A salt separation system using evaporation and crystallization

Abstract

The present disclosure relates to an evaporation crystallization salt separation system, which includes a sodium chloride crystallization device, a sodium sulfate crystallization device and a salt mixing device. Resin produced water enters the sodium chloride crystallization device from the resin water production pool through a lifting pump. The sodium chloride crystallization device includes a chloride ion nanofiltration unit, a first oxidation unit, a first evaporation unit and a first crystallization unit connected in sequence; the sodium sulfate crystallization device includes a sulfate ion nanofiltration unit, a second oxidation unit, a second evaporation unit and a second crystallization unit connected in sequence, and the input end of the sulfate ion nanofiltration unit is connected to the output end of the chloride ion nanofiltration unit; a salt mixing device, the salt mixing device is connected to the sodium chloride crystallization device and the sodium sulfate crystallization device through the first evaporation unit and the second evaporation unit, respectively, and the mother liquor of the first evaporation unit and the second evaporation unit is configured to be sent to the salt mixing device for mixing. The evaporation crystallization salt separation system provided by the present disclosure has excellent quality of crystallized salt and low impurity salt rate.

Description

Technical Field

[0001] The present disclosure relates to the technical field of water treatment, and more specifically, to an evaporation crystallization salt separation system. Background Art

[0002] The terminal water treatment process of most chemical production processes will produce a large amount of waste salts. Since the composition of waste salts is relatively complex and contains a small amount of impurities, most of the waste salts are treated as solid waste. Among these waste salts, waste salts containing sodium chloride and sodium sulfate are the main ones. With the increase in environmental protection efforts, the original sea discharge and landfill treatment methods have basically been terminated due to excessive pollution to the environment. The treatment of waste salts has become an urgent problem to be solved. Among them, how to efficiently and stably achieve the separation and refining of salt in waste salts is the key. The crystallization salt separation system in the prior art has a complex process, low product purity, and a high salt content. Utility Model Content

[0003] In view of this, an embodiment of the present disclosure provides an evaporation crystallization salt separation system to solve the technical defects existing in the prior art.

[0004] To achieve the above objectives, the present disclosure adopts the following technical solutions:

[0005] The present disclosure provides an evaporation crystallization salt separation system, comprising:

[0006] A sodium chloride crystallization device, wherein resin water is introduced into the sodium chloride crystallization device from the resin water production pool through a lifting pump, and the sodium chloride crystallization device comprises a chloride ion nanofiltration unit, a first oxidation unit, a first evaporation unit and a first crystallization unit connected in sequence, wherein the chloride ion nanofiltration unit is configured to separate chloride ions and sulfate ions, the first oxidation unit is configured to oxidize organic matter, the first evaporation unit is configured to evaporate sodium chloride solution, and the first crystallization unit is configured to crystallize and precipitate sodium chloride crystals;

[0007] A sodium sulfate crystallization device, comprising a sulfate ion nanofiltration unit, a second oxidation unit, a second evaporation unit and a second crystallization unit connected in sequence, wherein the sulfate ion nanofiltration unit is configured to separate chloride ions and sulfate ions, the second oxidation unit is configured to oxidize organic matter, the second evaporation unit is configured to evaporate sodium sulfate solution, the second crystallization unit is configured to crystallize and precipitate sodium sulfate crystals, and the input end of the sulfate ion nanofiltration unit is connected to the output end of the chloride ion nanofiltration unit;

[0008] A salt mixing device, wherein the salt mixing device is connected to the sodium chloride crystallization device and the sodium sulfate crystallization device through the first evaporation unit and the second evaporation unit respectively, and the mother liquors of the first evaporation unit and the second evaporation unit are configured to be sent to the salt mixing device for mixing.

[0009] In one embodiment of the present disclosure, the first oxidation unit comprises a first oxidation water pool and a second oxidation water pool connected in sequence, and the first produced water flows from the output end of the chloride ion nanofiltration unit into the input end of the first oxidation water pool, wherein the first produced water is produced water containing chloride ions output by the chloride ion nanofiltration unit;

[0010] The second oxidation unit includes a third oxidation water tank and a fourth oxidation water tank connected in sequence, and the first concentrated water flows from the output end of the sulfate ion nanofiltration unit into the input end of the third oxidation water tank, wherein the first concentrated water is concentrated water containing sulfate ions output from the chloride ion nanofiltration unit and flows into the sulfate ion nanofiltration unit.

