Zero-emission treatment system and process for steel reverse osmosis concentrated water

Abstract

The invention discloses a zero-discharge treatment system and process for steel reverse osmosis concentrated water, and the scheme successfully solves a big problem in the field of steel wastewater treatment, realizes effective conversion and utilization of wastewater resources, and has profound significance for environmental protection and sustainable development. According to the technical scheme, deep treatment is conducted on the steel wastewater, and it is ensured that salt in the wastewater is efficiently extracted and converted into sodium sulfate and sodium chloride products with high purity by accurately controlling reaction conditions and operation parameters in the treatment process; the products are widely applied to a plurality of fields such as chemical industry, light industry and building materials, and have relatively high market requirements and economic benefits; the steel reverse osmosis concentrated water zero discharge technical scheme provided by the invention shows huge potential in a steel green and environment-friendly production process by virtue of remarkable environment-friendly effect and economic value, and is an important force for promoting the sustainable development of the industry.

Description

Technical Field

[0001] The present invention relates to the technical field of steelmaking wastewater treatment, in particular to a zero-discharge treatment system and process for steel reverse osmosis concentrated water. Background Art

[0002] Steel companies generate a large amount of wastewater during the production process. These wastewaters contain pollutants such as heavy metals and organic matter. If they are discharged directly without treatment, they will cause serious damage to the environment. Reverse osmosis technology is a highly efficient steel wastewater treatment technology because of its low energy consumption, simple operation, and good desalination effect. However, while reverse osmosis technology produces high-quality fresh water, it also produces a certain proportion of concentrated water (also called "reverse osmosis concentrated water"), which has a much higher salt and organic matter concentration than the raw water. If it is discharged directly, it will pose a potential threat to the environment. Steel reverse osmosis concentrated water needs to be treated to avoid environmental pollution. The current steel reverse osmosis concentrated water treatment process has certain deficiencies and problems, which are specifically explained as follows:

[0003] For example, patent CN111792796A discloses a reverse osmosis brine treatment system comprising a crystallization device, an ozone-biochemical treatment device, and a homogeneous catalytic oxidation device for sequentially treating the brine. The crystallization device has a liquid inlet for admitting brine, and the crystallization device is used to crystallize the brine. The liquid inlet of the ozone-biochemical treatment device is connected to the liquid outlet of the crystallization device, and the ozone-biochemical treatment device is used to perform ozone oxidation and aerobic biochemical treatment on the brine treated by the crystallization device. The liquid inlet of the homogeneous catalytic oxidation device is connected to the liquid outlet of the ozone-biochemical treatment device, and a catalyst and ozone are introduced into the homogeneous catalytic oxidation device for catalytic oxidation of the brine treated by the ozone-biochemical treatment device. This system purifies the reverse osmosis brine and achieves efficient removal of salt and organic matter. This solution uses multi-pass ozone catalytic oxidation, which is relatively costly.

[0004] For example, patent CN104556533A discloses a method for treating reverse osmosis concentrate, which includes the following steps: adjusting the pH of the reverse osmosis concentrate to 2.0-4.0, and performing electrocatalytic oxidation; the effluent from the electrocatalytic oxidation undergoes a redox reaction in an electrolytic reactor filled with iron-carbon fillers sintered from iron and carbon; then adding hydrogen peroxide for further oxidative decomposition; adjusting the pH to 6.0-8.0, and adding a flocculant for flocculation and precipitation; the supernatant after flocculation and precipitation enters an aerated biological tank, where a co-substrate is added for biodegradation. The reverse osmosis concentrate, which has a COD of 70-200 mg / L and poor biodegradability after biochemical treatment and is then recycled through reverse osmosis, is treated to below 50 mg / L, thereby meeting the most stringent local emission standards. This solution does not involve salt removal or zero-emission treatment, and the discharged wastewater still contains a high salt content, which can easily cause harmful effects on the environment.

[0005] Another example is a high-concentration reverse osmosis concentrate salt and concentrate treatment process disclosed in patent CN105502786A, which includes the following steps: 1) injecting the salt-containing concentrate into a small reactor with stirring, adding Ca(OH)2 and Na2CO3, adjusting the pH value, and stirring; 2) injecting the stirred reverse osmosis concentrate into an external pressure ultrafiltration system, and the concentrate flows back to the small reactor; 3) the water produced by the ultrafiltration system enters the cation exchange resin to remove calcium and magnesium ions in the water; 4) the water softened by the resin enters the reverse osmosis system, the reverse osmosis water is used externally, and the concentrate enters the ultrafiltration system; 5) the water produced by the ultrafiltration system enters the nanofiltration system; 6) the salt in the water produced by the nanofiltration system is monovalent salt, and the salt in the concentrate is divalent salt; 7) the water produced by the nanofiltration system is evaporated and crystallized by MVR, and then centrifuged to obtain monovalent salt; 8) the concentrate of the nanofiltration system is crystallized by freezing, and then centrifuged to obtain divalent salt. This solution uses traditional hardness removal methods, which have relatively low hardness removal efficiency and do not pretreat the nanofiltration concentrate, which affects subsequent crystallization equipment and product purity. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the present invention provides a zero-discharge treatment system and process for steel reverse osmosis concentrated water, which can achieve zero discharge of steel reverse osmosis concentrated water, high treatment efficiency, and realize the recycling of resources.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A zero-discharge treatment system for steel reverse osmosis concentrated water, comprising a primary water inlet pump, a hardness removal sedimentation tank, an intelligent control dosing system, a secondary water inlet pump, a modified resin adsorption tower, a nanofiltration water inlet pump, a nanofiltration membrane assembly, a tertiary water inlet pump, a modified ozone tower, a sodium sulfate evaporator water inlet pump, a sodium sulfate evaporation crystallizer, a sodium chloride evaporator water inlet pump, and a sodium chloride evaporation crystallizer;

[0009] The first-stage water inlet pump, the hardness removal sedimentation tank, the second-stage water inlet pump, the modified resin adsorption tower, the nanofiltration water inlet pump and the nanofiltration membrane assembly are connected in sequence; the nanofiltration water outlet of the nanofiltration membrane assembly is connected to the sodium chloride evaporation crystallizer through the fifth-stage water inlet pump; the concentrated water outlet of the nanofiltration membrane assembly is connected to the third-stage water inlet pump, the modified ozone tower, the fourth-stage water inlet pump and the sodium sulfate evaporation crystallizer in sequence;

[0010] The intelligent control dosing system corresponds to the hardness removal sedimentation tank setting.

[0011] Further,

[0012] The hardness removal sedimentation tank includes a dosing and stirring zone, an inclined plate sedimentation zone and a neutralization and stirring zone arranged in sequence; the intelligent control dosing system includes a sodium hydroxide dosing zone and a modified hardness removal agent dosing zone, both of which are connected to the dosing and stirring zone; the intelligent control dosing system also includes a hydrochloric acid dosing zone, which is connected to the neutralization and stirring zone.

