Condensate tank, method and system for recovering polyacrylonitrile waste liquid and applications

Abstract

This invention discloses a condenser, a method and system for recovering polyacrylonitrile waste liquid, and its application. The condenser of this invention has a longitudinally arranged H-shaped structure at its bottom. i Block baffle, the H i ≥1; and when the H i When ≥2, the H i The baffles, arranged in a stepped manner within the condenser, have varying heights. This invention optimizes the existing condenser structure. The condenser of this invention features multiple longitudinal baffles, each with a progressively decreasing height, forming a stepped distribution. This structural design allows for multiple separations of light acrylonitrile components and heavy components such as water within the condenser, effectively improving the separation and recovery of acrylonitrile. Furthermore, this invention provides a system for recovering polyacrylonitrile waste liquid. In addition to the specially designed condenser, it employs a positive pressure condensation process for the material collected from the top of the distillation column. This solves the problem of excessively low temperatures during negative pressure condensation in previous processes, which caused material overcooling and blockage of the condenser pipes. This also improves the separation and reflux effect of the material collected from the top of the azeotropic distillation column, thereby enhancing the overall separation and recovery efficiency of polyacrylonitrile waste liquid.

Description

Technical Field

[0001] This invention relates to the technical field of polyacrylonitrile waste liquid recycling, and more specifically, to condenser tanks, methods and systems for polyacrylonitrile waste liquid recycling, and their applications. Background Technology

[0002] Polyacrylonitrile (PAN) is a widely used synthetic polymer material, found in synthetic fibers, plastics, rubber, and coatings. The synthesis and processing of PAN generates large quantities of waste liquid containing acrylonitrile monomers, dimethyl sulfoxide, and other chemicals. If this waste liquid is not treated or is improperly treated, it can cause serious environmental pollution and waste valuable resources.

[0003] CN114031230A discloses a method for treating acrylonitrile-containing wastewater. This method employs a high-boiling-point separation module and a low-boiling-point separation module, and achieves enrichment and separation of heavy components in the wastewater by changing pressure and temperature conditions. This method performs well in wastewater separation, but the equipment investment and operating costs are high, and it does not consider the recovery of valuable components in the wastewater.

[0004] CN220939177U discloses an acrylonitrile separation device that combines the extraction and stripping sections of a large-diameter recovery tower. It improves acrylonitrile separation efficiency by using multiple overflow trays with varying overflow rates. While this acrylonitrile separation device offers significant advantages in processing performance, the complexity of system integration and the difficulty of operation remain challenges that this technology needs to overcome.

[0005] CN103623531A discloses a chemical treatment method that utilizes catalysts and amine ligands to chemically decompose acrylonitrile in acrylonitrile wastewater. This method has significant advantages in treating acrylonitrile, effectively removing organic matter from the wastewater and improving the safety of wastewater treatment. However, it suffers from secondary pollution issues related to chemical treatment and is highly susceptible to environmental conditions.

[0006] Existing patent reports on waste liquid recovery processes typically employ distillation columns for separation and recovery. However, as the scale of polyacrylonitrile plants continues to expand, existing processes have encountered numerous engineering problems. For example, the inventors of this invention discovered the problem of condensation and blockage of condensers and pipes by the vapor phase material after the top material is collected from the distillation column; and the problem that light and heavy components cannot be completely separated in existing conventional condensers.

[0007] Therefore, there is a need to develop a better process for recovering polyacrylonitrile waste liquid. Summary of the Invention

[0008] To address the problems in existing technologies, this invention proposes a condenser, a method and system for recovering polyacrylonitrile waste liquid, and its application. This invention optimizes the existing condenser structure. The condenser of this invention has multiple longitudinal baffles, with the height of each baffle decreasing sequentially in a stepped distribution. Utilizing the structural design of the condenser of this invention, multiple separations of light components of acrylonitrile and heavy components such as water can be achieved within the condenser, effectively improving the separation and recovery efficiency of acrylonitrile. Furthermore, this invention also provides a system for recovering polyacrylonitrile waste liquid, which not only includes the specially designed condenser mentioned above but also employs a positive pressure condensation process for the material collected from the top of the distillation column. This solves the problem of excessively low material cooling and clogging of condenser pipes caused by negative pressure condensation in previous processes, thereby also improving the separation and reflux effect of the material collected from the top of the azeotropic distillation column, thus improving the overall separation and recovery efficiency of polyacrylonitrile waste liquid.

[0009] One objective of this invention is to provide a condenser, wherein the bottom of the condenser is longitudinally provided with an H-shaped structure. i Block baffle, the H i ≥1; and when the H i When ≥2, the H i The baffles are arranged in a stepped manner at different heights inside the condenser.

[0010] In the condenser tank described in this invention, preferably,

[0011] The condenser has a light component sampling outlet on one side; the baffles are arranged in a stepped manner at the bottom of the condenser, following the rule that the greater the lateral distance from the light component sampling outlet, the higher the baffle; the baffle with the lowest height is designated as the Hth. i The second lowest baffle is designated as the Hth baffle. i-1 The baffles, following this pattern, are designated as the H1th baffle; the feed inlet of the condenser is located in the upper part of the chamber formed by the H1th baffle and the other side of the condenser; and / or,

[0012] The bottom of the condenser is provided with a recombination and extraction outlet; and / or,

[0013] The upper part of the condenser is also provided with a condenser gas phase outlet;

[0014] Preferably;

[0015] H i The height of the baffle is greater than the height of the light component extraction outlet of the condenser.

