Device and method for recovering hydrogen fluoride gas

Abstract

The invention relates to a method for recovering hydrogen fluoride gas, which is used for recovering hydrogen fluoride gas in NF3 produced by an electrolytic method, and the method comprises the following steps: mixed gas discharged from a cathode of an electrolytic bath flows into a gas buffer tank; ammonium hydrogen fluoride in the mixed gas is condensed in the gas buffer tank, the residual hydrogen and hydrogen fluoride flow into the micro-channel unit, the hydrogen fluoride is condensed in the micro-channel unit, the condensed hydrogen fluoride flows back to the gas buffer tank, and the uncondensed hydrogen fluoride and hydrogen flow into the falling film absorption unit; the hydrogen fluoride is absorbed by an absorber in the falling film absorption unit, the hydrogen fluoride is recovered as a hydrofluoric acid solution, and the residual hydrogen and the residual hydrogen fluoride flow into a three-waste treatment pond; and residual hydrogen fluoride in the three-waste treatment tank is completely absorbed. According to the invention, the single-tube parallel micro-channel condenser is adopted as a condensation unit, and the tube diameter is as small as 10-1000 microns, so that the heat exchange area is greatly increased, the hydrogen fluoride gas can be more effectively condensed and recovered, and the recovery efficiency is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of cathode gas recovery in NF3 produced by electrolysis, and in particular to a device and method for recovering hydrogen fluoride gas. Background Art

[0002] With the rapid development of the electronics industry, nitrogen trifluoride (NF3 for short) gas has been widely used in the electronics industry. In the prior art, the main method for preparing NF3 gas is molten salt electrolysis, the electrolyte is a molten solution of HF and NH4HF2, the electrolysis temperature is 70-130°C, and under working conditions, gas is generated at the cathode and anode, an oxidation reaction occurs at the anode to generate NF3, and a reduction reaction occurs at the cathode to generate H2. At a temperature of 70-130°C, the hydrogen generated at the cathode will carry part of the hydrogen fluoride, resulting in a waste of hydrogen fluoride.

[0003] Chinese patent CN111085086A provides a system and method for recovering HF in the tail gas of an electrolytic system for preparing NF3 by electrolysis. The system includes an absorption tower, an absorption tower liquid storage tank, a cooling tower, a cooling tower liquid storage tank, a falling film absorber, a circulating acid tank and a circulating pump. The absorbent in the absorption tower absorbs HF and then undergoes low-temperature cooling, and finally is washed with water to meet the discharge standards, and the by-products can be reused accordingly. In this patent, HF can only be recovered to form hydrofluoric acid for sale, which will reduce the value of hydrogen fluoride by nearly half, resulting in a great waste of resources and increasing the production cost of NF3.

[0004] Chinese patent CN114534453B, the present invention provides a process for recovering HF in cathode tail gas discharged from a nitrogen trifluoride electrolyzer, using a KF solution spray absorption tower to collect all the HF generated by the cathode tail gas of the electrolyzer, achieving efficient collection of the generated HF, evaporating and removing water from the obtained KHF2, and then heating to obtain HF. In this patent, although the HF in the cathode tail gas is recovered with a purity of 98.5%, the recovery process is relatively complicated, wherein the HF in the cathode tail gas is absorbed by the KF solution to form KHF2, and then the KHF2 is evaporated and pyrolyzed to form HF, which consumes a lot of energy in the process and increases the cost of recovering HF. Summary of the invention

[0005] In order to overcome the technical problems of complicated HF recovery process, high energy consumption and high cost in the prior art, the present invention aims to provide a device and method for recovering part of HF entrained in cathode gas by using a microchannel condenser and falling film absorption process.

[0006] To achieve the purpose of the present invention, the specific technical solutions provided by the present invention are as follows:

[0007] A device for recovering hydrogen fluoride gas, comprising a gas buffer tank, a microchannel unit, a falling film absorption unit and a three-waste treatment pool connected in sequence through pipelines;

[0008] The gas buffer tank is provided with a gas feed port on the side; a gas discharge port on the top; and a liquid discharge port on the bottom. The gas feed port of the gas tank flushing tank is connected to the exhaust port on the top of the electrolytic cell through a pipeline, and the liquid discharge port of the gas tank flushing tank is connected to the liquid replenishment port on the side of the electrolytic cell through a pipeline.