[0013] The modified resin adsorption tower is filled with modified resin, the height and diameter ratio of the modified resin adsorption tower is 4-6:1, and the modified resin accounts for 80-90% of the entire filler adsorption tower by volume.

[0014] The pressure of the nanofiltration water inlet pump is 0.3-0.6 MPa.

[0015] The modified activated coke catalyst is placed in the ozone catalytic tower; the ozone catalytic tower is a closed cylinder, and the modified activated coke catalyst occupies 80-85% of the total volume of the ozone catalytic tower.

[0016] The effect liquid level of the sodium chloride evaporation crystallizer is 2.1-3.3 m, the evaporator effect pressure is 70-80 KPa, the effect temperature is 97-106° C., the forced circulation pump frequency is 40-45 Hz, and the compressor secondary steam temperature is 107-108° C.; the effect liquid level of the sodium sulfate evaporation crystallizer is 2.3-3.5 m, the evaporator effect pressure is 70-80 KPa, the effect temperature is 96-102° C., the forced circulation pump frequency is 48-50 Hz, and the compressor secondary steam temperature is 110-111° C.

[0017] A treatment process using the zero-discharge treatment system for steel reverse osmosis concentrated water comprises the following steps:

[0018] The steel reverse osmosis concentrate enters the hardness removal sedimentation tank through the first-stage water inlet pump. The intelligent control dosing system adds sodium hydroxide and modified hardness removal agents in the dosing and stirring zone. The steel reverse osmosis concentrate stays in the dosing and stirring zone for 3.5 to 6 minutes, with a mechanical stirring speed of 55 to 70 rpm. The steel reverse osmosis concentrate then enters the inclined plate sedimentation area, where it stays for 35 to 45 minutes. It then enters the neutralization and stirring zone, with a mechanical stirring speed of 45 to 55 rpm. The intelligent control dosing system adds 13 to 17% hydrochloric acid by mass to control the pH of the reverse osmosis concentrate in the dosing zone between 7.2 and 7.8.

[0019] The steel reverse osmosis concentrated water from the hardness removal sedimentation tank enters the modified resin adsorption tower through the secondary water inlet pump; after the steel reverse osmosis concentrated water is adsorbed by the resin, the reverse osmosis concentrated water then enters the nanofiltration membrane assembly through the nanofiltration water inlet pump; the nanofiltration membrane can effectively intercept divalent ions and molecular weight organic matter, while allowing monovalent ions to pass through;

[0020] The concentrated water from the nanofiltration membrane assembly enters the ozone catalytic tower through the three-stage water inlet pump. After passing through the ozone catalytic tower, the concentrated water enters the sodium sulfate evaporation crystallizer through the sodium sulfate evaporator water inlet pump for evaporation and crystallization to obtain sodium sulfate;

[0021] The nanofiltration water from the nanofiltration membrane assembly enters the sodium chloride evaporation crystallizer through the sodium chloride inlet pump for evaporation and crystallization to obtain sodium chloride.

[0022] Further,

[0023] The modified de-hardening agent addition area stores a modified de-hardening agent. The preparation method of the modified de-hardening agent comprises the following steps: 1) preparing a sodium carbonate solution with a mass concentration of 33-41% and a ferric chloride solution with a volume ratio of 11-15%, and forming a mixed solution at a volume ratio of 4-6:1; 2) selecting chitosan and activated carbon with a particle size of 1.3-1.4 mm, adding 23-45 mg of chitosan and 5-8 mg of activated carbon per liter of the mixed solution, and placing the mixed solution in a reactor; heating the reactor to 55-65° C. and reacting for 34-56 minutes; and preparing the modified de-hardening agent.

[0024] The modified resin adsorption tower stores oil-modified resin. The preparation method of the modified resin comprises the following steps: 1) adding 125-211g of polyvinyl chloride-divinylbenzene resin, 2-4.5g of potassium permanganate and 2-3.2g of sodium hydroxide per liter of pure water solution by volume, then heating the reactor to 42-45°C in a nitrogen atmosphere, stirring for 40-55min at a stirring speed of 25-35 rpm, cooling and filtering to form intermediate I; 2) adding 222-245g of intermediate I per liter of thionyl chloride solution, then heating the reactor to 46-47°C in a nitrogen atmosphere, stirring for 170-230min at a stirring speed of 25-3 5 rpm; after the reaction, the mixture is cooled, filtered, and washed with hydrochloric acid, water, and methanol 3 to 5 times in sequence to obtain intermediate II; 3) 102 to 105 g of intermediate II, 7 to 19 g of potassium permanganate, and 3.1 to 4.5 g of aluminum oxide are added to each liter of methanol, and then the reactor is cooled to -2 to 0° C. in a nitrogen atmosphere and stirred for 50 to 60 minutes at a stirring speed of 35 to 45 rpm. The reactor is then heated to 55 to 58° C. and stirred for 480 to 550 minutes at a stirring speed of 35 to 45 rpm. After the reaction, the mixture is cooled, filtered, and washed with water and methanol 3 to 5 times in sequence, and vacuum dried to obtain a modified salicylic acid chelate resin.

[0025] The modified ozone tower contains a modified activated coke catalyst. The preparation method of the modified activated coke catalyst comprises the following steps:

[0026] 1) Activated coke screening and activation: Select activated coke with a particle size of 2.5-2.8 mm and a specific surface area of 231.1-263.2 m 2 / g, immersing the activated coke particles in dilute hydrochloric acid with a concentration of 0.6-0.7% by mass for 125-255 minutes, then taking them out, drying them in a blast drying oven, and cooling them; 2) mixing a 3.4-4.8 mol / L copper chloride solution and a 12.1-14.2 mol / L manganese chloride solution in a volume ratio of 1:2-4 to form a composite solution; placing the activated coke into the composite solution in a solid-liquid ratio of 1:2 to form a mixed solution, and immersing the solution for 190-350 minutes; 3) then placing the mixed solution into a barrel plating drum, first heating the mixed solution to 73-75°C, using a copper sheet as a cathode and an iron plate as an anode in the barrel plating drum, with a distance between the cathode and the anode of 10-11 cm, a current density of 47-49 A, and a whole barrel plating process time of 45-51 minutes; and filtering and drying the resulting solution to prepare an activated coke-loaded copper-iron catalyst.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] The solution of the present invention successfully solves a major problem in the field of steel wastewater treatment, realizes the effective transformation and utilization of wastewater resources, and has far-reaching significance for environmental protection and sustainable development. If the wastewater generated in the traditional steel production process is directly discharged without proper treatment, it will seriously pollute the water environment and affect the ecological balance. The technical solution of the present invention deeply treats steel wastewater, and during the treatment process, by precisely controlling the reaction conditions and operating parameters, it ensures that the salt in the wastewater is efficiently extracted and converted into sodium sulfate and sodium chloride products with higher purity. These products are widely used in chemical industry, light industry, building materials and other fields, and have high market demand and economic benefits. The zero-discharge technical solution for steel reverse osmosis concentrated water proposed by the present invention, with its significant environmental protection effect and economic value, has demonstrated great potential in the green and environmentally friendly production process of steel, and is an important force in promoting the sustainable development of the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The following is a brief description of the contents and symbols in the drawings of this specification:

[0030] Figure 1 Schematic diagram of the processing system of the present invention.

