A static crystallization device, a static crystallization method and its application

Abstract

The present invention discloses a static crystallization device, a static crystallization method and its application. The static crystallization device comprises a device body, a heat exchanger and a temperature control unit. A barrel jacket is arranged on the outer wall side of the barrel of the device body; the heat exchanger is arranged inside the device body, and a first heat exchange medium inlet and a first heat exchange medium outlet are arranged on the heat exchanger; a second heat exchange medium inlet is arranged on one side of the barrel jacket, and a second heat exchange medium outlet is arranged on the side opposite to the second heat exchange medium inlet; the temperature control unit comprises a first temperature controller and a second temperature controller, the first temperature controller is arranged between the first heat exchange medium inlet and the first heat exchange medium outlet, and the second temperature controller is arranged between the second heat exchange medium inlet and the second heat exchange medium outlet. The present invention can significantly improve the efficiency of the crystallization and sweating process, and significantly reduce the energy consumption of the static crystallization process.

Description

Technical Field

[0001] The present invention relates to the technical field of static crystallization, and in particular to a static crystallization device, a static crystallization method and applications thereof. Background Art

[0002] Crystallization is a commonly used chemical separation method. The crystallization process can be used to separate and purify components based on the difference in melting points, and ultimately obtain the target product. Crystallization mainly includes evaporative crystallization, solvent crystallization, and melt crystallization. The melt crystallization process does not require a solvent, avoiding the solvent recovery step, which is not only more environmentally friendly, but also avoids affecting product quality. It is especially suitable for separation processes with high product purity requirements.

[0003] The melt crystallization process further includes suspended melt crystallization and layered melt crystallization. Among them, the crystals of suspended melt crystallization are suspended in the crystallization solution under stirring, and the crystals and the crystallization mother liquor need to be separated by means of centrifugal separation or filtration. The crystals of layered melt crystallization are directly attached to the cooling interface and can be directly separated from the mother liquor, which not only avoids the damage to the crystal particles during the mechanical separation process, but also avoids the separation difficulties, material blockage, product loss and other problems that are prone to occur in the solid-liquid separation of high melting point systems. It is particularly suitable for the crystallization separation of high melting point systems. According to the flow state of the molten liquid around the crystallization layer, layered melt crystallization further includes falling film crystallization and static crystallization.

[0004] In recent years, with the continuous development of food, medicine, materials and other fields, especially the continuous deepening of high-end chemical research, the requirements for product purity are getting higher and higher. Therefore, the use of melt crystallization process, especially static crystallization process, is becoming more and more widespread. However, in the traditional static crystallization process, the crystallization and sweating efficiency is low. Not only is the crystallization temperature low and the sweating temperature high, but it is often necessary to perform secondary crystallization of the crystallization mother liquor and sweating sweat to improve the efficiency of the entire crystallization process, which not only makes the process more complicated, but also increases the equipment and operating costs, and the energy consumption is also greater.

[0005] CN103754848A discloses a U-shaped tube static multi-stage melting crystallization method for preparing electronic-grade phosphoric acid. The technical scheme is to use food-grade phosphoric acid liquid as raw acid, add seed crystals to the wall of the U-shaped crystallization tube, pass ice brine into the U-shaped crystallization tube to cool the raw acid, and load the raw acid into the reaction tank. Crystals begin to grow outward from the surface of the U-shaped crystallization tube. When the weight of the crystal layer reaches 30-40% of the weight of the raw acid, stop passing and draining the ice brine in the U-shaped tube, and discharge the liquid phase; turn on the heating system to make the temperature inside the U-shaped crystallization tube rise slowly in a gradient, the crystal layer gradually melts, and four-stage sweating is performed; finally, the temperature and concentration of phosphoric acid are adjusted to obtain the finished electronic-grade phosphoric acid. This scheme is simple to operate, has low energy consumption, high product purity, and high product recovery rate. It is a production method with industrial application value that can meet the requirements for upgrading electronic-grade phosphoric acid products and has good economic benefits. However, the addition of solid crystal seeds is very inconvenient to operate and is not conducive to industrial production. More importantly, it cannot guarantee the uniformity of the crystallization process and is very prone to local crystallization, which has a great impact on subsequent sweating and the final product quality.

[0006] CN102502530A discloses a method for producing electronic-grade sulfuric acid by static melt crystallization, which comprises cooling and crystallizing high-purity electronic-grade sulfuric acid to produce crystal seeds; adding raw sulfuric acid to a sleeve-type crystallizer to cool and add sulfuric acid seeds of 0.2% to 5% of the raw material mass, and crystallizing in a step-by-step cooling manner. After the crystallization is completed, the crystal is cultivated. The residual liquid is released, and the temperature is gradually increased to sweat. After the sweating is completed, the sweating liquid is released, and the temperature is increased again to melt the crystal to obtain a primary crystallization product. The obtained primary crystallization liquid is repeated with the above operation for secondary static melt crystallization to obtain a secondary crystallization product, and the quality can reach MOS to BV-III level. The electronic-grade sulfuric acid produced by the present invention can reach MOS to BV-III level. However, since the static crystallizer contains a large number of heat exchange elements, such as fins or heat exchange tubes, reasonable auxiliary means are required to ensure the uniformity of the addition of crystal slurry; in addition, it is necessary to first prepare the crystal slurry through external refrigeration, and add the crystal slurry through power equipment such as pumps and circulate the material, which is bound to generate more energy consumption.

