Sodium sulfate wastewater treatment system

Abstract

The application relates to a sodium sulfate wastewater treatment system. The sodium sulfate wastewater treatment system comprises a direct cooling heat exchanger, a thickener, a compressor, a first condensing heat exchanger and a centrifuge; the direct cooling heat exchanger can directly contact sodium sulfate wastewater with a refrigerant, so that the refrigerant can crystallize sodium sulfate in the sodium sulfate wastewater in a gasification heat absorption mode to form slurry containing mirabilite crystals; the thickener is communicated with the direct cooling heat exchanger and can separate the slurry into solid and liquid, so that concentrated mirabilite slurry is obtained at the bottom and supernatant is obtained at the top; the compressor is communicated with the direct cooling heat exchanger and can compress the refrigerant after gasification heat absorption into liquid refrigerant; the first condensing heat exchanger is communicated with the thickener, the compressor and the direct cooling heat exchanger and can exchange heat between the supernatant and the liquid refrigerant to warm the supernatant and cool the liquid refrigerant; the centrifuge is communicated with the thickener and can separate sodium sulfate in the concentrated mirabilite slurry.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and in particular to a sodium sulfate wastewater treatment system. Background Technology

[0002] Sodium sulfate wastewater mainly originates from high-salinity wastewater from coal chemical industry, mine water, and new energy industry (such as lithium battery material production and rare earth smelting), as well as concentrated water from membrane treatment processes (such as nanofiltration / reverse osmosis). This type of wastewater generally has high organic content and high color, and usually contains varying amounts of sodium chloride. Therefore, currently, freeze crystallization is commonly used to produce mirabilite (sodium sulfate decahydrate), and the mirabilite is then hot-melted (recrystallized) to produce high-quality sodium sulfate crystalline salt.

[0003] Currently, most cryogenic crystallization heat exchangers used in the industry employ shell-and-tube heat exchangers, using calcium chloride or ethylene glycol aqueous solution as the refrigerant. They indirectly lower the temperature of the sodium sulfate concentrate to achieve sodium sulfate crystallization. The mother liquor after sodium sulfate crystallization and separation is discharged to the evaporation system for further evaporation and crystallization, primarily producing sodium chloride crystals, but possibly also mixed salts (depending on the content of other ions in the raw water and crystallization control).

[0004] However, existing cryo-crystallization systems generally suffer from problems such as high refrigeration energy consumption, frequent blockage of heat exchanger tubes, and poor operational stability. Utility Model Content

[0005] Therefore, it is necessary to provide a sodium sulfate wastewater treatment system to address the aforementioned technical problems.

[0006] A sodium sulfate wastewater treatment system, comprising:

[0007] The direct-cooling heat exchanger can directly contact sodium sulfate wastewater with refrigerant, so that the refrigerant can crystallize sodium sulfate in the sodium sulfate wastewater through vaporization and heat absorption to form a slurry containing sodium sulfate crystals.

[0008] The thickener, connected to the direct cooling heat exchanger, is capable of solid-liquid separation of the slurry, thereby obtaining concentrated sodium sulfate slurry at the bottom and supernatant at the top;

[0009] The compressor, connected to the direct-cooling heat exchanger, is capable of compressing the refrigerant after it has been vaporized and absorbed heat into a liquid refrigerant.

[0010] A first condensing heat exchanger, connected to the thickener, the compressor, and the direct-cooling heat exchanger, is capable of exchanging heat between the supernatant and the liquid refrigerant to raise the temperature of the supernatant and lower the temperature of the liquid refrigerant; and

[0011] A centrifuge, connected to the thickener, is capable of separating sodium sulfate from the concentrated sodium sulfate slurry.

[0012] In one embodiment, the direct-cooling heat exchanger has a first inlet, a second inlet, a first outlet, and a second outlet;

[0013] The first inlet is used to introduce the sodium sulfate wastewater;

[0014] The second inlet is located below the first inlet and is connected to the first condensing heat exchanger to allow the cooled liquid refrigerant to pass through;

[0015] The first outlet is located below the second inlet and is connected to the thickener to discharge the slurry;

[0016] The second outlet is located above the first inlet and is connected to the compressor to discharge the refrigerant after it has been vaporized and absorbed heat.

