Mine water treatment system

Abstract

The utility model belongs to the field of water treatment, and provides a mine water treatment system which comprises a first reverse osmosis device, a first-stage nanofiltration device, a second-stage nanofiltration device, a third-stage nanofiltration device, a fourth-stage nanofiltration device, a second reverse osmosis device and an evaporative crystallization device, the third-stage nanofiltration device and the fourth-stage nanofiltration device comprise calcium ion separation nanofiltration membranes. The treatment system provided by the utility model can realize resourceful treatment of mine water without adding chemicals for softening.

Description

Technical Field

[0001] This utility model belongs to the field of water treatment technology, and more specifically, relates to a method for treating mine water. Background Technology

[0002] Mine water is a byproduct of mineral resource extraction and is also an important type of unconventional water. It contains large amounts of calcium, sodium, magnesium, sulfate, and chloride ions, and typically also contains suspended solids and organic pollutants. Direct discharge of mine water can damage the ecological environment, leading to problems such as soil erosion and vegetation loss.

[0003] Traditional wastewater treatment processes mainly include pretreatment, advanced separation, and evaporation crystallization. Pretreatment typically involves softening to reduce the concentration of calcium and magnesium ions in the water. Specifically, to prevent scaling on downstream membrane elements and the evaporation system, pretreatment requires the use of chemicals to remove calcium and magnesium ions (softening agents such as sodium carbonate, sodium bicarbonate, and lime slurry). This not only results in high costs but also generates a large amount of sludge, making it neither economical nor environmentally friendly. Furthermore, compared to ordinary saline wastewater containing magnesium and calcium ions (such as desulfurization wastewater), mine water has a much higher concentration of calcium ions than magnesium ions, making it more polluting. Using traditional wastewater treatment systems to treat mine water leads to scaling, unstable operation, and prevents the resource recovery of mine water. Utility Model Content

[0004] This utility model aims to at least partially solve one of the technical problems in the related art.

[0005] This utility model provides a mine water treatment system, comprising: a first reverse osmosis unit, a first-stage nanofiltration unit, a second-stage nanofiltration unit, a third-stage nanofiltration unit, a fourth-stage nanofiltration unit, a second reverse osmosis unit, and an evaporation crystallization unit; wherein,

[0006] The inlet of the first reverse osmosis unit is connected to a water inlet pipe, and the concentrate outlet of the first reverse osmosis unit is connected to the inlet of the first-stage nanofiltration unit.

[0007] The concentrate outlet of the first-stage nanofiltration unit is connected to the inlet of the second-stage nanofiltration unit, and the inlet of the second-stage nanofiltration unit is also connected to a dilution water pipe, so that the concentrate and dilution water produced by the first nanofiltration unit can be combined and enter the second-stage nanofiltration unit.

[0008] The product water outlet of the first-stage nanofiltration unit, the product water outlet of the second-stage nanofiltration unit, and the concentrate outlet of the fourth-stage nanofiltration unit are respectively connected to the inlet of the third-stage nanofiltration unit.

[0009] The product water outlet of the three-stage nanofiltration unit is connected to the inlet of the four-stage nanofiltration unit;

[0010] The inlet of the second reverse osmosis unit is connected to the product water outlet of the fourth-stage nanofiltration unit, and the concentrate outlet of the second reverse osmosis unit is connected to the inlet of the evaporation crystallization unit.

[0011] The primary nanofiltration device and the secondary nanofiltration device each include a sulfate separation nanofiltration membrane, and the tertiary nanofiltration device and the quaternary nanofiltration device each include a calcium ion separation nanofiltration membrane.

[0012] The treatment system provided by this invention first uses a primary and secondary nanofiltration device with a sulfate separation nanofiltration membrane to filter out sulfate ions in the water, minimizing the precipitation of calcium sulfate and its potential fouling of the membrane during salt concentration. Then, a tertiary and quaternary nanofiltration device with a calcium ion separation nanofiltration membrane (which has a high calcium ion rejection rate) removes excess calcium ions from the water, reducing the risk of scaling and preventing membrane damage. This invention avoids the need for chemical softening in pretreatment, achieving the separation of sulfates and chlorides.

[0013] According to some embodiments of this utility model, one or more of the permeate outlets of the first reverse osmosis unit, the second reverse osmosis unit, and the evaporation crystallization unit are connected to the dilution water pipeline of the secondary nanofiltration unit, so that one or more of the permeate generated by the first reverse osmosis unit, the permeate generated by the second reverse osmosis unit, and the evaporation condensate generated by the evaporation crystallization unit can be used as dilution water. This type of reverse osmosis permeate and evaporation condensate has a low salt content, which allows for the recycling of system permeate and improves salt recovery rate.

[0014] According to some embodiments of the present invention, the processing system further includes a pretreatment unit, which includes a flocculation reaction tank, an ultrafiltration device, and a plate and frame filter press.

