Method and system for treatment of salt-containing wastewater and use thereof

Abstract

The present application relates to the technical field of salt-containing wastewater treatment, and discloses a treatment method and system for salt-containing wastewater and application thereof, which comprises the following steps: (1) adjusting the conductivity of the salt-containing wastewater to obtain first brine, wherein the conductivity of the first brine is not less than 390 s / cm; (2) extracting and separating the first brine to obtain second brine and a first organic phase; (3) performing ultrasonic micro-bubble reaction on the second brine to obtain third brine and a second organic phase; and (4) performing oxidation reaction on the third brine in the presence of cavitation bubbles to obtain clean brine. Through the treatment method, TOC of the salt-containing wastewater is removed step by step, water-soluble organic matter in the salt-containing wastewater can be efficiently removed, the obtained clean brine can meet the requirements of ion-exchange membrane electrolysis brine, and the production operation cost and investment cost are reduced, and the operation safety risk is also reduced.

Description

Technical Field

[0001] This invention relates to the field of saline wastewater treatment technology, specifically to a method and system for treating saline wastewater and its application. Background Technology

[0002] During the epoxy resin production process, with the continuous addition of NaOH and the continuous azeotropic distillation of water and epichlorohydrin, sodium chloride crystallizes out and disperses in the epoxy resin-epoxychloropropane solution in a solid state. Simultaneously, due to side reactions such as the hydrolysis of epichlorohydrin and the need to add large amounts of water to dissolve the crystallized sodium chloride during post-treatment, a large volume of wastewater is discharged. This wastewater also has a high COD (Chemical Oxygen Demand), with the main components being organic compounds of varying molecular weights such as glycerol, toluene, methyl ketones, chlorohydrin ethers, phenolic dicarboxylates, aliphatic ethers, phenolic ethers, and glycidyl polymers. For example, patent applications CN109231637A and CN105645634A describe the COD of epoxy resin wastewater as 50,000 ppm, while patent application CN105712580A describes it as 100,000 ppm.

[0003] In existing technologies, saline wastewater from epoxy resin production is mainly treated by dilution biochemical processes before discharge, followed by sodium chloride recovery through evaporation crystallization, Fenton oxidation combined with evaporation crystallization, and wet catalytic oxidation. However, the dilution biochemical method not only consumes a large amount of freshwater resources but also increases the volume of wastewater discharge, which does not comply with national energy conservation and emission reduction policies. CN108264180A discloses a process for recovering water and salts from high-salinity wastewater through pretreatment, volume reduction, and evaporation crystallization of high-salinity concentrate. While this solves the problem of high energy consumption in evaporation processes, the residual high-boiling-point organic matter in the evaporation crystallization process prevents the electrolytic reuse of solid sodium chloride. Fenton oxidation requires a low pH value and produces metallic sludge, again preventing the electrolytic reuse of solid sodium chloride. CN104925997A uses catalytic oxidation technology, but the brine only meets the requirements for membrane electrolysis, a technology restricted from further development by the state. The wet catalytic oxidation process uses high temperature and high pressure metal ion catalytic oxidation technology under acidic conditions. The low pH value increases the degree of equipment corrosion. At the same time, the use of metal ion catalysts makes it difficult to recover hydrated metal ions from brine.

[0004] Therefore, it is evident that the saline wastewater generated during epoxy resin production contains complex organic components. Wastewater containing sodium chloride is unsuitable for biological treatment. Furthermore, Hao Minsong et al., in their study "The Influence of TOC on Ion-Exchange Membrane Electrolyzers" in the 2009 issue 11 of *Chlor-Alkali Industry*, investigated the increase in voltage and decrease in chlorine purity in ion-exchange membrane electrolyzers, attributing it to excessive organic matter content in the primary brine. Existing treatment processes yield clean brine with TOC values ​​between 10-50 ppm, which is insufficient to meet the requirements for ion-exchange membrane electrolysis.

[0005] With increasingly stringent environmental protection requirements from the state and society, the treatment of epoxy resin production wastewater will have a profound impact on epoxy resin production. Achieving resource recycling while protecting the natural ecological environment necessitates strengthening technological innovation to achieve green production. Therefore, developing new processes and technologies that meet the requirements of ion-exchange membrane electrolysis of brine, and developing comprehensive utilization technologies for epoxy resin wastewater, plays a crucial role in the survival of the epoxy resin industry. Resource recycling and reducing emissions and waste are inevitable trends in development. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of poor removal efficiency and high treatment cost of water-soluble organic matter in saline wastewater during epoxy resin production in the existing technology, and to provide a method and system for treating saline wastewater, clean brine and its application, and a method for preparing chlor-alkali and epoxy resin. This method for treating saline wastewater can efficiently remove water-soluble organic matter from saline wastewater, requires no catalyst, is equipment-friendly, and has good technical and economic advantages.

[0007] To achieve the above objectives, the present invention provides a method for treating saline wastewater, the method comprising:

[0008] (1) The conductivity of the saline wastewater is adjusted to obtain primary brine, wherein the conductivity of the primary brine is not less than 390 s / cm;

[0009] (2) The primary brine is extracted and separated to obtain secondary brine and a first organic phase;

[0010] (3) The secondary brine is subjected to ultrasonic microbubble reaction to obtain tertiary brine and a second organic phase;

[0011] (4) In the presence of cavitation bubbles, the tertiary brine is oxidized to obtain clean brine.

[0012] A second aspect of the present invention provides a saline wastewater treatment system, the system comprising: a saline wastewater supply unit, a conductivity adjustment tank, an extraction unit, an ultrasonic microbubble reaction unit, an oxidation treatment unit, and a brine storage tank, which are connected sequentially along the material flow direction;

[0013] The system also includes an electrolyte supply unit, the outlet of which is connected to the inlet of the conductivity adjustment tank.

[0014] The third aspect of this invention provides the application of the method for treating saline wastewater provided in the first aspect and the system for treating saline wastewater provided in the second aspect in the production of epoxy resin.

[0015] On the one hand, in the existing wet catalytic oxidation technology for treating saline wastewater, the brine contains hydrated metal ions, which presents a problem in recovering the metal ions. Wet catalytic oxidation requires adjusting the pH of the brine to acidic, which is conducive to the generation of hydroxyl radicals. The problem is that the brine under acidic conditions is harsh on the material of the oxidation reactor under high temperature and high pressure, causing metal ions to remain in the brine.

[0016] On the other hand, in existing technologies, ion-electrolyzed brine mainly comes from underground brine or sea salt and mineral salt, which generally do not contain organic matter and do not require treatment. However, industrial by-product sodium chloride contains a large amount of organic matter and cannot be discharged. For this type of saline wastewater containing organic matter, if we want to recycle resources and truly achieve zero discharge, special processes must be used for treatment. The inventors of this invention have creatively proposed a method for treating saline wastewater. The clean brine obtained by this method can meet the requirements of ion-electrolyzed brine and achieve true zero discharge.

[0017] The saline wastewater treatment method provided by this invention does not require adjusting the wastewater pH value, does not use metal catalysts, causes minimal equipment corrosion, eliminates catalyst recovery, and completely avoids the impact of metal ions on the subsequent application of brine. This treatment method removes TOC from saline wastewater in stages, efficiently removing water-soluble organic matter, reducing production and operating costs and investment costs, while also lowering operational safety risks.

