Solvent recovery system and polymer production system and method

Abstract

The invention discloses a solvent recovery system and a polymer production system and method.The solvent recovery system comprises an extraction device, a gas-liquid separation unit, a rectification unit and a first membrane separator, the extraction device is provided with a first extraction discharge port and a second extraction discharge port, the first extraction discharge port is communicated with the gas-liquid separation unit, and the second extraction discharge port is communicated with the gas-liquid separation unit; and the second extraction discharge hole is communicated with the first membrane separator through the rectification unit. According to the solvent recovery system, the alcohol solvent and the aromatic solvent meeting the requirements can be recovered from the target waste solvent at least containing the alcohol solvent, the aromatic solvent and water, so that the recovered alcohol solvent and the recovered aromatic solvent can be reused, the solvent treatment cost is reduced, and resource waste is avoided.

Description

Technical Field

[0001] The present application belongs to the field of chemical technology, and in particular relates to a solvent recovery system, a polymer production system and a method. Background Art

[0002] Polyphenylene ether is an important engineering plastic with excellent mechanical properties, high temperature resistance, low dielectric constant, high steam resistance, flame retardancy and other advantages. It is widely used in electronics, automobile industry, household appliances, industrial machinery and other industries.

[0003] In the related art, 2,6-dimethylphenol can be used as a monomer to prepare polyphenylene ether by a phase solution polycondensation method, and a mixed solution is formed with water and toluene, and the polyphenylene ether in the mixed solution is precipitated by methanol. However, a large amount of toluene-methanol-water mixed waste solvents will be generated. The treatment cost of these mixed waste solvents is high and they cannot be reused, resulting in a waste of resources. Summary of the invention

[0004] In response to the above problems, the present application provides a solvent recovery system, a polymer production system and a method to recover alcohol solvents and aromatic solvents that meet the requirements from a target waste solvent containing at least an alcohol solvent, an aromatic solvent and water, so that the recovered alcohol solvents and aromatic solvents can be reused, thereby reducing solvent processing costs and avoiding waste of resources.

[0005] In a first aspect, the present application provides a solvent recovery system, comprising: an extraction device, a gas-liquid separation unit, a distillation unit and a first membrane separator, wherein the extraction device has a first extraction outlet and a second extraction outlet, the first extraction outlet is connected to the gas-liquid separation unit, and the second extraction outlet is connected to the first membrane separator through the distillation unit;

[0006] The feed port of the extraction device is used to be connected to the conveying pipeline of the target waste solvent, and the target waste solvent contains at least an alcohol solvent, an aromatic solvent and water; the first extraction outlet is used to convey the first extraction material containing the aromatic solvent to the gas-liquid separation unit, and the second extraction outlet is used to convey the second extraction material containing the alcohol solvent and water to the distillation unit.

[0007] In a second aspect, the present application also provides a polymer production system, comprising the solvent recovery system disclosed in the first aspect of the present application.

[0008] In a third aspect, the present application also provides a solvent recovery method, comprising:

[0009] Extracting the target waste solvent with an extraction solution to obtain a first extraction material and a second extraction material, wherein the target waste solvent contains at least an alcohol solvent, an aromatic solvent and water; the first extraction material contains the aromatic solvent, and the second extraction material contains the alcohol solvent and the water;

[0010] Performing gas-liquid separation on the first extraction material to obtain the aromatic solvent;

[0011] distilling the second extract material to obtain a first top fraction containing an alcohol aqueous solution and a first bottom fraction containing water;

[0012] The first fraction containing the alcohol aqueous solution is subjected to membrane separation to obtain the alcohol solvent, water and a separation residue, respectively.

[0013] In one or more technical solutions of the present application, the feed port of the extraction device is used to communicate with the delivery pipeline of the target waste solvent, so the extraction device can use the extraction solution to extract the target waste solvent to obtain the first extraction material and the second extraction material. The extraction device has a first extraction outlet and a second extraction outlet, and the first extraction outlet is connected to the gas-liquid separation unit, and the second extraction outlet is connected to the distillation unit. When the target waste solvent contains at least alcohol solvents, aromatic solvents and water, the extraction device can transport the first extraction material containing the aromatic solvent to the gas-liquid separation unit, so that the gas-liquid separation unit can separate the extracted aromatic solvent from the first extraction material. At the same time, the extraction device can also transport the second extraction material containing alcohol solvents and water to the distillation unit, and the second extraction outlet is connected to the first membrane separator through the distillation unit. Therefore, the distillation unit can extract the second extraction material, and then further separate it through the first membrane separator, thereby achieving the purpose of separating alcohol solvents and water. It can be seen that the technical solution of the present application can treat target waste solvents such as toluene-methanol-water mixed waste solvents containing at least alcohol solvents, aromatic solvents and water, so as to obtain alcohol solvents and aromatic solvents that meet the requirements, so that the recovered alcohol solvents and aromatic solvents can be reused, thereby reducing the solvent treatment cost and avoiding waste of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0015] Figure 1A schematic diagram of the structure of a polymer production system using polyphenylene ether as an example in an embodiment of the present application is shown;

[0016] Figure 2 A schematic structural diagram of a solvent recovery system according to an embodiment of the present application is shown;

[0017] Figure 3A A schematic diagram of the structure of a gas-liquid separation unit according to an embodiment of the present application is shown;

[0018] Figure 3B A basic structural schematic diagram of a distillation unit according to an embodiment of the present application is shown;

[0019] Figure 4 A schematic flow chart of a solvent recovery method according to an embodiment of the present application is shown;

[0020] Figure 5 A schematic structural diagram of a solvent recovery system according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0022] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0023] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0024] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0025] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0026] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0027] Polyphenylene ether is an important engineering plastic with excellent mechanical properties, high temperature resistance, low dielectric constant, high steam resistance, flame retardancy and other characteristics. It is widely used in electronics, automobile industry, household appliances, industrial machinery and other industries.