[0016] More preferably, the Hth i The height of the baffle at 1 / 3 to 5 / 6, preferably at 2 / 3, should be aligned with the position of the light component extraction outlet.

[0017] In the condenser tank described in this invention, preferably,

[0018] The condenser tank includes a top tank, a middle cylindrical tank, and a bottom tank; preferably,

[0019] The ratio of the height difference between adjacent baffles to the height of the intermediate cylindrical tank of the condenser is 0.01-0.6, preferably 0.01-0.3; for example, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.5, 0.6; and / or,

[0020] The ratio of the height of the highest baffle to the height of the intermediate cylindrical tank of the condenser is 0.1-0.6, preferably 0.2-0.6; for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6; and / or,

[0021] The ratio of the height of the intermediate cylindrical tank to the total height of the condenser is 1 / 2 to 4 / 5; for example, 0.5, 0.6, 0.7, or 0.8.

[0022] In the technical solution described in this invention, the condenser is provided with multiple longitudinal baffles, which are arranged in a stepped manner at the bottom of the condenser with the height of each baffle decreasing sequentially. The height difference between adjacent baffles refers to the difference between the higher baffle and the lower baffle. The height difference between the first and second baffles is △H1, the height difference between the first and second baffles is △H2, and so on.

[0023] In the condenser tank described in this invention, preferably,

[0024] In the condenser, the ratio of the lateral distance between adjacent baffles to the diameter of the condenser is 0.16-0.5, preferably 0.2-0.5; for example, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5. In this invention, the number of internal baffles varies depending on the size of the condenser; in this invention, the number of internal baffles is 2-5.

[0025] The working principle of the condenser of this invention is as follows:

[0026] The materials entering the condenser mainly consist of acrylonitrile and water. These materials first enter through the condenser's inlet and accumulate in the first chamber formed by the H1 baffle (the first baffle) and the other side of the condenser. In this first chamber, due to density differences, acrylonitrile and water undergo two-phase separation. The upper layer is the light acrylonitrile-rich phase, and the lower layer is the heavy water-rich phase. As the amount of material in the first chamber increases, the upper layer of light acrylonitrile-rich phase overflows into the second chamber formed by the H1 baffle (the first baffle) and the H2 baffle (the second baffle), undergoing the same material separation process as in the first chamber. This process continues until the light acrylonitrile-rich phase overflows into the H1 baffle and the side of the condenser. i Within each of the chambers, a separation process occurs between the light component (acrylonitrile-rich phase) and the heavy component (aqueous phase). Therefore, as the separation process progresses, the concentration of the light component (acrylonitrile-rich phase) is higher in the lower-height baffles, resulting in a greater degree of separation from the heavy component (aqueous phase). Finally, the light component (acrylonitrile-rich phase) with the highest acrylonitrile concentration is collected from the light component outlet, while the heavy component (aqueous phase) is collected from the outlet at the bottom of the condenser. It is evident that this invention, through the design of a special baffle in the condenser, enables multiple separations of light and heavy components under normal pressure conditions, reducing the residence time of acrylonitrile to prevent self-polymerization and effectively improving the separation and recovery efficiency of acrylonitrile.

[0027] The second objective of this invention is to provide a method for recovering polyacrylonitrile waste liquid, comprising the following steps:

[0028] (1) After azeotropic distillation of polyacrylonitrile waste liquid, the liquid phase in the bottom of the column is recycled for azeotropic distillation and / or the extraction system; the gas phase at the top of the column is extracted.

[0029] (2) Dry pressurize the extracted top gas phase, send the pressurized gas into the condenser and test the water content in the gas at the same time to obtain the condensed material.

[0030] (3) The condensed material is fed into a condenser; the light component rich in acrylonitrile and the heavy component rich in water are extracted from the condenser; the light component rich in acrylonitrile is extracted and recovered, and the heavy component rich in water is refluxed for azeotropic distillation and / or extraction system.

[0031] The condenser described herein is one of the objectives of this invention.

[0032] In the method for recovering polyacrylonitrile waste liquid according to the present invention, preferably,

[0033] The polyacrylonitrile waste liquid comprises polyacrylonitrile, dimethyl sulfoxide, and water; the polyacrylonitrile waste liquid of the present invention is a conventional polyacrylonitrile waste liquid, preferably comprising 0.8 wt% acrylonitrile, 99.192 wt% dimethyl sulfoxide, and 0.008 wt% water; and / or,

[0034] The process parameters for azeotropic distillation are:

[0035] The operating pressure is 0-12 kPaA, preferably 1-12 kPaA; for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 kPaA; and / or,

[0036] The operating temperature at the top of the tower is 3-25℃, preferably 15-20℃; for example, 3, 5, 8, 10, 13, 15, 18, 20, 23, 25℃; and / or,

[0037] The operating temperature of the column reboiler is 90-130℃, preferably 100-120℃; for example, 90, 95, 100, 105, 110, 115, 120, 125, 130℃; and / or,

[0038] The reflux ratio is 2-40, preferably 4-35; for example, 2, 4, 8, 10, 15, 20, 25, 30, 35.

