Gas phase side-draw pressure swing rectification heat integration apparatus and method

Abstract

The application discloses a gas phase side line variable pressure rectification heat integration device and method, which realizes high-purity separation of butanone-isopropyl alcohol-n-heptane ternary azeotrope at lower energy consumption and equipment cost by using gas phase side line, heat integration and variable pressure rectification technology; the ternary azeotrope enters a medium-pressure rectification tower, and butanone products with a purity of 99.9% are separated at the bottom; overhead distillate and a gas phase side line stream enter a high-pressure rectification tower, and n-heptane products with a purity of 99.9% are obtained at the bottom; overhead distillate and a gas phase side line stream enter a low-pressure rectification tower, and isopropyl alcohol products with a purity of 99.9% are obtained at the bottom; overhead distillate is recycled to the medium-pressure rectification tower; heat integration is carried out between the medium-pressure rectification tower and the high-pressure rectification tower; compared with a conventional variable pressure rectification process, the process has the advantages of high separation efficiency, low energy consumption and equipment cost, and has strong competitiveness in industrial application.

Description

Technical Field

[0001] This invention relates to a gas-phase side-stream pressure swing distillation heat integration process for separating a ternary azeotropic system of butanone-isopropanol-n-heptane, belonging to the field of separation and purification in chemical industrial production. Background Technology

[0002] Butanone (MEK) is a widely used fine chemical product with excellent solubility and hydrophilic-lipophilic balance. It is a very important organic chemical raw material and an excellent industrial solvent, and is widely used in pharmaceutical, coating, and fine chemical industries as a solvent or reaction medium.

[0003] At normal pressure, the mixture of butanone, isopropanol, and n-heptane forms an azeotrope with the lowest boiling point, severely hindering separation. Furthermore, both butanone and isopropanol are polar and can form hydrogen bonds, exhibiting non-ideal behavior with the non-polar n-heptane in the liquid phase, further increasing the complexity of separation.

[0004] Patent (CN113788746A) discloses a method for separating a ternary azeotrope of butanone-isopropanol-n-heptane. This patent achieves the separation of the mixture through three-tower pressure swing distillation, but the high energy consumption hinders the practical application of this process.

[0005] Patent (CN107721820B) discloses a method for separating acetonitrile-methanol-benzene ternary azeotrope. This patent achieves the separation of the mixture through three-tower pressure swing distillation and integrates the heat between the towers, but does not introduce a side stream. This method still has considerable potential for energy saving. Summary of the Invention

[0006] To address the challenge of high energy consumption in the separation of the methyl ethyl ketone (MEK)-isopropanol-n-heptane ternary azeotropic system, a gas-phase side-stream pressure swing distillation process with integrated heat is proposed. This invention, based on a three-tower pressure swing distillation process, introduces a gas-phase side-stream between the three towers to reduce separation difficulty and improve energy utilization efficiency. Using a genetic algorithm to optimize design parameters with an annual total cost as the target, an optimized process flow is obtained. Furthermore, heat integration technology is introduced to further reduce process energy consumption. Compared with traditional pressure swing distillation schemes, this process can significantly reduce equipment investment costs and process energy consumption.

[0007] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a gas-phase side-stream pressure-swapping distillation heat integration device, comprising the following parts: The system comprises a medium-pressure distillation column T1, a high-pressure distillation column T2, a low-pressure distillation column T3, condensers C1 and C3, reflux tanks D1, D2, and D3, an auxiliary reboiler R1, a heat exchanger R2, a reboiler R3, a reboiler R4, a compressor B1, and a compressor B2. The auxiliary reboiler R1 is connected to the bottom of the medium-pressure distillation column T1. Reboilers R3 and R4 are connected to the bottoms of the high-pressure distillation column T2 and the low-pressure distillation column T3, respectively. Heat exchanger R2 is used to transfer the heat load from the reboiler at the bottom of the medium-pressure distillation column T1 to the heat load from the high-pressure distillation column T2. The top condenser integrates the cooling load for heat transfer. Condenser C1 and reflux tank D1 are connected sequentially to the top of medium-pressure distillation column T1 via pipelines. Reflux tank D2 is connected to the top of high-pressure distillation column T2 via pipelines. Condenser C3 and reflux tank D3 are connected sequentially to the top of low-pressure distillation column T3 via pipelines. The methyl ethyl ketone (MEK)-isopropanol (IOP)-n-heptane mixture collected from the side stream of medium-pressure distillation column T1 enters high-pressure distillation column T2 via compressor B1. The MEK-isopropanol-n-heptane mixture collected from the side stream of high-pressure distillation column T2 enters low-pressure distillation column T3 via compressor B2.

