Crystal slurry thickening and filtrate filtering device

Abstract

The utility model discloses a kind of thickening and filtrating device of crystal slurry, including self-cleaning filter, cyclone, crystal slurry tank, refrigeration crystallizer and refrigeration mother liquor tank, wherein, the discharge port of refrigeration crystallizer is connected with the feed inlet of cyclone, cyclone is used to concentrate crystal slurry, the underflow outlet of cyclone is connected with the feed inlet of crystal slurry tank, the top flow outlet of cyclone is connected with the feed inlet of self-cleaning filter, self-cleaning filter is used to filter part top flow liquid discharged in cyclone, the blowdown of self-cleaning filter and the overflow of crystal slurry tank are connected with the feed inlet of refrigeration mother liquor tank respectively.The device of the utility model has small floor area and low operating cost.

Description

Technical Field

[0001] This utility model relates to the field of chemical resource recycling technology, and in particular to a crystal slurry thickening and clear liquid filtration device. Background Technology

[0002] In chemical resource recovery processes, conventional cryogenic crystallization systems mainly consist of refrigeration units, refrigerant circulation pumps, refrigerant storage tanks, refrigeration heat exchangers, cryogenic crystallizers, refrigeration circulation pumps, refrigeration auxiliary circulation pumps, refrigeration discharge pumps, thickeners, refrigeration centrifuges, refrigeration mother liquor tanks, refrigeration mother liquor pumps, refrigeration clear liquid tanks, refrigeration clear liquid pumps, material pipelines, refrigerant pipelines, and other auxiliary facilities.

[0003] Taking sodium sulfate cryogenic crystallization as an example, in a conventional refrigeration system, the sodium sulfate-containing feed solution (cryogenic feed) is pre-cooled by the cryogenic clear liquid and then enters the cryogenic crystallizer. It is circulated and cooled by a refrigeration circulation pump within the refrigeration heat exchanger and the cryogenic crystallizer system (heat exchange occurs between the refrigeration heat exchanger and the refrigerant via a wall-type heat exchange), precipitating sodium sulfate and forming sodium sulfate crystal slurry. The sodium sulfate crystal slurry (15%-20% solid-liquid ratio) is transported to a sodium sulfate thickener for thickening. The overflow clear liquid (virtually free of solids) enters the sodium sulfate clear liquid tank. The thickened sodium sulfate crystal slurry (40%-50% solid-liquid ratio) is centrifuged in a sodium sulfate centrifuge. The sodium sulfate crystals enter the downstream system, and the sodium sulfate centrifuged mother liquor (3%-5% solid-liquid ratio) enters the sodium sulfate mother liquor tank. Part of the sodium sulfate clear liquid is pre-cooled in the precooler before being sent to other systems, while the remaining clear liquid is used as internal circulating clear liquid and enters the sodium sulfate mother liquor tank. The sodium sulfate mother liquor is then refluxed into the cryogenic crystallizer for brine mixing. This process reduces the solid-liquid ratio, ensuring the fluidity of the sodium sulfate slurry, and also allows the sodium sulfate crystals in the mother liquor to participate in the circulation as seed crystals, reducing the frequency of pipe blockage. Taking a sodium sulfate flow rate of approximately 3 t / h as an example, the volume of this sodium sulfate thickener is typically 40 m³. 3 Approximately, nominal diameter DN4500mm.

[0004] The solid-liquid ratio for conveying sodium sulfate crystal slurry is generally 15%-20%. Excessive concentration can lead to frequent pipe blockages. To meet the feed concentration requirements of the sodium sulfate centrifuge (40%-50% solid-liquid ratio) and to separate a clear sodium sulfate solution (which must be virtually solid-free; otherwise, frequent blockages in the precooler will significantly reduce the precooling effect and greatly increase the cold crystallization load), a sodium sulfate thickener is generally required (to allow the crystals and clear solution to settle and separate naturally). However, the density of sodium sulfate at room temperature is 1.464 g / cm³. 3 ) and the density of the mother liquor (1.0-1.2 g / cm³) 3 The density difference is small, so a particularly large thickener is often required to meet the process requirements, resulting in high equipment and civil engineering costs. Summary of the Invention

[0005] To address the high investment costs of existing crystal slurry thickening and clear liquid filtration devices, this invention provides a new crystal slurry thickening and clear liquid filtration device that can thicken high-concentration salt solutions such as Glauber's salt solution, sodium chloride solution, and calcium chloride solution, and produce a clear liquid that is essentially free of solids. The device also has a small footprint and low investment cost.

