Continuous crystallization device and process

Abstract

The continuous crystallization device comprises a crystallization tank body, a driving motor is arranged at the top of the crystallization tank body, the driving motor is connected with a stirring device, a heat exchange jacket is arranged on the inner wall of the crystallization tank body, the heat exchange jacket is used for bearing a heat exchange medium, and the inner wall of the heat exchange jacket is of a wavy curved surface structure. A feeding hole and a crystal liquid discharging hole are further formed in the crystallization tank body, a heat exchange medium inlet and a heat exchange medium outlet are formed in the heat exchange jacket, and the heat exchange medium inlet and the heat exchange medium outlet are respectively connected with a circulating temperature control device and are used for realizing constant-temperature control of a heat exchange medium. According to the continuous crystallization device and the continuous crystallization process, the temperature gradient in the crystallization tank body can be more effectively eliminated, so that crystals grow in a uniform temperature environment, the particle size uniformity and the form regularity of the crystals are improved, the quality of crystallized products is improved, the production efficiency is improved, and the production cost is reduced. And meanwhile, the high stability of the nanofluid ensures the long-term stable operation of equipment, and the maintenance time is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical separation equipment, and particularly relates to a continuous crystallization device and process, which are applicable to crystal production in industries such as pharmaceuticals, chemicals, food, and metallurgy. Background Art

[0002] In many industries such as chemicals and pharmaceuticals, the crystallization process is an important means to achieve material separation and purification. The continuous crystallization tank body has been widely used in industrial production because it can continuously produce and improve production efficiency. However, during the crystallization process of the existing continuous crystallization tank body, the temperature is often uneven and there is a temperature gradient. During the crystallization process, the stability of the temperature has an important impact on the crystallization quality. The uneven temperature will lead to inconsistent crystal growth rates and different crystal sizes, thus affecting the crystallization quality. For example, problems such as uneven crystal size distribution and irregular crystal morphology will occur. In severe cases, the purity and yield of the product will also be reduced.

[0003] At present, the continuous crystallization tank body mainly controls the crystallization temperature through heat exchange with traditional heat transfer media such as hot water and cold water. However, the thermal conductivity coefficients of these traditional heat transfer media are limited, and temperature gradients are likely to occur during the heat transfer process, making it difficult to meet the strict requirements for temperature uniformity in the crystallization process. Nanofluids have a very high thermal conductivity coefficient and are easy to obtain, and can transfer heat more efficiently. However, they are limited because they are prone to agglomeration after long-term use, resulting in a significant decrease in the thermal conductivity of the nanofluid. Therefore, it is of great practical significance to develop a continuous crystallization tank body that can effectively solve the problem of uneven temperature during the crystallization process and improve the crystallization quality. Summary of the Invention

[0004] In view of the above problems, the purpose of the present invention is to provide a continuous crystallization device and process. By using nanofluid as the heat transfer medium and utilizing its high thermal conductivity coefficient characteristics, combined with a unique heat exchange jacket structure design, the problem of uneven temperature during the crystallization process is effectively solved, thereby improving the crystallization quality.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a continuous crystallization device, including a crystallization tank body. A driving motor is arranged at the top of the crystallization tank body. The driving motor is connected to a stirring device. A heat exchange jacket is arranged on the inner wall of the crystallization tank body. The heat exchange jacket is used to carry the heat transfer medium. The inner wall of the heat exchange jacket is a wavy curved surface structure. An inlet for feeding materials and an outlet for crystal liquid are also arranged on the crystallization tank body. An inlet for the heat transfer medium and an outlet for the heat transfer medium are arranged on the heat exchange jacket. The inlet for the heat transfer medium and the outlet for the heat transfer medium are respectively connected to a circulation temperature control device for realizing the constant temperature control of the heat transfer medium.

[0006] Preferably, the wavy curved surface structure includes a contraction section and an expansion end. The angle of the contraction section is 21° ± 2°, and the angle of the expansion section is 7° - 15°. The angle is defined as the included angle between the expansion section and the contraction section and the tangent line at the end point.

[0007] Further, the stirring device includes a rotating shaft rod extending into the interior of the crystallization tank body and stirring blades provided at the end of the rotating shaft rod.

