阅读说明：本技术 一种精馏-膜分离耦合法回收四氢呋喃的方法及装置 (Method and device for recovering tetrahydrofuran by rectification-membrane separation coupling method ) 是由 李仁海 朱志亮 吴华志 黄前程 黄娟 谢红伟 高甲 濮仁华 史路飞 李世元 于 2020-05-20 设计创作，主要内容包括：本发明涉及一种精馏-膜分离耦合法回收四氢呋喃的方法及装置,其步骤具体如下：将含水的四氢呋喃泵入精馏塔,精馏塔塔顶得到水和四氢呋喃的共沸物,共沸物部分经塔顶内冷器冷凝回流,进料量的10.8-15.9wt％以气相状态进入膜分离系统脱水；精馏塔塔底得到四氢呋喃含量小于100ppm的废水,四氢呋喃收率可达99.9％以上。膜分离系统为负压操作,渗透侧与真空系统连接,截留侧可获得纯度大于99.95％的四氢呋喃产品,渗透侧获得含少量四氢呋喃的废水重新循环进入精馏塔回收处理。本发明工艺简单,装置少,能耗低,废水有机物含量低,回收率高。(The invention relates to a method and a device for recovering tetrahydrofuran by a rectification-membrane separation coupling method, which comprises the following steps: pumping water-containing tetrahydrofuran into a rectifying tower, obtaining an azeotrope of water and the tetrahydrofuran at the top of the rectifying tower, condensing and refluxing the azeotrope part through a cooler in the top of the tower, and feeding 10.8-15.9 wt% of the feeding amount into a membrane separation system in a gas phase state for dehydration; the wastewater with tetrahydrofuran content less than 100ppm is obtained at the bottom of the rectifying tower, and the yield of the tetrahydrofuran can reach more than 99.9%. The membrane separation system is operated under negative pressure, the permeation side is connected with a vacuum system, the tetrahydrofuran product with the purity of more than 99.95 percent can be obtained at the interception side, and the wastewater containing a small amount of tetrahydrofuran obtained at the permeation side is recycled and enters the rectifying tower for recycling treatment. The invention has simple process, few devices, low energy consumption, low organic matter content in the wastewater and high recovery rate.)

1. A method for recovering tetrahydrofuran by a rectification-membrane separation coupling method is characterized by comprising the following steps: the method comprises the following steps:

(1) pumping the tetrahydrofuran containing water into a rectifying tower, after rectification separation, obtaining a gas-phase azeotrope of water and the tetrahydrofuran at the tower top, obtaining wastewater with the tetrahydrofuran content of less than 100ppm at the tower bottom of the rectifying tower, wherein the yield of the tetrahydrofuran can reach more than 99.9%;

(2) the gas-phase azeotrope is obtained at the top of the tower, part of the gas-phase azeotrope is condensed and condensed in the top of the tower and then flows back to enter a rectifying tower, the rest of the gas-phase azeotrope directly enters a membrane separation system in a gas form, tetrahydrofuran with the purity of more than 99.95 percent is obtained at the interception side of the membrane separation system, waste water containing a small amount of tetrahydrofuran is obtained at the permeation side of the membrane separation system, and the waste water circularly enters the rectifying tower.

2. The method for recovering tetrahydrofuran by rectification-membrane separation coupling method according to claim 1, wherein: the operation pressure of the rectifying tower in the step (1) is 0.2-0.3MPa, the tower bottom temperature is about 119-132 ℃, and the tower top temperature is 85-99 ℃.

3. The method for recovering tetrahydrofuran by rectification-membrane separation coupling method according to claim 1, wherein: and (3) performing negative pressure operation on the membrane separation system in the step (2), wherein the permeation side is connected with a vacuum system, and the vacuum pressure is 40-60 KPa.

4. The method for recovering tetrahydrofuran by rectification-membrane separation coupling according to claim 3, wherein: the vacuum pressure is 45-55 KPa.

5. The method for recovering tetrahydrofuran by rectification-membrane separation coupling method according to claim 1, wherein: the membrane separation system in the step (2) is composed of Octa-I type molecular sieve membranes produced by Zhejiang Conghui New Material Co.

6. The method for recovering tetrahydrofuran by rectification-membrane separation coupling method according to claim 1, wherein: the content of tetrahydrofuran in the water-containing tetrahydrofuran is 10-15%.

7. The method for recovering tetrahydrofuran by rectification-membrane separation coupling method according to claim 1, wherein: the reflux ratio in the rectifying tower is 0.1-1.2.

8. The method for recovering tetrahydrofuran by rectification-membrane separation coupling method according to claim 1, wherein: 10.8 to 15.9 wt% of the gas feed to the membrane separation system.

