A continuous crystallization machine for para-aminophenylamine and a method of continuous crystallization

Abstract

The application belongs to the technical field of continuous crystallization, and particularly relates to a continuous crystallization machine for p-aminoacetanilide and a continuous crystallization method. The continuous crystallization machine for p-aminoacetanilide comprises a dissolving mechanism, an automatic crystallization mechanism, a filtering mechanism and a recovery mechanism. The automatic crystallization mechanism comprises an automatic crystallization machine, which is divided into region I, region II and region III from right to left. A scraping stirring assembly connected with a transmission shaft through a gear set is arranged in each of the region I, the region II and the region III. The rotation speed of the scraping stirring assembly in the region I, the region II and the region III is increased in sequence, and the temperature in the region I, the region II and the region III is decreased in sequence. The automatic crystallization machine is used for continuously and automatically crystallizing p-aminoacetanilide. The whole process is closed, and the safety and environmental protection are improved. The production efficiency is high, the annual output is improved, the energy consumption is low, and the resource utilization rate is high in the production process.

Description

Technical Field

[0001] This invention belongs to the field of continuous crystallization technology, specifically relating to a continuous crystallizer and method for p-aminoacetanilide. Background Technology

[0002] p-Aminoacetanilide is a white needle-like crystal, mainly used as a dye intermediate. During production, due to the low purity of crude p-aminoacetanilide, purification is necessary. A common purification method is to dissolve the crude product in a solvent and then crystallize it to obtain the crystalline product.

[0003] Depending on the operation method, crystallization is divided into two modes: continuous crystallization and intermittent crystallization. The commonly used crystallizer is the stirred-tank crystallizer, which is an intermittent process. Intermittent crystallization takes place in a single tank, and the process parameters change dynamically over time. After the intermittent crystallization operation is completed, all the material is discharged at once. Because the operation of intermittent crystallization is discontinuous, the production efficiency is relatively low. Moreover, to meet the production volume requirements, the number of equipment and the floor space required are relatively large, resulting in higher production costs. Currently, the production of para-aminoacetanilide uses this stirred-tank crystallization process, but the annual output is small and cannot meet the requirements of large-scale crystallization. Furthermore, this process has high energy consumption and low resource utilization.

[0004] Continuous crystallization differs from intermittent crystallization in that it involves simultaneous feeding and discharging, with constant process parameters that do not change over time, resulting in a steady-state process. The crystallization operation is continuous, thus offering advantages such as high production efficiency and stable process control. Therefore, this invention develops a continuous crystallizer for p-aminoacetanilide and discloses its continuous crystallization method to overcome the aforementioned technical problems and defects in existing p-aminoacetanilide crystallization processes. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a continuous crystallizer and method for continuous crystallization of p-aminoacetanilide. The method uses an automated crystallizer to continuously and automatically crystallize p-aminoacetanilide. This method replaces the old batch crystallization process with a continuous and automated crystallization process. The entire process is closed, which improves safety and environmental protection. It also has high production efficiency, increased annual output, low energy consumption and high resource utilization during the production process.

[0006] The objective of this invention is achieved as follows: a continuous crystallizer for p-aminoacetanilide, comprising a dissolving mechanism, an automatic crystallization mechanism, a filtration mechanism, and a recovery mechanism, characterized in that the dissolving mechanism comprises a dissolving vessel I and a dissolving vessel II, both of which are equipped with a stirring assembly A; both the upper sidewalls of the dissolving vessels I and II are provided with a feed inlet on the right side; the upper sidewalls of the dissolving vessels I and II are respectively fixedly connected to a reflux main pipe and a reflux branch pipe connected to the reflux main pipe via a tee connector on the left side; the lower middle sections of the dissolving vessels I and II are respectively fixedly connected to a discharge branch pipe and a discharge main pipe connected to the discharge branch pipe via a tee connector; a metering diaphragm pump is installed on the discharge main pipe;

[0007] The automatic crystallization mechanism includes an automatic crystallizer. A jacket is fixedly connected to the inner wall of the automatic crystallizer. The upper right side of the jacket is connected to the reflux main pipe, and a circulation pump is installed on the reflux main pipe. A liquid delivery pipe is connected to the upper left side of the jacket. The upper right side of the automatic crystallizer is connected to the discharge main pipe. The interior of the automatic crystallizer is divided into three zones from right to left: zone I, zone II, and zone III. A drive shaft is connected to the middle of the left inner wall of the jacket via a bearing seat. The right end of the drive shaft passes through the jacket and the right side wall of the automatic crystallizer and is fixedly connected to the output shaft of the drive motor. Each zone I, zone II, and zone III is equipped with a scraping and stirring assembly connected to the drive shaft via a gear set. The rotation speed of the scraping and stirring assembly in zone I, zone II, and zone III increases sequentially. The temperature in zone I, zone II, and zone III is controlled by temperature control mechanisms connected to the lower right, middle, and left sides of the automatic crystallizer, respectively. The temperature in zone I, zone II, and zone III decreases sequentially.

