阅读说明：本技术 一种利用bdo焦油制备四氢呋喃的系统及方法 (System and method for preparing tetrahydrofuran by using BDO tar ) 是由 张雅坚 于 2020-12-04 设计创作，主要内容包括：本申请提供一种利用BDO焦油制备四氢呋喃的系统及方法。所述系统包括BDO焦油处理装置和提纯装置,BDO焦油处理装置包括依次连接的BDO脱轻塔、BDO原液槽、短程薄膜蒸发器、储液罐、BDO塔、BDO槽、THF反应器、THF脱水塔和THF塔,用于利用BDO焦油制备第一THF；提纯装置包括依次连接的加氢反应器、THF精制塔和THF产品槽,用于对第一THF进行精制提纯,最终得到THF。如此,整个系统可以从BDO焦油中提取出纯度较高的THF,处理过程不会产生有害物质,符合环保要求。同时也实现了BDO焦油的废物再利用,节约了资源,具有较高的经济效益。(The application provides a system and a method for preparing tetrahydrofuran by utilizing BDO tar. The system comprises a BDO tar treatment device and a purification device, wherein the BDO tar treatment device comprises a BDO lightness-removing tower, a BDO raw material tank, a short-range film evaporator, a liquid storage tank, a BDO tower, a BDO tank, a THF reactor, a THF dehydration tower and a THF tower which are sequentially connected and used for preparing first THF by utilizing BDO tar; the purification device comprises a hydrogenation reactor, a THF refining tower and a THF product tank which are connected in sequence and is used for refining and purifying the first THF to finally obtain the THF. Therefore, the whole system can extract THF with higher purity from BDO tar, harmful substances are not generated in the treatment process, and the requirement of environmental protection is met. Meanwhile, the waste recycling of BDO tar is realized, the resources are saved, and the economic benefit is higher.)

1. A system for preparing tetrahydrofuran by utilizing BDO tar is characterized by comprising a BDO tar treatment device and a purification device;

the BDO tar treatment device comprises a BDO lightness-removing tower, a BDO raw liquid tank, a short-range film evaporator, a liquid storage tank, a BDO tower, a BDO tank, a THF reactor, a THF dehydration tower and a THF tower which are connected in sequence and used for preparing THF by using BDO tar;

the feed end of the BDO raw liquid tank is connected with the discharge end of the BDO lightness-removing tower through a BDO tar pump, the feed end of the short-range film evaporator is connected with the discharge end of the BDO raw liquid tank through a BDO raw liquid pump, the feed end of the BDO tower is connected with the discharge end of the liquid storage tank through a coarse BDO pump, the discharge end of the BDO tower is further connected with the feed end of the BDO raw liquid tank, and the discharge end of the THF tower is further connected with the feed end of the THF dehydration tower;

the purification device comprises a hydrogenation reactor, a THF refining tower and a THF product tank which are connected in sequence and is used for further refining and purifying the product of the BDO tar treatment device; and the feeding end of the hydrogenation reactor is connected with the discharging end of the THF dehydration tower.

2. The system of claim 1, further comprising a low molecular weight polytetrahydrofuran reaction unit;

the low molecular weight polytetrahydrofuran reaction device comprises a polytetrahydrofuran tank and a degradation reactor which are connected in sequence and is used for treating the low molecular weight polytetrahydrofuran; the discharge end of the degradation reactor is connected with the feed end of the THF dehydration tower;

and the feed end of the degradation reactor is connected with the discharge end of the polytetrahydrofuran tank through a polytetrahydrofuran pump.

3. The system of claim 1, further comprising a debris handling device;

the residue treatment device comprises a BDO residue groove and a BDO device which are sequentially connected and is used for treating residues in the preparation process;

the feed end of the BDO device is connected with the discharge end of the BDO residue tank through a residue discharge pump;

and the feed end of the BDO residue tank is respectively connected with the discharge end of the BDO lightness-removing column through a distillation pump, the discharge end of the liquid storage tank through a residue pump and the discharge end of the THF reactor.

4. The system of claim 1, wherein the BDO lightness-removing column is a double-effect evaporation column and comprises a lightness-removing column upper column and a lightness-removing column lower column, and the distilled gas phase of the lightness-removing column lower column is used as a heating source of the lightness-removing column upper column.

