Multidimensional salt separation system and multidimensional salt separation method

Abstract

The invention discloses a multidimensional salt separation system and a multidimensional salt separation method. The multidimensional salt separation system comprises a softening and silicon removal device, a sodium chloride evaporation crystallization device, a sodium sulfate freezing crystallization device, a melting crystallization device and a multi-stage nanofiltration device; the multi-stage nanofiltration device comprises a primary nanofiltration unit, a secondary nanofiltration unit and a tertiary nanofiltration unit, the primary nanofiltration unit, the secondary nanofiltration unit and the tertiary nanofiltration unit are sequentially connected in series, the primary nanofiltration unit is also connected with the tertiary nanofiltration unit to realize that the primary nanofiltration concentrated water of the primary nanofiltration unit enters the tertiary nanofiltration unit, and the tertiary nanofiltration produced water of the tertiary nanofiltration unit also enters the secondary nanofiltration unit, the softening and silicon removal device is connected with the primary nanofiltration unit, the secondary nanofiltration unit is connected with the sodium chloride evaporation crystallization device, the sodium sulfate freezing crystallization device is connected with the tertiary nanofiltration unit, and the melting crystallization device is connected with the sodium sulfate freezing crystallization device. The multidimensional salt separation system of the invention has good salt separation effect, high purity of by-product salt and low impurity salt rate.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment and environmental protection, and in particular to a multidimensional salt separation system and a multidimensional salt separation method. Background Art

[0002] The scale of high-salinity wastewater in my country is constantly increasing, mainly from coal chemical plants, textile plants, soda ash plants, pesticide plants, and oil and gas collection and processing. If a large amount of high-salinity wastewater is directly discharged without treatment, it will not only waste a lot of water resources, but also cause great damage to the environment. At present, membrane method and distillation method have become the main technologies for high-salinity wastewater. Evaporation and salt separation mainly adopt "evaporation + freezing and salt separation" technology. This method has poor salt separation effect, and the quality of crystallized salt is easily affected by water quality fluctuations. The quality of by-product sodium chloride and wastewater sodium sulfate is low, and the impurity rate is large, which is >25%. Summary of the invention

[0003] Based on this, it is necessary to provide a multidimensional salt separation system and a multidimensional salt separation method with good salt separation effect, high purity of by-product salt and low impure salt rate.

[0004] A multi-dimensional salt separation system comprises a multi-stage nanofiltration device, a sodium chloride evaporation crystallization device, a sodium sulfate freezing crystallization device and a melt crystallization device; the sodium chloride evaporation crystallization device and the sodium sulfate freezing crystallization device are respectively connected to the multi-stage nanofiltration device, the secondary nanofiltration produced water of the multi-stage nanofiltration device enters the sodium chloride evaporation crystallization device, the secondary nanofiltration concentrated water of the multi-stage nanofiltration device enters the sodium sulfate freezing crystallization device, the melt crystallization device is connected to the sodium sulfate freezing crystallization device, the sodium sulfate freezing crystallization device freezes and crystallizes the sodium sulfate to obtain mirabilite, which is melt-crystallized by the melt crystallization device to obtain anhydrous sodium sulfate, and a part of the sodium sulfate crystallization mother liquor of the sodium sulfate freezing crystallization device after nanofiltration enters the miscellaneous salt evaporation crystallization device.

[0005] In one embodiment, the multi-stage nanofiltration device includes a primary nanofiltration unit, a secondary nanofiltration unit and a tertiary nanofiltration unit, and the primary nanofiltration unit, the secondary nanofiltration unit and the tertiary nanofiltration unit are connected in series in sequence, the primary nanofiltration unit is also connected to the tertiary nanofiltration unit to enable the primary nanofiltration concentrated water of the primary nanofiltration unit to enter the tertiary nanofiltration unit, and the tertiary nanofiltration produced water of the tertiary nanofiltration unit also enters the secondary nanofiltration unit, the softening and silicon removal device is connected to the primary nanofiltration unit, the secondary nanofiltration unit is connected to the sodium chloride evaporation crystallization device, the sodium sulfate freezing crystallization device is connected to the tertiary nanofiltration unit, and the melt crystallization device is connected to the sodium sulfate freezing crystallization device.

[0006] In one embodiment, the multi-dimensional salt separation system also includes a high-pressure nanofiltration device, which is connected to the sodium sulfate freezing crystallization device, and the high-pressure nanofiltration device is also connected to the primary nanofiltration unit. The sodium sulfate crystallization mother liquor of the sodium sulfate freezing crystallization device enters the high-pressure nanofiltration device for nanofiltration, part of the nanofiltration concentrated water of the high-pressure nanofiltration device enters the mixed salt evaporation crystallization device, and the nanofiltration product water of the high-pressure nanofiltration device enters the primary nanofiltration unit.

