Treatment method for absorbing THF-containing waste gas by using GBL

Abstract

The invention relates to a treatment method for absorbing THF-containing waste gas by using GBL, and belongs to the technical field of gas absorption treatment, and the treatment method comprises the following steps: S1, enabling THF-containing waste gas to firstly pass through an absorption tower, taking GBL as an adsorbent, recovering exhaust gas at the top of the tower, and taking GBL for absorbing THF at the bottom of the tower; s2, the THF-containing GBL adsorbent obtained in the step S1 is subjected to rectification separation, high-purity THF can be obtained at the tower top, and the THF-removed GBL adsorbent is obtained at the tower kettle; and S3, the circulating adsorbent GBL is sent out from the tower kettle, and is sent into the adsorption tower in the step S1 again for cyclic utilization after heat recovery. The THF in the waste gas can be effectively absorbed, the THF content range is wide, the exhaust gas with low THF content can be treated, the recovery rate is greater than or equal to 90%, and the formation of azeotrope can be avoided, so that the separation efficiency is improved, the separation difficulty is reduced, and the reduction of the product yield or the increase of the energy consumption is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of gas absorption treatment, and in particular to a treatment method for absorbing THF-containing waste gas by using GBL. Background Art

[0002] Tetrahydrofuran (THF) is an important organic synthetic raw material and excellent solvent. It is widely used as a reactive solvent and can also be used for surface coatings, protective coatings, inks, extractants and surface treatment of artificial leather. It is produced in the production process of polyesters, polyethers and copolymers such as polybutylene terephthalate (PBT), biodegradable plastics (PBAT), and PBS. THF in such VOCs is difficult to separate from the system and difficult to condense and recover under normal pressure. Most of them are discharged in the form of volatile organic compounds (VOCs). THF in the exhaust gas cannot be well collected and utilized. Therefore, there are many difficulties in emission control and treatment. Moreover, due to the low boiling point and volatile characteristics of THF, it can generate peroxides with potential explosion hazards when exposed to air or under light conditions. It is very easy to explode when exposed to open flames, high temperatures or under light conditions, which not only pollutes the environment, but also harms human health and has serious safety hazards. Therefore, controlling and treating the emission of VOCs containing THF is one of the important tasks of environmental protection and production safety.

[0003] At present, the polyester, polyether and copolymer industries mainly use combustion, membrane separation, solvent absorption and other methods to treat THF-containing exhaust gas. Among them, the direct combustion treatment method often requires the construction of a high-altitude torch, which consumes a lot of energy and is also a waste of THF. The solvent absorption method usually uses absorbents such as water and alcohols to absorb THF in the exhaust gas. However, when using the solvent absorption method to treat THF-containing exhaust gas, there are the following problems: (1) Since THF, alcohols and water easily form azeotropes, separation is difficult. Especially when the wastewater contains methanol, which has a close azeotropic point with THF, conventional distillation methods are difficult to treat the wastewater and separate THF.

[0004] (2) The prior art such as CN118851490A and CN112657310A does not further separate the THF absorbed in the wastewater to recover the THF therein. This results in a reduction in product yield or an increase in raw material unit consumption in the production process using THF as the product or the main raw material. At the same time, the THF-containing wastewater generated also increases the three wastes.

[0005] (3) The existing technology has high energy consumption and high cost when treating waste gas containing THF, which also limits its application.

[0006] Therefore, how to develop a waste gas treatment technology with low energy consumption, low cost, and the ability to effectively separate and recover THF is an urgent problem to be solved in this field. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a treatment method for absorbing THF-containing waste gas using GBL.

[0008] The purpose of the present invention can be achieved by the following technical solutions: The technical solution of the present invention is to provide a treatment method for absorbing THF-containing waste gas by using GBL (γ-butyrolactone), comprising the following steps: S1, the exhaust gas containing THF enters from the bottom of the absorption tower, contacts with the GBL adsorbent in countercurrent to absorb THF, and the GBL adsorbent containing THF is sent out from the bottom of the tower; S2, sending the THF-containing GBL adsorbent obtained in step S1 into a distillation tower for distillation, and obtaining high-purity THF from the top of the tower, which can be reused or sent to an upstream device for further purification as needed; the bottom of the tower contains the GBL adsorbent without THF; In steps S3 and S2, the GBL adsorbent from which THF is removed is sent out from the bottom of the tower to recover heat, and after cooling, it is sent back to the adsorption tower in step S1 for recycling.

