High-salt-content wastewater crystallization process

Abstract

The invention discloses a high-salt-content wastewater crystal. The high-salt-content wastewater crystallization comprises the following steps: S1, pretreatment: wastewater in a system enters a homogeneous regulation tank in S1, water is discharged from the homogeneous regulation tank to a high-density tank 1 #, PAC, PAM, lime sodium carbonate and NaOH are added into the high-density tank 1 # for reaction, water is discharged from the high-density tank 1 # to a high-density tank 2 #, PAC, PAM and sodium metaaluminate are added into the high-density tank 2 #, water is discharged from the high-density tank 2 # to a high-strength membrane tank, and water is discharged from the high-strength membrane tank to a two-stage weak acid cation bed; s2, evaporative crystallization: the concentrated water in the concentrated water feeding tank enters a triple-effect mixed salt evaporative crystallization device to separate out mixed salt of sodium chloride and sodium sulfate and part of carnallite. The high-salt-content wastewater crystal provided by the invention can achieve the purposes of salt separation and zero discharge, and recycling and reusing of produced water and saltpeter, and also realizes recycling of produced reclaimed water and resource reutilization of produced sodium sulfate and sodium chloride as industrial raw materials.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a high-salt wastewater crystallization process. Background Art

[0002] Stricter environmental supervision has been the main driving force for the development of my country's water treatment industry in recent years. On the one hand, it has rapidly promoted the construction of municipal sewage treatment infrastructure; on the other hand, it has forced industrial enterprises to increase environmental protection investment and reduce pollutant emissions. At present, the price of industrial water is generally low, and industrial enterprises lack the internal motivation to carry out sewage treatment. In the future, the price of industrial water will continue to rise (especially in some water-scarce areas) and the cost of water treatment will decrease, which will prompt industrial enterprises to change their sewage treatment from "passive improvement" to "active water conservation and water reuse."

[0003] Industrial wastewater refers to wastewater and waste liquid discharged during the production process, which contains industrial production materials, intermediate products, by-products and pollutants generated during the production process. It is an important cause of environmental pollution, especially water pollution. Although the treatment of industrial wastewater began as early as the end of the 19th century, due to the complex composition and variable nature of many industrial wastewaters, there are still some technical problems that have not been completely solved.

[0004] 1. According to the different degrees of pollution, industrial wastewater can be divided into two categories: production wastewater and production sewage. Production wastewater refers to water that is slightly polluted or has a higher temperature during use (such as equipment cooling water); production sewage refers to water that is seriously polluted during use, and most of them are seriously harmful.

[0005] 2. According to the chemical properties of the main pollutants contained in industrial wastewater, it can be divided into inorganic wastewater containing mainly inorganic pollutants, organic wastewater containing mainly organic pollutants, mixed wastewater containing both organic and inorganic substances, heavy metal wastewater, wastewater containing radioactive substances and cooling water only contaminated by heat. For example, electroplating wastewater and wastewater from mineral processing are inorganic wastewater, and wastewater from food or petroleum processing is organic wastewater.

[0006] 3. According to the products and processing objects of industrial enterprises, it can be divided into papermaking wastewater, textile wastewater, leather making wastewater, pesticide wastewater, metallurgical wastewater, oil refining wastewater, etc.

[0007] 4. According to the main components of pollutants contained in the wastewater, it can be divided into acidic wastewater, alkaline wastewater, phenol-containing wastewater, chromium-containing wastewater, organic phosphorus-containing wastewater and radioactive wastewater.

[0008] Industrial wastewater treatment is quite complicated. The choice of treatment method must be based on the quality and quantity of the wastewater, the receiving water body or the purpose of the water discharged, especially the treatment of high-salt wastewater. In the conventional evaporation concentration + crystallization process, the concentration multiple of the evaporator is relatively low, the evaporator has a significant scaling tendency, the system energy consumption is high, and the crystalline salt produced is a mixed salt and mixed with some organic matter. It can only be treated as hazardous waste with high disposal costs, resulting in high long-term operating costs and heavy burdens for the enterprise, and it is impossible to ensure long-term stable operation with zero discharge of concentrated brine.

[0009] Therefore, it is necessary to provide a high-salt wastewater crystallization process to solve the above technical problems. Summary of the invention

[0010] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a high-salt wastewater crystallization method that can achieve the purpose of zero salt discharge, water production and salt and nitrate recovery and reuse, while realizing the reuse of output water and the resource reuse of the produced sodium sulfate and sodium chloride as industrial raw materials.

[0011] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0012] The high-salt wastewater crystallization process includes: S1 pretreatment and S2 evaporation crystallization; the S1 pretreatment includes a homogenization regulating tank, a high-density tank 1# (high-density clarification tank), a high-density tank 2# (high-density clarification tank), a high-strength membrane tank, a two-stage weak acid cation bed (resin softening device), medium and high-pressure membranes (medium-pressure membrane device + high-pressure membrane device), an ozone + activated carbon device, and an ultra-high-pressure membrane device. S1 pretreatment: the wastewater in the system enters the homogenization regulating tank in the S1 for homogenization reaction, the effluent of the homogenization regulating tank is sent to the high-density tank 1# for hardness removal, PAC, PAM, lime soda ash, and NaOH are added to the high-density tank 1# for reaction, the effluent of the high-density tank 1# is sent to the high-density tank 2# for silicon removal, PAC, PAM, and sodium aluminate are added to the high-density tank 2#, the effluent of the high-density tank 2# is sent to the high-strength membrane tank, and the high-strength membrane The effluent from the pool is sent to a two-stage weak acid cation bed. The high-salinity wastewater is filtered through chemical softening to remove hardness, silicon, ultrafiltration membrane filtration, chemical reaction, physical adsorption and auxiliary ion exchange to remove most of the hardness of the raw water, as well as silicon and some fouling organic matter to prevent subsequent membrane elements from being fouled. The effluent from the two-stage weak acid cation bed is sent to the medium and high pressure membrane device. The concentrated water from the medium and high pressure membrane device is sent to the ozone + activated carbon device. The effluent from the ozone + activated carbon device is sent to the ultra-high pressure membrane device. The concentrated water from the ultra-high pressure membrane device is sent to the concentrated water feed tank. The concentrated water from the medium and high pressure membrane device enters the ozone + activated carbon device to remove COD and then enters the ultra-high pressure membrane device for further concentration. The water produced by the medium and pressure membrane device and the ultra-high pressure membrane device and the condensed water from the evaporation crystallization unit are collected in the product water tank and sent out for circulating water replenishment. The water quality meets the relevant water quality requirements of "Design Code for Industrial Circulating Cooling Water Treatment" GB 50050-2017.