[0015] The flocculation reaction tank is used to treat mine water by flocculation reaction to obtain supernatant and sludge.

[0016] The outlet of the flocculation reaction tank is connected to the inlet of the ultrafiltration device so that the supernatant can enter the ultrafiltration device for ultrafiltration treatment to obtain ultrafiltration concentrate and ultrafiltration permeate.

[0017] The sludge outlet of the flocculation reaction tank is connected to the feed inlet of the plate and frame filter press, so that the sludge can enter the plate and frame filter press for filter pressing to obtain sludge cake and filtrate.

[0018] The concentrated water outlet of the ultrafiltration device and the liquid outlet of the plate and frame filter press are respectively connected to the water inlet of the flocculation reaction tank so that the ultrafiltration concentrated water and filtrate can enter the flocculation reaction tank.

[0019] The product water outlet of the ultrafiltration unit is connected to the inlet pipe of the water to be treated, so that the ultrafiltration product water can enter the first reverse osmosis unit. By setting up this pretreatment unit, fluoride ions and suspended solids in the mine water can be removed.

[0020] According to some embodiments of this utility model, under 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 rejection rate of the sulfate separation nanofiltration membrane is ≥99%, the sodium chloride rejection rate is <15%, and the calcium chloride rejection rate is ≤50%.

[0021] According to some embodiments of this utility model, under operating conditions of 25°C, 1.5 MPa pressure, and 75% recovery rate, for a second aqueous solution containing 8850–8880 mg / L calcium chloride and 22320–33600 mg / L sodium chloride, the sodium chloride rejection rate of the calcium ion separation nanofiltration membrane is <10%, and the calcium chloride rejection rate is ≥80%.

[0022] According to some embodiments of the present invention, the first reverse osmosis device is a seawater desalination-grade reverse osmosis device.

[0023] According to some embodiments of the present invention, the second reverse osmosis device is an ultra-high pressure reverse osmosis device.

[0024] According to some embodiments of the present invention, the primary nanofiltration device, the secondary nanofiltration device, and the tertiary nanofiltration device are all spiral wound nanofiltration membrane devices.

[0025] According to some embodiments of this utility model, the secondary nanofiltration device is a disc tube nanofiltration membrane device.

[0026] According to some embodiments of this invention, the treatment system further includes an evaporation and concentration device, the inlet of which is connected to the concentrate outlet of the three-stage nanofiltration device. This further enables the recovery of calcium chloride.

[0027] According to some embodiments of this utility model, the evaporation crystallization device is an MVR evaporator or a multi-effect evaporator.

[0028] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] The above and / or additional aspects and advantages of this invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0030] Figure 1 This is a schematic diagram of a mine water treatment system according to an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of a mine water pretreatment unit according to an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of a mine water treatment system according to another embodiment of this application.

[0033] Explanation of reference numerals in the attached figures

[0034] 1: First reverse osmosis unit; 2: First-stage nanofiltration unit; 3: Third-stage nanofiltration unit; 4: Second-stage nanofiltration unit; 5: Fourth-stage nanofiltration unit; 6: Second reverse osmosis unit; 7: Evaporative crystallization unit; 80: Flocculation reaction tank; 90: Ultrafiltration unit; 100: Plate and frame filter press; 110: Evaporation and concentration unit; 8: Ultrafiltration permeate; 9: First reverse osmosis permeate; 10: First reverse osmosis concentrate; 11: Third-stage nanofiltration concentrate; 12: First-stage nanofiltration concentrate; 13: Dilution water; 4: Dilution water; 15: Secondary nanofiltration permeate; 16: Secondary nanofiltration concentrate; 17: Quaternary nanofiltration concentrate; 18: Primary nanofiltration permeate; 19: Mixed water; 20: Tertiary nanofiltration permeate; 21: Quaternary nanofiltration permeate; 22: Second reverse osmosis permeate; 23: Second reverse osmosis concentrate; 24: Sodium chloride product; 25: Evaporation condensate; 26: Mine water; 27: Supernatant; 28: Sludge; 29: Filtrate; 30: Flocculation feed water; 31: Ultrafiltration concentrate; 32: Sludge cake. Detailed Implementation

[0035] The embodiments of this utility model are described in detail below. The embodiments described below are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0036] The "scope" disclosed in this utility model is defined in the form of a lower limit and / or an upper limit. A given scope is defined by selecting a lower limit and / or an upper limit. The scope defined in this way may or may not include endpoints and can be arbitrarily combined. That is, any lower limit can be combined with any upper limit to form an undefined scope, and any lower limit can be combined with other lower limits to form an undefined scope; similarly, any upper limit can be combined with any other upper limit to form an undefined scope. Furthermore, each individually disclosed point or single value can itself serve as a lower limit or upper limit and can be combined with any other point or single value or with other lower limits or upper limits to form an undefined scope.

