A system and method for recovering tetrahydrofuran from the wastewater generated in the dehydrogenation synthesis of γ-butyrolactone from 1,4-butanediol

Abstract

The present invention belongs to the field of chemical production, and particularly relates to a system and method for recovering tetrahydrofuran from the wastewater generated in the dehydrogenation synthesis of γ-butyrolactone from 1,4-butanediol. The present invention uses water as an extraction agent, and an extraction tower is adopted to extract and separate the azeotrope of THF-water and the wastewater containing alcohol. Among them, the azeotrope of THF-water is rectified in a pressurized tower to obtain the finished product of THF, and the wastewater containing alcohol is subjected to alcohol removal in a de-alcoholization tower to separate the alcohol-water mixture, thereby completing the separation of alcohols, especially methanol and THF. The purity of the finished product of THF separated by the present invention is ≥99.8%, and the water content is <200 ppm, which has high practical application value.

Description

Technical Field

[0001] The present invention belongs to the field of chemical production, and particularly relates to a system and method for recovering tetrahydrofuran from the wastewater generated by the dehydrogenation of 1,4-butanediol to synthesize γ-butyrolactone. Background Art

[0002] γ-butyrolactone (GBL) is an important organic synthesis raw material and excellent solvent, and its demand is increasing continuously. At present, a large amount of wastewater containing tetrahydrofuran (THF), alcohols (such as n-butanol (NBA) and methanol), water and GBL (including other high-boiling impurities, etc.) will be generated during the process of dehydrogenating 1,4-butanediol (BDO) to produce GBL. Enterprises generally sell it at a low price or burn it as fuel, with low utilization rate and economic benefits. Recycling tetrahydrofuran and alcohols in the waste liquid will not only bring economic benefits to enterprises, but also greatly reduce the pressure on the environment and subsequent treatment, which is of great significance both economically and environmentally.

[0003] THF, alcohols and water are mutually soluble and form an azeotrope, making the separation difficult. At present, in the research on the separation and purification of related systems containing THF and alcohols, BASF uses multiple dividing-wall columns and distillation column systems to gradually separate the mixture of THF, GBL and BDO, and obtains THF and NBA with a relatively high mass fraction; other researchers use salt effect extraction, extractive distillation or double-effect distillation for the ternary system containing THF - alcohols - water, and also achieve the purpose of separation and purification. However, since the boiling point of a small amount of methanol in the wastewater is very close to the azeotropic point of THF - water, it is difficult to remove methanol in THF by conventional distillation. Therefore, how to separate methanol from THF is the focus of the research of the present invention. Summary of the Invention

[0004] Aiming at the problems and deficiencies existing in the prior art, the purpose of the present invention is to provide a system and method for recovering tetrahydrofuran from the wastewater generated by the dehydrogenation of 1,4-butanediol to synthesize γ-butyrolactone.

[0005] Based on the above purpose, the present invention adopts the following technical solutions:

[0006] In the first aspect of the present invention, a system for recovering tetrahydrofuran from the wastewater generated by the dehydrogenation synthesis of γ-butyrolactone from 1,4-butanediol is provided. The system includes an extraction subsystem, and the outlet of the extraction subsystem is connected to a rectification subsystem and a de-alcoholization subsystem; the extraction subsystem includes an extraction column under atmospheric pressure, the top of the extraction column is provided with an extraction column condensation device, and the bottom of the column is provided with an extraction column reboiler; the rectification subsystem includes a pressurized column, the pressure inside the column is 0.5-0.6 MPa, the top of the pressurized column is provided with a pressurized column condenser, the side of the column is provided with a finished product cooling device, and the bottom of the column is provided with a pressurized column reboiler; the de-alcoholization subsystem includes a de-alcoholization column under atmospheric pressure, the top of the de-alcoholization column is provided with a de-alcoholization column condensation device, and the bottom of the column is provided with a de-alcoholization column reboiler and a wastewater cooling device;

[0007] The top discharge port of the extraction column is connected to the extraction column condensation device; the reflux pipeline of the extraction column condensation device is connected to the extraction column, the discharge port of the extraction column condensation device is connected to the feed port of the pressurized column in the rectification subsystem, and the gas outlet of the extraction column condensation device is communicated to the outside area for treatment; the reflux pipeline of the extraction column reboiler is connected to the extraction column; the bottom discharge port is connected to the feed port of the de-alcoholization subsystem;

[0008] The top discharge port of the pressurized column is connected to the pressurized column condenser; the reflux pipeline of the pressurized column condenser is connected to the pressurized column, the discharge port of the pressurized column condenser is connected to the feed port of the raw materials of the extraction column, and the gas outlet of the pressurized column condenser is communicated to the outside area for treatment; the side discharge port is connected to the finished product cooling device; the discharge port of the finished product cooling device is respectively connected to the THF finished product outlet and the feed port of the raw materials of the extraction column; the reflux pipeline of the pressurized column reboiler is connected to the pressurized column; the bottom discharge port is connected to the feed port of the raw materials of the extraction column;

[0009] The top discharge port of the de-alcoholization column is connected to the de-alcoholization column condensation device; the reflux pipeline of the de-alcoholization column condensation device is connected to the de-alcoholization column, the discharge port of the de-alcoholization column condensation device is connected to the alcohol-water mixture outlet, and the gas outlet of the de-alcoholization column condensation device is communicated to the outside area for treatment; the reflux pipeline of the de-alcoholization column reboiler is connected to the de-alcoholization column; the bottom discharge port is connected to the wastewater cooling device; the discharge port of the wastewater cooling device is connected to the wastewater outlet.

[0010] More preferably, the reflux forms of the extraction column, the pressurized column and the de-alcoholization column are all external forced reflux. The extraction column is a packed column with 25-30 theoretical plates; the pressurized column is a packed column with 20-25 theoretical plates; the de-alcoholization column is a packed column with 15-20 theoretical plates.

[0011] Preferably, the raw material inlet of the extraction tower is located in the middle and lower part of the extraction tower. More preferably, the raw material (waste water from the dehydrogenation synthesis of γ-butyrolactone from 1,4-butanediol) is pumped into the raw material inlet of the extraction tower by a pump. Further, the parameters of the pump for pumping the raw material into the raw material inlet of the extraction tower are as follows: the flow rate Q is 0.7 m 3 / h, the head H is 40 m, the power is 1.1 kw, and the material is 304 stainless steel.

[0012] Preferably, the extractant inlet of the extraction tower is located in the middle and upper part of the extraction tower. More preferably, the extractant (reverse osmosis water) is pumped into the extractant inlet of the extraction tower by a pump. Further, the parameters of the pump for pumping the extractant into the extractant inlet of the extraction tower are as follows: the flow rate Q is 1.4 m 3 / h, the head H is 40 m, the power is 1.1 kw, and the material is 304 stainless steel.