[0013] The S1 pretreatment process mainly removes Ca2+, Mg2+, silicon, suspended solids, heavy metals, some fluorine and some organic matter, etc., to ensure the normal and stable operation of the subsequent membrane system and the quality and stability of evaporated crystallized salt and nitrate;

[0014] S2 evaporation crystallization: the concentrated water in the concentrated water feed tank enters the three-effect mixed salt evaporation crystallization device to separate the mixed salt of sodium chloride and sodium sulfate and some impurities, wherein the mixed salt of sodium chloride and sodium sulfate enters the salt nitrate hot melting tank, the water discharged from the salt nitrate hot melting tank is sent to the liquid storage tank, the water discharged from the liquid storage tank is sent to the precooler, the water discharged from the precooler is sent to the freezing crystallizer to obtain decahydrated nitrate and frozen mother liquor, wherein the decahydrated nitrate enters the sodium sulfate two-effect evaporation crystallization device through the hot melting nitrate tank, the precipitated nitrate is separated and dried to obtain the finished sodium sulfate, the impurities enter the single-effect impurities crystallizer and the mother liquor is spray dried to obtain the impurities;

[0015] The frozen mother liquor separated by the freezing crystallizer enters the frozen mother liquor tank, and then passes through the high-strength membrane device and NF for further salt separation. The nanofiltration concentrated water returns to the liquid storage tank, and the nanofiltration water passes through the salt concentrated water tank and enters the sodium chloride three-effect evaporation crystallization device. The salt is separated and dried to obtain the finished sodium chloride.

[0016] Preferably, the water produced by the medium- and high-pressure membrane devices and the ultra-high-pressure membrane device in S1 and the condensed water from the evaporation and crystallization unit in S2 are collected in a product water tank and sent out for circulating water replenishment.

[0017] Preferably, the impurities produced after the reaction in the high-density tank 1# are input into the sludge thickening tank, and the obtained sludge is pressed into a tank.

[0018] Preferably, the reflux liquid from the sludge thickening tank, the backwash drainage from the high-intensity membrane tank, the regeneration drainage from the two-stage weak acid cation bed, and the backwash drainage from the ozone + activated carbon device are all discharged into the homogenization regulating tank.

[0019] Preferably, the drainage from the high-strength membrane device, the salt mother liquor discharged from the sodium chloride three-effect evaporation crystallization device, and the nitrate mother liquor discharged from the sodium sulfate two-effect evaporation crystallization device are all discharged into the concentrated water feed tank.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention achieves the purpose of zero discharge of high-salt wastewater crystallization and salt separation, and recovery and reuse of produced water and salt nitrate, while realizing the reuse of output water and the recycling of produced sodium sulfate and sodium chloride as industrial raw materials, thus protecting the environment and contributing to the realization of circular economy and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a process flow chart of the present invention;

[0023] Figure 2 It is the water balance diagram of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The embodiments of the present invention include but are not limited to the following embodiments.

[0025] like Figure 1-2 As shown, the high-salt wastewater crystallization process provided by the present invention includes: S1 pretreatment and S2 evaporation crystallization; the S1 pretreatment includes a homogenization regulating tank, a high-density tank 1# (high-density clarification tank), a high-density tank 2# (high-density clarification tank), a high-strength membrane tank, a two-stage weak acid cation bed (resin softening device), medium and high-pressure membranes (medium-pressure membrane device + high-pressure membrane device), an ozone + activated carbon device, and an ultra-high-pressure membrane device. S1 pretreatment: the wastewater in the system enters the homogenization regulating tank in the S1 for homogenization reaction, the effluent of the homogenization regulating tank is sent to the high-density tank 1# for hardness removal, PAC, PAM, lime soda, and NaOH are added to the high-density tank 1# for reaction, the effluent of the high-density tank 1# is sent to the high-density tank 2# for silicon removal, PAC, PAM, and sodium aluminate are added to the high-density tank 2#, the effluent of the high-density tank 2# is sent to the high-strength membrane tank, and the high-strength membrane The effluent from the high-strength membrane pool is sent to a two-stage weak acid cation bed. The high-salinity wastewater is removed by chemical softening, silicon removal, ultrafiltration membrane filtration, chemical reaction, physical adsorption and auxiliary ion exchange to remove most of the hardness of the raw water, as well as silicon and some fouling organic matter to prevent subsequent membrane elements from being fouled. The effluent from the two-stage weak acid cation bed is sent to the medium and high pressure membrane device. The concentrated water from the medium and high pressure membrane device is sent to the ozone + activated carbon device. The effluent from the ozone + activated carbon device is sent to the ultra-high pressure membrane device. The concentrated water from the ultra-high pressure membrane device is sent to the concentrated water feed tank. The concentrated water from the medium and high pressure membrane device enters the ozone + activated carbon device to remove COD and then enters the ultra-high pressure membrane device for further concentration. The water produced by the medium and high pressure membrane device and the ultra-high pressure membrane device and the condensed water from the evaporation crystallization unit are collected in the product water tank and sent out for circulating water replenishment. The water quality meets the relevant water quality requirements of "Design Code for Industrial Circulating Cooling Water Treatment" GB 50050-2017.

[0026] The S1 pretreatment process mainly removes Ca2+, Mg2+, silicon, suspended solids, heavy metals, some fluorine and some organic matter, etc., to ensure the normal and stable operation of the subsequent membrane system and the quality and stability of evaporated crystallized saltpeter.

[0027] 1) Silicon removal

[0028] The desiliconization process uses commonly used chemicals and electrocoagulation. The comparison of the two desiliconization processes is shown in Table 1.

[0029] Table 1 Comparison of silicon removal methods

[0030]

[0031] The comparison shows that the effect of electrocoagulation silicon removal technology is not very ideal and has many problems; chemical silicon removal has a better effect on silicon dioxide removal and can adapt to more complex water quality. Therefore, this application uses a traditional stable clarifier and adds magnesium and sodium aluminate for chemical silicon removal.

