A steel comprehensive wastewater concentrated brine reduction and resource treatment combined method and system

Abstract

The application provides a steel comprehensive wastewater concentrated brine reduction and resource treatment combined method and system. The method comprises the following steps: making the concentrated brine generated after the treatment of the steel comprehensive wastewater sequentially enter a concentrated water high-density pool for removing hardness and fluorine, an activated carbon filtration and adsorption organic pollutant unit, a multi-medium filtration unit, a concentrated water ultrafiltration unit, an ion exchange limit hardness removal unit, a high-efficiency reverse osmosis unit, a silicon removal high-density pool unit, an immersed ultrafiltration unit, a nanofiltration unit, a high-pressure reverse osmosis unit and an MVR unit for treatment. The application can further treat the concentrated brine of the steel plant comprehensive wastewater, can achieve zero wastewater discharge, can realize the cascade utilization and resource recycling of the plant water, and can balance the economy and the popularization.

Description

Technical Field

[0001] This invention relates to a combined method and system for reducing and recycling concentrated brine from steelmaking wastewater, belonging to the field of industrial wastewater treatment technology. Background Technology

[0002] As major water and wastewater consumers, steel enterprises rely heavily on wastewater reuse to ensure the achievement of water consumption targets per ton of steel. Comprehensive wastewater accounts for over 70% of the total wastewater generated in steel plants (the remaining 30% includes small amounts of treated coking wastewater, cold rolling wastewater, desulfurization waste liquid, and other special wastewater, all of which are treated and disposed of independently). Comprehensive wastewater treatment and reuse in the steel industry is an effective water-saving measure that aligns with the development characteristics of steel enterprises, and its reuse cost is relatively low, making it an important direction for the resource utilization of wastewater in the steel industry.

[0003] However, even after reuse and concentration, 10-15% concentrated brine will still be generated in the total wastewater volume. In the past few years, steel companies have coordinated production to manage internal water use according to the principles of tiered water supply and differentiated utilization. This concentrated brine is mainly used for blast furnace slag flushing and steelmaking slag curing, which has basically achieved zero discharge of comprehensive wastewater from the plant area. However, with increasingly stringent environmental policies, some concentrated brine leakage is inevitable in blast furnace slag flushing and steelmaking slag curing. At the same time, users of this concentrated brine have raised feedback on the impact of the brine quality on the quality of subsequent products, and the corrosion of pipelines and equipment materials caused by high chloride ion content. In particular, blast furnace slag flushing has always been the largest user of concentrated brine, but the chloride ion enrichment in the concentrated brine has greatly affected the quality of the microcrystalline powder product (the chloride content of the finished microcrystalline powder should be less than 0.06%). Therefore, how to further optimize the quality of this concentrated brine, minimize its volume, and find better utilization directions has been a research and development topic that the steel industry has been actively promoting in recent years.

[0004] Currently, extensive research and engineering applications have been conducted on reducing the volume of high-salinity industrial wastewater, separating salts for resource recovery, and achieving zero discharge, resulting in numerous process routes for concentrated brine treatment. However, research and application in the treatment of concentrated brine from comprehensive wastewater in the steel industry are limited. Most research focuses on wastewater from industries with high treatment difficulty and stringent environmental regulations, such as coal chemical wastewater, coking wastewater, and organic high-salinity wastewater. Furthermore, current zero-discharge treatment approaches for high-salinity wastewater primarily involve separating salts and crystallizing them to prepare resource-based industrial salts, with a small portion of the mother liquor disposed of through the preparation of mixed salts. This approach results in a significant investment and limited resource recovery value, placing a heavy burden on enterprises, making the equipment unaffordable, and ultimately rendering it unusable.

[0005] Therefore, it is crucial to develop a stable treatment process that can reliably reduce the amount of concentrated brine, improve the quality of the concentrated brine, and utilize it as a resource to address the problem of concentrated brine treatment generated during the comprehensive wastewater reuse process in the steel industry. At the same time, the process must be compatible with the actual operation of the steel plant and be affordable to build and use.

[0006] Currently, existing technologies propose treatment process ideas for zero-discharge treatment of steel wastewater using membrane concentration and desalination. For example, CN111825259A discloses a method for zero-discharge treatment of steel wastewater using membrane concentration and desalination. The process route is as follows: the concentrated brine produced after steel wastewater is concentrated by reverse osmosis in a reuse unit is first treated with ozone catalytic oxidation to remove organic pollutants, and then enters a purification nanofiltration unit for desalination. The nanofiltration permeate enters the reverse osmosis unit for concentration, and the resulting concentrated brine enters a silica removal and softening unit for pretreatment to remove easily scale-forming substances. Afterward, it enters microfiltration and electrodialysis units to achieve re-enrichment of the concentrate, and finally enters an MVR evaporation unit to produce sodium chloride industrial salt. The nanofiltration concentrate directly enters the coking concentrate crystallization system in the plant area for direct salt evaporation. The main advantage of this technology is that it performs nanofiltration desalination on the concentrated steel wastewater, followed by volume reduction through membrane concentration, electrodialysis, and evaporation crystallization technologies to produce high-quality reclaimed water and industrial salt.

[0007] However, this technology has the following unreasonable aspects in its process unit setup: First, the pretreatment stage only uses chemical softening. Before entering nanofiltration for desalination, a first-stage reverse osmosis concentration is performed, but no further deep softening process is implemented. Chemical softening and precipitation processes can typically reduce wastewater hardness to 50 mg / L. After reverse osmosis concentration, the hardness on the concentrate side becomes concentrated. If this is not removed, it will lead to severe secondary and tertiary scaling problems in the subsequent nanofiltration desalination unit. Furthermore, the formed calcium scale is mainly calcium sulfate, which forms a dense crystalline structure on the nanofiltration membrane surface and penetrates deep into the membrane layer. This significantly increases the probability of membrane element damage during chemical cleaning. Second, the "silicon and fluoride removal + softening" process is placed on the nanofiltration permeate side. Typically, the nanofiltration permeate side is a brine system mainly composed of sodium chloride, with a large amount of divalent salts, such as calcium and magnesium, remaining on the concentrate side. Therefore, there is a significant risk of scaling in subsequent processes on the nanofiltration concentrate side.

[0008] CN105565569A discloses an enhanced deep concentration system and process for high-salinity industrial wastewater. The process route is as follows: Concentrated brine undergoes pretreatment in an equalization tank, softening sedimentation tank, and V-type filter to remove hardness. It then enters a dual-membrane process of ultrafiltration and reverse osmosis for concentration. The resulting concentrated water enters an ion exchange unit for further hardness removal, followed by a nanofiltration system. The nanofiltration concentrate enters a frequent-reverse-polarity electrodialysis (EDR) unit for concentration, and then enters a freeze crystallization system to prepare sodium sulfate decahydrate (Glauber's salt). The nanofiltration permeate undergoes a two-stage reverse osmosis concentration process, and its concentrate also enters a frequent-reverse-polarity electrodialysis (EDR) unit for further concentration, before entering an evaporation crystallization unit to prepare sodium chloride. The permeate from the EDR unit contains a small amount of organic pollutants, which are treated by an advanced oxidation unit before being stored in a permeate tank. The main advantages of this technology are the use of advanced oxidation technology, which effectively solves the problem of high COD content after highly concentrated brine, resulting in high purity crystallized salt. The system also utilizes frequent-reverse-polarity electrodialysis technology, resulting in low overall operating pressure in the concentration section.

[0009] Although this technology employs a frequent-reversal electrodialysis device, it is limited by the difficulty in preparing the electrodialysis membrane, resulting in a high system failure rate, frequent membrane module replacement, and numerous leaks, leading to high operation and maintenance costs and increased workload for workers. As a result, there are currently few application cases in the zero-discharge treatment of concentrated brine.

[0010] CN2055 28213U discloses a zero-discharge system for high-salinity industrial wastewater desalination. The process route is as follows: Wastewater first undergoes chemical softening and concentration / desalination treatment in a precision pretreatment unit and a membrane separation and concentration unit. The resulting concentrated brine then enters a first-stage desalination system. This system relies on nanofiltration for desalination. The nanofiltration concentrate and permeate are separated and concentrated by a high-pressure flat-plate membrane system before entering an advanced oxidation unit to further oxidize and remove enriched organic pollutants. After advanced oxidation treatment, the first-stage nanofiltration permeate and concentrate enter a second-stage desalination and concentration unit. The second-stage desalination system employs two processes: one uses two sets of multi-effect evaporators / MVR evaporators to concentrate the nanofiltration permeate and concentrate after the first-stage desalination, respectively; the other uses one set of multi-effect evaporators / MVR evaporators to concentrate the nanofiltration permeate after the first-stage desalination, and a freeze crystallization system to concentrate the nanofiltration concentrate after the first-stage desalination. The mother liquor from the freeze crystallization enters the multi-effect evaporator / MVR evaporator on the nanofiltration permeate side for further recovery of residual sodium chloride. The main advantage of this technology is that it complements the advantages of the so-called two-stage salt separation system, achieving the most complete separation of inorganic salts and minimizing the production of mixed salts. The first-stage salt separation serves as a guarantee for the second-stage salt separation, ensuring the salt separation efficiency of the entire system even when the influent water quality fluctuates greatly, and enhancing the system's resistance to shock loads.

[0011] However, the effectiveness of this technology in separating salts depends on the first-stage nanofiltration system. The second-stage system is essentially an evaporation and crystallization device for salt removal. If the first-stage separation is ineffective, it will lead to an increase in the yield of impurities in the second-stage system. As a zero-discharge process for separating high-salt industrial wastewater, this technology is characterized by a long process flow, numerous pieces of equipment, and high investment, making it unsuitable for widespread application.

