A method and system for separating a water-acrylonitrile-dimethyl sulfoxide ternary mixture

Abstract

The application discloses a method and system for separating a water-acrylonitrile-DMSO mixture, which comprises the following steps: (1) performing rectification treatment on the ternary mixture to obtain a DMSO-rich material and an acrylonitrile-water binary mixture; (2) performing liquid separation on the acrylonitrile-water binary mixture after cooling to obtain an acrylonitrile-rich liquid phase and a water-rich liquid phase; and (3) independently performing rectification on the acrylonitrile-rich liquid phase and the water-rich liquid phase to obtain pure acrylonitrile and pure water, respectively. Compared with the prior art, the application utilizes a conventional rectification mode to separate DMSO and an acrylonitrile-water binary mixture, the separation process avoids the introduction of impurities in the extractive rectification and avoids the problem that the control of the heterogeneous reflux of the light component azeotrope in the pressure swing rectification is difficult, so that the acrylonitrile in the return single can be directly reused as a raw material, and the influence of the direct use of the return single on the stability of a polymerization reaction and the quality of a polymerization product is avoided.

Description

Technical Field

[0001] This invention belongs to the field of material separation, and particularly relates to a method and system for separating a mixture of water, acrylonitrile, and DMSO. Background Technology

[0002] Polyacrylonitrile-based carbon fiber is a new material with excellent mechanical properties. It is an indispensable engineering material for aerospace and defense industries, and it also has wide applications in civilian fields such as sporting goods, transportation, medical devices, and civil engineering.

[0003] In the production of polyacrylonitrile-based carbon fiber precursor, acrylonitrile (AN) monomer undergoes polymerization using dimethyl sulfoxide (DMSO) as a solvent. The resulting polymer is then depolymerized and degassed before being used to produce carbon fiber precursor. During the depolymerization and degasting process, unreacted AN monomer, DMSO solvent, and water contained in the raw materials are temporarily stored after vaporization, condensation, and absorption by DMSO. This temporarily stored material is called "recycled monomer" or "recovered liquid." DMSO is the main component of the recycled monomer, while AN and water account for a smaller proportion. The recycled monomer can be directly used as a raw material for polymerization, but the trace amounts of water in the DMSO and AN added during the polymerization batching process cause the water content in the recycled monomer to accumulate, thus affecting the stability of the polymerization reaction and the quality of the polymer product. A more reasonable approach is to remove the water from the recycled monomer by separating the components. However, since AN and water are azeotropic, and their concentration is heterogeneous when it exceeds their solubility, the reflux is difficult to control when using pressure swing distillation technology because the light component azeotrope is heterogeneous. Extractive distillation requires the introduction of an extractant, and the residue of this extractant can negatively impact the polymerization reaction. Therefore, separating DMSO-AN-water to prevent water accumulation in the return sample is a technical challenge in this field. Summary of the Invention

[0004] 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. The method and system can remove water from the mixture and obtain acrylonitrile monomer and DMSO with high purity.

[0005] One of the objectives of this 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 includes: (1) distilling the ternary mixture to obtain a DMSO-rich material and an acrylonitrile-water binary mixture; (2) cooling the acrylonitrile-water binary mixture and separating it 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 generated during the production of polyacrylonitrile-based carbon fiber precursor. Acrylonitrile (AN) monomer undergoes polymerization in dimethyl sulfoxide (DMSO) as a solvent. The resulting polymer, after monomer removal and degassing, is used to produce carbon fiber precursor. During monomer removal and degassing, unreacted AN monomer, DMSO solvent, and water contained in the raw materials are temporarily stored after vaporization, condensation, and absorption by DMSO. This temporarily stored material is referred to as the "return sample." The return sample contains DMSO, acrylonitrile, and water.

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

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

[0009] In a preferred embodiment, the method is performed 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 at 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 stream is heated by the reboiler and then refluxed back into the DMSO separation tower (preferably the lower part), and the other stream is collected externally.

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

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

[0014] After extensive experimental research, the inventors discovered that compared to temperatures below 90°C (e.g., around 60°C), controlling the temperature of the DMSO separation tower bottom at 90–200°C can yield DMSO with higher purity.