[0007] Therefore, the existing static crystallization method has the defects of low crystallization efficiency, low sweating efficiency and high energy consumption. Based on this, the present invention aims to provide a new type of static crystallization device, and by regulating a reasonable and effective process method, fundamentally improve the crystallization efficiency and sweating efficiency, thereby improving the efficiency of the entire static crystallization process. Summary of the invention

[0008] In view of the above problems existing in the prior art, the present invention provides a static crystallization device, a static crystallization method and applications thereof. The device and method provided by the present invention have high crystallization efficiency, high sweating efficiency and low energy consumption.

[0009] A first aspect of the present invention provides a static crystallization device, comprising a device body, a heat exchanger and a temperature control unit, wherein a barrel jacket is provided on the outer wall side of the barrel of the device body;

[0010] The heat exchanger is arranged inside the device body, and a first heat exchange medium inlet and a first heat exchange medium outlet are arranged on the heat exchanger;

[0011] A second heat exchange medium inlet is provided on one side of the cylinder jacket, and a second heat exchange medium outlet is provided on the side opposite to the second heat exchange medium inlet;

[0012] The temperature control unit includes a first temperature controller and a second temperature controller, the first temperature controller is arranged between the first heat exchange medium inlet and the first heat exchange medium outlet, and the second temperature controller is arranged between the second heat exchange medium inlet and the second heat exchange medium outlet.

[0013] The inventors of the present invention have found that the traditional static crystallization device does not have an external jacket, and only introduces a heat exchange medium into the heat exchanger. During the cooling and crystallization process of the raw material to be crystallized, the cold gradually diffuses from the heat exchanger to the periphery and gradually disperses to the entire crystallization device, resulting in too much supersaturation in the crystallization process. It is necessary to reduce the crystallization temperature to a lower temperature to produce crystals. Therefore, the crystallization efficiency is very low and the energy consumption is also very high. Similarly, during the sweating process, as the heat diffuses outward, the heat exchange temperature difference between the heat exchanger and the wall of the device body is small, and the sweating efficiency is low, resulting in poor product quality. In order to increase product output, it is usually necessary to increase the sweating temperature or extend the sweating time to allow the impurities remaining in the crystal to "sweat" and seep out, resulting in higher energy consumption in the sweating process.

[0014] The static crystallization device provided by the present invention can effectively improve the crystallization efficiency, sweating efficiency and product quality, and reduce energy consumption by arranging a jacket outside the device and strictly controlling the temperature difference between the crystallization temperature of the heat exchange medium and the material to be crystallized, and the sweating temperature of the heat exchange medium and the crystals after crystallization.

[0015] According to some embodiments of the static crystallization device of the present invention, an inlet for the material to be crystallized is provided at the upper part of the device body, and a material outlet is provided at the lower part of the device body. The mother liquor remaining in the crystallization process, the sweat in the sweating process, and the molten liquid of the crystal product after sweating can all be discharged from the material outlet. In different embodiments of the present invention, a nitrogen inlet and a pressure measuring port can also be provided on the device body.

[0016] According to some embodiments of the static crystallization device of the present invention, the material to be crystallized is first subjected to heat exchange in a raw material heat exchanger before being fed into the device body, so as to control the temperature of the material when it is fed into the device body.

[0017] According to some embodiments of the static crystallization device of the present invention, a bottom jacket is further provided on the bottom outer wall side of the device body, a third heat exchange medium inlet is provided on one side of the bottom jacket, and a third heat exchange medium outlet is provided on the side opposite to the third heat exchange medium inlet.

[0018] According to some embodiments of the static crystallization device of the present invention, the temperature control unit further includes a third temperature controller, and the third temperature controller is disposed between the third heat exchange medium inlet and the third heat exchange medium outlet.

[0019] According to some embodiments of the static crystallization device of the present invention, when the second heat exchange medium in the barrel jacket and the third heat exchange medium in the barrel bottom jacket are the same heat exchange medium, the second temperature controller is also arranged between the third heat exchange medium inlet and the third heat exchange medium outlet.

[0020] In different embodiments of the present invention, the second heat exchange medium in the barrel jacket and the third heat exchange medium in the barrel bottom jacket may be the same or different. When the same heat exchange medium is used in the barrel jacket and the barrel bottom jacket, and the temperature of the heat exchange medium is the same, the closing of different valves is controlled and the temperature of the second heat exchange medium and the third heat exchange medium is controlled simultaneously by a second temperature controller.

[0021] According to some embodiments of the static crystallization device of the present invention, a first control valve is provided on the pipeline between the second heat exchange medium inlet and the second temperature controller.

[0022] According to some embodiments of the static crystallization device of the present invention, a second control valve is provided on the pipeline between the third heat exchange medium inlet and the second temperature controller.

[0023] According to some embodiments of the static crystallization device of the present invention, a third control valve is provided on the pipeline between the third heat exchange medium inlet and the third temperature controller.

