Crystallization kettle

Abstract

The crystallization kettle comprises a kettle body, a jacket and a stirring unit, the jacket is arranged on the periphery of the kettle body, a feeding port and a gas outlet are further formed in the top of the kettle body, a discharging port is formed in the bottom of the kettle body, the stirring unit is arranged at the center position in the kettle body, a medium inlet is formed in the lower portion of the jacket, and a medium outlet is formed in the upper portion of the jacket. A medium recovery unit is arranged outside the jacket and comprises a medium leading-out pipe, a liquid level meter, a medium control valve and a medium buffer tank, one end of the medium leading-out pipe is connected with the bottom of the jacket, the other end of the medium leading-out pipe is connected with the medium buffer tank, the liquid level meter is located at the bottom of the jacket, and the medium control valve is arranged on the medium leading-out pipe. According to the invention, high-efficiency precipitation of crystals is realized.

Description

Technical Field

[0001] The present application relates to the technical field of chemical equipment, and in particular to a crystallization kettle. Background Art

[0002] The process of a substance precipitating from a solution into a crystal state, or condensing from a molten state into a crystal state when cooled, is called crystallization. As we all know, a crystallization kettle is a mixing reaction equipment for mixing, heating, cooling, stirring, etc. of materials in the chemical, pharmaceutical, food and other industries. After the materials are mixed and reacted, chilled water or refrigerant water is passed into its interlayer to cause the materials in it to cool down rapidly and crystallize.

[0003] In the production process of 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid, the reaction steps of hydrazinolysis, cyclization, bromination, oxidation and saponification are required. In the hydrazinolysis reaction step, hydrazine hydrate reacts with 2,3,-dichloropyridine in the presence of ethylene glycol to generate 3-chloro-2-hydrazinopyridine, and then sodium ethoxide, anhydrous ethanol and diethyl maleate are added to 3-chloro-2-hydrazinopyridine through a cyclization reaction to obtain a solution with a qualified content of 3-chloro-2-hydrazinopyridine, and the 3-chloro-2-hydrazinopyridine solution and hydrochloric acid are introduced into a crystallization kettle, and water vapor is first introduced to increase the temperature, ethylene glycol is evaporated, and then the temperature is reduced to allow 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-carboxylic acid ethyl ester to crystallize and precipitate, and then the crystals are used for subsequent bromination, oxidation and saponification reaction steps.

[0004] In the prior art, when the temperature of the 3-chloro-2-hydrazinopyridine solution and the hydrochloric acid vapor is increased, the vapor in the jacket of the crystallization kettle exchanges heat with the material in the crystallization kettle, and a mixture of condensed water and vapor is obtained in the jacket, but the condensed water is not discharged in time, resulting in a decrease in the heat exchange efficiency between the vapor and the material in the crystallization kettle, resulting in a decrease in the evaporation efficiency of ethanol, and further resulting in slow crystallization of 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-carboxylic acid ethyl ester, which affects the yield of the product 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid. Utility Model Content

[0005] The present application provides a crystallization kettle to solve the above-mentioned problems mentioned in the background technology.

[0006] The present application provides a crystallization kettle, comprising: a kettle body, a jacket and a stirring unit, wherein the jacket is arranged on the outer periphery of the kettle body, a feed inlet and a gas outlet are provided on the top of the kettle body, a discharge port is provided on the bottom of the kettle body, the stirring unit is arranged at the center of the kettle body, a medium inlet is provided at the lower part of the jacket, and a medium outlet is provided at the upper part of the jacket.

[0007] A medium recovery unit is arranged outside the jacket, and the medium recovery unit includes a medium outlet pipe, a liquid level gauge, a first medium control valve and a medium buffer tank. One end of the medium outlet pipe is connected to the bottom of the jacket, and the other end of the medium outlet pipe is connected to the medium buffer tank. The liquid level gauge is located at the bottom of the jacket, and the first medium control valve is arranged on the medium outlet pipe.

[0008] Optionally, the outlet of the medium buffer tank is connected to a steam generator, and the steam outlet of the steam generator is in communication with the medium inlet.

[0009] Optionally, a filter is provided at the connection between the medium outlet pipe and the medium buffer tank.