[0008] The filtration mechanism includes a continuous filter, with a discharge pipe connected to the upper right side of the continuous filter and the other end of the discharge pipe connected to the lower left side of the automatic crystallizer. A diaphragm pump is installed on the discharge pipe, and a return pipe is connected to the lower left side of the continuous filter. A crystal outlet is provided in the middle of the lower side of the continuous filter.

[0009] The recovery mechanism includes a solvent recovery tank and a methanol mother liquor buffer tank. The upper right side of the solvent recovery tank is connected to a return pipe, and a diaphragm pump is installed on the return pipe. The upper right side of the methanol mother liquor buffer tank is connected to the lower left side of the solvent recovery tank via a delivery pipe, and a delivery pump is installed on the delivery pipe. A stirring assembly B is installed inside the solvent recovery tank. An overflow pipe is connected to the upper right side of the solvent recovery tank, and the other end of the overflow pipe is connected to the inlet of the condenser. The outlet of the condenser is connected to the delivery pipe.

[0010] Furthermore, the stirring assembly A includes a stirring shaft A, on which stirring blades A are fixedly connected. The upper end of the stirring shaft A penetrates the upper sidewalls of dissolving vessel I and dissolving vessel II and is fixedly connected to the output shaft of motor A. The stirring shaft A is connected to the upper sidewalls of dissolving vessel I and dissolving vessel II through bearings. The stirring assembly A stirs and dissolves the methanol and p-aminoacetanilide materials in dissolving vessel I and dissolving vessel II to prepare a p-aminoacetanilide methanol solution.

[0011] Furthermore, the stirring assembly B includes a stirring shaft B, with stirring blades B installed on both the lower left and right sides of the stirring shaft B. The upper end of the stirring shaft B penetrates the upper side wall of the solvent recovery tank and is fixedly connected to the output shaft of the motor B. The stirring shaft B is connected to the upper side wall of the solvent recovery tank through a bearing. The stirring assembly B stirs the solution with more impurities in the lower part of the solvent recovery tank. After stirring, the solution is pumped into the methanol mother liquor buffer tank by the infusion pump for collection.

[0012] Furthermore, the scraping and stirring assembly includes hollow tubes I, II, and III sequentially distributed in regions I, II, and III. A driven gear I is fixedly connected to the middle of the upper inner wall of hollow tube I. A driving gear I meshing with the driven gear I is fixedly connected to a transmission shaft. A fixed shaft I rotatably connected to the driven gear I passes through the right side wall of hollow tube I and is fixedly connected to the inner side wall of the jacket. Scraping and stirring vanes I are uniformly fixedly connected to the outer side wall of hollow tube I. The solution in region I is stirred by the scraping and stirring vanes I, so that the solution is heated evenly in region I, which is conducive to crystallization and can also prevent the material from adhering to the side wall of the automatic crystallizer.

[0013] Furthermore, a driven gear II is fixedly connected to the middle of the lower inner wall of the hollow tube II, and a driving gear II meshing with the driven gear II is fixedly connected to the transmission shaft. A fixed shaft II rotatably connected to the driven gear II passes through the right side wall of the hollow tube II and the hollow tube I and is fixedly connected to the inner side wall of the jacket. A scraping and stirring vane II is uniformly fixedly connected to the outer side wall of the hollow tube II. The solution in region II is stirred by the scraping and stirring vane II, so that the solution is heated evenly in region II, which is conducive to crystallization and can also prevent the material from adhering to the side wall of the automatic crystallizer.

[0014] Furthermore, a driven gear III is fixedly connected to the middle of the upper inner wall of the hollow tube III, and a driving gear III meshing with the driven gear III is fixedly connected to the transmission shaft. A fixed shaft III rotatably connected to the driven gear III passes through the left side wall of the hollow tube III and is fixedly connected to the inner side wall of the jacket. Scraping and stirring vanes III are uniformly fixedly connected to the outer side wall of the hollow tube III. The solution in region III is stirred by the scraping and stirring vanes III, so that the solution is heated evenly in region III, which is conducive to crystallization and can also prevent the material from adhering to the side wall of the automatic crystallizer.

[0015] Furthermore, the diameter ratio of the driving gear I to the driven gear I is 1:0.9, the diameter ratio of the driving gear II to the driven gear II is 1:0.6, and the diameter ratio of the driving gear III to the driven gear III is 1:0.4. Due to the gear ratios of the driving gear I to the driven gear I, the driving gear II to the driven gear II, and the driving gear III to the driven gear III, the rotational speeds of the scraping and stirring vane I, the scraping and stirring vane II, and the scraping and stirring vane III increase sequentially. This results in a shorter residence time of the solution in the higher temperature region and a longer residence time in the lower temperature region, which is beneficial for the solution to fully and continuously crystallize automatically in the automatic crystallizer.