[0008] Further, a draft tube is provided inside the crystallization tank body, and the draft tube is connected to the inner wall of the crystallization tank body through a support rod; a tank body temperature probe is also provided inside the crystallization tank body for monitoring the temperature of the crystallization material.

[0009] Further, the circulation temperature control device includes a temperature control medium inlet and a temperature control medium outlet. A medium storage tank is provided inside the circulation temperature control device. The medium storage tank is provided with a temperature control medium feed pipeline communicating with the temperature control medium inlet. An inlet temperature probe is provided inside the temperature control medium inlet, and the medium storage tank is communicated with the temperature control medium outlet through a pipeline.

[0010] Further, an infrared electric heating coil is provided outside the temperature control medium feed pipeline. A fan is provided inside the circulation temperature control device at a predetermined distance from the temperature control medium feed pipeline. An air inlet and an air outlet corresponding to the fan are provided on the circulation temperature control device, and microporous filter plates are provided at both the air inlet and the air outlet.

[0011] Further, a storage tank temperature probe is provided inside the medium storage tank, and a heat preservation jacket is provided outside the medium storage tank.

[0012] Further, the heat exchange medium outlet of the crystallization tank body is communicated with the temperature control medium inlet of the circulation temperature control device through a pipeline, and the temperature control medium outlet of the circulation temperature control device is communicated with the heat exchange medium inlet of the crystallization tank body through a pipeline. A circulation pump is provided on the connecting pipeline.

[0013] On the other hand, the present invention also proposes a continuous crystallization process, which is carried out based on the continuous crystallization device as described above, and includes the following steps: S1: Heat exchange medium preparation stage: Add the pre-prepared nanofluid into the medium storage tank, start the circulation pump to make the nanofluid circulate in the heat exchange jacket, set the nanofluid flow rate and start the stirring device at the same time; S2: Feeding stage: Input the raw material to be crystallized into the crystallization tank body through the feeding port, and continuously detect the feeding flow rate and the material temperature at the same time; S3: Crystallization stage: After the material enters the crystallization tank body, adjust the rotation speed of the stirring device to 200 - 250 r / min to make the material fully exchange heat with the nanofluid; as the crystallization process proceeds, use the circulation temperature control device to control the temperature inside the crystallization tank body to ensure that the temperature gradient is maintained within ±1°C; S4: Discharging stage: After crystallization is completed, the crystalline product is output through the crystal liquid discharge port, and at the same time, the output crystalline product is sampled and tested.

[0014] Furthermore, the nanofluid uses deionized water as the base fluid, and nano copper particles are uniformly dispersed. The mass fraction of the nano copper particles is between 3% and 5%.

[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) Improving crystallization quality: The inner wall of the crystallization tank body of the present invention adopts a unique internal curved surface structure. By utilizing the characteristics that the width of the curved surface structure is different and the fluid velocity increases and then decreases from wide to narrow, the fluid velocity can be intermittently increased, increasing the heat exchange efficiency. In addition, by using nanofluid, the agglomeration of nanofluid can be prevented, disturbing the agglomeration trend and maintaining a stable state for a long time. At the same time, due to the internal curved surface of the crystallization tank body, compared with the ordinary crystallization tank body, the heat exchange area is increased, and the temperature gradient in the crystallization tank body can be more effectively eliminated, enabling the crystals to grow in a uniform temperature environment, improving the particle size uniformity and morphological regularity of the crystals, and enhancing the quality of the crystalline product.

[0016] (2) Improving production efficiency: A stable temperature environment and enhanced heat exchange effect are conducive to the continuous and stable progress of the crystallization process, reducing production interruptions and product quality problems caused by temperature fluctuations, thereby improving production efficiency and reducing production costs. At the same time, the high stability of the nanofluid ensures the long-term stable operation of the equipment and reduces the maintenance time.