[0012] Therefore, developing a combined method and system for reducing and recycling concentrated brine from steelmaking wastewater remains one of the urgent problems to be solved in this field. Summary of the Invention

[0013] To address the aforementioned technical problems, the present invention aims to provide a combined method and system for reducing the volume and recycling the concentrated brine from steel plant wastewater. This method and system can further treat the concentrated brine after the steel plant's wastewater has been concentrated; it can also achieve cascaded utilization and resource recovery of water used within the plant area; and it simultaneously considers economic viability and scalability.

[0014] To achieve the above objectives, the first aspect of the present invention provides a combined method for reducing the volume and recycling the resources of concentrated brine from steelmaking wastewater, comprising the following steps:

[0015] (1) The concentrated brine produced after the treatment of the comprehensive wastewater of the iron and steel industry is fed into the hardening and defluoridation unit of the concentrated water high-density tank for treatment. In the hardening and defluoridation unit of the concentrated water high-density tank, sodium hydroxide, sodium carbonate, PFS, PAM and concentrated sulfuric acid are added in sequence to obtain the product water of the concentrated water high-density tank.

[0016] (2) The concentrated high-density tank product water is fed into the activated carbon filtration and adsorption unit for organic pollutant adsorption to obtain activated carbon filtration and adsorption product water.

[0017] (3) The activated carbon filtration adsorption product water is sequentially fed into the multi-media filtration unit and the concentrated water ultrafiltration unit for treatment to obtain concentrated water ultrafiltration product water.

[0018] (4) The concentrated ultrafiltration permeate is fed into the ion exchange extreme hardness removal unit for treatment to obtain ion exchange permeate;

[0019] (5) The ion exchange permeate is fed into a high-efficiency reverse osmosis unit for treatment to obtain high-efficiency reverse osmosis permeate as recycled water and high-efficiency reverse osmosis concentrate.

[0020] (6) The high-efficiency reverse osmosis concentrate is fed into the high-density desiliconization tank unit for treatment. Sodium hydroxide, sodium aluminate, PAC, PAM and concentrated sulfuric acid are added sequentially in the high-density desiliconization tank unit to obtain the high-density desiliconization tank permeate.

[0021] (7) The water produced by the high-density desiliconization tank is fed into the submerged ultrafiltration unit for treatment to obtain submerged ultrafiltration water;

[0022] (8) The submerged ultrafiltration permeate is fed into a nanofiltration unit for treatment to obtain nanofiltration permeate and nanofiltration concentrate as blast furnace slag flushing water.

[0023] (9) The nanofiltration permeate is fed into a high-pressure reverse osmosis unit for treatment to obtain high-pressure reverse osmosis permeate as recycled water and high-pressure reverse osmosis concentrate.

[0024] (10) The high-pressure reverse osmosis concentrate is fed into the MVR unit for treatment to obtain sodium chloride crystal salt, MVR evaporation mother liquor as blast furnace slag flushing water, and MVR condensate as recycled water.

[0025] In the above method, preferably, the concentrated brine is reverse osmosis concentrate produced after the steelmaking wastewater has been treated by an advanced treatment unit. The concentration factor of this reverse osmosis concentrate is approximately 8 times.

[0026] In the above method, preferably, the concentrated brine has the following characteristics: pH 7-8, COD content 100-150 mg / L, and Cl... - The content is 5000-10000 mg / L, SO4 2- The content is 2000-4000 mg / L, Na + The content is 11000~22000mg / L, F - The content is 10-25 mg / L, the total nitrogen content is 1-10 mg / L, the calcium content is 100-500 mg / L, the magnesium content is 10-100 mg / L, the TDS content is 18000-36000 mg / L, and the suspended solids content is 5-10 mg / L.

[0027] In the above method, preferably, in step (1), the added sodium hydroxide is a 30% sodium hydroxide solution, and the amount of sodium hydroxide added is 800-1500 mg / L; the added sodium carbonate is a 10% sodium carbonate solution, and the amount of sodium carbonate added is 500-1200 mg / L; the added PFS is a 10% PFS aqueous solution, and the amount of PFS added is 50-100 mg / L; the added PAM is a 0.1% PAM aqueous solution, and the amount of PAM added is 0.3-0.5 mg / L; the added concentrated sulfuric acid is a 98% concentrated sulfuric acid, and the amount added is 50-100 mg / L. It should be noted that the amounts of these substances added are all calculated based on the mass of the pure substances.

[0028] In the above method, preferably, in step (1), the total hardness of the concentrated water produced by the high-density tank is less than 50 mg / L and the fluoride content is less than 10 mg / L.

[0029] In this invention, RO concentrate is first pumped into the high-density concentrate tank for hardening and defluoridation treatment. Sodium hydroxide, soda ash, coagulant PFS, flocculant PAM, and concentrated sulfuric acid are added sequentially, and the order of dosing of different agents is optimized. Sodium hydroxide and soda ash are added first to make the pH of the wastewater about 11. Calcium and magnesium hardness and fluoride ions in the wastewater are removed by chemical softening. The pH value of the reaction zone is controlled to reduce the total hardness and fluoride content in the water with the least amount of reagents consumed, thereby achieving the maximum hardening and defluoridation effect.

[0030] In the above method, preferably, in step (2), the filtration rate of the activated carbon filter layer in the activated carbon filtration and adsorption unit for organic pollutants is 5 to 10 m / h.

[0031] In the above method, preferably, in step (2), the CODcr removal rate of the activated carbon filtration adsorption unit for organic pollutants is 60% to 90%.

[0032] In this invention, the concentrated brine produced by the high-density pool is then pumped into the activated carbon filtration and adsorption unit for organic pollutants. Through the adsorption of activated carbon, organic pollutants in the concentrated brine are effectively removed. The filtration speed of the activated carbon filter layer is designed to operate at 5 to 10 m / h.

[0033] In the above method, preferably, in step (3), the filter media in the multi-media filtration unit includes a combination of anthracite and quartz sand; the relative density of the anthracite is 1.4 to 1.6 and the particle size is 0.8 to 1.8 mm; the relative density of the quartz sand is 2.6 to 2.65 and the particle size is 0.5 to 1.2 mm.

[0034] In the above method, preferably, in step (3), the ultrafiltration membrane of the concentrate ultrafiltration unit retains substances with a particle size > 0.1 nm, the operating temperature is 15 to 40 °C, the operating pressure is 0.1 to 0.2 MPa, the water production rate is above 90%, and the SDI of the concentrate ultrafiltration water is < 5.

[0035] In this invention, the activated carbon filtration adsorption product water is pumped sequentially through a multi-media filtration unit and a concentrate ultrafiltration unit for treatment. The ultrafiltration membrane further separates particulate matter, macromolecular organic matter, microorganisms, etc. in the wastewater, achieving the effect of removing suspended solids and turbidity. The water production rate of the concentrate ultrafiltration unit is not less than 90%, ensuring that the product water SDI < 5, which meets the water quality requirements of the subsequent high-efficiency reverse osmosis unit.

[0036] In the above method, preferably, in step (4), the ion exchange limit hardening unit adopts a weak acidic cation exchange resin and / or a chelating cation exchange resin.

[0037] In the above method, preferably, step (4) further includes: pretreating and regenerating the cation exchange resin used in the ion exchange limit hardening unit with a sodium hydroxide solution in a co-current manner. The concentration of the sodium hydroxide solution can be conventionally adjusted by those skilled in the art, and the present invention does not impose any special limitations on it.

[0038] In the above method, preferably, in step (4), the total hardness of the ion exchange product water is less than 10 mg / L, more preferably less than 5 mg / L.

[0039] In this invention, the concentrated ultrafiltration permeate enters the ion exchange extreme hardness removal unit for treatment. Through weakly acidic cation exchange resin and / or chelating cation exchange resin, residual calcium and magnesium hardness in the water is completely removed, achieving extreme hardness removal even under high salinity conditions. The total hardness of the softened ion exchange permeate can be reduced to below 5 mg / L, ensuring the smooth operation of subsequent high-efficiency reverse osmosis and nanofiltration units and reducing the risk of scaling. The softened water then enters the high-efficiency reverse osmosis unit for further concentration and volume reduction. Simultaneously, the ion exchange resin is pretreated and regenerated using a sodium hydroxide solution fed in a co-current manner to ensure sufficient sodium ion conversion.

[0040] In the above method, preferably, in step (5), the high-efficiency reverse osmosis unit includes two reverse osmosis membranes and an inter-stage booster pump. The reverse osmosis membranes are anti-fouling reverse osmosis membranes. The inlet water temperature of the high-efficiency reverse osmosis unit is 20-35℃. The inlet water pressure of the first-stage reverse osmosis membrane is controlled at 1.5-2.0 MPa. The outlet water pressure of the first-stage reverse osmosis membrane decreases to below 0.15 MPa. The inter-stage booster pump increases the pressure to 2.0-2.5 MPa before it enters the second-stage reverse osmosis membrane. The water production rate of the high-efficiency reverse osmosis unit is 50%-65%.

[0041] In the above method, preferably, in step (5), the concentration factor of the high-efficiency reverse osmosis concentrate is 12 to 16 times.

[0042] In the above method, preferably, in step (5), the total removal rate of each solute in the high-efficiency reverse osmosis permeate is 95% to 97%, and the TDS is <1000 mg / L.

