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 chlorfenapyr production. The recovery system comprises a condenser, a deep freezer, a spray tower, a phenol and toluene liquid storage tank, a phenol storage tank and a toluene storage tank, the recovery method comprises the following steps: S1, condensing; and S2, purifying. The method has the advantages that mixed waste gas discharged during preparation of the intermediate 4-(p-chlorphenyl)-2-trifluoromethyl-3-oxazoline-5-ketone is firstly condensed through the condenser and the deep freezer to separate trifluoroacetyl chloride, and the trifluoroacetyl chloride can be directly used for preparing the intermediate; a phenol toluene solution is sprayed on gas discharged by the deep freezer through a spray tower to wash off residual trifluoroacetyl chloride in the gas to obtain purified hydrogen chloride gas, hydrogen chloride can be fed into an etherification reaction kettle, and excessive hydrogen chloride reacts with paraformaldehyde and ethanol to obtain another raw material chloromethyl ethyl alcohol ether for producing chlorfenapyr; the two etherification reaction kettles are arranged, so that excessive hydrogen chloride can be absorbed, and the utilization rate of hydrogen chloride is increased.

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 compound insecticide with a wide range of applications. It can be used for vegetables, fruit trees, ornamental plants, etc. It can be widely used to control pests and mites on various crops such as cotton, vegetables, citrus, grapes and soybeans. Its efficacy is 4-16 times higher than that of conventional agents such as methomyl and acephate. It can also be used to control termites. Its insecticidal mechanism is to block the oxidative phosphorylation of mitochondria. It has stomach poison and certain contact killing and systemic activity against pests.

[0003] 4-(p-chlorophenyl)-2-trifluoromethyl-3-oxazolin-5-one is an important intermediate in the synthesis of chlorfenapyr. It mainly uses p-chlorophenylglycine, phosphorus oxychloride and trifluoroacetic acid as raw materials to react in a lactone synthesis reactor. A large amount of mixed waste gas containing hydrogen chloride and trifluoroacetyl chloride is produced during the reaction, of which trifluoroacetyl chloride is about 30% and hydrogen chloride is about 70%. At present, this part of the mixed waste gas is mainly sent to a water absorption tower for treatment. Trifluoroacetyl chloride reacts with water to generate trifluoroacetic acid and hydrogen chloride, thereby forming waste hydrochloric acid containing trifluoroacetic acid. However, the treatment system of waste hydrochloric acid is complicated, difficult to treat, and energy consumption is high, which brings great inconvenience to the entire 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 freezer, 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 freezer through a first connecting pipe, the bottom outlet of the cryogenic freezer 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 phenol toluene storage tank, 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, 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: 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.

[0010] Furthermore, 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.

[0011] Furthermore, in S2, the phenol concentration of the phenol toluene solution is 5% to 50%. Furthermore, 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.

[0012] Furthermore, in S3, the mass ratio of the paraformaldehyde and ethanol fed into the etherification reactor is 11:16.

[0013] Furthermore, 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.

[0014] Furthermore, in S6, while the lower layer of liquid in the etherification reaction kettle is separated, the following operations are performed: first, polyformaldehyde and ethanol with 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 another 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 process of S4-S6 is repeated.

[0015] The invention has the following advantages: the mixed waste gas discharged during the preparation of the intermediate 4-(p-chlorophenyl)-2-trifluoromethyl-3-oxazoline-5-one is first condensed and separated into trifluoroacetyl chloride through a condenser and a deep freezer, and the trifluoroacetyl chloride can be directly used for the preparation of the intermediate for the production of chlorfenapyr, thereby realizing the recycling of the trifluoroacetyl chloride; the gas discharged from the deep freezer is sprayed with a phenol toluene solution through a spray tower to wash away the residual trifluoroacetyl chloride in the gas, thereby obtaining purified hydrogen chloride gas, and the hydrogen chloride can be fed into an etherification reaction kettle, and the excess hydrogen chloride reacts with polyformaldehyde and ethanol to obtain chloromethyl ethanol ether, another raw material for the production of chlorfenapyr; and two etherification reaction kettles 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

[0016] Figure 1 It is a schematic diagram of the overall structure of this embodiment.

[0017] Figure 2 This is a diagram of the controller connection.

[0018] 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 pipe 10, hydrogen chloride discharge pipe 11, circulation pump 12, circulation pipe 13, regeneration pipe 14, regeneration control valve 15, material pipe 16, first control valve 17, phenol concentration online detector 18, controller 19, paraformaldehyde storage tank 20, ethanol storage tank 21, etherification reactor 22, gas supply pipe 23, gas 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

[0019] Example 1: Figure 1 and Figure 2As shown, a recovery system for mixed waste gas in chlorfenapyr production comprises a condenser 1, a cryogenic freezer 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 a 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 freezer 2 through a first connecting pipe 8, the bottom outlet of the cryogenic freezer 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 pipe 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 phenol toluene 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 firstly cooled by the condenser 1, and then enters the cryogenic refrigerator 2 through the first connecting pipe 8 for deep cooling. The gas discharged from the cryogenic refrigerator 2 enters the spray tower 3 through the second connecting pipe 9, and is washed and purified by the phenol toluene solution sent by the circulating pump 12, and the trifluoroacetyl chloride carried therein is absorbed. The purified hydrogen chloride gas is discharged through the hydrogen chloride discharge pipe 11. Among them, the trifluoroacetyl chloride liquid discharged from the condenser 1 and the cryogenic refrigerator 2 is sent back to the lactone synthesis reactor 7 through the U-shaped tube 10, and is used as a raw material for preparing the intermediate 4-(p-chlorophenyl)-2-trifluoromethyl-3-oxazolin-5-one, thereby realizing the recycling of 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 to allow part of the phenol-toluene solution delivered by the circulation pump 12 to be delivered to the subsequent solvent regeneration system through the regeneration pipe 14, and at the same time, phenol and toluene are added to the phenol-toluene storage tank 4.

