A system and process for efficiently recovering DBP solvent in maleic anhydride production.

Abstract

This invention relates to the field of maleic anhydride solvent recovery technology, specifically a system and process for efficiently recovering DBP solvent from maleic anhydride production. The system includes a desorption tower, a tail gas scrubbing tower, an extraction tower, and a distillation tower. The desorption tower has a rich solvent feed line, a desorption discharge line, and a liquid outlet line connected to a vertical shell-and-tube reboiler. The desorption discharge line and the rich solvent feed line are connected via a feed preheater. The top feed line of the extraction tower is connected to the desorption discharge line, and the bottom of the extraction tower has a DBP solvent discharge line and an extractant DMI circulating feed line. The top of the distillation tower has a second crude maleic anhydride collection line, and the bottom of the distillation tower is connected to the extractant DMI circulating feed line. A portion of the extractant in the bottom of the distillation tower is cooled and then recycled back into the extraction tower, while the other portion is preheated and returned to the bottom of the distillation tower in gaseous form to participate in distillation. By setting up the extraction tower and distillation tower, this invention lowers the system's operating temperature, reduces the decomposition of DBP and the generation of tar in maleic anhydride, and minimizes the risk of equipment blockage and shutdown.

Description

Technical Field

[0001] This invention relates to the field of maleic anhydride solvent recovery technology, specifically to a system and process for efficiently recovering DBP solvent in maleic anhydride production. Background Technology

[0002] In the production of maleic anhydride, the DBP (dibutyl phthalate) solvent recovery process is a crucial step in ensuring efficient recovery of maleic anhydride and recycling of the solvent. This process mainly includes two core steps: absorption and desorption.

[0003] Absorption stage: Maleic anhydride in the reaction tail gas is absorbed by DBP solvent to achieve preliminary enrichment of the target product;

[0004] Desorption stage: Maleic anhydride is desorbed from DBP solvent by heating. Crude maleic anhydride is sent to the purification tower for purification, while lean solvent DBP is sent to the lean liquor purification unit to remove impurities and then returned to the absorption tower for recycling.

[0005] However, the current process has serious technical defects in the desorption stage, which directly affects the long-term stable operation of the system:

[0006] 1) DBP High-Temperature Decomposition Problem: The operating temperature at the bottom of the desorption tower reaches as high as 199℃. After being superheated to 215℃ by a heat exchanger, it enters the flash evaporator to further remove trace amounts of maleic anhydride from the bottom material of the desorption tower. Under these conditions, DBP is prone to thermal decomposition, generating small molecule byproducts such as phthalic anhydride and butanol. These substances further polymerize to form high-molecular-weight tar. Although vacuum operation is used to reduce the bottom temperature, DBP decomposition cannot be completely avoided and accumulates continuously in the system, eventually leading to pipeline blockage and even unplanned shutdowns.

[0007] 2) Energy loss and impurity accumulation: The high temperature carried by the product in the bottom of the desorption tower cannot be utilized, resulting in energy waste; in addition, the light components collected from the top of the desorption tower need to be processed separately, while the decomposition products remaining in the lean solvent at the bottom of the tower may reduce the absorption efficiency, forming a vicious cycle.

[0008] In summary, the insufficient thermal stability of DBP has become a core bottleneck restricting the efficient operation of maleic anhydride recovery processes. How to effectively inhibit DBP decomposition, reduce tar generation, and fully utilize the energy exchange during maleic anhydride production is a key technical challenge that urgently needs to be addressed. Summary of the Invention

[0009] The purpose of this invention is to provide a system and process for efficiently recovering DBP solvent in maleic anhydride production, thereby minimizing the system's operating temperature, reducing the decomposition of DBP and the generation of tar in maleic anhydride, and avoiding equipment blockage and shutdown as much as possible.

[0010] To achieve the above-mentioned technical effects, this invention discloses a system for efficiently recovering DBP solvent in maleic anhydride production. The system includes a desorption tower, a tail gas scrubbing tower, an extraction tower, and a distillation tower.