[0016] Furthermore, the fixed shaft I is connected to the right side wall of the hollow tube I via a bearing, the fixed shaft II is connected to the right side wall of the hollow tube II and the hollow tube I via a bearing, and the fixed shaft III is connected to the left side wall of the hollow tube III via a bearing.

[0017] Furthermore, the lower part of the continuous filter has an arc-shaped structure, which facilitates the discharge of the separated p-aminoacetanilide solid from the crystal outlet.

[0018] The present invention also discloses a continuous crystallization method for p-aminoacetanilide using a continuous crystallizer, comprising the following steps:

[0019] (1) Solvent methanol and p-aminoacetanilide are continuously transported from the inlet to dissolving tank I and dissolving tank II through a liquid conveying diaphragm pump and a solid material conveying pump. The materials are stirred and dissolved by stirring component A in dissolving tank I and dissolving tank II to prepare p-aminoacetanilide methanol solution.

[0020] (2) The prepared p-aminoacetanilide methanol solution is pumped into the automatic crystallizer through a metering diaphragm pump. The temperature of zone I inside the automatic crystallizer is controlled at 50-64℃, the temperature of zone II is controlled at 25-50℃, and the temperature of zone III is controlled at 5-25℃. That is, the solution passes through three temperature zones from right to left to achieve cooling and crystallization.

[0021] (3) After the prepared p-aminoacetanilide methanol solution enters the automatic crystallizer, the drive motor drives the transmission shaft to rotate. Driven gears I, II, and III rotate together with the transmission shaft. Driven gears I, II, and III rotate together with drive gears I, II, and III respectively. Hollow tubes I, II, and III rotate together with driven gears I, II, and III respectively. Scraper blades I, II, and III rotate together with hollow tubes I, II, and III respectively. Due to the rotation of drive gear I... The gear ratios of driven gear I, driving gear II and driven gear II, and driving gear III and driven gear III result in a sequential increase in the rotational speeds of scraper agitator I, scraper agitator II, and scraper agitator III. The agitation by the scraper agitator blades ensures that the solution in each region is heated evenly, which not only facilitates crystallization but also prevents material from adhering to the side wall of the automatic crystallizer. Furthermore, the different rotational speeds of the three-stage scraper agitator blades result in a shorter residence time for the solution in the higher temperature region and a longer residence time in the lower temperature region, which is conducive to the full, continuous, and automated crystallization of the solution in the automatic crystallizer.

[0022] (4) After crystallization, the methanol solution containing solid p-aminoacetanilide is pumped into a continuous filter through a diaphragm pump to separate the solid from the liquid. The separated methanol solvent is pumped into a solvent recovery tank through a diaphragm pump. The methanol solvent recovered in the upper part of the solvent recovery tank overflows into the condenser and then enters the jacket fixed to the inner wall of the automatic crystallizer. The flow direction of the methanol solvent in the jacket is from left to right, that is, the flow direction of the methanol solvent in the jacket is opposite to the flow direction of the p-aminoacetanilide methanol solution in the automatic crystallizer. The heat released during the material crystallization process is used to preheat the methanol solvent. The preheated methanol solvent is then circulated into dissolving tank I and dissolving tank II through a circulation pump for reuse.

[0023] (5) The solution in the lower part of the solvent recovery tank contains a lot of impurities. The solution with more impurities enters the methanol mother liquor buffer tank for collection under the stirring action of the stirring component B and the action of the infusion pump. After the tank is full, it is processed centrally.

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

[0025] 1. The automated crystallizer of the present invention is divided into three zones: Zone I, Zone II, and Zone III. The temperature in the three zones decreases progressively. The solution passes through the three temperature zones from right to left to achieve cooling crystallization. In Zone I, which has the highest temperature, the scraper stirring vane I rotates the slowest. In Zone III, which has the lowest temperature, the scraper stirring vane III rotates the fastest. In Zone II, which has a moderate temperature, the scraper stirring vane II rotates at a moderate speed. This ensures that the solution stays in the higher temperature zones for a shorter time and in the lower temperature zones for a longer time, which is beneficial for the solution to undergo full, continuous, and automated crystallization in the automated crystallizer.

[0026] 2. The automated crystallizer of the present invention has a jacket fixed to its inner wall. After crystallization, the methanol solution containing solid p-aminoacetanilide is separated into solid and liquid phases by a diaphragm pump and a continuous filter. The separated solid p-aminoacetanilide is discharged from the crystal outlet, and the separated methanol solvent is pumped into a solvent recovery tank. The recovered methanol solvent overflows from the upper part of the solvent recovery tank to the condenser and then enters the jacket. The flow direction of the methanol solvent in the jacket is from left to right, which is opposite to the flow direction of the p-aminoacetanilide methanol solution in the automated crystallizer. The heat released during the crystallization process of the material in the automated crystallizer is used to preheat the methanol solvent in the jacket. The preheated methanol solvent is then circulated into dissolving tank I and dissolving tank II by a circulation pump. This not only effectively utilizes the heat released during the crystallization process to reduce energy consumption, but also allows the methanol solvent to be recycled, improving resource utilization.