[0007] In one embodiment, the multi-dimensional salt separation system also includes a miscellaneous salt evaporation and crystallization device, which is connected to the sodium chloride evaporation and crystallization device, and is used to receive part of the sodium chloride crystallization mother liquor from the sodium chloride evaporation and crystallization device and evaporate the miscellaneous salt.

[0008] In one embodiment, the sodium chloride evaporation crystallization device is also connected to the sodium sulfate freezing crystallization device, and part of the sodium chloride crystallization mother liquor of the sodium chloride evaporation crystallization device enters the sodium sulfate freezing crystallization device for freezing crystallization.

[0009] In one embodiment, the multi-dimensional salt separation system further includes a first concentrating device, which is connected in series between the secondary nanofiltration unit and the sodium chloride evaporation crystallization device.

[0010] In one embodiment, the multi-dimensional salt separation system further includes a second concentrating device, which is connected in series between the three-stage nanofiltration unit and the sodium sulfate freezing crystallization device.

[0011] In one embodiment, the multi-dimensional salt separation system also includes a high-pressure nanofiltration device, which is connected in series between the sodium sulfate freezing crystallization device and the miscellaneous salt evaporation device, and the high-pressure nanofiltration device is also connected to the primary nanofiltration unit. The sodium sulfate crystallization mother liquor of the sodium sulfate freezing crystallization device enters the high-pressure nanofiltration device for nanofiltration, part of the nanofiltration concentrated water of the high-pressure nanofiltration device enters the miscellaneous salt evaporation crystallization device, and the nanofiltration product water of the high-pressure nanofiltration device enters the primary nanofiltration unit for connection.

[0012] In one of the embodiments, the high-pressure nanofiltration device is also connected to the second concentrating device, and part of the nanofiltration concentrate from the high-pressure nanofiltration device also enters the second concentrating device.

[0013] In one of the embodiments, the multi-dimensional salt separation system further includes a regulating tank, and the regulating tank is connected to the front end of the softening and desiliconizing device.

[0014] In one embodiment, the softening and desiliconizing device includes one or more of a high-density desiliconizing tank, a V-type filter tank, and an ultrafiltration device.

[0015] In one embodiment, the primary nanofiltration unit is a high-efficiency He nanofiltration unit;

[0016] And / or, the secondary nanofiltration unit is a high retention Hr nanofiltration unit;

[0017] And / or, the three-stage nanofiltration unit is a high-recovery Hc nanofiltration unit.

[0018] A multidimensional salt separation method comprises the following steps:

[0019] The high-salt wastewater is softened and desiliconized by a softening and desiliconizing device and then enters a multi-stage nanofiltration device for nanofiltration treatment. The first-stage nanofiltration concentrated water of the first-stage nanofiltration unit enters a third-stage nanofiltration unit. The first-stage nanofiltration produced water of the first-stage nanofiltration unit enters a second-stage nanofiltration unit. The second-stage nanofiltration concentrated water of the second-stage nanofiltration unit enters the third-stage nanofiltration unit. The second-stage nanofiltration produced water of the second-stage nanofiltration unit enters a sodium chloride evaporation and crystallization device for evaporation and crystallization to obtain sodium chloride. The second-stage nanofiltration concentrated water of the third-stage nanofiltration unit enters a sodium sulfate freezing and crystallization device for freezing and crystallization to obtain sodium sulfate. The second-stage nanofiltration produced water of the third-stage nanofiltration unit flows back to the second-stage nanofiltration unit.

[0020] In one embodiment, the multidimensional salt separation method further comprises the following steps:

[0021] Part of the sodium chloride crystals of the sodium chloride evaporation and crystallization device enter the miscellaneous salt evaporation and crystallization device and evaporate and crystallize the miscellaneous salt;

[0022] And / or, part of the sodium chloride crystallization mother liquor of the sodium chloride evaporation crystallization device enters the sodium sulfate freezing crystallization device for freezing crystallization to obtain sodium sulfate;

[0023] And / or, a portion of the nanofiltration concentrate from the sodium sulfate crystallization mother liquor of the sodium sulfate freezing crystallization device after nanofiltration by the high-pressure nanofiltration device enters the impure salt evaporation crystallization device and evaporates and crystallizes the impure salt, and another portion of the nanofiltration concentrate flows back to the second concentrator, and the nanofiltration product water of the high-pressure nanofiltration device flows back to the primary nanofiltration unit.

[0024] In one embodiment, the multi-dimensional salt separation method further includes the following steps: the sodium sulfate freezing crystallization device freezes and crystallizes the sodium sulfate to obtain Glauber's salt, and then melts and crystallizes the sodium sulfate to obtain anhydrous sodium sulfate in a melt crystallization device.

