Method and system for recovering ionic liquid

Abstract

The invention provides an ionic liquid recovery method and system, and belongs to the field of recovery and purification, the recovery method comprises the following steps: providing a mixed material containing an ionic liquid; and carrying out flash evaporation treatment on the mixed material to obtain the recycled ionic liquid. The ionic liquid in the mixed material can be recycled and reused, and application and popularization of the ionic liquid are facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of recovery and purification, in particular to a recovery method and system of ionic liquid. BACKGROUND

[0002] Ionic liquid is composed of organic cation and inorganic or organic anion, and the cation and anion thereof usually have large volume and asymmetry, resulting in special hydrogen bonding. The special hydrogen bonding network structure of ionic liquid makes it have some special properties, mainly embodied in low melting point, low vapor pressure, non-volatility, low toxicity, environmental friendliness, etc. The existence of these properties, especially the low toxicity, non-volatility, environmental friendliness, etc. which are superior to traditional organic solvents, makes ionic liquid perform well in extractive distillation field and can be used as extractant for difficult-to-separate materials.

[0003] However, the expensive cost of ionic liquid limits its application and promotion. SUMMARY

[0004] In view of the technical problems in the background art, the present application provides a recovery method and system of ionic liquid, which can recover and reuse ionic liquid in mixed materials, and is beneficial to the application and promotion of ionic liquid.

[0005] In a first aspect, the embodiments of the present application provide a recovery method of ionic liquid, comprising the following steps: providing mixed material containing ionic liquid; flash evaporation treatment is performed on the mixed material to obtain recovered ionic liquid.

[0006] Optionally, in some embodiments of the present application, the flash evaporation treatment comprises at least one flash evaporation process, and in the material conveying direction, the liquid phase component in the previous flash evaporation process is conveyed to the subsequent flash evaporation process for treatment.

[0007] Optionally, in some embodiments of the present application, the number of flash evaporation processes is 2-10.

[0008] Optionally, in some embodiments of the present application, the mixed material is derived from extract of extractive distillation process based on the ionic liquid; and / or, the mixed material further comprises a component to be separated, which comprises at least one component in a first mixed system or at least one component in a second mixed system, the first mixed system is a mixture of at least two of C1-C4 alkane, C2-C4 alkene, C2-C4 alkyne and C3-C4 cycloalkane, and the second mixed system is a mixture of at least one aromatic hydrocarbon and at least one non-aromatic cyclic hydrocarbon compound.

[0009] Optionally, in some embodiments of the present application, the ionic liquid comprises a cation component and an anion component, the cation component comprises at least one of imidazolium cation, pyrazolium cation, pyridinium cation, piperidinium cation, pyridazinium cation, pyrimidinium cation, pyrazinium cation, thiazolium cation and quaternary ammonium cation; the anion component comprises at least one of halide anion, carboxylate anion, phosphate anion, borate anion, sulfonate anion and sulfate anion.

[0010] Optionally, in some embodiments of the present application, the flash treatment is performed at a pressure of 0-0.1 MPa and a temperature of 30-200 ℃.

[0011] Optionally, in some embodiments of the present application, the purity of the recovered ionic liquid is greater than or equal to 98%.

[0012] In a second aspect, embodiments of the present application provide a system for recovering ionic liquid, comprising: an extractive distillation column having a liquid feed inlet and a column bottom outlet; a flash device in communication with the column bottom outlet, configured to perform flash treatment on the mixture output from the column bottom outlet; and a recovery pipeline having one end in communication with a liquid outlet of the flash device and the other end in communication with the liquid feed inlet.

[0013] Optionally, in some embodiments of the present application, the flash device comprises at least one flash tank, when the flash device comprises a plurality of flash tanks, the plurality of flash tanks are connected in sequence along a material flow direction, and in the material flow direction, the outlet of a previous flash tank is connected to the inlet of a subsequent flash tank.