[0008] Furthermore, in the apparatus of the present invention, a pump P1 is installed on the pipeline connecting the reflux tank D1 to the top of the medium-pressure distillation column T1; a pump P3 is installed on the pipeline connecting the reflux tank D2 to the top of the high-pressure distillation column T2; and a pump P5 is installed on the pipeline connecting the reflux tank D3 to the top of the low-pressure distillation column T3.

[0009] Furthermore, in the apparatus of the present invention, a pump P2 is provided on the bottom pipeline 0106 of the medium-pressure distillation column T1; a pump P4 is provided on the bottom pipeline 0109 of the high-pressure distillation column T2; and a pump P6 is provided on the bottom pipeline 0111 of the low-pressure distillation column T3.

[0010] Furthermore, in the apparatus of the present invention, a compressor B1 is provided on the pipeline connecting the side line of the medium-pressure distillation column T1 to the high-pressure distillation column T2; and a compressor B2 is provided on the pipeline connecting the side line of the high-pressure distillation column T2 to the low-pressure distillation column T3.

[0011] Secondly, the present invention provides a method for separating a ternary azeotropic mixture of butanone-isopropanol-n-heptane using the above-mentioned vapor-phase side-stream pressure-swing distillation heat integration device, comprising the following steps: (1) The raw material mixture of butanone-isopropanol-n-heptane enters the medium-pressure distillation column T1 through pipeline 0101. A portion of the material at the bottom of the medium-pressure distillation column T1 enters the heat exchanger R2, and after vaporization, returns to the bottom of the medium-pressure distillation column T1. The butanone product is collected through pipeline 0106 via pump P2 at the bottom of the medium-pressure distillation column T1. The vapor at the top of the medium-pressure distillation column T1 is condensed by condenser C1 and enters the reflux tank D1. A portion of it is returned to the top of the medium-pressure distillation column T1 via pump P1, and a portion enters the stripping section of the high-pressure distillation column T2 through pipeline 0105. The vapor stream from the side of the medium-pressure distillation column T1 is compressed by compressor B1 and enters the rectification section of the high-pressure distillation column T2. (2) The overhead stream and side stream from the medium-pressure distillation column T1 are fed into the high-pressure distillation column T2. ​​A portion of the material at the bottom of the high-pressure distillation column T2 enters the reboiler R3, is vaporized, and returns to the bottom of the high-pressure distillation column T2. ​​The n-heptane product is collected through pipeline 0109 via pump P4 at the bottom of the high-pressure distillation column T2. ​​The overhead vapor is condensed through heat exchanger R2 and enters the reflux tank D2. A portion is returned to the top of the high-pressure distillation column T2 via pump P3, and a portion enters the stripping section of the low-pressure distillation column T3 via pipeline 0108. The vapor stream from the side stream of the high-pressure distillation column T2 is compressed by compressor B2 and enters the rectification section of the low-pressure distillation column T3. (3) The overhead stream and side stream from the high-pressure distillation column T2 are fed into the low-pressure distillation column T3. A portion of the material at the bottom of the low-pressure distillation column T3 enters the reboiler R4, is vaporized, and then returns to the bottom of the low-pressure distillation column T3. The isopropanol product is collected through pipeline 0111 via pump P6 at the bottom of the low-pressure distillation column T3. The overhead vapor is condensed by condenser C3 and enters the reflux tank D3. A portion of it is returned to the top of the low-pressure distillation column T3 via pump P5, and a portion is collected through pipeline 0110 and circulated to the medium-pressure distillation column T1. (4) After introducing two gas phase side lines, the genetic algorithm in the optimization toolbox 8.4 of MATLAB 2019b is used to obtain the optimal parameters with the minimum annual total cost as the objective function. Data transmission between MATLAB and Aspen Plus is realized through COM technology. The genetic algorithm forms a new excellent population through selection, crossover and mutation. This is the key to the genetic algorithm to achieve increasingly optimized results. (5) After obtaining the gas phase side-stream pressure-switching distillation process, the medium-pressure distillation column T1 and the high-pressure distillation column T2 are heat-integrated, that is, the top steam of the high-pressure distillation column T2 is used to heat part of the bottom liquid of the medium-pressure distillation column T1, and the two exchange heat on the heat exchanger R2 through pipelines 0102 and 0103.

