Dichloromethane recovery system in benzodioxole production process

Abstract

The utility model provides a dichloromethane recovery system in a benzodioxole production process. The dichloromethane recovery system comprises a distillation kettle, a condenser and a circulation structure. A gas-phase outlet of the distillation kettle is communicated with a gas-phase inlet of the condenser through a steam pipeline, a liquid-phase outlet of the condenser is connected with a dichloromethane collecting tank, a top feed port of the distillation kettle is communicated with a feed pipe, the bottom of the distillation kettle is connected with a discharge pipe, and a jacket is arranged on the outer side of the distillation kettle. The circulating structure comprises a circulating pump and a circulating pipeline, one end of the circulating pipeline is communicated with the position, close to the distillation still, of the discharging pipe, the other end of the circulating pipeline is communicated with the position, close to the distillation still, of the feeding pipe, the circulating pump is arranged on the discharging pipe and located between the circulating pipeline and the bottom outlet of the distillation still, and a material returning valve is arranged on the circulating pipeline. One end, extending into the distillation kettle, of the feeding pipe is connected with a liquid distributor, and a stirring structure is arranged in the distillation kettle. According to the invention, the efficient recovery of dichloromethane in the production of benzodioxole is realized, and the loss of dichloromethane is reduced.

Description

Technical Field

[0001] This application relates to the technical field of purification of organic compounds, and particularly to a dichloromethane recovery system in the production process of piperylene. Background Art

[0002] Piperylene, chemically named 1,2-methylenedioxybenzene, piperylene and its derivatives have attracted extensive attention due to their special biochemical activities, and are widely used in the preparation of low-toxic pesticides, berberine, heliotropin, sesamol, antioxidants, etc. In the production process of piperylene, dichloromethane usually participates in the reaction both as a solvent and as a reactant. Therefore, in the crude piperylene product, a large amount of dichloromethane is often contained. Therefore, by heating and raising the temperature of the crude piperylene product, dichloromethane in the crude piperylene product is removed and recovered by distillation, and the purification purpose of piperylene is also achieved.

[0003] At present, there are problems in the distillation process of dichloromethane by a distillation kettle. For example, as the distillation proceeds, the viscosity of the materials in the distillation kettle increases, and the materials and dichloromethane are wrapped around each other, resulting in a long distillation process time, low dichloromethane recovery efficiency, and increased dichloromethane loss. Utility Model Content

[0004] This application provides a dichloromethane recovery system in the production process of piperylene to solve the above problems mentioned in the background art.

[0005] This application provides a dichloromethane recovery system in the production process of piperylene, including: a distillation kettle, a condenser and a circulation structure.

[0006] The gas phase outlet of the distillation kettle is connected to the gas phase inlet of the condenser through a steam pipeline. The liquid phase outlet of the condenser is connected with a dichloromethane collection tank. The top feed port of the distillation kettle is connected with a feed pipe. The bottom of the distillation kettle is connected with a discharge pipe. A jacket is arranged on the outside of the distillation kettle.

[0007] The circulation structure includes a circulation pump and a circulation pipeline. One end of the circulation pipeline is connected to the position of the discharge pipe close to the distillation kettle, and the other end of the circulation pipeline is connected to the position of the feed pipe close to the distillation kettle. The circulation pump is arranged on the discharge pipe at the position between the circulation pipeline and the bottom outlet of the distillation kettle. A return valve is arranged on the circulation pipeline.

[0008] One end of the feed pipe extending into the distillation kettle is connected with a liquid distributor, and a stirring structure is arranged inside the distillation kettle.

[0009] Optionally, the feed pipe and the liquid distributor are detachably connected through a bent pipe. The discharge direction of the liquid distributor faces the central axis of the distillation kettle, and the included angle between the discharge direction of the liquid distributor and the vertical direction is 25-60°.

[0010] Optionally, the liquid distributor includes a funnel-shaped distribution cavity and a distribution plate connected to the wider end of the distribution cavity. The narrower end of the distribution cavity communicates with the elbow pipe.

[0011] A plurality of through holes are formed through the distribution plate, and the ratio of the total area of the plurality of through holes to the cross-sectional area of the feed pipe is 1.5 - 2.

[0012] Optionally, the through holes are trumpet-shaped with a wider upper part and a narrower lower part along the fluid movement direction.