[0039] In the method for recovering polyacrylonitrile waste liquid according to the present invention, preferably,

[0040] The pressurized gas pressure is 0-5 kPaG; for example, 0, 1, 2, 3, 4, 5 kPaG; and / or,

[0041] The temperature of the condenser is 5-15°C lower than the acrylonitrile dew point temperature; for example, 5, 8, 10, 13, or 15°C; and / or,

[0042] The temperature inside the condenser is 2-8°C lower than the temperature of the condenser; for example, 2, 3, 4, 5, 6, 7, or 8°C.

[0043] In the method for recovering polyacrylonitrile waste liquid according to the present invention, preferably,

[0044] The pressurized gas pressure is 0-3 kPaG; and / or,

[0045] When the water content in the gas is 0.008wt%-0.5wt%, the condenser temperature is 15°C lower than the acrylonitrile dew point temperature; and / or,

[0046] When the water content in the gas is 0.5wt%-1wt%, excluding 0.5wt%, the condenser temperature is 5°C lower than the acrylonitrile dew point temperature; and / or,

[0047] The temperature inside the condenser is 3-6°C lower than the temperature of the condenser.

[0048] In the method for recovering polyacrylonitrile waste liquid according to the present invention, it is further preferably included in the following steps:

[0049] (1) Polyacrylonitrile waste liquid enters the azeotropic distillation column through the waste liquid feed pipeline and is separated in the distillation column. The gas phase at the top of the column mainly contains acrylonitrile and water, while the liquid phase at the bottom of the column mainly contains dimethyl sulfoxide.

[0050] (2) After being pressurized by a dry vacuum pump, the gas phase at the top of the column is sent to the condenser for condensation and then enters the condenser tank. The condenser tank is equipped with internal baffles. The light component rich in acrylonitrile is collected by the condenser tank discharge pump, and part of the heavy component rich in water is returned to the distillation column by the reflux pump and part is collected directly.

[0051] (3) In the bottom of the distillation column, part of the dimethyl sulfoxide-rich phase is pumped into the reboiler and refluxed back to the column by the discharge pump, and part is directly collected.

[0052] A third objective of this invention is to provide a system for recovering polyacrylonitrile waste liquid, comprising an azeotropic distillation column, a pressurization device, a moisture content detection device, a condenser, and a condensation tank.

[0053] The inlet of the azeotropic distillation column is connected to the outlet of the polyacrylonitrile waste liquid feed pipeline; the vapor outlet of the azeotropic distillation column is connected to the inlet of the booster device.

[0054] The outlet of the booster is connected to the inlet of the condenser, and a moisture content detection device is installed on the connecting pipeline between the booster and the condenser.

[0055] The condenser's outlet is connected to the condenser's inlet;

[0056] The condenser is provided with an outlet for the light component rich in acrylonitrile phase and an outlet for the heavy component rich in water phase; the condenser is the condenser described in one of the objectives of this invention.

[0057] The method for recovering polyacrylonitrile waste liquid according to the second objective of this invention preferably uses the system described above.

[0058] In the polyacrylonitrile waste liquid recovery system of the present invention, preferably,

[0059] The liquid outlet of the azeotropic distillation column is connected to the bottom liquid collection pipeline; and / or,

[0060] The liquid outlet of the azeotropic distillation column is connected to the reboiler, and then to the bottom liquid inlet of the azeotropic distillation column; and / or,

[0061] The discharge port of the heavy component water-rich phase in the condenser is connected to the water-rich phase extraction pipeline; and / or,

[0062] The discharge port of the heavy component-rich aqueous phase from the condenser is connected to the feed port of the azeotropic distillation column; and / or,

[0063] The outlet of the light component rich in acrylonitrile in the condenser is connected to the acrylonitrile-rich phase extraction pipeline.

[0064] In the polyacrylonitrile waste liquid recovery system of the present invention, preferably,

[0065] The azeotropic distillation column has n theoretical plates, where n ≥ 4 and n is a natural number; preferably, the inlet of the polyacrylonitrile waste liquid is located at theoretical plates n / 2 to n; more preferably, the inlet of the bottom liquid of the azeotropic distillation column is located at n theoretical plates; the inlet of the heavy component rich in aqueous phase from the condenser for recycling to the azeotropic distillation column is located at 1-3 theoretical plates; and / or,

[0066] When the azeotropic distillation column is a packed column; preferably, the specific surface area of ​​the packing in the azeotropic distillation column is ≥70 m². 2 / m 3 Preferred size ≥100m 2 / m 3 Further preferred is 100-200m 2 / m 3 ; and / or,

[0067] The pressurization device is a dry vacuum pump; and / or,

[0068] The moisture content detection device is a gas chromatograph.

[0069] In the technical solution described in this invention, when the azeotropic distillation column is a packed column, a distributor is provided at the top of the packing of each section of the distillation column; the packing is existing conventional packing.

[0070] In the technical solution described in this invention, the condenser is temperature-controlled by a temperature-regulating medium.

[0071] The fourth objective of this invention is to provide a method for recovering polyacrylonitrile waste liquid as described in the second objective of this invention, or a system for recovering polyacrylonitrile waste liquid as described in the third objective of this invention, for the application of polyacrylonitrile waste liquid recovery.