[0011] In one embodiment of the present disclosure, the first evaporation unit includes a first-effect evaporation tank, a second-effect evaporation tank and a third-effect evaporation tank connected in sequence, and the second product water flows from the output end of the first oxidation unit into the input end of the first-effect evaporation tank, wherein the second product water is the product water after oxidation treatment by the first oxidation unit;

[0012] The second evaporation unit is a sodium sulfate evaporation tank, and the second concentrated water flows from the output end of the second oxidation unit into the input end of the sodium sulfate evaporation tank. The second concentrated water is concentrated water that has been oxidized by the second oxidation unit.

[0013] In one embodiment of the present disclosure, the temperature of the first-effect evaporation tank is 100-110°C, the temperature of the second-effect evaporation tank is 80-85°C, the temperature of the first-effect evaporation tank is 60-70°C, and the temperature of the sodium sulfate evaporation tank is 100-110°C.

[0014] In one embodiment of the present disclosure, the evaporation crystallization salt separation system further comprises:

[0015] A steam device is configured to provide a heat source for the first evaporation unit and the second evaporation unit, and the steam generated by the first-effect evaporation tank is configured to be transported to the heat source of the second-effect evaporation tank, and the steam generated by the second-effect evaporation tank is configured to be transported to the heat source of the third-effect evaporation tank.

[0016] In one embodiment of the present disclosure, the chloride ion produced water separated by the sulfate ion nanofiltration unit flows from the water production output end of the sulfate ion nanofiltration unit into the resin water production pool.

[0017] In one embodiment of the present disclosure, the evaporation crystallization salt separation system further comprises:

[0018] An ozone unit is connected to the second oxidation unit, the ozone unit includes an oxygen generator and an ozone generator, and the ozone unit is configured to provide ozone to the second oxidation unit.

[0019] In one embodiment of the present disclosure, the evaporation crystallization salt separation system further comprises:

[0020] A centrifugal separation device, comprising a first centrifugal separation unit and a second centrifugal separation unit, wherein the first centrifugal separation unit and the second centrifugal separation unit are respectively connected to the first crystallization unit and the second crystallization unit, and the first centrifugal separation unit and the second centrifugal separation unit are respectively configured to separate sodium chloride crystals from sodium sulfate crystals.

[0021] In one embodiment of the present disclosure, the evaporation crystallization salt separation system further comprises:

[0022] A dry packaging device, comprising a first dry packaging unit and a second dry packaging unit, wherein the first dry packaging unit and the second dry packaging unit are respectively connected to the first centrifugal separation unit and the second centrifugal separation unit, and the first dry packaging unit and the second dry packaging unit are respectively configured to be used for dry packaging of sodium chloride and sodium sulfate.

[0023] In one embodiment of the present disclosure, the evaporation crystallization salt separation system further comprises:

[0024] A water recycling device is connected to the first evaporation unit and the second evaporation unit, and the water recycling device is configured to collect steam condensed water.

[0025] The evaporation crystallization salt separation system provided by the present disclosure has high-quality crystallized salt and low impure salt rate.

[0026] Other features and advantages of the present disclosure will become apparent from the following detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of an evaporation crystallization salt separation system provided by an embodiment of the present disclosure;

[0028] Figure 2 It is a structural schematic diagram of an evaporation crystallization salt separation system provided in another embodiment of the present disclosure.

[0029] 1-resin water production pool; 2-chloride ion nanofiltration unit; 3-sulfate ion nanofiltration unit; 4-first oxidation unit; 41-first oxidation water pool; 42-second oxidation water pool; 5-second oxidation unit; 51-third oxidation water pool; 52-fourth oxidation water pool; 6-first evaporation unit; 61-first effect evaporation tank; 62-second effect evaporation tank; 63-third effect evaporation tank; 7-second evaporation unit; 8-first crystallization unit; 9-second crystallization unit; 10-salt mixing device; 11-nanofiltration concentrated water pool; 12-sodium chloride crystallization water inlet pool; 13-sodium sulfate crystallization water inlet pool; 14-oxygen generator; 15-ozone generator; 16-first centrifugal separation unit; 17-second centrifugal separation unit; 18-first drying and packaging unit; 19-second drying and packaging unit; 20-rake dryer. DETAILED DESCRIPTION

[0030] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure unless otherwise specifically stated.

