A recovery system and recovery method for mixed waste gas in chlorfenapyr production

Abstract

The invention discloses a recovery system and a recovery method for mixed waste gas in the production of chlorfenapyr. The recovery system includes a condenser, a cryogenic freezer, a spray tower, a phenol-toluene storage tank, a phenol storage tank and a toluene storage tank; the recovery method includes the following steps: S1: condensation; S2: purification. Advantages: the mixed waste gas discharged from the preparation of the intermediate 4-(p-chlorophenyl)-2-trifluoromethyl-3-oxazoline-5-one is first condensed and separated by a condenser and a cryogenic freezer to separate trifluoroacetyl chloride, and trifluoroacetyl chloride can be directly used to prepare the intermediate; the gas discharged by the cryogenic freezer is sprayed with a phenol-toluene solution by a spray tower to wash away the residual trifluoroacetyl chloride in the gas, and purified hydrogen chloride gas is obtained, and the hydrogen chloride can be sent to an etherification reactor, and the excess hydrogen chloride reacts with polyformaldehyde and ethanol to obtain another raw material chloromethyl ethanol ether for producing chlorfenapyr; and two etherification reactors are provided, which can realize the absorption of excess hydrogen chloride and improve the utilization rate of hydrogen chloride.

Description

Technical Field

[0001] The invention relates to the technical field of chlorfenapyr production, and in particular to a method for recovering mixed waste gas in chlorfenapyr production. Background Art

[0002] Chlorfenapyr is a pyrrole insecticide with a wide range of applications, including use on vegetables, fruit trees, and ornamental plants. It is widely used to control insect pests and mites on crops such as cotton, vegetables, citrus fruits, grapes, and soybeans. It is 4-16 times more effective than conventional agents such as methomyl and acephate. It is also used to control termites. Its insecticidal mechanism is to block mitochondrial oxidative phosphorylation. It has stomach toxicity, limited contact activity, and systemic activity against pests.

[0003] 4-(p-Chlorophenyl)-2-trifluoromethyl-3-oxazolin-5-one is an important intermediate in the synthesis of brofenapyr. It primarily reacts with p-chlorophenylglycine, phosphorus oxychloride, and trifluoroacetic acid in a lactone synthesis reactor. This reaction produces a large amount of mixed waste gas containing hydrogen chloride and trifluoroacetyl chloride, with trifluoroacetyl chloride comprising approximately 30% and hydrogen chloride 70%. Currently, this mixed waste gas is primarily treated in a water absorption tower, where trifluoroacetyl chloride reacts with water to produce trifluoroacetic acid and hydrogen chloride, thereby forming waste hydrochloric acid containing trifluoroacetic acid. However, the waste hydrochloric acid treatment system is complex, difficult to process, and energy-intensive, significantly impacting overall production. Summary of the Invention

[0004] The first object of the present invention is to provide a system for recovering mixed waste gas in the production of chlorfenapyr.

[0005] The second object of the present invention is to provide a method for recovering mixed waste gas in the production of chlorfenapyr.

[0006] The first object of the present invention is achieved by the following scheme: a recovery system for mixed waste gas in the production of chlorfenapyr, which includes a condenser, a cryogenic refrigerator, a spray tower, a phenol toluene storage tank, a phenol storage tank and a toluene storage tank, the exhaust port of the lactone synthesis kettle is connected to the inlet of the condenser, the outlet of the condenser is connected to the top inlet of the cryogenic refrigerator through a first connecting pipe, the bottom outlet of the cryogenic refrigerator is connected to the air inlet of the spray tower through a second connecting pipe, the lower ends of the first connecting pipe and the second connecting pipe are respectively connected to the inlet of the lactone synthesis kettle through a U-shaped tube; the top of the spray tower is connected to a hydrogen chloride discharge pipe, and the bottom of the spray tower is connected to the phenol toluene storage tank. The inlet of the liquid tank is connected; the outlet of the phenol-toluene storage tank is connected to the inlet of the circulation pump, and the outlet of the circulation pump is divided into two paths, one path is connected to the liquid inlet of the spray tower through a circulation pipe, and the other path is connected to a regeneration pipe, and a regeneration control valve is installed on the regeneration pipe; the outlet of the phenol storage tank and the outlet of the toluene storage tank are respectively connected to the inlet of the phenol-toluene storage tank through a material pipe, and a first control valve is installed on the material pipe; a phenol concentration online detector is installed on the pipeline on the inlet side of the circulation pump, the phenol concentration online detector is connected to the input end of the controller, and the output end of the controller is respectively connected to the regeneration control valve and the first control valve.

