Tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column and extraction method

Abstract

This invention proposes an extractive distillation column and extraction method for a tetrahydrofuran-ethanol-methanol-water mixture. The column is divided into a first recovery column, a second recovery column, a third recovery column, a fourth recovery column, and a common stripping section by three vertical baffles spaced at intervals on the left and right sides. The first recovery column has an ethanol side-stream outlet at the top and a circulating extractant side-stream inlet at the top. The second recovery column has a tetrahydrofuran outlet at the top, a circulating extractant side-stream inlet at the top, and a tetrahydrofuran-ethanol-methanol-water mixture side-stream inlet at the bottom. The third recovery column has a methanol side-stream outlet at the top. The fourth recovery column has a water side-stream outlet at the top. The common stripping section has a bottom liquid outlet at the bottom. This invention achieves the separation and purification of each component through a single column, reducing separation difficulty and lowering separation costs.

Description

Technical Field

[0001] This invention relates to the field of multi-component azeotropic separation, and particularly to an extractive distillation column and extraction method for a tetrahydrofuran-ethanol-methanol-water mixture. Background Technology

[0002] Tetrahydrofuran, ethanol, and methanol are all commonly used organic solvents in chemical production, widely applied in pharmaceuticals, fine chemicals, coatings, and electronics industries. In actual production processes, multi-component mixtures of tetrahydrofuran, ethanol, methanol, and water are often generated. These mixtures readily form azeotropes with similar boiling points, making efficient separation difficult using conventional distillation methods. This results in low component recovery rates and substandard product purity, leading to resource waste and potential environmental pressure due to wastewater discharge. Currently, common methods for separating multi-component azeotropic mixtures include extractive distillation, pressure swing distillation, and azeotropic distillation. Among these, extractive distillation, by adding an extractant to alter the relative volatility of the components and disrupt the azeotropic equilibrium, is an effective means of separating azeotropic systems. Existing technologies, such as... Figure 1 As shown, the extractive distillation of tetrahydrofuran-ethanol-methanol-water mixtures often employs a multi-tower series process, which has problems such as large equipment investment, large footprint, high energy consumption, and complex operation. At the same time, the extractants used in some processes are difficult to regenerate and have high losses, which further increases the separation cost. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide a tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column and extraction method, which achieves the separation and purification of each component through a single column, reducing the separation difficulty and lowering the separation cost.

[0004] To achieve the above objectives, the present invention proposes a tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column, comprising a column body, wherein a first vertical baffle, a second vertical baffle, and a third vertical baffle are arranged at intervals on the left and right sides of the column body;

[0005] The upper and lower ends of the first vertical partition, the second vertical partition, and the third vertical partition are all left with gaps between them and the top and bottom ends of the tower body, and a first horizontal partition is provided between the top of the first vertical partition and the left side wall of the tower body.

[0006] The length of the second vertical partition is less than that of the first vertical partition, and the bottom height of the second vertical partition is higher than that of the first vertical partition. A second horizontal partition is provided between the top of the second vertical partition and the right side wall of the tower.

[0007] The bottom height of the third vertical partition is lower than the bottom height of the first vertical partition, and the top height is lower than the second horizontal partition but higher than the bottom height of the second vertical partition. A third horizontal partition is provided between the top of the third vertical partition and the right side wall of the tower.

[0008] The first vertical partition, the first horizontal partition, and the left side wall of the tower body form a first recycling tower; the first vertical partition, the second vertical partition, the first horizontal partition, the second horizontal partition, and the top of the tower body form a second recycling tower; the second vertical partition, the third vertical partition, the second horizontal partition, the third horizontal partition, and the right side wall of the tower body form a third recycling tower; the third vertical partition, the third horizontal partition, and the right side wall of the tower body form a fourth recycling tower; the tower space below the third vertical partition is a public stripping section;

[0009] The first, second, third, and fourth recovery towers each contain trays; a second gas phase splitter is located at the bottom of the first vertical partition, between the left side wall of the tower and the third vertical partition; a first gas phase splitter is located at the bottom of the second vertical partition, between the first and third vertical partitions; a third gas phase splitter is located at the bottom of the third vertical partition, between the left and right side walls of the tower.