[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] During extensive experimentation, the inventors discovered that separating water and acrylonitrile is easier at low temperatures, reducing both the acrylonitrile content on the water-rich side and the water content on the acrylonitrile-rich side. This also reduces the separation load in step 3. Specifically, the inventors found in their experiments 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; and 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] The materials used for the liquid separation include the condensed material from the gas phase after the distillation of the ternary mixture (i.e., the gas phase at the top of the DMSO separator, i.e., the acrylonitrile-water mixture), the condensed material from the gas phase after the distillation of the acrylonitrile-rich liquid phase (i.e., the gas phase at the top of the acrylonitrile separator), and the condensed material from the gas phase after the distillation of the water-rich liquid phase (i.e., the gas phase at the top of the water separator).

[0019] In a preferred embodiment, in step (3), the acrylonitrile-rich liquid phase is distilled to obtain pure acrylonitrile. 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 back to the distillation in step (1) as reflux liquid.

[0020] In a further preferred embodiment, the second aqueous liquid phase is returned to the top of the DMSO separation tower as reflux liquid. In this way, only the aqueous liquid phase is circulated back to the DMSO separation tower, without a large amount of acrylonitrile, thus reducing 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, and pure acrylonitrile is obtained at the bottom of the acrylonitrile separation tower. The top material of the acrylonitrile separation tower is cooled and recycled back to step (2) for the separation.

[0022] Through extensive experimental research, the inventors discovered that, compared to feeding from the middle, feeding the acrylonitrile-rich liquid phase at the top of the acrylonitrile separator results in acrylonitrile of higher purity at the bottom of the separator. Even if the top material of the acrylonitrile separator contains unrecovered acrylonitrile, it does not result in waste, as this material is recycled back to the separator for further separation. Furthermore, the acrylonitrile separator does not require a reflux tank at the top to return the acrylonitrile to the top, simplifying the equipment and saving energy.

[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 then refluxed back to the acrylonitrile separation tower (preferably the lower part). The other stream is externally sourced as pure acrylonitrile. More preferably, the other stream is cooled and then enters an acrylonitrile storage tank.

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

[0025] For example, the acrylonitrile separation tower is a distillation tower, and its conditions include: a tower top temperature range of -20℃, -10℃, 0℃, 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃, a tower top pressure range of 0.1kpa, 0.5kpa, 1kpa, 5kpa, 10kpa, 20kpa, 60kpa, 80kpa or 101.3kpa, a tower bottom temperature range of 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃ or 90℃, and a tower bottom pressure range of 1kpa (bas) to 101.3kpa (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 from the top, and pure water is obtained from the bottom of the water separation tower. The material at the top of the water separation tower is cooled and then recycled back to step (2) for the separation.

[0027] Through extensive experimental research, the inventors discovered that, compared to feeding the water-rich liquid phase at the top of the water separator, water with higher purity can be obtained at the bottom of the separator. Even if the top material contains unrecovered water, it is not wasted because it is recycled back to the separator for further separation. Furthermore, the water separator does not require a reflux tank at the top to return the water to the top, simplifying the equipment and saving energy.

[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 stream is heated by the reboiler and then returned to the water separation tower (preferably the lower part), and the other stream is externally sourced as pure water. More preferably, the other stream is cooled and then enters a water storage tank.

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

[0030] For example, the water separation tower is a distillation tower, and its conditions include: a tower top temperature range of -20℃, -10℃, 0℃, 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃; a tower top pressure range of 0.1kPa, 0.5kPa, 1kPa, 5kPa, 10kPa, 20kPa, 40kPa, 60kPa, 80kPa or 101.3kPa; a tower bottom temperature range of 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃ or 110℃; and a tower bottom pressure range of 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 the 100wt% of the water-rich liquid phase, the second water-rich liquid phase as the reflux liquid accounts for 15wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, or 85wt%.

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

[0034] In a further preferred embodiment, the separator is connected to a vacuum system, which allows the DMSO separator, acrylonitrile separator, and water separator to be 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 distilled independently. This means that the acrylonitrile-rich liquid phase and the water-rich liquid phase in the separatory tank described in step (2) are operated intermittently or continuously, respectively. Intermittent operation avoids situations where the acrylonitrile-rich liquid phase and / or water-rich liquid phase are lower than the feed rates to the acrylonitrile separator and / or water separator due to low acrylonitrile and / or water concentrations in the distillation log, thus improving system flexibility.