[0013] Optionally, the stirring structure includes a motor, a stirring shaft, and stirring paddles. The motor is arranged on the outer top of the distillation kettle. One end of the stirring shaft is connected to the output end of the motor, and the other end of the stirring shaft extends into the interior of the distillation kettle. The stirring paddles are fixedly arranged on the outer periphery of the stirring shaft.

[0014] The stirring paddles are located below the liquid distributor.

[0015] Optionally, the system is further provided with a distributor moving structure, which includes a telescopic cylinder and a telescopic cover. The fixed end of the telescopic cylinder is arranged on the outer wall of the distillation kettle, and the telescopic end of the telescopic cylinder horizontally extends into the distillation kettle and is detachably connected to the elbow pipe.

[0016] The telescopic cover is sleeved outside the telescopic cylinder. One end of the telescopic cover is arranged at the connection between the inner wall of the distillation kettle and the telescopic cylinder, and the other end of the telescopic cover is connected to the telescopic end of the telescopic cylinder.

[0017] Optionally, a temperature sensor is arranged inside the distillation kettle.

[0018] The dichloromethane recovery system provided in this application during the production process of piperylene achieves efficient recovery of dichloromethane during the production of piperylene. Compared with the prior art, it has the following beneficial effects:

[0019] (1) Through the heating medium in the jacket, the temperature of the crude piperylene is increased, and at the same time, the temperature of dichloromethane in the crude product is increased and evaporated, so that gaseous dichloromethane escapes from the crude product. By setting a condenser, the escaped gaseous dichloromethane is cooled and condensed to obtain liquid dichloromethane, which is collected in the dichloromethane collection tank and recycled for subsequent piperylene production processes, achieving the purpose of recovering dichloromethane. By setting a circulation structure, the material at the bottom of the distillation kettle is pumped out and returned to the distillation kettle through the liquid distributor at the top of the distillation kettle. The liquid distributor disperses the bottom material into more liquid streams. During the falling process of the bottom material, the heat exchange area of the bottom material is increased, thereby increasing the heating area of the bottom material, accelerating the separation efficiency of dichloromethane and the crude product, and further improving the recovery efficiency and recovery amount of dichloromethane.

[0020] (2) By providing a plurality of through holes penetrating through the distribution plate, and the ratio of the total area of the plurality of through holes to the cross-sectional area of the feed pipe being 1.5 - 2, the smoothness and stability of the bottom material circulation in the kettle are ensured, and the heat exchange area of the bottom material is increased, improving the recovery efficiency of dichloromethane and greatly reducing the loss of dichloromethane.

[0021] (3) By providing a distributor moving structure, including a telescopic cylinder and a telescopic cover, with the telescopic movement of the telescopic cylinder, the liquid distributor outputs materials while performing reciprocating motion, making the materials sprayed by the liquid distributor more dispersed, enabling the materials to heat up more quickly, and thus accelerating the evaporation of dichloromethane. The telescopic cover is used to protect the telescopic cylinder located inside the distillation kettle, preventing the materials from affecting the operation of the telescopic cylinder and improving the operating stability of the system. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 It is a schematic structural diagram of a dichloromethane recovery system during the production process of piperylene provided by an embodiment of the present application;

[0024] Figure 2 It is a schematic structural diagram of a liquid distributor provided by an embodiment of the present application;

[0025] Figure 3 It is a schematic structural diagram of a distillation kettle provided by an embodiment of the present application;

[0026] Description of the Reference Numerals in the Drawings:

[0027] 1: Distillation kettle, 2: Condenser, 3: Dichloromethane collection tank, 5: Liquid distributor, 110: Feed pipe, 120: Discharge pipe, 130: Jacket, 140: Elbow pipe, 150: Temperature sensor, 160: Discharge valve, 210: Steam pipeline, 410: Circulation pump, 420: Circulation pipeline, 421: Return valve, 510: Distribution cavity, 520: Distribution plate, 530: Through hole, 610: Motor, 620: Stirring shaft, 630: Stirring paddle, 710: Telescopic cylinder, 720: Telescopic cover. Detailed Embodiments

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following clearly and completely describes the technical solutions in the embodiments of this application. Apparently, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts also belong to the scope of protection of this application.

[0029] As Figure 1 shown, this application provides a dichloromethane recovery system in the production process of piperylene, including: a distillation kettle 1, a condenser 2, and a circulation structure.

