Process for the preparation of electronic grade hydrogen chloride and hydrogen fluoride from fluorine-containing lithium salt synthesis off-gas

Abstract

This invention discloses a method for preparing electronic-grade hydrogen chloride and hydrogen fluoride from the tail gas of fluorinated lithium salt synthesis. The steps are as follows: Fluorinated lithium salt synthesis tail gas A is sequentially passed through a cryogenic reactor and a cryogenic phase separator for liquefaction and gas-liquid separation. The resulting liquid phase is pumped into a hydrogen chloride distillation column for separation. The liquid phase obtained from the top gas phase of the hydrogen chloride distillation column is condensed and then passed into a cryogenic phase separator for solid-liquid separation. The resulting liquid phase is electronic-grade hydrogen chloride B, and the solid phase, after vaporization, is industrial-grade phosphorus pentafluoride C. The liquid phase obtained from the bottom of the column is passed into a hydrogen fluoride distillation column for separation. The liquid phase obtained from the top gas phase of the hydrogen fluoride distillation column is condensed and then passed into electronic-grade hydrogen fluoride D. The liquid phase obtained from the bottom of the column is industrial-grade hydrogen fluoride E. The gas phases obtained from the cryogenic phase separator and the top of the condenser are combined to form non-condensable tail gas F. The method of this invention yields electronic-grade hydrogen chloride and hydrogen fluoride with high purity, avoiding the high energy consumption and equipment corrosion problems caused by complex high-temperature compression; it also solves the difficulty of separating hydrogen chloride and phosphorus pentafluoride.

Description

Technical Field

[0001] This invention belongs to the field of gas separation and purification technology, specifically relating to a method for preparing electronic-grade hydrogen chloride and electronic-grade hydrogen fluoride from tail gas of fluorinated lithium salt synthesis. Background Technology

[0002] Fluorinated lithium salt electrolytes are an important component of new energy lithium-ion batteries, possessing advantages such as low cost, high stability, and simple preparation. Common fluorinated lithium salt electrolytes include lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, and lithium difluorosulfonylimide. Lithium hexafluorophosphate, with its superior overall performance, is currently the most widely used commercial lithium salt and remains irreplaceable in the medium term. The mainstream method for preparing lithium hexafluorophosphate is the hydrogen fluoride solvent method. First, phosphorus pentachloride reacts with anhydrous hydrogen fluoride to generate phosphorus pentafluoride. Then, phosphorus pentafluoride reacts with lithium fluoride dissolved in anhydrous hydrogen fluoride to obtain lithium hexafluorophosphate. The reaction equation is: PCl5 + 5HF + LiF → LiPF6 + 5HCl. This shows that the production of 1 mole of lithium hexafluorophosphate produces 5 moles of hydrogen chloride as a byproduct. Furthermore, hydrogen fluoride is in excess, and a certain amount of unreacted phosphorus pentafluoride is also present. Therefore, the synthesis of lithium hexafluorophosphate generates a large amount of toxic and harmful exhaust gases, requiring harmless treatment and comprehensive waste utilization. The more mature technology for treating the tail gas from the synthesis of fluorinated lithium salts is to use water to absorb and produce hydrochloric acid and hydrofluoric acid. However, this generates a high level of waste, and the expensive hydrogen fluoride raw material cannot be utilized in a closed loop, resulting in a high overall cost for the waste and raw materials.

[0003] Dry separation of hydrogen chloride, hydrogen fluoride, and phosphorus pentafluoride from the tail gas of fluorinated lithium salt synthesis into high-value-added products is a better treatment method. However, the boiling points of hydrogen chloride (-84.1℃@1atm) and phosphorus pentafluoride (-84.6℃@1atm) are extremely difficult to separate. WO2005061381 discloses a technical route for separating phosphorus pentafluoride and hydrogen chloride, whose boiling points are very close, using pressurized distillation (30-60 bar). However, this method has high operating pressure and energy consumption, and it does not involve the separation of hydrogen fluoride. CN112206631 discloses a method for separating hydrogen chloride and hydrogen fluoride using condensation to prepare liquid hydrogen fluoride and industrial-grade hydrogen chloride gas. It also uses multi-stage alumina adsorption to purify the industrial-grade hydrogen chloride gas to the electronic grade. However, condensation alone cannot achieve complete separation of hydrogen fluoride and hydrogen chloride, and it also does not involve the separation of phosphorus pentafluoride. CN114180527 discloses a method for separating hydrogen fluoride and hydrogen chloride using compression condensation and single-tower continuous distillation. However, the compression energy consumption is high, and there are problems such as high-temperature corrosion of liquid hydrogen fluoride. Furthermore, it does not address the separation of phosphorus pentafluoride. CN114477114 discloses a method for separating hydrogen chloride, hydrogen fluoride, and phosphorus pentafluoride using compression condensation and dual-tower continuous distillation. However, the compression energy consumption and the distillation energy consumption for a high reflux ratio of hydrogen chloride / phosphorus pentafluoride are both high, and there are problems such as high-temperature corrosion of liquid hydrogen fluoride.