[0013] Preferably, the extraction tower condensing device includes the extraction tower first cooler and the extraction tower second cooler in parallel; the extraction subsystem further includes an extraction tower reflux drum and an extraction tower top reflux pump;

[0014] The top outlet of the extraction tower is connected to the extraction tower first cooler, and the gas outlet of the extraction tower first cooler is connected to the extraction tower second cooler; the gas outlet of the extraction tower second cooler is communicated to the off-site area for treatment; the liquid outlets of the extraction tower first cooler and the extraction tower second cooler are both connected to the extraction tower reflux drum; the gas outlet of the extraction tower reflux drum is connected to the feed inlet of the extraction tower second cooler, and the liquid outlet of the extraction tower reflux drum is connected to the extraction tower top reflux pump; the outlet of the extraction tower top reflux pump is respectively connected to the top reflux pipeline and the feed inlet of the pressurization tower.

[0015] More preferably, a pump is connected to the pipeline where the bottom outlet of the extraction tower is connected to the feed inlet of the de-alcoholization subsystem, so as to feed the alcohol-containing waste water obtained at the bottom of the extraction tower into the de-alcoholization subsystem at a stable flow rate. Further, the parameters of the pump for pumping the alcohol-containing waste water into the de-alcoholization subsystem are as follows: the flow rate Q is 1.4 m 3 / h, the head H is 40 m, the power is 1.1 kw, and the material is 304 stainless steel.

[0016] Preferably, the feed inlet of the pressurization tower is located in the middle and upper part of the pressurization tower.

[0017] Preferably, the rectification subsystem further includes a pressurization tower top reflux pump; the outlet of the pressurization tower condenser is connected to the pressurization tower top reflux pump, and the outlet of the pressurization tower top reflux pump is respectively connected to the top reflux pipeline and the raw material inlet of the extraction tower. The parameters of the pressurization tower top reflux pump are as follows: the flow rate Q is 2.1 m 3 / h, the head H is 75 m, the power is 4 kw, and the material is 304 stainless steel.

[0018] Preferably, the finished product cooling device includes a series-connected first-stage pressurized tower cooler and second-stage pressurized tower cooler; the rectification subsystem further includes a THF finished product transfer tank, a THF finished product transfer pump, a THF crude product cooler, and a THF crude product temporary storage tank;

[0019] The finished product discharge port of the pressurized tower is connected to the first-stage pressurized tower cooler; the discharge port of the first-stage pressurized tower cooler is connected to the second-stage pressurized tower cooler; the discharge port of the second-stage pressurized tower cooler is connected to the THF finished product transfer tank; the gas outlet of the THF finished product transfer tank is communicated to the off-site area for treatment, and the discharge port of the THF finished product transfer tank is connected to the THF finished product transfer pump; the outlet of the THF finished product transfer pump is respectively connected to the THF crude product temporary storage tank and the THF finished product outlet; the bottom discharge port of the pressurized tower is respectively connected to the THF crude product cooler and the raw material feed port of the extraction tower; the discharge port of the THF crude product cooler is connected to the THF crude product temporary storage tank; the discharge port of the THF crude product temporary storage tank is connected to the raw material feed port of the extraction tower, and the gas outlet of the THF crude product temporary storage tank is communicated to the off-site area for treatment.

[0020] More preferably, the parameters of the THF finished product transfer pump are as follows: the flow rate Q is 3.2 m 3 / h, the head H is 32 m, the power is 2.2 kw, and the material is 304 stainless steel. Further, a pump is connected to the pipeline where the bottom discharge port of the pressurized tower and the discharge port of the THF crude product temporary storage tank are simultaneously connected to the raw material feed port of the extraction tower, aiming to feed the THF crude product taken from the bottom of the pressurized tower and obtained from the THF crude product temporary storage tank into the extraction subsystem at a stable flow rate. Further, the parameters of the pump for pumping the THF crude product into the extraction subsystem are: the flow rate Q is 3.2 m 3 / h, the head H is 32 m, the power is 2.2 kw, and the material is 304 stainless steel.

[0021] Preferably, before entering the raw material feed port of the extraction tower, the raw material first enters the first-stage pressurized tower cooler for heat exchange and temperature rise treatment as a cooling medium, and then enters the raw material feed port of the extraction tower.

[0022] Preferably, the feed port of the alcohol stripping tower is located in the middle and upper part of the alcohol stripping tower.

[0023] More preferably, the alcohol stripping subsystem further includes an alcohol-containing wastewater temporary storage tank for temporarily storing the alcohol-containing wastewater obtained from the bottom of the extraction tower; the alcohol-containing wastewater flowing out of the alcohol-containing wastewater temporary storage tank is pumped into the feed port of the alcohol stripping tower by a pump. Further, the parameters of the pump for pumping the alcohol-containing wastewater into the feed port of the alcohol stripping tower are: the flow rate Q is 1.4 m 3 / h, the head H is 40 m, the power is 1.1 kw, and the material is 304 stainless steel.

[0024] Preferably, the de-alcoholization tower condensation device includes a first-stage cooler of the de-alcoholization tower and a second-stage cooler of the de-alcoholization tower connected in parallel; the extraction subsystem further includes a reflux drum of the de-alcoholization tower and a top reflux pump of the de-alcoholization tower;

[0025] The top discharge port of the de-alcoholization tower is connected to the first-stage cooler of the de-alcoholization tower, and the gas outlet of the first-stage cooler of the de-alcoholization tower is connected to the second-stage cooler of the de-alcoholization tower; the gas outlet of the second-stage cooler of the de-alcoholization tower is communicated to the off-site area for treatment; the discharge ports of the first-stage cooler of the de-alcoholization tower and the second-stage cooler of the de-alcoholization tower are both connected to the reflux drum of the de-alcoholization tower; the gas outlet of the reflux drum of the de-alcoholization tower is connected to the feed port of the second-stage cooler of the de-alcoholization tower, and the discharge port of the reflux drum of the de-alcoholization tower is connected to the top reflux pump of the de-alcoholization tower; the outlet of the top reflux pump of the de-alcoholization tower is respectively connected to the top reflux pipeline and the outlet of the alcohol-water mixture.

[0026] Preferably, the wastewater cooling device includes a first-stage cooler of the de-alcoholization tower and a second-stage cooler of the de-alcoholization tower connected in series; the bottom discharge port of the de-alcoholization tower is connected to the first-stage cooler of the de-alcoholization tower; the discharge port of the first-stage cooler of the de-alcoholization tower is connected to the second-stage cooler of the de-alcoholization tower; the discharge port of the second-stage cooler of the de-alcoholization tower is connected to the wastewater outlet.

[0027] More preferably, the wastewater flowing out from the discharge port of the first-stage cooler of the de-alcoholization tower is pumped by a pump into the feed port of the second-stage cooler of the de-alcoholization tower. Further, the parameters of the pump for pumping the wastewater into the feed port of the second-stage cooler of the de-alcoholization tower are: the flow rate Q is 3.2 m 3 / h, the head H is 32 m, the power is 2.2 kw, and the material is 304 stainless steel.

[0028] Preferably, before entering the extraction agent feed port of the extraction tower, the extraction agent first enters the first-stage cooler of the de-alcoholization tower for heat exchange and temperature increase treatment as a cooling medium, and then enters the extraction agent feed port of the extraction tower.