[0030] The gas-phase outlet of the distillation kettle 1 is connected to the gas-phase inlet of the condenser 2 through a steam pipeline 210. A dichloromethane collection tank 3 is connected to the liquid-phase outlet of the condenser 2. The top feed port of the distillation kettle 1 is connected to a feed pipe 110. The bottom of the distillation kettle 1 is connected to a discharge pipe 120. A jacket 130 is provided on the outside of the distillation kettle 1.

[0031] The circulation structure includes a circulation pump 410 and a circulation pipeline 420. One end of the circulation pipeline 420 is connected to the position of the discharge pipe 120 close to the distillation kettle 1. The other end of the circulation pipeline 420 is connected to the position of the feed pipe 110 close to the distillation kettle 1. The circulation pump 410 is arranged on the discharge pipe 120 at the position between the circulation pipeline 420 and the bottom outlet of the distillation kettle 1. A return valve 421 is provided on the circulation pipeline 420.

[0032] One end of the feed pipe 110 extending into the distillation kettle 1 is connected to a liquid distributor 5. A stirring structure is provided inside the distillation kettle 1.

[0033] Specifically, the crude piperylene contains a large amount of dichloromethane and a small amount of cyclic high boilers. The dichloromethane in the crude product is distilled out, which not only purifies the piperylene but also recovers and reuses the dichloromethane, greatly reducing the waste of dichloromethane and lowering the production cost.

[0034] In the dichloromethane recovery system provided by this application, the crude piperylene is introduced into the distillation kettle 1 through the feed pipe 110. The stirring structure stirs the crude product. By introducing a heating medium into the jacket 130, heat exchange is carried out between the heating medium and the crude piperylene in the distillation kettle 1. The temperature of the crude piperylene rises, and at the same time, the temperature of dichloromethane in the crude product rises and evaporates. The gaseous dichloromethane escapes from the crude product, separating dichloromethane from the crude product. The condenser 2 is used to cool and condense the escaped gaseous dichloromethane to obtain liquid dichloromethane, which is collected in the dichloromethane collection tank 3 and reused in the subsequent piperylene production process to achieve the purpose of recovering dichloromethane. After the distillation is completed, the initial piperylene product is obtained at the bottom of the distillation kettle 1. An outlet valve 160 is provided at the bottom of the distillation kettle 1. The outlet valve 160 is opened, and the initial piperylene product is output through the discharge pipe 120 and transferred to the next purification process for further purification.

[0035] As the dichloromethane distillation process progresses, the viscosity of the material in the distillation kettle 1 increases, and the material and dichloromethane are wrapped around each other, resulting in the problem that the separation of piperylene and dichloromethane is not thorough. In the prior art, by adopting measures such as changing the stirring form or increasing the stirring frequency, the agitation amplitude of the material is increased to accelerate the escape of dichloromethane. However, it is found in actual operation that the recovery amount of dichloromethane does not increase significantly, and the separation effect between dichloromethane and the material is not improved significantly. Therefore, in this application, a circulation structure is set up to extract the material at the bottom of the distillation kettle 1 and return it to the distillation kettle 1 through the liquid distributor 5 at the top of the distillation kettle 1 for re-distillation. By utilizing the different volatilities of dichloromethane and the material, the separation effect between the material and dichloromethane is improved.

[0036] The circulation structure includes a circulation pump 410 and a circulation pipeline 420. During the distillation process, the return valve 421 and the circulation pump 410 are opened to extract the material at the bottom of the kettle, which is transported through the circulation pipeline 420 to the feed pipe 110. The liquid distributor 5 connected to the outlet end of the feed pipe 110 distributes the circulated bottom material of the kettle. When the bottom material of the kettle is output to the inside of the distillation kettle 1 through the liquid distributor 5, the bottom material is dispersed into more liquid streams. During the falling process of the bottom material of the kettle, the heat exchange area of the bottom material of the kettle is increased, thereby increasing the heating area of the bottom material of the kettle, accelerating the separation efficiency of dichloromethane and the crude product, and further improving the recovery efficiency and recovery amount of dichloromethane.

[0037] Through the above solution, the present application realizes the efficient recovery of dichloromethane in the production of piperylene. Through the heating medium in the jacket, the temperature of the crude piperylene is increased, and at the same time, the temperature of dichloromethane in the crude product is increased and evaporated, so that the gaseous dichloromethane escapes from the crude product. By setting a condenser to cool and condense the escaped gaseous dichloromethane, liquid dichloromethane is obtained and collected in a dichloromethane collection tank, and is reused in subsequent piperylene production processes to achieve the purpose of recovering dichloromethane. By setting a circulation structure, the material at the bottom of the distillation kettle is pumped out and returned to the distillation kettle through a liquid distributor at the top of the distillation kettle. The liquid distributor will disperse the bottom material into more liquid streams. During the falling process of the bottom material, the heat exchange area of the bottom material is increased, thereby increasing the heating area of the bottom material, accelerating the separation efficiency of dichloromethane and the crude product, and further increasing the recovery efficiency and recovery amount of dichloromethane.