[0037] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0038] In this utility model, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0039] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0040] This utility model provides a mine water treatment system. (Refer to...) Figure 1 and Figure 3 The treatment system includes: a first reverse osmosis unit 1, a first-stage nanofiltration unit 2, a second-stage nanofiltration unit 4, a third-stage nanofiltration unit 3, a fourth-stage nanofiltration unit 5, a second reverse osmosis unit 6, and an evaporation crystallization unit 7.

[0041] According to this invention, the primary nanofiltration device 2 and the secondary nanofiltration device 4 each include a sulfate separation nanofiltration membrane. The "sulfate separation nanofiltration membrane" refers to a membrane that, under the same operating conditions, has a significantly higher retention rate for sulfate than for other ions in mine water (such as Ca). 2+ Cl - Nanofiltration membranes with high rejection rates (etc.).

[0042] In some embodiments, the sulfate separation nanofiltration membrane meets the following conditions: under operating conditions of 25°C, 2.5 MPa, and 70% recovery rate, the calcium sulfate rejection rate in the first aqueous solution is ≥99%, the sodium chloride rejection rate is <15%, and the calcium chloride rejection rate is ≤50%; wherein, the first aqueous solution is composed of water and calcium chloride (CaCl2), calcium sulfate (CaSO4), and sodium chloride (NaCl) dissolved therein, with the following concentrations: CaCl2 14000~15120 mg / L (e.g., 14040 mg / L, 15117 mg / L), CaSO4 1150~2220 mg / L (e.g., 1157 mg / L, 2219 mg / L), and NaCl 38900~40200 mg / L (e.g., 38971 mg / L, 40172 mg / L).

[0043] According to this invention, the sulfate separation nanofiltration membrane is a polypiperazine composite membrane, such as, but not limited to, nanofiltration membranes from Dow's NF90, NF245, NF270 and other series of products.

[0044] According to this invention, the three-stage nanofiltration device 3 and the four-stage nanofiltration device 5 each include a calcium ion separation nanofiltration membrane. The calcium ion separation nanofiltration membrane refers to a nanofiltration membrane that, under the same operating conditions, has a high calcium ion separation and retention rate but a relatively low sodium ion retention rate. This nanofiltration membrane can achieve separation of calcium ions from sodium ions. 2+ with Na + Effective separation.

[0045] In some embodiments, the calcium ion separation nanofiltration membrane meets the following conditions: under operating conditions of 25°C, 1.5 MPa pressure, and 75% recovery rate, the sodium chloride rejection rate in the second aqueous solution is <10%, and the calcium chloride rejection rate is ≥80%, wherein the second aqueous solution is composed of water and calcium chloride (CaCl2) and sodium chloride (NaCl) dissolved therein, and the concentrations of each component are: CaCl2 8850~8880 mg / L (e.g., 8852 mg / L, 8880 mg / L), NaCl 22320~33600 mg / L (e.g., 22320 mg / L, 33577 mg / L).

[0046] According to this utility model, the calcium ion separation nanofiltration membrane can be an aromatic polyamide membrane, such as, but not limited to, the nanofiltration membranes of Hydranautics' ESNA1-K1, ESNA1-LF, ESNA1-LF2, ESNA1-LF-LD, ESNA1-LF2-LD and other series of products.

[0047] According to this invention, the calcium ion separation nanofiltration membrane has a higher retention efficiency for calcium chloride than the sulfate separation nanofiltration membrane. Compared with using only a sulfate separation nanofiltration membrane for salt separation, the calcium ion separation nanofiltration membrane can effectively separate sodium chloride and calcium chloride, thereby significantly reducing the number of nanofiltration stages and simplifying the process.

[0048] In some embodiments, the mine water has a TDS of 14–15 g / L, a calcium ion concentration of 1500–1600 mg / L, a magnesium ion concentration of 100–200 mg / L, a sulfate concentration of 300–400 mg / L, a chloride ion concentration of 8000–9000 mg / L, a sodium ion concentration of 3000–4000 mg / L, and a fluoride ion concentration of 0.2–1.5 mg / L. Furthermore, the total hardness of the mine water, calculated as calcium carbonate, can be 4000–5000 mg / L, the soluble silicon content, calculated as silica, can be 10–20 mg / L, and the electrical conductivity can be 15–20 mS / cm.

[0049] like Figure 1 and Figure 3 As shown, the inlet of the first reverse osmosis unit 1 is connected to a pipeline for the mine water to be treated, and the concentrate outlet of the first reverse osmosis unit 1 is connected to the inlet of the first-stage nanofiltration unit 2, so that the first reverse osmosis concentrate 10 can enter the first-stage nanofiltration unit 2.

[0050] The concentrate outlet of the primary nanofiltration unit 2 is connected to the inlet of the secondary nanofiltration unit 4, and the inlet of the secondary nanofiltration unit 4 is also connected to a dilution water pipe, so that the primary nanofiltration concentrate 12 and dilution water 13 produced by the primary nanofiltration unit 2 are combined and then dilution water 14 enters the secondary nanofiltration unit 4.

