Recovery treatment method for ammonia-containing tail gas in later stage of aromatic nitrile synthesis

Abstract

A recovery treatment method for ammonia-containing tail gas in the later stage of aromatic nitrile synthesis. The method comprises: introducing the ammonia-containing tail gas sequentially into a first spray absorption tower and a second spray absorption tower; absorbing, in a liquid phase, ammonia from the ammonia-containing tail gas to realize the recovery of ammonia; and directly discharging exhaust gas; an absorbent A in the first spray absorption tower is water; and an absorbent B in the second spray absorption tower comprises glycolic acid, vinylphosphonic acid and aluminum sulfate. In the method, the recovery of ammonia from the ammonia-containing tail gas is increased by means of two-stage spraying, and the ammonia content in the treated tail gas is low and satisfies emission standards.

Description

A method for recovering and treating ammonia-containing tail gas in the later stage of aromatic nitrile synthesis Technical Field

[0001] This invention relates to the field of tail gas separation and treatment, and more particularly to a method for recovering and treating ammonia-containing tail gas in the later stage of aromatic nitrile synthesis. Background Technology

[0002] Aromatic nitrile compounds are an important class of organic compounds containing a cyano (CN) group on the benzene ring, such as benzonitrile, isophthalonitrile, o-phthalonitrile, o-chlorobenzonitrile, p-chlorobenzonitrile, 2,6-dichlorobenzonitrile, and 3,4-dichlorobenzonitrile. They are widely used in the preparation of polymer materials, pharmaceuticals, and dyes. Traditional synthetic routes for aromatic nitrile compounds mainly include haloalkyl cyanation, ammoxidation, carboxyl nitrification, aldehyde nitrification, electrolytic synthesis, acetonitrile addition, acrylonitrile synthesis, and diazotization. Ammonia oxidation is a commonly used method. For example, the synthesis of o-chlorobenzonitrile from o-chlorotoluene via ammonia oxidation is currently the mainstream method in industrial production. This method uses o-chlorotoluene, ammonia, and air as reactants and employs a transition metal heterogeneous catalyst. The exhaust gas produced by this method contains a large amount of ammonia. Ammonia is a highly water-soluble, colorless, alkaline, irritating, and harmful gas that cannot be directly emitted. Furthermore, ammonia can be used to produce ammonia water, nitrogen fertilizer, ammonium salts, compound fertilizers, and soda ash, so directly emitting ammonia-containing exhaust gas would result in resource waste. Therefore, exhaust gas recovery and treatment are necessary.

[0003] Current technologies typically involve condensing ammonia-containing tail gas into dilute ammonia water or absorbing ammonia through a spray tower. However, the former results in low-concentration, large-volume dilute ammonia water, meaning only a small portion can be recycled, while the majority is difficult to treat or extremely costly. The latter generally uses water or hydrochloric acid to spray and absorb the ammonia tail gas into a corresponding ammonia nitrogen solution, which is then concentrated through evaporation for recycling. Using water for spray absorption requires multiple repeated sprays, resulting in low efficiency, while hydrochloric acid spraying is costly and cannot prevent ammonia emissions. Therefore, it is necessary to improve existing tail gas treatment processes for aromatic nitrile production. Summary of the Invention

[0004] In view of the above situation and in order to overcome the defects of the prior art, the present invention provides a method for recovering and treating ammonia-containing tail gas in the later stage of aromatic nitrile synthesis, which at least solves some of the problems in the prior art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for recovering and treating ammonia-containing tail gas in the later stage of aromatic nitrile synthesis includes sequentially passing the ammonia-containing tail gas into a first spray absorption tower and a second spray absorption tower to absorb the ammonia in the liquid phase, thereby recovering the ammonia and discharging the waste gas; wherein the absorbent in the first spray absorption tower includes absorbent A and absorbent B, wherein absorbent A is water and absorbent B contains glycolic acid, vinylphosphonic acid and aluminum sulfate.

[0007] In a further embodiment, the ammonia-containing tail gas is the tail gas generated in the production of aromatic nitrile compounds by the ammonia oxidation method; the aromatic nitrile compounds include, but are not limited to, any one of isophthalonitrile, o-phthalonitrile, o-chlorobenzonitrile, p-chlorobenzonitrile, 2,6-dichlorobenzonitrile, and 3,4-dichlorobenzonitrile.

