A freeze crystallization salt splitting device

Abstract

This utility model discloses a freeze crystallization and salt separation device, belonging to the field of freeze crystallization technology. It includes: a first loop comprising a crystallizer separator, a first pump, a first heat exchanger, and a central cylinder connected in sequence; a second loop comprising a first heat exchanger, a first valve, a refrigerant storage tank, a second pump, an ice machine, and a second valve connected in sequence; a third loop comprising a first heat exchanger, a third pump, a first buffer tank, and a second heat exchanger connected in sequence; and a fourth loop. When the tube wall of the first heat exchanger thickens, the first pump, the first valve, and the second valve can be closed, and the third pump opened to activate the third loop. The fourth loop then provides heat energy to the second heat exchanger in the third loop, causing the second heat exchanger to heat the refrigerant in the first heat exchanger. The refrigerant heats the tubes as it flows through the first heat exchanger, causing the wall-forming material within the tube layers to dissolve back into the material, thus eliminating the wall formation in the first heat exchanger and allowing it to maintain efficient heat exchange operation.

Description

Technical Field

[0001] This utility model relates to the field of cryo-crystallization technology, and in particular to a cryo-crystallization salt separation device. Background Technology

[0002] In recent years, with the rapid development of new energy vehicles and the continuous expansion of lithium battery production scale, the amount of lithium salt wastewater generated during lithium carbonate production has also been increasing. Lithium salt wastewater mainly contains sulfate ions, chloride ions, sodium ions, and other components. In the treatment of lithium salt wastewater, freeze crystallization separation technology is mostly used to separate sodium sulfate and prepare industrial-grade sodium sulfate, thereby reducing the generation of impurities and lowering wastewater treatment costs.

[0003] In cryogenic crystallization salt separation technology, the refrigeration system often employs a forced circulation shell-and-tube heat exchanger to cool the brine. During operation, the brine in the heat exchanger tube layer contacts the low-temperature tubes, causing the temperature to drop and the brine to become supersaturated. Under the influence of disturbances, oscillations, and impacts, crystal nuclei precipitate and grow. Because the tubes contain small defects and protrusions, which are not perfectly smooth, these defects and protrusions can also induce crystal growth in the supersaturated brine, leading to the formation of a crystalline layer on the inner side of the heat exchanger tubes, commonly known as a crystalline wall.

[0004] Wall thickening causes the heat exchanger tubes to become thicker and the effective tube diameter to become smaller, which in turn reduces the heat exchange efficiency. Utility Model Content

[0005] The purpose of this invention is to provide a freeze-crystallization and salt separation device to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions.

[0006] The technical solution adopted to solve the above-mentioned technical problems is as follows: A freeze crystallization and salt separation device, comprising: a first circuit, including a crystallization separator, a first heat exchanger, and a central cylinder connected in sequence, wherein the central cylinder is disposed inside the crystallization separator; a first pump for providing power to the first circuit; a second circuit, including the first heat exchanger, a first valve, a refrigerant storage tank, an ice machine, and a second valve connected in sequence, wherein the second valve is connected to the first heat exchanger, and the second circuit exchanges heat with the first circuit through the first heat exchanger; a second pump for providing power to the second circuit; a third circuit, including the first heat exchanger, a first buffer tank, and a second heat exchanger connected in sequence, wherein the second heat exchanger is connected to the first heat exchanger, and the third circuit communicates with the second circuit through the second heat exchanger; a third pump for providing power to the third circuit; and a fourth circuit for exchanging heat with the third circuit through the second heat exchanger.

[0007] This technical solution has at least the following beneficial effects: The crystallizer operates through the first loop and the first pump, and the second loop and the second pump provide refrigerant to the first heat exchanger. When the working time is long, the tube wall of the first heat exchanger becomes thick. Then, by closing the first pump, the first valve and the second valve, and opening the third pump, the third loop can be put into operation, and the fourth loop provides heat energy to the second heat exchanger in the third loop. This heats the refrigerant in the first heat exchanger through the second heat exchanger. When the refrigerant flows through the first heat exchanger, it heats the tubes, causing the wall-forming material in the tube layer to dissolve back into the material. This facilitates the elimination of wall formation in the first heat exchanger, allowing the first heat exchanger to maintain efficient heat exchange operation.

