Mine water treatment method

Abstract

The invention belongs to the field of water treatment, and provides a mine water treatment method which comprises the following steps: performing flocculent precipitation and ultrafiltration treatment on mine water to obtain ultrafiltration produced water; performing first concentration treatment on the ultrafiltration produced water to obtain first reverse osmosis produced water and first reverse osmosis concentrated water; the first reverse osmosis concentrated water is subjected to first nanofiltration separation to separate out sulfate radicals, and first-stage nanofiltration produced water, first-stage nanofiltration concentrated water and the like are obtained. The treatment method provided by the invention can replace the dosing and hardness removal link in the existing pretreatment, and can realize the recovery of calcium chloride in the mine water while maintaining the stable operation of the device.

Description

Technical Field

[0001] The present application belongs to the technical field of water treatment, and specifically, relates to a method for treating mine water. Background Art

[0002] According to water quality characteristics, mine water can be divided into five categories: clean mine water, mine water containing suspended matter, high-mineralization mine water, acidic mine water and mine water containing special pollutants. Among them, high-mineralization mine wastewater has complex water quality, large treatment volume and the greatest treatment difficulty. The main ions in mine water are SO 4 2- , Cl - , Ca 2+ , K + 、Na + and HCO 3- If directly discharged, it will lead to a fragile ecological environment, and cause problems such as soil erosion, salinization, and vegetation withering.

[0003] As for the treatment of mine water, the current mainstream process is still to treat mine water as sewage. In order to effectively alleviate the ecological and environmental problems caused by coal mining, it is necessary to further treat the mine water. How to efficiently utilize mine water resources has become a problem that needs to be solved urgently. Summary of the invention

[0004] In view of the above-mentioned problems, the purpose of this application is to provide a method for treating mine water. The method can realize resource treatment of mine water, has a simple process, and can achieve the purpose of reducing costs and increasing revenue.

[0005] To achieve the above objectives, the present application provides a method for treating mine water, comprising:

[0006] The mine water is subjected to flocculation precipitation and ultrafiltration treatment to obtain ultrafiltration product water containing sulfate, chloride ions, calcium ions, magnesium ions and sodium ions;

[0007] The ultrafiltration product water enters the first reverse osmosis device for first concentration treatment to obtain first reverse osmosis product water and first reverse osmosis concentrated water;

[0008] The first reverse osmosis concentrated water enters the primary nanofiltration device and is treated by the first nanofiltration to separate sulfate ions, thereby obtaining primary nanofiltration product water and primary nanofiltration concentrated water;

[0009] The primary nanofiltration concentrated water is mixed with dilution water, and the obtained dilution water enters the secondary nanofiltration device for second nanofiltration treatment to separate sulfate radicals, thereby obtaining secondary nanofiltration produced water and secondary nanofiltration concentrated water rich in sulfate;

[0010] The primary nanofiltration product water, the secondary nanofiltration product water and the fourth nanofiltration concentrated water are mixed, and the resulting mixed water enters the third nanofiltration device for a third nanofiltration treatment to separate calcium ions, thereby obtaining the third nanofiltration product water and the third nanofiltration concentrated water rich in chloride salt;

[0011] The third-stage nanofiltration produced water enters the fourth-stage nanofiltration device and is processed by the fourth nanofiltration to further separate calcium ions, thereby obtaining fourth-stage nanofiltration produced water and fourth-stage nanofiltration concentrated water;

[0012] The four-stage nanofiltration product water enters the second reverse osmosis device for second concentration treatment to obtain second reverse osmosis product water and second reverse osmosis concentrated water;

[0013] The second reverse osmosis concentrated water enters an evaporation crystallization device for evaporation crystallization to obtain evaporation condensed water and sodium chloride products.

[0014] The mine water treatment method provided by the present application does not use the step of adding drugs to remove hardness in pretreatment, but adopts a specific multi-stage nanofiltration method (first two-stage sulfate nanofiltration separation, then two-stage calcium ion separation) to achieve the recovery of chloride salts, especially calcium chloride, in the mine water while maintaining the stable operation of the device, which not only reduces the cost of adding drugs, but also effectively recovers the salt products. In addition, the treatment method of the present application can also coordinate the original resources of the mine to coordinate the disposal of the sulfate-rich wastewater generated in the treatment process.

[0015] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0017] Figure 1 It is a schematic diagram of a process flow of a mine water pretreatment process according to an embodiment of the present application;

[0018] Figure 2 It is a schematic flow chart of a mine water treatment process according to one embodiment of the present application.

[0019] Description of Reference Numerals

[0020] 1: first reverse osmosis device; 2: first nanofiltration device; 3: third nanofiltration device; 4: second nanofiltration device; 5: fourth nanofiltration device; 6: second reverse osmosis device; 7: evaporation crystallization device; 80: flocculation reaction tank; 90: ultrafiltration device; 100: plate and frame filter press device; 8: ultrafiltration water; 9: first reverse osmosis water; 10: first reverse osmosis concentrated water; 11: third nanofiltration concentrated water; 12: first nanofiltration concentrated water; 13: dilution water; 14: dilution water ; 15: Secondary nanofiltration water; 16: Secondary nanofiltration concentrate; 17: Fourth-stage nanofiltration concentrate; 18: Primary nanofiltration water; 19: Mixed water; 20: Third-stage nanofiltration water; 21: Fourth-stage nanofiltration water; 22: Second reverse osmosis water; 23: Second reverse osmosis concentrate; 24: Sodium chloride product; 25: Evaporation condensate; 26: Mine water; 27: Supernatant; 28: Sludge; 29: Filtrate; 30: Flocculation influent; 31: Ultrafiltration concentrate; 32: Mud cake. DETAILED DESCRIPTION

[0021] The following describes the implementation of the present application in detail. The implementation described below is exemplary and is only used to explain the present application, and cannot be understood as limiting the present application.

