An energy-saving coupled system for acetonitrile-water azeotropic distillation and a coupled reboiler

Abstract

The application discloses an energy-saving coupling system for acetonitrile-water azeotropic distillation and a coupling reboiler. The system comprises a high-pressure rectifying tower and a low-pressure rectifying tower stacked in an up-down mode, a coupling reboiler, an auxiliary reboiler and a steam re-compressor. The condensation heat at the top of the high-pressure rectifying tower is used to drive the reboiling of the low-pressure rectifying tower in the coupling reboiler; the steam at the top of the low-pressure rectifying tower is pressurized and heated by the steam re-compressor, and the condensation heat thereof is used to drive the reboiling of the high-pressure rectifying tower in the auxiliary reboiler, thus forming a double-closed-circuit energy cycle. The application further discloses a coupling reboiler which adopts a structure of central feeding, bidirectional flow separation and end-top gas collection, and can efficiently realize heat coupling and non-condensable gas separation. The application reduces the energy consumption of the distillation process, improves the separation efficiency of the rich acetonitrile stream, and has compact structure and reliable operation.

Description

Technical Field

[0001] This invention relates to the field of separation technology, specifically to an energy-saving coupled system for the distillation separation of acetonitrile-water azeotropic mixtures, and a coupled reboiler used in the system. Background Technology

[0002] Acetonitrile is an important chemical intermediate. In many chemical production processes, such as acrylonitrile production and the synthesis of certain fine chemicals, crude acetonitrile containing water is produced. The composition of crude acetonitrile varies greatly depending on the source of the raw materials.

[0003] For dilute acetonitrile feedstock containing a large amount of water, pressure swing distillation is commonly used in industry for separation. The classic process typically involves first separating the water in a low-pressure column, then transferring the azeotrope from the top of the column to a high-pressure column to separate the acetonitrile. While this method is technically mature, it suffers from significant energy consumption and a long process flow. Both the high-pressure and low-pressure distillation columns require independent reboilers and condensers. The reboiler consumes a large amount of fresh steam as a heat source, while the condenser discharges the latent heat of condensation of the top steam into the environment via cooling water, resulting in substantial energy waste and thermal pollution.

[0004] However, in specific industrial scenarios, when recovering solvents from the extract phase of organic reactions or refining pre-purified products, the raw materials are often acetonitrile-rich streams (acetonitrile content >85 wt%) with acetonitrile content exceeding the azeotropic point. For such special raw materials, using traditional pressure swing distillation processes leads to inefficient material circulation paths and reduced process efficiency. Furthermore, conventional single-tower distillation is insufficient to effectively remove residual azeotropic water.

[0005] Therefore, developing a separation device and system specifically designed for acetonitrile-rich raw materials, which can significantly reduce energy consumption, has a compact structure, and operates reliably, is of great practical significance for improving the processing efficiency of such materials, reducing production costs, and achieving energy conservation and emission reduction. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an energy-saving coupled system for acetonitrile-water azeotropic distillation. This system significantly reduces dependence on external steam and cooling water and improves processing efficiency through energy cascade utilization and internal circulation. This invention also provides a coupled reboiler to realize the low-pressure reboiling heat exchange function in the above system.

[0007] To achieve the above objectives, the energy-saving coupling system for acetonitrile-water azeotropic distillation of the present invention includes: High-pressure distillation column and low-pressure distillation column mounted thereon; The coupled reboiler has its shell side connected to the top of the high-pressure distillation column and its tube side connected to the bottom of the low-pressure distillation column. It is used to condense the top vapor of the high-pressure distillation column and use its latent heat of condensation to reboil the bottom material of the low-pressure distillation column. The latent heat of condensation of the high-pressure distillation column is used as the reboiling heat source of the low-pressure distillation column, thus forming the first layer of energy coupling. The vapor recompressor has its inlet connected to the top of the low-pressure distillation column; The auxiliary reboiler has its tube side connected to the outlet of the steam recompressor and its shell side connected to the bottom of the high-pressure distillation column. It is used to use the steam that has been pressurized and heated by the steam recompressor as the reboiling heat source for the high-pressure distillation column to heat the bottom material of the high-pressure distillation column, thus forming a second energy coupling.

