Method for resource utilization of calcium chloride hypersaline water containing high concentration of organic matter

Abstract

The application relates to the technical field of industrial wastewater treatment, and particularly provides a resource utilization method of calcium chloride high-salinity water containing high-concentration organic matters. The method comprises pretreatment-wet catalytic oxidation-salt type conversion-softening filtration-depth oxidation-nanofiltration purification-targeted adsorption, and not only does not have residual mother liquor and does not produce secondary pollution, but also the effluent organic matter is stable and up to the standard, the water quality and water volume fluctuation resistance is strong, heterogeneous and homogeneous catalysts are combined for catalysis, the homogeneous catalysts are recycled, in addition, most of the salts are recycled, the resource recycling is fully realized, the treatment cost is reduced, and the treated sodium chloride solution can be used as primary brine for subsequent ion membrane electrolysis.

Description

Technical Field

[0001] This application relates to the field of industrial wastewater treatment technology, specifically providing a method for the resource utilization of high-salt calcium chloride containing high concentrations of organic matter. Background Technology

[0002] In the chemical fiber industry, calcium chloride may be used as an auxiliary coagulant; in the production of epoxy resins and epichlorohydrin, calcium chloride may be generated as a byproduct; in the aramid industry, calcium chloride may be used in the synthesis of para-aramid; in pharmaceutical production, calcium chloride may be used as an auxiliary agent; in the dyeing and printing process, calcium chloride is often used to adjust the pH value or as an auxiliary agent; in the papermaking process, calcium chloride is often used to adjust the pH value of the pulp or as an auxiliary agent. Therefore, high-concentration calcium chloride wastewater is generated in industries such as chemical fibers, epoxy resins, epichlorohydrin, aramid, pharmaceuticals, dyeing and printing, and papermaking, and this wastewater often contains high concentrations of organic matter.

[0003] Wastewater containing high levels of calcium chloride and organic matter is characterized by high salinity, strong corrosiveness, easy scaling, and difficulty in biodegradation due to its high calcium chloride content. This makes the treatment of such wastewater very difficult and requires specific treatment technologies to effectively remove calcium chloride and reduce its environmental impact.

[0004] For wastewater with high calcium chloride and high organic matter content, the following treatment process is usually adopted: (1) Pretreatment: large particulate suspended solids and water quality and quantity are removed from the wastewater by means of equalization tank, reaction sedimentation, filtration, etc.; (2) Advanced oxidation: most of the organic matter in the wastewater is removed by means of Fenton oxidation, electrolytic oxidation, wet catalytic oxidation, etc.; (3) Evaporation process: calcium chloride solute is concentrated or even crystallized and separated by evaporation technologies such as low temperature evaporation and MVR; (4) Advanced treatment: for wastewater with high effluent requirements, advanced treatment is required, such as sand filtration, activated carbon adsorption, reverse osmosis, etc., to remove residual pollutants and purify water quality.

[0005] Due to the characteristics of wastewater with high calcium chloride and high organic matter content, traditional treatment methods may result in problems such as residual concentrate and excessive organic matter, posing safety hazards.

[0006] In the existing technical solutions, invention patent CN108658353A discloses a calcium chloride wastewater treatment process. First, a triple-effect multi-stage evaporator is used to treat the calcium chloride wastewater to obtain primary wastewater. The primary wastewater is then subjected to vacuum high-temperature flash evaporation to obtain secondary wastewater. The secondary wastewater undergoes solid-liquid separation to obtain calcium chloride dihydrate solid and mother liquor. Then, a portion of the mother liquor is transferred to a purification tank for impurity removal to obtain tertiary wastewater. The tertiary wastewater and the remaining mother liquor are returned to the triple-effect multi-stage evaporator for recycling. This triple-effect, flash evaporation, and impurity removal process achieves the recovery and utilization of calcium chloride. However, this method results in residual mother liquor, which, if not treated promptly, poses a significant safety hazard. Furthermore, this method is not suitable for treating calcium chloride wastewater with high organic content.

[0007] Invention patent CN102295392A discloses a water treatment and reuse method for calcium chloride wastewater. It employs optimized pretreatment, biochemical treatment, reverse osmosis water reuse, electrodialysis concentration, and evaporation recovery processes to essentially achieve zero wastewater discharge and the recovery of salt and water. However, this treatment method leaves residual mother liquor, and the concentration of calcium chloride is generally below 5%; otherwise, the quality of the biochemically treated effluent cannot be guaranteed.

[0008] Therefore, for wastewater with high calcium chloride and high organic matter content, how to effectively remove organic pollutants while recovering calcium chloride resources and avoiding the generation of difficult-to-treat secondary pollution is of great significance for the treatment of such wastewater. It is also of great significance for the development of industries such as titanium dioxide production, chemical fiber, epoxy resin, epichlorohydrin, aramid, pharmaceuticals, printing and dyeing, and papermaking.

[0009] In view of the above, this application is hereby submitted. Summary of the Invention

[0010] One of the purposes of this application is to provide a method for the resource utilization of high-concentration calcium chloride saline water containing high organic matter, which solves the shortcomings of existing processes that leave residual mother liquor after treatment, the difficulty in meeting the standards for organic matter in the effluent, and the fact that most existing technologies can only treat wastewater with low calcium chloride and low organic matter.