[0022] The "range" disclosed in the present application is defined in the form of a lower limit and / or an upper limit, and a given range is defined by selecting a lower limit and / or an upper limit. The range defined in this way can be inclusive or exclusive of end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form an unclearly recorded range, and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, each separately disclosed point or single value itself can be combined with any other point or single value as a lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0023] It should be noted that, in the present application, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0024] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0025] The traditional treatment process for mine water mainly includes pretreatment, deep separation treatment and evaporation crystallization. Among them, pretreatment usually includes a softening process to reduce the concentration of calcium and magnesium ions in water. In order to prevent scaling of the rear-end membrane elements and evaporation system, during the pretreatment process, the dosing method is often used to remove calcium and magnesium ions. The softening agent is, for example, sodium carbonate, sodium bicarbonate, and lime milk, which leads to relatively high costs and also produces a large amount of additional sludge, which is neither economical nor environmentally friendly. In addition, compared with ordinary saline wastewater containing magnesium ions and calcium ions (such as desulfurization wastewater), the calcium ion concentration in mine water is much higher than the magnesium ion concentration, and the pollution is higher. Compared with magnesium chloride, the calcium chloride phase in mine water is easier to pass through the nanofiltration membrane, and it is not easy to realize the recovery of calcium chloride, nor is it easy to obtain high-purity sodium chloride salt. When the retention rate of calcium chloride is increased by adjusting the pore size of the separation membrane, the retention rate of sodium chloride is often increased, which leads to a higher difficulty in resource utilization of mine water.

[0026] Accordingly, the present application provides a method for treating mine water, the method comprising:

[0027] The mine water was treated by flocculation, precipitation and ultrafiltration to obtain sulfate (SO 4 2- ), chloride ion (Cl - ), calcium ions (Ca 2+ ), magnesium ion (Mg 2+ ) and sodium ions (Na + ) of ultrafiltration water;

[0028] The ultrafiltration product water enters the first reverse osmosis device for first concentration treatment to obtain first reverse osmosis product water and first reverse osmosis concentrated water;

[0029] The first reverse osmosis concentrated water enters the primary nanofiltration device and is treated by the first nanofiltration to separate sulfate radicals, thereby obtaining primary nanofiltration product water and primary nanofiltration concentrated water;

[0030] The primary nanofiltration concentrated water is mixed with dilution water, and the obtained dilution water enters the secondary nanofiltration device to separate sulfate radicals, thereby obtaining secondary nanofiltration produced water and sulfate-rich secondary nanofiltration concentrated water;

[0031] The primary nanofiltration product water, the secondary nanofiltration product water and the fourth nanofiltration concentrated water are mixed, and the resulting mixed water enters a third-stage nanofiltration device to separate calcium ions, thereby obtaining third-stage nanofiltration product water and third-stage nanofiltration concentrated water rich in chloride salt;

[0032] The third-stage nanofiltration produced water enters the fourth-stage nanofiltration device and is processed by the fourth nanofiltration to further separate calcium ions, thereby obtaining fourth-stage nanofiltration produced water and fourth-stage nanofiltration concentrated water;

[0033] The four-stage nanofiltration product water enters the second reverse osmosis device for second concentration treatment to obtain second reverse osmosis product water and second reverse osmosis concentrated water;

[0034] The second reverse osmosis concentrated water enters an evaporation crystallization device for evaporation crystallization to obtain evaporation condensed water and sodium chloride products.

[0035] The treatment method provided by the present application first uses primary and secondary nanofiltration to filter out sulfate ions, so as to avoid calcium sulfate precipitation and thus contamination of the membrane during the salt separation and concentration process; and then uses tertiary and quaternary nanofiltration with a high retention rate for calcium ions to remove calcium ions, which will reduce the scaling risk of the entire process and avoid membrane damage. The treatment method of the present application not only replaces the dosing and softening link in the pretreatment, but also can realize the recovery of calcium chloride and sodium chloride.

[0036] In some embodiments, the TDS of the mine water is 14-15 g / L, the calcium ion concentration is 1500-1600 mg / L, the magnesium ion concentration is 100-200 mg / L, the sulfate concentration is 300-400 mg / L, the chloride ion concentration is 8000-9000 mg / L, the sodium ion concentration is 3000-4000 mg / L, and the fluoride ion concentration is 0.2-1.5 mg / L.

[0037] In addition, the total hardness of the mine water in terms of calcium carbonate may be 4000-5000 mg / L, the soluble silicon content in terms of silicon dioxide may be 2-20 mg / L, and the electrical conductivity may be 15-21 mS / cm.

[0038] In some embodiments, fluoride ions and suspended solids in mine water are removed by flocculation sedimentation and ultrafiltration.

[0039] As some specific implementation methods, the process of flocculation precipitation and ultrafiltration treatment includes:

[0040] In the flocculation reaction tank, a flocculant (such as one or more of polyaluminium chloride, polyferric chloride and polyacrylamide) is added to the mine water to carry out flocculation and precipitation to obtain a supernatant and sludge;

[0041] The supernatant is sent to an ultrafiltration device for ultrafiltration treatment to obtain ultrafiltration product water and ultrafiltration concentrated water;

[0042] The sludge is sent to a plate and frame filter press for filtration to obtain mud cake and filtrate;

[0043] Transport the mud cake to the tailings area for disposal;

[0044] The ultrafiltration concentrated water and filtrate are returned to the flocculation reaction tank.