[0009] The microchannel unit is provided with a gas inlet and a gas outlet, the gas inlet of the microchannel unit is connected to the gas outlet of the gas buffer tank through a pipeline, and the gas outlet of the microchannel unit is connected to the falling film absorption unit through a pipeline; the microchannel unit is also provided with a refrigerant inlet and a refrigerant outlet, and the refrigerant inlet and the refrigerant outlet of the microchannel unit are connected to the ethylene glycol refrigerant tank through a circulation pipeline.

[0010] Preferably, the microchannel unit is a single-tube parallel microchannel condenser, the diameter of the single tube is 10-1000 μm, the shell diameter is 50 mm, and a centrifugal pump or a shielded pump is installed on the circulation pipeline between the microchannel unit and the ethylene glycol refrigerant tank.

[0011] The single-tube parallel microchannel condenser of the present application has a tube diameter of 10-1000 μm and a heat exchange area much larger than that of a conventional condenser, which can effectively overcome the shortcomings of a conventional condenser and improve the condensation recovery efficiency of hydrogen fluoride.

[0012] Preferably, the falling film absorption unit comprises a primary absorber and a secondary absorber which are connected in sequence by pipelines, wherein the primary absorber is installed in a primary circulating water tank, and the primary absorber is connected and installed with a primary acid circulating pump; the secondary absorber is installed in a secondary circulating water tank, and the secondary absorber is connected and installed with a secondary acid circulating pump, and the primary acid circulating pump and the secondary acid circulating pump are centrifugal pumps or shielded pumps.

[0013] Preferably, the connecting pipes sequentially connecting the gas tank flushing tank, the microchannel unit, the falling film absorption unit and the three-waste treatment tank are made of silicon carbide or monel; the connecting pipes between the gas tank flushing tank and the electrolytic cell are made of silicon carbide or monel; the circulating pipeline between the microchannel unit and the ethylene glycol refrigerant tank is made of 316L stainless steel, and a radar level meter is installed in the gas buffer tank.

[0014] Preferably, the gas feed port of the gas tank flushing tank is connected to at least one exhaust port on the top of the electrolytic cell, so as to simultaneously recover the HF gas discharged from one or more electrolytic cells.

[0015] The present invention also provides a method for recovering hydrogen fluoride gas, which is carried out by a device for recovering hydrogen fluoride gas. The method is used for recovering hydrogen fluoride gas in the production of NF3 by electrolysis, and specifically comprises the following steps:

[0016] S1, the temperature in the electrolytic cell is 70-130°C, the pressure in the electrolytic cell is less than 0.05MPa, hydrogen is generated by electrolysis at the cathode, and part of the electrolyte ammonium bifluoride and hydrogen fluoride are entrained when the hydrogen is discharged, and the gas discharged from the cathode of the electrolytic cell flows into the gas buffer tank at a pressure of less than 0.05MPa;

[0017] When the electrolyzer is operating normally, hydrogen is produced at the cathode, and some ammonium bifluoride and hydrogen fluoride are entrained in the hydrogen. The formed mixed gas flows to the gas buffer tank under the action of positive pressure.

[0018] S2. The internal temperature of the gas buffer tank is 40-60°C. The ammonium bifluoride in the gas discharged from the cathode of the electrolyzer condenses in the gas buffer tank. The remaining hydrogen and hydrogen fluoride flow into the microchannel unit. The hydrogen fluoride is condensed in the microchannel unit. The condensed hydrogen fluoride flows back to the gas buffer tank. The uncondensed hydrogen fluoride and hydrogen flow into the falling film absorption unit.

[0019] The condensation point of ammonium bifluoride is 124°C. The ammonium bifluoride entrained in the hydrogen will condense in the gas buffer tank. One of the purposes of this buffer tank is to prevent the ammonium bifluoride from condensing and blocking the microchannel pipeline in the subsequent process, thus affecting the subsequent process.

[0020] The remaining hydrogen and hydrogen fluoride flow to the microchannel unit under pressure, and the hydrogen fluoride in the hydrogen condenses at low temperature and flows back into the gas buffer tank. Most of the hydrogen fluoride is condensed and recovered in this step.