[0024] In different embodiments of the present invention, different temperature controllers are controlled to work by controlling the opening and closing modes of the first control valve, the second control valve and the third control valve.

[0025] According to some embodiments of the static crystallization device of the present invention, the heat exchanger is selected from at least one group of fins and / or at least one group of heat exchange tubes.

[0026] According to some embodiments of the static crystallization device of the present invention, a support assembly is provided on the heat exchanger for fixing the crystals formed on the heat exchanger to prevent the crystals from sliding off the fins or the surface of the heat exchange tubes during the sweating process.

[0027] A second aspect of the present invention provides a static crystallization method using the above-mentioned static crystallization device, the crystallization method comprising the steps of:

[0028] Step A, feeding the material to be crystallized into the device body;

[0029] Step B, introducing a second heat exchange medium into the barrel jacket, and turning on the second temperature controller to control the temperature of the second heat exchange medium to be higher than the crystallization temperature of the material to be crystallized;

[0030] Step C, introducing a first heat exchange medium into the heat exchanger, and turning on the first temperature controller to control the temperature inside the heat exchanger to drop, so that crystals precipitate on the outer wall surface of the heat exchanger;

[0031] Step D, discharging the remaining mother liquor from the crystallization process, and controlling the temperature of the second heat exchange medium to be lower than the initial sweating temperature of the heat exchanger by the second temperature controller;

[0032] Step E: adjusting the temperature of the first heat exchange medium by the first temperature controller so that sweat is precipitated from the crystal layer after crystallization.

[0033] The static crystallization method provided by the present invention effectively improves the radial temperature gradient of the traditional static crystallization device during the crystallization process, can significantly reduce the supersaturation of the material to be crystallized in the static crystallization device, so that it can be crystallized at a higher temperature, thereby effectively reducing the amount of cooling required for the crystallization process, improving the crystallization efficiency, and reducing costs. In addition, if the crystallization mother liquor is further subjected to secondary crystallization to improve the yield of the entire static crystallization process, thereby improving the production capacity and reducing the cost, the improvement in the crystallization efficiency at this time helps to significantly reduce the amount of cooling consumed by the crystallization mother liquor during the secondary crystallization, that is, significantly reducing the energy consumption of the crystallization process.

[0034] Furthermore, in the static crystallization method provided by the present invention, the radial temperature gradient in the sweating process of step D and step E can be effectively improved, the problem of difficulty in sweating due to insufficient temperature difference between the heat exchanger and the wall of the device body can be avoided, the sweating efficiency can be improved, and a lower sweating temperature can be used to achieve the same sweating effect. Not only can the product quality of the obtained crystals be guaranteed, but also the heat consumption required by the heat exchanger during the sweating process is reduced, that is, the energy consumption of the sweating process is reduced.

[0035] According to some embodiments of the static crystallization method of the present invention, after step E, the method further includes: after the sweat is sweated out from the crystal layer after crystallization, the sweat is discharged from the material outlet at the bottom of the device body. Further, after the sweating process is completed, the remaining crystals in the device body are melted and discharged from the material outlet at the bottom of the device body to obtain a qualified product.

[0036] According to some embodiments of the static crystallization method of the present invention, step B further comprises: introducing a third heat exchange medium into the bottom jacket of the barrel, and turning on the third temperature controller to control the temperature of the third heat exchange medium to be higher than the crystallization temperature of the material to be crystallized.

[0037] According to some embodiments of the static crystallization method of the present invention, step D further comprises: controlling the temperature of the third heat exchange medium to be not lower than the end point sweating temperature of the heat exchanger by the third temperature controller.

[0038] According to some embodiments of the static crystallization method of the present invention, step B also includes: introducing a third heat exchange medium into the bottom jacket of the barrel, wherein the third heat exchange medium is the same as the second heat exchange medium, and controlling the temperature of the third heat exchange medium to be higher than the crystallization temperature of the material to be crystallized by the second temperature controller.

[0039] In different embodiments of the present invention, the specific material selection of the first heat exchange medium, the second heat exchange medium and the third heat exchange medium is not limited, and different heat exchange mediums can be selected according to different materials and the control of the crystallization and sweating temperature ranges of different materials. For example, in some embodiments of the present invention, the first heat exchange medium, the second heat exchange medium and the third heat exchange medium can be the same or different, and each is independently selected from at least one of water, ethanol, ethylene glycol and heat transfer oil.

[0040] According to some embodiments of the static crystallization method of the present invention, step A further comprises: the material to be crystallized is sent into the device body after heat exchange in the raw material heat exchanger, and preferably, the temperature of the material to be crystallized sent into the device body is 0.5-2°C higher than the initial crystallization temperature. Among them, due to the forced circulation of the material in the raw material heat exchanger, the heat exchange efficiency is significantly higher than that of the static crystallization device, and the use of the raw material heat exchanger to pre-cool the raw material to be crystallized can significantly reduce the cold consumption before the initial crystallization point, thereby reducing the energy consumption of the subsequent crystallization process.