5. The system of claim 1, wherein the BDO column is a vacuum column with a top pressure of 5Kpa absolute.

6. A method for preparing tetrahydrofuran by utilizing BDO tar, which is applied to a system for preparing tetrahydrofuran by utilizing BDO tar, and is characterized by comprising the following steps:

obtaining water-containing BDO tar;

inputting the water-containing BDO tar into the BDO lightness-removing tower to remove water, so as to obtain water-free BDO tar;

converging the water-free BDO tar into the BDO stock solution tank through the BDO tar pump to obtain BDO stock solution;

inputting the BDO stock solution into the short-range thin film evaporator through the BDO stock solution pump for evaporation to obtain crude BDO;

inputting the coarse BDO into the liquid storage tank, and then, feeding the coarse BDO into the BDO tower through the coarse BDO pump for refining to obtain BDO and BDO containing heavy components;

collecting the BDO containing heavy components into the BDO raw liquid tank;

inputting the BDO into the BDO groove, and then inputting the BDO into the THF reactor from the BDO groove to react to obtain a first mixture of THF and water; said first mixture of THF and water is in a vapor phase;

feeding the first mixture of THF and water to the THF dehydration column to obtain a first azeotrope of THF and water;

feeding the first THF and water azeotrope into the THF tower to obtain first THF and a second THF and water azeotrope; the second azeotrope of THF and water is used for returning and inputting into the THF dehydration tower, and the first THF is obtained;

inputting the first THF into the hydrogenation reactor for reaction to obtain second THF;

inputting the second THF into the THF refining tower for refining to obtain THF;

the THF was taken up into the THF product tank.

7. The method of claim 6, further comprising:

obtaining the low molecular weight polytetrahydrofuran;

after the low-molecular polytetrahydrofuran is input into the polytetrahydrofuran tank, the low-molecular polytetrahydrofuran enters the degradation reactor through the polytetrahydrofuran pump to carry out degradation reaction, and a second mixture of THF and water is obtained; said second mixture of THF and water is in a vapor phase;

feeding the second mixture of THF and water to the THF dehydration column to obtain the first azeotrope of THF and water.

8. The method of claim 6, further comprising:

feeding the distillate to the BDO residue tank through the distillation pump; the distillate is another product obtained after the water-containing BDO tar is input into the BDO lightness-removing tower to remove water;

inputting BDO residues into the liquid storage tank and inputting the BDO residues into the BDO residue tank through the residue pump; the BDO residue is another product obtained after the BDO stock solution is input into the short-range thin film evaporator through the BDO stock solution pump to be evaporated;

feeding THF tar into the BDO residue tank, and forming a residue mixture together with the distillate and the BDO residue; the THF tar is another product obtained after the BDO is input into the BDO groove and then input into the THF reactor from the BDO groove for reaction;

and inputting the residue mixture into the BDO device through the residue delivery pump for incineration treatment.

9. The process of claim 6, wherein the BDO lightness-removing column is a double-effect evaporation column which comprises a lightness-removing column upper column and a lightness-removing column lower column, and the distilled gas phase of the lightness-removing column lower column is used as a heating source of the lightness-removing column upper column.

10. The process of claim 6, wherein the BDO column is a vacuum column with a top pressure of 5Kpa absolute.

Technical Field

The application relates to the technical field of chemical industry, in particular to a system and a method for preparing tetrahydrofuran by utilizing BDO tar.

Background

BDO (English name: Butane-1,4-diol, Chinese name: 1, 4-butanediol) has a molecular formula of C₄H₁₀O₂The product is colorless or light yellow oily liquid, and is an important chemical raw material. In the normal production process of BDO, some byproducts and waste liquid are generated, which mainly comprise BDO tar and crude butanol, wherein the BDO tar mainly comprises BDO and THF (English full name: Tetrah)ydorfuran, chinese name: tetrahydrofuran), methanol, butanol, ethanol, etc.

At present, the BDO tar generated in the normal production process of BDO is generally treated by an incineration method, harmful substances can be generated by the method, the method does not meet the environmental protection requirement, resources are seriously wasted, and the economic benefit is low. Therefore, how to recycle the BDO tar efficiently is a problem to be solved by those skilled in the art.

In the research process, the inventor considers that THF is contained in the components of BDO tar, and the THF is not only an important organic synthetic raw material but also a solvent with excellent performance and has very wide application. Therefore, it is considered to extract THF from BDO tar.