[0027] 4. This invention utilizes an automated crystallizer to continuously and automatically crystallize p-aminoacetanilide, replacing the old batch crystallization process with a continuous and automated crystallization process. The entire process is operated in a closed system, which improves both safety and environmental friendliness. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the continuous crystallizer for p-aminoacetanilide according to the present invention.

[0029] Figure 2 This is a schematic diagram of the automatic crystallizer in the continuous crystallizer of the present invention.

[0030] Figure 3 This is a side sectional view of the hollow tube I in the automatic crystallizer of the present invention.

[0031] In the diagram: 1-Dissolving vessel I, 2-Inlet, 3-Motor A, 4-Agitator shaft A, 5-Reflux main pipe, 6-Reflux branch pipe, 7-Dissolving vessel II, 8-Agitator blade A, 9-Discharge main pipe, 10-Circulating pump, 11-Discharge branch pipe, 12-Metering diaphragm pump, 13-Automatic crystallizer, 131-Zone I, 132-Zone II, 133-Zone III, 14-Diaphragm pump, 15-Discharge pipe, 16-Continuous filter, 17-Crystal outlet, 18-Return pipe, 19-Diaphragm pump, 20-Jacket, 21-Liquid delivery pipe, 22-Condenser, 23-Overflow pipe, 24-Motor B, 25-Dissolving vessel II Agent recovery tank, 26-stirring shaft B, 27-stirring blade B, 28-infusion pipe, 29-infusion pump, 30-methanol mother liquor buffer tank, 31-drive motor, 32-transmission shaft, 33-drive gear I, 34-driven gear I, 35-fixed shaft I, 36-hollow tube I, 37-scraper stirring vane I, 38-temperature control mechanism, 39-fixed shaft II, 40-driven gear II, 41-drive gear II, 42-hollow tube II, 43-scraper stirring vane II, 44-driven gear III, 45-fixed shaft III, 46-drive gear III, 47-hollow tube III, 48-scraper stirring vane III. Detailed Implementation

[0032] The present invention will now be described in more detail with reference to the accompanying drawings and specific embodiments.

[0033] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not 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.

[0034] See Figures 1-3 A continuous crystallizer for p-aminoacetanilide includes a dissolving mechanism, an automatic crystallizer 13, a filtration mechanism, and a recovery mechanism. The dissolving mechanism comprises a dissolving vessel I1 and a dissolving vessel II7. A stirring assembly A is installed in both dissolving vessel I1 and dissolving vessel II7. A feed inlet 2 is provided on the right side of the upper sidewall of both dissolving vessel I1 and dissolving vessel II7. A reflux main pipe 5 and a reflux branch pipe 6 connected to the reflux main pipe 5 via a tee connector are respectively fixed to the left side of the upper sidewall of both dissolving vessel I1 and dissolving vessel II7. A discharge branch pipe 11 and a discharge main pipe 9 connected to the discharge branch pipe 11 via a tee connector are respectively fixed to the middle of the lower side of both dissolving vessel I1 and dissolving vessel II7. A metering diaphragm pump 12 is installed on the discharge main pipe 9.

[0035] The automatic crystallizer 13 includes an automatic crystallizer 13, with a jacket 20 fixedly connected to the inner wall of the automatic crystallizer 13. The upper right side of the jacket 20 is connected to the reflux main pipe 5, and a circulation pump 10 is installed on the reflux main pipe 5. A liquid delivery pipe 21 is connected to the upper left side of the jacket 20. The upper right side of the automatic crystallizer 13 is connected to the discharge main pipe 9. The interior of the automatic crystallizer 13 is divided into three regions from right to left: region I 131, region II 132, and region III 133. A drive shaft 32 is connected to the middle of the left inner wall of the jacket 20 via a bearing seat. The right end of the drive shaft 32 passes through the jacket 20. The right side wall of the automatic crystallizer 13 is fixedly connected to the output shaft of the drive motor 31. Each of the regions I 131, II 132 and III 133 is equipped with a scraping and stirring assembly connected to the transmission shaft 32 via a gear set. The rotation speed of the scraping and stirring assembly in the regions I 131, II 132 and III 133 increases sequentially. The temperature in the regions I 131, II 132 and III 133 is controlled by the temperature control mechanism 38 connected to the lower right, middle and left sides of the automatic crystallizer 13, respectively. The temperature in the regions I 131, II 132 and III 133 decreases sequentially.