[0032] 2) Remove suspended matter

[0033] At present, the water treatment structures that are widely used to remove suspended solids and other impurities are mainly mechanical stirring clarifiers and high-density clarifiers. The comparison of the two facilities is shown in Table 2

[0034] Table 2 Comparison of suspended solids removal structures

[0035]

[0036]

[0037]

[0038] Through a multi-factor comparison of the two structures, combined with the domestic operation and operation examples of high-salt wastewater, the quality characteristics of high-salt wastewater in this application and a large amount of high-salt concentrated water engineering practice, the high-density clarifier is more suitable for the treatment of complex high-salt wastewater, so the high-density clarifier is selected as the main process facility for pre-treatment to remove hardness, silicon and some impurities.

[0039] 3) Filter

[0040] The influent of the reverse osmosis membrane group device is usually based on the clarified water output. The combined water volume usually selects sand filtration, carbon filtration and pressure ultrafiltration devices or uses submerged ultrafiltration as pretreatment.

[0041] (1) Comparison between sand filtration + pressure ultrafiltration and submerged ultrafiltration

[0042] ① There are misunderstandings about the selection of ultrafiltration: pressure ultrafiltration was first used in the pretreatment of chemical water, and many phenomena of inapplicability appeared when it was extended to recycled water and high-salt wastewater;

[0043] ② In internal pressure ultrafiltration, pollutants are trapped in the inner pores of the membrane fibers and are most difficult to discharge from the membrane elements;

[0044] ③ In external pressure ultrafiltration, pollutants are trapped between the outer surface of the membrane fiber and the membrane shell, and it is also very difficult to discharge the membrane element;

[0045] ④ Immersed ultrafiltration, since there is no membrane shell, the trapped pollutants are very easy to shake out of the membrane box from the outer surface of the membrane fibers; plus the driving force is the negative pressure formed by the suction from the middle of the membrane fibers by an ordinary centrifugal pump, the operating flux is designed to be half of the external pressure type, the water output is good, and the protection for subsequent reverse osmosis is the best;

[0046] ⑤ Comparing the three versions of the design specifications DL / T5068-1996, DL / T5068-2006, and DL / T5068-2014, it can be seen that the requirements for the inlet water of pressure ultrafiltration are getting higher and higher. This shows that pressure ultrafiltration can only accept water with very low turbidity. When the turbidity cannot be guaranteed, it is necessary to add two units of medium filter (when the water volume is large, choose V-type filter tank) + self-cleaning filter as pretreatment of pressure ultrafiltration to ensure the operation of pressure ultrafiltration. At the same time, it also shows that the medium filter before pressure ultrafiltration is very important. Many projects do not use porous plates for multi-media, and the operation effect of multi-media is very poor, which seriously affects the protection of ultrafiltration. Therefore, the current trend is: in the reuse of reclaimed water and crystallization and salt separation, more and more submerged ultrafiltration is used instead of pressure ultrafiltration.

[0047] ⑥ Characteristics of submerged ultrafiltration technology:

[0048] Remove part of COD.

[0049] Resistant to higher suspended solids.

[0050] Resistant to higher sludge concentrations.

[0051] Very good at removing colloid.

[0052] The water recovery rate is as high as ≥95%, and the backwash drainage is still in the high-strength membrane pool.

[0053] Strong impact resistance and easy operation and management.

[0054] It is suitable for use in water reuse treatment and high-salinity wastewater before reverse osmosis systems.

[0055] The technical analysis and comparison of pressure ultrafiltration and immersion ultrafiltration is shown in Table 3, and the filtration process analysis and comparison is shown in Table 4. Table 3 Comparison of pressure ultrafiltration and immersion ultrafiltration technology analysis

[0056]

[0057] Table 4 Filtration process analysis comparison table

[0058]

[0059]

[0060]

[0061] After comparing the three schemes, the membrane desalination pretreatment process of high-density clarification tank + submerged UF is adopted. Chemicals are added to the clarification tank to remove Ca2+, Mg2+ and heavy metals. After filtering through the high-intensity membrane pool, it enters the ozone + activated carbon filter to remove some organic matter, and then enters the ion exchange section to deeply remove Ca2+ and Mg2+. The concentration of Ca2+ and Mg2+ in the ion exchange regeneration liquid is relatively high. This water flows back to the regulating tank in front of the high-density pool and is de-hardened again through the high-density pool.

[0062] S2 evaporation crystallization: the concentrated water in the concentrated water feed tank enters the three-effect mixed salt evaporation crystallization device to separate the mixed salt of sodium chloride and sodium sulfate and some impurities, wherein the mixed salt of sodium chloride and sodium sulfate enters the salt nitrate hot melting tank, the water discharged from the salt nitrate hot melting tank is sent to the liquid storage tank, the water discharged from the liquid storage tank is sent to the precooler, the water discharged from the precooler is sent to the freezing crystallizer to obtain decahydrated nitrate and frozen mother liquor, wherein the decahydrated nitrate enters the sodium sulfate two-effect evaporation crystallization device through the hot melting nitrate tank, the precipitated nitrate is separated and dried to obtain the finished sodium sulfate, the impurities enter the single-effect impurities crystallizer and the mother liquor is spray dried to obtain the impurities;

[0063] The frozen mother liquor separated by the freezing crystallizer enters the frozen mother liquor tank, and then passes through the high-strength membrane device and NF for further salt separation. The nanofiltration concentrated water returns to the liquid storage tank, and the nanofiltration water passes through the salt concentrated water tank and enters the sodium chloride three-effect evaporation crystallization device. The salt is separated and dried to obtain the finished sodium chloride.

[0064] 1. Salt separation process

[0065] Nanofiltration (NF) technology is used for salt separation to separate NaCL and Na2SO4. NF can effectively intercept polyvalent ions such as sulfate and hardness, and has a high permeability to monovalent ions such as chloride and bicarbonate, which can achieve the separation of monovalent and divalent ions, laying a good foundation for the subsequent production of high-quality NaCL and Na2SO4.

[0066] The pore size range of nanofiltration (NF) membrane is between reverse osmosis membrane and ultrafiltration membrane. It has a higher removal performance for divalent and polyvalent ions and organic matter with a molecular weight between 200 and 1000, while the removal rate for monovalent ions and small molecules is lower. The retention rate for divalent and polyvalent ions is significantly higher than that for monovalent ions. It has a strong anti-pollution property for hydrophobic colloids, oils, proteins and other organic matter. Compared with RO, NF has the characteristics of low operating pressure and large water flux. The operating pressure of nanofiltration membrane is generally lower than 1.0MPa, so it is called "low-pressure reverse osmosis". The low operating pressure makes the power consumption of the separation process low, which is beneficial to reducing the investment cost and operating cost of the equipment. Compared with microfiltration (MF), NF has a lower molecular weight cutoff limit and can effectively remove many medium molecular weight solutes, such as precursors of disinfection by-products, trace organic matter such as pesticides, mutagens and other impurities.