9. The device for recovering tetrahydrofuran by the rectification-membrane separation coupling method is characterized by comprising a rectification tower (1), wherein the output end of the top of the rectification tower (1) is connected with a membrane separation device (4), the interception side of the membrane separation device (4) is connected with an interception liquid condenser (5), the permeation side is connected with a buffer tank (8) through a permeation side condenser (6), the output end of the bottom of the buffer tank (8) is connected with a feeding pipe through a circulating pump (7), a tower bottom reboiler (3) is arranged at the lower part of the rectification tower (1), and an tower top internal cooler (2) is arranged at the top of the rectification tower (1).

10. The apparatus for recovery of tetrahydrofuran by rectification-membrane separation coupling according to claim 9, wherein the output end of the top of the buffer tank (8) is connected to the vacuum pump (10) through the vacuum buffer (9).

Technical Field

The invention relates to the field of chemical devices, in particular to a method and a device for recovering tetrahydrofuran by a rectification-membrane separation coupling method.

Background

Tetrahydrofuran is a solvent with excellent performance and wide application. The by-product produced in the direct esterification method for producing the polybutylene terephthalate mainly contains tetrahydrofuran. If the wastewater containing tetrahydrofuran is directly discharged, the environment can be seriously polluted, a rectification-membrane separation coupling method is adopted to recycle and reuse the byproduct tetrahydrofuran generated in the production process of polybutylene terephthalate (PBT), so that the energy conservation and the consumption reduction are realized, the tetrahydrofuran content in the discharged wastewater can be reduced to be less than 100ppm, the high-efficiency recovery of the tetrahydrofuran is realized, the pollution to the environment can be reduced, the production cost of enterprises can be effectively reduced, and the economic benefit of the enterprises is improved.

Disclosure of Invention

The invention aims to provide a method for purifying and recovering tetrahydrofuran by a rectification-membrane separation coupling method. The method can realize the purification and recovery of the tetrahydrofuran with lower energy consumption, and solves the problems of high energy consumption, long process flow, large equipment quantity and the like compared with the traditional multi-tower or double-tower rectification purification process.

The invention also aims to provide a device for purifying and recovering tetrahydrofuran by a rectification-membrane separation coupling method,

the purpose of the invention can be realized by the following technical scheme:

a method for recovering tetrahydrofuran by a rectification-membrane separation coupling method comprises the following steps:

(1) pumping the tetrahydrofuran containing water into a rectifying tower, after rectification separation, obtaining a gas-phase azeotrope of water and the tetrahydrofuran at the tower top, obtaining wastewater with the tetrahydrofuran content of less than 100ppm at the tower bottom of the rectifying tower, wherein the yield of the tetrahydrofuran can reach more than 99.9%;

(2) the gas-phase azeotrope is obtained at the top of the tower, part of the gas-phase azeotrope is condensed and condensed in the top of the tower and then flows back to enter a rectifying tower, the rest of the gas-phase azeotrope directly enters a membrane separation system in a gas form, tetrahydrofuran with the purity of more than 99.95 percent is obtained at the interception side of the membrane separation system, waste water containing a small amount of tetrahydrofuran is obtained at the permeation side of the membrane separation system, and the waste water circularly enters the rectifying tower.

The technical scheme of the invention is as follows: the operation pressure of the rectifying tower in the step (1) is 0.2-0.3MPa, the tower bottom temperature is about 119-132 ℃, and the tower top temperature is 85-99 ℃.

The technical scheme of the invention is as follows: and (3) performing negative pressure operation on the membrane separation system in the step (2), wherein the permeation side is connected with a vacuum system, and the vacuum pressure is 40-60 KPa. Preferably, the method comprises the following steps: the vacuum pressure is 45-55 KPa.

The technical scheme of the invention is as follows: the membrane separation system in the step (2) is composed of Octa-I type molecular sieve membranes produced by Zhejiang Conghui New Material Co.

The technical scheme of the invention is as follows: the content of tetrahydrofuran in the water-containing tetrahydrofuran is 10-15%.

The technical scheme of the invention is as follows: the reflux ratio in the rectifying tower is 0.1-1.2.

The technical scheme of the invention is as follows: 10.8 to 15.9 wt% of the gas feed to the membrane separation system.

The device comprises a rectifying tower, wherein the output end of the top of the rectifying tower is connected with a membrane separation device, the interception side of the membrane separation device is connected with an interception liquid condenser, the permeation side of the membrane separation device is connected with a buffer tank through an infiltration side condenser, the output end of the bottom of the buffer tank is connected with a feeding pipe through a circulating pump, a tower bottom reboiler is arranged at the lower part of the rectifying tower, and a tower top internal cooler is arranged at the top of the rectifying tower.

In the device, the output end at the top of the buffer tank is connected with the vacuum pump through the vacuum buffer.

