Resource utilization method of calcium chloride high-salt water containing high-concentration organic matters

Abstract

The invention relates to the technical field of industrial production wastewater treatment, and particularly provides a resource utilization method of calcium chloride high-salt water containing high-concentration organic matters. The method comprises the steps of pretreatment, wet catalytic oxidation, salt type conversion, softening filtration, deep oxidation, nanofiltration purification and targeted adsorption, no residual mother liquor exists, no secondary pollution is generated, organic matters in effluent are stable and reach the standard, the water quality and water quantity fluctuation resistance is high, heterogeneous and homogeneous catalysts are combined for catalysis, and the purification effect is good. According to the method, the sodium chloride solution is used as a raw material, the homogeneous catalyst is recycled, in addition, most of salt in the homogeneous catalyst is also recycled, resource reutilization is fully achieved, the treatment cost is reduced, and the treated sodium chloride solution can be used as primary saline water for subsequent ion membrane electrolysis.

Description

Technical Field

[0001] This application relates to the technical field of industrial production wastewater treatment, and specifically provides a method for resource utilization of high-calcium chloride brine containing high concentrations of organic matter. Background Art

[0002] In the chemical fiber industry, calcium chloride may be used as an auxiliary coagulant; in the production processes of epoxy resin and epichlorohydrin, calcium chloride may be produced as a by-product; in the aramid industry, calcium chloride may be used in the synthesis of para-aramid; in the pharmaceutical production process, calcium chloride may be used as an auxiliary agent; in the printing and dyeing 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, in industries such as chemical fiber, epoxy resin, epichlorohydrin, aramid, pharmaceuticals, printing and dyeing, and papermaking, high-concentration calcium chloride wastewater is generated, and such wastewater often contains high concentrations of organic matter.

[0003] High-calcium chloride and high-organic matter wastewater has the characteristics of high salinity, strong corrosiveness, easy scaling, and difficult biodegradation due to its high calcium chloride content, making the treatment of such wastewater very difficult and requiring specific treatment technologies to effectively remove calcium chloride and reduce its impact on the environment.

[0004] In view of the characteristics of high-calcium chloride and high-organic matter wastewater, the following treatment process is usually adopted: (1) Pretreatment, removing large particle suspended solids in the wastewater and adjusting the water quality and quantity through methods such as regulating ponds, reaction precipitation, and filtration; (2) Advanced oxidation, using methods such as Fenton oxidation, electrolytic oxidation, and wet catalytic oxidation to remove most of the organic matter in the wastewater; (3) Evaporation process, using evaporation technologies such as low-temperature evaporation and MVR to concentrate or even crystallize and separate the calcium chloride solute; (4) Advanced treatment, for wastewater with higher effluent requirements, advanced treatment such as sand filtration, activated carbon adsorption, and reverse osmosis is also required to remove residual pollutants and purify the water quality.

[0005] Due to the water quality characteristics of high-calcium chloride and high-organic matter wastewater, using traditional treatment methods may cause problems such as the generation of residual concentrated liquid and excessive organic matter, posing potential safety hazards.

[0006] In the existing technical solutions, the invention patent CN108658353A discloses a calcium chloride wastewater treatment process. First, a triple-effect multi-stage evaporator is used to treat 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 is subjected to solid-liquid separation to obtain calcium chloride dihydrate solids and mother liquor. Then, part of the mother liquor is transferred to an impurity removal 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 cyclic treatment. Treatment methods such as triple-effect, flash evaporation, and impurity removal are used to realize the recycling of calcium chloride. This treatment method will have remaining mother liquor. If not treated in time, it will bring great hidden dangers. In addition, this method is not applicable to the treatment of calcium chloride wastewater with high organic matter content.

[0007] The invention patent CN102295392A discloses a water treatment and reuse method for calcium chloride wastewater. By using process designs such as optimized pretreatment, biochemical treatment, reverse osmosis recycled water, electrodialysis concentration, and evaporation recovery, it basically achieves zero wastewater discharge, and salt and water can be recovered. However, this treatment method will have remaining mother liquor, and the concentration of calcium chloride is generally lower than 5%, otherwise it is difficult to guarantee the biochemical effluent.

[0008] Therefore, for high-calcium chloride and high-organic matter wastewater, how to effectively remove organic pollutants while recovering calcium chloride resources therein, and not produce difficult-to-treat secondary pollution, is of great significance for the treatment of high-calcium chloride and high-organic matter wastewater. At the same time, it is also of great significance for the development of industries such as titanium dioxide production, chemical fiber, epoxy resin, epichlorohydrin, aramid, pharmaceutical, printing and dyeing, and papermaking.