[0025] The multi-stage nanofiltration device of the present invention is composed of three groups of nanofiltration units. While ensuring the recovery rate, it has a high interception rate for sulfate radicals, and can better separate chloride ions and sulfate radicals to ensure the purity of by-product salts.

[0026] Compared with the traditional technology, the present invention innovatively combines the three methods of evaporation, freezing and high-pressure nanofiltration. For the NaCl solution and Na2SO4 solution separated by the multi-stage nanofiltration device system, the evaporation crystallization device produces high-purity sodium chloride, and the freezing + melt crystallization produces high-purity anhydrous sodium sulfate. Among them, part of the evaporated mother liquor is refluxed to the freezing crystallization device to increase the output of mirabilite, and the sodium sulfate crystallization mother liquor is secondary separated by high-pressure nanofiltration, the NaCl in the sodium sulfate crystallization mother liquor is recovered and the Na2SO4 is concentrated and refluxed, and the remaining small amount of sodium sulfate crystallization mother liquor and sodium chloride crystallization mother liquor are discharged to the impure salt evaporation crystallization device to produce impure salt. The multidimensional salt separation system of the present invention greatly improves the quality of sodium chloride (sodium chloride purity>97%) and the quality of anhydrous sodium sulfate (anhydrous sodium sulfate purity>97%) through the flexible combination of evaporation, freezing and high-pressure nanofiltration, and reduces the impure salt rate, which is less than 15%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of a multi-dimensional salt separation system according to an embodiment of the present invention;

[0028] Figure 2 for Figure 1 Schematic diagram of the multi-stage nanofiltration device of the multi-dimensional salt separation system shown in .

[0029] Description of Reference Numerals

[0030] 10. Multi-dimensional salt separation system; 100. Multi-stage nanofiltration device; 110. Primary nanofiltration unit; 120. Secondary nanofiltration unit; 130. Third-stage nanofiltration unit; 200. Softening and silicon removal device; 300. Sodium chloride evaporation crystallization device; 400. Sodium sulfate freezing crystallization device; 500. Melt crystallization device; 600. Miscellaneous salt evaporation crystallization device; 700. First concentration device; 800. Second concentration device; 900. High-pressure nanofiltration device; 1000. Regulating tank. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0032] In the description of the present invention, it should be understood that the terms "center", "upper", "lower", "bottom", "inside" and "outside" used in the present invention to indicate the orientation or position relationship are based on the orientation or position relationship shown in the drawings, which is 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 cannot be understood as a limitation on the present invention.

[0033] It should be understood that the present invention uses the terms "first", "second", etc. to describe various information, but these information should not be limited to these terms, and these terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, "first" information may also be referred to as "second" information, and similarly, "second" information may also be referred to as "first" information.

[0034] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements. That is, when an element is referred to as "fixed to" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there can be an intermediate element at the same time. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0036] Please also read Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a multi-dimensional salt separation system 10.

[0037] A multi-dimensional salt separation system 10 includes a softening and silicon removal device 200, a sodium chloride evaporation crystallization device 300, a sodium sulfate freezing crystallization device 400, a melting crystallization device 500 and a multi-stage nanofiltration device 100.

[0038] Please also read Figure 2As shown, the multi-stage nanofiltration device 100 includes a primary nanofiltration unit 110, a secondary nanofiltration unit 120, and a tertiary nanofiltration unit 130. The primary nanofiltration unit 110, the secondary nanofiltration unit 120, and the tertiary nanofiltration unit 130 are sequentially connected in series, and the primary nanofiltration unit 110 is also connected to the tertiary nanofiltration unit 130 to realize that the primary nanofiltration concentrated water of the primary nanofiltration unit 110 enters the tertiary nanofiltration unit 130, and the tertiary nanofiltration produced water of the tertiary nanofiltration unit 130 also enters the secondary nanofiltration unit 120, and the secondary nanofiltration produced water of the secondary nanofiltration unit 120 is used to enter the sodium chloride evaporation crystallization device 300, and the tertiary nanofiltration concentrated water of the tertiary nanofiltration unit 130 is used to enter the sodium sulfate freezing crystallization device 400.

[0039] The multi-stage nanofiltration device 100 of the present invention is composed of three groups of nanofiltration units. While ensuring the recovery rate, it has a high retention rate for sulfate ions, and can better separate chloride ions and sulfate ions to ensure the purity of by-product salt.

[0040] The softening and silicon removal device 200 is connected to the primary nanofiltration unit 110, the secondary nanofiltration unit 120 is connected to the sodium chloride evaporation crystallization device 300, the sodium sulfate freezing crystallization device 400 is connected to the tertiary nanofiltration unit 130, and the melting crystallization device 500 is connected to the sodium sulfate freezing crystallization device 400.

