Method and system for separating water-acrylonitrile-DMSO ternary mixed material

Abstract

The invention discloses a method and a system for separating a water-acrylonitrile-DMSO mixed material. The method comprises the following steps: (1) carrying out rectification treatment on a ternary mixed material to obtain a DMSO-rich material and an acrylonitrile-water binary mixture; (2) cooling the acrylonitrile-water binary mixture, and performing liquid separation to obtain an acrylonitrile-rich liquid phase and a water-rich liquid phase; and (3) respectively and independently rectifying the acrylonitrile-rich liquid phase and the water-rich liquid phase to respectively obtain pure acrylonitrile and pure water. Compared with the prior art, the method has the advantages that the DMSO and the acrylonitrile-water binary mixture are obtained through separation in a conventional rectification mode, introduction of impurities in extractive distillation is avoided in the separation process, the problem that heterogeneous reflux of pressure swing distillation light component azeotrope is difficult to control is solved, acrylonitrile in a receipt can be directly reused as a raw material, and the method is suitable for industrial production. The influence of direct use of the receipt on the polymerization reaction stability and the polymerization product quality is avoided.

Description

Technical Field

[0001] The invention belongs to the field of material separation, and in particular relates to a method and a system for separating a water-acrylonitrile-DMSO mixture. Background Art

[0002] Polyacrylonitrile-based carbon fiber is a new material with excellent mechanical properties. It is an indispensable engineering material for the aerospace and defense military industries. It is also widely used in civilian fields such as sporting goods, transportation, medical equipment, and civil engineering.

[0003] In the production process of polyacrylonitrile-based carbon fiber precursor, acrylonitrile (AN) monomer is polymerized with dimethyl sulfoxide (DMSO) as solvent, and the obtained polymer is used to produce carbon fiber precursor after de-monomerization and degassing. During the de-monomerization and degassing process, the unreacted monomer AN, the reaction solvent DMSO and the water contained in the raw materials in the polymerization liquid will be temporarily stored for use after gasification, condensation and DMSO absorption. This part of the material temporarily stored for use is called "return slip" or "recovery liquid". DMSO is the main component in the return slip, and AN and water account for a lower proportion. The return slip can be directly used as a raw material for polymerization, but the DMSO and AN added during the polymerization batching process contain trace amounts of water, which causes the water content in the return slip to accumulate, thereby affecting the stability of the polymerization reaction and the quality of the polymerization product. A more reasonable way is to remove the water in the return slip by separating the components, but because AN and water are azeotropes, and their concentration is heterogeneous when it is greater than the solubility, the light component azeotrope is heterogeneous when using pressure swing distillation technology, and the reflux is difficult to control. When extractive distillation is used, an extractant needs to be introduced, and the residue of the extractant has a certain influence on the polymerization reaction. Therefore, how to separate DMSO-AN-water and avoid the accumulation of water content in the return is a technical problem in this field. Summary of the invention

[0004] In order to overcome the problems existing in the prior art, the present invention provides a method and system for separating a water-acrylonitrile-DMSO ternary mixture, which can remove water from the mixture and obtain acrylonitrile monomer with higher purity and DMSO with higher purity.

[0005] One of the purposes of the present invention is to provide a method for separating a ternary mixture of water, acrylonitrile and DMSO, wherein the mixture contains DMSO, acrylonitrile and water, and the method comprises: (1) subjecting the ternary mixture to distillation to obtain a DMSO-rich material and an acrylonitrile-water binary mixture; (2) cooling the acrylonitrile-water binary mixture and separating the mixture into an acrylonitrile-rich liquid phase and a water-rich liquid phase; and (3) independently distilling the acrylonitrile-rich liquid phase and the water-rich liquid phase to obtain pure acrylonitrile and pure water, respectively.

[0006] In a preferred embodiment, the water-acrylonitrile-DMSO ternary mixture is produced in the production process of polyacrylonitrile-based carbon fiber precursor, and acrylonitrile (AN) monomer is polymerized with dimethyl sulfoxide (DMSO) as solvent, and the resulting polymer is used to produce carbon fiber precursor after de-monomerization and degassing. During the de-monomerization and degassing process, the unreacted monomer AN in the polymerization solution, the reaction solvent DMSO and the water contained in the raw materials will be temporarily stored after gasification, condensation and DMSO absorption. This part of the material temporarily stored for use is called the receipt. The receipt contains DMSO, acrylonitrile and water.

[0007] In a further preferred embodiment, the water-acrylonitrile-DMSO ternary mixture contains 1-98wt% DMSO, 1-98wt% acrylonitrile, and 0.5-98wt% water, preferably 50-98wt% DMSO, 1-40wt% acrylonitrile, and 0.5-10wt% water.