[0036] The filtration mechanism includes a continuous filter 16, with a discharge pipe 15 connected to the upper right side of the continuous filter 16. The other end of the discharge pipe 15 is connected to the lower left side of the automatic crystallizer 13. A diaphragm pump 14 is installed on the discharge pipe 15. A return pipe 18 is connected to the lower left side of the continuous filter 16. A crystal outlet 17 is provided in the middle of the lower side of the continuous filter 16.

[0037] The recovery mechanism includes a solvent recovery tank 25 and a methanol mother liquor buffer tank 30. The upper right side of the solvent recovery tank 25 is connected to a return pipe 18, and a diaphragm pump 19 is installed on the return pipe 18. The upper right side of the methanol mother liquor buffer tank 30 is connected to the lower left side of the solvent recovery tank 25 through a delivery pipe 28, and a delivery pump 29 is installed on the delivery pipe 28. A stirring assembly B is installed inside the solvent recovery tank 25. An overflow pipe 23 is connected to the upper right side of the solvent recovery tank 25, and the other end of the overflow pipe 23 is connected to the inlet end of the condenser 22. The outlet end of the condenser 22 is connected to a delivery pipe 21.

[0038] See Figure 1 The stirring assembly A includes a stirring shaft A4, on which stirring blades A8 are fixedly connected. The upper end of the stirring shaft A4 passes through the upper sidewall of dissolving vessel I1 and dissolving vessel II7 and is fixedly connected to the output shaft of motor A3. The stirring shaft A4 is connected to the upper sidewall of dissolving vessel I1 and dissolving vessel II7 through bearings. The stirring assembly A stirs and dissolves the methanol and p-aminoacetanilide materials in dissolving vessel I1 and dissolving vessel II7 to prepare a p-aminoacetanilide methanol solution.

[0039] See Figure 1 The stirring assembly B includes a stirring shaft B26, with stirring blades B27 installed on both the left and right sides of the lower part of the stirring shaft B26. The upper end of the stirring shaft B26 penetrates the upper side wall of the solvent recovery tank 25 and is fixedly connected to the output shaft of the motor B24. The stirring shaft B26 is connected to the upper side wall of the solvent recovery tank 25 through bearings. The stirring assembly B stirs the solution with more impurities in the lower part of the solvent recovery tank 25. After stirring, the solution is pumped into the methanol mother liquor buffer tank 30 by the infusion pump 29 for collection.

[0040] See Figure 1 and Figure 2 The scraping and stirring assembly includes hollow tubes I36, II42, and III47 sequentially distributed in regions I131, II132, and III133. A driven gear I34 is fixedly connected to the middle of the upper inner wall of hollow tube I36. A driving gear I33 meshing with the driven gear I34 is fixedly connected to the transmission shaft 32. A fixed shaft I35 rotatably connected to the driven gear I34 passes through the right side wall of hollow tube I36 and is fixedly connected to the inner wall of the jacket 20. Scraping and stirring vanes I37 are uniformly fixedly connected to the outer side wall of hollow tube I36. The solution in region I131 is stirred by the scraping and stirring vanes I37, so that the solution is heated evenly in region I131, which is conducive to crystallization and can also prevent the material from adhering to the side wall of the automatic crystallizer 13.

[0041] See Figure 1 and Figure 2 A driven gear II40 is fixedly connected to the middle of the lower inner wall of the hollow tube II42. The driving gear II41, which meshes with the driven gear II40, is fixedly connected to the transmission shaft 32. The fixed shaft II39, which is rotatably connected to the driven gear II40, passes through the right side wall of the hollow tube II42 and the hollow tube I36 and is fixedly connected to the inner wall of the jacket 20. A scraping and stirring vane II43 is uniformly fixedly connected to the outer wall of the hollow tube II42. The solution in region II132 is stirred by the scraping and stirring vane II43, so that the solution is heated evenly in region II132, which is conducive to crystallization and can also prevent the material from adhering to the side wall of the automatic crystallizer 13.

[0042] See Figure 1 and Figure 2 A driven gear III44 is fixedly connected to the middle of the upper inner wall of the hollow tube III47. A driving gear III46, which meshes with the driven gear III44, is fixedly connected to the transmission shaft 32. A fixed shaft III45, which is rotatably connected to the driven gear III44, passes through the left side wall of the hollow tube III47 and is fixedly connected to the inner wall of the jacket 20. A scraping and stirring vane III48 is uniformly fixedly connected to the outer side wall of the hollow tube III47. The solution in region III133 is stirred by the scraping and stirring vane III48, so that the solution is heated evenly in region III133, which is conducive to crystallization and can also prevent the material from adhering to the side wall of the automatic crystallizer 13.