[0008] As a further improvement to the above technical solution, the fourth loop includes a water tower, the ice machine, a third valve, and a second heat exchanger connected in sequence. The second heat exchanger is connected to the water tower, and the cooling water in the water tower cools the ice machine. When the first and second loops are working, the heat energy of the ice machine can be obtained through the fourth loop circulation. When it is necessary to remove the wall deposits on the first heat exchanger, the heat energy recovered from the ice machine can be used to heat the refrigerant in the first heat exchanger, dissolving the wall deposits in the first heat exchanger, thereby eliminating the wall deposits and enabling the first heat exchanger to maintain efficient heat exchange operation.

[0009] As a further improvement to the above technical solution, the fourth loop also includes a fourth valve. One end of the fourth valve is connected between the ice machine and the third valve, and the other end is connected between the water tower and the second heat exchanger. When the first and second loops are working normally, by opening the fourth valve and closing the third valve, the fourth loop can exchange heat with the ice machine without passing through the second heat exchanger, thereby improving heat exchange efficiency and ensuring the long-term use of the second heat exchanger.

[0010] As a further improvement to the above technical solution, a fifth loop and a fourth pump for powering the fifth loop are also included. The fifth loop includes the crystallizer, the third heat exchanger, and the central cylinder connected in sequence. When the wall thickness in the first heat exchanger reaches a certain level and needs to be eliminated, the first loop is closed and the fifth loop is opened. The third heat exchanger cools the material, allowing the crystallizer to continue operating through the fifth loop, thereby improving crystallization efficiency.

[0011] As a further improvement to the above technical solution, it also includes: a sixth loop, comprising the third heat exchanger, the fifth valve, the refrigerant storage tank, the ice machine, and the sixth valve connected in sequence, the sixth valve being connected to the third heat exchanger, the sixth loop exchanging heat with the fifth loop through the third heat exchanger, and the second pump also being used to provide power to the sixth loop; a seventh loop, comprising the third heat exchanger, the second buffer tank, and the fourth heat exchanger connected in sequence, the fourth heat exchanger being connected to the third heat exchanger; the fifth pump being used to provide power to the seventh loop; and an eighth loop being used to exchange heat with the seventh loop through the fourth heat exchanger.

[0012] The third heat exchanger in the fifth loop and the first heat exchanger in the first loop both use the same refrigerant storage tank and ice machine to supply refrigerant, reducing the cost of refrigerant supply. Meanwhile, the operation of the seventh and eighth loops can eliminate wall buildup on the third heat exchanger, ensuring its heat exchange efficiency.

[0013] As a further improvement to the above technical solution, the eighth loop includes the water tower, the ice machine, the seventh valve, and the fourth heat exchanger connected in sequence. The fourth heat exchanger is connected to the water tower, and the eighth loop exchanges heat with the sixth loop through the ice machine. After the water tower obtains heat energy from the ice machine through the eighth loop, it passes through the fourth heat exchanger and the seventh loop to heat the third heat exchanger in the fifth loop, thereby eliminating the wall formation on the third heat exchanger. That is, the first and third heat exchangers can use the same refrigerant storage tank and ice machine to alternately operate the crystallizer separator, and the third and first heat exchangers can also alternately absorb heat energy from the ice machine through the same water tower to achieve wall formation elimination. By rationally allocating the rotation time according to the actual working conditions, the working efficiency can be improved, and the device cost is low, the utilization efficiency of each component is high, and the economy is good.

[0014] As a further improvement to the above technical solution, the crystallizer is also sequentially connected to an eighth valve, a crystal slurry concentration tank, and a centrifuge. The bottom of the crystal slurry concentration tank is connected to the input end of the centrifuge. The material undergoes the first crystal slurry separation in the crystallizer. Part of the material in the crystallizer can flow into the crystal slurry concentration tank through the eighth valve. The bottom slurry in the crystal slurry concentration tank can flow into the centrifuge to separate the crystals and the centrifugal mother liquor, thereby enabling efficient crystal extraction.

[0015] As a further improvement to the above technical solution, the liquid output end of the centrifuge is connected to a crystal slurry separation tank, the crystal slurry concentration tank is equipped with a stirrer and an annular inner cylinder, the crystallizer is connected to the annular inner cylinder through the eighth valve, the crystal slurry concentration tank is connected to the crystal slurry separation tank through an overflow structure, and the bottom of the crystal slurry separation tank is provided with an inclined surface.

