Double-circulation melt crystallization method and system
By employing a dual-circulation method of heat-conducting medium and circulating gas during the melting and crystallization process, the problems of long sweating time, poor effect, and high energy consumption in the existing technology have been solved, achieving a faster sweating and melting process, improving product purity, and reducing energy consumption.
Patent Information
- Application Number
- CN202512050762.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-27
AI Technical Summary
Existing melt crystallization technology suffers from problems such as long sweating time, poor sweating effect, and high energy consumption.
A dual-cycle melting and crystallization method is adopted, in which heat exchange occurs simultaneously between the heat-conducting medium and the circulating gas on the inner and outer sides of the crystal layer to control the temperature difference. The gas phase circulation is used to accelerate the sweating process, and the gas flow is optimized by combining a gas phase circulation pump and a buffer tank.
It shortens the sweating and melting time, improves product purity, reduces energy consumption, and makes the crystals heat more evenly and efficiently.
Smart Images
Figure CN121731804A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of chemical technology, and in particular to a dual-cycle melt crystallization method and system. Background Technology
[0002] Melt crystallization is an important separation, purification, and concentration technology. Due to its high efficiency and low energy consumption, it is widely used in the refining and purification of chemical intermediates, pharmaceutical intermediates, and biochemical products. Common melt crystallization devices include static crystallizers and falling film crystallizers. A static crystallizer is a container containing many parallel cooling plates or tube bundles. The heat transfer medium (i.e., the hot and cold medium) circulates inside the plates, while the raw material liquid remains in a molten, static state, accumulating on the outside of the plates to form a crystal layer. A falling film crystallizer has many parallel crystallization tube bundles inside. The heat transfer medium circulates outside the tube bundles while the material circulates inside the tube bundles to form a falling film crystal layer. However, after crystallization, the thick layer of crystals adheres to the wall surface, resulting in poor heat transfer during evaporation. Furthermore, the small temperature difference between the heat transfer medium and the crystals during evaporation prolongs the evaporation time. Additionally, the impurity distribution in the crystal layer is characterized by a higher concentration on the outside and a lower concentration on the inside. Relying solely on the heat transfer medium inside the plates is insufficient to efficiently remove the outer impurities, affecting product purity and production efficiency.
[0003] Therefore, existing melting crystallization methods and equipment have drawbacks in chemical production processes, such as long sweating time, poor sweating effect, and high energy consumption. Summary of the Invention
[0004] In view of the shortcomings of the prior art described above, the purpose of this application is to provide a dual-cycle melting and crystallization method and system to solve the problems of long sweating time, poor sweating effect and high energy consumption in the existing melting and crystallization technology.
[0005] To achieve the above and other related objectives, this application provides a dual-cycle melt crystallization method, comprising the following steps: S1. Replace the gas inside the crystallizer with an inert gas and add the molten material to be crystallized into the crystallizer; S2, Cooling crystallization: A heat-conducting medium enters the crystallizer and exchanges heat with the material, causing it to cool down and crystallize, forming a crystal layer. After crystallization is complete, drain the mother liquor; S3, Inducing sweating and raising body temperature: The inert gas inside the crystallizer is used as the circulating gas for gas-phase circulation; A portion of the heat-conducting medium acts as a heat source to exchange heat with the circulating gas, adjusting the temperature of the circulating gas to the target value, and then enters the crystallizer together with another portion of the heat-conducting medium. The heat-conducting medium and the circulating gas simultaneously heat the inner and outer sides of the crystal layer, causing it to heat up and sweat. S4, Heating and Melting: After the sweating process ends, the temperature is raised again to allow for melting.
[0006] Furthermore, step S4 includes: After the sweating process ends, the inert gas inside the crystallizer continues to circulate in the gas phase. All heat-conducting media are used as heat sources to exchange heat with the circulating gas first, and the temperature of the circulating gas is adjusted to reach the target value before entering the crystallizer; The heat-conducting medium and the circulating gas simultaneously heat the inner and outer sides of the crystal layer, causing it to continue to heat up and melt.
[0007] Furthermore, the temperature of the heat-conducting medium entering the crystallizer is controlled to be higher than the temperature of the circulating gas.
[0008] Furthermore, the flow rate ratio of the heat-conducting medium and the circulating gas is adjusted to control the temperature difference between them.
[0009] Furthermore, the circulating gas entering the crystallizer flows from top to bottom.
[0010] Furthermore, the circulating gas entering the crystallizer is controlled to flow uniformly.
[0011] Furthermore, the dual-cycle melt crystallization method employs static crystallization or falling film crystallization processes for melt crystallization.