[0012] Furthermore, in the method of this invention, the operating pressure of the medium-pressure distillation column T1 is 1.005 atm absolute pressure, with 48 theoretical plates, 25 feed plates, 15 recirculating feed plates, 6 side stream exit points, and 16 side stream exit points leading to the high-pressure distillation column T2. ​​The reflux ratio of the medium-pressure distillation column T1 is 4.31. The operating pressure of the high-pressure distillation column T2 is 3.483 atm absolute pressure, with 33 theoretical plates, 30 feed plates, 5 side stream exit points, and the side stream entering the low-pressure distillation column T2. Position 3 represents 3 plates. The reflux ratio of high-pressure distillation column T2 is 1.86. The operating pressure of low-pressure distillation column T3 is absolute pressure 0.325 atm, with 26 theoretical plates and 11 feed positions. The reflux ratio of low-pressure distillation column T3 is 0.57. The top temperature of medium-pressure distillation column T1 is 74.69℃ and the bottom temperature is 86.69℃. The top temperature of high-pressure distillation column T2 is 114.21℃ and the bottom temperature is 149.80℃. The top temperature of low-pressure distillation column T3 is 45.74℃ and the bottom temperature is 65.46℃.

[0013] Furthermore, in the method of the present invention, the mass fraction of methyl ethyl ketone (MEK) obtained from the bottom of the medium-pressure distillation column T1 reaches 99.9%, and the MEK recovery rate reaches 99.9%; the mass fraction of n-heptane obtained from the bottom of the high-pressure distillation column T2 reaches 99.9%, and the n-heptane recovery rate reaches 99.9%; and the mass fraction of isopropanol obtained from the bottom of the low-pressure distillation column T3 reaches 99.9%, and the isopropanol recovery rate reaches 99.9%.

[0014] The specific description of the gas-phase side-stream pressure swing distillation heat integration process of the present invention for separating the butanone-isopropanol-n-heptane ternary azeotropic system is as follows: A mixture of butanone, isopropanol, and n-heptane feedstock is pumped through pipe 0101 into a medium-pressure distillation column T1 with an absolute pressure of 1.005 atm and 48 trays. The feed point is on tray 25, and the side stream exits from tray 6. Butanone is collected from the bottom of column T1 via pipe 0106. The vapor at the top of column T1 is condensed by condenser C1 and enters reflux tank D1. Part of the condensate is returned to the top of column T1, and part enters a high-pressure distillation column T2 with an absolute pressure of 3.483 atm and 33 trays via pipe 0105. The feed point is tray 30, and the side stream exits from tray 16 of column T2 via pipe 0104. Heptane is collected from the bottom of the column via pipe 0109. The vapor from the top of the column is condensed by heat exchanger R2 and enters reflux tank D2. Part of the condensate is returned to the top of the high-pressure distillation column T2, and part of it enters the low-pressure distillation column T3 with an absolute pressure of 0.325 atm and 26 trays via pipe 0108. The feed tray is located at tray 11, and the side stream is collected through pipe 0107 and enters tray 3 of the low-pressure distillation column T3. Isopropanol is collected from the bottom of the low-pressure distillation column T3 via pipe 0111. The vapor from the top of the column enters reflux tank D3 after passing through condenser C3. Part of the condensate is returned to the top of the low-pressure distillation column T3, and part of it is returned to the 15 trays of the medium-pressure distillation column T1 via pipe 0110.

[0015] The present invention has the following beneficial effects: (1) The ternary azeotropic mixture of butanone-isopropanol-n-heptane was successfully separated, and three high-purity products were obtained, which solved the problem of difficult separation of butanone-isopropanol-n-heptane azeotropic mixture.

[0016] (2) The present invention utilizes the heat integration process of gas phase side-stream pressure-swapping distillation, which has the advantages of significantly reducing energy consumption and reducing equipment investment costs. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the separation of the butanone-isopropanol-n-heptane ternary azeotropic system using a gas-phase side-stream pressure swing distillation heat integration process.

