Recovery system for effective components in by-products of NMP (N-Methyl Pyrrolidone) process

Abstract

The utility model provides a recovery system for effective components in NMP (N-Methyl Pyrrolidone) process byproducts, which comprises a first pipeline and a gas-liquid separation tank, and the gas-liquid separation tank is used for separating a gas-liquid mixture from the first pipeline; the multi-shell-pass reaction heat exchanger is connected with the bottom of the gas-liquid separation tank through a second pipeline, and the multi-shell-pass reaction heat exchanger is used for reaction and heat exchange; the top end and the middle part of the light component removal tower are respectively connected with the multi-shell-pass reaction heat exchanger through a third pipeline and a fourth pipeline; the bottom end of the light component removal tower is connected with the purification tower through a fifth pipeline; after being purified by the purifying tower, a part of components enter the multi-shell-pass reaction heat exchanger through a sixth pipeline for heat exchange treatment, and then are recycled through a first recycling pipe; and the other part of components enter the multi-shell-pass reaction heat exchanger through a seventh pipeline for heat exchange, and then are recovered through a second recovery pipe. The recovery system disclosed by the utility model solves the technical problems of low recovery efficiency of effective components in byproducts and serious resource waste in related technologies.

Description

Technical Field

[0001] The utility model relates to the technical field of chemical equipment, in particular to a recovery system for effective components in NMP process by-products. Background Art

[0002] The complex nature of the N-methylpyrrolidone (NMP) production process generates a certain amount of byproducts. These byproducts are highly complex, with chromatographic analysis revealing over ninety components. To maintain normal production, these byproducts must be continuously removed from the system, but this process also removes some of the active ingredients, particularly NMP. Given the significant industrial value of NMP, the loss of some NMP represents a significant economic loss.

[0003] In addition to NMP, the byproduct also contains another important active ingredient: 2-pyrrolidone (2PY). 2PY has a high boiling point and is present in high concentrations in the byproduct. Therefore, conventional disposal methods, such as incineration, can result in the waste of this active ingredient and generate large amounts of waste liquid, placing significant pressure on environmental protection.

[0004] Therefore, the prior art needs to be further developed. Utility Model Content

[0005] The purpose of the present invention is to overcome the above technical deficiencies and provide a system for recovering effective components in NMP process by-products, so as to solve the technical problems of low recovery efficiency of effective components in by-products and serious waste of resources in related technologies.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solutions: a system for recovering effective components in NMP process by-products is provided, comprising: a first pipeline for conveying NMP process by-products; a gas-liquid separation tank for separating the gas-liquid mixture from the first pipeline; a multi-shell-side reaction heat exchanger connected to the bottom of the gas-liquid separation tank via a second pipeline, the multi-shell-side reaction heat exchanger being used for reaction and heat exchange; a lightness removal tower for removing light components, the top and middle of the lightness removal tower being connected to the multi-shell-side reaction heat exchanger via a third pipeline and a fourth pipeline, respectively; a purification tower, the bottom end of the lightness removal tower being connected to the purification tower via a fifth pipeline; after purification in the purification tower, a portion of the effective components enter the multi-shell-side reaction heat exchanger via a sixth pipeline for heat exchange treatment, and are then recovered via a first recovery pipe; another portion of the effective components enter the multi-shell-side reaction heat exchanger via a seventh pipeline for heat exchange, and are then recovered via a second recovery pipe.

[0007] Furthermore, the height of the connection between the sixth pipeline and the purification tower is higher than the height of the connection between the seventh pipeline and the purification tower.

[0008] Furthermore, the multi-shell reaction heat exchanger is a reaction heat exchanger with multiple shells arranged in sequence in a vertical direction, the height of the connection between the seventh pipeline and the multi-shell reaction heat exchanger is higher than the height of the connection between the sixth pipeline and the multi-shell reaction heat exchanger, and the height of the connection between the sixth pipeline and the multi-shell reaction heat exchanger is higher than the height of the connection between the third pipeline and the multi-shell reaction heat exchanger.

[0009] Furthermore, the heat exchange tubes in the multi-shell reaction heat exchanger are all of a serpentine structure to improve the heat exchange efficiency.

[0010] Furthermore, a filter is provided between the first pipeline and the gas-liquid separation tank, and the filter is used to filter solid particles in the by-products.