[0014] Optionally, in some embodiments of the present application, the recovery pipeline is further provided with a first control unit, the first control unit comprises at least one of a first pressure adjusting device and a first heat exchanger.

[0015] Optionally, in some embodiments of the present application, the recovery system further comprises an ionic liquid supply pipeline, one end of the ionic liquid supply pipeline is in communication with the liquid feed inlet, and the other end is configured to be in communication with a supply device for providing ionic liquid.

[0016] Optionally, in some embodiments of the present application, the inlet of the flash tank is provided with a feed pipeline, the feed pipeline is provided with a second control unit, the second control unit comprises at least one of a second pressure adjusting device and a second heat exchanger.

[0017] The technical scheme provided in the application can separate the ionic liquid from the mixture smoothly, realize the recovery of the ionic liquid, reduce waste, avoid the limitation of the application and popularization of the ionic liquid due to the expensive cost of the ionic liquid, on the other hand, the ionic liquid is separated and purified by the flash evaporation, compared with the rectification, the energy consumption can be reduced, the recovery cost can be reduced, meanwhile, the damage of heat treatment to some temperature sensitive ionic liquid and material components can be avoided, and the application and popularization of the ionic liquid are more beneficial.

[0018] The above description is only a summary of the technical scheme of the application, in order to more clearly understand the technical means of the application, the specific embodiments of the application can be implemented according to the content of the description, and in order to make the above and other purposes, characteristics and advantages of the application more obvious and easy to understand, the following will specifically describe the embodiments of the application. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical scheme of the application, the drawings used in the application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0020] Figure 1 The flowchart of the recovery method of the ionic liquid for an embodiment of the application is shown in the figure; Figure 2 The structure diagram of the recovery system of the ionic liquid for the first embodiment of the application is shown in the figure; Figure 3 The structure diagram of the recovery system of the ionic liquid for the second embodiment of the application is shown in the figure; Figure 4 The structure diagram of the recovery system of the ionic liquid for the third embodiment of the application is shown in the figure; Figure 5 The structure diagram of the recovery system of the ionic liquid for the fourth embodiment of the application is shown in the figure; Explanation of reference signs: DETAILED DESCRIPTION

[0021] The embodiments of the technical scheme of the application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical scheme of the application, therefore, only as an example, and cannot limit the protection scope of the application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the use of the terms "including," "comprising," or "having" and variations thereof herein is intended to be broad and encompass the terms "consisting of" and "consisting essentially of" and variations thereof. Unless otherwise noted, the terms "including" and "comprising" are open-ended and do not exclude the presence of unrecited elements or limitations.

[0023] Various embodiments of the application can be presented in a range format; it is to be understood that the description in range format is merely for convenience and brevity and that one of ordinary skill in the art would understand that many aspects of the application can be encompassed by the range format. For example, a range of "1 to 6" would include any number from 1 to 6, e.g., 1, 2, 3, 4, 5, and 6, and would also include single numbers such as 1, 2, 3, 4, 5, and 6, as well as sub-ranges such as 2-4, 2-6, 3-6, 3- 5, and 4-5, and single numbers within the range, e.g., 1, 2, 3, 4, 5, and 6, unless otherwise indicated. Further, where a range of values is presented, it is understood that any intervening value, as well as the upper and lower limits of the ranges, are inherently disclosed.

[0024] In the description of the embodiments of the application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0025] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive or alternative embodiments. It is expressly understood that the embodiments described herein are merely examples from a whole class of comparable embodiments which those skilled in the art will readily identify. In the description of the embodiments of the application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0026] In the description of the embodiments of the application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0027] In the description of the embodiments of the present application, the term "at least one" refers to one or more, "a plurality of" refers to two or more (including two), and similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of pieces" refers to two or more pieces (including two pieces). "At least one", "at least one of the following" or the like refers to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can mean a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0028] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0029] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0030] The ionic liquid has good extraction effect as an extractant, especially for the separation of low-carbon hydrocarbon mixed systems, the separation of aromatic hydrocarbon mixed systems, and the separation and purification of aromatic hydrocarbon and non-aromatic hydrocarbon mixed systems, which has obvious effect.