[0051] The product water outlet of the first-stage nanofiltration unit 2, the product water outlet of the second-stage nanofiltration unit 4, and the concentrate outlet of the fourth-stage nanofiltration unit 5 are respectively connected to the inlet of the third-stage nanofiltration unit 3 so that the first-stage nanofiltration product water 18, the second-stage nanofiltration product water 15, and the fourth-stage nanofiltration concentrate water 17 are mixed and then enter the third-stage nanofiltration unit 3 as mixed water 19.

[0052] The product water outlet of the third-stage nanofiltration unit 3 is connected to the inlet of the fourth-stage nanofiltration unit 5 so that the product water 20 from the third-stage nanofiltration unit 20 enters the fourth-stage nanofiltration unit 5.

[0053] The inlet of the second reverse osmosis unit 6 is connected to the outlet of the fourth nanofiltration unit 5 so that the fourth nanofiltration product water 21 enters the second reverse osmosis unit 6.

[0054] The concentrate outlet of the second reverse osmosis unit 6 is connected to the inlet of the evaporation crystallization unit 7 so that the second reverse osmosis concentrate 23 enters the evaporation crystallization unit 7, and after evaporation and crystallization, sodium chloride product 24 and evaporation condensate 25 are obtained.

[0055] In some embodiments, the processing system further includes a preprocessing unit, such as... Figure 2 As shown, the pretreatment unit includes: a flocculation reaction tank 80, an ultrafiltration device 90, and a plate and frame filter press 100.

[0056] The flocculation reaction tank 80 is used to flocculate the mine water to obtain supernatant 27 and sludge 28. The outlet of the flocculation reaction tank 80 is connected to the inlet of the ultrafiltration device 90 so that the supernatant 27 can enter the ultrafiltration device 90 for ultrafiltration treatment to obtain ultrafiltration concentrate 31 and ultrafiltration permeate 8.

[0057] The sludge outlet of the flocculation reaction tank 80 is connected to the feed inlet of the plate and frame filter press 100 so that the sludge 28 can enter the plate and frame filter press 100 for filter pressing to obtain sludge cake 32 and filtrate 29.

[0058] The inlet of the flocculation reaction tank 80 is also connected to a raw water pipe to introduce mine water 26 into it;

[0059] The concentrated water outlet of the ultrafiltration device 90 and the liquid outlet of the plate and frame filter press 100 are respectively connected to the water inlet of the flocculation reaction tank 80 so that the ultrafiltration concentrated water 31 and filtrate 29 can be returned to the flocculation reaction tank 80 and treated together with the mine water 26 as the flocculation tank inlet water 30.

[0060] The product water outlet of the ultrafiltration device 90 is connected to the water inlet pipe to be treated, so that the ultrafiltration product water 8 is used as the feed water of the first reverse osmosis device 1.

[0061] In these embodiments, the mine water 26, etc., is subjected to flocculation sedimentation and ultrafiltration treatment by the pretreatment unit to remove fluoride ions and suspended solids, and to obtain a solution containing sulfate (SO4). 2- ), chloride ions (Cl) - ), calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ) and sodium ions (Na + ) Ultrafiltration permeate water 8.

[0062] In particular, the pretreatment process of this utility model does not include softening of mine water.

[0063] According to this utility model, the ultrafiltration permeate 8 enters the first reverse osmosis unit 1 for first concentration treatment. On the one hand, this reduces the processing capacity of the downstream nanofiltration unit, thereby reducing related investment and operating costs. On the other hand, the first reverse osmosis permeate 9 generated by reverse osmosis can provide dilution water in the secondary nanofiltration unit 4 to reduce costs.

[0064] In some embodiments, the conditions for the first concentration treatment include: an operating pressure of 50 to 70 bar, and a volume ratio of 1:(2 to 3) between the first reverse osmosis concentrate 10 and the first reverse osmosis permeate 9.

[0065] In some embodiments, the influent temperature in the first concentration process is 20–25°C, and the influent pH is 6–6.8.

[0066] To optimize the quality of the permeate, the first reverse osmosis unit 1 is preferably a seawater desalination-grade reverse osmosis unit, that is, it uses seawater desalination-grade reverse osmosis membrane elements. Accordingly, the first concentration treatment is carried out through the seawater desalination-grade reverse osmosis unit, and the resulting first reverse osmosis permeate 9 and first reverse osmosis concentrate 10 are seawater desalination-grade reverse osmosis permeate and seawater desalination-grade reverse osmosis concentrate, respectively.

[0067] According to this utility model, the first reverse osmosis concentrate 10 is subjected to first nanofiltration treatment by the first nanofiltration device 2, and the sulfate nanofiltration separation membrane therein is used to separate sulfate from the feed water, so as to obtain first nanofiltration permeate 18 containing chloride and a small amount of sulfate, and first nanofiltration concentrate 12 containing chloride and rich in sulfate.