[0017] In one embodiment, the second inlet is provided as multiple groups, and the multiple groups of the second inlet are arranged at intervals from top to bottom.

[0018] In one embodiment, the direct cooling heat exchanger is further provided with a perforated first water distributor, which is connected to the first inlet and has multiple first nozzles installed on it.

[0019] In one embodiment, the first water distributor includes a confluence section and a diversion section. The confluence section is annular and fixed to the inner wall of the direct-cooling heat exchanger. The diversion section is connected to the confluence section and located in the space enclosed by the confluence section. The diversion section has a plurality of water outlet holes, and the first nozzle is installed in the water outlet holes.

[0020] In one embodiment, the direct-cooling heat exchanger is further provided with a temperature sensor, which is located near the first outlet and acquires the temperature of the sodium sulfate wastewater;

[0021] The spray flow rate of the first nozzle can be adjusted based on the temperature of the sodium sulfate wastewater.

[0022] In one embodiment, the specific heat of the refrigerant is greater than 1.0 kJ / (kg·K).

[0023] In one embodiment, the sodium sulfate wastewater treatment system further includes a second condenser heat exchanger;

[0024] The second condensing heat exchanger is connected between the compressor and the first condensing heat exchanger, and can use a cold medium to cool the liquid refrigerant.

[0025] In one embodiment, the sodium sulfate wastewater treatment system further includes a transfer pump;

[0026] The transfer pump is connected between the direct cooling heat exchanger and the thickener, and is capable of pumping the slurry into the thickener.

[0027] In one embodiment, the sodium sulfate wastewater treatment system further includes an evaporator crystallizer;

[0028] The evaporator crystallizer is connected to the first condenser heat exchanger and is capable of evaporating and crystallizing the supernatant.

[0029] The aforementioned sodium sulfate wastewater treatment system employs a direct-cooling heat exchanger to achieve direct contact heat exchange between the sodium sulfate wastewater and the refrigerant. This improves heat exchange efficiency and eliminates the risks of scaling and clogging in traditional shell-and-tube heat exchangers. Furthermore, the direct-cooling heat exchanger can be designed with a hollow structure, resulting in lower material usage, lower manufacturing costs, and easier maintenance. In addition, the system also uses a first condensing heat exchanger to achieve heat exchange between the supernatant of the slurry and the refrigerant, thereby increasing the temperature of the supernatant and providing favorable conditions for subsequent evaporation and crystallization, thus reducing the overall energy consumption of the system. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a sodium sulfate wastewater treatment system provided in one embodiment of this application.

[0031] Figure 2 This is a schematic diagram of the treatment process of a sodium sulfate wastewater treatment system provided in an embodiment of this application.

[0032] Figure 3 A schematic diagram of the structure of the first water distributor of a sodium sulfate wastewater treatment system provided in one embodiment of this application.

[0033] The labels in the attached diagram are explained as follows:

[0034] 10. Sodium sulfate wastewater treatment system; 100. Direct cooling heat exchanger; 100a. First inlet; 100b. Second inlet; 100c. First outlet; 100d. Second outlet; 110. First water distributor; 111. Manifold; 112. Diverter; 200. Thickener; 300. Compressor; 400. First condensing heat exchanger; 500. Centrifuge; 600. Transfer pump. Detailed Implementation

[0035] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0036] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application.

[0037] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0038] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0039] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0040] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0041] Sodium sulfate wastewater mainly originates from high-salinity wastewater from coal chemical industry, mine water, and new energy industry (such as lithium battery material production and rare earth smelting), as well as concentrated water from membrane treatment processes (such as nanofiltration / reverse osmosis). This type of wastewater generally has high organic content and high color, and usually contains varying amounts of sodium chloride. Therefore, currently, freeze crystallization is commonly used to produce mirabilite (sodium sulfate decahydrate), and the mirabilite is then hot-melted (recrystallized) to produce high-quality sodium sulfate crystalline salt.