[0031] In the picture:

[0032] 1. Primary water inlet pump, 2. Hardness removal sedimentation tank, 3. Intelligent control dosing system, 4. Modified hardness removal agent, 5. Secondary water inlet pump, 6. Modified resin adsorption tower, 7. Modified resin, 8. Nanofiltration water inlet pump, 9. Nanofiltration membrane assembly, 10. Third-stage water inlet pump, 11. Modified ozone tower, 12. Modified activated coke catalyst, 13. Fourth-stage water inlet pump, 14. Sodium sulfate evaporation crystallizer, 15. Fifth-stage water inlet pump, 16. Sodium chloride evaporation crystallizer. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention will be further explained in detail below through description of embodiments with reference to the accompanying drawings.

[0034] like Figure 1 As shown, the zero-discharge treatment system for steel reverse osmosis concentrated water includes a primary water inlet pump, a hardness removal sedimentation tank, an intelligent control dosing system, a secondary water inlet pump, a modified resin adsorption tower, a nanofiltration water inlet pump, a nanofiltration membrane assembly, a tertiary water inlet pump, a modified ozone tower, a sodium sulfate evaporator water inlet pump, a sodium sulfate evaporation crystallizer, a sodium chloride evaporator water inlet pump and a sodium chloride evaporation crystallizer.

[0035] Its first-stage water inlet pump, hardness removal sedimentation tank, second-stage water inlet pump, modified resin adsorption tower, nanofiltration water inlet pump and nanofiltration membrane assembly are connected in sequence; the nanofiltration water outlet of the nanofiltration membrane assembly is connected to the sodium chloride evaporation crystallizer through the fifth-stage water inlet pump; the concentrated water outlet of the nanofiltration membrane assembly is connected to the third-stage water inlet pump, modified ozone tower, fourth-stage water inlet pump and sodium sulfate evaporation crystallizer in sequence; the intelligent control dosing system is set up corresponding to the hardness removal sedimentation tank, and sodium hydroxide and modified hardness removal agent as well as hydrochloric acid for neutralization are added into the hardness removal sedimentation tank through the intelligent control dosing system.

[0036] The zero-discharge treatment process for steel reverse osmosis concentrated water of the present invention is specifically as follows:

[0037] The water quality characteristics of steel reverse osmosis concentrated water are: pH 6.5-8.0, conductivity 17890-26120μs / cm, COD 69-87mg / L, calcium ion 345-787mg / L, and magnesium ion 67-78mg / L.

[0038] The steel industry's reverse osmosis brine enters the hardness removal sedimentation tank via the primary inlet pump. The tank is divided into a dosing and stirring zone, an inclined plate sedimentation zone, and a neutralization and stirring zone. An intelligent dosing system adds sodium hydroxide and a modified hardness removal agent to the dosing and stirring zone. The sodium hydroxide dosage is determined by the intelligent dosing system to maintain the pH of the reverse osmosis brine between 11 and 11.5. The modified hardness removal agent is also added by the intelligent dosing system at a dosage of 234 to 451 mg / L. The steel industry's reverse osmosis brine resides in the dosing and stirring zone for 3.5 to 6 minutes, with a mechanical agitation speed of 55 to 70 rpm. It then enters the inclined plate sedimentation zone, where the inclined plates are made of polypropylene, measuring 1.5 m x 1.5 m, with a plate spacing of 95 to 105 mm and a surface load of 12 to 13 m³ / m²·h. The steel industry's reverse osmosis brine resides for 35 to 45 minutes. Then it enters the neutralization and stirring zone with a mechanical stirring speed of 45 to 55 rpm. The intelligent control dosing system adds 13 to 17% hydrochloric acid by mass in the neutralization and stirring zone to control the pH of the reverse osmosis concentrated water in the dosing zone between 7.2 and 7.8.

[0039] A modified de-hardening agent is prepared based on the characteristics of steel reverse osmosis concentrate. The preparation method is as follows: 1) Prepare a sodium carbonate solution with a mass concentration of 33-41% and a ferric chloride solution with a volume ratio of 11-15% at a ratio of 4-6:1 to form a mixed solution. 2) Select chitosan and activated carbon with a particle size of 1.3-1.4 mm. Add 23-45 mg of chitosan and 5-8 mg of activated carbon per liter of the mixed solution. The mixed solution is placed in a reactor. The reactor is heated to 55-65°C and the reaction is allowed to proceed for 34-56 minutes. The resulting modified de-hardening agent. These chitosan-containing modified de-hardening agents can effectively reduce or eliminate the zeta potential of colloids in water, rapidly precipitating calcium and magnesium ions through a sweeping action.

[0040] After the steel reverse osmosis brine passes through the hardness removal sedimentation tank, the water quality of the steel reverse osmosis brine is: pH 7.2-7.8, conductivity 17890-26120μs / cm, COD 34-52mg / L, calcium ion 16-27mg / L, magnesium ion 3-9mg / L.

[0041] The steel industry's reverse osmosis concentrate enters the modified resin adsorption tower via a secondary inlet pump. The modified resin adsorption tower houses the modified resin. The tower's height-to-diameter ratio is 4-6:1, and the modified resin accounts for 80-90% of the total filler volume. The steel industry's reverse osmosis concentrate resides in the modified resin adsorption tower for 35-45 minutes.