[0031] Ionic liquids are relatively expensive, making the extraction cost relatively high. In order to reduce the cost, it is necessary to recycle and reuse the ionic liquid. However, it is found in actual application that it is difficult to recover the ionic liquid from the heavy component after participating in the extraction, and a lot of energy consumption is often required, for example, the heavy component can be subjected to rectification, but the energy consumption of rectification is high, and in order to achieve better recovery effect and improve the purity of the recovered ionic liquid, multiple rectifications are required, which undoubtedly further increases the recovery cost.

[0032] In view of this, in a first aspect, the embodiments of the present application provide a method for recycling ionic liquid. Please refer to Figure 1 The recycling method comprises the following steps: S10, providing a mixture containing ionic liquid; S20, performing flash evaporation treatment on the mixture to obtain recycled ionic liquid.

[0033] In the technical solution provided by the present application, the mixture is subjected to flash evaporation treatment, which can successfully separate the ionic liquid from the mixture, recycle the ionic liquid, reduce waste, avoid limiting the application and promotion of the ionic liquid due to its high cost, and on the other hand, the ionic liquid is separated and purified by using the flash evaporation method, which can help to reduce energy consumption and recycling cost compared with the rectification method, and can also avoid damage to some temperature-sensitive ionic liquids and material components caused by heat treatment, which is more conducive to the application and promotion of the ionic liquid.

[0034] The mixture refers to a mixed system containing ionic liquid and at least one organic compound. In some embodiments, the mixture can be an extraction mixture generated when ionic liquid is used as an extractant to extract the original solution in the extractive rectification process. The extraction mixture contains not only ionic liquid but also components in the original solution that can be dissolved in the ionic liquid. Specifically, the step S10 can further include the following steps: providing an original solution, the original solution comprising component A and component B; extracting the original solution with ionic liquid as an extractant to obtain component A and a mixture, the mixture comprising ionic liquid and component B, and the mixture being used for step S10. The method provided by the present application can separate ionic liquid from the mixture and recycle it for reuse. For ease of description, the component B in the mixture except ionic liquid is named as a component to be separated.

[0035] In some specific embodiments, the original solution can be a first mixed system or a second mixed system. The first mixed system is a mixture of low-carbon hydrocarbon compounds, for example, it can include but is not limited to a mixture of at least two of C1-C4 alkanes, C2-C4 alkenes, C2-C4 alkynes, and C3-C4 cycloalkanes. The second mixed system is a mixture of aromatic hydrocarbons and non-aromatic hydrocarbons, for example, it can be the material of the aromatic hydrocarbon extraction process in the crude oil separation, specifically, it can be a mixture of at least one aromatic hydrocarbon and at least one non-aromatic cyclic hydrocarbon compound. It should be noted that the types of aromatic hydrocarbons and non-aromatic hydrocarbons are not limited herein and can be any combination of aromatic hydrocarbons and non-aromatic hydrocarbons. Further, in other embodiments, the aromatic hydrocarbon can refer to benzene ring and its derivatives, polycyclic aromatic hydrocarbons with 10-18 ring atoms and their derivatives, etc.; the non-aromatic hydrocarbon can refer to C1-C22 aliphatic hydrocarbon, C1-C22 alicyclic hydrocarbon, etc.

[0036] It can be understood that when the original solution is the first mixed system, the component to be separated can be at least one component in the first mixed system; when the original solution is the second mixed system, the component to be separated can be at least one component in the second mixed system.

[0037] The application does not limit the type of ionic liquid. In some embodiments, the ionic liquid can include a cation component and an anion component. The cation component can include, but is not limited to, at least one of imidazolium cation, pyrazolium cation, pyridinium cation, piperidinium cation, pyridazinium cation, pyrimidinium cation, pyrazinium cation, thiazolium cation, and quaternary ammonium cation; the anion component can include, but is not limited to, at least one of halide anion, carboxylate anion, phosphate anion, borate ion, sulfonate ion, sulfate ion.