[0028] In the related technology, 2,6-dimethylphenol is usually used as a monomer to obtain polyphenylene ether through oxidative polycondensation reaction. The production process of polyphenylene ether includes solvent-free melting method, homogeneous solution polycondensation method, precipitation polycondensation method, and all-water medium method, among which the most popular production process is one of the current mainstream production processes.

[0029] When the homogeneous solution polycondensation method is used to produce polyphenylene ether, 2,6-dimethylphenol monomer can undergo alkylation reaction with oxygen in toluene solvent, and the generated polyphenylene ether, water and toluene form a mixed solution. Methanol is a poor solvent for polyphenylene ether. After obtaining a mixed solution formed by polyphenylene ether, water and toluene, the mixed solution can be subjected to a series of treatments, and finally methanol is used as an extraction solvent to extract polyphenylene ether from the mixed solution. In the process of extracting polyphenylene ether, a large amount of toluene-methanol-water mixed waste liquid is generated, and the toluene, methanol and water contained in the toluene-methanol-water mixed waste liquid are not easy to separate. Therefore, the toluene-methanol-water mixed waste liquid is usually discharged, resulting in large solvent consumption and high production cost.

[0030] In response to the above problems, an embodiment of the present application provides a polymer production system, which includes a solvent recovery system. The solvent recovery system can separate alcohol solvents, aromatic solvents and water from target waste solvents such as toluene-methanol-water mixed waste liquid containing alcohol solvents, aromatic solvents and water, thereby reducing waste liquid discharge and solvent consumption, and reducing production costs.

[0031] Figure 1 The schematic diagram of the structure of the polymer production system of the embodiment of the present application is shown, taking polyphenylene ether as an example. Figure 1 As shown, the polymer production system 100 of the embodiment of the present application includes a polyphenylene ether preparation system 101 and a solvent recovery system 102. The waste solvent conveying pipeline of the polyphenylene ether preparation system 101 is connected to the solvent recovery system 102. The polyphenylene ether preparation system 101 can convey the mixed waste solvent of toluene-methanol-water through the waste solvent conveying pipeline to the solvent recovery system 102, and the solvent recovery system 102 is used to separate the solvent of the mixed waste solvent of toluene-methanol-water, so as to obtain methanol, toluene and water that meet the specifications.

[0032] like Figure 1 As shown, the methanol can be connected to the polyphenylene ether preparation system 101 through the delivery pipeline of the alcohol solvent, so that the methanol can be reused for polyphenylene ether extraction. The toluene can be connected to the polyphenylene ether preparation system 101 through the delivery pipeline of the aromatic solvent, so that toluene can be used as a solvent and reused as a reaction solvent for polyphenylene ether. Considering that the toluene-methanol-water mixed waste liquid may also contain salt substances, the water separated from the toluene-methanol-water mixed waste solvent can be desalted water, and the remaining salt water can be concentrated to achieve final separation.

[0033] It can be seen that Figure 1As shown, the polymer production system 100 of the embodiment of the present application can separate toluene, methanol and desalted water that meet the requirements from the mixed waste solvent of toluene-methanol-water, wherein toluene and methanol can be reused in the preparation of polyphenylene ether, and desalted water can be reused in the mixed waste solvent of toluene-methanol-water, thereby reducing the amount of waste liquid discharged and the amount of solvent consumed, and lowering the production cost.

[0034] Figure 2 The schematic diagram of the structure of the solvent recovery system of the embodiment of the present application is shown. Figure 2 As shown, the solvent recovery system 200 of the embodiment of the present application comprises: an extraction device 201, a gas-liquid separation unit 202, a distillation unit 203 and a first membrane separator 2041. The extraction device 201 has a first extraction outlet and a second extraction outlet.

[0035] The feed port of the extraction device 201 is used to communicate with the delivery pipeline of the target waste solvent, and the target waste solvent contains at least an alcohol solvent, an aromatic solvent and water. The extraction device 201 can extract the target waste solvent so that the target waste solvent can be separated into oil and water to obtain a first extraction material containing an aromatic solvent and a second extraction material containing an alcohol solvent and water. This first extraction material can be considered as an oil phase, and the second extraction material can be considered as an aqueous phase.

[0036] The first extraction outlet is connected to the gas-liquid separation unit 202, and the first extraction outlet is used to transport the first extraction material containing the aromatic solvent to the gas-liquid separation unit 202. The gas-liquid separation unit 202 can further perform gas-liquid separation on the gas-liquid separation unit 202 to obtain the aromatic solvent. When the target waste solution is a waste solvent of a polymerization reaction, it may contain some polymers, which are not easy to gasify. Therefore, the aromatic solvent is separated in the gas phase through gas-liquid separation, and the polymer is separated in the liquid phase.

[0037] In some embodiments, Figure 2 As shown, the gas-liquid separation unit 202 includes a gasification device 2021 and a gas-liquid separator. The first extraction material outlet is connected to the gas-liquid separator 2022 through the gasification device 2021. At this time, the first extraction material can pass through the gasification device 2021 to gasify the vaporizable aromatic solvent in the first extraction material, and then the obtained gas-liquid mixture is sent to the gas-liquid separator 2022. The gas-liquid separator 2022 can perform gas-liquid separation on the gas-liquid mixture to obtain a gaseous aromatic solvent and a liquid residue. For example, when the target waste solvent is a toluene-methanol-water mixed waste liquid generated in the process of producing polyphenylene ether, the first extraction material can contain toluene and a small amount of oligomers (reaction by-products). At this time, the aromatic solvent is toluene, and the liquid residue contains a small amount of oligomers.