[0011] The desorption tower is equipped with a rich solvent feed line, a desorption discharge line, and a liquid outlet line connected to a vertical shell-and-tube reboiler. The desorption discharge line is heat-exchange connected to the rich solvent feed line. The rich solvent from the absorption unit is heated to 160-170°C after heat exchange with the liquid outlet of the desorption tower, and then enters the desorption tower through the rich solvent feed line. The liquid outlet of the desorption tower is cooled to 70-90°C after heat exchange and then enters the extraction tower through the desorption discharge line. The solution in the desorption tower is transported to the top of the vertical shell-and-tube reboiler for forced circulation by a pressure pump on the liquid outlet line. After the solution is heated to 190-200°C by steam, the gas phase returns to the bottom of the desorption tower.

[0012] The top feed line of the extraction tower is connected to the desorption discharge line, and the top discharge line of the extraction tower is connected to the distillation tower; the bottom of the extraction tower is equipped with a DBP solvent discharge line and an extractant DMI circulating feed line.

[0013] The top of the distillation column is equipped with a second crude maleic anhydride collection line; part of it is connected to the crude anhydride storage tank, and the other part is returned to the top of the distillation column to participate in distillation; the bottom of the distillation column is connected to the DMI extractant circulating feed line; part of the extractant in the distillation column bottom is cooled and then enters the extraction column for recycling, and the other part is preheated and returned to the bottom of the distillation column in gaseous form to participate in distillation.

[0014] As a preferred technical solution, the vertical shell-and-tube reboiler is located outside the column bottom, with its inlet connected to the bottom of the desorption column via a liquid outlet line, and its outlet connected to the lower part of the desorption column.

[0015] As a preferred technical solution, the desorption tower bottom is connected to the desorption discharge line, and the desorption discharge line and the rich solvent feed line are connected to the feed preheater for heat exchange.

[0016] As a preferred technical solution, the top discharge of the desorption tower is cooled by a condenser and then subjected to gas-liquid separation. The gas phase enters the tail gas scrubbing tower, and the liquid phase is returned to the desorption tower as reflux.

[0017] As a preferred technical solution, the top feed line of the extraction tower is connected to the outlet of the condenser.

[0018] As a preferred technical solution, the system also includes an extractant DMI storage tank and a feeding pipeline, wherein the feeding pipeline is connected to the extractant DMI circulating feed line.

[0019] As a preferred technical solution, the upper part of the desorption tower is provided with a first crude maleic anhydride production line, which is connected to the crude maleic anhydride storage tank together with the second crude maleic anhydride production line of the distillation tower.

[0020] As a preferred technical solution, the extraction tower is also equipped with an extractant DMI storage tank connected to the extractant circulation feed line for replenishing the extractant.

[0021] This invention also discloses a process method for utilizing the above-mentioned system for efficiently recovering DBP solvent in maleic anhydride production, comprising the following steps:

[0022] S1. The rich solvent from the absorption unit exchanges heat with the discharge from the bottom of the desorption tower and is heated to temperature T1, and then enters the middle of the desorption tower.

[0023] S2. The solution in the desorption tower is pumped to the top of the vertical shell-and-tube reboiler via a pressurized pump. It is heated to temperature T2 by steam to form a liquid film evaporation. The gas phase returns to the bottom of the desorption tower for heat and mass transfer, and the heavy components gradually accumulate in the liquid phase. At the same time, crude maleic anhydride is collected from the upper side of the desorption tower. The top discharge of the desorption tower mainly consists of acrylic acid and a small amount of maleic anhydride. It is cooled to temperature T3 by a condenser for gas-liquid separation. The gas phase enters the tail gas scrubbing tower, and the liquid phase returns to the top of the desorption tower to participate in heat and mass transfer.

[0024] S3. After cooling the desorption tower bottom feed to temperature T4, it is sent to the top of the extraction tower as the dispersed phase, and it is in countercurrent contact with the circulating extractant DMI entering from the bottom of the tower for mass transfer. The extractant containing maleic anhydride is obtained at the top of the tower, and the DBP solvent is separated at the bottom of the tower.