[0068] In some embodiments, the primary nanofiltration device 2 includes a spiral wound nanofiltration membrane element, i.e., a spiral wound nanofiltration membrane device.

[0069] In some embodiments, in the first nanofiltration process, the operating pressure of the first-stage nanofiltration unit 2 is 15-20 bar, the membrane flux is 15-20 LMH, and the recovery rate is 60%-70%.

[0070] In some embodiments, the influent temperature for the primary nanofiltration treatment is 15–20°C. Lower temperatures can improve the retention rate of sulfate ions.

[0071] Preferably, the first nanofiltration treatment has a sulfate rejection rate of 98% to 99.5%, a chloride rejection rate of 0% to 25%, and a calcium rejection rate of 30% to 70% in the first reverse osmosis concentrate 10.

[0072] In this invention, "recovery rate" refers to the percentage of product water volume to influent water volume, calculated as: product water volume ÷ influent water volume × 100%. Furthermore, chloride ion rejection rate is calculated in terms of chloride.

[0073] According to this invention, the diluted primary nanofiltration concentrate 12 is subjected to a second nanofiltration treatment via a secondary nanofiltration device 4. The sulfate separation nanofiltration membrane within the device separates sulfate ions from the influent, allowing chlorides to be separated as much as possible to the product water side. This results in secondary nanofiltration concentrate 16 containing chlorides and sodium sulfate, and secondary nanofiltration product water 15 containing small amounts of sulfates and chlorides, achieving effective separation of sulfates (calcium sulfate and a small amount of magnesium sulfate) and chlorides (sodium chloride, calcium chloride, and a small amount of magnesium chloride). The secondary nanofiltration concentrate 16 can be directly sent to tailings ponds or mineral processing areas for utilization.

[0074] In some embodiments, the secondary nanofiltration unit 4 includes a disc tube (DT) membrane module structure, namely a disc tube nanofiltration membrane device (DTNF). Mine water quality fluctuates greatly, and the sulfate concentration in the secondary nanofiltration unit 4 is much higher than in other nanofiltration units in the system, making it more prone to CaSO4 scaling. Using a DT membrane module can improve its resistance to fluctuations and its resistance to fouling.

[0075] According to this utility model, the dilution water 13 can be various types of clean water such as tap water and distilled water, or it can be the product water with a relatively low salt concentration in the treatment system.

[0076] In some embodiments, one or more of the permeate outlets of the first reverse osmosis unit 1, the second reverse osmosis unit 6, and the evaporation crystallization unit 7 are connected to the dilution water pipeline of the secondary nanofiltration unit 4, so that one or more of the first reverse osmosis permeate 9, the second reverse osmosis permeate 22, and the evaporation condensate 25 are used as dilution water 13. This allows for the recycling of process permeate and improves the recovery rate of salt products.

[0077] In some embodiments, in the second nanofiltration process, the operating pressure of the secondary nanofiltration unit 4 is 6 to 15 bar, the membrane flux is 12 to 20 LMH, and the recovery rate is 50% to 70%.

[0078] Preferably, the inlet water temperature of the secondary nanofiltration device 4 is above 25°C, and the CaSO4 concentration in the inlet water of the secondary nanofiltration device 4 is relatively high; increasing the temperature can improve its solubility. More preferably, the inlet water temperature of the secondary nanofiltration device is 25–30°C, for example, 28°C.

[0079] Preferably, the second nanofiltration treatment has a sulfate rejection rate of 98% to 99.5%, a chloride rejection rate of -10% to 30%, and a calcium rejection rate of 30% to 70% in the diluted water.

[0080] According to this invention, the primary nanofiltration permeate 18, the secondary nanofiltration permeate 15, and the quaternary nanofiltration concentrate 17 are used together as the feed water (mainly composed of chloride) to the tertiary nanofiltration unit 3, i.e., mixed water 19. Calcium ions are retained using a calcium ion separation nanofiltration membrane to obtain tertiary nanofiltration permeate 20 and chloride-rich tertiary nanofiltration concentrate 11. The tertiary nanofiltration concentrate 11 (mainly composed of calcium chloride) can be recovered by evaporation and concentration to obtain a 30% calcium chloride solution.

[0081] In some embodiments, the three-stage nanofiltration device 3 is a spiral wound nanofiltration membrane device.

[0082] In some embodiments, in the third nanofiltration process, the operating pressure of the three-stage nanofiltration unit 3 is 15-20 bar, the membrane flux is 18-22 LMH, and the recovery rate is 80%-90%.

[0083] Preferably, the third nanofiltration treatment has a calcium ion rejection rate of 70% to 80% and a sodium ion rejection rate of -2% to 20% in the mixed water 19.