[0010] Optionally, the stirring unit includes a motor, a rotating shaft and a rotating stirring paddle, the output end of the motor is connected to one end of the rotating shaft, and a plurality of rotating stirring paddles are arranged on the outer side of the rotating shaft.

[0011] The rotating stirring paddle includes a fixed sleeve, a bearing, a connecting rod and a stirring blade. The fixed sleeve is arranged on the outside of the rotating shaft. The fixed sleeve is fixedly provided with a bearing on the axial side of the rotating shaft. The bearing is connected to one end of the connecting rod. The stirring blade is arranged on the outside of the connecting rod.

[0012] Optionally, a first temperature sensor is arranged inside the kettle body, a second temperature sensor is arranged inside the jacket, and a second medium control valve is connected to the medium inlet.

[0013] Optionally, the crystallization kettle is further provided with a controller, which is respectively connected to the liquid level meter, the first medium control valve, the first temperature sensor, the second temperature sensor, the motor and the second medium control valve.

[0014] Optionally, the first medium control valve is a one-way valve.

[0015] The crystallization kettle provided in the present application realizes efficient crystal precipitation and has the following beneficial effects compared with the prior art:

[0016] (1) A jacket is provided and water vapor is first introduced into the jacket so that the water vapor exchanges heat with the material in the kettle, so that the temperature of the material in the kettle rises, and ethanol can be quickly and efficiently evaporated from the gas outlet, so that the solution in the kettle reaches a saturated state. After the ethanol is evaporated, a cooling medium is introduced into the jacket through the medium inlet so that the cooling medium exchanges heat with the material in the kettle, the temperature of the material in the kettle decreases, and crystals are precipitated. The cooling medium is discharged from the medium outlet, so as to achieve the purpose of crystallizing 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-carboxylic acid ethyl ester, and finally the crystals are discharged from the discharge port. In addition, a medium recovery unit is provided, and the liquid level of the condensed water in the jacket is detected in real time by a liquid level gauge, and the condensed water is discharged in time through the medium outlet pipe, which helps to improve the heat exchange efficiency of the jacket and the crystallization speed.

[0017] (2) The stirring unit includes a motor, a rotating shaft and a rotating stirring paddle, and the rotating shaft includes a fixed sleeve, a bearing, a connecting rod and a stirring blade. When the motor is started, the rotating shaft rotates, driving the connecting rod and the stirring blade to rotate on the radial direction of the rotating shaft, and at the same time contacting the material in the kettle body, stirring the material in the kettle body, thereby improving the heat exchange between the material and the medium in the jacket. At the same time, when the connecting rod and the stirring blade rotate around the rotating shaft, due to contact and interaction with the material, the connecting rod and the stirring blade rotate around the direction of rotation of the bearing under the rotation of the bearing, further improving the stirring of the material, facilitating the heat exchange between the material and the medium in the jacket, and further facilitating the precipitation of crystals.

[0018] (3) The present application sets a controller to control the opening of the first medium control valve and the second medium control valve according to the signal values ​​of the liquid level meter, the first temperature sensor, and the second temperature sensor, and controls the start and stop of the motor, thereby improving the degree of automation of the crystallization kettle of the present application and reducing the labor output of personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A schematic diagram of the structure of a crystallization kettle provided in one embodiment of the present application;

[0021] Figure 2 A schematic diagram of the structure of a crystallization kettle provided in another embodiment of the present application;

[0022] Figure 3 A schematic diagram of the structure of a crystallization kettle provided in yet another embodiment of the present application;

[0023] Figure 4 A connection diagram of a controller provided in one embodiment of the present application;

[0024] Description of reference numerals:

[0025] 1: kettle body, 2: jacket, 5: controller, 110: feed port, 120: gas outlet, 130: discharge port, 140: first temperature sensor, 210: medium inlet, 211: second medium control valve, 220: medium outlet, 230: second temperature sensor, 310: medium outlet pipe, 320: liquid level meter, 330: first medium control valve, 340: medium buffer tank, 350: steam generator, 360: filter, 410: motor, 420: rotating shaft, 430: rotating stirring paddle, 431: fixed sleeve, 432: bearing, 433: connecting rod, 434: stirring blade. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work also fall within the scope of protection of the present application.

