Device and method for recovering acrylonitrile and dimethyl sulfoxide in mixture

Abstract

The invention relates to the field of solvent recovery, in particular to a device and a method for recovering acrylonitrile and dimethyl sulfoxide in a mixture. The device comprises: a rectification unit I, which is used for carrying out rectification treatment on a mixture to obtain a dimethyl sulfoxide-containing product flow, a water phase and a light component phase; the rectification unit I is provided with a mixture side line feeding part and a water phase side line discharging part arranged below the mixture side line feeding part, the water phase side line discharging part is provided with a first membrane separation piece for separating water in water phase discharging to obtain a first circulating material, and a first circulating material discharging opening of the first membrane separation piece is communicated with the rectification unit; the rectification unit II is used for carrying out rectification treatment on the gas-phase discharged material of the rectification unit I to obtain a side-line product material flow containing acrylonitrile. By means of the device, efficient recovery of acrylonitrile and dimethyl sulfoxide can be achieved, and recovery energy consumption is low.

Description

Technical Field

[0001] The invention relates to the field of solvent recovery, and in particular to a device and a method for recovering acrylonitrile and dimethyl sulfoxide in a mixture. Background Art

[0002] Acrylonitrile-based carbon fiber has the characteristics of light weight, high strength, high modulus and high temperature resistance in non-oxidizing atmosphere, and is widely used in the national defense industry. De-monomerization and degassing are important steps in the preparation process of PAN-based carbon fiber. In the preparation process of PAN-based carbon fiber, the polymerization process of carbon fiber production using DMSO as solvent contains unreacted AN monomer in the polymerization liquid, and the polymerization product coming out of the polymerization kettle must be de-monomerized; there will be bubbles in the spinning liquid during the polymerization or transportation process, and larger bubbles will cause the interruption, deformation, and breakage of the spinning fine flow through the spinneret hole. Therefore, the bubbles and residual monomers in the spinning liquid must be completely removed before spinning. Generally, de-monomerization and degassing are carried out under vacuum. The residual monomer AN needs to be removed under vacuum conditions to reduce the monomer residue of the polymerization liquid to 100-300PPM, which becomes the spinning polymerization stock solution. In this process, a de-monomerization and degassing condensate is produced, which contains a large amount of dimethyl sulfoxide, acrylonitrile and trace water.

[0003] In the process of preparing carbon fiber, although the total amount of PAN-based carbon fiber degassing condensate is not large, it is very difficult to handle this material because it contains a certain amount of acrylonitrile: acrylonitrile and water are azeotropic, and dimethyl sulfoxide will also decompose due to high temperature during the distillation process. It is difficult to separate this material and reuse the acrylonitrile monomer by distillation alone. If the degassing condensate cannot be reasonably recycled, the loss of solvent dimethyl sulfoxide and monomer acrylonitrile will greatly increase, thereby increasing production costs; on the other hand, the monomer acrylonitrile will enter the emission system, which will cause serious environmental problems. Therefore, in the production process of PAN-based carbon fiber, the separation and recovery of dimethyl sulfoxide and acrylonitrile in the degassing condensate is also a very important issue. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem of high difficulty in separating dimethyl sulfoxide and acrylonitrile in the prior art, and to provide a device and method for recovering acrylonitrile and dimethyl sulfoxide in a mixture, wherein the device has the characteristics of high separation efficiency and low energy consumption.

[0005] To achieve the above object, a first aspect of the present invention provides a device for recovering acrylonitrile and dimethyl sulfoxide in a mixture. The device includes: a rectification unit I for rectifying the mixture to obtain a product stream containing dimethyl sulfoxide, an aqueous phase, and a light component phase; the rectification unit I is provided with a side-line feed section for the mixture and a side-line discharge section for the aqueous phase disposed below the side-line feed section for the mixture. The side-line discharge section for the aqueous phase is provided with a first membrane separation component for separating water in the discharged aqueous phase to obtain a first recycle material. The first recycle material discharge port of the first membrane separation component is communicated with the rectification unit; a rectification unit II for rectifying the gas-phase discharge of the rectification unit I to obtain a side-line product stream containing acrylonitrile.