[0038] Considering that the gas phase material usually contains more heat, and in order to make full use of the heat, the gas outlet of the gas-liquid separation unit 202 can be set to be connected to the heat source pipeline of the gasification device 2021, so that the gas phase benzene solvent can be introduced into the heat source pipeline, so as to use the heat of the gas phase benzene solvent to heat the first extraction material entering the gasification device 2021, so that the benzene solvent in the first extraction material is gasified. The gas phase benzene solvent is liquefied after heat exchange and discharged from the aromatic solvent delivery pipeline.

[0039] For example, Figure 2 As shown, the gasification device 2021 includes at least one heater connected in series between the first extraction material outlet and the gas-liquid separator 2022, the gas outlet of the gas-liquid separator 2022 is connected to the hot channel of at least one heater, and the hot channel outlet of the heater is connected to the conveying pipeline of the aromatic solvent. Here, the heater can exist in the form of a heat exchanger, and the heat exchanger can be a partition heat exchanger.

[0040] For example, Figure 2 As shown, since each heater is connected in series between the first extraction material outlet and the feed port of the gas-liquid separator 2022, the closer the distance between the heater and the first extraction material outlet is, the higher the temperature of the first extraction material entering the heater. Therefore, when the gas outlet of the gas-liquid separator 2022 is connected to the heat channel of the heater close to the first extraction material outlet, the temperature difference between the first extraction material entering the heater and the gas-phase aromatic solvent is the largest. Therefore, the heater can make full use of the heat of the gas-phase aromatic solvent to heat the first extraction material, thereby improving the thermal energy utilization rate and reducing unnecessary heat waste.

[0041] like Figure 2 As shown, the second extraction outlet is connected to the first membrane separator 2041 through the distillation unit 203. At this time, the second extraction outlet is used to transport the second extraction material containing alcohol solvent and water to the distillation unit 203, so as to extract the second extraction material by the distillation unit 203, and then further separate it through the first membrane separator 2041, so as to achieve the purpose of separating the alcohol solvent and water.

[0042] In practical applications, such as Figure 2 As shown, after distillation by the distillation unit 203, a first tower top fraction containing an alcohol aqueous solution and a first tower bottom fraction containing water can be separated, and the first tower bottom fraction containing an alcohol aqueous solution can be subjected to membrane separation to obtain an alcohol solvent and a separation residue, respectively. The separation residue can be an alcohol solvent with a lower concentration than that of the first tower top fraction.

[0043] In some embodiments, Figure 2As shown, the solvent recovery system 200 of the embodiment of the present application may further include a second membrane separator 2042. The top discharge port of the distillation unit 203 is connected to the first membrane separator 2041, and the bottom discharge port of the distillation unit 203 is connected to the second membrane separator 2042. Here, the first membrane separator 2041 and the second membrane separator 2042 may be selected from membrane separators in a narrow sense, or may be falling film evaporators, etc.

[0044] like Figure 2 As shown, the top discharge port of the distillation unit 203 is used to transport the first fraction containing the alcohol aqueous solution to the first membrane separator 2041, so that the first membrane separator 2041 can perform membrane separation on the first fraction containing the pure aqueous solution, thereby obtaining an alcohol solvent and a separation residue. When the target waste solvent also contains salt substances, the first tower bottom fraction also contains salt substances. At this time, the first tower bottom fraction contains a salt solution. The tower bottom discharge port of the distillation unit 203 is used to transport the second fraction containing the salt solution to the second membrane separator 2042, and the second membrane separator 2042 can perform membrane separation on the second fraction to obtain desalted water and saline wastewater, respectively.

[0045] In order to make full use of the target waste solvent, such as Figure 2 As shown, the first outlet of the first membrane separator 2041 of the embodiment of the present application is used to communicate with the delivery pipeline of the alcohol solvent, and the first outlet of the second membrane separator 2042 is used to communicate with the delivery pipeline of the saline wastewater. In addition, the second outlet of the first membrane separator 2041 is used to output desalted water, and the second outlet of the second membrane separator 2042 is used to output the separation residue.

[0046] Considering that the target waste solution can be extracted by an alcohol solvent, and the separation residue can be an alcohol aqueous solution with a lower concentration, therefore, Figure 2 As shown, the second outlet of the first membrane separator 2041 and the second outlet of the second membrane separator 2042 are both connected to the feed port of the extraction device 201, so that the desalted water and the separation residue constitute the extraction solution, and the extraction solution is passed into the extraction device 201 to extract the target waste solvent. In this way, the solvent used in the solvent recovery process can be reduced, the solvent recovery cost can be reduced, and the influence of metal ions on solvent recovery can also be avoided.

[0047] It can be seen that the technical scheme of the present application can treat target waste solvents such as toluene-methanol-water mixed waste solvents containing at least alcohol solvents, aromatic solvents and water, thereby realizing the separation of alcohol solvents, aromatic solvents and water. The separated alcohol solvents, aromatic solvents and water can meet the solvent recovery requirements. Therefore, the technical scheme of the embodiment of the present application separates the target waste solvents to achieve the purpose of reuse, thereby reducing the processing cost of the mixed waste solvents and reducing resource waste.

[0048] In an optional implementation, Figure 3A A schematic diagram of the structure of the gas-liquid separation unit of the embodiment of the present application is shown. Figure 3A As shown, the gas-liquid separation unit 202 of the embodiment of the present application includes a first heater 2021A, a second heater 2021B and a gas-liquid separator 2022, the first extract discharge port is connected to the feed port of the gas-liquid separator 2022 through the hot channel of the first heater 2021A and the hot channel of the second heater 2021B in sequence, the gas outlet of the gas-liquid separator 2022 is connected to the cold channel inlet of the first heater 2021A, the cold channel outlet of the first heater 2021A is connected to the delivery pipeline of the aromatic solvent, and the liquid outlet of the gas-liquid separator 2022 is connected to the oligomer delivery pipeline.