[0010] The first recovery tower has an ethanol side stream outlet at the top and a circulating extractant side stream inlet at the top; the second recovery tower has a tetrahydrofuran outlet at the top, a circulating extractant side stream inlet at the top, and a tetrahydrofuran-ethanol-methanol-water mixed solution side stream inlet at the middle and lower parts; the third recovery tower has a methanol side stream outlet at the top; the fourth recovery tower has a water side stream outlet at the top; and the bottom of the tower body has a bottom liquid outlet.

[0011] In the above scheme: a collection line is provided at the bottom liquid collection outlet of the tower and connected to the reboiler; a tower liquid reflux port is also provided at the bottom of the common stripping section; a reflux pipe is provided on the reboiler and connected to the tower liquid reflux port; a collection line is also provided on the reboiler and connected to the extractant condenser; and a collection line is provided on the extractant condenser and connected to the side inlets of the two circulating extractant lines respectively. The linkage between the reboiler and the extractant condenser realizes efficient regeneration and circulation of the extractant.

[0012] In the above scheme, an extractant replenishment line is also provided on the collection line between the extractant condenser and the circulating extractant side line inlet. The extractant replenishment line can replenish the extractant lost during the separation process in a timely manner, ensuring stable extraction effect and avoiding the impact of insufficient extractant on separation efficiency and product quality.

[0013] In the above scheme: a collection line is provided on the ethanol side-stream outlet and connected to the ethanol condenser; a collection line is provided on the ethanol condenser and connected to the ethanol reflux tank; an ethanol reflux port is also provided at the top of the first recovery tower; a reflux pipe is provided on the ethanol reflux tank and connected to the ethanol reflux port; and an ethanol collection line is also provided on the ethanol reflux tank. Through the cooperation of the ethanol condenser and the ethanol reflux tank, the ethanol product is further purified.

[0014] In the above scheme: a collection line is provided on the tetrahydrofuran collection outlet and connected to the tetrahydrofuran condenser; a collection line is provided on the tetrahydrofuran condenser and connected to the tetrahydrofuran reflux tank; a tetrahydrofuran reflux port is also provided at the top of the second recovery tower; a reflux pipe is provided on the tetrahydrofuran reflux tank and connected to the tetrahydrofuran reflux port; and a tetrahydrofuran collection line is also provided on the tetrahydrofuran reflux tank. Through the cooperation of the tetrahydrofuran condenser and the tetrahydrofuran reflux tank, the tetrahydrofuran product is further purified.

[0015] In the above scheme: a extraction line is installed at the methanol side-stream outlet and connected to the methanol condenser; an extraction line is installed on the methanol condenser and connected to the methanol reflux tank; a methanol reflux port is also installed at the top of the third recovery tower; a reflux pipe is installed on the methanol reflux tank and connected to the methanol reflux port; and a methanol extraction line is also installed on the methanol reflux tank. Through the cooperation of the methanol condenser and the methanol reflux tank, the methanol product is further purified.

[0016] In the above scheme: a sampling line is installed on the water side outlet and connected to the water condenser; a sampling line is installed on the water condenser and connected to the water return tank; a water return port is also installed at the top of the fourth recovery tower; a return pipe is installed on the water return tank and connected to the water return port; and a water sampling line is also installed on the water return tank. Through the cooperation of the water condenser and the water return tank, the aquatic products are further purified.

[0017] In the above scheme, the extractant is dimethyl sulfoxide (DMSO). DMSO can effectively change the relative volatility of each component in the mixture, break the azeotropic equilibrium, and improve separation efficiency and product purity. At the same time, DMSO has good stability and is easy to recover, and can be reused through a recycling system, reducing extractant loss and separation costs.

[0018] In the above scheme: the tops of the second vertical partition and the first vertical partition are flush; the number of trays in the first recovery tower is 50-55; the number of trays in the second recovery tower is 40-45; the number of trays in the third recovery tower is 80-85; and the number of trays in the fourth recovery tower is 23-28.