[0012] This application also provides a dual-cycle melt crystallization system, which includes a crystallizer, a heat transfer medium control unit, and a heat exchanger; The heat transfer medium control unit is used to control the entry and exit of the heat transfer medium into and out of the crystallizer, and to control the temperature of the heat transfer medium; The heat exchanger is the place where the heat transfer medium and the circulating gas exchange heat, and the circulating gas is the inert gas inside the crystallizer. The crystallizer and the heat exchanger are connected by a pipeline to form a gas phase circulation loop for the circulation gas to flow. The crystallizer, the heat transfer medium control unit, and the heat exchanger are connected end to end by pipelines to form a heat transfer medium circulation loop for the flow of heat transfer medium. The crystallizer and the heat transfer medium control unit are connected by a pipeline, forming a heat transfer medium bypass that allows the heat transfer medium to directly enter the crystallizer from the heat transfer medium control unit.
[0013] Furthermore, the dual-cycle melt crystallization system also includes a gas phase circulation pump, which is disposed on the gas phase circulation loop, preferably located between the gas phase outlet and the second fluid inlet, for driving the circulation gas to flow in the gas phase circulation loop.
[0014] Furthermore, the dual-cycle melt crystallization system also includes a gas phase buffer tank, which is disposed on the gas phase circulation loop, preferably located between the gas phase outlet and the gas phase circulation pump, for buffering the circulating gas.
[0015] Furthermore, the circulating gas enters from the top and exits from the bottom in the crystallizer.
[0016] Furthermore, a gas distributor is provided inside the crystallizer, which is used to control the uniform flow of circulating gas entering the crystallizer.
[0017] As described above, the dual-cycle melt crystallization method and system of this application have the following beneficial effects: 1. Fast sweating speed: By controlling the temperature of the heat-conducting medium and the circulating air, heat is exchanged with the crystal from the inner side and the outer surface of the crystal layer at the same time. Compared with the traditional sweating mode, the crystal can heat up faster, the heat exchange effect is faster, and the crystal is heated more evenly. At the same time, the circulating air blows from top to bottom, which can accelerate the liquid dripping speed, thereby making the sweating process shorter and faster.
[0018] 2. Uniform heating during sweating: During sweating, the heat-conducting medium and circulating gas exchange heat with the crystal from both the inside and outside of the crystal layer, making the entire crystal more uniformly heated and the temperature gradient smaller, thus solving the problem of uneven heating of the crystal during sweating in the prior art.
[0019] 3. Improved purity of crystallized products: Because the heat is more evenly distributed during sweating, impurities throughout the crystal are discharged as much as possible through sweating. Moreover, on the one hand, the hot gas washes over the outer surface of the crystal layer, removing more impurities from the outer surface through sweating. On the other hand, the hot gas can more easily enter the interior of the crystal layer's network structure, directly exchanging heat with the material and more easily washing out the impurities encased within the crystal layer. Therefore, with the same amount of sweating, more impurities can be discharged, thereby improving product purity.
[0020] 5. Reduced energy consumption: The method of this application can shorten the sweating time and improve the sweating efficiency, thereby reducing the energy consumption required in the sweating process.
[0021] 6. During the melting stage, gas-phase circulation can continue, and the heat transfer medium can be allowed to pass completely through the heat exchanger before entering the crystallizer. The heat transfer medium and the circulating gas simultaneously heat the crystal to melt it, which can also shorten the melting time and thus improve the efficiency of the entire melting and crystallization process.
[0022] 7. By controlling the temperature of the circulating gas and the temperature difference between them through heating the circulating gas with a heat-conducting medium, the heating temperature required for melting and crystallization of different materials can be adapted. At the same time, since the crystals closer to the heat-conducting medium (i.e., the inner side) in the crystal layer have high purity and high melting point, while the crystals closer to the circulating gas (i.e., the outer side) have low purity and low melting point, the temperature of the heat-conducting medium is higher than that of the circulating gas, which can make the crystals heat more uniformly and the temperature gradient smaller.
[0023] In summary, the technology provided in this application can not only shorten the sweating time and melting time, improve the sweating and melting effect, and shorten the melting and crystallization cycle, but also improve product purity and reduce energy consumption. Attached Figure Description
[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.
[0025] In the attached diagram: Figure 1 This is a flowchart illustrating the dual-cycle melt crystallization method and a structural diagram illustrating the dual-cycle melt crystallization system provided in the embodiments of this application.
[0026] The attached figures are labeled as follows: 1. Crystallizer, 2. Heat transfer medium control unit, 3. Heat exchanger, 4. Gas phase circulation pump, 5. Gas phase buffer tank. Detailed Implementation
[0027] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.