[0007] Furthermore, it also includes a paraformaldehyde storage tank, an ethanol storage tank and two etherification reactors, the outlet of the hydrogen chloride discharge pipe is connected to the air inlet of the two etherification reactors through an air supply pipe, and an air supply control valve is installed on the air supply pipe; the exhaust port of the etherification reactor is connected to the air inlet of another etherification reactor through a recovery pipe, and a recovery control valve is installed on the recovery pipe; the outlets of the paraformaldehyde storage tank and the ethanol storage tank are connected to the feed ports of the two etherification reactors through a feeding pipe, and a feeding control valve is installed on the feeding pipe.

[0008] Furthermore, a hydrogen chloride concentration detector is installed on the etherification reactor, the hydrogen chloride concentration detector is connected to the input end of the controller, and the output end of the controller is connected to the recovery control valve and the gas supply control valve.

[0009] The second object of the present invention is achieved by the following scheme: a method for recovering mixed waste gas in the production of chlorfenapyr, characterized in that it comprises the following steps:

[0010] S1: Condensation

[0011] The mixed waste gas discharged from the lactone synthesis reactor is initially cooled in a condenser and then deep-cooled in a cryogenic refrigerator, and the trifluoroacetyl chloride in the mixed waste gas is condensed into trifluoroacetyl chloride liquid;

[0012] S2: Purification

[0013] The gas discharged from the S1 condenser is sent to the spray tower, and the trifluoroacetyl chloride in the gas is absorbed by a phenol toluene solution at 25-35°C to obtain purified hydrogen chloride gas.

[0014] Furthermore, in S1, the temperature of the cooling medium of the condenser is 5-15°C, and the temperature of the cooling medium of the cryogenic freezer is -40°C to -70°C.

[0015] Furthermore, in S2, the phenol concentration of the phenol toluene solution is 5% to 50%.

[0016] Furthermore, it also includes the following steps:

[0017] S3: Open the corresponding feed control valves of the paraformaldehyde storage tank and the ethanol storage tank, and add paraformaldehyde and ethanol into an etherification reactor;

[0018] S4: After S3 is completed, the gas supply control valve corresponding to the etherification reaction kettle in S3 is opened, and the excess hydrogen chloride gas obtained in S2 is introduced into the etherification reaction kettle, the temperature is controlled at 0-5°C, and the reaction is carried out for 6 hours;

[0019] S5: After S4 is completed, the mixture is allowed to stand for 1 hour to achieve stratification of the material and liquid;

[0020] S6: After S5 is completed, the lower layer of liquid in the etherification reaction kettle is separated and the upper layer of chloromethyl ethyl ether is recovered.

[0021] Furthermore, in S3, the mass ratio of paraformaldehyde and ethanol fed into the etherification reactor is 11:16.

[0022] Furthermore, in S4, the concentration of hydrogen chloride in the etherification reactor is detected by a hydrogen chloride concentration detector, and when it is detected that the hydrogen chloride concentration reaches a set value, the corresponding gas supply control valve is closed.

[0023] Furthermore, in S6, while separating the lower layer of liquid in the etherification reaction kettle, the following operations are performed: first, paraformaldehyde and ethanol in a mass ratio of 11:16 are added to another etherification reaction kettle, and the temperature is controlled at 0-5°C; then, the recovery control valve corresponding to the etherification reaction kettle in S6 is opened to discharge the excess hydrogen chloride inside it into the other etherification reaction kettle, and then the recovery control valve corresponding to the etherification reaction kettle in S6 is closed; finally, the gas supply control valve corresponding to the other etherification reaction kettle is opened, and the processes of S4-S6 are repeated.

[0024] The advantages of the present invention are as follows: mixed waste gas discharged during the preparation of the intermediate 4-(p-chlorophenyl)-2-trifluoromethyl-3-oxazolin-5-one is first condensed and separated into trifluoroacetyl chloride through a condenser and a cryogenic refrigerator, and the trifluoroacetyl chloride can be directly used for the preparation of the intermediate for producing chlorfenapyr, thereby realizing the recycling of the trifluoroacetyl chloride; the gas discharged from the cryogenic refrigerator is sprayed with a phenol toluene solution through a spray tower to wash away residual trifluoroacetyl chloride in the gas, thereby obtaining purified hydrogen chloride gas, which can be fed into an etherification reactor, and excess hydrogen chloride reacts with paraformaldehyde and ethanol to obtain chloromethyl ethanol ether, another raw material for producing chlorfenapyr; and two etherification reactors are provided, thereby realizing the absorption of excess hydrogen chloride, improving the utilization rate of hydrogen chloride, and realizing the recycling of hydrogen chloride. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the overall structure of this embodiment.