[0009] In view of this, the present application is specifically proposed. Summary of the Invention

[0010] One of the purposes of the present application is to provide a resource utilization method for high-salt calcium chloride water containing high-concentration organic matter, which solves the disadvantages of the existing process having remaining mother liquor after treatment, the organic matter in the effluent being difficult to meet the standards, and most of the existing technologies can only treat low-calcium chloride and low-organic matter wastewater.

[0011] In order to achieve the above purpose, the present application adopts the following technical solutions:

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

[0013] S1 Pretreatment: The wastewater first enters the adjustment tank and then passes through a filter to remove large particle suspended solids and a small amount of macromolecular organic matter, and then enters the wet catalytic oxidation unit;

[0014] S2 Wet Catalytic Oxidation: Using heterogeneous noble metal oxides and homogeneous transition metals as catalysts, the wastewater is subjected to wet catalytic oxidation reaction under high temperature and high pressure to remove the organic matter in the wastewater, and the homogeneous catalyst is recycled to avoid the loss of the catalyst;

[0015] S3 Salt-Type Conversion: Add mirabilite to the effluent of wet catalytic oxidation to generate gypsum with calcium ions in the wastewater, and separate the gypsum through a sludge dewatering machine;

[0016] S4 Softening Filtration: Adopt the double-alkali method to generate calcium carbonate precipitation for the residual calcium ions in the supernatant of the salt-type conversion sludge dewatering machine. First, concentrate by ultrafiltration, and then separate the calcium carbonate precipitation through pressure filtration. The filtrate enters the advanced oxidation unit;

[0017] S5 Advanced Oxidation: By generating free radicals (· ) with strong oxidation ability, under the reaction conditions of electricity or oxidant, oxidize the refractory organic matter into low-toxic or non-toxic substances to achieve the effect of purifying the organic pollutants in the wastewater; substances to achieve the effect of purifying the organic pollutants in the wastewater;

[0018] S6 Nanofiltration Purification: First, filter to remove small molecule suspended solids in the wastewater, and then pass through the nanofiltration treatment unit to remove the remaining divalent ions. The nanofiltration concentrate enters the front end of the salt-type conversion unit, and the nanofiltration permeate enters the targeted adsorption unit;

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

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

[0021] S7-1: All enter the salt mixing tank, and by adding sodium chloride, a brine with a sodium chloride concentration of 305 ± 5 g / L is formed as the primary brine for the ion-exchange membrane caustic soda plant;

[0022] S7-2: Part enters the salt mixing tank, and part is subjected to evaporation crystallization. The evaporation crystallization condensate is recycled, and the mother liquor enters the salt mixing tank and is mixed with the original targeted adsorption effluent that has not been evaporated and crystallized to form a brine with a sodium chloride concentration of 305 ± 5 g / L as the primary brine for the ion-exchange membrane caustic soda plant.

[0023] In some embodiments, 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.

[0024] In some embodiments, in S2, the temperature of the high temperature and high pressure is 200°C to 300°C, 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 catalyst active component is 0.1 wt% - 2 wt%.

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

[0028] In some embodiments, in S2, the catalytic oxidation time is 2 - 4 h, and the residence time in the catalytic section is 15 min - 1 h.

[0029] In some embodiments, in S2, a fixed bed is provided inside the wet catalytic oxidation device, and metal oxidant fillers with a diameter of φ4 - 10 mm are filled as enhanced dispersers, and the filling density is 1.0 - 1.5 g / mL.

[0030] In some embodiments, in S2, after the waste liquid exits the reaction tower, 5% - 15% sodium hydroxide solution is added in the reaction section to fully form a precipitate of the homogeneous catalyst active component. Solid-liquid separation is achieved through the interception of the filter in the filtration section. 5% - 15% hydrochloric acid or sulfuric acid is added in the dissolution section to completely dissolve the intercepted solid. The dissolved catalyst is pumped into the wet catalytic oxidation device by a lift pump, and the time for both the catalyst reaction section and the dissolution section is 15 min - 30 min.

[0031] In some embodiments, in S3, sodium sulfate is added in solid form. When adding, the stirrer is turned on, the stirring speed is 50 - 200 rpm, and the reaction time is 20 - 30 min.

[0032] In some embodiments, in S3, the solid-liquid separation after gypsum formation is carried out using a centrifuge. The filtration accuracy of the centrifuge is 5 μm - 20 μm, the rotation speed is 1500 - 3000 rmp, and the moisture content of the filter cake is 15% - 50%.

[0033] In some embodiments, in S4, the double alkali is sodium hydroxide and sodium carbonate. The dosing concentration of sodium hydroxide is 5% - 15%, and the dosing concentration of sodium carbonate is 5% - 20%.