[0025] S4. The maleic anhydride-containing extractant at the top of the extraction column is sent to the distillation column for separation. Crude maleic anhydride product is obtained at the top of the column. A portion of the extractant at the bottom of the column is cooled to temperature T5 and then recycled back to the extraction column. The remaining portion is vaporized and returned to the distillation column to participate in distillation.

[0026] As a preferred technical solution, T1 is 160~170℃, and / or, T2 is 190~200℃, and / or, T3 is 92~98℃, and / or, T4 is 70~90℃, and / or, T5 is 70~90℃.

[0027] The beneficial effects of this invention are:

[0028] 1. By replacing the traditional post-flash distillation tower with a combined extraction and distillation tower system, the operating temperature of the tower bottom is significantly reduced, effectively inhibiting the decomposition of DBP solvent at high temperatures and reducing the generation of byproducts such as phthalic anhydride, butanol, and high molecular weight tar, thereby avoiding equipment blockage and unplanned shutdowns.

[0029] 2. The heat exchange design of desorption tower bottom discharge and rich solvent feed is adopted, which makes full use of the thermal energy of high-temperature materials, reduces energy waste, and improves the overall energy efficiency of the system.

[0030] 3. The desorption tower adopts a vertical shell-and-tube reboiler, which greatly improves heat transfer efficiency by utilizing the characteristics of rapid liquid film evaporation and short residence time, while avoiding the decomposition of DBP at high temperatures for a long time.

[0031] 4. The extraction column uses DMI as the extractant to achieve efficient separation of maleic anhydride and DBP at low temperature (70~90℃); the distillation column further purifies maleic anhydride and recovers the extractant for recycling, which not only ensures the DBP solvent recovery rate, but also reduces the risk of impurity accumulation.

[0032] 5. By adding a tail gas scrubbing tower and extractant replenishment facilities, the non-condensable gas treatment and solvent loss compensation mechanisms were improved, ensuring the stability and process continuity of long-term operation.

[0033] In summary, this invention solves the core problems of high-temperature DBP decomposition, tar blockage, and high energy consumption in traditional maleic anhydride production through innovative system design and process optimization, and significantly improves solvent recovery efficiency and equipment operation reliability. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0035] In the diagram: 1. Desorption tower; 11. Desorption discharge line; 12. Rich solvent feed line; 13. Feed preheater; 14. Liquid discharge line; 15. Vertical shell-and-tube reboiler; 16. Crude maleic anhydride storage tank; 17. First crude maleic anhydride discharge line; 18. First condenser; 19. Condenser; 2. Tail gas scrubbing tower; 21. Vacuum system; 22. Rich solvent storage tank; 3. Extraction tower; 31. Feed line; 32. Discharge line; 33. DBP solvent discharge line; 34. Extractant circulating feed line; 35. Extractant DMI storage tank; 36. Feed line; 37. Cooler; 4. Distillation tower; 41. Second crude maleic anhydride discharge line. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] like Figure 1 As shown, the present invention provides a system for efficiently recovering DBP solvent in maleic anhydride production, the system comprising a desorption tower 1, a tail gas scrubbing tower 2, an extraction tower 3, and a distillation tower 4;

[0039] After the rich solvent from the absorption unit exchanges heat with the effluent from the bottom of desorption tower 1 and is heated, it enters desorption tower 1. The solution in the bottom of desorption tower 1 is heated by a vertical shell-and-tube reboiler 15. The solution is evaporated and the gas phase returns to desorption tower 1 to transfer heat and mass with the liquid phase material from the top of the tower. The light component is discharged from the top of the tower, and crude maleic anhydride product can be collected from the side stream. The heavy component (DBP containing maleic anhydride) gradually accumulates in the liquid phase and is discharged from the bottom of desorption tower 1.