[0006] Specifically, the crystal slurry thickening and clear liquid filtration device of this utility model includes a self-cleaning filter, a hydrocyclone, a crystal slurry tank, a cryogenic crystallizer, and a cryogenic mother liquor tank. The outlet of the cryogenic crystallizer is connected to the inlet of the hydrocyclone. The hydrocyclone is used to concentrate the crystal slurry. The underflow outlet of the hydrocyclone is connected to the inlet of the crystal slurry tank. The topflow outlet of the hydrocyclone is connected to the inlet of the self-cleaning filter. The self-cleaning filter is used to filter part of the topflow liquid discharged from the hydrocyclone. The drain outlet of the self-cleaning filter and the overflow outlet of the crystal slurry tank are respectively connected to the inlet of the cryogenic mother liquor tank.

[0007] In this invention, the volume of the crystal slurry tank is 1m³. 3 Up to 10m 3 This invention replaces the traditional thickener with a combination of a hydrocyclone, a crystallizer tank, and a self-cleaning filter. The hydrocyclone achieves initial separation of the crystallizer slurry and the clear liquid. The crystallizer slurry is stored in a crystallizer tank with a significantly smaller volume than traditional thickeners, reducing equipment and construction costs. The self-cleaning filter further filters the liquid flowing from the top of the hydrocyclone, reducing the solid content and improving separation efficiency. The resulting clear liquid, which is essentially free of solids, is then pre-cooled. Using this device to manufacture products such as sodium sulfate, the combination of hydrocyclone, crystallizer tank, and self-cleaning filter in the refrigeration system reduces the footprint and investment costs.

[0008] Preferably, the above-mentioned device further includes a centrifuge, which is arranged between the crystal slurry tank and the freezing mother liquor tank, for centrifuging the crystal slurry from the crystal slurry tank to obtain crystals and centrifuged mother liquor, collecting the crystals, and introducing the centrifuged mother liquor into the freezing mother liquor tank.

[0009] Preferably, the above-mentioned device further includes a precooler disposed between the self-cleaning filter and the cryogenic crystallizer. The self-cleaning filter filters the top flow liquid discharged from the hydrocyclone to obtain crystal slurry and filtrate. The crystal slurry enters the cryogenic mother liquor tank through the drain port of the self-cleaning filter, and the filtrate is discharged into the precooler through the filtrate outlet of the self-cleaning filter. After the filtrate and the cryogenic feed exchange heat (e.g., through a partitioned heat exchange) in the precooler, the temperature of the cryogenic feed decreases and it enters the cryogenic crystallizer.

[0010] In this invention, the filtrate is pre-cooled using a precooler, which reduces the cooling load on the subsequent cryogenic crystallizer and improves crystallization efficiency. The dissolved materials in the filtrate can further precipitate after pre-cooling, thus increasing the material recovery rate.

[0011] Preferably, the above-mentioned device further includes a refrigeration heat exchanger connected to a refrigeration crystallizer. The refrigeration heat exchanger is configured to allow heat exchange between the external refrigerant (shell side) and the frozen feed (tube side). The frozen feed circulates between the refrigeration heat exchanger and the refrigeration crystallizer, gradually cooling and crystallizing to obtain frozen crystals. The frozen crystal slurry is then discharged into a hydrocyclone, and the frozen mother liquor from the frozen mother liquor tank is returned to the refrigeration crystallizer as a brine diluent. This serves two purposes: firstly, it provides seed crystals to the frozen feed, preventing explosive nucleation; secondly, it dilutes the frozen feed with brine, and the circulating solid-liquid ratio between the refrigeration heat exchanger and the refrigeration crystallizer is controlled by adjusting the amount of brine added.

[0012] The use of refrigeration heat exchangers reduces material cooling time, improving grain uniformity and quality. The combined use of refrigeration heat exchangers and freeze crystallizers can effectively improve crystallization efficiency and reduce energy consumption.

[0013] Preferably, the hydrocyclone includes a cylindrical section and a conical section. The angle between the sidewall of the conical section and the vertical direction is 150° to 165°. More preferably, the height of the conical section accounts for 1 / 3 to 2 / 3 of the total height of the hydrocyclone. The angle of the sidewall of the conical section of the hydrocyclone optimizes the distribution of centrifugal force, ensuring that the crystal slurry can settle quickly without clogging.