[0041] In a specific embodiment, the primary nanofiltration unit 110 is a high-efficiency He nanofiltration unit.

[0042] In a specific embodiment, the secondary nanofiltration unit 120 is a high cut-off Hr nanofiltration unit.

[0043] In one specific embodiment, the tertiary nanofiltration unit 130 is a high recovery Hc nanofiltration unit.

[0044] In a specific embodiment, the multi-dimensional salt separation system 10 further includes a miscellaneous salt evaporation crystallization device 600. The miscellaneous salt evaporation crystallization device 600 is connected to the sodium chloride evaporation crystallization device 300, and the miscellaneous salt evaporation crystallization device 600 is used to receive part of the sodium chloride crystallization mother liquor from the sodium chloride evaporation crystallization device 300 and evaporate the miscellaneous salt. Preferably, the miscellaneous salt evaporation crystallization device 600 can be a single-effect evaporation system.

[0045] In a specific embodiment, the sodium chloride evaporation crystallization device 300 is also connected to the sodium sulfate freezing crystallization device 400, and part of the sodium chloride crystallization mother liquor of the sodium chloride evaporation crystallization device 300 enters the sodium sulfate freezing crystallization device 400 for freezing crystallization.

[0046] In a specific embodiment, the multi-dimensional salt separation system 10 further includes a first concentrating device 700. The first concentrating device 700 is connected in series between the secondary nanofiltration unit 120 and the sodium chloride evaporation crystallization device 300. The first concentrating device 700 may be a high-pressure reverse osmosis concentrating device.

[0047] Preferably, the first concentration device 700 may be one or more of reverse osmosis, high pressure reverse osmosis, DTRO, electrodialysis and MVR.

[0048] In a specific embodiment, the multi-dimensional salt separation system 10 further includes a second concentrating device 800. The second concentrating device 800 is connected in series between the three-stage nanofiltration unit 130 and the sodium sulfate freezing crystallization device 400. The second concentrating device 800 may be a reverse osmosis concentrating device.

[0049] Preferably, the second concentration device 800 may be one or more of reverse osmosis, high pressure reverse osmosis, DTRO, electrodialysis and MVR.

[0050] Preferably, the sodium chloride evaporation crystallization device 300 can be one or more selected from falling film evaporator, rising film evaporator, TVR, MVR, single effect evaporation and multiple effect evaporation.

[0051] The sodium sulfate freezing crystallization device 400 can be any one or more selected from an OSLO evaporation crystallizer, a DTB evaporation crystallizer, a FC evaporation crystallizer, and a multi-effect evaporation crystallizer.

[0052] In a specific embodiment, the multi-dimensional salt separation system 10 further includes a high-pressure nanofiltration device 900. The high-pressure nanofiltration device 900 is connected in series between the sodium sulfate freezing crystallization device 400 and the impurity salt evaporation device, and the high-pressure nanofiltration device 900 is also connected to the primary nanofiltration unit 110. The sodium sulfate crystallization mother liquor of the sodium sulfate freezing crystallization device 400 enters the high-pressure nanofiltration device 900 for nanofiltration, and part of the nanofiltration concentrated water of the high-pressure nanofiltration device 900 enters the impurity salt evaporation crystallization device 600. The nanofiltration product water of the high-pressure nanofiltration device 900 enters the primary nanofiltration unit 110 for connection.

[0053] In a specific embodiment, the high-pressure nanofiltration device 900 is also connected to the second concentrating device 800 , and part of the nanofiltration concentrate of the high-pressure nanofiltration device 900 also enters the second concentrating device 800 .

[0054] In a specific embodiment, the multi-dimensional salt separation system 10 further includes a regulating tank 1000 , which is connected to the front end of the softening and silicon removal device 200 .

[0055] In a specific embodiment, the softening and desiliconizing device 200 includes one or more of a desiliconizing high-density tank, a V-type filter tank, and an ultrafiltration device.

[0056] A multidimensional salt separation method comprises the following steps:

[0057] After being softened and desiliconized by the softening and desiliconizing device 200, the high-salt wastewater enters the multi-stage nanofiltration device 100 for nanofiltration treatment. The first-stage nanofiltration concentrate of the first-stage nanofiltration unit 110 enters the third-stage nanofiltration unit 130. The first-stage nanofiltration product water of the first-stage nanofiltration unit 110 enters the second-stage nanofiltration unit 120. The second-stage nanofiltration concentrate of the second-stage nanofiltration unit 120 enters the third-stage nanofiltration unit 130. The second-stage nanofiltration product water of the second-stage nanofiltration unit 120 enters the sodium chloride evaporation and crystallization device 300 for evaporation and crystallization to obtain sodium chloride. The second-stage nanofiltration concentrate of the third-stage nanofiltration unit 130 enters the sodium sulfate freezing and crystallization device 400 for freezing and crystallization to obtain sodium sulfate. The second-stage nanofiltration product water of the third-stage nanofiltration unit 130 flows back to the second-stage nanofiltration unit 120.

