Continuous rectification device for maleic anhydride by DBP solvent absorption

Abstract

The utility model relates to maleic anhydride solvent recovery field, for a kind of maleic anhydride continuous rectification device using DBP solvent absorption, it mainly includes maleic anhydride desorption tower, first rectification tower and second rectification tower, and the efficient purification of crude maleic anhydride is realized by double-tower continuous negative pressure rectification process.Light component is removed under negative pressure in first rectification tower, second rectification tower is further refined and high-purity maleic anhydride product is taken out in upper lateral line.The device uses cascade control, nitrogen pressure interlock and multistage automatic regulating system, accurately controls tower kettle liquid level, reflux ratio and system pressure, ensures that operation is continuous and stable.Lateral line take-out pipeline is provided with jacket insulation and stabilizer automatic adding system, effectively prevent material solidification and metamorphism.The utility model has the advantages of low energy consumption, high product purity, stable and reliable operation, high degree of automation, and is suitable for continuous production high-purity maleic anhydride.

Description

Technical Field

[0001] This utility model relates to the field of maleic anhydride solvent recovery technology, specifically a continuous maleic anhydride distillation device using DBP solvent absorption. Background Technology

[0002] Maleic anhydride is an important organic chemical raw material, widely used in synthetic resins, coatings, pharmaceuticals, and other fields. Traditional maleic anhydride refining methods often employ batch distillation, but these methods have the following problems: 1) Steam consumption fluctuates greatly, with peak steam demand and unstable pressure, resulting in high energy consumption and increased operating costs; 2) Unstable operating conditions lead to large fluctuations in product quality, making it difficult to guarantee a continuous and stable output of high-purity products; 3) Impurities such as acrylic acid tend to accumulate locally in the equipment, leading to scaling, which requires frequent cleaning, complicates the operation, and affects continuous production; 4) The equipment configuration is complex, requiring a large number of cleaning pipes and instruments, resulting in high investment costs and difficult maintenance.

[0003] To overcome the above problems, this utility model provides a maleic anhydride continuous distillation device using DBP solvent absorption. Through measures such as dual-tower continuous distillation, negative pressure operation, automatic control and safety protection, a stable, efficient and low-consumption maleic anhydride purification process is achieved.

[0004] Therefore, there is an urgent need for a stable, efficient, and low-consumption continuous distillation device for maleic anhydride. Utility Model Content

[0005] To overcome the above problems, this utility model provides a maleic anhydride continuous distillation device using DBP solvent absorption. Through measures such as dual-tower continuous distillation, negative pressure operation, automatic control and safety protection, a stable, efficient and low-consumption maleic anhydride purification process is achieved.

[0006] To achieve the aforementioned technical effects, this utility model discloses a continuous maleic anhydride distillation apparatus using DBP solvent absorption, comprising a maleic anhydride desorption column, a first distillation column, and a second distillation column; the side feed outlet of the maleic anhydride desorption column is connected to the feed inlet of the first distillation column via a transfer pump; the top outlet of the first distillation column is connected to a first reflux tank via a first condenser, and the bottom outlet of the first reflux tank is connected to the top of the first distillation column and the maleic anhydride desorption column via pipelines; the bottom outlet of the first distillation column is connected to a first reboiler and a... A feed pump is provided, the outlet of which is connected to the feed inlet of the second distillation column; the top outlet of the second distillation column is connected to the second reflux tank via a second condenser, and the bottom outlet of the second reflux tank is connected to the top of the second distillation column and the first distillation column via pipelines; a side-stream outlet is provided at the top of the second distillation column, which is connected to the finished product tank via a cooler and a finished product pump in sequence; the bottom outlet of the second distillation column is connected to the second reboiler, the bottom liquid pump, and the crude anhydride tank via pipelines, and the outlet of the bottom liquid pump is connected to the maleic anhydride desorption column.

[0007] As a preferred technical solution, the first distillation column is a packed column, with at least two sections of structured packing inside, and / or, the top of the first distillation column is equipped with a liquid distributor, and / or, the bottom of the column is equipped with a liquid level detection device.

[0008] As a preferred technical solution, the top of the first distillation column is equipped with a pressure detection device, and interlock control is achieved through a nitrogen regulating valve and a reflux tank pressure valve.

[0009] As a preferred technical solution, the outlet pipeline of the first reboiler is equipped with a safety explosion-proof device; the safety explosion-proof device is an anti-arch type rupture disc.

[0010] As a preferred technical solution, the second distillation column is a three-stage packed column, and / or, the top of the column is equipped with a liquid distributor and a reflux distributor.