The invention has the beneficial effects that:

the invention provides a novel method for purifying and recycling tetrahydrofuran by a rectification-membrane separation coupling method. The tetrahydrofuran material containing water firstly enters a rectifying tower, a dephlegmator is arranged at the top of the rectifying tower, and high-concentration tetrahydrofuran gas-phase material can be obtained at the outlet of the dephlegmator; the gas phase material of tetrahydrofuran obtained by rectification is directly led into a membrane separation system, the tetrahydrofuran is purified and concentrated by utilizing the different dissolution and diffusion rates of water and tetrahydrofuran in membranes made of different materials, and the wastewater from which the tetrahydrofuran is separated is discharged from the bottom of a rectifying tower.

The method for recovering the tetrahydrofuran can effectively recover the tetrahydrofuran, and compared with the traditional multi-tower or double-tower rectification method, the method has the advantages that the energy consumption is reduced by 40-60%, the purity of the tetrahydrofuran is more than 99.95%, the content of the tetrahydrofuran in the wastewater discharged from the bottom of the tower after recovery can be reduced to be less than 100ppm, and the recovery rate of the tetrahydrofuran can be more than 99.9%.

Drawings

Fig. 1 is a process flow diagram of a tetrahydrofuran recovery apparatus provided in the present invention.

1. A rectifying tower; 2. an overhead internal cooler; 3. a tower bottom reboiler; 4. a membrane separation device; 5. a trapped liquid condenser; 6. a permeate condenser; 7. a circulation pump; 8. a buffer tank; 9. a vacuum buffer; 10. a vacuum pump.

Detailed Description

The invention is further illustrated by the following examples, without limiting the scope of the invention:

the embodiment of the invention adopts the following devices:

referring to fig. 1, the device for recovering tetrahydrofuran by rectification-membrane separation coupling method comprises a rectification column (1), wherein the output end of the top of the rectification column (1) is connected with a membrane separation device (4), the interception side of the membrane separation device (4) is connected with an interception liquid condenser (5), the permeation side is connected with a buffer tank (8) through an interception liquid condenser (6), the output end of the top of the buffer tank (8) is connected with a vacuum pump (10) through a vacuum buffer (9), the output end of the bottom of the buffer tank (8) is connected with a feeding pipe through a circulating pump (7), a tower bottom reboiler (3) is arranged at the lower part of the rectification column (1), and a tower top internal cooler (2) is arranged at the top of the rectification column (1).

Example 1

The material to be treated by the method is a byproduct generated in the production process of polybutylene terephthalate (PBT), wherein the tetrahydrofuran content is 10 percent, and the balance is mainly water. And (4) obtaining a tetrahydrofuran product which can be recycled through dehydration treatment of the by-product. The specific operation is as follows:

(1) pressurized internal cooling reflux of rectifying tower

The tetrahydrofuran containing water enters a rectifying tower, the water and the tetrahydrofuran form an azeotrope, the azeotrope is cooled and refluxed by an inner cooler on the top of the tower under the pressurized environment, and 10.8 wt% of the feeding amount enters a membrane separation system in a gas phase state for dehydration. The wastewater with tetrahydrofuran content less than 100ppm is obtained at the bottom of the rectifying tower, and the product yield is more than 99.9%.

(2) Membrane separation system

The membrane separation system adopts an Octa-I inorganic separation membrane produced by Zhejiang Congyuan new material Co., Ltd, the system is operated under negative pressure, the permeation side is connected with a buffer tank, the buffer tank is connected with a vacuum system, and the interception side obtains a tetrahydrofuran product with the purity of more than 99.95%; and the steam at the permeation side is condensed by a condenser, enters a buffer tank and is recycled to the rectifying tower for recycling treatment by a pump.

The operating conditions of this example were:

the feed tetrahydrofuran content was 10%;

and (3) rectification process: the pressure is 0.3Mpa (absolute pressure), the tower top temperature is 99 ℃, the tower bottom temperature is 132 ℃, and the reflux ratio is 1.1;

and (3) dehydrating: the pressure was 50KPa (absolute).

In the above embodiment, tetrahydrofuran is recovered from the byproduct waste liquid, the purity of the obtained tetrahydrofuran product is greater than 99.95%, the tetrahydrofuran content in the wastewater at the bottom of the rectification column is reduced to below 95ppm, the recovery rate of tetrahydrofuran reaches above 99.91%, and the wastewater containing a small amount of tetrahydrofuran obtained at the permeation side is recycled into the rectification column. Compared with the pressure swing distillation of two towers, the energy consumption of the process is reduced by 41 percent.

