CN112191081A - Method and system for treating hydrogen fluoride tail gas generated in nitrogen trifluoride preparation process - Google Patents
Method and system for treating hydrogen fluoride tail gas generated in nitrogen trifluoride preparation process Download PDFInfo
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Abstract
The invention discloses a method for treating hydrogen fluoride tail gas generated in a nitrogen trifluoride preparation process, wherein the tail gas enters from a gas inlet of a condensing tower, and a gas outlet of the condensing tower is connected with a gas inlet of a primary hydrogen fluoride absorption tower of a secondary recovery system; the gas outlet of the first-stage hydrogen fluoride absorption tower is connected with the gas inlet of the second-stage hydrogen fluoride absorption tower, the gas outlet of the second-stage hydrogen fluoride absorption tower is connected with the gas inlet of the tail gas treatment tower, and the gas outlet of the tail gas treatment tower is empty; the second-stage ammonium bifluoride solution storage tank is connected with the first-stage ammonium bifluoride solution storage tank through a pipeline and a valve. According to the invention, the hydrogen fluoride in the tail gas is recovered by combining condensation and ammonium fluoride absorption for the first time, and the produced pure hydrogen fluoride and ammonium bifluoride can be directly reused in production as production raw materials, so that the resource recycling is realized, and the production cost and the tail gas treatment cost are reduced.
Description
Technical Field
The invention relates to the technical field of tail gas treatment, in particular to a method and a system for treating hydrogen fluoride tail gas generated in a nitrogen trifluoride preparation process.
Background
High-purity nitrogen trifluoride gas is used as an excellent plasma etching gas in the microelectronics industry, has excellent etching rate and selectivity on silicon and silicon oxide, and therefore occupies an important position in industries such as integrated circuits, chip manufacturing and the like.
In the process of preparing high-purity nitrogen trifluoride by electrolysis, hydrogen fluoride and ammonium fluoride or ammonium bifluoride are taken as necessary production raw materials, in order to ensure that the reaction is smoothly carried out and high-quality nitrogen trifluoride is produced, excessive hydrogen fluoride raw materials are often required to be added, so that the electrolysis tail gas contains a large amount of hydrogen fluoride, and therefore the hydrogen fluoride in the tail gas must be treated, the tail gas is discharged up to the standard, and the environmental pollution is avoided. As the industrial scale of high purity nitrogen trifluoride electronic gas is expanded, the amount of tail gas generated by electrolysis is increased, the amount of hydrogen fluoride discharged is increased, and the problem of tail gas treatment is becoming one of the factors limiting the development of high purity nitrogen trifluoride gas industry.
At present, two main treatment modes are available for tail gas containing hydrogen fluoride in the electrolytic production process of high-purity nitrogen trifluoride, one mode is to carry out deep condensation recovery on the tail gas containing hydrogen fluoride, and the hydrogen fluoride is subjected to multistage condensation recovery through a heat exchanger, so that on one hand, a large amount of cold energy is consumed, the energy consumption is large, on the other hand, a condensation recovery mode is singly adopted, the hydrogen fluoride recovery efficiency is not high, and a large amount of hydrogen fluoride is still wasted; the other mode is a multi-stage alkali washing mode, and hydrogen fluoride in the waste gas is neutralized by adopting a multi-stage alkali liquor mode, so that on one hand, the waste of hydrogen fluoride resources is caused, on the other hand, a large amount of byproducts are generated, and the problem of secondary pollution is caused.
Therefore, the disadvantages of the current treatment process include the following:
(1) the energy consumption is high, and the recovery efficiency is low;
(2) the hydrogen fluoride is directly neutralized, so that the resource waste is caused, and the amount of byproducts is large.