[0072] 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.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] Compared with other processes, this invention, through the design of a special baffle in the condenser, can achieve multiple separations of light and heavy components under normal pressure conditions, reduce the residence time of acrylonitrile to prevent self-polymerization, and effectively improve the separation and recovery effect of acrylonitrile.

[0075] The inventors of this invention discovered that in existing processes, acrylonitrile vapor phase condensation at the top of the tower is generally carried out under negative pressure, which results in excessively low condensation temperatures of the acrylonitrile vapor phase, easily causing blockage of the pipeline. Compared with other existing processes, this invention carries out acrylonitrile vapor phase condensation at the top of the tower under positive pressure, ensuring that the condensation temperature of the acrylonitrile vapor phase is not too low. In other words, the condenser temperature of this invention does not need to be too low, thereby reducing the energy consumption of the condenser, increasing its efficiency, and eliminating the problem of pipeline blockage under low-temperature conditions.

[0076] Existing processes do not adjust the condenser temperature based on the water content in the gas, which also leads to high condenser energy consumption. Compared with other processes, this invention controls the condenser refrigerant through online measurement by a gas chromatograph, ensuring the condenser outlet temperature under different gas phase water contents, reducing condenser energy consumption, avoiding low-temperature blockage of materials, and improving economic efficiency. Attached Figure Description

[0077] Figure 1 A schematic diagram of a device for recovering polyacrylonitrile waste liquid provided by the present invention;

[0078] Figure 2 This is a schematic diagram of a condenser with an internal baffle provided by the present invention.

[0079] Figure 1 Marker explanation:

[0080] 101 Polyacrylonitrile waste liquid

[0081] 102 Distillation column vapor discharge

[0082] 103 Dry vacuum pump for gas phase discharge

[0083] 104 Condenser liquid phase discharge

[0084] 105 Condenser vapor discharge

[0085] 106 Light component discharge from condenser

[0086] 107 Condensation Tank Heavy Component Discharge

[0087] 108 Recycled Components Refluxed Material

[0088] 111 Liquid phase discharge from the bottom of the distillation column

[0089] 112 Discharge pump for liquid phase discharge

[0090] 113 Reboiler gas phase discharge

[0091] 121 Recombinant Component Discharge

[0092] 131 Light component discharge

[0093] E1 vapor phase condenser

[0094] E2 Reboiler

[0095] T1 Azeotropic Distillation Column

[0096] P1 Distillation column discharge pump

[0097] P2 Distillation column reflux pump

[0098] P3 Condensate Tank Discharge Pump

[0099] P4 dry vacuum pump

[0100] AIC Online Gas Chromatograph

[0101] Figure 2 Marker explanation:

[0102] V1 Condensate Tank

[0103] 1. First baffle

[0104] 2. Second baffle

[0105] 3. The third baffle

[0106] 4. The fourth baffle

[0107] The height of the intermediate cylindrical tank of the H-condenser

[0108] △H1 Height difference between the first baffle and the second baffle

[0109] △H2 Height difference between the second and third baffles

[0110] △H3 Height difference between the third baffle and the fourth baffle. Detailed Implementation

[0111] The present invention will now be described in detail with reference to the accompanying drawings and 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] Example 1

[0116] like Figure 2 As shown, a condenser V1 according to the present invention has an H-shaped structure longitudinally arranged at its bottom. i Block baffle, the H i ≥1; and when the H i When ≥2, the H i The baffles are arranged in a stepped manner inside the condenser due to their different heights.

[0117] The condenser has a light component extraction outlet on one side for extracting the light component acrylonitrile-rich phase. Baffles are installed at the bottom of the condenser according to the rule that the greater the lateral distance from the light component extraction outlet, the higher the baffle. The baffle with the lowest height is designated as the Hth baffle. i The second lowest baffle is designated as the Hth baffle. i-1 The baffles are arranged in a specific pattern, with the highest baffle designated as the H1 baffle. The inlet of the condenser is located in the upper part of the chamber formed by the H1 baffle and the other side of the condenser. i The height of the baffle is greater than the height of the light component extraction outlet; specifically, the Hth... i The height of the baffle at 1 / 3 to 5 / 6 of its length is preferably, in this embodiment, the height of the Hth section. i The height of the baffle at 2 / 3 of its length is aligned with the light component extraction outlet. The bottom of the condenser is equipped with a heavy component extraction outlet, located at the lower center of the chamber formed by the baffles, for extracting the water-rich phase of the heavy component. The upper part of the condenser is also equipped with a condenser gas phase outlet for extracting some non-condensable gases carried over from the azeotropic distillation column.

[0118] from Figure 2As can be seen from the diagram, the condenser of this invention is provided with multiple longitudinal baffles inside, and the height of each baffle decreases sequentially. The height difference between adjacent baffles refers to the difference between the higher baffle and the lower baffle. Specifically, the height difference between the first baffle 1 and the second baffle 2 is △H1, the height difference between the second baffle 2 and the third baffle 3 is △H2, the height difference between the third baffle 3 and the fourth baffle 4 is △H3, and so on.

