Device for separating ethanol-normal hexane-cyclohexane multi-element azeotrope through double-side-line extractive distillation

Abstract

The utility model discloses a device for separating ethanol-normal hexane-cyclohexane multi-element azeotrope by double-side-line extractive distillation, which comprises a first side-line extractive distillation tower, the first side-line extractive distillation tower is connected with a multi-element azeotrope feeding pipeline, a first extractant feeding pipeline and a first reboiler, the first side-line extractive distillation tower is connected with a first condenser and a first reflux tank, and the first reboiler is connected with a second condenser and a second reflux tank. The reflux tank I is connected with a reflux pipeline I and a cyclohexane extraction pipeline; the first side-line extractive distillation tower is connected with a feeding port of the second side-line extractive distillation tower through a first material extraction side line, the second side-line extractive distillation tower is connected with a second extraction agent feeding pipeline and a second reboiler, the second side-line extractive distillation tower is connected with a second condenser and a second reflux tank, and the second reflux tank is connected with a second reflux pipeline and an n-hexane extraction pipeline. According to the utility model, a part of liquid-phase material is extracted from the side-line material at the lower part of the side-line extractive distillation tower I and enters the side-line extractive distillation tower II, so that the thermal load of the reboiler is reduced on the basis of improving the thermodynamic efficiency in the tower, and the aim of saving energy is fulfilled.

Description

Technical Field

[0001] The utility model relates to the technical field of chemical separation, in particular to a device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extraction and rectification. Background Art

[0002] Ethanol is a common solvent and organic raw material for chemical enterprises. Ethanol can be used to make acetic acid, beverages, flavors, dyes, fuels, etc. In medicine, ethanol with a volume fraction of 70-75% is also commonly used as a disinfectant, etc. It has a wide range of uses in national defense chemical industry, medical and health, food industry, and industrial and agricultural production. N-hexane is mainly used as a solvent, such as vegetable oil extraction solvent, propylene polymerization solvent, rubber and coating solvent, pigment diluent, and is also used for the extraction of various edible oils and fats such as soybeans, rice bran, cottonseed, and spices. In addition, n-hexane isomerization is one of the important processes for producing high-octane gasoline blending components. Cyclohexane is used as a general solvent, chromatographic analysis standard substance, and for organic synthesis. It can be used in resins, coatings, fats, paraffin oils, and can also prepare organic substances such as cyclohexanol and cyclohexanone. In industry, ethanol and propionic acid are often used as raw materials to synthesize ethyl propionate, with n-hexane and cyclohexane as water carriers. In view of the uses of ethanol, n-hexane, and cyclohexane, it is particularly important to separate and recover ethanol, n-hexane, and cyclohexane.

[0003] However, ethanol and n-hexane / cyclohexane can form binary azeotropic mixtures under normal pressure, which are difficult to separate by ordinary distillation. The common method for this binary azeotrope is extractive distillation, but the disadvantage of conventional extractive distillation is that the energy consumption is too high, which increases the operating cost of the distillation tower and violates the new concept of energy conservation and emission reduction in industry. Utility Model Content

[0004] The technical problem to be solved by the utility model is: to overcome the shortcomings of the prior art and provide a device for separating ethanol-n-hexane-cyclohexane multi-electrode by double side-line extraction and distillation, in which part of the liquid phase material is extracted from the lower part of the side-line extraction and distillation tower one through the side-line material and enters the side-line extraction and distillation tower two, thereby reducing the heat load of the reboiler on the basis of improving the thermodynamic efficiency in the tower, thereby achieving the purpose of energy saving.

[0005] The technical solution of the utility model is:

[0006] The invention discloses a device for separating ethanol-n-hexane-cyclohexane multi-phase azeotrope by double side-line extractive distillation, comprising a side-line extractive distillation tower 1, the side-line extractive distillation tower 1 is connected with a multi-phase azeotrope feed pipeline, an extractant feed pipeline 1 and a reboiler 1, the top of the side-line extractive distillation tower 1 is connected with a condenser 1 through a pipeline, the condenser 1 is connected with a reflux tank 1 through a pipeline, the reflux tank 1 is connected with a reflux pipeline 1 and a cyclohexane extraction pipeline, and the reflux pipeline 1 is connected with the reflux port of the side-line extractive distillation tower 1; the side-line extractive distillation tower 1 is connected with a feed port of a side-line extractive distillation tower 2 through a material extraction side line 1, the side-line extractive distillation tower 2 is connected with an extractant feed pipeline 2 and a reboiler 2, the top of the side-line extractive distillation tower 2 is connected with a condenser 2 through a pipeline, and the condenser 2 is connected with a reflux tank 2 through a pipeline. , reflux tank two is connected with reflux pipeline two and n-hexane extraction pipeline, reflux pipeline two is connected with the reflux port of side-line extractive distillation tower two; side-line extractive distillation tower two is connected with the feed port of solvent recovery tower through material extraction side line two, solvent recovery tower is connected with reboiler three, the top of solvent recovery tower is connected with condenser three through pipeline, condenser three is connected with reflux tank three through pipeline, reflux tank three is connected with reflux pipeline three and ethanol extraction pipeline, reflux pipeline three is connected with the reflux port of solvent recovery tower; the bottoms of side-line extractive distillation tower one, side-line extractive distillation tower two and solvent recovery tower are respectively connected with extractant extraction branch pipelines, each extractant extraction branch pipeline is connected with extractant extraction main pipeline, and extractant extraction main pipeline is respectively connected with extractant feed pipeline one and extractant feed pipeline two.