[0004] In summary, most of the dry recovery technologies for fluorinated lithium salt synthesis tail gas disclosed in current literature and patents use compression condensation and distillation separation methods, without addressing the efficient preparation of both electronic-grade hydrogen chloride and electronic-grade hydrogen fluoride. Furthermore, the compression and high-pressure distillation of hydrogen fluoride pose a significant risk of stress corrosion, requiring the use of special materials such as HAC and Monel, resulting in high equipment costs. In addition, the energy consumption for separating hydrogen chloride and phosphorus pentafluoride using distillation is also high. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing electronic-grade hydrogen chloride and hydrogen fluoride from the tail gas of fluorinated lithium salt synthesis.

[0006] The technical solution of this invention is summarized as follows:

[0007] A method for preparing electronic-grade hydrogen chloride and hydrogen fluoride from the tail gas of fluorinated lithium salt synthesis includes the following steps: Fluorinated lithium salt synthesis tail gas A is passed into a cryogenic reactor 1 for liquefaction; the resulting liquid and gas phases are separately passed into a cryogenic phase separator 2 for gas-liquid separation; the separated liquid phase is passed through a liquid phase pump 3 into the middle of a hydrogen chloride distillation column 4 for further separation; the gas phase at the top of the hydrogen chloride distillation column 4 is condensed by a first condenser 5; the resulting liquid phase is divided into two streams, one stream is returned to the top of the hydrogen chloride distillation column 4, and the other stream is introduced from the top of a cryogenic phase separator 6 for solid-liquid separation; the separated solid phase is discharged from the bottom of the cryogenic phase separator 6; after further vaporization, industrial-grade phosphorus pentafluoride C is obtained; the separated liquid phase is then... The liquid phase flowing out from the middle of the cryogenic phase separator 6 is electronic-grade hydrogen chloride B; the liquid phase flowing out from the bottom of the hydrogen chloride distillation column 4 is divided into two streams, one of which is circulated and evaporated through the first reboiler 7; the other stream is fed into the middle of the hydrogen fluoride distillation column 8 for separation; the gas phase at the top of the hydrogen fluoride distillation column 8 is condensed through the second condenser 9, and the resulting liquid phase is divided into two streams, one of which flows back to the top of the hydrogen fluoride distillation column 8, and the other stream flows out as electronic-grade hydrogen fluoride D; the liquid phase flowing out from the bottom of the hydrogen fluoride distillation column 8 is divided into two streams, one of which is circulated and evaporated through the second reboiler 10; the other stream flows out as industrial-grade hydrogen fluoride E; the non-condensable tail gas generated by the cryogenic phase separator 2, the first condenser 5, and the second condenser 9 is combined into one stream as tail gas F, which is washed with water and used to produce acid.

[0008] Preferably, the pressure of the tail gas A from the synthesis of fluorinated lithium salt is 0.1 to 0.3 MPaG, and the temperature is -30°C to -10°C.

[0009] Preferably, the temperatures of the cryogenic reactor 1 and the cryogenic phase separation tank 2 are the same, ranging from -90°C to -60°C.

[0010] Preferably, the liquid phase pump 3 is a diaphragm pump or a canned pump, and the pump outlet pressure is 0.3 to 0.7 MPaG.

[0011] Preferably, the pressure of the hydrogen chloride distillation column 4 is 0.3 to 0.7 MPaG, the top temperature is -58°C to -38°C, and the bottom temperature is 65°C to 90°C.

[0012] Preferably, the subcooling degree of the first condenser 5 is 5–10°C.

[0013] Preferably, the temperature of the freezing phase separation tank 6 is -110℃ to -95℃.

