Method for separating tetrahydrofuran / methanol / water mixture through reactive extractive distillation

Abstract

The invention relates to the field of chemical separation and purification, in particular to a method for separating a tetrahydrofuran / methanol / water mixture through reactive extractive distillation. Comprising the following steps: water reactive distillation separation, tetrahydrofuran extractive distillation or low-pressure extractive distillation separation, and methanol extractive distillation separation. Heat exchange is carried out between the water reactive distillation tower or the methanol extractive distillation tower and the tetrahydrofuran extractive distillation low-pressure tower, so that partial heat integration is realized; wherein in the reactive distillation tower, water and ethylene oxide react to generate ethylene glycol with high utilization value. After a dimethyl sulfoxide material flow serving as an extracting agent at the bottom of the methanol extractive distillation tower flows out, the dimethyl sulfoxide material flow can flow back to the tetrahydrofuran extractive distillation tower or the tetrahydrofuran extractive distillation low-pressure tower after being cooled by a cooler and supplemented with the extracting agent. The molar purity of ethylene glycol obtained through separation can reach 99.9% or above, the molar purity of tetrahydrofuran and methanol can reach 99.5% or above, the product recovery rate is high, the process is simple, and energy consumption is low.

Description

Technical Field

[0001] The invention relates to the field of chemical separation and purification, in particular to a method for separating a tetrahydrofuran / methanol / water mixture by reaction extraction and rectification. Background Art

[0002] The tetrahydrofuran / methanol / water mixture is a liquid mixture consisting of tetrahydrofuran, methanol and water. Industries such as polyvinyl chloride plants and magnetic film plants produce wastewater containing a ternary azeotropic mixture of tetrahydrofuran / methanol / water. A chemical plant in Chongqing, China, often produces wastewater containing a tetrahydrofuran / methanol / water mixture. At atmospheric pressure, the tetrahydrofuran / methanol / water mixture contains two other azeotropes, tetrahydrofuran / methanol and tetrahydrofuran / water. At atmospheric pressure, methanol forms a minimum azeotrope - tetrahydrofuran / methanol with 50.79 mol% of tetrahydrofuran at 332.94K, while water forms another minimum azeotrope - tetrahydrofuran / water with 82.87 mol% of tetrahydrofuran at 336.58K. Therefore, it is impossible to separate the tetrahydrofuran / methanol / water mixture by simple distillation methods, and special distillation methods are required, such as extractive distillation, pressure swing distillation, reactive distillation, etc. Tetrahydrofuran and methanol, both of which have significant added value, are important raw materials and organic solvents in the fields of chemical, pharmaceutical, biochemical engineering, etc. Achieving the required purity of these solvents is very important for consumers. Tetrahydrofuran is often used as a solvent, reaction medium and starting material for various syntheses in the chemical industry, such as the preparation of adhesives, special paints, coatings, fibers, extraction of specific active substances, recrystallization of certain compounds or as a starting material for various syntheses in many reactions. After these uses, tetrahydrofuran is often contaminated with methanol or methanol and water. According to the global tetrahydrofuran market forecast, its compound annual growth rate is 6% from 2023 to 2026. More than 65% of tetrahydrofuran is used as a raw material for the production of polytetramethyl ether glycol, and its downstream products are value-added spandex and other polyurethanes. In addition, tetrahydrofuran has also been proposed as a sustainable biofuel for internal combustion engines. Methanol is one of the basic organic raw materials used to make a variety of organic products such as methyl chloride, methylamine and dimethyl sulfate. It is also a raw material for pesticides (insecticides, acaricides), medicines (sulfonamides, mycins, etc.), and one of the raw materials for the synthesis of dimethyl terephthalate, methyl methacrylate and methyl acrylate. On the one hand, the relevant process produces a large amount of tetrahydrofuran / methanol / water mixture; on the other hand, the recycling of azeotropic wastewater faces challenges such as low efficiency, high operating costs, and large amounts of secondary wastewater. Therefore, economically separating the tetrahydrofuran / methanol / water mixture is an urgent task to reduce energy costs and carbon dioxide emissions. Since both tetrahydrofuran and methanol are of great value, the effective separation of tetrahydrofuran / methanol / water mixtures has become an important link in industrial production. Determining a process that can achieve the separation of tetrahydrofuran / methanol / water mixtures is crucial to improving the production efficiency of related industries.

[0003] At present, the industrial distillation technology for separating tetrahydrofuran / methanol / water mixture mainly includes extractive distillation, membrane separation, pervaporation, and pressure swing distillation. Extractive distillation is a separation method that is widely used in practical applications. By introducing a third solvent, the extractant, the relative volatility of the components in the original mixture is changed, thereby achieving effective separation of the mixture, but the energy consumption of extractive distillation is relatively high. Membrane separation and pervaporation technologies are rarely used in actual production. Pressure swing distillation is also a separation method that is widely used in practical applications. It separates pressure-sensitive components in the mixture by changing the operating pressure of the distillation tower. Compared with extractive distillation, this separation method has the following advantages: first, pressure swing distillation does not require the introduction of additional solvents; second, pressure swing distillation has lower energy consumption. Although the energy consumption of pressure swing distillation is lower than that of extractive distillation, its energy consumption is still very high.

[0004] Chinese patent application number 201210520578.0 discloses a method for separating a tetrahydrofuran / methanol / water mixture by distillation using a packed tower, wherein a mixed solvent containing tetrahydrofuran / methanol / water is added from the middle of the packed tower, and an extractant is added to the middle and upper part of the packed tower, and finally tetrahydrofuran with a purity of more than 98.0% is obtained in the tower top stream. However, the separation method does not mention the separation of methanol and water in the mixture.

[0005] The Chinese patent application number 202010316029.6 discloses a three-tower intermittent distillation process for separating tetrahydrofuran / methanol / water. The mixture forms two binary azeotropes under different pressures, and three distillation towers are used to effectively separate the mixture. Tetrahydrofuran, methanol and water with a mass fraction of more than 99.9% are obtained through the distillation process. The product obtained by this process has a high purity, but under actual industrial conditions, the intermittent distillation method proposed by this process is not suitable for large-scale production, but is suitable for small-batch production, laboratory research or production environments that require flexible adjustment, and the equipment cost and energy consumption of this separation method are also high. Summary of the invention

[0006] The object of the present invention is to overcome the above-mentioned defects of the prior art, and propose a method for separating a tetrahydrofuran / methanol / water mixture by reactive extraction and rectification, which realizes efficient separation of the tetrahydrofuran / methanol / water mixture, so that the purity of the treated tetrahydrofuran, methanol and water products is greater than 99.5 mol%, and the recovery rate is greater than 99.5 mol%, so that resource utilization is maximized, the simplicity of the process is improved, and energy consumption and equipment investment are reduced.