[0008] Coupled reboilers are used to achieve efficient heat transfer and non-condensable gas separation. Coupled reboilers include: The shell has a steam inlet in the middle, which is connected to the top of the high-pressure distillation column; Liquid outlets are located at the bottom of both ends of the shell, and the liquid outlets are connected to the low-pressure distillation column through high-pressure azeotropic liquid pipes; Non-condensable gas outlets are provided at the top of both ends of the shell; The heat exchange tube bundle installed inside the shell has a reboiler circulating liquid inlet and a reboiler circulating liquid outlet located at the same end of the shell. The reboiler circulating liquid inlet and the reboiler circulating liquid outlet are respectively connected to the bottom of the low-pressure distillation column through low-pressure reboiler circulating pipe I and low-pressure reboiler circulating pipe II.

[0009] As a preferred embodiment, the shell is dumbbell-shaped, with the diameter at both ends being larger than the diameter at the middle. The upper part of both ends of the shell forms a gas collecting chamber for collecting non-condensable gases, and the non-condensable gas outlet is located at the top of the gas collecting chamber. The lower part of both ends of the shell forms a liquid collecting chamber for collecting condensate, and the liquid outlet is located at the bottom of the liquid collecting chamber.

[0010] To handle the non-condensable gases separated from the coupled reboiler, the system preferably also includes an auxiliary condenser for condensing and recovering valuable acetonitrile vapors entrained in the tail gas, and for discharging the final non-condensable gases from the system. The inlet of the auxiliary condenser is connected to the two non-condensable gas outlets of the coupled reboiler via a non-condensable gas pipe; the condensate outlet of the auxiliary condenser is connected to the high-pressure azeotropic liquid pipe via a condensate pipe, and the recovered condensate can be returned to the system via the condensate pipe; the gas outlet of the auxiliary condenser is connected to a gas discharge pipe.

[0011] The tube-side outlet of the auxiliary reboiler is connected to the feed pipe of the mixture leading to the high-pressure distillation column via a low-pressure azeotropic liquid pipe. This allows the low-pressure azeotrope condensed in the auxiliary reboiler to be returned to the high-pressure distillation column as a circulating stream, preheating the mixture entering the high-pressure distillation column. This not only completes the material circulation but also utilizes the sensible heat of the circulating liquid to preheat the fresh feed, further improving energy utilization efficiency.

[0012] The present invention also provides a coupled reboiler, comprising: a shell, a steam inlet in the middle of the shell, liquid outlets at the bottom of both ends, and non-condensable gas outlets at the top of both ends; The heat exchange tube bundle is installed inside the shell and has a reboiler circulating liquid inlet and a reboiler circulating liquid outlet located at the same end of the shell. It also includes several baffles installed inside the shell and on the heat exchange tube bundle, which force the steam entering from the central steam inlet to form a Z-shaped passage and flow bidirectionally to both ends of the shell, thereby enhancing turbulence.

[0013] Preferably, the shell is dumbbell-shaped, with the diameters at both ends being larger than the diameter at the middle. The upper part of both ends of the shell forms a gas collecting chamber, and the lower part forms a liquid collecting chamber. The non-condensable gas outlet is located at the top of the gas collecting chamber, and the liquid outlet is located at the bottom of the liquid collecting chamber.

[0014] Inclined guide vanes are also provided at both ends of the shell, downstream of the baffles. The inclined guide vanes are tilted upwards to guide the airflow into the gas collection chamber, thereby achieving active capture of non-condensable gases.

[0015] To ensure smooth discharge of condensate, the bottom of the baffle and the inclined guide plate are provided with notches for condensate to pass through.

[0016] As a preferred option, the heat exchange tube bundle is a U-shaped heat exchange tube bundle.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. System Energy-Saving Coupling: The coupled reboiler serves as both the condenser for the high-pressure distillation column and the reboiler for the low-pressure distillation column. It enables the high-pressure distillation column's condensation heat to drive the reboiling of the low-pressure distillation column (boiling occurs at a lower temperature under low pressure), converting the condensation heat that must be discharged from the high-pressure distillation column into the reboiling heat required by the low-pressure distillation column. Furthermore, it recovers the condensation heat from the top of the low-pressure distillation column, which would otherwise be discarded, through a heat cycle consisting of a steam recompressor and an auxiliary reboiler, driving the reboiling of the high-pressure distillation column. This forms a dual energy closed-loop cycle, minimizing the entire separation system's demand for external fresh steam and cooling water, saving significant amounts of external steam and cooling water consumption. The system primarily consumes the electricity of the steam recompressor, thus reducing operating costs. Moreover, it can simultaneously separate acetonitrile and water, improving separation efficiency.