[0067] Nanofiltration separation is a new type of membrane separation technology, and its technical principle is similar to mechanical screening. However, the nanofiltration membrane itself is charged. This is an important reason why it still has high desalination performance at very low pressure.

[0068] According to the current application of high-salt wastewater first passing through NF to separate monovalent, divalent and multivalent sulfate, the actual use effect is not good, mainly due to the impact of high COD on NF, resulting in blockage and frequent cleaning of NF to fluctuate the retention of divalent sulfate, affecting the quality of saltpeter, as well as the impact of monovalent nitrate passing through the salt side on the precipitation of sodium chloride. The operation of NF membrane before evaporation and crystallization is relatively poor, resulting in large fluctuations in the quality of saltpeter produced by the saltpeter evaporation and crystallization system, large membrane performance degradation during the service life, frequent replacement, and high cost. The present application sets up NF separation and purification for the frozen feed liquid, which completely solves the problems of short NF use cycle and poor quality of evaporated and crystallized sodium chloride. The NF membrane is used in this position to ensure that the NF membrane can operate for a long period of time, solve the problem of frequent replacement of NF membrane operation, and save costs.

[0069] Currently, the commonly used membrane concentration processes include RO, NF, DTRO / STRO, multi-effect evaporation concentration, MVR concentration, ED concentration, and ultra-high pressure RO concentration.

[0070] For TDS below 55000mg / L, it is recommended to use "conventional RO + desalination RO" for concentration. Conventional RO and desalination RO have low investment, mature products, and many operating cases. Within this range, other concentration processes have little advantage.

[0071] For TDS above 55000mg / L, DTRO / STRO, ultra-high pressure RO, multi-effect evaporation concentration, MVR concentration, ED concentration, etc. can be used.

[0072] 1) Disc-tube reverse osmosis DTRO

[0073] Reverse osmosis is a technology developed based on the principle of semipermeable membrane. Its basic principle is to apply pressure on the salt water side to force water molecules to pass through the semipermeable membrane. Most of the dissolved salts, organic matter, bacteria and suspended solids in the solution are mechanically intercepted by the membrane and discharged together with the system retentate. The resulting permeate is demineralized water or qualified discharge water.

[0074] DT separation membrane component technology is a major technological advancement in the field of reverse osmosis technology. It has a wide range of applications and successful cases in landfill leachate treatment, seawater, brackish water desalination and purification, material desalination and concentration, and wastewater treatment.

[0075] DT membrane assembly is a new type of flat-plate structure membrane assembly, which is completely different from the traditional roll-type membrane assembly. Its internal mechanism is as follows: the feed liquid enters the pressure vessel through the inlet, flows from the channel between the guide plate and the shell to the other end of the assembly, and at the flange at the other end, the feed liquid enters the guide plate through 8 channels (as shown in the figure). The treated liquid flows through the filter membrane quickly at the shortest distance, then reverses 180° to the other membrane surface, and then flows into the next guide plate from the notch in the center of the guide plate (as shown in the figure), thus forming a double "S" shaped route on the membrane surface from the circumference of the guide plate to the center of the circle, then to the circumference, and then to the center of the circle. The concentrated liquid finally flows out from the feed end flange. The distance between the two guide plates of the DT assembly is 3mm, and there are convex points arranged in a certain way on the surface of the guide plate. The core filter membrane package of the module (as shown in the figure) consists of two concentric annular membranes, with a layer of filamentary mesh sandwiched between the membranes to form a permeable grid. The clean water passing through the membrane flows along the filamentary grid to the permeate channel outside the central tie rod. The O-ring on the guide plate prevents the raw water from entering the permeate channel (as shown in the figure). The distance from the membrane to the center of the permeate is very short and is equal to all the filter membranes in the module.

[0076] The special hydraulic design of the DT membrane assembly allows the treated liquid to form turbulence when it flows through the filter membrane surface under pressure and collides with convex points, increasing the permeability and self-cleaning function, thereby effectively avoiding membrane blockage and concentration polarization, and successfully extending the service life of the membrane; it is also easy to clean the scale on the membrane during cleaning, ensuring that the DT membrane assembly is suitable for harsh water inlet conditions.

[0077] 2) Pipeline reverse osmosis STRO

[0078] The pipe network reverse osmosis belongs to the scroll structure component. Based on the traditional scroll RO component, the flow channel is widened and the grid structure is improved, so that the suspended solids in the influent are not easy to deposit on the membrane component. Its membrane area is larger than that of DTRO. It was initially developed to replace the disc-tube reverse osmosis for treating landfill leachate.

[0079] 3) High-pressure membrane concentration

[0080] High-pressure reverse osmosis is developed on the basis of seawater desalination membrane. It is a new type of high-fouling and plugging-resistant reverse osmosis designed for saline wastewater. It uses special membrane materials so that solid suspended matter in the influent water will not easily settle inside the membrane assembly. It has a wide range of applications and high cost-effectiveness.

[0081] 4) Multi-effect forced circulation evaporation crystallization

[0082] Multi-effect forced circulation evaporation crystallization is a series evaporation system that uses the secondary steam of the previous effect as the heating steam of the next effect. In multi-effect evaporation, the operating pressure of each effect, the corresponding heating steam temperature and the boiling point of the solution are reduced in sequence and balanced by themselves. In the evaporation crystallization process, the output of secondary steam is large and contains a large amount of latent heat, so it should be recovered and utilized. If the secondary steam is passed into the heating chamber of another evaporator, as long as the operating pressure and boiling point of the solution of the latter are lower than the operating pressure and boiling point of the original evaporator, the secondary steam can still play a heating role.

[0083] Each evaporator in the multi-effect forced circulation evaporation crystallization is called an effect. The evaporator that is fed with heating steam is called the first effect, and the evaporator that uses the secondary steam in the first effect evaporation chamber as a heat source is called the second effect, and so on. The purpose of using a multi-effect evaporator is to save the consumption of heating steam by using the secondary steam multiple times. Multi-effect forced circulation evaporation crystallization is suitable for working conditions with large changes in influent and large fluctuations in water quality. It has strong adaptability and generally uses three effects in combination with the amount of high-salinity wastewater.