[0042] Currently, most cryogenic crystallization heat exchangers used in the industry employ shell-and-tube heat exchangers, using calcium chloride or ethylene glycol aqueous solution as the refrigerant. They indirectly lower the temperature of the sodium sulfate concentrate to achieve sodium sulfate crystallization. The mother liquor after sodium sulfate crystallization and separation is discharged to the evaporation system for further evaporation and crystallization, primarily producing sodium chloride crystals, but possibly also mixed salts (depending on the content of other ions in the raw water and crystallization control).

[0043] However, existing cryo-crystallization systems generally suffer from problems such as high refrigeration energy consumption, frequent blockage of heat exchanger tubes, and poor operational stability.

[0044] For this, please refer to Figure 1 This application provides a sodium sulfate wastewater treatment system 10, which includes a direct-cooling heat exchanger 100, a thickener 200, a compressor 300, a first condensing heat exchanger 400, and a centrifuge 500. The direct-cooling heat exchanger 100 can directly contact the sodium sulfate wastewater with a refrigerant, allowing the refrigerant to crystallize and precipitate sodium sulfate from the wastewater through vaporization and heat absorption, forming a slurry containing sodium sulfate crystals. The thickener 200 is connected to the direct-cooling heat exchanger 100 and can process the slurry... Solid-liquid separation is performed to obtain concentrated sodium sulfate slurry at the bottom and supernatant at the top; compressor 300 is connected to direct cooling heat exchanger 100, which can compress the refrigerant after vaporization and heat absorption to form liquid refrigerant; first condensing heat exchanger 400 is connected to thickener 200, compressor 300 and direct cooling heat exchanger 100, which can exchange heat between supernatant and liquid refrigerant to raise the temperature of supernatant and lower the temperature of liquid refrigerant; centrifuge 500 is connected to thickener 200, which can separate sodium sulfate from concentrated sodium sulfate slurry.

[0045] The sodium sulfate wastewater treatment system 10 can be applied to fields such as coal chemical industry, mine water, and new energy industry (such as lithium battery production). It precipitates and separates sodium sulfate in wastewater in the form of sodium sulfate decahydrate (sodium sulfate decahydrate, also known as sodium sulfate decahydrate) through crystallization process. After hot melting and dehydration, the obtained sodium sulfate can produce high-purity anhydrous sodium sulfate crystal salt (such as industrial grade ≥99%).

[0046] See Figure 2 When treating sodium sulfate wastewater, the sodium sulfate wastewater and refrigerant are respectively introduced into the direct cooling heat exchanger 100. The refrigerant can directly contact the sodium sulfate wastewater and remove the heat from the sodium sulfate wastewater through gasification heat absorption. The temperature of the sodium sulfate wastewater can drop to a certain level (e.g., 2℃~5℃). At this time, the sodium sulfate in the sodium sulfate wastewater will crystallize out in the form of sodium sulfate, thus forming a slurry containing sodium sulfate crystals.

[0047] Afterwards, the slurry containing Glauber's salt crystals flows by gravity into the thickener 200. The slurry is separated by gravity sedimentation in the thickener 200. The supernatant at the top of the thickener 200 overflows to the first condenser heat exchanger 400, while the concentrated Glauber's salt slurry at the bottom of the thickener 200 is sent to the centrifuge 500 for dehydration to produce wet Glauber's salt.

[0048] The refrigerant that absorbs heat and vaporizes in the direct-cooling heat exchanger 100 is compressed and condensed into a liquid refrigerant by the compressor 300. It then enters the first condensing heat exchanger 400, where it is further cooled by the supernatant from the thickener 200, and subsequently returned to the direct-cooling heat exchanger 100 for reuse. The supernatant, after absorbing heat and heating up in the first condensing heat exchanger 400 (still containing trace amounts of dissolved salts), is discharged into the evaporator crystallizer for further concentration.