[0014] Preferably, the pressure of the hydrogen fluoride distillation column 8 is 0.15-0.3 MPaG, the top temperature is 48℃-65℃, and the bottom temperature is 50℃-70℃.

[0015] Preferably, the second condenser 9 has a subcooling degree of 5-10°C.

[0016] Preferably, the first and second reboilers are identical, and are either thermosiphon reboilers or kettle reboilers.

[0017] Advantages of this invention:

[0018] (1) The electronic-grade hydrogen chloride and electronic-grade hydrogen fluoride obtained by the method of the present invention have high purity.

[0019] (2) The method of the present invention is simple to operate and avoids the problems of using a complex, high-energy-consuming compressor for compression and the corrosion of the equipment by the high-temperature hydrogen fluoride gas after compression.

[0020] (3) It solves the long-standing difficulty of separating hydrogen chloride and phosphorus pentafluoride. The design of dual-tower continuous distillation and fractional condenser can simultaneously remove light and heavy components in hydrogen chloride and hydrogen fluoride. The impurities and product quality meet the requirements of electronic grade, satisfy the needs of semiconductor customers, and achieve the goal of obtaining electronic grade products from industrial tail gas through this method, thus achieving the effect of industrial production.

[0021] (4) It has the advantages of high safety, long equipment life, simple device, great operational flexibility, good economy and high product quality. Attached Figure Description

[0022] Figure 1 A flowchart illustrating a method for preparing electronic-grade hydrogen chloride and hydrogen fluoride from tail gas of fluorinated lithium salt synthesis.

[0023] In the diagram: 1 is a cryogenic reactor, 2 is a cryogenic phase separation tank, 3 is a liquid phase pump, 4 is a hydrogen chloride distillation column, 5 is the first condenser, 6 is a cryogenic phase separation tank, 7 is the first reboiler, 8 is a hydrogen fluoride distillation column, 9 is the second condenser, and 10 is the second reboiler. A is the tail gas from the synthesis of fluorinated lithium salts; B is electronic-grade hydrogen chloride; C is industrial-grade phosphorus pentafluoride; D is electronic-grade hydrogen fluoride; E is industrial-grade hydrogen fluoride; F is the tail gas. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but the present invention is not limited to these specific embodiments.

[0025] The tail gas from the synthesis of fluorinated lithium salts includes hydrogen chloride, hydrogen fluoride, phosphorus pentafluoride, low-boiling-point substances, and high-boiling-point substances; low-boiling-point substances are air components with a lower boiling point than hydrogen chloride, while high-boiling-point substances are moisture and heavy metal impurities with a higher boiling point than hydrogen fluoride.

[0026] The mass composition of the tail gas from the synthesis of fluorinated lithium salts is 57%-79.3% hydrogen chloride, 20%-40% hydrogen fluoride, 0.5%-2% phosphorus pentafluoride, 0.1%-0.5% low-boiling matter, and 0.1%-0.5% high-boiling matter.

[0027] The embodiments of the present invention take the following fluorine-containing lithium salt synthesis tail gas as an example:

[0028] The tail gas from the synthesis of fluorinated lithium salts contains 68% hydrogen chloride, 30% hydrogen fluoride, 1% phosphorus pentafluoride, 0.5% low-boiling-point substances, and 0.5% high-boiling-point substances.

[0029] Example 1

[0030] A method for preparing electronic-grade hydrogen chloride and hydrogen fluoride from tail gas of fluorinated lithium salt synthesis is described in [link to method]. Figure 1 The process includes the following steps: The tail gas A from the synthesis of fluorinated lithium salts is passed into a cryogenic reactor 1 for liquefaction. The resulting liquid and gas phases are then passed into a cryogenic phase separator 2 for gas-liquid separation. The separated liquid phase is then passed through a liquid phase pump 3 into the middle section of a hydrogen chloride distillation column 4 for further separation. The gas phase at the top of the hydrogen chloride distillation column 4 is condensed by a first condenser 5. The resulting liquid phase is divided into two streams: one stream flows back to the top of the hydrogen chloride distillation column 4, and the other stream is introduced from the top of a cryogenic phase separator 6 for solid-liquid separation. The separated solid phase is discharged from the bottom of the cryogenic phase separator 6. After further vaporization, industrial-grade phosphorus pentafluoride C is obtained. The separated liquid phase flows out from the middle section of the cryogenic phase separator 6. The liquid phase flowing out from the bottom of the hydrogen chloride distillation column 4 is divided into two streams. One stream is circulated and evaporated in the first reboiler 7, and the other stream is fed into the middle of the hydrogen fluoride distillation column 8 for separation. The gas phase at the top of the hydrogen fluoride distillation column 8 is condensed by the second condenser 9, and the resulting liquid phase is divided into two streams. One stream flows back to the top of the hydrogen fluoride distillation column 8, and the other stream flows out as electronic-grade hydrogen fluoride D. The liquid phase flowing out from the bottom of the hydrogen fluoride distillation column 8 is divided into two streams. One stream is circulated and evaporated in the second reboiler 10, and the other stream flows out as industrial-grade hydrogen fluoride E. The non-condensable tail gas generated by the cryogenic phase separator 2, the first condenser 5, and the second condenser 9 is combined into one stream as tail gas F, which is washed with water and used to produce acid.