[0031] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0032] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0033] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0034] The specific embodiments of the present disclosure are described below in conjunction with the accompanying drawings.

[0035] In this document, “upper”, “lower”, “front”, “back”, “left”, “right”, etc. are only used to indicate the relative position relationship between related parts, rather than to limit the absolute positions of these related parts.

[0036] In this article, "first", "second", etc. are only used to distinguish each other, and do not indicate the importance and order, or the premise of each other's existence.

[0037] In this document, “equal”, “same”, etc. are not strictly limited in a mathematical and / or geometric sense, but also include errors that can be understood by those skilled in the art and are allowed in manufacturing or use.

[0038] The present disclosure provides an evaporation crystallization salt separation system, which includes a sodium chloride crystallization device, a sodium sulfate crystallization device and a salt mixing device. Resin produced water enters the sodium chloride crystallization device from the resin water production pool through a lifting pump. The sodium chloride crystallization device includes a chloride ion nanofiltration unit, a first oxidation unit, a first evaporation unit and a first crystallization unit connected in sequence; the sodium sulfate crystallization device includes a sulfate ion nanofiltration unit, a second oxidation unit, a second evaporation unit and a second crystallization unit connected in sequence, and the input end of the sulfate ion nanofiltration unit is connected to the output end of the chloride ion nanofiltration unit; a salt mixing device, the salt mixing device is connected to the sodium chloride crystallization device and the sodium sulfate crystallization device through the first evaporation unit and the second evaporation unit, respectively, and the mother liquor of the first evaporation unit and the second evaporation unit is configured to be sent to the salt mixing device for mixing. The evaporation crystallization salt separation system provided by the present disclosure has excellent crystallized salt quality and low impurity salt rate.

[0039] For ease of understanding, refer to Figure 1 to Figure 2 , the specific structure and working principle of the evaporation crystallization salt separation system of the present invention are explained in detail with reference to an embodiment.

[0040] like Figure 1 As shown, the evaporation crystallization salt separation system in this embodiment includes a sodium chloride crystallization device, a sodium sulfate crystallization device and a salt mixing device 10. Among them, the sodium chloride crystallization device is used to crystallize out sodium chloride crystals, the sodium sulfate crystallization device is used to crystallize out sodium sulfate crystals, and the salt mixing device 10 is used to process miscellaneous salts.

[0041] In this embodiment, the resin produced water first enters the resin produced water pool 1 to even out the water quality and water volume, and then the resin produced water enters the sodium chloride crystallization device from the resin produced water pool 1 through a lift pump. Among them, the resin produced water contains chloride ions, sulfate ions, magnesium ions, calcium ions, nitrate ions and organic matter. The sodium chloride crystallization device includes a chloride ion nanofiltration unit 2, a first oxidation unit 4, a first evaporation unit 6 and a first crystallization unit 8 connected in sequence. The resin produced water is first pumped from the resin produced water pool 1 into the chloride ion nanofiltration unit 2 through a lift pump. The chloride ion nanofiltration unit 2 is configured to separate chloride ions and sulfate ions. The resin produced water is separated into produced water containing chloride ions and concentrated water containing sulfate ions in the chloride ion nanofiltration unit 2. The produced water containing chloride ions flows into the first oxidation unit 4, which is configured to oxidize organic matter. The produced water containing chloride ions oxidizes and decomposes organic matter in the first oxidation unit 4, and then enters the first crystallization unit 8. The first crystallization unit 8 is configured to crystallize and precipitate sodium chloride crystals.

[0042] As mentioned above, in this embodiment, the resin produced water is separated into produced water containing chloride ions and concentrated water containing sulfate ions in the chloride ion nanofiltration unit 2. The produced water containing chloride ions enters the sodium chloride crystallization device for crystallization to precipitate sodium chloride crystals, and the concentrated water containing sulfate ions enters the sodium sulfate crystallization device for crystallization to precipitate sodium sulfate crystals.