[0021] S3, in the falling film absorption unit, hydrogen fluoride is absorbed by a two-stage absorber, and the hydrogen fluoride is recovered as a hydrofluoric acid solution, and the remaining hydrogen and residual hydrogen fluoride flow into the three-waste treatment pool;

[0022] Although most of the hydrogen fluoride is condensed and recovered in the microchannel unit, some hydrogen fluoride is not condensed and recovered. The hydrogen fluoride that is not condensed and recovered can be recovered through the falling film absorption unit. Since hydrogen fluoride and water can be miscible in any proportion, the hydrogen fluoride can be recovered as hydrofluoric acid of a certain concentration in the falling film absorption unit.

[0023] S4. In the three-waste treatment pool, hydrogen and residual hydrogen fluoride are absorbed and treated, residual hydrogen fluoride is completely absorbed, and the treated hydrogen is discharged;

[0024] In order to prevent a small amount of unrecovered hydrogen fluoride from being discharged into the atmosphere, the residual hydrogen fluoride is absorbed by Ca(OH)2 / KOH, and the hydrogen that meets the emission requirements is discharged into the atmosphere.

[0025] Preferably, in step S2, when the liquid level in the gas buffer tank reaches 2 / 3, the ammonium bifluoride and hydrogen fluoride in the gas buffer tank are transported into the electrolytic cell for reuse by a pump.

[0026] Preferably, in step S2, hydrogen fluoride is condensed in the microchannel unit, the condensation medium is ethylene glycol, the refrigerant inlet temperature is -30±1°C, the refrigerant outlet temperature is -20±1°C, and the ethylene glycol refrigerant flow rate is 0.001-0.005m3 / h.

[0027] Preferably, in step S3, hydrogen fluoride is absorbed by a two-stage absorber to form a hydrofluoric acid solution, and the operating conditions of the falling film absorption unit are set such that the outlet pressure of the primary acid circulation pump is greater than 0.1 MPa, and the outlet flow rate of the primary acid circulation pump is 30-40 m 3 / h, the circulating water temperature of the primary absorber is 20-30℃, and the circulating water flow rate of the primary absorber is 20m 3 / h, the outlet pressure of the secondary acid circulation pump is greater than 0.1MPa, and the outlet flow rate of the secondary acid circulation pump is 30-40m 3 / h, the circulating water temperature of the secondary absorber is 20-30℃, and the circulating water flow rate of the secondary absorber is 20m 3 / h.

[0028] Preferably, in step S4, residual hydrogen fluoride is absorbed and treated in a waste treatment tank using a mixed solution of Ca(OH)2 and KOH.

[0029] The device and method for recovering hydrogen fluoride gas of the present invention have the following beneficial effects:

[0030] 1. By using a single-tube parallel microchannel condenser as the condensing unit, the tube diameter is as small as 10-1000μm, which greatly increases the heat exchange area. Compared with the traditional condenser, it can more effectively condense and recover hydrogen fluoride gas, significantly improving the recovery efficiency. In addition, the centrifugal pump or shielded pump installed on the circulation pipeline between the microchannel unit and the glycol refrigerant tank ensures the stable circulation of the refrigerant and further improves the condensation effect.

[0031] 2. The recovery device and method designed in the present invention effectively avoid the condensation and clogging problem of ammonium bifluoride in the subsequent process through the setting of the gas buffer tank, and at the same time realize the preliminary separation of hydrogen fluoride; the two-stage absorption design of the falling film absorption unit ensures the efficient absorption and conversion of hydrogen fluoride into hydrofluoric acid, further improving the resource utilization rate.

[0032] 3. In the waste treatment pool, a mixed solution of Ca(OH)2 and KOH is used to absorb the residual hydrogen fluoride, ensuring that all hydrogen fluoride is effectively absorbed and avoiding pollution to the environment.