[0018] In their paper "The Influence of Various Impurity Ions in Brine on the Performance of Ion-Exchange Membranes," presented at the 2nd National Chlor-Alkali Industry Brine Refining Technology Exchange Conference (2008, Zhongyan Jintan Cup), Jiang Xiongwang et al. found that the iron ion concentration in the brine entering ion-exchange membrane electrolysis should not exceed 50 ppm. Internal control regulations for chlor-alkali enterprises stipulate that the heavy metal ion concentration in the brine entering ion-exchange membrane electrolysis should not exceed 20 ppb. The pure brine prepared by the above-mentioned treatment method avoids the use of metal catalysts, effectively preventing the introduction of additional metals and meeting the aforementioned heavy metal ion concentration requirements for ion-exchange membrane electrolysis. Using the clean brine prepared above for ion-exchange membrane electrolysis to produce chlor-alkali offers significant advantages in terms of equipment corrosion and the safe and stable operation of the electrolytic ion-exchange membrane cell due to the extremely low TOC content. Attached Figure Description

[0019] Figure 1This is a schematic diagram of a saline wastewater treatment system according to one embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures

[0021] 1. Saline wastewater supply unit; 1-1 Saline wastewater storage tank; 1-2 Heating device

[0022] 2. Conductivity adjustment tank; 3. Extraction unit; 3-1. Micro-interface generator

[0023] 3-2 Separation Tower; 3-3 Extractant Supply Unit; 4 Ultrasonic Microbubble Reaction Unit

[0024] 5. Oxidation treatment unit; 6. Brine storage tank; 7. Electrolyte supply unit.

[0025] 8. Ion-exchange membrane electrolysis unit; 9. Epoxy resin preparation unit Detailed Implementation

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] The first aspect of this invention provides a method for treating saline wastewater, the method comprising:

[0028] (1) The conductivity of the saline wastewater is adjusted to obtain primary brine, wherein the conductivity of the primary brine is not less than 390 s / cm;

[0029] (2) The primary brine is extracted and separated to obtain secondary brine and a first organic phase;

[0030] (3) The secondary brine is subjected to ultrasonic microbubble reaction to obtain tertiary brine and a second organic phase;

[0031] (4) In the presence of cavitation bubbles, the tertiary brine is oxidized to obtain clean brine.

[0032] In existing wet catalytic oxidation technologies for treating saline wastewater, the brine contains hydrated metal ions, posing a challenge to metal ion recovery. Wet catalytic oxidation requires adjusting the pH of the brine to acidic conditions, which is conducive to the generation of hydroxyl radicals. However, the acidic brine conditions, under high temperature and high pressure, are harsh on the materials of the oxidation reactor, causing metal ions to remain in the brine.

[0033] Through continuous research, the inventors of this invention have developed a step-by-step removal of COD from saline wastewater using the aforementioned treatment method. The conductivity of the wastewater brine is adjusted using electrolytes, facilitating the extraction and separation of organic matter dissolved in the brine. Through extraction and ultrasonic microbubble reaction treatment, difficult-to-oxidize six-membered ring macromolecular compounds such as phenolic dicarboxylates, phenolic ether polymers, and glycidyl polymers are extracted from the saline wastewater in a graded manner. Water-soluble polyols or alcohol ethers in the brine are oxidized and decomposed into carbon dioxide and water under relatively mild conditions, reducing production and operating costs and investment costs, while also reducing operational safety risks.

[0034] The inventors of this invention have discovered that adjusting the conductivity of saline wastewater to a suitable range facilitates the subsequent removal of TOC from the wastewater. This treatment method does not require adjusting the wastewater pH, does not use a metal catalyst, causes minimal equipment corrosion, eliminates catalyst recovery, and completely avoids the impact of metal ions on the subsequent application of the brine. Preferably, the conductivity of the primary brine is 390-500 S / cm, more preferably 400-450 S / cm, and even more preferably 400-435 S / cm. For example, it can be any point or a range between two points from 400 S / cm, 405 S / cm, 410 S / cm, 415 S / cm, 420 S / cm, 425 S / cm, 430 S / cm, and 435 S / cm.

[0035] In this invention, the conductivity is measured using the method specified in GB / T11007-2008.

[0036] According to the present invention, preferably, the temperature of the primary brine is 50-90°C, more preferably 60-75°C. Controlling the temperature of the primary brine within the above temperature range helps to adjust the conductivity of the primary brine and facilitates interfacial contact during the extraction process in step (2), further contributing to improving the treatment effect of saline wastewater.

[0037] According to the present invention, the conductivity can be adjusted using conventional methods in the art, such as adjusting the temperature or adjusting the ion concentration in the saline solution, as long as the conductivity range described above is met. Those skilled in the art can choose the appropriate method based on the actual situation.

[0038] Preferably, the method for adjusting conductivity includes introducing an electrolyte into the saline wastewater. Using the above-mentioned preferred embodiment facilitates precise adjustment of conductivity, makes control easier, and further helps to improve the treatment effect of saline wastewater.

[0039] This invention allows for a wide range of choices regarding the type of electrolyte, employing substances conventional in the art and well-known to those skilled in the art. Preferably, the electrolyte is selected from at least one of inorganic acids, inorganic bases, and inorganic salts; more preferably, it is selected from at least one of hydrochloric acid, sodium hydroxide, sodium chloride, calcium chloride, sulfuric acid, calcium sulfate, phosphoric acid, sodium dihydrogen phosphate, potassium chloride, acetic acid, sodium acetate, calcium acetate, oxalic acid, sodium oxalate, calcium oxalate, and calcium carbonate; further preferably, it is selected from at least one of sodium hydroxide, sodium chloride, phosphoric acid, sodium dihydrogen phosphate, sodium acetate, oxalic acid, calcium chloride, and sodium oxalate. Using the above-mentioned preferred electrolyte types is beneficial for improving the treatment effect of saline wastewater.

[0040] In this invention, the range of suitable electrolyte dosage is relatively wide, as long as the conductivity of the primary brine meets the aforementioned range. Stable conductivity is a prerequisite for the extraction of macromolecular six-membered ring compounds from saline wastewater in this invention.

[0041] In this invention, there are no special requirements for the method of introducing the electrolyte; conventional operating methods in the art can be selected according to actual production or experimental needs. For example, under laboratory conditions, it can be introduced by dripping, while in large-scale industrial production, it can be controlled by a sequential function chart (SFC) program under a distributed control system (DCS). Using the above-mentioned program control can ensure the stability of the brine conductivity during continuous feeding.

[0042] In this invention, the extraction can be carried out using conventional operating methods and conditions in the art. Preferably, the extraction includes contacting the primary brine with the extractant. This invention does not impose particular limitations on the contact conditions, and those skilled in the art can select them according to actual needs. Preferably, the contact time is 2-30 minutes, more preferably 4-20 minutes.

[0043] In this invention, the extraction can be performed using conventional equipment in the art, such as an air flotation extraction device or a micro-interface generator. Preferably, the contact is performed in a micro-interface generator. Using the above-described preferred embodiments is beneficial for further improving the extraction effect and further reducing the TOC value in the resulting clean brine.

[0044] In this invention, the range of the amount of the extractant is relatively wide. Preferably, the mass ratio of the extractant to the primary brine is 0.25-0.35:1, and more preferably 0.28-0.3:1. By adopting the above preferred embodiments, the treatment effect of saline wastewater can be further improved.

[0045] In this invention, there are no particular limitations on the method of adding the extractant; those skilled in the art can choose according to the actual experimental and production conditions and needs. In industrial continuous processing, it is preferable to use a sequential function chart (SFC) to control the continuous entry of the extractant into the micro-interface generator. SFC control improves the stability and continuity of the extractant's mixing with the primary brine, ensuring the stability and continuity of the extraction process and contributing to improved treatment efficiency for saline wastewater.

[0046] In this invention, the selection range for the extractant is relatively wide, as long as it can achieve the above-mentioned extraction and separation effects, it can be selected from any conventional extractant in the art. Preferably, the extractant is selected from at least one of alkanes, halogenated hydrocarbons, aromatic hydrocarbons, alcohols, esters, ketones, ethers, sulfoxides, and nitriles.