[0014] Preferably, the volume of the crystal slurry tank is 1m³. 3 Up to 10m 3 The crystallizer tank is configured to allow the feed to reside in it for 5-20 minutes. The solid-liquid ratio of the hydrocyclone underflow crystallization already meets the solid-liquid ratio requirements of the centrifuge feed. The crystallizer tank only serves as a buffer, and its volume is equivalent to the feed flow rate and residence time of 5-20 minutes.

[0015] Preferably, the hydrocyclone is also connected to the cryogenic mother liquor tank to guide a portion of the topflow liquid into the cryogenic mother liquor tank.

[0016] Preferably, the self-cleaning filter includes a stirring mechanism and a filter screen. The stirring mechanism extends inside the self-cleaning filter, while the drive motor of the stirring mechanism is external. It includes a stirring shaft and scrapers and steel brushes mounted on the stirring shaft, extending from the stirring shaft to the sidewall of the filter screen. The combined design of the scrapers and steel brushes efficiently removes adhering particles from the filter screen, extending the equipment's operating cycle.

[0017] Preferably, the scraper and steel brush are connected to the stirring shaft via a spring bracket to reduce wear on the scraper and steel brush and to ensure that the outer sides of the scraper and steel brush are in contact with the filter screen.

[0018] According to one embodiment of this utility model, the ratio of scrapers to steel brushes is 1:1. When the device is running, the stirring rod of the self-cleaning filter rotates continuously to prevent particle accumulation in the crystal slurry, and the drain port is always open to discharge the crystal slurry in a timely manner. The distribution of scrapers and steel brushes at the end of the stirring rod is not particularly limited; scrapers or steel brushes can be continuously arranged, or they can be arranged alternately, and can be adjusted according to actual usage requirements.

[0019] Preferably, the scraper is a parallelogram, and more preferably a rectangular scraper with a length of 400-600mm, a width of 50-100mm, and a thickness of 2-8mm, such as a rectangular scraper of 80mm×500mm×6mm.

[0020] Preferably, the steel brush is a wire brush, which has a rectangular brush body and steel wires disposed on the brush body, the length of which is 30-50 mm; the pore size of the filter screen is 50-100 μm. The brush body has a length of 400-600 mm, a width of 50-100 mm, and a thickness of 2-8 mm. The brush body has multiple wire-planting holes, and the spacing between the wire-planting holes is less than 1 mm.

[0021] Preferably, the self-cleaning filter includes a motor for electrically controlling the self-cleaning filter so that the stirring mechanism in the self-cleaning filter can rotate continuously; preferably, the motor meets at least one of the following: power of 0.37-0.75kw; speed of 10-15rpm, for example, about 14rpm; the motor is also equipped with a heat dissipation mechanism; the motor protection level is IP55 or higher.

[0022] During the operation of the device of this invention, when using a traditional motor (1.1 kW power, approximately 20 rpm), the self-cleaning filter needs to be started intermittently to avoid overheating. Using the improved motor described above ensures continuous and stable operation of the self-cleaning filter.

[0023] Preferably, the above-mentioned cryo-crystallizer includes a fully mixed cryo-crystallizer and an OSLO cryo-crystallizer.

[0024] Preferably, the above-mentioned freezing mother liquor tank is connected to the freezing crystallizer, wherein the freezing mother liquor tank includes a stirring mechanism for mixing the dilute crystal slurry in the tank evenly, and the freezing mother liquor tank is configured to return the freezing mother liquor to the freezing crystallizer for brine mixing via a mother liquor pump. Attached Figure Description

[0025] Figure 1 This diagram shows the connection of the crystal slurry thickening and clear liquid filtration device in this invention;

[0026] Figure 2 This diagram shows another connection schematic of the crystal slurry thickening and clear liquid filtration device of this invention;

[0027] Figure 3 The diagram shows the front view, side view, and top view of the stirring mechanism in the self-cleaning filter of this invention.

[0028] Figure labels: 1-cyclone separator, 2-crystal slurry tank, 3-centrifuge, 4-self-cleaning filter, 5-crystallized clear liquid tank, 6-crystallized mother liquor tank. Detailed Implementation

[0029] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. Although the description of this utility model will be presented in conjunction with preferred embodiments, this does not mean that the features of this utility model are limited to this embodiment. On the contrary, the purpose of describing the utility model in conjunction with the embodiments is to cover other options or modifications that may be derived based on the claims of this utility model. To provide a deep understanding of this utility model, many specific details will be included in the following description. This utility model may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this utility model, some specific details will be omitted in the description. It should be noted that, without conflict, the embodiments and features in the embodiments of this utility model can be combined with each other.

