Trapping device and process for producing 2, 6-dichlorobenzonitrile
Technical Field
The invention relates to the technical field of chemical production, in particular to a trapping device and a trapping process for producing 2, 6-dichlorobenzonitrile.
Background
The 2, 6-dichlorobenzonitrile is a preemergence herbicide of plants, and is characterized by wide weed-removing object, high drug effect and low toxicity. 2, 6-difluorobenzonitrile produced from 2, 6-dichlorobenzonitrile as a main raw material is an important intermediate of herbicides and insecticides. In addition, 2, 6-dichlorobenzonitrile is also an important intermediate of 2, 6-difluoroaniline, kola, diflubenzuron and flufenoxuron. The 2, 6-dichlorobenzonitrile is also a main raw material of the special engineering plastic polyphenylene oxide nitrile, and the product has the characteristics of high heat resistance, oil resistance, loss resistance, corrosion resistance, good molding fluidity, excellent composite performance and the like. With the rapid development of these industries, the market prospect and market demand for 2, 6-dichlorobenzonitrile is very optimistic.
The synthetic methods of 2, 6-dichlorobenzonitrile are divided into organic synthesis methods and gas phase ammoxidation methods. The organic synthesis method is characterized in that 6-chloro-o-nitrotoluene is used as a raw material, chlorination reaction is carried out under the action of a catalyst, and then cyanation reaction is carried out with formic acid and hydroxylamine hydrochloride, so that the reaction steps are long, the energy consumption is high, the pollution is serious, and the industrialization difficulty is high. The gas-phase ammoxidation method is to prepare the 2, 6-dichlorobenzonitrile by carrying out the gas-phase ammoxidation reaction on the 2, 6-dichlorotoluene under the action of the catalyst, and the method has the advantages of simple process flow, continuous production, strong production capacity, obvious economic benefit, no waste acid treatment problem and environmental protection, so compared with an organic synthesis method, the process for preparing the 2, 6-dichlorobenzonitrile by the gas-phase ammoxidation method is more widely applied.
At present, the domestic ammonia oxidation trap mostly adopts thin wall entrapment, and gaseous phase product desublimation in the trap need use a large amount of circulating water indirect cooling product to need wash out with solid phase product in the trap with a large amount of water, then filter and dry, obtain qualified product, this entrapment mode is great to artifical demand, and on-the-spot operational environment is abominable, can't accomplish the continuous ejection of compact of product, and need consume a large amount of water and advance the nature and wash.
In addition, the collection mode of the 2, 6-dichlorobenzonitrile products in industrial continuous production mainly comprises a fixed bed or fluidized bed product adding washing device, the amount of generated wastewater is large, acid and alkali are additionally added for wastewater treatment, the salt amount generated by adding acid and alkali during wastewater treatment is larger than the salt amount generated by preparing the 2, 6-dichlorobenzonitrile through ammoxidation of the 2, 6-dichlorotoluene, the three-waste treatment is complex, the investment consumption is high, the products are hydrolyzed when meeting water, and the like.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide the trapping device and the process for producing the 2, 6-dichlorobenzonitrile, and the trapping device has simple and reasonable structural design and high implementation feasibility; the trapping process of the invention omits the rectification and purification process, remarkably improves the trapping and purification efficiency of the 2, 6-dichlorobenzonitrile and the trapping and purification efficiency of the byproduct ammonium chloride, realizes continuous discharging, improves the working environment on site, reduces the labor intensity of workers, remarkably reduces the generation amount of waste water and waste solids and the economic burden of enterprises on treating three wastes compared with the traditional wet trapping process, and meets the requirements of green and environment-friendly production.
The technical scheme of the invention is that the trapping device for producing 2, 6-dichlorobenzonitrile is designed, and comprises a first-stage trap, a second-stage trap, a third-stage trap, a water washing tower, a wastewater treatment device and a tail gas treatment device, wherein the first-stage trap, the second-stage trap and the third-stage trap are all dry traps, spray devices are arranged inside the first-stage trap and the third-stage trap, jackets are arranged outside the second-stage trap and the third-stage trap, and refrigerant media can be input into the jackets as required;
2, 6-dichlorobenzonitrile high-temperature mixed product from the reactor enters the primary trap through a feed inlet of the primary trap, a gas outlet at the top of the primary trap is connected with a feed inlet of the secondary trap, a gas outlet at the top of the secondary trap is connected with a feed inlet of the tertiary trap, a gas outlet at the top of the tertiary trap is connected with a gas inlet of the washing tower, a gas outlet at the top of the washing tower is connected with the tail gas treatment device, and a discharge outlet at the bottom of the washing tower is connected with a liquid inlet of the wastewater treatment device;
the discharge hole of the bottom of the first-level catcher is connected with a first centrifugal machine, the centrifugate outlet of the first centrifugal machine is connected with the feed inlet of the cooling kettle, the discharge hole of the bottom of the cooling kettle is connected with a second centrifugal machine, the centrifugate outlet of the second centrifugal machine is connected with the first centrifugal machine through a discharge pump and a pipeline, the discharge hole of the bottom of the second centrifugal machine is connected with a first drier, the discharge hole of the bottom of the first centrifugal machine is connected with a third centrifugal machine, the centrifugate outlet of the third centrifugal machine is connected with the spraying device inside the first-level catcher through a discharge pump and a pipeline, the discharge hole of the bottom of the third centrifugal machine is connected with a second drier, and the discharge hole of the second drier is connected with a first product bin;
the discharge hole at the bottom of the secondary catcher is connected with the first product bin;
the discharge gate of tertiary trap bottom be connected with fourth centrifuge, fourth centrifuge's centrifugate export is connected with the inside spray set of tertiary trap, the inside spray set of washing tower and effluent treatment plant through discharge pump and pipeline, the discharge gate of fourth centrifuge bottom is connected with the third desicator, the discharge gate of third desicator is connected with second product storehouse.