[0008] For example, the water-acrylonitrile-DMSO ternary mixture contains 1wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, 90wt% or 98wt% of DMSO, 1wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, 90wt% or 98wt% of acrylonitrile, 0.5wt%, 1wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, 90wt% or 98wt% of DMSO, and 1wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt% or 98wt% of water.

[0009] In a preferred embodiment, the method is carried out under vacuum conditions.

[0010] In a preferred embodiment, the distillation in step (1) is carried out in a DMSO separation tower, the water-acrylonitrile-DMSO ternary mixture enters the DMSO separation tower in the middle, the DMSO-rich material is obtained in the bottom of the tower, and the acrylonitrile-water binary mixture is obtained at the top of the tower.

[0011] Preferably, a reboiler is provided in the bottom of the DMSO separation tower. More preferably, the bottom material of the DMSO separation tower is divided into two streams, one of which is heated by the reboiler and refluxed to the DMSO separation tower (preferably the lower part), and the other is collected externally.

[0012] In a further preferred embodiment, the DMSO separation tower is a distillation tower, and its conditions include: a top temperature range of -20°C to 100°C, a top pressure range of 0.1 kpa to 101.3 kpa (abs), a bottom temperature range of 90 to 200°C (preferably 99.6°C to 189°C), and a bottom pressure range of 1 kpa to 101.3 kpa (abs).

[0013] For example, the DMSO separation tower is a distillation tower, and its conditions include: a top temperature range of -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, a top pressure range of 0.1 kpa, 0.5 kpa, 1 kpa, 5 kpa, 10 kpa, 20 kpa, 40 kpa, 60 kpa, 80 kpa or 101.3 kpa, a bottom temperature range of 90°C, 100°C, 120°C, 140°C, 160°C, 180°C or 200°C, and a bottom pressure range of 1 kpa, 5 kpa, 10 kpa, 20 kpa, 40 kpa, 60 kpa, 80 kpa or 101.3 kpa.

[0014] Among them, after a lot of experimental research, the inventors found that compared with below 90°C (for example, around 60°C), controlling the bottom temperature of the DMSO separation tower at 90-200°C can obtain DMSO with higher purity in the bottom of the tower.

[0015] In a preferred embodiment, the DMSO-rich material in step (1) can be purified by a DMSO distillation system.

[0016] In a preferred embodiment, in step (2), the temperature is cooled to 0-30°C, preferably 0-10°C.

[0017] Among them, the inventors found in a large number of experiments that it is easier to separate water and acrylonitrile at low temperatures, which can reduce the acrylonitrile content on the water-rich side and the water content on the acrylonitrile-rich side. And the separation load of step 3 can be reduced. Specifically, the inventors found in the experiment that: at 0°C, the solubility of water in acrylonitrile [(mass), %] is 2.10, and the solubility of acrylonitrile in water [(mass), %] is 7.15; at 10°C, the solubility of water in acrylonitrile [(mass), %] is 2.55, and the solubility of acrylonitrile in water [(mass), %] is 7.17; at 20°C, the solubility of water in acrylonitrile [(mass), %] is 3.08, and the solubility of acrylonitrile in water [(mass), %] is 7.30; at 30°C, the solubility of water in acrylonitrile [(mass), %] is 3.82, and the solubility of acrylonitrile in water [(mass), %] is 7.51.

[0018] Among them, the materials for the liquid separation include materials after condensation of the gas phase after distillation treatment of the ternary mixture material (i.e., the gas phase at the top of the DMSO separation tower, i.e., the acrylonitrile-water mixture), materials after condensation of the gas phase after distillation treatment of the acrylonitrile-rich liquid phase (i.e., the gas phase at the top of the acrylonitrile separation tower), and materials after condensation of the gas phase after distillation treatment of the water-rich liquid phase (i.e., the gas phase at the top of the water separation tower).

[0019] In a preferred embodiment, in step (3), the acrylonitrile-rich liquid phase is distilled to obtain pure acrylonitrile, and the water-rich liquid phase is divided into two streams (a first water-rich liquid phase and a second water-rich liquid phase). The first water-rich liquid phase is distilled to obtain pure water, and the second water-rich liquid phase is refluxed to the distillation in step (1) as reflux liquid.

[0020] In a further preferred embodiment, the second water-rich liquid phase is refluxed to the top of the DMSO separation tower as reflux liquid. In this way, only the water-rich liquid phase is circulated back to the DMSO separation tower without a large amount of acrylonitrile, which can reduce the acrylonitrile content in the bottom of the DMSO separation tower.