[0041] According to some embodiments of the static crystallization method of the present invention, in step B, the temperature of the second heat exchange medium and the third heat exchange medium is controlled to be 5-15° C. higher than the initial crystallization temperature of the material to be crystallized.

[0042] According to some embodiments of the static crystallization method of the present invention, in step D, the temperature of the second heat exchange medium is controlled to be 7-15° C. lower than the initial sweating temperature of the heat exchanger.

[0043] According to some embodiments of the static crystallization method of the present invention, in step D, the temperature of the third heat exchange medium is controlled to be 0-5° C. higher than the endpoint sweating temperature of the heat exchanger.

[0044] According to a preferred embodiment of the static crystallization method of the present invention, during the crystallization process of step B and step C, the temperature of the second heat exchange medium in the barrel jacket and the third heat exchange medium in the barrel bottom jacket may be the same or different. Preferably, the temperature of the second heat exchange medium in the barrel jacket and the third heat exchange medium in the barrel bottom jacket is controlled to be the same, and both are temperature-controlled by a second temperature controller, which can further reduce equipment control and operating costs.

[0045] According to a specific embodiment of the static crystallization method of the present invention, during the crystallization process of step B and step C, the temperature of the heat exchange medium in the barrel jacket and the barrel bottom jacket is controlled to be constant, that is, controlled to be a constant temperature operation, and the temperature of the second heat exchange medium in the barrel jacket and the third heat exchange medium in the barrel bottom jacket are controlled to be higher than the initial crystallization temperature of the material to be crystallized in the device body. Specifically, the temperature of the second heat exchange medium in the barrel jacket and the third heat exchange medium in the barrel bottom jacket is controlled to be 5 to 15°C higher than the initial crystallization temperature of the material to be crystallized.

[0046] According to a specific embodiment of the static crystallization method of the present invention, during the sweating process of step D and step E, the temperature of the heat exchange medium in the barrel jacket and the barrel bottom jacket is controlled to be constant, that is, controlled to be a constant temperature operation, and the temperature of the second heat exchange medium in the barrel jacket is controlled to be lower than the initial sweating temperature of the heat exchanger, and the temperature of the third heat exchange medium in the barrel bottom jacket is controlled to be higher than the terminal sweating temperature of the heat exchanger. Specifically, the temperature of the second heat exchange medium in the barrel jacket is controlled to be 7 to 15°C lower than the initial sweating temperature of the heat exchanger, and at the same time, the temperature of the third heat exchange medium in the barrel bottom jacket is controlled to be 0 to 5°C higher than the terminal sweating temperature of the heat exchanger.

[0047] According to a specific embodiment of the static crystallization method of the present invention, during the crystallization process and the sweating process, the temperature of the second heat exchange medium in the cylinder jacket is controlled to be variable, that is, it is controlled to be a variable temperature operation. In the crystallization process of step B and step C, the temperature difference between the second heat exchange medium in the cylinder jacket and the material to be crystallized in the device body is controlled to be maintained at a certain temperature, so that the crystallization process of the material can be realized at a higher temperature. In the sweating process of step D and step E, the temperature difference between the second heat exchange medium in the cylinder jacket and the crystallization crystals in the device body is controlled to be maintained at a certain temperature, so that the sweating process of the crystal layer can be realized at a lower temperature.

[0048] Therefore, the static crystallization method provided by the present invention not only ensures the temperature difference between the crystallization and sweating processes, but also reduces the energy consumption in the barrel jacket and the barrel bottom jacket as much as possible, thereby reducing the energy consumption of the crystallization and sweating processes.

[0049] The third aspect of the present invention provides an application of the above-mentioned static crystallization device or the above-mentioned static crystallization method in crystallization purification, but it is not limited thereto.

[0050] According to the preferred embodiment of the application described in the present invention, the application is particularly suitable for the crystallization purification process of high melting point materials such as ethylene carbonate, tetramethylene, p-dichlorobenzene, 2,6-diisopropylnaphthalene, glycolide and lactide, and is also suitable for the crystallization purification process of low melting point materials such as p-xylene.

[0051] Beneficial effects of the present invention:

[0052] The static crystallization device and static crystallization method provided by the present invention improve the crystallization efficiency and sweating efficiency by controlling the temperature of the barrel jacket, and can adopt a lower sweating temperature, cooperate with the reasonable temperature control of the barrel bottom jacket, and ensure the smooth discharge of sweat and crystals after melting. At the same time, the double jacket method of the barrel jacket and the barrel bottom jacket can avoid the use of a single jacket in the crystallization device, which requires the temperature of the entire jacket to be higher than the terminal sweating temperature. The technical solution of the present invention can further reduce the energy consumption of the entire static crystallization process.