[0011] Furthermore, the recovery system also includes an eighth pipeline and a mixer. The mixer is located between the filter and the gas-liquid separation tank. The eighth pipeline is used to introduce monomethylamine solution into the mixer. The by-products filtered by the filter are mixed and reacted with the monomethylamine solution in the mixer before entering the gas-liquid separation tank.

[0012] Furthermore, the mixer is a reverse vortex mixer, which is used to improve the mixing effect of the by-product and the monomethylamine solution.

[0013] Furthermore, a first pressure pump is provided on the second pipeline, and the first pressure pump is used to pump the mixed liquid in the gas-liquid separation tank into the multi-shell-pass reaction heat exchanger.

[0014] Furthermore, a second pressure pump is provided on the seventh pipeline, and a third pressure pump is provided on the sixth pipeline. The second pressure pump and the third pressure pump are both used to pump the components in the purification tower into the multi-shell reaction heat exchanger.

[0015] Furthermore, the recovery system also includes a ninth pipeline, which is connected to the multi-shell-side reaction heat exchanger. The components in the third pipeline are recovered through the ninth pipeline after heat exchange in the multi-shell-side reaction heat exchanger.

[0016] Beneficial effects:

[0017] 1. The recovery system of the present invention, through the combined use of a multi-shell reaction heat exchanger and a purification tower, can effectively separate and recover the important effective components NMP and 2-pyrrolidone (2PY) in the by-products. By precisely controlling the fluid path and temperature gradient of each link, the recovery rate can be significantly improved, avoiding the waste of effective components in traditional processes.

[0018] 2. The recovery system of the utility model effectively recovers the effective components of NMP and 2PY in the by-products through efficient heat exchange and separation technology, reducing resource waste and avoiding the emission of waste liquid and waste gas generated by conventional treatment methods (such as incineration), thereby effectively alleviating the pressure on the environment and meeting the requirements of green environmental protection and sustainable development.

[0019] 3. The recovery system of the present invention adopts three shell-side reaction heat exchangers with a serpentine structure, which effectively improves the heat exchange efficiency and makes full use of the heat energy in the recovery process, thereby improving the energy utilization rate of the entire system and reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a system for recovering effective components from NMP process by-products adopted in an embodiment of the present utility model.

[0021] The above drawings include the following reference numerals:

[0022] 1. First pipeline; 2. Gas-liquid separation tank; 3. Multi-shell reaction heat exchanger; 4. Second pipeline; 5. Lightness removal tower; 6. Third pipeline; 7. Fourth pipeline; 8. Purification tower; 9. Fifth pipeline; 10. Sixth pipeline; 11. First recovery pipe; 12. Seventh pipeline; 13. Second recovery pipe; 14. Filter; 15. Eighth pipeline; 16. Mixer; 17. First pressure pump; 18. Second pressure pump; 19. Third pressure pump; 20. Ninth pipeline; 21. Tenth pipeline; 22. Incinerator. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0024] According to the embodiment of the present invention, a system for recovering effective components in NMP process by-products is provided. Figure 1, including: a first pipeline 1 for transporting NMP process by-products; a gas-liquid separation tank 2 for separating the gas-liquid mixture from the first pipeline 1; a multi-shell reaction heat exchanger 3, connected to the bottom of the gas-liquid separation tank 2 through a second pipeline 4, and the multi-shell reaction heat exchanger 3 is used for reaction and heat exchange; a light-removing tower 5 for removing light components, and the top and middle of the light-removing tower 5 are connected to the multi-shell reaction heat exchanger 3 through a third pipeline 6 and a fourth pipeline 7 respectively; a purification tower 8, the bottom end of the light-removing tower 5 is connected to the purification tower 8 through a fifth pipeline 9; after purification by the purification tower 8, a part of the effective components enter the multi-shell reaction heat exchanger 3 through a sixth pipeline 10 for heat exchange treatment, and then are recovered through a first recovery pipe 11; another part of the effective components enter the multi-shell reaction heat exchanger 3 through a seventh pipeline 12 for heat exchange, and then are recovered through a second recovery pipe 13. NMP byproducts from the NMP production tank farm or facility enter the gas-liquid separator 2 via a first pipeline 1 for gas-liquid separation. Flashed light components are discharged from the top of the separator 2 via a tenth pipeline 21 and can also be recovered from the tail gas scrubber of the original NMP production facility. The byproduct mixture, after initial light component removal, is fed to a multi-shell-pass reaction heat exchanger 3, where it is maintained at a temperature of no less than 100°C for a sufficient time to hydrolyze the intermediate products. The byproduct mixture exiting the multi-shell-pass reaction heat exchanger 3, containing fully hydrolyzed intermediate products, is then depressurized and fed to a light component removal tower 5 via a second pipeline 4. Some of the light components entering the light removal column 5 are flashed and converted into gaseous form. Some of the light components remaining in the by-product mixed liquid flowing downward along the column tray flow to the bottom of the column and are completely evaporated by the heat provided by the reboiler. The light components at the top of the light removal column 5 are a mixed gas of water and monomethylamine, which is returned to the multi-shell-side reaction heat exchanger 3 through the third pipeline 6 at the top. In the multi-shell-side reaction heat exchanger 3, it is condensed into a low-concentration monomethylamine solution. This solution is connected to the original device through the ninth pipeline 20 and can be used as a raw material for the production of NMP. The bottom liquid of light removal tower 5 enters active component purification tower 8 via fifth pipeline 9, entering through the lower packing of the tower and then passing through the lower packing into the bottom of purification tower 8. At this point, the main light components in the bottom liquid mixture are NMP and 2PY. The bottom liquid is heated to a temperature above the boiling point of 2PY at the tower's operating pressure. 2PY with a higher boiling point is withdrawn from the lower middle portion of the tower and returned to the multi-shell-side reaction heat exchanger 3 via seventh pipeline 12 for heat recovery. After heat recovery is complete, 2PY is recovered to a temporary storage tank via first recovery pipeline 11. The bottom liquid of purification tower 8 is heated in the bottom reboiler, and NMP with a lower boiling point is withdrawn from the upper middle portion of the tower. The withdrawn NMP is returned to the multi-shell-side reaction heat exchanger 3 via sixth pipeline 10 for heat recovery. After heat recovery is complete, the NMP is recovered to another temporary storage tank via second recovery pipeline 13.

