A crude purification system for side-drawing residual liquid of a tetrahydrofuran purification device in PBAT production

Abstract

The utility model discloses a kind of crude purification systems of residual liquid side in PBAT production tetrahydrofuran purification device, it is related to the technical field of waste liquid purification, to solve the problem of tetrahydrofuran purification energy consumption cost is high, separation efficiency is low and residual liquid utilization value is low, including rectifying column, rectifying column is connected with extraction separator by feed line, extraction separator is connected in rectifying column by reflux line, extraction separator is connected with collection tank by overflow line, extraction separator is connected with desalted water inlet end by extraction liquid line, the outer wall of extraction separator is provided with cooling coil, feed line and extraction liquid line are all extended to the inner chamber of extraction separator, feed line extension length is 62-68% of extraction separator length, extraction liquid line extension length is 37-43% of extraction separator length. Use original rectifying column as material source, only newly add extraction separator and supporting pipeline, no additional rectifying column, reduce investment cost;And need not continuous heating.

Description

Technical Field

[0001] This utility model relates to the technical field of waste liquid purification, specifically a crude purification system for residual liquid collected from the side of a tetrahydrofuran purification device in PBAT production. Background Technology

[0002] In the production process of polybutylene terephthalate (PBAT), 1,4-butanediol (BDO) produces tetrahydrofuran (THF), methyltetrahydrofuran (MeTHF), and other impurities under high-temperature catalysis. While existing tetrahydrofuran purification towers can initially separate the mixed liquid, the residue collected from the purification tower still contains water and tetrahydrofuran, along with other impurities such as dimethyltetrahydrofuran and trimethyltetrahydrofuran. This characteristic leads to two major problems: first, subsequent distillation and purification of the residue is difficult; incineration poses both safety risks and wastes recyclable resources such as trimethyltetrahydrofuran; second, the high water and tetrahydrofuran content in the residue significantly increases downstream purification costs.

[0003] Current waste liquid treatment faces multiple technical bottlenecks: First, mainstream incineration methods cannot recover useful components and pose significant safety hazards; second, while some purification processes (such as patents CN114409615A and CN119350273A) target the purification of dimethyl and trimethyltetrahydrofuran, they require first reducing the water and tetrahydrofuran content in the waste liquid to ensure normal operation of subsequent purification processes. However, existing content reduction processes rely on simple distillation technology, requiring the addition of a distillation column, which not only incurs high investment costs but also maintains high energy consumption; third, methyltetrahydrofuran and water exhibit an unstable azeotropic phenomenon, resulting in low distillation separation efficiency, and the removal rate of tetrahydrofuran and water in the waste liquid is insufficient to meet the requirements of subsequent purification; fourth, existing systems lack precise parameter control, which easily leads to fluctuations in separation conditions and further reduces purification stability.

[0004] In summary, existing technologies cannot simultaneously solve the problems of "high investment, high energy consumption, azeotropic interference, and low residual liquid value." There is an urgent need for a residual liquid crude purification system that is adapted to PBAT production conditions, does not require the addition of a distillation column, can accurately control separation parameters, and can effectively avoid azeotropic phenomena. Utility Model Content

[0005] To address the aforementioned problems, specifically those raised in the background section, this invention proposes a crude purification system for the side-collected residue from a tetrahydrofuran purification unit in PBAT production. The system includes a distillation column connected to an extraction separator via a feed line. The extraction separator is connected to the distillation column via a reflux line and to a collection tank via an overflow line. The extraction separator is also connected to a demineralized water inlet via an extractant line. A cooling coil is installed on the outer wall of the extraction separator. Both the feed line and the extractant line extend into the inner cavity of the extraction separator. The feed line extends for 62-68% of the extraction separator's length, and the extractant line extends for 37-43% of the extraction separator's length.

[0006] A further feature of this invention is that a cooler and a first flow meter are provided on the feed pipeline.