[0021] In a preferred embodiment, the acrylonitrile-rich liquid phase is distilled in an acrylonitrile separation tower, the acrylonitrile-rich liquid phase enters the acrylonitrile separation tower at the top, pure acrylonitrile is obtained in the bottom of the acrylonitrile separation tower, and the top material of the acrylonitrile separation tower is cooled and recycled to step (2) for the liquid separation.

[0022] Among them, the inventors have found through a large number of experimental studies that, compared with feeding in the middle, when the acrylonitrile-rich liquid phase is fed at the top of the acrylonitrile separation tower, acrylonitrile with higher purity can be obtained in the bottom of the acrylonitrile separation tower. Even if the top material of the acrylonitrile separation tower contains unrecovered acrylonitrile, it will not cause waste, because the top material will be circulated back to the liquid separation for further separation. In addition, the top of the acrylonitrile separation tower does not need to be provided with a reflux tank to reflux back to the top of the tower, which simplifies the equipment and saves energy consumption.

[0023] Preferably, a reboiler is provided in the bottom of the acrylonitrile separation tower. More preferably, the bottom material of the acrylonitrile separation tower is divided into two streams, one stream is heated by the reboiler and refluxed to the acrylonitrile separation tower (preferably the lower part), and the other stream is collected externally and becomes the pure acrylonitrile. More preferably, the other stream enters the acrylonitrile storage tank after being cooled.

[0024] In a further preferred embodiment, the acrylonitrile separation tower is a distillation tower, and its conditions include: the top temperature range is -20°C to 80°C (preferably -23°C to 79.8°C), the top pressure range is 0.1kpa to 101.3kpa (abs), the bottom temperature range is 10°C to 90°C (preferably 10.5°C to 84.7°C), and the bottom pressure range is 1kpa to 101.3kpa (abs).

[0025] For example, the acrylonitrile separation tower is a distillation tower, and its conditions include: a top temperature range of -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C, a top pressure range of 0.1 kPa, 0.5 kPa, 1 kPa, 5 kPa, 10 kPa, 20 kPa, 60 kPa, 80 kPa or 101.3 kPa, a bottom temperature range of 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C, and a bottom pressure range of 1 kPa (bas) to 101.3 kPa (bas).

[0026] In a preferred embodiment, part or all of the water-rich liquid phase is separated in a water separation tower, the water-rich liquid phase enters the water separation tower at the top, pure water is obtained in the bottom of the water separation tower, and the top material of the water separation tower is cooled and recycled to step (2) for the liquid separation.

[0027] Among them, the inventors have found through a large number of experimental studies that, compared with feeding in the middle, when the water-rich liquid phase is fed at the top of the water separation tower, water with higher purity can be obtained in the bottom of the water separation tower. Even if the top material of the water separation tower contains unrecovered water, it will not cause waste, because the top material will be circulated back to the liquid separation for further separation. In addition, the top of the water separation tower does not need to be provided with a reflux tank to reflux back to the top of the tower, which simplifies the equipment and saves energy consumption.

[0028] Preferably, a reboiler is provided in the bottom of the water separation tower. More preferably, the bottom material of the water separation tower is divided into two streams, one of which is heated by the reboiler and refluxed to the water separation tower (preferably the lower part), and the other is collected externally and becomes the pure water. More preferably, the other stream enters the water storage tank after cooling.

[0029] In a further preferred embodiment, the water separation tower is a distillation tower, and its conditions include: the top temperature range is -20°C to 100°C (preferably -23°C to 97.6°C), the top pressure range is 0.1kpa to 101.3kpa (abs), the bottom temperature range is 30°C to 110°C (preferably 33°C to 106.3°C), and the bottom pressure range is 6kpa to 101.6kpa (abs).

[0030] For example, the water separation tower is a distillation tower, and its conditions include: the top temperature range is -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, the top pressure range is 0.1kpa, 0.5kpa, 1kpa, 5kpa, 10kpa, 20kpa, 40kpa, 60kpa, 80kpa or 101.3kpa, the bottom temperature range is 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C or 110°C, and the bottom pressure range is 6kpa, 10kpa, 20kpa, 40kpa, 60kpa, 80kpa or 101.6kpa.

[0031] In a preferred embodiment, in step (3), based on 100 wt% of the water-rich liquid phase, the second water-rich liquid phase as the reflux liquid accounts for 15 to 85 wt%, preferably 25 to 67 wt%.

[0032] For example, in step (3), based on 100 wt% of the water-rich liquid phase, the second water-rich liquid phase serving as the reflux liquid accounts for 15 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt% or 85 wt%.

[0033] In a preferred embodiment, the liquid separation in step (2) is carried out in a liquid separation tank.