[0026] Figure 2 This is a diagram of the controller connection.

[0027] Condenser 1, cryogenic cooler 2, spray tower 3, phenol-toluene storage tank 4, phenol storage tank 5, toluene storage tank 6, lactone synthesis reactor 7, first connecting pipe 8, second connecting pipe 9, U-shaped tube 10, hydrogen chloride discharge pipe 11, circulation pump 12, circulation pipe 13, regeneration pipe 14, regeneration control valve 15, feed pipe 16, first control valve 17, phenol concentration online detector 18, controller 19, paraformaldehyde storage tank 20, ethanol storage tank 21, etherification reactor 22, air supply pipe 23, air supply control valve 24, recovery pipe 25, recovery control valve 26, feed control valve 27, hydrogen chloride concentration detector 28, hydrogen chloride storage tank 29. DETAILED DESCRIPTION

[0028] Example 1: Figure 1 and Figure 2As shown, a recovery system for mixed waste gas in the production of chlorfenapyr comprises a condenser 1, a cryogenic refrigerator 2, a spray tower 3, a phenol-toluene storage tank 4, a phenol storage tank 5 and a toluene storage tank 6. The exhaust port of the lactone synthesis reactor 7 is connected to the inlet of the condenser 1, the outlet of the condenser 1 is connected to the top inlet of the cryogenic refrigerator 2 through a first connecting pipe 8, the bottom outlet of the cryogenic refrigerator 2 is connected to the air inlet of the spray tower 3 through a second connecting pipe 9, the lower ends of the first connecting pipe 8 and the second connecting pipe 9 are connected to the inlet of the lactone synthesis reactor 7 through a U-shaped tube 10 respectively; the top of the spray tower 3 is connected to a hydrogen chloride discharge pipe 11, and the bottom of the spray tower 3 is connected to the inlet of the phenol-toluene storage tank 4; The outlet of the benzene storage tank 4 is connected to the inlet of the circulation pump 12. The outlet of the circulation pump 12 is divided into two paths, one path is connected to the liquid inlet of the spray tower 3 through the circulation pipe 13, and the other path is connected to the regeneration pipe 14, and a regeneration control valve 15 is installed on the regeneration pipe 14; the outlet of the phenol storage tank 5 and the outlet of the toluene storage tank 6 are respectively connected to the inlet of the phenol-toluene storage tank 4 through the material pipe 16, and a first control valve 17 is installed on the material pipe 16; a phenol concentration online detector 18 is installed on the pipeline on the inlet side of the circulation pump 12, and the phenol concentration online detector 18 is connected to the input end of the controller 19, and the output end of the controller 19 is respectively connected to the regeneration control valve 15 and the first control valve 17. The mixed gas discharged from the lactone synthesis reactor 7 for preparing the intermediate 4-(p-chlorophenyl)-2-trifluoromethyl-3-oxazolin-5-one is first cooled by a condenser 1 and then enters a cryogenic refrigerator 2 for cryogenic cooling via a first connecting pipe 8. The gas discharged from the cryogenic refrigerator 2 enters a spray tower 3 via a second connecting pipe 9. The gas is then washed and purified with a phenol toluene solution delivered by a circulating pump 12, absorbing the trifluoroacetyl chloride carried therein. The purified hydrogen chloride gas is then discharged via a hydrogen chloride discharge pipe 11. The trifluoroacetyl chloride liquid discharged from the condenser 1 and cryogenic refrigerator 2 is returned to the lactone synthesis reactor 7 via a U-shaped pipe 10 and used as a raw material for preparing the intermediate 4-(p-chlorophenyl)-2-trifluoromethyl-3-oxazolin-5-one, thereby achieving the recycling of the trifluoroacetyl chloride. The phenol concentration in the phenol-toluene storage tank 4 can be detected by the phenol concentration online detector 18. When the phenol concentration is detected to be lower than the set value, the regeneration control valve 15 and the first control valve 17 are opened, so that part of the phenol-toluene solution sent out by the circulation pump 12 is sent to the subsequent solvent regeneration system through the regeneration pipe 14, and phenol and toluene are replenished into the phenol-toluene storage tank 4 at the same time.