[0007] Preferably, a condenser 4 is connected to the extractant extraction main pipeline.

[0008] Preferably, the multi-element azeotrope feed pipeline is connected to the middle and lower part of the side-line extractive distillation tower, the extractant feed pipeline is connected to the upper part of the side-line extractive distillation tower, and the material extraction side line is connected to the lower part of the side-line extractive distillation tower.

[0009] Preferably, the material extraction side line 1 is connected to the middle and lower part of the side line extractive distillation tower 2, the extractant feed pipeline 2 is connected to the upper part of the side line extractive distillation tower 2, and the material extraction side line 2 is connected to the lower part of the side line extractive distillation tower 2.

[0010] Preferably, the material extraction side line 2 is connected to the middle of the solvent recovery tower.

[0011] Preferably, the number of plates of the side-line extractive distillation tower 1 is 50-60, and the number of plates of the side-line extractive distillation tower 2 is 45-55.

[0012] Preferably, the multi-element azeotrope feed pipeline is connected to the 30-40 tower plate of the side-line extractive distillation tower one, the extractant feed pipeline one is connected to the 5-10 tower plate of the side-line extractive distillation tower one, and the material extraction side line one is connected to the 43-55 tower plate of the side-line extractive distillation tower one; the material extraction side line one is connected to the 22-35 tower plate of the side-line extractive distillation tower two, the extractant feed pipeline two is connected to the 5-10 tower plate of the side-line extractive distillation tower two, and the material extraction side line two is connected to the 40-50 tower plate of the side-line extractive distillation tower two.

[0013] Preferably, the number of plates of the solvent recovery tower is 20-30, and the second material extraction side line is connected to the 8th to 18th plate of the solvent recovery tower.

[0014] Preferably, the reflux pipeline 1, the material extraction side line 1, the reflux pipeline 2, the material extraction side line 2, the reflux pipeline 3 and the extractant extraction main pipeline are respectively provided with pumps.

[0015] Preferably, the extractant used in the extractant feed pipeline 1 is butyl butyrate.

[0016] On the other hand, the utility model provides a method for extracting and distilling an ethanol-n-hexane-cyclohexane mixture using the above-mentioned device, comprising the following steps:

[0017] S1 ethanol-n-hexane-cyclohexane multi-element azeotrope is fed from the middle and lower part of the side-line extractive distillation tower one, and the extractant is fed from the upper part of the side-line extractive distillation tower one. The material at the top of the side-line extractive distillation tower one is condensed in a condenser one and stored in a reflux tank one, and a part of it is extracted as a cyclohexane product, and the other part is refluxed to the side-line extractive distillation tower one;

[0018] S2: the liquid material extracted from the side line at the lower part of the side line extractive distillation tower enters from the middle and lower part of the side line extractive distillation tower 2, and the extractant is fed from the upper part of the side line extractive distillation tower 2. The material at the top of the side line extractive distillation tower 2 is condensed by the condenser 2 and stored in the reflux tank 2, and a part of it is extracted as the n-hexane product, and the other part is refluxed to the side line extractive distillation tower 2;

[0019] S3: The liquid material extracted from the side line of the lower part of the side line extractive distillation tower 2 enters the middle part of the solvent recovery tower. After the material at the top of the solvent recovery tower is condensed by the condenser 3 and stored in the reflux tank 3, a part of it is extracted as the ethanol product, and the other part is refluxed to the solvent recovery tower;

[0020] The bottom of S4 side-line extraction distillation tower 1, side-line extraction distillation tower 2 and solvent recovery tower are high-purity extractants, which are mixed and condensed in condenser 4 and then recycled.

[0021] Preferably, the pressure of the side-line extractive distillation tower 1, the side-line extractive distillation tower 2 and the solvent recovery tower is 0.5-2 atm, and the reflux ratio is 0.8-8.5.

[0022] Preferably, the top temperature of the side-line extractive distillation tower 1 is 78-85°C, and the bottom temperature is 120-128°C; the top temperature of the side-line extractive distillation tower 2 is 68-82°C, and the bottom temperature is 140-148°C; the top temperature of the solvent recovery tower is 72-80°C, and the bottom temperature is 165-173°C.

[0023] Compared with the prior art, the utility model has the following beneficial effects:

[0024] On the basis of conventional separation sequence, the utility model extracts part of liquid phase material from the lower part of side line extraction distillation tower one through side line material and enters side line extraction distillation tower two, thereby reducing the heat load of the reboiler on the basis of improving the thermodynamic efficiency in the tower and achieving the purpose of energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The utility model is a schematic diagram of the structure of a device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extraction and distillation.

[0026] Figure 2 It is a schematic diagram of the structure of a conventional device for separating ethanol-n-hexane-cyclohexane multi-phase azeotrope by extractive distillation.

