Pretreatment system for evaporation and crystallization of sodium sulfate wastewater

Abstract

The present invention discloses a pretreatment system for evaporation and crystallization of sodium sulfate wastewater. The pretreatment system includes a first liquid storage tank, a second liquid storage tank, an oil removal device, a mixing tank, a filter device, and an adjustment tank. The first liquid storage tank is used to store oil-containing first sodium sulfate wastewater, the second liquid storage tank is used to store alkaline second sodium sulfate wastewater, the oil removal device is used to remove oil from the first sodium sulfate wastewater to form a third sodium sulfate wastewater, the mixing tank is used to mix the first sodium sulfate wastewater and the third sodium sulfate wastewater to form a solid-liquid mixture containing heavy metal precipitates, the filter device is used to filter the solid-liquid mixture to obtain heavy metal slag and a filtrate, and the adjustment tank is used to adjust the pH value of the filtrate to form a weakly alkaline sodium sulfate solution. The pretreatment system for evaporation and crystallization of sodium sulfate wastewater removes oil and heavy metals from the sodium sulfate wastewater at a low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, in particular to a pretreatment system for evaporation and crystallization of sodium sulfate wastewater. Background Art

[0002] A large amount of wastewater is generated during the production of ternary precursors. The wastewater is mainly sodium sulfate wastewater containing heavy metals and organic matter. Sodium sulfate wastewater can be divided into oily wastewater and high alkaline wastewater according to its composition. The heavy metal ions mainly include Ni 2+ 、Mn 2+ 、Zn 2+ And other heavy metal ions.

[0003] Sodium sulfate wastewater must be treated to produce anhydrous sodium sulfate, primarily through evaporation and crystallization. However, direct evaporation and crystallization of sodium sulfate wastewater can easily lead to scaling and oil adhesion in the evaporation system, reducing heat exchange efficiency and significantly impacting the evaporation system's production capacity. It also affects the nucleation and growth of glauber salt crystals, resulting in low purity, poor whiteness, and fine particle size. In severe cases, the crystallization system can no longer function properly.

[0004] Prior to treating sodium sulfate wastewater, the prior art pre-treats it. This pre-treatment involves adding a precipitant to the wastewater to precipitate the heavy metals in the wastewater. However, this pre-treatment method fails to remove organic matter from the wastewater, and the treatment process is lengthy, consumes a large amount of precipitant, and is costly. Summary of the Invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0006] To this end, an embodiment of the present invention provides a pretreatment system for evaporation and crystallization of sodium sulfate wastewater, which can fully remove oil and heavy metals in the sodium sulfate wastewater at a low cost.

[0007] According to an embodiment of the present invention, a pretreatment system for evaporation and crystallization of sodium sulfate wastewater includes: a first liquid storage tank, the first liquid storage tank is used to store oil-containing first sodium sulfate wastewater; a second liquid storage tank, the second liquid storage tank is used to store alkaline second sodium sulfate wastewater; an oil removal device, the oil removal device is connected to the first liquid storage tank, the oil removal device is used to remove oil from the first sodium sulfate wastewater to form a third sodium sulfate wastewater; a mixing tank, the mixing tank is connected to the oil removal device and the second liquid storage tank, the mixing tank is used to mix the first sodium sulfate wastewater with the third sodium sulfate wastewater to form a solid-liquid mixture containing heavy metal precipitates; a filtering device, the filtering device is connected to the mixing tank, the filtering device is used to filter the solid-liquid mixture to obtain heavy metal slag and filtrate; and an adjusting tank, the adjusting tank is connected to the filtering device, the adjusting tank is used to adjust the pH value of the filtrate to form a weakly alkaline sodium sulfate solution.

[0008] According to an embodiment of the present invention, a pretreatment system for evaporation and crystallization of sodium sulfate wastewater is provided. An oil removal device is provided to remove oil from the oil-containing first sodium sulfate wastewater in the first liquid storage tank and form an oil-free third sodium sulfate wastewater. A mixing tank is provided to mix the alkaline second sodium sulfate wastewater in the second liquid storage tank with the third sodium sulfate wastewater to form a solid-liquid mixture containing heavy metal precipitates. A filtering device is provided to filter the solid-liquid mixture and obtain a filtrate. A filter tank is provided to adjust the pH of the filtrate to form a weakly alkaline sodium sulfate solution. Thus, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater according to an embodiment of the present invention can fully remove oil and heavy metals from the sodium sulfate wastewater. Moreover, since a precipitate can be generated after mixing the first sodium sulfate wastewater and the second sodium sulfate wastewater, the addition of a precipitant can be reduced during the pretreatment of the sodium sulfate wastewater, thereby reducing costs.