[0038] As Figure 2 and Figure 3 shown, optionally, the feed pipe 110 is detachably connected to the liquid distributor 5 through a bent pipe 140. The discharging direction of the liquid distributor 5 faces the central axis of the distillation kettle 1, and the included angle between the discharging direction of the liquid distributor 5 and the vertical direction is 25 - 60°.

[0039] Specifically, the feed pipe 110 is detachably connected to the liquid distributor 5 through a bent pipe 140, which is convenient for the maintenance and repair of the distillation kettle 1. Since the feed pipe 110 is close to the inner side wall of the distillation kettle 1, if the outlet surface of the liquid distributor 5 is vertically downward, there will be a problem that part of the material adheres to the kettle wall and the falling of the material is not sufficiently dispersed. Therefore, through the connection of the bent pipe 140, the discharging direction of the liquid distributor 5 faces the central axis of the distillation kettle 1, and the included angle between the discharging direction of the liquid distributor 5 and the vertical direction is 25 - 60°, which is beneficial to the material having a large heat exchange area with the heat in the distillation kettle 1 during the falling process, thereby increasing the recovery efficiency of dichloromethane.

[0040] As Figure 2 shown, optionally, the liquid distributor 5 includes a funnel-shaped distribution cavity 510 and a distribution plate 520 connected to the wider end of the distribution cavity 510. The narrower end of the distribution cavity 510 is communicated with the bent pipe 140.

[0041] A plurality of through holes 530 are penetrated on the distribution plate 520, and the ratio of the total area of the plurality of through holes 530 to the cross-sectional area of the feed pipe 110 is 1.5 - 2.

[0042] Specifically, after the material enters the distribution chamber 510 of the liquid distributor 5, it is output through the through holes 530 on the distribution plate 520. Since the material has a certain momentum, the material is in a jet state when it is output through the through holes 530. At the same time, the ratio of the total area of the multiple through holes 530 to the cross-sectional area of the feed pipe 110 is 1.5 - 2. In this way, when the material is ejected, it will not cause insufficient power when the material is ejected due to the too large total area of the through holes 530, nor will it affect the circulation efficiency of the bottom material in the kettle due to the too small total area of the through holes 530, and it increases the heat exchange area of the bottom material in the kettle and improves the recovery efficiency of dichloromethane.

[0043] As Figure 2 shown, optionally, the through hole 530 is in the shape of a horn that is wider at the top and narrower at the bottom along the fluid movement direction.

[0044] Specifically, when the material flows through and is output from the through hole 530, since the diameter of the through hole 530 decreases, the cross-sectional area through which the material flows decreases, thereby increasing the flow velocity of the material when it is output, improving the impact and contact of the material with the hot steam in the distillation kettle 1 and the material stirred at the bottom of the kettle, reducing the degree of mutual wrapping of the material and dichloromethane, and thus improving the distillation efficiency of dichloromethane.

[0045] As Figure 3 shown, optionally, the stirring structure includes a motor 610, a stirring shaft 620 and stirring paddles 630. The motor 610 is arranged at the outer top of the distillation kettle 1. One end of the stirring shaft 620 is connected to the output end of the motor 610, and the other end of the stirring shaft 620 vertically extends into the distillation kettle 1. The stirring paddles 630 are fixedly arranged on the outer circumference of the stirring shaft 620.

[0046] The stirring paddles 630 are located below the liquid distributor 5.

[0047] Specifically, power is provided by the motor 610 to drive the stirring shaft 620 to rotate, and then the stirring shaft 620 drives the stirring paddles 630 to rotate, while stirring the crude product to improve the heat exchange efficiency between the crude product and the jacket 130, and thus contribute to the distillation of dichloromethane.

[0048] The stirring paddles 630 are located below the liquid distributor 5, which is beneficial for the material ejected from the liquid distributor 5 to collide with the stirring paddles 630 during the descending process, making the material droplets more dispersed and the droplets further smaller, and at the same time further enhancing the heat exchange efficiency of the material, contributing to the rise in temperature of dichloromethane and its evaporation and escape.