The preferable technical scheme is that the device further comprises a centrifugal liquid tank, a centrifugal liquid outlet of the third centrifugal machine is connected with a liquid inlet of the centrifugal liquid tank, and a liquid outlet of the centrifugal liquid tank is respectively connected with the spraying device inside the first-stage catcher and the fourth centrifugal machine through a discharge pump and a pipeline.
Further preferred technical scheme has, still includes the waste water buffer tank, the discharge gate of washing tower bottom with the inlet of waste water buffer tank is connected, the liquid outlet of waste water buffer tank with waste water treatment facilities's inlet is connected.
The invention provides a trapping process for producing 2, 6-dichlorobenzonitrile, wherein the 2, 6-dichlorobenzonitrile is prepared by ammoxidation of 2, 6-dichlorotoluene, and the trapping process comprises the following steps:
s1: 2, 6-dichlorobenzonitrile high-temperature mixed product from the reactor enters a primary trap, at the moment, a spraying device sprays refrigerant spraying liquid into the primary trap according to the temperature of a feed inlet of the primary trap to evaporate and reduce the temperature, 80-99.6% of gaseous ammonium chloride becomes ammonium chloride solid and is separated out, less than 21% of gaseous 2, 6-dichlorobenzonitrile is solidified and separated out, a solid-liquid mixture generated in the primary trap is centrifugally separated out into a water phase and a solid phase, wherein the water phase is sequentially cooled, crystallized and centrifugally separated out into an ammonium chloride wet product and a centrifugal liquid, the ammonium chloride wet product is dried to obtain an ammonium chloride solid finished product, and the centrifugal liquid is circularly applied to a first centrifuge to be used as a solvent for dissolving ammonium chloride; washing and centrifuging the solid phase in sequence to separate a 2, 6-dichlorobenzonitrile solid wet product and a centrifugate, drying the 2, 6-dichlorobenzonitrile solid wet product to obtain a 2, 6-dichlorobenzonitrile solid finished product with the purity of more than or equal to 99.5%, recycling the centrifugate to the primary trap for use as a refrigerant spray solution, or recycling the centrifugate to the quaternary centrifuge for use as a washing solution, and allowing the mixed product atmosphere subjected to primary cooling by the primary trap to enter the secondary trap;
s2: at the moment, a refrigerant medium is introduced into a jacket of the secondary trap, more than 79% of gaseous 2, 6-dichlorobenzonitrile and trace gaseous ammonium chloride become solid and are separated out, the purity of the partial product is more than 99.5, the moisture content is less than 0.2%, and the product directly enters a first product bin;
s3: introducing a refrigerant medium into a jacket of the third-stage trap, wherein a small amount of gaseous 2, 6-dichlorobenzonitrile and other light components are changed into solid to be precipitated, spraying leacheate into the third-stage trap periodically to wash down the solid precipitate on the inner wall of the third-stage trap, and washing and centrifugally separating a solid-liquid mixture generated in the third-stage trap sequentially to obtain a water phase and a solid phase, wherein after the solid phase is dried, a 2, 6-dichlorobenzonitrile solid finished product with the purity of not less than 99% is obtained, the water phase is periodically sent into the third-stage trap to be used as the leacheate, or sent into a water washing tower to be recycled as the leacheate, or is treated and discharged, and the mixed product atmosphere after being cooled for three times by the third-stage trap enters the water washing;
s4: at the moment, the interior of the washing tower is sprayed with leacheate, the mixed product atmosphere discharged by the three-stage trap is discharged after being sequentially sprayed and cleaned by the washing tower and treated by the tail gas treatment device, and waste liquid generated in the washing tower after long-time operation enters the wastewater treatment device for treatment and then is discharged or recycled.
The preferable technical scheme is that in the step S1, the temperature in the primary catcher is controlled to be 115-130 ℃; in the step S2, the temperature in the secondary catcher is controlled to be 70-85 ℃; in the step S3, the temperature inside the three-stage trap is controlled to be 15-30 ℃.
In a more preferable embodiment, in S2, the coolant medium used is cooling water; in step S3, the cold medium used is brine ice.
Further preferably, the waste liquid discharged from the water scrubber is subjected to cyanogen breaking, ammonia extraction and oxidation treatment in sequence, and then discharged or recycled to be used as the eluent in the step S3 or S4.