[0084] 5) Mechanical vapor recompression technology MVR

[0085] MVR is the abbreviation of mechanical vapor recompression technology, which uses the secondary steam and its energy generated by the evaporation system itself to upgrade low-quality steam into a high-quality steam heat source through the mechanical work of the compressor. This cycle provides heat energy to the evaporation system, thereby reducing the demand for external energy, an energy-saving technology.

[0086] The MVR evaporation process is an energy-saving technology that reuses the energy of the secondary steam generated by itself, thereby reducing the demand for external energy. In the multi-effect evaporation process, the secondary steam of a certain effect of the evaporator cannot be directly used as the heat source of the main effect, but can only be used as the heat source of the secondary effect or several secondary effects. If it is used as a heat source of the main effect, it must be given additional energy to increase its temperature (pressure). The evaporator with MVR technology can compress all the secondary steam in the evaporator, compress the steam, increase the steam pressure and thermal enthalpy value, and then re-input it into the heating chamber for evaporation, and continuously circulate evaporation. The secondary steam generated by evaporation condenses in the heat exchange chamber and becomes condensed water and is discharged.

[0087] MVR is more suitable for low-concentration evaporation and concentration. If it is used for high-concentration evaporation and crystallization or liquid with high sodium chloride content, the boiling point rises, and multiple compressors are required to be connected in series or a high-speed compressor with high temperature rise and high pressure ratio is selected. The MVR evaporation and crystallization system has high requirements for the stability of water quantity and water quality. It is not suitable for conditions with large changes in water quantity and water quality. It has low adjustability. When the temperature rise is high, the compressor needs to be operated in series or a high-speed centrifuge. Due to the high speed, the equipment failure rate is high and there is no backup. Once a failure occurs, the system will be shut down intelligently. Compared with the multi-effect evaporation and crystallization MVR, the reliability is poor.

[0088] 6)ED ion membrane concentration

[0089] Ion exchange membranes are membranes that selectively permeate ions and can be roughly divided into cation exchange membranes and anion exchange membranes. Because the negative charge exchange groups of cation exchange membranes are fixed, cations can pass through, while anions are repelled by the negative charge and cannot pass through. Anion exchange membranes have the opposite effect.

[0090] Ion exchange resin is similar to ion exchange membrane. Ion exchange resin exchanges ions by adsorbing ions through granular ion exchange bodies. However, once the resin has no adsorption capacity, it needs to be regenerated, which will produce a large amount of regeneration waste liquid. In contrast, ion exchange membrane only concentrates high-salt wastewater through anion and cation membranes under the action of electric field. The process does not require regeneration and can be used continuously for a long time.

[0091] The electrically driven ion membrane device utilizes the selective permeability of ion exchange membranes to anions and cations. Under the action of a DC electric field, anions and cations are directed to migrate, thereby achieving the purpose of separation, purification and concentration of electrolyte solutions. Therefore, ion exchange membranes and DC electric fields are two necessary conditions for the process. The most common and basic use of ion membrane devices is for desalination or concentration of aqueous solutions. It has the following characteristics:

[0092] ED ion membrane technology is a combination of ion membrane dialysis diffusion and electrochemical process. By using selective permeable ion membrane, driven by an external DC electric field, ions in water continuously pass through the ion membrane, that is, ions continuously migrate from the fresh water chamber to the concentrated water chamber, while water is retained in the fresh water chamber, thereby achieving salt concentration and water separation at the same time.

[0093] ED ion membrane technology is used in the crystallization and salt separation process to achieve high concentration and purification of high-salinity wastewater. The system's high-salinity wastewater TDS can reach more than 200,000 mg / L. Under normal circumstances, the power consumption for treatment is low, and the energy consumption for treatment is ≤12kWh / ton of water.

[0094] The performance of the membrane stack is stable: This technology does not involve phase change during the concentration of high-salt wastewater, and can still maintain a high dynamic ion exchange capacity and low membrane surface resistance.

[0095] Standardization of membrane blocks: The device frames are made of Japanese high-alloy steel and composite corrosion-resistant materials, and are compressed by hydraulic devices. The super strong fastness and corrosion resistance can ensure stable operation for more than 10 years under high-salt conditions.

[0096] Comparison of membrane concentration processes is shown in Table 5

[0097]

[0098]

[0099]

[0100] According to the above comparison, both medium and high pressure membrane concentration processes are more suitable for the application in this application, with strong anti-pollution performance, low investment, low operating costs and obvious reduction degree.

[0101] 2. Evaporation crystallization process selection

[0102] At present, the main technologies used for evaporation and crystallization of high-salinity wastewater are multiple-effect evaporation (MED) and mechanical steam recompression (MVR).

[0103] Multi-effect evaporation crystallization technology (MED):

[0104] In single-effect evaporation, the unit heating steam consumption is greater than 1, that is, evaporating 1kg of water requires more than 1.1kg of heating steam. Therefore, for evaporation processes with large evaporation volumes, if single-effect operation is used, a large amount of heating steam will inevitably be consumed, which is economically unreasonable. In view of this, multi-effect evaporation is often used in industry. The order of the effect numbers in multi-effect evaporation is that the effect where the raw steam enters is the first effect, and the secondary steam flashing out of the first-effect evaporation chamber is used as heating steam to enter the second effect, and so on.

[0105] In multiple-effect evaporation, in order to ensure that each effect has a certain heat transfer driving force, the operating pressure of each effect must be reduced in turn, and accordingly, the boiling point and secondary steam pressure of each effect are reduced in turn. Therefore, multiple-effect evaporation can only be achieved when the pressure of the fresh heating steam provided is high and the final effect adopts vacuum. Multiple-effect evaporation technology (MED) is to circulate and reuse steam heat energy many times to reduce heat energy consumption and reduce operating costs. The heated brine evaporates in multiple evaporators in series, and the secondary steam generated by the front-effect evaporation is used as the heat source of the rear-effect evaporator. The boiling point temperature and pressure of the rear-effect wastewater are lower than those of the front effect, and the heat energy regeneration between effects can be repeated many times. Generally, only three to four effects are achieved at most, and the steam saving effect is better. It has good adaptability to the fluctuations in the amount and quality of high-salt wastewater. At present, multiple-effect evaporation crystallization processes are more commonly used on high-salt wastewater.

[0106] Steam Mechanical Recompression Crystallization Technology (MVR):

[0107] The process flow of falling film mechanical vapor compression recirculation evaporation technology is as follows:

[0108] 1) First, the salt-containing wastewater to be treated enters the liquid tank and is pumped into the heat exchanger. The last stage plate heat exchanger uses new steam to make the water temperature reach the boiling point. MVR uses boiling point feed.