[0049] As Figure 3 shown, optionally, the system is also provided with a distributor moving structure. The distributor moving structure includes a telescopic cylinder 710 and a telescopic cover 720. The fixed end of the telescopic cylinder 710 is arranged on the outer wall of the distillation kettle 1, and the telescopic end of the telescopic cylinder 710 horizontally extends into the distillation kettle 1 and is detachably connected to the elbow pipe 140.

[0050] The telescopic cover 720 is sleeved outside the telescopic cylinder 710. One end of the telescopic cover 720 is arranged at the connection between the inner wall of the distillation kettle 1 and the telescopic cylinder 710, and the other end of the telescopic cover 720 is connected to the telescopic end of the telescopic cylinder 710.

[0051] Specifically, the distributor moving structure is used to drive the liquid distributor 5 during the operation of the circulation structure, improve the dispersion efficiency of the material, thereby increasing the heat exchange efficiency of the material and increasing the evaporation amount of dichloromethane.

[0052] Through the telescopic movement of the telescopic cylinder 710, the elbow pipe 140 is driven to reciprocate, and then the liquid distributor 5 is driven to reciprocate while outputting the material, so that the material ejected by the liquid distributor 5 is more dispersed, the material can be heated up more quickly, and thus the distillation of dichloromethane is accelerated. The telescopic cover 720 is used to protect the telescopic cylinder 710 located in the distillation kettle 1, prevent the material from affecting the operation of the telescopic cylinder 710, and improve the operation stability of the system.

[0053] Optionally, a temperature sensor 150 is arranged inside the distillation kettle 1.

[0054] Specifically, the temperature sensor 150 is used to detect the temperature of the material in the distillation kettle 1, so as to control the amount of the heating medium entering the jacket 130 through the temperature value detected by the temperature sensor 150, and then accurately control the temperature of the material in the distillation kettle 1, so as to distill dichloromethane at a suitable temperature.

[0055] The technical solution of the present application will be described in detail below with specific embodiments.

[0056] In this embodiment, the dichloromethane recovery system in the production process of piperylene has the following operation flow during specific operation:

[0057] The crude piperylene is introduced into the distillation kettle 1 through the feed pipe 110. The motor 610 provides power to drive the stirring shaft 620 to rotate, and then the stirring shaft 620 drives the stirring paddle 630 to rotate to stir the crude product. By introducing the heating medium into the jacket 130, the heating medium exchanges heat with the crude piperylene in the distillation kettle 1, the temperature of the crude piperylene rises, and at the same time the temperature of dichloromethane in the crude product rises and evaporates, and the gaseous dichloromethane escapes from the crude product, separating dichloromethane from the crude product. The escaped gaseous dichloromethane enters the condenser 2 through the steam pipeline 210 for cooling and condensation to obtain liquid dichloromethane, which is collected in the dichloromethane collection tank 3 and reused for the subsequent piperylene production process to achieve the purpose of recovering dichloromethane.

[0058] During the distillation process, the return valve 421 and the circulation pump 410 are opened to extract the materials at the bottom of the kettle, which are transported through the circulation pipeline 420 to the feed pipe 110 and enter the distribution chamber 510 of the liquid distributor 5 through the outlet of the feed pipe 110. The materials are sprayed out into the distillation kettle 1 through the through holes 530, distributing the circulated bottom materials of the kettle, enhancing the impact and contact between the materials and the hot steam in the distillation kettle 1 and the agitated bottom materials of the kettle, reducing the degree of mutual encapsulation between the materials and dichloromethane, and thus improving the distillation efficiency of dichloromethane. Meanwhile, through the expansion and contraction of the telescopic cylinder 710, the liquid distributor 5 is driven to output materials while reciprocating, making the materials sprayed out by the liquid distributor 5 more dispersed, enabling the materials to heat up more quickly, and thus accelerating the evaporation of dichloromethane. The temperature sensor 150 is used to detect the temperature of the materials in the distillation kettle 1, facilitating the control of the amount of heating medium entering the jacket 130 based on the temperature value detected by the temperature sensor 150, and thus accurately controlling the temperature of the materials in the distillation kettle 1 to facilitate the evaporation of dichloromethane at an appropriate temperature.

