2 can be low-carbon steel, stainless steel, nickel or monel, preferably nickel or monel. In a specific embodiment of the present invention, the slag removal device 2 preferably adopts a method of enlarging the volume and reducing the gas flow rate to allow the solid or liquid particles entrained in the fluorine gas to settle and collect, thereby achieving gas-solid or gas-liquid separation.

[0057] The refining and purification equipment for preparing high-purity fluorine gas provided by the present invention comprises a low-pressure tank 3 whose inlet is connected to the outlet of the slag removal device 2; the low-pressure tank 3 is provided with a nitrogen automatic pressure-replenishing device. In the present invention, when the pressure of the low-pressure tank 3 is lower than the required value, the nitrogen automatic pressure-replenishing device replenishes nitrogen into the low-pressure tank 3 to adjust the pressure of the low-pressure tank 3 and ensure the stability of the pressure of the low-pressure tank 3. In the present invention, maintaining a stable pressure in the low-pressure tank 3 is a guarantee for the safe and stable operation of the fluorine-producing electrolytic cell 1. In the present invention, valves are preferably provided on the inlet and outlet pipelines of the low-pressure tank 3, and a valve is preferably also provided on the nitrogen pipeline through which the nitrogen automatic pressure-replenishing device introduces nitrogen into the low-pressure tank 3.

[0058] The refining and purification equipment for preparing high-purity fluorine gas provided by the present invention includes an HF cryogenic condensation system. In the present invention, the HF cryogenic condensation system includes a plurality of HF cryogenic condensers 4 connected in series, and the number of the HF cryogenic condensers 4 is preferably more than one, and more preferably 2 to 3; in the present invention, the gas inlet of the HF cryogenic condensation system is specifically the gas inlet of the first HF cryogenic condenser 4, and the gas inlet of the first HF cryogenic condenser 4 is connected to the outlet of the low-pressure tank 3; the gas outlet of the HF cryogenic condensation system is specifically the gas outlet of the last HF cryogenic condenser 4; in the present invention, the gas inlet and the gas outlet are preferably arranged at the top of the HF cryogenic condenser 4, and the gas inlet and the gas outlet of the HF cryogenic condenser 4 are preferably provided with valves; the bottom of the HF cryogenic condenser 4 is preferably also provided with an HF liquid outlet, the HF liquid outlet is connected to the HF recovery device 11, and the HF liquid outlet is preferably provided with a valve. In the present invention, the HF cryogenic condenser 4 is preferably provided with an inner coil or tube array inside, and preferably provided with an outer jacket outside, and the inner coil or tube array and the outer jacket are used to carry liquid nitrogen; the material of the part in contact with HF inside the HF cryogenic condenser 4 is preferably a corrosion-resistant alloy, and specifically preferably monel alloy or SS316L stainless steel; the structural schematic diagram of the HF cryogenic condenser 4 is as shown in Figure 2 As shown, 13-tower body, 14-outer jacket, 15-cooling inner tube array.

[0059] The refining and purification equipment for preparing high-purity fluorine gas provided by the present invention comprises a fluorine gas compressor 5 whose inlet is connected to the gas outlet of the HF condensation system; in the present invention, the fluorine gas compressor 5 is linked with the nitrogen automatic pressure replenishing device; when the pressure in the low-pressure tank 3 is higher than the required value, the fluorine gas compressor 5 is started or the speed of the fluorine gas compressor 5 is increased to keep the pressure in the low-pressure tank 3 within the required range. In the present invention, the fluorine gas compressor 5 is also used to pressurize the fluorine gas to meet the feed requirements of the subsequent fluorine gas distillation tower 7. In the present invention, valves are preferably provided at the inlet and outlet of the fluorine gas compressor 5.

[0060] The refining and purification equipment for preparing high-purity fluorine gas provided by the present invention comprises a fluorine gas precooler 6 whose inlet is connected to the outlet of the fluorine gas compressor 5. The present invention has no special requirements on the structure of the fluorine gas precooler 6, as long as it can achieve the precooling requirements.

[0061] The refining and purification equipment for preparing high-purity fluorine gas provided by the present invention comprises a fluorine gas distillation tower 7 whose inlet is connected to the outlet of the fluorine gas precooler 6; the top of the fluorine gas distillation tower 7 is provided with a tower top condenser 8, and the bottom of the tower is provided with a tower bottom reboiler 9. In the present invention, the inside of the tower top condenser 8 is preferably provided with an inner coil or tube array, and the outside is provided with an outer jacket, and the inner coil or tube array and the outer jacket are used to pass liquid nitrogen; the top of the tower top condenser 8 is preferably provided with a temperature measuring point, a pressure measuring point and a sampling point.

