A rectification system and rectification method for preparing N-vinylpyrrolidone

Abstract

The application discloses a rectification system and method for preparing N-vinyl pyrrolidone, which comprises a rectification tower, a flash tank, a thin film evaporator, a liquid collecting tank, a condenser, a vacuum separation tank and a reboiler, the rectification tower is connected with a feeding pipe, a discharging pipe, a circulating pipe, an exhaust pipe and a reflux pipe, a group of tower plates are arranged in the rectification tower in a staggered and stacked mode, and an overflow plate is arranged at the bottom of the inner cavity of the rectification tower. The application overcomes the defects of the prior art, the gas phase and the liquid phase are contacted more fully through the control of the material flow mode and the channel, the falling probability of the liquid phase from the sieve hole is reduced, and the application has high social use value and application prospect.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a distillation system and method for preparing N-vinylpyrrolidone. Background Technology

[0002] N-Vinylpyrrolidone is an organic compound widely used in polymers, pharmaceuticals, and cosmetics. N-Vinylpyrrolidone is abbreviated as N-VP, and α-pyrrolidone is abbreviated as 2-PY. In the production process, crude N-VP is purified by distillation in the light industry removal section. Through catalyst preparation, α-pyrrolidone is mixed with a certain proportion of 45% KOH solution to react and generate potassium pyrrolidone, i.e., K-PY. The prepared K-PY and 2-PY are then pumped into the reaction equipment to obtain crude N-vinylpyrrolidone, i.e., crude N-VP. Crude N-VP is then fed into subsequent purification processes.

[0003] In the existing production process, the liquid and gas phases are introduced into the distillation column used for light nitrate removal at the same time. Due to the initial insufficient supply of gas phase, the liquid phase falls through the holes in the sieve plate, resulting in incomplete contact between the liquid and gas phases, which makes the light nitrate removal distillation process take a long time.

[0004] Furthermore, after prolonged distillation, the pores on the sieve plates inside the distillation column will inevitably become clogged, directly affecting the path of the gas phase through the sieve holes and the contact between the liquid and gas phases. As the gas phase flow becomes obstructed, unstable pressure will also occur inside the column.

[0005] To this end, the inventors designed and developed a distillation system and method for the preparation of N-vinylpyrrolidone. By adjusting the liquid phase flow mode, the gas phase and liquid phase are made to contact more fully, thereby improving the efficiency of distillation. Summary of the Invention

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A distillation system for preparing N-vinylpyrrolidone includes a distillation column, a flash tank, a thin-film evaporator, a collection tank, a condenser, a vacuum separator, and a reboiler. The distillation column is connected to a feed pipe, a discharge pipe, a circulation pipe, an exhaust pipe, and a reflux pipe. The distillation column has trays stacked in a staggered manner, and an overflow plate is provided at the bottom of the inner cavity of the distillation column.

[0008] The flash tank, thin-film evaporator, and liquid collection tank are connected in sequence. The top of the thin-film evaporator is connected to a condenser, and the bottom of the condenser is connected to a vacuum separator. The top of the vacuum separator is connected to the feed pipe, and the outlet pipe and circulation pipe are connected to a reboiler.

[0009] Preferably, the tray assembly includes a perforated plate, with a liquid collection frame at one end and an overflow weir at the other end, and a downcomer plate on the perforated plate.

[0010] Preferably, a limiting groove is provided in the liquid collection frame, a sealing plate is provided in the limiting groove, a connecting column is provided on the sealing plate, and a first limiting hole is provided in the limiting groove to provide guidance for the sealing plate.

[0011] Preferably, the perforated plate is provided with a plate groove, and a liquid-blocking mechanism is fitted inside the plate groove; the perforated plate is also provided with a second limiting hole.

[0012] The liquid-blocking mechanism includes a liquid-blocking plate fitted with the plate groove, a balance plate fitted with the second limiting hole on the liquid-blocking plate, and a misalignment groove that slides and matches the connecting column on the balance plate.