[0058] In a specific embodiment, the multidimensional salt separation method further comprises the following steps:

[0059] Part of the sodium chloride crystals from the sodium chloride evaporation crystallization device 300 enters the impure salt evaporation crystallization device 600 and evaporates and crystallizes the impure salt.

[0060] In a specific embodiment, part of the sodium chloride crystallization mother liquor of the sodium chloride evaporation crystallization device 300 enters the sodium sulfate freezing crystallization device 400 for freezing crystallization to obtain sodium sulfate.

[0061] In a specific embodiment, a portion of the sodium sulfate crystallization mother liquor from the sodium sulfate freezing crystallization device 400 enters the impure salt evaporation crystallization device 600 after nanofiltration by the high-pressure nanofiltration device 900 and evaporates and crystallizes the impure salt, and another portion of the nanofiltration concentrate flows back to the second concentration device 800, and the nanofiltration product water of the high-pressure nanofiltration device 900 flows back to the primary nanofiltration unit 110.

[0062] In a specific embodiment, the multi-dimensional salt separation method further includes the following steps: sodium sulfate freezing crystallization device 400 freezes and crystallizes to obtain Glauber's salt, which is then melt-crystallized in melt crystallization device 500 to obtain anhydrous sodium sulfate.

[0063] Compared with the conventional technology, the present invention innovatively combines the three methods of evaporation, freezing and high-pressure nanofiltration. For the NaCl solution and Na2SO4 solution separated by the multi-stage nanofiltration device 100 system, the evaporation crystallization device produces high-purity sodium chloride, and the freezing + melt crystallization produces high-purity anhydrous sodium sulfate. Among them, part of the evaporated mother liquor is refluxed to the freezing crystallization device to increase the output of mirabilite, and the sodium sulfate crystallization mother liquor is secondary separated by high-pressure nanofiltration, the NaCl in the sodium sulfate crystallization mother liquor is recovered and the Na2SO4 is concentrated and refluxed, and the remaining small amount of sodium sulfate crystallization mother liquor and sodium chloride crystallization mother liquor are discharged to the impure salt evaporation crystallization device 600 to produce impure salt. The multidimensional salt separation system 10 of the present invention greatly improves the quality of sodium chloride (sodium chloride purity>97%) and the quality of anhydrous sodium sulfate (anhydrous sodium sulfate purity>97%) through the flexible combination of evaporation, freezing and high-pressure nanofiltration, and reduces the impure salt rate, which is less than 15%.

[0064] Example 1

[0065] This embodiment provides a multi-dimensional salt separation method.

[0066] The multi-dimensional salt separation method of this embodiment is used to treat high-salt wastewater from a coal chemical industry.

[0067] The coal chemical industry high-salt wastewater was tested and its water quality was as follows: pH: 6-8, COD: 110.0 mg / L, TOC: 25.0 mg / L, Ca 2+ :0.6mg / L,Mg 2+ :0.4mg / L,NH4 + :3.0mg / L,Na + :6692.5mg / L,K + :131.5mg / L,Cl - :4970.6mg / L,SO4 2- :7271.4mg / L, NO3 - :122.1mg / L,HCO 3- :76.5mg / L,CO3 2- : 4.0mg / L, SiO2: 31.7mg / L, TDS: 19304.2mg / L.

[0068] The high-salinity wastewater from coal chemical industry is recycled through a multi-dimensional salt separation method, including the following steps:

[0069] (1) High-salinity wastewater first enters the regulating tank 1000, and the inlet flow rate of the regulating tank 1000 is 97.5m 3 / h, the residence time is 4h.

[0070] (2) The high-salt wastewater is regulated in the regulating tank 1000 and then enters the softening and desiliconizing device 200. In this embodiment, the softening and desiliconizing device 200 includes a high-density desiliconizing tank, a V-type filter tank, and an ultrafiltration device. The SiO2 in the high-salt wastewater is reduced to 10.0 mg / L through the softening and desiliconizing device 200, and filtered through the V-type filter tank and the ultrafiltration device to reduce the SDI of the high-salt wastewater to below 3 and the turbidity to below 1 NTU.