[0029] It also includes a paraformaldehyde storage tank 20, an ethanol storage tank 21 and two etherification reaction kettles 22. The outlet of the hydrogen chloride discharge pipe 11 is connected to the inlet of the hydrogen chloride storage tank 29. The outlet of the hydrogen chloride storage tank 29 is connected to the air inlets of the two etherification reaction kettles 22 through an air supply pipe 23, and an air supply control valve 24 is installed on the air supply pipe 23; the exhaust port of the etherification reaction kettle 22 is connected to the air inlet of another etherification reaction kettle 22 through a recovery pipe 25, and a recovery control valve 26 is installed on the recovery pipe 25; the outlets of the paraformaldehyde storage tank 20 and the ethanol storage tank 21 are connected to the feed ports of the two etherification reaction kettles 22 through a feeding pipe 16, and a feeding control valve 27 is installed on the feeding pipe 16. The hydrogen chloride discharged from the hydrogen chloride discharge pipe 11 is stored in a hydrogen chloride storage tank 29. The paraformaldehyde storage tank 20 and the ethanol storage tank 21 provide paraformaldehyde and ethanol, respectively, to the etherification reactor 22. Two etherification reactors 22 are used as standby units. The hydrogen chloride discharged from the phenol-toluene storage tank 4 is fed into the etherification reactor 22 via the hydrogen chloride discharge pipe 11 until it becomes excessive. After the reaction is completed and unloading is required, paraformaldehyde and ethanol are first added to the standby etherification reactor 22. The etherification reactor 22 is then unloaded. Excess hydrogen chloride gas in the etherification reactor 22 is then fed to the standby etherification reactor 22 via the recovery pipe 25 to recover the hydrogen chloride gas. At the same time, the hydrogen chloride fed from the hydrogen chloride discharge pipe 11 is fed into the standby etherification reactor 22, which then becomes the etherification reactor 22 in production. The other etherification reactor 22 is then unloaded and placed in standby.

[0030] A hydrogen chloride concentration detector 28 is installed on the etherification reactor 22. This detector is connected to the input of the controller 19, while the output of the controller 19 is connected to the recovery control valve 26 and the gas supply control valve 24. The hydrogen chloride concentration detector 28 measures the hydrogen chloride concentration within the etherification reactor 22. When the hydrogen chloride concentration reaches a set level, the corresponding gas supply control valve 24 is closed.

[0031] Example 2: A method for recovering mixed waste gas in chlorfenapyr production, comprising the following steps:

[0032] S1: Condensation

[0033] The mixed exhaust gas from the lactone synthesis reactor is initially cooled in a condenser and then cryogenically cooled in a cryogenic freezer. The trifluoroacetyl chloride in the mixed exhaust gas is condensed into liquid trifluoroacetyl chloride. The cooling medium temperature of the condenser is 5-15°C, and the cooling medium temperature of the cryogenic freezer is -40°C to -70°C. The liquid trifluoroacetyl chloride condensed in the condenser and cryogenic freezer is returned to the lactone synthesis reactor through a U-shaped pipe for reuse.

[0034] S2: Purification

[0035] The gas discharged from the S1 condenser is sent to a spray tower, where it is absorbed by a phenol-toluene solution at 25-35°C, producing purified hydrogen chloride gas. The hydrogen chloride gas is then sent to a hydrogen chloride storage tank through a hydrogen chloride discharge pipe for storage. The phenol concentration in the phenol-toluene solution is 5% to 50%.

[0036] The phenol-toluene solution at the bottom of the spray tower is discharged into the phenol-toluene solution storage tank. The phenol concentration in the phenol-toluene storage tank can be detected by an online phenol concentration detector. When the phenol concentration is detected to be lower than the set value, the regeneration control valve and the first control valve are opened to allow part of the phenol-toluene solution sent out by the circulation pump to be sent to the subsequent solvent regeneration system through the regeneration pipe. At the same time, phenol and toluene are added to the phenol-toluene storage tank through the material pipe.

[0037] S3: Open the feeding control valves corresponding to the paraformaldehyde storage tank and the ethanol storage tank, add paraformaldehyde and ethanol in a mass ratio of 11:16 into an etherification reactor, and then close the feeding control valves.