[0033] 4. By connecting multiple electrolytic cells with a gas buffer tank, the HF gas released from multiple electrolytic cells can be recovered at the same time; by installing a radar level meter in the gas buffer tank, the liquid level in the tank can be monitored in real time to ensure that ammonium bifluoride and hydrogen fluoride are transported back to the electrolytic cell for reuse in time, avoiding waste of resources and improving the automation and intelligence level of the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic structural diagram of a hydrogen fluoride gas recovery device of the present invention;

[0035] Explanation of the markings in the figure: 1. Gas buffer tank; 2. Microchannel unit; 3. Falling film absorption unit; 4. Waste treatment pool; 5. Ethylene glycol refrigerant tank; 6. Electrolyzer. DETAILED DESCRIPTION

[0036] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0037] Device Example 1

[0038] like Figure 1 As shown, a hydrogen fluoride gas recovery device of the present invention comprises a gas buffer tank 1, a microchannel unit 2, a falling film absorption unit 3 and a three-waste treatment pool 4 which are sequentially connected by pipelines.

[0039] Among them, a gas feed port is arranged on the side of the gas buffer tank 1, and the gas feed port is connected to the exhaust port on the top of the electrolytic cell 6 through a pipeline; a liquid discharge port is arranged at the bottom of the gas buffer tank 1, and the liquid discharge port is connected to the liquid replenishing port on the side of the electrolytic cell 6 through a pipeline, and a centrifugal pump or a shielded pump is arranged on the connecting pipeline. A radar level meter is installed in the gas buffer tank 1. When the liquid level in the gas buffer tank 1 reaches 2 / 3, the liquid in the gas buffer tank 1 is transported into the electrolytic cell 6 for reuse through the pump; a gas discharge port is arranged on the top of the gas buffer tank 1, and the gas discharge port is connected to the gas inlet of the microchannel unit 2 through a pipeline.

[0040] The microchannel unit 2 is also provided with a refrigerant inlet and a refrigerant outlet. The refrigerant inlet and the refrigerant outlet of the microchannel unit 2 are connected to the ethylene glycol refrigerant tank 5 through a circulation pipeline. The circulation pump on the circulation pipeline provides power for the circulation of the ethylene glycol refrigerant. Among them, the microchannel unit 2 is a single-tube parallel microchannel condenser with a single tube diameter of 10-1000μm and a shell diameter of 50mm. The microchannel unit 2 is also provided with a gas outlet, which is connected to the falling film absorption unit 3 through a pipeline.

[0041] The falling film absorption unit 3 includes a primary absorber and a secondary absorber which are connected in sequence by pipelines. The primary absorber is installed in a primary circulating water tank, and is connected to a primary acid circulating pump; the secondary absorber is installed in a secondary circulating water tank, and is connected to a secondary acid circulating pump. The primary acid circulating pump and the secondary acid circulating pump adopt centrifugal pumps or shielded pumps; the gas outlet of the microchannel unit 2 is connected to the air inlet of the primary absorber through a pipeline, the air outlet of the primary absorber is connected to the air inlet of the secondary absorber through a pipeline, and the air outlet of the secondary absorber is connected to the three waste treatment tank 4 through a pipeline.

[0042] Among the above-mentioned connecting pipes, the connecting pipes of the gas tank flushing tank, microchannel unit 2, falling film absorption unit 3 and three-waste treatment tank 4 connected in sequence are made of silicon carbide or monel; the connecting pipe between the gas tank flushing tank and the electrolytic cell 6 is made of silicon carbide or monel; the material of the circulation pipeline between the microchannel unit 2 and the ethylene glycol refrigerant tank 5 is 316L stainless steel.

[0043] Device Example 2

[0044] On the basis of Example 1, the gas feed port of the gas tank flushing tank can be connected to the exhaust port on the top of multiple electrolytic cells 6, and the hydrogen fluoride gas discharged from multiple electrolytic cells 6 can be recovered at the same time.

[0045] Method Example 1

[0046] A method for recovering hydrogen fluoride gas is carried out using the device for recovering hydrogen fluoride gas of device embodiment 1. This method is used for recovering hydrogen fluoride gas in the production of NF3 by electrolysis, and specifically comprises the following steps:

[0047] S1. When the electrolytic cell 6 is operating normally, the temperature in the electrolytic cell 6 is 100°C, the pressure in the electrolytic cell 6 is less than 0.05MPa, and hydrogen is generated by electrolysis at the cathode. When the hydrogen is discharged, part of the electrolyte ammonium bifluoride and hydrogen fluoride are entrained. The hydrogen discharged from the cathode of the electrolytic cell 6 flows into the gas buffer tank 1 at a pressure less than 0.05MPa.