[0049] It should be noted that the refrigerant should be a solvent with a low boiling point, high latent heat of vaporization, and immiscibility with water. After the refrigerant vaporizes, most of it will separate from the sodium sulfate wastewater and be discharged from the direct cooling heat exchanger 100, while only a very small portion of the refrigerant will remain in the sodium sulfate wastewater. This very small portion of the refrigerant will be removed by evaporation in the subsequent sodium sulfate wastewater treatment process. Therefore, the direct contact heat exchange method adopted in this application will not affect the purity of sodium sulfate crystallization.

[0050] For economic reasons, the specific heat of the refrigerant should be greater than 1.0 kJ / (kg·K). If the specific heat of the refrigerant is less than 1.0 kJ / (kg·K), it will lead to excessive recycling. As an example, the refrigerant can be n-butane.

[0051] The sodium sulfate wastewater treatment system 10 uses a direct-cooling heat exchanger 100 to achieve direct contact heat exchange between the sodium sulfate wastewater and the refrigerant, which can improve heat exchange efficiency and eliminate the risk of scaling and clogging in traditional shell and tube heat exchangers. In addition, the direct-cooling heat exchanger 100 can be designed with a hollow structure, which has the advantages of less material, low manufacturing cost and convenient maintenance. Furthermore, the sodium sulfate wastewater treatment system 10 also uses a first condensing heat exchanger 400 to achieve heat exchange between the supernatant of the slurry and the refrigerant, so as to increase the temperature of the supernatant and provide favorable conditions for the subsequent evaporation and crystallization of the supernatant, thereby reducing the overall energy consumption of the system.

[0052] like Figure 1 As shown, in some embodiments of this application, the direct-cooling heat exchanger 100 has a first inlet 100a, a second inlet 100b, a first outlet 100c, and a second outlet 100d; the first inlet 100a is used to introduce sodium sulfate wastewater; the second inlet 100b is located below the first inlet 100a and is connected to the first condensing heat exchanger 400 to introduce refrigerant after secondary cooling; the first outlet 100c is located below the second inlet 100b and is connected to the thickener 200 to discharge slurry; the second outlet 100d is located above the first inlet 100a and is connected to the compressor 300 to discharge refrigerant after vaporization and heat absorption. By setting the positions of the first inlet 100a, the second inlet 100b, the first outlet 100c, and the second outlet 100d in this way, the refrigerant and the sodium sulfate wastewater can move in opposite directions in the direct cooling heat exchanger 100, so that the refrigerant can come into full contact with the sodium sulfate wastewater, which can increase the heat exchange effect of the refrigerant on the sodium sulfate wastewater and utilize the precipitation of sodium sulfate crystals in the sodium sulfate wastewater.

[0053] In some embodiments, the second inlet 100b is provided in multiple groups, and the multiple groups of second inlet 100b are arranged at intervals from top to bottom. This arrangement allows the refrigerant to enter the direct cooling heat exchanger 100 in a dispersed manner, resulting in a more uniform cooling effect of the direct cooling heat exchanger 100 on the sodium sulfate wastewater.

[0054] Each group of second inlets 100b includes multiple second inlets 100b, and these multiple second inlets 100b are evenly distributed along the circumference of the direct cooling heat exchanger 100. This arrangement also makes the cooling effect of the direct cooling heat exchanger 100 on sodium sulfate wastewater more uniform.

[0055] Optionally, such as Figure 1 As shown, the second inlet 100b is configured in two groups, one group located in the middle of the direct cooling heat exchanger 100, and the other group located at the bottom of the direct cooling heat exchanger 100. This arrangement of the number and location of the second inlet 100b minimizes the number of inlets while ensuring uniform cooling effect.

[0056] Optionally, each second inlet 100b is equipped with a second nozzle. This arrangement allows the refrigerant to enter the direct-cooling heat exchanger 100 in a dispersed manner, resulting in a more uniform cooling effect of the direct-cooling heat exchanger 100 on the sodium sulfate wastewater.