[0007] The technical solution of the present invention is: a method for separating a tetrahydrofuran / methanol / water mixture by reactive extraction and rectification, characterized in that it comprises the following steps:

[0008] Reaction distillation separation of water and ethylene oxide, extraction distillation separation of tetrahydrofuran, extraction distillation separation of methanol;

[0009] Alternatively, water and ethylene oxide are separated by reaction distillation, tetrahydrofuran is separated by low-pressure extraction distillation, and methanol is separated by extraction distillation;

[0010] Heat is exchanged between the water and ethylene oxide reaction distillation tower and the tetrahydrofuran extraction distillation low-pressure tower to achieve partial heat integration of the water and ethylene oxide reaction distillation tower and the tetrahydrofuran extraction distillation low-pressure tower;

[0011] Heat is exchanged between the methanol extraction distillation tower and the tetrahydrofuran extraction distillation low-pressure tower to achieve partial heat integration of the methanol extraction distillation tower and the tetrahydrofuran extraction distillation low-pressure tower;

[0012] In the water and ethylene oxide reaction distillation tower, water and ethylene oxide react to generate ethylene glycol with high utilization value. After the dimethyl sulfoxide stream, the extractant at the bottom of the methanol extraction distillation tower, flows out, it needs to be cooled by a cooler and supplemented with extractant before it can flow back to the tetrahydrofuran extraction distillation tower or the tetrahydrofuran extraction distillation low-pressure tower.

[0013] In the present invention, a reaction extraction distillation separation device is used to achieve the separation method, and the device includes the following devices connected in sequence:

[0014] A water and ethylene oxide reaction distillation tower, wherein a first condenser, a first reflux tank and a first delivery pump connected in sequence are provided at the top of the tower, the water and ethylene oxide reaction distillation tower is connected to a tetrahydrofuran extraction distillation tower via the first delivery pump, and a first reboiler is provided at the bottom of the reaction distillation tower;

[0015] A tetrahydrofuran extractive distillation tower, wherein a second reboiler and a second delivery pump connected in sequence are provided at the bottom of the tower, the methanol extractive distillation tower and the tetrahydrofuran extractive distillation tower are connected via the second delivery pump, and a second condenser and a second reflux tank are provided at the top of the tetrahydrofuran extractive distillation tower;

[0016] The methanol extraction distillation tower or the dimethyl sulfoxide extractant recovery tower is provided with a third reboiler and a third delivery pump connected in sequence at the bottom of the tower, the methanol extraction distillation tower and the tetrahydrofuran extraction distillation tower are connected through the third delivery pump, and the top of the methanol extraction distillation tower is provided with a third condenser and a third reflux tank.

[0017] Based on the above device, the method comprises the following steps:

[0018] A1. Reaction distillation separation of water and ethylene oxide:

[0019] The tetrahydrofuran / methanol / water mixed solution is transported from the middle of the water and ethylene oxide reaction distillation tower to the inside of the tower. The water and ethylene oxide reaction distillation tower is provided with two feed inlets, the feed composition of the upper feed inlet is 500 kmol / h of the tetrahydrofuran / methanol / water mixed solution, and the feed composition of the lower feed inlet is 187.5 kmol / h of ethylene oxide solution;

[0020] The operating pressure of the water and ethylene oxide reaction distillation tower is 1 atm, the tower top temperature is 332-334K, the tower bottom temperature is 468-470K, the theoretical number of tower plates is 6-12, the feed tower plates are the 2nd to 5th tower plates and the 6th to 8th tower plates, and the reaction section where water and ethylene oxide react is the 2nd to 4th tower plates and the 5th to 7th tower plates;

[0021] The water in the tetrahydrofuran / methanol / water mixed solution reacts with the reactant ethylene oxide to generate ethylene glycol, a byproduct with high utilization value, and ethylene glycol is obtained at the bottom of the water and ethylene oxide reaction distillation tower. After the ethylene glycol is vaporized in the first reboiler, the separated high-purity ethylene glycol is obtained;

[0022] The overhead steam of the water and ethylene oxide reaction distillation tower is condensed by the first condenser and the obtained stream is temporarily stored in the first reflux tank, and part of it is refluxed into the water and ethylene oxide reaction distillation tower according to the reflux ratio of 0.5-0.9, and the remaining part is sent into the tetrahydrofuran extraction distillation tower by the first delivery pump;

[0023] A2. Extractive distillation separation of tetrahydrofuran:

[0024] The material enters the tetrahydrofuran extraction distillation tower from the middle of the tetrahydrofuran extraction distillation tower. The operating pressure of the tetrahydrofuran extraction distillation tower is 1 atm, the tower top temperature is 337-339K, the tower bottom temperature is 372-374K, the theoretical number of plates is 43-49, the material feed tower plate from the first reflux tank is the 24th to 30th tower plate, and the dimethyl sulfoxide extractant circulating flow feed tower plate from the third delivery pump is the 2nd to 6th tower plate;

[0025] A tetrahydrofuran product is obtained at the top of the tetrahydrofuran extractive distillation tower. The top steam of the tetrahydrofuran extractive distillation tower is condensed by the second condenser to obtain a stream, which is temporarily stored in the second reflux tank and partially refluxed to the tetrahydrofuran extractive distillation tower according to a reflux ratio of 1.8-2.2, and the other part is the separated tetrahydrofuran obtained;

[0026] The bottom stream of the tetrahydrofuran extraction distillation tower is vaporized by the second reboiler and then transported to the methanol extraction distillation tower by the second delivery pump;

[0027] A3. Extraction and distillation separation of methanol:

[0028] The material enters the methanol extraction distillation tower from the middle of the methanol extraction distillation tower. The operating pressure of the methanol extraction distillation tower is 1 atm, the tower top temperature is 336-338K, the tower bottom temperature is 462-464K, the theoretical number of tower plates is 6-12, and the material feed tower plate from the bottom of the tetrahydrofuran extraction distillation tower is the 2nd to 6th tower plate;

[0029] A methanol product is obtained at the top of the methanol extraction distillation tower. The top vapor of the methanol extraction distillation tower is condensed by the second condenser to obtain a stream, which is temporarily stored in the second reflux tank and partially refluxed to the methanol extraction distillation tower at a reflux ratio of 0.1-0.2, and the other part is the separated methanol obtained;

[0030] The bottom stream of the methanol extraction distillation tower is vaporized in the third reboiler and then transported to the tetrahydrofuran extraction distillation tower by the third delivery pump;

[0031] In the present invention, the device may further include:

[0032] A water and ethylene oxide reaction distillation tower, wherein a first condenser, a first reflux tank and a first delivery pump connected in sequence are provided at the top of the tower, the water and ethylene oxide reaction distillation tower is connected to a tetrahydrofuran extraction distillation low-pressure tower via the first delivery pump, and a first reboiler is provided at the bottom of the reaction distillation tower;

[0033] A tetrahydrofuran extractive distillation low-pressure tower is provided at the bottom of the tower with a second reboiler and a second delivery pump connected in sequence, the methanol extractive distillation tower and the tetrahydrofuran extractive distillation low-pressure tower are connected via the second delivery pump, and a second condenser and a second reflux tank are provided at the top of the tetrahydrofuran extractive distillation low-pressure tower;

[0034] The methanol extraction distillation tower or the dimethyl sulfoxide extractant recovery tower is provided with a third reboiler and a third delivery pump connected in sequence at the bottom of the tower, the methanol extraction distillation tower and the tetrahydrofuran extraction distillation low-pressure tower are connected through the third delivery pump, and the top of the methanol extraction distillation tower is provided with a third condenser and a third reflux tank.