[0009] In some embodiments, the oil removal device includes a first oil remover and a second oil remover, the first oil remover is connected to the first liquid storage tank and the second oil remover, the second oil remover is connected to the mixing tank, the first oil remover is used for flotation oil removal of the first sodium sulfate wastewater, and the second oil remover is used for adsorption oil removal of the first sodium sulfate wastewater.

[0010] In some embodiments, the filtering device includes a first filter and a second filter, the first filter is connected to the mixing tank and the second filter, the second filter is connected to the adjusting tank, the first filter is used to filter the solid-liquid mixture to obtain part of the heavy metal slag and the primary filtrate, and the second filter is used to finely filter the primary filtrate to obtain another part of the heavy metal slag and the filtrate.

[0011] In some embodiments, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater further includes a heavy metal slag recovery pool, which is connected to the first filter and the second filter for recovering heavy metal slag in the first filter and the second filter.

[0012] In some embodiments, the filtration device further includes a filtrate tank, which is in communication with the first filter and the second filter, and is used to store the primary filtrate.

[0013] In some embodiments, the filtration device further includes a filtrate pump, which is connected to the filtrate tank and the second filter, and the filtrate pump is used to pass the primary filtrate in the filtrate tank into the second filter.

[0014] In some embodiments, the first filter is a filter press and the second filter is a fine filter.

[0015] In some embodiments, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater also includes a dilution tank and a dilution delivery pump, the dilution delivery pump is connected to the dilution tank and the adjustment tank, the dilution tank is used to dilute concentrated sulfuric acid to form dilute sulfuric acid, and the dilution delivery pump is used to pass the dilute sulfuric acid into the adjustment tank.

[0016] In some embodiments, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater further includes a flow meter, which is used to control the amount of dilute sulfuric acid entering the regulating tank.

[0017] In some embodiments, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater also includes a first delivery pump, a second delivery pump and a third delivery pump, the first delivery pump is connected to the first liquid storage tank and the first oil remover, the second delivery pump is connected to the first oil remover and the second oil remover, the third delivery pump is connected to the second liquid storage tank and the mixing tank, the first delivery pump is used to pass the first sodium sulfate wastewater in the first liquid storage tank into the first oil remover, the second delivery pump is used to pass the first sodium sulfate wastewater in the first oil remover into the second oil remover, and the third delivery pump is used to pass the second sodium sulfate wastewater in the second liquid storage tank into the mixing tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a schematic diagram of a pretreatment system for evaporation and crystallization of sodium sulfate wastewater according to an embodiment of the present invention.

[0019] Reference numerals:

[0020] 1. The first liquid storage tank;

[0021] 2. Second liquid storage tank;

[0022] 3. Oil removal device; 31. First oil remover; 32. Second oil remover; 33. Second delivery pump;

[0023] 4. Mixing tank;

[0024] 5. Filtering device; 51. First filter; 52. Second filter; 52. Filtrate tank; 53. Filtrate pump;

[0025] 6. Adjustment slot;

[0026] 7. Dilution tank; 71. Dilution delivery pump;

[0027] 8. The first delivery pump;

[0028] 9. The third delivery pump. DETAILED DESCRIPTION

[0029] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0030] Reference below Figure 1 A pretreatment system for evaporation and crystallization of sodium sulfate wastewater according to an embodiment of the present invention is described.

[0031] like Figure 1 As shown, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater according to an embodiment of the present invention includes a first liquid storage tank 1, a second liquid storage tank 2, an oil removal device 3, a mixing tank 4, a filtering device 5 and an adjustment tank 6.

[0032] like Figure 1 As shown, a first liquid storage tank 1 is used to store an oily first sodium sulfate wastewater, and a second liquid storage tank 2 is used to store an alkaline second sodium sulfate wastewater. An oil removal device 3 is connected to the first liquid storage tank 1 and is used to remove oil from the first sodium sulfate wastewater to form a third sodium sulfate wastewater. A mixing tank 4 is connected to the oil removal device 3 and the second liquid storage tank 2 and is used to mix the first sodium sulfate wastewater with the third sodium sulfate wastewater to form a solid-liquid mixture containing heavy metal precipitates. A filter device 5 is connected to the mixing tank 4 and is used to filter the solid-liquid mixture to obtain a heavy metal slag and a filtrate. An adjusting tank 6 is connected to the filter device 5 and is used to adjust the pH value of the filtrate to form a weakly alkaline sodium sulfate solution.

