Electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium bifluoride molten salt

Abstract

The invention relates to an electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium bifluoride molten salt. The electrolysis process system comprises an electrolytic bath, a high-frequency switch direct-current power supply system, a hydrogen fluoride and ammonia gas feeding system, a cathode gas system and an anode gas system, the electrolytic bath comprises a bath body, a bath cover, cathodes and anodes, the bath cover is located above the bath body, the anodes and the cathodes are hung on the bath cover, fluoroplastic skirts or monel metal skirts are arranged between the cathodes and the anodes, and the cathodes and the anodes are arranged into a plurality of groups; the high-frequency switch direct-current power supply system is used for controlling current and voltage in the process of preparing nitrogen trifluoride by electrolysis of the electrolytic tank; the hydrogen fluoride and ammonia gas feeding system is used for conveying purified liquid hydrogen fluoride and high-purity ammonia gas into a tank body of the electrolytic tank and is interlocked with the liquid level of the electrolytic tank to realize automatic material supplementing; and the cathode gas system and the anode gas system are used for pretreating gases generated by a cathode and an anode in electrolysis. Safe and stable operation of production can be guaranteed, the labor intensity of operators is reduced, and the operation automation level is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytic preparation of nitrogen trifluoride gas, and particularly to an electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium bifluoride molten salt. Background Art

[0002] NF3 is a special gas with very important applications in the semiconductor industry and liquid crystal panel factories. With the development of the electronics industry and the advent of the era of automation and intelligence, the demand for semiconductors and liquid crystal panels has increased year by year. NF3 is a colorless, peculiarly rotten-smelling, non-toxic and non-flammable gas under normal temperature and pressure, with a relative molecular mass of 71, a melting point of -206 °C, a boiling point of -129 °C, and a density of 1554 kg / m 3 , the liquid is slightly yellowish, chemically inert at normal temperature, and can act as an oxidant at high temperatures. It can be cracked to generate nitrogen and free fluorine at higher temperatures, and can react with organic substances and certain metals. When the temperature reaches above 350 °C or in the plasma state, the reaction activity of NF3 is higher than that of elemental fluorine. Due to these characteristics of NF3, it has been widely used in fields such as liquid crystal panel cleaning processes, etching and cleaning processes for the manufacture of ultra-large-scale integrated circuits, etc. As a special gas, NF3 can be used as an etchant for polysilicon, silicon nitride, etc., and a cleaning agent in the production of liquid crystal displays. As an important fluoride electronic gas, NF3 has become an indispensable key material in the manufacturing process of microelectronic devices.

[0003] Industrially, it is often prepared by electrolyzing the molten salt of ammonium bifluoride and hydrogen fluoride. By electrolyzing the molten (NH4HF2 + xHF) mixed electrolyte, crude NF3 gas can be obtained. The anode of the electrolytic cell is made of nickel plate, and the cathode is made of carbon steel plate, nickel plate or stainless steel plate, and the inter-electrode voltage is 5 - 10V. During the electrolysis process, NF3 gas (purity about 50 - 80%, the main impurity is N2) is generated at the anode, and H2 gas is generated at the cathode. During the electrolysis process, the electrolyte is a molten system of ammonium bifluoride and hydrogen fluoride, and the electrolysis temperature is controlled at 80 - 150 °C. Therefore, HF is inevitably carried out at the cathode and anode. The electrolysis reaction equations are as follows:

[0004] Main reaction: NH4HF2 + HF → NF3 (anode) + 3H2 (cathode);

[0005] Side reaction: 2NH4HF2 → 4HF + 3H2 (cathode) + N2 (anode).