[0011] As a preferred technical solution, the pipeline at the side outlet is equipped with a heat insulation structure.

[0012] As a preferred technical solution, the side-stream outlet pipeline is equipped with a stabilizer addition system for adding stabilizers to the finished maleic anhydride.

[0013] As a preferred technical solution, a vacuum system is also included to provide a negative pressure operating environment for the first distillation column and the second distillation column; the vacuum system adopts a liquid ring vacuum pump and is equipped with a non-condensable gas discharge pipeline and a sealing liquid circulation pipeline.

[0014] As a preferred technical solution, the sealing fluid of the vacuum system comes from the lean solvent feed pump, and the circulating fluid containing maleic anhydride and light components is transported to the lean solvent storage tank through the sealing fluid pump.

[0015] As a preferred technical solution, the reboilers of the first and second distillation columns are each equipped with at least two sets of liquid level detection devices, one of which is a backup; the liquid level of each reboiler is detected by an external balance tube to avoid false liquid levels.

[0016] The beneficial effects of this utility model are: This invention achieves efficient, stable, and low-consumption operation of maleic anhydride production by employing a process that combines DBP solvent absorption with dual-tower continuous negative pressure distillation and integrating multiple automatic control and safety measures. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process flow of the maleic anhydride continuous distillation apparatus of this utility model; In the picture: 1. Desorption tower side-stream pump; 2. First distillation column; 3. First condenser; 4. First reflux tank; 5. First reflux pump; 6. Vacuum system; 7. First reboiler; 8. Feed pump; 9. Second distillation column; 10. Bottom level gauge; 11. First flow control valve; 12. Steam flow meter; 13. Steam control valve; 14. First balance pipe; 15. First level gauge; 16. First reflux tank level gauge; 17. Second flow control valve; 18. First pressure measuring instrument; 19. Second pressure measuring instrument; 20. First nitrogen control valve; 21. First reflux tank control valve; 22. Rupture disc; 23. Second condenser; 24. Second reflux tank; 25. Second reflux pump; 26. Maleic anhydride product cooler; 27. Side-stream pump; 28. Maleic anhydride product tank; 29. ​​Jacket. Pipeline; 30. Stabilizer tank; 31. Finished product flow meter; 32. Stabilizer mixer; 33. Second reboiler; 34. Boiler liquid pump; 35. Boiler level gauge; 36. Third flow control valve; 37. Boiler flow meter; 38. Fourth flow control valve; 39. Second balance pipe; 40. Second level gauge; 41. Second level control valve; 42. Second reflux tank level gauge; 43. Fifth flow control valve; 44. Third pressure measuring instrument; 45. Fourth pressure measuring instrument; 46. Second nitrogen regulating valve; 47. Second reflux tank regulating valve; 48. Reflux pipeline flow meter; 49. Reflux delivery flow meter; 50. Fourth flow control valve; 51. Finished product output flow meter; 52. Sixth flow control valve; 53. Flow ratio meter; 54. Liquid distributor; 55. Reflux distributor. Detailed Implementation

[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0019] This invention provides a continuous maleic anhydride distillation apparatus using DBP solvent absorption, comprising a first distillation column 2 and a second distillation column 9. In the apparatus, the side feed outlet of the maleic anhydride desorption column is connected to the middle feed inlet of the first distillation column 2 via a crude anhydride pump 1; the top outlet of the first distillation column 2 is connected to a first reflux tank 4 via a first condenser 3, and the bottom outlet of the reflux tank is divided into two paths: one path flows back to the top of the first distillation column 2 via a first reflux pump 5, and the other path returns to the desorption column; the bottom outlet of the first distillation column 2 is also divided into two paths: one path circulates back to the bottom of the first distillation column 2 via a first reboiler 7, and the other path is transported to the middle of the second distillation column 9 via a feed pump 8.

[0020] The top outlet of the second distillation column 9 is connected to the second reflux tank 24 via the second condenser 23. The bottom outlet of the reflux tank is divided into two paths: one path is returned to the top of the second distillation column 9 via the second reflux pump 25, and the other path returns to the first distillation column 2. The upper part of the second distillation column 9 is provided with a side-stream outlet, which is connected to the finished product tank 28 via the cooler 26 and the outlet pump 27. The bottom outlet of the second distillation column 9 is divided into three paths: the first path is circulated back to the bottom of the second distillation column 9 via the second reboiler 33, the second path is sent back to the desorption column via the bottom liquid pump 34, and the third path returns to the crude anhydride tank.