[0028] In this application, unless otherwise stated, the term "multiple" means two or more.
[0029] The character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.
[0030] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.
[0031] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0032] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the present application. However, it will be apparent to those skilled in the art that embodiments of the present application may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the present application.
[0033] Please see Figure 1 One embodiment of this application provides a dual-cycle melt crystallization method, comprising the following steps: S1. Replace the gas inside the crystallizer 1 with an inert gas to ensure the gaseous environment in the crystallizer 1. The inert gas is, for example, nitrogen, but is not limited to this. Inert gases commonly used in the chemical field to maintain an inert protective atmosphere in the reaction environment, such as argon, can also be used. Then, the molten material to be crystallized (i.e., the crude material) is added to the crystallizer 1.
[0034] S2, Cooling crystallization: A heat-conducting medium enters the crystallizer 1, exchanges heat with the material, cools it, and crystallizes to form a crystal layer. The heat-conducting medium in the crystallizer 1 is primarily responsible for precise temperature control, achieving heating or cooling through internal circulation to maintain the temperature gradient required at different stages of the melting and crystallization process. Heat-conducting media include, but are not limited to, water, ethylene glycol aqueous solution, and heat-conducting oil. Common crystallizers 1 typically have internal plates or crystallization tubes. After entering the crystallizer 1, the heat-conducting medium circulates within the plates or falls onto the outside of the crystallization tubes, causing the crystals to adhere to the plates or the inner wall of the crystallization tubes, accumulating to form a crystal layer.
[0035] After crystallization, the mother liquor is discharged. To improve product yield, the mother liquor discharged during the cooling crystallization process can be recycled and reused for further melting and crystallization.
[0036] S3, Inducing sweating and raising body temperature: The inert gas inside crystallizer 1 is used as the circulating gas to perform gas phase circulation; A portion of the heat-conducting medium acts as a heat source to exchange heat with the circulating gas, adjusting the temperature of the circulating gas to the target value, and then enters the crystallizer 1 together with another portion of the heat-conducting medium. The heat-conducting medium and the circulating gas simultaneously heat the inner and outer sides of the crystal layer, causing it to heat up and sweat.
[0037] Gas-phase circulation refers to the extraction of inert gas from crystallizer 1 and its return to crystallizer 1, allowing it to circulate between the inside and outside of crystallizer 1. The temperature of the circulating gas can be controlled by heating it with a heat-conducting medium, thus adapting to the heating temperatures required for melting and crystallizing different materials.
[0038] During the sweating process, the heat-conducting medium and circulating gas simultaneously enter the crystallizer 1, exchanging heat with the crystal from both the inner and outer surfaces of the crystal layer. Compared to the traditional method of heating the crystal from the inside using the heat-conducting medium, this method allows the crystal to heat up faster, resulting in quicker heat exchange and more uniform heating. This shortens the sweating time and significantly reduces the loss of some target product during sweating, a common issue in traditional methods. Simultaneously, the circulating gas purging of the crystal surface accelerates the dripping of sweat. Since the outer surface of the crystal layer contains more impurities, these impurities are more easily removed after being purged by the hot gas, creating numerous tiny pores on the crystal surface. This facilitates the outflow of impurities from the inside of the crystal through sweating, allowing for greater removal of impurities from the outer surface. This improves the sweating effect, shortens the crystallization cycle, increases product purity, and reduces energy consumption.
[0039] S4, Heating and Melting: After the sweating process ends, the temperature is raised again to allow for melting.
[0040] In some embodiments of this application, step S4 includes: after sweating, continuing gas-phase circulation using the inert gas inside the crystallizer 1 as the circulating gas; all the heat-conducting medium acting as a heat source first exchanging heat with the circulating gas to adjust the temperature of the circulating gas to the target value before entering the crystallizer 1; the heat-conducting medium and the circulating gas simultaneously heat the inner and outer sides of the crystal layer, causing it to continue to heat up and melt. During the melting stage, gas-phase circulation can also continue, allowing the heat-conducting medium to completely pass through the heat exchanger 3 before entering the crystallizer 1. The heat-conducting medium and the circulating gas simultaneously heat the crystal to melt it, which can also shorten the melting time and thus improve the efficiency of the entire melting and crystallization process.