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited to the drawings and embodiments.

[0019] In the diagram: T1 - Medium-pressure distillation column; T2 - High-pressure distillation column; T3 - Low-pressure distillation column; D1, D2, D3 - Reflux tanks; C1, C3 - Condensers; R1, R3, R4 - Reboilers; R2 - Heat exchanger; P1, P2, P3, P4, P5, P6 - Pumps; B1, B2 - Compressors; The numbers represent the pipelines. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Example 1

[0021] See appendix Figure 1 This invention provides an integrated heat recovery device for gas-phase side-stream pressure-swapping distillation, comprising an attached... Figure 1 As can be seen, the apparatus of the present invention includes a medium-pressure distillation column T1, a high-pressure distillation column T2, a low-pressure distillation column T3, a condenser C1, a condenser C2, a reflux tank D1, a reflux tank D2, a reflux tank D3, an auxiliary reboiler R1, a heat exchanger R2, a reboiler R3, a reboiler R4, a compressor B1, and a compressor B2; wherein the auxiliary reboiler R1 is connected to the bottom of the medium-pressure distillation column T1, and the reboilers R3 and R4 are respectively connected to the bottom of the high-pressure distillation column T2 and the low-pressure distillation column T3. The heat exchanger R2 is used to integrate the heat load of the reboiler at the bottom of the medium-pressure distillation column T1 with the cold load of the condenser at the top of the high-pressure distillation column T2. Condenser C1 and reflux tank D1 are connected in sequence to the top of medium-pressure distillation column T1 via pipelines. Pump P1 is installed on the pipeline connecting reflux tank D1 to the top of medium-pressure distillation column T1. Reflux tank D2 is connected in sequence to the top of high-pressure distillation column T2 via pipelines. Pump P3 is installed on the pipeline connecting reflux tank D2 to the top of high-pressure distillation column T2. ​​Condenser C3 and reflux tank D3 are connected in sequence to the top of low-pressure distillation column T3 via pipelines. Pump P5 is installed on the pipeline connecting reflux tank D3 to the top of low-pressure distillation column T3. A mixture of butanone, isopropanol, and n-heptane drawn from the side stream of the medium-pressure distillation column T1 enters the high-pressure distillation column T2. ​​Compressor B1 is installed on the pipeline connecting the side stream of the medium-pressure distillation column T1 and the high-pressure distillation column T2. ​​A mixture of butanone, isopropanol, and n-heptane drawn from the side stream of the high-pressure distillation column T2 enters the low-pressure distillation column T3. Compressor B2 is installed on the pipeline connecting the side stream of the high-pressure distillation column T2 and the low-pressure distillation column T3. Pump P2 is installed on the bottom pipeline 0106 of the medium-pressure distillation column T1, pump P4 is installed on the bottom pipeline 0109 of the high-pressure distillation column T2, and pump P6 is installed on the bottom pipeline 0111 of the low-pressure distillation column T3. Example 2