[0035] Based on the above device, the method comprises the following steps:

[0036] B1. Reaction distillation separation of water and ethylene oxide:

[0037] The tetrahydrofuran / methanol / water mixed solution is transported from the middle of the water and ethylene oxide reaction distillation tower to the inside of the tower. The water and ethylene oxide reaction distillation tower is provided with two feed inlets, the feed composition of the upper feed inlet is 500 kmol / h of the tetrahydrofuran / methanol / water mixed solution, and the feed composition of the lower feed inlet is 187.5 kmol / h of ethylene oxide solution;

[0038] The operating pressure of the water and ethylene oxide reaction distillation tower is 1 atm, the tower top temperature is 332-334K, the tower bottom temperature is 468-470K, the theoretical number of tower plates is 6-12, the feed tower plates are the 2nd to 5th tower plates and the 6th to 8th tower plates, and the reaction section where water and ethylene oxide react is the 2nd to 4th tower plates and the 5th to 7th tower plates;

[0039] The water in the tetrahydrofuran / methanol / water mixed solution reacts with the reactant ethylene oxide to generate ethylene glycol, a byproduct with high utilization value, and ethylene glycol is obtained at the bottom of the water and ethylene oxide reaction distillation tower. After the ethylene glycol is vaporized in the first reboiler, the separated high-purity ethylene glycol is obtained;

[0040] The overhead steam of the water and ethylene oxide reaction distillation tower is condensed by the first condenser to obtain a stream which is temporarily stored in the first reflux tank, and part of it is refluxed to the water and ethylene oxide reaction distillation separation tower according to the reflux ratio of 0.5-0.9, and the remaining part is sent to the tetrahydrofuran extraction distillation low-pressure tower by the first delivery pump;

[0041] B2. Extractive distillation separation of tetrahydrofuran:

[0042] The material enters the tetrahydrofuran extraction and distillation low-pressure tower from the middle of the tetrahydrofuran extraction and distillation low-pressure tower. The operating pressure of the tetrahydrofuran extraction and distillation low-pressure tower is 0.1 atm, the tower top temperature is 281-283K, the tower bottom temperature is 313-315K, the theoretical number of plates is 30-36, the material feed tower plate from the first reflux tank is the 13th to 19th tower plate, and the dimethyl sulfoxide extractant circulating flow feed tower plate from the third delivery pump is the 2nd to 8th tower plate;

[0043] A tetrahydrofuran product is obtained at the top of the tetrahydrofuran extraction and distillation low-pressure tower. The top steam of the tetrahydrofuran extraction and distillation low-pressure tower is condensed by the second condenser to obtain a stream, which is temporarily stored in the second reflux tank and partially refluxed to the tetrahydrofuran extraction and distillation low-pressure tower according to a reflux ratio of 1.8-2.2, and the other part is the obtained separated tetrahydrofuran;

[0044] The bottom stream of the tetrahydrofuran extraction and distillation low-pressure tower is vaporized by the second reboiler and then transported to the methanol extraction and distillation separation tower by the second delivery pump;

[0045] B3. Extraction and distillation separation of methanol:

[0046] The material enters the methanol extraction distillation tower from the middle of the methanol extraction distillation tower. The operating pressure of the methanol extraction distillation tower is 1 atm, the tower top temperature is 336-338K, the tower bottom temperature is 462-464K, the theoretical number of tower plates is 6-12, and the material feed tower plate from the bottom of the tetrahydrofuran extraction distillation low-pressure tower is the 2nd to 6th tower plate;

[0047] A methanol product is obtained at the top of the methanol extraction distillation tower. The top vapor of the methanol extraction distillation tower is condensed by the second condenser to obtain a stream, which is temporarily stored in the second reflux tank and partially refluxed to the methanol extraction distillation tower according to a reflux ratio of 0.07-0.11, and the other part is the separated methanol obtained;

[0048] The bottom stream of the methanol extraction distillation tower is vaporized by the third reboiler and then transported to the tetrahydrofuran extraction distillation low-pressure tower by the third delivery pump;

[0049] Heat exchange occurs between the tower tops of the water and ethylene oxide reaction distillation tower and the methanol extraction distillation tower and the second reboiler at the bottom of the tetrahydrofuran extraction distillation low-pressure tower, and the tower tops of the water and ethylene oxide reaction distillation tower and the methanol extraction distillation tower provide heat for the second reboiler; and auxiliary condensers are provided at the tower tops of the water and ethylene oxide reaction distillation tower and the methanol extraction distillation tower.

[0050] Heat exchange occurs between the first condenser at the top of the water and ethylene oxide reaction distillation tower and the second reboiler at the bottom of the tetrahydrofuran extraction distillation low-pressure tower, and the top steam of the water and ethylene oxide reaction distillation tower provides heat for the operation of the second reboiler at the bottom of the tetrahydrofuran extraction distillation low-pressure tower;

[0051] An auxiliary condenser is provided at the top of the water and ethylene oxide reaction distillation tower, and the load of the auxiliary condenser is 3.177MW.

[0052] Heat exchange occurs between the third condenser at the top of the methanol extraction and distillation tower and the second reboiler at the bottom of the tetrahydrofuran extraction and distillation low-pressure tower, and the top steam of the methanol extraction and distillation tower provides heat for the second reboiler at the bottom of the tetrahydrofuran extraction and distillation low-pressure tower;

[0053] An auxiliary condenser is provided at the top of the methanol extraction distillation tower, and the load of the auxiliary condenser is 0.141 MW.

[0054] The beneficial effects of the present invention are:

[0055] (1) By adopting the method to separate the tetrahydrofuran / methanol / water mixture, three high-purity products can be obtained, wherein the molar purity of ethylene glycol can reach above 99.9%, and the molar purity of methanol and tetrahydrofuran can reach above 99.5%;

[0056] (2) Removing water from the tetrahydrofuran / methanol / water mixture by reacting water with ethylene oxide not only fully utilizes the water in the mixture but also generates ethylene glycol, a byproduct with high utilization value;

[0057] (3) The energy consumption of the reactive extraction distillation process is greatly reduced by applying partial heat integration technology for process intensification;

[0058] (4) Compared with the existing extraction and distillation process, the operation cost and equipment cost of the present invention are lower, the process is simple and the operability is strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 is a schematic diagram of the structure of the reactive extraction distillation device in Example 1;

[0060] Figure 2 is a schematic diagram of the structure of the reactive extraction distillation device in Example 3;

[0061] Figure 3 is a schematic diagram of the structure of the reactive extraction distillation device in Example 5;

[0062] Figure 4 It is a schematic diagram of the structure of the reactive extraction distillation device in Example 6.