[0027] like Figure 1 As shown, the present application provides a crystallization kettle, comprising: a kettle body 1, a jacket 2 and a stirring unit, the jacket 2 is arranged on the outer periphery of the kettle body 1, the top of the kettle body 1 is also provided with a feed inlet 110 and a gas outlet 120, the bottom of the kettle body 1 is provided with a discharge port 130, the stirring unit is arranged at the center position of the kettle body 1, the lower part of the jacket 2 is provided with a medium inlet 210, and the upper part of the jacket 2 is provided with a medium outlet 220.

[0028] A medium recovery unit is arranged outside the jacket 2, and the medium recovery unit includes a medium outlet pipe 310, a liquid level meter 320, a first medium control valve 330 and a medium buffer tank 340. One end of the medium outlet pipe 310 is connected to the bottom of the jacket 2, and the other end of the medium outlet pipe 310 is connected to the medium buffer tank 340. The liquid level meter 320 is located at the bottom of the jacket 2, and the first medium control valve 330 is arranged on the medium outlet pipe 310.

[0029] Specifically, the jacket 2 is used to provide heat or cold for the material in the kettle body 1. In this embodiment, the production process of 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid is taken as an example to explain the principle of the crystallization kettle of the present application. First, 3-chloro-2-hydrazinopyridine is generated by hydrazinolysis reaction, and then anhydrous ethanol and diethyl maleate are added to 3-chloro-2-hydrazinopyridine for cyclization reaction to generate a solution with a qualified content of 3-chloro-2-hydrazinopyridine. The 3-chloro-2-hydrazinopyridine solution and hydrochloric acid are passed into the crystallization kettle to generate a solution containing 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-ethyl carboxylate. At this time, it is necessary to obtain crystals of 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-ethyl carboxylate for subsequent bromination reaction. Therefore, water vapor is first introduced into the jacket 2 to heat the material in the kettle body 1, so that ethanol is heated and evaporated, and the amount of solvent is reduced, which is conducive to 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-ethyl formate reaching a saturated or supersaturated state, and is conducive to the crystallization and precipitation of 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-ethyl formate during subsequent cooling. The feed port 110 is used to introduce reactants into the kettle body 1, the gas outlet 120 is used to output the ethanol from the gas outlet 120 when the temperature is increased, and the discharge port 130 is used to output the crystals.

[0030] Ethanol is evaporated by heating: water vapor is input from the medium inlet 210. The water vapor has a relatively high temperature. The water vapor enters the jacket 2 from the medium inlet 210, rises and diffuses in the jacket 2, and exchanges heat with the material in the kettle body 1, so that the temperature of the material in the kettle body rises. At this time, the material in the kettle body 1 is continuously stirred by the stirring unit to improve the heat exchange efficiency between the material and the water vapor in the jacket 2, so that ethanol can be evaporated quickly and efficiently from the gas outlet 120, reducing the amount of the solution in the kettle body 1, so that the solution in the kettle body 1 reaches a saturated state, which is conducive to the subsequent precipitation of 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-carboxylic acid ethyl ester crystals.

[0031] During the temperature rise process, the water vapor in the jacket 2 continuously exchanges heat with the material in the kettle body 1, and the water vapor temperature drops to form condensate, and these condensates will continue to accumulate in the jacket 2. If the condensate is not discharged in time, the condensate will occupy a large amount of space in the jacket 2, which will greatly reduce the heat exchange efficiency between the water vapor and the material in the kettle body 1, and reduce the precipitation of crystals. Therefore, by setting a medium recovery unit, the condensate is discharged in time, which helps to improve the heat exchange efficiency of the jacket 2 and increase the crystallization rate. A liquid level gauge 320 is set at the bottom of the jacket 2 to detect the amount of accumulated condensate. The bottom of the jacket 2 is also connected to a medium outlet pipe 310. When the liquid level value detected by the liquid level gauge 320 reaches the first preset liquid level, the first medium control valve 330 on the medium outlet pipe 310 is opened to temporarily store the condensate in the jacket in the medium buffer tank 340. When the condensate level drops to the second preset liquid level value, the first medium control valve 330 is closed. The second preset liquid level value is set to at least make the liquid level higher than the connection between the bottom of the jacket 2 and the medium outlet pipe 310, so that water vapor will not be discharged along with the condensate when the condensate is discharged, which not only improves the heat exchange efficiency, but also avoids the waste of water vapor, saves resources, and has good economic benefits for the enterprise.