[0043] In this invention, the high-efficiency reverse osmosis unit concentrates the organic matter and dissolved solids in the wastewater. The reverse osmosis membrane is set in two sections and an inter-section booster pump is set. The reverse osmosis membrane is selected as an anti-fouling membrane. The high-efficiency reverse osmosis permeate meets the fresh water standard and can be reused as fresh water.

[0044] In the above method, preferably, in step (6), the added sodium hydroxide is a 30% sodium hydroxide solution, and the amount of sodium hydroxide added is 50-100 mg / L; the added sodium aluminate is a 10% sodium aluminate solution, and the amount of sodium aluminate added is 150-200 mg / L; the added PAC is a 10% PAC aqueous solution, and the amount of PAC added is 30-50 mg / L; the added PAM is a 0.1% PAM aqueous solution, and the amount of PAM added is 0.3-0.5 mg / L; the added concentrated sulfuric acid is a 98% concentrated sulfuric acid, and the amount added is 50-100 mg / L. It should be noted that the amounts of these substances added are all calculated based on the mass of the pure substances.

[0045] In the above method, preferably, in step (6), the total silicon content of the water produced by the high-density desiliconization tank is less than 20 mg / L.

[0046] In this invention, the concentrated water generated by high-efficiency reverse osmosis is pumped into a high-density desiliconization tank unit for separate desiliconization treatment. The concentration factor of the high-efficiency reverse osmosis concentrated water is about 12 to 16 times. At this time, the silicon content has been enriched by nearly 12 to 16 times, and the concentration has reached the upper limit of scaling tendency. Sodium hydroxide is added to adjust the pH of the wastewater to about 9. When the pH is about 9, sodium aluminate, coagulant PAC, and flocculant PAM are added. The dosage of the core agent sodium aluminate is twice the total silicon content of the influent, forming aluminum salt co-precipitation, removing silicon from the water in the form of precipitation. By controlling the reaction conditions in the desiliconization zone, the total silicon in the water is removed, and the total silicon in the treated wastewater is reduced to below 20 mg / L.

[0047] In the above method, preferably, in step (7), the ultrafiltration membrane of the submerged ultrafiltration unit retains substances with a particle size > 0.1 nm, the operating temperature is 15 to 40 °C, the operating pressure is 0.1 to 0.2 MPa, the water production rate is above 90%, and the SDI of the submerged ultrafiltration water is < 3.

[0048] In this invention, the permeate from the high-density silica removal tank flows into a submerged ultrafiltration unit by gravity for turbidity removal. The permeate rate of the submerged ultrafiltration unit is not less than 90%, achieving the effect of removing suspended solids and turbidity, ensuring that the permeate water SDI < 3, and meeting the influent water quality requirements of the subsequent nanofiltration unit. This invention does not use the existing "filter + external pressure ultrafiltration" combination process, greatly shortening the process flow and saving space.

[0049] In the above method, preferably, in step (8), the nanofiltration unit includes two nanofiltration membranes connected in series. The concentrate from the first nanofiltration membrane is the nanofiltration concentrate used as blast furnace slag flushing water. The permeate from the first nanofiltration membrane enters the second nanofiltration membrane for treatment. The concentrate from the second nanofiltration membrane enters the first nanofiltration membrane for recycling treatment. The permeate from the second nanofiltration membrane is the nanofiltration permeate.

[0050] In the above method, preferably, in step (8), the operating temperature of the nanofiltration unit is 20-35°C, the operating pressure is 1.0-2.5 MPa, the desalination rate is 50-60%, and the water production rate is 70-85%.

[0051] In the above method, preferably, in step (8), the sulfate removal rate of the nanofiltration unit is above 95%, and the COD removal rate is above 90%.

[0052] In the above method, preferably, in step (8), the chloride ion content of the nanofiltration concentrate is <2000 mg / L and the sulfate ion content is >8000 mg / L.

[0053] In this invention, the permeate from the submerged ultrafiltration system is pumped under pressure into a nanofiltration unit. The nanofiltration unit employs a two-stage nanofiltration membrane for salt separation. Utilizing the selective permeability of the nanofiltration membrane, monovalent ions (such as Cl-) can pass through the membrane element to the permeate side, while divalent ions (such as SO42-) can pass through. 2- Sodium chloride and organic matter are effectively retained on the concentrate side, achieving effective separation of sodium chloride from sodium sulfate and organic matter. The nanofiltration unit includes two nanofiltration membranes connected in series. The permeate from the first-stage nanofiltration membrane enters the second-stage nanofiltration membrane for further salt separation, thus obtaining a high-purity sodium chloride solution. This ensures the purity of sodium chloride in the nanofiltration permeate, facilitating the improvement of the quality of industrial salt produced by subsequent evaporation and crystallization. Simultaneously, the first-stage nanofiltration membrane is kept on standby for stable system operation. The concentrate from the first-stage nanofiltration membrane is pumped into an ultra-concentrated water tank for cascade disposal as blast furnace slag flushing water. The concentrate from the second-stage nanofiltration membrane returns to the feed water tank of the first-stage nanofiltration membrane for recycling. This invention employs a two-stage nanofiltration salt separation process, improving the overall system's salt separation efficiency and minimizing the production of mixed impurities.

[0054] In the above method, preferably, in step (9), the reverse osmosis membrane of the high-pressure reverse osmosis unit is a high-pressure resistant reverse osmosis membrane, the inlet water temperature of the high-pressure reverse osmosis unit is 20-35℃, the inlet water pressure is 6-8 MPa, the desalination rate is above 95%, and the water production rate is 60-75%.

[0055] In the above method, preferably, in step (9), the TDS of the high-pressure reverse osmosis permeate is <2000 mg / L.

[0056] In the above method, preferably, step (9) further includes: circulating a portion of the high-pressure reverse osmosis concentrate back to the inlet of the high-pressure reverse osmosis unit, wherein the circulating high-pressure reverse osmosis concentrate accounts for 10% to 20% (preferably 10% to 15%) of the total volume of the high-pressure reverse osmosis concentrate. Since the inlet water quality of the high-pressure reverse osmosis unit is relatively uniform, this invention adjusts the operating mode to circulate a portion of the high-pressure reverse osmosis concentrate back to the nanofiltration permeate tank, increasing the inlet water volume of the high-pressure reverse osmosis unit, reducing the tendency for scaling on the reverse osmosis membrane surface, and enabling the high-pressure reverse osmosis concentrate to achieve a high concentration rate.

[0057] In this invention, nanofiltration permeate enters a high-pressure reverse osmosis unit for high concentration. The reverse osmosis membrane is selected to be resistant to high pressure, with an inlet pressure of 6-8 MPa and a recovery rate of over 70%. This reduces the amount of water entering the MVR unit, and the high-pressure reverse osmosis permeate meets the fresh water standard for reuse.

[0058] In the above method, preferably, in step (10), the steam flow rate of the MVR unit is 0.45 times the amount of water to be processed, the steam temperature is 195-210℃, and the power is 15-20kw / ton of water.

[0059] In the above method, preferably, in step (10), the TDS of the MVR evaporation mother liquor is >10,0000 mg / L.

[0060] In the above method, preferably, in step (10), the TDS of the MVR condensate is <100 mg / L.

[0061] In this invention, the high-pressure reverse osmosis concentrate obtained by reducing the volume and increasing the concentration of the concentrated brine is pumped into the MVR unit for evaporation and crystallization, producing qualified sodium chloride crystals and achieving resource recovery and utilization. The mother liquor from the evaporation of the MVR unit is pumped into the ultra-concentrated water tank and used as blast furnace slag flushing water for cascade disposal, while the condensate is reused as fresh water.

[0062] A second aspect of the present invention provides a combined system for reducing and recycling concentrated brine from steelmaking wastewater, which is used to implement the aforementioned combined method for reducing and recycling concentrated brine from steelmaking wastewater. The system includes:

[0063] The high-density concentrate desulfurization and hardening removal unit is equipped with at least an inlet and a product outlet; the inlet of the high-density concentrate desulfurization and hardening removal unit is used to allow the concentrated brine produced after the treatment of the comprehensive steel wastewater to enter the system.

[0064] The activated carbon filtration and adsorption unit for organic pollutants is provided with at least an inlet and a product outlet; the product outlet of the high-density concentrate tank for hardening and defluorination is connected to the inlet of the activated carbon filtration and adsorption unit for organic pollutants.

[0065] A multi-media filtration unit is provided with at least an inlet and a outlet; the outlet of the activated carbon filtration and adsorption unit for organic pollutants is connected to the inlet of the multi-media filtration unit.

[0066] The concentrate ultrafiltration unit is provided with at least an inlet and a product outlet; the product outlet of the multi-media filtration unit and the inlet of the concentrate ultrafiltration unit are connected.

[0067] The ion exchange extreme hardness removal unit is provided with at least an inlet and a product outlet; the product outlet of the concentrate ultrafiltration unit is connected to the inlet of the ion exchange extreme hardness removal unit.

[0068] The high-efficiency reverse osmosis unit is provided with at least an inlet, a product water outlet, and a concentrate outlet; the product water outlet of the ion exchange extreme hardening unit is connected to the inlet of the high-efficiency reverse osmosis unit, and the product water outlet of the high-efficiency reverse osmosis unit produces high-efficiency reverse osmosis permeate, which is used as recycled water.

[0069] The high-density silica removal tank unit is provided with at least an inlet and a product water outlet; the concentrate outlet of the high-efficiency reverse osmosis unit is connected to the inlet of the high-density silica removal tank unit.

[0070] The submersible ultrafiltration unit is provided with at least an inlet and a product outlet; the product outlet of the high-density silica removal tank unit is connected to the inlet of the submersible ultrafiltration unit.

