Efficient denitration water system for mine wastewater

Abstract

The utility model provides an efficient nitrate water removal system for mine water wastewater, which comprises a nanofiltration salt separation membrane unit, the nanofiltration salt separation membrane unit is connected with a nitrate water hardness removal unit, and the nanofiltration salt separation membrane unit is sequentially connected with the nitrate water hardness removal unit, a nitrate water reverse osmosis membrane unit, a concentrated nitrate water crystallization unit and a nitrate water evaporation salt separation unit; communicated high-salinity wastewater is arranged at an inlet of the nanofiltration salt separation membrane unit, and the nanofiltration salt separation membrane unit comprises a high-salinity adjusting tank, a nanofiltration salt separation membrane and a nanofiltration salt separation concentrated discharge valve. Through the saltpeter water hardness removal unit, softening and hardness removal treatment is carried out on the saltpeter water reverse osmosis membrane unit before concentration, beam type precipitation and immersed ultrafiltration are adopted to improve the effluent quality, and it is guaranteed that the subsequent saltpeter water reverse osmosis membrane unit and the concentrated saltpeter water crystallization unit operate better. And through the concentrated nitrate water crystallization unit, the nitrate mother liquor crystallized by the concentrated nitrate water crystallization unit is subjected to secondary nanofiltration salt separation, so that the device has a relatively high popularization value.

Description

Technical Field

[0001] The utility model relates to the field of wastewater treatment, in particular to a high-efficiency denitrification system for mine wastewater. Background Art

[0002] The mine wastewater treatment process will produce a high-salt wastewater. If it is discharged directly into the environment, it will cause salt pollution, such as salinization of the land; if it is directly evaporated and crystallized into mixed salts, there will be serious environmental problems. The brine mainly contains two salts, sodium chloride and sodium sulfate. If these two salts can be efficiently separated to produce industrial-grade sodium chloride and sodium sulfate, the salt problem of high-salt mine wastewater will be solved.

[0003] At present, the mainstream processes are thermal process and membrane process. Since the thermal process requires high process control accuracy, especially the nitrate crystallizer requires very precise process control, once the process control fluctuates or the water quality fluctuates, the purity of the nitrate will be low and cannot meet the industrial grade requirements. The membrane process has a certain amount of energy waste because evaporation crystallization is a high-temperature operation and freezing crystallization is a low-temperature operation. For this reason, we propose an efficient denitrification water system for mine water wastewater to solve the above problems. Utility Model Content

[0004] The utility model provides a high-efficiency denitrification system for mine wastewater, which solves the problem that the thermal process control requires high precision, which easily leads to low purity of the nitrate, and fails to meet industrial-grade requirements; evaporation crystallization is a high-temperature operation, and freezing crystallization is a low-temperature operation, which results in a certain amount of energy waste.

[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is: a high-efficiency denitrification system for mine wastewater, including a nanofiltration salt separation membrane unit, the nanofiltration salt separation membrane unit is connected to a nitrate water hardness removal unit, the nanofiltration salt separation membrane unit is sequentially connected to the nitrate water hardness removal unit, the nitrate water reverse osmosis membrane unit, the concentrated nitrate water crystallization unit and the nitrate water evaporation salt separation unit;

[0006] A connected high-salt wastewater is provided at the inlet of the nanofiltration salt separation membrane unit, and the nanofiltration salt separation membrane unit comprises a high-salt regulating tank, a nanofiltration salt separation membrane and a nanofiltration salt separation concentrate discharge valve.

[0007] In the preferred embodiment, the high-salt regulating tank is connected to the nanofiltration salt separation membrane and the nanofiltration salt separation and concentration discharge valve in sequence, and the nanofiltration salt separation and concentration discharge valve is connected to the first intermediate tank.

[0008] In the preferred embodiment, the nitrate water hardness removal unit includes a hardness removal reaction tank and an immersed ultrafiltration membrane, the hardness removal reaction tank is connected to the first intermediate tank, the immersed ultrafiltration membrane is connected to the nitrate water tank, and the nitrate water tank is connected to the concentrating reverse osmosis membrane of the nitrate water reverse osmosis membrane unit.

[0009] In the preferred embodiment, the hardness removal reaction tank is connected to the beam sedimentation tank and the immersed ultrafiltration membrane in sequence, the beam sedimentation tank and the immersed ultrafiltration membrane are both connected to the hardness removal sludge pump, the hardness removal sludge pump is connected to the filter press, and the hardness removal sludge pump and the filter press are both connected to the hardness removal reaction tank.