[0033] According to the pretreatment system for sodium sulfate wastewater evaporation and crystallization of the embodiment of the present invention, when it is used in production, the oil-containing first sodium sulfate wastewater in the first liquid storage tank 1 is first passed into the oil removal device 3 for oil removal treatment to form an oil-free third sodium sulfate wastewater, and then the third sodium sulfate wastewater is passed into the mixing tank 4, the alkaline second sodium sulfate wastewater in the second liquid storage tank 2 is passed into the mixing tank 4 and mixed with the third sodium sulfate wastewater to form a solid-liquid mixture containing heavy metal precipitates, and then the solid-liquid mixture is filtered through the filter device 5 to obtain a filtrate, and then the filtrate is passed into the regulating tank 6 for adjustment to form a weakly alkaline sodium sulfate solution. Thus, the pretreatment system for sodium sulfate wastewater evaporation and crystallization of the embodiment of the present invention can fully remove oil and heavy metals in the sodium sulfate wastewater, and since the first sodium sulfate wastewater and the second sodium sulfate wastewater can generate a precipitate after mixing, the addition of a precipitant can be reduced during the pretreatment of the sodium sulfate wastewater, thereby reducing costs.

[0034] In some embodiments, as Figure 1 As shown, the oil removal device 3 includes a first oil remover 31 and a second oil remover 32. The first oil remover 31 is connected to the first liquid storage tank 1 and the second oil remover 32, and the second oil remover 32 is connected to the mixing tank 4. The first oil remover 31 is used for flotation oil removal of the first sodium sulfate wastewater, and the second oil remover 32 is used for adsorption oil removal of the first sodium sulfate wastewater. It can be understood that the oil-containing first sodium sulfate wastewater is first passed through the flotation treatment equipment to remove most of the oily organic matter in the first sodium sulfate wastewater, and then it is passed into the adsorption treatment equipment to remove finer oil stains and some soluble organic matter in the first sodium sulfate wastewater. Therefore, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater according to the embodiment of the present invention can completely remove the oily organic matter in the first sodium sulfate wastewater.

[0035] In some embodiments, as Figure 1 As shown, the filtering device 5 includes a first filter 51 and a second filter 52. The first filter 51 is connected to the mixing tank 4 and the second filter 52. The second filter 52 is connected to the regulating tank 6. The first filter 51 is used for pressure filtering the solid-liquid mixture to obtain part of the heavy metal slag and the primary filtrate. The second filter 52 is used for fine filtering the primary filtrate to obtain another part of the heavy metal slag and the filtrate.

[0036] Alternatively, as Figure 1 As shown, the first filter 51 can be a filter press, and the second filter 52 can be a fine filter. The pretreatment system for sodium sulfate wastewater evaporation and crystallization according to the embodiment of the present invention can further reduce impurities in the filtrate by providing a two-stage filtration device 5, thereby improving the purity of the subsequent filtrate evaporation and crystallization.

[0037] Furthermore, if Figure 1As shown, the filtering device 5 further includes a heavy metal slag recovery pool, which is connected to the first filter 51 and the second filter 52 , and is used to recycle the heavy metal slag in the first filter 51 and the second filter 52 .

[0038] In some embodiments, as Figure 1 As shown, the filtering device 5 further includes a filtrate tank 52 and a filtrate pump 53. The filtrate tank 52 is connected to the first filter 51 and the second filter 52, and is used to store the primary filtrate. The filtrate pump 53 is connected to the filtrate tank 52 and the second filter 52, and is used to pass the primary filtrate in the filtrate tank 52 into the second filter 52. The pretreatment system for sodium sulfate wastewater evaporation and crystallization according to the embodiment of the present invention can cause the primary filtrate to reprecipitate by providing the filtrate tank 52, so that the heavy metal residue in the primary filtrate settles to the bottom of the filtrate tank 52, thereby further reducing the heavy metal impurities in the filtrate.

[0039] In some embodiments, as Figure 1 As shown, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater further includes a first delivery pump 8, a second delivery pump 33, and a third delivery pump 9. The first delivery pump 8 is connected to the first liquid storage tank 1 and the first oil remover 31, the second delivery pump 33 is connected to the first oil remover 31 and the second oil remover 32, and the third delivery pump 9 is connected to the second liquid storage tank 2 and the mixing tank 4. The first delivery pump 8 is used to pass the first sodium sulfate wastewater in the first liquid storage tank 1 into the first oil remover 31, the second delivery pump 33 is used to pass the first sodium sulfate wastewater in the first oil remover 31 into the second oil remover 32, and the third delivery pump 9 is used to pass the second sodium sulfate wastewater in the second liquid storage tank 2 into the mixing tank 4.