The invention has the advantages and beneficial effects that:
1. the trapping device for producing the 2, 6-dichlorobenzonitrile, disclosed by the invention, has the advantages of no need of rectification equipment, simple and reasonable structural design, high implementation feasibility and strong practicability.
2. According to the trapping device and the process for producing 2, 6-dichlorobenzonitrile, the primary trap captures more than 80% of ammonium chloride and less than 21% of 2, 6-dichlorobenzonitrile by using a dry method, the secondary trap captures more than 79% of 2, 6-dichlorobenzonitrile by using a dry trapping method, the trapping efficiency of the 2, 6-dichlorobenzonitrile is obviously improved, a crude solid-liquid mixture product captured by the primary trap can be washed by water to obtain a 2, 6-dichlorobenzonitrile solid finished product with the purity of more than or equal to 99.5% and a byproduct ammonium chloride solid pure product, the operation steps are simple, and the efficiency is high; the purity of the 2, 6-dichlorobenzonitrile product captured by the secondary catcher is over 99.5 percent, and the product can be directly put into a warehouse for packaging and use.
3. According to the trapping device and the process for producing the 2, 6-dichlorobenzonitrile, disclosed by the invention, the first-stage trap fully utilizes the vaporization latent heat of water, the spraying water quantity is accurately controlled according to the inlet temperature of the first-stage trap, the accurate temperature control of the first-stage trap is realized, the using amount of spraying water is small, the 2, 6-dichlorobenzonitrile product obtained by dry trapping in the second-stage trapping stage can be directly fed into a finished product bin, the dry trapping and a small amount of leacheate are used for washing and discharging in the third-stage trapping stage, the centrifugal liquid generated by subsequent washing can be recycled, and in addition, the waste liquid generated by the washing tower can be recycled for use as the spraying liquid of the washing tower or the leacheate of the third-stage trap after being treated, so that the generation amount of the waste liquid is remarkably reduced, and the water consumption cost expense and the waste liquid treatment burden in the production.
4. The trapping process for producing 2, 6-dichlorobenzonitrile of the invention finally obtains two purities of 2, 6-dichlorobenzonitrile, the first-stage trapping stage and the second-stage trapping stage obtain the 2, 6-dichlorobenzonitrile solid finished product which accounts for more than 99% of the total mass of the 2, 6-dichlorobenzonitrile and has the purity of more than or equal to 99.5% in total, the 2, 6-dichlorobenzonitrile solid finished product which accounts for only about 0.4% of the total mass of the 2, 6-dichlorobenzonitrile and is obtained in the third-stage trapping stage, namely the production trapping efficiency of the 2, 6-dichlorobenzonitrile is obviously improved by trapping and purifying the 2, 6-dichlorobenzonitrile in batches according to different purities, and meanwhile, compared with the traditional wet trapping process, the rectification and purification process is omitted, thus the energy consumption in the production trapping process of the 2, 6-dichlorobenzonitrile is obviously reduced, and meets the energy-saving requirement.
5. The trapping process for producing the 2, 6-dichlorobenzonitrile provided by the invention obviously improves the trapping and purifying efficiency of the 2, 6-dichlorobenzonitrile and the trapping and purifying efficiency of the byproduct ammonium chloride, realizes continuous discharging, improves the working environment on site, reduces the labor intensity of workers, obviously reduces the generation amount of waste water and waste solids compared with the traditional wet trapping process, greatly reduces the economic burden of treating industrial waste water and waste solids by enterprises, and meets the requirement of green and environment-friendly production.
Drawings
FIG. 1 is a block diagram of a capture process flow for the production of 2, 6-dichlorobenzonitrile in accordance with the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Example 1
The invention relates to a trapping device for producing 2, 6-dichlorobenzonitrile, which comprises a primary trap, a secondary trap, a tertiary trap, a washing tower, a wastewater treatment device and a tail gas treatment device, wherein the primary trap, the secondary trap and the tertiary trap are all dry traps, spray devices are arranged inside the primary trap and the tertiary trap, jackets are arranged outside the secondary trap and the tertiary trap, and refrigerant media can be input into the jackets as required;
2, 6-dichlorobenzonitrile high-temperature mixed product from the reactor enters the primary trap through a feed inlet of the primary trap, a gas outlet at the top of the primary trap is connected with a feed inlet of the secondary trap, a gas outlet at the top of the secondary trap is connected with a feed inlet of the tertiary trap, a gas outlet at the top of the tertiary trap is connected with a gas inlet of the washing tower, a gas outlet at the top of the washing tower is connected with the tail gas treatment device, and a discharge outlet at the bottom of the washing tower is connected with a liquid inlet of the wastewater treatment device;
the discharge hole of the bottom of the first-level catcher is connected with a first centrifugal machine, the centrifugate outlet of the first centrifugal machine is connected with the feed inlet of the cooling kettle, the discharge hole of the bottom of the cooling kettle is connected with a second centrifugal machine, the centrifugate outlet of the second centrifugal machine is connected with the first centrifugal machine through a discharge pump and a pipeline, the discharge hole of the bottom of the second centrifugal machine is connected with a first drier, the discharge hole of the bottom of the first centrifugal machine is connected with a third centrifugal machine, the centrifugate outlet of the third centrifugal machine is connected with the spraying device inside the first-level catcher through a discharge pump and a pipeline, the discharge hole of the bottom of the third centrifugal machine is connected with a second drier, and the discharge hole of the second drier is connected with a first product bin;
the discharge hole at the bottom of the secondary catcher is connected with the first product bin;
the discharge gate of tertiary trap bottom be connected with fourth centrifuge, fourth centrifuge's centrifugate export is connected with the inside spray set of tertiary trap, the inside spray set of washing tower and effluent treatment plant through discharge pump and pipeline, the discharge gate of fourth centrifuge bottom is connected with the third desicator, the discharge gate of third desicator is connected with second product storehouse.