[0049] like Figure 3A As shown, when the first extraction material contains toluene and a small amount of oligomers, the first extraction material can be preheated by the first heater 2021A and the second heater 2021B in sequence, so that the toluene that is easy to vaporize is vaporized, while the oligomers are not easy to vaporize. Therefore, a gas-liquid mixture can be obtained, and the gas-liquid mixture can enter the gas-liquid separator 2022 for gas-liquid separation. The obtained gaseous toluene has a higher temperature and can be passed into the cold channel of the first heater 2021A to release heat, and the first extraction material entering the hot channel of the first heater 2021A is heated, so as to achieve the purpose of recovering the heat of the gaseous toluene, thereby reducing unnecessary heat waste. The gaseous toluene after heat release can be liquefied, and the recovered toluene obtained can be transported to the polyphenylene ether preparation system through the aromatic solvent delivery pipeline, and used as the reaction solvent of the polyphenylene ether.

[0050] like Figure 3A As shown, the cold channel inlet of the second heater 2021B is connected to the low-pressure steam pipeline, and the cold channel outlet of the second heater 2021B is connected to the first water return pipeline. The low-pressure steam pipeline can pass low-pressure steam into the cold channel of the second heater 2021B to release heat, so as to further heat the first extraction material entering the second heater 2021B, and the condensed water obtained after the low-pressure steam releases heat can be discharged through the first water return pipeline.

[0051] In an optional implementation, Figure 3B The basic structural diagram of the distillation unit of the embodiment of the present application is shown. Figure 3BAs shown, the distillation unit 203 of the embodiment of the present application includes a first distillation device 2031 and a second distillation device 2032, the second extraction outlet is connected to the feed port of the first distillation device 2031, the top outlet of the first distillation device 2031 is connected to the feed port of the extraction device 201, and the bottom outlet of the first distillation device 2031 is connected to the first membrane separator 2041 through the second distillation device 2032.

[0052] like Figure 3B As shown, the first distillation device 2031 can perform a first distillation on the second extraction material containing alcohol solvent and water to obtain a second tower bottom fraction and a second tower top fraction. The second tower bottom fraction contains inorganic salts, methanol and water. At this time, the second tower bottom fraction can be subjected to a second distillation by the second distillation device to obtain a first tower top fraction containing an alcohol aqueous solution and a first tower bottom fraction containing water.

[0053] like Figure 3B As shown, the second tower top fraction contains a methanol-toluene-water mixture, which can be re-sent to the extraction device 201 for extraction. However, considering that the second tower top fraction contains a high thermal energy, in order to ensure operational safety and to recover heat, the solvent recovery system 200 of the embodiment of the present application also includes a condenser 205, and the tower top discharge port of the first distillation device 2031 is connected to the feed port of the extraction device 201 through the condenser 205. At this time, after the second tower top fraction flows out from the tower top discharge port of the first distillation device 2031, it releases heat in the condenser 205 and then cools, and then mixes with the target waste solvent and re-enters the extraction device 201, thereby improving the solvent recovery efficiency. At the same time, after the condensate of the condenser 205 absorbs heat, it can carry heat to the area that needs to be heated.

[0054] like Figure 3B As shown, considering that the distillation unit 203 includes a first distillation device 2031 and a second distillation device 2032, its essence is a process of two-stage distillation of the second extraction material. Considering that the more distillation times, the more difficult it is to separate the obtained fractions, the two-stage distillation process is a distillation process from coarse to fine. For example, the number of theoretical plates of the second distillation device 2032 is greater than the number of theoretical plates of the first distillation device 2031, wherein the number of theoretical plates of the first distillation device 2031 is equal to 5 to 20, and the number of theoretical plates of the second distillation device 2032 is equal to 8 to 23. Preferably, the number of theoretical plates of the first distillation device 2031 is equal to 7 to 15, and the number of theoretical plates of the second distillation device 2032 is equal to 10 to 18.

[0055] The present application also provides a solvent recovery method, which can be applied to the solvent recovery system of the present application or other possible implementation methods. The solvent recovery method can be used to recover target waste solvents containing alcohol solvents, aromatic solvents and water, which can effectively reduce the recovery cost and reduce solvent waste.

[0056] Figure 4 The schematic diagram of the process of the solvent recovery method of the embodiment of the present application is shown. Figure 4 As shown, the solvent recovery method of the embodiment of the present application includes:

[0057] Step 401: extracting a target waste solvent with an extraction solution to obtain a first extraction material and a second extraction material, wherein the target waste solvent contains at least an alcohol solvent, an aromatic solvent and water.

[0058] In practical applications, the extraction solvent and the target waste solvent can be introduced into an extraction device so that the extraction solution contacts the target waste solvent in reverse in the extraction device, and the target waste solvent is extracted by the extraction solution to obtain a first extraction material and a second extraction material.

[0059] The first extraction material contains an aromatic solvent, and the second extraction material contains an alcohol solvent and water. According to the characteristics of the first extraction material and the second extraction material, step 402 can be selected to process the first extraction material, and step 403 can be selected to process the second extraction material.

[0060] Step 402: Perform gas-liquid separation on the first extraction material to obtain an aromatic solvent. For example, the first extraction material containing the aromatic solvent is heated to vaporize the aromatic solvent contained in the first extraction material to obtain a gas-liquid mixture, and the gas-liquid mixture is subjected to gas-liquid separation to obtain an aromatic solvent and a liquid residue.

[0061] The aromatic solvent is used to heat the first extraction material containing the aromatic solvent, thereby making full use of the heat contained in the aromatic solvent and reducing energy waste. After the aromatic solvent heats the first extraction material, the aromatic solvent can be introduced into the aromatic solvent delivery pipeline for use in polymer preparation.