[0006] The current common method in the industry for feeding materials in the electrolysis process of nitrogen trifluoride is to place solid ammonium bifluoride in a mixing tank, and then introduce hydrogen fluoride into the mixing tank for heating. The heating temperature is controlled at 80°C to 150°C, and the heating and melting time is 8 - 20 hours. After that, the electrolyte in the mixing tank is pumped into a transfer tank, and the transfer tank is transported to the electrolysis room for manual feeding. The liquid level is also measured manually. The feeding personnel need to wear protective clothing and gloves. In summer, the temperature in the electrolysis room is usually between 50°C and 80°C, and the working environment is harsh, often resulting in heatstroke and collapse. The height of the liquid level in the electrolytic cell requires the operator to insert a metal or non-metal rod into the electrolytic cell, and then judge the liquid level height in the cell according to the liquid trace hanging on the rod after extraction. When to feed also needs to be speculated based on experience, which poses a potential safety hazard to production.

[0007] The high-frequency switching power supply that supplies power to the electrolytic cell usually uses constant voltage control for external DC output, and there is also constant current control. The reason for using constant voltage control is to worry about the risk of generating fluorine gas caused by voltage fluctuations. However, the temperature and electrolyte concentration fluctuations during the operation of the electrolytic cell cause drastic changes in current, and the quality of the electrolytic gas generated also fluctuates accordingly. The operator needs to frequently adjust the electrolysis voltage to ensure relatively constant current. Similar problems will also occur with constant current control. When the current is constant, changes in the electrolyte concentration and temperature of the electrolytic cell will cause the voltage to fluctuate up and down. When the voltage is too high, the fluorine gas content in the anode gas is high, which will pose a risk of fire and explosion.

[0008] The purification and rectification process of nitrogen trifluoride anode gas is a key link in the production of high-purity nitrogen trifluoride. The anode gas containing polyfluoride impurities flowing out of the anode chamber of the electrolytic cell enters the buffer tank and then enters the cracking tower after buffering. The packing material inside the conventional cracking tower usually selects stainless steel or nickel materials. Due to the low catalytic activity of stainless steel or nickel, the decomposition temperature of polyfluorides is high. Too high a temperature will cause a large amount of fluorine gas to be generated by the cracking of nitrogen trifluoride, posing an explosion risk, and at the same time affecting the yield of nitrogen trifluoride. Too low a temperature will result in incomplete cracking of polyfluorides, causing the remaining polyfluorides to enter the low-temperature rectification section, resulting in the accumulation and explosion of polyfluorides. Summary of the Invention

[0009] The present invention provides an electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium bifluoride molten salt, which can solve the safety problems in the electrolysis process of preparing nitrogen trifluoride by electrolyzing ammonium bifluoride molten salt, ensure the safe and stable operation of production, reduce the labor intensity of operators, and improve the automation level of operation.

[0010] To achieve the purpose of the present invention, the specific technical solutions provided by the present invention are as follows:

[0011] An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium bifluoride molten salt, comprising an electrolytic cell, a high-frequency switching DC power supply system, a hydrogen fluoride and ammonia feeding system, a cathode gas system, and an anode gas system;

[0012] The electrolytic cell includes a cell body, a cell cover, an anode assembly, and a cathode assembly. The cell cover is located on the top of the cell body. A fluoroplastic skirt or a Monel metal skirt is provided between the anode assembly and the cathode assembly. There are several groups of anode assemblies and cathode assemblies, and the anode assemblies and cathode assemblies are alternately suspended on the cell cover;

[0013] The high-frequency switch DC power supply system is used to control the current and voltage during the electrolytic preparation of nitrogen trifluoride in the electrolytic cell;

[0014] The hydrogen fluoride and ammonia feeding system is used to transport the purified liquid hydrogen fluoride and high-purity ammonia into the interior of the cell body of the electrolytic cell, and realizes automatic feeding in interlock with the liquid level of the electrolytic cell;

[0015] The cathode gas system is used to pre-treat the gas generated by the cathode assembly during the electrolytic preparation of nitrogen trifluoride in the electrolytic cell;

[0016] The anode gas system is used to pre-treat the gas generated by the anode assembly during the electrolytic preparation of nitrogen trifluoride in the electrolytic cell.

[0017] A fluoroplastic skirt or a Monel metal skirt is provided between the anode assembly and the cathode assembly to prevent the mixing of cathode gas and anode gas.