[0071] The nanofiltration unit is provided with at least an inlet, a product outlet, and a concentrate outlet; the product outlet of the submerged ultrafiltration unit is connected to the inlet of the nanofiltration unit, and the concentrate outlet of the nanofiltration unit produces nanofiltration concentrate, which is used as blast furnace slag flushing water.

[0072] The high-pressure reverse osmosis unit is provided with at least an inlet, a product water outlet, and a concentrate outlet; the product water outlet of the nanofiltration unit is connected to the inlet of the high-pressure reverse osmosis unit, and the product water outlet of the high-pressure reverse osmosis unit produces high-pressure reverse osmosis permeate, which is used as recycled water;

[0073] The MVR unit is equipped with at least an inlet, a sodium chloride crystallization salt outlet, an MVR evaporation mother liquor outlet, and an MVR condensate outlet; the concentrate outlet of the high-pressure reverse osmosis unit is connected to the inlet of the MVR unit; the sodium chloride crystallization salt outlet of the MVR unit produces sodium chloride crystallization salt; the MVR evaporation mother liquor outlet produces MVR evaporation mother liquor, which is used as blast furnace slag flushing water; and the MVR condensate outlet produces MVR condensate, which is used as recycled water.

[0074] In the above system, preferably, the filter media in the multi-media filtration unit includes a combination of anthracite and quartz sand; the anthracite has a relative density of 1.4 to 1.6 and a particle size of 0.8 to 1.8 mm; the quartz sand has a relative density of 2.6 to 2.65 and a particle size of 0.5 to 1.2 mm.

[0075] In the above system, preferably, the ion exchange limit hardening unit uses a weakly acidic cation exchange resin and / or a chelating cation exchange resin.

[0076] In the above system, preferably, the high-efficiency reverse osmosis unit includes a two-stage reverse osmosis membrane and an inter-stage booster pump, wherein the reverse osmosis membrane is an anti-fouling reverse osmosis membrane.

[0077] In the above system, preferably, the nanofiltration unit comprises two nanofiltration membranes connected in series.

[0078] In the above system, preferably, the reverse osmosis membrane of the high-pressure reverse osmosis unit is a high-pressure resistant reverse osmosis membrane.

[0079] This invention provides a combined method and system for reducing and recycling concentrated brine from steel plant wastewater. The invention studies the water quality characteristics of concentrated brine from steel plant wastewater, classifying scaling components according to principles and removing them item by item. First, the concentrated brine (approximately 8 times concentrated) generated after treating the steel plant wastewater enters a high-density concentrate tank for hardening and defluoridation removal. Hardening and defluoridation are removed under high pH conditions using chemical dosing. Then, activated carbon filtration and adsorption are used to remove organic pollutants. Next, a multi-media filtration + ultrafiltration + ion exchange process is used to remove suspended solids, turbidity, and residual hardness. Afterwards, high-efficiency reverse osmosis is used for further concentration to obtain high-efficiency reverse osmosis concentrate (approximately 12-16 times concentrated). Then, a high-density silica removal tank is used under slightly alkaline conditions for silica removal. For the first time after the high-density silica removal tank, a submerged ultrafiltration system is used in series for turbidity removal, shortening the process flow and saving space and investment. Finally, two-stage nanofiltration is used for thorough salt separation, improving the salt separation accuracy and ensuring the preparation of high-purity resource-based by-products. High-pressure reverse osmosis is then employed, utilizing a unique internal circulation system to achieve a high concentration ratio. Finally, the MVR unit is used for evaporation and crystallization, producing qualified sodium chloride industrial salt, thus achieving resource recovery and utilization. The nanofiltration concentrate and MVR evaporation mother liquor, primarily composed of divalent salts, are discharged into the blast furnace slag flushing system for on-site disposal. The high-efficiency reverse osmosis permeate, high-pressure reverse osmosis permeate, and MVR condensate all meet fresh water standards and are reused as fresh water.

[0080] The technical solution of the present invention has at least the following beneficial effects:

[0081] The method and system of this invention have a simple process route, making them more suitable for zero-discharge treatment of comprehensive wastewater from steel plants. They align well with the needs of steel plant brine users, stably reducing the volume of brine in the comprehensive wastewater system, improving the quality of the brine, and achieving resource utilization of some salts while meeting water quality requirements, thus realizing high-quality recovery and reuse of brine. This invention can further treat the concentrated brine from steel plant wastewater to achieve zero wastewater discharge; it also enables cascade utilization and resource recovery of water used within the plant area, while considering both economic efficiency and scalability. The high-quality sodium chloride produced by this invention can be sold externally. High-efficiency reverse osmosis permeate, high-pressure reverse osmosis permeate, and MVR condensate are all reused as fresh production water. Nanofiltration concentrate and MVR evaporation mother liquor are mixed and sent to the blast furnace system for slag flushing, achieving zero discharge of comprehensive steel wastewater. This method requires low investment, is easy to operate, and operates stably. Therefore, this invention can achieve zero discharge and resource utilization of comprehensive wastewater from steel plants. After the process is implemented, it can be matched with the actual operation of steel plants, realize the cascade utilization of wastewater in the plant area, reduce the investment in the zero wastewater discharge system, and obtain good environmental benefits while meeting environmental protection requirements. Attached Figure Description

[0082] Figure 1 This is a schematic diagram of the process and system structure of the combined method for reducing and recycling concentrated brine from integrated steel wastewater, provided for a specific embodiment of the present invention.

[0083] Explanation of icon numbers:

[0084] 1-Concentrated water high-density tank for hardening and defluorination; 2-Activated carbon filtration and adsorption of organic pollutants; 3-Multi-media filtration unit; 4-Concentrated water ultrafiltration unit; 5-Ion exchange limit hardening unit; 6-High-efficiency reverse osmosis unit; 7-High-density silica removal tank unit; 8-Submerged ultrafiltration unit; 9-Nanofiltration unit; 10-High-pressure reverse osmosis unit; 11-MVR unit. Detailed Implementation

[0085] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0086] According to specific embodiments of the present invention, the first aspect of the present invention provides a combined method for reducing the volume and recycling resources of concentrated brine from steelmaking wastewater, such as... Figure 1 As shown, it includes the following steps:

[0087] (1) The concentrated brine produced after the treatment of the comprehensive wastewater of the iron and steel industry is fed into the high-density concentrated water tank for hardening and defluorination unit 1 for treatment. In the high-density concentrated water tank for hardening and defluorination unit 1, sodium hydroxide, sodium carbonate, PFS, PAM and concentrated sulfuric acid are added in sequence to obtain the high-density concentrated water tank product water.

[0088] (2) The concentrated high-density tank product water is fed into the activated carbon filtration and adsorption unit 2 for organic pollutant adsorption to obtain activated carbon filtration and adsorption product water.

[0089] (3) The activated carbon filtration adsorption product water is sequentially fed into the multi-media filtration unit 3 and the concentrated water ultrafiltration unit 4 for treatment to obtain concentrated water ultrafiltration product water.

[0090] (4) The concentrated ultrafiltration permeate is fed into the ion exchange extreme hardness removal unit 5 for treatment to obtain ion exchange permeate.

[0091] (5) The ion exchange permeate is fed into the high-efficiency reverse osmosis unit 6 for treatment to obtain high-efficiency reverse osmosis permeate as recycled water and high-efficiency reverse osmosis concentrate.

[0092] (6) The high-efficiency reverse osmosis concentrate is introduced into the high-density desiliconization tank unit 7 for treatment. Sodium hydroxide, sodium aluminate, PAC, PAM and concentrated sulfuric acid are added sequentially in the high-density desiliconization tank unit 7 to obtain the high-density desiliconization tank permeate.

[0093] (7) The water produced by the high-density desiliconization tank is fed into the submerged ultrafiltration unit 8 for treatment to obtain submerged ultrafiltration water;

[0094] (8) The submerged ultrafiltration permeate is fed into the nanofiltration unit 9 for treatment to obtain nanofiltration permeate and nanofiltration concentrate as blast furnace slag flushing water.

[0095] (9) The nanofiltration permeate is fed into the high-pressure reverse osmosis unit 10 for treatment to obtain high-pressure reverse osmosis permeate as recycled water and high-pressure reverse osmosis concentrate.

[0096] (10) The high-pressure reverse osmosis concentrate is fed into the MVR unit 11 for treatment to obtain sodium chloride crystal salt, MVR evaporation mother liquor as blast furnace slag flushing water, and MVR condensate as recycled water.

[0097] In some embodiments, the concentrated brine is reverse osmosis concentrate produced after the combined steel wastewater has been treated by an advanced treatment unit. The concentration factor of this reverse osmosis concentrate is approximately 8 times.

[0098] In some embodiments, the concentrated brine has the following characteristics: pH 7-8, COD content 100-150 mg / L, and Cl... - The content is 5000-10000 mg / L, SO4 2- The content is 2000-4000 mg / L, Na +The content is 11000-22000 mg / L, F- content is 10-25 mg / L, total nitrogen content is 1-10 mg / L, calcium content is 100-500 mg / L, magnesium content is 10-100 mg / L, TDS content is 18000-36000 mg / L, and suspended solids content is 5-10 mg / L.

[0099] In some embodiments, in step (1), the high-density concentrate tank hardening and defluorination unit 1 adopts a high-density tank.