[0006] A second aspect of the present invention provides a method for recovering acrylonitrile and dimethyl sulfoxide in a mixture, characterized in that the method is carried out in the device described in the first aspect, and includes:

[0007] (1) Feeding the mixture into the rectification unit I from the side-line feed section for the mixture, extracting a light component phase stream from the top of the rectification unit I, extracting the aqueous phase from the side-line discharge section for the aqueous phase, and extracting a product stream containing dimethyl sulfoxide from the bottom. Among them, the aqueous phase is dehydrated through the first membrane separation component to obtain a first recycle material and recycled back to the rectification unit I;

[0008] (2) After the light component phase extracted from the top of the rectification unit I is first condensed, at least a part is introduced into the rectification unit II, and optionally, a part is recycled back to the rectification unit I; the gas-phase discharge from the top of the rectification unit II is separated and dehydrated through a second membrane separation component, second condensed, and recycled back to the rectification unit II, and a product stream containing acrylonitrile is obtained at the side-line.

[0009] Through the above technical solutions, the present invention has the following advantages:

[0010] Through the device of the present invention, the efficient recovery of acrylonitrile and dimethyl sulfoxide can be realized, and the recovery energy consumption is low. Description of the Drawings

[0011] Figure 1 is a device and a flow chart according to a preferred embodiment of the present invention.

[0012] Description of the Reference Numerals in the Drawings

[0013] T1 Solvent Recovery Tower; 5, First Recovered Aqueous Phase;

[0014] R1 First Membrane Separation System; 6, Gas Phase at the Top of the Solvent Tower

[0015] E-1 First Condenser 7, First Reflux Liquid;

[0016] T2, Monomer Refining Tower 8, Light Fraction of the Solvent Tower;

[0017] R2 The second membrane separation system; 9. The gas phase at the top of the refining tower;

[0018] E-2 The second condenser; 10. The second recycled aqueous phase;

[0019] 1. The condensate of removing monomer and defoaming; 11. The gas phase after membrane separation;

[0020] 2. The first heavy component; 12. The second condensate;

[0021] 3. The side-draw material; 13. The second heavy component;

[0022] 4. The first recycle material; 14. The separated product. Specific embodiments

[0023] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0024] In the present invention, unless otherwise stated, the orientation terms such as "upper, lower, left, right" generally refer to the upper, lower, left, right shown in the reference drawings; "inner, outer" refer to the inner and outer of the contour of each component itself.

[0025] In the present invention, unless otherwise specified, "the bottom of the tower" refers to the position of 90 - 100% from top to bottom of the container; "the top of the tower" refers to the position of 0 - 10% from top to bottom of the container; "the upper part" refers to the position of 0 - 30% from top to bottom of the container; "the middle part" refers to the position of 30 - 70% from top to bottom of the container.

[0026] The present invention provides a device for recovering acrylonitrile and dimethyl sulfoxide from a mixture. The device includes: a distillation unit I for distilling the mixture to obtain a product stream containing dimethyl sulfoxide, an aqueous phase, and a light component phase; the distillation unit I is provided with a side-feed part for the mixture and a side-discharge part for the aqueous phase provided below the side-feed part for the mixture, and the side-discharge part for the aqueous phase is provided with a first membrane separation member for separating water in the discharged aqueous phase to obtain a first recycle material, and the first recycle material discharge port of the first membrane separation member is communicated with the distillation unit; a distillation unit II for distilling the gas-phase discharge of the distillation unit I to obtain a side-product stream containing acrylonitrile.

[0027] Through the device of the present invention, the efficient recovery of acrylonitrile and dimethyl sulfoxide can be realized, and the recovery energy consumption is low.

[0028] According to a preferred embodiment of the present invention, the rectification unit I is further provided with a light component reflux pipeline, and preferably, a condenser is provided on the light component reflux pipeline.