Based on this, a system for preparing tetrahydrofuran by utilizing BDO tar is needed at present, and the system is used for solving the problems that the existing BDO tar treatment method seriously wastes resources and further has low economic benefit.

Disclosure of Invention

The application provides a system and a method for preparing tetrahydrofuran by utilizing BDO tar, which can be used for solving the technical problems of serious resource waste and low economic benefit in the prior art.

In a first aspect, the embodiment of the present application provides a system for preparing tetrahydrofuran from BDO tar, wherein the system comprises a BDO tar treatment device and a purification device;

the BDO tar treatment device comprises a BDO lightness-removing tower, a BDO raw liquid tank, a short-range film evaporator, a liquid storage tank, a BDO tower, a BDO tank, a THF reactor, a THF dehydration tower and a THF tower which are connected in sequence and used for preparing THF by using BDO tar;

the feed end of the BDO raw liquid tank is connected with the discharge end of the BDO lightness-removing tower through a BDO tar pump, the feed end of the short-range film evaporator is connected with the discharge end of the BDO raw liquid tank through a BDO raw liquid pump, the feed end of the BDO tower is connected with the discharge end of the liquid storage tank through a coarse BDO pump, the discharge end of the BDO tower is further connected with the feed end of the BDO raw liquid tank, and the discharge end of the THF tower is further connected with the feed end of the THF dehydration tower;

the purification device comprises a hydrogenation reactor, a THF refining tower and a THF product tank which are connected in sequence and is used for further refining and purifying the product of the BDO tar treatment device; and the feeding end of the hydrogenation reactor is connected with the discharging end of the THF dehydration tower.

In one enablement of the first aspect, the system further includes a low molecular weight polytetrahydrofuran reaction apparatus;

the low molecular weight polytetrahydrofuran reaction device comprises a polytetrahydrofuran tank and a degradation reactor which are connected in sequence and is used for treating the low molecular weight polytetrahydrofuran; the discharge end of the degradation reactor is connected with the feed end of the THF dehydration tower;

and the feed end of the degradation reactor is connected with the discharge end of the polytetrahydrofuran tank through a polytetrahydrofuran pump.

In one implementation form of the first aspect, the system further comprises a residue processing device;

the residue treatment device comprises a BDO residue groove and a BDO device which are sequentially connected and is used for treating residues in the preparation process;

the feed end of the BDO device is connected with the discharge end of the BDO residue tank through a residue discharge pump;

and the feed end of the BDO residue tank is respectively connected with the discharge end of the BDO lightness-removing column through a distillation pump, the discharge end of the liquid storage tank through a residue pump and the discharge end of the THF reactor.

In one implementation manner of the first aspect, the BDO lightness-removing column is a double-effect evaporation column and comprises a lightness-removing column upper column and a lightness-removing column lower column, and the distilled gas phase of the lightness-removing column lower column is used as a heating source for the lightness-removing column upper column.

In one enablement of the first aspect, the BDO column is a vacuum column with a top pressure of 5Kpa absolute.

In a second aspect, the present embodiments provide a method for preparing tetrahydrofuran from BDO tar, the method being applied to the system for preparing tetrahydrofuran from BDO tar, the method comprising:

obtaining water-containing BDO tar;

inputting the water-containing BDO tar into the BDO lightness-removing tower to remove water, so as to obtain water-free BDO tar;

converging the water-free BDO tar into the BDO stock solution tank through the BDO tar pump to obtain BDO stock solution;

inputting the BDO stock solution into the short-range thin film evaporator through the BDO stock solution pump for evaporation to obtain crude BDO;

inputting the coarse BDO into the liquid storage tank, and then, feeding the coarse BDO into the BDO tower through the coarse BDO pump for refining to obtain BDO and BDO containing heavy components;

collecting the BDO containing heavy components into the BDO raw liquid tank;

inputting the BDO into the BDO groove, and then inputting the BDO into the THF reactor from the BDO groove to react to obtain a first mixture of THF and water; said first mixture of THF and water is in a vapor phase;

feeding the first mixture of THF and water to the THF dehydration column to obtain a first azeotrope of THF and water;

feeding the first THF and water azeotrope into the THF tower to obtain first THF and a second THF and water azeotrope; the second azeotrope of THF and water is used for returning and inputting into the THF dehydration tower, and the first THF is obtained;

inputting the first THF into the hydrogenation reactor for reaction to obtain second THF;

inputting the second THF into the THF refining tower for refining to obtain THF;

the THF was taken up into the THF product tank.