[0019] The present invention also proposes an extraction method for a tetrahydrofuran-ethanol-methanol-water mixture, comprising the above-mentioned tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column, and further comprising the following steps:

[0020] S1. A tetrahydrofuran-ethanol-methanol-water mixed solution is fed into the second recovery tower through the side inlet of the tetrahydrofuran-ethanol-methanol-water mixed solution. It enters the second recovery tower laterally and comes into countercurrent contact with the extractant. Extraction and separation are completed in the tower. The tetrahydrofuran gas phase component enters the tetrahydrofuran condenser through the tetrahydrofuran outlet. After being cooled into a liquid phase by the tetrahydrofuran condenser, the liquid phase enters the tetrahydrofuran reflux tank. A portion of it is collected as tetrahydrofuran product, and the remainder is refluxed back into the second recovery tower.

[0021] S2. The liquid phase of methanol, ethanol, water and extractant in the second recovery tower flows to the common stripping section. The rising gas in the common stripping section is separated into methanol, ethanol and water gas by the first gas phase splitter and enters the third recovery tower. Extraction and separation are completed in the tower. The methanol gas enters the methanol condenser from the methanol side stream outlet. After being condensed into liquid by the methanol condenser, the liquid enters the methanol reflux tank. Part of it is taken out as methanol product and the remainder is returned to the third recovery tower.

[0022] S3. The liquid phase of ethanol, water and extractant in the third recovery tower flows to the common stripping section. The rising gas in the common stripping section is separated into ethanol and water gas by the second gas phase splitter and enters the first recovery tower. Extraction and separation are completed in the tower. The ethanol gas enters the ethanol condenser from the ethanol side stream outlet. After being condensed into liquid by the ethanol condenser, the liquid enters the ethanol reflux tank. A portion is taken out as ethanol product and the remainder is returned to the first recovery tower.

[0023] S4. The liquid phase of water and extractant in the first recovery tower flows to the common stripping section. The rising gas in the common stripping section is separated into water gas by the third gas phase separator and enters the fourth recovery tower. Water vapor enters the water condenser from the water side line outlet and is condensed into liquid by the water condenser. The liquid enters the water return tank, part of which is taken out as aquatic product and the rest is returned to the fourth recovery tower.

[0024] S5. The liquid phase of the extractant in the fourth recovery tower flows to the common stripping section. The extractant enters the reboiler from the bottom liquid outlet. After being heated into a gas phase by the reboiler, part of it flows back to the common stripping section, and the rest enters the extractant condenser. The extractant cooled by the extractant condenser is mixed with the extractant in the extractant replenishment line. Finally, it flows back to the first recovery tower and the second recovery tower through the two circulating extractant side line inlets, respectively.

[0025] The beneficial effects of this invention are:

[0026] 1. The tower structure is rationally designed, dividing the internal cavity into four recovery towers and a common stripping section through three vertical baffles. This eliminates the need for multiple towers in series, achieving simultaneous separation of four components: tetrahydrofuran, ethanol, methanol, and water. This significantly reduces equipment investment costs, floor space requirements, simplifies the overall operation process, and lowers maintenance complexity. 2. The height matching and channel design of the vertical and horizontal baffles, combined with the precise flow distribution of three gas phase splitters, ensures orderly separation of each component, preventing interference between different components, improving separation efficiency, and ensuring the purity of each product meets standards. This solves the problems of incomplete separation and cross-contamination associated with traditional single-tower or multi-tower series processes. 3. Each recovery tower has a dedicated inlet and outlet for the mixed solution, ensuring more thorough countercurrent contact between the feed and extractant, resulting in more stable extraction and separation effects and further improving component recovery rates. 4. The integrated design of the common stripping section enables centralized processing of the liquid phase from each recovery tower and unified utilization of the heat source. Compared to traditional multi-tower independent stripping processes, this effectively reduces energy consumption and waste, aligning with the energy conservation and emission reduction trends in chemical production. 5. The overall structure is compact and the layout is reasonable. The synergistic effect of each channel and distributor makes the separation process continuous and stable, with strong adaptability. It can be adapted to the separation of tetrahydrofuran-ethanol-methanol-water mixtures with different component ratios, and has broad industrial application prospects. Attached Figure Description

[0027] Figure 1 This is a diagram of the original four-tower extraction and distillation process.