[0053] Furthermore, the static crystallization device and static crystallization method provided by the present invention adopt a double jacket method of a cylinder jacket and a cylinder bottom jacket, and in the static crystallization method, the temperature of the heat exchange medium in the cylinder jacket and the cylinder bottom jacket during the crystallization process is defined as being higher than the crystallization temperature of the material to be crystallized, and the temperature of the heat exchange medium in the cylinder jacket during the sweating process is defined as being lower than the initial sweating temperature, and the temperature of the heat exchange medium in the cylinder bottom jacket is higher than the terminal sweating temperature, so that in both the crystallization process and the sweating process, the radial temperature gradient in the crystallization device can be effectively improved, the efficiency of the crystallization process and the sweating process can be improved, and the crystallization temperature in the cooling crystallization process can be higher, and the sweating temperature in the heating sweating process can be lower, thereby reducing the cold required for the crystallization process and the heat required for the sweating process, and reducing energy consumption. At the same time, the improvement of the crystallization efficiency and the sweating efficiency can significantly reduce the cold consumption in the secondary crystallization process of the crystallization mother liquor and the sweating sweat liquid, and greatly reduce the energy consumption of the entire static crystallization process.

[0054] The static crystallization device and crystallization method provided by the present invention are suitable for crystallization purification of various materials. Preferably, the material to be crystallized can be high melting point materials such as ethylene carbonate, durene, p-dichlorobenzene, 2,6-diisopropylnaphthalene, glycolide, lactide, and low melting point materials such as p-xylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a schematic diagram of the structure of the static crystallization device provided in Example 1 of the present invention.

[0056] Description of reference numerals:

[0057] 1. Device body; 2. Cylinder jacket; 3. Cylinder bottom jacket; 4. Heat exchanger; 5. Support assembly; 6. Inlet for material to be crystallized; 7. Material outlet; 8. Inlet for second heat exchange medium; 9. Outlet for second heat exchange medium; 10. Inlet for third heat exchange medium; 11. Outlet for third heat exchange medium; 12. Thermocouple; 13. First control valve; 14. Second control valve; 15. Third control valve; 16. First temperature controller; 17. Second temperature controller; 18. Third temperature controller; 19. Raw material heat exchanger; DETAILED DESCRIPTION

[0058] In order to make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments and drawings. These embodiments are only for illustration and are not intended to limit the application scope of the present invention.

[0059] [Example 1]

[0060] like Figure 1 As shown, the static crystallization device provided in this embodiment includes a device body 1, a heat exchanger 4 arranged in the internal cavity of the device body 1, a temperature control unit and a raw material controller 19.

[0061] The temperature control unit includes a first temperature controller 16 , a second temperature controller 17 , and a third temperature controller 18 .

[0062] The upper part of the device body 1 is provided with a material inlet 6 for crystallization, and the bottom is provided with a material outlet 7. A thermocouple 12 is provided in the internal cavity of the device body 1. The outer wall side of the cylinder of the device body 1 is provided with a cylinder jacket 2, and the outer wall side of the bottom of the device body 1 is provided with a cylinder bottom jacket 3.

[0063] The heat exchanger 4 is provided with a first heat exchange medium inlet and a first heat exchange medium outlet, and a support assembly 5 is also provided on the surface of the heat exchanger 4 .

[0064] The lower part of one side of the barrel jacket 2 is provided with a second heat exchange medium inlet 8, and the upper part of the opposite side is provided with a second heat exchange medium outlet 9. The barrel bottom jacket 3 is provided with a third heat exchange medium inlet 10 on one side, and a third heat exchange medium outlet 11 on the opposite side.

[0065] The first temperature controller 16 is arranged between the first heat exchange medium inlet and the first heat exchange medium outlet. The second temperature controller 17 is arranged between the second heat exchange medium inlet 8, the third heat exchange medium inlet 10, the second heat exchange medium outlet 9, and the third heat exchange medium outlet 11. The third temperature controller 18 is arranged between the third heat exchange medium inlet 10 and the third heat exchange medium outlet 11.

[0066] A first control valve 13 is provided on the pipeline between the second heat exchange medium inlet 8 and the second temperature controller 17. A second control valve 14 is provided on the pipeline between the third heat exchange medium inlet 10 and the second temperature controller 17. A third control valve 15 is provided on the pipeline between the third heat exchange medium inlet 10 and the third temperature controller 18.

[0067] [Example 2]

[0068] The static crystallization device shown in Example 1 was used to crystallize and purify the crude lactide solution. The first heat exchange medium, the second heat exchange medium and the third heat exchange medium in the following operation process were all heat transfer oil.

[0069] The specific crystallization purification process is:

[0070] The crude lactide solution is precooled to 34° C. through the raw material heat exchanger 19 and fed into the device body 1 through the material inlet 6 for crystallization, wherein the heat exchanger 4 uses fins, and a support assembly 5 is arranged between the fins.

[0071] Close the second control valve 14, open the first control valve 13 and the third control valve 15, control the temperature of the second heat exchange medium in the barrel jacket 2 to 45°C through the second temperature controller 17, and control the temperature of the third heat exchange medium in the barrel bottom jacket 3 to 45°C through the third temperature controller 18. At the same time, the first temperature controller 16 performs program temperature control on the first heat exchange medium in the fins. When the temperature of the first heat exchange medium in the fins is 20°C and the temperature in the cavity of the device body 1 is 32.89°C, crystals begin to adhere to the fins. Continue to cool down, and when the temperature of the first heat exchange medium is 5°C and the temperature in the cavity of the device body 1 is 20.72°C, discharge the mother liquor. According to the gravimetric analysis, the crystallization rate of crude lactide is 70.28%.

