Systems and methods for recovering sodium carbonate and sodium chloride from mine water

Abstract

This invention relates to the field of coal mine water treatment technology, and discloses a system and method for recovering sodium carbonate and sodium chloride from mine water. The system includes a pretreatment unit (1), a concentration and softening unit (2), and an evaporation and crystallization unit (3). The pretreatment unit (1) pretreats the mine water to remove fine suspended solids and colloids, obtaining pretreated mine water. The concentration and softening unit (2) performs multi-stage concentration and softening on the pretreated mine water. The evaporation and crystallization unit (3) evaporates, dries, and crystallizes the water treated by the concentration and softening unit (2). In the system described in this invention, by performing pretreatment, multi-stage concentration, softening, and evaporation on the mine water, scaling during evaporation and crystallization is avoided, reducing the cost of mine water treatment. Simultaneously, the obtained sodium carbonate and sodium chloride meet market standards.

Description

Technical Field

[0001] This invention relates to the field of coal mine water treatment technology, specifically to a system and method for recovering sodium carbonate and sodium chloride from mine water. Background Technology

[0002] Coal mine production generates a large amount of mine water. In my country, mine water comes from various sources and can generally be classified based on the characteristics of its pollutants: clean mine water, mine water containing suspended solids, high-mineralized mine water, acidic mine water, and alkaline mine water. High-mineralized mine water refers to water with a salt content greater than 1000 mg / L. In my country, mine water is mostly characterized by low organic matter and high mineralization, with mineralization levels typically between 1000-3000 mg / L, and a small amount exceeding 4000 mg / L. The salt content primarily originates from calcium (Ca). 2+ Mg 2+ Na + SO4 2- Cl - HCO 3- The water from mines is often alkaline, has a bitter taste, and tends to be quite hard. With advancements in coal mining technology and increasing public demand, the discharge of mine water continues to rise, severely polluting the environment and contributing to water scarcity. Therefore, implementing zero-discharge mine water systems and realizing their resource utilization is crucial.

[0003] High-mineralization mine water should undergo advanced treatment for comprehensive utilization, achieving water resource recycling and the resource utilization of crystalline salts. Currently, the commonly used two-stage reverse osmosis technology in wastewater treatment can effectively concentrate wastewater and reduce discharge to some extent, but the wastewater recovery rate is not high, ultimately resulting in a significant amount of saline and low-concentration wastewater. Another commonly used concentrated water treatment method utilizes evaporation and crystallization units to form mixed salts, ultimately achieving zero wastewater discharge. However, this method also has certain drawbacks, such as high cost per ton of water and the need for special treatment of the resulting mixed salts as hazardous waste. Overall, current domestic methods for treating high-mineralization mine water are not yet mature and the treatment costs are high.

[0004] Sodium carbonate, a crystalline product, is not only used in the chemical industry, but also requires the addition of large quantities in many zero-emission projects due to their demand for hardening treatment, making its applications very wide-ranging. Furthermore, the produced sodium carbonate can be sold to other zero-emission project operators at a higher price than common sodium salts such as sodium chloride and sodium sulfate, making it easier to sell, reducing treatment costs, and enabling more economical resource utilization of mine water and wastewater.

[0005] Therefore, it is essential to develop a system and method for recovering sodium carbonate and sodium chloride from mine water. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low mine water recovery rate, large quantities of saline and low-concentration mine water remaining in the treatment of high-mineralized mine water, high cost per ton of water, and difficulty in treating the mixed salt formed in the existing technology. This invention provides a system and method for recovering sodium carbonate and sodium chloride from mine water. Through a pretreatment unit, a concentration and softening unit, and an evaporation and crystallization unit, this invention improves the mine water recovery rate and the economic efficiency of the subsequent evaporation and crystallization unit, reduces the hardness of the pretreated mine water, reduces scaling in the subsequent evaporation and crystallization system, and allows the obtained anhydrous sodium carbonate and sodium chloride crystals to be sold as chemical raw materials to surrounding production enterprises, reducing treatment costs and realizing the resource utilization of mine water.

[0007] To achieve the above objectives, the present invention provides a system for recovering sodium carbonate and sodium chloride from mine water. The system includes a pretreatment unit, a concentration and softening unit, and an evaporation and crystallization unit. The pretreatment unit is used to pretreat the mine water, removing fine suspended solids and colloids to obtain pretreated mine water. The concentration and softening unit is used to perform multi-stage concentration and softening of the pretreated mine water. The evaporation and crystallization unit is used to evaporate, dry, and crystallize the water treated by the concentration and softening unit.

[0008] Preferably, the concentration and softening unit includes a concentrate dividing tank, a particle reactor, a second reverse osmosis unit, a tubular ultrafiltration unit, a sodium bed, a forward osmosis unit, and a third reverse osmosis unit. The concentrated water obtained from the first reverse osmosis unit is fed into the concentrate dividing tank, and then sequentially enters the particle reactor and the second reverse osmosis unit for treatment. When the concentration of the concentrated water obtained after treatment by the second reverse osmosis unit is lower than a predetermined value, the concentrated water obtained after treatment by the second reverse osmosis unit is returned to the concentrate dividing tank and circulated back into the particle reactor and the second reverse osmosis unit for treatment. When the concentration of the concentrated water obtained after treatment by the second reverse osmosis unit reaches the predetermined value, the concentrated water obtained after treatment by the second reverse osmosis unit is returned to the concentrate dividing tank and then injected into the tubular ultrafiltration unit for treatment. The sodium bed is used to soften the concentrated water after treatment by the tubular ultrafiltration unit. The forward osmosis unit is used to perform forward osmosis treatment on the softened concentrated water. The third reverse osmosis unit is used to perform reverse osmosis treatment on the desalinated water obtained after forward osmosis treatment.

[0009] Preferably, the pretreatment unit includes a sedimentation tank, a filtration device, an ultrafiltration device, and a first reverse osmosis device, wherein the sedimentation tank is used to remove suspended solids and silt from the mine water; the filtration device is used to filter and separate the water obtained after treatment by the sedimentation tank; the ultrafiltration device is used to perform ultrafiltration treatment on the filtrate obtained after filtration and separation; and the first reverse osmosis device is used to perform reverse osmosis treatment on the water obtained after ultrafiltration treatment.

[0010] Preferably, the sedimentation tank includes a coagulation reaction zone, a flocculation zone, and a sedimentation zone arranged sequentially along the fluid flow direction.

[0011] Preferably, the pretreatment unit further includes a sludge treatment device, which is used to treat the sludge obtained after treatment in the sedimentation tank to remove harmful substances from the sludge.

[0012] Preferably, the evaporation crystallization unit includes: a freeze crystallization device, an evaporation crystallization device, and a mother liquor drying device, wherein the freeze crystallization device is used to freeze crystallize, centrifuge, and dry the concentrated water obtained after the forward osmosis treatment; the evaporation crystallization device is used to evaporate crystallize, centrifuge, and dry the first mother liquor after the freeze crystallization device treatment; and the mother liquor drying device is used to dry the second mother liquor after the evaporation crystallization device treatment, dissolve the separated impurities, and return them to the freeze crystallization device.

[0013] Preferably, the freeze crystallization apparatus includes a freeze crystallizer, a first centrifuge, and a first dryer, wherein the freeze crystallizer is used to freeze crystallize the concentrated water obtained after the forward osmosis treatment; the first centrifuge is used to centrifuge the product obtained after the freeze crystallization treatment; and the first dryer is used to dry the solid obtained after the treatment by the first centrifuge.

[0014] Preferably, the evaporation crystallization apparatus includes an evaporator crystallizer, a second centrifuge, and a second dryer, wherein the evaporator crystallizer is used to evaporate and crystallize the first mother liquor obtained after processing by the freeze crystallization apparatus; the second centrifuge is used to centrifuge the product obtained after the evaporation crystallization process; and the second dryer is used to dry the solid obtained after processing by the second centrifuge.

[0015] Preferably, the mother liquor drying device includes a third dryer and a mother liquor dryer, wherein the third dryer is used to dry the second mother liquor obtained after being processed by the evaporation crystallization device; the mother liquor dryer is used to dry the product obtained after being processed by the third dryer to obtain mixed salt; the mixed salt is dissolved and then passed into the freeze crystallizer for freeze crystallization.

[0016] A second aspect of the present invention provides a method for recovering sodium carbonate and sodium chloride from mine water, the method comprising the following steps:

[0017] (1) The mine water is fed into a sedimentation tank to remove suspended solids and silt. The treated water is then fed into a filtration device, an ultrafiltration device and a first reverse osmosis device in sequence. The first product water obtained by separation is then recovered.

[0018] (2) The concentrated water obtained from the first reverse osmosis device is fed into the concentrated water partitioning tank, and then sequentially fed into the particle reactor and the second reverse osmosis device for treatment. When the concentration of the concentrated water obtained after treatment by the second reverse osmosis device is lower than a predetermined value, the concentrated water obtained after treatment by the second reverse osmosis device is returned to the concentrated water partitioning tank and circulated back into the particle reactor and the second reverse osmosis device for treatment. When the concentration of the concentrated water obtained after treatment by the second reverse osmosis device reaches the predetermined value, the concentrated water obtained after treatment by the second reverse osmosis device is returned to the concentrated water partitioning tank and then injected into the tubular ultrafiltration device for treatment. The second product water obtained after treatment by the second reverse osmosis device is recovered. The concentrated water obtained after treatment by the tubular ultrafiltration device is fed into the sodium bed for softening treatment. The softened concentrated water is fed into the forward osmosis device for forward osmosis treatment. The fresh water obtained after forward osmosis treatment is fed into the third reverse osmosis device for reverse osmosis treatment. The separated third product water is recovered.