[0034] In a further preferred embodiment, the liquid separation tank is connected to a vacuum system, so that the DMSO separation tower, the acrylonitrile separation tower and the water separation tower can be placed in a vacuum state for distillation separation.

[0035] In a preferred embodiment, the acrylonitrile-rich liquid phase and the water-rich liquid phase in step (3) are independently distilled, which means that intermittent or continuous operation is determined separately or simultaneously according to the liquid level and storage of the acrylonitrile-rich liquid phase and the water-rich liquid phase in the liquid separation tank in step (2). When intermittent operation is adopted, it can be avoided that the amount of acrylonitrile-rich liquid phase and / or water-rich liquid phase is lower than the feed amount of the acrylonitrile separation tower and / or the water separation tower due to the low concentration of acrylonitrile and / or water in the return slip is avoided, thereby improving the flexibility of the system.

[0036] Compared with the prior art, the present invention uses conventional distillation to separate DMSO, and uses the principle that acrylonitrile-water binary mixture is heterogeneous when its concentration is greater than its solubility to separate acrylonitrile and water. The separation process avoids the introduction of impurities in extractive distillation and the problem of difficult control of heterogeneous reflux of light component azeotropes in pressure swing distillation, so that acrylonitrile in the return slip can be directly reused as a raw material, avoiding the influence of direct use of the return slip on the stability of the polymerization reaction and the quality of the polymerization product.

[0037] The second object of the present invention is to provide a system for separating a water-acrylonitrile-DMSO ternary mixture, preferably for carrying out the method described in one of the objects of the present invention, wherein the system comprises a DMSO separation tower, a liquid separation device, an acrylonitrile separation tower and a water separation tower.

[0038] In a preferred embodiment, a ternary mixture material inlet is provided in the middle of the DMSO separation tower; a gas phase outlet I is provided at the top of the DMSO separation tower for discharging acrylonitrile-water binary mixture; and a liquid phase outlet I is provided at the bottom of the DMSO separation tower for discharging DMSO-rich liquid phase.

[0039] In a further preferred embodiment, the gas phase outlet I of the DMSO separation tower is connected to the liquid separation device via a pipeline, and a condenser I is further arranged on the pipeline between the gas phase outlet I and the liquid separation device.

[0040] In a further preferred embodiment, the liquid phase outlet I of the DMSO separation tower is divided into two routes (preferably first connected to the discharge pump I through a pipeline and then divided into two routes): one route is connected to the DMSO separation tower (preferably the lower part) through the DMSO separation tower kettle circulation loop, and a reboiler I is provided on the circulation loop; the other route is provided with a DMSO-rich liquid phase extraction pipeline.

[0041] In a preferred embodiment, the liquid separation device is a liquid separation tank, which is provided with an acrylonitrile-water binary mixture feed inlet, an acrylonitrile-rich liquid phase discharge outlet (preferably arranged at the upper part), and a water-rich liquid phase discharge outlet (preferably arranged at the lower part).

[0042] In a further preferred embodiment, the liquid separation device is connected to a vacuum system.

[0043] In a further preferred embodiment, the acrylonitrile-rich liquid phase outlet of the liquid separation device is connected to the top of the acrylonitrile separation tower through a pipeline, and a feed pump I is preferably provided on the pipeline.

[0044] In a further preferred embodiment, the water-rich liquid phase discharge port of the liquid separation device is divided into two paths (preferably first connected to the feed pump II through a pipeline and then divided into two paths): one path is connected to the top of the water separation tower through a pipeline, and the other path is connected to the top or upper part of the DMSO separation tower through a water-rich liquid phase reflux pipeline.

[0045] In a preferred embodiment, an acrylonitrile-rich liquid phase feed inlet is provided at the top of the acrylonitrile separation tower, a gas phase outlet II is provided at the top, and a liquid phase outlet II is provided at the bottom.

[0046] In a further preferred embodiment, the acrylonitrile-rich liquid phase feed inlet of the acrylonitrile separation tower is connected to the acrylonitrile-rich liquid phase outlet of the liquid separation device via a pipeline; and / or, the gas phase outlet II of the acrylonitrile separation tower is connected to the acrylonitrile-water binary mixture feed inlet of the liquid separation device via a pipeline, and a condenser II is arranged on the pipeline; and / or, the liquid phase outlet II of the acrylonitrile separation tower is divided into two paths (preferably first connected to the discharge pump II via a pipeline and then divided into two paths): one path is connected to the lower part of the acrylonitrile separation tower via a pipeline, and the other path is provided with an acrylonitrile extraction pipeline.

[0047] In a further preferred embodiment, a condenser III and an acrylonitrile storage tank are sequentially arranged on the acrylonitrile production pipeline.

