Heat integration process for separating ethanol / tetrahydrofuran / n-hexane azeotropic system through intermediate heat exchange extraction pressure swing distillation

Abstract

The invention discloses a heat integration process for separating an ethanol-tetrahydrofuran-n-hexane azeotropic system through intermediate heat exchange extraction pressure swing distillation, which is characterized in that an ethanol-tetrahydrofuran-n-hexane mixed solution is separated through three-tower operation of an extraction reduced pressure distillation tower T1, an extraction distillation tower T2 and a solvent recovery reduced pressure distillation tower T3. Tower top steam of the extractive distillation tower T2 is used for exchanging heat for part of liquid phase of a middle plate of the extractive decompression distillation tower T1, the problem that traditional heat integration cannot be achieved due to the fact that the tower top temperature of the extractive distillation tower T2 is between the tower top temperature of the extractive decompression distillation tower T1 and the tower kettle temperature is solved, and a novel heat integration strengthening process is developed. According to the process, heat energy is fully utilized, and energy consumption and equipment cost are reduced. And the adopted extracting agent dimethyl sulfoxide is small in dosage, relatively weak in volatility, small in extracting agent loss, easy to recover and environment-friendly. The purity of separated ethanol is greater than 99.95%, the yield is greater than 99.95%, the purity of tetrahydrofuran is greater than 99.9%, the yield is greater than 99.9%, the purity of normal hexane is greater than 99.9%, the yield is greater than 99.9%, and the purity of an extracting agent dimethyl sulfoxide is greater than 99.99%, and the yield is greater than 99.99%.

Description

[Technical field]

[0001] The invention belongs to the field of chemical separation and purification, and specifically relates to a heat integration process for separating an ethanol / tetrahydrofuran / n-hexane azeotropic system by intermediate heat exchange extraction pressure swing distillation. [Background technology]

[0002] Ethanol is an important basic chemical that can be used to make beverages, flavors, disinfectants, etc. Anhydrous ethanol can be used as a gasoline additive, namely fuel ethanol, which can effectively improve the quality of gasoline and significantly reduce vehicle pollutant emissions. Tetrahydrofuran is an organic solvent with great industrial value and is widely used in polymerization reactions, chemical synthesis, and pharmaceuticals. In addition, tetrahydrofuran also plays an important role in lithium battery electrolytes. Due to its excellent solubility and low viscosity, it helps to improve reaction efficiency and battery performance. Hexane is an important industrial solvent that is widely used in edible oil extraction, synthetic rubber and plastic manufacturing, coatings and ink solvents, and precision cleaning in the pharmaceutical and electronics industries. It is favored for its excellent solubility, high volatility, and low toxicity.

[0003] A mixture of ethanol, tetrahydrofuran and n-hexane will form three binary azeotropic mixtures. Under normal pressure, the azeotropic point of ethanol-tetrahydrofuran is 65.8°C, the azeotropic point of ethanol-n-hexane is 58.4°C, and the azeotropic point of tetrahydrofuran-ethanol is 62.7°C. Ordinary distillation methods cannot achieve effective separation, so special distillation methods are required.

[0004] Patent (CN213912409U) discloses a tetrahydrofuran and ethanol fractionation recovery device, which has good and uniform heating effect, but fails to achieve heat integration in the separation process, and has a low heat utilization rate.

[0005] Patent (CN213912409U) discloses a method for separating a ternary azeotropic system of tetrahydrofuran, ethanol and water by reactive distillation combined with side-line extractive distillation. The method processes a tetrahydrofuran / ethanol / water mixture by reaction and separation, and the operation steps are complicated, which increases the equipment cost and load.