[0042] The modified adsorption resin is specially synthesized and prepared based on the water quality characteristics of steel reverse osmosis concentrate. The preparation process is as follows: 1) 125-211g of polyvinyl chloride-divinylbenzene resin, 2-4.5g of potassium permanganate, and 2-3.2g of sodium hydroxide are added to each liter of pure water by volume. The reaction mixture is then heated to 42-45°C in a nitrogen atmosphere and stirred at 25-35 rpm for 40-55 minutes. The mixture is cooled and filtered to produce Intermediate I. 2) 222-245g of Intermediate I is added to each liter of thionyl chloride solution. The reaction mixture is then heated to 46-47°C in a nitrogen atmosphere and stirred at 25-35 rpm for 170-230 minutes. The mixture is then cooled, filtered, and washed with hydrochloric acid, water, and methanol three to five times to produce Intermediate II. 3) 102-105 g of intermediate II, 7-19 g of potassium permanganate, and 3.1-4.5 g of aluminum oxide are added to each liter of methanol. The reactor is then cooled to -2-0° C. in a nitrogen atmosphere and stirred for 50-60 minutes at a stirring speed of 35-45 rpm. The reactor is then heated to 55-58° C. and stirred for 480-550 minutes at a stirring speed of 35-45 rpm. After the reaction, the mixture is cooled, filtered, and washed with water and methanol 3-5 times in sequence. The mixture is then vacuum-dried at 45° C. for 300 minutes to obtain a modified salicylic acid chelate resin. The modified salicylic acid chelate resin has a mass exchange capacity of 2.9-3.1 mmol / g and has a strong adsorption capacity for calcium and magnesium ions.

[0043] After the steel reverse osmosis concentrated water is adsorbed by resin, the water quality of the reverse osmosis concentrated water is: pH 7.2-7.8, conductivity 17890-26120μs / cm, COD 25-41mg / L, calcium ion 4-8mg / L, magnesium ion 0.5-1.8mg / L.

[0044] The reverse osmosis concentrate then enters the nanofiltration membrane assembly via a nanofiltration inlet pump. The pressure of the nanofiltration inlet pump is 0.3-0.6 MPa. The nanofiltration membrane effectively retains divalent ions and organic matter with low molecular weight, while allowing monovalent ions (such as sodium, potassium, and chloride) to pass through. The nanofiltration concentrate enters the ozone catalytic tower via a three-stage inlet pump, and the nanofiltration product water enters the sodium chloride evaporation crystallizer via a sodium chloride inlet pump. The nanofiltration concentrate water quality is as follows: pH 7.5-8.1, conductivity 25670-37420 μs / cm, COD 79-152 mg / L, calcium ion 12-23 mg / L, and magnesium ion 1.4-5.5 mg / L. Nanofiltration water quality: pH 7.0-7.5, conductivity 9890-14220μs / cm, COD 6-11mg / L, calcium ion 1.1-2.3mg / L, magnesium ion 0.1-0.3mg / L.

[0045] The nanofiltration concentrate enters the ozone catalytic tower via a three-stage inlet pump. Modified activated coke catalyst is placed in the tower, making up 80-85% of the total tower volume. The ozone reactor is a sealed cylindrical structure made of 316L stainless steel with a height-to-diameter ratio of 5:1. The nanofiltration concentrate resides in the adsorption tower for 35-47 minutes.

[0046] The modified activated coke catalyst is specially synthesized and prepared according to the water quality characteristics of the nanofiltration concentrated water. The preparation process is as follows: 1) Activated coke screening and activation: The activated coke particle size is selected to be 2.5-2.8mm and the specific surface area is 231.1-263.2m 2 / g. The activated coke particles are soaked in dilute hydrochloric acid with a concentration of 0.6-0.7% (mass percentage) for 125-255 minutes (dilute acid activation), then taken out, dried in a 105°C forced air drying oven, and cooled. 2) 3.4-4.8 mol / L copper chloride solution and 12.1-14.2 mol / L manganese chloride solution are mixed in a volume ratio of 1:2-4 to form a composite solution. The activated coke is placed in the composite solution in a solid-liquid ratio of 1:2 to form a mixed solution, and immersed for 190-350 minutes. 3) The mixed solution is then placed in a barrel for roller plating. First, the mixed solution is heated to 73-75°C. The barrel plating drum uses a copper sheet as the cathode and an iron plate as the anode. The distance between the cathode and the anode is 10-11 cm, the current density is 47-49 A, and the entire barrel plating process time is 45-51 minutes. After filtration and drying, an activated coke-loaded copper-iron catalyst with a specific surface area of 363.5-378.9 m 2 / g, has good catalytic and adsorption activity, and can effectively remove organic matter in nanofiltration concentrated water.

[0047] After the nanofiltration concentrated water passes through the ozone catalytic tower, the water quality of the nanofiltration concentrated water is: pH 7.5-8.1, conductivity 25670-37420μs / cm, COD 32-78mg / L, calcium ion 12-23mg / L, magnesium ion 1.4-5.5mg / L.

[0048] After passing through the ozone catalytic tower, the nanofiltration concentrate is pumped into the sodium sulfate evaporator crystallizer for evaporation and crystallization. The sodium sulfate evaporator crystallizer has an effect body liquid level of 2.3 to 3.5 m, an evaporator effect body pressure of 70 to 80 kPa, an effect body temperature of 96 to 102°C, a forced circulation pump frequency of 48 to 50 Hz, and a compressor secondary steam temperature of 110 to 111°C. After passing through the sodium sulfate evaporator crystallizer, the resulting sodium sulfate product has a purity of 98.1 to 98.3% and a total calcium and magnesium ion content of 0.05 to 0.1%.

[0049] Nanofiltration water is fed through the sodium chloride evaporator's inlet pump into a sodium chloride evaporator crystallizer for evaporation and crystallization. The sodium chloride evaporator crystallizer's effect level is 2.1 to 3.3 meters, the evaporator's effect pressure is 70 to 80 kPa, the effect temperature is 97 to 106°C, the forced circulation pump frequency is 40 to 45 Hz, and the compressor's secondary steam temperature is 107 to 108°C. After passing through the sodium chloride evaporator crystallizer, the resulting sodium chloride product has a purity of 98.8 to 99.1% and a total calcium and magnesium ion content of 0.05 to 0.1%.

[0050] The present invention prepares a modified hardness removal agent based on the characteristics of reverse osmosis concentrate. The modified hardness removal agent containing chitosan can effectively reduce or eliminate the zeta potential of colloids in water, rapidly precipitating calcium and magnesium ions through a sweeping action. A specially synthesized modified salicylic acid chelate adsorption resin is used to increase the mass exchange capacity and improve the adsorption capacity for calcium and magnesium ions. The ozone catalytic tower uses a modified activated coke catalyst, specially synthesized based on the water quality characteristics of nanofiltration concentrate, to enhance catalytic and adsorption activity and improve the ability to remove organic matter from the nanofiltration concentrate. The present invention achieves zero-discharge treatment of steel reverse osmosis concentrate and converts it into two industrial products, sodium sulfate and sodium chloride. This conversion process not only avoids environmental damage caused by wastewater but also achieves resource recycling and improves economic benefits.