[0045] Generally, the water quality of the ultrafiltration water meets SDI<3 before it can enter the back-end reverse osmosis membrane system. In particular, the pretreatment process of the present application does not include softening of mine water.

[0046] According to the method of the present application, the ultrafiltration water enters the first reverse osmosis device for the first concentration treatment. On the one hand, the processing capacity of the rear-end nanofiltration device is reduced to reduce related investment and operating costs. On the other hand, the fresh water produced by the reverse osmosis treatment can be used by the secondary nanofiltration device to reduce costs.

[0047] From the perspective of optimizing the quality of produced water, it is preferred that the first reverse osmosis device is a seawater-grade reverse osmosis device, that is, a seawater-desalination-grade reverse osmosis membrane element is used. Accordingly, the first reverse osmosis produced water and the first reverse osmosis concentrated water obtained by performing the first concentration treatment by the seawater-grade reverse osmosis device are seawater-grade reverse osmosis produced water and seawater-grade reverse osmosis concentrated water, respectively.

[0048] In some embodiments, the inlet water temperature in the first concentration treatment is 20-25° C., and the inlet water pH is 6-6.8.

[0049] In the present application, the pH of the water can be adjusted by hydrochloric acid, for example, 32 wt % hydrochloric acid.

[0050] Preferably, the operating pressure of the first concentration treatment is 50-70 bar, and the volume ratio of the first reverse osmosis concentrated water to the first reverse osmosis produced water is 1: (2-3), for example, 1: 3. Controlling the operating conditions within the range is beneficial to the operational stability of the reverse osmosis membrane device and can provide sufficient fresh water for the secondary nanofiltration device.

[0051] In the present application, the first-stage nanofiltration device and the second-stage nanofiltration device respectively use sulfate separation nanofiltration membranes. "Sulfate separation nanofiltration membrane" means that the retention effect of sulfate is much higher than that of other ions (such as Ca2+) in mine water under the same working conditions. 2+ , Cl - etc.) retention rate of nanofiltration membrane.

[0052] In some embodiments, the sulfate separation nanofiltration membrane meets the following conditions: under the operating conditions of 25°C, 2.5 MPa and 70% recovery rate, the calcium sulfate retention rate in the first aqueous solution is ≥99%, the sodium chloride retention rate is <15%, and the calcium chloride retention rate is ≤50%; wherein the first aqueous solution is composed of water and calcium chloride (CaCl 2 ), calcium sulfate (CaSO 4 ) and sodium chloride (NaCl), the concentration of each component is: CaCl 2 14000~15120mg / L (e.g. 14040mg / L, 15117mg / L), CaSO 4 1150~2220mg / L (e.g. 1157mg / L, 2219mg / L), NaCL 38900~40200mg / L (e.g. 38971mg / L, 40172mg / L).

[0053] As some examples, the sulfate separation nanofiltration membrane is a polypiperazine composite membrane, such as but not limited to, nanofiltration membranes in the NF90, NF245, NF270 and other series products from Dow.

[0054] According to the method of the present application, by subjecting the first reverse osmosis concentrate to a first nanofiltration treatment, the first nanofiltration product water containing chloride and a small amount of sulfate, and the first nanofiltration concentrate containing chloride and rich in sulfate can be obtained.

[0055] In some embodiments, the primary nanofiltration device is a rolled nanofiltration membrane device, that is, a nanofiltration separation device including a rolled nanofiltration membrane element.

[0056] In some embodiments, in the first nanofiltration treatment, the operating pressure of the first-stage nanofiltration device is 10-20 bar, the membrane flux is 15-20 LMH, and the recovery rate is 60%-70%.

[0057] In this application, "recovery rate" refers to the percentage of produced water volume to influent water volume, and the calculation formula = produced water volume ÷ influent water volume × 100%.

[0058] Preferably, the inlet water temperature of the primary nanofiltration treatment is 15-20° C. A lower temperature can increase the retention rate of the nanofiltration membrane for sulfate.

[0059] Preferably, the first nanofiltration treatment has a sulfate rejection rate of 98% to 99.5% in the first reverse osmosis concentrated water, a chloride rejection rate of 0% to 25%, and a calcium rejection rate of 30% to 70%.

[0060] In this application, the chloride ion retention rate is calculated based on chloride.

[0061] As some examples, in the primary nanofiltration product water and the primary nanofiltration concentrated water, the concentration ratio of chloride is 1:(1.1-2), and the concentration ratio of sulfate is (1-5):1000.

[0062] According to the method of the present application, by performing a second nanofiltration treatment on the primary nanofiltration concentrate, chloride can be separated as much as possible to the water production side, thereby obtaining a secondary nanofiltration concentrate containing chloride and sodium sulfate salt and a secondary nanofiltration produced water containing a small amount of sulfate and chloride, thereby achieving effective separation of sulfate (calcium sulfate and a small amount of magnesium sulfate) and chloride (sodium chloride, calcium chloride and a small amount of magnesium chloride). The secondary nanofiltration concentrate can be directly sent to the tailings pond and the mineral processing area for use.

[0063] In addition, in the second nanofiltration treatment, the primary nanofiltration concentrate is diluted with dilution water to avoid severe scaling, thereby reducing the possibility of subsequent membrane damage and stability impact due to excessive pressure required for concentration.

[0064] In some embodiments, in the second nanofiltration treatment, the operating pressure of the secondary nanofiltration device is 6 to 15 bar, the membrane flux is 12 to 20 LMH, and the recovery rate is 50% to 75%.