[0029] According to a preferred embodiment of the present invention, a second membrane separation component for separating water in the light component phase discharge to obtain a second recycle material is provided in the gas-phase discharge part of the rectification unit II. A light component phase reflux pipeline is provided between the second membrane separation component and the rectification unit II. Preferably, a condenser is provided on the light component phase reflux pipeline.

[0030] In the present invention, any membrane separation component includes a membrane module system, a vacuum system, and a temperature control system.

[0031] According to a preferred embodiment of the present invention, each of the condensers includes a vacuum system and a temperature control system.

[0032] According to a preferred embodiment of the present invention, the rectification unit I includes a rectification column I. The rectification column I has no less than 8 theoretical plates. Taking the rectification column I from bottom to top as 0 - 100% by volume, the aqueous phase side stream discharge part is located at 20 - 50% by volume (equivalent to the plates within the range of the 20 - 50% total theoretical plate number of the column in terms of plates), and the side stream feed part is located at 40 - 80% by volume.

[0033] According to a preferred embodiment of the present invention, the rectification unit II includes a rectification column II. The rectification column II has 10 - 30 theoretical plates. Taking the rectification column II from bottom to top as 0 - 100% by volume, the feed part is located at 20 - 60% by volume, and the side stream product logistics discharge part containing acrylonitrile is located at 10 - 40% by volume.

[0034] According to a preferred embodiment of the present invention, the membrane of the first membrane separation component is an inorganic molecular sieve membrane and / or an organic polymer membrane; preferably an inorganic molecular sieve membrane;

[0035] According to a preferred embodiment of the present invention, the membrane of the second membrane separation component is an inorganic molecular sieve membrane and / or an organic polymer membrane; preferably an inorganic molecular sieve membrane.

[0036] The present invention provides a method for recovering acrylonitrile and dimethyl sulfoxide in a mixture. This method is carried out in the described device and includes:

[0037] (1) Feeding the mixture into the rectification unit I from the mixture side stream feed part, taking out the light component phase logistics from the top of the rectification unit I, taking out the aqueous phase from the aqueous phase side stream discharge part, and taking out the product logistics containing dimethyl sulfoxide from the bottom. Among them, the aqueous phase is passed through the first membrane separation component to remove water to obtain a first recycle material and recycle it back to the rectification unit I;

[0038] (2) After the light component phase taken from the top of the rectification unit I is first condensed, at least part of it is introduced into the rectification unit II, and optionally, part of it is recycled back to the rectification unit I; the overhead gas discharge of the rectification unit II is separated and dehydrated by the second membrane separation element, and after the second condensation, it is recycled back to the rectification unit II, and a product stream containing acrylonitrile is obtained at the side line.

[0039] According to a preferred embodiment of the present invention, the content of dimethyl sulfoxide in the mixture is > 50 wt%, the content of acrylonitrile is ≤ 40 wt%, and the content of water is ≤ 8 wt%.

[0040] In the present invention, the contents of acrylonitrile and water in the mixture need to meet the requirements of rectification. Generally, the content of acrylonitrile is ≥ 2 wt%, preferably ≥ 5 wt%; the content of water is ≥ 1 wt%.

[0041] According to a preferred embodiment of the present invention, the conditions for the first condensation include: the temperature does not exceed 38 °C, preferably does not exceed 25 °C, and more preferably does not exceed 15 °C.

[0042] According to a preferred embodiment of the present invention, the conditions for the second condensation include: the temperature does not exceed 25 °C, preferably does not exceed 15 °C, and more preferably does not exceed 10 °C

[0043] According to a preferred embodiment of the present invention, the operating conditions of the rectification unit I include: the pressure is 7 - 25 kPa.

[0044] According to a preferred embodiment of the present invention, the operating conditions of the rectification unit I include: the bottom temperature is 100 - 140 °C.