[0013] Preferably, the bottom end of the liquid collection frame is provided with a drive shaft that is threadedly fitted with the sealing plate, the drive shaft has opposing threaded grooves, and the end of the drive shaft is connected to a drive motor installed on the outer wall of the distillation column.

[0014] Preferably, the liquid collection frame has a liquid delivery channel and the overflow weir has a leakage hole.

[0015] Preferably, the bottom surface of the sieve plate is provided with a cleaning mechanism and a sleeve rod. The cleaning mechanism includes a reciprocating screw, and the end of the reciprocating screw is provided with an impact impeller that is rotatably connected to the liquid dropper. A transverse block is mounted on the reciprocating screw, and a transverse plate is provided on the transverse block. Both ends of the transverse plate are provided with adapter plates.

[0016] Preferably, both the horizontal plate and the adapter plate are provided with brushes, and the horizontal plate is provided with a buckle that slides and fits with the sleeve rod.

[0017] Preferably, the end of the horizontal plate is provided with a displacement groove for fitting an adapter plate, and a slag removal port is provided on the displacement groove.

[0018] Preferably, the bottom surface of the sieve plate is provided with a guide plate, the guide plate has a guide groove, and the adapter plate is provided with a guide wheel that is fitted with the guide groove.

[0019] A distillation method for preparing N-vinylpyrrolidone includes the following steps:

[0020] S1: The crude N-VP is heated and vaporized by an externally connected steam heater and then introduced into the flash tank. At the same time, the high-boiling-point substances generated during the 2-PY production process are also introduced into the flash tank, so that the material is separated into gas and liquid phases under vacuum in the flash tank.

[0021] S2: The gas phase obtained after being processed by the flash tank is transported to the distillation column, and the liquid phase is pumped to the thin film evaporator. The thin film evaporator is kept under vacuum and electrically heated to 190-230℃. The liquid phase will be separated into light and heavy components again. The light components are transported to the distillation column in sequence through the condenser and the vacuum separator, and the heavy components are collected in the collection tank through pipelines.

[0022] S3: After the light components in the distillation column are processed by internal distillation to remove light components, a small amount of N-VP containing light components will be condensed and precipitated at the top of the distillation column, while the heavy components at the bottom of the distillation column will be pumped into the externally connected product column for collection through the discharge pipe.

[0023] S4: The light component condensed and precipitated at the top of the distillation column is crude N-VP, which needs to be transported to an externally connected batch distillation column for further distillation. During the distillation process, the light component will condense and precipitate, and the remaining part will be collected as pure N-VP.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. By setting up the hole cleaning mechanism, the material can fall through the hole and impact impeller in cooperation. During the fall, the material will impact the impeller, which will enable the horizontal plate and the adapter plate to drive the brush to clean the holes on the bottom of the screen plate. This effectively avoids the phenomenon of gas phase not being able to flow due to the blockage of the holes on the bottom of the screen plate.

[0026] 2. By setting up the horizontal plate and the adapter plate, and utilizing the cooperation between the guide groove and the guide wheel, the relative position between the horizontal plate and the adapter plate can be adjusted according to the position and shape of the holes on the bottom of the screen plate, thus providing conditions for complete cleaning of the holes on the bottom of the screen plate.

[0027] 3. By opening the liquid delivery channel, the material passing through the liquid collection frame can flow into the liquid collection frame of the next layer through the liquid delivery channel until each liquid collection frame is filled with material. Then, the material is allowed to pass through the perforated plate and overflow from the overflow weir, thereby improving the efficiency of the gas phase passing through the perforated plate.

[0028] 4. By setting up the liquid-blocking mechanism and the sealing plate, and by utilizing the cooperation between the sealing plate and the drive shaft, when the liquid delivery channel is opened, the liquid-blocking plate can raise the height of the material flow between the liquid collection frame and the sieve plate, allowing the material to flow smoothly from inside the liquid delivery channel and giving the gas phase enough time to pass through the holes on the sieve plate.