In an implementable manner of the second aspect, the method further comprises:

obtaining the low molecular weight polytetrahydrofuran;

after the low-molecular polytetrahydrofuran is input into the polytetrahydrofuran tank, the low-molecular polytetrahydrofuran enters the degradation reactor through the polytetrahydrofuran pump to carry out degradation reaction, and a second mixture of THF and water is obtained; said second mixture of THF and water is in a vapor phase;

feeding the second mixture of THF and water to the THF dehydration column to obtain the first azeotrope of THF and water.

In an implementable manner of the second aspect, the method further comprises:

feeding the distillate to the BDO residue tank through the distillation pump; the distillate is another product obtained after the water-containing BDO tar is input into the BDO lightness-removing tower to remove water;

inputting BDO residues into the liquid storage tank and inputting the BDO residues into the BDO residue tank through the residue pump; the BDO residue is another product obtained after the BDO stock solution is input into the short-range thin film evaporator through the BDO stock solution pump to be evaporated;

feeding THF tar into the BDO residue tank, and forming a residue mixture together with the distillate and the BDO residue; the THF tar is another product obtained after the BDO is input into the BDO groove and then input into the THF reactor from the BDO groove for reaction;

and inputting the residue mixture into the BDO device through the residue delivery pump for incineration treatment.

In an implementation manner of the second aspect, the BDO lightness-removing column is a double-effect evaporation column and comprises a lightness-removing column upper column and a lightness-removing column lower column, and a distillate gas phase of the lightness-removing column lower column is used as a heating source of the lightness-removing column upper column.

In one enablement of the second aspect, the BDO column is a vacuum column with a top pressure of 5Kpa absolute.

Therefore, the system for preparing tetrahydrofuran from BDO tar provided by the embodiment of the application can extract THF from BDO tar by using the BDO tar treatment device, further purify and refine the extracted THF by using the purification device, and does not directly burn the BDO tar, so that harmful substances are not generated in the treatment process, and the environment-friendly requirement is met. Meanwhile, the extracted THF has high purity, can be further used as an organic synthesis raw material, realizes the waste recycling of BDO tar, saves resources and has high economic benefit.

Drawings

FIG. 1 is a schematic diagram of a system for preparing tetrahydrofuran from BDO tar provided in the examples of the present application;

FIG. 2 is a schematic diagram showing the detailed structure of a system for preparing tetrahydrofuran from BDO tar provided in the examples of the present application;

FIG. 3 is a corresponding overall flow chart of a method for preparing tetrahydrofuran from BDO tar provided in the examples of the present application.

Detailed Description

To make the objects, technical solutions and advantages of the present application more clear, embodiments of the present application will be described in further detail below with reference to the accompanying drawings.

In order to solve the problems in the prior art, the embodiment of the application provides a system for preparing tetrahydrofuran by using BDO tar, and the system is specifically used for solving the problems that the existing BDO tar treatment method seriously wastes resources and further has low economic benefit. Fig. 1 schematically shows a structural diagram of a system for preparing tetrahydrofuran from BDO tar provided in the embodiments of the present application. As shown in figure 1, the system has the function of realizing the preparation of tetrahydrofuran by using BDO tar. The system provided by the embodiment of the application comprises a BDO tar processing device 100 and a purifying device 300.

The BDO tar treatment device 100 comprises a BDO lightness-removing tower 101, a BDO stock solution tank 102, a short-path thin film evaporator 103, a liquid storage tank 104, a BDO tower 105, a BDO tank 106, a THF reactor 107, a THF dehydration tower 108 and a THF tower 109 which are connected in sequence and used for preparing THF by using BDO tar.

The feed end of the BDO raw liquid tank 102 is connected with the discharge end of the BDO lightness-removing tower 101 through a BDO tar pump, the feed end of the short-range film evaporator 103 is connected with the discharge end of the BDO raw liquid tank 102 through a BDO raw liquid pump, the feed end of the BDO tower 105 is connected with the discharge end of the liquid storage tank 104 through a coarse BDO pump, the discharge end of the BDO tower 105 is also connected with the feed end of the BDO raw liquid tank 102, and the discharge end of the THF tower 109 is also connected with the feed end of the THF dehydration tower 108.