[0062] The refining and purification equipment for preparing high-purity fluorine gas provided by the present invention comprises a fluorine gas storage tank 10 whose inlet is connected to the outlet of the tower top condenser 8. In the present invention, high-purity fluorine gas is drawn out from the tower top condenser 8 and enters the fluorine gas storage tank 10 for storage; a valve is preferably provided at the inlet of the fluorine gas storage tank 10, and the fluorine gas storage tank 10 is also provided with a fluorine gas outlet, and a valve is preferably provided at the fluorine gas outlet.

[0063] The refining and purification equipment for preparing high-purity fluorine gas provided by the present invention comprises a hydrofluoric acid recovery device 12 whose inlet is connected to the outlet of the tower bottom reboiler 9. In the present invention, the heavy components in the distillation process are enriched in the tower bottom reboiler 9, and the heavy components are discharged to the hydrofluoric acid recovery device 12; and a valve is preferably provided at the outlet of the tower bottom reboiler 9.

[0064] In the present invention, according to the flow order of the gas, the material of the pipeline and valve after the fluorine gas compressor 5 is preferably corrosion-resistant and oxidation-resistant metal; the pipeline connection method after the fluorine gas compressor 5 is welding, and flange connection is prohibited to ensure the safe operation of the equipment.

[0065] The present invention also provides a method for preparing high-purity fluorine gas using the equipment described in the above scheme, comprising the following steps:

[0066] Fluorine is produced by electrolysis in the fluorine production electrolytic cell 1, and crude fluorine gas is produced at the anode;

[0067] The crude fluorine gas is deslagging in the deslagging device 2, and the deslagging crude fluorine gas enters the low-pressure tank 3. The nitrogen pressure replenishing device of the low-pressure tank 3 is linked with the fluorine gas compressor 5 to control the pressure of the low-pressure tank 3 at -2000~-500Pa;

[0068] The crude fluorine gas after the slag removal enters the HF low-temperature condenser 4 from the low-pressure tank 3, HF is condensed, and enters the HF recovery device 11 from the HF liquid outlet, and the remaining gas is the preliminarily purified fluorine gas;

[0069] The preliminarily purified fluorine gas enters the fluorine gas compressor 5 for pressurization, and the pressurized fluorine gas enters the fluorine gas precooler 6 for precooling, and then enters the fluorine gas distillation tower 7 for distillation. During the distillation process, the heavy components are enriched in the bottom of the tower and discharged into the hydrofluoric acid recovery device 12, and the high-purity fluorine gas is introduced into the fluorine gas storage tank 10 from the top condenser 8 as the light component.

[0070] The present invention performs electrolytic fluorine production in a fluorine production electrolytic cell 1, and the anode produces crude fluorine gas. The present invention has no special requirements for the specific method of electrolytic fluorine production, and a method well known to those skilled in the art can be used. Specifically, potassium bifluoride can be used as an electrolyte and anhydrous hydrofluoric acid can be used as a raw material for electrolytic fluorine production.

[0071] After the anode produces crude fluorine gas, the crude fluorine gas is deslagging in the deslagging device 2, and the crude fluorine gas after deslagging enters the low-pressure tank 3. In the present invention, the operating temperature of the deslagging device 2 is preferably room temperature, and the operating pressure is preferably -500 to 500Pa, more preferably -300 to 300Pa. In the present invention, the nitrogen pressure replenishing device of the low-pressure tank 3 is linked with the fluorine gas compressor 5 to control the pressure of the low-pressure tank 3 at -2000 to -500Pa. When the pressure of the low-pressure tank 3 is lower than the above range, the valve on the nitrogen pipeline is opened, and the nitrogen pressure replenishing device automatically replenishes nitrogen to the low-pressure tank 3. When the pressure of the low-pressure tank 3 is higher than the above range, the fluorine gas compressor 5 is started or the speed of the fluorine gas compressor 5 is increased to reduce the pressure of the low-pressure tank 3 to the above range; the operating temperature of the low-pressure tank 3 is preferably room temperature.