[0045] According to a preferred embodiment of the present invention, the operating conditions of the rectification unit I include: the reflux ratio is 0.5 - 20, preferably 2 - 10.

[0046] According to a preferred embodiment of the present invention, the operating conditions of the rectification unit II include: the pressure is 35 - 85 kPa.

[0047] According to a preferred embodiment of the present invention, the operating conditions of the rectification unit II include: the bottom temperature is 40 - 75 °C.

[0048] According to a preferred embodiment of the present invention, the temperature difference between the side line product stream containing acrylonitrile and the bottom temperature does not exceed 5 °C, preferably does not exceed 3 °C.

[0049] According to a preferred embodiment of the present invention, the operating conditions of the first membrane separation element include: the pressure is 5 - 20 kPa, preferably 5 - 15 kPa, and the membrane module temperature is 10 - 65 °C.

[0050] According to a preferred embodiment of the present invention, the operating conditions of the second membrane separation component include: a pressure of 5 - 30 kPa, preferably 10 - 25 kPa, and a membrane module temperature of 10 - 65 °C.

[0051] As Figure 1 , the present invention provides a device and a flow chart of a preferred embodiment:

[0052] The device includes: a solvent recovery tower T1, a first membrane separation system R1, a first condenser E-1, a monomer purification tower T2, a second membrane separation system R2, and a second condenser E-2, which are connected in sequence; the solvent recovery tower includes a rectification section, one end of which is connected to a stirred heating kettle or a heating section, the middle section is connected to the membrane separation system R1, and the top of the solvent recovery tower T1 is connected to the first condenser E-1; the outlet of the first condenser E-1 includes a reflux ratio distributor or a reflux drum and is provided with a circulation pipeline, part of the material is refluxed to the top of the solvent recovery tower, and the other part of the material extraction port is connected to the feed port of the monomer purification tower. The top of the monomer purification tower is connected to the membrane separation system R2, the back end of the membrane separation system is connected to the second condenser E-2, and the extraction end of the second condenser is connected to the top of the monomer purification tower T2; a side line discharge port is provided between the feed port and the bottom of the monomer purification tower.

[0053] The process includes:

[0054] The raw material degassed and defoamed condensate 1 enters the solvent recovery tower T1, the first heavy component 2 is separated from the bottom of the evaporation tower, the material 3 is extracted from the side line and enters the first membrane separation system R1, the first recycled material 4 after separating the first recovered aqueous phase 5 returns to the solvent recovery tower, the gas phase 6 at the top of the solvent recovery tower enters the condenser E-1 for condensation, part of the condensate (the first reflux liquid 7) is refluxed to the T1 tower, and the other part is taken out as the light fraction 8 of the solvent tower; the light fraction material 8 separated from the solvent recovery tower T1 enters the monomer purification tower T2, the gas phase 9 at the top of the purification tower T2 enters the second membrane separation system R2, the recovered aqueous phase 10 is directly separated from the membrane separation system to obtain the gas phase 11 after membrane separation and then enters the condenser E-2, the second condensate 12 after the material is condensed is fully refluxed to the T2 tower, the separated product 14 containing acrylonitrile is taken out from the side line of the T2 tower, and the second heavy component 13 is taken out from the bottom of the tower.

[0055] The present invention will be described in detail below through examples. In the following examples, all are carried out in the Figure 1 shown device. The moisture content parameter is measured by methods such as a moisture meter, and parameters such as DMSO and acrylonitrile content are measured by methods such as gas chromatography and refractometer; unless otherwise specified, the raw materials are commercially available products.

