Seed crystal method evaporation and concentration process applied to high-salinity and high-hardness wastewater

Abstract

According to the seed crystal method evaporation concentration process applied to the high-salinity and high-hardness wastewater, a seed crystal tank is provided with an online suspended matter (SS) analyzer at the same time, the concentration of seed crystals in mixed liquid in the seed crystal tank can be measured in real time, the recovery amount of the seed crystal liquid is adjusted according to data fed back by the online analyzer, and when the concentration of the seed crystals in the seed crystal tank is smaller than the designed concentration of the seed crystals, the recovery amount of the seed crystals is adjusted. The recovery amount of the seed crystal liquid is increased until the suspended matter online analyzer detects that the concentration in the seed crystal tank reaches the designed seed crystal concentration; and when the seed crystal concentration in the seed crystal tank is more than the designed seed crystal concentration, stopping recovering the seed crystal liquid. According to the invention, the concentrated solution generated by the evaporation and concentration device is cured and precipitated, and the concentrated solution with higher concentration and larger crystal particles at the bottom is recovered, so that crystal grain grading is realized, high-quality seed crystals are provided for the system, and scaling of equipment is effectively prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental wastewater treatment, and specifically is a seed crystal evaporation and concentration process applied to high-salt and high-hardness wastewater. Background Art

[0002] With the vigorous development of my country's modern industry, environmental problems have become increasingly prominent. Due to the shortage of water resources, achieving zero discharge of high-salt and high-hardness wastewater has become an important goal for industrial enterprises. The treatment process of high-salt and high-hardness wastewater is relatively complicated due to its large amount of water and a wide variety of components. It is usually concentrated and reduced first, and then the concentrate is treated separately to reduce the treatment cost. Regardless of whether thermal or membrane methods are used, high-salt and high-hardness wastewater usually needs to be treated for hardness removal first to prevent equipment scaling. The hardness removal treatment of high-salt and high-hardness wastewater has a high cost of chemicals, and the large amount of sludge generated in the process cannot be recycled and can only be treated as solid waste.

[0003] Therefore, it is of great significance to develop a process for treating difficult-to-treat industrial wastewater with high salt content and high hardness, which can effectively prevent equipment scaling, reduce production costs, and have simple and easy-to-operate procedures. Summary of the invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a seed crystal evaporation and concentration process for high-salt and high-hardness wastewater, so as to at least partially solve the above technical problems.

[0005] The technical solution adopted by the present invention is as follows:

[0006] The present invention proposes a seed crystal evaporation concentration process for high-salt and high-hardness wastewater, comprising the following process steps:

[0007] Step 1: The seed tank is also equipped with a suspended solid (SS) online analyzer, which can measure the seed concentration in the mixed solution in the seed tank in real time, and adjust the recovery amount of the seed solution according to the data fed back by the online analyzer. When the seed concentration in the seed tank is less than the designed seed concentration, the recovery amount of the seed solution is increased until the suspended solid online analyzer detects that the concentration in the seed tank reaches the designed seed concentration; when the seed concentration in the seed tank is more than the designed seed concentration, the recovery amount of the seed solution is stopped;

[0008] Step 2: The mixed liquid in the seed tank is sent to an evaporation concentration device. After evaporation and concentration, the discharge volume of the concentrated liquid is determined according to the water inlet, evaporation volume and solution concentration of the evaporation concentration device, and the concentrated liquid is quantitatively discharged into the concentration tank to maintain the ion concentration of the solution in the evaporation concentration device (a term in the evaporation industry, a circulating solution that is repeatedly heated and evaporated in the evaporation concentration device, referred to as circulating liquid, here changed to solution) in the evaporation concentration device. Balance;

[0009] Step 3: After the concentrate in the concentrate tank is matured and precipitated, the bottom is a concentrate with higher concentration and larger crystal particles, and the upper part is a concentrate with fine crystal particles and lower concentration.

[0010] In one embodiment of the present invention, the concentrated liquid at the bottom of the concentration tank is recovered to the seed tank and mixed with high-salt and high-hardness wastewater to enter the evaporation concentration device, and the concentrated liquid containing fine particles and lower concentration at the top of the concentration tank is discharged for further treatment.

[0011] In one embodiment of the present invention, a portion of seed solution is periodically discharged from the bottom of the concentrate tank to be mixed with the concentrate discharged from the upper part of the concentrate tank.