[0043] Specifically, the sodium sulfate crystallization device includes a sulfate ion nanofiltration unit 3, a second oxidation unit 5, a second evaporation unit 7, and a second crystallization unit 9 connected in sequence. The input end of the sulfate ion nanofiltration unit 3 is connected to the output end of the chloride ion nanofiltration unit 2, and the concentrated water containing sulfate ions flows from the output end of the chloride ion nanofiltration unit 2 to the input end of the sulfate ion nanofiltration unit 3, thereby entering the sulfate ion nanofiltration unit 3. Considering that the concentrated water separated in the chloride ion nanofiltration unit 2 may also contain chloride ions, the sulfate ion nanofiltration unit 3 is configured to separate chloride ions and sulfate ions, and the chloride ion water separated by the sulfate ion nanofiltration unit 3 flows from the water output end of the sulfate ion nanofiltration unit 3 into the resin water production pool 1, and the separated sulfate ion concentrated water enters the second oxidation unit 5. The second oxidation unit 5 is configured to oxidize organic matter, and the sulfate ion concentrated water oxidizes and decomposes the organic matter in the second oxidation unit 5, and performs decolorization treatment. The concentrated water coming out of the second oxidation unit 5 enters the second evaporation unit 7, which is configured to evaporate the sodium sulfate solution. The second evaporation unit 7 in this embodiment is a sodium sulfate evaporation tank. The sulfate ion concentrated water enters the sodium sulfate evaporation tank for evaporation and enters the second crystallization unit 9, which is configured to crystallize sodium sulfate crystals.

[0044] Since the resin produced water also contains nitrate ions, a salt mixing device 10 is also provided in this embodiment. The salt mixing device 10 is connected to the sodium chloride crystallization device and the sodium sulfate crystallization device through the first evaporation unit 6 and the second evaporation unit 7 respectively. The mother liquor of the first evaporation unit 6 and the second evaporation unit 7 is configured to be sent to the salt mixing device 10 for mixing. The salt mixing device 10 in this embodiment uses a salt mixing tank. The sodium chloride and sodium sulfate mother liquors enter the salt mixing tank for further concentration, and the sodium chloride and sodium sulfate mixed salts are crystallized. The mixed salt slurry is pumped to the thickener for sedimentation and crystal growth. The settled salt slurry is centrifuged by a centrifuge to obtain water-containing sodium chloride and sodium sulfate crystals. The centrifuge here uses a horizontal screw centrifuge. The water-containing sodium chloride and sodium sulfate crystals are discharged into the salt tank, dissolved with pre-treated produced water, and then pumped to the resin water production pool 1 for circulation treatment using brine. The mixed salt liquid separated by the centrifuge is transported to the rake dryer 20 for evaporation to obtain the impure salt, which is then packaged by the impure salt packaging machine and then transported for stabilization. The setting of the salt mixing device 10 can greatly reduce the amount of impure salt generated.

[0045] Considering that a single oxidation may lead to insufficient oxidation, Figure 2 As shown, in one embodiment of the present disclosure, the first oxidation unit 4 includes a first oxidation water tank 41 and a second oxidation water tank 42 which are connected in sequence, and the first produced water flows from the output end of the chloride ion nanofiltration unit 2 into the input end of the first oxidation water tank 41, wherein the first produced water is produced water containing chloride ions output by the chloride ion nanofiltration unit 2. Specifically, sodium hypochlorite is added to the first oxidation water tank 41, and the sodium hypochlorite is configured to be used for oxidative decomposition of organic matter and decolorization of the first produced water.

[0046] For the same reason, the second oxidation unit 5 includes a third oxidation water pool 51 and a fourth oxidation water pool 52 which are connected in sequence. Hydrogen peroxide is added to the first oxidation water pool 41 to be configured for oxidation and removal of organic matter, and the first concentrated water is decolorized. The first concentrated water flows from the output end of the sulfate ion nanofiltration unit 3 to the input end of the third oxidation water pool 51, wherein the first concentrated water is concentrated water containing sulfate ions output by the chloride ion nanofiltration unit 2 and flows into the sulfate ion nanofiltration unit 3. The first oxidation unit 4 and the second oxidation unit 5 are both provided with two oxidation water pools, which can ensure that the oxidation reaction is fully carried out, thereby making the removal rate of organic matter higher, the decolorization effect better, and improving the subsequent crystallization purity of sodium chloride and sodium sulfate.