[0019] (3) The concentrated water obtained after the forward osmosis treatment is fed into a freeze crystallizer for freeze crystallization. The product obtained after the freeze crystallization treatment is fed into a first centrifuge for centrifugation. The solid obtained after separation by the first centrifuge is fed into a first dryer for drying. The first mother liquor obtained after separation by the first centrifuge is fed into an evaporator for evaporator crystallization. The product obtained after evaporator crystallization is fed into a second centrifuge for centrifugation. The solid obtained after separation by the second centrifuge is fed into a second dryer for drying. The second mother liquor obtained after separation by the second centrifuge is fed into a third dryer for drying. The product obtained after treatment by the third dryer is fed into a mother liquor dryer for mother liquor drying to obtain mixed salts. The mixed salts are dissolved and fed into the freeze crystallizer for freeze crystallization. The predetermined value is that the total dissolved solids (TDS) of the concentrated water is 30,000-50,000 mg / L.

[0020] Preferably, the method further includes: in step (1), the sludge obtained after treatment in the sedimentation tank is fed into a sludge treatment device to remove harmful substances from the sludge.

[0021] Preferably, the method further includes: in the flocculation zone of the sedimentation tank, mine water and flocculant are mixed and reacted.

[0022] Preferably, the flocculant contains PAM.

[0023] Preferably, the method further includes: mixing and reacting the clarified liquid after sedimentation in the sedimentation tank with the flocculant.

[0024] Preferably, the method further includes: in step (2), adding a scale inhibitor to the concentrated water obtained after treatment by the particle reactor, and passing the concentrated water with the scale inhibitor into the second reverse osmosis device for reverse osmosis treatment.

[0025] Preferably, the scale inhibitor contains a monoatomic oxygen hydroxyl polymer.

[0026] Preferably, the method further includes: in step (2), introducing a draw solution into the forward osmosis apparatus.

[0027] Preferably, the extract contains sodium chloride.

[0028] Preferably, the mine water is high-mineralized mine water, and the mine water contains Ca. 2+ Mg 2+ Cl - SO4 2- CO3 2- HCO3 - The total inorganic salt content of the mine water is above 1000 mg / L, preferably 1000-6000 mg / L, and the Ca content is above 1000 mg / L. 2+ The concentration is above 100 mg / L, preferably 100-1000 mg / L, Mg 2+ The concentration is above 100 mg / L, preferably 100-1000 mg / L.

[0029] According to the technical solution described in this invention, by performing pretreatment, multi-stage concentration, softening and evaporation on mine water, the recovery rate of mine water is improved, scaling during evaporation and crystallization is avoided, and the cost of evaporation and crystallization is reduced. At the same time, the sodium carbonate and sodium chloride obtained meet the sales standards and can be sold as chemical raw materials to surrounding production enterprises, thus realizing the resource utilization of mine water wastewater in a more economical way. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the process flow for a system to recover sodium carbonate and sodium chloride from mine water.

[0031] Explanation of reference numerals in the attached figures

[0032] 1. Pretreatment unit; 11. Sedimentation tank; 12. Filtration device; 13. Ultrafiltration device; 14. First reverse osmosis device; 15. Sludge treatment device; 2. Concentration and softening unit; 21. Concentrate compartment tank; 22. Granular reactor; 23. Second reverse osmosis device; 24. Tubular ultrafiltration device; 25. Sodium bed; 26. Forward osmosis device; 27. Third reverse osmosis device; 3. Evaporation crystallization unit; 31. Freeze crystallization device; 311. Freeze crystallizer; 312. First centrifuge; 313. First dryer; 32. Evaporation crystallization device; 321. Evaporation crystallizer; 322. Second centrifuge; 323. Second dryer; 33. Mother liquor drying device; 331. Third dryer; 332. Mother liquor dryer. Detailed Implementation

[0033] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0034] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0035] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or implying the number of technical features indicated. Therefore, unless otherwise stated, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; "multiple" means two or more. The term "comprising" and any variations thereof mean non-exclusive inclusion, where one or more other features, integers, steps, operations, units, components, and / or combinations thereof may be present or added.

[0036] In addition, terms such as “center,” “horizontal,” “up,” “down,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer” that indicate orientation or positional relationship are based on the orientation or relative positional relationship shown in the accompanying drawings. They are only for the purpose of simplifying the description of this application and do not indicate that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0037] Furthermore, unless otherwise explicitly specified and limited, the terms "connected," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0038] The system for recovering sodium carbonate and sodium chloride from mine water described in this invention is described in [reference needed]. Figure 1 The system includes a pretreatment unit 1, a concentration and softening unit 2, and an evaporation and crystallization unit 3. The pretreatment unit 1 pretreats the mine water to remove fine suspended solids and colloids, obtaining pretreated mine water. The concentration and softening unit 2 performs multi-stage concentration and softening of the pretreated mine water. The evaporation and crystallization unit 3 evaporates, dries, and crystallizes the water treated by the concentration and softening unit 2. According to the system described in this invention, the hardness of high-mineralized mine water can be effectively reduced, scale formation during subsequent evaporation and crystallization can be avoided, the economic efficiency of the evaporation and crystallization unit can be improved, the recovery rate of mine water can be increased, treatment costs can be reduced, and the resource utilization of mine water can be realized.

[0039] In the system described in this invention, the concentration and softening unit 2 includes a concentrate divider tank 21, a particle reactor 22, a second reverse osmosis unit 23, a tubular ultrafiltration unit 24, a sodium bed 25, a forward osmosis unit 26, and a third reverse osmosis unit 27. The concentrated water obtained from the first reverse osmosis unit 14 is fed into the concentrate divider tank 21, and then sequentially enters the particle reactor 22 and the second reverse osmosis unit 23 for processing. When the concentration of the concentrated water obtained after treatment by the second reverse osmosis unit 23 is lower than a predetermined value, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrate divider tank 21 and circulated. The water is fed into the particle reactor 22 and the second reverse osmosis unit 23 for processing. When the concentration of the concentrated water obtained after treatment by the second reverse osmosis unit 23 reaches the predetermined value, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrated water partition tank 21 and then injected into the tubular ultrafiltration unit 24 for processing. The sodium bed 25 is used to soften the concentrated water after treatment by the tubular ultrafiltration unit 24. The forward osmosis unit 26 is used to perform forward osmosis treatment on the softened concentrated water. The third reverse osmosis unit 27 is used to perform reverse osmosis treatment on the fresh water obtained after forward osmosis treatment.

[0040] In the system described in this invention, in order to reduce the calcium carbonate content in the concentrate, the particle reactor 22 preferably comprises crystals, and more preferably, the crystals are quartz crystals.

[0041] In the system described in this invention, in order to increase the total dissolved solids (TDS) of the concentrate, the second reverse osmosis unit 23 preferably includes an antifouling membrane.

[0042] In this invention, the antifouling membrane can be commercially available or prepared using conventional methods in the art. For specific preparation methods, please refer to the content disclosed in patent application CN213294931U.

[0043] In the system described in this invention, in order to reduce the hardness of the mine water and avoid scaling in subsequent units, the sodium bed 25 preferably includes an ion exchange resin.

[0044] In this invention, the ion exchange resin can be commercially available or prepared using conventional methods in the art. For specific preparation methods, please refer to the content disclosed in patent application CN104403040B.

[0045] In the system described in this invention, the pretreatment unit 1 includes a sedimentation tank 11, a filtration device 12, an ultrafiltration device 13, and a first reverse osmosis device 14. The sedimentation tank 11 is used to remove suspended solids and silt from the mine water; the filtration device 12 is used to filter and separate the water obtained after treatment by the sedimentation tank 11; the ultrafiltration device 13 is used to perform ultrafiltration treatment on the filtrate obtained after filtration and separation; and the first reverse osmosis device 14 is used to perform reverse osmosis treatment on the water obtained after ultrafiltration treatment.

[0046] In the system described in this invention, the sedimentation tank 11 includes a coagulation reaction zone, a flocculation zone, and a sedimentation zone arranged sequentially along the fluid flow direction.

[0047] In the system described in this invention, in order to prevent sediment from depositing in the flocculation zone, the flocculation zone is preferably provided with a sedimentation propulsion zone, and the sedimentation propulsion zone is preferably provided with compressed air stirring. In a more preferred case, the top of the sedimentation propulsion zone is provided with a water passage hole.

[0048] In the system described in this invention, in order to improve sedimentation efficiency and reduce floor space, the sedimentation zone is preferably provided with inclined tube separation.

[0049] In the system described in this invention, in order to maintain the required sludge concentration in the flocculation zone, the sedimentation zone is preferably equipped with sludge recirculation.

[0050] In the system described in this invention, in order to improve sedimentation efficiency, the sedimentation tank 11 is preferably equipped with a sludge discharge pump and a magnetic powder separator. In a more preferred embodiment, the sludge discharge pump can be installed in the sludge discharge tank, and the magnetic powder separator can be connected to the coagulation reaction zone and the sludge discharge tank respectively through pipelines.