[0047] According to the present invention, preferably, the alkane has 1-11 carbon atoms, and may be at least one of methane, ethane, n-propane, isopropane, n-butane, isobutane, n-pentane, cyclopentane, n-hexane, and cyclohexane, more preferably selected from at least one of cyclohexane, cyclopentane, and propane. Preferably, the haloalkane is a compound in which hydrogen atoms in a hydrocarbon molecule are replaced by halogen atoms, wherein the halogen atom is preferably fluorine and / or chlorine, and the haloalkane is preferably selected from at least one of chloroform, chlorobenzene, and dichloropropane, more preferably chloroform. Preferably, the alcohol is a C1-C14 alcohol, and may be at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, n-hexanol, and n-heptanol, more preferably selected from at least one of ethanol, n-butanol, and n-pentanol. Preferably, the ether is a C2-C8 ether, more preferably selected from at least one of diethyl ether, tert-butyl ether, and isopropyl ether; more preferably tert-butyl ether and / or isopropyl ether. Preferably, the ketone is a C3-C6 ketone, preferably selected from at least one of acetone, methyl isobutyl ketone, and butanone. Preferably, the ester is selected from at least one of ethyl acetate, tributyl phosphate, butyl acetate, and diethyl sulfate, more preferably ethyl acetate and / or tributyl phosphate. Preferably, the aromatic hydrocarbon is selected from at least one of toluene, xylene, and chlorobenzene. Preferably, the nitrile is selected from at least one of acetonitrile, benzonitrile, and valerate. The sulfoxide is a compound containing a thionyl (>S=O) functional group, such as at least one of dioctyl sulfoxide, dimethyl sulfoxide, diphenyl sulfoxide, and thionyl chloride. Using the above-preferred extractants can further improve the extraction and separation effects.

[0048] In this invention, in order to achieve fractional extraction of organic compounds of different molecular weights in primary brine and further improve the extraction and separation effect, preferably, the extractant includes a first extractant and a second extractant, wherein the first extractant is selected from at least one of ethers, sulfoxides and esters, and the second extractant is selected from at least one of ketones, alcohols and alkanes.

[0049] Preferably, the mass ratio of the first extractant to the second extractant is 1:1-5; more preferably, it is 1:2-3. In the above preferred embodiments, this facilitates the separation of organic compounds containing different functional groups.

[0050] In this invention, the separation in step (2) can be carried out using conventional methods in the art, as long as the separation of the two phases in the extract product is achieved. For example, the separation method in step (2) can be selected from at least one of flash separation, stripping separation, and distillation separation, preferably flash separation. By using the above-mentioned preferred separation method, the separation effect between the secondary brine and the first organic phase can be further improved, and the extractant and the first organic phase obtained from the top of the flash tower can be repeatedly recycled without generating secondary waste. The recovered first and second organic phases can be reused in epoxy resin production.

[0051] Preferably, the flash separation temperature is 40-80℃, more preferably 40-60℃, and the flash separation pressure is 10-80 kPa, more preferably 20-60 kPa. Unless otherwise specified, all pressures mentioned in this invention are absolute pressures.

[0052] According to the present invention, preferably, the TOC in the tertiary brine does not exceed 4000 ppm, more preferably not exceed 3800 ppm, and even more preferably 2000-3500 ppm. Unless otherwise specified, all ppm values ​​mentioned in the present invention refer to mass ppm. The inventors of the present invention have found through extensive experiments that controlling the TOC in the tertiary brine within the above-mentioned preferred range is beneficial for reducing the temperature, pressure, and cavitation gas consumption of the oxidation reaction.

[0053] In this invention, the TOC of the saline solution was determined by the method of GB / T 13193-1991.

[0054] According to the present invention, the ultrasonic microbubble reaction refers to the formation of cavitation bubbles of a certain diameter and number at a certain frequency using the high energy and cavitation effect of ultrasound. During the bubble collapse process, enormous energy is generated, altering the interfacial tension of the brine and achieving the purpose of separating particulate matter from wastewater. Preferably, the ultrasonic microbubble reaction includes: contacting the secondary brine with microbubbles under ultrasonic conditions.

[0055] In this invention, preferably, the conditions for the ultrasonic microbubble reaction include: an ultrasonic frequency of 20-40 kHz and a reaction temperature of 50-120°C; more preferably, the ultrasonic frequency is 22-30 kHz and the reaction temperature is 70-100°C. Under these preferred conditions, the separation effect can be further improved.

[0056] This invention allows for a wide range of choices for the medium used in the microbubbles; any gaseous medium suitable for ultrasonic microbubble reactions can be used in this invention. Preferably, the medium for the microbubbles is selected from at least one of oxygen, air, and nitrogen.

[0057] In this invention, through the oxidation reaction in step (4), the presence of cavitation bubbles provides a large number of micro-reaction interfaces for the oxidation reaction, enhancing internal mass transfer. Furthermore, the cavitation bubbles generate limiting energy at the gas-liquid interface, accelerating the oxidative decomposition of small-molecule organic matter under certain temperature and pressure, further oxidizing the organic matter in saline wastewater into carbon dioxide and water. In existing wet catalytic oxidation technologies for treating saline wastewater, the brine contains hydrated metal ions, posing a challenge to metal ion recovery. Wet catalytic oxidation requires adjusting the brine pH to acidic, which is beneficial for the generation of hydroxyl radicals. However, the acidic brine under high temperature and pressure conditions is harsh on the oxidation reactor material, leaving metal ions in the brine. This invention effectively avoids these problems by employing an oxidation reaction with cavitation bubbles.

[0058] According to the present invention, preferably, the conditions for the oxidation reaction include: a temperature of 220-280℃, more preferably 220-250℃; and a pressure of 4-8 MPa, more preferably 5-5.5 MPa. The present invention, through multi-stage treatment and separation of saline wastewater, reduces the temperature and pressure of oxidation, enabling water-soluble polyols or alcohol ethers in the brine to oxidize and decompose into carbon dioxide and water under lower conditions. This reduces production and operating costs and investment costs, while also reducing operational safety risks. Furthermore, the reaction process does not require the use of a catalyst, thus avoiding the residue of metal catalysts in the brine and facilitating subsequent treatment of the resulting brine.

[0059] According to the present invention, preferably, the medium of the cavitation bubbles is an oxygen-containing gas. The present invention has a wide range of options for the oxygen content in the oxygen-containing gas, as long as it can meet the oxygen content required for the cavitation oxidation reaction. For example, the oxygen-containing gas can be oxygen or air.

[0060] In this invention, the range of possible sizes for the cavitation bubbles is relatively wide, and preferably the cavitation bubbles are microbubbles at the micrometer level.

[0061] In this invention, the range of possible amounts of cavitation gas is relatively wide, and can be selected based on the TOC content in the tertiary brine, as long as the organic matter in the tertiary brine can be further oxidized to obtain brine that meets the requirements of ion-exchange membrane electrolysis. Preferably, the mass ratio of oxygen in the cavitation gas to the chemical oxygen demand (COD) of the organic matter in the tertiary brine is 1-1.3:1.

[0062] The chemical oxygen demand (COD) of organic matter in the tertiary brine was measured using the standard method of HJ828-2017.

[0063] In this invention, preferably, the saline wastewater is wastewater generated during the epoxy resin production process. The wastewater in the conventional epoxy resin production process is alkaline, with a pH of about 10-12. This invention directly adjusts the conductivity of the saline wastewater, extracts it, and performs ultrasonic microbubble reaction, followed by cavitation oxidation. Compared with the existing wet catalytic oxidation process, it does not require the addition of acid or alkali to adjust the pH value, resulting in less corrosion to the material.

[0064] The present invention has a wide range of possible sources for the saline wastewater. The method can be applied to saline wastewater obtained during the production of epoxy resins of any type and under any preparation conditions in the art. For example, the saline wastewater is selected from the wastewater generated during the production of at least one of glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin and alicyclic epoxy type epoxy resin.

[0065] This invention does not specifically limit the TOC content in the saline wastewater. It is understood that the TOC content in saline wastewater obtained from different manufacturers or under different production conditions can vary widely. The saline wastewater treatment method described in this invention has good treatment effects on both low and high TOC content saline wastewater. For example, the TOC of the saline wastewater is 1000-10000 ppm, preferably 1000-9000 ppm.

[0066] In existing technologies, industrial byproduct sodium chloride cannot be discharged due to its high organic content, making resource recycling difficult for this type of saline wastewater containing organic matter. According to the treatment method provided by this invention, preferably, the TOC in the clean brine does not exceed 20 ppm, more preferably not more than 7 ppm, and even more preferably 4-6 ppm. Under these preferred conditions, the treated clean brine meets the requirements for ion-exchange membrane electrolysis, achieving true zero discharge.