[0029] 5. By using flash tanks, distillation columns, and thin-film evaporators, the efficiency of product preparation and the purity of the products can be improved through evaporation and distillation, resulting in a synergistic effect.

[0030] In summary, this invention overcomes the shortcomings of the prior art by controlling the material flow method and channel, allowing the gas phase and liquid phase to come into more sufficient contact, reducing the probability of the liquid phase falling from the sieve holes, and has high social use value and application prospects. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a process flow diagram of the present invention;

[0033] Figure 2 This is a schematic diagram of the distillation column in this invention;

[0034] Figure 3 This is a schematic diagram of the structural assembly of the tray assembly and the overflow plate in this invention;

[0035] Figure 4 This is a schematic diagram of the tower plate assembly in this invention;

[0036] Figure 5 This is an exploded view of the structure of the tower plate assembly and the hole cleaning mechanism in this invention;

[0037] Figure 6 This is a schematic diagram of the bottom structure of the tray assembly in this invention;

[0038] Figure 7 This is a schematic diagram showing the structural assembly of the liquid-blocking mechanism and the sealing plate in this invention;

[0039] Figure 8 This is a schematic diagram of the liquid-blocking mechanism in this invention;

[0040] Figure 9 This is a schematic diagram of the sealing plate in this invention;

[0041] Figure 10 This is a schematic cross-sectional view of the liquid collection frame in this invention;

[0042] Figure 11 This is a schematic diagram of the hole-cleaning mechanism in this invention;

[0043] Figure 12 This is a schematic diagram of the structural splicing of the horizontal plate and the adapter plate in this invention;

[0044] Figure 13 This is a partial structural diagram of the horizontal plate in this invention;

[0045] Figure 14 This is a top view of the tower plate assembly in this invention.

[0046] In the diagram: 100, Flash evaporator; 200, Thin-film evaporator; 300, Collection tank; 400, Condenser; 500, Vacuum separator; 600, Reboiler; 1, Distillation column; 101, Feed pipe; 102, Discharge pipe; 103, Circulation pipe; 104, Exhaust pipe; 105, Reflux pipe; 2, Tray assembly; 21, Limiting groove; 211, Drive shaft; 2111, Opposing wire groove; 22, First limiting hole; 23, Second limiting hole; 201, Perforated sieve plate; 2011, Plate groove; 202, Collection frame; 2021, Liquid delivery channel; 2 03. Overflow weir; 2031. Leakage hole; 204. Downcomer; 3. Liquid blocking mechanism; 301. Liquid blocking plate; 302. Balance plate; 3021. Misalignment groove; 4. Sealing plate; 41. Connecting column; 5. Hole cleaning mechanism; 501. Reciprocating screw; 502. Lateral block; 503. Horizontal plate; 504. Adaptor plate; 5041. Guide wheel; 505. Impact impeller; 506. Socket; 507. Brush; 51. Displacement groove; 511. Slag removal port; 6. Sleeve rod; 7. Guide plate; 71. Guide groove; 8. Drive motor; 9. Overflow plate. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1

[0049] Reference Figure 1-14A distillation system for preparing N-vinylpyrrolidone includes a distillation column 1, a flash tank 100, a thin-film evaporator 200, a collection tank 300, a condenser 400, a vacuum separator 500, and a reboiler 600. The distillation column 1 is connected to a feed pipe 101, a discharge pipe 102, a circulation pipe 103, an exhaust pipe 104, and a reflux pipe 105. The distillation column 1 has a tray assembly 2 stacked in a staggered manner, and an overflow plate 9 is provided at the bottom of the inner cavity of the distillation column 1.

[0050] Flash tank 100, thin film evaporator 200 and liquid collection tank 300 are connected in sequence. The top of thin film evaporator 200 is connected to condenser 400, the bottom of condenser 400 is connected to vacuum separator 500, the top of vacuum separator 500 is connected to feed pipe 101, and reboiler 600 is circulated on discharge pipe 102 and circulation pipe 103.