[0010] In the preferred embodiment, the concentrated nitrate crystallization unit includes a hardness removal intermediate tank, which is connected to the primary preheater, the secondary preheater, the main heater, the MVR flash tank, the centrifugal dehydrator and the mother liquor intermediate tank in sequence, the primary preheater is connected to the water production discharge unit, and the centrifugal dehydrator discharges sodium sulfate salt.

[0011] In the preferred embodiment, the concentrated nitrate crystallization unit discharges sodium chloride salt,

[0012] In the preferred embodiment, the concentrated nitric acid water crystallization unit also includes a non-condensable gas cooler, a main heater and an MVR flash tank form a circulating loop, the other end of the main heater forms a circulating loop with a secondary preheater, the secondary preheater is connected to the non-condensable gas cooler, and the non-condensable gas cooler is connected to the nitric acid water evaporation and salt separation unit.

[0013] In the preferred embodiment, the nitric acid water evaporation and salt separation unit includes a dilution tank, the dilution tank is connected to the nitric acid mother liquor nanofiltration membrane, the produced water effluent unit is connected to the dilution tank, and the produced water effluent unit includes a mixing tank.

[0014] The beneficial effects of the utility model are as follows: compared with the traditional membrane salt separation process, the advantages are: through the brine reverse osmosis membrane unit and the nitrate water reverse osmosis membrane unit, the brine and nitrate water after membrane salt separation are concentrated by high-pressure reverse osmosis membrane respectively, thereby reducing the scale of the evaporation crystallization unit and reducing the energy consumption of the system.

[0015] The nitrate water hardness removal unit softens and removes hardness from the nitrate water before concentration by the nitrate water reverse osmosis membrane unit, and "beam sedimentation + submerged ultrafiltration" is used to improve the effluent quality, ensuring better operation of the subsequent nitrate water reverse osmosis membrane unit and concentrated nitrate water crystallization unit.

[0016] Through the concentrated nitrate water crystallization unit, the nitrate mother liquor after crystallization of the concentrated nitrate water crystallization unit is subjected to secondary nanofiltration salt separation, and the nitrate water is used to evaporate the crystallization unit to increase the yield of nitrate. The purity of sodium sulfate can reach the industrial first-class product, and the sodium sulfate yield is greatly improved, which has great promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The utility model is further described below in conjunction with the accompanying drawings and embodiments;

[0018] Figure 1 It is a process principle diagram of the overall structure of the utility model;

[0019] Figure 2 It is a flow chart of the equipment of the overall structure of the utility model;

[0020] Figure 3 This is a flow chart of the nanofiltration salt separation membrane unit of the utility model;

[0021] Figure 4 This is a flow chart of the nitrate water hardness removal unit of the utility model;

[0022] Figure 5 This is a flow chart of the concentrated nitrate crystallization unit of the utility model;

[0023] Figure 6 This is a flow chart of the nitrate evaporation and salt separation unit of the utility model;

[0024] Figure 7 It is a thermal process principle diagram of the prior art of the utility model;

[0025] Figure 8 The utility model is a schematic diagram of the membrane process principle of the prior art;

[0026] In the figure: high-salt wastewater 1; nanofiltration salt separation membrane unit 2; high-salt regulating tank 201; nanofiltration salt separation membrane 202; nanofiltration salt separation and concentration valve 203; nitrate water hardness removal unit 6; hardness removal reaction tank 601; beam sedimentation tank 602; immersed ultrafiltration membrane 603; hardness removal sludge pump 604; filter press 605; nitrate water reverse osmosis membrane unit 7; concentrated nitrate water crystallization unit 8; hardness removal intermediate tank 801; primary preheater 802; secondary preheater 803; MVR condensate tank 804; main heater 805; MVR flash tank 806; centrifugal dehydrator 807; mother liquor intermediate tank 808; non-condensable gas cooler 809; nitrate water evaporation and salt separation unit 9; dilution tank 901; nitrate mother liquor nanofiltration membrane 902; produced water discharge unit 10; mixing tank 1001; nitrate water tank 12; first intermediate tank 13. DETAILED DESCRIPTION

[0027] Embodiment 1:

[0028] like Figure 1-8 In the invention, a high-efficiency denitrification system for mine wastewater includes a nanofiltration salt separation membrane unit 2, the nanofiltration salt separation membrane unit 2 is connected to a nitrate water hardness removal unit 6, the nanofiltration salt separation membrane unit 2 is sequentially connected to the nitrate water hardness removal unit 6, the nitrate water reverse osmosis membrane unit 7, the concentrated nitrate water crystallization unit 8 and the nitrate water evaporation salt separation unit 9;

[0029] The inlet of the nanofiltration salt separation membrane unit 2 is provided with a connected high-salt wastewater 1, and the nanofiltration salt separation membrane unit 2 includes a high-salt regulating tank 201, a nanofiltration salt separation membrane 202 and a nanofiltration salt separation concentration valve 203. With this structure, based on the basic principle of membrane separation, since the nitrate mother liquor is a salt solution close to saturation, the membrane system cannot process a saturated salt solution. Therefore, the utility model adopts a dilution process, using the clean water produced by other units in the system to dilute the nitrate mother liquor, and after reaching the working concentration of the nanofiltration salt separation membrane, the divalent salt and the monovalent salt are separated by the nanofiltration salt separation membrane. The water produced by the nanofiltration salt separation membrane of the nitrate water evaporation mother liquor is mainly a salt solution of sodium chloride, and the concentrated water of the nanofiltration salt separation membrane of the nitrate water evaporation mother liquor can be used as the inlet water of the concentrated nitrate water crystallization unit 8. In this way, the nitrate mother liquor can be circulated in the system after separating the monovalent and divalent salts, thereby improving the yield of nitrate.

[0030] The advantages of the conventional membrane salt separation process are: the nitrate water is concentrated by using a high-pressure reverse osmosis membrane through the nitrate water reverse osmosis membrane unit 7, thereby reducing the scale of the evaporation crystallization unit and reducing the energy consumption of the system.

[0031] The nitrate water hardness removal unit 6 softens and removes hardness from the nitrate water reverse osmosis membrane unit 7 before concentration, and "beam sedimentation + submerged ultrafiltration" is used to improve the effluent quality, ensuring better operation of the subsequent nitrate water reverse osmosis membrane unit 7 and concentrated nitrate water crystallization unit 8.

[0032] The concentrated nitrate water crystallization unit 8 is used to separate the nitrate mother liquor after crystallization by secondary nanofiltration, so that the water-producing brine and concentrated nitrate water are circulated to two sets of evaporation crystallization units respectively, thereby increasing the production of salt and nitrate, thereby greatly reducing the production of impurity salts. The purity of sodium chloride and sodium sulfate can reach industrial first-class products, and the yield of sodium chloride and sodium sulfate is greatly improved.

[0033] In the preferred embodiment, the high salt regulating tank 201 is connected to the nanofiltration salt separation membrane 202 and the nanofiltration salt separation and concentration discharge valve 203 in sequence, and the nanofiltration salt separation and concentration discharge valve 203 is connected to the first intermediate tank 13. According to this structure, the nanofiltration salt separation membrane unit 2 includes a high salt regulating tank 201, a nanofiltration salt separation membrane 202, a nanofiltration salt separation and concentration discharge valve 203, a high salt water booster pump and a nanofiltration salt separation membrane circulation pump, a high salt water booster pump is provided between the high salt regulating tank 201 and the nanofiltration salt separation membrane 202, and a nanofiltration salt separation membrane circulation pump is provided between the nanofiltration salt separation membrane 202 and the nanofiltration salt separation and concentration discharge valve 203.

[0034] The high-salt water booster pump provides reverse osmosis pressure for the nanofiltration salt separation membrane 202 to ensure the water production rate and separation efficiency; the nanofiltration salt separation membrane 202 plays the role of separating brine and nitrate water; the nanofiltration salt separation membrane circulation pump maintains a high flushing flow rate on the surface of the nanofiltration salt separation membrane 202 to reduce fouling; the nanofiltration salt separation concentrate valve 203 is the key to controlling the brine-nitrate water ratio, and the pressure on the concentrate side is controlled by controlling the opening of the valve, thereby controlling the brine output and nitrate water output.

[0035] To ensure a good salt separation efficiency, the head of the high-salt water booster pump needs to be 18bar~50bar. To reduce the fouling of the nanofiltration salt separation membrane 202, the flow rate of the nanofiltration salt separation membrane circulation pump needs to reach 0.2~2 times the flow rate of the high-salt water booster pump. To obtain a better separation effect, the flux of the nanofiltration salt separation membrane 202 is controlled at 10~30L / m2·h. The brine produced from the nanofiltration salt separation membrane unit 2 is concentrated by a brine concentration reverse osmosis membrane, and the water produced meets the standards and is discharged. The concentrated brine is sent to the concentrated nitric acid crystallization unit 8 to evaporate and crystallize sodium chloride salt.