[0056] Example 1

[0057] The polyacrylonitrile-based carbon fiber degassing condensate with an acrylonitrile content of 10 wt%, a water content of 2 wt%, and a dimethyl sulfoxide content of 88% is used as the raw material to be separated and enters the solvent recovery column T1 with a total of 8 theoretical plates at the 4th theoretical plate. Distillation is carried out under the conditions of 25 kPa and a column bottom temperature of 133 °C. The material is withdrawn from the side of the 3rd theoretical plate of the T1 column and enters the first membrane separation system. The operating pressure of the first membrane separation system is 15 kPa, and the temperature of the membrane separation module (molecular sieve membrane) is maintained at 55 °C; After R1 separates the first recovered aqueous phase 5, it returns to the solvent recovery column; The gas-phase material at the top of the solvent recovery column enters the condenser E-1, the condensation temperature does not exceed 30 °C, and the reflux ratio of the condensate is 10. The light fraction material withdrawn from the solvent recovery column enters the monomer refining column T2 with 10 theoretical plates at the 2nd theoretical plate (20%, based on the total volume, the same below). Distillation is carried out under the conditions of 80 kPa and a column bottom temperature of 70 °C. The gas-phase material enters the second membrane separation system from the top of the monomer refining column. The operating pressure of the second membrane separation system is 25 kPa, the temperature of the membrane separation module is maintained at 65 °C, and the condensation temperature is 30 °C. The logistics after the membrane separation system separates the recovered aqueous phase enters the condenser E-2 with a condensation temperature not exceeding 35 °C. After the material is condensed, it is fully refluxed. The fraction withdrawn from the side of the 1st theoretical plate of the T2 column (10%, based on the total volume, the same below) is the recovered acrylonitrile monomer product, and the temperature difference between the side draw temperature and the column bottom temperature does not exceed 2 °C.

[0058] After analysis, the DMSO content in the first heavy component is 99.04 wt%, the acrylonitrile content is 0.08 wt%, and the balance is mainly water; The purity of the acrylonitrile product withdrawn from the side of T2 is 99.66%, and the water content is 0.34 wt%.

[0059] Example 2

[0060] The polyacrylonitrile-based carbon fiber degassing condensate with an acrylonitrile content of 10 wt%, a water content of 2 wt%, and a dimethyl sulfoxide content of 88% is used as the raw material to be separated and enters a solvent recovery column with a total of 20 theoretical plates at the 16th theoretical plate. Distillation is carried out under the conditions of 20 kPa and a column bottom temperature of 129 °C. The material is taken from the side line at the 10th theoretical plate of Tower T1 and enters the first membrane separation system. The operating pressure of the first membrane separation system is 10 kPa, and the temperature of the membrane separation module is maintained at 46 °C; After the first recovered aqueous phase 5 is separated by R1, it is returned to the solvent recovery column; The gas-phase material at the top of the solvent recovery column enters condenser E-1, the condensation temperature does not exceed 25 °C, and the reflux ratio of the condensate is 8. The light fraction material taken from the solvent recovery column enters a monomer purification column containing 30 theoretical plates at the 18th theoretical tray (60%). Distillation is carried out under the conditions of 70 kPa and a column bottom temperature of 66 °C. The gas-phase material enters the second membrane separation system from the top of the monomer purification column. The operating pressure of the second membrane separation system is 20 kPa, the temperature of the membrane separation module is maintained at 60 °C, and the condensation temperature is 30 °C. The logistics after the membrane separation system separates the recovered aqueous phase enters condenser E-2 with a condensation temperature not exceeding 35 °C. After the material is condensed, it is fully refluxed. The fraction taken from the side line at the 12th theoretical plate (40%) of Tower T2 is the recovered acrylonitrile monomer product; The temperature difference between the side line draw temperature and the column bottom temperature does not exceed 1 °C.

[0061] After analysis, the DMSO content in the first heavy component is 98.86 wt%, the acrylonitrile content is 0.21 wt%, and the balance is mainly water; The purity of the acrylonitrile product taken from the side line of T2 is 99.87%, and the water content is 0.13 wt%.