[0065] From the perspective of reducing the risk of calcium sulfate precipitation, the inlet water temperature of the secondary nanofiltration device is preferably above 25°C. 4 Higher concentrations and higher temperatures can increase CaSO 4 More preferably, the water inlet temperature of the secondary nanofiltration device is 25-30°C, for example 28°C.

[0066] According to the method of the present application, the dilution water may be various clean waters such as tap water and distilled water, or may come from produced water with relatively low salt concentration during the method of the present application.

[0067] In some specific embodiments, in the second nanofiltration treatment, a mixed water from one or more of the first reverse osmosis produced water, the second reverse osmosis produced water and the evaporation condensation water is used as the dilution water. This type of produced water has a low salt content, which can not only recycle the process produced water, but also improve the recovery rate of the salt product.

[0068] Preferably, the volume ratio of the dilution water to the primary nanofiltration concentrated water is (1-4):1, such as 2:1, 3:1, 4:1, etc. Thus, while reducing the scaling risk of the secondary nanofiltration device, the water recovery rate and chloride ion permeability of the secondary nanofiltration are improved, the chloride concentration in the secondary nanofiltration concentrated water is reduced, and its impact on the tailings pond and the mineral processing area is reduced (a high chloride ion concentration will affect the mineral processing efficiency).

[0069] As some examples, in the secondary nanofiltration product water and the secondary nanofiltration concentrate, the concentration ratio of chloride is (0.8-1):1, and the concentration ratio of sulfate is (1-5):1000.

[0070] In some embodiments, the secondary nanofiltration device is a disc-tube nanofiltration membrane device (DTNF), that is, it includes a disc-tube (DT) membrane assembly. The water quality of the mine water fluctuates greatly, and the sulfate concentration in the secondary nanofiltration device is much higher than that of other nanofiltration devices in the system, which leads to the easy generation of CaSO during the second nanofiltration treatment process. 4 Scaling: Using DT structure membrane components can improve the device's anti-fluctuation and anti-pollution capabilities.

[0071] Depending on the water quality, the influent water (i.e., dilution water) of the secondary nanofiltration device may be added with a calcium sulfate scale inhibitor according to the situation. Specific examples of the calcium sulfate scale inhibitor include, but are not limited to, 1500, Titan ASD 200SC, etc.

[0072] As some examples, the dosage of the calcium sulfate antiscalant is 0-5 mg relative to 1 L of dilution water.

[0073] Preferably, the second nanofiltration treatment has a sulfate rejection rate of 98% to 99.5% in the diluted water, a chloride rejection rate of -10% to 30%, and a calcium rejection rate of 30% to 70%.

[0074] In the present application, the three-stage nanofiltration device and the four-stage nanofiltration device each independently include a calcium ion separation nanofiltration membrane. The calcium ion separation nanofiltration membrane refers to a nanofiltration membrane with a high calcium ion separation rejection rate and a relatively low sodium ion rejection rate under the same working conditions. The nanofiltration membrane can achieve Ca 2+ with Na + effective separation.

[0075] In the present application, compared with the sulfate separation nanofiltration membrane used in the primary nanofiltration device and the secondary nanofiltration device, the calcium ion separation nanofiltration membrane has a higher retention efficiency for calcium chloride. Compared with the use of only sulfate separation nanofiltration membrane for salt separation, the calcium ion separation nanofiltration membrane can achieve effective separation of sodium chloride and calcium chloride, which can significantly reduce the number of nanofiltration stages and simplify the process flow.

[0076] In some embodiments, the calcium ion separation nanofiltration membrane satisfies the following conditions: under the operating conditions of 25°C, 1.5 MPa and 75% recovery rate, the sodium chloride rejection rate in the second aqueous solution is less than 10%, and the calcium chloride rejection rate is ≥ 80%, wherein the second aqueous solution is composed of water and calcium chloride (CaCl 2 ) and sodium chloride (NaCl), the concentration of each component is: CaCl 2 8850~8880mg / L (e.g. 8852mg / L, 8880mg / L), NaCL 22320~33600mg / L (e.g. 22320mg / L, 33577mg / L).

[0077] As some examples, the calcium ion separation nanofiltration membrane is an aromatic polyamide membrane, such as but not limited to the nanofiltration membranes of Hydron's ESNA1-K1, ESNA1-LF, ESNA1-LF2, ESNA1-LF-LD, ESNA1-LF2-LD and other series of products.

[0078] According to the method of the present application, the sulfate concentration in the primary nanofiltration water, the secondary nanofiltration water and the quaternary nanofiltration concentrated water is very low, and its main component is chloride. The primary nanofiltration water, the secondary nanofiltration water and the quaternary nanofiltration concentrated water are used as the inlet water of the three-stage nanofiltration device, which can improve the recovery rate of chloride on the one hand, and is conducive to obtaining sodium chloride and calcium chloride respectively on the other hand.

[0079] In some embodiments, the third-stage nanofiltration device and the fourth-stage nanofiltration device are respectively rolled nanofiltration membrane devices.

[0080] In some embodiments, in the third nanofiltration treatment, the operating pressure of the three-stage nanofiltration device is 15-20 bar, the membrane flux is 18-22 LMH, and the recovery rate is 80%-90%.

[0081] Preferably, the third nanofiltration treatment has a calcium ion retention rate of 70% to 90% and a sodium ion retention rate of -2% to 20% in the mixed water.

[0082] As some examples, in the tertiary nanofiltration product water and the tertiary nanofiltration concentrate, the concentration ratio of chloride is 1:(3-6), the concentration ratio of calcium ions is 1:(40-60), and the concentration ratio of sodium ions is (1.2-2):1.

[0083] As some examples, in the tertiary nanofiltration product water, the concentration ratio of sodium ions to calcium ions can be (12-17):1.