[0038] S4: After S3 is completed, the gas supply control valve corresponding to the etherification reaction kettle in S3 is opened, and the excess hydrogen chloride gas obtained in S2 is introduced into the etherification reaction kettle, the temperature is controlled at 0-5°C, and the reaction is carried out for 6 hours;

[0039] During the process of introducing hydrogen chloride, the concentration of hydrogen chloride in the etherification reactor is detected by a hydrogen chloride concentration detector. When the concentration of hydrogen chloride reaches the set value, the corresponding gas supply control valve is closed.

[0040] S5: After S4, the mixture was allowed to stand for 1 hour to separate the material and liquid, with the upper layer being chloromethyl ethyl ether.

[0041] S6: After S5 is completed, the lower layer of liquid in the etherification reaction kettle is separated and the upper layer of chloromethyl ethyl ether is recovered.

[0042] In S6, while removing the lower layer of liquid in the etherification reactor, the following operations are performed: first, paraformaldehyde and ethanol in a mass ratio of 11:16 are added to another etherification reactor, and the temperature is controlled at 0-5°C; then, the recovery control valve corresponding to the etherification reactor in S6 is opened to discharge the excess hydrogen chloride therein into the other etherification reactor; then, the recovery control valve corresponding to the etherification reactor in S6 is closed; finally, the gas supply control valve corresponding to the other etherification reactor is opened, and the processes of S4-S6 are repeated. Through the above operations, the excess hydrogen chloride in the etherification reactor after the reaction can be recovered and reused, thereby improving the utilization rate of hydrogen chloride.

[0043] In addition, the trifluoroacetyl chloride liquid obtained by condensation of S1 can be used to replace trifluoroacetic acid for the preparation of 4-(p-chlorophenyl)-2-trifluoromethyl-3-oxazolin-5-one; specifically, the process comprises the following steps:

[0044] S7: Add 1580 kg of acetonitrile and 500 kg of p-chlorophenylglycine to a lactone synthesis kettle, stir for 15 minutes, and control the temperature at 20°C to 25°C;

[0045] S8: After S7 is completed, 486 kg of trifluoroacetyl chloride liquid obtained in S1 is added to the lactone synthesis kettle and kept warm for 30 minutes, with the temperature controlled at 20°C to 30°C;

[0046] S9: After S8, 13.76 kg of triethylamine was added dropwise to the internal chemical reaction kettle over a period of 1 to 1.5 hours. The mixture was kept warm for 15 minutes and the temperature was controlled at 20°C to 30°C.

[0047] S10: After S9 is completed, 440 kg of phosphorus trichloride is slowly added dropwise to the internal chemical reaction kettle within 1 to 1.5 hours, and the mixture is kept warm for 15 minutes;

[0048] S11: After S10, slowly raise the temperature to 60°C to 65°C and keep warm for 4 to 5 hours;

[0049] S12: After S11, the temperature is continued to rise to 70° C. to 75° C. and kept warm for 2 h to obtain 4-(p-chlorophenyl)-2-trifluoromethyl-3-oxazolin-5-one.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for recovering mixed waste gas in the production of chlorfenapyr, characterized in that: The invention relates to a method for recovering mixed waste gas containing hydrogen chloride and trifluoroacetyl chloride in a lactone synthesis kettle, wherein the method comprises a condenser, a cryogenic refrigerator, a spray tower, a phenol toluene storage tank, a phenol storage tank and a toluene storage tank, wherein the exhaust port of the lactone synthesis kettle is connected to the inlet of the condenser, the outlet of the condenser is connected to the top inlet of the cryogenic refrigerator through a first connecting pipe, the bottom outlet of the cryogenic refrigerator is connected to the air inlet of the spray tower through a second connecting pipe, the lower ends of the first connecting pipe and the second connecting pipe are respectively connected to the inlet of the lactone synthesis kettle through a U-shaped pipe; the top of the spray tower is connected to a hydrogen chloride discharge pipe, the bottom of the spray tower is connected to the inlet of the phenol toluene storage tank, and the bottom of the spray tower is connected to the inlet of the phenol toluene storage tank. The outlet of the phenol-toluene storage tank is connected with the inlet of a circulation pump, and the outlet of the circulation pump is divided into two paths, one path is connected with the liquid inlet of the spray tower through a circulation pipe, and the other path is connected with a regeneration pipe, and a regeneration control valve is installed on the regeneration pipe; the outlet of the phenol storage tank and the outlet of the toluene storage tank are respectively connected with the inlet of the phenol-toluene storage tank through a material pipe, and a first control valve is installed on the material pipe; a phenol concentration online detector is installed on the pipeline on the inlet side of the circulation pump, and the phenol concentration online detector is connected to the input end of the controller, and the output end of the controller is respectively connected to the regeneration control valve and the first control valve.