[0048] In a preferred embodiment, a water-rich liquid phase feed port is provided at the top of the water separation tower, a gas phase outlet III is provided at the top of the water separation tower, and a liquid phase outlet III is provided at the bottom of the water separation tower.

[0049] In a further preferred embodiment, the water-rich liquid phase feed port is connected to the water-rich liquid phase discharge port of the liquid separation device through a pipeline, the gas phase outlet III of the water separation tower is connected to the acrylonitrile-water binary mixture feed port of the liquid separation device through a pipeline, and a condenser IV is arranged on the pipeline; and / or, the liquid phase outlet III of the water separation tower is divided into two routes (preferably first connected to the discharge pump III through a pipeline and then divided into two routes): one route is connected to the lower part of the water separation tower through a pipeline, and the other route is provided with a water extraction pipeline.

[0050] In a further preferred embodiment, a condenser V and a water storage tank are sequentially arranged on the water production pipeline.

[0051] The endpoints and any values ​​of the scope disclosed in the present invention are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, the endpoint values ​​of each scope, the endpoint values ​​of each scope and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] (1) The present invention uses a conventional distillation method to separate DMSO, and uses the principle that acrylonitrile-water binary mixture is heterogeneous when the concentration is greater than the solubility to separate acrylonitrile and water. The separation process avoids the introduction of impurities in extractive distillation and the problem of difficult control of heterogeneous reflux of light component azeotropes in pressure swing distillation, so that acrylonitrile in the return slip can be directly reused as a raw material, avoiding the influence of direct use of the return slip on the stability of the polymerization reaction and the quality of the polymerization product;

[0054] (2) The present invention obtains DMSO with higher purity by controlling the conditions of the DMSO separation tower;

[0055] (3) The present invention obtains acrylonitrile with higher purity and water with higher purity by controlling the feeding method of the acrylonitrile separation tower and the water separation tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 A schematic diagram of the structure of the system of the present invention is shown.

[0057] C-101-DMSO separation tower, V-101-liquid separation device, C-102 acrylonitrile separation tower, C103-water separation tower, V-102-acrylonitrile storage tank, V-103-water storage tank; E-101-condenser I, E-102-reboiler I, E-103-condenser II, E-104-reboiler II, E-105-condenser III, E-106-condenser IV, E-107-reboiler III, E-108-condenser V; P-101-discharge pump I, P-102-feed pump I, P-103-discharge pump II, P-104-feed pump II, P-105-discharge pump III;

[0058] 1-ternary mixture material inlet of DMSO separation tower, 2-gas phase outlet I of DMSO separation tower, 3-liquid phase outlet I of DMSO separation tower, 4-DMSO-rich liquid phase production pipeline, 5-acrylonitrile-water binary mixture feed inlet of liquid separation device, 6-acrylonitrile-rich liquid phase discharge port of liquid separation device, 7-water-rich liquid phase discharge port of liquid separation device, 8-vacuum system, 9-water-rich liquid phase reflux pipeline, 10-acrylonitrile-rich liquid phase feed inlet of acrylonitrile separation tower, 11-gas phase outlet II of acrylonitrile separation tower, 12-liquid phase outlet II of acrylonitrile separation tower, 13-water-rich liquid phase feed inlet of water separation tower, 14-gas phase outlet III of water separation tower, 15-liquid phase outlet III of water separation tower, 16-acrylonitrile production pipeline, 17-water production pipeline. DETAILED DESCRIPTION

[0059] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0060] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0061] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0062] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0063] [Example 1]

[0064] The feed flow rate of stream 1 is 100kg / h, the mass concentration of DMSO is 94%, the mass concentration of water is 3%, and the mass concentration of acrylonitrile is 3%; the feed flow rate of stream 9 is 5kg / h, the mass concentration of water is 92.83%, and the mass concentration of acrylonitrile is 7.17%; C-101 has 15 tower plates, the tower top temperature is 4.8℃, the tower top pressure is 1kpa (abs), the tower bottom temperature is 103.2℃, and the tower bottom pressure is 6kpa (abs); the logistics rate of stream 4 is 94.2kg / h. The mass concentration of water in stream 2 is 72.2%, and the mass concentration of acrylonitrile is 27.8%; the mass concentration of DMSO in stream 4 is 99.8%, and the mass concentration of water is 0.2%.

[0065] The temperature of V-101 was controlled at 10° C. The mass concentration of water in the upper layer of liquid was 2.55%, and the mass concentration of acrylonitrile was 97.45%; the mass concentration of water in the lower layer of liquid was 92.83%, and the mass concentration of acrylonitrile was 7.17%.