[0067] In this invention, preferably, the method further includes: subjecting the clean brine to ion-exchange membrane electrolysis to obtain caustic soda, chlorine, and hydrogen. In this invention, there are no particular limitations on the specific method and conditions of the ion-exchange membrane electrolysis; those skilled in the art can select according to actual needs and may employ methods known in the art. For example, the clean brine can be fed into an ion-exchange membrane electrolyzer for electrolysis.

[0068] In this invention, preferably, the method further includes: recycling the caustic soda and chlorine as raw materials in the preparation of epoxy resin. By adopting the above preferred embodiment, the wastewater from the epoxy resin preparation process is recycled and treated before being reused in the epoxy resin preparation process, which is beneficial to resource recycling, effectively improves the utilization rate of raw materials, achieves "zero emissions" in epoxy resin production, and has significant environmental and social benefits, while also possessing good technical and economic efficiency. Preferably, the caustic soda is further concentrated before reuse.

[0069] Preferably, the method further includes drying and liquefying the obtained chlorine gas. The drying and liquefaction can be performed using methods conventional in the art, such as liquefaction by freezing liquid chlorine.

[0070] In this invention, there are no particular limitations on the method and conditions for preparing the epoxy resin. The product obtained by ion membrane electrolysis can be directly introduced into the existing epoxy resin preparation device or system as a raw material without the need for additional equipment.

[0071] According to the present invention, preferably, the preparation of the epoxy resin includes the following steps:

[0072] S1. Chlorine gas is reacted with propylene in a first reaction to obtain allyl chloride;

[0073] S2. The chloropropene is reacted with caustic soda in a second reaction to obtain epichlorohydrin;

[0074] S3. The epichlorohydrin, epoxy resin monomer and caustic soda are reacted in a third reaction to obtain epoxy resin.

[0075] According to the present invention, the selection range of the epoxy resin monomers is relatively wide, and those skilled in the art can select them according to actual needs. For example, the epoxy resin monomers can be selected from at least one of polyols, polyphenols, polycarboxylic acids, and polyamines.

[0076] In this invention, the range of reaction conditions for the preparation of the epoxy resin is relatively wide, and conventional conditions in the art can be used, which are well known to those skilled in the art and will not be described in detail here.

[0077] A second aspect of the present invention provides a saline wastewater treatment system, the system comprising: a saline wastewater supply unit 1, a conductivity adjustment tank 2, an extraction unit 3, an ultrasonic microbubble reaction unit 4, an oxidation treatment unit 5, and a brine storage tank 6, which are connected sequentially along the material flow direction.

[0078] The system also includes an electrolyte supply unit 7, the outlet of which is connected to the inlet of the conductivity adjustment tank 2.

[0079] According to the present invention, the saline wastewater supply unit 1 includes a saline wastewater storage tank 1-1 and a heating device 1-2. The saline wastewater storage tank 1-1 is used to collect saline wastewater from the epoxy resin preparation unit 9. The heating device 1-2 is used to heat the saline wastewater from the saline wastewater storage tank 1-1 and send the heated saline wastewater into the conductivity adjustment tank 2.

[0080] According to the present invention, preferably, the extraction unit 3 includes a micro-interface generator 3-1 and a separation tower 3-2; the micro-interface generator 3-1 is provided with a primary brine inlet, an extractant inlet and a mixed liquid outlet, for exchanging the primary brine from the conductivity adjustment tank 2 with the extractant to obtain a mixed liquid which is then fed into the separation tower 3-2.

[0081] The system also includes an extractant supply unit 3-3, the outlet of which is connected to the extractant inlet.

[0082] The separation tower 3-2 is equipped with a mixed liquid inlet, a first organic phase outlet at the top, and a secondary brine outlet at the bottom. These are used to separate the mixed liquid from the micro-interface generator 3-1, obtaining a secondary brine and a first organic phase. The secondary brine is sent to the ultrasonic microbubble reaction unit 4 through the secondary brine outlet, while the first organic phase is discharged from the system through the first organic phase outlet for recovery and reuse.

[0083] Preferably, the separation tower 3-2 is a flash tower.

[0084] The ultrasonic microbubble reaction unit 4 is an ultrasonic microbubble reactor, equipped with a secondary brine inlet, a tertiary brine outlet, and a second organic phase outlet. It is used to perform an ultrasonic microbubble reaction on the secondary brine from the extraction unit 3 to obtain tertiary brine and a second organic phase. The tertiary brine is fed into the oxidation treatment unit 5 through the tertiary brine outlet, and the second organic phase is discharged from the system through the second organic phase outlet.

[0085] The oxidation treatment unit 5 is equipped with a three-stage brine inlet, a cavitation gas inlet, and a clean brine outlet. It is used to disperse the cavitation gas into cavitation bubbles to form cavitation microbubble micro-interfaces, and to oxidize the three-stage brine from the ultrasonic microbubble reaction unit 4 to obtain clean brine, which is then sent to the brine storage tank 6.

[0086] According to the present invention, preferably, the system further includes an ion-exchange membrane electrolysis unit 8 for electrolyzing clean brine from the brine storage tank 6. The product obtained from the ion-exchange membrane electrolysis is recycled as a reaction raw material into the epoxy resin preparation unit 9.

[0087] The third aspect of this invention provides the application of the method for treating saline wastewater described in the first aspect and the system for treating saline wastewater described in the second aspect in the production of chlor-alkali and glycidyl ether.

[0088] The present invention will be described in detail below through embodiments.

[0089] In the following examples, the TOC of the saline solution was measured using the method of GB / T 13193-1991, and the conductivity was measured using the method of GB / T11007-2008.

[0090] Example 1

[0091] The saline wastewater treatment system used is as follows: Figure 1 As shown.

[0092] The saline wastewater stored in the saline wastewater storage tank 1-1 is sodium chloride wastewater from the production process of nonylphenol glycidyl ether, with a TOC value of 4500 ppm.

[0093] (1) The metered 10,000 kg of saline wastewater is heated to 65°C by heating device 1-2 through DCS and then sent to conductivity adjustment tank 2. The conductivity supply unit 7 is calculated and controlled by SFC sequential control module to add 210 kg of electrolyte calcium chloride to conductivity adjustment tank 2 and stirred for 10 minutes to obtain the first brine. The conductivity of the first brine is controlled to be 410 S / cm.

[0094] (2) The first brine is fed into the extraction unit 3 for extraction and separation.

[0095] The first extractant is acetone, and the second extractant is isopropyl ether. The mass ratio of acetone to isopropyl ether is controlled at 1:3. The extractant in the extractant supply unit 3-3 is continuously fed into the micro-interface generator 3-1 through the SFC sequential control module unit. The mass ratio of the total amount of extractant to the amount of primary brine is 0.28:1. The extractant is contacted with the primary brine for 20 minutes. The resulting mixture is fed into the separation tower 3-2, which is a flash evaporator with a bottom temperature of 50°C and an absolute pressure of 50 kPa. The first organic phase obtained from the top of the tower, the extractant, and the organic matter are recovered and reused. The secondary brine obtained from the bottom of the tower is continuously fed into the ultrasonic microbubble reaction unit 4 through a pump.

[0096] (3) The ultrasonic microbubble reaction unit 4 is an ultrasonic microbubble reactor with a set temperature of 85℃, an ultrasonic frequency of 20kHz, air as the medium of the microbubbles, and a second organic phase discharge system containing macromolecular organic matter. The TOC of the obtained tertiary brine is 3000ppm.

[0097] (4) The tertiary brine is heated to 230°C by heat exchange with the flue gas and pressurized to 5.5 MPa. It is then sent to the oxidation treatment unit 5 through a pipeline. The oxidation treatment unit 5 is a cavitation microbubble micro-interface oxidizer. The temperature is controlled at 230±10°C and the pressure at 5.5 MPa. Oxygen enters the reactor through the bottom of the cavitation interface oxidizer and is dispersed into micron-sized cavitation bubbles in the reactor. The mass ratio of oxygen in the cavitation bubbles to the chemical oxygen demand of organic matter in the tertiary brine is 1.2:1. The organic matter in the tertiary brine is further oxidized into carbon dioxide and water to obtain clean brine. The TOC of the clean brine is 5 ppm. The TOC in this crystallized brine is extremely low, which can meet the requirements of ion membrane electrolysis. It has significant advantages in preventing equipment corrosion and ensuring the safe and stable operation of the electrolytic ion membrane cell.