[0006] The present invention uses an intermediate heat exchange extraction pressure swing distillation method, uses dimethyl sulfoxide as an extractant, and utilizes the characteristics of the extractant's influence on the relative volatility of the azeotropic system and the pressure change's influence on the azeotropic composition of the azeotropic system to achieve high-purity separation and recovery of an ethanol / tetrahydrofuran / n-hexane mixture. Based on the phenomenon that the top temperature of the extractive distillation tower T2 is between the top temperature of the extractive vacuum distillation tower T1 and the tower bottom temperature, and the traditional heat integration cannot be achieved, the top steam of the extractive distillation tower T2 is used to exchange heat with part of the liquid phase of the middle plate of the extractive vacuum distillation tower T1, which greatly reduces the process energy consumption. The method can make the purity of ethanol, tetrahydrofuran and n-hexane reach more than 99.9%, and the high-purity extractant can be recycled and reused. The process of the present invention makes full use of thermal energy, reduces energy consumption and reduces equipment cost. The extractant dimethyl sulfoxide used is small in amount, weak in volatility, small in extractant loss, easy to recycle, and environmentally friendly. [Summary of the invention]

[0007] [Technical issues to be solved]

[0008] The purpose of the present invention is to provide a heat integration process for separating an ethanol / tetrahydrofuran / n-hexane azeotropic system by intermediate heat exchange extraction pressure swing distillation.

[0009] [Technical solution]

[0010] The temperature of the tower top and the tower bottom of the traditional heat integration should have a reasonable temperature difference to ensure effective heat transfer between the two, while avoiding excessive equipment costs and excessive heat loss. Because the temperature difference between the tower top and the tower bottom of each tower is not enough during the separation system, the traditional heat integration cannot be carried out, resulting in 36.3 tons of steam being consumed to separate one ton of ethanol / tetrahydrofuran / n-hexane. The present invention overcomes the disadvantage that the top temperature of the extractive distillation tower T2 is between the top temperature of the extractive vacuum distillation tower T1 and the tower bottom temperature, and the traditional heat integration process cannot be achieved, and proposes a heat integration process for separating the azeotropic system of ethanol / tetrahydrofuran / n-hexane by intermediate heat exchange extraction pressure swing distillation. The present invention utilizes the characteristics of the influence of the extractant on the relative volatility of the azeotropic system and the influence of the pressure change on the azeotropic composition of the azeotropic system, uses dimethyl sulfoxide as the extractant, and adopts the three-tower distillation method of extractive vacuum distillation tower, extractive distillation tower and solvent recovery vacuum distillation tower to separate high-purity ethanol, tetrahydrofuran and n-hexane, and uses the intermediate heat exchange process to achieve a significant reduction in energy consumption. The method solves the problems of complex process, large amount of extractant, high energy consumption and high equipment cost in the current technology.

[0011] The invention provides a method for separating an ethanol / tetrahydrofuran / normal-hexane azeotropic system in which the ethanol mass fraction accounts for 32-33%.

[0012] The present invention is realized by the following technical scheme: a heat integration process for separating ethanol / tetrahydrofuran / n-hexane azeotropic system by intermediate heat exchange extraction pressure swing distillation, characterized in that the device for realizing the method mainly comprises the following parts:

[0013] Extractive vacuum distillation tower T1, extractive distillation tower T2, solvent recovery vacuum distillation tower T3, condenser C1, condenser C2, condenser C3, cooler C4, reboiler B1, reboiler B2, reboiler B3, heat exchanger E1, mixer FS, centrifugal pump P1, centrifugal pump P2, centrifugal pump P3; wherein the raw material stream and the extractant stream are connected to the extractive vacuum distillation tower T1, the top gas phase outlet of the extractive vacuum distillation tower T1 is connected to the condenser C1, the bottom stream of the extractive vacuum distillation tower T1 is connected to the extractive distillation tower T2 through the centrifugal pump P1, and the liquid stream of the middle plate of the extractive vacuum distillation tower T1 is connected to the heat exchanger E1. 1 The cold stream inlet is connected to the extractive vacuum distillation tower T1 from the cold stream outlet of the heat exchanger E1 after heat exchange; the top gas stream of the extractive distillation tower T2 is connected to the hot stream inlet of the heat exchanger E1 after heat exchange, and the bottom stream of the extractive distillation tower T2 is connected to the solvent recovery vacuum distillation tower T3 through the centrifugal pump P2; the top gas stream of the solvent recovery vacuum distillation tower T3 is connected to the condenser C3, and the bottom stream of the solvent recovery vacuum distillation tower T3 is connected to the cooler C4 through the centrifugal pump P3, and after cooling, it is mixed with the supplementary extractant in the mixer FS and then refluxed to the extractive vacuum distillation tower T1 and the extractive distillation tower T2;