[0040] The feed from the bottom of desorption tower 1 and the rich solvent feed, after heat exchange in the preheater and cooling in the cooler, enter the top of extraction tower 3 as the dispersed phase. The circulating extractant DMI enters from the bottom of the tower as the continuous phase and flows between the trays through the riser. The dispersed phase exists in the form of droplets and undergoes mass transfer with the continuous phase. The top feed from extraction tower 3 is extractant plus maleic anhydride, which enters distillation tower 4. The bottom feed from extraction tower 3 is DBP solvent, which goes to the solvent regeneration unit for purification and reuse.

[0041] Distillation column 4 separates the extractant DMI and maleic anhydride from extraction column 3, obtaining crude maleic anhydride product at the top. Part of this product, along with the maleic anhydride product from desorption column 1, is sent to crude anhydride storage tank 16 for further purification, while the other part is condensed and returned to the top of the distillation column. The bottom product of distillation column 4 is the extractant, which, after being cooled by a cooler, can be returned to extraction column 3 for recycling. An extractant replenishment system is provided to compensate for losses during long-term operation.

[0042] The above technical solution improves the recovery efficiency of DBP solvent in maleic anhydride production from two aspects:

[0043] First, as is well known, the liquid phase residence time is relatively long and the gas phase residence time is short during distillation, and the thermosensitive reaction mainly takes place in the liquid phase; reducing the thermosensitive reaction is mainly achieved by lowering the heating temperature of the thermosensitive substance in the distillation equipment and shortening the heating time.

[0044] Secondly, therefore, the desorption tower 1 and reboiler 15 in this invention adopt a vertical shell-and-tube type. The pump located on the liquid outlet line pumps the solution from the bottom of the reboiler into the tube side. The liquid flows upward in the tube and absorbs the heat of the shell side heating medium at the same time, and the temperature gradually rises. When the liquid temperature reaches the boiling point, part of the liquid vaporizes, forming a vapor-liquid two-phase flow. The vaporization process is accompanied by volume expansion, which pushes the mixture upward to achieve forced circulation. The vapor-liquid mixture is discharged from the top of the reboiler and returned to the desorption tower.

[0045] Third, in addition, compared with other reboilers, the vertical shell-and-tube reboiler 15 has a high heat transfer coefficient. The material flows through the inner wall of the evaporation tube in one go, and the heating time on the tube wall is very short. The DBP in the tube does not have time to decompose, making it particularly suitable for the purification of heat-sensitive materials.

[0046] Secondly, in the existing process, the outlet temperature of desorption tower 1 is 200℃. After being superheated to 215℃ by a heat exchanger, it enters the flash evaporator to further remove trace amounts of maleic anhydride from the material in the bottom of desorption tower 1. Thermosensitive experiments on DBP show that at 215℃, the DBP solution darkens in color and produces an oily substance. In actual industrial plants, DBP solvent is prone to decomposition under excessively high operating temperatures for extended periods, and it also reacts with byproducts of other reactions to form high-molecular-weight tar substances.

[0047] Therefore, this invention changes the flash distillation tower to an extraction tower 3 + a distillation tower 4. In this invention, the rich solvent from the absorption unit exchanges heat with the bottom product of the desorption tower 1 and is heated to 160~170°C, and then enters the middle of the desorption tower 1. The solution in the bottom of the desorption tower 1 is pressurized by a pump and sent to the top of the vertical shell-and-tube reboiler 15, where the material is heated to 190~200°C by steam. The bottom product of the desorption tower 1 is cooled to 70~90°C after heat exchange and cooling, and then enters the top of the extraction tower 3. This temperature range is neither lower than the freezing point of maleic anhydride nor will it affect the extraction effect.

[0048] Since extraction does not require high temperatures, the presence of extraction column 3 effectively reduces the operating temperature of the column bottom, minimizes the decomposition loss of DBP, and prevents it from reacting with byproducts of other reactions to generate high-molecular-weight tar substances, which could lead to equipment blockage and shutdown.