[0011] To achieve the above objectives, this application adopts the following technical solution:

[0012] A method for resource utilization of high-concentration calcium chloride saline solution containing high organic matter, the method comprising the following steps:

[0013] S1 Pretreatment: Wastewater first enters the equalization tank and then is filtered to remove large particulate suspended solids and a small amount of macromolecular organic matter before entering the wet catalytic oxidation unit;

[0014] S2 wet catalytic oxidation: Heterogeneous noble metal oxides and homogeneous transition metals are used as catalysts to carry out wet catalytic oxidation of wastewater under high temperature and high pressure, remove organic matter from wastewater, and recycle homogeneous catalysts to avoid catalyst loss.

[0015] S3 salt conversion: Glauber's salt is added to the wet catalytic oxidation effluent to react with calcium ions in the wastewater to generate gypsum, which is then separated by a sludge dewatering machine;

[0016] S4 softening filtration: The dual alkali method is used to generate calcium carbonate precipitate from the residual calcium ions in the supernatant of the salt conversion sludge dewatering machine. Then, the precipitate is concentrated by ultrafiltration and separated by pressure filtration. The filtrate enters the deep oxidation unit.

[0017] S5 deep oxidation: through the generation of free radicals with strong oxidizing power (· Under electrical or oxidizing reaction conditions, to make Oxidize persistent organic matter into low-toxicity or non-toxic forms. These substances help purify organic pollutants in wastewater.

[0018] S6 nanofiltration purification: First, small molecule suspended solids in the wastewater are removed by filtration, and then the remaining divalent ions are removed by the nanofiltration treatment unit. The nanofiltration concentrate enters the front end of the salt conversion unit, and the nanofiltration permeate enters the targeted adsorption unit.

[0019] S7 Targeted Adsorption: Microcrystalline adsorption materials are used to adsorb and remove residual organic matter in nanofiltration permeate. The targeted adsorption effluent enters the permeate tank, and the waste liquid from the regeneration of the adsorption medium enters the front-end pretreatment unit for further treatment.

[0020] The treatment of the effluent from the product water tank by targeted adsorption is as follows: S7-1 or S7-2:

[0021] S7-1: All of it enters the salt mixing tank, and sodium chloride is added to form brine with a sodium chloride concentration of 305±5g / L, which is used as the primary brine for the ion-exchange membrane caustic soda unit.

[0022] S7-2: Part of the solution enters the salt mixing tank, and part undergoes evaporation and crystallization. The condensate from the evaporation and crystallization is reused, and the mother liquor enters the salt mixing tank and mixes with the original unevaporated and uncrystallized targeted adsorption effluent to form a brine with a sodium chloride concentration of 305±5g / L, which serves as the primary brine for the ion-exchange membrane caustic soda unit.

[0023] In some embodiments, in S1, the filtration uses a multi-media filter 1 with a filtration accuracy of 10-20 μm and an operating pressure of 0.1-0.5 MPa.

[0024] In some embodiments, in S2, the temperature of the high temperature and high pressure is 200℃~300℃, and the pressure is 3~10 MPa.

[0025] In some embodiments, in S2, the catalyst is a homogeneous and heterogeneous mixed system.

[0026] In some embodiments, in S2, the heterogeneous catalyst is one or more of fluorine-modified ruthenium-based, cerium-based, iron-based, and titanium-based catalysts, and the content of the active catalyst component is 0.1 wt% to 2 wt%.

[0027] In some embodiments, in S2, the homogeneous catalyst is one or more compounds of transition metal elements such as iron, copper, manganese, and nickel, and the content of the catalyst active component is 0.5 wt% to 5 wt%.

[0028] In some embodiments, in S2, the catalytic oxidation time is 2 to 4 hours, wherein the residence time of the catalytic section is 15 minutes to 1 hour.

[0029] In some embodiments, in S2, the wet catalytic oxidation device is equipped with a fixed bed filled with metal oxidant packing material of φ4~10mm as an enhanced disperser, with a packing density of 1.0~1.5g / mL.

[0030] In some embodiments, in S2, after the waste liquid exits the reaction tower, 5% to 15% sodium hydroxide solution is added to the reaction section to fully precipitate the homogeneous catalyst active components. Solid-liquid separation is achieved through the retention effect of the filter in the filtration section. In the dissolution section, 5% to 15% hydrochloric acid or sulfuric acid is added to completely dissolve the retained solids. The dissolved catalyst is then pumped into the wet catalytic oxidation device by a booster pump. The reaction section and dissolution section times are both 15 to 30 minutes.

[0031] In some embodiments, in S3, sodium sulfate is added as a solid, and the stirrer is turned on during addition, with a stirring speed of 50~200 rpm and a reaction time of 20~30 min.

[0032] In some embodiments, in S3, the solid-liquid separation after gypsum formation is performed using a centrifugal dehydrator with a filtration accuracy of 5μm~20μm, a rotation speed of 1500~3000 rpm, and a sludge cake moisture content of 15%~50%.

[0033] In some embodiments, in S4, the dual alkalis are sodium hydroxide and sodium carbonate, with the concentration of sodium hydroxide being 5% to 15% and the concentration of sodium carbonate being 5% to 20%.

[0034] In some embodiments, in S4, after the calcium carbonate precipitate is generated, it is concentrated using an ultrafiltration membrane with a pore size of 20~50nm and an operating pressure of 0.1~0.5MPa, and the concentrated SS reaches 150~400g / L.

[0035] In some embodiments, in S4, the calcium carbonate solid filtered by the ultrafiltration membrane is dehydrated by plate and frame pressure, with a feed pressure of 0.6~1.2MPa, a pressing pressure of 1.5~2.5MPa, a filter cloth mesh of 80~150 mesh, and a sludge cake moisture content of 15%~50%. The filtrate enters the electrolytic oxidation unit, and the sludge cake is used for in-furnace desulfurization.