[0048] S2, the condensation point of ammonium bifluoride is 124°C, the internal temperature of the gas buffer tank 1 is 50°C, and the ammonium bifluoride in the gas discharged from the cathode of the electrolytic cell 6 condenses in the gas buffer tank 1;

[0049] The ammonium bifluoride entrained in the hydrogen will condense in the gas buffer tank 1. One of the purposes of this buffer tank is to prevent the ammonium bifluoride from condensing and blocking the microchannel pipeline in the subsequent process, thereby affecting the subsequent process.

[0050] The remaining hydrogen and hydrogen fluoride flow to the microchannel unit 2 under pressure. The hydrogen fluoride in the hydrogen condenses at low temperature and flows back into the gas buffer tank 1. The hydrogen fluoride is condensed in the microchannel unit 2. The condensation medium is ethylene glycol. The refrigerant inlet temperature is -30±1℃, the refrigerant outlet temperature is -20±1℃, and the ethylene glycol refrigerant flow rate is 0.003m 3 / h;

[0051] The condensed hydrogen fluoride flows back to the gas buffer tank 1, and most of the hydrogen fluoride is condensed and recovered in this step. When the liquid level in the gas buffer tank 1 reaches 2 / 3, the ammonium bifluoride and hydrogen fluoride in the gas buffer tank 1 are transported into the electrolytic cell 6 for reuse by a pump; the uncondensed hydrogen fluoride and hydrogen flow into the falling film absorption unit 3.

[0052] S3. Although most of the hydrogen fluoride is condensed and recovered in the microchannel unit 2, some hydrogen fluoride is not condensed and recovered. The hydrogen fluoride that is not condensed and recovered can be recovered through the falling film absorption unit 3. In the falling film absorption unit 3, the hydrogen fluoride is absorbed by a two-stage absorber to form a hydrofluoric acid solution, and the hydrogen fluoride is recovered as a hydrofluoric acid solution. Because hydrogen fluoride and water can be miscible in any proportion, the hydrogen fluoride is recovered as a certain concentration of hydrofluoric acid in the falling film absorption unit 3 until the HF mass fraction of the hydrofluoric acid solution in the absorber is greater than 30%, and the hydrofluoric acid solution is recovered and sold;

[0053] In this process, the operating conditions of the falling film absorption unit 3 are set as follows: the outlet pressure of the primary acid circulation pump is greater than 0.1 MPa, and the outlet flow rate of the primary acid circulation pump is 35m 3 / h, the circulating water temperature of the primary absorber is 25℃, and the circulating water flow rate of the primary absorber is 20m 3 / h. The outlet pressure of the secondary acid circulation pump is greater than 0.1MPa, and the outlet flow rate of the secondary acid circulation pump is 35m 3 / h, the circulating water temperature of the secondary absorber is 25℃, and the circulating water flow rate of the secondary absorber is 20m 3 / h;

[0054] After passing through the falling film absorption unit 3 , the remaining hydrogen and residual hydrogen fluoride flow into the three-waste treatment pool 4 .

[0055] S4. To prevent a small amount of unrecovered hydrogen fluoride from being discharged into the atmosphere, the residual hydrogen fluoride is absorbed by Ca(OH)2 / KOH. In the three-waste treatment pool 4, a mixed solution of Ca(OH)2 and KOH with a mass concentration of 10% is used to absorb the hydrogen and the residual hydrogen fluoride. The residual hydrogen fluoride is completely absorbed, and the hydrogen that meets the emission requirements is discharged into the atmosphere.

[0056] Method Example 2

[0057] A method for recovering hydrogen fluoride gas is carried out using the device for recovering hydrogen fluoride gas of device embodiment 1. This method is used for recovering hydrogen fluoride gas in the production of NF3 by electrolysis, and specifically comprises the following steps:

[0058] S1. When the electrolytic cell 6 is operating normally, the temperature in the electrolytic cell 6 is 70°C, the pressure in the electrolytic cell 6 is less than 0.05MPa, and hydrogen is generated at the electrolytic cathode. When the hydrogen is discharged, it carries part of the electrolyte ammonium bifluoride and hydrogen fluoride. The hydrogen discharged from the cathode of the electrolytic cell 6 flows into the gas buffer tank 1 at a pressure less than 0.05MPa.