[0049] In addition, to fully realize the function of the desorption tower 1, the bottom of the desorption tower 1 is connected to the desorption discharge line 11 through the discharge port. The desorption discharge line 11 and the rich solvent feed line 12 are connected to the feed preheater 13 for heat exchange. After heat exchange, the rich solvent is heated to 160~170℃ and enters the desorption tower 1. The bottom of the tower (mainly maleic anhydride and DBP) is cooled to 70~90℃ after heat exchange and cooling and enters the extraction tower 3. The bottom of the desorption tower 1 is also provided with a liquid outlet connected to the liquid outlet line 14. The solution in the tank is pressurized by the pressure pump on the liquid outlet line and then transported to the top of the vertical shell and tube reboiler 15. The solution is heated to 190~200℃ by steam in the reboiler and continuously evaporates and returns to the desorption tower 1, where it exchanges heat and transfers mass with the liquid phase material from the top. A first crude maleic anhydride outlet line 17, connected to a crude maleic anhydride storage tank 16, is located on one side of the upper part of the desorption tower 1. The crude maleic anhydride leaves the desorption tower 1 and enters the crude maleic anhydride storage tank 16 via a discharge pump installed on the first crude maleic anhydride outlet line 17. The top discharge of the desorption tower 1 mainly consists of acrylic acid and a small amount of maleic anhydride. After being cooled to 92~98°C by the condenser 18, gas-liquid separation is performed. The non-condensable gas enters the tail gas scrubbing tower 2 from the bottom, while the liquid phase is returned to the desorption tower 1 via a reflux pump.

[0050] The absorbent solvent from the solvent recovery unit enters the tail gas scrubbing tower 2 from the top, where the gas and liquid phases come into countercurrent contact to achieve mass transfer and recover a small amount of maleic anhydride contained in the non-condensable gas. The tail gas at the top of the tail gas scrubbing tower 2 enters the vacuum system 21, while the maleic anhydride-containing material at the bottom of the tower is recycled back to the rich solvent storage tank 22.

[0051] To better achieve the function of separating maleic anhydride and DBP in extraction tower 3, the top of extraction tower 3 is equipped with a feed line 31 and a discharge line 32. The feed line 31, containing maleic anhydride and DBP, is connected to the outlet of the condenser 19. After extraction, the maleic anhydride containing extractant DMI is transported to the distillation tower 4 for separation through the discharge line 32. The bottom of extraction tower 3 is equipped with a DBP solvent discharge line 33 and an extractant DMI circulating feed line 34. The DBP solvent discharge line 33 transports the DBP recovered from the maleic anhydride to the regeneration unit. The extractant circulating feed line 34 cools the extractant from the distillation tower 4 through the cooler 37 and then sends it back to extraction tower 3 for recycling. To compensate for the loss of extractant after long-term operation, an extractant DMI storage tank 35 is also provided outside the extraction tower, connected to the extractant circulating feed line 34 via a feed line 36, for replenishing extractant to the extractant DMI circulating feed line 34. The amount of extractant replenished can be adjusted automatically according to the actual operating conditions.

[0052] To better realize the function of separating the extractant DMI and maleic anhydride in distillation column 4, the top of distillation column 4 is provided with a second crude maleic anhydride outlet line 41 connected to the crude anhydride storage tank 16. After gas-liquid phase mass and heat transfer in distillation column 4, the maleic anhydride separated from the extractant is condensed into a liquid phase by a condenser. Part of it is sent to the crude anhydride storage tank 16 through the second crude maleic anhydride outlet line 41, and the other part is returned to the top of distillation column 4 to participate in distillation. Part of the extractant in the bottom of distillation column 4 is cooled by cooler 37 and then enters extraction column 3 for recycling, while the other part enters preheater for preheating and then returns to the bottom of distillation column 4 in gaseous form to participate in distillation.

[0053] Example 2

[0054] Based on the apparatus of Example 1, this example discloses a production process for efficiently recovering DBP solvent in maleic anhydride production, comprising the following steps:

[0055] S1. The rich solvent from the absorption unit exchanges heat with the discharge from the bottom of the desorption tower 1 and is heated to 165°C, and then enters the middle part of the desorption tower 1.