[0038] It can be understood that the names of the above-mentioned cation components and anion components refer to a class of cations with this characteristic, and do not exclude ion types derived based on this characteristic. For example, imidazolium cation can refer to ; wherein X can be any common substituent, such as C1-C10 alkyl, C1-C10 alkoxy, C6-C10 aryl, halogen group, etc.; n is any integer from 0 to 4, and when n is not 0, each occurrence of R is independently selected from any common substituent, such as C1-C10 alkyl, C1-C10 alkoxy, C6-C10 aryl, halogen group, etc. Pyridinium cation can refer to ; wherein Y can be any common substituent, such as C1-C10 alkyl, C1-C10 alkoxy, C6-C10 aryl, halogen group, etc.; m is any integer from 0 to 5, and when m is not 0, each occurrence of R is independently selected from any common substituent, such as C1-C10 alkyl, C1-C10 alkoxy, C6-C10 aryl, halogen group, etc. Borate ion can be a borate ion containing a substituent, such as tetrafluoroborate ion (BF4 - ); phosphate ion can be a phosphate ion containing a substituent, such as hexafluorophosphate ion (PF6 - ); sulfonate ion can be a sulfonate ion containing a substituent, such as ethyl sulfonate ( ).

[0039] Further, in some embodiments, the ionic liquid has a cation component selected from imidazolium cation or pyridinium cation, and an anion component selected from borate ion or sulfonate ion. Such ionic liquid has obvious effect on separation of low carbon hydrocarbon (C2-C4) mixture, separation of aromatic hydrocarbon mixture, and separation and purification of aromatic hydrocarbon and non-aromatic hydrocarbon mixture. In some specific embodiments, the ionic liquid is selected from [C2lM][EtSO4] (formula 1 as follows) or [C1mPy][BF4] (formula 2 as follows).

[0040] Formula 1:

[0041] Formula 2:

[0042] In some embodiments of the present application, the flash treatment includes at least one flash procedure, and in the material conveying direction, the liquid phase component in the previous flash procedure is conveyed to the next flash procedure for treatment. When multi-stage flash is used, it helps to improve the separation efficiency, improve the purity of the recovered ionic liquid, and reduce the amount of ionic liquid supplement when recycled. At the same time, compared with multi-stage rectification and other methods, multi-stage flash is more conducive to reducing the energy consumption of the recovery process.

[0043] In some embodiments of the present application, the number of flash procedures is 2-10; for example, it can be 2, 3, 4, 5, 6, 7, 8, 9 or 10. In actual application, the number of flash procedures can be adjusted according to the separation effect.

[0044] In some embodiments, the purity of the recovered ionic liquid is greater than or equal to 98%.

[0045] In the flash, the pressure and temperature of the flash treatment can be controlled, for example, the pressure is reduced, the temperature is controlled in the temperature range conducive to separation, and the like. In some embodiments, when the mixture contains components such as the ionic liquid or the component to be separated as described above, the pressure of the flash treatment can be 0-0.1 MPa, and the temperature of the flash treatment can be 30-200°C.

[0046] In addition, in some embodiments, after step S20, a step of reusing the recovered ionic liquid can be further included. Specifically, the pressure and temperature of the recovered ionic liquid can be adjusted to approach the temperature and pressure of the ionic liquid in the extraction procedure, and then the ionic liquid is put into the extraction tower.

[0047] In a second aspect, the embodiments of the present application also provide a recovery system 100 of ionic liquid, please refer to Figure 2The recovery system 100 comprises an extractive distillation column 1, a flash device and a recovery pipeline 3. The extractive distillation column 1 has a liquid phase feed inlet and a bottom outlet. The flash device is connected to the bottom outlet and is used to flash the mixture discharged from the bottom outlet. One end of the recovery pipeline 3 is connected to a liquid phase outlet of the flash device, and the other end is connected to the liquid phase feed inlet.