Disclosure of Invention
The invention aims to solve the defects in the prior art, and provides a method for treating hydrogen fluoride tail gas generated in the preparation process of nitrogen trifluoride, which recovers hydrogen fluoride in the tail gas by combining condensation and an ammonium fluoride absorption mode, and the produced pure hydrogen fluoride and ammonium bifluoride can be directly reused as production raw materials on production, thereby realizing the cyclic utilization of resources, reducing the production cost and the tail gas treatment cost and having remarkable economic benefit; can safely and effectively carry out harmless treatment on the hydrogen fluoride-containing tail gas generated in the preparation process of nitrogen trifluoride, solves the problems of higher energy consumption, more generated byproducts and the like of the traditional treatment process, and has higher environmental protection benefit.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for treating hydrogen fluoride tail gas generated in the preparation process of nitrogen trifluoride comprises the following steps:
s1, introducing the tail gas containing hydrogen fluoride into a condensing tower, directly cooling the hydrogen fluoride in the tail gas into liquid hydrogen fluoride by using the low temperature provided by a cooling medium in the condensing tower to obtain pure liquid hydrogen fluoride, and allowing the liquid hydrogen fluoride to flow into a hydrogen fluoride storage tank;
s2, enabling the tail gas obtained after hydrogen fluoride recovery in the step S1 to sequentially enter a primary hydrogen fluoride absorption tower (5) and a secondary hydrogen fluoride absorption tower (6) through pipelines to carry out hydrogen fluoride absorption to obtain an ammonium bifluoride solution, enabling the saturated ammonium bifluoride solution generated by the primary hydrogen fluoride absorption tower (5) to flow into a primary ammonium bifluoride solution storage tank (3) and be discharged, and recycling the saturated ammonium bifluoride solution for production after concentration and crystallization;
s3, introducing the tail gas subjected to secondary hydrogen fluoride absorption into a tail gas treatment tower for deep defluorination, discharging gas in the tail gas treatment tower through a tower top outlet, introducing liquid into an alkali liquor pool through a tower bottom outlet, deeply absorbing fluorine ions in the liquid by alkali liquor in the alkali liquor pool, and discharging the fluorine ions after reaching the standard.
Further, the temperature of the condensing tower in the step S1 is controlled to be-30-10 ℃.
Further, the temperature of the primary hydrogen fluoride absorption tower and the secondary hydrogen fluoride absorption tower in the step S2 is controlled to be 40-60 ℃.
Further, in the step S2, when the mass concentration of the solution in the primary ammonium bifluoride storage tank reaches 50% through detection, the solution is discharged through an epicyclic pump for concentration and crystallization.
Further, in the step S2, the ammonium bifluoride solution in the first-stage ammonium bifluoride solution storage tank (3) and the second-stage ammonium bifluoride solution storage tank (4) is fed back to the corresponding absorption tower through a circulation pipeline to be used as the absorption mother solution for reuse; after solution passes through the turnover pump discharge in the one-level ammonium bifluoride storage tank, pour the ammonium bifluoride solution that absorbs in the two-level ammonium bifluoride storage tank into one-level ammonium bifluoride storage tank, act as the one-level mother liquor that absorbs to add the ammonium fluoride solution that mass concentration is 10% in the two-level ammonium bifluoride storage tank.
Further, in the step S2, the first-stage hydrogen fluoride absorption tower and the second-stage hydrogen fluoride absorption tower both use falling film absorbers, and the lining material is graphite or polytetrafluoroethylene.
Further, in the step 3, the material used in the lye tank is lime, calcium hydroxide or potassium hydroxide.
A treatment system for hydrogen fluoride tail gas generated in a nitrogen trifluoride preparation process comprises a primary recovery system, a secondary recovery system, a tail gas advanced treatment system and a temperature control system; the primary recovery system consists of a condensing tower and a hydrogen fluoride storage tank; the secondary absorption system consists of a primary hydrogen fluoride absorption tower, a primary ammonium bifluoride solution storage tank, a secondary hydrogen fluoride absorption tower and a secondary ammonium bifluoride solution storage tank; the tail gas advanced treatment system consists of a tail gas absorption tower and an alkali liquor pool;
tail gas enters from a gas inlet of a condensing tower, and a gas outlet of the condensing tower is connected with a gas inlet of a primary hydrogen fluoride absorption tower of a secondary recovery system; the gas outlet of the first-stage hydrogen fluoride absorption tower is connected with the gas inlet of the second-stage hydrogen fluoride absorption tower, the gas outlet of the second-stage hydrogen fluoride absorption tower is connected with the gas inlet of the tail gas treatment tower, and the gas outlet of the tail gas treatment tower is empty; the condensing tower is connected with the hydrogen fluoride storage tank through a pipeline; the primary hydrogen fluoride absorption tower is connected with the primary ammonium bifluoride solution storage tank through a first pipeline and used for enabling the absorbed ammonium bifluoride solution to flow into the primary ammonium bifluoride solution storage tank; the secondary hydrogen fluoride absorption tower is connected with the secondary ammonium bifluoride solution storage tank through a third pipeline and used for enabling the absorbed ammonium bifluoride solution to flow into the secondary ammonium bifluoride solution storage tank (4); the tail gas absorption tower is connected with the alkali liquor pool through a pipeline.