[0041] In some embodiments of this application, the temperature of the heat-conducting medium entering the crystallizer 1 is controlled to be higher than the temperature of the circulating gas. For example, the temperature of the heat-conducting medium entering the crystallizer 1 is controlled to be at least 1.5°C higher than the temperature of the circulating gas. Since the crystals near the heat-conducting medium (i.e., the inner side) have higher purity and higher melting points, while the crystals near the circulating gas (i.e., the outer side) have lower purity and lower melting points, a higher temperature for the heat-conducting medium than for the circulating gas allows for more uniform heating of the crystals and a smaller temperature gradient. The temperatures of the heat-conducting medium and the circulating gas, and the magnitude of their temperature difference, are related to the specific material conditions and operating conditions, and can be adjusted accordingly based on actual circumstances.
[0042] In some embodiments of this application, the flow rate ratio of the heat transfer medium and the circulating gas is adjusted to control the temperature difference between them. Controlling the flow rates of the heat transfer medium and the circulating gas allows the temperatures of the heat transfer medium and the circulating gas to reach target values while maintaining a certain temperature difference. For example, if the temperature difference is small, the flow rate of the heat transfer medium exchanging heat with the circulating gas is reduced, and vice versa.
[0043] In some embodiments of this application, the circulating gas entering the crystallizer 1 flows from top to bottom, that is, the circulating gas blows the crystal surface from top to bottom. This can accelerate the liquid dripping speed, remove impurities in the crystal more efficiently, thereby shortening the sweating time and improving the sweating efficiency.
[0044] In some embodiments of this application, the circulating gas entering the crystallizer 1 is controlled to flow uniformly. The uniform flow of hot gas in the crystallizer 1 enables the crystal layers in each region of the crystallizer 1 to be heated more evenly, thereby improving the sweating effect.
[0045] In some embodiments of this application, the cooling crystallization process in step S2 is temperature-controlled by programmed cooling, including at least primary and secondary cooling crystallization. First, the temperature is lowered to near the material's crystallization temperature for primary cooling crystallization. Then, the cooling rate is adjusted to continue cooling for secondary cooling crystallization. The cooling rate of the primary cooling crystallization process is higher than that of the secondary cooling crystallization process, for example, 0.02~1.0℃ / min. The specific cooling rate can be adjusted by changing the inlet temperature and flow rate of the heat transfer medium. Using this gradient cooling method of rapid and slow cooling for programmed cooling is beneficial for improving crystallization efficiency.
[0046] In some embodiments of this application, the heating and sweating process in step S3 involves a programmed continuous heating process, comprising at least a first-stage heating and sweating process and a second-stage heating and sweating process. First, the temperature is raised to near the material's crystallization temperature for the first-stage heating and sweating process. Then, the heating rate is adjusted, and the temperature continues to rise for the second-stage heating and sweating process. The heating rate in the first-stage heating and sweating process is higher than that in the second-stage process, for example, 0.02~0.1℃ / min. The specific heating rate can be adjusted by changing the inlet temperature and flow rate of the heat transfer medium. At the start of sweating, the temperature is first rapidly raised to slightly below the material's crystallization temperature and held for a period of time before slow heating and sweating begins, which helps improve sweating efficiency.
[0047] The technology provided in this application is highly adaptable and can be matched with different melt crystallization processes. In some embodiments of this application, the dual-cycle melt crystallization method uses static crystallization or falling film crystallization processes for melt crystallization. Furthermore, the specific temperature rise and fall ranges, crystallization, sweating, and melting durations during the melt crystallization process are determined based on the type of material to be crystallized and the actual production situation; other process details and parameter conditions not mentioned in this application are selected and implemented based on existing technology and actual conditions.
[0048] Please continue to refer to this. Figure 1 Another embodiment of this application provides a dual-cycle melt crystallization system, which includes a crystallizer 1, a heat transfer medium control unit 2, and a heat exchanger 3.
[0049] The crystallizer 1 is equipped with a material inlet, a material outlet, a heat transfer medium inlet, a heat transfer medium outlet, a circulating gas inlet, and a circulating gas outlet. The specific type of crystallizer is, for example, a static crystallizer or a falling film crystallizer, but is not limited to these. When the crystallizer 1 is a static crystallizer, it has multiple plates inside. When the crystallizer 1 is a falling film crystallizer, it has multiple crystallization tubes inside. The material inlet and material outlet are located at the top and bottom of the crystallizer 1, respectively. Molten material to be crystallized is added to the crystallizer 1 through the material inlet. Then, according to the requirements of each step of the above-described double-circulation melt crystallization method, the heat transfer medium flows into the plates inside the crystallizer 1 through the heat transfer medium inlet or falls outside the crystallization tubes. Circulating gas enters the crystallizer 1 or the crystallization tubes through the circulating gas inlet to exchange heat with the material. The mother liquor and purified product generated during the process are discharged from the material outlet. The heat transfer medium that has undergone heat exchange is sent out of the crystallizer 1 through the heat transfer medium outlet, and the circulating gas that has undergone heat exchange is drawn away through the circulating gas outlet. Preferably, the circulating gas in the crystallizer 1 is top-in and bottom-out, that is, the circulating gas inlet and the circulating gas outlet are respectively located at the top and bottom of the crystallizer 1.