[0008] In a further embodiment, the absorbent B comprises glycolic acid, vinylphosphonic acid, and aluminum sulfate in a molar ratio of 3–5:0.8–1:0.1–0.15.

[0009] The ammonia in the tail gas first passes through the first spray absorption tower. Part of the ammonia is absorbed by water in the liquid phase to obtain the first ammonia water. Some of the ammonia remains in the tail gas. The remaining tail gas is then passed into the second spray absorption tower. Taking advantage of the high solubility of ammonia in absorbent B in the second spray absorption tower, the ammonia in the tail gas is absorbed in the liquid phase to the maximum extent, thus achieving efficient removal and recovery of ammonia.

[0010] In a further preferred embodiment, the absorbent B further comprises pyrimethamine, wherein the molar ratio of pyrimethamine to glycolic acid in the absorbent B is 1:0.3 to 0.5.

[0011] In a further preferred embodiment, the pressure in the first spray absorption tower is 1.6 MPa to 2.0 MPa, and the temperature is 25°C to 38°C.

[0012] In a further preferred embodiment, the ammonia-containing tail gas is further introduced into a dust removal tower for dust removal before entering the first spray absorption tower.

[0013] Applying a certain pressure and appropriately increasing the temperature during the treatment of the tail gas in the first spray absorption tower helps to improve the absorption of ammonia by water, increase the recovery efficiency of ammonia, reduce the ammonia content in the remaining tail gas, and reduce the pressure for subsequent spray absorption.

[0014] In a further preferred embodiment, during the process of introducing the ammonia-containing tail gas into the second spray absorption tower, pressure is also applied to the second spray absorption tower; the pressure is 14.3 MPa to 20 MPa.

[0015] In a further embodiment, the method for recovering and treating ammonia-containing tail gas from the synthesis of aromatic nitrile further includes the following step: filtering the ammonia-containing absorbent B obtained from ammonia absorption in the second spray absorption tower using a nanofiltration membrane to obtain secondary ammonia water. Using an ammonium ion-selective permeable nanofiltration membrane to treat the ammonia-containing absorbent B can efficiently remove impurities and other ions, thereby improving ammonia recovery.

[0016] In a further embodiment, the method for recovering and treating ammonia-containing tail gas in the later stage of aromatic nitrile synthesis further includes the following steps: passing the ammonia-containing tail gas into the first spray tower to obtain primary ammonia water, combining it with secondary ammonia water, and then heating it under vacuum conditions to recover ammonia gas.

[0017] In a further preferred embodiment, the heating temperature during the heating process is 80℃~90℃.

[0018] The above-described method for recovering and treating ammonia-containing tail gas from the downstream stage of aromatic nitrile synthesis includes the following steps:

[0019] S1. The ammonia-containing tail gas is passed into the dust removal tower for dust removal, resulting in tail gas I;

[0020] S2. Tail gas I is fed into the first spray tower and absorbed by absorbent A to reduce the ammonia content in the tail gas, thus obtaining primary ammonia water and tail gas II.

[0021] S3. Tail gas II is fed into the second spray tower and absorbed by absorbent B to obtain ammonia-containing absorbent B. The remaining tail gas is discharged.

[0022] S4. The ammonia-containing absorbent B is filtered using a nanofiltration membrane to obtain secondary ammonia water;