[0029] The second aspect of the present invention provides a method for recovering tetrahydrofuran from the wastewater of synthesizing γ-butyrolactone by dehydrogenation of 1,4-butanediol by using the system described in the first aspect above, which includes the following steps:

[0030] (1) Add the wastewater of synthesizing γ-butyrolactone by dehydrogenation of 1,4-butanediol into the raw material feed port of the extraction tower in the system, and obtain a gaseous raw material after heating and vaporization by the reboiler of the extraction tower; continuously add the extraction agent into the extraction agent feed port of the extraction tower in the system, and at the same time control the top reflux ratio of the extraction tower, so that the gaseous raw material and the extraction agent perform gas-liquid exchange in the extraction tower, and obtain an azeotrope of THF-water from the top discharge port of the extraction tower and obtain alcohol-containing wastewater from the bottom discharge port of the extraction tower;

[0031] (2) Cool the azeotrope of THF - water obtained in step (1) and then add it to the feed inlet of the pressurizing column. Under the pressure condition of 0.5 - 0.6 MPa, by controlling the top reflux ratio of the pressurizing column, the water in the azeotrope of THF - water is enriched at the top of the pressurizing column. Then, an azeotrope of THF - water with a high water content is obtained from the top product outlet of the pressurizing column, a THF product is obtained from the finished product outlet of the pressurizing column, and a crude THF is obtained from the bottom product outlet of the pressurizing column. Among them, the azeotrope of THF - water with a high water content and the crude THF are both returned to the extraction column from the raw material feed inlet of the extraction column to re - conduct the gas - liquid exchange treatment in step (1).

[0032] (3) Add the alcohol - containing wastewater obtained in step (1) to the feed inlet of the alcohol - stripping column. By controlling the top reflux ratio of the alcohol - stripping column, the low - boiling alcohol - water mixture in the alcohol - containing wastewater is enriched at the top of the alcohol - stripping column. Then, an alcohol - water mixture is obtained from the top product outlet of the alcohol - stripping column, and high - boiling wastewater is obtained from the bottom product outlet of the alcohol - stripping column.

[0033] More preferably, the high - boiling wastewater obtained in step (3) can be added as an extractant to the extractant feed inlet of the extraction column to participate in the gas - liquid exchange in step (1). The excess high - boiling wastewater can be discharged after meeting the discharge requirements through sewage treatment.

[0034] Preferably, the mass ratio of THF to the extractant in the raw material is 1∶(1 - 1.5).

[0035] Preferably, the top temperature of the extraction column is 64.1 °C, the bottom temperature is 92 - 100 °C, the raw material feed temperature is 35 - 45 °C, the extractant feed temperature is 35 - 45 °C, and the top reflux ratio is 1.5; the top temperature of the pressurizing column is 120 °C, the bottom temperature is 125 - 126 °C, the feed temperature is 64 °C, and the top reflux ratio is 3; the top temperature of the alcohol - stripping column is 92 °C, the bottom temperature is 100 °C, the feed temperature is 92 - 100 °C, and the top reflux ratio is 2.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) In the process of producing γ-butyrolactone by dehydrogenation of 1,4-butanediol, the present invention uses water as an extractant, and an extraction tower is used to extract and separate the azeotrope of THF-water and the alcohol-containing wastewater. The azeotrope of THF-water is rectified in a pressurized tower to obtain THF products, the azeotrope of THF-water with high water content, and crude THF. The alcohol-containing wastewater is de-alcoholized in a de-alcoholization tower to separate the alcohol-water mixture and the high-boiling wastewater. Since the boiling point of methanol is very close to the azeotropic point of THF-water, it is difficult to remove methanol in THF by conventional rectification. The present invention realizes the separation of methanol and THF by extractive rectification, increasing the relative volatility of components. In one of the embodiments, the purity of the THF product simulated by the present invention is ≥99.8%, and the water content is <200 ppm, which has high practical application value.

[0038] (2) The azeotrope of THF-water with high water content and the crude THF obtained from the pressurized tower of the present invention can be returned to the extraction tower for reprocessing; the high-boiling wastewater generated by the de-alcoholization tower can be used as an extractant to participate in the next separation process, and after multiple cycles, it enters the wastewater treatment system as wastewater. Therefore, the present invention has less three wastes, is green and environmentally friendly, and has a high resource utilization rate.

[0039] (3) The tetrahydrofuran recovery system designed by the present invention can process 350 kg of tetrahydrofuran wastewater per hour, and can obtain THF with a purity of more than 99.8%. It efficiently utilizes waste materials, creates economic benefits, and has practical application value. Description of the Drawings

[0040] Figure 1 It is a schematic process flow diagram of the extraction subsystem in the embodiment of the present invention. Among them, T-100 is the extraction tower, V-102 is the extractant tank, E-102 is the first cooler of the extraction tower, E-103 is the second cooler of the extraction tower, V-101 is the reflux tank of the extraction tower, P-103AB is the top reflux pump of the extraction tower, and E-101 is the reboiler of the extraction tower;

[0041] Figure 2 It is a schematic process flow diagram of the rectification subsystem in the embodiment of the present invention. Among them, T-200 is the pressurized tower, E-202 is the condenser of the pressurized tower, P-201AB is the top reflux pump of the pressurized tower, E-203 is the raw material preheater, E-204 is the side draw cooler of the pressurized tower, E-201 is the reboiler of the pressurized tower, V-201 is the transfer tank for THF products, P-202 is the transfer pump for THF products, E-205 is the cooler for crude THF, and V-202 is the temporary storage tank for crude THF;

[0042] Figure 3This is a schematic process flow diagram of the alcohol removal subsystem in the embodiments of the present invention. Among them, T-300 is the alcohol removal tower, V-301 is the temporary storage tank for alcohol-containing wastewater, E-302 is the first cooler of the alcohol removal tower, E-303 is the second cooler of the alcohol removal tower, V-302 is the reflux drum of the alcohol removal tower, P-302AB is the top reflux pump of the alcohol removal tower, E-301 is the reboiler of the alcohol removal tower, E-304 is the extractant preheater, and E-305 is the bottom cooler of the alcohol removal tower;

[0043] Figure 4 This is the simulation process and results of the THF-water pressure swing distillation dehydration process in the embodiments of the present invention. Detailed implementation manners

[0044] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below through embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0046] Embodiment 1

[0047] The embodiments of the present invention provide a system for recovering tetrahydrofuran from the wastewater generated by the dehydrogenation synthesis of γ-butyrolactone from 1,4-butanediol. As Figures 1-3 shown, it includes an extraction subsystem, a rectification subsystem and an alcohol removal subsystem. The outlet of the extraction subsystem is connected to the rectification subsystem and the alcohol removal subsystem. Among them, the extraction subsystem includes an extraction tower T-100, an extractant tank V-102, the first cooler E-102 of the extraction tower, the second cooler E-103 of the extraction tower, an extraction tower reflux drum V-101, an extraction tower top reflux pump P-103AB and an extraction tower reboiler E-101; the rectification subsystem includes a pressurized tower T-200, a pressurized tower condenser E-202, a pressurized tower top reflux pump P-201AB, a raw material preheater E-203, a side draw cooler E-204 of the pressurized tower, a pressurized tower reboiler E-201, a THF finished product transfer tank V-201, a THF finished product transfer pump P-202, a THF crude product cooler E-205 and a THF crude product temporary storage tank V-202; the alcohol removal subsystem includes an alcohol removal tower T-300, an alcohol-containing wastewater temporary storage tank V-301, the first cooler E-302 of the alcohol removal tower, the second cooler E-303 of the alcohol removal tower, an alcohol removal tower reflux drum V-302, an alcohol removal tower top reflux pump P-302AB, an alcohol removal tower reboiler E-301, an extractant preheater E-304, and an alcohol removal tower bottom cooler E-305. Further, the reflux forms of the extraction tower T-100, the pressurized tower T-200 and the alcohol removal tower T-300 are all external forced reflux.