[0071] (3) After being treated by the softening and silicon removal device 200, the high-salt wastewater enters the multi-stage nanofiltration device 100. The recovery rate of the first-stage nanofiltration unit 110 of the multi-stage nanofiltration device 100 is 73%, the recovery rate of the second-stage nanofiltration unit 120 is 84%, and the recovery rate of the third-stage nanofiltration unit 130 is 70%. The water quality of the multi-stage nanofiltration device 100 is shown in Table 1 below.

[0072] Table 1

[0073]

[0074] As can be seen from the above table, the water produced by the secondary nanofiltration unit 120 is the secondary nanofiltration water Cl - / SO4 2- =5917.3 / 73.5, salt nitrate ratio (NaCl / Na2SO4) =89.6 / 1, the third-stage nanofiltration concentrated water Cl of the third-stage nanofiltration unit 130 - / SO4 2- =1204.8 / 53114.5, equivalent salt-nitrate ratio (NaCl / Na2SO4) = 1 / 39.6.

[0075] (4) The final water produced by the multi-stage nanofiltration device 100, i.e., the secondary nanofiltration produced water of the secondary nanofiltration unit 120, and the final concentrated water of the multi-stage nanofiltration device 100, i.e., the tertiary nanofiltration concentrated water of the tertiary nanofiltration unit 130, both enter the concentrating device to reduce the scale of sodium chloride and sodium sulfate crystallization. In this embodiment, the concentrating devices respectively use a first concentrating device 700 and a second concentrating device 800, wherein the first concentrating device 700 is a high-pressure reverse osmosis concentrating device. After the secondary nanofiltration produced water is concentrated by the first concentrating device 700, the water quality of the concentrated water side of the first concentrating device 700 is as follows: pH: 6-8, COD: 388.0 mg / L, TOC: 88.2 mg / L, Ca 2+ :0.5mg / L、Mg 2+ :0.4mg / L、NH4 + :11.6mg / L、Na + :18348.4mg / L, K + :628.2mg / L、Cl - :27732.5mg / L、SO4 2- :344.7mg / L、NO3 -:893.3mg / L, HCO 3- :640.5mg / L、CO3 2- : 38.3mg / L, SiO2: 120.4mg / L, TDS: 48758.7mg / L.

[0076] After the third-stage nanofiltration concentrate of the multi-stage nanofiltration device 100 passes through the second concentrator 800, the water quality of the concentrate side of the second concentrator 800 is as follows: pH: 6-8, COD: 2482.3.0 mg / L, TOC: 564.2 mg / L, Ca 2+ :19.9mg / L、Mg 2+ :13.2mg / L、NH4 + :72.6mg / L、Na + :41985.6mg / L, K + :2821.5mg / L、Cl - :1682.3mg / L、SO4 2- :88019.1mg / L, NO3 - : 236.7mg / L, HCO 3- :1131.9mg / L、CO3 2- : 13.3mg / L, SiO2: 248.1mg / L, TDS: 136244.4mg / L.

[0077] (5) The final water produced by the multi-stage nanofiltration device 100, i.e., the secondary nanofiltration water produced by the secondary nanofiltration unit 120, enters the sodium chloride evaporation crystallization device 300 after being concentrated by the first concentrator 700. In this embodiment, the sodium chloride evaporation crystallization device 300 can be an MVR evaporator. It is not difficult to understand that in other embodiments, the MVR evaporator can be replaced by a single-effect evaporator, a TVR evaporator or a multi-effect evaporator. The sodium chloride evaporation crystallization device 300 produces 0.72 t / h of sodium chloride with a purity of 97.2% and a water content of 4.7%. The remaining sodium chloride crystallization mother liquor is 0.5m 3 / h, of which 0.3m 3 / h is refluxed to the sodium sulfate freezing crystallization mother liquor inlet, and the remaining sodium chloride crystallization mother liquor enters the miscellaneous salt evaporation crystallization device 600. The water quality of the sodium chloride crystallization mother liquor is as follows: pH: 6-8, COD: 2482.3mg / L, TOC: 564.2mg / L, Ca 2+ :19.9mg / L、Mg 2+ :13.2mg / L、NH4 + :72.6mg / L、Na + :41985.6mg / L, K + :2821.5mg / L、Cl -:1682.3mg / L、SO4 2- :88019.1mg / L, NO3 - : 236.7mg / L, HCO 3- :1131.9mg / L、CO3 2- : 13.3mg / L, SiO2: 248.1mg / L, TDS: 136244.4mg / L.