[0034] In some embodiments, in S4, after calcium carbonate precipitation, ultrafiltration membrane concentration is used. The membrane pore size is 20 - 50 nm, the operating pressure is 0.1 - 0.5 MPa, and the SS after concentration reaches 150 - 400 g / L.

[0035] In some embodiments, in S4, the calcium carbonate solid after ultrafiltration membrane filtration is dewatered by plate and frame pressure. The feeding pressure is 0.6 - 1.2 MPa, the pressing pressure is 1.5 - 2.5 MPa, the mesh number of the filter cloth is 80 - 150 meshes, the water content of the filter cake is 15% - 50%, the filtrate enters the electrolytic oxidation unit, and the filter cake is used for in-furnace desulfurization.

[0036] In some embodiments, in S5, for deep oxidation, electrolytic oxidation or chemical oxidation can be used.

[0037] In some embodiments, in S5, in electrolytic oxidation, the oxidation current density is 1 - 10 A / dm 2 , the material is selected as boron-doped diamond or titanium substrate coated with graphene, and the hydraulic retention time is 10 - 60 min.

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

[0039] In some embodiments, in S6, the filtration is carried out using a multi-media filter 2, the filtration accuracy is 5 - 10 μm, and the working pressure is 0.1 - 0.5 MPa.

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

[0041] In some embodiments, in S6, the membrane flux of the nanofiltration membrane is 15 - 18 L / (m 2 ·h), the single membrane area is 34.5 m 2 , the highest operating pressure is 4.0 MPa, and the highest operating temperature ≤ 45°C.

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

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

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

[0045] The pre-treatment - wet catalytic oxidation - salt type conversion - softening filtration - advanced oxidation - nanofiltration purification - targeted adsorption technology in this application not only does not produce residual mother liquor and secondary pollution, but also the organic matter in the effluent meets the standards stably, and it has strong resistance to fluctuations in water quality and quantity. It combines heterogeneous and homogeneous catalysts for catalysis and recovers and utilizes the homogeneous catalyst. In addition, most of the salts are also recovered and utilized, 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-exchange membrane electrolysis.

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

[0047] (2) This application combines the advantages of heterogeneous and homogeneous catalysts. It not only gives play to the directionality and selectivity of heterogeneous catalysts based on organic components, especially for refractory organic matter, which has high catalytic activity, but also gives play to the advantages of large contact area of homogeneous catalysts, which can significantly reduce the activation energy of the reaction and accelerate the chemical reaction rate. In addition, it can also avoid the disadvantage that homogeneous catalysts are difficult to reuse. This application can recover the homogeneous catalyst introduced in the treatment process of high-calcium chloride and high-organic matter wastewater. Not only the recovered purity is high, but it can also be continuously used as the catalyst in the wet catalytic oxidation section of the water treatment process, achieving the purpose of resource recycling.

[0048] (3) The method provided by this application can effectively treat high-organic matter wastewater. The wastewater is first subjected to wet catalytic oxidation to remove most of the organic matter and decompose macromolecular organic matter into small-molecular organic matter; secondly, through advanced oxidation, the organic matter is further oxidized and 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, it is ensured that the concentration of organic matter in the effluent can meet the requirements of the primary brine of the ion-exchange membrane caustic soda device.

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

[0050] The various technical features of the present application and the relationships between them will be further described below with reference to the accompanying drawings. The accompanying drawings are exemplary. Some technical features are not shown in actual proportions, and in some of the drawings, technical features that are customary in the technical field to which the present application belongs and are not essential for understanding and implementing the present application may be omitted, or technical features that are not essential for understanding and implementing the present application may be additionally shown. That is, the combination of the various technical features shown in the drawings is not used to limit the present application. Additionally, throughout the present application, the content referred to by the same reference numerals is also the same. The specific description of the drawings is as follows:

[0051] Figure 1 is a process flow diagram of the method for resource utilization of high-calcium chloride brine containing high-concentration organic matter in the present application. Specific Embodiments

[0052] In order to enable those skilled in the art to better understand the technical solution of the present application, the technical solution of the present application will be further described in detail below in conjunction with specific embodiments.

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

[0054] The calcium chloride content in the high-calcium chloride and high-organic matter wastewater is 5% - 20%, and the TOC content is 2000 - 20000 mg / L.

[0055] (1) Pretreatment Unit

[0056] The wastewater first enters the regulation tank and then passes through a filter to remove large particulate suspensions and a small amount of macromolecular organic matter, and then enters the wet catalytic oxidation unit.

[0057] Suspended Solids (SS) refer to solid substances suspended in water, including organic and inorganic particulate matters, such as water-insoluble inorganic substances, organic substances, and sediment, clay, microorganisms, etc. The content of suspended solids in water is one of the indicators for measuring the degree of water pollution.