[0031] The pressure of the tail gas A from the synthesis of fluorinated lithium salts is 0.1–0.3 MPaG, and the temperature is -30℃ to -10℃.

[0032] The cryogenic cooler 1 and the cryogenic phase separation tank 2 have the same temperature, which is -90℃ to -60℃ (used to liquefy hydrogen chloride, hydrogen fluoride and phosphorus pentafluoride in the exhaust gas into liquid).

[0033] The refrigerant used in cryogenic reactor 1 and cryogenic phase separation tank 2 is the same: ethanol.

[0034] Liquid phase pump 3 is a diaphragm pump with an outlet pressure of 0.3–0.7 MPaG;

[0035] The pressure of hydrogen chloride distillation column 4 is 0.5 MPaG, the top temperature is -48℃, and the bottom temperature is 80℃.

[0036] The first condenser 5 has a subcooling degree of 8°C (the refrigerant used for subcooling is ethanol);

[0037] The temperature of the freezing phase separation tank 6 is -100℃ (the refrigerant used for freezing is ethanol);

[0038] The pressure of the hydrogen fluoride distillation column 8 is 0.22 MPaG, the top temperature is 55℃, and the bottom temperature is 60℃.

[0039] The second condenser 9 has a subcooling degree of 8°C (the refrigerant used for subcooling is circulating water);

[0040] The first reboiler and the second reboiler are the same, which is a thermosiphon reboiler (the heat medium used for heating the reboiler is 0.2MPaG low-pressure steam condensate).

[0041] The yield of electronic-grade hydrogen chloride was 96%, and the yield of electronic-grade hydrogen fluoride was 95%.

[0042] Table 1

[0043] project index Actual measurement project index Actual measurement Hydrogen chloride (vol%) ≥99.999 99.9996 Hydrogen fluoride (vol%) ≥99.999 99.9995 Oxygen + Argon (ppmv) ＜1.0 0.5 Oxygen + Argon (ppmv) ≤2 1.0 Nitrogen (ppmv) ＜2.0 1 Nitrogen (ppmv) ≤4 2 Carbon dioxide (ppmv) ＜2.0 1 Carbon dioxide (ppmv) ≤1 0.5 Carbon monoxide (ppmv) ＜1.0 0.5 Carbon monoxide (ppmv) ≤1 0.5 Moisture content (ppmv) ＜1.0 0.5 Moisture content (ppmv) ≤1 0.5 Hydrocarbons (ppmv) ＜1.0 0.5 Sulfur dioxide (ppmv) ≤1 0.5 Iron (mg / L) ≤0.5 0.2 Silicon (mg / L) ≤0.5 0.2 Other metallic elements (mg / L) ≤0.1 0.1 Other metallic elements (mg / L) ≤0.3 0.2

[0044] The specifications for electronic-grade hydrogen chloride in Tables 1, 2, and 3 are based on the People's Republic of China National Standard GB / T 14602-2014, "Gasical Hydrogen Chloride for Electronic Industry".

[0045] The specifications for electronic-grade hydrogen fluoride in Tables 1, 2, and 3 are based on the China Industrial Gases Industry Association Group Standard T / CCGA30006-2021, Electronic-grade Hydrogen Fluoride.