[0100] In some embodiments, in step (1), the added sodium hydroxide is a 30% sodium hydroxide solution, and the amount of sodium hydroxide added is 800-1500 mg / L; the added sodium carbonate is a 10% sodium carbonate solution, and the amount of sodium carbonate added is 500-1200 mg / L; the added PFS is a 10% PFS aqueous solution, and the amount of PFS added is 50-100 mg / L; the added PAM is a 0.1% PAM aqueous solution, and the amount of PAM added is 0.3-0.5 mg / L; the added concentrated sulfuric acid is a 98% concentrated sulfuric acid solution, and the amount added is 50-100 mg / L. It should be noted that the amounts of these substances added are all calculated based on the mass of the pure substances.

[0101] In some embodiments, in step (1), the total hardness of the concentrate high-density tank permeate is below 50 mg / L and the fluoride content is below 10 mg / L.

[0102] In some embodiments, in step (2), the activated carbon filtration adsorption unit 2 for organic pollutants employs an activated carbon filter.

[0103] In some embodiments, in step (2), the filtration rate of the activated carbon filter layer in the activated carbon filtration and adsorption unit 2 for organic pollutants is 5 to 10 m / h.

[0104] In some embodiments, in step (2), the CODcr removal rate of the activated carbon filtration adsorption unit 2 is 60% to 90%.

[0105] In some embodiments, in step (3), the multi-media filtration unit 3 employs a multi-media filter.

[0106] In some embodiments, in step (3), the filter media in the multi-media filtration unit 3 includes a combination of anthracite and quartz sand; the anthracite has a relative density of 1.4 to 1.6 and a particle size of 0.8 to 1.8 mm; the quartz sand has a relative density of 2.6 to 2.65 and a particle size of 0.5 to 1.2 mm.

[0107] In some embodiments, in step (3), the ultrafiltration membrane of the concentrate ultrafiltration unit 4 retains substances with a particle size > 0.1 nm, the operating temperature is 15 to 40 °C, the operating pressure is 0.1 to 0.2 MPa, the water production rate is above 90%, and the SDI of the concentrate ultrafiltration water is < 5.

[0108] In some embodiments, in step (4), the ion exchange limit hardening unit 5 employs a weakly acidic cation exchange resin and / or a chelating cation exchange resin.

[0109] In some embodiments, step (4) further includes: pretreating and regenerating the cation exchange resin used in the ion exchange limit hardening unit 5 with a sodium hydroxide solution in a co-current manner.

[0110] In some embodiments, in step (4), the total hardness of the ion-exchange permeate is less than 10 mg / L, preferably less than 5 mg / L.

[0111] In some embodiments, in step (5), the high-efficiency reverse osmosis unit 6 includes two reverse osmosis membranes and an inter-stage booster pump. The reverse osmosis membranes are anti-fouling reverse osmosis membranes. The inlet water temperature of the high-efficiency reverse osmosis unit 6 is 20-35°C. The inlet water pressure of the first-stage reverse osmosis membrane is controlled at 1.5-2.0 MPa. The outlet water pressure of the first-stage reverse osmosis membrane decreases to below 0.15 MPa. The inter-stage booster pump increases the pressure to 2.0-2.5 MPa before it enters the second-stage reverse osmosis membrane. The water production rate of the high-efficiency reverse osmosis unit 6 is 50%-65%.

[0112] In some embodiments, in step (5), the concentration factor of the high-efficiency reverse osmosis concentrate is 12 to 16 times.

[0113] In some embodiments, in step (5), the total removal rate of each solute in the high-efficiency reverse osmosis permeate is 95% to 97%, and the TDS is <1000 mg / L.

[0114] In some embodiments, in step (6), the high-density silicon removal cell unit 7 employs a high-density cell.

[0115] In some embodiments, in step (6), the added sodium hydroxide is a 30% sodium hydroxide solution, and the amount of sodium hydroxide added is 50-100 mg / L; the added sodium aluminate is a 10% sodium aluminate solution, and the amount of sodium aluminate added is 150-200 mg / L; the added PAC is a 10% PAC aqueous solution, and the amount of PAC added is 30-50 mg / L; the added PAM is a 0.1% PAM aqueous solution, and the amount of PAM added is 0.3-0.5 mg / L; the added concentrated sulfuric acid is a 98% concentrated sulfuric acid solution, and the amount added is 50-100 mg / L. It should be noted that the amounts of these substances added are all calculated based on the mass of the pure substances.

[0116] In some embodiments, in step (6), the total silicon content of the water produced by the high-density desiliconization tank is below 20 mg / L.

[0117] In some embodiments, in step (7), the ultrafiltration membrane of the submerged ultrafiltration unit 8 retains substances with a particle size > 0.1 nm, operates at a temperature of 15 to 40 °C, operates at a pressure of 0.1 to 0.2 MPa, and has a water production rate of over 90%, wherein the SDI of the submerged ultrafiltration water is < 3.

[0118] In some embodiments, in step (8), the nanofiltration unit 9 includes two nanofiltration membranes connected in series. The concentrate from the first nanofiltration membrane is the nanofiltration concentrate used as blast furnace slag flushing water. The permeate from the first nanofiltration membrane enters the second nanofiltration membrane for treatment. The concentrate from the second nanofiltration membrane enters the first nanofiltration membrane for recycling treatment. The permeate from the second nanofiltration membrane is the nanofiltration permeate.

[0119] In some embodiments, in step (8), the operating temperature of the nanofiltration unit 9 is 20-35°C, the operating pressure is 1.0-2.5 MPa, the desalination rate is 50-60%, and the water production rate is 70-85%.

[0120] In some embodiments, in step (8), preferably, the sulfate removal rate of the nanofiltration unit 9 is above 95%, and the COD removal rate is above 90%. That is, the sulfate removal rate of the nanofiltration permeate is above 95%, and the COD removal rate is above 90%.

[0121] In some embodiments, in step (8), the chloride ion content of the nanofiltration concentrate is <2000 mg / L and the sulfate ion content is >8000 mg / L.

[0122] In some embodiments, in step (9), the reverse osmosis membrane of the high-pressure reverse osmosis unit 10 is a high-pressure resistant reverse osmosis membrane, the feed water temperature of the high-pressure reverse osmosis unit 10 is 20-35°C, the feed water pressure is 6-8 MPa, the desalination rate is above 95%, and the water production rate is 60-75%.

[0123] In some embodiments, in step (9), the TDS of the high-pressure reverse osmosis permeate is <2000 mg / L.

[0124] In some embodiments, step (9) further includes: circulating a portion of the high-pressure reverse osmosis concentrate back to the inlet of the high-pressure reverse osmosis unit 10, wherein the circulating high-pressure reverse osmosis concentrate accounts for 10% to 20% of the total volume of the high-pressure reverse osmosis concentrate, preferably 10% to 15%.

[0125] In some embodiments, in step (10), the steam flow rate of the MVR unit 11 is 0.45 times the amount of water to be processed, the steam temperature is 195 to 210°C, and the power is 15 to 20 kW / ton of water.

[0126] In some embodiments, in step (10), the TDS of the MVR evaporation mother liquor is >10,0000 mg / L.

[0127] In some embodiments, in step (10), the TDS of the MVR condensate is <100 mg / L.

[0128] According to a specific embodiment of the present invention, a second aspect provides a combined system for reducing and recycling concentrated brine from steelmaking wastewater, which is used to implement the aforementioned combined method for reducing and recycling concentrated brine from steelmaking wastewater, such as... Figure 1 As shown, the system includes:

[0129] The high-density concentrate desulfurization and hardening removal unit 1 is equipped with at least an inlet and a product outlet; the inlet of the high-density concentrate desulfurization and hardening removal unit 1 is used to allow the concentrated brine produced after the treatment of the comprehensive steel wastewater to enter the system.

[0130] The activated carbon filtration and adsorption unit 2 for organic pollutants is provided with at least an inlet and a product outlet; the product outlet of the high-density concentrate tank for hardening and defluorination is connected to the inlet of the activated carbon filtration and adsorption unit 2 for organic pollutants.

[0131] The multi-media filtration unit 3 is provided with at least an inlet and a outlet; the outlet of the activated carbon filtration and adsorption unit 2 for organic pollutants is connected to the inlet of the multi-media filtration unit 3.

[0132] The concentrate ultrafiltration unit 4 is provided with at least an inlet and a product outlet; the product outlet of the multi-media filtration unit 3 and the inlet of the concentrate ultrafiltration unit 4 are connected.

[0133] The ion exchange extreme hardness removal unit 5 is provided with at least an inlet and a product outlet; the product outlet of the concentrate ultrafiltration unit 4 is connected to the inlet of the ion exchange extreme hardness removal unit 5.

[0134] The high-efficiency reverse osmosis unit 6 is provided with at least an inlet, a product water outlet, and a concentrate outlet; the product water outlet of the ion exchange extreme hardening unit 5 is connected to the inlet of the high-efficiency reverse osmosis unit 6, and the product water outlet of the high-efficiency reverse osmosis unit 6 produces high-efficiency reverse osmosis product water, which is used as recycled water.

[0135] The high-density silica removal tank unit 7 is equipped with at least an inlet and a product water outlet; the concentrate outlet of the high-efficiency reverse osmosis unit 6 is connected to the inlet of the high-density silica removal tank unit 7.

[0136] The submerged ultrafiltration unit 8 is provided with at least an inlet and a product outlet; the product outlet of the silica removal high-density tank unit 7 is connected to the inlet of the submerged ultrafiltration unit 8.

[0137] Nanofiltration unit 9 is provided with at least an inlet, a product water outlet, and a concentrate outlet; the product water outlet of submerged ultrafiltration unit 8 is connected to the inlet of nanofiltration unit 9, and nanofiltration concentrate is produced at the concentrate outlet of nanofiltration unit 9, which is used as blast furnace slag flushing water.