[0014] The above device is used to carry out a heat integration process for separating an ethanol / tetrahydrofuran / n-hexane azeotropic system by intermediate heat exchange extraction pressure swing distillation, comprising the following steps:

[0015] (1) The ethanol / tetrahydrofuran / n-hexane mixture enters the middle of the extractive vacuum distillation tower T1, and the extractant dimethyl sulfoxide enters the top of the extractive vacuum distillation tower T1. After effective contact and separation, the gas phase at the top of the extractive vacuum distillation tower T1 passes through the condenser C1, part of which is refluxed to the extractive vacuum distillation tower T1, and part of which is extracted as a high-purity product n-hexane. The bottom stream of the ethanol-tetrahydrofuran-extractant mixture is sent from the bottom of the extractive vacuum distillation tower T1 to the extractive distillation tower T2 by the centrifugal pump P1. The liquid phase of the middle plate of the tower enters the heat exchanger E1 for heat exchange and then refluxes to the extractive vacuum distillation tower T1;

[0016] (2) The ethanol-tetrahydrofuran-extractant mixture enters from the middle of the extractive distillation tower T2, and the extractant dimethyl sulfoxide enters from the top of the extractive distillation tower T2. The gas phase at the top of the extractive distillation tower T2 enters the heat exchanger E1 and exchanges heat with the flow stream from the middle plate of the extractive vacuum distillation tower T1. After the heat exchange, the gas phase stream at the top of the extractive distillation tower T2 enters the condenser C2, part of which is refluxed to the extractive distillation tower T2, and part of which is produced as a high-purity product tetrahydrofuran. The bottom stream ethanol-extractant mixture is sent to the solvent recovery vacuum distillation tower T3 by the centrifugal pump P2;

[0017] (3) The ethanol-extractant mixture enters the middle part of the solvent recovery vacuum distillation tower T3. The top gas phase of the solvent recovery vacuum distillation tower T3 passes through the condenser C3, and a part of it is refluxed to the solvent recovery vacuum distillation tower T3, and a part of it is extracted as a high-purity product ethanol. The bottom stream of the solvent recovery vacuum distillation tower T3 extracts high-purity extractant dimethyl sulfoxide and enters the cooler C4 through the centrifugal pump P3. After cooling, it is mixed with the supplementary extractant in the mixer FS and then refluxed to the extractive vacuum distillation tower T1 and the extractive distillation tower T2;

[0018] The operating pressure of the extractive vacuum distillation tower T1 is 0.2atm-0.3atm, the number of tower plates is 56, the raw material feeding position is the 43rd plate, the extractant feeding position is the 15th plate, the tower top temperature is 25.0℃-34.7℃, and the tower bottom temperature is 66.0℃-71.5℃;

[0019] The operating pressure of the extractive distillation tower T2 is 1 atm, the number of tower plates is 52, the feeding position of the ethanol-tetrahydrofuran-extractant mixture is the 30th plate, the feeding position of the extractant is the 6th plate, the tower top temperature is 66.0°C, and the tower bottom temperature is 126.1°C;

[0020] The operating pressure of the solvent recovery vacuum distillation tower T3 is 0.5-0.6 atm, the number of tower plates is 14, the ethanol-extractant mixture feed position is the 7th plate, the tower top temperature is 61.7°C-65.9°C, and the tower bottom temperature is 171.2°C-176.8°C.