[0018] 2. Reboiler Functional Coupling: Reboiling-condensation coupling simultaneously completes the reboiling process (tube side) of the low-pressure distillation column and the condensation process (shell side) of the high-pressure distillation column within the same unit, achieving direct and efficient energy transfer. The coupled reboiler features central steam feed that impacts the horizontal heat exchange tube bundle, dispersing the steam and improving efficiency. Liquid-non-condensable gas separation coupling, with bidirectional flow splitting and top-end gas collection, achieves active and efficient capture and separation of non-condensable gases, fundamentally avoiding the heat transfer dead zone in traditional condensers, ensuring extremely high separation efficiency and long-term stable system operation. Attached Figure Description

[0019] Figure 1 This is one of the overall structural schematic diagrams of the present invention; Figure 2 This is the second schematic diagram of the overall structure of the present invention (section view of the distillation column); Figure 3 This is a schematic diagram of the structural principle of the present invention; Figure 4 This is one of the structural schematic diagrams of a coupled reboiler; Figure 5 This is the second schematic diagram of a coupled reboiler. Figure 6 This is a cross-sectional view of a coupled reboiler; Figure 7 This is a schematic diagram of a coupled reboiler; Figure 8 This is a schematic diagram of the baffle plate structure; Figure 9 This is a schematic diagram of the inclined guide vane.

[0020] In the diagram: 1. High-pressure distillation column; 2. Low-pressure distillation column; 3. Coupled reboiler; 4. Auxiliary reboiler; 5. Auxiliary condenser; 6. Steam recompressor; 7. Mixed material feed pipe; 8. High-pressure reboiler circulation pipe I; 9. Reboiler circulation pipe II; 10. Acetonitrile discharge pipe; 11. High-pressure azeotropic steam pipe; 12. High-pressure azeotropic liquid pipe; 13. Low-pressure reboiler circulation pipe I; 14. Low-pressure reboiler circulation pipe II; 15. Non-condensable gas pipe; 16. Condensate pipe; 17. Gas discharge pipe; 18. Low-pressure azeotropic steam pipe; 19. Steam booster pipe; 20. Low-pressure azeotropic liquid pipe; 21. Pure water discharge pipe; 31. Shell; 311. Liquid collecting chamber; 312. Gas collecting chamber; 32. Reboiler circulating liquid inlet; 33. Reboiler circulating liquid outlet; 34. Steam inlet; 35. Liquid outlet; 36. Non-condensable gas outlet; 37. Heat exchanger tube bundle; 38. Baffle; 39. Inclined guide vane. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments.

[0022] The description of the present invention is merely a structural or even functional description of the embodiments, and the scope of the present invention is not limited by the embodiments described herein.

[0023] This embodiment discloses an energy-saving coupled system and coupled reboiler for acetonitrile-water azeotropic distillation. The system is used to process crude acetonitrile feedstock containing water, and through pressure swing distillation combined with thermal cycling, ultimately obtains high-purity acetonitrile and high-purity water.

[0024] like Figures 1-3 As shown, the overall system structure in this embodiment is achieved through the following technical solutions: The energy-saving coupling system of this embodiment includes concentric tower devices stacked vertically, namely a high-pressure distillation tower 1 located at the bottom and a low-pressure distillation tower 2 located at the top.

[0025] The system's feed section is a mixed material feed pipe 7, which is connected to the middle of the high-pressure distillation column 1.

[0026] The reboiling circuit of high-pressure distillation column 1 consists of high-pressure reboiling circulation pipe I8, auxiliary reboiler 4, and reboiling circulation pipe II9. The bottom liquid enters the shell side of auxiliary reboiler 4 through high-pressure reboiling circulation pipe I8, is heated, and then returns to the bottom of the column through reboiling circulation pipe II9. The high-purity acetonitrile product at the bottom of the column is led out through acetonitrile discharge pipe 10.