The preferable technical scheme is that the device further comprises a centrifugal liquid tank, a centrifugal liquid outlet of the third centrifugal machine is connected with a liquid inlet of the centrifugal liquid tank, and a liquid outlet of the centrifugal liquid tank is respectively connected with the spraying device inside the first-stage catcher and the fourth centrifugal machine through a discharge pump and a pipeline.
Further preferred technical scheme still includes the waste water buffer tank, the discharge gate of washing tower bottom with the inlet of waste water buffer tank is connected, the liquid outlet of waste water buffer tank with waste water treatment facilities's inlet is connected.
As shown in fig. 1, a capture process for the production of 2, 6-dichlorobenzonitrile, the 2, 6-dichlorobenzonitrile being produced by ammoxidation of 2, 6-dichlorotoluene, comprises the steps of:
a synthesis section: filling a catalyst in a reactor; taking 2, 6-dichlorotoluene, ammonia gas and air as raw materials, wherein the volume ratio of the raw materials to the raw materials is 1: 4: 17, carrying out ammoxidation continuous reaction for 12h at the temperature of 300-500 ℃ under normal pressure, and sending the prepared 2, 6-dichlorobenzonitrile high-temperature mixed product into a trapping working section, wherein the conversion rate of 2, 6-dichlorotoluene is more than 99%, and the selectivity and yield of the product 2, 6-dichlorobenzonitrile can reach more than 86%;
(II) a trapping section:
s1: 2, 6-dichlorobenzonitrile high-temperature mixed product from the reactor enters a primary trap, at the moment, a spraying device sprays refrigerant spraying liquid into the primary trap according to the temperature of a feed inlet of the primary trap to evaporate and reduce the temperature, 87.56g of ammonium chloride solid and 496.80g of 2, 6-dichlorobenzonitrile are precipitated by solidification, a solid-liquid mixture generated in the primary trap centrifugally separates out a water phase and a solid phase, wherein the water phase is sequentially subjected to cooling crystallization and centrifugal separation to separate out an ammonium chloride wet product and a centrifugal liquid, the ammonium chloride wet product is dried to obtain an ammonium chloride solid finished product, and the centrifugal liquid is circularly applied to a first centrifuge to be used as a solvent for dissolving ammonium chloride; washing and centrifuging the solid phase in sequence to separate a 2, 6-dichlorobenzonitrile solid wet product and a centrifugate, drying the 2, 6-dichlorobenzonitrile solid wet product to obtain a 2, 6-dichlorobenzonitrile solid finished product with the purity of more than or equal to 99.5%, recycling the centrifugate to the primary trap for use as a refrigerant spray solution, or recycling the centrifugate to the quaternary centrifuge for use as a washing solution, and allowing the mixed product atmosphere subjected to primary cooling by the primary trap to enter the secondary trap;
s2: at the moment, a refrigerant medium is introduced into a jacket of the secondary trap, 0.26g of ammonium chloride solid is separated out, 601.68g of 2, 6-dichlorobenzonitrile is solidified and separated out, the captured product is directly placed into a first product bin, and the mixed product atmosphere after secondary temperature reduction by the secondary trap enters a third-level trap;
s3: at the moment, a refrigerant medium is introduced into a jacket of the three-stage trap, 0.18g of ammonium chloride solid, 5.52g of 2, 6-dichlorobenzonitrile solid and a small amount of other light component solids are separated out, an leacheate is regularly sprayed into the three-stage trap to wash down solid precipitates on the inner wall of the three-stage trap, and a solid-liquid mixture generated in the three-stage trap is sequentially washed and centrifugally separated to obtain a water phase and a solid phase, wherein after the solid phase is dried, a 2, 6-dichlorobenzonitrile solid finished product with the purity of not less than 99% is obtained, the water phase is regularly sent into the three-stage trap to be used as the leacheate, or is sent into a water washing tower to be recycled as the leacheate, or is discharged after being treated, and the mixed product atmosphere after being cooled for three times by the;
s4: at the moment, the interior of the washing tower is sprayed with leacheate, the mixed product atmosphere discharged by the three-stage trap is discharged after being sequentially sprayed and cleaned by the washing tower and treated by the tail gas treatment device, and waste liquid generated in the washing tower after long-time operation enters the wastewater treatment device for treatment and then is discharged or recycled.