2. The system for recovering mixed waste gas in the production of chlorfenapyr according to claim 1, characterized in that: It also includes a paraformaldehyde storage tank, an ethanol storage tank and two etherification reactors. The outlet of the hydrogen chloride discharge pipe is connected to the inlet of the hydrogen chloride storage tank, and the outlet of the hydrogen chloride storage tank is connected to the air inlets of the two etherification reactors through air supply pipes, respectively, and an air supply control valve is installed on the air supply pipes; the exhaust port of the etherification reactor is connected to the air inlet of another etherification reactor through a recovery pipe, and a recovery control valve is installed on the recovery pipe; the outlets of the paraformaldehyde storage tank and the ethanol storage tank are connected to the feed ports of the two etherification reactors through feeding pipes, respectively, and a feeding control valve is installed on the feeding pipes.

3. The system for recovering mixed waste gas in the production of chlorfenapyr according to claim 2, characterized in that: A hydrogen chloride concentration detector is installed on the etherification reaction kettle. The hydrogen chloride concentration detector is connected to the input end of the controller, and the output end of the controller is connected to the recovery control valve and the gas supply control valve.

4. A method for recovering mixed waste gas in the production of chlorfenapyr, characterized in that: A system for recovering mixed waste gas in the production of chlorfenapyr as claimed in any one of claims 1 to 3 comprises the following steps: S1: Condensation The mixed waste gas discharged from the lactone synthesis reactor is initially cooled by a condenser and then deep-cooled by a deep cooler, and the trifluoroacetyl chloride in the mixed waste gas is condensed into trifluoroacetyl chloride liquid; S2: Purification The gas discharged from the S1 condenser is sent to a spray tower, and trifluoroacetyl chloride in the gas is absorbed by a phenol toluene solution at 25-35°C to obtain purified hydrogen chloride gas.

5. The method for recovering mixed waste gas in the production of chlorfenapyr according to claim 4, characterized in that: In S1, the cooling medium temperature of the condenser is 5-15°C, and the cooling medium temperature of the cryogenic freezer is -40°C to -70°C.

6. The method for recovering mixed waste gas in the production of chlorfenapyr according to claim 4, characterized in that: In S2, the phenol concentration of the phenol toluene solution is 5% to 50%.

7. The method for recovering mixed waste gas in the production of chlorfenapyr according to claim 4, characterized in that: It also includes the following steps: S3: Open the feeding control valves corresponding to the paraformaldehyde storage tank and the ethanol storage tank, and add paraformaldehyde and ethanol into an etherification reactor; S4: After S3 is completed, the gas supply control valve corresponding to the etherification reaction kettle in S3 is opened, and the hydrogen chloride gas obtained in S2 is excessively introduced into the etherification reaction kettle, the temperature is controlled at 0-5°C, and the reaction is carried out for 6 hours; S5: After S4 is completed, the mixture is allowed to stand for 1 hour to achieve stratification of the feed and liquid; S6: After S5 is completed, the lower layer of liquid in the etherification reaction kettle is separated and the upper layer of chloromethyl ethyl ether is recovered.

8. The method for recovering mixed waste gas in the production of chlorfenapyr according to claim 7, characterized in that: In S3, the mass ratio of the paraformaldehyde and ethanol fed into the etherification reactor is 11:

16.

9. The method for recovering mixed waste gas in the production of chlorfenapyr according to claim 7, characterized in that: In S4, the concentration of hydrogen chloride in the etherification reaction kettle is detected by a hydrogen chloride concentration detector, and when it is detected that the concentration of hydrogen chloride reaches a set value, the corresponding gas supply control valve is closed.

10. The method for recovering mixed waste gas in the production of chlorfenapyr according to claim 7, characterized in that: In S6, the lower layer liquid in the etherification reactor is separated and the following operations are performed at the same time: first, polyformaldehyde and ethanol in a mass ratio of 11:16 are added to another etherification reactor, and the temperature is controlled at 0-5°C; then, the recovery control valve corresponding to the etherification reactor in S6 is opened to discharge the excess hydrogen chloride inside it into another etherification reactor, and then the recovery control valve corresponding to the etherification reactor in S6 is closed; finally, the gas supply control valve corresponding to the other etherification reactor is opened, and the process of S4-S6 is repeated.

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