[0058] The high-calcium chloride and high-organic matter wastewater first enters the regulation tank. After the water volume of the regulation tank is adjusted and the water quality is balanced, it then enters the multi-media filter 1.

[0059] The regulation tank is in the form of a reinforced concrete or anti-corrosion assembled tank, with aeration stirring or mechanical stirring, a hydraulic retention time of 4 - 6 h, and a shape of a cuboid or cylinder.

[0060] The filtration accuracy of the multi-media filter 1 is 10 - 20 μm. The normal operating flow rate is generally controlled at 8 - 20 m / h, the backwash flow rate is 30 - 50 m / h, the backwash intensity is 8.0 L / (m²·s), and the backwash time is 5 - 10 min. The backwash expansion rate is 40%. The working pressure is usually between 0.1 MPa and 0.5 MPa. The filter media can be selected from quartz sand, anthracite, activated carbon, or one or more of them. The material is selected as 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 the catalysts, the wastewater is subjected to wet catalytic oxidation reaction under high temperature and high pressure to remove the organic matter in the wastewater, and then enters the salt form conversion unit. The wet catalytic oxidation is equipped with a catalyst recovery unit, and the catalyst is recycled through processes such as reaction, precipitation, filtration, and dissolution.

[0063] The wet oxidation / catalytic wet oxidation (WO / CWO for short) technology is a deep wastewater treatment technology. Under certain temperature and pressure conditions, in the reactor (without / with catalyst loading), using oxygen (air), the organic matter, TOC, ammonia nitrogen and other pollutants in high-concentration wastewater are oxidized and decomposed (contact time 0.1 - 2.0 h), turning them into harmless components such as CO2, N2 and water, and at the same time deodorizing, decolorizing and sterilizing, so as to achieve the purpose of purification treatment of the wastewater treatment new technology. This process does not produce sludge and can also recover heat energy.

[0064] In this application, the temperature of the wet catalytic oxidation reaction is 200°C - 300°C, the reaction pressure is 3 - 10 MPa, air or oxygen is used as the oxidant, and heterogeneous noble metal oxides and homogeneous transition metals are selected as the catalysts in this application.

[0065] The heterogeneous catalyst is one or more of ruthenium-based, cerium-based, iron-based, and titanium-based modified by fluorine, and the content of the catalyst active component is 0.1 wt% - 2 wt%; the homogeneous catalyst is one or more of transition metal element compounds such as iron, copper, manganese, and nickel, and the content of the catalyst active component is 0.5 wt% - 5 wt%. The catalytic oxidation time is 2 - 4 h, and the residence time in the catalytic section is 15 min - 1 h.

[0066] A fixed bed is arranged in the wet catalytic oxidation device, and metal oxidant fillers with a diameter of φ4 - 10 mm are filled as enhanced dispersers, and the filling density is 1.0 - 1.5 g / mL to increase the contact area between oxygen and water and play a catalytic role at the same time.

[0067] After the waste liquid exits the reaction tower, 5% - 15% sodium hydroxide solution is added in 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 in the dissolution section to completely dissolve the retained solid. The dissolved catalyst is pumped into the wet catalytic oxidation device by a lift pump. The reaction time in both the catalyst reaction section and the dissolution section is 15 min - 30 min.

[0068] (3)Salt form conversion unit

[0069] Sodium sulfate is added to the water discharged from the wet catalytic oxidation to generate gypsum from calcium ions. The wastewater after reaction and precipitation is subjected to solid-liquid separation by a centrifuge. The separated gypsum is sold as a gypsum product after drying in the sun.

[0070] Sodium sulfate is added in solid form. When adding, the stirrer is turned on, and the stirring speed is 50 - 200 rpm. The reaction time is 20 - 30 min.

[0071] The filtration accuracy of the centrifuge is 5 μm - 20 μm, the rotation speed is 1500 - 3000 rmp, and the water content of the filter cake is 15% - 50%.

[0072] (4)Softening and filtration unit

[0073] Sodium hydroxide solution and sodium carbonate solution are added to the supernatant of the centrifugal dehydration to generate calcium carbonate precipitation from the residual calcium ions in the solution. Then, it is first concentrated by ultrafiltration. The retained calcium carbonate solid is dehydrated by pressure filtration. The membrane permeate and the pressure filtrate are mixed and then enter the advanced oxidation unit.

[0074] The dosing concentration of sodium hydroxide is 5% - 15%, and the dosing concentration of sodium carbonate is 5% - 20%. When adding, the stirrer is turned on, and the stirring speed is 100 - 300 rpm. The reaction time is 30 - 60 min.