[0098] (5) The above-mentioned clean brine is fed into the ion membrane electrolysis unit 8 for ion membrane electrolysis to obtain caustic soda, chlorine and hydrogen; caustic soda and chlorine are recycled as raw materials into the epoxy resin preparation system.

[0099] Chlorine and propylene undergo a first reaction in a 30k-ton chloropropylene unit to obtain chloropropylene. Chlorine and caustic soda undergo a second reaction to prepare epichlorohydrin. Caustic soda, epichlorohydrin, and bisphenol A undergo a third reaction in a 0.3k-ton unit to prepare epoxy resin.

[0100] Example 2

[0101] The saline wastewater treatment system used is as follows: Figure 1 As shown.

[0102] The saline wastewater stored in the saline wastewater storage tank 1-1 is sodium chloride wastewater from the production process of o-cresolaldehyde glycidyl ether, with a TOC value of 6000 ppm.

[0103] (1) The metered 10,000 kg of saline wastewater is heated to 70°C by heating device 1-2 through DCS and then sent to conductivity adjustment tank 2. The conductivity supply unit 7 automatically adds 400 kg of electrolyte calcium chloride to conductivity adjustment tank 2 in the SFC sequential control module unit. Stirring is maintained for 20 minutes to obtain the first brine. The conductivity of the first brine is controlled to be 400 S / cm.

[0104] (2) The first brine is fed into the extraction unit 3 for extraction and separation.

[0105] The first extractant is acetone, and the second extractant is isopropyl ether. The mass ratio of acetone to isopropyl ether is controlled at 1:3. The extractant in the extractant supply unit 3-3 is continuously fed into the micro-interface generator 3-1 through the SFC sequential control module unit. The mass ratio of the total amount of extractant to the amount of primary brine is 0.3:1. The extractant is contacted with the primary brine for 20 minutes. The resulting mixture is fed into the separation tower 3-2, which is a flash evaporator with a bottom temperature of 60°C and an absolute pressure of 50 kPa. The first organic phase obtained from the top of the tower, the extractant, and the organic matter are recovered and reused. The secondary brine obtained from the bottom of the tower is continuously fed into the ultrasonic microbubble reaction unit 4 through a pump.

[0106] (3) The ultrasonic microbubble reaction unit 4 is an ultrasonic microbubble reactor with a set temperature of 85℃, an ultrasonic frequency of 30kHz, air as the medium of the microbubbles, and a second organic phase discharge system containing macromolecular organic matter. The TOC of the obtained tertiary brine is 3200ppm.

[0107] (4) The tertiary brine is heated to 230°C by heat exchange with the flue gas and pressurized to 5.5 MPa before being sent to the oxidation treatment unit 5 through a pipeline. The oxidation treatment unit 5 is a cavitation microbubble micro-interface oxidizer, with a controlled temperature of 230±10°C and a pressure of 5.5 MPa. Oxygen enters the reactor through the bottom of the cavitation interface oxidizer and is dispersed into micron-sized cavitation bubbles in the reactor. The mass ratio of oxygen in the cavitation bubbles to the chemical oxygen demand (COD) of the organic matter in the tertiary brine is 1.3:1. The organic matter in the tertiary brine is further oxidized into carbon dioxide and water to obtain clean brine with a TOC < 6 ppm.

[0108] (5) The above-mentioned clean brine is fed into the ion membrane electrolysis unit 8 for ion membrane electrolysis to obtain caustic soda, chlorine and hydrogen; caustic soda and chlorine are recycled as raw materials into the epoxy resin preparation system.

[0109] Chlorine and propylene undergo a first reaction in a 30k-ton allyl chloride unit to obtain allyl chloride. Allyl chloride undergoes a second reaction with caustic soda to prepare epichlorohydrin. Caustic soda, epichlorohydrin, and o-cresol resin undergo a third reaction in a 0.3k-ton unit to prepare o-cresol epoxy resin.

[0110] Example 3

[0111] The treatment system for the saline wastewater stored in saline wastewater storage tank 1-1 is as follows: Figure 1 As shown.

[0112] The saline wastewater used was sodium chloride wastewater from the production process of phenol aldehyde glycidyl ether, with a TOC value of 6400 ppm.

[0113] (1) The metered 10,000 kg of saline wastewater is heated to 70°C by heating device 1-2 through DCS and then sent to conductivity adjustment tank 2. The conductivity supply unit 7 is calculated and controlled by SFC sequential control module to add 600 kg of electrolyte calcium chloride to conductivity adjustment tank 2. Stirring is maintained for 15 minutes to obtain the first brine. The conductivity of the first brine is controlled to be 410 S / cm.

[0114] (2) The first brine is fed into the extraction unit 3 for extraction and separation.

[0115] The first extractant is acetone, and the second extractant is isopropyl ether. The mass ratio of acetone to isopropyl ether is controlled at 1:3. The extractant in the extractant supply unit 3-3 is continuously fed into the micro-interface generator 3-1 through the SFC sequential control module unit. The mass ratio of the total amount of extractant to the amount of primary brine is 0.3:1. The extractant is contacted with the primary brine for 20 minutes. The resulting mixture is fed into the separation tower 3-2, which is a flash evaporator with a bottom temperature of 60°C and an absolute pressure of 40 kPa. The first organic phase obtained from the top of the tower, the extractant, and the organic matter are recovered and reused. The secondary brine obtained from the bottom of the tower is continuously fed into the ultrasonic microbubble reaction unit 4 through a pump.

[0116] (3) The ultrasonic microbubble reaction unit 4 is an ultrasonic microbubble reactor with a set temperature of 80℃, an ultrasonic frequency of 20kHz, air as the medium of the microbubbles, and a second organic phase discharge system containing macromolecular organic matter. The TOC of the obtained tertiary brine is 3100ppm.

[0117] (4) The tertiary brine is heated to 230°C by heat exchange with the flue gas and pressurized to 5.5 MPa before being sent to the oxidation treatment unit 5 through a pipeline. The oxidation treatment unit 5 is a cavitation microbubble micro-interface oxidizer, with a controlled temperature of 230±10°C and a pressure of 5.5 MPa. Oxygen enters the reactor through the bottom of the cavitation interface oxidizer and is dispersed into micron-sized cavitation bubbles in the reactor. The mass ratio of oxygen in the cavitation bubbles to the chemical oxygen demand of organic matter in the tertiary brine is 1.3:1. The organic matter in the tertiary brine is further oxidized into carbon dioxide and water to obtain clean brine with a TOC < 5 ppm.

[0118] (5) The above-mentioned clean brine is fed into the ion membrane electrolysis unit 8 for ion membrane electrolysis to obtain caustic soda, chlorine and hydrogen; caustic soda and chlorine are recycled as raw materials into the epoxy resin preparation system.

[0119] Chlorine and propylene undergo a first reaction in a 30k-ton chloropropylene unit to obtain chloropropylene. Chlorine and caustic soda undergo a second reaction to prepare epichlorohydrin. Caustic soda, epichlorohydrin, and phenolic resin undergo a third reaction in a 0.3k-ton unit to prepare phenolic epoxy resin.

[0120] Example 4

[0121] The saline wastewater treatment system used is as follows: Figure 1 As shown.

[0122] The saline wastewater stored in the saline wastewater storage tank 1-1 is sodium chloride wastewater from the production process of glycerol triglycidyl ether, with a TOC value of 7000 ppm.

[0123] (1) The metered 10,000 kg of saline wastewater is heated to 70°C by heating device 1-2 through DCS and then sent to conductivity adjustment tank 2. The SFC sequential control module unit calculates and controls the conductivity supply unit 7 to add 1,000 kg of electrolyte calcium chloride to conductivity adjustment tank 2. Stirring is maintained for 15 minutes to obtain the first brine. The conductivity of the first brine is controlled to be 410 S / cm.