[0023] S5. Pass primary ammonia water and secondary ammonia water into the heating kettle, heat under vacuum conditions, and recover ammonia gas.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention provides a method for recovering and treating ammonia-containing tail gas in the later stages of aromatic nitrile synthesis. The method involves two-stage spray absorption of the tail gas using an absorbent, followed by membrane filtration, and finally vacuum heating to recover ammonia. This process, through the coordinated operation of each stage, significantly increases the recovery of ammonia from the tail gas, resulting in a low ammonia content and reduced air pollution. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] The following disclosure provides many different embodiments or examples for implementing the invention. To simplify the disclosure, specific examples are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0028] Ammonia oxidation is currently the mainstream method for the industrial production of aromatic nitrile compounds. The exhaust gas produced by this method contains a large amount of ammonia, and directly discharging this ammonia-containing exhaust gas would waste resources and cause pollution. Existing technologies generally condense the ammonia exhaust gas into dilute ammonia water or absorb the ammonia through a spray tower. However, the former produces dilute ammonia water with low concentration and large volume, meaning only a small portion can be recycled, and most of the dilute ammonia water is difficult to treat or extremely costly to treat. The latter typically uses water or hydrochloric acid to spray and absorb the ammonia exhaust gas into a corresponding ammonia nitrogen solution, which is then concentrated through evaporation for recycling. Using water for spray absorption requires multiple repeated sprays, resulting in low treatment efficiency, while hydrochloric acid spraying is costly and cannot completely prevent ammonia emissions.

[0029] This invention employs a two-stage spray absorption process using an absorbent to absorb ammonia from the exhaust gas. This maximizes the recovery of ammonia from the ammonia-containing exhaust gas, allowing the remaining exhaust gas to be directly discharged. The absorbent used to absorb the ammonia is then filtered through a membrane, and finally, the ammonia is recovered through vacuum heating, yielding ammonia with high purity. This process, through the coordinated operation of each stage, significantly increases the recovery of ammonia from the ammonia-containing exhaust gas, resulting in a low ammonia content in the treated exhaust gas and reducing air pollution.

[0030] To address the aforementioned issues, this invention provides a method for recovering and treating ammonia-containing tail gas in the downstream process of aromatic nitrile synthesis. The method involves sequentially passing the ammonia-containing tail gas into a first spray absorption tower and a second spray absorption tower, absorbing the ammonia in the tail gas into the liquid phase to achieve ammonia recovery, and directly discharging the waste gas.

[0031] Wherein, the absorbent A in the first spray absorption tower is water;

[0032] The absorbent B in the first spray absorption tower contains glycolic acid, vinylphosphonic acid, and aluminum sulfate.

[0033] In a further embodiment, the ammonia-containing tail gas is the tail gas generated in the production of aromatic nitrile compounds by the ammonia oxidation method; the aromatic nitrile compounds include, but are not limited to, any one of isophthalonitrile, o-phthalonitrile, o-chlorobenzonitrile, p-chlorobenzonitrile, 2,6-dichlorobenzonitrile, and 3,4-dichlorobenzonitrile.

[0034] In a further embodiment, the absorbent A of the first spray absorption tower is water; the absorbent B of the first spray absorption tower contains glycolic acid, vinylphosphonic acid and aluminum sulfate in a molar ratio of (3-5):(0.8-1):(0.1-0.15).

[0035] In a further preferred embodiment, the absorbent B further comprises pyrimethamine, and the molar ratio of pyrimethamine to glycolic acid in the absorbent B is 1:(0.3-0.5).

[0036] It should be noted that the ammonia in the ammonia-containing tail gas first passes through the first spray absorption tower. Part of the ammonia is absorbed by water in the liquid phase to obtain the first ammonia water, while some ammonia remains in the tail gas. The remaining tail gas is then passed into the second spray absorption tower. Utilizing the high solubility of ammonia in absorbent B in the second spray absorption tower, the ammonia in the tail gas is absorbed in the liquid phase to the maximum extent, thus achieving efficient removal and recovery of ammonia.

[0037] Furthermore, this invention uses a mixture of three substances in a specific ratio to form absorbent B. Compared to traditional spray absorption using sulfuric acid and phosphoric acid, this spray solution exhibits increased affinity for ammonia and higher solubility for ammonia, thereby improving the ammonia recovery rate. Moreover, its structure and phase remain unchanged before and after absorption, achieving highly efficient removal and recovery of ammonia. Additionally, this absorbent demonstrates high stability, maintaining excellent ammonia adsorption efficiency even after prolonged storage, allowing for continuous recycling and cost reduction. In actual production, it has been found that adding a certain amount of pyrimethamine to the absorbent further enhances the absorption of ammonia-containing gases and improves its stability.