The temperature control system respectively controls the temperature of the condensing tower, the primary hydrogen fluoride absorption tower and the secondary hydrogen fluoride absorption tower.
Furthermore, the temperature control system adopts a distributed control system DCS, and the temperatures of the condensing tower, the primary hydrogen fluoride absorption tower and the secondary hydrogen fluoride absorption tower are respectively controlled through DCS signals.
Further, the primary ammonium bifluoride solution storage tank is connected with the primary hydrogen fluoride absorption tower through a second pipeline, the second pipeline is also connected with a turnover pump and a valve communicated with the outside, and the turnover pump is used for feeding the ammonium bifluoride solution in the primary ammonium bifluoride solution storage tank back to the primary hydrogen fluoride absorption tower to be used as primary absorption mother liquor for reuse and is also used for discharging the solution in the primary ammonium bifluoride solution storage tank through the turnover pump for concentration and crystallization after the mass concentration of the solution in the primary ammonium bifluoride storage tank reaches 50 percent through detection;
the second-stage ammonium bifluoride solution storage tank is connected with the first-stage ammonium bifluoride solution storage tank through a fourth pipeline with a valve and a turnover pump, and the fourth pipeline is also connected with a second-stage hydrogen fluoride absorption tower; the fourth pipeline is used for pouring the ammonium bifluoride solution absorbed in the secondary ammonium bifluoride storage tank into the primary ammonium bifluoride storage tank to serve as primary absorption mother liquor when the solution in the primary ammonium bifluoride storage tank is discharged through the transfer pump; the fourth pipeline is also used for feeding back the ammonium bifluoride solution in the secondary ammonium bifluoride solution storage tank to the secondary hydrogen fluoride absorption tower to be used as secondary absorption mother liquor for repeated use;
the hydrogen fluoride storage tank, the primary ammonium bifluoride solution storage tank and the secondary ammonium bifluoride solution storage tank are respectively provided with a liquid level meter; the caustic solution pond bottom all is equipped with the turnover pump, hydrogen fluoride storage tank bottom is equipped with the pipeline of taking the valve.
The invention has the following beneficial effects:
1. according to the invention, the hydrogen fluoride in the tail gas is recovered by combining condensation and ammonium fluoride absorption for the first time, and the produced pure hydrogen fluoride and ammonium bifluoride can be directly reused in production as production raw materials, so that the resource recycling is realized, the production cost and the tail gas treatment cost are reduced, and the method has remarkable economic benefits;
2. the secondary recovery system of the invention consists of two stages of secondary hydrogen fluoride absorption treatment modules. The tail gas after hydrogen fluoride recovery is absorbed in the first-stage module more fully, and the residual hydrogen fluoride is further absorbed in the second-stage module. The saturation of the ammonium acid fluoride solution in the secondary module is therefore always low. In order to fully utilize the ammonium bifluoride solution in the secondary module, when the mass concentration of the ammonium bifluoride solution in the primary module meets the requirement and is discharged, the ammonium bifluoride solution in the secondary module is supplemented into the primary module for further absorption, and the ammonium fluoride solution with lower mass concentration is supplemented into the secondary module, so that the ammonium bifluoride solution can be fully utilized.
3. The method can safely and effectively carry out harmless treatment on the hydrogen fluoride-containing tail gas generated in the preparation process of nitrogen trifluoride, solves the problems of high energy consumption, generation of more byproducts and the like of the traditional treatment process, and has high environmental protection benefit.
Drawings
FIG. 1 is a schematic view of the process flow structure of the present invention.
In the figure, I is a primary recovery system; II, a secondary recovery system; III is a tail gas advanced treatment system; IV is a temperature control system.