[0062] In practical applications, the first extraction material can be heated by multiple heaters to vaporize the aromatic solvent in the first extraction material to obtain a gas-liquid mixture, and then the gas-liquid mixture is separated by a gas-liquid separator to obtain a gas-phase aromatic solvent and a liquid residue. Taking the mixed solution of toluene, methanol and water produced by the production of polyphenylene ether as an example, it contains some oligomers, which are extracted into the first extraction material together with toluene in the extraction device. In the process of heating the first extraction material, the boiling point of the oligomer is relatively high and will not be vaporized. After separation by the gas-liquid separator, the liquid residue obtained is an oligomer solution, and the obtained gaseous toluene can be passed into a heater near the first extraction outlet to further use the gaseous toluene to heat the first extraction material. The gaseous toluene liquefies after releasing heat in the heater, and then the aromatic solvent is passed into the polymer preparation system through the aromatic solvent delivery pipeline, so that the alcohol solvent can be reused in the preparation of polyphenylene ether, thereby reducing the amount of solvent used and reducing production costs.

[0063] For example, when the aromatic solvent is toluene, the toluene can be introduced into the polyphenylene ether preparation system through the aromatic solvent delivery pipeline, so that the toluene can be reused in the preparation of the polyphenylene ether, thereby reducing the amount of solvent used and lowering the production cost.

[0064] Step 403: distilling the second extraction material to obtain a first top fraction containing an alcohol aqueous solution and a first bottom fraction containing water.

[0065] In practical applications, the second extraction material is subjected to a first distillation to obtain a second bottom fraction and a second top fraction, the second top fraction is condensed and mixed with the target waste solvent, and the second bottom fraction is subjected to a second distillation to obtain a first top fraction containing an alcohol-water solution and a first bottom fraction containing water.

[0066] Exemplarily, the extraction device can perform two-stage distillation of the second extraction material through a first distillation device and a second distillation device, and perform membrane separation on the obtained first tower top fraction through a first membrane separator, thereby obtaining an alcohol solvent and a separation residue. The alcohol solvent can be input into the polymer production system through a delivery pipeline of the alcohol solvent. For example, if the alcohol solvent is methanol, the methanol can be introduced into the polyphenylene ether preparation system through a delivery pipeline of the alcohol solvent, so that the methanol can be reused in the post-processing of the polyphenylene ether, thereby reducing the amount of solvent used and reducing production costs.

[0067] Step 404: membrane separation is performed on the first tower top fraction containing the alcohol aqueous solution to obtain an alcohol solvent and a separation residue. For example, the first tower top fraction containing the alcohol aqueous solution can be membrane separated by a first membrane separator, and the separation residue obtained can be a low-concentration alcohol aqueous solution, while the alcohol solvent can be introduced into the extraction device as a part of the extraction solution to extract the target waste solvent.

[0068] When the target waste solvent, the second extraction material and the first bottom fraction all contain salt substances, the first bottom fraction containing water and salt substances can also be subjected to membrane separation to obtain desalted water and saline wastewater, respectively, so that the desalted water and the separation residue constitute the extraction solution. Here, the desalted water and the separation residue can constitute the extraction solvent and be passed into the extraction device to extract the target waste solvent.

[0069] Figure 5 FIG. 2 shows a schematic diagram of the structure of a solvent recovery system according to an embodiment of the present application. Figure 5 As shown, the solvent recovery system 500 of the embodiment of the present application may include: an extraction tower 501 , a gas-liquid separation unit 502 , a distillation unit 503 , a first membrane separator 5041 and a second membrane separator 5042 .

[0070] like Figure 5 As shown, the extraction tower 501 has a first material inlet A and a second material inlet B, and the first material inlet A is located below the second material inlet B. The first material inlet A is connected to the delivery pipeline of the target waste solvent, and the second material inlet B is connected to the delivery pipeline of the extraction solution. The number of plates of the extraction tower 501 is equal to 2 to 10, and the preferred number of plates of the extraction tower 501 is equal to 5 to 10.

[0071] like Figure 5 As shown, the gas-liquid separation unit 502 comprises a first material receiving tank V1, a first pump P1, a first heat exchanger E1, a second heat exchanger E2 and a gas-liquid separator 5021. The top of the extraction tower 501 is provided with a first extraction material outlet. The first extraction material outlet is connected to the feed port of the gas-liquid separator 5021 through the first material receiving tank V1, the first pump P1, the cold channel of the first heat exchanger E1, the cold channel of the second heat exchanger E2, and the gas outlet of the gas-liquid separator 5021 is connected to the conveying pipeline of the aromatic solvent through the hot channel of the first heat exchanger E1, and the liquid outlet of the gas-liquid separator 5021 is connected to the conveying pipeline of the oligomer solution.

[0072] like Figure 5As shown, the distillation unit 503 includes a first distillation tower 5031 and a second distillation tower 5032. The number of theoretical plates of the first distillation tower 5031 is 5 to 20, and the number of theoretical plates of the second distillation tower 5032 is 8 to 23. Preferably, the number of theoretical plates of the first distillation tower 5031 is 7 to 15, and the number of theoretical plates of the second distillation tower 5032 is 10 to 18.