[0012] In one embodiment of the present invention, the seed crystal evaporation concentration process applied to high-salt and high-hardness wastewater also includes the following process steps:

[0013] After the wastewater is pre-treated with a reducing agent and an adsorbent, it is concentrated using a high-pressure nanofiltration membrane and a high-pressure reverse osmosis membrane;

[0014] Wherein, the reducing agent is at least one of sodium sulfite, sodium sulfide, ferrous sulfate or ammonium sulfite;

[0015] The adsorbent is a chitosan / modified lignin / nano-sodium titanate hybrid composite hydrogel, which is prepared by free radical polymerization reaction using modified lignin, chitosan, acrylic acid and nano-sodium titanate as monomers; the modified lignin is prepared by modifying lignin by amination and phosphorylation;

[0016] The dosage of the reducing agent is 0.5 g / L to 1 g / L, and the dosage of the adsorbent is 4 g / L to 8 g / L.

[0017] In one embodiment of the present invention, lignin and sodium hydroxide solution are uniformly mixed to obtain a lignin alkaline solution, and then 3-chloro-2-hydroxypropyltrimethylammonium chloride is added, and the reaction is carried out at 80°C to 90°C for 2h to 3h to obtain a solution containing aminated lignin; a diammonium hydrogen phosphate solution with a mass concentration of 25% to 30% is prepared, epichlorohydrin and formaldehyde solution are added, and the reaction is carried out at 65°C to 85°C for 2h to 3h, and the reaction solution is mixed with the mixed solution containing aminated lignin, and the reaction is carried out at 80°C to 90°C for 3h to 6h, and dried to obtain the modified lignin.

[0018] In one embodiment of the present invention, the concentration of the sodium hydroxide solution is 20% to 50%; and / or

[0019] The concentration of the formaldehyde solution is 30% to 50%; and / or

[0020] The mass ratio of the lignin, 3-chloro-2-hydroxypropyltrimethylammonium chloride and epichlorohydrin is 1:0.2-0.3:0.2-0.5; and / or the feeding ratio of the lignin, sodium hydroxide solution and formaldehyde solution is 1g:10-20mL:0.7-1mL.

[0021] In one embodiment of the present invention, the preparation method of the adsorbent comprises the following steps: dissolving the modified lignin, chitosan, acrylic acid and nano sodium titanate in deionized water, adding sodium carboxymethyl cellulose, a crosslinking agent and an initiator in sequence, stirring evenly, and heating in a water bath at 35°C to 40°C to complete gelation to obtain the adsorbent.

[0022] In one embodiment of the present invention, the crosslinking agent is at least one of polyethylene glycol diglycidyl ether, ethylene glycol dimethacrylate or N,N-methylenebisacrylamide; and / or the initiator is at least one of hydrogen peroxide, ascorbic acid, potassium persulfate or ammonium persulfate.

[0023] In one embodiment of the present invention, the mass ratio of the modified lignin, chitosan, acrylic acid and nano-sodium titanate is 1:1-2.5:0.3-0.6:0.25-0.4; and / or the lignin is one of alkali lignin, enzymatic lignin, lignin sulfonate or lignin carboxylate.

[0024] In one embodiment of the present invention, the high pressure nanofiltration membrane is at least a two-stage concentrated water internal circulation structure; and / or the operating pressure of the high pressure nanofiltration membrane is 2.0MPa to 5.0MPa, and the temperature is 15°C to 45°C.

[0025] The beneficial effects of the technical solution of the present invention are:

[0026] By ripening and precipitating the concentrated liquid produced by the evaporation and concentration device, the concentrated liquid with high concentration and large crystal particles at the bottom is recovered to achieve grain classification, provide high-quality crystal seeds for the system, and effectively prevent equipment scaling.

[0027] By online monitoring of the crystal suspension concentration in the inlet water of the evaporation and concentration device, the recovery amount of the seed solution is adjusted to buffer the fluctuation of the inlet water, and the seed crystals of the system are kept in the optimal concentration range to maintain the stable operation of the system.

[0028] By reusing the crystals in the concentrated liquid as crystal seeds, the system operating cost is saved and the difficulty of handling the concentrated liquid is reduced.

[0029] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0031] Figure 1 This is a schematic structural diagram of a seed crystal evaporation and concentration process for high-salt and high-hardness wastewater proposed in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0033] The following describes a seed crystal evaporation and concentration process for high-salt and high-hardness wastewater according to an embodiment of the present invention with reference to the accompanying drawings.