[0021] According to another preferred embodiment of the present invention, it is characterized in that: the position of the intermediate heat exchange plate of the extractive vacuum distillation tower T1 is the 46th to 48th plate, and the heat exchange liquid phase flow rate is 2060-5477 kg / h.

[0022] According to another preferred embodiment of the present invention, it is characterized in that: the heat exchange flow temperature of the middle plate of the extractive vacuum distillation tower T1 is 46.0°C to 53.4°C, and the temperature after heat exchange is 56.0°C to 58.2°C.

[0023] According to another preferred embodiment of the present invention, it is characterized in that: the purity of the ethanol after separation is greater than 99.95%, the yield is greater than 99.95%, the purity of tetrahydrofuran is greater than 99.9%, the yield is greater than 99.9%, the purity of n-hexane is greater than 99.9%, the yield is greater than 99.9%, and the purity of the extractant dimethyl sulfoxide is greater than 99.99%, and the yield is greater than 99.99%.

[0024] According to another preferred embodiment of the present invention, it is characterized in that the amount of steam consumed for separating one ton of ethanol / tetrahydrofuran / n-hexane mixture is 31.5 tons to 34.0 tons.

[0025] [Beneficial Effects]

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The beneficial effect of the present invention is that the intermediate heat exchange extraction pressure swing distillation heat integration process is used to achieve efficient separation of the ethanol / tetrahydrofuran / n-hexane ternary azeotropic mixture.

[0028] (2) By using heat integration, the latent heat of the gas phase stream at the top of the extractive distillation tower T2 can heat the liquid phase in the middle plate of the extractive vacuum distillation tower T1, reducing energy consumption.

[0029] (3) The extraction agent has the advantages of small amount of extraction agent, simple process, small investment in equipment, high purity of ethanol, tetrahydrofuran and n-hexane after separation, etc. The extraction agent used is easy to recover, has good chemical and thermal stability, and is green and pollution-free.

Brief Description of the Drawings

[0030] Attached Figure 1 This is a process flow chart for separation of benzene / ethanol / butanone azeotropic system by heat-integrated extraction pressure swing distillation.

[0031] In the figure, T1-extractive vacuum distillation tower, T2-extractive distillation tower, T3-solvent recovery vacuum distillation tower, C1-condenser, C2-condenser, C3-condenser, C4-cooler, B1-reboiler, B2-reboiler, B3-reboiler, E1-heat exchanger, FS-mixer, P1-centrifugal pump, P2-centrifugal pump, P3-centrifugal pump. [Specific implementation method]

[0032] The following is further described in conjunction with the accompanying drawings, which does not limit the scope of the present invention.

[0033] Embodiment 1:

[0034] The feed flow rate is 6390kg / h, the feed contains 32.43% ethanol, 33.85% ethanol, and 33.71% butanone (mass fraction, the same below), the number of theoretical plates of the extractive vacuum distillation tower T1 is 56, the pressure is 0.22atm, the feed raw material enters from the 43rd plate of the extractive vacuum distillation tower T1, and the extractant dimethyl sulfoxide enters from the 15th plate of the extractive vacuum distillation tower T1, with a flow rate of 4375kg / h. The intermediate heat exchange plate is the 46th plate, the heat exchange flow rate is 2060kg / h, and the outlet temperature of the cold stream of the heat exchanger E1 is 56.0℃. 2154kg / h of 99.9% normal hexane is obtained at the top of the extractive vacuum distillation tower T1, and the temperature is 27.2℃; the bottom stream ethanol / tetrahydrofuran / extractant mixture enters from the 52nd plate of the extractive distillation tower T2, with a flow rate of 8612kg / h and a temperature of 67.6℃. The number of theoretical plates of the extractive distillation tower T2 is 52, and the pressure is atmospheric pressure. 2163kg / h of 99.9% tetrahydrofuran is obtained at the top of the extractive distillation tower T2, and the temperature is 66.0℃; the bottom stream ethanol-extractant mixture enters from the 7th plate of the solvent recovery vacuum distillation tower T3, with a flow rate of 7754kg / h and a temperature of 126.1℃. The number of theoretical plates of the solvent recovery vacuum distillation tower T3 is 14, and the pressure is 0.60atm. 2073.4kg / h of 99.9% ethanol is obtained at the top of the solvent recovery vacuum distillation tower T3, and the temperature is 65.9℃; 6172kg / h of 99.995% extractant dimethyl sulfoxide is obtained at the bottom of the tower, and the temperature is 176.8℃. The extractant at the bottom of the tower is cooled to 30°C by cooler C4 and supplemented with a small amount of extractant by mixer FS, and refluxed to the extractive vacuum distillation tower T1. The processing of one ton of ethanol / tetrahydrofuran / n-hexane consumes 31.8 tons of steam.