[0009] In some specific embodiments, in step S1, the THF content in the exhaust gas feed is in the range of 0.01% to 70%.

[0010] More preferably, the THF content in the exhaust gas feed is in the range of 0.1% to 55%.

[0011] In some specific embodiments, in step S1, the exhaust gas intake pressure is a slight positive pressure, the lowest of which is 2 kPaG, and the intake temperature is 5-60°C.

[0012] As a more preferred embodiment, the exhaust gas intake pressure is not less than 5 kPaG, and the intake temperature is 20-40°C.

[0013] In some embodiments, the feed amount of the GBL adsorbent is 1.0-300 m 3 / hr, the feed temperature of GBL adsorbent is 25~50℃.

[0014] As a more preferred embodiment, the feed amount of the GBL adsorbent is 10-200 m 3 / hr.

[0015] In some specific embodiments, in step S1, the THF content in the treated overhead exhaust gas is ≤0.005 mol%, and the recovery rate is ≥90%.

[0016] In some specific embodiments, in step S2, the purity of recycled THF distilled from the top of the tower is ≥99%, and the concentration of GBL in the GBL adsorbent for circulating in the bottom of the tower is ≥90%.

[0017] In some specific embodiments, in step S2, the distillation tower is a vacuum tower with an operating pressure of 1-70 kPaA and a temperature of 70-200°C.

[0018] More preferably, the operating pressure of the vacuum tower is 5 to 50 kPaA and the temperature is 110 to 180°C.

[0019] In some specific embodiments, in step S2, the reflux ratio in the distillation tower is 1.0-5.0.

[0020] In some specific embodiments, in step S3, the temperature of the circulating GBL adsorbent after cooling is 10-50°C.

[0021] More preferably, in step S3, the temperature of the circulating GBL adsorbent after cooling is 20-40°C.

[0022] In some specific embodiments, in step S3, the circulation amount of the GBL adsorbent is 1.0-300 m 3 / hr, feed temperature is 25~50℃.

[0023] As a more preferred embodiment, the circulation volume of the GBL adsorbent is 10 to 200 m 3 / hr.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention proposes a new adsorbent GBL (γ-butyrolactone) that can effectively absorb THF in exhaust gas. Compared with existing absorbents such as water and alcohols, the boiling point difference between GBL and THF is large, and it is not easy to form an azeotrope, which reduces the difficulty of separation and improves the separation efficiency of THF. This new absorbent and separation method can be widely used in the emission treatment of various volatile organic compounds, especially in the polyester, polyether and copolymer industries, and has broad application prospects.

[0025] (2) The present invention provides a new waste gas / water treatment method based on GBL, which separates and distills the GBL absorption liquid after absorbing THF to recover THF, thereby avoiding the problem of reduced product yield or increased raw material consumption, and also reduces the generation of THF-containing wastewater, reduces the "three wastes", and is beneficial to environmental protection. This method can be applied not only to the production process of THF, but also to other production processes that require the recovery of volatile organic compounds, which is of great significance for improving production efficiency, reducing production costs, and improving economic benefits.

[0026] (3) The present invention reduces the emission of pollutants by effectively absorbing and separating volatile organic compounds, which helps protect the environment and human health. This method can be widely used in the treatment of various industrial emissions, and plays an important role in reducing environmental pollution and improving air quality. In general, the present invention has broad application prospects and large market demand, and is expected to play an important role in the fields of gas absorption and treatment technology, chemical engineering, and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the process of the present invention.

[0028] The following are marked in the figure: 1 is a THF absorption tower, 2 is a cooler, 3 is a feed preheater, 4 is a THF distillation tower, 5 is a gas phase condenser, 6 is a THF recovery tank, 7 is a reflux pump, 8 is an absorption tower kettle pump, and 9 is a distillation tower kettle pump. DETAILED DESCRIPTION

[0029] In the following embodiments, if there is no special description of raw materials or processing techniques, it means that they are all conventional commercially available raw material products or conventional processing techniques in the art.