[0051] Specifically, the tray assembly 2 includes a perforated plate 201, a liquid collection frame 202 at one end of the perforated plate 201, an overflow weir 203 at the other end of the perforated plate 201, and a downcomer plate 204 on the perforated plate 201.

[0052] Specifically, a limiting groove 21 is provided in the liquid collection frame 202, and a sealing plate 4 is provided in the limiting groove 21. A connecting post 41 is provided on the sealing plate 4. A first limiting hole 22 is provided in the limiting groove 21 to guide the sealing plate 4. The sealing plate 4 can move left and right inside the limiting groove 21. The opening of the first limiting hole 22 allows the sealing plate 4 to be connected to the drive shaft 211. The rotation of the drive shaft 211 cooperates with the threaded fitting between the opposing thread groove 2111 and the sealing plate 4, allowing the sealing plate 4 to move left and right inside the limiting groove 21.

[0053] Specifically, a liquid delivery channel 2021 is provided inside the liquid collection frame 202, and a leakage hole 2031 is provided on the overflow weir 203. The liquid delivery channel 2021 prevents the material flowing into the liquid collection frame 202 from flowing into the next layer of liquid collection frame 202 through the sieve plate 201, the overflow weir 203 and the downcomer plate 204. Instead, the material flows directly into the next layer of liquid collection frame 202 through the liquid collection frame 202 and the liquid delivery channel 2021, so that the liquid collection frame 202 of each layer is evenly filled with material. The overflow plate 9 is also filled with material. When the material overflows from the overflow plate 9 to the bottom of the inner cavity of the distillation column 1, the liquid collection frame 202 of each layer is filled with material, and each layer is filled with the same amount of material.

[0054] Specifically, the bottom surface of the perforated plate 201 is provided with a cleaning mechanism 5 and a sleeve 6. The cleaning mechanism 5 includes a reciprocating screw 501, and an impact impeller 505 rotatably connected to the liquid descending plate 204 is provided at the end of the reciprocating screw 501. A transverse block 502 is mounted on the reciprocating screw 501, and a transverse plate 503 is provided on the transverse block 502. Adaptor plates 504 are provided at both ends of the transverse plate 503. The impact impeller 505 is installed directly below the leakage hole 2031, so that the material overflows. When the weir 203 overflows, the material falls through the leakage hole 2031, causing the material to impact the impact impeller 505, which rotates the impact impeller 505. This, in turn, drives the reciprocating screw 501 to rotate, allowing the transverse block 502 to drive the transverse plate 503 to reciprocate laterally. This allows the brush 507 to act on the bottom surface of the perforated plate 201, cleaning the holes on the bottom of the perforated plate 201 and preventing the gas phase from being obstructed due to hole blockage.

[0055] Specifically, both the horizontal plate 503 and the adapter plate 504 are equipped with brushes 507. The horizontal plate 503 is equipped with a buckle 506 that slides and fits with the sleeve rod 6. The sleeve rod 6 is designed to work with the buckle 506 to keep the horizontal plate 503 stable during reciprocating horizontal movement, so that the brushes 507 can act on the bottom holes of the screen plate 201.

[0056] Specifically, the end of the horizontal plate 503 is provided with a displacement groove 51 for fitting the adapter plate 504. The displacement groove 51 is provided with a slag removal port 511. The displacement groove 51 allows the adapter plate 504 to move within it, so that the relative position of the adapter plate 504 and the horizontal plate 503 can be adjusted. The slag removal port 511 allows the material or the cleaned-off impurities in the displacement groove 51 to be squeezed out.

[0057] Specifically, the bottom surface of the perforated plate 201 is provided with a guide plate 7, and a guide groove 71 is opened in the guide plate 7. The adapter plate 504 is provided with a guide wheel 5041 that is fitted with the guide groove 71. Through the setting of the guide plate 7, the guide wheel 5041 can move inside the guide groove 71 to adjust the relative position between the adapter plate 504 and the horizontal plate 503, so that the cooperation between the adapter plate 504 and the horizontal plate 503 can adapt and adjust the holes on the bottom surface of the perforated plate 201.