[0028] Figure 2 This is a schematic diagram of the tower structure of the present invention.

[0029] Figure 3 This is a diagram of an existing single-tower extractive distillation process. Detailed Implementation

[0030] like Figure 2 As shown, a tetrahydrofuran-ethanol-methanol-water mixture extraction distillation column has a first vertical baffle a, a second vertical baffle b, and a third vertical baffle c arranged at intervals on the left and right sides of the column body.

[0031] The upper and lower ends of the first vertical partition a, the second vertical partition b, and the third vertical partition c are all separated from the top and bottom of the tower body, and a first horizontal partition d is provided between the top of the first vertical partition a and the left side wall of the tower body.

[0032] The length of the second vertical partition b is less than that of the first vertical partition a, and the bottom height of the second vertical partition b is higher than that of the first vertical partition a. A second horizontal partition f is provided between the top of the second vertical partition b and the right side wall of the tower.

[0033] The bottom height of the third vertical partition c is lower than the bottom height of the first vertical partition a, and the top height is lower than the second horizontal partition f and higher than the bottom height of the second vertical partition b. A third horizontal partition h is provided between the top of the third vertical partition c and the right side wall of the tower.

[0034] The first vertical partition a, the first horizontal partition d, and the left side wall of the tower body form the first recycling tower I; the first vertical partition a, the second vertical partition b, the first horizontal partition d, the second horizontal partition f, and the top of the tower body form the second recycling tower II; the second vertical partition b, the third vertical partition c, the second horizontal partition f, the third horizontal partition h, and the right side wall of the tower body form the third recycling tower III; the third vertical partition c, the third horizontal partition h, and the right side wall of the tower body form the fourth recycling tower IV; the tower space below the third vertical partition c is the public stripping section V.

[0035] Each of the first recovery tower I, the second recovery tower II, the third recovery tower III, and the fourth recovery tower IV contains a tray e (only one tray is shown in the figure for each recovery tower); the bottom of the first vertical baffle a is provided with a second gas phase splitter 12, which is located between the left side wall of the tower body and the third vertical baffle c; the bottom of the second vertical baffle b is provided with a first gas phase splitter 11, which is located between the first vertical baffle a and the third vertical baffle c; the bottom of the third vertical baffle c is provided with a third gas phase splitter 13, which is located between the left side wall and the right side wall of the tower body.

[0036] The first recovery tower I is equipped with an ethanol side stream outlet 101 at the top and a circulating extractant side stream inlet 102 at the top; the second recovery tower II is equipped with a tetrahydrofuran outlet 103 at the top, a circulating extractant side stream inlet 102 at the top, and a tetrahydrofuran-ethanol-methanol-water mixed solution side stream inlet 104 at the middle and lower part; the third recovery tower III is equipped with a methanol side stream outlet 105 at the top; the fourth recovery tower IV is equipped with a water side stream outlet 106 at the top; and the bottom of the tower body is equipped with a bottom liquid outlet 107.

[0037] Specifically, a collection line is installed on the bottom liquid collection outlet 107 of the tower and connected to the reboiler 9. A bottom liquid reflux port is also installed at the bottom of the common stripping section V. A reflux pipe is installed on the reboiler 9 and connected to the bottom liquid reflux port. A collection line is also installed on the reboiler 9 and connected to the extractant condenser 10. A collection line is installed on the extractant condenser 10 and connected to the two circulating extractant side line inlets 102 respectively. The coordinated installation of the reboiler 9 and the extractant condenser 10 achieves efficient regeneration and circulation of the extractant.

[0038] Specifically, an extractant replenishment line 108 is also provided on the outlet line between the extractant condenser 10 and the circulating extractant side line inlet 102. The extractant replenishment line 108 can replenish the extractant lost during the separation process in a timely manner, ensuring stable extraction effect and avoiding the impact of insufficient extractant on separation efficiency and product quality.