[0016] Crystals in the crystal slurry concentration tank can be deposited downwards along the inner wall of the annular inner cylinder. When the material in the crystal slurry concentration tank is submerged to the lower edge of the annular inner cylinder and reaches the upper outlet of the crystal slurry concentration tank, the clear liquid flows over the lower edge of the annular inner cylinder and upwards to the upper outlet of the crystal slurry concentration tank, flowing into the crystal slurry separation tank for further crystal slurry separation. When the crystal slurry ratio in the crystal slurry concentration tank reaches 15%-40%, the centrifuge is turned on to separate the crystals and centrifugal mother liquor. The centrifugal mother liquor flows into the crystal slurry separation tank for further crystal slurry separation. The clear liquid and mother liquor after treatment by the crystal slurry concentration tank and centrifuge still contain 1%-5% of fine crystals that have not been completely separated, which can be deposited at the bottom of the crystal slurry separation tank for reuse.

[0017] As a further improvement to the above technical solution, a sixth pump is connected to the bottom of the crystal slurry separator, and the output end of the sixth pump is connected to the central cylinder. When the sixth pump is started, the material in the crystal slurry separator flows back into the central cylinder. The fine crystals in the flowing material mix and impact with the supersaturated material after freezing in the central cylinder. The fine crystals continue to grow as crystal nuclei, which promptly eliminates the supersaturation of the material in the central cylinder, reduces the number of fine crystals automatically formed in the crystallizer, and thus extends the wall formation cycle in the first heat exchanger.

[0018] As a further improvement to the above technical solution, it also includes a raw material tank and a seventh pump for pumping the liquid from the raw material tank into the central cylinder. A fifth heat exchanger is connected between the seventh pump and the central cylinder. An eighth pump is connected to the upper part of the crystal slurry separation tank, and the output end of the eighth pump is sequentially connected to the fifth heat exchanger and the clear liquid tank. When the material level in the crystal slurry separation tank exceeds the upper outlet of the crystal slurry separation tank, the eighth pump is activated. The clear liquid flows through the fifth heat exchanger to pre-cool and heat the feed material before entering the clear liquid tank. The clear liquid can pre-cool and heat the feed material through the fifth heat exchanger, fully utilizing the energy of the clear liquid to achieve energy saving. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0020] Figure 1 This is an overall schematic diagram of an embodiment of the present utility model;

[0021] Figure 2 This is a schematic diagram showing the connection between the first heat exchanger and the third heat exchanger in an embodiment of this utility model.

[0022] 100. Raw material tank; 210. Seventh pump; 220. Fifth heat exchanger; 310. First pump; 320. Fourth pump; 330. Central cylinder; 340. Crystallizer separator; 350. Separator drain valve; 360. Eighth valve; 370. Overflow port; 411. First vent valve; 412. First drain valve; 413. First heat exchanger; 4141. Second valve; 4142. First valve; 4143. Third pump; 4144. First buffer tank; 4145. Second heat exchanger; 421. Second vent valve; 422. Second drain valve; 423, Third heat exchanger; 4241, Sixth valve; 4242, Fifth valve; 4243, Fifth pump; 4244, Second buffer tank; 4245, Fourth heat exchanger; 431, Third valve; 432, Seventh valve; 433, Fourth valve; 434, Ice machine; 435, Refrigerant storage tank; 436, Second pump; 437, Water tower; 510, Crystal slurry concentration tank; 511, Annular inner cylinder; 520, Centrifuge; 530, Crystal slurry separation tank; 540, Sixth pump; 550, Eighth pump; 600, Clear liquid tank. Detailed Implementation

[0023] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0024] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this 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 this utility model.

[0025] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first" or "second" is used in the description, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0026] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0027] Reference Figure 1-2 The freeze crystallization and salt separation device includes a first circuit, a first pump 310, a second circuit, a second pump 436, a third circuit, a third pump 4143, a fourth circuit, a fifth circuit, a fourth pump 320, a sixth circuit, a seventh circuit, a fifth pump 4243, and an eighth circuit.

[0028] The first circuit includes a crystallizer 340, a first heat exchanger 413, and a central cylinder 330 connected sequentially by pipes. The central cylinder 330 is located in the middle of the interior of the crystallizer 340. A first pump 310 is connected between the first heat exchanger 413 and the crystallizer 340 and is installed on the top side of the crystallizer 340. The first pump 310 draws the material between the inner wall of the crystallizer 340 and the outer wall of the central cylinder 330 into the first heat exchanger 413 for freezing treatment, and then guides it back into the central cylinder 330 from the top. It is understood that the interior of the central cylinder 330 is hollow and its bottom is connected to the crystallizer 340.