Wherein 1, a condensing tower; 2. a hydrogen fluoride storage tank; 3. a primary ammonium bifluoride solution storage tank; 4. a secondary ammonium bifluoride solution storage tank; 5. a first-stage hydrogen fluoride absorption tower; 6. a secondary hydrogen fluoride absorption tower; 7. a tail gas treatment tower; 8. an alkaline solution pool; 9. DCS temperature controller.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather should be construed as broadly as the present invention is capable of modification in various respects, all without departing from the spirit and scope of the present invention.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not represent the only embodiments.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
A method for treating hydrogen fluoride tail gas generated in a nitrogen trifluoride preparation process comprises the following steps:
s1, introducing the tail gas containing hydrogen fluoride generated in the nitrogen trifluoride preparation process into a condensation tower 1, directly cooling the hydrogen fluoride in the tail gas into liquid hydrogen fluoride by using the low temperature provided by a cooling medium in the condensation tower 1 to obtain pure liquid hydrogen fluoride, and allowing the liquid hydrogen fluoride to flow into a hydrogen fluoride storage tank 2;
when the liquid level of the hydrogen fluoride storage tank 2 reaches a set value, the liquid hydrogen fluoride can be discharged and recovered through a valve at the bottom of the tank.
And S2, enabling the tail gas obtained after the hydrogen fluoride is recovered in the step S1 to sequentially enter a primary hydrogen fluoride absorption tower 5 and a secondary hydrogen fluoride absorption tower 6 through pipelines to be subjected to hydrogen fluoride absorption, and obtaining an ammonium bifluoride solution. Wherein, the first-stage hydrogen fluoride absorption tower 5 obtains saturated ammonium bifluoride solution, flows into a first-stage ammonium bifluoride solution storage tank 3, is discharged, and is recycled for production after concentration and crystallization; the ammonium bifluoride solution obtained by the secondary hydrogen fluoride absorption tower 6 flows into the primary ammonium bifluoride solution storage tank 3 to supplement the discharge of the ammonium bifluoride solution of the primary hydrogen fluoride absorption tower 5.
S3, introducing the tail gas subjected to secondary hydrogen fluoride absorption into the tail gas treatment tower 7 for deep defluorination, discharging the gas in the tail gas treatment tower 7 through a tower top outlet, introducing the liquid into the alkali liquor pool 8 through a tower bottom outlet, deeply absorbing the fluorine ions in the liquid by the alkali liquor in the alkali liquor pool 8, and discharging the fluorine ions after reaching the standard.
The temperature of the condensing tower 1 in the step S1 is controlled to be-30-10 ℃. In the step S2, the temperature of the primary hydrogen fluoride absorption tower 5 and the secondary hydrogen fluoride absorption tower 6 is controlled to be 40-60 ℃.
In the step S2, the ammonium bifluoride solutions in the first-stage ammonium bifluoride solution storage tank 3 and the second-stage ammonium bifluoride solution storage tank 4 are fed back to the corresponding absorption towers through circulation pipelines to be used as absorption mother liquor.
The first-stage ammonium bifluoride storage tank 3 is also provided with an outer discharge pipeline, and the second-stage ammonium bifluoride storage tank 4 is provided with a cascade pipeline for discharging an ammonium bifluoride solution into the first-stage ammonium bifluoride storage tank 3. The outer discharge line and the cascade line may be designed in combination with the above-described circulation line. As shown in fig. 1, a first-stage ammonium bifluoride storage tank 3 is connected with a first-stage hydrogen fluoride absorption tower 5 through a circulation pipeline, a circulation pump is arranged in the circulation pipeline, an outer discharge pipeline is led out from the middle part of the circulation pipeline, and a valve is arranged on the outer discharge pipeline. The second-stage ammonium bifluoride storage tank 4 is connected with the second-stage hydrogen fluoride absorption tower 6 through a circulating pipeline, a turnover pump is arranged in the circulating pipeline, and a cascade pipeline is led out of the middle of the circulating pipeline and connected with the first-stage ammonium bifluoride storage tank 3. The cascade pipeline is provided with a valve.
And when the mass concentration of the solution in the primary ammonium bifluoride storage tank 3 reaches 50% through detection, the solution is discharged through an external discharge pipeline through a turnover pump for concentration and crystallization. In the step S2, after the solution in the primary ammonium bifluoride storage tank 3 is discharged, the ammonium bifluoride solution absorbed in the secondary ammonium bifluoride storage tank 4 is introduced into the primary ammonium bifluoride storage tank 3 through a cascade pipeline to serve as the primary absorption mother solution, and the ammonium bifluoride solution with the mass concentration of 10% is added into the secondary ammonium bifluoride storage tank 4.