[0021] Preferably, the first distillation column 2 adopts a double-layer packing structure, with two sections of structured packing arranged from top to bottom, with heights of 2500mm and 5000mm respectively. A trough-type liquid distributor 54 is installed at the top of the column, and a first level gauge 15 is installed at the bottom. A cascade control strategy is used to regulate the steam flow rate of the first reboiler 7 and the bottom feed flow rate to achieve stable level control. A pressure detection device is installed at the top of the column, and is interlocked with the reflux tank pressure valve via a nitrogen regulating valve 20 to ensure stable column pressure. An anti-arch type rupture disc 22 is installed at the outlet of the first reboiler 7. Its front-side design pressure is -0.084MPa, and the burst pressure is set to 1.6MPa. As a key safety protection measure, it effectively mitigates the impact of reboiler system instability on the first distillation column 2.

[0022] The second distillation column 9 is preferably a three-section packed structure, with packing heights of 2500mm, 5000mm, and 3000mm from top to bottom. A trough-type liquid distributor 54 and a reflux distributor 55 are installed at the top of the column, and the spray density is controlled at 2m³. 3 / m 2•hr. Given the low melting point and easy sublimation of maleic anhydride, to reduce the risk of condensation nucleus blockage, a jacketed pipeline 29 and a stabilizer addition system are installed on the side-stream outlet pipeline of the second distillation column 9. The core principle of the jacketed pipeline 29 is to wrap a sealed sleeve around the outside of the side-stream outlet pipeline, forming an annular cavity to maintain the pipeline temperature and prevent material solidification. The stabilizer addition system includes a stabilizer tank 30, a flow meter 31, and a mixer 32, which can automatically add stabilizer as needed to ensure product stability. Preferably, the heat stabilizer is added once a month, with each addition being 7 kg. Okay, this is a very specific technical detail. In the maleic anhydride continuous distillation apparatus described in this utility model, the connection method and working principle of the stabilizer addition system are key to ensuring stable product quality.

[0023] Preferably, the stabilizer addition system includes a stabilizer tank 30, a finished product flow meter 31, and a mixer 32. High-purity liquid maleic anhydride is drawn from the side stream of the second distillation column and flows through a jacketed insulated pipeline. The finished product flow meter 31 is installed on the finished maleic anhydride pipeline to monitor the instantaneous and cumulative flow of the finished maleic anhydride in real time and continuously. The finished product flow meter 31 transmits the detected flow signal to a flow ratio meter 53. The flow ratio meter calculates according to the preset stabilizer to maleic anhydride addition ratio and outputs a quantitative amount via a sixth flow regulating valve 52. The precisely metered stabilizer is combined with the mainstream maleic anhydride product in the stabilizer mixer, and the final product after uniform mixing is transported to the finished maleic anhydride tank for storage.

[0024] The device also includes a vacuum system 6 to maintain a negative pressure operating environment for the first and second distillation columns 9. Vacuum system 6 uses a liquid ring vacuum pump with an intake pressure of 15 kPaA. Its non-condensable gases are transported to the tail gas treatment system via a pressurized blower. The sealing fluid comes from a lean solvent feed pump and is used to replenish the circulating fluid in vacuum system 6, while the circulating fluid containing maleic anhydride and light components is transported to the lean solvent storage tank via a sealing fluid pump. To maintain stable vacuum levels in both columns, system pressure balance is achieved through interlocking control between the column pressure and nitrogen regulating valves.

[0025] Furthermore, the first and second distillation columns 9 maintain pressure balance through a nitrogen interlock mechanism; the liquid level in each reboiler is detected by an external balance pipe, effectively avoiding false liquid level phenomena. Preferably, two sets of online liquid level gauges are installed in the bottom of each column, one set as a backup to deal with blockages, significantly improving the stability and continuity of system operation.

[0026] The working principle of this utility model is as follows: Crude maleic anhydride, at a temperature of 90℃ and a purity of approximately 95%, is continuously fed into the middle section of the first distillation column 2 by the side-stream pump 1 from the desorption tower. Under a negative pressure operating condition of 15 kPa, the light component gas in the crude maleic anhydride is discharged from the top of the column and enters the first condenser 3, where it is condensed by the shell-side circulating warm water. The condensed light component liquid enters the first reflux tank 4, flows out from the bottom, and is then returned to the top of the first distillation column 2 by the first reflux pump 5. The vacuum tail gas (i.e., uncondensed gas) at the top of the reflux tank of the first distillation column 2 enters the vacuum system 6 for treatment.