[0029] The second loop includes a first heat exchanger 413, a first valve 4142, a refrigerant storage tank 435, an ice machine 434, and a second valve 4141, connected sequentially by pipes. One end of the second valve 4141 is connected to the ice machine 434, and the other end is connected to the first heat exchanger 413. A second pump 436 is connected between the refrigerant storage tank 435 and the ice machine 434. When the second pump 436 is started, the refrigerant in the refrigerant storage tank 435 flows through the second pump 436, the ice machine 434, the second valve 4141, the first heat exchanger 413, and the first valve 4142 back to the refrigerant storage tank 435, where the refrigerant is cooled in the ice machine 434. In other words, the two heat exchange channels of the first heat exchanger 413 are connected to the first loop and the second loop respectively, allowing the refrigerant generated in the second loop to freeze the materials in the first loop via the first heat exchanger 413.

[0030] The third loop includes a first heat exchanger 413, a first buffer tank 4144, and a second heat exchanger 4145 connected sequentially by pipes. One end of one heat exchange channel of the second heat exchanger 4145 is connected to the first buffer tank 4144, and the other end is connected to the first heat exchanger 413. The input end of the third pump 4143 is connected to the first heat exchanger 413, or in other words, the input end of the third pump 4143 is connected to the end of the first valve 4142 away from the refrigerant storage tank 435, and the output end of the third pump 4143 is connected to the first buffer tank 4144. It can be understood that the third loop shares one heat exchange channel of the first heat exchanger 413 with the second loop, and the other heat exchange channel of the first heat exchanger 413 is connected to the first loop.

[0031] The fourth loop includes a water tower 437, an ice machine 434, a third valve 431, and a second heat exchanger 4145 connected sequentially by pipes. One heat exchange channel of the second heat exchanger 4145 is connected to the fourth loop, with one end connected to the third valve 431 and the other end connected to the water tower 437; the other heat exchange channel of the second heat exchanger 4145 is connected to the third loop. It is understood that the ice machine 434 cools the refrigerant. When the cooling water in the water tower 437 passes through the ice machine 434, it absorbs some heat to cool the ice machine 434, thus raising the temperature of the cooling water. When the cooling water at a certain temperature passes through the second heat exchanger 4145, it can raise the temperature of the refrigerant in the third loop, thereby raising the temperature of the material in the first loop through the first heat exchanger 413, achieving the effect of eliminating wall caking.

[0032] The fourth circuit also includes a fourth valve 433. One end of the fourth valve 433 is connected between the water tower 437 and the second heat exchanger 4145, and the other end of the fourth valve 433 is connected between the third valve 431 and the ice machine 434. When the ice machine is being cooled and the second heat exchanger 4145 is not needed, the cooling water can be prevented from passing through the second heat exchanger 4145 by opening the fourth valve 433 and closing the third valve 431, thereby improving the cooling effect and protecting the second heat exchanger 4145.

[0033] The fifth loop includes a crystallizer 340, a third heat exchanger 423, and a central cylinder 330 connected in sequence by pipes. The inlet of a fourth pump 320 is connected between the inner wall of the crystallizer 340 and the outer wall of the central cylinder 330, and the fourth pump 320 is installed on the other side of the top of the crystallizer 340. The outlet of the fourth pump 320 is connected to one of the heat exchange channels of the third heat exchanger 423, the other end of which is connected to the top of the central cylinder 330. Refrigerant flows through the other heat exchange channel of the third heat exchanger 423. The material between the inner wall of the crystallizer 340 and the outer wall of the central cylinder 330 is drawn into the third heat exchanger 423 for freezing treatment by the fourth pump 320, and then guided back into the central cylinder 330 from the top.

[0034] The sixth loop includes a third heat exchanger 423, a fifth valve 4242, a refrigerant storage tank 435, a second pump 436, an ice machine 434, and a sixth valve 4241, which are connected in sequence by pipes. One end of the sixth valve 4241 is connected to the ice machine 434, and the other end is connected to one end of another heat exchange channel of the third heat exchanger 423. The other end of this heat exchange channel is connected to the fifth valve 4242, thus providing refrigerant to the third heat exchanger 423 through the sixth loop.

[0035] The seventh loop includes a third heat exchanger 423, a second buffer tank 4244, a fifth pump 4243, and a fourth heat exchanger 4245, which are connected sequentially by pipes. One end of one heat exchange channel of the fourth heat exchanger 4245 is connected to a refrigerant storage tank 435, and the other end is connected to one end of another heat exchange channel of the third heat exchanger 423. It is understood that the seventh loop shares one heat exchange channel of the third heat exchanger 423 with the sixth loop, and the other heat exchange channel of the third heat exchanger 423 is connected to the fifth loop.