[0063] In the figure: 1 water and ethylene oxide reaction distillation tower, 2 tetrahydrofuran extraction distillation tower, 3 methanol extraction distillation tower, 4 first condenser, 5 first reflux tank, 6 first delivery pump, 7 first reboiler, 8 second condenser, 9 second reflux tank, 10 second reboiler, 11 second delivery pump, 12 third condenser, 13 third reflux tank, 14 third reboiler, 15 third delivery pump, 16 tetrahydrofuran extraction distillation low-pressure tower, 17 auxiliary condenser, 18 auxiliary condenser. DETAILED DESCRIPTION

[0064] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0065] In the following description, specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in a variety of other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0066] Example 1

[0067] The method for separating tetrahydrofuran / methanol / water ternary azeotropic mixture by reactive extraction and distillation of the present invention adopts dimethyl sulfoxide as the extractant, which can significantly increase the relative volatility between tetrahydrofuran and methanol. Figure 1 The reactive extractive distillation apparatus shown.

[0068] The device comprises a water and ethylene oxide reaction distillation tower 1, a tetrahydrofuran extraction distillation tower 2, and a methanol extraction distillation tower 3 which are connected in sequence.

[0069] The top of the water and ethylene oxide reaction distillation tower 1 is provided with a first condenser 4, a first reflux tank 5, and a first delivery pump 6. The top steam outlet of the water and ethylene oxide reaction distillation tower 1 is connected to the first condenser 4, the outlet of the first condenser 4 is connected to the first reflux tank 5, and the outlet of the first reflux tank 5 is respectively connected in parallel with the top liquid inlet of the water and ethylene oxide reaction distillation tower 1 and the tetrahydrofuran extraction distillation tower 2. The bottom of the water and ethylene oxide reaction distillation tower 1 is provided with a first reboiler 7.

[0070] After the tetrahydrofuran / methanol / water mixture enters the water and ethylene oxide reaction distillation tower 1 from the feed inlet in the middle of the water and ethylene oxide reaction distillation tower 1, ethylene glycol is obtained at the bottom of the water and ethylene oxide reaction distillation tower 1, and the ethylene glycol is vaporized by the first reboiler 7 and then flows out and is collected.

[0071] The top steam of the water and ethylene oxide reaction distillation tower 1 passes through the first condenser 4 and is temporarily stored in the first reflux tank 5. A part of the condensate flow in the first reflux tank 5 is refluxed into the water and ethylene oxide reaction distillation tower 1, and the other part is directly transported to the tetrahydrofuran extraction distillation tower 2.

[0072] A second condenser 8 and a second reflux tank 9 are provided at the top of the tetrahydrofuran extractive distillation tower 2. The top steam outlet of the tetrahydrofuran extractive distillation tower 2 is connected to the second condenser 8, the outlet of the second condenser 8 is connected to the second reflux tank 9, and the outlet of the second reflux tank 9 is connected to the top liquid inlet of the tetrahydrofuran extractive distillation tower 2. A second reboiler 10 and a second delivery pump 11 are provided at the bottom of the tetrahydrofuran extractive distillation tower 2, and the bottom stream of the tetrahydrofuran extractive distillation tower 2 is connected to the methanol extractive distillation tower 3 through the second delivery pump 11.

[0073] After the logistics flows into the tetrahydrofuran extraction distillation tower 2 from the feed inlet at the upper middle part of the tetrahydrofuran extraction distillation tower 2, the tetrahydrofuran product is obtained in the top logistics of the tetrahydrofuran extraction distillation tower 2, and the bottom logistics of the tetrahydrofuran extraction distillation tower 2 is vaporized by the second reboiler 10 and then sent to the methanol extraction distillation tower 3 by the second delivery pump 11.

[0074] A third condenser 12 and a third reflux tank 13 are provided at the top of the methanol extraction distillation tower 3. The top steam outlet of the methanol extraction distillation tower 3 is connected to the third condenser 12, the outlet of the third condenser 12 is connected to the third reflux tank 13, and the outlet of the third reflux tank 13 is connected to the top liquid inlet of the methanol extraction distillation tower 3. A third reboiler 14 and a third delivery pump 15 are provided at the bottom of the methanol extraction distillation tower 3, and the extractant flow at the bottom of the methanol extraction distillation tower 3 is connected to the tetrahydrofuran extraction distillation tower 2 through the third delivery pump 15.

[0075] After the logistics flows into the methanol extraction distillation tower 3 from the feed inlet in the middle of the methanol extraction distillation tower 3, the methanol product is obtained in the top logistics of the methanol extraction distillation tower 3, and the bottom extractant logistics of the methanol extraction distillation tower 3 is vaporized by the third reboiler 14 and sent to the cooler by the third delivery pump 15 for cooling, and finally sent to the tetrahydrofuran extraction distillation tower 2 to form an extractant circulation stream.

[0076] The method for separating the tetrahydrofuran / methanol / water mixture using the above-mentioned reactive extraction distillation device is as follows.

[0077] The first step is the separation of water from the mixture.

[0078] The tetrahydrofuran / methanol / water mixed solution is transported from the middle of the water and ethylene oxide reaction distillation tower 1 to the tower. In this embodiment, two liquid inlets are provided in the middle of the water and ethylene oxide reaction distillation tower 1. The tetrahydrofuran / methanol / water mixed solution enters the tower through the upper liquid inlet, and its feed rate is 500 kmol / h. The ethylene oxide solution enters the tower through the lower liquid inlet, and its feed rate is 187.5 kmol / h.

[0079] In the water and ethylene oxide reaction distillation tower 1, water in the tetrahydrofuran / methanol / water mixed solution reacts chemically with ethylene oxide to produce ethylene glycol, and a by-product ethylene glycol product is obtained in the bottom stream of the water and ethylene oxide reaction distillation tower 1. The chemical equation of the reaction of water and ethylene oxide is shown in formula (1), and the reaction kinetics is shown in formula (2).

[0080] C2H4O+H2O→C2H6O2 (1)

[0081] r(kmol / (m 3 ×s))=3.15×10 12 exp[-9547 / T]x EO x water (2)

[0082] Among them, C2H4O represents ethylene oxide, H2O represents water, and C2H6O2 represents ethylene glycol. The activation energy is 9547, and the unit is kJ / kmol, x EO and x water Represent the molar fractions of ethylene oxide and water, respectively. It is worth noting that the process uses a non-catalytic hydration reaction of ethylene oxide. In order to avoid the problem that the water in the tetrahydrofuran / methanol / water mixture solution cannot be completely removed or that too much ethylene oxide causes subsequent separation difficulties, the molar ratio of ethylene oxide to water in the reactant feed of the water and ethylene oxide reaction distillation tower 1 must be 1:1.

[0083] Through the above-mentioned hydration reaction of ethylene oxide, water in the tetrahydrofuran / methanol / water mixture can be removed, and ethylene glycol, a byproduct with high utilization value, can be produced.

[0084] In this embodiment, the feed rate of tetrahydrofuran / methanol / water mixture solution is 500 kmol / h, and the feed rate of ethylene oxide solution is 187.5 kmol / h. The operating pressure of water and ethylene oxide reaction distillation tower 1 is 1 atm, and the number of tower plates is 9.

[0085] After the ethylene glycol product is vaporized in the first reboiler 7, part of it flows back to the water and ethylene oxide reaction distillation tower 1 according to a certain reboil ratio, and the other part flows out to the outside, so that the separated ethylene glycol is collected in the outside.