Example 2

The material to be treated by the method is a byproduct generated in the production process of polybutylene terephthalate (PBT), wherein the tetrahydrofuran content is 12 percent, and the balance is mainly water. And (4) obtaining a tetrahydrofuran product which can be recycled through dehydration treatment of the by-product. The specific operation is as follows:

(1) pressurized internal cooling reflux of rectifying tower

The tetrahydrofuran containing water enters a rectifying tower, the water and the tetrahydrofuran form an azeotrope, the azeotrope is cooled and refluxed by an inner cooler on the top of the tower under the pressurized environment, and 12.8 wt% of the feeding amount enters a membrane separation system in a gas phase state for dehydration. The wastewater with tetrahydrofuran content less than 100ppm is obtained at the bottom of the rectifying tower, and the product yield is more than 99.9%.

(2) Membrane separation system

The membrane separation system adopts an Octa-I inorganic separation membrane produced by Zhejiang Congyuan new material Co., Ltd, the system is operated under negative pressure, the permeation side is connected with a buffer tank, the buffer tank is connected with a vacuum system, and the interception side obtains a tetrahydrofuran product with the purity of more than 99.95%; and the steam at the permeation side is condensed by a condenser, enters a buffer tank and is recycled to the rectifying tower for recycling treatment by a pump.

The operating conditions of this example were:

the feed tetrahydrofuran content was 12%;

and (3) rectification process: the pressure is 0.3MPa (absolute pressure), the tower top temperature is 94 ℃, the tower bottom temperature is 132 ℃, and the reflux ratio is 0.8;

and (3) dehydrating: the pressure was 50KPa (absolute).

In the above embodiment, tetrahydrofuran is recovered from the byproduct waste liquid, the purity of the obtained tetrahydrofuran product is greater than 99.95%, the tetrahydrofuran content in the wastewater at the bottom of the rectification column is reduced to below 96ppm, the recovery rate of tetrahydrofuran reaches above 99.92%, and the wastewater containing a small amount of tetrahydrofuran obtained at the permeation side is recycled into the rectification column. Compared with the pressure swing distillation of two towers, the energy consumption of the process is reduced by 53 percent.

Example 3: the invention relates to a process for recovering tetrahydrofuran by a rectification-membrane separation coupling method, which adopts a single tower and a membrane separation system for continuous operation, and adopts equipment which mainly comprises a rectification tower, a tower top internal cooler, a tower bottom reboiler, the membrane separation system, a trapped liquid condenser, a penetrating liquid condenser, a buffer tank, a vacuum buffer, a vacuum pump and the like, wherein the rectification tower is a packed tower filled with high-efficiency structured packing, and is shown in figure 1.

The material to be treated by the method is a byproduct generated in the production process of polybutylene terephthalate (PBT), wherein the tetrahydrofuran content is 15 percent, and the balance is mainly water. And (4) obtaining a tetrahydrofuran product which can be recycled through dehydration treatment of the by-product. The specific operation is as follows:

(1) pressurized internal cooling reflux of rectifying tower

The tetrahydrofuran containing water enters a rectifying tower, the water and the tetrahydrofuran form an azeotrope, the azeotrope is cooled and refluxed by an inner cooler on the top of the tower under the pressurized environment, and 15.9 wt% of the feeding amount enters a membrane separation system in a gas phase state for dehydration. The wastewater with tetrahydrofuran content less than 100ppm is obtained at the bottom of the rectifying tower, and the product yield is more than 99.9%.

(2) Membrane separation system

The membrane separation system adopts an Octa-I inorganic separation membrane produced by Zhejiang Congyuan new material Co., Ltd, the system is operated under negative pressure, the permeation side is connected with a buffer tank, the buffer tank is connected with a vacuum system, and the interception side obtains a tetrahydrofuran product with the purity of more than 99.95%; and the steam at the permeation side is condensed by a condenser, enters a buffer tank and is recycled to the rectifying tower for recycling treatment by a pump.

The operating conditions of this example were:

the feed tetrahydrofuran content was 15%;

and (3) rectification process: the pressure is 0.3MPa (absolute pressure), the tower top temperature is 90 ℃, the tower bottom temperature is 132 ℃, and the reflux ratio is 0.5;

and (3) dehydrating: the pressure was 50KPa (absolute).

In the above embodiment, tetrahydrofuran is recovered from the byproduct waste liquid, the purity of the obtained tetrahydrofuran product is greater than 99.95%, the tetrahydrofuran content in the wastewater at the bottom of the rectification tower is reduced to below 99ppm, the recovery rate of tetrahydrofuran reaches above 99.9%, and the wastewater containing a small amount of tetrahydrofuran obtained at the permeation side is recycled into the rectification tower. Compared with the pressure swing distillation of two towers, the energy consumption of the process is reduced by 60 percent. In the present invention,% refers to weight unless otherwise specified.