[0034] like Figure 1 As shown, the embodiment of the present invention provides a seed crystal evaporation concentration process for high-salt and high-hardness wastewater, comprising the following process steps:

[0035] Step 1: The seed tank is also equipped with a suspended solid (SS) online analyzer, which can measure the seed concentration in the mixed solution in the seed tank in real time, and adjust the recovery amount of the seed solution according to the data fed back by the online analyzer. When the seed concentration in the seed tank is less than the designed seed concentration, the recovery amount of the seed solution is increased until the suspended solid online analyzer detects that the concentration in the seed tank reaches the designed seed concentration; when the seed concentration in the seed tank is more than the designed seed concentration, the recovery amount of the seed solution is stopped;

[0036] Step 2: The mixed liquid in the seed tank is sent to an evaporation concentration device. After evaporation and concentration, the discharge volume of the concentrated liquid is determined according to the water inlet, evaporation volume and solution concentration of the evaporation concentration device, and the concentrated liquid is quantitatively discharged into the concentration tank to maintain the ion concentration of the solution in the evaporation concentration device (a term in the evaporation industry, a circulating solution that is repeatedly heated and evaporated in the evaporation concentration device, referred to as circulating liquid, here changed to solution) in the evaporation concentration device. Balance;

[0037] Step 3: After the concentrate in the concentrate tank is matured and precipitated, the bottom is a concentrate with higher concentration and larger crystal particles, and the upper part is a concentrate with fine crystal particles and lower concentration.

[0038] In a specific application of the embodiment of the present invention, an online suspended solids (SS) analyzer is configured in the seed tank to achieve accurate monitoring and control of the seed concentration. By measuring the seed concentration of the mixed liquid in the seed tank in real time and adjusting the recovery amount of the seed liquid according to the feedback data, it can be ensured that the seed concentration in the seed tank is always maintained within the designed concentration range.

[0039] When the seed concentration is less than the design concentration, increasing the recovery of seed solution can ensure that there are enough seeds to participate in the subsequent evaporation and concentration process. Sufficient seeds can provide more crystal nuclei for substances such as salt in the solution, promoting the efficient crystallization process. When the seed concentration is higher than the design concentration, stop recovering the seed solution to avoid the negative effects of too many seeds, such as uneven crystal growth or overcrowding, affecting crystal quality and evaporation and concentration efficiency.

[0040] A stable seed crystal concentration contributes to the stable operation of the entire evaporation and concentration process. During the evaporation and concentration process, the seed crystal plays an important role in guiding the crystallization of the solute. If the seed crystal concentration fluctuates greatly, it will make it difficult to stably control the crystallization process in the subsequent evaporation and concentration device. Accurate control of the seed crystal concentration lays a good foundation for subsequent efficient evaporation and concentration.

[0041] Quantitative discharge of concentrated liquid into the concentration tank can prevent the ion concentration in the solution from being too high or too low. If the ion concentration is too high, it may cause equipment scaling, corrosion and other problems; while too low ion concentration will affect the efficiency of evaporation concentration and crystallization effect. By maintaining the balance of ion concentration, the service life of the equipment can be extended and the stability and reliability of the entire process can be improved.

[0042] The method of controlling ion concentration is conducive to improving the efficiency of evaporation and concentration equipment. When the ion concentration in the solution is within the appropriate range, the evaporation of the solution and the crystallization of the solute can proceed more smoothly. For example, the viscosity of the solution will not increase significantly due to excessive ion concentration, thereby affecting heat transfer and evaporation rate. After ripening and precipitation, the concentrated liquid in the concentrate tank can achieve the separation of concentrated liquids of different concentrations and particle sizes. A concentrated liquid with a higher concentration and larger crystal particles is formed at the bottom. The crystals in this concentrated liquid are relatively pure and coarse, which is convenient for subsequent treatment or recycling.

[0043] The upper part of the concentrated liquid containing fine crystal particles and a lower concentration can be further processed, for example, by suitable filtration or secondary sedimentation, etc., to further separate the fine crystals therein, thereby improving the resource recovery efficiency and wastewater treatment effect of the entire process.

[0044] In one embodiment of the present invention, the concentrated liquid at the bottom of the concentration tank is recovered to the seed tank and mixed with the high-salt and high-hardness wastewater to enter the evaporation concentration device. The concentrated liquid containing fine particles and lower concentration at the top of the concentration tank is discharged for further treatment, and a portion of the seed liquid is regularly discharged from the bottom of the concentrated liquid tank to be mixed with the concentrated liquid discharged from the top of the concentrated liquid tank for treatment.