[0027] High-pressure distillation column 1 and low-pressure distillation column 2 are thermally coupled via a coupled reboiler 3. The top of high-pressure distillation column 1 is connected to the shell side of coupled reboiler 3 via a high-pressure azeotropic vapor pipe 11. The reboiler circuit of low-pressure distillation column 2 consists of a low-pressure reboiler circulation pipe I13, the tube side of coupled reboiler 3, and a low-pressure reboiler circulation pipe II14. The high-pressure azeotropic liquid condensed in the shell side of coupled reboiler 3 is fed into the middle of low-pressure distillation column 2 via a high-pressure azeotropic liquid pipe 12. A pure water outlet pipe 21 is provided at the bottom of low-pressure distillation column 2 or on its reboiler circulation pipe for separating water.

[0028] The system's thermal circulation loop consists of the top of the low-pressure distillation column 2, the low-pressure azeotropic vapor tube 18, the vapor recompressor 6, the vapor booster tube 19, the tube side of the auxiliary reboiler 4, and the low-pressure azeotropic liquid tube 20. The low-pressure azeotropic liquid tube 20 eventually merges with the mixed material feed tube 7 to form a closed loop.

[0029] The exhaust gas treatment circuit of the system consists of the non-condensable gas outlet 36 of the coupled reboiler 3, the non-condensable gas pipe 15, the auxiliary condenser 5, the condensate pipe 16, and the gas discharge pipe 17.

[0030] like Figures 4-9As shown, the main body of the coupled reboiler 3 of the present invention is a dumbbell-shaped shell 31, with gas collecting chambers 312 formed at the upper part of both ends and liquid collecting chambers 311 formed at the lower part. A steam inlet 34 is provided at the top of the middle part of the shell, liquid outlets 35 are provided at the bottom of both ends, and non-condensable gas outlets 36 are provided at the top of both ends. A U-shaped heat exchange tube bundle 37 is inserted into the shell, with its two ends (reboiler circulating liquid inlet 32 ​​and reboiler circulating liquid outlet 33) located on the same side of the shell. The shell is also provided with Z-shaped baffles 38 and inclined guide plates 39 at the ends. After the high-pressure azeotropic steam enters from the steam inlet 34 at the top of the middle, a portion of the hot steam directly impacts the horizontally arranged heat exchange tube bundle 37, enhancing the heat transfer in the middle. Subsequently, the steam is guided to the larger diameter cavities on both sides for diversion. Multiple baffles 38 are provided inside the shell, forcing the steam to flow through the heat exchange tube bundle 37 in a Z-shaped path, enhancing turbulence and improving heat transfer efficiency. At both ends of the shell, upward-sloping guide vanes 39 are provided to actively guide the non-condensable gas-rich airflow to the top collection chamber 312. After the non-condensable gas is fully separated from the entrained liquid droplets in the collection chamber 312, it is discharged from the non-condensable gas outlet 36 at the top. The condensed liquid flows along the semi-circular notches at the bottom of the baffle 38 and the inclined guide vanes 39 towards the bottom of the shell, eventually collecting in the liquid collection chambers 311 at both ends and discharging from the liquid outlet 35. This design integrates condensation-reboil, non-condensable gas separation, and collection functions into a compact structure.

[0031] Overall System Workflow This system is specifically designed for the efficient separation and purification of acetonitrile-rich feedstocks (acetonitrile content > 85 wt%) with acetonitrile content higher than the azeotropic point, in order to simultaneously obtain high-purity acetonitrile and high-purity water.

[0032] Feed and high-pressure separation produce pure acetonitrile: External acetonitrile-rich feed (containing some water) and circulating liquid from low-pressure azeotropic liquid pipe 20 are mixed and preheated in mixed feed pipe 7 before entering high-pressure distillation column 1. Because the acetonitrile concentration in the feed is higher than the azeotropic composition at this high pressure (4.0 barA), acetonitrile exhibits relatively low volatility under these conditions. After distillation, high-purity acetonitrile accumulates at the bottom of the column, forming a product that is discharged through acetonitrile discharge pipe 10. At the top of the column, vapor with a composition close to that of the high-pressure azeotropic liquid is separated (high-pressure azeotropic vapor pipe 11, approximately 120°C at 4.0 barA).