[0119] As a preferred implementation method,

[0120] In the condenser, the ratio of the height difference between adjacent baffles to the height of the intermediate cylindrical tank body of the condenser is 0.01-0.6, more preferably 0.01-0.3.

[0121] As a preferred implementation method,

[0122] The ratio of the height of the highest baffle to the height of the intermediate cylindrical tank of the condenser is 0.1-0.6, more preferably 0.2-0.6.

[0123] As a preferred implementation method,

[0124] In the condenser, the ratio of the lateral distance between adjacent baffles to the diameter of the condenser is 0.16-0.5, preferably 0.25-0.5.

[0125] The working principle of the condenser of this invention is as follows:

[0126] The materials entering the condenser mainly consist of acrylonitrile and water. These materials first enter through the condenser's inlet and accumulate in the first chamber formed by the H1 baffle (the first baffle) and the other side of the condenser. In this first chamber, due to density differences, acrylonitrile and water undergo two-phase separation. The upper layer is the light acrylonitrile-rich phase, and the lower layer is the heavy water-rich phase. As the amount of material in the first chamber increases, the upper layer of light acrylonitrile-rich phase overflows into the second chamber formed by the H1 baffle (the first baffle) and the H2 baffle (the second baffle), undergoing the same material separation process as in the first chamber. This process continues until the light acrylonitrile-rich phase overflows into the H1 baffle and the side of the condenser. iWithin each of the chambers, a separation process occurs between the light component (acrylonitrile-rich phase) and the heavy component (aqueous phase). Therefore, as the separation process progresses, the concentration of the light component (acrylonitrile-rich phase) is higher in the lower-height baffles, resulting in a greater degree of separation from the heavy component (aqueous phase). Finally, the light component (acrylonitrile-rich phase) with the highest acrylonitrile concentration is collected from the light component outlet, while the heavy component (aqueous phase) is collected from the outlet at the bottom of the condenser. It is evident that this invention, through the design of a special baffle in the condenser, enables multiple separations of light and heavy components under normal pressure conditions, reducing the residence time of acrylonitrile to prevent self-polymerization and effectively improving the separation and recovery efficiency of acrylonitrile.

[0127] Example 2

[0128] like Figure 1 As shown, the system for recovering polyacrylonitrile waste liquid according to the present invention includes an azeotropic distillation column, a pressurization device, a moisture content detection device, a condenser, and a condenser tank. The specific structure of the condenser tank is as follows: Figure 2 As shown.

[0129] The azeotropic distillation column has its inlet connected to the outlet of the polyacrylonitrile waste liquid feed pipeline; its liquid outlet is connected to the bottom liquid collection pipeline; its liquid outlet is also connected to the reboiler, which in turn is connected to the bottom liquid inlet of the azeotropic distillation column; its vapor outlet is connected to the inlet of the booster unit; its outlet is connected to the inlet of the condenser, and a moisture content detection device is installed on the connecting pipeline between the booster unit and the condenser; its outlet is connected to the inlet of the condenser; the condenser has an outlet for the light component rich in acrylonitrile and an outlet for the heavy component rich in water; the outlet for the light component rich in acrylonitrile is connected to the acrylonitrile-rich phase collection pipeline; the outlet for the heavy component rich in water is connected to the water-rich phase collection pipeline; and the outlet for the heavy component rich in water is also connected to the inlet of the azeotropic distillation column.

[0130] In the above embodiments of the present invention, when the azeotropic distillation column T1 is a packed column; the pressurization device is a dry vacuum pump P4; the moisture content detection device is an online gas chromatograph AIC; and the condenser is a gas phase condenser E1.

[0131] In this invention, after the polyacrylonitrile waste liquid 101 passes through the azeotropic distillation column T1, the gas phase output 102 of the distillation column mainly contains water and acrylonitrile monomer, and the liquid phase output 111 of the distillation column mainly contains dimethyl sulfoxide.

[0132] At the top of the distillation column, the vapor output 102 is collected from the top of the column and sent to the dry vacuum pump P4 to increase the pressure. Subsequently, most of the vapor output 103 from the dry vacuum pump is sent to the vapor condenser E1 for condensation, and a small portion is tested for water content in the gas by an online gas chromatograph (AIC). The liquid output 104 from the condenser enters the condenser tank V1 for gas-liquid separation. Inside the condenser V1, some non-condensable gases are collected as condenser gas phase discharge 105 from the system. The liquid phase material can be separated into light and heavy components through the internal baffle design of the condenser. The light component rich in acrylonitrile is collected as condenser light component discharge 106 by condenser discharge pump P3. The collected light component discharge 131 is recycled. The heavy component rich in water phase is collected as condenser heavy component discharge 107 from the condenser. Part of the condenser heavy component discharge 107 is returned to the azeotropic distillation column T1 as heavy component reflux material 108 by distillation column reflux pump P2, and part of it is directly collected as heavy component discharge 121 from the system.

[0133] In the bottom of the distillation column, the liquid phase 111 of the distillation column bottom is a dimethyl sulfoxide-rich phase. A portion of it is sent to the reboiler E2 by the distillation column feed pump P1, forming the reboiler gas phase 113, which is then refluxed back to the azeotropic distillation column T1. The other portion is directly collected as the liquid phase 112 of the feed pump.