[0045] In a specific application of the embodiment of the present invention, the concentrated liquid recovered from the bottom of the concentration tank contains a large amount of salt and other substances, which are recycled into the seed tank and mixed with high-salt and high-hardness wastewater before entering the evaporation concentration device. The salt and impurities in the recovered concentrated liquid can be used as "supplementary substances" for the seed crystals. During the evaporation concentration process, the presence of the seed crystals can provide more nucleation sites, making it easier for the salt in the solution to crystallize. For example, for some salts with higher solubility, the seed crystals can induce them to crystallize at a lower supersaturation, thereby improving the efficiency and effect of crystallization.

[0046] The recovered concentrated liquid already contains a certain amount of salt. Mixing it back into the high-salt and high-hardness wastewater to be treated is equivalent to recycling this part of the salt, which can reduce the amount of fresh high-salt and high-hardness wastewater that needs to be treated in the subsequent treatment process and reduce the raw material input cost of the entire treatment process. For example, if it is not recycled, more fresh wastewater will be required to enter the evaporation and concentration device, consuming more energy and treatment agents and other resources. Mixing it with high-salt and high-hardness wastewater and entering the evaporation and concentration device can make the properties of the mixed liquid entering the device more stable, which helps the evaporation and concentration process to be carried out under relatively stable conditions, and is conducive to operators to better control the various parameters of evaporation and concentration, such as temperature, pressure, evaporation rate, etc., thereby improving the reliability and stability of the entire process.

[0047] The concentrate at the top of the concentration tank contains fine particles and has a low concentration. If this part of the concentrate continues to remain in the evaporation concentration device, these fine particles may gradually accumulate during the evaporation process, which may clog the pipeline, affect the heat transfer efficiency, or interfere with the crystallization process. Discharging it separately for separate treatment can avoid the continuous accumulation of these impurities in the evaporation concentration device and ensure the normal operation of the device. During the evaporation and concentration process, relatively pure salts or other recyclable substances are obtained. Since this part of the concentrate at the top of the concentration tank contains more impurities, if it is not treated separately and mixed into the final product, it will reduce the purity of the product. Through separate discharge and treatment, it can ensure that the final crystalline salt or concentrated substance has a higher quality and meets higher industrial application standards or environmental emission requirements.

[0048] Discharging it separately for treatment can adopt more targeted treatment methods. For example, for concentrates with low concentrations and fine particles, relatively mild and low-cost treatment methods such as filtration and adsorption can be used, instead of complex treatment processes for high-concentration, large-particle concentrates, thereby improving the efficiency and economy of the entire treatment process. The seed liquid at the bottom of the concentrate tank has certain characteristics. Regularly discharging a part of it and mixing it with the concentrate discharged from the upper part of the concentrate tank can reasonably adjust the total amount and composition of the liquid to be treated according to the actual treatment capacity and treatment requirements. For example, in the case of limited treatment capacity, mixed treatment can avoid exceeding the load of the treatment equipment when a certain concentrate is treated alone. At the same time, mixed treatment also helps to make full use of certain beneficial components in the seed liquid and further treat or optimize the concentrate discharged from the upper part.

[0049] In a possible embodiment, the seed crystal evaporation concentration process applied to high-salt and high-hardness wastewater also includes the following process steps: pre-treating the wastewater with a reducing agent and an adsorbent, and then concentrating it with a high-pressure nanofiltration membrane and a high-pressure reverse osmosis membrane; wherein the reducing agent is at least one of sodium sulfite, sodium sulfide, ferrous sulfate or ammonium sulfite; the adsorbent is a chitosan / modified lignin / nano-sodium titanate hybrid composite hydrogel, which is prepared by free radical polymerization of modified lignin, chitosan, acrylic acid and nano-sodium titanate as monomers; the modified lignin is prepared by modifying lignin by amination and phosphorylation; the dosage of the reducing agent is 0.5g / L~1g / L, and the dosage of the adsorbent is 4g / L~8g / L.

[0050] In a specific application of the embodiment of the present invention, when there are oxidizing substances in the wastewater, a reducing agent such as sodium sulfite, sodium sulfide, ferrous sulfate or ammonium sulfite (dosage is 0.5 g / L-1 g / L) can react chemically with the oxidizing substances in the wastewater. For example, sodium sulfite can react with oxidizing substances such as residual chlorine that may exist in the wastewater to reduce them, thereby preventing the oxidizing substances from corroding subsequent treatment equipment (such as membrane components).