[0018] Preferably, the cell cover and the cell body are hermetically connected by means of a flange and an insulating gasket. The anode assembly is composed of an anode plate and an anode joint welded together. A gasket is provided between the anode joint at the upper part of the anode assembly and the cell cover, and a tetrafluoro sleeve is provided between the anode plate at the lower part of the anode assembly and the cell cover. The gasket and the tetrafluoro sleeve electrically isolate the anode assembly from the cell cover.

[0019] Preferably, several anode gas outlets a and two cathode gas outlets b are provided on the top of the cell cover of the electrolytic cell. The anode gas outlets a are horizontally arrayed on the top of the cell cover, and the cathode gas outlets b are located at the diagonal corners of the top of the cell cover; several liquid hydrogen fluoride feeding ports c and several ammonia feeding ports d are provided on the cell body of the electrolytic cell. The hydrogen fluoride feeding ports c and the ammonia feeding ports d are distributed on both sides of the cell body. Hydrogen fluoride and ammonia mixed with nitrogen slowly mix at the bottom of the cell to form an electrolyte.

[0020] Preferably, liquid hydrogen fluoride inlet flanges and ammonia inlet flanges are provided on both sides of the cell body. The liquid hydrogen fluoride inlet flange is located at the hydrogen fluoride feeding port c, and the ammonia inlet flange is located at the ammonia feeding port d; Fluoroplastic distribution pipes are also respectively provided on both sides of the cell body to observe the feeding rates of liquid hydrogen fluoride and ammonia. Providing inlet flanges for distribution on both sides of the cell body can stably control the reaction rate and prevent the violent reaction between hydrogen fluoride and ammonia from affecting the stable operation of the electrolytic cell.

[0021] Preferably, the high-frequency switched DC power supply system adopts an IGBT high-frequency switched power supply to control the current and voltage during the electrolytic preparation of nitrogen trifluoride in the electrolytic cell. The operation mode of the high-frequency switched DC power supply system adopts a constant current and voltage-limiting mode, and the high-frequency switched DC power supply system is electrically connected to the anode assembly and the cathode assembly. Adopting constant current and voltage-limiting control is more conducive to increasing the output of nitrogen trifluoride, while ensuring the stable operation of the electrolytic cell, reducing the labor intensity of the operator, and improving labor productivity.

[0022] Preferably, the hydrogen fluoride and ammonia feeding system includes a control interlock system composed of an automatic control valve and a mass flowmeter for controlling the feeding ratio of liquid hydrogen fluoride and ammonia; the control interlock loop composed of the ammonia automatic control valve and the first mass flowmeter controls the feeding amount of ammonia, and the control interlock loop composed of the hydrogen fluoride automatic control valve and the second mass flowmeter controls the feeding amount of liquid hydrogen fluoride.

[0023] Preferably, the hydrogen fluoride and ammonia feeding system further includes a liquid level transmitter, which transmits the height of the electrolyte liquid level inside the electrolytic cell to the DCS system and combines with the control interlock system composed of the automatic control valve and the mass flowmeter to implement automatic feeding.

[0024] The hydrogen fluoride and ammonia feeding system realizes automatic feeding, which can avoid problems such as internal explosion caused by the mixing of anode unit gas and cathode unit gas due to too low electrolyte liquid level and imbalance of electrolyte ratio caused by gas entrainment in the electrolyte due to too high electrolyte liquid level; at the same time, the feeding system can continuously introduce nitrogen at the feeding port during the shutdown of the electrolytic cell to prevent blockage of the feeding pipe inside the electrolytic cell.

[0025] Preferably, the cathode gas system is provided with a first condenser. The inlet of the first condenser is connected to the cathode gas outlet b, and the outlet of the first condenser is connected to the falling film absorption section.

[0026] Preferably, the anode gas system is provided with a second condenser and a catalytic cracking tower connected in series. The inlet of the second condenser is connected to the anode gas outlet a, the outlet of the second condenser is connected to the inlet of the catalytic cracking tower, and the outlet of the catalytic cracking tower is connected to the purification and rectification section of the anode gas.