[0048] The extractive distillation column 1 is used to extractively distill the original solution. The separated components are condensed and discharged from the top of the column. The mixture of ionic liquid and remaining components is discharged from the bottom outlet of the column and enters the flash device for flash treatment to obtain recovered ionic liquid. The recovered ionic liquid is transported to the liquid phase feed inlet through the recovery pipeline 3 for reuse as an extractant.

[0049] The flash device comprises at least one flash tank 21. The flash tank 21 has a feed inlet, a top outlet and a bottom outlet. Among the at least one flash tank 21, the bottom outlet of the flash tank 21 farthest from the extractive distillation column 1 constitutes the liquid phase outlet of the flash device. Please refer to Figure 3 When the flash device comprises a plurality of flash tanks 21, the plurality of flash tanks 21 are connected in sequence along the material flow direction, and the bottom outlet of the previous flash tank 21 is connected to the feed inlet of the subsequent flash tank 21 in the material flow direction. The material flow direction can be understood as the direction of the material containing ionic liquid in the recovery system 100. Taking the example of three flash tanks 21, they are named as a first flash tank 211, a second flash tank 212 and a third flash tank 213 in the order of gradually far away from the extractive distillation column 1 in the material flow direction. The bottom outlet of the extractive distillation column 1 is connected to the feed inlet of the first flash tank 211. The bottom outlet of the first flash tank 211 is connected to the feed inlet of the second flash tank 212. The bottom outlet of the second flash tank 212 is connected to the feed inlet of the third flash tank 213. The bottom outlet of the third flash tank 213 is connected to the liquid phase feed inlet through the recovery pipeline 3.

[0050] In order to better regulate the flash effect, the temperature and / or pressure of the material can be regulated before entering the flash tank 21. In some embodiments, the feed pipe on the feed inlet of the flash tank 21 is provided with a second regulating unit 6, and the second regulating unit 6 comprises one or both of a second pressure regulating device 62 and a second heat exchanger 61. In this way, when the second regulating unit 6 is the second pressure regulating device 62, the pressure of the material entering the flash tank 21 can be regulated; when the second regulating unit 6 is the second heat exchanger 61, the temperature of the material entering the flash tank 21 can be regulated; when the second regulating unit 6 is the second pressure regulating device 62 and the second heat exchanger 61, the temperature and pressure of the material entering the flash tank 21 can be regulated. In actual application, the recovery system 100 can be provided with both the second pressure regulating device 62 and the second heat exchanger 61, and in use, one or both of the pressure regulating device and the heat exchanger can be selectively regulated according to needs, or according to the types of mixed materials to be treated by the recovery system 100, the second heat exchanger 61 or the second pressure regulating device 62 can be selectively configured for each flash tank 21, or the second heat exchanger 61 and the second pressure regulating device 62 can be simultaneously configured to reduce equipment cost.

[0051] After flash treatment, the pressure and temperature of the recovered ionic liquid can be quite different from the temperature and pressure of the ionic liquid in the extraction process. In order to ensure smooth circulation, in some embodiments, the recovery pipe 3 is further provided with a first regulating unit 5, and the first regulating unit 5 comprises at least one of a first pressure regulating device 52 and a first heat exchanger 51. In this way, the pressure and temperature of the recovered ionic liquid can be adjusted to approach the temperature and pressure of the ionic liquid in the extraction process before being fed into the extraction tower.

[0052] In addition, in order to better realize recycling, the recovery pipe 3 can be further provided with a circulating pump 4.

[0053] In this application, pressure regulation can be achieved by a compressor or a pressure reducing valve. In some embodiments, the first pressure regulating device 52 can be a compressor or a pressure reducing valve, and the second pressure regulating device 62 can be a compressor or a pressure reducing valve. It can be understood that when the flash tank 21 is provided with multiple flash tanks 21, the pressure regulating device corresponding to each flash tank 21 can be the same or different.