[0062] Example 3

[0063] The polyacrylonitrile-based carbon fiber desing and degassing condensate with an acrylonitrile content of 10wt%, a water content of 2wt% and a dimethyl sulfoxide content of 88% is used as the raw material to be separated, and enters a solvent recovery tower with a total of 15 theoretical plates from the 9th theoretical plate, and is distilled under the conditions of 15kPa and a bottom temperature of 120°C. The side line material from the 3rd theoretical plate of tower T1 enters the first membrane separation system, the operating pressure of the first membrane separation system is 8kPa, and the temperature of the membrane separation component is maintained at 42°C; R1 separates the first recovered water phase 5 and returns it to the solvent recovery tower; the gas phase material at the top of the solvent recovery tower enters the condenser E-1, the condensation temperature does not exceed 15°C, and the reflux ratio of the condensate is 5. The light fraction material extracted from the solvent recovery tower enters the monomer refining tower with 20 theoretical plates from the 8th theoretical plate (40%), and is distilled under the conditions of 60kPa and 60°C tower bottom temperature. The gaseous material enters the second membrane separation system from the top of the monomer refining tower. The operating pressure of the second membrane separation system is 15kPa, and the temperature of the membrane separation component is maintained at 55°C. The logistics after the membrane separation system separates the recovered water phase enters the condenser E-2 with a condensation temperature not exceeding 35°C. After the material is condensed, it is fully refluxed. The fraction extracted from the side line at the 5th theoretical plate (25%) of the T2 tower is the recovered acrylonitrile monomer product; the temperature difference between the side line extraction temperature and the tower bottom temperature does not exceed 1°C.

[0064] After analysis, the DMSO content in the first heavy component was 99.12wt%, the acrylonitrile content was 0.02wt%, and the remainder was mainly water; the acrylonitrile product extracted from the T2 side line had a purity of 99.75%, and the water content was 0.25wt%.

[0065] Example 4

[0066] The polyacrylonitrile-based carbon fiber desing and degassing condensate with an acrylonitrile content of 10wt%, a water content of 2wt% and a dimethyl sulfoxide content of 88% is used as the raw material to be separated, and enters a solvent recovery tower with a total of 8 theoretical plates from the third theoretical plate, and is distilled under the conditions of 9kPa and a bottom temperature of 118°C. The side line material from the third theoretical plate of the T1 tower enters the first membrane separation system, the operating pressure of the first membrane separation system is 5kPa, and the temperature of the membrane separation component is 35°C; R1 separates the first recovered water phase and returns it to the solvent recovery tower; the gas phase material at the top of the solvent recovery tower enters the condenser E-1, the condensation temperature does not exceed 12°C, and the reflux ratio of the condensate is 2. The light fraction material extracted from the solvent recovery tower enters the monomer refining tower with 25 theoretical plates from the 7th theoretical plate (30%), and is distilled under the conditions of 50kPa and a bottom temperature of 57°C. The gaseous material enters the second membrane separation system from the top of the monomer refining tower. The operating pressure of the second membrane separation system is 12kPa, the temperature of the membrane separation component is maintained at 50°C, and the condensation temperature is 20°C. The logistics after the membrane separation system separates the recovered water phase enters the condenser E-2 with a condensation temperature not exceeding 20°C. After the material is condensed, it is fully refluxed. The fraction extracted from the side line at the 5th theoretical plate (20%) of the T2 tower is the recovered acrylonitrile monomer product; the temperature difference between the side line extraction temperature and the bottom temperature does not exceed 3°C.

[0067] After analysis, the DMSO content in the first heavy component was 98.74wt%, the acrylonitrile content was 0.24wt%, and the remainder was mainly water; the acrylonitrile product extracted from the T2 side line had a purity of 99.68wt%, and the water content was 0.32wt%.