[0078] (6) The final concentrated water of the multi-stage nanofiltration device 100, i.e., the third-stage nanofiltration concentrated water, is concentrated by the first concentrator 700 and then concentrated into the sodium sulfate freezing crystallization mother liquor. The sodium sulfate freezing crystallization mother liquor produces 0.91 t / h of sodium sulfate with a purity of 99% and a water content of 4.6%. The water quality of the sodium sulfate crystallization mother liquor is as follows: pH: 6-8, COD: 3032.0 mg / L, TOC: 687.0 mg / L, Ca 2+ :22.3mg / L、Mg 2+ :14.9mg / L、NH4 + :92.2mg / L、Na + :17969.9mg / L, K + :3783.1mg / L、Cl - :7336.0mg / L、SO4 2- :30000.0mg / L、NO3 - :1255.1mg / L, HCO 3- :1951.0mg / L、CO3 2- : 57.3 mg / L, SiO2: 405.4 mg / L, TDS: 62887.1 mg / L, the sodium sulfate crystallization mother liquor enters the high-pressure nanofiltration device 900.

[0079] (7) The nanofiltration product water of the high-pressure nanofiltration device 900 flows back to the water inlet of the first-stage nanofiltration unit 110 of the multi-stage nanofiltration device 100, part of the nanofiltration concentrate of the high-pressure nanofiltration device 900 enters the salt evaporation crystallization device 600, and part of the nanofiltration concentrate of the high-pressure nanofiltration device 900 flows back to the water inlet of the second concentration device 800. The water quality of the nanofiltration concentrate of the high-pressure nanofiltration device 900 is as follows: pH: 6-8, COD: 7255.14 mg / L, TOC: 1648.9 mg / L, Ca: 0.0847 g / L, 0.13 g / L, 0.22 g / L, 0.12 g / L, 0.24 g / L, 0.14 ... 2+ :63.9mg / L、Mg 2+ :42.6mg / L、NH4 + :221.4mg / L、Na + :40621.3mg / L, K + :8551.7mg / L、Cl - :489.1mg / L、SO4 2-:93000.0mg / L、NO3 - :1196.5mg / L、HCO 3- :3084.3mg / L、CO3 2- : 37.2mg / L, SiO2: 405.4mg / L, TDS: 148154.0mg / L.

[0080] (8) The sodium chloride crystallization mother liquor and the nanofiltration concentrated water from the high-pressure nanofiltration device 900 enter the impure salt evaporation crystallization device 600 together. In this embodiment, the impure salt evaporation crystallization device 600 uses a single-effect evaporation system. This embodiment finally produces 0.21 t / h of impure salt, and the overall impure salt rate of the project is 11.3%, which greatly reduces the treatment cost of hazardous waste.

[0081] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0082] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A multidimensional salt distribution system, characterized in that: It includes a multi-stage nanofiltration device, a high-pressure nanofiltration device, a sodium chloride evaporation crystallization device, a sodium sulfate freezing crystallization device, a melt crystallization device, a softening and desiliconizing device, and a regulating tank; the sodium chloride evaporation crystallization device and the sodium sulfate freezing crystallization device are respectively connected to the multi-stage nanofiltration device, the secondary nanofiltration produced water of the multi-stage nanofiltration device enters the sodium chloride evaporation crystallization device, the secondary nanofiltration concentrated water of the multi-stage nanofiltration device enters the sodium sulfate freezing crystallization device, the melt crystallization device is connected to the sodium sulfate freezing crystallization device, the sodium sulfate freezing crystallization device freezes and crystallizes to obtain mirabilite, and then melts and crystallizes to obtain anhydrous sodium sulfate through a melt crystallization device, a part of the sodium sulfate crystallization mother liquor of the sodium sulfate freezing crystallization device after nanofiltration enters the miscellaneous salt evaporation crystallization device, the regulating tank is connected to the front end of the softening and desiliconizing device, the softening and desiliconizing device includes one or more of a high-density tank, a filter tank and an ultrafiltration device, the softening and desiliconizing device is connected to the multi-stage nanofiltration device, and the multi-stage nanofiltration device includes a primary nanofiltration unit, A secondary nanofiltration unit and a tertiary nanofiltration unit, wherein the primary nanofiltration unit, the secondary nanofiltration unit and the tertiary nanofiltration unit are connected in series in sequence, the primary nanofiltration unit is also connected to the tertiary nanofiltration unit to realize that the primary nanofiltration concentrated water of the primary nanofiltration unit enters the tertiary nanofiltration unit, and the tertiary nanofiltration produced water of the tertiary nanofiltration unit also enters the secondary nanofiltration unit, the softening and silicon removal device is connected to the primary nanofiltration unit, the secondary nanofiltration unit is connected to the sodium chloride evaporation crystallization device, the sodium sulfate freezing crystallization device is connected to the tertiary nanofiltration unit, the melt crystallization device is connected to the sodium sulfate freezing crystallization device, the high-pressure nanofiltration device is connected to the sodium sulfate freezing crystallization device, the high-pressure nanofiltration device is also connected to the primary nanofiltration unit, the sodium sulfate crystallization mother liquor of the sodium sulfate freezing crystallization device enters the high-pressure nanofiltration device for nanofiltration, part of the nanofiltration concentrated water of the high-pressure nanofiltration device enters the miscellaneous salt evaporation crystallization device, and the nanofiltration produced water of the high-pressure nanofiltration device enters the primary nanofiltration unit.