Preferably, in the step S1, the temperature inside the primary catcher is controlled to be 100-105 ℃; in the step S2, the temperature in the secondary catcher is controlled to be 75-80 ℃; in the step S3, the temperature in the three-stage trap is controlled to be 22-25 ℃; in the step S2, the refrigerant medium used is cooling water; in the step S3, the refrigerant medium used is brine ice; and (3) sequentially carrying out cyanogen breaking, ammonia extraction and oxidation treatment on the waste liquid discharged from the water washing tower, and then discharging or circularly applying the waste liquid to the step S3 or S4 for use as an eluent.
Wherein, the first-stage catcher is about 750g of spray water for controlling the temperature, the third centrifuge is added with about 100g of fresh clean water, the synthesis section generates about 340g of water, and the generated waste water is about 440g (the generated waste water is the fresh clean water added by the third centrifuge plus the synthesis section generated water).
Example 2
Example 2 differs from example 1 in that the (second) capture section:
s1: 2, 6-dichlorobenzonitrile high-temperature mixed product from the reactor enters a primary trap, at the moment, a spraying device sprays refrigerant spraying liquid into the primary trap according to the temperature of a feed inlet of the primary trap to evaporate and reduce the temperature, 87.21g of ammonium chloride solid and 220.80g of 2, 6-dichlorobenzonitrile are precipitated by solidification, a solid-liquid mixture generated in the primary trap centrifugally separates out a water phase and a solid phase, wherein the water phase is sequentially subjected to cooling crystallization and centrifugal separation to separate out an ammonium chloride wet product and a centrifugal liquid, the ammonium chloride wet product is dried to obtain an ammonium chloride solid finished product, and the centrifugal liquid is circularly applied to a first centrifuge to be used as a solvent for dissolving ammonium chloride; washing and centrifuging the solid phase in sequence to separate a 2, 6-dichlorobenzonitrile solid wet product and a centrifugate, drying the 2, 6-dichlorobenzonitrile solid wet product to obtain a 2, 6-dichlorobenzonitrile solid finished product with the purity of more than or equal to 99.5%, recycling the centrifugate to the primary trap for use as a refrigerant spray solution, or recycling the centrifugate to the quaternary centrifuge for use as a washing solution, and allowing the mixed product atmosphere subjected to primary cooling by the primary trap to enter the secondary trap;
s2: at the moment, a refrigerant medium is introduced into a jacket of the secondary trap, 0.53g of ammonium chloride solid is separated out, 878.78g of 2, 6-dichlorobenzonitrile is solidified and separated out, the captured product is directly placed into a first product bin, and the mixed product atmosphere after secondary temperature reduction by the secondary trap enters a third-level trap;
s3: at the moment, a refrigerant medium is introduced into a jacket of the three-stage trap, 0.35g of ammonium chloride solid, 4.42g of 2, 6-dichlorobenzonitrile solid and a small amount of other light component solids are separated out, an leacheate is regularly sprayed into the three-stage trap to wash down solid precipitates on the inner wall of the three-stage trap, and a solid-liquid mixture generated in the three-stage trap is sequentially washed and centrifugally separated to obtain a water phase and a solid phase, wherein after the solid phase is dried, a 2, 6-dichlorobenzonitrile solid finished product with the purity of not less than 99% is obtained, the water phase is regularly sent into the three-stage trap to be used as the leacheate, or is sent into a water washing tower to be recycled as the leacheate, or is discharged after being treated, and the mixed product atmosphere after being cooled for three times by the;
s4: at the moment, the interior of the washing tower is sprayed with leacheate, the mixed product atmosphere discharged by the three-stage trap is discharged after being sequentially sprayed and cleaned by the washing tower and treated by the tail gas treatment device, and waste liquid generated in the washing tower after long-time operation enters the wastewater treatment device for treatment and then is discharged or recycled.
Preferably, in the step S1, the temperature inside the primary catcher is controlled to be 115-120 ℃; in the step S2, the temperature in the secondary catcher is controlled to be 70-75 ℃; in the step S3, the temperature inside the three-stage trap is controlled to be 15-20 ℃; in the step S2, the refrigerant medium used is cooling water; in the step S3, the refrigerant medium used is brine ice; and (3) sequentially carrying out cyanogen breaking, ammonia extraction and oxidation treatment on the waste liquid discharged from the water washing tower, and then discharging or circularly applying the waste liquid to the step S3 or S4 for use as an eluent.
Wherein, the first-stage catcher is about 730g of shower water for controlling the temperature, the third centrifuge is added with about 100g of fresh clean water, the synthesis section generates about 340g of water, and the generated waste water is about 440g (the generated waste water is the fresh clean water added by the third centrifuge plus the synthesis section generated water).