[0073] like Figure 5 As shown, the above-mentioned distillation unit 503 also includes: a second receiving tank V2, a second pump P2, a third heat exchanger E3, a third receiving tank V3, a third pump P3, a first reboiler H1, a fourth pump P4, a fifth heat exchanger E5, a fourth receiving tank V4, a fifth pump P5, a second reboiler H2, a sixth pump P6 and a sixth heat exchanger E6. The solvent recovery system 500 also includes a fourth heat exchanger E4. The tower kettle of the extraction tower 501 has a second extraction material outlet, and the second extraction material outlet is connected to the feed port of the first distillation tower 5031 through the second receiving tank V2 and the second pump P2 in sequence. The top outlet of the first distillation tower 5031 is connected to the top reflux port of the first distillation tower 5031 and the feed port of the third receiving tank V3 through the hot channel of the third heat exchanger E3. The discharge port of the third receiving tank V3 is connected to the first material inlet A through the third pump P3 and the fourth heat exchanger E4 in sequence, and the discharge port of the bottom of the first distillation tower 5031 is connected to the bottom reflux port of the first distillation tower 5031 through the first reboiler H1.

[0074] like Figure 5 As shown, the bottom discharge port of the first distillation tower 5031 is also connected to the feed port of the second distillation tower 5032 through the fourth pump P4, the top discharge port of the second distillation tower 5032 is respectively connected to the top reflux port of the second distillation tower 5032 and the feed port of the fourth receiving tank V4 through the heat channel of the fifth heat exchanger E5, the discharge port of the fourth receiving tank V4 is connected to the feed port of the first membrane separator 5041 through the fifth pump P5, the bottom discharge port of the second distillation tower 5032 is connected to the bottom reflux port of the second distillation tower 5032 through the second reboiler H2, and the bottom discharge port of the second distillation tower 5032 is also connected to the feed port of the second membrane separator 5042 through the heat channels of the sixth pump P6 and the sixth heat exchanger E6 in sequence.

[0075] like Figure 5 As shown, the first outlet of the first membrane separator 5041 is connected to the alcohol solvent delivery pipeline, the first outlet of the second membrane separator 5042 is connected to the salt wastewater delivery pipeline, and the second outlet of the first membrane separator 5041 and the second outlet of the second membrane separator 5042 are both connected to the second material inlet B.

[0076] The above-mentioned target waste solvent is a mixed solvent waste liquid, which includes toluene, methanol, ether, inorganic salts and oligomers. The mixed solvent waste liquid can be a waste solution generated in the process of producing polyphenylene ether by a homogeneous solution polycondensation method, or it can be a waste solution mixed with various solvents.

[0077] like Figure 5 As shown, the target waste solution is input into the extraction tower 501 through the target waste solution conveying pipeline through the first material inlet A, and the extraction solution is introduced into the extraction tower 501 through the extraction solution conveying pipeline through the second material inlet B. Since the first material inlet A is located below the second material inlet B, for example, the first material inlet A is located at the lower part of the bottom plate of the extraction tower 501, and the second material inlet B is located at the upper part of the top plate, the target waste solution and the extraction solution are extracted in the extraction tower 501 by a reverse contact method, and the first extraction material is output through the first extraction material outlet, and the second extraction material is output through the second extraction material outlet.

[0078] like Figure 5 As shown, the first extraction material is received by the first receiving tank and then transported to the cold channel of the first heat exchanger E1 and the cold channel of the second heat exchanger E2 in sequence by the first pump P1 for preheating. Since the first extraction material contains toluene, oligomers, trace water and trace methanol, among which the oligomers will not be vaporized, a gas-liquid mixture is obtained after being preheated twice by the first heat exchanger E1 and the second heat exchanger E2. The gas-liquid mixture can enter the gas-liquid separator 5021 for gas-liquid separation, and the oligomer solution is discharged through the liquid outlet of the gas-liquid separator 5021, while the gas phase solvent with a higher temperature is discharged through the gas outlet of the gas-liquid separator 5021. The gas phase solvent mainly contains toluene, which can be passed into the cold channel of the first heat exchanger E1 to exchange heat with the first extraction material entering the hot channel of the first heat exchanger E1 to heat the first extraction material, thereby recovering the heat contained in the gas phase solvent, so that the gas phase solution is liquefied into recovered toluene that meets the use requirements, and output through the output pipeline of the aromatic solvent. The delivery pipeline of the aromatic solvent can deliver the recovered toluene to the polyphenylene ether preparation system and use it as a solvent for the polyphenylene ether reaction. Low-pressure steam can be passed into the hot channel of the second heat exchanger E2 to further preheat the first extraction material preheated by the first heat exchanger E1 using low-pressure steam to form a gas-liquid mixture, and the low-pressure steam is liquefied into condensed water and discharged through the first return water pipeline.

[0079] like Figure 5As shown, the first extraction material is received by the second receiving tank V2 and then sequentially transported to the first distillation tower 5031 by the second pump P2. Here, the first extraction material contains water, methanol, inorganic salts and a small amount of toluene. The first extraction material can be roughly distilled in the first distillation tower 5031 to extract the volatile top fraction of the first distillation tower 5031 and the non-volatile bottom fraction of the first distillation tower 5031.

[0080] like Figure 5 As shown, the top fraction of the first distillation tower 5031 is condensed through the hot channel of the third heat exchanger E3 and then enters the first distillation tower 5031 and the third receiving tank V3 according to a certain reflux ratio. The top fraction of the first distillation tower 5031 in the third receiving tank V3 is a methanol-toluene-water mixture, which is basically the same as the components in the target waste solvent. Therefore, the top fraction of the first distillation tower 5031 in the third receiving tank V3 can enter the hot channel of the fourth heat exchanger E4 through the third pump P3 to release heat, and then cool to 30°C~50°C, and enter the first material feed port of the extraction tower 501 to prevent the safety risk caused by the top fraction of the first distillation tower 5031 entering the extraction tower 501 when the temperature is too high.

[0081] like Figure 5 As shown, the bottom fraction of the first distillation tower 5031 is vaporized through the first reboiler H1 according to a certain reflux ratio, and then refluxed into the first distillation tower 5031. The bottom fraction of the first distillation tower 5031 is a methanol-water mixed liquid containing inorganic salts. Therefore, the bottom fraction of the first distillation tower 5031 also enters the second distillation tower 5032 through the fourth pump P4. The bottom fraction of the first distillation tower 5031 is further distilled by the second distillation tower 5032, so as to obtain the top fraction of the second distillation tower 5032 which is easily volatile and the bottom fraction of the second distillation tower 5032 which is not easily volatile.