[0057] See also Figure 1 In one embodiment, the direct-cooling heat exchanger 100 is further provided with a perforated first water distributor 110, which is connected to the first inlet 100a and is equipped with a plurality of first nozzles (not shown in the figures). Through the cooperation of the first water distributor 110 and the first nozzles, sodium sulfate wastewater can be dispersedly introduced into the direct-cooling heat exchanger 100, increasing the contact area with the refrigerant and thus enhancing the heat exchange effect of the refrigerant on the sodium sulfate wastewater, which is beneficial for the crystallization and precipitation of sodium sulfate in the wastewater.

[0058] Optionally, such as Figure 3 As shown, the first water distributor 110 may include a confluence section 111 and a branch section 112. The confluence section 111 is annular and fixed to the inner wall of the direct-cooling heat exchanger 100. The branch section 112 is connected to the confluence section 111 and located in the space enclosed by the confluence section 111. The branch section 112 has multiple water outlet holes, and first nozzles are installed in the water outlet holes. This structure of the first water distributor 110 allows for the arrangement of a large number of first nozzles in the cross-section of the direct-cooling heat exchanger 100, and also allows for the formation of a perforated area at the branch section 112 for the refrigerant to pass through after vaporization and heat absorption. The branch section 112 may consist of multiple parallel "I"-shaped branch pipes. Figure 3 The cross arrangement shown is as described. Of course, the manifold 111 may also have multiple water outlets, and the water outlets are also equipped with first nozzles.

[0059] Of course, a second water distributor can also be installed inside the direct cooling heat exchanger 100. The second water distributor is connected to the corresponding second inlet 100b and has an air outlet for installing the second nozzle. The structure of the second water distributor may be the same as or different from that of the first water distributor 110.

[0060] In some embodiments of this application, the direct-cooling heat exchanger 100 is further equipped with a temperature sensor (not shown in the figures), which is located near the first outlet 100c and acquires the temperature of the sodium sulfate wastewater; the injection flow rate of the first nozzle can be adjusted based on the temperature of the sodium sulfate wastewater. The first nozzle may be equipped with a valve, the opening of which is adjustable, thereby regulating the injection flow rate of the first nozzle. The valve may be an electric valve or a solenoid valve. By controlling the amount of refrigerant injected, the cooling rate and final temperature of the sodium sulfate wastewater are controlled, resulting in a high degree of automation and convenient operation of the sodium sulfate wastewater treatment system 10.

[0061] Optionally, the sodium sulfate wastewater treatment system 10 also includes a control module (not shown in the figures), which is electrically connected to a temperature sensor and a valve on the first nozzle. The control module can adjust the opening of the valve based on the temperature information sent by the temperature sensor.

[0062] In some embodiments of this application, the sodium sulfate wastewater treatment system 10 further includes a second condensing heat exchanger (not shown in the figures); the second condensing heat exchanger is connected between the compressor 300 and the first condensing heat exchanger 400, and can use a cooling medium to cool the liquid refrigerant. Before the supernatant exchanges heat with the liquid refrigerant, the liquid refrigerant can be pre-cooled using a cooling medium (e.g., circulating water) to avoid the liquid refrigerant failing to reach the preset temperature after heat exchange with the supernatant due to heat imbalance with the supernatant.

[0063] The second condensing heat exchanger can have the same structure as the first condensing heat exchanger 400, for example, it can be a shell-and-tube heat exchanger. Of course, the second condensing heat exchanger can also have a different structure from the first condensing heat exchanger 400.

[0064] like Figure 1 As shown in some embodiments of this application, the sodium sulfate wastewater treatment system 10 further includes a transfer pump 600; the transfer pump 600 is connected between the direct cooling heat exchanger 100 and the thickener 200, and is capable of pumping the slurry into the thickener 200. The transfer pump 600 facilitates the flow of the slurry from the direct cooling heat exchanger 100 into the thickener 200. The transfer pump 600 can be a water pump.