[0036] In some implementations, in S5, deep oxidation may be performed by electrolytic oxidation or chemical oxidation.

[0037] In some embodiments, in S5, during electrolytic oxidation, the oxidation current density is 1~10 A / dm³. 2 The material is made of diamond-doped boron or titanium-coated graphene, and the hydraulic residence time is 10~60min.

[0038] In some embodiments, in S5, during chemical oxidation, the oxidant can be one of hydrogen peroxide, sodium hypochlorite, or ozone. The hydraulic residence time for hydrogen peroxide oxidation is 1-4 hours; the hydraulic residence time for sodium hypochlorite oxidation is 10-120 minutes; and the hydraulic residence time for ozone oxidation is 10-60 minutes.

[0039] In some embodiments, in S6, the filtration uses a multi-media filter 2 with a filtration accuracy of 5-10 μm and an operating pressure of 0.1-0.5 MPa.

[0040] In some embodiments, in S6, the nanofiltration is a two-stage process, where the concentrate from the first-stage nanofiltration is used as the feed water for the second-stage nanofiltration for further concentration.

[0041] In some embodiments, in step S6, the membrane flux of the nanofiltration membrane is 15~18 L / (m²). 2 (·h), the area of ​​a single membrane is 34.5m². 2 The maximum operating pressure is 4.0 MPa, and the maximum operating temperature is ≤45℃.

[0042] In some embodiments, in S7, the flow rate for targeted adsorption is 0.2~1 BV / H, and the adsorption temperature is 20~35°C.

[0043] In some embodiments, in S7-1, if the targeted adsorption effluent is partially introduced into the salt mixing tank and partially introduced into the evaporation crystallization tank, the ratio of the effluent entering the salt mixing tank is 25% to 85%. When the solid content of the evaporation crystallization is 3% to 8%, the effluent entering the salt mixing tank is mixed with the directly introduced targeted adsorption effluent to form a brine with a sodium chloride concentration of 305±5 g / L.

[0044] Compared with the prior art, the technical effects of this application are as follows:

[0045] The pretreatment-wet catalytic oxidation-salt conversion-softening filtration-deep oxidation-nanofiltration purification-targeted adsorption technology in this application not only produces no residual mother liquor and no secondary pollution, but also ensures that the effluent organic matter meets the standards and has strong resistance to fluctuations in water quality and quantity. It combines heterogeneous and homogeneous catalysts for catalysis and recycles the homogeneous catalyst. In addition, most of the salt is also recycled, which not only fully realizes the reuse of resources, but also reduces the treatment cost. The treated sodium chloride solution can be used as the primary brine for subsequent ion membrane electrolysis.

[0046] (1) This application can recover calcium ions from high-chloride and high-organic wastewater to produce high-purity gypsum, and recover chloride ions as primary brine for ion-exchange membrane caustic soda device. This not only solves the problem of high-salt wastewater treatment, but also creates economic value, saves treatment costs, and achieves the goals of clean production and energy conservation and emission reduction.

[0047] (2) This application combines the advantages of heterogeneous catalysts and homogeneous catalysts. It leverages the directionality and selectivity of heterogeneous catalysts based on organic components, especially for recalcitrant organic compounds, exhibiting high catalytic activity. It also utilizes the advantages of homogeneous catalysts, such as a large contact area, which significantly reduces the activation energy and accelerates the chemical reaction rate. Furthermore, it avoids the drawback of homogeneous catalysts being difficult to reuse. This application can recover homogeneous catalysts introduced during the treatment of wastewater with high calcium chloride and high organic matter content. The recovered catalysts not only have high purity but can also be continuously used as catalysts in the wet catalytic oxidation stage of water treatment processes, achieving the goal of resource recycling.

[0048] (3) The method provided in this application can effectively treat wastewater with high organic matter content. The wastewater is first subjected to wet catalytic oxidation to remove most of the organic matter and decompose the large organic molecules into small organic molecules. Secondly, through deep oxidation, the organic matter is further oxidized, decomposed and removed. Thirdly, through nanofiltration technology, organic matter with a particle size greater than 10 nm is intercepted and separated. Finally, through targeted adsorption technology, the concentration of organic matter in the effluent can be guaranteed to meet the requirements of the primary brine of the ion membrane caustic soda unit.

[0049] (4) This application improves the environmental protection level of wastewater treatment, realizes the closed-loop circulation of resources and energy in the process of wastewater treatment, and makes the resource integration and utilization more optimized, the product structure more reasonable, the environment more friendly, and the benefits more obvious. Attached Figure Description

[0050] The various technical features of this application and their relationships will be further explained below with reference to the accompanying drawings. The drawings are exemplary; some technical features are not shown to scale, and some drawings may omit technical features commonly used in the art to which this application pertains that are not essential for understanding and implementing this application, or additionally show technical features that are not essential for understanding and implementing this application. In other words, the combination of various technical features shown in the drawings is not intended to limit this application. Furthermore, throughout this application, the same reference numerals refer to the same things. Specific descriptions of the drawings are as follows:

[0051] Figure 1 This is a process flow diagram of the resource utilization method of calcium chloride high-salt water containing high concentrations of organic matter in this application. Detailed Implementation

[0052] To enable those skilled in the art to better understand the technical solutions of this application, the technical solutions described in this application will be further described in detail below with reference to specific embodiments.