[0054] In some embodiments of the present application, the recovery system 100 further comprises an ionic liquid supply conduit 7, one end of the ionic liquid supply conduit is in communication with the liquid phase feed inlet, and the other end is used to communicate with a supply device for providing ionic liquid, and the ionic liquid can be delivered into the extractive distillation column 1 to extract the original solution. Further, the ionic liquid supply conduit 7 can also be in communication with the recovery conduit 3, so that the recovered ionic liquid can be sent into the ionic liquid supply conduit 7 and put into the extractive distillation column 1 for extraction.

[0055] In addition, in some embodiments, the recovery system 100 can further comprise a mixer 8. The flash tank 21 is provided with a plurality of times, and the tank top discharge port of each flash tank 21 is in communication with the mixer 8 through a conduit, so that the gaseous phase stream separated by the flash tank is sent out of the device after being mixed by the mixer 8.

[0056] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are used to explain the present application, and cannot be understood as a limitation of the present application. If the specific technology or condition is not specified in the embodiments, it is carried out according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0057] Embodiment 1 The ionic liquid in the propylene / propane separation process based on ionic liquid extractive distillation is recovered by a multi-stage flash method, and the recovery system 100 is shown in FIG. 4. The recovery system 100 of this embodiment comprises an extractive distillation column 1, a first-stage flash tank 211, a second-stage flash tank 212 and a recovery conduit 3 connected in sequence. The extractive distillation column 1 has a liquid phase feed inlet and a column bottom discharge port, the liquid phase feed inlet is connected with an ionic liquid supply conduit 7, and the column bottom discharge port is in communication with the first-stage flash tank 211 through a first conduit, and the first conduit is provided with a second heat exchanger a and a second pressure regulating device a in sequence, and the second pressure regulating device a is a pressure reducing valve. The tank bottom discharge port of the first-stage flash tank 211 is in communication with the feed inlet of the second-stage flash tank 212 through a second conduit, and the second conduit is provided with a second pressure regulating device b, and the second pressure regulating device b is a pressure reducing valve. One end of the recovery conduit 3 is in communication with the tank bottom discharge port of the second-stage flash tank 212, and the other end is in communication with the ionic liquid supply conduit 7, and the recovery conduit 3 is provided with a first pressure regulating device 52, a first heat exchanger 51 and a circulating pump 4.

[0058] A comparison group is provided in this embodiment, and the recovery system 100 of the comparison group comprises an extractive distillation column 1 and a rectification column, and the column bottom discharge port of the extractive distillation column 1 is in communication with the feed inlet of the rectification column, and the rectification column is used for recovering ionic liquid from the mixture material output from the column bottom discharge port.

[0059] The raw material F of this embodiment is a low carbon hydrocarbon mixture system (containing propylene and propane). The initial temperature of the raw material F is 64°C, the pressure is 2.7 MPa, and the total mass flow rate is 16480 kg / h. The ionic liquid is [C2lM][EtSO4], the feeding temperature of the ionic liquid is 30°C, the pressure is 2.1 MPa, and the total mass flow rate is 19000 kg / h. The extractive distillation column 1 has 34 trays, the top of the column uses a total condenser, and the bottom of the column uses a kettle-type reboiler. The temperature of the condensed liquid phase at the top of the column is 47°C, the pressure is 1.95 MPa, and the molar fraction of propylene in the condensed liquid phase at the top of the column reaches 99.6%, with high purity. The temperature of the bottom effluent (S1) is 154°C, and the pressure is 2.1 MPa.