[0030] like Figure 1 As shown, the present invention provides a treatment method for absorbing THF-containing waste gas by using GBL (γ-butyrolactone), comprising the following steps: S1, the exhaust gas containing THF enters from the bottom of the THF absorption tower 1, and contacts with the GBL adsorbent in countercurrent to absorb THF, the GBL adsorbent containing THF is sent out from the bottom of the tower, and the exhaust gas after absorbing THF is recovered from the top of the tower; S2, sending the THF-containing GBL adsorbent obtained in step S1 into a distillation tower for distillation, and obtaining high-purity THF from the top of the tower, which can be reused or sent to an upstream device for further purification as needed; the bottom of the tower contains the GBL adsorbent without THF; In steps S3 and S2, the GBL adsorbent removed from the tower bottom is sent out to recover heat, and after cooling, it is sent back to the THF absorption tower 1 in step S1 for recycling.

[0031] In some specific embodiments, in step S1, the THF content in the exhaust gas feed is in the range of 0.01% to 70%.

[0032] More preferably, the THF content in the exhaust gas feed is in the range of 0.1% to 55%.

[0033] In some specific embodiments, in step S1, the exhaust gas intake pressure is a slight positive pressure, the lowest of which is 2 kPaG, and the intake temperature is 5-60°C.

[0034] As a more preferred embodiment, the exhaust gas intake pressure is not less than 5 kPaG, and the intake temperature is 20-40°C.

[0035] In some specific embodiments, in step S1, the feed amount of the GBL adsorbent is 1.0-300 m 3 / hr, and the feed temperature of GBL adsorbent was 25~50℃.

[0036] As a more preferred embodiment, the feed amount of the GBL adsorbent is 10-200 m 3 / hr.

[0037] In some specific embodiments, in step S1, the THF content in the treated overhead exhaust gas is ≤0.005 mol%, and the recovery rate is ≥90%.

[0038] In some specific embodiments, in step S2, the purity of recycled THF distilled from the top of the tower is ≥99%, and the concentration of GBL in the GBL adsorbent for circulating in the bottom of the tower is ≥90%.

[0039] In some specific embodiments, in step S2, the distillation tower is a vacuum tower with an operating pressure of 1-70 kPaA and a temperature of 70-200°C.

[0040] More preferably, the operating pressure of the vacuum tower is 5 to 50 kPaA and the temperature is 110 to 180°C.

[0041] In some specific embodiments, in step S2, the reflux ratio in the THF distillation tower 4 is 1.0-5.0.

[0042] In some specific embodiments, in step S3, the temperature of the circulating GBL adsorbent after cooling is 10-50°C.

[0043] More preferably, in step S3, the temperature of the circulating GBL adsorbent after cooling is 20-40°C.

[0044] In some specific embodiments, in step S3, the circulation amount of the GBL adsorbent is 1.0-300m3 / hr, feed temperature is 25~50℃.

[0045] As a more preferred embodiment, the circulation volume of the GBL adsorbent is 10 to 200 m 3 / hr.

[0046] In a specific implementation, an absorption tower kettle pump 8 may be provided at the tower kettle outlet of the THF absorption tower 1. A distillation tower kettle pump 9 is provided at the tower kettle outlet of the THF distillation tower 4. A feed preheater 3 is provided in the passage between the tower kettle outlet of the THF absorption tower 1 and the feed inlet of the THF distillation tower 4. A cooler 2 is provided in the passage between the tower kettle outlet of the THF distillation tower 4 and the tower top GBL adsorbent inlet of the THF absorption tower 1. A gas phase condenser 5, a THF recovery tank 6, and a reflux pump 7 are also provided at the tower top THF outlet of the THF distillation tower 4, and the reflux pump 7 is also connected to the tower top THF outlet of the THF distillation tower 4 and the recovered THF, respectively.

[0047] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments. Example 1

[0048] This embodiment uses Figure 1 The method of the present invention shown in the figure absorbs THF-containing waste gas from a polytetramethylene ether glycol unit (PTMEG), and the waste gas composition and feed conditions entering the THF absorption tower 1 are as follows:

[0049] The steps include: 1) The exhaust gas containing THF from the PTMEG unit enters the absorption tower from the bottom and contacts with the GBL adsorbent in countercurrent to absorb THF, and the GBL adsorbent containing THF is sent out from the bottom of the tower; The exhaust gas feed pressure was 5 kPaG, the temperature was 40°C, and the exhaust gas feed rate was 10 kmol / hr.

[0050] The GBL adsorbent feed and subsequent circulation volumes were 20 m 3 / hr, temperature is 40℃.