[0048] Among them, the extraction tower T-100 is an atmospheric tower, a packed tower, with 25 - 30 theoretical plates; the extraction tower T-100 is provided with a raw material feed inlet, an extractant feed inlet, a top product outlet, a top reflux inlet, a bottom product outlet, and a bottom gas-phase inlet; the pressurized tower T-200 is a distillation tower with a tower pressure of 0.5 - 0.6 MPa, a packed tower, with 20 - 25 theoretical plates; the pressurized tower T-200 is provided with a feed inlet, a top product outlet, a top reflux inlet, a finished product outlet, a bottom product outlet, and a bottom gas-phase inlet; the alcohol removal tower T-300 is an atmospheric tower, a packed tower, with 15 - 20 theoretical plates; the alcohol removal tower T-300 is provided with a feed inlet, a top product outlet, a top reflux inlet, a bottom product outlet, and a bottom gas-phase inlet.

[0049] In the extraction subsystem, as Figure 1 shown, the raw material feed inlet of the extraction tower is located in the middle and lower part of the extraction tower T-100; the raw material (waste water generated from the dehydrogenation of 1,4-butanediol to prepare γ-butyrolactone) is pumped into the raw material feed inlet of the extraction tower by a pump (the parameters of the pump are: flow rate Q is 0.7 m 3 / h, head H is 40 m, power is 1.1 kw, and the material is 304 stainless steel), and before entering the raw material feed inlet of the extraction tower, it first enters the raw material preheater E-203 of the distillation subsystem as a cooling medium for heat exchange and temperature rise treatment, and then enters the raw material feed inlet of the extraction tower after temperature rise and preheating. The extractant feed inlet of the extraction tower is located in the middle and upper part of the extraction tower T-100. The extractant (reverse osmosis water) first enters the extractant tank V-102, and the extractant flowing out of the extractant tank V-102 is pumped into the extractant feed inlet of the extraction tower by a pump (the parameters of the pump are: flow rate Q is 1.4 m 3 / h, head H is 40 m, power is 1.1 kw, and the material is 304 stainless steel), and before entering the extractant feed inlet of the extraction tower, it first enters the extractant preheater E-304 of the alcohol removal subsystem as a cooling medium for heat exchange and temperature rise treatment, and then enters the extractant feed inlet of the extraction tower after temperature rise and preheating. The top product outlet of the extraction tower is connected to the feed inlet of the first-stage cooler E-102 of the extraction tower, and the gas outlet of the first-stage cooler E-102 of the extraction tower is connected to the feed inlet of the second-stage cooler E-103 of the extraction tower; the gas outlet of the second-stage cooler E-103 of the extraction tower is connected to the off-site gas outlet; the outlet of the first-stage cooler E-102 of the extraction tower and the outlet of the second-stage cooler E-103 of the extraction tower are both connected to the feed inlet of the extraction tower reflux drum V-101; the outlet of the extraction tower reflux drum V-101 is connected to the inlet of the extraction tower top reflux pump P-103AB, and the gas outlet of the extraction tower reflux drum V-101 is connected to the feed inlet of the second-stage cooler E-103 of the extraction tower; the outlet of the extraction tower top reflux pump P-103AB is respectively connected to the top reflux inlet of the extraction tower and the feed inlet of the pressurized tower in the distillation subsystem. The parameters of the extraction tower top reflux pump P-103AB are: flow rate Q is 3.2 m 3 / h, the head H is 80 m, the power is 5.5 kw, and the material is 304 stainless steel. The bottom discharge port of the extraction column is respectively connected to the inlet of the reboiler E-101 of the extraction column and the alcohol-containing wastewater storage tank V-301 of the alcohol removal subsystem; the outlet of the reboiler E-101 of the extraction column is connected to the bottom gas inlet of the extraction column. There is a pump (the parameters of the pump are: the flow rate Q is 1.4 m 3 / h, the head H is 40 m, the power is 1.1 kw, and the material is 304 stainless steel) connected in the middle of the pipeline connecting the bottom discharge port of the extraction column to the alcohol-containing wastewater storage tank V-301, aiming to introduce the alcohol-containing wastewater obtained at the bottom of the extraction column T-100 into the alcohol removal subsystem at a stable flow rate.

[0050] In the rectification subsystem, as Figure 2 shown, the feed port of the pressurized column is located in the upper middle part of the pressurized column T-200. The top discharge port of the pressurized column is connected to the inlet of the condenser E-202 of the pressurized column; the gas outlet of the condenser E-202 of the pressurized column is connected to the gas outlet of the off-site area, and the outlet of the condenser E-202 of the pressurized column is first connected to the inlet of the top reflux pump P-201AB of the pressurized column. The outlet of the top reflux pump P-201AB of the pressurized column is respectively connected to the top reflux port of the pressurized column and the feed port of the raw materials of the extraction column. The parameters of the top reflux pump P-201AB of the pressurized column are: the flow rate Q is 2.1 m 3 / h, the head H is 75 m, the power is 4 kw, and the material is 304 stainless steel. The finished product discharge port of the pressurized column is connected to the inlet of the raw material preheater E-203; the outlet of the raw material preheater E-203 is connected to the inlet of the side draw cooler E-204 of the pressurized column; the outlet of the side draw cooler E-204 of the pressurized column is connected to the inlet of the THF finished product transfer tank V-201; the outlet of the THF finished product transfer tank V-201 is connected to the inlet of the THF finished product transfer pump P-202, and the gas outlet of the THF finished product transfer tank V-201 is connected to the gas outlet of the off-site area; the outlet of the THF finished product transfer pump P-202 is respectively connected to the inlet of the THF crude product storage tank V-202 and the THF finished product outlet. The parameters of the THF finished product transfer pump P-202 are: the flow rate Q is 3.2 m 3 / h, the head H is 32 m, the power is 2.2 kw, and the material is 304 stainless steel. The bottom discharge port of the pressurizing tower is connected to the inlet of the pressurizing tower reboiler E-201, the inlet of the THF crude product cooler E-205, and the raw material inlet of the extraction tower at the same time; the outlet of the pressurizing tower reboiler E-201 is connected to the bottom gas phase inlet of the pressurizing tower; the outlet of the THF crude product cooler E-205 is connected to the inlet of the THF crude product temporary storage tank V-202; the outlet of the THF crude product temporary storage tank V-202 is connected to the raw material inlet of the extraction tower, and the gas outlet of the THF crude product temporary storage tank V-202 is connected to the off-site area gas outlet. Pumps are installed in the pipelines where the bottom discharge port of the pressurizing tower and the outlet of the THF crude product temporary storage tank V-202 are both connected to the raw material inlet of the extraction tower at the same time, aiming to feed the THF crude product obtained from the bottom of the pressurizing tower T-200 and the THF crude product temporary storage tank V-202 into the extraction subsystem at a stable flow rate. Further, the parameters of the pump for pumping the THF crude product into the extraction subsystem are: the flow rate Q is 3.2 m 3 / h, the head H is 32 m, the power is 2.2 kw, and the material is 304 stainless steel.