[0027] In the figure, 1, side line extractive distillation tower 1; 101, extractant feed pipeline 1; 102, reboiler 1; 103, condenser 1; 104, reflux tank 1; 105, reflux pipeline 1; 106, material extraction side line 1; 2, side line extractive distillation tower 2; 201, extractant feed pipeline 2; 202, reboiler 2; 203, condenser 2; 204, reflux tank 2; 205, reflux pipeline 2; 206, material extraction side line 2; 3, multi-component azeotrope feed pipeline; 4, cyclohexane extraction pipeline; 5, n-hexane extraction pipeline; 6, solvent recovery tower; 601, reboiler 3; 602, condenser 3; 603, reflux tank 3; 604, reflux pipeline 3; 7, Ethanol production pipeline; 8. Extraction agent production branch pipeline; 9. Extraction agent production main pipeline; 10. Condenser four; 11. Extraction distillation tower one; 1101. Extraction agent feed pipeline three; 1102. Reboiler four; 1103. Condenser five; 1104. Reflux tank four; 1105. Reflux pipeline four; 12. Extraction distillation tower two; 1201. Extraction agent feed pipeline four; 1202. Reboiler five; 1203. Condenser six; 1204. Reflux tank five; 1205. Reflux pipeline five; 1301. Reboiler six; 1302. Condenser seven; 1303. Reflux tank six; 1304. Reflux pipeline six; 1305. Extraction agent production pipeline; 14. Condenser eight. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0029] like Figure 1 As shown, the device for separating ethanol-n-hexane-cyclohexane multi-phase azeotrope by double side-line extractive distillation in the following embodiments comprises a side-line extractive distillation tower 1, the side-line extractive distillation tower 1 is connected with a multi-phase azeotrope feed pipeline 3, an extractant feed pipeline 101 and a reboiler 102, and the extractant feed pipeline 101 uses butyl butyrate as the extractant; the top of the side-line extractive distillation tower 1 is connected with a condenser 103 through a pipeline, and the condenser 103 is connected with a reflux tank 104 through a pipeline. , the reflux tank 104 is connected to a reflux pipeline 105 and a cyclohexane extraction pipeline 4, the reflux pipeline 105 is connected to the reflux port of the side-line extractive distillation tower 1; the side-line extractive distillation tower 1 is connected to the feed port of the side-line extractive distillation tower 2 through a material extraction side line 106, the side-line extractive distillation tower 2 is connected to an extractant feed pipeline 201 and a reboiler 202, the top of the side-line extractive distillation tower 2 is connected to a condenser 203 through a pipeline, and the condenser 203 is connected to a reflux port through a pipeline. The reflux tank 204 is connected to a reflux pipeline 205 and a n-hexane extraction pipeline 5, and the reflux pipeline 205 is connected to the reflux port of the side-line extractive distillation tower 2; the side-line extractive distillation tower 2 is connected to the feed port of the solvent recovery tower 6 through the material extraction side line 206, and the solvent recovery tower 6 is connected to a reboiler 3 601, and the top of the solvent recovery tower 6 is connected to a condenser 3 602 through a pipeline, and the condenser 3 602 is connected to a reflux tank 3 603 through a pipeline, and the reflux tank 3 603 is connected to It is connected to a reflux pipeline three 604 and an ethanol extraction pipeline 7, and the reflux pipeline three 604 is connected to the reflux port of the solvent recovery tower 6; the bottoms of the side-line extractive distillation tower one 1, the side-line extractive distillation tower two 2 and the solvent recovery tower 6 are respectively connected to extractant extraction branch pipelines 8, each extractant extraction branch pipeline 8 is connected to an extractant extraction main pipeline 9, and the extractant extraction main pipeline 9 is respectively connected to an extractant feed pipeline one 101 and an extractant feed pipeline two 201; a condenser four 10 is connected to the extractant extraction main pipeline 9.

[0030] Among them, pumps are respectively provided on the reflux pipeline 1 105, the material extraction side line 1 106, the reflux pipeline 2 205, the material extraction side line 2 206, the reflux pipeline 3 604 and the extractant extraction main pipeline 9.