[0086] The top steam of the water and ethylene oxide reaction distillation tower 1 is condensed by the first condenser 4 and temporarily stored in the first reflux tank 5. The logistics in the first reflux tank 5 is refluxed to the water and ethylene oxide reaction distillation tower 1 according to a certain reflux ratio, and the other part of the logistics directly flows into the tetrahydrofuran extraction distillation tower 2. In this embodiment, the reflux ratio is 0.767.

[0087] The second step is the separation of tetrahydrofuran.

[0088] The material flowed out from the first reflux tank 5 flows into the tetrahydrofuran extractive distillation tower 2, and the tetrahydrofuran product is obtained in the top material flow of the tetrahydrofuran extractive distillation tower 2.

[0089] In this embodiment, the operating pressure of the tetrahydrofuran extractive distillation tower 2 is 1 atm, and the number of tower plates is 46.

[0090] After the overhead steam of the tetrahydrofuran extractive distillation tower 2 is condensed by the second condenser 8, it is temporarily stored in the second reflux tank 9. According to a certain reflux ratio, a part of the logistics in the second reflux tank 9 is refluxed to the tetrahydrofuran extractive distillation tower 2, and the other part of the logistics directly flows out to recover the tetrahydrofuran product. In the present embodiment, the reflux ratio is 2.033.

[0091] After the bottom product of the tetrahydrofuran extraction distillation tower 2 is vaporized in the second reboiler 10 , part of it is refluxed into the tetrahydrofuran extraction distillation tower 2 according to a certain reboil ratio, and the other part is directly sent to the methanol extraction distillation tower 3 by the second delivery pump 11 .

[0092] The third step is the separation of methanol.

[0093] The flow from the bottom of the tetrahydrofuran extractive distillation tower 2 flows into the methanol extractive distillation tower 3 , and the methanol product is obtained in the top flow of the methanol extractive distillation tower 3 .

[0094] In this embodiment, the operating pressure of the methanol extraction distillation tower 3 is 1 atm, and the number of tower plates is 9.

[0095] After the top steam of the methanol extraction distillation tower 3 is condensed by the third condenser 12, it is temporarily stored in the third reflux tank 13. According to a certain reflux ratio, part of the logistics in the third reflux tank 13 is refluxed to the methanol extraction distillation tower 3, and the other part of the logistics is directly discharged to recover the methanol product. In this embodiment, the reflux ratio is 0.128.

[0096] After the bottom product of the methanol extraction distillation tower 3 is vaporized by the third reboiler 14, part of it is refluxed into the methanol extraction distillation tower 3 according to a certain reboil ratio, and the other part is sent to the tetrahydrofuran extraction distillation tower 2 by the third delivery pump 15, thereby forming an extractant circulation stream.

[0097] Example 2

[0098] In this embodiment, two feed ports are provided on the water and ethylene oxide reaction distillation tower 1, and the feed composition of the upper feed port includes 37.5 mol% methanol, 25.0 mol% tetrahydrofuran and 37.5 mol% water, and the feed flow rate is 500 kmol / h. The feed composition of the lower feed port is 100 mol% ethylene oxide mixed liquid, and the feed flow rate is 187.5 kmol / h. The operating pressure of the water and ethylene oxide reaction distillation tower 1 is 1 atm, the theoretical number of plates is 9 plates, the feed plates are the 5th plate and the 6th plate, respectively, and the reaction section is the 3rd plate to the 5th plate.

[0099] The operating pressure of the tetrahydrofuran extraction distillation tower 2 is 1 atm, the theoretical number of plates is 46 plates, the feed plate of the logistics flowing in from the first reflux tank 5 is the 27th plate, and the feed plate of the extractant circulating logistics flowing in from the bottom of the methanol extraction distillation tower 3 is the 4th plate.

[0100] The operating pressure of the methanol extraction distillation tower 3 is 1 atm, the number of theoretical plates is 9, and the feed plate for the logistics flowing in from the bottom of the tetrahydrofuran extraction distillation tower 2 is the 4th plate.

[0101] In this embodiment, the operating parameter information table of each extractive distillation tower is shown in Table 1 below.

[0102] Table 1 Process operating parameters of Example 2

[0103]

[0104] After separation by the method described in this example, the purity of the obtained ethylene glycol can reach 99.94%, the purity of tetrahydrofuran can reach 99.5%, and the purity of methanol can reach 99.8%.

[0105] The rest is the same as in Example 1.

[0106] Example 3

[0107] Different from Example 1, the reaction extraction distillation device used in this example includes a water and ethylene oxide reaction distillation tower 1, a tetrahydrofuran extraction distillation low-pressure tower 16 and a methanol extraction distillation tower 3 connected in sequence. Figure 2 shown.

[0108] The outlet of the first reflux tank 5 is connected in parallel with the top liquid inlet of the water and ethylene oxide reaction distillation tower 1 and the tetrahydrofuran extraction distillation low-pressure tower 16 respectively.

[0109] The top steam of the water and ethylene oxide reaction distillation tower 1 passes through the first condenser 4 and is temporarily stored in the first reflux tank 5. A part of the condensate flow in the first reflux tank 5 flows back to the water and ethylene oxide reaction distillation tower 1, and the other part directly flows into the tetrahydrofuran extraction distillation low-pressure tower 16.

[0110] A part of the condensate flow in the second reflux tank 9 is refluxed into the tetrahydrofuran extractive distillation low-pressure tower 16, and the other part is directly discharged to recover the tetrahydrofuran product. The bottom flow of the tetrahydrofuran extractive distillation low-pressure tower 16 is vaporized by the second reboiler 10 according to a certain reboil ratio, and a part of it is refluxed into the tetrahydrofuran extractive distillation low-pressure tower 16, and the other part is directly delivered to the methanol extractive distillation tower 3 by the second delivery pump 11.

[0111] A part of the condensate flow in the third reflux tank 13 is refluxed into the methanol extraction distillation tower 3, and the other part is directly discharged to recover the methanol product. The bottom flow of the methanol extraction distillation tower 3 is vaporized by the third reboiler 14 according to a certain reboil ratio, and part of it is refluxed into the methanol extraction distillation tower 3, and the other part is sent to the tetrahydrofuran extraction distillation low-pressure tower 16 by the third delivery pump 15 to form an extractant circulating flow.

[0112] The method for separating the tetrahydrofuran / methanol / water ternary azeotropic mixture using the reactive extraction distillation device described in this embodiment includes the following steps.

[0113] The first step is the separation of water.

[0114] The second step is the separation of tetrahydrofuran.

[0115] The material flowed out from the first reflux tank 5 enters the tetrahydrofuran extractive distillation low-pressure tower 16, which is a low-pressure tower. The tetrahydrofuran product is obtained at the top of the tetrahydrofuran extractive distillation low-pressure tower 16.

[0116] In this embodiment, the operating pressure of the tetrahydrofuran extractive distillation low-pressure tower 16 is 0.1 atm, and the number of tower plates is 33.

[0117] The overhead steam of the tetrahydrofuran extractive distillation low-pressure tower 16 is temporarily stored in the second reflux tank 9 after being condensed by the second condenser 8. The logistics in the second reflux tank 9, according to a certain reflux ratio, part of the logistics is refluxed into the tetrahydrofuran extractive distillation low-pressure tower 16, and the other part of the logistics directly flows out to the outside for collection, thereby obtaining the separated tetrahydrofuran product. In the present embodiment, the reflux ratio is 1.221.