[0051] In the alcohol removal subsystem, as Figure 3 shown, the feed port of the alcohol removal tower is located in the middle and upper parts of the alcohol removal tower T-300. The alcohol-containing wastewater obtained from the bottom of the extraction tower T-100 first enters the alcohol-containing wastewater temporary storage tank V-301 for temporary storage, and the alcohol-containing wastewater flowing out of the alcohol-containing wastewater temporary storage tank V-301 is pumped into the feed port of the alcohol removal tower by a pump (the parameters of the pump are: the flow rate Q is 1.4 m 3 / h, the head H is 40 m, the power is 1.1 kw, and the material is 304 stainless steel). The top discharge port of the alcohol removal tower is connected to the inlet of the first cooler E-302 of the alcohol removal tower, and the gas outlet of the first cooler E-302 of the alcohol removal tower is connected to the inlet of the second cooler E-303 of the alcohol removal tower; the gas outlet of the second cooler E-303 of the alcohol removal tower is connected to the off-site area gas outlet; the outlets of the first cooler E-302 of the alcohol removal tower and the second cooler E-303 of the alcohol removal tower are both connected to the inlet of the reflux tank V-302 of the alcohol removal tower; the outlet of the reflux tank V-302 of the alcohol removal tower is connected to the inlet of the top reflux pump P-302AB of the alcohol removal tower, and the gas outlet of the reflux tank V-302 of the alcohol removal tower is connected to the inlet of the second cooler E-303 of the alcohol removal tower; the outlet of the top reflux pump P-302AB of the alcohol removal tower is respectively connected to the top reflux port and the alcohol-water mixture outlet of the alcohol removal tower. The parameters of the top reflux pump P-302AB of the alcohol removal tower are: the flow rate Q is 3.2 m 3 / h, the head H is 32m, the power is 2.2kw, and the material is 304 stainless steel. The bottom discharge port of the de-alcoholization tower is connected to the inlet of the de-alcoholization tower reboiler E-301 and the feed port of the extractant preheater E-304 at the same time; the outlet of the de-alcoholization tower reboiler E-301 is connected to the bottom gas phase inlet of the de-alcoholization tower; the outlet of the extractant preheater E-304 is connected to the feed port of the de-alcoholization tower bottom cooler E-305; the outlet of the de-alcoholization tower bottom cooler E-305 is connected to the high-boiling waste water discharge port. The high-boiling waste water flowing out of the outlet of the extractant preheater E-304 is pumped by a pump (the parameters of the pump are: flow rate Q is 3.2m 3 / h, the head H is 32m, the power is 2.2kw, and the material is 304 stainless steel) into the feed port of the de-alcoholization tower bottom cooler E-305.

[0052] Example 2

[0053] A THF wastewater from the dehydrogenation synthesis of γ-butyrolactone from 1,4-butanediol, the main components are: THF: 43%, n-butanol: 21%, water: 27%, methanol: 0.37%, other high-boiling impurities 8.63%;

[0054] The embodiment of the present invention provides a method for recovering tetrahydrofuran from the above THF wastewater by using the system described in Example 1, which includes the following steps:

[0055] (1) Add the above THF wastewater to the raw material feed port of the extraction tower in the system, the feed temperature is 35-45°C, and after being heated and vaporized by the extraction tower reboiler E-101, a gaseous raw material is obtained, wherein the bottom temperature is 92-100°C; then continuously add the extractant to the extractant feed port of the extraction tower in the system, the feed temperature is 35-45°C, and at the same time control the top reflux ratio of the extraction tower T-100 to be 1.5, and the top temperature is 64.1, so that the gaseous raw material and the extractant perform gas-liquid exchange in the extraction tower T-100, and a THF-water azeotrope is obtained from the top discharge port of the extraction tower, and an alcohol-containing wastewater is obtained from the bottom discharge port of the extraction tower. The system is the system described in Example 1, specifically including an extraction subsystem, a rectification subsystem and a de-alcoholization subsystem.

[0056] The THF wastewater is pumped into the raw material feed port of the extraction tower by a pump, and before entering the raw material feed port of the extraction tower, it first enters the raw material preheater E-203 as a cooling medium for heat exchange and then enters the raw material feed port of the extraction tower (the parameters of the pump for pumping the raw material into the raw material feed port of the extraction tower are: flow rate Q is 0.7m 3 / h, the head H is 40 m, the power is 1.1 kw, and the material is 304 stainless steel). The THF wastewater entering the extraction column enters the extraction column reboiler E-101 through the bottom outlet of the extraction column. After being heated and vaporized by the extraction column reboiler E-101, the gaseous THF wastewater is obtained. The reverse osmosis water enters the extractant tank V-102 for temporary storage as an extractant. The extractant flowing out of the extractant tank V-102 is pumped into the extractant inlet of the extraction column by a pump. Before entering the extractant inlet of the extraction column, it first enters the extractant preheater E-304 for heat exchange as a cooling medium, and then enters the extractant inlet of the extraction column (the parameters of the pump for pumping the extractant into the extractant inlet of the extraction column are: the flow rate Q is 1.4 m 3 / h, the head H is 40 m, the power is 1.1 kw, and the material is 304 stainless steel). After the THF-water-methanol in the THF wastewater is heated and vaporized by the extraction column reboiler E-101, it enters the extraction column. It undergoes gas-liquid exchange with the reverse osmosis water entering the extraction column from the upper-middle part of the column on the surface of the packing. Under the action of the extractant, the relative volatility between components changes. Methanol falls to the bottom of the column and accumulates with the extractant, and THF accumulates at the top of the column. After reaching equilibrium, an azeotrope (gaseous) of THF-water containing about 5.2% water is obtained from the top outlet of the extraction column, and an alcohol-containing wastewater without THF (liquid) is obtained from the bottom outlet of the extraction column.

[0057] (2) The azeotrope (gaseous) of THF-water obtained in step (1) enters the first-stage cooler E-102 of the extraction column for condensation to obtain a liquid azeotrope of THF-water, and enters the extraction column reflux drum V-101 for temporary storage; the excess azeotrope (gaseous) of THF-water enters the second-stage cooler E-103 of the extraction column through the outlet of the first-stage cooler E-102 of the extraction column. After condensation, an azeotrope of THF-water (liquid) is obtained, which also enters the extraction column reflux drum V-101 for temporary storage; the gas in the extraction column reflux drum V-101 enters the second-stage cooler E-103 of the extraction column for treatment, and the collected waste gas is discharged from the second-stage cooler E-103 of the extraction column to the out-of-plant area for post-treatment; the azeotrope (liquid) of THF-water in the extraction column reflux drum V-101 is transported in two ways by the extraction column top reflux pump P-103AB. One way is pumped back into the extraction column T-100 through the top reflux port of the extraction column, and the other way is directly pumped into the pressurized column T-200 through the feed port of the pressurized column.