[0047] like Figure 1 to Figure 2 As shown, in one embodiment of the present disclosure, a nanofiltration concentrated water pool 11 is further provided between the chloride ion nanofiltration unit 2 and the sulfate ion nanofiltration unit 3. Concentrated water containing sulfate ions enters the nanofiltration concentrated water pool 11 from the chloride ion nanofiltration unit 2, and is lifted to the sulfate ion nanofiltration unit 3 by a secondary nanofiltration lifting pump. The nanofiltration concentrated water pool 11 can evenly distribute the water quality and water quantity of the effluent from the chloride ion nanofiltration unit 2, so that the water inlet of the sulfate ion nanofiltration unit 3 is more uniform.

[0048] like Figure 2As shown, in one embodiment of the present disclosure, the first evaporation unit 6 includes a first-effect evaporation tank 61, a second-effect evaporation tank 62, and a third-effect evaporation tank 63 connected in sequence. The second produced water flows from the output end of the first oxidation unit 4 into the input end of the first-effect evaporation tank 61, wherein the second produced water is produced water after oxidation treatment by the first oxidation unit 4. Specifically, the effluent of the first oxidation unit 4 flows into the sodium chloride crystallization water inlet pool 12 by gravity, and then enters the first-effect evaporation tank 61 after being lifted by the sodium chloride crystallization water inlet pump and heat exchanged by the preheater. The second produced water is evaporated and concentrated step by step through the first-effect evaporation tank 61, the second-effect evaporation tank 62, and the third-effect evaporation tank 63 in sequence, wherein the temperature of the first-effect evaporation tank 61 is 100-110°C, the temperature of the second-effect evaporation tank 62 is 80-85°C, and the temperature of the first-effect evaporation tank 61 is 60-70°C. This is because sodium chloride needs low-temperature crystallization, so the temperatures of the first-effect evaporation tank 61, the second-effect evaporation tank 62, and the third-effect evaporation tank 63 are gradually reduced.

[0049] The second evaporation unit 7 is a sodium sulfate evaporation tank, and the second concentrated water flows from the output end of the second oxidation unit 5 into the input end of the sodium sulfate evaporation tank. The second concentrated water is concentrated water after oxidation treatment by the second oxidation unit 5. The temperature of the sodium sulfate evaporation tank is 100-110° C. Specifically, the effluent of the second oxidation unit 5 flows by gravity into the sodium sulfate crystallization water inlet pool 13, and then is lifted by the sodium sulfate crystallization water inlet pump and enters the sodium sulfate evaporation tank after heat exchange in the preheater.

[0050] In this embodiment, the evaporation crystallization salt separation system also includes a steam device, which is configured to provide a heat source for the first evaporation unit 6 and the second evaporation unit 7. The heat source comes from low-pressure saturated steam from the plant area, and the steam parameters are 0.5MPa and 159°C. Furthermore, in order to save resources, the multi-effect evaporation principle is also used in this embodiment to specifically set up the steam device, that is, the steam generated by the first-effect evaporation tank 61 is configured as a heat source for transporting to the second-effect evaporation tank 62, and the steam generated by the second-effect evaporation tank 62 is configured as a heat source for transporting to the third-effect evaporation tank 63. In addition, the sealing water process is the key to the stable operation of the evaporation crystallization unit. The pump bodies in this embodiment all require external mechanical sealing water, and there are requirements for sealing water pressure and flow. Under the premise of ensuring the sealing water pressure and flow of the circulating pump, the safety and service life of the circulating pump can be greatly improved. In this embodiment, two sealing water pumps are designed, one for use and one for backup.

[0051] In this embodiment, the evaporation crystallization salt separation system also includes a water recycling device, which is connected to the first evaporation unit 6 and the second evaporation unit 7, and is configured to collect steam condensed water. The setting of the water recycling device can ensure the maximum utilization of resources. In addition, the circulating water in this embodiment comes from the plant circulating water main, which is used to condense the final secondary steam through the surface condenser to form a vacuum; at the same time, the non-condensable gas in each tank is pumped out through a water ring vacuum pump to maintain the pressure parameters in each tank.