[0072] After the crude fluorine gas after the slag removal flows out from the low-pressure tank 3, it enters the HF cryogenic condenser 4, HF is condensed, and enters the HF recovery device 11 from the HF liquid outlet, and the remaining gas is the preliminarily purified fluorine gas. In the present invention, the operating temperature of the HF cryogenic condenser 4 is preferably -80 to -65°C, more preferably -75 to -70°C, and the operating pressure is preferably -2000 to -500Pa, more preferably -1500 to -500Pa; in the present invention, according to the order of crude fluorine gas circulation, the HF cryogenic condenser 4 in the HF cryogenic condensation system is sequentially recorded as a first-stage HF cryogenic condenser, a second-stage HF cryogenic condenser...n-stage HF cryogenic condenser, and from the first-stage HF cryogenic condenser to the n-stage HF cryogenic condenser, the operating temperature of the condenser is preferably gradually reduced; in a specific embodiment of the present invention, when the HF cryogenic condensation system includes two condensers, the temperature of the first-stage HF cryogenic condenser is preferably -70 to -65°C, and the temperature of the second-stage HF cryogenic condenser is preferably -80 to -75°C.

[0073] In the present invention, liquid nitrogen is preferably used to provide low temperature in the HF cryogenic condenser 4, and the liquid nitrogen flows through the inner coil or tube array and the outer jacket of the HF cryogenic condenser 4; the crude fluorine gas enters from the top of the HF cryogenic condenser 4 and is inserted below the middle of the tank body; the HF cryogenic condenser 4 is preferably placed on a weighing device, and the amount of HF recovered and discharged is determined by weight changes; the weighing device is preferably a scale or a weighing module.

[0074] In a specific embodiment of the present invention, the volume fraction of HF in the crude fluorine gas can be reduced to below 4% after condensation by the HF low temperature condenser 4. The liquid HF recovered in the HF recovery device 11 is preferably returned to the electrolytic cell 1 for reuse.

[0075] After the preliminarily purified fluorine gas flows out of the HF cryogenic condenser 4, it enters the fluorine gas compressor 5 for pressurization, and the pressurized fluorine gas enters the fluorine gas precooler 6 for precooling, and then enters the fluorine gas distillation tower 7 for rectification. During the distillation process, the heavy component is enriched in the tower bottom and discharged into the hydrofluoric acid recovery device 12, and the high-purity fluorine gas is introduced into the fluorine gas storage tank 10 from the tower top condenser 8 as a light component. In the present invention, the preliminarily purified fluorine gas is preferably pressurized to 1.5 to 3.5 MPa in the fluorine gas compressor 5, and more preferably 1.5 to 2.5 MPa; the pressurized fluorine gas is precooled to -100 to -80°C, and more preferably -95 to -85°C in the fluorine gas precooler 6; liquid nitrogen is preferably used as a cold source in the fluorine gas precooler 6.

[0076] In the present invention, the pressure of the fluorine gas distillation tower 7 is preferably 1.5 to 3.5 MPa, more preferably 2 to 2.5 MPa, and the distillation temperature is preferably -180 to -140°C, more preferably -170 to -160°C; specifically, during the distillation process, the temperature of the top condenser 8 is preferably -170 to -165°C, and the temperature of the bottom reboiler 9 is preferably -168 to -160°C. During the distillation process, hydrogen fluoride (HF), carbon tetrafluoride (CF 4 ), nitrogen (N 2 ), oxygen (O 2 ), Oxygen difluoride (OF 2 ) etc. are enriched in the tower bottom in the form of heavy components, and the fluorine gas is introduced into the fluorine gas storage tank 10 from the top of the tower top condenser 8 as a light component, thereby achieving the purification of the fluorine gas. In a specific embodiment of the present invention, after the heavy components in the tower bottom are enriched to a certain amount, they are discharged into the hydrofluoric acid recovery system 12 for the production of aqueous acid.

[0077] In the present invention, the tower top condenser 8 preferably uses liquid nitrogen as a cold source, and the liquid nitrogen flows through the inner coil or tube and outer jacket of the tower top condenser 8. In the present invention, the liquid nitrogen preferably first passes through the tower top condenser 8, then flows to the fluorine gas precooler 6, then flows to the HF low temperature condenser 4, and then is vented. The present invention can make full use of cold capacity, reduce waste, and realize the comprehensive utilization of liquid nitrogen by controlling the flow direction of liquid nitrogen.

[0078] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0079] Example 1

[0080] The structure of the refining and purification equipment for preparing high-purity fluorine gas used in this embodiment is as follows: Figure 1 As shown, the HF low temperature condensation system includes two HF low temperature condensers 4 connected in series. Figure 1 The equipment shown in the figure prepares high-purity fluorine gas, and the specific steps are as follows:

[0081] The raw fluorine gas produced by the fluorine production electrolytic cell 1 contains HF (volume ratio) 12%, CF 4 (volume ratio) 1.5%, nitrogen (volume ratio) 5%, and a trace amount of oxygen (O 2 ), Oxygen difluoride (OF 2 ) and impurities such as entrained solid electrolyte.