[0118] After the bottom flow of the tetrahydrofuran extraction distillation low-pressure tower 16 is vaporized by the second reboiler 10 , part of it is refluxed into the tetrahydrofuran extraction distillation low-pressure tower 16 according to a certain reboil ratio, and the other part is sent to the methanol extraction distillation tower 3 through the second delivery pump 11 .

[0119] The third step is the separation of methanol.

[0120] The stream flowing out from the bottom of the tetrahydrofuran extractive distillation low-pressure tower 16 flows into the methanol extractive distillation tower 3 , and the methanol product is obtained in the top stream of the methanol extractive distillation tower 3 .

[0121] In this embodiment, the operating pressure of the methanol extraction distillation tower 3 is 1 atm, and the number of tower plates is 9.

[0122] After the top steam of the methanol extraction distillation tower 3 is condensed by the third condenser 12, it is temporarily stored in the third reflux tank 13. According to a certain reflux ratio, part of the logistics in the third reflux tank 13 is refluxed to the methanol extraction distillation tower 3, and the other part of the logistics is directly discharged to recover the methanol product. In this embodiment, the reflux ratio is 0.090.

[0123] After the bottom product of the methanol extraction distillation tower 3 is vaporized by the third reboiler 14, part of it is refluxed into the methanol extraction distillation tower 3 according to a certain reboil ratio, and the other part is sent to the tetrahydrofuran extraction distillation low-pressure tower 16 by the third delivery pump 15, thereby forming an extractant circulation stream.

[0124] The rest is the same as in Example 1.

[0125] Example 4

[0126] In this embodiment, two feed ports are provided on the water and ethylene oxide reaction distillation tower 1, and the feed composition of the upper feed port includes 37.5 mol% methanol, 25.0 mol% tetrahydrofuran and 37.5 mol% water, and the feed flow rate is 500 kmol / h. The feed composition of the lower feed port is 100 mol% ethylene oxide mixed liquid, and the feed flow rate is 187.5 kmol / h. The operating pressure of the water and ethylene oxide reaction distillation tower 1 is 1 atm, the theoretical number of plates is 9 plates, the feed plates are the 5th plate and the 6th plate, respectively, and the reaction section is the 3rd plate to the 5th plate.

[0127] The operating pressure of the tetrahydrofuran extractive distillation low-pressure tower 16 is 0.1 atm, the theoretical number of tower plates is 33, the logistics feed plate flowing in from the first reflux tank 5 is the 16th tower plate, and the extractant circulating logistics feed plate flowing in from the bottom of the methanol extractive distillation tower 3 is the 5th tower plate.

[0128] The operating pressure of the methanol extraction distillation tower 3 is 1 atm, the number of theoretical plates is 9, and the feed plate of the logistics flowing in from the bottom of the tetrahydrofuran extraction distillation low-pressure tower 16 is the 4th tower plate.

[0129] In this embodiment, the operating parameter information table of each extractive distillation tower is shown in Table 2 below.

[0130] Table 2 Process operating parameters of Example 4

[0131]

[0132] After separation by the method described in this example, the purity of the obtained ethylene glycol can reach 99.94%, the purity of tetrahydrofuran can reach 99.6%, and the purity of methanol can reach 99.9%.

[0133] The rest is the same as in Example 3.

[0134] Example 5

[0135] This embodiment proposes a partial heat integration scheme for separating tetrahydrofuran / methanol / water ternary azeotropic mixture by reaction extraction and distillation based on embodiment 3. In this scheme, the structure of the reaction extraction and distillation device used in embodiment 3 is improved.

[0136] like Figure 3 As shown, a first reflux tank 5 and a first delivery pump 6 are provided at the top of the water and ethylene oxide reaction distillation tower 1, and heat exchange is generated between the water and ethylene oxide reaction distillation tower 1 and the second reboiler 10 to provide heat for the operation of the second reboiler 10.

[0137] In this embodiment, the heat at the top of the water and ethylene oxide reaction distillation tower 1 is transferred to the second reboiler 10 to provide heat for the second reboiler 10 .

[0138] Since the top of the water and ethylene oxide reaction distillation tower 1 can provide sufficient heat for the second reboiler 10, that is, the heat at the top of the water and ethylene oxide reaction distillation tower 1 is greater than the heat demand for the operation of the second reboiler 10, it is necessary to set an auxiliary condenser 17 at the top of the water and ethylene oxide reaction distillation tower 1 to remove excess heat from the top of the water and ethylene oxide reaction distillation tower 1.

[0139] In this embodiment, the tower top temperature of the water and ethylene oxide reaction distillation tower 1 is 333.1K, and the tower bottom temperature of the tetrahydrofuran extraction distillation low-pressure tower 16 is 314.0K, and there is a temperature difference between the tower top temperature of the water and ethylene oxide reaction distillation tower 1 and the tower bottom temperature of the tetrahydrofuran extraction distillation low-pressure tower 16. The load of the second reboiler 10 of the tetrahydrofuran extraction distillation low-pressure tower 16 is 1.878MW, and the load of the auxiliary condenser 17 of the water and ethylene oxide reaction distillation tower 1 is 3.177MW.

[0140] This embodiment realizes a partial heat integration process between the water and ethylene oxide reaction distillation tower 1 and the tetrahydrofuran extractive distillation low-pressure tower 16. Compared with the traditional extractive distillation process, the annual total cost is reduced by 28.6%.

[0141] The rest is the same as in Example 3.

[0142] Example 6

[0143] This embodiment proposes a partial heat integration scheme for separating tetrahydrofuran / methanol / water ternary azeotropic mixture by reaction extraction and distillation based on embodiment 3. In this scheme, the structure of the reaction extraction and distillation device used in embodiment 3 is improved.

[0144] like Figure 4 As shown, a second reboiler 10 and a second delivery pump 11 are provided at the bottom of the tetrahydrofuran extraction distillation low-pressure tower 16, and a third reflux tank 13 is provided at the top of the methanol extraction distillation tower 3. Heat exchange occurs between the methanol extraction distillation tower 3 and the second reboiler 10 to provide heat for the operation of the second reboiler 10.

[0145] In this embodiment, the heat at the top of the methanol extraction distillation tower 3 is transferred to the second reboiler 10 to provide heat for the second reboiler 10 .

[0146] Since the top of the methanol extraction distillation tower 3 can provide sufficient heat for the second reboiler 10, that is, the heat at the top of the methanol extraction distillation tower 3 is greater than the heat demand for the operation of the second reboiler 10, it is necessary to set an auxiliary condenser 18 at the top of the methanol extraction distillation tower 3 to remove excess heat from the top of the methanol extraction distillation tower 3.