[0058] Pump the azeotrope of THF - water (liquid) into the pressurized tower T - 200. The feed temperature is 64°C. It enters the reboiler E - 201 of the pressurized tower through the bottom outlet of the pressurized tower. After being heated and vaporized by the reboiler E - 201 of the pressurized tower, a gaseous azeotrope of THF - water is obtained, where the bottom temperature is 125 - 126°C. Under the pressure condition of 0.5 - 0.6 MPa for the gaseous azeotrope of THF - water, the azeotropic ratio of water in the THF - water azeotrope increases. Then, by controlling the top reflux ratio of the pressurized tower T - 200 to be 3 and the top temperature to be 120°C, the water in the THF - water azeotrope is enriched at the top of the pressurized tower T - 200. Finally, a high - water - content azeotrope of THF - water (gaseous) containing about 10% water is obtained from the top outlet of the pressurized tower, a THF product (liquid) is obtained from the finished product outlet of the pressurized tower, and a crude THF (liquid) is obtained from the bottom outlet of the pressurized tower. Further, to ensure the pressure safety inside the pressurized tower T - 200, a safety valve is installed above the top outlet of the pressurized tower.

[0059] The high - water - content azeotrope of THF - water (gaseous) obtained from the top outlet of the pressurized tower enters the condenser E - 202 of the pressurized tower and is condensed to obtain a high - water - content azeotrope of THF - water (liquid). The waste gas in the condenser is discharged to the out - of - bounds area for post - treatment; the high - water - content azeotrope of THF - water (liquid) is transported in two routes by the top reflux pump P - 201AB of the pressurized tower (the parameters of the pump are: flow rate Q is 2.1 m 3 / h, head H is 75 m, power is 4 kw, and the material is 304 stainless steel). One route is returned to the pressurized tower T - 200 as reflux liquid, and the other route is taken out and sent to the extraction tower T - 100 for re - treatment.

[0060] The THF product (liquid) obtained from the finished product outlet of the pressurized tower enters the raw material pre - heater E - 203 and the side - draw cooler E - 204 of the pressurized tower for temperature reduction treatment in sequence, and then enters the THF product transfer tank V - 201 for temporary storage. The waste gas in the tank is discharged to the out - of - bounds area for post - treatment. The THF product (liquid) flowing out of the THF product transfer tank V - 201 is transported in two routes by the THF product transfer pump P - 202 (the parameters of the pump are: flow rate Q is 3.2 m 3 / h, head H is 32 m, power is 2.2 kw, and the material is 304 stainless steel). The qualified THF product (liquid) after inspection directly enters the THF product outlet for discharging; the unqualified THF product (liquid) after inspection enters the crude THF temporary storage tank V - 202, and then is pumped into the THF waste water raw material by a pump. The waste gas in the crude THF temporary storage tank V - 202 is discharged to the out - of - bounds area for post - treatment.

[0061] The crude THF (liquid) obtained from the bottom outlet of the pressurized tower is transported in two routes by a pump (the parameters of the pump are: flow rate Q is 3.2 m 3Pump it into the THF wastewater raw material at a flow rate Q of 1.4 m³ / h, a head H of 32 m, a power of 2.2 kw, and a material of 304 stainless steel, and repeat the treatment process in step (1). Among them, one route is first cooled by the THF crude product cooler E-205 and then enters the THF crude product temporary storage tank V-202. The THF crude product (liquid) flowing out of the THF crude product temporary storage tank V-202 is pumped into the THF wastewater raw material by a pump, and the other route is directly pumped into the THF wastewater raw material by a pump.

[0062] (3)The alcohol-containing wastewater (liquid) without THF obtained in step (1) is pumped into the alcohol-containing wastewater temporary storage tank V-301 in the alcohol removal subsystem by a pump (the parameters of the pump are: flow rate Q is 1.4 m³ / h, head H is 40 m, power is 1.1 kw, and the material is 304 stainless steel). The waste gas in the alcohol-containing wastewater temporary storage tank V-301 is discharged into the out-of-bounds area for post-treatment. The alcohol-containing wastewater (liquid) flowing out of the alcohol-containing wastewater temporary storage tank V-301 is pumped into the feed inlet of the alcohol removal tower by a pump (the parameters of the pump are: flow rate Q is 1.4 m³ / h, head H is 40 m, power is 1.1 kw, and the material is 304 stainless steel), and the feed temperature is 92 - 100 °C. The alcohol-containing wastewater (liquid) entering the alcohol removal tower T-300 enters the alcohol removal tower reboiler E-301 through the bottom discharge port of the alcohol removal tower, and after being heated and vaporized by the alcohol removal tower reboiler E-301, gaseous alcohol-containing wastewater is obtained, where the bottom temperature is 100 °C. By controlling the top reflux ratio of the alcohol removal tower T-300 to be 2 and the top temperature to be 92 °C, the low-boiling alcohol-water mixture in the alcohol-containing wastewater (gaseous) is enriched at the top of the alcohol removal tower T-300, and then an alcohol-water mixture (gaseous) is obtained from the top discharge port of the alcohol removal tower, and high-boiling wastewater (liquid) is obtained from the bottom discharge port of the alcohol removal tower. 3 / h, a head H of 40 m, a power of 1.1 kw, and a material of 304 stainless steel) is pumped into the alcohol-containing wastewater temporary storage tank V-301 in the alcohol removal subsystem. The waste gas in the alcohol-containing wastewater temporary storage tank V-301 is discharged into the out-of-bounds area for post-treatment. The alcohol-containing wastewater (liquid) flowing out of the alcohol-containing wastewater temporary storage tank V-301 is pumped into the feed inlet of the alcohol removal tower by a pump (the parameters of the pump are: flow rate Q is 1.4 m³ / h, head H is 40 m, power is 1.1 kw, and the material is 304 stainless steel), and the feed temperature is 92 - 100 °C. The alcohol-containing wastewater (liquid) entering the alcohol removal tower T-300 enters the alcohol removal tower reboiler E-301 through the bottom discharge port of the alcohol removal tower, and after being heated and vaporized by the alcohol removal tower reboiler E-301, gaseous alcohol-containing wastewater is obtained, where the bottom temperature is 100 °C. By controlling the top reflux ratio of the alcohol removal tower T-300 to be 2 and the top temperature to be 92 °C, the low-boiling alcohol-water mixture in the alcohol-containing wastewater (gaseous) is enriched at the top of the alcohol removal tower T-300, and then an alcohol-water mixture (gaseous) is obtained from the top discharge port of the alcohol removal tower, and high-boiling wastewater (liquid) is obtained from the bottom discharge port of the alcohol removal tower. 3 / h, a head H of 40 m, a power of 1.1 kw, and a material of 304 stainless steel) is pumped into the feed inlet of the alcohol removal tower. The alcohol-containing wastewater (liquid) entering the alcohol removal tower T-300 enters the alcohol removal tower reboiler E-301 through the bottom discharge port of the alcohol removal tower, and after being heated and vaporized by the alcohol removal tower reboiler E-301, gaseous alcohol-containing wastewater is obtained, where the bottom temperature is 100 °C. By controlling the top reflux ratio of the alcohol removal tower T-300 to be 2 and the top temperature to be 92 °C, the low-boiling alcohol-water mixture in the alcohol-containing wastewater (gaseous) is enriched at the top of the alcohol removal tower T-300, and then an alcohol-water mixture (gaseous) is obtained from the top discharge port of the alcohol removal tower, and high-boiling wastewater (liquid) is obtained from the bottom discharge port of the alcohol removal tower.