[0134] As a preferred implementation method,

[0135] The theoretical number of plates in an azeotropic distillation column is n, where n ≥ 4 and n is a natural number.

[0136] A further preferred embodiment,

[0137] The inlet for polyacrylonitrile waste liquid is located at theoretical plates n / 2 to n; the inlet for the bottom liquid of the azeotropic distillation column is located at n theoretical plates; the inlet for the heavy component water-rich phase of the condenser to be recycled to the azeotropic distillation column is located at 1 theoretical plate.

[0138] Example 3

[0139] A method for recovering polyacrylonitrile waste liquid, using the polyacrylonitrile waste liquid recovery system as shown in Example 2, includes the following steps:

[0140] (1) After azeotropic distillation of polyacrylonitrile waste liquid, part of the liquid phase in the bottom of the column is refluxed for azeotropic distillation, and the other part is collected out of the system; the gas phase at the top of the column is collected.

[0141] The polyacrylonitrile waste liquid contains 0.8 wt% acrylonitrile, 99.192 wt% dimethyl sulfoxide and 0.008 wt% water.

[0142] The process parameters for azeotropic distillation are: operating pressure 12 kPaA, top operating temperature 24.3℃, bottom operating temperature 126.4℃, and reflux ratio 2. When the azeotropic distillation column is a packed column, the specific surface area of ​​the packing is 100 m². 2 / m 3 The azeotropic distillation column has 10 theoretical plates, and the inlet for the polyacrylonitrile waste liquid is located at the 6th theoretical plate.

[0143] (2) The gas phase at the top of the tower after extraction is dry-pressurized to a pressure of 3 kPaG. The pressurized gas is sent to the condenser and the water content in the gas is tested at the same time. The water content in the gas is 0.49 wt%. The temperature of the condenser is 15°C lower than the acrylonitrile dew point temperature. The condensed material is obtained.

[0144] (3) The condensed material is fed into the condenser; the temperature inside the condenser is 6°C lower than the temperature of the condenser. The light component rich in acrylonitrile and the heavy component rich in water are collected from the condenser. The light component rich in acrylonitrile is collected and recovered, and part of the heavy component rich in water is refluxed for azeotropic distillation, and the other part is collected from the system. The number of baffles inside the condenser is 3. The ratio of the height difference between adjacent baffles to the height of the middle cylindrical tank of the condenser is 0.2. The ratio of the height of the highest baffle to the height of the middle cylindrical tank of the condenser is 0.6. The ratio of the lateral distance between adjacent baffles to the diameter of the condenser is 0.25. The ratio of the height of the middle cylindrical tank to the total height of the condenser is 0.8.

[0145] Example 4

[0146] A method for recovering polyacrylonitrile waste liquid, using the polyacrylonitrile waste liquid recovery system as shown in Example 2, includes the following steps:

[0147] (1) After azeotropic distillation of polyacrylonitrile waste liquid, part of the liquid phase in the bottom of the column is refluxed for azeotropic distillation, and the other part is collected out of the system; the gas phase at the top of the column is collected.

[0148] The polyacrylonitrile waste liquid contains 0.8 wt% acrylonitrile, 99.192 wt% dimethyl sulfoxide and 0.008 wt% water.

[0149] The process parameters for azeotropic distillation are:

[0150] The operating pressure is 9 kPaA, the top operating temperature is 16.1℃, the bottom operating temperature is 119.9℃, and the reflux ratio is 11.5. When the azeotropic distillation column is a packed column, the specific surface area of ​​the packing is 200 m². 2 / m 3 The azeotropic distillation column has 20 theoretical plates, and the inlet for the polyacrylonitrile waste liquid is located at the 11th theoretical plate.

[0151] (2) The gas phase at the top of the tower after extraction is dry-pressurized to a pressure of 5 kPaG. The pressurized gas is sent to the condenser and the water content in the gas is tested at the same time. The water content in the gas is 0.9 wt%. The temperature of the condenser is 5 °C lower than the acrylonitrile dew point temperature. The condensed material is obtained.

[0152] (3) The condensed material is fed into the condenser; the temperature inside the condenser is 3°C lower than the temperature of the condenser. The light component rich in acrylonitrile and the heavy component rich in water are collected from the condenser. The light component rich in acrylonitrile is collected and recovered, and part of the heavy component rich in water is refluxed for azeotropic distillation, and the other part is collected from the system. The number of baffles inside the condenser is 4. The ratio of the height difference between adjacent baffles to the height of the middle cylindrical tank of the condenser is 0.15. The ratio of the height of the highest baffle to the height of the middle cylindrical tank of the condenser is 0.6. The ratio of the lateral distance between adjacent baffles to the diameter of the condenser is 0.2. The ratio of the height of the middle cylindrical tank to the total height of the condenser is 0.8.

[0153] Example 5

[0154] A method for recovering polyacrylonitrile waste liquid, using the polyacrylonitrile waste liquid recovery system as shown in Example 2, includes the following steps:

[0155] (1) After azeotropic distillation of polyacrylonitrile waste liquid, part of the liquid phase in the bottom of the column is refluxed for azeotropic distillation, and the other part is collected out of the system; the gas phase at the top of the column is collected.

[0156] The polyacrylonitrile waste liquid contains 0.8 wt% acrylonitrile, 99.192 wt% dimethyl sulfoxide and 0.008 wt% water.