[0053] This application provides a method for the resource utilization of high-salt calcium chloride containing high concentrations of organic matter, such as... Figure 1 As shown, the main processes or procedures include "pretreatment - wet catalytic oxidation - salt conversion - softening filtration - deep oxidation - nanofiltration purification - targeted adsorption", and a catalyst recovery unit is provided.

[0054] Wastewater with high calcium chloride and high organic matter content has a calcium chloride content of 5% to 20% and a TOC content of 2000 to 20000 mg / L.

[0055] (1) Preprocessing unit

[0056] Wastewater first enters the equalization tank, then is filtered to remove large particulate suspended solids and a small amount of macromolecular organic matter, before entering the wet catalytic oxidation unit.

[0057] Suspended solids (SS) refer to solid matter suspended in water, including organic and inorganic particulate matter, such as inorganic and organic matter that are poorly soluble in water, as well as silt, clay, and microorganisms. The content of suspended solids in water is one of the indicators for measuring the degree of water pollution.

[0058] Wastewater with high calcium chloride and high organic matter content first enters the equalization tank. After the water volume is adjusted and the water quality is balanced in the equalization tank, it then enters the multi-media filter 1.

[0059] The equalization tank is made of reinforced concrete or corrosion-resistant assembled tank, with aeration and stirring or mechanical stirring, and a hydraulic retention time of 4~6 hours. It is rectangular or cylindrical in shape.

[0060] The multi-media filter 1 has a filtration accuracy of 10~20μm. Normal operating flow rate is generally controlled at 8~20m / h, backwash flow rate at 30~50m / h, backwash intensity at 8.0L / (m²·s), and backwash time at 5-10min. The backwash expansion rate is 40%. Operating pressure is typically between 0.1MPa and 0.5MPa. Filter media can be one or more of the following: quartz sand, anthracite, and activated carbon. The material used is SUS304 or SS316L.

[0061] (2) Wet catalytic oxidation unit

[0062] Using air or oxygen as the oxidant and heterogeneous noble metal oxides and homogeneous transition metals as catalysts, wastewater undergoes a wet catalytic oxidation reaction under high temperature and pressure to remove organic matter. The wastewater then enters a salt-type conversion unit. The wet catalytic oxidation process includes a catalyst recovery unit, which recovers and reuses the catalyst through processes such as reaction, precipitation, filtration, and dissolution.

[0063] Wet oxidation / catalytic wet oxidation (WO / CWO) technology is an advanced wastewater treatment technology. This process involves oxidizing and decomposing pollutants such as organic matter, TOC, and ammonia nitrogen in high-concentration wastewater under specific temperature and pressure conditions in a reactor (without or without a catalyst). The oxidation process utilizes oxygen (air) to convert these pollutants into harmless components such as CO2, N2, and water, while simultaneously deodorizing, decolorizing, and sterilizing, thus achieving wastewater purification. This new technology does not produce sludge and can also recover heat energy.

[0064] In this application, the wet catalytic oxidation reaction temperature is 200℃~300℃, the reaction pressure is 3~10MPa, and air or oxygen is used as the oxidant. This application selects heterogeneous noble metal oxides and homogeneous transition metals as catalysts.

[0065] The heterogeneous catalyst is one or more of fluorine-modified ruthenium-based, cerium-based, iron-based, and titanium-based catalysts, with an active component content of 0.1 wt% to 2 wt%. The homogeneous catalyst is one or more of transition metal element compounds such as iron, copper, manganese, and nickel, with an active component content of 0.5 wt% to 5 wt%. The catalytic oxidation time is 2 to 4 hours, with a catalytic residence time of 15 minutes to 1 hour.

[0066] The wet catalytic oxidation device is equipped with a fixed bed filled with φ4~10mm metal oxidant packing material as an enhanced disperser, with a packing density of 1.0~1.5g / mL, to increase the contact area between oxygen and water, and at the same time play a catalytic role.

[0067] After the waste liquid exits the reaction tower, 5%~15% sodium hydroxide solution is added to the reaction section to fully precipitate the active components of the homogeneous catalyst. Solid-liquid separation is achieved through the retention effect of the filter in the filtration section. 5%~15% hydrochloric acid or sulfuric acid is added to the dissolution section to completely dissolve the retained solids. The dissolved catalyst is then pumped into the wet catalytic oxidation unit by a booster pump. The reaction and dissolution times for the catalyst are both 15min~30min.

[0068] (3) Salt-type conversion unit

[0069] Glauber's salt is added to the effluent from wet catalytic oxidation to generate gypsum from calcium ions. The wastewater after the reaction and precipitation is separated into solid and liquid by a centrifugal dewatering machine. The separated gypsum is dried and then sold as a gypsum product.

[0070] Glauber's salt is added as a solid. When adding it, turn on the stirrer and stir at a speed of 50~200 rpm for a reaction time of 20~30 min.

[0071] The centrifugal dewatering machine has a filtration accuracy of 5μm~20μm, a rotation speed of 1500~3000 rpm, and a moisture content of 15%~50% for the sludge cake.

[0072] (4) Softening filter unit

[0073] Sodium hydroxide solution and sodium carbonate solution are added to the supernatant of centrifugation and dehydration to precipitate calcium ions remaining in the solution into calcium carbonate. The precipitate is then concentrated by ultrafiltration. The retained calcium carbonate solid is dehydrated by pressure filtration. The membrane permeate and the filtrate are mixed and then enter the deep oxidation unit.

[0074] The concentration of sodium hydroxide is 5%~15%, and the concentration of sodium carbonate is 5%~20%. When adding, turn on the stirrer and stir at a speed of 100~300 rpm. The reaction time is 30~60 min.