[0036] The eighth loop includes a water tower 437, an ice machine 434, a seventh valve 432, and a fourth heat exchanger 4245 connected in sequence by pipes. One heat exchange channel of the fourth heat exchanger 4245 is connected to the seventh loop. One end of the other heat exchange channel of the fourth heat exchanger 4245 is connected to the seventh valve 432, and the other end is connected to the water tower 437.

[0037] Understandably, the ice machine 434 cools the refrigerant, and the cooling water in the water tower 437 absorbs some heat from the ice machine 434 as it passes through it, thus raising the temperature of the cooling water. When the cooling water at a certain temperature passes through the fourth heat exchanger 4245, it can heat the refrigerant in the seventh loop, thereby heating the material in the fifth loop through the third heat exchanger 423, achieving the effect of eliminating wall caking.

[0038] A crystallizer 340 is connected in sequence to an eighth valve 360, a crystal slurry concentration tank 510, a centrifuge 520, and a crystal slurry separation tank 530, located slightly below the outer wall of the crystallizer 340. The bottom of the crystal slurry separation tank 530 has an inclined surface. The crystal slurry concentration tank 510 is equipped with a stirrer and an annular inner cylinder 511, the bottom of which is connected to the bottom of the crystal slurry concentration tank 510. The stirring head of the stirrer is located below the annular inner cylinder 511. The crystallizer 340 is connected to the top of the annular inner cylinder 511 via the eighth valve 360. The crystal slurry concentration tank 510 is connected to the middle of the crystal slurry separation tank 530, near the higher side of the inclined surface, via an overflow structure. The input end of the centrifuge 520 is connected to the bottom of the crystal slurry concentration tank 510. The centrifugal liquid output end of the centrifuge 520 is connected to the middle of the crystal slurry separation tank 530, near the higher side of the inclined surface.

[0039] The eighth valve 360 ​​has a certain height difference with the annular inner cylinder 511, allowing material to automatically flow into the annular inner cylinder 511 when the eighth valve 360 ​​is opened. The upper overflow channel of the crystal slurry concentrator 510 is located at 3 / 4-4 / 5 of the height of the tank wall. The upper edge of the annular inner cylinder 511 is 15-25cm higher than the upper outlet of the crystal slurry concentrator 510, and the lower edge of the annular inner cylinder 511 is 30-40cm lower than the upper outlet of the crystal slurry concentrator 510. There is a 15-25cm gap between the annular inner cylinder 511 and the inner wall of the crystal slurry concentrator 510. The inlet of the crystal slurry separator 530 is located at 1 / 3-2 / 3 of the height of the tank wall, and the bottom of the crystal slurry separator 530 has a certain angle X with the horizontal plane, 30°≤X≤75°.

[0040] Furthermore, the lowest point of the crystal slurry separator 530 is connected to a sixth pump 540 via a pipe. The input end of the sixth pump 540 is connected to the crystal slurry separator 530, and the output end is connected to the top of the central cylinder 330.

[0041] The cryogenic crystallization and salt separation device also includes a raw liquid tank 100, a seventh pump 210, a fifth heat exchanger 220, an eighth pump 550, and a clear liquid tank 600.

[0042] The input end of the seventh pump 210 is connected to the bottom outlet of the raw liquid tank 100, and the output end is connected to one end of one heat exchange channel of the fifth heat exchanger 220. The other end of this heat exchange channel is connected to the top of the central cylinder 330. This allows the raw liquid in the raw liquid tank 100 to be introduced into the central cylinder 330. The input end of the eighth pump 550 is connected via a pipe to the top opening of the crystal slurry separator 530, which is located at 3 / 4-4 / 5 of the tank wall height. The output end of the eighth pump 550 is connected to one end of another heat exchange channel of the fifth heat exchanger 220, the other end of which is connected to the top of the clear liquid tank 600. This means that the clear liquid in the crystal slurry separator 530 can pre-cool and heat-exchange the feed through the fifth heat exchanger 220, fully utilizing the energy of the clear liquid and achieving energy-saving effects.

[0043] In addition, a first vent valve 411 is installed in the pipe from the first heat exchanger 413 back to the central cylinder 330. The first vent valve 411 is located at the highest point of the first loop. A second vent valve 421 is installed in the pipe from the third heat exchanger 423 back to the central cylinder 330. The second vent valve 421 is located at the highest point of the fifth loop.