[0084] In some embodiments, such as Figure 3 As shown, the processing system also includes an evaporation and concentration device 110. The concentrated water outlet of the three-stage nanofiltration device 3 is connected to the inlet of the evaporation and concentration device 110 to evaporate and concentrate the concentrated water 11 of the three-stage nanofiltration device to obtain calcium chloride concentrate.

[0085] According to this invention, the main component of the three-stage nanofiltration permeate is chloride, including a large amount of sodium chloride and a small amount of calcium chloride. The three-stage nanofiltration permeate 20 is subjected to a fourth nanofiltration treatment by a four-stage nanofiltration device 5, which further retains calcium ions using a calcium ion separation nanofiltration membrane, to obtain four-stage nanofiltration permeate 21 and four-stage nanofiltration concentrate 22.

[0086] In some embodiments, the four-stage nanofiltration device 5 includes spiral wound nanofiltration membrane elements.

[0087] In some embodiments, in the fourth nanofiltration process, the operating pressure of the four-stage nanofiltration device 5 is 8 to 15 bar, the membrane flux is 20 to 25 LMH, and the recovery rate is 90% to 95%.

[0088] Preferably, the fourth nanofiltration treatment has a calcium ion rejection rate of 80% to 90% and a sodium ion rejection rate of 0% to 20% in the tertiary nanofiltration permeate 20.

[0089] According to this utility model, the second reverse osmosis device 6 can further reduce the volume of the fourth-stage nanofiltration permeate 21 by performing a second concentration treatment, thereby reducing the amount of concentrate, increasing the TDS of the concentrate, and reducing the investment and operating costs of evaporation and crystallization.

[0090] In some embodiments, the second reverse osmosis device 6 is an ultra-high pressure reverse osmosis device, preferably an ultra-high pressure pipeline reverse osmosis device.

[0091] Preferably, the operating pressure of the second concentration treatment is 50-110 bar, more preferably 80-110 bar; the volume ratio of the second reverse osmosis concentrate 23 to the second reverse osmosis permeate 22 is 1:(2-6), for example 1:2, 1:3, 1:3.7, 1:4, 1:5, etc.

[0092] According to this invention, by evaporating and crystallizing the second reverse osmosis concentrate 23 using the evaporation crystallization device 7, sodium chloride product 24 (i.e., sodium chloride crystals) and evaporation condensate 25 can be obtained. The sodium chloride product 24 meets the industrial salt standards.

[0093] In some embodiments, the evaporation crystallization apparatus 7 is an MVR evaporation crystallization or multi-effect evaporation crystallization.

[0094] In some embodiments, the evaporation and crystallization temperature is 50–80°C, for example 70°C or 75°C.

[0095] The processing system provided in this application achieves stable operation of the device without using chemical hardening in the pretreatment process, and can recover chloride and calcium chloride from mine water.

[0096] The following describes embodiments of the present invention. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0097] In the following embodiments, reference is made to Figures 1 to 3 This invention describes a method for treating mine water using the treatment system of this invention. Specifically, the first reverse osmosis unit 1 is a seawater desalination reverse osmosis membrane device; the first-stage nanofiltration unit 2, the third-stage nanofiltration unit 3, and the fourth-stage nanofiltration unit 5 are spiral wound nanofiltration membrane devices; the second-stage nanofiltration unit 4 is a disc tube nanofiltration membrane device (DTNF); the second reverse osmosis unit 6 is an ultra-high pressure pipeline reverse osmosis membrane device; and the evaporation and crystallization unit 7 is an MVR evaporator.

[0098] In the primary and secondary nanofiltration units, the nanofiltration membranes are made of NF270 polypiperazine composite membranes (under operating conditions of 25℃, 2.5MPa pressure and 70% recovery rate, for water containing 1157mg / L CaSO4, 14040mg / L CaCl2 and 38971mg / L NaCl, the CaSO4 rejection rate is 99%, the CaCl2 rejection rate is 41% and the NaCl rejection rate is 0%).

[0099] In the three-stage and four-stage nanofiltration units, the nanofiltration membrane is an ESNA1-LF2 aromatic polyamide membrane (under operating conditions of 25℃, 1.5MPa and 75% recovery rate, for water containing 8852mg / L CaCl2 and 33577mg / L NaCl, its NaCl rejection rate is 7% and CaCl2 rejection rate is 81%).