[0027] The crude maleic anhydride with a purity of approximately 99.5% discharged from the bottom of the first distillation column 2 is partially returned to the bottom of the column after being heated and vaporized by steam in the first reboiler 7. This is used to heat and vaporize the crude maleic anhydride that has entered the middle of the column. The other part is transported to the second distillation column 9 for further purification via the feed pump 8.

[0028] The bottom of the first distillation column 2 is equipped with a liquid level control and regulation loop. Automatic cascade control is achieved via the signal from the column bottom level gauge 10. The flow rate of crude maleic anhydride output to the second distillation column 9 is regulated via the first flow regulating valve 11 to maintain a stable column bottom liquid level and includes high / low level alarm functions. Simultaneously, the reboiler steam flow rate of the first distillation column 2 is automatically controlled via a steam flow meter 12. Based on the flow signal, the cascade regulating steam valve 13 is used to stabilize the column bottom liquid level and is equipped with corresponding alarm functions.

[0029] The condensate from the first reboiler 7 is automatically controlled by the first level gauge 15 on the first balance pipe 14, and the condensate discharge is regulated by the level regulating valve. The level of the first reflux tank 4 is monitored by the first reflux tank level gauge 16, and the second flow regulating valve 17 is cascaded through the level signal to regulate the top reflux flow of the first distillation column 2, so as to maintain the stability of the reflux tank level and set a high level alarm.

[0030] The first distillation column 2 is equipped with a first pressure measuring instrument 18 at the bottom and a second pressure measuring instrument 19 at the top. The pressure at the top of the column is automatically controlled by the pressure difference signal between the bottom and the top of the column, and is coordinated by the first nitrogen regulating valve 20 and the first reflux tank regulating valve 21 to ensure the stability of the pressure at the top of the column. The first distillation column 2 and the second distillation column 9 jointly maintain the stability and balance of the system vacuum through a nitrogen interlock mechanism.

[0031] A rupture disc 22 is installed on the outlet pipeline of the first reboiler 7 as a safety protection device. Its front-side design pressure is -0.084MPa, and the burst pressure is set to 1.6MPa, which effectively ensures the safe operation of the reboiler circulation system of the first distillation column 2.

[0032] The crude maleic anhydride, after the removal of light components and a purity increase to 99.5%, continuously enters the middle section of the second distillation column 9 for continuous purification under a negative pressure of 15 kPa. The crude maleic anhydride gas containing trace amounts of light components (approximately 0.13%) is discharged from the top of the second distillation column 9 and enters the second condenser 23 for condensation by shell-side warm water. The condensate enters the second reflux tank 24; a portion is refluxed back to the top of the second distillation column 9 via the second reflux pump 25, while the other portion is returned to the first distillation column 2 for further processing. The vacuum exhaust gas from the top of the second reflux tank 24 is also introduced into the vacuum system 6.

[0033] The maleic anhydride product from the upper side stream of the second distillation column 9 has a purity of up to 99.9%. After being cooled by the product cooler 26, it is transported to the product tank 28 by the side stream pump 27. The product delivery pipeline adopts a jacketed insulation design 29 to effectively prevent material solidification and blockage. At the same time, an automatic stabilizer addition system is provided. The stabilizer is delivered from the stabilizer tank 30 according to the signal ratio of the product flow meter 31 and mixed with the maleic anhydride product in the stabilizer mixer 32 to ensure product stability.

[0034] The crude maleic anhydride containing approximately 21.03% heavy components is discharged from the bottom of the second distillation column 9. Part of it is vaporized by steam heating in the second reboiler 33 and returned to the bottom of the column for reboiling the feed; the other part is sent back to the desorption column as bottom liquid via bottom liquid pump 34.

[0035] The bottom of the second distillation column 9 is equipped with a level control loop, which achieves automatic cascade control via the column bottom level gauge 35. The reboiler steam flow rate is adjusted via the third flow regulating valve 36 to maintain a stable level and includes high / low alarm functions. The column bottom flow meter 37 controls the fourth flow regulating valve 38 to adjust the flow rate of the heavy component output to the desorption column, thus stabilizing the column bottom level. The condensate from the second reboiler 33 is automatically controlled by the second level gauge 40 on the second balance pipe 39, and discharged via the level regulating valve 41. The level of the second reflux tank 24 is monitored by the second reflux tank level gauge 42, and the level signal cascades to control the fifth flow regulating valve 43, adjusting the top reflux flow rate of the second distillation column 9 to maintain a stable reflux tank level and includes a high level alarm.