[0082] like Figure 5 As shown, the top fraction of the second distillation tower 5032 is condensed through the heat channel of the fifth heat exchanger E5 and then enters the second distillation tower 5032 and the fourth receiving tank V4 according to a certain reflux ratio. The top fraction of the second distillation tower 5032 in the fourth receiving tank V4 is an aqueous methanol solution. Therefore, the top fraction of the second distillation tower 5032 in the fourth receiving tank V4 can enter the first membrane separator 5041 through the fifth pump P5 for membrane separation, so as to utilize the first membrane separator 5041 to separate the methanol solvent and the methanol-water mixed solution from the top fraction of the second distillation tower 5032. The obtained methanol solvent meets the preparation requirements of polyphenylene ether, and can be transported to the polyphenylene ether preparation system through the alcohol solvent transportation pipeline to be used as a polyphenylene ether extraction solvent.

[0083] like Figure 5As shown, the bottom fraction of the second distillation tower 5032 is vaporized through the second reboiler H2 according to a certain reflux ratio, and then refluxed into the second distillation tower 5032. The bottom fraction of the second distillation tower 5032 is a saline solution. Therefore, the bottom fraction of the second distillation tower 5032 also enters the heat channel of the sixth heat exchanger E6 through the sixth pump P6 for cooling, and then enters the second membrane separator 5042 for membrane separation to separate desalted water and saline waste water from the bottom fraction of the second distillation tower 5032. The saline waste water can be discharged through the saline waste water transportation pipeline, and the obtained desalted water meets the extraction requirements.

[0084] It should be noted that if Figure 5 As shown, in the initial operation stage of the solvent recovery system, desalted water can be used as the extraction solvent. After the operation is stable, the methanol-water mixed solution obtained by the first membrane separator 5041 and the desalted water obtained by the second membrane separator 5042 can be transported to the extraction tower 501 through the extraction solution delivery pipeline for extraction of the target waste solvent.

[0085] like Figure 5 As shown, the first heat exchanger E1 and the second heat exchanger E2 can also be replaced by a falling film evaporator, or only one heat exchanger is used to preheat the first extraction material, the cold channel inlet of the third heat exchanger E3, the cold channel inlet of the fourth heat exchanger E4, the cold channel inlet of the fifth heat exchanger E5 and the cold channel inlet of the sixth heat exchanger E6 can all be connected to the condensed water pipeline, and the cold channel outlet of the third heat exchanger E3, the cold channel outlet of the fourth heat exchanger E4, the cold channel outlet of the fifth heat exchanger E5 and the cold channel outlet of the sixth heat exchanger E6 can all be connected to the second return water pipeline.

[0086] In order to demonstrate the recovery effect of the solvent recovery system of the embodiment of the present application, Figure 5 The solvent recovery system shown in the figure is used as an example to carry out relevant solvent recovery tests, and the test results are shown in Table 1. It should be understood that the following embodiments are only used for illustration and are not intended to be limiting.

[0087] 1. If Figure 5 As shown, the key process parameters in the solvent recovery system of the embodiment of the present application include: the number of plates of the extraction tower 501 is equal to 6, the volume of the first receiving tank is equal to 0.5m 3 The outlet material temperature of the second heat exchanger E2 is equal to 125°C; the volume of the gas-liquid separator 5021 is equal to 3m 3 , the volume of the second receiving tank V2 is equal to 2m 3, the theoretical plate number of the first distillation tower 5031 is equal to 12, the operating pressure of the first distillation tower 5031 is equal to 20 KPa (G), and the outlet material temperature of the fourth heat exchanger E4 is equal to 40°C; the plate number of the second distillation tower 5032 is equal to 15, the operating pressure of the second distillation tower 5032 is equal to 20 KPa (G); the outlet material temperature of the sixth heat exchanger E6 is equal to 40°C.

[0088] The solvent recovery system of the embodiment of the present application performs solvent recovery on a target waste solvent, the components of which include 55.39wt% to 64.96wt% of methanol, 28.12wt% to 37.56wt% of toluene, 6.57wt% to 6.90wt%, 0.06wt% to 0.1wt% of oligomers, and 0.09wt% to 0.12wt%, with a flow rate equal to 727kg / h to 764kg / h.

[0089] 2. If Figure 5 As shown, at the start-up stage of the solvent recovery system, the extraction solution is desalted water, participating in the extraction and separation operation of the extraction tower 501. After the operation of the solvent recovery system is stable (the impurity content of the separated toluene, methanol and desalted water is stable), the extraction solution is changed to the methanol-water mixed solution discharged by the first membrane separator 5041 and the desalted water obtained by the second membrane separator 5042.

[0090] Table 1 Test results of solvent recovery system

[0091]

[0092]

[0093] It can be concluded from Table 1 that when the target waste solvent is subjected to solvent recovery, the components of the target waste solvent include 55.39wt% to 64.96wt% of methanol, 28.12wt% to 37.56wt% of toluene, 6.57wt% to 6.90wt%, 0.06wt% to 0.1wt% of oligomers, and 0.09wt% to 0.12wt%, and when its flow rate is equal to 727kg / h to 764kg / h, the recovered toluene obtained contains 99.52wt% to 99.59wt% of toluene, 0.35wt% to 0.400wt% of methanol and 0.06wt% to 0.09wt%, and the methanol solvent obtained contains 98.71wt% to 99.04wt% of methanol and 0.96wt% to 1.29wt% of water.