[0124] (2) The first brine is fed into the extraction unit 3 for extraction and separation.

[0125] The first extractant is acetone, and the second extractant is isopropyl ether. The mass ratio of acetone to isopropyl ether is controlled at 1:3. The extractant in the extractant supply unit 3-3 is continuously fed into the micro-interface generator 3-1 through the SFC sequential control module unit. The mass ratio of the total amount of extractant to the amount of primary brine is 0.3:1. The extractant is contacted with the primary brine for 20 minutes. The resulting mixture is fed into the separation tower 3-2, which is a flash evaporator with a bottom temperature of 80°C and an absolute pressure of 40 kPa. The first organic phase obtained from the top of the tower, the extractant, and the organic matter are recovered and reused. The secondary brine obtained from the bottom of the tower is continuously fed into the ultrasonic microbubble reaction unit 4 through a pump.

[0126] (3) The ultrasonic microbubble reaction unit 4 is an ultrasonic microbubble reactor with a set temperature of 80℃, an ultrasonic frequency of 40kHz, air as the medium of the microbubbles, and a second organic phase discharge system containing macromolecular organic matter. The TOC of the obtained tertiary brine is 3100ppm.

[0127] (4) The tertiary brine is heated to 230°C by heat exchange with the flue gas and pressurized to 5.5 MPa before being sent to the oxidation treatment unit 5 through a pipeline. The oxidation treatment unit 5 is a cavitation microbubble micro-interface oxidizer, with a controlled temperature of 230±10°C and a pressure of 5.5 MPa. Oxygen enters the reactor through the bottom of the cavitation interface oxidizer and is dispersed into micron-sized cavitation bubbles in the reactor. The mass ratio of oxygen in the cavitation bubbles to the chemical oxygen demand of organic matter in the tertiary brine is 1.3:1. The organic matter in the tertiary brine is further oxidized into carbon dioxide and water to obtain clean brine with a TOC < 5 ppm.

[0128] (5) The above-mentioned clean brine is fed into the ion membrane electrolysis unit 8 for ion membrane electrolysis to obtain caustic soda, chlorine and hydrogen; caustic soda and chlorine are recycled as raw materials into the epoxy resin preparation system.

[0129] Chlorine and propylene undergo a first reaction in a 30k-ton chloropropylene unit to obtain chloropropylene. Chlorine and caustic soda undergo a second reaction to prepare epichlorohydrin. Caustic soda, epichlorohydrin, and glycerol undergo a third reaction in a 0.3k-ton unit to prepare glycerol triglycidyl epoxy resin.

[0130] Example 5

[0131] The saline wastewater treatment system used is as follows: Figure 1 As shown.

[0132] The saline wastewater stored in the saline wastewater storage tank 1-1 is sodium chloride wastewater from the production process of bisphenol F glycidyl ether, with a TOC value of 6500 ppm.

[0133] (1) The metered 10,000 kg of saline wastewater is heated to 75°C by heating device 1-2 through DCS and then sent into conductivity adjustment tank 2. The conductivity supply unit 7 automatically adds 1,000 kg of electrolyte calcium chloride to conductivity adjustment tank 2 by SFC sequential control module unit calculation and control. Stirring is maintained for 15 minutes to obtain the first brine. The conductivity of the first brine is controlled to be 400 S / cm.

[0134] (2) The first brine is fed into the extraction unit 3 for extraction and separation.

[0135] The first extractant is acetone, and the second extractant is isopropyl ether. The mass ratio of acetone to isopropyl ether is controlled at 1:3. The extractant in the extractant supply unit 3-3 is continuously fed into the micro-interface generator 3-1 through the SFC sequential control module unit. The mass ratio of the total amount of extractant to the amount of primary brine is 0.3:1. The extractant is contacted with the primary brine for 20 minutes. The resulting mixture is fed into the separation tower 3-2, which is a flash evaporator with a bottom temperature of 80°C and an absolute pressure of 40 kPa. The first organic phase obtained from the top of the tower, the extractant, and the organic matter are recovered and reused. The secondary brine obtained from the bottom of the tower is continuously fed into the ultrasonic microbubble reaction unit 4 through a pump.

[0136] (3) The ultrasonic microbubble reaction unit 4 is an ultrasonic microbubble reactor with a set temperature of 80℃, an ultrasonic frequency of 30KHz, air as the medium of the microbubbles, and a second organic phase discharge system containing macromolecular organic matter. The TOC of the obtained tertiary brine is 3100ppm.

[0137] (4) The tertiary brine is heated to 230°C by heat exchange with the flue gas and pressurized to 5.5 MPa before being sent to the oxidation treatment unit 5 through a pipeline. The oxidation treatment unit 5 is a cavitation microbubble micro-interface oxidizer, with a controlled temperature of 230±10°C and a pressure of 5.5 MPa. Oxygen enters the reactor through the bottom of the cavitation interface oxidizer and is dispersed into micron-sized cavitation bubbles in the reactor. The mass ratio of oxygen in the cavitation bubbles to the chemical oxygen demand of organic matter in the tertiary brine is 1.3:1. The organic matter in the tertiary brine is further oxidized into carbon dioxide and water to obtain clean brine with a TOC < 5 ppm.

[0138] (5) The above-mentioned clean brine is fed into the ion membrane electrolysis unit 8 for ion membrane electrolysis to obtain caustic soda, chlorine and hydrogen; caustic soda and chlorine are recycled as raw materials into the epoxy resin preparation system.

[0139] Chlorine and propylene undergo a first reaction in a 30k-ton chloropropylene unit to obtain chloropropylene. Chlorine and caustic soda undergo a second reaction to prepare epichlorohydrin. Caustic soda, epichlorohydrin, and bisphenol F undergo a third reaction in a 0.3k-ton unit to prepare bisphenol F epoxy resin.

[0140] Example 6

[0141] The method in Example 1 was followed, except that an air flotation extraction device was used instead of a micro-interface generator, resulting in a TOC of 4500 ppm for the tertiary brine and a TOC of 430 ppm for the clean brine.

[0142] Example 7

[0143] The method is the same as in Example 1, except that the conductivity of the first saline solution is controlled to be 390 S / cm.

[0144] The TOC of the obtained tertiary brine was 3300 ppm; the TOC of the clean brine was 17 ppm.

[0145] Example 8

[0146] The method is the same as in Example 1, except that the conductivity of the first saline solution is controlled to be 450 S / cm.

[0147] The TOC of the obtained tertiary brine was 3200 ppm; the TOC of the clean brine was 11 ppm.

[0148] Example 9

[0149] The method is the same as in Example 1, except that an equal mass of acetone is used instead of isopropyl ether.

[0150] The TOC of the obtained tertiary brine was 3300 ppm; the TOC of the clean brine was 6 ppm.

[0151] Comparative Example 1

[0152] The treatment system and method for saline wastewater in Example 1 are different except that they do not include the conductivity adjustment tank 2 and the micro-interface generator 3-1.

[0153] (1) The metered 10,000 kg of saline wastewater was heated to 65°C by DCS and stirred for 10 minutes;

[0154] (2) The above-mentioned saline wastewater is sent to the separation tower 3-2. The separation tower is a flash evaporator with a bottom temperature of 50°C and an absolute pressure of 50kPa. The first organic phase obtained from the top of the tower, the extractant and organic matter are recycled and reused. The secondary brine obtained from the bottom of the tower is continuously sent to the ultrasonic microbubble reaction unit 4 by a pump.

[0155] (3) The ultrasonic microbubble reaction unit 4 is an ultrasonic microbubble reactor with a set temperature of 85℃, an ultrasonic frequency of 20kHz, air as the medium of the microbubbles, and a second organic phase discharge system containing macromolecular organic matter. The TOC of the obtained tertiary brine is 4500ppm.