[0027] Preferably, the inside of the catalytic cracking tower is filled with nickel foam packing. The nickel foam packing can efficiently decompose easily explosive components such as polyfluorides. Under the condition of ensuring complete decomposition of polyfluorides, the nickel foam packing can reduce the cracking temperature by 35°C to 60°C, thus effectively reducing the decomposition of nitrogen trifluoride caused by too high temperature inside the catalytic cracking tower and avoiding the generation of excessive fluorine gas. This not only improves the yield of nitrogen trifluoride products but also ensures the stable and safe operation of the purification and rectification refining system in the subsequent section.

[0028] An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium bifluoride molten salt according to the present invention has the following beneficial effects: This invention patent can solve the electrolysis process problems of preparing nitrogen trifluoride by electrolyzing ammonium bifluoride molten salt, ensure the safe and stable operation of production, reduce the labor intensity of operators, and improve the level of operation automation.

[0029] 1. In the present invention, the hydrogen fluoride and ammonia feeding system realizes the automatic feeding of hydrogen fluoride and ammonia, which can avoid the problems of internal explosion caused by the mixing of anode unit gas and cathode unit gas due to too low electrolyte liquid level and the imbalance of electrolyte ratio caused by the entrainment of gas and electrolyte due to too high electrolyte liquid level; at the same time, the feeding system can continuously introduce nitrogen at the feeding port during the shutdown of the electrolytic cell to prevent the blockage of the feeding pipe inside the electrolytic cell.

[0030] 2. In the present invention, the high-frequency switching DC power supply system adopts an IGBT high-frequency switching power supply and uses constant current and voltage limiting control, which is more conducive to expanding the output of nitrogen trifluoride, ensuring the stable operation of the electrolytic cell, reducing the labor intensity of operators, and improving labor productivity.

[0031] 3. In the present invention, a fluoroplastic skirt or a Monel metal skirt is arranged between the cathode and the anode, which can effectively prevent the mixing of cathode gas and anode gas; inlet flanges for distribution are arranged on both sides of the cell body, which can smoothly control the reaction rate and prevent the violent reaction between hydrogen fluoride and ammonia from affecting the stable operation of the electrolytic cell.

[0032] 4. In the present invention, the catalytic cracking tower is filled with nickel foam packing inside. The nickel foam packing can efficiently decompose explosive components such as polyfluorides. Under the condition of ensuring the complete decomposition of polyfluorides, the nickel foam packing can reduce the cracking temperature by 35°C to 60°C, thus effectively reducing the decomposition of nitrogen trifluoride caused by too high temperature inside the catalytic cracking tower and avoiding the generation of excessive fluorine gas. This not only improves the yield of nitrogen trifluoride products but also ensures the stable and safe operation of the purification and rectification refining systems in the subsequent process sections. Description of the Drawings

[0033] Figure 1 It is a schematic diagram of the electrolysis process system for preparing nitrogen trifluoride according to the present invention;

[0034] Figure 2 It is the front view of the electrolytic cell according to the present invention;

[0035] Figure 3 It is the top view of the electrolytic cell according to the present invention;

[0036] Figure 4 It is the left view of the electrolytic cell according to the present invention;

[0037] Marking Explanation in the Figure: 1. Electrolytic cell; 11. Anode assembly; 12. Cathode assembly; 13. Hydrogen fluoride feed port c; 14. Ammonia feed port d; 15. Anode gas outlet a; 16. Cathode gas outlet b; 2. High-frequency switch DC power supply system; 3. Hydrogen fluoride and ammonia feed system; 31. Ammonia automatic control valve; 32. Hydrogen fluoride automatic control valve; 33. Liquid level transmitter; 34. First mass flowmeter; 35. Second mass flowmeter; 4. Cathode gas system; 41. First condenser; 5. Anode gas system; 51. Second condenser; 52. Catalytic cracking tower. Detailed Embodiment

[0038] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in conjunction with preferred embodiments, details the specific embodiments, structures, features, and their effects according to the present invention as follows.