[0075] After calcium carbonate precipitate is generated, it is concentrated using an ultrafiltration membrane. The membrane permeate flux is typically 60~100 L / m²·hr, the membrane pore size is 20~50 nm, the membrane material is PVDF, the operating pressure is 0.1~0.5 MPa, and the SS after concentration reaches 150~400 g / L.

[0076] The calcium carbonate solids filtered by ultrafiltration membrane are dehydrated by plate and frame pressure dewatering. The feed pressure is 0.6~1.2MPa, the pressing pressure is 1.5~2.5MPa, the filter cloth mesh is 80~150 mesh, and the moisture content of the sludge cake is 15%~50%. The filtrate enters the electrolytic oxidation unit, and the sludge cake is used for in-furnace desulfurization.

[0077] (5) Deep oxidation unit

[0078] Electrolytic oxidation or chemical oxidation can be used to purify organic pollutants in wastewater.

[0079] If electrolytic oxidation is selected, the oxidation current density is 1~10 A / dm³. 2 The material is made of diamond-doped boron or titanium-coated graphene, and the hydraulic residence time is 10~60min.

[0080] If chemical oxidation is used, the oxidant can be one of hydrogen peroxide, sodium hypochlorite, or ozone. The hydraulic residence time for hydrogen peroxide oxidation is 1 to 4 hours; the hydraulic residence time for sodium hypochlorite oxidation is 10 to 120 minutes; and the hydraulic residence time for ozone oxidation is 10 to 60 minutes.

[0081] (6) Nanofiltration purification unit

[0082] After filtration removes small molecule suspended solids from the wastewater, it then passes through a nanofiltration unit to remove the remaining divalent ions. The nanofiltration concentrate enters the front end of the salt conversion unit, while the nanofiltration permeate enters the targeted adsorption unit.

[0083] The filtration system employs a multi-media filter 2, with a filtration accuracy of 5–10 μm. Normal operating flow rate is typically controlled at 8–10 m / h, backwash flow rate at 15–30 m / h, backwash intensity at 8.0 L / (m²·s), backwash time at 5–10 min, and backwash expansion rate at 40%. Operating pressure is usually between 0.1 MPa and 0.5 MPa. Filter media selected include one or more of quartz sand, anthracite, and activated carbon. The material chosen is SUS304 or SS316L.

[0084] Nanofiltration achieves a removal rate of >95% for divalent ions; the nanofiltration membrane is designed with a flux of 15~18 L / (m²). 2 (·h), the area of ​​a single membrane is 34.5m². 2 The maximum operating pressure is 4.0 MPa, and the maximum operating temperature is ≤45℃. The first-stage nanofiltration permeability is approximately 80%, and the second-stage nanofiltration permeability is approximately 60%. The second-stage nanofiltration concentrate is mixed with the wet catalytic oxidation effluent, and the mixture of the first-stage and second-stage nanofiltration permeates then enters the targeted adsorption unit.

[0085] (7) Targeted adsorption unit

[0086] Microcrystalline adsorption materials are used to adsorb and remove residual organic matter in nanofiltration permeate, ensuring that the treatment effect meets the requirements of chlor-alkali primary brine influent. The waste liquid from adsorption medium regeneration enters the front-end pretreatment unit for further treatment.

[0087] The treatment of the effluent from the product water tank by targeted adsorption is as follows: S7-1 or S7-2:

[0088] S7-1: All of it enters the salt mixing tank, where sodium chloride is added to form a brine with a sodium chloride concentration of 305±5g / L, which is used as the primary brine for the ion-exchange membrane caustic soda unit.

[0089] S7-2: Part of the solution enters the salt mixing tank, and part undergoes evaporation and crystallization. The condensate from the evaporation and crystallization is reused, and the mother liquor enters the salt mixing tank and mixes with the original unevaporated and uncrystallized targeted adsorption effluent to form a brine with a sodium chloride concentration of 305±5g / L, which serves as the primary brine for the ion-exchange membrane caustic soda unit.

[0090] The targeted adsorption unit is filled with microcrystalline material, which is an artificially hydrothermally synthesized aluminosilicate crystal. Leveraging the large specific surface area and adsorption characteristics of the microcrystalline adsorption material, residual organic matter in the purified brine is adsorbed and removed. The liquid flow rate is 0.2~1 BV / H, and the adsorption temperature is 20~35℃. When the TOC of the adsorbed wastewater is below 8 mg / L, it can directly enter the next treatment unit. When the TOC of the adsorbed wastewater exceeds 8 mg / L, the microcrystalline material needs to be regenerated, and the regenerated solution enters the wet catalytic oxidation unit.

[0091] If all the effluent from the targeted adsorption process enters the brine mixing tank, sodium chloride is added to form a brine with a sodium chloride concentration of 305±5 g / L, which serves as the primary brine for the ion-exchange membrane caustic soda unit. If a portion enters the brine mixing tank and a portion enters the evaporation and crystallization tank, the ratio entering the brine mixing tank is 25%~85%. When the solid content of the evaporated crystals is approximately 5%, the effluent enters the brine mixing tank and mixes with the directly entering targeted adsorption permeate to form a brine with a sodium chloride concentration of 305±5 g / L.

[0092] The present application is further described below with reference to specific embodiments. The advantages and features of the present application will become clear from the description. The embodiments described are merely exemplary and do not constitute any limitation on the scope of the present application. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present application without departing from the spirit and scope of the present application, but such modifications and substitutions all fall within the protection scope of the present application.