[0032] Cooling and crystallization: After the ethanol is evaporated, the solution in the kettle 1 reaches a saturated state. At this time, the temperature of the material in the kettle 1 is reduced to allow the crystals of 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-carboxylic acid ethyl ester to precipitate. Close the liquid level meter 320 and the first medium control valve 330, and input the cooling medium into the jacket 2 through the medium inlet 210, so that the cooling medium and the material in the kettle 1 are heat-exchanged, the temperature of the material in the kettle 1 is reduced, and the crystals are precipitated. The cooling medium is discharged from the medium outlet 220, so as to achieve the purpose of crystallizing 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-carboxylic acid ethyl ester, and finally the crystals are discharged from the discharge port 130.

[0033] The present application realizes the efficient precipitation of crystals by the above scheme, by setting a jacket, and first passing water vapor into the jacket, so that water vapor and the material in the kettle body are heat exchanged, so that the material temperature in the kettle body rises, so that ethanol can be quickly and efficiently steamed out by the gas outlet, so that the solution in the kettle body reaches a saturated state. After ethanol is steamed out, a cooling medium is input into the jacket by the medium inlet, so that the cooling medium and the material in the kettle body are heat exchanged, and the temperature of the material in the kettle body is reduced, so that crystals are precipitated, and the cooling medium is discharged from the medium outlet, so as to achieve the purpose of crystallization of 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-ethyl formate, and finally the crystal is discharged from the discharge port. And by setting a medium recovery unit, the liquid level of the condensed water in the jacket is detected in real time by a liquid level gauge, and the condensed water is discharged in time by a medium outlet pipe, which helps to improve the heat exchange efficiency of the jacket and improve the crystallization rate.

[0034] like Figure 2 As shown, optionally, the outlet of the medium buffer tank 340 is connected to a water vapor generator 350 , and the water vapor outlet of the water vapor generator 350 is in communication with the medium inlet 210 .

[0035] Specifically, the condensate discharged from the jacket 2 through the medium outlet pipe 310 is transported to the medium buffer tank 340, and the condensate is transported to the steam generator 350 for reheating and evaporation to obtain water vapor, and then transported to the jacket through the medium inlet 210 again to heat the material in the kettle body 1, thereby realizing the recycling of water resources and avoiding the waste of water resources.

[0036] like Figure 2 As shown, optionally, a filter 360 is provided at the connection between the medium outlet pipe 310 and the medium buffer tank 340 .

[0037] Specifically, the filter 360 is provided to filter the condensed water from the jacket to remove impurities, thereby preventing the condensed water from entering the steam generator 350 and clogging the pipeline when evaporating again, so that the equipment can operate stably for a long time.

[0038] like Figure 3 As shown, optionally, the stirring unit includes a motor 410 , a rotating shaft 420 and a rotating stirring paddle 430 , the output end of the motor 410 is connected to one end of the rotating shaft 420 , and a plurality of rotating stirring paddles 430 are arranged on the outer side of the rotating shaft 420 .

[0039] The rotating stirring paddle 430 includes a fixed sleeve 431, a bearing 432, a connecting rod 433 and a stirring blade 434. The fixed sleeve 431 is sleeved on the outer side of the rotating shaft 420. The fixed sleeve 431 is fixedly provided with a bearing 432 around the axial side of the rotating shaft 420. The bearing 432 is connected to one end of the connecting rod 433. The stirring blade 434 is arranged on the outer side of the connecting rod 433.

[0040] Specifically, the motor 410 provides power and drives the rotating shaft 420 to rotate. The rotating shaft 420 drives the rotating stirring paddle 430 to rotate, stirring the material in the kettle body 1, improving the heat exchange efficiency between the material in the kettle body 1 and the medium in the jacket 2, thereby improving the crystallization efficiency.