[0065] In some embodiments of this application, the sodium sulfate wastewater treatment system 10 further includes an evaporator crystallizer (not shown in the drawings); the evaporator crystallizer is connected to the first condenser heat exchanger 400 and is capable of evaporating and crystallizing the supernatant. The supernatant still contains trace amounts of dissolved salts, which can be further concentrated using the evaporator crystallizer.

[0066] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0067] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A sodium sulfate wastewater treatment system, characterized in that, include: The direct-cooling heat exchanger can directly contact sodium sulfate wastewater with refrigerant, so that the refrigerant can crystallize sodium sulfate in the sodium sulfate wastewater through vaporization and heat absorption to form a slurry containing sodium sulfate crystals. The thickener, connected to the direct cooling heat exchanger, is capable of solid-liquid separation of the slurry, thereby obtaining concentrated sodium sulfate slurry at the bottom and supernatant at the top; The compressor, connected to the direct-cooling heat exchanger, is capable of compressing the refrigerant after it has been vaporized and absorbed heat to form a liquid refrigerant. The first condensing heat exchanger is connected to the thickener, the compressor and the direct cooling heat exchanger, and is able to exchange heat between the supernatant and the liquid refrigerant to raise the temperature of the supernatant and lower the temperature of the liquid refrigerant. as well as A centrifuge, connected to the thickener, is capable of separating sodium sulfate from the concentrated sodium sulfate slurry.

2. The sodium sulfate wastewater treatment system according to claim 1, characterized in that, The direct-cooling heat exchanger has a first inlet, a second inlet, a first outlet, and a second outlet; The first inlet is used to introduce the sodium sulfate wastewater; The second inlet is located below the first inlet and is connected to the first condensing heat exchanger to allow the cooled liquid refrigerant to pass through; The first outlet is located below the second inlet and is connected to the thickener to discharge the slurry; The second outlet is located above the first inlet and is connected to the compressor to discharge the refrigerant after it has been vaporized and absorbed heat.

3. The sodium sulfate wastewater treatment system according to claim 2, characterized in that, The second inlet is set in multiple groups, and the multiple groups of the second inlet are arranged at intervals from top to bottom.

4. The sodium sulfate wastewater treatment system according to claim 2, characterized in that, The direct cooling heat exchanger is also provided with a hollow first water distributor, which is connected to the first inlet and has multiple first nozzles installed on it.

5. The sodium sulfate wastewater treatment system according to claim 4, characterized in that, The first water distributor includes a confluence section and a diversion section. The confluence section is annular and fixed to the inner wall of the direct cooling heat exchanger. The diversion section is connected to the confluence section and is located in the space enclosed by the confluence section. The diversion section has multiple water outlet holes, and the first nozzle is installed in the water outlet holes.

6. The sodium sulfate wastewater treatment system according to claim 4, characterized in that, The direct cooling heat exchanger is also equipped with a temperature sensor, which is located near the first outlet and acquires the temperature of the sodium sulfate wastewater. The spray flow rate of the first nozzle can be adjusted based on the temperature of the sodium sulfate wastewater.

7. The sodium sulfate wastewater treatment system according to any one of claims 1 to 6, characterized in that, The specific heat of the refrigerant is greater than 1.0 kJ / (kg·K).

8. The sodium sulfate wastewater treatment system according to any one of claims 1 to 6, characterized in that, The sodium sulfate wastewater treatment system also includes a second condenser heat exchanger; The second condensing heat exchanger is connected between the compressor and the first condensing heat exchanger, and can use a cold medium to cool the liquid refrigerant.

9. The sodium sulfate wastewater treatment system according to any one of claims 1 to 6, characterized in that, The sodium sulfate wastewater treatment system also includes a transfer pump; The transfer pump is connected between the direct cooling heat exchanger and the thickener, and is capable of pumping the slurry into the thickener.

10. The sodium sulfate wastewater treatment system according to any one of claims 1 to 6, characterized in that, The sodium sulfate wastewater treatment system also includes an evaporator crystallizer; The evaporator crystallizer is connected to the first condenser heat exchanger and is capable of evaporating and crystallizing the supernatant.

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