[0036] Compared to existing technologies, this invention utilizes conventional distillation to separate DMSO. It separates acrylonitrile and water based on the principle that the acrylonitrile-water binary mixture is heterogeneous when the concentration is greater than the solubility. The separation process avoids the introduction of impurities in extractive distillation and the problem of difficult-to-control heterogeneous reflux of light component azeotropes in pressure swing distillation. This allows the acrylonitrile in the recycled sample to be directly reused as raw material, avoiding the impact of direct use of the recycled sample on the stability of the polymerization reaction and the quality of the polymerization product.

[0037] A second objective of this invention is to provide a system for separating a water-acrylonitrile-DMSO ternary mixtures, preferably for carrying out the method described in one objective of this invention. The system includes a DMSO separation tower, a liquid separation device, an acrylonitrile separation tower, and a water separation tower.

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

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

[0040] In a further preferred embodiment, the liquid phase outlet I of the DMSO separator is divided into two paths (preferably first connected to the discharge pump I via a pipeline and then divided into two paths): one path is connected to the DMSO separator (preferably the lower part) through the DMSO separator bottom circulation loop, and a reboiler I is provided on the circulation loop; the other path is provided with a DMSO-rich liquid phase collection pipeline.

[0041] In a preferred embodiment, the liquid separation device is a liquid separation tank, which is provided with an acrylonitrile-water binary mixture inlet, an acrylonitrile-rich liquid phase outlet (preferably located at the top), and an aqueous liquid phase outlet (preferably located at the bottom).

[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 separator is connected to the top of the acrylonitrile separation tower via a pipeline, and preferably a feed pump I is installed on the pipeline.

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

[0045] In a preferred embodiment, an acrylonitrile-rich liquid phase 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 inlet of the acrylonitrile separator is connected to the acrylonitrile-rich liquid phase outlet of the liquid separator via a pipeline; and / or, the gas phase outlet II of the acrylonitrile separator is connected to the acrylonitrile-water binary mixture inlet of the liquid separator via a pipeline, and a condenser II is installed on the pipeline; and / or, the liquid phase outlet II of the acrylonitrile separator 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 separator via a pipeline, and the other path is provided with an acrylonitrile collection pipeline.

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

[0048] In a preferred embodiment, a water-rich liquid phase inlet 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 inlet is connected to the water-rich liquid phase outlet of the liquid separator via a pipeline, the gas phase outlet III of the water separator is connected to the acrylonitrile-water binary mixture inlet of the liquid separator via a pipeline, and a condenser IV is installed on the pipeline; and / or, the liquid phase outlet III of the water separator is divided into two paths (preferably first connected to the discharge pump III via a pipeline and then divided into two paths): one path is connected to the lower part of the water separator via a pipeline, and the other path is provided with a water extraction pipeline.

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

[0051] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

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

[0053] (1) This invention uses conventional distillation to separate DMSO. It 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 avoids the problem of difficult control of heterogeneous reflux of light component azeotropes in pressure swing distillation. It allows acrylonitrile in the return sample to be directly reused as raw material, avoiding the impact of direct use of the return sample on the stability of the polymerization reaction and the quality of the polymerization product.

[0054] (2) This invention obtains DMSO with high purity by controlling the conditions of the DMSO separation tower;

[0055] (3) The present invention obtains acrylonitrile and water with high purity by controlling the feeding method of the acrylonitrile separation tower and the water separation tower. Attached Figure Description

[0056] Figure 1 A schematic diagram of the system described in this invention is shown.

[0057] C-101 - DMSO separation tower, V-101 - liquid separator, 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 inlet of DMSO separator; 2 - Vapor phase outlet I of DMSO separator; 3 - Liquid phase outlet I of DMSO separator; 4 - DMSO-rich liquid phase collection pipeline; 5 - Acrylonitrile-water binary mixture inlet of liquid separator; 6 - Acrylonitrile-rich liquid phase outlet of liquid separator; 7 - Water-rich liquid phase outlet of liquid separator; 8 - Vacuum system; 9 - Water-rich liquid phase reflux pipeline; 10 - Acrylonitrile-rich liquid phase inlet of acrylonitrile separator; 11 - Vapor phase outlet II of acrylonitrile separator; 12 - Liquid phase outlet II of acrylonitrile separator; 13 - Water-rich liquid phase inlet of water separator; 14 - Vapor phase outlet III of water separator; 15 - Liquid phase outlet III of water separator; 16 - Acrylonitrile collection pipeline; 17 - Water collection pipeline. Detailed Implementation