[0038] In a further embodiment, the pressure in the first spray absorption tower is 1.6 MPa to 2.0 MPa, and the temperature is 25°C to 38°C.

[0039] It should be noted that applying a certain pressure and appropriately increasing the temperature during the treatment of the tail gas in the first spray absorption tower helps to improve the absorption of ammonia by water, increase the recovery efficiency of ammonia, reduce the ammonia content in the remaining tail gas, and reduce the pressure for subsequent spray absorption.

[0040] In a further embodiment, the ammonia-containing tail gas is further introduced into a dust removal tower for dust removal before entering the first spray absorption tower.

[0041] In a further embodiment, during the process of the ammonia-containing tail gas being introduced into the second spray absorption tower, pressure is also applied to the second spray absorption tower; the pressure is 14.3 MPa to 20 MPa.

[0042] It should be noted that during the process of treating the tail gas in the second spray absorption tower, applying appropriate pressure can further improve the absorption of ammonia in the ammonia-containing tail gas into the absorbent, thereby improving the recovery of ammonia.

[0043] In a further embodiment, the method for recovering and treating ammonia-containing tail gas in the downstream stage of aromatic nitrile synthesis further includes the following step: filtering the ammonia-containing absorbent B obtained from ammonia absorption in the second spray absorption tower using a nanofiltration membrane to obtain secondary ammonia water. Using an ammonium ion-selective permeable nanofiltration membrane to treat the ammonia-containing absorbent B can efficiently remove impurities and other ions, thereby improving ammonia recovery.

[0044] In a further embodiment, the method for recovering and treating ammonia-containing tail gas in the later stage of synthesizing aromatic nitrile further includes the following steps: the primary ammonia water obtained after passing the ammonia-containing tail gas into the first spray tower is combined with the secondary ammonia water and heated under vacuum conditions to recover ammonia gas.

[0045] In a further embodiment, the heating temperature during the heating process is 80°C to 90°C.

[0046] The present invention will be further described below by way of specific embodiments.

[0047] Example 1: A method for recovering and treating ammonia-containing tail gas in the later stage of aromatic nitrile synthesis, comprising the following steps:

[0048] S1. Ammonia-containing tail gas (tail gas from isophthalonitrile production) is passed into a dust removal tower for dust removal, resulting in tail gas I.

[0049] S2. Tail gas I is introduced into the first spray tower. The first spray tower is subjected to a pressure of 1.6MPa and a temperature of 25℃. Water is used for absorption to reduce the ammonia content in the tail gas, resulting in first-grade ammonia water and tail gas II.

[0050] S3. Tail gas II is fed into the second spray tower and absorbed by absorbent B to obtain ammonia-containing absorbent B. The remaining tail gas meets the emission standards.

[0051] Absorbent B was prepared by mixing glycolic acid, vinylphosphonic acid and aluminum sulfate in a molar ratio of 3:0.8:0.1.

[0052] S4. Absorbent B is filtered using a nanofiltration membrane to obtain secondary ammonia water;

[0053] S5. Pass the primary ammonia water and the secondary ammonia water into the heating kettle, heat to 80°C under vacuum conditions, and recover ammonia gas.

[0054] Example 2: A method for recovering and treating ammonia-containing tail gas in the later stage of aromatic nitrile synthesis, comprising the following steps:

[0055] S1. Ammonia-containing tail gas (tail gas from o-chlorobenzonitrile production) is passed into a dust removal tower for dust removal, resulting in tail gas I;

[0056] S2. Tail gas I is introduced into the first spray tower. The first spray tower is subjected to a pressure of 2.0 MPa and a temperature of 38°C. Water is used for absorption to reduce the ammonia content in the tail gas, resulting in first-grade ammonia water and tail gas II.

[0057] S3. Tail gas II is fed into the second spray tower and absorbed by absorbent B to obtain ammonia-containing absorbent B. The remaining tail gas meets the emission standards.

[0058] Absorbent B was prepared by mixing glycolic acid, vinylphosphonic acid and aluminum sulfate in a molar ratio of 5:1:0.15.

[0059] S4. The amino acid-containing spray solution is filtered using a nanofiltration membrane to obtain secondary ammonia water;

[0060] S5. Pass the primary ammonia water and the secondary ammonia water into the heating kettle, heat to 90°C under vacuum conditions, and recover ammonia gas.