[0050] The heat transfer medium control unit 2 is used to control the entry and exit of the heat transfer medium into and out of the crystallizer 1, and to control the temperature of the heat transfer medium. It is equipped with a heat transfer medium inlet and a heat transfer medium outlet. After the heat transfer medium is sent out of the crystallizer 1 from the heat transfer medium outlet, it enters the heat transfer medium control unit 2 from the heat transfer medium inlet. After being adjusted to the target temperature value, it is then sent back into the crystallizer 1 from the heat transfer medium outlet.
[0051] The heat exchanger 3 is a place for heat exchange between the heat transfer medium and the circulating gas. It is provided with a first fluid inlet and a first fluid outlet for the heat transfer medium to enter and exit, and a second fluid inlet and a second fluid outlet for the circulating gas to enter and exit. The circulating gas is an inert gas inside the crystallizer 1.
[0052] The crystallizer 1 and the heat exchanger 3 are connected by a pipeline to form a gas-phase circulation loop for the circulation gas. Specifically, the gas-phase circulation loop is formed by connecting the circulation gas outlet, the second fluid inlet, the second fluid outlet, and the circulation gas inlet sequentially through pipelines.
[0053] The crystallizer 1, the heat transfer medium control unit 2, and the heat exchanger 3 are connected end-to-end by pipes to form a heat transfer medium circulation loop for the flow of heat transfer medium. Specifically, the heat transfer medium circulation loop is formed by connecting the heat transfer medium outlet, the heat transfer medium inlet, the heat transfer medium outlet, the first fluid inlet, the first fluid outlet, and the heat transfer medium inlet in sequence by pipes.
[0054] The crystallizer 1 and the heat transfer medium control unit 2 are connected by a pipeline, forming a heat transfer medium bypass that allows the heat transfer medium to directly enter the crystallizer 1 from the heat transfer medium control unit 2. Specifically, the heat transfer medium bypass is formed by connecting the heat transfer medium outlet and the heat transfer medium inlet through a pipeline.
[0055] Compared to traditional melting and crystallization systems, the dual-cycle melting and crystallization system provided in this application adds a heat exchanger 3, as well as a gas phase circulation loop and a heat transfer medium circulation loop. This allows melting and crystallization to be carried out according to the above-mentioned dual-cycle melting and crystallization method, thereby solving the defects of traditional melting and crystallization devices such as long sweating time, poor sweating effect and high energy consumption.
[0056] In some embodiments of this application, the heat transfer medium circulation loop and the heat transfer medium bypass are connected to the heat transfer medium inlet via the same pipe, and the heat transfer medium circulation loop and the heat transfer medium bypass are connected to the heat transfer medium outlet via the same pipe. For example, the heat transfer medium outlet is connected to a first main pipe, the first main pipe is connected to a first branch pipe and a second branch pipe, the first branch pipe is connected to a first fluid inlet; the first fluid outlet is connected to the heat transfer medium inlet via a second main pipe, and the other end of the second branch pipe is connected to the middle of the second main pipe. In this way, a heat transfer medium circulation loop is formed between the heat transfer medium control unit 2, the first main pipe, the first branch pipe, the heat exchanger 3, the second main pipe, and the crystallizer 1; a heat transfer medium bypass is formed between the heat transfer medium control unit 2, the first main pipe, the second branch pipe, the second main pipe, and the crystallizer. Furthermore, valves for controlling the flow rate of the heat transfer medium can be installed on the first and second branch pipes. By adjusting the valves, the flow rate of the heat transfer medium entering the heat exchanger 3 can be adjusted while maintaining a stable total flow rate, thereby regulating the heat exchange between the heat transfer medium and the circulating gas, and consequently, regulating the temperature of the circulating gas and the temperature difference between them. Further, flow sensors and temperature sensors can be installed on the pipes. By detecting the temperature and flow rate of the heat transfer medium, as well as the temperature of the circulating gas, and based on the relationship between temperature and flow rate, the flow rate can be adjusted to ensure that the temperatures of the heat transfer medium and the circulating gas reach target values, and that the temperature difference between them remains within a preset range.