[0030] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0031] In the description of this embodiment, it should be noted that the terms "upper", "lower", "inner", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use. They are only for the convenience of describing the utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the utility model.

[0032] In the description of this embodiment, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment based on the specific circumstances.

[0033] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0034] Figure 1 This diagram illustrates the connection of a crystal slurry thickening and clarifying liquid filtration device according to one embodiment of the present invention. The device includes a self-cleaning filter, a hydrocyclone, a crystal slurry tank, a cryogenic crystallizer, and a cryogenic mother liquor tank. The outlet of the cryogenic crystallizer is connected to the inlet of the hydrocyclone, which is used to concentrate the crystal slurry. The underflow outlet of the hydrocyclone is connected to the inlet of the crystal slurry tank, and the topflow outlet of the hydrocyclone is connected to the inlet of the self-cleaning filter. The self-cleaning filter is used to filter a portion of the topflow liquid discharged from the hydrocyclone. The drain outlet of the self-cleaning filter and the overflow outlet of the crystal slurry tank are respectively connected to the inlet of the cryogenic mother liquor tank.

[0035] In this embodiment, the crystal slurry thickening and clear liquid filtration device also includes a refrigeration heat exchanger connected to a refrigeration crystallizer. The external refrigerant (shell side) and the frozen feed (tube side) exchange heat in the refrigeration heat exchanger. The frozen feed circulates between the refrigeration heat exchanger and the refrigeration crystallizer, gradually cooling down and crystallizing to obtain frozen crystals. The frozen crystal slurry is then discharged into a hydrocyclone. The frozen mother liquor from the frozen mother liquor tank is returned to the refrigeration crystallizer as a brine diluent. On the one hand, it provides seed crystals to the frozen feed to prevent explosive nucleation. On the other hand, it dilutes the frozen feed with brine. The circulating solid-liquid ratio between the refrigeration heat exchanger and the refrigeration crystallizer is controlled by adjusting the amount of brine added.

[0036] refer to Figure 2 Taking the crystal slurry thickening and clear liquid filtration device of this embodiment for manufacturing sodium sulfate products as an example, the cryo-crystallizer (not shown) has an internal spiral cooling surface and a conical discharge port, which can improve the precipitation efficiency and discharge efficiency of sodium sulfate crystals. Of course, in other embodiments of this utility model, the cryo-crystallizer may also have a flat plate or tubular cooling surface, selected according to the characteristics of the material being cooled.

[0037] The crystal slurry (15%-20% solid-liquid ratio) discharged from the cryo-crystallizer enters hydrocyclone 1 (the height of the cone section accounts for 1 / 3 of the total height of the hydrocyclone). The underflow from hydrocyclone 1 is thickened to a solid-liquid ratio of 40-50% before entering crystal slurry tank 2 (8m³). 3Considering a 20-30 minute residence time for the crystal slurry (mainly to ensure stable feed to the centrifuge), it then enters centrifuge 3 to produce Glauber's salt crystals. In this embodiment, the hydrocyclone 1 includes a cylindrical section and a conical section, with the sidewall of the conical section forming a 150° angle with the vertical direction. A portion of the top flow (1-5% solid-liquid ratio) from the hydrocyclone 1 is returned to the cryogenic mother liquor tank 6 for brine mixing, while a portion enters a self-cleaning filter 4 with a 100μm pore size for filtration. The filtered clear liquid (filtrate) enters the cryogenic clear liquid tank 5, and the sludge (crystal slurry) discharged from the self-cleaning filter 4 enters the cryogenic mother liquor tank 6. In this embodiment, the cryogenic mother liquor tank 6 is equipped with a stirrer to ensure uniform mixing of the dilute crystal slurry within the tank. The cryogenic crystal slurry is then returned to the cryogenic crystallizer via a mother liquor pump. In other embodiments of this invention, the filtrate produced by the self-cleaning filter 4 is temporarily stored in the cryogenic clear liquid tank 5. After pre-cooling the cryogenic feed with the filtrate, it is sent to other processing stages.