[0044] A first drain valve 412 is installed in the pipe connecting the first heat exchanger 413 to the first pump 310. The other end of the first drain valve 412 is connected to the top of the raw material tank 100. The first drain valve 412 is located at the lowest point of the first loop. A second drain valve 422 is installed in the pipe connecting the third heat exchanger 423 to the fourth pump 320. The other end of the second drain valve 422 is connected to the top of the raw material tank 100. The second drain valve 422 is located at the lowest point of the fifth loop.

[0045] The bottom of the crystallizer 340 is connected to a separator drain valve 350 via a pipe, and the other end of the separator drain valve 350 is connected to the top of the raw liquid tank 100. The crystallizer 340 is provided with an overflow port 370, which is connected to the top of the raw liquid tank 100 via a pipe.

[0046] The overflow port 370, the separator drain valve 350, the first drain valve 412, and the second drain valve 422 are all at a certain height from the top of the raw liquid tank 100. When the drain valve is opened or the material in the crystallizer separator 340 exceeds the overflow port 370, the material can automatically flow back into the raw liquid tank 100.

[0047] For example, the method of using the above-mentioned device may include the following steps:

[0048] 1) Feeding: The material in the raw liquid tank 100 is pumped to the crystallizer 340 by the seventh pump 210. When the feed reaches the designated level, the first pump 310 is started. The material flows from the crystallizer 340 through the first heat exchanger 413 and the central cylinder 330 back to the crystallizer 340. Feeding stops when the crystallizer 340 reaches the designated level again. If too much material is fed, it flows back to the raw liquid tank 100 through the overflow port 370.

[0049] 2) Refrigeration: Open the fourth valve 433, start the water tower 437, and the circulating cooling water flows from the water tower 437 through the ice machine 434 and the fourth valve 433 back to the water tower 437; open the second valve 4141 and the first valve 4142, start the second pump 436, and the refrigerant flows from the refrigerant storage tank 435 through the second pump 436, the ice machine 434, the second valve 4141, the first heat exchanger 413, and the first valve 4142 back to the refrigerant storage tank 435, opening the second circuit; start the third pump 4143, and at this time, the refrigerant flows from the first heat exchanger 413 through the third pump 4143, the first buffer tank 4144, and the second heat exchanger 4145 back to the first heat exchanger 413, opening the third circuit; start the ice machine 434 and set the refrigerant temperature; begin freezing the materials.

[0050] 3) Discharge: As freezing and cooling proceed, the solubility of the solute in the material continuously decreases, and crystals begin to precipitate. When the crystal concentration in the crystallizer 340 reaches 5%-20%, the eighth valve 360 ​​is opened to begin discharging into the crystal slurry concentration tank 510. The crystals deposit downwards along the inner wall of the annular inner cylinder 511. When the material in the crystal slurry concentration tank 510 is submerged at the lower edge of the annular inner cylinder 511 and reaches the upper outlet of the crystal slurry concentration tank 510, the clear liquid flows upwards through the lower edge of the annular inner cylinder 511 to the upper outlet of the crystal slurry concentration tank 510 and flows into the crystal slurry separation tank 530 for further crystal slurry separation. When the crystal-to-slurry ratio in the crystal slurry concentration tank 510 reaches 15%-40%, the centrifuge 520 is turned on to separate the crystals and centrifugal mother liquor. The centrifugal mother liquor flows into the crystal slurry separation tank 530. After a second crystallization separation, the clear liquid and mother liquor processed by the crystallization slurry concentration tank 510 and centrifuge 520 still contain 1%-5% fine crystals that have not been completely separated and will settle at the bottom of the crystallization slurry separation tank 530. The sixth pump 540 is started, and the material in the crystallization slurry separation tank 530 flows back to the central cylinder 330. The fine crystals in the returned material are mixed and impacted with the supersaturated material after freezing in the central cylinder 330. The fine crystals continue to grow as crystal nuclei, which timely eliminates the supersaturation of the material in the central cylinder 330 and reduces the fine crystals formed by automatic nucleation in the crystallizer 340, thereby extending the wall formation cycle in the first heat exchanger 413. During the discharge process, the seventh pump 210 should be started in time to replenish the material according to the liquid level in the crystallizer 340.

[0051] 4) Operation: After continuing to freeze to the target temperature, the flow rate of the sixth pump 540 can be appropriately reduced. When the material level in the crystal slurry separator 530 exceeds the upper outlet of the crystal slurry separator 530, the eighth pump 550 is turned on. The clear liquid flows through the fifth heat exchanger 220 to pre-cool and exchange heat with the feed before entering the clear liquid tank 600. At the same time, according to the solute concentration of the feed, the feed rate of the seventh pump 210, the crystal slurry return flow rate of the sixth pump 540, and the output rate of the eighth pump 550 are adjusted to ensure that the material level in the crystallizer 340 is maintained at a stable level, and the crystal slurry ratio in the crystallizer 340 is kept stable at 5%-20%.