[0052] like Figure 2 As shown, in one embodiment of the present disclosure, the evaporation crystallization salt separation system further includes an ozone unit, which is connected to the second oxidation unit 5, and includes an oxygen generator 14 and an ozone generator 15, and the ozone unit is configured to provide ozone to the second oxidation unit 5. Specifically, the oxygen generator 14 produces ozone, which is passed into the ozone generator 15, and the ozone generator 15 transports the ozone to the second oxidation unit 5 for oxidative decomposition of organic matter. The provision of the ozone unit further improves the oxidative capacity of the second oxidation unit 5 and improves the efficiency of oxidative decomposition of organic matter.

[0053] like Figure 2 As shown, in one embodiment of the present disclosure, the evaporation crystallization salt separation system further includes a centrifugal separation device and a dry packaging device. The centrifugal separation device includes a first centrifugal separation unit 16 and a second centrifugal separation unit 17, the first centrifugal separation unit 16 and the second centrifugal separation unit 17 are respectively connected to the first crystallization unit 8 and the second crystallization unit 9, and the first centrifugal separation unit 16 and the second centrifugal separation unit 17 are respectively configured to separate sodium chloride crystals and sodium sulfate crystals. The dry packaging device includes a first dry packaging unit 18 and a second dry packaging unit 19, the first dry packaging unit 18 and the second dry packaging unit 19 are respectively connected to the first centrifugal separation unit 16 and the second centrifugal separation unit 17, and the first dry packaging unit 18 and the second dry packaging unit 19 are respectively configured to dry-package sodium chloride and sodium sulfate.

[0054] Specifically, the sodium chloride crystals crystallized in the first crystallization unit 8 are directly sent to the sodium chloride thickener for sedimentation and crystal growth through the sodium chloride slurry pump, and the settled salt slurry is centrifuged, dried, and packaged by a double-push centrifuge for resource utilization. The sodium sulfate crystals crystallized in the second crystallization unit 9 are discharged into the sodium sulfate slurry barrel, and then sent to the thickener for sedimentation and crystal growth through the slurry pump, and the settled salt slurry is centrifuged, dried, and packaged by a double-push centrifuge for resource utilization.

[0055] The evaporation crystallization salt separation system provided by the present disclosure has high-quality crystallized salt and low impure salt rate.

[0056] It should be noted that, for the above-mentioned method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should know that the present disclosure is not limited by the described action sequence, because according to the present disclosure, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present disclosure.

[0057] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0058] The preferred embodiments of the present disclosure disclosed above are only used to help explain the present disclosure. The optional embodiments do not describe all the details in detail, nor do they limit the invention to only the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of the present disclosure. The present disclosure selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present disclosure, so that those skilled in the art can well understand and use the present disclosure. The present disclosure is limited only by the claims and their full scope and equivalents.

Claims

1. An evaporation crystallization salt separation system, characterized in that: include: A sodium chloride crystallization device, wherein resin produced water enters the sodium chloride crystallization device from a resin produced water pool (1) through a lift pump, the sodium chloride crystallization device comprising a chloride ion nanofiltration unit (2), a first oxidation unit (4), a first evaporation unit (6) and a first crystallization unit (8) connected in sequence, the chloride ion nanofiltration unit (2) being configured to separate chloride ions and sulfate ions, the first oxidation unit (4) being configured to oxidize organic matter, the first evaporation unit (6) being configured to evaporate a sodium chloride solution, and the first crystallization unit (8) being configured to crystallize and precipitate sodium chloride crystals; A sodium sulfate crystallization device, the sodium sulfate crystallization device comprising a sulfate ion nanofiltration unit (3), a second oxidation unit (5), a second evaporation unit (7) and a second crystallization unit (9) connected in sequence, the sulfate ion nanofiltration unit (3) being configured to separate chloride ions and sulfate ions, the second oxidation unit (5) being configured to oxidize organic matter, the second evaporation unit (7) being configured to evaporate a sodium sulfate solution, the second crystallization unit (9) being configured to crystallize and precipitate sodium sulfate crystals, and the input end of the sulfate ion nanofiltration unit (3) being connected to the output end of the chloride ion nanofiltration unit (2); A salt mixing device (10), wherein the salt mixing device (10) is connected to the sodium chloride crystallization device and the sodium sulfate crystallization device respectively through the first evaporation unit (6) and the second evaporation unit (7), and the mother liquor of the first evaporation unit (6) and the second evaporation unit (7) is configured to be sent to the salt mixing device (10) for mixing.