[0040] In some embodiments, as Figure 1 As shown, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater also includes a dilution tank 7 and a dilution delivery pump 71. The dilution delivery pump 71 is connected to the dilution tank 7 and the regulating tank 6. The dilution tank 7 is used to dilute concentrated sulfuric acid to form dilute sulfuric acid, and the dilution delivery pump 71 is used to pass the dilute sulfuric acid into the regulating tank 6. Specifically, concentrated sulfuric acid is first added to the dilution tank 7 for dilution treatment to dilute the concentrated sulfuric acid into dilute sulfuric acid with a content of 15%-25%. The dilute sulfuric acid is then fed into the regulating tank 6 via the dilution delivery pump 71, and the sodium sulfate solution is adjusted to be weakly alkaline. Since the weakly alkaline sodium sulfate solution is more likely to form crystals in the subsequent evaporation and crystallization process and can improve the quality of the anhydrous sodium sulfate product, the pH of the sodium sulfate solution is preferably 7-8.

[0041] Alternatively, as Figure 1As shown, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater further includes a flow meter, which is connected to the dilution tank 7 and the regulating tank 6. Therefore, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater in the embodiment of the present invention can adjust the amount of dilute sulfuric acid entering the regulating tank 6 by controlling the flow meter to control the pH of the sodium sulfate solution in the regulating tank 6 to be 7-8.

[0042] The following describes a pretreatment system for evaporation and crystallization of sodium sulfate wastewater according to some specific examples of the invention with reference to the accompanying drawings.

[0043] like Figure 1 As shown, the pretreatment system for evaporation and crystallization of sodium sulfate wastewater includes a first liquid storage tank 1, a second liquid storage tank 2, an oil removal device 3, a mixing tank 4, a filter device 5, an adjustment tank 6, a heavy metal slag recovery tank, a dilution tank 7, a flow meter, a dilution delivery pump 71, a first delivery pump 8, a second delivery pump 33, and a third delivery pump 9. The oil removal device 3 includes a first oil remover 31 and a second oil remover 32. The filter device 5 includes a first filter 51, a second filter 52, a filtrate tank 52, and a filtrate pump 53.

[0044] like Figure 1 As shown, the first liquid storage tank 1, the first delivery pump 8, the first deoiler 31, the second delivery pump 33, the second deoiler 32, and the mixing tank 4 are sequentially connected. The first liquid storage tank 1 is used to store the first sodium sulfate wastewater containing oil. The first delivery pump 8 is used to pass the first sodium sulfate wastewater into the first deoiler 31. The first deoiler 31 is used to flotation-deoil the first sodium sulfate wastewater. The first deoiler 31 is then passed through the second delivery pump 33 to the second deoiler 32. The second deoiler 32 is used to absorb and deoil finer oil and some soluble organic matter in the first sodium sulfate wastewater.

[0045] like Figure 1 As shown, the second liquid storage tank 2, the third delivery pump 9, and the mixing tank 4 are sequentially connected. The second liquid storage tank 2 is used to store the third sodium sulfate wastewater containing oil, and the third delivery pump 9 is used to pass the second sodium sulfate wastewater from the second liquid storage tank 2 into the mixing tank 4. In the mixing tank 4, the second sodium sulfate wastewater and the third sodium sulfate wastewater are mixed to form a solid-liquid mixture containing heavy metal precipitates. Since the second sodium sulfate wastewater and the third sodium sulfate wastewater can form a precipitate after mixing, the addition of precipitants can be reduced during the sodium sulfate wastewater pretreatment, reducing costs.

[0046] like Figure 1As shown, the mixing tank 4, the first filter 51, the filtrate tank 52, the filtrate pump 53, the second filter 52, and the regulating tank 6 are sequentially connected. The first filter 51 is used to filter the solid-liquid mixture to obtain a portion of heavy metal slag and a primary filtrate. The primary filtrate enters the filtrate tank 52 for precipitation, and then is passed into the second filter 52 via the filtrate pump 53. The second filter 52 performs fine filtration on the primary filtrate to obtain another portion of heavy metal slag and a filtrate. The heavy metal slag produced by the first and second filters 51, 52 can be passed into a heavy metal slag recovery tank for recycling, and the filtrate is passed into the regulating tank 6 for pH adjustment.