[0022] The method for separating a ternary azeotropic mixture of butanone-isopropanol-n-heptane using the gas-phase side-stream pressure swing distillation heat integration device described in Example 1 comprises the following steps: (1) The raw material mixture of butanone-isopropanol-n-heptane enters the medium-pressure distillation column T1 through pipeline 0101. A portion of the material at the bottom of the medium-pressure distillation column T1 enters the heat exchanger R2, and after vaporization, returns to the bottom of the medium-pressure distillation column T1. The butanone product is collected through pipeline 0106 via pump P2 at the bottom of the medium-pressure distillation column T1. The vapor at the top of the medium-pressure distillation column T1 is condensed by condenser C1 and enters the reflux tank D1. A portion of it is returned to the top of the medium-pressure distillation column T1 via pump P1, and a portion enters the stripping section of the high-pressure distillation column T2 through pipeline 0105. The vapor stream from the side of the medium-pressure distillation column T1 is compressed by compressor B1 and enters the rectification section of the high-pressure distillation column T2. (2) The overhead stream and side stream from the medium-pressure distillation column T1 are fed into the high-pressure distillation column T2. ​​A portion of the material at the bottom of the high-pressure distillation column T2 enters the reboiler R3, is vaporized, and returns to the bottom of the high-pressure distillation column T2. ​​The n-heptane product is collected through pipeline 0109 via pump P4 at the bottom of the high-pressure distillation column T2. ​​The overhead vapor is condensed through heat exchanger R2 and enters the reflux tank D2. A portion is returned to the top of the high-pressure distillation column T2 via pump P3, and a portion enters the stripping section of the low-pressure distillation column T3 via pipeline 0108. The vapor stream from the side stream of the high-pressure distillation column T2 is compressed by compressor B2 and enters the rectification section of the low-pressure distillation column T3. (3) The overhead stream and side stream from the high-pressure distillation column T2 are fed into the low-pressure distillation column T3. A portion of the material at the bottom of the low-pressure distillation column T3 enters the reboiler R4, is vaporized, and then returns to the bottom of the low-pressure distillation column T3. The isopropanol product is collected through pipeline 0111 via pump P6 at the bottom of the low-pressure distillation column T3. The overhead vapor is condensed by condenser C3 and enters the reflux tank D3. A portion of it is returned to the top of the low-pressure distillation column T3 via pump P5, and a portion is collected through pipeline 0110 and circulated to the medium-pressure distillation column T1. (4) After introducing two gas phase side lines, the genetic algorithm in the optimization toolbox 8.4 of MATLAB 2019b is used to obtain the optimal parameters with the minimum annual total cost as the objective function. Data transmission between MATLAB and Aspen Plus is realized through COM technology. The genetic algorithm forms a new excellent population through selection, crossover and mutation. This is the key to the genetic algorithm to achieve increasingly optimized results. (5) After obtaining the gas phase side-stream pressure-switching distillation process, the medium-pressure distillation column T1 and the high-pressure distillation column T2 are heat-integrated, that is, the top steam of the high-pressure distillation column T2 is used to heat part of the bottom liquid of the medium-pressure distillation column T1, and the two exchange heat on the heat exchanger R2 through pipelines 0102 and 0103.

[0023] In this embodiment, the feed flow rate is 1000 kg / h, the feed temperature is 25°C, and the feed composition is 80% (mass fraction) methyl ethyl ketone, 10% (mass fraction) n-heptane, and 10% (mass fraction) isopropanol. The medium-pressure distillation column T1 has a theoretical number of 48 plates and a pressure of 1.005 atm (absolute pressure). Feed is supplied from the 25th plate, with the recirculated feed from the 15th plate. The side stream exits from the 6th plate, and the side stream enters the high-pressure distillation column T2 at plate 16, with a reflux ratio of 4.31. The high-pressure distillation column T2 has a theoretical number of 33 plates and a pressure of 3.483 atm (absolute pressure). Feed is supplied from the 30th plate, with the side stream exiting from the 5th plate. The side stream enters the low-pressure distillation column T3 at plate 3, with a reflux ratio of 1.86. The low-pressure distillation column T3 has a theoretical number of 26 plates and a pressure of 0.325 atm (absolute pressure). Feed is supplied from the 11th plate, with a reflux ratio of 0.57. The parameters of the distillation columns are shown in Table 1.

[0024] Table 1. Information on Distillation Columns

[0025] After separation using the apparatus and method of this invention, the concentration of methyl ethyl ketone (MEK) was 99.9%, with a recovery rate of 99.9%; the concentration of n-heptane (NHK) was 99.9%, with a recovery rate of 99.9%; and the concentration of isopropanol (IOU) was 99.9%, with a recovery rate of 99.9%. Specific results are shown in Table 2.

[0026] Table 2 Logistics Information Table

[0027] To compare the energy consumption advantages of the gas-phase side-stream pressure swing distillation heat integration process, the energy consumption data of the traditional pressure swing distillation and the gas-phase side-stream pressure swing distillation heat integration process are listed in Table 3.

[0028] Table 3 Comparison of Energy Consumption Data

[0029] Table 4 shows a comparison of the total annual cost of the gas-phase side-stream pressure-swing heating integrated process and the conventional pressure-swing distillation process. The process in this application saves a significant amount of cost.