In a preferred embodiment, in step S2, the primary hydrogen fluoride absorption tower 5 and the secondary hydrogen fluoride absorption tower 6 both use falling film absorbers, and the lining material is graphite or polytetrafluoroethylene. In the step 3, the material used in the lye tank 8 is lime, calcium hydroxide or potassium hydroxide.
As shown in fig. 1, a system for treating hydrogen fluoride tail gas generated in a nitrogen trifluoride preparation process comprises a primary recovery system, a secondary recovery system and a tail gas advanced treatment system; the primary recovery system consists of a condensing tower 1 and a hydrogen fluoride storage tank 2; the secondary absorption system consists of a primary hydrogen fluoride absorption tower 5, a primary ammonium bifluoride solution storage tank 3, a secondary hydrogen fluoride absorption tower 6 and a secondary ammonium bifluoride solution storage tank 4; the tail gas advanced treatment system consists of a tail gas absorption tower 7 and an alkali liquor pool 8; tail gas enters from a gas inlet of a condensing tower 1, and a gas outlet of the condensing tower 1 is connected with a gas inlet of a primary hydrogen fluoride absorption tower 5 of a secondary recovery system; the gas outlet of the first-stage hydrogen fluoride absorption tower 5 is connected with the gas inlet of the second-stage hydrogen fluoride absorption tower 6, the gas outlet of the second-stage hydrogen fluoride absorption tower 6 is connected with the gas inlet of the tail gas treatment tower 7, and the gas outlet of the tail gas treatment tower 7 is empty; condensing tower 1 passes through the pipeline with hydrogen fluoride storage tank 2 and links to each other, one-level hydrogen fluoride absorption tower 5 passes through the pipeline with one-level ammonium bifluoride solution storage tank 3 and links to each other, second grade hydrogen fluoride absorption tower 6 passes through the pipeline with second grade ammonium bifluoride solution storage tank 4 and links to each other, tail gas absorption tower 7 passes through the pipeline with alkali lye pond 8 and links to each other. The treatment system further comprises a DCS temperature control system 9, wherein the DCS temperature control system 9 controls the temperature of the condensation tower 1, the first-stage hydrogen fluoride absorption tower 5 and the second-stage hydrogen fluoride absorption tower 6 respectively through DCS signals.
The primary ammonium bifluoride solution storage tank 3 is connected with the primary hydrogen fluoride absorption tower 5 through a second pipeline, the second pipeline is also connected with a turnover pump and a valve communicated with the outside, and the turnover pump is used for feeding the ammonium bifluoride solution in the primary ammonium bifluoride solution storage tank 3 back to the primary hydrogen fluoride absorption tower 5 to be used as primary absorption mother liquor for reuse and is also used for discharging the solution in the primary ammonium bifluoride solution storage tank 5 through the turnover pump for concentration and crystallization after the mass concentration of the solution reaches 50 percent through detection;
the secondary ammonium bifluoride solution storage tank 4 is connected with the primary ammonium bifluoride solution storage tank 3 and the secondary hydrogen fluoride absorption tower 6 through a fourth pipeline with a valve and a transfer pump; the fourth pipeline is used for discharging the ammonium bifluoride solution in the secondary ammonium bifluoride storage tank 4 into the primary ammonium bifluoride storage tank 3 to serve as primary absorption mother liquor when the solution in the primary ammonium bifluoride storage tank 5 is discharged through the transfer pump; the fourth pipeline is also used for feeding back the ammonium bifluoride solution in the secondary ammonium bifluoride solution storage tank 4 to the secondary hydrogen fluoride absorption tower 6 to be used as secondary absorption mother liquor for repeated use;
the hydrogen fluoride storage tank 2, the first-stage ammonium bifluoride solution storage tank 3 and the second-stage ammonium bifluoride solution storage tank 4 are all provided with liquid level meters.
The bottom of the lye pool 8 is communicated with the tail gas absorption tower 7 through a pipeline with a turnover pump, and is used for realizing circulation of lye.
The bottom of the hydrogen fluoride storage tank 2 is provided with a pipeline with a valve for realizing the discharge of liquid when the liquid level exceeds the set height.