[0031] like Figure 2As shown, the following comparative example adopts a conventional extractive distillation device for separating ethanol-n-hexane-cyclohexane multi-electrode, including an extractive distillation tower 11, the extractive distillation tower 11 is connected to a multi-electrode feed pipeline 3, an extractant feed pipeline 3 1101 and a reboiler 4 1102, the top of the extractive distillation tower 11 is connected to a condenser 5 1103 through a pipeline, the condenser 5 1103 is connected to a reflux tank 4 1104 through a pipeline, and the reflux tank 4 1104 is connected to the top of the extractive distillation tower 11. 04 is connected to a reflux pipeline four 1105 and a cyclohexane extraction pipeline 4, and the reflux pipeline four 1105 is connected to the reflux port of the extractive distillation tower one 11; the bottom of the extractive distillation tower one 11 is connected to the extractive distillation tower two 12 through a discharge pipeline, and the extractive distillation tower two 12 is connected to the extractant feed pipeline four 1201 and the reboiler five 1202, and the top of the extractive distillation tower two 12 is connected to the condenser six 1203 through a pipeline, and the condenser six 1203 is connected through a pipeline There is a reflux tank 5 1204, the reflux tank 5 1204 is connected to a reflux pipeline 5 1205 and a n-hexane extraction pipeline 5, and the reflux pipeline 5 1205 is connected to the reflux port of the extractive distillation tower 2 12; the bottom of the extractive distillation tower 2 12 is connected to the feed port of the solvent recovery tower 6 through a discharge pipeline, the solvent recovery tower 6 is connected to a reboiler 6 1301, and the top of the solvent recovery tower 6 is connected to a condenser 7 1302 through a pipeline, and the condenser 7 1302 is connected to the solvent recovery tower 6 through a pipeline. A reflux tank six 1303 is connected, the reflux tank six 1303 is connected to a reflux pipeline six 1304 and an ethanol production pipeline 7, the reflux pipeline six 1304 is connected to the reflux port of a solvent recovery tower 6, the bottom of the solvent recovery tower 6 is connected to an extractant production pipeline 1305, the extractant production pipeline 1305 is connected to an extractant feed pipeline three 1101 and an extractant feed pipeline four 1201, and the extractant production pipeline 1305 is connected to a condenser eight 14.

[0032] Example 1

[0033] In the device for separating ethanol-n-hexane-cyclohexane multi-phase azeotrope by double side-line extraction and distillation of this embodiment, the side-line extraction and distillation tower 1 has 55 plates, the side-line extraction and distillation tower 2 has 50 plates, and the solvent recovery tower 6 has 22 plates. The process of extracting and distilling ethanol-n-hexane-cyclohexane multi-phase azeotrope by using the device is as follows:

[0034] S1 is a polyazeotropic mixture of ethanol, normal hexane and cyclohexane (molar ratio of 0.3:0.5:0.2) with a flow rate of 100 kmol / h, which is fed to the 35th plate of the side-line extractive distillation tower-1, and an extractant with a flow rate of 200 kmol / h is fed to the 7th plate of the side-line extractive distillation tower-1. The operation is carried out at a pressure of 1 atm, a reflux ratio of 0.99, a top temperature of 80.7°C, and a bottom temperature of 125°C. After the material at the top of the tower is condensed by a condenser-103 and stored in a reflux tank-104, a part of it is produced as a cyclohexane product, and the other part is refluxed to the side-line extractive distillation tower-1, wherein the molar fraction of the cyclohexane product is greater than 0.999%, and the bottom of the tower is an extractant with a molar fraction greater than 0.9999%.

[0035] The S2 side line material is produced from the 48th tower plate of the side line extractive distillation tower 1, and enters from the 23rd tower plate of the side line extractive distillation tower 2. The extractant with a flow rate of 150 kmol / h is fed to the 6th tower plate of the side line extractive distillation tower 2. The operation is carried out at a pressure of 1 atm, a reflux ratio of 5.2, a top temperature of 70°C, and a bottom temperature of 145°C. After the material at the top of the tower is condensed by the condenser 203 and stored in the reflux tank 204, a part of it is produced as the n-hexane product, and the other part is refluxed to the side line extractive distillation tower 2, wherein the molar fraction of the n-hexane product is greater than 0.999%, and the bottom of the tower is the extractant with a molar fraction greater than 0.9999%.

[0036] The S3 side line material is extracted from the 44th tower plate of the side line extraction distillation tower 2, and enters from the 9th tower plate of the solvent recovery tower 6. It is operated at a pressure of 1 atm, with a reflux ratio of 1.2, a top temperature of 75°C, and a bottom temperature of 167°C. After the material at the top of the tower is condensed by the condenser 602 and stored in the reflux tank 603, a part of it is extracted as an ethanol product, and the other part is refluxed to the solvent recovery tower 6, wherein the molar fraction of the ethanol product is greater than 0.999%, and the bottom of the tower is an extractant with a molar fraction greater than 0.9999%.

[0037] The extractants from the side-line extractive distillation tower 1, the side-line extractive distillation tower 2 and the bottom of the solvent recovery tower 6 are collected in the extractant extraction main pipeline 9, and then condensed in the condenser 4 10 and circulated to the side-line extractive distillation tower 1 and the side-line extractive distillation tower 2 for use.

[0038] Some of the extractant will be lost during the operation of S5, so a small amount of extractant needs to be added during the process.

[0039] Comparative Example 1

[0040] In the device for extractive distillation separation of ethanol-n-hexane-cyclohexane multi-aqueous azeotrope of Comparative Example 1, the extractive distillation tower 11 has 55 plates, the extractive distillation tower 2 12 has 50 plates, and the solvent recovery tower 6 has 22 plates. The process of separating ethanol-n-hexane-cyclohexane multi-aqueous azeotrope using the device is as follows:

[0041] S1 is a polyazeotropic mixture of ethanol, normal hexane and cyclohexane (molar ratio of 0.3:0.5:0.2) with a flow rate of 100 kmol / h. It is fed to the 35th plate of the extractive distillation tower-11, and the extractant with a flow rate of 200 kmol / h is fed to the 7th plate of the extractive distillation tower-11. The operation is carried out at a pressure of 1 atm, with a reflux ratio of 0.99, a top temperature of 80.7°C, and a bottom temperature of 125°C. After the material at the top of the tower is condensed by the condenser five 1103 and stored in the reflux tank four 1104, a part of it is produced as the cyclohexane product, and the other part is refluxed to the extractive distillation tower-11, wherein the molar fraction of the cyclohexane product is greater than 0.999%.