[0063] The alcohol-water mixture (gaseous) obtained from the top discharge port of the alcohol removal tower enters the first-stage cooler E-302 of the alcohol removal tower for condensation to obtain an alcohol-water mixture (liquid), and enters the reflux tank V-302 of the alcohol removal tower for temporary storage; the excessive THF-water azeotrope (gaseous) enters the second-stage cooler E-303 of the alcohol removal tower through the gas outlet of the first-stage cooler E-302 of the alcohol removal tower, and after condensation, an alcohol-water mixture (liquid) is obtained, which also enters the reflux tank V-302 of the alcohol removal tower; the gas in the reflux tank V-302 of the alcohol removal tower enters the second-stage cooler E-303 of the alcohol removal tower for treatment, and the collected waste gas is discharged from the second-stage cooler E-303 of the alcohol removal tower into the out-of-bounds area for post-treatment; the alcohol-water mixture (liquid) in the reflux tank V-302 of the alcohol removal tower is transported in two routes by the top reflux pump P-302AB of the alcohol removal tower. One route is pumped back to the alcohol removal tower T-300 through the top reflux port of the alcohol removal tower, and the other route is discharged through the alcohol-water mixture outlet.

[0064] The high-boiling wastewater (liquid) obtained from the bottom discharge port of the alcohol removal tower enters the extractant preheater E-304 for temperature reduction treatment and then is pumped by a pump (the parameters of the pump are: flow rate Q is 3.2 m³ / h3 (pumping rate: 1 t / h, head: 32 m, power: 2.2 kw, material: 304 stainless steel) is pumped into the bottom cooler E-305 of the alcohol stripper for secondary cooling, and finally enters the off-site area for sewage treatment or is added as an extractant to the extraction column T-100 to participate in the gas-liquid exchange in step (1).

[0065] The inventor used PROII software to perform numerical simulation calculations on the above wastewater, and the results are as Figure 4 shown. It can be seen from the figure that T1 is the extraction column, T2 is the pressurized column, T3 is the alcohol stripper. The THF wastewater finally produces qualified THF products from the middle side line of the pressurized column after extractive distillation and pressure swing distillation, and the remaining mixed alcohol enters the alcohol stripper for recovery. The processing capacity of the recovery system simulated by the present invention is 350 kg / h (specific parameters: 1 t / h, running for 200 days, 1000 t / year, running once a month, running for 10 days each time). The purity of the recovered THF is ≥99.8%, and the water content is <200 ppm. Therefore, it has high industrial application value.

[0066] In summary, the present invention effectively overcomes the deficiencies in the prior art and has high industrial utilization value. The role of the above embodiments is to illustrate the substantial content of the present invention, but does not limit the protection scope of the present invention. Those of ordinary skill in the art should understand that the technical solution of the present invention can be modified or equivalently replaced without departing from the essence and protection scope of the technical solution of the present invention.

Claims

1. A system for recovering tetrahydrofuran from the wastewater generated by the dehydrogenation synthesis of γ-butyrolactone from 1,4-butanediol, characterized in that, The system includes an extraction subsystem, and the outlet of the extraction subsystem is connected to a rectification subsystem and a de-alcoholization subsystem; the extraction subsystem includes an extraction column under atmospheric pressure, the top of the extraction column is provided with an extraction column condensation device, and the bottom of the column is provided with an extraction column reboiler; the rectification subsystem includes a pressurized column with a pressure of 0.5 - 0.6 MPa inside the column, the top of the pressurized column is provided with a pressurized column condenser, the side of the column is provided with a finished product cooling device, and the bottom of the column is provided with a pressurized column reboiler; the de-alcoholization subsystem includes a de-alcoholization column under atmospheric pressure, the top of the de-alcoholization column is provided with a de-alcoholization column condensation device, and the bottom of the column is provided with a de-alcoholization column reboiler and a wastewater cooling device; The top discharge port of the extraction column is connected to the extraction column condensation device; the top reflux pipeline of the extraction column condensation device is connected to the extraction column, the discharge port of the extraction column condensation device is connected to the feed port of the pressurized column, and the gas outlet of the extraction column condensation device is communicated to the out-of-plant area for treatment; the gas phase outlet pipeline of the extraction column reboiler is connected to the extraction column; the bottom discharge port is connected to the feed port of the de-alcoholization subsystem; The top discharge port of the pressurized column is connected to the pressurized column condenser; the top reflux pipeline of the pressurized column condenser is connected to the pressurized column, the discharge port of the pressurized column condenser is connected to the raw material feed port of the extraction column, and the gas outlet of the pressurized column condenser is communicated to the out-of-plant area for treatment; the side discharge port is connected to the finished product cooling device; the discharge port of the finished product cooling device is respectively connected to the THF finished product outlet and the raw material feed port of the extraction column; the gas phase outlet pipeline of the pressurized column reboiler is connected to the pressurized column; the bottom discharge port is connected to the raw material feed port of the extraction column; The top discharge port of the de-alcoholization column is connected to the de-alcoholization column condensation device; the top reflux pipeline of the de-alcoholization column condensation device is connected to the de-alcoholization column, the discharge port of the de-alcoholization column condensation device is connected to the alcohol-water mixture outlet, and the gas outlet of the de-alcoholization column condensation device is communicated to the out-of-plant area for treatment; the gas phase outlet pipeline of the de-alcoholization column reboiler is connected to the de-alcoholization column; the bottom discharge port is connected to the wastewater cooling device; the discharge port of the wastewater cooling device is connected to the wastewater outlet; A method for recovering tetrahydrofuran from the wastewater of the dehydrogenation synthesis of γ-butyrolactone from 1,4-butanediol using the above system comprises the following steps: (1) Add the wastewater of the dehydrogenation synthesis of γ-butyrolactone from 1,4-butanediol to the raw material feed port of the extraction column in the system, and obtain a gaseous raw material after heating and vaporization by the extraction column reboiler; then continuously add the extractant to the extractant feed port of the extraction column in the system, and at the same time control the top reflux ratio of the extraction column, so that the gaseous raw material and the extractant perform gas-liquid exchange in the extraction column, and obtain an azeotrope of THF-water from the top discharge port of the extraction column, and obtain alcohol-containing wastewater from the bottom discharge port of the extraction column; The wastewater of the dehydrogenation synthesis of γ-butyrolactone from 1,4-butanediol mainly contains: THF: 43%, n-butanol: 21%, water: 27%, methanol: 0.37%, and other high-boiling impurities 8.63%; (2) Cool the azeotrope of THF - water obtained in step (1) and add it to the feed inlet of the pressurized tower. Under the pressure condition of 0.5 - 0.6 MPa, by controlling the top reflux ratio of the pressurized tower, the water in the azeotrope of THF - water is enriched at the top of the pressurized tower. Then, an azeotrope of THF - water with a high water content is obtained from the top product outlet of the pressurized tower, a THF product is obtained from the finished product outlet of the pressurized tower, and a crude THF is obtained from the bottom product outlet of the pressurized tower. Among them, the azeotrope of THF - water with a high water content and the crude THF both return to the extraction tower from the raw material feed inlet of the extraction tower to re - perform the gas - liquid exchange treatment in step (1). (3) Add the alcohol - containing wastewater obtained in step (1) to the feed inlet of the alcohol - removal tower. By controlling the top reflux ratio of the alcohol - removal tower, the low - boiling alcohol - water mixture in the alcohol - containing wastewater is enriched at the top of the alcohol - removal tower. Then, an alcohol - water mixture is obtained from the top product outlet of the alcohol - removal tower, and high - boiling wastewater is obtained from the bottom product outlet of the alcohol - removal tower.