Example 3
Example 3 differs from example 1 in that the (second) capture section:
s1: 2, 6-dichlorobenzonitrile high-temperature mixed product from the reactor enters a primary trap, at the moment, a spraying device sprays refrigerant spraying liquid into the primary trap according to the temperature of a feed inlet of the primary trap to evaporate and reduce the temperature, 87.12g of ammonium chloride solid and 210.80g of 2, 6-dichlorobenzonitrile are precipitated by solidification, a solid-liquid mixture generated in the primary trap centrifugally separates out a water phase and a solid phase, the water phase is sequentially cooled and crystallized and centrifugally separated out an ammonium chloride wet product and a centrifugal liquid, the ammonium chloride wet product is dried to obtain an ammonium chloride solid finished product, and the centrifugal liquid is circularly applied to a first centrifugal machine to be used as a solvent for dissolving ammonium chloride; washing and centrifuging the solid phase in sequence to separate a 2, 6-dichlorobenzonitrile solid wet product and a centrifugate, drying the 2, 6-dichlorobenzonitrile solid wet product to obtain a 2, 6-dichlorobenzonitrile solid finished product with the purity of more than or equal to 99.5%, recycling the centrifugate to the primary trap for use as a refrigerant spray solution, or recycling the centrifugate to the quaternary centrifuge for use as a washing solution, and allowing the mixed product atmosphere subjected to primary cooling by the primary trap to enter the secondary trap;
s2: at the moment, a refrigerant medium is introduced into a jacket of the secondary trap, 0.70g of ammonium chloride solid is separated out, 890.99g of 2, 6-dichlorobenzonitrile is solidified and separated out, the captured product is directly placed into a first product bin, and the mixed product atmosphere after secondary temperature reduction by the secondary trap enters a third-level trap;
s3: at the moment, a refrigerant medium is introduced into a jacket of the three-stage trap, 0.18g of ammonium chloride solid, 2.21g of 2, 6-dichlorobenzonitrile solid and a small amount of other light component solids are separated out, an leacheate is regularly sprayed into the three-stage trap to wash down solid precipitates on the inner wall of the three-stage trap, and a solid-liquid mixture generated in the three-stage trap is sequentially washed and centrifugally separated to obtain a water phase and a solid phase, wherein after the solid phase is dried, a 2, 6-dichlorobenzonitrile solid finished product with the purity of not less than 99% is obtained, the water phase is regularly sent into the three-stage trap to be used as the leacheate, or is sent into a water washing tower to be recycled as the leacheate, or is discharged after being treated, and the mixed product atmosphere after being cooled for three times by the;
s4: at the moment, the interior of the washing tower is sprayed with leacheate, the mixed product atmosphere discharged by the three-stage trap is discharged after being sequentially sprayed and cleaned by the washing tower and treated by the tail gas treatment device, and waste liquid generated in the washing tower after long-time operation enters the wastewater treatment device for treatment and then is discharged or recycled.
Preferably, in the step S1, the temperature inside the primary catcher is controlled to be 125-130 ℃; in the step S2, the temperature in the secondary catcher is controlled to be 80-85 ℃; in the step S3, the temperature inside the three-stage trap is controlled to be 25-30 ℃; in the step S2, the refrigerant medium used is cooling water; in the step S3, the refrigerant medium used is brine ice; and (3) sequentially carrying out cyanogen breaking, ammonia extraction and oxidation treatment on the waste liquid discharged from the water washing tower, and then discharging or circularly applying the waste liquid to the step S3 or S4 for use as an eluent.
Wherein, the first-stage catcher is used for controlling the temperature, the spray water is about 720g, the third centrifuge is used for adding about 100g of fresh clean water, the water generated in the synthesis section is about 340g, and the generated waste water is about 440g (the generated waste water is the fresh clean water added by the third centrifuge plus the water generated in the synthesis section).
Example 4
Example 4 differs from example 1 in that the (second) capture section:
s1: 2, 6-dichlorobenzonitrile high-temperature mixed product from the reactor enters a primary trap, at the moment, a spraying device sprays refrigerant spraying liquid into the primary trap according to the temperature of a feed inlet of the primary trap to evaporate and reduce the temperature, 87.21g of ammonium chloride solid and 200.80g of 2, 6-dichlorobenzonitrile are precipitated by solidification, a solid-liquid mixture generated in the primary trap centrifugally separates out a water phase and a solid phase, wherein the water phase is sequentially subjected to cooling crystallization and centrifugal separation to separate out an ammonium chloride wet product and a centrifugal liquid, the ammonium chloride wet product is dried to obtain an ammonium chloride solid finished product, and the centrifugal liquid is circularly applied to a first centrifuge to be used as a solvent for dissolving ammonium chloride; washing and centrifuging the solid phase in sequence to separate a 2, 6-dichlorobenzonitrile solid wet product and a centrifugate, drying the 2, 6-dichlorobenzonitrile solid wet product to obtain a 2, 6-dichlorobenzonitrile solid finished product with the purity of more than or equal to 99.5%, recycling the centrifugate to the primary trap for use as a refrigerant spray solution, or recycling the centrifugate to the quaternary centrifuge for use as a washing solution, and allowing the mixed product atmosphere subjected to primary cooling by the primary trap to enter the secondary trap;
s2: at the moment, a refrigerant medium is introduced into a jacket of the secondary trap, 0.26g of ammonium chloride solid is separated out, 887.91g of 2, 6-dichlorobenzonitrile is solidified and separated out, the captured product is directly placed into a first product bin, and the mixed product atmosphere after secondary temperature reduction by the secondary trap enters a third-level trap;
s3: at the moment, a refrigerant medium is introduced into a jacket of the three-stage trap to precipitate 0.62g of ammonium chloride solid, 5.29g of 2, 6-dichlorobenzonitrile solid and a small amount of other light component solids, an leacheate is regularly sprayed into the three-stage trap to flush down solid precipitates on the inner wall of the three-stage trap, and a solid-liquid mixture generated in the three-stage trap is sequentially washed and centrifugally separated to obtain a water phase and a solid phase, wherein after the solid phase is dried, a 2, 6-dichlorobenzonitrile solid finished product with the purity of not less than 99% is obtained, the water phase is regularly sent into the three-stage trap to be used as the leacheate, or is sent into a water washing tower to be recycled as the leacheate, or is discharged after being treated, and the mixed product atmosphere after being cooled for three times by the three-;
s4: at the moment, the interior of the washing tower is sprayed with leacheate, the mixed product atmosphere discharged by the three-stage trap is discharged after being sequentially sprayed and cleaned by the washing tower and treated by the tail gas treatment device, and waste liquid generated in the washing tower after long-time operation enters the wastewater treatment device for treatment and then is discharged or recycled.