[0038] In the production of sodium sulfate using traditional equipment with a thickener, the density of the sodium sulfate solution is similar to that of sodium sulfate crystals. To ensure that the sodium sulfate solution is essentially free of solids, it is necessary to control the cross-section and maximum size of the sodium sulfate thickener (the thickener is designed to accommodate sodium sulfate crystals with a settling velocity of approximately 1 m / h; taking a sodium sulfate flow rate of approximately 3 t / h as an example, the volume is typically 40 m³ / h). 3 Only by employing centrifugal filtration with a hydrocyclone instead of sedimentation filtration with a thickener can the desired effects of thickening the crystal slurry and separating the clear liquid be achieved.

[0039] Since the top flow of the hydrocyclone still has a solid-liquid ratio, which does not meet the requirements for clear sodium sulfate solution, this embodiment uses an electric brush self-cleaning filter for secondary filtration, which can achieve the requirement that the clear sodium sulfate solution is basically free of solids. The flow rate of the self-cleaning filter is selected according to the amount of clear liquid calculated by the system material balance. Generally, the flow rate of the top flow of the hydrocyclone is greater than the flow rate of the clear liquid. The excess top flow of the hydrocyclone is returned to the mother liquor tank and, together with the centrifuged mother liquor, is returned to the freeze crystallizer as the brine return liquid.

[0040] Furthermore, due to the high hardness and large quantity of Glauber's salt crystals, this embodiment modifies the conventional self-cleaning filter, replacing it with a combination of an electric scraper and a steel brush for self-cleaning. (Reference) Figure 3 The self-cleaning filter includes a stirring mechanism and a filter screen with a pore size of approximately 70 μm. The stirring mechanism extends into the interior of the self-cleaning filter (the drive motor of the stirring mechanism is external and not shown), and includes a stirring shaft and scrapers and steel brushes mounted on the stirring shaft. The scrapers and steel brushes extend from the stirring shaft to the side wall of the filter screen. The scrapers and steel brushes are connected to the stirring shaft by spring brackets to reduce wear on the scrapers and steel brushes. The outer sides of the scrapers and steel brushes are in contact with the filter screen. Figure 3 The left side shows a schematic diagram of the steel brush connected to the stirring shaft via a spring bracket, and the right side shows a schematic diagram of the scraper connected to the stirring shaft via a spring bracket. Both the steel brush and the scraper are attached to the filter screen via spring brackets.

[0041] Furthermore, by employing an improved motor (0.50 kW power, approximately 14 rpm speed, equipped with a heat dissipation mechanism, and with an IP55 or higher protection rating), the self-cleaning filter can be set to continuously rotate the brushes and keep the drain port open, continuously outputting crystal slurry. In this embodiment, the number of scrapers and steel brushes is also adjusted, using a half-scraper, half-steel brush configuration with the brushes and scrapers facing each other, ensuring continuous and stable operation of the self-cleaning filter.

[0042] Of course, in other embodiments of this utility model, the self-cleaning filter can use a common motor, such as a motor with a speed of about 20 rpm and a power of about 1.1 kW. The self-cleaning filter starts intermittently, for example, it can run for one minute and then pause for one minute, and so on, to avoid overheating of the device. The drain port of the self-cleaning filter starts and closes synchronously with the motor.

[0043] In this embodiment, the scraper has a rectangular cross-section, with a width of 5cm and a length of 50cm. The steel brush is a wire brush with approximately 120 steel wires, each approximately 3cm long. This invention does not limit the shape of the scraper and steel brush, as long as they enable continuous and stable operation of the self-cleaning filter.

[0044] Although the present invention has been illustrated and described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the present invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the present invention to these descriptions. Those skilled in the art can make various changes in form and detail, including some simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A device for thickening crystal slurry and filtering clarified liquid, characterized in that, The device includes a self-cleaning filter, a hydrocyclone, a crystal slurry tank, a cryogenic crystallizer, and a cryogenic mother liquor tank. The outlet of the cryogenic crystallizer is connected to the inlet of the hydrocyclone. The hydrocyclone is used to concentrate the crystal slurry. The underflow outlet of the hydrocyclone is connected to the inlet of the crystal slurry tank. The topflow outlet of the hydrocyclone is connected to the inlet of the self-cleaning filter. The self-cleaning filter is used to filter a portion of the topflow liquid discharged from the hydrocyclone. The drain outlet of the self-cleaning filter and the overflow outlet of the crystal slurry tank are respectively connected to the inlet of the cryogenic mother liquor tank.