[0138] The high-pressure reverse osmosis unit 10 is provided with at least an inlet, a product water outlet, and a concentrate outlet; the product water outlet of the nanofiltration unit 9 is connected to the inlet of the high-pressure reverse osmosis unit 10, and the product water outlet of the high-pressure reverse osmosis unit 10 produces high-pressure reverse osmosis product water, which is used as recycled water.

[0139] MVR unit 11 is provided with at least an inlet, a sodium chloride crystal salt outlet, an MVR evaporation mother liquor outlet, and an MVR condensate outlet; the concentrate outlet of high-pressure reverse osmosis unit 10 is connected to the inlet of MVR unit 11, the sodium chloride crystal salt outlet of MVR unit 11 produces sodium chloride crystal salt, the MVR evaporation mother liquor outlet produces MVR evaporation mother liquor, which is used as blast furnace slag flushing water, and the MVR condensate outlet produces MVR condensate, which is used as recycled water.

[0140] It should be noted that, Figure 1 A water recycling tank is also shown, but the system of the present invention may not include the water recycling tank.

[0141] Example 1

[0142] This embodiment employs the aforementioned combined method and system for reducing and recycling concentrated brine from integrated steel wastewater to treat the concentrated brine generated after the treatment of integrated steel wastewater.

[0143] This concentrated brine is reverse osmosis concentrate produced after advanced treatment of steel wastewater. The concentration factor of this reverse osmosis concentrate is approximately 8 times. The water quality of this concentrated brine is as follows: pH 7.5, COD content 120 mg / L, Cl- content 7300 mg / L, SO42- content... 2- The content is 2300 mg / L, Na +The content is 15800 mg / L, F- content is 10 mg / L, total nitrogen content is 1 mg / L, calcium content is 200 mg / L, magnesium content is 50 mg / L, TDS content is 26000 mg / L, and suspended solids content is 5 mg / L.

[0144] In step (1), the added sodium hydroxide is a 30% sodium hydroxide solution, and the amount of sodium hydroxide added is 800 mg / L; the added sodium carbonate is a 10% sodium carbonate solution, and the amount of sodium carbonate added is 600 mg / L; the added PFS is a 10% PFS aqueous solution, and the amount of PFS added is 80 mg / L; the added PAM is a 0.1% PAM aqueous solution, and the amount of PAM added is 0.3 mg / L; the added concentrated sulfuric acid is a 98% concentrated sulfuric acid, and the amount of concentrated sulfuric acid added is 50 mg / L.

[0145] In step (1), the total hardness of the concentrated water produced by the high-density tank is below 50 mg / L and the fluoride content is below 10 mg / L.

[0146] In step (2), the filtration rate of the activated carbon filter layer in the activated carbon filtration adsorption unit 2 for organic pollutants is 5 m / h. The CODcr removal rate of the activated carbon filtration adsorption unit 2 for organic pollutants is 60%–90%.

[0147] In step (3), the filter media in the multi-media filtration unit 3 includes a combination of anthracite and quartz sand; the anthracite has a relative density of 1.4 to 1.6 and a particle size of 0.8 to 1.8 mm; the quartz sand has a relative density of 2.6 to 2.65 and a particle size of 0.5 to 1.2 mm.

[0148] In step (3), the ultrafiltration membrane of the concentrate ultrafiltration unit 4 retains substances with a particle size > 0.1 nm, the operating temperature is 15 to 40 °C, the operating pressure is 0.1 to 0.2 MPa, the water production rate is above 90%, and the SDI of the concentrate ultrafiltration water is < 5.

[0149] In step (4), the ion exchange limit hardening unit 5 uses a weakly acidic cation exchange resin and / or a chelating cation exchange resin.

[0150] Step (4) further includes: pretreating and regenerating the cation exchange resin used in the ion exchange limit hardening unit 5 with sodium hydroxide solution in a co-current feeding manner.

[0151] In step (4), the total hardness of the ion-exchange permeate is below 5 mg / L.

[0152] In step (5), the high-efficiency reverse osmosis unit 6 includes two reverse osmosis membranes and an inter-stage booster pump. The reverse osmosis membranes are anti-fouling reverse osmosis membranes. The inlet water temperature of the high-efficiency reverse osmosis unit 6 is 20-35℃. The inlet water pressure of the first-stage reverse osmosis membrane is controlled at 1.5-2.0 MPa. The outlet water pressure of the first-stage reverse osmosis membrane decreases to below 0.15 MPa. The inter-stage booster pump increases the pressure to 2.0-2.5 MPa before it enters the second-stage reverse osmosis membrane. The permeate rate of the high-efficiency reverse osmosis unit 6 is 50%-65%. The concentration factor of the high-efficiency reverse osmosis concentrate is 16 times.

[0153] In step (5), the total removal rate of each solute in the high-efficiency reverse osmosis permeate is 95% to 97%, and the TDS is 750 mg / L.

[0154] In step (6), the high-density cell unit 7 for silicon removal adopts a high-density cell.

[0155] In step (6), the added sodium hydroxide is a 30% sodium hydroxide solution, and the amount of sodium hydroxide added is 80 mg / L; the added sodium aluminate is a 10% sodium aluminate solution, and the amount of sodium aluminate added is 150 mg / L; the added PAC is a 10% PAC aqueous solution, and the amount of PAC added is 50 mg / L; the added PAM is a 0.1% PAM aqueous solution, and the amount of PAM added is 0.3 mg / L; the added concentrated sulfuric acid is a 98% concentrated sulfuric acid, and the amount added is 50 mg / L.

[0156] In step (6), the total silicon content of the water produced by the high-density desiliconization tank is below 20 mg / L.

[0157] In step (7), the ultrafiltration membrane of the submerged ultrafiltration unit 8 retains substances with a particle size > 0.1 nm, operates at a temperature of 15 to 40 °C, operates at a pressure of 0.1 to 0.2 MPa, and has a water production rate of over 90%. The SDI of the submerged ultrafiltration water is < 3.

[0158] In step (8), the nanofiltration unit 9 includes two nanofiltration membranes connected in series. The concentrate from the first nanofiltration membrane is the nanofiltration concentrate used as blast furnace slag flushing water. The permeate from the first nanofiltration membrane enters the second nanofiltration membrane for treatment. The concentrate from the second nanofiltration membrane enters the first nanofiltration membrane for recycling treatment. The permeate from the second nanofiltration membrane is the nanofiltration permeate.

[0159] In step (8), the operating temperature of nanofiltration unit 9 is 20-35°C, the operating pressure is 1.0-2.5 MPa, the desalination rate is 50-60%, and the water production rate is 70-85%.

[0160] In step (8), preferably, the sulfate removal rate of nanofiltration unit 9 is above 95%, and the COD removal rate is above 90%.

[0161] In step (8), the nanofiltration concentrate has a TDS > 30000 mg / L, chloride ions < 1500 mg / L, and sulfate ions > 11000 mg / L.

[0162] In step (9), the reverse osmosis membrane of the high-pressure reverse osmosis unit 10 is a high-pressure resistant reverse osmosis membrane. The inlet water temperature of the high-pressure reverse osmosis unit 10 is 20-35℃, the inlet water pressure is 6-8 MPa, the desalination rate is above 95%, and the water production rate of the high-pressure reverse osmosis unit 10 is 70%.

[0163] In step (9), the TDS of the high-pressure reverse osmosis permeate is <1000 mg / L.

[0164] Step (9) further includes: circulating a portion of the high-pressure reverse osmosis concentrate back to the inlet of the high-pressure reverse osmosis unit 10, wherein the circulating high-pressure reverse osmosis concentrate accounts for 15% of the total volume of the high-pressure reverse osmosis concentrate.

[0165] In step (10), the steam flow rate of MVR unit 11 is 2.0t / h (0.45 times the amount of water to be treated), the steam temperature is 190℃, the compression ratio is 3:1, and the power is 90kw / ton of water.

[0166] In step (10), the purity of the sodium chloride crystal salt is 97.5%.

[0167] In step (10), the TDS of the MVR evaporation mother liquor is >100000 mg / L.

[0168] In step (10), the TDS of the MVR condensate is <100 mg / L.

[0169] Example 2

[0170] This embodiment employs the aforementioned combined method and system for reducing and recycling concentrated brine from integrated steel wastewater to treat the concentrated brine generated after the treatment of integrated steel wastewater.

[0171] This concentrated brine is reverse osmosis concentrate produced after advanced treatment of steel wastewater. The concentration factor of this reverse osmosis concentrate is approximately 8 times. The water quality of this concentrated brine is as follows: pH 7-8, COD content 120 mg / L, Cl- content 9000 mg / L, SO42- content... 2- The content is 2800 mg / L, Na + The content is 19100 mg / L, F- content is 20 mg / L, total nitrogen content is 5 mg / L, calcium content is 250 mg / L, magnesium content is 40 mg / L, TDS content is 31000 mg / L, and suspended solids content is 5 mg / L.

[0172] In step (1), the added sodium hydroxide is a 30% sodium hydroxide solution, and the amount of sodium hydroxide added is 800 mg / L; the added sodium carbonate is a 10% sodium carbonate solution, and the amount of sodium carbonate added is 500 mg / L; the added PFS is a 10% PFS aqueous solution, and the amount of PFS added is 50 mg / L; the added PAM is a 0.1% PAM aqueous solution, and the amount of PAM added is 0.3 mg / L; the added concentrated sulfuric acid is a 98% concentrated sulfuric acid, and the amount of concentrated sulfuric acid added is 50 mg / L.