[0156] (4) The tertiary brine is heated to 230°C by heat exchange with the flue gas and pressurized to 5.5 MPa before being piped to oxidation treatment unit 5. Oxidation treatment unit 5 is a cavitation microbubble micro-interface oxidizer, with a controlled temperature of 230±10°C and a pressure of 5.5 MPa. Oxygen enters the reactor through the bottom of the cavitation interface oxidizer and disperses into micron-sized cavitation bubbles. The mass ratio of oxygen in the cavitation bubbles to the chemical oxygen demand (COD) of the organic matter in the tertiary brine is 1.3:1. The organic matter in the tertiary brine is further oxidized to carbon dioxide and water to obtain treated brine. The TOC of the treated brine is 450 ppm, which does not meet the requirements of ion-exchange membrane electrolysis.

[0157] Comparative Example 2

[0158] The treatment system and method for saline wastewater in Example 1 are the same, except that they do not include the conductivity adjustment tank 2.

[0159] (1) The metered 10,000 kg of saline wastewater was heated to 65°C by DCS and stirred for 10 minutes;

[0160] (2) The above-mentioned saline wastewater is sent to the extraction unit 3 for extraction and separation.

[0161] The first extractant is acetone, and the second extractant is isopropyl ether. The mass ratio of acetone to isopropyl ether is controlled to be 1:3. The extractant in the extractant supply unit 3-3 is continuously fed into the micro-interface generator 3-1 through the SFC sequential control module unit, and contacts the primary brine for 20 minutes. The resulting mixture is sent to the separation tower 3-2, which is a flash evaporator with a bottom temperature of 50°C and an absolute pressure of 50 kPa. The first organic phase obtained from the separation at the top of the tower, the extractant and organic matter are recovered and reused. The secondary brine obtained from the bottom of the tower is continuously fed into the ultrasonic microbubble reaction unit 4 through a pump.

[0162] (3) The ultrasonic microbubble reaction unit 4 is an ultrasonic microbubble reactor with a set temperature of 85℃, an ultrasonic frequency of 20kHz, air as the medium of the microbubbles, and a second organic phase discharge system containing macromolecular organic matter. The TOC of the obtained tertiary brine is 5000ppm.

[0163] (4) The tertiary brine is heated to 230°C by heat exchange with the flue gas and pressurized to 5.5 MPa before being sent to the oxidation treatment unit 5 through a pipeline. The oxidation treatment unit 5 is a cavitation microbubble micro-interface oxidizer, with a controlled temperature of 230±10°C and a pressure of 5.5 MPa. Oxygen enters the reactor through the bottom of the cavitation interface oxidizer and is dispersed into micron-sized cavitation bubbles in the reactor. The mass ratio of oxygen in the cavitation bubbles to the chemical oxygen demand of organic matter in the tertiary brine is 1.3:1. The organic matter in the tertiary brine is further oxidized into carbon dioxide and water. The TOC of the treated brine is 220 ppm, which does not meet the requirements of ion membrane electrolysis.

[0164] Comparative Example 3

[0165] The treatment system and method for saline wastewater in Example 1 are different except that they do not contain the micro-interface generator 3-1.

[0166] (1) The metered 10,000 kg of saline wastewater is heated to 65°C by DCS and then sent to conductivity adjustment tank 2. The SFC sequential control module unit calculates and automatically adds 210 kg of electrolyte calcium chloride to conductivity adjustment tank 2. Stirring is maintained for 10 minutes to obtain the first brine. The conductivity of the first brine is controlled to be 410 S / cm.

[0167] (2) The first brine is sent to the separation tower 3-2. The separation tower is a flash tower with a bottom temperature of 50°C and an absolute pressure of 50kPa. The first organic phase obtained from the top of the tower is recycled and reused. The secondary brine obtained from the bottom of the tower is continuously sent to the ultrasonic microbubble reaction unit 4 by a pump.

[0168] (3) The ultrasonic microbubble reaction unit 4 is an ultrasonic microbubble reactor with a set temperature of 85°C, an ultrasonic frequency of 20Hz, air as the medium of the microbubbles, and a second organic phase discharge system containing macromolecular organic matter. The TOC of the obtained tertiary brine is 5000ppm.

[0169] (4) The tertiary brine is heated to 230°C by heat exchange with the flue gas and pressurized to 5.5 MPa before being piped to oxidation treatment unit 5. Oxidation treatment unit 5 is a cavitation microbubble micro-interface oxidizer, with a controlled temperature of 230±10°C and a pressure of 5.5 MPa. Oxygen enters the reactor through the bottom of the cavitation interface oxidizer and disperses into micron-sized cavitation bubbles. The mass ratio of oxygen in the cavitation bubbles to the chemical oxygen demand (COD) of the organic matter in the tertiary brine is 1.3:1. The organic matter in the tertiary brine is further oxidized into carbon dioxide and water. The TOC of the treated brine is 320 ppm, which does not meet the requirements of ion-exchange membrane electrolysis.

[0170] Comparative Example 4

[0171] The difference between the saline wastewater treatment system and method in Example 1 is that the oxidation treatment unit 5 is a cavitation oxidizer, that is, cavitation gas is directly introduced into the oxidation treatment unit 5 without generating microbubble interfaces.

[0172] Step (4) specifically includes: controlling the temperature at 230±10℃ and the pressure at 5.5MPa; oxygen enters the reactor through the bottom of the cavitation interface oxidizer; the ratio of oxygen usage to the chemical oxygen demand (COD) of the organic matter in the tertiary brine is 1.3:1; the organic matter in the tertiary brine is further oxidized into carbon dioxide and water; the TOC of the treated brine is 740ppm. This does not meet the requirements of ion-exchange membrane electrolysis.

[0173] As can be seen from the above embodiments and comparative examples, the saline wastewater treatment method provided by the present invention does not require adjusting the wastewater pH value, does not use a metal catalyst, and completely avoids the impact of metal ions on the subsequent application of brine. This treatment method removes TOC from saline wastewater in stages, efficiently removing water-soluble organic matter. The resulting clean brine meets the requirements for ion-exchange membrane electrolysis, reducing production and operating costs and investment costs, while also reducing operational safety risks.

[0174] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for treating saline wastewater, characterized in that, The method includes: (1) The conductivity of the saline wastewater is adjusted to obtain primary brine, wherein the conductivity of the primary brine is not less than 390 s / cm; the saline wastewater is selected from at least one of the epoxy resins produced during the production process of epoxy resins, namely glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin and alicyclic epoxy type epoxy resin. (2) The primary brine is extracted and separated to obtain secondary brine and a first organic phase; (3) The secondary brine is subjected to an ultrasonic microbubble reaction to obtain a tertiary brine and a second organic phase; (4) In the presence of cavitation bubbles, the tertiary brine is subjected to an oxidation reaction to obtain clean brine; The method further includes: electrolyzing the clean brine through an ion-exchange membrane to obtain caustic soda, chlorine, and hydrogen, and using the caustic soda and chlorine as raw materials for the preparation of epoxy resin; The preparation of the epoxy resin includes the following steps: S1. Chlorine gas is reacted with propylene in a first reaction to obtain allyl chloride; S2. The chloropropene is reacted with caustic soda in a second reaction to obtain epichlorohydrin; S3. The epichlorohydrin, epoxy resin monomer and caustic soda are reacted in a third reaction to obtain epoxy resin.

2. The processing method according to claim 1, wherein, The conductivity of the primary brine is 390-500 S / cm.

3. The processing method according to claim 2, wherein, The conductivity of the primary brine is 400-450 S / cm.

4. The processing method according to claim 3, wherein, The conductivity of the primary brine is 400-435 S / cm.

5. The processing method according to claim 1, wherein, The temperature of the primary brine is 50-90℃.

6. The processing method according to claim 5, wherein, The temperature of the primary brine is 60-75℃.

7. The processing method according to claim 1 or 2, wherein, The method for adjusting conductivity includes introducing an electrolyte into the saline wastewater.

8. The processing method according to claim 7, wherein, The electrolyte is selected from at least one of inorganic acids, inorganic bases, and inorganic salts.