[0093] Implementation Case 1:

[0094] The wastewater, which is high in calcium chloride and organic matter, comes from the titanium dioxide production wastewater of a heavy industry enterprise. The volume is 900,000 tons / year. The pH is measured to be 6-9, the TOC is about 3750 mg / L, the main organic components are monochloropropanol, dichloropropanol and glycerol, etc., and the calcium chloride content is 15%-17%. The water quality is shown in the table below.

[0095]

[0096] Pretreatment: Wastewater with high calcium chloride and high organic matter first enters the equalization tank. After the water volume is adjusted and the water quality is balanced in the equalization tank, it passes through the multi-media filter 1. The working pressure is usually between 0.1MPa and 0.3MPa, and the TOC of the effluent is about 3563mg / L.

[0097] Wet catalytic oxidation: The temperature of wet catalytic oxidation is 270℃, the pressure is 8MPa, the heterogeneous catalyst is a fluorine-modified ruthenium-based catalyst with an active component content of about 1wt%, the homogeneous catalyst is copper chloride with a concentration of 10000mg / L, air is continuously introduced, catalytic oxidation is carried out for 2 hours, and the TOC of the effluent is about 534mg / L.

[0098] Salt conversion: 31.9 t / h of Glauber's salt is added to the reaction tank. Glauber's salt reacts with calcium chloride to produce calcium sulfate dihydrate, i.e. gypsum, with a water content of 50% and a yield of about 23 t / h, which is sold as a product.

[0099] Softening filtration: Residual calcium ions are converted into calcium carbonate by adding a 10% sodium carbonate solution, and then separated using an ultrafiltration membrane. The separated calcium carbonate is dehydrated to produce calcium carbonate sludge, which is used for in-furnace desulfurization. The dehydrated calcium carbonate sludge has a moisture content of about 50% and a content of about 0.28 t / h.

[0100] Deep oxidation: Deep oxidation is performed using electrolytic oxidation, with a current density of 5 A / dm³. 2 The material used is boron-doped diamond, and the hydraulic retention time of the electrolytic oxidation device is 10-20 minutes. After electrolytic oxidation, the TOC of the effluent is approximately 254 mg / L.

[0101] Nanofiltration purification: Before entering the nanofiltration membrane, the effluent from electrolysis and oxidation first passes through a multi-media filter 2 to remove small molecule suspended solids. The filtration accuracy of the multi-media filter 2 is 5μm, and the normal operating flow rate is controlled at 10m / h. The operating pressure is usually below 0.5MPa.

[0102] The effluent from the multi-media filter 2 enters the nanofiltration membrane. The nanofiltration process is two-stage: the concentrate from the first-stage nanofiltration is used as the feed water for the second-stage nanofiltration for further concentration. The permeate yield of the first-stage nanofiltration is approximately 80%, and that of the second-stage nanofiltration is approximately 60%. The permeate from the first and second stages is mixed. After nanofiltration purification, the TOC of the nanofiltration permeate is approximately 25 mg / L, and the sodium chloride concentration is approximately 14%.

[0103] Targeted adsorption: The adsorbed water has a TOC of less than 8 mg / L, a calcium ion concentration of less than 0.01 mmol / L, and a sodium chloride concentration of approximately 14%.

[0104] MVR: 80.9% of the targeted adsorption effluent enters the MVR evaporator, and 19.1% of the targeted adsorption effluent directly enters the sodium chloride brine tank. The brine entering the MVR evaporator is evaporated and crystallized until the solid mass percentage is approximately 5%, and then discharged directly into the sodium chloride brine tank through the salt leg of the MVR crystallizer. Because the sodium chloride concentration is within the range of 305±5 g / L, calcium and magnesium ions are below 10 mg / L, TOC is below 8 mg / L, and the purity is above 98%, it can be used as primary brine for ion-exchange membrane caustic soda treatment.

[0105] The above production process produces no residual concentrate, achieving complete resource recovery of wastewater high in calcium chloride and organic matter. If a homogeneous catalyst is used alone, the removal rate of organic matter through wet catalytic oxidation is 60%–80%. If a heterogeneous and homogeneous catalyst are used simultaneously, the removal rate can reach 80%–95%. Furthermore, the cost of adding chemicals to copper chloride via wet catalytic oxidation is approximately 423 yuan per ton of water; the catalyst recovery unit avoids this ongoing expense. The total cost of adding chemicals to this project is approximately 97.8 yuan per ton of water, while the revenue generated from gypsum products, brine recovery, and reclaimed water is approximately 104.8 yuan per ton of water, exceeding the cost of adding chemicals. The remaining direct operating cost is no more than 30 yuan per ton, significantly reducing operating expenses.

[0106] Implementation Case 2:

[0107] A wastewater with high calcium chloride and high organic matter content, originating from a pharmaceutical process, has a flow rate of 20 t / h, a measured pH of 6-9, a TOC of approximately 4500 mg / L, and a calcium chloride content of 20%. The treatment process is as follows.

[0108] Pretreatment: Wastewater with high calcium chloride and high organic matter first enters the equalization tank. After the water volume is adjusted and the water quality is balanced in the equalization tank, it passes through the multi-media filter 1. The working pressure is usually between 0.1MPa and 0.3MPa, and the TOC of the effluent is about 4270mg / L.

[0109] Wet catalytic oxidation: The temperature of wet catalytic oxidation is 280℃, the pressure is 8MPa, the heterogeneous catalyst is a fluorine-modified ruthenium-based catalyst with an active component content of about 1.5wt%, the homogeneous catalyst is copper chloride with a concentration of 10000mg / L, air is continuously introduced, catalytic oxidation is carried out for 2 hours, and the organic matter in the effluent is about 641mg / L.