[0084] In this application, unless otherwise specified, the ratio of concentrations of different substances refers to the ratio of mass concentrations.

[0085] According to the method of the present application, the concentrated water from the third-stage nanofiltration can be directly discharged or the calcium chloride product therein can be recovered. The main component of the concentrated water is calcium chloride.

[0086] In some embodiments, the method further comprises: sending the tertiary nanofiltration concentrated water to an evaporation device for concentration to obtain a concentrated solution with a calcium chloride concentration of not less than 30 wt %.

[0087] According to the method of the present application, the main component of the water produced by the three-stage nanofiltration is chloride, including a large amount of sodium chloride and a small amount of calcium chloride. In order to further obtain a high-purity sodium chloride product (i.e., sodium chloride crystals), the water produced by the three-stage nanofiltration needs to enter the four-stage nanofiltration device for the fourth nanofiltration treatment.

[0088] In some embodiments, in the fourth nanofiltration treatment, the operating pressure of the four-stage nanofiltration device is 8 to 15 bar, the membrane flux is 20 to 25 LMH, and the recovery rate is 90% to 95%.

[0089] Preferably, the fourth nanofiltration treatment has a calcium ion retention rate of 80% to 90% in the tertiary nanofiltration product water, and a sodium ion retention rate of 0 to 20%.

[0090] As some examples, in the fourth-stage nanofiltration product water and the fourth-stage nanofiltration concentrate, the concentration ratio of chloride is 1: (5-6), the concentration ratio of calcium ions is 1: (80-100), and the concentration ratio of sodium ions is 1: (3-5).

[0091] According to the method of the present application, the concentrated water from the fourth-stage nanofiltration contains a large amount of calcium chloride and sodium chloride, which is returned as the inlet water of the third-stage nanofiltration unit, which can further improve the separation efficiency of calcium chloride and sodium chloride.

[0092] According to the method of the present application, the water produced by the four-stage nanofiltration enters the second reverse osmosis device for the second concentration treatment, which can further reduce the amount of concentrated water, reduce the amount of concentrated water, increase the TDS of concentrated water, and reduce the investment and operating costs of evaporation and crystallization.

[0093] In some embodiments, the second reverse osmosis device is an ultra-high pressure reverse osmosis device, preferably a pipe network reverse osmosis device.

[0094] In some embodiments, the operating pressure of the second concentration treatment is 50-110 bar, preferably 80-110 bar, and the volume ratio of the second reverse osmosis concentrated water to the second reverse osmosis produced water is 1:(2-6), for example 1:2, 1:3, 1:3.7, 1:4, 1:5, etc.

[0095] As some examples, the ratio of chloride concentration in the second reverse osmosis product water to the second reverse osmosis concentrated water is 1:(90-125).

[0096] According to the method of the present application, sodium chloride product and evaporation condensed water can be obtained by evaporating and crystallizing the second reverse osmosis concentrated water. The sodium chloride product meets the industrial salt standard. The obtained evaporation condensed water can be reused as dilution water for the primary nanofiltration concentrated water.

[0097] According to the method of the present application, the evaporation crystallization method may include MVR evaporation crystallization or multi-effect evaporation crystallization.

[0098] In some embodiments, the temperature of the evaporative crystallization is 50-80°C, such as 70°C or 75°C.

[0099] The treatment method provided in the present application achieves stable operation of the device without using the step of adding chemicals to remove hard substances in the pretreatment, and can recover chloride salts and calcium chloride in mine water.

[0100] Figure 2According to an embodiment of the present application, a mine water treatment process is performed in a mine water treatment system. The treatment system includes: a pretreatment unit (such as Figure 1 As shown), a first reverse osmosis device 1, a nanofiltration separation unit, a second reverse osmosis device 6 and an evaporation crystallization device 7; wherein,

[0101] The pretreatment unit includes a flocculation reaction tank 80, an ultrafiltration device 90 and a plate-frame filter press device 100. The flocculation reaction tank 80 is used to flocculate the mine water to obtain a supernatant 27 and sludge 28.

[0102] The water outlet of the flocculation reaction tank 80 is connected to the water inlet of the ultrafiltration device 90, so that the supernatant 27 can enter the ultrafiltration device 90 for ultrafiltration treatment to obtain ultrafiltration product water 8 and ultrafiltration concentrated water 31;

[0103] The sludge outlet of the flocculation reaction tank 80 is connected to the feed port of the plate-frame filter press device 100, so that the sludge 28 can enter the plate-frame filter press device 100 for filter pressing treatment to obtain a mud cake 32 and a filtrate 29;

[0104] The water inlet of the flocculation reaction tank 80 is also connected to a raw water pipeline to introduce the mine water 26 therein;

[0105] The concentrated water outlet of the ultrafiltration device 90 and the liquid outlet of the plate-frame filter press device 100 are respectively connected to the water inlet of the flocculation reaction tank 80, so that the ultrafiltration concentrated water 31 and the filtrate 29 can be returned to the flocculation reaction tank 80 and treated together with the mine water 26 as the flocculation tank influent 30;

[0106] The nanofiltration separation unit includes a primary nanofiltration device 2, a secondary nanofiltration device 4, a tertiary nanofiltration device 3 and a quaternary nanofiltration device 5;

[0107] The first-stage nanofiltration device 2 and the second-stage nanofiltration device 4 respectively use sulfate separation nanofiltration membranes, and the third-stage nanofiltration device 3 and the fourth-stage nanofiltration device 5 respectively use calcium ion separation nanofiltration membranes;