[0043] See Figure 1 and Figure 2 The diameter ratio of the driving gear I33 to the driven gear I34 is 1:0.9, the diameter ratio of the driving gear II41 to the driven gear II40 is 1:0.6, and the diameter ratio of the driving gear III46 to the driven gear III44 is 1:0.4. Due to the gear ratios of the driving gear I33 to the driven gear I34, the driving gear II41 to the driven gear II40, and the driving gear III46 to the driven gear III44, the rotational speeds of the scraping and stirring vane I37, the scraping and stirring vane II43, and the scraping and stirring vane III48 increase sequentially. This results in a shorter residence time for the solution in the higher temperature region and a longer residence time in the lower temperature region, which is beneficial for the solution to fully and continuously crystallize automatically in the automatic crystallizer 13.

[0044] See Figure 1 and Figure 2 The fixed shaft I 35 is connected to the right side wall of the hollow tube I 36 via a bearing, the fixed shaft II 39 is connected to the right side wall of the hollow tube II 42 and the hollow tube I 36 via a bearing, and the fixed shaft III 45 is connected to the left side wall of the hollow tube III 47 via a bearing.

[0045] See Figure 1 The lower part of the continuous filter 16 has an arc-shaped structure, which facilitates the discharge of the separated p-aminoacetanilide solid from the crystal outlet 17.

[0046] The continuous crystallization method for p-aminoacetanilide using a continuous crystallizer according to the present invention comprises the following steps:

[0047] (1) Solvent methanol and p-aminoacetanilide are continuously transported to dissolving tank I1 and dissolving tank II7 through liquid transport diaphragm pump and solid material transport pump. The materials are stirred and dissolved by stirring component A in dissolving tank I1 and dissolving tank II7 to prepare p-aminoacetanilide methanol solution.

[0048] (2) The prepared p-aminoacetanilide methanol solution is pumped into the automatic crystallizer 13 through the metering diaphragm pump 12. The temperature of zone I 131 inside the automatic crystallizer 13 is controlled at 50-64℃, the temperature of zone II 132 is controlled at 25-50℃, and the temperature of zone III 133 is controlled at 5-25℃. That is, the solution passes through three temperature zones from right to left to achieve cooling crystallization.

[0049] (3) After the prepared p-aminoacetanilide methanol solution enters the automatic crystallizer 13, the drive motor 31 drives the transmission shaft 32 to rotate. The driving gears I 33, II 41, and III 46 rotate together with the transmission shaft 32. The driven gears I 34, II 40, and III 44 rotate together with the driving gears I 33, II 41, and III 46, respectively. The hollow tubes I 36, II 42, and III 47 rotate together with the driven gears I 34, II 40, and III 46, respectively. The moving gear Ⅲ44 rotates together, and the scraping and stirring vanes Ⅰ37, Ⅱ43, and Ⅲ48 rotate with the hollow tubes Ⅰ36, Ⅱ42, and Ⅲ47 respectively. The rotation speeds of the scraping and stirring vanes Ⅰ37, Ⅱ43, and Ⅲ48 increase sequentially. The different rotation speeds of the three-stage scraping and stirring vanes result in a shorter residence time for the solution in the higher temperature region and a longer residence time in the lower temperature region, which is beneficial for the solution to fully and continuously crystallize automatically in the automatic crystallizer 13.

[0050] (4) After crystallization, the methanol solution containing solid p-aminoacetanilide is pumped into the continuous filter 16 through the diaphragm pump 14 to separate the solid from the liquid. The separated methanol solvent is pumped into the solvent recovery tank 25 through the diaphragm pump 19. The methanol solvent recovered in the upper part of the solvent recovery tank 25 overflows into the condenser 22 and then enters the jacket 20 fixed to the inner wall of the automatic crystallizer 13. The flow direction of the methanol solvent in the jacket 20 is from left to right. The flow direction of the methanol solvent in the jacket 20 is opposite to the flow direction of the p-aminoacetanilide methanol solution in the automatic crystallizer 13. The heat released during the material crystallization process is used to preheat the methanol solvent. The preheated methanol solvent is then circulated into the dissolving tank I1 and dissolving tank II7 through the circulation pump 10 for reuse.

[0051] (5) The solution in the lower part of the solvent recovery tank 25 contains a lot of impurities. The solution containing more impurities enters the methanol mother liquor buffer tank 30 for collection under the stirring action of the stirring component B and the action of the infusion pump 29. After the tank is full, it is processed centrally.

[0052] This invention utilizes an automated crystallizer to continuously and automatically crystallize p-aminoacetanilide. The continuous and automated crystallization process replaces the old batch crystallization process, and the entire operation is closed, which improves both safety and environmental protection. Furthermore, the heat released during crystallization is used to preheat the methanol solvent separated after crystallization. The preheated methanol solvent is then circulated into dissolving tanks I and II via a circulation pump. This not only effectively utilizes the heat released during crystallization to reduce energy consumption, but also allows for the recycling of methanol solvent, improving resource utilization.