[0110] Salt conversion: Add 6.7 t / h of Glauber's salt to the reaction tank. Glauber's salt reacts with calcium chloride to produce calcium sulfate dihydrate, i.e., gypsum, with a water content of 50% and a yield of about 4.8 t / h, which is sold as a product.

[0111] Softening filtration: Residual calcium ions are converted into calcium carbonate by adding a 10% sodium carbonate solution, and then separated using an ultrafiltration membrane. The separated calcium carbonate is dehydrated to produce calcium carbonate sludge, which is used for in-furnace desulfurization. The dehydrated calcium carbonate sludge has a moisture content of about 50% and a content of about 0.06 t / h.

[0112] Deep oxidation: Deep oxidation is performed using electrolytic oxidation, with a current density of 6 A / dm³. 2 The material used is boron-doped diamond, and the hydraulic retention time of the electrolytic oxidation device is 15-30 minutes. After electrolytic oxidation, the TOC of the effluent is approximately 295 mg / L.

[0113] Nanofiltration purification: Before entering the nanofiltration membrane, the effluent from electrolysis and oxidation first passes through a multi-media filter 2 to remove small molecule suspended solids. The filtration accuracy of the multi-media filter 2 is 5μm, and the normal operating flow rate is controlled at 10m / h. The operating pressure is usually below 0.5MPa.

[0114] The effluent from the multi-media filter 2 enters the nanofiltration membrane. The nanofiltration process is two-stage: the concentrate from the first-stage nanofiltration is used as the feed water for the second-stage nanofiltration for further concentration. The permeate yield of the first-stage nanofiltration is approximately 80%, and that of the second-stage nanofiltration is approximately 60%. The permeate from the first and second stages is mixed. After nanofiltration purification, the TOC of the nanofiltration permeate is approximately 30 mg / L, and the sodium chloride concentration is approximately 17%.

[0115] Targeted adsorption: The adsorbed water has a TOC of less than 8 mg / L, a calcium ion concentration of less than 0.01 mmol / L, and a sodium chloride concentration of approximately 17%.

[0116] MVR: 15% of the targeted adsorption effluent enters the MVR evaporator, and 85% of the targeted adsorption effluent directly enters the sodium chloride brine tank. The brine entering the MVR evaporator is evaporated and crystallized until the solid mass percentage is approximately 5%, and then discharged directly into the sodium chloride brine tank through the salt leg of the MVR crystallizer. Because the sodium chloride concentration is within the range of 305±5 g / L, calcium and magnesium ions are below 10 mg / L, TOC is below 8 mg / L, and the purity is above 97%, it can be used as primary brine for ion-exchange membrane caustic soda treatment.

[0117] The above production process produces no residual concentrate, achieving complete resource recovery of wastewater high in calcium chloride and organic matter. If a homogeneous catalyst is used alone, the removal rate of organic matter through wet catalytic oxidation is 60%–85%. If a heterogeneous and homogeneous catalyst are used simultaneously, the removal rate can reach 85%–95%. Furthermore, the cost of adding chemicals to copper chloride via wet catalytic oxidation is approximately 420 yuan per ton of water; the catalyst recovery unit avoids this ongoing expense. The cost of adding chemicals to ton of water in this project is approximately 104.8 yuan, while the revenue from gypsum products, brine recovery, and reclaimed water is approximately 116.7 yuan per ton, exceeding the cost of adding chemicals. The remaining direct operating cost is no more than 30 yuan per ton, significantly reducing operating expenses.

[0118] Unless otherwise defined, all technical and scientific terms used throughout this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any inconsistency, the meaning as stated in this application or derived from the content described herein shall prevail. Furthermore, the terminology used in this description is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0119] Note that the above are merely preferred embodiments and the technical principles employed in this application. Those skilled in the art will understand that this application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the technical concept of this application, all of which fall within the scope of protection of this application.

Claims

1. A method for the resource utilization of high-concentration calcium chloride saline solution containing high organic matter, characterized in that, The method includes the following steps: S1 Pretreatment: Wastewater first enters the equalization tank and then is filtered to remove large particulate suspended solids and a small amount of macromolecular organic matter before entering the wet catalytic oxidation unit; S2 wet catalytic oxidation: using air or oxygen as the oxidant and heterogeneous and homogeneous catalysts as catalysts, wastewater is subjected to wet catalytic oxidation reaction under high temperature and pressure to remove organic matter from the wastewater and recycle the homogeneous catalyst to avoid catalyst loss. The heterogeneous catalyst is one or more of fluorine-modified ruthenium-based, cerium-based, iron-based, and titanium-based catalysts, and the content of the active component of the catalyst is 0.1 wt%~2 wt%. The homogeneous catalyst is one or more compounds of transition metal elements, and the content of the active component of the catalyst is 0.5 wt%~5 wt%. S3 salt conversion: Glauber's salt is added to the wet catalytic oxidation effluent to react with calcium ions in the wastewater to generate gypsum, which is then separated by a sludge dewatering machine; S4 softening filtration: The dual alkali method is used to generate calcium carbonate precipitate from the residual calcium ions in the supernatant of the salt conversion sludge dewatering machine. Then, the precipitate is concentrated by ultrafiltration and separated by pressure filtration. The filtrate enters the deep oxidation unit. S5 deep oxidation: By generating free radicals ·OH with strong oxidizing power, under the reaction conditions of electricity or oxidants, it oxidizes large molecules of difficult-to-degrade organic matter into low-toxicity or non-toxic small molecules, thereby purifying organic pollutants in wastewater. S6 nanofiltration purification: First, small molecule suspended solids in the wastewater are removed by filtration, and then the remaining divalent ions are removed by the nanofiltration treatment unit. The nanofiltration concentrate enters the front end of the salt conversion unit, and the nanofiltration permeate enters the targeted adsorption unit. S7 Targeted Adsorption: Microcrystalline adsorption materials are used to adsorb and remove residual organic matter in nanofiltration permeate. The targeted adsorption effluent enters the permeate tank, and the waste liquid from the regeneration of the adsorption medium enters the front-end pretreatment unit for further treatment. The treatment of the effluent from the product water tank by targeted adsorption is as follows: S7-1 or S7-2: S7-1: All of it enters the salt mixing tank, and sodium chloride is added to form brine with a sodium chloride concentration of 305±5g / L, which is used as the primary brine for the ion-exchange membrane caustic soda unit. S7-2: Part of the solution enters the salt mixing tank, and part undergoes evaporation and crystallization. The condensate from the evaporation and crystallization is reused, and the mother liquor enters the salt mixing tank and mixes with the original unevaporated and uncrystallized targeted adsorption effluent to form a brine with a sodium chloride concentration of 305±5g / L, which serves as the primary brine for the ion-exchange membrane caustic soda unit.