[0059] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still 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 embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0061] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0062] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0063]

Example 1

[0064] Stream 1 has a feed flow rate of 100 kg / h, with DMSO concentration of 94%, water concentration of 3%, and acrylonitrile concentration of 3%. Stream 9 has a feed flow rate of 5 kg / h, with water concentration of 92.83% and acrylonitrile concentration of 7.17%. C-101 has 15 trays, a top temperature of 4.8℃, a top pressure of 1 kPa (abs), a bottom temperature of 103.2℃, and a bottom pressure of 6 kPa (abs). Stream 4 has a flow rate of 94.2 kg / h. Stream 2 has a water concentration of 72.2% and an acrylonitrile concentration of 27.8%. Stream 4 has a DMSO concentration of 99.8% and a water concentration of 0.2%.

[0065] V-101 temperature control is 10℃. The upper liquid has a water concentration of 2.55% and an acrylonitrile concentration of 97.45%; the lower liquid has a water concentration of 92.83% and an acrylonitrile concentration of 7.17%.

[0066] Ten streams have a feed flow rate of 40 kg / h, with an acrylonitrile concentration of 97.45% and a water concentration of 2.55%. These ten streams are fed from the top of acrylonitrile separator C-102. C-102 has 11 trays, a top temperature of 16.3℃, a top pressure of 8 kPa (abs), and a bottom temperature of 34.4℃ with a bottom pressure of 18 kPa (abs). Stream 16 has a flow rate of 9 kg / h. Stream 11 has a water concentration of 3.23% and an acrylonitrile concentration of 96.77%. Stream 16 has a water concentration of 0.2% and an acrylonitrile concentration of 99.8%.

[0067] Stream 13 has a feed flow rate of 120 kg / h, with an acrylonitrile concentration of 7.17% and a water concentration of 92.83%. Stream 13 is fed from the top of water separator C-103. C-103 has 14 trays, a top temperature of -5.76℃, a top pressure of 0.5 kPa (abs), a bottom temperature of 31.01℃, and a bottom pressure of 4.5 kPa (abs). Stream 17 has a flow rate of 97 kg / h. Stream 14 has a water concentration of 62.59% and an acrylonitrile concentration of 37.41%. Stream 17 has an acrylonitrile concentration of less than 1 ppm.

[0068]

Example 2

[0069] Stream 1 has a feed flow rate of 100 kg / h, with DMSO concentration of 85%, water concentration of 15%, and acrylonitrile concentration of 5%. Stream 9 has a feed flow rate of 7 kg / h, with water concentration of 92.70% and acrylonitrile concentration of 7.30%. C-101 has 12 trays, a top temperature of 57.5℃, a top pressure of 20 kPa (abs), a bottom temperature of 113.7℃, and a bottom pressure of 25 kPa (abs). Stream 4 has a flow rate of 85.2 kg / h. Stream 2 has a water concentration of 72.2% and an acrylonitrile concentration of 27.8%. Stream 4 has a DMSO concentration of 93.9% and a water concentration of 6.1%.

[0070] V-101 temperature control is 20℃. The upper liquid has a water concentration of 3.08% and an acrylonitrile concentration of 96.92%; the lower liquid has a water concentration of 92.70% and an acrylonitrile concentration of 7.30%.

[0071] Stream 10 has a feed flow rate of 100 kg / h, with an acrylonitrile mass concentration of 96.92% and a water mass concentration of 3.08%. Stream C-102 has 17 trays, a top temperature of 58.75℃, a top pressure of 50 kPa (ABS), a bottom temperature of 68.02℃, and a bottom pressure of 65 kPa (ABS). Stream 16 has a flow rate of 45 kg / h. Stream 11 has a water mass concentration of 5.59% and an acrylonitrile mass concentration of 94.41%; stream 16 has a water mass concentration of 0.02% and an acrylonitrile mass concentration of 99.98%.