[0039] Specifically, an ethanol side-stream outlet 101 is equipped with an outlet line connected to the ethanol condenser 2. The ethanol condenser 2 is also equipped with an outlet line connected to the ethanol reflux tank 1. An ethanol reflux port is also provided at the top of the first recovery tower I. A reflux pipe is provided on the ethanol reflux tank 1 connected to the ethanol reflux port, and an ethanol outlet line 109 is also provided on the ethanol reflux tank 1. Through the cooperation of the ethanol condenser 2 and the ethanol reflux tank 1, the ethanol product is further purified.

[0040] Specifically, a collection line is installed on the tetrahydrofuran outlet 103, connected to the tetrahydrofuran condenser 3. The tetrahydrofuran condenser 3 is also equipped with a collection line connected to the tetrahydrofuran reflux tank 4. A tetrahydrofuran reflux port is also installed at the top of the second recovery tower II. A reflux pipe is installed on the tetrahydrofuran reflux tank 4, connected to the tetrahydrofuran reflux port. A tetrahydrofuran collection line 110 is also installed on the tetrahydrofuran reflux tank 4. Through the cooperation of the tetrahydrofuran condenser 3 and the tetrahydrofuran reflux tank 4, the tetrahydrofuran product is further purified.

[0041] Specifically, a methanol side-stream outlet 105 is equipped with a production line connected to the methanol condenser 5. The methanol condenser 5 is also equipped with a production line connected to the methanol reflux tank 6. The upper part of the third recovery tower III is also equipped with a methanol reflux port. The methanol reflux tank 6 is equipped with a reflux pipe connected to the methanol reflux port, and a methanol production line 111 is also installed on the methanol reflux tank 6. Through the cooperation of the methanol condenser 5 and the methanol reflux tank 6, the methanol product is further purified.

[0042] Specifically, a sampling line is installed on the water side outlet 106, which is connected to the water condenser 7. The water condenser 7 is also equipped with a sampling line connected to the water return tank 8. A water return port is also installed at the top of the fourth recovery tower IV. A return pipe is installed on the water return tank 8, which is connected to the water return port. A water sampling line 112 is also installed on the water return tank 8. Through the cooperation of the water condenser 7 and the water return tank 8, the aquatic products are further purified.

[0043] Specifically, the extractant is dimethyl sulfoxide (DMSO). DMSO can effectively change the relative volatility of the components in the mixture, break the azeotropic equilibrium, and improve separation efficiency and product purity. At the same time, DMSO has good stability and is easy to recover, and can be reused through a recycling system, reducing extractant loss and separation costs.

[0044] Specifically, the tops of the second vertical partition b and the first vertical partition a are flush. The number of trays e in the first recovery tower I is 50 to 55, the number of trays e in the second recovery tower II is 40 to 45, the number of trays e in the third recovery tower III is 80 to 85, and the number of trays e in the fourth recovery tower IV is 23 to 28.

[0045] like Figure 3 As shown, an extraction method for a tetrahydrofuran-ethanol-methanol-water mixture, based on the above-mentioned tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column, mainly consists of the following steps:

[0046] S1. A tetrahydrofuran-ethanol-methanol-water mixed solution is fed into the second recovery tower II through the side inlet 104. The solution enters the second recovery tower II laterally and comes into countercurrent contact with the extractant. Extraction and separation are completed in the tower. The tetrahydrofuran gaseous component enters the tetrahydrofuran condenser 3 through the tetrahydrofuran outlet 103. After being cooled into a liquid phase by the tetrahydrofuran condenser 3, the liquid phase enters the tetrahydrofuran reflux tank 4. A portion of the liquid phase is collected as tetrahydrofuran product, and the remainder is refluxed back into the second recovery tower II.