[0072] The crude crystals obtained in the above process were sweated, the second control valve 14 was closed, the first control valve 13 and the third control valve 15 were opened, the temperature of the second heat exchange medium in the barrel jacket 2 was controlled to be 22°C by the second temperature controller 17, and the temperature of the third heat exchange medium in the barrel bottom jacket 3 was controlled to be 40°C by the third temperature controller 18. At the same time, the initial sweating temperature of the first heat exchange medium in the fin was controlled to be 30°C by the first temperature controller 16, and the terminal sweating temperature was 37°C. After the sweating process was completed, according to the weight analysis, the sweating rate of the crude lactide crystals was 58.19%.

[0073] [Example 3]

[0074] The operating procedure is the same as that of Example 2, except that the crude lactide solution raw material is replaced by ethylene carbonate raw material, and the temperature control conditions of the crystallization purification process are shown in Table 1 below.

[0075] The crystallization rate of the ethylene carbonate obtained in this example is 81.53%, and the sweating rate of the ethylene carbonate crystals is 50.14%.

[0076] [Example 4]

[0077] The operating procedure is the same as that of Example 2, except that the crude lactide solution raw material is replaced by glycolide raw material, and the temperature control conditions of the crystallization purification process are shown in Table 1 below.

[0078] The crystallization rate of glycolide obtained in this example is 72.45%, and the sweating rate of glycolide crystals is 49.62%.

[0079] [Example 5]

[0080] The operating procedure is the same as that of Example 2, except that the crude lactide solution raw material is replaced by 2,6-diisopropylnaphthalene raw material, and the temperature control conditions of the crystallization purification process are shown in Table 1 below.

[0081] The crystallization rate of 2,6-diisopropylnaphthalene obtained in this example was 75.23%, and the sweating rate of 2,6-diisopropylnaphthalene crystals was 49.25%.

[0082] [Example 6]

[0083] The operating procedure is the same as that of Example 2, except that the crude lactide solution raw material is replaced by durene raw material, and the temperature control conditions of the crystallization purification process are shown in Table 1 below.

[0084] The crystallization rate of durenyl obtained in this example is 66.82%, and the sweating rate of durenyl crystals is 55.38%.

[0085] [Example 7]

[0086] The operating procedure is the same as that of Example 2, except that the crude lactide solution raw material is replaced by p-dichlorobenzene raw material, and the temperature control conditions of the crystallization purification process are shown in Table 1 below.

[0087] The crystallization rate of p-dichlorobenzene obtained in this example is 62.80%, and the sweating rate of p-dichlorobenzene crystals is 51.47%.

[0088] [Example 8]

[0089] The operation process is the same as that of Example 2, except that the crude lactide solution raw material is replaced by p-xylene raw material, and the temperature control conditions of the crystallization purification process are shown in Table 1 below.

[0090] The crystallization rate of p-xylene obtained in this example is 60.39%, and the sweating rate of p-xylene crystals is 50.51%.

[0091] [Comparative Example 1]

[0092] The difference between this comparative example and Example 2 is that the static crystallization device used in this comparative example is not provided with a barrel jacket and a barrel bottom jacket.

[0093] The crude lactide solution is precooled to 34°C through a raw material heat exchanger and fed into the device body through an inlet for the material to be crystallized. The heat exchanger uses fins, and support components are arranged between the fins.

[0094] The heat exchange medium in the fins was programmed to be temperature controlled by an external temperature controller, and the temperature control rate was the same as that in Example 2. When the temperature of the heat exchange medium in the fins was 2°C and the temperature in the cavity of the device body was 16.92°C, crystals began to adhere to the fins. The temperature was continuously lowered, and when the temperature of the heat exchange medium was -5°C and the temperature in the cavity of the device body was 12.37°C, the mother liquor was discharged. According to the gravimetric analysis, the crystallization rate of the crude lactide was 55.46%.

[0095] The crude crystals obtained in the above process were sweated, and the initial sweating temperature of the heat exchange medium in the fins was controlled by an external temperature controller to be 30°C and the terminal sweating temperature to be 37°C, which was the same as the process in Example 2. After the sweating process was completed, according to weight analysis, the sweating rate of the crude lactide crystals was 48.35%. Moreover, at the same sweating rate, the sweating temperature was further increased, and when the terminal sweating temperature was 41°C, the sweating rate of the crude lactide crystals was 58.11%.

[0096] [Comparative Example 2]

[0097] The operating procedure is the same as that of Comparative Example 1, except that the crude lactide solution raw material is replaced by ethylene carbonate raw material, and the temperature control conditions of the crystallization purification process are shown in Table 2 below.

[0098] The crystallization rate of the ethylene carbonate obtained in this comparative example is 73.25%, and the sweating rate of the ethylene carbonate crystals is 40.39%. When the sweating temperature is further increased and the terminal sweating temperature is 38.3° C., the sweating rate of the ethylene carbonate crystals is 49.86%.

[0099] [Comparative Example 3]

[0100] The operating procedure is the same as that of Comparative Example 1, except that the crude lactide solution raw material is replaced by glycolide raw material, and the temperature control conditions of the crystallization purification process are shown in Table 2 below.