[0041] At the same time, the rotating shaft 420 includes a fixed sleeve 431, a bearing 432, a connecting rod 433 and a stirring blade 434. The fixed sleeve 431 is sleeved on the outer side of the rotating shaft 420. The fixed sleeve 431 is fixedly provided with a bearing 432 around the axial side of the rotating shaft 420. The fixed sleeve 431 is fixedly connected to the outer ring of the bearing 432 for fixing the bearing 432. The inner ring of the bearing 432 is fixedly connected to one end of the connecting rod 433. In this way, when the motor 410 is started, the rotating shaft 420 rotates, and the connecting rod 433 and the stirring blade 434 are also driven to rotate on the radial direction of the rotating shaft 420, and at the same time contact with the material in the kettle body 1, stir the material in the kettle body 1, and improve the heat exchange between the material and the medium in the jacket 2. At the same time, as the connecting rod 433 and the stirring blade 434 rotate around the rotating shaft 420, due to the contact and interaction with the material, the connecting rod 433 and the stirring blade 434 rotate around the direction of rotation of the bearing under the rotation of the bearing 432, further improving the agitation of the material, facilitating the heat exchange between the material and the medium in the jacket 2, and further facilitating the precipitation of crystals.

[0042] like Figure 2 As shown, optionally, a first temperature sensor 140 is disposed inside the kettle body 1 , a second temperature sensor 230 is disposed inside the jacket 2 , and a second medium control valve 211 is connected to the medium inlet 210 .

[0043] Specifically, the first temperature sensor 140 is used to detect the temperature of the material in the kettle body 1, and the second temperature sensor 230 is used to detect the temperature of the medium in the jacket 2. The medium inlet 210 is connected to the second medium control valve 211. When the temperature of the material in the kettle body 1 detected by the first temperature sensor 140 is lower than the first temperature preset value, the opening of the second medium control valve 211 is increased to increase the amount of the medium entering the jacket 2, so that the temperature of the material in the kettle body 1 reaches the first temperature preset value.

[0044] When the temperature of the medium in the jacket 2 detected by the second temperature sensor 230 reaches a second preset temperature value, the first medium control valve 330 is closed. The second preset temperature value is the temperature of the cooling medium.

[0045] like Figure 4 As shown, optionally, the crystallization kettle is further provided with a controller 5, which is respectively connected to the liquid level meter 320, the first medium control valve 330, the first temperature sensor 140, the second temperature sensor 230, the motor 410 and the second medium control valve 211.

[0046] Specifically, the controller 5 controls the opening of the first medium control valve 330 and the second medium control valve 211 according to the signal values ​​of the liquid level meter 320 , the first temperature sensor 140 , and the second temperature sensor 230 , and controls the start and stop of the motor 410 .

[0047] Optionally, the first medium control valve 330 is a one-way valve.

[0048] Specifically, the first medium control valve 330 is a one-way valve, which prevents the liquid in the medium buffer tank 340 from returning to the jacket 2 again, and helps to efficiently and stably perform heat exchange in the jacket 2.

[0049] The technical solution of the present application is described in detail below with reference to specific embodiments.

[0050] The operation flow of the crystallization kettle in this embodiment is as follows:

[0051] The 3-chloro-2-hydrazinopyridine solution and hydrochloric acid are introduced into the crystallization kettle from the feed port 110 to generate a solution containing 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-carboxylic acid ethyl ester.

[0052] Heating and distilling ethanol: The controller 5 opens the second medium control valve 211, and water vapor is input from the medium inlet 210. The water vapor has a relatively high temperature. The water vapor enters the jacket 2 from the medium inlet 210, rises and diffuses in the jacket 2, and exchanges heat with the material in the kettle body 1, so that the temperature of the material in the kettle body rises. At this time, the controller 5 controls the motor 410 to start, drive the rotating shaft 420 to rotate, and drive the connecting rod 433 and the stirring blade 434 to rotate on the radial direction of the rotating shaft 420. When the connecting rod 433 and the stirring blade 434 rotate around the rotating shaft 420, due to contact and interaction with the material, the connecting rod 433 and the stirring blade 434 rotate around the direction of the bearing rotation under the rotation of the bearing 432, further improving the stirring of the material. The heat exchange efficiency between the material and the water vapor in the jacket 2 is improved, so that the ethanol can be quickly and efficiently distilled from the gas outlet 120, and the amount of the solution in the kettle body 1 is reduced, so that the solution in the kettle body 1 reaches a saturated state.