[0051] In the system described in this invention, the ultrafiltration device 13 may include a ceramic membrane. Preferably, the ceramic membrane may have strong chemical stability, temperature resistance, heat resistance, corrosion resistance, organic solvent resistance, regenerability, thermal stability, and pore stability. The pore size of the ceramic membrane may be 0.01-0.03 μm, preferably 0.015-0.025 μm.

[0052] In this invention, the ceramic membrane can be commercially available or prepared by uniform sintering of alumina and zirconium oxide composites according to conventional methods in the art. For specific preparation methods, please refer to the content disclosed in patent application CN108155412B.

[0053] In the system described in this invention, the pretreatment unit 1 further includes a sludge treatment device 15, which is used to treat the sludge obtained after treatment by the sedimentation tank 11 to remove harmful substances from the sludge.

[0054] In the system described in this invention, the evaporation crystallization unit 3 includes: a freeze crystallization device 31, an evaporation crystallization device 32, and a mother liquor drying device 33. The freeze crystallization device 31 is used to freeze crystallize, centrifuge, and dry the concentrated water obtained after the forward osmosis treatment. The evaporation crystallization device 32 is used to evaporate crystallize, centrifuge, and dry the first mother liquor after the freeze crystallization device 31. The mother liquor drying device 33 is used to dry the second mother liquor after the evaporation crystallization device 32, dissolve the separated impurities, and return them to the freeze crystallization device 31.

[0055] In the system described in this invention, the freeze crystallization apparatus 31 includes a freeze crystallizer 311, a first centrifuge 312, and a first dryer 313, wherein the freeze crystallizer 311 is used to freeze crystallize the concentrated water obtained after the forward osmosis treatment; the first centrifuge 312 is used to centrifuge the product obtained after the freeze crystallization treatment; and the first dryer 313 is used to dry the solid obtained after the treatment by the first centrifuge 312.

[0056] In the system described in this invention, the evaporation crystallization apparatus 32 includes an evaporation crystallizer 321, a second centrifuge 322, and a second dryer 323. The evaporation crystallizer 321 is used to evaporate and crystallize the first mother liquor obtained after processing by the freeze crystallization apparatus 31; the second centrifuge 322 is used to centrifuge the product obtained after the evaporation crystallization process; and the second dryer 323 is used to dry the solid obtained after processing by the second centrifuge 322.

[0057] In the system described in this invention, the mother liquor drying device 33 includes a third dryer 331 and a mother liquor dryer 332, wherein the third dryer 331 is used to dry the second mother liquor obtained after being processed by the evaporation crystallization device 32; the mother liquor dryer 332 is used to dry the product obtained after being processed by the third dryer 331 to obtain mixed salts; the mixed salts are dissolved and then passed into the freeze crystallizer 311 for freeze crystallization.

[0058] In the system described in this invention, the pipelines for conveying mine water, first produced water, second produced water, and third produced water can be spiral steel pipes.

[0059] In the system described in this invention, the filter screens of the filtration device 12 and the ultrafiltration device 13 are made of at least one of stainless steel 316, duplex steel 2205, duplex steel 2507, titanium tube, stainless steel 1.4526, and stainless steel 1.4529.

[0060] In the system described in this invention, the pipe valves in the first reverse osmosis device 14 can be at least one of UPVC, stainless steel 304, duplex steel 2205, duplex steel 2507, titanium pipe, stainless steel 1.4526, and stainless steel 1.4529.

[0061] In the system described in this invention, the pipe valves in the second reverse osmosis device 23 can be at least one of UPVC, stainless steel 316L, duplex steel 2205, duplex steel 2507, titanium pipe, stainless steel 1.4526, and stainless steel 1.4529.

[0062] In the system described in this invention, the pipeline for conveying the concentrated water obtained after the forward osmosis treatment can be at least one of duplex steel 2205, duplex steel 2507, titanium pipe, stainless steel 1.4526, and stainless steel 1.4529.

[0063] In the system described in this invention, the sodium bed 25 can be made of Q235B rubber-lined material.

[0064] In some embodiments, the system for recovering sodium carbonate and sodium chloride from mine water includes: a pretreatment unit 1, a concentration and softening unit 2, and an evaporation and crystallization unit 3, wherein the pretreatment unit 1 is used to pretreat the mine water to remove fine suspended solids and colloids to obtain pretreated mine water; the concentration and softening unit 2 is used to concentrate and soften the pretreated mine water in multiple stages; and the evaporation and crystallization unit 3 is used to evaporate, dry, and crystallize the water after treatment by the concentration and softening unit 2. The pretreatment unit 1 includes a sedimentation tank 11, a filtration device 12, an ultrafiltration device 13, and a first reverse osmosis device 14. The sedimentation tank 11 is used to remove suspended solids and silt from the mine water. The filtration device 12 is used to filter and separate the water obtained after treatment by the sedimentation tank 11. The ultrafiltration device 13 is used to perform ultrafiltration treatment on the filtrate obtained after filtration and separation. The first reverse osmosis device 14 is used to perform reverse osmosis treatment on the water obtained after ultrafiltration treatment. The sedimentation tank 11 is equipped with a sludge discharge pump and a magnetic powder separator. The ultrafiltration device 13 includes a ceramic membrane. The concentration and softening unit 2 includes a concentrate divider tank 21, a particle reactor 22, a second reverse osmosis unit 23, a tubular ultrafiltration unit 24, a sodium bed 25, a forward osmosis unit 26, and a third reverse osmosis unit 27. The concentrated water obtained from the first reverse osmosis unit 14 is fed into the concentrate divider tank 21, and then sequentially enters the particle reactor 22 and the second reverse osmosis unit 23 for processing. When the concentration of the concentrated water obtained after treatment by the second reverse osmosis unit 23 is lower than a predetermined value, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrate divider tank 21 and circulated back into the particle reactor 22 and the second reverse osmosis unit 23 for further processing. When the concentration of the concentrate obtained after treatment by the second reverse osmosis unit 23 reaches the predetermined value, the concentrate obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrate partition tank 21 and then injected into the tubular ultrafiltration unit 24 for treatment; the sodium bed 25 is used to soften the concentrate after treatment by the tubular ultrafiltration unit 24; the forward osmosis unit 26 is used to perform forward osmosis treatment on the softened concentrate; the third reverse osmosis unit 27 is used to perform reverse osmosis treatment on the desalinated water obtained after forward osmosis treatment; wherein, the particle reactor 22 includes quartz crystals, the second reverse osmosis unit 23 includes an antifouling membrane, and the sodium bed 25 includes ion exchange resin.The evaporation crystallization unit 3 includes a freeze crystallization device 31, an evaporation crystallization device 32, and a mother liquor drying device 33. The freeze crystallization device 31 is used to freeze crystallize, centrifuge, and dry the concentrated water obtained after the forward osmosis treatment. The evaporation crystallization device 32 is used to evaporate crystallize, centrifuge, and dry the first mother liquor after the freeze crystallization device 31. The mother liquor drying device 33 is used to dry the second mother liquor after the evaporation crystallization device 32, dissolve the separated impurities, and return them to the freeze crystallization device 31. The freeze crystallization device 31 includes a freeze crystallizer 311, a first centrifuge 312, and a first dryer 313. The freeze crystallizer 311 is used to freeze crystallize the concentrated water obtained after the forward osmosis treatment. The first centrifuge 312 is used to centrifuge the product obtained after the freeze crystallization treatment. The first dryer 313 is used to dry the solid obtained after the first centrifuge 312. The evaporation crystallization apparatus 32 includes an evaporator crystallizer 321, a second centrifuge 322, and a second dryer 323. The evaporator crystallizer 321 is used to evaporate and crystallize the first mother liquor obtained after treatment by the freeze crystallization apparatus 31. The second centrifuge 322 is used to centrifuge the product obtained after the evaporation crystallization treatment. The second dryer 323 is used to dry the solid obtained after treatment by the second centrifuge 322. The mother liquor drying apparatus 33 includes a third dryer 331 and a mother liquor dryer 332. The third dryer 331 is used to dry the second mother liquor obtained after treatment by the evaporation crystallization apparatus 32. The mother liquor dryer 332 is used to dry the product obtained after treatment by the third dryer 331 to obtain mixed salts. The mixed salts are dissolved and then passed into the freeze crystallizer 311 for freeze crystallization.

[0065] This invention also provides a method for recovering sodium carbonate and sodium chloride from mine water. This method is carried out in the aforementioned system and includes the following steps:

[0066] (1) The mine water is fed into the sedimentation tank 11 to remove suspended solids and silt. The treated water is then fed into the filter device 12, the ultrafiltration device 13 and the first reverse osmosis device 14 in sequence to recover the first product water obtained from the separation.

[0067] (2) The concentrated water obtained from the first reverse osmosis unit 14 is fed into the concentrated water separation tank 21, and then sequentially enters the particle reactor 22 and the second reverse osmosis unit 23 for processing. When the concentration of the concentrated water obtained after processing by the second reverse osmosis unit 23 is lower than a predetermined value, the concentrated water obtained after processing by the second reverse osmosis unit 23 is returned to the concentrated water separation tank 21 and circulated back into the particle reactor 22 and the second reverse osmosis unit 23 for processing; when the concentration of the concentrated water obtained after processing by the second reverse osmosis unit 23 reaches the predetermined value... The concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrated water separation tank 21 and then injected into the tubular ultrafiltration unit 24 for treatment; the second product water obtained after treatment by the second reverse osmosis unit 23 is recycled; the concentrated water after treatment by the tubular ultrafiltration unit 24 is fed into the sodium bed 25 for softening treatment; the softened concentrated water is fed into the forward osmosis unit 26 for forward osmosis treatment; the fresh water obtained after forward osmosis treatment is fed into the third reverse osmosis unit 27 for reverse osmosis treatment; and the separated third product water is recycled.