[0147] In this embodiment, the top temperature of the methanol extraction distillation tower 3 is 337.7K, and the bottom temperature of the tetrahydrofuran extraction distillation low-pressure tower 16 is 314.0K, and there is a temperature difference between the top temperature of the methanol extraction distillation tower 3 and the bottom temperature of the tetrahydrofuran extraction distillation low-pressure tower 16. The load of the second reboiler 10 of the tetrahydrofuran extraction distillation low-pressure tower 16 is 1.878MW, and the load of the auxiliary condenser 18 of the methanol extraction distillation tower 3 is 0.141MW.

[0148] This embodiment realizes a partial heat integration process between the methanol extraction and distillation tower 3 and the tetrahydrofuran extraction and distillation low-pressure tower 16. Compared with the traditional extraction and distillation process, the annual total cost is reduced by 29.1%.

[0149] The rest is the same as in Example 3.

[0150] The above is a detailed introduction to a method for separating a tetrahydrofuran / methanol / water ternary azeotropic mixture by reaction extraction and distillation provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention, and the description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in the technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The above description of the disclosed embodiments enables professionals and technicians in this field to implement or use the present invention. Various modifications to these embodiments will be obvious to professionals and technicians in this field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for separating a tetrahydrofuran / methanol / water mixture by reactive extraction and rectification, characterized in that: The following steps are involved: Reaction distillation separation of water and ethylene oxide, extraction distillation separation of tetrahydrofuran, extraction distillation separation of methanol; Alternatively, water and ethylene oxide are separated by reaction distillation, tetrahydrofuran is separated by low-pressure extraction distillation, and methanol is separated by extraction distillation; Heat is exchanged between the water and ethylene oxide reaction distillation tower and the tetrahydrofuran extraction distillation low-pressure tower to achieve partial heat integration of the water and ethylene oxide reaction distillation tower and the tetrahydrofuran extraction distillation low-pressure tower; Heat is exchanged between the methanol extraction distillation tower and the tetrahydrofuran extraction distillation low-pressure tower to achieve partial heat integration of the methanol extraction distillation tower and the tetrahydrofuran extraction distillation low-pressure tower; In the water and ethylene oxide reaction distillation tower, water and ethylene oxide react to generate ethylene glycol with high utilization value. After the dimethyl sulfoxide stream, the extractant at the bottom of the methanol extraction distillation tower, flows out, it needs to be cooled by a cooler and supplemented with extractant before it can flow back to the tetrahydrofuran extraction distillation tower or the tetrahydrofuran extraction distillation low-pressure tower.

2. The method for separating a tetrahydrofuran / methanol / water ternary mixture by reactive extraction and rectification according to claim 1, characterized in that: The method is implemented by using a reaction extraction distillation separation device, which includes: A water and ethylene oxide reaction distillation tower, wherein a first condenser, a first reflux tank and a first delivery pump connected in sequence are provided at the top of the tower, the water and ethylene oxide reaction distillation tower is connected to a tetrahydrofuran extraction distillation tower via the first delivery pump, and a first reboiler is provided at the bottom of the reaction distillation tower; A tetrahydrofuran extractive distillation tower, wherein a second reboiler and a second delivery pump connected in sequence are provided at the bottom of the tower, the methanol extractive distillation tower and the tetrahydrofuran extractive distillation tower are connected via the second delivery pump, and a second condenser and a second reflux tank are provided at the top of the tetrahydrofuran extractive distillation tower; The methanol extraction distillation tower or the dimethyl sulfoxide extractant recovery tower is provided with a third reboiler and a third delivery pump connected in sequence at the bottom of the tower, the methanol extraction distillation tower and the tetrahydrofuran extraction distillation tower are connected through the third delivery pump, and the top of the methanol extraction distillation tower is provided with a third condenser and a third reflux tank.

3. The method for separating a tetrahydrofuran / methanol / water ternary mixture by reactive extraction and rectification according to claim 2, characterized in that: The following steps are involved: A1. Reaction distillation separation of water and ethylene oxide: The tetrahydrofuran / methanol / water mixed solution is transported from the middle of the water and ethylene oxide reaction distillation tower to the inside of the tower. The water and ethylene oxide reaction distillation tower is provided with two feed inlets, the feed composition of the upper feed inlet is 500 kmol / h of the tetrahydrofuran / methanol / water mixed solution, and the feed composition of the lower feed inlet is 187.5 kmol / h of ethylene oxide solution; The operating pressure of the water and ethylene oxide reaction distillation tower is 1 atm, the tower top temperature is 332-334K, the tower bottom temperature is 468-470K, the theoretical number of tower plates is 6-12, the feed tower plates are the 2nd to 5th tower plates and the 6th to 8th tower plates, and the reaction section where water and ethylene oxide react is the 2nd to 4th tower plates and the 5th to 7th tower plates; The water in the tetrahydrofuran / methanol / water mixed solution reacts with the reactant ethylene oxide to generate ethylene glycol, a byproduct with high utilization value, and ethylene glycol is obtained at the bottom of the water and ethylene oxide reaction distillation tower. After the ethylene glycol is vaporized in the first reboiler, the separated high-purity ethylene glycol is obtained; The overhead steam of the water and ethylene oxide reaction distillation tower is condensed by the first condenser and the obtained stream is temporarily stored in the first reflux tank, and part of it is refluxed into the water and ethylene oxide reaction distillation tower according to the reflux ratio of 0.5-0.9, and the remaining part is sent into the tetrahydrofuran extraction distillation tower by the first delivery pump; A2. Extractive distillation separation of tetrahydrofuran: The material enters the tetrahydrofuran extraction distillation tower from the middle of the tetrahydrofuran extraction distillation tower. The operating pressure of the tetrahydrofuran extraction distillation tower is 1 atm, the tower top temperature is 337-339K, the tower bottom temperature is 372-374K, the theoretical number of plates is 43-49, the material feed tower plate from the first reflux tank is the 24th to 30th tower plate, and the dimethyl sulfoxide extractant circulating flow feed tower plate from the third delivery pump is the 2nd to 6th tower plate; A tetrahydrofuran product is obtained at the top of the tetrahydrofuran extractive distillation tower. The top steam of the tetrahydrofuran extractive distillation tower is condensed by the second condenser to obtain a stream, which is temporarily stored in the second reflux tank and partially refluxed to the tetrahydrofuran extractive distillation tower according to a reflux ratio of 1.8-2.2, and the other part is the separated tetrahydrofuran obtained; The bottom stream of the tetrahydrofuran extraction distillation tower is vaporized by the second reboiler and then transported to the methanol extraction distillation tower by the second delivery pump; A3. Extraction and distillation separation of methanol: The material enters the methanol extraction distillation tower from the middle of the methanol extraction distillation tower. The operating pressure of the methanol extraction distillation tower is 1 atm, the tower top temperature is 336-338K, the tower bottom temperature is 462-464K, the theoretical number of tower plates is 6-12, and the material feed tower plate from the bottom of the tetrahydrofuran extraction distillation tower is the 2nd to 6th tower plate; A methanol product is obtained at the top of the methanol extraction distillation tower. The top vapor of the methanol extraction distillation tower is condensed by the second condenser to obtain a stream, which is temporarily stored in the second reflux tank and partially refluxed to the methanol extraction distillation tower at a reflux ratio of 0.1-0.2, and the other part is the separated methanol obtained; The bottom stream of the methanol extraction distillation tower is vaporized in the third reboiler and then transported to the tetrahydrofuran extraction distillation tower by the third delivery pump.