Preferably, in the step S1, the temperature inside the primary catcher is controlled to be 120-125 ℃; in the step S2, the temperature in the secondary catcher is controlled to be 75-80 ℃; in the step S3, the temperature in the three-stage trap is controlled to be 22-25 ℃; in the step S2, the refrigerant medium used is cooling water; in the step S3, the refrigerant medium used is brine ice; and (3) sequentially carrying out cyanogen breaking, ammonia extraction and oxidation treatment on the waste liquid discharged from the water washing tower, and then discharging or circularly applying the waste liquid to the step S3 or S4 for use as an eluent.
Wherein, the first-stage catcher is used for controlling the temperature, the spray water is about 710g, the third centrifuge is used for adding about 100g of fresh clean water, the water generated in the synthesis section is about 340g, and the generated waste water is about 440g (the generated waste water is the fresh clean water added by the third centrifuge plus the water generated in the synthesis section).
Example 5
Example 5 differs from example 1 in that the (second) capture section:
s1: 2, 6-dichlorobenzonitrile high-temperature mixed product from the reactor enters a primary trap, at the moment, a spraying device sprays refrigerant spraying liquid into the primary trap according to the temperature of a feed inlet of the primary trap to evaporate and reduce the temperature, 78.94g of ammonium chloride solid and 110.40g of 2, 6-dichlorobenzonitrile are precipitated by solidification, a solid-liquid mixture generated in the primary trap centrifugally separates out a water phase and a solid phase, wherein the water phase is sequentially subjected to cooling crystallization and centrifugal separation to separate out an ammonium chloride wet product and a centrifugal liquid, the ammonium chloride wet product is dried to obtain an ammonium chloride solid finished product, and the centrifugal liquid is circularly applied to a first centrifuge to be used as a solvent for dissolving ammonium chloride; washing and centrifuging the solid phase in sequence to separate a 2, 6-dichlorobenzonitrile solid wet product and a centrifugate, drying the 2, 6-dichlorobenzonitrile solid wet product to obtain a 2, 6-dichlorobenzonitrile solid finished product with the purity of more than or equal to 99.5%, recycling the centrifugate to the primary trap for use as a refrigerant spray solution, or recycling the centrifugate to the quaternary centrifuge for use as a washing solution, and allowing the mixed product atmosphere subjected to primary cooling by the primary trap to enter the secondary trap;
s2: at the moment, a refrigerant medium is introduced into a jacket of the secondary trap, 8.36g of ammonium chloride solid is separated out, 983.66g of 2, 6-dichlorobenzonitrile is solidified and separated out, the captured product is directly placed into a first product bin, and the mixed product atmosphere after secondary temperature reduction by the secondary trap enters a third-level trap;
s3: at the moment, a refrigerant medium is introduced into a jacket of the three-stage trap to precipitate 0.70g of ammonium chloride solid, 9.94g of 2, 6-dichlorobenzonitrile solid and a small amount of other light component solids, an leacheate is regularly sprayed into the three-stage trap to flush down solid precipitates on the inner wall of the three-stage trap, and a solid-liquid mixture generated in the three-stage trap is sequentially washed and centrifugally separated to obtain a water phase and a solid phase, wherein after the solid phase is dried, a 2, 6-dichlorobenzonitrile solid finished product with the purity of not less than 99% is obtained, the water phase is regularly sent into the three-stage trap to be used as the leacheate, or is sent into a water washing tower to be recycled as the leacheate, or is discharged after being treated, and the mixed product atmosphere after being cooled for three times by the three-;
s4: at the moment, the interior of the washing tower is sprayed with leacheate, the mixed product atmosphere discharged by the three-stage trap is discharged after being sequentially sprayed and cleaned by the washing tower and treated by the tail gas treatment device, and waste liquid generated in the washing tower after long-time operation enters the wastewater treatment device for treatment and then is discharged or recycled.