9. The processing method according to claim 8, wherein, The electrolyte is selected from at least one of hydrochloric acid, sodium hydroxide, sodium chloride, calcium chloride, sulfuric acid, calcium sulfate, phosphoric acid, sodium dihydrogen phosphate, potassium chloride, acetic acid, sodium acetate, calcium acetate, oxalic acid, sodium oxalate, calcium oxalate, and calcium carbonate.

10. The processing method according to claim 9, wherein, The electrolyte is selected from at least one of sodium hydroxide, sodium chloride, phosphoric acid, sodium dihydrogen phosphate, sodium acetate, oxalic acid, calcium chloride, and sodium oxalate.

11. The processing method according to any one of claims 1-6, wherein, The extraction involves contacting the primary brine with an extractant.

12. The processing method according to claim 11, wherein, The contact time is 2-30 minutes.

13. The processing method according to claim 12, wherein, The contact time is 4-20 minutes.

14. The processing method according to claim 11, wherein, The contact is performed in a miniaturized interface generator.

15. The processing method according to claim 11, wherein, The mass ratio of the extractant to the primary brine is 0.25-0.35:

1.

16. The processing method according to claim 15, wherein, The mass ratio of the extractant to the primary brine is 0.28-0.3:

1.

17. The processing method according to claim 11, wherein, The extractant is selected from at least one of alkanes, halogenated hydrocarbons, aromatic hydrocarbons, alcohols, esters, ketones, ethers, sulfoxides, and nitriles.

18. The processing method according to claim 17, wherein, The alkanes have 1-11 carbon atoms.

19. The processing method according to claim 17, wherein, The alkane is selected from at least one of cyclohexane, cyclopentane, and propane.

20. The processing method according to claim 17, wherein, The halogenated hydrocarbon is selected from at least one of chloroform, chlorobenzene, and dichloropropane.

21. The processing method according to claim 20, wherein, The halogenated hydrocarbon is chloroform.

22. The processing method according to claim 17, wherein, The alcohol is a C1-C14 alcohol.

23. The processing method according to claim 22, wherein, The alcohol is selected from at least one of ethanol, n-butanol, and n-pentanol.

24. The processing method according to claim 17, wherein, The ether is a C2-C8 ether.

25. The processing method according to claim 24, wherein, The ether is selected from at least one of diethyl ether, tert-butyl ether, and isopropyl ether.

26. The processing method according to claim 25, wherein, The ether is tert-butyl ether and / or isopropyl ether.

27. The processing method according to claim 17, wherein, The ketone is a C3-C6 ketone.

28. The processing method according to claim 27, wherein, The ketone is selected from at least one of acetone, methyl isobutyl ketone, and butanone.

29. The processing method according to claim 17, wherein, The ester is selected from at least one of ethyl acetate, tributyl phosphate, butyl acetate, and diethyl sulfate.

30. The processing method according to claim 29, wherein, The ester is ethyl acetate and / or tributyl phosphate.

31. The processing method according to claim 17, wherein, The aromatic hydrocarbon is selected from at least one of toluene, xylene, and chlorobenzene.

32. The processing method according to claim 17, wherein, The nitrile is selected from at least one of acetonitrile, benzonitrile, and valerate.

33. The processing method according to claim 17, wherein, The extractant includes a first extractant and a second extractant, wherein the first extractant is selected from at least one of ethers, sulfoxides and esters, and the second extractant is selected from at least one of ketones, alcohols and alkanes.

34. The processing method according to claim 33, wherein, The mass ratio of the first extractant to the second extractant is 1:1-5.

35. The processing method according to any one of claims 1-6, wherein, The separation method described in step (2) is selected from at least one of flash separation, stripping separation and simple distillation.

36. The processing method according to claim 35, wherein, The separation method described in step (2) is flash separation.

37. The processing method according to claim 36, wherein, The flash separation temperature is 40-60℃, and the flash separation pressure is 20-60kPa.

38. The processing method according to any one of claims 1-6, wherein, The TOC in the tertiary brine does not exceed 4000 ppm.

39. The processing method according to claim 38, wherein, The TOC in the tertiary brine does not exceed 3800 ppm.

40. The processing method according to claim 39, wherein, The TOC in the tertiary brine is 2000-3500 ppm.

41. The processing method according to any one of claims 1-6, wherein, The ultrasonic microbubble reaction includes: contacting the secondary saline solution with microbubbles under ultrasonic conditions.

42. The processing method according to claim 41, wherein, The conditions for the ultrasonic microbubble reaction include: an ultrasonic frequency of 20-40 kHz and a reaction temperature of 50-120 °C.

43. The processing method according to claim 41, wherein, The conditions for the ultrasonic microbubble reaction include: an ultrasonic frequency of 22-30 kHz and a reaction temperature of 70-100℃.

44. The processing method according to claim 41, wherein, The medium of the microbubbles is selected from at least one of oxygen, air and nitrogen.

45. The processing method according to any one of claims 1-6, wherein, The conditions for the oxidation reaction include: a temperature of 200-280℃ and a pressure of 4-8MPa.

46. ​​The processing method according to any one of claims 1-6, wherein, The conditions for the oxidation reaction include: a temperature of 220-250℃ and a pressure of 5-5.5MPa.

47. The processing method according to any one of claims 1-6, wherein, The medium for the cavitation bubbles is oxygen-containing gas.

48. The processing method according to claim 47, wherein, The medium for the cavitation bubbles is oxygen or air.

49. The processing method according to any one of claims 1-6, wherein, The mass ratio of oxygen in the cavitation bubbles to the chemical oxygen demand of organic matter in the tertiary brine is 1-1.3:

1.

50. The processing method according to any one of claims 1-6, wherein, No catalyst is used in the oxidation reaction.

51. The processing method according to any one of claims 1-6, wherein, The TOC in the clean saline solution does not exceed 20 ppm.

52. The processing method according to claim 51, wherein, The TOC in the clean brine does not exceed 7 ppm.

53. The processing method according to claim 51, wherein, The TOC in the clean brine is 4-6 ppm.

54. A saline wastewater treatment system for use in the method for treating saline wastewater according to any one of claims 1-53, characterized in that, The system includes: a saline wastewater supply unit (1), a conductivity adjustment tank (2), an extraction unit (3), an ultrasonic microbubble reaction unit (4), an oxidation treatment unit (5), and a brine storage tank (6) connected sequentially along the logistics direction. The system also includes an electrolyte supply unit (7), the outlet of which is connected to the inlet of the conductivity adjustment tank (2).

55. The processing system according to claim 54, wherein, The extraction unit (3) includes a micro-interface generator (3-1) and a separation tower (3-2); the micro-interface generator (3-1) is provided with a primary brine inlet, an extractant inlet and a mixed liquid outlet, which is used to exchange the primary brine from the conductivity adjustment tank (2) with the extractant to obtain a mixed liquid that is sent to the separation tower (3-2). The separation tower (3-2) is provided with a mixed liquid inlet, a first organic phase outlet at the top of the tower, and a secondary brine outlet at the bottom of the tower, for separating the mixed liquid from the micro-interface generator (3-1) to obtain secondary brine and the first organic phase; The ultrasonic microbubble reaction unit (4) is an ultrasonic microbubble reactor, which is equipped with a secondary brine inlet, a tertiary brine outlet, and a second organic phase outlet. It is used to perform ultrasonic microbubble reaction on the secondary brine from the extraction unit (3) to obtain tertiary brine and a second organic phase. The oxidation treatment unit (5) is a cavitation microbubble micro-interface oxidizer, which is equipped with a three-stage brine inlet, a cavitation gas inlet and a clean brine outlet. It is used to oxidize the three-stage brine from the ultrasonic microbubble reaction unit (4) to obtain clean brine, and then send the clean brine into the brine storage tank (6).

56. The processing system according to claim 55, wherein, The separation tower (3-2) is a flash tower.

57. The processing system according to claim 55 or 56, wherein, The system also includes an ion-exchange membrane electrolysis unit (8) for electrolyzing clean brine from the brine storage tank (6) using an ion-exchange membrane.

58. The application of the method for treating saline wastewater according to any one of claims 1-53 or the system for treating saline wastewater according to any one of claims 54-57 in the production of chlor-alkali and glycidyl ether.

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