2. The system according to claim 1, wherein The extraction tower condenser device includes the extraction tower first cooler and the extraction tower second cooler connected in parallel; the extraction subsystem also includes an extraction tower reflux drum and an extraction tower top reflux pump. The top product outlet of the extraction tower is connected to the extraction tower first cooler, the gas outlet of the extraction tower first cooler is connected to the extraction tower second cooler; the gas outlet of the extraction tower second cooler is communicated to the off - site area for treatment; the liquid outlets of the extraction tower first cooler and the extraction tower second cooler are both connected to the extraction tower reflux drum; the gas outlet of the extraction tower reflux drum is connected to the feed inlet of the extraction tower second cooler, and the liquid outlet of the extraction tower reflux drum is connected to the extraction tower top reflux pump; the outlet of the extraction tower top reflux pump is respectively connected to the top reflux pipeline and the feed inlet of the pressurized tower.

3. The system according to claim 2, characterized in that, The rectification subsystem also includes a pressurized tower top reflux pump; the outlet of the pressurized tower condenser is connected to the pressurized tower top reflux pump, and the outlet of the pressurized tower top reflux pump is respectively connected to the top reflux pipeline and the raw material feed inlet of the extraction tower. The finished product cooling device includes the pressurized tower first cooler and the pressurized tower second cooler connected in series; the rectification subsystem also includes a THF finished product transfer tank, a THF finished product transfer pump, a crude THF cooler, and a crude THF temporary storage tank; the finished product outlet of the pressurized tower is connected to the pressurized tower first cooler; the outlet of the pressurized tower first cooler is connected to the pressurized tower second cooler; the outlet of the pressurized tower second cooler is connected to the THF finished product transfer tank; the gas outlet of the THF finished product transfer tank is communicated to the off - site area for treatment, and the liquid outlet of the THF finished product transfer tank is connected to the THF finished product transfer pump; the outlet of the THF finished product transfer pump is respectively connected to the crude THF temporary storage tank and the THF finished product outlet; the bottom product outlet of the pressurized tower is respectively connected to the crude THF cooler and the raw material feed inlet of the extraction tower; the outlet of the crude THF cooler is connected to the crude THF temporary storage tank; the liquid outlet of the crude THF temporary storage tank is connected to the raw material feed inlet of the extraction tower, and the gas outlet of the crude THF temporary storage tank is communicated to the off - site area for treatment.

4. The system according to claim 3, characterized in that The de-alcoholization tower condensation device includes a first-stage cooler of the de-alcoholization tower and a second-stage cooler of the de-alcoholization tower connected in parallel; the de-alcoholization subsystem further includes a de-alcoholization tower reflux drum and a de-alcoholization tower top reflux pump; the top discharge port of the de-alcoholization tower is connected to the first-stage cooler of the de-alcoholization tower, and the gas outlet of the first-stage cooler of the de-alcoholization tower is connected to the second-stage cooler of the de-alcoholization tower; the gas outlet of the second-stage cooler of the de-alcoholization tower is communicated to the off-site area for treatment; the discharge ports of the first-stage cooler of the de-alcoholization tower and the second-stage cooler of the de-alcoholization tower are both connected to the de-alcoholization tower reflux drum; the gas outlet of the de-alcoholization tower reflux drum is connected to the feed port of the second-stage cooler of the de-alcoholization tower, and the discharge port of the de-alcoholization tower reflux drum is connected to the de-alcoholization tower top reflux pump; the outlet of the de-alcoholization tower top reflux pump is respectively connected to the top reflux pipeline and the alcohol-water mixture outlet; The waste water cooling device includes a first-stage cooler of the de-alcoholization tower and a second-stage cooler of the de-alcoholization tower connected in series; the bottom discharge port of the de-alcoholization tower is connected to the first-stage cooler of the de-alcoholization tower; the discharge port of the first-stage cooler of the de-alcoholization tower is connected to the second-stage cooler of the de-alcoholization tower; the discharge port of the second-stage cooler of the de-alcoholization tower is connected to the waste water outlet.

5. The system according to claim 4, wherein The reflux forms of the extraction tower, the pressurization tower and the de-alcoholization tower are all external forced reflux; the raw material feed port of the extraction tower is located in the middle and lower part of the extraction tower, and the extractant feed port of the extraction tower is located in the middle and upper part of the extraction tower; the feed port of the pressurization tower is located in the middle and upper part of the pressurization tower; the feed port of the de-alcoholization tower is located in the middle and upper part of the de-alcoholization tower.

6. The system according to claim 5, wherein The extraction tower is a packed tower with a theoretical plate number of 25 - 30; the pressurization tower is a packed tower with a theoretical plate number of 20 - 25; the de-alcoholization tower is a packed tower with a theoretical plate number of 15 - 20.

7. The system according to claim 6, wherein Before the raw material enters the raw material feed port of the extraction tower, it first enters the first-stage cooler of the pressurization tower in the rectification subsystem for heat exchange and temperature increase treatment as a cooling medium, and then enters the raw material feed port of the extraction tower; before the extractant enters the extractant feed port of the extraction tower, it first enters the first-stage cooler of the de-alcoholization tower in the de-alcoholization subsystem for heat exchange and temperature increase treatment as a cooling medium, and then enters the extractant feed port of the extraction tower.

8. The system according to claim 1, wherein The mass ratio of THF to the extractant in the raw material is 1∶(1 - 1.5).

9. The system according to claim 1, wherein The top temperature of the extraction tower is 64.1 °C, the bottom temperature is 92 - 100 °C, the raw material feed temperature is 35 - 45 °C, the extractant feed temperature is 35 - 45 °C, and the top reflux ratio is 1.5; the top temperature of the pressurization tower is 120 °C, the bottom temperature is 125 - 126 °C, the feed temperature is 64 °C, and the top reflux ratio is 3; the top temperature of the de-alcoholization tower is 92 °C, the bottom temperature is 100 °C, the feed temperature is 92 - 100 °C, and the top reflux ratio is 2.

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