[0066] The feed flow rate of stream 10 is 40kg / h, the mass concentration of acrylonitrile is 97.45%, and the mass concentration of water is 2.55%; stream 10 is fed from the top of acrylonitrile separation tower C-102; C-102 has 11 trays, the top temperature is 16.3℃, the top pressure is 8kPa (abs), the bottom temperature is 34.4℃, and the bottom pressure is 18kPa (abs); the logistics rate of stream 16 is 9kg / h. The mass concentration of water in stream 11 is 3.23%, and the mass concentration of acrylonitrile is 96.77%; the mass concentration of water in stream 16 is 0.2%, and the mass concentration of acrylonitrile is 99.8%.

[0067] The feed rate of stream 13 is 120kg / h, the mass concentration of acrylonitrile is 7.17%, and the mass concentration of water is 92.83%; stream 13 is fed from the top of water separation tower C-103; C-103 has 14 trays, the top temperature is -5.76℃, the top pressure is 0.5kpa (abs), the bottom temperature is 31.01℃, and the bottom pressure is 4.5kpa (abs); the logistics rate of stream 17 is 97kg / h. The mass concentration of water in stream 14 is 62.59%, and the mass concentration of acrylonitrile is 37.41%; the mass concentration of acrylonitrile in stream 17 is less than 1ppm.

[0068] [Example 2]

[0069] The feed flow rate of stream 1 is 100kg / h, the mass concentration of DMSO is 85%, the mass concentration of water is 15%, and the mass concentration of acrylonitrile is 5%; the feed flow rate of stream 9 is 7kg / h, the mass concentration of water is 92.70%, and the mass concentration of acrylonitrile is 7.30%; C-101 has 12 tower plates, the tower top temperature is 57.5℃, the tower top pressure is 20kpa (abs), the tower bottom temperature is 113.7℃, and the tower bottom pressure is 25kpa (abs); the logistics rate of stream 4 is 85.2kg / h. The mass concentration of water in stream 2 is 72.2%, and the mass concentration of acrylonitrile is 27.8%; the mass concentration of DMSO in stream 4 is 93.9%, and the mass concentration of water is 6.1%.

[0070] The temperature of V-101 was controlled at 20° C. The mass concentration of water in the upper layer liquid was 3.08%, and the mass concentration of acrylonitrile was 96.92%; the mass concentration of water in the lower layer liquid was 92.70%, and the mass concentration of acrylonitrile was 7.30%.

[0071] The feed flow rate of stream 10 is 100 kg / h, the mass concentration of acrylonitrile is 96.92%, and the mass concentration of water is 3.08%; C-102 has 17 trays, the top temperature is 58.75°C, the top pressure is 50 kPa (abs), the bottom temperature is 68.02°C, and the bottom pressure is 65 kPa (abs); the logistics rate of stream 16 is 45 kg / h. The mass concentration of water in stream 11 is 5.59%, and the mass concentration of acrylonitrile is 94.41%; the mass concentration of water in stream 16 is 0.02%, and the mass concentration of acrylonitrile is 99.98%.

[0072] The feed flow rate of stream 13 is 46kg / h, the mass concentration of acrylonitrile is 7.30%, and the mass concentration of water is 92.70%; C-103 has 9 trays, the top temperature is 92.48℃, the top pressure is 83kPa (abs), the bottom temperature is 97.63℃, and the bottom pressure is 93kPa (abs); the logistics rate of stream 17 is 25kg / h. The mass concentration of water in stream 14 is 84.00%, and the mass concentration of acrylonitrile is 16.00%; the mass concentration of acrylonitrile in stream 17 is less than 1ppm.

[0073] [Example 3]

[0074] The feed flow rate of stream 1 is 100kg / h, the mass concentration of DMSO is 70%, the mass concentration of water is 10%, and the mass concentration of acrylonitrile is 20%; the feed flow rate of stream 9 is 12kg / h, the mass concentration of water is 92.49%, and the mass concentration of acrylonitrile is 7.51%; C-101 has 8 plates, the top temperature is 88.2℃, the top pressure is 90kpa (abs), the bottom temperature is 184.6℃, and the bottom pressure is 95kpa (abs); the logistics rate of stream 4 is 70.3kg / h. The mass concentration of water in stream 2 is 52.0%, and the mass concentration of acrylonitrile is 48.0%; the mass concentration of DMSO in stream 4 is 99.6%, and the mass concentration of water is 0.4%.

[0075] The temperature of V-101 was controlled at 30° C. The mass concentration of water in the upper layer of liquid was 3.82%, and the mass concentration of acrylonitrile was 96.18%; the mass concentration of water in the lower layer of liquid was 92.49%, and the mass concentration of acrylonitrile was 7.51%.