[0058] Example 2

[0059] Reference Figure 1-14 The difference between this embodiment and embodiment 1 is that a plate groove 2011 is provided on the perforated plate 201, a liquid blocking mechanism 3 is installed in the plate groove 2011, and a second limiting hole 23 is also provided on the perforated plate 201.

[0060] The liquid-blocking mechanism 3 includes a liquid-blocking plate 301 fitted with the plate groove 2011. The liquid-blocking plate 301 is provided with a balance plate 302 fitted with the second limiting hole 23. The balance plate 302 has a misalignment groove 3021 that slides and matches the connecting column 41. The opening of the plate groove 2011 allows the liquid-blocking plate 301 to be embedded within it, enabling vertical height adjustment of the liquid-blocking plate 301 to adjust the communication height between the liquid collection frame 202 and the sieve plate 201. The lateral movement of the sealing plate 4 adapts to the connection column 41 and the misalignment groove 3021. The interaction between the two adjusts the height of the baffle plate 301 within the plate groove 2011. When the sealing plate 4 blocks the liquid delivery channel 2021, the baffle plate 301 lowers, allowing the material inside the collection frame 202 to flow through the sieve plate 201 instead of through the liquid delivery channel 2021. When the sealing plate 4 opens the liquid delivery channel 2021, the baffle plate 301 rises, allowing the material inside the collection frame 202 to flow into the next layer of collection frame 202 through the liquid delivery channel 2021.

[0061] Specifically, the bottom of the liquid collection frame 202 is provided with a drive shaft 211 that is threadedly fitted with the sealing plate 4. The drive shaft 211 has opposing threaded grooves 2111. The end of the drive shaft 211 is connected to a drive motor 8 installed on the outer wall of the distillation column 1. Through the setting of the drive shaft 211, the drive motor 8 drives the drive shaft 211 to rotate. Through the connection between the opposing threaded grooves 2111 and the sealing plate 4, the sealing plate 4 can move laterally in the left and right directions inside the limiting groove 21 to complete the closing and opening of the liquid delivery channel 2021.

[0062] Other undescribed structures are described in Example 1.

[0063] Example 3

[0064] Reference Figure 1 A distillation method for preparing N-vinylpyrrolidone includes the following steps:

[0065] S1: The crude N-VP product is heated and vaporized by an externally connected steam heater and then introduced into the flash tank 100. At the same time, the high-boiling substances generated during the 2-PY production process are also introduced into the flash tank 100, so that the material is separated into gas phase and liquid phase under vacuum in the flash tank 100.

[0066] S2: The gas phase obtained after processing by the flash tank 100 is transported to the distillation column 1, and the liquid phase is pumped to the thin film evaporator 200. The thin film evaporator 200 is kept under vacuum and electrically heated to 190-230℃. The liquid phase will be separated into light components and heavy components again. The light components are transported to the distillation column 1 in sequence through the condenser 400 and the vacuum separator 500, and the heavy components are collected in the collection tank 300 through the pipeline.

[0067] S3: After the light components in the distillation column 1 are processed by internal distillation to remove light components, a small amount of N-VP containing light components will be condensed and precipitated at the top of the distillation column 1, while the heavy components at the bottom of the distillation column 1 will be pumped into the externally connected product column for collection via the discharge pipe 102.

[0068] S4: The light component condensed and precipitated at the top of distillation column 1 is crude N-VP, which needs to be transported to an externally connected batch distillation column for further distillation. During the distillation process, the light component will condense and precipitate, and the remaining part will be collected as pure N-VP.