[0025] See Figure 1In this embodiment of the system for recovering effective components from NMP process byproducts, the height of the connection between sixth pipeline 10 and purification tower 8 is higher than the height of the connection between seventh pipeline 12 and purification tower 8. The separation process in purification tower 8 relies on an effective temperature gradient and component stratification. The height difference between sixth pipeline 10 and seventh pipeline 12 facilitates better control of the heat exchange process between different components within the purification tower, ensuring efficient heat recovery and distribution.

[0026] See Figure 1 In this embodiment, the system for recovering effective components from NMP process byproducts comprises a multi-shell reaction heat exchanger 3 comprising multiple shell-side reaction heat exchangers arranged vertically. The seventh pipeline 12 is connected to the multi-shell reaction heat exchanger 3 at a higher elevation than the sixth pipeline 10, which is also higher than the third pipeline 6. The multi-shell reaction heat exchanger 3 comprises three shell-side reaction heat exchangers, each configured as a serpentine structure. Each flow path connects to a different shell-side reaction heat exchanger. The seventh pipeline 12 is used to recover higher-boiling-point components and is connected to a higher position in the multi-shell reaction heat exchanger 3, ensuring that higher-boiling-point components flow preferentially to the high-temperature region of the heat exchanger for heat exchange. The sixth pipeline 10 is used to recover lower-boiling-point components and is connected to a lower position in the heat exchanger, ensuring that lower-boiling-point components undergo heat exchange first. This layered design helps improve the recovery efficiency of different components, avoids interference during the heat exchange process, and ensures the purity and efficiency of the recovery. Due to the optimized heat exchange process, low-boiling point and high-boiling point components are recovered in layers, avoiding cross-contamination between components and ensuring the high purity of the final recovered components.

[0027] See Figure 1 In the recovery system of the effective components in the NMP process by-products of this embodiment, the heat exchange tubes in the three-shell heat exchanger are all of a coiled tube structure to improve the heat exchange efficiency.

[0028] In this embodiment, the NMP byproduct from the original production plant first enters filter 14 for filtration. Filter 14, with a precision of less than 1 μm, is used to filter out metallic and non-metallic particulates, thereby improving the quality of the subsequent distillation product. The monomethylamine solution from the original plant, with a monomethylamine concentration based on the original plant, is fed in an amount determined by the gamma-butyrolactone (GBL) content of the byproduct feed, ensuring a molar ratio of monomethylamine to GBL greater than 1.05. The filtered byproduct and the proportionately prepared monomethylamine solution are then passed through eighth pipeline 15 to a reverse vortex mixer 16. This mixer 16 provides ample time and contact for the reaction between monomethylamine and GBL. The GBL content of the byproduct is ≤1% before entering mixer 16 and is less than 50 ppm after exiting the mixer.