[0068] (3) The concentrated water obtained after the forward osmosis treatment is fed into the freeze crystallizer 311 for freeze crystallization. The product obtained after the freeze crystallization treatment is fed into the first centrifuge 312 for centrifugation. The solid obtained after separation by the first centrifuge 312 is fed into the first dryer 313 for drying. The sodium carbonate obtained after separation is recovered. The first mother liquor obtained after separation by the first centrifuge 312 is fed into the evaporator crystallizer 321 for evaporation crystallization. The product obtained after the evaporation crystallization treatment is fed into the second centrifuge 322 for centrifugation. The solid obtained after separation by the second centrifuge 322 is fed into the second dryer 323 for drying. The sodium chloride obtained after separation is recovered. The second mother liquor obtained after separation by the second centrifuge 322 is fed into the third dryer 331 for drying. The product obtained after treatment by the third dryer 331 is fed into the mother liquor dryer 332 for mother liquor drying to obtain mixed salts. The mixed salts are dissolved and fed into the freeze crystallizer 321 for freeze crystallization.

[0069] The method described in this invention can effectively remove fine suspended solids and colloids from mine water, reduce the hardness of pretreated mine water, reduce scaling during subsequent evaporation and crystallization processes, and obtain anhydrous sodium carbonate and sodium chloride crystals, thereby improving the recovery rate of mine water, reducing treatment costs, and realizing the resource utilization of mine water.

[0070] In the method described in this invention, the predetermined value is the total dissolved solids (TDS) of the concentrated water, which can be 30,000-50,000 mg / L, preferably 35,000-50,000 mg / L.

[0071] In the method described in this invention, the method may further include: in step (1), the sludge obtained after being treated by the sedimentation tank 11 is fed into the sludge treatment device 15, and harmful substances in the sludge are removed in the sludge treatment device 15.

[0072] In the method described in this invention, the mine water can sequentially pass through the coagulation reaction zone, the flocculation zone, and the sedimentation zone in the sedimentation tank 11 along the fluid flow direction.

[0073] In the method described in this invention, in order to improve sedimentation efficiency and reduce costs, the upward flow velocity of the sedimentation tank 11 is preferably 4-12 m / h, more preferably 5-10 m / h.

[0074] In the method described in this invention, the method may further include: the sludge in the sedimentation zone is returned to the flocculation zone, and the return flow rate can be 3-11%, preferably 4-10%.

[0075] In the method described in this invention, the method may further include: in the coagulation reaction zone, mine water and coagulant are mixed and reacted.

[0076] In the method described in this invention, the coagulant may contain PAC.

[0077] In this invention, the PAC can be polymeric alumina and / or polymeric ferric sulfate.

[0078] In this invention, the weight-average molecular weight of the PAC can be 2000-10000, preferably 2000-3000, the concentration of the PAC can be 10-20%, preferably 11-20%, and the dosage of the PAC is 50-100 mg / L, preferably 60-100 mg / L.

[0079] In the method described in this invention, the method may further include: in the flocculation zone, mine water and flocculant are mixed and reacted.

[0080] In the method described in this invention, the flocculant may contain PAM.

[0081] In this invention, the PAM may contain anionic polyacrylamide.

[0082] In this invention, the weight-average molecular weight of the PAM can be 2 million to 4 million, preferably 2.5 million to 3.5 million, the concentration of the PAM can be 0.4-2% by weight, preferably 0.5-2% by weight, and the dosage of the PAM is 0.4-1 mg / L, preferably 0.5-1 mg / L.

[0083] In the method described in this invention, the method may further include: mixing and reacting the clarified liquid after treatment in the sedimentation tank 11 with the flocculant.

[0084] In the method described in this invention, the pore diameter of the filter membrane of the filter device 12 can be 0.001-0.02 μm, preferably 0.005-0.15 μm.

[0085] In the method described in this invention, the ultrafiltration accuracy of the ultrafiltration device 13 can be 0.001-0.02 μm, preferably 0.005-0.15 μm.

[0086] In the method described in this invention, the recovery rate of the ultrafiltration device 13 can be controlled at 95% or higher, preferably 95-98%.

[0087] In the method described in this invention, the recovery rate of the first reverse osmosis device 14 can be controlled at 60-80%, preferably 65-75%; the total dissolved solids (TDS) of the separated first product water can be 1-50 mg / L, preferably 5-20 mg / L; the total dissolved solids (TDS) of the separated concentrate can be 4000-7000 mg / L, preferably 4000-5000 mg / L.

[0088] In the method described in this invention, in step (2), the flow rate of the circulation can be 40-100 m / s, preferably 40-60 m / s.

[0089] In the method described in this invention, calcium carbonate can adhere to the surface of quartz crystals in the particle reactor 22, and calcium carbonate particles can be discharged when the particle diameter is 1-5 mm.

[0090] In the method described in this invention, the method may further include: in step (2), adding a scale inhibitor to the concentrated water obtained after treatment by the particle reactor 22, and passing the concentrated water with the scale inhibitor into the second reverse osmosis device 23 for reverse osmosis treatment.

[0091] In the method described in this invention, the scale inhibitor may contain a monoatomic oxygen hydroxyl polymer and a dispersant.

[0092] In this invention, the concentration of the scale inhibitor can be 4-10 ppm, preferably 5-10 ppm.

[0093] In this invention, the weight-average molecular weight of the scale inhibitor can be 7000-15000, preferably 10000-13000.

[0094] In the method described in this invention, the dispersant is at least one of polyacrylic acid, polyphosphate, and polyvinylpyrrolidone.

[0095] In the method described in this invention, the recovery rate of the second reverse osmosis device 23 can be controlled at 70-90%, preferably 75-85%; the total dissolved solids (TDS) of the separated second product water can be 50-200 mg / L, preferably 50-100 mg / L; the total dissolved solids (TDS) of the separated concentrate can be 10000-50000 mg / L, preferably 35000-50000 mg / L.

[0096] In the method described in this invention, the ultrafiltration accuracy of the tubular ultrafiltration device 24 can be 0.001-0.02 μm, preferably 0.005-0.01 μm.

[0097] In the method described in this invention, in the sodium bed 25, the exchangeable ions on the ion exchange resin can undergo an exchange reaction with ions in the water to exchange calcium ions and magnesium ions from the water.

[0098] In the method described in this invention, the exchangeable ions can be sodium ions and hydrogen ions.

[0099] In the method described in this invention, the pH value of the sodium bed 25 can be controlled between 6 and 11, preferably between 7 and 9.

[0100] In the method described in this invention, the method may further include: in step (2), introducing a draw solution into the forward osmosis device 26.

[0101] In the method described in this invention, the extracting liquid may contain sodium chloride.

[0102] In this invention, the concentration of sodium chloride in the extracting solution can be 10,000-55,000 mg / L, preferably 10,000-50,000 mg / L.

[0103] In the method described in this invention, the recovery rate of the forward osmosis device 26 can be controlled at 60-80%, preferably 70-75%; the total dissolved solids (TDS) of the separated fresh water can be 200-1000 mg / L, preferably 200-300 mg / L; the total dissolved solids (TDS) of the separated concentrated water can be 90000-160000 mg / L, preferably 100000-150000 mg / L.

[0104] In the method described in this invention, the recovery rate of the third reverse osmosis unit 27 can be controlled at 70-90%, preferably 80-85%; the total dissolved solids (TDS) of the separated third product water can be 20-100 mg / L, preferably 20-50 mg / L.

[0105] In the method described in this invention, the cryo-crystallizer 311 can adopt a seed-freezing dual-cycle process to induce sodium carbonate to crystallize. During the cycle, the crystallization is accelerated. After the supercooled material comes into contact with the crystal particles in the crystallization chamber, the crystal particles are promoted to grow, resulting in high-purity sodium carbonate crystals.

[0106] In the method described in this invention, the cryo-crystallizer 311 can be a device employing a seed crystal freezing dual-cycle process, and the specific device can be found in the content disclosed in patent application CN206642403U.

[0107] In the method described in this invention, the conditions for freeze crystallization may include: a temperature of -20 to 30°C, preferably -20 to 25°C; and a pressure of 0.1 to 0.5 MPa, preferably 0.2 to 0.3 MPa. In this document, the pressure is gauge pressure.

[0108] In the method described in this invention, the rotational speed of the first centrifuge 312 can be 1000-7000 rpm, preferably 2000-3500 rpm.

[0109] In the method described in this invention, the temperature of the first dryer 313 can be 100-200℃, preferably 150-200℃.

[0110] In the method described in this invention, the sodium carbonate can be of dry quality that meets the Class II superior grade standard of "Industrial Sodium Carbonate" (GB210.1-2004).

[0111] In the method described in this invention, the conditions for evaporation and crystallization may include: a temperature of 100-200℃, preferably 100-120℃; and a pressure of 0.1-0.5MPa, preferably 0.1-0.2MPa.

[0112] In the method described in this invention, the rotational speed of the second centrifuge 322 can be 1000-7000 rpm, preferably 2000-3000 rpm.