[0051] In high-salt and high-hardness wastewater, certain oxidizing substances may induce redox reactions of some ions in the water, thereby forming scaling substances. The addition of reducing agents can prevent the occurrence of such reactions, reduce the possibility of scaling, and ensure the stable operation of the entire treatment system. The adsorbent is a chitosan / modified lignin / nano-sodium titanate hybrid composite hydrogel, and its addition amount is 4g / L-8g / L. This composite hydrogel is prepared by free radical polymerization of multiple monomers, in which the modified lignin is prepared by amination and phosphorylation of lignin, which can effectively adsorb organic impurities, heavy metal ions and other pollutants in wastewater. For example, trace organic pollutants that may exist in wastewater can be removed by adsorption, thereby improving the water quality of wastewater and reducing the burden of subsequent treatment.

[0052] Since it can adsorb a variety of pollutants, it can significantly reduce the turbidity, color and other indicators of wastewater, which is very beneficial for subsequent membrane concentration treatment, because the improvement of water quality can reduce the risk of membrane pollution and increase the flux and service life of the membrane.

[0053] After pretreatment, the wastewater enters the high-pressure nanofiltration membrane for concentration treatment. The high-pressure nanofiltration membrane can selectively separate the ions in the wastewater according to the size and charge properties of the ions. In high-salt and high-hardness wastewater, it can effectively intercept divalent and higher ions, such as calcium and magnesium ions, while allowing monovalent ions (such as sodium ions) and small molecular organic matter to pass through. This can achieve the initial separation and concentration of wastewater salts and reduce the pressure of subsequent reverse osmosis membrane treatment.

[0054] Through the concentration effect of nanofiltration membrane, a part of the water in the wastewater can be separated. The water quality of this part of water is relatively good and can be reused, for example, in some industrial links that do not have particularly high requirements for water quality, such as cooling water replenishment, etc., thereby improving the recycling rate of water resources and reducing the water cost of enterprises. High-pressure reverse osmosis membrane can deeply desalinate wastewater treated by nanofiltration membrane. In the treatment of high-salt and high-hardness wastewater, it can effectively remove the remaining salt in the wastewater and further improve the purity of the water. Water treated by reverse osmosis membrane can reach higher water quality standards, for example, it can be used in some industrial production processes with high water quality requirements or as miscellaneous water for life.

[0055] While desalinating, the reverse osmosis membrane further concentrates the salt and other pollutants in the wastewater, greatly reducing the volume of the wastewater. This helps reduce the amount of treatment in subsequent evaporation and crystallization processes, lowers treatment costs, and also facilitates further treatment and disposal of the concentrated salt and pollutants, such as extracting valuable salt substances or safely landfilling them.

[0056] In a possible embodiment, lignin and sodium hydroxide solution are uniformly mixed to obtain a lignin alkaline solution, and then 3-chloro-2-hydroxypropyltrimethylammonium chloride is added, and the mixture is reacted at 80° C. to 90° C. for 2 h to 3 h to obtain a solution containing aminated lignin; a diammonium hydrogen phosphate solution with a mass concentration of 25% to 30% is prepared, epichlorohydrin and formaldehyde solution are added, and the mixture is reacted at 65° C. to 85° C. for 2 h to 3 h, and the reaction solution is mixed with the mixed solution containing aminated lignin. The reaction is carried out at 80°C to 90°C for 3h to 6h, and then dried to obtain modified lignin. The concentration of the sodium hydroxide solution is 20% to 50%; and / or the concentration of the formaldehyde solution is 30% to 50%; and / or the mass ratio of lignin, 3-chloro-2-hydroxypropyltrimethylammonium chloride and epichlorohydrin is 1:0.2-0.3:0.2-0.5; and / or the feed ratio of lignin, sodium hydroxide solution and formaldehyde solution is 1g:10-20mL:0.7-1mL.

[0057] In a specific application of the embodiment of the present invention, first, lignin is mixed with a sodium hydroxide solution to form a lignin alkaline solution to provide a suitable reaction environment for subsequent chemical reactions. The sodium hydroxide solution (concentration of 20%-50%) can cause changes in the molecular structure of lignin, exposing some active groups in the lignin molecules, which is beneficial to subsequent reactions with other reagents. When treating high-salt and high-hardness wastewater, the amine group can react with certain ions in the wastewater to form a complex, which helps to remove harmful substances in the wastewater.