[0100] Example 1

[0101] The groundwater from a certain mine is used as the mine water to be treated, and its water quality composition is shown in Table 1:

[0102] Table 1

[0103]

[0104]

[0105] Preprocessing: The flow rate is 50m³ / min. 3 Mine water at a rate of / h is fed into a flocculation reactor, and polyaluminum chloride and polyacrylamide are added. The amount of polyaluminum chloride added is 200 mg / L, and the amount of polyacrylamide added is 2 mg / L, resulting in supernatant and sludge. The supernatant is then diverted at a flow rate of 50 m³ / h. 3 Ultrafiltration is performed at a rate of / h, with the overall operating pressure during the ultrafiltration process being 0–3 bar, yielding 5m³. 3 / h ultrafiltration concentrate and 45m 3 / h of ultrafiltration permeate, ultrafiltration concentrate and cleaning wastewater are returned to the flocculation reaction tank;

[0106] First concentration process: 45m 3 The ultrafiltration permeate is sent to the first reverse osmosis unit 1 for concentration treatment. The operating pressure is 55 bar, the temperature is 25°C, and the pH is adjusted to 6.5 to obtain 11.25 m³ / h of concentrated water. 3 / h of first reverse osmosis concentrate and 33.75m 3 / h First reverse osmosis permeate;

[0107] The first nanofiltration process separates sulfate ions: 11.25m 3 The first reverse osmosis concentrate is fed into the first-stage nanofiltration unit 2 for first-stage nanofiltration separation. The operating pressure is 15 bar, the membrane flux is 15.5 LMH, the temperature is 20°C, and the pH is adjusted to 7, yielding 4.39 m³ / h. 3 / h of first-stage nanofiltration concentrate and 6.86m 3 / h of primary nanofiltration permeate;

[0108] The second nanofiltration process separates sulfate ions: 4.39m 3The concentrate from the first-stage nanofiltration process is mixed with the first-stage reverse osmosis permeate (used as dilution water) at a volume ratio of 1:3 and then fed into the second-stage nanofiltration unit for secondary nanofiltration treatment. The operating pressure is 10 bar, the membrane flux is 14.1 LMH, the temperature is 28°C, and the pH is adjusted to 7 to obtain 5.05 mM... 3 / h of secondary nanofiltration concentrate and 12.49m 3 The secondary nanofiltration permeate is produced at a rate of / h, and the secondary nanofiltration concentrate is discharged to the tailings area for use.

[0109] The third nanofiltration process separates calcium ions: 6.86m 3 / h primary nanofiltration permeate, 12.49m 3 / h secondary nanofiltration permeate and 0.97m 3 The concentrate from the four-stage nanofiltration process is mixed and sent to a three-stage nanofiltration unit for the third nanofiltration treatment. The operating pressure is 16 bar, the membrane flux is 21.7 LMH, the temperature is 25 °C, and the pH is adjusted to 7 to obtain 1.02 m... 3 The three-stage nanofiltration concentrate has a flow rate of / h and a concentration of 19.31m³. 3 The three-stage nanofiltration permeate is produced per hour; the concentrated water from the three-stage nanofiltration is sent to an evaporation and concentration unit for concentration to obtain a calcium chloride concentrate with a concentration of 30 wt%.

[0110] The fourth nanofiltration process separates calcium ions: 19.31m 3 The permeate from the third-stage nanofiltration unit is fed into the fourth-stage nanofiltration unit 5 for fourth-stage nanofiltration treatment. The operating pressure is 8 bar, the temperature is 25°C, the membrane flux is 20.7 LMH, and the pH is adjusted to 7 to obtain 0.97 mM... 3 The four-stage nanofiltration concentrate has a flow rate of / h and a concentration of 18.34m³. 3 Four-stage nanofiltration permeate water per hour;

[0111] Second concentration process: 18.34m 3 The permeate from the fourth-stage nanofiltration process enters the reverse osmosis concentration unit at an operating pressure of 100 bar and a temperature of 25°C. The pH is adjusted to 6.5 to obtain 3.94 m³ / h of permeate. 3 / h of second reverse osmosis concentrate and 14.4m 3 / h of second reverse osmosis permeate;

[0112] Evaporation and crystallization: The second reverse osmosis concentrate is fed into an evaporation and crystallization device for crystallization treatment. The device uses plate heat exchange and the evaporation temperature is 70°C. Evaporation condensate and sodium chloride products are obtained respectively.

[0113] The water quality of permeate and concentrate at each stage of the above treatment process is shown in Table 2.

[0114] Table 2

[0115]

[0116] Results: The total calcium sulfate in the secondary nanofiltration concentrate accounts for 99.0% of the total calcium sulfate in the original water, meaning that 99% of the calcium sulfate in the wastewater has been removed.

[0117] The total calcium chloride in the tertiary nanofiltration concentrate accounts for 58.6% of the total calcium chloride in the original water, and more than 55% of the calcium chloride in the wastewater is recovered. After evaporation, concentration and separation, the tertiary nanofiltration concentrate yields a calcium chloride concentrate with a concentration of 30 wt%, which can meet the requirements of industrial-grade liquid calcium chloride.

[0118] The total sodium chloride content in the fourth-stage nanofiltration permeate accounts for 95% of the total sodium chloride content in the raw water (mine water), meaning that more than 90% of the sodium chloride in the wastewater has been recovered.