[0046] Example 2

[0047] A method for preparing electronic-grade hydrogen chloride and hydrogen fluoride from the tail gas of fluorinated lithium salt synthesis includes the following steps: Fluorinated lithium salt synthesis tail gas A is passed into a cryogenic reactor 1 for liquefaction; the resulting liquid and gas phases are separately passed into a cryogenic phase separator 2 for gas-liquid separation; the separated liquid phase is passed through a liquid phase pump 3 into the middle of a hydrogen chloride distillation column 4 for further separation; the gas phase at the top of the hydrogen chloride distillation column 4 is condensed by a first condenser 5; the resulting liquid phase is divided into two streams, one stream is returned to the top of the hydrogen chloride distillation column 4, and the other stream is introduced from the top of a cryogenic phase separator 6 for solid-liquid separation; the separated solid phase is discharged from the bottom of the cryogenic phase separator 6; after further vaporization, industrial-grade phosphorus pentafluoride C is obtained; the separated liquid phase is then... The liquid phase flowing out from the middle of the cryogenic phase separator 6 is electronic-grade hydrogen chloride B; the liquid phase flowing out from the bottom of the hydrogen chloride distillation column 4 is divided into two streams, one of which is circulated and evaporated through the first reboiler 7; the other stream is fed into the middle of the hydrogen fluoride distillation column 8 for separation; the gas phase at the top of the hydrogen fluoride distillation column 8 is condensed through the second condenser 9, and the resulting liquid phase is divided into two streams, one of which flows back to the top of the hydrogen fluoride distillation column 8, and the other stream flows out as electronic-grade hydrogen fluoride D; the liquid phase flowing out from the bottom of the hydrogen fluoride distillation column 8 is divided into two streams, one of which is circulated and evaporated through the second reboiler 10; the other stream flows out as industrial-grade hydrogen fluoride E; the non-condensable tail gas generated by the cryogenic phase separator 2, the first condenser 5, and the second condenser 9 is combined into one stream as tail gas F, which is washed with water and used to produce acid.

[0048] The pressure of the tail gas A from the synthesis of fluorinated lithium salts is 0.1–0.3 MPaG, and the temperature is -30℃ to -10℃.

[0049] The cryogenic reactor 1 and the cryogenic phase separation tank 2 have the same temperature, which is -90℃ to -60℃;

[0050] The refrigerant used in cryogenic reactor 1 and cryogenic phase separation tank 2 is the same, which is Freon (liquid nitrogen can also be selected);

[0051] Liquid phase pump 3 is a diaphragm pump with an outlet pressure of 0.3–0.7 MPaG;

[0052] The pressure of hydrogen chloride distillation column 4 is 0.3 MPaG, the top temperature is -58℃, and the bottom temperature is 65℃.

[0053] The first condenser 5 has a subcooling degree of 5°C (the refrigerant used for subcooling is Freon, or liquid nitrogen can also be selected);

[0054] The temperature of the freezing phase separation tank 6 is -110℃ (the refrigerant used for freezing is Freon, or liquid nitrogen can also be selected);

[0055] The pressure of the hydrogen fluoride distillation column 8 is 0.15 MPaG, the top temperature is 48℃, and the bottom temperature is 50℃.

[0056] The second condenser 9 has a subcooling of 5°C (the refrigerant used for subcooling is 7°C low-temperature water);

[0057] The first reboiler and the second reboiler are the same, and are both kettle-type reboilers (the heat medium used for heating the reboiler is 85°C hot water).

[0058] The yield of electronic-grade hydrogen chloride was 94%, and the yield of electronic-grade hydrogen fluoride was 93%.

[0059] The compositional analysis results of electronic-grade hydrogen chloride and hydrogen fluoride products are shown in Table 2.

[0060] Table 2

[0061] project index Actual measurement project index Actual measurement Hydrogen chloride (vol%) ≥99.999 99.9998 Hydrogen fluoride (vol%) ≥99.999 99.9997 Oxygen + Argon (ppmv) ＜1.0 0.2 Oxygen + Argon (ppmv) ≤2 0.5 Nitrogen (ppmv) ＜2.0 0.5 Nitrogen (ppmv) ≤4 1.5 Carbon dioxide (ppmv) ＜2.0 0.5 Carbon dioxide (ppmv) ≤1 0.2 Carbon monoxide (ppmv) ＜1.0 0.2 Carbon monoxide (ppmv) ≤1 0.2 Moisture content (ppmv) ＜1.0 0.2 Moisture content (ppmv) ≤1 0.2 Hydrocarbons (ppmv) ＜1.0 0.2 Sulfur dioxide (ppmv) ≤1 0.2 Iron (mg / L) ≤0.5 0.1 Silicon (mg / L) ≤0.5 0.1 Other metallic elements (mg / L) ≤0.1 0.1 Other metallic elements (mg / L) ≤0.3 0.1