[0033] Driving the low-pressure distillation column: The high-temperature, high-pressure azeotropic vapor separated from the top of the high-pressure distillation column 1 (high-pressure azeotropic vapor tube 11) enters the shell side of the coupled reboiler 3. The vapor enters from the central vapor inlet 34, impacts the horizontal heat exchange tube bundle 37, is dispersed by the heat exchange tube bundle 37 to improve efficiency, and flows to both sides and condenses under the guidance of the baffle 38 and inclined guide plate 39. The latent heat of condensation released is used to heat the liquid at the bottom of the low-pressure distillation column 2 (low-pressure reboiler circulation tube I13 and low-pressure reboiler circulation tube II14) circulating in the tube side through the tube wall of the heat exchange tube bundle 37, providing all the reboiling heat for the low-pressure distillation column 2. The liquid boils in the tubes, easily forming a stable thermosiphon or forced circulation, with high flow rate and large heat transfer coefficient.

[0034] Low-pressure separation product water: The high-pressure azeotropic liquid condensed in the shell side of the coupled reboiler 3 is discharged from the liquid outlets 35 at both ends and enters the low-pressure distillation column 2 after being depressurized through the high-pressure azeotropic liquid pipe 12. Since the acetonitrile concentration of this feed is lower than the azeotropic composition at this low pressure (0.8 barA), water is a relatively non-volatile component under these conditions. After distillation, high-purity water is enriched at the bottom of the column and discharged through the pure water outlet pipe 21. At the top of the column, acetonitrile / water vapor (approximately 70°C), which is close to the low-pressure azeotropic composition, is separated and sent to the steam recompressor 6 through the low-pressure azeotropic steam pipe 18 to enter the next heat cycle.

[0035] The high-pressure distillation column is driven by a thermal cycle: the low-pressure azeotropic vapor at the top of the low-pressure distillation column 2 (low-pressure azeotropic vapor tube 18) is compressed by the vapor recompressor 6, significantly increasing its pressure and temperature (to approximately 6.0 barA and approximately 155°C). The compressed and heated vapor enters the tube side of the auxiliary reboiler 4 via the vapor booster tube 19 for exothermic condensation. This heat heats the bottom circulating liquid of the high-pressure distillation column 1 (high-pressure reboiler circulation tube I8 and reboiler circulation tube II9) through the shell side, providing all the reboiling heat for the high-pressure column. The condensed low-pressure azeotrope is then returned to the feed system of the high-pressure column via the low-pressure azeotrope liquid tube 20, forming a closed-loop cycle.

[0036] Non-condensable gas emission: During the condensation process in the coupled reboiler 3, the non-condensable gas carried in by the raw material is enriched and guided into the gas collection chamber 312 by the inclined guide plate 39, and then exited from the non-condensable gas outlet 36. This exhaust gas enters the auxiliary condenser 5 through the non-condensable gas pipe 15, where the entrained acetonitrile vapor is deeply condensed and recovered (condensate pipe 16). The final non-condensable gas is discharged from the system through the gas discharge pipe 17 and sent to the subsequent processing unit, thereby ensuring the purity and efficiency of the main cycle.

[0037] The pressure systems within the system are interconnected and dynamically balanced. The pressure of the low-pressure distillation column 2 is primarily determined by the inlet suction pressure of the vapor recompressor 6, ensuring its stability at a low level (0.8 barA). The operating pressure of the high-pressure distillation column 1 is based on the thermodynamic temperature difference requirement: its top condensing temperature must be sufficient to drive the reboiling of the low-pressure distillation column 2. The pressure maintenance of the high-pressure column is mainly achieved by adjusting the heat load of the auxiliary reboiler 4 (i.e., the compressor's exhaust state) and the non-condensable gas discharge rate of the auxiliary condenser 5. This dual-column coupled control ensures that the system achieves a closed-loop energy cycle while meeting the heat transfer temperature difference requirements.

[0038] Of course, the above description is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the embodiments of the present invention. The present invention is also not limited to the above examples, and all equivalent changes and improvements made by those skilled in the art within the scope of the present invention should fall within the patent coverage of the present invention.

Claims

1. An energy-saving coupling system for acetonitrile-water azeotropic distillation, characterized in that, include: High-pressure distillation column (1) and low-pressure distillation column (2) disposed thereon; The coupled reboiler (3) has its shell side connected to the top of the high-pressure distillation column (1) and its tube side connected to the bottom of the low-pressure distillation column (2). It is used to condense the top vapor of the high-pressure distillation column (1) and use its latent heat of condensation to reboil the bottom material of the low-pressure distillation column (2). A steam recompressor (6) has its inlet connected to the top of the low-pressure distillation column (2); The auxiliary reboiler (4) has its tube side connected to the outlet of the steam recompressor (6) and its shell side connected to the bottom of the high-pressure distillation column (1). It is used to heat the bottom material of the high-pressure distillation column (1) with the steam after being pressurized and heated by the steam recompressor (6).