[0057] Please continue to refer to this. Figure 1 In some embodiments of this application, the dual-cycle melt crystallization system further includes a gas-phase circulation pump 4, which is disposed on the gas-phase circulation loop, preferably located between the gas-phase outlet and the second fluid inlet, for driving the circulating gas to flow in the gas-phase circulation loop. When gas-phase circulation is required, the gas-phase circulation pump 4 is turned on, which drives the gas in the crystallizer 1 as circulating gas and makes it circulate in the gas-phase circulation loop.
[0058] Please continue to refer to this. Figure 1 In some embodiments of this application, the dual-cycle melt crystallization system further includes a gas phase buffer tank 5. The gas phase buffer tank 5 is disposed on the gas phase circulation loop, preferably at the bottom of the crystallizer 1, and located between the gas phase outlet and the gas phase circulation pump 4, for buffering the circulating gas. Exemplarily, the circulating gas outlet is connected to the gas phase buffer tank 5 via a first gas pipe, the gas phase buffer tank 5 is connected to the gas phase circulation pump 4 via a second gas pipe, the gas phase circulation pump 4 is connected to the second fluid inlet via a third gas pipe, and the second fluid outlet is connected to the circulating gas inlet via a fourth gas pipe, thereby forming a gas phase circulation loop. Further, a valve for controlling the circulating gas flow rate can be provided on the third gas pipe. By adjusting the valve, the flow rate of the circulating gas entering the heat exchanger 3 can be controlled, thereby adjusting the circulating gas temperature and flow rate.
[0059] In some embodiments of this application, a gas distributor (not shown in the figure) is provided inside the crystallizer 1, which is used to control the uniform flow of circulating gas entering the crystallizer 1.
[0060] In some embodiments of this application, a heat-conducting medium distributor is also provided in the crystallizer 1. The heat-conducting medium is introduced into the interior of each plate and circulates through the heat-conducting medium distributor, or the heat-conducting medium circulates outside each crystallizer tube through the heat-conducting medium distributor.
[0061] It should be noted that the dual-cycle melting and crystallization system provided in the above embodiments and the dual-cycle melting and crystallization method provided in the above embodiments belong to the same concept. The specific operation methods of each instrument and unit have been described in detail in the method embodiments, and will not be repeated here.
[0062] The following detailed examples illustrate the present invention. It should also be understood that the following examples are for illustrative purposes only and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values in the examples below.
[0063] Example 1 This embodiment provides a dual-cycle melt crystallization method using a static crystallizer. The specific implementation steps are as follows: 1. Purge the crystallizer 1 with nitrogen to ensure a suitable gaseous environment. Place the molten material to be crystallized into the static crystallizer 1, which has an effective operating volume of 12L. The volume of the material is 80% of the effective volume of the crystallizer 1. In this embodiment, the material to be crystallized is isomentheptyl alcohol with a purity of 98.4%.
[0064] 2. A heat transfer medium, consisting of an ethylene glycol aqueous solution at 15°C, is introduced into crystallizer 1 through the heat transfer medium inlet. The heat transfer medium is directly introduced into each plate of crystallizer 1 via a heat transfer medium distributor. The temperature is controlled to initiate a programmed cooling process for crystallization. After heat exchange with the material, the medium is discharged from the heat transfer medium outlet. The temperature is first rapidly reduced to 11°C, then the cooling rate is adjusted to 0.04°C / min for continuous cooling. After cooling to the final crystallization temperature of 0°C and maintaining this temperature for 1 hour, crystallization is complete, and the mother liquor is discharged.
[0065] 3. Initiate heating and sweating. Adjust the valves to allow some of the heat transfer medium to pass through heat exchanger 3 before entering crystallizer 1, while simultaneously starting the gas-phase circulation pump 4. Adjust the valves to control the amount of heat transfer medium entering heat exchanger 3, thereby controlling the circulating gas temperature and maintaining a temperature difference of 1.5℃ between the circulating gas and the heat transfer medium. Continuously raise the temperature of the heat transfer medium through a program, maintaining a 1.5℃ temperature difference between the circulating gas and the heat transfer medium during this period. First, rapidly raise the temperature to 8.5℃, then increase it to 11℃ at a rate of 0.04℃ / min to initiate sweating.
[0066] 4. After the sweating process is completed, the gas phase circulation continues and the temperature is rapidly increased to melt the product. The product is then discharged from the material outlet of crystallizer 1 and collected. The final purified product has a purity of 99.5%.