[0113] In the method described in this invention, the temperature of the second dryer 323 can be 100-200°C, preferably 150-200°C.

[0114] In the method described in this invention, the quality of the sodium chloride can meet the first-grade standard of refined industrial dry salt in "Industrial Salt" (GB / T5462-2015).

[0115] In the method described in this invention, the temperature of the third dryer 333 can be 100-200℃, preferably 150-200℃.

[0116] In the method described in this invention, the temperature of the mother liquor drying device 33 can be 100-200℃, preferably 150-200℃.

[0117] In the method described in this invention, the mine water is high-mineralization mine water, and the mine water contains Ca. 2+ Mg 2 + Cl - SO4 2- CO3 2- HCO3 - The total inorganic salt content of the mine water can be above 1000 mg / L, preferably 1000-6000 mg / L, and Ca... 2+ The concentration is above 100 mg / L, preferably 100-1000 mg / L, Mg 2+ The concentration is above 100 mg / L, preferably 100-1000 mg / L.

[0118] In some embodiments, the method for recovering sodium carbonate and sodium chloride from mine water, carried out in the system described above, includes the following steps:

[0119] (1) Mine water with a total inorganic salt content of more than 1000 mg / L is introduced into sedimentation tank 11 to remove suspended solids and silt. The upward flow velocity of sedimentation tank 11 is 4-12 m / h and the sludge return flow rate is 3-11%. The treated water is then sequentially introduced into a filter device 12 with a filter membrane pore diameter of 0.001-0.02 μm, an ultrafiltration device 13 with an ultrafiltration accuracy of 0.001-0.02 μm, and a first reverse osmosis device 14 with a recovery rate controlled at more than 60-80%. The first product water obtained by separation is recovered.

[0120] (2) The concentrated water obtained from the first reverse osmosis unit 14 is fed into the concentrated water separation tank 21, and then sequentially enters the particle reactor 22 and the second reverse osmosis unit 23 with a recovery rate controlled at 70-90% for treatment. A scale inhibitor is added to the concentrated water before it enters the second reverse osmosis unit 23. When the total dissolved solids (TDS) of the concentrated water obtained after treatment by the second reverse osmosis unit 23 is lower than 30,000-50,000 mg / L, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrated water separation tank 21 and circulated back into the particle reactor 22 and the second reverse osmosis unit 23 for treatment. The circulation flow rate is 40-100 m / s. When the total dissolved solids (TDS) of the concentrated water obtained after treatment by the second reverse osmosis unit 23 reaches 30... When the concentration is 000-50000 mg / L, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrated water separation tank 21 and then injected into the tubular ultrafiltration unit 24 with an ultrafiltration accuracy of 0.001-0.02 μm for further treatment; the second product water obtained after treatment by the second reverse osmosis unit 23 is recovered; the concentrated water after treatment by the tubular ultrafiltration unit 24 is passed into the sodium bed 25 with a pH value controlled at 6-11 for softening treatment; sodium chloride solution is added to the forward osmosis unit 26, and the softened concentrated water is passed into the forward osmosis unit 26 with a recovery rate controlled at 60-80% for forward osmosis treatment; the fresh water obtained after forward osmosis treatment is passed into the third reverse osmosis unit 27 with a recovery rate controlled at 70-90% for reverse osmosis treatment, and the separated third product water is recovered;

[0121] (3) The concentrated water obtained after the forward osmosis treatment is passed into a freeze crystallizer 311 at a temperature of -20 to -30°C and a pressure of 0.1 to 0.5 MPa for freeze crystallization. The product obtained after freeze crystallization is passed into a first centrifuge 312 at a speed of 1000 to 7000 rpm for centrifugation. The solid obtained after separation by the first centrifuge 312 is passed into a first dryer 313 at a temperature of 100 to 200°C for drying, and the separated sodium carbonate is recovered. The first mother liquor obtained after separation by the first centrifuge 312 is passed into an evaporator crystallizer 321 at a temperature of 100 to 200°C and a pressure of 0.1 to 0.5 MPa for evaporation crystallization. The product obtained after the evaporation and crystallization process is centrifuged in a second centrifuge 322 with a rotation speed of 1000-7000 rpm. The solid obtained after separation in the second centrifuge 322 is dried in a second dryer 323 with a temperature of 100-200℃ to recover the separated sodium chloride. The second mother liquor obtained after separation in the second centrifuge 322 is dried in a third dryer 331 with a temperature of 100-200℃. The product obtained after processing in the third dryer 331 is dried in a mother liquor dryer 332 with a temperature of 100-200℃ to obtain mixed salts. The mixed salts are dissolved and then passed into the freeze crystallizer 321 for freeze crystallization.

[0122] In other embodiments, the method for recovering sodium carbonate and sodium chloride from mine water, carried out in the system described above, includes the following steps:

[0123] (1) Mine water with a total inorganic salt content of 1000-6000 mg / L is introduced into sedimentation tank 11 to remove suspended solids and silt. The upward flow velocity of sedimentation tank 11 is 5-10 m / h, and the sludge return flow rate is 4-10%. The treated water is then sequentially introduced into a filter device 12 with a filter membrane pore diameter of 0.005-0.015 μm, an ultrafiltration device 13 with an ultrafiltration accuracy of 0.005-0.015 μm, and a first reverse osmosis device 14 with a recovery rate controlled at 65-75%. The first product water obtained by separation is then recovered.

[0124] (2) The concentrated water obtained from the first reverse osmosis unit 14 is fed into the concentrated water separation tank 21, and then sequentially enters the particle reactor 22 and the second reverse osmosis unit 23 with a recovery rate controlled at 75-85% for treatment. A scale inhibitor is added to the concentrated water before it enters the second reverse osmosis unit 23. When the total dissolved solids (TDS) of the concentrated water obtained after treatment by the second reverse osmosis unit 23 is lower than 35,000-50,000 mg / L, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrated water separation tank 21 and circulated back into the particle reactor 22 and the second reverse osmosis unit 23 for treatment. The circulation flow rate is 40-60 m / s. When the total dissolved solids (TDS) of the concentrated water obtained after treatment by the second reverse osmosis unit 23 reaches 350 mg / L... When the concentration is 0.00-50000 mg / L, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrated water separation tank 21 and then injected into the tubular ultrafiltration unit 24 with an ultrafiltration accuracy of 0.005-0.15 μm for further treatment; the second product water obtained after treatment by the second reverse osmosis unit 23 is recovered; the concentrated water after treatment by the tubular ultrafiltration unit 24 is passed into the sodium bed 25 with a pH value controlled at 7-9 for softening treatment; sodium chloride solution is added to the forward osmosis unit 26, and the softened concentrated water is passed into the forward osmosis unit 26 with a recovery rate controlled at 70-75% for forward osmosis treatment; the fresh water obtained after forward osmosis treatment is passed into the third reverse osmosis unit 27 with a recovery rate controlled at 80-85% for reverse osmosis treatment, and the separated third product water is recovered;

[0125] (3) The concentrated water obtained after the forward osmosis treatment is passed into a freeze crystallizer 311 at a temperature of -20 to -25℃ and a pressure of 0.2 to 0.3 MPa for freeze crystallization. The product obtained after freeze crystallization is passed into a first centrifuge 312 at a speed of 2000 to 3500 rpm for centrifugation. The solid obtained after separation by the first centrifuge 312 is passed into a first dryer 313 at a temperature of 150 to 200℃ for drying, and the separated sodium carbonate is recovered. The first mother liquor obtained after separation by the first centrifuge 312 is passed into an evaporator crystallizer 321 at a temperature of 100 to 120℃ and a pressure of 0.1 to 0.2 MPa for evaporation crystallization. The product obtained after the evaporation and crystallization process is centrifuged in a second centrifuge 322 at a speed of 2000-3000 rpm. The solid obtained after separation in the second centrifuge 322 is dried in a second dryer 323 at a temperature of 150-200℃ to recover the separated sodium chloride. The second mother liquor obtained after separation in the second centrifuge 322 is dried in a third dryer 331 at a temperature of 150-200℃. The product obtained after processing in the third dryer 331 is dried in a mother liquor dryer 332 at a temperature of 150-200℃ to obtain mixed salts. The mixed salts are dissolved and then passed into the freeze crystallizer 321 for freeze crystallization.