[0068] Example 5

[0069] The acrylonitrile-based carbon fiber degassing condensate with an acrylonitrile content of 10 wt%, a water content of 2 wt%, and a dimethyl sulfoxide content of 88% is used as the raw material to be separated. It enters a solvent recovery column with a total of 25 theoretical plates at the 13th theoretical plate, and distillation is carried out under the conditions of 7 kPa and a column bottom temperature of 105 °C. The material is taken out from the side line at the 7th theoretical plate of the T1 column and enters the first membrane separation system. The operating pressure of the first membrane separation system is 5 kPa, and the temperature of the membrane separation module is 35 °C; after R1 separates the first recycled aqueous phase, it returns to the solvent recovery column; the gas-phase material at the top of the solvent recovery column enters condenser E-1, the condensation temperature does not exceed 10 °C, and the reflux ratio of the condensate is 1. The light fraction material taken out from the solvent recovery column enters a monomer refining column with 15 theoretical plates at the 8th theoretical plate (50%), and distillation is carried out under the conditions of 40 kPa and a column bottom temperature of 52 °C. The gas-phase material enters the second membrane separation system from the top of the monomer refining column. The operating pressure of the second membrane separation system is 10 kPa, the temperature of the membrane separation module is maintained at 46 °C, and the condensation temperature is 20 °C. The logistics after the membrane separation system separates the recycled aqueous phase enters condenser E-2 with a condensation temperature not exceeding 20 °C. After the material is condensed, it is fully refluxed, and the fraction taken out from the side line at the 5th theoretical plate (30%) of the T2 column is the recovered acrylonitrile monomer product, and the temperature difference between the side line take-out temperature and the column bottom temperature does not exceed 3 °C.

[0070] After analysis, the DMSO content in the first heavy component is 97.34 wt%, and the balance is mainly water; the purity of the acrylonitrile product taken out from the side line of T2 is 99.61%.

[0071] Comparative Example 1

[0072] The polyacrylonitrile-based carbon fiber degassing condensate with an acrylonitrile content of 10 wt%, a water content of 2 wt%, and a dimethyl sulfoxide content of 88% is used as the raw material to be separated. It enters the solvent recovery column T1 with a total of 8 theoretical plates at the 4th theoretical plate. Distillation is carried out under the conditions of 25 kPa and a tower bottom temperature of 133 °C. The material is taken from the side line at the 7th theoretical plate of the T1 tower and enters the first membrane separation system. The operating pressure of the first membrane separation system is 15 kPa, and the temperature of the membrane separation module (molecular sieve membrane) is maintained at 55 °C; after R1 separates the first recovered aqueous phase 5, it returns to the solvent recovery column; the gas-phase material at the top of the solvent recovery column enters the condenser E-1, the condensation temperature does not exceed 30 °C, and the reflux ratio of the condensate is 10. The light fraction material taken from the solvent recovery column enters the monomer purification column T2 with 10 theoretical plates at the 2nd theoretical plate (20%). Distillation is carried out under the conditions of 80 kPa and a tower bottom temperature of 70 °C. The gas-phase material enters the second membrane separation system from the top of the monomer purification column. The operating pressure of the second membrane separation system is 25 kPa, the temperature of the membrane separation module is maintained at 65 °C, and the condensation temperature is 30 °C. The logistics after the membrane separation system separates the recovered aqueous phase enters the condenser E-2 with a condensation temperature not exceeding 35 °C. After the material is condensed, it is fully refluxed. The fraction taken from the side line at the 1st theoretical plate (10%) of the T2 tower is the recovered acrylonitrile monomer product, and the temperature difference between the side line extraction temperature and the tower bottom temperature is 2 °C.

[0073] After analysis, the DMSO content in the first heavy component is 97.33 wt%, the acrylonitrile content is 0.84 wt%, and the balance is mainly water; the purity of the acrylonitrile product taken from the side line of T2 is 98.52%, and the water content is 1.48 wt%.

[0074] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An apparatus for recovering acrylonitrile and dimethyl sulfoxide from a mixture, characterized in that, the apparatus comprises: Rectification unit I, which is used for rectifying the mixture to obtain a product stream containing dimethyl sulfoxide, an aqueous phase and a light component phase; the rectification unit I is provided with a side-line feed section for the mixture, and a side-line discharge section for the aqueous phase provided below the side-line feed section for the mixture. The side-line discharge section for the aqueous phase is provided with a first membrane separation member for separating water from the discharged aqueous phase to obtain a first recycle material, and a first recycle material discharge port of the first membrane separation member is communicated with the rectification unit; Rectification unit II, which is used for rectifying the gas-phase discharge of rectification unit I to obtain a side-line product stream containing acrylonitrile.