[0082] In the first step, the crude fluorine gas first enters the slag removal device 2 matched with the electrolytic cell 1, where the solid electrolyte is precipitated and removed to obtain the slag-free crude fluorine gas. The operating temperature of the slag removal device 2 is room temperature and the pressure is -300 to 500 Pa.

[0083] In the second step, the crude fluorine gas from the slag removal enters the low-pressure tank 3. The operating temperature of the low-pressure tank 3 is room temperature. The low-pressure tank 3 is coordinated and controlled by the nitrogen pressure supplement device and the fluorine gas compressor 5 to stabilize the pressure in the tank at -800 to -500 Pa. When the pressure is high, the fluorine gas compressor 5 is started or the speed of the fluorine gas compressor 5 is increased to extract air; when the pressure is low, the nitrogen valve is opened to automatically supplement nitrogen.

[0084] In the third step, the crude fluorine gas from the slag removal enters the HF low-temperature condensation system of the two-stage HF low-temperature condenser 4 in series, wherein the temperature of the first-stage condenser is -70~-65℃, the temperature of the second-stage condenser is -80~-75℃, the pressure of the first-stage and second-stage condensers are both -800~-500Pa, and the condenser is placed on a weighing module, and the amount of liquid HF collected and discharged is observed by weight increase and decrease.

[0085] Sampling was performed at the top of the secondary condenser. After the fluorine gas was converted into chlorine gas using a potassium chloride adsorption column, the amount of chlorine gas was detected by gas chromatography instead of fluorine gas. The analysis results showed that HF ​​(volume ratio) was 2.8%, CF4 (volume ratio) 1.56%, nitrogen (volume ratio) 7.8%, and trace amounts of oxygen (O 2 ), Oxygen difluoride (OF 2 ), the nitrogen content increases due to the pressure adjustment of low-pressure tank 3.

[0086] In the fourth step, the initially purified fluorine gas is pressurized to 2.0-2.2 MPa by a fluorine gas compressor 5.

[0087] In the fifth step, the pressurized fluorine gas enters the fluorine gas precooler 6 and the temperature drops to -100 to -95°C.

[0088] In the sixth step, the pre-cooled fluorine gas enters the fluorine gas distillation tower 7 for distillation. The temperature of the top condenser 8 is -170~-165℃, the temperature of the bottom of the tower is -168~-160℃, and the pressure of the top of the tower is 2.0~2.2MPa. During the distillation process, hydrogen fluoride (HF) and carbon tetrafluoride (CF 4 ), nitrogen (N 2 ) and oxygen (O 2 ), Oxygen difluoride (OF 2 ) etc. are enriched in the tower bottom in the form of heavy components, and high-purity fluorine gas is introduced into the fluorine gas storage tank 10 from the top of the tower top condenser 8 as light components.

[0089] Sampling and analysis were performed at the top of the tower top condenser 8. After the fluorine gas was converted into chlorine gas by a potassium chloride adsorption column, the amount of chlorine gas was detected by gas chromatography instead of the amount of fluorine gas. The analysis results showed that the fluorine gas (volume ratio) was greater than 99.99%, and the HF (volume ratio) was 10ppm. The product quality can meet the use of the semiconductor industry.