[0053] Unless otherwise defined, the technical or scientific terms used herein should be understood in their ordinary sense as would be understood by one of ordinary skill in the art to which this invention pertains. The use of terms such as "a" or "an" in this specification and claims does not necessarily indicate a limitation of quantity. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0054] The exemplary embodiments of the present invention have been described in detail above with reference to preferred embodiments. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of the present invention, and various combinations can be made to the various technical features and structures proposed in the present invention without exceeding the protection scope of the present invention.

Claims

1. A continuous crystallizer for p-aminoacetanilide, comprising a dissolving mechanism, an automatic crystallizing mechanism, a filtering mechanism, and a recovery mechanism, characterized in that, The dissolving mechanism includes a dissolving vessel I and a dissolving vessel II. Both dissolving vessels I and II are equipped with a stirring assembly A. Both dissolving vessels I and II have a feed inlet on the right side of their upper sidewalls. The left side of the upper sidewalls of both dissolving vessels I and II are respectively fixedly connected to a reflux main pipe and a reflux branch pipe connected to the reflux main pipe via a tee connector. The lower middle part of both dissolving vessels I and II is respectively fixedly connected to a discharge branch pipe and a discharge main pipe connected to the discharge branch pipe via a tee connector. A metering diaphragm pump is installed on the discharge main pipe. The automatic crystallization mechanism includes an automatic crystallizer. A jacket is fixedly connected to the inner wall of the automatic crystallizer. The upper right side of the jacket is connected to the reflux main pipe, and a circulation pump is installed on the reflux main pipe. A liquid delivery pipe is connected to the upper left side of the jacket. The upper right side of the automatic crystallizer is connected to the discharge main pipe. The interior of the automatic crystallizer is divided into three zones from right to left: zone I, zone II, and zone III. A drive shaft is connected to the middle of the left inner wall of the jacket via a bearing seat. The right end of the drive shaft passes through the jacket and the right side wall of the automatic crystallizer and is fixedly connected to the output shaft of the drive motor. Each zone I, zone II, and zone III is equipped with a scraping and stirring assembly connected to the drive shaft via a gear set. The rotation speed of the scraping and stirring assembly in zone I, zone II, and zone III increases sequentially. The temperature in zone I, zone II, and zone III is controlled by temperature control mechanisms connected to the lower right, middle, and left sides of the automatic crystallizer, respectively. The temperature in zone I, zone II, and zone III decreases sequentially. The filtration mechanism includes a continuous filter, with a discharge pipe connected to the upper right side of the continuous filter and the other end of the discharge pipe connected to the lower left side of the automatic crystallizer. A diaphragm pump is installed on the discharge pipe, and a return pipe is connected to the lower left side of the continuous filter. A crystal outlet is provided in the middle of the lower side of the continuous filter. The recovery mechanism includes a solvent recovery tank and a methanol mother liquor buffer tank. The upper right side of the solvent recovery tank is connected to a return pipe, and a diaphragm pump is installed on the return pipe. The upper right side of the methanol mother liquor buffer tank is connected to the lower left side of the solvent recovery tank via a delivery pipe, and a delivery pump is installed on the delivery pipe. A stirring assembly B is installed inside the solvent recovery tank. An overflow pipe is connected to the upper right side of the solvent recovery tank, and the other end of the overflow pipe is connected to the inlet of the condenser. The outlet of the condenser is connected to the delivery pipe.

2. The continuous crystallizer for p-aminoacetanilide as described in claim 1, characterized in that, The stirring assembly A includes a stirring shaft A, on which stirring blades A are fixedly connected. The upper end of the stirring shaft A passes through the upper sidewalls of dissolving vessel I and dissolving vessel II and is fixedly connected to the output shaft of motor A. The stirring shaft A is connected to the upper sidewalls of dissolving vessel I and dissolving vessel II through bearings.

3. The continuous crystallizer for p-aminoacetanilide as described in claim 1, characterized in that, The stirring assembly B includes a stirring shaft B, with stirring blades B installed on both the lower left and right sides of the stirring shaft B. The upper end of the stirring shaft B penetrates the upper side wall of the solvent recovery tank and is fixedly connected to the output shaft of the motor B. The stirring shaft B is connected to the upper side wall of the solvent recovery tank through a bearing.

4. The continuous crystallizer for p-aminoacetanilide as described in claim 1, characterized in that, The scraping and stirring assembly includes hollow tubes I, II, and III, which are sequentially distributed in regions I, II, and III. A driven gear I is fixedly connected to the middle of the upper inner wall of hollow tube I. A driving gear I that meshes with the driven gear I is fixedly connected to a transmission shaft. A fixed shaft I that is rotatably connected to the driven gear I passes through the right side wall of hollow tube I and is fixedly connected to the inner side wall of the jacket. Scraping and stirring vanes I are uniformly fixedly connected to the outer side wall of hollow tube I.