2. The multidimensional salt distribution system according to claim 1, characterized in that: The multi-dimensional salt separation system also includes a miscellaneous salt evaporation and crystallization device, which is connected to the sodium chloride evaporation and crystallization device and is used to receive part of the sodium chloride crystallization mother liquor from the sodium chloride evaporation and crystallization device and evaporate miscellaneous salts.

3. The multidimensional salt distribution system according to claim 1, characterized in that: The sodium chloride evaporation crystallization device is also connected to the sodium sulfate freezing crystallization device, and part of the sodium chloride crystallization mother liquor of the sodium chloride evaporation crystallization device enters the sodium sulfate freezing crystallization device for freezing crystallization.

4. The multidimensional salt distribution system according to any one of claims 1 to 3, characterized in that: The multi-dimensional salt separation system further comprises a first concentrating device, which is connected in series between the secondary nanofiltration unit and the sodium chloride evaporation crystallization device.

5. The multidimensional salt distribution system according to any one of claims 1 to 3, characterized in that: The multi-dimensional salt separation system also includes a second concentrating device, which is connected in series between the three-stage nanofiltration unit and the sodium sulfate freezing crystallization device.

6. The multi-dimensional salt distribution system according to claim 5, characterized in that: The high-pressure nanofiltration device is connected in series between the sodium sulfate freezing crystallization device and the mixed salt evaporation crystallization device, and part of the nanofiltration concentrated water of the high-pressure nanofiltration device enters the mixed salt evaporation crystallization device.

7. The multi-dimensional salt distribution system according to claim 6, characterized in that: The high-pressure nanofiltration device is also connected to the second concentrating device, and part of the nanofiltration concentrated water from the high-pressure nanofiltration device also enters the second concentrating device.

8. The multidimensional salt distribution system according to any one of claims 1 to 3, characterized in that: The first-level nanofiltration unit is a high-efficiency He nanofiltration unit; And / or, the secondary nanofiltration unit is a high retention Hr nanofiltration unit; And / or, the three-stage nanofiltration unit is a high-recovery Hc nanofiltration unit.

9. A multidimensional salt separation method, characterized in that: The multidimensional salt distribution system according to any one of claims 1 to 8 comprises the following steps: The high-salt wastewater is softened and desiliconized by a softening and desiliconizing device and then enters a multi-stage nanofiltration device for nanofiltration treatment. The first-stage nanofiltration concentrated water of the first-stage nanofiltration unit enters a third-stage nanofiltration unit. The first-stage nanofiltration produced water of the first-stage nanofiltration unit enters a second-stage nanofiltration unit. The second-stage nanofiltration concentrated water of the second-stage nanofiltration unit enters the third-stage nanofiltration unit. The second-stage nanofiltration produced water of the second-stage nanofiltration unit enters a sodium chloride evaporation and crystallization device for evaporation and crystallization to obtain sodium chloride. The second-stage nanofiltration concentrated water of the third-stage nanofiltration unit enters a sodium sulfate freezing and crystallization device for freezing and crystallization to obtain sodium sulfate. The second-stage nanofiltration produced water of the third-stage nanofiltration unit flows back to the second-stage nanofiltration unit. A part of the nanofiltration concentrated water of the sodium sulfate crystallization mother liquor of the sodium sulfate freezing and crystallization device after nanofiltration by the high-pressure nanofiltration device enters the miscellaneous salt evaporation and crystallization device and evaporates and crystallizes miscellaneous salts, and another part of the nanofiltration concentrated water flows back to the second concentration device. The nanofiltration produced water of the high-pressure nanofiltration device flows back to the first-stage nanofiltration unit.

10. The multidimensional salt separation method according to claim 9, characterized in that: The following steps are also included: Part of the sodium chloride crystals of the sodium chloride evaporation and crystallization device enter the miscellaneous salt evaporation and crystallization device and evaporate and crystallize the miscellaneous salt; And / or, part of the sodium chloride crystallization mother liquor of the sodium chloride evaporation crystallization device enters the sodium sulfate freezing crystallization device for freezing crystallization to obtain sodium sulfate.

11. The multidimensional salt separation method according to claim 9 or 10, characterized in that: The method also includes the following steps: the sodium sulfate freezing crystallization device freezes and crystallizes the sodium sulfate to obtain mirabilite, and then the sodium sulfate is melt-crystallized in a melt-crystallization device to obtain anhydrous sodium sulfate.

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