[0076] The feed flow rate of stream 10 is 30kg / h, the mass concentration of acrylonitrile is 96.18%, and the mass concentration of water is 3.82%; C-102 has 7 trays, the top temperature is 75.90℃, the top pressure is 90kPa (abs), the bottom temperature is 79.57℃, and the bottom pressure is 95kPa (abs); the logistics rate of stream 16 is 7kg / h. The mass concentration of water in stream 11 is 4.97%, and the mass concentration of acrylonitrile is 95.03%; the mass concentration of water in stream 16 is 0.03%, and the mass concentration of acrylonitrile is 99.97%.

[0077] The feed flow rate of stream 13 is 543kg / h, the mass concentration of acrylonitrile is 7.51%, and the mass concentration of water is 92.49%; C-103 has 13 trays, the top temperature is 60.22℃, the top pressure is 22.1kpa (abs), the bottom temperature is 72.90℃, and the bottom pressure is 35.3kpa (abs); the logistics rate of stream 17 is 325kg / h. The mass concentration of water in stream 14 is 81.29%, and the mass concentration of acrylonitrile is 18.71%; the mass concentration of acrylonitrile in stream 17 is less than 1ppm.

[0078] [Comparative Example 1]

[0079] The feed flow rate of stream 1 is 100kg / h, the mass concentration of DMSO is 94%, the mass concentration of water is 3%, and the mass concentration of acrylonitrile is 3%; the feed flow rate of stream 9 is 19kg / h, the mass concentration of water is 92.83%, and the mass concentration of acrylonitrile is 7.17%; C-101 has 15 tower plates, the tower top temperature is 47.3℃, the tower top pressure is 28kpa (abs), the tower bottom temperature is 79.43℃, and the tower bottom pressure is 30kpa (abs); the logistics rate of stream 4 is 94kg / h. The mass concentration of water in stream 2 is 19.9%, and the mass concentration of acrylonitrile is 80.1%; the mass concentration of DMSO in stream 4 is 64.9%, the mass concentration of water is 34.2%, and the mass concentration of acrylonitrile is 0.9%.

[0080] The mass concentration of acrylonitrile in the bottom flow of the tower is 0.9%, which is relatively high and has a poor separation effect.

[0081] [Comparative Example 2]

[0082] The process of Example 1 was repeated, except that:

[0083] The feed flow rate of stream 10 is 40kg / h, the mass concentration of acrylonitrile is 97.45%, and the mass concentration of water is 2.55%; stream 10 is fed from the sixth tray of acrylonitrile separation tower C-102; C-102 has 11 trays, the top temperature is 16.1°C, the top pressure is 8kPa (abs), the bottom temperature is 34.2°C, and the bottom pressure is 18kPa (abs); the logistics rate of stream 16 is 9kg / h. The mass concentration of water in stream 11 is 3.20%, and the mass concentration of acrylonitrile is 96.80%; the mass concentration of water in stream 16 is 0.3%, and the mass concentration of acrylonitrile is 99.7%.

[0084] Compared with Example 1, the feed position in Comparative Example 2 was moved down to the sixth tray, and the mass concentration of acrylonitrile in the 16th stream decreased. In the actual production process, since the feed position is close to the bottom of the tower, even if there is a small fluctuation in the system, it will have a great impact on the purity of acrylonitrile in the bottom of the tower.

[0085] [Comparative Example 3]

[0086] The process of Example 1 was repeated, except that:

[0087] The feed flow rate of stream 13 is 120kg / h, the mass concentration of acrylonitrile is 7.17%, and the mass concentration of water is 92.83%; stream 13 is fed from the eighth tray of water separation tower C-103; C-103 has 14 trays, the top temperature is -13.53℃, the top pressure is 0.5kpa (abs), the bottom temperature is 30.97℃, and the bottom pressure is 4.5kpa (abs); the logistics rate of stream 17 is 97kg / h. The mass concentration of water in stream 14 is 24.64%, and the mass concentration of acrylonitrile is 75.36%; the mass concentration of acrylonitrile in stream 17 is 116ppm.

[0088] Compared with Example 1, the feed position in Comparative Example 3 was moved down to the eighth tray, and the mass concentration of acrylonitrile in stream 17 increased. In the actual production process, since the feed position is close to the bottom of the tower, even if there is a small fluctuation in the system, it will have a great impact on the purity of acrylonitrile in the bottom of the tower.

[0089] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A method for separating a water-acrylonitrile-DMSO ternary mixture, the method comprising: (1) subjecting the ternary mixed material to a distillation treatment to obtain a DMSO-rich material and an acrylonitrile-water binary mixture; (2) The acrylonitrile-water binary mixture is cooled and separated to obtain an acrylonitrile-rich liquid phase and a water-rich liquid phase; (3) The acrylonitrile-rich liquid phase and the water-rich liquid phase are independently distilled to obtain pure acrylonitrile and pure water, respectively.