[0035] Embodiment 2:

[0036] The feed flow rate is 6390.74kg / h, the feed contains 32.43% ethanol, 33.85% ethanol, and 33.71% butanone (mass fraction, the same below), the theoretical number of plates of the extractive vacuum distillation tower T1 is 56, the pressure is 0.30atm, the feed material enters from the 43rd plate of the extractive vacuum distillation tower T1, and the extractant dimethyl sulfoxide enters from the 15th plate of the extractive vacuum distillation tower T1, with a flow rate of 4375.56kg / h. The intermediate heat exchange plate is the 47th plate, the heat exchange flow rate is 3208kg / h, and the outlet temperature of the cold stream of the heat exchanger E1 is 57.0℃. 2154.1kg / h of 99.9% n-hexane is obtained from the top of the extractive vacuum distillation tower T1, with a temperature of 34.7°C; the bottom stream ethanol / tetrahydrofuran / extractant mixture enters from the 52nd plate of the extractive distillation tower T2, with a flow rate of 8612.2kg / h and a temperature of 71.5°C. The number of theoretical plates of the extractive distillation tower T2 is 52, and the pressure is 1atm. 2163.5kg / h of 99.9% tetrahydrofuran is obtained from the top of the extractive distillation tower T2, with a temperature of 66.0°C; the bottom stream ethanol-extractant mixture enters from the 7th plate of the solvent recovery vacuum distillation tower T3, with a flow rate of 7754kg / h and a temperature of 126.1°C. The number of theoretical plates of the solvent recovery vacuum distillation tower T3 is 14, and the pressure is 0.6atm. The solvent recovery vacuum distillation tower T3 obtains 2073.4 kg / h of 99.9% ethanol at the top with a temperature of 65.9°C; 6172.4 kg / h of 99.995% extractant dimethyl sulfoxide at the bottom with a temperature of 176.8°C. 31.5 tons of steam are consumed to process one ton of ethanol / tetrahydrofuran / n-hexane.

[0037] Embodiment 3:

[0038] The feed flow rate is 6390.74kg / h, the feed contains 32.43% ethanol, 33.85% ethanol, and 33.71% butanone (mass fraction, the same below), the theoretical number of plates of the extractive vacuum distillation tower T1 is 56, the pressure is 0.20atm, the feed material enters from the 43rd plate of the extractive vacuum distillation tower T1, and the extractant dimethyl sulfoxide enters from the 15th plate of the extractive vacuum distillation tower T1, with a flow rate of 4375.56kg / h. The intermediate heat exchange plate is the 48th plate, the heat exchange flow rate is 5470kg / h, and the outlet temperature of the cold stream of the heat exchanger E1 is 58.2℃. 2154.1kg / h of 99.9% n-hexane is obtained from the top of the extractive vacuum distillation tower T1, with a temperature of 25.0°C; the bottom stream ethanol / tetrahydrofuran / extractant mixture enters from the 52nd plate of the extractive distillation tower T2, with a flow rate of 8612.2kg / h and a temperature of 67.6°C. The number of theoretical plates of the extractive distillation tower T2 is 52, and the pressure is 1atm. 2163.5kg / h of 99.9% tetrahydrofuran is obtained from the top of the extractive distillation tower T2, with a temperature of 66.0°C; the bottom stream ethanol-extractant mixture enters from the 7th plate of the solvent recovery vacuum distillation tower T3, with a flow rate of 7754kg / h and a temperature of 126.1°C. The number of theoretical plates of the solvent recovery vacuum distillation tower T3 is 14, and the pressure is 0.5atm. The solvent recovery vacuum distillation tower T3 obtains 2073.4 kg / h of 99.9% ethanol at the top, with a temperature of 61.7°C; the tower bottom obtains 6172.4 kg / h of 99.995% extractant dimethyl sulfoxide at a temperature of 171.2°C. The extractant at the bottom of the tower is cooled to 30°C by cooler C4 and supplemented with a small amount of extractant by mixer FS, and refluxed to the extractive vacuum distillation tower T1. The steam consumption for processing one ton of ethanol / tetrahydrofuran / n-hexane is 31.5 tons.

Claims

1. A heat integration process for separating ethanol / tetrahydrofuran / n-hexane azeotropic system by intermediate heat exchange extraction pressure swing distillation, characterized in that The device for implementing the method mainly includes the following parts: Extractive vacuum distillation tower T1, extractive distillation tower T2, solvent recovery vacuum distillation tower T3, condenser C1, condenser C2, condenser C3, cooler C4, reboiler B1, reboiler B2, reboiler B3, heat exchanger E1, mixer FS, centrifugal pump P1, centrifugal pump P2, centrifugal pump P3; wherein the raw material stream and the extractant stream are connected to the extractive vacuum distillation tower T1, the top gas phase outlet of the extractive vacuum distillation tower T1 is connected to the condenser C1, the bottom stream of the extractive vacuum distillation tower T1 is connected to the extractive distillation tower T2 through the centrifugal pump P1, and the liquid stream of the middle plate of the extractive vacuum distillation tower T1 is connected to the heat exchanger E1. 1 The cold stream inlet is connected to the extractive vacuum distillation tower T1 from the cold stream outlet of the heat exchanger E1 after heat exchange; the top gas stream of the extractive distillation tower T2 is connected to the hot stream inlet of the heat exchanger E1 after heat exchange, and the bottom stream of the extractive distillation tower T2 is connected to the solvent recovery vacuum distillation tower T3 through the centrifugal pump P2; the top gas stream of the solvent recovery vacuum distillation tower T3 is connected to the condenser C3, and the bottom stream of the solvent recovery vacuum distillation tower T3 is connected to the cooler C4 through the centrifugal pump P3, and after cooling, it is mixed with the supplementary extractant in the mixer FS and then refluxed to the extractive vacuum distillation tower T1 and the extractive distillation tower T2; The above device is used to carry out a heat integration process for separating an ethanol / tetrahydrofuran / n-hexane azeotropic system by intermediate heat exchange extraction pressure swing distillation, comprising the following steps: (1) The ethanol / tetrahydrofuran / n-hexane mixture enters the middle of the extractive vacuum distillation tower T1, and the extractant dimethyl sulfoxide enters the top of the extractive vacuum distillation tower T1. After effective contact and separation, the gas phase at the top of the extractive vacuum distillation tower T1 passes through the condenser C1, part of which is refluxed to the extractive vacuum distillation tower T1, and part of which is extracted as a high-purity product n-hexane. The bottom stream of the ethanol-tetrahydrofuran-extractant mixture is sent from the bottom of the extractive vacuum distillation tower T1 to the extractive distillation tower T2 by the centrifugal pump P1. The liquid phase of the middle plate of the tower enters the heat exchanger E1 for heat exchange and then refluxes to the extractive vacuum distillation tower T1; (2) The ethanol-tetrahydrofuran-extractant mixture enters from the middle of the extractive distillation tower T2, and the extractant dimethyl sulfoxide enters from the top of the extractive distillation tower T2. The gas phase at the top of the extractive distillation tower T2 enters the heat exchanger E1 and exchanges heat with the flow stream from the middle plate of the extractive vacuum distillation tower T1. After the heat exchange, the gas phase stream at the top of the extractive distillation tower T2 enters the condenser C2, part of which is refluxed to the extractive distillation tower T2, and part of which is produced as a high-purity product tetrahydrofuran. The bottom stream ethanol-extractant mixture is sent to the solvent recovery vacuum distillation tower T3 by the centrifugal pump P2; (3) The ethanol-extractant mixture enters the middle part of the solvent recovery vacuum distillation tower T3. The top gas phase of the solvent recovery vacuum distillation tower T3 passes through the condenser C3, and a part of it is refluxed to the solvent recovery vacuum distillation tower T3, and a part of it is extracted as a high-purity product ethanol. The bottom stream of the solvent recovery vacuum distillation tower T3 extracts high-purity extractant dimethyl sulfoxide and enters the cooler C4 through the centrifugal pump P3. After cooling, it is mixed with the supplementary extractant in the mixer FS and then refluxed to the extractive vacuum distillation tower T1 and the extractive distillation tower T2; The operating pressure of the extractive vacuum distillation tower T1 is 0.2atm-0.3atm, the number of tower plates is 56, the raw material feeding position is the 43rd plate, the extractant feeding position is the 15th plate, the tower top temperature is 25.0℃-34.7℃, and the tower bottom temperature is 66.0℃-71.5℃; The operating pressure of the extractive distillation tower T2 is 1 atm, the number of tower plates is 52, the feeding position of the ethanol-tetrahydrofuran-extractant mixture is the 30th plate, the feeding position of the extractant is the 6th plate, the tower top temperature is 66.0°C, and the tower bottom temperature is 126.1°C; The operating pressure of the solvent recovery vacuum distillation tower T3 is 0.5-0.6 atm, the number of tower plates is 14, the ethanol-extractant mixture feed position is the 7th plate, the tower top temperature is 61.7°C-65.9°C, and the tower bottom temperature is 171.2°C-176.8°C.