[0126] The following examples further illustrate the system and method for recovering sodium carbonate and sodium chloride from mine water according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0127] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0128] The following examples illustrate the process of recovering sodium carbonate and sodium chloride from mine water according to... Figure 1The system implementation shown specifically includes: a pretreatment unit 1, a concentration and softening unit 2, and an evaporation and crystallization unit 3. The pretreatment unit 1 is used to pretreat the mine water to remove fine suspended solids and colloids, thereby obtaining pretreated mine water. The concentration and softening unit 2 is used to concentrate and soften the pretreated mine water in multiple stages. The evaporation and crystallization unit 3 is used to evaporate, dry, and crystallize the water after it has been treated by the concentration and softening unit 2. The pretreatment unit 1 includes a sedimentation tank 11, a filtration device 12, an ultrafiltration device 13, and a first reverse osmosis device 14. The sedimentation tank 11 is used to remove suspended solids and silt from the mine water. The filtration device 12 is used to filter and separate the water obtained after treatment by the sedimentation tank 11. The ultrafiltration device 13 is used to perform ultrafiltration treatment on the filtrate obtained after filtration and separation. The first reverse osmosis device 14 is used to perform reverse osmosis treatment on the water obtained after ultrafiltration. The sedimentation tank 11 is equipped with a sludge discharge pump and a magnetic powder separator. The ultrafiltration device 13 includes a ceramic membrane with a pore size of 0.02 μm. The concentration and softening unit 2 includes a concentrate divider tank 21, a particle reactor 22, a second reverse osmosis unit 23, a tubular ultrafiltration unit 24, a sodium bed 25, a forward osmosis unit 26, and a third reverse osmosis unit 27. The concentrated water obtained from the first reverse osmosis unit 14 is fed into the concentrate divider tank 21, and then sequentially enters the particle reactor 22 and the second reverse osmosis unit 23 for processing. When the concentration of the concentrated water obtained after treatment by the second reverse osmosis unit 23 is lower than a predetermined value, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrate divider tank 21 and circulated back into the particle reactor 22 and the second reverse osmosis unit 23 for further processing. When the concentration of the concentrate obtained after treatment by the second reverse osmosis unit 23 reaches the predetermined value, the concentrate obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrate partition tank 21 and then injected into the tubular ultrafiltration unit 24 for treatment; the sodium bed 25 is used to soften the concentrate after treatment by the tubular ultrafiltration unit 24; the forward osmosis unit 26 is used to perform forward osmosis treatment on the softened concentrate; the third reverse osmosis unit 27 is used to perform reverse osmosis treatment on the desalinated water obtained after forward osmosis treatment; wherein, the particle reactor 22 includes quartz crystals, the second reverse osmosis unit 23 includes an antifouling membrane, and the sodium bed 25 includes ion exchange resin.The evaporation crystallization unit 3 includes a freeze crystallization device 31, an evaporation crystallization device 32, and a mother liquor drying device 33. The freeze crystallization device 31 is used to freeze crystallize, centrifuge, and dry the concentrated water obtained after the forward osmosis treatment. The evaporation crystallization device 32 is used to evaporate crystallize, centrifuge, and dry the first mother liquor after the freeze crystallization device 31. The mother liquor drying device 33 is used to dry the second mother liquor after the evaporation crystallization device 32, dissolve the separated impurities, and return them to the freeze crystallization device 31. The freeze crystallization device 31 includes a freeze crystallizer 311, a first centrifuge 312, and a first dryer 313. The freeze crystallizer 311 is used to freeze crystallize the concentrated water obtained after the forward osmosis treatment. The first centrifuge 312 is used to centrifuge the product obtained after the freeze crystallization treatment. The first dryer 313 is used to dry the solid obtained after the first centrifuge 312. The evaporation crystallization device 32 includes an evaporator crystallizer 321, a second centrifuge 322, and a second dryer 323. The evaporator crystallizer 321 is used to evaporate and crystallize the first mother liquor obtained after treatment by the freeze crystallization device 31. The second centrifuge 322 is used to centrifuge the product obtained after the evaporation crystallization treatment. The second dryer 323 is used to dry the solid obtained after treatment by the second centrifuge 322. The mother liquor drying device 33 includes a third dryer 331 and a mother liquor dryer 332. The third dryer 331 is used to dry the second mother liquor obtained after treatment by the evaporation crystallization device 32. The mother liquor dryer 332 is used to dry the product obtained after treatment by the third dryer 331 to obtain mixed salts. The mixed salts are dissolved and then passed into the freeze crystallizer 311 for freeze crystallization. The freeze crystallizer 311 employs a seed crystal freezing dual-cycle process.

[0129] Example 1

[0130] (1) Mine water with a total inorganic salt content of 3000 mg / L was introduced into sedimentation tank 11. The upward flow velocity of sedimentation tank 11 was 7 m / h, and the sludge return flow rate was 7%. In the coagulation reaction zone, 10% PAC (provided by Shandong Xinhai Purification Technology Co., Ltd., brand name polyaluminum chloride 01) was added at a dosage of 100 mg / L. The main component of PAC is polyalumina. In the flocculation zone, 1% PAM (provided by Fuhong Environmental Chemical Co., Ltd., brand name polyacrylamide 01) was added at a dosage of 1%. The concentration is 0.7 mg / L. The main component of PAM is anionic polyacrylamide. Suspended solids and silt are removed in sedimentation tank 11. After the treated water is added with PAM at a concentration of 1% by weight, it is sequentially passed through a filter device 12 with a pore diameter of 0.01 μm, an ultrafiltration device 13 with an ultrafiltration accuracy of 0.01 μm (provided by Asahi Kasei Corporation, brand name UNA-620A), and a first reverse osmosis device 14 (provided by DuPont Corporation, brand name CR100) with a recovery rate controlled at 70%. The first product water obtained by separation is recovered.

[0131] (2) The concentrated water obtained from the first reverse osmosis unit 14 is fed into the concentrated water separation tank 21, and then sequentially fed into the particle reactor 22 (provided by Guoneng Langxinming Company, brand name LXMWL01) and the second reverse osmosis unit 23 (provided by DuPont Company, brand name XC70) with a recovery rate controlled at 80% for treatment. Before entering the second reverse osmosis unit 23, a scale inhibitor with a concentration of 5 ppm (provided by Shibo Hengye Company, brand name SPE0109) is added to the concentrated water. When the total dissolved solids (TDS) of the concentrated water obtained after treatment by the second reverse osmosis unit 23 is less than 40,000 mg / L, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrated water separation tank 21 and circulated back into the particle reactor 22 and the second reverse osmosis unit 23 for treatment, with a circulation flow rate of 50 m / s. When the total dissolved solids (TDS) of the concentrated water obtained after treatment by the second reverse osmosis unit 23 reaches 40,000 mg / L, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrated water separation tank 21 and circulated back into the particle reactor 22 and the second reverse osmosis unit 23 for treatment. The concentrate obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrate separation tank 21 and then injected into the tubular ultrafiltration unit 24 with an ultrafiltration precision of 0.01 μm for further treatment. The second permeate obtained after treatment by the second reverse osmosis unit 23 is recovered. The concentrate after treatment by the tubular ultrafiltration unit 24 is passed into the sodium bed 25 with the pH value controlled at 8 for softening treatment. A sodium chloride solution of 30000 mg / L is added to the forward osmosis unit 26, and the softened concentrate is passed into the forward osmosis unit 26 (supplied by FTS, brand name HBCR) with a recovery rate controlled at 75% for forward osmosis treatment. The desalinated water obtained after forward osmosis treatment is passed into the third reverse osmosis unit 27 (supplied by DuPont, brand name BW30-440) with a recovery rate controlled at 85% for reverse osmosis treatment, and the separated third permeate is recovered. The total dissolved solids (TDS), calcium ion concentration, and magnesium ion concentration of the concentrate obtained after forward osmosis treatment are recorded in Table 1.

[0132] (3) The concentrated water obtained after forward osmosis is passed into a freeze crystallizer 311 (provided by Shenzhen Ruixue Company, brand name RX500B) at a temperature of -25℃ and a pressure of 0.2MPa for freeze crystallization. The product obtained after freeze crystallization is passed into a first centrifuge 312 at a speed of 3000rpm for centrifugation. The solid obtained after separation by the first centrifuge 312 is passed into a first dryer 313 at a temperature of 180℃ for drying. The separated sodium carbonate is recovered. The purity of sodium carbonate is recorded in Table 2. The first mother liquor obtained after separation by the first centrifuge 312 is passed into an evaporator crystallizer 321 at a temperature of 110℃ and a pressure of 0.2MPa for evaporation and crystallization. The product obtained after evaporation and crystallization is passed into a second centrifuge 322 at a speed of 2500rpm for centrifugation. The solid obtained after separation by the second centrifuge 322 is passed into a second dryer 323 at a temperature of 180℃ for drying. The sodium chloride obtained after separation is recovered. The purity of sodium chloride is recorded in Table 2.

[0133] The second mother liquor obtained after separation by the second centrifuge 322 is passed into the third dryer 331 at a temperature of 180°C for drying. The product obtained after treatment by the third dryer 331 is passed into the mother liquor dryer 332 at a temperature of 180°C for mother liquor drying to obtain mixed salt. After the mixed salt is dissolved, it is passed into the freeze crystallizer 321 for freeze crystallization.

[0134] Example 2

[0135] (1) Mine water with a total inorganic salt content of 1000 mg / L was introduced into sedimentation tank 11. The upward flow velocity of sedimentation tank 11 was 5 m / h, and the sludge return flow rate was 4%. In the coagulation reaction zone, PAC (provided by Gongyi Fuda Water Purification Materials Co., Ltd., brand name GYFD002) with a concentration of 11% by weight was added at a dosage of 80 mg / L. The main component of PAC is polyalumina. In the flocculation zone, PAM (provided by Wuxi Lanbo Chemical Co., Ltd., brand name aliba16) with a concentration of 0.5% by weight was added. -1825), with a dosage of 1 mg / L, wherein the main component of PAM is anionic polyacrylamide. Suspended solids and silt are removed in sedimentation tank 11. The treated water is then sequentially passed through a filter device 12 with a pore diameter of 0.005 μm, an ultrafiltration device 13 with an ultrafiltration accuracy of 0.005 μm (provided by DuPont, brand name SFP-2880), and a first reverse osmosis device 14 (provided by Toray Industries, brand name TML20D-400) with a recovery rate controlled at 65%. The first product water obtained from the separation is recovered.