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

[0073]

Example 3

[0074] Stream 1 has a feed flow rate of 100 kg / h, with DMSO concentration of 70%, water concentration of 10%, and acrylonitrile concentration of 20%. Stream 9 has a feed flow rate of 12 kg / h, with water concentration of 92.49% and acrylonitrile concentration of 7.51%. C-101 has 8 trays, a top temperature of 88.2℃, a top pressure of 90 kPa (abs), a bottom temperature of 184.6℃, and a bottom pressure of 95 kPa (abs). Stream 4 has a flow rate of 70.3 kg / h. Stream 2 has a water concentration of 52.0% and an acrylonitrile concentration of 48.0%. Stream 4 has a DMSO concentration of 99.6% and a water concentration of 0.4%.

[0075] V-101 temperature control is 30℃. The upper liquid has a water concentration of 3.82% and an acrylonitrile concentration of 96.18% by mass; the lower liquid has a water concentration of 92.49% and an acrylonitrile concentration of 7.51% by mass.

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

[0077] Stream 13 has a feed flow rate of 543 kg / h, an acrylonitrile concentration of 7.51%, and a water concentration of 92.49%. Stream C-103 has 13 trays, a top temperature of 60.22℃, a top pressure of 22.1 kPa (abs), a bottom temperature of 72.90℃, and a bottom pressure of 35.3 kPa (abs). Stream 17 has a flow rate of 325 kg / h. Stream 14 has a water concentration of 81.29% and an acrylonitrile concentration of 18.71%. Stream 17 has an acrylonitrile concentration of less than 1 ppm.

[0078] Comparative Example 1

[0079] Stream 1 has a feed flow rate of 100 kg / h, with DMSO concentration of 94%, water concentration of 3%, and acrylonitrile concentration of 3%. Stream 9 has a feed flow rate of 19 kg / h, with water concentration of 92.83% and acrylonitrile concentration of 7.17%. C-101 has 15 trays, a top temperature of 47.3℃, a top pressure of 28 kPa (abs), a bottom temperature of 79.43℃, and a bottom pressure of 30 kPa (abs). Stream 4 has a flow rate of 94 kg / h. Stream 2 has a water concentration of 19.9% ​​and an acrylonitrile concentration of 80.1%. Stream 4 has a DMSO concentration of 64.9%, a water concentration of 34.2%, and an acrylonitrile concentration of 0.9%.

[0080] The acrylonitrile concentration in the bottom stream was 0.9%, which is relatively high and results in poor separation.

[0081] Comparative Example 2

[0082] Repeat the process of Example 1, except that:

[0083] Stream 10 has a feed flow rate of 40 kg / h, with an acrylonitrile concentration of 97.45% and a water concentration of 2.55%. Stream 10 is fed from the sixth tray of acrylonitrile separator C-102. C-102 has 11 trays, a top temperature of 16.1℃, a top pressure of 8 kPa (abs), a bottom temperature of 34.2℃, and a bottom pressure of 18 kPa (abs). Stream 16 has a flow rate of 9 kg / h. Stream 11 has a water concentration of 3.20% and an acrylonitrile concentration of 96.80%. Stream 16 has a water concentration of 0.3% and an acrylonitrile concentration of 99.7%.

[0084] Compared to Example 1, in Comparative Example 2, the feed position was moved down to the sixth tray, resulting in a decrease in the mass concentration of acrylonitrile in the 16 streams. Furthermore, in actual production, because the feed position is close to the reboiler, even small fluctuations in the system can significantly affect the purity of acrylonitrile in the reboiler.

[0085] Comparative Example 3

[0086] Repeat the process of Example 1, except that:

[0087] Stream 13 has a feed flow rate of 120 kg / h, with an acrylonitrile concentration of 7.17% and a water concentration of 92.83%. Stream 13 is fed from the eighth tray of water separator C-103. C-103 has 14 trays, a top temperature of -13.53℃, a top pressure of 0.5 kPa (abs), a bottom temperature of 30.97℃, and a bottom pressure of 4.5 kPa (abs). Stream 17 has a flow rate of 97 kg / h. Stream 14 has a water concentration of 24.64% and an acrylonitrile concentration of 75.36%. Stream 17 has an acrylonitrile concentration of 116 ppm.