[0020] 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 a gas supply pipe 23, and a gas supply control valve 24 is installed on the gas 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 the hydrogen chloride storage tank 29, and the polyformaldehyde storage tank 20 and the ethanol storage tank 21 provide polyformaldehyde and ethanol to the etherification reactor 22 respectively, and the two etherification reactors 22 are used in a standby mode; the hydrogen chloride discharged from the phenol toluene storage tank 4 is sent to the etherification reactor 22 through the hydrogen chloride discharge pipe 11 until it is excessive. After the reaction is completed, when unloading is required, polyformaldehyde and ethanol are first added to the standby etherification reactor 22, and then the etherification reactor 22 after the reaction is unloaded, and at the same time, the excess hydrogen chloride gas in the etherification reactor 22 after the reaction is sent to the standby etherification reactor 22 through the recovery pipe 25 to realize the recovery of hydrogen chloride gas, and at the same time, the hydrogen chloride sent from the hydrogen chloride discharge pipe 11 is passed into the standby etherification reactor 22, and the standby etherification reactor 22 is converted into the etherification reactor 22 in production. The other etherification reactor 22 is ready for use after unloading.

[0021] A hydrogen chloride concentration detector 28 is installed on the etherification reactor 22. The hydrogen chloride concentration detector 28 is connected to the input end of the controller 19, and the output end 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 can detect the hydrogen chloride concentration in the etherification reactor 22. When the concentration of hydrogen chloride reaches the set concentration, the corresponding gas supply control valve 24 can be closed.

[0022] Embodiment 2: A method for recovering mixed waste gas in the production of chlorfenapyr, comprising the following steps: S1: Condensation The mixed waste gas discharged from the lactone synthesis reactor is initially cooled by the condenser and then deep-cooled by the cryocooler, and the trifluoroacetyl chloride in the mixed waste gas is condensed into trifluoroacetyl chloride liquid; the cooling medium temperature of the condenser is 5-15℃, and the cooling medium temperature of the cryocooler is -40℃~-70℃. The trifluoroacetyl chloride liquid condensed by the condenser and the cryocooler is sent back to the lactone synthesis reactor through a U-shaped pipe for reuse.

[0023] S2: Purification The gas discharged from the S1 condenser is sent to the spray tower, and the trifluoroacetyl chloride in the gas is absorbed by the phenol toluene solution at 25-35°C to obtain purified hydrogen chloride gas, which is sent to the hydrogen chloride storage tank through the hydrogen chloride discharge pipe for storage. Among them, the phenol concentration of the phenol toluene solution is 5% to 50%.

[0024] 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 delivered by the circulation pump to be delivered 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.

[0025] 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 valve.

[0026] S4: After S3 is completed, the gas supply control valve corresponding to the etherification reaction kettle described in S3 is opened, and the hydrogen chloride gas obtained in S2 is excessively introduced into the etherification reaction kettle, and the temperature is controlled at 0-5°C, and the reaction is carried out for 6 hours; 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 it is detected that the concentration of hydrogen chloride reaches a set value, the corresponding gas supply control valve is closed.

[0027] S5: After S4 is completed, the mixture is allowed to stand for 1 hour to separate the material and liquid into layers, with the upper layer being chloromethyl ethyl ether.

[0028] 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.

[0029] In S6, the lower layer liquid in the etherification reactor is separated and the following operations are performed: first, polyformaldehyde and ethanol with 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 another etherification reactor is opened, and the process of S4-S6 is repeated. Through the above operations, the excess hydrogen chloride in the etherification reactor after the reaction can be recycled and the utilization rate of hydrogen chloride can be improved.

[0030] In addition, the trifluoroacetyl chloride liquid obtained by condensation of S1 can replace trifluoroacetic acid for preparing and synthesizing 4-(p-chlorophenyl)-2-trifluoromethyl-3-oxazolin-5-one; specifically, the method comprises the following steps: S7: In a lactone synthesis reactor, add 1580 kg of acetonitrile and 500 kg of p-chlorophenylglycine, stir for 15 minutes, and control the temperature at 20°C to 25°C; S8: After S7 is completed, 486 kg of trifluoroacetyl chloride liquid obtained in S1 is added to the lactone synthesis kettle, and the temperature is kept at 20°C to 30°C for 30 minutes; 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, and the mixture was kept warm for 15 minutes with the temperature controlled at 20°C to 30°C; 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 temperature is kept for 15 minutes; S11: After S10, slowly raise the temperature to 60℃~65℃ and keep it for 4~5h; S12: After S11, the temperature is continued to rise to 70°C-75°C and kept warm for 2 hours to obtain 4-(p-chlorophenyl)-2-trifluoromethyl-3-oxazolin-5-one.

[0031] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned 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: It 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, and 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, and the bottom of the spray tower is connected to the inlet of the phenol-toluene storage tank; the phenol-toluene storage tank The outlet is connected with the inlet of the 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 the circulation pipe, and the other path is connected with the 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 the 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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