[0052] 5) Heat exchange system switching: When the current of the first pump 310 exceeds the limit, the fourth pump 320 is started. The material flows from the crystallizer 340 through the third heat exchanger 423 and the central cylinder 330 back to the crystallizer 340. The sixth valve 4241 and the fifth valve 4242 are opened, and the second valve 4141 and the first valve 4142 are closed. At this time, the refrigerant flows from the refrigerant storage tank 435 through the second pump 436, the ice machine 434, the sixth valve 4241, the third heat exchanger 423, and the fifth valve 4242 back to the refrigerant storage tank 435, opening the sixth loop; the fifth pump 4243 is started. At this time, the refrigerant flows from the third heat exchanger 423 through the fifth pump 4243, the second buffer tank 4244, and the fourth heat exchanger 4245 back to the third heat exchanger 423, opening the seventh loop; the first pump 310 is shut down.

[0053] 6) Thawing: Open the third valve 431 and close the fourth valve 433. At this time, the circulating cooling water flows from the water tower 437 through the ice machine 434, the third valve 431 and the second heat exchanger 4145 and returns to the water tower 437, starting the fourth loop. After the circulating cooling water completes heat exchange in the ice machine 434, the temperature of the circulating cooling water is 20℃-40℃. It flows through the second heat exchanger 4145 and exchanges heat with the refrigerant in the third loop, causing the refrigerant temperature to rise. When the refrigerant flows through the first heat exchanger 413, it heats the tubes, causing the wall-forming material in the tube layer to dissolve back into the material. After the wall formation is eliminated, open the fourth valve 433 and close the third valve 431. The material dissolved in the first heat exchanger 413 can be discharged back to the original liquid tank 100 by opening the first vent valve 411 and the first drain valve 412, or it can be transferred to the crystallizer 340 through material circulation when the heat exchange system is switched next time.

[0054] 7) Shutdown: After the material is processed, after the crystals have been discharged from the crystallizer 340, the first vent valve 411, the first drain valve 412, the separator drain valve 350, the second vent valve 421, and the second drain valve 422 can be opened to discharge the material in the system back to the original liquid tank 100.

[0055] The two heat exchange loop systems are used in a backup manner. When one heat exchange system is running, the other heat exchange system is thawed or on standby. When switching from the fifth loop to the first loop, the operation steps are similar to steps 5) and 6).

[0056] Therefore, this application adopts a dual heat exchange system, with one system serving as a backup for the other, which can achieve uninterrupted switching between them. This can completely solve the problem of shutdown caused by the wall formation on the inner side of the heat exchanger tubes. Furthermore, the defrosting process cleverly uses the heat energy of the circulating cooling water to heat up the wall-forming material, defrost and desalinate it, avoiding the need for additional heating devices and cleaning water.

[0057] Compared to conventional refrigeration systems, this application adds crystal slurry reflux, which can promptly eliminate the supersaturation of the material in the central cylinder 330, greatly reducing the generation of fine crystals and extending the wall-forming cycle of the heat exchanger tubes to 10-15 days. It also makes the entire unit more adaptable to materials with large fluctuations in feed solute concentration. When the material concentration is high, the feed rate and the amount of clear liquid collected can be reduced, while the crystal slurry reflux rate can be increased to collect the crystals in time, reduce the crystal slurry concentration in the crystal separator, reduce the load on the circulating pump, and avoid the problem that the unit temperature is difficult to reduce to the target value due to the large amount of clear liquid collected.

[0058] This application uses a crystal slurry concentration tank 510 instead of a conventional thickener design, which completely solves the problem of crystals in the material short-circuiting and directly flowing out of the overflow port. At the same time, it can also avoid the problem of the thickener overflowing due to crystal blockage of the overflow sawtooth weir.

[0059] This application uses a crystal slurry separator 530 instead of the conventional "mother liquor tank + precision filter" design, which reduces the amount of crystals carried away by the clear liquid and avoids the problem of having to clean the precision filter frequently.