[0075] After generating calcium carbonate precipitation, ultrafiltration membrane concentration is adopted. The membrane water permeation flux is usually 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 solid filtered by the ultrafiltration membrane is dehydrated by plate and frame pressure. The feeding pressure is 0.6 - 1.2 MPa, the pressing pressure is 1.5 - 2.5 MPa, the mesh number of the filter cloth is 80 - 150 meshes, the water content of the filter cake is 15% - 50%, the filtrate enters the electrolytic oxidation unit, and the filter cake is used for in - furnace desulfurization.

[0077] (5)Advanced oxidation unit

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

[0079] If electrolytic oxidation is selected, the oxidation current density is 1 - 10 A / dm 2 , the material is selected as boron-doped diamond or titanium substrate coated with graphene, and the hydraulic retention time is 10 - 60 min.

[0080] If chemical oxidation is adopted, the oxidant can be one of hydrogen peroxide, sodium hypochlorite or ozone. The hydraulic retention time for hydrogen peroxide oxidation is 1 - 4 h; the hydraulic retention time for sodium hypochlorite oxidation is 10 - 120 min, and the hydraulic retention time for ozone oxidation is 10 - 60 min.

[0081] (6) Nanofiltration purification unit

[0082] After filtering to remove small molecule suspended solids in the wastewater, and then passing through the nanofiltration treatment unit to remove the remaining divalent ions, the nanofiltration concentrated water enters the front end of the salt form conversion unit, and the nanofiltration produced water enters the targeted adsorption unit.

[0083] The filtration is carried out using a multi-media filter 2. The filtration accuracy of the multi-media filter 2 is 5 - 10 μm. The normal operating flow rate is generally controlled at 8 - 10 m / h, the backwash flow rate is 15 - 30 m / h, the backwash intensity is 8.0 L / (m²·s), the backwash time is 5 - 10 min, and the backwash expansion rate is 40%. The working pressure is usually between 0.1 MPa and 0.5 MPa, and the filter media is selected as one or more of quartz sand, anthracite, and activated carbon. The material is selected as SUS304 or SS316L.

[0084] The removal rate of divalent ions by nanofiltration > 95%; the designed membrane flux of the nanofiltration membrane is 15 - 18 L / (m 2 ·h), the single membrane area is 34.5 m 2 , the maximum operating pressure is 4.0 MPa, and the maximum operating temperature ≤ 45 °C. The water production rate of the first-stage nanofiltration is about 80%, and the water production rate of the second-stage nanofiltration is about 60%. The concentrated water of the second-stage nanofiltration is mixed with the effluent of the wet catalytic oxidation. The produced water of the first-stage nanofiltration and the produced water of the second-stage nanofiltration are mixed and then enter the targeted adsorption unit.

[0085] (7) Targeted adsorption unit

[0086] The residual organic matter in the nanofiltration produced water is adsorbed and removed by using a microcrystalline adsorption material to ensure that the treatment effect meets the requirements of the primary brine inlet for chlor-alkali, and the regeneration waste liquid of the adsorption medium enters the front-end pretreatment unit for further treatment.

[0087] The treatment of the targeted adsorption effluent in the production pool is as follows S7-1 or S7-2:

[0088] S7-1: All enter the salt mixing tank. By adding sodium chloride, brine with a sodium chloride concentration of 305 ± 5 g / L is formed, which serves as the primary brine for the ion-exchange membrane caustic soda plant.

[0089] S7-2: Part enter the salt mixing tank and part undergo evaporation crystallization. The condensate water from evaporation crystallization is recycled, and the mother liquor enters the salt mixing tank and is mixed with the targeted adsorption effluent that has not undergone evaporation crystallization originally to form brine with a sodium chloride concentration of 305 ± 5 g / L, which serves as the primary brine for the ion-exchange membrane caustic soda plant.

[0090] The targeted adsorption is filled with microcrystalline materials. The microcrystalline materials are artificially hydrothermally synthesized aluminosilicate crystals. Through the huge specific surface area and adsorption characteristics of the microcrystalline adsorption materials, the organic matters remaining in the purified brine are adsorbed and removed. The liquid flow rate is 0.2 - 1 BV / H, and the adsorption temperature is 20 - 35 °C. 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 materials need to be regenerated, and the regenerant enters the wet catalytic oxidation unit.

[0091] If all of the targeted adsorption effluent enters the salt mixing tank, by adding sodium chloride, brine with a sodium chloride concentration of 305 ± 5 g / L is formed, which serves as the primary brine for the ion-exchange membrane caustic soda plant. If part enters the salt mixing tank and part enters evaporation crystallization, the ratio entering the salt mixing tank is 25% - 85%. When the solid content of evaporation crystallization is about 5%, it enters the salt mixing tank and is mixed with the directly entering targeted adsorption product water to form brine with a sodium chloride concentration of 305 ± 5 g / L.