[0017] (3) By setting up a circulating temperature control device, the temperature of the heat exchange medium is controlled, and then the temperature of the crystallization material in the crystallization tank body is controlled, providing a stable crystallization temperature environment and ensuring that the temperature gradient is maintained within a suitable range. Description of the Drawings

[0018] Figure 1 is a schematic structural diagram of the continuous crystallization device of the present invention; Figure 2 is a schematic structural diagram of the circulating temperature control device of the present invention; In the figure: 1, driving motor; 2, crystallization tank body; 201, heat exchange jacket; 202, feed port; 203, crystal liquid discharge port; 204, heat exchange medium inlet; 205, heat exchange medium outlet; 206, tank body temperature probe; 3, draft tube; 31, support rod; 4, circulating temperature control device; 401, temperature control medium inlet; 402, temperature control medium outlet; 403, medium storage tank; 404, temperature control medium feed pipeline; 405, fan; 406, inlet temperature probe; 407, storage tank temperature probe; 408, heat preservation sleeve; 409, air inlet; 410, air outlet; 411, infrared electric heating coil; 5, rotating shaft rod; 6, stirring blade. Detailed implementation mode

[0019] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other implementation manners obtained by those of ordinary skill in the art without creative efforts shall fall within the scope protected by the present invention. Embodiment 1

[0020] As Figure 1 shown, a continuous crystallization device includes a crystallization tank body 2, a driving motor 1 is arranged at the top of the crystallization tank body 2, the driving motor 1 is connected with a stirring device, the stirring device includes a rotating shaft rod 5 extending into the interior of the crystallization tank body 2 and a stirring blade 6 arranged at the end of the rotating shaft rod 5. A heat exchange jacket 201 is arranged on the inner wall of the crystallization tank body 2, and the heat exchange jacket 201 is used to carry a heat exchange medium. The inner wall of the heat exchange jacket 201 is a wavy curved surface structure. The wavy curved surface structure includes a contraction section and an expansion end. The angle of the contraction section is 21° ± 2°, and the angle of the diffusion section is 7° - 15°. A feed port 202 and a crystal liquid discharge port 203 are further arranged on the crystallization tank body 2, and a heat exchange medium inlet 204 and a heat exchange medium outlet 205 are arranged on the heat exchange jacket 201. The heat exchange medium inlet 204 and the heat exchange medium outlet 205 are respectively connected with a circulation temperature control device 4 to realize the constant temperature control of the heat exchange medium.

[0021] The driving motor 1 is a frequency-adjustable motor.

[0022] The rotating shaft rod 5 is connected to the driving motor 1, and the stirring blade 6 is fixed at the lower end. The stirring blade 6 is a propeller type, which can form an axial fluid and mix more evenly. The position is 20 - 30 cm above the inner surface of the crystallization tank body 2.

[0023] The crystallization tank body 2 is cylindrical, with a heat exchange jacket 201. The feed port 202 at the upper end feeds materials, and the heat exchange medium is introduced from the heat exchange medium inlet 204, fills the heat exchange jacket 201, and exits from the heat exchange medium outlet 205. The discharged heat exchange medium is connected to the temperature control medium inlet 401 of the circulation temperature control device 4, and then exits from the temperature control medium outlet 402 and enters the circulation again from the heat exchange medium inlet 204, so as to accurately control the crystallization temperature. The heat exchange medium of the present invention is applicable to nanofluids and can maintain the stability of nanofluids for a long time.

[0024] The draft tube 3 is connected to the inner wall of the crystallization tank body 2 through a support rod 31, and the position is ≤ 50 mm from the bottom of the crystallization tank body 2, which increases the fluid uniformity in the crystallization tank body 2. At the same time, since the flow rate of the fluid through the bottom end of the draft tube 3 is increased, the deposition of crystals is reduced, and the axial flow rate is strengthened to prevent local supersaturation from being excessive.

[0025] Inside the crystallization tank body 2, a tank body temperature probe 206 is also provided for monitoring the temperature of the crystallization material. The tank body temperature probe 206 is located at the lower middle part of the crystallization tank body 2, at the 1 / 2 position, and is suspended.