[0051] Preferred embodiment 1 of the present invention:

[0052] like Figure 1 As shown, a technical solution for zero discharge of steel reverse osmosis concentrated water includes a first-stage water inlet pump 1, a hardness removal sedimentation tank 2, an intelligent control dosing system 3, a modified hardness removal agent 4, a second-stage water inlet pump 5, a modified resin adsorption tower 6, a modified resin 7, a nanofiltration water inlet pump 8, a nanofiltration membrane assembly 9, a third-stage water inlet pump 10, a modified ozone tower 11, a modified activated coke catalyst 12, a sodium sulfate evaporator water inlet pump 13, a sodium sulfate evaporation crystallizer 14, a sodium chloride evaporator water inlet pump 15, and a sodium chloride evaporation crystallizer 16.

[0053] The water quality characteristics of steel reverse osmosis concentrated water are: pH 6.5, conductivity 17890μs / cm, COD 69mg / L, calcium ion 345mg / L, and magnesium ion 67mg / L.

[0054] The steel industry's reverse osmosis brine enters the hardness removal sedimentation tank via the primary inlet pump. The tank is divided into a dosing and stirring zone, an inclined plate sedimentation zone, and a neutralization and stirring zone. An intelligent dosing system adds sodium hydroxide and a modified hardness removal agent to the dosing and stirring zone. The sodium hydroxide dosage is determined by the intelligent dosing system. The pH of the reverse osmosis brine in the dosing zone is 11.1. The modified hardness removal agent is also added by the intelligent dosing system at a dosage of 234 mg / L. The steel industry's reverse osmosis brine resides in the dosing and stirring zone for 3.5 minutes, with a mechanical agitation speed of 55 rpm. It then enters the inclined plate sedimentation zone. The inclined plates in this zone are made of polypropylene, measure 1.5 m x 1.5 m, have a plate spacing of 95 mm, and a surface load of 12.2 m³ / m²·h. The steel industry's reverse osmosis brine resides for 35 minutes. Then it enters the neutralization and stirring zone with a mechanical stirring speed of 45 rpm. The intelligent control dosing system adds 13% hydrochloric acid by mass in the neutralization and stirring zone to control the pH of the reverse osmosis concentrated water in the dosing zone at 7.3.

[0055] A modified de-hardening agent is prepared based on the characteristics of steel reverse osmosis concentrate. The preparation method is as follows: 1) Prepare a 33% sodium carbonate solution and an 11% ferric chloride solution in a 4:1 volume ratio to form a mixed solution. 2) Select chitosan and activated carbon with a 1.3 mm particle size, add 23 mg of chitosan and 5 mg of activated carbon per liter of the mixed solution, and place the mixed solution in a reactor. Heat the reactor to 55°C and react for 34 minutes. This results in a modified de-hardening agent. These chitosan-containing modified de-hardening agents can effectively reduce or eliminate the zeta potential of colloids in water, rapidly precipitating calcium and magnesium ions through a sweeping action.

[0056] After the steel reverse osmosis brine passes through the hardness removal sedimentation tank, the water quality of the steel reverse osmosis brine is: pH 7.3, conductivity 18350μs / cm, COD 34mg / L, calcium ion 16mg / L, magnesium ion 3mg / L.

[0057] The steel industry's reverse osmosis concentrate enters the modified resin adsorption tower via a secondary inlet pump. The modified resin adsorption tower houses the modified resin. The tower's height to diameter ratio is 4:1, and the modified resin accounts for 80% of the total filler volume. The steel industry's reverse osmosis concentrate resides in the modified resin adsorption tower for 35 minutes.

[0058] The modified adsorption resin was specifically synthesized based on the water quality characteristics of steel reverse osmosis concentrate. The preparation process is as follows: 1) 125g of polyvinyl chloride-divinylbenzene resin, 2g of potassium permanganate, and 2g of sodium hydroxide were added to each liter of pure water by volume. The reaction mixture was then heated to 42°C in a nitrogen atmosphere and stirred at 25 rpm for 40 minutes. The mixture was cooled and filtered to produce Intermediate I. 2) 222g of Intermediate I was added to each liter of thionyl chloride solution. The reaction mixture was then heated to 46°C in a nitrogen atmosphere and stirred at 25 rpm for 170 minutes. After the reaction, the mixture was cooled, filtered, and washed three times with hydrochloric acid, water, and methanol to produce Intermediate II. 3) 102 g of intermediate II, 7 g of potassium permanganate, and 3.1 g of aluminum oxide were added to each liter of methanol. The reactor was then cooled to -2°C under a nitrogen atmosphere and stirred at 35 rpm for 50 minutes. The reactor was then heated to 55°C and stirred at 35 rpm for 480 minutes. After the reaction, the mixture was cooled, filtered, and washed three times with water and methanol, respectively. The mixture was then dried under vacuum at 45°C for 300 minutes to obtain a modified salicylic acid chelate resin. The modified salicylic acid chelate resin had a mass exchange capacity of 2.9 mmol / g and exhibited strong adsorption capacity for calcium and magnesium ions.

[0059] After the steel reverse osmosis concentrated water is adsorbed by resin, the water quality of the reverse osmosis concentrated water is: pH 7.2, conductivity 19100μs / cm, COD 25mg / L, calcium ion 4mg / L, magnesium ion 0.5mg / L.

[0060] The reverse osmosis concentrate then enters the nanofiltration membrane via the nanofiltration inlet pump. The pressure of the nanofiltration inlet pump is 0.3-0.6 MPa. The nanofiltration membrane effectively retains divalent ions and small-molecule organic matter, while allowing monovalent ions (such as sodium, potassium, and chloride) to pass through. The nanofiltration concentrate enters the ozone catalytic tower via a three-stage inlet pump, while the nanofiltration product water enters the sodium chloride evaporation crystallizer via the sodium chloride inlet pump. The nanofiltration concentrate quality is: pH 7.5, conductivity 27670 μs / cm, COD 79 mg / L, calcium ion content 12 mg / L, and magnesium ion content 1.4 mg / L. The nanofiltration product water quality is: pH 7.0, conductivity 10190 μs / cm, COD 6 mg / L, calcium ion content 1.1 mg / L, and magnesium ion content 0.1 mg / L.

[0061] The nanofiltration concentrate enters the ozone catalytic tower via a three-stage inlet pump. Modified activated coke catalyst is placed in the tower, accounting for 80% of the total tower volume. The ozone reactor is a sealed cylindrical structure made of 316L stainless steel with a height-to-diameter ratio of 5:1. The nanofiltration concentrate resides in the adsorption tower for 35 minutes.