[0136] (2) The concentrated water obtained from the first reverse osmosis unit 14 is fed into the concentrated water separation tank 21, and then sequentially fed into the particle reactor 22 (provided by Guoneng Langxinming Company, brand name LXMWL002) and the second reverse osmosis unit 23 (provided by Toray Industries, brand name TML20D-400) with a recovery rate controlled at 75% for treatment. Before entering the second reverse osmosis unit 23, a scale inhibitor with a concentration of 5 ppm (provided by Shandong Puniao Water Treatment Technology Co., Ltd., brand name PO-100) is added to the concentrated water. When the total dissolved solids (TDS) of the concentrated water obtained after treatment by the second reverse osmosis unit 23 is less than 35000 mg / L, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrated water separation tank 21 and circulated back into the particle reactor 22 and the second reverse osmosis unit 23 for treatment, with a circulation flow rate of 40 m / s. When the total dissolved solids (TDS) of the concentrated water obtained after treatment by the second reverse osmosis unit 23 reaches 35000 mg / L... The concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrated water separation tank 21 and then injected into the tubular ultrafiltration unit 24 with an ultrafiltration accuracy of 0.005 μm for further treatment. The second permeate obtained after treatment by the second reverse osmosis unit 23 is recycled. The concentrated water after treatment by the tubular ultrafiltration unit 24 is passed into the sodium bed 25 with a pH value controlled at 7 for softening treatment. A sodium chloride solution of 10000 mg / L is added to the forward osmosis unit 26, and the softened concentrated water is passed into the forward osmosis unit 26 (provided by FTS Corporation, brand name HBCR) with a recovery rate controlled at 70% for forward osmosis treatment. The desalinated water obtained after forward osmosis treatment is passed into the third reverse osmosis unit 27 (provided by Toray Industries Corporation, brand name TM720D-440) with a recovery rate controlled at 80% for reverse osmosis treatment. The separated third permeate is recycled. The total dissolved solids (TDS), calcium ion concentration, and magnesium ion concentration of the concentrated water obtained after forward osmosis treatment are recorded in Table 1.

[0137] (3) The concentrated water obtained after forward osmosis treatment is passed into a freeze crystallizer 311 (provided by Wuxi Guanya Company, brand name GY03) at a temperature of -20℃ and a pressure of 0.3MPa for freeze crystallization. The product obtained after freeze crystallization is passed into a first centrifuge 312 at a speed of 2000rpm for centrifugation. The solid obtained after separation by the first centrifuge 312 is passed into a first dryer 313 at a temperature of 150℃ for drying. The separated sodium carbonate is recovered. The purity of sodium carbonate is recorded in Table 2. The first mother liquor obtained after separation by the first centrifuge 312 is passed into an evaporator crystallizer 321 at a temperature of 100℃ and a pressure of 0.1MPa. Evaporation crystallization is performed. The product obtained after evaporation crystallization is centrifuged in a second centrifuge 322 at a speed of 2000 rpm. The solid obtained after separation in the second centrifuge 322 is dried in a second dryer 323 at a temperature of 150°C. The sodium chloride obtained after separation is recovered. The purity of sodium chloride is recorded in Table 2. The second mother liquor obtained after separation in the second centrifuge 322 is dried in a third dryer 331 at a temperature of 150°C. The product obtained after treatment in the third dryer 331 is dried in a mother liquor dryer 332 at a temperature of 150°C to obtain mixed salts. The mixed salts are dissolved and then passed into a freeze crystallizer 321 for freeze crystallization.

[0138] Example 3

[0139] (1) Mine water with a total inorganic salt content of 6000 mg / L was introduced into sedimentation tank 11. The upward flow velocity of sedimentation tank 11 was 10 m / h, and the sludge return flow rate was 10%. In the coagulation reaction zone, PAC (provided by Lianyungang Yibang Machinery Co., Ltd., brand name LYGYB003) with a concentration of 20% by weight was added at a dosage of 60 mg / L. The main component of PAC is polyferric sulfate. In the flocculation zone, PAM (provided by Wuxi Lanbo Chemical Co., Ltd., brand name aliba16) with a concentration of 2% by weight was added. -1825), with a dosage of 0.5 mg / L, wherein the main component of PAM is anionic polyacrylamide. Suspended solids and silt are removed in sedimentation tank 11. The treated water is then sequentially passed through a filter device 12 with a pore diameter of 0.02 μm, an ultrafiltration device 13 with an ultrafiltration accuracy of 0.02 μm (provided by Asahi Kasei Corporation, brand name UNA-620AB), and a first reverse osmosis device 14 (provided by DuPont Corporation, brand name BW-FR400) with a recovery rate controlled at 75%. The first product water obtained from the separation is recovered.

[0140] (2) The concentrated water obtained from the first reverse osmosis unit 14 is fed into the concentrated water separation tank 21, and then sequentially into the particle reactor 22 (provided by Guoneng Langxinming Company, brand name LXMWL01) and the second reverse osmosis unit 23 (provided by DuPont Company, brand name XC80) with a recovery rate controlled at 85% for treatment. Before entering the second reverse osmosis unit 23, a scale inhibitor with a concentration of 10 ppm (provided by Shandong Shounuo Environmental Protection Technology Co., Ltd., brand name PSW0203) is added to the concentrated water. When the total dissolved solids (TDS) of the concentrated water obtained after treatment by the second reverse osmosis unit 23 is less than 50,000 mg / L, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrated water separation tank 21 and circulated back into the particle reactor 22 and the second reverse osmosis unit 23 for treatment, with a circulation flow rate of 60 m / s. When the total dissolved solids (TDS) of the concentrated water obtained after treatment by the second reverse osmosis unit 23 reaches 50,000 mg / L, the concentrated water obtained after treatment by the second reverse osmosis unit 23 is... The concentrate obtained after treatment by the second reverse osmosis unit 23 is returned to the concentrate separation tank 21 and then injected into the tubular ultrafiltration unit 24 with an ultrafiltration precision of 0.01 μm for further treatment. The second permeate obtained after treatment by the second reverse osmosis unit 23 is recovered. The concentrate after treatment by the tubular ultrafiltration unit 24 is passed into the sodium bed 25 with a pH value controlled at 9 for softening treatment. A sodium chloride solution of 50,000 mg / L is added to the forward osmosis unit 26, and the softened concentrate is passed into the forward osmosis unit 26 (supplied by FTS, brand name HBCR) with a recovery rate controlled at 75% for forward osmosis treatment. The desalinated water obtained after forward osmosis treatment is passed into the third reverse osmosis unit 27 (supplied by DuPont, brand name BW30-440) with a recovery rate controlled at 85% for reverse osmosis treatment. The separated third permeate is recovered. The total dissolved solids (TDS), calcium ion concentration, and magnesium ion concentration of the concentrate obtained after treatment by the concentration and softening unit 2 are recorded in Table 1.

[0141] (3) The concentrated water obtained after forward osmosis treatment is passed into a freeze crystallizer 311 (provided by Shenzhen Ruixue Company, brand name RX500B) at a temperature of -30℃ and a pressure of 0.3MPa for freeze crystallization. The product obtained after freeze crystallization is passed into a first centrifuge 312 at a speed of 3500rpm for centrifugation. The solid obtained after separation by the first centrifuge 312 is passed into a first dryer 313 at a temperature of 200℃ for drying. The separated sodium carbonate is recovered. The purity of sodium carbonate is recorded in Table 2. The first mother liquor obtained after separation by the first centrifuge 312 is passed into an evaporator crystallizer 321 at a temperature of 120℃ and a pressure of 0.2MPa. Evaporation crystallization is performed. The product obtained after evaporation crystallization is centrifuged in a second centrifuge 322 at a speed of 3000 rpm. The solid obtained after separation in the second centrifuge 322 is dried in a second dryer 323 at a temperature of 200°C. The sodium chloride obtained after separation is recovered. The purity of sodium chloride is recorded in Table 2. The second mother liquor obtained after separation in the second centrifuge 322 is dried in a third dryer 331 at a temperature of 200°C. The product obtained after treatment in the third dryer 331 is dried in a mother liquor dryer 332 at a temperature of 200°C to obtain mixed salts. The mixed salts are dissolved and then passed into a freeze crystallizer 321 for freeze crystallization.

[0142] Comparative Example 1

[0143] In the system used in this comparative example, the concentrate divider 21, the particle reactor 22, and the second reverse osmosis unit 23 are not installed after the first reverse osmosis unit 14, and the rest of the operation is the same as in Example 1.

[0144] The method of Example 1 is different in that the concentrated water obtained by the first reverse osmosis device 14 is not passed into the concentrated water separation tank 21, the particle reactor 22 and the second reverse osmosis device 23 for treatment, but is directly injected into the tubular ultrafiltration device 24 for treatment.

[0145] Comparative Example 2

[0146] In the system used in this comparative example, the forward osmosis device 26 is not installed after the sodium bed 25. The concentrated water treated by the sodium bed 25 is directly passed into the cryogenic crystallizer 311. The rest of the operation is the same as in Example 1.

[0147] The method is the same as in Example 1, except that the concentrated water after treatment by the sodium bed 25 is not passed into the forward osmosis device 26 for further treatment, but is directly passed into the cryogenic crystallizer 311 for further treatment.