[0026] The circulating temperature control device 4 includes a temperature control medium inlet 401 and a temperature control medium outlet 402. Inside the circulating temperature control device 4, a medium storage tank 403 is provided. The medium storage tank 403 is provided with a temperature control medium feed pipeline 404 communicating with the temperature control medium inlet 401, and the medium storage tank 403 is communicated with the temperature control medium outlet 402 through a pipeline. A storage tank temperature probe 407 is provided inside the medium storage tank 403, and a heat preservation sleeve 408 is provided outside the medium storage tank 403. An infrared electric heating coil 411 is provided outside the temperature control medium feed pipeline 404. A blower 405 is provided inside the circulating temperature control device 4 at a predetermined distance from the temperature control medium feed pipeline 404. An air inlet 409 and an air outlet 410 corresponding to the blower 405 are provided on the circulating temperature control device 4, and microporous filter plates are provided at both the air inlet 409 and the air outlet 410.

[0027] An inlet temperature probe 406 is provided inside the temperature control medium inlet 401 for detecting the medium temperature in advance to facilitate subsequent temperature control. The inlet temperature probe 406 detects the temperature of the temperature control medium in real time and feeds back. Through the respective actions of the infrared electric heating coil and the blower, the temperature of the temperature control medium is regulated. When the detected temperature decreases, the infrared electric heating coil is started for heating. On the contrary, the blower is started for cooling. The medium with the regulated temperature enters the medium storage tank 403. There is a heat preservation sleeve 408 outside the medium storage tank 403, and the heat exchange medium in the medium storage tank 403 is output for circulation through the temperature control medium outlet 402. Example 2

[0028] A continuous crystallization process is described by taking the preparation of copper sulfate crystals as an example, and it includes the following process steps: Heat exchange medium preparation stage: Add the pre-prepared nanofluid to the medium storage tank 403. The nanofluid uses deionized water as the base fluid and uniformly disperses nano copper particles, ensuring that the mass fraction of nano copper particles is between 3% - 5%. Start the circulating pump to make the nanofluid circulate in the heat exchange jacket 201. The nanofluid flow rate is set at 300L per hour, and at the same time, start the stirring device.

[0029] Feeding stage: Through the feed port 202, slowly input the copper sulfate raw material material into the crystallization tank body at a flow rate of 50 - 80L / h, and at the same time, continuously monitor the feed flow rate and the material temperature to ensure that the material temperature is 40°C.

[0030] Crystallization stage: After the material enters the crystallization tank body 2, the rotation speed of the stirring device is adjusted to 200 - 250 r / min to enable the material to fully exchange heat with the nanofluid. As the crystallization process progresses, the temperature inside the crystallization tank body 2 is controlled by the circulating temperature control device 4 to ensure that the temperature gradient is maintained within ±1°C.

[0031] Discharging stage: When crystallization is completed, the crystallization product is output through the crystal liquid discharge port 203, and the discharging speed is controlled at 30 - 50 L / h. At the same time, the output crystallization product is sampled and tested, mainly testing indicators such as crystal particle size and morphology.

[0032] After continuous production for 8 hours, the discharging device discharges stably. After testing, the particle size of the produced copper sulfate crystals is uniform, the average particle size deviation is controlled within ±0.05 mm, the crystal purity reaches 99.5%, and the production efficiency is increased by 35% compared with the traditional crystallization tank body used before (referring to the traditional process, to reach the level of the same crystallization particles, the required time is shortened by 35%).

[0033] Traditional crystallization tank body: Usually a mechanical stirring type crystallizer, the structural characteristics include: Main body structure: A cylindrical tank body with an opening at the top or bottom, equipped with a stirrer, a jacket or a coil (through which chilled brine passes). Auxiliary devices: Temperature sensor, pH meter, feed / discharge port. Working principle: The solution is evenly mixed by stirring, and the temperature (heating or cooling) is controlled to adjust the solubility of the solute. After the solute is supersaturated, crystals precipitate, and the crystals grow in the tank body and are finally separated by filtration or centrifugation.

[0034] General process of traditional technology: Slowly input the raw material containing copper sulfate into the crystallization tank body → Slowly cool down → Supersaturated crystallization → Solid-liquid separation.