[0058] Prepare a diammonium phosphate solution with a mass concentration of 25%-30%, add epichlorohydrin and formaldehyde solution (concentration of 30%-50%), react at 65℃-85℃ for 2h-3h, then mix with the mixed solution containing aminated lignin, and react at 80℃-90℃ for 3h-6h. In this process, the reaction products between diammonium phosphate, epichlorohydrin and formaldehyde are mixed with aminated lignin to further modify the molecular structure of lignin. Formaldehyde may act as a cross-linking agent in the reaction, so that a more stable structure is formed between lignin molecules or between lignin and other reaction products.

[0059] The feed ratio of lignin, sodium hydroxide solution and formaldehyde solution is 1g: 10-20mL: 0.7-1mL. This feed ratio helps to control the progress and degree of the reaction. The amount of sodium hydroxide solution can ensure that the alkalization degree of lignin is moderate, creating good conditions for subsequent reactions; and the amount of formaldehyde solution within this range can achieve effective structural modification without excessive cross-linking resulting in a decrease in the performance of lignin. In each reaction stage, different temperature and time combinations, such as reaction at 80℃-90℃ for 3h-6h, can ensure that the reaction proceeds in the predetermined direction, so that the reactants are fully reacted and converted into the target product. Appropriate temperature and time can improve the conversion rate of the reaction and reduce the unreacted raw material residues, thereby improving the quality of the modified lignin and its effect in the treatment of high-salt and high-hardness wastewater.

[0060] In a possible embodiment, the preparation method of the adsorbent comprises the following steps: dissolving modified lignin, chitosan, acrylic acid and nano sodium titanate in deionized water, adding sodium carboxymethyl cellulose, a crosslinking agent and an initiator in sequence, stirring evenly, heating in a water bath at 35°C to 40°C to complete gelation, and obtaining an adsorbent, wherein the crosslinking agent is at least one of polyethylene glycol diglycidyl ether, ethylene glycol dimethacrylate or N,N-methylenebisacrylamide; and / or the initiator is hydrogen peroxide, At least one of ascorbic acid, potassium persulfate or ammonium persulfate, the mass ratio of modified lignin, chitosan, acrylic acid and nano-sodium titanate is 1:1-2.5:0.3-0.6:0.25-0.4; and / or the lignin is one of alkali lignin, enzymatic lignin, lignin sulfonate or lignin carboxylate, the high-pressure nanofiltration membrane is at least a two-stage concentrated water internal circulation structure; and / or the operating pressure of the high-pressure nanofiltration membrane is 2.0MPa-5.0MPa, and the temperature is 15°C-45°C.

[0061] In a specific application of an embodiment of the present invention, a combination of modified lignin, chitosan, acrylic acid and nano sodium titanate is used: the modified lignin itself has certain adsorption properties, and its active sites may increase after modification. When combined with chitosan, chitosan has good biocompatibility and adsorption properties, and can adsorb certain ions or organic matter in wastewater. The addition of acrylic acid may increase the hydrophilicity of the adsorbent and its affinity for specific substances. Nano sodium titanate has special physical and chemical properties, for example, it may have a higher specific surface area, which helps to improve the overall adsorption capacity of the adsorbent. They are mixed in a mass ratio of 1:1-2.5:0.3-0.6:0.25-0.4. Such a proportional relationship can optimize the comprehensive performance of the adsorbent, so that the components complement each other and synergistically play the adsorption effect on various pollutants in high-salt and high-hardness wastewater.

[0062] One of the lignin sources, such as alkaline lignin, enzymatic lignin, lignin sulfonate or lignin carboxylate, is used in the preparation of the adsorbent. Lignin from different sources has different chemical structures and properties, which provides more options for adjusting the performance of the adsorbent. For example, lignin sulfonate may have good water solubility, which helps to better disperse in the system when preparing the adsorbent, thereby ensuring the uniformity of the internal structure of the adsorbent and improving the adsorption effect.

[0063] The initiator is at least one of hydrogen peroxide, ascorbic acid, potassium persulfate or ammonium persulfate. The initiator plays a role in initiating the polymerization reaction during the preparation of the adsorbent. During the gelation process, the initiator can promote the polymerization reaction of the monomers in the system, so that the adsorbent forms a desired structure. For example, hydrogen peroxide can decompose to produce free radicals, which initiate the polymerization of monomers such as acrylic acid, thereby effectively combining the components together to form an overall structure with good adsorption performance.