[0047] S2. The liquid phase of methanol, ethanol, water, and extractant in the second recovery tower II flows to the common stripping section V. The rising gas in the common stripping section V is separated into methanol, ethanol, and water gases by the first gas phase splitter 11 and enters the third recovery tower III. Extraction and separation are completed in the tower. The methanol gas enters the methanol condenser 5 from the methanol side stream outlet 105. After being condensed into liquid by the methanol condenser 5, the liquid enters the methanol reflux tank 6. A portion is collected as methanol product, and the remainder is refluxed back to the third recovery tower III.

[0048] S3. The liquid phase of ethanol, water and extractant in the third recovery tower III flows to the common stripping section V. The rising gas in the common stripping section V is separated into ethanol and water gas by the second gas phase splitter 12 and enters the first recovery tower I. Extraction and separation are completed in the tower. The ethanol gas enters the ethanol condenser 2 from the ethanol side stream outlet 101. After being condensed into liquid by the ethanol condenser 2, the liquid enters the ethanol reflux tank 1. A portion is collected as ethanol product, and the remainder is returned to the first recovery tower I.

[0049] S4. The liquid phase of water and extractant in the first recovery tower I flows to the common stripping section V. The gas rising in the common stripping section V passes through the third gas phase splitter 13 to separate the water gas into the fourth recovery tower IV. The water vapor enters the water condenser 7 from the water side outlet 106 and is condensed into liquid by the water condenser 7. The liquid enters the water return tank 8, part of which is taken out as aquatic product and the remainder is returned to the fourth recovery tower IV.

[0050] S5. The liquid phase of the extractant in the fourth recovery tower IV flows to the common stripping section V. The extractant enters the reboiler 9 from the bottom liquid outlet 107. After being heated into a gas phase by the reboiler 9, part of it flows back to the common stripping section V, and the rest enters the extractant condenser 10. The extractant cooled by the extractant condenser 10 is mixed with the extractant in the extractant replenishment line 108. Finally, it flows back to the first recovery tower I and the second recovery tower II through the two circulating extractant side line inlets 102, respectively.

[0051] Application Example 1

[0052] A mixed solution from a chemical and pharmaceutical company, after separation, comprises: 10% tetrahydrofuran, 10% ethanol, 10% methanol, and 70% water, with a total flow rate of 100 kmol / h. The temperature is 45℃, the pressure is 1.2 bar, and the extractant DMSO is used at a rate of 26.344 kmol / hr at 45℃ and 1.2 bar. Specific parameters are shown in the table below.

[0053]

[0054] Application Example 2

[0055] A mixed solution from a chemical and pharmaceutical company, after separation, comprises: 12% tetrahydrofuran, 9% ethanol, 11% methanol, and 68% water. The temperature is 50℃, the pressure is 1.4 bar, and the total flow rate is 120 kmol / h. The extractant DMSO is used at a rate of 30.42 kmol / hr, with the temperature at 50℃ and the pressure at 1.4 bar. Specific parameters are shown in the table below.

[0056]

[0057] Application Example 3

[0058] A mixed solution from a chemical and pharmaceutical company, after separation, comprises: 9% tetrahydrofuran, 8% ethanol, 12% methanol, and 69% water. The temperature is 48℃, the pressure is 1.3 bar, and the total flow rate is 110 kmol / h. The extractant DMSO is used at a rate of 27.25 kmol / hr, at 48℃, and at a pressure of 1.3 bar. Specific parameters are shown in the table below.

[0059]