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

[0093] Embodiment 1:

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

[0095]

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

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

[0098] Salt form conversion: 31.9 t / h of mirabilite is added to the reaction tank. Mirabilite reacts with calcium chloride to form calcium sulfate dihydrate, namely gypsum, with a water content of 50% and a production of about 23 t / h, which is sold as a product.

[0099] Softening filtration: The remaining calcium ions form calcium carbonate by adding a 10% sodium carbonate solution, and then ultrafiltration membrane separation is used. The separated calcium carbonate is dehydrated to form calcium carbonate mud for use in in-furnace desulfurization. The water content of the dehydrated calcium carbonate mud is about 50%, and the content is about 0.28 t / h.

[0100] Advanced oxidation: Advanced oxidation uses electrolytic oxidation. The current density is selected as 5 A / dm 2 , and the material is selected as boron-doped diamond. The hydraulic retention time of the electrolytic oxidation device is 10 - 20 min. After electrolytic oxidation, the effluent TOC is about 254 mg / L.

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

[0102] The effluent of the multi-media filter 2 enters the nanofiltration membrane. Nanofiltration adopts a two-stage method, that is, the concentrated water of the first-stage nanofiltration is used as the feed water of the second-stage nanofiltration for further concentration. The water production rate of the first-stage nanofiltration is about 80%, and the water production rate of the second-stage nanofiltration is about 60%. The water produced in the first stage is mixed with the water produced in the second stage. After nanofiltration purification, the TOC of the nanofiltration product water is about 25 mg / L, and the concentration of sodium chloride is about 14%.

[0103] Targeted adsorption: The TOC of the adsorbed effluent is lower than 8 mg / L, the calcium ion is lower than 0.01 mmol / L, and the concentration of sodium chloride is about 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 pool. The brine entering the MVR evaporator is evaporated and crystallized until the solid mass ratio reaches about 5%, and then it is directly discharged into the sodium chloride brine pool through the salt leg of the MVR crystallizer. Since the sodium chloride concentration is in the range of 305±5 g / L, the calcium and magnesium ions are less than 10 mg / L, the TOC is less than 8 mg / L, and the purity is above 98%, it can be used as the primary brine for ion-exchange membrane caustic soda.

[0105] During the above production process, no residual concentrated liquid is generated, and the high-calcium chloride and high-organic wastewater is completely resourcefully treated. If a homogeneous catalyst is used alone, the removal rate of organic matter by wet catalytic oxidation is 60% - 80%. If a heterogeneous catalyst and a homogeneous catalyst are used simultaneously, the removal rate of organic matter by wet catalytic oxidation can reach 80% - 95%. In addition, the cost of adding cupric chloride for wet catalytic oxidation is about 423 yuan per ton of water, and the catalyst recovery unit can avoid the continuous generation of this part of the cost. The chemical dosing cost per ton of water for this project is about 97.8 yuan, and the income per ton of water generated from gypsum products, brine recovery, and recycled water is about 104.8 yuan, exceeding the chemical dosing cost. The remaining direct operating cost does not exceed 30 yuan per ton, greatly reducing the operating cost.

[0106] Implementation Case 2:

[0107] For a certain high-calcium chloride and high-organic wastewater from a pharmaceutical process, the water volume is 20 t / h, the measured pH is 6 - 9, the TOC is about 4500 mg / L, and the calcium chloride content is 20%. The treatment process is as follows.

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

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

[0110] Salt form conversion: 6.7 t / h of mirabilite is added to the reaction tank. Mirabilite reacts with calcium chloride to form calcium sulfate dihydrate, that is, gypsum, with a moisture content of 50% and a production of about 4.8 t / h, which is sold as a product.

[0111] Softening filtration: The remaining calcium ions form calcium carbonate by adding 10% sodium carbonate solution, and then ultrafiltration membrane separation is adopted. After the separated calcium carbonate is dehydrated, calcium carbonate mud is generated for in-furnace desulfurization. The water content of the dehydrated calcium carbonate mud is about 50%, and the content is about 0.06 t / h.

[0112] Advanced oxidation: Advanced oxidation uses electrolytic oxidation. The current density is selected as 6 A / dm 2 , and the material is selected as boron-doped diamond. The hydraulic retention time of the electrolytic oxidation device is 15 - 30 min. After electrolytic oxidation, the TOC of the effluent is about 295 mg / L.