[0062] The modified activated coke catalyst is specially synthesized and prepared according to the water quality characteristics of the nanofiltration concentrated water. The preparation process is as follows: 1) Activated coke screening and activation: The activated coke particle size is selected to be 2.5mm and the specific surface area is 231.1m 2 / g. Soak the activated coke particles in dilute hydrochloric acid with a concentration of 0.6% (mass percentage) for 125 minutes (dilute acid activation), then take them out, dry them in a 105°C forced air drying oven, and cool them. 2) Mix 3.4 mol / L copper chloride solution and 12.1 mol / L manganese chloride solution in a volume ratio of 1:2 to form a compound solution. Put the activated coke into the compound solution in a solid-liquid ratio of 1:2 to form a mixed solution, and immerse it for 190 minutes. 3) Then put the mixed solution into a roller plating drum, first heat the mixed solution to 73°C, the roller plating drum uses a copper sheet as the cathode and an iron plate as the anode, the distance between the cathode and the anode is 10 cm, the current density is 47A, and the entire roller plating process time is 45 minutes. After filtration and drying, an activated coke-loaded copper-iron catalyst with a specific surface area of 363.5m 2 / g, has good catalytic and adsorption activity, and can effectively remove organic matter in nanofiltration concentrated water.

[0063] After the nanofiltration concentrated water passes through the ozone catalytic tower, the water quality of the nanofiltration concentrated water is: pH 7.5, conductivity 27670μs / cm, COD 32mg / L, calcium ion 12mg / L, and magnesium ion 1.4mg / L.

[0064] After passing through the ozone catalytic tower, the nanofiltration concentrate enters the sodium sulfate evaporation crystallizer via the sodium sulfate evaporator inlet pump. The sodium sulfate evaporation crystallizer has an effect level of 2.3 m, an evaporator effect pressure of 70 kPa, an effect temperature of 96°C, a forced circulation pump frequency of 48 Hz, and a compressor secondary steam temperature of 110°C. After passing through the sodium sulfate evaporation crystallizer, the resulting sodium sulfate product has a purity of 98.1% and a total calcium and magnesium ion content of 0.05%.

[0065] Nanofiltration water is fed into the sodium chloride evaporator crystallizer via the sodium chloride evaporator inlet pump. The sodium chloride evaporator crystallizer has an effect level of 2.1 m, an effect pressure of 70 kPa, an effect temperature of 97°C, a forced circulation pump frequency of 40 Hz, and a compressor secondary steam temperature of 107°C. After passing through the sodium chloride evaporator crystallizer, the resulting sodium chloride product has a purity of 98.8% and a total calcium and magnesium ion content of 0.05%.

[0066] The zero-discharge technical solution for steel reverse osmosis concentrated water proposed in the present invention converts steel reverse osmosis concentrated water into two industrial products, sodium sulfate and sodium chloride. This conversion process not only avoids the damage of wastewater to the environment, but also realizes the recycling of resources and improves economic benefits.

[0067] Preferred embodiment 2 of the present invention:

[0068] like Figure 1 As shown, a technical solution for zero discharge of steel reverse osmosis concentrated water includes a first-stage water inlet pump 1, a hardness removal sedimentation tank 2, an intelligent control dosing system 3, a modified hardness removal agent 4, a second-stage water inlet pump 5, a modified resin adsorption tower 6, a modified resin 7, a nanofiltration water inlet pump 8, a nanofiltration membrane assembly 9, a third-stage water inlet pump 10, a modified ozone tower 11, a modified activated coke catalyst 12, a sodium sulfate evaporator water inlet pump 13, a sodium sulfate evaporation crystallizer 14, a sodium chloride evaporator water inlet pump 15, and a sodium chloride evaporation crystallizer 16.

[0069] The water quality characteristics of steel reverse osmosis concentrated water are: pH 8.0, conductivity 26120μs / cm, COD 87mg / L, calcium ion 787mg / L, and magnesium ion 78mg / L.

[0070] The steel industry's reverse osmosis brine enters the hardness removal sedimentation tank via the primary inlet pump. The tank is divided into a dosing and stirring zone, an inclined plate sedimentation zone, and a neutralization and stirring zone. An intelligent dosing system adds sodium hydroxide and a modified hardness removal agent to the dosing and stirring zone. The sodium hydroxide dosage is determined by the intelligent dosing system to maintain the pH of the reverse osmosis brine at 11.5. The modified hardness removal agent is also added by the intelligent dosing system at a dosage of 451 mg / L. The steel industry's reverse osmosis brine resides in the dosing and stirring zone for 6 minutes, with a mechanical agitation speed of 70 rpm. It then enters the inclined plate sedimentation zone, where the inclined plates are made of polypropylene, measuring 1.5 m x 1.5 m, with a plate spacing of 105 mm and a surface load of 13 m³ / m²·h. The steel industry's reverse osmosis brine resides for 45 minutes. Then it enters the neutralization and stirring zone with a mechanical stirring speed of 55 rpm. The intelligent control dosing system adds 17% hydrochloric acid by mass in the neutralization and stirring zone to control the pH of the reverse osmosis concentrated water in the dosing zone at 7.8.

[0071] A modified de-hardening agent is prepared based on the characteristics of steel reverse osmosis concentrate. The preparation method is as follows: 1) Prepare a 41% sodium carbonate solution and a 15% ferric chloride solution in a 6:1 volume ratio to form a mixed solution. 2) Select chitosan and activated carbon with a 1.4 mm particle size, add 45 mg of chitosan and 8 mg of activated carbon per liter of the mixed solution, and place the mixed solution in a reactor. Heat the reactor to 65°C and react for 56 minutes. This results in a modified de-hardening agent. These chitosan-containing modified de-hardening agents can effectively reduce or eliminate the zeta potential of colloids in water, rapidly precipitating calcium and magnesium ions through a sweeping action.

[0072] After the steel reverse osmosis brine passes through the hardness removal sedimentation tank, the water quality of the steel reverse osmosis brine is: pH 7.8, conductivity 26120μs / cm, COD 52mg / L, calcium ion 27mg / L, magnesium ion 9mg / L.

[0073] The steel industry's reverse osmosis concentrate enters the modified resin adsorption tower via a secondary inlet pump. The modified resin adsorption tower houses the modified resin. The tower has a height-to-diameter ratio of 6:1, and the modified resin accounts for 90% of the total filler volume. The steel industry's reverse osmosis concentrate resides in the modified resin adsorption tower for 45 minutes.

[0074] The modified adsorption resin was synthesized specifically based on the water quality characteristics of steel reverse osmosis concentrate. The preparation process is as follows: 1) 211g of polyvinyl chloride-divinylbenzene resin, 4.5g of potassium permanganate, and 3.2g of sodium hydroxide were added to each liter of pure water by volume. The reaction mixture was then heated to 45°C in a nitrogen atmosphere and stirred at 35 rpm for 55 minutes. The mixture was cooled and filtered to produce Intermediate I. 2) 245g of Intermediate I was added to each liter of thionyl chloride solution. The reaction mixture was then heated to 47°C in a nitrogen atmosphere and stirred at 35 rpm for 230 minutes. After the reaction, the mixture was cooled, filtered, and washed five times with hydrochloric acid, water, and methanol to produce Intermediate II. 3) 105 g of intermediate II, 19 g of potassium permanganate, and 4.5 g of aluminum oxide were added to each liter of methanol. The reactor was then cooled to 0° C. under a nitrogen atmosphere and stirred at 45 rpm for 60 minutes. The reactor was then heated to 58° C. and stirred at 45 rpm for 550 minutes. After the reaction, the mixture was cooled, filtered, and washed five times with water and methanol, respectively. The mixture was then dried under vacuum at 45° C. for 300 minutes to obtain a modified salicylic acid chelate resin. The modified salicylic acid chelate resin had a mass exchange capacity of 3.1 mmol / g and exhibited strong adsorption capacity for calcium and magnesium ions.