[0108] The water output outlet of the ultrafiltration device 90 is connected to the water inlet of the first reverse osmosis device 1, so that the ultrafiltration water 8 enters the first reverse osmosis device 1 for first concentration treatment to obtain first reverse osmosis water 9 and first reverse osmosis concentrated water 10;

[0109] The concentrated water outlet of the first reverse osmosis device 1 is connected to the water inlet of the first nanofiltration device 2, so that the first reverse osmosis concentrated water 10 enters the first nanofiltration device 2 and is processed by the first nanofiltration to obtain the first nanofiltration product water 18 and the first nanofiltration concentrated water 12;

[0110] The concentrate outlet of the primary nanofiltration device 2 is connected to the water inlet of the secondary nanofiltration device 4, and a dilution water pipeline is provided on the secondary nanofiltration device 4, so that the first nanofiltration concentrate 12 and the dilution water 13 are mixed and then enter the secondary nanofiltration device 4 for the second nanofiltration treatment to obtain the secondary nanofiltration product water 15 and the secondary nanofiltration concentrate 16;

[0111] The output water outlet of the primary nanofiltration device 1, the output water outlet of the secondary nanofiltration device 4 and the concentrated water outlet of the quaternary nanofiltration device 5 are connected to the water inlet of the tertiary nanofiltration device 3, so that the primary nanofiltration output water 18, the secondary nanofiltration output water 15 and the quaternary nanofiltration concentrated water 17 are mixed and then enter the tertiary nanofiltration device 3 as mixed water 19 for the third nanofiltration treatment to obtain tertiary nanofiltration output water 20 and tertiary nanofiltration concentrated water 11;

[0112] The water output outlet of the tertiary nanofiltration device 3 is connected to the water inlet of the quaternary nanofiltration device 5, so that the tertiary nanofiltration output water 20 is processed by the third nanofiltration to obtain the quaternary nanofiltration output water 21 and the quaternary nanofiltration concentrated water 17;

[0113] The water output outlet of the four-stage nanofiltration device 5 is connected to the water inlet of the second reverse osmosis device 6, so that the four-stage nanofiltration water 21 enters the second reverse osmosis device 6 for second concentration treatment to obtain second reverse osmosis water 22 and second reverse osmosis concentrated water 23;

[0114] The concentrated water outlet of the second reverse osmosis device 6 is connected to the water inlet of the evaporation crystallization device 7, so that the second reverse osmosis concentrated water 23 is evaporated and crystallized to obtain evaporated condensed water 25 and sodium chloride product 24.

[0115] In some embodiments, one or more of the water outlet of the first reverse osmosis device 1, the water outlet of the second reverse osmosis device 6, and the water outlet of the evaporation crystallization device 7 are connected to the dilution water pipeline of the secondary nanofiltration device 4, so that one or more streams from the first reverse osmosis water 9, the second reverse osmosis water 22, and the evaporation condensate 25 can be used as dilution water 13 for the primary nanofiltration concentrated water 12.

[0116] The mine water treatment system of the present application can realize stable operation of the device without using the step of adding chemicals to remove hardness in pretreatment, and can recover chloride salt and calcium chloride in mine water.

[0117] The following describes embodiments of the present application. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application.

[0118] In the following examples, inductively coupled plasma (ICP) and ion chromatography (IC) were used to determine the components and their contents in water. Figure 1 and Figure 2The process shown is for treating mine water, wherein the first reverse osmosis device is a seawater desalination reverse osmosis membrane device, the secondary nanofiltration device is a disc tube nanofiltration membrane device (DTNF), and the primary, tertiary and quaternary nanofiltration devices are all roll nanofiltration membrane devices; the second reverse osmosis device is an ultra-high pressure pipe network reverse osmosis membrane device, and the evaporation crystallization device is an MVR evaporator.

[0119] In the primary and secondary nanofiltration devices, the nanofiltration membrane uses NF270 polypiperazine composite membrane (under the operating conditions of 25°C, 2.5MPa pressure and 70% recovery rate, for the content of 1157mg / L CaSO 4 、14040mg / L CaCl 2 and 38971mg / L NaCl, its CaSO 4 The rejection rate is 99%, CaCl 2 Retention rate 41%, NaCl retention rate 0%).

[0120] In the three-stage and four-stage nanofiltration devices, the nanofiltration membrane is an aromatic polyamide membrane of ESNA1-LF2 (under the operating conditions of 25°C, 1.5MPa and a recovery rate of 75%, for a sample containing 8852mg / L of CaCl 2 and 33577mg / L NaCl, with a NaCl retention rate of 7%, CaCl 2 Retention rate 81%).

[0121] Take the groundwater of a mine as the mine water to be treated, and its water quality components are shown in Table 1:

[0122] Table 1

[0123]

[0124]

[0125] Example 1

[0126] Pretreatment: Set the flow rate to 50m 3 / h of mine water was sent to the flocculation reaction tank, and polyaluminium chloride and polyacrylamide were added. The amount of polyaluminium chloride added was 200mg / L, and the amount of polyacrylamide added was 2mg / L to obtain supernatant and sludge. The supernatant was precipitated at 50m 3 / h for ultrafiltration treatment, the overall operating pressure of the ultrafiltration process is 0~3bar, and 5m 3 / h ultrafiltration concentrated water and 45m 3 / h ultrafiltration water production (composition see Table 2), ultrafiltration concentrated water and cleaning wastewater return to the flocculation reaction tank;

[0127] Table 2

[0128]

[0129] First concentration treatment: 45m 3 / h ultrafiltration water was sent to the first reverse osmosis device for concentration treatment, with an operating pressure of 55 bar, a temperature of 25 ° C, and a pH of 6.5 to obtain 11.25 m 3 / h of the first reverse osmosis concentrated water and 33.75m 3 / h first reverse osmosis produced water (volume ratio is 1:3), the composition of which is shown in Table 3.