[0059] S2, the condensation point of ammonium bifluoride is 124°C, the internal temperature of the gas buffer tank 1 is 60°C, and the ammonium bifluoride in the gas discharged from the cathode of the electrolytic cell 6 condenses in the gas buffer tank 1;

[0060] The remaining hydrogen and hydrogen fluoride flow to the microchannel unit 2 under pressure. The hydrogen fluoride in the hydrogen condenses at low temperature and flows back into the gas buffer tank 1. The hydrogen fluoride is condensed in the microchannel unit 2. The condensation medium is ethylene glycol. The refrigerant inlet temperature is -30±1℃, the refrigerant outlet temperature is -20±1℃, and the ethylene glycol refrigerant flow rate is 0.005m 3 / h;

[0061] Uncondensed hydrogen fluoride and hydrogen flow into the falling film absorption unit 3 .

[0062] S3, in the falling film absorption unit 3, hydrogen fluoride is absorbed by a two-stage absorber to form a hydrofluoric acid solution, and the hydrogen fluoride is recovered as a hydrofluoric acid solution until the HF mass fraction of the hydrofluoric acid solution in the absorber is greater than 30%, and the hydrofluoric acid solution is recovered and sold;

[0063] In this process, the operating conditions of the falling film absorption unit 3 are set as follows: the outlet pressure of the primary acid circulation pump is greater than 0.1 MPa, and the outlet flow rate of the primary acid circulation pump is 30m 3 / h, the circulating water temperature of the primary absorber is 30℃, and the circulating water flow rate of the primary absorber is 20m 3 / h. The outlet pressure of the secondary acid circulation pump is greater than 0.1MPa, and the outlet flow rate of the secondary acid circulation pump is 40m 3 / h, the circulating water temperature of the secondary absorber is 20℃, and the circulating water flow rate of the secondary absorber is 20m 3 / h;

[0064] After passing through the falling film absorption unit 3 , the remaining hydrogen and residual hydrogen fluoride flow into the three-waste treatment pool 4 .

[0065] S4. To prevent a small amount of unrecovered hydrogen fluoride from being discharged into the atmosphere, the residual hydrogen fluoride is absorbed by Ca(OH)2 / KOH. A mixed solution of Ca(OH)2 and KOH is used in the three-waste treatment pool 4 to absorb the hydrogen and the residual hydrogen fluoride. The residual hydrogen fluoride is completely absorbed, and the hydrogen that meets the emission requirements is discharged into the atmosphere.

[0066] Method Example 3

[0067] A method for recovering hydrogen fluoride gas is carried out using the device for recovering hydrogen fluoride gas of device embodiment 1. This method is used for recovering hydrogen fluoride gas in the production of NF3 by electrolysis, and specifically comprises the following steps:

[0068] S1. When the electrolytic cell 6 is operating normally, the temperature in the electrolytic cell 6 is 130°C, the pressure in the electrolytic cell 6 is less than 0.05MPa, and hydrogen is generated at the electrolytic cathode. When the hydrogen is discharged, it carries part of the electrolyte ammonium bifluoride and hydrogen fluoride. The hydrogen discharged from the cathode of the electrolytic cell 6 flows into the gas buffer tank 1 at a pressure less than 0.05MPa.

[0069] S2, the condensation point of ammonium bifluoride is 124°C, the internal temperature of the gas buffer tank 1 is 40°C, and the ammonium bifluoride in the gas discharged from the cathode of the electrolytic cell 6 condenses in the gas buffer tank 1;

[0070] The remaining hydrogen and hydrogen fluoride flow to the microchannel unit 2 under pressure. The hydrogen fluoride in the hydrogen condenses at low temperature and flows back into the gas buffer tank 1. The hydrogen fluoride is condensed in the microchannel unit 2. The condensation medium is ethylene glycol. The refrigerant inlet temperature is -30±1℃, the refrigerant outlet temperature is -20±1℃, and the ethylene glycol refrigerant flow rate is 0.001m 3 / h;

[0071] Uncondensed hydrogen fluoride and hydrogen flow into the falling film absorption unit 3 .