[0109] 2) The heated high-salt wastewater uses steam to pass through a deaerator to remove oxygen, carbon dioxide, non-condensable gases, etc. in the water, reducing corrosion and scaling hazards to the evaporator system.

[0110] 3) The brine enters the bottom tank of the concentrator and mixes with the high-salt wastewater circulating inside the concentrator, and is then pumped to the water distribution device at the top of the heat exchanger for membrane spreading.

[0111] The brine flows into the tube through the liquid distributor at the top of the heat exchange tube, is evenly distributed on the inner wall of the tube, and flows down to the bottom tank in the form of a thin film. When the high-salt wastewater flows down along the tube wall, it exchanges heat with the steam in the shell side for concentration and evaporation, and the steam and the unevaporated high-salt wastewater fall to the bottom tank together. The secondary steam generated by evaporation enters the steam compressor through the demister, and the steam temperature and pressure are increased after compression. The compressed steam enters the shell side of the heat exchanger for heat exchange. The compressed steam condenses in the shell side through heat exchange, releasing latent heat, heating the brine film with a lower temperature that falls along the inner wall of the tube, causing part of the brine to evaporate.

[0112] After the compressed steam releases latent heat, it condenses into water on the outer wall of the heat exchange tube, descends along the tube wall, accumulates at the bottom of the heating chamber, and is pumped to the primary plate heat exchanger. When the condensed water flows through the heat exchanger, it heats the feed high-salt wastewater, and then enters the evaporation system after being heated to a point close to the boiling point of the feed liquid through the steam plate exchanger. By discharging a small amount of high-salt wastewater, the concentration of brine in the evaporation concentrator can be properly controlled. When using mechanical compression cycle evaporation technology to treat wastewater, in addition to the need for external steam at startup, the feed liquid still needs a certain amount of steam to supplement the feed liquid so that the feed liquid reaches the boiling point; during normal operation, the heat energy required to evaporate the wastewater is mainly provided by the heat energy released or exchanged during steam condensation and condensed water cooling.

[0113] The crystallization form of MVR crystallizer is similar to that of MED crystallizer, which will not be elaborated here. In addition to using steam to heat the feed brine to boiling point and remove the steam for non-condensables, a large amount of fresh steam is required at startup. Electricity is mainly used instead of steam as the heat source during the evaporation process.

[0114] The technical comparison of MED and MVR is shown in Table 6, and the economic comparison of MED and MVR systems is shown in Table 7

[0115] Table 6 Technical comparison of MED and MVR

[0116]

[0117]

[0118] After high-salt wastewater is concentrated by membrane, the organic matter, sodium nitrate and impurity content will be separated and concentrated along with the large amount of sodium sulfate and sodium chloride precipitated, and the enrichment concentration will be very high. A certain amount of mother liquor will be discharged through the crystallization effect of the mixed salt evaporation crystallizer, thereby balancing the enrichment concentration of the impurity content of the evaporation crystallization system, preventing the impact on the crystallization of the sodium sulfate and sodium chloride purification process, and reducing the entrained impurities in the salt and nitrate precipitation process.

[0119] Table 7 Economic comparison of MED and MVR systems

[0120]

[0121]

[0122]

[0123] Note: 1. In the above table, the high-pressure reverse osmosis concentrated water evaporation crystallization uses MED three-effect evaporation crystallizer and MVR evaporation crystallizer for comparison, sodium sulfate recrystallization and sodium chloride are in multi-effect form, and the mixed salt crystallization system uses evaporation crystallization and spray drying system.

[0124] 2. The above electricity charges are calculated at 0.48 yuan / KWh, steam is calculated at 98 yuan / ton, and the circulating water is reused using the water produced in this application. The circulating water cost of 0.1 yuan / m3 is included in the cost.

[0125] Due to the complexity of drainage in the park, the amount of water and water quality fluctuate greatly, and the concentration process is difficult to control. In particular, the saltpeter is relatively large and the required boiling point rise varies greatly, which is not conducive to the selection and operation of the MVR steam compressor, resulting in large changes in the amount of evaporated water and poor system stability and reliability.

[0126] MVR is mainly used for the concentration of high-salt wastewater and is not suitable for evaporation and crystallization of high-boiling-point wastewater. Considering that the changes in water volume and water quality in this application may be relatively large and frequent, MVR falling film evaporation is more likely to cause salt deposition in the falling film tube main pipe or large changes in concentrated concentration, resulting in main pipe blockage and affecting the MVR heat exchange efficiency. The TDS of concentrated water in the MVR concentration process changes greatly and is difficult to control. Unstable concentrated water will have a great impact on the operation of the evaporation and crystallization system, and the system operation stability and reliability are poor. Considering the stability of the steam in this application and the overall steam consumption of the system, the operation reliability and the response to changes in water volume and quality, this project chooses MED with higher reliability.

[0127] Based on the above considerations, both MED and MVR are mature technologies, but MVR is mostly used in the concentration stage. Combined with the water quality of this application, sodium chloride is the main component, which requires a higher boiling point rise, and the water quality changes greatly. Considering that during the crystallization process, the boiling point of the feed liquid rises higher, and the overall steam consumption and electricity consumption are comprehensively compared, MED has a slight advantage in operating costs. Considering the stability and reliability of the evaporation crystallization process, this application selects triple-effect evaporation crystallization for the mixed salt purification evaporation crystallization process.

[0128] 3. Comparison of evaporation crystallizer types

[0129] 1) FC crystallizer

[0130] FC crystallizer is also called forced circulation crystallizer or growth crystallizer. This crystallizer has the characteristics of simple structure and easy operation. The crystal growth area is at the lower end of the crystallizer separator. A crystal elutriator is usually configured at the bottom of the crystallizer. When designing the crystallizer, it is necessary to select a suitable circulating feeding method to avoid crystal breakage or crystallized salt hanging on the wall, consider the anti-short circuit measures of the circulating liquid, and sufficient growth space for the crystal.

[0131] FC crystallizer can be combined with multi-effect evaporation concentration technology to form a multi-effect forced circulation evaporation crystallizer, which has good energy-saving effect and has great utilization value in reducing production costs in the production environment.

[0132] This type of crystallizer is generally used in situations where the crystal size requirement is not high or the crystal is easy to grow, such as the evaporation crystallization of sodium chloride, sodium sulfate, etc.