[0007] A further feature of this invention is that the cooling water inlet of the cooler is connected to a cooling water inlet end via a pipeline, and the cooling water outlet of the cooler is connected to a cooling water outlet end via a pipeline.

[0008] A further feature of this invention is that a third flow meter and a regulating valve are provided on the return pipeline.

[0009] A further feature of this invention is that a first sight glass and a second flow meter are provided on the overflow pipeline.

[0010] A further feature of this invention is that the chilled water inlet of the cooling coil is connected to a chilled water inlet end via a pipeline, and the chilled water outlet of the cooling coil is connected to a chilled water outlet end via a pipeline.

[0011] A further feature of this invention is that the extraction separator is equipped with a thermometer, a level gauge, and a second sight glass.

[0012] The beneficial technical effects of this utility model are as follows: This utility model uses the existing distillation column as the material source, only adding an extraction separator and supporting pipelines, without additional distillation columns, thus reducing investment costs; and it does not require continuous heating, reducing operating energy consumption compared to traditional distillation processes, while not affecting the stable operation of the original PBAT production system.

[0013] By combining extraction and separation with low-temperature control (<10℃), the content of tetrahydrofuran and water in the residual liquid can be effectively reduced, thereby reducing the difficulty of subsequent processing and significantly reducing the solubility of water and dimethyltetrahydrofuran, thus avoiding the azeotropic phenomenon between the two. The upper purified liquid can be directly entered into the subsequent refining process or sold externally, avoiding resource waste and incineration safety risks. The lower liquid, which has a higher content of tetrahydrofuran and water, is refluxed to the distillation column for further purification, significantly improving economic benefits.

[0014] The feed line is equipped with a first flow meter to precisely control the condensate feed rate; the extract line is equipped with a flow control component to ensure a stable amount of demineralized water added; the reflux line is equipped with a third flow meter and a regulating valve to control the reflux flow rate to 60-65% of the feed rate; the extraction separator is equipped with a thermometer, a level gauge and a second sight glass to monitor the temperature, level and stratification status in real time, ensuring stable separation conditions and avoiding a decrease in purification efficiency due to parameter fluctuations.

[0015] The feed line extends to 62-68% of the extraction separator length, while the extractant line extends to 37-43%. This elevation difference design ensures sufficient counter-current contact between the residual liquid condensate and the demineralized water within the extraction separator, thereby improving the extraction rate of the target extractant and reducing its ineffective loss in the residual liquid. The miscibility of water and methyltetrahydrofuran decreases with decreasing temperature, while temperature changes have a relatively small impact on their miscibility. Utilizing this characteristic, readily available and environmentally friendly demineralized water is selected as the extractant, and combined with temperature control, the system's extraction efficiency can be effectively improved. The composition of the residual liquid after crude purification is simplified, significantly reducing the processing difficulty and cost of subsequent refining processes. Attached Figure Description

[0016] Figure 1 A process flow diagram of this utility model is shown.

[0017] Reference numerals: 1. Distillation column; 2. Cooler; 3. Extraction separator; 4. Collection tank; 5. First flow meter; 6. Cooling water outlet; 7. Cooling water inlet; 8. Demineralized water inlet; 9. Chilled water outlet; 10. Second flow meter; 11. Chilled water inlet; 12. Thermometer; 13. Third flow meter; 14. Control valve; 15. First sight glass; 16. Level gauge; 17. Second sight glass. Detailed Implementation

[0018] The following is a reference to the appendix. Figure 1 The preferred embodiments of this utility model are described below. Those skilled in the art should understand that these embodiments are merely for explaining the technical principles of this utility model and are not intended to limit the scope of protection of this utility model.