[0088] Compared with Example 1, in Comparative Example 3, the feed position was moved down to the eighth tray, and the mass concentration of acrylonitrile in the 17 streams increased. Furthermore, in actual production, because the feed position is close to the reboiler, even small fluctuations in the system can significantly affect the purity of acrylonitrile in the reboiler.

[0089] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for separating a water-acrylonitrile-DMSO ternary mixture, the method comprising: (1) The ternary mixture is subjected to distillation to obtain DMSO-rich material and acrylonitrile-water binary mixture; (2) The acrylonitrile-water binary mixture is cooled and then 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 separately distilled to obtain pure acrylonitrile and pure water, respectively. 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 at the bottom of the tower, and the acrylonitrile-water binary mixture is obtained at the top of the tower. The DMSO separation column is a distillation column, and its conditions include: top temperature range of -20℃ to 100℃, top pressure range of 0.1kpa to 101.3kpa, bottom temperature range of 90 to 200℃, and bottom pressure range of 1kpa to 101.3kpa.

2. The method according to claim 1, characterized in that, In step (2), the temperature is cooled to 0~30℃.

3. The method according to claim 1, characterized in that, In step (2), the temperature is cooled to 0~10℃.

4. 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 at the bottom of the acrylonitrile separation tower. The material at the top of the acrylonitrile separation tower is cooled and then recycled back to step (2) for the separation.

5. The method according to claim 4, characterized in that, The acrylonitrile separation tower is a distillation tower, and its conditions include: a tower top temperature range of -20℃ to 80℃, a tower top pressure range of 0.1 kPa to 101.3 kPa, a tower bottom temperature range of 10℃ to 90℃, and a tower bottom pressure range of 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. The material at the top of the water separation tower is cooled and then recycled back to step (2) for the liquid separation.

7. The method according to claim 6, characterized in that, The water separation tower is a distillation tower, and its conditions include: a tower top temperature range of -20℃ to 100℃, a tower top pressure range of 0.1 kPa to 101.3 kPa, a tower bottom temperature range of 30℃ to 110℃, and a tower bottom pressure range of 6 kPa to 101.6 kPa.

8. The method according to any one of claims 1 to 7, characterized in that, The method employs a system for separating a ternary mixture of water, acrylonitrile, and DMSO, the system comprising a DMSO separation tower, a liquid separator, an acrylonitrile separation tower, and a water separation tower.

9. The method according to claim 8, characterized in that, The DMSO separation tower is provided with a ternary mixture inlet in the middle; a gas outlet I is provided at the top of the DMSO separation tower for discharging the acrylonitrile-water binary mixture; and a liquid outlet I is provided at the bottom of the DMSO separation tower for discharging the DMSO-rich liquid phase.

10. The method according to claim 9, characterized in that, 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 installed on the pipeline between the gas phase outlet I and the liquid separation device.

11. The method according to claim 8, characterized in that, The liquid separation device is a liquid separation tank, which is equipped with an acrylonitrile-water binary mixture inlet, an acrylonitrile-rich liquid phase outlet, and a water-rich liquid phase outlet.

12. The method according to claim 11, characterized in that, The acrylonitrile-rich liquid phase outlet of the liquid separator is connected to the top of the acrylonitrile separation tower via a pipeline.

13. The method according to claim 11, characterized in that, An acrylonitrile-rich liquid feed inlet is provided at the top of the acrylonitrile separation tower, a gas outlet II is provided at the top, and a liquid outlet II is provided at the bottom.

14. The method according to claim 13, characterized in that, The acrylonitrile-rich liquid phase inlet of the acrylonitrile separation tower is connected to the acrylonitrile-rich liquid phase outlet of the liquid separator via a pipeline; and / or, the gas phase outlet II of the acrylonitrile separation tower is connected to the acrylonitrile-water binary mixture inlet of the liquid separator via a pipeline, and a condenser II is installed on the pipeline.

15. The method according to claim 11, characterized in that, A water-rich liquid phase inlet 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.

16. The method according to claim 15, characterized in that, The water-rich liquid phase inlet is connected to the water-rich liquid phase outlet of the liquid separator via a pipeline, and the gas phase outlet III of the water separation tower is connected to the acrylonitrile-water binary mixture inlet of the liquid separator via a pipeline.

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