[0061] Example 3: The difference from Example 2 is that no pressure is applied to the first spray tower in this example.

[0062] Example 4: The difference from Example 2 is that the absorbent B in the second spray tower in this example is prepared by mixing glycolic acid, vinylphosphonic acid and aluminum sulfate in a molar ratio of 2:1:0.05.

[0063] Example 5: The difference from Example 2 is that the absorbent B in the second spray tower in this example is prepared by mixing glycolic acid, vinylphosphonic acid and aluminum sulfate in a molar ratio of 6:1:0.2.

[0064] Example 6: The difference from Example 2 is that the absorbent B in the second spray tower in this example is only glycolic acid.

[0065] Example 7: The difference from Example 2 is that the absorbent B in the second spray tower in this example is prepared by mixing glycolic acid and vinylphosphonic acid in a molar ratio of 5:1.

[0066] Example 8: The difference from Example 2 is that the absorbent B in the second spray tower in this example is prepared by mixing glycolic acid and aluminum sulfate in a molar ratio of 5:0.15.

[0067] Example 9: The difference from Example 2 is that the spray liquid B in the second spray tower in this example is prepared by mixing glycolic acid, vinylphosphonic acid, aluminum sulfate and pyrimethamine in a molar ratio of 5:1:0.15:1.5.

[0068] Example 10: The difference from Example 2 is that a pressure of 14.3 MPa is applied in the second spray tower in this example.

[0069] Example 11: The difference from Example 2 is that a pressure of 20 MPa is applied in the second spray tower in this example.

[0070] Example 12: The difference from Example 2 is that a pressure of 25 MPa is applied in the second spray tower in this example.

[0071] Comparative Example 1: The difference from Example 2 is that the absorbent B in the second spray tower in this comparative example is sulfuric acid.

[0072] Comparative Example 2: The difference from Example 2 is that this comparative example does not include the step of spraying absorbent B. The specific steps are as follows:

[0073] S1. The ammonia-containing tail gas is passed into the dust removal tower for dust removal, resulting in tail gas I;

[0074] S2, exhaust gas I is introduced into the first spray tower. The first spray tower is subjected to a pressure of 2.0 MPa and a temperature of 38°C. Water is used for absorption to reduce the ammonia content in the exhaust gas, resulting in first-grade ammonia water and exhaust gas.

[0075] S3. Pass the primary ammonia solution into the heating kettle and heat it to 90°C under vacuum to recover the ammonia gas.

[0076] Comparative Example 3: The difference from Example 2 is that there is no water spraying step in this comparative example. The specific steps are as follows:

[0077] S1. The ammonia-containing tail gas is passed into the dust removal tower for dust removal, resulting in tail gas I;

[0078] S2. Tail gas I is fed into the second spray tower and absorbed by absorbent B to obtain ammonia-containing absorbent B. The remaining tail gas is discharged in compliance with standards.

[0079] Absorbent B was prepared by mixing glycolic acid, vinylphosphonic acid and aluminum sulfate in a molar ratio of 5:1:0.15.

[0080] S3. Ammonia-containing absorbent B is filtered using a nanofiltration membrane to obtain secondary ammonia water;

[0081] S4. Pass the primary ammonia solution and the secondary ammonia solution into the heating kettle, heat under vacuum conditions, and recover ammonia gas.

[0082] Experimental Example 1: The results of the treatment of ammonia-containing tail gas in the later stage of the synthesis of o-chlorobenzonitrile / isophthalonitrile in the above examples and comparative examples are shown in Table 1 below.