[0173] In step (1), the total hardness of the concentrated water produced by the high-density tank is below 50 mg / L and the fluoride content is below 10 mg / L.

[0174] In step (2), the filtration rate of the activated carbon filter layer in the activated carbon filtration and adsorption unit 2 for organic pollutants is 6 m / h.

[0175] In step (2), the CODcr removal rate of activated carbon filtration adsorption unit 2 is 60% to 90%.

[0176] In step (3), the filter media in the multi-media filtration unit 3 includes a combination of anthracite and quartz sand; the anthracite has a relative density of 1.4 to 1.6 and a particle size of 0.8 to 1.8 mm; the quartz sand has a relative density of 2.6 to 2.65 and a particle size of 0.5 to 1.2 mm.

[0177] In step (3), the ultrafiltration membrane of the concentrate ultrafiltration unit 4 retains substances with a particle size > 0.1 nm, the operating temperature is 15 to 40 °C, the operating pressure is 0.1 to 0.2 MPa, the water production rate is above 90%, and the SDI of the concentrate ultrafiltration water is < 5.

[0178] In step (4), the ion exchange limit hardening unit 5 uses a weakly acidic cation exchange resin and / or a chelating cation exchange resin.

[0179] Step (4) further includes: pretreating and regenerating the cation exchange resin used in the ion exchange limit hardening unit 5 with sodium hydroxide solution in a co-current feeding manner.

[0180] In step (4), the total hardness of the ion-exchange permeate is below 10 mg / L.

[0181] In step (5), the high-efficiency reverse osmosis unit 6 includes two reverse osmosis membranes and an inter-stage booster pump. The reverse osmosis membranes are anti-fouling reverse osmosis membranes. The inlet water temperature of the high-efficiency reverse osmosis unit 6 is 20-35℃. The inlet water pressure of the first-stage reverse osmosis membrane is controlled at 1.5-2.0 MPa. The outlet water pressure of the first-stage reverse osmosis membrane decreases to below 0.15 MPa. The inter-stage booster pump increases the pressure to 2.0-2.5 MPa before it enters the second-stage reverse osmosis membrane. The water production rate of the high-efficiency reverse osmosis unit 6 is 50%-65%.

[0182] In step (5), the concentration factor of the high-efficiency reverse osmosis concentrate is 16 times.

[0183] In step (5), the total removal rate of each solute in the high-efficiency reverse osmosis permeate is 95% to 97%, and the TDS is <1000 mg / L.

[0184] In step (6), the high-density cell unit 7 for silicon removal adopts a high-density cell.

[0185] In step (6), the added sodium hydroxide is a 30% sodium hydroxide solution, and the amount of sodium hydroxide added is 50-100 mg / L; the added sodium aluminate is a 10% sodium aluminate solution, and the amount of sodium aluminate added is 150-200 mg / L; the added PAC is a 10% PAC aqueous solution, and the amount of PAC added is 30-50 mg / L; the added PAM is a 0.1% PAM aqueous solution, and the amount of PAM added is 0.3-0.5 mg / L; the added concentrated sulfuric acid is a 98% concentrated sulfuric acid, and the amount added is 80 mg / L.

[0186] In step (6), the total silicon content of the water produced by the high-density desiliconization tank is below 20 mg / L.

[0187] In step (7), the ultrafiltration membrane of the submerged ultrafiltration unit 8 retains substances with a particle size > 0.1 nm, operates at a temperature of 15 to 40 °C, operates at a pressure of 0.1 to 0.2 MPa, and has a water production rate of over 90%. The SDI of the submerged ultrafiltration water is < 3.

[0188] In step (8), the nanofiltration unit 9 includes two nanofiltration membranes connected in series. The concentrate from the first nanofiltration membrane is the nanofiltration concentrate used as blast furnace slag flushing water. The permeate from the first nanofiltration membrane enters the second nanofiltration membrane for treatment. The concentrate from the second nanofiltration membrane enters the first nanofiltration membrane for recycling treatment. The permeate from the second nanofiltration membrane is the nanofiltration permeate.

[0189] In step (8), the operating temperature of nanofiltration unit 9 is 20-35°C, the operating pressure is 1.0-2.5 MPa, the desalination rate is 50-60%, and the water production rate is 70-85%.

[0190] In step (8), the sulfate removal rate of nanofiltration unit 9 is above 95%, and the COD removal rate is above 90%.

[0191] In step (8), the nanofiltration concentrate has a TDS > 31000 mg / L, chloride ions < 2000 mg / L, and sulfate ions > 13000 mg / L.

[0192] In step (9), the reverse osmosis membrane of the high-pressure reverse osmosis unit 10 is a high-pressure resistant reverse osmosis membrane. The inlet water temperature of the high-pressure reverse osmosis unit 10 is 20-35℃, the inlet water pressure is 6-8 MPa, the desalination rate is over 95%, and the water production rate is 70%.

[0193] In step (9), the TDS of the high-pressure reverse osmosis permeate is <1500 mg / L.

[0194] Step (9) further includes: circulating a portion of the high-pressure reverse osmosis concentrate back to the inlet of the high-pressure reverse osmosis unit 10, wherein the circulating high-pressure reverse osmosis concentrate accounts for 15% of the total volume of the high-pressure reverse osmosis concentrate.

[0195] In step (10), the steam flow rate of MVR unit 11 is 3t / h (0.45 times the amount of water to be processed), the steam temperature is 195℃, the compression ratio is 3:1, and the power is 120kw / ton of water.

[0196] In step (10), the purity of the sodium chloride crystal salt is 97.5%.

[0197] In step (10), the TDS of the MVR evaporation mother liquor is >120000 mg / L.

[0198] In step (10), the TDS of the MVR condensate is <1000 mg / L.

[0199] Comparative Example 1

[0200] This comparative example treats the concentrated brine produced after the treatment of integrated steel wastewater. This concentrated brine is the same as that in Example 1, and is the reverse osmosis concentrate produced after the integrated steel wastewater has been treated by an advanced treatment unit. The concentration factor of this reverse osmosis concentrate is approximately 8 times. The water quality of this concentrated brine is: pH 7.5, COD content 120 mg / L, Cl- content 7300 mg / L, SO42- content... 2- The content is 2300 mg / L, Na + The content is 15800 mg / L, F- content is 10 mg / L, total nitrogen content is 1 mg / L, calcium content is 200 mg / L, magnesium content is 50 mg / L, TDS content is 26000 mg / L, and suspended solids content is 5 mg / L.

[0201] The difference between this comparative example and Example 1 is that the removal process for COD and total silica was not considered in the initial design of the project. The activated carbon filtration adsorption unit 2 and the high-density silica removal tank unit 7 were not set up in the process. In actual operation, there is organic pollution (manifested in the frequent chemical cleaning of the high-efficiency reverse osmosis unit 6, which consumes a large amount of alkaline reagents) and silica scale enrichment effect in the nanofiltration unit 9 (the scale cannot be effectively removed by conventional acid washing or calcium sulfate cleaning agents). Although the above two problems have little impact on the overall water quality of the system, they cause frequent cleaning of the high-efficiency reverse osmosis unit 6 and the nanofiltration unit 9.

[0202] Compared to Comparative Example 1, the embodiment of the present invention adds the process design of activated carbon filtration and adsorption of organic pollutants unit 2 and high-density desiliconization tank unit 7 to the system process, providing guarantee measures for the operation of high-efficiency reverse osmosis unit 6 and nanofiltration unit 9 respectively. Under the premise of ensuring stable system operation, compared with Comparative Example 1, Example 1 reduces the difficulty of on-site operation and maintenance, saves cleaning agents, and the estimated cost per ton of water is reduced by 15%.

Claims

1. A combined method for reducing the volume and recovering the resources of concentrated brine from steelmaking wastewater, comprising the following steps: (1) The concentrated brine produced after the treatment of the comprehensive wastewater of the iron and steel industry is fed into the hardening and defluoridation unit of the concentrated water high-density tank for treatment. In the hardening and defluoridation unit of the concentrated water high-density tank, sodium hydroxide, sodium carbonate, PFS, PAM and concentrated sulfuric acid are added in sequence to obtain the product water of the concentrated water high-density tank. The total hardness of the product water of the concentrated water high-density tank is less than 50 mg / L and the fluoride content is less than 10 mg / L. (2) The concentrated high-density tank product water is fed into the activated carbon filtration and adsorption unit for organic pollutant adsorption to obtain activated carbon filtration and adsorption product water. (3) The activated carbon filtration adsorption product water is sequentially fed into the multi-media filtration unit and the concentrated water ultrafiltration unit for treatment to obtain concentrated water ultrafiltration product water. (4) The concentrated ultrafiltration permeate is fed into the ion exchange extreme hardness removal unit for treatment to obtain ion exchange permeate; (5) The ion exchange permeate is fed into a high-efficiency reverse osmosis unit for treatment to obtain high-efficiency reverse osmosis permeate as recycled water and high-efficiency reverse osmosis concentrate. (6) The high-efficiency reverse osmosis concentrate is fed into the high-density desiliconization tank unit for treatment. Sodium hydroxide, sodium aluminate, PAC, PAM and concentrated sulfuric acid are added sequentially in the high-density desiliconization tank unit to obtain high-density desiliconization tank permeate. The total silicon content of the high-density desiliconization tank permeate is less than 20 mg / L. (7) The water produced by the high-density desiliconization tank is fed into the submerged ultrafiltration unit for treatment to obtain submerged ultrafiltration water; (8) The submerged ultrafiltration permeate is fed into a nanofiltration unit for treatment to obtain nanofiltration permeate and nanofiltration concentrate as blast furnace slag flushing water. (9) The nanofiltration permeate is fed into a high-pressure reverse osmosis unit for treatment to obtain high-pressure reverse osmosis permeate as recycled water and high-pressure reverse osmosis concentrate. (10) The high-pressure reverse osmosis concentrate is fed into the MVR unit for treatment to obtain sodium chloride crystal salt, MVR evaporation mother liquor as blast furnace slag flushing water, and MVR condensate as recycled water.

2. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, The concentrated brine is reverse osmosis concentrate produced after the comprehensive steel wastewater has been treated by a deep treatment unit.

3. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1 or 2, wherein, The concentrated brine has the following characteristics: pH 7-8, COD content 100-150 mg / L, and Cl... - The content is 5000-10000 mg / L, SO4 2- The content is 2000-4000 mg / L, Na + The content is 11000~22000mg / L, F - The content is 10-25 mg / L, the total nitrogen content is 1-10 mg / L, the calcium content is 100-500 mg / L, the magnesium content is 10-100 mg / L, the TDS content is 18000-36000 mg / L, and the suspended solids content is 5-10 mg / L.

4. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (1), the added sodium hydroxide is a 30% sodium hydroxide solution, and the amount of sodium hydroxide added is 800-1500 mg / L; the added sodium carbonate is a 10% sodium carbonate solution, and the amount of sodium carbonate added is 500-1200 mg / L; the added PFS is a 10% PFS aqueous solution, and the amount of PFS added is 50-100 mg / L; the added PAM is a 0.1% PAM aqueous solution, and the amount of PAM added is 0.3-0.5 mg / L; the added concentrated sulfuric acid is a 98% concentrated sulfuric acid, and the amount added is 50-100 mg / L.

5. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (2), the filtration rate of the activated carbon filter layer in the activated carbon filtration and adsorption unit for organic pollutants is 5 to 10 m / h.

6. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (2), the CODcr removal rate of the activated carbon filtration adsorption unit for organic pollutants is 60% to 90%.

7. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (3), the ultrafiltration membrane of the concentrate ultrafiltration unit retains substances with a particle size > 0.1 nm, the operating temperature is 15 to 40 °C, the operating pressure is 0.1 to 0.2 MPa, the water production rate is above 90%, and the SDI of the concentrate ultrafiltration water is < 5.

8. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (4), the ion exchange limit hardening unit uses a weakly acidic cation exchange resin and / or a chelating cation exchange resin.

9. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, Step (4) further includes: pretreating and regenerating the cation exchange resin used in the ion exchange limit hardening unit with sodium hydroxide solution in a co-current feeding manner.

10. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (4), the total hardness of the ion-exchange permeate is below 10 mg / L.

11. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (5), the high-efficiency reverse osmosis unit includes two reverse osmosis membranes and an inter-stage booster pump. The reverse osmosis membranes are anti-fouling reverse osmosis membranes. The inlet water temperature of the high-efficiency reverse osmosis unit is 20-35℃. The inlet water pressure of the first-stage reverse osmosis membrane is controlled at 1.5-2.0 MPa. The outlet water pressure of the first-stage reverse osmosis membrane decreases to below 0.15 MPa. The inter-stage booster pump increases the pressure to 2.0-2.5 MPa before it enters the second-stage reverse osmosis membrane. The water production rate of the high-efficiency reverse osmosis unit is 50%-65%.

12. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (5), the concentration factor of the high-efficiency reverse osmosis concentrate is 12 to 16 times.

13. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (5), the total removal rate of each solute in the high-efficiency reverse osmosis permeate is 95% to 97%, and the TDS is <1000 mg / L.

14. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (6), the added sodium hydroxide is a 30% sodium hydroxide solution, and the amount of sodium hydroxide added is 50-100 mg / L; the added sodium aluminate is a 10% sodium aluminate solution, and the amount of sodium aluminate added is 150-200 mg / L; the added PAC is a 10% PAC aqueous solution, and the amount of PAC added is 30-50 mg / L; the added PAM is a 0.1% PAM aqueous solution, and the amount of PAM added is 0.3-0.5 mg / L; the added concentrated sulfuric acid is a 98% concentrated sulfuric acid, and the amount added is 50-100 mg / L.

15. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (7), the ultrafiltration membrane of the submerged ultrafiltration unit retains substances with a particle size > 0.1 nm, the operating temperature is 15 to 40 °C, the operating pressure is 0.1 to 0.2 MPa, the water production rate is above 90%, and the SDI of the submerged ultrafiltration water is < 3.

16. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (8), the nanofiltration unit includes two nanofiltration membranes connected in series. The concentrate from the first nanofiltration membrane is the nanofiltration concentrate used as blast furnace slag flushing water. The permeate from the first nanofiltration membrane enters the second nanofiltration membrane for treatment. The concentrate from the second nanofiltration membrane enters the first nanofiltration membrane for recycling treatment. The permeate from the second nanofiltration membrane is the nanofiltration permeate.

17. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (8), the nanofiltration unit operates at a temperature of 20–35°C, an operating pressure of 1.0–2.5 MPa, a desalination rate of 50–60%, and a water production rate of 70–85%.

18. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (8), the sulfate removal rate of the nanofiltration unit is above 95%, and the COD removal rate is above 90%.

19. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (8), the chloride ion content of the nanofiltration concentrate is <2000 mg / L and the sulfate ion content is >8000 mg / L.

20. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (9), the reverse osmosis membrane of the high-pressure reverse osmosis unit is a high-pressure resistant reverse osmosis membrane. The inlet water temperature of the high-pressure reverse osmosis unit is 20-35℃, the inlet water pressure is 6-8 MPa, the desalination rate is above 95%, and the water production rate is 60-75%.

21. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (9), the TDS of the high-pressure reverse osmosis permeate is <2000 mg / L.

22. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, Step (9) further includes: circulating a portion of the high-pressure reverse osmosis concentrate back to the inlet of the high-pressure reverse osmosis unit, wherein the circulating high-pressure reverse osmosis concentrate accounts for 10% to 20% of the total volume of the high-pressure reverse osmosis concentrate.

23. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (10), the steam flow rate of the MVR unit is 0.45 times the amount of water to be processed, the steam temperature is 195-210℃, and the power is 15-20kw / ton of water.

24. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (10), the TDS of the MVR evaporation mother liquor is >10,000 mg / L.

25. The combined method for reducing and recycling concentrated brine from steelmaking wastewater according to claim 1, wherein, In step (10), the TDS of the MVR condensate is <100 mg / L.

26. A combined system for reducing and recycling concentrated brine from steelmaking wastewater, used to implement the combined method for reducing and recycling concentrated brine from steelmaking wastewater as described in any one of claims 1-25, the system comprising: The high-density concentrate desulfurization and hardening removal unit is equipped with at least an inlet and a product outlet; the inlet of the high-density concentrate desulfurization and hardening removal unit is used to allow the concentrated brine produced after the treatment of the comprehensive steel wastewater to enter the system. The activated carbon filtration and adsorption unit for organic pollutants is provided with at least an inlet and a product outlet; the product outlet of the high-density concentrate tank for hardening and defluorination is connected to the inlet of the activated carbon filtration and adsorption unit for organic pollutants. A multi-media filtration unit is provided with at least an inlet and a outlet; the outlet of the activated carbon filtration and adsorption unit for organic pollutants is connected to the inlet of the multi-media filtration unit. The concentrate ultrafiltration unit is provided with at least an inlet and a product outlet; the product outlet of the multi-media filtration unit and the inlet of the concentrate ultrafiltration unit are connected. The ion exchange extreme hardness removal unit is provided with at least an inlet and a product outlet; the product outlet of the concentrate ultrafiltration unit is connected to the inlet of the ion exchange extreme hardness removal unit. The high-efficiency reverse osmosis unit is provided with at least an inlet, a product water outlet, and a concentrate outlet; the product water outlet of the ion exchange extreme hardening unit is connected to the inlet of the high-efficiency reverse osmosis unit, and the product water outlet of the high-efficiency reverse osmosis unit produces high-efficiency reverse osmosis permeate, which is used as recycled water. The high-density silica removal tank unit is provided with at least an inlet and a product water outlet; the concentrate outlet of the high-efficiency reverse osmosis unit is connected to the inlet of the high-density silica removal tank unit. The submersible ultrafiltration unit is provided with at least an inlet and a product outlet; the product outlet of the high-density silica removal tank unit is connected to the inlet of the submersible ultrafiltration unit. The nanofiltration unit is provided with at least an inlet, a product outlet, and a concentrate outlet; the product outlet of the submerged ultrafiltration unit is connected to the inlet of the nanofiltration unit, and the concentrate outlet of the nanofiltration unit produces nanofiltration concentrate, which is used as blast furnace slag flushing water. The high-pressure reverse osmosis unit is provided with at least an inlet, a product water outlet, and a concentrate outlet; the product water outlet of the nanofiltration unit is connected to the inlet of the high-pressure reverse osmosis unit, and the product water outlet of the high-pressure reverse osmosis unit produces high-pressure reverse osmosis permeate, which is used as recycled water; The MVR unit is equipped with at least an inlet, a sodium chloride crystallization salt outlet, an MVR evaporation mother liquor outlet, and an MVR condensate outlet; the concentrate outlet of the high-pressure reverse osmosis unit is connected to the inlet of the MVR unit; the sodium chloride crystallization salt outlet of the MVR unit produces sodium chloride crystallization salt; the MVR evaporation mother liquor outlet produces MVR evaporation mother liquor, which is used as blast furnace slag flushing water; and the MVR condensate outlet produces MVR condensate, which is used as recycled water.

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