[0029] The byproduct mixture exiting mixer 16 enters separator 2 for gas-liquid separation, flash-evaporating some monomethylamine and light components such as water. The gas phase overhead from separator 2 is treated by the tail gas scrubber in the original unit (connected to the original unit via the tenth pipeline 21) to recover the monomethylamine. After the initial light removal, the byproduct mixture is fed by a first booster pump 17 into a serpentine multi-shell-pass reaction heat exchanger 3, where it is subjected to a reaction temperature of no less than 100°C for a period of no less than 1.5 hours. The shell side of multi-shell-pass reaction heat exchanger 3 is a three-stage design, which recovers waste heat from subsequent distillation products. This not only provides the hydrolysis temperature for the tube side of multi-shell-pass reaction heat exchanger 3, but also cools the subsequent distillation products, significantly reducing the use of heat transfer oil and circulating water, thereby saving energy and reducing consumption. The byproduct mixture exiting the tube side of multi-shell-pass reaction heat exchanger 3, in which the intermediate products are completely hydrolyzed, is then depressurized and fed into lightness removal tower 5. After entering the tower, it first flashes on the feed tray, where some of the light components are converted to gas. The remaining light components in the byproduct mixture, which flows downward along the tray, reach the bottom of the tower and are completely evaporated by the heat provided by the reboiler. The water content in the bottom produced liquid is less than 500 ppm. The light components at the top of the tower are a mixed gas of water and monomethylamine. After passing through the first shell (i.e., the lowest shell) of the multi-shell-pass reaction heat exchanger 3, they are condensed into a low-concentration monomethylamine solution. This solution is treated using the original tail gas scrubbing system. The bottom liquid of the light removal tower 5 enters the effective component purification tower 8, entering through the lower packing and then passing through the lower packing into the bottom of the purification tower 8. At this point, the main light components in the bottom mixture are NMP and 2PY. The bottom of the tower is heated to a temperature above the boiling point of 2PY at the tower's operating pressure. Because the purification tower 8 uses total reflux, the vacuum environment in the purification tower 8 is maintained by the original vacuum pump and overhead condenser. After the liquid in the bottom of the purification tower 8 is heated by the tower bottom reboiler, it is refluxed from the middle and lower part (that is, Figure 1 The 2PY with a higher boiling point is extracted from the seventh pipeline 12 in the purification tower 8) and is pressurized by the second pressure pump 18 and then passes through the third shell side (the highest shell side) of the multi-shell reaction heat exchanger 3 to recover heat. After the heat recovery is completed, it enters the 2PY temporary storage tank. After the bottom liquid of the purification tower 8 is heated by the bottom reboiler, it is refluxed from the middle and upper part (that is, Figure 1 NMP with a lower boiling point is extracted from the connection between the sixth pipeline 10 and the purification tower 8. The extracted NMP is pressurized by the third pressure pump 19 and then passes through the second shell side (intermediate shell side) of the multi-shell-pass reaction heat exchanger to recover heat. After heat recovery, it enters the NMP temporary storage tank. When the NMP+2PY content in the bottom liquid of the purification tower 8 falls below 5%, the bottom liquid is sent to the incinerator 22 for incineration.

[0030] Because the boiling points of GBL and NMP differ by 2°C, separation via distillation is difficult. The recovery system of the present invention allows for flexible adjustment of the molar ratio of monomethylamine based on the GBL content in the heavy fraction, minimizing GBL contamination of the active ingredients. This represents a significant improvement over existing technologies. Furthermore, since NMP can only be obtained through hydrolysis of the intermediate product produced by the reaction of GBL and monomethylamine, the heat of hydrolysis of the intermediate product is derived entirely from waste heat recovered from distillation.

[0031] In the original NMP production process, increasing the purity of the NMP product requires increasing byproduct discharge. This is because the accumulation of byproducts in the system severely impacts the NMP purification process. Therefore, large-scale discharge of byproducts from the original plant is beneficial to improving the quality of the original plant product. However, current byproduct recovery methods and the economic value of NMP have led to concerns about discharge. By using this solution's recovery system to recover the active components, these concerns are eliminated, and the original plant product can be elevated to a higher level. NMP and 2PY have high economic value, and effective recovery can significantly reduce costs and increase efficiency for enterprises.