5. The continuous crystallizer for p-aminoacetanilide as described in claim 4, characterized in that, A driven gear II is fixedly connected to the middle of the lower inner wall of the hollow tube II. A driving gear II that meshes with the driven gear II is fixedly connected to the transmission shaft. A fixed shaft II that is rotatably connected to the driven gear II passes through the right side wall of the hollow tube II and the hollow tube I and is fixedly connected to the inner side wall of the jacket. A scraping and stirring vane II is uniformly fixedly connected to the outer side wall of the hollow tube II.

6. The continuous crystallizer for p-aminoacetanilide as described in claim 5, characterized in that, A driven gear III is fixedly connected to the middle of the upper inner wall of the hollow tube III. A driving gear III that meshes with the driven gear III is fixedly connected to the transmission shaft. A fixed shaft III that is rotatably connected to the driven gear III passes through the left side wall of the hollow tube III and is fixedly connected to the inner side wall of the jacket. A scraping and stirring vane III is uniformly fixedly connected to the outer side wall of the hollow tube III.

7. The continuous crystallizer for p-aminoacetanilide as described in claim 6, characterized in that, The diameter ratio of the driving gear I to the driven gear I is 1:0.9, the diameter ratio of the driving gear II to the driven gear II is 1:0.6, and the diameter ratio of the driving gear III to the driven gear III is 1:0.

4.

8. The continuous crystallizer for p-aminoacetanilide as described in claim 6, characterized in that, The fixed shaft I is connected to the right side wall of the hollow tube I via a bearing, the fixed shaft II is connected to the right side wall of the hollow tube II and the hollow tube I via a bearing, and the fixed shaft III is connected to the left side wall of the hollow tube III via a bearing.

9. The continuous crystallizer for p-aminoacetanilide as described in claim 1, characterized in that, The lower part of the continuous filter has an arc-shaped structure.

10. A continuous crystallization method for p-aminoacetanilide using a continuous crystallizer as described in any one of claims 1 to 9, characterized in that, Includes the following steps: (1) Solvent methanol and p-aminoacetanilide are continuously transported from the inlet to dissolving tank I and dissolving tank II through a liquid conveying diaphragm pump and a solid material conveying pump. The materials are stirred and dissolved by stirring component A in dissolving tank I and dissolving tank II to prepare p-aminoacetanilide methanol solution. (2) The prepared p-aminoacetanilide methanol solution is pumped into the automatic crystallizer through a metering diaphragm pump. The temperature of zone I inside the automatic crystallizer is controlled at 50-64℃, the temperature of zone II is controlled at 25-50℃, and the temperature of zone III is controlled at 5-25℃. That is, the solution passes through three temperature zones from right to left to achieve cooling and crystallization. (3) After the prepared p-aminoacetanilide methanol solution enters the automatic crystallizer, the drive motor drives the transmission shaft to rotate. Driven gears I, II, and III rotate together with the transmission shaft. Driven gears I, II, and III rotate together with drive gears I, II, and III respectively. Hollow tubes I, II, and III rotate together with driven gears I, II, and III respectively. Scraper blades I, II, and III rotate together with hollow tubes I, II, and III respectively. Due to the rotation of drive gear I... The gear ratios of driven gear I, driving gear II and driven gear II, and driving gear III and driven gear III result in a sequential increase in the rotational speeds of scraper agitator I, scraper agitator II, and scraper agitator III. The agitation by the scraper agitator blades ensures that the solution in each region is heated evenly, which not only facilitates crystallization but also prevents material from adhering to the side wall of the automatic crystallizer. Furthermore, the different rotational speeds of the three-stage scraper agitator blades result in a shorter residence time for the solution in the higher temperature region and a longer residence time in the lower temperature region, which is conducive to the full, continuous, and automated crystallization of the solution in the automatic crystallizer. (4) After crystallization, the methanol solution containing solid p-aminoacetanilide is pumped into a continuous filter through a diaphragm pump to separate the solid from the liquid. The separated methanol solvent is pumped into a solvent recovery tank through a diaphragm pump. The methanol solvent recovered in the upper part of the solvent recovery tank overflows into the condenser and then enters the jacket fixed to the inner wall of the automatic crystallizer. The flow direction of the methanol solvent in the jacket is from left to right, that is, the flow direction of the methanol solvent in the jacket is opposite to the flow direction of the p-aminoacetanilide methanol solution in the automatic crystallizer. The heat released during the material crystallization process is used to preheat the methanol solvent. The preheated methanol solvent is then circulated into dissolving tank I and dissolving tank II through a circulation pump for reuse. (5) The solution in the lower part of the solvent recovery tank contains a lot of impurities. The solution with more impurities enters the methanol mother liquor buffer tank for collection under the stirring action of the stirring component B and the action of the infusion pump. After the tank is full, it is processed centrally.

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