[0157] The process parameters for azeotropic distillation are:

[0158] The operating pressure is 3 kPaA, the top operating temperature is 4.3℃, the bottom operating temperature is 100.2℃, the reflux ratio is 11.5, and the azeotropic distillation column is a packed column; the specific surface area of ​​the packing in the azeotropic distillation column is 200 m². 2 / m 3 The azeotropic distillation column has 20 theoretical plates, and the inlet for the polyacrylonitrile waste liquid is located at the 11th theoretical plate.

[0159] (2) The gas phase at the top of the tower after extraction is dry-pressurized to a pressure of 5 kPaG. The pressurized gas is sent to the condenser and the water content in the gas is tested at the same time. The water content in the gas is 1 wt%. The temperature of the condenser is 5 °C lower than the acrylonitrile dew point temperature. The condensed material is obtained.

[0160] (3) The condensed material is fed into the condenser; the temperature inside the condenser is 2°C lower than the temperature of the condenser. The light component rich in acrylonitrile and the heavy component rich in water are collected from the condenser. The light component rich in acrylonitrile is collected and recovered, and part of the heavy component rich in water is refluxed for azeotropic distillation, and the other part is collected from the system. The number of baffles inside the condenser is 5. The ratio of the height difference between adjacent baffles to the height of the middle cylindrical tank of the condenser is 0.1. The ratio of the height of the highest baffle to the height of the middle cylindrical tank of the condenser is 0.6. The ratio of the lateral distance between adjacent baffles to the diameter of the condenser is 0.167. The ratio of the height of the middle cylindrical tank to the total height of the condenser is 0.8.

[0161] Comparative Example 1

[0162] It uses the same process conditions as Example 4, the only difference being that the condenser used is a conventional condenser without the baffle of the present invention.

[0163] Comparative Example 2

[0164] It uses the same process conditions as Example 4, except that it does not use a pressurizing device for pressurization. Instead, it directly enters the condenser at a negative pressure of 9 kPaA for the condensation of the top gas phase. In order to achieve the condensation of the acrylonitrile gas phase, the temperature of the condenser needs to be further reduced.

[0165] Comparative Example 3

[0166] It uses the same process conditions as Example 4, the only difference being that the water content in the pressurized gas is not tested, and the temperature of the condenser is maintained at the acrylonitrile dew point temperature for condensation.

[0167] The effects of the above-described embodiments and comparative examples on the recovery of polyacrylonitrile waste liquid are shown in Table 1 below:

[0168] Table 1

[0169]

[0170] A comparison of the results of Example 4 and Comparative Example 1 shows that the present invention, through the design of a special baffle in the condenser, can achieve multiple separations of light and heavy components in the condenser under normal pressure conditions, thereby improving the separation effect of the condenser on acrylonitrile. This also helps to improve the separation and reflux effect of the top material of the azeotropic distillation column, thus improving the overall separation and recovery effect of polyacrylonitrile waste liquid.

[0171] By comparing the results of Example 4 and Comparative Example 2, it can be seen that in Comparative Example 2, which is similar to the existing process, the vapor-phase condensation of acrylonitrile at the top of the tower is carried out under negative pressure, which easily causes the material to block the pipeline. The present invention carries out the vapor-phase condensation of acrylonitrile at the top of the tower under positive pressure, which has low energy consumption, high efficiency and no problem of material blockage in the pipeline.

[0172] By comparing the results of Example 4 and Comparative Example 3, it can be seen that the existing process of Comparative Example 3 does not adjust the temperature of the condenser based on the water content in the gas, which will significantly increase the energy consumption of the condenser. Compared with other processes, the present invention controls the refrigerant of the condenser by online measurement of the gas chromatograph, ensuring the condenser outlet temperature under different gas phase water contents, reducing the energy consumption of the condenser, avoiding low-temperature blockage of materials, reducing the energy consumption of the condenser and improving economic efficiency.

[0173] 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.

[0174] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0175] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0176] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

Claims

1. A condenser, wherein the bottom of the condenser is longitudinally provided with an H... i Block baffle, the H i ≥1; and when the H i When ≥2, the H i The baffles are arranged in a stepped manner at different heights inside the condenser.

2. The condenser tank according to claim 1, characterized in that: The condenser has a light component sampling outlet on one side; the baffles are arranged in a stepped manner at the bottom of the condenser, following the rule that the greater the lateral distance from the light component sampling outlet, the higher the baffle; the baffle with the lowest height is designated as the Hth. i The second lowest baffle is designated as the Hth baffle. i-1 The baffles, following this pattern, are designated as the H1th baffle; the feed inlet of the condenser is located in the upper part of the chamber formed by the H1th baffle and the other side of the condenser; and / or, The bottom of the condenser is provided with a recombination and extraction outlet; and / or, The upper part of the condenser is also provided with a condenser gas phase outlet; Preferably; H i The height of the baffle is greater than the height of the light component extraction outlet of the condenser. More preferably, the Hth i The height of the baffle at 1 / 3 to 5 / 6, preferably at 2 / 3, should be aligned with the position of the light component extraction outlet.