[0042] The bottom material of S2 extractive distillation tower 11 enters extractive distillation tower 2 12 from the 23rd tower plate, and the extractant with a flow rate of 150 kmol / h is fed to the 6th tower plate of extractive distillation tower 2 12. It is operated at a pressure of 1 atm, with a reflux ratio of 5.2, a top temperature of 70°C, and a bottom temperature of 145°C. After the material at the top of the tower is condensed by condenser 6 1203 and stored in reflux tank 5 1204, a part of it is produced as n-hexane product, and the other part is refluxed to the extractive distillation tower 2 12, and the molar fraction of the n-hexane product is greater than 0.999%.

[0043] The bottom material of S3 extractive distillation tower 2 12 enters from the 15th tower plate of solvent recovery tower 6, and is operated at a pressure of 1 atm, with a reflux ratio of 1.8, a tower top temperature of 75°C, and a tower bottom temperature of 167°C; after the top material is condensed by condenser 7 1302 and stored in reflux tank 6 1303, a part of it is extracted as ethanol product, and the other part is refluxed to solvent recovery tower 6, and the molar fraction of ethanol product is greater than 0.999%.

[0044] The bottom of the S4 solvent recovery tower 6 contains an extractant with a molar fraction greater than 0.9999%, which is condensed in the condenser eight 14 and then returned to the extractive distillation tower one 11 and the extractive distillation tower two 12 for recycling as an extractant.

[0045] Some of the extractant will be lost during the operation of S5, so a small amount of extractant needs to be added during the process.

[0046] When the ethanol-n-hexane-cyclohexane multi-element azeotrope is separated using the apparatus of Example 1 and Comparative Example 1, the energy consumption comparison is shown in Table 1:

[0047] Table 1 Comparison of energy consumption when separating ethanol-n-hexane-cyclohexane multi-element azeotrope between Example 1 and Comparative Example 1

[0048]

[0049] Example 2

[0050] In the device for separating ethanol-n-hexane-cyclohexane multi-phase azeotrope by double side-line extraction and distillation of this embodiment, the side-line extraction and distillation tower 1 has 57 plates, the side-line extraction and distillation tower 2 has 52 plates, and the solvent recovery tower 6 has 20 plates. The process of extracting and distilling ethanol-n-hexane-cyclohexane multi-phase azeotrope by using the device is as follows:

[0051] S1 is a polyazeotropic mixture of ethanol, normal hexane and cyclohexane (molar ratio of 0.4:0.3:0.3) with a flow rate of 100 kmol / h, which is fed to the 36th plate of the side-line extractive distillation tower-1, and an extractant with a flow rate of 195 kmol / h is fed to the 8th plate of the side-line extractive distillation tower-1. The operation is carried out at a pressure of 1 atm, a reflux ratio of 0.9, a top temperature of 78°C, and a bottom temperature of 120°C. After the material at the top of the tower is condensed in a condenser-103 and stored in a reflux tank-104, a part of it is produced as a cyclohexane product, and the other part is refluxed to the side-line extractive distillation tower-1, wherein the molar fraction of the cyclohexane product is greater than 0.999%, and the bottom of the tower is an extractant with a molar fraction greater than 0.9999%.

[0052] The S2 side line material is produced from the 50th tower plate of the side line extractive distillation tower 1, and enters from the 25th tower plate of the side line extractive distillation tower 2. The extractant with a flow rate of 140 kmol / h is fed to the 7th tower plate of the side line extractive distillation tower 2. The operation is carried out at a pressure of 1 atm, with a reflux ratio of 3.98, a top temperature of 68°C, and a bottom temperature of 140°C. After the material at the top of the tower is condensed by the condenser 203 and stored in the reflux tank 204, a part of it is produced as the n-hexane product, and the other part is refluxed to the side line extractive distillation tower 2, wherein the molar fraction of the n-hexane product is greater than 0.999%, and the bottom of the tower is the extractant with a molar fraction greater than 0.9999%.

[0053] The S3 side line material is extracted from the 45th tower plate of the side line extraction distillation tower 2, and enters from the 9th tower plate of the solvent recovery tower 6. It is operated at a pressure of 1 atm, with a reflux ratio of 1.39, a top temperature of 72°C, and a bottom temperature of 165°C. After the material at the top of the tower is condensed by the condenser 602 and stored in the reflux tank 603, a part of it is extracted as an ethanol product, and the other part is refluxed to the solvent recovery tower 6, wherein the molar fraction of the ethanol product is greater than 0.999%, and the bottom of the tower is an extractant with a molar fraction greater than 0.9999%.