2. The method according to claim 1, characterized in that, In S1, the filtration uses a multi-media filter 1 with a filtration accuracy of 10-20 μm and a working pressure of 0.1-0.5 MPa.

3. The method according to claim 1, characterized in that, In S2, the temperature of the high temperature and high pressure is 200℃~300℃, and the pressure is 3~10Mpa; The catalytic oxidation time is 2-4 hours, of which the residence time in the catalytic zone is 15 minutes to 1 hour. The wet catalytic oxidation unit is equipped with a fixed bed filled with φ4~10mm metal oxidant packing as an enhanced disperser, with a packing density of 1.0~1.5g / mL; After the waste liquid exits the reaction tower, 5%~15% sodium hydroxide solution is added to the reaction section to fully precipitate the active components of the homogeneous catalyst. Solid-liquid separation is achieved through the retention effect of the filter in the filtration section. 5%~15% hydrochloric acid or sulfuric acid is added to the dissolution section to completely dissolve the retained solids. The dissolved catalyst is then pumped into the wet catalytic oxidation unit by a booster pump. The reaction and dissolution times for the catalyst are both 15min~30min.

4. The method according to claim 1, characterized in that, In S3, sodium sulfate is added as a solid. When adding it, the stirrer is turned on and the stirring speed is 50~200 rpm. The reaction time is 20~30 min. The solid-liquid separation after gypsum production is carried out using a centrifugal dewatering machine with a filtration accuracy of 5μm~20μm and a rotation speed of 1500~3000rpm. The water content of the sludge cake is 15%~50%.

5. The method according to claim 1, characterized in that, In S4, the two alkalis are sodium hydroxide and sodium carbonate, with the concentration of sodium hydroxide being 5%~15% and the concentration of sodium carbonate being 5%~20%. After calcium carbonate precipitate is formed, it is concentrated by ultrafiltration membrane with a pore size of 20~50nm and an operating pressure of 0.1~0.5MPa. The SS after concentration reaches 150~400g / L. The calcium carbonate solids filtered by ultrafiltration membrane are dehydrated by plate and frame pressure dewatering. The feed pressure is 0.6~1.2MPa, the pressing pressure is 1.5~2.5MPa, the filter cloth mesh is 80~150 mesh, and the moisture content of the sludge cake is 15%~50%. The filtrate enters the electrolytic oxidation unit, and the sludge cake is used for in-furnace desulfurization.

6. The method according to claim 1, characterized in that, In S5, deep oxidation is achieved through electrolytic oxidation or chemical oxidation; In electrolytic oxidation, the oxidation current density is 1~10 A / dm³. 2 The material is made of diamond boron-doped or titanium substrate coated with graphene, and the hydraulic residence time is 10~60min. In chemical oxidation, the oxidant is one of hydrogen peroxide, sodium hypochlorite, or ozone. The hydraulic residence time for hydrogen peroxide oxidation is 1-4 hours; the hydraulic residence time for sodium hypochlorite oxidation is 10-120 minutes; and the hydraulic residence time for ozone oxidation is 10-60 minutes.

7. The method according to claim 1, characterized in that, In S6, the filtration uses a multi-media filter 2 with a filtration accuracy of 5-10 μm and a working pressure of 0.1-0.5 MPa.

8. The method according to claim 1, characterized in that, In S6, the nanofiltration adopts a two-stage process, with the concentrate from the first-stage nanofiltration serving as the feed water for the second-stage nanofiltration for further concentration. The membrane flux of nanofiltration membranes is 15~18 L / (m²). 2 (·h), the area of ​​a single membrane is 34.5m². 2 The maximum operating pressure is 4.0 MPa, and the maximum operating temperature is ≤45℃.

9. The method according to claim 1, characterized in that, In S7, the flow rate for targeted adsorption is 0.2~1 BV / H, and the adsorption temperature is 20~35℃.

10. The method according to claim 1, characterized in that, In S7-1, 25% to 85% of the targeted adsorption effluent enters the brine mixing tank. When the solid content of the evaporated crystals is 3% to 8%, the effluent enters the brine mixing tank and mixes with the directly entering targeted adsorption effluent to form a brine with a sodium chloride concentration of 305±5 g / L.

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