[0035] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, and all should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. A continuous crystallization device, characterized in that, It includes a crystallization tank body (2), a driving motor (1) is arranged at the top of the crystallization tank body (2), the driving motor (1) is connected with a stirring device, a heat exchange jacket (201) is arranged on the inner wall of the crystallization tank body (2), and the heat exchange jacket (201) is used to carry a heat exchange medium. The inner wall of the heat exchange jacket (201) is a wavy curved surface structure. A feed inlet (202) and a crystal liquid discharge outlet (203) are also arranged on the crystallization tank body (2). A heat exchange medium inlet (204) and a heat exchange medium outlet (205) are arranged on the heat exchange jacket (201). The heat exchange medium inlet (204) and the heat exchange medium outlet (205) are respectively connected with a circulation temperature control device (4) to realize the constant temperature control of the heat exchange medium.

2. The continuous crystallization device according to claim 1, wherein The wavy curved surface structure includes a contraction section and an expansion end. The angle of the contraction section is 21°±2°, and the angle of the expansion section is 7°-15°.

3. A continuous crystallization device according to claim 1, characterized in that, The stirring device includes a rotating shaft rod (5) extending into the interior of the crystallization tank body (2) and stirring blades (6) arranged at the end of the rotating shaft rod (5).

4. A continuous crystallization device according to claim 1, characterized in that, A draft tube (3) is arranged inside the crystallization tank body (2), and the draft tube (3) is connected to the inner wall of the crystallization tank body (2) through a support rod (31). A tank body temperature probe (206) is also arranged inside the crystallization tank body (2) for temperature monitoring of the crystallization material.

5. A continuous crystallization device according to claim 2, characterized in that, The circulation temperature control device (4) includes a temperature control medium inlet (401) and a temperature control medium outlet (402). A medium storage tank (403) is arranged inside the circulation temperature control device (4). The medium storage tank (403) is provided with a temperature control medium feed pipeline (404) communicated with the temperature control medium inlet (401). An inlet temperature probe (406) is arranged inside the temperature control medium inlet (401). The medium storage tank (403) is communicated with the temperature control medium outlet (402) through a pipeline.

6. The continuous crystallization device according to claim 5, characterized in that, An infrared electric heating coil (411) is arranged outside the temperature control medium feed pipeline (404). A blower (405) is arranged inside the circulation temperature control device (4) at a predetermined distance from the temperature control medium feed pipeline (404). An air inlet (409) and an air outlet (410) corresponding to the blower (405) are arranged on the circulation temperature control device (4). Microporous filter plates are arranged at both the air inlet (409) and the air outlet (410).

7. A continuous crystallization device according to claim 4, characterized in that, A storage tank temperature probe (407) is arranged inside the medium storage tank (403), and a heat preservation sleeve (408) is arranged outside the medium storage tank (403).

8. A continuous crystallization device according to claim 4, wherein The heat exchange medium outlet (205) of the crystallization tank body (2) is communicated with the temperature control medium inlet (401) of the circulation temperature control device (4) through a pipeline. The temperature control medium outlet (402) of the circulation temperature control device (4) is communicated with the heat exchange medium inlet (204) of the crystallization tank body (2) through a pipeline. A circulation pump is arranged on the communicating pipeline.

9. A continuous crystallization process, which is carried out based on the continuous crystallization device according to any one of claims 5-8, characterized in that, It includes the following steps: S1: Heat exchange medium preparation stage: Add the pre-prepared nanofluid into the medium storage tank (403), start the circulation pump to make the nanofluid circulate in the heat exchange jacket (201), set the nanofluid flow rate and start the stirring device at the same time; S2: Feeding stage: Feed the raw material to be crystallized into the crystallization tank body (2) through the feed inlet (202), and continuously detect the feed flow rate and the material temperature at the same time; S3: Crystallization stage: After the material enters the crystallization tank body (2), adjust the rotation speed of the stirring device to 200 - 250 r / min to enable the material to fully exchange heat with the nanofluid; As the crystallization process proceeds, use the circulating temperature control device (4) to control the temperature inside the crystallization tank body (2) to ensure that the temperature gradient is maintained within ±1°C; S4: Discharging stage: After crystallization is completed, output the crystallization product through the crystal liquid discharge port (203), and simultaneously conduct sampling inspection on the output crystallization product.

10. A continuous crystallization process according to claim 9, characterized in that, The nanofluid uses deionized water as the base fluid and uniformly disperses nano copper particles, and the mass fraction of the nano copper particles is between 3% - 5%.

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