[0075] After the steel reverse osmosis concentrated water is adsorbed by resin, the water quality of the reverse osmosis concentrated water is: pH 7.8, conductivity 25870μs / cm, COD 40mg / L, calcium ion 7mg / L, magnesium ion 1.6mg / L.

[0076] The reverse osmosis concentrate then enters the nanofiltration membrane via a nanofiltration inlet pump. The pressure of the nanofiltration inlet pump is 0.6 MPa. The nanofiltration membrane effectively retains divalent ions and organic matter with a low molecular weight, while allowing monovalent ions (such as sodium, potassium, and chloride) to pass through. The nanofiltration concentrate enters the ozone catalytic tower via a three-stage inlet pump, while the nanofiltration product water enters the sodium chloride evaporation crystallizer via a sodium chloride inlet pump. The nanofiltration concentrate water quality is: pH 8.1, conductivity 35120 μs / cm, COD 145 mg / L, calcium ion content 20 mg / L, and magnesium ion content 4.5 mg / L. The nanofiltration product water quality is: pH 7.3, conductivity 11510 μs / cm, COD 9 mg / L, calcium ion content 2.1 mg / L, and magnesium ion content 0.3 mg / L.

[0077] The nanofiltration concentrate enters the ozone catalytic tower via a three-stage inlet pump. Modified activated coke catalyst is placed in the tower, accounting for 85% of the total tower volume. The ozone reactor is a sealed cylindrical structure made of 316L stainless steel with a height-to-diameter ratio of 5:1. The nanofiltration concentrate resides in the adsorption tower for 47 minutes.

[0078] The modified activated coke catalyst is specially synthesized and prepared according to the water quality characteristics of the nanofiltration concentrated water. The preparation process is as follows: 1) Activated coke screening and activation: The activated coke particle size is selected to be 2.8mm and the specific surface area is 263.2m 2 / g. The activated coke particles were soaked in dilute hydrochloric acid with a concentration of 0.7% (mass percentage) for 255 minutes (dilute acid activation), then taken out, dried in a 105°C forced air drying oven and cooled. 2) 4.8 mol / L copper chloride solution and 14.2 mol / L manganese chloride solution were mixed in a volume ratio of 1:4 to form a compound solution. The activated coke was placed in the compound solution at a solid-liquid ratio of 1:2 to form a mixed solution, and immersed for 350 minutes. 3) The mixed solution was then placed in a roller plating drum. First, the mixed solution was heated to 75°C. The roller plating drum used a copper sheet as the cathode and an iron plate as the anode. The distance between the cathode and the anode was 11 cm, the current density was 49A, and the entire roller plating process time was 51 minutes. After filtration and drying, an activated coke-loaded copper-iron catalyst was prepared with a specific surface area of 375.4m 2 / g, has good catalytic and adsorption activity, and can effectively remove organic matter in nanofiltration concentrated water.

[0079] After the nanofiltration concentrated water passes through the ozone catalytic tower, the water quality of the nanofiltration concentrated water is: pH 8.1, conductivity 36920μs / cm, COD 78mg / L, calcium ion 20mg / L, and magnesium ion 4.5mg / L.

[0080] After passing through the ozone catalytic tower, the nanofiltration concentrate enters the sodium sulfate evaporation crystallizer via the sodium sulfate evaporator inlet pump. The sodium sulfate evaporation crystallizer has an effect level of 3.5 m, an evaporator effect pressure of 80 kPa, an effect temperature of 102°C, a forced circulation pump frequency of 50 Hz, and a compressor secondary steam temperature of 111°C. After passing through the sodium sulfate evaporation crystallizer, the resulting sodium sulfate product has a purity of 98.1% and a total calcium and magnesium ion content of 0.1%.

[0081] Nanofiltration water is fed into the sodium chloride evaporator crystallizer via the sodium chloride evaporator inlet pump. The sodium chloride evaporator crystallizer has an effect level of 3.3 m, an effect pressure of 80 kPa, an effect temperature of 106°C, a forced circulation pump frequency of 45 Hz, and a compressor secondary steam temperature of 108°C. After passing through the sodium chloride evaporator crystallizer, the resulting sodium chloride product has a purity of 99.1% and a total calcium and magnesium ion content of 0.1%.

[0082] The zero-discharge technical solution for steel reverse osmosis concentrated water proposed in the present invention converts steel reverse osmosis concentrated water into two industrial products, sodium sulfate and sodium chloride. This conversion process not only avoids the damage of wastewater to the environment, but also realizes the recycling of resources and improves economic benefits.

[0083] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A zero-discharge treatment system for steel reverse osmosis concentrated water, characterized by: Including the first-stage water inlet pump, hardness removal sedimentation tank, intelligent control dosing system, second-stage water inlet pump, modified resin adsorption tower, nanofiltration water inlet pump, nanofiltration membrane assembly, third-stage water inlet pump, modified ozone tower, sodium sulfate evaporator water inlet pump, sodium sulfate evaporation crystallizer, sodium chloride evaporator water inlet pump and sodium chloride evaporation crystallizer; The first-stage water inlet pump, the hardness removal sedimentation tank, the second-stage water inlet pump, the modified resin adsorption tower, the nanofiltration water inlet pump and the nanofiltration membrane assembly are connected in sequence; the nanofiltration water outlet of the nanofiltration membrane assembly is connected to the sodium chloride evaporation crystallizer through the fifth-stage water inlet pump; the concentrated water outlet of the nanofiltration membrane assembly is connected to the third-stage water inlet pump, the modified ozone tower, the fourth-stage water inlet pump and the sodium sulfate evaporation crystallizer in sequence; The intelligent control dosing system corresponds to the hardness removal sedimentation tank setting.

2. The zero-discharge treatment system for steel reverse osmosis concentrated water according to claim 1, characterized in that: The hardness removal sedimentation tank includes a dosing and stirring zone, an inclined plate sedimentation zone and a neutralization and stirring zone arranged in sequence; the intelligent control dosing system includes a sodium hydroxide dosing zone and a modified hardness removal agent dosing zone, both of which are connected to the dosing and stirring zone; the intelligent control dosing system also includes a hydrochloric acid dosing zone, which is connected to the neutralization and stirring zone.