[0060] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

Claims

1. A freeze-crystallization and salt separation apparatus, characterized in that, include: The first circuit includes a crystallizer (340), a first heat exchanger (413), and a central cylinder (330) connected in sequence, wherein the central cylinder (330) is disposed inside the crystallizer (340); The first pump (310) is used to provide power to the first circuit; The second circuit includes the first heat exchanger (413), the first valve (4142), the refrigerant storage tank (435), the ice machine (434), and the second valve (4141) connected in sequence. The second valve (4141) is connected to the first heat exchanger (413), and the second circuit exchanges heat with the first circuit through the first heat exchanger (413). The second pump (436) is used to provide power to the second circuit; The third loop includes the first heat exchanger (413), the first buffer tank (4144), and the second heat exchanger (4145) connected in sequence. The second heat exchanger (4145) is connected to the first heat exchanger (413), and the third loop is connected to the second loop through the second heat exchanger (4145). The third pump (4143) is used to provide power to the third circuit; The fourth loop is used for heat exchange with the third loop via the second heat exchanger (4145).

2. The freeze-crystallization and salt separation apparatus according to claim 1, characterized in that: The fourth circuit includes a water tower (437), an ice machine (434), a third valve (431), and a second heat exchanger (4145) connected in sequence. The second heat exchanger (4145) is connected to the water tower (437), and the cooling water in the water tower (437) cools the ice machine.

3. The freeze-crystallization and salt separation apparatus according to claim 2, characterized in that: The fourth circuit also includes a fourth valve (433), one end of which is connected between the ice machine (434) and the third valve (431), and the other end is connected between the water tower (437) and the second heat exchanger (4145).

4. The freeze-crystallization and salt separation apparatus according to claim 2 or 3, characterized in that: It also includes a fifth circuit and a fourth pump (320) for powering the fifth circuit, the fifth circuit comprising the crystallizer (340), the third heat exchanger (423) and the central cylinder (330) connected in sequence.

5. The freeze-crystallization and salt separation apparatus according to claim 4, characterized in that: Also includes: The sixth loop includes the third heat exchanger (423), the fifth valve (4242), the refrigerant storage tank (435), the ice machine (434), and the sixth valve (4241) connected in sequence. The sixth valve (4241) is connected to the third heat exchanger (423). The sixth loop exchanges heat with the fifth loop through the third heat exchanger (423). The second pump (436) is also used to provide power to the sixth loop. The seventh circuit includes the third heat exchanger (423), the second buffer tank (4244), and the fourth heat exchanger (4245) connected in sequence, with the fourth heat exchanger (4245) connected to the third heat exchanger (423). The fifth pump (4243) is used to power the seventh circuit; The eighth loop is used for heat exchange with the seventh loop via the fourth heat exchanger (4245).

6. The freeze-crystallization and salt separation apparatus according to claim 5, characterized in that: The eighth circuit includes the water tower (437), the ice machine (434), the seventh valve (432), and the fourth heat exchanger (4245) connected in sequence. The fourth heat exchanger (4245) is connected to the water tower (437), and the eighth circuit exchanges heat with the sixth circuit through the ice machine.

7. The freeze-crystallization and salt separation apparatus according to claim 1, characterized in that: The crystallizer (340) is also connected in sequence to an eighth valve (360), a crystal slurry concentration tank (510) and a centrifuge (520), with the bottom of the crystal slurry concentration tank (510) connected to the input end of the centrifuge (520).

8. The freeze-crystallization and salt separation apparatus according to claim 7, characterized in that: The centrifuge (520) has a liquid output end connected to a crystal slurry separation tank (530). The crystal slurry concentration tank (510) is equipped with a stirrer and an annular inner cylinder (511). The crystal separator (340) is connected to the annular inner cylinder (511) through the eighth valve (360). The crystal slurry concentration tank (510) is connected to the crystal slurry separation tank (530) through an overflow structure. The bottom of the crystal slurry separation tank (530) is provided with an inclined surface.

9. The freeze-crystallization and salt separation apparatus according to claim 8, characterized in that: The bottom of the crystal slurry separator (530) is connected to a sixth pump (540), and the output end of the sixth pump (540) is connected to the central cylinder (330).

10. The freeze-crystallization and salt separation apparatus according to claim 8, characterized in that: It also includes a raw liquid tank (100) and a seventh pump (210) for pumping the liquid in the raw liquid tank (100) into the central cylinder (330). A fifth heat exchanger (220) is connected between the seventh pump (210) and the central cylinder (330). An eighth pump (550) is connected to the upper part of the crystal slurry separation tank (530). The output end of the eighth pump (550) is connected to the fifth heat exchanger (220) and the clear liquid tank (600) in sequence.

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