Example 1
Referring to the attached figure 1, a tail gas treatment system is installed, tail gas enters from a gas inlet of a condensing tower, and a gas outlet of the condensing tower 1 is connected with a gas inlet of a primary hydrogen fluoride absorption tower 5 of a secondary recovery system; the gas outlet of the first-stage hydrogen fluoride absorption tower 5 is connected with the gas inlet of the second-stage hydrogen fluoride absorption tower 6, the gas outlet of the second-stage hydrogen fluoride absorption tower 6 is connected with the gas inlet of the tail gas treatment tower 7, and the gas outlet of the tail gas treatment tower 7 is empty; the secondary ammonium bifluoride solution storage tank 4 is connected with the primary ammonium bifluoride solution storage tank 3 through a pipeline and a valve; the DCS temperature control system 9 controls the temperatures of the condensation tower 1, the primary hydrogen fluoride absorption tower 5, and the secondary hydrogen fluoride absorption tower 6, respectively, by DCS signals. The operation temperature of the condensing tower is controlled to be about-30 ℃ through a DCS temperature control system, the operation temperature of the ammonium fluoride solution absorption tower is controlled to be about 40 ℃, and after tail gas containing hydrogen fluoride is introduced, the concentration of fluorine ions at the outlet of the tail gas treatment tower 7 is detected to be 6 ppm. The hydrogen fluoride obtained by condensation and the ammonium bifluoride obtained by concentration, temperature reduction, crystallization and drying can be directly reused for production by detection.
Example 2
Referring to the attached figure 1, a tail gas treatment system is installed, tail gas enters from a gas inlet of a condensing tower, and a gas outlet of the condensing tower 1 is connected with a gas inlet of a primary hydrogen fluoride absorption tower 5 of a secondary recovery system; the gas outlet of the first-stage hydrogen fluoride absorption tower 5 is connected with the gas inlet of the second-stage hydrogen fluoride absorption tower 6, the gas outlet of the second-stage hydrogen fluoride absorption tower 6 is connected with the gas inlet of the tail gas treatment tower 7, and the gas outlet of the tail gas treatment tower 7 is empty; the secondary ammonium bifluoride solution storage tank 4 is connected with the primary ammonium bifluoride solution storage tank 3 through a pipeline and a valve; the DCS temperature control system 9 controls the temperatures of the condensation tower 1, the primary hydrogen fluoride absorption tower 5, and the secondary hydrogen fluoride absorption tower 6, respectively, by DCS signals. Controlling the operation temperature of the condensing tower to be about-10 ℃ through a DCS temperature control system, controlling the operation temperature of the ammonium fluoride solution absorption tower to be about 60 ℃, and detecting that the concentration of fluorine ions at the outlet of the tail gas treatment tower is 7ppm after introducing tail gas containing hydrogen fluoride. The hydrogen fluoride obtained by condensation and the ammonium bifluoride obtained by concentration, temperature reduction, crystallization and drying can be directly reused for production by detection.
Example 3
Referring to the attached figure 1, a tail gas treatment system containing hydrogen fluoride is installed, tail gas enters from a gas inlet of a condensing tower, and a gas outlet of the condensing tower 1 is connected with a gas inlet of a primary hydrogen fluoride absorption tower 5 of a secondary recovery system; the gas outlet of the first-stage hydrogen fluoride absorption tower 5 is connected with the gas inlet of the second-stage hydrogen fluoride absorption tower 6, the gas outlet of the second-stage hydrogen fluoride absorption tower 6 is connected with the gas inlet of the tail gas treatment tower 7, and the gas outlet of the tail gas treatment tower 7 is empty; the secondary ammonium bifluoride solution storage tank 4 is connected with the primary ammonium bifluoride solution storage tank 3 through a pipeline and a valve; the DCS temperature control system 9 controls the temperatures of the condensation tower 1, the primary hydrogen fluoride absorption tower 5, and the secondary hydrogen fluoride absorption tower 6, respectively, by DCS signals. The operation temperature of the condensing tower is controlled to be about 0 ℃ through a DCS temperature control system, the operation temperature of the ammonium fluoride solution absorption tower is controlled to be about 50 ℃, and after the tail gas containing hydrogen fluoride is introduced, the concentration of fluorine ions at the outlet of the tail gas treatment tower is detected to be 3 ppm. The hydrogen fluoride obtained by condensation and the ammonium bifluoride obtained by concentration, temperature reduction, crystallization and drying can be directly reused for production by detection.