Preferably, in the step S1, the temperature inside the primary catcher is controlled to be 120-125 ℃; in the step S2, the temperature in the secondary catcher is controlled to be 75-80 ℃; in the step S3, the temperature inside the three-stage trap is controlled to be 20-25 ℃; in the step S2, the refrigerant medium used is cooling water; in the step S3, the refrigerant medium used is brine ice; and (3) sequentially carrying out cyanogen breaking, ammonia extraction and oxidation treatment on the waste liquid discharged from the water washing tower, and then discharging or circularly applying the waste liquid to the step S3 or S4 for use as an eluent.
Wherein, the spraying water for controlling the temperature of the first-stage catcher is about 700g, the fresh clean water is about 100g is added into the third centrifuge, the water generated in the synthesis section is about 340g, and the generated waste water is about 440g (the generated waste water is the fresh clean water added into the third centrifuge plus the water generated in the synthesis section).
Comparative example 1
The difference between the comparative example 1 and the examples 1 to 5 is that the collecting section (II):
the traditional wet catching method adopts a two-stage or even three-stage wet catching mode to catch the 2, 6-dichlorobenzonitrile generated by the reaction, then uses sulfuric acid to absorb ammonia gas to form ammonium sulfate, and the gas passes through a water absorption tower; substances generated by main and side reactions are absorbed by the wet captured water, and all products need to be refined again after being washed by water; the amount of wastewater generated in the production of 1kg of 2, 6-dichlorobenzonitrile product was about 2kg, i.e., 2208g of wastewater was required in the production of 2, 6-dichlorobenzonitrile product (1104g) having the same mass as in examples 1 to 5.
TABLE 1 Experimental data for ammonium chloride capture in examples 1-5
TABLE 2 Experimental data for Capture of 2, 6-Dichlorobenzonitrile and amount of wastewater produced in examples 1 to 5 and comparative example 1
The experimental data show that:
the second trapping section in the embodiment 1 adopts the trapping device for producing 2, 6-dichlorobenzonitrile, so that the temperature inside the first-stage trap is relatively reduced, the trapping yield of the first-stage trap to ammonium chloride is obviously improved, but the trapping yield of the first-stage trap to 2, 6-dichlorobenzonitrile is obviously improved, namely a large amount of 2, 6-dichlorobenzonitrile crude products are introduced into ammonium chloride solids trapped in the first-stage trap, and the washing and purifying burden of the ammonium chloride crude products is increased;
in the second trapping section of embodiments 2-4, the trapping device and the process for producing 2.6-dichlorobenzonitrile are adopted, the ammonium chloride solid captured by the first-stage trap is sequentially washed with water, cooled, crystallized and centrifuged to obtain a pure ammonium chloride solid product, and the 2, 6-dichlorobenzonitrile crude product captured by the second-stage trap is washed with water for several times to obtain a 2, 6-dichlorobenzonitrile liquid finished product with the purity of more than or equal to 99.5%; the 2, 6-dichlorobenzonitrile crude product trapped by the third-stage trap needs to be washed by water for multiple times to obtain a 2, 6-dichlorobenzonitrile liquid finished product with the purity of more than or equal to 99 percent, wherein the purity of the 2, 6-dichlorobenzonitrile liquid finished product is lower than that of the products collected in the first-stage trap and the second-stage trap; the method has simple process operation and less waste water production, and can produce 1104g of 2, 6-dichlorobenzonitrile liquid finished product to generate about 440g of waste water;
the second trapping section in the embodiment 5 adopts the trapping device for producing 2, 6-dichlorobenzonitrile, so that the temperature inside the first-stage trap is increased, the ammonium chloride trapping yield of the first-stage trap is obviously reduced, the ammonium chloride trapping efficiency of the second-stage trap is increased, the ammonium chloride impurities in the 2, 6-dichlorobenzonitrile liquid crude product captured by the second-stage trap are more, and the washing and purifying burden of the 2, 6-dichlorobenzonitrile liquid crude product is increased;
in the comparative example 1, 1104g of 2, 6-dichlorobenzonitrile is prepared by adopting a traditional wet trapping process and through production, rectification and purification, wherein all intermediate crude products of the 2, 6-dichlorobenzonitrile need to be rectified and purified, while the 2, 6-dichlorobenzonitrile products produced in the examples 2-4 only need to be subjected to centrifugal washing and drying treatment, so that the rectification and purification process is omitted; the production of 1104g of 2, 6-dichlorobenzonitrile in comparative example 1 produced 2208g of wastewater, which is about 5 times (2208 g/440 g. apprxeq.5) the amount of 2, 6-dichlorobenzonitrile produced in examples 2 to 4 of equivalent mass;
in conclusion, the trapping device and the process for producing 2, 6-dichlorobenzonitrile achieve high production efficiency and economy with low energy consumption, and meanwhile, the production amount of wastewater is low, so that the economic burden of enterprises on treating industrial wastewater is remarkably reduced, and the development requirement of environmental protection is met.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the technical principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.