[0056] S2. The solution in the reactor of desorption tower 1 is pressurized by a pressure pump and then transported to the top of the vertical shell-and-tube reboiler 15. It is heated to 192°C by steam. The solution continuously evaporates, and the gaseous material returning to the bottom of desorption tower 1 undergoes heat and mass transfer (heat exchange and mass transfer) with the liquid material from the top of the tower. The heavy components gradually accumulate in the liquid phase. The crude maleic anhydride product can be side-collected from the top of desorption tower 1 and enters the crude anhydride storage tank 16. The top output of desorption tower 1 mainly consists of acrylic acid and a small amount of maleic anhydride. After being cooled to 95°C by a condenser, gas-liquid separation is performed. The gas phase enters the tail gas scrubbing tower 2, while the liquid phase is returned to the top of desorption tower 1 by a reflux pump to participate in heat and mass transfer.

[0057] S3. The bottom feed of desorption column 1 includes a maleic anhydride solution containing DBP. This material, along with the rich solvent, is cooled to 80°C after passing through a preheater and cooler, and then enters extraction column 3 from the top. It exists as a dispersed phase in the form of droplets, initially forming a liquid layer on the tray. After accumulating a certain amount of energy, it passes through the sieve and enters the next tray. The bottom of extraction column 3 is supplied with circulating extractant DMI from distillation column 4. This extractant flows between the trays through risers, undergoing mass transfer with the dispersed phase. After extraction, the extractant and maleic anhydride are sent from the top of the column to distillation column 4 for separation; the DBP separated from the maleic anhydride is sent from the bottom of the column to the regeneration unit.

[0058] S4. After gas-liquid phase heat and mass transfer within the distillation column 4, the maleic anhydride separated from the extractant is condensed into a liquid phase by a condenser. Part of the liquid is sent to the crude anhydride storage tank 16, and the other part is returned to the top of the distillation column 4 to participate in distillation. Part of the extractant in the bottom of the distillation column 4 is cooled to 75°C by the cooler 37 and then recycled back into the extraction column 3. The other part is preheated by the preheater and returned to the bottom of the distillation column 4 in gaseous form to participate in distillation. An extractant replenishment tank 35 is provided in the device, and the extractant is replenished through pipeline 36 to compensate for the loss of DMI during long-term operation.

[0059] Although the 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 invention. In particular, features in the embodiments disclosed herein can be combined in any way, provided there is no structural conflict. The lack of an exhaustive description of these combinations in this specification is merely for brevity and resource conservation. Therefore, the 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 system for efficiently recovering DBP solvent in maleic anhydride production, characterized in that: The system includes a desorption tower, a tail gas scrubbing tower, an extraction tower, and a distillation tower; The desorption tower is equipped with a rich solvent feed line, a desorption discharge line, and a liquid outlet line connected to a vertical shell-and-tube reboiler. The desorption discharge line is heat-exchange connected to the rich solvent feed line. The rich solvent from the absorption unit is heated to 160-170°C after heat exchange with the liquid outlet of the desorption tower, and then enters the desorption tower through the rich solvent feed line. The liquid outlet of the desorption tower is cooled to 70-90°C after heat exchange and then enters the extraction tower through the desorption discharge line. The solution in the desorption tower is transported to the top of the vertical shell-and-tube reboiler for forced circulation by a pressure pump on the liquid outlet line. After the solution is heated to 190-200°C by steam, the gas phase returns to the bottom of the desorption tower. The top feed line of the extraction tower is connected to the desorption discharge line, and the top discharge line of the extraction tower is connected to the distillation tower; the bottom of the extraction tower is equipped with a DBP solvent discharge line and an extractant DMI circulating feed line. The top of the distillation column is equipped with a second crude maleic anhydride collection line; part of it is connected to the crude anhydride storage tank, and the other part is returned to the top of the distillation column to participate in distillation; the bottom of the distillation column is connected to the DMI extractant circulating feed line; part of the extractant in the distillation column bottom is cooled and then enters the extraction column for recycling, and the other part is preheated and returned to the bottom of the distillation column in gaseous form to participate in distillation.