[0083] Table 1

[0084] Ammonia content in exhaust gas by group, mg / m³ 3 Ammonia recovery rate, % Example 1 0.28 98.7 Example 2 0.21 99.0 Example 3 0.43 97.4 Example 4 0.84 94.7 Example 5 0.67 98.5 Example 6 1.10 92.0 Example 7 0.78 95.0 Example 8 0.94 94.1 Example 9 0.06 99.8 Example 10 0.10 99.5 Example 11 0.07 99.6 Example 12 0.15 99.2 Comparative Example 1 0.98 92.8 Comparative Example 2 2.55 85.1 Comparative Example 3 1.18 90.6

[0085] As shown in Table 1, the ammonia concentration in the tail gas treated by the ammonia-containing tail gas treatment and recovery method provided by this invention is less than 0.3 mg / m³, as determined by Nessler's reagent spectrophotometry (HJ535-2009). 3 The lowest level reached was 0.06 mg / m³. 3 The concentration of pollutants must be below 1.5 mg / m³, as stipulated in the "Integrated Emission Standard for Air Pollutants". 3 The ammonia recovery rate is over 98%, with a maximum of over 99.5%, indicating a high ammonia recovery rate.

[0086] Experimental Example 2: Take absorbent B from Examples 1, 2 and 4 to 9, place it in an absorption tank, introduce ammonia gas at room temperature with stirring, and wait for the ammonia absorbent to reach absorption equilibrium. Calculate the amount of ammonia absorbed by measuring the change in ammonia pressure in the absorption tank.

[0087] After exposing spray solution B to air for 100 days, its ammonia absorption capacity was tested to examine its stability.

[0088] The test results are shown in Table 2 below.

[0089] Table 2

[0090] Group Hydrogen absorption capacity (mol / kg) after 100 days Hydrogen absorption capacity (mol / kg) Example 1 8.1 17.38 Example 2 8.1 77.50 Example 4 7.1 35.21 Example 5 7.9 45.45 Example 6 5.8 53.28 Example 7 7.0 55.13 Example 8 6.4 84.07 Example 9 8.8 68.32

[0091] As shown in Table 2, the absorbent B provided by this invention exhibits excellent ammonia absorption capacity, exceeding 8 mol / kg, and even after 100 days, its ammonia absorption capacity remains above 7 mol / kg, demonstrating high stability. This indicates that the present invention, by mixing three or four substances in a certain proportion to form absorbent B, improves the absorbent's ammonia absorption capacity and stability.

[0092] This application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this application without departing from the spirit of this application.

Claims

1. A method for recovering and treating ammonia-containing tail gas in the downstream process of aromatic nitrile synthesis, characterized in that, Includes the following steps: S1. The ammonia-containing tail gas is passed into the dust removal tower for dust removal, resulting in tail gas I; S2. Tail gas I is fed into the first spray tower and absorbed by absorbent A to reduce the ammonia content in the tail gas, resulting in primary ammonia water and tail gas II. S3. Tail gas II is fed into the second spray tower and absorbed by absorbent B to obtain ammonia-containing absorbent B. The remaining tail gas is discharged. S4. The ammonia-containing absorbent B is filtered using a nanofiltration membrane to obtain secondary ammonia water; S5. Pass the primary ammonia solution and the secondary ammonia solution into the heating kettle, heat under vacuum conditions, and recover ammonia gas; Wherein, the absorbent A is water; The absorbent B comprises glycolic acid, vinylphosphonic acid, and aluminum sulfate in a molar ratio of 3–5:0.8–1:0.1–0.15; The pressure in the first spray absorption tower is 1.6MPa to 2.0MPa, and the temperature is 25℃ to 38℃.

2. The method for recovering and treating ammonia-containing tail gas in the downstream process of synthesizing aromatic nitrile according to claim 1, characterized in that, The absorbent B also contains pyrimethamine, and the molar ratio of pyrimethamine to glycolic acid in the absorbent B is 1:0.3 to 0.

5.

3. The method for recovering and treating ammonia-containing tail gas in the downstream process of synthesizing aromatic nitrile according to claim 1, characterized in that, During the process of the ammonia-containing tail gas being introduced into the second spray absorption tower, pressure is also applied to the second spray absorption tower.

4. The method for recovering and treating ammonia-containing tail gas in the later stage of aromatic nitrile synthesis according to claim 3, characterized in that, The applied pressure is 14.3 MPa to 20 MPa.

5. The method for recovering and treating ammonia-containing tail gas in the downstream process of synthesizing aromatic nitrile according to claim 1, characterized in that, In step S5, the heating temperature during the heating process is 80℃~90℃.