[0054] The extractants from the side-line extractive distillation tower 1, the side-line extractive distillation tower 2 and the bottom of the solvent recovery tower 6 are collected in the extractant extraction main pipeline 9, and then condensed in the condenser 4 10 and circulated to the side-line extractive distillation tower 1 and the side-line extractive distillation tower 2 for use.

[0055] Some of the extractant will be lost during the operation of S5, so a small amount of extractant needs to be added during the process.

[0056] Comparative Example 2

[0057] In the device for extractive distillation separation of ethanol-n-hexane-cyclohexane multi-aqueous azeotrope of Comparative Example 2, the extractive distillation tower 11 has 57 plates, the extractive distillation tower 2 12 has 52 plates, and the solvent recovery tower 6 has 20 plates. The process of separating ethanol-n-hexane-cyclohexane multi-aqueous azeotrope using the device is as follows:

[0058] S1 is a polyazeotropic mixture of ethanol, normal hexane and cyclohexane (molar ratio of 0.4:0.3:0.3) with a flow rate of 100 kmol / h. It is fed to the 36th plate of the extractive distillation tower-11, and the extractant with a flow rate of 195 kmol / h is fed to the 8th plate of the extractive distillation tower-11. The operation is carried out at a pressure of 1 atm, a reflux ratio of 0.9, a top temperature of 78°C, and a bottom temperature of 120°C. After the material at the top of the tower is condensed by the condenser five 1103 and stored in the reflux tank four 1104, a part of it is produced as the cyclohexane product, and the other part is refluxed to the extractive distillation tower-11, wherein the molar fraction of the cyclohexane product is greater than 0.999%.

[0059] The bottom material of S2 extractive distillation tower 11 enters extractive distillation tower 2 12 from the 25th tower plate, and the extractant with a flow rate of 140 kmol / h is fed to the 7th tower plate of extractive distillation tower 2 12. It is operated at a pressure of 1 atm, with a reflux ratio of 3.98, a top temperature of 68°C, and a bottom temperature of 140°C. After the material at the top of the tower is condensed by condenser 6 1203 and stored in reflux tank 5 1204, a part of it is produced as n-hexane product, and the other part is refluxed to the extractive distillation tower 2 12, and the molar fraction of the n-hexane product is greater than 0.999%.

[0060] The bottom material of S3 extractive distillation tower 2 12 enters from the 9th tower plate of solvent recovery tower 6 and is operated at a pressure of 1 atm, with a reflux ratio of 1.39, a tower top temperature of 72°C, and a tower bottom temperature of 165°C. After the top material is condensed by condenser 7 1302 and stored in reflux tank 6 1303, a part of it is extracted as ethanol product and the other part is refluxed to solvent recovery tower 6, and the molar fraction of ethanol product is greater than 0.999%.

[0061] The bottom of the S4 solvent recovery tower 6 contains an extractant with a molar fraction greater than 0.9999%, which is condensed in the condenser eight 14 and then returned to the extractive distillation tower one 11 and the extractive distillation tower two 12 for recycling as an extractant.

[0062] Some of the extractant will be lost during the operation of S5, so a small amount of extractant needs to be added during the process.

[0063] When the apparatus of Example 2 and Comparative Example 2 are used to separate ethanol-n-hexane-cyclohexane polyhydric azeotrope, the energy consumption comparison is shown in Table 2:

[0064] Table 2 Comparison of energy consumption when separating ethanol-n-hexane-cyclohexane multi-element azeotrope between Example 2 and Comparative Example 2

[0065]

[0066] Example 3

[0067] In the device for separating ethanol-n-hexane-cyclohexane multi-phase azeotrope by double side-line extraction and distillation of this embodiment, the side-line extraction and distillation tower 1 has 53 plates, the side-line extraction and distillation tower 2 has 48 plates, and the solvent recovery tower 6 has 20 plates. The process of extracting and distilling ethanol-n-hexane-cyclohexane multi-phase azeotrope by using the device is as follows:

[0068] S1 is a polyazeotropic mixture of ethanol-n-hexane-cyclohexane (molar ratio of 0.5:0.3:0.2) with a flow rate of 100 kmol / h, which is fed to the 34th plate of the side-line extractive distillation tower-1, and an extractant with a flow rate of 175 kmol / h is fed to the 5th plate of the side-line extractive distillation tower-1. The operation is carried out at a pressure of 1 atm, a reflux ratio of 1.02, a top temperature of 85°C, and a bottom temperature of 128°C. After the material at the top of the tower is condensed by a condenser-103 and stored in a reflux tank-104, a part of it is produced as a cyclohexane product, and the other part is refluxed to the side-line extractive distillation tower-1, wherein the molar fraction of the cyclohexane product is greater than 0.999%, and the bottom of the tower is an extractant with a molar fraction greater than 0.9999%.

[0069] The S2 side line material is produced from the 44th tower plate of the side line extractive distillation tower 1, and enters from the 26th tower plate of the side line extractive distillation tower 2. The extractant with a flow rate of 135 kmol / h is fed to the 9th tower plate of the side line extractive distillation tower 2. The operation is carried out at a pressure of 1 atm, a reflux ratio of 4.55, a top temperature of 82°C, and a bottom temperature of 148°C. After the material at the top of the tower is condensed by the condenser 203 and stored in the reflux tank 204, a part of it is produced as the n-hexane product, and the other part is refluxed to the side line extractive distillation tower 2, wherein the molar fraction of the n-hexane product is greater than 0.999%, and the bottom of the tower is the extractant with a molar fraction greater than 0.9999%.