[0039] Embodiment 1

[0040] This embodiment provides an electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt. As Figure 1 shown, it is a schematic diagram of the electrolysis process system for preparing nitrogen trifluoride according to the present invention.

[0041] An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt includes an electrolytic cell 1, a high-frequency switch DC power supply system 2, a hydrogen fluoride and ammonia feed system 3, a cathode gas system 4, and an anode gas system 5 connected to the electrolytic cell.

[0042] Figures 2 - 4 It is a schematic diagram of the structure of the electrolytic cell according to the present invention. The electrolytic cell 1 includes a cell body, a cell cover, an anode assembly 11, and a cathode assembly 12. The cell cover is located above the cell body. A fluoroplastic skirt or a skirt made of Monel metal is provided between the anode assembly 11 and the cathode assembly 12. There are several groups of anode assemblies 11 and cathode assemblies 12, and the anode assemblies 11 and cathode assemblies 12 are alternately suspended on the cell cover. Providing a fluoroplastic skirt or a skirt made of Monel metal between the anode assembly 11 and the cathode assembly 12 can effectively prevent the mixing of cathode gas and anode gas.

[0043] The cell cover and the cell body of the electrolytic cell 1 are hermetically connected by means of a flange and an insulating gasket. The anode assembly 11 is composed of an anode plate and an anode joint welded together. A gasket is provided between the anode joint at the upper part of the anode assembly 11 and the cell cover, and a tetrafluoro sleeve is provided between the anode plate at the lower part of the anode assembly 11 and the cell cover. The gasket and the tetrafluoro sleeve electrically isolate the anode assembly 11 from the cell cover.

[0044] On the top of the cover of the electrolytic cell 1, there are 6 anodic gas outlets a15, namely anodic gas outlets a1 - a6, which are horizontally arrayed on the top of the cover; on the top of the cover, there are also 2 cathodic gas outlets b16, namely cathodic gas outlets b1 and b2. The cathodic gas outlets b1 and b2 are located at the diagonal corners of the top of the cover and are centrosymmetrically arranged.

[0045] On one side of the cell body of the electrolytic cell 1, there are 7 liquid hydrogen fluoride inlets c13, namely liquid hydrogen fluoride inlets c1 - c7. On the opposite side of the cell body to the liquid hydrogen fluoride inlets c13, there are 7 ammonia inlets d14, namely ammonia inlets d1 - d7. The liquid hydrogen fluoride inlets c13 and the ammonia inlets d14 are symmetrically arranged and are located at positions on the side wall of the cell body close to the bottom. Hydrogen fluoride and ammonia mixed with nitrogen can slowly mix at the bottom of the electrolytic cell 1 to form an electrolyte.

[0046] On both sides of the cell body, there are also a liquid hydrogen fluoride inlet flange and an ammonia inlet flange. The liquid hydrogen fluoride inlet flange is located at the liquid hydrogen fluoride inlets c13, and the ammonia inlet flange is located at the ammonia inlets d14; on both sides of the cell body, there are also fluoroplastic distribution pipes respectively, which are used to observe the feeding rates of liquid hydrogen fluoride and ammonia.

[0047] Setting the inlet flanges that play a distribution role on both sides of the cell body can stably control the reaction rate and prevent the violent reaction between hydrogen fluoride and ammonia from affecting the stable operation of the electrolytic cell 1.

[0048] The high - frequency switch DC power supply system 2 adopts an IGBT high - frequency switch power supply, which is used to control the current and voltage during the process of electrolytically preparing nitrogen trifluoride in the electrolytic cell 1; the operation mode of the high - frequency switch DC power supply system 2 adopts a constant - current and voltage - limiting control mode.

[0049] Adopting constant - current and voltage - limiting control is more conducive to increasing the output of nitrogen trifluoride, ensuring the operation of the electrolytic cell 1 at the same time, reducing the labor intensity of the operator, and improving labor productivity.