[0059] When the kettle temperature rises to 45 °C, dichloromethane fractions flow out. When the kettle temperature reaches 50 °C, a large amount of dichloromethane is extracted. When the kettle temperature rises to 58 °C, by observation, the dichloromethane fractions decrease. When the temperature stabilizes until no dichloromethane fractions are extracted, the distillation is completed, and a piperylene crude product is obtained at the bottom of the distillation kettle 1. An outlet valve 160 is provided at the bottom of the distillation kettle 1. The outlet valve 160 is opened, and the piperylene crude product is output through the discharge pipe 120 and transferred to the next purification process for further purification.

[0060] In this embodiment, before distillation, the piperylene crude product contains 69.6% dichloromethane, 28% piperylene, and 2.4% high-boiling substances. After distillation, the obtained piperylene crude product contains 5% dichloromethane, 88% piperylene, and 7.5% high-boiling substances.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A dichloromethane recovery system in a piperine production process, characterized in that: include: Still (1), condenser (2) and circulation structure; The gas phase outlet of the still (1) is connected to the gas phase inlet of the condenser (2) via a steam pipeline (210); the liquid phase outlet of the condenser (2) is connected to a dichloromethane collecting tank (3); the top feed port of the still (1) is connected to a feed pipe (110); the bottom of the still (1) is connected to a discharge pipe (120); and a jacket (130) is provided on the outside of the still (1); The circulation structure comprises a circulation pump (410) and a circulation pipeline (420), one end of the circulation pipeline (420) is connected to a position of the discharge pipe (120) close to the distillation kettle (1), and the other end of the circulation pipeline (420) is connected to a position of the feed pipe (110) close to the distillation kettle (1), the circulation pump (410) is arranged on the discharge pipe (120) at a position between the circulation pipeline (420) and the bottom outlet of the distillation kettle (1), and a return valve (421) is arranged on the circulation pipeline (420); One end of the feed pipe (110) extending into the interior of the distillation kettle (1) is connected to a liquid distributor (5), and a stirring structure is provided inside the distillation kettle (1).

2. The dichloromethane recovery system in the piperine production process according to claim 1, characterized in that: The feed pipe (110) is detachably connected to the liquid distributor (5) via a bend pipe (140); the discharge direction of the liquid distributor (5) is toward the central axis of the distillation kettle (1), and the angle between the discharge direction of the liquid distributor (5) and the vertical direction is 25-60°.

3. The dichloromethane recovery system in the piperine production process according to claim 2, characterized in that, The liquid distributor (5) comprises a funnel-shaped distribution chamber (510) and a distribution plate (520) connected to the wider end of the distribution chamber (510); the narrower end of the distribution chamber (510) is connected to the elbow (140); The distribution plate (520) is provided with a plurality of through holes (530), and the ratio of the total area of ​​the plurality of through holes (530) to the area of ​​the cross section of the feed pipe (110) is 1.5-2.

4. The dichloromethane recovery system in the piperine production process according to claim 3, characterized in that: The through hole (530) is in a trumpet shape along the fluid movement direction, being wider at the top and narrower at the bottom.

5. The dichloromethane recovery system in the piperine production process according to claim 1, characterized in that: The stirring structure comprises a motor (610), a stirring shaft (620) and a stirring paddle (630), wherein the motor (610) is arranged at the outer top of the distillation kettle (1), one end of the stirring shaft (620) is connected to the output end of the motor (610), the other end of the stirring shaft (620) extends into the interior of the distillation kettle (1), and the stirring paddle (630) is fixedly arranged on the outer periphery of the stirring shaft (620); The stirring paddle (630) is located below the liquid distributor (5).

6. The dichloromethane recovery system in the piperine production process according to claim 2, characterized in that, The system is also provided with a distributor moving structure, the distributor moving structure comprising a telescopic cylinder (710) and a telescopic cover (720), the fixed end of the telescopic cylinder (710) being arranged on the outer wall of the distillation kettle (1), the telescopic end of the telescopic cylinder (710) extending horizontally into the distillation kettle (1) and being detachably connected to the bent pipe (140); The telescopic cover (720) is sleeved on the outside of the telescopic cylinder (710), one end of the telescopic cover (720) is arranged at the connection between the inner wall of the distillation kettle (1) and the telescopic cylinder (710), and the other end of the telescopic cover (720) is connected to the telescopic end of the telescopic cylinder (710).

7. The dichloromethane recovery system in the piperine production process according to claim 6, characterized in that: A temperature sensor (150) is provided inside the distillation kettle (1).

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