[0019] This invention proposes a crude purification system for the residual liquid from the side-collected tetrahydrofuran purification unit in PBAT production. The system includes a distillation column 1, which is connected to an extraction separator 3 via a feed line. The tetrahydrofuran residual liquid is purified using the extraction separator 3. The extraction separator 3 has a slender design to facilitate better internal liquid extraction and stratification. The mixed gas collected from the feed line passes through a cooler 2, and the condensate is controlled by a first flow meter 5 to enter the extraction separator 3.

[0020] Extraction separator 3 is connected to distillation column 1 via a reflux line. The lower layer liquid, which has a high content of water and tetrahydrofuran, is refluxed back to distillation column 1 for further purification.

[0021] Extraction separator 3 is connected to collection tank 4 via overflow pipeline. The upper liquid methyltetrahydrofuran with higher purity is sent to collection tank 4 for further purification or sale.

[0022] The extraction separator 3 is connected to the demineralized water inlet 8 via an extraction liquid pipeline. The extraction liquid pipeline is equipped with a flow control component to ensure a stable extraction liquid feed rate. A cooling coil is installed on the outer wall of the extraction separator 3 for easy temperature adjustment. The miscibility of water with methyltetrahydrofuran decreases with decreasing temperature, while temperature changes have a relatively small impact on the miscibility of water and tetrahydrofuran. Utilizing this characteristic, selecting inexpensive, readily available, and environmentally friendly demineralized water as the extraction agent, combined with temperature control, can effectively improve the system's extraction efficiency.

[0023] Both the feed line and the extractant line extend into the inner cavity of the extraction separator 3. The feed line extends for 62-68% of the length of the extraction separator 3, and the extractant line extends for 37-43% of the length of the extraction separator 3. This height difference can effectively increase the separation effect and allow the internal liquid to be better extracted and exchanged.

[0024] A cooler 2 and a first flow meter 5 are installed on the feed pipeline to facilitate precise control of the amount of condensate added.

[0025] The cooling water inlet of cooler 2 is connected to cooling water inlet 7 via a pipeline, and the cooling water outlet of cooler 2 is connected to cooling water outlet 6 via a pipeline. The cooling water circulation path formed by the cooling water inlet and outlet will cool the side-collected residual liquid mixed gas input from the side-collected pipe of the original distillation column 1 into condensate, so as to provide raw materials for the subsequent separation process of extraction separator 3.

[0026] A third flow meter 13 and a regulating valve 14 are installed on the return pipeline to facilitate precise control of the return ratio and ensure normal system operation.

[0027] The overflow line is equipped with a first sight glass 15 and a second flow meter 10 to facilitate precise control of the output flow rate of tetrahydrofuran.

[0028] The chilled water inlet of the cooling coil is connected to a chilled water inlet 11 via a pipeline, and the chilled water outlet of the cooling coil is connected to a chilled water outlet 9 via a pipeline. The cooling coil is used to reduce the liquid temperature inside the extraction separator 3. The cold source is chilled water at 6-8℃, which can accurately control the temperature of the mixture of residual liquid condensate and extract liquid inside the extraction separator 3 to <10℃. At low temperatures, the solubility of water and methyltetrahydrofuran decreases, and the content of tetrahydrofuran and water in the upper liquid will be significantly reduced. This provides the key temperature conditions for subsequent liquid-liquid stratification and efficient reduction of water and tetrahydrofuran content in the residual liquid. At the same time, this temperature range can ensure the cooling effect and avoid energy waste caused by excessively low chilled water temperature.

[0029] The extraction separator 3 is equipped with a thermometer 12, a level gauge 16, and a second sight glass 17. The second sight glass 17 facilitates observation of the liquid separation process inside the extraction separator 3.

[0030] Example 1 The design dimensions of the extraction separator 3 are: diameter 500mm, height 3000mm, feed line extending 2000mm into the inner cavity of the extraction separator 3, and extract liquid line extending 1200mm into the inner cavity of the extraction separator 3.

[0031] Principles and methods of side-sampling residual liquid purification system: The quantities of each substance in the feed line, overflow line, and return line are detailed in Table 1.