Claims

1. A tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column, comprising a column body, characterized in that: The tower body is provided with a first vertical partition (a), a second vertical partition (b), and a third vertical partition (c) spaced apart on the left and right sides. The upper and lower ends of the first vertical partition (a), the second vertical partition (b), and the third vertical partition (c) are all left with gaps between them and the top and bottom ends of the tower body, and a first horizontal partition (d) is provided between the top end of the first vertical partition (a) and the left side wall of the tower body. The length of the second vertical partition (b) is less than that of the first vertical partition (a), and the bottom height of the second vertical partition (b) is higher than that of the first vertical partition (a). A second horizontal partition (f) is provided between the top of the second vertical partition (b) and the right side wall of the tower. The bottom height of the third vertical partition (c) is lower than the bottom height of the first vertical partition (a), and the top height is lower than the second horizontal partition (f) and higher than the bottom height of the second vertical partition (b). A third horizontal partition (h) is provided between the top of the third vertical partition (c) and the right side wall of the tower. The first vertical partition (a), the first horizontal partition (d), and the left side wall of the tower body form a first recycling tower (I); the first vertical partition (a), the second vertical partition (b), the first horizontal partition (d), the second horizontal partition (f), and the top of the tower body form a second recycling tower (II); the second vertical partition (b), the third vertical partition (c), the second horizontal partition (f), the third horizontal partition (h), and the right side wall of the tower body form a third recycling tower (III); the third vertical partition (c), the third horizontal partition (h), and the right side wall of the tower body form a fourth recycling tower (IV); the tower space below the third vertical partition (c) is a public transport section (V); The first recovery tower (I), the second recovery tower (II), the third recovery tower (III), and the fourth recovery tower (IV) are all equipped with trays (e); a second gas phase splitter (12) is provided at the bottom of the first vertical partition (a), and the second gas phase splitter (12) is arranged between the left side wall of the tower body and the third vertical partition (c); a first gas phase splitter (11) is provided at the bottom of the second vertical partition (b), and the first gas phase splitter (11) is arranged between the first vertical partition (a) and the third vertical partition (c); a third gas phase splitter (13) is provided at the bottom of the third vertical partition (c), and the third gas phase splitter (13) is arranged between the left side wall of the tower body and the right side wall of the tower body; The first recovery tower (I) is provided with an ethanol side stream outlet (101) at the top and a circulating extractant side stream inlet (102) at the top; the second recovery tower (II) is provided with a tetrahydrofuran outlet (103) at the top, a circulating extractant side stream inlet (102) at the top, and a tetrahydrofuran-ethanol-methanol-water mixed solution side stream inlet (104) at the middle and lower part; the third recovery tower (III) is provided with a methanol side stream outlet (105) at the top; the fourth recovery tower (IV) is provided with a water side stream outlet (106) at the top; and the bottom of the tower body is provided with a bottom liquid outlet (107).

2. The tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column according to claim 1, characterized in that: The bottom liquid outlet (107) of the tower is provided with a collection line connected to the reboiler (9). The bottom of the common stripping section (V) is also provided with a bottom liquid reflux port. The reboiler (9) is provided with a reflux pipe connected to the bottom liquid reflux port. The reboiler (9) is also provided with a collection line connected to the extractant condenser (10). The extractant condenser (10) is provided with a collection line connected to the two circulating extractant side line inlets (102) respectively.

3. The tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column according to claim 2, characterized in that: An extractant replenishment line (108) is also provided on the extraction line between the extractant condenser (10) and the circulating extractant side line inlet (102).

4. The tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column according to claim 3, characterized in that: An ethanol side-line outlet (101) is provided with an outlet line connected to an ethanol condenser (2). An ethanol condenser (2) is provided with an outlet line connected to an ethanol reflux tank (1). An ethanol reflux port is also provided on the upper part of the first recovery tower (I). A reflux pipe is provided on the ethanol reflux tank (1) and connected to the ethanol reflux port. An ethanol outlet line (109) is also provided on the ethanol reflux tank (1).

5. The tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column according to claim 4, characterized in that: The tetrahydrofuran outlet (103) is provided with an outlet line connected to the tetrahydrofuran condenser (3), the tetrahydrofuran condenser (3) is provided with an outlet line connected to the tetrahydrofuran reflux tank (4), the upper part of the second recovery tower (II) is also provided with a tetrahydrofuran reflux port, the tetrahydrofuran reflux tank (4) is provided with a reflux pipe connected to the tetrahydrofuran reflux port, and the tetrahydrofuran reflux tank (4) is also provided with a tetrahydrofuran outlet line (110).

6. The tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column according to claim 5, characterized in that: The methanol side-line outlet (105) is provided with an outlet line connected to the methanol condenser (5), the methanol condenser (5) is provided with an outlet line connected to the methanol reflux tank (6), the third recovery tower (III) is also provided with a methanol reflux port at the top, the methanol reflux tank (6) is provided with a reflux pipe connected to the methanol reflux port, and the methanol reflux tank (6) is also provided with a methanol outlet line (111).