[0101] The crystallization rate of glycolide obtained in this comparative example is 61.70%, and the sweating rate of glycolide crystals is 39.97%. When the sweating temperature is further increased and the terminal sweating temperature is 82°C, the sweating rate of glycolide crystals is 49.44%.

[0102] [Comparative Example 4]

[0103] The operating procedure is the same as that of Comparative Example 1, except that the crude lactide solution raw material is replaced by 2,6-diisopropylnaphthalene raw material, and the temperature control conditions of the crystallization purification process are shown in Table 2 below.

[0104] The crystallization rate of 2,6-diisopropylnaphthalene obtained in this comparative example is 64.09%, and the sweating rate of 2,6-diisopropylnaphthalene crystals is 41.23%. When the sweating temperature is further increased and the terminal sweating temperature is 70°C, the sweating rate of 2,6-diisopropylnaphthalene crystals is 49.08%.

[0105] [Comparative Example 5]

[0106] The operating procedure is the same as that of Comparative Example 1, except that the crude lactide solution raw material is replaced with durene raw material, and the temperature control conditions of the crystallization purification process are shown in Table 2 below.

[0107] The crystallization rate of durenyl obtained in this comparative example is 54.14%, and the sweating rate of durenyl crystals is 47.62%. When the sweating temperature is further increased and the terminal sweating temperature is 79° C., the sweating rate of durenyl crystals is 55.31%.

[0108] [Comparative Example 6]

[0109] The operating procedure is the same as that of Comparative Example 1, except that the crude lactide solution raw material is replaced with p-dichlorobenzene raw material, and the temperature control conditions of the crystallization purification process are shown in Table 2 below.

[0110] The crystallization rate of p-dichlorobenzene obtained in this comparative example is 50.56%, and the sweating rate of p-dichlorobenzene crystals is 43.58%. When the sweating temperature is further increased and the terminal sweating temperature is 54° C., the sweating rate of p-dichlorobenzene crystals is 51.29%.

[0111] [Comparative Example 7]

[0112] The operating procedure is the same as that of Comparative Example 1, except that the crude lactide solution raw material is replaced by p-xylene raw material, and the temperature control conditions of the crystallization purification process are shown in Table 2 below.

[0113] The crystallization rate of p-xylene obtained in this comparative example is 50.13%, and the sweating rate of p-xylene crystals is 41.45%. When the sweating temperature is further increased and the terminal sweating temperature is 14°C, the sweating rate of p-xylene crystals is 50.30%.

[0114] Table 1

[0115] Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Raw material temperature ℃ 38 67 68.5 65.5 52 12.5 Crystallization process Cylinder temperature ℃ 42 80 72 78 58 15 Bottom temperature of cylinder ℃ 42 80 72 75 56 15 Initial crystallization point The first heat transfer medium temperature ℃ 35 57 65 60 47 5 Temperature inside the device ℃ 36.35 65.05 66.96 64.93 50.90 9.95 Crystallization endpoint The first heat transfer medium temperature ℃ 17 41 52 40 39 -10 Temperature inside the device ℃ 19.10 52.78 54.28 47.44 45.20 0.98 Crystallization rate % 81.53 72.45 75.23 66.82 62.80 60.39 Sweating process Cylinder temperature ℃ 28 60 56 62 40 0 Bottom temperature of cylinder ℃ 39 85 71 80 54 13.5 Initial sweating temperature ℃ 35 75 63 72 49 10 End point sweating temperature 36.8 80 67 77 52.5 12.5 Sweating rate% 50.14 49.62 49.25 55.38 51.47 50.51

[0116] Table 2

[0117]

[0118]

[0119] By comparing Example 2 and Comparative Example 1, the vertical crystallization device without a double jacket structure is used in Comparative Example 1, and the initial crystallization temperature is greatly reduced by 15.97°C, which consumes more cold. At the same time, at a lower crystallization temperature, the crystallization rate not only does not increase, but is reduced by 14.82% compared with Example 2, and the crystallization efficiency is significantly lower. At this time, to achieve the same crystallization rate, it is necessary to continue to reduce the temperature, resulting in a continued increase in the consumption of cold. In addition, the reduction in the crystallization rate in Comparative Example 1 also leads to a significant increase in the lactide content in the crystallization mother liquor, which in turn leads to a significant increase in the cold during the secondary crystallization of the crystallization mother liquor. Therefore, the energy consumption of Comparative Example 1 will be significantly increased compared with Example 2.

[0120] Similarly, in Comparative Example 1, relative to Example 2, the vertical crystallization device without a double jacket structure is used. At the same sweating temperature, the sweating efficiency of lactide is lower, and the sweating rate is reduced by 9.84%, resulting in a decrease in the product quality of the remaining crystals. At this time, to achieve the same sweating rate, it is necessary to continue to increase the sweating temperature (increased by 4°C) or extend the sweating time, or it is necessary to continue to crystallize and sweat the residual crystals to improve the crystal quality, resulting in more heat consumption. That is to say, when the vertical crystallization device without a double jacket structure is used for sweating in Comparative Example 1, the energy consumption is greater than that of Example 2.