2. The evaporation crystallization salt separation system according to claim 1, characterized in that: The first oxidation unit (4) comprises a first oxidation water pool (41) and a second oxidation water pool (42) which are connected in sequence, and first produced water flows from the output end of the chloride ion nanofiltration unit (2) into the input end of the first oxidation water pool (41), wherein the first produced water is produced water containing chloride ions output by the chloride ion nanofiltration unit (2); The second oxidation unit (5) comprises a third oxidation water pool (51) and a fourth oxidation water pool (52) which are connected in sequence, and first concentrated water flows from the output end of the sulfate ion nanofiltration unit (3) into the input end of the third oxidation water pool (51), wherein the first concentrated water is concentrated water containing sulfate ions output from the chloride ion nanofiltration unit (2) and flowing into the sulfate ion nanofiltration unit (3).

3. The evaporation crystallization salt separation system according to claim 1, characterized in that: The first evaporation unit (6) comprises a first-effect evaporation tank (61), a second-effect evaporation tank (62) and a third-effect evaporation tank (63) which are connected in sequence, and the second produced water flows from the output end of the first oxidation unit (4) into the input end of the first-effect evaporation tank (61), wherein the second produced water is produced water after oxidation treatment by the first oxidation unit (4); The second evaporation unit (7) is a sodium sulfate evaporation tank, and the second concentrated water flows from the output end of the second oxidation unit (5) into the input end of the sodium sulfate evaporation tank. The second concentrated water is concentrated water that has been oxidized by the second oxidation unit (5).

4. The evaporation crystallization salt separation system according to claim 3, characterized in that: The temperature of the first-effect evaporation tank (61) is 100-110° C., the temperature of the second-effect evaporation tank (62) is 80-85° C., the temperature of the first-effect evaporation tank (61) is 60-70° C., and the temperature of the sodium sulfate evaporation tank is 100-110° C.

5. The evaporation crystallization salt separation system according to claim 4, characterized in that: Also includes: A steam device, the steam device being configured to provide a heat source for the first evaporation unit (6) and the second evaporation unit (7), and the steam generated by the first-effect evaporation tank (61) being configured to be transported to the heat source of the second-effect evaporation tank (62), and the steam generated by the second-effect evaporation tank (62) being configured to be transported to the heat source of the third-effect evaporation tank (63).

6. The evaporation crystallization salt separation system according to claim 1, characterized in that: The chloride ion produced water separated by the sulfate ion nanofiltration unit (3) flows from the produced water output end of the sulfate ion nanofiltration unit (3) into the resin produced water pool (1).

7. The evaporation crystallization salt separation system according to claim 1, characterized in that: Also includes: An ozone unit, the ozone unit is connected to the second oxidation unit (5), the ozone unit comprises an oxygen generator (14) and an ozone generator (15), and the ozone unit is configured to provide ozone to the second oxidation unit (5).

8. The evaporation crystallization salt separation system according to claim 1, characterized in that: Also includes: A centrifugal separation device, comprising a first centrifugal separation unit (16) and a second centrifugal separation unit (17), wherein the first centrifugal separation unit (16) and the second centrifugal separation unit (17) are respectively connected to the first crystallization unit (8) and the second crystallization unit (9), and the first centrifugal separation unit (16) and the second centrifugal separation unit (17) are respectively configured to separate sodium chloride crystals from sodium sulfate crystals.

9. The evaporation crystallization salt separation system according to claim 8, characterized in that: Also includes: A dry packaging device, comprising a first dry packaging unit (18) and a second dry packaging unit (19), wherein the first dry packaging unit (18) and the second dry packaging unit (19) are respectively connected to the first centrifugal separation unit (16) and the second centrifugal separation unit (17), and the first dry packaging unit (18) and the second dry packaging unit (19) are respectively configured to dry-package sodium chloride and sodium sulfate.

10. The evaporation crystallization salt separation system according to claim 1, characterized in that: Also includes: A water recycling device, the water recycling device is connected to the first evaporation unit (6) and the second evaporation unit (7), and the water recycling device is configured to collect steam condensate.

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