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

[0114] The effluent of the multi-media filter 2 enters the nanofiltration membrane. The nanofiltration adopts a two-stage method, that is, the concentrated water of the first-stage nanofiltration is used as the feed water of the second-stage nanofiltration for further concentration. The water production rate of the first-stage nanofiltration is about 80%, and the water production rate of the second-stage nanofiltration is about 60%. The water production of the first stage and the water production of the second stage are mixed. After nanofiltration purification, the TOC of the nanofiltration effluent is about 30 mg / L, and the concentration of sodium chloride is about 17%.

[0115] Targeted adsorption: The TOC of the adsorption effluent is lower than 8 mg / L, the calcium ions are lower than 0.01 mmol / L, and the concentration of sodium chloride is about 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 pool. The brine entering the MVR evaporator is evaporated and crystallized until the solid mass ratio reaches about 5% and then discharged directly into the sodium chloride brine pool through the salt leg of the MVR crystallizer. Since the sodium chloride concentration is in the range of 305 ± 5 g / L, the calcium and magnesium ions are lower than 10 mg / L, the TOC is lower than 8 mg / L, and the purity is above 97%, it can be used as the primary brine for ion-exchange membrane caustic soda.

[0117] No residual concentrated liquid is generated in the above production process, and the high-calcium chloride and high-organic wastewater is completely resourcefully treated. If a homogeneous catalyst is used alone, the removal rate of organic matter by wet catalytic oxidation is 60% - 85%. If a heterogeneous catalyst and a homogeneous catalyst are used simultaneously, the removal rate of organic matter by wet catalytic oxidation can reach 85% - 95%. In addition, the cost of adding cupric chloride for wet catalytic oxidation is about 420 yuan per ton of water, and the catalyst recovery unit can avoid the continuous generation of this part of the cost. The chemical addition cost per ton of water in this project is about 104.8 yuan, and the income per ton of water generated from gypsum products, brine recovery and recycled water is about 116.7 yuan, exceeding the chemical addition cost. The remaining direct operating cost does not exceed 30 yuan per ton, greatly reducing the operating cost.

[0118] Unless otherwise defined, all technical and scientific terms used throughout this application shall 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 set forth in the text of this application or the meaning derived from the content recorded in the text of this application shall prevail. Additionally, the terms used in this specification are for the purpose of describing the embodiments of this application only and are not intended to limit this application.

[0119] Note that the above is only a preferred embodiment of this application and the technical principles applied. Those skilled in the art will understand that this application is not limited to the specific embodiments described herein, and various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of this application. Therefore, although this application has been described in relatively detail through the above embodiments, this application is not limited to the above embodiments only. Without departing from the technical concept of this application, more other equivalent embodiments can also be included, all of which fall within the scope of protection of this application.

Claims

1. A method for resource utilization of high-concentration calcium chloride brine containing high-concentration organic matter, characterized in that, The method includes the following steps: S1 Pretreatment: The wastewater first enters the regulation tank and then passes through a filter to remove large particulate suspended matter and a small amount of macromolecular organic matter, and then enters the wet catalytic oxidation unit; S2 Wet catalytic oxidation: Using air or oxygen as the oxidant, heterogeneous noble metal oxides and homogeneous transition metals as the catalysts, the wastewater is subjected to wet catalytic oxidation reaction under high temperature and high pressure to remove the organic matter in the wastewater, and the homogeneous catalyst is recycled to avoid the loss of the catalyst; S3 Salt form conversion: Glauber's salt is added to the effluent of wet catalytic oxidation to generate gypsum with calcium ions in the wastewater, and the gypsum is separated by a sludge dewatering machine; S4 Softening filtration: Using the double-alkali method, calcium carbonate precipitate is generated from the residual calcium ions in the supernatant of the salt form conversion sludge dewatering machine. First, it is concentrated by ultrafiltration, and then the calcium carbonate precipitate is separated by pressure filtration. The filtrate enters the advanced oxidation unit; S5 Advanced oxidation: By generating free radicals (·OH) with strong oxidation ability, under the reaction conditions of electricity or oxidant, the macromolecular and difficult-to-degrade organic matter is oxidized into low-toxic or non-toxic small molecule substances, achieving the effect of purifying the organic pollutants in the wastewater; S6 Nanofiltration purification: First, the small molecule suspended matter in the wastewater is removed by filtration, and then it passes through the nanofiltration treatment unit to remove the remaining divalent ions. The nanofiltration concentrate enters the front end of the salt form conversion unit, and the nanofiltration product water enters the targeted adsorption unit; S7 Targeted adsorption: Using microcrystalline adsorption materials to adsorb and remove the residual organic matter in the nanofiltration product water. The targeted adsorption effluent enters the product water tank, and the adsorption medium regeneration waste liquid enters the front-end pretreatment unit for further treatment; The treatment of the targeted adsorption effluent in the product water tank is as follows in S7-1 or S7-2: S7-1: All enter the salt preparation tank, and by adding sodium chloride, brine with a sodium chloride concentration of 305 ± 5 g / L is formed as the primary brine for the ion-exchange membrane caustic soda device; S7-2: Part enters the salt preparation tank, part is subjected to evaporation crystallization, the evaporation crystallization condensate is recycled, and the mother liquor enters the salt preparation tank and is mixed with the original targeted adsorption effluent that has not been evaporated and crystallized to form brine with a sodium chloride concentration of 305 ± 5 g / L as the primary brine for the ion-exchange membrane caustic soda device.