7. The tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column according to claim 6, characterized in that: The water side outlet (106) is provided with an outlet line connected to the water condenser (7), the water condenser (7) is provided with an outlet line connected to the water return tank (8), the upper part of the fourth recovery tower (IV) is also provided with a water return port, the water return tank (8) is provided with a return pipe connected to the water return port, and the water return tank (8) is also provided with a water outlet line (112).

8. The tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column according to claim 1, characterized in that: The extractant is dimethyl sulfoxide.

9. The tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column according to claim 1, characterized in that: The tops of the second vertical partition (b) and the first vertical partition (a) are flush. The number of trays (e) in the first recovery tower (I) is 50 to 55, the number of trays (e) in the second recovery tower (II) is 40 to 45, the number of trays (e) in the third recovery tower (III) is 80 to 85, and the number of trays (e) in the fourth recovery tower (IV) is 23 to 28.

10. A method for extracting a tetrahydrofuran-ethanol-methanol-water mixture, characterized in that: The tetrahydrofuran-ethanol-methanol-water mixture extractive distillation column according to any one of claims 7-9 further includes the following steps: S1. The tetrahydrofuran-ethanol-methanol-water mixed solution is fed into the side inlet (104) of the tetrahydrofuran-ethanol-methanol-water mixed solution and enters the second recovery tower (II) laterally to contact the extractant in countercurrent. The extraction and separation are completed in the tower. The tetrahydrofuran gas phase component enters the tetrahydrofuran condenser (3) from the tetrahydrofuran outlet (103). After being cooled into a liquid phase by the tetrahydrofuran condenser (3), the liquid phase enters the tetrahydrofuran reflux tank (4). A portion is collected as tetrahydrofuran product, and the remaining portion is returned to the second recovery tower (II). S2. The liquid phase of methanol, ethanol, water and extractant in the second recovery tower (II) flows to the common stripping section (V). The gas rising in the common stripping section (V) passes through the first gas phase splitter (11) to split the methanol, ethanol and water gas into the third recovery tower (III). Extraction and separation are completed in the tower. The methanol gas enters the methanol condenser (5) from the methanol side line outlet (105). After being condensed into liquid by the methanol condenser (5), the liquid enters the methanol reflux tank (6). A portion is taken out as methanol product, and the remainder is returned to the third recovery tower (III). S3. The liquid phase of ethanol, water and extractant in the third recovery tower (III) flows to the common stripping section (V). The gas rising in the common stripping section (V) is separated into ethanol and water gas by the second gas phase splitter (12) and enters the first recovery tower (I). Extraction and separation are completed in the tower. Ethanol gas enters the ethanol condenser (2) from the ethanol side line outlet (101). After being condensed into liquid by the ethanol condenser (2), the liquid enters the ethanol reflux tank (1). A portion is taken out as ethanol product and the remainder is returned to the first recovery tower (I). S4. The liquid phase of water and extractant in the first recovery tower (I) flows to the common stripping section (V). The gas rising in the common stripping section (V) passes through the third gas phase separator (13) to separate the water gas into the fourth recovery tower (IV). The water vapor enters the water condenser (7) from the water side line outlet (106), and is condensed into liquid by the water condenser (7). The liquid enters the water return tank (8), part of which is taken out as aquatic products, and the remaining part is returned to the fourth recovery tower (IV). S5. The liquid phase of the extractant in the fourth recovery tower (IV) flows to the common stripping section (V). The extractant enters the reboiler (9) from the bottom liquid outlet (107). After being heated into a gas phase by the reboiler (9), a portion flows back to the common stripping section (V), and the remaining portion enters the extractant condenser (10). The extractant cooled by the extractant condenser (10) is mixed with the extractant in the extractant replenishment line (108). Finally, it flows back to the first recovery tower (I) and the second recovery tower (II) through the two circulating extractant side line inlets (102).

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