[0036] In the preferred embodiment, the nitrate water hardness removal unit 6 includes a hardness removal reaction tank 601 and an immersed ultrafiltration membrane 603, the hardness removal reaction tank 601 is connected to the first intermediate tank 13, the immersed ultrafiltration membrane 603 is connected to the nitrate water tank 12, and the nitrate water tank 12 is connected to the concentrated reverse osmosis membrane of the nitrate water reverse osmosis membrane unit 7. With this structure, the nitrate water reacts with the softening agent sodium hydroxide and sodium carbonate in the hardness removal reaction tank 601, and the calcium and magnesium ions in the nitrate water become precipitates. The muddy water mixture first passes through the beam sedimentation tank 602 to remove most of the sedimentation mud, and the supernatant passes through the immersed ultrafiltration membrane 603 to remove the suspended matter to below 50ppm, thereby solving the problem of calcium and magnesium scaling for the subsequent membrane concentration unit. The mud intercepted in the beam sedimentation tank 602 and the immersed ultrafiltration membrane 603 is transported to two places by the hardness removal mud pump 604. One is the filter press 605, so that the hardness removal sludge is discharged from the system, and the other is the hardness removal reaction tank 601, which serves as a precipitation seed to promote the precipitation and growth of the hardness removal reaction precipitation, and facilitate the separation of the beam precipitation. In order to ensure that the calcium and magnesium in the nitrate water are fully precipitated, the pH value in the hardness removal reaction tank 601 is controlled between 10 and 12. In order to ensure that the beam sedimentation tank 602 has a better mud-water separation effect, the calcium and magnesium precipitates need to have a sufficiently large particle size. The mud concentration in the hardness removal mud pump 604 to the hardness removal reaction tank 601 ensures that the suspended matter content in the hardness removal reaction tank 601 is 1~10g / L. In order to ensure that the immersed ultrafiltration membrane 603 is not easily blocked by dirt, its flux is controlled at 2~6 L / m2·h.

[0037] In the preferred embodiment, the hardness removal reaction tank 601 is connected to the beam sedimentation tank 602 and the immersed ultrafiltration membrane 603 in sequence, the beam sedimentation tank 602 and the immersed ultrafiltration membrane 603 are both connected to the hardness removal sludge pump 604, the hardness removal sludge pump 604 is connected to the filter press 605, and the hardness removal sludge pump 604 and the filter press 605 are both connected to the hardness removal reaction tank 601.

[0038] In the preferred embodiment, the concentrated nitrate crystallization unit 8 includes a hardness removal intermediate tank 801, which is connected to the primary preheater 802, the secondary preheater 803, the main heater 805, the MVR flash tank 806, the centrifugal dehydrator 807 and the mother liquor intermediate tank 808 in sequence. The primary preheater 802 is connected to the water production and discharge unit 10, and the centrifugal dehydrator 807 discharges sodium sulfate salt. With this structure, the concentrated nitrate crystallization unit 8 adopts a mechanical steam recompression evaporation crystallization process. The primary preheater 802 and the secondary preheater 803 respectively recover the heat of the condensate and non-condensable gas discharged from the system; a nitrate MVR compressor is provided between the main heater 805 and the MVR flash tank 806.

[0039] The nitrate water MVR compressor heats and pressurizes the secondary steam generated by the MVR flash tank 806 and then presses it into the main heater 805 to recover the latent heat in the steam, thereby improving thermal efficiency; the MVR flash tank 806 is provided with a nitrate water MVR slurry effluent pump that forms a loop connection, and the nitrate water MVR slurry effluent pump outlet is provided with two routes, one route goes to the centrifugal dehydrator 807 to separate the nitrate, and the other route is used as a circulation to ensure that there is always flowing fluid in the pipeline to avoid the deposition and blockage of the nitrate slurry in the pipeline;

[0040] A connected nitric acid mother liquor lifting pump is provided on one side of the mother liquor intermediate tank 808.

[0041] There are two routes at the outlet of the nitrate mother liquor lifting pump. One route is circulated back to the inlet of the main heater 805 for recirculation heating and evaporation of nitrate, and the second route is sent to the nitrate water evaporation and salt separation unit 9 for salt separation to increase the overall salt production of the system.