The purification device 300 comprises a hydrogenation reactor 301, a THF refining tower 302 and a THF product tank 303 which are connected in sequence and used for further refining and purifying the product of the BDO tar treatment device 100; the feed end of the hydrogenation reactor 301 is connected with the discharge end of the THF dehydration column 108.

It should be noted that, the connections between the apparatuses mentioned in this application are all pipeline connections, and a pump is disposed on the pipeline between the individual apparatuses, and the feeding is completed by the pump. In addition, the sequential connection in this application means that the discharge end of each device is connected with the feed end of the next device.

Specifically, the BDO lightness-removing column 101 is a double-effect evaporation column including an upper column and a lower column, and the distilled gas phase of the lower column is used as a heating source for the upper column. The BDO lightness-removing column 101 is used to vaporize the feed and remove a portion of the light components.

Because the moisture evaporation capacity in the BDO lightness-removing column 101 is large, a double-effect evaporation column design is adopted for saving steam.

BDO tower 105 is a vacuum tower with top pressure of 5Kpa absolute. The BDO column 105 is used to further refine the feedstock in the storage tank 104.

The purification apparatus 300 may further comprise a THF storage tank 304 having a feed end connected to a discharge end of the THF product tank 303 for storing THF.

Therefore, the system for preparing tetrahydrofuran from BDO tar provided by the embodiment of the application can extract THF from BDO tar by using the BDO tar treatment device, further purify and refine the extracted THF by using the purification device, and does not directly burn the BDO tar, so that harmful substances are not generated in the treatment process, and the environment-friendly requirement is met. Meanwhile, the extracted THF has high purity, can be further used as an organic synthesis raw material, realizes the waste recycling of BDO tar, saves resources and has high economic benefit.

FIG. 2 schematically shows a specific structural diagram of a system for preparing tetrahydrofuran from BDO tar provided by the embodiment of the application. As shown in fig. 2, the system provided in the embodiment of the present application further includes a low molecular weight polytetrahydrofuran reaction apparatus 200.

The low molecular weight polytetrahydrofuran reaction device 200 comprises a polytetrahydrofuran tank 201 and a degradation reactor 202 which are connected in sequence and are used for processing low molecular weight polytetrahydrofuran. The discharge end of the degradation reactor 202 is connected to the feed end of the THF dehydration column 108.

The feed end of the degradation reactor 202 is connected with the discharge end of the polytetrahydrofuran tank 201 through a polytetrahydrofuran pump.

By adopting the low-molecular polytetrahydrofuran reaction device, the low-molecular polytetrahydrofuran can be added as a part of raw materials for producing THF, and the low-molecular polytetrahydrofuran can be used for making a candidate in time when the catalyst is replaced in the THF reactor, so that the running continuity of the BDO tar treatment device is met, the THF extraction process can be carried out uninterruptedly, and the practical value is high.

The system provided by the embodiment of the application further comprises a residue processing device 400.

The residue treatment apparatus 400 includes a BDO residue tank 401 and a BDO apparatus 402 connected in sequence for treating the residue during the preparation process.

The feed end of the BDO device 402 is connected to the discharge end of the BDO sludge tank 401 by a sludge discharge pump.

The feed end of the BDO residue tank 401 is connected to the discharge end of the BDO lightness-removing column 101 through a distillation pump, to the discharge end of the liquid storage tank 104 through a residue pump, and to the discharge end of the THF reactor 107, respectively.

Adopt above-mentioned residue processing apparatus, can collect in real time and handle the residue waste material that produces in the whole preparation process, not only comparatively environmental protection, it is very convenient and high-efficient moreover, have higher practicality.

Therefore, the system for preparing tetrahydrofuran from BDO tar provided by the embodiment of the application can extract THF from BDO tar by using the BDO tar treatment device, further purify and refine the extracted THF by using the purification device, and does not directly burn the BDO tar, so that harmful substances are not generated in the treatment process, and the environment-friendly requirement is met. Meanwhile, the extracted THF has high purity, can be further used as an organic synthesis raw material, realizes the waste recycling of BDO tar, saves resources and has high economic benefit.

The following are examples of the process of the present application, which may be applied to the system of the present application for producing tetrahydrofuran from BDO tar. For details not disclosed in the process examples of the present application, please refer to the system examples of the present application for preparing tetrahydrofuran using BDO tar.