[0130] Table 3

[0131]

[0132] The first nanofiltration treatment separates sulfate: 11.25m 3 The first reverse osmosis concentrated water with a flow rate of 1.5 h was passed into the first nanofiltration device for the first nanofiltration separation. The operating pressure was 15 bar, the membrane flux was 15.5 LMH, the temperature was 20 ° C, and the pH was adjusted to 7 to obtain 4.39 m 3 / h of primary nanofiltration concentrate and 6.86m 3 / h of primary nanofiltration water production (volume ratio of 4:6), the main composition is shown in Table 4;

[0133] Table 4

[0134]

[0135] Second nanofiltration treatment to separate sulfate: 4.39m 3 / hThe primary nanofiltration concentrated water was mixed with the first reverse osmosis product water (as dilution water) at a volume ratio of 1:3 and sent to the secondary nanofiltration device for the second nanofiltration treatment. The operating pressure was 10 bar, the membrane flux was 14.1 LMH, the temperature was 28 ° C, the pH was adjusted to 7, and 5.05 m 3 / h of secondary nanofiltration concentrate and 12.49m 3 / h of secondary nanofiltration produced water (volume ratio of 3:7), the main composition of which is shown in Table 5, and the secondary nanofiltration concentrated water is discharged to the tailings area for use;

[0136] Table 5

[0137]

[0138] The third nanofiltration treatment separates calcium ions: 6.86m 3 / h first-stage nanofiltration water production, 12.49m 3 / h secondary nanofiltration water production and 0.97m 3 / hThe four-stage nanofiltration concentrated water was mixed and sent to the three-stage nanofiltration device for the third nanofiltration treatment. The operating pressure was 16 bar, the membrane flux was 21.7 LMH, the temperature was 25 ° C, and the pH was adjusted to 7 to obtain 1.02m3 / h of three-stage nanofiltration concentrated water and 19.31m 3 / h of three-stage nanofiltration produced water (volume ratio of 1:19), the main composition of which is shown in Table 6. The main component of the three-stage nanofiltration concentrated water is calcium chloride, which is sent to an evaporation concentration device for concentration to obtain a calcium chloride concentrate with a concentration of 30wt%.

[0139] Table 6

[0140]

[0141] The fourth nanofiltration treatment separates calcium ions: 19.31m 3 / hThe third-stage nanofiltration produced water was sent to the fourth-stage nanofiltration device for the fourth nanofiltration treatment. The operating pressure was 8 bar, the temperature was 25 ° C, the membrane flux was 20.7LMH, and the pH was adjusted to 7 with hydrochloric acid to obtain 0.97m 3 / h of four-stage nanofiltration concentrated water and 18.34m 3 / h of four-stage nanofiltration water production (volume ratio of 1:19), the main components of which are shown in Table 7.

[0142] Table 7

[0143]

[0144] Second concentration treatment: 18.34m 3 / h four-stage nanofiltration water enters the reverse osmosis concentration device, the operating pressure is 100 bar, the temperature is 25 ° C, the pH is adjusted to 6.5, and 3.94m 3 / h of the second reverse osmosis concentrated water and 14.4m 3 / h of the second reverse osmosis produced water (volume ratio of 1:3.7), the main composition of which is shown in Table 8.

[0145] Table 8

[0146]

[0147] Evaporation crystallization: The second reverse osmosis concentrated water is sent to the evaporation crystallization device for crystallization treatment, and the evaporation temperature is 70°C; evaporation condensed water and sodium chloride products are obtained respectively.

[0148] Effect description: The total amount of calcium sulfate in the secondary nanofiltration concentrated water accounts for 99.0% of the total amount of calcium sulfate in the raw water, that is, 99% of the calcium sulfate in the wastewater is removed;

[0149] The total amount of calcium chloride in the tertiary nanofiltration concentrated water accounts for 58.6% of the total amount of calcium chloride in the raw water, and more than 55% of the calcium chloride in the wastewater is recovered. After further evaporation, concentration and separation, the calcium chloride concentrate (concentration 30wt%) is obtained to meet the requirements of industrial-grade liquid calcium chloride.

[0150] The total amount of sodium chloride in the water produced by the four-stage nanofiltration accounts for 95% of the total amount of sodium chloride in the raw water (mine water), that is, more than 90% of the sodium chloride in the wastewater is recovered;

[0151] After the second reverse osmosis concentrated water is evaporated and crystallized, the purity of the obtained sodium chloride product is 99.1%, which meets the standard for industrial salt use.

[0152] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for treating mine water, characterized in that: The treatment method includes: The mine water is subjected to flocculation precipitation and ultrafiltration treatment to obtain ultrafiltration product water containing sulfate, chloride ions, calcium ions, magnesium ions and sodium ions; The ultrafiltration product water enters the first reverse osmosis device for first concentration treatment to obtain first reverse osmosis product water and first reverse osmosis concentrated water; The first reverse osmosis concentrated water enters the primary nanofiltration device and is treated by the first nanofiltration to separate sulfate radicals, thereby obtaining primary nanofiltration product water and primary nanofiltration concentrated water; The primary nanofiltration concentrated water is mixed with dilution water, and the obtained dilution water enters the secondary nanofiltration device for second nanofiltration treatment to separate sulfate radicals, thereby obtaining secondary nanofiltration produced water and secondary nanofiltration concentrated water rich in sulfate; The primary nanofiltration product water, the secondary nanofiltration product water and the fourth nanofiltration concentrated water are mixed, and the resulting mixed water enters the third nanofiltration device for a third nanofiltration treatment to separate calcium ions, thereby obtaining the third nanofiltration product water and the third nanofiltration concentrated water rich in chloride salt; The third-stage nanofiltration produced water enters the fourth-stage nanofiltration device and is processed by the fourth nanofiltration to further separate calcium ions, thereby obtaining fourth-stage nanofiltration produced water and fourth-stage nanofiltration concentrated water; The four-stage nanofiltration product water enters the second reverse osmosis device for second concentration treatment to obtain second reverse osmosis product water and second reverse osmosis concentrated water; The second reverse osmosis concentrated water enters an evaporation crystallization device for evaporation crystallization to obtain evaporation condensed water and sodium chloride products.