[0148] Table 1

[0149]

[0150] Table 2

[0151] Example number Purity (%) of sodium carbonate Sodium chloride purity (%) Example 1 99.2 99.1 Example 2 98.8 98.5 Example 3 98.5 98.4 Comparative Example 1 97.2 96.3 Comparative Example 2 96.1 95.7

[0152] As can be seen from the results in Tables 1 and 2, the embodiments of the system and method for recovering sodium carbonate and sodium chloride in mine water according to the present invention can effectively reduce the concentration of calcium and magnesium ions in high-mineralization mine water, thereby softening the mine water, avoiding scaling during subsequent evaporation and crystallization, increasing the TDS of the concentrated water, reducing treatment costs, and obtaining sodium carbonate and sodium chloride with high purity.

[0153] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for recovering sodium carbonate and sodium chloride from mine water, characterized in that, The method is implemented in the following system, which includes: a pretreatment unit (1), a concentration and softening unit (2), and an evaporation and crystallization unit (3), wherein the pretreatment unit (1) is used to pretreat mine water to remove fine suspended solids and colloids to obtain pretreated mine water; the concentration and softening unit (2) is used to concentrate and soften the pretreated mine water in multiple stages; the evaporation and crystallization unit (3) is used to evaporate, dry, and crystallize the water after treatment by the concentration and softening unit (2); the pretreatment unit (1) includes a sedimentation tank (11), a filtration device (12), an ultrafiltration device (13), and a first reverse osmosis device (14), wherein the sedimentation tank (11) is used ...1) includes a sedimentation tank (11), a filtration device (12), an ultrafiltration device (13), and a first reverse osmosis device (14). Suspended solids and silt in mine water; the filtration device (12) is used to filter and separate the water obtained after treatment in the sedimentation tank (11); the ultrafiltration device (13) is used to perform ultrafiltration treatment on the filtrate obtained after filtration and separation; the first reverse osmosis device (14) is used to perform reverse osmosis treatment on the water obtained after ultrafiltration treatment; wherein, the sedimentation tank (11) is equipped with a sludge discharge pump and a magnetic powder separator, the ultrafiltration device (13) includes a ceramic membrane with a pore size of 0.02μm; the concentration and softening unit (2) includes a concentration water separation tank (21), a particle reactor (22), a second reverse osmosis device (23), a tubular ultrafiltration device (24), and a sodium bed. (25) A forward osmosis unit (26) and a third reverse osmosis unit (27), wherein the concentrated water obtained by the first reverse osmosis unit (14) is fed into the concentrated water separation tank (21), and then sequentially enters the particle reactor (22) and the second reverse osmosis unit (23) for processing. When the concentration of the concentrated water obtained after processing by the second reverse osmosis unit (23) is lower than a predetermined value, the concentrated water obtained after processing by the second reverse osmosis unit (23) is returned to the concentrated water separation tank (21) and circulated into the particle reactor (22) and the second reverse osmosis unit (23) for processing; when ... particle reactor (22) and the second reverse osmosis unit (23) for processing. When the concentration reaches the predetermined value, the concentrated water obtained after treatment by the second reverse osmosis device (23) is returned to the concentrated water partitioning tank (21) and then injected into the tubular ultrafiltration device (24) for further treatment; the sodium bed (25) is used to soften the concentrated water after treatment by the tubular ultrafiltration device (24); the forward osmosis device (26) is used to perform forward osmosis treatment on the softened concentrated water; the third reverse osmosis device (27) is used to perform reverse osmosis treatment on the fresh water obtained after forward osmosis treatment; wherein, the particle reactor (22) includes quartz crystals, the second reverse osmosis device (23) includes an antifouling membrane, and the sodium bed (25) includes ion exchange resin;The evaporation crystallization unit (3) includes: a freeze crystallization device (31), an evaporation crystallization device (32), and a mother liquor drying device (33). The freeze crystallization device (31) is used to freeze crystallize, centrifuge, and dry the concentrated water obtained after the forward osmosis treatment. The evaporation crystallization device (32) is used to evaporate crystallize, centrifuge, and dry the first mother liquor after the freeze crystallization device (31). The mother liquor drying device (33) is used to dry the second mother liquor after the evaporation crystallization device (32). The separated impurities are dissolved and returned to the freeze crystallization apparatus (31). The freeze crystallization apparatus (31) includes a freeze crystallizer (311), a first centrifuge (312), and a first dryer (313). The freeze crystallizer (311) is used to freeze crystallize the concentrated water obtained after the forward osmosis treatment. The first centrifuge (312) is used to centrifuge the product obtained after the freeze crystallization treatment. The first dryer (313) is used to dry the product obtained after the first centrifuge (312). The solid is dried; the evaporation crystallization device (32) includes an evaporation crystallizer (321), a second centrifuge (322), and a second dryer (323), wherein the evaporation crystallizer (321) is used to evaporate and crystallize the first mother liquor obtained after processing by the freeze crystallization device (31); the second centrifuge (322) is used to centrifuge the product obtained after the evaporation crystallization process; and the second dryer (323) is used to dry the solid obtained after processing by the second centrifuge (322). The mother liquor drying device (33) includes a third dryer (331) and a mother liquor dryer (332), wherein the third dryer (331) is used to dry the second mother liquor obtained after being processed by the evaporation crystallization device (32); the mother liquor dryer (332) is used to dry the product obtained after being processed by the third dryer (331) to obtain mixed salt; the mixed salt is dissolved and then passed into the freeze crystallizer (311) for freeze crystallization, wherein the freeze crystallizer (311) adopts a seed crystal freezing double circulation process; The method includes the following steps: (1) Mine water with a total inorganic salt content of 3000 mg / L is introduced into sedimentation tank (11). The upward flow velocity of sedimentation tank (11) is 7 m / h, and the sludge return flow rate is 7%. In the coagulation reaction zone, PAC with a concentration of 10% by weight is added at a dosage of 100 mg / L. The main component of PAC is polyalumina. In the flocculation zone, PAM with a concentration of 1% by weight is added at a dosage of 0.7 mg / L. The main component of PAM is anionic polyacrylamide. Suspended solids and silt are removed in sedimentation tank (11). After the treated water is added with PAM with a concentration of 1% by weight, it is sequentially introduced into a filter device (12) with a pore diameter of 0.01 μm, an ultrafiltration device (13) with an ultrafiltration accuracy of 0.01 μm, and a first reverse osmosis device (14) with a recovery rate controlled at 70%. The first product water obtained by separation is recovered. (2) The concentrated water obtained from the first reverse osmosis unit (14) is fed into the concentrated water separation tank (21), and then sequentially fed into the particle reactor (22) and the second reverse osmosis unit (23) with a recovery rate controlled at 80% for treatment. Before entering the second reverse osmosis unit (23), a scale inhibitor with a concentration of 5 ppm is added to the concentrated water. When the total dissolved solids of the concentrated water obtained after treatment by the second reverse osmosis unit (23) is less than 40,000 mg / L, the concentrated water obtained after treatment by the second reverse osmosis unit (23) is returned to the concentrated water separation tank (21) and circulated into the particle reactor (22) and the second reverse osmosis unit (23) for treatment. The circulation flow rate is 50 m / s. When the total dissolved solids of the concentrated water obtained after treatment by the second reverse osmosis unit (23) reaches 40,000 mg / L, the concentrated water is returned to the concentrated water separation tank (21) and circulated into the particle reactor (22) and the second reverse osmosis unit (23) for treatment. When the concentration is / L, the concentrated water obtained after treatment by the second reverse osmosis unit (23) is returned to the concentrated water separation tank (21) and then injected into the tubular ultrafiltration unit (24) with an ultrafiltration accuracy of 0.01μm for treatment; the second product water obtained after treatment by the second reverse osmosis unit (23) is recycled; the concentrated water after treatment by the tubular ultrafiltration unit (24) is passed into the sodium bed (25) with pH controlled at 8 for softening treatment; 30000mg / L sodium chloride solution is added to the forward osmosis unit (26), and the concentrated water after softening treatment is passed into the forward osmosis unit (26) with a recovery rate controlled at 75% for forward osmosis treatment, and the fresh water obtained after forward osmosis treatment is passed into the third reverse osmosis unit (27) with a recovery rate controlled at 85% for reverse osmosis treatment, and the separated third product water is recycled; (3) The concentrated water obtained after forward osmosis is passed into a freeze crystallizer (311) at a temperature of -25℃ and a pressure of 0.2MPa for freeze crystallization. The product obtained after freeze crystallization is passed into a first centrifuge (312) at a speed of 3000rpm for centrifugation. The solid obtained after separation by the first centrifuge (312) is passed into a first dryer (313) at a temperature of 180℃ for drying. The sodium carbonate obtained after separation is recovered. The first mother liquor obtained after separation by the first centrifuge (312) is passed into an evaporator crystallizer (321) at a temperature of 110℃ and a pressure of 0.2MPa for evaporation crystallization. The product obtained after processing is centrifuged in a second centrifuge (322) with a rotation speed of 2500 rpm. The solid obtained after separation by the second centrifuge (322) is dried in a second dryer (323) with a temperature of 180°C to recover the sodium chloride obtained after separation. The second mother liquor obtained after separation by the second centrifuge (322) is dried in a third dryer (331) with a temperature of 180°C. The product obtained after processing by the third dryer (331) is dried in a mother liquor dryer (332) with a temperature of 180°C to obtain mixed salt. The mixed salt is dissolved and then passed into a freeze crystallizer (311) for freeze crystallization.

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