2. The apparatus according to claim 1, wherein, the rectification unit I is further provided with a light component reflux pipeline, and preferably a condenser is provided on the light component reflux pipeline.

3. The apparatus according to claim 1 or 2, wherein, the gas-phase discharge section of the rectification unit II is provided with a second membrane separation member for separating water from the discharged light component phase to obtain a second recycle material, and a light component phase reflux pipeline is provided between the second membrane separation member and the rectification unit II. Preferably, a condenser is provided on the light component phase reflux pipeline.

4. The apparatus according to any one of claims 1-3, wherein, the rectification unit I comprises a rectification column I, and the theoretical number of trays of the rectification column I is not less than 8. Taking the rectification column I from bottom to top as 0-100% by volume, the side-line discharge section for the aqueous phase is located at 20-50% by volume, and the side-line feed section is located at 40-80% by volume.

5. The apparatus according to any one of claims 1-4, wherein, the rectification unit II comprises a rectification column II, and the theoretical number of trays of the rectification column II is 10-30. Taking the rectification column II from bottom to top as 0-100% by volume, the feed section is located at 20-60% by volume, and the side-line product stream discharge section containing acrylonitrile is located at 10-40% by volume.

6. The apparatus according to any one of claims 1-5, wherein, the membrane of the first membrane separation member is an inorganic molecular sieve membrane and / or an organic polymer membrane; preferably an inorganic molecular sieve membrane; the membrane of the second membrane separation member is an inorganic molecular sieve membrane and / or an organic polymer membrane; preferably an inorganic molecular sieve membrane.

7. A method for recovering acrylonitrile and dimethyl sulfoxide from a mixture, characterized in that, the method is carried out in the apparatus described in claims 1-6, and comprises: (1) Feeding the mixture into the rectification unit I from the side-line feed section for the mixture, taking out the light component phase stream from the top of the rectification unit I, taking out the aqueous phase from the side-line discharge section for the aqueous phase, and taking out the product stream containing dimethyl sulfoxide from the bottom. Among them, the aqueous phase is dehydrated by the first membrane separation member to obtain a first recycle material and recycled back to the rectification unit I; (2) Condensing the light component phase taken out from the top of the rectification unit I for the first time, and at least partially introducing it into the rectification unit II, and optionally partially recycling it back to the rectification unit I; the gas-phase discharge from the top of the rectification unit II is separated and dehydrated by the second membrane separation member, condensed for the second time and recycled back to the rectification unit II, and a product stream containing acrylonitrile is obtained at the side-line.

8. The method according to claim 7, Among them, the content of dimethyl sulfoxide in the mixture is > 50 wt%, the content of acrylonitrile is ≤ 40 wt%, and the content of water is ≤ 8 wt%.

9. The method according to claim 7 or 8, wherein, the operating conditions of the first distillation unit include: the pressure is 7 - 25 kPa; and / or the bottom temperature is 100 - 140 °C; and / or the reflux ratio is 0.5 - 20, preferably 2 - 10; and / or the operating conditions of the second distillation unit include: the pressure is 35 - 85 kPa; and / or the bottom temperature is 40 - 75 °C; and / or the temperature difference between the side stream acrylonitrile-containing product stream extraction temperature and the bottom temperature does not exceed 5 °C, preferably does not exceed 3 °C.

10. The method according to any one of claims 7 - 9, wherein, the operating conditions of the first membrane separation element include: the pressure is 5 - 20 kPa, preferably 5 - 15 kPa, and the membrane module temperature is 10 - 65 °C; and / or the operating conditions of the second membrane separation element include: the pressure is 5 - 30 kPa, preferably 10 - 25 kPa, and the membrane module temperature is 10 - 65 °C.

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