3. The condenser tank according to claim 1, characterized in that: The condenser tank includes a top tank, a middle cylindrical tank, and a bottom tank; preferably, The ratio of the height difference between adjacent baffles to the height of the intermediate cylindrical tank of the condenser is 0.01-0.6, preferably 0.01-0.3; and / or, The ratio of the height of the highest baffle to the height of the intermediate cylindrical tank of the condenser is 0.1-0.6, preferably 0.2-0.6; and / or, The ratio of the height of the intermediate cylindrical tank to the total height of the condenser is 1 / 2 to 4 / 5.

4. The condenser tank according to claim 1, characterized in that: In the condenser, the ratio of the lateral distance between adjacent baffles to the diameter of the condenser is 0.16-0.5, preferably 0.2-0.

5.

5. A method for recovering polyacrylonitrile waste liquid, characterized in that, Includes the following steps: (1) After azeotropic distillation of polyacrylonitrile waste liquid, the liquid phase in the bottom of the column is recycled for azeotropic distillation and / or the extraction system; the gas phase at the top of the column is extracted. (2) Dry pressurize the extracted top gas phase, send the pressurized gas into the condenser and test the water content in the gas at the same time to obtain the condensed material. (3) The condensed material is fed into a condenser; the light component rich in acrylonitrile and the heavy component rich in water are extracted from the condenser; the light component rich in acrylonitrile is extracted and recovered, and the heavy component rich in water is refluxed for azeotropic distillation and / or extraction system. The condenser is the condenser according to any one of claims 1-4.

6. The method for recovering polyacrylonitrile waste liquid according to claim 5, characterized in that: The polyacrylonitrile waste liquid includes polyacrylonitrile, dimethyl sulfoxide, and water; and / or, The process parameters for azeotropic distillation are: The operating pressure is 0-12 kPaA, preferably 1-12 kPaA; and / or, The operating temperature at the top of the tower is 3-25℃, preferably 15-20℃; and / or, The operating temperature of the column reboiler is 90-130℃, preferably 100-120℃; and / or, The reflux ratio is 2-40, preferably 4-35.

7. The method for recovering polyacrylonitrile waste liquid according to claim 5, characterized in that: The pressurized gas pressure is 0-5 kPaG; and / or, The temperature of the condenser is 5-15°C lower than the acrylonitrile dew point temperature; and / or, The temperature inside the condenser is 2-8°C lower than the temperature of the condenser.

8. The method for recovering polyacrylonitrile waste liquid according to claim 7, characterized in that: The pressurized gas pressure is 0-3 kPaG; and / or, When the water content in the gas is 0.008wt%-0.5wt%, the condenser temperature is 15°C lower than the acrylonitrile dew point temperature; and / or, When the water content in the gas is 0.5wt%-1wt%, excluding 0.5wt%, the condenser temperature is 5°C lower than the acrylonitrile dew point temperature; and / or, The temperature inside the condenser is 3-6°C lower than the temperature of the condenser.

9. A system for recovering polyacrylonitrile waste liquid, comprising an azeotropic distillation column, a pressurization device, a moisture content detection device, a condenser, and a condensate tank: in, The feed inlet of the azeotropic distillation column is connected to the outlet of the polyacrylonitrile waste liquid feed pipeline; the vapor outlet of the azeotropic distillation column is connected to the feed inlet of the booster unit. The outlet of the booster is connected to the inlet of the condenser, and a moisture content detection device is installed on the connecting pipeline between the booster and the condenser. The condenser's outlet is connected to the condenser's inlet; The condenser is provided with an outlet for the light component rich in acrylonitrile phase and an outlet for the heavy component rich in water phase; the condenser is the condenser according to any one of claims 1-4; The system described in the method for recovering polyacrylonitrile waste liquid according to any one of claims 5-8 is preferred.

10. The system for recovering polyacrylonitrile waste liquid according to claim 9, characterized in that: The liquid outlet of the azeotropic distillation column is connected to the bottom liquid collection pipeline; and / or, The liquid outlet of the azeotropic distillation column is connected to the reboiler, and then to the bottom liquid inlet of the azeotropic distillation column; and / or, The discharge port of the heavy component water-rich phase in the condenser is connected to the water-rich phase extraction pipeline; and / or, The discharge port of the heavy component-rich aqueous phase from the condenser is connected to the feed port of the azeotropic distillation column; and / or, The outlet of the light component rich in acrylonitrile in the condenser is connected to the acrylonitrile-rich phase extraction pipeline.

11. The system for recovering polyacrylonitrile waste liquid according to claim 9, characterized in that: The azeotropic distillation column has a theoretical plate number of n, where n ≥ 4 and n is a natural number; preferably, the inlet of the polyacrylonitrile waste liquid is located at a theoretical plate number between n / 2 and n; and / or, When the azeotropic distillation column is a packed column; preferably, the specific surface area of ​​the packing in the azeotropic distillation column is ≥70 m². 2 / m 3 Preferred size ≥100m 2 / m 3 Further preferred is 100-200m 2 / m 3 ; and / or, The pressurization device is a dry vacuum pump; and / or, The moisture content detection device is a gas chromatograph.

12. The application of a method for recovering polyacrylonitrile waste liquid as described in any one of claims 5-8 or a system for recovering polyacrylonitrile waste liquid as described in any one of claims 9-11 in the recovery of polyacrylonitrile waste liquid.

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