[0032] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in a sequence other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0033] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments, and this embodiment will not be described in detail here.

[0034] The serial numbers of the above embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0035] In the above embodiments of the present application, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0036] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A system for recovering effective components in NMP process by-products, characterized in that: include: The first pipeline (1) is used to transport NMP process by-products; A gas-liquid separation tank (2) for separating the gas-liquid mixture from the first pipeline (1); A multi-shell reaction heat exchanger (3) is connected to the bottom of the gas-liquid separation tank (2) via a second pipeline (4), and the multi-shell reaction heat exchanger (3) is used for reaction and heat exchange; A light-removal tower (5) for removing light components, wherein the top and middle of the light-removal tower (5) are connected to the multi-shell-pass reaction heat exchanger (3) via a third pipeline (6) and a fourth pipeline (7), respectively; The bottom end of the light removal tower (5) is connected to the purification tower (8) through a fifth pipeline (9); after purification in the purification tower (8), a portion of the effective components enters the multi-shell reaction heat exchanger (3) through a sixth pipeline (10) for heat exchange treatment, and is then recovered through a first recovery pipe (11); another portion of the effective components enters the multi-shell reaction heat exchanger (3) through a seventh pipeline (12) for heat exchange, and is then recovered through a second recovery pipe (13).

2. the recovery system of effective component in the NMP process by-product according to claim 1, is characterized in that, The height of the connection between the sixth pipeline (10) and the purification tower (8) is higher than the height of the connection between the seventh pipeline (12) and the purification tower (8).

3. the recovery system of effective component in the NMP process byproduct according to claim 2, is characterized in that, The multi-shell reaction heat exchanger (3) is a reaction heat exchanger with multiple shells arranged in sequence in a vertical direction. The height of the connection between the seventh pipeline (12) and the multi-shell reaction heat exchanger (3) is higher than the height of the connection between the sixth pipeline (10) and the multi-shell reaction heat exchanger (3). The height of the connection between the sixth pipeline (10) and the multi-shell reaction heat exchanger (3) is higher than the height of the connection between the third pipeline (6) and the multi-shell reaction heat exchanger (3).

4. the recovery system of effective component in the NMP process byproduct according to claim 3, is characterized in that, The heat exchange tubes in the multi-shell reaction heat exchanger (3) are all of a serpentine structure to improve the heat exchange efficiency.

5. the recovery system of effective component in the NMP process byproduct according to claim 1, is characterized in that, A filter (14) is provided between the first pipeline (1) and the gas-liquid separation tank (2), and the filter (14) is used to filter solid particles in the by-products.

6. the recovery system of effective component in the NMP process byproduct according to claim 5, is characterized in that, The recovery system further comprises an eighth pipeline (15) and a mixer (16), wherein the mixer (16) is located between the filter (14) and the gas-liquid separation tank (2), and the eighth pipeline (15) is used to pass the monomethylamine solution into the mixer (16); The by-product filtered through the filter (14) is mixed with the monomethylamine solution in the mixer (16) for reaction, and then enters the gas-liquid separation tank (2).

7. The recovery system of effective components in the NMP process by-product according to claim 6, is characterized in that, The mixer (16) is a reverse vortex mixer, which is used to improve the mixing effect of the by-product and the monomethylamine solution.

8. The recovery system of effective components in the NMP process byproduct according to claim 1, wherein The second pipeline (4) is provided with a first pressure pump (17), and the first pressure pump (17) is used to pump the mixed liquid in the gas-liquid separation tank (2) into the multi-shell reaction heat exchanger (3).

9. the recovery system of effective component in the NMP process byproduct according to claim 1 is characterized in that, The seventh pipeline (12) is provided with a second pressure pump (18), and the sixth pipeline (10) is provided with a third pressure pump (19). The second pressure pump (18) and the third pressure pump (19) are both used to pump the components in the purification tower (8) into the multi-shell reaction heat exchanger (3).

10. The recovery system of effective components in the NMP process by-product according to claim 3, characterized in that, The recovery system further comprises a ninth pipeline (20), the ninth pipeline (20) being connected to the multi-shell reaction heat exchanger (3), and the components in the third pipeline (6) are recovered through the ninth pipeline (20) after heat exchange in the multi-shell reaction heat exchanger (3).

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