[0072] S3, in the falling film absorption unit 3, hydrogen fluoride is absorbed by a two-stage absorber to form a hydrofluoric acid solution, and the hydrogen fluoride is recovered as a hydrofluoric acid solution until the HF mass fraction of the hydrofluoric acid solution in the absorber is greater than 30%, and the hydrofluoric acid solution is recovered and sold;

[0073] In this process, the operating conditions of the falling film absorption unit 3 are set as follows: the outlet pressure of the primary acid circulation pump is greater than 0.1 MPa, and the outlet flow rate of the primary acid circulation pump is 40m 3 / h, the circulating water temperature of the primary absorber is 20℃, and the circulating water flow rate of the primary absorber is 20m 3 / h. The outlet pressure of the secondary acid circulation pump is greater than 0.1MPa, and the outlet flow rate of the secondary acid circulation pump is 30m 3 / h, the circulating water temperature of the secondary absorber is 30℃, and the circulating water flow rate of the secondary absorber is 20m 3 / h;

[0074] After passing through the falling film absorption unit 3 , the remaining hydrogen and residual hydrogen fluoride flow into the three-waste treatment pool 4 .

[0075] S4. To prevent a small amount of unrecovered hydrogen fluoride from being discharged into the atmosphere, the residual hydrogen fluoride is absorbed by Ca(OH)2 / KOH. A mixed solution of Ca(OH)2 and KOH is used in the three-waste treatment pool 4 to absorb the hydrogen and the residual hydrogen fluoride. The residual hydrogen fluoride is completely absorbed, and the hydrogen that meets the emission requirements is discharged into the atmosphere.

[0076] Comparative Example 1

[0077] Compared with method example 1, the single-tube parallel microchannel condenser is replaced by a conventional condenser, and the other conditions remain the same as those in method example 1.

[0078] The test showed that the amount of hydrogen fluoride condensed in the condenser and refluxed to the gas buffer tank 1 was reduced by 90% compared with that in Example 1, indicating that the single-tube parallel microchannel condenser can improve the condensation recovery efficiency of hydrogen fluoride compared with the conventional condenser.

[0079] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A device for recovering hydrogen fluoride gas, characterized in that: It comprises a gas buffer tank (1), a microchannel unit (2), a falling film absorption unit (3) and a three-waste treatment pool (4) which are sequentially connected through pipelines; The gas buffer tank (1) is provided with a gas feed port on the side; a gas discharge port on the top; and a liquid discharge port on the bottom; the gas feed port of the gas tank flush tank is connected to the exhaust port on the top of the electrolytic cell (6) via a pipeline, and the liquid discharge port of the gas tank flush tank (1) is connected to the liquid replenishing port on the side of the electrolytic cell (6) via a pipeline; The microchannel unit (2) is provided with a gas inlet and a gas outlet, the gas inlet of the microchannel unit (2) is connected to the gas outlet of the gas buffer tank (1) through a pipeline, and the gas outlet of the microchannel unit (2) is connected to the falling film absorption unit (3) through a pipeline; the microchannel unit (2) is also provided with a refrigerant inlet and a refrigerant outlet, and the refrigerant inlet and the refrigerant outlet of the microchannel unit (2) are connected to the ethylene glycol refrigerant tank (5) through a circulation pipeline.

2. The device for recovering hydrogen fluoride gas according to claim 1, characterized in that: The microchannel unit (2) is a single-tube parallel microchannel condenser, the diameter of the single tube is 10-1000 μm, and the shell diameter is 50 mm. A centrifugal pump or a shielded pump is installed on the circulation pipeline between the microchannel unit (2) and the ethylene glycol refrigerant tank (5).

3. The device for recovering hydrogen fluoride gas according to claim 1, characterized in that: The falling film absorption unit (3) comprises a primary absorber and a secondary absorber which are connected in sequence by pipelines, wherein the primary absorber is installed in a primary circulating water tank, and a primary acid circulating pump is connected and installed in the primary absorber; the secondary absorber is installed in a secondary circulating water tank, and a secondary acid circulating pump is connected and installed in the secondary absorber, and the primary acid circulating pump and the secondary acid circulating pump are centrifugal pumps or shielded pumps.