[0070] The S3 side line material is extracted from the 43rd tower plate of the side line extraction distillation tower 2, and enters from the 10th tower plate of the solvent recovery tower 6. It is operated at a pressure of 1 atm, with a reflux ratio of 1.55, a top temperature of 80°C, and a bottom temperature of 173°C. After the material at the top of the tower is condensed by the condenser 602 and stored in the reflux tank 603, a part of it is extracted as an ethanol product, and the other part is refluxed to the solvent recovery tower 6, wherein the molar fraction of the ethanol product is greater than 0.999%, and the bottom of the tower is an extractant with a molar fraction greater than 0.9999%.

[0071] The extractants from the side-line extractive distillation tower 1, the side-line extractive distillation tower 2 and the bottom of the solvent recovery tower 6 are collected in the extractant extraction main pipeline 9, and then condensed in the condenser 4 10 and circulated to the side-line extractive distillation tower 1 and the side-line extractive distillation tower 2 for use.

[0072] Some of the extractant will be lost during the operation of S5, so a small amount of extractant needs to be added during the process.

[0073] Comparative Example 3

[0074] In the device for extractive distillation separation of ethanol-n-hexane-cyclohexane multi-aqueous azeotrope of Comparative Example 3, the extractive distillation tower 11 has 53 plates, the extractive distillation tower 2 12 has 48 plates, and the solvent recovery tower 6 has 18 plates. The process of separating ethanol-n-hexane-cyclohexane multi-aqueous azeotrope using the device is as follows:

[0075] S1 is a polyazeotropic mixture of ethanol, normal hexane and cyclohexane (molar ratio of 0.5:0.3:0.2) with a flow rate of 100 kmol / h, which is fed to the 34th plate of the extractive distillation tower-11, and an extractant with a flow rate of 175 kmol / h is fed to the 5th plate of the extractive distillation tower-11. The operation is carried out at a pressure of 1 atm, with a reflux ratio of 1.02, a top temperature of 85°C, and a bottom temperature of 128°C. After the material at the top of the tower is condensed in a condenser five 1103 and stored in a reflux tank four 1104, a part of it is produced as a cyclohexane product, and the other part is refluxed to the extractive distillation tower-11, wherein the molar fraction of the cyclohexane product is greater than 0.999%.

[0076] The bottom material of S2 extractive distillation tower 11 enters extractive distillation tower 2 12 from the 26th tower plate, and the extractant with a flow rate of 135 kmol / h is fed to the 9th tower plate of extractive distillation tower 2 12. It is operated at a pressure of 1 atm, with a reflux ratio of 4.55, a tower top temperature of 82°C, and a tower bottom temperature of 148°C. After the material at the top of the tower is condensed by condenser 6 1203 and stored in reflux tank 5 1204, a part of it is produced as n-hexane product, and the other part is refluxed to the extractive distillation tower 2 12, and the molar fraction of the n-hexane product is greater than 0.999%.

[0077] The bottom material of S3 extractive distillation tower 2 12 enters from the 10th tower plate of solvent recovery tower 6, and is operated at a pressure of 1 atm, with a reflux ratio of 1.55, a tower top temperature of 80°C, and a tower bottom temperature of 173°C; after the top material is condensed by condenser 7 1302 and stored in reflux tank 6 1303, a part of it is extracted as ethanol product, and the other part is refluxed to solvent recovery tower 6, and the molar fraction of ethanol product is greater than 0.999%.

[0078] The bottom of the S4 solvent recovery tower 6 contains an extractant with a molar fraction greater than 0.9999%, which is condensed in the condenser eight 14 and then returned to the extractive distillation tower one 11 and the extractive distillation tower two 12 for recycling as an extractant.

[0079] Some of the extractant will be lost during the operation of S5, so a small amount of extractant needs to be added during the process.

[0080] When the apparatus of Example 3 and Comparative Example 3 are used to separate ethanol-n-hexane-cyclohexane polyhydric azeotrope, the energy consumption comparison is shown in Table 3:

[0081] Table 3 Comparison of energy consumption when separating ethanol-n-hexane-cyclohexane multi-element azeotrope between Example 3 and Comparative Example 3

[0082]

[0083] By comparing Examples 1-3 with Comparative Examples 1-3, it can be seen that the utility model reduces the degree of remixing in the tower through side line extraction, improves the thermodynamic efficiency of the distillation tower, makes the reboiler energy consumption low, and the heat load at the bottom of the tower is small, thereby achieving energy saving and consumption reduction. In addition, when the method of the utility model is used to separate ethanol-n-hexane-cyclohexane multi-element azeotrope, the extractant can be directly recycled, which reduces costs and also reduces environmental pollution; and the purity of the separated ethanol, n-hexane and cyclohexane products is greater than 0.999%, and the purity of the recovered extractant is greater than 0.9999%, which has the advantages of no need to introduce an azeotropic agent, high product purity, simple operation, and energy saving.