[0032] Feed line: Mixed gas is drawn from the side line of the original distillation column 1, passes through cooler 2, and the condensate flow rate is controlled at 60-80 kg / h by the first flow meter 5 before entering the extraction separator 3.

[0033] Extraction liquid pipeline: The extraction liquid is added to the extraction separator 3 at a rate of 50-60 kg / h. The amount of extraction liquid added should not be too large to prevent agitation of the liquid in the extraction separator 3, and the liquid residence time in the extraction separator 3 must be guaranteed.

[0034] The temperature of the extraction separator 3 needs to be controlled below 10℃. Under low temperature conditions, the solubility of water and methyltetrahydrofuran decreases, and the content of tetrahydrofuran and water in the lower liquid will be significantly reduced.

[0035] Overflow line: The flow rate of the upper liquid is controlled at 30-40 kg / h by the second flow meter 10 before entering the collection tank 4.

[0036] Reflux line: The flow rate of the lower liquid is controlled at 70-100 kg / h by the third flow meter 13 and the regulating valve 14 and refluxed back into the distillation column 1. The regulating valve 14 controls the reflux flow rate to be about 60-65% of the feed to ensure the stable operation of the system.

[0037] Table 1 Although the present invention has been described with reference to preferred embodiments, various modifications can be made to it and components can be replaced with equivalents without departing from the scope of the present invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0038] In the description of this utility model, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] Furthermore, it should be noted that, in the description of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0040] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to those processes, articles, or apparatus / devices.

[0041] The technical solution of this utility model has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the protection scope of this utility model is obviously not limited to these specific embodiments. Without departing from the principle of this utility model, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of this utility model.

Claims

1. A crude purification system for the side-collected residue of a tetrahydrofuran purification unit in PBAT production, comprising a distillation column (1), characterized in that: The distillation column (1) is connected to an extraction separator (3) via a feed line. The extraction separator (3) is connected to the distillation column (1) via a reflux line. The extraction separator (3) is connected to a collection tank (4) via an overflow line. The extraction separator (3) is connected to a demineralized water inlet (8) via an extraction liquid line. The outer wall of the extraction separator (3) is provided with a cooling coil. Both the feed line and the extraction liquid line extend into the inner cavity of the extraction separator (3). The extension length of the feed line is 62-68% of the length of the extraction separator (3), and the extension length of the extraction liquid line is 37-43% of the length of the extraction separator (3).

2. The crude purification system for the side-collected residue of the tetrahydrofuran purification unit in PBAT production according to claim 1, characterized in that: A cooler (2) and a first flow meter (5) are installed on the feed pipeline.

3. The crude purification system for the side-collected residue of the tetrahydrofuran purification unit in PBAT production according to claim 2, characterized in that: The cooling water inlet of the cooler (2) is connected to the cooling water inlet end (7) via a pipeline, and the cooling water outlet of the cooler (2) is connected to the cooling water outlet end (6) via a pipeline.

4. The crude purification system for the side-collected residue of the tetrahydrofuran purification unit in PBAT production according to claim 1, characterized in that: A third flow meter (13) and a regulating valve (14) are installed on the return pipeline.

5. A crude purification system for the side-collected residue of a tetrahydrofuran purification unit in PBAT production according to claim 1, characterized in that: The overflow pipeline is equipped with a first sight glass (15) and a second flow meter (10).

6. A crude purification system for the side-collected residue of a tetrahydrofuran purification unit in PBAT production according to claim 1, characterized in that: The chilled water inlet of the cooling coil is connected to a chilled water inlet end (11) via a pipeline, and the chilled water outlet of the cooling coil is connected to a chilled water outlet end (9) via a pipeline.

7. A crude purification system for the side-collected residue of a tetrahydrofuran purification unit in PBAT production according to claim 1, characterized in that: The extraction separator (3) is equipped with a thermometer (12), a level gauge (16), and a second sight glass (17).

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