[0133] It is characterized by simple structure and easy operation. In terms of structural design, it should be noted that the position of the evaporation crystallization chamber should be 4-6m higher than that of the heating chamber (the distance from the liquid level of the evaporation crystallization chamber to the upper tube plate of the heating chamber) to ensure that the upper tube part of the heat exchange tube does not boil, and no crystals will precipitate in the heat exchange tube, which will reduce the heat exchange efficiency. Secondly, the flow rate in the upper circulation tube should be less than 1m / s, and the flow rate in the lower circulation tube can be designed as 1.3m~1.5m / s. The purpose is that when the heated solution enters the evaporation crystallization chamber, bubbles will be generated in the upper circulation tube due to the influence of the vacuum degree. In order to prevent sudden boiling, the tube diameter should be slightly larger than the lower circulation tube.

[0134] 2) DTB crystallizer

[0135] DTB type crystallizer evaporation crystallizer, namely, draft tube plus baffle evaporation crystallizer, is a fine crystal slurry circulation crystallizer. DTB (DTB = draft tube battle) refers to the two words draft barrel and baffle, so this type should be called draft barrel and baffle type crystallizer. There are many kinds of structures in industry. The most typical and commonly used is the Swenson type DTB crystallizer. The internal draft barrel is generally made into a variable diameter (thin at the bottom and thick at the top) to ensure that the flow rate at the top of the draft barrel is relatively gentle, forming a uniform supersaturation zone, preventing splashing, and reducing crystal scars on the surface of the crystallizer. This type of crystallizer is divided into two areas by a baffle to achieve their respective functions. This type of crystallizer can produce larger particles, has a higher production intensity, and is not easy to scar inside the device. It has become one of the main forms of continuous crystallizers and can be used for crystallization operations of vacuum cooling, evaporation, direct contact freezing and reaction methods.

[0136] The structural design of the DTB type crystallizer is relatively complex. The vacuum evaporation has a heating chamber and a condensing water bucket. The vacuum flash cooling only has an evaporation crystallization chamber. When designing, the sedimentation area should be designed according to the different sedimentation velocities of the evaporation zone, crystallization zone, and mother liquor zone, so as to calculate the diameter of the crystallizer. The sedimentation rate is determined by the characteristics of the crystallized material. Generally speaking, the rising speed in the flow tube is ≤1m / s, the sedimentation speed in the evaporation chamber is ≤0.2m / s, the sedimentation speed in the crystallization zone is ≤0.1m / s, and the mother liquor zone is ≤0.05m / s. The design of the vertical axial flow pump is the key to the DTB crystallizer. It is a special axial flow pump with large flow, low head, low speed, and large impeller diameter. The size of the crystal particle size is often closely related to its design.

[0137] 3) Oslo Crystallizer

[0138] OSLO type evaporation crystallizer is also called Oslo crystallizer, Krystal crystallizer or particle size classification crystallizer, which is a mother liquid circulation continuous crystallizer. It is widely used in the crystallization of material crystals with high requirements for crystal size in the food, medicine and chemical industries. It consists of a suspension chamber, a cooler and a circulation pump. The cooler is generally a single-pass tube cooler. The hot concentrated liquid is added before the circulation pump, mixed with the circulating mother liquid and cooled together through the cooler to produce supersaturation. The key point of operation is to make this supersaturation in the metastable zone to avoid spontaneous nucleation. The product suspension is drawn out from the bottom of the crystallizer.

[0139] The characteristic of the Oslo type crystallizer is that it can allow the crystal nucleus to grow in the boiling layer without being restricted by the residence time. It can crystallize larger particles than the FC type and DTB type, and the crystal size can be above 3.0mm. It consists of a heating chamber, a condensing water bucket, an evaporation crystallization chamber, a horizontal axial flow pump, and a circulation pipe; the evaporation crystallization chamber consists of a central circulation pipe (boiling layer), an evaporation chamber, and a crystal cultivation chamber. The size of the crystal cultivation chamber should be designed according to the characteristics of the material and the crystal size requirements. The larger the particle size requirement, the longer the crystallization time, and the larger the volume of the crystal cultivation chamber. The crystallization time is often 6 to 10 hours, or even longer. The volume of the crystal cultivation chamber is 6 to 10 times the feed rate (m3 / h).

[0140] Combined with the analysis and comparison of the above crystallizers, considering that this process is only to purify and precipitate sodium sulfate and sodium chloride, so that the supersaturated precipitation of sodium sulfate and sodium chloride is separated from the mother liquor enriched with a large amount of impurities, it creates favorable conditions for the subsequent salt separation to obtain sodium sulfate and sodium chloride of better quality. It is an intermediate separation process and does not pursue large-particle salt. This application recommends the use of a FC three-effect forced circulation evaporation crystallizer with wide adaptability.

[0141] 4. Salt disposal

[0142] In order to ensure the quality of crystallized salt, the mixed salt crystallizer discharges a part of the mother liquor enriched with impurities into the mixed salt crystallizer for further evaporation and crystallization to precipitate the impurity salt, and discharges part of the mother liquor into the mother liquor drying system to form mixed salt. This part of mixed salt contains complex organic components, so it is temporarily stored or disposed of as hazardous waste by a qualified treatment unit.

[0143] 5. Sludge disposal process selection

[0144] The sludge generated in this application mainly comes from the clarification tank. In order to reduce the volume of the dehydrated sludge for easy transportation and prevent it from dripping during transportation, the moisture content of the dehydrated sludge is generally required to be below 70%. Dehydration equipment is a key equipment for solid-liquid separation. The selection of dehydration equipment is often determined based on the properties of the sludge, taking into account technical, economic, environmental and operation management factors, and after comprehensive comparison. Dehydration equipment requires stability, durability, continuous production, satisfactory treatment effect, easy operation and maintenance, low investment cost, and economical operation cost. At present, the mechanical dehydration equipment used at home and abroad is mainly vacuum filtration, belt filter press, plate and frame filter press and centrifugal dehydration. The performance comparison is shown in Table 8

[0145] Table 8 Comparison of sludge disposal processes

[0146]

[0147] Through the above comparison, previous design experience and the operation of the existing plate and frame filter press (sludge moisture content ≤ 70%), this application adopts a plate and frame filter press, which is more economical and has reliable performance. The main components of the sludge produced in this application are inorganic sludge such as calcium carbonate and magnesium hydroxide. According to the "General Standards for Identification of Hazardous Wastes" (GB 5085.7-2019), it is not a hazardous waste and is treated in accordance with the latest solid waste treatment standards and specifications, national policies, laws, regulations and standards.