Claims

1. A device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extraction and distillation, characterized in that: The invention comprises a side-line extractive distillation tower (1), wherein the side-line extractive distillation tower (1) is connected to a multi-element azeotropic feed pipeline (3), an extractant feed pipeline (101) and a reboiler (102), wherein the top of the side-line extractive distillation tower (1) is connected to a condenser (103) via a pipeline, wherein the condenser (103) is connected to a reflux tank (104) via a pipeline, wherein the reflux tank (104) is connected to a reflux pipeline (105) and a cyclohexane extraction pipeline (4), wherein the reflux pipeline (105) is connected to the side-line extractive distillation tower (1). The reflux port of the distillation tower (1) is connected; the side-line extraction distillation tower (1) is connected to the feed port of the side-line extraction distillation tower (2) through the material extraction side line (106); the side-line extraction distillation tower (2) is connected to the extractant feed pipeline (201) and the reboiler (202); the top of the side-line extraction distillation tower (2) is connected to the condenser (203) through a pipeline; the condenser (203) is connected to the reflux tank (204) through a pipeline; the reflux tank (204) is connected to the reflux pipeline (201) 205) and the n-hexane extraction pipeline (5), the reflux pipeline 2 (205) is connected to the reflux port of the side line extraction distillation tower 2 (2); the side line extraction distillation tower 2 (2) is connected to the feed port of the solvent recovery tower (6) through the material extraction side line 2 (206), the solvent recovery tower (6) is connected to the reboiler 3 (601), the top of the solvent recovery tower (6) is connected to the condenser 3 (602) through a pipeline, the condenser 3 (602) is connected to the reflux tank 3 (603) through a pipeline, and the reflux tank 3 (603) is connected to A reflux pipeline three (604) and an ethanol extraction pipeline (7) are connected, and the reflux pipeline three (604) is connected to the reflux port of the solvent recovery tower (6); the bottoms of the side line extraction distillation tower one (1), the side line extraction distillation tower two (2) and the solvent recovery tower (6) are respectively connected to extraction agent extraction branch pipelines (8), and each extraction agent extraction branch pipeline (8) is connected to an extraction agent extraction main pipeline (9), and the extraction agent extraction main pipeline (9) is respectively connected to an extraction agent feed pipeline one (101) and an extraction agent feed pipeline two (201).

2. The device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extractive distillation as claimed in claim 1, characterized in that: The extractant extraction main pipeline (9) is connected to a condenser four (10).

3. The device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extractive distillation as claimed in claim 1, characterized in that: The multi-element azeotrope feed pipeline (3) is connected to the middle and lower part of the side-line extractive distillation tower (1), the extractant feed pipeline (101) is connected to the upper part of the side-line extractive distillation tower (1), and the material extraction side line (106) is connected to the lower part of the side-line extractive distillation tower (1).

4. The device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extractive distillation as claimed in claim 1, characterized in that: The material extraction side line 1 (106) is connected to the middle and lower part of the side line extraction distillation tower 2 (2), the extractant feeding pipeline 2 (201) is connected to the upper part of the side line extraction distillation tower 2 (2), and the material extraction side line 2 (206) is connected to the lower part of the side line extraction distillation tower 2 (2).

5. The device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extractive distillation as claimed in claim 1, characterized in that: The material extraction side line 2 (206) is connected to the middle of the solvent recovery tower (6).

6. The device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extractive distillation as claimed in claim 1, characterized in that: The number of plates of the side-line extractive distillation tower 1 (1) is 50-60, and the number of plates of the side-line extractive distillation tower 2 (2) is 45-55.

7. The device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extractive distillation as claimed in claim 6, characterized in that: The multi-element azeotrope feed pipeline (3) is connected to the 30-40th plate of the side-line extractive distillation tower (1), the extractant feed pipeline (101) is connected to the 5-10th plate of the side-line extractive distillation tower (1), and the material extraction side line (106) is connected to the 43-55th plate of the side-line extractive distillation tower (1); the material extraction side line (106) is connected to the 22-35th plate of the side-line extractive distillation tower (2), the extractant feed pipeline (201) is connected to the 5-10th plate of the side-line extractive distillation tower (2), and the material extraction side line (206) is connected to the 40-50th plate of the side-line extractive distillation tower (2).

8. The device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extractive distillation as claimed in claim 1, characterized in that: The number of plates of the solvent recovery tower (6) is 20-30, and the second material extraction side line (206) is connected to the 8th to 18th plate of the solvent recovery tower (6).

9. The device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extractive distillation as claimed in claim 1, characterized in that: Pumps are respectively provided on the reflux pipeline 1 (105), the material extraction side line 1 (106), the reflux pipeline 2 (205), the material extraction side line 2 (206), the reflux pipeline 3 (604) and the extractant extraction main pipeline (9).

10. The device for separating ethanol-n-hexane-cyclohexane multi-element azeotrope by double-side line extractive distillation according to claim 1, characterized in that: The extractant used in the extractant feed pipeline 1 (101) is butyl butyrate.

Images