[0042] In order to ensure the stable evaporation of sodium sulfate and control the scaling tendency of each device in this unit, the liquid phase temperature in the 3MVR flash tank 806 is controlled at 50~65℃. In order to ensure that the energy consumption of the evaporation process is at a relatively economical level and the salt output rate is guaranteed, the pressure ratio of the nitrate water MVR compressor is controlled at 1.5~2.2. In order to ensure that there is no scaling or salt accumulation inside the main heater 805, the main heater 805 adopts a vertical single-tube fixed tube plate heat exchanger, with brine flowing in the tube side and steam flowing in the shell side. The brine flow rate in the tube side is 1.5~3m / s. As the concentrated nitrate water crystallization unit 8 concentrates and crystallizes the concentrated nitrate water, sodium sulfate and sodium chloride will reach the eutectic point. If it is further concentrated, a eutectic mixed salt of sodium sulfate and sodium chloride will be produced instead of pure sodium sulfate. Therefore, an appropriate amount of concentrated nitrate water mother liquor needs to be discharged.

[0043] A small amount of the discharged concentrated nitrate mother liquor is discharged to the impure salt drying and crystallization unit 5 to produce impure salts according to the concentration of divalent impurity ions in the raw water to ensure that there is no accumulation of impurities in the system. Most of it is discharged to the nitrate water evaporation and salt separation unit 9 for secondary salt separation.

[0044] In the preferred embodiment, the concentrated nitrate crystallization unit 8 discharges sodium chloride salt.

[0045] In the preferred embodiment, the concentrated nitrate crystallization unit 8 also includes a non-condensable gas cooler 809, a main heater 805 and an MVR flash tank 806 form a circulating loop, and the other end of the main heater 805 forms a circulating loop with a secondary preheater 803, and the secondary preheater 803 is connected to the non-condensable gas cooler 809, and the non-condensable gas cooler 809 is connected to the nitrate evaporation and salt separation unit 9. With this structure, based on the basic principle of membrane separation, since the nitrate mother liquor is a salt solution close to saturation, the membrane system cannot process a saturated salt solution, so the utility model adopts a dilution process, and the nitrate mother liquor is diluted by the clean water produced by other units in the system, and after reaching the working concentration of the nanofiltration salt separation membrane, the divalent salt and the monovalent salt are separated by the nanofiltration salt separation membrane. The concentrated water of the nitrate evaporation mother liquor nanofiltration salt separation membrane can be used as the water inlet of the concentrated nitrate crystallization unit 8. With this nitrate mother liquor, after separating the monovalent and divalent salts, it can be circulated in the system, thereby improving the yield of salt and nitre.

[0046] In the preferred embodiment, the nitrate water evaporation and salt separation unit 9 includes a dilution tank 901, the dilution tank 901 is connected to the nitrate mother liquid nanofiltration membrane 902, the produced water effluent unit 10 is connected to the dilution tank 901, and the produced water effluent unit 10 includes a mixing tank 1001. According to this structure, a nitrate mother liquid nanofiltration and salt separation booster pump is provided between the dilution tank 901 and the nitrate mother liquid nanofiltration membrane 902, a nitrate mother liquid nanofiltration and salt separation concentration discharge valve is provided on one side of the nitrate mother liquid nanofiltration membrane 902, and a nitrate mother liquid nanofiltration and salt separation circulation pump is provided between the nitrate mother liquid nanofiltration and salt separation concentration discharge valve and the nitrate mother liquid nanofiltration and salt separation booster pump.

[0047] The function of the dilution tank 901 is to dilute the nitrate mother liquor to meet the salt concentration applicable to the nitrate mother liquor nanofiltration membrane 902;