[0064] Heating in a water bath at 35-40°C to complete gelation is a key step. This temperature range may be optimized. At this temperature, the reaction in the system can proceed smoothly, and the reaction rate will not be too slow due to too low a temperature, nor will certain components decompose or produce side reactions due to too high a temperature. The gelation process can transform the adsorbent from a solution state into a gel adsorbent with a certain shape and structure. This gel structure helps the adsorbent adsorb pollutants in wastewater, for example, it can provide more pore structures and increase the contact opportunities between pollutants and the active sites of the adsorbent.

[0065] In the first stage of nanofiltration, most of the water and some small molecules can pass through the nanofiltration membrane, while the concentrate still contains high concentrations of pollutants such as salt and hardness ions. By circulating the concentrate into the next stage of nanofiltration, the pollutants in the concentrate can be further separated and concentrated, thereby improving the entire system's ability to treat high-salt and high-hardness wastewater and reducing the amount of wastewater that is ultimately discharged or further treated.

[0066] The operating pressure of high-pressure nanofiltration membrane is 2.0MPa-5.0MPa. The appropriate operating pressure can ensure that the nanofiltration membrane has a good separation effect on ions and small molecules in high-salt and high-hardness wastewater. If the pressure is too low, it may not be able to overcome the resistance of the membrane, resulting in the wastewater cannot be effectively separated through the nanofiltration membrane; if the pressure is too high, it may cause damage to the nanofiltration membrane, shorten the service life of the nanofiltration membrane, and may also lead to increased energy consumption.

[0067] The temperature of 15℃-45℃ is suitable for the normal operation of the nanofiltration membrane. Within this temperature range, the performance of the nanofiltration membrane is relatively stable. For example, the performance indicators such as the membrane flux and retention rate can be maintained at a good level. Too low temperature may increase the viscosity of the wastewater and reduce the flux of the nanofiltration membrane; too high temperature may affect the material properties of the nanofiltration membrane, causing changes in the structure of the membrane, thereby affecting its separation effect.

[0068] The seed crystal evaporation concentration process, in combination with this specially prepared adsorbent and a high-pressure nanofiltration membrane with specific structure and operating parameters, has a significant beneficial effect on the treatment of high-salt and high-hardness wastewater. The adsorbent can pre-remove some pollutants in the wastewater, reducing the burden of the subsequent nanofiltration membrane and evaporation concentration process. The nanofiltration membrane can perform preliminary separation and concentration of the wastewater, effectively intercepting salt and hardness ions, while allowing part of the water to pass through. The seed crystal evaporation concentration process can further concentrate the pretreated wastewater, ultimately achieving efficient treatment of high-salt and high-hardness wastewater, reducing the volume of wastewater, recovering useful substances in it, and reducing pollution to the environment.

[0069] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0070] The above description of the present invention and its implementation methods is not restrictive. The drawings show only one implementation method of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it and design structural methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A seed crystal evaporation and concentration process for high-salt and high-hardness wastewater, characterized in that: The process steps include: Step 1: The seed tank is also equipped with a suspended solid (SS) online analyzer, which can measure the seed concentration in the mixed solution in the seed tank in real time, and adjust the recovery amount of the seed solution according to the data fed back by the online analyzer. When the seed concentration in the seed tank is less than the designed seed concentration, the recovery amount of the seed solution is increased until the suspended solid online analyzer detects that the concentration in the seed tank reaches the designed seed concentration; when the seed concentration in the seed tank is more than the designed seed concentration, the recovery amount of the seed solution is stopped; Step 2: The mixed liquid in the seed tank is sent to an evaporation concentration device. After evaporation and concentration, the discharge volume of the concentrated liquid is determined according to the water inlet, evaporation volume and solution concentration of the evaporation concentration device, and the concentrated liquid is quantitatively discharged into the concentration tank to maintain the ion concentration of the solution in the evaporation concentration device (a term in the evaporation industry, a circulating solution that is repeatedly heated and evaporated in the evaporation concentration device, referred to as circulating liquid, here changed to solution) in the evaporation concentration device. Balance; Step 3: After the concentrate in the concentrate tank is matured and precipitated, the bottom is a concentrate with higher concentration and larger crystal particles, and the upper part is a concentrate with fine crystal particles and lower concentration.