The embodiment of the present application provides a method for preparing tetrahydrofuran from BDO tar, which is applied to a system for preparing tetrahydrofuran from BDO tar, fig. 3 exemplarily shows an overall flowchart corresponding to the method for preparing tetrahydrofuran from BDO tar provided by the embodiment of the present application, and as shown in fig. 3, the method for preparing tetrahydrofuran from BDO tar specifically includes the following steps:

step 301, obtaining aqueous BDO tar.

Step 302, inputting the water-containing BDO tar into a BDO lightness-removing tower to remove water, and obtaining the water-free BDO tar.

Step 303, pumping the BDO tar without water into a BDO raw liquid tank through a BDO tar pump to obtain BDO raw liquid.

And step 304, inputting the BDO stock solution into a short-range thin film evaporator through a BDO stock solution pump for evaporation to obtain crude BDO.

And 305, inputting the crude BDO into a liquid storage tank, and then, feeding the crude BDO into a BDO tower through a crude BDO pump for refining to obtain BDO and BDO containing heavy components.

And step 306, collecting the BDO containing the heavy components into a BDO raw liquid tank.

And 307, inputting BDO into the BDO tank, and inputting the BDO into the THF reactor from the BDO tank to react to obtain a first mixture of THF and water. Wherein the first mixture of THF and water is in a vapor phase.

Step 308, the first mixture of THF and water is fed to a THF dehydration column to obtain a first azeotrope of THF and water.

Step 309, the first azeotrope of THF and water is fed into the THF column to obtain the first THF and a second azeotrope of THF and water.

In step 310, a second azeotrope of THF and water is used to feed back into the THF dehydration column and obtain the first THF.

And 311, inputting the first THF into a hydrogenation reactor for reaction to obtain second THF.

And step 312, inputting the second THF into a THF refining tower for refining to obtain THF.

At step 313, the THF is pooled into the THF product tank.

Specifically, in steps 301 to 303, the aqueous BDO tar is preheated in the overhead heat exchanger of the BDO lightness-removing column 101, and the condensate is used as the internal reflux of the upper column. Part of the light components and moisture in the aqueous BDO tar are evaporated in the upper column and the gas phase is condensed in a condenser. The unevaporated BDO and moisture enter the lower column as reflux.

Feeding the water-containing BDO tar into the tower kettle below the BDO lightness-removing tower 101. The gas phase of the lower tower enters a middle heat exchanger to be used as a heating source of the upper tower, the gas phase condensate and the distillate of the upper tower enter a distillation tank together, and the distillate is sent out by a distillation pump to be used as a diluent of the residue. BDO and residues in the tower kettle enter a liquid tank of the tower kettle to exchange heat to provide a heat source for the lower tower. The BDO tar without water in the tower kettle is pumped to the BDO stock solution tank 102 by the BDO tar, and the BDO tar without water is produced.

That is, after moisture-containing BDO tar is fed to the BDO lightness-removing column 101 to be dehydrated, one of the obtained products is moisture-free BDO tar, and the other one of the obtained products is a distillate.

In the BDO stock solution tank 102, some BDO tar stock solution (i.e. containing no water BDO tar) can be purchased outside and then is merged into the BDO stock solution tank 102, so as to increase the raw materials for preparing THF.

In step 304, the BDO stock solution (i.e., without water BDO tar) in the BDO stock solution tank 102 is pumped into the short-range thin film evaporator 103 by the BDO stock solution pump. In the short-path film evaporator 103, BDO stock solution is scraped into a film along the wall, the BDO in the stock solution is gasified at high temperature and absolute pressure of 1Kpa, and is directly condensed by an inner condensing tube to form crude BDO. At the same time, a further product, BDO residue, is obtained.

In steps 305-306, the crude BDO is first transferred to the storage tank 104 for storage and then fed to the BDO tower 105 by the crude BDO pump. BDO residues also enter the storage tank 104 for storage and are pumped out by the residue pump.

The crude BDO enters a BDO tower 105 for further refining, the refined BDO at the top of the tower is condensed in a condenser, part of the BDO flows back, and part of the BDO flows to a BDO tank 106. BDO containing heavy components in the tower bottom returns to the BDO stock solution tank 102.

In step 307, BDO from BDO tank 106 enters THF reactor 107, a first mixture of THF and water is formed under the action of a catalyst, the first mixture is distilled out from the top of THF reactor 107, and passes through a separation column at the top of THF reactor 107, after unreacted BDO is separated, the first mixture of THF and water enters THF dehydration column 108. A small amount of THF tar, which is another product obtained after the reaction in the THF reactor 107, was also discharged from the bottom of the THF reactor 107.