[0048] The nitrate mother liquor nanofiltration salt separation booster pump provides reverse osmosis pressure for the separation membrane to ensure the water production rate and separation efficiency; the nitrate mother liquor nanofiltration membrane 902 plays the role of separating brine and nitrate water; the nitrate mother liquor nanofiltration salt separation circulation pump maintains a high flushing flow rate on the surface of the nitrate mother liquor nanofiltration membrane 902 to reduce fouling and clogging; the nitrate mother liquor nanofiltration salt separation concentrate discharge valve is the key to controlling the brine-nitrate water ratio. By controlling the opening of the valve, the concentrate side pressure is controlled, thereby controlling the brine output and nitrate water output. The mixing ratio of nitrate mother liquor and clean water is between 1:4 and 1:10. In order to ensure a good salt separation efficiency, the head of the nitrate mother liquor nanofiltration salt separation booster pump needs to be 60bar~120bar. In order to reduce the fouling and clogging of the nanofiltration separation membrane, the flow rate of the nitrate mother liquor nanofiltration salt separation circulation pump needs to reach 0.3~3 times the flow rate of the nitrate mother liquor nanofiltration salt separation booster pump. In order to obtain a better separation effect, the flux of the nitrate mother liquor nanofiltration membrane 902 is controlled at 5~15L / m2·h.

[0049] The main function of the water production and discharge unit 10 is to mix the qualified purified water produced by each unit and then discharge it.

[0050] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. An efficient denitrification system for mine wastewater, characterized by: The nanofiltration salt separation membrane unit (2) is connected to the nitrate water hardness removal unit (6), and the nanofiltration salt separation membrane unit (2) is sequentially connected to the nitrate water hardness removal unit (6), the nitrate water reverse osmosis membrane unit (7), the concentrated nitrate water crystallization unit (8) and the nitrate water evaporation salt separation unit (9); The inlet of the nanofiltration salt separation membrane unit (2) is provided with high-salt wastewater (1) in communication, and the nanofiltration salt separation membrane unit (2) comprises a high-salt adjustment tank (201), a nanofiltration salt separation membrane (202), and a nanofiltration salt separation concentration discharge valve (203).

2. The high-efficiency denitrification system for mine wastewater according to claim 1, characterized in that: The high-salt regulating tank (201) is connected in sequence to the nanofiltration salt separation membrane (202) and the nanofiltration salt separation concentrate discharge valve (203), and the nanofiltration salt separation concentrate discharge valve (203) is connected to the first intermediate tank (13).

3. The high-efficiency denitrification system for mine wastewater according to claim 1 is characterized by: The nitrate water hardness removal unit (6) comprises a hardness removal reaction tank (601) and an immersed ultrafiltration membrane (603), the hardness removal reaction tank (601) is connected to the first intermediate tank (13), the immersed ultrafiltration membrane (603) is connected to the nitrate water tank (12), and the nitrate water tank (12) is connected to the concentrating reverse osmosis membrane of the nitrate water reverse osmosis membrane unit (7).

4. A highly efficient denitrification system for mine wastewater according to claim 3, characterized in that: The hardness removal reaction tank (601) is connected to the beam sedimentation tank (602) and the immersed ultrafiltration membrane (603) in sequence, the beam sedimentation tank (602) and the immersed ultrafiltration membrane (603) are both connected to the hardness removal mud pump (604), the hardness removal mud pump (604) is connected to the filter press (605), and the hardness removal mud pump (604) and the filter press (605) are both connected to the hardness removal reaction tank (601).

5. The high-efficiency denitrification system for mine wastewater according to claim 1 is characterized by: The concentrated nitrate crystallization unit (8) includes a hardness removal intermediate tank (801), which is connected to a primary preheater (802), a secondary preheater (803), a main heater (805), an MVR flash tank (806), a centrifugal dehydrator (807) and a mother liquor intermediate tank (808) in sequence, and the primary preheater (802) is connected to a water production discharge unit (10), and the centrifugal dehydrator (807) discharges sodium sulfate salt.

6. A highly efficient denitrification system for mine wastewater according to claim 5, characterized in that: The concentrated nitrate crystallization unit (8) discharges sodium chloride salt.

7. The high-efficiency denitrification system for mine wastewater according to claim 5 is characterized by: The concentrated nitrate water crystallization unit (8) also includes a non-condensable gas cooler (809), a main heater (805) and an MVR flash tank (806) form a circulating loop, the other end of the main heater (805) forms a circulating loop with a secondary preheater (803), the secondary preheater (803) is connected to the non-condensable gas cooler (809), and the non-condensable gas cooler (809) is connected to the nitrate water evaporation and salt separation unit (9).

8. The high-efficiency denitrification system for mine wastewater according to claim 1 is characterized by: The nitrate water evaporation and salt separation unit (9) comprises a dilution tank (901), the dilution tank (901) is connected to the nitrate mother liquid nanofiltration membrane (902), the produced water discharge unit (10) is connected to the dilution tank (901), and the produced water discharge unit (10) comprises a mixing tank (1001).

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