[0050] The hydrogen fluoride and ammonia feeding system 3 is used to transport the purified liquid hydrogen fluoride and high - purity ammonia into the cell body of the electrolytic cell 1 and realizes automatic feeding in interlock with the internal liquid level of the electrolytic cell 1;

[0051] Specifically, it includes a control interlock system composed of automatic control valves and mass flow meters, which is used to control the feeding ratio of liquid hydrogen fluoride and ammonia; the feeding amount of ammonia is controlled by a control interlock loop composed of an ammonia automatic control valve 31 and a first mass flow meter 34, and the feeding amount of liquid hydrogen fluoride is controlled by a control interlock loop composed of a hydrogen fluoride automatic control valve 32 and a second mass flow meter 35.

[0052] The hydrogen fluoride and ammonia feeding system 3 further includes a liquid level transmitter 33 which transmits the height of the electrolyte liquid level inside the electrolytic cell 1 to the DCS system, and combines with the automatic control valve and the mass flowmeter to form a control interlock system for automated feeding.

[0053] The hydrogen fluoride and ammonia feeding system 3 realizes automated feeding, which can avoid the problems of internal explosion caused by the mixing of anode unit gas and cathode unit gas due to too low electrolyte liquid level and the imbalance of electrolyte ratio caused by the entrainment of gas and electrolyte due to too high electrolyte liquid level; meanwhile, the feeding system can continuously introduce nitrogen at the feeding port during the shutdown of the electrolytic cell 1 to prevent the blockage of the feeding pipe inside the electrolytic cell 1.

[0054] The cathode gas system 4 is provided with a first condenser 41. The feeding port of the first condenser 41 is communicated with the cathode gas outlet b16, and the discharging port of the first condenser 41 is communicated with the falling film absorption section.

[0055] The anode gas system 5 is provided with a second condenser 51 and a catalytic cracking tower 52 which are communicated. The feeding port of the second condenser 51 is communicated with the anode gas outlet a15, the discharging port of the second condenser 51 is communicated with the feeding port of the catalytic cracking tower 52, and the inside of the catalytic cracking tower 52 is filled with nickel foam packing. The discharging port of the catalytic cracking tower 52 is communicated with the purification and rectification section of the anode gas. The subsequent purification and rectification process is the same as the conventional purification process in current industrial production.

[0056] The nickel foam packing can efficiently decompose explosive components such as polyfluorides. Under the condition of ensuring the complete decomposition of polyfluorides, the nickel foam packing can reduce the cracking temperature by 35°C to 60°C, thereby effectively reducing the decomposition of nitrogen trifluoride caused by too high temperature inside the catalytic cracking tower and avoiding the generation of excessive fluorine gas. This not only improves the yield of the nitrogen trifluoride product but also ensures the stable and safe operation of the purification and rectification refining system in the subsequent section.

[0057] The above is only a preferred embodiment of the present invention, and it is not intended to limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to form equivalent embodiments with equivalent changes, but as long as it does not depart from the technical content of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt, characterized in that, It includes an electrolytic cell (1), a high-frequency switching DC power supply system (2), a hydrogen fluoride and ammonia feeding system (3), a cathode gas system (4) and an anode gas system (5); The electrolytic cell (1) includes a cell body, a cell cover, an anode assembly (11) and a cathode assembly (12). The cell cover is located at the top of the cell body. A fluoroplastic skirt or a Monel metal skirt is arranged between the anode assembly (11) and the cathode assembly (12). There are several groups of the anode assembly (11) and the cathode assembly (12), and the anode assembly (11) and the cathode assembly (12) are alternately suspended on the cell cover; The high-frequency switching DC power supply system (2) is used to control the current and voltage during the electrolytic preparation of nitrogen trifluoride in the electrolytic cell (1); The hydrogen fluoride and ammonia feeding system (3) is used to transport the purified liquid hydrogen fluoride and high-purity ammonia into the interior of the cell body of the electrolytic cell (1), and realizes automatic feeding in interlock with the liquid level inside the electrolytic cell (1); The cathode gas system (4) is used to pre-treat the gas generated by the cathode assembly (12) during the electrolytic preparation of nitrogen trifluoride in the electrolytic cell (1); The anode gas system (5) is used to pre-treat the gas generated by the anode assembly (11) during the electrolytic preparation of nitrogen trifluoride in the electrolytic cell (1).