2. The processing method according to claim 1, characterized in that: The primary nanofiltration device and the secondary nanofiltration device respectively include sulfate separation nanofiltration membranes; Preferably, the sulfate separation nanofiltration membrane is a polypiperazine composite membrane; Preferably, under the operating conditions of 25° C., 2.5 MPa pressure and 70% recovery rate, for a first aqueous solution containing 14000-15120 mg / L calcium chloride, 1150-2220 mg / L calcium sulfate and 38900-40200 mg / L sodium chloride, the calcium sulfate retention rate of the sulfate separation nanofiltration membrane is ≥99%, the sodium chloride retention rate is <15%, and the calcium chloride retention rate is ≤50%.

3. The processing method according to claim 1 or 2, characterized in that: The three-stage nanofiltration device and the four-stage nanofiltration device respectively include a calcium ion separation nanofiltration membrane; Preferably, the calcium ion separation nanofiltration membrane is an aromatic polyamide membrane; Preferably, under the operating conditions of 25° C., 1.5 MPa pressure and 75% recovery rate, for the second aqueous solution containing 8850-8880 mg / L calcium chloride and 22320-33600 mg / L sodium chloride, the sodium chloride retention rate of the calcium ion separation nanofiltration membrane is less than 10%, and the calcium chloride retention rate is ≥80%.

4. The processing method according to any one of claims 1 to 3, characterized in that: The first reverse osmosis device is a desalination-grade reverse osmosis device, and the second reverse osmosis device is an ultra-high pressure reverse osmosis device; Preferably, the operating pressure of the first concentration treatment is 50-70 bar, and the volume ratio of the first reverse osmosis concentrated water to the first reverse osmosis produced water is 1:(2-3); Preferably, the operating pressure of the second concentration treatment is 50-110 bar, and the volume ratio of the second reverse osmosis concentrated water to the second reverse osmosis produced water is 1:(2-6).

5. The processing method according to any one of claims 1 to 4, characterized in that: The TDS of the mine water is 14-15 g / L, the calcium ion concentration is 1500-1600 mg / L, the magnesium ion concentration is 100-200 mg / L, the sulfate concentration is 300-400 mg / L, the chloride ion concentration is 8000-9000 mg / L, the sodium ion concentration is 3000-4000 mg / L, and the fluoride ion concentration is 0.2-1.5 mg / L.

6. The processing method according to any one of claims 1 to 5, characterized in that: In the first nanofiltration treatment, the operating pressure of the first-stage nanofiltration device is 15-20 bar, the membrane flux is 15-20 LMH, and the recovery rate is 60%-70%; Preferably, the water inlet temperature of the primary nanofiltration device is 15-20°C; Preferably, the first nanofiltration treatment has a sulfate rejection rate of 98% to 99.5% in the first reverse osmosis concentrated water, a chloride rejection rate of 0% to 25%, and a calcium rejection rate of 30% to 70%.

7. The processing method according to any one of claims 1 to 6, characterized in that: The secondary nanofiltration device is a disc-tube nanofiltration membrane device; Preferably, in the second nanofiltration treatment, the operating pressure of the secondary nanofiltration device is 6 to 15 bar, the membrane flux is 12 to 20 LMH, and the recovery rate is 50% to 75%; Preferably, the water inlet temperature of the secondary nanofiltration device is above 25°C, more preferably 25-30°C; Preferably, the second nanofiltration treatment has a sulfate rejection rate of 98% to 99.5% in the diluted water, a chloride rejection rate of -10% to 30%, and a calcium rejection rate of 30% to 70%.

8. The processing method according to any one of claims 1 to 7, characterized in that: In the second nanofiltration treatment, one or more of the first reverse osmosis produced water, the second reverse osmosis produced water and the evaporation condensation water are used as the dilution water; Preferably, the volume ratio of the dilution water to the primary nanofiltration concentrated water is (1-4):

1.

9. The processing method according to any one of claims 1 to 8, characterized in that: In the third nanofiltration treatment, the operating pressure of the three-stage nanofiltration device is 15-20 bar, the membrane flux is 18-22 LMH, and the recovery rate is 80%-95%; Preferably, the third nanofiltration treatment has a calcium ion retention rate of 70% to 80% and a sodium ion retention rate of -2% to 20% in the mixed water; The treatment method further comprises: sending the chloride-rich tertiary nanofiltration concentrated water into an evaporation concentration device for concentration to obtain a calcium chloride concentrated solution with a mass concentration of not less than 30%.

10. The processing method according to any one of claims 1 to 9, characterized in that: In the fourth nanofiltration treatment, the operating pressure of the four-stage nanofiltration device is 8-15 bar, the membrane flux is 20-25 LMH, and the recovery rate is 90%-95%; Preferably, the fourth nanofiltration treatment has a calcium ion retention rate of 80% to 90% in the tertiary nanofiltration product water, and a sodium ion retention rate of 0 to 20%.

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