[0090] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing high-purity fluorine gas, characterized in that: The refining and purification equipment used to prepare high-purity fluorine gas includes: A fluorine-producing electrolytic cell (1); the fluorine-producing electrolytic cell (1) is provided with an anode outlet and a cathode outlet; A slag removal device (2) whose inlet is connected to the anode outlet of the fluorine-producing electrolytic cell (1); the slag removal device (2) is used to remove solid or liquid electrolyte in the crude fluorine gas; the slag removal device (2) is made of low-carbon steel, stainless steel, nickel or monel; A low-pressure tank (3) whose inlet is connected to the outlet of the slag removal device (2), and the low-pressure tank (3) is provided with a nitrogen automatic pressure replenishing device; An HF low-temperature condensation system, the HF low-temperature condensation system comprising a plurality of HF low-temperature condensers (4) connected in series; a gas inlet of a first HF low-temperature condenser (4) of the HF low-temperature condensation system is connected to an outlet of the low-pressure tank (3); an HF liquid outlet is provided at the bottom of the HF low-temperature condenser (4), and the HF liquid outlet is connected to an HF recovery device (11); A fluorine gas compressor (5) whose inlet is connected to the gas outlet of the last HF low-temperature condenser (4) of the HF low-temperature condensation system; the fluorine gas compressor (5) is linked to the nitrogen automatic pressure replenishing device; a fluorine gas precooler (6) whose inlet is connected to the outlet of the fluorine gas compressor (5); a fluorine gas distillation tower (7) whose inlet is connected to the outlet of the fluorine gas precooler (6); a tower top condenser (8) is provided at the top of the fluorine gas distillation tower (7), and a tower bottom reboiler (9) is provided at the bottom of the tower; a fluorine gas storage tank (10) whose inlet is connected to the outlet of the tower top condenser (8); a hydrofluoric acid recovery device (12) whose inlet is connected to the outlet of the tower bottom reboiler (9); The method for preparing high-purity fluorine gas comprises the following steps: Electrolysis is performed in a fluorine production electrolytic cell (1) to produce fluorine, and crude fluorine gas is produced at the anode; The crude fluorine gas is deslagging in the deslagging device (2), and the deslagging crude fluorine gas enters the low-pressure tank (3). The nitrogen pressure replenishing device of the low-pressure tank (3) is linked with the fluorine gas compressor (5) to control the pressure of the low-pressure tank (3) to -2000~-500Pa; The crude fluorine gas after the slag removal enters the HF low-temperature condenser (4) from the low-pressure tank (3), HF is condensed, and enters the HF recovery device (11) from the HF liquid outlet, and the remaining gas is the preliminarily purified fluorine gas; The preliminarily purified fluorine gas enters a fluorine gas compressor (5) for pressurization, the pressurized fluorine gas enters a fluorine gas precooler (6) for precooling, and then enters a fluorine gas rectification tower (7) for rectification. During the rectification process, the heavy components are enriched in the bottom of the tower and discharged into a hydrofluoric acid recovery device (12), and the high-purity fluorine gas is introduced from the tower top condenser (8) into a fluorine gas storage tank (10) as a light component; The operating temperature of the HF low-temperature condenser (4) is -80 to -65°C, and the operating pressure is -2000 to -500 Pa; the preliminarily purified fluorine gas is pressurized to 1.5 to 3.5 MPa in the fluorine gas compressor (5); the pressure of the fluorine gas rectification tower (7) is 1.5 to 3.5 MPa; and the temperature of the tower top condenser (8) during the rectification process is -170 to -165°C.

2. The method according to claim 1, characterized in that The number of the HF low-temperature condensers (4) is at least one.

3. The method according to claim 1, characterized in that The HF low-temperature condenser (4) is provided with an inner coil or a tube array inside and an outer jacket outside.

4. The method according to claim 1, characterized in that: The tower top condenser (8) is provided with an inner coil or tube array inside and an outer jacket outside; a temperature measuring point, a pressure measuring point and a sampling point are provided at the top of the tower top condenser (8).

5. The method according to claim 1, characterized in that A valve is provided on the pipeline at the cathode outlet of the fluorine-producing electrolytic cell (1); valves are provided at the inlet and outlet of the low-pressure tank (3); valves are provided at the gas inlet, gas outlet and HF liquid outlet of the HF low-temperature condenser (4); valves are provided at the inlet and outlet of the fluorine gas compressor (5); a valve is provided at the outlet of the tower kettle reboiler (9); a valve is provided at the inlet of the fluorine gas storage tank (10), and the fluorine gas storage tank (10) is also provided with a fluorine gas outlet, and a valve is provided at the fluorine gas outlet.

6. The method according to claim 5, characterized in that According to the gas circulation sequence, the materials of the pipelines and valves after the fluorine gas compressor (5) are all corrosion-resistant and oxidation-resistant metals; and the pipeline connection method after the fluorine gas compressor (5) is all welding.

7. The method according to claim 1, characterized in that The operating temperature of the slag removal device (2) is room temperature, and the operating pressure is -500~500Pa; The operating temperature of the low-pressure tank (3) is room temperature; The pressurized fluorine gas is precooled to -100~-80°C in a fluorine gas precooler (6); The distillation temperature of the fluorine gas distillation tower (7) is -180 to -140°C.

8. The method according to claim 7, characterized in that In the HF cryogenic condenser (4), liquid nitrogen is used as a cold source, and the liquid nitrogen flows through the inner coil or tube array and the outer jacket of the HF cryogenic condenser (4); crude fluorine gas enters from the top of the HF cryogenic condenser (4) and is inserted below the middle of the condenser tank; The tower top condenser (8) uses liquid nitrogen as a cold source, and the liquid nitrogen flows through the inner coil or tube array and the outer jacket of the tower top condenser (8); The fluorine gas precooler (6) uses liquid nitrogen as a cooling source.

9. The method according to claim 8, characterized in that The liquid nitrogen first passes through the tower top condenser (8), then flows to the fluorine gas precooler (6), then flows to the HF low temperature condenser, and then is discharged.

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