4. The method for separating a tetrahydrofuran / methanol / water ternary mixture by reactive extraction and rectification according to claim 1, characterized in that: The method is implemented by using a reaction extraction distillation separation device, which includes: A water and ethylene oxide reaction distillation tower, wherein a first condenser, a first reflux tank and a first delivery pump connected in sequence are provided at the top of the tower, the water and ethylene oxide reaction distillation tower is connected to a tetrahydrofuran extraction distillation low-pressure tower via the first delivery pump, and a first reboiler is provided at the bottom of the reaction distillation tower; A tetrahydrofuran extractive distillation low-pressure tower is provided at the bottom of the tower with a second reboiler and a second delivery pump connected in sequence, the methanol extractive distillation tower and the tetrahydrofuran extractive distillation low-pressure tower are connected via the second delivery pump, and a second condenser and a second reflux tank are provided at the top of the tetrahydrofuran extractive distillation low-pressure tower; The methanol extraction distillation tower or the dimethyl sulfoxide extractant recovery tower is provided with a third reboiler and a third delivery pump connected in sequence at the bottom of the tower, the methanol extraction distillation tower and the tetrahydrofuran extraction distillation low-pressure tower are connected through the third delivery pump, and the top of the methanol extraction distillation tower is provided with a third condenser and a third reflux tank.

5. The method for separating a tetrahydrofuran / methanol / water ternary mixture by reactive extraction and rectification according to claim 4, characterized in that: The following steps are involved: B1. Reaction distillation separation of water and ethylene oxide: The tetrahydrofuran / methanol / water mixed solution is transported from the middle of the water and ethylene oxide reaction distillation tower to the inside of the tower. The water and ethylene oxide reaction distillation tower is provided with two feed inlets, the feed composition of the upper feed inlet is 500 kmol / h of the tetrahydrofuran / methanol / water mixed solution, and the feed composition of the lower feed inlet is 187.5 kmol / h of ethylene oxide solution; The operating pressure of the water and ethylene oxide reaction distillation tower is 1 atm, the tower top temperature is 332-334K, the tower bottom temperature is 468-470K, the theoretical number of tower plates is 6-12, the feed tower plates are the 2nd to 5th tower plates and the 6th to 8th tower plates, and the reaction section where water and ethylene oxide react is the 2nd to 4th tower plates and the 5th to 7th tower plates; The water in the tetrahydrofuran / methanol / water mixed solution reacts with the reactant ethylene oxide to generate ethylene glycol, a byproduct with high utilization value, and ethylene glycol is obtained at the bottom of the water and ethylene oxide reaction distillation tower. After the ethylene glycol is vaporized in the first reboiler, the separated high-purity ethylene glycol is obtained; The overhead steam of the water and ethylene oxide reaction distillation tower is condensed by the first condenser to obtain a stream which is temporarily stored in the first reflux tank, and part of it is refluxed to the water and ethylene oxide reaction distillation separation tower according to the reflux ratio of 0.5-0.9, and the remaining part is sent to the tetrahydrofuran extraction distillation low-pressure tower by the first delivery pump; B2. Extractive distillation separation of tetrahydrofuran: The material enters the tetrahydrofuran extraction and distillation low-pressure tower from the middle of the tetrahydrofuran extraction and distillation low-pressure tower. The operating pressure of the tetrahydrofuran extraction and distillation low-pressure tower is 0.1 atm, the tower top temperature is 281-283K, the tower bottom temperature is 313-315K, the theoretical number of plates is 30-36, the material feed tower plate from the first reflux tank is the 13th to 19th tower plate, and the dimethyl sulfoxide extractant circulating flow feed tower plate from the third delivery pump is the 2nd to 8th tower plate; A tetrahydrofuran product is obtained at the top of the tetrahydrofuran extraction and distillation low-pressure tower. The top steam of the tetrahydrofuran extraction and distillation low-pressure tower is condensed by the second condenser to obtain a stream, which is temporarily stored in the second reflux tank and partially refluxed to the tetrahydrofuran extraction and distillation low-pressure tower according to a reflux ratio of 1.8-2.2, and the other part is the obtained separated tetrahydrofuran; The bottom stream of the tetrahydrofuran extraction and distillation low-pressure tower is vaporized by the second reboiler and then transported to the methanol extraction and distillation separation tower by the second delivery pump; B3. Extraction and distillation separation of methanol: The material enters the methanol extraction distillation tower from the middle of the methanol extraction distillation tower. The operating pressure of the methanol extraction distillation tower is 1 atm, the tower top temperature is 336-338K, the tower bottom temperature is 462-464K, the theoretical number of tower plates is 6-12, and the material feed tower plate from the bottom of the tetrahydrofuran extraction distillation low-pressure tower is the 2nd to 6th tower plate; A methanol product is obtained at the top of the methanol extraction distillation tower. The top vapor of the methanol extraction distillation tower is condensed by the second condenser to obtain a stream, which is temporarily stored in the second reflux tank and partially refluxed to the methanol extraction distillation tower according to a reflux ratio of 0.07-0.11, and the other part is the separated methanol obtained; The bottom stream of the methanol extraction distillation tower is vaporized by the third reboiler and then transported to the tetrahydrofuran extraction distillation low-pressure tower by the third delivery pump.

6. The method for separating a tetrahydrofuran / methanol / water ternary mixture by reactive extraction and rectification according to claim 4, characterized in that: Heat exchange occurs between the tower tops of the water and ethylene oxide reaction distillation tower and the methanol extraction distillation tower and the second reboiler at the bottom of the tetrahydrofuran extraction distillation low-pressure tower, and the tower tops of the water and ethylene oxide reaction distillation tower and the methanol extraction distillation tower provide heat for the second reboiler; and auxiliary condensers are provided at the tower tops of the water and ethylene oxide reaction distillation tower and the methanol extraction distillation tower.

7. The method for separating a tetrahydrofuran / methanol / water ternary mixture by reactive extraction and rectification according to claim 5, characterized in that: Heat exchange occurs between the first condenser at the top of the water and ethylene oxide reaction distillation tower and the second reboiler at the bottom of the tetrahydrofuran extraction distillation low-pressure tower, and the top steam of the water and ethylene oxide reaction distillation tower provides heat for the operation of the second reboiler at the bottom of the tetrahydrofuran extraction distillation low-pressure tower; An auxiliary condenser is provided at the top of the water and ethylene oxide reaction distillation tower, and the load of the auxiliary condenser is 3.177MW.

8. The method for separating a tetrahydrofuran / methanol / water ternary mixture by reactive extraction and rectification according to claim 4 or 5, characterized in that: Heat exchange occurs between the third condenser at the top of the methanol extraction and distillation tower and the second reboiler at the bottom of the tetrahydrofuran extraction and distillation low-pressure tower, and the top steam of the methanol extraction and distillation tower provides heat for the second reboiler at the bottom of the tetrahydrofuran extraction and distillation low-pressure tower; An auxiliary condenser is provided at the top of the methanol extraction distillation tower, and the load of the auxiliary condenser is 0.141 MW.

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