[0060] The bottom effluent (S1) is first cooled to 40°C, then depressurized to 0.04 MPa, and then introduced into a first flash tank 211. After flashing in the first flash tank 211, the top gas phase material and the bottom material (S3) are obtained. The purity of propane in the top gas phase material reaches 96.8%, which is comparable to the separation effect of the distillation column in the comparative group. The purity of the ionic liquid in the bottom material (S3) is less than 98%. The bottom material (S8) is further depressurized to 0.0005 MPa and then introduced into a second flash tank 212 for flashing. The excess propane is evaporated, and the ionic liquid in the bottom material (S5) of the second flash tank 212 reaches a purity of more than 98%, which is suitable for recycling. The temperature of the bottom material (S5) is 20°C, and the pressure is 0.0005 MPa. The temperature and pressure of the bottom material (S5) are adjusted to approximately 30°C and 2.1 MPa through a first heat exchanger 51 and a first pressure regulating device 52. The recovered ionic liquid after pressure and temperature adjustment is recycled. It is detected that there is a small amount of loss of ionic liquid in this process, and the amount of ionic liquid to be supplemented is about 0.3 kg / h, which corresponds to a ionic liquid recovery rate of 99.998%.

[0061] Example 2 The ion liquid in the aromatic / non-aromatic separation process based on the ion liquid extractive distillation is recovered by the multi-stage flash method. The recovery system 100 is shown in Fig. 5. The recovery system 100 of the embodiment comprises an extractive distillation column 1, a first-stage flash tank 211, a second-stage flash tank 212, a third-stage flash tank 213 and a recovery pipeline 3 connected in sequence. The extractive distillation column 1 has a liquid phase feed inlet and a column bottom outlet. The liquid phase feed inlet is connected with the ion liquid supply pipeline 7. The column bottom outlet is connected with the first-stage flash tank 211 through a first pipeline. The first pipeline is provided with a second heat exchanger a. The tank bottom outlet of the first-stage flash tank 211 is connected with the feed inlet of the second-stage flash tank 212 through a second pipeline. The second pipeline is provided with a second heat exchanger b and a second pressure regulating device a. The tank bottom outlet of the second-stage flash tank 212 is connected with the feed inlet of the third-stage flash tank 213 through a third pipeline. The third pipeline is provided with a second heat exchanger c and a second pressure regulating device b. One end of the recovery pipeline 3 is connected with the tank bottom outlet of the third-stage flash tank 213. The other end of the recovery pipeline 3 is connected with the ion liquid supply pipeline 7. The recovery pipeline 3 is provided with a first pressure regulating device 52, a first heat exchanger 51 and a circulating pump 4.

[0062] The raw material F of the embodiment is an aromatic / non-aromatic mixed system, which is derived from the reforming oil raw material rich in aromatics (containing benzene, toluene, xylene, C4 to C8 alkanes, C4 to C8 cycloalkanes, etc.) in the aromatic extraction process of crude oil separation. The initial temperature of the raw material F is 40°C, the pressure is 0.1 MPa, and the total mass flow rate is 55716 kg / h. The ion liquid is [C1mPy][BF4], the feed temperature is 30°C, the pressure is 0.1 MPa, and the total mass flow rate is 134245 kg / h. The extractive distillation column 1 has 45 trays, a total condenser at the top and a kettle reboiler at the bottom. The temperature of the condensed liquid phase at the top is 72°C, the pressure is 0.1 MPa, and the mass fraction of non-aromatic hydrocarbons in the condensed liquid phase at the top reaches 99%, which meets the separation requirements. The temperature of the liquid at the bottom is 112°C, and the pressure is 0.1 MPa.

[0063] The rectification column bottom effluent (S1) is warmed to 160°C and introduced into a first flash tank 211, with a flash pressure of 0.1 MPa, and a portion of the aromatic product is obtained at the top of the first flash tank 211; the effluent (S3) from the bottom of the first flash tank 211 is warmed and pressure-adjusted, to 170°C and 0.05 MPa, and then introduced into a second flash tank 212, and a portion of the aromatic product is obtained at the top of the second flash tank 212; the effluent (S5) from the bottom of the second flash tank 212 is warmed and pressure-adjusted, to 180°C and 0.02 MPa, and then introduced into a third flash tank 213. A portion of the aromatic product is separated at the top of the third flash tank 213, and the bottom effluent (S7) is output, with a purity of the ionic liquid in S7 of more than 98.4%, which can meet the conditions for recycling. The temperature and pressure of S7 are adjusted to be close to 30°C and 0.1 MPa by a first heat exchanger 51 and a first pressure adjusting device 52, and the recovered ionic liquid after pressure and temperature adjustment is introduced into the recycling. It is detected that there is a small amount of loss of ionic liquid in this process, and the amount of ionic liquid to be supplemented is about 651 kg / h, which corresponds to a ionic liquid recovery rate of 99.515%.