According to the invention, hydrogen fluoride in the tail gas is recovered by combining condensation and ammonium fluoride absorption, and the produced pure hydrogen fluoride and ammonium bifluoride can be directly reused in production as production raw materials, so that the cyclic utilization of resources is realized, the production cost and the tail gas treatment cost are reduced, and the method has remarkable economic benefits; can safely and effectively carry out harmless treatment on the hydrogen fluoride-containing tail gas generated in the preparation process of nitrogen trifluoride, solves the problems of higher energy consumption, more generated byproducts and the like of the traditional treatment process, and has higher environmental protection benefit.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (10)
1. A method for treating hydrogen fluoride tail gas generated in a nitrogen trifluoride preparation process is characterized by comprising the following steps:
s1, introducing the tail gas containing hydrogen fluoride into a condensing tower (1), directly cooling the hydrogen fluoride in the tail gas into liquid hydrogen fluoride by using the low temperature provided by a cooling medium in the condensing tower (1) to obtain pure liquid hydrogen fluoride, and allowing the liquid hydrogen fluoride to flow into a hydrogen fluoride storage tank (2);
s2, enabling the tail gas obtained after hydrogen fluoride recovery in the step S1 to sequentially enter a primary hydrogen fluoride absorption tower (5) and a secondary hydrogen fluoride absorption tower (6) through pipelines to carry out hydrogen fluoride absorption to obtain an ammonium bifluoride solution, enabling the saturated ammonium bifluoride solution generated by the primary hydrogen fluoride absorption tower (5) to flow into a primary ammonium bifluoride solution storage tank (3) and be discharged, and recycling the saturated ammonium bifluoride solution for production after concentration and crystallization;
s3, introducing the tail gas subjected to secondary hydrogen fluoride absorption into a tail gas treatment tower (7) for deep fluorine removal, discharging the gas in the tail gas treatment tower (7) through a tower top outlet, introducing the liquid into an alkali liquor pool (8) through a tower bottom outlet, deeply absorbing fluorine ions in the liquid by alkali liquor in the alkali liquor pool (8), and discharging after reaching the standard.
2. The method for treating hydrogen fluoride off-gas generated in the preparation process of nitrogen trifluoride according to claim 1, wherein the temperature of the condensing tower (1) in the step S1 is controlled to be-30 ℃ to 10 ℃.
3. The method for treating the hydrogen fluoride off-gas generated in the preparation process of nitrogen trifluoride according to claim 1, wherein the temperatures of the primary hydrogen fluoride-absorbing tower (5) and the secondary hydrogen fluoride-absorbing tower (6) in the step S2 are controlled to be 40 ℃ to 60 ℃.
4. The method for treating the hydrogen fluoride off-gas generated in the preparation process of nitrogen trifluoride according to claim 1, wherein in step S2, when the mass concentration of the solution in the primary ammonium bifluoride storage tank (5) reaches 50%, the solution is discharged by an epicyclic pump for concentration and crystallization.
5. The method for treating tail gas of hydrogen fluoride generated in the preparation process of nitrogen trifluoride according to claim 1, wherein in step S2, the ammonium bifluoride solution in the primary ammonium bifluoride solution storage tank (3) and the secondary ammonium bifluoride solution storage tank (4) is fed back to the corresponding absorption tower through a circulation pipeline to be used as the absorption mother liquor;
after the solution is discharged through the turnover pump in the first-stage ammonium bifluoride storage tank (3), the ammonium bifluoride solution absorbed in the second-stage ammonium bifluoride storage tank (4) is poured into the first-stage ammonium bifluoride storage tank (3) to serve as a first-stage absorption mother liquor, and an ammonium fluoride solution with the mass concentration of 10% is added into the second-stage ammonium bifluoride storage tank (4).
6. The method according to claim 1, wherein the first hydrogen fluoride absorption tower (5) and the second hydrogen fluoride absorption tower (6) in step S2 both use falling film absorbers, and the lining material is graphite or polytetrafluoroethylene.
7. The method for treating the hydrogen fluoride off-gas generated in the preparation process of nitrogen trifluoride according to claim 1, wherein in the step 3, the material used in the alkali solution tank (8) is lime, calcium hydroxide or potassium hydroxide.