In step 308, the first mixture of THF and water is introduced into a THF dehydration column 108, the first azeotrope of THF and water is withdrawn from the top of the column, after condensation, part of the first azeotrope is refluxed, part of the first azeotrope is fed into a THF column 109, and the remaining water is discharged from the bottom of the column. Wherein the first azeotrope of THF and water is in the gas phase.

In steps 309 and 310, the THF column 109 is a pressurized column, a first azeotrope of THF and water is fed from the top of the column, the azeotrope composition changes in the pressurized column, a second azeotrope of THF and water is taken out from the top of the column, and the vapor phase is returned to the THF dehydration column 108.

The first THF product is obtained in the bottom of the THF tower 109.

In steps 311 to 313, after the first THF at the bottom of the THF column 109 exchanges heat, the first THF enters the hydrogenation reactor 301 under the action of its own pressure to react, and a second THF is obtained, wherein the hydrogenation reactor 301 is a trickle-bed reactor.

The second THF at the bottom of the hydrogenation reactor 301 is fed under its own pressure to the THF refining column 302.

The second THF is further purified in THF purification column 302, overhead purified THF is condensed in a condenser, partially refluxed, partially sent to THF product tank 303 and loaded via THF truck pump or sent to THF storage tank 304 for storage.

In an implementation manner, the method for preparing tetrahydrofuran by using BDO tar provided in the embodiment of the present application further includes:

obtaining the low molecular polytetrahydrofuran.

Inputting low-molecular polytetrahydrofuran into a polytetrahydrofuran tank 201, and then, entering a degradation reactor 202 through a polytetrahydrofuran pump for degradation reaction to obtain a second mixture of THF and water; wherein the second mixture of THF and water is in a vapor phase.

The second mixture of THF and water is fed to THF dehydration column 108 to obtain THF and water first azeotrope.

In particular, low molecular weight polytetrahydrofuran can be obtained commercially. The low molecular weight polytetrahydrofuran is degraded into THF under the action of the degradation catalyst, a second mixture of THF and water is distilled out from the top of the degradation reactor 202, and the gas phase enters the THF dehydration tower 108.

In an implementation manner, the method for preparing tetrahydrofuran by using BDO tar provided in the embodiment of the present application further includes:

the distillate was fed to the BDO residue tank 401 through a distillation pump. Wherein, the distillate is another product obtained by inputting the water-containing BDO tar into a BDO lightness-removing tower 101 to remove water;

the BDO residue is input into the liquid storage tank 104 and is input into the BDO residue tank 401 through the residue pump. Wherein the BDO residue is another product obtained by inputting a BDO stock solution into the short-range thin film evaporator 103 through a BDO stock solution pump for evaporation.

The THF tar was fed into a BDO residue tank 401 and combined with the distillate and BDO residue to form a residue mixture. Wherein the THF tar is another product obtained by introducing BDO into the BDO tank 106 and then introducing the BDO into the THF reactor 107 from the BDO tank 106 for reaction.

The residue mixture was fed to the BDO apparatus 402 through the residue discharge pump and incinerated.

Specifically, the distillate of the other product obtained in step 302, the residue of the BDO of the other product obtained in step 304, and the THF tar of the other product obtained in step 307 together form a residue mixture, and are fed to the BDO device 402 and incinerated.

In one implementation mode, the BDO lightness-removing column is a double-effect evaporation column and comprises a lightness-removing column upper column and a lightness-removing column lower column, and the distilled gas phase of the lightness-removing column lower column is used as a heating source of the lightness-removing column upper column.

In one implementation, the BDO column is a vacuum column with a top pressure of 5Kpa absolute.

Therefore, the system for preparing tetrahydrofuran from BDO tar provided by the embodiment of the application can extract THF from BDO tar by using the BDO tar treatment device, further purify and refine the extracted THF by using the purification device, and does not directly burn the BDO tar, so that harmful substances are not generated in the treatment process, and the environment-friendly requirement is met. Meanwhile, the extracted THF has high purity, can be further used as an organic synthesis raw material, realizes the waste recycling of BDO tar, saves resources and has high economic benefit.

The present application has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to limit the application. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the presently disclosed embodiments and implementations thereof without departing from the spirit and scope of the present disclosure, and these fall within the scope of the present disclosure. The protection scope of this application is subject to the appended claims.