2. The heat integration process for separating ethanol / tetrahydrofuran / n-hexane azeotropic system by intermediate heat exchange extraction pressure swing distillation according to claim 1, characterized in that: The intermediate heat exchange plates of the extractive vacuum distillation tower T1 are located at plates 46-48, and the heat exchange liquid phase flow rate is 2060-5477 kg / h.

3. The heat integration process for separating ethanol / tetrahydrofuran / n-hexane azeotropic system by intermediate heat exchange extraction pressure swing distillation according to claim 1, characterized in that: The heat exchange flow temperature of the middle plate of the extractive vacuum distillation tower T1 is 46.0℃~53.4℃, and the temperature after heat exchange is 56.0℃~58.2℃.

4. The heat integration process for separating ethanol / tetrahydrofuran / n-hexane azeotropic system by intermediate heat exchange extraction pressure swing distillation according to claim 1, characterized in that: The purity of the separated ethanol is greater than 99.95%, and the yield is greater than 99.95%. The purity of tetrahydrofuran is greater than 99.9%, and the yield is greater than 99.9%. The purity of n-hexane is greater than 99.9%, and the yield is greater than 99.9%. The purity of the extractant dimethyl sulfoxide is greater than 99.99%, and the yield is greater than 99.99%.

5. The heat integration process for separating ethanol / tetrahydrofuran / n-hexane azeotropic system by intermediate heat exchange extraction pressure swing distillation according to claim 1, characterized in that: The amount of steam consumed to separate one ton of ethanol / tetrahydrofuran / n-hexane mixture is 31.5 tons to 34.0 tons.

Images