[0064] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration and playing the same role and effect as the technical idea within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the gist of the present application, various modifications that can be thought of by those skilled in the art, and other modes constructed by combining a part of the configuration elements of the embodiments are also included in the scope of the present application.

Claims

1. A method for recovering an ionic liquid, characterized in that: The following steps are involved: Providing a mixed material containing an ionic liquid; The mixed material is flash-evaporated to obtain a recovered ionic liquid.

2. The method for recovering an ionic liquid according to claim 1, wherein: The flash evaporation treatment includes at least one flash evaporation process, and in the material conveying direction, the liquid phase component in the previous flash evaporation process is conveyed to the next flash evaporation process for treatment.

3. The method for recovering ionic liquid according to claim 2, wherein: The number of flash evaporation steps is 2 to 10 times.

4. The method for recovering ionic liquid according to claim 1, wherein: The ionic liquid includes a cationic component and an anionic component, wherein the cationic component includes at least one of an imidazolium cation, a pyrazolium cation, a pyridinium cation, a piperidinium cation, a pyridazinium cation, a pyrimidinium cation, a pyrazinium cation, a thiazolium cation and a quaternary ammonium cation; and the anionic component includes at least one of a halogen anion, a carboxylic acid anion, a phosphate anion, a borate ion, a sulfonate ion and a sulfate ion.

5. The method for recovering ionic liquid according to claim 1, wherein: The mixed material is derived from an extract of an extractive distillation process based on the ionic liquid; and / or The mixed material also includes components to be separated, and the components to be separated include at least one component in the first mixed system or at least one component in the second mixed system. The first mixed system is a mixture of at least two of C1~C4 alkanes, C2~C4 alkenes, C2~C4 alkynes, and C3~C4 cycloalkanes, and the second mixed system is a mixture of at least one aromatic hydrocarbon and at least one non-aromatic cyclic hydrocarbon compound.

6. The method for recovering an ionic liquid according to claim 4 or 5, characterized in that: The pressure of the flash evaporation treatment is 0-0.1 MPa, and the temperature of the flash evaporation treatment is 30-200°C.

7. The method for recovering ionic liquid according to claim 1, characterized in that: The purity of the recovered ionic liquid is greater than or equal to 98%.

8. An ionic liquid recovery system, characterized in that: include: An extractive distillation tower having a liquid phase feed inlet and a tower bottom discharge port; a flash evaporation device, connected to the tower bottom discharge port, for flash evaporating the mixed material output from the tower bottom discharge port; as well as, A recovery pipeline has one end connected to the liquid phase output port of the flash evaporation device and the other end connected to the liquid phase feed port.

9. The ionic liquid recovery system according to claim 8, characterized in that: The flash evaporation device includes at least one flash tank. When the flash evaporation device includes a plurality of flash tanks, the plurality of flash tanks are connected in sequence along the material flow direction, and in the material flow direction, the tank bottom discharge port of the preceding flash tank is connected to the feed port of the succeeding flash tank; and / or, The recovery pipeline is further provided with a first regulating unit, the first regulating unit including at least one of a first pressure regulating device and a first heat exchanger; and / or, The recovery system further comprises an ionic liquid feeding pipeline, one end of which is connected to the liquid phase feeding port, and the other end of which is used to be connected to a feeding device for providing the ionic liquid.

10. The ionic liquid recovery system according to claim 9, characterized in that: A feed pipe is provided on the feed port of the flash tank, and a second regulating unit is provided on the feed pipe. The second regulating unit includes at least one of a second pressure regulating device and a second heat exchanger.

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