2. The method according to claim 1, wherein 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, wherein In S2, the temperature of the high temperature and high pressure is 200°C to 300°C, and the pressure is 3 - 10 Mpa; The heterogeneous catalyst is one or more of ruthenium-based, cerium-based, iron-based, and titanium-based modified by fluorine, and the catalyst active component content is 0.1 wt% - 2 wt%; The homogeneous catalyst is one or more of transition metal element compounds, and the catalyst active component content is 0.5 wt% - 5 wt%; The catalytic oxidation time is 2 - 4 h, and the residence time in the catalytic section is 15 min - 1 h; A fixed bed is arranged in the wet catalytic oxidation device, and metal oxidant fillers with a diameter of φ4 - 10 mm are filled as the enhanced disperser, and the filling density is 1.0 - 1.5 g / mL; After the waste liquid exits the reaction tower, 5% - 15% sodium hydroxide solution is added in the reaction section to fully precipitate the active components of the homogeneous catalyst. Solid-liquid separation is achieved through the retention of the filter in the filtration section. 5% - 15% hydrochloric acid or sulfuric acid is added in the dissolution section to completely dissolve the retained solid. The dissolved catalyst is pumped into the wet catalytic oxidation device by a lift pump. The time for both the catalyst reaction section and the dissolution section is 15 min - 30 min.

4. The method according to claim 1, wherein In S3, sodium sulfate is added in solid form. When adding, the stirrer is turned on, and the stirring speed is 50 - 200 rpm. The reaction time is 20 - 30 min. After gypsum is generated, solid-liquid separation is carried out using a centrifugal dehydrator. The filtration accuracy of the dehydrator is 5 μm - 20 μm, the rotation speed is 1500 - 3000 rmp, and the water content of the filter cake is 15% - 50%.

5. The method according to claim 1, wherein In S4, the double alkali is sodium hydroxide and sodium carbonate. The dosing concentration of sodium hydroxide is 5% - 15%, and the dosing concentration of sodium carbonate is 5% - 20%. After calcium carbonate precipitate is generated, ultrafiltration membrane concentration is adopted. The membrane pore size is 20 - 50 nm, the operating pressure is 0.1 - 0.5 MPa, and the SS after concentration reaches 150 - 400 g / L. The calcium carbonate solid after ultrafiltration membrane filtration is dewatered by plate and frame pressure. The feed pressure is 0.6 - 1.2 MPa, the pressing pressure is 1.5 - 2.5 MPa, the mesh number of the filter cloth is 80 - 150 meshes, the water content of the filter cake is 15% - 50%, the filtrate enters the electrolytic oxidation unit, and the filter cake is used for in-furnace desulfurization.

6. The method according to claim 1, characterized in that In S5, deep oxidation can adopt electrolytic oxidation or chemical oxidation. In electrolytic oxidation, the oxidation current density is 1 - 10 A / dm 2 , the material is selected as boron-doped diamond or titanium substrate coated with graphene, and the hydraulic retention time is 10 - 60 min; In chemical oxidation, the oxidant can be one of hydrogen peroxide, sodium hypochlorite or ozone. The hydraulic retention time for hydrogen peroxide oxidation is 1 - 4 h; the hydraulic retention time for sodium hypochlorite oxidation is 10 - 120 min; the hydraulic retention time for ozone oxidation is 10 - 60 min.

7. The method according to claim 1, characterized in that In S6, the filtration adopts 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, wherein In S6, the nanofiltration adopts a two-stage method. The concentrated water from the first-stage nanofiltration is used as the feed water for the second-stage nanofiltration for further concentration. The membrane flux of the nanofiltration membrane is 15~18 L / (m 2 ·h), the membrane area of a single membrane is 34.5 m 2 , the maximum operating pressure is 4.0 MPa, and the maximum operating temperature ≤ 45 °C.

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

10. The method according to claim 1, wherein In S7-1, 25% - 85% of the effluent from the targeted adsorption enters the salt mixing tank. When the solid content of the evaporation crystallization is 3% - 8%, it enters the salt mixing tank and is mixed with the targeted adsorption effluent directly entering to form brine with a sodium chloride concentration of 305 ± 5 g / L.

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