[0030] Table 4. Annual Total Expenses Comparison Table

[0031] Based on the embodiments of this invention, this invention adds two vapor side streams to the traditional pressure-swing distillation process: one from the medium-pressure distillation column T1 leading to the high-pressure distillation column T2, and the other from the high-pressure distillation column T2 leading to the low-pressure distillation column T3. Then, using a genetic algorithm to optimize the design parameters with the total annual cost as the target, the optimal process is obtained. Finally, the heat load of the reboiler at the bottom of the medium-pressure distillation column T1 and the cold load of the condenser at the top of the high-pressure distillation column T2 are integrated through heat exchanger R2, resulting in a significant reduction in energy consumption. This method solves the problems of high energy consumption and high equipment cost in current technologies and reduces the difficulty of product separation.

[0032] It should be further noted that the above embodiments are merely for understanding the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. Any obvious adjustments and modifications made to the technical solution of the present invention that fall within the inventive concept should also fall within the scope of protection of the present invention.

Claims

1. A gas-phase side-stream pressure-swapping distillation heat integration device, characterized in that, The device includes the following parts: The system comprises a medium-pressure distillation column T1, a high-pressure distillation column T2, a low-pressure distillation column T3, condensers C1 and C2, reflux tanks D1, D2, and D3, an auxiliary reboiler R1, a heat exchanger R2, a reboiler R3, a reboiler R4, a compressor B1, and a compressor B2. The auxiliary reboiler R1 is connected to the bottom of the medium-pressure distillation column T1. Reboilers R3 and R4 are connected to the bottoms of the high-pressure distillation column T2 and the low-pressure distillation column T3, respectively. Heat exchanger R2 is used to transfer the heat load from the reboiler at the bottom of the medium-pressure distillation column T1 to the cooling load at the top of the high-pressure distillation column T2. The condenser's cold load is integrated for heat transfer. Condenser C1 and reflux tank D1 are connected sequentially to the top of medium-pressure distillation column T1 via pipelines. Reflux tank D2 is connected to the top of high-pressure distillation column T2 via pipelines. Condenser C3 and reflux tank D3 are connected sequentially to the top of low-pressure distillation column T3 via pipelines. The methyl ethyl ketone (MEK)-isopropanol (IOP)-n-heptane mixture collected from the side stream of medium-pressure distillation column T1 enters high-pressure distillation column T2 via compressor B1. The methyl ethyl ketone (MEK)-isopropanol (IOP)-n-heptane mixture collected from the side stream of high-pressure distillation column T2 enters low-pressure distillation column T3 via compressor B2.

2. The integrated heat recovery device for vapor-phase side-stream pressure-swapping distillation according to claim 1, characterized in that: Pump P1 is installed on the pipeline connecting the reflux tank D1 to the top of the medium-pressure distillation column T1; pump P3 is installed on the pipeline connecting the reflux tank D2 to the top of the high-pressure distillation column T2; and pump P5 is installed on the pipeline connecting the reflux tank D3 to the top of the low-pressure distillation column T3.

3. The integrated heat recovery device for vapor-phase side-stream pressure-swapping distillation according to claim 1, characterized in that: Pump P2 is installed on the bottom pipeline 0106 of the medium-pressure distillation column T1; pump P4 is installed on the bottom pipeline 0109 of the high-pressure distillation column T2; and pump P6 is installed on the bottom pipeline 0111 of the low-pressure distillation column T3.

4. The integrated heat recovery device for vapor-phase side-stream pressure-swapping distillation according to claim 1, characterized in that: A compressor B1 is installed on the pipeline connecting the side line of the medium-pressure distillation column T1 to the high-pressure distillation column T2; a compressor B2 is installed on the pipeline connecting the side line of the high-pressure distillation column T2 to the low-pressure distillation column T3.