[0121] In summary, by comparing Examples 2-8 with Comparative Examples 1-7, it can be clearly found that the present invention can not only significantly improve the efficiency of the crystallization and sweating processes, but also significantly reduce the energy consumption of the static crystallization process.

[0122] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this field, under the technical enlightenment provided by the present invention, as common knowledge in the field, other equivalent variations and improvements can also be made, which should also be regarded as the protection scope of the present invention.

Claims

1. A static crystallization method, characterized in that: The static crystallization method is carried out using a static crystallization device, which includes a device body, a heat exchanger and a temperature control unit, and a cylinder jacket is arranged on the outer wall side of the cylinder of the device body; The heat exchanger is arranged inside the device body, and a first heat exchange medium inlet and a first heat exchange medium outlet are arranged on the heat exchanger; A second heat exchange medium inlet is provided on one side of the cylinder jacket, and a second heat exchange medium outlet is provided on the side opposite to the second heat exchange medium inlet; The temperature control unit comprises a first temperature controller and a second temperature controller, the first temperature controller is arranged between the first heat exchange medium inlet and the first heat exchange medium outlet, and the second temperature controller is arranged between the second heat exchange medium inlet and the second heat exchange medium outlet; A bottom jacket is also provided on the bottom outer wall side of the device body, a third heat exchange medium inlet is provided on one side of the bottom jacket, and a third heat exchange medium outlet is provided on the side opposite to the third heat exchange medium inlet; The temperature control unit further includes a third temperature controller, and the third temperature controller is arranged between the third heat exchange medium inlet and the third heat exchange medium outlet; The crystallization method comprises the steps of: Step A, feeding the material to be crystallized into the device body; Step B, introducing a second heat exchange medium into the barrel jacket, and turning on the second temperature controller to control the temperature of the second heat exchange medium to be higher than the crystallization temperature of the material to be crystallized; Step C, introducing a first heat exchange medium into the heat exchanger, and turning on the first temperature controller to control the temperature inside the heat exchanger to drop, so that crystals precipitate on the outer wall surface of the heat exchanger; Step D, discharging the remaining mother liquor in the crystallization process, and controlling the temperature of the second heat exchange medium to be lower than the initial sweating temperature of the heat exchanger by the second temperature controller, and controlling the temperature of the third heat exchange medium to be not lower than the terminal sweating temperature of the heat exchanger by the third temperature controller; Step E: adjusting the temperature of the first heat exchange medium by the first temperature controller so that sweat is precipitated from the crystal layer after crystallization.

2. The static crystallization method according to claim 1, characterized in that When the second heat exchange medium in the barrel jacket and the third heat exchange medium in the barrel bottom jacket are the same heat exchange medium, the second temperature controller is further arranged between the third heat exchange medium inlet and the third heat exchange medium outlet.

3. The static crystallization method according to claim 1 or 2, characterized in that A first control valve is provided on the pipeline between the second heat exchange medium inlet and the second temperature controller; and / or, A second control valve is provided on the pipeline between the third heat exchange medium inlet and the second temperature controller; and / or, A third control valve is provided on the pipeline between the third heat exchange medium inlet and the third temperature controller.

4. The static crystallization method according to claim 1 or 2, characterized in that The heat exchanger is selected from at least one group of fins and / or at least one group of heat exchange tubes; and / or, The heat exchanger is provided with a support assembly for fixing the crystals formed on the heat exchanger.

5. The static crystallization method according to claim 1 or 2, characterized in that Step B also includes: introducing a third heat exchange medium into the bottom jacket of the cylinder, and starting the third temperature controller to control the temperature of the third heat exchange medium to be higher than the crystallization temperature of the material to be crystallized.

6. The static crystallization method according to claim 1 or 2, characterized in that Step B also includes: introducing a third heat exchange medium into the bottom jacket of the cylinder, the third heat exchange medium being the same as the second heat exchange medium, and controlling the temperature of the third heat exchange medium to be higher than the crystallization temperature of the material to be crystallized by the second temperature controller.

7. The static crystallization method according to claim 1 or 2, characterized in that Step A also includes: the material to be crystallized is heat exchanged in a raw material heat exchanger and then fed into the device body; and / or, In step B, the temperature of the second heat exchange medium and the third heat exchange medium is controlled to be 5-15° C. higher than the initial crystallization temperature of the material to be crystallized; and / or, In step D, the temperature of the second heat exchange medium is controlled to be 7-15° C. lower than the initial sweating temperature of the heat exchanger; and / or, In step D, the temperature of the third heat exchange medium is controlled to be 0-5° C. higher than the end point sweating temperature of the heat exchanger.

8. The static crystallization method according to claim 7, characterized in that Step A also includes: the temperature of the material to be crystallized fed into the device body is 0.5-2° C. higher than the initial crystallization temperature.

9. Use of the static crystallization method described in any one of claims 1 to 8 in crystallization purification.

10. The use according to claim 9, characterized in that: The application is application in the crystallization and purification of ethylene carbonate, durene, p-dichlorobenzene, 2,6-diisopropylnaphthalene, glycolide, lactide and p-xylene.

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