[0036] The flow rate of heavy components at the bottom of the second distillation column 9 is automatically controlled by the column bottom flow meter 37 and accurately output via the fourth flow regulating valve 38; the reflux flow rate at the top of the column is monitored by the reflux line flow meter 48 and regulated by the fifth flow regulating valve 43; the output of condensate at the top of the column is automatically controlled by the reflux delivery flow meter 49 and controlled by the corresponding regulating valve; the output of the finished product from the side stream is automatically controlled by the signal from the finished product output flow meter 51 and quantitatively output via the sixth flow regulating valve 52; the ratio between the reflux flow rate at the top of the column and the output of the finished product from the side stream is automatically controlled by the flow ratio meter 53.

[0037] The second distillation column 9 is equipped with a third pressure measuring instrument 44 at the bottom and a fourth pressure measuring instrument 45 at the top. The pressure at the top of the column is automatically controlled by the pressure difference signal between the bottom and the top of the column. The pressure at the top of the column is maintained stably by the coordinated action of the second nitrogen regulating valve 46 and the second reflux tank regulating valve 47. The first distillation column 2 and the second distillation column 9 continue to ensure the stability and balance of the vacuum degree of the entire system through a nitrogen interlocking mechanism.

[0038] Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the features in the embodiments disclosed in this invention can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A continuous maleic anhydride distillation apparatus employing DBP solvent absorption, characterized in that, The system includes a maleic anhydride desorption column, a first distillation column, and a second distillation column. The side outlet of the maleic anhydride desorption column is connected to the feed inlet of the first distillation column via a transfer pump. The top outlet of the first distillation column is connected to a first reflux tank via a first condenser. The bottom outlet of the first reflux tank is connected to the top of the first distillation column and the maleic anhydride desorption column via pipelines. The bottom outlet of the first distillation column is connected to a first reboiler and a feed pump via pipelines. The outlet of the feed pump is connected to the feed inlet of the second distillation column. The top outlet of the second distillation column is connected to a second reflux tank via a second condenser. The bottom outlet of the second reflux tank is connected to the top of the second distillation column and the first distillation column via pipelines. The upper part of the second distillation column has a side outlet, which is connected to a finished product tank via a cooler and a finished product pump. The bottom outlet of the second distillation column is connected to a second reboiler, a bottom liquid pump, and a crude anhydride tank via pipelines. The outlet of the bottom liquid pump is connected to the maleic anhydride desorption column.

2. The maleic anhydride continuous distillation apparatus according to claim 1, characterized in that, The first distillation column is a packed column, with at least two sections of structured packing inside, and / or, the top of the first distillation column is equipped with a liquid distributor, and / or, the bottom of the column is equipped with a liquid level detection device.

3. The maleic anhydride continuous distillation apparatus according to claim 2, characterized in that, The first distillation column is equipped with a pressure detection device at the top, and is interlocked with the nitrogen regulating valve and the reflux tank pressure valve.

4. The maleic anhydride continuous distillation apparatus according to claim 2, characterized in that, The outlet pipeline of the first reboiler is equipped with a safety explosion-proof device; the safety explosion-proof device is an inverted arch-shaped rupture disc.

5. The maleic anhydride continuous distillation apparatus according to claim 1, characterized in that, The second distillation column is a three-stage packed column, and / or, the top of the column is equipped with a liquid distributor and a reflux distributor.

6. The maleic anhydride continuous distillation apparatus according to claim 5, characterized in that, The side-line outlet pipeline is equipped with a heat insulation structure.

7. The maleic anhydride continuous distillation apparatus according to claim 6, characterized in that, The side-stream outlet pipeline is equipped with a stabilizer addition system for adding stabilizers to the finished maleic anhydride.

8. The maleic anhydride continuous distillation apparatus according to claim 1, characterized in that, It also includes a vacuum system for providing a negative pressure operating environment for the first and second distillation columns; the vacuum system employs a liquid ring vacuum pump and is equipped with a non-condensable gas discharge pipeline and a sealing liquid circulation pipeline.

9. The maleic anhydride continuous distillation apparatus according to claim 8, characterized in that, The sealing fluid of the vacuum system comes from the lean solvent feed pump, and the circulating fluid containing maleic anhydride and light components is delivered to the lean solvent storage tank through the sealing fluid pump.

10. The maleic anhydride continuous distillation apparatus according to claim 1, characterized in that, The first and second distillation columns are each equipped with at least two sets of liquid level detection devices, one of which is a backup; the liquid level of each reboiler is detected by an external balance pipe to avoid false liquid level readings.

Images