2. The system for efficiently recovering DBP solvent in maleic anhydride production as described in claim 1, characterized in that: The vertical shell-and-tube reboiler is located outside the column bottom, with its inlet connected to the bottom of the desorption column via a liquid outlet line, and its outlet connected to the lower part of the desorption column.

3. The system for efficiently recovering DBP solvent in maleic anhydride production as described in claim 1, characterized in that: The desorption tower bottom is connected to the desorption discharge line, and the desorption discharge line and the rich solvent feed line are connected to the feed preheater for heat exchange.

4. The system for efficiently recovering DBP solvent in maleic anhydride production as described in claim 1, characterized in that: The material discharged from the top of the desorption tower is cooled by a condenser and then subjected to gas-liquid separation. The gas phase enters the tail gas scrubbing tower, while the liquid phase is returned to the desorption tower as reflux.

5. The system for efficiently recovering DBP solvent in maleic anhydride production as described in claim 4, characterized in that: The top feed line of the extraction tower is connected to the outlet of the condenser.

6. The system for efficiently recovering DBP solvent in maleic anhydride production as described in claim 2, characterized in that: It also includes an extractant DMI storage tank and a feed line, wherein the feed line is connected to the extractant DMI circulating feed line.

7. The system for efficiently recovering DBP solvent in maleic anhydride production as described in claim 1, characterized in that: The upper part of the desorption tower is equipped with a first crude maleic anhydride production line, which, together with the second crude maleic anhydride production line of the distillation tower, is connected to the crude maleic anhydride storage tank.

8. The system for efficiently recovering DBP solvent in maleic anhydride production as described in claim 1, characterized in that: The extraction tower is also equipped with an extractant DMI storage tank connected to the extractant circulation feed line for replenishing the extractant.

9. A process method for efficiently recovering DBP solvent in maleic anhydride production using the system described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. The rich solvent from the absorption unit exchanges heat with the discharge from the bottom of the desorption tower and is heated to temperature T1, and then enters the middle of the desorption tower. S2. The solution in the desorption tower bottom is pumped to the top of the vertical shell-and-tube reboiler via a pressurized pump. It is heated to temperature T2 by steam to form a liquid film evaporation. The gas phase returns to the bottom of the desorption tower for heat and mass transfer, and the heavy components gradually accumulate in the liquid phase. At the same time, crude maleic anhydride is collected from the upper side of the desorption tower. The top discharge of the desorption tower mainly consists of acrylic acid and a small amount of maleic anhydride. It is cooled to temperature T3 for gas-liquid separation. The gas phase enters the tail gas scrubbing tower, and the liquid phase returns to the top of the desorption tower to participate in heat and mass transfer. S3. After cooling the desorption tower bottom feed to temperature T4, it is sent to the top of the extraction tower as the dispersed phase, and it is in countercurrent contact with the circulating extractant DMI entering from the bottom of the tower for mass transfer. The extractant containing maleic anhydride is obtained at the top of the tower, and the DBP solvent is separated at the bottom of the tower. S4. The maleic anhydride-containing extractant at the top of the extraction column is sent to the distillation column for separation. Crude maleic anhydride product is obtained at the top of the column. A portion of the extractant at the bottom of the column is cooled to temperature T5 and then recycled back to the extraction column. The remaining portion is vaporized and returned to the distillation column to participate in distillation. The extractant DMI is replenished periodically to maintain system balance.

10. The process method for efficiently recovering DBP solvent in maleic anhydride production as described in claim 9, characterized in that, The T1 is 160~170℃, and / or the T2 is 190~200℃, and / or the T3 is 92~98℃, and / or the T4 is 70~90℃, and / or the T5 is 70~90℃.

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