3. The zero-discharge treatment system for steel reverse osmosis concentrated water according to claim 1, characterized in that: The modified resin adsorption tower is filled with modified resin, the height and diameter ratio of the modified resin adsorption tower is 4-6:1, and the modified resin accounts for 80-90% of the entire filler adsorption tower by volume.

4. The zero-discharge treatment system for steel reverse osmosis concentrated water according to claim 1, characterized in that: The pressure of the nanofiltration water inlet pump is 0.3-0.6 MPa.

5. The zero-discharge treatment system for steel reverse osmosis concentrated water according to claim 1, characterized in that: The modified activated coke catalyst is placed in the ozone catalytic tower; the ozone catalytic tower is a closed cylinder, and the modified activated coke catalyst accounts for 80-85% of the total volume of the ozone catalytic tower.

6. The zero-discharge treatment system for steel reverse osmosis concentrated water according to claim 1, characterized in that: The effect liquid level of the sodium chloride evaporation crystallizer is 2.1-3.3 m, the evaporator effect pressure is 70-80 KPa, the effect temperature is 97-106° C., the forced circulation pump frequency is 40-45 Hz, and the compressor secondary steam temperature is 107-108° C.; the effect liquid level of the sodium sulfate evaporation crystallizer is 2.3-3.5 m, the evaporator effect pressure is 70-80 KPa, the effect temperature is 96-102° C., the forced circulation pump frequency is 48-50 Hz, and the compressor secondary steam temperature is 110-111° C.

7. A treatment process using the zero-discharge treatment system for steel reverse osmosis concentrated water according to any one of claims 1 to 6, characterized in that: The treatment process comprises the following steps: The steel reverse osmosis concentrate enters the hardness removal sedimentation tank through the first-stage water inlet pump. The intelligent control dosing system adds sodium hydroxide and modified hardness removal agents in the dosing and stirring zone. The steel reverse osmosis concentrate stays in the dosing and stirring zone for 3.5 to 6 minutes, with a mechanical stirring speed of 55 to 70 rpm. The steel reverse osmosis concentrate then enters the inclined plate sedimentation area, where it stays for 35 to 45 minutes. It then enters the neutralization and stirring zone, with a mechanical stirring speed of 45 to 55 rpm. The intelligent control dosing system adds 13 to 17% hydrochloric acid by mass to control the pH of the reverse osmosis concentrate in the dosing zone between 7.2 and 7.

8. The steel reverse osmosis concentrated water from the hardness removal sedimentation tank enters the modified resin adsorption tower through the secondary water inlet pump; after the steel reverse osmosis concentrated water is adsorbed by the resin, the reverse osmosis concentrated water then enters the nanofiltration membrane assembly through the nanofiltration water inlet pump; the nanofiltration membrane can effectively intercept divalent ions and molecular weight organic matter, while allowing monovalent ions to pass through; The concentrated water from the nanofiltration membrane assembly enters the ozone catalytic tower through the three-stage water inlet pump. After passing through the ozone catalytic tower, the concentrated water enters the sodium sulfate evaporation crystallizer through the sodium sulfate evaporator water inlet pump for evaporation and crystallization to obtain sodium sulfate; The nanofiltration water from the nanofiltration membrane assembly enters the sodium chloride evaporation crystallizer through the sodium chloride inlet pump for evaporation and crystallization to obtain sodium chloride.

8. The treatment process according to claim 7, wherein: The modified de-hardening agent addition area stores a modified de-hardening agent. The preparation method of the modified de-hardening agent comprises the following steps: 1) preparing a sodium carbonate solution with a mass concentration of 33-41% and a ferric chloride solution with a volume ratio of 11-15%, and forming a mixed solution at a volume ratio of 4-6:1; 2) selecting chitosan and activated carbon with a particle size of 1.3-1.4 mm, adding 23-45 mg of chitosan and 5-8 mg of activated carbon per liter of the mixed solution, and placing the mixed solution in a reactor; heating the reactor to 55-65° C. and reacting for 34-56 minutes; and preparing the modified de-hardening agent.

9. The process according to claim 7, wherein: The modified resin adsorption tower stores oil-modified resin. The preparation method of the modified resin comprises the following steps: 1) adding 125-211g of polyvinyl chloride-divinylbenzene resin, 2-4.5g of potassium permanganate and 2-3.2g of sodium hydroxide per liter of pure water solution by volume, then heating the reactor to 42-45°C in a nitrogen atmosphere, stirring for 40-55min at a stirring speed of 25-35 rpm, cooling and filtering to form intermediate I; 2) adding 222-245g of intermediate I per liter of thionyl chloride solution, then heating the reactor to 46-47°C in a nitrogen atmosphere, stirring for 170-230min at a stirring speed of 25-3 5 rpm; after the reaction, the mixture is cooled, filtered, and washed with hydrochloric acid, water, and methanol 3 to 5 times in sequence to obtain intermediate II; 3) 102 to 105 g of intermediate II, 7 to 19 g of potassium permanganate, and 3.1 to 4.5 g of aluminum oxide are added to each liter of methanol, and then the reactor is cooled to -2 to 0° C. in a nitrogen atmosphere and stirred for 50 to 60 minutes at a stirring speed of 35 to 45 rpm. The reactor is then heated to 55 to 58° C. and stirred for 480 to 550 minutes at a stirring speed of 35 to 45 rpm. After the reaction, the mixture is cooled, filtered, and washed with water and methanol 3 to 5 times in sequence, and vacuum dried to obtain a modified salicylic acid chelate resin.

10. The treatment process according to claim 7, wherein: The modified ozone tower contains a modified activated coke catalyst. The preparation method of the modified activated coke catalyst comprises the following steps: 1) Activated coke screening and activation: Select activated coke with a particle size of 2.5-2.8 mm and a specific surface area of 231.1-263.2 m 2 / g, immersing the activated coke particles in dilute hydrochloric acid with a concentration of 0.6-0.7% by mass for 125-255 minutes, then taking them out, drying them in a blast drying oven, and cooling them; 2) mixing a 3.4-4.8 mol / L copper chloride solution and a 12.1-14.2 mol / L manganese chloride solution in a volume ratio of 1:2-4 to form a composite solution; placing the activated coke into the composite solution in a solid-liquid ratio of 1:2 to form a mixed solution, and immersing the solution for 190-350 minutes; 3) then placing the mixed solution into a barrel plating drum, first heating the mixed solution to 73-75°C, using a copper sheet as a cathode and an iron plate as an anode in the barrel plating drum, with a distance between the cathode and the anode of 10-11 cm, a current density of 47-49 A, and a whole barrel plating process time of 45-51 minutes; and filtering and drying the resulting solution to prepare an activated coke-loaded copper-iron catalyst.

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