2. The seed crystal evaporation concentration process for high-salt and high-hardness wastewater according to claim 1 is characterized in that: The concentrated liquid at the bottom of the concentration tank is recovered to the seed tank and mixed with the high-salt and high-hardness wastewater to enter the evaporation concentration device. The concentrated liquid containing fine particles and lower concentration at the top of the concentration tank is discharged for further treatment.

3. The seed crystal evaporation concentration process for high-salt and high-hardness wastewater according to claim 1 is characterized in that: A portion of the seed solution is regularly discharged from the bottom of the concentrate tank to be mixed with the concentrate discharged from the upper part of the concentrate tank.

4. The seed crystal evaporation concentration process for high-salt and high-hardness wastewater according to claim 1, characterized in that: The following process steps are also included: After the wastewater is pre-treated with a reducing agent and an adsorbent, it is concentrated using a high-pressure nanofiltration membrane and a high-pressure reverse osmosis membrane; Wherein, the reducing agent is at least one of sodium sulfite, sodium sulfide, ferrous sulfate or ammonium sulfite; The adsorbent is a chitosan / modified lignin / nano-sodium titanate hybrid composite hydrogel, which is prepared by free radical polymerization reaction using modified lignin, chitosan, acrylic acid and nano-sodium titanate as monomers; the modified lignin is prepared by modifying lignin by amination and phosphorylation; The dosage of the reducing agent is 0.5 g / L to 1 g / L, and the dosage of the adsorbent is 4 g / L to 8 g / L.

5. The seed crystal evaporation concentration process for high-salt and high-hardness wastewater according to claim 1, characterized in that: The lignin and the sodium hydroxide solution are uniformly mixed to obtain a lignin alkaline solution, and then 3-chloro-2-hydroxypropyltrimethylammonium chloride is added, and the mixture is reacted at 80°C to 90°C for 2h to 3h to obtain a solution containing aminated lignin; a diammonium hydrogen phosphate solution with a mass concentration of 25% to 30% is prepared, epichlorohydrin and formaldehyde solution are added, and the mixture is reacted at 65°C to 85°C for 2h to 3h, and the reaction solution is mixed with the mixed solution containing aminated lignin, and the mixture is reacted at 80°C to 90°C for 3h to 6h, and dried to obtain the modified lignin.

6. The seed crystal evaporation concentration process for high-salt and high-hardness wastewater according to claim 1, characterized in that: The concentration of the sodium hydroxide solution is 20% to 50%; and / or The concentration of the formaldehyde solution is 30% to 50%; and / or The mass ratio of the lignin, 3-chloro-2-hydroxypropyltrimethylammonium chloride and epichlorohydrin is 1:0.2-0.3:0.2-0.5; and / or the feeding ratio of the lignin, sodium hydroxide solution and formaldehyde solution is 1g:10-20mL:0.7-1mL.

7. The seed crystal evaporation concentration process for high-salt and high-hardness wastewater according to claim 1, characterized in that: The preparation method of the adsorbent comprises the following steps: dissolving the modified lignin, chitosan, acrylic acid and nano sodium titanate in deionized water, sequentially adding sodium carboxymethyl cellulose, a crosslinking agent and an initiator, stirring evenly, heating in a water bath at 35°C to 40°C to complete gelation, and obtaining the adsorbent.

8. The seed crystal evaporation concentration process for high-salt and high-hardness wastewater according to claim 1, characterized in that: The crosslinking agent is at least one of polyethylene glycol diglycidyl ether, ethylene glycol dimethacrylate or N,N-methylenebisacrylamide; and / or the initiator is at least one of hydrogen peroxide, ascorbic acid, potassium persulfate or ammonium persulfate.

9. The seed crystal evaporation concentration process for high-salt and high-hardness wastewater according to claim 1, characterized in that: The mass ratio of the modified lignin, chitosan, acrylic acid and nano-sodium titanate is 1:1-2.5:0.3-0.6:0.25-0.4; and / or the lignin is one of alkali lignin, enzymatic lignin, lignin sulfonate or lignin carboxylate.

10. The seed crystal evaporation concentration process for high-salt and high-hardness wastewater according to claim 1, characterized in that: The high-pressure nanofiltration membrane is at least a two-stage concentrated water internal circulation structure; and / or the operating pressure of the high-pressure nanofiltration membrane is 2.0MPa-5.0MPa, and the temperature is 15°C-45°C.

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