[0062] Example 3

[0063] The method for preparing electronic-grade hydrogen chloride and hydrogen fluoride from the tail gas of fluorinated lithium salt synthesis includes the following steps: Fluorinated lithium salt synthesis tail gas A is passed into a cryogenic reactor 1 for liquefaction. The resulting liquid and gas phases are separately passed into a cryogenic phase separator 2 for gas-liquid separation. The separated liquid phase is then passed through a liquid phase pump 3 into the middle of a hydrogen chloride distillation column 4 for further separation. The gas phase at the top of the hydrogen chloride distillation column 4 is condensed by a first condenser 5. The resulting liquid phase is divided into two streams: one stream is returned to the top of the hydrogen chloride distillation column 4, and the other stream is introduced from the top of a cryogenic phase separator 6 for solid-liquid separation. The separated solid phase is discharged from the bottom of the cryogenic phase separator 6. After further vaporization, industrial-grade phosphorus pentafluoride C is obtained. The separated liquid phase is then discharged from the bottom of the cryogenic phase separator 6. The liquid phase flowing out from the middle of the cryogenic phase separation tank 6 is electronic-grade hydrogen chloride B; the liquid phase flowing out from the bottom of the hydrogen chloride distillation column 4 is divided into two streams, one of which is circulated and evaporated through the first reboiler 7; the other stream is fed into the middle of the hydrogen fluoride distillation column 8 for separation; the gas phase at the top of the hydrogen fluoride distillation column 8 is condensed through the second condenser 9, and the resulting liquid phase is divided into two streams, one of which flows back to the top of the hydrogen fluoride distillation column 8, and the other stream flows out as electronic-grade hydrogen fluoride D; the liquid phase flowing out from the bottom of the hydrogen fluoride distillation column 8 is divided into two streams, one of which is circulated and evaporated through the second reboiler 10; the other stream flows out as industrial-grade hydrogen fluoride E; the non-condensable tail gas generated by the cryogenic phase separation tank 2, the first condenser 5, and the second condenser 9 is combined into one stream as tail gas F, which is washed with water and used to produce acid.

[0064] The pressure of the tail gas A from the synthesis of fluorinated lithium salts is 0.1–0.3 MPaG, and the temperature is -30℃ to -10℃.

[0065] The cryogenic reactor 1 and the cryogenic phase separation tank 2 have the same temperature, which is -90℃ to -60℃;

[0066] The refrigerant used in cryogenic reactor 1 and cryogenic phase separation tank 2 is the same, namely Glacier refrigerant;

[0067] Liquid phase pump 3 is a canned motor pump with an outlet pressure of 0.3–0.7 MPaG;

[0068] The pressure of hydrogen chloride distillation column 4 is 0.7 MPaG, the top temperature is -38℃, and the bottom temperature is 90℃.

[0069] The first condenser 5 has a subcooling degree of 10℃ (the refrigerant used for subcooling is Glacier refrigerant);

[0070] The temperature of the freezing phase separation tank 6 is -95℃ (the refrigerant used for freezing is Glacier).

[0071] The pressure of the hydrogen fluoride distillation column 8 is 0.3 MPaG, the top temperature is 65℃, and the bottom temperature is 70℃.

[0072] The second condenser 9 has a subcooling degree of 10℃ (the refrigerant used for subcooling is circulating water);

[0073] The first and second reboilers are identical, being thermosiphon-type reboilers; (the heat medium used for heating the reboilers is 0.2 MPaG low-pressure steam).

[0074] The yield of electronic-grade hydrogen chloride was 98%, and the yield of electronic-grade hydrogen fluoride was 97%.

[0075] The compositional analysis results of electronic-grade hydrogen chloride and electronic-grade hydrogen fluoride products are shown in Table 3.