2. The method according to claim 1, characterized in that The distillation in step (1) is carried out in a DMSO separation tower. The water-acrylonitrile-DMSO ternary mixture enters the DMSO separation tower in the middle, the DMSO-rich material is obtained in the bottom of the tower, and the acrylonitrile-water binary mixture is obtained at the top of the tower.

3. The method according to claim 2, characterized in that The DMSO separation tower is a distillation tower, and its conditions include: the tower top temperature ranges from -20°C to 100°C, the tower top pressure ranges from 0.1kpa to 101.3kpa, the tower bottom temperature ranges from 90 to 200°C, and the tower bottom pressure ranges from 1kpa to 101.3kpa.

4. The method according to claim 1, characterized in that: In step (2), the temperature is cooled to 0 to 30°C, preferably 0 to 10°C.

5. The method according to claim 1, characterized in that The acrylonitrile-rich liquid phase is distilled in an acrylonitrile separation tower, the acrylonitrile-rich liquid phase enters the acrylonitrile separation tower at the top, pure acrylonitrile is obtained in the bottom of the acrylonitrile separation tower, and the top material of the acrylonitrile separation tower is cooled and recycled to step (2) for the liquid separation; Preferably, the acrylonitrile separation tower is a distillation tower, and its conditions include: the tower top temperature ranges from -20°C to 80°C, the tower top pressure ranges from 0.1 kpa to 101.3 kpa, the tower bottom temperature ranges from 10°C to 90°C, and the tower bottom pressure ranges from 1 kpa to 101.3 kpa.

6. The method according to claim 1, characterized in that Part or all of the water-rich liquid phase is separated in a water separation tower, the water-rich liquid phase enters the water separation tower at the top, pure water is obtained in the bottom of the water separation tower, and the top material of the water separation tower is cooled and recycled to step (2) for the liquid separation; Preferably, the water separation tower is a distillation tower, and its conditions include: the tower top temperature ranges from -20°C to 100°C, the tower top pressure ranges from 0.1kpa to 101.3kpa, the tower bottom temperature ranges from 30°C to 110°C, and the tower bottom pressure ranges from 6kpa to 101.6kpa.

7. A system for separating a water-acrylonitrile-DMSO ternary mixture, preferably used for carrying out the method according to any one of claims 1 to 6, the system comprising a DMSO separation tower, a liquid separation device, an acrylonitrile separation tower and a water separation tower.

8. The system according to claim 7, characterized in that The middle part of the DMSO separation tower is provided with a ternary mixture material inlet; the top of the DMSO separation tower is provided with a gas phase outlet I for discharging acrylonitrile-water binary mixture; the bottom of the DMSO separation tower is provided with a liquid phase outlet I for discharging DMSO-rich liquid phase; Preferably, the gas phase outlet I of the DMSO separation tower is connected to the liquid separation device via a pipeline, and a condenser I is further arranged on the pipeline between the gas phase outlet I and the liquid separation device.

9. The system according to claim 7 or 8, characterized in that: The liquid separation device is a liquid separation tank, on which an acrylonitrile-water binary mixture feed port, an acrylonitrile-rich liquid phase discharge port, and a water-rich liquid phase discharge port are arranged; preferably, the acrylonitrile-rich liquid phase discharge port of the liquid separation device is connected to the top of the acrylonitrile separation tower through a pipeline.

10. The system according to claim 9, characterized in that An acrylonitrile-rich liquid phase feed inlet is arranged at the top of the acrylonitrile separation tower, a gas phase outlet II is arranged at the top, and a liquid phase outlet II is arranged at the bottom; preferably, the acrylonitrile-rich liquid phase feed inlet of the acrylonitrile separation tower is connected to the acrylonitrile-rich liquid phase outlet of the liquid separation device through a pipeline; and / or, the gas phase outlet II of the acrylonitrile separation tower is connected to the acrylonitrile-water binary mixture feed inlet of the liquid separation device through a pipeline, and a condenser II is arranged on the pipeline.

11. The system according to claim 9, characterized in that A water-rich liquid phase feed inlet is arranged at the top of the water separation tower, a gas phase outlet III is arranged at the top of the water separation tower, and a liquid phase outlet III is arranged at the bottom of the water separation tower; preferably, the water-rich liquid phase feed inlet is connected to the water-rich liquid phase discharge port of the liquid separation device through a pipeline, and the gas phase outlet III of the water separation tower is connected to the acrylonitrile-water binary mixture feed inlet of the liquid separation device through a pipeline.

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