[0051] The THF content in the treated adsorption tower top exhaust gas is ≤0.005 mol%, and the recovery rate is 99.81%. The specific composition is as follows:

[0052] 2) The GBL adsorbent containing THF from the bottom of the absorption tower is sent to the distillation tower to purify the recovered THF. High-purity THF is distilled from the top of the tower, and the bottom of the tower is GBL adsorbent without THF. The operating pressure is 30±1kPaA. The purity of the circulating GBL in the bottom of the tower is 98.2%, and the purity of the THF distilled from the top of the tower is 99.97%.

[0053] 3) The GBL sent out from the bottom of the tower recovers heat, is finally cooled to 40°C and then returned to the absorption tower for recycling.

[0054] Comparative Example 1: Compared with Example 1, most of them are the same, except that GBL is replaced with water to obtain a water adsorbent containing THF. The THF content in the exhaust gas from the top of the adsorption tower after treatment is 0.71 mol%, and the recovery rate is only 51.5%. The specific composition is as follows:

[0055] The purity of THF distilled from the second step distillation tower is only 91.2%.

[0056] Compare Column 2: Compared with Example 1, most of them are the same, except that GBL is replaced with 1,4-butanediol BDO to obtain a BDO adsorbent containing THF. The THF content in the exhaust gas from the top of the adsorption tower after treatment is 0.029 mol%, and the recovery rate is only 51.5%. The specific composition is as follows:

[0057] The purity of THF distilled from the second step distillation tower is only 95%.

[0058] The energy consumption of the above embodiment and the comparative example is compared, and the results are as follows:

[0059] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for treating THF-containing waste gas by absorbing it with GBL, characterized in that: The steps include: S1, the exhaust gas containing THF enters from the bottom of the absorption tower, contacts with the GBL adsorbent in countercurrent to absorb THF, and the GBL adsorbent containing THF is sent out from the bottom of the tower; S2, sending the THF-containing GBL adsorbent obtained in step S1 into a distillation tower for distillation, and obtaining high-purity THF from the top of the tower, which can be reused or sent to an upstream device for further purification as needed; the bottom of the tower contains the GBL adsorbent without THF; In steps S3 and S2, the GBL adsorbent from which THF is removed is sent out from the bottom of the tower to recover heat, and after cooling, it is sent back to the adsorption tower in step S1 for recycling.

2. The method for treating THF-containing waste gas by using GBL according to claim 1, characterized in that: In step S1, the THF content in the exhaust gas feed is in the range of 0.01% to 70%.

3. The method for treating THF-containing waste gas by absorbing it with GBL according to claim 1, characterized in that: In step S1, the exhaust gas intake pressure is a slight positive pressure, reaching a minimum of 2 kPaG, and the intake temperature is 5-60°C.

4. The method for treating THF-containing waste gas by using GBL according to claim 1, characterized in that: In step S1, the feed amount of the GBL adsorbent is 1.0-300m 3 / hr, and the feed temperature of GBL adsorbent was 25~50℃.

5. The method for treating THF-containing waste gas by absorbing it with GBL according to claim 1, characterized in that: In step S1, the THF content in the treated overhead exhaust gas is ≤0.005 mol%, and the recovery rate is ≥90%.

6. The method for treating THF-containing waste gas by absorbing it with GBL according to claim 1, characterized in that: In step S2, the purity of the recycled THF distilled from the top of the tower is ≥99%, and the concentration of GBL in the GBL adsorbent for circulating in the bottom of the tower is ≥90%.

7. The method for treating THF-containing waste gas by absorbing it with GBL according to claim 1, characterized in that: In step S2, the distillation tower is a vacuum tower with an operating pressure of 1-70 kPaA and a temperature of 70-200°C.

8. The method for treating THF-containing waste gas by absorbing it with GBL according to claim 1, characterized in that: In step S2, the reflux ratio in the distillation tower is 1.0-5.

0.

9. The method for treating THF-containing waste gas by absorbing it with GBL according to claim 1, characterized in that: In step S3, the temperature of the circulating GBL adsorbent after cooling is 10-50°C.

10. The method for treating THF-containing waste gas by absorbing it with GBL according to claim 1, characterized in that: In step S3, the circulation amount of the GBL adsorbent is 1.0-300m 3 / hr, feed temperature is 25~50℃.

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