[0067] Comparative Example 1 This comparative example provides a melt crystallization method using a static crystallizer, and the specific implementation steps are as follows: 1. Purge the crystallizer 1 with nitrogen to ensure a suitable gaseous environment. Place the molten material to be crystallized into the static crystallizer 1, which has an effective operating volume of 12L. The volume of the material is 80% of the effective volume of the crystallizer 1. In this embodiment, the material to be crystallized is isomentheptyl alcohol with a purity of 98.4%.
[0068] 2. A heat transfer medium, consisting of an ethylene glycol aqueous solution at 15°C, is introduced into crystallizer 1 through the heat transfer medium inlet. The heat transfer medium is then distributed into each plate of crystallizer 1 via a heat transfer medium distributor. The temperature is controlled to initiate a programmed cooling process for crystallization. After heat exchange with the material, the medium is discharged from the heat transfer medium outlet. The temperature is first rapidly reduced to 11°C, then the cooling rate is adjusted to 0.04°C / min for continuous cooling. The temperature is maintained at 0°C for 1 hour to complete the crystallization process, at which point the mother liquor is discharged.
[0069] 3. To induce sweating, first rapidly raise the temperature of the heat transfer medium to 8.5℃, then raise it to 11℃ at a rate of 0.04℃ / min to induce sweating.
[0070] 4. After the sweating process is completed, the temperature is rapidly increased to melt the product. The product is then discharged from the material outlet of crystallizer 1 and collected. The final purified product has a purity of 99.2%.
[0071] Example 2 This embodiment provides a dual-cycle melt crystallization method using a static crystallizer. The specific implementation steps are as follows: 1. Purge the crystallizer 1 with nitrogen to ensure a suitable gaseous environment. Place the molten material to be crystallized into the static crystallizer 1, which has an effective operating volume of 12L, filling 80% of the effective volume of the crystallizer 1. In this embodiment, the material to be crystallized is dimethyl carbonate with a purity of 99.5%.
[0072] 2. A heat transfer medium, consisting of an ethylene glycol aqueous solution at 10°C, is introduced into crystallizer 1 through the heat transfer medium inlet. The heat transfer medium is directly introduced into each plate of crystallizer 1 via a heat transfer medium distributor. The temperature of the heat transfer medium is controlled to initiate a programmed cooling process for crystallization. After heat exchange with the material, the medium is discharged from the heat transfer medium outlet. The temperature is first rapidly reduced to 5°C, then the cooling rate is adjusted to 0.04°C / min for continuous cooling. After cooling to the final crystallization temperature of -5°C and maintaining this temperature for 1 hour, crystallization is complete, and the mother liquor is discharged.
[0073] 3. Initiate heating and sweating. Adjust the valves to allow some of the heat transfer medium to pass through heat exchanger 3 before entering crystallizer 1, while simultaneously starting the gas-phase circulation pump 4. Adjust the valves to control the amount of heat transfer medium entering heat exchanger 3, thereby controlling the circulating gas temperature and maintaining a temperature difference of 1.5℃ between the circulating gas and the heat transfer medium. Continuously raise the temperature of the heat transfer medium through a program, maintaining a 1.5℃ temperature difference between the circulating gas and the heat transfer medium during this period. First, rapidly raise the temperature to 1℃, then increase it to 4℃ at a rate of 0.04℃ / min to initiate sweating.
[0074] 4. After the sweating process is completed, the gas phase circulation continues and the temperature is rapidly increased to melt the product. The product is then discharged from the material outlet of crystallizer 1 and collected. The final purified product has a purity of 99.994%.
[0075] Comparative Example 2 This comparative example provides a melt crystallization method using a static crystallizer, and the specific implementation steps are as follows: 1. Purge the crystallizer 1 with nitrogen to ensure a suitable gaseous environment. Place the molten material to be crystallized into the static crystallizer 1, which has an effective operating volume of 12L, filling 80% of the effective volume of the crystallizer 1. In this embodiment, the material to be crystallized is dimethyl carbonate with a purity of 99.5%.
[0076] 2. A heat transfer medium, consisting of an ethylene glycol aqueous solution at 10°C, is introduced into crystallizer 1 through the heat transfer medium inlet. The heat transfer medium is then distributed into each plate of crystallizer 1 via a heat transfer medium distributor. The temperature is controlled to initiate a programmed cooling process for crystallization. After heat exchange with the material, the medium is discharged from the heat transfer medium outlet. The temperature is first rapidly reduced to 5°C, then the cooling rate is adjusted to 0.04°C / min for continuous cooling. The temperature is maintained at 0°C for 1 hour to complete the crystallization process, at which point the mother liquor is discharged.