[0094] It can be seen that the embodiments of the present application can utilize a solvent recovery system based on a tower membrane coupled separation process to separate and recover target waste solvents of different proportions and different flow rates, and the separation purity can meet the solvent reuse requirements, and can achieve the recycling of toluene and methanol. This can reduce the treatment cost and recovery cost of the target waste solvent, reduce the operating cost of the polyphenylene ether production system, and meet the environmental protection requirements of "green chemistry".

[0095] The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. At the same time, other implementation methods can be derived from the above-mentioned embodiments, so that structural and logical replacements and changes can be made without departing from the scope of this disclosure.

[0096] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that <24P11511CN>

[0097] For ordinary technicians, several modifications and improvements can be made without departing from the concept of this application, which all belong to the protection scope of this application. Therefore, the protection scope of the patent of this application shall be based on the attached claims.

Claims

1. A solvent recovery system, characterized in that: include: An extraction device, a gas-liquid separation unit, a distillation unit and a first membrane separator, wherein the extraction device has a first extraction outlet and a second extraction outlet, the first extraction outlet is connected to the gas-liquid separation unit, and the second extraction outlet is connected to the first membrane separator through the distillation unit; The feed port of the extraction device is used to be connected to the conveying pipeline of the target waste solvent, and the target waste solvent contains at least an alcohol solvent, an aromatic solvent and water; the first extraction outlet is used to convey the first extraction material containing the aromatic solvent to the gas-liquid separation unit, and the second extraction outlet is used to convey the second extraction material containing the alcohol solvent and water to the distillation unit.

2. The solvent recovery system according to claim 1, characterized in that: The gas-liquid separation unit comprises a gasification device and a gas-liquid separator, and the first extraction material outlet is connected to the gas-liquid separator through the gasification device.

3. The solvent recovery system according to claim 2, characterized in that: The gasification device comprises at least one heater connected in series between the first extraction material outlet and the gas-liquid separator; The gas outlet of the gas-liquid separator is communicated with the hot channel inlet of at least one of the heaters, and the hot channel outlet of the heater is communicated with the conveying pipeline of the aromatic solvent.

4. The solvent recovery system according to claim 1, characterized in that: The distillation unit includes a first distillation device and a second distillation device, the second extraction outlet is connected to the feed port of the first distillation device, the top outlet of the first distillation device is connected to the feed port of the extraction device, and the bottom outlet of the first distillation device is connected to the first membrane separator through the second distillation device.

5. The solvent recovery system according to claim 4, characterized in that: The number of theoretical plates of the second distillation device is greater than the number of theoretical plates of the first distillation device; The number of theoretical plates of the first distillation device is 5-20, and the number of theoretical plates of the second distillation device is 8-23.

6. The solvent recovery system according to claim 4, characterized in that: The solvent recovery system further comprises a condenser, and the top outlet of the first distillation device is connected with the feed inlet of the extraction device through the condenser.

7. The solvent recovery system according to any one of claims 1 to 6, characterized in that: The solvent recovery system further comprises a second membrane separator, the top discharge port of the distillation unit is in communication with the first membrane separator, and the bottom discharge port of the distillation unit is in communication with the second membrane separator; The target waste solvent and the second extraction material also contain salt substances. The top outlet of the distillation unit is used to transport the first fraction containing the alcohol aqueous solution to the first membrane separator, and the bottom outlet of the distillation unit is used to transport the second fraction containing the salt water solution to the second membrane separator.

8. The solvent recovery system according to claim 7, characterized in that: The first outlet of the first membrane separator is used to communicate with the alcohol solvent delivery pipeline, the first outlet of the second membrane separator is used to communicate with the salt wastewater delivery pipeline, and the second outlet of the first membrane separator and the second outlet of the second membrane separator are both connected to the feed port of the extraction device.

9. A polymer production system, characterized in that: The invention comprises the solvent recovery system according to any one of claims 1 to 8.

10. A solvent recovery method, characterized in that: include: Extracting the target waste solvent with an extraction solution to obtain a first extraction material and a second extraction material, wherein the target waste solvent contains at least an alcohol solvent, an aromatic solvent and water; the first extraction material contains the aromatic solvent, and the second extraction material contains the alcohol solvent and the water; Performing gas-liquid separation on the first extraction material to obtain the aromatic solvent; distilling the second extract material to obtain a first top fraction containing an alcohol aqueous solution and a first bottom fraction containing water; The first top fraction containing the alcohol aqueous solution is subjected to membrane separation to obtain the alcohol solvent and the separation residue, respectively.

11. The solvent recovery method according to claim 10, characterized in that: The step of performing gas-liquid separation on the first extraction material to obtain the aromatic solvent comprises: Heating the first extraction material containing the aromatic solvent to vaporize the aromatic solvent contained in the first extraction material to obtain a gas-liquid mixture; The gas-liquid mixture is subjected to gas-liquid separation to obtain an aromatic solvent and a liquid residue, and the aromatic solvent is used to heat the first extraction material containing the aromatic solvent.

12. The solvent recovery method according to claim 10, characterized in that: The step of distilling the second extraction material to obtain a first top fraction containing an alcohol aqueous solution and a first bottom fraction containing water comprises: performing a first distillation on the second extract material to obtain a second bottom fraction and a second top fraction; The second tower top fraction is condensed and mixed with the target waste solvent, and the second tower bottom fraction is subjected to a second distillation to obtain a first tower top fraction containing an alcohol aqueous solution and a first tower bottom fraction containing water.

13. The solvent recovery method according to claim 10, characterized in that: The target waste solvent, the second extraction material and the first bottom fraction all contain salt substances, and the solvent recovery method further comprises: The first bottom fraction containing the water and the salt substances is subjected to membrane separation to obtain desalted water and saline waste water respectively, so that the desalted water and the separation residue constitute the extraction solution.

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