2. The energy-saving coupling system for acetonitrile-water azeotropic distillation according to claim 1, characterized in that, The coupled reboiler (3) includes: The shell (31) has a steam inlet (34) in the middle, which is connected to the top of the high-pressure distillation column (1); the bottom of both ends of the shell (31) has a liquid outlet (35), which is connected to the low-pressure distillation column (2) through a high-pressure azeotropic liquid pipe (12); the top of both ends of the shell (31) has a non-condensable gas outlet (36). The heat exchange tube bundle (37) is installed in the shell (31). The heat exchange tube bundle (37) has a reboiler circulating liquid inlet (32) and a reboiler circulating liquid outlet (33) located at the same end of the shell (31). The reboiler circulating liquid inlet (32) and the reboiler circulating liquid outlet (33) are respectively connected to the bottom of the low-pressure distillation column (2) through low-pressure reboiler circulating pipe I (13) and low-pressure reboiler circulating pipe II (14).

3. The energy-saving coupling system for acetonitrile-water azeotropic distillation according to claim 2, characterized in that, The shell (31) is dumbbell-shaped, with the diameter at both ends being larger than the diameter at the middle. The upper part of both ends of the shell (31) forms a gas collecting chamber (312) for collecting non-condensable gas, and the non-condensable gas outlet (36) is located at the top of the gas collecting chamber (312). The lower part of both ends of the shell (31) forms a liquid collecting chamber (311) for collecting condensate, and the liquid outlet (35) is located at the bottom of the liquid collecting chamber (311).

4. The energy-saving coupling system for acetonitrile-water azeotropic distillation according to claim 2 or 3, characterized in that, Also includes: The auxiliary condenser (5) has its inlet connected to the two non-condensable gas outlets (36) of the coupled reboiler (3) via a non-condensable gas pipe (15); The condensate outlet of the auxiliary condenser (5) is connected to the high-pressure azeotropic liquid pipe (12) through the condensate pipe (16); the gas outlet of the auxiliary condenser (5) is connected to the gas discharge pipe (17).

5. The energy-saving coupling system for acetonitrile-water azeotropic distillation according to claim 1, characterized in that, The tube outlet of the auxiliary reboiler (4) is connected to the feed pipe (7) of the mixture to the high-pressure distillation column (1) via the low-pressure azeotropic liquid pipe (20). This is used to return the low-pressure azeotrope condensed in the auxiliary reboiler (4) to the high-pressure distillation column (1) as a circulating stream and to preheat the mixture entering the high-pressure distillation column (1).

6. A coupled reboiler, characterized in that, include: The shell (31) has a steam inlet (34) in the middle, a liquid outlet (35) at the bottom of both ends, and a non-condensable gas outlet (36) at the top of both ends. The heat exchange tube bundle (37) is disposed in the shell (31) and has a reboiler circulation liquid inlet (32) and a reboiler circulation liquid outlet (33) located at the same end of the shell (31). It also includes a number of baffles (38) disposed inside the shell (31) and located on the heat exchange tube bundle (37). The number of baffles (38) form a Z-shaped passage to guide the steam entering from the steam inlet (34) to flow to both ends of the shell (31).

7. The coupled reboiler according to claim 6, characterized in that, The shell (31) is dumbbell-shaped, with the diameter at both ends being larger than the diameter at the middle. The upper part of the shell (31) forms a gas collecting chamber (312), and the lower part forms a liquid collecting chamber (311). The non-condensable gas outlet (36) is located at the top of the gas collecting chamber (312), and the liquid outlet (35) is located at the bottom of the liquid collecting chamber (311).

8. The coupled reboiler according to claim 7, characterized in that, At both ends of the housing (31) and downstream of the baffle (38), there are also inclined guide plates (39), which are inclined upward to guide the airflow to the gas collection chamber (312).

9. The coupled reboiler according to claim 8, characterized in that, The bottom of the baffle (38) and the inclined guide plate (39) are provided with notches for condensed liquid to pass through.

10. The coupled reboiler according to claim 6, characterized in that, The heat exchange tube bundle (37) is a U-shaped heat exchange tube bundle.

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