8. A treatment system for hydrogen fluoride tail gas generated in a nitrogen trifluoride preparation process is characterized by comprising a primary recovery system, a secondary recovery system, a tail gas advanced treatment system and a temperature control system; the primary recovery system consists of a condensing tower (1) and a hydrogen fluoride storage tank (2); the secondary absorption system consists of a primary hydrogen fluoride absorption tower (5), a primary ammonium bifluoride solution storage tank (3), a secondary hydrogen fluoride absorption tower (6) and a secondary ammonium bifluoride solution storage tank (4); the tail gas advanced treatment system consists of a tail gas absorption tower (7) and an alkali liquor pool (8);
tail gas enters from a gas inlet of the condensing tower (1), and a gas outlet of the condensing tower (1) is connected with a gas inlet of a primary hydrogen fluoride absorption tower (5) of a secondary recovery system; the air outlet of the first-stage hydrogen fluoride absorption tower (5) is connected with the air inlet of the second-stage hydrogen fluoride absorption tower (6), the air outlet of the second-stage hydrogen fluoride absorption tower (6) is connected with the air inlet of the tail gas treatment tower (7), and the air outlet of the tail gas treatment tower (7) is empty; the condensing tower (1) is connected with the hydrogen fluoride storage tank (2) through a pipeline; the primary hydrogen fluoride absorption tower (5) is connected with the primary ammonium bifluoride solution storage tank (3) through a first pipeline and is used for enabling the absorbed ammonium bifluoride solution to flow into the primary ammonium bifluoride solution storage tank (3); the secondary hydrogen fluoride absorption tower (6) is connected with the secondary ammonium bifluoride solution storage tank (4) through a third pipeline and used for enabling the absorbed ammonium bifluoride solution to flow into the secondary ammonium bifluoride solution storage tank (4); the tail gas absorption tower (7) is connected with the alkali liquor pool (8) through a pipeline;
the temperature control system respectively controls the temperature of the condensing tower (1), the primary hydrogen fluoride absorption tower (5) and the secondary hydrogen fluoride absorption tower (6).
9. The system for treating the hydrogen fluoride off-gas generated in the process of preparing nitrogen trifluoride according to claim 8, wherein the temperature control system adopts a distributed control system DCS, and the temperatures of the condensing tower (1), the primary hydrogen fluoride absorption tower (5) and the secondary hydrogen fluoride absorption tower (6) are respectively controlled by DCS signals.
10. The system for treating the hydrogen fluoride off-gas generated in the process of preparing nitrogen trifluoride according to claim 8, wherein the primary ammonium bifluoride solution storage tank (3) is connected to the primary hydrogen fluoride absorption tower (5) through a second pipeline, the second pipeline is further connected with a turnover pump and a valve communicated with the outside, and the turnover pump is used for feeding the ammonium bifluoride solution in the primary ammonium bifluoride solution storage tank (3) back to the primary hydrogen fluoride absorption tower (5) to be reused as a primary absorption mother liquor and discharging the solution in the primary ammonium bifluoride storage tank (5) for concentration and crystallization after the mass concentration of the solution reaches 50% through detection;
the secondary ammonium bifluoride solution storage tank (4) is connected with the primary ammonium bifluoride solution storage tank (3) and the secondary hydrogen fluoride absorption tower (6) through a fourth pipeline with a valve and a turnover pump; the fourth pipeline is used for discharging the ammonium bifluoride solution in the secondary ammonium bifluoride storage tank (4) into the primary ammonium bifluoride storage tank (3) to serve as primary absorption mother liquor when the solution in the primary ammonium bifluoride storage tank (5) is discharged through the turnover pump; the fourth pipeline is also used for feeding back the ammonium bifluoride solution in the secondary ammonium bifluoride solution storage tank (4) to the secondary hydrogen fluoride absorption tower (6) to be used as secondary absorption mother liquor for repeated use;
liquid level meters are arranged on the hydrogen fluoride storage tank (2), the primary ammonium bifluoride solution storage tank (3) and the secondary ammonium bifluoride solution storage tank (4);
the alkali liquor pool (8) is communicated with the tail gas absorption tower (7) through a pipeline with a turnover pump, and a pipeline with a valve is arranged at the bottom of the hydrogen fluoride storage tank (2).
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