[0119] After the second reverse osmosis concentrate is evaporated and crystallized, the resulting sodium chloride product has a purity of 99.1%, which meets the standards for industrial salt use.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model, and they should all be covered within the scope of the claims and specification of this utility model. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This utility model is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A mine water treatment system, characterized in that, The treatment system includes: a first-stage reverse osmosis unit, a first-stage nanofiltration unit, a second-stage nanofiltration unit, a third-stage nanofiltration unit, a fourth-stage nanofiltration unit, a second-stage reverse osmosis unit, and an evaporation crystallization unit; wherein, The inlet of the first reverse osmosis unit is connected to a water inlet pipe, and the concentrate outlet of the first reverse osmosis unit is connected to the inlet of the first-stage nanofiltration unit. The concentrate outlet of the first-stage nanofiltration unit is connected to the inlet of the second-stage nanofiltration unit, and the inlet of the second-stage nanofiltration unit is also connected to a dilution water pipe, so that the concentrate and dilution water produced by the first nanofiltration unit can be combined and enter the second-stage nanofiltration unit. The product water outlet of the first-stage nanofiltration unit, the product water outlet of the second-stage nanofiltration unit, and the concentrate outlet of the fourth-stage nanofiltration unit are respectively connected to the inlet of the third-stage nanofiltration unit. The product water outlet of the three-stage nanofiltration unit is connected to the inlet of the four-stage nanofiltration unit; The inlet of the second reverse osmosis unit is connected to the product water outlet of the fourth-stage nanofiltration unit, and the concentrate outlet of the second reverse osmosis unit is connected to the inlet of the evaporation crystallization unit. The primary nanofiltration device and the secondary nanofiltration device each include a sulfate separation nanofiltration membrane, and the tertiary nanofiltration device and the quaternary nanofiltration device each include a calcium ion separation nanofiltration membrane.

2. The processing system according to claim 1, characterized in that, One or more of the permeate outlets of the first reverse osmosis unit, the second reverse osmosis unit, and the evaporation crystallization unit are connected to the dilution water pipeline of the secondary nanofiltration unit, so that one or more of the permeate water generated by the first reverse osmosis unit, the permeate water generated by the second reverse osmosis unit, and the evaporation condensate water generated by the evaporation crystallization unit are used as dilution water.

3. The processing system according to claim 1, characterized in that, The treatment system also includes a pretreatment unit, which includes a flocculation reaction tank, an ultrafiltration device, and a plate and frame filter press. The flocculation reaction tank is used to treat mine water by flocculation reaction to obtain supernatant and sludge. The outlet of the flocculation reaction tank is connected to the inlet of the ultrafiltration device so that the supernatant can enter the ultrafiltration device for ultrafiltration treatment to obtain ultrafiltration concentrate and ultrafiltration permeate. The sludge outlet of the flocculation reaction tank is connected to the feed inlet of the plate and frame filter press, so that the sludge can enter the plate and frame filter press for filter pressing to obtain sludge cake and filtrate. The concentrated water outlet of the ultrafiltration device and the liquid outlet of the plate and frame filter press are respectively connected to the water inlet of the flocculation reaction tank so that the ultrafiltration concentrated water and filtrate can enter the flocculation reaction tank. The product water outlet of the ultrafiltration device is connected to the water inlet pipe to be treated, so that the ultrafiltration product water can enter the first reverse osmosis device.

4. The processing system according to any one of claims 1-3, characterized in that, Under operating conditions of 25°C, 2.5 MPa, and a recovery rate of 70%, 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 sulfate separation nanofiltration membrane exhibits a calcium sulfate rejection rate ≥99%, a sodium chloride rejection rate <15%, and a calcium chloride rejection rate ≤50%.

5. The processing system according to any one of claims 1-3, characterized in that, Under operating conditions of 25°C, 1.5 MPa pressure, and 75% recovery rate, for a second aqueous solution containing 8850–8880 mg / L calcium chloride and 22320–33600 mg / L sodium chloride, the sodium chloride rejection rate of the calcium ion separation nanofiltration membrane is <10%, and the calcium chloride rejection rate is ≥80%.

6. The processing system according to any one of claims 1-3, characterized in that, The first reverse osmosis unit is a seawater desalination-grade reverse osmosis unit, and / or The second reverse osmosis device is an ultra-high pressure reverse osmosis device.

7. The processing system according to any one of claims 1-3, characterized in that, The primary nanofiltration device, secondary nanofiltration device, and tertiary nanofiltration device are all spiral wound nanofiltration membrane devices.

8. The processing system according to any one of claims 1-3, characterized in that, The secondary nanofiltration device is a disc tube nanofiltration membrane device.

9. The processing system according to any one of claims 1-3, characterized in that, The treatment system also includes an evaporation and concentration device, the inlet of which is connected to the concentrate outlet of the three-stage nanofiltration device.

10. The processing system according to any one of claims 1-3, characterized in that, The evaporation and crystallization device is an MVR evaporator or a multi-effect evaporator.

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