4. The device for recovering hydrogen fluoride gas according to claim 1, characterized in that: The connecting pipes sequentially connecting the gas tank flushing tank (1), the microchannel unit (2), the falling film absorption unit (3) and the three-waste treatment tank (4) are made of silicon carbide or monel; the connecting pipes between the gas tank flushing tank (1) and the electrolytic cell (6) are made of silicon carbide or monel; the circulating pipeline between the microchannel unit (2) and the ethylene glycol refrigerant tank (5) is made of 316L stainless steel, and a radar level meter is installed in the gas buffer tank (1).

5. The device for recovering hydrogen fluoride gas according to claim 1, characterized in that: The gas feed port of the gas tank flushing tank (1) is connected to the exhaust port on the top of at least one electrolytic cell (6) so as to simultaneously recover the hydrogen fluoride gas discharged from one or more electrolytic cells (6).

6. A method for recovering hydrogen fluoride gas, characterized in that: The method is carried out using a device for recovering hydrogen fluoride gas as described in any one of claims 1 to 4, and the method is used for recovering hydrogen fluoride gas in the production of NF3 by electrolysis, and the method comprises the following steps: S1, the temperature in the electrolytic cell (6) is 70-130°C, the pressure in the electrolytic cell (6) is less than 0.05MPa, hydrogen is generated by electrolysis at the cathode, and part of the ammonium bifluoride and hydrogen fluoride in the electrolyte are entrained when the hydrogen is discharged, and the gas discharged from the cathode of the electrolytic cell (6) flows into the gas buffer tank (1) at a pressure of less than 0.05MPa; S2, the internal temperature of the gas buffer tank (1) is 40-60° C., the ammonium bifluoride in the gas discharged from the cathode of the electrolytic cell (6) condenses in the gas buffer tank (1), the remaining hydrogen and hydrogen fluoride flow into the microchannel unit (2), the hydrogen fluoride is condensed in the microchannel unit (2), the condensed hydrogen fluoride flows back to the gas buffer tank (1), and the uncondensed hydrogen fluoride and hydrogen flow into the falling film absorption unit (3); S3, in the falling film absorption unit (3), hydrogen fluoride is absorbed by a two-stage absorber, and the hydrogen fluoride is recovered as a hydrofluoric acid solution, and the remaining hydrogen and residual hydrogen fluoride flow into the three-waste treatment pool (4); S4. In the three-waste treatment pool (4), the hydrogen and the residual hydrogen fluoride are absorbed and treated, the residual hydrogen fluoride is completely absorbed, and the treated hydrogen is discharged.

7. A method for recovering hydrogen fluoride gas according to claim 6, characterized in that: In step S2, when the liquid level in the gas buffer tank (1) reaches 2 / 3, the ammonium bifluoride and hydrogen fluoride in the gas buffer tank (1) are transported into the electrolytic cell (6) for reuse by a pump.

8. A method for recovering hydrogen fluoride gas according to claim 6, characterized in that: In step S2, hydrogen fluoride is condensed in the microchannel unit (2), the condensation medium is ethylene glycol, the refrigerant inlet temperature is -30±1°C, the refrigerant outlet temperature is -20±1°C, and the ethylene glycol refrigerant flow rate is 0.001-0.005m 3 / h.

9. A method for recovering hydrogen fluoride gas according to claim 6, characterized in that: In step S3, hydrogen fluoride is absorbed by a two-stage absorber to form a hydrofluoric acid solution. The operating conditions of the falling film absorption unit (3) are set such that the outlet pressure of the primary acid circulation pump is greater than 0.1 MPa and the outlet flow rate of the primary acid circulation pump is 30-40 m 3 / h, the circulating water temperature of the primary absorber is 20-30℃, and the circulating water flow rate of the primary absorber is 20m 3 / h, the outlet pressure of the secondary acid circulation pump is greater than 0.1MPa, and the outlet flow rate of the secondary acid circulation pump is 30-40m 3 / h, the circulating water temperature of the secondary absorber is 20-30℃, and the circulating water flow rate of the secondary absorber is 20m 3 / h.

10. A method for recovering hydrogen fluoride gas according to claim 6, characterized in that: In step S4, residual hydrogen fluoride is absorbed and treated in the waste treatment pool (4) using a mixed solution of Ca(OH)2 and KOH.

Images