[0069] Working principle: In this invention, the feed pipe 101 is first connected to the flash tank 100 and the vacuum separator 500 respectively, so that the material can enter the interior of the distillation column 1 through the feed pipe 101. Then, the discharge pipe 102 is connected to the external conveying pipeline, and the discharge pipe 102 is connected to the circulation pipe 103 through the reboiler 600 for circulating distillation of the material. The exhaust pipe 104 and the reflux pipe 105 are connected to the external condenser, and the external condenser is also connected to the subsequent batch distillation column through the pipeline.

[0070] Before starting the equipment, the drive motor 8 installed on the outer wall of the distillation column 1 is turned on simultaneously, so that the output shaft of the drive motor 8 drives the drive shaft 211 to rotate. Through the cooperation between the opposing wire groove 2111 and the sealing plate 4, the sealing plate 4 opens the channel of the liquid delivery channel 2021. At the same time, the height of the baffle plate 301 is increased, which increases the flow space of the liquid collection frame 202 for dry materials. The material entering the interior of the distillation column 1 through the feed pipe 101 will flow into the liquid collection frame 202, and then flow through the liquid delivery channel 2021 to the next layer of liquid collection frame 202, until the liquid collection frame 202 and the overflow plate 9 are full of material, and the material will enter the bottom of the inner cavity of the distillation column 1.

[0071] Steam is introduced into the distillation column 1 through the circulation pipe 103, allowing the steam to pass through the holes on the surface of the sieve plate 201, thereby controlling the steam flow pressure.

[0072] Then, the drive motor 8 is turned on in reverse synchronously, so that the sealing plate 4 blocks the liquid delivery channel 2021, so that the material in the liquid collection frame 202 will no longer pass through the liquid delivery channel 2021. As the liquid delivery channel 2021 is closed, the height of the baffle plate 301 is reduced, and the material in each layer of liquid collection frame 202 will enter the sieve plate 201 synchronously, so that the material can be in stable contact with the steam.

[0073] When the material flows through the overflow weir 203 into the lower liquid collection frame 202, some material will fall through the leakage hole 2031. Using gravitational potential energy, the impact impeller 505 is rotated, which makes the reciprocating screw 501 rotate synchronously. This allows the transverse block 502 to drive the transverse plate 503 and the adapter plate 504 to move reciprocally, so that the brush 507 can clean the bottom surface of the screen plate 201 and prevent the holes on the screen plate 201 from being blocked and affecting the passage of steam. When the adapter plate 504 moves, the relative position between the adapter plate 504 and the transverse plate 503 is adjusted according to the shape of the bottom surface of the screen plate 201 through the cooperation between the guide wheel 5041 and the guide groove 71.

[0074] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0075] In this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," "link," and "fix" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0076] The control method of this invention is automatic control through a controller. The control circuit of the controller can be implemented by simple programming by those skilled in the art. The power supply is also common knowledge in the art. Furthermore, since this invention is mainly used to protect mechanical devices, the control method and circuit connection will not be explained in detail here.

[0077] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A distillation system for preparing N-vinylpyrrolidone, comprising a distillation column (1), a flash tank (100), a thin-film evaporator (200), a collection tank (300), a condenser (400), a vacuum separator (500), and a reboiler (600), characterized in that: The distillation column (1) is connected to a feed pipe (101), a discharge pipe (102), a circulation pipe (103), an exhaust pipe (104), and a reflux pipe (105). The distillation column (1) is equipped with a tray group (2) stacked in a staggered manner, and an overflow plate (9) is provided at the bottom of the inner cavity of the distillation column (1). The flash tank (100), thin film evaporator (200) and liquid collection tank (300) are connected in sequence. The top of the thin film evaporator (200) is connected to a condenser (400), and the bottom of the condenser (400) is connected to a vacuum separator (500). The top of the vacuum separator (500) is connected to the feed pipe (101), and the outlet pipe (102) and the circulation pipe (103) are connected to a reboiler (600). The tray assembly (2) includes a perforated plate (201), a liquid collection frame (202) is provided at one end of the perforated plate (201), an overflow weir (203) is provided at the other end of the perforated plate (201), and a downcomer (204) is provided on the perforated plate (201). The liquid collection frame (202) has a limiting groove (21) inside, a sealing plate (4) is provided inside the limiting groove (21), a connecting column (41) is provided on the sealing plate (4), and a first limiting hole (22) is provided inside the limiting groove (21) to provide guidance for the sealing plate (4). The liquid collection frame (202) is provided with a liquid delivery channel (2021), and the overflow weir (203) is provided with a leakage hole (2031). A plate groove (2011) is provided on the perforated plate (201), and a liquid-blocking mechanism (3) is installed inside the plate groove (2011). A second limiting hole (23) is also provided on the perforated plate (201). The liquid blocking mechanism (3) includes a liquid blocking plate (301) fitted with the plate groove (2011), and a balance plate (302) fitted with the second limiting hole (23) is provided on the liquid blocking plate (301). The balance plate (302) is provided with a misalignment groove (3021) that slides and matches the connecting column (41). When the sealing plate (4) blocks the liquid delivery channel (2021), the baffle plate (301) descends; when the sealing plate (4) opens the liquid delivery channel (2021), the height of the baffle plate (301) rises.