[0148] 6. Steam source

[0149] The process steam and heating steam in this application are connected from the main pipe network laid in the park, with design parameters of 0.5MPa, 158℃, and a steam consumption of about 17t / h.

[0150] Water balance

[0151] The water inlet volume of the three-effect mixed salt evaporation crystallization unit is 28.6m3 / h (28.26m3 / h of concentrated water from the ultra-high pressure membrane unit of the pretreatment device + 0.32m3 / h of drainage from the sodium chloride evaporation crystallization unit and the sodium sulfate evaporation crystallization unit). Through the three-effect mixed salt evaporation crystallization device, sodium sulfate and sodium chloride mixed salt are produced by downstream evaporation and crystallization, and part of the mixed salt mother liquor is discharged into the single-effect mixed salt evaporation crystallization unit for further evaporation and crystallization separation to obtain mixed salt. The mixed salt evaporation crystallizer discharges the mixed salt mother liquor for drying treatment, and the sodium sulfate and sodium chloride separated by the mixed salt evaporation crystallizer are heat-dissolved to configure saturated feed liquid. The salt-nitre mixture enters the freezing crystallization system to separate decahydrate nitre, and the decahydrate nitre is heat-dissolved and enters the second-effect evaporation crystallizer to produce sodium sulfate; the frozen supernatant is separated by NF, and the NF water enters the sodium chloride evaporation crystallizer to obtain the sodium chloride product.

[0152] The water inlet volume of the sodium chloride evaporation crystallization unit is 4.79m 3 / h(Concentrated water nanofiltration produces 4.79m 3 / h), passes through the salt concentration water tank, and enters the sodium chloride three-effect downstream evaporation crystallization system, and is finally separated and dried to obtain sodium chloride salt through evaporation crystallization.

[0153] The water inlet volume of the sodium sulfate evaporation crystallization unit is 2.30m 3 / h, passes through the hot-melt nitrate tank, enters the sodium sulfate second-effect evaporation crystallization system, and finally separates and dries the sodium sulfate.

[0154] The water inlet volume of the mixed salt evaporation crystallization unit is about 2.0m 3 / h, through the single-effect impure salt evaporation crystallization system, the impure salt is separated, and the impure salt mother liquor is about 0.3m 3 / hFinally the mixed salt is dried out.

[0155] The water quality of the system water (influent) in the above embodiment is shown in Table 9

[0156] Table 9 Influent water quality table

[0157]

[0158]

[0159] The water quality of the produced water is shown in Table 10

[0160]

[0161]

[0162] The above embodiment is only one of the preferred implementation modes of the present invention and should not be used to limit the protection scope of the present invention. Any changes or modifications that are made to the main design concept and spirit of the present invention and have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention.

Claims

1. A high-salinity wastewater crystallization process, characterized in that: The steps include: S1 pretreatment and S2 evaporation crystallization; S1 pretreatment: the wastewater in the system enters the homogenization regulating tank in S1, the effluent from the homogenization regulating tank is sent to high-density tank 1#, PAC, PAM, lime soda ash and NaOH are added to high-density tank 1# for reaction, the effluent from high-density tank 1# is sent to high-density tank 2#, PAC, PAM and sodium aluminate are added to high-density tank 2#, the effluent from high-density tank 2# is sent to high-strength membrane tank, the effluent from high-strength membrane tank is sent to two-stage weak acid cation bed, the effluent from two-stage weak acid cation bed is sent to medium and high pressure membrane device, the concentrated water from medium and high pressure membrane device is sent to ozone + activated carbon device, the effluent from ozone + activated carbon device is sent to ultra-high pressure membrane device, the concentrated water from ultra-high pressure membrane device is sent to concentrated water feed tank; S2 evaporation crystallization: the concentrated water in the concentrated water feed tank enters the three-effect mixed salt evaporation crystallization device to separate the mixed salt of sodium chloride and sodium sulfate and some impurities, wherein the mixed salt of sodium chloride and sodium sulfate enters the salt nitrate hot melting tank, the water discharged from the salt nitrate hot melting tank is sent to the liquid storage tank, the water discharged from the liquid storage tank is sent to the precooler, the water discharged from the precooler is sent to the freezing crystallizer to obtain decahydrated nitrate and frozen mother liquor, wherein the decahydrated nitrate enters the sodium sulfate two-effect evaporation crystallization device through the hot melting nitrate tank, the precipitated nitrate is separated and dried to obtain the finished sodium sulfate, the impurities enter the single-effect impurities crystallizer and the mother liquor is spray dried to obtain the impurities; The frozen mother liquor separated by the freezing crystallizer enters the frozen mother liquor tank, and then passes through the high-strength membrane device and NF for further salt separation. The nanofiltration concentrated water returns to the liquid storage tank, and the nanofiltration water passes through the salt concentrated water tank and enters the sodium chloride three-effect evaporation crystallization device. The salt is separated and dried to obtain the finished sodium chloride.

2. A high-salinity wastewater crystallization process according to claim 1, characterized in that: The water produced by the medium- and high-pressure membrane devices and the ultra-high-pressure membrane devices in S1 and the condensed water of the evaporation and crystallization unit in S2 are collected in a product water tank and sent out for circulating water replenishment.

3. A high-salinity wastewater crystallization process according to claim 1, characterized in that: The impurities produced after the reaction in high-density tank 1# are input into the sludge thickening tank, and the obtained sludge is pressed into a tank.

4. A high-salinity wastewater crystallization process according to claim 1, characterized in that: The impurities produced after the reaction in the high-density tank 2# are input into the silicon removal concentration tank, and the obtained sludge is pressed into a tank.

5. A high-salinity wastewater crystallization process according to claim 1, characterized in that: The reflux liquid from the sludge concentration tank, the backwash drainage from the high-intensity membrane tank, the regeneration drainage from the two-stage weak acid cation bed, and the backwash drainage from the ozone + activated carbon device are all discharged into the homogenization regulating tank.

6. A high-salinity wastewater crystallization process according to claim 1, characterized in that: The drainage of the high-strength membrane device, the salt mother liquor discharged from the sodium chloride three-effect evaporation crystallization device, and the nitrate mother liquor discharged from the sodium sulfate two-effect evaporation crystallization device are all discharged to the concentrated water feed tank.

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