2. The crystal slurry thickening and clear liquid filtration device as described in claim 1, characterized in that, The apparatus further includes a centrifuge disposed between the crystal slurry tank and the frozen mother liquor tank. The centrifuge centrifuges the crystal slurry from the crystal slurry tank to obtain crystals and centrifuged mother liquor, collects the crystals, and introduces the centrifuged mother liquor into the frozen mother liquor tank.

3. The crystal slurry thickening and clear liquid filtration device as described in claim 1, characterized in that, The device further includes a precooler disposed between the self-cleaning filter and the cryogenic crystallizer. The self-cleaning filter filters the top-flow liquid discharged from the hydrocyclone to obtain crystal slurry and filtrate. The crystal slurry enters the cryogenic mother liquor tank through the drain port of the self-cleaning filter, and the filtrate is discharged into the precooler through the filtrate outlet of the self-cleaning filter. After the filtrate and the cryogenic feed exchange heat through the precooler, the cryogenic feed enters the cryogenic crystallizer.

4. The crystal slurry thickening and clear liquid filtration device as described in claim 1, characterized in that, The apparatus further includes a refrigeration heat exchanger connected to the refrigeration crystallizer. The refrigeration heat exchanger is configured to allow external refrigerant and refrigeration feed to exchange heat in the refrigeration heat exchanger. The refrigeration feed circulates between the refrigeration heat exchanger and the refrigeration crystallizer to obtain refrigerated crystal slurry. The refrigerated crystal slurry is then discharged into the hydrocyclone, and the refrigeration mother liquor from the refrigeration mother liquor tank is returned to the refrigeration crystallizer as a brine mixing solution.

5. The crystal slurry thickening and clear liquid filtration apparatus according to any one of claims 1-4, characterized in that, The device satisfies at least one of the following: The hydrocyclone includes a cylindrical section and a conical section, wherein the sidewall of the conical section forms an angle of 150° to 165° with the vertical direction, and the height of the conical section accounts for 1 / 3 to 2 / 3 of the total height of the hydrocyclone. The volume of the crystal slurry tank is 1m³. 3 Up to 10m 3 ; The hydrocyclone is also connected to the cryogenic mother liquor tank and is used to introduce a portion of the topflow liquid into the cryogenic mother liquor tank.

6. The crystal slurry thickening and clarifying liquid filtration apparatus according to any one of claims 1-4, characterized in that, The self-cleaning filter includes a stirring mechanism and a filter screen. The stirring mechanism extends into the interior of the self-cleaning filter and includes a stirring shaft and a scraper and a steel brush disposed on the stirring shaft. The scraper and the steel brush extend from the stirring shaft to the side wall of the filter screen.

7. The crystal slurry thickening and clear liquid filtration device as described in claim 6, characterized in that, The scraper is rectangular, with a length of 400-600mm, a width of 50-100mm, and a thickness of 2-8mm; and / or the steel brush is a wire brush, which has a rectangular brush body and steel wires disposed on the brush body, with the steel wires having a length of 30-50mm; the filter screen has a pore size of 50-100μm.

8. The crystal slurry thickening and clear liquid filtration apparatus according to any one of claims 1-4, characterized in that, The self-cleaning filter includes a motor for electrically controlling the self-cleaning filter, so that the stirring mechanism in the self-cleaning filter can rotate continuously.

9. The crystal slurry thickening and clear liquid filtration device as described in claim 8, characterized in that, The motor meets at least one of the following requirements: power is 0.37-0.75kw; speed is 10-15rpm; the motor is also equipped with a heat dissipation mechanism; the protection level of the motor is IP55 or higher.

10. The crystal slurry thickening and clear liquid filtration apparatus according to any one of claims 1-4, characterized in that, The cryo-crystallizers include fully mixed cryo-crystallizers and OSLO cryo-crystallizers.

11. The crystal slurry thickening and clear liquid filtration apparatus according to any one of claims 1-4, characterized in that, The frozen mother liquor tank is connected to the frozen crystallizer, wherein the frozen mother liquor tank includes a stirring mechanism for uniformly mixing the dilute crystal slurry in the tank, and the frozen mother liquor tank is configured to return the frozen mother liquor to the frozen crystallizer for brine mixing via a mother liquor pump.

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