2. The distillation system for preparing N-vinylpyrrolidone according to claim 1, characterized in that: The bottom surface of the sieve plate (201) is provided with a hole cleaning mechanism (5) and a sleeve (6). The hole cleaning mechanism (5) includes a reciprocating screw (501). The end of the reciprocating screw (501) is provided with an impact impeller (505) that is rotatably connected to the liquid drop plate (204). A transverse block (502) is fitted on the reciprocating screw (501). A transverse plate (503) is provided on the transverse block (502). Both ends of the transverse plate (503) are provided with adapter plates (504).

3. The distillation system for preparing N-vinylpyrrolidone according to claim 2, characterized in that: Both the horizontal plate (503) and the adapter plate (504) are provided with brushes (507), and the horizontal plate (503) is provided with a buckle (506) that slides and fits with the sleeve rod (6).

4. The distillation system for preparing N-vinylpyrrolidone according to claim 3, characterized in that: The end of the horizontal plate (503) is provided with a displacement groove (51) for fitting the adapter plate (504), and a slag removal port (511) is provided on the displacement groove (51).

5. The distillation system for preparing N-vinylpyrrolidone according to claim 4, characterized in that: The bottom surface of the sieve plate (201) is provided with a guide plate (7), and a guide groove (71) is provided in the guide plate (7). The adapter plate (504) is provided with a guide wheel (5041) that is guided and fitted with the guide groove (71).

6. A distillation method for preparing N-vinylpyrrolidone, employing a distillation system for preparing N-vinylpyrrolidone as described in any one of claims 1-5, characterized in that, Includes the following steps: S1: Crude N-vinylpyrrolidone (N-VP) is heated and vaporized by an externally connected steam heater and then introduced into a flash tank (100). At the same time, high-boiling substances generated during the production of α-pyrrolidone (2-PY) are introduced into the flash tank (100), so that the material is separated into gas and liquid phases under vacuum in the flash tank (100). S2: The gas phase obtained after being processed by the flash tank (100) is transported to the distillation column (1), and the liquid phase is pumped to the thin film evaporator (200). The thin film evaporator (200) is kept under vacuum, and the liquid phase will be separated into light components and heavy components again. The light components are transported to the distillation column (1) in sequence through the condenser (400) and the vacuum separator (500), and the heavy components are collected in the collection tank (300) through the pipeline. S3: After the light components in the distillation column (1) are distilled and de-lighted, a small amount of N-VP containing light components will be condensed and precipitated at the top of the distillation column (1), while the heavy components at the bottom of the distillation column (1) will be pumped into the externally connected product column for collection via the discharge pipe (102). S4: The light component condensed and precipitated at the top of the distillation column (1) is crude N-VP, which needs to be transported to an externally connected batch distillation column for further distillation. During the distillation process, the light component will condense and precipitate, and the remaining part will be collected as pure N-VP.

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