[0047] like Figure 1 As shown, the dilution tank 7, dilution delivery pump 71, flow meter, and mixing tank 4 are sequentially connected. The dilution tank 7 is used to dilute concentrated sulfuric acid to form dilute sulfuric acid, and the dilution delivery pump 71 is used to pass the dilute sulfuric acid into the regulating tank 6. The flow meter is controlled to adjust the amount of dilute sulfuric acid entering the regulating tank 6 to adjust the filtrate in the regulating tank 6 to a sodium sulfate solution with a pH of 7-8.

[0048] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0050] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0051] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0052] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0053] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A pretreatment system for evaporation and crystallization of sodium sulfate wastewater, characterized in that: include: a first liquid storage tank, wherein the first liquid storage tank is used to store the first oil-containing sodium sulfate wastewater; a second liquid storage tank, wherein the second liquid storage tank is used to store alkaline second sodium sulfate wastewater; an oil removal device, the oil removal device being in communication with the first liquid storage tank, and the oil removal device being configured to remove oil from the first sodium sulfate wastewater to form third sodium sulfate wastewater; a mixing tank, the mixing tank being in communication with the oil removal device and the second liquid storage tank, and being used for mixing the second sodium sulfate wastewater with the third sodium sulfate wastewater to form a solid-liquid mixture containing heavy metal precipitates; a filtering device, the filtering device being in communication with the mixing tank, and the filtering device being used to filter the solid-liquid mixture to obtain heavy metal slag and a filtrate; an adjusting tank, the adjusting tank being in communication with the filtering device, the adjusting tank being used to adjust the pH value of the filtrate to form a weakly alkaline sodium sulfate solution, the filtering device comprising a first filter and a second filter, the first filter being in communication with the mixing tank and the second filter, the second filter being in communication with the adjusting tank, the first filter being used to filter the solid-liquid mixture to obtain a portion of the heavy metal slag and a primary filtrate, the second filter being used to finely filter the primary filtrate to obtain another portion of the heavy metal slag and the filtrate; a heavy metal slag recovery pool, the heavy metal slag recovery pool being in communication with the first filter and the second filter, and being used to recover heavy metal slag in the first filter and the second filter; a filtrate tank, the filtrate tank being in communication with the first filter and the second filter, and the filtrate tank being used to store the primary filtrate; A dilution tank and a dilution delivery pump, wherein the dilution delivery pump is connected to the dilution tank and the regulating tank, the dilution tank is used to dilute concentrated sulfuric acid to form dilute sulfuric acid, and the dilution delivery pump is used to pass the dilute sulfuric acid into the regulating tank.

2. The pretreatment system for sodium sulfate wastewater evaporation crystallization according to claim 1, wherein The oil removal device includes a first oil remover and a second oil remover. The first oil remover is connected to the first liquid storage tank and the second oil remover. The second oil remover is connected to the mixing tank. The first oil remover is used for flotation oil removal of the first sodium sulfate wastewater. The second oil remover is used for adsorption oil removal of the first sodium sulfate wastewater.

3. The pretreatment system for sodium sulfate wastewater evaporation crystallization according to claim 2, wherein The device further comprises a first delivery pump, a second delivery pump and a third delivery pump, wherein the first delivery pump is connected to the first liquid storage tank and the first oil remover, the second delivery pump is connected to the first oil remover and the second oil remover, and the third delivery pump is connected to the second liquid storage tank and the mixing tank. The first delivery pump is used to pass the first sodium sulfate wastewater in the first liquid storage tank into the first oil remover, the second delivery pump is used to pass the first sodium sulfate wastewater in the first oil remover into the second oil remover, and the third delivery pump is used to pass the second sodium sulfate wastewater in the second liquid storage tank into the mixing tank.

4. The pretreatment system for sodium sulfate wastewater evaporation and crystallization according to claim 1, wherein The filtering device further includes a filtrate pump, which is connected to the filtrate tank and the second filter, and is used to pass the primary filtrate in the filtrate tank into the second filter.

5. The pretreatment system for sodium sulfate wastewater evaporation and crystallization according to claim 1, wherein The first filter is a filter press, and the second filter is a fine filter.

6. The pretreatment system for sodium sulfate wastewater evaporation and crystallization according to claim 1, wherein: The system further comprises a flow meter for controlling the amount of the dilute sulfuric acid entering the adjustment tank.

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