[0077] 3. Continue to heat up and induce sweating. First, rapidly heat up to 1°C, then heat up to 4°C at a rate of 0.04°C / min to induce sweating.
[0078] 4. After the sweating process is completed, the temperature is rapidly increased to melt the product. The product is then discharged from the material outlet of crystallizer 1 and collected. The final purified product has a purity of 99.988%.
[0079] Table 1
[0080] As shown in Table 1, comparing Example 1 with Comparative Example 1 and Example 2 with Comparative Example 2, it can be seen that using a heat-conducting medium and circulating gas to heat the inner and outer sides of the crystal layer simultaneously during the sweating and melting process can shorten the sweating time and melting time compared to the method of heating the inner side of the crystal layer only by using a heat-conducting medium. This can shorten the melting and crystallization cycle and also improve the purity of the product.
[0081] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.
Claims
1. A dual-cycle melt crystallization method, characterized in that, Includes the following steps: S1. Replace the gas inside the crystallizer with an inert gas and add the molten material to be crystallized into the crystallizer; S2, Cooling crystallization: A heat-conducting medium enters the crystallizer and exchanges heat with the material, causing it to cool down and crystallize, forming a crystal layer. After crystallization is complete, drain the mother liquor; S3, Inducing sweating and raising body temperature: The inert gas inside the crystallizer is used as the circulating gas for gas-phase circulation; A portion of the heat-conducting medium acts as a heat source to exchange heat with the circulating gas, adjusting the temperature of the circulating gas to the target value, and then enters the crystallizer together with another portion of the heat-conducting medium. The heat-conducting medium and the circulating gas simultaneously heat the inner and outer sides of the crystal layer, causing it to heat up and sweat. S4, Heating and Melting: After the sweating process ends, the temperature is raised again to allow for melting.
2. The dual-cycle melt crystallization method according to claim 1, characterized in that: Step S4 includes: After the sweating process ends, the inert gas inside the crystallizer continues to circulate in the gas phase. All heat-conducting media are used as heat sources to exchange heat with the circulating gas first, and the temperature of the circulating gas is adjusted to reach the target value before entering the crystallizer; The heat-conducting medium and the circulating gas simultaneously heat the inner and outer sides of the crystal layer, causing it to continue to heat up and melt.
3. The dual-cycle melt crystallization method according to claim 1, characterized in that: The temperature of the heat transfer medium entering the crystallizer is controlled to be higher than the temperature of the circulating gas.
4. The dual-cycle melt crystallization method according to claim 3, characterized in that: Adjust the flow rate ratio of the heat transfer medium and the circulating gas to control their temperature difference.
5. The dual-cycle melt crystallization method according to claim 1, characterized in that: The circulating gas entering the crystallizer flows from top to bottom; And / or, control the uniform flow of circulating gas entering the crystallizer.
6. The dual-cycle melt crystallization method according to any one of claims 1 to 5, characterized in that: The dual-cycle melt crystallization method employs static crystallization or falling film crystallization processes for melt crystallization.
7. A dual-cycle melt crystallization system, characterized in that: The dual-circulation melt crystallization system includes a crystallizer, a heat transfer medium control unit, and a heat exchanger; The heat transfer medium control unit is used to control the entry and exit of the heat transfer medium into and out of the crystallizer, and to control the temperature of the heat transfer medium; The heat exchanger is the place where the heat transfer medium and the circulating gas exchange heat, and the circulating gas is the inert gas inside the crystallizer. The crystallizer and the heat exchanger are connected by a pipeline to form a gas phase circulation loop for the circulation gas to flow. The crystallizer, the heat transfer medium control unit, and the heat exchanger are connected end to end by pipelines to form a heat transfer medium circulation loop for the flow of heat transfer medium. The crystallizer and the heat transfer medium control unit are connected by a pipeline, forming a heat transfer medium bypass that allows the heat transfer medium to directly enter the crystallizer from the heat transfer medium control unit.
8. The dual-cycle melt crystallization system according to claim 7, characterized in that: The dual-cycle melt crystallization system also includes a gas phase circulation pump, which is installed on the gas phase circulation loop to drive the circulation gas to flow in the gas phase circulation loop.
9. The dual-cycle melt crystallization system according to claim 7, characterized in that: The dual-cycle melting and crystallization system also includes a gas phase buffer tank, which is installed on the gas phase circulation loop to buffer the circulating gas.
10. The dual-cycle melt crystallization system according to any one of claims 7 to 9, characterized in that: The circulating gas enters from the top and exits from the bottom in the crystallizer; And / or, the crystallizer is provided with a gas distributor, which is used to control the uniform flow of circulating gas entering the crystallizer.