2. The electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt according to claim 1, characterized in that, The cell cover and the cell body are hermetically connected by means of a flange and an insulating gasket. The anode assembly (11) is composed of an anode plate and an anode joint welded together. A gasket is arranged between the anode joint at the upper part of the anode assembly (11) and the cell cover, and a tetrafluoro sleeve is arranged between the anode plate at the lower part of the anode assembly (11) and the cell cover. The gasket and the tetrafluoro sleeve electrically isolate the anode assembly (11) from the cell cover.

3. An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt according to claim 1, characterized in that, Several anode gas outlets a (15) and two cathode gas outlets b (16) are arranged at the top of the cell cover of the electrolytic cell (1). The anode gas outlets a (15) are horizontally arrayed at the top of the cell cover, and the cathode gas outlets b (16) are located at the diagonal corners of the top of the cell cover; Several liquid hydrogen fluoride feeding ports c (13) and several ammonia feeding ports d (14) are arranged on the cell body of the electrolytic cell (1). The hydrogen fluoride feeding ports c (13) and the ammonia feeding ports d (14) are distributed on both sides of the cell body.

4. An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt according to claim 3, characterized in that, Liquid hydrogen fluoride inlet flanges and ammonia inlet flanges are arranged on both sides of the cell body. The liquid hydrogen fluoride inlet flange is located at the hydrogen fluoride feeding port c (13), and the ammonia inlet flange is located at the ammonia feeding port d (14); Fluoroplastic distribution pipes are also respectively arranged on both sides of the cell body for observing the feeding rates of liquid hydrogen fluoride and ammonia.

5. An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt according to claim 1, characterized in that, The high-frequency switching DC power supply system (2) adopts an IGBT high-frequency switching power supply to control the current and voltage during the electrolytic preparation of nitrogen trifluoride in the electrolytic cell (1). The operation mode of the high-frequency switching DC power supply system (2) adopts a constant current and voltage-limiting mode. The high-frequency switching DC power supply system (2) is electrically connected to the anode assembly (11) and the cathode assembly (12).

6. An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt according to claim 1, characterized in that, The hydrogen fluoride and ammonia feeding system (3) includes a control interlock system composed of an automatic control valve and a mass flow meter for controlling the feeding ratio of liquid hydrogen fluoride and ammonia; the control interlock loop composed of the ammonia automatic control valve (31) and the first mass flow meter (34) is used to control the feeding amount of ammonia, and the control interlock loop composed of the hydrogen fluoride automatic control valve (32) and the second mass flow meter (35) is used to control the feeding amount of liquid hydrogen fluoride.

7. An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt according to claim 6, characterized in that, The hydrogen fluoride and ammonia feeding system (3) further includes a liquid level transmitter (33). The liquid level transmitter (33) transmits the height of the electrolyte liquid level inside the electrolytic cell (1) to the DCS system, and combines with the control interlock system composed of the automatic control valve and the mass flow meter to implement automatic feeding.

8. An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt according to claim 3, characterized in that, The cathode gas system (4) is provided with a first condenser (41). The feed inlet of the first condenser (41) is communicated with the cathode gas outlet b (16), and the discharge outlet of the first condenser (41) is communicated with the falling film absorption section.

9. An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt according to claim 3, characterized in that, The anode gas system (5) is provided with a second condenser (51) and a catalytic cracking tower (52) which are communicated with each other. The feed inlet of the second condenser (51) is communicated with the anode gas outlet a (15), the discharge outlet of the second condenser (51) is communicated with the feed inlet of the catalytic cracking tower (52), and the discharge outlet of the catalytic cracking tower (52) is communicated with the purification and rectification section of the anode gas.

10. An electrolysis process system for preparing nitrogen trifluoride by electrolyzing ammonium hydrogen fluoride molten salt according to claim 9, characterized in that, The inside of the catalytic cracking tower (52) is filled with nickel foam packing.

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