[0076] Table 3

[0077] project index Actual measurement project index Actual measurement Hydrogen chloride (vol%) ≥99.999 99.9993 Hydrogen fluoride (vol%) ≥99.999 99.9992 Oxygen + Argon (ppmv) ＜1.0 0.8 Oxygen + Argon (ppmv) ≤2 1.5 Nitrogen (ppmv) ＜2.0 1.5 Nitrogen (ppmv) ≤4 3 Carbon dioxide (ppmv) ＜2.0 1.5 Carbon dioxide (ppmv) ≤1 0.8 Carbon monoxide (ppmv) ＜1.0 0.8 Carbon monoxide (ppmv) ≤1 0.8 Moisture content (ppmv) ＜1.0 0.8 Moisture content (ppmv) ≤1 0.8 Hydrocarbons (ppm) ＜1.0 0.8 Sulfur dioxide (ppmv) ≤1 0.8 Iron (mg / L) ≤0.5 0.4 Silicon (mg / L) ≤0.5 0.4 Other metallic elements (mg / L) ≤0.1 0.1 Other metallic elements (mg / L) ≤0.3 0.3

Claims

1. Process for the production of electronic grade hydrogen chloride and hydrogen fluoride from a synthesis off-gas containing fluoro-lithium salts, characterized in that The method comprises the following steps: the fluorine-containing lithium salt synthesis tail gas A is introduced into a deep cooling device (1) for liquefaction treatment, the obtained liquid phase and gas phase are introduced into a deep cooling phase separation tank (2) for gas-liquid separation, the obtained liquid phase is introduced into a middle part of a hydrogen chloride rectification tower (4) through a liquid phase pump (3) for separation; the gas phase at the top of the hydrogen chloride rectification tower (4) is condensed through a first condenser (5), the obtained liquid phase is divided into two parts, one part is returned to the top of the hydrogen chloride rectification tower (4), and the other part is introduced into a top part of a frozen phase separation tank (6) and is subjected to solid-liquid separation, the obtained solid phase is discharged from the bottom of the frozen phase separation tank (6); after vaporization, industrial-grade phosphorus pentafluoride C is obtained; the obtained liquid phase is discharged from the middle part of the frozen phase separation tank (6) and is electronic-grade hydrogen chloride B; the liquid phase discharged from the bottom of the hydrogen chloride rectification tower (4) is divided into two parts, one part is circulated and evaporated through a first reboiler (7); the other part is introduced into a middle part of a hydrogen fluoride rectification tower (8) for separation; the gas phase at the top of the hydrogen fluoride rectification tower (8) is condensed through a second condenser (9), the obtained liquid phase is divided into two parts, one part is returned to the top of the hydrogen fluoride rectification tower (8), and the other part is discharged as electronic-grade hydrogen fluoride D; the liquid phase discharged from the bottom of the hydrogen fluoride rectification tower (8) is divided into two parts, one part is circulated and evaporated through a second reboiler (10); the other part is discharged as industrial-grade hydrogen fluoride E; the incondensable tail gas generated by the deep cooling phase separation tank (2), the first condenser (5) and the second condenser (9) is combined into one part, is washed with water, and is used for acid production.

2. The method of claim 1, wherein The pressure of the fluorine-containing lithium salt synthesis tail gas A is 0.1-0.3 MPaG, and the temperature is-30-10 ℃.

3. The method of claim 1, wherein The temperature of the deep cooling device (1) and the deep cooling phase separation tank (2) is consistent, and is-90-60 ℃.

4. The method of claim 1, wherein The liquid phase pump (3) is a diaphragm pump or a canned motor pump, and the pump outlet pressure is 0.3-0.7 MPaG.

5. The method of claim 1 wherein The pressure of the hydrogen chloride rectification tower (4) is 0.3-0.7 MPaG, the tower top temperature is-58-38 ℃, and the tower bottom temperature is 65-90 ℃.

6. The method of claim 1, wherein The supercooling degree of the first condenser (5) is 5-10 ℃.

7. The method of claim 1 wherein The temperature of the frozen phase separation tank (6) is-110-95 ℃.

8. The method of claim 1 wherein The pressure of the hydrogen fluoride rectification tower (8) is 0.15-0.3 MPaG, the tower top temperature is 48-65 ℃, and the tower bottom temperature is 50-70 ℃.

9. The method of claim 1 wherein The supercooling degree of the second condenser (9) is 5-10 ℃.

10. The method of claim 1, wherein The first reboiler and the second reboiler are the same, and are thermosyphon reboilers or kettle-type reboilers.

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