[0053] When the liquid level signal received by the controller 5 from the liquid level meter 320 reaches the first preset liquid level, the first medium control valve 330 on the medium outlet pipe 310 is opened to temporarily store the condensate in the jacket in the medium buffer tank 340. When the condensate level drops to the second preset liquid level value, the first medium control valve 330 is closed. The second preset liquid level value is set to at least make the liquid level higher than the connection between the bottom of the jacket 2 and the medium outlet pipe 310. When the temperature of the material in the kettle body 1 detected by the first temperature sensor 140 is lower than the first temperature preset value, the opening of the second medium control valve 211 is increased to increase the amount of medium entering the jacket 2, so that the temperature of the material in the kettle body 1 reaches the first temperature preset value.

[0054] Cooling and crystallization: After the ethanol is evaporated, the solution in the kettle 1 reaches a saturated state. At this time, the temperature of the material in the kettle 1 is reduced, so that the crystals of 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-ethyl formate are precipitated. The controller 5 opens the second medium control valve 211, and the cooling medium is input into the jacket 2 through the medium inlet 210. When the temperature of the medium in the jacket 2 detected by the second temperature sensor 230 reaches the second preset temperature value, the first medium control valve 330 is closed, and the second preset temperature value is the temperature of the cooling medium. The cooling medium enters the jacket 2 and performs heat exchange with the material in the kettle 1. The temperature of the material in the kettle 1 is reduced, so that the crystals are precipitated. The cooling medium is discharged from the medium outlet 220, so as to achieve the purpose of crystallizing 1-(3-chloro-2-pyridyl)-3-pyrazolidinone-5-ethyl formate. Finally, the crystals are discharged from the discharge port 130.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, ordinary technicians in the field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, 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 crystallization kettle, characterized in that: include: A kettle body (1), a jacket (2) and a stirring unit, wherein the jacket (2) is arranged on the outer periphery of the kettle body (1), the top of the kettle body (1) is also provided with a feed inlet (110) and a gas outlet (120), the bottom of the kettle body (1) is provided with a discharge port (130), the stirring unit is arranged at the center of the kettle body (1), the lower part of the jacket (2) is provided with a medium inlet (210), and the upper part of the jacket (2) is provided with a medium outlet (220); A medium recovery unit is arranged outside the jacket (2), and the medium recovery unit comprises a medium outlet pipe (310), a liquid level meter (320), a first medium control valve (330) and a medium buffer tank (340). One end of the medium outlet pipe (310) is connected to the bottom of the jacket (2), and the other end of the medium outlet pipe (310) is connected to the medium buffer tank (340). The liquid level meter (320) is located at the bottom of the jacket (2), and the first medium control valve (330) is arranged on the medium outlet pipe (310).

2. The crystallization kettle according to claim 1, characterized in that The outlet of the medium buffer tank (340) is connected to a water vapor generator (350), and the water vapor outlet of the water vapor generator (350) is in communication with the medium inlet (210).

3. The crystallization kettle according to claim 1, characterized in that A filter (360) is provided at the connection between the medium outlet pipe (310) and the medium buffer tank (340).

4. The crystallization kettle according to any one of claims 1 to 3, characterized in that: The stirring unit comprises a motor (410), a rotating shaft (420) and a rotating stirring paddle (430), wherein the output end of the motor (410) is connected to one end of the rotating shaft (420), and a plurality of rotating stirring paddles (430) are arranged on the outer side of the rotating shaft (420); The rotating stirring paddle (430) comprises a fixed sleeve (431), a bearing (432), a connecting rod (433) and a stirring blade (434); the fixed sleeve (431) is sleeved on the outer side of the rotating shaft (420); the fixed sleeve (431) is fixedly provided with the bearing (432) around the axial side of the rotating shaft (420); the bearing (432) is connected to one end of the connecting rod (433); and the stirring blade (434) is arranged on the outer side of the connecting rod (433).

5. The crystallization kettle according to claim 4, characterized in that: A first temperature sensor (140) is arranged inside the kettle body (1), a second temperature sensor (230) is arranged inside the jacket (2), and a second medium control valve (211) is connected to the medium inlet (210).

6. The crystallization kettle according to claim 5, characterized in that: The crystallization kettle is also provided with a controller (5), and the controller (5) is respectively connected to the liquid level meter (320), the first medium control valve (330), the first temperature sensor (140), the second temperature sensor (230), the motor (410) and the second medium control valve (211).

7. The crystallization kettle according to claim 6, characterized in that: The first medium control valve (330) is a one-way valve.

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