5. The method for separating a ternary azeotropic mixture of butanone-isopropanol-n-heptane using the gas-phase side-stream pressure-swing distillation heat integrated device according to any one of claims 1-4, characterized in that... The steps are as follows: (1) The raw material mixture of butanone-isopropanol-n-heptane enters the medium-pressure distillation column T1 through pipeline 0101. A portion of the material at the bottom of the medium-pressure distillation column T1 enters the heat exchanger R2, and after vaporization, returns to the bottom of the medium-pressure distillation column T1. The butanone product is collected through pipeline 0106 via pump P2 at the bottom of the medium-pressure distillation column T1. The vapor at the top of the medium-pressure distillation column T1 is condensed by condenser C1 and enters the reflux tank D1. A portion of it is returned to the top of the medium-pressure distillation column T1 via pump P1, and a portion enters the stripping section of the high-pressure distillation column T2 through pipeline 0105. The vapor stream from the side of the medium-pressure distillation column T1 is compressed by compressor B1 and enters the rectification section of the high-pressure distillation column T2. (2) The overhead stream and side stream from the medium-pressure distillation column T1 are fed into the high-pressure distillation column T2. ​​A portion of the material at the bottom of the high-pressure distillation column T2 enters the reboiler R3, is vaporized, and returns to the bottom of the high-pressure distillation column T2. ​​The n-heptane product is collected through pipeline 0109 via pump P4 at the bottom of the high-pressure distillation column T2. ​​The overhead vapor is condensed through heat exchanger R2 and enters the reflux tank D2. A portion is returned to the top of the high-pressure distillation column T2 via pump P3, and a portion enters the stripping section of the low-pressure distillation column T3 via pipeline 0108. The vapor stream from the side stream of the high-pressure distillation column T2 is compressed by compressor B2 and enters the rectification section of the low-pressure distillation column T3. (3) The overhead stream and side stream from the high-pressure distillation column T2 are fed into the low-pressure distillation column T3. A portion of the material at the bottom of the low-pressure distillation column T3 enters the reboiler R4, is vaporized, and then returns to the bottom of the low-pressure distillation column T3. The isopropanol product is collected through pipeline 0111 via pump P6 at the bottom of the low-pressure distillation column T3. The overhead vapor is condensed by condenser C3 and enters the reflux tank D3. A portion of it is returned to the top of the low-pressure distillation column T3 via pump P5, and a portion is collected through pipeline 0110 and circulated to the medium-pressure distillation column T1. (4) After introducing two gas phase side lines, the genetic algorithm in the optimization toolbox 8.4 of MATLAB 2019b is used to obtain the optimal parameters with the minimum annual total cost as the objective function. Data transmission between MATLAB and Aspen Plus is realized through COM technology. The genetic algorithm forms a new excellent population through selection, crossover and mutation. (5) After obtaining the gas phase side-stream pressure-switching distillation process, the medium-pressure distillation column T1 and the high-pressure distillation column T2 are heat-integrated, that is, the top steam of the high-pressure distillation column T2 is used to heat part of the bottom liquid of the medium-pressure distillation column T1, and the two exchange heat on the heat exchanger R2 through pipelines 0102 and 0103.

6. The method for separating a ternary azeotropic mixture of butanone-isopropanol-n-heptane using the gas-phase side-stream pressure-swing distillation heat integration device according to claim 5, characterized in that: The operating pressure of the medium-pressure distillation column T1 is 1.005 atm absolute, with 48 theoretical plates. There are 25 feed plates, 15 recirculating feed plates, 6 side-stream exit points, and 16 side-stream exit points leading to the high-pressure distillation column T2. ​​The reflux ratio of the medium-pressure distillation column T1 is 4.

31. The operating pressure of the high-pressure distillation column T2 is 3.483 atm absolute, with 33 theoretical plates. There are 30 feed plates, 5 side-stream exit points, and 3 side-stream exit points leading to the low-pressure distillation column T3. The high-pressure distillation column T2 has a reflux ratio of 1.86; the low-pressure distillation column T3 operates at an absolute pressure of 0.325 atm, has 26 theoretical plates, 11 feed points, and a reflux ratio of 0.57; the medium-pressure distillation column T1 has a top temperature of 74.69℃ and a bottom temperature of 86.69℃; the high-pressure distillation column T2 has a top temperature of 114.21℃ and a bottom temperature of 149.80℃; and the low-pressure distillation column T3 has a top temperature of 45.74℃ and a bottom temperature of 65.46℃.

7. The method for separating a ternary azeotropic mixture of butanone-isopropanol-n-heptane using the gas-phase side-stream pressure-swing distillation heat integration device according to claim 5, characterized in that: The mass fraction of methyl ethyl ketone (MEK) obtained from the bottom of the medium-pressure distillation column T1 reached 99.9%, and the MEK recovery rate reached 99.9%. The mass fraction of n-heptane obtained from the bottom of the high-pressure distillation column T2 reached 99.9%, and the n-heptane recovery rate reached 99.9%. The mass fraction of isopropanol obtained from the bottom of the low-pressure distillation column T3 reached 99.9%, and the isopropanol recovery rate reached 99.9%.

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